JP4525515B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a feedback oil quality determination device that determines whether or not the amount of feedback oil returned to a compressor of a refrigeration cycle is insufficient, and a refrigeration cycle device to which the feedback oil quality determination device is applied. It is suitable for use in an air conditioner.

  Conventionally, in a vehicle air conditioner, when the cooling heat load of the evaporator is small, the discharge capacity of the compressor is reduced compared with that during normal operation to save power in the vehicle air conditioner.

  By the way, since the refrigerant circulating in the refrigeration cycle is mixed with oil for lubricating the sliding portion of the compressor, when the discharge capacity of the compressor decreases, the flow rate of refrigerant circulating in the cycle decreases and the feedback returns to the compressor. The amount of oil is also reduced. When the amount of feedback oil decreases, insufficient lubrication of the compressor sliding portion occurs, which adversely affects the durability of the compressor.

  Therefore, in Patent Document 1, when the amount of return oil is insufficient, the discharge capacity of the compressor is forcibly increased to increase the circulating refrigerant flow rate in the cycle, thereby eliminating the shortage of return oil amount. Further, the return oil quality determination for determining whether or not the return oil amount is insufficient is performed based on the difference between the evaporator intake air temperature Ta and the target evaporator outlet temperature TEO.

Specifically, when Ta-TEO is equal to or less than a predetermined determination value (for example, 2 ° C.), it is uniformly determined that the amount of feedback oil is insufficient. This is presumed that when Ta-TEO falls below a predetermined judgment value, the cooling heat load of the evaporator decreases, the discharge capacity of the compressor decreases, the refrigerant flow rate in the cycle decreases, and the amount of return oil is insufficient. Because.
JP-A-11-123930

  By the way, according to the study by the present inventor, it has been found that not only the low pressure side physical quantity in the cycle but also the high pressure side physical quantity has a great influence on the feedback oil quality determination. This is because, for example, if the high pressure in the cycle changes, the circulating refrigerant flow rate in the cycle changes and the amount of return oil also changes.

  However, in the prior art, the return oil quality determination is performed based on the evaporator intake air temperature Ta and the target evaporator outlet temperature TEO related to the low pressure side physical quantity, and the determination considering the high pressure side physical quantity is not performed.

  For this reason, in the conventional feedback oil quality judgment, for example, if the Ta-TEO judgment value is set large so that the feedback oil quality judgment can be made when the high pressure is low, the high pressure rises and the feedback oil amount increases. Even if it increases and the compressor can be sufficiently lubricated, it is determined that the amount of return oil is insufficient. As a result, even if the amount of feedback oil is good, the discharge capacity of the compressor is unnecessarily increased, and power saving of the refrigeration cycle apparatus is hindered.

  Furthermore, if the judgment value is set to be small so that the return oil quality can be judged when the high pressure is high, the return oil is reduced even if the compressor becomes poorly lubricated because the high pressure decreases and the amount of feedback oil decreases. It will be determined that the amount is good. As a result, even if the amount of feedback oil is insufficient, the operation is continued without increasing the discharge capacity of the compressor, which causes a problem in that the durability of the compressor is adversely affected.

  In view of the above points, it is an object of the present invention to perform appropriate feedback oil quality determination.

To achieve the above object, the invention described in claim 1, is configured to change the discharge capacity by controlling current from the outside (In), for sucking and discharging a refrigerant oil for lubrication is mixed swash The plate-type variable capacity compressor (11), the control signal calculation means (S9) for calculating the control signal (In) for controlling the discharge capacity of the compressor (11), and the cooling capacity by evaporating the refrigerant. The compressor (11) includes an evaporator (9) that exhibits and target cooling degree calculation means (S91 to S95, S901 to S905) that calculates a target value (TEO) of the cooling degree of the evaporator (9). A swash plate that changes the discharge volume by changing the inclination angle according to the pressure (Pc) of the refrigerant in the swash plate chamber, and an electromagnetic capacity control valve (11a) that changes the pressure (Pc) of the refrigerant in the swash plate chamber ) And an electromagnetic capacity control valve (11 ) Is a pressure responsive mechanism that generates a force according to the suction refrigerant pressure (Ps), and an electromagnetic force that is opposed to the force according to the suction refrigerant pressure (Ps) and that is determined by the control signal (In). The control signal calculation means (S9) is configured to have an electromagnetic mechanism, calculates the control current (In) so that the actual cooling degree (Te) approaches the target value (TEO), and further controls the control current (In ) Is a refrigeration cycle apparatus that is determined such that the target low pressure (Pst) of the suction refrigerant pressure (Ps) decreases in accordance with an increase in
The return oil shortage region and the return oil good region determined based on the suction refrigerant pressure (Ps) sucked into the compressor (11) and the discharge refrigerant pressure (Pd) discharged from the compressor (11) in advance are classified. Feedback oil pass / fail judgment means (S97, S906) storing the return oil pass / fail threshold line, and the return oil pass / fail judgment means (S97, S906) is a control current calculated by the control signal calculation means (S9). The point determined by the temporary physical quantity having correlation with the suction refrigerant pressure (Ps) and the discharge refrigerant pressure (Pd) when (In) is output to the compressor (11) belongs to the feedback oil shortage region. has become so determining acceptability of the feedback amount of oil depending on whether the control signal calculating means (S9), the feedback oil quality determination unit (S97, S906) a feedback amount of oil When it is determined the insufficient control current (In), the points and changes to a value that avoids belong to continuously feedback oil shortage areas.

