WO2017098655A1

WO2017098655A1 - Refrigeration cycle device

Info

Publication number: WO2017098655A1
Application number: PCT/JP2015/084789
Authority: WO
Inventors: 千歳田中; 拓也松田; 航祐田中
Original assignee: 三菱電機株式会社
Priority date: 2015-12-11
Filing date: 2015-12-11
Publication date: 2017-06-15
Also published as: JP6522154B2; JPWO2017098655A1

Abstract

In this refrigeration cycle device (100), a refrigerant circulates in the order of: a compressor (1); a condenser (2); a first expansion valve (4); and an evaporator (5). The refrigeration cycle device (100) is equipped with a first bypass flow path (11). The first bypass flow path (11) branches off from a first flow path connecting the compressor (1) and the condenser (2), and is connected, with a second valve (7) interposed therebetween, to a second flow path connecting the condenser (2) and the first expansion valve (4) or a third flow path connecting the evaporator (5) and the compressor (1). The opening degree of the second valve (7) in the cases when the evaporation temperature in the evaporator (5) is less than a first reference value is larger than that in the cases when the evaporation temperature is more than the first reference value.

Description

Refrigeration cycle equipment

The present invention relates to a refrigeration cycle apparatus.

Conventionally, a refrigeration cycle apparatus capable of controlling the capacity is known. Japanese Patent Laid-Open No. 09-053861 (Patent Document 1) discloses a configuration for controlling the capacity of a refrigeration cycle apparatus by controlling the amount of liquid refrigerant accumulated in a condenser.

JP 09-038661 A

In a multi-type air conditioner in which a plurality of indoor heat exchangers are connected to a large-capacity outdoor heat exchanger, the indoor heat during operation is the same as when only one of the indoor heat exchangers is operated. When the total capacity of the exchanger is much smaller than the capacity of the outdoor heat exchanger, the amount of heat exchanged by the outdoor heat exchanger and the amount of heat exchanged by the indoor heat exchanger become imbalanced. When performing a cooling operation, the amount of heat released to the outside air by the outdoor heat exchanger functioning as a condenser is larger than the amount of heat recovered by the indoor heat exchanger functioning as an evaporator. When the refrigeration cycle is continued in such a state, the evaporation pressure in the indoor heat exchanger decreases. As a result, the risk of the evaporation temperature being lowered and the indoor heat exchanger freezing increases.

In addition, when the cooling operation is performed in a state where the temperature of the outside air is low, the condensation pressure of the outdoor heat exchanger decreases. The evaporation pressure of the indoor heat exchanger decreases in response to the decrease in the condensation pressure. As a result, the evaporation temperature is lowered, and the possibility that the indoor heat exchanger will freeze increases.

Generally, when the evaporator is frozen, the air passage is blocked, heat exchange becomes impossible, and air conditioning by a subsequent refrigeration cycle may become impossible. In addition, when the piping is compressed and destroyed by volume expansion due to water solidification, the refrigerant leaks to the atmosphere. Therefore, it is necessary to prevent the evaporator from freezing.

When the possibility of freezing of the evaporator is increased, the refrigeration cycle apparatus is stopped to suppress a decrease in the evaporation temperature of the evaporator and to prevent the evaporator from freezing. However, if the refrigeration cycle apparatus stops every time the risk of freezing of the evaporator increases, the refrigeration cycle apparatus repeatedly stops and restarts, and the cooling operation is not stably performed. As a result, extra energy is required every time the refrigeration cycle apparatus is restarted, and user comfort may be impaired.

Japanese Patent Laid-Open No. 09-038661 (Patent Document 1) does not disclose a configuration for controlling the refrigeration cycle apparatus so as to prevent the evaporator from freezing.

The present invention has been made in order to solve the above-described problems, and an object of the present invention is to prevent the evaporator from freezing while suppressing the refrigeration cycle apparatus from repeatedly stopping and restarting. A refrigeration cycle apparatus is provided.

In the refrigeration cycle apparatus according to the present invention, the refrigerant circulates in the order of the compressor, the condenser, the first expansion valve, and the evaporator. The refrigeration cycle apparatus includes a first bypass flow path. The first bypass flow path branches off from the first flow path connecting the compressor and the condenser, the second flow path connecting the condenser and the first expansion valve via the second valve, and evaporation Connected to one of the third flow paths connecting the compressor and the compressor. The opening degree of the second valve is larger when the evaporation temperature in the evaporator is lower than the first reference value and when the evaporation temperature is higher than the first reference value.

According to the present invention, by suppressing the decrease in the evaporation temperature while operating the refrigeration cycle apparatus, it is possible to prevent the evaporator from freezing while suppressing the refrigeration cycle apparatus from repeatedly stopping and restarting. As a result, the cooling operation can be continued stably, and energy saving performance and user comfort can be ensured.

1 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 1. FIG. FIG. 2 is a Ph diagram of a refrigeration cycle performed by the refrigeration cycle apparatus of FIG. 1. It is a flowchart for demonstrating the process performed at the time of air_conditionaing | cooling operation by the control apparatus of FIG. 3 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 2. FIG. FIG. 5 is a Ph diagram of a refrigeration cycle performed by the refrigeration cycle apparatus of FIG. 4. 5 is a flowchart for explaining processing performed by the control device of FIG. 4 during cooling operation. 6 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 3. FIG. It is a flowchart for demonstrating the process performed by the control apparatus of FIG. 7 at the time of air_conditionaing | cooling operation. 6 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 4. FIG. FIG. 10 is a Ph diagram of a refrigeration cycle performed by the refrigeration cycle apparatus of FIG. 9. 10 is a flowchart for explaining processing performed by the control device of FIG. 9 during cooling operation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a configuration diagram of a refrigeration cycle apparatus 100 according to the first embodiment. As shown in FIG. 1, the refrigeration cycle apparatus 100 includes a compressor 1, a condenser 2, an internal heat exchanger 3, a first expansion valve 4, an evaporator 5, a second expansion valve 6, A valve 7, a circulation channel 10, a first bypass channel 11, a second bypass channel 12, and a control device 20 are provided.

The circulation channel 10 connects the compressor 1, the condenser 2, the internal heat exchanger 3, the first expansion valve 4, and the evaporator 5 with piping to circulate the refrigerant.

The compressor 1 has a rotational speed controlled based on a driving frequency from the control device 20, and compresses and discharges the gas refrigerant.

The condenser 2 condenses the gas refrigerant discharged from the compressor 1 and discharges the liquid refrigerant.
The first expansion valve 4 expands and depressurizes the refrigerant from the internal heat exchanger 3. The opening degree of the first expansion valve 4 can be adjusted. The first expansion valve 4 is, for example, an electronically controlled expansion valve (LEV).

The evaporator 5 evaporates the liquid refrigerant (liquid refrigerant) discharged from the first expansion valve 4 and discharges the gas refrigerant (gas refrigerant).

1st bypass flow path 11 branches from branch point B1 located in the part of the circulation flow path 10 from the compressor 1 to the condenser 2. The first bypass flow path 11 passes through the valve 7. The first bypass channel 11 merges at a junction J1 located at a portion of the circulation channel 10 extending from the condenser 2 to the internal heat exchanger 3.

