JP4203915B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to an air conditioner, an outdoor unit, and a refrigeration apparatus that use a vapor compression refrigeration cycle, and is suitable for a wide range of uses from a low-priced product to a high-priced product and for facilitating the development of models.

Refrigerant compressors used in air conditioners, outdoor units and refrigeration systems that use a vapor compression refrigeration cycle include constant-speed compressors that are driven at a substantially constant rotational speed, and inverter-type compressors that are controlled in rotational speed. In addition, an induction motor provided with a squirrel-cage conductor (winding) is often adopted because it can be easily driven by an AC voltage of commercial frequency. Further, from the viewpoint of high efficiency, it is also possible to employ a DC motor having a rotor in which a permanent magnet is provided on a rotor core and an armature in which a three-phase winding is provided on an armature core. It is known as described in the Gazette.
Furthermore, for industrial motors, embedded magnet synchronous motors have been proposed as those that can drive commercial power sources with high efficiency in response to demands for energy conservation. For example, Hirano et al. 3: New high-rate motor and application: Technical report Yaskawa, No. 62, No. 4, 1998, Vol.

JP-A-5-211796 Hirano et al., “New High Rate Motor and Application” Technical Report Yaskawa, Vol. 62, No. 4, 1998, Vol.

In the above prior art, what is described in JP-A-5-211796 is good in terms of high efficiency, but in order to start, it is necessary to employ an inverter whose frequency can be varied for the power supply. When a power supply circuit or the like is complicated and viewed as a system having a refrigeration cycle, it may be more complicated than necessary and expensive depending on the application.
In addition, in order to employ the above-described prior art synchronous magnet synchronous motor for an air conditioner, an outdoor unit, and a refrigeration apparatus in which a refrigeration cycle is used, for example, the refrigerant discharge amount required for the refrigeration cycle with respect to the rotational speed of the motor The efficiency of the refrigeration cycle must be taken into consideration, and the volume of the compression chamber of the compressor, the overall size of the compressor, and the size of the outdoor unit on which the compressor is mounted must not be increased.

Further, when starting the refrigeration cycle, if the differential pressure between the discharge side and the suction side of the compressor is large, even the embedded magnet synchronous motor may not be able to start or its reliability may be insufficient. There is a fear.
Furthermore, if an overload occurs during steady operation of the refrigeration cycle, i.e., during synchronous operation, the rotor of the embedded magnet synchronous motor will greatly stall, or the winding temperature of the motor will rise and in the worst case, The insulation material is deteriorated or the insulation breakdown of the winding is caused, so that the reliability of the device is remarkably impaired.
Furthermore, it is necessary to minimize the influence on the deterioration of refrigerant and lubricating oil circulating in the refrigeration cycle of the permanent magnet of the embedded magnet synchronous motor.

An object of the present invention is to obtain a highly reliable refrigeration apparatus that can reduce power consumption, increase efficiency, and drive a commercial power source .

In order to solve the above problems, the present invention provides a variable speed compressor controlled in capacity by an inverter and a rotor iron core in a refrigeration apparatus having a refrigeration cycle including a plurality of compressors driven by an electric motor. A constant-speed compressor having a cage-shaped conductor and a permanent magnet, driven by a commercial power supply, driven in an asynchronous state as an induction motor at start- up , and driven as a synchronous motor at a synchronous speed during steady operation ; If the a plurality discharge side of the compressor and a suction side bypassing the discharge pressure of the plurality of compressors is a set pressure defined in relation to the stall of the compressor, said plurality A bypass circuit for bypassing the discharge side and the suction side of the compressor, and a check valve provided on the discharge side of the constant speed compressor, starting the variable speed compressor, and then starting the constant speed High speed compressor It is intended to drive.

  Moreover, in the above, it is preferable that the constant speed compressor is a scroll compressor.

  Furthermore, in the above, it is desirable that the refrigeration apparatus is an air conditioner including an outdoor heat exchanger and an indoor heat exchanger.

