JP4745208B2 - Oil-free screw compressor - Google Patents

Description

  The present invention relates to a control device for a rotational speed variable oilless screw compressor, and more particularly to a rotational speed variable oilless screw compressor having a low pressure stage compressor body and a high pressure stage compressor body.

  As an air compressor, there is a method of using two compressor bodies and compressing in two stages up to a predetermined pressure, and this method is generally used particularly in an oil-free compressor. In this compressor, after the air is compressed to a predetermined pressure by the low-pressure stage compressor body, the compressed air is primarily cooled by an intermediate cooling device (intercooler), and further, the air is compressed to a predetermined required pressure by the high-pressure stage compressor body. It is structured to be compressed and cooled with an aftercooler.

  In such a two-stage oil-free screw compressor, various variable speed control type compressors have been proposed (see, for example, Patent Document 1).

JP 2002-138777 A

  In the conventional rotary speed variable two-stage oilless screw compressor configured as described above, the amount of intake air decreases at low loads (during low speed operation). If used, it will be overcooled and drainage will occur. In the rotational speed variable type two-stage oil-free screw compressor, various considerations regarding energy saving have been proposed, but the current situation is that no consideration is given to problems caused by drains generated in the intermediate stage.

  For example, a two-stage oilless screw compressor detects the pressure on the outlet side of the aftercooler, and performs capacity control to change the rotation speed according to the amount of air consumed so that this pressure becomes constant. When the amount of consumed air is 100%, the temperature at the outlet of the intercooler is configured to be 15 ° C. to 20 ° C. higher than the suction temperature. In the rotational speed control, the amount of air consumed is controlled to 40 to 50%. However, in this state, the amount of intake air is 40 to 50%. Drainage occurs when the air amount is lower by about 10 ° C. to 15 ° C. than the state of 100%. This drain is taken away to the main body of the high-pressure stage compressor, and at the time of low load, it causes a failure due to rusting or the like of the main body of the high-pressure stage compressor, and its reliability is lowered.

  The present invention has been made in view of the above-described problems, and its object is to reduce the amount of drain generated at low load and to ensure the reliability of the high-pressure compressor main body, and to provide a variable rotational speed oilless It is in providing a type screw compressor.

  To achieve the above object, the first invention provides a low-pressure compressor main body and a high-pressure compressor main body having variable rotation speeds, and a pipe connecting the low-pressure compressor main body and the high-pressure compressor main body. In an oil-free screw compressor provided with an intercooler provided in the middle, on the discharge side of the high-pressure stage compressor body, a pressure sensor for detecting the pressure of high-pressure air discharged from the high-pressure stage compressor body, When the air consumption is calculated based on at least two cooling fans that cool the intercooler and the detected pressure value detected by the pressure sensor, and the air consumption falls below a preset air consumption And a control device for stopping and controlling one of the cooling fans.

  Further, the second invention is the first invention according to the present invention, in the venting branch pipe provided in the pipe connecting the low-pressure stage compressor body and the high-pressure stage compressor body, and the venting branch pipe. The control device calculates an air consumption based on a detected pressure value detected by the pressure sensor, and presets if the air consumption is less than or equal to a preset air consumption. The lower limit rotational speed command is output, and a command is output to the venting solenoid valve so as to perform a venting decompression operation.

Furthermore, a third aspect of the invention relates to a low-pressure compressor main body and a high-pressure compressor main body having a variable rotation speed, and an intercooler provided in the middle of a pipe connecting the low-pressure compressor main body and the high-pressure compressor main body. And an oil-free screw compressor comprising at least two cooling fans for cooling the intercooler, a temperature sensor for detecting the intake air temperature of the low pressure stage compressor body, and the intake air of the high pressure stage compressor body A temperature sensor for detecting temperature and a control device for calculating a temperature difference from the temperature sensor and stopping one cooling fan when the temperature difference is equal to or less than a preset temperature difference.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the low pressure stage side cooling device configured by the intercooler and its cooling fan, and the high pressure stage side cooling configured by the after cooler and its cooling fan. These cooling devices are each divided and formed.

  Furthermore, in a fifth aspect according to any one of the first to fourth aspects, when the control device sequentially stops the cooling fan, the control device stops from the one that stopped first, and When the cooling fans are operated sequentially, control is performed so that the cooling fans are operated from those other than the one that was first operated last time.

