Method of controlling capacity of compressor and capacity control device

Abstract

To reduce power consumption in an unloading operation by alleviating vacuum that is generated in a suction flow passage on the suction valve secondary side such that vacuum generated at the position during an unloaded operation is not excessively alleviated.SOLUTION: A vacuum alleviation circuit 13 that provides communication between a suction-valve secondary-side suction flow passage 42 and a receiver tank 32 is provided, and a vacuum relief valve 14 is provided in the vacuum alleviation circuit 13. During an unloaded operation in which the air intake of a compressor body 20 is blocked, by performing opening and closing operation, preferably opening adjustment, of the vacuum relief valve 14 according to pressure in the suction-valve secondary-side suction flow passage 42 so that the pressure in the suction-valve secondary-side suction flow passage 42 approaches and / or coincides with a prescribed threshold (a proper pressure), only compressed air of a quantity necessary for the pressure in the suction-valve secondary-side suction flow passage to approach and / or coincide with the threshold (the proper pressure) is introduced from the receiver tank 32.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a capacity control method and a capacity control device for a compressor, and more specifically, to a capacity control device equipped with an suction valve that opens and closes an suction passage through which air, which is the gas to be compressed, is introduced into the compressor body, and a control circuit that controls the opening and closing operation of the suction valve, which makes it possible to alleviate the vacuum generated in the suction passage secondary to the suction valve during unloading operation in which the compressor body is operated with the suction valve closed. [Background technology]

[0002] The compressor is usually provided with a capacity control device 510 including a suction valve 511 for opening and closing a suction passage 540 of a compressor body 520 and a control circuit 512 for controlling the opening and closing operation of the suction valve 511 .

[0003] In the capacity control device 510 provided in the compressor 500 shown in FIG. 8, the aforementioned control circuit 512 is composed of a pressure regulator 512a, a flow path 512b communicating between the inlet of the pressure regulator 512a and the receiver tank 532, and a flow path 512c communicating between the outlet of the pressure regulator 512a and the closed-valve pressure receiving chamber of the suction valve 511. When the pressure in the receiver tank 532 rises above the operation start pressure of the pressure regulator 512a, the pressure regulator 512a begins to open and the introduction of compressed air in the receiver tank 532 begins to the closed-valve pressure receiving chamber of the suction valve 511, throttling or closing the suction valve 511. When the pressure in the receiver tank 532 falls below the operation start pressure of the pressure regulator 512a, the pressure regulator 512a closes and the introduction of compressed air to the closed-valve pressure receiving chamber of the suction valve 511 stops, and the suction valve 511 becomes fully open.

[0004] As a result, when the pressure in the receiver tank 532 rises above the pressure at which the pressure regulator 512a is fully opened (the unloaded operation start pressure) as a result of, for example, the consumption of compressed air on the consumption side being stopped, the operation transitions to unloaded operation in which the suction valve 511 is closed and the intake of air by the compressor main body and the generation of compressed air are stopped, and when the consumption of compressed air on the consumption side is resumed as a result and the pressure in the receiver tank 532 falls below the pressure at which the pressure regulator 512a is fully opened (the unloaded operation start pressure), the operation transitions to loaded operation in which the suction valve 511 begins to open and the intake of air by the compressor main body 520 begins to generate compressed air, and the configuration is such that compressed air at a stable pressure can be supplied to the consumption side by generating an amount of compressed air according to the compressed air consumption situation on the consumption side.

[0005] In a compressor 500 equipped with such a capacity control device 510, during unloaded operation, the compressor main body 520 is operated with the suction passage 540 closed by the suction valve 511, so that the degree of vacuum (vacuum level) in the suction passage 542 secondary to the suction valve becomes high.

[0006] When the degree of vacuum in the suction passage 542 on the secondary side of the suction valve increases in this manner, the compressor body 520 begins to generate vibrations and noise that do not occur during loaded operation. Therefore, in order to suppress these vibrations and noise that occur during unloaded operation, it has also been proposed to add a vacuum mitigation circuit to the capacity control device 510 for mitigating the vacuum in the suction passage 542 on the secondary side of the suction valve.

[0007] As such a vacuum relaxation circuit, Patent Document 1, cited below, proposes a vacuum relaxation circuit indicated by reference numeral 513 in FIG.

[0008] This vacuum relief circuit 513 is equipped with a valve 514 that opens and closes using the secondary side pressure of pressure regulator 512a as the operating pressure, a flow path 515 that connects the inlet of valve 514 to receiver tank 532, and a flow path 516 that connects the outlet of valve 514 to suction flow path 542 on the secondary side of the suction valve.When pressure regulator 512a opens, compressed air is introduced into the closed valve pressure chamber of suction valve 511, causing the suction valve 511 to transition to unloaded operation with the closed valve, and the pressure on the secondary side of pressure regulator 512a causes valve 514 to connect flow paths 515, 516 to connect suction flow path 542 on the secondary side of the suction valve with receiver tank 532, thereby relieving the vacuum in suction flow path 542 on the secondary side of the suction valve.

[0009] Furthermore, the capacity control device 510 described in Patent Document 2 listed below is equipped with a vacuum relief circuit 513 composed of a three-way solenoid valve 514', a flow path 515 connecting the three-way solenoid valve 514' and a receiver tank 532, and a flow path 516 connecting the three-way solenoid valve 514' and an intake flow path 542 on the secondary side of the intake valve, as shown in Figure 9. When the intake valve 511 is closed and the operation shifts to unloaded operation, the pressure switch VS outputs a detection signal detecting a drop in pressure in the intake flow path 542 on the secondary side of the intake valve, so that the three-way solenoid valve 514' connects the flow paths 515 and 516 to connect the intake flow path 542 on the secondary side of the intake valve to the receiver tank 532, thereby relieving the vacuum in the intake flow path 542 on the secondary side of the intake valve.

[0010] In addition, in the capacity control device 510 of Patent Document 2, in addition to the above-mentioned vacuum relaxation circuit 513, an automatic relief valve indicated by the symbol 518 is provided, and during unloaded operation, the automatic relief valve 518 is kept open to release the compressed air in the receiver tank 532 to the atmosphere, thereby reducing the back pressure of the compressor main body 520 and reducing the power required during unloaded operation. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 11-101192 [Patent Document 2] Publication No. 5-17435 Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, in the capacity control device 510 equipped with the vacuum relief circuit 513, during unloaded operation, the suction passage 542 on the secondary side of the suction valve is connected to the receiver tank 532, thereby relieving the vacuum in the suction passage 542 on the secondary side of the suction valve, thereby suppressing vibrations and noise generated in the compressor main body 520 during unloaded operation.

[0013] However, in unloaded operation, in which the compressor main body 520 is operated with the suction passage 540 blocked by the suction valve 511, the compressor main body 520 is in an unloaded operating state in which it neither draws in nor compresses air, resulting in an operating state with extremely low power consumption.As described above, during unloaded operation, when compressed air from the receiver tank 532 is introduced into the suction passage 542 on the secondary side of the suction valve, the compressor main body 520 compresses the air introduced from the receiver tank 532.

[0014] As a result, the compressor body 520 is under load even during unloaded operation, increasing the power consumption. Therefore, it is desirable to relax the vacuum in the suction passage 542 on the secondary side of the suction valve during unloaded operation to a pressure (optimum pressure) that can simultaneously suppress vibration and noise and suppress the increase in power consumption. Not only is it unnecessary to relax the vacuum excessively beyond the optimum pressure to an even higher pressure (low vacuum), but such excessive relaxation of the vacuum is actually undesirable since it increases the power consumption of the compressor.

