Dehumidifier and method for controlling dehumidifier

Abstract

To achieve reduction of electric power consumption in a dehumidifier.SOLUTION: A humidifier 1 comprises: a refrigerant circuit RC having a refrigerant compressor 10, a condenser 12, an expansion valve 13 and an evaporator 14; an air flow path AP having an air compressor 20 and in which the compressed air discharged from the air compressor 20 flows via the evaporator 14; a motor 11 driving the refrigerant compressor 10; a temperature sensor 23 detecting the temperature of the compressed air at the outlet of the evaporator 14; and a control part 30 controlling revolution of the motor 11. The control part 30 controls the motor 11 so that the revolution of the motor 11 decreases when the temperature of the compressed air at the outlet of the evaporator 14 dips from a prescribed temperature range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dehumidifier and a method for controlling a dehumidifier. [Background technology]

[0002] The compressed air dehumidifier of Patent Document 1 adjusts the refrigeration capacity of the refrigeration cycle according to the outdoor temperature to change the dew point temperature of the compressed air, thereby reducing power consumption. For example, in summer, when the outdoor temperature is high and there is no need to completely dehumidify the compressed air, the refrigeration capacity of the refrigeration cycle is adjusted so that the compressed air is cooled to a temperature slightly higher than the target dew point temperature at which the compressed air can be dehumidified without causing condensation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-326126 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, when it is desired to maintain the temperature of the compressed air at or below a target dew point temperature, it is not possible to reduce power consumption.

[0005] An object of the present invention is to reduce power consumption in a dehumidifier. [Means for solving the problem]

[0006] One aspect of the present invention provides a dehumidifier comprising a refrigerant circuit having a refrigerant compressor, a condenser, an expansion valve, and an evaporator; an air flow path having an air compressor, in which compressed air discharged from the air compressor flows through the evaporator; a motor for driving the refrigerant compressor; a temperature sensor for detecting the temperature of the compressed air at an outlet of the evaporator; and a control unit for controlling the rotation speed of the motor, wherein the control unit controls the motor so that the rotation speed of the motor is reduced when the temperature of the compressed air at the outlet of the evaporator falls below a predetermined temperature range.

[0007] When the temperature of the compressed air at the outlet of the evaporator is below a predetermined temperature range, the refrigeration capacity of the refrigerant circuit is greater than the refrigeration capacity required to maintain the temperature of the compressed air at the outlet of the evaporator within the predetermined temperature range. According to this configuration, when the refrigeration capacity of the refrigerant circuit is excessively large, the number of rotations of the motor is reduced, thereby reducing the power consumption of the dehumidifier.

[0008] The predetermined temperature range may be a temperature range that includes a target dew point temperature of the compressed air at the outlet of the evaporator.

[0009] For example, if the target dew point temperature is 10°C, the predetermined temperature range is, for example, from 8°C to 10°C.

[0010] The control unit may be provided with a load detection unit that detects the load on the motor, and when the temperature of the compressed air at the outlet of the evaporator exceeds the specified temperature range, the control unit may control the motor so that the rotation speed of the motor decreases when the load on the motor exceeds a preset upper limit value, and the rotation speed of the motor increases when the load on the motor is equal to or lower than the upper limit value.

[0011] When the temperature of the compressed air at the outlet of the evaporator exceeds a predetermined temperature range, the refrigeration capacity of the refrigerant circuit is insufficient to maintain the temperature of the compressed air at the outlet of the evaporator within the predetermined temperature range. With this configuration, even if the refrigeration capacity of the refrigerant circuit is insufficient, if the load on the motor is excessive, the motor rotation speed is reduced to reduce the load on the motor and protect the motor. On the other hand, if the refrigeration capacity of the refrigerant circuit is insufficient but the load on the motor is not excessive, the motor rotation speed is increased to increase the refrigeration capacity of the refrigerant circuit, thereby lowering the temperature of the compressed air at the outlet of the evaporator.

