Operation control method for compressor, and compressor

Abstract

To prevent a compressor body from rotating in reverse when a driving source is stopped, while ensuring stable oil supply to the compressor body during cooling operation.SOLUTION: An operation control method for a compressor comprises: dividing cooling operation into a shutdown preparation period, which is a predetermined period immediately before a driving source such as an engine is stopped, and a main operation period, which is a period from the start of the cooling operation until the shutdown preparation period; during the main operation period, setting a pressure in a receiver tank 60 to a stable pressure P3 or higher, which enables stable oil supply to a compressor main body 40; during the shutdown preparation period, reducing the pressure in the receiver tank 60 to a lower limit stable pressure P4, which is a pressure that does not cause the compressor main body 40 to rotate in reverse when the driving source is stopped; and then stopping the driving source.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an operation control method for a compressor and a compressor that executes the operation control method, and more specifically to an operation control method for a compressor that performs a predetermined cooling operation before stopping a driving source such as an engine that drives the compressor body, and that has characteristics in its behavior during the cooling operation, and a compressor that executes the operation control method. [Background technology]

[0002] FIG. 8 shows an example of the configuration of an engine-driven compressor 300 having, as a compressor body 340, an oil-cooled screw compressor that compresses gas to be compressed together with lubricating oil and discharges the compressed gas as a gas-liquid mixed fluid.

[0003] In addition to the compressor main body 340 and engine (not shown), this engine-driven compressor 300 is equipped with a receiver tank 360 that introduces the compressed gas discharged by the compressor main body 340 as a gas-liquid mixed fluid with lubricating oil and separates the lubricating oil from the compressed gas, and is configured so that the compressed gas after the lubricating oil has been separated in this receiver tank 360 can be supplied to an air work machine (not shown) connected to a service valve 366, and so that the lubricating oil recovered in the receiver tank 360 can be supplied to the compressor main body 340 via an oil supply passage 364 equipped with an oil cooler 363 and an oil filter 365, using the pressure within the receiver tank 360.

[0004] Such an engine-driven compressor 300 is provided with an intake adjustment device 310 that adjusts the intake volume of the compressor main body 340 according to the pressure in the receiver tank 360 so as to ensure a stable supply of compressed gas to the consumption side.

[0005] In the engine-driven compressor 300 shown in Figure 8, the intake adjustment device 310 is composed of an intake adjustment valve 311 that opens and closes the intake port of the compressor main body 340, a control flow path 312 that connects the closed valve pressure chamber 311a of the intake adjustment valve 311 to the receiver tank 360, and a pressure regulator 313 that controls the opening and closing of the control flow path 312.

[0006] By providing such an intake adjustment device 310, when compressed gas is consumed on the consumption side and the pressure in the receiver tank 360 drops below the pressure at which the pressure regulator 313 starts to operate, the pressure regulator 313 closes the control flow path 312, and as a result, no operating pressure is introduced into the closed valve pressure chamber 311a of the intake adjustment valve 311, and the intake adjustment valve 311 opens, causing the compressor main body 340 to suck in and compress the gas to be compressed, thereby generating compressed gas.

[0007] On the other hand, when the pressure in the receiver tank 360 rises due to the consumption of compressed gas on the consumption side stopping, etc., and the pressure regulator 313 opens, the introduction of compressed gas into the closed valve pressure chamber 311a of the intake control valve 311 begins, and the intake control valve 311 narrows or closes the intake port of the compressor main body 340 in response to the increase in pressure in the receiver tank 360, causing the compressor main body 340 to reduce the amount of compressed gas produced or stop producing compressed gas.

[0008] In the engine-driven compressor 300 configured as described above, even if the power switch is turned OFF and a command to stop the engine-driven compressor 300 is input, the engine is not stopped immediately, but rather a so-called "cooling operation" is performed in which the engine and compressor main body 340 continue to operate under low load conditions until the temperature of the engine and compressor main body 340 (for example, the temperature of the coolant or lubricating oil) drops to a predetermined temperature or until a predetermined cooling time has elapsed, and then the engine is stopped.

[0009] As an engine-driven compressor that performs such cooling operation, Patent Document 1, cited below, describes an engine-driven compressor 300 that is equipped with a bypass flow path (323, 324) that bypasses the pressure regulator 313 and connects the receiver tank 360 to the closed-valve pressure chamber 311a of the intake control valve 311, electromagnetic on-off valves (331, 332) that open and close the bypass flow path, and a relief flow path 314 that releases the compressed gas in the closed-valve pressure chamber 311a of the intake control valve 311 through a throttle 315.

[0010] In the engine-driven compressor 300 described in Patent Document 1, during cooling operation, the electromagnetic on-off valves 331, 332 are opened to introduce compressed gas in the receiver tank 360 into the closed-valve pressure chamber 311a of the intake regulating valve 311 via the bypass flow paths 323, 324, and the compressed gas in the closed-valve pressure chamber 311a is released via the relief flow path 314, so that cooling operation can be performed with the pressure in the receiver tank 360 reduced, and even if the pressure regulator 313 closes the control flow path 312 due to a decrease in pressure in the receiver tank 360, the closed state of the intake regulating valve 311 is maintained by introducing compressed gas into the closed-valve pressure chamber 311a via the bypass flow paths 323, 324 (paragraphs

[0112] -

[0117] of Patent Document 1). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent Publication No. 2021-179186 Summary of the Invention [Problem to be solved by the invention]

[0012] In the engine-driven compressor 300 described in Patent Document 1, which has been explained with reference to Figure 8, during cooling operation, the intake port of the compressor main body 340 is blocked by the intake control valve 311, and the pressure in the receiver tank 360 is reduced to reduce the back pressure of the compressor main body 340, thereby reducing the load on the compressor main body 340 during cooling operation, and therefore the load on the engine.This not only makes it possible to efficiently cool the engine and compressor main body 340, but also enables cooling operation to be performed with low fuel consumption.

[0013] Here, if one wishes to further reduce the load on the engine during cooling operation, one option is to reduce the pressure in the receiver tank 360 to a pressure close to atmospheric pressure, thereby reducing the back pressure of the compressor main body 340 as much as possible.

[0014] However, in order to efficiently cool the compressor main body 40 during cooling operation and to prevent the compressor main body 340 from seizing, etc., it is necessary to steadily supply lubricating oil that has been cooled by passing through the oil cooler 363 to the compressor main body 340.However, as mentioned above, the lubricating oil is supplied to the compressor main body 340 using the pressure within the receiver tank 360, and therefore, if the pressure within the receiver tank 360 is significantly reduced during cooling operation, it will no longer be possible to supply oil to the compressor main body 340.

[0015] Therefore, even though the pressure in the receiver tank 360 during cooling operation is lower than during normal operation, it must be set to a relatively high pressure so that lubricating oil can be supplied stably to the compressor body 340 even when oil is supplied through an oil supply passage 364 equipped with equipment that causes pressure loss, such as an oil filter 365 or an oil cooler 363.

[0016] On the other hand, when the engine is stopped and the cooling operation is terminated, the compressor main body 340 stops rotating as the engine is stopped, and the compressed gas in the receiver tank 360 starts to flow into the compressor main body 340. At this time, if the pressure in the receiver tank 360 is high and the torque of the compressed gas flowing into the compressor main body 340 to rotate the screw rotor in the reverse direction is greater than the rotational resistance that the stopped engine applies to the screw rotor, the screw rotor of the compressor main body 340 is reversed and the engine connected to the rotor shaft of the compressor main body 340 is also reversed.

[0017] Such reversal of the compressor body 340 or the engine can have adverse effects on the components of the engine-driven compressor 300, such as shortening the life of the oil seals installed in the compressor body 340 and causing the engine fan belt to slip, thereby shortening the life of the fan belt.

