EP4368920A1

EP4368920A1 - Accumulator and refrigeration cycle device

Info

Publication number: EP4368920A1
Application number: EP21949287.3A
Authority: EP
Inventors: Hiroki Ishiyama
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2021-07-07
Filing date: 2021-07-07
Publication date: 2024-05-15
Also published as: WO2023281653A1; CN117581070A; JPWO2023281653A1; US20240255200A1; EP4368920A4

Abstract

An accumulator (5) includes a container (51) where refrigerant is accumulated, an inflow pipe (52) for flow of refrigerant into the container (51), an outflow pipe (53) for flow of refrigerant out of the container (51), an oil return portion (54) provided with an opening for suction of oil, and a decompressing pipe (56) to decompress refrigerant. In the accumulator (5), the decompressing pipe (56) and the oil return portion (54) are arranged on the outflow pipe (53).

Description

TECHNICAL FIELD

The present disclosure relates to an accumulator and a refrigeration cycle apparatus.

BACKGROUND ART

A refrigeration cycle apparatus including an accumulator has conventionally been known. The accumulator is provided between an evaporator and a compressor. Refrigerant that flows out of the evaporator flows into the accumulator. Refrigerant that flows into the accumulator is composed of gas refrigerant and a liquid mixture. The liquid mixture contains liquid refrigerant and oil for lubrication of the compressor. The accumulator prevents such liquid carry-over as flow of liquid refrigerant into the compressor due to accumulation of excessive liquid refrigerant. The accumulator prevents oil exhaustion due to increase in amount of discharge of oil from the compressor, by return of oil from an oil return portion.
Too large a diameter of a hole in the oil return portion may lead to increase in inflow flow rate and cause liquid carry-over. When the diameter of the hole is simply made smaller, the inflow flow rate may become too low and return of oil may be insufficient. Though a length of an outflow pipe may be increased or a straw tube for return of oil may separately be provided in order to increase an amount of return of oil, the apparatus increases in size.
In Japanese Patent Laying-Open No. 2014-203736 (PTL 1), in a gas-liquid separator as an accumulator, a mixing ratio adjustment apparatus that adjusts a ratio of flow of a liquid mixture by adjustment of an opening of a liquid return hole as an oil return portion is provided.

CITATION LIST

PATENT LITERATURE

PTL 1: Japanese Patent Laying-Open No. 2014-203736

SUMMARY OF INVENTION

TECHNICAL PROBLEM

The refrigeration cycle apparatus in PTL 1 activates a hole opening adjustment valve provided in the mixing ratio adjustment apparatus by driving an electric motor for suppression of a superheated state of refrigerant. Such a refrigeration cycle apparatus in PTL 1 is able to regulate a flow rate of the liquid mixture that flows from the accumulator into a compressor, whereas it is unable to return a proper amount of oil because an amount of oil with respect to the liquid mixture is not taken into consideration. In addition, the mixing ratio adjustment apparatus has been a large apparatus including an electric motor.
An object of the present disclosure is to provide an accumulator small in size and a refrigeration cycle apparatus that allow an appropriate amount of oil to flow into a compressor.

SOLUTION TO PROBLEM

The present disclosure relates to an accumulator provided between an evaporator of a refrigeration cycle apparatus and a refrigerant suction side of a compressor of the refrigeration cycle apparatus. The accumulator includes a container where refrigerant is accumulated, an inflow pipe for flow of refrigerant into the container, an outflow pipe for flow of refrigerant out of the container, an oil return portion provided with an opening for suction of oil, and a decompressing apparatus to decompress refrigerant. In the accumulator, the decompressing apparatus and the oil return portion are arranged on the outflow pipe.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, with an accumulator small in size, an appropriate amount of oil can flow into the compressor.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a diagram showing a circuit configuration of a refrigeration cycle apparatus in a first embodiment.
Fig. 2 is a diagram for illustrating an accumulator in the first embodiment.
Fig. 3 is a diagram showing a cross-section along III-III in Fig. 2.
Fig. 4 is a diagram for illustrating an accumulator in a second embodiment.
Fig. 5 is a diagram showing a cross-section along V-V in Fig. 4.
Fig. 6 is a diagram showing a circuit configuration of a refrigeration cycle apparatus in a third embodiment.
Fig. 7 is a diagram for illustrating an accumulator in the third embodiment.
Fig. 8 is a flowchart showing control of a second expansion valve in the third embodiment.
Fig. 9 is a diagram showing a circuit configuration of a refrigeration cycle apparatus in a fourth embodiment.
Fig. 10 is a flowchart showing control of the second expansion valve in the fourth embodiment.
Fig. 11 is a diagram showing a circuit configuration of a refrigeration cycle apparatus in a fifth embodiment.
Fig. 12 is a flowchart showing control of a first expansion valve and the second expansion valve in the fifth embodiment.
Fig. 13 is a diagram showing a circuit configuration of a refrigeration cycle apparatus in a sixth embodiment.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will be described in detail below with reference to the drawings. When the number or an amount is mentioned in an embodiment described below, the scope of the present disclosure is not necessarily limited to the number or the amount unless otherwise specified. The same or corresponding elements have the same reference characters allotted and redundant description may not be repeated. Combination of features in embodiments as appropriate is originally intended.

First Embodiment.

