JP6373034B2 - refrigerator - Google Patents

Description

  The present invention relates to a refrigerator having a two-stage compressor including a low-stage compression section, a high-stage compression section, and a motor that drives each compression section.

  In a compressor, each component used has temperature constraints.

  Conventionally, in a refrigerator having a compressor for compressing refrigerant, in order to prevent deterioration and damage of the stator of the compressor motor, the refrigerant is decompressed by the expansion means, and the low-temperature refrigerant is supplied into the motor chamber. There are refrigerators that cool the motor (see, for example, Patent Document 1 and Patent Document 2).

  Patent Document 1 describes motor cooling of a compressor in a refrigerator having a two-stage compressor having a low-stage compressor and a high-stage compressor, and the refrigerant used for motor cooling is used as an intermediate stage. That is, it is made to merge between the low stage discharge part and the high stage suction part. Patent Document 2 describes that the expansion means is controlled in accordance with the amount of heat generated by the motor, and the amount of refrigerant supplied into the motor chamber is controlled.

JP 2012-102967 A (page 7, FIG. 1) JP-A-7-139820 (page 3, FIG. 1)

  In Patent Documents 1 and 2 described above, the amount of refrigerant used for motor cooling is controlled by the expansion means. Examples of the expansion means include a capillary tube and an electronic expansion valve. Among them, as an expansion valve that is easier to control. There is a linear electronic expansion valve. The linear electronic expansion valve is not controlled to be fully closed because of its structural reasons, if the valve is fully closed during operation, an error may occur in the valve opening. Therefore, when a linear electronic expansion valve is used as the expansion means used for cooling the motor, the refrigerant is supplied to the motor chamber even in an operating state where the motor temperature falls below the target cooling temperature and supply of the refrigerant to the motor chamber is unnecessary. Therefore, there is a problem that the refrigerant is supplied into the motor chamber more than necessary.

Since the refrigerant for cooling the motor is returned to the intermediate stage as described above, the amount of refrigerant returned to the intermediate stage increases as the amount of refrigerant used for motor cooling increases, and the intermediate pressure increases. When the intermediate pressure increases, the compression ratio [(low stage discharge pressure = intermediate pressure) / low stage suction pressure] of the low stage compression section increases .

Then, the volumetric efficiency of the low-stage compressing section due to the increase of the low-stage compressing section of the compression ratio deteriorates, the refrigerating capacity defeated low, compressor power is increased.

  Therefore, when the refrigerant is supplied more than necessary into the motor chamber, there is a problem that the coefficient of performance (cooling capacity / compressor power) is lowered as a result.

  The present invention has been made in view of the above points, and can prevent the refrigerant for cooling the motor from being supplied to the motor more than necessary, thereby suppressing an increase in the intermediate pressure, and having a good coefficient of performance. The purpose is to provide.

A refrigerator according to the present invention includes a low-stage compression unit, a high-stage compression unit, a two-stage compressor having a motor that drives the compression unit, a condenser, and a decompression device, and a refrigerant circuit in which a refrigerant circulates. And a pipe that forms a refrigerant flow path that branches a part of the refrigerant from the condenser to the decompression device and supplies the motor chamber in which the motor is installed in the two-stage compressor, and a linear electronic expansion provided in the pipe A valve, an on-off valve provided in the pipe, a temperature detecting means for detecting a temperature corresponding to the amount of heat generated by the motor, and a linear type so that the temperature detected by the temperature detecting means becomes a preset target cooling temperature. And a control device that controls the electronic expansion valve. Even if the control device controls the linear electronic expansion valve to the minimum control opening, the temperature detected by the temperature detection means is lower than the target cooling temperature. In this case, the on-off valve is fully closed .

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the refrigerant | coolant for motor cooling is supplied to a motor more than necessary, can suppress the raise of an intermediate pressure, and can obtain the refrigerator with a favorable coefficient of performance.

It is the schematic of the refrigerant circuit of the two-stage screw refrigerator which concerns on Embodiment 1 of this invention. It is a flowchart of the motor cooling control method of the two-stage compressor in the two-stage screw refrigerator which concerns on Embodiment 1 of this invention. It is the schematic of the refrigerant circuit of the two-stage screw refrigerator which concerns on Embodiment 2 of this invention.

