Relief valve and relief valve device including relief valve

Abstract

An electromagnetic relief valve (100) includes: a back pressure chamber (8) to which hydraulic oil for biasing a main poppet (5) in the valve closing direction is guided; a pilot poppet (20) for allowing or preventing communication between the back pressure chamber (8) and a discharge flow path for discharging the hydraulic oil; and a solenoid unit (S) for biasing the pilot poppet (20) in the valve closing direction. The solenoid unit (S) includes: a plunger (72) that presses the pilot poppet (20); a spring (74) that biases the pilot poppet (20) in the valve closing direction; and a coil (75) that applies, to the plunger (72), a reaction force against the biasing force of the spring (74) to which a current is applied. When reducing the pressure of a high-pressure passage (H) to the pressure of a low-pressure passage (L), a current (Ir) that generates a reaction force greater than the biasing force with which the spring (74) biases the pilot poppet (20) in the valve-closing direction is applied to the coil (75).

Description

Relief valve and relief valve device equipped with relief valve

[0001] The present invention relates to a relief valve and a relief valve device including the relief valve.

[0002] JPH4-136374U discloses a relief valve that opens when the pressure of the hydraulic oil in a high-pressure passage reaches a set relief pressure, thereby releasing the hydraulic oil from a supply port to a relief port.

[0003] For example, in a hydraulic circuit, the pressure in the high-pressure flow path may need to be reduced to the pressure in the low-pressure flow path (atmospheric pressure or tank pressure) during maintenance or replacement work. In this case, a relief valve such as that described in JPH4-136374U can reduce the pressure of the hydraulic oil on the supply port side to a set relief pressure, but cannot reduce the pressure of the hydraulic oil on the supply port side to the pressure in the low-pressure flow path.

[0004] Therefore, it is necessary to provide a pressure relief valve in addition to the relief valve, which increases costs accordingly.

[0005] The object of the present invention has been made in consideration of the above problems, and is to provide a relief valve that can reduce the pressure in the high-pressure side flow path to the pressure in the low-pressure side flow path.

[0006] According to one aspect of the present invention, there is provided a relief valve comprising: a main valve element which connects or blocks a high-pressure side passage and a low-pressure side passage; a back pressure chamber into which working fluid is guided which urges the main valve element in a valve closing direction; a pilot valve element which connects or blocks the back pressure chamber and a discharge flow path for discharging the working fluid; and a biasing portion which biases the pilot valve element in a valve closing direction, wherein the biasing portion has a plunger portion which presses the pilot valve element; a biasing member which is provided on the opposite side of the plunger portion from the pilot valve element and urges the pilot valve element in a valve closing direction; and a coil which, when an electric current is applied, applies a reaction force to the plunger portion which opposes the biasing force of the biasing member, and when the pressure of the high-pressure side passage is reduced to that of the low-pressure side passage, an electric current which generates a reaction force greater than the biasing force with which the biasing member urges the pilot valve element in a valve closing direction is applied to the coil.

[0007] Fig. 1 is a schematic diagram of a relief valve device and an electromagnetic relief valve according to an embodiment of the present invention. Fig. 2 is a graph showing the relationship between applied current and set pressure of the electromagnetic relief valve according to an embodiment of the present invention. Fig. 3 is a schematic diagram of the electromagnetic relief valve according to an embodiment of the present invention in a pressure release mode.

[0008] Referring to FIG. 1, an electromagnetic relief valve 100 according to an embodiment of the present invention and a relief valve device VS including the electromagnetic relief valve 100 will be described.

[0009] The relief valve device VS includes an electromagnetic relief valve 100 as a relief valve, and a control device C that controls the current I applied to the coil 75 of the electromagnetic relief valve 100.

[0010] The electromagnetic relief valve 100 is an inverse proportional type electromagnetic relief valve, which is configured so that the relief pressure decreases as the value of current applied to a solenoid (described later) increases.

[0011] The electromagnetic relief valve 100 is provided, for example, in a hydraulic control circuit that controls the operation of construction machinery. The electromagnetic relief valve 100 opens when the pressure of the hydraulic oil in the high-pressure passage H reaches a set pressure (relief pressure), and by releasing the hydraulic oil from the high-pressure passage H to the low-pressure passage L, prevents the pressure of the hydraulic oil in the high-pressure passage H from becoming abnormally high. 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.

