Refrigeration device, environment forming device and refrigeration method

Abstract

To enable an evaporator to adjust a refrigeration capacity while stably driving a compressor with suction injection using a bypass flow path.SOLUTION: A refrigeration device 10 comprises: a main circuit 15 in which a compressor 1, a condenser 2, an expansion valve 3 and an evaporator 4 are provided and which circulates a refrigerant; a bypass flow path 16 in which a flow control valve 11 is provided and which branches off from the main circuit 15, and in which the refrigerant liquefied in the condenser 2 is cooled by the flow control valve 11 and suctioned into the compressor 1 without passing through the evaporator 4; expansion control means 102 which controls the expansion valve 3 in accordance with a required degree of refrigeration; superheat degree control means 104 which controls the flow control valve 11 so that a superheat degree for a temperature equivalent to the suction pressure of the compressor 1 becomes a target value; and change means 105 which changes the target value of the superheat degree.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a refrigeration device, an environment creating device, and a refrigeration method. [Background technology]

[0002] Conventionally, as disclosed in the following Patent Document 1, a refrigeration device equipped with a refrigeration circuit having a bypass flow path for suction injection is known. The bypass flow path is connected to a main circuit of the refrigeration circuit provided with a compressor, a condenser, an expansion valve, and an evaporator, and is a flow path for lowering the temperature and pressure of a part of the high-pressure liquid refrigerant obtained in the condenser, and returning it to the suction port of the compressor while bypassing the expansion valve and the evaporator. The temperature of the discharge pipe of the compressor can be reduced by sucking the refrigerant that has flowed through the bypass flow path into the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 6-4560 Summary of the Invention [Problem to be solved by the invention]

[0004] In a configuration in which a bypass passage is connected to a main circuit, such as the refrigeration system disclosed in Patent Document 1, the compressor discharge pipe temperature can be lowered, making it possible to protect the compressor. On the other hand, if a constant flow rate of refrigerant continues to flow through the bypass passage, a certain flow rate of refrigerant will flow through the bypass passage even when cooling of the compressor is not actually required, and the amount of refrigerant flowing to the evaporator will decrease accordingly, resulting in a decrease in the refrigeration capacity exhibited by the evaporator. Therefore, while the compressor is overprotected, the refrigeration capacity may be sacrificed.

[0005] Therefore, the present invention has been made in consideration of the above-mentioned conventional technology, and an object of the present invention is to provide a refrigeration system that enables adjustment of the refrigeration capacity by the evaporator while stably driving the compressor by suction injection using a bypass flow path. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the refrigeration device of the present invention comprises a main circuit provided with a compressor, a condenser, an expansion valve, and an evaporator, and for circulating a refrigerant, a bypass flow path provided with a flow control valve and branching off from the main circuit between the condenser and the expansion valve, the bypass flow path lowering the temperature of the refrigerant liquefied in the condenser by the flow control valve and allowing the refrigerant to be sucked into the compressor without passing through the evaporator, an expansion control means for controlling the expansion valve in accordance with a degree of refrigeration demand, a superheat control means for controlling the flow control valve so that the superheat degree for a temperature equivalent to the suction pressure of the compressor becomes a target value, and a change means for changing the target value of the superheat degree.

[0007] In the refrigeration device according to the present invention, the expansion valve of the main circuit is adjusted by the expansion control means according to the degree of refrigeration demand, so that the flow rate of the refrigerant flowing through the evaporator is adjusted according to the degree of refrigeration demand. Therefore, the evaporator can exert a refrigeration capacity according to the degree of refrigeration demand. On the other hand, since a part of the refrigerant condensed in the condenser is sucked into the compressor through the bypass flow path without passing through the evaporator, the cooling effect of the compressor (effect of lowering the temperature of the discharge pipe) is obtained, but the refrigeration capacity exerted by the evaporator may decrease. However, since the valve opening degree of the flow control valve provided in the bypass flow path can be adjusted, the flow rate of the refrigerant flowing through the bypass flow path can be adjusted, and the target value of the superheat degree of the refrigerant sucked into the compressor, which is the control target of the flow control valve, can be changed by the changing means. Therefore, the valve opening degree of the flow control valve is adjusted according to the change amount of the target value of the superheat degree, so that the amount of reduction in the flow rate of the refrigerant flowing through the evaporator can be changed. Therefore, it is possible to adjust the refrigeration capacity by the evaporator while stably driving the compressor, and it is possible to suppress an imbalance between the protection of the compressor and the refrigeration capacity.

[0008] The changing means may be configured to change the target value of the degree of superheat depending on the required degree of refrigeration.

[0009] In this embodiment, the target value of the degree of superheat is changed according to the degree of freezing demand, so that the valve opening of the flow control valve can be adjusted according to the degree of freezing demand. That is, while the expansion valve is adjusted to an opening according to the degree of freezing demand, the flow control valve is adjusted so as to obtain a target value of the degree of superheat according to the degree of freezing demand. Therefore, the opening of the expansion valve is adjusted so that a refrigeration capacity according to the degree of freezing demand is exerted, but the refrigerant flow rate of the evaporator obtained by adjusting the expansion valve also changes according to the adjustment of the valve opening of the flow control valve. Therefore, even if the refrigerant flow rate of the evaporator decreases as the refrigerant flows into the bypass flow passage, the amount of decrease in the refrigeration capacity can be adjusted by adjusting the valve opening of the flow control valve.

[0010] The change means may be configured to change the target value of the degree of superheat in accordance with an opening degree of the expansion valve.

[0011] In this embodiment, the target value of the degree of superheat changes according to the opening of the expansion valve, and the valve opening of the flow control valve is adjusted accordingly. That is, the opening of the expansion valve is adjusted to an opening according to the refrigeration demand, but the refrigerant flow rate of the evaporator obtained by adjusting the expansion valve also changes according to the adjustment of the valve opening of the flow control valve. Therefore, even if the refrigerant flow rate of the evaporator decreases as the refrigerant flows into the bypass flow path, the amount of decrease in the refrigeration capacity can be adjusted by adjusting the valve opening of the flow control valve.

