REFRIGERATION CYCLE DEVICE

Abstract

 In a refrigeration cycle apparatus, a cooling refrigerant flow passage 93 is formed to pass through a position where heat of refrigerant flowing through the cooling refrigerant flow passage 93 is transferred to an inverter heat radiating portion 111, a first oil flow passage 90 is formed to pass through a position where heat of refrigerating machine oil flowing through the first oil flow passage 90 is not transferred to the inverter heat radiating portion 111, a second oil flow passage 91 is formed to pass through a position where heat of refrigerating machine oil flowing through the second oil flow passage 91 is transferred to the inverter heat radiating portion 111, and a controller 7 is configured to control a second pressure reducing device and an oil flow rate control unit on the basis of a detection value measured by an inverter temperature detection device 112.

Description

Technical Field

[0001] The present invention relates to a refrigeration cycle apparatus that makes it possible to prevent damage due to radiated heat and condensation in an inverter in an inverter-integrated refrigerant compressor.

Background Art

[0002] In recent years, to enhance partial load efficiency, refrigeration cycle apparatuses in which an inverter controls an operating frequency of a compressor have grown in number. When the inverter converts a frequency, heat is radiated due to electrical losses in various electrical circuits, electrical components, and other elements.

[0003] A portion where heat is radiated as above is hereinafter referred to as an inverter heat radiating portion.

[0004] The inverter has temperature limitations, and the inverter heat radiating portion has to be cooled to prevent damage due to overheating of an electrical circuit and an electrical component caused by the radiated heat.

[0005] As a cooling measure in the inverter heat radiating portion, a method has been known in which refrigerant is used (see Patent Literature 1, for example).

[0006] According to Patent Literature 1, an inverter cooling expansion valve is controlled on the basis of either the temperature of an inverter heat radiating portion or the degree of superheat of suction gas (refrigerant gas) to be sucked into a compressor, thereby cooling the inverter heat radiating portion.

Citation List

Patent Literature

[0007] 

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2003-21406

Patent Literature 2: Japanese Patent No. 2768092

Summary of Invention

Technical Problem

[0008] In Patent Literature 1, for example, in the case where an inverter is installed in a position that is likely to be affected by a suction gas temperature, such as in the vicinity of a motor frame, the inverter heat radiating portion is excessively cooled during operation at a low suction gas temperature even when the opening degree of the inverter cooling expansion valve is reduced to a minimum, raising a concern that an electrical circuit and an electrical component may be damaged by condensation.

[0009] Here, as an existing technique for preventing condensation, a technique has been known in which high-temperature refrigerating machine oil (hereinafter referred to as oil) having passed through an oil separator is caused to flow to the vicinity of a portion (terminal block) where it is desired to prevent condensation (see Patent Literature 2, for example).

[0010] According to Patent Literature 2, oil is caused to flow by differential pressure, and a flow rate is not able to be controlled. Thus, when the existing technique disclosed in Patent Literature 2 is applied to the inverter heat radiating portion disclosed in Patent Literature 1 to prevent condensation, high-temperature oil is caused to flow to the vicinity of the inverter heat radiating portion regardless of the temperature of the inverter heat radiating portion. As a result, in some cases, high-temperature oil is caused to flow even when the temperature of the inverter heat radiating portion rises, raising a concern that electrical components and other elements constituting the inverter heat radiating portion may be damaged by radiated heat.

[0011]  The present invention has been made to solve such drawbacks and provides a refrigeration cycle apparatus that is highly reliable and also highly efficient. Solution to Problem

[0012] A refrigeration cycle apparatus according to one embodiment of the present invention includes a refrigeration cycle in which a compressor in which an inverter including an inverter heat radiating portion being a portion where heat is radiated is integrated, an oil separator, a condenser, a first pressure reducing device, and an evaporator are connected by a pipe, and through which refrigerant circulates, a cooling refrigerant flow passage branching off from a flow passage between the condenser and the first pressure reducing device and merging with a flow passage between the evaporator and the compressor, a second pressure reducing device provided in the cooling refrigerant flow passage, a first oil flow passage and a second oil flow passage through which refrigerating machine oil separated in the oil separator flows to the compressor, an oil flow rate control unit configured to control a flow rate of refrigerating machine oil flowing through the first oil flow passage and a flow rate of refrigerating machine oil flowing through the second oil flow passage, an inverter temperature detection device configured to measure a temperature of the inverter heat radiating portion, and a controller. The cooling refrigerant flow passage is formed to pass through a position where heat of refrigerant flowing through the cooling refrigerant flow passage is transferred to the inverter heat radiating portion. The first oil flow passage is formed to pass through a position where heat of refrigerating machine oil flowing through the first oil flow passage is not transferred to the inverter heat radiating portion. The second oil flow passage is formed to pass through a position where heat of refrigerating machine oil flowing through the second oil flow passage is transferred to the inverter heat radiating portion. The controller is configured to control the second pressure reducing device and the oil flow rate control unit on the basis of a detection value measured by the inverter temperature detection device.

Advantageous Effects of Invention

[0013] In the refrigeration cycle apparatus of one embodiment of the present invention, when the second pressure reducing device and the oil flow rate control unit are controlled on the basis of a detection value measured by the inverter temperature detection device configured to measure the temperature of the inverter heat radiating portion, the inverter heat radiating portion can be caused to reach an appropriate temperature. Thus, overheating of the inverter heat radiating portion is prevented, thereby making it possible to prevent damage to an electrical circuit and an electrical component, and excessive cooling of the inverter heat radiating portion is also prevented, thereby making it possible to prevent the occurrence of condensation.

[0014] Furthermore, in preventing excessive cooling of the inverter heat radiating portion, the inverter heat radiating portion is heated and oil is cooled. Cooled high-viscosity oil is returned to a compression chamber, thereby making it possible to prevent leakage from a clearance gap between a screw rotor and a casing, and also making it possible to prevent an increase in discharge temperature to reduce input.