Further, the sixth invention is a plurality of low-pressure stage compressor main body and high-pressure stage compressor main body with variable rotation speed, and a plurality of pipes provided in the middle of the pipe connecting the low-pressure stage compressor main body and the high-pressure stage compressor main body . In an oil-free screw compressor including an intercooler, a pressure sensor for detecting a pressure of high-pressure air discharged from the high-pressure stage compressor body on the discharge side of the high-pressure stage compressor body, and the plurality of intercoolers Based on the piping that bypasses the inlet and outlet of one intercooler of each of the coolers , at least two two-way valves provided in these piping, and the detected pressure value detected by the pressure sensor And a controller that sequentially opens the two-way valve when the amount of air is calculated and the amount of consumed air is equal to or less than a preset amount of consumed air.

  According to the present invention, it is possible to reduce the amount of drain at the intercooler outlet that is likely to occur at low loads by changing the rotational speed of the air-cooled two-stage oilless screw compressor. The inflow to can be suppressed. As a result, the cause of failure due to rusting or the like of the high-pressure stage compressor body can be suppressed, and the reliability can be improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a rotary variable speed two-stage oilless screw compressor according to the present invention will be described below with reference to the drawings.
1 to 3 show an embodiment of a rotary variable speed two-stage oilless screw compressor according to the present invention. FIG. 1 shows a rotary variable speed two-stage oilless screw compressor according to the present invention. FIG. 2 is a diagram showing the configuration of the first embodiment, FIG. 2 is a diagram showing the relationship between the amount of air consumed and the amount of generated intercooler drain in the conventional system, and FIG. 3 is a rotary variable speed two-stage oilless screw compressor according to the present invention. It is a figure which shows the relationship between the air consumption and drain generation amount in 1st Embodiment of this, and operation | movement of a cooling fan.
In FIG. 1, a rotary variable speed air-cooled two-stage oilless screw compressor 100 has a low-pressure stage compressor body 1 and a high-pressure stage compressor body 2 in a casing 101. The low-pressure stage compressor body 1 houses a pair of screw rotors of a male rotor 3A and a female rotor 3B in a casing having a cooling jacket formed on the outer peripheral portion. And this pair of screw rotor rotates synchronously when the timing gear 4 attached to the shaft end of each rotor meshes.

  On the other hand, a low-pressure stage pinion gear 5 is attached to the shaft end of the male rotor 3A opposite to the timing gear 4. Similarly, the high-pressure compressor body 2 houses a pair of screw rotors, a male rotor 6A and a female rotor 6B, in a casing in which a cooling jacket is formed on the outer periphery. And this pair of screw rotor rotates synchronously when the timing gear 7 attached to the shaft end part of each rotor meshes. On the other hand, a high-pressure stage pinion gear 8 is attached to the shaft end of the male rotor 6A opposite to the timing gear 7.

  Both pinion gears 5 and 8 mesh with a bull gear 10 attached to the rotation shaft of the motor 9 and are housed in a gear casing 11. The motor 9 is configured to change the rotation speed according to a command from the inverter 12. An oil sump for lubricating oil is formed in the lower portion of the gear casing 11. The lubricating oil in the oil sump is sucked up by the oil pump 13 to cool the jacket portions of the compressor main bodies 1 and 2, the bearings of the compressor main bodies 1 and 2, the timing gears 4 and 7, the bull gear 10, and the pinion gear. Lubricate 5 and 8.

  A suction filter 15 is attached to the suction air passage 14 of the low-pressure compressor main body 1. An intercooler 16 is provided between the discharge side of the low-pressure stage compressor body 1 and the suction side of the high-pressure stage compressor body 2. The low-pressure stage compressor body 1 and the intercooler 16 are connected by an air pipe 17A, and the intercooler 16 and the high-pressure stage compressor body 2 are connected by an air pipe 17B.

  In this embodiment, the output of the motor 9 is an example of a compressor with a large capacity of 160 kW. In order to reduce the size of the unit and share parts with the small capacity machine, two intercoolers 16 are used. Each of the air pipes 17A and 17B is branched and connected.

