Freezer and freezing method

Abstract

To achieve energy saving while enabling injection of a refrigerant into a middle portion of a compression process in a compressor.SOLUTION: A freezer 10 includes: a first injection flow passage 16 which is branched from a main circuit 15, and which injects a refrigerant in a middle portion of a compression process of a compressor 1 via a subcooler 12; a first injection adjusting valve 11 which is positioned further on an upstream side than the subcooler 12 in the first injection flow passage 16; first valve control means 104 for controlling the first injection adjusting valve 11 in such a manner that an overheat degree of an injection refrigerant by the first injection flow passage 16 becomes a target overheat degree; a reception part 101 for receiving a freezing request degree; and target overheat degree control means 102 which defines the target overheat degree as a first value in the case where the freezing request degree received by the reception part 101 is the first freezing request degree, and which defines the target overheat degree as a second value higher than the first value in the case where the received freezing request degree is a second freezing request degree lower than the first freezing request degree.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a refrigeration apparatus and a refrigeration method. [Background technology]

[0002] Conventionally, as disclosed in the following Patent Document 1, a refrigeration device is known in which a flow path is provided to inject a gas refrigerant into the intermediate pressure of a compressor provided in a refrigeration circuit. Specifically, the refrigeration device includes a main circuit in which a compressor, a condenser, an economizer heat exchanger, an expansion valve, and an evaporator are provided in this order to circulate the refrigerant, and an intermediate injection circuit connected to the main circuit. The intermediate injection circuit reduces the pressure of the liquid refrigerant condensed in the condenser with a second expansion valve, and then passes the liquid refrigerant through an economizer heat exchanger in the main circuit to vaporize the liquid refrigerant before injecting it into the intermediate pressure of the compressor. The second expansion valve provided in the intermediate injection circuit is controlled so that the superheat degree of the gas refrigerant discharged from the compressor is a predetermined superheat degree. This causes the refrigerant injected into the compressor through the intermediate injection circuit to be saturated, preventing damage to the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-60179 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the refrigeration device described in the above Patent Document 1, it is possible to control the discharge pipe temperature by injecting gas into the intermediate pressure of the compressor. However, from the viewpoint of energy saving, there is still room for improvement. That is, the power of the compressor increases by injecting the gas refrigerant into the compressor, so there is still room for improvement from the viewpoint of energy saving.

[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 achieve energy savings while enabling the injection of refrigerant to an intermediate location in the compression process of a compressor. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the refrigeration device of the present invention includes a main circuit provided with a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator, and which circulates a refrigerant; a first injection flow path which branches off from the main circuit downstream of the condenser and which injects a refrigerant into an intermediate portion of a compression process in the compressor via the subcooler; a first injection regulating valve disposed in the first injection flow path at a position upstream of the subcooler; a first valve control means which controls the first injection regulating valve so that a superheat degree of the refrigerant injected into the compressor through the first injection flow path becomes a target superheat degree; a reception unit which receives a required freezing degree; and target superheat degree control means which sets the target superheat degree to a first value when the required freezing degree received by the reception unit is a first required freezing degree, and sets the target superheat degree to a second value higher than the first value when the required freezing degree received by the reception unit is a second required freezing degree which is lower than the first required freezing degree.

[0007] In the refrigeration device according to the present invention, the first injection passage passes through the subcooler, so that the refrigerant flowing through the first injection passage can subcool the refrigerant flowing through the main circuit. Moreover, since the first injection passage is a passage for injecting the refrigerant into an intermediate portion of the compression process in the compressor, even when the refrigerant flows from the main circuit to the first injection passage, the refrigerant can be circulated through the main circuit without decreasing the flow rate flowing to the evaporator. Moreover, by changing the opening degree of the first injection adjustment valve to change the flow rate of the refrigerant flowing through the first injection passage, the degree of subcooling of the refrigerant passing through the subcooler in the main circuit can be changed, so that the refrigeration capacity can be adjusted accordingly.

[0008] On the other hand, the degree of superheat of the refrigerant injected into the compressor through the first injection flow path also changes. When the first valve control means controls the first injection regulating valve, the first valve control means controls the first injection regulating valve so that the degree of superheat of the refrigerant becomes the target degree of superheat. When the degree of freezing requirement received by the reception unit is the first degree of freezing requirement, a first value is given as the target degree of superheat by the target degree of superheat control means. When the degree of freezing requirement received is a second degree of freezing requirement that is lower than the first degree of freezing requirement, a second value higher than the first value is given as the target degree of superheat. That is, when the degree of freezing requirement is relatively low (second degree of freezing requirement) compared to when the degree of freezing requirement is relatively high (first degree of freezing requirement), the target degree of superheat is set so that the target degree of superheat is higher. Therefore, when the degree of freezing requirement is relatively low, compared to when the target degree of superheat is maintained at a constant value, the opening degree of the first injection regulating valve is controlled to be more closed. This reduces the flow rate of the refrigerant injected through the first injection passage into the intermediate portion of the compression process in the compressor. This allows the injection flow rate to be reduced more than when the target degree of superheat is maintained at a constant value, thereby reducing the workload (power) of the compressor. This allows the power of the compressor to be reduced more when the required level of refrigeration is relatively low, resulting in energy savings.

