Relief Valve

Abstract

To stabilize an operation of a relief valve.SOLUTION: A relief valve 100 comprises a pilot passage 10 arranged at a main poppet 5, and facing a high-pressure passage H and a backpressure chamber 8, a first passage 11 arranged in a sleeve 7 so as to make a drain chamber 12 and the backpressure chamber 8 communicate with each other, and a second passage 13 in which a throttle 13a is arranged. The second passage 13 makes the pilot passage 10 and the backpressure chamber 8 communicate with each other, the main poppet 5 has a main body part 50 which is separated from and seated on a suction poppet 3, and a pilot piston 51 slidably arranged in a slide hole 50a which is formed at the main body part 50, and separated from and seated on the main body part 50. The pilot passage 10 makes the backpressure chamber 8 and the first passage 11 communicate with each other, and the pilot piston 51 is separated from the main body part 50 according to the pressure of the high-pressure passage H, moves toward the sleeve 7, and throttles a flow of a working fluid introduced into the first passage 11 from the backpressure chamber 8 through a clearance between the pilot piston 51 and the sleeve 7.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a relief valve. [Background technology]

[0002] Patent Document 1 discloses a relief valve including: a suction poppet that is provided in a valve case and that allows working fluid to flow from a low pressure passage to a high pressure passage in an open state where it is lifted off a first seat provided on an equipment body, and that blocks communication between the high pressure passage and the low pressure passage in a closed state where it is seated on the first seat; a main poppet that is provided within the suction poppet and that allows working fluid to flow from the high pressure passage to the low pressure passage in an open state where it is lifted off a second seat provided on the suction poppet, and that blocks communication between the high pressure passage and the low pressure passage in a closed state where it is seated on the second seat; a guide plug that defines a back pressure chamber between the suction poppet and the main poppet; and a pilot poppet that is provided in the main poppet and that opens and closes a pilot passage that communicates between the high pressure passage and the back pressure chamber, and a passage that communicates between the back pressure chamber and a drain chamber provided in the guide plug.

[0003] In the relief valve described in Patent Document 1, hydraulic oil in the high-pressure passage is guided to the back-pressure chamber through a throttle in the pilot passage, and a pressure difference corresponding to the throttle is generated between the back-pressure chamber and the high-pressure passage. When the pressure difference between the high-pressure passage and the back-pressure chamber increases, the pilot piston moves against the biasing force of the spring. When the pressure difference between the high-pressure passage and the back-pressure chamber further increases, the main poppet lifts off the suction poppet and opens. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-158099 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the relief valve described in Patent Document 1, hydraulic oil in the back pressure chamber flows out to the drain chamber through a drain passage communicating with the back pressure chamber. If the opening area between the back pressure chamber and the drain chamber is large, hydraulic oil is likely to flow out of the back pressure chamber, and the pressure in the back pressure chamber is likely to drop significantly. Since the main poppet moves due to the pressure difference between the high pressure passage and the back pressure chamber, if the pressure in the back pressure chamber is likely to drop significantly, the position of the main poppet is likely to fluctuate significantly, which may adversely affect the operation of the relief valve.

[0006] The present invention has been made in consideration of the above problems, and has an object to stabilize the operation of a relief valve. [Means for solving the problem]

[0007] The present invention is a relief valve comprising a valve housing attached to an equipment body in which a high pressure passage and a low pressure passage are provided, a suction poppet provided within the valve housing and configured to allow a flow of working fluid between the high pressure passage and the low pressure passage by lifting off and seating on the equipment body, a main poppet provided within the suction poppet and configured to communicate and block the flow of working fluid between the high pressure passage and the low pressure passage by lifting off and seating on the suction poppet, a sleeve within the suction poppet that defines a back pressure chamber between the main poppet and the sleeve, and a valve seat provided on the main poppet that faces the high pressure passage and the back pressure chamber. a pilot passage, a drain chamber provided in the sleeve through which the working fluid in the back pressure chamber is discharged, a first passage provided in the sleeve so as to communicate the drain chamber with the back pressure chamber, and a second passage configured to communicate the pilot passage or the first passage with the back pressure chamber and provided with a throttle for providing resistance to the working fluid passing therethrough, the main poppet has a body portion which is lifted off and seated on the suction poppet, and a pilot piston which is slidably provided in a slide hole provided in the body portion and lifted off and seated on the body portion, the pilot passage opens into an end face of a tip portion of the pilot piston which faces the sleeve, The pilot piston has a tapered portion that seats on a seat portion provided on the sleeve, The pilot piston is lifted off the main body and moves toward the sleeve in response to the pressure in the high-pressure passage. Tapered part ofand sleeve Seat section Between A gap is formed to throttle the flow of the working fluid, and the first passage communicates with the back pressure chamber through the gap. It is characterized by:

[0008] In this invention, when the pilot piston leaves the main body and moves toward the sleeve, the gap between the pilot piston and the sleeve becomes smaller, making it difficult for the working fluid to be guided from the back pressure chamber to the first passage through the gap between the pilot piston and the sleeve. As a result, the working fluid in the back pressure chamber is guided to the pilot passage through the second passage and flows out from the opening at the tip of the pilot piston to the first passage. The throttling of the second passage provides resistance to the working fluid flowing from the back pressure chamber to the first passage through the second passage, so that a pressure drop in the back pressure chamber is suppressed. This makes it possible to suppress large fluctuations in the position of the main poppet.

[0009] In addition, the present invention is characterized in that the pilot passage has a first pilot passage provided in the pilot piston and facing the high pressure passage, and a second pilot passage provided in the pilot piston and facing the back pressure chamber, and the second passage is a communication hole that opens to an outer peripheral surface of the pilot piston and communicates between the second pilot passage and the back pressure chamber.

