overflow valve

Abstract

An electromagnetic spill valve (100) is provided with: a pilot passage (10) facing a high-pressure passage (H) and a back pressure chamber (8); a first passage (11) communicating a discharge chamber (12) and the back pressure chamber (8); a second passage (13) provided with a throttle portion (13a), the second passage (13) communicating the pilot passage (10) and the back pressure chamber (8), and a main poppet valve (5) having: a body portion (50) unseated and seated to a suction poppet valve (3); a pilot piston (51) unseated and seated to the body portion (50), the pilot passage (10) communicating the back pressure chamber (8) and the first passage (11), the pilot piston (51) being configured to unseat from the body portion (50) and move toward a sleeve (7) in accordance with a pressure of the high-pressure passage (H), thereby throttling a flow of working fluid guided from the back pressure chamber (8) to the first passage (11) via between the pilot piston (51) and the sleeve (7).

Description

Overflow valve Technical Field

[0001] This invention relates to an overflow valve. Background Technology

[0002] Japanese Patent Application Publication No. JP2019-158099A discloses an overflow valve comprising: a suction lift valve disposed within a valve housing, which, in an open state (unseaten from a first seat portion disposed on the device body), allows the flow of working fluid from a low-pressure passage to a high-pressure passage, and, in an open state (seaten on the first seat portion), cuts off the connection between the high-pressure passage and the low-pressure passage; a main lift valve disposed within the suction lift valve, which, in an open state (unseaten from a second seat portion disposed on the suction lift valve), allows the flow of working fluid from the high-pressure passage to the low-pressure passage, and, in an open state (seaten on the second seat portion), cuts off the connection between the high-pressure passage and the low-pressure passage; a guide plug disposed within the suction lift valve, dividing a back pressure chamber between itself and the main lift valve; a pilot passage disposed within the main lift valve, connecting the high-pressure passage and the back pressure chamber; and a pilot lift valve that opens and closes a passage connecting the back pressure chamber and a discharge chamber disposed within the guide plug.

[0003] In the relief valve described in Japanese Patent Application Publication JP2019-158099A, the working oil in the high-pressure passage is guided to the back pressure chamber through a throttling process in the pilot passage, creating a differential pressure between the back pressure chamber and the high-pressure passage corresponding to the throttling. When the pressure difference between the high-pressure passage and the back pressure chamber increases, the pilot piston moves by overcoming the force of the spring. When the pressure difference between the high-pressure passage and the back pressure chamber increases further, the main lift valve disengages from the suction lift valve, and the main lift valve opens. Summary of the Invention

[0004] In the relief valve described in Japanese Patent Application Publication JP2019-158099A, the working oil in the back pressure chamber flows out to the discharge chamber via a drain passage connected to the back pressure chamber. When the opening areas of the back pressure chamber and the discharge chamber are large, the working oil easily flows out of the back pressure chamber, thus causing a significant drop in the pressure of the back pressure chamber. Since the main lift valve moves due to the pressure difference between the high-pressure passage and the back pressure chamber, when the pressure in the back pressure chamber easily drops significantly, the position of the main lift valve easily changes significantly, potentially adversely affecting the operation of the relief valve.

[0005] The purpose of this invention is to stabilize the operation of the overflow valve.

[0006] According to one aspect of the present invention, an overflow valve comprises: a valve housing mounted on a device body having a high-pressure passage and a low-pressure passage; a suction lift valve disposed within the valve housing, which allows the flow of working fluid between the high-pressure passage and the low-pressure passage by disengaging from and repositioning on the device body; a main lift valve disposed within the suction lift valve, which connects and disconnects the working fluid between the high-pressure passage and the low-pressure passage by disengaging from and repositioning on the suction lift valve; a sleeve within the suction lift valve, which divides a back pressure chamber between itself and the main lift valve; a pilot passage disposed within the main lift valve and facing the high-pressure passage and the back pressure chamber; a discharge chamber disposed within the sleeve, which discharges the working fluid from the back pressure chamber; and a first passage for... The discharge chamber and the back pressure chamber are connected within the sleeve; a second passage is configured to connect the pilot passage or the first passage and the back pressure chamber, and is provided with a throttling section that applies resistance to the flowing working fluid; the main lift valve has: a body portion that is separated from and seated in the suction lift valve; a pilot piston that is slidably disposed in a sliding hole provided on the body portion, and is separated from and seated in the body portion; the pilot passage opens at the top end of the pilot piston opposite to the sleeve; the pilot piston is configured to be separated from the body portion and move toward the sleeve according to the pressure of the high pressure passage, thereby throttling the flow of working fluid guided from the back pressure chamber to the first passage via the pilot piston and the sleeve. Attached Figure Description

[0007] Figure 1 is a cross-sectional view of the electromagnetic relief valve according to an embodiment of the present invention.

[0008] Figure 2 is a cross-sectional view of the pilot piston of the electromagnetic relief valve according to an embodiment of the present invention in the state of being off the body.

[0009] Figure 3 is a cross-sectional view of the electromagnetic relief valve in the embodiment of the present invention with the main lift valve open.

[0010] Figure 4 is a cross-sectional view of the electromagnetic relief valve according to an embodiment of the present invention, with the pilot piston seated in the sleeve.

[0011] Figure 5 is a cross-sectional view showing a first modified example of the electromagnetic relief valve according to an embodiment of the present invention.

[0012] Figure 6 is a cross-sectional view showing a second modified example of the electromagnetic relief valve according to an embodiment of the present invention.

