Dryer

Abstract

We can provide a dryer that shortens the drying process time. [Solution] The dryer according to the present disclosure comprises a storage tank for storing an object, a heat pump device connecting a compressor, a condenser, an expansion mechanism, and an evaporator with refrigerant piping for circulating a refrigerant, an air passage member defining an air passage between the storage tank and the heat pump device, a fan provided in the air passage member for circulating air between the storage tank and the heat pump device, a first sensor provided in the condenser for measuring a first temperature of the refrigerant, and a control unit for controlling the compressor and the expansion mechanism. The expansion mechanism has a flow rate adjustment unit that can change the flow rate of the incoming refrigerant, and the control unit controls the flow rate adjustment unit so that the flow rate of the refrigerant flowing into the expansion mechanism increases when the first temperature exceeds a first threshold.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a dryer. BACKGROUND ART

[0002] For example, Patent Document 1 discloses a dryer including a heat pump device in which a compressor, a condenser, an expansion means, and an evaporator are sequentially connected in an annular configuration. The heat pump device dehumidifies and heats air in a tub to dry clothes.

[0003] The dryer described in Patent Document 1 further includes an auxiliary cooler on the air inlet side of the evaporator for cooling air flowing into the evaporator. As drying progresses, when the operating pressure of the heat pump device rises, the auxiliary cooler cools the air flowing into the evaporator to suppress an excessive increase in evaporation pressure. PRIOR ART DOCUMENT PATENT DOCUMENT

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2008-48811 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0005] Suppressing an increase in the operating pressure of the heat pump device can avoid interruption of the operation of the compressor. On the other hand, when air flowing into the evaporator is cooled as in Patent Document 1, the absolute humidity of the air increases, which may prolong the drying process. Therefore, there is still room for improvement in terms of shortening the drying process time while suppressing an increase in the operating pressure of the heat pump device.

[0006] An object of the present disclosure is to solve the above problem and provide a dryer with a shortened drying process time. MEANS FOR SOLVING THE PROBLEM

[0007] A dryer according to one aspect of the present disclosure includes a storage tank for storing an object, a heat pump device connecting a compressor, a condenser, an expansion mechanism, and an evaporator with refrigerant piping for circulating a refrigerant, an air passage member defining an air passage between the storage tank and the heat pump device, a fan provided in the air passage member for circulating air between the storage tank and the heat pump device, a first sensor provided in the condenser for measuring a first temperature of the refrigerant, and a control unit for controlling the compressor and the expansion mechanism, wherein the expansion mechanism has a flow rate adjustment unit that can change the flow rate of the incoming refrigerant, and the control unit controls the flow rate adjustment unit so that the flow rate of the refrigerant flowing into the expansion mechanism increases when the first temperature exceeds a first threshold. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a dryer that shortens the drying process time. [Brief explanation of the drawing]

[0009] [Figure 1] Schematic cross-sectional view of a dryer according to the embodiment of this disclosure [Figure 2] Schematic diagram of a heat pump system [Figure 3] Mollier diagram of the thermal cycle realized by a heat pump device [Figure 4A] Schematic diagram of an electronic expansion valve [Figure 4B] Schematic diagram of an electronic expansion valve [Figure 5] Flowchart of the first action [Figure 6] Operational diagram showing the first temperature and the opening degree of the electronic expansion valve in the first operation. [Figure 7] Mollier diagram of the thermal cycle realized by a heat pump device [Figure 8] Flowchart of the second action [Figure 9] Operational diagram showing the second temperature and the opening degree of the electronic expansion valve in the second operation. [Figure 10] schematic cross-section of an evaporator [Figure 11] Flowchart of the third action [Figure 12]Operation diagram showing the third temperature and the opening degree of the electronic expansion valve in the third operation DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] Embodiment 1 A dryer 1 according to an embodiment of the present disclosure will be described. The dryer 1 is an apparatus for drying objects to be subjected to a drying process, such as wet clothes, towels and sheets. In Embodiment 1, the dryer 1 is a washer-dryer further having a washing function (a so-called drum-type washer-dryer). Note that the dryer 1 does not need to have a washing function.

[0011] FIG. 1 is a schematic cross-sectional view of the dryer 1 according to Embodiment 1 of the present disclosure. FIG. 2 is a schematic diagram of a heat pump apparatus 6.

[0012] In FIG. 1, two directions orthogonal to each other in a horizontal plane are defined as a width direction X and a front-rear direction Y, and a vertical direction orthogonal to the horizontal plane is defined as an up-down direction Z.

[0013] As shown in FIG. 1, the dryer 1 includes a housing 2, an outer tub 3, a storage tub 4, a drive unit 5, a heat pump apparatus 6, a case 8, an air duct member 9, a fan 10, and a control unit 12.

[0014] The housing 2 is a member forming the outer appearance of the dryer 1. An opening 20 and an openable / closable door 21 covering the opening 20 are provided on a front surface of the housing 2.

[0015] The outer tub 3 is a substantially cylindrical member provided inside the housing 2 and having a function of storing washing water. The outer tub 3 may also be referred to as a water tub or a tub. The outer tub 3 is provided with an opening 31 at a position facing the opening 20 of the housing 2, and an edge of the opening 31 is connected to the opening 20 by a bellows 32.

[0016] The storage tub 4 is a substantially cylindrical member rotatably provided about the rotation axis V0 inside the outer tub 3 and capable of storing objects. The storage tub 4 may also be referred to as a drum, an inner tub or a washing tub. A plurality of through-holes 40 are formed in the storage tub 4, and the through-holes 40 allow communication between the storage tub 4 and the outer tub 3. The storage tub 4 is provided with an opening 41 at a position facing the opening 20 of the housing 2 and the opening 31 of the outer tub 3. When a user of the dryer 1 opens the door 21, the user can put objects into the storage tub 4 through the openings 20, 31, and 41.

[0017] The rotation axis V0 of the storage tub 4 extends inclining downward toward the rear side (+Y side). Note that the rotation axis V0 may extend parallel to the horizontal direction.

[0018] The driving unit 5 is a member that rotationally drives the storage tub 4 about the rotation axis V0. The driving unit 5 includes, for example, a motor that rotates the storage tub 4.

[0019] The heat pump device 6 is a device that adjusts the humidity and temperature of passing air. As shown in FIG. 2, the heat pump device 6 includes a compressor 61, an expansion mechanism 62, an evaporator 63, a condenser 64, and a refrigerant pipe 65. The evaporator 63, the compressor 61, the condenser 64, and the expansion mechanism 62 are connected in sequence by the refrigerant pipe 65 that circulates a refrigerant.

[0020] The evaporator 63 is a heat exchanger that cools surrounding air by vaporizing the inflowing refrigerant. The evaporator 63 dehumidifies the air by cooling the air to condense moisture contained in the air. The evaporator 63 may also be referred to as a cooler or a dehumidifying heat exchanger. The evaporator 63 includes, for example, a plurality of fins formed of thin metal plates, and heat transfer tubes that penetrate through the surfaces of the fins, communicate with the refrigerant pipe 65 and allow the refrigerant to flow therethrough.

