air conditioning equipment

Abstract

To eliminate a pressure control valve for controlling an evaporation pressure of a refrigerant in an air conditioner.SOLUTION: A refrigerant circuit (50) of an air conditioner (10) includes a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54). The air conditioner (10) performs a refrigeration cycle by circulating a refrigerant in the refrigerant circuit (50), and cools air in the evaporator (54). The air conditioner (10) includes a pressure detecting unit (61) and a controller (70). The pressure detecting unit (61) detects the evaporation pressure of the refrigerant in the evaporator (54). The controller (70) controls the opening of the expansion valve (53) on the basis of the evaporation pressure detected by the pressure detecting unit (61).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an air conditioning apparatus. [Background technology]

[0002] BACKGROUND ART Air conditioners equipped with a refrigerant circuit have been known for some time. In the refrigerant circuit of an air conditioner, a refrigeration cycle is performed by circulating a refrigerant.

[0003] In air conditioners, a pressure control valve is sometimes provided downstream of the evaporator in the refrigerant circuit. Patent Document 1 discloses an air conditioner equipped with such a pressure control valve. An air conditioner equipped with a pressure control valve adjusts the evaporation pressure of the refrigerant in the evaporator by adjusting the opening degree of the pressure control valve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-035880 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, to air-condition a test room that houses a large object such as a vehicle, an air conditioner with extremely high capacity is required. In such a high-capacity air conditioner, a pipe with an extremely large diameter (e.g., an inner diameter of 200 mm or more) is used as the piping through which the gas refrigerant flowing from the evaporator flows. The pressure control valve attached to such a large-diameter pipe becomes extremely large (e.g., a height of 1500 mm or more and a weight of 200 kg or more).

[0006] When installing such a very large pressure regulating valve, there are significant restrictions on the layout when installing the air conditioner, and because pressure regulating valves are expensive, the cost required to install the air conditioner increases.

[0007] An object of the present disclosure is to omit a pressure adjustment valve for adjusting the evaporation pressure of a refrigerant in an air conditioning apparatus. [Means for solving the problem]

[0008] A first aspect of the present disclosure is an air conditioner (10) including a refrigerant circuit (50) having a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54), which performs a refrigeration cycle by circulating a refrigerant in the refrigerant circuit (50) and cools air in the evaporator (54), and further including a pressure detection unit (61) that detects an evaporation pressure of the refrigerant in the evaporator (54), and a controller (70) that controls an opening degree of the expansion valve (53) based on the evaporation pressure detected by the pressure detection unit (61).

[0009] In the first aspect, the controller (70) controls the aperture of the expansion valve (53) based on the evaporation pressure of the refrigerant detected by the pressure detector (61). When the aperture of the expansion valve (53) changes, the pressure of the refrigerant flowing into the evaporator (54) changes, and as a result, the evaporation pressure of the refrigerant in the evaporator (54) changes. Therefore, while maintaining the function of the air conditioner (10) of “controlling the evaporation pressure of the refrigerant in the evaporator (54),” a pressure control valve for adjusting the evaporation pressure can be omitted from the refrigerant circuit (50) of the air conditioner (10).

[0010] A second aspect of the present disclosure is the first aspect, wherein the pressure detection unit (61) is a pressure sensor provided between the expansion valve (53) and the evaporator (54) in the refrigerant circuit (50) and measures the pressure of the refrigerant flowing from the expansion valve (53) to the evaporator (54) as the evaporation pressure.

[0011] In the second aspect, a pressure sensor that measures the pressure of the refrigerant flowing from the expansion valve (53) toward the evaporator (54) constitutes a pressure detection section (61) that detects the evaporation pressure of the refrigerant in the evaporator (54).

[0012] A third aspect of the present disclosure is the first or second aspect, wherein the refrigerant circuit (50) includes a gas supply passage (55) that supplies gas refrigerant discharged from the compressor (51) to a position between the expansion valve (53) and the evaporator (54) in the refrigerant circuit (50), and an adjustment valve (56) with a variable opening that is provided in the gas supply passage (55), and the controller (70) controls the opening of the adjustment valve (56) based on the degree of superheat of the refrigerant at an outlet of the evaporator (54) and the rotation speed of the compressor (51).