[0013] Figure 7A is a cross-sectional view showing a third modified example of the electromagnetic relief valve according to an embodiment of the present invention.

[0014] Figure 7B is a cross-sectional view of the pilot piston along line AA in Figure 7A.

[0015] Figure 8A is a cross-sectional view showing a fourth modified example of the electromagnetic relief valve according to an embodiment of the present invention.

[0016] Figure 8B is a cross-sectional view of the pilot piston along line BB in Figure 8A.

[0017] Figure 9 is a cross-sectional view showing a fifth modified example of the electromagnetic relief valve according to an embodiment of the present invention.

[0018] Figure 10 is a cross-sectional view (one of the six variations) of the electromagnetic relief valve according to an embodiment of the present invention.

[0019] Figure 11 is a cross-sectional view (second example) showing a sixth modified example of the electromagnetic relief valve according to an embodiment of the present invention. Detailed Implementation

[0020] Referring to the accompanying drawings, the relief valve according to an embodiment of the present invention will be described. Hereinafter, the case where the relief valve is an electromagnetic relief valve 100 having a solenoid section 70 will be described.

[0021] The electromagnetic relief valve 100 opens when the pressure of the working oil in the high-pressure passage H reaches a set pressure, releasing the working oil from the high-pressure passage H to the low-pressure passage L, thereby preventing the working oil pressure in the high-pressure passage H from abnormally becoming high. Furthermore, the electromagnetic relief valve 100 has a solenoid section 70, through which the set pressure can be changed. Additionally, the electromagnetic relief valve 100 has an anti-void function, preventing cavitation by opening when the high-pressure passage H becomes negatively pressured and supplying working oil from the low-pressure passage L to the high-pressure passage H. In this embodiment, working oil is used as the working fluid; however, other fluids such as working water or compressed air may also be used.

[0022] The electromagnetic relief valve 100 is installed on the equipment body 1 by threaded fastening. The equipment body 1 is the body of a hydraulic device including a hydraulic cylinder, a hydraulic pump, a hydraulic motor, and a valve block containing multiple valves. A high-pressure passage H and a low-pressure passage L are provided on the equipment body 1, with the electromagnetic relief valve 100 as the boundary. A seating portion 1a is provided on the equipment body 1 between the high-pressure passage H and the low-pressure passage L for the suction poppet valve 3 (described later) to sit on. Furthermore, the equipment body 1 is not limited to the body of the hydraulic device; it can also be a block disposed between various hydraulic devices.

[0023] As shown in Figure 1, the electromagnetic relief valve 100 includes: a valve housing 2, which is installed in a device body 1 having a high-pressure passage H and a low-pressure passage L; a suction lift valve 3, which is disposed within the valve housing 2 and allows the flow of working oil, which is the working fluid, between the high-pressure passage H and the low-pressure passage L by moving away from and sitting on the device body 1; and a main lift valve 5, which is disposed within the suction lift valve 3 and connects and disconnects the high-pressure passage H and the low-pressure passage L by moving away from and sitting on the suction lift valve 3. The system includes: a sleeve 7, which is located within the suction lift valve 3 and divides a back pressure chamber 8 between itself and the main lift valve 5; a pilot passage 10, which is located within the main lift valve 5 and faces the high pressure passage H and the back pressure chamber 8; a discharge chamber 12, which is located within the sleeve 7 and discharges the working oil from the back pressure chamber 8; a first passage 11, which is located within the sleeve 7 to connect the discharge chamber 12 and the back pressure chamber 8; and a second passage 13, which is configured to connect the pilot passage 10 and the back pressure chamber 8 and is provided with a throttling section 13a that applies resistance to the flowing working fluid. A solenoid housing 71, which houses the solenoid section 70, is connected to the valve housing 2. The structure of the electromagnetic relief valve 100 is classified into the portion housed within the valve housing 2, and the solenoid section 70 and the solenoid housing 71.

[0024] First, referring to Figure 1, the structure of the part housed in the valve housing 2 will be described.

[0025] A suction lift valve 3 is housed on the valve housing 2. The suction lift valve 3 houses a main lift valve 5 and a sleeve 7 that houses a pilot lift valve 9 for opening and closing the first passage 11. The suction lift valve 3, the main lift valve 5, and the pilot lift valve 9 are provided to connect or disconnect the high-pressure passage H and the low-pressure passage L.

[0026] The valve housing 2 is a cylindrical component, having a first end 2a mounted on the device body 1 on the high-pressure passage H side, and a second end 2b connected to the solenoid housing 71 on the side opposite to the first end 2a. On the second end 2b, a female thread 2c is provided that engages with the male thread 71c of the solenoid housing 71, which will be described later.

[0027] The suction lift valve 3 is a bottomed cylindrical shape having a cylindrical portion 3a and a bottom 3b. The suction lift valve 3 is disposed within the valve housing 2 in a manner that allows it to move axially, and a portion of it protrudes from the opening at the first end 2a of the valve housing 2. A high-pressure port 3H communicating with a high-pressure passage H is provided at the bottom 3b of the suction lift valve 3, and a low-pressure port 3L communicating with a low-pressure passage L is provided near the bottom 3b of the cylindrical portion 3a.