[0012] As shown in Fig. 1 , 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. Note that, in this embodiment, an example is shown in which the electromagnetic relief valve 100 is attached to the equipment body 1, but the electromagnetic relief valve 100 is not limited to this and can be applied to various devices, pipelines, and the like. Furthermore, in this embodiment, an example is described in which hydraulic oil is used as the working fluid of the equipment body 1, but the working fluid may be other liquids such as hydraulic water, or may be gas such as compressed air.

[0013] The device body 1 is provided with a high-pressure passage H and a low-pressure passage L, with the electromagnetic relief valve 100 as the boundary. The device 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 device body 1 is not limited to the main body of a hydraulic device, and may be a block body or the like installed between hydraulic devices.

[0014] As shown in FIG. 1, the electromagnetic relief valve 100 includes a valve portion V for connecting or disconnecting a high-pressure passage H and a low-pressure passage L, and a solenoid portion S as a biasing portion for adjusting a set pressure (relief pressure).

[0015] As shown in FIG. 1 , the valve section V includes a valve housing 2 attached to a device main 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 connect or disconnect the high-pressure passage H and the low-pressure passage L by lifting off or seating on a seat portion 1a, and a main poppet 5 as a main valve element provided within the suction poppet 3 and configured to connect or disconnect the high-pressure passage H and the low-pressure passage L by lifting off or seating on a seat portion 3f as a second valve seat formed on the suction poppet 3. Within the suction poppet 3, there is provided a back pressure chamber 8 into which hydraulic oil is introduced from the high pressure passage H to urge the main poppet 5 in the valve closing direction, a sleeve 7 which separates the back pressure chamber 8 from the main poppet 5, a pilot passage 10 which is provided in the main poppet 5 and connects the high pressure passage H and the back pressure chamber 8, a drain chamber 12 which is provided in the sleeve 7 and from which the hydraulic oil in the back pressure chamber 8 is discharged, a first communication passage P1 which is provided in the sleeve 7 and connects the drain chamber 12 and the back pressure chamber 8, and a pilot poppet 20 which is provided in the sleeve 7 and opens and closes the first communication passage P1.

[0016] 1, the valve housing 2 is a cylindrical member having a first cylindrical portion 2a attached to the device body 1 and a second cylindrical portion 2b connected to a connecting member 90 on the opposite side to the first cylindrical portion 2a. The valve housing 2 is connected to the solenoid housing 71 of the solenoid portion S by the connecting member 90.

[0017] The suction poppet 3 is a cylindrical member having a cylindrical portion 3a and a bottom portion 3b. The suction poppet 3 is provided axially movable within the valve housing 2, with a portion of it protruding from the opening of the first cylindrical portion 2a of the valve housing 2. A high-pressure port 3H communicating with the high-pressure passage H is provided in 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.

[0018] 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 when this corner 3c is seated on the seat portion 1a of the device body 1, communication between the high-pressure passage H and the low-pressure passage L through the device body 1 and the suction poppet 3 is blocked. A first accommodation hole 3d for accommodating the main poppet 5 is provided on the bottom portion 3b side of the suction poppet 3, and a second accommodation hole 3e, which has a larger diameter than the first accommodation hole 3d and for accommodating the sleeve 7, is provided at the end opposite the bottom portion 3b.

[0019] The main poppet 5 has a main body portion 50 that can slide within the first accommodating hole 3d, and a pilot piston 51 that can slide within a sliding hole 50a that is formed axially through the main body portion 50.

[0020] The main body 50 has a valve portion 50b that seats on a seat portion 3f formed inside a corner 3c of the suction poppet 3. When the valve portion 50b seats 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 (O-ring) is provided between the outer peripheral surface of the main body 50 and the inner peripheral surface of the suction poppet 3 to seal the gap between the main body 50 and the suction poppet 3.