[0010] In addition, the present invention is characterized in that the pilot passage includes a first pilot passage provided in the pilot piston and facing the high pressure passage, a second pilot passage provided in the pilot piston and facing the back pressure chamber, and a third pilot passage communicating with the first pilot passage and the second pilot passage and formed by an outer peripheral surface of the pilot piston and a slide hole in the main body, and the second passage is provided in the outer peripheral surface of the pilot piston and communicates between the third pilot passage and the back pressure chamber.

[0011] In these inventions, the second passage provides resistance to the working fluid flowing out of the back pressure chamber, reducing the amount of working fluid flowing out of the back pressure chamber and preventing a large drop in pressure in the back pressure chamber, thereby preventing the main poppet from fluctuating greatly in position.

[0012] The present invention also relates to , PaWhen the tapered portion of the pilot piston is seated on the seat portion of the sleeve, the flow of working fluid guided from the back pressure chamber through the gap between the tapered portion and the seat portion to the first passage is blocked.

[0013] In this invention, when the tapered portion of the pilot piston is seated on the seat portion of the sleeve, the working fluid flows out of the back pressure chamber only through the second passage, which further suppresses large fluctuations in the pressure in the back pressure chamber and the position of the main poppet, making the operation of the relief valve more stable.

[0014] In addition, the present invention is characterized in that the second passage is a groove provided in a tapered portion of the pilot piston, and when the tapered portion of the pilot piston is seated on a seat portion of the sleeve, the working fluid is guided from the back pressure chamber through the groove to the first passage.

[0016] this In the present invention, the second passage provides resistance to the working fluid flowing out of the back pressure chamber, reducing the amount of working fluid flowing out of the back pressure chamber and preventing a large drop in pressure in the back pressure chamber, thereby preventing the main poppet from fluctuating greatly in position. Effect of the Invention

[0017] According to the present invention, the operation of the relief valve is stabilized. [Brief description of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of an electromagnetic relief valve according to an embodiment of the present invention. FIG. [Diagram 2] 4 is a cross-sectional view of the electromagnetic relief valve according to the embodiment of the present invention in a state where a pilot piston is lifted off a main body portion. FIG. [Diagram 3] 1 is a cross-sectional view of an electromagnetic relief valve according to an embodiment of the present invention in a state where a main poppet is open. [Figure 4] 1 is a cross-sectional view of an electromagnetic relief valve according to an embodiment of the present invention, showing a state in which a pilot piston is seated on a sleeve. FIG. [Diagram 5] FIG. 4 is a cross-sectional view showing a first modified example of an electromagnetic relief valve according to an embodiment of the present invention. [Figure 6] FIG. 4 is a cross-sectional view showing a second modified example of the electromagnetic relief valve according to the embodiment of the present invention. [Figure 7A] FIG. 11 is a cross-sectional view showing a third modified example of the electromagnetic relief valve according to the embodiment of the present invention. [Figure 7B] FIG. 7B is a cross-sectional view of the pilot piston taken along line AA in FIG. 7A. [Figure 8A] FIG. 11 is a cross-sectional view showing a fourth modified example of the electromagnetic relief valve according to the embodiment of the present invention. [Figure 8B] FIG. 8B is a cross-sectional view of the pilot piston taken along line BB in FIG. 8A. [Figure 9] FIG. 11 is a cross-sectional view showing a fifth modified example of the electromagnetic relief valve according to the embodiment of the present invention. [Figure 10] FIG. 11 is a sectional view (part 1) showing a sixth modified example of the electromagnetic relief valve according to the embodiment of the present invention. [Figure 11] FIG. 13 is a second cross-sectional view showing a sixth modified example of the electromagnetic relief valve according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A relief valve according to an embodiment of the present invention will be described with reference to the drawings. In the following, a case in which the relief valve is an electromagnetic relief valve 100 having a solenoid portion 70 will be described.

[0020] The electromagnetic relief valve 100 opens when the pressure of the hydraulic oil in the high-pressure passage H reaches a set pressure, and releases the hydraulic oil from the high-pressure passage H to the low-pressure passage L, thereby preventing the pressure of the hydraulic oil in the high-pressure passage H from becoming abnormally high. The electromagnetic relief valve 100 is provided with a solenoid unit 70, which can change the set pressure. The electromagnetic relief valve 100 also has an anti-void function, and opens when the high-pressure passage H becomes negative pressure, and supplies the hydraulic oil from the low-pressure passage L to the high-pressure passage H, thereby preventing the occurrence of cavitation. In this embodiment, hydraulic oil is used as the hydraulic fluid, but other fluids such as hydraulic water or compressed air may be used.

[0021] The electromagnetic relief valve 100 is attached to an equipment body 1 by screw fastening. The equipment body 1 is the main body of a hydraulic device such as a hydraulic cylinder, a hydraulic pump, a hydraulic motor, or a valve block having a plurality of valves. A high pressure passage H and a low pressure passage L are provided in the equipment body 1 with the electromagnetic relief valve 100 as a boundary. The equipment body 1 is provided with a seat portion 1a between the high pressure passage H and the low pressure passage L on which a suction poppet 3, which will be described later, sits. Note that the equipment body 1 is not limited to the main body of the hydraulic device, and may be a block body installed between each hydraulic device.