[0028] The corner 3c between the cylindrical portion 3a and the bottom 3b of the suction lift valve 3 is formed into a conical shape. This corner 3c sits on the sitting portion 1a of the equipment body 1, thereby cutting off the connection between the high-pressure passage H and the low-pressure passage L through the equipment body 1 and the suction lift valve 3. A first receiving hole 3d for receiving the main lift valve 5 is provided on the bottom 3b side of the suction lift valve 3, and a second receiving hole 3e for receiving the sleeve 7 is provided on the end opposite to the bottom 3b.

[0029] The main lift valve 5 includes: a body portion 50, which disengages from and is seated in the suction lift valve 3; and a pilot piston 51, which is slidably disposed within a sliding hole 50a provided on the body portion 50, and disengages from and is seated in the body portion 50. The sliding hole 50a is formed to extend axially through the body portion 50.

[0030] The main body 50 is slidable within the first receiving hole 3d. The main body 50 has a valve portion 50b that sits on a seating portion 3f formed inside the corner portion 3c of the suction lift valve 3. By sitting on the seating portion 3f with the valve portion 50b, the communication between the high-pressure passage H and the low-pressure passage L between the suction lift valve 3 and the main lift valve 5 is cut off. A sealing member is provided between the outer peripheral surface of the main body 50 and the inner peripheral surface of the suction lift valve 3 to seal the gap between the main body 50 and the suction lift valve 3.

[0031] The pilot lift valve 51 includes: a flange portion 51a, which is configured to face a back pressure chamber 8, the back pressure chamber 8 being a space divided by the inner circumferential surface of the suction lift valve 3, the main lift valve 5, and the sleeve 7; a cylindrical shaft portion 51b (see Figure 2) extending axially from the flange portion 51a and inserted into a sliding hole 50a; a tapered portion 51c seated on a seat portion 11b (see Figure 4) provided on the sleeve 7; a top end portion 51c opposite to the sleeve; and an end face 51e of the top end portion 51d. The end of the shaft portion 51b opposite to the top end portion 51d protrudes from the top end face of the body portion 50 facing the high-pressure passage H. The tapered portion 51c is formed to extend laterally from the flange portion 51a in the direction opposite to the shaft portion 51b, and its diameter decreases as it moves away from the flange portion 51a.

[0032] Additionally, a pilot passage 10 is provided in the main lift valve 5. Specifically, as shown in FIG2, the pilot passage 10 is provided inside the pilot piston 51 and between the outer peripheral surface of the pilot piston 51 and the body portion 50. The pilot passage 10 connects the high-pressure passage H to the back pressure chamber 8, and connects to the first passage 11 via the back pressure chamber 8. The pilot passage 10 includes: a top-side passage 10a, serving as a first pilot passage, which is disposed within the pilot piston 51 and faces the high-pressure passage H; a base-side passage 10b, serving as a second pilot passage, which is disposed within the pilot piston 51 and faces the back pressure chamber 8; a throttling passage 10c, serving as a third pilot passage, which communicates with the top-side passage 10a and the base-side passage 10b, and is formed by the outer peripheral surface of the pilot piston 51 and the sliding hole 50a of the body portion 50; a through hole 10d, which connects the top-side passage 10a and the throttling passage 10c; and a through hole 10c, which connects the throttling passage 10c and the base-side passage 10b. Specifically, the top-side passage 10a and the base-side passage 10b are disposed in the pilot piston 51 such that they extend axially in the pilot piston 51. The top-side passage 10a has an opening on the end face 51e. That is, the pilot passage 10 opens on the end face 51e of the top part 51d of the pilot piston 51 opposite to the sleeve 7. The throttling passage 10c is an annular passage that communicates with the top side passage 10a and the base side passage 10b through the through holes 10d and 10e respectively, and applies resistance to the flow of the working fluid.

[0033] Furthermore, a second passage 13 with a throttling section 13a is formed on the pilot piston 51. In this embodiment, the entire second passage 13 is formed as the throttling section 13a. The throttling section 13a may also be formed as a part of the second passage 13. Since the second passage 13 has the throttling section 13a, the working oil of the high-pressure passage H is mainly guided directly from the pilot passage 10 to the back pressure chamber 8. The second passage 13 is a connecting hole that opens on the outer peripheral surface of the pilot piston 51 and connects the base end side passage 10b and the back pressure chamber 8. Specifically, the second passage 13 extends radially in the pilot piston 51 and connects the base end side passage 10b and the back pressure chamber 8. The second passage 13 is located near the flange portion 51a on the side closer to the top end side passage 10a than the flange portion 51a. Thus, although the second passage 13 is formed in such a way that it connects the pilot passage 10 and the back pressure chamber 8, it is not always connected to the back pressure chamber 8. The second passage 13 is not connected to the back pressure chamber 8 when the pilot piston 51 is seated in the body part 50 as shown in FIG. 1, and is connected to the back pressure chamber 8 when the pilot piston 51 is removed from the body part 50 as shown in FIG. 2. The base end side passage 10b of the pilot passage 10, the second passage 13, and the first passage 11 that communicates with the discharge chamber 12 are open on the back pressure chamber 8.

[0034] The sleeve 7 has a top end 7a that is inserted into the suction lift valve 3, a base end 7b that engages with the solenoid housing 71, and a receiving hole 7c that opens at the axial end opposite to the top end 7a, and is engaged with the valve housing 2 via the solenoid housing 71. Therefore, the suction lift valve 3 is supported by the top end 7a of the sleeve 7 to slide freely. A sealing member is provided between the outer peripheral surface of the top end 7a of the sleeve 7 and the inner peripheral surface of the suction lift valve 3 to seal the gap between the sleeve 7 and the suction lift valve 3.

