Air conditioner

Abstract

To improve energy saving performance in an air conditioner.SOLUTION: An air conditioner includes a refrigerant circuit (50) having a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54), performs a refrigeration cycle by circulating a refrigerant in the refrigerant circuit (50), and cools air in the evaporator (54). The air conditioner includes a first detecting unit (65, 66) for detecting at least one of the temperature and the humidity of the air passing through the evaporator (54), and a controller (70) for controlling the opening of the expansion valve (53) on the basis of the detection result of the first detecting unit (65, 66).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an air conditioner.

Background Art

[0002] Conventionally, an air conditioner equipped with a refrigerant circuit has been known. In the refrigerant circuit of the air conditioner, a refrigeration cycle is performed by circulating the refrigerant.

[0003] In an air conditioner, the opening degree of an expansion valve provided upstream of an evaporator in a refrigerant circuit may be controlled based on the superheat degree of the refrigerant at the outlet of the evaporator (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, when the temperature in the set range for air conditioning is as wide as -20°C to 50°C, the size of the evaporator (direct expansion coil) is set to a size that can cool air down to -20°C. In this case, when the set temperature is 50°C, the size (heat transfer area) of the evaporator is too large, so the heat exchange amount becomes excessive compared to the required cooling amount, and it gets too cold. This is because in the above superheat control, the opening degree of the expansion valve is controlled from the viewpoint of completely gasifying the refrigerant at the outlet of the evaporator, and the opening degree of the expansion valve is not controlled from the viewpoint of bringing the temperature of the air cooled by the evaporator closer to the set temperature. If the temperature of the air cooled by the evaporator is much lower than the set temperature, it is necessary to heat the cooled air with a heater or the like to bring it closer to the set temperature. As a result, the energy efficiency is lowered.

[0006] An object of the present disclosure is to improve energy efficiency in an air conditioner.

Means for Solving the Problems

[0007] A first aspect of the present disclosure is directed to an air conditioner. The air conditioner includes a refrigerant circuit (50) having a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54). The refrigerant is circulated in the refrigerant circuit (50) to perform a refrigeration cycle, and air is cooled in the evaporator (54). The air conditioner includes a first detection unit (65, 66) that detects at least one of the temperature and humidity of the air that has passed through the evaporator (54), and a controller (70) that controls the opening degree of the expansion valve (53) based on the detection result of the first detection unit (65, 66).

[0008] According to the first aspect, since the opening degree of the expansion valve (53) can be controlled so that at least one of the temperature and humidity of the air that has passed through the evaporator (54) approaches a target value (desired value), energy efficiency can be improved.

[0009] A second aspect of the present disclosure is the above first aspect, wherein the first detection unit (65) detects the temperature of the air that has passed through the evaporator (54), and the controller (70) determines the opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection unit (65), and controls the opening degree of the expansion valve (53) so as to be the determined opening degree.

[0010] According to the second aspect, since the opening degree of the expansion valve (53) can be controlled so that the temperature of the air that has passed through the evaporator (54) approaches the target temperature, energy efficiency can be improved.

[0011] A third aspect of the present disclosure is the above first aspect, wherein the first detection unit (66) detects the humidity of the air that has passed through the evaporator (54), and the controller (70) determines the opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection unit (66), and controls the opening degree of the expansion valve (53) so as to be the determined opening degree.

[0012] According to the third aspect, since the opening degree of the expansion valve (53) can be controlled so that the humidity of the air passing through the evaporator (54) approaches the target humidity, the energy saving performance can be improved.

[0013] According to a fourth aspect of the present disclosure, in the first aspect, the first detection units (65, 66) detect the temperature of the air passing through the evaporator (54) and the humidity of the air passing through the evaporator (54), and the controller (70) determines a first opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection units (65, 66), determines a second opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection units (65, 66), and controls the opening degree of the expansion valve (53) so as to be the larger one of the first opening degree and the second opening degree.

[0014] According to the fourth aspect, since the opening degree of the expansion valve (53) can be controlled so that the temperature or humidity of the air passing through the evaporator (54) approaches the target value (desired value), the energy saving performance can be improved.

[0015] According to a fifth aspect of the present disclosure, in the first aspect, the air conditioner includes a second detection unit (63) that detects the temperature of the refrigerant flowing from the evaporator (54) toward the compressor (51), and a third detection unit (62) that detects the pressure of the refrigerant flowing from the evaporator (54) toward the compressor (51), and the controller (70) further controls the opening degree of the expansion valve (53) based on the detection result of the second detection unit (63) and the detection result of the third detection unit (62).

[0016] According to the fifth aspect, it is possible to suppress a decrease in the superheat degree of the refrigerant at the outlet of the evaporator and protect the compressor.

