Solenoid relief valve

Abstract

An electromagnetic relief valve (100) comprises: a pilot poppet (20) that connects or disconnects a high-pressure-side passage and a low-pressure-side passage; and a biasing part S that biases the pilot poppet (20) in a valve-closing direction. A plunger (72) is provided with a through-hole (72a) for guiding, to a spring chamber (78), hydraulic oil discharged from the high-pressure-side passage in conjunction with opening of the pilot poppet (20). The electromagnetic relief valve (100) further comprises a through-hole (72b) for discharging the hydraulic oil from the spring chamber (78) to the outside.

Description

Technical Field

[0001] The present invention relates to an electromagnetic relief valve.

Background Art

[0002] JP2022-12406A discloses an electromagnetic relief valve that opens when the pressure of hydraulic oil in a high-pressure passage reaches a set pressure, and discharges the hydraulic oil from the high-pressure passage to a low-pressure passage, thereby preventing the pressure of the hydraulic oil in the high-pressure passage from becoming abnormally high.

[0003] Furthermore, the electromagnetic relief valve described in JP2022-12406A includes a solenoid unit that enables the set pressure to be changed.

Summary of Invention

[0004] After being inspected at the time of shipment, the electromagnetic relief valve described in JP2022-12406A is transported, and then attached to hydraulic equipment such as a valve block. In the electromagnetic relief valve described in JP2022-12406A, air may enter the interior of the valve due to influences such as vibration during transportation.

[0005] For example, if air enters a spring chamber that accommodates a spring biasing a plunger of the solenoid unit, the air expands and contracts as the plunger moves, which may cause unstable operation of the electromagnetic relief valve.

[0006] The present invention has been made in view of the above problem, and an object of the present invention is to provide an electromagnetic relief valve capable of preventing air from being retained in a biasing member chamber that accommodates a biasing member for biasing a plunger.

[0007] According to one aspect of the present invention, an electromagnetic relief valve comprises a valve body that connects or blocks a high-pressure side passage and a low-pressure side passage, and a biasing part that biases the valve body in the closing direction, wherein the biasing part includes a rod that presses the valve body, a plunger fixed to the rod, a first biasing member provided on the opposite side of the valve body from the plunger and biasing the valve body in the closing direction via the plunger, a biasing member chamber in which the first biasing member is housed, and a coil that, when an electric current is applied, applies a reaction force to the plunger that is opposite to the biasing force of the first biasing member, wherein the rod is provided with a first connecting passage that guides the working fluid discharged from the high-pressure side passage to the biasing member chamber when the valve body opens, and further includes a discharge passage that discharges the working fluid to the outside at a pressure lower than the pressure in the first connecting passage when the working fluid from the high-pressure side is guided from the biasing member chamber. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of an electromagnetic relief valve according to a first embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the first embodiment of the present invention. [Figure 3] Figure 3 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the first embodiment of the present invention. [Figure 4] Figure 4 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the first embodiment of the present invention. [Figure 5] Figure 5 is a cross-sectional view of an electromagnetic relief valve according to a second embodiment of the present invention. [Figure 6] Figure 6 is a cross-sectional view of an electromagnetic relief valve according to a third embodiment of the present invention. [Figure 7] Figure 7 is a cross-sectional view of an electromagnetic relief valve according to a fourth embodiment of the present invention. [Figure 8] Figure 8 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the fourth embodiment of the present invention. [Figure 9] Figure 9 is a cross-sectional view of an electromagnetic relief valve according to a fifth embodiment of the present invention. [Figure 10] Figure 10 is a cross-sectional view of an electromagnetic relief valve according to the sixth embodiment of the present invention. [Figure 11] Figure 11 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the sixth embodiment of the present invention. [Figure 12] Figure 12 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the second embodiment of the present invention. [Figure 13] Figure 13 is a cross-sectional view of a modified example of the electromagnetic relief valve according to the fifth embodiment of the present invention. [Modes for carrying out the invention]

[0009] <First Embodiment> Referring to Figure 1, an electromagnetic relief valve 100 according to the first embodiment of the present invention will be described. Figure 1 is a cross-sectional view of the electromagnetic relief valve 100.

[0010] The electromagnetic relief valve 100 is an inverse-proportional type pilot-operated electromagnetic relief valve. An inverse-proportional type is a relief valve configured such that the relief pressure decreases as the current value applied to the coil 75 of the biasing unit S (described later) increases.

[0011] The electromagnetic relief valve 100 opens when the pressure of the hydraulic fluid in the high-pressure passage H reaches a set pressure (relief pressure), releasing the hydraulic fluid from the high-pressure passage H to the low-pressure passage L, thereby preventing the pressure of the hydraulic fluid in the high-pressure passage H from becoming abnormally high. In addition, the electromagnetic relief valve 100 has an antivoid function, opening when the high-pressure passage H becomes negative pressure, and supplying hydraulic fluid from the low-pressure passage L to the high-pressure passage H, thereby preventing cavitation.

[0012] As shown in Figure 1, the electromagnetic relief valve 100 is attached to the equipment body 1 by screw fastening. The equipment body 1 is the main body of hydraulic equipment such as a hydraulic cylinder, hydraulic pump, hydraulic motor, or valve block having multiple valves. In this embodiment, the case in which hydraulic oil is used as the working fluid for the equipment body 1 is described as an example, but the working fluid may be other liquids such as working water.

[0013] The main body of the equipment 1 is provided with a high-pressure passage H and a low-pressure passage L, separated by an electromagnetic relief valve 100. The main body of the equipment 1 is provided with a seat portion 1a, which serves as a first valve seat, between the high-pressure passage H and the low-pressure passage L, on which a suction poppet 3 (described later) is seated. Note that the main body of the equipment 1 is not limited to the main body of the hydraulic equipment, but may also be a block body installed between each hydraulic piece of equipment.

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

[0015] As shown in Figure 1, the valve section V includes a valve housing 2 attached to the main body 1 of the equipment, which is provided with a high-pressure passage H and a low-pressure passage L; a suction poppet 3 provided inside the valve housing 2, which connects or blocks the high-pressure passage H and the low-pressure passage L by moving away from or sitting on the seat portion 1a; a main poppet 5 provided inside the suction poppet 3, which serves as a main valve body and connects or blocks the high-pressure passage H and the low-pressure passage L by moving away from or sitting on the seat portion 3f formed on the suction poppet 3; and the suction poppet 3 The valve comprises a back pressure chamber 8 through which hydraulic fluid is introduced from a high-pressure passage H to bias the main poppet 5 in the closing direction; a sleeve 7 as a housing member that partitions the back pressure chamber 8 from the main poppet 5; a pilot passage 10 provided in the main poppet 5 and connecting the high-pressure passage H and the back pressure chamber 8; a drain chamber 12 provided in the sleeve 7 through which the hydraulic fluid from the back pressure chamber 8 is discharged; a connecting passage 7f provided in the sleeve 7 and connecting the drain chamber 12 and the back pressure chamber 8; and a pilot poppet 20 provided in the sleeve 7 and serving as a pilot valve body that opens and closes the connecting passage 7f. The pilot poppet 20 also corresponds to the "valve body" in the claims.

[0016] As shown in Figure 1, the valve housing 2 is a cylindrical member having a first cylindrical portion 2a attached to the main body 1 of the equipment and a second cylindrical portion 2b having a larger diameter than the first cylindrical portion 2a. The valve housing 2 is connected to the base member 71 of the biasing portion S.

