JP2017002733A - Oil free compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil free compressor capable of reducing air consumption of an ejector to reduce pressure in an oil tank.SOLUTION: An oil free compressor 2 comprises: a first stage compressor body 13 and a second stage compressor body 14 for two stage compression operation; an oil tank 22; an ejector 30; a solenoid valve 38; and a controller 40. The oil tank 22 stores oil to be supplied to bearings 13d and 14d of the first stage compressor body 13 and the second stage compressor body 14. The ejector 30 is used for reducing pressure inside the oil tank 22. The solenoid valve 38 is fluidically connected to the ejector 30, discharge piping 4c and intermediary piping 4b and can be switched to a first state where the ejector 30 is communicated only with the discharge piping 4c, a second state where the ejector 30 is communicated only with the intermediary piping 4b, or a third state where the valve is fully closed. The controller 40 controls switching operation of the solenoid valve 38.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oil-free compressor.

  Oil-free compressors are known in which oil is supplied to a bearing of a compressor and lubricated, and used oil is collected in an oil tank so as not to be mixed into discharged air. Such an oil-free compressor is disclosed in Patent Document 1, for example.

  The oil-free compressor of Patent Document 1 has a function of exhausting oil smoke generated in a speed increaser or an oil tank. In this apparatus, an ejector that uses the discharge pressure of a smoke exhaust fan and a compressor can be selectively used for smoke emission. In order to prevent the situation where smoke cannot be exhausted and to improve the reliability of the apparatus, a smoke exhaust fan is used when the discharge pressure is low, and an ejector is used when the discharge pressure is high.

JP 2005-248771 Gazette

  However, the device of Patent Document 1 is expensive because two smoke exhaust devices are required. Further, this apparatus does not consider the loss of discharge air necessary for driving the ejector.

  This invention makes it a subject to provide the oil-free compressor which can reduce the air consumption in the ejector for decompressing an oil tank.

  The first aspect of the present invention provides a first-stage compressor body and a second-stage compressor body for performing two-stage compression, and bearings for the first-stage compressor body and the second-stage compressor body. An oil tank for storing oil to be supplied; an ejector for reducing the pressure in the oil tank; the ejector; a discharge pipe for supplying compressed air from the second-stage compressor body to a discharge destination; A first state where the first stage compressor body is fluidly connected to an intermediate pipe for supplying compressed air from the first stage compressor body to the second stage compressor body, and only the ejector and the discharge pipe communicate with each other; An oil-free compression comprising a switching valve capable of switching between a second state in which only the ejector and the intermediate pipe communicate with each other and a third state in a fully closed state, and a controller for controlling switching of the switching valve. Provide a machine.

  According to this configuration, the air consumption can be reduced by setting the pressure of the air supplied to the ejector for decompressing the oil tank as low as possible. In addition, when the switching valve is in the second state, the pressure after the first stage compression is reduced. In this case, the pressure in the second stage compressor body is reduced, and the shaft power is maintained even with the same air consumption. Decrease. Therefore, the efficiency is improved as compared with the case where the switching valve is in the first state.

  It is preferable that a pressure sensor for measuring the pressure in the oil tank is further provided, and the switching of the switching valve by the controller is performed based on the pressure measured by the pressure sensor.

  Thereby, necessary control is possible according to the pressure in the oil tank. Therefore, it is possible to reliably prevent the pressure in the oil tank from exceeding a certain level. For this reason, for example, there is no risk of leakage of air that contains oil in the compressor body or the atmosphere during unloading, preventing oil from entering the discharge air discharged from the discharge piping, The danger that becomes fatal to the product can be avoided.

  A temperature sensor for measuring the temperature in the oil tank is further provided, and the switching of the switching valve by the controller is preferably performed based on the pressure measured by the pressure sensor and the temperature measured by the temperature sensor. .

  Thereby, further necessary control is possible according to the temperature in the oil tank. Therefore, even when the compressor is stopped, if the temperature in the oil tank is high and oil smoke is generated, the pressure in the oil tank can be limited and prevented from exceeding a certain level. For this reason, oil smoke can be prevented from leaking out to the compressor body or the outside.