Further, in those described above, the scroll compressor and a orbiting scroll and the fixed scroll, said orbiting scroll in the motor which is Uchifu the pressure vessel is driven Rukoto is desirable.

According to the present invention described above, the following effects can be obtained.
(B) In a refrigeration system having a refrigeration cycle having a plurality of compressors driven by an electric motor, a variable speed compressor whose capacity is controlled by an inverter, and a cage conductor and a permanent magnet provided on the rotor core A constant speed compressor having an electric motor driven in an asynchronous state as an induction motor at start- up , and driven as a synchronous motor at a synchronous speed during steady operation , and discharge of the plurality of compressors bypass the side and suction side, wherein if the discharge pressure of the plurality of compressors is a set pressure defined in relation to the stall of the compressor, suction and discharge side of the plurality of compressors And a bypass circuit that bypasses the discharge side, so that the discharge side and the suction side are bypassed when the discharge pressure of a plurality of compressors reaches a set pressure determined in connection with the stall of the compressor Ni Therefore, the discharge-side pressure during operation can be reduced, and the stall of a constant speed compressor having an electric motor that is provided with a squirrel-cage conductor and a permanent magnet in the rotor core and driven by a commercial power source can be prevented. . As a result, an abnormality in the refrigeration cycle can be prevented, and a highly reliable refrigeration apparatus can be obtained.
(B) In a refrigeration apparatus having a refrigeration cycle having a plurality of compressors driven by an electric motor, a variable speed compressor whose capacity is controlled by an inverter, and a squirrel-cage conductor and a permanent magnet provided on the rotor core And a constant speed compressor having an electric motor that is driven in an asynchronous state as an induction motor at start- up, and that is operated as a synchronous motor at a synchronous speed during steady operation. Since the constant speed compressor is started after that, the differential pressure between the discharge side pressure and the suction side pressure increases when the constant speed compressor is started. In the present invention, the constant speed compressor Since the check valve is provided on the discharge side, the constant pressure compressor can be started by reducing the differential pressure even while the variable speed compressor is being driven. Therefore, it is possible to easily start the constant speed compressor having the electric motor provided with the cage conductor and the permanent magnet on the iron core of the rotor and driven by the commercial power source.
(C) a variable speed type compressor which is capacitively controlled by the inverter is driven by a commercial power supply provided cage conductor and the permanent magnet to the core of the rotor, during startup is driven asynchronously state as an induction motor, the steady operation When equipped with a constant speed compressor that has a motor that operates as a synchronous motor at a synchronous speed, it has a large capacity, a large capacity variable width, fine control, and a highly efficient refrigeration system. Obtainable.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In order to improve the efficiency of an air conditioner that uses a vapor compression refrigeration cycle, it is effective to improve the efficiency of an electric motor that is used in a refrigerant compressor that consumes the largest amount of power among the components that make up the refrigeration cycle. Conventionally, induction motors are often used for refrigerant compressors, but synchronous motors in which permanent magnets are embedded in a rotor core are known as motors with higher efficiency. Since the synchronous motor rotates by utilizing the magnetic field generated by the permanent magnet embedded in the rotor of the motor and the stator, the induction motor generates a secondary current that flows to the motor rotor. Therefore, the efficiency is increased because there is no energy loss.
However, when using a synchronous motor as an electric motor used for a refrigerant compressor, the following must be considered.

  When a synchronous motor is used as the motor for the refrigerant compressor and a commercial power source is directly connected to the synchronous motor, the rotating magnetic field generated from the stator of the motor is a rotating speed (synchronous speed) corresponding to the power frequency (50/60 Hz). It becomes. Since the rotor of the electric motor used for the refrigerant compressor is integrated with the rotating parts of the refrigerant compressor, the inertial force is large. Therefore, at the time of starting, the rotor cannot follow the rotation speed of the rotating magnetic field generated from the stator, and the refrigeration cycle cannot be started. Therefore, when a constant speed compressor is required, it is preferable to use a commercial power supply, and thus a synchronous motor cannot be used.

