JP6522154B2 - Refrigeration cycle device - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus.

  Conventionally, a refrigeration cycle apparatus capable of controlling the capacity is known. Japanese Patent Application 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.

Japanese Patent Application Laid-Open No. 09-053861

  In a multi-type air conditioner in which a plurality of indoor heat exchangers are connected to a large-capacity outdoor heat exchanger, as in the case of operating only one of the indoor heat exchangers, the indoor heat during operation If the total capacity of the exchanger is much smaller than the capacity of the outdoor heat exchanger, the heat amount exchanged by the outdoor heat exchanger and the heat amount exchanged by the indoor heat exchanger become unbalanced. When the cooling operation is performed, the amount of heat released by the outdoor heat exchanger functioning as a condenser to the outside air 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 is reduced. As a result, the evaporation temperature is lowered and the possibility of freezing the indoor heat exchanger is increased.

  In addition, if 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 is reduced. The evaporation pressure of the indoor heat exchanger decreases in response to the decrease in the condensation pressure. As a result, the evaporation temperature decreases, and the possibility of the indoor heat exchanger freezing increases.

  In general, when the evaporator freezes, the air passage may be blocked, heat exchange may not be possible, and air conditioning by the subsequent refrigeration cycle may not be possible. When the pipe is compressed and destroyed due to volumetric expansion due to solidification of water, the refrigerant leaks to the atmosphere. Therefore, it is necessary to prevent freezing of the evaporator.

  When the possibility of freezing of the evaporator is increased, the lowering of the evaporation temperature of the evaporator can be suppressed by stopping the refrigeration cycle device, and the freezing of the evaporator can be prevented. However, if the refrigeration cycle apparatus is stopped whenever the possibility of freezing of the evaporator increases, the refrigeration cycle apparatus is repeatedly stopped and restarted, and the cooling operation can not be stably performed. As a result, extra energy is required each time the refrigeration cycle apparatus is restarted, and the user's comfort may be impaired.

  Japanese Patent Application Laid-Open No. 09-053861 (Patent Document 1) does not disclose a configuration for controlling the refrigeration cycle apparatus so as to prevent freezing of the evaporator.

  The present invention has been made to solve the problems as described above, and its object is to prevent freezing of the evaporator while suppressing the refrigeration cycle device from repeatedly stopping and restarting. It is providing a refrigerating cycle device.

  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 passage. The first bypass channel branches from the first channel connecting the compressor and the condenser, and the second channel connecting the condenser and the first expansion valve via the second valve, and evaporation It is connected to any of the 3rd flow paths which connect a tank and a compressor. The opening degree of the second valve is larger when the evaporation temperature in the evaporator is less 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 evaporation temperature while operating the refrigeration cycle device, it is possible to prevent freezing of the evaporator while suppressing the repetition of stop and restart of the refrigeration cycle device. As a result, cooling operation can be stably continued, and energy saving performance and user comfort can be ensured.

FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 1. It is a Ph diagram of the refrigerating cycle performed by the refrigerating cycle device of FIG. It is a flowchart for demonstrating the process performed at the time of air conditioning operation by the control apparatus of FIG. FIG. 6 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 2. It is a Ph diagram of the refrigerating cycle performed by the refrigerating cycle device of FIG. It is a flowchart for demonstrating the process performed by the control apparatus of FIG. 4 at the time of air_conditionaing | cooling operation. FIG. 8 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 3. It is a flowchart for demonstrating the process performed by the control apparatus of FIG. 7 at the time of air_conditionaing | cooling operation. FIG. 10 is a block diagram of a refrigeration cycle apparatus according to a fourth embodiment. It is a Ph diagram of the refrigerating cycle performed by the refrigerating cycle device of FIG. It is a flowchart for demonstrating the process performed by the control apparatus of FIG. 9 at the time of air_conditionaing | 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 portions are denoted by the same reference characters and description thereof will not be repeated.

First Embodiment
FIG. 1 is a block diagram of a refrigeration cycle apparatus 100 according to a 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, and a second expansion valve 6. A valve 7, a circulation flow passage 10, a first bypass flow passage 11, a second bypass flow passage 12, and a control device 20 are provided.

  The circulation flow path 10 connects the compressor 1, the condenser 2, the internal heat exchanger 3, the first expansion valve 4, and the evaporator 5 by piping, and circulates the refrigerant.

  The rotational speed of the compressor 1 is controlled based on the drive frequency from the control device 20, and the gas refrigerant is compressed and discharged.

The condenser 2 condenses the gas refrigerant discharged from the compressor 1 and discharges the liquid refrigerant.
The first expansion valve 4 expands and reduces the pressure of the refrigerant from the internal heat exchanger 3. The opening degree of the first expansion valve 4 is adjustable. The first expansion valve 4 is, for example, an electronically controlled expansion valve (LEV: Linear Expansion Valve).

