JP2013064573A - Refrigerating apparatus for container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating apparatus for a container, in which such a control is performed that pressure on the low-pressure side of a refrigeration cycle is reduced while pressure on the high-pressure side of the refrigeration cycle is increased under the high-temperature environment of a cooling medium for cooling a refrigerant flowing through a gas cooler, and in which the temperature of the refrigerant discharged from a compressor on a high stage side can be suppressed to be low.SOLUTION: An economizer circuit 50 is a circuit causing a part of the refrigerant from a gas cooler to join the refrigerant flowing between a low-stage compressor 21 and a high-stage compressor 22. The economizer circuit 50 includes a bypass circuit 53 having a bypass stop valve 54 and configured to bypass an economizer heat exchanger 41. A control unit 7 reduces a discharged refrigerant temperature by setting the bypass stop valve 54 to be in an open state when the temperature of the refrigerant flowing through a high-stage discharged refrigerant pipe 34 increases.

Description

  The present invention relates to a container refrigeration apparatus.

  A refrigeration apparatus that performs a refrigeration cycle includes a container refrigeration apparatus that cools the inside of a container. An example of such a refrigeration apparatus is a container refrigeration apparatus in which a gas cooler is arranged outside the container and an evaporator is arranged inside the container, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2011-112270). It is done.

  The container refrigeration apparatus as described above is used under various control conditions under various environments. For example, the container refrigeration apparatus may be used in an environment where the temperature outside the warehouse is very high and under controlled conditions in which the inside of the warehouse is frozen rather than refrigerated.

  Thus, in an environment where the temperature of the cooling medium for cooling the refrigerant flowing in the gas cooler is high, control for increasing the pressure on the high pressure side in the multistage compression refrigeration cycle is performed in order to obtain the capability of the evaporator.

  Further, when control is performed to lower the evaporation pressure, such as using an evaporator to freeze the interior of the refrigerator, control is performed to lower the low-pressure side pressure in the refrigeration cycle.

  In this way, for containers that control to lower the pressure on the low pressure side of the refrigeration cycle while increasing the pressure on the high pressure side of the multistage compression refrigeration cycle in an environment where the temperature of the cooling medium for cooling the refrigerant flowing in the gas cooler is high In the refrigeration apparatus, the temperature of the refrigerant discharged from the higher stage compressor becomes abnormally high. As described above, when the temperature of the refrigerant discharged from the high-stage compressor becomes high, there are problems such as deterioration of the refrigerating machine oil and burning of the motor used in the compressor.

  On the other hand, in the multistage compression refrigeration cycle, a part of the refrigerant that has passed through the gas cooler of the refrigeration cycle is passed through the economizer heat exchanger, and the refrigerant is injected into the intermediate pressure portion between the high pressure side and the low pressure side. Thus, the refrigerating capacity can be improved. In this multistage compression refrigeration cycle, it is conceivable that the refrigerant discharged from the high-stage compressor is lowered by injecting the refrigerant into the intermediate pressure portion of the refrigeration cycle.

  However, in a container refrigeration system that controls the pressure on the low pressure side of the refrigeration cycle while increasing the pressure on the high pressure side of the refrigeration cycle in an environment where the temperature of the cooling medium supplied to the gas cooler is high, The refrigerant injected into the pressure portion (that is, the refrigerant after passing through the economizer heat exchanger) already has a large degree of superheat. For this reason, the effect of lowering the temperature of the refrigerant sucked into the high-stage compressor is not sufficient, and the temperature of the refrigerant discharged from the high-stage compressor cannot be sufficiently reduced.

  The present invention has been made in view of the above-described points, and an object of the present invention is to reduce the pressure on the high-pressure side of the refrigeration cycle in an environment where the temperature of the cooling medium for cooling the refrigerant flowing in the gas cooler is high. An object of the present invention is to make it possible to keep the temperature of the refrigerant discharged from the high-stage compression mechanism low in a container refrigeration apparatus that performs control to lower the pressure on the low pressure side of the refrigeration cycle while increasing it.

  A container refrigeration apparatus according to a first aspect of the present invention is a container refrigeration apparatus having a low-stage compression mechanism, a high-stage compression mechanism, a gas cooler, an expansion mechanism, and an evaporator, and includes an economizer circuit and an economizer heat exchange. Device, a bypass circuit, a bypass valve, an intermediate expansion valve, a detection unit, and a control unit. The economizer circuit guides a part of the refrigerant from the gas cooler toward the evaporator to join the refrigerant from the low-stage compression mechanism to the high-stage compression mechanism. The economizer heat exchanger exchanges heat between the refrigerant flowing through the economizer circuit and the refrigerant from the gas cooler toward the evaporator. The bypass circuit connects the upstream portion and the downstream portion of the economizer heat exchanger in the middle of the economizer circuit without going through the economizer heat exchanger. The bypass valve can be switched between open and closed states, or the valve opening can be adjusted. This bypass valve is provided in the middle of the bypass circuit. The intermediate expansion valve is provided in the middle of the economizer circuit. The detection unit is equivalent to the temperature or superheat value of the refrigerant discharged from the high stage compression mechanism, the temperature or superheat value of the refrigerant sucked into the high stage compression mechanism, or any of these values. Detect physical quantities. The control unit increases the refrigerant combined flow rate that merges from the economizer circuit with respect to the refrigerant from the low-stage compression mechanism to the high-stage compression mechanism when the detection value of the detection unit increases and the first predetermined condition is not satisfied. As described above, the valve opening of the intermediate expansion valve is adjusted, and the opening / closing state of the bypass valve is switched or the valve opening of the bypass valve is adjusted. The high-stage compression mechanism and the low-stage compression mechanism may have a common drive shaft and may be driven in common, or may have separate drive shafts and are driven separately. It may be a thing. The compression mechanism may be configured to include not only two high-stage compression mechanisms and low-stage compression mechanisms but also three or more multi-stage compression mechanisms.

  In this container refrigeration system, a part of the refrigerant that has passed through the gas cooler of the refrigeration cycle is passed through the economizer heat exchanger, and the refrigerant is injected into a portion of the intermediate pressure between the high-pressure side and the low-pressure side. Thus, the refrigerating capacity can be improved.

  In a general refrigeration system, under a controlled condition where the temperature of the cooling medium for cooling the refrigerant flowing in the gas cooler is high and the refrigeration cycle is performed at a low evaporation pressure for the purpose of refrigeration, etc. An abnormal increase in the temperature of the refrigerant discharged from the high-stage compression mechanism can occur. On the other hand, in this container refrigeration apparatus, the cooling effect of lowering the temperature of the refrigerant discharged from the high-stage compression mechanism is obtained by the refrigerant injected to the suction side of the high-stage compression mechanism through the economizer circuit.

  Furthermore, when the refrigerant injected into the suction side of the high-stage compression mechanism through the economizer circuit becomes overheated after heat exchange in the economizer heat exchanger, the cooling effect may be insufficient. In contrast, this container refrigeration system further includes a bypass circuit that connects the upstream side and the downstream side of the economizer heat exchanger in the economizer circuit, and out of the amount of refrigerant flowing through the economizer circuit, economizer heat. The amount of refrigerant passing through the exchanger can be reduced. Thereby, the heat exchange amount by which the refrigerant injected into the suction side of the high-stage compression mechanism through the economizer circuit passes through the economizer heat exchanger can be reduced. Accordingly, the cooling effect of lowering the temperature of the refrigerant discharged from the high-stage compression mechanism can be further enhanced by the refrigerant injected to the suction side of the high-stage compression mechanism through the economizer circuit.

  The container refrigeration apparatus according to a second aspect of the present invention is the container refrigeration apparatus according to the first aspect, wherein the control unit detects the detection unit in a state where the valve opening degree of the intermediate expansion valve is equal to or greater than a predetermined opening degree. When the value does not satisfy the first predetermined condition due to an increase in value, the bypass valve is controlled so as to switch from the closed state to the open state or to increase the valve opening. The predetermined opening degree of the intermediate expansion valve may be fully open, or may be an opening degree that is smaller than the fully open position and not fully closed.

  In this container refrigeration apparatus, when the opening degree of the intermediate expansion valve is equal to or larger than the predetermined opening degree, the refrigerant can be injected into the intermediate pressure portion between the high pressure side and the low pressure side through the economizer circuit. . And it can suppress that the refrigerant | coolant made to inject with respect to the part of intermediate pressure is warmed by passing the inside of an economizer heat exchanger. Thereby, the temperature of the suction refrigerant of the high stage compression mechanism can be lowered, and the temperature of the discharge refrigerant of the high stage compression mechanism can be lowered.