[0018] In order to prevent such reverse rotation of the compressor main body 340 or the engine, it is possible to provide a check valve between the compressor main body 340 and the receiver tank 360 to prevent compressed gas from flowing into the compressor main body 340, or to provide a locking mechanism to prevent reverse rotation of the engine or compressor main body 340, but adding such a check valve or locking mechanism would increase the manufacturing cost of the engine-driven compressor 300.

[0019] Although the above explanation has been given using an engine-driven compressor with an engine as the driving source as an example, similar problems can arise when performing cooling operations on compressors with driving sources other than an engine, such as motors.

[0020] Therefore, the present invention has been made to eliminate the drawbacks of the above-mentioned conventional technology, and has as its first object to provide a compressor operation control method and a compressor that executes the operation control method, which can prevent the compressor body or driving source from reversing when the driving source such as an engine is stopped to terminate the cooling operation in a compressor that performs the above-mentioned cooling operation.

[0021] A second object of the present invention is to provide a compressor operation control method that can prevent the compressor body and drive source from reversing when the drive source is stopped and cooling operation is terminated, as well as ensure stable oil supply to the compressor body even during cooling operation that is performed by reducing the pressure in the receiver tank, and a compressor that executes the operation control method. [Means for solving the problem]

[0022] 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 intended to clarify the correspondence between 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.

[0023] In order to achieve the above object, the operation control method of the compressor 1 of the present invention includes: The compressor comprises an oil-cooled compressor body 40, a drive source (not shown) such as an engine or motor that drives the compressor body 40, a receiver tank 60 that introduces compressed gas discharged from the compressor body 40, an oil supply flow path 64 that connects the receiver tank 60 to the compressor body 40 and supplies oil to the compressor body 40 using the pressure in the receiver tank 60, and a discharge flow path 20 that discharges the compressed gas in the receiver tank 60, and an intake adjustment valve 11 that opens and closes the intake port of the compressor body 40, an unloading operation in which the intake control valve 11 is closed and the pressure in the receiver tank 60 is maintained at a predetermined unloading operation pressure P1; In the compressor 1 that performs cooling operation, the compressor 1 is operated in a state where the intake control valve 11 is closed and the pressure in the receiver tank 60 is reduced by discharging compressed gas through the discharge flow path 20 before the driving source is stopped, When the intake control valve 11 is closed, a small amount of compressed gas can be introduced into the compressor body 40, The cooling operation period is divided into a stop preparation period, which is the period immediately before the driving source is stopped, and a main operation period, which is the period from the start of the cooling operation until the stop preparation period, By changing the flow path area of ​​the discharge flow path 20, During the main operation period, the pressure in the receiver tank 60 is reduced to a stable pressure P3 (for example, 0.3 MPa) which is a predetermined lower pressure than the unloading operation pressure P1 and enables stable oil supply to the compressor body 40. During the stop preparation period, the pressure in the receiver tank 60 is lowered to a lower limit stable pressure P4 (for example, 0.1 MPa) which is lower than the stable pressure P3 and higher than the atmospheric pressure P0, and which does not cause the compressor main body 40 to rotate in reverse when the driving source is stopped. Thereafter, the driving source is stopped to terminate the cooling operation (claim 1).

[0024] In the main operation period, it is preferable that the pressure in the receiver tank 60 is reduced to the stable pressure P3, and then maintained at the stable pressure P3 until the main operation period ends (claim 2).

[0025] In the above-mentioned operation control method, a reference pressure P2 (for example, 0.5 MPa) is set, which is lower than the unload operation pressure P1 and is a predetermined higher pressure than the stable pressure P3 (for example, 0.3 MPa), The change in flow path area of ​​the discharge flow path 20 during the main operation period may be performed so that the rate at which the pressure in the receiver tank 60 drops from the unloading operation pressure P1 to the reference pressure P2 is faster than the rate at which the pressure drops from the reference pressure P2 to the stable pressure P3 (Claim 3).

[0026] Furthermore, after the cooling operation is completed, it is preferable to continue releasing the compressed gas through the release passage 20 to reduce the pressure in the receiver tank 60 to atmospheric pressure (claim 4).

[0027] Furthermore, the compressor 1 of the present invention is a receiver tank 60 for introducing compressed gas discharged from the compressor main body 40; an oil supply passage 64 that connects the receiver tank 60 to the compressor main body 40 and supplies oil to the compressor main body 40 using the pressure in the receiver tank 60; a discharge passage 20 that discharges the compressed gas in the receiver tank 60 and is also provided with an intake adjustment valve 11 that opens and closes the intake port of the compressor main body 40; a compressor 1 that performs a cooling operation in which the compressor 1 is operated with the intake adjustment valve 11 closed and so as to maintain a predetermined unload operation pressure P1; and a cooling operation in which the compressor 1 is operated with the intake adjustment valve 11 closed and with the pressure in the receiver tank 60 reduced by the discharge of compressed gas via the discharge passage 20 before the drive source is stopped, A minute intake flow path (not shown) that introduces a small amount of compressed gas into the compressor body 40 when the intake adjustment valve 11 is closed, a variable throttle mechanism 30 that changes the flow path area of ​​the discharge flow path 20, and a control device 70 that controls the operation of the variable throttle mechanism 30 and the drive source are provided, and the cooling operation period is divided in advance into a stop preparation period, which is the period immediately before the drive source is stopped, and a main operation period, which is the period from the start of the cooling operation until the stop preparation period, The control device 70 The termination conditions of the main operation period and the stop preparation period are stored, and the operation of the variable throttle mechanism 30 and the drive source is controlled, During the main operation period, the flow path area of ​​the discharge flow path 20 is set so that the pressure in the receiver tank 60 is reduced to a stable pressure P3, which is a predetermined lower pressure than the unload operation pressure P1 and enables stable oil supply to the compressor body 40, During the stop preparation period, the flow path area of ​​the discharge flow path 20 is set so that the pressure in the receiver tank 60 is lower than the stable pressure P3 and higher than the atmospheric pressure P0, and is reduced to a lower limit stable pressure P4, which is a pressure that does not cause the compressor body 40 to rotate in reverse when the driving source is stopped, and Thereafter, the driving source is stopped to terminate the cooling operation (claim 5).

[0028] It is preferable that the control device 70 is configured to control the variable throttling mechanism 30 so that the flow path area of ​​the discharge flow path 20 is maintained at the stable pressure P3 after reducing the pressure in the receiver tank 60 to the stable pressure P3 during the main operation period (Claim 6).

[0029] In any of the above compressors 1, a pressure detection means (pressure sensor) for detecting when the pressure in the receiver tank 60 reaches a reference pressure P2 that is lower than the unloading operation pressure P1 and is a predetermined higher pressure than the stable pressure P3; The control device 70 The variable throttling mechanism 30 may be configured to be controlled to change the flow path area from the start of the cooling operation until the pressure detection means 25 detects the reference pressure P2, and the flow path area after the reference pressure P2 is detected, so that the rate of pressure drop when the pressure in the receiver tank 60 drops from the unloading operation pressure P1 to the reference pressure P2 during the main operation period is faster than the rate of pressure drop when the pressure drops from the reference pressure P2 to the stable pressure P3 (Claim 7).

[0030] It is preferable that the variable throttle mechanism 30 is configured to maintain the discharge passage 20 in an open state even after the cooling operation has ended (claim 8).

[0031] The variable throttle mechanism 30 can be configured by a plurality of electromagnetic on-off valves 31, 32 with different drill diameters arranged in parallel in the discharge flow path 20 (claim 9; Fig. 1).

[0032] When the variable throttling mechanism 30 is constructed by a plurality of electromagnetic valves 31, 32 with different drill diameters arranged in parallel in the discharge flow path 20, it is preferable that at least one of the electromagnetic valves 31, 32 be a normally open (NO type) electromagnetic valve (Claim 10; Figure 1).

[0033] Furthermore, the variable throttle mechanism 30 can include electropneumatic proportional valves 33, 35 in its configuration (claim 11: Figs. 3 and 6).

