Solenoid proportional relief valve

Abstract

To provide a solenoid proportional relief valve capable of achieving a small size, weight saving, and a simple structure, and controlling a relief pressure with high accuracy by preventing an oscillation during operation.SOLUTION: A solenoid proportional relief valve 1 comprises: a joint 40 in which a flow channel 60 is arranged; a coil 36 that is wound so as to enable an electric conduction; a movable element 42 that is supported so as to be movable along a shaft line direction of the coil 36; and a stator 39 that generates a suction force for the movable element 42 by excitation of the coil 36. The movable element 42 is formed in a cylindrical shape with a bottom having a wall part 42A and a bottom part 42B, and is constructed as an energization member housing chamber 42C in which an energization member 46 is housed in a state where an inner cylinder part occurs a resilient force. An inner surface of the bottom part 42B is constructed as a reception part 42a of the energization member 46, and a valve part 52 is integrally provided at an outer surface of the bottom part 42B.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Working vehicles such as forklifts and construction machinery are equipped with working devices such as forks and buckets that are driven by a fluid (specifically, "hydraulic oil") at a predetermined pressure that is pressurized and delivered by a hydraulic pump. In the circuits that drive such working devices, relief valves are provided as appropriate to control the pressure of the fluid, i.e., to open the valve to release the pressure when the pressure of the fluid exceeds a set value (hereinafter sometimes referred to as "relief pressure").

[0003] As an example of a relief valve, an electromagnetic proportional relief valve is known, which variably adjusts the relief pressure by changing the thrust of a proportional solenoid (see Patent Document 1: Japanese Patent Laid-Open Publication No. 6-323451). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-323451 Summary of the Invention [Problem to be solved by the invention]

[0005] The electromagnetic proportional relief valve exemplified in Patent Document 1 can reduce the number of pilot piping and pressure switching parts compared to conventional pilot-operated relief valves, making it possible to reduce the size, weight, and structure, and also to reduce manufacturing costs. However, on the other hand, a problem has been that vibration (chattering) tends to occur during operation. [Means for solving the problem]

[0006] The present invention has been made in view of the above circumstances, and has an object to provide an electromagnetic proportional relief valve that can be made small, lightweight, and has a simplified structure, and that can prevent vibration during operation and control relief pressure with high precision.

[0007] In one embodiment, the above problem is solved by the solution disclosed below.

[0008] The disclosed electromagnetic proportional relief valve is In one embodiment, an electromagnetic proportional relief valve having a valve element and a valve seat that move toward and away from each other, provided in a flow path through which liquid of a predetermined pressure flows; the valve element and the valve seat are moved away from each other to release the pressure when the pressure of the liquid in the flow path exceeds a set value, and the set value is variably adjusted; the valve comprises: a joint in which the flow path is disposed; a coil wound in a manner that allows current to be applied; a moving element supported so as to be movable along the axial direction of the coil; and a stator that generates an attractive force on the moving element when the coil is excited; the moving element is formed in a cylindrical shape with a wall and a bottom; the inner cylindrical portion is configured as an urging member accommodating chamber in which an urging member is accommodated in a state in which a resilient force is generated; the inner surface of the bottom on the side not facing the valve seat is configured as a force receiving portion of the urging member; and the valve element is integrally formed on an outer surface of the bottom on the side facing the valve seat. The movable element is formed such that the valve body portion protrudes from the outer surface of the bottom toward the valve seat portion, and the mass of the movable element excluding the valve body portion is set to be 30 times or more the mass of the valve body portion, and the movable element has a through-hole that connects the inner surface and the outer surface of the bottom to allow the liquid to flow, and a plurality of the through-holes are provided at equal intervals in the circumferential direction at positions adjacent to the valve body portion. The following are requirements. In another embodiment, an electromagnetic proportional relief valve is provided in which a valve element and a valve seat that move toward and away from each other are provided in a flow path through which a liquid of a predetermined pressure flows, and when the pressure of the liquid in the flow path exceeds a set value, the valve element is caused to move away from the valve seat to release the pressure, and the set value is variably adjusted, the electromagnetic proportional relief valve comprising: a joint in which the flow path is disposed; a coil wound in a manner that allows current to be applied; a moving element supported so as to be movable along the axial direction of the coil; and a stator that generates an attractive force on the moving element by exciting the coil, the moving element being formed in a bottomed cylindrical shape having a wall and a bottom, the inner cylindrical portion being configured as an urging member accommodating chamber in which an urging member is accommodated in a state in which a resilient force is generated, the inner surface of the bottom on the side not facing the valve seat being configured as a force receiving portion of the urging member, and the part facing the valve seat at the bottom being configured as a force receiving portion of the urging member. the valve body is integrally formed on the outer surface of the wall facing the valve seat, the valve body of the movable element is formed on the outer surface of the bottom so as to protrude towards the valve seat, and the mass of the movable element excluding the valve body is set to be 30 times or more the mass of the valve body, the movable element has a communication groove on its outer peripheral surface that communicates between an end face of the wall portion facing the valve seat and an end face of the wall portion not facing the valve seat to allow the liquid to flow, and further comprises a cylindrical bobbin around which the coil is wound, the movable element is slidably supported via a bushing in the inner cylindrical part of a joint or a moving support part provided on a sleeve fitted into the inner cylindrical part of the bobbin, and a plurality of the communication grooves are provided at equal intervals in the circumferential direction of the valve body on the outer peripheral surface including the sliding area for the bushing.