[0017] The suction poppet 3 is a member formed into a bottomed cylindrical shape having a cylindrical portion 3a and a bottom portion 3b. The suction poppet 3 is provided axially movably inside the valve housing 2, and a part of the suction poppet 3 protrudes 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 on 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 portion 3c between the cylindrical portion 3a and the bottom portion 3b of the suction poppet 3 is formed in a tapered shape. When this corner portion 3c is seated on the seat portion 1a of the device main body 1, communication between the high-pressure passage H and the low-pressure passage L through the gap between the device main body 1 and the suction poppet 3 is blocked. A first accommodation hole 3d that accommodates 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 accommodates a part of the sleeve 7, is provided at the end opposite to the bottom portion 3b.

[0019] Between the inner circumferential surface of the valve housing 2 and the outer circumferential surface of the suction poppet 3, a communication passage 4 that is always in communication with the low-pressure passage L is formed.

[0020] The main poppet 5 comprises a main body portion 50 slidable within the first accommodation hole 3d, and a pilot piston 51 slidable within a sliding hole 50a formed axially penetrating through the main body portion 50.

[0021] The main body portion 50 has a valve portion 50b that seats on a seat portion 3f formed inside the corner portion 3c of the suction poppet 3. When the valve portion 50b is seated on the seat portion 3f, communication between the high-pressure passage H and the low-pressure passage L through the gap between the suction poppet 3 and the main poppet 5 is blocked. A sealing member (O-ring) that seals the gap between the main body portion 50 and the suction poppet 3 is provided between the outer circumferential surface of the main body portion 50 and the inner circumferential surface of the suction poppet 3.

[0022] The pilot piston 51 has a flange portion 51a facing the back pressure chamber 8, which is a space partitioned by the inner circumferential surface of the suction poppet 3, the main poppet 5, and the sleeve 7, and a cylindrical shaft portion 51b that extends axially from the flange portion 51a and is inserted into the sliding 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 is also provided with a pilot passage 10 that connects the high-pressure passage H and the back pressure chamber 8. The pilot passage 10 is provided with a throttling that provides resistance to the hydraulic fluid flowing through the pilot passage 10.

[0023] The sleeve 7 has a tip portion 7a that is inserted into the suction poppet 3, a base portion 7b that is coupled to the base member 71 of the biasing portion S (described later), a housing hole 7c that opens on the axial end face of the base portion 7b on the biasing portion S side, an intermediate portion 7d provided between the tip portion 7a and the base portion 7b, with its outer circumferential surface exposed between the suction poppet 3 and the base member 71, and a plurality of through holes 7e that penetrate the base portion 7b axially on the outer circumferential side of the housing hole 7c of the base portion 7b. The sleeve 7 slidably supports the suction poppet 3 at the tip portion 7a. A sealing member (O-ring) is provided between the outer circumferential surface of the tip portion 7a of the sleeve 7 and the inner circumferential surface of the suction poppet 3 to seal the gap between the sleeve 7 and the suction poppet 3.

[0024] Furthermore, the sleeve 7 has a connecting passage 7f that opens at one end to the back pressure chamber 8 and at the other end to the bottom surface of the housing hole 7c, connecting the back pressure chamber 8 and the housing hole 7c. In this embodiment, the connecting passage 7f corresponds to the "high-pressure side passage" in the claims.

[0025] A seat portion 7g is provided at the open end of the communication passage 7f that opens into the housing hole 7c, onto which the valve portion 23 of the pilot poppet 20 sits and unseats. The seat portion 7g is formed so that its central axis coincides with the central axis of the housing hole 7c.

[0026] The drain chamber 12 is a space partitioned between the bottom surface of the housing hole 7c and the pilot poppet 20 in the housing hole 7c, and the hydraulic fluid discharged from the back pressure chamber 8 through the communication passage 7f flows into it.

[0027] As shown in Figure 1, the pilot poppet 20 is a substantially cylindrical member and is slidably housed in the housing hole 7c of the sleeve 7. The pilot poppet 20 has a first sliding portion 21 and a second sliding portion 22 that slide against the inner circumferential surface of the housing hole 7c and are arranged in order from the biasing portion S side, a valve portion 23 that is conically formed and protrudes axially from the second sliding portion 22, an annular groove 24 provided between the first sliding portion 21 and the second sliding portion 22, a plurality of communication holes 25 that open to the bottom surface of the annular groove 24, a communication passage 26 that communicates with the communication holes 25 and extends axially from the pilot poppet 20, and a rod portion 27 that is smaller in diameter than the first sliding portion 21 and extends from the end face of the first sliding portion 21 toward the plunger 72. The housing hole 7c of the sleeve 7 corresponds to the "valve body housing chamber" in the claims.

[0028] The first sliding portion 21 is formed so that its outer diameter is approximately the same as the inner diameter of the housing hole 7c. As a result, the space between the first sliding portion 21 and the housing hole 7c is almost sealed.

[0029] A communication passage 22a is provided on the outer circumferential surface of the second sliding portion 22, formed by a groove or a planar notch along the axial direction. As a result, the hydraulic fluid discharged from the communication passage 7f to the drain chamber 12 flows into the annular groove 24 through the communication passage 22a provided on the outer circumferential surface of the second sliding portion 22. As described above, the space between the first sliding portion 21 and the housing hole 7c is almost sealed, so the hydraulic fluid that flows into the annular groove 24 is guided to the communication passage 26 through the communication hole 25.

[0030] The pilot poppet 20 is slidably supported by a housing hole 7c formed coaxially with the seat portion 7g. In other words, the pilot poppet 20 is supported by the housing hole 7c so that its central axis does not tilt relative to the central axis of the seat portion 7g. By preventing the pilot poppet 20 from tilting relative to the seat portion 7g in this way, uneven contact with the seat portion 7g is prevented when the valve portion 23 sits on the seat portion 7g. This prevents damage or deformation of the seat portion 7g, and as a result, the seating performance when the valve portion 23 sits on the seat portion 7g can be improved.

[0031] As shown in Figure 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 base member 71. The spring 81 biases the pilot piston 51 so that the flange portion 51a contacts the main body portion 50 of the main poppet 5, and also biases the main body portion 50 via the flange portion 51a so that the main body portion 50 sits on the seat portion 3f of the suction poppet 3. On the other hand, the spring 82 biases the suction poppet 3 so that the corner portion 3c of the suction poppet 3 sits on the seat portion 1a of the equipment body 1.

[0032] Next, we will explain the biasing unit S.

[0033] The biasing section S includes a base member 71, a plunger 72 slidably housed within the base member 71 and acting as a plunger for pressing the pilot poppet 20, a spring 74 provided on the opposite side of the plunger 72 from the pilot poppet 20 and acting as a first biasing member for biasing the pilot poppet 20 in the valve closing direction via the plunger 72, a coil 75 supported by the base member 71 and, when current is applied, applies a reaction force to the plunger 72 that is opposite to the biasing force of the spring 74, a yoke 76 provided so as to surround the coil 75, a fixed iron core 77 attached to the yoke 76 and generating a magnetic force when current is applied to the coil 75, and an adjustment member 79 attached to the fixed iron core 77 so as to be movable in the axial direction. In this embodiment, the solenoid section is composed of the base member 71, the plunger 72, the coil 75, the yoke 76, and the fixed iron core 77.

[0034] The base member 71 is a member made of a cylindrical magnetic material. The base member 71 has a cylindrical portion 71a that is inserted into the yoke 76, a flange portion 71b that is larger in diameter than the cylindrical portion 71a and restricts the axial movement of the coil 75, a housing hole 71c formed across the cylindrical portion 71a and the flange portion 71b and housing the plunger 72, and a connecting portion 71d provided on the opposite side of the cylindrical portion 71a, with the flange portion 71b in between.

