Liquid-supplied gas compressor

Abstract

Provided is an oil-supplied gas compressor capable of suppressing the temperature on the discharge side of a compressor main body at the time of restart. An oil-supplied air compressor (1) includes a compressor main body (3) driven by an electric motor (2); a separator (6) that separates oil from compressed air discharged from the compressor main body (3); an oil supply system (8) that supplies the oil separated by the separator (6) to a working chamber of the compressor main body (3); an oil cooler (15) provided in the oil supply system (8) and cooling the oil using cooling air generated by a cooling fan (13); and a control device (9). The control device (9) stops the electric motor (2) and the cooling fan (13) when the duration of no-load operation reaches a prescribed value. Also, based on the detection history of a discharge-side pressure sensor (14), the time of recovery at which the electric motor (2) is restarted is predicted, and the temperature on the discharge side of the compressor main body (3) at the time of recovery is predicted. In the case where the predicted temperature on the discharge side exceeds a prescribed allowable value, the cooling fan (13) is restarted prior to the electric motor (2).

Description

Technical Field

[0001] This invention relates to a liquid-supply gas compressor that supplies liquid to a working chamber and compresses gas. Background Technology

[0002] Patent Document 1 discloses an oil-supply air compressor, one type of liquid-supply gas compressor. The oil-supply air compressor of Patent Document 1 includes: an electric motor; a compressor body driven by the electric motor, which supplies oil (liquid) to the working chamber while compressing air (gas); a separator that separates oil from the compressed air (compressed gas) discharged from the compressor body; an oil supply system (liquid supply system) that supplies the oil separated by the separator to the working chamber of the compressor body; a cooling fan; and an oil cooler (liquid cooler) provided in the oil supply system that uses cooling air generated by the cooling fan to cool the oil. Heat is generated when air is compressed in the working chamber of the compressor body, causing the temperature of the compressed air to rise. The compressed air is cooled by the oil supplied to the working chamber of the compressor body, thereby suppressing the temperature of the compressed air.

[0003] Patent Document 1's oil-supply type air compressor further includes: an intake throttle valve disposed on the intake side of the compressor body; a discharge side pressure sensor for detecting the discharge side pressure of the compressor body; and a control device for controlling the motor and the intake throttle valve. During motor operation, when the discharge side pressure detected by the discharge side pressure sensor rises to a predetermined upper limit, the control device switches the intake throttle valve from an open state to a closed state, switching from load operation to no-load operation. Furthermore, when the duration of no-load operation reaches a predetermined value, the motor is stopped. Then, when the discharge side pressure detected by the discharge side pressure sensor drops to a predetermined lower limit, the motor is restarted, and the intake throttle valve is switched to an open state, switching back to load operation. Energy saving is achieved by operating or stopping the compressor body under no-load conditions based on the discharge side pressure of the compressor body.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-072708 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Although not explicitly described in Patent Document 1, the control device controls the cooling fan, for example, in conjunction with the motor. That is, the cooling fan stops when the motor stops after a predetermined duration of no-load operation. Furthermore, the cooling fan restarts when the discharge-side pressure detected by the discharge-side pressure sensor drops to a predetermined lower limit and the motor restarts.

[0009] During the period when the motor and cooling fan are stopped, no compression heat is generated, and the oil is not forcibly cooled. Therefore, the oil temperature decreases slowly only through natural heat dissipation, and the discharge side temperature of the compressor body also decreases slowly. Furthermore, if, for example, the stop time of the motor and cooling fan is short, the motor may be restarted before the oil temperature and the discharge side temperature of the compressor body have sufficiently decreased. Moreover, as the motor speed increases, the heat generated by the compressor body increases sharply, so the discharge side temperature of the compressor body may become excessively high.

[0010] The present invention was made in view of the above circumstances, and one of its objectives is to suppress the discharge side temperature of the compressor body during restart.