[0009] Furthermore, it is preferable that the movable element has at least one of a through hole that connects the inner surface and the outer surface of the bottom portion to allow the liquid to flow therethrough, a through hole that connects the end face of the wall portion facing the valve seat portion with the end face not facing the valve seat portion to allow the liquid to flow therethrough, or a communication groove that is provided on the outer surface and connects the end face of the wall portion facing the valve seat portion with the end face not facing the valve seat portion to allow the liquid to flow therethrough, and that the valve body portion is formed on the outer surface of the bottom portion in a shape that protrudes toward the valve seat portion, and that the mass of the movable element excluding the valve body portion is set to be 30 times or more the mass of the valve body portion.

[0010] Further, it is preferable that a holding member is provided which holds the biasing member in the biasing member accommodating chamber in a state in which the tip thereof presses the biasing member to generate the elastic force, the holding member is arranged with the tip thereof inserted into the biasing member accommodating chamber, and the elastic force can be adjusted by changing the amount of insertion, and the biasing member is held by the holding member in a state in which it does not protrude from the inside of the biasing member accommodating chamber to the outside.

[0011] It is also preferable that the valve has a cylindrical bobbin around which the coil is wound, the valve seat portion is supported by the inner cylindrical portion of a joint fitted into the inner cylindrical portion of the bobbin, and the movable element having the valve body portion is slidably supported via a bushing in the inner cylindrical portion of a joint fitted into the inner cylindrical portion of the bobbin or a moving support portion provided on a sleeve.

[0012] It is also preferable that the axial length of the bush is set to be 1.2 times or more the axial length of the valve body portion. [Effects of the Invention]

[0013] The disclosed electromagnetic proportional relief valve can prevent vibration during operation, enabling stable pressure control without fluctuation, i.e., highly accurate control of the liquid pressure. Furthermore, it can be made smaller, lighter, and has a simpler structure. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a circuit diagram showing an example of the configuration of a circuit in which an electromagnetic proportional relief valve according to an embodiment of the present invention is incorporated. [Figure 2] 1 is a front cross-sectional view showing an example of an electromagnetic proportional relief valve (pull type) according to an embodiment of the present invention. FIG. [Figure 3] FIG. 3 is an enlarged view of part III in FIG. 2. [Figure 4] 1 is a front cross-sectional view showing an example of an electromagnetic proportional relief valve (push type) according to an embodiment of the present invention. [Figure 5] FIG. 5 is an enlarged view of a portion V in FIG. [Figure 6] FIG. 2 is a side view illustrating an example of a mover of the proportional electromagnetic relief valve according to the embodiment of the present invention. [Figure 7] FIG. 10 is a side view showing another example of a mover of the electromagnetic proportional relief valve according to the embodiment of the present invention. [Figure 8] FIG. 10 is a side view showing another example of a mover of the electromagnetic proportional relief valve according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a circuit diagram (schematic diagram) showing an example of the configuration of a circuit into which a proportional electromagnetic relief valve according to an embodiment of the present invention is incorporated. For convenience of explanation, arrows may be used in the drawings to indicate forward and backward directions. In addition, in all drawings used to explain the embodiment, members having the same function are given the same reference numerals, and repeated explanations thereof may be omitted.