  The container refrigeration apparatus according to a third aspect of the present invention is the container refrigeration apparatus according to the second aspect, wherein the control unit increases the detection value of the detection unit in a state where the valve opening of the intermediate expansion valve is fully open. When the first predetermined condition is no longer satisfied, the bypass valve is controlled to switch from the closed state to the open state, or the valve opening degree is increased.

  In this container refrigeration system, the valve opening of the intermediate expansion valve is in a fully open state, and the valve opening of the intermediate expansion valve cannot be increased any further. Therefore, the intermediate pressure through the economizer circuit The amount of refrigerant injection cannot be further increased.

  In contrast, here, the control unit controls the bypass valve to switch from the closed state to the open state, or increases the valve opening. For this reason, it can suppress that the refrigerant | coolant made to inject with respect to the part of an intermediate | middle pressure is warmed by passing the inside of an economizer heat exchanger. Thereby, even if the valve opening degree of the intermediate expansion valve is in a fully open state and the valve opening degree of the intermediate expansion valve cannot be increased any more, the temperature of the suction refrigerant of the high stage compression mechanism is lowered. And the temperature of the refrigerant discharged from the high-stage compression mechanism can be lowered.

  The container refrigeration apparatus according to the fourth aspect of the present invention is the container refrigeration apparatus according to any one of the first to third aspects, wherein the bypass valve is an on-off valve. The intermediate expansion valve is provided in the middle of the economizer circuit and further upstream than the upstream portion of the connecting portion between the bypass circuit and the economizer circuit.

  In this container refrigeration apparatus, the flow rate of the refrigerant flowing through the economizer circuit can be adjusted by controlling the opening degree of the intermediate expansion valve. The intermediate expansion valve is provided in the middle of the economizer circuit and further upstream than the upstream portion of the connecting portion between the bypass circuit and the economizer circuit. For this reason, the refrigerant | coolant which is going to flow to the economizer heat exchanger side among the refrigerant | coolants which passed the intermediate | middle expansion valve receives the pressure loss for flowing in the economizer heat exchanger side. On the other hand, among the refrigerants that have passed through the intermediate expansion valve, the refrigerant that is about to flow to the bypass circuit side where the bypass valve is fully open has a smaller pressure loss than the refrigerant that is about to flow in the economizer heat exchanger. For this reason, even if it is the structure which made the bypass valve the cheap on-off valve, the refrigerant | coolant amount which flows through a bypass circuit can be increased, suppressing the refrigerant | coolant amount which flows through the economizer heat exchanger side.

  The container refrigeration apparatus according to the fifth aspect of the present invention is the container refrigeration apparatus according to any one of the first to third aspects, wherein the bypass valve is an expansion valve capable of adjusting a flow rate of the refrigerant passing therethrough. The intermediate expansion valve is provided in the middle of the economizer circuit and between the upstream portion of the connecting portion between the bypass circuit and the economizer circuit and the inlet of the economizer heat exchanger.

  In this container refrigeration apparatus, the flow rate of the refrigerant flowing through the economizer circuit can be adjusted by controlling the opening degree of the intermediate expansion valve. The intermediate expansion valve is provided in the middle of the economizer circuit and between the upstream portion of the connecting portion between the bypass circuit and the economizer circuit and the inlet of the economizer heat exchanger. For this reason, the total amount of the refrigerant flowing through the economizer heat exchanger and the refrigerant flowing through the bypass circuit among the refrigerant flowing through the economizer circuit is determined by the valve opening control of the intermediate expansion valve and the valve opening control of the bypass valve. Can be adjusted. Moreover, among the refrigerant flowing through the economizer circuit, the ratio between the refrigerant amount flowing through the economizer heat exchanger side and the refrigerant amount flowing through the bypass circuit side is also determined by the valve opening control of the intermediate expansion valve and the valve opening control of the bypass valve. Can be adjusted. As a result, while adjusting the economizer effect obtained by adjusting the amount of refrigerant flowing through the economizer circuit, the temperature of the refrigerant discharged from the high-stage compression mechanism is lowered by the refrigerant injected to the suction side of the high-stage compression mechanism through the economizer circuit. It is possible to adjust the degree of the cooling effect.

  In the container refrigeration apparatus of the fifth aspect, the following effects can be obtained as compared with the case where the bypass valve is an on-off valve. For example, when the bypass valve is an on-off valve and is in a closed state, the intermediate expansion valve is in a fully open state and the valve opening degree cannot be increased any more, and when the cooling effect is increased, it is in the closed state. There is no choice but to switch the bypass valve fully open. In this case, it becomes difficult to finely adjust the amount of refrigerant passing through the economizer heat exchanger, so that the cooling effect becomes excessive or detailed adjustment of the cooling effect becomes difficult. On the other hand, in the container refrigeration apparatus of the fifth aspect, the cooling effect can be adjusted in more detail.

  The container refrigeration apparatus according to a sixth aspect of the present invention is the container refrigeration apparatus according to the fifth aspect, wherein the control unit performs the first control. In the first control, if the intermediate expansion valve is not fully opened at the time when the first predetermined condition is not satisfied due to an increase in the detection value of the detection unit, the valve opening degree of the intermediate expansion valve is increased, and the intermediate expansion valve If is fully open, the valve opening degree of the bypass valve is increased.

  In this container refrigeration system, the refrigerant flow rate of the bypass circuit can be increased by increasing the valve opening degree of either the intermediate expansion valve or the bypass valve by performing the first control. Here, when increasing the combined flow rate of refrigerant injected through the economizer circuit with respect to the refrigerant from the low-stage compression mechanism to the high-stage compression mechanism, the opening degree of the bypass valve until the opening degree of the intermediate expansion valve is fully opened. Can be avoided. For this reason, the refrigerant | coolant amount which passes an economizer heat exchanger can be ensured as much as possible. Thereby, it is possible to obtain the economizer effect as much as possible while preventing the temperature of the refrigerant discharged from the high-stage compression mechanism from rising abnormally.

  The container refrigeration apparatus according to the seventh aspect of the present invention is the container refrigeration apparatus according to the sixth aspect, in which the control unit performs the second control. In the second control, the control unit performs the first control, and when the degree of decrease in the detection value of the detection unit does not satisfy the second predetermined condition even though the intermediate expansion valve is fully opened. The operation of decreasing the valve opening of the intermediate expansion valve and the operation of increasing the valve opening of the bypass valve are performed simultaneously.

  In this container refrigeration apparatus, there may be a case where it is desired to further reduce the temperature of the refrigerant discharged from the high-stage compression mechanism in a state where the first control is performed and the intermediate expansion valve is fully open. Here, by performing the second control, the amount of heat exchange when the refrigerant passing through the economizer circuit with respect to the refrigerant heading from the low-stage compression mechanism to the high-stage compression mechanism is passed through the economizer heat exchanger. It can be kept small. Thereby, about the state of the refrigerant | coolant injected, a superheat degree can further be lowered | hung or a dryness can be lowered | hung. In addition, the degree of superheat and dryness of the injected refrigerant can be finely adjusted by gradually adjusting the valve opening of the intermediate expansion valve and the valve opening of the bypass valve. For this reason, it is possible to reduce the temperature of the refrigerant discharged from the high-stage compression mechanism while suppressing the degree of reduction in the economizer effect accompanying the reduction in the flow rate of the refrigerant passing through the economizer heat exchanger.

  The container refrigeration apparatus according to the eighth aspect of the present invention is the container refrigeration apparatus according to the seventh aspect, in which the control unit performs the third control. In the third control, the control unit increases the valve opening of the intermediate expansion valve when the degree of decrease in the detection value of the detection unit satisfies the second predetermined condition after performing the second control, The operation of lowering the valve opening is simultaneously performed.

  In this container refrigeration apparatus, the degree of heat exchange (heat exchange amount) when passing through the economizer heat exchanger can be increased for the refrigerant injected between the low-stage compression mechanism and the high-stage compression mechanism. For this reason, the economizer heat exchanger is maintained while keeping the temperature of the refrigerant discharged from the high-stage compression mechanism low by adjusting the refrigerant amount passing through the economizer heat exchanger side and the refrigerant amount passing through the bypass circuit side. The economizer effect can be increased by increasing the flow rate of the refrigerant passing through.

  The container refrigeration apparatus according to the ninth aspect of the present invention is the container refrigeration apparatus according to any one of the first to eighth aspects, wherein the refrigerant is directed from the discharge side of the low stage compression mechanism to the suction side of the high stage compression mechanism. An intercooler is further provided for cooling.