According to this, since the return oil quality determination is performed based on the suction refrigerant pressure (Ps) and the discharge refrigerant pressure (Pd) in consideration of the change in the high / low pressure difference in the cycle, etc., an appropriate feedback oil quality determination is made. It can be performed.

Further , when the return oil quality determination means (S97, S906) determines that the return oil amount is insufficient, the control signal calculation means (S9) changes the control current (In) and the points continuously belong to the feedback oil shortage region. Since this is avoided, adverse effects on the durability of the compressor can be prevented.

In addition, since proper feedback oil quality judgment is performed, it is possible to prevent the compressor discharge capacity from being forcibly increased by changing the control current (In) unnecessarily, and to save power in the air conditioner Can be achieved. Further, since it is possible to avoid operating the compressor (11) in a state where the amount of return oil is insufficient, it is possible to prevent adverse effects on the durability of the compressor (11).

Further , as a means for avoiding continuous belonging to the feedback oil shortage region, specifically, the control signal (In) may be changed to a value at which the point shifts to the feedback oil good region. Further, the control signal (In) may be changed to a value at which the compressor (11) is intermittently inactivated.

As in the invention described in claim 2, in the refrigeration cycle apparatus according to claim 1, the temporary physical quantity is a control current calculated so that the actual cooling degree (Te) approaches the target value (TEO) ( temporary calculated value of in) may be the (Int).

  According to this, since the low-voltage side information value is a temporarily calculated value (Int) of the control current (In), the low-voltage side information value can be easily grasped without newly installing a means for detecting the low-voltage side information value, The effect of the second feature can be easily exhibited.

As in the invention described in claim 2, in the refrigeration cycle apparatus described in claim 1, the temporary physical quantity is a temporary target value (TEOt) of the degree of cooling calculated to determine the target value (TEO). Also good.

  Even in this case, since the low pressure side information value is the temporary target value (TEOt) of the degree of cooling, the low pressure side information value can be easily grasped without newly installing a means for detecting the low pressure side information value. The effect of the second feature can be easily exhibited.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
In this embodiment, the refrigeration cycle apparatus of the present invention is applied to a vehicle air conditioner, and FIG. 1 shows the overall configuration of the vehicle air conditioner. The vehicle air conditioner includes an indoor air conditioning unit 1 disposed on the inside of an instrument panel (instrument panel) at the forefront of the vehicle interior. This indoor air-conditioning unit 1 has a case 2 and constitutes an air passage through which air is blown toward the vehicle interior.

  An inside / outside air switching box 5 having an inside air introduction port 3 and an outside air introduction port 4 is arranged at the most upstream part of the air passage of the case 2. Inside / outside air switching box 5, an inside / outside air switching door 6 as inside / outside air switching means is rotatably arranged.

  The inside / outside air switching door 6 is driven by a servo motor 7, and an inside air mode for introducing inside air (vehicle compartment air) from the inside air introduction port 3 and an outside air for introducing outside air (vehicle compartment outside air) from the outside air introduction port 4. Switch between a mode and a semi-inside air mode that introduces inside air and outside air at the same time.

  On the downstream side of the inside / outside air switching box 5, an electric blower 8 that blows air toward the passenger compartment is disposed. The blower 8 is configured to drive a centrifugal blower fan 8a by a motor 8b. An evaporator 9 serving as a cooling heat exchanger for cooling the blown air is disposed on the downstream side of the blower 8.

  The evaporator 9 is one of the elements constituting the refrigeration cycle 10. The low-pressure refrigerant that has flowed into the evaporator 9 absorbs heat from the blown air blown by the blower 8 and evaporates, thereby cooling the blown air. The refrigeration cycle 10 includes an evaporator 9, a compressor 11, a condenser 12, a gas-liquid separator 13, an expansion valve 14, and the like.

  The compressor 11 sucks, compresses and discharges the refrigerant, and is driven to rotate by transmitting the rotational power of the vehicle engine E via the pulley and the belt V. Details of the compressor 11 will be described later.