The valve 7 may have any form as long as the flow rate of the refrigerant can be adjusted by adjusting the opening. The valve 7 may be an expansion valve such as LEV.

The internal heat exchanger 3 includes a flow path (high pressure side flow path 301) through which the refrigerant from the junction J1 passes and a flow path (low pressure side flow path 302) through which the refrigerant from the second expansion valve 6 passes. The internal heat exchanger 3 serves to cool the refrigerant from the junction J1 by causing the refrigerant from the second expansion valve 6 to absorb the heat of the refrigerant from the junction J1. The internal heat exchanger 3 is, for example, a double tube heat exchanger.

The second expansion valve 6 expands the refrigerant to reduce the pressure. The second expansion valve 6 is, for example, a LEV.

The second bypass flow path 12 branches from a branch point B2 located at a part of the circulation flow path 10 extending from the internal heat exchanger 3 to the first expansion valve 4. The second bypass flow path 12 passes through the internal heat exchanger 3 next to the second expansion valve 6. The second bypass flow path 12 merges at a merge point J2 located at a portion of the circulation flow path 10 from the evaporator 5 to the compressor 1.

The control device 20 includes a microcomputer 201, drive

circuits

202 and 203, a pressure detection unit 204, and a temperature detection unit 205. The microcomputer 201 drives the compressor 1 by controlling the drive circuit 202. The microcomputer 201 controls the opening degree of the second expansion valve 6 and the valve 7 by controlling the drive circuit 203. The microcomputer 201 acquires the pressure at the inlet (low pressure side) of the compressor 1 and the pressure at the outlet (high pressure side) of the compressor 1 from the pressure detection unit 204. The pressure detection unit 204 calculates the pressure on the low pressure side based on a signal from the pressure sensor 31 attached to the inlet of the compressor 1. The pressure detection unit 204 calculates the pressure on the high pressure side based on a signal from the pressure sensor 32 attached to the outlet of the compressor 1.

The microcomputer 201 calculates the degree of supercooling at the outlet of the high-pressure side passage 301 of the internal heat exchanger 3 based on the pressure on the high-pressure side and the temperature of the outlet of the high-pressure side passage 301 of the internal heat exchanger 3. The microcomputer 201 calculates the degree of superheat at the outlet of the low-pressure side passage 302 of the internal heat exchanger 3 based on the pressure on the low-pressure side and the temperature of the outlet of the low-pressure side passage 302 of the internal heat exchanger 3.

The microcomputer 201 acquires the temperature of the outlet of the high-pressure side channel 301 of the internal heat exchanger 3 and the temperature of the outlet of the low-pressure side channel 302 of the internal heat exchanger 3 from the temperature detection unit 205. The temperature detection unit 205 calculates the temperature of the outlet of the high-pressure side channel 301 of the internal heat exchanger 3 based on a signal from the temperature sensor 33 attached to the outlet of the high-pressure side channel 301 of the internal heat exchanger 3. To do. The temperature detection unit 205 calculates the temperature of the outlet of the low-pressure side passage 302 of the internal heat exchanger 3 based on a signal from the temperature sensor 34 attached to the outlet of the low-pressure side passage 302 of the internal heat exchanger 3. To do.

The control device 20 further includes a microcomputer 206, a drive circuit 207, and a temperature detection unit 208. The microcomputer 206 controls the drive circuit 207 to adjust the opening degree of the first expansion valve 4. The microcomputer 206 acquires the temperature of the pipe inlet of the evaporator 5 and the temperature of the pipe outlet of the evaporator 5 from the temperature detection unit 208. The temperature detection unit 208 calculates the temperature of the pipe inlet of the evaporator 5 based on a signal from the temperature sensor 35 attached to the pipe inlet of the evaporator 5. The temperature detection unit 208 calculates the temperature of the pipe outlet of the evaporator 5 based on a signal from the temperature sensor 36 attached to the pipe outlet of the evaporator 5.

The microcomputer 206 acquires a high-pressure side pressure and a low-pressure side pressure from the microcomputer 201. The microcomputer 206 calculates the degree of superheat at the pipe outlet of the evaporator 5 based on the pressure on the low pressure side and the temperature of the pipe outlet of the evaporator 5. The microcomputer 206 adjusts the opening degree of the first expansion valve 4 so that the superheat degree at the pipe outlet of the evaporator 5 approaches a target value (for example, the superheat degree of 1 ° C.) (superheat degree control).

Refrigerant repeatedly absorbs and releases heat while repeating state changes between liquid refrigerant and gas refrigerant in the refrigeration cycle. Hereinafter, each process of the refrigeration cycle will be described with reference to FIG.

FIG. 2 is a Ph diagram showing the relationship between the pressure of the refrigeration cycle performed by the refrigeration cycle apparatus 100 of FIG. 1 and the specific enthalpy. In FIG. 2, point CP is the critical point of the refrigerant. A curve SL is a saturated liquid line of the refrigerant. A curve SV is a saturated vapor line of the refrigerant. A cycle C0 that returns from the point S1 to the point S1 through the points S2, S3, and S4 represents a normal refrigeration cycle in the refrigeration cycle apparatus 100. The state change from the point S1 to the point S2 represents the process of compressing the refrigerant by the compressor 1. The state change from the point S2 to the point S3 represents the process of condensing the refrigerant by the condenser 2. The state change from the point S3 to the point S4 represents the process of depressurizing the refrigerant by the first expansion valve 4. The state change from the point S4 to the point S1 represents the process of evaporation of the refrigerant by the evaporator 5.

The refrigerant near the inlet of the compressor 1 is a low-temperature and low-pressure gas refrigerant. This gas refrigerant is sucked into the compressor 1, compressed by the compressor 1, and discharged as a high-temperature and high-pressure gas refrigerant. Energy is added to the refrigerant by the compression by the compressor 1. As a result, the specific enthalpy of the refrigerant increases. The process of compressing the refrigerant by the compressor 1 is represented as a state change from the point S1 to the point S2 in FIG. The specific enthalpy and pressure at point S2 are both higher than the specific enthalpy and pressure at point S1.

The gas refrigerant discharged from the compressor 1 is condensed at a high pressure in the condenser 2 to become a liquid refrigerant. When the gas refrigerant condenses into a liquid refrigerant, the heat of condensation is released to the outside air. That is, when the refrigerant passes through the condenser 2, the specific enthalpy of the refrigerant decreases. The process of condensing the refrigerant by the condenser 2 is expressed as a state change from the point S2 to the point S3 in FIG. The specific enthalpy at the point S3 is smaller than the specific enthalpy at the point S2. The pressure at point S3 is almost the same as the pressure at point S2. To be exact, a pressure loss occurs when the refrigerant passes through the condenser 2. In this case, the refrigerant pressure gradually decreases as the refrigerant advances through the condenser 2. Therefore, the pressure at point S3 is slightly smaller than the pressure at point S2.