[0015] That is, the refrigeration cycle apparatus that is highly reliable and also highly efficient can be provided.

Brief Description of Drawings

[0016] 

[Fig. 1] Fig. 1 illustrates the configuration of a refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 3] Fig. 3 illustrates the configuration of a refrigeration cycle apparatus according to Embodiment 2 of the present invention.

[Fig. 4] Fig. 4 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 2 of the present invention.

[Fig. 5] Fig. 5 illustrates the configuration of a refrigeration cycle apparatus according to Embodiment 3 of the present invention.

[Fig. 6] Fig. 6 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 3 of the present invention.

[Fig. 7] Fig. 7 illustrates the configuration of a refrigeration cycle apparatus according to Embodiment 4 of the present invention.

[Fig. 8] Fig. 8 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 4 of the present invention. Description of Embodiments

[0017] Embodiments of the present invention will be described below with reference to the drawings. In the drawings to be described below, elements denoted by the same reference signs are the same or corresponding elements, and the reference signs are common throughout Embodiments to be described below. Then, the forms of components described in the specification are merely illustrative examples, and forms are not limited to the forms described in the specification.

Embodiment 1

[0018] Fig. 1 illustrates the configuration of a refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[0019] As illustrated in Fig. 1, in the refrigeration cycle apparatus according to Embodiment 1, a screw compressor 1, an oil separator 2, a condenser 3, a main expansion valve 4, and an evaporator 5 are sequentially connected by a refrigerant pipe to form a refrigerant circulation passage 92, thereby constituting a refrigeration cycle in which refrigerant circulates through the refrigerant circulation passage 92. Furthermore, a cooling refrigerant flow passage 93 is formed that branches off from a flow passage (refrigerant circulation passage 92) between the condenser 3 and the main expansion valve 4, passes through the vicinity of an inverter heat radiating portion 111 of an inverter 110 to be described, and merges with a flow passage (refrigerant circulation passage 92) between the evaporator 5 and the screw compressor 1. In the cooling refrigerant flow passage 93, an inverter cooling expansion valve 9 is provided upstream from the inverter heat radiating portion 111.

[0020] On a flow passage (hereinafter referred to as an oil flow passage) through which refrigerating machine oil (hereinafter referred to as oil) separated in the oil separator 2 flows to the screw compressor 1, a three-way valve 6 is provided. Between the three-way valve 6 and the screw compressor 1, a first oil flow passage 90 is formed through which oil separated in the oil separator 2 flows directly to a compression chamber 101 a without passing through the vicinity of the inverter heat radiating portion 111 and a second oil flow passage 91 is formed through which oil separated in the oil separator 2 passes through the vicinity of the inverter heat radiating portion 111 to be described and then flows to the screw compressor 1. That is, the oil flow passage is divided by the three-way valve 6 into two flow passages, which are the first oil flow passage 90 and the second oil flow passage 91. A flow passage through which oil separated in the oil separator 2 flows is switched by the three-way valve 6 between the first oil flow passage 90 and the second oil flow passage 91.

[0021] Here, the vicinity of the inverter heat radiating portion 111 refers to a position where heat of refrigerant flowing through the cooling refrigerant flow passage 93 or heat of oil flowing through the oil flow passage can be transferred to the inverter heat radiating portion 111, and the same applies to the following description.

[0022] Although, in Fig. 1, the oil separator 2 and the screw compressor 1 are separately placed, the oil separator 2 may be built into the screw compressor 1.

[0023] The three-way valve 6 corresponds to "oil flow rate control unit" of the present invention.

[0024] The screw compressor 1 is composed of an integrated combination of a compressor mechanism portion 101 and the inverter 110. In the inverter 110, heat-generating elements, such as a rectifier circuit, a smoothing capacitor, and an inverter circuit, are placed so that a joint portion between a container constituting an outer casing of the inverter 110 and the compressor mechanism portion 101 acts as the inverter heat radiating portion 111.

[0025] Although, the screw compressor 1 is used in Embodiment 1, a compressor is not limited to a screw compressor. Any other types of compressors, such as a reciprocating compressor and a turbo-compressor, into which an inverter is integrated may be used.

[0026] That is, the inverter 110 includes the inverter heat radiating portion 111 in which the above-described heat-generating elements are housed. In the inverter 110, an inverter temperature detection device 112 that measures the temperature of the inverter heat radiating portion 111 is provided. Furthermore, in the screw compressor 1, the compression chamber 101 a and a motor 101 b that rotationally drives a screw rotor, which will be described later, included in the compression chamber 101 a are connected in series to compress and discharge refrigerant.

[0027] The compression chamber 101 a includes the screw rotor (not illustrated) and a gate rotor (not illustrated) that engages with screw grooves provided on the screw rotor. In the compression chamber 101 a composed of the screw grooves (not illustrated) and a casing that houses the gate rotor and the screw rotor, refrigerant is compressed.

[0028] Here, although, the single screw compressor is taken as an example in Embodiment 1, a twin screw compressor composed of a pair of male and female screw rotors may be used.

[0029] Refrigerant liquid having flowed out of the condenser 3 is divided to flow to the refrigerant circulation passage 92 and the cooling refrigerant flow passage 93. Refrigerant divided to flow to the refrigerant circulation passage 92 is reduced in pressure by the main expansion valve 4 and then flows into the evaporator 5.

[0030] On the other hand, refrigerant divided to flow to the cooling refrigerant flow passage 93 is reduced in pressure by the inverter cooling expansion valve 9, and a stream of the refrigerant reduced in pressure passes through the vicinity of the inverter heat radiating portion 111 and meets a stream of outlet gas from the evaporator 5. That is, when the opening degree of the inverter cooling expansion valve 9 is controlled, refrigerant liquid is reduced in pressure, and the inverter heat radiating portion 111 is cooled by using the refrigerant reduced in pressure. Furthermore, when the opening degree of the inverter cooling expansion valve 9 is controlled, a flow rate of refrigerant that flows through the cooling refrigerant flow passage 93 is regulated.