[0013] In the third aspect, the controller (70) controls the aperture of the regulator valve (56) provided in the gas supply passage (55). When the aperture of the regulator valve (56) changes, the flow rate of the gas refrigerant flowing through the gas supply passage (55) changes, and as a result, the state of the refrigerant flowing into the evaporator (54) changes. When the state of the refrigerant flowing into the evaporator (54) changes, the state of the refrigerant flowing out of the evaporator (54) changes, and as a result, the rotation speed of the compressor (51) may change. Therefore, the controller (70) controls the aperture of the regulator valve (56) based on the degree of superheat of the refrigerant at the outlet of the evaporator (54) and the rotation speed of the compressor (51).

[0014] A fourth aspect of the present disclosure is related to the third aspect, wherein the controller (70) sets the aperture of the control valve (56) determined to set the superheat degree of the refrigerant at the outlet of the evaporator (54) to a set superheat degree as a first aperture, sets the aperture of the control valve (56) determined to set the rotation speed of the compressor (51) to a set speed as a second aperture, and sets the aperture of the control valve (56) to the larger of the first aperture and the second aperture.

[0015] In the fourth mode, the controller (70) sets the opening of the control valve (56) to the larger of the first opening and the second opening, so that the degree of superheat of the refrigerant at the outlet of the evaporator (54) is maintained at or above the set superheat, and the rotation speed of the compressor (51) is maintained at or above the set speed. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a schematic diagram of a user-side unit of an air conditioner. [Figure 2] FIG. 2 is a piping diagram showing the refrigerant circuit of the air conditioner. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment will now be described. An air conditioner (10) of this embodiment provides air conditioning for a test room (100) used for automobile driving tests and the like.

[0018] The air conditioner (10) includes a utilization side unit (20) and a heat source side unit (40), and also includes a refrigerant circuit (50).

[0019] -User unit- As shown in Fig. 1, the user-side unit (20) is a so-called air handling unit. The user-side unit (20) includes a casing (25). An inlet (27) is formed in one end surface of the casing (25), and an outlet (28) is formed in the other end surface of the casing (25). An air flow path (26) is formed inside the casing (25) from the inlet (27) to the outlet (28).

[0020] The utilization side unit (20) is connected to the test chamber (100) via a suction duct (16) and a discharge duct (17). The suction duct (16) is connected to an inlet (27) of the casing (25) and connects the air flow path (26) to the interior space of the test chamber (100). The discharge duct (17) is connected to an outlet (28) of the casing (25) and connects the air flow path (26) to the interior space of the test chamber (100).

[0021] The air flow path (26) in the casing (25) is provided with a filter (31), an evaporator (54), an electric heater (32), and a user-side fan (33) in this order from the suction port (27) side toward the discharge port (28) side. The filter (31) collects dust and other particles contained in the air flowing in through the suction port (27). The evaporator (54) is connected to the refrigerant circuit (50) and cools the air. The electric heater (32) heats the air that has passed through the evaporator (54). The user-side fan (33) draws in the air that has passed through the electric heater (32) and blows it out toward the discharge port (28).

[0022] <Driving operation> The operation of the user unit (20) will now be described.

[0023] When the user-side fan (33) is activated, air in the interior space of the test chamber (100) flows through the intake duct (16) into the air flow path (26) in the casing (25). The air flowing through the air flow path (26) passes through the filter (31), the evaporator (54), and the electric heater (32) in this order.

[0024] The air is cooled while passing through the evaporator (54) and heated while passing through the electric heater (32). Note that the electric heater (32) may temporarily stop heating the air. The air that has passed through the electric heater (32) is blown out from the user-side fan (33) and flows into the blow-out duct (17), and then blown into the interior space of the test chamber (100).

[0025] -Air temperature sensor, heater controller- The air conditioner (10) includes an air temperature sensor (36) and a heater controller (37).