[0034] The variable throttling mechanism 30 may be configured to have a normally closed (NC type) electropneumatic proportional valve 33 and a normally open (NO type) electromagnetic opening / closing valve 34 arranged in parallel in the discharge flow path 20 (Claim 12; Figure 3).

[0035] Alternatively, the variable throttle mechanism 30 may be configured by a normally open (NO type) electropneumatic proportional valve 35 provided in the discharge flow path 20 (claim 13; FIG. 6). [Effects of the Invention]

[0036] With the configuration of the present invention described above, the compressor 1 of the present invention can provide the following significant effects.

[0037] During the period in which the cooling operation is being performed, the pressure in the receiver tank 60 is reduced to the lower stable pressure P4 during the stop preparation period, which is the period immediately before the drive source is stopped, and then the drive source is stopped to terminate the cooling operation, thereby preventing the compressor main body 40 and the drive source from reversing even when the drive source, and therefore the compressor main body 40, is stopped.

[0038] As a result, it was possible to prevent deterioration of the oil seals and fan belts that occurs when the compressor body or the drive source (for example, an engine) is reversed when the drive source is stopped.

[0039] In addition to the above configuration, a configuration in which the pressure in the receiver tank 60 is reduced to a stable pressure P3 during the main operation period and then maintained at the stable pressure P3 until the end of the main operation period not only prevents the compressor main body 40 and the drive source from reversing when the drive source is stopped, but also reliably prevents the compressor main body from seizing due to insufficient oil supply, even during cooling operation in which the pressure in the receiver tank 60 is reduced.

[0040] If a reference pressure P2 is set that is lower than the unloaded operating pressure P1 and that is a predetermined higher pressure than the stable pressure P3, and the change in the flow path area of ​​the discharge flow path 20 during the main operation period is performed so that the rate at which the pressure in the receiver tank 60 drops from the unloaded operating pressure P1 to the reference pressure P2 is faster than the rate at which the pressure drops from the reference pressure P2 to the stable pressure P3, the pressure in the receiver tank 60 can be reduced at an early stage when cooling operation begins, and the load on the driving source can be reduced early, making it possible to efficiently cool the driving source (e.g., engine) and the compressor body, as well as reducing fuel consumption during cooling operation.

[0041] In a configuration in which the discharge flow path 20 continues to discharge compressed gas from the receiver tank 60 even after the drive source is stopped, the pressure in the receiver tank 60 can be reduced to atmospheric pressure P0, making it possible to smoothly start the compressor the next time.

[0042] By configuring the variable throttling mechanism 30 provided in the discharge flow path 20 with multiple electromagnetic on-off valves 31, 32 of different drill diameters arranged in parallel in the discharge flow path 20, the flow path area of ​​the discharge flow path 20 can be easily changed by changing the opening and closing pattern of the multiple electromagnetic on-off valves 31, 32 provided.

[0043] Moreover, with this configuration, it is possible to provide a compressor that executes the operation control method of the present invention relatively simply and at low cost, by leaving the main configuration of the conventional engine-driven compressor 300 described with reference to Figure 8 intact, and simply replacing the electromagnetic on-off valve used with one having a predetermined drill diameter, and rewriting the program of the control device that controls the operation of the electromagnetic on-off valve.

[0044] As described above, when the variable throttling mechanism 30 is formed by a plurality of electromagnetic on-off valves 31, 32 with different drill diameters arranged in parallel in the discharge flow path 20, by making at least one of the electromagnetic on-off valves 31, 32 (the second electromagnetic on-off valve 32 in the embodiment of Figure 1) a normally open (NO type) electromagnetic on-off valve, when the power supply to the electromagnetic on-off valves 31, 32 stops as the driving source stops, the normally open (NO type) electromagnetic on-off valve opens, making it possible to continue releasing the compressed gas in the receiver tank 60 through the discharge flow path 20 even after the driving source has stopped, and thereby reducing the pressure in the receiver tank 60 to atmospheric pressure P0 and making it possible to smoothly start the compressor 1 the next time.

[0045] The variable throttle mechanism 30 may include electropneumatic proportional valves 33, 35 as components, thereby enabling the flow path area of ​​the discharge flow path 20 to be varied in various ways by the electropneumatic proportional valves 33, 35.

[0046] When a normally closed (NC) electro-pneumatic proportional valve 33 is provided in the variable throttle mechanism 30, a normally open (NO) electromagnetic valve 34 is arranged in parallel with the electro-pneumatic proportional valve 33. Even if the power supply to the electro-pneumatic proportional valve 33 and the electromagnetic valve 34 is stopped when the drive source is stopped, the electromagnetic valve 34 will open, making it possible to continue releasing the compressed gas in the receiver tank 60 through the discharge flow path 20 even after the cooling operation has stopped.

[0047] Furthermore, if the variable throttling mechanism 30 is configured using a normally open (NO type) electro-pneumatic proportional valve 35, when the power supply to the electro-pneumatic proportional valve 35 stops as the drive source stops, the electro-pneumatic proportional valve 35 opens to its maximum opening and the compressed gas in the receiver tank 60 is released.Therefore, it is possible to continue releasing the compressed gas in the receiver tank 60 even after the drive source stops without installing an electromagnetic opening / closing valve in parallel with this electro-pneumatic proportional valve 35, thereby reducing the pressure in the receiver tank 60 to atmospheric pressure P0. [Brief explanation of the drawings]

[0048] [Figure 1] FIG. 2 is an explanatory diagram of the compressor of the first embodiment. [Figure 2] 4 is a time chart showing the operation of each part of the compressor in the first embodiment after the engine is stopped through a normal operation (unloaded operation) and a cooling operation. [Figure 3] FIG. 6 is an explanatory diagram of a compressor according to a second embodiment. [Figure 4] 6 is a time chart showing the operation of each part of the compressor in the second embodiment after the engine is stopped through a normal operation (unloaded operation) and a cooling operation. [Figure 5] 10 is a time chart showing the operation of each part of the compressor in the third embodiment after the engine is stopped through a normal operation (unloaded operation) and a cooling operation. [Figure 6] FIG. 10 is an explanatory diagram of a compressor according to a fourth embodiment. [Figure 7] 10 is a time chart showing the operation of each part of the compressor in the fourth embodiment after the engine is stopped through a normal operation (unloaded operation) and a cooling operation. [Figure 8] FIG. 1 is an explanatory diagram of a conventional compressor (corresponding to FIG. 1 of Patent Document 1). DETAILED DESCRIPTION OF THE INVENTION

[0049] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0050] In the embodiments described below, the compressor of the present invention will be described as an engine-driven compressor having an engine as a driving source, but the configuration of the compressor of the present invention can also be applied to a driving source other than an engine, for example, a motor-driven compressor having a motor as a driving source.

[0051] 1. Example 1 [Overall configuration of engine-driven compressor] The reference numeral 1 in Figure 1 denotes the engine-driven compressor of the present invention, and this engine-driven compressor 1 comprises a compressor main body 40, an engine (not shown) that drives the compressor main body 40, and a receiver tank 60 that stores compressed gas discharged from the compressor main body 40, and is configured so that the compressed gas discharged from the compressor main body 40 can be stored in the receiver tank 60 and then supplied to an air work machine or the like (not shown) connected to a service valve 66 via a pressure regulating valve 61.

[0052] The compressor body 40 mentioned above is an oil-cooled screw compressor that compresses the gas to be compressed together with lubricating oil for lubrication, cooling, and sealing, and the compressed gas discharged by the compressor body 40 as a gas-liquid mixed fluid with the lubricating oil is introduced into the receiver tank 60 via the discharge flow path 62, so that the compressed gas and the lubricating oil can be separated within the receiver tank 60.

[0053] The lubricating oil separated and recovered in the receiver tank 60 is pushed out by the pressure inside the receiver tank 60 and supplied to the compressor body 40 via an oil supply passage 64 equipped with an oil cooler 63 and an oil filter 65.