[0031] The main expansion valve 4 and the inverter cooling expansion valve 9 are each a pressure reducing device that reduces the pressure of refrigerant to expand the refrigerant. The main expansion valve 4 and the inverter cooling expansion valve 9 each have an opening degree variably controllable and are each composed of, for example, an electronic expansion valve.

[0032] The main expansion valve 4 corresponds to "first pressure reducing device" of the present invention, and the inverter cooling expansion valve 9 corresponds to "second pressure reducing device" of the present invention.

[0033] A detection value measured by the inverter temperature detection device 112 is output to a controller 7. The controller 7 controls the three-way valve 6 on the basis of the detection information (detection value measured by the inverter temperature detection device 112) and determines a passage for returning oil separated in the oil separator 2 to the compression chamber 101 a.

[0034] The controller 7 can be composed of hardware, such as a circuit device that implements functions of the controller 7, or can also be composed of an arithmetic unit, such as a microcomputer and a CPU, and software run on the arithmetic unit.

[0035] Here, the configuration of oil flow passages in the refrigeration cycle apparatus according to Embodiment 1 will be described.

[0036] High-temperature oil contained in refrigerant gas discharged from the compression chamber 101 a is recovered by the oil separator 2. Then, in the case where the three-way valve 6 is open to the first oil flow passage 90, oil having passed through the oil separator 2 passes through the first oil flow passage 90 and flows directly to the compression chamber 101 a. In the case where the three-way valve 6 is open to the second oil flow passage 91, oil having passed through the oil separator 2 flows to the second oil flow passage 91, passes through the vicinity of the inverter heat radiating portion 111, and can thus exchange heat with the inverter heat radiating portion 111.

[0037] That is, in the case where the inverter heat radiating portion 111 is excessively cooled by refrigerant gas, the inverter heat radiating portion 111 is heated by oil, thereby reducing the difference in temperature between the inverter heat radiating portion 111 and outdoor air and making it possible to prevent condensation.

[0038] Next, the action of the refrigeration cycle apparatus according to Embodiment 1 will be described step by step with reference to Fig. 1.

[0039] Refrigerant compressed in the compressor mechanism portion 101 of the screw compressor 1 is discharged from the screw compressor 1 and separated into refrigerant gas and oil in the oil separator 2. The oil passes through the first oil flow passage 90 or the second oil flow passage 91 through the three-way valve 6 and returns to the compression chamber 101 a. The refrigerant gas flows into the condenser 3. The refrigerant gas having flowed into the condenser 3 is condensed into refrigerant liquid, and the refrigerant liquid is divided to flow to the refrigerant circulation passage 92 and the cooling refrigerant flow passage 93.

[0040] Refrigerant liquid that flows to the refrigerant circulation passage 92 is reduced in pressure by the main expansion valve 4 and then sent to the evaporator 5. Then, the refrigerant sent to the evaporator 5 is subjected to heat exchange there to turn into refrigerant gas, and the refrigerant gas flows into the screw compressor 1.

[0041] On the other hand, refrigerant liquid that flows to the cooling refrigerant flow passage 93 is reduced in pressure by the inverter cooling expansion valve 9, and the refrigerant then passes through the vicinity of the inverter heat radiating portion 111 and flows into an outlet pipe of the evaporator 5.

[0042] When a detection value measured by the inverter temperature detection device 112 is greater than or equal to a preset target temperature lower limit (for example, 35 degrees C), the three-way valve 6 is opened to the first oil flow passage 90. When a detection value measured by the inverter temperature detection device 112 is greater than or equal to a preset target temperature upper limit (for example, 45 degrees C), the opening degree of the inverter cooling expansion valve 9 is regulated to cool the inverter heat radiating portion 111.

[0043] On the other hand, in the state where a detection value measured by the inverter temperature detection device 112 is less than the preset target temperature lower limit, that is, in the case where condensation may possibly occur in the inverter heat radiating portion 111, the three-way valve 6 is opened to the second oil flow passage 91, high-temperature oil is caused to flow to the vicinity of the inverter heat radiating portion 111 to heat the inverter heat radiating portion 111, and the opening degree of the inverter cooling expansion valve 9 is regulated so that a detection value measured by the inverter temperature detection device 112 reaches or exceeds a preset threshold value (for example, 40 degrees C). After the oil exchanges heat with the inverter heat radiating portion 111, the oil is injected into an intermediate-pressure space in the middle of compression in the compression chamber 101 a. Note that the relationship of target temperature lower limit ≤ threshold value ≤ target temperature upper limit is satisfied.

[0044] Fig. 2 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[0045] Next, a flow of control of the refrigeration cycle apparatus according to Embodiment 1 will be described with reference to Fig. 2. Processes illustrated in the flowchart of Fig. 2 are implemented at certain set control time intervals.

(Step S11)

[0046] As described above, the controller 7 controls the three-way valve 6 on the basis of detection information measured by the inverter temperature detection device 112 provided to the inverter heat radiating portion 111. Specifically, when a temperature of the inverter heat radiating portion 111 measured in the inverter temperature detection device 112 is greater than or equal to the preset target temperature lower limit, it is determined that steady operation is performed. When the temperature of the inverter heat radiating portion 111 is less than the preset target temperature lower limit, it is determined that transient operation is performed.

[0047] Processes performed when it is determined that steady operation is performed will be described below, and then processes performed when it is determined that transient operation is performed will be described.

[In Steady Operation]

(Step S12)

[0048] When the controller 7 determines in step S11 that steady operation is performed, the controller 7 opens the three-way valve 6 to the first oil flow passage 90.

(Step S13 to Step S14)

[0049] When a detection value measured by the inverter temperature detection device 112 is greater than or equal to the preset target temperature upper limit, the opening degree of the inverter cooling expansion valve 9 is increased to increase the flow rate of refrigerant that flows through the cooling refrigerant flow passage 93 and cools the inverter heat radiating portion 111.