  In this container refrigeration apparatus, the refrigerant discharged from the low-stage compression mechanism is cooled by passing through the intercooler. For this reason, the temperature of the refrigerant sucked by the high-stage compression mechanism can be lowered. Thereby, the temperature of the refrigerant discharged from the high-stage compression mechanism can be lowered.

  The container refrigeration apparatus according to a tenth aspect of the present invention is the container refrigeration apparatus according to any one of the first to ninth aspects, wherein the refrigerant is a carbon dioxide refrigerant.

  In this container refrigeration apparatus, carbon dioxide is used as a refrigerant. For this reason, a refrigeration cycle in which the pressure of the refrigerant discharged from the high-stage compression mechanism exceeds the critical pressure and becomes a supercritical state may be performed, and the refrigerant discharged from the high-stage compression mechanism becomes hot. Cheap. In contrast, in this container refrigeration apparatus, even when a refrigerant that is operated under conditions where the temperature of the refrigerant discharged from the high-stage compression mechanism is high is used, the refrigerant discharged from the high-stage compression mechanism Abnormal temperature rise can be suppressed.

  In the container refrigeration apparatus according to the first aspect of the present invention, the cooling effect of lowering the temperature of the refrigerant discharged from the high-stage compression mechanism can be further enhanced.

  In the container refrigeration apparatus according to the second aspect of the present invention, the temperature of the suction refrigerant of the high-stage compression mechanism can be lowered, and the temperature of the discharge refrigerant of the high-stage compression mechanism can be lowered.

  In the container refrigeration apparatus according to the third aspect of the present invention, the valve opening degree of the intermediate expansion valve is fully opened, and even if the valve opening degree of the intermediate expansion valve cannot be increased any more, The temperature of the suction refrigerant of the stage compression mechanism can be lowered, and the temperature of the discharge refrigerant of the high stage compression mechanism can be lowered.

  In the container refrigeration apparatus according to the fourth aspect of the present invention, the amount of refrigerant flowing through the bypass circuit is increased while suppressing the amount of refrigerant flowing through the economizer heat exchanger even if the bypass valve is configured as an inexpensive on-off valve. Can be made.

  In the container refrigeration apparatus according to the fifth aspect of the present invention, the refrigerant is injected into the suction side of the high-stage compression mechanism through the economizer circuit while adjusting the economizer effect obtained by adjusting the amount of refrigerant flowing through the economizer circuit. The degree of the cooling effect that lowers the temperature of the refrigerant discharged from the high-stage compression mechanism can also be adjusted.

  In the container refrigeration apparatus according to the sixth aspect of the present invention, the economizer effect can be obtained as much as possible while preventing the temperature of the refrigerant discharged from the high-stage compression mechanism from rising abnormally.

  In the container refrigeration apparatus according to the seventh aspect of the present invention, the temperature of the refrigerant discharged from the high-stage compression mechanism is reduced while suppressing the degree of decrease in the economizer effect accompanying the decrease in the refrigerant flow rate passing through the economizer heat exchanger. It becomes possible to make it.

  In the container refrigeration apparatus according to the eighth aspect of the present invention, the refrigerant discharged from the high-stage compression mechanism is adjusted by adjusting the amount of refrigerant passing through the economizer heat exchanger and the amount of refrigerant passing through the bypass circuit. The economizer effect can be increased by increasing the flow rate of refrigerant passing through the economizer heat exchanger while keeping the temperature low.

  In the container refrigeration apparatus according to the ninth aspect of the present invention, the temperature of the refrigerant discharged from the high stage compression mechanism can be reduced by reducing the temperature of the refrigerant sucked by the high stage compression mechanism.

  In the container refrigeration apparatus according to the tenth aspect of the present invention, the discharge of the high-stage compression mechanism is performed even when the refrigerant is operated under the condition that the temperature of the discharge refrigerant of the high-stage compression mechanism is high. Abnormal increase in the temperature of the refrigerant can be suppressed.

1 is a schematic configuration diagram of a refrigeration vehicle in which a container refrigeration apparatus according to an embodiment of the present invention is employed. It is the schematic perspective view seen from the front side of the refrigeration apparatus for containers. It is a schematic arrangement block diagram of the container refrigeration equipment. It is a refrigerant circuit figure of the refrigeration equipment for containers. It is a PH diagram of the refrigerating cycle at the time of normal control in which a bypass on-off valve is closed. It is a PH diagram of the refrigerating cycle performed with a bypass on-off valve opened. It is a block diagram which shows a system configuration. It is a control flowchart concerning one embodiment of the present invention. It is a refrigerant circuit figure concerning other embodiments (7-1). It is a control flowchart which concerns on other embodiment (7-1).

  Hereinafter, a container refrigeration apparatus 10 that is an example of an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of a refrigeration vehicle employing a container refrigeration apparatus. In FIG. 2, the schematic perspective view seen from the front side of the container refrigeration apparatus 10 is shown. FIG. 3 shows a schematic arrangement configuration diagram of the container refrigeration apparatus 10. FIG. 4 shows a refrigerant circuit diagram of the container refrigeration apparatus 10. FIG. 5 shows a PH diagram of the refrigeration cycle. FIG. 6 shows a block diagram of the system configuration.

(1) Arrangement of Refrigeration Vehicle 1 and Container Refrigeration Device 10 A container refrigeration device 10 according to this embodiment is provided and used in a refrigeration vehicle 1 as shown in FIG.

  The refrigeration vehicle 1 includes a container 2, a trailer 3, and a tractor 4.

  The trailer 3 is loaded with the container 2 and the container refrigeration apparatus 10.

  The tractor 4 pulls the trailer 3. The tractor 4 can transport the container 2 loaded on the trailer 3 with the container refrigeration apparatus 10 attached.

  The container 2 is a substantially rectangular parallelepiped housing that is partitioned to maintain the interior IS at a temperature lower than that of the exterior OS, and includes a heat insulating material. As shown in FIG. 2, the container 2 has a top surface 2c, a bottom surface 2b, a front surface 2f, a back surface (not shown), and left and right side surfaces. Among these, the container refrigeration apparatus 10 is installed on the front surface 2 f of the container 2. In addition, the ventilation mechanism 5 opened in the front-back direction is provided in the front surface 2f of the container 2, and it is possible to maintain the state where the interior IS is filled with fresh air.

  An internal partition plate 8 that partitions the space in the front-rear direction is provided on the front side inside the container 2. The internal partition plate 8 is provided with a gap between the upper end portion and the top surface 2c and between the lower end portion and the bottom surface 2b. The internal partition plate 8 divides the internal space of the container 2 into an internal storage chamber SP2 between the internal partition plate 8 and the front surface 2f, and an interior IS on the back side of the internal partition plate 8. An evaporator 46, an internal fan 47, an internal fan motor 47m, and the like, which will be described later, are disposed in the internal storage chamber SP2. When the internal fan motor 47m is driven, as shown by arrows F1 and F2 in FIG. 3, the air flow F1 from the internal IS to the internal storage chamber SP2 through the gap above the internal partition plate 8, and the internal An air flow F <b> 2 is generated from the internal storage chamber SP <b> 2 toward the interior IS through the gap below the partition plate 8.

  In addition, the front surface 2f of the container 2 has a recessed portion formed such that the lower portion is recessed on the back surface side. An external partition plate 6 is provided on the front side of the recessed portion of the front surface 2 f of the container 2. The external partition plate 6 is provided with openings that communicate with each other in the front-rear direction at the upper end portion and the lower end portion. The external partition plate 6 is partitioned into an external storage chamber SP1 between the back side thereof and the recessed portion of the front surface 2f of the container 2 and an external OS. In the external storage chamber SP1, a compression mechanism 23, a gas cooler 27, an intercooler 24, an external fan 28, an external fan motor 28m, and the like, which will be described later, are disposed. When this outside fan motor 28m is driven, as indicated by arrows F3 and F4 in FIG. 3, the air flow F3 from the outside OS to the external storage room SP1 through the opening below the external partition plate 6, and the outside An air flow F4 from the external storage chamber SP1 toward the outside OS is generated through the opening above the partition plate 6.

  As shown in FIG. 2, a control unit 7 is provided on the front surface 2 f of the container 2. The control unit 7 is provided with an operation panel 73 so that operation input can be performed from the front side of the container 2.

(2) Configuration of container refrigeration apparatus 10 As shown in FIGS. 4 and 6, the container refrigeration apparatus 10 includes a refrigerant circuit 10a for performing a refrigeration cycle, an external fan 28, an external fan motor 28m, and an internal storage. It has a fan 47, an internal fan motor 47m, a control unit 7, and various sensors 61-69, 75-77, 85-87.