[0021] The refrigerant in the evaporator 63 changes from a two-phase state in which a gas phase and a liquid phase are mixed to a gas phase state from the refrigerant inlet toward the refrigerant outlet. Therefore, the refrigerant flowing out of the evaporator 63 is sent to the compressor 61 in a gas phase state. Failure of the compressor 61 can be suppressed by suppressing liquid refrigerant from flowing into the compressor 61.

[0022] The compressor 61 is a device that compresses the incoming refrigerant. Specifically, the compressor 61 has a rotating mechanism, and compresses the refrigerant by the kinetic energy of the rotating mechanism. The compressed refrigerant is sent to the condenser 64.

[0023] The pressure of the refrigerant flowing into the compressor 61 (i.e., the pressure on the low-pressure side) is defined as pressure P1, and the pressure on the high-pressure side after compression is defined as pressure P2. To prevent failure of the compressor 61, an upper limit P0 is set for the high-pressure side pressure P2.

[0024] The condenser 64 is a heat exchanger that heats the surrounding air by liquefying the incoming refrigerant. The condenser 64 may also be referred to as a heater or a heating heat exchanger. The condenser 64 has, for example, multiple fins and heat transfer tubes, similar to the evaporator 63.

[0025] The refrigerant in the condenser 64 changes from a gaseous state to a two-phase state and then to a liquid state as it moves from the refrigerant inlet to the refrigerant outlet in the condenser 64. The refrigerant that flows out of the condenser 64 is sent to the expansion mechanism 62.

[0026] The expansion mechanism 62 is a mechanism that reduces the pressure of the refrigerant flowing in from the condenser 64. In Embodiment 1, the expansion mechanism 62 has an electronic expansion valve 66 (see Figures 4A and 4B) that can change the flow rate of the refrigerant flowing into the expansion mechanism 62. Alternatively, the expansion mechanism 62 may have other components that can change the flow rate of the incoming refrigerant, such as another expansion valve or a capillary tube, instead of the electronic expansion valve 66. The reduced-pressure refrigerant is sent to the evaporator 63 and circulates within the heat pump device 6.

[0027] Returning to Figure 1, in Embodiment 1, the evaporator 63 and the condenser 64 are arranged side by side in the front-to-back direction Y. Specifically, the evaporator 63 and the condenser 64 are arranged such that the main surfaces of the fins of the evaporator 63 and the condenser 64 face the width direction X and extend in the front-to-back direction Y. Considering the airflow (see arrow A), the evaporator 63 is located upstream of the condenser 64, and the air passes through the evaporator 63 and the condenser 64 in sequence, being dehumidified and heated.

[0028] The heat pump unit 6 is located at the top of the housing 2. Specifically, the heat pump unit 6 is located above the outer tank 3.

[0029] Case 8 is a component that houses the heat pump device 6. Case 8 has an inlet 81 upstream of the evaporator 63 and an outlet 82 downstream of the condenser 64. In Embodiment 1, the inlet 81 and outlet 82 are aligned in the front-to-back direction Y, and the air inside Case 8 flows from the inlet 81 towards the outlet 82, towards the rear (+Y side).

[0030] The air passage member 9 is provided inside the housing 2 and defines an air passage R between the housing tank 4 and the heat pump device 6. In Embodiment 1, the air passage member 9 has a first air passage member 91 and a second air passage member 92. The first air passage member 91 connects an opening 33 provided in the outer tank 3 to an inlet 81 of the case 8. The second air passage member 92 connects an outlet 82 of the case 8 to an opening 34 provided in the outer tank 3.

[0031] The air passage member 9 is equipped with multiple temperature sensors 74 for measuring the temperature of the air flowing through it. One temperature sensor 74 is located near the opening 33 of the outer tank 3. This arrangement allows for measurement of the air temperature both upstream and downstream of the containment tank 4. The temperature sensors 74 may be located at any position on the air passage member 9 or on the outer tank 3.

[0032] Fan 10 is installed in the air passage member 9 and circulates air between the storage tank 4 and the heat pump device 6. Fan 10 circulates the air that has passed through the case 8 back to the storage tank 4 (see arrow A). Specifically, when fan 10 is driven, humid air from the storage tank 4 flows into the case 8 from the inlet 81 through the first air passage member 91. The air that has been dehumidified and heated by the heat pump device 6 is returned to the storage tank 4 from the outlet 82 of the case 8 through the second air passage member 92.

[0033] Fan 10 may have any type of fan, for example, an axial fan or a centrifugal fan.

[0034] In Embodiment 1, the fan 10 is positioned downstream of the heat pump device 6.

[0035] The control unit 12 is a device that controls the operation of the dryer 1. The control unit 12 controls the components of the dryer 1, such as the drive unit 5, the heat pump device 6, and the fan 10. The control unit 12 may, for example, include a memory (not shown) that stores a program and a processing circuit (not shown) corresponding to a processor such as a CPU, and the processor may function as these elements by executing the program.

[0036] Specifically, the control unit 12 controls the rotation mechanism of the compressor 61 and the electronic expansion valve of the expansion mechanism 62 in the heat pump device 6.

[0037] Next, the heat pump device 6 will be described in more detail with reference to Figures 2 and 3. Figure 3 is a Mollier diagram showing the relationship between pressure P and enthalpy H in the thermal cycle realized by the heat pump device 6. In Figure 3, line R1 represents the change in the compressor 61, line R2 represents the change in the expansion mechanism 62, line R3 represents the change in the evaporator 63, and line R4 represents the change in the condenser 64.

[0038] As shown in Figure 2, the heat pump device 6 further includes a first sensor 71, a second sensor 72, and a third sensor 73 for measuring the temperature of the refrigerant. In this specification, sensors 71 to 73 measure the temperature of the pipes through which the refrigerant flows, and estimate the temperature of the measured pipes to be the temperature of the refrigerant itself.

[0039] The temperature measured by sensors 71-73 allows for the estimation of the state of the thermal cycle realized by the heat pump device 6. Specifically, as shown in Figure 3, based on a Mollier diagram assuming an isentropic state (i.e., the compressor 61 is operating at 100% efficiency), the temperature measured by sensors 71-73 allows for the estimation of the refrigerant pressure and the temperature of the refrigerant at other locations.

[0040] The first sensor 71 is located in the condenser 64 and measures the first temperature T1 of the refrigerant in the condenser 64. In Embodiment 1, the first sensor 71 is located in the condenser 64 at a position where the refrigerant is in a two-phase state where the liquid phase and gas phase are mixed. The first sensor 71 is located, for example, in the center of the condenser 64.

[0041] The first temperature T1 is correlated with the high-pressure side pressure P2 of the compressor 61. Therefore, the high-pressure side pressure P2 can be estimated from the first temperature T1. Since an upper limit P0 is set for the high-pressure side pressure P2, it is necessary to suppress an excessive increase in the first temperature T1, and a first threshold S1 corresponding to the upper limit P0 is set for the first temperature T1. If the state in which the first temperature T1 exceeds the first threshold S1 continues for a predetermined time, it is necessary to stop the compressor 61.

[0042] The second sensor 72 is located at the refrigerant inlet of the evaporator 63 and measures the second temperature T2 of the refrigerant flowing into the evaporator 63.

