Cooling fan control method of oil cooling type compressor, and oil cooling type compressor

Abstract

To lower a cooling temperature of lubricant in an oil cooler as much as possible while preventing condensed water from being mixed into lubricant.SOLUTION: In an oil cooling type compressor 1 in which an after-cooler 32 and an oil cooler 42 are cooled by a common cooling fan 50, and a rotation speed of the cooling fan 50 is made variable, a discharge temperature Td discharged by a compressor body 10 is measured, and a rotation speed R of the cooling fan 50 is changed between a minimum rotation speed Rmin and a maximum rotation speed Rmax in correspondence with a change in the discharge temperature Td. At this time, a suction ambient temperature To of ambient air that the compressor body 10 sucks is measured, and a discharge temperature Td at the minimum rotation speed Rmin, and a discharge temperature Td at the maximum rotation speed Rmax are changed according to the measurement value of the suction ambient temperature To so as to raise the rotation speed R when the suction ambient temperature To is low.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cooling fan control method for an oil-cooled compressor and an oil-cooled compressor that executes the cooling fan control method, and more specifically, to a cooling fan control method in an oil-cooled compressor in which an air-cooled oil cooler used to cool lubricating oil and an air-cooled aftercooler that cools the compressed air supplied to the consumption side are cooled by a common cooling fan, and to an oil-cooled compressor that executes the cooling fan control method. [Background technology]

[0002] The compressor body of an oil-cooled compressor, for example a screw type, is configured to compress the air (outside air) sucked in as the gas to be compressed together with lubricating oil, so that the lubricating oil can seal, lubricate, and cool the compression space.

[0003] In an oil-cooled compressor 100 equipped with such an oil-cooled compressor body 110, the compressed air generated by the compressor body 110 is discharged as a gas-liquid mixed fluid with lubricating oil, and therefore, as shown in FIG. 6, the compressed air discharged by the compressor body 110 is introduced into a receiver tank 121 of a gas-liquid separation device 120, where gas-liquid separation of the compressed air and the lubricating oil is performed in the receiver tank 121, and the lubricating oil remaining in the compressed air after the lubricating oil has been separated is removed by passing it through an oil separator 122, and then it is configured so that it can be supplied as service air to the consumer side to which pneumatic equipment, etc. (not shown), is connected via a compressed air supply passage 130.

[0004] In addition, an oil supply passage 140 is provided between the receiver tank 121 and the compressor main body 110 for supplying the lubricating oil recovered in the receiver tank 121 by the above-mentioned gas-liquid separation to the compressor main body 110, and the lubricating oil discharged by the compressor main body 110 together with the compressed air is recovered in the receiver tank 121 and then supplied again to the compressor main body 110 for circulating use.

[0005] In the oil-cooled compressor 100 configured as above, the compressed air generated by the compressor body 110 is heated to a high temperature due to the heat of compression and contains a large amount of water vapor. Therefore, an aftercooler 132, which is an air-cooled heat exchanger, is provided in the compressed air supply passage 130 described above, so that the compressed air can be cooled before being supplied to the consumption side, and the moisture generated by condensation during this cooling is removed as drain before being supplied to the consumption side.

[0006] In addition, an oil cooler 142, which is an air-cooled heat exchanger, is provided in the oil supply passage 140 between the receiver tank 121 and the compressor main body 110, and by cooling the lubricating oil before it is supplied to the compressor main body 110, the compressor main body 110 can be cooled effectively and performance degradation and premature deterioration of the lubricating oil due to use at high temperatures can be prevented.

[0007] A common cooling fan 150 is provided for the aftercooler 132 and oil cooler 142 described above, so that the cooling air required for heat exchange in the aftercooler 132 and oil cooler 142 can be generated.

[0008] As a method of controlling the cooling fan 150 of the oil-cooled compressor 100 configured as described above, Patent Document 1, which will be described later, proposes making the rotation speed of the fan motor 151 of the cooling fan 150 controllable by an inverter 152, providing a temperature sensor 161 that detects the oil temperature in the receiver tank 121 as the discharge temperature of the compressor main body 110, and controlling the cooling fan so that the discharge temperature of the compressor main body 110 (oil temperature in the receiver tank 121) detected by the temperature sensor 161 becomes a target value by increasing the rotation speed of the fan motor 151 as the discharge temperature of the compressor main body 110 (oil temperature in the receiver tank 121) becomes higher and decreasing the rotation speed of the fan motor 151 as the discharge temperature becomes lower (Patent Document 1

[0041] ,

[0042] , [Fig. 1]). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2020-190240 A Summary of the Invention [Problem to be solved by the invention]

[0010] As described above, in the oil-cooled compressor 100 in which cooling air is introduced to both the aftercooler 132 and the oil cooler 142 by a common cooling fan 150, cooling air is introduced to both the aftercooler 132 and the oil cooler 142 in the same way, so if the rotational speed of the cooling fan 150 is increased and the air flow rate is increased in order to increase the degree of reduction in the compressed air temperature due to cooling in the aftercooler 132, the degree of reduction in the temperature of the lubricating oil cooled in the oil cooler 142 also increases.

[0011] Here, in cooling the compressed air in the aftercooler 132, the lower the temperature of the cooled compressed air, the more preferable it is in that the amount of moisture in the compressed air supplied to the consumption side can be reduced.

[0012] However, if the oil cooler 142 cools the lubricating oil excessively and the temperature of the compressed air discharged from the compressor body 110 drops below the dew point, the moisture in the compressed air will condense and become mixed into the lubricating oil recovered in the receiver tank 121.

[0013] If lubricating oil that has become contaminated with water in this way is supplied to the compressor main body 110 again and used, the lubricating oil and water will mix and emulsify due to the stirring that occurs during compression, and the lubricating oil will no longer perform as intended, which may cause the compressor main body to malfunction or break down, as well as causing the lubricating oil to deteriorate prematurely.

[0014] Therefore, it is necessary to control the rotation speed of the cooling fan 150 and the flow of the lubricating oil into the oil cooler 142 so that the cooling of the lubricating oil by the oil cooler 142 does not result in such overcooling.

[0015] In the oil-cooled compressor 100 described in the above-mentioned Patent Document 1, a configuration is adopted in which the higher the discharge temperature of the compressor main body 110, the higher the rotation speed of the fan motor 151 is set, and the lower the discharge temperature, the lower the rotation speed of the fan motor 151 is set, thereby controlling the rotation speed of the cooling fan 150 so that the discharge temperature detected by the temperature sensor 161 becomes a target value. On the other hand, when it is necessary to increase the temperature of the lubricating oil, a configuration is adopted in which the lubricating oil in the receiver tank 121 is supplied directly to the compressor main body 110 via the bypass circuit 180 without passing through the oil cooler 142 (see Patent Document 1

[0043] , Figure 1), thereby making it possible to maintain the temperature of the compressed air discharged from the compressor main body 110 at a temperature above the target value.

[0016] Therefore, in the control method of Patent Document 1, the target value for the discharge temperature of the compressor main body 110 is set to a temperature that is a necessary margin higher than the dew point temperature of the compressed air generated by the compressor main body, thereby preventing moisture in the compressed air from condensing and mixing with the lubricating oil.

[0017] However, the method described in Patent Document 1 requires the provision of a bypass circuit 180 and a temperature control valve that controls the opening and closing of the bypass circuit 180 in order to prevent the occurrence of supercooling, and the resulting increase in the number of parts increases the number of labor hours during manufacturing and increases the manufacturing costs of the oil-cooled compressor.

[0018] Possible factors that cause a change in the discharge temperature of the compressor main body 110 include a change in the temperature of the outside air sucked into the compressor main body 110 and a change in pressure on the discharge side of the compressor main body.

[0019] In other words, if the discharge side pressure of the compressor main body 110 is the same, the higher the temperature of the outside air, which is the gas to be compressed, the higher the temperature of the compressed air discharged from the compressor main body 110 will be, and the lower the temperature of the outside air, the lower the temperature of the compressed air discharged from the compressor main body 110 will be.

[0020] Furthermore, if the temperature of the outside air sucked into the compressor body 110 is the same, the higher the discharge side pressure of the compressor body 110, the higher the temperature of the compressed air due to the heat of compression, and the lower the pressure, the lower the temperature of the compressed air generated.

[0021] On the other hand, the higher the intake outside air temperature (outside air temperature), the more water vapor the intake air (outside air) may contain, and therefore the amount of water vapor contained in the compressed air generated by the compressor body also tends to increase, which can result in a higher dew point temperature of the generated compressed air.

[0022] In addition, the higher the pressure of compressed air, the higher the dew point temperature.

[0023] Therefore, in order to reliably prevent the mixing of condensed water with the lubricating oil and the resulting emulsification in a configuration in which the rotation speed of the cooling fan 150 is controlled based solely on changes in the discharge temperature of the compressor main body 110, as in the control method described in the above-mentioned Patent Document 1, it is necessary to set the target value of the discharge temperature of the compressor main body 110 based on the upper limit of the outside air temperature that can be assumed in the usage environment of the oil-cooled compressor 100, and, if the setting of the discharge side pressure of the compressor main body 110 is variable, it is necessary to set it based on the settable upper limit pressure.