[0009] In the refrigeration device, the first valve control means may control the first injection regulating valve so that the superheat degree of the refrigerant becomes the target superheat degree, on condition that the discharge pipe temperature of the compressor does not exceed a threshold value.

[0010] In this embodiment, when the degree of superheat of the refrigerant is controlled to the target degree of superheat, the condition is that the discharge pipe temperature of the compressor does not exceed a threshold value. In other words, the discharge pipe temperature control takes precedence over the target degree of superheat control. Therefore, when the required degree of refrigeration is relatively low, the discharge pipe temperature is prevented from rising too high, so that energy can be saved while suppressing adverse effects on the compressor.

[0011] The refrigeration apparatus may include a second injection flow path branching off from the main circuit downstream of the condenser and injecting the refrigerant obtained in the condenser into an intermediate portion of the compression process of the compressor.

[0012] In this embodiment, by injecting the refrigerant through the second injection passage into a portion of the compressor during the compression process, the discharge pipe temperature of the compressor can be reduced more effectively.

[0013] The refrigeration device may include a second injection regulating valve arranged in the second injection flow path and capable of adjusting the flow rate of the refrigerant, a discharge pipe temperature detector that detects a discharge pipe temperature of the compressor, and a second valve control means that controls the second injection regulating valve according to a detection result by the discharge pipe temperature detector.

[0014] In this embodiment, the second injection regulating valve is controlled according to the detection result by the discharge pipe temperature detector, so the second injection flow rate can be adjusted independently of the adjustment of the degree of subcooling by the subcooler in the first injection flow path, thereby optimizing the refrigerant flow rate through the second injection flow path.

[0015] The target superheat degree control means may set a value of the target superheat degree so that the target superheat degree gradually increases as the value of the required degree of refrigeration received by the reception unit decreases.

[0016] In this embodiment, the lower the required degree of refrigeration becomes, the larger the target degree of superheat becomes, so the first injection regulating valve is controlled so that the first injection flow rate becomes smaller. Therefore, the lower the required degree of refrigeration becomes, the smaller the degree of supercooling by the supercooler can be (closer to the saturation temperature), and the smaller the refrigeration capacity by the evaporator can be. Therefore, when the refrigeration load is small, it is possible to achieve further energy saving while exhibiting an appropriate refrigeration capacity.

[0017] The refrigeration device may include a second injection flow path branching off from the main circuit downstream of the condenser and injecting the refrigerant obtained in the condenser into an intermediate portion of a compression process in the compressor. In this case, the first valve control means may control the first injection adjustment valve to stop injection of the refrigerant into the compressor through the first injection flow path when the degree of freezing requirement received by the reception unit is a third degree of freezing requirement that is lower than the second degree of freezing requirement.

[0018] In this embodiment, the lower the value of the required freezing level, the smaller the first injection flow rate becomes, and the first injection control valve is controlled so that the first injection is stopped when the received required freezing level is the third required freezing level. That is, the first injection can be stopped after gradually reducing the first injection flow rate. Therefore, when the first injection is stopped, it is possible to prevent disturbance in the control of the subcooling level by the subcooler. Moreover, if the second injection is functioning, the injection of refrigerant into the compressor can suppress an increase in the discharge pipe temperature of the compressor.

[0019] A refrigeration method according to the present invention uses a refrigeration device including a main circuit provided with a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator, and for circulating a refrigerant, a first injection flow path branching from the main circuit downstream of the condenser and for injecting a refrigerant into an intermediate portion of a compression process in the compressor via the subcooler, and a first injection regulating valve disposed in the first injection flow path at a position upstream of the subcooler. In this refrigeration method, a reception unit receives a degree of freezing request, and when the degree of freezing request received by the reception unit is a first degree of freezing request, a target degree of superheat is set to a first value, and when the degree of freezing request received by the reception unit is a second degree of freezing request that is lower than the first degree of freezing request, the target degree of superheat is set to a second value higher than the first value, and the first injection regulating valve is controlled so that the degree of superheat of the refrigerant injected into the compressor through the first injection flow path becomes the target degree of superheat. Effect of the Invention