[0022] As shown in FIG. 1, the electromagnetic relief valve 100 includes a valve housing 2 attached to an equipment body 1 in which a high pressure passage H and a low pressure passage L are provided, a suction poppet 3 provided within the valve housing 2 and configured to allow a flow of hydraulic oil as a working fluid between the high pressure passage H and the low pressure passage L by lifting off and seating on the equipment body 1, and a main valve 3 provided within the suction poppet 3 and configured to communicate and block the flow of hydraulic oil between the high pressure passage H and the low pressure passage L by lifting off and seating on the suction poppet 3. The electromagnetic relief valve 100 includes a poppet 5, a sleeve 7 that defines a back pressure chamber 8 between the main poppet 5 and the suction poppet 3, a pilot passage 10 provided in the main poppet 5 and facing the high pressure passage H and the back pressure chamber 8, a drain chamber 12 provided in the sleeve 7 to drain the hydraulic oil in the back pressure chamber 8, a first passage 11 provided in the sleeve 7 to communicate the drain chamber 12 with the back pressure chamber 8, and a second passage 13 configured to communicate the pilot passage 10 with the back pressure chamber 8 and provided with a throttle 13a that applies resistance to the hydraulic fluid passing through. A solenoid housing 71 that accommodates a solenoid portion 70 is connected to the valve housing 2. The electromagnetic relief valve 100 is roughly divided into a portion accommodated in the valve housing 2, the solenoid portion 70, and the solenoid housing 71.

[0023] First, the configuration of the portion accommodated in the valve housing 2 will be described with reference to FIG.

[0024] The valve housing 2 accommodates a suction poppet 3, which accommodates a main poppet 5 and a sleeve 7 that accommodates a pilot poppet 9 that opens and closes a first passage 11. The suction poppet 3, the main poppet 5, and the pilot poppet 9 are provided to connect or disconnect the high pressure passage H and the low pressure passage L.

[0025] The valve housing 2 is a cylindrical member having a first end 2a attached to the device body 1 on the side of the high pressure passage H, and a second end 2b connected to the solenoid housing 71 on the opposite side to the first end 2a. The second end 2b is provided with a female thread portion 2c that screws into a male thread portion 71c of the solenoid housing 71, which will be described later.

[0026] The suction poppet 3 is cylindrical with a bottom, having a cylindrical portion 3a and a bottom portion 3b. The suction poppet 3 is provided within the valve housing 2 so as to be movable in the axial direction, and a portion of it protrudes from the opening of the first end portion 2a of the valve housing 2. A high pressure port 3H communicating with the high pressure passage H is provided at the bottom portion 3b of the suction poppet 3, and a low pressure port 3L communicating with the low pressure passage L is provided near the bottom portion 3b of the cylindrical portion 3a.

[0027] A corner 3c between the cylindrical portion 3a and the bottom portion 3b of the suction poppet 3 is formed in a tapered shape, and this corner 3c is seated on the seat portion 1a of the device body 1, thereby blocking communication between the high pressure passage H and the low pressure passage L through between the device body 1 and the suction poppet 3. A first accommodation hole 3d in which the main poppet 5 is accommodated is provided on the bottom portion 3b side of the suction poppet 3, and a second accommodation hole 3e in which the sleeve 7 is accommodated is provided on the end opposite to the bottom portion 3b.

[0028] The main poppet 5 has a body portion 50 which lifts off and seats on the suction poppet 3, and a pilot piston 51 which is slidably provided in a slide hole 50a provided in the body portion 50 and lifts off and seats on the body portion 50. The slide hole 50a is formed penetrating the body portion 50 in the axial direction.

[0029] The main body 50 is slidable within the first housing hole 3d. The main body 50 has a valve portion 50b seated on a seat portion 3f formed on the inside of the corner portion 3c of the suction poppet 3, and when the valve portion 50b is seated on the seat portion 3f, communication between the high pressure passage H and the low pressure passage L through the space between the suction poppet 3 and the main poppet 5 is blocked. A seal member is provided between the outer circumferential surface of the main body 50 and the inner circumferential surface of the suction poppet 3 to seal a gap between the main body 50 and the suction poppet 3.

[0030] The pilot piston 51 has a flange portion 51a provided facing the back pressure chamber 8, which is a space defined by the inner peripheral surface of the suction poppet 3, the main poppet 5, and the sleeve 7, a cylindrical shaft portion 51b (see FIG. 2) extending in the axial direction from the flange portion 51a and inserted into the slide hole 50a, a tapered portion 51c seated on a seat portion 11b (see FIG. 4) provided on the sleeve 7, a tip portion 51d facing the sleeve, and an end face 51e of the tip portion 51d. The end of the shaft portion 51b opposite to the tip portion 51d protrudes from the tip face of the main body portion 50 facing the high pressure passage H. The tapered portion 51c extends in the axial direction from the flange portion 51a in the opposite direction to the shaft portion 51b, and is formed so that the diameter becomes smaller as it moves away from the flange portion 51a.

[0031] Further, the pilot passage 10 is provided in the main poppet 5. Specifically, as shown in Fig. 2, the pilot passage 10 is provided inside the pilot piston 51 and between the outer circumferential surface of the pilot piston 51 and the main body 50. The pilot passage 10 communicates between the high pressure passage H and the back pressure chamber 8, and communicates with the first passage 11 through the back pressure chamber 8. The pilot passage 10 includes a tip-side passage 10a as a first pilot passage provided in the pilot piston 51 and facing the high pressure passage H, a base-side passage 10b as a second pilot passage provided in the pilot piston 51 and facing the back pressure chamber 8, a throttle passage 10c as a third pilot passage communicating with the tip-side passage 10a and the base-side passage 10b and formed by the outer circumferential surface of the pilot piston 51 and a slide hole 50a of the main body 50, a through hole 10d communicating with the tip-side passage 10a and the throttle passage 10c, and a through hole 10e communicating with the throttle passage 10c and the base-side passage 10b. Specifically, the tip-side passage 10a and the base-side passage 10b are provided in the pilot piston 51 so as to extend in the axial direction of the pilot piston 51. The tip-side passage 10a opens to an end face 51e. That is, the pilot passage 10 opens to an end face 51e of the tip portion 51d of the pilot piston 51 that faces the sleeve 7. The throttle passage 10c is an annular passage that communicates with the tip-side passage 10a and the base-end-side passage 10b via the through-holes 10d, 10e, respectively, and applies resistance to the flow of the working fluid passing therethrough.