[0021] The pilot piston 51 has a flange portion 51a provided facing the back pressure chamber 8, which is a space defined by the inner circumferential surface of the suction poppet 3, the main poppet 5, and the sleeve 7, and a cylindrical shaft portion 51b extending axially from the flange portion 51a and inserted into the slide hole 50a. The tip of the shaft portion 51b protrudes from the tip surface of the main body portion 50 facing the high-pressure passage H. The pilot piston 51 also has a pilot passage 10 that communicates between the high-pressure passage H and the back pressure chamber 8. The pilot passage 10 has a throttle that applies resistance to the hydraulic oil flowing through the pilot passage 10.

[0022] The sleeve 7 has a tip end 7a that is inserted into the suction poppet 3, a base end 7b that is connected to the connecting member 90, an accommodation hole 7c that opens to the axial end opposite the tip end 7a, and an intermediate portion 7d that is provided between the tip end 7a and the base end 7b and whose outer circumferential surface is exposed between the suction poppet 3 and the connecting member 90. The sleeve 7 slidably supports the suction poppet 3 at the tip end 7a. A seal member (O-ring) that seals the gap between the sleeve 7 and the suction poppet 3 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.

[0023] The sleeve 7 also has a first communication passage P1, one end of which opens into the back pressure chamber 8 and the other end of which opens into the bottom surface of the accommodating hole 7c, connecting the back pressure chamber 8 and the accommodating hole 7c, and a drain passage 13, one end of which opens into the inner surface of the accommodating hole 7c and the other end of which opens into the outer surface of the intermediate portion 7d.

[0024] A seat portion 11a on which the valve portion 22 of the pilot poppet 20 seats and leaves is provided at the open end of the first communication passage P1 that opens into the accommodating bore 7c. The seat portion 11a is formed coaxially with the accommodating bore 7c so that its central axis coincides with the central axis of the accommodating bore 7c. In addition, a throttle 11b is provided in the first communication passage P1 between the seat portion 11a and the back pressure chamber 8 to provide resistance to the flow of hydraulic oil flowing through the first communication passage P1.

[0025] The drain chamber 12 is a space defined by the receiving hole 7 c and the pilot poppet 20 .

[0026] The drain passage 13 is constantly in communication with the drain chamber 12 and the low-pressure passage L through a gap 14 between the outer peripheral surface of the suction poppet 3 and the inner peripheral surface of the valve housing 2 .

[0027] 1, the pilot poppet 20 is a member formed in a substantially cylindrical shape and is accommodated in the accommodation hole 7c of the sleeve 7. The pilot poppet 20 has a main body portion 21 slidably supported in the accommodation hole 7c, and a conical valve portion 22 that protrudes axially from the main body portion 21.

[0028] The main body 21 of the pilot poppet 20 is provided with an annular groove 21a formed to be constantly in communication with the drain passage 13, a first notch 21b formed along the axial direction from the annular groove 21a toward the valve portion 22 side, and a second notch 21c formed along the axial direction from the annular groove 21a toward the solenoid portion S side.

[0029] The first notch 21b is formed by cutting out a flat portion of the outer peripheral surface of the main body 21. By forming the first notch 21b in the main body 21 in this manner, the drain chamber 12 communicates with the low-pressure passage L through a passage defined by the inner peripheral surface of the accommodating hole 7c and the first notch 21b, the annular groove 21a, the drain passage 13, and the gap 14. The passage defined by the inner peripheral surface of the accommodating hole 7c and the first notch 21b also functions as a first throttle that applies resistance to the hydraulic oil being discharged from the back pressure chamber 8 to the low-pressure passage L. Hereinafter, the passage defined by the inner peripheral surface of the accommodating hole 7c and the first notch 21b, the annular groove 21a, the drain passage 13, and the gap 14 will be referred to as a "second communication passage P2."

[0030] The second cutout 21c is formed by cutting out a flat portion of the outer peripheral surface of the main body 21 along the axial direction from the annular groove 21a toward the solenoid S so that the end of the pilot poppet 20 on the side of the solenoid S is always exposed from the accommodation hole 7c. By forming the second cutout 21c in the main body 21 in this manner, the space SP where the rear end of the pilot poppet 20 is exposed communicates with the low-pressure passage L through a passage defined by the inner peripheral surface of the accommodation hole 7c and the second cutout 21c, the annular groove 21a, the drain passage 13, and the gap 14.