  The condenser 12 is a radiator that cools the refrigerant by exchanging heat between the refrigerant discharged from the compressor 11 and the outside air. A blower fan 12a that blows outside air to the condenser 12 is driven by a motor 12b. The refrigerant flowing out of the condenser 12 flows into a gas-liquid separator 13 (receiver) that separates the refrigerant into a gas-phase refrigerant and a liquid-phase refrigerant.

  The expansion valve 14 expands the liquid phase refrigerant separated by the gas-liquid separator 13 under reduced pressure. In the present embodiment, a temperature type expansion valve is used that controls the throttle opening so that the degree of superheat of the refrigerant sucked into the compressor 11 becomes a predetermined value.

  The refrigerant expanded under reduced pressure flows into the evaporator 9 and evaporates, and then flows into the compressor 11 again. Thus, a known refrigeration cycle in which the refrigerant circulates in the order of the compressor 11 → the condenser 12 → the gas-liquid separator 13 → the expansion valve 14 → the evaporator 9 → the compressor 11 is configured.

  On the other hand, in the indoor air conditioning unit 1, a heater core 15 that heats the air flowing in the case 2 is disposed on the downstream side of the evaporator 9. The heater core 15 is a heat exchanger for heating that uses the vehicle engine coolant as a heat source (the engine coolant circuit is not shown) and heats the air (cold air) after passing through the evaporator 9. A bypass passage 16 is formed on the side of the heater core 15, and the bypass air of the heater core 15 flows through the bypass passage 16.

  Between the evaporator 9 and the heater core 15, an air mix door 17 serving as a temperature adjusting means is rotatably arranged. The air mix door 17 is driven by a servo motor 18 so that its rotational position (opening degree) can be continuously adjusted.

  The ratio of the amount of air passing through the heater core 15 (warm air amount) and the amount of air passing through the bypass passage 16 and bypassing the heater core 15 (cold air amount) is adjusted by the opening degree of the air mix door 17. The temperature of the air blown into the room is adjusted.

  At the most downstream part of the air passage of the case 2, a defroster outlet 19 for blowing conditioned air toward the front window glass W of the vehicle, a face outlet 20 for blowing conditioned air toward the face of the occupant, A total of three types of air outlets 21 are provided, which are foot outlets 21 for blowing air-conditioned air toward the feet of passengers.

  A defroster door 22, a face door 23, and a foot door 24 are rotatably disposed upstream of the air outlets 19 to 21. The doors 22 to 24 are opened and closed by a common servo motor 25 via a link mechanism (not shown).

  Next, the compressor 11 will be described. The compressor 11 of the present embodiment is a swash plate type variable displacement compressor capable of continuously variably controlling the discharge capacity by a control signal from the outside.

  Specifically, by controlling the pressure Pc of the swash plate chamber (not shown) using the discharge refrigerant pressure Pd and the suction refrigerant pressure Ps, the inclination angle of the swash plate is varied to change the stroke of the piston. Thereby, the discharge capacity is continuously changed in a range of approximately 0% to 100%. The discharge capacity is adjusted by changing the discharge capacity.

  Here, the discharge capacity is the geometric volume of the working space where the refrigerant is sucked and compressed, and specifically, the cylinder volume between the top dead center and the bottom dead center of the piston stroke.

  In this embodiment, among the swash plate type variable displacement compressors, a low pressure control type swash plate type variable displacement compressor that controls the suction refrigerant pressure Ps of the compressor 11 by changing the discharge capacity is used.

  Here, the control of the pressure Pc in the swash plate chamber in the low-pressure control type swash plate type variable displacement compressor will be described. The compressor 11 includes an electromagnetic capacity control valve 11a. The electromagnetic capacity control valve 11a includes: A pressure responsive mechanism (not shown) for generating a force due to the suction refrigerant pressure Ps of the compressor 11 and an electromagnetic mechanism (not shown) for generating an electromagnetic force opposite to the force due to the suction refrigerant pressure Ps are incorporated. is doing.

  The electromagnetic force of this electromagnetic mechanism is determined by a control current In output from an air conditioning control device 30 described later. Then, the pressure Pc in the swash plate chamber is changed by changing the ratio of introducing the discharged refrigerant pressure Pd into the swash plate chamber by a valve body (not shown) that is displaced by a force corresponding to the suction refrigerant pressure Ps and an electromagnetic force. I am letting.

  In a swash plate type variable displacement compressor, as is well known, the pressure Pc in the control chamber decreases → the tilt angle of the swash plate increases → the piston stroke increases → the discharge capacity increases. The discharge capacity changing mechanism is configured so as to rise, decrease the inclination angle of the swash plate, decrease the piston stroke, and decrease the discharge capacity.