[0035] The cylindrical portion 71a is connected to the fixed iron core 77 via the tube member 91. A guide member 90 is provided in the housing hole 71c to slidably support the plunger 72.

[0036] The connecting portion 71d is formed in a cylindrical shape. A female thread is formed on the inner circumferential surface of the connecting portion 71d, and a male thread is formed on the outer circumferential surface. The female thread formed on the inner circumferential surface of the connecting portion 71d is screwed into the male thread formed on the outer circumferential surface of the base end portion 7b of the sleeve 7, thereby connecting the sleeve 7 and the base member 71. In addition, the male thread formed on the outer circumferential surface of the connecting portion 71d is screwed into the female thread formed on the inner circumferential surface of the second cylindrical portion 2b of the valve housing 2, thereby connecting the valve housing 2 and the base member 71.

[0037] The biasing member S is provided inside the connecting portion 71d and further includes a spring 83 that biases the pilot poppet 20 in the valve closing direction, and a spring seat 30 that supports one end of the spring 83. The spring seat 30 is provided with an insertion hole 30a through which the rod portion 27 of the pilot poppet 20 is inserted, and a plurality of through holes 30b through which the hydraulic fluid passes. In this embodiment, the spring 83 corresponds to the "second biasing member" in the claims.

[0038] The plunger 72 is formed of a magnetic material. The plunger 72 is formed to penetrate axially and has through holes 72a and 72b through which hydraulic fluid flows. In this embodiment, the through hole 72a corresponds to the “first passage” in the claims.

[0039] The spring 74 is formed from a coil spring, with one end supported by the adjustment member 79 and the other end supported by the plunger 72. The biasing force of the spring 74 acts to bias the pilot poppet 20 in the valve closing direction via the plunger 72. In other words, the spring 74 biases the pilot poppet 20 so that the valve portion 23 of the pilot poppet 20 seats on the seat portion 7g.

[0040] When current is applied, the coil 75 imparts a thrust to the plunger 72 that counteracts the biasing force of the spring 74. As the current applied to the coil 75 increases, the biasing force of the spring 74 acting on the pilot poppet 20 via the plunger 72 decreases. As a result, the pressure required to separate the valve portion 23 of the pilot poppet 20 from the seat portion 7g, the so-called cracking pressure, decreases. In the electromagnetic relief valve 100, the set pressure at which the pilot poppet 20 opens (relief pressure) can be changed by controlling the current applied to the coil 75 and thereby changing the biasing force of the spring 74 acting on the pilot poppet 20.

[0041] The fixed core 77 is made of a magnetic material. The fixed core 77 has a through hole 77a. On the outside of the through hole 77a, there is a female thread that engages with the adjustment member 79. Between the plunger 72 and the adjustment member 79 in the through hole 77a of the fixed core 77, a spring chamber 78 is formed, which serves as a biasing member chamber that houses the spring 74.

[0042] The adjustment member 79 is a so-called flat-ended grub screw, with male threads formed on the outer circumferential surface of a cylindrical member. The adjustment member 79 has an end face 79a against which one end of the spring 74 abuts. The biasing force of the spring 74 can be adjusted by moving the adjustment member 79 axially relative to the fixed iron core 77. The axial movement of the adjustment member 79 is restricted by tightening the lock nut 80. The adjustment member 79 corresponds to the "support member" in the claims.

[0043] Next, the operation of the electromagnetic relief valve 100 will be explained.

[0044] The hydraulic fluid in the high-pressure passage H is guided to the connecting passage 7f through the pilot passage 10 and the back pressure chamber 8. When the pressure of the hydraulic fluid guided to the connecting passage 7f reaches the set pressure (cracking pressure) of the pilot poppet 20 set by the biasing unit S, or in other words, when the biasing force on the pilot poppet 20 in the valve-opening direction due to the pressure of the hydraulic fluid guided to the connecting passage 7f becomes greater than the biasing force on the pilot poppet 20 in the valve-closing direction due to the biasing unit S, the valve portion 23 of the pilot poppet 20 separates from the seat portion 7g.

[0045] When the valve portion 23 of the pilot poppet 20 separates from the seat portion 7g, the hydraulic fluid in the back pressure chamber 8 flows into the spring chamber 78 through the communication passage 7f, the drain chamber 12, the communication passage 22a, the annular groove 24, the communication hole 25, the communication passage 26, and the through hole 72a. The hydraulic fluid that has flowed into the spring chamber 78 is discharged to the low-pressure passage L through the through hole 72b, the through hole 30b, the through hole 7e, the area outside the intermediate portion 7d, and the communication passage 4. In this embodiment, the flow path from the spring chamber 78 to the low-pressure passage L corresponds to the "discharge flow path" in the claims, and the communication hole 25 and the communication passage 26 correspond to the "second communication passage" in the claims.

[0046] The back pressure chamber 8 is constantly supplied with hydraulic fluid from the high-pressure passage H through the pilot passage 10. However, the supply of hydraulic fluid from the high-pressure passage H to the back pressure chamber 8 is restricted by a throttling mechanism in the pilot passage 10. As a result, when the valve 23 separates from the seat 7g and the hydraulic fluid 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.

[0047] Thus, when the pressure in the back pressure chamber 8 decreases, the biasing force exerted by the pressure in the back pressure chamber 8 that causes the main body portion 50 of the main poppet 5 to seat on the seat portion 3f of the suction poppet 3 decreases. 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 main body portion 50 of the main poppet 5 separates from the seat portion 3f of the suction poppet 3, and the main poppet 5 opens. As a result, the hydraulic fluid is discharged from the high-pressure passage H to the low-pressure passage L. This prevents the pressure in the high-pressure passage H from becoming abnormally high. In this embodiment, the passage from the drain chamber 12 to the low-pressure passage L described above corresponds to the "low-pressure side passage" in the claims.

[0048] Incidentally, during transport of the electromagnetic relief valve 100 configured in this way, air may enter the electromagnetic relief valve 100. In an inversely proportional type electromagnetic relief valve 100, such as the one in this embodiment, where the set pressure (relief pressure) increases as the amount of current supplied to the coil 75 increases, when the pilot poppet 20 moves to open the valve, the plunger 72 moves accordingly, and the volume of the spring chamber 78 decreases. At this time, due to the air that has entered the electromagnetic relief valve 100, the pilot poppet 20 may open excessively (overshoot), potentially causing oscillation. When the plunger 72 oscillates in this way, the pressure of the equipment being relieved may fluctuate, potentially leading to vibration and noise generation.

[0049] Therefore, in this embodiment, in order to prevent the hydraulic fluid from accumulating in the spring chamber 78, as described above, the hydraulic fluid discharged from the back pressure chamber 8 during relief operation is configured to pass through the spring chamber 78 and be discharged into the low-pressure passage L. As a result, the air accumulated in the spring chamber 78 can be discharged into the low-pressure passage L together with the hydraulic fluid, thereby suppressing oscillation of the plunger 72 caused by the accumulation of air.

[0050] Next, a modified example of the electromagnetic relief valve 100 will be described with reference to Figures 2 to 4.

[0051] The modified electromagnetic relief valve 100 shown in Figure 2 differs from the electromagnetic relief valve 100 according to the first embodiment in that a pipe 40 serving as a guide is attached to the plunger 72.