[0012] The upper limit value of the target degree of superheat may be set to decrease as the internal temperature, the outlet temperature of the evaporator, the evaporation temperature of the refrigerant, or the temperature at the outlet side of the flow control valve, or the value obtained by subjecting a plurality of these temperatures to a predetermined processing, decreases.

[0013] In this embodiment, the cooling effect of the compressor can be further improved. For example, in the case of a certain degree of freezing demand, when the temperature inside the cabinet is low, the evaporation temperature needs to be lower than when the temperature inside the cabinet is high for the same degree of freezing demand, so the expansion valve tends to be throttled. Therefore, the lower the temperature inside the cabinet, the lower the refrigerant circulation flow rate tends to be, making it difficult to obtain the cooling effect of the compressor. Therefore, by setting the upper limit of the target value of the degree of superheat to be smaller as the temperature inside the cabinet becomes lower, the flow control valve is opened more. This makes it easier to obtain the cooling effect of the compressor even when the expansion valve is throttled. The same applies to the case where the outlet temperature of the evaporator and the evaporation temperature of the refrigerant are low.

[0014] In addition, since the temperature at the outlet side of the flow control valve depends on the suction pressure to the compressor (the low pressure of the refrigeration circuit), this temperature decreases as the opening of the expansion valve decreases. Therefore, if the upper limit of the target value of the superheat degree is set to decrease as the temperature decreases, it is possible to obtain the same effect as decreasing the upper limit of the target value of the superheat degree as the opening of the expansion valve decreases. Therefore, it is possible to easily obtain the cooling effect of the compressor.

[0015] The refrigeration apparatus may further include a bypass temperature detector arranged in the bypass flow path and detecting a temperature of the refrigerant downstream of the flow control valve, and a suction temperature detector arranged in the main circuit and detecting a temperature of the refrigerant suctioned into the compressor. In this case, the degree of superheat may be calculated from a temperature difference between the detected temperature of the suction temperature detector and the detected temperature of the bypass temperature detector.

[0016] The temperature detected by the bypass temperature detector is the saturation temperature equivalent to the suction pressure. Therefore, the degree of superheat of the refrigerant drawn into the compressor is calculated from the temperature difference between the bypass temperature detector, which detects the temperature of the refrigerant drawn into the compressor where the refrigerant from the bypass flow path and the refrigerant that has passed through the evaporator join, and the bypass temperature detector.

[0017] The refrigeration system may further include a hot gas bypass flow path having a hot gas valve and branching off from between the compressor and the condenser in the main circuit, for sucking the refrigerant compressed by the compressor into the compressor without passing through the evaporator, and a hot gas control means for opening the hot gas valve so that the pressure of the refrigerant sucked into the compressor does not fall below a set pressure.

[0018] In this embodiment, the hot gas control means controls the hot gas flow rate control valve so that the suction pressure of the compressor does not fall below the set pressure. That is, when the opening of the expansion valve is reduced, the suction pressure of the compressor falls accordingly, so that if the opening of the expansion valve is reduced very much to reduce the refrigeration capacity as much as possible, the suction pressure of the compressor may fall too much and stable operation may not be possible. Therefore, when the suction pressure is about to fall below the set pressure, hot gas is sucked into the compressor through the hot gas bypass passage, so that the suction pressure does not fall below the set pressure. Therefore, it is possible to minimize the refrigeration capacity while ensuring stable operation of the compressor.

[0019] The hot gas control means may control the hot gas valve in response to the refrigeration demand.

[0020] In this embodiment, when the refrigeration demand is low and the expansion control means controls to throttle the expansion valve, the hot gas control means can control to open the hot gas valve more. Therefore, when the refrigeration demand is low, the refrigeration capacity can be reduced as much as possible, while the suction pressure can be prevented from falling below the set pressure by sucking hot gas into the compressor through the hot gas bypass passage. Therefore, it is possible to reduce the refrigeration capacity as much as possible while ensuring stable operation of the compressor.

[0021] The environment creating device according to the present invention includes an environment chamber and the refrigeration device for cooling the inside of the environment chamber.

[0022] In the environment creating device according to the present invention, when the target value of the degree of superheat is lowered in the refrigeration device, the opening of the flow control valve is controlled to be larger, so that the flow rate of the refrigerant flowing into the evaporator can be further reduced. Therefore, the refrigeration capacity exerted by the evaporator can be reduced compared to when the target value of the degree of superheat is fixed.

[0023] The refrigeration method of the present invention is a refrigeration method using a refrigeration device including a main circuit provided with a compressor, a condenser, an expansion valve, and an evaporator, and for circulating a refrigerant, and a bypass flow path provided with a flow control valve and branching off from the main circuit between the condenser and the expansion valve, in which the refrigerant liquefied in the condenser is cooled to a low temperature by the flow control valve and is sucked into the compressor without passing through the evaporator, wherein a reception unit receives a degree of refrigeration request and controls the expansion valve in accordance with the degree of refrigeration request received by the reception unit, changes a target value of the degree of superheat for a temperature equivalent to the suction pressure of the compressor in accordance with the degree of refrigeration request or an opening degree of the expansion valve, and controls the flow control valve so that the degree of superheat becomes the changed target value.

[0024] If the refrigeration apparatus further includes a bypass temperature detector arranged in the bypass flow path and detecting a temperature of the refrigerant downstream of the flow control valve, and a suction temperature detector arranged in the main circuit and detecting a temperature of the refrigerant suctioned into the compressor, the refrigeration method may include determining the degree of superheat from a temperature difference between the suction temperature detector and the bypass temperature detector.