[0031] The pilot poppet 20 thus formed is slidably supported by the accommodation hole 7c formed coaxially with the seat portion 11a. That is, the pilot poppet 20 is supported by the accommodation hole 7c so that its central axis is not tilted relative to the central axis of the seat portion 11a. In this way, the pilot poppet 20 is prevented from being tilted relative to the seat portion 11a, thereby preventing the valve portion 22 from making uneven contact with the seat portion 11a when seated on the seat portion 11a. This prevents damage or deformation of the seat portion 11a, resulting in improved seating properties when the valve portion 22 seats on the seat portion 11a.

[0032] Although the annular groove 21 a is formed on the outer peripheral surface of the main body 21 of the pilot poppet 20, the annular groove 21 a may alternatively be formed on the inner peripheral surface of the accommodation hole 7 c. Furthermore, although the first notch 21 b and the second notch 21 c are formed on the outer peripheral surface of the main body 21 of the pilot poppet 20, the first notch 21 b and the second notch 21 c may alternatively be formed as grooves in the axial direction on the inner peripheral surface of the accommodation hole 7 c.

[0033] 1, 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 connecting member 90. The spring 81 urges the pilot piston 51 so that the flange portion 51a abuts against the main body portion 50 of the main poppet 5, and also 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. Meanwhile, 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 equipment main body 1.

[0034] Next, the solenoid portion S will be described with reference to FIG.

[0035] The solenoid section S includes a plunger 72 slidably housed within a solenoid housing 71, a rod 73 fixed to the plunger 72 and having a tip that abuts against the pilot poppet 20, a spring 74 as a biasing member that is engaged within the solenoid housing 71 and biases the plunger 72 toward the pilot poppet 20, a coil 75 housed within the solenoid housing 71 and applies a reaction force to the plunger 72 that opposes the biasing force of the spring 74, an adjuster 76 that adjusts the biasing force of the spring 74, and an air bleed mechanism 79 that connects or blocks communication between a spring chamber 77 (described later) and the atmosphere. In this embodiment, the housing that covers the coil 75 is also included in the solenoid housing 71. In this embodiment, the plunger 72 and the rod 73 correspond to the "plunger section" in the claims.

[0036] The solenoid housing 71 is a cylindrical member with a bottom, and an accommodation hole 71c for accommodating the plunger 72 is formed at an end 71a, and the end 71a is connected to the connecting member 90. The solenoid housing 71 is formed with a spring chamber 77, which is continuous with the accommodation hole 71c in the axial direction and serves as a biasing member chamber for accommodating the spring 74.

[0037] The biasing force of the spring 74 acts to bias the pilot poppet 20 in the valve closing direction via the plunger 72 and the rod 73 connected to the plunger 72. In other words, the spring 74 biases the pilot poppet 20 so that the valve portion 22 of the pilot poppet 20 is seated on the seat portion 11 a.

[0038] When current I is applied to the coil 75, the coil 75 applies a thrust to the plunger 72 that counteracts the biasing force of the spring 74. As the current I applied to the coil 75 increases, the biasing force of the spring 74 acting on the pilot poppet 20 via the plunger 72 and the rod 73 decreases. As a result, the pressure required to separate the valve portion 22 of the pilot poppet 20 from the seat portion 11 a, known as the cracking pressure, decreases. In the electromagnetic relief valve 100, the set pressure (relief pressure) at which the pilot poppet 20 opens can be changed by controlling the current I applied to the coil 75 to change the biasing force of the spring 74 acting on the pilot poppet 20.

[0039] The connecting member 90, which connects the valve housing 2 and the solenoid housing 71, is a cylindrical member and has a first connecting portion 90a to which the valve housing 2 is connected, a second connecting portion 90b to which the solenoid housing 71 is connected, an accommodating hole 90c provided inside the first connecting portion 90a, and a through hole 90d that communicates with the accommodating hole 90c and axially penetrates the inside of the second connecting portion 90b. The base end 7b of the sleeve 7 is connected to the accommodating hole 90c, and the pilot poppet 20 protruding from the sleeve 7 is accommodated in the accommodating hole 90c. When the solenoid housing 71 is connected to the connecting member 90, the rod 73 is inserted through the through hole 90d.