Fig. 1 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 100 in a first embodiment. Refrigeration cycle apparatus 100 includes a compressor 1, a first heat exchanger 2, a second heat exchanger 4, a first expansion valve 3, an accumulator 5, and a control device 10.
Refrigeration cycle apparatus 100 has refrigerant circulate sequentially through compressor 1, first heat exchanger 2, first expansion valve 3, second heat exchanger 4, and accumulator 5 during a heating operation.
Compressor 1 suctions, compresses, and discharges refrigerant. First heat exchanger 2 functions as a condenser. First heat exchanger 2 exchanges heat between air and refrigerant with the use of a not-shown fan to condense refrigerant. First expansion valve 3 is arranged between first heat exchanger 2 and second heat exchanger 4 and expands or decompresses refrigerant. First expansion valve 3 is, for example, an apparatus capable of freely controlling an opening of an electronic expansion valve or the like. Control device 10 controls the opening of first expansion valve 3.
Second heat exchanger 4 functions as an evaporator. Second heat exchanger 4 evaporates low-pressure liquid refrigerant decompressed by first expansion valve 3. Gas-liquid two-phase refrigerant evaporated by second heat exchanger 4 flows into accumulator 5. Refrigerating machine oil (which is also simply referred to as oil below) is enclosed in a refrigerant circuit of refrigeration cycle apparatus 100. Accumulator 5 provided between compressor 1 and second heat exchanger 4 separates into gas and liquid, gas-liquid two-phase refrigerant composed of gas refrigerant and a liquid mixture of oil and liquid refrigerant. Gas refrigerant and the liquid mixture adjusted in amount of oil that have passed through accumulator 5 return to compressor 1.
Control device 10 includes a central processing unit (CPU) 11, a memory 12 (a read only memory (ROM) and a random access memory (RAM)), and a not-shown input and output apparatus for input of various signals. CPU 11 develops on the RAM or the like, programs stored in the ROM and executes the programs. The programs stored in the ROM are programs in which a procedure of processing in control device 10 is written. Control device 10 controls each device in refrigeration cycle apparatus 100 in accordance with these programs. In this control, processing by dedicated hardware (electronic circuitry) can also be performed, without being limited to processing by software.

Fig. 2 is a diagram for illustrating accumulator 5 in the first embodiment. Accumulator 5 includes a container 51, an inflow pipe 52, an outflow pipe 53, an oil return portion 54, and a decompressing pipe 56 as a decompressing apparatus.
A liquid mixture of liquid refrigerant and oil is accumulated in container 51. Inflow pipe 52 is used for flow of gas refrigerant and the liquid mixture into container 51. Inflow pipe 52 extends toward a wall surface in container 51 and has a bent tip end. Outflow pipe 53 is bent in a U shape, and of gas refrigerant and the liquid mixture, gas refrigerant flows in through an inlet of outflow pipe 53. Gas refrigerant and the liquid mixture adjusted in amount of oil flow out of an outlet of outflow pipe 53. Outflow pipe 53 is in such a shape that a gas refrigerant inflow end is located at a position higher than oil return portion 54 and decompressing pipe 56 in container 51 and a gas refrigerant outflow end is located at a position protruding out of container 51.
Oil return portion 54 is an opening for suction of oil, the opening being provided in an arc portion of outflow pipe 53. Accumulator 5 prevents liquid carry-over which causes lowering in capability or reliability of compressor 1, by returning oil (refrigerating machine oil) as the liquid mixture, together with a small amount of liquid refrigerant, from oil return portion 54 to compressor 1. Gas refrigerant and oil flow out of the outlet of outflow pipe 53. Though a meshed cover for removal of dirt is provided at the opening of oil return portion 54, it is not shown for the sake of convenience of description.
Decompressing pipe 56 is provided between the inlet of outflow pipe 53 and oil return portion 54 and it is smaller in diameter than outflow pipe 53. Decompressing pipe 56 decompresses gas refrigerant. When decompressing pipe 56 is provided at a tip end of outflow pipe 53, a flow velocity at the tip end increases and efficiency in gas-liquid separation becomes poor. When the decompressing pipe is provided in the middle of outflow pipe 53, however, efficiency of gas-liquid separation can be prevented from lowering.
Fig. 3 is a diagram showing a cross-section along III-III in Fig. 2. As shown in Fig. 3, oil return portion 54 provided with a hole smaller in diameter than outflow pipe 53 is arranged in outflow pipe 53. Relation of P2 > P1 is satisfied where P1 represents a pressure in outflow pipe 53, P2 represents a pressure outside outflow pipe 53, and ΔP represents a pressure in oil return portion 54. A flow rate in oil return portion 54 is determined by relation of P2 - P1 = ΔP.