[0025] In the case where the refrigeration apparatus is provided with a hot gas valve and further includes a hot gas bypass flow path that branches off from between the compressor and the condenser in the main circuit and causes the refrigerant compressed by the compressor to be sucked into the compressor without passing through the evaporator, the refrigeration method may also open the hot gas valve so that the pressure of the refrigerant sucked into the compressor does not become equal to or lower than a set pressure. Effect of the Invention

[0026] As described above, according to the present invention, it is possible to stably drive the compressor by suction injection using a bypass flow path, while adjusting the refrigeration capacity by the evaporator. [Brief description of the drawings]

[0027] [Figure 1] 1 is a diagram illustrating a schematic configuration of a refrigeration device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a control device including a controller of the refrigeration apparatus. [Diagram 3] FIG. 4 is a diagram for explaining the relationship between the inside temperature and the target value of the degree of superheat. [Figure 4] FIG. 4 is a diagram for explaining a control flow of the refrigeration device. [Diagram 5] FIG. 4 is a diagram illustrating a schematic configuration of a refrigeration device according to a modified example of the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating a schematic configuration of a refrigeration device according to a second embodiment. [Figure 7] FIG. 10 is a diagram illustrating a schematic configuration of a refrigeration device according to a modified example of the second embodiment. [Figure 8] FIG. 2 is a diagram illustrating a control device including a controller of the refrigeration apparatus. [Figure 9] FIG. 13 is a diagram illustrating an environment forming device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0029] (First embodiment) As shown in Fig. 1, a refrigeration device 10 according to the first embodiment includes a main circuit 15 in which a refrigerant is sealed, and a bypass passage 16 connected to the main circuit 15. The refrigerant may be a low GWP refrigerant such as R449A or R448A.

[0030] The main circuit 15 is provided with a compressor 1, a condenser 2, an expansion valve 3, and an evaporator 4 in this order. When the compressor 1 operates, a refrigerant circulates in the main circuit 15, thereby performing a vapor compression refrigeration cycle. The refrigeration device 10 may be used to cool the air inside a freezer or a refrigerator, or may be used to generate cooling water in a chiller. Alternatively, the refrigeration device 10 may be used in an environment forming device such as an environmental testing device for providing a temperature environment at a predetermined temperature. In this embodiment, the refrigeration device 10 is used in a freezer.

[0031] The compressor 1 is responsible for the compression process of the refrigeration cycle, and is configured to suck in and compress the refrigerant. The compressor 1 is equipped with a compression mechanism, such as a scroll type or a screw type, and is configured to drive the compression mechanism by a motor with a constant rotation speed. The compressor 1 may be configured so that the rotation speed of the motor can be adjusted by an inverter. The compressor 1 may also be configured so that two compressors 1 with the same capacity or different capacities are connected in parallel.

[0032] The condenser 2 is responsible for the condensation process of the refrigeration cycle, and is configured to exchange heat between the refrigerant discharged from the compressor 1 and a cooling medium such as air, water, or a refrigerant, thereby condensing the refrigerant.

[0033] The expansion valve 3 is responsible for the expansion process of the refrigeration cycle, and is configured to expand the liquid refrigerant condensed in the condenser 2.

[0034] The expansion valve 3 is, for example, an electronic expansion valve. Therefore, by adjusting the valve opening degree, the flow rate of the liquid refrigerant flowing through the evaporator 4 in the main circuit 15 can be changed arbitrarily.

[0035] The evaporator 4 is responsible for the evaporation process of the refrigeration cycle, and is configured to evaporate the liquid refrigerant by exchanging heat with air, the liquid refrigerant being made low pressure in the expansion valve 3. The evaporator 4 cools the air supplied to the inside of the freezer.

[0036] The bypass flow path 16 branches off from the main circuit 15 downstream of the condenser 2. That is, one end of the bypass flow path 16 is connected to the main circuit 15 between the condenser 2 and the expansion valve 3. The other end of the bypass flow path 16 is connected to the main circuit 15 between the evaporator 4 and the compressor 1. Therefore, the refrigerant that has flowed through the bypass flow path 16 merges with the refrigerant evaporated in the evaporator 4, and is then sucked into the compressor 1.

[0037] A flow rate control valve 11 is disposed in the bypass flow path 16. The flow rate control valve 11 is configured by an electronic expansion valve. Therefore, by adjusting the opening degree of the flow rate control valve 11, the flow rate of the refrigerant flowing through the bypass flow path 16 is adjusted.

[0038] A bypass temperature detector 21 that detects the temperature of the refrigerant flowing through the bypass flow path 16 is provided in the bypass flow path 16 downstream of the flow rate regulating valve 11. The bypass temperature detector 21 outputs a signal indicative of the detected temperature.

[0039] The main circuit 15 is provided with a suction temperature detector 22 that detects the temperature of the refrigerant suctioned into the compressor 1. The suction temperature detector 22 outputs a signal indicating the detected temperature.

[0040] The signals output from the detectors 21, 22 are input to the controller 100. The controller 100 is composed of a microcomputer having a CPU for executing arithmetic processing, a ROM for storing processing programs and data, and a RAM for temporarily storing data. By executing the processing programs stored in the controller 100, the controller 100 can function as a reception unit 101, an expansion control means 102, a superheat degree calculation unit 103, a superheat degree control means 104, and a change means 105, as shown in FIG. 2.

[0041] The reception unit 101 is configured to repeatedly receive the degree of freezing requirement at predetermined time intervals and temporarily store the received degree of freezing requirement. The degree of freezing requirement is generated by a generator 120, and the degree of freezing requirement generated by the generator 120 is input to the reception unit 101. Note that, although the illustrated example shows an example in which the generator 120 is configured separately from the controller 100, the generator 120 of the degree of freezing requirement may be one function of the controller 100.