  The switching of the switching valve by the controller is switched to the second state when the pressure measured by the pressure sensor is lower than a predetermined pressure target value at the time of start-up and normal operation, and the pressure measured by the pressure sensor. Is switched to the first state when it is equal to or greater than a predetermined pressure target value, and when unloaded, the pressure sensor is switched to the first state regardless of the pressure measured by the pressure sensor, and measured by the pressure sensor when stopped. When the measured pressure is less than the predetermined pressure target value and the temperature measured by the temperature sensor is less than the predetermined temperature target value, the state is switched to the third state, and otherwise, the state is switched to the first state. It is preferable to be controlled as described above.

  Thereby, optimal control can be performed according to the pressure and temperature in the oil tank. Specifically, during startup and normal operation, air consumption can be reduced by reducing the pressure of air supplied to the ejector as low as possible based on the internal pressure of the oil tank. When unloading, the pressure of the air after the first stage compression (air from the intermediate pipe) becomes negative, so it is stable by supplying the air after the second stage compression (air from the discharge pipe) to the ejector. Thus, the air in the oil tank can be sucked and kept below the target pressure. When the operation is stopped, since the compressor is not operating, no oil mist is generated by stirring, but there is a risk that oil smoke is generated by oil that has become hot during operation. By this control, the ejector is operated at a temperature at which oil smoke is generated based on the temperature in the oil tank, and the air consumption is reduced by not operating the ejector at a temperature at which oil smoke is not generated. Further, when the switching valve is fully closed (third state) when unnecessary, it is possible to prevent the backflow of the oil-containing air and to prevent the high-pressure discharge air from flowing down.

  The pressure target value is preferably equal to or lower than atmospheric pressure, and is the pressure closest to the outside of the shaft seal during unloading.

  As a result, when the pressure target value is equal to or lower than the atmospheric pressure, air leakage from the oil tank to the outside can be prevented, and when the pressure is close to the outside of the shaft seal during unloading, it is 1 It is possible to prevent backflow of air containing oil to the stage and second stage compressor bodies. Moreover, since the inside of the oil tank is not depressurized more than necessary, the air consumption at the ejector can be reduced.

  It is preferable that a flow rate adjusting valve for adjusting a flow rate of air supplied to the ejector is further provided between the switching valve and the ejector. Moreover, it is preferable that the opening degree of the flow rate adjusting valve is adjusted by the controller so that the pressure in the oil tank becomes the pressure target value.

  According to this configuration, the supply pressure to the ejector can be controlled not only in two patterns of the first state and the second state, but also more finely. Therefore, by reducing the air supply amount to the ejector, the air consumption amount is minimized. Can be further reduced.

  According to a second aspect of the present invention, a first-stage compressor body and a second-stage compressor body for performing two-stage compression, and the first-stage compressor body and the second-stage compressor body are supplied. An oil tank for storing oil, an ejector for reducing the pressure in the oil tank, and an intermediate air after compression in the first-stage compressor body and before compression in the second-stage compressor body A switching valve for switching between air and discharged air that is compressed air in the second-stage compressor body, a pressure sensor for measuring the pressure in the oil tank, and the oil In an oil-free compressor equipped with a temperature sensor for measuring the temperature in the tank, the switching of the switching valve is such that the pressure measured by the pressure sensor is less than a predetermined pressure target value at startup and during normal operation. If the intermediate air When the pressure supplied to the ejector and the pressure measured by the pressure sensor is equal to or higher than a predetermined pressure target value, the discharged air is supplied to the ejector, and the unload is performed regardless of the pressure measured by the pressure sensor. When the discharge air is supplied to the ejector and the pressure measured by the pressure sensor is less than a predetermined pressure target value at the time of stopping, and the temperature measured by the temperature sensor is less than the predetermined temperature target value, A control method for an oil-free compressor is provided in which the switching valve is fully closed, and in other cases, the discharge air is supplied to the ejector.

  According to the present invention, the amount of air consumption can be reduced by setting the pressure of the air supplied to the ejector for decompressing the oil tank as low as possible. Further, supplying air from the intermediate pipe to the ejector reduces the shaft power and improves the efficiency of the compressor.