[0017] The sixth aspect of the present disclosure is, in the fifth aspect described above, the first detection unit (65) detects the temperature of the air that has passed through the evaporator (54), and the controller (70) determines a third opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection unit (65), determines a fourth opening degree of the expansion valve (53) based on the temperature of the refrigerant detected by the second detection unit (63) and the pressure of the refrigerant detected by the third detection unit (62), and controls the opening degree of the expansion valve (53) so as to be the smaller one of the third opening degree and the fourth opening degree.

[0018] According to the sixth aspect, it is possible to improve energy saving while suppressing a decrease in the superheat degree of the refrigerant at the outlet of the evaporator.

[0019] The seventh aspect of the present disclosure is, in the fifth aspect described above, the first detection unit (66) detects the humidity of the air that has passed through the evaporator (54), and the controller (70) determines a fifth opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection unit (66), determines a sixth opening degree of the expansion valve (53) based on the temperature of the refrigerant detected by the second detection unit (63) and the pressure of the refrigerant detected by the third detection unit (62), and controls the opening degree of the expansion valve (53) so as to be the smaller one of the fifth opening degree and the sixth opening degree.

[0020] According to the seventh aspect, it is possible to improve energy saving while suppressing a decrease in the superheat degree of the refrigerant at the outlet of the evaporator.

[0021] The eighth aspect of the present disclosure is that, in the fifth aspect, the first detection units (65, 66) detect the temperature of the air that has passed through the evaporator (54) and the humidity of the air that has passed through the evaporator (54), and the controller (70) determines a seventh opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection units (65, 66), determines an eighth opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection units (65, 66), determines a ninth opening degree which is the larger one of the seventh opening degree and the eighth opening degree, determines a tenth opening degree of the expansion valve (53) based on the temperature of the refrigerant detected by the second detection unit (63) and the pressure of the refrigerant detected by the third detection unit (62), and controls the opening degree of the expansion valve (53) to be the smaller one of the ninth opening degree and the tenth opening degree.

[0022] According to the eighth aspect, it is possible to enhance energy saving while suppressing a decrease in the superheat degree of the refrigerant at the outlet of the evaporator.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that the present disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical idea of the present disclosure. Since each drawing is for conceptually explaining the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for easy understanding. In each embodiment, modification example, and figure, the same or corresponding parts are denoted by the same reference numerals, and detailed descriptions and explanations of their accompanying effects, etc., will not be repeated.

[0025] - First Embodiment - An embodiment will be described. The air conditioner (10) of this embodiment performs air conditioning in a test chamber (100) used for automobile driving tests and the like.

[0026] The air conditioner (10) includes a user-side unit (20) and a heat source-side unit (40). The air conditioner also includes a refrigerant circuit (50).

[0027] - User-Side 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 intake port (27) is formed on one end face of the casing (25), and an outlet port (28) is formed on the other end face of the casing (25). An air flow path (26) is formed inside the casing (25) from the intake port (27) to the outlet port (28).

[0028] The user-side unit (20) is connected to the test chamber (100) via an intake duct (16) and an outlet duct (17). The intake duct (16) is connected to the intake port (27) of the casing (25) and communicates the air flow path (26) with the internal space of the test chamber (100). The outlet duct (17) is connected to the outlet port (28) of the casing (25) and communicates the air flow path (26) with the internal space of the test chamber (100).

[0029] In the air flow path (26) within the casing (25), a filter (31), an evaporator (54), an electric heater (32), and a user-side fan (33) are provided in order from the suction port (27) side toward the blowout port (28) side. The filter (31) collects dust and the like contained in the air flowing in from 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) sucks in the air that has passed through the electric heater (32) and blows the air toward the blowout port (28).

[0030] 〈Operation〉 The operation of the user-side unit (20) will be described.

[0031] When the user-side fan (33) operates, the air in the internal space of the test chamber (100) flows into the air flow path (26) within the casing (25) through the suction duct (16). The air flowing through the air flow path (26) passes through the filter (31), the evaporator (54), and the electric heater (32) in order.

[0032] The air is cooled in the process of passing through the evaporator (54) and heated in the process of 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 blowout duct (17), and then is blown out into the internal space of the test chamber (100).

[0033] -Air temperature sensor, heater controller- The air conditioner (10) includes an air temperature sensor (36) and a heater controller (37).

[0034] The air temperature sensor (36) is provided in the blowout duct (17) and measures the temperature of the air flowing through the blowout duct (17). The measured value of the air temperature sensor (36) indicates the temperature of the air that the user-side unit (20) supplies to the internal space of the test chamber (100).

[0035] The measured value of the air temperature sensor (36) is input to the heater controller (37). The heater controller (37) controls the heating amount of the electric heater (32) based on the measured value of the air temperature sensor (36). Specifically, the heater controller (37) adjusts the heating amount of the electric heater (32) so that the measured value of the air temperature sensor (36) becomes the set air temperature. When the measured value of the air temperature sensor (36) is lower than the set air temperature, the heater controller (37) increases the heating amount of the electric heater (32). When the measured value of the air temperature sensor (36) is higher than the set air temperature, the heater controller (37) decreases the heating amount of the electric heater (32).