[0012] The air compressor may have a variable discharge flow rate.

[0013] The air flow path may include a heat exchanger that exchanges heat between the compressed air upstream of the evaporator and the compressed air downstream of the evaporator.

[0014] The lower the temperature of the compressed air flowing into the evaporator, the less refrigeration capacity is required to maintain the temperature of the compressed air at the outlet of the evaporator within a predetermined temperature range. In other words, the lower the temperature of the compressed air flowing into the evaporator, the lower the number of rotations of the motor of the refrigerant compressor required to prevent the temperature of the compressed air at the outlet of the evaporator from exceeding the predetermined temperature range. With this configuration, the temperature of the compressed air flowing into the evaporator is reduced by exchanging heat between the compressed air upstream of the evaporator and the compressed air downstream of the evaporator that has been cooled by the evaporator. As a result, power consumption can be reduced.

[0015] The motor may have a motor coil, and the load detection unit may detect a winding temperature of the motor coil as the load of the motor.

[0016] According to this configuration, since the load detection unit detects the winding temperature of the motor coil, it is possible to more effectively prevent the motor from burning out compared to a case where the motor load is detected from the motor current, for example.

[0017] Another aspect of the present invention provides a control method for a dehumidifier comprising a refrigerant circuit having a refrigerant compressor, a condenser, an expansion valve, and an evaporator, an air flow path having an air compressor in which compressed air discharged from the air compressor flows through the evaporator, a motor for driving the refrigerant compressor, and a temperature sensor for detecting the temperature of the compressed air at an outlet of the evaporator, the control method reducing the rotation speed of the motor when the temperature of the compressed air at the outlet of the evaporator falls below a predetermined temperature range. Effect of the Invention

[0018] According to the present invention, it is possible to reduce power consumption in a dehumidifier. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of a dehumidifier according to an embodiment of the present invention. [Diagram 2] 4 is a diagram showing the relationship between the cooling heat load and the temperature of compressed air at the outlet of the evaporator. [Diagram 3] 5 is a flowchart of motor rotation speed control executed by a control unit during operation of the dehumidifier according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0021] FIG. 1 is a schematic configuration diagram of a dehumidifier 1 according to this embodiment.

[0022] (Overall composition) 1, the dehumidifier 1 includes a refrigerant compressor 10, a motor 11, a condenser 12, an expansion valve 13, and an evaporator 14. The dehumidifier 1 also includes an air compressor 20, an aftercooler 21, and an economizer heat exchanger 22. The dehumidifier 1 further includes a control unit 30 and an inverter 31.

[0023] (Refrigerant circuit) The refrigerant compressor 10, the condenser 12, the expansion valve 13, and the evaporator 14 constitute a refrigerant circuit RC. In the refrigerant circuit RC, the refrigerant flows and circulates through the refrigerant compressor 10, the condenser 12, the expansion valve 13, and the evaporator 14 in this order. The refrigerant in this embodiment is a natural refrigerant such as ammonia or an artificial refrigerant such as fluorocarbons, and does not contain air.

[0024] The refrigerant compressor 10 is a variable displacement compressor that compresses and discharges the refrigerant.

[0025] The motor 11 is a variable speed motor that is mechanically connected to the refrigerant compressor 10 and drives the refrigerant compressor 10. That is, as described in detail later, the rotation speed of the motor 11 (the number of times the motor 11 rotates per unit time) can be increased and decreased within a certain range by the inverter 31. A load detection unit 15 that detects the load on the motor 11 is connected to the motor 11. The load detection unit 15 in this embodiment detects a winding temperature Tm of a motor coil (not shown) of the motor 11. In this embodiment, when the winding temperature Tm detected by the load detection unit 15 exceeds a preset upper limit value, the rotation speed of the motor 11 is reduced.