1 and 2 show an air conditioner according to an embodiment of the present invention, in which a compressor is a constant speed compressor driven by a commercial power source, and a rotor core of an electric motor used in the compressor. However, below the synchronous speed, a synchronous motor acting as an induction motor is incorporated, that is, a permanent magnet magnetized in two poles is embedded in the rotor core.
The air conditioner shown in FIG. 1 is configured by sequentially connecting a constant speed compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an outdoor expansion device 5, an indoor expansion device 6, an indoor heat exchanger 7, and an accumulator 9. ing. As an electric motor used for the constant speed compressor 1, a squirrel-cage winding (conductor) is formed in the rotor in the vicinity of the outer periphery of the rotor, and a permanent magnet is embedded in the rotor. Thus, it acts as an induction motor until the rotational speed of the rotor reaches the synchronous speed, and acts as a synchronous motor when the rotational speed of the rotor reaches the synchronous speed. Therefore, it is possible to start without using an inverter, and at the time of operation at a synchronous speed, that is, steady operation at a rotational speed (3000 r / min, 3600 r / min) determined by the power frequency (50/60 Hz) of the commercial power source. In some cases, since no secondary current is generated in the rotor of the electric motor, the efficiency can be improved.

Further, as a motor used in the constant speed compressor 1, a permanent magnet is embedded in the rotor of the motor, but a simple permanent magnet type synchronous motor and an induction that can be driven to near the synchronous speed of the synchronous motor. You may combine with an electric motor. In this case, at the start, power is supplied only to the induction motor, and when the rotation speed of the motor reaches the synchronization speed of the synchronous motor, the power supply to the induction motor is cut off and the power is supplied to the synchronous motor at the same time. Supply. Thereby, the compressor 1 is driven only by the synchronous motor in the steady operation, the operation efficiency of the motor and the compressor 1 is increased, and the efficiency of the entire air conditioner is greatly improved.
In other words, since the synchronous motor does not cause slippage between the stator and the rotor that was in the induction motor, the fluctuation in the rotational speed of the rotor is smaller than that of the induction motor. Since the rotational speed becomes faster, the amount of refrigerant compressed by the refrigerant compression mechanism portion of the compressor 1 also increases, the refrigerant discharge amount of the compressor 1 increases, and in the normal load range of the refrigeration cycle as shown in FIG. The ability can be improved.

  In particular, even when the refrigeration cycle is overloaded, the slip is zero in the synchronized state and no current flows through the cage conductor, so the capacity is improved compared to the large slip when the induction motor is overloaded. The effect to do becomes very large. Furthermore, if the compressor 1 is a scroll compressor, the fluctuation in the compression torque is small, and therefore the load fluctuation on the electric motor is small, so that the efficiency can be further improved. In addition, although the example at the time of air_conditionaing | cooling operation is shown in FIG. 2, it is the same also at the time of heating operation.

  In addition, since the rotation speed of the rotor of the motor is inversely proportional to the number of poles of the motor, the rotation speed of the rotor of the motor is increased by setting the number of poles of the motor to the minimum two poles. The refrigerant discharge amount increases. Therefore, the volume of the compression chamber of the compressor 1 can be reduced, and the size of the compressor 1 and the outdoor unit 20 on which the compressor 1 is mounted can be reduced. Furthermore, the variable speed type air conditioner using an inverter can share the compression mechanism section or other parts required for the refrigeration cycle, and the model can be easily and inexpensively developed.

Details of the compressor 1 and the rotor 52 will be described with reference to FIGS.
The compressor mechanism unit is formed by meshing a spiral wrap 63 standing upright on the end plate 61 of the fixed scroll 60 and a spiral wrap 68 standing upright on the end plate 58 of the orbiting scroll 57. The compression operation is performed by the turning motion by 55.
Of the compression chambers 59 (59a, 59b...) Formed by the fixed scroll 60 and the orbiting scroll 57, the compression chamber located on the outermost diameter side is directed toward the center of the scrolls 60 and 57 along with the orbiting motion. It moves and the volume gradually decreases. When both compression chambers 59a and 59b reach the vicinity of the centers of both scrolls 60 and 57, the compressed refrigerant gas in both compression chambers is discharged from a discharge port 62 communicating with the compression chamber. The discharged refrigerant gas passes through gas passages provided in the fixed scroll 60 and the frame 56, reaches the compression container below the frame 56, and is discharged out of the compressor from a discharge pipe 64 provided on the side wall of the compression container. .