  A downstream of the high-pressure compressor body 2 is connected to an aftercooler 20 and an air pipe 21 </ b> A via a stainless precooler 18 and a check valve 19. A drain separator 22 is provided on the downstream side of the aftercooler 20. The outlet side of the drain separator 22 is guided to the use side by an air pipe 21B. A pressure sensor 23 that detects the pressure of compressed air discharged from the oil-free screw compressor 100 is attached to the air pipe 21B. The detected value of the pressure sensor 23 is input to the control device 24.

  On the other hand, on the cooling air side, three cooling fans 25A, 25B, and 25C are provided in the upper part of the intercooler 16 in this example. The cooling air generated by the rotation of the three cooling fans 25A, 25B, and 25C is guided from the cooling air suction port 26A to the cooling air exhaust port 26B. The cooling air is heat-exchanged by the intercooler 16 with the compressed air that has become high temperature in the low-pressure stage compressor body 2.

  Similarly, a cooling fan 27 is also provided on the upper portion of the aftercooler 20. The cooling air generated by the rotation of the cooling fan 27 is guided from the cooling air suction port 28A to the cooling air exhaust port 28B. The cooling air is heat-exchanged by the aftercooler 20 with the compressed air that has become high temperature in the high-pressure stage compressor body 2.

  Further, the low-pressure stage discharge pipe 1 is branched from the middle of the air pipe 17A connecting the low-pressure stage compressor body 1 and the intercooler 16, and a low-pressure stage discharge valve 30A is provided. Similarly, a high-pressure stage vent pipe 29B branches from the upstream side of the check valve 19 in the middle of the air pipe 21A connecting the high-pressure stage compressor body 2 and the aftercooler 20, and a high-pressure stage vent valve 30A is provided. ing.

  When the amount of air consumed is reduced and the discharge air amount may be, for example, 100% to 40% of the specified discharge air amount, the control device 24 described above stores the detection value from the pressure sensor 23 in the storage unit in the control device 24. A first function for performing so-called load operation control for changing the rotational speed of the screw rotors of the compressor bodies 1 and 2 so as to be equal to a preset target pressure, and the discharge air amount is a specified discharge air amount. For example, when it may be about 40% or less, an open command is sent to the venting solenoid valves 30A and 30B. Specifically, if the detected pressure value of the pressure sensor 23 exceeds the upper limit pressure (upper limit pressure> target pressure) preset in the storage unit of the control device 24, the motor 9 is controlled to maintain the set lower limit rotation speed. At the same time, an opening command is sent to the discharge solenoid valves 30A, 30B, and the second air pressure is controlled so as to reduce the outlet air pressure of the low-pressure stage compressor body 1 and the outlet air pressure of the high-pressure stage compressor body 2; And the three cooling fans 25A, 25B, and 25C are sequentially stopped when the air consumption is reduced based on the detected pressure value from the pressure sensor 23 in order to suppress the generation of drain in the intercooler 16. And a third function for outputting the command to the cooling fans 25A, 25B, and 25C.

The third function of the control device 24 described above will be described with reference to FIGS.
2A shows the characteristics of the intercooler drain generation amount (cc / min) with respect to the consumed air amount (%), and FIG. 2B shows the intercooler outlet air temperature (° C.) with respect to the consumed air amount (%). It shows the characteristics and is the weather condition where the suction temperature is 30 ° C and the relative humidity is 80% and the drainage is most likely to occur. The pressure and temperature of the compressor are the same as described above. The specified discharge air volume is 27.5m3 / min. This shows the amount of drain generation when calculated in the case of.

  As is apparent from FIG. 2, when the amount of air consumed is between 100% and 40%, the rotational speed of the compressor bodies 1 and 2 is changed to adjust the discharge air amount. Since the amount of compressed air passing through the cooler 16 is reduced, the outlet air temperature of the intercooler 16 is lowered by 10 to 15 ° C. when the amount of consumed air is 100% as shown in FIG. As a result, drainage is generated. That is, the amount of generated drain increases sequentially as the amount of air consumed decreases sequentially from 80% as shown in FIG. In FIG. 2, when the drain generation amount is negative, it indicates that no drain is generated.

