REFRIGERATION CYCLE DEVICE

Abstract

A refrigeration cycle device includes: a compressor having a compression mechanism forming a compression chamber for compressing refrigerant, and a cooled portion cooled by the refrigerant before being compressed by the compression mechanism; a radiator that radiates the refrigerant compressed by the compressor; a decompressor that decompresses the refrigerant radiated by the radiator; an evaporator that evaporates the refrigerant decompressed by the decompressor; an acquisition unit that acquires the state of the refrigerant after cooling the cooled portion and before flowing into the compression chamber; and a control unit that controls the superheat degree of the refrigerant flowing into the compression chamber based on the state of the refrigerant acquired by the acquisition unit.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation application of International Patent Application No. PCT/JP2021/000821 filed on Jan. 13, 2021, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2020-27082 filed on Feb. 20, 2020 and Japanese Patent Application No. 2020-187226 filed on Nov. 10, 2020. The entire disclosures of all of the above applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle device that cools a compressor with a refrigerant.

BACKGROUND

In an electric compressor used in a refrigeration cycle device, a motor is cooled with a refrigerant. The compressor has a housing and a compression unit in addition to the motor. The housing houses the motor and the compression unit. Refrigerant vaporized by the evaporator of the refrigeration cycle device flows into the housing. The refrigerant flowing into the housing absorbs heat from the motor and then is sucked into the compression unit to be compressed. The refrigerant absorbs heat from the motor to cool the motor.

SUMMARY

A refrigeration cycle device according to one aspect of the present disclosure includes a compressor, a radiator, an evaporator decompressor, an evaporator, an acquisition unit, and a control unit. The compressor has a compression mechanism that forms a compression chamber for compressing the refrigerant, and a cooled portion that is cooled by the refrigerant before being compressed by the compression mechanism. The radiator radiates heat of the refrigerant compressed by the compressor. The evaporator decompressor decompresses the refrigerant radiated by the radiator. The evaporator evaporates the refrigerant decompressed by the evaporator decompressor. The acquisition unit acquires the state of the refrigerant after cooling the cooled portion and before flowing into the compression chamber. The control unit controls a degree of superheat of the refrigerant flowing into the compression chamber based on the state of the refrigerant acquired by the acquisition unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall configuration diagram showing a refrigeration cycle device according to a first embodiment.

FIG. 2 is a cross-sectional view showing a compressor of the first embodiment.

FIG. 3 is a block diagram showing an electrical control unit of the first embodiment.

FIG. 4 is a flowchart showing a control process executed by a control device of the first embodiment.

FIG. 5 is a Mollier diagram showing a change in the state of refrigerant in the refrigeration cycle device of the first embodiment.

FIG. 6 is an overall configuration diagram showing a refrigeration cycle device according to a second embodiment.

FIG. 7 is a flowchart showing a control process executed by a control device of the second embodiment.

FIG. 8 is an overall configuration diagram showing a refrigeration cycle device according to a third embodiment.

FIG. 9 is an overall configuration diagram showing a refrigeration cycle device according to a fourth embodiment.

FIG. 10 is an explanatory diagram showing a procedure for calculating a degree of superheat by a control device according to a fifth embodiment.

FIG. 11 is an explanatory diagram showing a method of calculating a density of refrigerant sucked into a compressor by a control device of the fifth embodiment.

FIG. 12 is an overall configuration diagram showing a refrigeration cycle device according to a sixth embodiment.

FIG. 13 is a flowchart showing a control process executed by a control device of the sixth embodiment.

FIG. 14 is a Mollier diagram showing a change in the state of refrigerant in the refrigeration cycle device of the sixth embodiment.

DESCRIPTION OF EMBODIMENT

To begin with, examples of relevant techniques will be described.

An electric compressor is used in a refrigeration cycle device, in which a motor is cooled with a refrigerant.

This compressor has a housing and a compression unit in addition to the motor. The housing houses the motor and the compression unit. Refrigerant vaporized by the evaporator of the refrigeration cycle device flows into the housing. The refrigerant flowing into the housing absorbs heat from the motor and then is sucked into the compression unit to be compressed. The refrigerant absorbs heat from the motor to cool the motor.

Since the refrigerant vaporized by the evaporator flows into the housing and is sucked by the compressor, the density of the refrigerant sucked into the compression unit decreases when the refrigerant absorbs heat from the motor.

As the density of the refrigerant sucked into the compression unit decreases, the flow rate (specifically, the weight flow rate) of the refrigerant discharged by the compression unit decreases. Since the flow rate of the refrigerant circulating in the refrigeration cycle device is reduced, the capacity of the refrigeration cycle device is reduced.

In particular, the higher the heat load of the refrigeration cycle device, the greater the power required for the compressor. Since the amount of heat generated by the motor is increased, the density of the refrigerant sucked into the compression unit significantly decreases. In this case, the capacity of the refrigeration cycle device is reduced.

The present disclosure provides a refrigeration cycle device whose capacity is suppressed from decreasing.

A refrigeration cycle device according to one aspect of the present disclosure includes a compressor, a radiator, an evaporator decompressor, an evaporator, an acquisition unit, and a control unit.

The compressor has a compression mechanism that forms a compression chamber for compressing the refrigerant, and a cooled portion that is cooled by the refrigerant before being compressed by the compression mechanism. The radiator radiates heat of the refrigerant compressed by the compressor. The evaporator decompressor decompresses the refrigerant radiated by the radiator. The evaporator evaporates the refrigerant decompressed by the evaporator decompressor.