[0026] The air temperature sensor (36) is provided in the discharge duct (17) and measures the temperature of the air flowing through the discharge duct (17). The measured value of the air temperature sensor (36) indicates the temperature of the air supplied by the utilization side unit (20) to the internal space of the test room (100).

[0027] The heater controller (37) receives the measurement value of the air temperature sensor (36). The heater controller (37) controls the amount of heat generated by the electric heater (32) based on the measurement value of the air temperature sensor (36). Specifically, the heater controller (37) adjusts the amount of heat generated by the electric heater (32) so that the measurement value of the air temperature sensor (36) becomes the set air temperature. When the measurement value of the air temperature sensor (36) is lower than the set air temperature, the heater controller (37) increases the amount of heat generated by the electric heater (32). When the measurement value of the air temperature sensor (36) is higher than the set air temperature, the heater controller (37) decreases the amount of heat generated by the electric heater (32).

[0028] -Refrigerant circuit- The refrigerant circuit (50) is a closed circuit filled with a refrigerant, and performs a refrigeration cycle by circulating the refrigerant.

[0029] 2, the refrigerant circuit (50) includes a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54). In the refrigerant circuit (50), the condenser (52), the expansion valve (53), and the evaporator (54) are arranged in this order from the discharge port to the suction port of the compressor (51).

[0030] The compressor (51) compresses and discharges the drawn refrigerant. Although not shown, the compressor (51) includes a compression mechanism and an electric motor for driving the compression mechanism. The condenser (52) is a cross-fin type air heat exchanger that exchanges heat between the refrigerant and outdoor air. The expansion valve (53) is an electric expansion valve with a variable opening. The evaporator (54) is a cross-fin type air heat exchanger that exchanges heat between the refrigerant and air in the air flow path (26).

[0031] The refrigerant circuit (50) also includes a gas supply pipe (55). The gas supply pipe (55) constitutes a gas supply passage. One end of the gas supply pipe (55) is connected to a pipe between the discharge port of the compressor (51) and the condenser (52). The other end of the gas supply pipe (55) is connected to a pipe between the expansion valve (53) and the evaporator (54). The gas supply pipe (55) is provided with a control valve (56). The control valve (56) is an electrically operated valve whose opening degree is variable.

[0032] <Refrigeration cycle> The refrigeration cycle performed by the refrigerant circuit (50) will be described.

[0033] When the compressor (51) is operated, refrigerant circulates in the refrigerant circuit (50). The refrigerant discharged from the compressor (51) flows into the condenser (52) and condenses by dissipating heat to the outdoor air passing through the condenser (52). The refrigerant flowing out of the condenser (52) is reduced in pressure while passing through the expansion valve (53) and then flows into the evaporator (54).

[0034] When the control valve is open, a portion of the gas refrigerant (hot gas) discharged from the compressor flows into the gas supply pipe (55). The gas refrigerant flowing through the gas supply pipe (55) flows into the evaporator (54) together with the refrigerant that has passed through the expansion valve (53). The refrigerant that has flowed into the evaporator (54) absorbs heat from the air passing through the evaporator (54) and evaporates. The refrigerant that has flowed out of the evaporator (54) is drawn into the compressor (51) and compressed. The compressor (51) compresses the drawn refrigerant and discharges it.

[0035] -Heat source unit- The heat source side unit (40) is provided with a compressor (51) and a condenser (52) of a refrigerant circuit (50). The heat source side unit (40) also includes a heat source side fan (41) and an inverter (42). The heat source side fan (41) supplies outdoor air to the condenser (52). Although not shown, the inverter (42) is connected to an external power source such as a commercial power source. The inverter (42) converts the frequency of the supplied AC current to a set frequency and supplies the AC current of the set frequency to the motor of the compressor (51). Changing the output frequency of the inverter (42) changes the rotation speed of the compressor (51).

[0036] -Suction pressure sensor, compressor controller- The heat source side unit (40) includes a suction pressure sensor (46) and a compressor controller (47).

