JP2020190240A - Hydraulic cooling type screw compressor - Google Patents

Abstract

To secure stable oil supply to a rotor chamber even if the discharge pressure of a compressor main body is low, and a rotation number of the compressor is small.SOLUTION: A hydraulic cooling type screw compressor 1 comprises an auxiliary oil supply flow passage 31 for fluidly connecting an oil sump 4a of a main oil supply flow passage 11 or an oil separation/collection implement 4 and a rotor chamber 21c, and guiding oil in the oil sump 4a to the rotor chamber 2c by compressed air discharged from the compressor main body 2 and a pressure difference in the rotor chamber 2c. An oil flow control part 32 which can switch a first state that a flow of the oil passing the auxiliary oil supply flow passage 31 is blocked or limited, and a second state that the flow of the oil passing the auxiliary oil supply flow passage 31 is permitted or alleviated in the limit is arranged in the auxiliary oil supply flow passage 31. When pressure detected by a pressure detection part 42 is dropped to threshold pressure or lower, and a rotation number of the compressor main body 2 reaches a threshold rotation number or smaller, a control device 100 switches the oil flow control part 32 to the second state from the first state.SELECTED DRAWING: Figure 1

Description

The present invention relates to an oil-cooled screw compressor.

The oil-cooled screw compressor disclosed in Patent Document 1 is provided with an oil supply flow path that guides oil from the oil separation / recovery device to the oil supply portion of the compressor body without pressurizing with a pump.

JP-A-2003-32843

In the oil-cooled screw compressor, the inventors of the present invention provide an oil-cooled screw compressor provided with an oil supply flow path for guiding oil from the oil separation / recovery device to the rotor chamber of the compressor body without being pressurized by a pump. In, a new phenomenon was found in which the amount of oil supplied to the rotor chamber was not stable. Specifically, the inventors of the present invention have an oil-cooled air compressor having such an oil supply flow path when the discharge pressure of the compressor body is low and the rotation speed of the compressor body is low. It was newly discovered that the oil supply to the rotor chamber becomes unstable and the amount of oil supplied to the rotor chamber may decrease unexpectedly.

The present invention has been made to solve such newly discovered problems. That is, according to the present invention, in an oil-cooled screw compressor provided with an oil supply flow path that guides oil from the oil separation / recovery device to the rotor chamber of the compressor body without being pressurized by a pump, the discharge pressure of the compressor body is low. Therefore, it is an issue to secure stable refueling to the rotor chamber even when the rotation speed of the compressor main body is low.

One aspect of the present invention is a compressor main body including a rotor chamber containing a pair of rotors for compressing air, and an oil separation / recovery device that separates and recovers oil from the compressed air discharged from the compressor main body. A main oil flow path that fluidly connects the oil sump of the oil separation and recovery device and the rotor chamber and guides the oil in the oil sump to the rotor chamber by the pressure difference between the compressed air and the rotor chamber, and the above. The oil cooler provided in the main oil supply flow path is fluidly connected to the oil reservoir of the main oil supply flow path or the oil separation / recovery device and the rotor chamber, and the oil in the oil pool is supplied by the pressure difference. The auxiliary oil flow path leading to the rotor chamber, the first state provided in the auxiliary oil supply flow path and blocking or restricting the flow of the oil through the auxiliary oil supply flow path, and the oil passing through the auxiliary oil supply flow path. An oil flow control unit that can switch to a second state that allows or relaxes the flow, a pressure detection unit that directly or indirectly detects the pressure of the compressed air, and the pressure detected by the pressure detection unit. An oil-cooled screw compressor including a control device for switching the oil flow control unit from the first state to the second state when is equal to or lower than the threshold pressure and the rotation speed of the compressor main body is equal to or lower than the threshold rotation speed. I will provide a.

The discharge pressure detected by the pressure detector is below the threshold pressure and the rotation speed of the compressor body is below the threshold speed, that is, the discharge pressure of the compressor body is low and the rotation speed of the compressor body is low. Then, the amount of oil guided from the oil separation / recovery device to the rotor chamber via the main oil supply flow path is reduced. However, in this state, the control device switches the oil flow control unit from the first state to the second state. By this switching, oil is supplied from the oil separation / recovery device to the rotor chamber via the auxiliary oil supply flow path. That is, when the discharge pressure of the compressor body is low and the rotation speed of the compressor body is low, the oil separation and recovery device is used in the rotor chamber not only through the main oil supply flow path but also through the auxiliary oil supply flow path. Oil is supplied to the compressor. As a result, even when the discharge pressure of the compressor body is low and the rotation speed of the compressor body is low, stable refueling to the rotor chamber can be ensured, and the required amount of refueling to the rotor chamber can be secured.

The auxiliary refueling flow path may be connected to the suction port side of the compressor main body rather than the connection position of the main refueling flow path in the rotor chamber.

The auxiliary refueling flow path may be branched from the main refueling flow path on the compressor main body side of the oil cooler.