  Further, since the electromagnetic force is a force that opposes the force corresponding to the suction refrigerant pressure Ps, when the electromagnetic force is increased, the pressure Pc in the control chamber is lowered and the discharge capacity of the compressor 11 is increased. Therefore, the target low pressure Pst of the refrigerant sucked by the compressor 11 is determined by the electromagnetic force.

  Further, since the electromagnetic force is determined according to the control current In supplied to the electromagnetic mechanism of the electromagnetic capacity control valve 11a, as shown in FIG. The target low pressure Pst is reduced.

  Although the control current In is usually a method of changing by duty control due to the configuration of the current control circuit, the value of the control current In is directly (analog-like) regardless of the duty control. ) May be changed.

  Further, in the compressor 11, the discharge capacity can be continuously changed from 100% to about 0% by adjusting the control pressure Pc. Therefore, by reducing the discharge capacity to about 0%, the compressor 11 It can be substantially deactivated. Therefore, in this embodiment, it is the structure of a clutchless which always connects the rotating shaft of the compressor 11 to a vehicle engine via a pulley and a belt V. Of course, power may be transmitted from the vehicle engine via an electromagnetic clutch.

  Next, the outline of the electric control unit according to the present embodiment will be described. The air conditioning control device 30 includes a known microcomputer including a CPU, a ROM, a RAM, and the like and peripheral circuits thereof. The air conditioning control device 30 stores an air conditioning device control program in its ROM, and performs various calculations and processes based on the air conditioning device control program.

  Sensor detection signals are input from the air conditioning sensor groups 31 to 36 to the input side of the air conditioning control device 30, and various air conditioning operation switches provided on the air conditioning operation panel 37 disposed in the vicinity of the instrument panel in the front of the passenger compartment. An operation signal is input from 38 to 43.

  Specifically, the air conditioning sensor group includes an outside air sensor 31 that detects the outside air temperature Tam, an inside air sensor 32 that detects the inside air temperature Tr, a solar radiation sensor 33 that detects the amount of solar radiation Ts incident on the vehicle interior, and the evaporator 9. An evaporator temperature sensor 34 for detecting the evaporator blown air temperature Te, a water temperature sensor 35 for detecting the engine coolant temperature Tw flowing into the heater core 15, and a discharge refrigerant pressure discharged from the compressor 11. A high pressure sensor 36 for detecting Pd is provided.

  Here, in this embodiment, the evaporator blown air temperature Te, which is a detection value of the evaporator temperature sensor 34, is a value indicating the degree of cooling of the evaporator 9. In addition, you may detect and use the temperature of the heat exchange part component parts (for example, heat exchange part fin) of the evaporator 9 as a value which shows the cooling degree of the evaporator 9. FIG.

  Further, the discharge refrigerant pressure Pd, which is a detection value of the high pressure sensor 36, becomes a high pressure side information value. The high-pressure sensor 36 is provided to detect a pressure abnormality in the refrigeration cycle. In order to detect the high-pressure side information value by using the detection value Pd of the high-pressure sensor 36 as a high-pressure side information value. There is no need to install a dedicated detection means.

  The air-conditioning operation panel 37 has various air-conditioning operation switches, such as a blow mode switch 38 for manually setting the blow mode switched by the blow mode doors 22 to 24, and an internal / external air switch for manually setting the internal / external air suction mode by the internal / external air switching door 6. A switch 39, an air conditioner switch 40 for outputting an operation command signal for the compressor 11, a blower operation switch 41 for manually setting the air volume of the blower 8, an auto switch 42 for outputting a command signal for an air conditioning automatic control state, and a temperature for setting a vehicle interior temperature A temperature setting switch 43 or the like serving as setting means is provided.

  On the output side of the air-conditioning control device 30, there are an electromagnetic capacity control valve 11a of the compressor 11, servo motors 7, 18, and 25 serving as electric drive means for each device, a motor 8b of the blower 8, and a condenser cooling fan 12a. The motor 12 b is connected, and the operation of these devices is controlled by the output signal of the air conditioning control device 30.

  Next, control processing executed by the air conditioning control device 30 in the present embodiment will be described based on the flowchart of FIG. This control routine starts when the auto switch 42 is turned on in a state where an ignition switch of a vehicle engine (not shown) is turned on.

  First, in step S1, flags, timers, etc. are initialized, and in the next step S2, an operation signal of the air conditioning operation panel 37 is read. In the next step S3, the vehicle environmental state signal, that is, the detection signal detected by the sensor groups 31 to 36 is read.