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

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

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

  The internal heat exchanger 3 includes a flow passage (high pressure side flow passage 301) through which the refrigerant from the junction J1 passes and a flow passage (low pressure side flow passage 302) through which the refrigerant from the second expansion valve 6 passes. The internal heat exchanger 3 has a function of absorbing the heat of the refrigerant from the junction point J1 into the refrigerant from the second expansion valve 6 and cooling the refrigerant from the junction point J1. The internal heat exchanger 3 is, for example, a double-pipe heat exchanger.

  The second expansion valve 6 expands and reduces the pressure of the refrigerant. The second expansion valve 6 is, for example, an LEV.

  The second bypass passage 12 branches from a branch point B2 located in a portion of the circulation passage 10 from the internal heat exchanger 3 to the first expansion valve 4. The second bypass passage 12 passes through the internal heat exchanger 3 next to the second expansion valve 6. The second bypass channel 12 joins a junction J2 located in the portion of the circulation channel 10 from the evaporator 5 to the compressor 1.

  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 controls the drive circuit 202 to drive the compressor 1. The microcomputer 201 controls the drive circuit 203 to adjust the opening degree of the second expansion valve 6 and the valve 7. The microcomputer 201 obtains 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 the 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 the signal from the pressure sensor 32 attached to the outlet of the compressor 1.

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

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

  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 at the pipe inlet of the evaporator 5 and the temperature at the pipe outlet of the evaporator 5 from the temperature detection unit 208. The temperature detection unit 208 calculates the temperature at the inlet of the evaporator 5 based on the signal from the temperature sensor 35 attached to the inlet of the evaporator 5. The temperature detection unit 208 calculates the temperature at the pipe outlet of the evaporator 5 based on the signal from the temperature sensor 36 attached to the pipe outlet of the evaporator 5.

  The microcomputer 206 obtains the pressure on the high pressure side and the pressure on the low pressure side from the microcomputer 201. The microcomputer 206 calculates the degree of superheat of 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 degree of superheat at the pipe outlet of the evaporator 5 approaches a target value (for example, degree of superheat 1 ° C.) (superheat degree control).

  The refrigerant repeats heat absorption and release while repeating the state change between the liquid refrigerant and the 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 and the specific enthalpy of the refrigeration cycle performed by the refrigeration cycle apparatus 100 of FIG. In FIG. 2, point CP is the critical point of the refrigerant. Curve SL is a saturated liquid line of the refrigerant. Curve SV is a saturated vapor line of the refrigerant. A cycle C0 which 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 point S1 to point S2 represents the process of compression of the refrigerant by the compressor 1. The state change from point S2 to point S3 represents the process of condensation of the refrigerant by the condenser 2. The state change from the point S3 to the point S4 represents the process of pressure reduction of the refrigerant by the first expansion valve 4. The state change from point S4 to 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. The gas refrigerant is sucked into the compressor 1, compressed by the compressor 1, and discharged as a high-temperature, high-pressure gas refrigerant. The compression by the compressor 1 adds energy to the refrigerant. As a result, the specific enthalpy of the refrigerant is increased. The process of compression of 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 with high pressure in the condenser 2 and becomes liquid refrigerant. Heat of condensation is released to the outside air when the gas refrigerant condenses and becomes liquid refrigerant. That is, when the refrigerant passes through the condenser 2, the specific enthalpy of the refrigerant decreases. The process of condensation of 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 point S3 is less than the specific enthalpy at point S2. The pressure at point S3 is almost the same as that at point S2. To be precise, a pressure loss occurs when the refrigerant passes through the condenser 2. In this case, as the refrigerant travels inside the condenser 2, the pressure of the refrigerant gradually decreases. 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 in the first expansion valve 4. The liquid refrigerant is depressurized by the first expansion valve 4. As a result, a 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 point S3 to point S4 in FIG. The pressure at point S4 is less than the pressure at point S3. Since the process of depressurizing the refrigerant by the first expansion valve 4 is adiabatic expansion, the specific enthalpy at point S4 and the specific enthalpy at point S3 are almost the same. In addition, since the 2nd expansion valve 6 is closed at the time of normal, cooling by internal heat exchanger 3 is not performed.

  The liquid refrigerant of 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 to be a gas refrigerant, the heat of evaporation is absorbed from the air in the room. 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 represented as a state change from point S4 to point S1 in FIG. The specific enthalpy at point S1 is greater than the specific enthalpy at point S4. The pressure at the point S1 is slightly reduced from the pressure at the point S4 due to the pressure loss that occurs when the refrigerant passes through the evaporator 5.

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

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

  In general, when the evaporator 5 is frozen, the air outlet or the air inlet may be blocked, heat exchange in the evaporator 5 may not be performed, and a subsequent cooling operation may be disabled. In addition, the pipe is compressed and destroyed by volumetric expansion due to solidification of water, and the refrigerant leaks to the atmosphere. Therefore, it is necessary to prevent freezing of the evaporator.

