JP5538061B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus equipped with a two-stage screw compressor as one component of a refrigeration cycle.

  Conventionally, there is a refrigeration apparatus equipped with a screw compressor as one component of the refrigeration cycle. As such, “in addition to a single-stage or multi-stage screw compressor, a refrigerant circulation closed passage including at least a condenser, a first expansion valve, and an evaporator is provided. In a screw type refrigerator having a cooling flow path for cooling a driving motor with the refrigerant, the cooling flow path is branched from the circulation closed flow path on the inlet side of the first expansion valve, It was formed by communicating with a gas confined space that does not communicate with the suction port and the discharge port of the screw compressor that passes through the motor through the expansion valve, passes through the motor, and sends the refrigerant to the condenser. '' A screw-type refrigeration apparatus has been proposed (see, for example, Patent Document 1).

  The two-stage screw refrigeration apparatus is a refrigerant including at least a condenser, a first expansion valve, and an evaporator in addition to the two-stage screw compressor, like the screw refrigeration apparatus shown in FIG. In general, a configuration is provided that includes a closed flow path and a flow path for cooling a motor that drives the two-stage screw compressor using a high-pressure refrigerant. In addition, like this two-stage screw refrigeration system, the refrigerant used for cooling the motor of the two-stage screw compressor is cooled and injected into the high-pressure stage compression chamber or into the high-pressure stage suction section. It has become common to do.

Japanese Patent Application Laid-Open No. 07-180917 (pages 2, 3 and 1)

  In the two-stage screw refrigeration apparatus as described in Patent Document 1, the refrigerant used for motor cooling is injected into the compression chamber of the high-pressure stage, or is injected into the high-pressure stage suction section. When the two-stage screw compressor is operated under a low differential pressure operating condition where the differential pressure between the high pressure and the low pressure is small, an overcompressed state occurs. That is, the high stage suction part pressure becomes higher than the high pressure of the high stage discharge part. Under such operating conditions, the motor cooling refrigerant does not flow, the motor overheats, and the operation cannot be continued.

  Therefore, in order to operate under such operating conditions, operation control is performed to lower the injection position pressure of the refrigerant for cooling the motor by using the low-pressure stage compressor as an unloader. However, when such operation control is performed, there is a problem in that the refrigeration function force under low differential pressure operation conditions is reduced.

  The present invention has been made to solve the above problems, and can sufficiently perform motor cooling even under operating conditions in which it is determined that the motor has not been sufficiently cooled. An object of the present invention is to provide a refrigeration apparatus equipped with a two-stage screw compressor capable of continuing operation without reducing the refrigeration function.

The refrigeration apparatus according to the present invention includes a two-stage screw compressor having a low-pressure stage-side screw compression mechanism section and a high-pressure stage-side screw compression mechanism section, a housing casing for a motor that drives the two-stage screw compressor, and the two-stage A condenser into which refrigerant discharged from the screw compressor flows in, a first expansion valve that decompresses the refrigerant that flows out from the condenser, and an evaporator into which the refrigerant decompressed by the first expansion valve flows in are connected by piping. A closed circuit, a first flow path connecting the condenser and the first expansion valve, and a storage casing of the motor via a second expansion valve; a storage casing of the motor and the high pressure stage side A second flow path that connects the compression chamber of the screw compression mechanism section of the motor, and a third flow path that connects the housing casing of the motor and the suction section of the screw compression mechanism section on the low-pressure stage side. The solenoid valve provided in each of the second flow path and the third flow path, based on a differential pressure between high pressure and low pressure of the circulating closed circuit, by controlling the opening and closing of the electromagnetic valves, the motor wherein the flow of the cooling refrigerant high pressure stage side of the screw compression unit of compression chambers, or, characterized in that you switch the suction portion of the screw compressor mechanism section of the low pressure stage.