Next, in step S4, a target blowing temperature TAO of the vehicle cabin blowing air is calculated. The target blowing temperature TAO is calculated by the following formula E1 based on the air conditioning thermal load fluctuation, the passenger compartment temperature (inside air temperature) Tr, and the set temperature Tset set by the temperature setting switch 43.
TAO = Kset × Tset−Kr × Tr−Kam × Tam−Ks × Ts + C (E1)
Here, Tr is the inside air temperature detected by the inside air sensor 32, Tam is the outside air temperature detected by the outside air sensor 31, Ts is the amount of solar radiation detected by the solar radiation sensor 33, Kset, Kr, Kam, Ks are the control gain and C is a constant for correction.

  Next, in step S <b> 5, a target air blowing amount of air blown by the blower 8 is determined. Specifically, the blower motor voltage to be applied to the motor 8b is determined based on TAO with reference to a control map stored in advance in the air conditioning control device 30.

  In this embodiment, the blower motor voltage is set to a high voltage near the maximum value in the extremely low temperature region (maximum cooling region) and the extremely high temperature region (maximum heating region) of TAO, and the air volume of the blower 8 is controlled to be near the maximum air volume. Further, when TAO rises from the extremely low temperature region toward the intermediate temperature region, the blower motor voltage is decreased according to the increase in TAO, and the air volume of the blower 8 is decreased. Further, when TAO decreases from the extremely high temperature range toward the intermediate temperature range, the blower motor voltage is decreased according to the decrease in TAO, and the air volume of the blower 8 is decreased. When TAO enters a predetermined intermediate temperature range, the blower motor voltage is set to the minimum value and the air volume of the blower 8 is set to the minimum value.

  Next, in step S6, the inside / outside air mode is determined. The inside / outside air mode is also determined based on TAO with reference to a control map stored in the air conditioning control device 30 in advance. In the present embodiment, the inside air mode is set when the inside air temperature Tr is higher than a predetermined temperature with respect to the set temperature Tset (at the time of cooling high load), and as the TAO rises from the low temperature side to the high temperature side, the whole inside air mode → Switch from mixed mode to all outside air mode.

  Next, in step S7, the blowing mode is determined. This blowing mode is also determined based on TAO with reference to a control map stored in the air conditioning control device 30 in advance. In the present embodiment, as the TAO rises from the low temperature range to the high temperature range, the blowing mode is sequentially switched from the foot mode → bilevel (B / L) mode → face mode.

Next, in step S8, the target opening degree SW of the air mix door 17 is set to the above TAO, the evaporator blown air temperature Te (detected temperature of the evaporator temperature sensor 34), and the engine cooling water temperature Tw (detected by the water temperature sensor 35). Based on (temperature), the following formula E2 is used.
SW = [(TAO−Te) / (Tw−Te)] × 100 (%) (E2)
SW = 0 (%) is the maximum cooling position of the air mix door 17, and the bypass passage 16 is fully opened, and the ventilation path on the heater core 15 side is fully closed. On the other hand, SW = 100 (%) is the maximum heating position of the air mix door 17 and fully closes the bypass passage 16 and fully opens the ventilation path on the heater core 15 side.

  Next, in step S9, the discharge capacity of the compressor 11 is determined. Specifically, the control current In supplied to the electromagnetic capacity control valve 11a is calculated. Details of step S9 will be described with reference to FIG.

  First, steps S91 to S95 are target cooling degree calculation means in the present embodiment, and calculate a target evaporator outlet temperature TEO which is a target value of the cooling degree of the evaporator 9. This target evaporator outlet temperature TEO is a target value of the air blown into the passenger compartment cooled by the evaporator 9, and is a temperature necessary for adjusting the temperature of the air blown out of the passenger compartment.

  First, in step S91, the first target evaporator outlet temperature TEO1 is determined. Specifically, it is determined with reference to the control map shown in FIG. 5 stored in advance in the air conditioning control device 30 based on the target outlet temperature TAO. In the present embodiment, as described above, TEO1 decreases as TAO decreases.

  Next, in step S92, the second target evaporator outlet temperature TEO2 is determined. Specifically, it is determined based on the outside air temperature Tam with reference to a control map shown in FIG. In the present embodiment, since it is necessary to ensure the dehumidifying capacity in order to prevent the window glass W from fogging in the low temperature range, TEO2 is lowered with a decrease in the outside air temperature Tam. Further, since the necessity for cooling and dehumidification decreases in the intermediate temperature range, TEO2 is increased. Furthermore, in order to ensure the cooling capacity in the high temperature range, TEO2 is lowered as the outside air temperature Tam increases.

  Here, TEOmn shown in FIGS. 5 and 6 is a lower limit value of the target evaporator outlet temperature TEO set to prevent frost formation on the evaporator 9, and in this embodiment, TEOmn is 3 (° C.). It is said.

  Next, in steps S93 to S95, the lower one of the TEO1 and TEO2 is determined as the target evaporator outlet temperature TEO, and the process proceeds to step S96. By determining in this way, the TEO necessary for cooling and dehumidifying the air blown into the passenger compartment is determined.