[0050]  The process of step S13 to the process of step S14 are implemented at control time intervals. Consequently, in steady operation, that is, while a detection value measured by the inverter temperature detection device 112 is greater than or equal to the preset target temperature lower limit, cooling can be appropriately performed by regulating the opening degree of the inverter cooling expansion valve 9 so that a detection value measured by the inverter temperature detection device 112 is less than or equal to the preset target temperature upper limit.

[In Transient Operation]

(Step S21)

[0051] When the controller 7 determines in step S11 that transient operation is performed, the controller 7 opens the three-way valve 6 to the second oil flow passage 91, causes high-temperature oil to flow to the vicinity of the inverter heat radiating portion 111 to heat the inverter heat radiating portion 111, and then injects the oil into an intermediate pressure space in the middle of compression in the compression chamber 101 a.

(Step S22 to Step S24)

[0052] Until the opening degree of the inverter cooling expansion valve 9 reaches a minimum, or until a detection value measured by the inverter temperature detection device 112 reaches or exceeds the preset threshold value, the controller 7 reduces the opening degree of the inverter cooling expansion valve 9 to reduce the flow rate of refrigerant that flows through the cooling refrigerant flow passage 93 and cools the inverter heat radiating portion 111.

[0053] The process of step S22 to the process of step S24 are implemented at control time intervals. Consequently, in transient operation, that is, when the temperature of the inverter heat radiating portion 111 is less than the preset target temperature lower limit, the temperature of the inverter heat radiating portion 111 can be caused to reach or exceed the preset target temperature lower limit by heating the inverter heat radiating portion 111 using high-temperature oil having passed through the oil separator 2. This configuration prevents excessive cooling of the inverter heat radiating portion 111 and can reduce the difference in temperature between the inverter heat radiating portion 111 and outdoor air.

[Effects of Embodiment 1]

[0054] As described above, in Embodiment 1, in steady operation, the opening degree of the inverter cooling expansion valve 9 is regulated to appropriately perform cooling so that the inverter heat radiating portion 111 has a temperature less than or equal to the preset target temperature upper limit, thereby preventing overheating of the inverter heat radiating portion 111 and making it possible to prevent damage to an electrical circuit and an electrical component.

[0055] Also, in such transient operation that low-temperature suction gas (refrigerant gas) passes through the vicinity of a motor frame and excessively cools the inverter heat radiating portion 111, the inverter heat radiating portion 111 is heated using high-temperature oil having passed through the oil separator 2, thereby reducing the difference in temperature between outdoor air and the inverter heat radiating portion 111, preventing excessive cooling of the inverter heat radiating portion 111, and making it possible to prevent the occurrence of condensation.

[0056] Furthermore, in preventing excessive cooling of the inverter heat radiating portion 111, the inverter heat radiating portion 111 is heated and oil is cooled. Cooled high-viscosity oil is returned to a compression chamber, thereby making it possible to prevent leakage from a clearance gap between the screw rotor and the casing, and also making it possible to prevent an increase in discharge temperature to reduce input.

[0057] That is, the refrigeration cycle apparatus according to Embodiment 1 achieves high reliability and also high efficiency.

Embodiment 2

[0058] Embodiment 2 of the present invention will be described below, some descriptions of components that are the same as those in Embodiment 1 are omitted, and the components that are the same as or correspond to those in Embodiment 1 are denoted by the same reference signs.

[0059] A refrigeration cycle apparatus according to Embodiment 2 differs from that according to Embodiment 1 in that the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 that are provided in Embodiment 1 are removed, and in that the inverter heat radiating portion 111 is cooled by using not refrigerant flowing through the cooling refrigerant flow passage 93 but suction gas (refrigerant gas).

[0060] A description will be given below with emphasis on a respect in which Embodiment 2 differs from Embodiment 1.

[0061] In Embodiment 1 described above, the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 that are specially designed for cooling the inverter heat radiating portion 111 are provided, and, when the inverter heat radiating portion 111 is excessively cooled, the inverter heat radiating portion 111 is heated by high-temperature oil having passed through the oil separator 2.

[0062] Fig. 3 illustrates the configuration of the refrigeration cycle apparatus according to Embodiment 2 of the present invention.

[0063] Unlike Embodiment 1, in Embodiment 2, the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 that are specially designed for cooling the inverter heat radiating portion 111 are not provided as illustrated in Fig. 3, refrigerant flowing through the refrigerant circulation passage 92 is subjected to heat exchange in the evaporator 5 to turn into refrigerant gas, and then the refrigerant gas passes through the vicinity of the inverter heat radiating portion 111 before flowing into the screw compressor 1. That is, the inverter heat radiating portion 111 is cooled by using suction gas (refrigerant gas). The configuration of a refrigerant circuit, for example, other than the above configuration is the same as that in Embodiment 1.

[0064] Next, the action of the refrigeration cycle apparatus according to Embodiment 2 will be described step by step with reference to Fig. 3.

[0065] Refrigerant compressed in the compressor mechanism portion 101 of the screw compressor 1 is discharged from the screw compressor 1 and separated into refrigerant gas and oil in the oil separator 2. The oil passes through the first oil flow passage 90 or the second oil flow passage 91 through the three-way valve 6 and returns to the compression chamber 101 a. The refrigerant gas flows into the condenser 3. The refrigerant gas having flowed into the condenser 3 is condensed into refrigerant liquid, and the refrigerant liquid is reduced in pressure by the main expansion valve 4 and then sent to the evaporator 5. The refrigerant sent to the evaporator 5 is subjected to heat exchange there to turn into refrigerant gas, and the refrigerant gas flows into the screw compressor 1.

[0066] When a detection value measured by the inverter temperature detection device 112 is greater than or equal to a preset target temperature lower limit (for example, 35 degrees C), the three-way valve 6 is opened to the first oil flow passage 90. When a detection value measured by the inverter temperature detection device 112 is greater than or equal to a preset target temperature upper limit (for example, 45 degrees C), the opening degree of the main expansion valve 4 is regulated to cool the inverter heat radiating portion 111.