[0020] As described above, according to the present invention, it is possible to inject refrigerant into an intermediate portion of the compression process in a compressor, and further to achieve energy savings. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating a schematic configuration of a refrigeration device according to a first embodiment. [Diagram 2] FIG. 4 is a diagram illustrating a schematic configuration of a refrigeration device according to a modified example of the first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating a control device including a controller of the refrigeration apparatus. [Figure 4] FIG. 4 is a diagram for explaining the relationship between a required degree of refrigeration and a target degree of superheat. [Diagram 5] FIG. 4 is a diagram for explaining the relationship between a required degree of refrigeration and a target degree of superheat. [Figure 6] FIG. 4 is a diagram for explaining the relationship between a required degree of refrigeration and a target degree of superheat. [Figure 7]5 is a diagram for explaining a control flow of a first flow rate adjustment valve in the refrigeration device. FIG. [Figure 8] FIG. 6 is a diagram illustrating a schematic configuration of a refrigeration device according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a schematic configuration of a refrigeration device according to a modified example of the second embodiment. [Figure 10] FIG. 2 is a diagram illustrating a control device including a controller of the refrigeration apparatus. [Figure 11] 5 is a diagram for explaining a control flow of a first flow rate adjustment valve in the refrigeration device. FIG. [Figure 12] 5 is a diagram for explaining a control flow of a second flow rate adjustment valve in the refrigeration device. FIG. [Figure 13] FIG. 13 is a diagram illustrating an environment forming device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0023] (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 first injection flow path 16 connected to the main circuit 15. The refrigerant may be a low GWP refrigerant such as R449A or R448A.

[0024] The main circuit 15 is provided with a compressor 1, a condenser 2, a subcooler 12, an expansion mechanism 3, and an evaporator 4 in this order. When the compressor 1 is operated, the 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.

[0025] 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 different capacities are connected in parallel.

[0026] 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.

[0027] The expansion mechanism 3 is responsible for the expansion step of the refrigeration cycle, and is configured to expand the liquid refrigerant condensed in the condenser 2. When the subcooler 12 is functioning, the refrigerant flowing into the expansion mechanism 3 is in a state in which the degree of subcooling is greater than that in the subcooler 12.

[0028] The expansion mechanism 3 is configured by, for example, an electronic expansion valve. Therefore, by adjusting the valve opening, the flow rate of the liquid refrigerant flowing through the subcooler 12 and the evaporator 4 in the main circuit 15 can be changed arbitrarily.

[0029] 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 that has become low pressure in the expansion mechanism 3. The evaporator 4 cools the air supplied to the inside of the freezer.

[0030] The first injection flow path 16 branches off from the main circuit 15 downstream of the condenser 2. That is, one end of the first injection flow path 16 is connected to the main circuit 15 between the condenser 2 and the expansion mechanism 3. Note that, in FIG. 1, one end of the first injection flow path 16 is connected to the main circuit 15 between the condenser 2 and the subcooler 12, but as shown in FIG. 2, it may be connected to the main circuit 15 between the subcooler 12 and the expansion mechanism 3.

[0031] The other end of the first injection flow passage 16 is connected to a portion in the process of compressing the refrigerant in the compressor 1. That is, in the compressor 1, the refrigerant is compressed in a compression space (not shown). The first injection flow passage 16 is connected to open to the compression space in the middle of the compression process. Therefore, the refrigerant that has flowed through the first injection flow passage 16 is injected into the compression space in the compressor 1 in the middle of compression.

[0032] A first flow rate adjustment valve 11 (first injection adjustment valve) is disposed in the first injection flow path 16. The first flow rate adjustment valve 11 is configured by an electronic expansion valve. Therefore, by adjusting the opening degree of the first flow rate adjustment valve 11, the flow rate of the refrigerant flowing through the first injection flow path 16 can be adjusted.

[0033] The first injection flow path 16 passes through the subcooler 12 downstream of the first flow rate control valve 11. Therefore, in the subcooler 12, heat exchange occurs between the liquid refrigerant flowing through the main circuit 15 and the liquid refrigerant flowing through the first injection flow path 16. As a result, the liquid refrigerant whose temperature has been reduced by the first flow rate control valve 11 in the first injection flow path 16 is heated by the liquid refrigerant in the main circuit 15 and evaporates. Meanwhile, the liquid refrigerant in the main circuit 15 is cooled and enters a subcooled state.

[0034] The first injection flow path 16 is provided with an inlet temperature detector 22 that detects the temperature of the refrigerant flowing into the supercooler 12, and an outlet temperature detector 23 that detects the temperature of the refrigerant flowing out from the supercooler 12. The inlet temperature detector 22 and the outlet temperature detector 23 each output a signal indicating the detected temperature.