[0042] Generator 120 repeatedly receives signals from, for example, sensor 121 that detects the inside temperature and input device 122 that inputs the set value of the inside temperature at predetermined time intervals, and calculates the degree of required freezing each time. The degree of required freezing indicates the refrigeration load inside the freezer as a dimensionless numerical value, and is calculated, for example, from the difference between the detected value of the inside temperature and the set value. For this reason, the greater the difference between the detected value of the inside temperature and the set value of the inside temperature, the greater the degree of required freezing. Since the degree of required freezing can change from moment to moment, generator 120 outputs the degree of required freezing at predetermined time intervals.

[0043] The expansion control means 102 is configured to adjust the opening degree of the expansion valve 3 according to the received degree of freezing demand every time the receiving unit 101 receives the degree of freezing demand. That is, the expansion control means 102 controls the expansion valve 3 so that the higher the degree of freezing demand, the larger the opening degree of the expansion valve 3, and controls the expansion valve 3 so that the lower the degree of freezing demand, the smaller the opening degree of the expansion valve 3. This makes it possible to adjust the flow rate of the refrigerant flowing through the evaporator 4 to a flow rate according to the degree of freezing demand, thereby making it possible to obtain a refrigeration capacity according to the degree of freezing demand.

[0044] The superheat degree calculation unit 103 is configured to derive the difference value between the temperature detected by the suction temperature detector 22 and the temperature detected by the bypass temperature detector 21 as the superheat degree of the refrigerant drawn into the compressor 1. That is, in the bypass flow passage 16, the liquid refrigerant decompressed by the flow rate control valve 11 is in a saturated state or a state close to it. This liquid refrigerant is mixed with the gas refrigerant evaporated in the evaporator 4, whereby its temperature increases and it is drawn into the compressor 1. For this reason, the temperature difference between the temperature of the gas refrigerant drawn into the compressor 1 and the temperature of the liquid refrigerant downstream of the flow rate control valve 11 in the bypass flow passage 16 corresponds to the superheat degree of the refrigerant drawn into the compressor 1.

[0045] The degree of superheat of the refrigerant sucked into the compressor 1 can also be calculated by other methods. For example, a pressure detector that detects the pressure of the refrigerant sucked into the compressor 1 can be provided, and the degree of superheat can be calculated using a saturated vapor temperature corresponding to this detected pressure and a temperature detected by the suction temperature detector 22.

[0046] The superheat control means 104 is configured to control the flow rate regulating valve 11 so that the degree of superheat of the gas refrigerant derived by the superheat degree calculation unit 103 becomes a target value. That is, when the opening degree of the flow rate regulating valve 11 is reduced, the flow rate of the refrigerant flowing through the bypass flow path 16 decreases, so that the ratio of the flow rate of the refrigerant flowing through the bypass flow path 16 to the flow rate of the refrigerant passing through the evaporator 4 decreases, and the degree of superheat of the refrigerant increases. On the other hand, when the opening degree of the flow rate regulating valve 11 is increased, the flow rate of the refrigerant flowing through the bypass flow path 16 increases, so that the ratio of the flow rate of the refrigerant flowing through the bypass flow path 16 to the flow rate of the refrigerant passing through the evaporator 4 increases, and the degree of superheat of the refrigerant decreases. Therefore, by adjusting the opening degree of the flow rate regulating valve 11, the degree of superheat of the gas refrigerant can be brought closer to the target value.

[0047] The change means 105 is configured to change the target value of the degree of superheat of the refrigerant sucked into the compressor 1 in accordance with the degree of required freezing received by the reception unit 101. The change means 105 sets the target superheat value to a first value when the received degree of required freezing is a first degree of required freezing, and sets the target superheat value to a second value lower than the first value when the received degree of required freezing is a second degree of required freezing that is lower than the first degree of required freezing.

[0048] As shown in Fig. 3, an upper limit and a lower limit are set for the target superheat degree value, and the target superheat degree value takes a value between the upper limit and the lower limit depending on the required refrigeration degree. The target superheat degree value is set to be higher as the required refrigeration degree increases and to be lower as the required refrigeration degree decreases. When the required refrigeration degree is expressed as a value between 0% and 100%, the target superheat degree value is set to the upper limit when the required refrigeration degree is 100%, and is set to the lower limit when the required refrigeration degree is 0%.

[0049] The upper limit of the target superheat degree includes, but is not limited to, a region in which the upper limit varies depending on the temperature inside the freezer (or refrigerator) (internal temperature) and a region in which the upper limit is constant regardless of the internal temperature. The upper limit of the target superheat degree may be set to a higher value as the internal temperature increases over the entire range of possible internal temperatures, or the upper limit of the target superheat degree may be set to the same value over the entire range of possible internal temperatures. When the refrigeration device 10 is configured as a chiller, the "internal temperature" may be interpreted as the temperature of the cooling liquid introduced into the evaporator 4.

[0050] The lower limit of the target superheat degree is constant over the entire range of possible internal temperatures, but may be set to include a region in which the lower limit of the target superheat degree becomes higher as the internal temperature increases. Also, the lower limit of the target superheat degree may be set to become higher over the entire range of possible internal temperatures as the internal temperature increases.

[0051] Here, a refrigeration method using the refrigeration device 10 having the above-mentioned configuration will be described.

[0052] When the target temperature for the inside temperature is set and the operation of the refrigeration device 10 is started, the controller 100 receives the degree of required refrigeration generated by the generator 120 (step ST11), as shown in Fig. 4. The controller 100 also receives the suction temperature, which is a value detected by the suction temperature detector 22, and the bypass temperature, which is a value detected by the bypass temperature detector 21 (step ST12). The degree of required refrigeration, suction temperature, and bypass temperature are repeatedly received by the controller 100 at predetermined time intervals.

[0053] The superheat degree calculation unit 103 of the controller 100 calculates the superheat degree of the refrigerant sucked into the compressor 1 using the suction temperature (the value detected by the suction temperature detector 22) and the bypass temperature (the value detected by the bypass temperature detector 21) (step ST13).