A flow of refrigerant in the first embodiment will be described. Gas refrigerant and the liquid mixture of liquid refrigerant and oil that have flowed out of second heat exchanger 4 flow into accumulator 5. Gas refrigerant and the liquid mixture pass through inflow pipe 52 in accumulator 5 and flow into container 51. Gas refrigerant and the liquid mixture are separated into gas and liquid; gas refrigerant flows into outflow pipe 53 and the liquid mixture is accumulated in container 51. Gas refrigerant that has flowed into outflow pipe 53 flows through decompressing pipe 56 while the pressure thereof is lowered. Lowering of the pressure can also be expressed as pressure loss.
The liquid mixture accumulated in container 51 flows from oil return portion 54 into outflow pipe 53. In accumulator 5, in accordance with a pressure difference ΔP between P2 which is the pressure at the inlet of oil return portion 54 in container 51 and pressure P1 in the inside of outflow pipe 53, oil in a lower portion of the liquid mixture flows in from oil return portion 54 and merges with gas refrigerant. Merged gas refrigerant and oil pass through outflow pipe 53 and flow out of accumulator 5 into compressor 1.
When the diameter of the hole in oil return portion 54 is excessively large, the inflow flow rate increases and liquid carry-over may occur. When the diameter of the hole is simply made smaller, the inflow flow rate may become too low and return of oil may be insufficient. Though a distance from the end to the hole of outflow pipe 53 may be increased or a straw tube for return of oil may separately be provided in order to increase an amount of return of oil, the apparatus increases in size.
In accumulator 5 in the present embodiment, decompressing pipe 56 and oil return portion 54 are sequentially arranged in the middle of outflow pipe 53 in a direction of flow of refrigerant. Therefore, a differential pressure can be increased without increase in size of accumulator 5, and an appropriate amount of oil can flow into compressor 1.

Second Embodiment.

Fig. 4 is a diagram for illustrating an accumulator 5A in a second embodiment. Accumulator 5A in the second embodiment is different from accumulator 5 in the first embodiment in that a first oil return portion 54A and a second return portion 54B are provided as two oil return portions and decompressing pipe 56 is arranged between the two oil return portions. The accumulator is otherwise similar in construction to accumulator 5 in the first embodiment. Differences from the first embodiment will mainly be described in the description below.
First oil return portion 54A and second oil return portion 54B are openings for suction of oil provided in the arc portion of outflow pipe 53. Accumulator 5A prevents liquid carry-over which causes lowering in capability or reliability of compressor 1, by returning oil from first oil return portion 54A and second oil return portion 54B to compressor 1. Gas refrigerant and oil flow out of the outlet of outflow pipe 53.
Decompressing pipe 56 is provided between first oil return portion 54A and second oil return portion 54B and it is smaller in diameter than outflow pipe 53. Decompressing pipe 56 decompresses gas refrigerant and the liquid mixture.
Fig. 5 is a diagram showing a cross-section along V-V in Fig. 4. As shown in Fig. 5, second oil return portion 54B smaller in diameter than outflow pipe 53 is provided in outflow pipe 53. Relation of P2' > P1' is satisfied where P1' represents a pressure in outflow pipe 53, P2' represents a pressure outside outflow pipe 53, and ΔP' represents a pressure in second oil return portion 54B. A flow rate in second oil return portion 54B is determined by relation of P2' - P1' = ΔP'.
First oil return portion 54A in the cross-section along III-III in Fig. 4 is the same as oil return portion 54 in Fig. 3. Relation of P2 > P1 is satisfied where P1 represents a pressure in outflow pipe 53, P2 represents a pressure outside the outflow pipe, and ΔP represents a pressure in first oil return portion 54A. A flow rate in first oil return portion 54A is determined by relation of P2 - P1 = ΔP.
Accumulator 5A satisfies relation of P2 ≅ P2' and satisfies relation of P1 > P1' attributed to decompressing pipe 56. Therefore, the flow rate in second oil return portion 54B is higher than the flow rate in first oil return portion 54A.

A flow of refrigerant in the second embodiment will be described. Gas refrigerant and the liquid mixture of liquid refrigerant and oil that have flowed out of second heat exchanger 4 flow into accumulator 5A. Gas refrigerant and the liquid mixture pass through inflow pipe 52 of accumulator 5A and flow into container 51. Gas refrigerant and the liquid mixture are separated into gas and liquid; gas refrigerant flows into outflow pipe 53 and the liquid mixture is accumulated in container 51. Gas refrigerant that has flowed into outflow pipe 53 flows through decompressing pipe 56 while the pressure thereof is lowered.
The liquid mixture accumulated in container 51 flows from first oil return portion 54A into outflow pipe 53. In accumulator 5A, in accordance with pressure difference ΔP between P2 which is the pressure at the inlet of first oil return portion 54A in container 51 and pressure P1 in the inside of outflow pipe 53, oil in the lower portion of the liquid mixture flows in from first oil return portion 54A and merges with gas refrigerant. Merged gas refrigerant and oil flow through decompressing pipe 56 while the pressure thereof is lowered.
Thereafter, the liquid mixture accumulated in container 51 flows from second oil return portion 54B into outflow pipe 53. In accordance with pressure difference ΔP' between P2' which is the pressure at the inlet of second oil return portion 54B in container 51 and pressure P1' in the inside of outflow pipe 53, oil in the lower portion of the liquid mixture flows in from second oil return portion 54B. Merged gas refrigerant and oil pass through outflow pipe 53 and flow out of accumulator 5 into compressor 1.
In accumulator 5A, first oil return portion 54A, decompressing pipe 56, and second oil return portion 54B are sequentially arranged in the middle of outflow pipe 53 in the direction of flow of refrigerant. Therefore, when the flow rate of refrigerant in the refrigerant circuit is low, the flow rate of inflow into first oil return portion 54A can be lowered to suppress liquid carry-over and to improve performance. When the flow rate of refrigerant in the refrigerant circuit is high, oil can return through first oil return portion 54A and second return portion 54B and reliability can be improved. An appropriate amount of oil can thus flow into compressor 1 without increase in size of accumulator 5A.