The acquisition unit acquires the state of the refrigerant after cooling the cooled portion and before flowing into the compression chamber. The control unit controls a degree of superheat of the refrigerant flowing into the compression chamber based on the state of the refrigerant acquired by the acquisition unit.

Since it is possible to suppress a decrease in the density of the refrigerant sucked into the compression mechanism, the capacity of the refrigeration cycle device can be suppressed from decreasing while the cooled portion is cooled.

The following will describe embodiments for carrying out the present disclosure with reference to the drawings. In each embodiment, portions corresponding to those described in the preceding embodiment are denoted by the same reference numerals, and redundant descriptions may be omitted. In a case where only a part of a configuration is described in each embodiment, the other embodiments described above are capable of being applied for the other parts of the configuration. The present disclosure is not limited to combinations of embodiments which combine parts that are explicitly described as being combinable. As long as no problem is present, the various embodiments may be partially combined with each other even if not explicitly described.

First Embodiment

A refrigeration cycle device 10 shown in FIG. 1 heats air blown to an air-conditioned space in the air-conditioning device.

The refrigeration cycle device 10 has a vapor compression refrigeration cycle including a compressor 11, a radiator 12, an expansion valve 13 for an evaporator, and an evaporator 14. The compressor 11 compresses and discharges a refrigerant.

The radiator 12 radiates heat by exchanging heat between the refrigerant discharged from the compressor 11 and the air blown to the air-conditioned space.

The expansion valve 13 is an evaporator decompressor that reduces the pressure of the refrigerant flowing out of the radiator 12. The expansion valve 13 is an electric variable throttle mechanism including a valve body in which the throttle degree is variable and an electric actuator for changing the opening degree of the valve body.

The evaporator 14 evaporates the refrigerant decompressed by the expansion valve 13 by heat exchange. In this embodiment, the evaporator 14 exchanges heat between the refrigerant and outside air to absorb heat from the outside air. The blower 30 is an outside air blower unit that blows the outside air to the evaporator 14. The blower 30 is an electric blower that drives a fan with an electric motor.

The refrigeration cycle device 10 employs an HFC-based refrigerant (specifically, R134a) as the refrigerant, and configures a subcritical refrigeration cycle in which a high-pressure side refrigerant pressure does not exceed a critical pressure of the refrigerant. An HFO-based refrigerant (for example, R1234yf) or the like may be employed as the refrigerant. Refrigerator oil (hereinafter referred to as oil) for lubricating the sliding portion in the compressor 11 is mixed in the refrigerant, and a part of the oil circulates in the cycle together with the refrigerant.

The compressor 11 is an electric compressor having a compression mechanism 111, a motor unit 112, a shaft 113, and a housing 114. The compression mechanism 111 sucks in the refrigerant, compresses it, and discharges it. The motor unit 112 is a rotational drive source that rotationally drives the compression mechanism 111. The motor unit 112 is an electric motor that outputs a rotational driving force by being supplied with electric power. The motor unit 112 is a cooled portion to be cooled by the refrigerant.

The shaft 113 is a rotating shaft that transmits the rotational driving force output from the motor unit 112 to the compression mechanism 111. The housing 114 forms the outer shell of the compressor 11. The compression mechanism 111, the motor unit 112, and the shaft 113 are integrated through the housing 114.

The compressor 11 is configured as a so-called horizontal type in which the shaft 113 extends in a substantially horizontal direction while the compressor 11 is mounted on the refrigeration cycle device 10.

The compression mechanism 111 has a movable scroll and a fixed scroll. The movable scroll revolves by the rotational driving force transmitted from the shaft 113. The fixed scroll is fixed to the housing 114 and meshes with the movable scroll. A compression chamber 115 for compressing the refrigerant is formed between the movable scroll and the fixed scroll.

A suction port 114a is formed in the housing 114 in the vicinity of the motor unit 112. The suction port 114a sucks the refrigerant flowing out of the evaporator 14 into the housing 114.

As shown by the arrow in FIG. 2, the refrigerant sucked into the housing 114 from the suction port 114a flows around the motor unit 112, absorbs heat from the motor unit 112, and then is sucked into the compression chamber 115 of the compression mechanism 111.

A discharge port 114b is formed in the housing 114 in the vicinity of the compression mechanism 111. The discharge port 114b discharges the refrigerant discharged from the compression mechanism 111 toward the refrigerant inlet of the radiator 12.

Next, an outline of an electric control unit of the present embodiment will be described. The control device 20 shown in FIG. 3 is composed of a well-known microcomputer including a CPU, ROM, RAM, and the like, and peripheral circuits thereof. The control device 20 performs various calculations and processes based on control programs stored in the ROM, and controls the operation of various control target devices connected to an output side of the control device 20. The equipment to be controlled is the compressor 11, the expansion valve 13, the blower 30, and the like.

The input side of the control device 20 is connected with the inside temperature sensor 61, the outside temperature sensor 62, the solar radiation sensor 63, the discharge refrigerant pressure sensor 64, the discharge refrigerant temperature sensor 65, the radiator temperature sensor 66, the suction refrigerant pressure sensor 67, and the temperature sensor 68 in front of the compression chamber. Detection signals of the sensors are input into the control device 20.

The inside temperature sensor 61 is an internal air temperature detection unit that detects the cabin inside temperature Tr (hereinafter referred to as the inside air temperature Tr). The outside temperature sensor 62 is an outside air temperature detection unit that detects a cabin outside temperature Tam (hereinafter referred to as an outside air temperature Tam). The solar radiation sensor 63 is an insolation amount detection unit that detects the amount of insolation As irradiated into the cabin.