[0035] The main circuit 15 is provided with a discharge pipe temperature detector 21 that detects the discharge pipe temperature (the temperature of the refrigerant discharged from the compressor 1) of the compressor 1. The discharge pipe temperature detector 21 outputs a signal indicating the detected temperature.

[0036] The signals output from the detectors 22, 23, 21 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, a target superheat degree control means 102, a superheat degree calculation unit 103, a first valve control means 104, and an expansion control means 105, as shown in Fig. 3.

[0037] 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.

[0038] 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 required freezing degree each time. The required freezing degree 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 inside temperature and the set value of the inside temperature, the greater the required freezing degree. Since the required freezing degree can change from moment to moment, generator 120 outputs the required freezing degree at predetermined time intervals.

[0039] The target superheat degree control means 102 is configured to set a target superheat degree, which is a target value of the degree of superheat of the refrigerant injected into the compressor 1 through the first injection flow path 16. The target superheat degree control means 102 sets the value of the target superheat degree to a first value when the received degree of required freezing is a first degree of required freezing, and sets the target superheat degree to a second value higher than the first value when the received degree of required freezing is a second degree of required freezing which is lower than the first degree of required freezing.

[0040] As shown in Fig. 4, not only the region where the target superheat degree is set to be higher as the required degree of refrigeration decreases, but also the region where the target superheat degree is constant regardless of the required degree of refrigeration may be included. Also, as shown in Fig. 5, the target superheat degree may be set to be higher as the required degree of refrigeration decreases in the entire region from the minimum value to the maximum value of the required degree of refrigeration. Furthermore, as shown in Fig. 6, the target superheat degree may be set to be higher in a stepwise manner as the required degree of refrigeration decreases. In these cases, the lower the value of the required degree of refrigeration, the gradually larger the target superheat degree becomes, so the lower the value of the required degree of refrigeration, the smaller the degree of supercooling by the supercooler (the closer to the saturation temperature).

[0041] The superheat degree calculation unit 103 is configured to derive the difference value between the temperature detected by the outlet temperature detector 23 and the temperature detected by the inlet temperature detector 22 as the superheat degree of the refrigerant injected into the compressor 1 through the first injection flow path 16. That is, in the first injection flow path 16, the liquid refrigerant (liquid refrigerant flowing into the subcooler 12) decompressed by the first flow control valve 11 is in a saturated state or a state close to it. Therefore, the temperature difference between the temperature of the gas refrigerant flowing out from the subcooler 12 and the temperature of the liquid refrigerant flowing into the subcooler 12 corresponds to the superheat degree of the refrigerant injected into the compressor 1. Note that the refrigerant injected into the compressor 1 through the first injection flow path 16 is assumed to be completely gasified, but in a region where the superheat degree is small, such as in the case of the lowest superheat degree, liquid refrigerant may be included.

[0042] The degree of superheat of the injected refrigerant can be calculated by other methods as well, for example, using the detection values ​​of a temperature detector (outlet temperature detector 23) and a pressure detector disposed downstream of the subcooler 12 in the first injection flow passage 16.

[0043] The first valve control means 104 is configured to control the first flow rate control valve 11 so that the superheat degree of the gas refrigerant derived by the superheat degree calculation unit 103 becomes the target superheat degree. That is, when the opening degree of the first flow rate control valve 11 is reduced, the flow rate of the refrigerant flowing through the first injection flow path 16 is reduced, so that the refrigerant is more superheated in the subcooler 12, and the superheat degree of the injected refrigerant becomes larger. On the other hand, when the opening degree of the first flow rate control valve 11 is increased, the flow rate of the refrigerant flowing through the first injection flow path 16 is increased, so that the refrigerant is not so superheated in the subcooler 12, and the superheat degree of the injected refrigerant becomes smaller. Therefore, by adjusting the opening degree of the first flow rate control valve 11, the superheat degree of the gas refrigerant can be brought closer to the target superheat degree.

[0044] When controlling the first flow rate control valve 11, the first valve control means 104 controls the first flow rate control valve 11 while referring to the detection value by the discharge pipe temperature detector 21. That is, when the flow rate of the refrigerant injected into the compressor 1 through the first injection flow path 16 decreases, the cooling effect of the compressor 1 decreases, and the temperature of the gas refrigerant discharged from the compressor 1 also tends to increase. For this reason, by controlling the first flow rate control valve 11 while referring to the discharge pipe temperature, it is possible to suppress an excessive rise in the discharge pipe temperature. That is, by the first valve control means 104 controlling the first flow rate control valve 11 while monitoring the discharge pipe temperature, an excessive rise in the discharge pipe temperature caused by reducing the refrigerant injection flow rate into the compressor 1 is avoided, and a reduction in the power of the compressor 1 is achieved by reducing the refrigerant injection flow rate.