  According to the refrigeration apparatus according to the present invention, a refrigerant circuit that injects into the low-pressure stage side screw compression mechanism is configured under an operating condition in which it is determined that the motor is not sufficiently cooled, and the flow of the refrigerant is controlled. Therefore, even under such conditions, the motor cooling refrigerant is sufficiently injected into the motor, and the motor can be sufficiently cooled. Therefore, according to the refrigeration apparatus according to the present invention, the operation can be continued without reducing the refrigeration capacity.

It is a schematic circuit block diagram which shows the refrigerant circuit structure of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a schematic circuit block diagram which shows the refrigerant circuit structure of the freezing apparatus which concerns on Embodiment 2 of this invention. It is a schematic circuit block diagram which shows the refrigerant circuit structure of the freezing apparatus which concerns on Embodiment 3 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1.
FIG. 1 is a schematic circuit configuration diagram showing a refrigerant circuit configuration of a refrigeration apparatus 100 according to Embodiment 1 of the present invention. Based on FIG. 1, the structure and operation | movement of the freezing apparatus 100 are demonstrated. The refrigeration apparatus 100 according to Embodiment 1 is a screw refrigeration apparatus equipped with a two-stage screw compressor 50 as one component of the refrigeration cycle. The refrigeration apparatus 100 is used as, for example, a refrigerated warehouse, a frozen warehouse, a freezer, or the like. In addition, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one.

  The refrigeration apparatus 100 includes, as component devices, a low-pressure stage screw compression mechanism 1, a high-pressure stage screw compression mechanism 2, a condenser 3, a first expansion valve 4, an evaporator 5, a second expansion valve 7, and a motor. 8, a solenoid valve 11 and a solenoid valve 13 are provided. Further, the refrigeration apparatus 100 includes a closed circulation circuit (refrigerant circuit) 6, a cooling flow path (first flow path) 9, a cooling flow path (second flow path) 10, and a cooling flow path (first flow path). 3 flow paths) 12 are formed. The low-pressure stage screw compression mechanism 1 and the high-pressure stage screw compression mechanism 2 constitute a two-stage screw compressor. In the first embodiment, the two-stage screw compressor 50 and the motor 8 are integrally provided in a semi-sealed casing.

  The circulation closed circuit 6 circulates the refrigerant by connecting the low pressure stage screw compression mechanism 1, the high pressure stage screw compression mechanism 2, the condenser 3, the first expansion valve 4, and the evaporator 5 by piping. It is configured as possible. The cooling channel 9 is branched from the circulation closed circuit 6 on the inlet side of the first expansion valve 4 (between the condenser 3 and the first expansion valve 4), passes through the second expansion valve 7, and passes through the motor 8 (details). Is configured to reach the storage casing of the motor 8. The cooling flow path 10 is configured to allow the refrigerant that has passed through the motor 8 to communicate with the compression chamber of the screw compression mechanism 2 on the high-pressure stage side. The cooling flow path 12 is configured to allow the refrigerant branched from the cooling flow path 10 to pass through the motor 8 to communicate with the suction portion of the screw compression mechanism portion 1 on the low pressure stage side.

  The low-pressure stage side screw compression mechanism 1 sucks low-pressure refrigerant, compresses the refrigerant, and conveys the refrigerant to the high-pressure stage screw compression mechanism 2. The high-pressure stage-side screw compression mechanism 2 sucks the refrigerant discharged from the low-pressure stage-side screw compression mechanism 1, compresses the refrigerant, and conveys the refrigerant to the condenser 3. The condenser 3 performs heat exchange between a heat medium (not shown) (for example, air, water, brine, and the like) and a refrigerant flowing in the circulation closed circuit 6. The first expansion valve 4 is for decompressing and expanding the refrigerant flowing through the circulation closed circuit 6, and may be constituted by a valve whose opening degree can be variably controlled, for example, an electronic expansion valve.