[0037] The suction pressure sensor (46) is connected to the refrigerant circuit (50). The suction pressure sensor (46) is attached to a pipe connected to the suction port of the compressor (51) and measures the pressure of the refrigerant sucked into the compressor (51).

[0038] The compressor controller (47) receives the measurement value of the suction pressure sensor (46) and controls the rotation speed of the compressor (51) based on the measurement value of the suction pressure sensor (46).

[0039] Specifically, the compressor controller (47) adjusts the rotation speed of the compressor (51) so that the measurement value of the suction pressure sensor (46) becomes equal to the set suction pressure. When the measurement value of the suction pressure sensor (46) is lower than the set suction pressure, the compressor controller (47) reduces the output frequency of the inverter (42) to reduce the rotation speed of the compressor (51). When the measurement value of the suction pressure sensor (46) is higher than the set suction pressure, the compressor controller (47) increases the output frequency of the inverter (42) to increase the rotation speed of the compressor (51).

[0040] -Sensor- The air conditioner (10) includes an inlet pressure sensor (61), an outlet pressure sensor (62), an outlet temperature sensor (63), and a frequency sensor (64).

[0041] The inlet pressure sensor (61), the outlet pressure sensor (62), and the outlet temperature sensor (63) are connected to the refrigerant circuit (50). The inlet pressure sensor (61) is attached to a pipe connected to the inlet of the evaporator (54) and measures the pressure of the refrigerant flowing into the evaporator (54). The inlet pressure sensor (61) is a pressure detector that detects the evaporation pressure of the refrigerant in the evaporator (54). The outlet pressure sensor (62) and the outlet temperature sensor (63) are attached to a pipe connected to the outlet of the evaporator (54). The outlet pressure sensor (62) measures the pressure of the refrigerant flowing out from the evaporator (54). The outlet temperature sensor (63) measures the temperature of the refrigerant flowing out from the evaporator (54).

[0042] The frequency sensor (64) is provided on an electric power supply wiring that connects the inverter (42) to the motor of the compressor (51). The frequency sensor (64) measures the output frequency of the inverter (42). The measured value of the frequency sensor (64) is the frequency of the AC current supplied from the inverter (42) to the compressor (51).

[0043] -Controller- The air conditioner (10) includes an expansion valve controller (75), a first controller (76), a second controller (77), and a selector (78). The expansion valve controller (75), the first controller (76), the second controller (77), and the selector (78) constitute a controller (70) that controls the expansion valve (53) and the control valve (56).

[0044] <Expansion valve controller> The expansion valve controller (75) receives the measurement value of the inlet pressure sensor (61) and controls the opening degree of the expansion valve (53) based on the measurement value of the inlet pressure sensor (61).

[0045] Specifically, the expansion valve controller (75) calculates the degree of opening of the expansion valve (53) such that the measurement value of the inlet pressure sensor (61) becomes the set evaporation pressure, and determines the calculated degree of opening as a third command value for the degree of opening of the expansion valve (53). The expansion valve controller (75) transmits the determined third command value to the expansion valve (53). As a result, the degree of opening of the expansion valve (53) becomes the degree of opening corresponding to the third command value.

[0046] When the measurement value of the inlet pressure sensor (61) is lower than the set evaporation pressure, the expansion valve controller (75) transmits a third command value to the expansion valve (53) that is greater than the current opening of the expansion valve (53). The opening of the expansion valve (53) is increased to the opening corresponding to the third command value. When the opening of the expansion valve (53) is increased, the pressure of the refrigerant at the outlet of the expansion valve (53) increases. As a result, the pressure of the refrigerant flowing into the evaporator (54) increases, and the evaporation pressure of the refrigerant in the evaporator (54) increases.

[0047] When the measurement value of the inlet pressure sensor (61) is higher than the set evaporation pressure, the expansion valve controller (75) transmits a smaller opening degree than the current opening degree of the expansion valve (53) as a third command value to the expansion valve (53). The opening degree of the expansion valve (53) is reduced to the opening degree corresponding to the third command value. When the opening degree of the expansion valve (53) is reduced, the pressure of the refrigerant at the outlet of the expansion valve (53) is reduced. As a result, the pressure of the refrigerant flowing into the evaporator (54) is reduced, and the evaporation pressure of the refrigerant in the evaporator (54) is reduced.