[0043] The second temperature T2 is an indicator of the phase state of the refrigerant in the evaporator 63. Specifically, the pressure of the refrigerant in the evaporator 63 can be estimated based on the second temperature T2. The pressure of the refrigerant in the evaporator 63 is related to the state of the refrigerant (whether it is in a two-phase state or a gaseous state). Therefore, based on the second temperature T2, the position in the evaporator 63 where the refrigerant switches from a two-phase state to a gaseous state can be estimated.

[0044] The third sensor 73 is located between the compressor 61 and the condenser 64 and measures the third temperature T3 of the refrigerant discharged from the compressor 61. In Embodiment 1, the third sensor 73 is located in the discharge pipe of the compressor 61, where the refrigerant is discharged toward the condenser 64. Therefore, the third temperature T3 measured by the third sensor 73 may also be referred to as the discharge pipe temperature.

[0045] The third temperature T3 is correlated with the refrigerant pressure P2 on the high-pressure side of the compressor 61. A fifth threshold S5 is also provided for the third temperature T3. If the third temperature T3 exceeds the fifth threshold S5 for a predetermined period of time, the compressor 61 is required to be stopped.

[0046] From the temperature difference between the third temperature T3 and the second temperature T2, the temperature difference of the refrigerant at the refrigerant outlet and refrigerant inlet of the evaporator 63 can be estimated. The temperature difference of the refrigerant at the refrigerant outlet and refrigerant inlet of the evaporator 63 may also be called the suction superheat (SH). Suction SH is an indicator of the heat conversion efficiency of the evaporator 63, and a stable suction SH indicates that the evaporator 63 is being used with high efficiency. Suction SH varies depending on the operating conditions of the heat pump device 6 and the progress of the drying process, and is, for example, between 1°C and 10°C.

[0047] Furthermore, if the operation of the compressor 61 deviates significantly from the ideal isentropic state, i.e., the state of 100% operating efficiency, an additional sensor may be installed between the evaporator 63 and the compressor 61 to measure the temperature of the refrigerant flowing into the compressor 61. In this case, the suction SH is the difference between the temperature measured by the additional sensor and the second temperature T2.

[0048] Furthermore, the temperature difference between the refrigerant inlet and outlet of the condenser 64 can be estimated from the temperature difference between the third temperature T3 and the first temperature T1. The temperature difference between the refrigerant inlet and outlet of the condenser 64 may be called the discharge superheat (SH). Discharge SH is an indicator of the heat conversion efficiency of the condenser 64, and a stable discharge SH indicates that the condenser 64 is being used with high efficiency.

[0049] Figures 4A and 4B are schematic diagrams of a portion of the electronic expansion valve 66 of the expansion mechanism 62.

[0050] As shown in Figures 4A and 4B, the electronic expansion valve 66 has a cylindrical portion 75 and a needle 76. The cylindrical portion 75 is a cylindrical member with an opening 75A defined at its tip. The needle 76 is a rod-shaped member with a tapered shape, which is inserted into the cylindrical portion 75 and can seal the opening 75A. The needle 76 is movable in the longitudinal direction L relative to the cylindrical portion 75 between a position that seals the opening 75A and a position that opens the opening 75A.

[0051] The needle 76 has a first tapered portion 77 and a second tapered portion 78 in order toward the tip 76A. The sides of the tapered portions 77 and 78 are inclined at an angle with respect to the longitudinal direction L, and the cross-sectional area of ​​the needle 76 perpendicular to the longitudinal direction L decreases toward the tip 76A of the needle 76.

[0052] The inclination angle of the second tapered section 78 is smaller than that of the first tapered section 77. Therefore, the rate of change of the cross-sectional area per unit length in the longitudinal direction L is smaller for the second tapered section 78 than for the first tapered section 77.

[0053] In Embodiment 1, the needle 76 is movable in the longitudinal direction L within the range in which the second tapered portion 78 is inserted into the opening 75A. This movement changes the distance between the side surface of the second tapered portion 78 and the edge of the cylindrical portion 75 that defines the opening 75A, and changes the area of ​​the open opening 75A. The area of ​​the open opening 75A may be referred to as the degree of opening.

[0054] For example, when the needle 76 moves from the position shown in Figure 4A to the position shown in Figure 4B, the gap G1 decreases to the gap G2, and the opening decreases. On the other hand, when the needle 76 moves in the opposite direction, the opening increases.

[0055] The flow rate of refrigerant flowing into the expansion mechanism 62 through the opening 75A can be adjusted by increasing or decreasing the opening. When the opening decreases, the flow rate of refrigerant flowing into the expansion mechanism 62 also decreases, and when the opening increases, the flow rate of refrigerant flowing into the expansion mechanism 62 also increases.

[0056] Furthermore, since the needle 76 moves within the range in which the second tapered portion 78 is inserted into the opening 75A, the increase or decrease in the opening degree with respect to the amount of movement in the longitudinal direction L can be reduced compared to the case where the first tapered portion 77 moves within the range in which it is inserted into the opening 75A. Therefore, the opening degree can be controlled with higher precision.

[0057] The movement of the needle 76 in the longitudinal direction L is controlled by the control unit 12.

[0058] [Example of operation: First operation] Next, as an example of the operation of the dryer 1 having the above configuration, the first operation will be described. Figure 5 is a flowchart of the first operation. Figure 6 is an operation diagram showing the first temperature T1 and the opening degree J of the electronic expansion valve 66 in the first operation. Figure 7 is a Mollier diagram of the thermal cycle realized by the heat pump device 6 in the first operation.

[0059] As shown in Figure 5, the control unit 12 starts the drying process in response to user operation of the dryer 1.

[0060] Next, the control unit 12 obtains the opening degree J of the electronic expansion valve 66 and sets it to the first opening degree J1 (S11).

[0061] In Embodiment 1, from step S11 onward, the control unit 12 keeps the rotational speed of the compressor 61 constant.

[0062] Next, the control unit 12 acquires the first temperature T1 of the first sensor 71 (S12). The control unit 12 may perform step S12 simultaneously with step S11.

[0063] Next, the control unit 12 determines whether the acquired first temperature T1 exceeds the first threshold S1 (S13). The first threshold S1 is the temperature corresponding to the upper limit P0 of the high-pressure side pressure P2 in the compressor 61, and is, for example, 70°C.

[0064] If the first temperature T1 is less than the first threshold S1 (No in S13), the control unit 12 returns to step S11. If the first temperature T1 is less than the first threshold S1, the control unit 12 may control the opening degree J of the electronic expansion valve 66 based on a parameter different from the first temperature T1. For example, the control unit 12 may control the opening degree J of the electronic expansion valve 66 based on the intake SH.

[0065] When the first temperature T1 exceeds the first threshold S1 (Yes in S13), the control unit 12 determines whether the opening degree J of the electronic expansion valve 66 has already been increased (S14). Specifically, the control unit 12 determines whether it is the first increase in the opening degree J since step S13 has been executed, or the second or subsequent increase in the opening degree J. The control unit 12 may make this determination by referring to, for example, a memory (not shown).

[0066] If it is the first increase in the opening degree J (No in S14), the control unit 12 increases the opening degree J of the electronic expansion valve 66 by the first increment ΔJ1 (S15). As shown in Figure 6, the control unit 12 increases the opening degree J of the electronic expansion valve 66 from the first opening degree J1 to the second opening degree J2 by ​​the first increment ΔJ1. In Embodiment 1, the control unit 12 increases the opening degree J to the second opening degree J2 immediately after the determination.