[0040] When the valve housing 2 and the solenoid housing 71 are connected via the connecting member 90 having the above-described shape, the spring chamber 77 formed in the solenoid housing 71 communicates with the low-pressure passage L through the through hole 72a axially penetrating the plunger 72, the through hole 90d and the accommodating hole 90c (space SP) of the connecting member 90, a passage defined by the inner circumferential surface of the accommodating hole 7c and the second notch 21c, the annular groove 21a, the drain passage 13, and the gap 14. Hereinafter, the passage defined by the through hole 72a, the through hole 90d, the accommodating hole 90c (space SP), and the passage defined by the inner circumferential surface of the accommodating hole 7c and the second notch 21c will be referred to as the "third communication passage P3." The passage defined by the inner circumferential surface of the accommodating hole 7c and the second notch 21c functions as a second throttle that applies resistance to the hydraulic oil flowing through the third communication passage P3.

[0041] 1, the adjuster 76 is attached by screwing to a through-hole 78 formed at the end of the solenoid housing 71 so as to pass through the solenoid housing 71. By rotating the adjuster 76, the adjuster 76 moves in the axial direction of the solenoid housing 71, thereby adjusting the biasing force of the spring 74. In other words, the adjuster 76 can also be used to change the relief pressure of the electromagnetic relief valve 100.

[0042] The air bleed mechanism 79 has a plug 79 a that fits into a through-hole 76 a that passes through the adjuster 76 .

[0043] The plug 79a and the through hole 76a are threadedly coupled to each other at a threaded portion 79b, and by rotating the plug 79a, the plug 79a moves in the axial direction relative to the adjuster 76.

[0044] A valve portion 79c formed by a tapered surface is provided at one end of the plug 79a, and a port 79d for connecting a tube or the like is provided at the other end. When the valve portion 79c of the plug 79a abuts against a step portion 76b provided in the through-hole 76a of the adjuster 76, communication between the spring chamber 77 and the atmosphere is blocked. In contrast, when the valve portion 79c of the plug 79a moves away from the step portion 76b, the spring chamber 77 communicates with the atmosphere through a gap between the valve portion 79c and the step portion 76b and through a through-hole 79e formed in the plug 79a.

[0045] In this embodiment, the relief pressure (set pressure) Pr of the electromagnetic relief valve 100 is set by controlling the current I applied to the coil 75 by the control device C. As shown in Fig. 2, in the electromagnetic relief valve 100, the relief pressure (set pressure) Pr decreases as the current I applied to the coil 75 increases.

[0046] The control device C has two control modes for the electromagnetic relief valve 100: a normal mode and a pressure release mode.

[0047] The normal mode is selected when the electromagnetic relief valve 100 is used within a preset relief pressure range R1 (settable range). In other words, the normal mode is used when the electromagnetic relief valve 100 is used as a relief valve that defines the upper limit of the pressure in the hydraulic control circuit.

[0048] In the normal mode, the relief pressure (set pressure) can be changed by changing the magnitude of the current I applied to the coil 75 between 0 and Ic using the control device C (see FIG. 2).

[0049] The pressure release mode is selected when it is necessary to reduce the pressure in the high-pressure passage H to the pressure (atmospheric pressure or tank pressure) in the low-pressure passage L during maintenance, replacement, etc. In other words, the pressure release mode is used when the electromagnetic relief valve 100 is used as a pressure release valve for reducing the pressure in the hydraulic control circuit to the tank pressure or atmospheric pressure.

[0050] In the pressure release mode, the control device C applies to the coil 75 a current Ir or more that is greater than the maximum current (current Ic) in the normal mode and that generates a reaction force greater than the force of the spring 74 that urges the pilot poppet 20 in the valve closing direction.

[0051] Next, the operation of the electromagnetic relief valve 100 will be described.

[0052] The hydraulic oil in the high-pressure passage H is led to the first communication passage P1 through the pilot passage 10 and the back pressure chamber 8. When the pressure of the hydraulic oil led to the first communication passage P1 reaches the set pressure (cracking pressure) of the pilot poppet 20 set by the solenoid section S, the pressure of the hydraulic oil causes the valve section 22 of the pilot poppet 20 to separate from the seat section 11a.