  If it is difficult to avoid the freezing of the evaporator 5 even if 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 whenever the possibility of freezing of the evaporator 5 increases, the operation of the refrigeration cycle apparatus 100 is repeatedly stopped and restarted, and the cooling operation can not be performed stably. As a result, an extra energy is required each 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 to the outside air by the condenser 2 (condensing ability Lower). 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, so that freezing of the evaporator 5 is prevented without stopping the refrigeration cycle apparatus 100. Can. As a result, cooling operation can be stably continued, 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 the evaporator 5 is increased will be described with reference to FIG. 2. The case where the possibility of freezing of the evaporator 5 is increased is, for example, the case where the pipe temperature Te of the evaporator 5 becomes less than 1 ° C. In FIG. 2, the cycle C1 from the point S11 to the point S12, the point S13A, the point S13B, and the point S14 and returning to the point S11 is performed by the refrigeration cycle apparatus 100 when the possibility of freezing the evaporator 5 is increased. Represents a refrigeration cycle. The state change from point S11 to point S12 represents the process of compression of the refrigerant by the compressor 1. The state change from point S12 to point S13A represents the process of condensation of the refrigerant by the condenser 2. The state change from point S13A to point S13B represents a process in which the specific enthalpy of the refrigerant increases as the refrigerant from the first bypass flow passage 11 joins the refrigerant from the condenser 2. The state change from the point S13B to the point S14 represents the process of pressure reduction of the refrigerant by the first expansion valve 4. The state change from point S14 to point S11 represents the process of evaporation of the refrigerant by the evaporator 5.

  When the risk of freezing of the evaporator 5 is increased, the controller 20 increases the opening degree of the valve 7 to increase the amount of refrigerant passing through the second bypass flow passage. The amount of refrigerant passing through the condenser 2 is reduced. As a result, the condensation pressure in the condenser 2 is lower than usual. 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 indicates a decrease in the condensation pressure of the condenser 2.

  Since the refrigerant from the first bypass channel 11 has not passed through the condenser 2, little heat is released. Therefore, when the refrigerant from the first bypass flow passage 11 joins the refrigerant from the condenser 2, the specific enthalpy of the refrigerant from the junction J1 becomes higher than that in the normal case. The fact that the specific enthalpy at point S13B in FIG. 2 is higher than the specific enthalpy at point S3 indicates 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. Therefore, depending on the degree of subcooling 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 smaller average density than the liquid refrigerant, the flow rate at which the wet steam passes through the first expansion valve 4 is smaller than the flow rate at which the liquid refrigerant passes through the first expansion valve 4. Therefore, if the refrigerant remains wet vapor, the pressure (evaporation pressure) of the refrigerant after passing through the first expansion valve 4 is reduced as compared to the case where 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 channel 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 moist vapor, noise will be generated when the moist vapor passes through the minute flow path in the first expansion valve 4, and the quality of the refrigeration cycle apparatus 100 is preferable. Absent.

  So, in Embodiment 1, the refrigerant from junction point J1 is cooled by internal heat exchanger 3, and the gas-liquid two-phase state in the refrigerant from junction point J1 is eliminated.

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

  As described above, the specific enthalpy of the refrigerant from the junction J1 is larger than the specific enthalpy at the normal time, so that the refrigerant needs to be absorbed from the indoor air in the evaporator 5 to continue the refrigeration cycle. The amount of heat decreases. The amount of heat absorbed by the refrigerant from the air in the room is proportional to the difference between the temperature of the evaporator 5 (evaporation temperature) and the room temperature (temperature gradient) (Fourier's law). Therefore, in order to reduce the heat absorption amount (evaporation ability) of the evaporator 5, it is necessary to raise the evaporation temperature of the evaporator 5 to reduce the temperature difference between the evaporator 5 and the room. The control device 20 raises the evaporation temperature of the evaporator 5 by adjusting the opening degree of the first expansion valve 4 and raising 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 the process performed by the control device 20 of FIG. 1 during the cooling operation. The process shown in FIG. 3 is called at fixed 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 pipe temperature Te of the evaporator 5 is equal to or higher than a reference value (1 ° C.) in step S101 (hereinafter, the step is simply expressed as S). When measuring a plurality of locations of the evaporator 5, the lowest value is adopted as the pipe temperature Te. In the first embodiment, the lower one of the temperatures detected by the temperature sensors 35 and 36 is adopted. If the pipe temperature Te is equal to or higher than the reference value (YES in S101), the control device 20 advances the process to S102, assuming that the possibility that the evaporator 5 is frozen is low.

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

  In S103, the control device 20 determines whether the degree of superheat SH1 at the outlet of the low pressure side flow passage 302 of the internal heat exchanger 3 is equal to or higher than a reference value (1 ° C.). If the degree of superheat SH1 is equal to or higher than the reference value (YES in S103), the control device 20 advances the process to S116, assuming that the flow rate of the refrigerant flowing in the low pressure side flow path 302 of the internal heat exchanger 3 is appropriate. If the degree of superheat SH1 is less than the reference value (NO in S103), the control device 20 advances the process to S115 on the assumption that the excess refrigerant is flowing in the low pressure side flow path 302 of the internal heat exchanger 3. The control device 20 reduces the opening degree of the second expansion valve 6 in S115 and advances the process to S116.