[0035] Furthermore, a spring 81 is provided between the flange 51a of the pilot piston 51 and the sleeve 7, and a spring 82 is provided between the suction lift valve 3 and the solenoid section 70. The spring 81 applies force to the pilot piston 51 by means of the flange 51a resting on the body section 50, and applies force to the body section 50 via the flange 51a by means of the body section 50 resting on the sitting section 3f of the suction lift valve 3. On the other hand, the spring 82 applies force to the suction lift valve 3 by means of the corner portion 3c resting on the sitting section 1a of the equipment body 1.

[0036] As shown in Figure 1, with the pilot piston 51 seated on the body portion 50, the second passage 13 and the back pressure chamber 8 are not connected. In this state, the back pressure chamber 8 is connected to the pilot passage 10 and the first passage 11. As shown in Figure 2, when the pilot piston 51 leaves the body portion 50, it slides toward the sleeve 7, the gap A between the pilot piston 51 and the sleeve 7 (specifically, the space between the tapered portion 51c and the sleeve 7) decreases, and the second passage 13 is connected to the back pressure chamber 8. In this state, the back pressure chamber 8 is connected to the pilot passage 10, the second passage 13, and the first passage 11.

[0037] Within the sleeve 7, a discharge chamber 12 is formed, communicating with the low-pressure passage L via a gap 2d (see Figure 1) between the outer peripheral surface of the suction lift valve 3 and the inner peripheral surface of the valve housing 2. The discharge chamber 12 communicates with the back pressure chamber 8 via a first passage 11 formed within the sleeve 7. A seating portion 11b is provided at the connection between the first passage 11 and the back pressure chamber 8 for the conical portion 51c of the pilot piston 51 to sit on. A pilot lift valve 9, which opens and closes the first passage 11, is housed in a receiving hole 7c, and the pilot lift valve 9 is slidably supported in the receiving hole 7c. Thus, the pilot lift valve 9 is housed within the valve housing 2 via the sleeve 7 and the suction lift valve 3.

[0038] The pilot lift valve 9 is a generally cylindrical component, having a conical valve portion 9a at one end and a flange portion 9b at the other end that protrudes radially outward in an annular manner. A seating portion 11a is provided on the first passage 11 for the valve portion 9a of the pilot lift valve 9 to sit on.

[0039] In addition, a spring 83 is provided between the flange 9b of the pilot lift valve 9 and the sleeve 7 to apply force to the pilot lift valve 9 so that the other end of the pilot lift valve 9 abuts against the rod 73 of the solenoid section 70 described later.

[0040] Next, referring to FIG1, the structure of the solenoid section 70 and the solenoid housing 71 that holds the solenoid section 70 will be described.

[0041] The solenoid section 70 includes: a plunger 72, which is slidably housed within the solenoid housing 71; a rod 73, one end of which is connected to the plunger 72, and the other end of which abuts against the pilot lift valve 9; a spring 74, which is locked within the solenoid housing 71 and applies force to the plunger 72 toward the pilot lift valve 9; and a coil 75, which is housed within the solenoid housing 71 and applies a thrust to the plunger 72 that overcomes the force of the spring 74. Furthermore, a housing covering the coil 75 is also included within the solenoid housing 71.

[0042] The solenoid housing 71 is a bottomed cylindrical component with an opening 71b at its end 71a that accommodates a plunger 72. A male thread 71c, which engages with the female thread 2c of the valve housing 2, is provided at the top of the opening 71b. The inner diameter of the opening 71b is larger than the outer diameter of the plunger 72. Therefore, the plunger 72 can be easily inserted into the opening 71b from the end 71a of the solenoid housing 71.

[0043] A spring chamber 77 is formed on the solenoid housing 71 in an axially continuous manner with the opening 71b. A spring 74 is formed inside the spring chamber 77, with one end locked to the plunger 72 and the other end locked inside the solenoid housing 71.

[0044] The force of the spring 74 acts on the pilot lift valve 9 via the plunger 72 and the rod 73 connected to the shaft of the plunger 72. That is, the spring 74 applies force to the pilot lift valve 9 by drawing the valve part 9a into the seat part 11a.

[0045] When current is supplied to the coil 75 of the solenoid section 70 of the above-described structure, a thrust that overcomes the force of the spring 74 acts on the plunger 72. Therefore, the force of the spring 74 acting on the pilot lift valve 9 via the plunger 72 and the rod 73 decreases. As a result, the pressure required for the valve section 9a of the pilot lift valve 9 to disengage from the seat section 11a, the so-called cracking pressure, decreases. Thus, by controlling the energization of the coil 75 to change the force of the spring 74 acting on the pilot lift valve 9, the set pressure at which the pilot lift valve 9 opens can be altered.

[0046] Next, the main operation of the electromagnetic relief valve 100 involved in this embodiment will be explained.

[0047] The working oil in the high-pressure passage H is guided to the back pressure chamber 8 via the pilot passage 10. The working oil in the high-pressure passage H flows into the back pressure chamber 8 through the throttling passage 10c of the pilot passage 10 until the pressure in the high-pressure passage H reaches the opening pressure of the main lift valve 5, thereby creating a differential pressure between the back pressure chamber 8 and the high-pressure passage H corresponding to the throttling of the throttling passage 10c. When the pressure in the high-pressure passage H reaches the set pressure (opening pressure) of the pilot lift valve 9 set by the solenoid section 70, the pilot lift valve 9 opens. With the pilot lift valve 9 open, the working oil in the back pressure chamber 8 flows to the discharge chamber 12 via the first passage 11 and is discharged to the low-pressure passage L through the gap 2d between the outer peripheral surface of the suction lift valve 3 and the inner peripheral surface of the valve housing 2.