An electric motor is enclosed in the pressure vessel (electric motor chamber), and the orbiting scroll 57 is driven by the electric motor to perform a compression operation.
An oil sump 66 is provided at the lower part of the electric motor, and the lubricating oil in the oil reservoir 66 passes through an oil hole 65 provided in the crankshaft 55 due to a pressure difference caused by a rotational motion, so that the orbiting scroll 57 and the crankshaft 55 Lubricate the sliding parts and sliding bearings.
The electric motor is an embedded magnet type synchronous motor including a stator 51 and a rotor 52. The stator 51 has a stator core 53 and an armature winding (conductor) wound around the stator core 53, and rotates. The rotor 52 is provided with a rotor core 52 having a permanent magnet 71 embedded therein and a slit 73 between magnets.
FIG. 7 shows a detailed structure of the rotor 52, in which a permanent magnet 71 is magnetized in two poles, and a conductor is embedded in the vicinity of the outer periphery of the rotor 52 to form a cage conductor (winding) 72. .

Next, another embodiment will be described with reference to FIG.
When starting the refrigeration cycle, if the pressure difference between the discharge side and the suction side of the compressor 1 is large, the start-up becomes impossible or the reliability becomes insufficient. Therefore, it is necessary to ensure a sufficient starting torque of the motor. There is. Therefore, even if the refrigeration cycle is started as an induction motor and then operated as a synchronous motor, the action as an induction motor is increased in order to increase the starting torque of the motor, that is, the amount of rotor cage conductors is increased. In order to increase the current, the wire diameter must be increased, and the compressor 1 may be increased in size. In order to make it compact, it is structurally difficult to embed a permanent magnet in the iron core of the rotor provided with the cage conductor. In addition, it takes several minutes for the pressure in the refrigeration cycle to be balanced after the compressor 1 is stopped.

  Therefore, the discharge side and the suction side of the compressor 1 are connected by a bypass pipe, and an opening / closing valve 10 for opening and closing the bypass circuit is provided, and the opening / closing valve 10 is opened before starting, whereby the difference between the discharge pressure and the suction pressure is established. Since the pressure can be reduced, the compressor 1 can be started easily and the amount of the cage conductor can be reduced, so that a permanent magnet can be easily provided on the rotor 52, which is suitable for downsizing and ensures reliability. can do.

Furthermore, during operation of the compressor 1, when the torque applied to the rotor 52 of the motor of the compressor 1 increases, that is, when the discharge pressure increases, the rotor of the motor may stall. Therefore, a discharge pressure value Pdset at which the rotor 52 of the electric motor does not stall is set, the discharge pressure is measured by the discharge pressure detection device 14, and when the discharge pressure rises to Pdset, the discharge pressure is lowered by opening the on-off valve 10. Thus, it is possible to prevent an abnormality in the refrigeration cycle due to the stall of the electric motor. Furthermore, if the compressor is a scroll compressor, the fluctuation of the compression torque is small, so that the abnormality of the refrigeration cycle can be further prevented, the reliability can be improved, and the noise can be reduced.
The pressure detection device 14 may be a pressure switch set so that the switch of the electric circuit is opened (or closed) when the set pressure Pdset is reached.