[0053] When the valve portion 22 of the pilot poppet 20 leaves the seat portion 11a, the hydraulic oil in the back pressure chamber 8 is discharged to the low pressure passage L through the first communication passage P1, the gap between the valve portion 22 and the seat portion 11a, the drain chamber 12, and the second communication passage P2.

[0054] The back pressure chamber 8 is constantly supplied with hydraulic oil from the high pressure passage H through the pilot passage 10. However, the supply of hydraulic oil from the high pressure passage H to the back pressure chamber 8 is limited by a throttle provided in the pilot passage 10. Therefore, when the valve element 22 leaves the seat portion 11a and the hydraulic oil in the back pressure chamber 8 is discharged, the pressure in the back pressure chamber 8 gradually becomes lower than the pressure in the high pressure passage H.

[0055] In this way, when the pressure in the back pressure chamber 8 decreases, the biasing force due to the pressure in the back pressure chamber 8 acting in a direction to seat the body 50 of the main poppet 5 on the seat 3f of the suction poppet 3 decreases. Then, when the pressure difference between the pressure in the back pressure chamber 8 and the pressure in the high pressure passage H exceeds a predetermined pressure difference, the body 50 of the main poppet 5 lifts off the seat 3f of the suction poppet 3, and the main poppet 5 opens. This causes hydraulic oil to be discharged from the high pressure passage H to the low pressure passage L. In this way, the pressure in the high pressure passage H is prevented from becoming abnormally high.

[0056] When the pressure in the high-pressure passage H decreases, the pressure of the hydraulic oil guided from the high-pressure passage H through the pilot passage 10 to the back pressure chamber 8 also decreases. When the pressure in the first communication passage P1 acting on the pilot poppet 20 decreases to the set pressure (cracking pressure) of the pilot poppet 20 set by the solenoid portion S, the valve portion 22 of the pilot poppet 20 seats on the seat portion 11a. This increases the pressure in the back pressure chamber 8, and when the pressure difference between the pressure in the back pressure chamber 8 and the pressure in the high-pressure passage H becomes equal to or less than the preset pressure difference, the main poppet 5 closes.

[0057] In the relief valve device VS, when the electromagnetic relief valve 100 is used within the relief pressure range R1, i.e., when the electromagnetic relief valve 100 is used as a relief valve, the normal mode is selected. In the normal mode, the upper limit of the pressure in the high-pressure passage H can be set to the relief pressure (set pressure) as described above. Furthermore, in the normal mode, the relief pressure (set pressure) can be changed by changing the current I applied to the coil 75.

[0058] On the other hand, when performing maintenance or replacement work on equipment in a hydraulic circuit in which the electromagnetic relief valve 100 is installed, i.e., when using the electromagnetic relief valve 100 as a pressure relief valve, the pressure relief mode is selected. In the pressure relief mode, the control device C applies to the coil 75 a current Ir that is greater than the maximum current Ic in the normal mode. More preferably, a current Ir1 is applied to the coil 75 such that the plunger 72 (rod 73) is always positioned closer to the spring 74 than the position where the plunger 72 (rod 73) presses the pilot poppet 20 against the seat 11a (see the position shown in FIG. 3). Note that when the current Ir1 is applied to the coil 75 (the state shown in FIG. 3), the pilot poppet 20 is freely movable in the axial direction between the rod 73 and the seat 11a.

[0059] In the pressure release mode, the coil 75 applies an attractive force (reaction force) to the plunger 72 that exceeds the biasing force of the spring 74 in the valve closing direction, and therefore the biasing force of the spring 74 in the valve closing direction acting on the pilot poppet 20 becomes zero. As a result, only the pressure of the backpressure chamber 8 acts on the pilot poppet 20 in the valve opening direction through the first communication passage P1, and the valve portion 22 of the pilot poppet 20 lifts off the seat portion 11a.

[0060] When the valve portion 22 of the pilot poppet 20 leaves the seat portion 11a, the main poppet 5 opens in the same manner as in the normal mode. As a result, the hydraulic oil is discharged from the high-pressure passage H to the low-pressure passage L.