  Next, in step S96, a temporary control current Int that is a temporary calculation value of the control current In supplied to the electromagnetic capacity control valve 11a is calculated. This temporary control current Int is a low-voltage side information value in the present embodiment. Specifically, Int calculates a deviation En (En = Te−TEO) between the evaporator blowing air temperature Te and the target evaporator blowing temperature TEO, and based on this deviation En, Int is set so that Te approaches TEO. It is calculated by a feedback control method such as proportional-integral control (PI control).

  Next, in step S97, feedback oil quality determination is performed based on the temporary control current Int and the high-pressure refrigerant pressure Pd. Specifically, if the temporary control current Int is equal to or less than the control current threshold value Ind indicating the feedback oil pass / fail threshold value, it is determined that the feedback oil amount is insufficient.

  Here, the control current threshold value Ind and the feedback oil quality determination will be described. The refrigerant circulation flow rate in the cycle of the refrigeration cycle apparatus can be roughly grasped based on the suction refrigerant pressure Ps sucked into the compressor 11 and the discharge refrigerant pressure Pd discharged from the compressor 11. Further, since the return oil amount is determined by the in-cycle refrigerant circulation flow rate, it is possible to determine whether the return oil is appropriate or not by grasping the in-cycle circulation flow rate.

  In view of this, the feedback oil shortage region is examined in advance by a test within the range that the discharge refrigerant pressure Pd and the suction refrigerant pressure Ps can take. According to the study of the present inventor, it is known that in the vehicle air conditioner of the present embodiment, the return oil shortage region is a range indicated by the hatched portion in FIG.

Here, the return oil pass / fail threshold line shown in FIG. 7 divides the return oil shortage region and the return oil good region, and can be expressed as an equation E3 using the approximate function f1.
Ps = f1 (Pd) (E3)
On the other hand, as described above, in the low pressure control type compressor 11, the control current In and the target low pressure Pst have the relationship shown in FIG. Since the actual suction refrigerant pressure Ps changes so as to approach the target low pressure Pst determined by the control current In, the target low pressure Pst becomes a value substantially equal to the suction refrigerant pressure Ps. Therefore, the suction refrigerant pressure Ps and the control current In also have the relationship shown in FIG.

Here, if the control current In with respect to the suction refrigerant pressure Ps on the feedback oil pass / fail threshold line is a control current threshold value Ind, Ps and Ind can be expressed as an equation E4 using the approximate function f2.
Ps = f2 (Ind) (E4)
Then, by solving the equations E3 and E4, as shown in FIG. 8, the return oil pass / fail threshold line is determined using the function g1 shown in the equation E5 based on the control current threshold value Ind and the discharge refrigerant pressure Pd. can do.
Ind = g1 (Pd) (E5)
Furthermore, the equation E5 is stored in advance in the air conditioning control device 30, and the control current threshold value Ind can be determined based on the discharged refrigerant pressure Pd read in step S3. Then, by comparing the control current threshold value Ind and the temporary control current Int determined in step S96, it can be determined whether or not the feedback oil amount is insufficient. That is, if Int ≧ Ind, the feedback oil is good, and if Int <Ind, the feedback oil is insufficient.

  Accordingly, in step S97, the low pressure side information value Int and the high pressure side information value Pd are determined based on the feedback oil pass / fail threshold line that divides the predetermined feedback oil shortage region and the feedback oil good region. It is determined whether or not the point to be assigned belongs to the return oil shortage region.

  If it is determined in step S97 that it belongs to the feedback oil good region, the process proceeds to step S98, and finally the control current In output to the electromagnetic capacity control valve 11a is set to Int, and the process proceeds to step S10. On the other hand, if it is determined in step S97 that it belongs to the feedback oil shortage region, the process proceeds to step S99, and the control current In is set to Ind.

  Next, the process proceeds to step S10, and the air conditioner control device 30 applies various actuator drive devices (11a, 7, 18, 25, 8b, 12b) so as to obtain the control state determined in steps S5 to S9. Output signal. In the next step S11, the system waits for the control cycle τ, and returns to step S2 when it is determined that the control cycle τ has elapsed.

  Through the control as described above, it is possible to make an appropriate feedback oil quality determination based on the low pressure side information value (Int) and the high pressure side information value (Pd). Since In is changed so that the amount of feedback oil becomes good, the durability of the compressor 11 is not adversely affected.

  Furthermore, since the appropriate return oil quality determination is performed, the control current In is not increased unnecessarily and the discharge flow rate of the compressor 11 is not increased, and the power saving of the air conditioner can be achieved.