  The refrigerant circuit 10a includes a compression mechanism 23, an intercooler 24, a gas cooler 27, an economizer circuit 50, an economizer heat exchanger 41, a liquid gas heat exchanger 42, a first expansion valve 43, a receiver 44, a second expansion valve 45, and an evaporator. 46 and various refrigerant pipes 31, 32, 33, 34, and 35. These various refrigerant pipes include a low-stage intake refrigerant pipe 31, a low-stage discharge refrigerant pipe 32, a high-stage intake refrigerant pipe 33, a high-stage discharge refrigerant pipe 34, a high-pressure side connection refrigerant pipe 35, and the like. In the refrigerant circuit 10a, carbon dioxide refrigerant is used as the working refrigerant.

  The compression mechanism 23 is a multistage compression mechanism having a low stage compressor 21 and a high stage compressor 22. The low stage compressor 21 and the high stage compressor 22 are connected in series, and sequentially pressurize the refrigerant. The low stage compressor 21 has a low stage suction refrigerant pipe 31 connected to the suction side and a low stage discharge refrigerant pipe 32 connected to the discharge side. The high stage compressor 22 has a high stage suction refrigerant pipe 33 connected to the suction side and a high stage discharge refrigerant pipe 34 connected to the discharge side. Each of the low-stage compressor 21 and the high-stage compressor 22 is provided with a drive source (not shown), and individual inverter control of the drive frequency is possible.

  The intercooler 24 has an inlet side of refrigerant flowing through the intercooler 24 connected to the low-stage discharge refrigerant pipe 32 and an outlet side connected to the high-stage intake refrigerant pipe 33. The intercooler 24 is disposed in the external storage chamber SP1 as described above, and can cool the refrigerant flowing inside by heat exchange with the air of the outside OS.

  The gas cooler 27 is connected to the high-stage discharge refrigerant pipe 34 on the inlet side of the refrigerant flowing inside. Similarly to the intercooler 24, the gas cooler 27 is also disposed in the external storage chamber SP1, and can cool the refrigerant flowing inside by heat exchange with the air of the outside OS.

  The external fan 28 and the external fan motor 28m are arranged in the external storage room SP1. By driving and controlling the outside fan motor 28 m by the control unit 7, the outside fan 28 is rotationally driven, and the air of the outside OS can be supplied to both the intercooler 24 and the gas cooler 27.

  The high stage side connecting refrigerant pipe 35 extends from the outlet side of the gas cooler 27 and is connected to the main circuit side, not the economizer circuit 50 side of the economizer heat exchanger 41.

  The economizer circuit 50 includes an economizer refrigerant pipe 51, an economizer expansion valve 52, a bypass circuit 53, and a bypass opening / closing valve 54. As shown in FIG. 4, the economizer refrigerant pipe 51 branches from an economizer inlet F that is in the middle of the high stage side refrigerant pipe 35 (between the outlet of the gas cooler 27 and the main circuit side inlet of the economizer heat exchanger 41). Then, the economizer heat exchanger 41 extends to the economizer outlet D in the middle of the high stage intake refrigerant pipe 33 (between the outlet of the intercooler 24 and the intake side of the high stage compressor 22). The economizer expansion valve 52 is provided between the economizer inlet F and the economizer heat exchanger 41 in the economizer refrigerant pipe 51. The economizer expansion valve 52 is capable of adjusting a minute opening degree by the valve opening of the valve being controlled by the control unit 7 and adjusting the amount of refrigerant passing therethrough or adjusting the degree of decompression of the refrigerant. The bypass circuit 53 is a refrigerant pipe that connects the upstream side (one side) and the downstream side (the other side) of the economizer heat exchanger 41 in the economizer refrigerant pipe 51. The upstream side of the bypass circuit 53 branches at a bypass inlet H between the economizer expansion valve 52 of the economizer refrigerant pipe 51 and the main circuit side inlet of the economizer heat exchanger 41, and the economizer of the economizer refrigerant pipe 51 is economizer. It extends to a bypass outlet K between the outlet of the heat exchanger 41 and the economizer outlet D. A bypass opening / closing valve 54 is provided in the middle of the bypass circuit 53, and switching control is performed between the open state and the closed state by the control unit 7. Here, a passing point between the bypass opening / closing valve 54 and the bypass outlet K in the bypass circuit 53 is referred to as a “bypass passing point J”. Further, a passing point between the economizer heat exchanger 41 and the bypass outlet K in the economizer refrigerant pipe 51 is referred to as “economizer passing point I”. The economizer heat exchanger 41 includes a refrigerant that flows into the economizer circuit 50 from the economizer inlet F and passes through the economizer expansion valve 52, and a refrigerant that has not flown from the economizer inlet F to the economizer circuit 50 side (a refrigerant that has flowed out of the gas cooler 27). Heat exchange without mixing the refrigerant with the refrigerant flowing on the main circuit side).

  The liquid gas heat exchanger 42 exchanges heat between the refrigerant flowing through the main circuit side that has passed through the economizer heat exchanger 41 and the refrigerant flowing through the low-stage intake refrigerant pipe 31 without mixing the refrigerant.

  The first expansion valve 43 is provided at a position where the refrigerant flowing on the main circuit side that has passed through the economizer heat exchanger 41 has passed through the liquid gas heat exchanger 42. The first expansion valve 43 controls the valve opening degree by the control unit 7, thereby adjusting the amount of refrigerant passing therethrough or adjusting the degree of decompression of the refrigerant to bring the refrigerant into a gas-liquid two-phase state.

  Of the refrigerant that has passed through the first expansion valve 43, the receiver 44 allows only the liquid refrigerant to flow downstream of the refrigerant circuit 10a. In the receiver 44, the refrigerant is saturated.

  The second expansion valve 45 is provided at a position through which the liquid refrigerant after passing through the receiver 44 passes. The second expansion valve 45 controls the valve opening degree by the control unit 7, thereby adjusting the amount of refrigerant passing through the liquid or adjusting the pressure of the refrigerant to be reduced to bring the refrigerant into a gas-liquid two-phase state. .

  The evaporator 46 is arranged so that the inlet side of the refrigerant flowing inside is the second expansion valve 45 side, and the outlet side is the low-stage intake refrigerant pipe 31 side. As shown in FIG. 3, the evaporator 46 is disposed in the internal storage chamber SP <b> 2, exchanges heat with air flowing from the internal IS into the internal storage chamber SP <b> 2, and flows in the gas-liquid two-phase state refrigerant. Evaporates.

  The internal fan 47 and the internal fan motor 47m are arranged in the internal storage room SP2. When the internal fan motor 47m is driven and controlled by the control unit 7, the internal fan 47 is rotationally driven, and the air that flows into the internal storage chamber SP2 from the internal IS to the evaporator 46 as described above. Can be supplied.

  As shown in FIG. 2, the control unit 7 is arranged on the front side of the container 2. As shown in FIG. 6, the control unit 7 includes a CPU 71, a memory 72, an operation panel 73, an output unit 74, and the like. The operation panel 73 is an interface that accepts various settings from the user, and accepts designations such as a set temperature and various operation modes, for example. The CPU 71 performs low-level processing based on information input via the operation panel 73, information stored in advance in the memory 72, and information obtained from the various sensors 61-69, 75-77, 85-87. The compressor 21, the high stage compressor 22, the outside fan motor 28m, the inside fan motor 47m, the first expansion valve 43, the second expansion valve 45, the economizer expansion valve 52, and the bypass opening / closing valve 54 are controlled.

  Specifically, the various sensors 61 to 69, 75 to 77, and 85 to 87 include a low pressure sensor 61, a low stage suction refrigerant temperature sensor 62, an intermediate pressure sensor 63, an intermediate refrigerant temperature sensor 64, and a high pressure switch. 65, high pressure sensor 66, high stage discharge refrigerant temperature sensor 67, evaporator inflow refrigerant temperature sensor 68, evaporator outflow refrigerant temperature sensor 69, first economizer refrigerant temperature sensor 75, second economizer refrigerant temperature sensor 76, third economizer A refrigerant temperature sensor 77, an outside temperature sensor 85, an intake temperature sensor 86, and an outlet temperature sensor 87 are exemplified.