[0024] However, if the target value for the discharge temperature of the compressor main body 110 is set based on the upper limit of the possible outside air temperature or the upper limit of the discharge pressure, when the outside air temperature is low or the discharge pressure of the compressor main body is low, the temperature at which moisture actually condenses will be significantly lower than the target temperature, and the target value will have an excessive margin.

[0025] As a result, when the outside air temperature is low or the discharge side pressure of the compressor body is low, even if the amount of cooling air introduced into the oil cooler 142 is increased to lower the temperature of the lubricating oil to a lower temperature, the moisture in the compressed air will not condense and emulsification of the lubricating oil can be prevented. Meanwhile, by lowering the oil temperature, the cooling efficiency of the compressor body 110 can be increased and the life of the lubricating oil can be extended.

[0026] Furthermore, in a configuration in which the aftercooler 132 is cooled together with the oil cooler 142 by a common cooling fan 150, when the outside air temperature is low or the discharge side pressure of the compressor main body 110 is low, the introduction of cooling air to the aftercooler 132 is excessively suppressed. Therefore, by increasing the amount of cooling air introduced to the aftercooler 132, the compressed air by the aftercooler 132 is cooled to a lower temperature, and compressed air with a lower moisture content can be supplied to the consumer side.

[0027] In particular, when the discharge side pressure of the compressor main body 110 is low, the volume of the compressed air increases compared to high-pressure compressed air, and the flow rate (volumetric flow rate) of the compressed air passing through the aftercooler 132 increases. Therefore, if the cooling efficiency of the aftercooler 132 is low, there is a possibility that the moisture in the compressed air will not be sufficiently removed in the aftercooler 132 and will be supplied to the consumer side.

[0028] Therefore, it is desirable to operate the cooling fan at as high a rotational speed as possible without condensing the water in the compressed air, in accordance with the operating conditions of the oil-cooled compressor (e.g., outside air temperature and the pressure of the compressed air being generated), thereby enabling the cooling temperature of the lubricating oil by the oil cooler and the cooling temperature of the compressed air by the aftercooler to be reduced as much as possible.

[0029] Therefore, the present invention has been made to eliminate the drawbacks of the above-mentioned conventional technology, and aims to provide a cooling fan control method for an oil-cooled compressor that can keep the cooling temperature of the lubricating oil in the oil cooler and the cooling temperature of the compressed air in the aftercooler as low as possible while preventing condensed water from mixing with the lubricating oil, and an oil-cooled compressor that executes the control method. [Means for solving the problem]

[0030] The means for solving the problems are described below together with the reference numerals used in the description of the embodiment of the invention. These reference numerals are described in order to clarify the correspondence between the description of the claims and the description of the embodiment of the invention, and needless to say, are not used to restrict the interpretation of the technical scope of the present invention.

[0031] In order to achieve the above object, the cooling fan control method of the oil-cooled compressor 1 of the present invention includes the following steps: A method for controlling a cooling fan 50 of an oil-cooled compressor 1 comprising: an oil-cooled compressor body 10 that compresses intake air together with lubricating oil to generate compressed air and discharges the compressed air as a gas-liquid mixed fluid with the lubricating oil; a gas-liquid separation device 20 that introduces the compressed air discharged from the compressor body 10 and separates it into gas and liquid; a compressed air supply flow path 30 that introduces the compressed air from which the lubricating oil has been separated by the gas-liquid separation device 20 to a consumption side; and an oil supply flow path 40 that introduces the lubricating oil recovered in the gas-liquid separation device 20 by the gas-liquid separation into the compressor body 10, and further comprising an aftercooler 32 provided in the compressed air supply flow path 30, an oil cooler 42 provided in the oil supply flow path 40, and a cooling fan 50 common to the aftercooler 32 and the oil cooler 42, The temperature that can prevent condensation of moisture in the compressed air is set to the low-temperature side reference temperature TLc, which is a temperature that is a minimum discharge temperature of the compressor body 10 with a necessary margin added thereto. The temperature obtained by adding a predetermined temperature to the low-temperature side reference temperature TLc is set as the high-temperature side reference temperature THc, The correspondence relationship between the change in the intake outside air temperature To of the compressor body 10 and the change in the low-temperature side reference temperature TLc is previously obtained as a first correspondence relationship (see the lower graph in FIG. 2 ). The correspondence relationship between the change in the intake outside air temperature To of the compressor body 10 and the change in the high temperature side reference temperature THc is obtained in advance as a second correspondence relationship (see the upper graph in FIG. 2), The intake outside air temperature To and the discharge temperature Td of the compressor body 10 are measured, When the measured value of the discharge temperature Td is equal to the temperature defined as the low-temperature side determination reference temperature TLc corresponding to the measured value of the intake outside air temperature To in the first correspondence relationship (Td = TLc), the cooling fan 50 is operated at the minimum rotation speed Rmin, When the measured value of the discharge temperature Td exceeds the temperature defined as the low-temperature side determination reference temperature TLc corresponding to the measured value of the intake outside air temperature To in the first correspondence relationship, but is less than the temperature defined as the high-temperature side determination reference temperature THc corresponding to the measured value of the intake outside air temperature To in the second correspondence relationship (TLc < Td < THc), the cooling fan 50 is operated at an intermediate rotation speed Rmid that is equal to or higher than the minimum rotation speed Rmin and lower than the maximum rotation speed Rmax, and When the measured value of the discharge temperature Td is equal to or higher than the temperature defined as the high-temperature side determination reference temperature THc corresponding to the measured value of the intake outside air temperature To in the second correspondence relationship (Td ≧ THc), the cooling fan 50 is operated at the maximum rotation speed Rmax (Claim 1).

[0032] It is preferable to increase the intermediate rotation speed Rmid as the measured value of the discharge temperature Td increases and to decrease the intermediate rotation speed Rmid as the measured value of the discharge temperature Td decreases (Claim 2).

[0033] When the measured value of the discharge temperature Td is less than the temperature defined as the low-temperature side determination reference temperature TLc corresponding to the measured value of the intake outside air temperature To in the first correspondence relationship (Td < TLc), it is preferable to stop the rotation of the cooling fan 50 (Claim 3).

[0034] In the first correspondence relationship and the second correspondence relationship, the first correspondence relationship and the second correspondence relationship that are applicable when the measured value of the discharge side pressure P of the compressor body 10 is a predetermined high pressure PH, the first correspondence relationship at high pressure and the second correspondence relationship at high pressure, and The first correspondence relationship and the second correspondence relationship that are applicable when the measured value of the discharge-side pressure P of the compressor body 10 is a predetermined low pressure PL, including the first correspondence relationship at low pressure and the second correspondence relationship at low pressure, measure the discharge-side pressure P of the compressor body 10, When the measured value of the discharge-side pressure P is the predetermined high pressure PH (P = PH), control the rotational speed of the cooling fan 50 based on the first correspondence relationship at high pressure and the second correspondence relationship at high pressure, When the measured value of the discharge-side pressure P is the predetermined low pressure PL (P = PL), it may be configured to control the rotational speed of the cooling fan 50 based on the first correspondence relationship at low pressure and the second correspondence relationship at low pressure (Claim 4).

[0035] In this case, the first correspondence relationship and the second correspondence relationship further include the first correspondence relationship and the second correspondence relationship that are applicable when the measured value of the discharge-side pressure P of the compressor body 10 exceeds the predetermined low pressure PL and is less than the predetermined high pressure PH (PL < P < PH), including the first correspondence relationship at intermediate times and the second correspondence relationship at intermediate times, When the measured value of the discharge-side pressure P exceeds the predetermined low pressure PL and is less than the predetermined high pressure PH (PL < P < PH), it may be configured to control the rotational speed of the cooling fan 50 based on the first correspondence relationship at intermediate times and the second correspondence relationship at intermediate times (Claim 5).

[0036] In this case, further, the low-temperature-side determination reference temperature TLc of the first correspondence relationship at intermediate times and the high-temperature-side determination reference temperature THc of the second correspondence relationship at intermediate times may be increased as the measured value of the discharge-side pressure P increases and decreased as the measured value of the discharge-side pressure P decreases (Claim 6).

[0037] In the above control method, the measurement of the discharge temperature Td can be performed in the receiver tank 21 provided in the gas-liquid separation device 20 (Claim 7), and the measurement of the discharge-side pressure P can be performed on the secondary side of the aftercooler 32 (Claim 8).

[0038] Furthermore, correction values ​​for the low-temperature side reference temperature TLc of the first correspondence relationship and the high-temperature side reference temperature THc of the second correspondence relationship with respect to the change in the intake outdoor air humidity Ho based on the change in the dew-point temperature of the compressed air that occurs in response to the change in the intake outdoor air humidity Ho of the compressor main body 10 are obtained in advance, The intake outside air humidity Ho may be measured, and the low temperature side reference temperature TLc of the first correspondence relationship and the high temperature side reference temperature THc of the second correspondence relationship may be corrected with a correction value corresponding to the measured intake outside air humidity Ho to control the rotation speed of the cooling fan 50 (claim 9).