[0054] The expansion control means 102 of the controller 100 adjusts the opening degree of the expansion valve 3 based on the received degree of freezing demand (step ST14). The degree of freezing demand changes from moment to moment, and the generator 120 outputs the degree of freezing demand at predetermined time intervals. For this reason, the expansion control means 102 adjusts the opening degree of the expansion valve 3 every time it receives the degree of freezing demand. In this case, the expansion control means 102 controls the expansion valve 3 so that the higher the degree of freezing demand, the larger the opening degree of the expansion valve 3 becomes, and the lower the degree of freezing demand, the smaller the opening degree of the expansion valve 3 becomes. As a result, a flow rate of refrigerant according to the degree of freezing demand flows through the evaporator 4, and the evaporator 4 exhibits a refrigeration capacity according to the degree of freezing demand.

[0055] The degree of freezing requirement is also used to set a target value of the degree of superheat of the refrigerant drawn into the compressor 1. That is, the change means 105 changes the target value of the degree of superheat of the refrigerant drawn into the compressor 1 in accordance with the degree of freezing requirement received by the reception unit 101 (step ST15). At this time, the target value of superheat is changed so that the higher the degree of freezing requirement, the higher the target value of superheat, and the lower the degree of freezing requirement, the lower the target value of superheat.

[0056] The superheat degree control means 104 controls the flow rate adjustment valve 11 so that the superheat degree becomes the changed target value (step ST16). Specifically, when the refrigeration demand is high, the superheat degree target value is changed to be higher than the current value, so that the superheat degree control means 104 controls the flow rate adjustment valve 11 so that the opening degree of the flow rate adjustment valve 11 becomes smaller. That is, when the refrigeration demand is high, the flow rate adjustment valve 11 is narrowed. This reduces the flow rate of the refrigerant flowing through the bypass flow passage 16. Accordingly, the flow rate of the refrigerant flowing into the evaporator 4 can be increased. That is, although the opening degree of the expansion valve 3 is set to a value according to the refrigeration demand by the expansion control means 102, the flow rate of the refrigerant flowing through the evaporator 4 can be increased as the flow rate adjustment valve 11 is narrowed. Therefore, the refrigeration capacity exhibited by the evaporator 4 can be increased compared to when the target value of the superheat degree is fixed.

[0057] On the other hand, when the refrigeration demand is low, the superheat degree target value is changed to be lower than the current value. As a result, the superheat degree control means 104 controls the flow rate control valve 11 so that the valve opening degree of the flow rate control valve 11 is increased. That is, when the refrigeration demand is low, the opening degree of the expansion valve 3 is narrowed and the circulation flow rate of the main circuit 15 is small, so that it is difficult to obtain the cooling effect of the compressor 1. Therefore, by increasing the valve opening degree of the flow rate control valve 11 and increasing the flow rate of the refrigerant flowing through the bypass flow path 16, the flow rate of the refrigerant sucked into the compressor 1 can be increased, and the cooling effect of the compressor 1 can be improved. On the other hand, with the increase in the refrigerant flow rate through the bypass flow path 16, the flow rate of the refrigerant flowing into the evaporator 4 is further reduced under the opening degree of the expansion valve 3 controlled by the expansion control means 102. Therefore, the refrigeration capacity exhibited by the evaporator 4 can be further reduced compared to when the target value of the superheat degree is fixed.

[0058] As described above, in this embodiment, the expansion valve 3 is adjusted by the expansion control means 102 according to the degree of refrigeration demand, so that the flow rate of the refrigerant flowing through the evaporator 4 is adjusted according to the degree of refrigeration demand. Therefore, the evaporator 4 can exert a refrigeration capacity according to the degree of refrigeration demand. On the other hand, since a part of the refrigerant condensed in the condenser 2 is sucked into the compressor 1 through the bypass passage 16 without passing through the evaporator 4, the cooling effect of the compressor 1 (effect of lowering the temperature of the discharge pipe) can be obtained, but the refrigeration capacity exerted by the evaporator 4 may decrease. However, since the target value of the superheat degree of the refrigerant sucked into the compressor 1, which is the control target of the flow rate regulating valve 11 of the bypass passage 16, can be changed by the changing means 105, it is possible to adjust the flow rate of the refrigerant flowing through the bypass passage 16. Moreover, the target value of the superheat degree of the refrigerant sucked into the compressor 1, which is the control target of the flow rate regulating valve 11, can be changed by the changing means. Therefore, the valve opening degree of the flow rate regulating valve 11 is adjusted according to the change amount of the target value of the superheat degree, so that the amount of reduction in the flow rate of the refrigerant flowing through the evaporator 4 can be changed. Therefore, it is possible to adjust the refrigeration capacity by the evaporator 4 while adjusting the discharge pipe temperature of the compressor 1, and it is possible to suppress an imbalance between protection of the compressor 1 and the refrigeration capacity.

[0059] Moreover, since the target value of the degree of superheat is changed according to the degree of refrigeration demand, the valve opening of the flow control valve 11 can be adjusted according to the degree of refrigeration demand. That is, while the expansion valve 3 is adjusted to an opening according to the degree of refrigeration demand, the flow control valve 11 is adjusted so as to obtain a target value of the degree of superheat according to the degree of refrigeration demand. Therefore, the opening of the expansion valve 3 is adjusted so as to exert a refrigeration capacity according to the degree of refrigeration demand, but the refrigerant flow rate of the evaporator 4 obtained by adjusting the expansion valve 3 also changes according to the adjustment of the valve opening of the flow control valve 11. Therefore, even if the refrigerant flow rate of the evaporator 4 decreases as the refrigerant flows into the bypass flow passage 16, the amount of decrease in the refrigeration capacity can be adjusted by adjusting the valve opening of the flow control valve 11.