  The low pressure sensor 61 detects the pressure of the refrigerant flowing through the low stage suction refrigerant pipe 31. The temperature of the refrigerant flowing through the low stage intake refrigerant temperature sensor 62 and the low stage intake refrigerant pipe 31 is detected. The intermediate pressure sensor 63 detects the pressure of the refrigerant flowing between the economizer outlet D of the high stage suction refrigerant pipe 33 and the suction side of the high stage compressor 22. The intermediate refrigerant temperature sensor 64 detects the temperature of the refrigerant flowing between the economizer outlet D of the high stage intake refrigerant pipe 33 and the intake side of the high stage compressor 22. The high-pressure switch 65 operates when the pressure of the refrigerant flowing through the high-stage discharge refrigerant pipe 34 exceeds a predetermined protective pressure, and functions as a trigger that causes the control unit 7 to stop operation. The high pressure sensor 66 detects the pressure of the refrigerant flowing through the high stage discharge refrigerant pipe 34. The high stage discharge refrigerant temperature sensor 67 detects the temperature of the refrigerant flowing through the high stage discharge refrigerant pipe 34. The evaporator inflow refrigerant temperature sensor 68 detects the temperature of the refrigerant immediately after flowing into the evaporator 46 after passing through the second expansion valve 45. The evaporator outflow refrigerant temperature sensor 69 detects the temperature of the refrigerant immediately after passing through the evaporator 46.

  The first economizer refrigerant temperature sensor 75 detects the refrigerant temperature immediately after passing through the economizer expansion valve 52. The second economizer refrigerant temperature sensor 76 detects the refrigerant temperature immediately after passing through the outlet of the economizer heat exchanger 41 in the economizer refrigerant pipe 51. The third economizer refrigerant temperature sensor 77 detects the refrigerant temperature immediately after passing through the bypass outlet K in the economizer refrigerant pipe 51.

  The outside temperature sensor 85 detects the outside temperature of the outside OS. The suction temperature sensor 86 detects the temperature of the air flowing into the internal storage room SP2 from the internal IS, that is, the internal temperature. The blowing temperature sensor 87 detects the air temperature immediately after passing through the evaporator 46.

  Hereinafter, an example of the refrigeration cycle when the bypass opening / closing valve 54 of the bypass circuit 53 is in the closed state and an example of the refrigeration cycle when the control unit 7 is in the open state will be described.

(3) Example of refrigeration cycle of container refrigeration apparatus 10 with bypass on / off valve 54 closed When compression mechanism 23 of container refrigeration apparatus 10 is driven to perform a refrigeration cycle, the PH diagram of FIG. The state changes of the refrigerant as shown in FIG. 5 occur (the points A to P in FIG. 5 respectively correspond to the points on the refrigerant circuit in FIG. 4).

  The low-stage compressor 21 increases the pressure of the refrigerant to the intermediate pressure (point B) by sucking and compressing the overheated refrigerant (point A).

  When the refrigerant whose pressure has increased to the intermediate pressure passes through the intercooler 24, it is cooled by the air in the outside OS (point C), and then merges with the refrigerant that has flowed through the economizer circuit 50 (economizer outlet D). It is sucked into the high stage compressor 22.

  The refrigerant whose pressure is further increased in the high-stage compressor 22 and exceeds the critical pressure (point E) is cooled by the air in the outside OS in the gas cooler 27 (economizer inlet F). A part of the refrigerant cooled by the gas cooler 27 flows on the economizer circuit 50 side, and the other part flows on the main circuit side.

  The refrigerant that has flowed into the economizer circuit 50 in a state exceeding the critical pressure (economizer inlet F) is reduced to a pressure lower than the critical pressure in the economizer expansion valve 52 to become a gas-liquid two-phase refrigerant (bypass inlet H). ).

  Here, since the bypass on-off valve 54 of the bypass circuit 53 is in a closed state, all the refrigerant flowing through the economizer refrigerant pipe 51 passes through the economizer heat exchanger 41 and exchanges heat with the refrigerant flowing through the main circuit side. (Economizer passage point I, bypass outlet K), and then merge with the refrigerant (point C) flowing through the high-stage intake refrigerant pipe 33 (economizer outlet D).

  The refrigerant (point G) that has passed through the main circuit side of the economizer heat exchanger 41 exchanges heat with the refrigerant (point P) that passes through the liquid gas heat exchanger 42 and flows through the low-stage intake refrigerant pipe 31. (Point L), the pressure is reduced by the first expansion valve 43 until saturated (point M).

  The refrigerant (point M) depressurized to the saturated state becomes only the liquid refrigerant in the saturated state by the receiver 44 (point N), and is further depressurized by the second expansion valve 45 to become the refrigerant in the gas-liquid two-phase state (point O). ).

  The refrigerant in the gas-liquid two-phase state (point O) flows into the evaporator 46 and evaporates by being heated while cooling the air flowing into the internal storage room SP2 from the internal IS, and becomes superheated ( Point P).

  Thereafter, by passing through the liquid gas heat exchanger 42, the degree of superheat of the refrigerant is further increased and sucked into the low-stage compressor 21 (point A).

  Then, the above refrigeration cycle is repeated.

(4) Example of refrigeration cycle of container refrigeration apparatus 10 with bypass on / off valve 54 open When bypass on / off valve 54 is in an open state, it flows through economizer circuit 50 as shown in the PH diagram of FIG. Among the refrigerants, since the passage resistance in the economizer heat exchanger 41 is larger than the passage resistance of the bypass circuit 53, the amount of refrigerant passing through the economizer heat exchanger 41 is reduced, and most of the refrigerant flows through the bypass circuit 53. (In FIG. 6, a case where the refrigerant does not pass through the economizer heat exchanger 41 is shown.) For this reason, most of the refrigerant flowing through the economizer circuit 50 is not heated by the economizer heat exchanger 41, but remains in the gas-liquid two-phase state decompressed by the economizer expansion valve 52 (bypass inlet H), and high-stage suction. It merges with the refrigerant (point C) flowing through the refrigerant pipe 33 (economizer outlet D ′).

  For this reason, the refrigerant sucked by the high-stage compressor 22 when the bypass opening / closing valve 54 of the bypass circuit 53 is open is lower in temperature than when the bypass opening / closing valve 54 of the bypass circuit 53 is closed. Therefore, the temperature of the refrigerant (point E ′) discharged from the high-stage compressor 22 when the bypass opening / closing valve 54 of the bypass circuit 53 is open is also higher than that when the bypass opening / closing valve 54 of the bypass circuit 53 is closed. Can be lowered (see arrow in FIG. 6).

(5) Control flowchart In the container refrigeration apparatus 10, the control unit 7 realizes the set temperature received from the user via the operation panel 73 while maintaining the bypass on / off valve 54 of the bypass circuit 53 in the closed state. Thus, the normal control of controlling the low stage compressor 21, the high stage compressor 22, the external fan motor 28m, the first expansion valve 43, the second expansion valve 45, and the internal fan motor 47m is performed.

  In this normal control, the set temperature received by the operation panel 73, the detected value of the evaporator inflow refrigerant temperature sensor 68, the detected value of the evaporator outflow refrigerant temperature sensor 69, the detected value of the outside temperature sensor 85, and the suction temperature sensor 86. The control unit 7 controls the low stage compressor 21, the high stage compressor 22, the outside fan motor 28m, the first expansion valve 43 based on the detected value (internal temperature) and the detected value of the blowing temperature sensor 87. The second expansion valve 45 and the internal fan motor 47m are controlled.

  More specifically, in normal control, the control unit 7 controls each control object as follows. The driving frequency of the low stage compressor 21 is controlled based on the temperature detected by the blowing temperature sensor 87. The driving frequency of the high stage compressor 22 is controlled so as to optimize the intermediate pressure (the suction pressure of the high stage compressor 22). The outside fan motor 28m is controlled to have a rotational speed determined based on the temperature (outside air temperature) detected by the outside temperature sensor 85. The valve opening degree of the first expansion valve 43 is controlled so that the pressure of the refrigerant discharged from the high stage compressor 22 becomes the target high pressure. The valve opening degree of the second expansion valve 45 is controlled based on the degree of superheat of the refrigerant flowing through the outlet of the evaporator 46. The rotation speed of the internal fan motor 47m is controlled so as to be the rotational speed determined based on the target internal temperature.