Next, another embodiment according to the present invention will be described with reference to FIG.
In this air conditioner, a liquid receiver 11 is provided between the outdoor heat exchanger 3 and the indoor heat exchanger 7 (the outdoor heat exchanger 3 and the indoor expansion device 6). A bypass pipe for bypassing the gas refrigerant in the liquid receiver 11 on the downstream side with respect to the flow direction of the refrigerant inlet / outlet pipe or the main pipe, and on-off valves 10a and 10b for opening and closing the bypass circuit. Yes.
During the cooling operation, by opening the on-off valve 10b, the gas refrigerant in the liquid receiver 11 can be led out, the degree of refrigerant evacuation at the inlet / outlet of the liquid receiver 11 is increased, and the outdoor heat exchanger that functions as a condenser Since the degree of refrigerant at the outlet of No. 3 increases, it can be effectively used as a condenser, so that the condensation pressure can be kept low and the discharge pressure can be lowered. By opening the on-off valve 10a during heating, the same effect as during cooling can be obtained.
Using this, the discharge pressure Pdset is set so that the rotor 52 of the electric motor used in the compressor 1 does not stall, the discharge pressure is detected by the discharge pressure detection device 14, and when the pressure rises to Pdset, the on-off valve 10 b is set during cooling. During heating, the discharge pressure can be lowered by opening the on-off valve 10a, and an abnormality in the refrigeration cycle can be prevented.

Another embodiment will be described with reference to FIG.
As the compressor 1, a variable speed compressor 1a and a constant speed compressor 1b driven by one or more commercial power sources are mounted, and a check valve 13 is provided on the discharge side of the constant speed compressor 1b. Furthermore, an oil separator 12 is provided.

  A plurality of indoor units are provided such as 21a and 21b, and the load varies greatly depending on the use state. When the load on the indoor unit side is small, it is not necessary to drive all the compressors 1a and 1b, and the capacity control operation is performed by driving only the variable speed compressor 1a. When only the variable speed compressor 1a is driven, the load on the indoor unit side increases, and if the variable speed compressor 1a alone cannot secure the capacity, the constant speed compressor 1b is driven. At that time, since the variable speed compressor 1a is already driven, the differential pressure between the discharge side pressure and the suction side pressure becomes large when viewed as the constant speed compressor 1b. Therefore, even if the check valve 13 is installed on the discharge side of the constant speed compressor 1b and the variable speed compressor 1a is being driven, the pressure difference between the discharge side pressure and the suction side pressure of the constant speed compressor 1b. Can be reduced to facilitate starting with a commercial power source. Therefore, even when a large capacity is required as in a multi-air conditioner, it is possible to realize a large capacity variable width and fine control without adding an inverter power supply.

In the above, if the neodymium, iron, boron magnet, or samarium-cobalt magnet having a large magnetic force is used as the compressor 1 as a permanent magnet embedded in the iron core of the rotor 52 of the electric motor, the size of the permanent magnet is reduced. And the number can be reduced. Therefore, it is structurally easy to provide the cage conductor and the permanent magnet in the iron core of the rotor 52, and the compressor 1 can be downsized. And since efficiency is also improved, the magnitude | size of the outdoor unit (outdoor unit) 20 which mounts the compressor 1 can be made small.
Furthermore, when neodymium, iron, boron magnets or samarium / cobalt magnets are used as the permanent magnets of the electric motor, the rare earth elements such as neodymium and samarium, which are constituent materials of the permanent magnets, come into contact with the refrigerant and lubricating oil and the permanent magnets. Acts as a powerful catalyst, degrades the lubricating oil, and the deteriorated product precipitates as sludge in the low temperature part of the refrigeration cycle, clogs the capillary, obstructing the flow of the refrigerant, and the temperature of the refrigerant compressor It rises abnormally.
However, by coating the surface of the permanent magnet with coating, nickel plating, or aluminum plating, the refrigerant and lubricating oil in the compressor 1 and the permanent magnet are not in direct contact with each other, so that deterioration of the lubricating oil is suppressed. And reliability can be improved.

  As described above, since the refrigeration cycle is operated by a commercial power source, it can be simplified as a system having a refrigeration cycle and can be applied to a wide range of applications. In addition, since the permanent magnet embedded in the rotor has two poles, the refrigeration cycle can be operated at a relatively high rotational speed (3000 r / min, 3600 r / min) even though the commercial power supply has a low frequency of 50 Hz or 60 Hz. Steady operation can be performed, and the compressor, the outdoor unit, the refrigeration apparatus, etc. can be made compact and compact, which is advantageous for improving the efficiency of the refrigeration cycle and reducing noise. In particular, the efficiency of the refrigeration cycle is such that the motor is in a synchronized state during steady operation and no electric power is required for slipping, and the compressor speed does not change even when the outside air temperature changes and the load increases, reducing the compression efficiency. In addition, the fact that the refrigeration cycle itself can be stabilized even when there is a load variation on the refrigeration cycle can be further improved.