The schematic diagram which shows the compressor which concerns on 1st Embodiment of this invention. The control flow at the time of starting which concerns on 1st Embodiment of this invention, and normal operation. The control flow at the time of unloading which concerns on 1st Embodiment of this invention. The control flow at the time of a stop concerning a 1st embodiment of the present invention. The graph which shows the relationship between the pressure and volume in a compression process. The schematic diagram which shows the compressor which concerns on 2nd Embodiment of this invention. The control flow at the time of starting and a normal operation according to the second embodiment of the present invention. The control flow at the time of unloading concerning 2nd Embodiment of this invention. The control flow at the time of a stop concerning a 2nd embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
As shown in FIG. 1, an oil-free compressor (hereinafter simply referred to as a compressor) 2 of the present embodiment compresses air supplied from a suction port 6 through an air pipe 4 and discharges it from a discharge port 8. The compressor 2 includes an intake adjustment valve 10, a compressor body 12, and a cooler 16, which are fluidly connected by an air pipe 4.

  The air pipe 4 includes a suction pipe 4a, an intermediate pipe 4b, and a discharge pipe 4c.

  The suction pipe 4 a is a pipe for sucking air and introducing it into the compressor body 12. Therefore, one end is fluidly connected to the compressor body 12 and the other end is fluidly connected to the outside of the compressor 2.

  The intermediate pipe 4 b is a pipe that connects the compressor body 12. The compressor body 12 is a two-stage type, and includes a first-stage compressor body 13 and a second-stage compressor body 14. The intermediate pipe 4b fluidly connects the first stage compressor body 13 and the second stage compressor body 14. Therefore, one end is fluidly connected to the first stage compressor body 13 and the other end is fluidly connected to the second stage compressor body 14.

  The discharge pipe 4 c is a pipe that discharges compressed air from the compressor 2. Accordingly, one end is fluidly connected to the second stage compressor body 14 and the other end is fluidly connected to the outside of the compressor 2.

  The intake adjustment valve 10 is interposed in a suction pipe 4a extending from the suction port 6 to the compressor main body 12, and adjusts the amount of air supplied to the compressor main body 12 by adjusting the opening degree.

  The first-stage compressor body 13 and the second-stage compressor body 14 include intake ports 13a and 14a and exhaust ports 13b and 13b, respectively. An air pipe 4 is fluidly connected to the intake ports 13a and 14a and the exhaust ports 13b and 14b. The compressor main body 12 includes a motor (not shown) and a bull gear driven by the motor, and the input shafts 13c and 14c are driven by the motor (not shown) and the bull gear driven by the motor. A first stage compressor body 13 and a second stage compressor body 14 are mechanically connected to the input shafts 13c and 14c to perform compression. When the first-stage compressor main body 13 and the second-stage compressor main body 14 suck the gas (for example, air) from the intake ports 13a and 14a, respectively, the sucked air is compressed inside and is discharged from the exhaust ports 13b and 14b. It is discharged through the air pipe 4.

  The cooler 16 cools the compressed air that has been compressed by the compressor body 12 and heated by the compression heat. The cooler 16 of this embodiment includes an intercooler 17 and an aftercooler 18 for use with the two-stage compressor body 12. The intercooler 17 cools the compressed air (intermediate air) after being compressed by the first-stage compressor body 13 and before being compressed by the second-stage compressor body 14 from the first-stage compressor body 13. An intermediate pipe 4b extending to the compressor body 14 is provided. The aftercooler 18 is provided in a discharge pipe 4c extending from the second stage compressor body 14 to the discharge destination 19 in order to cool the compressed air (discharged air) after being compressed by the second stage compressor body 14.

  The discharge pipe 4 c extending to the discharge destination 19 is provided with a check valve 20 downstream of the aftercooler 18, and the compressed air does not flow back upstream from the check valve 20.

  Further, since the compressor 2 is an oil-free type, no oil is used in the compression chamber of the compressor body 12, but it is used in the bearings 13d and 14d of the input shafts 13c and 14c. An oil tank 22 for storing the oil is provided in the compressor body 12. A temperature sensor 24 and a pressure sensor 26 are installed in the oil tank 22, and the temperature and pressure inside the oil tank 22 can be measured.

