WO2022264345A1

WO2022264345A1 - Refrigeration cycle device

Info

Publication number: WO2022264345A1
Application number: PCT/JP2021/022981
Authority: WO
Inventors: 克也前田; 光晃松尾; 雅章上川
Original assignee: 三菱電機株式会社
Priority date: 2021-06-17
Filing date: 2021-06-17
Publication date: 2022-12-22

Abstract

In this refrigeration cycle device, a compressor, an oil separator, a condenser, a first expansion valve, and an evaporator are cyclically connected by first refrigerant piping, and a refrigerant circulates through the refrigeration cycle device, wherein: the refrigeration cycle device comprises second refrigerant piping that is connected to the compressor and that branches from the first refrigerant piping between the condenser and the first expansion valve, oil piping that is connected to the oil separator and the compressor and that has flowing therethrough oil separated by the separator, an oil cooler that is provided to the second piping, that cools the oil flowing through the oil piping by using the refrigerant flowing through the second refrigerant piping, and that discharges to the compressor, a second expansion valve that is provided in the second refrigerant piping between the condenser and the oil cooler, a discharge temperature sensor that is provided in the first refrigerant piping on the discharge side of the compressor, and a control device that controls the second expansion valve; the control device controls the aperture of the second expansion valve such that the discharge temperature of the compressor based on the result of detection by the discharge temperature sensor reaches a temperature within a predetermined temperature range; the temperature range has a first threshold value as an upper-limit value and has a second threshold value as a lower-limit value; and the first threshold value is a temperature that is lower, by a predetermined first set temperature, than a protection threshold value serving as a reference for stopping the compressor when reached by the discharge temperature.

Description

refrigeration cycle equipment

The present disclosure relates to a refrigeration cycle device including a compressor.

In a refrigeration cycle device, if the discharge gas temperature of the compressor rises excessively, the lubricating oil may deteriorate and damage the resin parts that make up the compressor. Therefore, in order to control the temperature of the discharge gas of the compressor to the allowable upper limit, there is known a method of lowering the temperature of the refrigerant gas during compression using cooled lubricating oil. Patent Literature 1 discloses a refrigeration cycle device that cools lubricating oil by causing refrigerant sent from a condenser to flow through an oil cooling mechanism provided inside a compressor.

JP 2013-253734 A

However, in the refrigeration cycle device of Patent Document 1, the internal structure of the compressor is complicated because the oil cooling mechanism is provided inside the compressor.

The present disclosure has been made to solve the above problems, and simplifies the structure of the compressor in the refrigeration cycle device.

A refrigeration cycle device according to the present disclosure is a refrigeration cycle device in which a compressor, an oil separator, a condenser, a first expansion valve, and an evaporator are annularly connected by a first refrigerant pipe and a refrigerant circulates, A second refrigerant pipe branched from between the condenser and the first expansion valve in the first refrigerant pipe and connected to the compressor, an oil separator and the compressor, and the oil separated by the oil separator a flowing oil pipe, an oil cooler provided in the second refrigerant pipe for cooling the oil flowing through the oil pipe with the refrigerant flowing through the second refrigerant pipe and sending the oil to the compressor, and a condenser and the oil in the second refrigerant pipe. a second expansion valve provided between the cooler, a discharge temperature sensor provided on the discharge side of the compressor in the first refrigerant pipe, and a control device for controlling the second expansion valve; controls the degree of opening of the second expansion valve so that the discharge temperature of the compressor based on the detection result of the discharge temperature sensor is within a predetermined temperature range, and the temperature range has the first threshold as the upper limit. A second threshold is a lower limit value, and the first threshold is a temperature lower than a predetermined first set temperature than a protection threshold that serves as a reference for stopping the compressor when the discharge temperature reaches.

In the present disclosure, the control device controls the opening of the second expansion valve provided between the condenser and the oil cooler, thereby controlling the discharge temperature of the compressor to a temperature within a predetermined temperature range. be done. Thus, in the refrigeration cycle apparatus of the present disclosure, in order to control the discharge temperature of the compressor, it is not necessary to provide a mechanism for cooling the lubricating oil inside the compressor, thereby simplifying the structure of the compressor. can be done.

1 is a circuit diagram showing refrigeration cycle apparatus 1 according to Embodiment 1. FIG. 2 is a functional block diagram showing control device 40 according to Embodiment 1. FIG. 4 is a flow chart showing a control method of the second expansion valve 11 based on discharge temperature according to Embodiment 1. FIG. 4 is a flow chart showing a method of controlling the third expansion valve 13 based on the temperature of the motor 23 according to Embodiment 1. FIG. FIG. 5 is a circuit diagram showing a refrigeration cycle apparatus 1A according to Embodiment 2; FIG. 10 is a functional block diagram showing a control device 40 according to Embodiment 2; FIG. 8 is a flow chart showing a control method of the second expansion valve 11 based on the discharge temperature according to Embodiment 2. FIG. FIG. 11 is a circuit diagram showing a refrigeration cycle device 1B according to Embodiment 3; FIG. 11 is a functional block diagram showing a control device 40 according to Embodiment 3; 10 is a flow chart showing a method of controlling the second expansion valve 11 based on the discharge temperature and the oil temperature according to Embodiment 3. FIG.

Embodiment 1.
Embodiments of the present disclosure will be described below with reference to the drawings. Here, in the following drawings, the same reference numerals denote the same or corresponding parts, and are common throughout the embodiments described below. In addition, the forms of the components shown in the entire specification are merely examples and are not limited to these descriptions. In particular, combinations of constituent elements are not limited to combinations in each embodiment, and constituent elements described in other embodiments can be appropriately applied to other embodiments. It is assumed that the level of the temperature is not determined in relation to an absolute value, but is relatively determined by the state, operation, etc. of the system, device, or the like.