The liquid refrigerant discharged from the condenser 2 passes through the internal heat exchanger 3 and adiabatically expands at the first expansion valve 4. The liquid refrigerant is decompressed by the first expansion valve 4. As a result, part of the liquid refrigerant becomes a gas refrigerant and is in a state called wet steam. The process of depressurizing the refrigerant by the first expansion valve 4 is represented as a state change from the point S3 to the point S4 in FIG. The pressure at point S4 is less than the pressure at point S3. Since the process of decompressing the refrigerant by the first expansion valve 4 is adiabatic expansion, the specific enthalpy at the point S4 and the specific enthalpy at the point S3 are almost the same. Since the second expansion valve 6 is normally closed, cooling by the internal heat exchanger 3 is not performed.

The liquid refrigerant in the wet steam discharged from the first expansion valve 4 evaporates at a low pressure in the evaporator 5 and is discharged as a low-temperature and low-pressure gas refrigerant. When the liquid refrigerant evaporates into a gas refrigerant, the heat of evaporation is absorbed from the indoor air. That is, when the refrigerant passes through the evaporator 5, the specific enthalpy of the refrigerant increases. The process of evaporation of the refrigerant in the evaporator 5 is expressed as a state change from the point S4 to the point S1 in FIG. The specific enthalpy at the point S1 is higher than the specific enthalpy at the point S4. The pressure at point S1 is slightly less than the pressure at point S4 due to the pressure loss that occurs when the refrigerant passes through the evaporator 5.

The low-temperature and low-pressure gas refrigerant discharged from the evaporator 5 is again sucked into the compressor 1 and the above-described process is repeated.

When cooling operation is performed in the refrigeration cycle apparatus 100, the evaporator 5 may freeze depending on the situation. For example, when the cooling operation is performed in the refrigeration cycle apparatus 100 in a state where the temperature of the outside air is low, the condensation pressure of the outdoor condenser 2 decreases. The evaporation pressure of the evaporator 5 in the room decreases in response to the decrease in the condensation pressure. As a result, even if the compressor 1 is operated at the lower limit frequency, the evaporation temperature continues to decrease, and the possibility that the indoor evaporator 5 will freeze increases.

Generally, when the evaporator 5 is frozen, the air blowing port or the suction port is blocked, and heat exchange in the evaporator 5 becomes impossible, and subsequent cooling operation may be impossible. Also, the piping is compressed and destroyed by volume expansion due to the solidification of water, and the refrigerant leaks to the atmosphere. Therefore, it is necessary to prevent the evaporator from freezing.

If it is difficult to avoid freezing of the evaporator 5 even when the compressor 1 is operated at the lower limit frequency, the freezing of the evaporator 5 can be prevented by stopping the refrigeration cycle apparatus 100. However, if the refrigeration cycle apparatus 100 is stopped every time the risk of freezing of the evaporator 5 increases, the operation of the refrigeration cycle apparatus 100 is repeatedly stopped and restarted, and the cooling operation is not stably performed. As a result, extra energy is required every time the refrigeration cycle apparatus 100 is restarted, and the user's comfort may be impaired.

In view of such a problem, in the first embodiment, the first bypass flow path 11 is provided to reduce the amount of refrigerant sucked into the condenser 2, and the amount of heat released by the condenser 2 to the outside air (condensing capacity). ). With such a configuration, it is possible to suppress a decrease in the evaporation temperature of the evaporator 5 while continuing the operation of the refrigeration cycle apparatus 100. Therefore, it is possible to prevent the evaporator 5 from freezing without stopping the refrigeration cycle apparatus 100. Can do. As a result, the cooling operation can be continued stably, and energy saving performance and user comfort can be ensured.

Hereinafter, the refrigeration cycle performed by the refrigeration cycle apparatus 100 when the risk of freezing of the evaporator 5 is increased will be described with reference to FIG. The case where the risk of freezing of the evaporator 5 is increased is, for example, the case where the pipe temperature Te of the evaporator 5 is less than 1 ° C. In FIG. 2, a cycle C1 returning from the point S11 to the point S11 via the points S12, S13A, S13B, and S14 is performed by the refrigeration cycle apparatus 100 when the risk of freezing of the evaporator 5 increases. Represents a refrigeration cycle. The state change from the point S11 to the point S12 represents the process of compressing the refrigerant by the compressor 1. The state change from the point S12 to the point S13A represents a process of condensing the refrigerant by the condenser 2. The state change from the point S13A to the point S13B represents a process in which the specific enthalpy of the refrigerant increases due to the refrigerant from the first bypass passage 11 joining the refrigerant from the condenser 2. The state change from the point S13B to the point S14 represents the process of decompressing the refrigerant by the first expansion valve 4. The state change from the point S14 to the point S11 represents the process of evaporation of the refrigerant by the evaporator 5.

When the risk of freezing of the evaporator 5 increases, the control device 20 increases the amount of refrigerant passing through the second bypass flow path by increasing the opening of the valve 7. The amount of refrigerant passing through the condenser 2 is reduced. As a result, the condensation pressure in the condenser 2 is lower than normal. In FIG. 2, the state change from the point S12 to the point S13A being performed on the lower pressure side than the state change from the point S2 to the point S3 represents a decrease in the condensation pressure of the condenser 2.

The refrigerant from the first bypass channel 11 hardly releases heat because it does not pass through the condenser 2. Therefore, when the refrigerant from the first bypass channel 11 merges with the refrigerant from the condenser 2, the specific enthalpy of the refrigerant from the junction J1 becomes higher than in the normal case. In FIG. 2, the fact that the specific enthalpy at the point S13B is higher than the specific enthalpy at the point S3 represents this.

The refrigerant from the first bypass channel 11 is a gas refrigerant. On the other hand, the refrigerant from the condenser 2 is a liquid refrigerant. Accordingly, depending on the degree of supercooling of the refrigerant from the condenser 2 and the amount of refrigerant from the first bypass channel 11, the refrigerant from the junction J1 may become wet vapor in a gas-liquid two-phase state. Since the wet steam has a lower average density than the liquid refrigerant, the flow rate of the wet vapor passing through the first expansion valve 4 is smaller than the flow rate of the liquid refrigerant passing through the first expansion valve 4. Therefore, if the refrigerant remains wet steam, the pressure (evaporation pressure) of the refrigerant after passing through the first expansion valve 4 is lower than when the refrigerant is a liquid refrigerant. A decrease in evaporation pressure means a decrease in evaporation temperature. That is, if the refrigerant from the first bypass passage 11 is excessively increased, there is a possibility that the freezing of the evaporator 5 is promoted.

Further, if the refrigerant sucked into the first expansion valve 4 is wet steam, noise is generated when the wet steam passes through the micro flow path in the first expansion valve 4, which is preferable in terms of the quality of the refrigeration cycle apparatus 100. Absent.

Therefore, in the first embodiment, the refrigerant from the junction J1 is cooled by the internal heat exchanger 3, and the gas-liquid two-phase state in the refrigerant from the junction J1 is eliminated.

When the refrigerant from the junction J1 is in a gas-liquid two-phase state, in FIG. 2, the point S13B exceeds the curve SL (saturated liquid line) and is located between the curve SL and the curve SV (saturated vapor line). become. In such a case, the refrigerant is converted into a liquid refrigerant by cooling by the internal heat exchanger 3, and the point S13B in FIG. 2 is returned to the side having a lower specific enthalpy than the curve SL.