[0039] In addition, the oil-cooled screw compressor of the present invention has the following features: An oil-cooled compressor 1 is provided with an oil-cooled compressor body 10 that compresses intake air together with lubricating oil to generate compressed air and discharges the compressed air as a gas-liquid mixed fluid with the lubricating oil, a gas-liquid separation device 20 that introduces the compressed air discharged from the compressor body 10 and performs gas-liquid separation, a compressed air supply flow path 30 that introduces the compressed air after the lubricating oil has been separated by the gas-liquid separation device 20 to the consumption side, and an oil supply flow path 40 that introduces the lubricating oil recovered in the gas-liquid separation device 20 by the gas-liquid separation to the compressor body 10, and is also provided with an aftercooler 32 provided in the compressed air supply flow path 30, an oil cooler 42 provided in the oil supply flow path 40, and a cooling fan 50 common to the aftercooler 32 and the oil cooler 42, The temperature that can prevent condensation of moisture in the compressed air is set to the low-temperature side reference temperature TLc, which is a temperature that is a minimum discharge temperature of the compressor body 10 with a necessary margin added thereto. The temperature obtained by adding a predetermined temperature to the low-temperature side reference temperature TLc is set as the high-temperature side reference temperature THc, a storage means 72 storing a first correspondence relationship which is a correspondence relationship between a change in the low-temperature side reference temperature TLc and a change in the intake outside air temperature To of the compressor body 10, and a second correspondence relationship which is a correspondence relationship between a change in the high-temperature side reference temperature THc and a change in the intake outside air temperature To of the compressor body 10; An outside air temperature detection means 62 for detecting the intake outside air temperature To of the compressor body 10; Discharge temperature detection means 61 for detecting the discharge temperature Td of the compressor body 10, Based on the intake outside air temperature To detected by the outside air temperature detection means 62, the discharge temperature Td detected by the discharge temperature detection means 61, and the first correspondence relationship and the second correspondence relationship stored in the storage means 72, a rotational speed control means 71 for controlling the rotational speed of the cooling fan 50 is provided. The rotational speed control means 71, When the detected value of the discharge temperature Td coincides with the temperature defined as the low-temperature side determination reference temperature TLc corresponding to the detected value of the intake outside air temperature To in the first correspondence relationship (Td = TLc), the cooling fan 50 is operated at the minimum rotational speed Rmin. When the detected value of the discharge temperature Td exceeds the temperature defined as the low-temperature side determination reference temperature TLc corresponding to the detected value of the intake outside air temperature To in the first correspondence relationship, but is less than the temperature defined as the high-temperature side determination reference temperature THc corresponding to the detected value of the intake outside air temperature To in the second correspondence relationship (TLc < Td < THc), the cooling fan 50 is operated at an intermediate rotational speed Rmid that is equal to or higher than the minimum rotational speed Rmin and lower than the maximum rotational speed Rmax. At the same time, When the detected value of the discharge temperature Td is equal to or higher than the temperature defined as the high-temperature side determination reference temperature THc corresponding to the detected value of the intake outside air temperature To in the second correspondence relationship (Td ≧ THc), the cooling fan 50 is operated at the maximum rotational speed Rmax (Claim 10).

[0040] The rotational speed control means 71, The intermediate rotational speed Rmid may be increased as the detected value of the discharge temperature Td increases, and decreased as the detected value of the discharge temperature Td decreases (Claim 11).

[0041] The rotational speed control means 71, When the detected value of the discharge temperature Td is lower than the low-temperature side determination reference temperature TLc corresponding to the detected value of the intake outside air temperature To in the first correspondence relationship (Td < TLc), the rotation of the cooling fan 50 may be stopped (Claim 12).

[0042] Furthermore, the first correspondence relationship and the second correspondence relationship stored in the storage means 72 are the first correspondence relationship and the second correspondence relationship that are applicable when the detected value of the discharge side pressure P of the compressor main body 10 is a predetermined high pressure PH, the first correspondence relationship at high pressure and the second correspondence relationship at high pressure, and the first correspondence relationship and the second correspondence relationship that are applicable when the detected value of the discharge side pressure P of the compressor main body 10 is a predetermined low pressure PL, the first correspondence relationship at low pressure and the second correspondence relationship at low pressure, and include pressure detection means 63 for detecting the discharge side pressure P of the compressor main body 10 is provided, the rotation speed control means 71 When the detected value of the discharge side pressure P by the pressure detection means 63 is the predetermined high pressure PH (P = PH), the rotation speed of the cooling fan 50 is controlled based on the first correspondence relationship at high pressure and the second correspondence relationship at high pressure, When the detected value of the discharge side pressure P by the pressure detection means 63 is the predetermined low pressure PL (P = PL), the rotation speed of the cooling fan 50 may be controlled based on the first correspondence relationship at low pressure and the second correspondence relationship at low pressure (Claim 13).

[0043] In this case, the first correspondence relationship and the second correspondence relationship stored in the storage means 72 further include the first correspondence relationship and the second correspondence relationship that are applicable when the detected value of the discharge side pressure P of the compressor main body 10 exceeds the predetermined low pressure PL and is less than the predetermined high pressure PH, the first correspondence relationship at intermediate pressure and the second correspondence relationship at intermediate pressure, the rotation speed control means 71 When the detected value of the discharge-side pressure P by the pressure detection means 63 exceeds the predetermined low pressure PL and is less than the predetermined high pressure PH (PL < P < PH), the rotational speed of the cooling fan 50 may be controlled based on the first intermediate correspondence relationship and the second intermediate correspondence relationship (Claim 14).

[0044] In this case, further, the rotational speed control means 71 corrects the low-temperature-side determination reference temperature TLc of the first intermediate correspondence relationship and the high-temperature-side determination reference temperature THc of the second intermediate correspondence relationship to increase as the discharge-side pressure P detected by the pressure detection means 63 increases and to decrease as the discharge-side pressure P detected by the pressure detection means 63 decreases (Claim 15).

[0045] In the oil-cooled compressor having the above configuration, a dryer 34 may be further provided in the compressed air supply passage 30 on the secondary side of the aftercooler 32 (Claim 16).

[0046] Also, the discharge temperature detection means 61 may be provided in the receiver tank 21 of the gas-liquid separation device 20 (Claim 17), and the pressure detection means 63 may be provided in the compressed air supply passage 30 on the secondary side of the aftercooler 32 (Claim 18).

[0047] Furthermore, an intake outside air humidity detection means 64 for detecting the intake outside air humidity Ho of the compressor body 10 is provided, the storage means 72 stores correction values for the low-temperature-side determination reference temperature TLc of the first correspondence relationship and the high-temperature-side determination reference temperature THc of the second correspondence relationship with respect to the change in the intake outside air humidity Ho based on the change in the dew point temperature of the compressed air that occurs corresponding to the change in the intake outside air humidity Ho, and the rotational speed control means 71 The rotation speed of the cooling fan 50 may be controlled by correcting the low temperature side reference temperature TLc of the first correspondence relationship and the high temperature side reference temperature THc of the second correspondence relationship with a correction value corresponding to the detection value of the intake outside air humidity Ho by the intake outside air humidity detection means 64 (Claim 19). Effect of the Invention

[0048] In the oil-cooled compressor 1 which implements the cooling fan control method of the present invention described above, the following remarkable effects can be obtained.

[0049] The above-mentioned first and second correspondence relationships, which are the correspondence relationships between the changes in the low-temperature side and high-temperature side reference temperatures TLc, THc and the changes in the intake outside air temperature To of the compressor body 10, are respectively obtained, and based on these correspondence relationships, the rotation speed of the cooling fan 50 is controlled to change between the minimum rotation speed Rmin, the intermediate rotation speed Rmid, and the maximum rotation speed Rmax in response to the change in the intake outside air temperature To. This makes it possible to cool the lubricating oil by the oil cooler 42 and cool the compressed air by the aftercooler 32 to the lowest possible temperature in response to the change in the outside air temperature To sucked into the compressor body 10, while preventing the condensation of moisture in the compressed air and therefore the incorporation of moisture into the lubricating oil and emulsification that occur due to such condensation of moisture.

[0050] In particular, in a configuration in which the rotation speed control means 71 changes the intermediate rotation speed Rmid applied when the discharge temperature Td is an intermediate value between the low-temperature side reference temperature TLc defined by the first correspondence relationship and the high-temperature side reference temperature THc defined by the second correspondence relationship, the intermediate rotation speed Rmid becomes higher as the measured value of the discharge temperature Td becomes higher and the intermediate rotation speed Rmid becomes lower as the measured value of the discharge temperature Td becomes lower, it becomes possible to change the rotation speed R of the cooling fan 50 in a stepwise or stepless manner in accordance with the change in the discharge temperature Td, and the cooling fan 50 can be operated at a more optimal rotation speed R that corresponds to the changes in the discharge temperature Td and the intake outside air temperature To.