  The evaporator 5 performs heat exchange between a heat medium (not shown) (for example, air, water, brine, and the like) and a refrigerant flowing in the circulation closed circuit 6. The second expansion valve 7 is provided in the cooling flow path 9 and expands the refrigerant flowing through the cooling flow path 9 by depressurizing it. The opening degree of the second expansion valve 7 can be controlled variably, such as an electronic expansion valve. It is good to comprise. The motor 8 drives the screw compression mechanism 1 on the low pressure stage side and the screw compression mechanism 2 on the high pressure stage side. As described above, the motor 8 is provided in a semi-sealed casing (storage casing) integrally with the two-stage screw compressor 50.

  The electromagnetic valve 11 is provided in the cooling flow path 10 and opens and closes the cooling flow path 10 by controlling opening and closing. The electromagnetic valve 13 is provided in the cooling flow path 12 and opens and closes the cooling flow path 12 by controlling the opening and closing thereof. The electromagnetic valve 11 and the electromagnetic valve 13 are opened and closed by a control device (not shown) that performs overall control of the operation of the refrigeration apparatus 100.

  The control device (not shown) is configured by a microcomputer or the like, and a blower is provided in the vicinity of various actuators (for example, the motor 8, the condenser 3, and the evaporator 5) based on instructions from a remote controller or the like. In that case, the blower, the electromagnetic valve 11, the electromagnetic valve 13, etc.) are controlled to adjust the flow of the refrigerant.

  The refrigeration apparatus 100 is provided with a temperature sensing cylinder 14 and a temperature sensing cylinder 15. The temperature sensing cylinder 14 is provided in the circulation closed circuit 6 on the outlet side of the evaporator 5 (between the evaporator 5 and the screw compression mechanism 1 on the low pressure stage side), and detects the temperature and pressure at that location. The opening degree of the first expansion valve 4 is adjusted so that the degree of superheat in the section becomes constant. The temperature sensing cylinder 15 is provided in the cooling flow path 10 between the motor 8 and the two-stage screw compressor 50, and detects the temperature and pressure at that location so that the degree of superheat at the detection unit becomes constant. The opening degree of the second expansion valve 7 is adjusted.

The operation of the refrigeration apparatus 100 will be described.
When electric power is supplied to the motor 8, the two-stage screw compressor 50 starts operation. When the two-stage screw compressor 50 starts operation, the refrigerant flowing through the closed circuit 6 is sucked into the low-pressure stage-side screw compression mechanism 1. This refrigerant is discharged after being compressed by the screw compression mechanism 1 on the low-pressure stage side. The refrigerant discharged from the low-pressure stage screw compression mechanism 1 is sucked into the high-pressure stage screw compression mechanism 2. This refrigerant is discharged after being compressed by the screw compression mechanism 2 on the high-pressure stage side.

  The refrigerant discharged from the high-pressure stage side screw compression mechanism 2 flows into the condenser 3. The refrigerant flowing into the condenser 3 is condensed while releasing heat to the heat medium. A part of the refrigerant flowing out of the condenser 3 is decompressed by the first expansion valve 4. The refrigerant flowing out of the first expansion valve 4 flows into the evaporator 5 and is evaporated while absorbing heat from the heat medium. The refrigerant that has flowed out of the evaporator 5 is again sucked into the two-stage screw compressor 50. On the other hand, the remaining part of the refrigerant flowing out of the condenser 3 flows into the cooling flow path 9 and is decompressed by the second expansion valve 7. The refrigerant that has flowed out of the second expansion valve 7 flows into the storage casing of the motor 8, cools the motor 8, and then flows out of the storage casing of the motor 8.