Third Embodiment.

Fig. 6 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 100A in a third embodiment. Refrigeration cycle apparatus 100A in the third embodiment is different from refrigeration cycle apparatus 100 in the first embodiment in that accumulator 5 is changed to an accumulator 5B and a discharge superheat sensor 61 is provided as a sensor between compressor 1 and first heat exchanger 2. The refrigeration cycle apparatus is otherwise similar in configuration to refrigeration cycle apparatus 100 in the first embodiment. Differences from the first embodiment will mainly be described in the description below.
Discharge superheat sensor 61 is a sensor to detect a superheat of refrigerant discharged from compressor 1. The discharge superheat refers to a superheat of refrigerant gas expressed by a difference between a temperature of refrigerant discharged from compressor 1 (which is also referred to as a discharge temperature below) and a saturation gas temperature corresponding to a pressure of refrigerant discharged from the compressor (which is also referred to as a discharge pressure below). Discharge superheat sensor 61 measures the discharge temperature and the discharge pressure. A signal resulting from measurement is transmitted to control device 10. Control device 10 calculates as a sensing value, the discharge superheat based on a detected signal value. A differential pressure gauge may be employed as discharge superheat sensor 61.

Fig. 7 is a diagram for illustrating an accumulator 5B in the third embodiment. Accumulator 5B in the third embodiment is different from accumulator 5 in the first embodiment in position of oil return portion 54 and in arrangement of a second expansion valve 57 instead of decompressing pipe 56 as the decompressing apparatus. The accumulator is otherwise similar in construction to accumulator 5 in the first embodiment. Differences from the first embodiment will mainly be described in the description below.
Oil return portion 54 is an opening for suction of oil, the opening being provided around the center in the arc portion of outflow pipe 53. Second expansion valve 57 is provided between the inlet of outflow pipe 53 and oil return portion 54 and decompresses gas refrigerant that flows in from outflow pipe 53. An opening of second expansion valve 57 is adjustable in accordance with the flow rate in the refrigerant circuit. As shown in Fig. 6, control device 10 controls the opening of second expansion valve 57 based on the sensing value of the discharge superheat.

Fig. 8 is a flowchart showing control of second expansion valve 57 in the third embodiment. As shown in Fig. 8, control device 10 determines in step S1 whether or not compressor 1 is operating. When control device 10 determines that compressor 1 is not operating (NO in step S1), the process ends. When control device 10 determines that compressor 1 is operating (YES in step S1), transition to processing in step S2 is made.
In step S2, control device 10 obtains the sensing value of the discharge superheat based on the value obtained by discharge superheat sensor 61. Control device 10 then compares a predetermined reference value and the sensing value with each other (step S3). When control device 10 determines that the sensing value is smaller than the reference value (YES in step S3), it decreases the opening of second expansion valve 57 from the current opening (step S4) and transition to processing in step S1 is made. When control device 10 determines that the sensing value is equal to or larger than the reference value (NO in step S3), it increases the opening of second expansion valve 57 from the current opening (step S5) and transition to processing in step S1 is made.
Control device 10 may increase or decrease the opening of second expansion valve 57 in predetermined steps. Control device 10 may quit processing for adjusting the opening when the opening of second expansion valve 57 is set to a predetermined smallest or largest opening.

A flow of refrigerant in the third embodiment will be described. Gas refrigerant and the liquid mixture of liquid refrigerant and oil that have flowed out of second heat exchanger 4 flow into accumulator 5B. Gas refrigerant and the liquid mixture pass through inflow pipe 52 of accumulator 5B and flow into container 51. Gas refrigerant and the liquid mixture are separated into gas and liquid; gas refrigerant flows into outflow pipe 53 and the liquid mixture is accumulated in container 51. Gas refrigerant that has flowed into outflow pipe 53 flows through second expansion valve 57 while the pressure thereof is lowered.
The liquid mixture accumulated in container 51 flows from oil return portion 54 into outflow pipe 53. In accumulator 5, in accordance with pressure difference ΔP between P2 which is the pressure at the inlet of oil return portion 54 in container 51 and pressure P1 in the inside of outflow pipe 53, oil in the lower portion of the liquid mixture flows in from oil return portion 54 and merges with gas refrigerant. Merged gas refrigerant and oil pass through outflow pipe 53 and flow out of accumulator 5 into compressor 1.

In refrigeration cycle apparatus 100A, during an unstable operation at the time of start-up or the like of compressor 1, the sensing value is smaller than the reference value. In this case, as shown in step S4 in Fig. 8, the opening of second expansion valve 57 decreases from the current opening. In accumulator 5B, decrease in opening of second expansion valve 57 leads to increase in lowering of the pressure in second expansion valve 57.
Thus, in refrigeration cycle apparatus 100A, the pressure difference between the inlet and the outlet of outflow pipe 53 can be increased without increase in size of accumulator 5B, and the inflow flow rate of oil into oil return portion 54 increases. Refrigeration cycle apparatus 100A can suppress oil exhaustion and improve reliability by increasing the amount of return of oil to compressor 1 when return of oil is necessary during the unstable operation at the time of start-up or the like.

