Relief valve and relief valve device including relief valve

Abstract

To provide a relief valve capable of reducing pressure of a passage on a high pressure side to pressure of a passage on a low pressure side by the relief valve.SOLUTION: A solenoid relief valve 100 includes a back pressure chamber 8 to which working oil for energizing a main poppet 5 in a valve closing direction is guided, a pilot poppet 20 for communicating or blocking the back pressure chamber 8 and a discharge flow passage for discharging the working oil, and a solenoid part S for energizing the pilot poppet 20 in the valve closing direction. The solenoid section S includes the plunger 72 that presses the pilot poppet 20, the spring 74 that biases the pilot poppet 20 in the valve closing direction, and the coil 75 that applies a reaction force to the plunger 72 against the biasing force of the spring 74 when a current is applied, and when the pressure in the high-pressure passage H is reduced to the pressure in the low-pressure passage L, a current Ir that generates a reaction force larger than the biasing force of the spring 74 that biases the pilot poppet 20 in the valve closing direction is applied to the coil 75.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 4-136374 Summary of the Invention [Problem to be solved by the invention]

[0004] 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 Patent Document 1 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.

[0005] Therefore, it is necessary to provide a pressure relief valve in addition to the relief valve, which increases costs accordingly.

[0006] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a relief valve that can reduce the pressure in a high-pressure flow path to the pressure in a low-pressure flow path. [Means for solving the problem]

[0007] The present invention is 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 is characterized in that, 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 of the biasing member which urges the pilot valve element in a valve closing direction is applied to the coil.

[0008] In this invention, when the pressure in the high-pressure passage is reduced to the pressure in the low-pressure passage, the coil generates a reaction force greater than the biasing force with which the biasing member biases the pilot valve element in the valve closing direction, so the relief pressure (set pressure) of the electromagnetic relief valve can be made substantially "0." As a result, when the pressure in the high-pressure passage acts on the pilot valve element, the pilot valve element opens, so the pressure in the high-pressure passage can be reduced to the pressure in the low-pressure passage.

[0009] Furthermore, in the present invention, 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 portion is always positioned closer to the biasing member than the position where the plunger portion presses the pilot valve body against the seat portion.

[0010] In this invention, when the pressure in the high-pressure passage is reduced to that of the low-pressure passage, the plunger portion is always positioned closer to the biasing member than the position where the plunger portion presses the pilot valve body against the seat portion, so that even if the pilot valve body is opened by the pressure in the high-pressure passage, the biasing force from the plunger portion does not act on the pilot valve body. Therefore, the pilot valve body does not close until the pressure in the high-pressure passage reaches the pressure in the low-pressure passage, so that the pressure in the high-pressure passage can be reliably reduced to that of the low-pressure passage.

[0011] The present invention also provides a solenoid relief valve according to the above invention, and a control device that controls a current applied to a coil of the solenoid relief valve, wherein the control device has, as control modes of the solenoid relief valve, a normal mode that controls the magnitude of the current applied to the coil within a preset relief pressure range of the solenoid relief valve, and a pressure release mode that applies to the coil a current that generates a reaction force greater 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.

[0012] In this invention, the pressure in the high-pressure passage can be easily reduced to the pressure in the low-pressure passage by simply switching the control mode of the control device. [Effects of the Invention]

[0013] According to the present invention, the pressure in the high-pressure passage can be reduced to the pressure in the low-pressure passage by the relief valve. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a relief valve device and an electromagnetic relief valve according to an embodiment of the present invention; [Figure 2] 4 is a graph showing the relationship between the applied current and the set pressure of the electromagnetic relief valve according to the embodiment of the present invention. [Figure 3] FIG. 2 is a schematic configuration diagram of an electromagnetic relief valve according to an embodiment of the present invention in a pressure release mode. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] 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.

[0017] The electromagnetic relief valve 100 is an inverse proportional type electromagnetic relief valve. An inverse proportional type is a relief valve configured so that the relief pressure decreases as the value of current applied to a solenoid, which will be described later, increases.

[0018] 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, it 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 by supplying the hydraulic oil from the low-pressure passage L to the high-pressure passage H, it prevents the occurrence of cavitation.

[0019] 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 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 this is not limiting, and the electromagnetic relief valve 100 can be applied to various devices, pipelines, and the like. Also, 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.

[0020] 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, is seated. 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.

[0021] 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).

[0022] As shown in FIG. 1, the valve section V includes a valve housing 2 attached to an equipment main body 1 in which a high-pressure passage H and a low-pressure passage L are provided, a suction poppet 3 provided in the valve housing 2, which opens or closes 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 in the suction poppet 3, which opens or closes 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 which 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 which connects the drain chamber 12 and the back pressure chamber 8, and a pilot poppet 20 which is provided in the sleeve 7 and which opens and closes the first communication passage P1.

[0023] 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.

[0024] The suction poppet 3 is a cylindrical member with a bottom, 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.