[0026] The condenser 12 is disposed on the discharge side (downstream side) of the refrigerant compressor 10, and is fluidly connected to the refrigerant compressor 10 via a first refrigerant flow path 16. The condenser 12 is a heat exchanger that cools and liquefies the high-temperature, high-pressure refrigerant gas discharged from the refrigerant compressor 10.

[0027] The expansion valve 13 is disposed downstream of the condenser 12, and is fluidly connected to the condenser 12 via a second refrigerant flow path 17. The expansion valve 13 reduces the pressure of the refrigerant liquefied in the condenser 12 to a low temperature and low pressure.

[0028] The evaporator 14 is disposed downstream of the expansion valve 13 and on the suction side (upstream side) of the refrigerant compressor 10. The evaporator 14 is fluidly connected to the expansion valve 13 via a third refrigerant flow path 18, and is fluidly connected to the refrigerant compressor 10 via a fourth refrigerant flow path 19. The evaporator 14 is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit RC and the air introduced into the evaporator 14. The liquid refrigerant that has been reduced to a low temperature and low pressure by the expansion valve 13 is heated and evaporated by the evaporator 14, and is sucked into the refrigerant compressor 10. On the other hand, the air introduced into the evaporator 14 is cooled by the evaporator 14.

[0029] When the air introduced into the evaporator 14 is cooled by the evaporator 14, moisture contained in the air is condensed, and drain is generated. A drain outlet 14c is provided at the bottom of the evaporator 14 for discharging drain accumulated in the evaporator 14. A drain outlet 14c is fluidly connected to a drain outlet passage 14d that guides the drain discharged from the drain outlet 14c to the outside. In addition, a drain outlet valve 14e that opens and closes the drain outlet passage 14d is provided in the drain outlet passage 14d. The drain outlet valve 14e of this embodiment is an electromagnetic valve. The drain outlet valve 14e may be opened periodically, or may be opened when a sensor (not shown) detects that a predetermined amount of drain has accumulated in the evaporator 14. The drain outlet valve 14e is not limited to an electromagnetic valve, and may be a free float type air trap. If it is a free float type air trap, electrical opening and closing control is not required, so that the drain can be automatically discharged without opening and closing control.

[0030] (Air flow path) In this embodiment, the air compressor 20, the aftercooler 21, the economizer heat exchanger 22, and the evaporator 14 constitute an air flow path AP. In the air flow path AP, a temperature sensor 23 is provided downstream of the evaporator 14 (specifically, a fifth air flow path 28 described later) for detecting the temperature of the compressed air at the outlet 14b of the evaporator 14 (outlet temperature To).

[0031] The air compressor 20 is a variable displacement compressor that compresses and discharges air sucked in through the first air flow path 24. The air compressor 20 is driven by a variable speed motor (not shown), and the rotation speed of the variable speed motor can be increased and decreased within a certain range by an inverter (not shown).

[0032] The aftercooler 21 is disposed on the discharge side (downstream side) of the air compressor 20, and is fluidly connected to the air compressor 20 via a second air flow path 25. The aftercooler 21 cools the compressed air discharged from the air compressor 20.

[0033] The economizer heat exchanger 22 is disposed downstream of the aftercooler 21. The economizer heat exchanger 22 includes a first portion 22a fluidly connected to the aftercooler 21 via a third air passage 26. The first portion 22a is fluidly connected to an inlet 14a for introducing compressed air to the evaporator 14 via a fourth air passage 27.

[0034] The economizer heat exchanger 22 also includes a second portion 22b that is fluidly connected to an outlet 14b for discharging the compressed air from the evaporator 14 via a fifth air passage 28. The compressed air that has passed through the second portion 22b is supplied to the outside via a sixth air passage 29.