FIG. 1 is a circuit diagram showing a refrigeration cycle device 1 according to Embodiment 1. FIG. As shown in FIG. 1, the refrigeration cycle device 1 includes a first refrigerant pipe 2, a second refrigerant pipe 3, a third refrigerant pipe 4, an oil pipe 5, a compressor 6, an oil separator 7, a condenser 8, a first An expansion valve 9 , an evaporator 10 , a second expansion valve 11 , an oil cooler 12 and a third expansion valve 13 are provided.

The first refrigerant pipe 2 annularly connects the compressor 6, the oil separator 7, the condenser 8, the first expansion valve 9, and the evaporator 10. The second refrigerant pipe 3 branches from between the condenser 8 and the first expansion valve 9 in the first refrigerant pipe 2, and passes through the second expansion valve 11 and the refrigerant flow path side of the oil cooler 12, which will be described later. It is connected to the intermediate pressure chamber 25 of the compressor 6 . The third refrigerant pipe 4 branches from between the condenser 8 and the first expansion valve 9 in the first refrigerant pipe 2, and is connected to the motor chamber 24 of the compressor 6, which will be described later, via the third expansion valve 13. ing.

A refrigerant circuit is configured by the first refrigerant pipe 2, the second refrigerant pipe 3, the third refrigerant pipe 4, and the devices to which the first refrigerant pipe 2, the second refrigerant pipe 3, and the third refrigerant pipe 4 are connected. , the refrigerant circulates in the refrigerant circuit. As the refrigerant, for example, an HFC refrigerant such as R410A or an HFO mixed refrigerant such as R448A or R449A is used.

The oil pipe 5 is connected from the oil separator 7 to a low-stage compression section 21 and a high-stage compression section 22 of the compressor 6, which will be described later, via the oil flow path side of the oil cooler 12. An oil supply path is configured by the oil pipe 5 , the oil separator 7 , and the oil cooler 12 . The lubricating oil separated from the refrigerant by the oil separator 7 flows through the oil supply path through the oil separator 7, the oil cooler 12, and the compressor 6 in this order. The lubricating oil is supplied to the compressor 6 for the purpose of lubricating each part of the compressor 6, cooling the parts, or the like. For the lubricating oil, for example, polyol ester oil (POE) is used when an HFC refrigerant is used, and polyvinyl ether oil (PVE) is used in addition to polyol ester oil (POE) when an HFO mixed refrigerant is used. .

The compressor 6 is, for example, a two-stage screw compressor, which sucks in low-temperature and low-pressure refrigerant, compresses the sucked refrigerant, converts it into high-temperature and high-pressure refrigerant, and discharges it. The compressor 6 has a low stage compression section 21 , a high stage compression section 22 and a motor 23 . The low-stage compression section 21 compresses the sucked refrigerant from low pressure to intermediate pressure. The high-stage compression section 22 further compresses the refrigerant compressed by the low-stage compression section 21 from intermediate pressure to high pressure. A motor 23 is connected in series with the low-stage compression section 21 and the high-stage compression section 22 to rotationally drive them. Also, the motor 23 is controlled by, for example, an inverter (not shown). The motor 23 has a motor frame 23a as an outer shell and is housed in a motor chamber 24. As shown in FIG. Between the low stage compression section 21 and the high stage compression section 22, an intermediate pressure chamber 25 is formed through which refrigerant that is being compressed flows.

The compressor 6 includes, for example, an insulator of the motor 23, an insulating sleeve, a coating of wiring, a bearing holding portion, and parts for forming a compression chamber together with the screw rotor in the gate rotor (none of them are shown) made of resin. Consists of parts. As the resin member, all or part of PPS resin, polyamide resin, epoxy resin, aramid resin, fluorine resin, polyethylene terephthalate resin, or polyester resin is used. The heat resistance temperature of these resin members is generally around 100°C. For example, the heat resistance temperature of polyamide resin is about 90°C, the heat resistance temperature of epoxy resin is about 150°C, and the heat resistance temperature of polyester resin is about 130°C.

The oil separator 7 separates lubricating oil from the refrigerant discharged from the compressor 6 . The oil separator 7 may be either demister type or cyclone type. The condenser 8 exchanges heat between the refrigerant and the outside air to condense the refrigerant. The first expansion valve 9 is provided between the condenser 8 and the evaporator 10 in the refrigerant circuit. The first expansion valve 9 decompresses and expands the refrigerant, and is, for example, an electronic expansion valve whose opening degree can be variably controlled. The evaporator 10 exchanges heat between the refrigerant and the outside air to evaporate the refrigerant.

The second expansion valve 11 is provided between the branched portion of the second refrigerant pipe 3 from the first refrigerant pipe 2 and the oil cooler 12 . The second expansion valve 11 decompresses and expands the refrigerant, and is, for example, an electronic expansion valve whose opening degree can be variably controlled. The oil cooler 12 is provided between the second expansion valve 11 and the compressor 6 in the second refrigerant pipe 3 and between the oil separator 7 and the compressor 6 in the oil pipe 5 . The oil cooler 12 is connected to the second refrigerant pipe 3 and has a refrigerant channel through which the refrigerant flows, and an oil channel connected to the oil pipe 5 and through which lubricating oil flows. The oil cooler 12 performs heat exchange between the refrigerant flowing through the refrigerant channel and the lubricating oil flowing through the oil channel to cool the lubricating oil. Oil cooler 12 delivers cooled oil to compressor 6 .

The third expansion valve 13 is provided between the branched portion of the third refrigerant pipe 4 from the first refrigerant pipe 2 and the compressor 6 . The third expansion valve 13 decompresses and expands the refrigerant, and is, for example, an electronic expansion valve whose opening degree can be variably controlled.