[0015] Incidentally, excessive vacuum relaxation in the suction passage 542 on the secondary side of the suction valve occurs when the receiver tank 532, which is under high internal pressure, is connected to the suction passage 542 on the secondary side of the suction valve. In addition to the vacuum relaxation circuit 513, the capacity control device 510 (see Figure 9) introduced in the above-mentioned Patent Document 2 is provided with an automatic relief valve 518 that releases (purges) the compressed air in the receiver tank 532 during unloaded operation.

[0016] Therefore, during unloading operation, the pressure inside the receiver tank 532 decreases due to the release (purging) of compressed air, so when the release (purging) is completed and the pressure inside the receiver tank 532 stops decreasing, even if the receiver tank 532 is connected to the intake passage 542 on the secondary side of the intake valve, excessive vacuum relaxation of the intake passage 542 on the secondary side of the intake valve will not occur.

[0017] However, since it takes a certain amount of time for the automatic relief valve 518 to complete the air release, the receiver tank 532 is under high pressure from the time of switching to unloaded operation until the air release is completed, and excessive vacuum relaxation is performed on the intake passage 542 secondary to the intake valve, resulting in excess power consumption, and there is still room for improvement.

[0018] In addition, as a method for preventing the vacuum in the intake passage 542 secondary side of the intake valve from being excessively relaxed when connected to the receiver tank 532 under high pressure, it is possible to provide a throttle in the vacuum relaxation circuit 513 to limit the amount of air flowing into the intake passage 542 secondary side of the intake valve.

[0019] However, the pressure in receiver tank 532 when unloaded operation begins differs depending on the specifications of compressor 500, and the amount of air sucked in by compressor main body 520 also changes depending on the specifications of compressor main body 520 and the rotational speed during unloaded operation. Therefore, if a throttle is provided in vacuum relief circuit 513 to bring the pressure in intake passage 542 secondary to the intake valve closer to the appropriate pressure, the throttle used in vacuum relief circuit 513 must be designed specifically for each compressor specification, which is costly.

[0020] Therefore, there is a high demand for a capacity control device equipped with a versatile vacuum relaxation circuit that can be commonly applied to compressors with different specifications.

[0021] Therefore, the present invention has been made to eliminate the drawbacks of the above-mentioned conventional technology, and aims to provide a capacity control method and capacity control device that, while having a relatively simple structure, can suppress both vibration and noise during unloaded operation and the increase in power consumption by preventing the vacuum in the suction flow path secondary to the suction valve from being relaxed more than necessary, while also providing versatility that allows it to be applied to compressors with different specifications. [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 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.

[0023] In order to achieve the above object, the compressor capacity control method of the present invention comprises the steps of: A compressor capacity control method in which an intake passage 40 for introducing compressed air into a compressor body 20 is opened and closed by an intake valve 11 in response to pressure changes in a supply passage 30 provided on the discharge side of the compressor body 20, and the operating state is switched between a loaded operation in which the compressor body 20 is operated with the intake valve 11 open, and an unloaded operation in which the compressor body 20 is operated with the intake valve 11 closed, thereby controlling the pressure of compressed air supplied to the consumer side to approach a predetermined set discharge pressure, A vacuum relief circuit 13 is provided to communicate the suction passage 42 on the secondary side of the suction valve with the supply passage 30, and a vacuum relief valve 14 is provided in the vacuum relief circuit 13 to open and close the vacuum relief circuit 13. This is characterized by the fact that the vacuum relief valve 14 is opened and closed in response to pressure changes in the intake passage 42 secondary to the intake valve so as to bring the pressure in the intake passage 42 secondary to the intake valve close to and / or equal to a predetermined threshold value that is previously set as an appropriate pressure in the unloaded operation state (Claim 1).

[0024] It is preferable that the opening and closing operation of the vacuum relief valve 14 includes an opening adjustment, and the opening adjustment brings the pressure in the intake passage 42 on the secondary side of the intake valve closer to and / or equal to the threshold value (claim 2).

[0025] During the unloading operation, the compressed air in the supply flow passage 30 is released, The threshold value may also be set to a value corresponding to the pressure in the intake passage 42 secondary side of the intake valve when the unloading operation is performed with the supply passage 30 open and the pressure therein has stopped decreasing due to the completion of the air release (Claim 3).

[0026] The vacuum relaxation circuit 13 can be connected to the supply flow passage 30 via a receiver tank 32 provided in the supply flow passage 30 (claim 4).

[0027] a pressure adjusting circuit (17) for introducing compressed air in the supply passage (30) into the closed valve pressure receiving chamber of the intake valve (11) during the load operation; The pressure of the compressed air introduced into the closed-valve pressure chamber 116 of the suction valve 11 can be changed by a regulator 171 provided in the pressure regulating circuit 17, thereby decreasing the opening of the suction valve 11 in response to an increase in pressure in the supply passage 30, and increasing the opening of the suction valve in response to a decrease in pressure in the supply passage 30 (Claim 5).

[0028] In addition, the capacity control device 10 of the present invention has A compressor capacity control device 10 is provided with a suction valve 11 that opens and closes a suction passage 40 that introduces air, which is a gas to be compressed, into a compressor body 20, and a control circuit 12 that opens and closes the suction valve 11 in response to pressure changes in a supply passage 30 provided on the discharge side of the compressor body 20, and controls the pressure of the compressed air supplied to the consumer side to approach a predetermined set discharge pressure by switching the operating state between a load operation in which the compressor body 20 is operated with the suction valve 11 open, and an unload operation in which the compressor body 20 is operated with the suction valve 11 closed. A vacuum relief circuit 13 is provided to communicate the suction passage 42 on the secondary side of the suction valve with the supply passage 30, and a vacuum relief valve 14 is provided in the vacuum relief circuit 13 to open and close the vacuum relief circuit 13. The vacuum relief valve 14 is configured to open and close in response to the pressure in the intake passage 42 secondary to the intake valve so that the pressure in the intake passage 42 secondary to the intake valve approaches and / or matches a predetermined threshold value previously set as an appropriate pressure in the unloaded operation state (Claim 6).

[0029] In the capacity control device 10 having the above configuration, the opening and closing operation of the vacuum relief valve 14 is The opening adjustment may include adjusting the pressure in the intake passage 42 on the secondary side of the intake valve to approach and / or match the threshold value (claim 7).

[0030] The capacity control device 10 may further be provided with an air release circuit 18 for releasing compressed air in the supply passage 30 when in the unloaded operation state, in which case the threshold value may be set to a value corresponding to the pressure in the intake passage 42 secondary to the intake valve when the unloaded operation is performed with the supply passage 30 in communication and the pressure therein no longer decreasing due to completion of the air release (Claim 8).

[0031] The vacuum relaxation circuit 13 may be connected to the supply flow passage 30 via a receiver tank 32 provided in the supply flow passage 30 (claim 9).

[0032] The vacuum relief valve 14 may be an automatic opening / closing valve in which the working pressure chamber 146a is connected to the suction passage 42 on the secondary side of the suction valve and which opens and closes using the pressure in the suction passage 42 on the secondary side of the suction valve as the working pressure (Claim 10).

[0033] The valve box of the vacuum relief valve 14 can be directly attached to the valve box of the suction valve 11, and in this configuration, the working pressure chamber 146a and outlet 142 of the vacuum relief valve 14 can be connected to the suction flow passage 42 on the secondary side of the suction valve via flow passages 147, 148 provided within the wall thickness of the valve box of the suction valve 11 (Claim 11).