[0011] Methods for solving problems

[0012] To solve the aforementioned problems, the structure described within the scope of the claims is applied. The present invention includes several solutions for solving the aforementioned problems; one example includes: an electric motor; a compressor body driven by the electric motor, supplying liquid to the working chamber and compressing gas; an intake throttle valve disposed on the intake side of the compressor body; a separator for separating liquid from the compressed gas discharged from the compressor body, and a liquid supply system for supplying the liquid separated by the separator to the working chamber of the compressor body; a cooling fan; a liquid cooler disposed in the liquid supply system, using cooling air generated by the cooling fan to cool the liquid; a discharge side pressure sensor for detecting the discharge side pressure of the compressor body; and a control device for controlling the electric motor, the intake throttle valve, and the cooling fan, wherein, during the driving of the electric motor, when the discharge side pressure detected by the discharge side pressure sensor rises to a predetermined upper limit value, the control device controls the intake throttle valve to switch from load operation to no-load operation, and when the duration of the no-load operation reaches a predetermined value... The control device stops the motor and then restarts it when the discharge pressure detected by the discharge pressure sensor drops to a predetermined lower limit. It also controls the intake throttle valve to switch to load operation. In the riser-type liquid-supply gas compressor, the control device stops the cooling fan when the duration of no-load operation reaches the predetermined value and the motor stops. Based on the detection history of the discharge pressure sensor during the motor stoppage or no-load operation, it predicts the recovery time when the discharge pressure of the compressor body drops to the predetermined lower limit and the motor restarts. It also predicts the discharge temperature of the compressor body at the recovery time when the cooling fan is stopped until the recovery time. If the predicted discharge temperature is below a predetermined allowable value, the cooling fan remains stopped. If the predicted discharge temperature exceeds the predetermined allowable value, the cooling fan is restarted before the motor.

[0013] Invention Effects

[0014] According to the present invention, the discharge side temperature of the compressor body during restart can be suppressed.

[0015] Furthermore, the topics, structures, and effects other than those mentioned above will be made clearer through the following explanation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the structure of the oil-supply air compressor according to the first embodiment of the present invention.

[0017] Figure 2This is a flowchart illustrating the control sequence of the inhalation throttle valve according to the first embodiment of the present invention.

[0018] Figure 3 This is a flowchart illustrating the control sequence of the electric motor and cooling fan according to the first embodiment of the present invention.

[0019] Figure 4 This is a timing diagram showing the operation of the electric motor and cooling fan in the first embodiment of the present invention, as well as the changes in the discharge side pressure and discharge side temperature of the compressor body.

[0020] Figure 5 This is a schematic diagram showing the structure of an oil-supply air compressor according to a first modification of the present invention.

[0021] Figure 6 This is a flowchart illustrating the control sequence of the electric motor and cooling fan according to the second embodiment of the present invention.

[0022] Figure 7 This is a timing diagram showing the operation of the electric motor and cooling fan in the second embodiment of the present invention, as well as the changes in the discharge side pressure and discharge side temperature of the compressor body.

[0023] Figure 8 This is a flowchart illustrating the control sequence of the electric motor and cooling fan in the second variation of the present invention. Detailed Implementation

[0024] The first embodiment of the present invention will be described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram showing the structure of the oil-supply air compressor of this embodiment.

[0026] The oil-supply air compressor 1 (hereinafter simply referred to as compressor 1) of this embodiment includes: an electric motor 2; a compressor body 3 driven by the electric motor 2, which supplies oil (liquid) to the working chamber while compressing air (gas); an air filter 4 and an intake throttle valve 5 provided on the intake side of the compressor body 3; a separator 6 for separating oil from the compressed air (compressed gas) discharged from the compressor body 3; a compressed air supply system 7 (compressed gas supply system) for supplying the compressed air separated by the separator 6 to the outside of the compressor 1; an oil supply system 8 (liquid supply system) for supplying the oil separated by the separator 6 to the working chamber of the compressor body 3; and a control device 9. Furthermore, the compressor 1 is configured as an assembly housing the above-mentioned components.