Here, the operation of the refrigeration cycle device 1 and the flow of refrigerant and lubricating oil will be described. First, refrigerant compressed in the low-stage compression section 21 of the compressor 6 passes through the intermediate pressure chamber 25 and is further compressed in the high-stage compression section 22 before being discharged from the high-stage compression section 22 . The refrigerant discharged from the high-stage compression section 22 is separated into gas refrigerant and lubricating oil by the oil separator 7 , and the gas refrigerant flows into the condenser 8 . The gas refrigerant that has flowed into the condenser 8 is condensed into liquid refrigerant and sent to the first expansion valve 9 . The liquid refrigerant that has flowed into the first expansion valve 9 is decompressed and expanded into a low-pressure wet gas state and sent to the evaporator 10 . The refrigerant sent to the evaporator 10 exchanges heat with air, evaporates into a gaseous state, and flows into the compressor 6 .

Also, part of the liquid refrigerant condensed by the condenser 8 flows into the second refrigerant pipe 3 , is decompressed by the second expansion valve 11 , expands, and is sent to the oil cooler 12 . The refrigerant sent to the oil cooler 12 exchanges heat with the lubricating oil flowing through the oil passage, becomes gaseous, and flows into the intermediate pressure chamber 25 of the compressor 6 .

On the other hand, the high-temperature lubricating oil separated from the gas refrigerant in the oil separator 7 is cooled by exchanging heat with the refrigerant flowing through the refrigerant flow path in the oil cooler 12, and then the low-stage compression part of the compressor 6 21 and high-stage compression section 22 .

Further, part of the liquid refrigerant condensed in the condenser 8 flows into the third refrigerant pipe 4, is decompressed by the third expansion valve 13, expands, becomes an intermediate pressure saturated wet gas state, and enters the motor chamber. sent to 24. The coolant sent to the motor chamber 24 cools the motor 23 .

The refrigeration cycle device 1 also includes a discharge temperature sensor 31 , a motor temperature sensor 32 and a control device 40 . The discharge temperature sensor 31 is provided on the discharge side of the compressor 6 in the first refrigerant pipe 2 . The discharge temperature sensor 31 is composed of a thermocouple, for example, and detects the temperature state, etc. on the discharge side of the compressor 6 . The discharge temperature sensor 31 outputs detection results to the control device 40 . The motor temperature sensor 32 is mounted on the motor frame 23a. The motor temperature sensor 32 may be provided near the motor 23 and may be built in the motor frame 23 a or the motor 23 . The motor temperature sensor 32 is composed of a thermocouple, for example, and detects the temperature state of the motor 23 or the motor frame 23a. Motor temperature sensor 32 outputs the detection result to control device 40 .

The controller 40 controls the degree of opening of the second expansion valve 11 so that the discharge temperature based on the detection result of the discharge temperature sensor 31 falls within a predetermined temperature range. The discharge temperature is the temperature of gas refrigerant discharged from the compressor 6 . Specifically, the control device 40 increases the opening of the second expansion valve 11 , thereby increasing the amount of refrigerant flowing into the oil cooler 12 . As the amount of refrigerant flowing into the oil cooler 12 increases, the amount of heat exchanged in the oil cooler 12 increases, and the temperature of the lubricating oil supplied to the compressor 6 decreases. As the temperature of the lubricating oil drops, the temperature of the refrigerant gas during compression drops, and finally the discharge temperature of the refrigerant gas discharged from the compressor 6 drops.

Also, the control device 40 reduces the degree of opening of the second expansion valve 11, so that the amount of refrigerant flowing into the oil cooler 12 is reduced. As the amount of refrigerant flowing into the oil cooler 12 decreases, the heat exchange amount in the oil cooler 12 decreases, and the temperature of the lubricating oil supplied to the compressor 6 rises. As the temperature of the lubricating oil rises, the temperature of the refrigerant gas during compression also rises, and finally the discharge temperature of the refrigerant gas discharged from the compressor 6 rises.

In addition, the control device 40 controls the inverter and adjusts the operating frequency of the compressor 6 so that the discharge temperature reaches a predetermined temperature. Specifically, the discharge temperature is raised by increasing the operating frequency of the compressor 6 . Also, by reducing the operating frequency of the compressor 6, the discharge temperature is lowered.

In addition, the control device 40 controls the degree of opening of the third expansion valve 13 so that the temperature of the motor 23 based on the detection result of the motor temperature sensor 32 reaches a predetermined temperature. Specifically, the control device 40 increases the degree of opening of the third expansion valve 13 , thereby increasing the amount of refrigerant supplied to the motor chamber 24 . Further, the control device 40 reduces the degree of opening of the third expansion valve 13, so that the amount of refrigerant supplied to the motor chamber 24 is reduced.

The control device 40 is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer or processor) that executes programs stored in dedicated hardware or a storage unit 45 (not shown). called). If the control device 40 is dedicated hardware, the control device 40 may be, for example, a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Applicable. Each functional unit implemented by the control device 40 may be implemented by separate hardware, or each functional unit may be implemented by one piece of hardware.

FIG. 2 is a functional block diagram showing the control device 40 according to the first embodiment. As shown in FIG. 2, the control device 40 has a discharge temperature measurement section 41, a motor temperature measurement section 42, and a control section 43 as functional sections. The control device 40 also has a storage unit 45 .

When the control device 40 is a CPU, each functional unit executed by the control device 40 is implemented by software, firmware, or a combination of software and firmware. Software and firmware are written as programs and stored in the storage unit 45 . The CPU implements each functional unit by reading and executing a program stored in the storage unit 45 . A part of the functions of the control device 40 may be realized by dedicated hardware, and a part thereof may be realized by software or firmware.

The discharge temperature measurement unit 41 measures the discharge temperature based on the detection results from the discharge temperature sensor 31 . The discharge temperature measurement unit 41 communicates the measured discharge temperature to the control unit 43 . A motor temperature measurement unit 42 measures the temperature of the motor 23 based on the detection result of the motor temperature sensor 32 . The motor temperature measurement unit 42 communicates the measured temperature of the motor 23 to the control unit 43 .