In refrigeration cycle apparatus 100A, during a stable operation of compressor 1, the sensing value is equal to or larger than the reference value. In this case, as shown in step S5 in Fig. 8, the opening of second expansion valve 57 increases from the current opening. In accumulator 5B, increase in opening of second expansion valve 57 leads to decrease in lowering of the pressure in second expansion valve 57.
Thus, in refrigeration cycle apparatus 100A, the pressure difference between the inlet and the outlet of outflow pipe 53 can be decreased without increase in size of accumulator 5B, and the inflow flow rate of oil into oil return portion 54 lowers. Refrigeration cycle apparatus 100A can prevent liquid carry-over by decreasing the amount of return of oil to compressor 1 when return of oil is not necessary during the stable operation, and can obtain improvement in reliability and performance. Since pressure loss in outflow pipe 53 is reduced during the stable operation in refrigeration cycle apparatus 100A, performance of a circuit apparatus as a whole can be improved.

Fourth Embodiment.

Fig. 9 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 100B in a fourth embodiment. Refrigeration cycle apparatus 100B in the fourth embodiment is different from refrigeration cycle apparatus 100A in the third embodiment in that an oil concentration sensor 62 instead of discharge superheat sensor 61 is provided as the sensor in compressor 1. The refrigeration cycle apparatus is otherwise similar in configuration to refrigeration cycle apparatus 100A in the third embodiment. Differences from the third embodiment will mainly be described in the description below.
Oil concentration sensor 62 is a sensor to detect a concentration of oil in compressor 1. A signal relating to the concentration of oil measured by the oil concentration sensor is transmitted to control device 10. Control device 10 calculates as the sensing value, the concentration of oil based on a detected signal value. Control device 10 controls second expansion valve 57 based on the sensing value of the concentration of oil. A sensor to detect a state of liquid such as a sensor to sense a concentration of liquid based on a capacitance, a sensor to sense ultrasound, a sensor to sense an index of refraction, or the like may be employed as oil concentration sensor 62.

Fig. 10 is a flowchart showing control of second expansion valve 57 in the fourth embodiment. As shown in Fig. 10, control device 10 determines in step S11 whether or not compressor 1 is operating. When control device 10 determines that compressor 1 is not operating (NO in step S11), the process ends. When control device 10 determines that compressor 1 is operating (YES in step S11), transition to processing in step S12 is made.
In step S12, control device 10 obtains the sensing value from oil concentration sensor 62. Control device 10 then compares a predetermined reference value and the sensing value with each other (step S13). When control device 10 determines that the sensing value is smaller than the reference value (YES in step S13), it decreases the opening of second expansion valve 57 from the current opening (step S14) and transition to processing in step S11 is made. When control device 10 determines that the sensing value is equal to or larger than the reference value (NO in step S13), it increases the opening of second expansion valve 57 from the current opening (step S15) and transition to processing in step S11 is made.
Control device 10 may increase or decrease the opening of second expansion valve 57 in predetermined steps. Control device 10 may quit processing for adjusting the opening when the opening of second expansion valve 57 is set to a predetermined smallest or largest opening.

In refrigeration cycle apparatus 100B, during an unstable operation at the time of start-up or the like of compressor 1, the sensing value is smaller than the reference value. In this case, as shown in step S14 in Fig. 10, the opening of second expansion valve 57 decreases from the current opening. In accumulator 5B, decrease in opening of second expansion valve 57 leads to increase in lowering of the pressure in second expansion valve 57.
Thus, in refrigeration cycle apparatus 100B, the pressure difference between the inlet and the outlet of outflow pipe 53 can be increased without increase in size of accumulator 5B, and the inflow flow rate of oil into oil return portion 54 increases. Refrigeration cycle apparatus 100B can suppress oil exhaustion and improve reliability by increasing the amount of return of oil to compressor 1 when return of oil is necessary during the unstable operation at the time of start-up or the like.

In refrigeration cycle apparatus 100B, during a stable operation of compressor 1, the sensing value is equal to or larger than the reference value. In this case, as shown in step S15 in Fig. 10, the opening of second expansion valve 57 increases from the current opening. In accumulator 5B, increase in opening of second expansion valve 57 leads to decrease in lowering of the pressure in second expansion valve 57.
Thus, in refrigeration cycle apparatus 100B, the pressure difference between the inlet and the outlet of outflow pipe 53 can be decreased without increase in size of accumulator 5B, and the inflow flow rate of oil into oil return portion 54 lowers. Refrigeration cycle apparatus 100B can prevent liquid carry-over by decreasing the amount of return of oil to compressor 1 when return of oil is not necessary during the stable operation and can obtain improvement in reliability and performance. Since pressure loss in outflow pipe 53 is reduced during the stable operation in refrigeration cycle apparatus 100B, performance of the circuit apparatus as a whole can be improved.

Fifth Embodiment.