  A pressure reducing pipe 28 for reducing the internal pressure is fluidly connected to the oil tank 22. One end of the pressure reducing pipe 28 is fluidly connected to the oil tank 22, and the other end is opened to the outside of the compressor 2. An ejector 30 and a filter 32 are interposed in the pressure reducing tube 28. By the ejector 30, the fluid in the oil tank 22 in which oil and air are mixed is sucked into the pressure reducing pipe 28. The mixed fluid of oil and air passes through the filter 32 to remove oil, and the air from which oil has been removed is exhausted to the outside of the compressor 2. The oil removed by the filter 32 is returned to the oil tank 22 again.

  In addition to the decompression pipe 28, a communication pipe 34 that supplies working air is fluidly connected to the ejector 30. The ejector 30 is supplied with working air from the communication pipe 34, thereby sucking air from the oil tank 22 through the pressure reducing pipe 28 and reducing the pressure in the oil tank 22.

  One end of the communication pipe 34 is connected to the ejector 30 and the other end is branched and fluidly connected to two locations in the compressor 2 via an electromagnetic valve (switching valve) 38. One place is a discharge pipe 4 c downstream from the check valve 20 extending to the discharge destination 19, and the other place is an intermediate pipe 4 b extending from the intercooler 17 to the second stage compressor body 14. Hereinafter, the former is referred to as a first communication pipe 35 and the latter is referred to as a second communication pipe 36. However, the second communication pipe 36 may be fluidly connected to the air pipe 4 extending from the first stage compressor body 13 to the second stage compressor body 14. Therefore, in addition to the aspect of the present embodiment, it may be fluidly connected to the intermediate pipe 4 b extending from the first-stage compressor body 13 upstream of the intercooler 17 to the intercooler 17.

  An electromagnetic valve 38 is provided at the junction of the first communication pipe 35 and the second communication pipe 36. The electromagnetic valve 38 includes a first port 38a, a second port 38b, and a third port 38c. The first port 38a is fluidly connected to the communication pipe 34, the second port 38b is fluidly connected to the first communication pipe 35, and the third port 38c is fluidly connected to the second communication pipe 36. The electromagnetic valve 38 can be switched between three states.

  In the first state, only the ejector 30 and the discharge pipe 4c communicate with each other via the communication pipe 34 and the first communication pipe 35, that is, the first port 38a and the second port 38b are opened, and the third port 38c is Closed.

  In the second state, only the ejector 30 and the intermediate pipe 4b communicate with each other via the communication pipe 34 and the second communication pipe 36, that is, the first port 38a and the third port 38c are opened, and the second port 38b is Closed.

  The third state is a fully closed state, that is, the first port 38a, the second port 38b, and the third port 38c are closed.

  Further, the compressor 2 includes a controller 40. The controller 40 is constructed by hardware including a storage device such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and software installed therein. The controller 40 is electrically connected to the electromagnetic valve 38 (see the broken line in FIG. 1). Further, the temperature sensor 24 and the pressure sensor 26 output the measurement value to the controller 40 (see the broken line in FIG. 1). The controller 40 switches the electromagnetic valve 38 based on the temperature and pressure in the oil tank 22 measured by the temperature sensor 24 and the pressure sensor 26.

  The ejector 30 has a property that the amount of intake air from the pressure reducing pipe 28 increases as high pressure air is supplied to the communication pipe 34. Comparing the pressure of air in the first communication pipe 35 and the second communication pipe 36, the pressure of air in the first communication pipe 35 is higher. This is because the air in the first communication pipe 35 is the discharge air after two-stage compression, whereas the air in the second communication pipe 36 is intermediate air after the first-stage compression and before the second-stage compression. is there. Therefore, due to the nature of the ejector 30, the amount of intake air from the decompression pipe 28 increases when high-pressure discharge air is supplied from the first communication pipe 35 to the ejector 30. However, in this case, since a part of the discharge air is consumed, the efficiency of the compressor 2 as a whole is lowered. When intermediate air having a lower pressure is supplied from the second communication pipe 36 to the ejector 30, the amount of intake air from the pressure reducing pipe 28 by the ejector 30 is reduced compared to the case where the discharge air is supplied from the first communication pipe 35. The consumption of air used at 30 is also reduced. In the compressor 2 of the present embodiment, the air supplied to the ejector 30 is switched between the discharge air from the first communication pipe 35 and the intermediate air from the second communication pipe 36 as necessary to optimize efficiency. It has become.