[0032] Further, the pilot piston 51 is formed with a second passage 13 having a throttle 13a. In this embodiment, the entire second passage 13 is formed as the throttle 13a. The throttle 13a may be formed in a part of the second passage 13. Since the second passage 13 has the throttle 13a, the hydraulic oil in the high pressure passage H is mainly led directly from the pilot passage 10 to the back pressure chamber 8. The second passage 13 is a communication hole that opens to the outer circumferential surface of the pilot piston 51 and communicates the base end passage 10b with the back pressure chamber 8. Specifically, the second passage 13 extends in the radial direction of the pilot piston 51 and communicates the base end passage 10b with the back pressure chamber 8. The second passage 13 is provided in the vicinity of the flange portion 51a and closer to the tip side passage 10a than the flange portion 51a. Therefore, the second passage 13 is formed to communicate between the pilot passage 10 and the back pressure chamber 8, but does not always communicate with the back pressure chamber 8. When the pilot piston 51 is seated on the main body 50 as shown in Fig. 1, the second passage 13 does not communicate with the back pressure chamber 8, but communicates with the back pressure chamber 8 when the pilot piston 51 is separated from the main body 50 as shown in Fig. 2. The back pressure chamber 8 is connected to a base end side passage 10b of the pilot passage 10, the second passage 13, and a first passage 11 which communicates with the drain chamber 12.

[0033] The sleeve 7 has a tip end 7a inserted into the suction poppet 3, a base end 7b coupled to the solenoid housing 71, and an accommodation hole 7c opening at the axial end opposite the tip end 7a, and is coupled to the valve housing 2 via the solenoid housing 71. Therefore, the suction poppet 3 is slidably supported by the tip end 7a of the sleeve 7. A seal member is provided between the outer circumferential surface of the tip end 7a of the sleeve 7 and the inner circumferential surface of the suction poppet 3 to seal the gap between the sleeve 7 and the suction poppet 3.

[0034] A spring 81 is provided between the flange portion 51a of the pilot piston 51 and the sleeve 7, and a spring 82 is provided between the suction poppet 3 and the solenoid portion 70. The spring 81 urges the pilot piston 51 so that the flange portion 51a seats on the main body portion 50, and urges the main body portion 50 via the flange portion 51a so that the main body portion 50 seats on the seat portion 3f of the suction poppet 3. On the other hand, the spring 82 urges the suction poppet 3 so that the corner portion 3c of the suction poppet 3 seats on the seat portion 1a of the device main body 1.

[0035] 1, when the pilot piston 51 is seated on the main body 50, the second passage 13 does not communicate with the back pressure chamber 8. In this state, the back pressure chamber 8 communicates with the pilot passage 10 and the first passage 11. As shown in FIG. 2, when the pilot piston 51 leaves the main body 50, it slides toward the sleeve 7, and the gap A between the pilot piston 51 and the sleeve 7 (specifically, the space between the tapered portion 51c and the sleeve 7) becomes smaller, and the second passage 13 communicates with the back pressure chamber 8. In this state, the back pressure chamber 8 communicates with the pilot passage 10, the second passage 13, and the first passage 11.

[0036] A drain chamber 12 is formed in the sleeve 7, and communicates with the low pressure passage L through a gap 2d (see FIG. 1) between the outer circumferential surface of the suction poppet 3 and the inner circumferential surface of the valve housing 2. The drain chamber 12 communicates with the back pressure chamber 8 through a first passage 11 formed in the sleeve 7. A seat portion 11b on which a tapered portion 51c of a pilot piston 51 is seated is provided at a communicating portion between the first passage 11 and the back pressure chamber 8. A pilot poppet 9 that opens and closes the first passage 11 is accommodated in the accommodation hole 7c, and the pilot poppet 9 is slidably supported in the accommodation hole 7c. In this manner, the pilot poppet 9 is accommodated in the valve housing 2 via the sleeve 7 and the suction poppet 3.

[0037] The pilot poppet 9 is a member formed in a generally cylindrical shape, and has a cone-shaped valve portion 9a at one end and a flange portion 9b formed to protrude radially outward in an annular shape at the other end. The first passage 11 is provided with a seat portion 11a on which the valve portion 9a of the pilot poppet 9 is seated.

[0038] A spring 83 is provided between the flange portion 9b of the pilot poppet 9 and the sleeve 7, for biasing the pilot poppet 9 so that the other end of the pilot poppet 9 abuts against a rod 73 of a solenoid portion 70, which will be described later.

[0039] Next, the configuration of the solenoid portion 70 and the solenoid housing 71 that holds the solenoid portion 70 will be described with reference to FIG.

[0040] The solenoid portion 70 has a plunger 72 slidably housed in a solenoid housing 71, a rod 73 having one end connected to the plunger 72 and the other end abutting against the pilot poppet 9, a spring 74 engaged in the solenoid housing 71 and biasing the plunger 72 toward the pilot poppet 9, and a coil 75 housed in the solenoid housing 71 and applying a thrust to the plunger 72 against the biasing force of the spring 74. The solenoid housing 71 also includes a housing that covers the coil 75.

[0041] The solenoid housing 71 is a bottomed cylindrical member having an opening 71b formed at an end 71a in which the plunger 72 is housed, and a female threaded portion 71c that is screwed into the female threaded portion 2c of the valve housing 2 is provided at the tip of the opening 71b. The inner diameter of the opening 71b is formed to be larger than the outer diameter of the plunger 72. Therefore, the plunger 72 can be easily inserted from the end 71a side of the solenoid housing 71 into the opening 71b.

[0042] A spring chamber 77 is formed in the solenoid housing 71 so as to be continuous with the opening 71b in the axial direction. A spring 74 is disposed in the spring chamber 77. One end of the spring 74 is engaged with the plunger 72 and the other end is engaged within the solenoid housing 71.