[0027] The compressor body 3, for example, has a pair of meshing male and female screw rotors and a housing for housing the screw rotors, with multiple working chambers formed in the tooth grooves of the screw rotors. Each working chamber moves axially along the rotor as it rotates, and sequentially performs the processes of intake air, compression air, and discharge compressed air. A discharge-side temperature sensor 10 is provided between the compressor body 3 and the separator 6. The discharge-side temperature sensor 10 detects the discharge-side temperature of the compressor body 3 and outputs it to the control device 9.

[0028] The compressed air supply system 7 includes a pressure regulating check valve 11 and an aftercooler 12 (compressed gas cooler) located downstream of the pressure regulating check valve 11. The aftercooler 12 cools the compressed air using cooling air generated by a cooling fan 13. A discharge side pressure sensor 14 is provided downstream of the aftercooler 12. The discharge side pressure sensor 14 detects the discharge side pressure of the compressor body 3 and outputs it to the control device 9.

[0029] The oil supply system 8 supplies oil to the working chamber of the compressor body 3 by utilizing the pressure difference between the separator 6 and the working chamber of the compressor body 3. The oil supply system 8 includes: an oil cooler 15 (liquid cooler); a bypass path 16 that bypasses the oil cooler 15; a temperature regulating valve 17 that adjusts the flow ratio of the oil cooler 15 and the flow ratio of the bypass path 16 according to the oil temperature; and an oil filter 18 located downstream of the confluence of the oil from the oil cooler 15 and the oil from the bypass path 16. The oil cooler 15 cools the oil using cooling air generated by a cooling fan 13.

[0030] Furthermore, the temperature regulating valve 17 in this embodiment is configured such that the flow ratio of the oil cooler 15 is 100% in some cases, but not in others. However, for example, if a portion of the cooling air generated by the cooling fan 13 is used to directly cool the compressor body 3, the temperature regulating valve 17 may also be configured such that the flow ratio of the oil cooler 15 is 0%.

[0031] The control device 9 has a processor that executes processes according to a program, and a memory that stores programs and data. The control device 9 controls the aforementioned motor 2, intake throttle valve 5, and cooling fan 13.

[0032] Next, use Figure 2 The control of the intake throttle valve 5 of the control device 9 based on this embodiment will be described. Figure 2 This is a flowchart illustrating the control sequence of the intake throttle valve in this embodiment.

[0033] According to the operation of the operation switch (not shown), the control device 9 starts the motor 2 and the cooling fan 13 (step S1) and controls the intake throttle valve 5 to be in the open state to carry out load operation (step S2).

[0034] During load operation, the control device 9 determines whether the discharge side pressure detected by the discharge side pressure sensor 14 has risen to the predetermined upper limit value Pu (step S3). When the discharge side pressure detected by the discharge side pressure sensor 14 rises to the predetermined upper limit value Pu, the intake throttle valve 5 is controlled to be closed, switching to no-load operation (step S4).

[0035] During no-load operation, the control device 9 determines whether the duration of no-load operation has reached a predetermined value A (step S5), and determines whether the discharge side pressure detected by the discharge side pressure sensor 14 has dropped to a predetermined lower limit value Pd (step S6). If the duration of no-load operation has not reached the predetermined value A, and the discharge side pressure detected by the discharge side pressure sensor 14 has dropped to the predetermined lower limit value Pd, the control device 9 controls the intake throttle valve 5 to open, switching to load operation (step S2).

[0036] Next, use Figure 3 The control of the electric motor 2 and the cooling fan 13 based on the control device 9 in this embodiment will be described. Figure 3 This is a flowchart illustrating the control steps of the electric motor and cooling fan in this embodiment.