As described above, the specific enthalpy of the refrigerant from the junction J1 is larger than the normal enthalpy at the normal time, and as a result, the refrigerant needs to be absorbed from the indoor air in the evaporator 5 in order to continue the refrigeration cycle. The amount of heat is reduced. The amount of heat absorbed by the refrigerant from the indoor air is proportional to the difference (temperature gradient) between the temperature of the evaporator 5 (evaporation temperature) and room temperature (Fourier's law). Therefore, in order to reduce the endothermic amount (evaporation capability) of the evaporator 5, it is necessary to increase the evaporation temperature of the evaporator 5 to reduce the temperature difference between the evaporator 5 and the room. The control device 20 increases the evaporation temperature of the evaporator 5 by adjusting the opening of the first expansion valve 4 and increasing the evaporation pressure of the evaporator 5. In FIG. 2, the fact that the state change from the point S14 to the point S11 is performed on the higher pressure side than the state change from the point S4 to the point S1 represents an increase in the evaporation pressure of the evaporator 5.

FIG. 3 is a flowchart for explaining a process performed by the control device 20 of FIG. 1 during the cooling operation. The process shown in FIG. 3 is called at regular time intervals by the main routine (not shown) of the cooling operation.

As shown in FIG. 3, the control device 20 determines whether or not the piping temperature Te of the evaporator 5 is equal to or higher than a reference value (1 ° C.) in step S 101 (hereinafter, the step is simply referred to as S). When measuring several places of the evaporator 5, the minimum value is employ | adopted as piping temperature Te. In the first embodiment, the one having the lower temperature detected by the

temperature sensors

35 and 36 is employed. If pipe temperature Te is equal to or higher than the reference value (YES in S101), control device 20 proceeds to S102 because the possibility that evaporator 5 is frozen is low.

In S102, the control device 20 determines whether or not the supercooling degree SC at the outlet of the high-pressure side passage 301 of the internal heat exchanger 3 is equal to or higher than a reference value (5 ° C.). If supercooling degree SC is equal to or greater than the reference value (YES in S102), control device 20 determines that the gas-liquid two-phase state of the refrigerant from junction J1 has been eliminated by internal heat exchanger 3 and proceeds to S103. Proceed. If supercooling degree SC is less than the reference value (NO in S102), control device 20 proceeds to S111 because the gas-liquid two-phase state of the refrigerant from confluence J1 may not be eliminated. .

In S103, the control device 20 determines whether or not the superheat degree SH1 at the outlet of the low pressure side flow path 302 of the internal heat exchanger 3 is equal to or higher than a reference value (1 ° C.). If superheat degree SH1 is equal to or greater than the reference value (YES in S103), control device 20 advances the process to S116, assuming that the flow rate of the refrigerant flowing through low-pressure channel 302 of internal heat exchanger 3 is appropriate. If superheat degree SH1 is less than the reference value (NO in S103), control device 20 advances the process to S115, assuming that excess refrigerant is flowing in low-pressure side flow path 302 of internal heat exchanger 3. The control device 20 decreases the opening of the second expansion valve 6 in S115, and advances the process to S116.

The control device 20 waits for a certain time (for example, 1 minute) in S116. Thereafter, the process is returned to the main routine of the cooling operation.

When the pipe temperature Te is less than the reference value (NO in S101), the control device 20 advances the process to S104 on the assumption that the evaporator 5 is likely to freeze. The controller 20 increases the opening degree of the valve 7 in S104, and advances the process to S105.

In S105, the control device 20 determines whether or not the degree of supercooling SC at the outlet of the high-pressure channel 301 of the internal heat exchanger 3 is equal to or higher than a reference value (5 ° C.). If supercooling degree SC is equal to or higher than the reference value (YES in S105), control device 20 determines that the gas-liquid two-phase state of the refrigerant from junction J1 has been eliminated by internal heat exchanger 3, and proceeds to S103. Proceed. If supercooling degree SC is less than the reference value (NO in S105), control device 20 advances the process to S106 on the assumption that the gas-liquid two-phase state of the refrigerant from confluence J1 may not be eliminated. .

In S106, the control device 20 determines whether or not the superheat degree SH1 at the outlet of the low pressure side flow path 302 of the internal heat exchanger 3 is equal to or higher than a reference value (1 ° C.). If superheat degree SH1 is equal to or greater than the reference value (YES in S106), control device 20 assumes that further cooling can be expected by increasing the flow rate of the refrigerant flowing through low-pressure side flow path 302 of internal heat exchanger 3, and processing is performed. To S107. In S107, the control device 20 increases the opening degree of the second expansion valve 6 and advances the process to S116. When superheat degree SH1 is less than the reference value (NO in S106), control device 20 cannot expect further cooling even if the flow rate of the refrigerant flowing through low pressure side flow path 302 of internal heat exchanger 3 is increased, and the gas-liquid Assuming that the two-phase state cannot be resolved, the process proceeds to step 108.

In S108, the control device 20 stops the compressor 1 and advances the process to S109. In S108, the control device 20 may fully close the first expansion valve 4. Even in this case, the refrigerant can continue to circulate by passing through the second bypass flow path 12. Alternatively, the control device 20 may fully close the first expansion valve 4 and stop the compressor 1.

Control device 20 waits for a certain time (for example, 3 minutes) in step 109. Thereafter, the control device 20 advances the process to S110. The control device 20 restarts the compressor 1 in S110 and returns the process to S101.

Control device 20 has a low possibility that evaporator 5 is frozen (YES in S101), and there is a possibility that the gas-liquid two-phase state of the refrigerant from junction J1 may not be resolved (NO in S102). In S111, the opening degree of the valve 7 is increased and the process proceeds to S112.

In S112, the control device 20 determines whether or not the superheat degree SH1 at the outlet of the low pressure side flow path 302 of the internal heat exchanger 3 is equal to or higher than a reference value (1 ° C.). When superheat degree SH1 is equal to or higher than the reference value (YES in S112), control device 20 assumes that further cooling can be expected by increasing the flow rate of the refrigerant flowing through low-pressure side flow path 302 of internal heat exchanger 3, and processing is performed. To S113. In S113, the control device 20 increases the opening degree of the second expansion valve 6 and advances the process to S116. When superheat degree SH1 is less than the reference value (NO in S112), control device 20 advances the process to step 114, assuming that the flow rate of the refrigerant flowing through low-pressure channel 302 of internal heat exchanger 3 is excessive. . In S114, the controller 20 decreases the opening of the second expansion valve 6 and advances the process to S116.

The specific reference value and the fixed time shown in the description of FIG. 3 are examples. The reference value and the fixed time may be other values. The reference value and the fixed time can be appropriately determined by actual machine experiments or simulations.

As described above, according to the refrigeration cycle apparatus 100, the evaporator 5 can be prevented from freezing by suppressing the decrease in the evaporation temperature while continuing the cooling operation. As a result, the cooling operation can be continued stably, and energy saving performance and user comfort can be ensured.