[0043] The biasing force of the spring 74 acts on the pilot poppet 9 via the plunger 72 and the rod 73 connected to the axis of the plunger 72. In other words, the spring 74 biases the pilot poppet 9 so that the valve portion 9a of the pilot poppet 9 is seated on the seat portion 11a.

[0044] When current is supplied to the coil 75 of the solenoid unit 70 configured as described above, a thrust force against the biasing force of the spring 74 acts on the plunger 72. This reduces the biasing force of the spring 74 acting on the pilot poppet 9 via the plunger 72 and the rod 73, and as a result, the pressure required to separate the valve portion 9a of the pilot poppet 9 from the seat portion 11a, that is, the so-called cracking pressure, is reduced. In this way, the biasing force of the spring 74 acting on the pilot poppet 9 is changed by controlling the supply of current to the coil 75, thereby making it possible to change the set pressure at which the pilot poppet 9 opens.

[0045] Next, the main operation of the electromagnetic relief valve 100 according to this embodiment will be described.

[0046] The hydraulic oil in the high pressure passage H is led to the back pressure chamber 8 through the pilot passage 10. Until the pressure in the high pressure passage H reaches the cracking pressure of the main poppet 5, the hydraulic oil in the high pressure passage H flows into the back pressure chamber 8 through the throttle passage 10c of the pilot passage 10, and a pressure difference is generated between the back pressure chamber 8 and the high pressure passage H according to the throttle of the throttle passage 10c. When the pressure in the high pressure passage H reaches the set pressure (cracking pressure) of the pilot poppet 9 set by the solenoid unit 70, the pilot poppet 9 opens. When the pilot poppet 9 opens, the hydraulic oil in the back pressure chamber 8 flows into the drain chamber 12 through the first passage 11 and is discharged to the low pressure passage L through the gap 2d between the outer circumferential surface of the suction poppet 3 and the inner circumferential surface of the valve housing 2.

[0047] 2, when the pressure difference between the high pressure passage H and the back pressure chamber 8 increases, the pilot piston 51 moves away from the main body 50 against the biasing force of the spring 81 due to the pressure difference between the high pressure passage H and the back pressure chamber 8, and moves to the vicinity of the sleeve 7. The pilot piston 51 moves away from the main body 50 and toward the sleeve 7 in response to the pressure of the high pressure passage H, throttling the flow of hydraulic oil guided from the back pressure chamber 8 to the first passage 11 through between the pilot piston 51 and the sleeve 7. Therefore, as the pilot piston 51 approaches the sleeve 7, the gap A between the pilot piston 51 and the sleeve 7 gradually becomes smaller.

[0048] 3, when the pressure difference between the high pressure passage H and the back pressure chamber 8 becomes larger, the hydraulic oil in the back pressure chamber 8 is led to the low pressure passage L through the first passage 11 and the drain chamber 12, and at the same time, the body portion 50 is lifted off the seat portion 3f of the suction poppet 3, and the main poppet 5 opens. As a result, the hydraulic oil is led from the high pressure passage H to the low pressure passage L, and the pressure in the high pressure passage H is prevented from becoming abnormally high.

[0049] If the opening between the backpressure chamber and the first passage is wide, a large amount of hydraulic oil may flow out of the backpressure chamber when the main poppet opens, causing a large drop in pressure in the backpressure chamber. Because the main poppet moves due to the pressure difference between the high-pressure passage and the backpressure chamber, if the pressure in the backpressure chamber is likely to drop significantly, the position of the main poppet may fluctuate significantly, which may adversely affect the operation of the relief valve.

[0050] In contrast, in the electromagnetic relief valve 100 according to the present embodiment, when the pilot piston 51 leaves the main body 50, it moves toward the sleeve 7, and the gap A between the pilot piston 51 and the sleeve 7 becomes smaller. The pilot passage 10 and the first passage 11 communicate with the back pressure chamber 8 through the gap A. When the gap A becomes smaller, the resistance applied to the hydraulic oil passing through the gap A increases, so that the amount of hydraulic oil passing through the gap A decreases, and instead, the amount of hydraulic oil passing through the second passage 13 increases. In other words, when the pilot piston 51 leaves the main body 50 and the gap A becomes smaller, the amount of hydraulic oil flowing from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of hydraulic oil flowing from the back pressure chamber 8 through the second passage 13 to the first passage 11 increases. Since resistance is applied to the hydraulic oil flowing from the back pressure chamber 8 through the second passage 13 to the first passage 11, the amount of hydraulic oil flowing out of the back pressure chamber 8 decreases, and a large drop in pressure in the back pressure chamber 8 is suppressed. The main poppet 5 moves due to the pressure difference between the high pressure passage H and the back pressure chamber 8. Therefore, by suppressing a large drop in pressure in the back pressure chamber 8, the position of the main poppet 5 is prevented from fluctuating significantly, and the operation of the electromagnetic relief valve 100 is stabilized.

[0051] Also, as shown in FIG. 4, when the pilot piston 51 makes a full stroke against the biasing force of the spring 81, the tapered portion 51c is seated on the seat portion 11b of the sleeve 7. Specifically, the tapered portion 51c and the seat portion 11b are in line contact with each other. When the tapered portion 51c is seated on the seat portion 11b of the sleeve 7, the flow of hydraulic oil from the back pressure chamber 8 to the first passage 11 through the gap between the tapered portion 51c and the seat portion 11b is blocked. In other words, the hydraulic oil in the back pressure chamber 8 does not flow out to the first passage 11 and the drain chamber 12 through the gap A, but flows out to the first passage 11 and the drain chamber 12 through the second passage 13 and the pilot passage 10. This prevents a large amount of hydraulic oil from flowing out of the back pressure chamber 8. This further suppresses large fluctuations in the pressure in the back pressure chamber 8 and the position of the main poppet 5, and the operation of the electromagnetic relief valve 100 becomes more stable. In addition, because pilot piston 51 and sleeve 7 are in line contact, the flow of hydraulic oil can be more reliably blocked at the contact surface between pilot piston 51 and sleeve 7 compared to when pilot piston 51 and sleeve 7 are in surface contact, and similarly, the operation of electromagnetic relief valve 100 becomes more stable.