[0037] During load operation, the control device 9 variably controls the target speed of the cooling fan 13 so that the discharge side temperature detected by the discharge side temperature sensor 10 reaches a predetermined target value T1 (see below). Figure 4 During no-load operation, the target speed of the cooling fan 13 can be variably controlled so that the discharge side temperature detected by the discharge side temperature sensor 10 is below a specified target value T1, and the target speed of the cooling fan 13 is above a specified minimum value.

[0038] Control device 9 in the above Figure 2 In step S5, when the duration of no-load operation reaches a predetermined value A, the motor 2 and cooling fan 13 are stopped (step S7). Then, the detection history of the discharge-side pressure sensor 14 and the discharge-side temperature sensor 10 for the predetermined time is stored. However, it is also possible to store the detection history of the discharge-side pressure sensor 14 during the period when the motor 2 is stopped, or, based on this, the detection history of the discharge-side pressure sensor 14 during the no-load operation period.

[0039] After the predetermined time has elapsed since the motor 2 and cooling fan 13 stopped, the control device 9 predicts, based on the detection history of the discharge-side pressure sensor 14, the recovery time when the discharge-side pressure of the compressor body 3 drops to a predetermined lower limit value Pd and the motor 2 restarts (step S8). Furthermore, assuming the cooling fan 13 is stopped until the recovery time, the control device 9 predicts the discharge-side temperature of the compressor body 3 at the recovery time in that case based on the detection history of the discharge-side temperature sensor 10 (step S9).

[0040] The control device 9 determines whether the predicted discharge side temperature exceeds the specified allowable value T2 (in other words, even if the discharge side temperature of the compressor body 3 rises as the speed of the motor 2 increases, the initial value of the discharge side temperature can be suppressed within the allowable range) (step S10). If the predicted discharge side temperature is below the specified allowable value T2, the cooling fan 13 continues to be stopped (step S11). Then, when the discharge side pressure detected by the discharge side pressure sensor 14 reaches the specified lower limit value Pd, the motor 2 and the cooling fan 13 are restarted (steps S12, S13).

[0041] If the predicted discharge side temperature exceeds the specified allowable value T2, the control device 9 restarts the cooling fan 13 before the motor 2 (step S14). Then, when the discharge side pressure detected by the discharge side pressure sensor 14 reaches the specified lower limit value Pd, the motor 2 is restarted again (steps S15, 16).

[0042] Next, using Figure 4 The operation and effects of this embodiment will be explained. Figure 4 This is a timing diagram showing the operation of the electric motor and cooling fan in this embodiment, as well as the changes in the discharge side pressure and discharge side temperature of the compressor body.

[0043] When the user operates the operation switch (time t1), the motor 2 and cooling fan 13 start, and the intake throttle valve 5 is controlled to open. That is, load operation is initiated. Furthermore, due to the balance between the amount of compressed air supplied from the compressor 1 to the outside and the amount of compressed air used outside, the discharge pressure of the compressor body 3 changes. Based on the change in the discharge pressure of the compressor body 3, load operation and no-load operation are switched.

[0044] When the duration of no-load operation reaches a predetermined value A (time t2), motor 2 and cooling fan 13 stop. After a predetermined time (time t3) has elapsed since motor 2 and cooling fan 13 stopped, control device 9 predicts the restart time of motor 2 (time t4). Additionally, as... Figure 4As shown by the dashed line, assuming the cooling fan 13 is stopped until the recovery time, the discharge side temperature of the compressor body 3 at the recovery time under this condition is predicted.

[0045] like Figure 4 As shown by the dashed line, if the predicted discharge temperature of the compressor body 3 exceeds the specified allowable value T2, the control device 9 will restart the cooling fan 13 before the motor 2. Thus, as... Figure 4 As shown by the solid line, the discharge side temperature of the compressor body 3 at the recovery time can be suppressed to below the specified allowable value T2. Furthermore, the oil temperature can also be reduced. Therefore, even if the heat generated by the compressor body 3 increases sharply with the increase of the motor 2's speed, the discharge side temperature of the compressor body 3 will not become excessively high. As a result, unnecessary alarms and control shutdowns can be prevented.