[0036] - Refrigerant circuit - The refrigerant circuit (50) is a closed circuit filled with refrigerant. The refrigerant circuit (50) performs a refrigeration cycle by circulating the refrigerant.

[0037] As shown in FIG. 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 order from the discharge port to the suction port of the compressor (51). A receiver (57) for storing the surplus refrigerant due to the fluctuation of the heat load is provided between the condenser (52) and the expansion valve (53) in the refrigerant circuit (50).

[0038] The compressor (51) compresses and discharges the inhaled 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 variable opening degree. The evaporator (54) is a cross - fin type air heat exchanger that exchanges heat between the refrigerant and the air in the air flow path (26).

[0039] 〈Refrigeration cycle〉 The refrigeration cycle performed by the refrigerant circuit (50) will be described.

[0040] When the compressor (51) operates, the refrigerant circulates in the refrigerant circuit (50). The refrigerant discharged from the compressor (51) flows into the condenser (52), releases heat to the outdoor air passing through the condenser (52), and condenses. The refrigerant flowing out from the condenser (52) is depressurized in the process of passing through the expansion valve (53), and then flows into the evaporator (54).

[0041] The refrigerant flowing into the evaporator (54) absorbs heat from the air passing through the evaporator (54) and evaporates. The refrigerant flowing out from the evaporator (54) is sucked into the compressor (51) and compressed. The compressor (51) compresses and discharges the sucked refrigerant.

[0042] -Heat source unit- The heat source side unit (40) is provided with the compressor (51) and the condenser (52) of the refrigerant circuit (50). Further, the heat source side unit (40) 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, an external power source such as a commercial power supply is connected to the inverter (42). The inverter (42) converts the supplied AC frequency into a set frequency and supplies the AC of the set frequency to the motor of the compressor (51). When the output frequency of the inverter (42) is changed, the rotational speed of the compressor (51) changes.

[0043] The heat source side unit (40) includes a suction pressure sensor (46). The suction pressure sensor (46) is connected to the refrigerant circuit (50). The suction pressure sensor (46) is attached to the pipe connected to the suction port of the compressor (51) and measures (detects) the pressure of the refrigerant sucked into the compressor (51).

[0044] 〈Compressor controller〉 The heat source side unit (40) includes a compressor controller (47). The measured value of the suction pressure sensor (46) is input to the compressor controller (47). The compressor controller (47) is configured to control the rotational speed of the compressor (51) based on the measured value of the suction pressure sensor (46).

[0045] Specifically, the compressor controller (47) adjusts the rotational speed of the compressor (51) such that the measured value of the suction pressure sensor (46) becomes the set suction pressure. When the measured value of the suction pressure sensor (46) is lower than the set suction pressure, the compressor controller (47) reduces the rotational speed of the compressor (51) by lowering the output frequency of the inverter (42). When the measured value of the suction pressure sensor (46) is higher than the set suction pressure, the compressor controller (47) increases the rotational speed of the compressor (51) by increasing the output frequency of the inverter (42).

[0046] - Sensor - The air conditioner (10) includes a frequency sensor (64) and a temperature sensor (65).

[0047] The frequency sensor (64) is provided on the power supply electrical 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 alternating current that the inverter (42) supplies to the compressor (51), in other words, the drive frequency of the compressor (51).

[0048] The temperature sensor (65) detects the temperature of the air that has passed through the evaporator (54). The temperature sensor (65) is provided downstream of the evaporator (54) in the air flow path provided to pass through the evaporator (54), and detects the temperature of the air downstream of the evaporator (54). The temperature sensor (65) is provided around the evaporator (54) and detects the temperature of the air around the evaporator (54). In the first embodiment, the temperature sensor (65) is provided, for example, between the evaporator (54) and the electric heater (32) inside the casing (25), and detects the temperature of the air between the evaporator (54) and the electric heater (32). The measured value of the temperature sensor (65) indicates the temperature of the air that has passed through the evaporator (54). The air is cooled by heat exchange with the refrigerant when passing through the evaporator (54). The temperature sensor (65) is the first example of the first detection unit.

[0049] - Controller - The air conditioner (10) includes a first expansion valve controller (75). The compressor controller (47) and the first expansion valve controller (75) constitute a controller (70) that controls the expansion valve (53).

[0050] 〈First Expansion Valve Controller〉 The measured value of the temperature sensor (65) is input to the first expansion valve controller (75). The first expansion valve controller (75) is configured to calculate a first command value regarding the opening degree of the expansion valve (53) based on the measured value of the temperature sensor (65).