[0052] As shown in Figure 2, the pipe 40 is attached to the plunger 72 so as to extend from the end face of the plunger 72 toward the spring chamber 78. The pipe 40 has a through hole 40a that communicates with the through hole 72a of the plunger 72. The hydraulic fluid that has passed through the through hole 72a of the plunger 72 is guided to the back side of the spring chamber 78 (towards the adjustment member 79) through the through hole 40a of the pipe 40. Air tends to accumulate at the back side of the spring chamber 78. Therefore, by providing a pipe 40 that is continuous with the through hole 72a of the plunger 72, the hydraulic fluid can be guided to the back side of the spring chamber 78. As a result, the hydraulic fluid can flow to the back side of the spring chamber 78, so that air accumulated in the spring chamber 78 can be discharged more reliably.

[0053] Next, a modified example shown in Figure 3 will be described. The electromagnetic relief valve 100 according to the modified example shown in Figure 3 differs from the electromagnetic relief valve 100 according to the first embodiment in that a guide portion 72d is formed integrally with the plunger 72, and a protrusion 72e for pressing the pilot poppet 20 is provided on the plunger 72.

[0054] In this modified example, the guide portion 72d is formed to protrude from the end face of the plunger 72 on the spring chamber 78 side. The through hole 72a opens to the tip face of the guide portion 72d. By providing such a guide portion 72d, the hydraulic fluid can be guided to the back of the spring chamber 78. As a result, the hydraulic fluid can flow to the back of the spring chamber 78, so that air trapped in the spring chamber 78 can be discharged more reliably.

[0055] Furthermore, the protrusion 72e is formed to protrude from the end face of the plunger 72 on the pilot poppet 20 side. The diameter of the protrusion 72e is smaller than that of the other parts (for example, about the same diameter as the rod portion 27). In the electromagnetic relief valve 100 shown in Figure 2, in order to prevent uneven contact between the pilot poppet 20 and the plunger 72, it is necessary to flatten the entire end face of the plunger 72 on the pilot poppet 20 side. In contrast, in this modified example (the modified example shown in Figure 3), it is only necessary to flatten the tip surface of the protrusion 72e, thus reducing the processing time.

[0056] Next, a modified example shown in Figure 4 will be described. The electromagnetic relief valve 100 in the modified example shown in Figure 4 differs from the electromagnetic relief valve 100 in the modified example shown in Figure 3 in that the pilot poppet 20 and plunger 72 are integrated into a single unit.

[0057] In this modified configuration, the pilot poppet 20 and the plunger 72 are integrated into a single unit, thus reducing the number of parts in addition to the effects of the above modified configuration. Furthermore, in this modified configuration, the spring 83 and spring seat 30 that bias the pilot poppet 20 can be omitted. This further reduces the number of parts.

[0058] <Second Embodiment> Referring to Figure 5, the solenoid relief valve 200 according to the second embodiment will be described. Figure 5 is a cross-sectional view of the solenoid relief valve 200.

[0059] In the first embodiment of the electromagnetic relief valve 100, the hydraulic fluid discharged from the back pressure chamber 8 passes through the inside of the pilot poppet 20, whereas in the second embodiment of the electromagnetic relief valve 200, the hydraulic fluid discharged from the back pressure chamber 8 passes outside the pilot poppet 220. Furthermore, in the electromagnetic relief valve 100 according to the first embodiment, the hydraulic fluid guided to the spring chamber 78 is discharged through the electromagnetic relief valve 100 to the low-pressure passage L, whereas in the electromagnetic relief valve 200 according to the second embodiment, the hydraulic fluid guided to the spring chamber 78 is discharged directly to the outside. Specifically, in the electromagnetic relief valve 100 according to the first embodiment, the sleeve 7 has a through hole 7e, whereas in the electromagnetic relief valve 200 according to the second embodiment, the sleeve 7 does not have a through hole 7e. Also, in the electromagnetic relief valve 100 according to the first embodiment, the adjustment member 79 attached to the fixed iron core 77 does not have a passage that communicates with the outside, whereas in the electromagnetic relief valve 200 according to the second embodiment, an adjustment member 279 is attached to the fixed iron core 77 that has a through hole 279b connecting the spring chamber 78 and the outside. In the following, only the differences from the electromagnetic relief valve 100 according to the first embodiment will be described, and identical components will be given the same numbering and their description will be omitted.

[0060] As shown in Figure 5, the electromagnetic relief valve 200 is provided within the sleeve 7 and includes a pilot poppet 220 as a pilot valve body that opens and closes the communication passage 7f, and a biasing unit S1 for adjusting the set pressure (relief pressure).

[0061] As shown in Figure 5, the pilot poppet 220 is a substantially cylindrical member that is slidably housed in the housing hole 7c of the sleeve 7. The pilot poppet 220 has a first sliding portion 221 and a second sliding portion 222 that slide against the inner circumferential surface of the housing hole 7c and are arranged in order from the biasing portion S1 side, a valve portion 223 that protrudes axially from the second sliding portion 222 and is formed in a conical shape, an annular groove 224 provided between the first sliding portion 221 and the second sliding portion 222, and a rod portion 227 that has a smaller diameter than the first sliding portion 221 and extends from the end face of the first sliding portion 221 toward the plunger 272.

[0062] The outer circumferential surfaces of the first sliding portion 221 and the second sliding portion 222 are provided with connecting passages 221a and 222a, respectively, formed by grooves or planar notches along the axial direction. As a result, the hydraulic fluid discharged from the connecting passage 7f to the drain chamber 12 can flow into the biasing portion S1 (base member 71) through the connecting passages 221a and 222a.

[0063] Next, we will explain the biasing unit S1.

[0064] The biasing unit S1 includes a base member 71, a plunger 272 slidably housed within the base member 71 and pressing against the pilot poppet 220, a spring 74 as a first biasing member provided on the opposite side of the plunger 272 from the pilot poppet 220 and biasing the pilot poppet 220 in the valve closing direction via the plunger 272, a coil 75 supported by the base member 71 and, when current is applied, applying a reaction force to the plunger 272 that is opposite to the biasing force of the spring 74, a yoke 76 provided so as to surround the coil 75, a fixed iron core 77 attached to the yoke 76, and an adjustment member 279 attached to the fixed iron core 77.

[0065] The plunger 272 is made of a magnetic material. The plunger 272 is provided with a number of through holes 272b that are formed to penetrate in the axial direction and through which hydraulic fluid flows.

[0066] The adjustment member 279 is a cylindrical member that is screwed to the fixed core 77. The biasing force of the spring 74 can be adjusted by moving the adjustment member 279 axially relative to the fixed core 77. The axial movement of the adjustment member 279 is restricted by tightening the lock nut 80.

[0067] The adjustment member 279 has an end face 279a to which one end of the spring 74 abuts, a through hole 279b that penetrates the adjustment member 279 axially and connects the spring chamber 78 to the outside, and a threaded portion 279c for connecting to external piping. A pipe (not shown) communicating with a low-pressure passage L or a tank is connected to the threaded portion 279c. In this embodiment, the adjustment member 279 corresponds to the "support member" in the claims.

[0068] Next, the operation of the electromagnetic relief valve 200 will be explained.

[0069] The hydraulic fluid in the high-pressure passage H is guided to the connecting passage 7f through the pilot passage 10 and the back pressure chamber 8. When the pressure of the hydraulic fluid guided to the connecting passage 7f reaches the set pressure (cracking pressure) of the pilot poppet 220 set by the biasing unit S1, or in other words, when the biasing force on the pilot poppet 220 in the valve-opening direction due to the pressure of the hydraulic fluid guided to the connecting passage 7f becomes greater than the biasing force on the pilot poppet 220 in the valve-closing direction due to the biasing unit S1, the valve portion 223 of the pilot poppet 220 separates from the seat portion 7g.