[0051] When the measured value of the discharge temperature Td is lower than the low-temperature-side determination reference temperature TLc corresponding to the measured value of the intake outside air temperature To in the first correspondence relationship (Td < TLc), in the configuration in which the rotation speed control means 71 is configured to stop the cooling fan 50, it is possible to prevent the cooling of the lubricating oil from stopping before the discharge temperature Td drops to a temperature equal to or lower than the dew point temperature and the discharge temperature Td from dropping excessively to cause condensation of moisture.

[0052] In the first correspondence relationship and the second correspondence relationship stored in the storage means 72, the high-pressure-time first correspondence relationship and the high-pressure-time second correspondence relationship applied when the detected value of the discharge-side pressure P of the compressor body 10 is a predetermined high pressure PH, and the low-pressure-setting-time first correspondence relationship and the low-pressure-setting-time second correspondence relationship applied when the detected value of the discharge-side pressure P is a predetermined low set pressure PL are included. In the configuration in which the rotation speed of the cooling fan is controlled by selectively using the two correspondence relationships based on the detected value of the discharge-side pressure P detected by the pressure detection means 63, while preventing condensation of moisture in the compressed air and emulsification of the lubricating oil accompanying this, it is possible to cool the lubricating oil by the oil cooler 42 and cool the compressed air by the aftercooler 32 to as low a temperature as possible in accordance with changes in the discharge-side pressure P.

[0053] Further, in the configuration including the intermediate-time first correspondence relationship and the intermediate-time second correspondence relationship applied when the discharge-side pressure P of the compressor body 10 exceeds the predetermined low pressure PL and is less than the predetermined high pressure PH (PL < P < PH) in the first correspondence relationship and the second correspondence relationship, even when the detected value of the discharge-side pressure P of the compressor body 10 is a pressure intermediate between the predetermined high pressure PH and the predetermined low pressure PL, it is possible to operate the cooling fan 50 at an optimal rotation speed in accordance with changes in the discharge-side pressure P while preventing condensation of moisture and emulsification of the lubricating oil accompanying this.

[0054] In this case, the higher the discharge side pressure P detected by the pressure detection means 63, the higher the low temperature side reference temperature TLc of the intermediate-time first correspondence relationship and the high temperature side reference temperature THc of the intermediate-time second correspondence relationship are corrected to be increased in a stepwise or stepless manner, and the lower the discharge side pressure P detected by the pressure detection means 63, the higher the low temperature side reference temperature TLc of the intermediate-time first correspondence relationship and the high temperature side reference temperature THc of the intermediate-time second correspondence relationship are corrected to be decreased in a stepwise or stepless manner.In this configuration, the rotation speed of the cooling fan 50 can be changed in a stepwise or stepless manner in accordance with changes in the discharge side pressure P, and the cooling fan 50 can be operated at a more appropriate rotation speed in accordance with changes in the discharge side pressure P.

[0055] In a configuration in which a dryer 34 is provided in the compressed air supply passage 30 on the secondary side of the aftercooler 32, dry compressed air can be provided to the consumer side. In particular, in the configuration of the oil-cooled compressor 1 of the present invention, it is possible to increase the rotational speed of the cooling fan 50 as much as possible within a range that does not condense the moisture in the compressed air in response to changes in the intake outside air temperature To and the discharge side pressure P of the compressor main body 10. This makes it possible to lower the cooling temperature of the compressed air in the aftercooler 32 as much as possible and to lower the temperature of the compressed air introduced into the dryer 34. Therefore, the compressed air can be cooled in the dryer 34 with less energy consumption, and the temperature difference when the temperature is subsequently raised can be made larger, making it possible to provide compressed air with a high degree of dryness (low relative humidity) even when a small dryer 34 is used.

[0056] In addition, in the oil-cooled compressor 1, a temperature sensor for detecting abnormalities in the discharge temperature is usually provided in the receiver tank 21 of the gas-liquid separation device 20, and a pressure sensor for detecting the pressure of the service air to be displayed on a discharge pressure gauge provided on a monitor, etc. is provided in the compressed air supply passage 30 on the secondary side of the aftercooler 32.

[0057] Therefore, by adopting a configuration in which the discharge temperature detection means 61 is provided in the receiver tank 21 of the gas-liquid separation device 20, and a configuration in which the pressure detection means 63 is provided in the compressed air supply passage 30 on the secondary side of the aftercooler 32, it becomes possible to use the temperature sensor and pressure sensor already provided in the oil-cooled compressor 1 in combination as the discharge temperature detection means 61 and pressure detection means 63 used in the control of the present application, thereby making it possible to reduce the number of parts and, as a result, reduce the assembly labor and reduce costs.

[0058] Furthermore, in a configuration in which an intake outdoor air humidity detection means 64 is provided to detect the intake outdoor air humidity Ho of the compressor main body 10, and the rotational speed control means 71 corrects the low temperature side reference temperature TLc of the first correspondence relationship and the high temperature side reference temperature THc of the second correspondence relationship based on the intake outdoor air humidity Ho detected by the intake outdoor air humidity detection means 64, the rotational speed of the cooling fan 50 can be appropriately controlled in response to the humidity of the environment in which the oil-cooled compressor is used. [Brief description of the drawings]

[0059] [Figure 1] FIG. 1 is an explanatory diagram showing the overall configuration of an oil-cooled compressor according to the present invention. [Diagram 2] 1 is a graph of a first correspondence relationship and a second correspondence relationship. [Diagram 3] A graph of the first correspondence relationship at low pressure and the second correspondence relationship at low pressure (solid line), and a graph of the first correspondence relationship at high pressure and the second correspondence relationship at high pressure (dashed line). [Figure 4] FIG. 4 is a flow diagram of a cooling fan control method according to the present invention. [Diagram 5] FIG. 6 is a flow diagram of another cooling fan control method of the present invention. [Figure 6] FIG. 1 is an explanatory diagram showing an overall configuration of a conventional oil-cooled compressor (corresponding to FIG. 1 of Patent Document 1). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0061] [Overall configuration of oil-cooled compressor] FIG. 1 shows the overall configuration of an oil-cooled compressor 1 of the present invention.

[0062] This oil-cooled compressor 1 comprises an oil-cooled compressor main body 10 which compresses and discharges both the outside air sucked in through the suction passage 11 and the lubricating oil supplied through the oil supply port 12, which in this embodiment is an oil-cooled screw compressor main body, a gas-liquid separation device 20 which introduces compressed air discharged from the discharge port 13 of the compressor main body 10 as a gas-liquid mixed fluid with the lubricating oil, a compressed air supply passage 30 which introduces the compressed air after the lubricating oil has been separated by the gas-liquid separation device 20 to the consumption side, and an oil supply passage 40 which introduces the lubricating oil recovered in the receiver tank 21 by gas-liquid separation in the receiver tank 21 to the oil supply port 12 of the compressor main body 10.

[0063] The gas-liquid separation device 20 described above is equipped with a receiver tank 21 which introduces the compressed air discharged by the compressor main body 10 as a gas-liquid mixed fluid with lubricating oil and separates it into lubricating oil and compressed air, and an oil separator 22 which further removes the oil in the compressed air after separation in the receiver tank 21, and is configured so that the compressed air after the oil has been removed by the oil separator 22 can be supplied to the consumer side.

[0064] The aforementioned compressed air supply passage 30, which supplies the compressed air after passing through the gas-liquid separation device 20 to the consumption side, is provided with an aftercooler 32, which is an air-cooled heat exchanger for cooling the compressed air flowing within the compressed air supply passage 30.This allows the compressed air to be supplied to the consumption side after the moisture in the compressed air has been condensed and removed by cooling in the aftercooler 32.

[0065] In this embodiment, a dryer 34 is further provided in the aforementioned compressed air supply passage 30 on the secondary side of the aftercooler 32, and the compressed air after the condensed moisture in the aftercooler 32 is removed as drain is further cooled in the dryer 34 to condense and remove the moisture, and is also heated so that the relative humidity is reduced and dry compressed air can be supplied to the consumer side.

[0066] In addition, an oil cooler 42, which is an air-cooled heat exchanger, is provided in the oil supply passage 40, which introduces the lubricating oil recovered in the receiver tank 21 into the oil supply port 12 of the compressor main body 10, and is configured so that the lubricating oil passing through the oil supply passage 40 can be cooled before being introduced into the compressor main body 10.

[0067] Furthermore, the oil-cooled compressor 1 is provided with a motor-driven cooling fan 50 for blowing cooling air to the aftercooler 32 and the oil cooler 42 described above.

[0068] The fan motor 51 of this cooling fan 50 is connected to an inverter device 52, which enables the rotational speed of the fan motor 51, and therefore the rotational speed of the cooling fan 50, to be controlled so as to vary the amount of cooling air blown to the aftercooler 32 and the oil cooler 42.

[0069] The oil-cooled compressor 1 of the present invention is further provided with a discharge temperature detection means 61 for detecting the discharge temperature Td of the compressor body 10.

[0070] This discharge temperature detection means 61 may be located anywhere on the discharge side of the compressor main body 10 as long as it is capable of detecting the discharge temperature Td of the compressor main body 10, but in the illustrated embodiment, as an example, the discharge temperature detection means 61 is a temperature sensor that detects the temperature of the compressed air in the receiver tank 21.