(Second Embodiment)
In the first embodiment, the return oil quality determination is performed using the temporary control current Int as the low pressure side information value. However, in this embodiment, the return oil quality is determined using the temporary target evaporator outlet temperature TEOt as the low pressure side information value. Make a decision. This TEOt is a temporary target value for determining a target evaporator outlet temperature TEO that is a target value of the degree of cooling of the evaporator 9.

  For this reason, the control processing content of step S9 (compressor discharge capacity determination) of FIG. 3 is changed as shown in FIG. Other configurations and control of the air conditioning control device 30 are the same as those in the first embodiment.

  The control process of step S9 executed by the air conditioning control device 30 in this embodiment will be described with reference to FIG. First, in steps S901 to S905, a temporary target value TEOt of the degree of cooling of the evaporator 9 is calculated. Steps S901 to S905 are target cooling degree calculation means in the present embodiment, and TEOt is calculated by the control processing in steps S91 to S95 of the first embodiment.

  Next, in step S906, the quality of the feedback oil is determined based on TEOt and the high-pressure refrigerant pressure Pd. Specifically, if TEOt is equal to or higher than the target evaporator blowing temperature threshold value TEOd indicating the return oil pass / fail threshold value, it is determined that the feedback oil is insufficient.

  Here, the target evaporator outlet temperature threshold value TEOd and the feedback oil quality determination will be described. Similar to the first embodiment, the return oil pass / fail threshold line can be expressed by the discharge refrigerant pressure Pd and the suction refrigerant pressure Ps as in the above-described equation E3.

Incidentally, the refrigerant evaporation temperature Tev and the refrigerant pressure in the evaporator 9 are determined based on the saturation vapor pressure characteristic of the refrigerant, and the refrigerant pressure in the evaporator 9 is equal to the intake refrigerant pressure Ps that is the intake pressure of the compressor 11. The evaporation temperature Tev and the suction refrigerant pressure Ps have a relationship as shown in FIG. Therefore, the refrigerant evaporating temperature Tev and the suction refrigerant pressure Ps can be expressed as an equation E6 using the approximate function f3.
Tev = f3 (Ps) (E6)
In addition, since the control current In is determined so that the evaporator outlet air temperature Te approaches the target evaporator outlet temperature TEO in step S908 described later, the refrigerant evaporation temperature Tev and the target evaporator outlet temperature TEO become substantially equal values. . Therefore, by solving the equations E3 and E6, as shown in FIG. 11, the relationship between the target evaporator outlet temperature threshold value TEOd and the discharge refrigerant pressure Pd is expressed as an equation E7 using the approximate function g2. Can do.
TEOd≈Tev = g2 (Pd) (E7)
Further, the air conditioning control device 30 stores the equation E7 in advance, and the target evaporator outlet temperature threshold value TEOd can be determined based on the discharged refrigerant pressure Pd read in step S3. Then, by comparing TEOd with the temporary target evaporator outlet temperature TEOt determined in steps S901 to 905, it can be determined whether or not the amount of return oil is insufficient. That is, if TEOt ≦ TEOd, it is a return oil good region, and if TEOt> TEOd, it is a return oil insufficient region.

  Accordingly, in step S906, the low pressure side information value TEOt and the high pressure side information value Pd are determined based on the feedback oil pass / fail threshold line dividing the predetermined return oil shortage region and the return oil good region. It is determined whether or not the point to be assigned belongs to the return oil shortage region.

  If it is determined in step S906 that it belongs to the feedback oil good region, the process proceeds to step S907, the target evaporator outlet temperature TEO is set as TEOt as the final target value, and the process proceeds to step S908. In step S908, similarly to step S96 of the first embodiment, the control current In is determined so that the evaporator blown air temperature Te approaches the TEO.

  If it is determined in step S906 that the feedback oil is insufficient, the process proceeds to step S909. Here, in order to avoid a shortage of feedback oil, the target evaporator outlet temperature TEO, which is the final target value, may be set to be equal to or lower than the target evaporator outlet temperature threshold TEOd. Since the lower limit value TEOmn is set in order to prevent frost, TEO cannot be changed to TEOd if it falls within the feedback oil failure region and falls within the region where TEOd <TEOmn (the thin hatched portion in FIG. 11). .

  Therefore, in this embodiment, the pseudo intermittent operation of the compressor 11 is executed in step S909. Specifically, as shown in FIG. 12, when it is determined that the oil feedback is insufficient, the control current In is controlled to 0 (A), the refrigerant discharge capacity is set to approximately 0%, and the compressor 11 is controlled. Is deactivated.

  When the evaporator outlet air temperature Te rises to the temporary target evaporator outlet temperature TEOt + α, TEO is changed to TEOt, and the control current In is calculated and the compressor 11 is put into an operating state in the same manner as in step S908. . When the compressor 11 is in an operating state and Te decreases to TEO, the TEO is again controlled so that the control current In becomes 0 (A). Here, α is a hysteresis width for preventing hunting and is set to 1 ° C. in the present embodiment.