  Hereinafter, a two-stage screw refrigerator according to an embodiment of the present invention will be described with reference to the drawings. Here, in all drawings, the same reference numerals denote the same or equivalent parts, and this is common throughout the entire specification. Furthermore, the form of the constituent elements appearing in the whole specification is merely an example, and is not limited to these descriptions.

  Hereinafter, a configuration of a two-stage screw refrigerator that is an example of a refrigerator having a two-stage compressor that includes a low-stage compressor, a high-stage compressor, and a motor that drives each compressor will be described.

Embodiment 1 FIG.
1 is a schematic diagram of a refrigerant circuit of a two-stage screw refrigerator according to Embodiment 1 of the present invention. In FIG. 1, a solid line arrow indicates a refrigerant system, and a broken line arrow indicates an oil system.
The two-stage screw refrigerator includes a two-stage compressor 1, an oil separator 2, a condenser 3, a main expansion valve 4 that is a decompression device, and an evaporator 5, which are sequentially connected by a refrigerant pipe. The refrigerant circuit is configured.

  The two-stage compressor 1 is a two-stage single screw compressor. As shown in FIG. 1, the two-stage compressor 1 has a cylindrical casing 1a, a low-stage compressor 10 accommodated in the casing 1a, and a high-stage compressor. A stage compression unit 20 and a motor 30 that rotationally drives the low stage compression unit 10 and the high stage compression unit 20 are provided.

  Each of the low-stage compression section 10 and the high-stage compression section 20 is constituted by a screw-type compression section. The low-stage compression section 10 includes a low-stage screw rotor 11 and a gate rotor 12, and the high-stage compression section 20. Includes a high-stage screw rotor 21 and a gate rotor 22.

  A plurality of helical screw grooves 11 a are formed on the outer peripheral portion of the low-stage screw rotor 11, and a plurality of helical screw grooves 21 a are similarly formed on the outer peripheral portion of the high-stage screw rotor 21.

  Two gate rotors 12 of the low-stage compression unit 10 are arranged so as to sandwich the low-stage screw rotor 11 in the radial direction of the low-stage screw rotor 11, and the gate rotor 22 of the high-stage compression unit 20 is the same as the high-stage screw rotor 21. One is arranged in the radial direction. In addition, a plurality of tooth portions 12 a and 22 a are formed on the outer peripheral portions of the gate rotors 12 and 22, and these tooth portions 12 a and 22 a are screw grooves 11 a of the low-stage screw rotor 11 and screws of the high-stage screw rotor 21. The grooves 21a are engaged with each other to form a low-stage compression chamber and a high-stage compression chamber, respectively. Here, although three gate rotors are provided, four gate rotors are provided, and two gate rotors are arranged so as to sandwich the low-stage screw rotor 11 in the radial direction of the low-stage screw rotor 11. It is good also as a form arrange | positioned so that the high stage screw rotor 21 may be pinched | interposed into the radial direction of 21. FIG.

  The motor 30 includes a stator 31 that is inscribed and fixed to the casing 1 a and a motor rotor 32 that is disposed inside the stator 31, and is disposed in the motor chamber 33. The motor 30 is configured such that its rotational speed is controlled when the drive circuit is an inverter system.

  The motor chamber 33 communicates with an intermediate chamber 40 between the low-stage screw rotor 11 and the high-stage screw rotor 21, but is separated from the suction side (low-pressure side) of the low-stage screw rotor 11 by a shaft seal 34. ing. The low-stage screw rotor 11, the high-stage screw rotor 21, and the motor rotor 32 are arranged on the same axis line, and are all fixed to the screw shaft 50. In the motor chamber 33, a motor chamber wall temperature sensor 60 configured by, for example, a thermistor and detecting the wall temperature of the motor chamber 33 is disposed. The motor chamber wall temperature sensor 60 constitutes temperature detection means of the present invention that detects the temperature according to the amount of heat generated by the motor 30.