[0054] [Intake adjustment device] The engine-driven compressor 1 configured as described above is provided with an intake adjustment device 10 that controls the intake volume of the compressor main body 40 so that compressed gas can be supplied stably to the consumption side even if the consumption amount of compressed gas on the consumption side changes.

[0055] This intake adjustment device 10 is composed of an intake adjustment valve 11 that controls the opening and closing of the intake port of the compressor main body 40, a control flow path 12 that connects the closed-valve pressure chamber 113 of this intake adjustment valve 11 to the receiver tank 60, and a pressure regulator 13 that controls the opening and closing of the control flow path 12 depending on the pressure in the receiver tank 60, and is also equipped with a relief flow path 14 that releases the compressed gas in the closed-valve pressure chamber 113 of the intake adjustment valve 11 through a throttle 15.

[0056] In the engine-driven compressor 1 of the present invention, a minute intake passage (not shown) is provided that introduces a relatively small amount of compressed gas into the compressor body 40 even when the intake control valve 11 is closed, so that the pressure in the receiver tank 60 during unloaded operation can be maintained at a predetermined unloaded operating pressure P1 even by continuous release of compressed gas through the relief passage 14.

[0057] Various configurations can be adopted for this minute intake flow path (not shown), but for example, a drilled hole can be provided that penetrates the valve body of the intake adjustment valve 11, and this can be used as the aforementioned minute intake flow path (not shown), or even when the intake adjustment valve 11 is closed, it can remain slightly open rather than closing completely, and this gap can be used as the minute intake flow path.

[0058] By providing such a minute intake passage (not shown), a small amount of compressed gas is introduced from the compressor body 40 to the receiver tank 60 even during unloaded operation with the intake adjustment valve 11 closed.

[0059] Therefore, by adjusting the flow rate of compressed gas passing through the control flow path 12 so that the pressure inside the receiver tank 60 is balanced at the unloaded operation pressure P1 described above, the pressure inside the receiver tank 60 during unloaded operation can be maintained at the unloaded operation pressure P1 described above.

[0060] In addition, in a configuration in which the driving source is an engine, such as the compressor (engine-driven compressor) 1 of this embodiment, the engine rotation speed may be configured to change in accordance with the opening and closing operation of the intake adjustment valve 11 provided in the intake adjustment device 10.

[0061] In this case, it is preferable to set the no-load rotational speed, which is the rotational speed during unloaded operation or cooling operation when the intake control valve 11 is closed, to a lower rotational speed than the full-load rotational speed, which is the rotational speed of the engine during full-load operation when the intake control valve 11 is fully open, thereby reducing the load on the engine during unloaded operation or cooling operation and decreasing fuel consumption.

[0062] [Discharge flow path and variable throttle mechanism] The engine-driven compressor 1 of the present invention is configured so that even if a stop command is input by operating a power switch (not shown) provided on a control panel (not shown) or the like, the engine is not immediately stopped, but a predetermined cooling operation is performed in which the engine and compressor main body 40 are operated with the aforementioned intake control valve 11 closed and the compressed gas in the receiver tank 60 released to reduce the pressure in the receiver tank 60, and then the engine is stopped.

[0063] In this way, in order to enable cooling operation in which the compressed gas in the receiver tank 60 is released and the receiver tank 60 is operated under reduced pressure, one end of a discharge flow path 20 for releasing the compressed gas in the receiver tank 60 is connected to the receiver tank 60.

[0064] Furthermore, this discharge flow path 20 is provided with a variable throttle mechanism 30 that makes the flow path area of ​​the discharge flow path 20 variable, and by changing the flow rate of the compressed gas, the pressure inside the receiver tank 60 can be changed.

[0065] In this embodiment, the compressed gas released through this discharge passage 20 is used as the operating pressure that causes the intake control valve 11 to close during cooling operation, so that the other end of the discharge passage 20 is connected to the valve closing pressure chamber 113 of the intake control valve 11.

[0066] By configuring in this manner, during cooling operation, the compressed gas in the receiver tank 60 is released through the discharge passage 20, the closed valve pressure chamber 113 of the intake control valve 11, and the relief passage 14, thereby not only reducing the pressure in the receiver tank 60 to a pressure lower than the unloaded operating pressure P1, but also, even after the pressure regulator 13 closes the control passage 12 due to the decrease in pressure in the receiver tank 60, the operating pressure is introduced into the closed valve pressure chamber 113 of the intake control valve 11 through the discharge passage 20, thereby maintaining the intake control valve 11 in a closed state.

[0067] As mentioned above, in this embodiment, in order to have the discharge flow path 20 close the intake regulating valve 11 during cooling operation, a configuration is adopted in which the other end of the discharge flow path 20 is connected to the closed valve pressure chamber 113 of the intake regulating valve 11. However, the configuration of the engine-driven compressor 1 of the present invention is not limited to this configuration, and a configuration may be provided separate from the discharge flow path 20 to close the intake regulating valve 11 during cooling operation, and the other end of the discharge flow path 20 may be opened to the atmosphere without passing through the closed valve pressure chamber 113 of the intake regulating valve 11.

[0068] In the embodiment shown in Figure 1, the aforementioned discharge flow path 20 is composed of a main flow path 21 connected at one end to the receiver tank 60, a manifold 22 connected to the other end of the main flow path 21, and branch flow paths 23 and 24 that branch off from the manifold 22 and are connected to the closed valve pressure chamber 113 of the intake control valve 11.

[0069] One of the branch flow paths 23, 24 provided in the discharge flow path 20 is provided with a first electromagnetic on-off valve 31 having a first drill diameter, and the other branch flow path 24 is provided with a second electromagnetic on-off valve 32 having a second drill diameter.In this way, the first electromagnetic on-off valve 31 and the second electromagnetic on-off valve 32 arranged in parallel form a variable throttling mechanism 30 that makes the flow path area of ​​the discharge flow path 20 variable.

[0070] In other words, the first and second electromagnetic on-off valves 31, 32 provided in the aforementioned branch flow paths 23, 24 function as "throttles" that narrow the flow path area of ​​each branch flow path 23, 24, and the drill diameter, which represents the inner diameter of the flow path formed within the body of the first and second electromagnetic on-off valves 31, 32, corresponds to the flow path area of ​​the electromagnetic on-off valves 31, 32, which are the aforementioned "throttles."

[0071] In the configuration shown in Figure 1 in which the first and second electromagnetic on-off valves 31, 32 are arranged in parallel, the flow path area of ​​the discharge flow path 20 can be changed between 0 (zero: fully closed), a first flow path area O1 corresponding to the first drill diameter, a second flow path area O2 corresponding to the second drill diameter, and the total area (O1 + O2) of the first flow path area and the second flow path area when both the first and second electromagnetic on-off valves 31, 32 are closed, when only the first electromagnetic on-off valve 31 is open, when only the second electromagnetic on-off valve 32 is open, and when both the first electromagnetic on-off valve 31 and the second electromagnetic on-off valve 32 are open, and the pressure inside the receiver tank 60 can be changed by changing this flow path area.

[0072] In this embodiment, the first flow path area O1 corresponding to the first drill diameter is formed as a flow path area that can be maintained while reducing the pressure in the receiver tank 60 to a stable pressure P3 (0.3 MPa, for example), which is a pressure lower than the pressure P1 before the start of cooling operation and which enables stable oil supply to the compressor main body, and the second flow path area O2 corresponding to the second drill diameter is formed as a flow path area that can be maintained while reducing the pressure in the receiver tank 60 to a lower stable pressure P4 (0.1 MPa, for example), which is a pressure lower than the stable pressure P3 (0.3 MPa, for example) and higher than atmospheric pressure P0 (0 MPa), which does not cause the compressor main body 40 and the engine to reverse when the engine is stopped.