[0067] On the other hand, in the state where a detection value measured by the inverter temperature detection device 112 is less than the preset target temperature lower limit, that is, in the case where condensation may possibly occur in the inverter heat radiating portion 111, the three-way valve 6 is opened to the second oil flow passage 91, high-temperature oil is caused to flow to the vicinity of the inverter heat radiating portion 111 to heat the inverter heat radiating portion 111, and the opening degree of the main expansion valve 4 is regulated so that a detection value measured by the inverter temperature detection device 112 reaches or exceeds a preset threshold value (for example, 40 degrees C). After the oil exchanges heat with the inverter heat radiating portion 111, the oil is injected into an intermediate-pressure space in the middle of compression in the compression chamber 101 a. Note that the relationship of target temperature lower limit ≤ threshold value ≤ target temperature upper limit is satisfied.

[0068] Fig. 4 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 2 of the present invention.

[0069] Next, a flow of control of the refrigeration cycle apparatus according to Embodiment 2 will be described with reference to Fig. 4. Processes illustrated in the flowchart of Fig. 4 are implemented at certain set control time intervals.

(Step S11)

[0070] As described above, the controller 7 controls the three-way valve 6 on the basis of detection information measured by the inverter temperature detection device 112 provided to the inverter heat radiating portion 111. Specifically, when a temperature of the inverter heat radiating portion 111 measured in the inverter temperature detection device 112 is greater than or equal to the preset target temperature lower limit, it is determined that steady operation is performed. When the temperature of the inverter heat radiating portion 111 is less than the preset target temperature lower limit, it is determined that transient operation is performed.

[0071] Processes performed when it is determined that steady operation is performed will be described below, and then processes performed when it is determined that transient operation is performed will be described.

[In Steady Operation]

(Step S12)

[0072] When the controller 7 determines in step S11 that steady operation is performed, the controller 7 opens the three-way valve 6 to the first oil flow passage 90.

(Step S13 to Step S14).

[0073] When a detection value measured by the inverter temperature detection device 112 is greater than or equal to the preset target temperature upper limit, the opening degree of the main expansion valve 4 is increased to cool the inverter heat radiating portion 111.

[0074] The process of step S13 to the process of step S14 are implemented at control time intervals. Consequently, in steady operation, that is, while a detection value measured by the inverter temperature detection device 112 is greater than or equal to the preset target temperature lower limit, cooling can be appropriately performed by regulating the opening degree of the main expansion valve 4 so that a detection value measured by the inverter temperature detection device 112 is less than or equal to the preset target temperature upper limit.

[In Transient Operation]

(Step S31)

[0075] When the controller 7 determines in step S11 that transient operation is performed, the controller 7 opens the three-way valve 6 to the second oil flow passage 91, causes high-temperature oil to flow to the vicinity of the inverter heat radiating portion 111 to heat the inverter heat radiating portion 111, and then injects the oil into an intermediate-pressure space in the middle of compression in the compression chamber 101 a.

(Step S32 to Step S34)

[0076] Until the opening degree of the main expansion valve 4 reaches a minimum, or until a detection value measured by the inverter temperature detection device 112 reaches or exceeds the preset threshold value, the controller 7 reduces the opening degree of the main expansion valve 4 to reduce the flow rate of refrigerant that flows through the cooling refrigerant flow passage 93 and cools the inverter heat radiating portion 111.

[0077] The process of step S32 to the process of step S34 are implemented at control time intervals. Consequently, in transient operation, that is, when the temperature of the inverter heat radiating portion 111 is less than the preset target temperature lower limit, the temperature of the inverter heat radiating portion 111 can be caused to reach or exceed the preset target temperature lower limit by heating the inverter heat radiating portion 111 using high-temperature oil having passed through the oil separator 2. This configuration prevents excessive cooling of the inverter heat radiating portion 111 and can reduce the difference in temperature between the inverter heat radiating portion 111 and outdoor air.

[Effects of Embodiment 2]

[0078] As described above, in Embodiment 2, the same effects as in Embodiment 1 can be achieved, and the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 do not have to be provided, thereby enabling simplification of the configuration of the refrigeration cycle apparatus and cost reductions.

Embodiment 3

[0079] Embodiment 3 of the present invention will be described below, some descriptions of components that are the same as those in Embodiments 1 and 2 are omitted, and the components that are the same as or correspond to those in Embodiments 1 and 2 are denoted by the same reference signs.

[0080] A refrigeration cycle apparatus according to Embodiment 3 differs from those according to Embodiments 1 and 2 in that the three-way valve 6 provided in Embodiments 1 and 2 is removed, and in that a first flow rate control valve 61 and a second flow rate control valve 62 are provided in the first oil flow passage 90 and the second oil flow passage 91, respectively.

[0081] A description will be given below with emphasis on a respect in which Embodiment 3 differs from Embodiments 1 and 2.

[0082] In Embodiments 1 and 2 described above, the three-way valve 6 switches the flow passage between the first oil flow passage 90 and the second oil flow passage 91 serving as flow passages for returning oil having passed through the oil separator 2 to the compression chamber 101 a. That is, oil is returned to the compression chamber 101 a through one of the first oil flow passage 90 and the second oil flow passage 91 at all times.

[0083] Fig. 5 illustrates the configuration of the refrigeration cycle apparatus according to Embodiment 3 of the present invention.

[0084] Unlike Embodiments 1 and 2, in Embodiment 3, the first flow rate control valve 61 and the second flow rate control valve 62 are provided in the first oil flow passage 90 and the second oil flow passage 91, respectively, in place of the three-way valve 6 as illustrated in Fig. 5. The configuration of the refrigerant circuit, for example, other than the above configuration is the same as that in Embodiment 1.

[0085] The first flow rate control valve 61 and the second flow rate control valve 62 correspond to "oil flow rate control unit" of the present invention.