[0016] The electromagnetic proportional relief valve 1 according to this embodiment is incorporated into a circuit (hydraulic circuit) for a fluid of a predetermined pressure (in this embodiment, "hydraulic oil" will be used as an example) that drives a working device of a working vehicle 2, and is a device for controlling the hydraulic oil, that is, for setting and changing (variably adjusting) the relief pressure. As an example, the relief pressure is set to about 2 to 40 MPa. Below, a "forklift" will be used as an example of the working vehicle 2. However, examples of working vehicles into which the electromagnetic proportional relief valve 1 is incorporated are not limited to this, and the circuit configuration (particularly the control valve) is not limited to the example below.

[0017] A work vehicle (here, a forklift) 2 having the circuit configuration shown in Fig. 1 is equipped with a mast 3 and forks 4 as working implements driven by hydraulic oil. The work vehicle also has a drive source (engine or electric motor) 9 that drives the traveling device and working implement, a hydraulic pump 10 that is driven by the drive source 9 and discharges hydraulic oil, a tank 11 that stores hydraulic oil, a control valve 12 disposed between the hydraulic pump 10 and the working implement, a lift operation lever 13 that operates the forks 4, and a tilt operation lever 14 that operates the mast 3. The work vehicle also has a lift operation detection sensor 18, a tilt operation detection sensor 19, and a controller 21.

[0018] Here, the work vehicle 2 is provided with a lift cylinder 6 that moves the fork 4 up and down, and a tilt cylinder 7 that tilts the mast 3. In specific operations, when the lift cylinder 6 extends, the fork 4 rises, and when the lift cylinder 6 retracts, the fork 4 descends. In addition, when the tilt cylinder 7 extends, the mast 3 tilts forward, and when the tilt cylinder 7 retracts, the mast 3 tilts backward.

[0019] The control valve 12 also has a lift electromagnetic proportional control valve 15, a tilt electromagnetic proportional control valve 16, and an electromagnetic proportional relief valve 1.

[0020] Here, the lift electromagnetic proportional control valve 15 is disposed between the hydraulic pump 10 and the lift cylinder 6. The lift electromagnetic proportional control valve 15 controls the flow rate of hydraulic oil supplied from the hydraulic pump 10 to the lift cylinder 6 by changing its opening in proportion to the control current value input to the solenoid section.

[0021] In addition, the tilt electromagnetic proportional control valve 16 is disposed between the hydraulic pump 10 and the tilt cylinder 7. The tilt electromagnetic proportional control valve 16 controls the flow rate of hydraulic oil supplied from the hydraulic pump 10 to the tilt cylinder 7 by changing its opening in proportion to the control current value input to the solenoid section.

[0022] On the other hand, the electromagnetic proportional relief valve 1 is an electromagnetic proportional type relief valve that opens when the pressure between the hydraulic pump 10 and the lift cylinder 6 or the pressure between the hydraulic pump 10 and the tilt cylinder 7 reaches a relief pressure (the detailed configuration will be described later). When the electromagnetic proportional relief valve 1 opens, hydraulic oil supplied from the main port 28 is sent to the tank port 29, thereby releasing the pressure. This controls the pressure of the hydraulic oil so that it does not exceed the relief pressure. The electromagnetic proportional relief valve 1 can change the relief pressure in proportion to the control current value input to the solenoid unit (proportional solenoid drive unit 30, described later).

[0023] Next, the lift operation detection sensor 18 detects the operation state (operation direction and operation amount) of the lift operation lever 13. The tilt operation detection sensor 19 detects the operation state (operation direction and operation amount) of the tilt operation lever 14.

[0024] Furthermore, the lift control valve control section 22 controls the lift electromagnetic proportional control valve 15 in accordance with the operation state of the lift operation lever 13 detected by the lift operation detection sensor 18. Specifically, the lift control valve control section 22 outputs a control current value corresponding to the operation amount of the lift operation lever 13 to the solenoid section of the lift electromagnetic proportional control valve 15.