[0048] <First controller> The first controller (76) receives the measurement value of the outlet side pressure sensor (62) and the measurement value of the outlet side temperature sensor (63). The first controller (76) is configured to calculate a first command value for the opening degree of the regulator valve (56) based on the measurement values ​​of the outlet side pressure sensor (62) and the outlet side temperature sensor (63).

[0049] First, the first controller (76) calculates the degree of superheat of the refrigerant at the outlet of the evaporator (54). The first controller (76) calculates the degree of superheat SH (=T-Ts) of the refrigerant at the outlet of the evaporator (54) by subtracting the “saturation temperature Ts of the refrigerant corresponding to the measurement value of the outlet pressure sensor (62)” from the “measurement value T of the outlet temperature sensor (63).”

[0050] Next, the first controller (76) calculates the opening of the regulating valve (56) so that the degree of superheat of the refrigerant at the outlet of the evaporator (54) becomes the set degree of superheat. The opening calculated by the first controller (76) is the first opening. The first controller (76) determines the calculated first opening as a first command value for the opening of the regulating valve (56). The first controller (76) transmits the determined first command value to the selector (78).

[0051] If the refrigerant at the outlet of the evaporator (54) becomes wet, the liquid refrigerant may be drawn into the compressor (51), which may result in damage to the compressor (51). Therefore, in order to prevent damage to the compressor (51), it is necessary to keep the refrigerant at the outlet of the evaporator (54) in a single-phase gas state.

[0052] On the other hand, when the aperture of the regulating valve (56) is changed, the flow rate of the gas refrigerant flowing through the gas supply pipe (55) changes. This changes the state of the refrigerant flowing into the evaporator (54), which in turn changes the state of the refrigerant at the outlet of the evaporator (54). Therefore, the first controller (76) calculates the aperture of the regulating valve (56) so that the degree of superheat of the refrigerant at the outlet of the evaporator (54) becomes the set degree of superheat.

[0053] When the opening degree of the control valve (56) increases, the flow rate of the gas refrigerant flowing through the gas supply pipe (55) increases. Therefore, the wetness of the refrigerant flowing into the evaporator (54) decreases, and as a result, the degree of superheat of the refrigerant at the outlet of the evaporator (54) increases. Therefore, when the degree of superheat of the refrigerant at the outlet of the evaporator (54) is lower than the set degree of superheat, the second controller (77) determines, as the first command value, an opening degree of the control valve (56) that is larger than the current opening degree.

[0054] On the other hand, when the opening degree of the control valve (56) is reduced, the flow rate of the gas refrigerant flowing through the gas supply pipe (55) is reduced. Therefore, the wetness of the refrigerant flowing into the evaporator (54) increases, and as a result, the degree of superheat of the refrigerant at the outlet of the evaporator (54) decreases. Therefore, when the degree of superheat of the refrigerant at the outlet of the evaporator (54) is higher than the set degree of superheat, the second controller (77) determines, as the first command value, an opening degree smaller than the current opening degree of the control valve (56).

[0055] <Second controller> The measurement value of the frequency sensor (64) is input to the second controller (77). The second controller (77) is configured to calculate a second command value for the opening of the regulator valve (56) based on the measurement value of the frequency sensor (64).

[0056] Specifically, the second controller (77) calculates the opening of the regulator valve (56) so that the measurement value of the frequency sensor (64) becomes the set frequency. The opening calculated by the second controller (77) is the second opening. The second controller (77) determines the calculated second opening as a second command value for the opening of the regulator valve (56). The second controller (77) transmits the determined second command value to the selector (78).