[0071] In the illustrated embodiment, the temperature of the compressed air in the receiver tank 21 is detected as the discharge temperature Td, but instead of this configuration, the temperature of the lubricating oil recovered in the receiver tank 21 may be detected as the discharge temperature Td.

[0072] The oil-cooled compressor 1 of the present invention also includes an outside air temperature detection means 62 for detecting the temperature of the outside air sucked into the compressor body 10 (outside air intake temperature).

[0073] In the illustrated embodiment, the outside air temperature detection means 62 is a temperature sensor that detects the temperature on the secondary side of an air filter provided in the intake passage 11 of the compressor main body 10, but the location of the outside air temperature detection means 62 is not limited to the location shown in the figure as long as it is capable of detecting the temperature of the outside air that the compressor main body 10 intakes as the compressed gas.

[0074] In the case where the oil-cooled compressor 1 of the present invention is one in which the pressure setting of the compressed air (service air) supplied to the consumption side is variable, for example, and the discharge side pressure P of the compressor main body 10 changes between a predetermined high pressure PH and a predetermined low pressure PL, a pressure detection means 63 for detecting the secondary side pressure P of the compressor main body 10 is further provided.

[0075] In the illustrated embodiment, the pressure sensor that detects the pressure in the compressed air supply passage 30 on the secondary side of the aftercooler 32 is the aforementioned pressure detection means 63, but the pressure detection means 63 may be provided at any position on the discharge side of the compressor main body 10 as long as it is capable of measuring the secondary side pressure P of the compressor main body 10, and is not limited to the placement position shown in the figure.

[0076] The oil-cooled compressor 1 of the present invention may further be provided with an outside air humidity detection means 64 for detecting the humidity (intake outside air humidity) Ho of the outside air inhaled by the compressor main body 10 as the compressed gas, and in the illustrated embodiment, this outside air humidity detection means 64 is provided in the intake passage 11 of the compressor main body 10 together with the above-mentioned outside air temperature detection means 62.

[0077] In addition, the symbol 70 in Figure 1 is a control device consisting of an electronic control device such as a microcontroller, and the control device 70 receives the discharge temperature Td, the intake outdoor air temperature To, the secondary side pressure P of the compressor main body 10, and the intake outdoor air humidity Ho detected by the aforementioned discharge temperature detection means 61, the outdoor air temperature detection means 62, the pressure detection means 63, and the outdoor air humidity detection means 64, and outputs a control signal to the inverter device 52 based on the received information in accordance with a predetermined correspondence stored in advance in a memory means 72 provided in the control device 70, to control the rotation speed of the fan motor 51.

[0078] Therefore, a rotation speed control means 71 for controlling the rotation speed of the cooling fan 50 is realized by this control device 70 .

[0079] [Storage means] The storage means 72 provided in the control device 70 described above stores the following correspondence relationships required for controlling the rotation speed of the cooling fan 50 by the method of the present invention.

[0080] (1) First and second correspondence relationships The lower graph in FIG. 2 defines the correspondence relationship (first correspondence relationship) of how the low temperature reference temperature TLc changes with respect to the change in the intake outside air temperature To.

[0081] This low temperature side reference temperature TLc is set as a temperature that is a necessary margin above the minimum discharge temperature of the compressor body 10 that can prevent condensation of moisture in the compressed air.

[0082] In addition, the temperature margin added to the minimum discharge temperature of the compressor main body 10 at which condensation of moisture in the compressed air can be prevented does not always have to be a constant value. In the example shown in Figures 2 and 3, the minimum discharge temperature at which condensation can be prevented changes as the intake outdoor air temperature To changes when the intake outdoor air temperature To is in the range below To1 and when it is above To3, but the aforementioned margin is set so that the low temperature side judgment reference temperature TLc is a constant value in this range.

[0083] On the other hand, the upper graph in FIG. 2 specifies the correspondence relationship (second correspondence relationship) of how the high temperature side reference temperature THc changes with respect to the change in the intake outside air temperature To.

[0084] This higher temperature reference temperature THc is set as a temperature obtained by adding a predetermined temperature to the lower temperature reference temperature TLc.

[0085] In addition, the discharge temperature Td of the compressor main body 10 is configured to issue an alarm / warning when it becomes an abnormal temperature (high temperature), and it is desirable to set the ``predetermined temperature'' that is ``added'' to the high temperature side reference temperature THc relative to the low temperature side reference temperature TLc so that the discharge side temperature of the compressor main body 10 does not reach such an abnormal temperature (high temperature).

[0086] In the embodiment shown in FIG. 2, the high-side reference temperature THc is a constant value added to the low-side reference temperature TLc as a "predetermined temperature", and the interval between the graphs of the low-side reference temperature TLc and the high-side reference temperature THc is always constant; however, for example, from the standpoint of reducing power consumption, suppressing wind noise caused by the cooling fan 50 rotating at high speed, and achieving the lowest possible oil temperature, the temperature added to the low-side reference temperature TLc may be increased as the intake outside air temperature To or the discharge temperature Td increases, or decreased as the intake outside air temperature To or the discharge temperature Td decreases, etc., and a value that is changed may be added as the aforementioned "predetermined temperature", and the interval between the graphs of the low-side reference temperature TLc and the high-side reference temperature THc may be changed (see FIG. 3).

[0087] From the first and second correspondence relationships defined as above, it can be seen that when the intersection of the measured intake outside air temperature To and the measured discharge temperature Td overlaps with the line indicating the first correspondence relationship (the lower line in Figure 2), it is necessary to slow down the rotation speed R of the cooling fan 50 to the minimum rotation speed Rmin in order to prevent condensation of moisture in the compressed air.

[0088] On the other hand, when the intersection of the measured intake outside air temperature To and the measured discharge temperature Td overlaps with the line indicating the second correspondence relationship (the upper line in Figure 2), or is above that position on the paper in Figure 2, it can be seen that condensation of moisture in the compressed air can be prevented even when the rotation speed R of the cooling fan 50 is increased to the maximum rotation speed Rmax and operated.

[0089] Furthermore, when the intersection point of the measured value of the intake outside air temperature To and the measured value of the discharge temperature Td is between the line indicating the second correspondence relationship (the upper line in FIG. 2) and the line indicating the first correspondence relationship (the lower line in FIG. 2) (TLc < Td < THc), the rotation speed R of the cooling fan 50 is operated at an intermediate rotation speed Rmid that is equal to or higher than the minimum rotation speed Rmin and lower than the maximum rotation speed Rmax.

[0090] If the measured value of the intake outside air temperature To is the same, this intermediate rotation speed Rmid can be changed closer to the maximum rotation speed Rmax and faster as the measured value of the discharge temperature Td increases, and closer to the minimum rotation speed Rmin and slower as the measured value of the discharge temperature Td decreases. Such a change in the intermediate rotation speed Rmid may be performed stepwise for each predetermined change width of the discharge temperature Td, or may be performed steplessly in proportion to the change in the discharge temperature Td. If necessary, the storage means stores the correspondence relationship between such a change in the intermediate rotation speed Rmid and the change in the discharge temperature Td.

[0091] By obtaining such first and second correspondence relationships in advance, it is possible to easily determine how to change the discharge temperature Td to which the maximum rotation speed Rmax and the minimum rotation speed Rmin are applied in response to a change in the intake outside air temperature To.

[0092] As an example, in the embodiment shown in FIG. 2, when the intake outside air temperature To is To3, the range of the discharge temperature Td3 to Td5 corresponds to the range equal to or higher than the minimum rotation speed Rmin and lower than the maximum rotation speed Rmax of the cooling fan 50.

[0093] On the other hand, when the intake outside air temperature To drops to To1, the range of discharge temperatures Td1 to Td3 corresponds to a range in which the rotation speed of the cooling fan 50 is above Rmin and below Rmax, and the rotation speed R of the cooling fan 50 applied at the same discharge temperature Td increases compared to when the intake air temperature To is To3 (as an example, at the intake outside air temperature To3, the rotation speed R at the discharge temperature Td3 is the minimum rotation speed Rmin, but at the intake outside air temperature To1, the rotation speed R at the same discharge temperature Td3 can be increased to the maximum rotation speed Rmax).

[0094] (2) First and second correspondence relationships taking into account changes in discharge air pressure The first and second correspondence relationships described with reference to Figure 2 specify correspondence relationships that do not take into account changes in the discharge side pressure P of the compressor main body 10. However, when the discharge side pressure P of the compressor main body 10 changes, such as when the pressure of the service air supplied by the oil-cooled compressor 1 can be changed, the dew point temperature of the compressed air increases as the discharge side pressure P increases, and the dew point temperature of the compressed air decreases as the discharge side pressure P decreases.

[0095] Therefore, when the discharge side pressure P of the compressor main body 10 is low, it is possible to prevent moisture in the compressed air from condensing and mixing with the lubricating oil, even if the rotation speed of the cooling fan 50 is increased, compared to when the discharge side pressure P is high.