[0051] Specifically, the first expansion valve controller (75) calculates the opening degree of the expansion valve (53) such that the measured value of the temperature sensor (65) becomes a predetermined target temperature, and determines the calculated opening degree as the first command value regarding the opening degree of the expansion valve (53). The first expansion valve controller (75) transmits the determined first command value to the expansion valve (53). As a result, the opening degree of the expansion valve (53) becomes the opening degree corresponding to the first command value. According to this, it is possible to suppress the heat exchange amount from becoming excessive compared to the required cooling amount in the evaporator (54), and the temperature of the air after cooling by the evaporator (54) can be brought closer to the predetermined target temperature. As a result, it is possible to suppress the temperature of the air after cooling by the evaporator (54) from deviating from the predetermined target temperature, and it becomes unnecessary to perform a heat treatment for bringing the air after cooling by the evaporator (54) closer to the predetermined target temperature, so the energy efficiency can be improved.

[0052] When the measured value of the temperature sensor (65) is higher than the predetermined target temperature, the first expansion valve controller (75) transmits, as the first command value, an opening degree larger than the current opening degree of the expansion valve (53) to the expansion valve (53). The opening degree of the expansion valve (53) expands to the opening degree corresponding to the first command value. When the opening degree of the expansion valve (53) expands, the amount of refrigerant flowing into the evaporator (54) increases. As a result, the cooling of the air by the evaporator (54) is promoted.

[0053] When the measured value of the temperature sensor (65) is lower than a predetermined target temperature, the first expansion valve controller (75) transmits, as a first command value, an opening degree smaller than the current opening degree of the expansion valve (53) to the expansion valve (53). The opening degree of the expansion valve (53) is reduced to the opening degree corresponding to the first command value. When the opening degree of the expansion valve (53) is reduced, the amount of refrigerant flowing into the evaporator (54) decreases. As a result, the cooling of the air by the evaporator (54) is suppressed.

[0054] - Second Embodiment - A second embodiment of the air conditioner (10) will be described. Hereinafter, mainly the differences from the first embodiment will be described.

[0055] As shown in FIG. 3, the air conditioner (10) of the second embodiment is different from the first embodiment in that it further includes a humidity sensor (66) and a second expansion valve controller (76), and does not include a temperature sensor (65) and a first expansion valve controller (75).

[0056] In the second embodiment, the second expansion valve controller (76) constitutes a controller (70) that controls the expansion valve (53).

[0057] The humidity sensor (66) detects the humidity of the air that has passed through the evaporator (54). The humidity sensor (66) is provided downstream of the evaporator (54) in the air flow path provided so as to pass through the evaporator (54), and detects the humidity of the air downstream of the evaporator (54). The humidity sensor (66) is provided around the evaporator (54) and detects the humidity of the air around the evaporator (54). In the second embodiment, the humidity sensor (66) is provided, for example, between the evaporator (54) and the electric heater (32) inside the casing (25), and detects the humidity of the air between the evaporator (54) and the electric heater (32). The measured value of the humidity sensor (66) indicates the humidity of the air that has passed through the evaporator (54). The humidity sensor (66) is a second example of the first detection unit.

[0058] 〈Second Expansion Valve Controller〉 The measurement value of the humidity sensor (66) is input to the second expansion valve controller (76). The second expansion valve controller (76) is configured to calculate a second command value regarding the opening degree of the expansion valve (53) based on the measurement value of the humidity sensor (66).

[0059] Specifically, the second expansion valve controller (76) calculates the opening degree of the expansion valve (53) such that the measurement value of the humidity sensor (66) becomes a predetermined target humidity, and determines the calculated opening degree as the second command value regarding the opening degree of the expansion valve (53). The second expansion valve controller (76) transmits the determined second command value to the expansion valve (53). As a result, the opening degree of the expansion valve (53) becomes the opening degree corresponding to the second command value. According to this, the humidity of the air after dehumidification by the evaporator (54) can be made closer to the predetermined target humidity. As a result, it is possible to suppress the deviation of the humidity of the air after dehumidification by the evaporator (54) from the predetermined target humidity, and it is not necessary to perform a humidification process to bring the humidity of the air after dehumidification by the evaporator (54) closer to the predetermined target humidity, so the energy efficiency can be improved.

[0060] When the measurement value of the humidity sensor (66) is higher than the predetermined target humidity, the second expansion valve controller (76) transmits, as the second command value, an opening degree larger than the current opening degree of the expansion valve (53) to the expansion valve (53). The opening degree of the expansion valve (53) expands to the opening degree corresponding to the second command value. When the opening degree of the expansion valve (53) expands, the amount of refrigerant flowing into the evaporator (54) increases. As a result, the dehumidification of the air by the evaporator (54) is promoted.

[0061] When the measurement value of the humidity sensor (66) is lower than the predetermined target temperature, the second expansion valve controller (76) transmits, as the second command value, an opening degree smaller than the current opening degree of the expansion valve (53) to the expansion valve (53). The opening degree of the expansion valve (53) contracts to the opening degree corresponding to the second command value. When the opening degree of the expansion valve (53) contracts, the amount of refrigerant flowing into the evaporator (54) decreases. As a result, the dehumidification of the air by the evaporator (54) is suppressed.