The control unit 43 controls the opening degree of the second expansion valve 11 based on the results of comparison between the discharge temperature measured by the discharge temperature measurement unit 41 and the protection threshold, first threshold, second threshold, and third threshold. do. The protection threshold, the first threshold, the second threshold, and the third threshold are determined stepwise for the purpose of both protecting the resin material inside the compressor 6 and maintaining the operating efficiency of the refrigeration cycle device 1. there is The protection threshold is the allowable upper limit of the discharge temperature, and is a reference threshold for stopping the operation of the compressor 6 . The protection threshold is generally determined from within the range of 100°C to 150°C. Here, a case where the protection threshold is set to 100° C. will be described as an example.

The first threshold is a temperature lower than the protection threshold by a predetermined first set temperature. The first preset temperature is set within a range of 10° C. to 20° C., for example. Here, a case where the first preset temperature is set to 20° C., that is, the first threshold is set to 80° C. will be described as an example. The second threshold is a temperature that is a predetermined second set temperature lower than the first threshold. The second preset temperature is set within the range of 5° C. to 10° C., for example. Here, the case where the second set temperature is set to 5° C., that is, the second threshold is set to 75° C. will be described as an example. The third threshold is a temperature lower than the protection threshold by a predetermined third set temperature and lower than the heat resistant temperature of the resin member. The third preset temperature is set within a range of 5° C. to 10° C., for example. Here, a case where the third preset temperature is set to 5° C., that is, the third threshold is set to 95° C. will be described as an example.

The control unit 43 determines whether or not the discharge temperature of the compressor 6 is equal to or higher than the protection threshold. The control unit 43 immediately stops the operation of the compressor 6 in a short time when the discharge temperature is equal to or higher than the protection threshold. As a result, the parts inside the compressor 6 are protected from wear and tear. The controller 43 continues the operation of the compressor 6 when the discharge temperature is less than the protection threshold.

The control unit 43 determines whether or not the ejection temperature is equal to or lower than the first threshold. When the discharge temperature exceeds the first threshold, the control unit 43 increases the degree of opening of the second expansion valve 11 to lower the oil temperature, thereby lowering the discharge temperature.

The control unit 43 determines whether or not the ejection temperature is equal to or higher than the second threshold. When the discharge temperature is less than the second threshold value, the control unit 43 reduces the degree of opening of the second expansion valve 11 to increase the oil temperature, thereby increasing the discharge temperature.

The control unit 43 maintains the opening degree of the second expansion valve 11 when the discharge temperature is equal to or lower than the first threshold and equal to or higher than the second threshold. Thus, the control unit 43 controls the opening degree of the second expansion valve 11 based on the discharge temperature and the result of comparison between the first threshold value and the second threshold value. As a result, the control unit 43 can control the discharge temperature to a temperature within a temperature range determined by setting the first threshold as the upper limit and the second threshold as the lower limit, that is, to a temperature between 75° C. and 80° C. here. can.

The control unit 43 determines whether or not the ejection temperature is equal to or higher than the third threshold. When the discharge temperature is equal to or higher than the third threshold, the controller 43 reduces the frequency of the compressor 6 to reduce the refrigerant flow rate. As a result, even if the suction temperature of the compressor 6 rises sharply, the rise in the discharge temperature is suppressed. This prevents the discharge temperature from reaching the protection threshold.

Also, the control unit 43 controls the opening degree of the third expansion valve 13 based on the results of comparison between the motor temperature measured by the motor temperature measurement unit 42, the first motor threshold value, and the second motor threshold value. The first motor threshold is the upper limit of the motor temperature for the purpose of suppressing abnormal heating of the motor 23 . The first motor threshold is, for example, 70°C. The second motor threshold is the lower limit of the motor temperature for the purpose of suppressing condensation of the motor 23 . The second motor threshold is, for example, 20°C.

The control unit 43 determines whether or not the motor temperature is equal to or lower than the first motor threshold. When the motor temperature exceeds the first motor threshold value, the controller 43 increases the degree of opening of the third expansion valve 13 to increase the amount of refrigerant supplied to the motor chamber 24, thereby lowering the motor temperature.

The control unit 43 determines whether or not the motor temperature is equal to or higher than the second motor threshold. When the motor temperature is less than the second motor threshold value, the control unit 43 decreases the degree of opening of the third expansion valve 13 to decrease the amount of refrigerant supplied to the motor chamber 24, thereby increasing the motor temperature. .

The control unit 43 maintains the opening degree of the third expansion valve 13 when the motor temperature is equal to or lower than the first motor threshold and equal to or higher than the second motor threshold. In this manner, the control unit 43 controls the opening degree of the third expansion valve 13 based on the motor temperature and the result of comparison between the first motor threshold value and the second motor threshold value. Thereby, the controller 43 can control the motor temperature to a temperature between the first motor threshold value and the second motor threshold value, that is, a temperature between 20.degree. C. and 70.degree.

Although the control device 40 also controls the opening of the first expansion valve 9, a conventional method can be applied to that control, so a description thereof will be omitted here.

The storage unit 45 is, for example, nonvolatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM. The storage unit 45 stores, for example, setting information related to control of the refrigeration cycle apparatus 1, such as a protection threshold, a first threshold, a second threshold, and a third threshold. In addition, the storage unit 45 temporarily or continuously stores measurement results such as the discharge temperature and the temperature of the motor 23 .

FIG. 3 is a flow chart showing a control method for the second expansion valve 11 based on the discharge temperature according to the first embodiment. The processing shown in FIG. 3 is performed periodically. First, the controller 43 determines whether or not the ejection temperature is equal to or lower than the first threshold (S1). When the ejection temperature is equal to or lower than the first threshold (S1: YES), the controller 43 determines whether or not the ejection temperature is equal to or higher than the second threshold (S2). If the discharge temperature is equal to or higher than the second threshold (S2: YES), the controller 43 maintains the opening of the second expansion valve 11 (S3). If the discharge temperature is less than the second threshold (S2: NO), the controller 43 reduces the opening of the second expansion valve 11 (S4). This increases the oil temperature and discharge temperature.