[0060] In addition, in this embodiment, the change means 105 lowers the target value of the superheat degree when the refrigeration requirement is low. That is, when the refrigeration requirement is low, the target value of the superheat degree is lowered and the valve opening of the flow control valve 11 is increased, so that the flow rate of the refrigerant flowing through the bypass flow passage 16 (suction injection flow rate) is increased compared to when the superheat requirement is fixed. On the other hand, when the refrigeration requirement is low, the opening of the expansion valve 3 is reduced to reduce the refrigeration capacity exerted by the evaporator 4, so that the flow rate of the refrigerant circulating through the main circuit 15 is reduced. Therefore, as the refrigerant circulation flow rate decreases, it tends to be difficult to obtain the cooling effect of the compressor 1, but since the suction injection flow rate increases, it is possible to avoid a situation in which it is difficult to obtain the cooling effect of the compressor 1. Note that the target value of the superheat degree is not adjusted based on the discharge pipe temperature of the compressor 1, so the opening of the flow control valve 11 is adjusted regardless of whether the discharge pipe temperature increases. Therefore, the refrigeration capacity of the evaporator 4 can be more appropriately adjusted according to the refrigeration requirement.

[0061] Moreover, as the valve opening degree of the flow control valve 11 becomes larger, the refrigerant flow rate flowing through the bypass passage 16 increases, so that the refrigerant flow rate of the evaporator 4 can be further reduced at the opening degree of the expansion valve 3 set to a value according to the refrigeration requirement degree by the expansion control means 102. This makes it possible to further reduce the refrigeration capacity of the evaporator 4. Therefore, compared with the case where the target value of the superheat degree is fixed, the refrigeration capacity of the evaporator 4, which is adjusted according to the refrigeration requirement degree, can be further reduced. This makes it possible to prevent a situation in which the refrigeration capacity becomes excessive when a state in which the refrigeration requirement degree is low continues.

[0062] In addition, in this embodiment, in a region where the inside temperature is low, the upper limit of the target value of the degree of superheat is set to be smaller as the inside temperature decreases, so that the cooling effect of the compressor 1 can be further improved. For example, in the case of a certain degree of freezing requirement, when the inside temperature is low, the evaporation temperature needs to be lower than when the inside temperature is high for the same degree of freezing requirement, so the expansion valve 3 tends to be throttled. Therefore, the lower the inside temperature is, the lower the refrigerant circulation flow rate tends to be, so that it becomes difficult to obtain the cooling effect of the compressor 1. Therefore, by setting the upper limit of the target value of the degree of superheat to be smaller as the inside temperature decreases, the flow rate control valve is opened more. As a result, even when the expansion valve 3 is in a throttled state, the cooling effect of the compressor 1 can be easily obtained.

[0063] In this embodiment, the change means 105 changes the target value of the degree of superheat for the temperature equivalent to the suction pressure of the compressor 1 according to the refrigeration demand. Alternatively, the target value of the degree of superheat may be changed according to the opening of the expansion valve 3. In this case, the target value of the degree of superheat changes according to the opening of the expansion valve 3, and the valve opening of the flow control valve 11 is adjusted accordingly. That is, since the opening of the expansion valve 3 is adjusted to an opening according to the refrigeration demand, the target value of the degree of superheat is changed according to the opening of the expansion valve 3, and the valve opening of the flow control valve 11 is adjusted to an opening according to the refrigeration demand. In this case, the change means 105 lowers the target value of the degree of superheat when the opening of the expansion valve 3 is small. That is, when the opening of the expansion valve 3 is small, the suction pressure to the compressor 1 decreases, and the discharge pipe temperature of the compressor 1 is likely to increase accordingly. In this case, since the target value of the superheat degree is lowered by the changing means 105, the superheat degree control means 104 controls the flow rate control valve 11 so as to increase the valve opening degree of the flow rate control valve 11. Therefore, the flow rate (suction injection flow rate) of the refrigerant flowing through the bypass flow path 16 increases, so that the rise in the discharge pipe temperature can be suppressed.

[0064] In the above embodiment, the upper limit of the target superheat degree changes according to the inside temperature, but the present invention is not limited to this. For example, a region may be provided in which the upper limit of the target superheat degree decreases as the outlet temperature of the evaporator 4 or the evaporation temperature of the refrigerant decreases instead of the inside temperature. Also, the upper limit of the target superheat degree may be set to decrease as the outlet temperature of the evaporator 4 or the evaporation temperature of the refrigerant decreases over the entire range of these temperatures. Even in these cases, the cooling effect of the compressor 1 can be easily obtained.

[0065] Also, the upper limit of the target superheat degree may be set to decrease as the temperature detected by the bypass temperature detector 21 (i.e., the temperature at the outlet side of the flow rate control valve 11) decreases instead of the internal temperature. That is, since the temperature detected by the bypass temperature detector 21 depends on the suction pressure to the compressor 1 (low pressure in the main circuit 15), the temperature detected by the bypass temperature detector 21 decreases as the opening of the expansion valve 3 decreases. Therefore, if the upper limit of the target superheat degree is set to decrease as the temperature detected by the bypass temperature detector 21 decreases, it is possible to obtain the same effect as that of decreasing the upper limit of the target superheat degree as the opening of the expansion valve 3 decreases. Therefore, it is possible to easily obtain the cooling effect of the compressor 1.

[0066] In addition, by referring to multiple temperatures among the internal temperature, the outlet temperature of the evaporator 4, the evaporation temperature of the refrigerant, and the detected temperature of the bypass temperature detector 21, and subjecting these multiple temperatures to a predetermined processing (e.g., averaging processing), the upper limit of the target superheat degree may be set to be smaller when the value obtained as a result becomes low.