The main oil supply flow path is provided with an oil filter arranged closer to the oil separation and recovery device than the oil cooler, and the auxiliary oil supply flow path is the main oil supply flow between the oil filter and the oil cooler. It may branch off the road.

With this configuration, it is possible to prevent the clogging of the oil cooler from affecting the refueling to the rotor chamber via the auxiliary refueling flow path.

The main oil supply flow path is provided with an oil filter arranged closer to the oil separation and recovery device than the oil cooler, and the auxiliary oil supply flow path is the main oil filter between the oil separation and recovery device and the oil filter. It may branch from the refueling flow path.

With this configuration, it is possible to prevent the clogging of the oil filter from affecting the oil supply to the rotor chamber via the auxiliary oil supply flow path.

The auxiliary oil supply flow path may directly connect the oil sump of the oil separation and recovery device and the rotor chamber without passing through the main oil supply flow path.

The pressure detection unit may be a pressure sensor that detects the pressure in the oil separation / recovery device.

The pressure detection unit may be a pressure sensor that detects the pressure in the air flow path connecting the discharge port of the compressor body and the oil separation / recovery device.

The pressure detection unit may be a pressure sensor that detects the pressure of the oil in the main oil supply flow path through which the oil pressurized by the compressed air flows.

The pressure pressure detecting unit may be a flow rate sensor that detects the flow rate of oil in the main oil supply flow path through which the oil pressurized by the compressed air flows.

The main oil supply flow path may be connected to the compression side space of the rotor chamber, and the auxiliary oil supply flow path may be connected to the suction side space of the rotor chamber.

The oil cooler may be an air-cooled oil cooler that is cooled by a fan whose rotation speed is controlled based on the temperature of the compressed air discharged from the compressor body or the temperature of the oil in the oil sump.

The oil-cooled screw compressor further includes a motor for driving the compressor body and an inverter for controlling the rotation speed of the motor, and one shaft of the pair of rotors is integrated with the output shaft of the motor. It is a structure, and the rotation speed of the compressor body may be the rotation speed of the motor.

According to the oil-cooled screw compressor of the present invention, stable refueling to the rotor chamber can be ensured even when the discharge pressure of the compressor body is low and the rotation speed of the compressor body is low.

The schematic block diagram of the oil-cooled screw compressor which concerns on 1st Embodiment of this invention. A flowchart for explaining the control of the solenoid valve during operation. A flowchart for explaining the control of the solenoid valve at the time of starting. A graph showing the relationship between the number of revolutions of the main body and the amount of refueling. The schematic block diagram of the oil-cooled screw compressor which concerns on 1st modification of 1st Embodiment. The schematic block diagram of the oil-cooled screw compressor which concerns on 2nd modification of 1st Embodiment. The schematic block diagram of the oil-cooled screw compressor which concerns on 3rd modification of 1st Embodiment. The schematic block diagram of the oil-cooled screw compressor which concerns on 4th modification of 1st Embodiment. The schematic block diagram of the oil-cooled screw compressor which concerns on 2nd Embodiment of this invention. The schematic block diagram of the oil-cooled air compressor which concerns on 3rd Embodiment of this invention. The schematic block diagram of the oil-cooled air compressor which concerns on 4th Embodiment of this invention. A graph showing the relationship between the main body rotation speed and the amount of oil supplied in a conventional oil-cooled air compressor.

In the oil-cooled screw compressor, the inventors of the present invention provide an oil-cooled screw compressor provided with an oil supply flow path for guiding oil from the oil separation / recovery compressor to the rotor chamber of the compressor body without pressurizing with a pump. We have newly found a possible decrease in the amount of oil supplied to the rotor chamber. This point will be described below.

FIG. 12 shows the rotation speed (main body rotation speed) of the compressor body in an oil-cooled screw compressor provided with an oil supply flow path for guiding oil from the oil separation / recovery device to the rotor chamber of the compressor main body without being pressurized by a pump. It is a graph showing the relationship between the amount of oil supplied to the rotor chamber and the amount of oil supplied to the rotor chamber.

In the graph of FIG. 12, the “◆” mark indicates that the discharge pressure is P1 of the design discharge pressure, the “■” mark indicates that the discharge pressure is P2, and the “▲” mark indicates that the discharge pressure is P1 of the design discharge pressure and the oil cooler. When the rotation speed control of the fan for the oil cooler is executed, the "x" mark indicates that the discharge pressure is P2 and the rotation speed control of the fan for the oil cooler is executed, and the "*" mark indicates that the discharge pressure is P3 for the oil cooler. When the fan speed control is executed, the "●" mark indicates that the discharge pressure is P4 and the oil cooler fan speed control is executed (the oil supply temperature is the upper limit), and the "+" mark indicates that the discharge pressure is P4. When the rotation speed control of the fan for the oil cooler is executed in (the refueling temperature is the lower limit). Regarding the main body rotation speed, V1 is the rated rotation speed, and the rotation speed is higher in the order of V1, V2, V3, V4, V5, V6. Regarding the discharge pressure, the discharge pressure is higher in the order of P1, P2, P3, P4. In controlling the rotation speed of the fan for the oil cooler, the higher the oil temperature in the oil pool of the oil separation / recovery device, the higher the rotation speed of the fan.