[0062] -Third Embodiment- A third embodiment of the air conditioner (10) will be described. Hereinafter, the differences from the first embodiment will mainly be described.

[0063] As shown in FIG. 4, the air conditioner (10) of the third embodiment is different from the first embodiment in that it further includes a humidity sensor (66), a second expansion valve controller (76), and a first selector (77).

[0064] In the third embodiment, the first expansion valve controller (75), the second expansion valve controller (76), and the first selector (77) constitute a controller (70) that controls the expansion valve (53).

[0065] 〈First Selector〉 The first selector (77) receives the first command value output by the first expansion valve controller (75) and the second command value output by the second expansion valve controller (76). The first selector (77) compares the first command value and the second command value, and is configured to transmit the larger one of the first command value and the second command value to the expansion valve (53).

[0066] The expansion valve (53) sets its opening degree to the opening degree corresponding to the received one of the first command value and the second command value. As described above, the opening degree of the expansion valve (53) corresponding to the first command value is the first opening degree, and the opening degree of the expansion valve (53) corresponding to the second command value is the second opening degree. Therefore, the opening degree of the expansion valve (53) is set to the larger one of the first opening degree and the second opening degree.

[0067] When the first command value is larger than the second command value, the first selector (77) transmits the first command value to the expansion valve (53). Therefore, since the opening degree of the expansion valve (53) is set to the first opening degree, when the expansion valve (53) cools and dehumidifies the air, the temperature of the air can be brought close to a predetermined target temperature. Therefore, air having a temperature near the predetermined target temperature can be sent to the test chamber (100).

[0068] In this case, the first opening degree corresponding to the first command value is larger than the second opening degree corresponding to the second command value. Therefore, when the opening degree of the expansion valve (53) is set to the first opening degree, the humidity of the air cooled and dehumidified by the expansion valve (53) becomes lower than a predetermined target humidity. Accordingly, it is possible to avoid sending air having a humidity higher than the predetermined target humidity to the test chamber (100).

[0069] When the second command value is larger than the first command value, the first selector (77) transmits the second command value to the expansion valve (53). Therefore, since the opening degree of the expansion valve (53) is set to the second opening degree, it is possible to bring the humidity of the air close to the predetermined target humidity when the expansion valve (53) cools and dehumidifies the air. Accordingly, it is possible to send air having a humidity near the predetermined target humidity to the test chamber (100).

[0070] In this case, the second opening degree corresponding to the second command value is larger than the first opening degree corresponding to the first command value. Therefore, when the opening degree of the expansion valve (53) is set to the second opening degree, the temperature of the air cooled and dehumidified by the expansion valve (53) becomes lower than a predetermined target temperature. Accordingly, it is possible to avoid sending air having a temperature higher than the predetermined target temperature to the test chamber (100).

[0071] -Fourth Embodiment- A fourth embodiment of the air conditioner (10) will be described. Hereinafter, mainly the differences from the first embodiment will be described.

[0072] As shown in FIG. 5, the air conditioner (10) according to the fourth embodiment is different from the first embodiment in that it further includes an outlet-side pressure sensor (62), an outlet-side temperature sensor (63), a third expansion valve controller (78), and a second selector (79).

[0073] In the fourth embodiment, the first expansion valve controller (75), the third expansion valve controller (78), and the second selector (79) constitute a controller (70) that controls the expansion valve (53).

[0074] The outlet pressure sensor (62) and the outlet temperature sensor (63) are attached to the pipe connected to the outlet of the evaporator (54). The outlet pressure sensor (62) detects the pressure of the refrigerant flowing out of the evaporator (54) and the pressure of the refrigerant flowing from the evaporator (54) toward the compressor (51). The outlet pressure sensor (62) is an example of a third detection unit. The outlet temperature sensor (63) detects the temperature of the refrigerant flowing out of the evaporator (54) and the temperature of the refrigerant flowing from the evaporator (54) toward the compressor (51). The outlet temperature sensor (63) is an example of a second detection unit.

[0075] 〈Third Expansion Valve Controller〉 The measured value of the outlet pressure sensor (62) and the measured value of the outlet temperature sensor (63) are input to the third expansion valve controller (78). The third expansion valve controller (78) is configured to calculate a third command value regarding the opening degree of the expansion valve (53) based on the measured values of the outlet pressure sensor (62) and the outlet temperature sensor (63).

[0076] First, the third expansion valve controller (78) calculates the superheat degree of the refrigerant at the outlet of the evaporator (54). The third expansion valve controller (78) uses the value obtained by subtracting the "saturation temperature Ts of the refrigerant corresponding to the measured value of the outlet pressure sensor (62)" from the "measured value T of the outlet temperature sensor (63)" as the superheat degree SH (= T - Ts) of the refrigerant at the outlet of the expansion valve (53).