[0096] Based on the change in dew point temperature accompanying the change in discharge side pressure P, a correspondence relationship is defined that further includes a correspondence relationship with the discharge side pressure P in addition to the first and second correspondence relationships described with reference to Figure 2, as shown in Figure 3.

[0097] In Figure 3, in addition to the first and second correspondence relationships mentioned above, a first and second correspondence relationship at high pressure (graph with dashed lines in Figure 3) is defined as the first and second correspondence relationship which applies when the detected value of the discharge side pressure P of the compressor main body 10 is a predetermined high pressure PH, and a first and second correspondence relationship at low pressure (graph with solid lines in Figure 3) is defined as the first and second correspondence relationship which applies when the detected value of the discharge side pressure P of the compressor main body 10 is a predetermined low pressure PL.

[0098] In this manner, in a configuration of an oil-cooled compressor in which the pressure of the service air supplied to the consumer side can be switched between a high pressure setting of 0.9 MPa and a low pressure setting of 0.5 MPa by respectively setting the first and second correspondence relationships at high pressure that are suitable when the detected discharge side pressure P is a predetermined high pressure, and the first and second correspondence relationships at low pressure that are suitable when the detected discharge side pressure P is a predetermined low pressure, when the detected value of the discharge side pressure P of the compressor main body 10 is a predetermined high pressure PH corresponding to the supply pressure of the service air of 0.9 MPa, the first and second correspondence relationships at high pressure (the dashed line graph in FIG. 3) are used to control the cooling fan 50 3. Meanwhile, when the detected value of the discharge side pressure P of the compressor main body 10 is a predetermined low pressure PL corresponding to the service air supply pressure of 0.5 MPa, the rotation speed of the cooling fan 50 is controlled using a graph of the first and second correspondence relationships at low pressure (solid line graph in FIG. 3) obtained by shifting the graph of the first and second correspondence relationships at high pressure (dashed line graph in FIG. 3) downward on the page of FIG. 3, thereby making it possible to increase the rotation speed of the cooling fan as the discharge side pressure P decreases while preventing condensation of moisture in the compressed air, and therefore the mixing of moisture into the lubricating oil and the resulting emulsification.

[0099] In addition, in controlling the rotation speed of the cooling fan 50 taking into consideration the discharge side pressure P of the compressor main body 10, for example, in a configuration in which the pressure of the service air supplied by the oil-cooled compressor 1 can be set alternatively to either a high pressure setting (0.9 MPa as an example) or a low pressure setting (0.5 MPa as an example), the rotation speed of the cooling fan can be controlled by alternatively selecting between the first and second correspondence relationships at high pressure (dashed line graph in Figure 3) and the first and second correspondence relationships at low pressure (solid line graph in Figure 3) depending on the discharge pressure P detected corresponding to the selected setting.

[0100] On the other hand, in a configuration of the oil-cooled compressor 1 that allows for an intermediate setting (0.7 MPa as an example) in addition to a high pressure setting (0.9 MPa as an example) and a low pressure setting (0.5 MPa as an example), although not shown in the figure, the first correspondence relationship and the second correspondence relationship further include an intermediate-time first / second correspondence relationship, which is the first correspondence relationship and the second correspondence relationship that are applicable when the detected value of the discharge side pressure P of the compressor main body 10 is a pressure corresponding to the intermediate pressure, and when the discharge side pressure P detected by the discharge air pressure detection means 63 is an intermediate pressure that exceeds a predetermined low pressure PL and is less than the predetermined high pressure PH, the rotation speed of the cooling fan can be controlled based on this intermediate-time first / second correspondence relationship.

[0101] Furthermore, in a configuration of the oil-cooled compressor 1 in which the set pressure of the service air can be changed, for example, in a stepwise or stepless manner between a high pressure setting (0.9 MPa as an example) and a low pressure setting (0.5 MPa as an example), a plurality of patterns of the first and second intermediate-time correspondence relationships may be provided and stored in the memory means 72, or a correction value for correcting the low temperature side reference temperature TLc of the first intermediate-time correspondence relationship and the high temperature side reference temperature THc of the second intermediate-time correspondence relationship in accordance with changes in the discharge side pressure P may be stored in the memory means 72.

[0102] By configuring in this manner, the low temperature side judgment reference temperature TLc and the high temperature side judgment reference temperature THc of the intermediate-time first / second correspondence relationship can be corrected so as to be increased as the detected value of the discharge side pressure P becomes higher, and decreased as the detected value of the discharge side pressure P becomes lower.

[0103] (3) Relationship between the first and second correspondence relationships and the intake outdoor air humidity It should be noted that the above-mentioned first and second correspondence relationships (first and second correspondence relationship at high pressure, first and second correspondence relationship at low pressure) explained with reference to Figures 2 and 3 are set on the assumption that the humidity of the outside air (intake outside air humidity) Ho sucked into the compressor main body 10 is a constant value (for example, relative humidity 80%). However, in a configuration in which the oil-cooled compressor 1 is provided with intake outside air humidity detection means 64 for detecting the intake outside air humidity of the compressor main body 10 as described above, the rotation speed of the cooling fan may also be controlled based on the first and second correspondence relationships corrected based on the intake outside air humidity Ho detected by the intake outside air humidity detection means 64.

[0104] In this case, a correction value (correction formula) for correcting the low-temperature side reference temperature TLc of the first correspondence relationship (first correspondence relationship at high pressure, first correspondence relationship at low pressure) and the high-temperature side reference temperature THc of the second correspondence relationship (second correspondence relationship at high pressure, second correspondence relationship at low pressure) in response to changes in the intake outside air humidity Ho is pre-stored in the memory means 72.

[0105] [Operation of the rotation speed control means 71] In the oil-cooled compressor 1 of the present invention described above, the rotation speed of the cooling fan 50 is controlled by the rotation speed control means 71 in the following manner.

[0106] (1) Rotation speed control based on intake outside air temperature To and discharge temperature Td The operation of the rotation speed control means 71 in a control example based on the intake outside air temperature To and the discharge temperature Td (a control example using the first and second correspondence relationships shown in FIG. 2) will be described with reference to FIG.

[0107] When the oil-cooled compressor 1 starts up and the compressor main body 10 begins to generate compressed air, the discharge temperature detection means 61 provided in the receiver tank 21 detects the temperature of the compressed air in the receiver tank 21 as the discharge temperature Td, and the detection signal is received by the rotational speed control means 71 (step 1).

[0108] In addition, the outside air temperature detection means 62 provided in the intake passage 11 of the compressor body 10 detects the intake outside air temperature To sucked in by the compressor body 10, and the detection signal is received by the rotation speed control means 71 (step 1).

[0109] Furthermore, if the oil-cooled compressor 1 is equipped with an outside air humidity detection means 64 that detects the humidity of the outside air sucked in by the compressor main body 10, the intake outside air humidity To detected by the outside air humidity detection means 64 is received by the rotational speed control means 71 (step 1).

[0110] The rotation speed control means 71 receives detection signals from the discharge temperature detection means 61 and the outside air temperature detection means 62, and determines the low temperature side reference temperature TLc and the high temperature side reference temperature THc corresponding to the intake outside air temperature To detected by the outside air temperature detection means 62 based on the first and second correspondence relationships (see Figure 2) stored in the memory means 72 (step 2).

[0111] At this time, if the oil-cooled compressor 1 is provided with the aforementioned outside air humidity detection means 64, the rotation speed control means 71 calculates a correction value from the detected outside air humidity To based on the correspondence between the change in the intake outside air humidity To stored in the memory means 72 and the change in the correction value for the low-temperature side reference temperature TLc and the high-temperature side reference temperature THc, and makes the necessary corrections to the low-temperature side reference temperature TLc and the high-temperature side reference temperature THc using the calculated correction value (step 3).

[0112] Then, if the discharge temperature Td detected by the discharge temperature detection means 61 is equal to or higher than the high temperature side judgment reference temperature (Td≧THc) (yes in step 4), the rotation speed control means 71 outputs a command signal to the inverter device 52 to instruct it to output a frequency that rotates the fan motor 51 at the maximum rotation speed Rmax (step 5).

[0113] Also, when the discharge temperature Td detected by the discharge temperature detection means 61 is the low-temperature side determination reference temperature TLc (Td = TLc) (yes in step 6), the rotation speed control means 71 outputs a command signal for commanding the inverter device 52 to output a frequency for rotating the fan motor 51 at the minimum rotation speed Rmin (step 7).

[0114] Furthermore, when the discharge temperature Td detected by the discharge temperature detection means 61 is less than the low-temperature side determination reference temperature TLc (Td < TLc) (yes in step 8), the rotation speed control means 71 outputs a command signal for stopping the fan motor 51 to the inverter device 52 (step 9).

[0115] Furthermore, when the discharge temperature Td detected by the discharge temperature detection means 61 exceeds the low-temperature side determination reference temperature TLc but is less than the high-temperature side determination reference temperature THc (TLc < Td < THc) (yes in step 10), the rotation speed control means 71 outputs to the inverter device 52 a command signal for commanding the fan motor 51 to rotate at an intermediate rotation speed Rmid that is equal to or higher than the minimum rotation speed Rmin and lower than the maximum rotation speed Rmax. As an example, the fan motor 51 is rotated at the intermediate rotation speed Rmid that changes in proportion to the change in the discharge temperature Td detected by the discharge temperature detection means 61 (step 11).