[0057] When the rotation speed of the compressor (51) is low, the flow velocity of the refrigerant flowing through the refrigerant circuit (50) is low, and refrigeration oil discharged from the compressor (51) together with the refrigerant is likely to accumulate in the evaporator (54), piping, etc. Therefore, when the compressor (51) operates at a relatively low rotation speed (for example, 20% or less of the maximum rotation speed) for a long period of time, the amount of refrigeration oil accumulating outside the compressor (51) increases, and the amount of refrigeration oil remaining inside the compressor (51) decreases. As a result, the amount of refrigeration oil supplied to the sliding parts of the compressor (51) becomes insufficient, which may damage the compressor (51).

[0058] On the other hand, if the rotation speed of the compressor (51) is maintained at a relatively high rotation speed (for example, 80% or more of the maximum rotation speed), a sufficient amount of refrigeration oil is returned to the compressor (51) together with the refrigerant. Therefore, a sufficient amount of refrigeration oil is stored in the compressor (51), and damage to the compressor (51) is prevented.

[0059] Therefore, the second controller (77) calculates the opening of the control valve (56) so that the measurement value of the frequency sensor (64) becomes the set frequency. The measurement value of the frequency sensor (64) is the actual measurement value of the output frequency of the inverter (42). Therefore, when the measurement value of the frequency sensor (64) becomes the set frequency, the rotation speed of the compressor (51) becomes the set speed, and as a result, the amount of refrigeration oil returning to the compressor (51) together with the refrigerant is ensured.

[0060] Here, when the cooling load of the evaporator (54) (specifically, the amount of heat removed by the refrigerant from the air in the evaporator (54)) decreases, the amount of refrigerant evaporated in the evaporator (54) decreases, and the measured value of the suction pressure sensor (46) decreases. Therefore, if no action is taken, the compressor controller (47) reduces the rotational speed of the compressor (51) to maintain the measured value of the suction pressure sensor (46) at the set suction pressure. In such a case, the decrease in the rotational speed of the compressor (51) can be suppressed by increasing the flow rate of gas refrigerant flowing through the gas supply pipe (55).

[0061] The reason for this will be explained below. The refrigerant that has passed through the expansion valve (53) and the gas refrigerant flowing through the gas supply pipe (55) are mixed and then flow into the evaporator (54). A part of the liquid refrigerant contained in the refrigerant that has passed through the expansion valve (53) is heated by the gas refrigerant flowing through the gas supply pipe (55) and evaporates. Therefore, when the opening of the control valve (56) increases and the flow rate of the gas refrigerant flowing through the gas supply pipe (55) increases, the amount of gas refrigerant that the compressor (51) draws from the evaporator (54) increases. As a result, the decrease in the measurement value of the suction pressure sensor (46) is suppressed, and the decrease in the rotational speed of the compressor (51) is also suppressed.

[0062] Therefore, when the measurement value of the frequency sensor (64) is lower than the set frequency, the second controller (77) determines, as the second command value, an opening degree of the regulator valve (56) that is greater than the current opening degree.

[0063] On the other hand, when the measurement value of the frequency sensor (64) is higher than the set frequency, there is a possibility that the rotation speed of the compressor (51) can be maintained at or above the set speed even if the opening of the regulator valve (56) is reduced. Therefore, when the measurement value of the frequency sensor (64) is higher than the set frequency, the second controller (77) determines, as the second command value, an opening smaller than the current opening of the regulator valve (56).

[0064] Incidentally, if the aperture of the control valve (56) changes significantly in a short period of time, the pressure of the refrigerant flowing into the evaporator (54) changes, and accordingly, the expansion valve controller (75) may change the aperture of the expansion valve (53). Therefore, the second controller (77) determines the second command value so that the aperture of the control valve (56) changes gradually to such an extent that the measurement value of the inlet pressure sensor (61) is kept substantially constant.

[0065] <selector> The selector (78) receives the first command value output by the first controller (76) and the second command value output by the second controller (77). The selector (78) is configured to compare the first command value with the second command value and transmit the larger of the first command value and the second command value to the regulator valve (56).

[0066] The regulator valve (56) sets its opening to the opening corresponding to the received first command value or the second command value. As described above, the opening of the regulator valve (56) corresponding to the first command value is the first opening, and the opening of the regulator valve (56) corresponding to the second command value is the second opening. Therefore, the opening of the regulator valve (56) is set to the larger of the first opening and the second opening.