[0070] When the valve portion 223 of the pilot poppet 220 separates from the seat portion 7g, the hydraulic fluid in the back pressure chamber 8 flows into the spring chamber 78 through the connecting passage 7f, the drain chamber 12, the connecting passage 222a, the annular groove 224, the connecting passage 221a, the through hole 30b, and the through hole 272b. The hydraulic fluid that has flowed into the spring chamber 78 is discharged to the outside through the through hole 279b of the adjustment member 279. In this embodiment, the through hole 272b of the plunger 272 corresponds to the "first connecting passage" in the claims, and the through hole 279b of the adjustment member 279 corresponds to the "discharge passage" in the claims.

[0071] Thus, in the electromagnetic relief valve 200 of this embodiment, the hydraulic fluid discharged from the back pressure chamber 8 during relief operation is configured to pass through the spring chamber 78 and be discharged to the outside. This allows air accumulated in the spring chamber 78 to be discharged to the outside along with the hydraulic fluid, thereby suppressing oscillation of the plunger 272 caused by air accumulation.

[0072] Furthermore, in the electromagnetic relief valve 200, the hydraulic fluid that has passed through the through hole 272b of the plunger 272 is configured to flow from one end to the other end of the spring chamber 78, so that any air trapped in the spring chamber 78 can be reliably discharged.

[0073] <Third Embodiment> Referring to Figure 6, the electromagnetic relief valve 300 according to the third embodiment will be described. Figure 6 is a cross-sectional view of the electromagnetic relief valve 300.

[0074] The electromagnetic relief valve 100 according to the first embodiment is a pilot-operated electromagnetic relief valve, while the electromagnetic relief valve 300 according to the third embodiment is a direct-acting electromagnetic relief valve. Specifically, the electromagnetic relief valve 300 differs in that the pilot poppet 20 according to the first embodiment functions as the main poppet (main poppet 320), and the sleeve 7 according to the first embodiment and the sleeve 307 according to the third embodiment have different shapes. However, the pilot poppet 20 of the electromagnetic relief valve 100 according to the first embodiment and the main poppet 320 of the electromagnetic relief valve 300 according to the third embodiment have the same shape. In the following, only the differences from the electromagnetic relief valve 100 according to the first embodiment will be described, and identical components will be given the same numbering and their description will be omitted.

[0075] As shown in Figure 6, the sleeve 307 of the electromagnetic relief valve 300 has a tip portion 307a that is inserted into the main body 1 of the equipment, a base portion 307b that is coupled to the base member 71 of the biasing portion S, a housing hole 307c that opens to the axial end face of the base portion 307b on the biasing portion S side, and a plurality of through holes 307e that penetrate the base portion 307b axially on the outer circumference of the base portion 307b from the housing hole 307c.

[0076] The tip portion 307a sits on the seat portion 1a formed between the high-pressure passage H and the low-pressure passage L in the main body of the equipment 1.

[0077] Furthermore, the sleeve 307 has a connecting passage 307f formed therein, which opens at one end to the high-pressure passage H and at the other end to the bottom surface of the housing hole 307c, connecting the high-pressure passage H and the housing hole 307c.

[0078] A seat portion 307g is provided at the open end of the communication passage 307f that opens into the housing hole 307c, onto which the valve portion 23 of the main poppet 320 sits and unseats. The seat portion 307g is formed such that its central axis coincides with the central axis of the housing hole 307c. In this embodiment, the communication passage 307f corresponds to the "high-pressure side passage" in the claims. The housing hole 307c of the sleeve 307 corresponds to the "valve body housing chamber" in the claims.

[0079] Next, the operation of the electromagnetic relief valve 300 will be explained.

[0080] The hydraulic fluid in the high-pressure passage H is led to the connecting passage 307f. When the pressure of the hydraulic fluid led to the connecting passage 307f reaches the set pressure (cracking pressure) of the main poppet 320 set by the biasing unit S, or in other words, when the biasing force on the main poppet 320 in the valve-opening direction due to the pressure of the hydraulic fluid led to the connecting passage 307f becomes greater than the biasing force on the main poppet 320 in the valve-closing direction due to the biasing unit S, the valve portion 23 of the main poppet 320 separates from the seat portion 307g.

[0081] When the valve portion 23 of the main poppet 320 separates from the seat portion 307g, the hydraulic fluid in the high-pressure passage H flows into the spring chamber 78 through the connecting passage 307f, the drain chamber 12, the connecting passage 22a, the annular groove 24, the connecting hole 25, the connecting passage 26, and the through hole 772a. The hydraulic fluid that has flowed into the spring chamber 78 is then discharged to the low-pressure passage L through the through holes 72b, 30b, and 307e. This prevents the pressure in the high-pressure passage H from becoming abnormally high. In this embodiment, the passage from the drain chamber 12 to the low-pressure passage L corresponds to the "low-pressure side passage" in the claims.

[0082] Furthermore, when the pressure in the high-pressure passage H decreases, the valve portion 23 of the main poppet 320 sits on the seat portion 307g, blocking communication between the connecting passage 307f and the drain chamber 12.

[0083] In this way, even in the electromagnetic relief valve 300, the hydraulic fluid discharged from the high-pressure passage H during relief operation passes through the spring chamber 78, so that the air accumulated in the spring chamber 78 can be discharged into the low-pressure passage L along with the hydraulic fluid. Therefore, oscillation of the plunger 72 caused by the accumulation of air can be suppressed.

[0084] <Fourth Embodiment> Referring to Figure 7, the electromagnetic relief valve 400 according to the fourth embodiment will be described. Figure 7 is a cross-sectional view of the electromagnetic relief valve 400.

[0085] The electromagnetic relief valve 400 according to the fourth embodiment differs from the electromagnetic relief valve 100 according to the first embodiment in that it includes a rod 473 that penetrates the plunger 72, and that the adjustment member 479 is provided with a recess 479b into which the end of the rod 473 fits. In the following, only the differences from the electromagnetic relief valve 100 according to the first embodiment will be described, and identical components will be given the same numbering and their descriptions will be omitted.

[0086] As shown in Figure 7, the electromagnetic relief valve 400 includes a rod 473 fixed to the plunger 72 and pressing against the pilot poppet 20. The rod 473 is included in the "plunger portion" as defined in the claims and corresponds to the "guide portion" as defined in the claims.

[0087] The rod 473 is inserted through a through hole 472a provided in the plunger 72. The rod 473 is formed from a rod-shaped member and has a through hole 473a as a first communication passage that penetrates axially. One end of the through hole 473a faces (communicates with) the communication passage 26 of the pilot poppet 20.

[0088] The adjustment member 479 is provided with a recess 479b that opens on the end face 479a into which the other end of the rod 473 fits, and a plurality of connecting passages 479c, one end of which opens on the end face 479a and the other end of which opens on the side surface of the recess 479b. When the other end of the rod 473 fits into the recess 479b, one end of the through hole 473a of the rod 473 is connected to the inside of the recess 479b. As a result, the hydraulic fluid that has passed through the through hole 473a of the rod 473 is guided to the spring chamber 78 through the recess 479b and the connecting passages 479c.