  The control unit 7 grasps the temperature of the refrigerant discharged from the high-stage compressor 22 while performing this normal control, and increases the valve opening of the economizer expansion valve 52 when the temperature of the discharged refrigerant rises abnormally, and Alternatively, discharge temperature control for opening the bypass opening / closing valve 54 of the bypass circuit 53 is performed. In the discharge temperature control, the temperature of the refrigerant discharged from the high-stage compressor 22 (discharge refrigerant temperature Td) is a temperature lower than a predetermined discharge temperature upper limit threshold Tdu and a predetermined discharge temperature lower limit threshold Tdl. The opening degree of the economizer expansion valve 52 and / or the opening / closing state of the bypass opening / closing valve 54 are controlled so that the temperature can be maintained within a predetermined temperature range that is higher than the opening temperature. The control unit 7 grasps the temperature of the refrigerant discharged from the high stage compressor 22 as a detection value of the high stage discharge refrigerant temperature sensor 67.

  A specific control flowchart by the control unit 7 is shown in FIG.

  In step S10, the control unit 7 continues the normal control described above.

  In step S11, the control unit 7 determines whether or not the discharge refrigerant temperature Td exceeds the discharge temperature upper limit threshold Tdu. If the discharge temperature upper limit threshold Tdu is exceeded, the process proceeds to step S12. If the discharge temperature upper limit threshold Tdu is not exceeded, the process returns to step S10 and normal control is continued.

  In step S12, the control unit 7 determines whether or not the valve opening of the economizer expansion valve 52 is fully open. Here, when the valve opening degree of the economizer expansion valve 52 is not yet fully opened, the process proceeds to step S16. If the valve opening of the economizer expansion valve 52 has already been fully opened, the process proceeds to step S13.

  In step S13, the control unit 7 switches the bypass opening / closing valve 54, which has been maintained in the closed state, to the open state, and reduces the amount of refrigerant passing through the economizer heat exchanger 41 among the refrigerants flowing through the economizer circuit 50, thereby bypassing The amount of refrigerant passing through the circuit 53 is increased, and the degree of superheat or dryness of the refrigerant toward the economizer outlet D is lowered, and the process proceeds to step S14.

  In step S14, the control unit 7 determines whether or not the discharged refrigerant temperature Td can be lowered to a level that is lower than the discharged temperature lower limit threshold value Tdl. If the discharge temperature lower limit threshold value Tdl is not reached, the process proceeds to step S15. If it is not below the discharge temperature lower limit threshold Tdl, the process proceeds to step S17.

  In step S15, the control unit 7 has been able to sufficiently lower the discharged refrigerant temperature Td. Therefore, the bypass opening / closing valve 54 is returned to the closed state, and the process proceeds to step S10 to perform normal control again.

  In step S16, the control unit 7 performs control to increase the opening degree of the economizer expansion valve 52 by a minute opening degree by pulse control, and the amount of refrigerant flowing through the economizer circuit 50 (high-stage intake refrigerant pipe 33 at the economizer outlet D). The amount of the refrigerant that merges with (2) is increased, and the process proceeds to step S14.

  In step S17, the control unit 7 determines whether or not the discharge refrigerant temperature Td exceeds the discharge temperature upper limit threshold Tdu. If the discharge temperature upper limit threshold Tdu is exceeded, the process proceeds to step S12, and control for further decreasing the discharge refrigerant temperature Td is advanced. If the discharge temperature upper limit threshold Tdu is not exceeded, the process returns to step S14. If the discharge temperature upper limit threshold Tdu is not exceeded, the discharge refrigerant temperature Td is lower than the discharge temperature upper limit threshold Tdu and higher than the discharge temperature lower limit threshold Tdl. While the range is maintained, the operations of step S14 and step S17 are repeated, and when the discharge temperature upper limit threshold Tdu is exceeded, the process proceeds to step S12, and when the discharge temperature lower limit threshold Tdl is lower, the process proceeds to step S15. Will do.

(6) Features (6-1)
In the container refrigeration apparatus 10 of the above embodiment, the temperature of the refrigerant flowing through the high-stage discharge refrigerant pipe 34 is abnormally increased by cooling the refrigerant sucked by the high-stage compressor 22 by using the economizer circuit 50. Can be avoided.

  Furthermore, even when the temperature of the refrigerant flowing through the high-stage discharge refrigerant pipe 34 rises while the economizer expansion valve 52 is fully open, the bypass on-off valve 54 of the bypass circuit 53 is switched to the open state. The refrigerant temperature flowing toward the economizer outlet D can be reduced by reducing the degree to which the refrigerant flowing through the economizer refrigerant pipe 51 is heated by the economizer heat exchanger 41. Thereby, it is possible to more reliably avoid an abnormal rise in the temperature of the refrigerant flowing through the high-stage discharge refrigerant pipe 34.

(6-2)
Under the usage environment of the container refrigeration apparatus 10, for example, when the temperature of the outside OS is very high, the air temperature of the outside OS supplied to the gas cooler 27 by the outside fan 28 is also high. Thus, it is difficult to sufficiently cool the refrigerant flowing through the outlet of the gas cooler 27 (that is, it is difficult to make the point L further left (low enthalpy side) in the PH diagram of FIG. 5). For this reason, when using a refrigerant having the property that the isotherm is inclined obliquely downward to the right on the PH diagram, the enthalpy of the refrigerant flowing through the outlet of the gas cooler 27 is lowered by increasing the discharge pressure, Refrigeration capacity will be secured.

  On the other hand, if the use of the in-chamber IS is not refrigerated but is used in a refrigeration application that greatly falls below 0 ° C., it is necessary to lower the evaporation temperature, so the low pressure in the refrigeration cycle is reduced. Become.

  As a result, the differential pressure between the high pressure and the low pressure becomes very large, and not only the cycle efficiency decreases, but also the temperature of the refrigerant discharged from the high stage compressor 22 tends to abnormally increase.

  On the other hand, in the container refrigeration apparatus 10 of the above embodiment, a multistage compression refrigeration cycle is employed, and the compression mechanism 23 includes a plurality of compressors including a low stage compressor 21 and a high stage compressor 22. They are connected in series. Thereby, the compression ratio which one compressor bears can be made small. Further, in the container refrigeration apparatus 10, the refrigerant discharged from the low stage compressor 21 can be cooled by the intercooler 24 before being sucked into the high stage compressor 22. Further, since the economizer circuit 50 is employed in the container refrigeration apparatus 10, it is possible to further reduce the temperature of the refrigerant sucked in the high stage compressor 22. Moreover, since the economizer circuit 50 is provided with the economizer expansion valve 52, it is possible to adjust the ratio between the refrigerant amount flowing through the main circuit side of the refrigerant circuit 10a and the refrigerant amount flowing through the economizer circuit 50 side. Therefore, it is possible to adjust the degree to which the refrigerant temperature sucked by the high stage compressor 22 is lowered. Furthermore, in the container refrigeration apparatus 10, the economizer expansion valve 52 of the economizer circuit 50 is fully opened, and the high-stage compressor 22 is discharged in a state where the flow rate of the economizer circuit 50 cannot be increased any more. Even when the refrigerant temperature is high, the refrigerant temperature sucked into the high-stage compressor 22 can be further lowered by switching the bypass opening / closing valve 54 of the bypass circuit 53 to the open state. . Thereby, it is possible to prevent the refrigerant temperature discharged from the high stage compressor 22 from rising abnormally. Thus, by preventing an abnormal rise in the temperature of the refrigerant discharged from the high-stage compressor 22, deterioration of the refrigerant, deterioration of refrigerating machine oil used together with the refrigerant, damage to various motors and driving units of the high-stage compressor 22 Etc. can be prevented.

(7) Other Embodiments Embodiments of the present invention are not limited to the above-described embodiments. For example, the following embodiments are also included in the embodiments of the present invention.

(7-1)
In the above embodiment, the bypass circuit 53 is provided in the bypass circuit 53, and the refrigerant circuit 10a having the economizer circuit 50 in which the economizer expansion valve 52 is provided near the economizer inlet F has been described as an example.

  However, the embodiment of the present invention is not limited to this.

  For example, the refrigerant circuit 210a having the economizer circuit 250 shown in FIG. 9 may be used. Since the configuration other than the economizer circuit 250 is the same as that of the above embodiment, the description thereof is omitted.

  The economizer circuit 250 of the refrigerant circuit 210a includes an economizer refrigerant pipe 251, an economizer expansion valve 252, a bypass circuit 253, and a bypass expansion valve 254.

  As shown in FIG. 9, the economizer refrigerant pipe 251 branches from an economizer inlet F that is in the middle of the high stage side refrigerant pipe 35 (between the outlet of the gas cooler 27 and the main circuit side inlet of the economizer heat exchanger 41). Then, the economizer heat exchanger 41 extends to the economizer outlet D in the middle of the high stage intake refrigerant pipe 33 (between the outlet of the intercooler 24 and the intake side of the high stage compressor 22).