[0086] Next, the action of the refrigeration cycle apparatus according to Embodiment 3 will be described step by step with reference to Fig. 5.

[0087] Refrigerant compressed in the compressor mechanism portion 101 of the screw compressor 1 is discharged from the screw compressor 1 and separated into refrigerant gas and oil in the oil separator 2. The oil passes through either one or both of the first flow rate control valve 61 provided in the first oil flow passage 90 and the second flow rate control valve 62 provided in the second oil flow passage 91 and returns to the compression chamber 101 a. The refrigerant gas flows into the condenser 3. Proportions of oil to be returned from the first oil flow passage 90 and oil to be returned from the second oil flow passage 91 to the compression chamber 101 a can be controlled by regulating the opening degrees of the first flow rate control valve 61 and the second flow rate control valve 62.

[0088] The refrigerant gas having flowed into the condenser 3 is condensed into refrigerant liquid, and the refrigerant liquid is divided to flow to the refrigerant circulation passage 92 and the cooling refrigerant flow passage 93.

[0089] Refrigerant liquid that flows to the refrigerant circulation passage 92 is reduced in pressure by the main expansion valve 4 and then sent to the evaporator 5. Then, the refrigerant sent to the evaporator 5 is subjected to heat exchange there to turn into refrigerant gas, and the refrigerant gas flows into the screw compressor 1.

[0090] On the other hand, refrigerant liquid that flows to the cooling refrigerant flow passage 93 is reduced in pressure by the inverter cooling expansion valve 9, and the refrigerant then passes through the vicinity of the inverter heat radiating portion 111 and flows into the outlet pipe of the evaporator 5.

[0091] Here, the opening degrees of the first flow rate control valve 61 and the second flow rate control valve 62 are controlled so that a detection value measured by the inverter temperature detection device 112 falls below a preset threshold value (for example, 40 degrees C), thereby keeping a flow rate of oil that returns to the compression chamber 101 a constant even when the opening degrees of the first flow rate control valve 61 and the second flow rate control valve 62 are changed.

[0092] Specifically, the opening degree of the second flow rate control valve 62 is increased and simultaneously the opening degree of the first flow rate control valve 61 is reduced so that a detection value measured by the inverter temperature detection device 112 reaches or exceeds the preset threshold value, thereby causing high-temperature oil having passed through the oil separator 2 to flow to the vicinity of the inverter heat radiating portion 111 to heat the inverter heat radiating portion 111.

[0093]  Subsequently, the opening degree of the inverter cooling expansion valve 9 is regulated so that a detection value measured by the inverter temperature detection device 112 falls within the range from the preset threshold value to a preset target temperature upper limit (for example, 45 degrees C) inclusive. In the case where a detection value measured by the inverter temperature detection device 112 is greater than the preset target temperature upper limit even when the opening degree of the inverter cooling expansion valve 9 is increased to a maximum opening degree, the opening degree of the first flow rate control valve 61 is increased and simultaneously the opening degree of the second flow rate control valve 62 is reduced, thereby preventing overheating of the inverter heat radiating portion 111.

[0094] Fig. 6 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 3 of the present invention.

[0095] Next, a flow of control of the refrigeration cycle apparatus according to Embodiment 3 will be described with reference to Fig. 6. Processes illustrated in the flowchart of Fig. 6 are implemented at certain set control time intervals.

(Step S41 to Step S43)

[0096] As described above, the controller 7 controls the first flow rate control valve 61 and the second flow rate control valve 62 on the basis of a detection value measured by the inverter temperature detection device 112 provided to the inverter heat radiating portion 111. Until a condition that a detection value measured by the inverter temperature detection device 112 is greater than or equal to the preset threshold value, a condition that the opening degree of the first flow rate control valve 61 is a minimum opening degree, or a condition that the opening degree of the second flow rate control valve 62 is a maximum opening degree is satisfied, the opening degree of the first flow rate control valve 61 is reduced and the opening degree of the second flow rate control valve 62 is increased.

(Step S51 to Step S54)

[0097] The opening degree of the inverter cooling expansion valve 9 is regulated so that a detection value measured by the inverter temperature detection device 112 falls within the range from the preset threshold value to the preset target temperature upper limit inclusive.

(Step S55 to Step S58)

[0098] When a detection value measured by the inverter temperature detection device 112 is greater than the preset target temperature upper limit and when the opening degree of the inverter cooling expansion valve 9 is fully open, the opening degree of the first flow rate control valve 61 is increased and the opening degree of the second flow rate control valve 62 is reduced so that a detection value measured by the inverter temperature detection device 112 reaches or falls below the preset target temperature upper limit. This configuration reduces the flow rate of oil that flows to the vicinity of the inverter heat radiating portion 111, thereby preventing overheating of the inverter heat radiating portion 111.

[0099] The process of step S41 to the process of step S58 are implemented at control time intervals. Consequently, the flow rate of oil caused to flow to the vicinity of the inverter heat radiating portion 111 is regulated by using the first flow rate control valve 61 and the second flow rate control valve 62, and a detection value measured by the inverter temperature detection device 112 provided to the inverter heat radiating portion 111 can thus be regulated. Additionally, the opening degree of the inverter cooling expansion valve 9 is regulated so that a detection value measured by the inverter temperature detection device 112 falls within the range from the preset threshold value to the preset target temperature upper limit inclusive.

[Effects of Embodiment 3]

[0100] As described above, in Embodiment 3, the temperature of the inverter heat radiating portion 111 can be finely controlled and changes in the temperature of oil to be returned to the compression chamber 101 a can be stabilized in comparison with Embodiment 1. This configuration can prevent, for example, seizure due to an abnormal reduction in the distance of a clearance gap between the screw rotor and the casing caused by changes in temperature, thereby increasing reliability.