[0048] As shown in Figure 2, when the pressure difference between the high-pressure passage H and the back pressure chamber 8 increases, the pilot piston 51 is dislodged from the body portion 50 by overcoming the force of the spring 81 and moves to the vicinity of the sleeve 7. The pilot piston 51 is configured to dislodge from the body portion 50 and move toward the sleeve 7 according to the pressure of the high-pressure passage H, thereby throttling the flow of working oil guided from the back pressure chamber 8 to the first passage 11 through the space 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 decreases.

[0049] As shown in Figure 3, when the pressure difference between the high-pressure passage H and the back-pressure chamber 8 further increases, the working oil in the back-pressure chamber 8 is guided to the low-pressure passage L via the first passage 11 and the discharge chamber 12. Simultaneously, the main body 50 disengages from the seat 3f of the suction lift valve 3, and the main lift valve 5 opens. This guides the working oil from the high-pressure passage H to the low-pressure passage L, thus preventing the pressure in the high-pressure passage H from abnormally becoming high.

[0050] Here, with a large opening between the back pressure chamber and the first passage, when the main lift valve opens, a significant amount of working oil flows out of the back pressure chamber, potentially causing a substantial drop in pressure within the chamber. Since the main lift valve moves due to the pressure difference between the high-pressure passage and the back pressure chamber, a significant drop in pressure in the back pressure chamber can easily lead to a large change in the position of the main lift valve, potentially adversely affecting the operation of the relief valve.

[0051] In contrast, in the electromagnetic relief valve 100 of this embodiment, when the pilot piston 51 is removed from the body 50, it moves toward the sleeve 7, and the gap A between the pilot piston 51 and the sleeve 7 decreases. The pilot passage 10 and the first passage 11 are connected to the back pressure chamber 8 via the gap A. When the gap A decreases, the resistance applied to the working oil flowing through the gap A increases, thereby reducing the amount of working oil flowing through the gap A. Instead, the amount of working oil flowing through the second passage 13 increases. That is, when the pilot piston 51 is removed from the body 50 and the gap A decreases, the amount of working oil flowing from the back pressure chamber 8 through the gap A to the first passage 11 decreases, and the amount of working 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 working oil flowing from the back pressure chamber 8 through the second passage 13 to the first passage 11, the amount of working oil flowing out of the back pressure chamber 8 decreases, suppressing a large drop in the pressure of the back pressure chamber 8. Since the main lift valve 5 moves through the pressure difference between the high-pressure passage H and the back pressure chamber 8, the large drop in pressure in the back pressure chamber 8 is suppressed, thereby suppressing the large positional change of the main lift valve 5, and the operation of the electromagnetic relief valve 100 becomes stable.

[0052] Furthermore, as shown in Figure 4, when the pilot piston 51 completes its full stroke against the force of the spring 81, the conical portion 51c sits on the sitting portion 11b of the sleeve 7. Specifically, the conical portion 51c and the sitting portion 11b are in line contact. With the conical portion 51c seated on the sitting portion 11b of the sleeve 7, the flow of working oil from the back pressure chamber 8, guided to the first passage 11 through the space between the conical portion 51c and the sitting portion 11b, is cut off. That is, the working oil in the back pressure chamber 8 does not flow out through gap A to the first passage 11 and the discharge chamber 12, but instead flows out through the second passage 13 and the pilot passage 10 to the first passage 11 and the discharge chamber 12. This prevents excessive working oil from flowing out of the back pressure chamber 8. Consequently, large fluctuations in the pressure of the back pressure chamber 8 and the position of the main lift valve 5 are further suppressed, and the operation of the electromagnetic relief valve 100 is further stabilized. Furthermore, since the pilot piston 51 and the sleeve 7 are in line contact, compared with the case where the pilot piston 51 and the sleeve 7 are in surface contact, the flow of working oil is more reliably cut off through the contact surface of the pilot piston 51 and the sleeve 7. Therefore, the operation of the electromagnetic relief valve 100 is further stabilized.

[0053] Furthermore, when the high-pressure passage H becomes negative, that is, when the pressure in the high-pressure passage H is lower than the pressure in the low-pressure passage L, the suction lift valve 3 dismounts from the seat 1a of the equipment body 1, and the suction lift valve 3 opens. This allows working oil to be guided from the low-pressure passage L to the high-pressure passage H.

[0054] According to the above implementation method, the following effects were achieved.

[0055] When the pilot piston 51 moves from the body 50 toward the sleeve, the gap A between the pilot piston 51 and the sleeve 7 decreases. As a result, the amount of working oil flowing from the back pressure chamber 8 through gap A to the first passage 11 decreases, while the amount of working oil flowing from the back pressure chamber 8 through the second passage 13 to the first passage 11 increases. Because resistance is applied to the working oil flowing from the back pressure chamber 8 through the second passage 13 to the first passage 11, the amount of working oil flowing out of the back pressure chamber 8 decreases, suppressing a significant drop in pressure in the back pressure chamber 8. This suppresses large positional changes in the main lift valve 5, stabilizing the operation of the lift valve.