  At S116, control device 20 waits for processing for a predetermined period of time (for example, one minute). Thereafter, the processing is returned to the main routine of the cooling operation.

  If the pipe temperature Te is less than the reference value (NO in S101), the control device 20 advances the process to S104 because it is highly likely that the evaporator 5 is frozen. The control device 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 the degree of subcooling SC at the outlet of the high pressure side flow passage 301 of the internal heat exchanger 3 is equal to or higher than a reference value (5 ° C.). If the degree of subcooling SC is equal to or higher than the reference value (YES in S105), the control device 20 determines that the gas-liquid two-phase state of the refrigerant from the junction J1 has been eliminated by the internal heat exchanger 3 and proceeds to S103. Advance. If the degree of subcooling SC is less than the reference value (NO in S105), the control device 20 proceeds the processing to S106 as there is a possibility that the gas-liquid two-phase state of the refrigerant from the junction J1 has not been eliminated. .

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

  In S108, control device 20 stops 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 channel 12. Alternatively, the control device 20 may fully close the first expansion valve 4 and stop the compressor 1.

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

  In the case where control device 20 is unlikely to freeze evaporator 5 (YES in S101) and there is a possibility that the gas-liquid two-phase state of the refrigerant from junction J1 has not been eliminated (NO in S102) In step S111, the opening degree of the valve 7 is increased, and the process proceeds to step S112.

  At S112, the control device 20 determines whether the degree of superheat SH1 at the outlet of the low pressure side flow passage 302 of the internal heat exchanger 3 is equal to or higher than a reference value (1 ° C.). When the degree of superheat SH1 is equal to or higher than the reference value (YES in S112), the control device 20 is supposed that further cooling can be expected by increasing the flow rate of the refrigerant flowing through the low pressure side flow path 302 of the internal heat exchanger 3. Advance to S113. In S113, the control device 20 increases the opening degree of the second expansion valve 6 and advances the process to S116. If the degree of superheat SH1 is less than the reference value (NO in S112), the control device 20 proceeds the process to step 114 noting that the flow rate of the refrigerant flowing in the low pressure side flow path 302 of the internal heat exchanger 3 is excessive. . In S114, the controller 20 reduces the opening degree 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 an example. The reference value and the fixed time may be other values. The reference value and the fixed time can be appropriately determined by an actual machine experiment or simulation.

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

Second Embodiment
In the first embodiment, in order to prevent freezing of the evaporator 5, a part of the refrigerant discharged from the compressor 1 is caused to pass through the first bypass flow passage 11 to reduce the condensation pressure of the condenser 2. The case where the evaporation pressure of the evaporator 5 is increased is described. That is, when the process shown in FIG. 3 is performed, the ratio (compression ratio) of the condensation pressure to the evaporation pressure decreases. When the compression ratio becomes 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 a compressor 1 or a non-return valve (not shown) can be mentioned, for example. If the airtightness of the refrigeration cycle apparatus 100 is deteriorated, the possibility that the refrigerant leaks from the point where the airtightness is deteriorated is increased. Leakage of the refrigerant degrades the performance of the refrigeration cycle apparatus 100 and increases the possibility of failure. In addition, the vibration and noise from the refrigeration cycle apparatus 100 become large, and the possibility of impairing the user's comfort increases.

  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 processing to prevent freezing of the evaporator 5 while preventing the compression ratio from becoming smaller than the reference value.

  The second embodiment differs from the first embodiment in that it has a configuration for controlling the amount of refrigerant circulating in the circulation flow path. The other configurations are the same, and therefore the description will not be repeated.

  FIG. 4 is a block diagram of a 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, and a second expansion valve 6. A valve 7, a valve 8, a receiver 9, a circulation flow path 10B, a first bypass flow path 11, a second bypass flow path 12, and a control device 20B.

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

  Control device 20B includes a microcomputer 201B and a drive circuit 203B. The microcomputer 201B adjusts 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 be in any form as long as the flow rate of the refrigerant can be adjusted by adjusting the opening degree. The valve 8 may be an expansion valve such as, for example, an LEV.

  The receiver 9 temporarily accumulates the liquid refrigerant from the valve 8. When the opening degree of the valve 8 is adjusted by the controller 20B, the amount of liquid refrigerant sucked into the 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 falls below 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 the second embodiment, when the compression ratio is less than the reference value, controller 20B decreases the opening degree of valve 8 to reduce the amount of refrigerant drawn into receiver 9. Assuming that the amount of refrigerant drawn into the compressor 1 is substantially constant, the amount of refrigerant discharged from the receiver 9 is substantially constant. Therefore, when the opening degree of the valve 8 is reduced, the amount of liquid refrigerant temporarily stored in the liquid receiver 9 is reduced. On the other hand, the amount of liquid refrigerant discharged from the condenser 2 is reduced by reducing the opening degree of the valve 8. That is, the amount of liquid refrigerant in the condenser 2 increases.