The discharge refrigerant pressure sensor 64 is a discharged refrigerant pressure detection unit that detects the pressure Pd of the refrigerant discharged from the compressor 11. The discharge refrigerant temperature sensor 65 is a discharged refrigerant temperature detection unit that detects the temperature Td of the refrigerant discharged from the compressor 11. The radiator temperature sensor 66 is a radiator temperature detection unit that detects the temperature of the radiator 12 (hereinafter referred to as the radiator temperature).

The suction refrigerant pressure sensor 67 is a suction refrigerant pressure detection unit that detects the pressure Ps of the refrigerant sucked into the compressor 11. That is, the suction refrigerant pressure sensor 67 detects a low pressure side pressure of the refrigeration cycle device 10.

The temperature sensor 68 in front of the compression chamber detects the temperature Tin of the refrigerant sucked into the compression chamber 115 of the compressor 11. That is, the temperature sensor 68 in front of the compression chamber detects the temperature Tin of the refrigerant after absorbing heat from the motor unit 112 and before being sucked into the compression mechanism 111. The temperature sensor 68 in front of the compression chamber is an acquisition unit that acquires the state of the refrigerant after cooling the motor unit 112 and before flowing into the compression chamber 115.

The input side of the control device 20 is connected to an operation panel 70 disposed adjacent to the instrument panel in a front portion of the cabin. Operation signals from various operation switches provided on the operation panel 70 are input to the control device 20.

Specific examples of the various operation switches provided on the operation panel 70 include an auto switch, an air volume setting switch, a temperature setting switch, and the like.

The auto switch is an operation unit that sets or cancels the automatic control operation of the air conditioner for a vehicle. The temperature setting switch is an operation unit that sets the target temperature Tset in the cabin.

The control device 20 of the present embodiment is integrally configured with control units that control various controlled devices connected to the output side of the control device 20. The control device 20 has configurations (hardware and software) as the control units to control the operation of the target devices respectively.

For example, the control device 20 has a compressor control unit 201 for controlling the refrigerant discharge capacity of the compressor 11 (specifically, the rotation speed of the compressor 11). The control device 20 has an expansion valve control unit 202 for controlling the expansion valve 13. The control device 20 has a calculation unit 203 that performs various calculations.

Operations of the above configurations according to the present embodiment will be described next. The control device 20 determines the increase/decrease amount ΔIVO in the rotation speed of the compressor 11. The increase/decrease amount ΔIVO is determined so that the actual radiator temperature approaches the target radiator temperature by the feedback control method based on the deviation between the target radiator temperature and the actual radiator temperature.

The target radiator temperature is determined with reference to the control map based on the target outlet temperature TAO. In the control map of the present embodiment, it is determined that the target radiator temperature rises as the target outlet temperature TAO rises. The target outlet temperature TAO is a target temperature of air blown into the cabin. The target outlet temperature TAO is calculated by using the inside air temperature Tr detected by the inside temperature sensor 61, the outside air temperature Tam detected by the outside temperature sensor 62, the amount of solar radiation As detected by the solar radiation sensor 63, and the set temperature Tset set by the temperature setting switch.

In the refrigeration cycle device 10, the high-pressure refrigerant discharged from the compressor 11 flows into the radiator 12 and exchanges heat with the air blown to the air-conditioned space to dissipate heat. The air is heated as a result. The refrigerant flowing out of the radiator 12 is decompressed by the expansion valve 13 to be a low-pressure refrigerant, and flows into the evaporator 14. The refrigerant flowing into the evaporator 14 absorbs heat from the outside air to evaporate. The refrigerant flowing out of the evaporator 14 is sucked into the compressor 11 and compressed again.

The refrigeration cycle device 10 of the present embodiment operates as described above, and can heat air in the cabin.

As shown in the flowchart of FIG. 4, the control device 20 determines the opening degree of the expansion valve 13. In step S100, the detection signal of the suction refrigerant pressure sensor 67 and the detection signal of the temperature sensor 68 in front of the compression chamber are read. That is, the refrigerant pressure Ps detected by the suction refrigerant pressure sensor 67 (hereinafter referred to as suction pressure Ps) and the refrigerant temperature Tin in front of the compression chamber detected by the temperature sensor 68 (hereinafter referred to as front chamber temperature Tin) are read.

In step S110, the superheat degree SH of the refrigerant in front of the compression chamber 115 is calculated based on the suction pressure Ps and the front chamber temperature Tin, and it is determined whether the calculated superheat degree SH is less than 5 deg, in a range more than or equal to 5 deg and less than 10 deg, or 10 deg or more. In step S110, 5 deg is a first reference temperature and 10 deg is a second reference temperature.

When the calculated superheat degree SH is less than 5 deg, the process proceeds to step S120, and the opening degree of the expansion valve 13 is reduced. As a result, the flow rate of the refrigerant flowing into the evaporator 14 is reduced, so that the superheat degree of the refrigerant flowing out of the evaporator 14 is increased.

When the calculated superheat degree SH is in a range 5 deg or more and less than 10 deg, the process proceeds to step S130, and the opening degree of the expansion valve 13 is maintained as it is. As a result, the flow rate of the refrigerant flowing into the evaporator 14 does not change substantially, so that the superheat degree of the refrigerant flowing out of the evaporator 14 does not change.

When the calculated superheat degree SH is 10 deg or more, the process proceeds to step S140 to increase the opening degree of the expansion valve 13. As a result, the flow rate of the refrigerant flowing into the evaporator 14 increases, so that the superheat degree of the refrigerant flowing out of the evaporator 14 becomes low.