[0034] The capacity control device of the present invention may further include a pressure regulating circuit 17 that introduces compressed air in the supply passage into the closed valve pressure chamber of the suction valve 11 during load operation, and the pressure regulating circuit 17 may be provided with a regulator 171 that increases the opening degree in response to an increase in pressure in the supply passage 30 and decreases the opening degree in response to a decrease in pressure in the supply passage 30 (Claim 12). Effect of the Invention

[0035] With the configuration of the present invention as described above, the capacity control method and capacity control device 10 of the present invention can provide the following significant effects.

[0036] In the capacity control method of the present invention, the vacuum relief valve 14 limits the amount of compressed air introduced into the intake passage 42 on the secondary side of the intake valve so as to bring the pressure in the intake passage 42 on the secondary side of the intake valve close to and / or equal to the threshold value (appropriate pressure), thereby preventing the pressure in the intake passage 42 on the secondary side of the intake valve from significantly exceeding the threshold value (appropriate pressure) and being excessively relaxed.

[0037] As a result, it is possible to prevent unnecessary load from being applied to the compressor body 20 during unloaded operation, and to reduce the power consumption during unloaded operation.

[0038] Furthermore, the capacity control device 10 of the present invention, regardless of the specifications of the compressor it is applied to, operates to bring the pressure in the suction passage 42 secondary to the suction valve closer to and / or to the aforementioned threshold pressure (proper pressure), making it versatile and applicable to different models of compressors.Therefore, there is no need to design it specifically for each model, as is the case when a throttle is used to limit the amount of compressed air introduced into the suction passage secondary to the suction valve.

[0039] The operation of the vacuum relief valve 14, which brings the pressure in the intake passage 42 secondary to the intake valve closer to and / or to the threshold value, can involve operation between two positions, open and closed, as well as adjustment of the opening degree.Therefore, by adjusting the vacuum relief valve 14 to an appropriate opening degree in response to changes in pressure in the intake passage 42 secondary to the intake valve, the pressure in the intake passage 42 secondary to the intake valve can be brought closer to or matched to a pressure that is closer to the threshold value (appropriate pressure).

[0040] During unloaded operation, if the compressed air in the supply passage 30 is released and the threshold value is set to a value corresponding to the pressure in the intake passage 42 secondary to the suction valve when the unloaded operation is performed while the supply passage 30 is connected and the pressure has stopped decreasing due to the completion of the air release, not only can the back pressure of the compressor main body 20 be reduced during unloaded operation, thereby further reducing power consumption, but the pressure in the intake passage 42 secondary to the suction valve can be maintained at an approximately constant pressure from the high pressure in the supply passage 30 (in this embodiment, the receiver tank 32) immediately after the start of unloaded operation, to after the air release is completed and the pressure in the supply passage 30 (receiver tank 32) has stopped decreasing and become stable.

[0041] In addition, when the vacuum relief valve 14 is configured as a mechanical automatic opening and closing valve that opens and closes using the pressure in the intake passage 42 on the secondary side of the intake valve as the operating pressure by connecting the working pressure chamber 146a of the vacuum relief valve 14 with the intake passage 42 on the secondary side of the intake valve, it is possible to control the pressure in the intake passage 42 on the secondary side of the intake valve to approach a threshold pressure (proper pressure) simply by providing the above-mentioned vacuum relief valve 14, without performing electrical control, etc.

[0042] Furthermore, by directly attaching the valve box of the vacuum relief valve 14 to the valve box of the suction valve 11 and connecting the working pressure chamber 146a and outlet 142 of the vacuum relief valve 14 to the suction flow passage 42 on the secondary side of the suction valve via flow passages 147, 148 formed within the thickness of the valve box of the suction valve 11, the space required for the placement of the vacuum relief valve 14 can be eliminated and piping space between the suction valve 11 and the vacuum relief valve 14 is no longer necessary, thereby increasing the freedom of layout.

[0043] Furthermore, in a configuration in which a pressure regulating circuit 17 is provided which introduces compressed air in the supply passage 30 into the closed valve pressure chamber 116 of the suction valve 11 during loaded operation, and a regulator 171 is provided in the pressure regulating circuit 17 which opens and closes the pressure regulating circuit 17 and increases its opening in response to an increase in pressure in the supply passage 30 and decreases its opening in response to a decrease in pressure in the supply passage 30, the opening of the suction valve 11 during unloaded operation can be changed linearly in response to the pressure in the supply passage 30, and compressed air of a stable pressure with little change can be supplied to the consumption side, and in the configuration of the present invention, the vacuum relief valve 14 is controlled to open and close based on the pressure in the suction passage 42 secondary to the suction valve, so that even when such a pressure regulating circuit 17 is provided, there is no need to design the vacuum relief valve 14 for each model, and the configuration is versatile. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a circuit diagram of a compressor equipped with a capacity control device according to the present invention (first embodiment). [Diagram 2] FIG. 4 is a cross-sectional view of a suction valve and a vacuum relief valve. [Diagram 3] An enlarged view of the vacuum relief valve part (encircled by dashed line) in Figure 2 (closed state). [Figure 4] An enlarged view of the vacuum relief valve part (encircled by dashed line) in Figure 2 (open state). [Diagram 5] 1 is a time chart showing the changes in each part during unloaded operation when air release (purging) is not performed, where (A) is the present invention and (B) is the conventional technology (corresponding to Patent Document 1). [Figure 6] 1 is a time chart showing the changes in each part during unloaded operation when releasing air (purging), where (A) is the present invention and (B) is the conventional technology (corresponding to Patent Document 2). [Figure 7] FIG. 4 is a circuit diagram of a compressor equipped with another capacity control device of the present invention (Example 2). [Figure 8] FIG. 1 is a circuit diagram of a compressor equipped with a conventional capacity control device (corresponding to Patent Document 1). [Figure 9] FIG. 1 is a circuit diagram of a compressor equipped with a conventional capacity control device (corresponding to Patent Document 2). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0046] [Overall configuration of compressor] FIG. 1 shows the overall configuration of a compressor 1 equipped with a capacity control device 10 of the present invention.

[0047] In FIG. 1, reference numeral 20 denotes a compressor body, and in this embodiment, an oil-cooled screw compressor body is adopted as the compressor body 20.

[0048] This oil-cooled screw compressor body 20 compresses the intake air together with lubricating oil supplied through an oil inlet (not shown), and the lubricating oil lubricates, seals, and cools the compression space.With this configuration, the compressor body 20 discharges compressed air as a gas-liquid mixed fluid with lubricating oil.

[0049] In this manner, in this embodiment, an oil-cooled screw compressor body is adopted as the compressor body 20, so that the compressed air discharged as a gas-liquid mixed fluid with lubricating oil can be separated into gas and liquid, and the compressed air after the lubricating oil has been removed can be supplied to the consumption side. In order to do this, a receiver tank 32 is provided in the supply passage 30 leading from the compressor body 20 to the consumption side, for introducing the compressed air discharged by the compressor body 20 via the discharge passage 31 and separating it into gas and liquid.

[0050] The compressed air from which the lubricating oil has been separated by gas-liquid separation in the receiver tank 32 is configured so that it can be supplied to the consumption side via a consumption flow path 33 that communicates with the receiver tank 32.

[0051] In the embodiment shown in Figure 1, an oil-cooled screw compressor body is used as the compressor body 20, and therefore a configuration is adopted in which a receiver tank 32 is provided in the supply flow path 30.However, if the compressor body 20 discharges compressed air that does not contain oil, such as an oil-free screw compressor that does not require oil to be added to the compression working space, there is no need to provide a receiver tank 32 for gas-liquid separation in the supply flow path 30, and the capacity control device 10 of the present invention can also be used for a compressor 1 that does not have such a receiver tank 32.