[0025] Furthermore, the tilt control valve control section 23 controls the tilt electromagnetic proportional control valve 16 in accordance with the operation state of the tilt operation lever 14 detected by the tilt operation detection sensor 19. Specifically, the tilt control valve control section 23 outputs a control current value corresponding to the operation amount of the tilt operation lever 14 to the solenoid section of the tilt electromagnetic proportional control valve 16.

[0026] Furthermore, the relief pressure setting unit 24 sets the relief pressure of the electromagnetic proportional relief valve 1. Furthermore, the relief valve control unit 25 controls the electromagnetic proportional relief valve 1 in accordance with the relief pressure set by the relief pressure setting unit 24. Specifically, the relief valve control unit 25 outputs a control current value corresponding to a set value (relief pressure) of the pressure of the hydraulic oil that drives the cylinder to a proportional solenoid driving unit 30 (described later) of the electromagnetic proportional relief valve 1.

[0027] With this configuration, the electromagnetic proportional relief valve 1 opens (opens a branch flow path 60, which will be described later) when the pressure of the hydraulic oil flowing through a flow path (specifically, the main flow path 20 from the hydraulic pump 10 to the lift cylinder 6 and the tilt cylinder 7) reaches a set relief pressure. At this time, the hydraulic oil pumped from the hydraulic pump 10 passes through the electromagnetic proportional relief valve 1 and is discharged into the tank 11.

[0028] As described above, a problem with electromagnetic proportional relief valves is that they are prone to vibration during operation, specifically when the pressure of the hydraulic oil reaches the relief pressure and the valve opens and closes.

[0029] Therefore, the proportional electromagnetic relief valve 1 according to this embodiment has the following configuration, thereby making it possible to solve this problem.

[0030] First, we will explain the overall configuration of the electromagnetic proportional relief valve 1 according to this embodiment. As described above, the electromagnetic proportional relief valve 1 controls the pressure of hydraulic oil flowing through a flow path to be controlled in a hydraulic circuit, and is configured as two types depending on the operation: a pull type as shown in Fig. 2 and a push type as shown in Fig. 4.

[0031] 2 and 4, the proportional electromagnetic relief valve 1 is configured to include, as its main components, a proportional solenoid drive unit 30, a sleeve 38, and a joint 40. As an example, the sleeve 38 is disposed on the rear end side of the proportional solenoid drive unit 30 (specifically, the bobbin 34 described below), and the joint 40 is disposed on the front end side.

[0032] The sleeve 38 has a cylindrical shape (here, a substantially cylindrical shape having a plurality of inner diameters and a plurality of outer diameters and provided with a flange-shaped portion or the like at the rear end). As an example, the sleeve 38 is formed using a soft magnetic material such as carbon steel or free-cutting steel. A holding member 70, which will be described later, is threadedly mounted on the sleeve 38.

[0033] The joint 40 has a cylindrical shape (here, a substantially cylindrical shape having a plurality of inner diameters and a plurality of outer diameters, and having a male thread portion or the like provided on the outer cylindrical portion). As an example, the joint 40 is formed using a soft magnetic material such as carbon steel or free-cutting steel. The joint 40 is provided with a flow path 60 through which hydraulic oil flows. The flow path 60 is configured as a flow path (branch flow path) branching off from the flow path (main flow path) 20 through which hydraulic oil flows, which is pumped from the hydraulic pump 10 via the main port 28 to the operating device (in this embodiment, the lift cylinder 6 and the tilt cylinder 7).

[0034] The flow path 60 includes a first flow path 60A communicating with the main port 28 on the primary side and a second flow path 60B communicating with the tank port 29 on the secondary side. A valve seat 51 and a valve element 52 are provided along the flow path 60, specifically at the boundary between the first flow path 60A and the second flow path 60B, to open and close the flow path 60 (i.e., to switch between a connected state and a disconnected state). In this embodiment, the first flow path 60A, the second flow path 60B, and the valve seat 51 are provided in a joint internal member 40A within the joint 40. While the joint internal member 40A is formed separately from the joint 40 as an example, they may be formed integrally. Meanwhile, the valve element 52 is provided in a mover 42 (described later) of the proportional solenoid driver 30.