Therefore, the superheat degree SH of the refrigerant flowing into the compression chamber 115 can be maintained in the range equal to or more than 5 deg and less than 10 deg. As a result, it is possible to suppress a decrease in the density of the refrigerant flowing into the compression chamber 115 while cooling the motor unit 112.

FIG. 5 is a Mollier diagram showing a change in the state of the refrigerant in the present embodiment. Point a1 represents the state of the refrigerant flowing into the compressor 11 and before cooling the motor unit 112. Point b1 represents the state of the refrigerant cooling the motor unit 112 in the compressor 11 and before flowing into the compression chamber 115. Point c1 represents the state of the refrigerant discharged from the compressor 11.

Since the superheat degree of the refrigerant at Point b1 (that is, the refrigerant after cooling the motor unit 112) is maintained at 5 deg or more and less than 10 deg, the refrigerant at Point al (that is, before cooling the motor unit 112) is in gas-liquid two-phase state.

The gas-liquid two-phase refrigerant flowing into the compressor 11 absorbs heat from the motor unit 112, but the amount of heat absorbed is spent on the evaporation of the liquid refrigerant, so that the superheat degree of the refrigerant after the heat absorption is suppressed to a small value. Therefore, since the expansion in volume of the refrigerant due to the superheat degree of the refrigerant can be suppressed to a small extent, the decrease in the weight flow rate of the refrigerant discharged by the compressor 11 can be reduced.

In the present embodiment, the temperature sensor 68 detects the temperature Tin of the refrigerant after cooling the motor unit 112 of the compressor 11 and before flowing into the compression chamber 115 of the compression mechanism 111. The control device 20 controls the superheat degree SH of the refrigerant flowing into the compression chamber 115 of the compression mechanism 111 based on the temperature Tin of the refrigerant in front of the compression chamber, which is acquired by the temperature sensor 68.

As a result, it is possible to suppress a decrease in the density of the refrigerant sucked into the compression mechanism 111. Thus, it is possible to suppress a decrease in the capacity of the refrigeration cycle device while the motor unit 112 is cooled.

In the present embodiment, the control device 20 controls the expansion valve 13 based on the front chamber temperature Tin detected by the temperature sensor 68 in front of the compression chamber. Thus, the control device 20 controls the superheat degree SH of refrigerant flowing into the compression chamber 115 of the compression mechanism 111. This makes it possible to accurately control the superheat degree of the refrigerant flowing into the compression chamber 115.

Second Embodiment

In the first embodiment, the opening degree of the expansion valve 13 is controlled based on the superheat degree of the refrigerant flowing into the compression chamber 115. In the present embodiment, as shown in FIGS. 6 to 7, the opening degree of a bypass expansion valve 15 is controlled based on the superheat degree of the refrigerant flowing into the compression chamber 115.

The bypass expansion valve 15 shown in FIG. 6 decompresses the refrigerant flowing out of the radiator 12 and flowing through a bypass passage 16. The bypass expansion valve 15 is an electric variable throttle mechanism including a valve body whose throttle degree is variable and an electric actuator for changing the opening degree of the valve body.

The bypass passage 16 is a bypass unit that bypasses the expansion valve 13 and the evaporator 14 to guide the refrigerant flowing out of the radiator 12 to the suction side of the compressor 11.

The refrigerant that has passed through the bypass expansion valve 15 contains a larger amount of liquid phase refrigerant than the gas phase refrigerant (so-called liquid-rich state). The liquid-rich refrigerant that has passed through the bypass expansion valve 15 is mixed with the gas-phase refrigerant that has passed through the evaporator 14, so that the gas-liquid two-phase refrigerant can be supplied to the compressor 11.

As shown in the flowchart of FIG. 7, the control device 20 determines the opening degree of the bypass expansion valve 15. In step S200, the detection signal of the temperature sensor 68 in front of the compression chamber and the detection signal of the suction refrigerant pressure sensor 67 are read. That is, the temperature Tin in front of the compression chamber detected by the temperature sensor 68 and the suction pressure Ps detected by the suction refrigerant pressure sensor 67 are read.

In step S210, the superheat degree of the refrigerant in front of the compression chamber 115 is calculated based on the suction pressure Ps and the front chamber temperature Tin. It is determined whether the calculated degree of superheat is less than 5 deg, in a range more than or equal to 5 deg and less than 10 deg, or 10 deg or more. In step S210, 5 deg is a first reference temperature and 10 deg is a second reference temperature.

When the calculated degree of superheat is less than 5 deg, the process proceeds to step S220 to reduce the opening degree of the bypass expansion valve 15. As a result, the flow rate of the refrigerant passing through the bypass expansion valve 15 decreases, so that the superheat degree of the refrigerant flowing into the compressor 11 increases.

When the calculated degree of superheat is in a range 5 deg or more and less than 10 deg, the process proceeds to step S230, and the opening degree of the bypass expansion valve 15 is maintained as it is. As a result, the flow rate of the refrigerant passing through the bypass expansion valve 15 does not change substantially, so that the superheat degree of the refrigerant flowing into the compressor 11 does not change.

When the calculated degree of superheat is 10 deg or more, the process proceeds to step S140 to increase the opening degree of the bypass expansion valve 15. As a result, the flow rate of the refrigerant passing through the bypass expansion valve 15 increases, so that the superheat degree of the refrigerant flowing into the compressor 11 decreases.

Therefore, the superheat degree of the refrigerant flowing into the compression chamber 115 can be maintained in a range of 5 deg or more and less than 10 deg, so that the same effect as that of the first embodiment can be obtained.