[0035] The economizer heat exchanger 22 is a heat exchanger that exchanges heat between compressed air on the upstream side of the evaporator 14 flowing through the first portion 22a and compressed air on the downstream side of the evaporator 14 (compressed air cooled by the evaporator 14) flowing through the second portion 22b. The compressed air on the upstream side of the evaporator 14 is cooled by the economizer heat exchanger 22, and the compressed air on the downstream side of the evaporator 14 is heated by the economizer heat exchanger 22.

[0036] (Air flow) Air taken in from the outside into the air flow path AP is dehumidified while flowing through the air flow path AP and is supplied from the air flow path AP to the outside.

[0037] First, air taken into the air flow path AP from the outside is compressed by the air compressor 20 and discharged as compressed air. In this embodiment, the discharge pressure of the air compressor 20 is, for example, 0.69 MPa.

[0038] The compressed air is then cooled in the aftercooler 21. In this embodiment, the temperature of the compressed air at the outlet of the aftercooler 21 is, for example, 40°C.

[0039] The compressed air is then further cooled in the economizer heat exchanger 22. In this embodiment, the temperature of the compressed air at the outlet of the economizer heat exchanger 22 is, for example, 30°C.

[0040] Thereafter, the compressed air is introduced into the evaporator 14, where it is cooled and dehumidified. In this embodiment, the temperature of the compressed air at the outlet 14b of the evaporator 14 (outlet temperature To) is, for example, 10°C. That is, the dew point temperature of the compressed air at the outlet 14b of the evaporator 14 under a pressure of 0.69 MPa is 10°C. At this time, the dew point temperature of the compressed air under atmospheric pressure is -17.3°C.

[0041] Finally, the compressed air dehumidified by the evaporator 14 is heated by the economizer heat exchanger 22 and then supplied to the outside through the air flow path AP.

[0042] (Control unit / inverter) The control unit 30 is composed of a microcomputer, an input / output circuit, etc. A signal indicating the outlet temperature To is input from the temperature sensor 23 to the control unit 30, and a signal indicating the load of the motor 11 is input from the load detection unit 15 every moment. The control unit 30 calculates a target rotation speed of the motor 11 based on the signals from the temperature sensor 23 and the load detection unit 15, and outputs a motor rotation speed command signal to the inverter 31, thereby controlling the rotation speed of the motor 11 (the number of times the motor 11 rotates per unit time).

[0043] The inverter 31 controls the rotation speed of the motor 11 by outputting a drive signal to the motor 11 based on a motor rotation speed command signal input from the control unit 30. The inverter 31 is also electrically connected to a power source 32, and receives AC power from the power source 32.

[0044] (Relationship between compressed air temperature and cooling heat load in the evaporator) Fig. 2 is a graph showing the relationship, with other conditions being the same, between the temperature of the compressed air at the outlet 14b of the evaporator 14 (outlet temperature To) and the cooling heat load in the evaporator 14. In Fig. 2, the horizontal axis represents the outlet temperature To [°C], and the vertical axis represents the cooling heat load in the evaporator 14 [arbitrary scale].

[0045] 2 moves downward (see the two-dot chain line in FIG. 2) when the discharge flow rate of the air compressor 20 decreases or when the temperature of the compressed air introduced into the evaporator 14 decreases. This is because the refrigeration capacity required to maintain the outlet temperature To within a predetermined temperature range, that is, the cooling heat load in the evaporator 14, decreases.

[0046] Referring to FIG. 2, the higher the outlet temperature To, the greater the cooling heat load in the evaporator 14. The dehumidifier 1 is set so that the outlet temperature To is within a predetermined temperature range. In FIG. 2, the region where the outlet temperature To is below the predetermined temperature range is indicated by the X region, the region where the outlet temperature To is within the predetermined temperature range is indicated by the Y region, and the region where the outlet temperature To is above the predetermined temperature range is indicated by the Z region. The predetermined temperature range is a temperature range including the target dew point temperature of the compressed air at the outlet of the evaporator. That is, as long as the target dew point temperature is included within the predetermined temperature range, the upper limit of the predetermined temperature range may be the target dew point temperature, and the lower limit of the predetermined temperature range may be the target dew point temperature. It is preferable that the upper limit of the predetermined temperature range is the target dew point temperature. Moreover, the target dew point temperature in this embodiment is the target dew point temperature of the compressed air under a pressure of 0.69 MPa. In this embodiment, the target dew point temperature is 10°C, and the predetermined temperature range is, for example, from 8°C to 10°C.