With reference to FIG. 12, if the discharge pressures are high P1, P2, P3, the amount of oil supplied to the rotor chamber is the amount of oil supplied to the rotor chamber even when the main body rotation speed is V2 to V6, which is lower than the rated rotation speed V1, that is, even in the partial load operation. It is stable and there is no significant reduction in the amount of oil supplied to the rotor chamber compared to operation at rated speed V1, that is, full load operation. On the other hand, in the case of low discharge pressure P4, the amount of oil supplied to the rotor chamber is unstable during operation at the main body rotation speed V2 to V6 (partial load operation), and the rotor chamber is compared to full load operation. The amount of refueling is significantly reduced. In particular, even with the same low discharge pressure P4, when the refueling temperature is the lower limit value, the amount of refueling to the rotor chamber during partial load operation becomes more unstable and decreases more than when the refueling temperature is the upper limit value.

As described above, in the oil-cooled screw compressor provided with an oil supply flow path that guides oil from the oil separation / recovery device to the rotor chamber of the compressor body without pressurizing by a pump, the discharge pressure is low and the rotation speed of the main body is low. A new finding has been obtained that the oil supply to the rotor chamber may become unstable under low operating conditions, and the amount of oil supplied to the rotor chamber may unexpectedly decrease. The following embodiments are based on such new findings.

(First Embodiment)
Referring to FIG. 1, the oil-cooled screw compressor 1 according to the first embodiment of the present invention is discharged from the compressor main body 2, the motor 3 for driving the compressor main body 2, and the compressor main body 2. An oil separation / recovery device 4 that separates and recovers oil from compressed air is provided.

The compressor main body 2 includes a pair of rotors, that is, a rotor chamber 2c in which a male rotor 2a and a female rotor 2b are housed. Further, the compressor main body 2 includes a suction port 2d in which outside air is sucked in through a filter 5 and an intake air regulating valve 6, and a discharge port 2e in which compressed air compressed by male and female rotors 2a and 2b is discharged.

In the present embodiment, the shaft 2f of the male rotor 2a has an integral structure with the output shaft 3a of the motor 3. The rotation speed of the motor 3, and therefore the rotation speeds of the male and female rotors 2a and 2b of the compressor body 2, are controlled by the inverter 21.

The oil-cooled screw compressor 1 includes an air flow path 7 for sending the compressed air generated by the compressor main body 2 to a supply destination of compressed air (not shown). The air flow path 7 is a first portion 7a that fluidly connects the discharge port 2e of the compressor main body 2 and the oil separation / recovery device 4, and a second portion that fluidly connects the oil separation recovery device 4 and the aftercooler 9. 7b and a third portion 7c that fluidly connects the aftercooler 9 and the supply destination are provided. A pressure-holding check valve 8 is provided in the second portion 7b.

In the present embodiment, oil is separated from the compressed air that has flowed into the oil separation / recovery device 4 from the first portion 7a of the air flow path 7 by a separation action by centrifugal force. The separated oil is collected in the oil sump 4a at the lower part of the oil separation and recovery device 4. Further, the oil separation / recovery device 4 includes an element 4b for secondary oil separation. The compressed air led out from the oil separation / recovery device 4 to the second portion 7b of the air flow path 7 is air-cooled by the aftercooler 9 and then sent to the supply destination via the third portion 7c of the air flow path 7.

The oil-cooled screw compressor 1 includes a main oil supply flow path 11 for returning the oil in the oil sump 4a of the oil separation / recovery device 4 to the rotor chamber 2c of the compressor main body 2.

The main oil supply flow path 11 in the present embodiment is a first portion 11a that fluidly connects the oil sump 4a of the oil separation and recovery device 4 and the oil cooler 12, and compression after the oil cooler 12 and the rotor chamber 2c are closed. It includes a second portion 11b that fluidly connects the side space. An oil filter 13 is provided in the first portion 11a of the main oil supply flow path 11. Further, a temperature control valve 14 is provided so as to connect the first portion 11a and the second portion 11b by bypassing the oil cooler 12. Further, a refueling flow path 15 for refueling the bearing of the compressor main body 2, the shaft sealing portion, etc., which branches from the second portion 11b of the main refueling flow path 11, is provided. A pump for refueling is not provided in the main refueling flow path 11, and the rotor chamber 2c is provided only by the discharge pressure of the compressor body 1 without pressurizing the oil in the oil sump 4a of the oil separation and recovery device 4 with the pump. Lead to. That is, due to the pressure difference between the compressed air discharged from the compressor main body 1 into the oil separation / recovery device 4 and the rotor chamber 2c, the oil in the oil sump 4a of the oil separation / recovery device 4 passes through the main oil supply flow path 11 to the rotor. Guided to room 2c.