[Embodiment 2]
In the first embodiment, in order to prevent the evaporator 5 from freezing, a part of the refrigerant discharged from the compressor 1 is allowed to pass through the first bypass passage 11 to reduce the condensation pressure of the condenser 2. The case where the evaporation pressure of the evaporator 5 is increased has been described. That is, when the process shown in FIG. 3 is performed, the ratio (compression ratio) between the condensation pressure and the evaporation pressure becomes small. When the compression ratio is smaller than the reference value, the airtightness of the refrigeration cycle apparatus 100 is deteriorated. As what maintains airtightness by the difference of a condensation pressure and evaporation pressure, the scroll (not shown) in the compressor 1 or a non-return valve (not shown) can be mentioned, for example. When the airtightness of the refrigeration cycle apparatus 100 is deteriorated, the possibility that the refrigerant leaks from a location where the airtightness is deteriorated increases. When the refrigerant leaks, the performance of the refrigeration cycle apparatus 100 decreases and the possibility of failure increases. Further, vibration and noise from the refrigeration cycle apparatus 100 are increased, and the possibility that the user's comfort is impaired is increased.

Therefore, in the second embodiment, a configuration will be described in which the compression ratio is prevented from becoming smaller than the reference value by controlling the amount of refrigerant circulating in the circulation flow path. In the second embodiment, it is possible to perform a process for preventing the evaporator 5 from freezing while preventing the compression ratio from becoming smaller than the reference value.

Embodiment 2 differs from Embodiment 1 in that a configuration for controlling the amount of refrigerant circulating in the circulation channel is provided. Since it is the same about the structure of those other than this, description is not repeated.

FIG. 4 is a configuration diagram of the refrigeration cycle apparatus 200 according to the second embodiment. As shown in FIG. 4, the refrigeration cycle apparatus 200 includes a compressor 1, a condenser 2, an internal heat exchanger 3, a first expansion valve 4, an evaporator 5, a second expansion valve 6, The valve 7, the valve 8, the liquid receiver 9, the circulation channel 10 B, the first bypass channel 11, the second bypass channel 12, and the control device 20 B are provided.

The circulation flow path 10B connects the compressor 1, the condenser 2, the internal heat exchanger 3, the valve 8, the liquid receiver 9, the first expansion valve 4, and the evaporator 5 with piping to circulate the refrigerant.

The control device 20B includes a microcomputer 201B and a drive circuit 203B. The microcomputer 201B controls the opening degree of the second expansion valve 6, the valve 7, and the valve 8 by controlling the drive circuit 203B.

The valve 8 may have any form as long as the flow rate of the refrigerant can be adjusted by adjusting the opening. The valve 8 may be an expansion valve such as LEV.

The liquid receiver 9 temporarily stores the liquid refrigerant from the valve 8. When the opening degree of the valve 8 is adjusted by the control device 20B, the amount of liquid refrigerant sucked into the liquid receiver 9 changes. When the amount of liquid refrigerant sucked into the liquid receiver 9 exceeds the amount of liquid refrigerant discharged from the liquid receiver 9, the amount of liquid refrigerant temporarily stored in the liquid receiver 9 increases. Conversely, when the amount of liquid refrigerant sucked into the liquid receiver 9 is less than the amount of liquid refrigerant discharged from the liquid receiver 9, the amount of liquid refrigerant temporarily stored in the liquid receiver 9 decreases. .

In Embodiment 2, when the compression ratio is less than the reference value, the control device 20B reduces the amount of refrigerant sucked into the liquid receiver 9 by reducing the opening degree of the valve 8. Assuming that the amount of refrigerant sucked into the compressor 1 is substantially constant, the amount of refrigerant discharged from the liquid receiver 9 is substantially constant. Therefore, when the opening degree of the valve 8 is decreased, the amount of liquid refrigerant temporarily stored in the liquid receiver 9 is decreased. On the other hand, the amount of liquid refrigerant discharged from the condenser 2 is reduced by reducing the opening of the valve 8. That is, the amount of liquid refrigerant in the condenser 2 increases.

When the amount of liquid refrigerant in the condenser 2 increases, the heat exchangeable surface area (effective heat transfer area) of the gas refrigerant decreases. Moreover, since the gas refrigerant in the condenser 2 is compressed when the amount of the liquid refrigerant in the condenser 2 increases, the condensation pressure of the gas refrigerant in the condenser 2 increases. As the condensation pressure increases, the condensation temperature also increases. The heat radiation amount (condensation capacity) of the condenser 2 is proportional to the product of the effective heat transfer area and the difference between the temperature of the outside air and the condensation temperature. As the condensation temperature increases, the difference between the outside air temperature and the condensation temperature increases. Therefore, even if the amount of liquid refrigerant accumulated in the condenser 2 is increased, the effective heat transfer area is reduced, but the difference between the temperature of the outside air and the condensation temperature is increased, so that the heat radiation amount of the condenser 2 is hardly changed. . That is, by increasing the amount of liquid refrigerant that accumulates in the condenser 2, the condensation pressure can be increased without substantially changing the condensation capacity of the condenser 2.

Also, the temperature of the liquid refrigerant near the outlet of the condenser 2 is close to the temperature of the outside air. As described above, when the amount of liquid refrigerant accumulated in the condenser 2 increases, the difference between the temperature of the outside air and the condensation temperature increases. Therefore, the degree of supercooling of the liquid refrigerant in the vicinity of the outlet of the condenser 2 can be increased by increasing the amount of the liquid refrigerant accumulated in the condenser 2. Therefore, in the second embodiment, more gas refrigerant can be merged with the liquid refrigerant from the condenser 2 by increasing the opening degree of the valve 7 than in the first embodiment. As a result, the evaporation pressure and evaporation temperature in the evaporator 5 can be further increased.

FIG. 5 is a Ph diagram of the refrigeration cycle performed by the refrigeration cycle apparatus 200 of FIG. In FIG. 5, the cycle C2 from the point S21 to the point S21 via the points S22, S23A, S23B, and S24 is performed by the refrigeration cycle apparatus 200 when the risk of freezing of the evaporator 5 increases. Represents a refrigeration cycle. FIG. 5 is a diagram in which a cycle C2 is added to FIG. Point S21, point S22, point S23A, point S23B, and point S24 in cycle C2 correspond to point S11, point S12, point S13A, point S13B, and point S14 in cycle C1, respectively.

As shown in FIG. 5, the state change from the point S22 to the point S23A (Embodiment 2) is performed on the higher pressure side than the state change from the point S12 to the point S13A (Embodiment 1). This indicates that the condensation pressure in the second embodiment is higher in the condenser 2 than in the first embodiment in the refrigeration cycle when the risk of freezing of the evaporator 5 is increased.

The portion of the state change from the point S22 to the point S23A (Embodiment 2) that has a lower specific enthalpy than the curve SL is more than the curve SL of the state change from the point S12 to the point S13A (Embodiment 1). The specific enthalpy is longer than the lower part. This indicates that in the refrigeration cycle when the risk of freezing of the evaporator 5 increases, the degree of supercooling of the liquid refrigerant discharged from the condenser 2 is greater in the second embodiment than in the first embodiment. ing.

The specific enthalpy of point S23B (Embodiment 2) is larger than the specific enthalpy of point S13B (Embodiment 1). This is because, in the refrigeration cycle when the risk of freezing of the evaporator 5 is increased, the second embodiment joins a larger amount of gas refrigerant to the liquid refrigerant from the condenser 2 than the first embodiment. Means.