[0035] Next, the proportional solenoid driver 30 is disposed at the rear end of the joint 40 and includes a case 32, a coil 36 wound around a bobbin 34 while insulating a long conductor member, a stator 39 through which magnetic flux lines generated by excitation of the coil 36 pass to generate a magnetic force (attraction force), and a mover 42 that is attracted by the magnetic force (attraction force) generated in the stator 39 by excitation of the coil 36 and moves along the axial direction of the coil 36 (i.e., the direction along the axis of the central axis S of the coil 36 wound around the bobbin 34; the same applies below). Note that, by design, the central axis S of the coil 36 coincides with the central axes of the respective components (case 32, bobbin 34, sleeve 38, stator 39, joint 40, mover 42, bushing 44, biasing member 46, valve seat portion 51, valve body portion 52, and retaining member 70).

[0036] Case 32 is a tubular (here, cylindrical, but a rectangular tubular shape may also be used) member that houses coil 36, stator 39, mover 42, etc. As an example, case 32 is formed using a soft magnetic material such as carbon steel or free-cutting steel.

[0037] The bobbin 34 is a tubular (here, cylindrical) member having flange-shaped portions at the front and rear ends. As an example, the bobbin 34 is made of an insulating metal material, a resin material, or the like.

[0038] Coil 36 is an elongated, insulating conductor wound around bobbin 34 and configured to be electrically conductive or non-conductive. Coil 36 is in an excited state when energized and in a demagnetized state when non-energized. As an example, the conductor is a wire made of a copper alloy or the like and having a circular or square cross section, but a tape material, sheet material, or the like (not shown) may also be used.

[0039] The stator 39 is a member that generates a magnetic force (attraction force) by passing magnetic flux lines generated by exciting (energizing) the coil 36, and attracts the mover 42 with the attraction force. As an example, the stator 39 is made of a soft magnetic material such as carbon steel or free-cutting steel.

[0040] In the case of the pull-type electromagnetic proportional relief valve 1 shown in FIGS. 2 and 3 (enlarged views of part III in FIG. 2), the stator 39 is provided at the front end of the sleeve 38. In this embodiment, the sleeve 38 and the stator 39 are integrally formed (i.e., an integral structure formed by cutting or the like from a single material member). It should be noted that they may also be formed as separate bodies and fixed (not shown). On the other hand, in the case of the push-type electromagnetic proportional relief valve 1 shown in FIGS. 4 and 5 (enlarged views of part V in FIG. 4), the stator 39 is provided at the rear end of the joint 40. In this embodiment, the joint 40 and the stator 39 are integrally formed (i.e., an integral structure formed by cutting or the like from a single material member). It should be noted that they may also be formed as separate bodies and fixed (not shown).

[0041] The mover 42 is a component through which magnetic flux lines generated when the coil 36 is excited pass, and which moves along the axial direction of the coil 36 due to an attractive force toward the stator 39 caused by the magnetic flux lines. The mover 42 is supported movably in the axial direction by a bushing 44 on an inner cylindrical portion 41A of the cylindrical movement support portion 41. As an example, the mover 42 is formed using a soft magnetic material such as carbon steel or free-cutting steel. The bushing 44 is formed using a magnetic metal material (for example, SPCC, S20C, copper alloy, or the like, which may have a resin material coated on its surface). The thickness is not particularly limited, and the bushing 44 may be in the form of a thin sheet (film).

[0042] In the case of the pull-type electromagnetic proportional relief valve 1 shown in FIGS. 2 and 3, the moving support part 41 is provided at the rear end of the joint 40. In this embodiment, the joint 40 and the moving support part 41 are integrally formed (i.e., an integral structure formed by cutting or the like from a single material member). It should be noted that they may also be formed as separate parts and fixed (not shown). On the other hand, in the case of the push-type electromagnetic proportional relief valve 1 shown in FIGS. 4 and 5, the moving support part 41 is provided at the front end of the sleeve 38. In this embodiment, the sleeve 38 and the moving support part 41 are integrally formed (i.e., an integral structure formed by cutting or the like from a single material member). It should be noted that they may also be formed as separate parts and fixed (not shown).