Embodiment 4

[0101] Embodiment 4 of the present invention will be described below, some descriptions of components that are the same as those in Embodiments 1 to 3 are omitted, and the components that are the same as or correspond to those in Embodiments 1 to 3 are denoted by the same reference signs.

[0102] A refrigeration cycle apparatus according to Embodiment 4 differs from that according to Embodiment 3 in that the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 that are provided in Embodiment 3 are removed, and in that the inverter heat radiating portion 111 is cooled by using not refrigerant flowing through the cooling refrigerant flow passage 93 but suction gas (refrigerant gas).

[0103] A description will be given below with emphasis on a respect in which Embodiment 4 differs from Embodiment 3.

[0104] In Embodiment 3 described above, the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 that are specially designed for cooling the inverter heat radiating portion 111 are provided, and, when the inverter heat radiating portion 111 is excessively cooled, the inverter heat radiating portion 111 is heated by high-temperature oil having passed through the oil separator 2.

[0105] Fig. 7 illustrates the configuration of the refrigeration cycle apparatus according to Embodiment 4 of the present invention.

[0106] Unlike Embodiment 3, in Embodiment 4, the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 that are specially designed for cooling the inverter heat radiating portion 111 are not provided as illustrated in Fig. 7, refrigerant flowing through the refrigerant circulation passage 92 is subjected to heat exchange in the evaporator 5 to turn into refrigerant gas, and then the refrigerant gas passes through the vicinity of the inverter heat radiating portion 111 before flowing into the screw compressor 1. That is, the inverter heat radiating portion 111 is cooled by using suction gas. The configuration of the refrigerant circuit, for example, other than the above configuration is the same as that in Embodiment 3.

[0107] Next, the action of the refrigeration cycle apparatus according to Embodiment 4 will be described step by step with reference to Fig. 7.

[0108] Refrigerant compressed in the compressor mechanism portion 101 of the screw compressor 1 is discharged from the screw compressor 1 and separated into refrigerant gas and oil in the oil separator 2. The oil passes through either one or both of the first flow rate control valve 61 provided in the first oil flow passage 90 and the second flow rate control valve 62 provided in the second oil flow passage 91 and returns to the compression chamber 101 a. The refrigerant gas flows into the condenser 3.

[0109] Proportions of oil to be returned from the first oil flow passage 90 and the second oil flow passage 91 to the compression chamber 101 a can be controlled by regulating the opening degrees of the first flow rate control valve 61 and the second flow rate control valve 62.

[0110] The refrigerant gas having flowed into the condenser 3 is condensed into refrigerant liquid, and the refrigerant liquid is reduced in pressure by the main expansion valve 4 and then sent to the evaporator 5. The refrigerant sent to the evaporator 5 is subjected to heat exchange there to turn into refrigerant gas, and the refrigerant gas flows into the screw compressor 1.

[0111] Here, the opening degrees of the first flow rate control valve 61 and the second flow rate control valve 62 are controlled so that a detection value measured by the inverter temperature detection device 112 falls below a preset threshold value (for example, 40 degrees C), thereby keeping a flow rate of oil that returns to the compression chamber 101 a constant even when the opening degrees of the first flow rate control valve 61 and the second flow rate control valve 62 are changed.

[0112] Specifically, the opening degree of the second flow rate control valve 62 is increased and simultaneously the opening degree of the first flow rate control valve 61 is reduced so that a detection value measured by the inverter temperature detection device 112 reaches or exceeds the threshold value, thereby causing high-temperature oil having passed through the oil separator 2 to flow to the vicinity of the inverter heat radiating portion 111 to heat the inverter heat radiating portion 111.

[0113] Subsequently, the opening degree of the main expansion valve 4 is regulated so that a detection value measured by the inverter temperature detection device 112 falls within the range from the preset threshold value to a preset target temperature upper limit (for example, 45 degrees C) inclusive. In the case where a detection value measured by the inverter temperature detection device 112 is greater than the preset target temperature upper limit even when the opening degree of the main expansion valve 4 is increased to a maximum opening degree, the opening degree of the first flow rate control valve 61 is increased and simultaneously the opening degree of the second flow rate control valve 62 is reduced, thereby preventing overheating of the inverter heat radiating portion 111.

[0114] Fig. 8 is a flowchart illustrating an example of control of the refrigeration cycle apparatus according to Embodiment 4 of the present invention.

[0115] Next, a flow of control of the refrigeration cycle apparatus according to Embodiment 4 will be described with reference to Fig. 8. Processes illustrated in the flowchart of Fig. 8 are implemented at certain set control time intervals.

(Step S41 to Step S43)

[0116] As described above, the controller 7 controls the first flow rate control valve 61 and the second flow rate control valve 62 on the basis of a detection value measured by the inverter temperature detection device 112 provided to the inverter heat radiating portion 111. Until a condition that a detection value measured by the inverter temperature detection device 112 is greater than or equal to the preset threshold value, a condition that the opening degree of the first flow rate control valve 61 is a minimum opening degree, or a condition that the opening degree of the second flow rate control valve 62 is a maximum opening degree is satisfied, the opening degree of the first flow rate control valve 61 is reduced and the opening degree of the second flow rate control valve 62 is increased.

(Step S61 to Step S64)

[0117] The opening degree of the main expansion valve 4 is regulated so that a detection value measured by the inverter temperature detection device 112 falls within the range from the preset threshold value to the preset target temperature upper limit inclusive.

(Step S65 to Step S68)

[0118] When a detection value measured by the inverter temperature detection device 112 is greater than the preset target temperature upper limit and when the opening degree of the main expansion valve 4 is fully open, the opening degree of the first flow rate control valve 61 is increased and the opening degree of the second flow rate control valve 62 is reduced so that a detection value measured by the inverter temperature detection device 112 reaches or falls below the preset target temperature upper limit. This configuration reduces the flow rate of oil that flows to the vicinity of the inverter heat radiating portion 111, thereby preventing overheating of the inverter heat radiating portion 111.