[0045] The expansion control means 105 is configured to adjust the opening degree of the expansion mechanism 3 in accordance with the degree of freezing requirement received by the reception unit 101. That is, the expansion control means 105 is configured to adjust the flow rate of the refrigerant flowing into the evaporator 4 in accordance with the degree of freezing requirement.

[0046] The system may further include an evaporation temperature detector for detecting the temperature (evaporation temperature) of the refrigerant flowing into the evaporator 4, and the expansion control means 105 may be configured to adjust the expansion mechanism 3 in response to the evaporation temperature in addition to the required degree of refrigeration.

[0047] Here, a refrigeration method using the refrigeration device 10 having the above-mentioned configuration will be described.

[0048] When the target temperature of the inside of the refrigerator is set and the operation of the refrigeration device 10 is started, the controller 100 receives the discharge pipe temperature, which is the detection value by the discharge pipe temperature detector 21, and also receives the degree of freezing requirement generated by the generator 120. The controller 100 also receives the detection value by the inlet temperature detector 22 and the detection value by the outlet temperature detector 23. The expansion control means 105 of the controller 100 adjusts the opening degree of the expansion mechanism 3 based on the received degree of freezing requirement. That is, the target opening degree or the target evaporation temperature of the expansion mechanism 3 is set based on the degree of freezing requirement, and the expansion control means 105 adjusts the opening degree of the expansion mechanism 3 based on these target values. As a result, a flow rate according to the degree of freezing requirement is obtained in the supercooler 12. Also, when the target evaporation temperature is set, an evaporation temperature according to the degree of freezing requirement is obtained.

[0049] As shown in FIG. 7, the controller 100 judges whether the received discharge pipe temperature is lower than the reference temperature range (step ST12). This reference temperature range is a preset temperature range, and the discharge pipe temperature is controlled so that it falls within this temperature range. If the judgment in step ST12 is NO, the process proceeds to step ST13, and target discharge pipe temperature control is executed. In this control, if the detection value by the discharge pipe temperature detector 21 is within the reference temperature range, the opening degree of the first flow rate adjustment valve 11 is maintained, while if the detection value by the discharge pipe temperature detector 21 exceeds the reference temperature range, the opening degree of the first flow rate adjustment valve 11 is increased. As a result, the discharge pipe temperature is adjusted to be equal to or lower than the reference temperature range.

[0050] If the received discharge pipe temperature is lower than the management reference temperature range, the process proceeds to step ST14, and the target superheat degree control means 102 sets the target superheat degree. That is, the reception unit 101 repeatedly receives the required refrigeration degree at predetermined time intervals, and the target superheat degree control means 102 derives the target superheat degree corresponding to the required refrigeration degree every time it receives the required refrigeration degree.

[0051] On the other hand, the superheat degree calculation unit 103 calculates the degree of superheat of the refrigerant injected into the compressor 1 through the first injection flow path 16, using signals from the inlet temperature detector 22 and the outlet temperature detector 23. Then, target superheat degree control is performed (step ST15). That is, the target superheat degree control is performed on the condition that the discharge pipe temperature of the compressor 1 does not exceed a threshold value.

[0052] In the target superheat control, the first valve control means 104 controls the first flow rate control valve 11 so that the superheat of the refrigerant calculated by the superheat calculation unit 103 approaches the target superheat set in step ST14. At this time, when the received refrigeration requirement is the first refrigeration requirement, the target superheat is set to a first value, and when the received refrigeration requirement is the second refrigeration requirement lower than the first refrigeration requirement, the target superheat is set to a second value higher than the first value. Therefore, when the cooling load is small and the value of the refrigeration requirement is small, the target superheat becomes larger. Therefore, the opening of the first flow rate control valve 11 is narrowed, and the flow rate of the refrigerant injected into the intermediate portion of the compression process in the compressor 1 is further reduced, which contributes to reducing the power of the compressor 1.

[0053] Then, while the target superheat degree control is being performed, the process returns to step ST12 to monitor the discharge pipe temperature, and the opening control of the first flow rate control valve 11 (step ST13) is performed again as necessary. For example, when the required freezing degree decreases, the target superheat degree is increased, so that the opening of the first flow rate control valve 11 becomes smaller and the discharge pipe temperature is more likely to rise. However, by performing the target discharge pipe temperature control (step ST13) again, the discharge pipe temperature can be adjusted to within the management reference temperature range. Therefore, even if the amount of refrigerant gas injected is reduced in step ST15, an excessive rise in the discharge pipe temperature is prevented.