For this reason, in this embodiment, in order to suppress the above-described drain generation, the control device 24 outputs a command to sequentially stop the three cooling fans 25A, 25B, and 25C when the air consumption decreases. However, the setting contents will be described with reference to FIG.
3A shows the intercooler drain generation amount (cc / min) relative to the consumed air amount (%), and FIG. 3B shows the intercooler outlet air temperature (° C.) relative to the consumed air amount (%). (c) is a figure which shows the driving | running state of cooling fan 25A, 25B, 25C with respect to air consumption (%). Here, it is assumed that the capacity of the cooling fan to be stopped has such a capacity that the temperature of the outlet air of the intercooler 16 increases by 5 ° C. when one fan is stopped.

  As shown in FIG. 3, the control device 24 relates to the intercooler outlet air temperature (° C.) and the intercooler drain generation amount (cc / min) shown in FIG. On the other hand, for example, when it is 100%, all the cooling fans 25A, 25B, and 25C are operated, and when the amount of consumed air is reduced to 80%, the cooling fan 25C is stopped and the amount of consumed air is If it is reduced to 60%, the cooling fan 25B is then controlled to stop. When the air consumption is 60% or less, only the cooling fan 25A is operated.

  In this way, the cooling fan 25A, 25B is sequentially stopped and controlled in accordance with the decrease in the amount of air consumption, thereby reducing the intercooler outlet air temperature (° C.) as shown in FIG. Accordingly, as shown in FIG. 3 (a), the amount of drain generated in the entire consumption air amount region turns negative and is controlled so as not to generate drain.

Next, the operation of the first embodiment of the rotary variable speed two-stage oilless screw compressor of the present invention described above will be described with reference to FIGS.
When the motor 9 is operated, the rotational force of the motor 9 is transmitted to the low-pressure stage compressor body 1 and the high-pressure stage compressor body 2 via the bull gear 10 and the pinion gears 5 and 8. As a result, the pair of screw rotors in the low-pressure stage compressor main body 1 and the high-pressure stage compressor main body 2 rotate synchronously to compress air. Air sucked from the suction port 36 (for example, 30 ° C.) is compressed by the low-pressure stage compressor body 1 to increase the pressure to 0.17 MPa and the temperature rises to about 160 ° C.

  This high-temperature compressed air is cooled to about 50 ° C. (intake air temperature + 20 ° C.) by the intercooler 16 through the air pipe 17A. The compressed air cooled by the intercooler 16 is guided to the high-pressure compressor main body 2 through the air pipe 17B, and is further pressurized to a predetermined pressure (for example, 0.69 MPa) and the temperature rises to about 180 ° C. The compressed air whose temperature has risen is primarily cooled by the precooler 18 through the air pipe 21A, and then cooled to about 45 ° C. (intake air temperature + 15 ° C.) by the aftercooler 20 through the check valve 19. The compressed air cooled by the aftercooler 20 contains a drain, and the drain separator 22 removes the drain and is supplied from the discharge air pipe 21B to the user side.

  Here, when the amount of air consumed on the use side decreases, the pressure detected by the pressure sensor 23 increases. This detected pressure value is input to the control device 24. The control device 24 outputs a command signal for reducing the rotation speed of the motor 9 to the inverter 12 based on the detection value of the pressure sensor 23. Thereby, the rotational speed of the motor 9 falls. When the rotational speed of the motor 9 is reduced, the rotational speeds of the screw rotors of the low-pressure stage compressor body 1 and the high-pressure stage compressor body 2 are reduced, and the discharge air amount is reduced.

  That is, when the amount of air consumption decreases and the discharge air amount may be 100% to 40% of the specified discharge air amount, the control device 24 makes the pressure detection value from the pressure sensor 23 the same as the preset target pressure. As described above, the amount of discharge air is changed by changing the rotational speed of the screw rotors of the compressor main bodies 1 and 2. This region is a load operation.

  Here, when the amount of consumed air on the use side is 100% of the specified discharge air amount, the control device 24 determines that all the cooling fans 25A, 25B, and 25C are based on the pressure detection value from the pressure sensor 23. When the air consumption is reduced to 80%, the cooling fan 25C is stopped. When the air consumption is reduced to 60%, the cooling fan 25B is stopped, and further, the air consumption is 60%. In the following cases, control is performed so that only the cooling fan 25A is operated.

  As a result, when the amount of air consumed on the user side is between 100% and 40% of the specified discharge air amount, the air temperature at the outlet of the intercooler 16 has a sawtooth characteristic as shown in FIG. Accordingly, as shown in FIG. 3A, an increase in the amount of generated drain is suppressed.