  The refrigerant that has flowed out of the housing casing of the motor 8 flows into the cooling flow path 10 and is divided into a refrigerant that flows through the cooling flow path 12 according to the cooling of the motor 8 and a refrigerant that flows through the cooling flow path 10 as it is. Is done. In the refrigeration apparatus 100, during normal operation, the electromagnetic valve 11 is controlled to be open and the electromagnetic valve 13 is closed. However, during operation under a low differential pressure condition where the motor 8 cannot be sufficiently cooled (a condition where the differential pressure between the high pressure and the low pressure is small), in the refrigeration apparatus 100, the electromagnetic valve 11 is closed and the electromagnetic valve 13 is opened. Be controlled. That is, the refrigeration apparatus 100 controls the solenoid valve 11 to be opened and the solenoid valve 13 to be closed during normal operation, but the differential pressure between the high pressure and the low pressure is more than a predetermined value that assumes that the motor 8 cannot be sufficiently cooled. When it becomes smaller, the flow of the refrigerant is switched by closing the electromagnetic valve 11 and opening the electromagnetic valve 13.

  As described above, the refrigeration apparatus 100 has a flow path for injecting into the suction section of the screw compression mechanism section 1 on the low pressure stage side in addition to the flow path (second flow path) for injecting the refrigerant that has cooled the motor 8 into the conventional position. (Third flow path) is additionally provided, and the refrigerant injection destination used for cooling the motor 8 under the low differential pressure condition where the motor 8 cannot be sufficiently cooled is changed from the conventional position to the screw compression mechanism 1 on the low pressure stage side. It is possible to switch to the suction part and operate.

  Therefore, in the refrigeration apparatus 100, a refrigerant circuit that injects the refrigerant used for cooling the motor 8 into the screw compression mechanism 1 on the low-pressure stage side under the low differential pressure condition and controls the flow of the refrigerant. Even under the low differential pressure condition, the refrigerant for cooling the motor 8 is sufficiently injected into the motor 8, and the motor 8 can be sufficiently cooled. Thereby, in the refrigeration apparatus 100, the operation of the two-stage screw compressor 50 can be performed without unloading the screw compression mechanism 1 on the low-pressure stage side and reducing the refrigeration capacity even under a low differential pressure condition. Can continue.

Embodiment 2. FIG.
FIG. 2 is a schematic circuit configuration diagram showing a refrigerant circuit configuration of a refrigeration apparatus 100a according to Embodiment 2 of the present invention. Based on FIG. 2, the structure and operation | movement of the freezing apparatus 100a are demonstrated. The refrigeration apparatus 100a according to Embodiment 2 is a screw refrigeration apparatus equipped with a two-stage screw compressor 50 as one component of the refrigeration cycle. This refrigeration apparatus 100a is used, for example, as a refrigerated warehouse, a frozen warehouse, a freezer, or the like. In the second embodiment, differences from the first embodiment will be mainly described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The refrigeration apparatus 100 a is provided with a temperature sensor 16 for detecting the cooling state of the motor 8. The temperature sensor 16 is attached at a position where the temperature of the motor 8 can be detected. The temperature detected by the temperature sensor 16 is sent to a control device (not shown) that performs overall control of the operation of the refrigeration apparatus 100. The control device controls the opening and closing of the solenoid valve 11 and the solenoid valve 13 based on the temperature information sent from the temperature sensor 16.

  In the refrigeration apparatus 100a, the solenoid valve 11 is controlled to be opened and the solenoid valve 13 is controlled to be closed during normal operation. However, during operation under conditions where the motor 8 cannot be sufficiently cooled (conditions where the temperature detected by the temperature sensor 16 is greater than a predetermined value set in advance), the refrigeration apparatus 100 closes the solenoid valve 11. The electromagnetic valve 13 is controlled to open. That is, the refrigeration apparatus 100 controls the solenoid valve 11 to open and the solenoid valve 13 to be closed during normal operation, but the temperature detected by the temperature sensor 16 is higher than a predetermined value that assumes that the motor 8 cannot be sufficiently cooled. In the case where the pressure increases, the flow of the refrigerant is switched by closing the electromagnetic valve 11 and controlling the electromagnetic valve 13 to open.