[0046] In addition, in the first embodiment, the example described is the case where the control device 9 stores the detection history of the discharge side temperature sensor 10 during the shutdown period of the cooling fan 13, and then predicts the discharge side temperature of the compressor body 3 at the recovery time when the cooling fan 13 is stopped to the recovery time based on the detection history of the discharge side temperature sensor 10, but it is not limited to this.

[0047] The first modification of the present invention will be described with reference to the accompanying drawings. Figure 5 This is a schematic diagram showing the structure of the oil-supply air compressor in this modified example. Furthermore, in this modified example, the same reference numerals are used for parts that are the same as in the first embodiment, and descriptions are appropriately omitted.

[0048] The compressor 1 in this modified example further includes an suction side temperature sensor 19 for detecting the suction side temperature of the compressor body 3.

[0049] The control device 9 acquires time-series data of the discharge side temperature of the compressor body 3 based on the detection history of the discharge side temperature sensor 10 during the periods when the motor 2 and cooling fan 13 are stopped. Additionally, it acquires the suction side temperature detected by the suction side temperature sensor 19 during the periods when the motor 2 and cooling fan 13 are stopped. Furthermore, it calculates the load rate based on the time of load operation and the time of no-load operation before the motor 2 and cooling fan 13 stop. The time-series data of the discharge side temperature, along with the suction side temperature and load rate, are then transmitted via the communication network 20 to an external server 21. The external server 21 stores the time-series data of the multiple discharge side temperatures received from the multiple compressors 1 together with the corresponding suction side temperature and load rate.

[0050] Similar to the first embodiment, control device 9 stops the motor 2 and cooling fan 13 when the duration of no-load operation reaches a predetermined value A. At this time, the load rate is calculated, and time-series data of the discharge side temperature, which includes the load rate and the suction side temperature detected by the suction side temperature sensor 19, is obtained from external server 21 via communication network 20. Then, based on the time-series data of the discharge side temperature obtained from external server 21, the discharge side temperature of the compressor body 3 at the recovery time is predicted, assuming the cooling fan 13 is stopped until the recovery time.

[0051] In this modified example configured as described above, the same effects as in the first embodiment can also be obtained.

[0052] The second embodiment of the present invention will be described with reference to the accompanying drawings. This embodiment determines whether to stop the cooling fan or continue driving it when the motor stops after a predetermined period of no-load operation. Furthermore, in this embodiment, the parts that are the same as in the first embodiment (see...) Figure 1 and Figure 2 Use the same labels and omit descriptions where appropriate.

[0053] Figure 6 This is a flowchart illustrating the control sequence of the electric motor and cooling fan in this embodiment.

[0054] When the duration of no-load operation reaches a predetermined value A, the control device 9 stops the motor 2 (step S17). Furthermore, based on the detection history of the discharge side pressure sensor 14 during no-load operation, the control device 9 predicts the downtime until the discharge side pressure of the compressor body 3 drops to a predetermined lower limit value Pd and the motor 2 restarts (step S18).

[0055] The control device 9 determines whether the predicted downtime is above the specified allowable value B (in other words, assuming the cooling fan 13 is stopped until the recovery time, the minimum downtime at the recovery time in which the discharge side temperature is below the specified allowable value T2) (step S19).

[0056] If the predicted downtime is greater than or equal to the specified allowable value B, the control device 9 stops the cooling fan 13 (step S20). Then, when the discharge side pressure detected by the discharge side pressure sensor 14 reaches the specified lower limit value Pd, the motor 2 and the cooling fan 13 are restarted (steps S12, S13).

[0057] If the predicted downtime is less than the specified allowable value B, the control device 9 continues to drive the cooling fan 13 (step S21). Then, when the discharge side pressure detected by the discharge side pressure sensor 14 reaches the specified lower limit value Pd, the motor 2 is restarted (steps S15, 16).