[0077] Next, the third expansion valve controller (78) calculates the opening degree of the expansion valve (53) such that the superheat degree of the refrigerant at the outlet of the evaporator (54) becomes the set superheat degree. The opening degree calculated by this third expansion valve controller (78) is the third opening degree. The third expansion valve controller (78) determines the calculated third opening degree as the third command value regarding the opening degree of the expansion valve (53). The third expansion valve controller (78) transmits the determined third command value to the expansion valve (53). As a result, the opening degree of the expansion valve (53) becomes the third opening degree corresponding to the third command value.

[0078] Here, when the refrigerant at the outlet of the evaporator (54) becomes wet, liquid refrigerant may be sucked into the compressor (51), and as a result, the compressor (51) may be damaged. 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 gas single-phase state.

[0079] On the other hand, when the opening degree of the expansion valve (53) is changed, the amount of refrigerant flowing into the evaporator (54) changes, and as a result, the state of the refrigerant at the outlet of the evaporator (54) changes. Therefore, the third expansion valve controller (78) calculates the opening degree of the expansion valve (53) such that the superheat degree of the refrigerant at the outlet of the evaporator (54) becomes the set superheat degree (for example, a value within the range of 5K or more and 10K or less), so as to completely gasify the refrigerant at the outlet of the evaporator (54).

[0080] When the opening degree of the expansion valve (53) is reduced, the amount of refrigerant flowing into the evaporator (54) decreases, and as a result, the superheat degree of the refrigerant at the outlet of the evaporator (54) increases. Therefore, when the superheat degree of the refrigerant at the outlet of the evaporator (54) is lower than the set superheat degree, the third expansion valve controller (78) determines an opening degree smaller than the current opening degree of the expansion valve (53) as the third command value.

[0081] On the other hand, when the opening degree of the expansion valve (53) is increased, the amount of refrigerant flowing into the evaporator (54) increases, and as a result, the superheat degree of the refrigerant at the outlet of the evaporator (54) decreases. Therefore, when the superheat degree of the refrigerant at the outlet of the evaporator (54) is higher than the set superheat degree, the third expansion valve controller (78) determines an opening degree larger than the current opening degree of the expansion valve (53) as the third command value.

[0082] <Second Selector> The second selector (79) receives the first command value output by the first expansion valve controller (75) and the third command value output by the third expansion valve controller (78). The second selector (79) compares the first command value and the third command value, and is configured to transmit the smaller one of the first command value and the third command value to the expansion valve (53).

[0083] The expansion valve (53) sets its opening degree to the opening degree corresponding to the received one of the first command value and the third command value. As described above, the opening degree of the expansion valve (53) corresponding to the first command value is the first opening degree, and the opening degree of the expansion valve (53) corresponding to the third command value is the third opening degree. Therefore, the opening degree of the expansion valve (53) is set to the smaller one of the first opening degree and the third opening degree.

[0084] When the first command value is smaller than the third command value, the second selector (79) transmits the first command value to the expansion valve (53). Therefore, the opening degree of the expansion valve (53) is set to the first opening degree.

[0085] In this case, the first opening degree corresponding to the first command value is smaller than the third opening degree corresponding to the third command value. Therefore, when the opening degree of the expansion valve (53) is set to the first opening degree, the superheat degree of the refrigerant at the outlet of the evaporator (54) becomes higher than the set superheat degree. Accordingly, the refrigerant sucked into the compressor (51) is kept in a gas single-phase state, and damage to the compressor (51) caused by sucking liquid refrigerant is avoided.

[0086] When the third command value is smaller than the first command value, the second selector (79) transmits the third command value to the expansion valve (53). Therefore, the opening degree of the expansion valve (53) is set to the third opening degree, and the superheat degree of the refrigerant at the outlet of the evaporator (54) becomes the set superheat degree. Accordingly, the refrigerant sucked into the compressor (51) is kept in a gas single-phase state, and damage to the compressor (51) caused by sucking liquid refrigerant is avoided.

[0087] In this case, the third opening degree corresponding to the third command value is smaller than the first opening degree corresponding to the first command value. Therefore, when the opening degree of the expansion valve (53) is set to the third opening degree, it is possible to avoid sending air at a temperature higher than a predetermined target temperature to the test chamber (100).

[0088] - Fifth Embodiment - The fifth embodiment of the air conditioner (10) will be described. Hereinafter, mainly the differences from the second embodiment will be described.

[0089] As shown in FIG. 6, the air conditioner (10) of the fifth embodiment is different from the second embodiment in that it further includes an outlet-side pressure sensor (62), an outlet-side temperature sensor (63), a third expansion valve controller (78), and a third selector (80).

[0090] In the fifth embodiment, the second expansion valve controller (76), the third expansion valve controller (78), and the third selector (80) constitute a controller (70) that controls the expansion valve (53).