Fig. 11 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 100C in a fifth embodiment. Refrigeration cycle apparatus 100B in the fifth embodiment is different from refrigeration cycle apparatus 100A in the third embodiment in that a suction superheat sensor 63 instead of discharge superheat sensor 61 is provided as a sensor between second heat exchanger 4 and accumulator 5B. The refrigeration cycle apparatus is otherwise similar in configuration to refrigeration cycle apparatus 100A in the third embodiment. Differences from the third embodiment will mainly be described in the description below.
Suction superheat sensor 63 is a sensor to detect a superheat of refrigerant to be suctioned into compressor 1. The suction superheat refers to the superheat of refrigerant gas expressed by a difference between a temperature of refrigerant to be suctioned by compressor 1 (which is also referred to as a suction temperature below) and a saturation gas temperature corresponding to a pressure of refrigerant to be suctioned by the compressor (which is also referred to as a suction pressure below). Suction superheat sensor 63 measures the suction temperature and the suction pressure. A signal resulting from measurement is transmitted to control device 10. Control device 10 calculates as a sensing value, the suction superheat based on a detected signal value. Control device 10 controls second expansion valve 57 based on the sensing value of the suction superheat. A differential pressure gauge may be employed as suction superheat sensor 63.

Fig. 12 is a flowchart showing control of first expansion valve 3 and second expansion valve 57 in the fifth embodiment. As shown in Fig. 12, in step S21, control device 10 determines whether or not it has received a signal to stop operation of compressor 1, the signal being transmitted to control device 10 in response to an operation by a user. When control device 10 determines that it has not received the signal to stop operation of compressor 1 (NO in step S21), the process ends. When control device 10 determines that it has received the signal to stop operation of compressor 1 (YES in step S21), transition to processing in step S22 is made.
In step S22, control device 10 determines whether or not compressor 1 is operating. When control device 10 determines that compressor 1 is not operating (NO in step S22), the process ends. When control device 10 determines that compressor 1 is operating (YES in step S22), transition to processing in step S23 is made.
In step S23, control device 10 obtains a sensing value of the suction superheat from a value obtained by suction superheat sensor 63. In step S24, the control device then increases the opening of second expansion valve 57 from the current opening. Control device 10 then compares a predetermined reference value and the sensing value with each other (step S25). When control device 10 determines that the sensing value is smaller than the reference value (YES in step S25), it decreases the opening of first expansion valve 3 from the current opening (step S26) and transition to processing in step S21 is made. When control device 10 determines that the sensing value is equal to or larger than the reference value (NO in step S25), it increases the opening of first expansion valve 3 from the current opening (step S27) and transition to processing in step S21 is made.
In step S21, control device 10 starts counting from a time point of reception of the signal to stop operation of compressor 1. When transition to processing in step S26 is made, the control device may increase a count value, and when transition to processing in step S27 is made, the control device may reset the count value and set a stop flag. Control device 10 may determine that the operation of compressor 1 has been stopped when the stop flag is set. In processing in steps S21 and S22, control device 10 adjusts the opening of first expansion valve 3 and second expansion valve 57 in processing from reception of the signal to stop compressor 1 until compressor 1 completely stops. The suction superheat can thus sufficiently be improved during a period from reception of the signal to stop compressor 1 until complete stop of compressor 1.
Control device 10 may increase or decrease the opening of first expansion valve 3 and second expansion valve 57 in predetermined steps. Control device 10 may quit processing for adjusting the opening when the opening of first expansion valve 3 and second expansion valve 57 is set to a predetermined smallest or largest opening.

At the time when control device 10 receives a signal to stop compressor 1 in refrigeration cycle apparatus 100C, a degree of dryness of refrigerant at the inlet of accumulator 5B may have increased due to continued operation. In such a case, gas refrigerant and oil flow into accumulator 5B. Gas refrigerant and oil pass through inflow pipe 52 of accumulator 5B and flow into container 51. Gas refrigerant and oil are separated into gas and liquid; gas refrigerant flows into outflow pipe 53 and oil is accumulated in container 51.
In refrigeration cycle apparatus 100C, as shown in steps S21 to S24, control device 10 increases the opening of second expansion valve 57 from the current opening during a period from reception of the signal to stop compressor 1 until complete stop of compressor 1. In accumulator 5B, the opening of second expansion valve 57 increases so that lowering of the pressure in second expansion valve 57 decreases.
Thus, in refrigeration cycle apparatus 100C, the pressure difference between the inlet and the outlet of outflow pipe 53 can be decreased without increase in size of accumulator 5B, and the inflow flow rate of oil into oil return portion 54 lowers. Refrigeration cycle apparatus 100C can achieve improvement in reliability by accumulation of oil necessary for start-up in container 51 of accumulator 5B at the time of stop of the operation.
In refrigeration cycle apparatus 100C, when the sensing value is smaller than the reference value, control device 10 decreases the opening of first expansion valve 3 from the current opening as shown in step S26 to increase lowering of the pressure in first expansion valve 3. Increase in degree of dryness of refrigerant thus increases the suction superheat. With increase in suction superheat, an amount of oil that flows into accumulator 5B can be increased.
In refrigeration cycle apparatus 100C, when the sensing value is equal to or larger than the reference value, control device 10 increases the opening of first expansion valve 3 from the current opening as shown in step S27 to decrease lowering of the pressure in first expansion valve 3. Lowering in degree of dryness of refrigerant thus lowers the suction superheat. With lowering in suction superheat, an amount of oil that flows into accumulator 5B can be decreased.
Thus, in refrigeration cycle apparatus 100C, first expansion valve 3 and second expansion valve 57 are controlled at the time of reception of the stop signal to adjust the amount of oil that will flow into compressor 1 at the time of next start-up without increase in size of accumulator 5B, and reliability of compressor 1 can be improved.

Sixth Embodiment.