The oil-cooled screw compressor 1 of the present embodiment branches from the second portion 11b of the main oil supply flow path 11, more specifically, from the second portion 11b on the oil cooler 12 side of the branch position of the oil supply flow path 15. An auxiliary oil supply flow path 31 connected to the rotor chamber 2c is provided. A pump for refueling is not provided in the auxiliary refueling flow path 31, and the rotor chamber 2c is provided only by the discharge pressure of the compressor body 1 without pressurizing the oil in the oil sump 4a of the oil separation and recovery device 4 with the pump. Lead to. That is, due to the pressure difference between the compressed air discharged from the compressor main body 1 into the oil separation / recovery device 4 and the rotor chamber 2c, the oil in the oil pool 4a of the oil separation / recovery device 4 passes through the auxiliary oil supply flow path 31 to the rotor. Guided to room 2c.

The auxiliary oil supply flow path 31 is connected to the rotor chamber 2c on the suction port 2d side of the connection position of the second portion 11b of the main oil supply flow path 11 to the rotor chamber 2c. The connection position of the auxiliary oil supply flow path 31 to the rotor chamber 2c can be set within a range from the suction port 2d to the connection position of the second portion 11b of the main oil supply flow path 11 to the rotor chamber 2c. With this setting, it is possible to realize refueling via the auxiliary refueling flow path 31 using only the discharge pressure of the compressor main body 1. In order to ensure refueling through the auxiliary refueling flow path 31 using only the discharge pressure, the connection position of the suction port 2d of the auxiliary refueling flow path 31 is the suction side before closing on the suction port 2d side of the compression side space. It is more preferable to set it in space. In order to secure a larger amount of refueling, the auxiliary refueling flow path 31 may be connected to the rotor chamber 2c at a plurality of locations.

The auxiliary oil supply flow path 31 is provided with a normally closed solenoid valve 32, which is an example of the oil flow control unit in the present invention. When the solenoid valve 32 is closed (first state), the flow of oil to the rotor chamber 2c via the auxiliary oil supply flow path 31 is blocked, and when the solenoid valve 32 is opened (second state), the flow of oil is blocked. The flow of oil to the rotor chamber 2c through the auxiliary oil supply flow path 31 is allowed.

The oil-cooled screw compressor 1 includes an aftercooler 9 and a fan 22 for air cooling in the oil cooler 12. The fan 22 is driven by a fan motor 24 whose rotation speed is controlled by an inverter 23.

The oil-cooled screw compressor 1 includes a pressure sensor 41 (pressure detection unit) that detects the pressure of the compressed air in the oil separation / recovery device 4. Further, the oil-cooled screw compressor 1 includes a temperature sensor 42 that detects the temperature of the oil accumulated in the oil reservoir 4a in the oil separation / recovery device 4.

The control device 100 controls the components of the oil-cooled screw compressor 1, including the inverter 21 of the motor 3 that drives the compressor body 1, the inverter 23 of the fan motor 24 that drives the fan 22, and the solenoid valve 32. To control. A detection signal is input to the control device 100 from the pressure sensor 41 and the temperature sensor 42.

The control device 100 controls the rotation speed of the fan 22 by the inverter 23 of the fan motor 24 based on the detection signal input from the temperature sensor 42. Specifically, the control device 100 controls the rotation speed of the fan 22 so that the temperature of the compressed air discharged from the compressor main body 1, which correlates with the temperature Td of the oil in the oil sump 4a, becomes a predetermined value. In the present embodiment, in the control device 100, the higher the oil temperature Td of the oil sump 4a of the oil separation / recovery device 4 detected by the temperature sensor 42, the higher the rotation speed of the fan 22, and the lower the detected temperature Td. The rotation speed of the fan 22 is lowered. A sensor for directly measuring the temperature of the compressed air discharged from the compressor main body 1 is provided, and the control device 100 controls the rotation speed of the fan 22 so that the temperature of the compressed air detected by this sensor becomes a predetermined value. May be good.

The temperature control valve 14 in the present embodiment is a wax type automatic temperature control valve. The temperature control valve 14 operates autonomously so that the refueling temperature of the compressor main body 2 is adjusted to a predetermined temperature. Specifically, when it is necessary to lower the oil supply temperature of the compressor main body 2 of the temperature control valve 14, the amount of oil supplied from the oil separation / recovery device 4 to the rotor chamber 2c via the oil cooler 12 is relative. It will be in a state of increasing. Further, when the temperature control valve 14 needs to raise the oil supply temperature of the compressor main body 2, the amount of oil supplied from the oil separation / recovery device 4 to the rotor chamber 2c without passing through the oil cooler 12 is relative. It will be in a state of increasing.

Hereinafter, the control of the solenoid valve 32 executed by the control device 100 will be described.

During the operation of the compressor main body 2, the oil in the oil sump 4a of the oil separation / recovery device 4 is supplied to the rotor chamber 2c via the main oil supply flow path 11 by the discharge pressure of the compressor main body 2. During the operation of the compressor main body 2, the following control shown in FIG. 2 is executed.