[0116] And the rotation speed control means 71 repeats the above-described operation until the oil-cooled compressor 1 stops, based on the detection signals continuously received from the discharge temperature detection means 61, the outside air temperature detection means 62, and, when provided, the outside air humidity detection means 64.

[0117] (2) Control Considering Discharge Air Pressure The oil-cooled compressor 1 further includes a pressure detection means 63 for detecting the discharge-side pressure P of the compressor body 10. The storage means 72 stores, as the first and second correspondence relationships, a high-pressure first and second correspondence relationship (the broken-line graph in FIG. 3) that is applicable when the detected value of the discharge pressure P of the compressor body 10 is a predetermined high pressure PH, a low-pressure first and second correspondence relationship (the solid-line graph in FIG. 3) that is applicable when the pressure is a predetermined low pressure PL, and an intermediate first and second correspondence relationship (not shown) that is applicable when the pressure is an intermediate pressure between the predetermined high pressure PH and the predetermined low pressure PL. When this is the case, before performing the rotational speed control described with reference to FIG. 4, the rotational speed control means 71 further executes the process described with reference to FIG. 5 below.

[0118] When the generation of compressed air is started by starting the oil-cooled compressor 1, the pressure detection means 63 detects the pressure of the compressed air in the compressed air supply passage 30 as the discharge-side pressure P of the compressor body 10, and the rotation speed control means 71 receives this detection signal (step0-1).

[0119] The rotation speed control means 71 that has received the discharge-side pressure P detected by the pressure detection means 63 compares the discharge-side pressure P with the predetermined low pressure PL and the predetermined high pressure PH, and determines whether the detected value of the discharge-side pressure P matches the predetermined high pressure PH (P = PH), matches the predetermined low pressure PL (P = PL), or is in the range (PL < P < PH) exceeding the predetermined low pressure PL and less than the predetermined high pressure PH (step0-2).

[0120] As a result of the determination, when the discharge-side pressure P detected by the pressure detection means 63 matches the predetermined high pressure PH (P = PH), the rotation speed control means 71 starts the rotation speed control of the cooling fan 50 using the high-pressure first and second correspondence relationship (the broken-line graph in FIG. 3) among the correspondence relationships stored in the storage means 72 as the first and second correspondence relationships (step0-3), and thereafter, the same process as described with reference to FIG. 4 is performed.

[0121] Further, when the rotation speed control means 71 determines that the discharge-side pressure P detected by the pressure detection means 63 matches a predetermined low pressure PL (P = PL), the rotation speed control of the cooling fan 50 is started using the low-pressure first and second correspondence relationships (the graphs shown by solid lines in FIG. 3) among the correspondence relationships stored in the storage means 72 as the first and second correspondence relationships (step 0-4). Thereafter, the same processing as described with reference to FIG. 4 is performed.

[0122] Furthermore, when the rotation speed control means 71 determines that the discharge-side pressure P detected by the pressure detection means 63 exceeds a predetermined low pressure PL but is less than a predetermined high pressure PH (PL < P < PH), the rotation speed control of the cooling fan is started using the intermediate first and second correspondence relationships among the correspondence relationships stored in the storage means 72 as the first and second correspondence relationships (step 0-5). Thereafter, the same processing as described with reference to FIG. 4 is performed.

[0123] At this time, when the storage means 72 stores a plurality of intermediate first and second correspondence relationships set for each predetermined numerical range of the discharge-side pressure P, the rotation speed control means 71 selects and uses the intermediate first and second correspondence relationship corresponding to the discharge-side pressure P detected by the pressure detection means 63 from among the plurality of intermediate first and second correspondence relationships.

[0124] Also, when the storage means 72 stores the correspondence relationship between the correction values of the high-temperature-side determination reference temperature THc and the low-temperature-side determination reference temperature TLc of the intermediate first and second correspondence relationships with respect to the change in the discharge-side pressure P, the rotation speed control is performed by correcting the high-temperature-side determination reference temperature THc and the low-temperature-side determination reference temperature TLc of the intermediate first and second correspondence relationships based on the discharge-side pressure P detected by the pressure detection means 63.

[0125] When the pressure detection means 63, the discharge temperature detection means 61, the outside air temperature detection means 62, and the outside air humidity detection means 64 are provided, the rotation speed control means 71 further repeats the above-described operation based on the detection signal continuously received from the outside air humidity detection means 64 until the oil-cooled compressor 1 stops.

Explanation of Reference Numerals

[0126] 1 Oil-cooled compressor 10 Compressor body 11 Suction channel 12 Fuel filler 13 Outlet 20 Gas-liquid separation equipment 21 Receiver tank 22 Oil separator 30 Compressed air supply passage 32 Aftercooler 34 Dryer 40 Oil supply passage 42 Oil cooler 50 Cooling Fan 51 Fan motor 52 Inverter device 61 Discharge temperature detection means (temperature sensor) 62 Outside air temperature detection means (temperature sensor) 63 Pressure detection means (pressure sensor) 64 Outside air humidity detection means (humidity sensor) 70 Control device 71 Rotational speed control means 72 Memory means 100 Oil-cooled compressor 110 Compressor body 120 Gas-liquid separation equipment 121 Receiver Tank 122 Oil separator 130 Compressed air supply passage 132 Aftercooler 140 Oil supply passage 142 Oil cooler 150 Cooling Fan 151 Fan motor 152 Inverter 161 Temperature Sensor 180 Bypass Circuit Td discharge temperature To Intake outside air temperature P (Compressor body) discharge pressure PH High Pressure Setting PL Low pressure setting Ho Intake outside air humidity R Rotational speed (of the cooling fan) Rmax Maximum rotational speed Rmin Minimum rotation speed Rmid Mid rotation speed TLc Low temperature side judgment reference temperature THc High temperature side judgment reference temperature

Claims

1. A method for controlling a cooling fan of an oil-cooled compressor comprising: an oil-cooled compressor main body that compresses intake air together with lubricating oil to generate compressed air and discharges the compressed air as a gas-liquid mixed fluid with the lubricating oil; a gas-liquid separation device that introduces the compressed air discharged from the compressor main body and performs gas-liquid separation; a compressed air supply flow path that introduces the compressed air from which the lubricating oil has been separated by the gas-liquid separation device to a consumption side; and an oil supply flow path that introduces the lubricating oil recovered in the gas-liquid separation device by the gas-liquid separation to the compressor main body, and further comprising an aftercooler provided in the compressed air supply flow path, an oil cooler provided in the oil supply flow path, and a cooling fan common to the aftercooler and the oil cooler, A temperature that can prevent condensation of moisture in the compressed air and is obtained by adding a necessary margin to the minimum discharge temperature of the compressor body is set as a low-temperature side reference temperature, A temperature obtained by adding a predetermined temperature to the low-temperature side reference temperature is set as a high-temperature side reference temperature, A correspondence relationship between a change in the low-temperature side reference temperature and a change in the intake outside air temperature of the compressor body is previously obtained as a first correspondence relationship, A correspondence relationship between a change in the high temperature side reference temperature and a change in the intake outside air temperature of the compressor body is obtained in advance as a second correspondence relationship, Measure the intake air temperature and discharge air temperature of the compressor body, When the measured value of the discharge temperature coincides with a temperature defined as the low-temperature side reference temperature corresponding to the measured value of the intake outside air temperature in the first correspondence relationship, the cooling fan is operated at a minimum rotation speed; When the measured value of the discharge temperature exceeds a temperature defined as the low-temperature side reference temperature corresponding to the measured value of the intake outside air temperature in the first correspondence relationship, but is less than a temperature defined as the high-temperature side reference temperature corresponding to the measured value of the intake outside air temperature in the second correspondence relationship, operating the cooling fan at an intermediate rotation speed that is equal to or greater than the minimum rotation speed and less than the maximum rotation speed, a cooling fan control method for an oil-cooled compressor, characterized in that when the measured value of the discharge temperature is equal to or higher than a temperature defined as the high-temperature side reference temperature corresponding to the measured value of the intake outside air temperature in the second correspondence relationship, the cooling fan is operated at the maximum rotation speed.

2. 2. The method for controlling a cooling fan of an oil-cooled compressor according to claim 1, wherein the intermediate rotation speed is increased as the measured value of the discharge temperature increases and is decreased as the measured value of the discharge temperature decreases.

3. 3. The cooling fan control method for an oil-cooled compressor according to claim 1, wherein when the measured discharge temperature is lower than the low-temperature side reference temperature corresponding to the measured intake outside air temperature in the first correspondence relationship, rotation of the cooling fan is stopped.