[0058] Next, using Figure 7 The operation and effects of this embodiment will be explained. Figure 7 This is a timing diagram showing the operation of the electric motor and cooling fan in this embodiment, as well as the changes in the discharge side pressure and discharge side temperature of the compressor body.

[0059] When the no-load operation duration reaches the specified value A (time t2), motor 2 stops. At this time, control device 9 predicts the downtime of motor 2. If the predicted downtime is less than the specified allowable value B, control device 9 continues to drive cooling fan 13. In other words, if... Figure 7 As shown by the dashed line, if the cooling fan 13 is stopped, it will continue to operate if the exhaust temperature at the recovery time (t4) exceeds the specified allowable value T2. Therefore, as... Figure 7 As shown by the solid line, the discharge side temperature of the compressor body 3 at the recovery time can be suppressed to below the specified allowable value T2. Furthermore, the oil temperature can also be reduced. Therefore, even if the heat generated by the compressor body 3 increases sharply with the increase of the motor 2's speed, the discharge side temperature of the compressor body 3 will not become excessively high. As a result, unnecessary alarms and control shutdowns can be prevented.

[0060] Furthermore, in the second embodiment, although not specifically described, it is possible, for example, as follows: Figure 8 As shown in the second variation, after the control device 9 continues driving the cooling fan 13 in step S21 (in other words, the motor 2 is stopped but the cooling fan 13 is running), it determines whether the discharge side temperature detected by the discharge side temperature sensor 10 is below the predetermined allowable value T2 (step S22). If the discharge side temperature detected by the discharge side temperature sensor 10 is below the predetermined allowable value T2, the cooling fan 13 is stopped (step S20). On the other hand, if the discharge side temperature detected by the discharge side temperature sensor 10 exceeds the predetermined allowable value T2, the cooling fan 13 continues to run (step S21). In this variation, the same effects as in the second embodiment can be obtained. Furthermore, compared to the second embodiment, the driving time of the cooling fan 13 can be reduced, achieving energy savings.

[0061] Furthermore, in the first and second embodiments and the first and second modifications, the case where the control device 9 variably controls the target speed of the cooling fan 13 based on the detection result of the exhaust side temperature sensor 10 was described as an example, but it is not limited to this. The control device 9 may also control the target speed of the cooling fan 13 fixedly regardless of the detection result of the exhaust side temperature sensor 10.

[0062] Furthermore, as described above, the application of the present invention to an oil-supply air compressor (i.e., a structure that supplies oil to the working chamber while compressing air) has been used as an example, but it is not limited thereto. The present invention can also be applied to other liquid-supply gas compressors (i.e., structures that supply liquids other than oil to the working chamber, or structures that compress gases other than air).

[0063] Explanation of reference numerals in the attached figures

[0064] 1… Oil-fed air compressor

[0065] 2… Electric motor

[0066] 3…Compressor body

[0067] 5…Intake throttle valve

[0068] 6…Separator

[0069] 8… Oil supply system (liquid supply system)

[0070] 9…Control device

[0071] 10…Discharge side temperature sensor

[0072] 13… Cooling Fan

[0073] 14…Exhaust side pressure sensor

[0074] 15… Oil cooler (liquid cooler)

[0075] 19…Inhalation side temperature sensor

[0076] 21…External server.