[0073] In this embodiment, a normally closed type (NC type) is used as the first solenoid valve 31, and a normally open type (NO type) is used as the second solenoid valve 32. After the engine is stopped, even when the power supply to the first solenoid valve 31 and the second solenoid valve 32 is stopped, the second solenoid valve 32 remains open. As a result, even if the engine is stopped when the pressure in the receiver tank 60 is at the lower stable pressure P4, the compressed gas in the receiver tank 60 continues to be released even after the engine is stopped, so that the pressure in the receiver tank 60 can be reduced to atmospheric pressure P0.

[0074] [Control device] The engine-driven compressor 1 of the present invention configured as described above is provided with a control device 70 consisting of an electronic control device such as a microcontroller, and this control device 70 controls the operation of the first electromagnetic on-off valve 31 and the second electromagnetic on-off valve 32 that constitute the variable throttling mechanism 30, thereby changing the flow path area of ​​the discharge flow path 20 and thereby changing the pressure in the receiver tank 60 during cooling operation.

[0075] In the present invention, the cooling operation is divided into a stop preparation period, which is the period immediately before the engine is stopped, and a main operation period, which is the period from the start of the cooling operation until the stop preparation period (see Figure 2), and by having the control device 70 control the operation of the variable throttle mechanism 30, During the main operation period, the pressure in the receiver tank 60 is reduced from the unload operation pressure P1 to a stable pressure P3, which is a predetermined lower pressure than the unload operation pressure P1 and enables stable oil supply to the compressor body 40, and is maintained at the stable pressure P3. During the stop preparation period, the pressure in the receiver tank 60 is reduced from the stable pressure P3 to a lower limit stable pressure P4, which is a pressure lower than the stable pressure P3 and higher than atmospheric pressure P0, and which does not cause the compressor body 40 and the engine to rotate in reverse when the engine is stopped, Thereafter, the engine is stopped to terminate the cooling operation.

[0076] By configuring in this manner, stable oil supply to the compressor body is achieved during the main operating period of cooling operation, thereby preventing seizure, etc., while by lowering the pressure in the receiver tank 60 to the lower stable pressure P4 during the stop preparation period just before the engine is stopped, reverse rotation of the compressor body and engine when the engine is stopped is prevented, and deterioration of the compressor body's oil seal and the engine's fan belt that would occur as a result of this reverse rotation is prevented.

[0077] Furthermore, in this embodiment, a reference pressure P2 (for example, 0.5 MPa) is set which is lower than the unloaded operation pressure P1 and which is a predetermined higher pressure than the stable pressure P3 (for example, 0.3 MPa), and the flow path area of ​​the discharge flow path 20 during the main operation period described above is changed so that the rate of pressure drop when the pressure in the receiver tank 60 drops from the unloaded operation pressure P1 to the reference pressure P2 is faster than the rate of pressure drop when the pressure drops from the reference pressure P2 to the stable pressure P3. This allows the back pressure of the compressor main body 40 to be rapidly reduced to the reference pressure P2 after the start of cooling operation, thereby enabling the load on the compressor main body 40, and therefore the engine, to be reduced early.

[0078] [Operation description] The operation of each part of the engine-driven compressor 1 of the present invention configured as above during cooling operation and before and after the start of the cooling operation will be described with reference to the time chart shown in FIG.

[0079] When the engine-driven compressor 1 is stopped, pneumatic equipment not shown connected to the service valve 66 of the engine-driven compressor 1 is stopped in advance, and the consumption of compressed gas on the consumption side is stopped.As a result, the pressure in the receiver tank 60 rises above the operating pressure of the pressure regulator 13 provided in the control flow path 12, and the intake port of the compressor main body 40 is closed by the intake adjustment valve 11, resulting in an unloaded operation state.

[0080] In this manner, in the unloaded operation state before the start of cooling operation, the control device 70 keeps the first normally closed (NC type) electromagnetic valve in a non-energized (OFF) state and the second normally open (NO type) electromagnetic valve in an energized (ON) state, so that both the first electromagnetic valve 31 and the second electromagnetic valve 32 are in a closed state and no compressed gas is released from the receiver tank 60 via the release flow path 20 (T0).

[0081] From this state, when a power switch (not shown) provided on an operation panel (not shown) or the like of the engine-driven compressor 1 is turned off, the main operation period of the cooling operation begins (T1).

[0082] When the cooling operation starts, the control device 70 starts energizing (ON) the first electromagnetic on-off valve 31 and de-energizes (OFF) the second electromagnetic on-off valve (T1).

[0083] The first electromagnetic valve 31 has a small drill diameter and is of the normally closed type (NC type), so it can open even when there is a relatively large pressure difference between the primary and secondary sides, and the first electromagnetic valve 31 opens immediately when current begins to flow (T1).

[0084] As a result, during unloaded operation, the pressure in the receiver tank 60, which had been maintained at a predetermined pressure P1 solely by the release of compressed gas from the control flow path 12 of the intake adjustment device 10, begins to drop (T1-T2) as it is no longer able to maintain the pressure P1 that was present before the start of cooling operation due to the increase in the flow path area caused by the opening of the first electromagnetic opening / closing valve 31.

[0085] On the other hand, the second electromagnetic on-off valve 32, which has a large drill diameter and is of the normally open type (NO type), is provided with a relatively large valve body. Therefore, when the pressure difference between the primary and secondary sides is large, not only is a large force applied in the direction of seating the valve body on the valve seat (valve closing direction), but the normally open type (NO type) second electromagnetic on-off valve 32 performs the valve opening operation using only the biasing force of the return spring, so the force moving the valve body away from the valve seat is weak.

[0086] As a result, when the pressure in the receiver tank 60 is high and the pressure difference between the primary and secondary sides is large, the second electromagnetic valve 32 cannot open immediately even when it is switched off (OFF), and will only open when the pressure in the receiver tank 60 decreases due to the opening of the first electromagnetic valve 31 and the pressure difference between the primary and secondary sides decreases to a pressure difference at which the second electromagnetic valve 32 can operate (T2).

[0087] When the second electromagnetic on-off valve 32 opens, the flow path area of ​​the discharge flow path 20 becomes the total area (O1 + O2) of the first flow path area O1 corresponding to the cut diameter (first cut diameter) of the first electromagnetic on-off valve 31 and the second flow path area O2 corresponding to the cut diameter (second cut diameter) of the second electromagnetic on-off valve 32, thereby increasing the rate at which the pressure drops in the receiver tank 60, and thereby enabling the back pressure of the compressor main body 40 to be reduced earlier.

[0088] When the pressure in the receiver tank 60 drops below the activation pressure of the pressure regulator 13 provided in the control flow path 12, compressed gas is no longer introduced from the control flow path 12 into the closed valve pressure chamber 113 of the intake control valve 11, but compressed gas in the receiver tank 60 continues to be introduced into the closed valve pressure chamber 113 of the intake control valve 11 via the discharge flow path 20, so that the intake control valve 11 remains closed even after transitioning to cooling operation.

[0089] Then, when the pressure sensor 25 provided in the manifold 22 receives a detection signal indicating that the pressure in the receiver tank 60 has dropped to a reference pressure P2 (for example, 0.5 MPa), the control device 70 de-energizes (OFF) the second electromagnetic valve 32 to close it, and continues to energize (ON) the first electromagnetic valve 31 to maintain the first electromagnetic valve 31 in an open state, thereby reducing the flow area of ​​the discharge flow path 20 to a first flow area O1 corresponding to the drill diameter of the first electromagnetic valve 31 (T3).

[0090] In this way, the flow path area of ​​the discharge flow path 20 is reduced, and although the rate of pressure drop in the receiver tank 60 decreases, the pressure in the receiver tank 60 continues to drop, dropping to a stable pressure P3 and stabilizing at this stable pressure P3.