[0052] The compressor main body 20 is connected to an intake passage 40 for introducing air, which is the gas to be compressed, into the compressor main body 20, and an air filter 43 is attached to the end of the intake passage 40 opposite the compressor main body 20, so that the air can be introduced into the compressor main body 20 after foreign matter such as dust present in the air has been removed by the air filter 43.

[0053] [Basic configuration of capacity control device] The compressor 1 configured as above is provided with a capacity control device 10 including a suction valve 11 and a control circuit 12 that controls the opening and closing operation of the suction valve 11.

[0054] Of these, the suction valve 11 controls the intake of the compressor body 20 by opening and closing the suction passage 40 .

[0055] An example of the configuration of this suction valve 11 is shown in FIG.

[0056] In the example shown in Figure 2, the aforementioned suction valve 11 and a vacuum relief valve 14 provided in a vacuum relaxation circuit 13 described below are configured as an integrated unit, and in Figure 2, the part surrounded by a dashed line is the vacuum relief valve 14, and the other part is the aforementioned suction valve 11.

[0057] The suction valve 11 shown in Figure 2 has a function as a check valve, and prevents the compressed air being compressed in the compressor main body 20 from flowing back through the suction passage 40 toward the air filter 43 together with the lubricating oil when the compressor main body 20 is stopped, etc., thereby preventing the air filter 43 from being contaminated by the lubricating oil.

[0058] The upper portion of this intake valve 11 is provided with a cylinder chamber 111 and a piston 112 which moves back and forth within the cylinder chamber 111 in the vertical direction of the page, as well as a valve shaft 113 whose upper end is attached to the center of the piston 112 and which moves in the vertical direction together with the piston 112.

[0059] This valve shaft 113 penetrates the lower end wall of the cylinder chamber 111, passes through the center of a valve seat 114 provided below the cylinder chamber 111, and protrudes further downward.The valve body 115 attached to the lower end side of the valve shaft 113 is seated on the valve seat 114 from below, so that the communicating passage formed inside surrounded by the valve seat 114 can be closed.

[0060] A closed-valve pressure chamber 116 of the suction valve 11 is formed between the piston 112 and the lower end wall of the cylinder chamber 111. When compressed air is not being introduced into the closed-valve pressure chamber 116, the piston 112 is pushed down to the lower end position within the cylinder chamber 111 by the biasing force of a piston spring 117, as shown in FIG. 2.

[0061] At this time, the valve body 115 attached to the lower end of the valve shaft 113 is pushed upward by the valve body spring 118 and is seated on the valve seat 114 from below, preventing backflow of fluid. However, the valve body spring 118 seats the valve body 115 on the valve seat 114 with a relatively weak force, so that when the compressor body 20 starts operating and begins to suck in air, creating a vacuum in the suction passage 42 on the secondary side of the suction valve, the valve body 115 moves away from the valve seat 114 against the biasing force of the valve body spring 118, allowing air to be introduced into the compressor body 20. In this state, the suction valve 11 is in an open state.

[0062] On the other hand, when compressed air from the receiver tank 32 is introduced into the closed valve pressure chamber 116 formed between the piston 112 and the lower end wall 111a of the cylinder chamber 111, the piston 112 moves upward within the cylinder chamber 111 against the biasing force of the piston spring 117.

[0063] This movement of the piston 112 causes the valve stem 113 to rise as well, and a stopper 119 attached to the lower end of the valve stem 113 comes into contact with the lower end of the valve body 115 , pressing the valve body 115 firmly against the valve seat 114 .

[0064] As a result, even if the inside of the suction passage 42 on the secondary side of the suction valve 11 becomes a vacuum due to the operation of the compressor body 20, the valve body 115 cannot leave the valve seat 114, and the suction valve 11 is kept in a closed state.

[0065] Returning to Figure 1, the aforementioned control circuit 12 includes a control valve 121, a flow path 122 connecting the control valve 121 and the closed-valve pressure chamber 116 of the suction valve 11, and a flow path 123 connecting the control valve 121 and the supply flow path 30 (in the illustrated example, a receiver tank 32 provided in the supply flow path 30), and is configured so that by connecting or blocking the flow paths 122 and 123 using the control valve 121, it is possible to control the start and stop of the introduction of compressed air in the supply flow path 30 as the operating pressure to the closed-valve pressure chamber 116 of the suction valve 11.

[0066] The control circuit 12 may be connected to the supply passage 30 at any position in the supply passage 30 from the compressor main body 20 to the consumption side, but if the supply passage 30 is equipped with a check valve 33a, it is connected to the primary side of the check valve 33a, and in this embodiment it is connected to a receiver tank 32 provided in the supply passage 30.

[0067] In the illustrated embodiment, the above-mentioned control valve 121 is configured as a solenoid valve, and the operation of this solenoid control valve 121 is controlled by an electronic control device (not shown), such as a microcontroller.

[0068] The control of the solenoid control valve 121 by this electronic control device (not shown) can be, for example, by having the electronic control device (not shown) monitor the pressure in the receiver tank 32 and the pressure in the consumption flow path 33 based on the detection signal of a pressure sensor (not shown) that detects the pressure in the receiver tank 32 and the detection signal of a pressure sensor (not shown) that detects the pressure in the consumption flow path 33 on the secondary side of the check valve 33a, and when the pressure in the receiver tank 32 becomes equal to or higher than a predetermined unload operation start pressure, the electronic control device (not shown) sets the solenoid control valve 121 to the open position to connect the flow paths 122 and 123 to close the suction valve 11, and when the pressure in the consumption flow path 33 drops to a pressure equal to or lower than a predetermined load operation return pressure, the electronic control device (not shown) sets the electronic control valve 121 to the closed position to block the passages 122 and 123, thereby opening the suction valve 11.

[0069] In the illustrated embodiment, a configuration example is shown in which the control valve 121 provided in the control circuit 12 is an electromagnetic control valve (solenoid valve). However, instead of this electromagnetic control valve 121, similar to the configuration of the control circuit 512 of the conventional capacity control device 510 described with reference to Figures 8 and 9, a mechanical pressure regulator 512a may be used to control the start and stop of the introduction of compressed air (operating pressure) to the closed valve pressure chamber 116 of the suction valve 11.

[0070] Also, reference numeral 18 in FIG. 1 denotes an air release circuit, which releases compressed air in the receiver tank 32 to the atmosphere via a throttle 18a during unloading operation when the electromagnetic control valve 121 is open.

[0071] This reduces the back pressure of the compressor body 20, making it possible to keep the power consumed by the operation of the compressor body 20 during unloaded operation low.

[0072] Incidentally, the air release circuit 18 is not an essential component of the capacity control device 10 of the present invention, and may be provided as necessary.

[0073] In addition, in the embodiment shown in Figure 1, a configuration is shown in which a constriction 18a is provided in the air release circuit 18, but this constriction 18a may also be realized by making the pipe diameter of the air release circuit itself thinner, and is not limited to the configuration shown in the figure.

[0074] Furthermore, in the illustrated embodiment, the air release circuit 18 is connected to the intake passage 41 on the primary side of the intake valve, and the compressed air in the receiver tank 32 is released into the atmosphere through the air filter 43, so that the air filter 43 acts as a silencer to reduce the air release noise. However, instead of this configuration, the air release circuit 18 may not be connected to the intake passage 41, and may be directly released into the atmosphere through a silencer or the like (not shown).