When the discharge temperature exceeds the first threshold (S1: NO), the controller 43 increases the opening of the second expansion valve 11 (S5). This lowers the oil temperature and the discharge temperature. After the degree of opening of the second expansion valve 11 is increased, the controller 43 determines whether or not the discharge temperature is equal to or higher than the third threshold (S6). When the discharge temperature is equal to or higher than the third threshold (S6: YES), the controller 43 reduces the operating frequency of the compressor 6 (S7). This lowers the ejection temperature. The control unit 43 repeats the processes of S6 and S7 until the ejection temperature becomes less than the third threshold. When the ejection temperature is less than the threshold (S6: NO), the controller 43 determines again whether the ejection temperature is equal to or lower than the first threshold (S1). The above process is repeated until the discharge temperature becomes equal to or lower than the first threshold value and equal to or higher than the second threshold value, and the opening degree of the second expansion valve 11 is maintained (S3).

FIG. 4 is a flow chart showing a method of controlling the third expansion valve 13 based on the temperature of the motor 23 according to Embodiment 1. FIG. The processing shown in FIG. 4 is performed periodically. First, the control unit 43 determines whether or not the temperature of the motor 23 is equal to or lower than the first motor threshold (S101). When the temperature of the motor 23 is equal to or lower than the first motor threshold (S101: YES), the controller 43 determines whether the temperature of the motor 23 is equal to or higher than the second motor threshold (S102). When the temperature of the motor 23 is equal to or higher than the second motor threshold value (S102: YES), the controller 43 maintains the opening degree of the third expansion valve 13 (S103). When the temperature of the motor 23 is less than the second motor threshold value (S102: NO), the controller 43 reduces the degree of opening of the third expansion valve 13 (S104). As a result, the temperature of the motor 23 rises.

When the temperature of the motor 23 exceeds the first motor threshold (S101: NO), the controller 43 increases the opening of the third expansion valve 13 (S105). As a result, the temperature of the motor 23 is lowered. Then, the control unit 43 determines again whether the temperature of the motor 23 is equal to or lower than the first motor threshold value (S101). The above process is repeated until the temperature of the motor 23 becomes equal to or lower than the first motor threshold value and equal to or higher than the second motor threshold value, and the degree of opening of the third expansion valve 13 is maintained (S103).

As described above, according to Embodiment 1, the control device 40 controls the degree of opening of the second expansion valve 11 provided between the condenser 8 and the oil cooler 12 so that the compressor 6 is controlled within a predetermined temperature range. As described above, in the refrigeration cycle apparatus 1 of Embodiment 1, in order to control the discharge temperature of the compressor 6, it is not necessary to provide a mechanism for cooling the lubricating oil inside the compressor 6. The structure can be simplified.

Also, by simplifying the structure of the compressor 6, it is possible to reduce the design load and reduce the manufacturing cost.

Further, generally, when the discharge temperature of the compressor 6 reaches the protection threshold and the operation of the compressor 6 is stopped, the refrigeration cycle device 1 is stopped until the compressor 6 starts operating again. The operating efficiency of the refrigerating cycle device 1 is lowered. On the other hand, if an attempt is made to maintain the operating efficiency of the refrigeration cycle apparatus 1 by increasing the protection threshold value, wear of the resin material inside the compressor 6 may be accelerated. In particular, with refrigerants such as R410A, R448A, or R449A, whose temperature tends to rise, it has been an important issue to achieve both protection of the resin material inside the compressor 6 and maintenance of the operating efficiency of the refrigeration cycle device 1. . Furthermore, in the case of low-temperature equipment such as air conditioners in distribution warehouses, even a single stoppage of operation has a large effect on stored items in the warehouse. On the other hand, in Embodiment 1, the second expansion valve 11 opening is controlled. As a result, the operation of the refrigeration cycle device 1 can be controlled so that the discharge temperature does not reach the protection threshold while the protection threshold is set to a temperature that does not accelerate the wear of the resin material inside the compressor 6. Therefore, in Embodiment 1, both the protection of the resin material inside the compressor 6 and the maintenance of the operating efficiency of the refrigeration cycle device 1 are achieved.

Further, according to Embodiment 1, an HFC refrigerant may be used as the refrigerant, and a polyol ester oil may be used as the lubricating oil. Then, the control device 40 performs control based on a third threshold lower than the heat-resistant temperature of the resin member. Therefore, it is possible to maintain the operating efficiency of the refrigerating cycle device 1 and to extend the life of the resin member.

Further, according to Embodiment 1, an HFO mixed refrigerant may be used as the refrigerant, and polyol ester oil or polyvinyl ether oil may be used as the lubricating oil. Then, the control device 40 performs control based on a third threshold lower than the heat-resistant temperature of the resin member. Therefore, it is possible to maintain the operating efficiency of the refrigerating cycle device 1 and to extend the life of the resin member.

Also, in general, when the lubricating oil is excessively cooled, the refrigerant gas supplied to the intermediate pressure chamber 25 increases and the intermediate pressure rises. When the intermediate pressure rises excessively, the compression efficiency of the low-stage compression section 21 decreases, and the required electrical input increases. On the other hand, in the first embodiment, the control device 40 sets the second threshold 5° C. to 10° C. lower than the first threshold so that excessive cooling of the lubricating oil can A decrease in compression efficiency and an increase in required electrical input can be suppressed.

Embodiment 2.
FIG. 5 is a circuit diagram showing a refrigeration cycle apparatus 1A according to Embodiment 2. As shown in FIG. As shown in FIG. 5, the refrigeration cycle apparatus 1A has a heater 34. As shown in FIG. The heater 34 is provided in the oil separator 7 and heats the lubricating oil inside the oil separator 7 . In the second embodiment, the same reference numerals are assigned to the same parts as in the first embodiment, and the description thereof is omitted.