[0091] In this way, during the main operation period, which is the period from the start of cooling operation to the shutdown preparation period, the pressure in the receiver tank 60 is above the stable pressure P3, which enables a stable supply of lubricating oil to the compressor main body 40, thereby ensuring a stable supply of oil to the compressor main body 40.

[0092] In this embodiment, the lapse of a predetermined time (for example, 120 seconds) from the start of cooling operation is set as the end condition for the aforementioned main operation period and is stored in the control device 70. When the aforementioned predetermined time has elapsed (T4), the control device 70 stops the flow of electricity to both the first solenoid valve 31 and the second solenoid valve 32, closes the normally closed type (NC type) first solenoid valve 31, and opens the normally open type (NO type) second solenoid valve 32, thereby transitioning to the shutdown preparation period.

[0093] In this embodiment, the end of the main operation period is set to be the point at which a predetermined time (for example, 120 seconds) has elapsed since the start of cooling operation, but instead of this configuration, the main operation period may be terminated and the shutdown preparation period may be initiated, for example, when the temperature of the engine coolant and / or the temperature of the lubricating oil in the compressor body drops below a predetermined temperature; the conditions for terminating the main operation period are not limited to the conditions described above.

[0094] In this way, when the main operation period ends and the operation shifts to the shutdown preparation period, the flow path area of ​​the discharge flow path 20 becomes the second flow path area O2 corresponding to the drill diameter of the second electromagnetic on-off valve 32.

[0095] This second flow path area O2 is a flow path area that reduces and maintains the pressure in the receiver tank 60 at the lower limit stable pressure P4, and the stop preparation period is set to a time (60 seconds in this embodiment as an example) that is longer than the time required for the pressure to decrease from the stable pressure P3 to the lower limit stable pressure P4 when the compressed gas in the receiver tank 60 is released at the flow path area O2.

[0096] As a result, when the engine enters the stop preparation period and the release of compressed gas begins via the second electromagnetic on-off valve 32 provided in the release flow path 20, the pressure in the receiver tank 60 drops from the stable pressure P3 to the lower limit stable pressure P4, and then remains at the lower limit stable pressure P4. When the stop preparation period of a predetermined time (for example, 60 seconds) expires, the control device 70 stops the engine and terminates the cooling operation (T5).

[0097] Furthermore, since the pressure in the receiver tank 60 is maintained at a pressure higher than atmospheric pressure P0 even during the shutdown preparation period, lubricating oil is supplied to the compressor main body 40, but stable oil supply cannot be ensured as during the main operation period. Therefore, it is preferable to set the shutdown preparation period to as short a time as possible. For example, the control device 70 may be configured to stop the engine and terminate cooling operation (shutdown preparation period) when the pressure sensor 25 provided in the manifold 22 detects that the pressure in the receiver tank 60 has reached the above-mentioned lower stable pressure P4, and is not limited to the configuration described above.

[0098] When the engine is stopped and the compressor main body 40 is stopped, the compressed gas in the receiver tank 60 begins to flow into the compressor main body 40, but because the engine is stopped while the pressure in the receiver tank 60 is low, the torque in the reverse direction generated by the compressed gas flowing into the compressor main body 40 is smaller than the rotational resistance that the stopped engine applies to the screw rotor. In other words, because the pressure in the receiver tank 60 when the engine is stopped is reduced to the lower limit stable pressure P4 at which the compressor main body 40 and the engine cannot be reversed, deterioration of the oil seal due to reverse rotation of the compressor main body 40 and deterioration due to slippage of the fan belt due to reverse rotation of the engine are preferably prevented.

[0099] When the engine is stopped, the power supply (ACC power supply) to the electrical equipment installed in the engine-driven compressor 1 is turned off, and both the first electromagnetic on-off valve 31 and the second electromagnetic on-off valve 32 are de-energized (OFF). However, the second electromagnetic on-off valve 32, which is a normally open type (NO type), remains open, so that the compressed gas in the receiver tank 60 continues to be released through the discharge passage 20 even after the engine is stopped, causing the pressure in the receiver tank 60 to drop to atmospheric pressure P0.

[0100] In this way, the pressure inside the receiver tank 60 drops to atmospheric pressure P0, making it possible to smoothly start the engine-driven compressor 1 the next time.

[0101] 2. Example 2 In the engine-driven compressor 1 (Example 1) described with reference to Figures 1 and 2, the above-mentioned discharge flow path 20 is provided in addition to the control flow path 12 provided in the intake adjustment device 10, and an example is shown in which a variable throttling mechanism 30 is formed by a first electromagnetic opening / closing valve 31 and a second electromagnetic opening / closing valve 32 provided in parallel in the discharge flow path 20.

[0102] In contrast to this, in the engine-driven compressor 1 of this embodiment (embodiment 2) which will be described below with reference to Figures 3 and 4, a variable throttling mechanism 30 is formed by an electro-pneumatic proportional valve 33 and an electromagnetic opening / closing valve 34 which are arranged in parallel to the discharge flow path 20, and this electro-pneumatic proportional valve 33 is given the function of the pressure regulator 13 which is arranged in the control flow path 12 of the engine-driven compressor 1 which was described with reference to Figure 1, so that the control flow path 12 and the pressure regulator 13 are excluded from the configuration.

[0103] The other configuration is the same as that of the engine-driven compressor 1 described with reference to FIG.

[0104] The discharge flow path 20 of this embodiment (embodiment 2), like the embodiment (embodiment 1) described with reference to Figure 1, is configured by connecting a manifold 22 to one end of a main flow path 21, the other end of which is connected to a receiver tank 60, and by branching into two branch flow paths 23, 24 via this manifold 22, each of which is connected to the closed valve pressure chamber 113 of the intake control valve 11.

[0105] One of these branch flow paths 23, 24 is provided with a normally closed (NC) electro-pneumatic proportional valve 33, and the other branch flow path 24 is provided with a normally open (NO) electromagnetic on-off valve 34.A variable throttling mechanism 30 is formed by the electro-pneumatic proportional valve 33 and the electromagnetic on-off valve 34 arranged in parallel in this manner.

[0106] The normally closed (NC) electro-pneumatic proportional valve 33 described above is configured to be able to increase the flow path area in response to an input signal from a fully closed state in which no control signal is input, thereby enabling the opening to be changed during cooling operation between a "small" opening corresponding to the first flow path area O1, a "medium" opening corresponding to the second flow path area O2, and a "large" opening corresponding to the combined area of ​​the first flow path area O1 and the second flow path area O2, as shown in Figure 4.

[0107] In contrast, the other branch flow path 24 is provided with a normally open (NO type) electromagnetic valve 34, which is configured so that when electricity is applied (ON) to the electromagnetic valve 34, the other branch flow path 24 is closed, and when electricity is not applied (OFF), the other branch flow path 24 is open.

[0108] The cut diameter of this electromagnetic on-off valve 34 is not particularly limited, and electromagnetic on-off valves 34 with various cut diameters can be used, but as an example, in this embodiment, an electromagnetic on-off valve 34 with a cut diameter corresponding to the second flow path area O2 is used.

[0109] The operation of the variable throttle mechanism 30 configured as above is controlled by a control device 70 consisting of an electronic control device such as a microcontroller.

[0110] The state of control of each part by this control device 70 will be explained below with reference to the time chart shown in FIG.

[0111] The control device 70 keeps the normally open (NO type) electromagnetic on-off valve 34 energized (ON) and maintains the other branch flow path 24 of the discharge flow path 20 in a closed state (T0) while the engine-driven compressor 1 is operating, whether in normal operation before the cooling operation is started or in cooling operation.

[0112] On the other hand, when the engine-driven compressor 1 is in unloaded operation before starting cooling operation, the control device 70 opens the electro-pneumatic proportional valve 33 to a relatively small opening (an opening between "fully closed" and "small" in Figure 4) that can maintain the pressure in the receiver tank 60 at the pressure P1 before the cooling operation began, thereby introducing compressed gas into the closing valve pressure chamber 113 of the intake control valve 11 through one of the branch flow paths 23, thereby closing the intake control valve 11 (T0).