[0067] The first degree of opening is the degree of opening of the regulating valve (56) determined by the first controller (76) so that the degree of superheat of the refrigerant at the outlet of the evaporator (54) becomes a set degree of superheat. The second degree of opening is the degree of opening of the regulating valve (56) determined by the second controller (77) so that the measurement value of the frequency sensor (64) becomes a set frequency.

[0068] If the first command value is greater than the second command value, the selector (78) transmits the first command value to the regulator valve (56). As a result, the opening of the regulator valve (56) is set to the first opening, and the degree of superheat of the refrigerant at the outlet of the evaporator (54) becomes the set superheat. Therefore, the refrigerant drawn into the compressor (51) is kept in a single-phase gas state, and damage to the compressor (51) caused by drawing liquid refrigerant is avoided.

[0069] In this case, the first opening corresponding to the first command value is larger than the second opening corresponding to the second command value. Therefore, when the opening of the control valve (56) is set to the first opening, the measurement value of the frequency sensor (64) becomes higher than the set frequency, and as a result, the rotation speed of the compressor (51) becomes higher than the set speed. Therefore, a sufficient amount of refrigeration oil is ensured to return to the compressor (51) together with the refrigerant, and damage to the compressor (51) due to a shortage of refrigeration oil is prevented.

[0070] If the second command value is greater than the first command value, the selector (78) transmits the second command value to the regulator valve (56). As a result, the degree of opening of the regulator valve (56) is set to the second degree of opening, and the output frequency of the inverter (42) becomes the set frequency. As a result, the rotation speed of the compressor (51) becomes the set speed. Therefore, a sufficient amount of refrigerating machine oil is ensured to return to the compressor (51) together with the refrigerant, and damage to the compressor (51) due to a shortage of refrigerating machine oil is avoided.

[0071] In this case, the second opening corresponding to the second command value is larger than the first opening corresponding to the first command value. Therefore, when the opening of the control valve (56) is set to the second opening, the degree of superheat of the refrigerant at the outlet of the evaporator (54) becomes higher than the set degree of superheat. Therefore, the refrigerant drawn into the compressor (51) is kept in a single-phase gas state, and damage to the compressor (51) due to drawing in liquid refrigerant is avoided.

[0072] -Features of the embodiment (1)- In the air conditioner of this embodiment, the controller (70) controls the opening of the expansion valve (53) based on the measurement value of the inlet pressure sensor (61). That is, the controller (70) controls the opening of the expansion valve (53) based only on the evaporation pressure of the refrigerant in the evaporator (54). When the opening of the expansion valve (53) changes, the pressure of the refrigerant flowing into the evaporator (54) changes, and as a result, the evaporation pressure of the refrigerant in the evaporator (54) changes.

[0073] Therefore, according to this embodiment, a pressure control valve for adjusting the evaporation pressure can be omitted from the refrigerant circuit (50) of the air conditioner (10) while maintaining the function of the air conditioner (10) of "controlling the evaporation pressure of the refrigerant in the evaporator (54)." As a result, layout restrictions when installing the air conditioner (10) can be reduced. Furthermore, since an expensive pressure control valve can be omitted, the cost required for installing the air conditioner (10) can be reduced.

[0074] -Features of the embodiment (2)- In the air conditioner of this embodiment, the controller (70) controls the aperture of the regulator valve (56) provided in the gas supply pipe (55). When the aperture of the regulator valve (56) changes, the flow rate of the gas refrigerant flowing through the gas supply pipe (55) changes, and as a result, the state of the refrigerant flowing into the evaporator (54) changes.

[0075] When the state of the refrigerant flowing into the evaporator (54) changes, the state of the refrigerant flowing out of the evaporator (54) changes, and further, the state of the refrigerant drawn into the compressor (51) changes. When the state of the refrigerant drawn into the compressor (51) changes, the rotation speed of the compressor (51) may change due to the control operation of the compressor controller (47). Therefore, the controller (70) controls the opening of the control valve (56) based on the degree of superheat of the refrigerant at the outlet of the evaporator (54) and the rotation speed of the compressor (51).