[0047] In the Y region where the outlet temperature To is within a predetermined temperature range, the refrigeration capacity of the refrigerant circuit RC is neither excessive nor insufficient with respect to the refrigeration capacity required to maintain the outlet temperature To within the predetermined temperature range. Therefore, when the outlet temperature To falls within the Y region, there is no need to change the rotation speed of the motor 11.

[0048] In the X region where the outlet temperature To is below the lower limit of the predetermined temperature range, the refrigeration capacity of the refrigerant circuit RC is greater than the refrigeration capacity required to maintain the outlet temperature To within the predetermined temperature range. When the outlet temperature To falls within the X region, the rotation speed of the motor 11 is reduced, so that the outlet temperature To transitions from the X region to the Y region, and the outlet temperature To is maintained within the predetermined temperature range. Therefore, when the outlet temperature To falls within the X region, there is room to reduce the power consumption by reducing the rotation speed of the motor 11.

[0049] On the other hand, in the Z region where the outlet temperature To exceeds the upper limit of the predetermined temperature range, the refrigeration capacity of the refrigerant circuit RC is insufficient to maintain the outlet temperature To at or below the target dew point temperature. Therefore, when the outlet temperature To falls within the Z region, it is necessary to increase the rotation speed of the motor 11 to increase the refrigeration capacity of the refrigerant circuit RC.

[0050] (Motor speed control) The following describes the rotation speed control of the motor 11 executed by the control unit 30 while the dehumidifier 1 is in operation. Fig. 3 is a flowchart showing the rotation speed control of the motor 11 executed by the control unit 30 while the dehumidifier 1 is in operation.

[0051] 3, when air compressor 20 is started, control unit 30 starts control of the rotation speed of motor 11. The rotation speed of motor 11 immediately after control of the rotation speed of motor 11 is started is set in advance.

[0052] First, the control unit 30 acquires the temperature of the compressed air at the outlet of the evaporator 14 (outlet temperature To) from the temperature sensor 23 (step S1).

[0053] Next, the control unit 30 determines to which of the above-mentioned X, Y, or Z regions (shown in FIG. 2) the acquired outlet temperature To belongs (step S2).

[0054] If it is determined in step S2 that the outlet temperature To belongs to the X region, the control unit 30 reduces the rotation speed of the motor 11 (step S7). After that, the control of the rotation speed of the motor 11 proceeds to step S6.

[0055] If it is determined in step S2 that the outlet temperature To belongs to the Y region, the control unit 30 does not change the rotation speed of the motor 11. After that, the control of the rotation speed of the motor 11 proceeds to step S6.

[0056] If it is determined in step S2 that the outlet temperature To belongs to the Z region, the control unit 30 acquires load information of the motor 11 (in this embodiment, the winding temperature Tm of the motor coil) from the load detection unit 15 (step S3).

[0057] Thereafter, the control unit 30 determines whether or not the load on the motor 11 is equal to or lower than an upper limit (step S4). In this embodiment, it determines whether or not the winding temperature Tm of the motor coil is equal to or lower than a preset upper limit.

[0058] In this embodiment, if it is determined in step S4 that the motor coil winding temperature Tm exceeds a preset upper limit, the control unit 30 reduces the rotation speed of the motor 11 (step S7). If the motor coil winding temperature Tm exceeds the preset upper limit, the motor 11 is in an overload state, and therefore the rotation speed of the motor 11 is reduced to protect the motor 11. Thereafter, the control of the rotation speed of the motor 11 proceeds to step S6.