[0075] With the capacity control device 10 having the basic structure described above, when the pressure in the receiver tank 32 rises above a specified unloaded operation start pressure due to, for example, the cessation of consumption of compressed air on the consumption side, an electronic control device (not shown) opens the electromagnetic control valve 121 and introduces the compressed air in the receiver tank 32 as operating pressure into the closed valve pressure chamber 116 of the suction valve 11 to close the suction valve 11 and transition to unloaded operation, and at the same time, the compressed air in the receiver tank 32 is gradually released (purged) into the atmosphere via the air release circuit 18 to reduce the back pressure of the compressor main body 20, thereby reducing the power required to operate the compressor main body 20 during unloaded operation.

[0076] On the other hand, the pressure in the consumption flow path 33 secondary to the check valve 33a is maintained at a pressure above the unload operation start pressure by the release (purging) of compressed air in the receiver tank 32. However, when the pressure in the consumption flow path 33 secondary to the check valve 33a drops below a specified load operation return pressure due to, for example, the resumption of consumption of compressed air on the consumption side, an electronic control device (not shown) closes the electromagnetic control valve 121 to stop the release (purging) of compressed air in the receiver tank 32 to the atmosphere, and the introduction of operating pressure to the closed valve pressure chamber 116 of the suction valve 11 stops, causing the suction valve 11 to open and return to load operation.

[0077] [Vacuum relaxation circuit] In addition to the basic structure of the capacity control device 10 described above, the capacity control device 10 of the present invention further includes a vacuum relief circuit 13 for alleviating the vacuum that occurs in the intake passage 42 secondary side of the intake valve during unloaded operation.

[0078] This vacuum relief circuit 13 is provided with a vacuum relief valve 14 that opens and closes in response to pressure changes in the suction passage 42 secondary to the suction valve so that the pressure in the suction passage 42 secondary to the suction valve approaches and / or matches a predetermined threshold value, and is configured by connecting an inlet 141 of the vacuum relief valve 14 to the supply passage 30 on the primary side of the check valve 33a, or in the illustrated embodiment, to the receiver tank 32, and connecting an outlet 142 of the vacuum relief valve 14 to the suction passage 42 secondary to the suction valve.

[0079] The opening and closing operation of this vacuum relief valve 14 may be configured so that the vacuum relief valve 14 can be switched alternatively between two positions, for example, an open position and a closed position; when the pressure in the intake passage 42 on the secondary side of the intake valve 11 drops to a predetermined pressure below the aforementioned threshold value during unloaded operation, the vacuum relief valve 14 opens and compressed air in the receiver tank 32 is introduced into the intake passage 42 on the secondary side of the intake valve 11; when the introduction of this compressed air causes the pressure in the intake passage 42 on the secondary side of the intake valve 11 to rise to a predetermined pressure exceeding the aforementioned threshold value, the vacuum relief valve 14 closes and the introduction of compressed air to the intake passage 42 on the secondary side of the intake valve 11 is stopped; with this configuration, the pressure in the intake passage 42 on the secondary side of the intake valve 11 will vary slightly up and down around the threshold value, but it can be brought close to a pressure near this threshold value.

[0080] Instead of the vacuum relief valve 14 being configured to be switchable between two positions, an open position and a closed position, as described above, it may be configured to have an adjustable opening, increasing the opening in response to a drop in pressure in the intake passage 42 secondary to the intake valve and decreasing the opening in response to an increase in pressure in the intake passage secondary to the intake valve.In this case, the pressure fluctuation in the intake passage 42 secondary to the intake valve can be reduced, making it possible to approach or match a value closer to the threshold value (appropriate pressure).

[0081] In this way, in the configuration of the present invention, the opening and closing operation and change in opening of the vacuum relief valve 14 introduces only the amount of compressed air necessary to bring the pressure in the intake passage 42 secondary to the intake valve close to the aforementioned threshold value.Therefore, by setting the aforementioned "threshold value" to a pressure (appropriate pressure) that can simultaneously suppress the occurrence of vibrations and noise during unloaded operation and suppress the increase in power consumption, it is possible to suppress the increase in power consumption of the compressor main body 20 during unloaded operation while preventing the occurrence of abnormal vibrations and noise caused by the pressure in the intake passage 42 secondary to the intake valve becoming a high vacuum.

[0082] In addition, if the capacity control device 10 is equipped with an air release circuit 18 that releases (purges) the compressed air in the receiver tank 32 during unloaded operation, the aforementioned threshold value can be set to a value corresponding to the pressure in the intake passage 42 secondary to the intake valve when unloaded operation is performed while the receiver tank 32 is in a connected state and the pressure has stopped decreasing due to completion of the air release (purging), so that the pressure in the intake passage 42 secondary to the intake valve during unloaded operation can be maintained approximately constant at the aforementioned threshold pressure from immediately after the start of unloaded operation until after the air release in the receiver tank 32 is completed.

[0083] In addition, the configuration of the aforementioned vacuum relief valve 14 provided in the vacuum relaxation circuit 13 is not particularly limited, and for example, it may be formed by an electromagnetic valve or an electropneumatic valve, and the opening / closing and opening degree of the vacuum relief valve 14 may be controlled based on a detection signal from a pressure sensor that detects the pressure in the intake passage 42 secondary side of the intake valve 11.

[0084] In this embodiment, the aforementioned vacuum relief valve 14 is configured as a mechanical automatic opening and closing valve which opens and closes by introducing operating pressure into an operating pressure chamber 146a provided in the vacuum relief valve 14, and by connecting the operating pressure chamber 146a of this automatic opening and closing valve to the intake passage 42 on the secondary side of the intake valve 11, it is configured so that the opening and closing and the opening degree are automatically adjusted according to pressure changes in the intake passage 42 on the secondary side of the intake valve 11.

[0085] An example of the configuration of such a vacuum relief valve 14 is shown in FIGS.

[0086] In addition, while Figure 1 shows the vacuum relief valve 14 provided in the vacuum relief circuit 13 and the suction valve 11 that opens and closes the suction passage 40 as independent components, the vacuum relief valve 14 provided in the vacuum relief circuit 13 may also be configured as an integral part of the suction valve 11, sharing part of the valve box with the suction valve 11, as shown in Figure 2.

[0087] In the configuration shown in FIG. 2, the portion surrounded by the dashed line in the figure is a component of the vacuum relief valve 14 provided in the vacuum relaxation circuit 13, and the other portions are components of the suction valve 11.

[0088] In the configuration of the vacuum relief valve 14 shown in Figure 2, a valve seat 143 is provided between an inlet 141 connected to the receiver tank 32 and an outlet 142 connected to the suction passage 42 on the secondary side of the suction valve, and a valve body 144 is configured to seat on this valve seat 143 from the left side of the page.

[0089] The valve body 144 is constantly biased in a direction to seat on the valve seat 143 by a valve body spring 144a.

[0090] This valve body 144 is provided with a valve shaft 144b which penetrates a flow passage formed in the center of the valve seat 143 and protrudes to the right side of the paper. A piston 145 whose tip is abutted against this valve shaft 144b and a cylinder chamber 146 which accommodates the piston 145 so that it can move back and forth are provided on the right side of the paper relative to the valve shaft 144b. The part of the cylinder chamber 146 to the left of the part partitioned off by the piston 145 constitutes an operating pressure chamber 146a which introduces an operating pressure for opening and closing the vacuum relief valve 14. This operating pressure chamber 146a is connected to the secondary suction flow passage 42 of the suction valve 11 via a flow passage 147 formed within the thickness of the valve body of the suction valve 11.