  Next, control for optimizing the efficiency of the compressor 2 according to this embodiment will be described with reference to FIGS.

  As shown in FIGS. 2 to 4, the compressor 2 of the present embodiment has three control flows. FIG. 2 is a control flow during start-up and normal operation, FIG. 3 is a control flow during unloading, and FIG. 4 is a control flow during stop.

  First, the control flow during startup and normal operation will be described with reference to FIG. When the compressor 2 starts or shifts to a normal operation state (step S1-1), the electromagnetic valve 38 is switched so as to supply discharge air from the first communication pipe 35 to the ejector 30 (step S1-2). Then, the motor mechanically connected to the input shafts 13c and 14c of the compressor body 12 is driven (step S1-3). Thereafter, the intake adjustment valve 10 is opened (step S1-4), and air is supplied to the compressor body 12. If the internal pressure of the oil tank 22 measured by the pressure sensor 26 is equal to or higher than the predetermined target pressure TH1, the state is maintained (step S1-5), and if it is lower than the predetermined target pressure TH1, the second communication pipe is maintained. The solenoid valve 38 is switched so that intermediate air is supplied from 36 to the ejector 30 (step S1-6). When the internal pressure of the oil tank 22 is lower than the predetermined target pressure TH2, the state is maintained (step S1-7), and when the internal pressure is higher than the predetermined target pressure TH2, the first communication pipe 35 transfers to the ejector 30. The electromagnetic valve 38 is switched so as to supply the discharge air (step S1-8).

  Second, the control flow during unloading will be described with reference to FIG. When the unload signal is received (step S2-1), the solenoid valve 38 is switched so as to supply discharge air from the first communication pipe 35 to the ejector 30 (step S2-2), and the intake adjustment valve is closed (step S2). -3).

  Third, the control flow at the time of stop will be described with reference to FIG. When the compressor 2 shifts to a stopped state (step S3-1), the electromagnetic valve 38 is switched so as to supply discharge air from the first communication pipe 35 to the ejector 30 (step S3-2), and the intake adjustment valve is turned on. Close (step S3-3). And the drive of a motor is stopped (step S3-4). Thereafter, when the internal pressure of the oil tank 22 is smaller than the predetermined target pressure TH1 (step S3-5) and the temperature in the oil tank 22 is lower than normal temperature (step S3-6), the condition is not satisfied. If the condition is satisfied, the solenoid valve 38 is fully closed (step S3-7).

  FIG. 5 is a graph showing the relationship between pressure and volume in the compression process of the compressor 2. The horizontal axis indicates the volume V of compressed air, and the vertical axis indicates the pressure P. When P1 is inhaled, P2 is after one-stage compression, and P3 is after two-stage compression. When the solid line supplies the discharged air after two-stage compression to the ejector 30, the broken line indicates the intermediate air after the first-stage compression. The case where it supplies to is represented. As shown in FIG. 5, when compression is performed from P1 to P2 by the first-stage compressor body 13, the broken line in the case where the intermediate air is supplied to the ejector 30 at P2 is lower in pressure than the solid line. . That is, when the intermediate air after the first stage compression is supplied to the ejector 30, the pressure after the first stage compression is further reduced. Then, the compression is performed by the two-stage compressor body 12 and reaches P3. In the case of the broken line that supplies the intermediate air to the ejector 30, the pressure inside the second stage compressor body 14 decreases, so the shaft power decreases even with the same air consumption. In the graph, the enclosed area indicated by the hatched portion represents the decrease in shaft power. Accordingly, the efficiency of the compressor 2 is improved by a reduction in the shaft power, compared with the case where the discharge air after the two-stage compression is supplied to the ejector 30. Moreover, the air consumption used by the ejector 30 can be reduced by making the pressure of the air supplied to the ejector 30 as low as possible.

  Thus, since necessary control is performed according to the pressure in the oil tank 22, it is possible to reliably prevent the pressure in the oil tank 22 from exceeding a certain level. For this reason, for example, there is no risk of leakage of air that contains oil in the compressor body 12 or the atmosphere during unloading, and it is possible to prevent the oil from being mixed into the discharge air discharged from the discharge port 8. Avoid critical risks to processes and products.