  The two-stage screw refrigerator further includes a liquid pipe 6 that branches a part of the refrigerant (liquid refrigerant) from the condenser 3 toward the main expansion valve 4 and forms a refrigerant flow path that is supplied to the motor chamber 33. Thus, by supplying a part of the liquid refrigerant from the condenser 3 toward the main expansion valve 4 to the motor chamber 33, the motor 30 is cooled. A linear electronic expansion valve 7 capable of controlling the amount of refrigerant supplied to the motor chamber 33 is disposed in the liquid pipe 6. The liquid pipe 6 is further provided with an on-off valve 8 composed of, for example, an electromagnetic valve that can open and close the refrigerant flow path of the liquid pipe 6. Here, the on-off valve 8 is arranged upstream of the linear electronic expansion valve 7 in the liquid pipe 6. However, the arrangement position of the on-off valve 8 may be on the liquid pipe 6. It doesn't matter if it is upstream or downstream.

  The two-stage screw refrigerator includes a control device 70 configured with a microcomputer or the like. The control device 70 includes a CPU, a RAM for storing various data, and a ROM (none of which is shown) for storing a program for performing operation control, etc., and a two-stage screw according to the program in the ROM. Control the entire refrigerator.

  Further, the control device 70 adjusts the valve opening degree of the linear electronic expansion valve 7 so that the motor chamber wall temperature detected by the motor chamber wall temperature sensor 60 becomes a preset target cooling temperature. The refrigerant supply amount to 33 is controlled, and the on-off valve 8 is controlled.

  Incidentally, as described above, the linear electronic expansion valve 7 that controls the amount of refrigerant for cooling the motor may cause an error in the valve opening degree if it is fully closed during operation due to the structural reason. Therefore, it is not controlled fully closed. Therefore, the linear electronic expansion valve 7 cannot block the refrigerant flow path of the liquid pipe 6. For this reason, for example, when the load on the motor 30 is small and the amount of heat generated by the motor 30 is small, the motor chamber 33 is connected via the liquid pipe 6 even if the valve opening degree of the linear electronic expansion valve 7 is set to the minimum in control. The liquid refrigerant continues to be supplied. In this case, the motor 30 may be cooled more than necessary, and the motor chamber wall temperature detected by the motor chamber wall temperature sensor 60 may be lower than the target cooling temperature. Therefore, in the present invention, the on-off valve 8 is provided in the liquid pipe 6 so that the refrigerant flow in the liquid pipe 6 can be blocked.

Next, the operation of the two-stage single screw compressor 1 according to Embodiment 1 and the refrigerant flow in the refrigerant circuit will be described.
By supplying power to the stator 31 from a power supply source (not shown), the motor rotor 32, the screw shaft 50, the low-stage screw rotor 11, and the high-stage screw rotor 21 rotate. Further, the gate rotors 12 and 22 engaged with the low-stage screw rotor 11 and the high-stage screw rotor 21 also rotate. Thus, the low-temperature and low-pressure gas refrigerant is sucked into the low-stage compression chamber formed by the screw groove 11a of the low-stage screw rotor 11 and the tooth portion 12a of the gate rotor 12, and the first-stage compression is performed. The gas refrigerant compressed in the low-stage compression chamber is discharged to the intermediate chamber 40.

  The gas refrigerant discharged to the intermediate chamber 40 is sucked into the high-stage compression chamber formed by the screw groove 21a of the high-stage screw rotor 21 and the tooth portion 22a of the gate rotor 22, and the second-stage compression is performed. The gas refrigerant that has been compressed in the high-stage compression chamber to a high temperature and pressure is discharged to the oil separator 2.

  The gas refrigerant discharged to the oil separator 2 contains oil. In the oil separator 2, the gas refrigerant is separated into gas refrigerant and oil, and the gas refrigerant reaches the condenser 3. In the condenser 3, the gas refrigerant is condensed by exchanging heat with an external heat source, and becomes a high-pressure liquid refrigerant.

  The high-pressure liquid refrigerant is expanded by the main expansion valve 4 to become a low-temperature and low-pressure liquid refrigerant and reaches the evaporator 5. In the evaporator 5, the liquid refrigerant evaporates by exchanging heat with an external heat source, becomes a low-temperature and low-pressure gas refrigerant, and is sucked into the low-stage compression chamber. This is the main refrigerant flow in the two-stage screw refrigerator.