In step S1, when the pressure of the compressed air in the oil separation / recovery device 4 detected by the pressure sensor 41, that is, the discharge pressure Po becomes equal to or less than the first threshold pressure Poth1, the process proceeds to step S2. In step S2, when the rotation speed (main body rotation speed) Vcomp of the compressor main body 2 becomes equal to or less than the first threshold rotation speed Vth1, the process proceeds to step S3.

As described above, in the present embodiment, the shaft 2f of the male rotor 2a has an integral structure with the output shaft 3a of the motor 3, so that the main body rotation speed Vcomp is determined from the drive frequency of the inverter 21 that supplies power to the motor 3. can get. Since the control device 100 drives the inverter 21, the main body rotation speed Vcomp is constantly acquired. For example, when a reduction gear or a speed-up gear is interposed between the motor 3 and the compressor body 2, the body speed Vcomp is calculated from the motor speed and the reduction ratio or the speed-up ratio obtained from the drive frequency of the inverter 21. Can be obtained.

In step S3, the solenoid valve 32 is switched from the closed valve to the open valve, and the timer Tim is started to be timed. When the solenoid valve 32 is opened, the oil in the oil sump 4a of the oil separation / recovery device 4 is supplied to the rotor chamber 2c via the auxiliary oil supply flow path 31 by the discharge pressure of the compressor main body 2.

The first threshold pressure Poth1 in step S1 is the discharge pressure of the compressor main body 2 at which the amount of oil supplied to the rotor chamber 2c begins to become unstable in relation to the rotation speed of the compressor main body 2. The first threshold pressure Poth1 can be obtained experimentally. The first threshold pressure Poth1 is equal to or lower than the rated pressure (the discharge pressure at which the appropriate operation or performance of the compressor main body 2 is compensated, which is lower than the maximum discharge pressure).

The first threshold rotation speed Vth1 in step S2 is the rotation speed of the compressor main body 2 at which the amount of oil supplied to the rotor chamber 2c begins to become unstable in relation to the discharge pressure of the compressor main body 2. The first threshold rotation speed Vth1 can be obtained experimentally. The first threshold rotation speed Vth1 is 80% or less of the maximum rotation speed of the compressor main body 2.

In step S1, the condition that the discharge pressure Po is the first threshold pressure Poth1 is satisfied, and in step S2, the condition that the main body rotation speed Vcomp is the first threshold rotation speed Vth1 or less is satisfied because the discharge pressure of the compressor main body 2 is satisfied. It is in a low state and the rotation speed of the compressor main body 2 is low. In this state, the amount of oil guided from the oil separation / recovery device 4 to the rotor chamber 2c via the main oil supply flow path 11 decreases. By opening the solenoid valve 32 in step S3, that is, by opening the solenoid valve 32 when the discharge pressure of the compressor main body 2 is low and the rotation speed of the compressor main body 2 is low. Oil is supplied from the oil separation / recovery device 4 to the rotor 2c chamber not only through the main oil supply flow path 11 but also through the auxiliary oil supply flow path 31. As a result, even when the discharge pressure of the compressor main body 2 is low and the rotation speed of the compressor main body 2 is low, the required amount of oil supply to the rotor chamber 2c can be secured.

After opening the solenoid valve 32 in step S3, that is, after starting refueling to the rotor chamber 2c via the auxiliary refueling flow path 31, the processes of steps S4 to S8 are executed.

First, in step S4, when the discharge pressure Po becomes equal to or higher than the second pressure threshold value Poth2, the process proceeds to step S5. In the present embodiment, the second pressure threshold value Poth2 is lower than the first pressure threshold value Poth1. The second pressure threshold Poth2 can be set in the range of 0.1 MPa lower than the first pressure threshold Poth1 below the first pressure threshold Poth1 value. In step S4, the fact that the condition that the discharge pressure Po is equal to or higher than the second pressure threshold value Poth2 is not satisfied means that the discharge pressure Po is further lower than the first pressure threshold value Poth1, that is, the value required for refueling via the auxiliary refueling flow path 31. It means that it is in such a state.

In step S5, if the discharge pressure Po is less than the third pressure threshold value Poth3, the process proceeds to step S6, and if the discharge pressure Po is greater than or equal to the third pressure threshold value Poth3, the process proceeds to step S7. In the present embodiment, the third pressure threshold value Poth3 is higher than the first pressure threshold value Poth1. The third pressure threshold value Poth3 can be set in a range of 0.1 MPa higher pressure than the first pressure threshold value Poth1 at the first pressure threshold value Poth1 or higher. In step S5, the condition that the discharge pressure Po is equal to or higher than the third pressure threshold value Poth3 is satisfied, the discharge pressure Po sufficiently exceeds the value required for refueling via the auxiliary oil supply flow path 31 (first pressure threshold value Poth1). It means that it is.

Both the second pressure threshold value Poth2 and the third pressure threshold value Poth3 may have the same value as the first pressure threshold value Poth1, but the opening / closing timing of the solenoid valve 32 may be within 0.1 MPa in order to avoid frequent opening / closing timing. It is preferable to provide a differential pressure.