  Further, since necessary control is performed in accordance with the temperature in the oil tank 22, even when the compressor 2 is stopped, if the temperature in the oil tank 22 is high and oil smoke is generated, the oil It is possible to prevent the pressure in the tank from exceeding a certain level by limiting the pressure in the tank. For this reason, oil smoke can be prevented from leaking out to the compressor body 12 or the outside.

  Specifically, during startup and normal operation, the air consumption can be reduced by reducing the pressure of the air supplied to the ejector 30 as low as possible based on the internal pressure of the oil tank 22. At the time of unloading, the pressure of the intermediate air from the second communication pipe 36 becomes a negative pressure. Therefore, the oil tank 22 is stably supplied by supplying the discharge air from the first communication pipe 35 having a higher pressure to the ejector 30. The air inside can be sucked and kept below the target pressure. When the operation is stopped, since the compressor 2 is not operating, oil mist due to stirring is not generated, but there is a possibility that oil smoke is generated by oil that has become hot during operation. In the compressor 2 of the present embodiment, the ejector 30 is operated at a temperature at which oil smoke is generated based on the temperature in the oil tank 22, and the air consumption is reduced by not operating the ejector 30 at a temperature at which oil smoke is not generated. ing. Further, when decompression by the ejector 30 is unnecessary, the solenoid valve 38 is fully closed to prevent the backflow of air containing oil into the communication pipe 34, and the high pressure discharge air in the first communication pipe 35 is prevented. Dripping can also be prevented.

  Preferably, when the predetermined pressure target values TH1 and TH2 are equal to or lower than the atmospheric pressure, air leakage from the oil tank 22 to the outside can be prevented. Preferably, the predetermined pressure target values TH1 and TH2 are the pressures immediately outside the shaft seal during unloading, so that the first-stage compressor body 13 and the second-stage compressor body 14 from the oil tank 22 during unloading. This prevents backflow of air containing oil. Moreover, since the inside of the oil tank 22 is not depressurized more than necessary, the air consumption in the ejector 30 can be reduced.

  In the present embodiment, the predetermined target pressures TH1 and TH2 are adopted as threshold values for switching the electromagnetic valve 38 in the control flow of FIGS. 2 to 4, but these target pressures may be different or the same. There is no particular limitation.

(Second Embodiment)
FIG. 6 shows the compressor 2 of the second embodiment. The compressor 2 of this embodiment is provided with an automatic operation valve (fluid regulating valve) 42 in the communication pipe 34 and a pressure sensor 44 for measuring the pressure of the intermediate air supplied to the second communication pipe 36. The configuration other than the portion relating to is substantially the same as that of the first embodiment of FIG. Therefore, the same parts as those shown in FIG.

  Referring to FIG. 6, in the compressor 2 of the present embodiment, an automatic operation valve 42 is provided in a communication pipe 34 extending from the electromagnetic valve 38 to the ejector 30. Therefore, the flow rate of the compressed air supplied from the electromagnetic valve 38 to the ejector 30 can be adjusted by the automatic operation valve 42. The air pipe 4 extending from the intercooler 17 to the second-stage compressor body 14 is provided with a pressure sensor 44 for measuring the supply pressure of the intermediate air to the second communication pipe 36. Further, the communication pipe 34 is provided with a pressure sensor 45 for measuring the supply pressure of air to the ejector 30. The pressure sensors 44 and 45 output the measured pressure to the controller 40 (see the broken line in FIG. 6).

  Control for optimizing the efficiency of the compressor 2 according to this embodiment will be described with reference to FIGS.

  As shown in FIGS. 7 to 9, the compressor 2 of the present embodiment has three control flows as in the first embodiment. FIG. 7 is a control flow at start-up and normal operation, FIG. 8 is a control flow at unloading, and FIG. 9 is a control flow at stop.