In the present embodiment, the control device 20 controls the bypass expansion valve 15 based on the front chamber temperature Tin detected by the temperature sensor 68, thereby controlling the superheat degree of the refrigerant flowing into the compression chamber 115 of the compression mechanism 111.

As a result, the liquid phase refrigerant can be reliably supplied to the compressor 11, so that it is possible to reliably suppress a decrease in the density of the refrigerant sucked into the compression mechanism 111.

Third Embodiment

In the first embodiment, the flow rate of the liquid refrigerant flowing into the compressor 11 is adjusted by controlling the opening degree of the expansion valve 13. In the present embodiment, as shown in FIG. 8, the flow rate of the liquid refrigerant flowing into the compressor 11 is adjusted by controlling an opening area of an oil return hole of the accumulator 17.

The accumulator 17 is a gas-liquid separator that separates the refrigerant flowing out of the evaporator 14 between gas and liquid. The accumulator 17 is capable of allowing the separated gas-phase refrigerant and liquid-phase refrigerant to flow out separately.

The accumulator 17 has a pipe 17a formed in a U shape. The pipe 17a is arranged in the internal space of the accumulator 17 so that the bent portion is located on the lower side. One end of the pipe 17a is connected to the suction port of the compressor 11. The gas phase refrigerant in the accumulator 17 is sucked from the other end of the pipe 17a.

A minute oil return hole is formed at the lower end of the pipe 17a. The oil return hole is an oil return unit that sucks the oil accumulated at the bottom of the accumulator 17 into the lower end of the pipe 17a, and the oil is mixed with the gas phase refrigerant flowing through the pipe 17a, so as to flow to the compressor 11. Thus, the accumulator 17 restricts the compressor 11 from drawing and compressing the liquid-phase refrigerant.

An oil return adjusting valve 17b is arranged in the oil return hole of the accumulator 17. The oil return adjusting valve 17b is an oil return adjusting unit that adjusts the opening area of the oil return hole. The oil return adjusting valve 17b is an electric opening area adjusting mechanism including a valve body whose opening degree is variable and an electric actuator for changing the opening degree of the valve body. The operation of the oil return adjusting valve 17b is controlled by the control device 20. The flow rate of the liquid refrigerant flowing into the compressor 11 (in other words, the latent heat amount) increases when the opening degree of the oil return adjusting valve 17b is increased by the control device 20.

When the opening degree of the oil return adjusting valve 17b is reduced by the control device 20, the flow rate of the liquid refrigerant flowing into the compressor 11 (in other words, the latent heat amount) is reduced.

Therefore, since the superheat degree of the refrigerant flowing into the compression chamber 115 can be controlled as in the above embodiment, the same effect as that of the above embodiment can be obtained.

In the present embodiment, the superheat degree of the refrigerant flowing into the compression chamber 115 of the compression mechanism 111 is controlled by controlling the oil return adjusting valve 17b of the accumulator 17 based on the front chamber temperature Tin detected by the temperature sensor 68.

As a result, the liquid phase refrigerant can be reliably supplied to the compressor 11 by using the accumulator 17, so that the decrease in the density of the refrigerant sucked into the compression mechanism 111 can be suppressed by a simple configuration.

Fourth Embodiment

In the third embodiment, the flow rate of the liquid refrigerant flowing into the compressor 11 is adjusted by controlling the opening area of the oil return hole of the accumulator 17 with the oil return adjusting valve 17b. In the present embodiment, as shown in FIG. 9, the passage area of a liquid refrigerant passage 18 provided between the bottom surface of the accumulator 17 and the suction port of the compressor 11 is controlled by a liquid refrigerant adjusting valve 19, so as to control the flow rate of the liquid refrigerant flowing into the compressor 11.

The liquid refrigerant passage 18 is a liquid return unit that guides the liquid refrigerant separated by the accumulator 17 to the compressor 11. The liquid refrigerant adjusting valve 19 is a liquid passage adjusting unit that adjusts the passage area of the liquid refrigerant passage 18. The liquid refrigerant adjusting valve 19 is an electric opening area adjusting mechanism including a valve body whose opening degree is variable and an electric actuator for changing the opening degree of the valve body. The operation of the liquid refrigerant adjusting valve 19 is controlled by the control device 20. When the opening degree of the liquid refrigerant adjusting valve 19 is increased by the control device 20, the flow rate of the liquid refrigerant flowing into the compressor 11 (in other words, the latent heat amount) increases. When the opening degree of the liquid refrigerant adjusting valve 19 is reduced by the control device 20, the flow rate of the liquid refrigerant flowing into the compressor 11 (in other words, the latent heat amount) is reduced. Therefore, the same effect as that of the third embodiment can be obtained.

In the present embodiment, the control device 20 controls the liquid refrigerant adjusting valve 19 based on the front chamber temperature Tin detected by the temperature sensor 68 in front of the compression chamber, so that the superheat degree of refrigerant flowing into the compression chamber 115 of the compression mechanism 111 is controlled.

As a result, the liquid phase refrigerant can be reliably supplied to the compressor 11, so that it is possible to reliably suppress a decrease in the density of the refrigerant sucked into the compression mechanism 111.

Fifth Embodiment

In the above embodiment, the control device 20 calculates the superheat degree SH using the front chamber temperature Tin detected by the temperature sensor 68. In the present embodiment, the control device 20 calculates the superheat degree SH without using the front chamber temperature Tin detected by the temperature sensor 68.