[0067] In Embodiment 1, the first increment ΔJ1 is a predetermined value, but it may be a value determined based on the acquired first temperature T1.

[0068] Increasing the opening degree J of the electronic expansion valve 66 increases the flow rate of refrigerant into the expansion mechanism 62. As a result, as shown in Figure 7, the amount of refrigerant pressure reduction in the expansion mechanism 62 decreases (length of line R2). When the amount of pressure reduction decreases, the differential pressure between the high-pressure side (line R4) and the low-pressure side (line R3) decreases, and the pressure P2 on the high-pressure side decreases. Consequently, the pressure P2 on the high-pressure side becomes lower than the upper limit P0, and the compressor 61 can continue to operate.

[0069] If it is the second or subsequent increase in the opening degree J (Yes in S14), the control unit 12 increases the opening degree J of the electronic expansion valve 66 by a second increment ΔJ2 over a predetermined period of time (S16). By executing step S16 after step S15, even if the first temperature T1 is not sufficiently lowered by the first increment ΔJ1, the opening degree J of the electronic expansion valve 66 can be increased in stages to lower the first temperature T1.

[0070] In Embodiment 1, the second increment ΔJ2 is determined based on the acquired first temperature T1. Specifically, the control unit 12 determines the second increment ΔJ2 based on the difference between the first temperature T1 and the first threshold S1. On the other hand, the second increment ΔJ2 may be a default value.

[0071] As shown in Figure 6, in Embodiment 1, the second increment ΔJ2 is smaller than the first increment ΔJ1. This configuration prevents the pressure P2 on the high-pressure side from decreasing excessively. Also, the amount of change in the opening degree J per unit time in step S16 is smaller than the amount of change in step S15.

[0072] Next, as shown in Figure 5, the control unit 12 acquires the first temperature T1 from the first sensor 71 again (S17).

[0073] Next, the control unit 12 determines whether the acquired first temperature T1 is below the second threshold S2 (S18). The second threshold S2 is a temperature lower than the first threshold S1, for example, 68°C.

[0074] If the first temperature T1 does not fall below the second threshold S2 (No in S18), the control unit 12 proceeds directly to step S101.

[0075] When the first temperature T1 falls below the second threshold S2 (Yes in S18), the control unit 12 reduces the opening degree J of the electronic expansion valve 66 (S19). As shown in Figure 6, the control unit 12 reduces the opening degree J of the electronic expansion valve 66 to the third opening degree J3 over a predetermined period of time. In Embodiment 1, the third opening degree J3 is smaller than the first opening degree J1.

[0076] The control unit 12 may immediately reduce the opening degree J to the third opening degree J3 after the determination. The third opening degree J3 may also be greater than or equal to the first opening degree J1.

[0077] Next, as shown in Figure 5, the control unit 12 determines whether or not the drying time has elapsed (S101).

[0078] If the drying time has not elapsed (No in S101), the control unit 12 returns to step S14. By repeating steps S14 to S17, the control unit 12 can gradually increase the opening degree J of the electronic expansion valve 66 by the second increment ΔJ2 until the first temperature T1, which is above the first threshold S1, falls below the second threshold S2.

[0079] Once the drying time has elapsed (Yes in S101), the control unit 12 terminates the first operation.

[0080] [Example of operation: Second operation] Next, as an example of another operation of the dryer 1, the second operation will be described. Figure 8 is a flowchart of the second operation. Figure 9 is an operation diagram showing the second temperature T2 and the opening degree J of the electronic expansion valve 66 in the second operation. Figure 10 is a schematic cross-sectional view of the evaporator 63.

[0081] In response to the user's operation of the dryer 1, the control unit 12 starts the drying process. Then, as shown in Figure 8, the control unit 12 performs the first control. In the first control, the control unit 12 first obtains the opening degree J of the electronic expansion valve 66 and sets it to the fourth opening degree J4 (S21).

[0082] Next, the control unit 12 determines whether the current time is the second half of the drying process (S22). In this specification, the "second half" of the drying process means the drying process from the point in time when the amount of water evaporated from the object in the containment tank 4 reaches its maximum.

[0083] The control unit 12 indirectly determines the point in time when the amount of water evaporated from the object reaches its maximum. Specifically, when at least one of the first predetermined condition, the second predetermined condition, and the third predetermined condition is met, the control unit 12 determines that the current time is after the point in time when the amount of water evaporated from the object reaches its maximum. The first predetermined condition is that the air temperature or temperature difference measured by the temperature sensor 74 provided in the air passage member 9 is below a predetermined value. The second predetermined condition is that the rotational speed of the compressor 61 is below a predetermined value. The third predetermined condition is that the third temperature T3 measured by the third sensor 73 is above a predetermined value.

[0084] In Embodiment 1, when all of the first, second, and third predetermined conditions are met, the control unit 12 determines that the current time is the latter half of the drying process. Alternatively, the control unit 12 may determine that the current time is the latter half of the drying process when at least one of the first, second, and third predetermined conditions is met.

[0085] If it is not the latter half of the drying process (No in S22), the control unit 12 returns to step S21.

[0086] If it is the latter half of the drying process (Yes in S22), the control unit 12 switches from the first control to the second control. The control unit 12 may also perform other steps in the first control.

[0087] In the second control, first, the control unit 12 reduces the opening degree J of the electronic expansion valve 66 (S23). By reducing the opening degree J of the electronic expansion valve 66, the opening degree J of the electronic expansion valve 66 in the second control becomes smaller than the opening degree J in the first control. As shown in Figure 9, the control unit 12 reduces the opening degree J of the electronic expansion valve 66 from the fourth opening degree J4 to the fifth opening degree J5 over a predetermined period of time. The fifth opening degree J5 is a default value.

[0088] By reducing the opening degree J of the electronic expansion valve 66, the flow rate of refrigerant flowing into the expansion mechanism 62 is reduced. As a result, in the expansion mechanism 62, the pressure P1 on the low-pressure side of the compressor 61 decreases, the temperature of the refrigerant at the refrigerant inlet of the evaporator 63 (i.e., the second temperature T2) decreases, and the dew point temperature of the refrigerant relative to the air near the refrigerant inlet of the evaporator 63 can be maintained. In this state, the air passing near the refrigerant inlet of the evaporator 63 can be dehumidified.

[0089] In Embodiment 1, the control unit 12 reduces the opening degree J of the electronic expansion valve 66 and then maintains the fifth opening degree J5 for a predetermined time.

[0090] Next, as shown in Figure 8, the control unit 12 acquires the second temperature T2 of the second sensor 72 (S24).

[0091] Next, the control unit 12 determines whether the acquired second temperature T2 exceeds the third threshold S3 (S25).

[0092] When the second temperature T2 exceeds the third threshold S3 (Yes in S25), the control unit 12 reduces the opening degree J of the electronic expansion valve 66 (S26). By reducing the opening degree J of the electronic expansion valve 66, the flow rate of refrigerant flowing into the electronic expansion valve 66 decreases, the pressure P1 on the low-pressure side of the compressor 61 decreases, and the second temperature T2 decreases.