In step S6, if the main body rotation speed Vcomp is the second threshold rotation speed Vth2 or more, the process proceeds to step S7, and if the main body rotation speed Vcomp is less than the second threshold rotation speed Vth2, the process returns to step S4. The second threshold rotation speed Vth2 is faster than the first threshold rotation speed Vth1 in the present embodiment. The second threshold rotation number Vth2 can be set in the range of 125% of the first threshold rotation number Vth1 at the first threshold rotation number Vth1 or higher. If the condition that the main body rotation speed Vcomp is equal to or higher than the second threshold rotation speed Vth2 is satisfied in step S6, the main body rotation speed Vcomp determines the value (first threshold rotation speed Vth1) that requires refueling via the auxiliary refueling flow path 31. It means that it exceeds enough.

The second threshold rotation speed Vth2 may be the same value as the first threshold rotation speed Vth1, but in order to avoid frequent opening / closing timing of the electromagnetic valve 32, the second threshold rotation speed Vth2 approaches the rated rotation speed. In this embodiment, it is preferable that the second threshold rotation speed Vth2 is 125% or less of the first threshold rotation speed Vth1 because the energy saving property is lowered as much as possible.

In step S7, if the timer Tim that started timing when the solenoid valve 32 is opened (step S3) has passed the predetermined auxiliary refueling time Tup, the process proceeds to step S8, and the timer Tim moves to the auxiliary refueling time. If Tup has not passed, the process returns to step S4.

In step S8, the solenoid valve 32 is switched from opening to closing. By closing the solenoid valve 32, the flow of oil from the oil separation / recovery device 4 to the rotor chamber 2c via the auxiliary oil supply path 31 is blocked. After the solenoid valve 32 is closed, oil is supplied from the oil separation / recovery device 4 to the rotor chamber 2c only through the main oil supply path 11. After closing the solenoid valve 32 in step S8, the process returns to step S1.

As described above, in the present embodiment, after the solenoid valve 32 is switched from the valve closing to the valve opening, the solenoid valve 32 is closed from the valve opening when any one of the following valve closing conditions 1 and 2 is satisfied. Return to the valve.

Valve closing condition 1:
The discharge pressure Po of the compressor body 1 is equal to or higher than the third threshold pressure Poth3, and the time counting time of the timer Tim has passed the auxiliary refueling time Tup.

Valve closing condition 2:
The discharge pressure Po of the compressor main body 1 is the second threshold pressure Poth2 or more, the main body rotation speed Vcomp is the second threshold rotation speed Vth2 or more, and the time counting time of the timer Tim has passed the auxiliary refueling time Tup.

As described above, the conditions for switching the solenoid valve 32 from the closed valve to the open valve are that the discharge pressure Po of the compressor main body 1 is the first threshold pressure Poth1 or less and the main body rotation speed Vcomp is the first threshold rotation speed Vth1 or less. .. That is, when the discharge pressure Po of the compressor main body 2 is low and the rotation speed Vcomp of the compressor main body 2 is low, refueling to the rotor chamber 2c via the auxiliary refueling flow path 31 is executed. On the other hand, the valve closing condition 1 means that the state in which the discharge pressure Po of the compressor main body 2 is sufficiently high continues for a certain period of time. Further, the valve closing condition 2 means that the state in which the rotation speed Vcomp of the compressor main body 2 is sufficiently high continues for a certain period of time. That is, when either the discharge pressure Po of the compressor main body 2 or the rotation speed Vcomp of the compressor main body 2 recovers, the refueling to the rotor chamber 2c via the auxiliary refueling flow path 31 is completed.

When the compressor main body 2 is started, the control shown in FIG. 3 is executed. When the compressor body 2 is started, the discharge pressure Po of the compressor body 2 and the rotation speed Vcomp of the compressor body 2 are both low, so that the discharge pressure Po of the compressor body 2 and the rotation speed Vcomp of the compressor body 2 are Until one of them rises, the electromagnetic valve 32 is opened and the rotor chamber 2c is refueled via the auxiliary refueling path 31. Specifically, steps S11 to S16 in FIG. 3 are the same as steps S3 to S8 in FIG.

FIG. 4 is a graph showing the relationship between the rotation speed of the compressor main body (main body rotation speed) and the amount of oil supplied to the rotor chamber. In this graph, the “●” mark and the “+” mark are for a conventional oil-cooled screw compressor not provided with an auxiliary oil supply flow path, and are the same as those in FIG. Other symbols in FIG. 4 are the same as those in FIG. 12 unless otherwise specified. In FIG. 4, the “●” mark indicates that the fan 22 rotation speed control is executed when the discharge pressure is P4 (the refueling temperature is the upper limit value), and the “+” mark indicates that the fan 22 rotation speed control is executed when the discharge pressure is P4. (The refueling temperature is the lower limit). On the other hand, in FIG. 4, the “◆” mark and the “■” mark indicate the case of the oil-cooled screw compressor 1 according to the present embodiment, the discharge pressure of the compressor main body 1 is low, and the rotation of the compressor main body 2 When the number is low, refueling is performed by the auxiliary refueling flow path 31. The "◆" mark indicates that the discharge pressure is P4 and the fan 22 rotation speed control is executed (refueling temperature is the upper limit), and the "■" mark indicates that the discharge pressure is P4 and the fan 22 rotation speed control is executed (refueling). The temperature is the lower limit). From the graph of FIG. 12, in the oil-cooled screw compressor 1 according to the present embodiment, the rotor chamber is operated even during partial load operation in which the discharge pressure of the compressor body is low and the rotation speed of the compressor body is low. It can be understood that the amount of oil supplied to 2c is stable and the required amount of oil can be secured.