[0043] In both the pull-type (FIGS. 2 and 3) and push-type (FIGS. 4 and 5) configurations, the armature 42 is formed in a cylindrical shape with a bottom having a wall 42A and a bottom 42B. The inner cylindrical portion 42C is configured as a biasing member accommodating chamber for accommodating the biasing member 46. The inner surface 42a of the armature 42, which is not facing the valve seat 51, is configured as a force-receiving portion (a portion that receives a biasing force) of the biasing member 46. The valve body 52 is integrally formed (i.e., integrally formed with the armature 42) on the outer surface 42b of the bottom 42B facing the valve seat 51. This configuration reduces the number of parts and assembly steps, thereby reducing manufacturing costs. The biasing member 46 may be directly engaged with the force-receiving portion 42a, as in this embodiment, or may be engaged with a spacer (not shown) or other device disposed between the force-receiving portion 42a and the armature 42.

[0044] As described above, the valve seat 51 is supported by the inner cylindrical portion of the joint 40, which is fitted into the inner cylindrical portion 34A of the bobbin 34. Meanwhile, the movable element 42 having the valve element 52 is slidably supported by the inner cylindrical portion 41A of the moving support member 41 via a bushing 44. Here, in the case of the pull type (FIGS. 2 and 3), the moving support member 41 is provided on the joint 40, which is fitted into the inner cylindrical portion 34A of the bobbin 34. Also, in the case of the push type (FIGS. 4 and 5), the moving support member 41 is provided on the sleeve 38, which is fitted into the inner cylindrical portion 34A of the bobbin 34. This allows the central axis of the valve seat 51 and the central axis of the valve element 52 to be aligned with high precision by using a common support member (the inner cylindrical portion 34A of the bobbin 34). Therefore, it is possible to prevent vibrations that occur during operation (opening and closing) due to slight misalignment between the respective central axes.

[0045] As a specific configuration example, it is preferable that the axial length of the bushing 44 is set to be 1.2 times or more the axial length of the valve body portion 52. With this setting, the linearity of the valve body portion 52 when it moves can be maintained with high precision, and the problem of the valve body portion 52 vibrating when it moves (i.e., when the valve opens and closes) can be prevented.

[0046] Next, as an example, a coil spring made of a non-magnetic metal material (such as a stainless steel alloy) is used as the biasing member 46. The biasing member 46 biases the valve body 52 in the axial direction toward the valve seat 51 by its resilient force (biasing force), thereby bringing the valve body 52 and the valve seat 51 into pressure contact. Note that the biasing member 46 is not limited to a coil spring, and other springs (such as an air spring) may also be used (not shown).

[0047] In this embodiment, a holding member 70 is provided that holds the biasing member 46 in the biasing member accommodating chamber 42C in a state in which the biasing member 46 is pressed by the tip end portion 70a to generate a resilient force (biasing force). That is, the biasing member 46 is sandwiched between the holding member 70 (tip end portion 70a) and the force receiving portion 42a, thereby generating a resilient force in the biasing member 46. The holding member 70 is rotatably threaded onto the inner cylindrical portion of the sleeve 38, and is disposed with the tip end portion 70a inserted inside the biasing member accommodating chamber 42C.

[0048] Therefore, the initial setting value of the relief pressure in the electromagnetic proportional relief valve 1 is set by the elastic force of the biasing member 46, and the elastic force can be adjusted by rotating the holding member 70 (specifically, by changing the amount of insertion of the tip portion 70a). This eliminates the influence of individual differences between the biasing members 46, making it possible to accurately adjust the pressure setting.

[0049] Furthermore, the biasing member 46 is held by the holding member 70 in a state where it does not protrude from the inside to the outside of the biasing member accommodating chamber 42C (i.e., in a state where it is accommodated on the bottom portion 42B side of the second end face 42d). This makes it possible to configure the axial dimension of the electromagnetic proportional relief valve 1 to be small (shortened).