[0052] When the high pressure passage H becomes negative, that is, when the pressure in the high pressure passage H becomes lower than the pressure in the low pressure passage L, the suction poppet 3 leaves the seat 1a of the device body 1 and opens. This allows the hydraulic oil to flow from the low pressure passage L to the high pressure passage H.

[0053] According to the above-described embodiment, the following advantageous effects are obtained.

[0054] When the pilot piston 51 leaves the body 50 and moves toward the sleeve, the gap A between the pilot piston 51 and the sleeve 7 becomes smaller. Therefore, the amount of hydraulic oil flowing out from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of hydraulic oil flowing out from the back pressure chamber 8 through the second passage 13 to the first passage 11 increases. Since resistance is applied to the hydraulic oil flowing out from the back pressure chamber 8 through the second passage 13 to the first passage 11, the amount of hydraulic oil flowing out from the back pressure chamber 8 decreases, and a large drop in pressure in the back pressure chamber 8 is suppressed. This suppresses large fluctuations in the position of the main poppet 5, and stabilizes the operation of the relief valve.

[0055] When the pilot piston 51 makes a full stroke against the biasing force of the spring 81, the tapered portion 51c seats on the seat portion 11b of the sleeve 7. In a state in which the tapered portion 51c seats on the seat portion 11b of the sleeve 7, the hydraulic oil flows out of the back pressure chamber 8 through the second passage 13 and the pilot passage 10. This prevents a large amount of hydraulic oil from flowing out of the back pressure chamber 8. This further suppresses large fluctuations in the pressure in the back pressure chamber 8 and the position of the main poppet 5, making the operation of the electromagnetic relief valve 100 more stable.

[0056] In addition, the following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the above embodiment, or to combine the configurations described in the different modified examples below.

[0057] <Variation 1> In the above embodiment, the second passage 13 having the throttle 13a is formed in the pilot piston 51. Alternatively, as shown in FIG. 5, the second passage 113 having the throttle 113a may be formed in the sleeve 7 and communicate between the back pressure chamber 8 and the first passage 11. That is, the second passage may be formed so as to communicate between the pilot passage 10 and the back pressure chamber 8, or between the back pressure chamber 8 and the first passage 11. In this configuration, when the pilot piston 51 leaves the body portion 50, the gap A between the pilot piston 51 and the sleeve 7 becomes smaller, the amount of hydraulic oil guided from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of hydraulic oil flowing from the back pressure chamber 8 through the second passage 113 to the first passage 11 increases, so that the same effect as in the above embodiment is achieved.

[0058] <Variation 2> In the above embodiment, the second passage 13 having the throttle 13a is formed so as not to communicate with the back pressure chamber 8 when the pilot piston 51 is seated on the main body 50. Alternatively, as shown in FIG. 6, the second passage 213 having the throttle 213a may be formed so as to communicate with the back pressure chamber 8 when the pilot piston 51 is seated on the main body 50. Specifically, the second passage 213 is formed on the end face 51e side of the flange portion 51a of the pilot piston 51. Even with this configuration, when the pilot piston 51 leaves the main body 50, the gap A between the pilot piston 51 and the sleeve 7 becomes smaller, the amount of hydraulic oil guided from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of hydraulic oil flowing from the back pressure chamber 8 to the first passage 11 through the second passage 213 increases, so that the same effect as the above embodiment is achieved.

[0059] <Variation 3> 7A and 7B, the second passage 313 having the throttle 313a may be an annular passage provided on the outer circumferential surface of the pilot piston 51 and communicating the throttle passage 10c with the back pressure chamber 8. Specifically, the second passage 313 is provided between the outer circumferential surface of the pilot piston 51 and the inner circumferential surface of the slide hole 50a. Even with this configuration, when the pilot piston 51 leaves the body portion 50, the gap A between the pilot piston 51 and the sleeve 7 becomes smaller, the amount of hydraulic oil guided from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of hydraulic oil flowing out from the back pressure chamber 8 to the first passage 11 through the second passage 313 increases, so that the same effect as in the above embodiment is achieved.

[0060] <Modification 4> 8A and 8B, the second passage 413 having the throttle 413a may be a communication groove provided on the outer peripheral surface of the pilot piston 51 along the axial direction and communicating between the throttle passage 10c and the back pressure chamber 8. Specifically, the second passage 413 is provided extending linearly in the axial direction of the pilot piston 51. Even with this configuration, when the pilot piston 51 leaves the main body 50, the gap A between the pilot piston 51 and the sleeve 7 becomes smaller, the amount of hydraulic oil guided from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of hydraulic oil flowing out from the back pressure chamber 8 to the first passage 11 through the second passage 413 increases, so that the same effect as in the above embodiment is achieved.

[0061] <Variation 5> In the above embodiment, the second passage 13 having the throttle 13a is a communication hole that opens to the outer circumferential surface of the pilot piston 51 and communicates between the pilot passage 10 and the back pressure chamber 8. Alternatively, as shown in FIG. 9, the second passage 513 having the throttle 513a may be a groove provided in the seat portion 11b of the sleeve 7, and the working fluid may be guided from the back pressure chamber 8 to the first passage 11 through the groove when the tapered portion 51c of the pilot piston 51 is seated on the seat portion 11b of the sleeve 7. Specifically, the second passage 513 is provided linearly along the seat portion 11b of the sleeve 7. Even with this configuration, when the tapered portion 51c of the pilot piston 51 is seated on the seat portion 11b of the sleeve 7, the amount of working oil guided to the first passage 11 through the second passage 513 decreases, so that the same effect as the above embodiment can be achieved.