[0091] 〈Third Selector〉 The third selector (80) receives the second command value output by the second expansion valve controller (76) and the third command value output by the third expansion valve controller (78). The third selector (80) compares the second command value and the third command value, and is configured to transmit the smaller one of the second command value and the third command value to the expansion valve (53).

[0092] The expansion valve (53) sets its opening degree to the opening degree corresponding to the received one of the second command value and the third command value. As described above, the opening degree of the expansion valve (53) corresponding to the second command value is the second opening degree, and the opening degree of the expansion valve (53) corresponding to the third command value is the third opening degree. Therefore, the opening degree of the expansion valve (53) is set to the smaller one of the second opening degree and the third opening degree.

[0093] When the second command value is smaller than the third command value, the third selector (80) transmits the second command value to the expansion valve (53). Therefore, the opening degree of the expansion valve (53) is set to the second opening degree.

[0094] In this case, since the second opening degree corresponding to the second command value is smaller than the third opening degree corresponding to the third command value, the superheat degree of the refrigerant at the outlet of the evaporator (54) becomes higher than the set superheat degree. Therefore, the refrigerant sucked into the compressor (51) is kept in a gas single-phase state, and damage to the compressor (51) caused by sucking liquid refrigerant is avoided.

[0095] When the third command value is smaller than the second command value, the third selector (80) transmits the third command value to the expansion valve (53). Therefore, the opening degree of the expansion valve (53) is set to the third opening degree.

[0096] In this case, the third opening degree corresponding to the third command value is smaller than the second opening degree corresponding to the second command value. Therefore, when the opening degree of the expansion valve (53) is set to the third opening degree, it is possible to avoid sending air with a humidity higher than a predetermined target humidity to the test chamber (100).

[0097] - Sixth Embodiment - A sixth embodiment of the air conditioner (10) will be described. Hereinafter, mainly the differences from the third embodiment will be described.

[0098] As shown in FIG. 7, the air conditioner (10) of the sixth embodiment is different from the third embodiment in that it further includes an outlet-side pressure sensor (62), an outlet-side temperature sensor (63), a third expansion valve controller (78), and a fourth selector (81).

[0099] Further, in the air conditioner (10) of the sixth embodiment, the command value output by the first selector (77) is transmitted not to the expansion valve (53) but to the fourth selector (81), which is different from the third embodiment.

[0100] As described above, the first selector (77) outputs the larger command value of the first command value and the second command value. Hereinafter, the command value output by the first selector (77) (the larger command value of the first command value and the second command value) may be referred to as the fourth command value. The opening degree of the expansion valve (53) corresponding to the fourth command value may be referred to as the fourth opening degree.

[0101] In the sixth embodiment, the first expansion valve controller (75), the second expansion valve controller (76), the first selector (77), the third expansion valve controller (78), and the fourth selector (81) constitute a controller (70) that controls the expansion valve (53).

[0102] 〈Fourth Selector〉 The fourth selector (81) receives the third command value output by the third expansion valve controller (78) and the fourth command value output by the first selector (77). The fourth selector (81) compares the third command value with the fourth command value, and is configured to transmit the smaller one of the third command value and the fourth command value to the expansion valve (53).

[0103] The expansion valve (53) sets its opening degree to the opening degree corresponding to the received one of the third command value and the fourth command value. As described above, the opening degree of the expansion valve (53) corresponding to the third command value is the third opening degree, and the opening degree of the expansion valve (53) corresponding to the fourth command value is the fourth opening degree. Therefore, the opening degree of the expansion valve (53) is set to the smaller one of the third opening degree and the fourth opening degree.

[0104] When the third command value is smaller than the fourth command value, the fourth selector (81) transmits the third command value to the expansion valve (53). Therefore, the opening degree of the expansion valve (53) is set to the third opening degree.

[0105] When the fourth command value is smaller than the third command value, the fourth selector (81) transmits the fourth command value to the expansion valve (53). Therefore, the opening degree of the expansion valve (53) is set to the fourth opening degree.

[0106] 《Other Embodiments》 Regarding the air conditioner (10) of the above embodiment, the following modifications may be applied. Note that the following modifications may be appropriately combined or replaced as long as the functions of the air conditioner (10) are not impaired.

[0107] The object for which the air conditioners (10) of the first to sixth embodiments perform air conditioning is not limited to the laboratory (100). The air conditioners (10) of the first to sixth embodiments may be used, for example, for air conditioning large spaces such as halls.

[0108] Also, in the air conditioner (10) of the first to sixth embodiments, each of the first expansion valve controller (75), the second expansion valve controller (76), the first selector (77), the third expansion valve controller (78), the second selector (79), the third selector (80), and the fourth selector (81) may include a microcomputer. Further, the controller (70) may be constituted by one microcomputer. Further, the microcomputer constituting the controller (70) may be configured to perform control operations performed by at least one of the compressor controller (47) and the heater controller (37).