  As 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 by the increase in the amount of liquid refrigerant in the condenser 2, the condensation pressure of the gas refrigerant in the condenser 2 increases. As the condensation pressure rises, the condensation temperature also rises. The heat release amount (condensing capacity) of the condenser 2 is proportional to the effective heat transfer area and the product of the difference between the temperature of the outside air and the condensing temperature. As the condensation temperature rises, the difference between the temperature of the outside air and the condensation temperature increases. Therefore, even if the amount of liquid refrigerant accumulated in the condenser 2 increases, the effective heat transfer area decreases, but the difference between the temperature of the outside air and the condensation temperature increases, so the heat release amount of the condenser 2 hardly changes. . That is, by increasing the amount of liquid refrigerant accumulated in the condenser 2, the condensation pressure can be increased with almost no change in the condensation capacity of the condenser 2.

  Further, 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, by increasing the amount of liquid refrigerant accumulated in the condenser 2, the degree of subcooling of the liquid refrigerant near the outlet of the condenser 2 can be increased. Therefore, in the second embodiment, more gas refrigerant can be joined to the liquid refrigerant from the condenser 2 by increasing the opening degree of the valve 7 as compared with the first embodiment. As a result, the evaporation pressure and the evaporation temperature in the evaporator 5 can be further raised.

  FIG. 5 is a Ph diagram of the refrigeration cycle performed by the refrigeration cycle apparatus 200 of FIG. 4. In FIG. 5, the cycle C2 from the point S21 to the point S22, the point S23A, the point S23B, and the point S24 and returning to the point S21 is performed by the refrigeration cycle apparatus 200 when the possibility of freezing the evaporator 5 increases. Represents a refrigeration cycle. FIG. 5 is a diagram in which a cycle C2 is added to FIG. The points S21, S22, S23A, S23B, and S24 in the cycle C2 correspond to the points S11, S12, S13A, S13B, and S14 in the cycle C1, respectively.

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

  The portion on the side where the specific enthalpy is lower than the curve SL in the state change from the point S22 to the point S23A (Embodiment 2) is 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 the degree of subcooling of the liquid refrigerant discharged from the condenser 2 is larger in the second embodiment than in the first embodiment in the refrigeration cycle when the possibility of freezing of the evaporator 5 is increased. ing.

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

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

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

  FIG. 6 is a flowchart for explaining the process 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 the main routine (not shown) of the cooling operation.

  As shown in FIG. 6, after adjusting the opening degree of the second expansion valve 6 and the valve 7 as in the first embodiment (S101 to S115), the control device 20B controls the outlet of the compressor 1 (S201). It is determined whether the ratio of the pressure Pd on the high pressure side to the pressure Ps on the inlet (low pressure side) of the compressor 1 is equal to or greater than a reference value (for example, 1.4). Since the pressure Pd is a condensation pressure and the pressure Ps is an evaporation pressure, the ratio of the pressure Pd to the pressure Ps can be said to be a ratio (compression ratio) of the condensation pressure to the evaporation pressure. If the compression ratio is less than the reference value (NO in S201), control device 20B advances the process to S202. After reducing the opening degree of the valve 8 in S202, the control device 20B proceeds with the process to S116. If the compression ratio is equal to or higher than the reference value (YES in S201), control device 20B advances the process to S203.

  In S203, the control device 20B determines whether the pressure Pd (condensing pressure) is less than or equal to a reference value (for example, 4.0 MPa). If the pressure Pd is less than or equal to the reference value (YES in S203), the control device 20B advances the process to S116, assuming that the condensing pressure is within the appropriate range. If the pressure Pd is larger than the reference value (NO in S203), the control device 20B proceeds with the process to S204 noting that the condensing pressure is excessive. After increasing the opening degree of the valve 8 in S204, the control device 20B advances the process to S116. At S116, control device 20B waits for a fixed time (for example, one minute), and returns the process to the main routine of the cooling operation.

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

  Moreover, according to the refrigeration cycle apparatus 200, it is possible to perform the process of preventing the freezing of the evaporator 5 while preventing the compression ratio from becoming smaller than the reference value. That is, while performing processing for preventing freezing of the evaporator 5, it is possible to maintain the airtightness of the refrigeration cycle apparatus 200 by maintaining the difference between the condensation pressure and the evaporation pressure at an appropriate value. As a result, for example, the leakage of the refrigerant can be prevented, and the performance deterioration and failure of the refrigeration cycle apparatus 200 can be prevented. Moreover, the generation of vibration and noise due to the leakage of the refrigerant can be prevented, and the comfort of the user can be secured.