  A part of the liquid refrigerant condensed in the condenser 3 is supplied to the motor chamber 33 through the liquid pipe 6 and expanded to a low temperature and a low pressure by the linear electronic expansion valve 7, thereby cooling the motor 30. The refrigerant after cooling the motor 30 flows into the intermediate chamber 40 and is sucked into the high stage compression chamber together with the refrigerant discharged from the low stage compression chamber. The flow of the refrigerant after this is as described above.

  Further, the oil separated in the oil separator 2 is injected into the low-stage compression unit 10 and the high-stage compression unit 20 through the oil pipe 9.

FIG. 2 is a flowchart of the motor cooling control method for the two-stage compressor in the two-stage screw refrigerator according to the first embodiment of the present invention. The flowchart of FIG. 2 is implemented at every control interval. Here, it is assumed that the on-off valve 8 is controlled to be fully opened.
The control device 70 compares the motor chamber wall temperature detected by the motor chamber wall temperature sensor 60 with a preset target cooling temperature (S1), and if the motor chamber wall temperature is higher than the target cooling temperature, a linear type is obtained. The electronic expansion valve 7 is operated in the opening direction by a preset opening degree (S2). On the other hand, if the motor chamber wall temperature is equal to or lower than the target cooling temperature, it is checked whether or not the motor chamber wall temperature matches the target cooling temperature (S3). If it is lower than that, then it is checked whether the valve opening degree of the linear electronic expansion valve 7 is not the minimum in control (S4). If the opening degree of the linear electronic expansion valve 7 is not the minimum in control, the control device 70 operates the linear electronic expansion valve 7 in the closing direction by a predetermined opening degree set in advance (S5).

  On the other hand, if the opening degree of the linear electronic expansion valve 7 is the minimum in control in step S4, the control device 70 fully closes the on-off valve 8 (S6). If the motor chamber wall temperature is equal to the target cooling temperature in step S3, the control device 70 maintains the linear electronic expansion valve 7 at the current opening.

  By repeating the control of the above flowchart at every control interval, while the motor chamber wall temperature is higher than the target cooling temperature, the opening degree of the linear electronic expansion valve 7 is widened by a predetermined opening degree, and the liquid pipe 6 is passed through. Thus, the flow rate of the liquid refrigerant supplied to the motor chamber 33 is increased, and the motor chamber 33 is cooled. On the other hand, while the motor chamber wall temperature is lower than the target cooling temperature, the opening degree of the linear electronic expansion valve 7 is narrowed, and the flow rate of the liquid refrigerant supplied to the motor chamber 33 through the liquid pipe 6 is reduced. Improving overcooling of the motor chamber 33 is improved. If the motor chamber wall temperature is lower than the target cooling temperature even when the linear electronic expansion valve 7 is at the minimum control opening, the on-off valve 8 is fully closed and the liquid refrigerant is supplied to the motor chamber 33. Blocked. With the above control, it is possible to prevent the liquid refrigerant from being supplied into the motor chamber 33 more than necessary.

  Here, the linear electronic expansion valve 7 is controlled so that the motor chamber wall temperature detected by the motor chamber wall temperature sensor 60 becomes the target cooling temperature. However, the linear electronic expansion valve 7 is maintained within a predetermined range including the target cooling temperature. Of course, the linear electronic expansion valve 7 may be controlled.

  Here, the opening degree of the linear electronic expansion valve 7 is operated in the opening direction or the closing direction by a predetermined opening degree at every control interval. However, for example, the temperature between the motor chamber wall temperature and the target cooling temperature is used. You may make it operate | move so that it may become the opening degree according to a difference.

  As described above, in the first embodiment, the liquid pipe 6 through which the liquid refrigerant for cooling the motor chamber 33 passes is provided with the on-off valve 8 in addition to the linear electronic expansion valve 7, and the refrigerant in the liquid pipe 6 is provided. It was possible to cut off the flow. As a result, even when the valve opening degree of the linear electronic expansion valve 7 is minimized, the motor chamber wall temperature is still lower than the target cooling temperature, and the liquid refrigerant is supplied to the motor chamber 33 more than necessary. At this time, it is possible to prevent unnecessary liquid refrigerant from being supplied to the motor chamber 33 by fully closing the on-off valve 8. As a result, the amount of gas refrigerant after the motor cooling back to the intermediate chamber 40 is suppressed, the pressure in the intermediate chamber 40 can be suppressed low, and a refrigerator having a high coefficient of performance (operation efficiency) can be obtained.