[0054] As described above, in this embodiment, since the first injection flow passage 16 passes through the subcooler 12, the refrigerant flowing through the first injection flow passage 16 can subcool the refrigerant flowing through the main circuit 15. Moreover, since the first injection flow passage 16 is a flow passage for injecting the refrigerant into an intermediate portion of the compression process in the compressor 1, even when the refrigerant flows from the main circuit 15 to the first injection flow passage 16, the refrigerant can be circulated through the main circuit 15 without decreasing the flow rate flowing through the evaporator 4. Moreover, by changing the opening degree of the first flow control valve 11 to change the flow rate of the refrigerant flowing through the first injection flow passage 16, the degree of subcooling of the refrigerant passing through the subcooler 12 in the main circuit 15 can be changed, and the refrigeration capacity can be adjusted accordingly.

[0055] On the other hand, by controlling the first flow rate control valve 11, the superheat degree of the refrigerant injected into the compressor 1 through the first injection flow path 16 also changes. When the first valve control means 104 controls the first flow rate control valve 11, the first valve control means 104 controls the first flow rate control valve 11 so that the superheat degree of the refrigerant becomes the target superheat degree. When the freezing requirement degree received by the reception unit 101 is the first freezing requirement degree, a first value is given as the target superheat degree. When the freezing requirement degree received is the second freezing requirement degree that is lower than the first freezing requirement degree, a second value higher than the first value is given as the target superheat degree. In other words, the target superheat degree is set so that the target superheat degree is higher when the freezing requirement degree is relatively low (second freezing requirement degree) than when the freezing requirement degree is relatively high (first freezing requirement degree). For this reason, when the required degree of refrigeration is relatively low, the opening degree of the first flow control valve 11 is controlled to be more closed compared to when the target degree of superheat is maintained at a constant value. As a result, the flow rate of the refrigerant injected during compression in the compressor 1 through the first injection passage 16 is further reduced. Therefore, compared to when the target degree of superheat is maintained at a constant value, the injected flow rate can be further reduced, and the workload (power) of the compressor 1 can be further reduced. For this reason, when the required degree of refrigeration is relatively low, the power of the compressor 1 can be further reduced, resulting in energy savings.

[0056] In this embodiment, when controlling the degree of superheat of the refrigerant to the target degree of superheat, the discharge pipe temperature of the compressor 1 must not exceed a threshold value. That is, the target discharge pipe temperature control (step ST13) takes precedence over the target degree of superheat control (step ST15). Therefore, when the required degree of refrigeration is relatively low, it is possible to prevent the discharge pipe temperature from rising too much, thereby making it possible to reduce adverse effects on the compressor 1 and to achieve energy savings.

[0057] Second embodiment 8 shows the second embodiment. Note that the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0058] In the second embodiment, a second injection flow passage 17 is added. The second injection flow passage 17 is a flow passage for injecting the refrigerant obtained in the condenser 2 into an intermediate portion of the compression process in the compressor 1 without passing through the subcooler 12. One end of the second injection flow passage 17 is connected to a portion between the condenser 2 and the subcooler 12 in the main circuit 15, and the other end is connected to a portion between the subcooler 12 and the compressor 1 in the first injection flow passage 16. The liquid refrigerant flowing through the second injection flow passage 17 may flow in a completely liquid state, or may be reduced in pressure by the second flow control valve 13 described later and become a gas-liquid mixed state. In addition, the liquid refrigerant flowing through the second injection flow passage 17 may merge with the refrigerant flowing through the first injection flow passage 16, so that a part or all of the liquid refrigerant may be gasified.

[0059] Note that one end of the second injection flow passage 17 does not have to be connected to a portion in the main circuit 15 between the condenser 2 and the subcooler 12. As shown in Fig. 9, one end of the second injection flow passage 17 may be connected to a portion in the main circuit 15 between the subcooler 12 and the expansion mechanism 3.

[0060] A second flow rate control valve 13 (second injection control valve) is disposed in the second injection flow path 17. The second flow rate control valve 13 is configured by an electronic expansion valve. Therefore, by adjusting the opening degree of the second flow rate control valve 13, the flow rate of the refrigerant flowing through the second injection flow path 17 can be adjusted.

[0061] As shown in Fig. 10, the functions of the controller 100 also include a second valve control means 106. The second valve control means 106 is configured to control the second flow rate adjustment valve 13 according to the detection result by the discharge pipe temperature detector 21. In other words, the second valve control means 106 controls the second flow rate adjustment valve 13 to keep the discharge pipe temperature within the control reference temperature range. For this reason, in the second embodiment, unlike the first embodiment, the first valve control means 104 does not refer to the detection value by the discharge pipe temperature detector 21 when controlling the first flow rate adjustment valve 11.

[0062] That is, in the second embodiment, the target superheat degree control shown in FIG. 11 and the target discharge pipe temperature control shown in FIG. 12 are performed separately and independently.