[0113] From this state, when the power switch provided on the control panel of the engine-driven compressor is turned OFF, the cooling operation starts and the control device 70 changes the opening of the electro-pneumatic proportional valve 33 to "large" (T1).

[0114] As a result, the pressure in the receiver tank 60 begins to drop rapidly from the unloaded operation pressure P1.

[0115] When the control device 70 receives a detection signal from the pressure sensor 25 that detects that the pressure in the receiver tank 60 has dropped to the reference pressure P2, it reduces the opening of the electro-pneumatic proportional valve 33 to "small" (T3).

[0116] This "small" opening corresponds to the flow path area O1 that reduces and maintains the pressure in the receiver tank 60 to the stable pressure P3.As a result, the pressure in the receiver tank 60 continues to decrease from the reference pressure P2 to the stable pressure P3, albeit at a slower rate, and by being maintained at the stable pressure P3, stable supply of lubricating oil to the compressor body 40 is ensured.

[0117] When a predetermined time (for example, 120 seconds) has elapsed since the start of cooling operation (T4), the control device 70 changes the opening of the electro-pneumatic proportional valve 33 to "medium," and the cooling operation transitions from the main operation phase to the shutdown preparation phase.

[0118] In this embodiment, the transition from the main operation period to the stop preparation period is also made when a predetermined time (for example, 120 seconds) has elapsed since the start of cooling operation. However, instead of this configuration, the transition from the main operation period to the stop preparation period may be made on the condition that, for example, the temperature of the engine coolant and / or the temperature of the lubricating oil in the compressor body has dropped below a predetermined temperature, and the transition conditions are not limited to the examples described above.

[0119] The "medium" opening of the electro-pneumatic proportional valve 33 during the stop preparation period corresponds to the second flow path area O2 that reduces and maintains the pressure in the receiver tank 60 to the lower stable pressure P4. As a result, the pressure in the receiver tank 60 starts to drop from the stable pressure P3 and drops to the lower stable pressure P4, which is maintained, and when a predetermined time (for example, 60 seconds) has elapsed during the stop preparation period, the control device 70 stops the engine and ends the cooling operation (T5).

[0120] When the engine is stopped, the compressor main body 40 stops rotating, and the pressure in the receiver tank 60 flows toward the compressor main body 40. However, the pressure in the receiver tank 60 drops to a lower stable pressure P4 at which the compressor main body 40 or engine cannot be reversed even by the inflow of compressed gas. This effectively prevents deterioration of the oil seal due to the compressor main body 40 rotating in reverse, and deterioration due to slippage of the fan belt due to the engine rotating in reverse.

[0121] When the engine stops, the power supply (ACC power supply) to the electrical equipment installed in the engine-driven compressor 1 is turned off, and when the electromagnetic valve 34 installed in the other branch flow path 24 is de-energized (OFF), the normally open (NO type) electromagnetic valve 34 opens the other branch flow path 24.

[0122] As a result, even if the electro-pneumatic proportional valve 33, which is a normally closed type (NC type), is de-energized (OFF) and becomes fully closed, the compressed gas in the receiver tank 60 is released through the other branch flow path 24, thereby reducing the pressure in the receiver tank 60 to atmospheric pressure P0.

[0123] 3. Example 3 In the embodiment (embodiment 2) described above with reference to Figures 3 and 4, the normally open (NO type) electromagnetic valve 34 provided in the other branch flow path 24 is maintained in a closed state while the engine-driven compressor 1 is operating, regardless of whether it is in normal operation or cooling operation, and is configured to open only when power is stopped due to the engine being stopped, and a configuration has been described in which the flow path area of ​​the discharge flow path 20 during cooling operation is changed only by adjusting the opening of the electro-pneumatic proportional valve 33.

[0124] In contrast, the time chart shown in Figure 5 shows that in an engine-driven compressor 1 having the same structure as that shown in Figure 3, at the timing (T4) of transition from the main operation period to the stop preparation period, the control device 70 stops (OFF) the supply of electricity to the normally closed (NC type) electro-pneumatic proportional valve 33 and the normally open (NO type) solenoid valve 34, thereby fully closing the electro-pneumatic proportional valve 33 and opening the solenoid valve 34, thereby releasing the compressed gas in the receiver tank 60 during the stop preparation period via the solenoid valve 34 (the other branch flow path 24), and the other operations are the same as those in the embodiment (embodiment 2) described with reference to Figure 4.

[0125] The drill diameter of the electromagnetic on-off valve 34 provided in the other branch flow path 24 corresponds to the second flow path area O2 that reduces and maintains the pressure in the receiver tank 60 to the lower stable pressure P4, as described above.Therefore, during the shutdown preparation period, the electro-pneumatic proportional valve 33 is fully closed to close one of the branch flow paths 23, and the compressed gas in the receiver tank 60 is released through the other branch flow path 24 equipped with the electromagnetic on-off valve 34, so that the pressure in the receiver tank 60 can be reduced to the lower stable pressure P4 and stabilized.

[0126] Then, even when the stop preparation period expires and the control device 70 stops the engine and the ACC power is turned off, the normally open (NO type) electromagnetic valve 34 continues to remain open, so that the compressed gas in the receiver tank 60 continues to be discharged even after the engine is stopped, causing the pressure in the receiver tank 60 to drop to atmospheric pressure P0.

[0127] 4. Example 4 In the embodiments (embodiments 2 and 3) described with reference to Figure 3 above, a normally closed (NC type) electro-pneumatic proportional valve 33 is used as the electro-pneumatic proportional valve provided in the variable throttling mechanism 30, and a normally open (NO type) electromagnetic on-off valve 34 is provided in parallel with this electro-pneumatic proportional valve 33, so that the compressed gas in the receiver tank 60 can be released through the other branch flow path 24 opened by this electromagnetic on-off valve 34 after the engine is stopped and cooling operation is completed.

[0128] In contrast to this, in this embodiment (embodiment 4) shown in Figures 6 and 7, a normally open (NO type) electro-pneumatic proportional valve 35 is provided as the electro-pneumatic proportional valve, so that the flow path area of ​​the discharge flow path 20 during cooling operation can be changed by this electro-pneumatic proportional valve 35, and the release of compressed gas in the receiver tank 60 after the engine is stopped and cooling operation is completed can also be performed via the electro-pneumatic proportional valve 35.

[0129] That is, in the embodiment (embodiment 4) shown in Figures 6 and 7, a variable throttle mechanism 30 is configured that makes the flow path area of ​​the discharge flow path 20 variable using only a normally open (NO type) electropneumatic proportional valve 35.

[0130] In this configuration, when the engine-driven compressor 1 is in unloaded operation before starting cooling operation, the control device 70 slightly opens the electro-pneumatic proportional valve 35 to an opening between "fully closed" and "small" to introduce operating pressure into the closed valve pressure chamber 113 of the intake control valve 11.

[0131] In this state, when the power switch is turned OFF to command the engine-driven compressor 1 to stop, the cooling operation starts and the control device 70 sets the opening of the electro-pneumatic proportional valve 35 to "large" to rapidly reduce the pressure in the receiver tank 60 (T1).

[0132] When the control device 70 receives a detection signal from the pressure sensor 25 that detects that the pressure in the receiver tank 60 has dropped to the reference pressure P2 (T3), it reduces the opening of the electro-pneumatic proportional valve 35 to "small" corresponding to the first flow path area O1, causing the pressure in the receiver tank 60 to drop further from the reference pressure P2 and stabilize at a stable pressure P3.