[0093] If the second temperature T2 does not exceed the third threshold S3 (No in S25), the control unit 12 increases the opening degree J of the electronic expansion valve 66 (S27). Increasing the opening degree J of the electronic expansion valve 66 increases the flow rate of refrigerant into the electronic expansion valve 66, which raises the pressure P1 on the low-pressure side of the compressor 61 and raises the second temperature T2.

[0094] In step S27, when increasing the opening degree J of the electronic expansion valve 66, the control unit 12 maintains the opening degree J at or below the fourth opening degree J4 in the first control. Specifically, the control unit 12 maintains the opening degree J at or below the minimum value of the fourth opening degree J4 in the first control.

[0095] In steps S25 to S27, the control unit 12 can bring the second temperature T2 closer to the third threshold S3 by adjusting the opening degree J of the electronic expansion valve 66. In Embodiment 1, the third threshold S3 is the temperature at which the refrigerant in at least a portion of the evaporator 63 is in a two-phase state. That is, by adjusting the opening degree J of the electronic expansion valve 66, the control unit 12 can bring the second temperature T2 closer to the third threshold S3 and maintain the state in which the refrigerant in at least a portion of the evaporator 63 is in a two-phase state.

[0096] As shown in Figure 10, the evaporator 63 has several rows 93 to 95. Each row 93 to 95 has several fins 98 arranged in the width direction X, and heat transfer tubes 99 that penetrate the fins 98 in the width direction X. The heat transfer tubes 99 of each row 93 to 95 are connected in series in sequence.

[0097] Rows 93-95 are arranged sequentially from upstream to downstream with respect to the airflow indicated by arrow A, that is, from the inlet 81 to the outlet 82 (see Figure 1) of case 8. Considering the airflow, the second row 94 is located downstream of the first row 93, and the third row 95 is located downstream of the second row 94.

[0098] On the other hand, as indicated by arrow B, the refrigerant passes through the heat transfer tubes 99 in the order of the third row 95, the second row 94, and the first row 93 from the expansion mechanism 62. Therefore, considering the flow of the refrigerant, the second row 94 is located downstream of the third row 95, and the first row 93 is located downstream of the second row 94.

[0099] The control unit 12 can adjust the second temperature T2 by adjusting the opening degree J of the electronic expansion valve 66, thereby adjusting the state of the refrigerant in each row 93 to 95.

[0100] From row 3, 95 to row 1, 93, the refrigerant changes from a two-phase state to a gaseous state.

[0101] In Embodiment 1, when the second temperature T2 is the third threshold S3, all the refrigerant in the third row 95 enters a two-phase state, while the refrigerants in rows 94 and 93 enter a gaseous state. With this configuration, the two-phase state can be maintained in the third row 95, allowing the air to be dehumidified by the third row 95. On the other hand, since the air is not dehumidified in rows 94 and 93, no dehumidified water adheres to rows 94 and 93. Therefore, the drying process for the evaporator 63 after the drying process is completed can be shortened.

[0102] When the second temperature T2 exceeds the third threshold S3, the range in which the refrigerant is in a two-phase state expands, and dehumidified water adheres to rows 94 and 93. On the other hand, when the second temperature T2 falls below the third threshold S3, the range in which the refrigerant is in a two-phase state shrinks, and the dehumidification function of the evaporator 63 deteriorates excessively.

[0103] Furthermore, the third threshold S3 is not limited to the settings described above, and may be set so that, in addition to the third column 95, less than half the volume of the refrigerant in the second column 94 is in a two-phase state. Also, the third threshold S3 may be set so that at least a portion of the refrigerant in the third column 95 is in a two-phase state.

[0104] In steps S26 and S27, when changing the opening degree J of the electronic expansion valve 66, the control unit 12 maintains the rotational speed of the compressor 61.

[0105] Furthermore, in steps S26 and S27, the control unit 12 may acquire the third temperature T3 measured by the third sensor 73 and determine the change in the opening degree J (i.e., the change in flow rate) in steps S26 and S27 based on the third temperature T3. The control unit 12 may also determine the change in the opening degree J based, for example, on the difference between the third temperature T3 and the fifth threshold S5. For example, if the difference between the third temperature T3 and the fifth threshold S5 is large, the control unit 12 may increase the change in the opening degree J.

[0106] Next, as shown in Figure 8, the control unit 12 determines whether or not the drying time has elapsed (S28). If the drying time has not elapsed (No in S28), the control unit 12 returns to step S25 and repeats the operation. If the drying time has elapsed (Yes in S28), the control unit 12 terminates the second operation.

[0107] [Example of operation: Third operation] Next, as an example of another operation of the dryer 1, the third operation will be described. Figure 11 is a flowchart of the third operation. Figure 12 is an operation diagram showing the third temperature T3 and the opening degree J of the electronic expansion valve 66 in the third operation.

[0108] In response to user operation of the dryer 1, the control unit 12 starts the drying process. Then, as shown in Figure 11, the control unit 12 executes a third control.

[0109] In the third control, first, the control unit 12 controls the opening degree J of the electronic expansion valve 66 based on one or more parameters, including parameters different from the third temperature T3. For example, the control unit 12 may control the opening degree J of the electronic expansion valve 66 based on the rotational speed of the compressor 61. The control unit 12 may also control the opening degree J of the electronic expansion valve 66 based on the intake SH calculated from the second temperature T2 and the third temperature T3. The control unit 12 may also control the opening degree J of the electronic expansion valve 66 based on the discharge SH calculated from the first temperature T1 and the third temperature T3.

[0110] Next, the control unit 12 determines whether the current time is the latter half of the drying process (S32). In Embodiment 1, the control unit 12 performs the determination in step S32 in the same way as in step S22 of the second operation.

[0111] If it is not in the latter half of the drying process (No in S32), the control unit 12 will execute step S32 again after a predetermined time has elapsed.

[0112] If it is the latter half of the drying process (Yes in S32), the control unit 12 switches from the third control to the fourth control. The control unit 12 may also perform other steps in the third control.

[0113] In the fourth control, first the control unit 12 acquires the third temperature T3 from the third sensor 73 (S33).

[0114] Next, the control unit 12 determines whether the acquired third temperature T3 exceeds the fourth threshold S4 (S34). The fourth threshold S4 is a temperature lower than the fifth threshold S5, which corresponds to the upper limit P0 of the high-pressure side pressure P2 in the compressor 61.

[0115] When the third temperature T3 exceeds the fourth threshold S4 (Yes in S34), the control unit 12 increases the opening degree J of the electronic expansion valve 66 (S35). Increasing the opening degree J of the electronic expansion valve 66 increases the flow rate of cold refrigerant into the compressor 61, thereby cooling the compressor 61. As a result, the rise in the third temperature T3 of the refrigerant flowing out of the compressor 61 can be suppressed.

[0116] As shown in Figure 12, the control unit 12 increases the opening degree J of the electronic expansion valve 66 by a fourth increment ΔJ4 over a predetermined time. The fourth increment ΔJ4 may be determined based on the third temperature T3.

[0117] As shown in Figure 11, if the third temperature T3 does not exceed the fourth threshold S4 (No in S34), the control unit 12 maintains the opening degree J of the electronic expansion valve 66 (S36).