FIG. 6 is a functional block diagram showing the control device 40 according to the second embodiment. As shown in FIG. 6, in addition to controlling the discharge temperature and the temperature of the motor 23 described in the first embodiment, the control unit 43 of the control device 40 controls the discharge temperature measured by the discharge temperature measurement unit 41 and the fourth The degree of opening of the second expansion valve 11 is controlled based on the comparison result with the threshold value. A fourth threshold is determined based on the viscosity of the lubricating oil. Specifically, the fourth threshold is set to such an extent that when the discharge temperature becomes equal to or lower than the fourth threshold, the viscosity of the lubricating oil increases and injection into the compressor 6 is prevented by viscous resistance. The fourth threshold is 0° C., for example.

The control unit 43 determines whether or not the ejection temperature is equal to or lower than the fourth threshold. When the discharge temperature is equal to or lower than the fourth threshold, the controller 43 activates the heater 34 to heat the lubricating oil. The controller 43 stops the heater 34 when the ejection temperature exceeds the fourth threshold. However, when the heater 34 is stopped, the controller 43 does not start the heater 34 .

The storage unit 45 stores a fourth threshold in addition to the information described in the first embodiment.

FIG. 7 is a flow chart showing a control method for the second expansion valve 11 based on the discharge temperature according to the second embodiment. The processing shown in FIG. 7 is performed periodically. Since the processes of S1 to S7 are the same as those of the first embodiment, they are omitted. In Embodiment 2, when the control unit 43 reduces the degree of opening of the second expansion valve 11 (S4), it determines whether or not the discharge temperature is equal to or lower than the fourth threshold (S8). If the ejection temperature is equal to or lower than the fourth threshold (S8: YES), the controller 43 activates the heater 34 (S9). Thereby, the lubricating oil inside the oil separator 7 is heated. If the ejection temperature exceeds the fourth threshold (S8: NO), the controller 43 stops or does not start the heater 34 (S10). After controlling the heater 34, the controller 43 again determines whether or not the ejection temperature is equal to or lower than the first threshold (S1). The above process is repeated until the discharge temperature becomes equal to or lower than the first threshold and equal to or higher than the second threshold, and the degree of opening of the second expansion valve 11 is maintained (S3).

As described above, in the refrigeration cycle apparatus 1A of the second embodiment as well, in order to control the discharge temperature of the compressor 6 as in the first embodiment, it is necessary to provide a mechanism for cooling the lubricating oil inside the compressor 6. , the structure of the compressor 6 can be simplified.

Also, in general, when the discharge temperature becomes equal to or lower than the fourth threshold, the lubricating state of the bearings of the compressor 6 deteriorates, and as a result, problems such as accelerated wear or breakage of the bearings may occur. In contrast, in the second embodiment, the heater 34 is activated when the ejection temperature becomes equal to or lower than the fourth threshold. As a result, the state in which the oil temperature is low and the viscosity of the lubricating oil is high is resolved, and the compressor 6 is supplied with oil. Therefore, wear and damage of the bearings are suppressed, and the reliability of the compressor 6 can be kept high.

Embodiment 3.
FIG. 8 is a circuit diagram showing a refrigeration cycle apparatus 1B according to Embodiment 3. As shown in FIG. As shown in FIG. 8, the refrigeration cycle device 1B has an oil temperature sensor 33. As shown in FIG. In the third embodiment, the same reference numerals are assigned to the same parts as in the first embodiment, and the description thereof is omitted.

The oil temperature sensor 33 is provided in the oil separator 7. The oil temperature sensor 33 is composed of a thermocouple, for example, and detects the temperature state of the oil separator 7 and the like. The oil temperature sensor 33 outputs detection results to the control device 40 .

The control device 40 controls the degree of opening of the second expansion valve 11 so that the discharge temperature based on the detection result of the discharge temperature sensor 31 and the oil temperature based on the detection result of the oil temperature sensor 33 reach predetermined temperatures. The oil temperature is the temperature of lubricating oil stored in the oil separator 7 .

FIG. 9 is a functional block diagram showing the control device 40 according to the third embodiment. Control device 40 has an oil temperature measurement section 44 as a functional section in addition to the configuration described in the first embodiment. The oil temperature measuring section 44 measures the oil temperature based on the detection result of the oil temperature sensor 33 .

The control unit 43 controls the opening degree of the second expansion valve 11 based on the results of comparison between the discharge temperature measured by the discharge temperature measurement unit 41 and the protection threshold, first threshold, second threshold, and third threshold. do. Further, the control unit 43 controls the degree of opening of the second expansion valve 11 based on the result of comparing the oil temperature measured by the oil temperature measuring unit 44 with the first oil temperature threshold value and the second oil temperature threshold value. .

The first oil temperature threshold is a temperature that is 5°C to 10°C lower than the second threshold. Here, the case where the first oil temperature threshold is set to 70° C. will be described as an example. The second oil temperature threshold is a temperature lower than the first oil temperature threshold. Here, the oil temperature will be described with an example in which the second oil temperature threshold is set to 35°C.

The control unit 43 determines whether or not the oil temperature is equal to or higher than the first oil temperature threshold. When the oil temperature is equal to or higher than the first oil temperature threshold, the control unit 43 increases the degree of opening of the second expansion valve 11 to lower the oil temperature.

The control unit 43 determines whether or not the oil temperature is equal to or lower than the second oil temperature threshold. When the oil temperature is equal to or lower than the second oil temperature threshold, the control unit 43 reduces the degree of opening of the second expansion valve 11 to raise the oil temperature.

The control unit 43 maintains the degree of opening of the second expansion valve 11 when the oil temperature is less than the first oil temperature threshold and exceeds the second oil temperature threshold. In this manner, the control unit 43 controls the degree of opening of the second expansion valve 11 based on the oil temperature and the result of comparison between the first oil temperature threshold value and the second oil temperature threshold value, thereby reducing the oil temperature. It can be controlled between a first oil temperature threshold and a second oil temperature threshold, here between 35°C and 70°C.