[0056] When the pilot piston 51 completes its full stroke against the force of the spring 81, the conical portion 51c sits on the sitting portion 11b of the sleeve 7. With the conical portion 51c seated on the sitting portion 11b of the sleeve 7, working oil flows out from the back pressure chamber 8 through the second passage 13 and the pilot passage 10. This prevents excessive working oil from flowing out of the back pressure chamber 8. Consequently, it further suppresses large fluctuations in the pressure of the back pressure chamber 8 and the position of the main lift valve 5, and further stabilizes the operation of the solenoid relief valve 100.

[0057] Furthermore, the following modifications are also within the scope of the present invention, and it is possible to combine the structures shown in the modifications with the structures described in the above embodiments, or to combine the structures described in the following different modifications with each other.

[0058] <Variation Example 1>

[0059] In the above embodiment, a second passage 13 having a throttling section 13a is formed in the pilot piston 51. Alternatively, as shown in FIG5, a second passage 113 having a throttling section 113a can also be formed in the sleeve 7, connecting the back pressure chamber 8 and the first passage 11. That is, the second passage only needs to be formed in a way that connects the pilot passage 10 and the back pressure chamber 8, or the back pressure chamber 8 and the first passage 11. In this structure, when the pilot piston 51 is removed from the body 50, the gap A between the pilot piston 51 and the sleeve 7 decreases, the amount of working oil guided from the back pressure chamber 8 to the first passage 11 through the gap A decreases, and the amount of working oil flowing out of the back pressure chamber 8 to the first passage 11 through the second passage 113 increases, thus achieving the same effect as the above embodiment.

[0060] <Variation Example 2>

[0061] In the above embodiment, the second passage 13 with the throttling portion 13a is formed such that it is not connected to the back pressure chamber 8 when the pilot piston 51 is seated in the body portion 50. Alternatively, as shown in FIG6, the second passage 213 with the throttling portion 213a can also be formed such that it is connected to the back pressure chamber 8 when the pilot piston 51 is seated in the body portion 50. Specifically, the second passage 213 is formed on the end face 51e side of the pilot piston 51 compared to the flange portion 51a. Even in this structure, when the pilot piston 51 is removed from the body portion 50, the gap A between the pilot piston 51 and the sleeve 7 becomes smaller, the amount of working oil guided from the back pressure chamber 8 to the first passage 11 through the gap A decreases, and the amount of working oil flowing out of the back pressure chamber 8 to the first passage 11 through the second passage 213 increases. Therefore, the same effect as the above embodiment is achieved.

[0062] <Variation Example 3>

[0063] As shown in Figures 7A and 7B, the second passage 313 with the throttling section 313a can also be an annular passage disposed on the outer peripheral surface of the pilot piston 51 and connecting the throttling passage 10c and the back pressure chamber 8. Specifically, the second passage 313 is disposed between the outer peripheral surface of the pilot piston 51 and the inner peripheral surface of the sliding hole 50a. Even in this structure, when the pilot piston 51 is removed from the body 50, the gap A between the pilot piston 51 and the sleeve 7 decreases, the amount of working oil guided from the back pressure chamber 8 to the first passage 11 through the gap A decreases, and the amount of working oil flowing out of the back pressure chamber 8 through the second passage 313 to the first passage 11 increases. Therefore, the same effect as in the above embodiment is achieved.

[0064] <Variation Example 4>

[0065] As shown in Figures 8A and 8B, the second passage 413 with the throttling section 413a can also be a connecting groove provided axially on the outer peripheral surface of the pilot piston 51, connecting the throttling passage 10c and the back pressure chamber 8. Specifically, the second passage 413 is provided in a straight line extending in the axial direction of the pilot piston 51. Even in this structure, when the pilot piston 51 is removed from the body 50, the gap A between the pilot piston 51 and the sleeve 7 decreases, the amount of working oil guided from the back pressure chamber 8 to the first passage 11 through the gap A decreases, and the amount of working oil flowing out of the back pressure chamber 8 through the second passage 413 to the first passage 11 increases. Therefore, the same effect as in the above embodiment is achieved.

[0066] <Variation Example 5>

[0067] In the above embodiment, the second passage 13 with the throttling section 13a is a connecting hole that opens on the outer peripheral surface of the pilot piston 51 and connects the pilot passage 10 and the back pressure chamber 8. Alternatively, as shown in FIG9, the second passage 513 with the throttling section 513a can also be a groove provided in the seat portion 11b of the sleeve 7, in which working fluid is guided from the back pressure chamber 8 to the first passage 11 via the groove when the conical portion 51c of the pilot piston 51 is seated in the seat portion 11b of the sleeve 7. Specifically, the second passage 513 is arranged linearly along the seat portion 11b of the sleeve 7. Even in this structure, when the conical portion 51c of the pilot piston 51 is seated in the seat portion 11b of the overflow valve 7, the amount of working oil guided to the first passage 11 via the second passage 513 is reduced, thus achieving the same effect as the above embodiment.