  First, the control flow during startup and normal operation will be described with reference to FIG. Referring to FIG. 7, when the compressor 2 starts or shifts to a normal operation state (step S <b> 1-1), the electromagnetic valve 38 is switched so as to supply discharge air from the first communication pipe 35 to the ejector 30 ( Step S1-2). Then, the motor mechanically connected to the input shafts 13c and 14c of the compressor body 12 is driven (step S1-3). Thereafter, the intake adjustment valve 10 is opened (step S1-4), and air is supplied to the compressor body 12. Then, the opening degree of the automatic operation valve 42 is adjusted so that the internal pressure of the oil tank 22 becomes a predetermined target pressure TH3 (step S1-9). At this time, when the supply pressure to the ejector 30 is equal to or higher than the pressure in the second communication pipe 36 (step S1-10), the opening degree adjustment of the automatic operation valve 42 is continued (step S1-9). When the pressure of the intermediate air in the second communication pipe 36 is smaller than the supply pressure to the ejector 30 (step S1-10), the intermediate valve is supplied from the second communication pipe 36 to the ejector 30 by switching the electromagnetic valve 38 (step S1-10). Step S1-11). Then, the opening degree of the automatic operation valve 42 is adjusted so that the internal pressure of the oil tank 22 becomes a predetermined target pressure TH3 (step S1-12). Thereafter, until the opening degree of the automatic operation valve 42 is maximized (step S1-13), the adjustment of the opening degree of the automatic operation valve 42 is continued (step S1-12). When the opening degree of the automatic operation valve 42 reaches the maximum (step S1-13), the solenoid valve 38 is switched to supply the discharge air from the first communication pipe 35 to the ejector 30 (step S1-14). Then, the opening degree of the automatic operation valve 42 is adjusted again so that the internal pressure of the oil tank 22 becomes a predetermined target pressure TH3 (step S1-9).

  Second, the control flow during unloading will be described with reference to FIG. When the unload signal is received (step S2-1), the solenoid valve 38 is switched so as to supply discharge air from the first communication pipe 35 to the ejector 30 (step S2-2), and the intake adjustment valve is closed (step S2). -3). Then, the opening degree of the automatic operation valve 42 is adjusted so that the internal pressure of the oil tank 22 becomes a predetermined target pressure TH3 (step S2-4).

  Third, the control flow at the time of stop will be described with reference to FIG. When the compressor 2 shifts to a stopped state (step S3-1), the electromagnetic valve 38 is switched so as to supply discharge air from the first communication pipe 35 to the ejector 30 (step S3-2), and the intake adjustment valve is turned on. Close (step S3-3). And the drive of a motor is stopped (step S3-4). Thereafter, the opening degree of the automatic operation valve 42 is adjusted so that the internal pressure of the oil tank 22 becomes a predetermined target pressure TH3 (step S3-8). When the condition that the temperature in the oil tank 22 is lower than the normal temperature (step S3-6) is not satisfied, the state is maintained, and when the condition is satisfied, the electromagnetic valve 38 is fully closed (step S3-7). .

  As described above, the compressor 2 according to the present embodiment adjusts the supply pressure to the ejector 30 by adjusting not only the two patterns of the high pressure of the discharge air and the low pressure of the intermediate air but also the opening degree of the automatic operation valve 42. Fine control. Therefore, the air consumption can be further reduced by minimizing the amount of air supplied to the ejector 30.

  Although the automatic operation valve 42 is provided in the communication pipe 34 extending from the electromagnetic valve 38 to the ejector 30 in this embodiment, the present invention is not limited to this. For example, the automatic operation valve 42 may alternatively be provided in the first communication pipe 35. In this case, the flow rate of the intermediate air from the second communication pipe 36 cannot be adjusted, but the flow rate of the high-pressure discharge air from the first communication pipe 35 that is highly necessary to adjust the flow rate can be adjusted. As described above, the position of the automatic operation valve 42 may be changed as necessary.

  In the first and second embodiments described above, control is performed to switch the solenoid valve 38 by providing a threshold value of a predetermined target pressure with respect to the internal pressure of the oil tank 22, but the control is based on the changing pressure gradient. May be performed.