[0063] In the target superheat degree control, when the target temperature of the inside temperature is set and the operation of the refrigeration device 10 is started, the target superheat degree control means 102 sets the target superheat degree (step ST22). That is, the reception unit 101 receives the required refrigeration degree at predetermined time intervals, and the target superheat degree control means 102 derives the target superheat degree corresponding to the required refrigeration degree received by the reception unit 101. The superheat degree calculation unit 103 calculates the superheat degree of the refrigerant injected into the compressor 1 through the first injection flow path 16. Then, in the target superheat degree control in step ST23, the first valve control means 104 controls the first flow rate adjustment valve 11 so that the calculated superheat degree of the refrigerant approaches the target superheat degree set in step ST22. As shown in Figs. 4 to 6 and the like, the target superheat degree is set so that the value (second value) for a low required refrigeration degree (second required refrigeration degree) is higher than the value (first value) for a high required refrigeration degree (first required refrigeration degree). Therefore, when the cooling load is small and the value of the required degree of freezing is small, the target degree of superheat becomes larger, and the flow rate of the refrigerant injected into the part during compression in the compressor 1 is further reduced. This setting of the target degree of superheat (step ST22) and the control of the target degree of superheat (step ST23) are repeated every time the reception unit 101 receives the required degree of freezing. Therefore, as the temperature inside the refrigerator approaches the set temperature, the flow rate of the refrigerant injected into the compressor 1 is reduced.

[0064] On the other hand, when the target temperature for the inside temperature is set and operation of the refrigeration device 10 is started, as shown in Fig. 12, the controller 100 receives the discharge pipe temperature, which is the value detected by the discharge pipe temperature detector 21. The controller 100 determines whether the received discharge pipe temperature is within the control reference temperature range (step ST32). If the value detected by the discharge pipe temperature detector 21 is within the control reference temperature range, the opening degree of the second flow rate control valve 13 is maintained. For example, at the start of operation, since the discharge pipe temperature is within the control reference temperature range, the second flow rate control valve 13 is maintained in a closed state.

[0065] When the detected discharge pipe temperature fluctuates and the determination in step ST32 becomes NO, target discharge pipe temperature control is executed (step ST33). In this control, if the value detected by the discharge pipe temperature detector 21 is outside the control reference temperature range, the opening of the second flow rate adjustment valve 13 is increased. On the other hand, if the value detected by the discharge pipe temperature detector 21 is lower than the control reference temperature range, the opening of the second flow rate adjustment valve 13 is decreased. In this way, the discharge pipe temperature is adjusted to be within the control reference temperature range. The target discharge pipe temperature control (step ST33) is repeatedly performed every time the controller 100 receives a detection signal from the discharge pipe temperature detector 21.

[0066] Therefore, in the second embodiment, the refrigerant can be injected through the second injection passage 17 into a portion of the compressor 1 during compression, so that the discharge pipe temperature of the compressor 1 can be reduced more effectively.

[0067] Moreover, since the second flow rate adjustment valve 13 is controlled according to the detection result by the discharge pipe temperature detector 21, the refrigerant flow rate in the second injection flow path 17 can be adjusted independently of the adjustment of the degree of subcooling in the subcooler 12 by adjusting the refrigerant flow rate flowing through the first injection flow path 16. Therefore, the refrigerant flow rate through the second injection flow path 17 can be optimized.

[0068] In addition, in the target superheat control (step ST23), the first flow rate control valve 11 may be controlled so that the injection of the refrigerant into the compressor 1 through the first injection flow path 16 is stopped. That is, when the required freezing degree received by the reception unit is a third required freezing degree that is lower than the second required freezing degree, the refrigerant injection flow rate through the first injection flow path 16 is reduced, so that the discharge pipe temperature of the compressor 1 is likely to rise. In that case, the injection of the refrigerant through the first injection flow path 16 may be stopped because the injection of the refrigerant into the compressor 1 through the second injection flow path 17 is performed by the target discharge pipe temperature control (step ST33). In that case, the compressor 1 is efficiently cooled, which also contributes to reducing the power of the compressor 1.

[0069] In this case, the target superheat degree control means 102 may set the value of the target superheat degree so that the target superheat degree gradually increases as the value of the required degree of refrigeration decreases. For example, the value of the target superheat degree is set so as to change linearly or curvedly. In this way, even when the injection of the refrigerant through the first injection passage 16 is stopped, it is possible to prevent disturbance in the control of the supercooling degree by the subcooler 12.

[0070] Although a description of the other configurations, operations, and effects will be omitted, the description of the first embodiment can be applied to the second embodiment.

[0071] Third embodiment 13 shows the third embodiment. Note that the same components as those in the first or second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0072] 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.

[0073] 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.