[0091] When the pressure in the intake passage 42 on the secondary side of the intake valve is high (the degree of vacuum is low) and the pressure in the working pressure chamber 146a is relatively high (the degree of vacuum is low), the piston 145 described above is biased by the piston spring 145a and moves to the right side of the paper as shown in Figures 2 and 3, and the valve body 144 is maintained seated on the valve seat 143 by the biasing force of the valve body spring 144a. However, when the pressure in the intake passage 42 on the secondary side of the intake valve falls below a predetermined threshold value (proper pressure) and the pressure in the working pressure chamber 146a falls (the degree of vacuum increases), The piston 145 is configured to move to the left side of the paper against the biasing force of the piston spring 145a. As the piston 145 moves leftward on the paper, the tip of the piston 145 pushes the valve stem 144b of the valve body 144 to the left side of the paper, as shown in Figure 4, and the valve body 144 begins to move away from the valve seat 143. The compressed air from the receiver tank 32 introduced from the inlet 141 enters the flow passage 148 on the outlet 142 side through the gap δ generated between the valve body 144 and the valve seat 143, and is introduced into the intake flow passage 42 on the secondary side of the intake valve 11 via the outlet 142.

[0092] On the other hand, when compressed air is introduced into the intake passage 42 on the secondary side of the intake valve 11 in this manner, and the pressure in the intake passage 42 on the secondary side of the intake valve 11 rises above a threshold value (proper pressure), the pressure in the working pressure chamber 146a increases, causing the piston 145, which was pushing the valve shaft 144b to the left side of the paper, to move to the right side of the paper due to the biasing force of the piston spring 145a, and the valve body 144 seats on the valve seat 143, and the introduction of compressed air into the intake passage 42 on the secondary side of the intake valve 11 is stopped.

[0093] In addition, in the vacuum relief valve 14 shown in Figures 2 to 4, due to the configuration described above, when the pressure in the intake passage 42 secondary to the intake valve, which is connected to the working pressure chamber 146a, drops to a predetermined pressure below the threshold value, the opening degree increases as the pressure further drops, and the opening degree decreases as the pressure in the intake passage 42 secondary to the intake valve increases, and the valve closes at a predetermined pressure that exceeds the aforementioned threshold value.

[0094] [Effect, etc.] (1) Purging during unloaded operation The capacity control device 10 of the compressor 1 described with reference to Figure 1 is provided with an air release circuit 18. However, as described above, the air release circuit 18 is not a required component in the capacity control device 10 of the present invention. Therefore, in the operation explanation given below with reference to Figure 5, the operation when air release (purging) is not performed during unloaded operation will be explained, and the configuration for performing air release (purging) during unloaded operation will be explained later with reference to Figure 6.

[0095] As shown in the time chart of Figure 5 (A), when the pressure in the receiver tank 32 rises above the unloading operation start pressure due to, for example, the cessation of consumption of compressed air on the consumption side, the electromagnetic control valve 121 opens, the compressed air in the receiver tank 32 is introduced into the closed valve pressure chamber 116 of the suction valve 11, the suction valve 11 closes, and the system transitions to unloading operation.

[0096] When the suction valve 11 closes and the system transitions to unloaded operation, the vacuum in the suction passage 42 secondary to the suction valve increases to a predetermined pressure below a threshold value, and the vacuum relief valve 14 provided in the vacuum relief circuit 13 opens to an opening degree corresponding to the pressure in the suction passage 42 secondary to the suction valve, and the compressed air in the receiver tank 32 is introduced into the suction passage 42 secondary to the suction valve.

[0097] During unloading operation, the vacuum relief valve 14 is adjusted to an opening degree corresponding to the pressure in the intake passage 42 secondary to the intake valve, thereby controlling the pressure in the intake passage 42 secondary to the intake valve to approach and / or match the threshold pressure.

[0098] In Figure 5 (A), an example of a configuration is shown in which the vacuum relief valve 14 is configured to perform opening and closing operations with adjustment of the opening degree in response to pressure changes in the intake passage 42 secondary to the intake valve, as explained with reference to Figures 2 to 4, thereby making it possible to bring the pressure in the intake passage 42 secondary to the intake valve closer to and / or to match the threshold pressure.However, the configuration of the vacuum relief valve 14 is not limited to this configuration, and it may also be, for example, an electromagnetic opening / closing valve that selectively switches between two positions, an open position and a closed position.

[0099] In addition, as explained with reference to Figure 5 (A), if a vacuum relief valve 14 is adopted that adjusts its opening in response to pressure changes in the suction passage 42 secondary to the suction valve, once the vacuum relief valve 14 opens, during unloaded operation, the vacuum relief valve 14 may only adjust its opening without becoming fully open or fully closed. However, the "opening and closing operation" of the vacuum relief valve 14 in the capacity control method of the present invention may also include such "opening adjustment" that does not become fully open or fully closed during unloaded operation.

[0100] In this way, in the capacity control device 10 of the present invention, the vacuum relief valve 14 controls the opening degree in accordance with the pressure in the intake passage 42 secondary to the intake valve so as to bring the pressure in the intake passage 42 secondary to the intake valve closer to and / or equal to the above-mentioned threshold value. Therefore, even if the capacity control device 10 does not have an air release circuit 18 and the receiver tank 32 is maintained at a high pressure even during unloaded operation as shown in Figure 5(A), the pressure in the intake passage 42 secondary to the intake valve can be brought closer to and / or equal to the threshold value, which is the appropriate pressure.

[0101] On the other hand, in the configuration of the conventional capacity control device 510 previously introduced in Patent Document 1 (see Figure 8), during unloading operation, the suction passage 542 secondary to the suction valve 511 is maintained in communication with the receiver tank 532, so that compressed air is continuously introduced from the receiver tank 532 to the suction passage 542 secondary to the suction valve.

[0102] The automatic relief valve 519 is provided in the circuit configuration of Patent Document 1 and releases the compressed air in the receiver tank 532 when the compressor 500 is stopped (Patent Document 1

[0025] ). Since the compressed air in the receiver tank 532 is not released during unloaded operation, the pressure in the receiver tank 532 is maintained at a high pressure even after switching to unloaded operation.

[0103] As a result, in the circuit configuration of Patent Document 1, unless the amount of compressed air introduced into the intake passage 542 on the secondary side of the intake valve 511 is appropriately restricted by, for example, providing a specially designed throttle in the vacuum relaxation circuit 513, during unloading operation, the pressure inside the intake passage 542 on the secondary side of the intake valve will be maintained at a pressure significantly higher than the appropriate pressure by the introduction of compressed air from the receiver tank 532, as shown in the time chart of Figure 5 (B).

[0104] As a result, during unloaded operation, the compressor main body 520 compresses a large amount of air corresponding to the pressure difference with respect to the appropriate pressure, and the power consumed by the operation of the compressor main body 520 during unloaded operation increases accordingly.

[0105] Specifically, the power of the portion shown by hatching in FIG. 5(B) is consumed in excess as compared to the case where the capacity control of the present invention is performed.

[0106] (2) Purging during unloading The explanation with reference to Figures 5(A) and (B) is based on the assumption that the compressed air in the receiver tank is not released (purged) during unloaded operation, and therefore high pressure is maintained in the receiver tank 32 even after transition to unloaded operation.

[0107] In contrast to this, the operation of the capacity control device 10 when it is provided with a configuration for releasing the compressed air in the receiver tank during unloading operation will be described with reference to Figs. 6(A) and (B).

[0108] In the capacity control device 10 of the present invention, even when a configuration is adopted in which compressed air in the receiver tank 32 is released during unloading operation, the pressure in the intake passage 42 secondary to the intake valve is brought close to and / or equal to a threshold value (proper pressure), similar to the capacity control device 10 not provided with the air release circuit 18 described with reference to Figure 5 (A).