[0062] <Variation 6> In the above embodiment, when the pilot piston 51 makes a full stroke against the biasing force of the spring 81, the tapered portion 51c of the pilot piston 51 is seated on the seat portion 11b of the sleeve 7, and the second passage 13 is a communication hole that opens to the outer circumferential surface of the pilot piston 51 and communicates the pilot passage 51 with the back pressure chamber 8. Alternatively, as shown in Fig. 10, the pilot piston 651 may be configured not to make a full stroke against the biasing force of the spring 681 by a spring 681 having a stronger biasing force than the spring 81. In this case, the tip portion 651d facing the sleeve 607 is formed in a cylindrical shape, and the sleeve 607 has an accommodation portion 611c that communicates between the back pressure chamber 8 and the first passage 11 and accommodates the tip portion 651d as the pilot piston 651 moves toward the sleeve 607. The second passage 613 having the throttle 613a may have a gap 613b formed by an inner circumferential surface of the accommodation portion 611c and an outer circumferential surface of a tip end portion 651d of the pilot piston 651 accommodated in the accommodation portion 611c, and communicating the pilot passage 10 with the back pressure chamber 8. Specifically, the second passage 613 is provided between an outer circumferential surface of the tip end portion 651d of the pilot piston 651 and an inner circumferential surface of the accommodation portion 611c. As shown in FIG. 11, the second passage 713 having the throttle 713a may further have a communication groove 713b provided in an end face 651e of the tip end portion 651d, and communicating the pilot passage 10 with the back pressure chamber 8. Specifically, the second passage 713 is provided extending linearly along the end face 651e. In these configurations, when the tip portion 51d of the pilot piston 51 is accommodated in the accommodation portion 611c of the sleeve 607, the amount of hydraulic oil guided to the first passage 11 through the second passages 613, 713 decreases, thereby achieving the same effect as in the above embodiment.

[0063] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0064] The electromagnetic relief valve 100 as a relief valve comprises a valve housing 2 attached to an equipment body 1 in which a high pressure passage H and a low pressure passage L are provided, a suction poppet 3 provided within the valve housing 2 and configured to allow a flow of working fluid between the high pressure passage H and the low pressure passage L by lifting off and seating on the equipment body 1, a main poppet 5 provided within the suction poppet 3 and configured to communicate and block the flow of working fluid between the high pressure passage H and the low pressure passage L by lifting off and seating on the suction poppet 3, a sleeve 7,607 defining a back pressure chamber 8 between the main poppet 5 and the suction poppet 3, a pilot passage 10 provided in the main poppet 5 and facing the high pressure passage H and the back pressure chamber 8, a drain chamber 12 provided within the sleeve 7,607 and from which the working fluid in the back pressure chamber 8 is discharged, a first passage 11 provided within the sleeve 7,607 to communicate between the drain chamber 12 and the back pressure chamber 8, and a second passage 12 provided within the sleeve 7,607 to communicate between the drain chamber 12 and the back pressure chamber 8 and a second passage 13 for connecting the working fluid passing through the first passage 13 and the second passage 14. and second passages 13-813 in which throttles 13a-813a for applying resistance are provided. The second passages 13-813 are formed to communicate between the pilot passage 10 and the back pressure chamber 8, or between the back pressure chamber 8 and the first passage 11. The main poppet 5 includes a main body portion 50 which is lifted off from the suction poppet 3 and seated on the suction poppet 3, and a pilot piston 51 which is slidably provided within a slide hole 50a provided in the main body portion 50 and lifted off from and seated on the main body portion 50, 651, and the pilot passage 10 opens to end faces 51e, 651e of the tip portions 51d, 651d of the pilot piston 51, 651 that face the sleeve 7, 607, and the pilot piston 51, 651 is configured to move away from the main body portion 50 toward the sleeve 7, 607 in response to the pressure of the high-pressure passage H and to throttle the flow of working fluid guided from the back pressure chamber 8 to the first passage 11 through between the pilot piston 51, 651 and the sleeve 7, 607.

[0065] In this configuration, when the pilot piston 51, 651 leaves the main body 50, the gap A between the pilot piston 51, 651 and the sleeve 7, 607 becomes smaller, and the hydraulic oil is less likely to be guided from the back pressure chamber 8 to the first passage 11 through the gap A between the pilot piston 51, 651 and the sleeve 7, 607. Accordingly, the hydraulic oil in the back pressure chamber 8 is guided to the pilot passage 10 through the second passages 13-813 and flows out from the openings of the tip ends 51d, 651d of the pilot piston 51, 651 to the first passage 11. Since resistance is applied to the hydraulic fluid flowing out from the back pressure chamber 8 to the first passage 11 through the second passages 13-813, the amount of hydraulic fluid flowing out from the back pressure chamber 8 is reduced, and a large drop in the pressure of the back pressure chamber 8 is suppressed. As a result, the position of the main poppet 5 is suppressed from fluctuating greatly, and the operation of the relief valve 100 is stabilized.

[0066] The pilot passage 10 has a tip-side passage 10a that is provided in the pilot piston 51 and faces the high pressure passage H, and a base-end side passage 10b that is provided in the pilot piston 51 and faces the back pressure chamber 8, and the second passages 13, 213 are communicating holes that open to the outer peripheral surface of the pilot piston 51 and communicate between the base-end side passage 10b and the back pressure chamber 8.

[0067] The pilot passage 10 has a tip-side passage 10a that is provided in the pilot piston 51 and faces the high pressure passage H, a base-end side passage 10b that is provided in the pilot piston 51 and faces the back pressure chamber 8, and a throttle passage 10c that communicates with the tip-end side passage 10a and the base-end side passage 10b and is formed by the outer circumferential surface of the pilot piston 51 and a sliding hole 50a of the main body 50, and second passages 313, 413 are provided in the outer circumferential surface of the pilot piston 51 and communicate the throttle passage 10c with the back pressure chamber 8.