[0074] 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. A sensor 121 for detecting the indoor temperature is disposed in the environmental chamber 51. An input device 122 is used to input the set temperature for the temperature in the environmental chamber 51. The environmental forming device 50 can set a wide range of temperatures, such as a negative temperature range, a normal temperature range, or a high temperature range, and may have a program operation function for changing the temperature stepwise or continuously between a plurality of set temperatures.

[0075] 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 .

[0076] 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 degree of supercooling is obtained by controlling the expansion mechanism 3 of the refrigeration device 10, and a predetermined refrigeration capacity is exerted, but since the temperature detected by the sensor 121 may fall below the set temperature, the heater 54 fine-tunes the room temperature. Therefore, if excessive cooling by the refrigeration device 10 can be suppressed, not only can the power of the refrigeration device 10 be suppressed, but also the power of the heater 54 can be suppressed. In this regard, when the required degree of refrigeration is small, the refrigerant injection flow rate through the first injection flow path 16 is reduced, thereby reducing the refrigeration capacity, and the power of the heater 54 can be suppressed, thereby achieving further energy saving. In addition, by controlling the target superheat control means 102 to change the target superheat, both the ability to follow the set temperature and energy saving after the temperature is reached can be obtained. Therefore, it is particularly suitable for executing a program operation in which the temperature is changed stepwise or continuously between multiple set temperatures.

[0077] 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.

[0078] (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]

[0079] 1: Compressor 2: Condenser 3: Expansion mechanism 4: Evaporator 10: Refrigeration equipment 11: First flow control valve 12:Supercooler 13: Second flow control valve 15: Main circuit 16: First injection channel 17: Second injection channel 21: Discharge pipe temperature detector 101: Reception 102:Target superheat degree control means 104: First valve control means 106: Second valve control means

Claims

1. a main circuit including a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator, and circulating a refrigerant; a first injection flow path that branches off from the main circuit downstream of the condenser and injects the refrigerant into an intermediate portion of a compression process in the compressor via the subcooler; a first injection regulating valve disposed in the first injection flow passage at a position upstream of the subcooler; a first valve control means for controlling the first injection regulating valve so that a degree of superheat of the refrigerant injected into the compressor through the first injection passage becomes a target degree of superheat; A reception unit for receiving a freezing request level; a target superheat degree control means for setting the target superheat degree to a first value when the required freezing degree received by the reception unit is a first required freezing degree, and setting the target superheat degree to a second value higher than the first value when the required freezing degree received by the reception unit is a second required freezing degree that is lower than the first required freezing degree; The refrigeration device comprises:

2. The refrigeration apparatus according to claim 1, wherein the first valve control means controls the first injection regulating valve so that the degree of superheat of the refrigerant becomes the target degree of superheat, on condition that a discharge pipe temperature of the compressor does not exceed a threshold value.

3. 2. The refrigeration apparatus according to claim 1, further comprising a second injection flow path that branches off from the main circuit downstream of the condenser and injects the refrigerant obtained in the condenser into an intermediate portion of a compression process in the compressor.

4. a second injection adjustment valve disposed in the second injection flow passage and capable of adjusting a flow rate of the refrigerant; a discharge pipe temperature detector for detecting a temperature of a discharge pipe of the compressor; a second valve control means for controlling the second injection regulating valve in response to a detection result by the discharge pipe temperature detector; The refrigeration system of claim 3 .

5. 2. The refrigeration apparatus according to claim 1, wherein the target superheat degree control means sets the value of the target superheat degree so that the target superheat degree gradually increases as the value of the requested degree of refrigeration received by the reception unit decreases.

6. a second injection flow path that branches off from the main circuit downstream of the condenser and injects the refrigerant obtained in the condenser into an intermediate portion of a compression process of the compressor; The refrigeration device according to claim 5, wherein the first valve control means controls the first injection adjustment valve so that injection of refrigerant into the compressor through the first injection flow path is stopped when the freezing requirement level received by the receiving unit is a third freezing requirement level that is lower than the second freezing requirement level.

7. a main circuit including a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator, and circulating a refrigerant; a first injection flow path that branches off from the main circuit downstream of the condenser and injects the refrigerant into an intermediate portion of a compression process in the compressor via the subcooler; a first injection regulating valve disposed in the first injection flow passage at a position upstream of the subcooler; A refrigeration method using a refrigeration device comprising: The reception department receives the freezing request level, When the degree of required freezing received by the reception unit is a first degree of required freezing, the target degree of superheat is set to a first value, and when the degree of required freezing received by the reception unit is a second degree of required freezing which is a lower degree of required freezing than the first degree of required freezing, the target degree of superheat is set to a second value which is higher than the first value; a control unit for controlling the first injection regulating valve so that a degree of superheat of the refrigerant injected into the compressor through the first injection passage becomes the target degree of superheat.

Images