[0061] In the pressure release mode, as described above, the biasing force of the spring 74 acting on the pilot poppet 20 in the valve closing direction becomes zero, so the pilot poppet 20 remains open. Therefore, the backpressure chamber 8 is in communication with the low-pressure passage L through the first communication passage P1, the gap between the valve portion 22 and the seat portion 11a, the drain chamber 12, and the second communication passage P2. The main poppet 5 remains open due to the pressure difference between the backpressure chamber 8 and the high-pressure passage H. As a result, hydraulic oil in the high-pressure passage H continues to flow into the low-pressure passage L, and the pressure in the high-pressure passage H drops to the pressure in the low-pressure passage L. Even if the pressure difference between the backpressure chamber 8 and the high-pressure passage H falls below a predetermined pressure difference and the main poppet 5 closes, hydraulic oil in the high-pressure passage H is discharged to the low-pressure passage L through the pilot passage 10, the first communication passage P1, and the second communication passage P2. In this way, in the pressure release mode, by applying to the coil 75 a current Ir that is larger than the maximum current Ic in the normal mode, the pressure in the high-pressure passage H can be reduced to the pressure in the low-pressure passage L. From another perspective, the pressure release mode can also be said to be a mode in which the relief pressure (set pressure) is set to "0".

[0062] Furthermore, since the relief valve device VS of this embodiment has a normal mode and a pressure relief mode, the electromagnetic relief valve 100 can function not only as a relief valve but also as a pressure relief valve. This eliminates the need for a pressure relief valve, thereby suppressing increases in costs.

[0063] In the above embodiment, the control device C has a normal mode and a depressurization mode, and the control mode is switched between them. However, this is not limiting. For example, when a worker performs maintenance or replacement work, the worker may operate the control device C to temporarily increase the current I applied to the coil 75 to the current Ir or the current Ir1.

[0064] Furthermore, the coil 75 of the electromagnetic relief valve 100 may be one whose allowable current range, taking into consideration a safety factor, is less than the current Ir. In the pressure release mode (the time required for pressure release), the energization time is not particularly long (about several minutes), so there is no risk of the coil 75 burning out even if the current Ir is applied. In other words, a coil 75 that will not burn out even when used in the pressure release mode should be selected, taking into consideration the current value and energization time in the pressure release mode.

[0065] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0066] The electromagnetic relief valve 100 includes a main poppet 5 (main valve element) that connects or blocks a high-pressure passage H (high-pressure side passage) and a low-pressure passage L (low-pressure side passage), a back pressure chamber 8 into which hydraulic oil (working fluid) is introduced to urge the main poppet 5 (main valve element) in a valve-closing direction, a pilot poppet 20 (pilot valve element) that connects or blocks communication between the back pressure chamber 8 and a discharge flow path for discharging the hydraulic oil (working fluid), and a solenoid section S (biasing section) that urges the pilot poppet 20 (pilot valve element) in a valve-closing direction. The solenoid section S (biasing section) includes a plunger 72 (plunger section) that presses the pilot poppet 20 (pilot valve element), and a plunger The valve has a spring 74 (biasing member) that is provided on the opposite side of the plunger 72 (plunger portion) from the pilot poppet 20 (pilot valve body) and that biases the pilot poppet 20 (pilot valve body) in the valve closing direction, and a coil 75 that, when a current Ir is applied, applies a reaction force to the plunger 72 (plunger portion) that is opposite to the biasing force of the spring 74 (biasing member).When the pressure in the high-pressure passage H (high-pressure side passage) is reduced to the pressure in the low-pressure passage L (low-pressure side passage), a current Ir that generates a reaction force greater than the biasing force of the spring 74 (biasing member) that biases the pilot poppet 20 (pilot valve body) in the valve closing direction is applied to the coil 75.

[0067] In this configuration, the coil 75 generates a reaction force greater than the biasing force of the spring 74 (biasing member) that biases the pilot poppet 20 (pilot valve element) in the valve closing direction, so the relief pressure (set pressure) of the electromagnetic relief valve 100 can be made substantially "0." As a result, when the pressure in the high-pressure passage H (high-pressure side passage) acts on the pilot poppet 20 (pilot valve element), the pilot poppet 20 (pilot valve element) opens, so the pressure in the high-pressure passage H (high-pressure side passage) can be reduced to the pressure in the low-pressure passage L (low-pressure side passage).