When controlling the degree of opening of the second expansion valve 11 based on the oil temperature, the adjustment unit of the degree of opening is changed from that when controlling the degree of opening of the second expansion valve 11 based on the discharge temperature. may That is, for example, when controlling the degree of opening of the second expansion valve 11 based on the oil temperature, the degree of opening is expanded or enlarged more finely than when controlling the degree of opening of the second expansion valve 11 based on the discharge temperature. You may make it shrink.

In addition to the information described in the first embodiment, the storage unit 45 temporarily or continuously stores the measurement result of the oil temperature.

FIG. 10 is a flow chart showing a control method for the second expansion valve 11 based on the discharge temperature and oil temperature according to the third embodiment. The processing shown in FIG. 10 is performed periodically. Since the processes of S1 to S3 and S5 to S7 are the same as those of the first embodiment, they are omitted. In Embodiment 3, when the discharge temperature is less than the second threshold (S2: NO), the control unit 43 determines whether or not the oil temperature is equal to or higher than the first oil temperature threshold (S11). If the oil temperature is equal to or higher than the first oil temperature threshold (S11: YES), the controller 43 increases the opening of the second expansion valve 11 (S12). This lowers the oil temperature. The processing of S11 and S12 is repeated until the oil temperature becomes less than the first oil temperature threshold.

When the oil temperature is less than the first oil temperature threshold (S11: NO), the control unit 43 determines whether the oil temperature is equal to or less than the second oil temperature threshold (S13). If the oil temperature is equal to or lower than the second oil temperature threshold (S13: YES), the controller 43 reduces the degree of opening of the second expansion valve 11 (S14). The processing from S11 to S14 is repeated until the oil temperature falls below the first oil temperature threshold and exceeds the second oil temperature threshold. When the oil temperature is less than the first oil temperature threshold value and exceeds the second oil temperature threshold value (S13: NO), the control unit 43 determines that the oil temperature has sufficiently decreased while maintaining the minimum allowable temperature. Then, the degree of opening of the second expansion valve 11 is reduced (S15), and it is determined again whether or not the discharge temperature is equal to or lower than the first threshold value (S1). The above process is repeated until the discharge temperature becomes equal to or lower than the first threshold and equal to or higher than the second threshold, and the degree of opening of the second expansion valve 11 is maintained (S3).

As described above, in the refrigeration cycle apparatus 1B of Embodiment 3 as well as in Embodiment 1, in order to control the discharge temperature of the compressor 6, it is necessary to provide a mechanism for cooling the lubricating oil inside the compressor 6. , the structure of the compressor 6 can be simplified.

Also, in general, when the outside air temperature is low, although the discharge temperature is below the second threshold, the oil temperature is high, and high-temperature oil may be supplied to the low-stage compression section 21 . As a result, the deterioration of the bearings of the compressor 6 and seizure of the screw (not shown) of the low-stage compression section 21 may be accelerated. On the other hand, in Embodiment 3, the opening degree of the second expansion valve 11 is controlled based on the result of comparison between the oil temperature and the first and second oil temperature thresholds. As a result, the oil temperature is adjusted to a temperature between the first oil temperature threshold and the second oil temperature threshold. etc. can be suppressed.

The above is the description of the embodiment of the present disclosure, but it is not limited to the configuration of the above embodiment, and various modifications or combinations are possible within the scope of the technical idea. For example, the compressor 6 may be a constant speed machine instead of a form in which the operating frequency is adjusted by control of the inverter. When the compressor 6 is a constant speed machine, for example, a slide valve whose opening degree can be controlled is provided on the suction side of the compressor 6, and the timing of starting compression is changed to perform mechanical capacity control. can be When the discharge temperature is equal to or higher than the third threshold value, the discharge temperature can be lowered by mechanical capacity control as in the first embodiment.

In each embodiment, when the discharge temperature is equal to or higher than the third threshold, the inverter-type capacity control is performed. However, when the discharge temperature is equal to or higher than the third threshold value, even if the opening degree of the second expansion valve 11 is increased and the opening degree of the second expansion valve 11 is fully opened, the discharge temperature does not fall below the third threshold value. , the operating frequency of the compressor 6 may be gradually lowered by an inverter. Further, if the discharge temperature does not fall below the third threshold even with the inverter type capacity control, the mechanical capacity control may be performed. Specifically, for example, if the discharge temperature does not fall below the third threshold value even when the degree of opening of the second expansion valve 11 is fully opened, the inverter reduces the operating frequency by 10%. If the discharge temperature still does not fall below the third threshold, the operating frequency is further reduced by 10%. Then, when the discharge temperature does not fall below the third threshold value even when the operating frequency is lowered to the lowest operating frequency or a preset frequency, in addition to the control of the second expansion valve and the inverter type capacity control, the mechanical type Perform capacity control.

The above control takes into consideration the operating efficiency of the refrigeration cycle device 1 as follows. Inverter-type capacity control is for decelerating the compressor 6 within the range of normal operation for stable operation. On the other hand, the mechanical capacity control is intended to protect the compressor 6, and to reduce the discharge temperature at once. Therefore, when the discharge temperature is lowered by the inverter type capacity control, the time until the operation of the compressor 6 is restored can be shortened compared to when the discharge temperature is lowered by the mechanical type capacity control. Since the mechanical capacity control reduces the low pressure at once, it effectively lowers the discharge temperature. executed.

Also, in each embodiment, a two-stage screw compressor is taken as an example, but the compressor 6 does not have to be equipped with a mechanism for cooling oil. The content of the present disclosure can be applied regardless of whether the compressor 6 is, for example, a single-stage compressor, a scroll compressor, a rotary compressor, a reciprocating compressor, or the like.