  In addition, when the discharge air amount may be about 40% or less of the specified discharge air amount, the control device 24 sends an open command to the discharge air solenoid valves 30A and 30B. Specifically, if the detected pressure value of the pressure sensor 23 exceeds the upper limit pressure (upper limit pressure> target pressure) preset in the control device 24, the control device 24 performs control so as to maintain the set lower limit rotation speed. Then, the control device 24 sends an open command to the discharge valve, and performs an operation of reducing the pressure of the low-pressure stage compressor body 1 outlet air pressure and the high-pressure stage compressor body 2 outlet air pressure.

  Thus, no-load operation is performed, and the low-pressure stage compressor body 1 outlet air pressure is about 0.05 MPa, and the high-pressure stage compressor body 2 outlet air pressure is about 0.10 MPa. By performing this decompression operation, the amount of drain generation further decreases. When the no-load operation is continued, the discharge air pressure of the pressure sensor 23 decreases, so that the control device 24 closes the venting electromagnetic valves 30A and 30B when the pressure is lower than a preset pressure (target pressure). A command is issued and load operation starts. That is, when the discharge air amount is about 40% or less, the load operation and the no-load operation are repeated. The relationship between the amount of air consumed and the amount of drain generated at this time is shown in FIG. 3, but all the amount of drain generated turns negative in the entire consumed air amount region, and the generation of drain can be suppressed.

  Further, the cooling fan, the cooling air intake port, and the cooling air exhaust port are separately provided on the intercooler 16 side and the aftercooler 20 side, and the low pressure stage cooling device 31 on the intercooler 16 side and the high pressure stage cooling device 32 on the aftercooler 20 side. Are each independently partitioned. The reason for this is that the lower the outlet air temperature at the outlet of the aftercooler 20 is, the better as viewed from the utilization device side, and only the outlet temperature of the intercooler 20 is accurately controlled.

  In addition, the cooling fan operation stop operation can be controlled to operate the first operation that was stopped last time and to stop the operation that was first operated last time, or to be switched at a predetermined time. is there. Thereby, the operation of the cooling fan can be leveled.

  By the way, in this embodiment, the example which provided the three cooling fans which cool the intercooler 16 is shown. In particular, a large compressor requires a large cooling fan. However, since the cooling fan is circular, if the size of the cooling fan is increased, the arrangement is limited and the entire unit is increased in size. Therefore, the use of a small cooling fan which is used in a small compressor and has high mass productivity can reduce the size of the entire unit, and at the same time can be configured at low cost.

  According to the embodiment of the present invention, it is possible to reduce the drain amount at the outlet of the intercooler that is likely to occur at low load by varying the rotational speed of the air-cooled two-stage oilless screw compressor, and the high-pressure stage compressor body Reliability can be improved. Furthermore, it can also contribute to power reduction at low load. And the thing which reduced the temperature of the supply compressed air to the utilization apparatus side at the time of low load can be supplied.

  In this embodiment, an example in which three cooling fans (25A, 25B, 25C) for cooling the intercooler 16 are used, but two cooling fans (25A, 25B) are used. You can also. In this case, as shown in FIG. 4B, when the consumption air amount on the use side is 100% of the specified discharge air amount, the control device 24 detects the pressure detection value from the pressure sensor 23. Based on the above, when all the cooling fans 25A and 25B are operated and the amount of consumed air is reduced to 70%, the cooling fan 25B is stopped, and when the amount of consumed air is 70% or less, the cooling fan 25A is stopped. Control so that only driving.

  As a result, when the air consumption on the use side is between 100% and 60% with respect to the specified discharge air amount, the intercooler 16 outlet air temperature has a sawtooth characteristic as shown in FIG. Accordingly, as shown in FIG. 4A, an increase in the amount of drain generation is suppressed.

  It is also possible to use one cooling fan. In this case, by controlling the number of rotations of the cooling fan with the control device, it is possible to obtain the same effect as the above-described embodiment, and the drain amount of the intercooler outlet portion that is likely to occur at low load, It can be mitigated finely.