  Also, at the time of start-up, the refrigerant liquid returns to the compressor in a large amount to lower the oil viscosity of the lubricating oil, or the start-up worsens at the start of heating operation, but the refrigerant gas passes through the motor room, Since it is driven in a non-synchronized state from the start to the start of synchronization with a commercial power supply, the heat generated by the motor heats the refrigerant and lubricating oil, preventing damage to the compressor bearings and increasing heating capacity. can do.

  Furthermore, at least in the case of heating operation, since the refrigeration cycle is started as an induction motor, the heat generated by the motor heats the refrigerant and lubricating oil to prevent a decrease in viscosity, prevent damage to the compressor bearing, and increase the heating capacity. be able to. In spite of this, since the electric motor is in a synchronized state and the rotation speed of the compressor does not change, it is possible to prevent a reduction in compression efficiency even when the outside air temperature changes and the load increases.

  Furthermore, even when the variable speed compressor is in operation, the check valve can reduce the differential pressure between the discharge side pressure and the suction side pressure of the constant speed compressor to facilitate starting with a commercial power supply. Therefore, even when the capacity is increased, the capacity variable width can be increased and fine control can be realized without increasing the inverter power supply accordingly.

The system diagram of the refrigerating cycle by one embodiment concerning the present invention. The graph which shows the relationship of the cooling capacity with respect to the external temperature of the air conditioner by one Embodiment which concerns on this invention. The systematic diagram of the refrigerating cycle by other embodiment which concerns on this invention. The systematic diagram of the refrigerating cycle by other embodiment which concerns on this invention. The systematic diagram of the refrigerating cycle by other embodiment which concerns on this invention. 1 is a side sectional view of a compressor according to an embodiment of the present invention. Sectional drawing of the rotor of the electric motor by one Embodiment which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1b ... Constant speed compressor, 1a ... Inverter compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Outdoor fan, 5, 5a ... Outdoor expansion device, 6, 6a, 6b ... Indoor expansion device 7, 7a, 7b ... indoor heat exchangers, 8, 8a, 8b ... indoor air blower, 9 ... accumulator, 10, 10a, 10b ... electromagnetic on-off valve, 11 ... liquid receiver, 12 ... oil separator 13 ... reverse Stop valve, 14 ... discharge pressure detection device, 20 ... outdoor unit, 21, 21a, 21b ... indoor unit.

Claims (4)

In a refrigeration apparatus having a refrigeration cycle comprising a plurality of compressors driven by an electric motor,
A variable speed compressor whose capacity is controlled by an inverter;
A constant-speed motor having a squirrel-cage conductor and a permanent magnet on the rotor core, driven by a commercial power supply, driven asynchronously as an induction motor at startup, and operated as a synchronous motor at a synchronous speed during steady operation A compressor,
If the a plurality discharge side of the compressor and a suction side bypassing the discharge pressure of the plurality of compressors is a set pressure defined in relation to the stall of the compressor, said plurality A bypass circuit for bypassing the discharge side and the suction side of the compressor of
A check valve provided on the discharge side of the constant speed compressor,
A refrigerating apparatus, wherein the variable speed compressor is started, and then the constant speed compressor is driven.   2. The refrigeration apparatus according to claim 1, wherein the constant speed compressor is a scroll compressor.   2. The refrigeration apparatus according to claim 1, wherein the refrigeration apparatus is an air conditioner including an outdoor heat exchanger and an indoor heat exchanger.   3. The refrigeration apparatus according to claim 2, wherein the scroll compressor has a fixed scroll and a turning scroll, and the turning scroll is driven by the electric motor enclosed in a pressure vessel.

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