  As described above, the refrigeration apparatus 100a has a flow path for injecting the refrigerant having cooled the motor 8 into the suction section of the screw compression mechanism 1 on the low pressure stage side in addition to the flow path (second flow path) for injecting the refrigerant into the conventional position. (Third flow path) is additionally provided, and the refrigerant injection destination used for cooling the motor 8 under the low differential pressure condition where the motor 8 cannot be sufficiently cooled is changed from the conventional position to the screw compression mechanism 1 on the low pressure stage side. It is possible to switch to the suction part and operate.

  Therefore, in the refrigeration apparatus 100a, a refrigerant circuit that injects into the screw compression mechanism unit 1 on the low-pressure stage side is configured under an operating condition in which it is determined that the motor 8 is not sufficiently cooled, and the refrigerant flow is controlled. Therefore, even under such conditions, the coolant for cooling the motor 8 is sufficiently injected into the motor 8, and the motor 8 can be sufficiently cooled. As a result, in the refrigeration apparatus 100a, the screw compression mechanism 1 on the low-pressure stage side is unloaded even under conditions where the motor 8 is not sufficiently cooled, that is, under conditions where the temperature of the motor 8 exceeds a predetermined value. The operation of the two-stage screw compressor 50 can be continued without reducing the refrigerating capacity without using a loader.

Embodiment 3 FIG.
FIG. 3 is a schematic circuit configuration diagram showing a refrigerant circuit configuration of a refrigeration apparatus 100b according to Embodiment 3 of the present invention. The configuration and operation of the refrigeration apparatus 100b will be described based on FIG. The refrigeration apparatus 100b according to Embodiment 3 is a screw refrigeration apparatus equipped with a two-stage screw compressor 50 as one component of the refrigeration cycle. This refrigeration apparatus 100b is used, for example, as a refrigerated warehouse, a frozen warehouse, a freezer, or the like. In the third embodiment, differences from the first and second embodiments will be mainly described, and the same parts as those in the first and second embodiments will be denoted by the same reference numerals and the description thereof will be omitted. It shall be.

  In the first embodiment and the second embodiment, the example in which the refrigerant injection destination used for cooling the motor 8 is switched using two electromagnetic valves (the electromagnetic valve 11 and the electromagnetic valve 13) has been described. In the third embodiment, an example in which the injection destination of the refrigerant used for cooling the motor 8 is switched using one three-way electromagnetic valve 17 will be described. That is, the refrigeration apparatus 100 b is provided with the three-way electromagnetic valve 17 without providing the electromagnetic valve 11 and the electromagnetic valve 13. The three-way solenoid valve 17 is provided at a connection portion between the cooling flow path 10 and the cooling flow path 12.

  In the three-way solenoid valve 17, one of the three sides is connected to the housing casing of the motor 8 via the cooling flow path 10, and one of the three directions is connected to the screw compression mechanism portion 2 on the high-pressure stage side via the cooling flow path 10. One of the three sides is connected to the suction portion of the screw compression mechanism portion 1 on the low pressure stage side via the cooling flow path 12. Therefore, the three-way solenoid valve 17 allows the refrigerant used for cooling the motor 8 to be injected into the screw compression mechanism unit 2 on the high-pressure stage side via the cooling channel 10 by switching the refrigerant channel. The refrigerant used for cooling the motor 8 is injected into the screw compression mechanism 1 on the low pressure stage side through the cooling flow path 12.

  In the refrigeration apparatus 100b, during normal operation, the three-way solenoid valve 17 is operated so that the refrigerant used for cooling the motor 8 is injected into the screw compression mechanism unit 2 on the high-pressure stage side. However, during operation under conditions in which the motor 8 cannot be sufficiently cooled (low differential pressure conditions or conditions in which the temperature detected by the temperature sensor 16 is greater than a predetermined value set in advance) The three-way solenoid valve 17 is operated so that the refrigerant used for cooling the motor 8 is injected into the suction side of the screw compression mechanism 1 on the low pressure stage side.