[0109] In the following embodiment described with reference to Figure 6(A), the vacuum relief valve 14 is configured so that its opening changes in response to pressure changes in the intake passage 42 secondary to the intake valve, as described with reference to Figure 5(A), but instead of this configuration, a vacuum relief valve 14 may be used that is switchable between two positions, an open position and a closed position, like an electromagnetic opening / closing valve, and the pressure in the intake passage 42 secondary to the intake valve may be controlled to approach a pressure near a threshold value by opening and closing the vacuum relief valve 14.

[0110] In this embodiment, which employs a vacuum relief valve 14 configured to change its opening in response to pressure changes in the intake passage 42 secondary to the intake valve, when the intake valve 11 closes and the system transitions to unloaded operation, the vacuum in the intake passage 42 secondary to the intake valve increases and reaches a predetermined pressure below a threshold value, the vacuum relief valve 14 provided in the vacuum relief circuit 13 opens to an opening corresponding to the pressure in the intake passage 42 secondary to the intake valve, and the compressed air in the receiver tank 32 is introduced into the intake passage 42 secondary to the intake valve.

[0111] As shown in Figure 6(A), the vacuum relief valve 14 can open to an opening corresponding to the pressure in the intake passage 42 secondary to the intake valve, thereby making the pressure in the intake passage 42 secondary to the intake valve approach and / or match the threshold pressure.

[0112] In addition, in the capacity control device 10 equipped with the air release circuit 18, during unloaded operation, the pressure in the receiver tank 32 decreases over time due to air release (purging) by the air release circuit 18, so as shown in Figure 6 (A), the vacuum relief valve 14 increases its opening over time to bring the pressure in the intake passage 42 secondary to the intake valve closer to and / or equal to the threshold pressure, and when the air release is completed and the pressure in the receiver tank 32 stops decreasing, it opens fully, and the vacuum relief valve 14 is maintained in the fully open state until load operation is resumed.

[0113] On the other hand, even if the configuration is such that the suction passage 542 on the secondary side of the suction valve is kept connected to the receiver tank 532 during unloaded operation, as in the conventional technology introduced in Patent Document 2 above (see Figure 9), in which the compressed air in the receiver tank 532 is released during unloaded operation, after the pressure in the receiver tank 532 stops decreasing as shown in Figure 6 (B), the amount of air introduced into the suction passage 542 on the secondary side of the suction valve becomes minimal, and vacuum relaxation is achieved at an appropriate pressure.

[0114] However, since it takes some time from when the compressed air in the receiver tank 532 starts to be released until the pressure in the receiver tank 532 stops decreasing and stabilizes, during this period the intake passage 542 on the secondary side of the intake valve still communicates with the receiver tank 532 which is in a high-pressure state, and so the pressure becomes higher than the appropriate pressure.

[0115] As a result, from the time of transition to unloaded operation until the completion of the release of compressed air in the receiver tank 532, the compressor main body 520 is still operated under a load higher than necessary, and extra power is consumed in the shaded area in Figure 6(B) compared to the case where the capacity control of the present application is performed, which can maintain the pressure in the suction passage 542 secondary side of the suction valve at a pressure close to the threshold value (proper pressure) from the initial start of unloaded operation.

[0116] [Example of change] FIG. 7 shows a configuration example of a capacity control device 10 according to a modified embodiment of the present invention.

[0117] The embodiment shown in Figure 7 differs from the configuration of the capacity control device 10 described with reference to Figure 1 in that a pressure regulating circuit 17 is provided in the control flow path 122 on the secondary side of the solenoid control valve 121, which adjusts the pressure of compressed air from the receiver tank 32 using a regulator 171 and introduces it into the control flow path 122.

[0118] In addition, the capacity control device 10 shown in FIG. 7 is configured so that the compressed air introduced into the secondary side of the electromagnetic control valve 121 via the pressure regulating circuit 17 is not released via the air release circuit 18.

[0119] As an example of the regulator 171 provided in the pressure regulating circuit 17, an electro-pneumatic regulator can be used, and based on the pressure change in the receiver tank 32 detected by a pressure sensor (not shown), the opening of the electro-pneumatic regulator 171 is increased as the pressure in the receiver tank 32 increases, and the opening of the electro-pneumatic regulator 171 is controlled to decrease as the pressure in the receiver tank 32 decreases, thereby changing the pressure of the compressed air introduced into the closed valve pressure chamber 116 of the suction valve 11 within a range below the pressure at which the suction valve 11 is fully closed.

[0120] As a result, when the pressure in the receiver tank 32 is below the unload operation start pressure and the solenoid control valve 121 is in a state where the control passage 12 is closed, i.e., even during load operation, compressed air whose pressure has been adjusted by the regulator 171 is introduced into the closed valve pressure chamber 116 of the suction valve 11 via the pressure regulating circuit 17.

[0121] This enables control to be performed in response to pressure changes within the receiver tank 32, and therefore changes in the consumption of compressed air on the consumption side, by linearly narrowing the suction valve 11 as the pressure within the receiver tank 32 increases (decreasing consumption of compressed air) to reduce the amount of compressed air generated, and by linearly increasing the opening of the suction valve 11 as the pressure within the receiver tank 32 decreases (increasing consumption of compressed air) to increase the amount of compressed air generated.

[0122] When the pressure in the receiver tank 32 rises above a specified unloading operation start pressure, the electromagnetic control valve 121 opens and compressed air of a pressure higher than that which fully closes the suction valve 11 is introduced from the receiver tank 32 via the control passage 12, causing the suction valve 11 to fully close, and the system is configured to transition to unloading operation.

[0123] In the capacity control device 10 configured as described above, the vacuum relief valve 14 that opens and closes the vacuum relaxation circuit 13 is operated based on the pressure (vacuum) in the intake passage 42 secondary to the intake valve, so that vacuum relaxation is performed to bring the pressure in the intake passage 42 secondary to the intake valve close to a threshold value (proper pressure), and excessive vacuum relaxation is prevented.

[0124] Furthermore, in the configuration of the present invention, the aforementioned threshold value (appropriate pressure) which serves as the basis for the opening and closing operation of the vacuum relief valve 14 is a pressure corresponding to the vacuum generated in the intake passage 42 secondary to the intake valve during unloaded operation, so even if the intake valve is throttled and the pressure in the intake passage 42 secondary to the intake valve drops during loaded operation, the pressure in the intake passage 42 secondary to the intake valve does not drop below the threshold value.As a result, even if a pressure regulating circuit 17 is added to the capacity control device 10 without adjusting the setting of the vacuum relief valve 14, the vacuum relief valve 14 will not open during loaded operation and the compressed air in the receiver tank 32 will not be introduced into the intake passage 42 secondary to the intake valve.

[0125] Furthermore, although the unload operation starting pressure and the pressure range of the compressed air introduced through the pressure regulating circuit 17 differ depending on the model of compressor, the vacuum relief valve 14 in the capacity control device 10 shown in Figure 7 also operates based on the pressure (vacuum) in the suction passage 42 secondary to the suction valve, so there is no need to change the settings of the vacuum relief valve 14 even in capacity control devices 10 equipped with compressors 1 of different models and therefore regulators 171 with different pressure adjustment ranges.

[0126] In contrast, in the case of a capacity control device 510 in which the valve 514 provided in the vacuum relief circuit 513 is operated by the secondary pressure of the pressure regulator 512a as explained with reference to Figure 8, if the pressure regulating circuit 17 shown in Figure 7 is added to this capacity control device 510, even during load operation when the pressure regulator 512a is in a closed state, the valve 514 provided in the vacuum relief circuit 513 may be opened by compressed air from the regulator 171, and compressed air from the receiver tank 532 may be introduced into the intake passage 542 on the secondary side of the intake valve.