Fig. 13 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 100D in a sixth embodiment. Refrigeration cycle apparatus 100D in the sixth embodiment is different from refrigeration cycle apparatus 100 in the first embodiment in that a four-way valve 6 is provided on a refrigerant discharge side of compressor 1. The refrigeration cycle apparatus is otherwise similar in configuration to refrigeration cycle apparatus 100 in the first embodiment. Differences from the first embodiment will mainly be described in the description below.
Four-way valve 6 switches a direction of flow of refrigerant discharged from compressor 1 through a flow path by changing between a first state and a second state. In Fig. 13, a solid line shown in four-way valve 6 is similar to the flow path in refrigeration cycle apparatus 100 in the first embodiment. Control device 10 can control four-way valve 6 to switch the flow path shown with the solid line to a flow path shown with a dashed line.
In refrigeration cycle apparatus 100D, in a cooling operation during which switching to the flow path shown with the dashed line is made, refrigerant circulates sequentially through compressor 1, second heat exchanger 4, first expansion valve 3, first heat exchanger 2, and accumulator 5. Such a configuration including four-way valve 6 is applicable also to the second to fifth embodiments.

The present disclosure relates to accumulator 5 provided between second heat exchanger 4 which is an evaporator of refrigeration cycle apparatus 100 and a refrigerant suction side of compressor 1. Accumulator 5 includes container 51 where refrigerant is accumulated, inflow pipe 52 for flow of refrigerant into container 51, outflow pipe 53 for flow of refrigerant out of container 51, oil return portion 54 provided with an opening for suction of oil, and decompressing pipe 56 as a decompressing apparatus to decompress refrigerant. In accumulator 5, decompressing pipe 56 and oil return portion 54 are arranged on outflow pipe 53.
Preferably, the decompressing apparatus is composed of decompressing pipe 56 smaller in diameter than the outflow pipe. In accumulator 5, decompressing pipe 56 and oil return portion 54 are arranged in this order on outflow pipe 53 in a direction of flow of refrigerant.
Preferably, the oil return portion includes first oil return portion 54A and second oil return portion 54B. The decompressing apparatus is composed of decompressing pipe 56 smaller in diameter than outflow pipe 53. In accumulator 5A, first oil return portion 54A, decompressing pipe 56, and second oil return portion 54B are arranged in this order on outflow pipe 53 in a direction of flow of refrigerant.
Preferably, the decompressing apparatus is composed of second expansion valve 57 an opening of which is adjustable. In accumulator 5B, second expansion valve 57 and oil return portion 54 are arranged in this order on outflow pipe 53 in a direction of flow of refrigerant.
The present disclosure relates to refrigeration cycle apparatus 100A including accumulator 5B. Refrigeration cycle apparatus 100A includes compressor 1, first heat exchanger 2, second heat exchanger 4, first expansion valve 3, discharge superheat sensor 61 as the first sensor to measure a discharge superheat of refrigerant discharged from compressor 1, and control device 10 to control an opening of second expansion valve 57. When second heat exchanger 4 functions as the evaporator, refrigerant sequentially flows through compressor 1, first heat exchanger 2, first expansion valve 3, second heat exchanger 4, and accumulator 5B. Control device 10 controls an opening of second expansion valve 57 in accordance with the discharge superheat of refrigerant calculated from a value obtained by discharge superheat sensor 61.
The present disclosure relates to refrigeration cycle apparatus 100B including accumulator 5B. Refrigeration cycle apparatus 100B includes compressor 1, first heat exchanger 2, second heat exchanger 4, first expansion valve 3, oil concentration sensor 62 as the second sensor to measure a state of oil in compressor 1, and control device 10 to control an opening of second expansion valve 57. When second heat exchanger 4 functions as the evaporator, refrigerant sequentially flows through compressor 1, first heat exchanger 2, first expansion valve 3, second heat exchanger 4, and accumulator 5B. Control device 10 controls an opening of second expansion valve 57 in accordance with the state of oil detected by oil concentration sensor 62.
The present disclosure relates to refrigeration cycle apparatus 100C including accumulator 5B. Refrigeration cycle apparatus 100C includes compressor 1, first heat exchanger 2, second heat exchanger 4, first expansion valve 3, suction superheat sensor 63 as the third sensor to measure a suction superheat of refrigerant that flows into accumulator 5B, and control device 10 to control an opening of first expansion valve 3 and second expansion valve 57. When second heat exchanger 4 functions as the evaporator, refrigerant sequentially flows through compressor 1, first heat exchanger 2, first expansion valve 3, second heat exchanger 4, and accumulator 5B. After control device 10 receives a signal to stop compressor 1, control device 10 increases the opening of second expansion valve 57 as compared with the opening before compressor 1 is stopped, and controls the opening of first expansion valve 3 in accordance with the suction superheat of refrigerant calculated from a value obtained by suction superheat sensor 63.
The present disclosure relates to refrigeration cycle apparatus 100 including accumulator 5. Refrigeration cycle apparatus 100 includes compressor 1, first heat exchanger 2, second heat exchanger 4, and first expansion valve 3. When second heat exchanger 4 functions as the evaporator, refrigerant sequentially flows through compressor 1, first heat exchanger 2, first expansion valve 3, second heat exchanger 4, and accumulator 5.
Accumulator 5, 5A, or 5B in the present embodiment is configured as above, so that an appropriate amount of oil can flow into compressor 1 owing to accumulator 5 small in size. Refrigeration cycle apparatus 100, 100A, 100B, or 100C in the present embodiment is configured as above to implement a refrigerant circuit in which an appropriate amount of oil flows into compressor 1 owing to accumulator 5 small in size.