[0068] <Variation Example 6>

[0069] In the above embodiment, when the pilot piston 51 completes its full stroke by overcoming the force of the spring 81, the tapered portion 51c of the pilot piston 51 sits on the sitting portion 11b of the spring 7, and the second passage 13 is a connecting hole that opens on the outer peripheral surface of the pilot piston 51 and connects the pilot passage 10 and the back pressure chamber 8. Alternatively, as shown in FIG10, the pilot piston 651 can also be configured such that it does not complete its full stroke by overcoming the force of the spring 681, which has a stronger force than the spring 81. In this case, the top end portion 651d opposite the sleeve 607 is formed into a cylindrical shape. Inside the sleeve 607, a receiving portion 611c is provided that connects the back pressure chamber 8 and the first passage 11 and accommodates the top end portion 651d as the pilot piston 651 moves toward the sleeve 607. The second passage 613 having a throttling section 613a has a gap 613b formed by the inner peripheral surface of the receiving section 611c and the outer peripheral surface of the tip portion 651d of the pilot piston 651 received in the receiving section 611c, connecting the pilot passage 10 and the back pressure chamber 8. Specifically, the second passage 613 is provided between the outer peripheral surface of the tip portion 651d of the pilot piston 651 and the inner peripheral surface of the receiving section 611c. Additionally, as shown in FIG11, the second passage 713 having a throttling section 713a may also have a connecting groove 713b provided on the end face 651e of the tip portion 651d, connecting the pilot passage 10 and the back pressure chamber 8. In this case, the second passage 713 is provided in a straight line extending along the end face 651e. In the above structure, when the top end 51d of the pilot piston 51 is housed in the housing portion 611c of the sleeve 607, the amount of working oil guided to the first passage 11 via the second passages 613 and 713 is reduced, thus achieving the same effect as the above embodiment.

[0070] The structure, function, and effects of the embodiments of the present invention as described above are summarized and explained.

[0071] The electromagnetic relief valve 100, acting as a relief valve, comprises: a valve housing 2, which is mounted on a device body 1 having a high-pressure passage H and a low-pressure passage L; a suction lift valve 3, which is disposed within the valve housing 2 and allows the flow of working fluid between the high-pressure passage H and the low-pressure passage L by moving away from and settling into the device body 1; and a main lift valve 5, which is disposed within the suction lift valve 3 and allows the flow of working fluid between the high-pressure passage H and the low-pressure passage L by moving away from and settling into the suction lift valve 3. The low-pressure passage L connects and disconnects the working fluid; sleeves 7 and 607, which are located within the suction lift valve 3 and divide the back pressure chamber 8 between the suction lift valve 3 and the main lift valve 5; pilot passage 10, which is located within the main lift valve 5 and faces the high-pressure passage H and the back pressure chamber 8; discharge chamber 12, which is located within sleeves 7 and 607 and discharges the working fluid from the back pressure chamber 8; first passage 11, which is located within sleeves 7 and 607 in a manner that connects the discharge chamber 12 and the back pressure chamber 8; second passages 13 to 81 3. It is provided with throttling sections 13a to 813a that apply resistance to the flowing working fluid. The second passages 13 to 813 are formed to connect the pilot passage 10 and the back pressure chamber 8, or the back pressure chamber 8 and the first passage 11. The main lift valve 5 has: a body portion 50, which is disengaged from the suction lift valve 3 and seated in the suction lift valve 3; pilot pistons 51 and 651, which are slidably disposed in sliding holes 50a provided on the body portion 50 and disengaged from the body portion 50. The pilot passage 10 is located in the main body 50 and opens on the end faces 51e and 651e of the top portions 51d and 651d of the pilot pistons 51 and 651 opposite to the sleeves 7 and 607. The pilot pistons 51 and 651 are configured to move away from the main body 50 and toward the sleeves 7 and 607 according to the pressure of the high pressure passage H, thereby throttling the flow of working fluid that is guided from the back pressure chamber 8 to the first passage 11 through the pilot pistons 51 and 651 and the sleeves 7 and 607.

[0072] In this structure, when the pilot pistons 51 and 651 disengage from the body 50, the gap A between the pilot pistons 51 and 651 and the sleeves 7 and 607 decreases, making it difficult for the working oil to be guided from the back pressure chamber 8 through the gap A between the pilot pistons 51 and 651 and the sleeves 7 and 607 to the first passage 11. Simultaneously, the working fluid in the back pressure chamber 8 is guided to the pilot passage 10 through the second passages 13 to 813, and flows out from the openings at the top ends 51d and 651d of the pilot pistons 51 and 651 to the first passage 11. Because resistance is applied to the working fluid flowing from the back pressure chamber 8 through the second passages 13 to 813 to the first passage 11, the amount of working fluid flowing out of the back pressure chamber 8 is reduced, suppressing a significant drop in pressure in the back pressure chamber 8. This suppresses large changes in the position of the main lift valve 5, stabilizing the operation of the electromagnetic lift valve 100.

[0073] The pilot passage 10 has: a top side passage 10a, which is disposed inside the pilot piston 51 and faces the high pressure passage H; a base side passage 10b, which is disposed inside the pilot piston 51 and faces the back pressure chamber 8; and second passages 13 and 213 are connecting holes that open on the outer peripheral surface of the pilot piston 51 and connect the base side passage 10b and the back pressure chamber 8.

[0074] The pilot passage 10 has: a top-side passage 10a, which is disposed inside the pilot piston 51 and faces the high-pressure passage H; a base-side passage 10b, which is disposed inside the pilot piston 51 and faces the back pressure chamber 8; a throttling passage 10c, which communicates with the top-side passage 10a and the base-side passage 10b, and is formed by the outer peripheral surface of the pilot piston 51 and the sliding hole 50a of the body portion 50; and second passages 313 and 413 are disposed on the outer peripheral surface of the pilot piston 51 and connect the throttling passage 10c and the back pressure chamber 8.