[0118] Next, the control unit 12 acquires the third temperature T3 from the third sensor 73 again (S37).

[0119] Next, the control unit 12 determines whether the acquired third temperature T3 exceeds the fifth threshold S5 (S38). The fifth threshold S5 corresponds to the upper limit P0 of the high-pressure side pressure P2 in the compressor 61.

[0120] When the third temperature T3 exceeds the fifth threshold S5 (Yes in S38), the control unit 12 increases the opening degree J of the electronic expansion valve 66 (S39).

[0121] As shown in Figure 12, the control unit 12 increases the opening degree J of the electronic expansion valve 66 by a fifth increment ΔJ5 over a predetermined time. The fifth increment ΔJ5 may be determined based on the third temperature T3 and is greater than the fourth increment ΔJ4. Also, the amount of change in the opening degree J per unit time in step S39 is greater than the amount of change in step S35.

[0122] As shown in Figure 11, if the third temperature T3 does not exceed the fifth threshold S5 (No in S38), the control unit 12 maintains the opening degree J of the electronic expansion valve 66 (S36).

[0123] Next, the control unit 12 determines whether the drying time has elapsed (S40). If the drying time has not elapsed (No in S40), the control unit 12 returns to step S33 and repeats the operation. If the drying time has elapsed (Yes in S40), the control unit 12 terminates the third operation.

[0124] Before step S40, the control unit 12 may acquire the third temperature T3 of the third sensor 73 and determine whether the acquired third temperature T3 is below the sixth threshold S6. The sixth threshold S6 is smaller than the fourth threshold S4. If the third temperature T3 is below the sixth threshold S6, the control unit 12 may switch from the fourth control to another control that controls the opening degree J of the electronic expansion valve 66 based on the same parameters as the third control.

[0125] The dryer 1 according to Embodiment 1 can achieve the following effects.

[0126] [Effect 1] The dryer 1 according to Embodiment 1 comprises a storage tank 4 for storing objects, a heat pump device 6, an air passage member 9 that defines an air passage between the storage tank 4 and the heat pump device 6, and a fan 10 provided on the air passage member 9 for circulating air between the storage tank 4 and the heat pump device 6. The heat pump device 6 connects a compressor 61, a condenser 64, an expansion mechanism 62, and an evaporator 63 with refrigerant piping 65 for circulating refrigerant. The dryer 1 further comprises a first sensor 71 provided on the condenser 64 for measuring a first temperature T1 of the refrigerant, and a control unit 12 that controls the compressor 61 and the expansion mechanism 62. The expansion mechanism 62 has an electronic expansion valve 66 (flow rate adjustment unit) that can change the flow rate of the incoming refrigerant. When the first temperature T1 exceeds a first threshold S1, the control unit 12 controls the electronic expansion valve 66 so that the flow rate of refrigerant flowing into the expansion mechanism 62 increases.

[0127] With this configuration, increasing the opening degree J of the electronic expansion valve 66 reduces the amount of pressure reduction, thereby reducing the pressure difference caused by the compressor 61 and lowering the pressure P2 on the high-pressure side. As a result, the pressure P2 on the high-pressure side is prevented from reaching the design upper limit P0 of the compressor 61, and the operation of the compressor 61 can be continued. Consequently, the drying process time can be shortened compared to when the compressor 61 is stopped.

[0128] Furthermore, in the dryer 1 according to Embodiment 1, when the first temperature T1 exceeds the first threshold S1, the control unit 12 controls the electronic expansion valve 66 so that the flow rate of refrigerant flowing into the expansion mechanism 62 increases by a first increment ΔJ1.

[0129] This configuration makes it possible to prevent the pressure P2 on the high-pressure side from reaching the upper limit P0.

[0130] Furthermore, in the dryer 1 according to Embodiment 1, the control unit 12 controls the electronic expansion valve 66 by the first increment ΔJ1, and then, when the first temperature T1 exceeds the first threshold S1, determines a second increment ΔJ2 based on the first temperature T1. The control unit 12 controls the electronic expansion valve 66 so that the flow rate of refrigerant flowing into the expansion mechanism 62 increases by the second increment ΔJ2.

[0131] This configuration makes it more reliable to prevent the high-pressure side pressure P2 from reaching the upper limit P0.

[0132] Furthermore, in the dryer 1 according to Embodiment 1, the control unit 12 controls the electronic expansion valve 66 such that the flow rate of refrigerant flowing into the expansion mechanism 62 decreases when the first temperature T1 falls below a second threshold S2 which is lower than the first threshold S1.

[0133] This configuration suppresses an excessive drop in the pressure P2 on the high-pressure side, thus improving the drying function. This can suppress the decline. Furthermore, lowering the second threshold S2 to a lower value than the first threshold S1 can suppress hysteresis.

[0134] [Effect 2] The dryer 1 according to Embodiment 1 comprises a storage tank 4 for storing objects, a heat pump device 6, an air passage member 9 that defines an air passage between the storage tank 4 and the heat pump device 6, and a fan 10 provided on the air passage member 9 for circulating air between the storage tank 4 and the heat pump device 6. The heat pump device 6 connects a compressor 61, a condenser 64, an expansion mechanism 62, and an evaporator 63 with refrigerant piping 65 for circulating refrigerant. The dryer 1 further comprises a second sensor 72 for measuring the second temperature T2 of the refrigerant flowing into the evaporator 63, and a control unit 12 for controlling the compressor 61 and the expansion mechanism 62. The expansion mechanism 62 has an electronic expansion valve 66 (flow rate adjustment unit) that can change the flow rate of the incoming refrigerant. The control unit 12 is capable of executing a first control and a second control that controls the electronic expansion valve 66 so that the flow rate of refrigerant flowing into the expansion mechanism 62 becomes smaller than that of the first control. When predetermined conditions are met, the control unit 12 switches from the first control to the second control. In the second control, when the second temperature T2 exceeds the third threshold S3 (threshold), the control unit 12 controls the electronic expansion valve 66 to reduce the flow rate of refrigerant flowing into the expansion mechanism 62.

[0135] With this configuration, by reducing the opening degree J of the electronic expansion valve 66 and increasing the refrigerant flow rate, the pressure on the low-pressure side decreases, the temperature of the refrigerant at the refrigerant inlet of the evaporator 63 decreases, and the two-phase state of the refrigerant near the refrigerant inlet of the evaporator 63 can be maintained. The air passing near the refrigerant inlet of the evaporator 63 can be dehumidified, and the air dehumidification capacity of the evaporator 63 can be maintained. Therefore, the drying process time can be shortened.

[0136] Furthermore, in the dryer 1 according to Embodiment 1, in the second control, if the second temperature T2 is less than or equal to the third threshold S3, the control unit 12 controls the electronic expansion valve 66 to increase the flow rate of refrigerant flowing into the expansion mechanism 62.

[0137] This configuration prevents all refrigerant from becoming gaseous in the evaporator 63, thereby suppressing an excessive decrease in the dehumidification function of the evaporator 63.

[0138] Furthermore, in the dryer 1 according to Embodiment 1, in the second control, when the second temperature T2 is less than or equal to the third threshold S3 and the electronic expansion valve 66 is controlled to increase the flow rate of refrigerant flowing into the expansion mechanism 62, the control unit 12 maintains the rotational speed of the compressor 61.