The calculation unit 203 of the control device 20 is a superheat degree calculation unit for calculating the superheat degree SH. In other words, the calculation unit 203 is an acquisition unit that acquires the state of the refrigerant after cooling the motor unit 112 and before flowing into the compression chamber 115.

The calculation unit 203 calculates the superheat degree SH by the procedure shown in FIG. 10. The control device 20 calculates a volumetric efficiency ηv and a compression efficiency ηc of the compressor 11 based on the rotation speed NC of the compressor 11, the discharge capacity of the compressor 11, the suction pressure Ps of the compressor 11, and the control map stored in advance.

The calculation unit 203 of the control device 20 calculates the density ρs of the refrigerant sucked into the compressor 11 (hereinafter, referred to as compressor suction refrigerant density ρs) based on the suction pressure Ps, the discharge temperature Td, the discharge pressure Pd, and the compression efficiency ηc of the compressor 11.

That is, in the Mollier diagram shown in FIG. 11, the position of Point c5 can be known from the discharge temperature Td and the discharge pressure Pd. The smaller the compression efficiency ηc, the smaller the slope of the line Lc representing the compression stroke than the isentropic line Li. Therefore, the line Lc of the compression stroke can be known from the compression efficiency ηc. Since the position of Point a5 on the Mollier diagram shown in FIG. 11 can be known based on the compression stroke line Lc and the suction pressure Ps, the dryness of refrigerant sucked into the compression chamber 115 can be known. Therefore, the compressor suction refrigerant density ρs can be calculated.

The calculation unit 203 of the control device 20 calculates a flow rate Gc of the refrigerant sucked into the compressor 11 (hereinafter, compressor suction refrigerant flow rate Gc) based on the rotation speed NC, the discharge capacity and the volumetric efficiency ηv of the compressor 11, and the compressor suction refrigerant density ρs.

The calculation unit 203 of the control device 20 calculates the motor heat generation value Qm based on the motor power. The calculation unit 203 of the control device 20 calculates the enthalpy difference ΔI between the refrigerant sucked into the compression chamber 115 and the refrigerant sucked into the compressor 11 based on the motor heat generation value Qm and the compressor suction refrigerant flow rate Gc. Specifically, since the flow rate of the refrigerant sucked into the compression chamber 115 is the same as the compressor suction refrigerant flow rate Gc, the enthalpy difference ΔI can be calculated by dividing the motor heat generation value Qm by the compressor suction refrigerant flow rate Gc.

The calculation unit 203 of the control device 20 calculates an enthalpy lc of the refrigerant sucked into the compressor 11 (hereinafter referred to as an actual suction enthalpy Ic) based on the discharge temperature Td, the discharge pressure Pd, and the compression efficiency ηc of the compressor 11. Specifically, the actual suction enthalpy lc can be seen from the position of Point a5 in FIG. 11.

The calculation unit 203 of the control device 20 calculates the enthalpy Iin of the refrigerant sucked into the compression chamber 115 by adding the enthalpy difference ΔI to the enthalpy lc of the refrigerant sucked into the compressor 11 (see FIG. 5). The calculation unit 203 of the control device 20 calculates the superheat degree SH of the refrigerant sucked into the compression chamber 115 based on the enthalpy Iin and the suction pressure Ps of the compressor 11. Specifically, the temperature of the refrigerant sucked into the compression chamber 115 (that is, the front chamber temperature Tin) is calculated based on the enthalpy Iin. The superheat degree SH of the refrigerant is calculated based on the front chamber temperature Tin and the suction pressure Ps of the compressor 11.

According to this embodiment, since the temperature Tin in front of the compression chamber can be acquired without using the temperature sensor 68, the number of components can be reduced.

In the present embodiment, the calculation unit 203 of the control device 20 calculates the front chamber temperature Tin based on the amount of power to drive the electric motor, the number of revolutions of the electric motor, the pressure Ps of the refrigerant sucked by the compressor 11, and the pressure Pd and the temperature Td of the refrigerant discharged by the compressor 11.

According to this, since the front chamber temperature Tin can be calculated without using the temperature sensor 68, the configuration can be simplified.

Sixth Embodiment

In this embodiment, as shown in FIG. 12, a hot gas passage 31 and a flow rate adjusting valve 32 are added to the first embodiment.

The hot gas passage 31 bypasses the radiator 12, the expansion valve 13, and the evaporator 14 to guide the refrigerant discharged from the compressor 11 to the suction side of the compressor 11.

The flow rate adjusting valve 32 is a flow rate adjusting unit that reduces the pressure of the refrigerant discharged from the compressor 11 to flow through the hot gas passage 31, and adjusts the flow rate (mass flow rate) of the refrigerant flowing through the hot gas passage 31. The flow rate adjusting valve 32 is an electric variable throttle mechanism including a valve body whole throttle degree is variable and an electric actuator for changing the opening degree of the valve body. The flow rate adjusting valve 32 is capable of fully closing the hot gas passage 31. The flow rate adjusting valve 32 is controlled by the control device 20.

The refrigerant that has passed through the hot gas passage 31 has a higher degree of superheat than the vapor phase refrigerant that has passed through the evaporator 14. Since the highly superheated refrigerant that has passed through the hot gas passage 31 is mixed with the refrigerant that has passed through the evaporator 14, the superheat degree of the refrigerant supplied to the compressor 11 can be increased.

In the present embodiment, the refrigerant discharged from the compressor 11 circulates in order of the radiator 12, the expansion valve 13, the evaporator 14, and the suction port of the compressor 11. At the same time, a part of the refrigerant discharged from the compressor 11 circulates in order of the flow rate adjusting valve 32 and the suction port of the compressor 11 via the hot gas passage 31.