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

  In the second embodiment, the arrangement of the valve 8 and the receiver 9 is not limited to the arrangement shown in FIG. 4, but it is desirable that the refrigerant passing through the valve 8 be in a subcooled state. Therefore, the arrangement of the valve 8 and the receiver 9 is preferably the arrangement of FIG. 4 where the liquid refrigerant cooled by the internal heat exchanger 3 passes through the valve 8.

  The second embodiment has described the case where it is determined in S201 whether the compression ratio is equal to or greater than the reference value. In S201, for example, it may be determined whether the pressure (evaporation pressure) of the evaporator 5 is equal to or higher than a reference value.

Third Embodiment
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 refrigerant circulating in the circulation flow passage 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.

  The third embodiment differs from the second embodiment in the configuration for controlling the amount of refrigerant circulating in the circulation channel 10 and the control of the configuration by the control device 20C. The configuration other than these is the same, so the description will not be repeated.

  FIG. 7 is a block diagram of a 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, and a second expansion valve 6. The valve 7, the circulation flow path 10, the first bypass flow path 11, the second bypass flow path 12, the refrigerant tank 40, the valves 41 and 42, the third bypass flow path 13, and the control device 20C Prepare.

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

  Control device 20C includes a microcomputer 201C and a drive circuit 203C. The microcomputer 201C adjusts the opening degree of the second expansion valve 6 and the valve 7 and controls the valve 41 and the valve 42 by controlling the drive circuit 203C.

  The controller 20C adjusts the amount of refrigerant discharged from the refrigerant tank 40 to the circulation flow passage 10 by controlling the opening and closing of the valve 41 and the valve 42. FIG. 8 is a flowchart for explaining the process 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 the main routine (not shown) of the cooling operation.

  As shown in FIG. 8, after adjusting the opening degrees of the second expansion valve 6 and the valve 7 (S101 to 115) as in the first embodiment, the controller 20C controls the outlet of the compressor 1 (S201). It is determined whether the ratio (compression ratio) of the pressure Pd on the high pressure side to the pressure Ps on 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. After opening the valve 42 in S301, the control device 20C advances the process to S203. If the compression ratio is equal to or higher than the reference value (YES in S201), control device 20C advances the process to S302. After closing the valve 42 in S302, the control device 20C advances the process to S203.

  In S203, the controller 20C determines whether the pressure Pd (condensing pressure) is less than or equal to a reference value (for example, 4.0 MPa). If the pressure Pd is less than or equal to the reference value (YES in S203), the control device 20C advances the process to S303 on the assumption that the condensation pressure is within the appropriate range. After closing the valve 41 in S303, the control device 20C advances the process to S116. If the pressure Pd is higher than the reference value (NO in S203), the control device 20C advances the process to S304, assuming that the condensation pressure is excessive. After opening the valve 41 in S304, the control device 20C advances the process to S116. At S116, control device 20C waits for a fixed time (for example, one 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, freezing of the evaporator 5 can be prevented by suppressing the decrease in evaporation temperature while continuing the cooling operation. As a result, cooling operation can be stably continued, and energy saving performance and user comfort can be ensured.

  Furthermore, according to the refrigeration cycle apparatus 300, as in the second embodiment, it is possible to perform processing to prevent freezing of the evaporator 5 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. By being able to maintain the airtightness of the refrigeration cycle apparatus 200, for example, it is possible to prevent the leakage of the refrigerant and to prevent the performance degradation and failure of the refrigeration cycle apparatus 200. Moreover, the generation of vibration and noise due to the leakage of the refrigerant can be prevented, and the comfort of the user can be secured.

  In FIG. 8, the structure which controls the quantity of the refrigerant | coolant discharge | released from the refrigerant | coolant tank 40 to the circulation flow path 10 was demonstrated by opening and closing valve 41,42. The valves 41 and 42 may be valves capable of adjusting the opening degree. By adjusting the opening degree of the valves 41 and 42, it is possible to more finely control the amount of refrigerant discharged from the refrigerant tank 40 to the circulation flow path 10.

Fourth Embodiment
In the first to third embodiments, the case where the junction point J1 of the first bypass channel 11 is located in a 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 at a portion from the evaporator 5 to the compressor 1. In the fourth embodiment, the case where the junction point of the second bypass flow passage is located in a portion from the evaporator 5 to the compressor 1 will be described.

  The fourth embodiment is different from the first embodiment in that the junction J1D of the first bypass passage 11D is located in a portion from the evaporator 5 to the compressor 1, and control performed during the cooling operation. It is control by device 20D. The other points are the same, and therefore the description will not be repeated.

  FIG. 9 is a block diagram of a 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, and a second expansion valve 6. A valve 7, a circulation flow path 10, a first bypass flow path 11D, a second bypass flow path 12, and a control device 20D.