The state change from the point S24 to the point S21 (Embodiment 2) is performed on the higher pressure side than the state change from the point S14 to the point S11 (Embodiment 1). This means that in the refrigeration cycle when the risk of freezing of the evaporator 5 is increased, the evaporation pressure in the evaporator 5 is larger in the second embodiment than in the first embodiment.

The interval (second embodiment) between the state change from the point S22 to the point S23A and the state change from the point S24 to the point S21 is the state change from the point S12 to the point S13A and the state change from the point S14 to the point S11. Is larger than the interval (Embodiment 1). This means that in the refrigeration cycle when the risk of freezing of the evaporator 5 is increased, the difference between the condensation pressure and the evaporation pressure is greater in the second embodiment than in the first embodiment.

FIG. 6 is a flowchart for explaining processing performed by the control device 20B of FIG. 4 during the cooling operation. The process shown in FIG. 6 is called at regular time intervals by a main routine (not shown) of the cooling operation.

As shown in FIG. 6, after adjusting the opening degrees of the second expansion valve 6 and the valve 7 in the same manner as in the first embodiment (S101 to S115), the control device 20B, in S201, controls the outlet of the compressor 1 ( It is determined whether or not the ratio between the pressure Pd on the high pressure side and the pressure Ps at the inlet (low pressure side) of the compressor 1 is a reference value (for example, 1.4) or more. Since the pressure Pd is a condensation pressure and the pressure Ps is an evaporation pressure, the ratio between the pressure Pd and the pressure Ps can be said to be a ratio (compression ratio) between the condensation pressure and the evaporation pressure. If the compression ratio is less than the reference value (NO in S201), control device 20B advances the process to S202. The controller 20B advances the process to S116 after reducing the opening of the valve 8 in S202. If the compression ratio is greater than or equal to the reference value (YES in S201), control device 20B advances the process to S203.

Control device 20B determines in S203 whether or not pressure Pd (condensation pressure) is a reference value (for example, 4.0 MPa) or less. If pressure Pd is equal to or lower than the reference value (YES in S203), control device 20B advances the process to S116, assuming that the condensation pressure is within an appropriate range. If pressure Pd is larger than the reference value (NO in S203), control device 20B advances the process to S204, assuming that the condensation pressure is excessive. In S204, the control device 20B increases the opening degree of the valve 8, and then advances the processing to S116. In S116, control device 20B waits for a fixed time (for example, 1 minute), and returns the process to the main routine of the cooling operation.

As described above, according to the refrigeration cycle apparatus 200, freezing of the evaporator 5 can be prevented by suppressing the decrease in the evaporation temperature while continuing the cooling operation as in the first embodiment. As a result, the cooling operation can be continued stably, and energy saving performance and user comfort can be ensured.

Further, according to the refrigeration cycle apparatus 200, it is possible to perform a process for preventing the evaporator 5 from freezing while preventing the compression ratio from becoming smaller than the reference value. That is, during the process of preventing the evaporator 5 from freezing, the difference between the condensation pressure and the evaporation pressure can be maintained at an appropriate value, and the airtightness of the refrigeration cycle apparatus 200 can be maintained. As a result, for example, leakage of the refrigerant can be prevented, and a decrease in performance and failure of the refrigeration cycle apparatus 200 can be prevented. Further, vibration and noise due to refrigerant leakage can be prevented, and user comfort can be ensured.

Furthermore, according to the refrigeration cycle apparatus 200, the evaporation temperature can be further increased than in the first embodiment. As a result, freezing of the evaporator 5 can be prevented more reliably.

In Embodiment 2, the arrangement of the valve 8 and the liquid receiver 9 is not limited to the arrangement shown in FIG. 4, but the refrigerant passing through the valve 8 is preferably in a supercooled state. Therefore, the arrangement of the valve 8 and the liquid receiver 9 is preferably the arrangement of FIG. 4 in which the liquid refrigerant cooled by the internal heat exchanger 3 passes through the valve 8.

In Embodiment 2, the case where it is determined whether or not the compression ratio is equal to or higher than the reference value in S201 has been described. In S201, for example, it may be determined whether or not the pressure of the evaporator 5 (evaporation pressure) is equal to or higher than a reference value.

[Embodiment 3]
In the second embodiment, the configuration including the valve 8 and the liquid receiver 9 has been described as the configuration for controlling the amount of the refrigerant circulating in the circulation flow path 10. The configuration for controlling the amount of refrigerant circulating in the circulation channel 10 is not limited to the configuration of the second embodiment. In the third embodiment, another configuration for controlling the amount of refrigerant circulating in the circulation flow path 10 will be described.

Embodiment 3 differs from Embodiment 2 in the configuration for controlling the amount of refrigerant circulating in the circulation channel 10 and the control for the configuration by the control device 20C. Since the configuration other than these is the same, the description will not be repeated.

FIG. 7 is a configuration diagram of the refrigeration cycle apparatus 300 according to the third embodiment. As shown in FIG. 1, the refrigeration cycle apparatus 100 includes a compressor 1, a condenser 2, an internal heat exchanger 3, a first expansion valve 4, an evaporator 5, a second expansion valve 6, The valve 7, the circulation channel 10, the first bypass channel 11, the second bypass channel 12, the refrigerant tank 40, the

valves

41 and 42, the third bypass channel 13, and the control device 20C. Prepare.

The third bypass flow path 13 branches from a branch point B3 located between the branch point B2 and the first expansion valve 4 in a portion of the circulation flow path 10 from the internal heat exchanger 3 to the first expansion valve 4. To do. The branch point B3 may be disposed anywhere as long as it is a part (a part on the high pressure side) from the compressor 1 to the evaporator 5 in the circulation flow path 10. The third bypass passage 13 passes through the valve 41, the refrigerant tank 40, and the valve 42 in this order. The third bypass flow path 13 joins the junction J3 located between the evaporator 5 and the junction J2 in the portion of the circulation path 10 from the evaporator 5 to the compressor 1. The junction J3 may be disposed anywhere as long as it is a portion (a portion on the low pressure side) of the circulation flow path 10 from the evaporator 5 to the compressor 1.

The control device 20C includes a microcomputer 201C and a drive circuit 203C. The microcomputer 201C controls the drive circuit 203C to adjust the opening degree of the second expansion valve 6 and the valve 7, and opens and closes the valve 41 and the valve 42.

The control device 20C adjusts the amount of refrigerant discharged from the refrigerant tank 40 to the circulation flow path 10 by controlling the opening and closing of the valve 41 and the valve 42. FIG. 8 is a flowchart for explaining processing performed by the control device 20C of FIG. 7 during the cooling operation. The process shown in FIG. 8 is called at regular time intervals by a main routine (not shown) of the cooling operation.

As shown in FIG. 8, after adjusting the opening degree of the second expansion valve 6 and the valve 7 in the same manner as in the first embodiment (S101 to 115), the control device 20C, in S201, controls the outlet ( It is determined whether or not the ratio (compression ratio) between the pressure Pd on the high pressure side and the pressure Ps at the inlet (low pressure side) of the compressor 1 is a reference value (for example, 1.4) or more. If the compression ratio is less than the reference value (NO in S201), control device 20C advances the process to S301. The control device 20C advances the process to S203 after opening the valve 42 in S301. If the compression ratio is greater than or equal to the reference value (YES in S201), control device 20C advances the process to S302. The control device 20C advances the process to S203 after closing the valve 42 in S302.