2 Compressor 4 Air Piping 4a Suction Piping 4b Intermediate Piping 4c Discharge Piping 6 Suction Port 8 Discharge Port 10 Intake Adjustment Valve 12 Compressor Body 13 First Stage Compressor Body 13a Inlet Port 13b Exhaust Port 13c Input Shaft 13d Bearing 14 Second Stage Eye compressor main body 14a Intake port 14b Exhaust port 14c Input shaft 14d Bearing 16 Cooler 17 Intercooler 18 After cooler 19 Discharge destination 20 Check valve 22 Oil tank 24 Temperature sensor 26 Pressure sensor 28 Pressure reducing pipe 30 Ejector 32 Filter 34 Communication pipe 35 First communication pipe 36 Second communication pipe 38 Solenoid valve (switching valve)
38a First port 38b Second port 38c Third port 40 Controller 42 Automatic operation valve (fluid regulating valve)
44, 45 Pressure sensor

Claims (8)

A first-stage compressor body and a second-stage compressor body for performing two-stage compression;
An oil tank for storing oil to be supplied to bearings of the first stage compressor body and the second stage compressor body;
An ejector for reducing the pressure in the oil tank;
The ejector, a discharge pipe for supplying compressed air from the second-stage compressor body to the discharge destination, and an intermediate for supplying compressed air from the first-stage compressor body to the second-stage compressor body A first state in which only the ejector and the discharge pipe are in fluid communication with each other; a second state in which only the ejector and the intermediate pipe are in communication; and a third state in which the ejector is in a fully closed state. A switching valve capable of switching between states,
An oil-free compressor comprising: a controller that controls switching of the switching valve. A pressure sensor for measuring the pressure in the oil tank;
The oil-free compressor according to claim 1, wherein the switching of the switching valve by the controller is performed based on a pressure measured by the pressure sensor. A temperature sensor for measuring the temperature in the oil tank;
The oil-free compressor according to claim 2, wherein the switching of the switching valve by the controller is performed based on a pressure measured by the pressure sensor and a temperature measured by the temperature sensor. The switching of the switching valve by the controller is as follows:
When the pressure measured by the pressure sensor is lower than a predetermined pressure target value at the time of start-up and normal operation, when switching to the second state and the pressure measured by the pressure sensor is greater than or equal to the predetermined pressure target value , Switch to the first state,
At the time of unloading, regardless of the pressure measured by the pressure sensor, switching to the first state,
At the time of stopping, when the pressure measured by the pressure sensor is less than a predetermined pressure target value and the temperature measured by the temperature sensor is less than the predetermined temperature target value, switch to the third state, otherwise In this case, the oil-free compressor according to claim 3, wherein the oil-free compressor is controlled to switch to the first state.   5. The oil-free compressor according to claim 4, wherein the pressure target value is equal to or lower than atmospheric pressure and is a pressure immediately outside the shaft seal at the time of unloading.   The oil-free compressor according to any one of claims 3 to 5, further comprising a flow rate adjusting valve that adjusts a flow rate of air supplied to the ejector between the switching valve and the ejector.   The oil-free compressor according to claim 6, wherein the controller adjusts the opening of the flow rate adjusting valve so that the pressure in the oil tank becomes the pressure target value. A first-stage compressor body and a second-stage compressor body for performing two-stage compression;
An oil tank for storing oil to be supplied to the first stage compressor body and the second stage compressor body;
An ejector for reducing the pressure in the oil tank;
Either of the intermediate air, which is air before compression in the main body of the first stage and before compression in the main body of the second stage compressor, or the discharge air, which is air after compression in the main body of the second stage, is described above. A switching valve that switches between supplying to the ejector and
A pressure sensor for measuring the pressure in the oil tank;
In an oil-free compressor equipped with a temperature sensor for measuring the temperature in the oil tank,
The switching of the switching valve is
During startup and normal operation, if the pressure measured by the pressure sensor is less than a predetermined pressure target value, the intermediate air is supplied to the ejector, and the pressure measured by the pressure sensor is equal to or higher than the predetermined pressure target value. If it is, supply the discharge air to the ejector,
At the time of unloading, regardless of the pressure measured by the pressure sensor, the discharge air is supplied to the ejector,
When the pressure measured by the pressure sensor is less than a predetermined pressure target value and the temperature measured by the temperature sensor is less than a predetermined temperature target value at the time of stopping, the switching valve is fully closed, Otherwise, the control method of the oil-free compressor, wherein the discharge air is supplied to the ejector.

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