(Modified example of the first embodiment)
5 to 8 show various modifications of the first embodiment. The configurations of these modified examples can also be applied to the second to fourth embodiments (FIGS. 9 to 11) described later.

In the modified example of FIG. 5, a flow rate control valve 33 is provided in the auxiliary oil supply path 31 instead of the solenoid valve 32 (see FIG. 1). The flow rate control valve 33 has a first state of limiting the flow of oil to the rotor chamber 2c through the auxiliary oil supply flow path 31 to a minute flow rate, and a first state in which the restriction is relaxed to the rotor chamber 21 via the auxiliary oil supply flow path 31. It is possible to switch to a second state that allows a sufficient flow of oil. When the condition for closing the solenoid valve 32 in the first embodiment is satisfied, the control device 100 sets the flow control valve 33 in the first state, and the condition for opening the solenoid valve 32 in the first embodiment is satisfied. In this case, the flow control valve 33 is set to the second state.

In the modified example of FIG. 6, the auxiliary oil supply flow path 31 branches from the main oil supply flow path 11 (first portion 11a) between the oil filter 13 and the oil cooler 12. With this configuration, it is possible to prevent the clogging of the oil cooler 12 from affecting the refueling to the rotor chamber 2c via the auxiliary refueling flow path 31.

In the modified example of FIG. 7, the auxiliary oil supply flow path 31 branches from the main oil supply flow path 11 (first portion 11a) between the oil separation / recovery device 4 and the oil filter 12. With this configuration, it is possible to prevent the clogging of the oil filter 13 from affecting the oil supply to the rotor chamber 2c via the auxiliary oil supply flow path 11.

In the modified example of FIG. 8, the auxiliary oil supply flow path 31 directly connects the oil sump 4a of the oil separation / recovery device 4 and the rotor chamber 2c. By configuring the auxiliary oil supply path 31 in this way, it is possible to effectively reduce the pressure loss of the oil flowing from the oil reservoir 4a of the oil separation and recovery device 4 to the rotor chamber 2c. Therefore, the connection position of the auxiliary refueling path 31 of this modification to the rotor chamber 2c can be set in the compression side space after confinement.

Two or more of the auxiliary refueling paths 31 according to the first embodiment (FIG. 1) and the modified examples of FIGS. 6 to 8 may be provided in one oil-cooled screw compressor 1.

Hereinafter, the second to fourth embodiments of the present invention will be described. The elements and functions not particularly mentioned with respect to these embodiments are the same as those of the first embodiment.

(Second Embodiment)
In the oil-cooled screw compressor 1 according to the second embodiment of the present invention shown in FIG. 9, the pressure sensor (pressure detection unit) 41 is not the oil separation / recovery device 4, but the discharge port 2e of the compressor body 2 and the oil. It is provided in an air flow path 7 (first portion 7a) that connects to the separation / recovery device 4. The pressure sensor 41 detects the pressure of the compressed air in the first portion 7a of the air flow path 7.

(Third Embodiment)
In the oil-cooled screw compressor 1 according to the third embodiment of the present invention shown in FIG. 10, the pressure sensor 41 (see FIGS. 1 and 9) does not have to be provided, and the pressure Ps of the oil in the main oil supply flow path 11 A pressure sensor (pressure detection unit) 43 for detecting the above is provided. The main oil supply flow path 11 guides the oil in the oil sump 4a of the oil separation / recovery device 4 to the rotor chamber 2c of the compressor main body 2 without pressurizing it with a pump. That is, the oil in the oil sump 4a of the oil separation / recovery device 4 is guided to the rotor chamber 2c by the pressure difference between the compressed air discharged from the compressor main body 1 into the oil separation / recovery device 4 and the rotor chamber 2c. Therefore, the discharge pressure Po of the compressor main body 2 can be indirectly detected by detecting the oil pressure Ps of the main oil supply flow path 11.

(Fourth Embodiment)
In the oil-cooled screw compressor 1 according to the fourth embodiment of the present invention shown in FIG. 11, the pressure sensor 41 (FIGS. 1 and 9) does not have to be provided, and the flow rate FL of the oil in the main oil supply flow path 11 is measured. A flow rate sensor (pressure detection unit) 44 for detection is provided. Similar to the above embodiment, the main oil flow path 11 guides the oil in the oil reservoir 4a of the oil separation and recovery device 4 to the rotor chamber 2c of the compressor main body 2 without pressurizing the oil in the oil reservoir 4a. The flow rate FL of is positively correlated with the discharge pressure Po of the compressor body 2. Therefore, the discharge pressure Po of the compressor main body 2 can be indirectly detected by detecting the flow rate FL of the oil in the main oil supply flow path 11.