[0133] Then, when a predetermined time (for example, 120 seconds) has elapsed since the start of the cooling operation (T4), the control device 70 changes the opening of the electro-pneumatic proportional valve 35 to "medium" corresponding to the second flow path area O2, transitioning the cooling operation from the main operation phase to the stop preparation phase and reducing the pressure in the receiver tank 60 from the stable pressure P3 to the lower stable pressure P4, and when the predetermined time (for example, 60 seconds) of the stop preparation phase has elapsed, the control device 70 stops the engine and ends the cooling operation (T5).

[0134] When the engine stops, the ACC power supply is turned off and the power supply to the electro-pneumatic proportional valve 35 is stopped, and the electro-pneumatic proportional valve 35 opens to a large (fully open) position, so that the compressed gas in the receiver tank 60 continues to be released even after the engine has stopped, and the pressure in the receiver tank 60 can be reduced to atmospheric pressure P0. [Explanation of symbols]

[0135] 1 (Engine-driven) compressor 10. Intake adjustment device 11 Intake adjustment valve 113 Closed valve pressure chamber (intake control valve) 12 Control Channel 13 Pressure Regulator 14 Relief channel 15 aperture 20 Discharge channel 21 Main channel 22 Manifold 23 Branch channel (one side) 24 Branch flow path (other) 25 Pressure Sensor 30 Variable aperture mechanism 31 First solenoid valve (NC type) 32 Second electromagnetic shut-off valve (NO type) 33 Electro-pneumatic proportional valve (NC type) 34 Solenoid valve (NO type) 35 Electro-pneumatic proportional valve (NO type) 40 Compressor body 60 Receiver Tank 61 Pressure Regulating Valve 62 discharge flow path 63 Oil cooler 64 Oil supply passage 65 Oil filter 66 Service valve 70 Control device 300 Engine-driven compressor 310 Intake adjustment device 311 Intake adjustment valve 311a Closed valve pressure chamber 312 Control Channel 313 Pressure Regulator 314 Relief channel 315 Aperture 323,324 Bypass flow path 331,332 Solenoid valve 340 Compressor body 360 receiver tank 363 Oil cooler 364 Oil supply channel 365 Oil Filter 366 Service Valve 365 Oil Filter

Claims

1. an oil-cooled compressor body; a drive source for driving the compressor body; a receiver tank for introducing compressed gas discharged from the compressor body; and an oil supply flow path for communicating the receiver tank with the compressor body and for supplying oil to the compressor body using the pressure in the receiver tank; a discharge passage for discharging compressed gas in the receiver tank; an intake adjustment valve that opens and closes the intake port of the compressor body, an unloading operation in which the intake control valve is closed and the pressure in the receiver tank is maintained at a predetermined unloading operation pressure; a compressor that performs a cooling operation in which the compressor is operated with the intake control valve closed and with the pressure in the receiver tank reduced by releasing compressed gas through the release flow path before the drive source is stopped, When the intake control valve is closed, a small amount of compressed gas can be introduced into the compressor body, and The cooling operation is divided into a stop preparation period, which is a period immediately before stopping the driving source, and a main operation period, which is a period from the start of the cooling operation to the stop preparation period, By changing the flow path area of ​​the discharge flow path, During the main operation period, the pressure in the receiver tank is reduced to a stable pressure that is a predetermined lower pressure than the unload operation pressure and that enables stable oil supply to the compressor body, and During the stop preparation period, the pressure in the receiver tank is reduced to a lower limit stable pressure that is lower than the stable pressure but higher than atmospheric pressure and that does not cause the compressor body to rotate in reverse when the driving source is stopped, Thereafter, the driving source is stopped to terminate the cooling operation.

2. 2. The compressor operation control method according to claim 1, wherein, during the main operation period, the pressure in the receiver tank is reduced to the stable pressure, and then maintained at the stable pressure until the main operation period ends.

3. A reference pressure is set which is lower than the unloaded operation pressure and is a predetermined higher pressure than the stable pressure; 2. The compressor operation control method according to claim 1, wherein the flow path area of ​​the discharge flow path during the main operation period is changed so that a pressure drop rate when the pressure in the receiver tank drops from the unload operation pressure to the reference pressure is faster than a pressure drop rate when the pressure drops from the reference pressure to the stable pressure.

4. 4. The compressor operation control method according to claim 1, wherein after the cooling operation is completed, the discharge of compressed gas through the discharge passage is continued to reduce the pressure in the receiver tank to atmospheric pressure.

5. The compressor includes an oil-cooled compressor body, a drive source for driving the compressor body, a receiver tank for introducing compressed gas discharged from the compressor body, an oil supply flow path that connects the receiver tank and the compressor body and supplies oil to the compressor body using the pressure in the receiver tank, and a discharge flow path that discharges the compressed gas in the receiver tank; an intake adjustment valve that opens and closes the intake port of the compressor body, an unloading operation in which the intake control valve is closed and a predetermined unloading operation pressure is maintained; a compressor that performs a cooling operation in which the compressor is operated with the intake control valve closed and with the pressure in the receiver tank reduced by releasing compressed gas through the release flow path before the drive source is stopped, a minute intake flow path that introduces a small amount of compressed gas into the compressor body when the intake adjustment valve is closed, a variable throttle mechanism that changes the flow path area of ​​the discharge flow path, and a control device that controls the operation of the variable throttle mechanism and the driving source, and the cooling operation period is divided in advance into a stop preparation period that is a period immediately before the driving source is stopped, and a main operation period that is a period from the start of the cooling operation until the stop preparation period, The control device The termination conditions of the main operation period and the stop preparation period are stored, and the operation of the variable throttle mechanism and the drive source is controlled, a flow path area of ​​the discharge flow path is set so that, during the main operation period, the pressure in the receiver tank is reduced to a stable pressure that is a predetermined lower pressure than the unload operation pressure and that enables stable oil supply to the compressor body; a flow path area of ​​the discharge flow path is set so that, during the stop preparation period, the pressure in the receiver tank is reduced to a lower limit stable pressure that is lower than the stable pressure but higher than atmospheric pressure and that does not cause the compressor body to rotate in reverse when the drive source is stopped; Thereafter, the driving source is stopped to terminate the cooling operation.

6. 6. The compressor according to claim 5, wherein the control device, after reducing the pressure in the receiver tank to the stable pressure during the main operation period, controls the variable throttle mechanism so that the flow path area of ​​the discharge flow path is such that the stable pressure is maintained.

7. a pressure detection means for detecting when the pressure in the receiver tank reaches a reference pressure that is lower than the unloading operation pressure and is a predetermined higher pressure than the stable pressure; The control device 6. The compressor according to claim 5, wherein the variable throttle mechanism is controlled so that a pressure drop rate when the pressure in the receiver tank drops from the unload operation pressure to the reference pressure during the main operation period is faster than a pressure drop rate when the pressure drops from the reference pressure to the stable pressure, and the flow path area after the reference pressure is detected is changed relative to a flow path area from the start of the cooling operation until the pressure detecting means detects the reference pressure.

8. 8. The compressor according to claim 5, wherein the variable throttle mechanism is configured to maintain the discharge passage in an open state even after the cooling operation is completed.

9. 8. The compressor according to claim 5, wherein the variable throttle mechanism is composed of a plurality of electromagnetic on-off valves with different drill diameters arranged in parallel in the discharge flow path.

10. the variable throttle mechanism is composed of a plurality of electromagnetic on-off valves with different drill diameters arranged in parallel in the discharge flow path, 9. The compressor according to claim 8, wherein at least one of the electromagnetic on-off valves is a normally open type electromagnetic on-off valve.

11. 8. The compressor according to claim 5, wherein the variable throttle mechanism includes an electro-pneumatic proportional valve.

12. 9. The compressor according to claim 8, wherein the variable throttle mechanism comprises a normally closed electropneumatic proportional valve and a normally open solenoid on-off valve, which are arranged in parallel in the discharge flow passage.

13. 9. A compressor according to claim 8, wherein the variable throttle mechanism is constituted by a normally open electropneumatic proportional valve provided in the discharge flow path.

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