  The first bypass channel 11D branches from a branch point B1 located in a portion of the circulation channel 10 from the compressor 1 to the condenser 2. The first bypass flow passage 11 D passes through the valve 7. The first bypass flow passage 11D merges with a junction J1D located in a portion of the circulation flow passage 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 at 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 the signal from the temperature sensor 37 attached near the inlet of the compressor 1. The microcomputer 201D calculates the superheat degree SH2 of the inlet of the compressor 1 based on the pressure on the low pressure side and the temperature of the inlet of the compressor 1.

  When the possibility of freezing of the evaporator 5 is increased, the control device 20D increases the opening degree of the valve 7 to increase the amount of refrigerant passing through the first bypass channel 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 usual.

  The gas refrigerant from the first bypass flow passage 11D is a gas refrigerant discharged from the compressor 1 and thus has a high temperature. Therefore, when the refrigerant from the first bypass flow passage 11D merges with the low temperature gas refrigerant from the evaporator 5, the temperature of the merged gas refrigerant rises more than usual. If the temperature of the gas refrigerant sucked into the compressor 1 rises excessively, the compressor 1 is stopped by the 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 flow passage 12. Adjustment of the amount of low temperature gas refrigerant to be merged with the gas refrigerant from the evaporator 5 is performed by adjusting the opening degree of the second expansion valve 6.

  As 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 the evaporator 5 is increased, the evaporation temperature of the evaporator 5 is increased. As a result, the evaporation pressure of the evaporator 5 is increased.

  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 from the point S41 to the point S42, the point S43, and the point S44 to return to the point S41 is a refrigeration cycle performed by the refrigeration cycle apparatus 400 when the risk of freezing 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 means that the amount of refrigerant passing through the condenser 2 is reduced by increasing the amount of refrigerant passing through the first bypass flow passage 11D, and as a result, the condensation pressure of the condenser 2 is lowered. . 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 means that the amount of refrigerant passing through the evaporator 5 is reduced by increasing the amount of refrigerant passing through the second bypass passage 12, and as a result, the evaporation pressure of the evaporator 5 is increased. .

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

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

  The control device 20D determines in S101 whether or not the pipe temperature Te of the evaporator 5 is equal to or higher than a reference value (1 ° C.). Also 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 the pipe temperature Te is less than the reference value (NO in S101), after performing S108 to S110 as in the first embodiment, the process returns to S401. If the pipe temperature Te is equal to or higher than the reference value (YES in S101), the controller 20D decreases the opening degree of the valve 7 in S403 to increase the cooling capacity, and then advances the process to S405.

  If the cooling capacity is excessive (YES in S401), controller 20D increases the opening degree of valve 7 in S404 in order to reduce the cooling capacity, and then proceeds the process to S405.

  At S405, the control device 20D determines whether the degree of superheat SH2 at the inlet of the compressor 1 is equal to or higher than a reference value (for example, 1 ° C.). If the degree of superheat SH2 is less than the reference value (NO in S405), the control device 20D processes the gas refrigerant from the evaporator 5 as being excessively cooled by the gas refrigerant from the second bypass flow passage 12 Advance to S406. After reducing the opening degree of the second expansion valve 6 in S406, the control device 20D advances the process to S116. If degree of superheat SH2 is equal to or greater than the reference value (YES in S405), control device 20D advances the process to S407.

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

  As described above, according to the refrigeration cycle apparatus 400, as in the first embodiment, freezing of the evaporator 5 can be prevented by suppressing the decrease in evaporation temperature while continuing the cooling operation. As a result, cooling operation can be stably continued, 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 heat absorption 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 approximately the same as room temperature, and freezing of the evaporator 5 is effectively prevented.

  As in the second embodiment, the compression ratio may be controlled by applying the valve 8 and the liquid receiver 9 in the second embodiment to the fourth embodiment. Also, 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 as in the second embodiment to maintain the compression ratio properly. I don't care.

  The embodiments disclosed this time are also planned to be implemented in combination as appropriate. It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims.

  Reference Signs List 1 compressor, 2 condenser, 3 internal heat exchanger, 4 first expansion valve, 5 evaporator, 6 second expansion valve, 7, 8, 41, 42 valve, 9 liquid receiver, 10, 10B circulation flow path , 11, 11D first bypass channel, 12 second bypass channel, 13 third bypass channel, 20, 20B, 20C, 20D controller, 31, 32 pressure sensor, 33, 34, 35, 36, 37 temperature Sensors, 40 refrigerant tanks, 100, 200, 300, 400 refrigeration cycle devices, 201, 201 B, 201 C, 201 D, 206 microcomputers, 202, 203, 203 B, 203 C, 207 drive circuits, 204 pressure detection units, 205, 205 D, 208 temperature detection unit, 301 high pressure side flow passage, 302 low pressure side flow passage, B1, B2, B3 branch point, J1, J1 D, J2, J3 junction point.