  As described above, the refrigeration apparatus 100b has a flow path for injecting into the suction portion of the screw compression mechanism section 1 on the low pressure stage side in addition to the flow path (second flow path) for injecting the refrigerant that has cooled the motor 8 into the conventional position. (Third flow path) is additionally provided, and the refrigerant injection destination used for cooling the motor 8 under the low differential pressure condition where the motor 8 cannot be sufficiently cooled is changed from the conventional position to the screw compression mechanism 1 on the low pressure stage side. It is possible to switch to the suction part and operate.

  Therefore, in the refrigeration apparatus 100b, a refrigerant circuit that injects into the screw compression mechanism unit 1 on the low-pressure stage side is configured under an operating condition in which it is determined that the motor 8 is not sufficiently cooled, and the refrigerant flow is controlled. Therefore, even under such conditions, the coolant for cooling the motor 8 is sufficiently injected into the motor 8, and the motor 8 can be sufficiently cooled. Thereby, in the refrigeration apparatus 100b, even if the motor 8 is not sufficiently cooled (for example, a low differential pressure condition or a condition in which the temperature of the motor 8 is higher than a predetermined value), The operation of the two-stage screw compressor 50 can be continued without unloading the screw compression mechanism 1 and without reducing the refrigeration capacity.

  Further, in comparison with the refrigeration apparatus according to the first and second embodiments, in the refrigeration apparatus 100b according to the third embodiment, the number of parts can be reduced by reducing the number of solenoid valves from two to one. Cost can be reduced.

  Although the embodiments of the refrigeration apparatus according to the present invention have been described with different configurations, the refrigeration apparatus may be configured by appropriately combining the features of the embodiments. If the embodiments are appropriately combined, the effects of the features of the embodiments can be obtained in a superimposed manner.

  DESCRIPTION OF SYMBOLS 1 Screw compression mechanism part of low pressure stage side 2 Screw compression mechanism part of high pressure stage side 3 Condenser, 4 First expansion valve, 5 Evaporator, 6 Circulation closed circuit, 7 Second expansion valve, 8 Motor, 9 Cooling Flow path (first flow path), 10 Cooling flow path (second flow path), 11 Solenoid valve, 12 Cooling flow path (third flow path), 13 Solenoid valve, 14 Temperature sensing cylinder, 15 Temperature sensing Cylinder, 16 temperature sensor, 17 three-way solenoid valve, 50 two-stage screw compressor, 100 refrigeration apparatus, 100a refrigeration apparatus, 100b refrigeration apparatus.

Claims (2)

A two-stage screw compressor having a low-pressure stage screw compression mechanism and a high-pressure stage screw compression mechanism, a housing casing for a motor that drives the two-stage screw compressor, and a refrigerant discharged from the two-stage screw compressor A condenser into which the refrigerant flows out, a first expansion valve that depressurizes the refrigerant that has flowed out of the condenser, and a closed circuit that pipes an evaporator into which the refrigerant decompressed by the first expansion valve flows, and
A first flow path connecting the condenser and the first expansion valve and a housing casing of the motor via a second expansion valve;
A second flow path connecting the housing casing of the motor and the compression chamber of the high-pressure stage side screw compression mechanism;
A third flow path connecting the housing casing of the motor and the suction portion of the screw compression mechanism on the low-pressure stage side,
An electromagnetic valve is provided in each of the second flow path and the third flow path,
Based on the differential pressure between the high pressure and the low pressure of the closed circuit, the flow of the refrigerant that has cooled the motor is controlled by opening and closing each solenoid valve, or the compression chamber of the screw compression mechanism section on the high-pressure stage side, or the refrigeration system, characterized in that you switch the suction portion of the screw compressor mechanism section of the low pressure stage. Connecting the second flow path and the third flow path via a three-way solenoid valve;
By controlling the three-way solenoid valve, the flow of refrigerant to cool the motor high pressure stage side of the screw compression unit of compression chambers, or, it you switch the suction portion of the screw compressor mechanism section of the low pressure stage side The refrigeration apparatus according to claim 1 .

Images