[0109] Also, for the air conditioner (10) of the first to sixth embodiments, a gas supply pipe that bypasses the condenser (52) and sends the gas refrigerant (hot gas) discharged from the compressor (51) to the evaporator (54) may be provided in the refrigerant circuit (50). A regulating valve may be provided in the gas supply pipe, and a hot gas flow control configuration may be provided to control the supply amount of hot gas to the evaporator (54) by adjusting the opening degree of the regulating valve based on the pressure of the refrigerant flowing out of the evaporator (54).

[0110] As described above, the embodiments and modified examples have been described. It will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. Also, the elements according to the above embodiments, modified examples, and other embodiments may be combined or replaced as appropriate. Also, the descriptions such as "first", "second", "third",... in the specification and claims are used to distinguish the phrases to which these descriptions are given, and do not limit the number or order of these phrases either.

Industrial Applicability

[0111] As described above, the present disclosure is useful for air conditioners.

Explanation of Signs

[0112] 10 Air conditioner 50 Refrigerant circuit 51 Compressor 52 Condenser 53 Expansion valve 54 Evaporator 62 Outlet side temperature sensor (third detection unit) 63 Outlet side pressure sensor (second detection unit) 65 Air conditioner (first detection unit) 66 Air conditioner (first detection unit) 70 Controller

Claims

1. An air conditioner comprising a refrigerant circuit (50) having a compressor (51), a condenser (52), an expansion valve (53), and an evaporator (54), circulating refrigerant in the refrigerant circuit (50) to perform a refrigeration cycle, and cooling air in the evaporator (54), a first detection unit (65, 66) for detecting at least one of the temperature and humidity of the air that has passed through the evaporator (54), and a controller (70) for controlling the opening degree of the expansion valve (53) based on the detection result of the first detection unit (65, 66). An air conditioner comprising the above components.

2. The first detection unit (65) detects the temperature of the air that has passed through the evaporator (54), and the controller (70) determines the opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection unit (65), and controls the opening degree of the expansion valve (53) to be the determined opening degree. The air conditioner according to claim 1.

3. The first detection unit (66) detects the humidity of the air that has passed through the evaporator (54), and the controller (70) determines the opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection unit (66), and controls the opening degree of the expansion valve (53) to be the determined opening degree. The air conditioner according to claim 1.

4. The first detection unit (65, 66) detects the temperature of the air that has passed through the evaporator (54), and the humidity of the air that has passed through the evaporator (54), and the controller (70) determines a first opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection unit (65), determines a second opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection unit (66), and controls the opening degree of the expansion valve (53) to be the larger of the first opening degree and the second opening degree. The air conditioner according to claim 1.

5. a second detection unit (63) for detecting the temperature of the refrigerant flowing from the evaporator (54) toward the compressor (51), and a third detection unit (62) for detecting the pressure of the refrigerant flowing from the evaporator (54) toward the compressor (51), and the controller (70) further controls the opening degree of the expansion valve (53) based on the detection result of the second detection unit (63) and the detection result of the third detection unit (62). The air conditioner according to claim 1.

6. The first detection unit (65) detects the temperature of the air that has passed through the evaporator (54), The controller (70) determines a third opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection unit (65), determines a fourth opening degree of the expansion valve (53) based on the temperature of the refrigerant detected by the second detection unit (63) and the pressure of the refrigerant detected by the third detection unit (62), The air conditioner according to claim 5, wherein the opening degree of the expansion valve (53) is controlled to be the smaller one of the third opening degree and the fourth opening degree.

7. The first detection unit (66) detects the humidity of the air that has passed through the evaporator (54), The controller (70) determines a fifth opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection unit (66), determines a sixth opening degree of the expansion valve (53) based on the temperature of the refrigerant detected by the second detection unit (63) and the pressure of the refrigerant detected by the third detection unit (62), The air conditioner according to claim 5, wherein the opening degree of the expansion valve (53) is controlled to be the smaller one of the fifth opening degree and the sixth opening degree.

8. The first detection units (65, 66) detect the temperature of the air that has passed through the evaporator (54) and the humidity of the air that has passed through the evaporator (54), The controller (70) determines a seventh opening degree of the expansion valve (53) based on the temperature of the air detected by the first detection unit (65), determines an eighth opening degree of the expansion valve (53) based on the humidity of the air detected by the first detection unit (66), determines a ninth opening degree which is the larger one of the seventh opening degree and the eighth opening degree, determines a tenth opening degree of the expansion valve (53) based on the temperature of the refrigerant detected by the second detection unit (63) and the pressure of the refrigerant detected by the third detection unit (62), The air conditioner according to claim 5, wherein the opening degree of the expansion valve (53) is controlled to be the smaller one of the ninth opening degree and the tenth opening degree.

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