In the first embodiment, accumulator 5 may be varied in size of the opening of oil return portion 54 and in diameter of the decompressing pipe as appropriate, depending on the flow rate of refrigerant.
In the second embodiment, three or more openings as the oil return portions may be provided. The number of oil return portions can thus be changed depending on the flow rate. Accumulator 5A may be different in size of the opening for each of a plurality of oil return portions. Accumulator 5A may be provided with decompressing pipe 56 in each interval between oil return portions, or the plurality of decompressing pipes 56 may be different from one another in diameter.
In the fifth embodiment, suction superheat sensor 63 is provided between second heat exchanger 4 and accumulator 5B. Suction superheat sensor 63 may be provided between accumulator 5B and compressor 1.
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present disclosure is defined by the terms of the claims rather than the description of the embodiments above and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

REFERENCE SIGNS LIST

1 compressor; 2 first heat exchanger; 3 first expansion valve; 4 second heat exchanger; 5, 5A, 5B accumulator; 6 four-way valve; 10 control device; 51 container; 52 inflow pipe; 53 outflow pipe; 54, 54A, 54B oil return portion; 56 decompressing pipe; 57 second expansion valve; 61 discharge superheat sensor; 62 oil concentration sensor; 63 suction superheat sensor; 100, 100A, 100B, 100C, 100D refrigeration cycle apparatus

Claims

An accumulator provided between an evaporator of a refrigeration cycle apparatus and a refrigerant suction side of a compressor of the refrigeration cycle apparatus, the accumulator comprising:
a container where refrigerant is accumulated;

an inflow pipe for flow of refrigerant into the container;

an outflow pipe for flow of refrigerant out of the container;

an oil return portion provided with an opening for suction of oil; and

a decompressing apparatus to decompress refrigerant, wherein

in the accumulator, the decompressing apparatus and the oil return portion are arranged on the outflow pipe.
The accumulator according to claim 1, wherein
the decompressing apparatus is composed of a decompressing pipe smaller in diameter than the outflow pipe, and

in the accumulator, the decompressing pipe and the oil return portion are arranged in this order on the outflow pipe in a direction of flow of refrigerant.
The accumulator according to claim 1, wherein
the oil return portion comprises a first oil return portion and a second oil return portion,

the decompressing apparatus is composed of a decompressing pipe smaller in diameter than the outflow pipe, and

in the accumulator, the first oil return portion, the decompressing pipe, and the second oil return portion are arranged in this order on the outflow pipe in a direction of flow of refrigerant.
The accumulator according to claim 1, wherein
the decompressing apparatus is composed of a second expansion valve an opening of which is adjustable, and

in the accumulator, the second expansion valve and the oil return portion are arranged in this order on the outflow pipe in a direction of flow of refrigerant.
A refrigeration cycle apparatus comprising:
the accumulator according to claim 4;

the compressor;

a first heat exchanger;

a second heat exchanger;

a first expansion valve;

a first sensor to measure a discharge superheat of refrigerant discharged from the compressor; and

a control device to control an opening of the second expansion valve, wherein

when the second heat exchanger functions as the evaporator, refrigerant sequentially flows through the compressor, the first heat exchanger, the first expansion valve, the second heat exchanger, and the accumulator, and

the control device controls the opening of the second expansion valve in accordance with the discharge superheat of refrigerant calculated from a value obtained by the first sensor.
A refrigeration cycle apparatus comprising:
the accumulator according to claim 4;

the compressor;

a first heat exchanger;

a second heat exchanger;

a first expansion valve;

a second sensor to measure a state of oil in the compressor; and

a control device to control an opening of the second expansion valve, wherein

when the second heat exchanger functions as the evaporator, refrigerant sequentially flows through the compressor, the first heat exchanger, the first expansion valve, the second heat exchanger, and the accumulator, and

the control device controls the opening of the second expansion valve in accordance with the state of oil detected by the second sensor.
A refrigeration cycle apparatus comprising:
the accumulator according to claim 4;

the compressor;

a first heat exchanger;

a second heat exchanger;

a first expansion valve;

a third sensor to measure a suction superheat of refrigerant that flows into the accumulator; and

a control device to control an opening of the first expansion valve and the second expansion valve, wherein

when the second heat exchanger functions as the evaporator, refrigerant sequentially flows through the compressor, the first heat exchanger, the first expansion valve, the second heat exchanger, and the accumulator, and

after the control device receives a signal to stop the compressor, the control device increases the opening of the second expansion valve as compared with the opening before the compressor is stopped, and controls the opening of the first expansion valve in accordance with the suction superheat of refrigerant calculated from a value obtained by the third sensor.
A refrigeration cycle apparatus comprising:
the accumulator according to any one of claims 1 to 3;

the compressor;

a first heat exchanger;

a second heat exchanger; and

a first expansion valve, wherein

when the second heat exchanger functions as the evaporator, refrigerant sequentially flows through the compressor, the first heat exchanger, the first expansion valve, the second heat exchanger, and the accumulator.