[0089] In the electromagnetic relief valve 400 configured in this way, when the valve portion 23 of the pilot poppet 20 separates from the seat portion 7g, the hydraulic fluid in the back pressure chamber 8 flows into the spring chamber 78 through the communication passage 7f, the drain chamber 12, the communication passage 22a, the annular groove 24, the communication hole 25, the communication passage 26, the through hole 473a, the recess 479b, and the communication passage 479c. The hydraulic fluid that has flowed into the spring chamber 78 is discharged to the low-pressure passage L through the through hole 72b, the through hole 30b, the through hole 7e, the area outside the intermediate portion 7d, and the communication passage 4.

[0090] Since the connecting passage 479c opens to the end face 479a of the adjustment member 479, the hydraulic fluid discharged from the back pressure chamber 8 passes through the entire spring chamber 78 from one end to the other. Therefore, by adopting this configuration, air accumulated in the corners of the spring chamber 78 can be discharged more reliably.

[0091] Now, let's discuss variations.

[0092] For example, as shown in Figure 8, in the electromagnetic relief valve 400, the adjustment member 479 may be provided with a passage 60 that connects the recess 479b and the threaded portion of the adjustment member 479 and the fixed core 77. In this way, hydraulic fluid is guided from the passage 60 to the threaded portion of the adjustment member 479 and the fixed core 77, and further guided from the threaded portion to the spring chamber 78, thereby allowing air accumulated in the threaded portion of the adjustment member 479 and the fixed core 77 to be discharged to the outside through the spring chamber 78. Alternatively, one end of the passage 60 may be directly connected to the spring chamber 78 instead of the recess 479b.

[0093] <Fifth Embodiment> Referring to Figure 9, the solenoid relief valve 500 according to the fifth embodiment will be described. Figure 9 is a cross-sectional view of the solenoid relief valve 500.

[0094] The electromagnetic relief valve 500 according to the fifth embodiment differs from the electromagnetic relief valve 400 according to the fourth embodiment in that it includes a third connecting passage 507h for directly guiding the hydraulic fluid discharged from the high-pressure side passage (connecting passage 7f) to the discharge passage (connecting passage 4). The electromagnetic relief valve 500 will be described in detail below with reference to Figure 9.

[0095] As shown in Figure 9, the electromagnetic relief valve 500 is provided with a communication passage 507h that connects the housing hole 7c and the area outside the intermediate portion 7d in the sleeve 7. The communication passage 507h is composed of a plurality of through holes that penetrate the intermediate portion 7d of the sleeve 7.

[0096] The connecting passage 507h directs a portion of the hydraulic fluid discharged from the back pressure chamber 8 through the connecting passage 7f to the drain chamber 12 upon opening of the pilot poppet 20 directly to the low-pressure passage L through the connecting passage 4. In other words, the connecting passage 507h discharges a portion of the hydraulic fluid discharged from the back pressure chamber 8 through the connecting passage 7f to the drain chamber 12, bypassing the spring chamber 78.

[0097] The operation of the electromagnetic relief valve 500 is the same as that of the electromagnetic relief valve 400 according to the fourth embodiment, so its explanation is omitted.

[0098] In the electromagnetic relief valve 500, the hydraulic fluid discharged from the high-pressure passage H during relief operation passes through the spring chamber 78, so that the air accumulated in the spring chamber 78 can be discharged into the low-pressure passage L along with the hydraulic fluid. Therefore, oscillation of the plunger 72 caused by air accumulation can be suppressed.

[0099] In the electromagnetic relief valve 400 according to the fourth embodiment, the entire amount of hydraulic fluid discharged into the drain chamber 12 flows into the spring chamber 78. As a result, if the flow rate of hydraulic fluid discharged into the drain chamber 12 is large, the pressure in the spring chamber 78 will rise, and a biasing force will act on the plunger 72 that biases the pilot poppet 20 in the closing direction, which may cause oscillation. Therefore, in the electromagnetic relief valve 500 of this embodiment, a portion of the hydraulic fluid discharged into the drain chamber 12 is discharged to the low-pressure passage L via the communication passage 507h, bypassing the spring chamber 78. This reduces the flow rate of hydraulic fluid flowing into the spring chamber 78, thereby suppressing the rise in pressure in the spring chamber 78 and more reliably preventing the plunger 72 from oscillating.

[0100] <Sixth Embodiment> Referring to Figure 10, the electromagnetic relief valve 600 according to the sixth embodiment will be described. Figure 10 is a cross-sectional view of the electromagnetic relief valve 600. The electromagnetic relief valve 600 according to the sixth embodiment differs from the electromagnetic relief valve 100 according to the first embodiment in the position of the O-ring 679e provided on the adjustment member 679. In the following, only the differences from the electromagnetic relief valve 100 according to the first embodiment will be described, and identical components will be given the same numbering and their description will be omitted.

[0101] As shown in Figure 10, in the electromagnetic relief valve 600, the adjustment member 679 has a male threaded portion 679d that screws into a female threaded portion formed in the through hole 77a of the fixed core 77, and an O-ring 679e provided on the spring chamber 78 side of the male threaded portion 679d to seal the space between the adjustment member 679 and the fixed core 77.

[0102] For example, in the electromagnetic relief valve 100 shown in Figure 1, a washer 79f is provided to hold down the O-ring that seals the space between the adjustment member 79 and the fixed iron core 77. However, in the electromagnetic relief valve 600, the O-ring 679e is provided on the spring chamber 78 side of the male thread portion 679d, so the washer 79f can be made unnecessary. This reduces the number of parts.

[0103] In the electromagnetic relief valves 100, 300-600 of the first and third to sixth embodiments described above, the case in which a through hole 72b is formed as the passage (discharge passage) for the hydraulic fluid in the plunger 72 was explained as an example. However, instead, slits 72c (see Figure 11) that open to both ends of the plunger 72 may be formed on the outer circumferential surface of the plunger 72. Also, in the electromagnetic relief valve 200 of the second embodiment, the case in which a through hole 272b is formed as the passage (first connecting passage) for the hydraulic fluid in the plunger 272 was explained as an example. However, instead, slits 272c (see Figure 12) that open to both ends of the plunger 272 may be formed on the outer circumferential surface of the plunger 272. In these cases, for example, the hydraulic fluid will pass through the gaps between the guide members 90 that are aligned in the axial direction, and the gap between the base member 71 and the fixed iron core 77 in the axial direction, so it is possible to suppress the accumulation of air in these gaps.

[0104] Furthermore, in the electromagnetic relief valve 500 (Figure 9) according to the fifth embodiment, a case was described in which a communication passage 507h is provided in the sleeve 7 that connects the housing hole 7c and the area outside the intermediate portion 7d in order to directly guide the hydraulic fluid discharged from the high-pressure side passage (communication passage 7f) to the discharge passage (communication passage 4), but the invention is not limited to this. For example, as shown in Figure 13, the communication passage 507h may be formed to communicate with the discharge passage (communication passage 4) from the space partitioned by the bottom surface of the housing hole 7c and the second sliding portion 22 in the drain chamber 12.

[0105] The configuration, operation, and effects of the embodiment of the present invention configured as described above will be explained in summary.