Claims

1. A liquid-supply type gas compressor, characterized in that, include: Electric motor; The compressor body, driven by the electric motor, supplies liquid to the working chamber and compresses gas; A suction throttle valve is installed on the suction side of the compressor body; A separator that separates liquid from compressed gas discharged from the compressor body; A liquid supply system that supplies the liquid separated by the separator to the working chamber of the compressor body; Cooling fan; A liquid cooler, which is installed in the liquid supply system, uses cooling air generated by the cooling fan to cool the liquid; A discharge-side pressure sensor that detects the discharge-side pressure of the compressor body; and A control device for controlling the electric motor, the intake throttle valve, and the cooling fan. The control device, During the operation of the electric motor, when the discharge side pressure detected by the discharge side pressure sensor rises to a predetermined upper limit value, the intake throttle valve is controlled to switch from load operation to no-load operation. When the duration of no-load operation reaches a predetermined value, the motor is stopped. Then, when the discharge-side pressure detected by the discharge-side pressure sensor drops to a predetermined lower limit, the motor is restarted, and the intake throttle valve is controlled to switch to load operation. The control device, When the no-load operation duration reaches the specified value and the motor stops, the cooling fan is stopped. Based on the detection history of the discharge-side pressure sensor during the period when the motor is stopped or during the no-load operation, the recovery time when the discharge-side pressure of the compressor body drops to the predetermined lower limit and the motor restarts is predicted, and the discharge-side temperature of the compressor body at the recovery time is predicted if the cooling fan is stopped until the recovery time. If the predicted discharge temperature is below the specified allowable value, the cooling fan remains stopped; if the predicted discharge temperature exceeds the specified allowable value, the cooling fan is restarted before the motor.

2. The liquid-supply gas compressor as described in claim 1, characterized in that: It has a discharge-side temperature sensor that detects the discharge-side temperature of the compressor body. The control device, Store the detection history of the exhaust-side temperature sensor during periods when the cooling fan is stopped. Subsequently, based on the detection history of the discharge-side temperature sensor, the discharge-side temperature of the compressor body at the recovery time is predicted, assuming the cooling fan is stopped until the recovery time.

3. The liquid-supply gas compressor as described in claim 1, characterized in that: It has an suction-side temperature sensor for detecting the suction-side temperature of the compressor body. The control device, The load factor is calculated based on the time the motor and cooling fan operated under load and the time they operated without load before stopping. Obtain time-series data from an external server, including the calculated load rate and the suction side temperature detected by the suction side temperature sensor, under the same conditions, and during the periods when the motor and the cooling fan are stopped. Based on the time-series data of the discharge side temperature, the discharge side temperature of the compressor body at the recovery time is predicted, assuming the cooling fan is stopped until the recovery time.

4. A liquid-supply type gas compressor, characterized in that, include: Electric motor; The compressor body, driven by the electric motor, supplies liquid to the working chamber and compresses gas; A suction throttle valve is installed on the suction side of the compressor body; A separator that separates liquid from compressed gas discharged from the compressor body; A liquid supply system that supplies the liquid separated by the separator to the working chamber of the compressor body; Cooling fan; A liquid cooler, which is installed in the liquid supply system, uses cooling air generated by the cooling fan to cool the liquid; A discharge-side pressure sensor that detects the discharge-side pressure of the compressor body; and A control device for controlling the electric motor, the intake throttle valve, and the cooling fan. The control device, During the operation of the electric motor, when the discharge side pressure detected by the discharge side pressure sensor rises to a predetermined upper limit value, the intake throttle valve is controlled to switch from load operation to no-load operation. When the duration of no-load operation reaches a predetermined value, the motor is stopped. Then, when the discharge-side pressure detected by the discharge-side pressure sensor drops to a predetermined lower limit, the motor is restarted, and the intake throttle valve is controlled to switch to load operation. The control device, When the no-load operation duration reaches the predetermined value and the motor stops, based on the detection history of the discharge-side pressure sensor during the no-load operation period, the downtime until the discharge-side pressure of the compressor body drops to the predetermined lower limit value and the motor restarts is predicted. If the predicted downtime exceeds the specified allowable value, the cooling fan is stopped; if the predicted downtime is less than the specified allowable value, the cooling fan continues to run.

5. The liquid-supply gas compressor as described in claim 4, characterized in that: It has a discharge-side temperature sensor that detects the discharge-side temperature of the compressor body. The control device stops the cooling fan when the motor stops and the cooling fan is driven, and the discharge side temperature detected by the discharge side temperature sensor is below a predetermined allowable value.

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