[0076] -Features of the embodiment (3)- In the air conditioning apparatus of this embodiment, the selector (78) of the controller (70) transmits the larger of the first command value and the second command value to the regulator valve (56). As a result, the opening of the regulator valve (56) is set to the larger of the “first opening corresponding to the first command value” and the “second opening corresponding to the second command value.”

[0077] The selector (78) functions to maintain the degree of superheat of the refrigerant at the outlet of the evaporator (54) at a set superheat or higher level, so that the refrigerant drawn into the compressor (51) is kept in a single-phase gas state, thereby preventing damage to the compressor (51) due to drawing in liquid refrigerant.

[0078] Furthermore, the function of the selector (78) maintains the rotation speed of the compressor (51) at a set speed or higher, thereby ensuring a sufficient amount of refrigerating machine oil returning to the compressor (51) together with the refrigerant, thereby preventing damage to the compressor (51) due to a shortage of refrigerating machine oil.

[0079] Other Embodiments The following modifications may be applied to the air conditioner (10) of the above embodiment. The following modifications may be combined or substituted as appropriate, as long as the functionality of the air conditioner (10) is not impaired.

[0080] The object for air conditioning by the air conditioner (10) of this embodiment is not limited to the test room (100). The air conditioner (10) of this embodiment may also be used to air condition a large space such as a hall, for example.

[0081] In the air conditioner (10) of this embodiment, the controller (70) may be configured as a single microcomputer. In this case, the microcomputer constituting the controller (70) performs the control operations performed by the expansion valve controller (75), the first controller (76), the second controller (77), and the selector (78). In this case, the microcomputer constituting the controller (70) may also be configured to perform the control operations performed by one or both of the heater controller (37) and the compressor controller (47).

[0082] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and detail are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate. Furthermore, the terms "first," "second," "third," etc. in the specification and claims are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0083] As described above, the present disclosure is useful for air conditioning apparatuses. [Explanation of symbols]

[0084] 10 Air conditioning equipment 50 Refrigerant circuit 51 Compressor 52 Condenser 53 Expansion valve 54 Evaporator 55 Gas supply pipe (gas supply passage) 56 Control valve 61 Inlet pressure sensor (pressure detection part) 70 Controller

Claims

1. An air conditioner (10) comprising a refrigerant circuit (50) having a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54), in which a refrigerant is circulated in the refrigerant circuit (50) to perform a refrigeration cycle, and air is cooled in the evaporator (54), a pressure detector (61) for detecting the evaporation pressure of the refrigerant in the evaporator (54); a controller (70) that controls the opening of the expansion valve (53) based on the evaporation pressure detected by the pressure detection section (61); The refrigerant circuit (50) a gas supply passageway (55) for supplying the gas refrigerant discharged from the compressor (51) to a portion of the refrigerant circuit (50) between the expansion valve (53) and the evaporator (54); a variable opening control valve (56) provided in the gas supply passage (55), The controller (70) controls the opening of the control valve (56) based on the degree of superheat of the refrigerant at the outlet of the evaporator (54) and the rotation speed of the compressor (51). Air conditioning equipment.

2. The pressure detection section (61) a pressure sensor provided between the expansion valve (53) and the evaporator (54) in the refrigerant circuit (50) for measuring the pressure of the refrigerant flowing from the expansion valve (53) to the evaporator (54) as the evaporation pressure; The air conditioning apparatus according to claim 1.

3. The controller (70) an opening degree of the control valve (56) determined to set the superheat degree of the refrigerant at the outlet of the evaporator (54) to a set superheat degree is defined as a first opening degree; the degree of opening of the control valve (56) determined to set the rotation speed of the compressor (51) to a set speed is designated as a second degree of opening; The opening of the control valve (56) is set to the larger of the first opening and the second opening. The air conditioning apparatus according to claim 1 or 2.

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