Also, the method of controlling the second expansion valve 11 or the third expansion valve 13 based on the control of each discharge temperature, the temperature of the motor, or the temperature of the oil is not limited to those described in each embodiment. For example, the control of the second expansion valve 11 based on the oil temperature described in Embodiment 3 may be performed independently of the control of the third expansion valve 13 based on the discharge temperature.

1 refrigeration cycle device, 1A refrigeration cycle device, 1B refrigeration cycle device, 2 first refrigerant pipe, 3 second refrigerant pipe, 4 third refrigerant pipe, 5 oil pipe, 6 compressor, 7 oil separator, 8 condenser, 9 first expansion valve, 10 evaporator, 11 second expansion valve, 12 oil cooler, 13 third expansion valve, 21 low-stage compression section, 22 high-stage compression section, 23 motor, 23a motor frame, 24 motor room, 25 Intermediate pressure chamber 31 Discharge temperature sensor 32 Motor temperature sensor 33 Oil temperature sensor 34 Heater 40 Control device 41 Discharge temperature measurement unit 42 Motor temperature measurement unit 43 Control unit 44 Oil temperature measurement unit 45 memory unit.

Claims

A refrigeration cycle device in which a compressor, an oil separator, a condenser, a first expansion valve, and an evaporator are annularly connected by a first refrigerant pipe, and refrigerant circulates,
a second refrigerant pipe branched from between the condenser and the first expansion valve in the first refrigerant pipe and connected to the compressor;
an oil pipe connected to the oil separator and the compressor, through which the oil separated by the oil separator flows;
An oil cooler that is provided in the second refrigerant pipe, cools the oil flowing in the oil pipe with the refrigerant flowing in the second refrigerant pipe, and sends the oil to the compressor;
a second expansion valve provided between the condenser and the oil cooler in the second refrigerant pipe;
a discharge temperature sensor provided on the discharge side of the compressor in the first refrigerant pipe;
a control device that controls the second expansion valve,
The control device is
controlling the degree of opening of the second expansion valve so that the discharge temperature of the compressor based on the detection result of the discharge temperature sensor is within a predetermined temperature range;
The temperature range has a first threshold as an upper limit and a second threshold as a lower limit,
The first threshold is a predetermined first set temperature lower than a protection threshold that serves as a reference for stopping the compressor when the discharge temperature reaches the refrigeration cycle device.
The refrigeration cycle apparatus according to claim 1, wherein the second threshold is a temperature lower than the first threshold by a predetermined second set temperature.
The control device is
when the discharge temperature exceeds the first threshold, increasing the degree of opening of the second expansion valve;
The refrigerating cycle apparatus according to claim 1 or 2, wherein the degree of opening of the second expansion valve is reduced when the discharge temperature is less than the second threshold.
The control device is
Capacity control is performed so as to reduce the refrigerant flow rate of the compressor when the discharge temperature exceeds a third threshold that is a predetermined third set temperature lower than the protection threshold. A refrigeration cycle apparatus as described.
The control device is
when the discharge temperature exceeds the third threshold, increasing the degree of opening of the second expansion valve;
If the discharge temperature exceeds the third threshold value when the degree of opening of the second expansion valve is maximized, the operating frequency of the compressor is adjusted to reduce the refrigerant flow rate of the compressor. The refrigeration cycle apparatus according to claim 4, wherein capacity control is performed.
The control device is
6. The refrigeration cycle according to claim 5, wherein mechanical capacity control is performed when the discharge temperature exceeds the third threshold when the operating frequency of the compressor is lowered to the lowest operating frequency or a preset frequency. Device.
HFC refrigerant is used as a refrigerant,
Polyol ester oil is used as oil,
The compressor is
Having a resin member made of all or part of PPS resin, polyamide resin, epoxy resin, aramid resin, fluororesin, polyethylene terephthalate resin, or polyester resin,
The refrigeration cycle apparatus according to any one of claims 4 to 6, wherein the third threshold is lower than the heat resistant temperature of the resin member.
HFO mixed refrigerant is used as a refrigerant,
Polyol ester oil or polyvinyl ether oil is used as oil,
The compressor is
Having a resin member made of all or part of PPS resin, polyamide resin, epoxy resin, aramid resin, fluororesin, polyethylene terephthalate resin, or polyester resin,
The refrigeration cycle apparatus according to any one of claims 4 to 6, wherein the third threshold is lower than the heat resistant temperature of the resin member.
Further comprising a heater provided in the oil separator,
The control device is
The refrigeration cycle apparatus according to any one of claims 1 to 8, wherein the heater is activated when the discharge temperature is equal to or lower than a fourth threshold.
a third refrigerant pipe branched from between the condenser and the first expansion valve in the first refrigerant pipe and connected to the compressor;
a third expansion valve provided in the third refrigerant pipe;
a motor temperature sensor provided in a motor that drives the compressor,
The control device is
The degree of opening of the third expansion valve is controlled so that the temperature of the motor based on the detection result of the motor temperature sensor is between a first motor threshold value and a second motor threshold value. The refrigeration cycle device according to the item.
The compressor is a two-stage screw compressor,
a low-stage compression unit that compresses the sucked refrigerant;
a high-stage compression section that further compresses the refrigerant compressed by the low-stage compression section;
an intermediate pressure chamber provided between the low-stage compression section and the high-stage compression section, through which the refrigerant during compression flows;
a motor chamber that houses the motor,
The second refrigerant pipe is connected to the intermediate pressure chamber,
The third refrigerant pipe is connected to the motor chamber,
The refrigeration cycle apparatus according to claim 10, wherein the oil pipe is connected to the low-stage compression section and the high-stage compression section.
Further comprising an oil temperature sensor provided in the oil separator,
The control device is
The refrigeration cycle apparatus according to any one of claims 1 to 11, wherein the degree of opening of the second expansion valve is increased when the oil temperature based on the detection result of the oil temperature sensor exceeds the first oil temperature threshold.