  The bypass circuit 253 is a refrigerant pipe that connects the upstream side (one side) and the downstream side (the other side) of the economizer heat exchanger 41 in the economizer refrigerant pipe 251. The upstream side of the bypass circuit 253 branches at a bypass upstream side inlet X between the economizer inlet F of the economizer refrigerant pipe 251 and the main circuit side inlet of the economizer heat exchanger 41, and the economizer refrigerant pipe 251 It extends to a bypass outlet K between the outlet of the economizer heat exchanger 41 and the economizer outlet D. A bypass expansion valve 254 is provided in the middle of the bypass circuit 253. The bypass expansion valve 254 is adjustable in minute opening degree by the valve opening degree of the valve being controlled by the control unit 7.

  The economizer expansion valve 252 is provided between the bypass upstream side inlet X and the economizer heat exchanger 41 inlet in the economizer refrigerant pipe 251. The economizer expansion valve 252 is capable of adjusting a minute opening degree by the valve opening of the valve being controlled by the control unit 7, and adjusting the amount of refrigerant passing therethrough and adjusting the degree of decompression of the refrigerant.

  Hereinafter, an operation example of the refrigeration cycle by the refrigerant circuit 210a will be described.

  The control unit 7 performs normal control similar to the above-described embodiment so as to realize the set temperature received from the user via the operation panel 73 while maintaining the bypass expansion valve 254 of the bypass circuit 253 in the fully closed state. .

  The control unit 7 grasps the refrigerant temperature discharged from the high stage compressor 22 while performing this normal control, and increases the valve opening of the economizer expansion valve 252 when the temperature of the discharged refrigerant abnormally rises. Or discharge temperature control of raising the valve opening degree of the bypass expansion valve 254 of the bypass circuit 253 is performed. In this discharge temperature control, the temperature of the refrigerant discharged from the high-stage compressor 22 (discharge refrigerant temperature Td) is lower than a predetermined discharge temperature upper limit threshold Tdu and is set to a predetermined discharge temperature lower limit threshold. The valve opening degree of the economizer expansion valve 252 and / or the valve opening degree of the bypass expansion valve 254 is controlled so that it can be maintained in a predetermined temperature range that is higher than Tdl.

  Hereinafter, the flow of control will be described with reference to the control flowchart of FIG.

  In step S40, the control unit 7 continues the normal control described above.

  In step S41, the control unit 7 determines whether or not the discharge refrigerant temperature Td exceeds the discharge temperature upper limit threshold Tdu. If the discharge temperature upper limit threshold Tdu is exceeded, the process proceeds to step S42. If the discharge temperature upper limit threshold Tdu is not exceeded, the process returns to step S40 and normal control is continued.

  In step S42, the control unit 7 determines whether or not the valve opening of the economizer expansion valve 252 is fully open. Here, when the valve opening degree of the economizer expansion valve 252 is not yet fully opened, the process proceeds to step S44. If the valve opening of the economizer expansion valve 252 has already been fully opened, the process proceeds to step S43.

  In step S43, the control unit 7 increases the valve opening degree of the bypass expansion valve 254 that has been maintained in the fully closed state by a minute opening degree, and passes through the economizer heat exchanger 41 among the refrigerant flowing through the economizer circuit 250. The amount of refrigerant to be reduced is decreased, the amount of refrigerant passing through the bypass circuit 253 is increased, and the degree of superheat or dryness of the refrigerant toward the economizer outlet D is reduced, and the process proceeds to step S45.

  In step S44, the control unit 7 performs control to increase the valve opening of the economizer expansion valve 252 by a minute opening amount by pulse control, and the amount of refrigerant flowing through the economizer circuit 250 (high-stage intake refrigerant pipe 33 at the economizer outlet D). The amount of the refrigerant that merges with is increased, and the process proceeds to step S45.

  In step S45, the control unit 7 determines whether or not the discharge refrigerant temperature Td is equal to a value that is smaller than the discharge temperature upper limit threshold Tdu by a predetermined value α. Here, if the discharge temperature upper limit threshold Tdu is equal to a value smaller by a predetermined value α, step S45 is repeated. Here, by setting α as a small value, the discharge refrigerant temperature Td can be maintained at a value close to the discharge temperature upper limit threshold Tdu. If the discharge temperature upper limit threshold Tdu is not equal to a value smaller by a predetermined value α, the process proceeds to step S46.

  In step S46, the control unit 7 determines whether or not the discharged refrigerant temperature Td is larger than a value obtained by subtracting the predetermined value α from the discharged temperature upper limit threshold Tdu. Here, when it is larger than the value obtained by subtracting the predetermined value α from the discharge temperature upper limit threshold Tdu, the process proceeds to step S47. If it is not larger than the value obtained by subtracting the predetermined value α from the discharge temperature upper limit threshold Tdu, the process proceeds to step S48.

  In step S47, the control unit 7 increases the valve opening degree of the bypass expansion valve 254 by a minute opening degree, and simultaneously controls the economizer expansion valve 252 to reduce the valve opening degree by the minute opening degree. The state in which the degree of superheat of the refrigerant heading toward the economizer outlet D is lowered is returned to step S45.

  In step S48, the control unit 7 controls the economizer circuit 250 to lower the valve opening of the bypass expansion valve 254 by a minute opening and simultaneously increase the valve opening of the economizer expansion valve 252 by the minute opening. After increasing the degree of superheat of the refrigerant toward the economizer outlet D, the process proceeds to step S49.

  In step S49, the control unit 7 determines whether or not the valve opening degree of the bypass expansion valve 254 is fully closed. When the valve opening degree of the bypass expansion valve 254 is fully closed, the process returns to the normal control in step S40. When the valve opening degree of the bypass expansion valve 254 is not fully closed, the process returns to step S45.

  According to the control of the other embodiment (7-1) described above, the superheat degree of the refrigerant from the economizer refrigerant pipe 251 to the economizer outlet D is finely adjusted while suppressing the fluctuation range of the refrigerant amount flowing through the economizer circuit 250 to be small. It becomes possible.

  It should be noted that the economizer refrigerant pipe while increasing the amount of refrigerant flowing through the economizer circuit 250 by appropriately combining the adjustment opening of the economizer expansion valve 252 and the adjustment opening of the bypass expansion valve 254. Control for increasing the degree of superheat of the refrigerant from 251 to the economizer outlet D, Control for decreasing the degree of superheat of the refrigerant from the economizer refrigerant pipe 251 to the economizer outlet D while increasing the amount of refrigerant flowing through the economizer circuit 250, refrigerant flowing through the economizer circuit 250 Control to increase the degree of superheat of the refrigerant from the economizer refrigerant pipe 251 to the economizer outlet D while reducing the amount, and degree of superheat of the refrigerant from the economizer refrigerant pipe 251 to the economizer outlet D while reducing the quantity of refrigerant flowing through the economizer circuit 250 Control to lower It is possible to perform. This makes it possible to reduce the temperature of the refrigerant discharged from the high stage compressor 22 while obtaining the economizer effect as much as possible.

(7-2)
In the above embodiment and the other embodiment (7-1), the temperature of the refrigerant flowing through the high stage discharge refrigerant pipe 34 is grasped by the high stage discharge refrigerant temperature sensor 67 and the control unit 7 discharges from the high stage compressor 22. The case where the control for lowering the refrigerant temperature is performed has been described as an example.

  However, the embodiment of the present invention is not limited to this. For example, the refrigerant temperature at which the control unit 7 is discharged from the high-stage compressor 22 by grasping the degree of superheat of the refrigerant sucked into the high-stage compressor 22. You may make it perform control for lowering. The grasping of the degree of superheat of the refrigerant sucked into the high-stage compressor 22 by the control unit 7 is not particularly limited. For example, the refrigerant saturation temperature corresponding to the refrigerant pressure detected by the intermediate pressure sensor 63 May be identified from the difference between the refrigerant saturation temperature and the intermediate refrigerant temperature sensor 64.

  Further, the control unit 7 determines whether the control unit 7 is based on the condensation temperature of the refrigerant in the refrigerant circuit 10a, the degree of superheat of the refrigerant flowing through the high-stage discharge refrigerant pipe 34, the refrigerant temperature sucked by the high-stage compressor 22, or the like. Control for lowering the temperature of the refrigerant discharged from the high-stage compressor 22 may be performed.

(7-3)
In the embodiment and the other embodiment (7-1), after the economizer expansion valve 52 and the economizer expansion valve 252 are fully opened, the valve opening degree of the bypass on-off valve 54 and the bypass expansion valve 254 is increased. The case where the control is performed is described as an example.