The control device 20 controls the opening degree of the expansion valve 13 and the flow rate adjusting valve 32 so that the superheat degree SH of the refrigerant in front of the compression chamber 115 is within a predetermined range. Specifically, as shown in the flowchart of FIG. 13, the control device 20 determines the opening degree of the expansion valve 13 and the flow rate adjusting valve 32. In step S300, the detection signal of the temperature sensor 68 and the detection signal of the suction refrigerant pressure sensor 67 are read. That is, the temperature Tin in front of the compression chamber detected by the temperature sensor 68 and the suction pressure Ps detected by the suction refrigerant pressure sensor 67 are read.

In step S310, the superheat degree of the refrigerant in front of the compression chamber 115 is calculated based on the suction pressure Ps and the front chamber temperature Tin, and it is determined whether the calculated degree of superheat is less than 5 deg, in a range equal to or more than 5 deg and less than 10 deg, or 10 deg or more. In step S210, 5 deg is a first reference temperature and 10 deg is a second reference temperature.

When the calculated degree of superheat is less than 5 deg, the process proceeds to step S320, and the opening degree of the expansion valve 13 is reduced or the opening degree of the flow rate adjusting valve 32 is increased. As a result, the superheat degree of the refrigerant flowing into the compressor 11 increases. The air volume with respect to the evaporator 14 (that is, the air volume of the blower 30) may be increased. As a result, the amount of heat exchanged in the evaporator 14 increases, so that the superheat degree of the refrigerant flowing out of the evaporator 14 increases. Thus, the superheat degree of the refrigerant flowing into the compressor 11 increases.

When the calculated degree of superheat is in the range equal to or more than 5 deg and less than 10 deg, the process proceeds to step S330, and the opening degrees of the expansion valve 13 and the flow rate adjusting valve 32 are maintained as they are. As a result, the flow rate of the refrigerant passing through the flow rate adjusting valve 32 does not change, so that the superheat degree of the refrigerant flowing into the compressor 11 does not change. Further, the air volume with respect to the evaporator 14 (that is, the air volume of the blower 30) is maintained as it is.

When the calculated degree of superheat is 10 deg or more, the process proceeds to step S340 to increase the opening degree of the expansion valve 13 or decrease the opening degree of the flow rate adjusting valve 32. As a result, the superheat degree of the refrigerant flowing into the compressor 11 is reduced. The air volume with respect to the evaporator 14 (that is, the air volume of the blower 30) may be reduced. For example, the blower 30 may be stopped to set the air volume of the blower 30 to zero. As a result, the amount of heat exchanged in the evaporator 14 is reduced, so that the superheat degree of the refrigerant flowing out of the evaporator 14 is reduced. Thus, the superheat degree of the refrigerant flowing into the compressor 11 is lowered.

Therefore, the superheat degree of the refrigerant flowing into the compression chamber 115 is maintained in the range between 5 deg and 10 deg.

In the refrigeration cycle device 10 of the present embodiment, as shown in the Mollier diagram of FIG. 14, the state of the refrigerant changes. That is, the refrigerant discharged from the compressor 11 (Point a14 in FIG. 14) is branched between the radiator 12 and the flow rate adjusting valve 32. The refrigerant branched to the radiator 12 flows into the radiator 12 and dissipates heat to the air (from Point a14 to Point b14 in FIG. 14). As a result, the air blown to the air-conditioned space is heated.

The refrigerant flowing out of the radiator 12 flows into the expansion valve 13 and is depressurized (from Point b14 to Point c14 in FIG. 14). The refrigerant having a relatively low enthalpy flowing out from the expansion valve 13 flows into the evaporator 14. The refrigerant flowing into the evaporator 14 exchanges heat with the outside air.

The refrigerant branched to the flow rate adjusting valve 32 flows into the hot gas passage 31. The flow rate of the refrigerant flowing into the hot gas passage 31 is adjusted by the flow rate adjusting valve 32 to reduce the pressure (from Point a14 to Point d14 in FIG. 14). The refrigerant with a relatively high enthalpy decompressed by the flow rate adjusting valve 32 is mixed with the refrigerant heat-exchanged by the evaporator 14 and sucked into the compressor 11 (from Point c14 to Point e14, and from Point d14 to Point e14 in FIG. 14).

At this time, the superheat degree SH of the refrigerant sucked into the compressor 11 approaches a predetermined range (5 deg or more and less than 10 deg). The mixed refrigerant is sucked into the compressor 11 and compressed again.

As described above, in the present embodiment, the control device 20 controls at least one of the expansion valve 13 and the flow rate adjusting valve 32 based on the temperature Tin detected by the temperature sensor 68 in front of the compression chamber. Thus, the superheat degree of the refrigerant flowing into the compression chamber 115 of the compression mechanism 111 is controlled. This makes it possible to increase the flow rate of the refrigerant circulating in the refrigeration cycle device 10.

The present disclosure is not limited to the above-described embodiments, and can be variously modified as follows without departing from the gist of the present disclosure.

In the embodiment, in the control process executed by the control device 20, the first reference temperature is set to 5 deg and the second reference temperature is set to 10 deg, but the first reference temperature and the second reference temperature may be changed.

In the embodiment, the motor unit 112 of the compressor 11 is cooled by the refrigerant, but various heat generating devices of the compressor 11 may be cooled by the refrigerant. For example, the inverter of the compressor 11 may be cooled by the refrigerant.