[0068] Furthermore, when the electromagnetic relief valve 100 reduces the pressure in the high-pressure passage H (high-pressure side passage) to the pressure in the low-pressure passage L (low-pressure side passage), a current Ir1 is applied to the coil 75 such that the positions of the plunger 72 and the rod 73 (plunger portion) are always closer to the spring 74 (biasing member) than the positions where the plunger 72 and the rod 73 (plunger portion) press the pilot poppet 20 (pilot valve body) against the seat portion 11 a.

[0069] In this configuration, when the pressure in the high-pressure passage H (high-pressure side passage) is reduced to that of the low-pressure passage L (low-pressure side passage), the plunger 72 and rod 73 (plunger portion) are always positioned closer to the spring 74 (biasing member) than the position where the plunger 72 and rod 73 (plunger portion) press the pilot poppet 20 (pilot valve body) against the seat portion 11 a, so that even if the pilot poppet 20 (pilot valve body) is opened by the pressure in the high-pressure passage H (high-pressure side passage), the biasing force from the plunger 72 and rod 73 (plunger portion) does not act on the pilot poppet 20 (pilot valve body). Therefore, the pilot poppet 20 (pilot valve body) does not close until the pressure in the high-pressure passage H (high-pressure side passage) reaches the pressure of the low-pressure passage L (low-pressure side passage), so that the pressure in the high-pressure passage H (high-pressure side passage) can be reliably reduced to the pressure of the low-pressure passage L (low-pressure side passage).

[0070] The relief valve device VS includes an electromagnetic relief valve 100 (relief valve) and a control device C that controls the current applied to the coil 75 of the electromagnetic relief valve 100 (relief valve). The control device C has the following control modes for the electromagnetic relief valve 100 (relief valve): a normal mode that controls the magnitude of the current applied to the coil 75 within a preset relief pressure range of the electromagnetic relief valve 100 (relief valve), and a pressure release mode that applies to the coil 75 a current Ir that is larger than the current in the normal mode and generates a reaction force larger than the biasing force with which the spring 74 (biasing member) biases the pilot poppet 20 (pilot valve body) in the valve closing direction, in order to reduce the pressure in the high-pressure passage H (high-pressure side passage) to that of the low-pressure passage L (low-pressure side passage).

[0071] In this configuration, by simply switching the control mode of the control device C, the pressure in the high-pressure passage H (the passage on the high-pressure side) can be easily reduced to the pressure in the low-pressure passage L (the passage on the low-pressure side).

[0072] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate 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 embodiments.

[0073] This application claims priority based on Japanese Patent Application No. 2024-114262, filed with the Japan Patent Office on July 17, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A relief valve comprising: a main valve element which connects or blocks a high-pressure side passage and a low-pressure side passage; a back pressure chamber into which working fluid is guided which urges the main valve element in a valve closing direction; a pilot valve element which connects or blocks the back pressure chamber with a discharge flow path for discharging the working fluid; and a biasing portion which biases the pilot valve element in a valve closing direction, wherein the biasing portion has: a plunger portion which presses the pilot valve element; a biasing member which is provided on the opposite side of the plunger portion to the pilot valve element and urges the pilot valve element in the valve closing direction; and a coil which, when an electric current is applied, applies a reaction force to the plunger portion which opposes the biasing force of the biasing member, wherein, when the pressure of the high-pressure side passage is reduced to that of the low-pressure side passage, an electric current is applied to the coil which generates a reaction force greater than the biasing force with which the biasing member urges the pilot valve element in the valve closing direction.

2. A relief valve as claimed in claim 1, wherein, when the pressure in the high-pressure passage is reduced to the pressure in the low-pressure passage, a current is applied to the coil such that the plunger is always positioned closer to the biasing member than the position where the plunger presses the pilot valve body against the seat.

3. A relief valve device comprising: a relief valve according to claim 1; and a control device that controls the current applied to the coil of the relief valve, wherein the control device has as control modes for the relief valve: a normal mode that controls the magnitude of the current applied to the coil within a preset relief pressure range of the relief valve; and a pressure release mode that applies to the coil a current that is larger than the current in the normal mode and that generates a reaction force larger than the biasing force with which the biasing member biases the pilot valve element in the valve closing direction, in order to reduce the pressure in the high-pressure side passage to that of the low-pressure side passage.

Images