[0127] Even when the pressure regulating circuit 17 shown in FIG. 7 is provided in the configuration of the capacity control device 510 in FIG. 8, in order to prevent the valve 514 of the vacuum relaxation circuit 513 from operating during load operation, it is necessary to set the operating pressure of the valve 514 to a value equal to or higher than the maximum value of the secondary side pressure of the regulator 171 and equal to or lower than the secondary side pressure of the pressure regulator 512a when the valve is open.

[0128] In this case, the secondary side pressure of regulator 171 and the secondary side pressure of pressure regulator 512a when the valve is open differ depending on the specifications of compressor 1, so if the pressure regulating circuit 17 shown in Figure 7 is added to the configuration of the conventional capacity control device 510 shown in Figure 8, it is necessary to design valve 514 specifically for each model of compressor, and it is not possible to provide a capacity control device that is versatile enough to be applied to different models of compressors like the present invention. [Explanation of symbols]

[0129] 1 Compressor 10 Capacity control device 11 Intake valve 111 Cylinder chamber 112 Piston 113 Valve stem 114 Valve seat 115 Valve body 116 Closed valve pressure chamber 117 Piston spring 118 Valve body spring 119 Stopper 12 Control circuit 121 Solenoid control valve 122 Flow path (between solenoid control valve and suction valve) 123 Flow path (between solenoid control valve and receiver tank) 13 Vacuum relaxation circuit 14 (Automatic) Vacuum Relief Valve 141 Entrance 142 Exit 143 Valve seat 144 Valve body 144a Valve body spring 144b Valve stem 145 Piston 145a Piston spring 146 Cylinder chamber 146a Working pressure chamber 146b Space 147,148 Channels 17 Pressure Regulating Circuit 171 Regulator (electro-pneumatic regulator) 18 Ventilation circuit 18a Aperture 20 Compressor body 30 Supply Channel 31 Discharge flow path 32 Receiver tank 33 Consumption flow path 33a Check valve 40 Suction channel 41 Intake passage on the primary side of the suction valve 42 Suction passage on the secondary side of the suction valve 43 Air Filter 500 Compressor 510 Capacity Control Device 511 Intake valve 512 Control circuit 512a Pressure Regulator 512b, 512c Channel 513 Vacuum relaxation circuit 514 Valve 514' Three-way solenoid valve 515,516 Flow path 518,519 Automatic relief valve 520 Compressor body 521 Intake port 530 Supply Channel 532 Receiver Tank 533 Consumption flow path 540 Suction flow path 541 Intake passage on the primary side of the suction valve 542 Suction passage on the secondary side of the suction valve VS Pressure Switch

Claims

1. A compressor capacity control method in which an intake passage for introducing compressed air into a compressor body is opened and closed by an intake valve in response to a pressure change in a supply passage provided on the discharge side of the compressor body, and an operating state is switched between a loaded operation in which the compressor body is operated with the intake valve open and an unloaded operation in which the compressor body is operated with the intake valve closed, thereby controlling the pressure of compressed air supplied to a consumer side to approach a predetermined set discharge pressure, a vacuum relief circuit is provided which communicates the suction passage on the secondary side of the suction valve with the supply passage, and a vacuum relief valve is provided in the vacuum relief circuit for opening and closing the vacuum relief circuit; A compressor capacity control method comprising the steps of: opening and closing the vacuum relief valve in response to pressure changes in the intake passage on the secondary side of the intake valve so as to bring the pressure in the intake passage on the secondary side of the intake valve close to and / or equal to a predetermined threshold value previously set as an appropriate pressure in the unloaded operation state.

2. 2. The compressor capacity control method according to claim 1, wherein the opening and closing operation of the vacuum relief valve includes adjusting an opening degree, and the pressure in the intake passage on the secondary side of the intake valve is brought closer to and / or equal to the threshold value by adjusting the opening degree.

3. When the compressor is in the unloaded operation state, the compressed air in the supply flow path is released, A compressor capacity control method according to claim 1 or 2, characterized in that the threshold value is set to a value corresponding to the pressure in the suction passage secondary side of the suction valve when the unloading operation is performed with the supply passage open and the pressure therein has stopped decreasing due to the completion of the air release.

4. 3. A method for controlling a capacity of a compressor according to claim 1, wherein the vacuum relaxation circuit is connected to the supply passage through a receiver tank provided in the supply passage.

5. a pressure adjusting circuit for introducing compressed air in the supply passage into a closed valve pressure receiving chamber of the suction valve during the load operation; 3. A compressor capacity control method according to claim 1, wherein a regulator provided in the pressure regulating circuit changes the pressure of the compressed air introduced into the closed valve pressure chamber of the suction valve, thereby decreasing the opening of the suction valve in response to an increase in pressure in the supply flow path and increasing the opening of the suction valve in response to a decrease in pressure in the supply flow path.

6. A compressor capacity control device 10 includes a suction valve that opens and closes a suction passage that introduces air, which is a gas to be compressed, into a compressor body, and a control circuit that opens and closes the suction valve in response to pressure changes in a supply passage provided on the discharge side of the compressor body, and controls the pressure of compressed air supplied to the consumer side to approach a predetermined set discharge pressure by switching the operating state between a loaded operation in which the compressor body is operated with the suction valve open and an unloaded operation in which the compressor body is operated with the suction valve closed. a vacuum relief circuit is provided which communicates the suction passage on the secondary side of the suction valve with the supply passage, and a vacuum relief valve is provided in the vacuum relief circuit for opening and closing the vacuum relief circuit; a pressure relief valve configured to open and close in response to the pressure in the suction passage secondary to the suction valve so that the pressure in the suction passage secondary to the suction valve approaches and / or coincides with a predetermined threshold value that is preset as an appropriate pressure in the unloaded operation state.

7. The opening and closing operation of the vacuum relief valve 7. The compressor capacity control device according to claim 6, further comprising an opening adjustment for adjusting the pressure in the suction passage on the secondary side of the suction valve to approach and / or match the threshold value.

8. The present invention further provides an air release circuit for releasing compressed air from the supply flow path when the engine is in the unloaded operation state, A compressor capacity control device as described in claim 6 or 7, characterized in that the threshold value is set to a value corresponding to the pressure in the suction passage secondary side of the suction valve when the unloading operation is performed with the supply passage open in a state in which the pressure has stopped decreasing due to the completion of the air release.

9. 8. A capacity control device for a compressor according to claim 6, wherein the vacuum relaxation circuit is connected to the supply passage through a receiver tank provided in the supply passage.

10. 8. A compressor capacity control device according to claim 6, wherein the vacuum relief valve is an automatic on-off valve whose working pressure chamber is connected to the suction passage on the secondary side of the suction valve and which opens and closes using the pressure in the suction passage on the secondary side of the suction valve as its working pressure.

11. The valve body of the vacuum relief valve is directly attached to the valve body of the suction valve, 11. A compressor capacity control device according to claim 10, wherein the working pressure chamber and the outlet of the vacuum relief valve are connected to a suction flow passage on the secondary side of the suction valve via a flow passage provided within the wall thickness of the valve body of the suction valve.

12. a pressure adjusting circuit for introducing compressed air in the supply flow passage into a closed valve pressure receiving chamber of the suction valve during the load operation; 8. A compressor capacity control device according to claim 6, further comprising a regulator in the pressure regulating circuit, the regulator increasing its opening in response to a pressure increase in the supply passage and decreasing its opening in response to a pressure decrease in the supply passage.

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