1 Oil-cooled screw compressor 2 Compressor body 2a Male rotor 2b Female rotor 2c Rotor chamber 2d Suction port 2e Discharge port 2f Shaft 3 Motor 3a Output shaft 4 Oil separation and recovery device 4a Oil pool 4b Element 5 Air filter 6 Intake control valve 7 Air flow path 7a 1st part 7b 2nd part 7c 3rd part 8 Pressure-holding check valve 9 Aftercooler 11 Main oil flow path 11a 1st part 11b 2nd part 12 Oil cooler 13 Oil filter 14 Temperature control valve 15 Oil flow Roads 21 and 23 Inverter 22 Fan 24 Fan motor 31 Auxiliary oil supply flow path 32 Electromagnetic valve 41,43 Pressure sensor (pressure detector)
42 Temperature sensor 44 Flow sensor (pressure detector)
33 Flow control valve 100 Control device

Claims (13)

A compressor body with a rotor chamber containing a pair of rotors that compress air,
An oil separation / recovery device that separates and recovers oil from the compressed air discharged from the compressor body.
A main oil supply flow path that fluidly connects the oil sump of the oil separation and recovery device and the rotor chamber and guides the oil in the oil sump to the rotor chamber by the pressure difference between the compressed air and the rotor chamber.
An oil cooler provided in the main refueling flow path and
An auxiliary oil flow path that fluidly connects the oil pool of the main oil flow path or the oil separation / recovery device and the rotor chamber, and guides the oil in the oil pool to the rotor chamber by the pressure difference.
A first state provided in the auxiliary oil supply flow path to block or restrict the flow of the oil through the auxiliary oil supply flow path, and a second state to allow or relax the flow of the oil through the auxiliary oil supply flow path. Oil flow control unit that can be switched to
A pressure detector that directly or indirectly detects the pressure of the compressed air,
Control to switch the oil flow control unit from the first state to the second state when the pressure detected by the pressure detection unit becomes equal to or less than the threshold pressure and the rotation speed of the compressor main body becomes equal to or less than the threshold rotation speed. An oil-cooled screw compressor equipped with a device. The oil-cooled screw compressor according to claim 1, wherein the auxiliary oil supply flow path is connected to the suction port side of the compressor main body from the connection position of the main oil supply flow path in the rotor chamber. The oil-cooled screw compressor according to claim 1 or 2, wherein the auxiliary oil supply flow path branches from the main oil supply flow path on the compressor main body side of the oil cooler. An oil filter arranged on the oil separation / recovery device side of the oil cooler is provided in the main oil supply flow path.
The oil-cooled screw compressor according to claim 1 or 2, wherein the auxiliary oil supply flow path branches from the main oil supply flow path between the oil filter and the oil cooler. An oil filter arranged on the oil separation / recovery device side of the oil cooler is provided in the main oil supply flow path.
The oil-cooled screw compressor according to claim 1 or 2, wherein the auxiliary oil supply flow path branches from the main oil supply flow path between the oil separation and recovery device and the oil filter. The oil-cooled screw according to claim 1 or 2, wherein the auxiliary oil supply flow path connects the oil sump of the oil separation and recovery device and the rotor chamber without passing through the main oil supply flow path. Compressor. The oil-cooled screw compressor according to any one of claims 1 to 6, wherein the pressure detection unit is a pressure sensor that detects the pressure in the oil separation / recovery device. The pressure detection unit is a pressure sensor that detects the pressure in the air flow path connecting the discharge port of the compressor body and the oil separation / recovery device, according to any one of claims 1 to 6. The oil-cooled screw compressor described. The oil according to any one of claims 1 to 6, wherein the pressure detection unit is a pressure sensor that detects the pressure in the main oil supply flow path through which the oil pressurized by the compressed air flows. Cold screw compressor. The pressure detection unit is the flow rate sensor that detects the flow rate of oil in the main oil flow path through which the oil pressurized by the compressed air flows, according to any one of claims 1 to 6. Oil-cooled screw compressor. The main lubrication flow path is connected to the compression side space of the rotor chamber, and is connected to the compression side space.
The oil-cooled screw compressor according to claim 1, wherein the auxiliary oil supply flow path is connected to the suction side space of the rotor chamber. 11. The oil cooler according to claim 11, wherein the oil cooler is an air-cooled oil cooler that is cooled by a fan whose rotation speed is controlled based on the temperature of the compressed air discharged from the compressor body or the temperature of the oil in the oil sump. Oil-cooled screw compressor. The motor that drives the compressor body and
Further equipped with an inverter that controls the rotation speed of the motor,
One shaft of the pair of rotors has an integral structure with the output shaft of the motor.
The oil-cooled screw compressor according to claim 1 or 12, wherein the rotation speed of the compressor body is the rotation speed of the motor.

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