[0119] The process of step S41 to the process of step S68 are implemented at control time intervals. Consequently, the flow rate of oil caused to flow to the vicinity of the inverter heat radiating portion 111 is regulated by using the first flow rate control valve 61 and the second flow rate control valve 62, and a detection value measured by the inverter temperature detection device 112 provided to the inverter heat radiating portion 111 can thus be regulated. Additionally, the opening degree of the main expansion valve 4 is regulated so that a detection value measured by the inverter temperature detection device 112 falls within the range from the preset threshold value to the preset target temperature upper limit inclusive.

[Effects of Embodiment 4]

[0120] As described above, in Embodiment 4, the same effects as in Embodiment 3 can be achieved, and the cooling refrigerant flow passage 93 and the inverter cooling expansion valve 9 do not have to be provided, thereby enabling simplification of the configuration of the refrigeration cycle apparatus and cost reductions. Reference Signs List

[0121] 1 screw compressor 2 oil separator 3 condenser 4 main expansion valve 5 evaporator 6 three-way valve 7 controller 9 inverter cooling expansion valve 61 first flow rate control valve 62 second flow rate control valve 90 first oil flow passage 91 second oil flow passage 92 refrigerant circulation passage 93 cooling refrigerant flow passage 101 compressor mechanism portion 101 a compression chamber 101b motor 110 inverter 111 inverter heat radiating portion 112 inverter temperature detection device

Claims

1. A refrigeration cycle apparatus comprising:

a refrigeration cycle in which a compressor in which an inverter including an inverter heat radiating portion being a portion where heat is radiated is integrated, an oil separator, a condenser, a first pressure reducing device, and an evaporator are connected by a pipe, and through which refrigerant circulates;

a cooling refrigerant flow passage branching off from a flow passage between the condenser and the first pressure reducing device and merging with a flow passage between the evaporator and the compressor;

a second pressure reducing device provided in the cooling refrigerant flow passage;

a first oil flow passage and a second oil flow passage through which refrigerating machine oil separated in the oil separator flows to the compressor;

an oil flow rate control unit configured to control a flow rate of refrigerating machine oil flowing through the first oil flow passage and a flow rate of refrigerating machine oil flowing through the second oil flow passage;

an inverter temperature detection device configured to measure a temperature of the inverter heat radiating portion; and

a controller,

the cooling refrigerant flow passage being formed to pass through a position where heat of refrigerant flowing through the cooling refrigerant flow passage is transferred to the inverter heat radiating portion,

the first oil flow passage being formed to pass through a position where heat of refrigerating machine oil flowing through the first oil flow passage is not transferred to the inverter heat radiating portion,

the second oil flow passage being formed to pass through a position where heat of refrigerating machine oil flowing through the second oil flow passage is transferred to the inverter heat radiating portion,

the controller being configured to control the second pressure reducing device and the oil flow rate control unit on a basis of a detection value measured by the inverter temperature detection device.

2. A refrigeration cycle apparatus comprising:

a refrigeration cycle in which a compressor in which an inverter including an inverter heat radiating portion being a portion where heat is radiated is integrated, an oil separator, a condenser, a first pressure reducing device, and an evaporator are connected by a pipe, and through which refrigerant circulates;

a first oil flow passage and a second oil flow passage through which refrigerating machine oil separated in the oil separator flows to the compressor;

an oil flow rate control unit configured to control a flow rate of refrigerating machine oil flowing through the first oil flow passage and a flow rate of refrigerating machine oil flowing through the second oil flow passage;

an inverter temperature detection device configured to measure a temperature of the inverter heat radiating portion; and

a controller,

the inverter heat radiating portion being placed in a position where heat of refrigerant gas to be sucked into the compressor is transferred,

the refrigeration cycle being formed such that heat of refrigerant gas to be sucked into the compressor is transferred to the inverter heat radiating portion,

the first oil flow passage being formed to pass through a position where heat of refrigerating machine oil flowing through the first oil flow passage is not transferred to the inverter heat radiating portion,

the second oil flow passage being formed to pass through a position where heat of refrigerating machine oil flowing through the second oil flow passage is transferred to the inverter heat radiating portion,

the controller being configured to control the first pressure reducing device and the oil flow rate control unit on a basis of a detection value measured by the inverter temperature detection device.

3. The refrigeration cycle apparatus of claim 1,
wherein the controller is configured to,
when a detection value measured by the inverter temperature detection device is less than a preset target temperature lower limit, control the oil flow rate control unit so that a detection value measured by the inverter temperature detection device reaches or exceeds a preset threshold value, and
when a detection value measured by the inverter temperature detection device is greater than or equal to a preset target temperature upper limit, control the second pressure reducing device so that a detection value measured by the inverter temperature detection device falls below the preset target temperature upper limit, and
wherein the preset threshold value is greater than or equal to the preset target temperature lower limit and less than or equal to the preset target temperature upper limit.

4. The refrigeration cycle apparatus of claim 2,
wherein the controller is configured to,
when a detection value measured by the inverter temperature detection device is less than a preset target temperature lower limit, control the oil flow rate control unit so that a detection value measured by the inverter temperature detection device reaches or exceeds a preset threshold value, and
when a detection value measured by the inverter temperature detection device is greater than or equal to a preset target temperature upper limit, control the first pressure reducing device so that a detection value measured by the inverter temperature detection device falls below the preset target temperature upper limit, and
wherein the preset threshold value is greater than or equal to the preset target temperature lower limit and less than or equal to the preset target temperature upper limit.

5. The refrigeration cycle apparatus of any one of claims 1 to 4, wherein the oil flow rate control unit comprises a three-way valve configured to switch a flow passage through which refrigerating machine oil separated in the oil separator flows between the first oil flow passage and the second oil flow passage.

6. The refrigeration cycle apparatus of any one of claims 1 to 4, wherein the oil flow rate control unit includes a first flow rate control valve configured to control a flow rate in the first oil flow passage and a second flow rate control valve configured to control a flow rate in the second oil flow passage.

Drawing