[0050] The electromagnetic proportional relief valve 1 having the above configuration operates as follows. When the coil 36 is energized, the stator 39 generates an attractive force on the armature 42. Therefore, the armature 42 generates a driving force (a force that tries to move) due to the attractive force. As a result, the spring force (bias) of the biasing member 46 is changed (added or subtracted). On the other hand, when the coil 36 is deenergized, the stator 39 does not generate an attractive force on the armature 42. Therefore, the armature 42 does not generate a driving force (a force that tries to move) due to the attractive force. As a result, the spring force (bias) of the biasing member 46 is not changed. Because the configuration of this embodiment is a so-called proportional solenoid, the attractive force on the armature 42 generated by the stator 39, i.e., the driving force of the armature 42, can be changed by changing (adding or subtracting) the control current value described above, i.e., the current value that excites the coil 36 (setting the excitation intensity). (Usually, the amount of change in driving force is proportional to the current value.) As a result, it is possible to change (add or subtract) the resilient force (biasing force) of the biasing member 46, thereby changing the force that presses the valve body 52 against the valve seat 51. In other words, by changing the current value, it is possible to variably adjust the relief pressure of the hydraulic oil (to any value within the design range).

[0051] Specifically, in the case of the pull-type electromagnetic proportional relief valve 1 (FIGS. 2 and 3), when the coil 36 is energized, the attractive force of the stator 39 generates a thrust force on the armature 42 in the attractive direction (in this case, a rearward direction along the axial direction). This thrust force acts in the opposite direction to the resilient force (biasing force) of the biasing member 46. For example, as the current value of the coil 36 increases, the attractive force increases. Therefore, the thrust force of the armature 42, which acts in the opposite direction to (i.e., cancels) the resilient force (biasing force) of the biasing member 46, increases. This allows the set value of the relief pressure to be lowered. In other words, the set value of the relief pressure decreases in proportion to the current value of the coil 36. Note that when the current value is zero, the relief pressure is at an initial value set solely by the resilient force (biasing force) of the biasing member 46.

[0052] On the other hand, in the case of the push-type electromagnetic proportional relief valve 1 (FIGS. 4 and 5), when the coil 36 is energized, the attractive force of the stator 39 generates a driving force on the armature 42 in the attracting direction (in this case, a forward direction along the axial direction). This driving force acts in the same direction as the resilient force (biasing force) of the biasing member 46. For example, when the current value of the coil 36 increases, the attractive force increases. Therefore, the driving force of the armature 42, which acts in the same direction as (i.e., adds weight to) the resilient force (biasing force) of the biasing member 46, increases. This allows the set value of the relief pressure to be increased. In other words, the set value of the relief pressure increases in proportion to the current value of the coil 36. Note that when the current value is zero, the relief pressure is at an initial value set solely by the resilient force (biasing force) of the biasing member 46.

[0053] According to the proportional electromagnetic relief valve 1 of this embodiment, in both the pull type (FIGS. 2 and 3) and the push type (FIGS. 4 and 5), it is possible to prevent the occurrence of a problem in which the valve element portion 52 vibrates during operation (when the valve is opened or closed). According to research by the inventors of the present application, the reason for this is thought to be largely due to the configuration in which the valve element portion 52 is formed integrally with the moving element 42. Specifically, it is thought that this is because, compared to conventional proportional electromagnetic relief valves, the mass of the component acting as the valve element portion 52 has been drastically (significantly) increased, thereby realizing a configuration that falls within the natural frequency band in which vibration is suppressed.

[0054] As a specific configuration example, it is preferable that the movable element 42 is set so that, in a state in which a predetermined through-hole 58 (described later) is formed, the mass of the movable element 42 excluding the valve element portion 52 is 30 times or more (more preferably 50 times or more) the mass of the valve element portion 52. Research by the inventors of the present application has verified that the above setting is effective in preventing the occurrence of problems such as vibration of the valve element portion 52.

[0055] As a configuration example applicable to both the pull type (FIGS. 2 and 3) and the push type (FIGS. 4 and 5), the mover 42 is preferably configured to have a plurality of (four, as one example) through holes 58 (first through holes 58A) provided at equal intervals in the circumferential direction, which allow hydraulic oil to flow by communicating between the inner surface 42a and the outer surface 42b of the bottom portion 42B. The mover 42 is preferably configured to have a plurality of (four, as one example) through holes 58 (second through holes 58B) provided at equal intervals in the circumferential direction, which allow hydraulic oil to flow by communicating between the end face (first end face) 42c of the wall portion 42A facing the valve seat portion 51 and the end face (second end face) 42d of the wall portion 42A not facing the valve seat portion 51. Specifically, the through holes 58 may be configured to include both first through holes 58A and second through holes 58B as shown in Figures 3 and 6 (side views of the mover 42 shown in Figure 3), or one of the through holes (second through hole 58B) may be omitted as shown in Figures 5 and 7 (side views of the mover 42 shown in Figure 5). Although not shown, the first through hole 58A may also be omitted. Note that the set numbers of first through holes 58A and second through holes 58B are not limited to those described above.