[0139] This configuration simplifies the control of the electronic expansion valve 66.

[0140] Furthermore, in the dryer 1 according to Embodiment 1, the predetermined conditions include at least one of the following: the air temperature measured by the temperature sensor 74 (fourth sensor) provided in the air passage member 9 is below a predetermined value; the rotational speed of the compressor 61 is below a predetermined value; and the refrigerant temperature measured by the third sensor 73 is above a predetermined value.

[0141] With this configuration, the control unit 12 can determine whether or not the current time is in the latter half of the drying process.

[0142] [Effect 3] The dryer 1 according to Embodiment 1 comprises a storage tank 4 for storing the object to be stored, a heat pump device 6, an air passage member 9 that defines an air passage between the storage tank 4 and the heat pump device 6, and a fan 10 provided on the air passage member 9 for circulating air between the storage tank 4 and the heat pump device 6. The heat pump device 6 connects a compressor 61, a condenser 64, an expansion mechanism 62, and an evaporator 63 with refrigerant piping 65 for circulating the refrigerant. The dryer 1 further comprises a third sensor 73 provided between the compressor 61 and the condenser 64 for measuring the third temperature T3 of the refrigerant, and a control unit 12 that controls the compressor 61 and the expansion mechanism 62. The expansion mechanism 62 has an electronic expansion valve 66 (flow rate adjustment unit) that can change the flow rate of the incoming refrigerant. When the third temperature T3 exceeds a fourth threshold S4, the control unit 12 controls the electronic expansion valve 66 so that the flow rate of the refrigerant flowing into the expansion mechanism 62 increases.

[0143] With this configuration, increasing the opening degree J of the electronic expansion valve 66 increases the flow rate of the refrigerant, thereby increasing the flow rate of cold refrigerant into the compressor 61 and cooling the compressor 61. This suppresses the rise in the third temperature T3 of the refrigerant flowing out of the compressor 61, allowing the compressor 61 to continue operating. Consequently, while suppressing the rise in the third temperature T3 of the refrigerant, the drying process time can be shortened compared to when the compressor 61 is stopped.

[0144] Furthermore, in the dryer 1 according to Embodiment 1, when the third temperature T3 exceeds the fourth threshold S4, the control unit 12 controls the electronic expansion valve 66 so that the flow rate of refrigerant flowing into the expansion mechanism 62 increases by a fifth increment ΔJ5.

[0145] This configuration makes it possible to more reliably prevent the high-pressure side pressure P2 of the compressor 61 from reaching the design upper limit P0.

[0146] Furthermore, in the dryer 1 according to Embodiment 1, when the third temperature exceeds a fifth threshold greater than the fourth threshold, the control unit controls the electronic expansion valve 66 so that the flow rate of refrigerant flowing into the expansion mechanism increases by a sixth increment ΔJ6 greater than the fifth increment.

[0147] This configuration makes it possible to more reliably prevent the high-pressure side pressure P2 of the compressor 61 from reaching the design upper limit P0.

[0148] Furthermore, in the dryer 1 according to Embodiment 1, the control unit is capable of performing a third control and a fourth control that controls the electronic expansion valve 66 so as to increase the flow rate of refrigerant flowing into the expansion mechanism 62 when the third temperature T3 exceeds the fourth threshold S4. The control unit 12 switches from the first control to the fourth control when predetermined conditions are met.

[0149] This configuration suppresses an excessive drop in the high-pressure side pressure P2 compared to the case where only the fourth control is operational, thereby suppressing a decrease in drying function.

[0150] Furthermore, in the dryer 1 according to Embodiment 1, the predetermined conditions include at least one of the following: the air temperature measured by the temperature sensor 74 (fourth sensor) provided in the air passage member 9 is below a predetermined value; the rotational speed of the compressor 61 is below a predetermined value; and the refrigerant temperature measured by the third sensor 73 is above a predetermined value.

[0151] With this configuration, the control unit 12 can determine whether or not the current time is in the latter half of the drying process.

[0152] Furthermore, the dryer 1 according to Embodiment 1 is further equipped with a second sensor 72 provided between the evaporator 63 and the expansion mechanism 62 for measuring the second temperature T2 of the refrigerant. In the third control, the control unit 12 controls the electronic expansion valve 66 based on the second temperature T2.

[0153] This configuration makes it easier to control the heat pump device 6 based on the intake SH, improve the efficiency of heat exchange in the evaporator 63, and thereby improve the drying function in the third control.

[0154] Furthermore, the dryer 1 according to Embodiment 1 is further equipped with a first sensor 71 provided in the condenser 64 that can detect a first temperature T1 of the refrigerant. In the third control, the control unit 12 controls the electronic expansion valve 66 based on the first temperature T1.

[0155] This configuration makes it easier to control the heat pump device 6 based on the discharge SH, improve the efficiency of heat exchange in the condenser 64, and thereby improve the drying function in the third control.

[0156] Furthermore, in the dryer 1 according to Embodiment 1, in the third control, the control unit 12 controls the electronic expansion valve 66 based on the rotational speed of the compressor 61.

[0157] This configuration makes it easier to improve the efficiency of the compressor 61 and enhance the drying function in the third control.

[0158] This disclosure is not limited to the embodiments described above, and can be implemented in various other forms.

[0159] In Embodiment 1, an example was described in which the control unit 12 increases the opening degree J of the electronic expansion valve 66, but the invention is not limited to this. The expansion mechanism 62 only needs to be controllable by the control unit 12 and have a mechanism that can change the flow rate of the refrigerant flowing into the expansion mechanism 62. For example, if the expansion mechanism 62 has a capillary tube that defines multiple paths, the control unit 12 may change the flow rate of the refrigerant flowing into the expansion mechanism 62 by changing the number of open paths.

[0160] In Embodiment 1, an example was described in which the needle 76 of the electronic expansion valve 66 has two tapered portions 77 and 78, but the invention is not limited to this. For example, the needle 76 may have only one tapered portion, or it may have other shapes.

[0161] The dryer 1 may also have a pressure sensor instead of the temperature sensors 71-73.

[0162] In Embodiment 1, an example was described in which the dryer 1 has a second sensor 72, but the invention is not limited to this. The dryer 1 may have only a first sensor 71 and a third sensor 73.

[0163] In the first operation of Embodiment 1, an example was described in which the control unit 12 maintains a constant rotational speed of the compressor 61, but the operation is not limited to this. When the opening degree J of the electronic expansion valve 66 reaches the maximum design opening degree, the control unit 12 may reduce the rotational speed of the compressor 61 or stop the operation of the compressor 61.

[0164] In the first operation, if the first temperature T1 exceeds the first threshold S1 in step S13 (Yes in S13), the control unit 12 may reduce the rotational speed of the compressor 61 before increasing the opening degree J of the electronic expansion valve 66. Such an operation can more reliably lower the first temperature T1. If the first temperature T1 still exceeds the first threshold S1 after the rotational speed of the compressor 61 has been reduced, the control unit 12 increases the opening degree J of the electronic expansion valve 66.