The controller 20C determines whether or not the pressure Pd (condensation pressure) is equal to or lower than a reference value (for example, 4.0 MPa) in S203. If pressure Pd is equal to or lower than the reference value (YES in S203), control device 20C advances the process to S303, assuming that the condensation pressure is within an appropriate range. After closing valve 41 in S303, control device 20C advances the process to S116. If pressure Pd is greater than the reference value (NO in S203), control device 20C advances the process to S304, assuming that the condensation pressure is excessive. The control device 20C advances the process to S116 after opening the valve 41 in S304. In S116, control device 20C waits for a fixed time (for example, 1 minute), and returns the process to the main routine of the cooling operation.

As described above, according to the refrigeration cycle apparatus 300, as in the first embodiment, the evaporator 5 can be prevented from freezing by suppressing the decrease in the evaporation temperature while continuing the cooling operation. As a result, the cooling operation can be continued stably, and energy saving performance and user comfort can be ensured.

Furthermore, according to the refrigeration cycle apparatus 300, similarly to the second embodiment, it is possible to perform the process of preventing the evaporator 5 from being frozen while preventing the compression ratio from becoming smaller than the reference value. As a result, the airtightness of the refrigeration cycle apparatus 200 can be maintained. Since the airtightness of the refrigeration cycle apparatus 200 can be maintained, for example, leakage of refrigerant can be prevented, and a decrease in performance and failure of the refrigeration cycle apparatus 200 can be prevented. Further, vibration and noise due to refrigerant leakage can be prevented, and user comfort can be ensured.

In FIG. 8, the configuration in which the amount of refrigerant discharged from the refrigerant tank 40 to the circulation flow path 10 is controlled by opening and closing the

valves

41 and 42 has been described. The

valves

41 and 42 may be valves capable of adjusting the opening degree. Since the opening degree of the

valves

41 and 42 can be adjusted, the amount of the refrigerant discharged from the refrigerant tank 40 to the circulation channel 10 can be controlled more finely.

[Embodiment 4]
In the first to third embodiments, the case where the junction J1 of the first bypass flow path 11 is located in the portion from the condenser 2 to the internal heat exchanger 3 has been described. The junction point of the second bypass flow path may be located in a portion from the evaporator 5 to the compressor 1. In the fourth embodiment, a case where the confluence of the second bypass channel is located in a portion from the evaporator 5 to the compressor 1 will be described.

The fourth embodiment differs from the first embodiment in that the confluence J1D of the first bypass flow path 11D is located in a portion from the evaporator 5 to the compressor 1 and the control performed during the cooling operation. This is control by the device 20D. Since it is the same about other points, description is not repeated.

FIG. 9 is a configuration diagram of the refrigeration cycle apparatus 400 according to the fourth embodiment. As shown in FIG. 9, the refrigeration cycle apparatus 400 includes a compressor 1, a condenser 2, an internal heat exchanger 3, a first expansion valve 4, an evaporator 5, a second expansion valve 6, The valve 7, the circulation channel 10, the first bypass channel 11 D, the second bypass channel 12, and the control device 20 D are provided.

1st bypass flow path 11D branches from the branch point B1 located in the part from the compressor 1 to the condenser 2 of the circulation flow path 10. FIG. The first bypass channel 11D passes through the valve 7. The first bypass flow path 11D joins the junction J1D located in the part of the circulation flow path 10 from the evaporator 5 to the compressor 1.

Control device 20D includes a microcomputer 201D and a temperature detection unit 205D. The microcomputer 201D acquires the temperature of the inlet of the compressor 1 from the temperature detection unit 205D. The temperature detection unit 205D calculates the temperature near the inlet of the compressor 1 based on a signal from the temperature sensor 37 attached near the inlet of the compressor 1. The microcomputer 201D calculates the superheat degree SH2 at the inlet of the compressor 1 based on the pressure on the low pressure side and the temperature at the inlet of the compressor 1.

When the risk of freezing of the evaporator 5 increases, the control device 20D increases the opening of the valve 7 to increase the amount of refrigerant passing through the first bypass passage 11D. Along with this, the amount of refrigerant passing through the condenser 2 decreases. As a result, the condensation pressure in the condenser 2 is lower than normal.

The gas refrigerant from the first bypass passage 11D is a high temperature because it is a gas refrigerant discharged from the compressor 1. Therefore, when the refrigerant from the first bypass passage 11D merges with the low-temperature gas refrigerant from the evaporator 5, the temperature of the gas refrigerant after merging rises more than usual. If the temperature of the gas refrigerant sucked into the compressor 1 rises excessively, the compressor 1 stops due to protection control. Therefore, in the fourth embodiment, in order to cool the gas refrigerant sucked into the compressor 1, the low-temperature gas refrigerant is merged with the gas refrigerant from the evaporator 5 by the second bypass passage 12. The amount of the low-temperature gas refrigerant to be merged with the gas refrigerant from the evaporator 5 is adjusted by adjusting the opening degree of the second expansion valve 6.

When the amount of refrigerant passing through the second bypass passage 12 increases, the amount of low-temperature refrigerant passing through the evaporator 5 decreases. Therefore, when the risk of freezing of the evaporator 5 increases, the evaporation temperature of the evaporator 5 increases. As a result, the evaporation pressure of the evaporator 5 increases.

FIG. 10 is a Ph diagram of the refrigeration cycle performed by the refrigeration cycle apparatus 400 of FIG. In FIG. 10, a cycle C4 that returns from the point S41 to the point S41 via the points S42, S43, and S44 is performed by the refrigeration cycle apparatus 400 when the risk of freezing of the evaporator 5 increases. Represents.

As shown in FIG. 10, the state change from the point S42 to the point S43 is performed on the lower pressure side than the state change from the point S2 to the point S3. This indicates that the amount of refrigerant passing through the condenser 2 is decreased by increasing the amount of refrigerant passing through the first bypass flow path 11D, and as a result, the condensation pressure of the condenser 2 is reduced. . Further, the state change from the point S44 to the point S41 is performed on the higher pressure side than the state change from the point S4 to the point S1. This indicates that the amount of refrigerant passing through the evaporator 5 is decreased by increasing the amount of refrigerant passing through the second bypass flow path 12, and as a result, the evaporation pressure of the evaporator 5 is increased. .

FIG. 11 is a flowchart for explaining processing performed by the control device 20D of FIG. 9 during the cooling operation. The process shown in FIG. 11 is called at regular time intervals by the main routine (not shown) of the cooling operation.

As shown in FIG. 11, the control device 20D determines whether or not the cooling capacity is excessive in S401 (for example, the room temperature is lower than the reference value or higher than the target temperature). If the cooling capacity is not excessive (NO in S401), control device 20D advances the process to S101, assuming that there is room for further increasing the cooling capacity.