[0067] In addition, in this embodiment, the superheat degree calculation unit 103 derives the difference value between the temperature detected by the suction temperature detector 22 and the temperature detected by the bypass temperature detector 21 as the superheat degree of the refrigerant sucked into the compressor 1, but is not limited to this. For example, as shown in Fig. 5, the bypass temperature detector 21 may be omitted, and a pressure detector 31 that detects the pressure of the refrigerant sucked into the compressor 1 may be provided. Then, the superheat degree calculation unit 103 may derive the difference value between the temperature detected by the suction temperature detector 22 and the saturated vapor temperature corresponding to the pressure detected by the pressure detector 31 as the superheat degree of the suction refrigerant.

[0068] Second embodiment As shown in Fig. 6, the refrigeration device 10 according to the second embodiment includes a hot gas bypass passage 17. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0069] The hot gas bypass flow path 17 is a flow path for sucking a part of the refrigerant discharged from the compressor 1 into the compressor 1 without passing through the condenser 2, the expansion valve 3, and the evaporator 4. One end of the hot gas bypass flow path 17 is connected to a portion between the compressor 1 and the condenser 2 in the main circuit 15, and the other end is connected to a portion between the evaporator 4 and the compressor 1 in the main circuit 15.

[0070] The hot gas bypass passage 17 is provided with the hot gas valve 12, which is a mechanical expansion valve. For this reason, the hot gas valve 12 is always open with a predetermined opening degree set. However, this is not limited to this, and the hot gas valve 12 may be controlled to open and close by the controller 100 as shown in Figs. 7 and 8. That is, the hot gas valve 12 may be controlled to open when the suction pressure of the compressor 1 may be equal to or lower than the set pressure, such as when the expansion valve 3 is closed (or the opening degree becomes very small), and closed otherwise. This set pressure may be a pressure determined from the design conditions of the compressor 1, which are set as a range in which the compressor 1 can stably operate.

[0071] In this embodiment, the hot gas control means 106 of the controller 100 controls the hot gas valve 12 so that the suction pressure of the compressor 1 does not fall below the set pressure. That is, when the opening of the expansion valve 3 is reduced, the suction pressure of the compressor 1 falls accordingly, so that if the opening of the expansion valve 3 is closed (or made very small) to reduce the refrigeration capacity as much as possible, the suction pressure of the compressor 1 may fall too much and stable operation may not be possible. Therefore, when the suction pressure is about to fall below the set pressure, the hot gas control means 106 opens the hot gas valve 12. As a result, hot gas is sucked into the compressor 1 through the hot gas bypass passage 17, so that the suction pressure can be prevented from falling below the set pressure. Therefore, it is possible to minimize the refrigeration capacity of the evaporator 4 while ensuring stable operation of the compressor 1.

[0072] When the hot gas valve 12 opens, the degree of superheat of the refrigerant drawn into the compressor 1 increases, but in response to this, the superheat control means 104 increases the valve opening degree of the flow control valve 11 so that the degree of superheat approaches the target value. Therefore, even if the hot gas valve 12 opens, the degree of superheat of the drawn refrigerant does not become excessively high.

[0073] The hot gas valve 12 may be an electronic expansion valve. In this case, the hot gas control means 106 is configured to control the opening of the hot gas valve 12. For example, the hot gas control means 106 may control the opening of the hot gas valve 12 in conjunction with the opening control of the expansion valve 3 by the expansion control means 102 or in response to the refrigeration demand. In this case, the hot gas control means 106 controls the hot gas valve 12 to open at least when the expansion valve 3 is closed. This makes it possible to minimize the refrigeration capacity of the evaporator 4. Furthermore, when the hot gas valve 12 is controlled in response to the refrigeration demand, the hot gas valve 12 is controlled so that the opening of the hot gas valve 12 becomes larger as the refrigeration demand decreases, thereby making it possible to ensure the suction pressure of the compressor 1. Furthermore, when a pressure sensor 31 is provided to detect the pressure of the refrigerant sucked into the compressor 1, it is also possible to control the hot gas valve 12 so that the suction pressure of the compressor 1 does not fall below a predetermined pressure.

[0074] It should be noted that the description of the other configurations, operations, and effects will not be repeated, but the description of the first embodiment can be applied to the second embodiment.

[0075] Third embodiment 9 shows the third embodiment. Note that the same components as those in the first or second embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0076] The third embodiment is an example in which the refrigeration apparatus 10 is applied to an environment creating apparatus 50 such as an environmental testing apparatus. The refrigeration apparatus 10 may be the refrigeration apparatus of either the first embodiment or the second embodiment.

[0077] The environment forming device 50 has an environment chamber 51 and adjusts the inside of the environment chamber 51 to a predetermined temperature environment. The environment forming device 50 further includes an air conditioning chamber 52 for generating air with an adjusted temperature, and the evaporator 4 of the refrigeration device 10 is disposed in the air conditioning chamber 52.

[0078] In the air-conditioning chamber 52, a heater 54 for heating air and a blower 55 for blowing the temperature-adjusted air into the environmental chamber 51 are disposed downstream of the evaporator 4. In the environmental chamber 51, a sensor 121 for detecting the indoor temperature is disposed. An input device 122 is used to input the set temperature of the temperature in the environmental chamber 51. In this embodiment, the "interior temperature" in the first and second embodiments is read as "indoor temperature". In other words, the sensor 121 detects the air temperature of the room to which the air cooled by the evaporator 4 is supplied.

[0079] The generator 120 calculates the required degree of refrigeration using the temperature detected by the sensor 121 and the set temperature from the input unit 122 .