Claims (8)

A refrigeration cycle apparatus in which a refrigerant circulates in the order of a compressor, a condenser, a first expansion valve, and an evaporator,
Branched from the first passage which connects the condenser and the compressor, via the second valve, the first being connected to the second passage for connecting the condenser and the first expansion valve Bypass flow path,
Provided between a first portion of the second flow passage connected to the condenser and a second portion of the second flow passage connected to the first expansion valve, and an inlet is connected to the first portion And a second internal flow path having an outlet connected to the second portion, and the refrigerant passing through the first internal flow path and passing through the second internal flow path An internal heat exchanger configured to exchange heat with the refrigerant;
And a second bypass flow path branched from the second portion and connected to a third flow path connecting the evaporator and the compressor via a second expansion valve and the second internal flow path. Equipped with
The first bypass channel is connected to the first portion,
The opening degree of the second valve when the evaporation temperature in the evaporator is lower than the first reference value, the evaporation temperature is rather larger than the opening degree of the second valve when the larger first reference value,
When the evaporation temperature is higher than the first reference value, the opening degree of the second valve when the degree of subcooling of the refrigerant at the inlet of the first expansion valve is less than a second reference value is It has smaller than the opening degree of the second valve when the subcooling degree is greater than the second reference value, the refrigeration cycle apparatus. The opening degree of the second expansion valve when the degree of supercooling is below the second reference value is greater than the opening degree of the supercooling degree is the second expansion valve when the larger second reference value, The refrigeration cycle apparatus according to claim 1 . A first valve is provided between a connection point of the second bypass passage and the second portion and the first expansion valve.
A receiver is provided between the first valve and the first expansion valve,
When the ratio of the condensation pressure of the condenser to the evaporation pressure of the evaporator is less than a third reference value, the opening degree of the first valve is greater than the third reference value. The refrigeration cycle apparatus according to claim 2, which is smaller than the opening degree of the valve. A first valve is provided between a connection point of the second bypass passage and the second portion and the first expansion valve,
A receiver is provided between the first valve and the first expansion valve,
The opening degree of the first valve when the condensing pressure of the condenser is less than the fourth reference value is smaller than the opening degree of the first valve when the condensing pressure is larger than the fourth reference value. refrigeration cycle apparatus according to 2. Branching from any one of the first flow path and the second flow path, the third flow path, the first expansion valve, and the evaporator via a third valve, a refrigerant tank, and a fourth valve And a third bypass channel connected to any of the fourth channels connecting
When the ratio of the condensation pressure of the condenser to the evaporation pressure of the evaporator is less than a fifth reference value, the opening degree of the third valve is greater than the fifth reference value. Less than the opening of the valve,
Opening of the fourth valve when the ratio is less than the fifth reference value is greater than the opening degree of the fourth valve when the ratio is larger than the fifth reference value, according to claim 2 Refrigeration cycle equipment. Branching from any one of the first flow path and the second flow path, the third flow path, the first expansion valve, and the evaporator via a third valve, a refrigerant tank, and a fourth valve And a third bypass channel connected to any of the fourth channels connecting
The opening degree of the third valve when the condensing pressure of the condenser is less than the sixth reference value is smaller than the opening degree of the third valve when the condensing pressure is larger than the sixth reference value,
Opening of the fourth valve when the condensing pressure is less than the sixth reference value is greater than the opening degree of the fourth valve when the larger condensing pressure is the sixth reference value, to claim 2 Refrigeration cycle device as described. A refrigeration cycle apparatus in which a refrigerant circulates in the order of a compressor, a condenser, a first expansion valve, and an evaporator,
A first bypass flow branched from a first flow path connecting the compressor and the condenser and connected to a third flow path connecting the evaporator and the compressor via a second valve Equipped with
The evaporator is disposed in a specific space,
The opening degree of the second valve when the temperature difference obtained by subtracting the temperature of the specific space from the target temperature of the specific space is larger than an eighth reference value is the opening degree of the second case where the temperature difference is less than the eighth reference value Greater than the opening of 2 valves,
The opening degree of the second valve when the temperature difference is less than the eighth reference value, and the evaporation temperature in the evaporator is less than the first reference value, the evaporation temperature being higher than the first reference value The refrigeration cycle apparatus, which is larger than the opening degree of the second valve when it is large. A first portion of a second flow path connecting the condenser and the first expansion valve connected to the condenser and a second portion of the second flow path connected to the first expansion valve A first internal flow passage provided between the first and second parts, the inlet being connected to the first part and the outlet being connected to the second part, and the second internal flow path, passing through the first internal flow path An internal heat exchanger configured to exchange heat between the refrigerant and the refrigerant passing through the second internal flow path;
It further comprises a second bypass flow passage branched from the second portion and connected to the third flow passage via a second expansion valve and the second internal flow passage,
The degree of opening of the second expansion valve when the degree of superheat at the inlet of the compressor is greater than the seventh reference value is greater than the degree of opening of the second expansion valve when the degree of superheat is less than the seventh standard value. The refrigeration cycle apparatus according to claim 7 .

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