  Further, in a refrigerator having an economizer (not shown) in the refrigerant circuit and constituting an economizer cycle, the amount of heat exchanged in the economizer increases due to a decrease in the intermediate pressure, thereby increasing the refrigeration effect. That is, the refrigerating capacity can be increased.

Embodiment 2. FIG.
In the second embodiment, a winding temperature sensor 61 that detects the winding temperature of the stator 31 of the motor 30 is provided in place of the motor chamber wall temperature sensor 60 of the first embodiment. The winding temperature sensor 61 constitutes a temperature detecting means of the present invention that detects a temperature corresponding to the amount of heat generated by the motor 30. Other configurations and operations of the refrigerant circuit, the flow of the motor cooling control shown in FIG. 2, and the like are the same as those in the first embodiment. Further, the modification applied in the configuration part of the first embodiment is similarly applied to the same configuration part of the second embodiment.

FIG. 3 is a schematic diagram of the refrigerant circuit of the two-stage screw refrigerator according to Embodiment 2 of the present invention. In FIG. 3, a solid line arrow indicates a refrigerant system, and a broken line arrow indicates an oil system.
In the two-stage compressor 1 of the two-stage screw refrigerator of the second embodiment, the winding temperature sensor 61 is arranged in a state embedded in the stator 31, detects the temperature of the winding, and controls the detected temperature. Output to 70. The control device 70 controls the linear electronic expansion valve 7 and the on-off valve 8 as in the first embodiment so that the winding temperature becomes a preset target cooling temperature.

  According to the second embodiment, the same effects as those of the first embodiment can be obtained and the following effects can be obtained. That is, since the winding temperature sensor 61 is embedded and arranged inside the stator 31, the temperature responsiveness is superior to that of the first embodiment in which the temperature is detected by the motor chamber wall and the accuracy is higher than that of the first embodiment. High motor cooling control can be realized.

  In the first and second embodiments, the low-stage compression unit 10 and the high-stage compression unit 20 are both single screw compression units. You can also.

  Moreover, in the said Embodiment 1, 2, although the form with which the evaporator 5 was equipped with the refrigerator was shown, the form provided in the equipment side may be sufficient as the evaporator 5.

  1 2-stage compressor, 1a casing, 2 oil separator, 3 condenser, 4 main expansion valve, 5 evaporator, 6 liquid piping (piping), 7 linear electronic expansion valve, 8 on-off valve, 9 oil piping, 10 Low stage compression part, 11 Low stage screw rotor, 11a Screw groove, 12 Gate rotor, 12a tooth part, 20 High stage compression part, 21 High stage screw rotor, 21a Screw groove, 22 Gate rotor, 22a Tooth part, 30 Motor, 31 stator, 32 motor rotor, 33 motor chamber, 34 shaft seal, 40 intermediate chamber, 50 screw shaft, 60 motor chamber wall temperature sensor, 61 winding temperature sensor, 70 control device.

Claims (4)

A low-stage compression unit, a high-stage compression unit, a two-stage compressor having a motor that drives these compression units, a condenser, and a refrigerant circuit in which a refrigerant circulates, and a decompressor.
A pipe that branches a part of the refrigerant from the condenser toward the pressure reducing device and forms a refrigerant flow path that supplies the motor chamber in which the motor is installed in the two-stage compressor;
A linear electronic expansion valve provided in the pipe;
An on-off valve provided in the pipe ;
Temperature detecting means for detecting a temperature corresponding to the amount of heat generated by the motor;
A controller for controlling the linear electronic expansion valve so that the temperature detected by the temperature detection means becomes a preset target cooling temperature ,
When the temperature detected by the temperature detecting means is lower than the target cooling temperature even when the linear electronic expansion valve is controlled to the minimum control opening degree, the control device fully closes the on-off valve. refrigerator according to claim <br/> be. It said temperature sensing means, the refrigerator according to claim 1, wherein the detecting the temperature of the wall of the motor chamber. It said temperature sensing means, the refrigerator according to claim 1, wherein the detecting the winding temperature of the motor. The refrigerator according to any one of claims 1 to 3 , wherein the low-stage compression section and the high-stage compression section are both screw-type compression sections.

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