[0068] In these configurations, the working fluid flowing out of the back pressure chamber is provided with resistance by the second passage, so the amount of working fluid flowing out of the back pressure chamber is reduced and a large drop in pressure in the back pressure chamber is suppressed. This prevents the position of the main poppet from fluctuating significantly and stabilizes the operation of the relief valve.

[0069] The pilot piston 51 has a tapered portion 51c that seats on a seat portion 11b provided on the sleeve 7, and when the tapered portion 51c of the pilot piston 51 seats on the seat portion 11b of the sleeve 7, the flow of working fluid guided from the back pressure chamber 8 to the first passage 11 through between the tapered portion 51c and the seat portion 11b is blocked.

[0070] In this configuration, when the tapered portion of the pilot piston 51 is seated on the seat portion 11b of the sleeve 7, the working fluid flows out of the back pressure chamber 8 only through the second passages 13-513. This further suppresses large fluctuations in the pressure in the back pressure chamber 8 and the position of the main poppet 5, making the operation of the relief valve 100 more stable.

[0071] The second passage 513 is a groove provided in the tapered portion 51c of the pilot piston 51, and when the tapered portion 51c of the pilot piston 51 is seated on the seat portion 11b of the sleeve 7, the working fluid is guided from the back pressure chamber 8 through the groove to the first passage.

[0072] Pilot piston 651 has a cylindrical tip portion 651d that faces sleeve 607, and sleeve 607 has an accommodating portion 611c that communicates with the back pressure chamber 8 and the first passage 11 and accommodates tip portion 651d as pilot piston 651 moves toward sleeve 607, and second passages 613, 713, 813 are formed by the inner circumferential surface of accommodating portion 611c and the outer circumferential surface of tip portion 651d of pilot piston 651 accommodated in accommodating portion 611c.

[0073] In these configurations, the working fluid flowing out of the back pressure chamber is provided with resistance by the second passage, so the amount of working fluid flowing out of the back pressure chamber is reduced and a large drop in pressure in the back pressure chamber is suppressed. This prevents the position of the main poppet from fluctuating significantly and stabilizes the operation of the relief valve.

[0074] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0075] 1...Equipment body, 2...Valve housing, 3...Suction poppet, 5...Main poppet, 7,607...Sleeve, 8...Back pressure chamber, 10...Pilot passage, 10a...Tip side passage (first pilot passage), 10b...Base side passage (second pilot passage), 10c...Throttling passage (third pilot passage), 11...First passage, 11b seat portion, 12 drain chamber, 13 to 713 second passage, 13a to 713a throttle, 50 main body portion, 50a slide hole, 51, 651 pilot piston, 51c tapered portion, 51d, 651d tip portion, 100 solenoid relief valve (relief valve), 611c accommodation hole, H high pressure passage, L low pressure passage

Claims

1. a valve housing attached to an equipment body in which a high pressure passage and a low pressure passage are provided; a suction poppet provided in the valve housing and configured to allow a flow of working fluid between the high pressure passage and the low pressure passage by being seated on and off the device body; a main poppet provided in the suction poppet and configured to communicate and block the working fluid between the high pressure passage and the low pressure passage by separating from and seating on the suction poppet; a sleeve in the suction poppet that defines a back pressure chamber between the main poppet and the sleeve; a pilot passage provided in the main poppet and facing the high pressure passage and the back pressure chamber; a drain chamber provided in the sleeve and into which the working fluid in the back pressure chamber is discharged; a first passage provided in the sleeve so as to communicate between the drain chamber and the back pressure chamber; a second passage configured to communicate the pilot passage or the first passage with the back pressure chamber, the second passage having a throttle that applies resistance to the working fluid passing through the second passage, The main poppet is a main body portion that is seated on and separated from the suction poppet; a pilot piston that is slidably provided in a slide hole provided in the main body portion and that lifts off and seats on the main body portion, the pilot passage opens to a tip end portion of the pilot piston facing the sleeve, The pilot piston has a tapered portion that seats on a seat portion provided on the sleeve, the pilot piston is separated from the main body portion and moves toward the sleeve in response to the pressure of the high-pressure passage, and a gap that throttles the flow of the working fluid is formed between the tapered portion of the pilot piston and the seat portion of the sleeve, The first passage communicates with the back pressure chamber through the gap.

2. 2. The relief valve according to claim 1, The pilot passage includes: a first pilot passage provided in the pilot piston and facing the high pressure passage; a second pilot passage provided in the pilot piston and facing the back pressure chamber, a second passageway that is a communication hole that opens to an outer circumferential surface of the pilot piston and communicates between the second pilot passageway and the back pressure chamber;

3. 2. The relief valve according to claim 1, The pilot passage includes: a first pilot passage provided in the pilot piston and facing the high pressure passage; a second pilot passage provided in the pilot piston and facing the back pressure chamber; a third pilot passage communicating with the first pilot passage and the second pilot passage and formed by an outer circumferential surface of the pilot piston and the slide hole of the main body portion, The second passage is provided on an outer circumferential surface of the pilot piston and connects the third pilot passage to the back pressure chamber.

4. A relief valve according to any one of claims 1 to 3, a relief valve configured to block a flow of working fluid from the back pressure chamber through a gap between the tapered portion and the seat portion to the first passage when the tapered portion of the pilot piston is seated on the seat portion of the sleeve.

5. 5. The relief valve according to claim 4, the second passage is a groove provided in the tapered portion of the pilot piston, a relief valve configured to guide working fluid from the back pressure chamber through the groove to the first passage when the tapered portion of the pilot piston is seated on the seat portion of the sleeve.

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