[0106] The electromagnetic relief valves 100, 200, 300, 400, 500, and 600 include pilot poppets 20, 220 and main poppet 320 (valve bodies) that connect or block the high-pressure side passage (connecting passage 7f, connecting passage 307f) and the low-pressure side passage (passage from drain chamber 12 to low-pressure passage L), and biasing parts S, S1 that bias the pilot poppets 20, 220 and main poppet 320 (valve bodies) in the closing direction, and the biasing parts S, S1 are pip A plunger section (plunger 72, 272, rod 473) that presses against the pilot poppet 20, 220 and the main poppet 320 (valve body), and a section provided on the opposite side of the plunger section (plunger 72, 272, rod 473) from the pilot poppet 20, 220 and the main poppet 320 (valve body), via the plunger section (plunger 72, 272, rod 473) The valve body has a spring 74 (first biasing member) that biases it in the closing direction, a spring chamber 78 (biasing member chamber) that houses the spring 74 (first biasing member), and a coil 75 that, when current is applied, applies a reaction force to the plunger section (plungers 72, 272, rod 473) that is opposite to the biasing force of the spring 74 (first biasing member), and the plunger section (plungers 72, 272, rod 473) has a pilot poppet 20 220, through holes 72a, 473a, and 272b (first connecting passages) are provided to guide the hydraulic fluid discharged from the high-pressure side passage when the main poppet 320 (valve body) opens to the spring chamber 78 (biasing member chamber), and a discharge passage is further provided to discharge the hydraulic fluid to the outside at a lower pressure than the pressure inside the through holes 72a, 473a, and 272b (first connecting passages) when the high-pressure side hydraulic fluid is guided from the spring chamber 78 (biasing member chamber).

[0107] In this configuration, the hydraulic fluid discharged from the high-pressure side passage (connecting passage 7f, connecting passage 307f) is guided to the spring chamber 78 (biasing member chamber) through the through holes 72a, 473a, 272b (first connecting passage) provided in the plunger section (plungers 72, 272, rod 473). This allows the air in the spring chamber 78 (biasing member chamber) where the spring 74 (first biasing member) is housed to be discharged to the outside along with the hydraulic fluid. This prevents air from accumulating in the spring chamber 78 (biasing member chamber) where the spring 74 (first biasing member) that biases the plunger section (plungers 72, 272, rod 473) is housed.

[0108] Furthermore, in the electromagnetic relief valves 100, 400, and 500, the plunger section (plunger 72, rod 473) comprises a plunger 72 made of a magnetic material, and a guide section (pipe 40, guide section 72d, rod 473) that extends from the end face of the plunger 72 toward the spring chamber 78 (biasing member chamber), is hollow, and guides the hydraulic fluid (working oil) passing through the through holes 72a, 473a (first connecting passage) to the spring chamber 78 (biasing member chamber).

[0109] In this configuration, the hydraulic fluid can flow all the way to the back of the spring chamber 78 (biasing member chamber), so that any air trapped inside the spring chamber 78 can be more reliably discharged.

[0110] In addition, in the electromagnetic relief valve 100, the guide section is a pipe 40 attached to the plunger 72.

[0111] In this configuration, the guide section can be easily provided simply by attaching the pipe 40 to the plunger 72. Furthermore, because the guide section is formed from the pipe 40, the length of the guide section can be easily adjusted.

[0112] In the electromagnetic relief valve 100, the guide portion 72d is formed integrally with the plunger 72.

[0113] In this configuration, the guide portion 72d is formed integrally with the plunger 72, thus reducing the number of parts.

[0114] In the electromagnetic relief valves 400 and 500, the guide section is a hollow rod 473 that passes through the plunger 72 axially and presses against the pilot poppet 20 (valve body).

[0115] In this configuration, the guide section can be easily provided as it only requires attaching the rod 473 to the plunger 72. Furthermore, since the rod 473 presses against the pilot poppet 20 (valve body), the direct load acting on the plunger 72 can be suppressed, thus preventing damage to the plunger 72.

[0116] In the electromagnetic relief valve 100, the plunger 72 has a projection 72e that protrudes from the end face on the pilot poppet 20 (valve body) side and presses against the pilot poppet 20 (valve body).

[0117] In this configuration, it is not necessary to bevel the entire end face of the plunger 72 on the pilot poppet 20 side in order to prevent uneven contact between the pilot poppet 20 (valve body) and the plunger 72. In other words, in this configuration, only the tip surface of the protruding portion 72e needs to be beveled, thus reducing processing time.

[0118] Furthermore, in the electromagnetic relief valves 400 and 500, the biasing section S further includes an adjustment member 479 (support member) that supports the end of the spring chamber 78 (biasing member chamber) opposite to the plunger section (plunger 72). The adjustment member 479 (support member) has a recess 479b that opens to the end face facing one end of the plunger section (plunger 72), and one end of the through hole 473a (first connecting passage) is connected to the recess 479b.

[0119] In this configuration, one end of the through-hole 473a (first connecting passage) is connected to a recess 479b formed in the adjustment member 479 (support member), allowing the hydraulic fluid to be guided to the vicinity of the end of the spring 74 (first biasing member) where air tends to accumulate. This makes it possible to more reliably prevent air from accumulating in the spring chamber 78 (biasing member chamber).

[0120] In the electromagnetic relief valve 400, the biasing section S generates a magnetic force when current is applied to the coil 75 and further comprises a fixed iron core 77 into which an adjustment member 479 (support member) is movably screwed. The adjustment member 479 (support member) is provided with at least one of a recess 479b and a spring chamber 78 (biasing member chamber), and a communication passage 60 that connects the adjustment member 479 (support member) and the screwed portion of the fixed iron core 77.

[0121] In this configuration, hydraulic fluid is introduced from the connecting passage 60 to the threaded portion of the adjustment member 479 (support member) and the fixed iron core 77. Furthermore, by introducing the hydraulic fluid from the threaded portion to the spring chamber 78, air accumulated in the threaded portion of the adjustment member 479 (support member) and the fixed iron core 77 can be discharged to the outside through the spring chamber 78.

[0122] In electromagnetic relief valves 100, 300, 400, 500, and 600, the discharge passage (through hole 72b, slit 72c) is provided in the plunger section (plunger 72).

[0123] In this configuration, since the plunger section (plunger 72) is provided with a discharge channel (through hole 72b, slit 72c), there is no need to secure separate space for the discharge channel.

[0124] Furthermore, in the electromagnetic relief valves 100, 300, 400, 500, and 600, the discharge passage is a slit 72c formed on the outer circumferential surface of the plunger portion (plunger 72) and opening at both ends of the plunger portion (plunger 72).

[0125] In this configuration, the hydraulic fluid passes through the gaps between the guide members 90 aligned in the axial direction and the gap between the base member 71 and the fixed iron core 77 in the axial direction, thus preventing air from accumulating in these gaps.

[0126] Furthermore, in the electromagnetic relief valve 200, the first communication passage is a slit 272c formed on the outer circumferential surface of the plunger portion (plunger 272) and opening at both ends of the plunger portion (plunger 272).

[0127] In this configuration, the hydraulic fluid passes through the gaps between the guide members 90 aligned in the axial direction and the gap between the base member 71 and the fixed iron core 77 in the axial direction, thus preventing air from accumulating in these gaps.

[0128] The electromagnetic relief valves 100, 300, 400, 500, and 600 further include a housing hole 7c and a housing hole 307c (valve body housing chamber) for movably housing a pilot poppet 20 and a main poppet 320 (valve body). The pilot poppet 20 and the main poppet 320 (valve body) have a first sliding part 21 and a second sliding part 22 that slide against the inner circumferential surface of the housing hole 7c and the housing hole 307c (valve body housing chamber) and are arranged in order from the plunger 72 side, and a communication hole 25 and a communication passage 26 (second communication passage) that open between the first sliding part 21 and the second sliding part 22 and pass through the inside of the pilot poppet 20 and the main poppet 320 (valve body) and are connected to through holes 72a and 473a (first communication passage).