FIG. 5 shows a block diagram of a second embodiment of the oil-free screw compressor of the present invention. In FIG. 5, the same reference numerals as those in FIG. Detailed description is omitted.
In this embodiment, a temperature sensor 33 for detecting the intake air temperature of the low-pressure stage compressor body 1 is provided in the suction passage 14 upstream of the low-pressure stage compressor body 1, and the temperature from the intercooler 16 to the high-pressure stage compressor body 2 is provided. A temperature sensor 34 for detecting the air temperature at the outlet of the intercooler 16 is provided in the air pipe. The temperature detection values detected by the temperature sensors 33 and 34 are sent to the control device 24.

  Here, the temperature sensor 34 that detects the intake air temperature of the high-pressure stage compressor body 2 is provided to protect the high-pressure stage compressor body 2 when the performance of the intercooler 16 is reduced due to the influence of dust or the like. Yes. When the detected temperature value of the temperature sensor 34 becomes, for example, 70 ° C., the control device 24 stops the compressor.

  The control device 24 takes in the outlet air temperature of the intercooler 16 detected by the temperature sensor 34 and the suction temperature of the low-pressure compressor 1 detected by the temperature sensor 33, calculates this temperature difference, and calculates this temperature difference. Is a preset temperature difference (here, a value slightly lower than 15 ° C.), one cooling fan is stopped. On the contrary, when the temperature difference becomes a preset temperature difference (here, a value slightly higher than 20 ° C.), one cooling fan is operated.

  According to this embodiment, similarly to the above-described embodiment, it is possible to reduce the drain amount at the outlet portion of the intercooler that is likely to occur at low loads by changing the rotation speed of the air-cooled two-stage oilless screw compressor. And the reliability of the high-pressure compressor body can be improved. Furthermore, it can also contribute to power reduction at low load. And the thing which reduced the temperature of the supply compressed air to the utilization apparatus side at the time of low load can be supplied.

FIG. 6 shows a block diagram of a third embodiment of the rotary variable speed two-stage oilless screw compressor of the present invention. In FIG. 5, the same reference numerals as those in FIG. 1 are the same. Since it is a part, the detailed description is abbreviate | omitted.
In this embodiment, an inlet air pipe 17A and an outlet air pipe 17B of the intercooler 16 are connected by a bypass pipe 35, and two two-way solenoid valves 36A and 36B are attached to the bypass pipe 35. The control device 24 takes in the detected pressure value from the pressure sensor 23, calculates the amount of air consumption, and when the calculated amount of air consumption is less than or equal to the amount of air consumption preset in the storage unit of the control device 24, Then, an opening command is sent to the two-way solenoid valve 36A (or 36B), and when the air consumption exceeds a preset amount, control is performed so that a closing command is sent to the two-way solenoid valve 36A (or 36B). In this case, the opening / closing operation of the two-way solenoid valves 36A, 36B may be controlled in the same manner as the cooling fan operation stop control in the above-described embodiment.

  In this embodiment, by the opening operation of the two-way solenoid valve 36A (or 36B), a part of the compressed air passes through the bypass pipe 35 and bypasses the intercooler 16 and flows to the outlet side. Here, the inlet temperature of the intercooler 16 is about 160 ° C., and in order to increase the outlet temperature by 5 ° C. from 45 ° C. to 50 ° C., about 5% of the discharged air amount may be bypassed. The one-way solenoid valve 36A (or 36B) can be composed of a relatively small solenoid valve. In this case, the power reduction effect of the cooling fan cannot be obtained, but it is difficult to have a plurality of cooling fans especially in the case of a small machine, and it can be constituted by an inexpensive solenoid valve, which is an effective means for the small machine. Moreover, in this embodiment, although the example which provided two two-way solenoid valves is shown, it is also possible to provide three.

  According to this embodiment, similarly to the above-described embodiment, it is possible to reduce the drain amount at the outlet portion of the intercooler that is likely to occur at low loads by changing the rotation speed of the air-cooled two-stage oilless screw compressor. And the reliability of the high-pressure compressor body can be improved. Furthermore, it can also contribute to power reduction at low load.

It is a lineblock diagram showing a 1st embodiment of an oil-free screw compressor of the present invention. It is a characteristic view which shows the amount of air consumption and the amount of drain generation of an intercooler. It is a characteristic view which shows an example of the air consumption which concerns on this invention, and the amount of drain generation of an intercooler. It is a characteristic view which shows the other example of the air consumption which concerns on this invention, and the amount of drain generation of an intercooler. It is a block diagram which shows 2nd Embodiment of the oilless type screw compressor of this invention. It is a block diagram which shows 3rd Embodiment of the oil-free type screw compressor of this invention.