[0059] On the other hand, in this embodiment, when it is determined in step S4 that the motor coil winding temperature Tm is equal to or lower than a preset upper limit, the control unit 30 increases the rotation speed of the motor 11 (step S5). After that, the rotation speed control of the motor 11 proceeds to step S6.

[0060] In step S6, the control unit 30 determines whether the air compressor 20 is stopped or not.

[0061] If it is determined in step S6 that the air compressor 20 is stopped, the control unit 30 ends the control of the rotation speed of the motor 11.

[0062] On the other hand, if it is determined in step S6 that the air compressor 20 is not stopped, the control of the rotation speed of the motor 11 returns to step S1 again.

[0063] The dehumidifier 1 of this embodiment has the following functions.

[0064] When the temperature of the compressed air at the outlet of the evaporator 14 (outlet temperature To) is below a predetermined temperature range, the refrigeration capacity of the refrigerant circuit RC is greater than the refrigeration capacity required to maintain the outlet temperature To within the predetermined temperature range. In this embodiment, when the refrigeration capacity of the refrigerant circuit RC is greater than the required refrigeration capacity, the rotation speed of the motor 11 is reduced, so that the power consumption of the dehumidifier 1 can be reduced.

[0065] When the air compressor 20 is a variable displacement compressor as in this embodiment, the flow rate of compressed air introduced into the evaporator 14 increases and decreases. When the flow rate of compressed air introduced into the evaporator 14 decreases, the outlet temperature To decreases if the refrigeration capacity of the refrigerant circuit RC is constant. According to the dehumidifier 1 of this embodiment, when the outlet temperature To decreases and falls below a predetermined temperature range, it is possible to reduce power consumption. For this reason, this is particularly effective when the air compressor 20 is a variable displacement compressor.

[0066] When the outlet temperature To is above a predetermined temperature range, the refrigeration capacity of the refrigerant circuit RC is insufficient to maintain the outlet temperature To within the predetermined temperature range. In this embodiment, even when the refrigeration capacity of the refrigerant circuit RC is insufficient to the required refrigeration capacity, if the load on the motor 11 is excessively large, the rotation speed of the motor 11 is reduced to reduce the load on the motor 11 and protect the motor 11. On the other hand, when the refrigeration capacity of the refrigerant circuit RC is insufficient to the required refrigeration capacity, if the load on the motor 11 is not excessive, the rotation speed of the motor 11 is increased to increase the refrigeration capacity of the refrigerant circuit RC, thereby lowering the outlet temperature To.

[0067] The lower the temperature of the compressed air flowing into the evaporator 14, the less the refrigeration capacity required to maintain the outlet temperature To within a predetermined temperature range. In other words, the rotation speed of the motor 11 of the refrigerant compressor 10 required to prevent the outlet temperature To from exceeding the predetermined temperature range decreases. In this embodiment, the economizer heat exchanger 22 exchanges heat between the compressed air upstream of the evaporator 14 and the compressed air downstream of the evaporator 14 that has been cooled by the evaporator 14, thereby lowering the temperature of the compressed air flowing into the evaporator 14. As a result, power consumption can be reduced.

[0068] As described above, according to the dehumidifier 1 of this embodiment, the temperature of the compressed air at the outlet of the evaporator 14 can be controlled to a predetermined temperature, so that even if the discharge air volume of the air compressor 20 changes, a required dew point temperature can be maintained while preventing a decrease in the efficiency of the refrigerant circuit RC (i.e., the refrigeration type dehumidifier) ​​due to excessive cooling of the compressed air. This makes it possible to obtain the best efficiency for the refrigerant circuit RC (refrigeration type dehumidifier) ​​and reduce power consumption.

[0069] Furthermore, according to the dehumidifier 1 of this embodiment, the load detection unit 15 detects the winding temperature of the motor coil, so that burnout of the motor 11 can be more effectively prevented compared to, for example, detecting the load of the motor 11 by the motor current.