[0075] In the above structure, the working fluid flowing out of the back pressure chamber 8 is resisted through the second passages 13, 213, 313, and 413. Therefore, the amount of working fluid flowing out of the back pressure chamber 8 is reduced, suppressing a large drop in pressure in the back pressure chamber 8. This suppresses large changes in the position of the main lift valve 5, and the operation of the electromagnetic lift valve 100 is stable.

[0076] The pilot piston 51 has a tapered portion 51c that sits on the sitting portion 11b provided on the sleeve 7. When the tapered portion 51c of the pilot piston 51 sits on the sitting portion 11b of the sleeve 7, the flow of working fluid that is guided from the back pressure chamber 8 to the first passage 11 through the tapered portion 51c and the sitting portion 11b is cut off.

[0077] In this structure, with the conical base of the pilot piston 51 seated in the seat portion 11b of the sleeve 7, the working fluid flows out from the back pressure chamber 8 only through the second passages 13-513. This further suppresses large fluctuations in the pressure of the back pressure chamber 8 and the position of the main lift valve 5, and further stabilizes the operation of the electromagnetic relief valve 100.

[0078] The second passage 513 is a groove provided in the conical portion 51c of the pilot piston 51. When the conical portion 51c of the pilot piston 51 is seated in the seat portion 11b of the sleeve 7, the working fluid is guided from the back pressure chamber 8 to the first passage 11 via the groove.

[0079] The top end 651d of the pilot piston 651, which is opposite to the sleeve 607, is formed into a cylindrical shape. Inside the sleeve 607, there is a receiving part 611c that connects the back pressure chamber 8 and the first passage 11 and receives the top end 651d as the pilot piston 651 moves toward the sleeve 607. The second passages 613, 713, and 813 are formed by the inner peripheral surface of the receiving part 611c and the outer peripheral surface of the top end 651d of the pilot piston 651 received in the receiving part 611c.

[0080] In the above structure, the working fluid flowing out of the back pressure chamber 8 is resisted by the second passages 513, 613, 713, and 813. Therefore, the amount of working fluid flowing out of the back pressure chamber 8 is reduced, suppressing a large drop in pressure in the back pressure chamber 8. This suppresses large changes in the position of the main lift valve 5, and the operation of the electromagnetic lift valve 100 is stable.

[0081] The embodiments of the present invention have been described above. However, the above embodiments are merely some examples of the application of the present invention and are not intended to limit the technical scope of the present invention to the specific structures of the above embodiments.

[0082] This application claims priority based on Japanese Patent Application 2020-114219 filed with the Japan Patent Office on July 1, 2020, the entire contents of which are incorporated herein by reference.

Claims

1. An overflow valve comprising: a valve housing mounted on a device body, wherein a high-pressure passage and a low-pressure passage are provided on the device body; a suction lift valve disposed within the valve housing, which allows the flow of working fluid between the high-pressure passage and the low-pressure passage by disengaging from and repositioning itself on the device body; and a main lift valve disposed within the suction lift valve, which connects and disconnects the working fluid between the high-pressure passage and the low-pressure passage by disengaging from and repositioning itself on the suction lift valve. A sleeve, which is located inside the suction lift valve, divides a back pressure chamber between itself and the main lift valve; a pilot passage, which is located in the main lift valve and faces the high pressure passage and the back pressure chamber; A discharge chamber is provided inside the sleeve and discharges the working fluid from the back pressure chamber; A first passage is provided within the sleeve to connect the discharge chamber and the back pressure chamber; a second passage is configured to connect the pilot passage or the first passage to the back pressure chamber and is provided with a throttling section that applies resistance to the flowing working fluid; the main lift valve has: a body portion that is disengaged from and seated in the suction lift valve; a pilot piston that is slidably disposed in a sliding hole provided on the body portion, and disengaged from and seated in the body portion; the pilot passage is located at the top of the pilot piston opposite the sleeve. The pilot piston has an end opening and a tapered portion. The tapered portion is seated on a seat portion provided on the sleeve. The pilot piston is configured to move away from the body portion and toward the sleeve according to the pressure of the high-pressure passage, thereby throttling the flow of working fluid guided from the back pressure chamber to the first passage through the space between the pilot piston and the sleeve. When 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 to the first passage through the space between the tapered portion and the seat portion is cut off.

2. The overflow valve as claimed in claim 1, wherein, The pilot passage has: a first pilot passage disposed inside the pilot piston and facing the high-pressure passage; and a second pilot passage disposed inside the pilot piston and facing the back pressure chamber, wherein the second passage is a connecting hole that opens on the outer peripheral surface of the pilot piston and connects the second pilot passage to the back pressure chamber.

3. The overflow valve as described in claim 1, wherein, The pilot passage has: a first pilot passage disposed within the pilot piston and facing the high-pressure passage; The second pilot passage is disposed inside the pilot piston and faces the back pressure chamber; the third pilot passage is connected to the first pilot passage and the second pilot passage, and is formed by the outer peripheral surface of the pilot piston and the sliding hole of the body portion. The second passage is disposed on the outer peripheral surface of the pilot piston and connects the third pilot passage to the back pressure chamber.

4. The relief valve as described in any one of claims 1 to 3, wherein, The second passage is a groove provided in the conical portion of the pilot piston. When the conical portion of the pilot piston is seated in the seat portion of the sleeve, working fluid is guided from the back pressure chamber to the first passage through the groove.

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