  However, the embodiment of the present invention is not limited to this. For example, when the opening degree of the economizer expansion valve 52 or the economizer expansion valve 252 is increased to a predetermined opening degree that is narrower than the full opening degree, the bypass opening / closing is performed. You may make it perform control that the valve opening degree of the valve 54 or the bypass expansion valve 254 is raised. In addition, as this predetermined opening degree, from the viewpoint of obtaining the economizer effect as much as possible, a state close to full opening is preferable, and for example, the opening degree may be 80% or more of the full opening state.

(7-4)
In the above-described embodiment, an example is given in which control is performed such that the open / close valve 54 is opened while the economizer expansion valve 52 is kept fully open after the economizer expansion valve 52 is fully opened. Explained.

  However, the embodiment of the present invention is not limited to this. For example, after the economizer expansion valve 52 is fully opened, the opening degree of the economizer expansion valve 52 is narrowed by a small opening degree, and at the same time, the bypass on-off valve 54 is used. You may make it perform the control of making into an open state. In this case, it is possible to avoid a sudden change in the heat exchange amount in the economizer heat exchanger 41.

(7-5)
In the said embodiment and said other embodiment (7-1), the refrigerant | coolant which flows through the inside of the gas cooler 27 arrange | positioned in external storage chamber SP1 was cooled with the air of OS outside a store | warehouse | chamber, and it arrange | positioned in internal storage chamber SP2 The case where the air in the warehouse IS is cooled by the refrigerant flowing inside the evaporator 46 has been described as an example.

  However, the heat medium of the embodiment of the present invention is not limited to these. For example, as a coolant for the refrigerant flowing inside the gas cooler 27, a coolant such as water may be used instead of the air of the outside OS. Further, the object to be cooled by the refrigerant flowing inside the evaporator 46 does not need to be the air in the warehouse IS, and may be a secondary refrigerant circulating between the warehouse IS and the internal storage chamber SP2. Good. The outside fan 28 and the inside fan 47 can be appropriately replaced with a pump or the like according to the type of the heat medium.

(7-6)
In the embodiment and the other embodiment (7-1), the case where the compression mechanism 23 is a two-stage compression mechanism having the low-stage compressor 21 and the high-stage compressor 22 has been described as an example.

  However, the embodiment of the present invention is not limited to this. For example, the container refrigeration apparatus may include a multistage compression mechanism having three or more stages.

(7-7)
In the said embodiment and said other embodiment (7-1), the case where each of the low stage compressor 21 and the high stage compressor 22 was inverter-driven was mentioned as an example, and was demonstrated.

  However, the embodiment of the present invention is not limited to this. For example, the container refrigeration apparatus may include a coaxial drive compression mechanism in which the drive shafts of a plurality of compressors are shared.

(7-8)
Naturally, embodiments of the present invention also include embodiments configured by partially combining the above embodiments and other embodiments (7-1) to (7-7). It is.

  Since the container refrigeration apparatus of the present invention can keep the temperature of the refrigerant discharged from the high-stage compression mechanism low, in an environment where the temperature of the cooling medium for cooling the refrigerant flowing in the gas cooler is high, This is particularly useful in a container refrigeration apparatus that performs control to increase the pressure on the high pressure side of the refrigeration cycle while lowering the pressure on the low pressure side of the refrigeration cycle.

DESCRIPTION OF SYMBOLS 1 Refrigeration vehicle 2 Container 3 Trailer 4 Tractor 7 Control unit (control part)
10 Refrigeration equipment for containers 10a Refrigerant circuit 21 Low stage compressor (low stage compression mechanism)
22 High stage compressor (High stage compression mechanism)
23 Compression mechanism 24 Intercooler 27 Gas cooler 41 Economizer heat exchanger 43 First expansion valve (expansion mechanism)
45 Second expansion valve (expansion mechanism)
46 Evaporator 50 Economizer Circuit 52 Economizer Expansion Valve (Intermediate Expansion Valve)
53 Bypass circuit 54 Bypass on-off valve (bypass valve)
63 Intermediate pressure sensor (detector)
64 Intermediate refrigerant temperature sensor (detector)
66 High pressure sensor (detector)
67 High stage discharge refrigerant temperature sensor (detector)
252 Economizer expansion valve (intermediate expansion valve)
254 Bypass expansion valve (bypass valve)

JP 2011-112270 A

Claims (10)

A container refrigeration apparatus (10) having a low stage compression mechanism (21), a high stage compression mechanism (22), a gas cooler (27), an expansion mechanism (43, 45) and an evaporator (46),
An economizer circuit (50) for guiding a part of the refrigerant from the gas cooler toward the evaporator to join the refrigerant from the low-stage compression mechanism to the high-stage compression mechanism;
An economizer heat exchanger (41) for performing heat exchange between the refrigerant flowing through the economizer circuit and the refrigerant from the gas cooler toward the evaporator;
A bypass circuit (53) for connecting an upstream portion and a downstream portion of the economizer heat exchanger in the middle of the economizer circuit without passing through the economizer heat exchanger;
A bypass valve (54, 254) provided in the middle of the bypass circuit, capable of switching the open / close state or adjusting the valve opening;
Intermediate expansion valves (52, 252) provided in the middle of the economizer circuit;
The temperature or superheat value of the refrigerant discharged from the high-stage compression mechanism, the temperature or superheat value of the refrigerant sucked into the high-stage compression mechanism, or a physical quantity equivalent to any of the above values A detection unit (63, 64, 66, 67) to detect;
When the detection value of the detection unit rises and the first predetermined condition is not satisfied, the refrigerant combined flow rate that merges from the economizer circuit with respect to the refrigerant from the low-stage compression mechanism to the high-stage compression mechanism is increased. And adjusting the opening degree of the intermediate expansion valve (52, 252) and switching the opening / closing state of the bypass valve (54, 254) or changing the opening degree of the bypass valve (54, 254). A control unit (7) to be adjusted;
A container refrigeration apparatus (10). When the valve opening degree of the intermediate expansion valve (52, 252) is equal to or greater than a predetermined opening degree and the detection value of the detection unit rises, the control unit does not satisfy the first predetermined condition. The bypass valve (54, 254) is controlled so as to switch from the closed state to the open state or to increase the valve opening degree.
The container refrigeration apparatus according to claim 1. The control unit is in a closed state when the valve opening degree of the intermediate expansion valve (52, 252) is fully open and the detection value of the detection unit increases and the first predetermined condition is not satisfied. The bypass valve (54, 254) is controlled so as to switch to an open state or increase the valve opening degree,
The container refrigeration apparatus according to claim 2. The bypass valve (54) is an on-off valve,
The intermediate expansion valve (52) is provided in the middle of the economizer circuit and further upstream than the upstream portion of the connection portion between the bypass circuit and the economizer circuit.
The container refrigeration apparatus according to any one of claims 1 to 3. The bypass valve (254) is an expansion valve capable of adjusting the flow rate of refrigerant passing therethrough,
The intermediate expansion valve (252) is provided in the middle of the economizer circuit and between an upstream side portion of a connection portion between the bypass circuit and the economizer circuit and an inlet of the economizer heat exchanger. ing,
The container refrigeration apparatus according to any one of claims 1 to 3. The control unit, when the detection value of the detection unit rises, when the first predetermined condition is not satisfied,
If the intermediate expansion valve (252) is not fully open, the valve opening of the intermediate expansion valve (252) is increased,
If the intermediate expansion valve (252) is fully open, the valve opening of the bypass valve (254) is increased.
The first control is performed.
The container refrigeration apparatus according to claim 5. The controller is
After performing the first control, even if the intermediate expansion valve (252) is fully open, the degree of decrease in the detection value of the detection unit does not satisfy the second predetermined condition,
The operation of decreasing the valve opening of the intermediate expansion valve (252) and the operation of increasing the valve opening of the bypass valve (254) are performed simultaneously.
The second control is performed.
The container refrigeration apparatus according to claim 6. The controller is
After performing the second control, when the degree of decrease in the detection value of the detection unit satisfies the second predetermined condition,
The operation of increasing the valve opening of the intermediate expansion valve (252) and the operation of decreasing the valve opening of the bypass valve (254) are performed simultaneously.
The third control is performed.
The container refrigeration apparatus according to claim 7. An intercooler (24) for cooling the refrigerant from the discharge side of the low-stage compression mechanism toward the suction side of the high-stage compression mechanism;
The container refrigeration apparatus according to any one of claims 1 to 8. The refrigerant is a carbon dioxide refrigerant.
The container refrigeration apparatus according to any one of claims 1 to 9.

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