[0070] Although specific embodiments of the present invention and modifications thereof have been described above, the present invention is not limited to the above-described embodiments and can be practiced with various modifications within the scope of the present invention.

[0071] For example, the air compressor 20 in the embodiment is an inverter type variable displacement compressor, but is not limited to this, and the discharge amount may be changed by throttling the suction.

[0072] Further, the air compressor 20 in the embodiment is an inverter type variable displacement compressor, but is not limited to this and may be a fixed displacement compressor.

[0073] Although the load detection unit 15 in the embodiment detects the winding temperature Tm of the motor coil, the present invention is not limited to this and may detect the motor current of the motor 11. [Explanation of symbols]

[0074] 1 Dehumidifier 10 Refrigerant compressor 11 Motor 12 Condenser 13 Expansion valve 14 Evaporator 14a Entrance 14b Exit 14c Drain outlet 14d Drain discharge flow path 14e Drain discharge valve 15 Load detection section 20. Air Compressor 21 Aftercooler 22 Economizer heat exchanger 22a Part 1 22b Part 2 23 Temperature Sensor 30 Control section 31 Inverter RC refrigerant circuit AP Air Flow Path

Claims

1. a refrigerant circuit having a refrigerant compressor, a condenser, an expansion valve, and an evaporator; an air flow path including an air compressor, in which compressed air discharged from the air compressor flows through the evaporator; A motor that drives the refrigerant compressor; A load detection unit that detects a load on the motor; a temperature sensor for detecting a temperature of the compressed air at an outlet of the evaporator; A control unit for controlling the number of rotations of the motor; Equipped with the control unit controls the motor so as to reduce the number of revolutions of the motor when the temperature of the compressed air at the outlet of the evaporator falls below a predetermined temperature range including a target dew point temperature, thereby maintaining the refrigeration capacity of the refrigerant circuit in a state that is neither excessive nor insufficient with respect to the refrigeration capacity required to maintain the temperature of the compressed air at the outlet of the evaporator within the predetermined temperature range; The control unit controls the motor so that, when the temperature of the compressed air at the outlet of the evaporator exceeds the specified temperature range, the motor rotation speed decreases when the motor load exceeds a preset upper limit value, and the motor rotation speed increases when the motor load is equal to or lower than the upper limit value.

2. The dehumidifier according to claim 1 , wherein the air compressor has a variable discharge flow rate.

3. The dehumidifier according to claim 1 or 2, wherein the air flow path includes a heat exchanger for exchanging heat between the compressed air upstream of the evaporator and the compressed air downstream of the evaporator.

4. The motor has a motor coil. The dehumidifier according to claim 1 , wherein the load detection unit detects a winding temperature of the motor coil as the load of the motor.

5. a refrigerant circuit having a refrigerant compressor, a condenser, an expansion valve, and an evaporator; an air flow path including an air compressor, in which compressed air discharged from the air compressor flows through the evaporator; A motor that drives the refrigerant compressor; A load detection unit that detects a load on the motor; a temperature sensor for detecting the temperature of the compressed air at an outlet of the evaporator; In a dehumidification device comprising: When the temperature of the compressed air at the outlet of the evaporator falls below a predetermined temperature range including a target dew point temperature, the rotation speed of the motor is reduced to maintain the refrigeration capacity of the refrigerant circuit in a state that is neither excessive nor insufficient with respect to the refrigeration capacity required to maintain the temperature of the compressed air at the outlet of the evaporator within the predetermined temperature range, A control method for a dehumidification device, comprising: when the temperature of the compressed air at the outlet of the evaporator exceeds the temperature range, reducing the rotation speed of the motor when the load on the motor exceeds a preset upper limit value, and increasing the rotation speed of the motor when the load on the motor is equal to or lower than the upper limit value.

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