[0080] The heater 54 is output-controlled based on the temperature detected by the sensor 121 and the set temperature from the input device 122. That is, a predetermined refrigeration capacity is exerted by controlling the expansion valve 3 of the refrigeration device 10 based on the refrigeration demand degree, but since the temperature detected by the sensor 121 may fall below the set temperature, the heater 54 finely adjusts the room temperature. Therefore, if excessive cooling by the refrigeration device 10 can be suppressed, not only the power of the refrigeration device 10 but also the power of the heater 54 can be suppressed. In this regard, when the refrigeration demand degree is small, the change means 105 lowers the target value of the superheat degree, so that the flow rate control valve 11 is controlled accordingly so that the opening degree of the flow rate control valve 11 becomes larger. Accordingly, the flow rate of the refrigerant flowing into the evaporator 4 can be further reduced under the opening degree of the expansion valve 3 controlled by the expansion control means 102. Therefore, compared to the case where the target value of the superheat degree is fixed, the refrigeration capacity exerted by the evaporator 4 can be reduced, and the power of the heater 54 can be suppressed, thereby achieving further energy saving. It is possible to omit the heater 54.

[0081] In addition, the upper limit of the target value of the degree of superheat is set to decrease as the indoor temperature decreases. Therefore, when the refrigeration requirement is 100%, the lower the indoor temperature, the more the expansion valve 3 tends to be throttled and the more the flow control valve 11 is opened, so that the flow rate of the refrigerant flowing to the evaporator 4 decreases. Therefore, the cooling capacity of the evaporator 4 can be further reduced and the output of the heater 54 can be suppressed, so that the energy saving of the environment creating device 50 can be achieved.

[0082] It should be noted that the description of the other configurations, operations, and effects will be omitted, but the description of the first or second embodiment can be applied to the third embodiment.

[0083] (Other embodiments) It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0084] 1: Compressor 2: Condenser 3: Expansion valve 4: Evaporator 10: Refrigeration equipment 11: Flow control valve 12: Hot gas valve 15: Main circuit 16: Bypass flow path 17: Hot gas bypass passage 21: Bypass temperature detector 22: Intake temperature detector 101: Reception 102: Expansion control means 104:Superheat degree control means 105: Change method 106: Hot gas control means

Claims

1. a main circuit provided with a compressor, a condenser, an expansion valve, and an evaporator, and circulating a refrigerant; a bypass flow path provided with a flow rate control valve and branching off from the main circuit between the condenser and the expansion valve, the bypass flow path lowering the temperature of the refrigerant liquefied in the condenser by the flow rate control valve and allowing the refrigerant to be sucked into the compressor without passing through the evaporator; an expansion control means for controlling the expansion valve in accordance with a degree of refrigeration demand; a superheat degree control means for controlling the flow rate regulating valve so that the superheat degree for a temperature equivalent to a suction pressure of the compressor becomes a target value; A change means for changing the target value of the degree of superheat; A refrigeration device comprising:

2. 2. The refrigeration apparatus according to claim 1, wherein the change means is configured to change the target value of the degree of superheat in accordance with the required degree of refrigeration.

3. 2. The refrigeration system according to claim 1, wherein the change means is configured to change the target value of the degree of superheat in accordance with an opening degree of the expansion valve.

4. 2. The refrigeration device according to claim 1, wherein an upper limit value of the target value of the degree of superheat is set to become smaller as a value obtained by performing a predetermined process on an internal temperature, an outlet temperature of the evaporator, an evaporation temperature of the refrigerant, or a temperature at the outlet side of the flow control valve, or a plurality of these temperatures, becomes lower.

5. a bypass temperature detector disposed in the bypass flow path and detecting a temperature of the refrigerant downstream of the flow rate regulating valve; a suction temperature detector disposed in the main circuit and detecting a temperature of the refrigerant suctioned into the compressor; Further equipped with 5. The refrigeration apparatus according to claim 1, wherein the degree of superheat is determined from a temperature difference between the temperature detected by the suction temperature detector and the temperature detected by the bypass temperature detector.

6. a hot gas bypass flow path provided with a hot gas valve, branching off from between the compressor and the condenser in the main circuit, for sucking the refrigerant compressed by the compressor into the compressor without passing through the evaporator; hot gas control means for opening the hot gas valve so that the pressure of the refrigerant sucked into the compressor does not become equal to or lower than a set pressure; The refrigeration apparatus according to any one of claims 1 to 4, further comprising:

7. 7. The refrigeration system according to claim 6, wherein said hot gas control means controls said hot gas valve in response to said degree of refrigeration demand.

8. An environmental chamber; A refrigeration device according to any one of claims 1 to 4 for cooling the inside of the environmental chamber; An environment forming device comprising:

9. a main circuit provided with a compressor, a condenser, an expansion valve, and an evaporator, and circulating a refrigerant; a bypass flow path provided with a flow rate control valve and branching off from the main circuit between the condenser and the expansion valve, the bypass flow path lowering the temperature of the refrigerant liquefied in the condenser by the flow rate control valve and allowing the refrigerant to be sucked into the compressor without passing through the evaporator; A refrigeration method using a refrigeration device comprising: The reception department receives the freezing request level, controlling the expansion valve in response to the refrigeration requirement received by the reception unit; A target value of a degree of superheat for a temperature equivalent to a suction pressure of the compressor is changed in accordance with the refrigeration demand degree or the opening degree of the expansion valve; A refrigeration method comprising controlling the flow control valve so that the degree of superheat becomes the changed target value.

10. The refrigeration device comprises: a bypass temperature detector disposed in the bypass flow path and detecting a temperature of the refrigerant downstream of the flow rate regulating valve; a suction temperature detector disposed in the main circuit and detecting a temperature of the refrigerant suctioned into the compressor; It also has 10. The refrigeration method according to claim 9, wherein the degree of superheat is determined from a temperature difference between the suction temperature detector and the bypass temperature detector.

11. The refrigeration device comprises: a hot gas bypass flow path provided with a hot gas valve, branching off from between the compressor and the condenser in the main circuit and allowing the refrigerant compressed by the compressor to be drawn into the compressor without passing through the evaporator; 11. The refrigeration method according to claim 9, wherein the hot gas valve is opened so that the pressure of the refrigerant sucked into the compressor does not become equal to or lower than a set pressure.

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