The control device 20D determines whether or not the piping temperature Te of the evaporator 5 is equal to or higher than a reference value (1 ° C.) in S101. In the fourth embodiment, as in the first embodiment, the lower one of the temperatures detected by the

temperature sensors

35 and 36 is adopted as the pipe temperature Te. If pipe temperature Te is less than the reference value (NO in S101), S108 to S110 are performed as in the first embodiment, and then the process returns to S401. If pipe temperature Te is equal to or higher than the reference value (YES in S101), control device 20D advances the process to S405 after decreasing the opening degree of valve 7 in S403 in order to increase the cooling capacity.

If the cooling capacity is excessive (YES in S401), control device 20D advances the process to S405 after increasing the opening of valve 7 in S404 in order to decrease the cooling capacity.

In S405, the control device 20D determines whether or not the superheat degree SH2 at the inlet of the compressor 1 is equal to or higher than a reference value (eg, 1 ° C.). When superheat degree SH2 is less than the reference value (NO in S405), control device 20D determines that the gas refrigerant from evaporator 5 is excessively cooled by the gas refrigerant from second bypass flow path 12. To S406. Control device 20D advances the process to S116 after decreasing the opening degree of second expansion valve 6 in S406. If superheat degree SH2 is greater than or equal to the reference value (YES in S405), control device 20D advances the process to S407.

Control device 20D determines in S407 whether superheat degree SH2 is a reference value (for example, 3 ° C.) or less. If superheat degree SH2 is greater than the reference value (NO in S407), control device 20D advances the process to S408, assuming that the temperature of the gas refrigerant sucked into compressor 1 has risen excessively. After increasing the opening degree of the second expansion valve 6 in S408, the control device 20D advances the process to S116. If superheat degree SH2 is equal to or greater than the reference value (YES in S407), control device 20D advances the process to S116, assuming that the temperature of the gas refrigerant sucked into compressor 1 is appropriate. In S116, control device 20D waits for a fixed time (for example, 1 minute), and returns the process to the main routine of the cooling operation.

As described above, according to the refrigeration cycle apparatus 400, the evaporator 5 can be prevented from freezing by suppressing the decrease in the evaporation temperature while continuing the cooling operation as in the first embodiment. As a result, the cooling operation can be continued stably, and energy saving performance and user comfort can be ensured.

Furthermore, according to the refrigeration cycle apparatus 400, most of the refrigerant discharged from the compressor 1 may pass through the first bypass channel 11D and the second bypass channel 12. In such a case, almost no refrigerant passes through the evaporator 5. That is, according to the refrigeration cycle apparatus 400, the endothermic amount of the evaporator 5 can be made almost zero without stopping the compressor 1. As a result, the temperature of the evaporator 5 becomes substantially the same as the room temperature, and the freezing of the evaporator 5 is effectively prevented.

The valve 8 and the liquid receiver 9 in the second embodiment may be applied to the fourth embodiment to control the compression ratio as in the second embodiment. In addition, the valve 41, the valve 42, and the refrigerant tank 40 in the third embodiment are applied to the fourth embodiment, and the condensation pressure is increased and the compression ratio is appropriately maintained as in the second embodiment. It doesn't matter.

The embodiments disclosed this time are also scheduled to be implemented in appropriate combinations. The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 compressor, 2 condenser, 3 internal heat exchanger, 4 first expansion valve, 5 evaporator, 6 second expansion valve, 7, 8, 41, 42 valve, 9 receiver, 10, 10B

circulation flow path

11, 11D first bypass flow path, 12 second bypass flow path, 13 third bypass flow path, 20, 20B, 20C, 20D control device, 31, 32 pressure sensor, 33, 34, 35, 36, 37 temperature Sensor, 40 refrigerant tank, 100, 200, 300, 400 refrigeration cycle apparatus, 201, 201B, 201C, 201D, 206 microcomputer, 202, 203, 203B, 203C, 207 drive circuit, 204 pressure detector, 205, 205D, 208, temperature detector, 301, high pressure side flow path, 302, low pressure side flow path, B1, B2, B3 branch point, J1, J1D, J2 J3 confluence.

Claims

The refrigerant is a refrigeration cycle device in which a compressor, a condenser, a first expansion valve, and an evaporator are circulated in order,
A second flow path branching from a first flow path connecting the compressor and the condenser and connecting the condenser and the first expansion valve via a second valve; and the evaporator A first bypass flow path connected to one of the third flow paths connecting the compressor;
The opening degree of the second valve is a refrigeration cycle apparatus in which the evaporation temperature in the evaporator is less than the first reference value than when the evaporation temperature is greater than the first reference value.
Provided between the first part of the second flow path connected to the condenser and the second part of the second flow path connected to the first expansion valve, the inlet connected to the first part And a first internal flow path whose outlet is connected to the second portion and a second internal flow path, and passes through the refrigerant passing through the first internal flow path and the second internal flow path. An internal heat exchanger configured to exchange heat with the refrigerant;
The second bypass channel according to claim 1, further comprising a second bypass channel branched from the second portion and connected to the third channel via a second expansion valve and the second internal channel. Refrigeration cycle equipment.
The first bypass channel is connected to the first portion;
When the degree of supercooling of the refrigerant at the inlet of the first expansion valve is less than the second reference value, the degree of opening of the second expansion valve is greater than the second reference value. The refrigeration cycle apparatus according to claim 2, which is larger.
A first valve is provided between a connection point of the second bypass flow path and the second portion and the first expansion valve;
A liquid receiver is provided between the first valve and the first expansion valve;
The opening degree of the first valve is greater when the ratio of the condensation pressure of the condenser and the evaporation pressure of the evaporator is less than a third reference value than when the ratio is greater than the third reference value. The refrigeration cycle apparatus according to claim 3, which is small.
A first valve is provided between a connection point of the second bypass flow path and the second portion and the first expansion valve;
A liquid receiver is provided between the first valve and the first expansion valve;
The refrigeration according to claim 3, wherein the opening degree of the first valve is smaller when the condensation pressure of the condenser is less than a fourth reference value than when the condensation pressure is greater than the fourth reference value. Cycle equipment.
The third flow path, the first expansion valve, and the evaporator branch from either the first flow path or the second flow path, and pass through the third valve, the refrigerant tank, and the fourth valve. And a third bypass flow path connected to any of the fourth flow paths connecting the
The opening degree of the third valve is greater when the ratio of the condensation pressure of the condenser and the evaporation pressure of the evaporator is less than a fifth reference value than when the ratio is greater than the fifth reference value. small,
The refrigeration cycle apparatus according to claim 3, wherein the opening degree of the fourth valve is greater when the ratio is less than the fifth reference value and when the ratio is greater than the fifth reference value.
The third flow path, the first expansion valve, and the evaporator branch from either the first flow path or the second flow path, and pass through the third valve, the refrigerant tank, and the fourth valve. And a third bypass flow path connected to any of the fourth flow paths connecting the
The opening of the third valve is smaller when the condensation pressure of the condenser is less than a sixth reference value than when the condensation pressure is greater than the sixth reference value,
4. The refrigeration cycle apparatus according to claim 3, wherein the opening degree of the fourth valve is greater when the condensation pressure is less than the sixth reference value than when the condensation pressure is greater than the sixth reference value. .
The first bypass channel is connected to the third channel;
The opening degree of the second expansion valve is larger when the degree of superheat at the inlet of the compressor is larger than a seventh reference value than when the degree of superheat is less than the seventh reference value. Refrigeration cycle equipment.