[0025] A corner 3c between the cylindrical portion 3a and the bottom portion 3b of the suction poppet 3 is formed in a tapered shape, and this corner 3c is seated on the seat portion 1a of the equipment body 1, thereby blocking communication between the high-pressure passage H and the low-pressure passage L through the space between the equipment body 1 and the suction poppet 3. A first accommodating hole 3d for accommodating the main poppet 5 is provided on the bottom portion 3b side of the suction poppet 3, and a second accommodating hole 3e, which has a larger diameter than the first accommodating hole 3d and for accommodating the sleeve 7, is provided at the end opposite the bottom portion 3b.

[0026] 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 slide hole 50a that is formed so as to penetrate the main body portion 50 in the axial direction.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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, communicating between 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.

[0031] A seat portion 11a on which the valve portion 22 of the pilot poppet 20 seats and disengages is provided at the open end of the first communication passage P1 that opens into the accommodating hole 7c. The seat portion 11a is formed coaxially with the accommodating hole 7c so that its central axis coincides with the central axis of the accommodating hole 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.

[0032] The drain chamber 12 is a space defined by the receiving hole 7c and the pilot poppet 20.

[0033] 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 .

[0034] 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 valve portion 22 formed in a conical shape and projecting from the main body portion 21 in the axial direction.

[0035] 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.

[0036] The first cutout 21b is formed by cutting out a flat portion of the outer circumferential surface of the main body 21. By forming the first cutout 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 circumferential surface of the accommodating hole 7c and the first cutout 21b, the annular groove 21a, the drain passage 13, and the gap 14. The passage defined by the inner circumferential surface of the accommodating hole 7c and the first cutout 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. Note that hereinafter, the passage defined by the passage defined by the inner circumferential surface of the accommodating hole 7c and the first cutout 21b, the annular groove 21a, the drain passage 13, and the gap 14 will be referred to as a "second communication passage P2."

[0037] Additionally, second cutout 21c is formed by cutting out a flat portion of the outer peripheral surface of main body 21 along the axial direction from annular groove 21a toward solenoid S so that the end on the solenoid S side is always exposed from accommodating hole 7c. By forming second cutout 21c in main body 21 in this manner, space SP where the rear end side of pilot poppet 20 is exposed communicates with low-pressure passage L through a passage defined by the inner peripheral surface of accommodating hole 7c and second cutout 21c, annular groove 21a, drain passage 13, and gap 14.

[0038] 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. By preventing the pilot poppet 20 from being tilted relative to the seat portion 11a in this way, the valve portion 22 is prevented from unevenly contacting the seat portion 11a when seated on the seat portion 11a. This prevents the seat portion 11a from being damaged or deformed, resulting in improved seating properties when the valve portion 22 seats on the seat portion 11a.

[0039] Although the annular groove 21a is formed in the outer peripheral surface of the main body 21 of the pilot poppet 20, the annular groove 21a may alternatively be formed in the inner peripheral surface of the accommodation hole 7c. Furthermore, the first notch 21b and the second notch 21c are formed in the outer peripheral surface of the main body 21 of the pilot poppet 20, but instead the first notch 21b and the second notch 21c may be formed as grooves in the axial direction in the inner peripheral surface of the accommodation hole 7c.

[0040] 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. On the other hand, the spring 82 urges the suction poppet 3 so that the corner portion 3c of the suction poppet 3 seats on the seat portion 1a of the equipment main body 1.

[0041] Next, the solenoid section S will be described with reference to FIG.

[0042] 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.

[0043] The solenoid housing 71 is a cylindrical member with a bottom, in which 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.

[0044] 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 11a.

[0045] When current I is applied to coil 75, it applies a thrust to plunger 72 that counteracts the biasing force of spring 74. As current I applied to coil 75 increases, the biasing force of spring 74 acting on pilot poppet 20 via plunger 72 and rod 73 decreases. As a result, the pressure required to separate valve portion 22 of pilot poppet 20 from seat portion 11a, known as cracking pressure, decreases. In electromagnetic relief valve 100, the set pressure (relief pressure) at which pilot poppet 20 opens can be changed by controlling the current I applied to coil 75 to change the biasing force of spring 74 acting on pilot poppet 20.

[0046] 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.

[0047] 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 cutout 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 cutout 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 cutout 21c functions as a second throttle that applies resistance to the hydraulic oil flowing through the third communication passage P3.

[0048] 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 penetrate 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 relief pressure of the electromagnetic relief valve 100 can also be changed by the adjuster 76.

[0049] The air vent mechanism 79 has a plug 79 a that fits into a through-hole 76 a that passes through the adjuster 76 .

[0050] The plug 79a and the through-hole 76a are threadedly coupled to each other at a threaded portion 79b, and the plug 79a moves in the axial direction relative to the adjuster 76 by rotating the plug 79a.

[0051] One end of the plug 79a is provided with a valve portion 79c formed by a tapered surface, and the other end is provided with a port 79d for connecting a tube or the like. When the valve portion 79c of the plug 79a abuts against a step portion 76b formed 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 the gap between the valve portion 79c and the step portion 76b and through a through-hole 79e formed in the plug 79a.