  By executing the pseudo intermittent operation of the compressor 11 in this way, the compressor 11 is intermittently moved to the non-operating state to shift to the feedback oil good region, and further, the compressor 11 continues in the feedback oil shortage region. Since the operation can be avoided, the durability of the compressor 11 can be prevented from being adversely affected. Of course, when the engine power is transmitted to the compressor 11 via an electromagnetic clutch, the same intermittent control may be performed by switching between the energized state and the non-energized state of the electromagnetic clutch.

  Even by the control as described above, it is possible to accurately determine whether or not the feedback oil is good based on the low pressure side information value (TEOt) and the high pressure side information value (Pd), and obtain the same effect as in the first embodiment. be able to.

It is a whole block diagram of 1st Embodiment. It is a characteristic view which shows the relationship between the control current of 1st Embodiment, and a target low voltage | pressure. It is a flowchart which shows control of the air-conditioning control apparatus of 1st Embodiment. It is a flowchart which shows the principal part of control of the air-conditioning control apparatus of 1st Embodiment. It is a characteristic view for determining the 1st cooling target temperature of a 1st embodiment. It is a characteristic view for determining the 2nd cooling target temperature of a 1st embodiment. It is explanatory drawing which shows the threshold line of return oil by discharge refrigerant pressure and suction | inhalation refrigerant pressure. It is explanatory drawing which shows a return oil pass / fail threshold line by discharge refrigerant pressure and temporary control current. It is a flowchart which shows the principal part of control of the air-conditioning control apparatus of 2nd Embodiment. FIG. 6 is a characteristic diagram showing a relationship between suction refrigerant pressure and refrigerant evaporation temperature. It is explanatory drawing which shows a return oil pass / fail threshold line by discharge refrigerant pressure and temporary target evaporator blowing temperature. It is explanatory drawing explaining the compressor pseudo intermittent operation of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 9 ... Evaporator, 11 ... Compressor, 11a ... Electromagnetic capacity control valve, 30 ... Air conditioning control apparatus.

Claims (3)

A swash plate type variable displacement compressor (11) configured to be able to change a discharge capacity by an external control signal (In) and sucking and discharging a refrigerant mixed with lubricating oil;
Control signal calculation means (S9) for calculating a control current (In) for controlling the discharge capacity of the compressor (11);
An evaporator (9) that evaporates the refrigerant and exhibits cooling capacity;
Target cooling degree calculating means (S91 to S95, S901 to S905) for calculating a target value (TEO) of the cooling degree of the evaporator (9),
The compressor (11) changes the inclination angle according to the refrigerant pressure (Pc) in the swash plate chamber to change the discharge capacity, and changes the refrigerant pressure (Pc) in the swash plate chamber. An electromagnetic capacity control valve (11a);
The electromagnetic capacity control valve (11a) is opposed to a pressure responsive mechanism for generating a force corresponding to the suction refrigerant pressure (Ps) and a force corresponding to the suction refrigerant pressure (Ps) and the control signal (In). Comprising an electromagnetic mechanism for generating an electromagnetic force determined by
The control signal calculation means (S9) calculates the control current (In) so that the actual cooling degree (Te) approaches the target value (TEO),
Furthermore, the refrigeration cycle apparatus is determined such that a target low pressure (Pst) of the suction refrigerant pressure (Ps) is decreased according to an increase in the control current (In),
A feedback oil shortage region and a feedback oil good region determined in advance based on the suction refrigerant pressure (Ps) sucked into the compressor (11) and the discharge refrigerant pressure (Pd) discharged from the compressor (11) ; Return oil pass / fail judgment means (S97, S906) storing a return oil pass / fail threshold line
The return oil pass / fail judgment means (S97, S906) determines the temporary physical quantity correlated with the suction refrigerant pressure (Ps) when the control current (In) is output to the compressor (11) and the discharge. The point determined by the refrigerant pressure (Pd) is determined as to whether the return oil amount is good or not based on whether or not it belongs to the return oil shortage region,
When the feedback oil quality determination means (S97, S906) determines that the feedback oil amount is insufficient, the control signal calculation means (S9) continues the control current (In) and the point continues to the feedback oil shortage region. The refrigeration cycle apparatus is characterized in that the value is changed to a value that avoids belonging to the target. The temporary physical quantity is a temporary calculated value (Int) of the control current (In) calculated so that the actual cooling degree (Te) approaches the target value (TEO). The refrigeration cycle apparatus according to 1. The refrigeration cycle apparatus according to claim 1, wherein the temporary physical quantity is a temporary target value (TEOt) of the degree of cooling calculated to determine the target value (TEO).

Images