In the embodiment, the compressor 11 is a scroll type compressor, but the compressor 11 may be a compressor of various types. For example, the compressor 11 may be a piston type compressor, a vane type compressor, or the like.

In the embodiment, the radiator 12 is a heat exchanger that exchanges heat between the refrigerant discharged from the compressor 11 and the air blown to the air-conditioned space. Alternatively, the radiator 12 may be a heat exchanger that exchanges heat between the refrigerant discharged from the compressor 11 and a heat medium. Then, the air blown to the air-conditioned space may be heated by a heat exchanger that exchanges heat between the heat medium heated by the radiator 12 and the air.

In the embodiment, the refrigeration cycle device 10 is applied to an air conditioner that heats the air blown to the air-conditioned space, but the application of the refrigeration cycle device 10 is not limited to this. For example, the refrigeration cycle device 10 may be applied to an air conditioner that cools air blown to the air-conditioned space. For example, the refrigeration cycle device 10 may be applied to a heat pump type water heater.

In the sixth embodiment, when the flow rate adjusting valve 32 opens the hot gas passage 31, the blower 30 may be stopped so that the evaporator 14 does not exchange heat. That is, when the refrigerant that has passed through the hot gas passage 31 is mixed with the refrigerant that has passed through the evaporator 14, the amount of heat exchanged in the evaporator 14 may be set to zero.

In the embodiment, the suction refrigerant pressure sensor 67 detects the suction pressure Ps of the refrigerant sucked into the compressor 11. Alternatively, the suction refrigerant pressure sensor 67 may detect a pressure of refrigerant after absorbing heat from the motor unit 112 and before being sucked into the compression mechanism 111 as the suction pressure Ps. According to this, the suction refrigerant pressure sensor 67 and the temperature sensor 68 can be integrated to simplify the structure.

Although the present disclosure has been made in accordance with the embodiments, it is understood that the present disclosure is not limited to such embodiments and structures. The present disclosure encompasses various modifications and variations within the scope of equivalents. In addition, as the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.

Claims

1. A refrigeration cycle device comprising:

a compressor having a compression mechanism forming a compression chamber to compress a refrigerant, and a cooled portion cooled by the refrigerant before being compressed by the compression mechanism;

a radiator configured to radiate heat from the refrigerant compressed by the compressor;

an evaporator decompressor configured to decompress the refrigerant radiated by the radiator;

an evaporator configured to evaporate the refrigerant decompressed by the evaporator decompressor;

an acquisition unit configured to acquire a state of the refrigerant after cooling the cooled portion and before flowing into the compression chamber; and

a control unit configured to control a superheat degree of the refrigerant flowing into the compression chamber based on the state of the refrigerant acquired by the acquisition unit, wherein

the cooled portion is cooled by the refrigerant after being evaporated by the evaporator and before being compressed by the compression mechanism.

2. The refrigeration cycle device according to claim 1, wherein the control unit controls the superheat degree by controlling the evaporator decompressor based on the state of the refrigerant acquired by the acquisition unit.

3. The refrigeration cycle device according to claim 1, further comprising:

a bypass unit that bypasses the evaporator decompressor and the evaporator to guide the refrigerant radiated by the radiator to the compressor; and

a bypass decompressor configured to decompress the refrigerant flowing through the bypass unit, wherein

the control unit controls the superheat degree by controlling the bypass decompressor based on the state of the refrigerant acquired by the acquisition unit.

4. The refrigeration cycle device according to claim 1, further comprising:

a hot gas passage that bypasses the radiator, the evaporator decompressor, and the evaporator to guide the refrigerant compressed by the compressor to the compressor; and

a flow rate adjusting unit configured to reduce a pressure of the refrigerant flowing through the hot gas passage and adjust a flow rate of the refrigerant flowing in the hot gas passage, wherein

the control unit controls the superheat degree by controlling at least one of the evaporator decompressor or the flow rate adjusting unit based on the state of the refrigerant acquired by the acquisition unit.

5. The refrigeration cycle device according to claim 1, further comprising:

a gas-liquid separator configured to separate the refrigerant, after being evaporated by the evaporator and before being sucked into the compressor, between gas and liquid, wherein

the gas-liquid separator has an oil return adjusting unit that adjusts a passage area of an oil return unit that returns an oil mixed in the refrigerant from the gas-liquid separator to the compressor, and

the control unit controls the superheat degree by controlling the oil return adjusting unit based on the state of the refrigerant acquired by the acquisition unit.

6. The refrigeration cycle device according to claim 1, further comprising:

a gas-liquid separator configured to separate the refrigerant, after being evaporated by the evaporator and before being sucked into the compressor, between a gas refrigerant and a liquid refrigerant;

a liquid return unit that guides the liquid refrigerant separated by the gas-liquid separator to the compressor; and

a liquid passage adjusting unit that adjusts a passage area of the liquid return unit, wherein

the control unit controls the superheat degree by controlling the liquid passage adjusting unit based on the state of the refrigerant acquired by the acquisition unit.

7. The refrigeration cycle device according to claim 1, wherein

the cooled portion includes an electric motor that drives the compression mechanism, and

the acquisition unit calculates a state of the refrigerant after cooling the cooled portion and before flowing into the compression chamber based on an amount of electric power for driving the electric motor, a rotation speed of the electric motor, a pressure of the refrigerant sucked by the compressor, and a pressure and a temperature of the refrigerant discharged by the compressor.

8. The refrigeration cycle device according to claim 1, wherein the acquisition unit detects a temperature and a pressure of the refrigerant after cooling the cooled portion and before flowing into the compression chamber.