[0052] 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 using 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.

[0053] The control device C has two control modes for the electromagnetic relief valve 100: a normal mode and a pressure release mode.

[0054] 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.

[0055] 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 by the control device C (see FIG. 2).

[0056] 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 tank pressure or atmospheric pressure.

[0057] 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.

[0058] Next, the operation of the electromagnetic relief valve 100 will be described.

[0059] 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.

[0060] 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.

[0061] Hydraulic oil is constantly supplied to the back pressure chamber 8 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.

[0062] 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 that acts 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 preset 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.

[0063] 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 backpressure 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 section S, the valve section 22 of the pilot poppet 20 seats on the seat section 11a. This increases the pressure in the backpressure chamber 8, and when the pressure difference between the pressure in the backpressure 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.

[0064] In the relief valve device VS, when the electromagnetic relief valve 100 is used within the relief pressure range R1, that is, when the electromagnetic relief valve 100 is used as a relief valve, the normal mode is selected. In the normal mode, as described above, the upper limit of the pressure in the high-pressure passage H can be set to the relief pressure (set pressure). Furthermore, in the normal mode, the relief pressure (set pressure) can be changed by changing the current I applied to the coil 75.

[0065] 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 larger than the maximum current Ic in the normal mode. More preferably, a current Ir1 is applied to the coil 75 such that the position of the plunger 72 (rod 73) is always 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.

[0066] 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 0 (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.

[0067] 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. This causes the hydraulic oil to be discharged from the high-pressure passage H to the low-pressure passage L.

[0068] 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 0 (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, so that the main poppet 5 remains open due to the pressure difference between the pressure in the backpressure chamber 8 and the pressure in 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 decreases to the pressure in the low-pressure passage L. Note that even if the pressure difference between the pressure in the backpressure chamber 8 and the pressure in the high-pressure passage H becomes equal to or less than the preset 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".

[0069] Furthermore, the relief valve device VS of this embodiment has a normal mode and a pressure relief mode, so 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.

[0070] 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, the present invention is not limited to this. 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.

[0071] 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 (several minutes), so there is no risk of the coil 75 burning out even if the current Ir is applied. Conversely, 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.

[0072] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0073] 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 to 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 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 spring 74 (biasing member) is provided on the opposite side of the plunger 72 (plunger portion) from the pilot poppet 20 (pilot valve body), and 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.

[0074] 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).

[0075] 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 so that the positions of the plunger 72 and the rod 73 (plunger portion) are always closer to the spring 74 (biasing member) than the position where the plunger 72 and the rod 73 (plunger portion) press the pilot poppet 20 (pilot valve body) against the seat portion 11a.

[0076] 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 11a, so 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) becomes the pressure in the low-pressure passage L (low-pressure side passage), so 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).

[0077] The relief valve device VS comprises 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).

[0078] In this configuration, by simply switching the control mode of the control device C, the pressure in the high-pressure passage H (passage on the high-pressure side) can be easily reduced to the pressure in the low-pressure passage L (passage on the low-pressure side).

[0079] 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. [Explanation of symbols]

[0080] VS···Relief valve device, 100···Solenoid relief valve (relief valve), 5···Main poppet (main valve element), 8···Back pressure chamber, 10···Pilot passage, 20···Pilot poppet (pilot valve element), 71···Solenoid housing, 72···Plunger (plunger portion), 72a···Through hole, 73···Rod (plunger portion), 74···Spring (biasing member), 75···Coil, C···Control device, H···High pressure passage, S···Solenoid portion (biasing portion), W···Gap

Claims

1. A relief valve, a main valve body that connects or disconnects a high-pressure side passage and a low-pressure side passage; a back pressure chamber into which a working fluid is introduced to bias the main valve element in a valve closing direction; a pilot valve body that connects or blocks communication between the back pressure chamber and a discharge flow path for discharging the working fluid; a biasing portion that biases the pilot valve element in a valve closing direction, The biasing portion is a plunger portion that presses the pilot valve body; a biasing member provided on the opposite side of the plunger portion from the pilot valve body, the biasing member biasing the pilot valve body in a valve closing direction; a coil that applies a reaction force to the plunger portion opposite to the biasing force of the biasing member when a current is applied thereto, a current that generates a reaction force greater than the biasing force with which the biasing member biases the pilot valve element in the valve closing direction when the pressure in the high-pressure side passage is reduced to the pressure in the low-pressure side passage is applied to the coil.

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

3. A relief valve according to claim 1; a control device that controls a current applied to the coil of the relief valve, The control device may select, as a control mode of the relief valve, a normal mode in which the magnitude of the current applied to the coil is controlled within a preset relief pressure range of the relief valve; a pressure release mode in which a current larger than the current in the normal mode is applied to the coil to reduce the pressure in the high-pressure side passage to the pressure in the low-pressure side passage, the current generating a reaction force larger than the biasing force with which the biasing member biases the pilot valve element in the valve closing direction.

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