4. The first correspondence relationship and the second correspondence relationship are a high-pressure first correspondence relationship and a high-pressure second correspondence relationship, which are the first correspondence relationship and the second correspondence relationship that are adapted when a measured value of a discharge side pressure of the compressor body is a predetermined high pressure; a low-pressure first correspondence relationship and a low-pressure second correspondence relationship, which are the first correspondence relationship and the second correspondence relationship that are adapted when a measured value of the discharge side pressure of the compressor body is a predetermined low pressure, Measure the discharge side pressure of the compressor body, when the measured value of the discharge side pressure is the predetermined high pressure, controlling a rotation speed of the cooling fan based on the first correspondence relationship under high pressure and the second correspondence relationship under high pressure; 2. The method for controlling a cooling fan of an oil-cooled compressor according to claim 1, wherein, when the measured value of the discharge side pressure is the predetermined low pressure, the rotation speed of the cooling fan is controlled based on the first correspondence relationship at low pressure and the second correspondence relationship at low pressure.

5. The first correspondence relationship and the second correspondence relationship further include an intermediate-time first correspondence relationship and an intermediate-time second correspondence relationship, which are the first correspondence relationship and the second correspondence relationship that are adapted when the measured value of the discharge side pressure of the compressor body exceeds the predetermined low pressure and is lower than the predetermined high pressure, 5. The cooling fan control method for an oil-cooled compressor according to claim 4, wherein when the measured value of the discharge side pressure exceeds the predetermined low pressure and is less than the predetermined high pressure, the rotation speed of the cooling fan is controlled based on the intermediate-time first correspondence relationship and the intermediate-time second correspondence relationship.

6. 6. The cooling fan control method for an oil-cooled compressor according to claim 5, wherein the low-temperature side reference temperature of the intermediate-time first correspondence relationship and the high-temperature side reference temperature of the intermediate-time second correspondence relationship are increased as the measured value of the discharge side pressure becomes higher, and are decreased as the measured value of the discharge side pressure becomes lower.

7. 3. The method for controlling a cooling fan of an oil-cooled compressor according to claim 1, wherein the discharge temperature is measured in a receiver tank of the gas-liquid separator.

8. 7. The method for controlling a cooling fan of an oil-cooled compressor according to claim 4, wherein the discharge side pressure is measured on the secondary side of the aftercooler.

9. a correction value for the low-temperature side reference temperature of the first correspondence relationship and a correction value for the high-temperature side reference temperature of the second correspondence relationship with respect to the change in the intake outdoor air humidity are calculated in advance based on a change in a dew-point temperature of the compressed air that occurs in response to a change in the intake outdoor air humidity of the compressor body; 7. A method for controlling a cooling fan of an oil-cooled compressor according to claim 1, 2, 4, 5, or 6, characterized in that the intake outdoor air humidity is measured, and the low-temperature side reference temperature of the first correspondence relationship and the high-temperature side reference temperature of the second correspondence relationship are corrected with a correction value corresponding to the measured intake outdoor air humidity, thereby controlling the rotation speed of the cooling fan.

10. An oil-cooled compressor comprising: an oil-cooled compressor body which compresses intake air together with lubricating oil to produce compressed air and discharges the compressed air as a gas-liquid mixed fluid with the lubricating oil; a gas-liquid separation device which introduces the compressed air discharged from the compressor body and performs gas-liquid separation; a compressed air supply flow path which introduces the compressed air from which the lubricating oil has been separated by the gas-liquid separation device to a consumption side; and an oil supply flow path which introduces the lubricating oil recovered in the gas-liquid separation device by the gas-liquid separation to the compressor body, and which is also equipped with an aftercooler provided in the compressed air supply flow path, an oil cooler provided in the oil supply flow path, and a cooling fan common to the aftercooler and the oil cooler, A temperature that can prevent condensation of moisture in the compressed air and is obtained by adding a necessary margin to the minimum discharge temperature of the compressor body is set as a low-temperature side reference temperature, A temperature obtained by adding a predetermined temperature to the low-temperature side reference temperature is set as a high-temperature side reference temperature, a storage means for storing a first correspondence relationship which is a correspondence relationship between a change in the low-temperature side reference temperature and a change in the intake outside air temperature of the compressor body, and a second correspondence relationship which is a correspondence relationship between a change in the high-temperature side reference temperature and a change in the intake outside air temperature of the compressor body; an outside air temperature detection means for detecting the temperature of the intake outside air of the compressor body; A discharge temperature detection means for detecting the discharge temperature of the compressor body; a rotation speed control means for controlling a rotation speed of the cooling fan based on the intake outside air temperature detected by the outside air temperature detection means, the discharge temperature detected by the discharge temperature detection means, and the first correspondence relationship and the second correspondence relationship stored in the storage means, The rotation speed control means operating the cooling fan at a minimum rotation speed when the detected value of the discharge temperature coincides with a temperature defined as the low-temperature side reference temperature corresponding to the detected value of the intake outside air temperature in the first correspondence relationship; When the detected value of the discharge temperature exceeds a temperature defined as the low-temperature side reference temperature corresponding to the detected value of the intake outside air temperature in the first correspondence relationship, but is less than a temperature defined as the high-temperature side reference temperature corresponding to the detected value of the intake outside air temperature in the second correspondence relationship, the cooling fan is operated at an intermediate rotation speed that is equal to or greater than the minimum rotation speed and less than the maximum rotation speed, and operating the cooling fan at the maximum rotation speed when the detected value of the discharge temperature is equal to or higher than a temperature defined as the high-temperature side reference temperature corresponding to the detected value of the intake outside air temperature in the second correspondence relationship.

11. The rotation speed control means 11. The oil-cooled compressor according to claim 10, wherein the intermediate rotation speed is increased as the detected value of the discharge temperature increases and is decreased as the detected value of the discharge temperature decreases.

12. The rotation speed control means 12. The oil-cooled compressor according to claim 10, wherein the rotation of the cooling fan is stopped when the detected value of the discharge temperature is lower than the low-temperature side reference temperature that corresponds to the detected value of the intake outside air temperature in the first correspondence relationship.

13. The first correspondence relationship and the second correspondence relationship stored in the storage means are a high-pressure first correspondence relationship and a high-pressure second correspondence relationship, which are the first correspondence relationship and the second correspondence relationship that are adapted when a detection value of the discharge side pressure of the compressor main body is a predetermined high pressure; a low-pressure first correspondence relationship and a low-pressure second correspondence relationship, which are the first correspondence relationship and the second correspondence relationship that are adapted when a detection value of the discharge side pressure of the compressor main body is a predetermined low pressure, a pressure detection means for detecting the discharge side pressure of the compressor body, The rotation speed control means when a detection value of the discharge side pressure by the pressure detection means is the predetermined high pressure, controlling a rotation speed of the cooling fan based on the first correspondence relationship under high pressure and the second correspondence relationship under high pressure; 11. The oil-cooled compressor according to claim 10, wherein when a detection value of the discharge side pressure by the pressure detection means is the predetermined low pressure, the rotation speed of the cooling fan is controlled based on the first correspondence relationship at low pressure and the second correspondence relationship at low pressure.

14. The first correspondence relationship and the second correspondence relationship stored in the storage means further include an intermediate-time first correspondence relationship and an intermediate-time second correspondence relationship, which are the first correspondence relationship and the second correspondence relationship that are adapted when a detection value of the discharge side pressure of the compressor main body exceeds the predetermined low pressure and is lower than the predetermined high pressure, The rotation speed control means 14. The oil-cooled compressor according to claim 13, characterized in that, when a detection value of the discharge side pressure by the pressure detection means exceeds the predetermined low pressure and is lower than the predetermined high pressure, the rotation speed of the cooling fan is controlled based on the intermediate-time first correspondence relationship and the intermediate-time second correspondence relationship.

15. The rotation speed control means 15. The oil-cooled compressor according to claim 14, wherein a low-temperature side reference temperature of the first correspondence relationship at intermediate setting and a high-temperature side reference temperature of the second correspondence relationship at intermediate setting are corrected to be increased as the discharge-side pressure detected by the pressure detection means increases and are corrected to be decreased as the discharge-side pressure detected by the pressure detection means decreases.

16. 12. The oil-cooled compressor according to claim 10, further comprising a dryer provided in the compressed air supply passage on the secondary side of the aftercooler.

17. 12. The oil-cooled compressor according to claim 10, wherein the discharge temperature detection means is provided in a receiver tank of the gas-liquid separator.

18. 16. The oil-cooled compressor according to claim 13, wherein the pressure detection means is provided in the compressed air supply passage on the secondary side of the aftercooler.

19. providing an intake outside air humidity detection means for detecting the intake outside air humidity of the compressor body; the storage means stores a correction value for the low-temperature side reference temperature of the first correspondence relationship and the high-temperature side reference temperature of the second correspondence relationship with respect to the change in the intake outdoor air humidity, taking into consideration a change in the dew-point temperature of the compressed air that occurs in response to the change in the intake outdoor air humidity; and The rotation speed control means 16. The oil-cooled compressor according to claim 10, 11, 13, 14 or 15, characterized in that the rotation speed of the cooling fan is controlled by correcting the low temperature side reference temperature of the first correspondence relationship and the high temperature side reference temperature of the second correspondence relationship with a correction value corresponding to the detection value of the intake outside air humidity by the intake outside air humidity detection means.

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