Explanation of symbols

100 Oil-free screw compressor 1 Low pressure stage compressor body 2 High pressure stage compressor body 9 Motor 10 Bull gear 11 Gear casing 12 Inverter 13 Oil pump 14 Suction air passage 15 Suction filter 16 Intercoolers 17A, 17B Low pressure stage side air piping 18 Precooler 19 Check valve 20 After cooler 21A, 21B High pressure stage side air piping 22 Drain separator 23 Pressure sensor 24 Controller 25A, 25B, 25C Intercooler side cooling fan,
30A Low pressure stage discharge solenoid valve 30B High pressure stage release solenoid valve 31 Low pressure stage side cooling device 32 High pressure stage side cooling device 33 Low pressure stage suction air temperature sensor 34 High pressure stage suction air temperature sensor 35 Bypass piping 36A, 36B Two-way solenoid valve

Claims (6)

  Oil-free screw comprising a low-pressure compressor main body and a high-pressure compressor main body with variable rotation speed, and an intercooler provided in the middle of a pipe connecting the low-pressure compressor main body and the high-pressure compressor main body. In the compressor, on the discharge side of the high-pressure stage compressor main body, a pressure sensor for detecting the pressure of high-pressure air discharged from the high-pressure stage compressor main body, at least two cooling fans for cooling the intercooler, A control device for calculating the amount of air consumption based on the detected pressure value detected by the pressure sensor, and for stopping and controlling one of the cooling fans when the amount of consumed air falls below a preset amount of consumed air; An oil-free screw compressor characterized by comprising:   2. The oil-free screw compressor according to claim 1, wherein the air outlet branch pipe and the air outlet branch pipe provided in the pipe connecting the low pressure stage compressor body and the high pressure stage compressor body are provided. The control device calculates the amount of air consumption based on the detected pressure value detected by the pressure sensor, and preset if the air consumption is less than or equal to the preset air consumption amount. An oil-free screw compressor characterized by outputting a command for a lower limit rotation speed and outputting a command to the venting solenoid valve to perform a venting decompression operation. A low-pressure compressor main body and a high-pressure compressor main body with variable rotation speed, an intercooler provided in the middle of a pipe connecting the low-pressure compressor main body and the high-pressure compressor main body, and the intercooler is cooled. In an oil-free screw compressor provided with at least two cooling fans, a temperature sensor that detects the intake air temperature of the low-pressure stage compressor body, a temperature sensor that detects the intake air temperature of the high-pressure stage compressor body, An oil-free screw compressor, comprising: a controller that calculates a temperature difference from the temperature sensor and stops one cooling fan when the temperature difference is equal to or less than a preset temperature difference.   The oilless screw compressor according to any one of claims 1 to 3, wherein the intercooler and a low-pressure stage cooling device including the cooling fan, and an aftercooler and the cooling fan are included in the high-pressure stage cooling device. These cooling devices are each divided and formed, and the rotation speed variable type air-cooled two-stage oilless screw compressor.   The oilless screw compressor according to any one of claims 1 to 4, wherein when the cooling fan is sequentially stopped, the control device stops the cooling fan from the one that was stopped first, and then the cooling fan. An oil-free screw compressor characterized in that when the fans are operated sequentially, control is performed so that the fans are operated from those other than the one that was first operated last time. Oil-free provided with a low-pressure stage compressor body and a high-pressure stage compressor body with variable rotation speed, and a plurality of intercoolers provided in the middle of a pipe connecting the low-pressure stage compressor body and the high-pressure stage compressor body In the type screw compressor, a pressure sensor for detecting a pressure of high-pressure air discharged from the high-pressure stage compressor main body , and an intercooler of the plurality of intercoolers on a discharge side of the high-pressure stage compressor main body The air consumption is calculated based on the piping that bypasses the inlet portion and the outlet portion of each, the two-way valves provided in these piping, and the detected pressure value detected by the pressure sensor. An oil-free screw compressor comprising: a control device that sequentially opens the two-way valve when air is less than or equal to a preset air consumption amount.

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