[0129] In this configuration, the hydraulic fluid discharged from the high-pressure side passage (connecting passage 7f, connecting passage 307f) passes through the inside of the pilot poppet 20, the main poppet 320 (valve body), and the plunger section (plunger 72, rod 473), thus allowing the device to be miniaturized.

[0130] The electromagnetic relief valve 500 further comprises a sleeve 7 (housing member) having a housing hole 7c (valve body housing chamber) formed therein for movably housing a pilot poppet 20 (valve body), and the sleeve 7 (housing member) is provided with a connecting passage 507h (third connecting passage) that connects the housing hole 7c (valve body housing chamber) to the discharge passage and directly guides a portion of the hydraulic fluid discharged from the high-pressure side passage when the pilot poppet 20 (valve body) opens to the discharge passage.

[0131] In this configuration, a portion of the hydraulic fluid discharged into the drain chamber 12 can be bypassed through the spring chamber 78 (biasing member chamber) and discharged directly into the low-pressure passage L from the communication passage 507h (third communication passage). This reduces the flow rate of hydraulic fluid into the spring chamber 78 (biasing member chamber), thereby suppressing an increase in pressure within the spring chamber 78 (biasing member chamber) and preventing the plunger 72 from oscillating.

[0132] The electromagnetic relief valves 100, 200, 300, 400, 500, and 600 further include a spring 83 (second biasing member) that directly biases the pilot poppet 20, 220 and the main poppet 320 (valve body) in the closing direction.

[0133] In this configuration, when the plunger section (plungers 72, 272, rod 473) becomes immobile and is unable to press the pilot poppets 20, 220 and main poppet 320 (valve body) in the closing direction, the biasing force of the spring 83 (second biasing member) can close the pilot poppets 20, 220 and main poppet 320 (valve body).

[0134] In the electromagnetic relief valve 200, the biasing section S further includes an adjustment member 279 (support member) that supports the end of the spring 74 (first biasing member) opposite to the plunger section (plunger 272), and the discharge passage is a through hole 279b formed in the adjustment member 279 (support member) that connects the spring 74 (first biasing member) to the outside.

[0135] In this configuration, the hydraulic fluid (working oil) introduced into the spring chamber 78 (biasing member chamber) is discharged directly to the outside through a through hole 279b formed in the adjustment member 279 (support member), thus shortening the length of the discharge path. This reduces the flow resistance.

[0136] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0137] In the above embodiment, adjustment members 79, 279 are provided, but this invention can also be applied to electromagnetic relief valves that do not have such members for adjusting the biasing force of the spring 74. Furthermore, the shapes of pilot poppets 20, 220, main poppet 320, etc. can be changed as appropriate, as long as they do not deviate from the technical concept of the present invention.

[0138] Furthermore, although the electromagnetic relief valve 400 shown in Figure 8 was described in which the adjustment member 479 is provided with a recess 479b and a communication passage 60 that connects the adjustment member 479 and the threaded portion of the fixed iron core 77, the invention is not limited to this, and other embodiments may also be provided, for example, in the electromagnetic relief valve 100, the adjustment member 79 may be provided with a communication passage 60 that connects the adjustment member 79 and the threaded portion of the fixed iron core 77 and the spring chamber 78.

[0139] In addition, the communication passage 507h of the electromagnetic relief valve 500 according to the fifth embodiment may be provided in the electromagnetic relief valve 100 or the like.

[0140] This application claims priority under Japanese Patent Application No. 2023-112833, filed with the Japan Patent Office on 10 July 2023, and all contents of that application are incorporated herein by reference.

Claims

1. It is an electromagnetic relief valve, A valve body that connects or blocks the high-pressure passage and the low-pressure passage, The valve body is provided with a biasing part that biases it in the closing direction, The biasing unit is, A plunger portion that presses against the valve body, A first biasing member is provided on the opposite side of the valve body from the plunger portion, and biases the valve body in the closing direction via the plunger portion, A biasing member chamber in which the first biasing member is housed, The device includes a coil that, when current is applied, applies a reaction force to the plunger portion that is opposite to the biasing force of the first biasing member, The plunger portion is provided with a first connecting passage that guides the working fluid discharged from the high-pressure side passage when the valve body opens to the biasing member chamber. An electromagnetic relief valve further comprising a discharge channel for discharging the working fluid to the outside at a pressure lower than the pressure in the first communication passage when the working fluid on the high-pressure side is introduced from the biasing member chamber.

2. An electromagnetic relief valve as described in claim 1, The plunger portion is A plunger made of magnetic material, An electromagnetic relief valve having a guide portion that extends from the end face of the plunger toward the biasing member chamber, is hollow, and guides the working fluid passing through the first communication passage toward the biasing member chamber.

3. An electromagnetic relief valve as described in claim 2, The guide portion is a solenoid relief valve, which is a pipe attached to the plunger.

4. An electromagnetic relief valve as described in claim 2, The guide portion is an electromagnetic relief valve formed integrally with the plunger.

5. An electromagnetic relief valve as described in claim 2, The guide portion is a hollow rod that penetrates the plunger axially and presses against the valve body, in an electromagnetic relief valve.

6. An electromagnetic relief valve as described in claim 2, The plunger has a protruding portion that extends from the end face on the valve body side and presses against the valve body, forming an electromagnetic relief valve.

7. An electromagnetic relief valve as described in claim 1, The biasing portion further includes a support member that supports the end of the first biasing member opposite to the plunger portion, The support member has a recess formed in its end face that is facing one end of the plunger portion, One end of the first communication passage is an electromagnetic relief valve that opens into the recess.

8. An electromagnetic relief valve as described in claim 7, The biasing unit further comprises a fixed iron core into which the support member is movably screwed, which generates a magnetic force when current is applied to the coil. The electromagnetic relief valve is provided with a support member having at least one of the recess and the biasing member chamber, and a communication passage connecting the support member and the threaded portion of the fixed iron core.

9. An electromagnetic relief valve as described in claim 1, The aforementioned discharge channel is an electromagnetic relief valve provided in the plunger section.

10. An electromagnetic relief valve as described in claim 1, The discharge channel is an electromagnetic relief valve, which is a slit formed on the outer circumferential surface of the plunger portion and opening on both end faces of the plunger portion.

11. An electromagnetic relief valve as described in claim 1, The first communication passage is a slit formed on the outer circumferential surface of the plunger portion and opening at both end faces of the plunger portion, in the electromagnetic relief valve.

12. An electromagnetic relief valve as described in claim 1, The housing member further comprises a valve housing chamber formed therein for movably housing the valve body, The valve body is, The first sliding part and the second sliding part slide against the inner circumferential surface of the valve body housing chamber and are arranged in order from the plunger part side, An electromagnetic relief valve having a second communication passage that opens between the first sliding portion and the second sliding portion and is connected to the first communication passage by passing through the inside of the valve body.

13. An electromagnetic relief valve as described in claim 1, The housing member further comprises a valve housing chamber formed therein for movably housing the valve body, The aforementioned housing member is provided with a third communication passage that connects the valve body housing chamber and the discharge passage, and directs a portion of the working fluid discharged from the high-pressure side passage when the valve body opens directly into the discharge passage.

14. An electromagnetic relief valve as described in claim 1, An electromagnetic relief valve further comprising a second biasing member that directly biases the valve body in the closing direction.

15. An electromagnetic relief valve as described in claim 1, The biasing portion further includes a support member that supports the end of the first biasing member opposite to the plunger portion, The discharge channel is an electromagnetic relief valve formed in the support member, which is a through-hole connecting the biasing member chamber to the outside.

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