[0165] Furthermore, in the first operation, after increasing the opening degree J of the electronic expansion valve 66 by the first increment ΔJ1 or the second increment ΔJ2, if the first temperature T1 obtained in step S17 exceeds the first threshold S1, the control unit 12 may reduce the rotational speed of the compressor 61. Moreover, if the first temperature T1 does not fall below the second threshold S2 in step S18 (No in S18), the control unit 12 may reduce the rotational speed of the compressor 61.

[0166] In Embodiment 1, an example was described in which the opening degree J is increased by a first increment ΔJ1 and then by a second increment ΔJ2 in the first operation, but the invention is not limited to this. For example, after increasing the opening degree J by the first increment ΔJ1, the control unit 12 may maintain the opening degree J until the first temperature T1 falls below the second threshold S2.

[0167] In Embodiment 1, an example was described in which, in the first operation, the control unit 12 increases the actual first opening degree J1 obtained in step S11 in step S15, but the invention is not limited to this. For example, the control unit 12 may store a target value for the opening degree J, and in step S15, increase the opening degree J of the electronic expansion valve 66 relative to the target value.

[0168] In Embodiment 1, an example was described in which the evaporator 63 has three rows. However, the evaporator 63 is not limited to this, and it is sufficient if the evaporator 63 has two or more rows in which the heat transfer tubes 99 are connected in series and arranged in the direction of airflow.

[0169] In Embodiment 1, an example was described in which the opening degree J of the electronic expansion valve 66 is controlled in the second operation to bring the second temperature T2 closer to the third threshold S3, but the invention is not limited to this. The control unit 12 may omit steps S24 to S25 in the latter half of the drying process and reduce the opening degree J of the electronic expansion valve 66 to lower the second temperature T2.

[0170] In Embodiment 1, an example was described in which, in the third operation, the control unit 12 determines whether the third temperature T3 exceeds the threshold for both the fourth threshold S4 and the fifth threshold S5, but the invention is not limited to this. The control unit 12 may also determine whether the third temperature T3 exceeds the threshold for only one of the thresholds S4 and S5.

[0171] The dryer in the first embodiment includes a storage tank for storing an object, a heat pump device connecting a compressor, a condenser, an expansion mechanism, and an evaporator with refrigerant piping for circulating a refrigerant, an air passage member defining an air passage between the storage tank and the heat pump device, a fan provided in the air passage member for circulating air between the storage tank and the heat pump device, a first sensor provided in the condenser for measuring a first temperature of the refrigerant, and a control unit for controlling the compressor and the expansion mechanism. The expansion mechanism has a flow rate adjustment unit that can change the flow rate of the incoming refrigerant, and the control unit controls the flow rate adjustment unit so that the flow rate of the refrigerant flowing into the expansion mechanism increases when the first temperature exceeds a first threshold.

[0172] In the second embodiment of the dryer, in the dryer of the first embodiment, the control unit controls the flow rate adjustment unit so that when the first temperature exceeds a first threshold, the flow rate of the refrigerant flowing into the expansion mechanism increases by a first increment.

[0173] In the third embodiment of the dryer, in the dryer of the second embodiment, the control unit controls the flow rate adjustment unit by the first increment, and when the first temperature exceeds the first threshold, determines the second increment based on the first temperature and controls the flow rate adjustment unit so that the flow rate of the refrigerant flowing into the expansion mechanism increases by the second increment.

[0174] In the fourth embodiment, as a dryer in any of the first to third embodiments, the control unit controls the flow rate adjustment unit so that the flow rate of refrigerant flowing into the expansion mechanism decreases when the first temperature falls below a second threshold which is lower than the first threshold.

[0175] As a dryer in the fifth embodiment, in a dryer in any of the first to fourth embodiments, the control unit controls the flow rate adjustment unit so that when the first temperature exceeds the first threshold, the rotational speed of the compressor is reduced, and after the rotational speed of the compressor is reduced, when the first temperature exceeds the first threshold, the flow rate of the refrigerant flowing into the expansion mechanism is increased.

[0176] As a dryer in the sixth embodiment, in a dryer in any of the first to fifth embodiments, the control unit controls the flow rate adjustment unit so as to increase the flow rate of refrigerant flowing into the expansion mechanism when the first temperature exceeds a first threshold, and after controlling the flow rate adjustment unit, when the first temperature exceeds a first threshold, the rotational speed of the compressor is reduced.

[0177] While this disclosure is adequately described in relation to preferred embodiments with reference to the accompanying drawings, various modifications and alterations will be obvious to those skilled in the art. Such modifications and alterations should be understood to be included within the scope of the invention as defined by the appended claims. [Industrial applicability]

[0178] The dryer of this disclosure is useful as a household clothes dryer, a commercial clothes dryer, any type of washer-dryer (e.g., a household drum-type washer-dryer, a top-loading washer-dryer), and other garment processing machines with drying functions, as it can shorten the drying process time. [Explanation of Symbols]

[0179] 1 Dryer 2 cabinets 3 Outer tank 4 Storage tank 6. Heat pump system 8 cases 9. Airflow members 10 Fans 61 Compressor 62 Expansion Mechanism 63 Evaporator 64 Condenser 65 Refrigerant piping 66 Electronic expansion valve 71 First Sensor 72. Second Sensor 73 Third Sensor

Claims

1. A storage tank for containing the object, A heat pump system is formed by circulating a refrigerant through refrigerant piping, connecting a compressor, condenser, expansion mechanism, and evaporator. An air passage member that defines an air passage between the storage tank and the heat pump device, A fan is provided in the air passage member to circulate air between the containment tank and the heat pump device, A first sensor is provided in the condenser for measuring the first temperature of the refrigerant, The system comprises a control unit that controls the compressor and the expansion mechanism, The expansion mechanism has a flow rate adjustment unit that can change the flow rate of the incoming refrigerant, A dryer in which the control unit controls the flow rate adjustment unit so that the flow rate of the refrigerant flowing into the expansion mechanism increases when the first temperature exceeds a first threshold.

2. The dryer according to claim 1, wherein the control unit controls the flow rate adjustment unit so that when the first temperature exceeds the first threshold, the flow rate of the refrigerant flowing into the expansion mechanism increases by a first increment.

3. The dryer according to claim 2, wherein the control unit controls the flow rate adjustment unit by the first increment, and when the first temperature exceeds a first threshold, determines a second increment based on the first temperature and controls the flow rate adjustment unit so that the flow rate of refrigerant flowing into the expansion mechanism increases by the second increment.

4. The dryer according to any one of claims 1 to 3, wherein the control unit controls the flow rate adjustment unit so that the flow rate of refrigerant flowing into the expansion mechanism decreases when the first temperature falls below a second threshold which is lower than the first threshold.

5. The control unit, When the first temperature exceeds the first threshold, the rotational speed of the compressor is reduced. The dryer according to any one of claims 1 to 3, wherein, after reducing the rotational speed of the compressor, the flow rate adjustment unit is controlled to increase the flow rate of the refrigerant flowing into the expansion mechanism when the first temperature exceeds a first threshold.

6. The control unit, When the first temperature exceeds the first threshold, the flow rate adjustment unit is controlled to increase the flow rate of the refrigerant flowing into the expansion mechanism. A dryer according to any one of claims 1 to 3, wherein, after controlling the flow rate adjustment unit, the rotation speed of the compressor is reduced when the first temperature exceeds the first threshold.

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