[0056] This configuration can prevent the occurrence of a pressure difference between the front and rear of the movable member 42 (i.e., the difference between the pressure of the hydraulic oil acting on the front surface (the surface having the outer surface 42b of the bottom portion 42B and the end surface 42c of the wall portion 42A) and the pressure of the hydraulic oil acting on the rear surface (the surface having the inner surface 42a of the bottom portion 42B and the end surface 42d of the wall portion 42A). Therefore, it is possible to prevent the operation from becoming unstable due to the pressure difference, and it is possible to control the relief pressure extremely accurately. Note that, as a modified example, a configuration (see FIG. 8) in which a communication groove 59 is provided in the outer peripheral surface of the movable member 42 so as to communicate in the front-rear direction (specifically, so as to communicate the first end surface 42c and the second end surface 42d) instead of (or in addition to) the configuration having the through hole 58 described above can also achieve the same effect.

[0057] As described above, the disclosed electromagnetic proportional relief valve can prevent vibration during operation and achieve stable pressure control without fluctuation, i.e., it is possible to control the relief pressure of a liquid such as hydraulic oil with high precision. Furthermore, it is possible to reduce the size, weight, and structure of the valve.

[0058] In particular, the present invention has been described with reference to a hydraulic circuit for driving a working device in a work vehicle as an example of an object into which the electromagnetic proportional relief valve is to be incorporated, but the present invention is not limited to this. [Explanation of symbols]

[0059] 1. Proportional relief valve 30 Proportional solenoid driver 38 Sleeve 39 Stator 40 joints 42 Mover 46 biasing member 51 Valve seat 52 Valve body 60 flow paths

Claims

1. An electromagnetic proportional relief valve having a valve body and a valve seat that move toward and away from each other in a flow path through which a liquid of a predetermined pressure flows, and which functions to release the pressure by moving the valve body away from the valve seat when the pressure of the liquid in the flow path exceeds a set value, and which variably adjusts the set value, a joint having the flow passage disposed therein; a coil wound in a manner that allows current to flow; a mover supported so as to be movable along the axial direction of the coil; a stator that generates an attractive force on the mover by exciting the coil, the movable element is formed in a cylindrical shape with a bottom, having a wall portion and a bottom portion, the inner cylindrical portion being configured as a biasing member accommodating chamber in which a biasing member is accommodated in a state in which a resilient force is generated, the inner surface of the bottom portion on the side not facing the valve seat portion being configured as a force receiving portion of the biasing member, and the valve body portion is integrally formed on the outer surface of the bottom portion on the side facing the valve seat portion, the movable member is formed such that the valve body portion protrudes from the outer surface of the bottom portion toward the valve seat portion, and the mass of the movable member excluding the valve body portion is set to be 30 times or more the mass of the valve body portion, the movable element has a through-hole that communicates the inner surface and the outer surface of the bottom portion and allows the liquid to flow through; The through holes are provided in a plurality at adjacent positions on the valve body at equal intervals in the circumferential direction. An electromagnetic proportional relief valve characterized by:

2. The through hole is provided at a position where an extension line of the outer peripheral surface of the conical portion of the valve body intersects with the outer surface of the bottom portion in a cross section parallel to the axial direction.

2. The electromagnetic proportional relief valve according to claim 1,

3. a cylindrical bobbin around which the coil is wound, the valve seat is supported by an inner cylindrical portion of a joint fitted into the inner cylindrical portion of the bobbin, The movable element having the valve body portion is slidably supported via a bushing in the inner cylindrical portion of a joint or a moving support portion provided on a sleeve fitted into the inner cylindrical portion of the bobbin.

3. The electromagnetic proportional relief valve according to claim 1 or 2, wherein:

4. The axial length of the bush is set to be 1.2 times or more the axial length of the valve body portion.

4. The electromagnetic proportional relief valve according to claim 3, wherein:

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