direction switching valve

Abstract

Provided is a directional control valve capable of setting the pressure and flow rate of fluid controlled by a spool to be large and capable of performing stable control while preventing unstable operation of the spool. The directional control valve (1) of the present invention includes: a housing (10) having a cylindrical spool hole (20) that communicates with an inflow port (16) through which fluid flows in from an external supply source (2) and an outflow port (18A, 18B) through which fluid flows out to a working cylinder (4); a spool (22) that moves within the spool hole to vary the outflow amount of fluid; a first solenoid driving portion (30A) having a first movable element (22A) provided at a first end portion (22a) of the spool to drive the spool; and a second solenoid driving portion (30B) having a second movable element (22B) provided at a second end portion (22b) of the spool to drive the spool, and a pressure equalization circuit that applies pressure equally to both the first end portion side and the second end portion side of the spool is provided.

Description

Technical Field

[0001] This invention relates to a directional switching valve. Background Technology

[0002] Forklifts, construction machinery, and other similar work vehicles are equipped with forks, buckets, and other work devices driven by pressurized fluid (hereinafter sometimes simply referred to as "fluid"). In order to control the drive of such work devices, directional valves that switch the direction of fluid flow and stop it have traditionally been used.

[0003] In particular, in work vehicles equipped with work devices that generate large outputs, the pressure and flow rate of the fluid controlled by the directional switching valve are set to be relatively high. A pilot-operated switching valve with an electromagnetic proportional pressure reducing valve has been developed to suit the control of such fluids.

[0004] As an example, the pilot-operated switching valve disclosed in Patent Document 1 (Japanese Patent Application Publication No. 2004-232764) is configured to include a pressure reducing valve that generates pilot pressure, a proportional solenoid that controls the pressure reducing valve, and a spool that is driven (moved) according to the pilot pressure.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-232764 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] According to Patent Document 1, the pilot-operated switching valve equipped with an electromagnetic proportional pressure reducing valve can set the pressure and flow rate of the fluid controlled by the spool valve to be large, making it suitable for achieving high output of the operating device. However, on the other hand, in order to include an electromagnetic proportional pressure reducing valve, the size increases, the weight increases, and the structure becomes more complex. Moreover, a pilot pressure (standby pressure) for driving the spool valve needs to be generated at all times, thus deteriorating the fuel efficiency (including electrical efficiency) performance of the vehicle. Therefore, it is a problem to realize a switching valve that can set the pressure and flow rate of the fluid controlled by the spool valve to be large without relying on a large size.

[0010] For example, it is conceivable that if the electromagnetic proportional pressure reducing valve is simply omitted and a configuration is adopted in which the slide valve is directly driven (moved) by a solenoid drive unit, a smaller, lighter, and simpler structure can be achieved without increasing the size of the valve. However, on the other hand, the inventors of this application have discovered through research that in a direct-drive configuration, the greater the pressure and flow rate of the fluid to be controlled, the less the slide valve will act according to the control command, resulting in unstable fluid control.

[0011] Solution for solving the problem

[0012] The present invention was made in view of the above circumstances, and its object is to provide a directional switching valve that, in a configuration in which the slide valve is directly driven by a solenoid drive unit, allows for setting a large pressure and flow rate of the fluid controlled by the slide valve, and prevents unstable operation of the slide valve to achieve stable fluid control.

[0013] As one implementation method, the above-mentioned problems are solved by the following disclosed solution.

[0014] The disclosed directional switching valve comprises: a housing having a cylindrical spool valve orifice communicating with an inlet port for fluid supplied from an external source at a predetermined pressure and an outlet port for the fluid to flow out to a working cylinder that drives an external working device; a spool valve configured to move in the axial direction within the spool valve orifice to vary the outflow rate of the fluid; a first solenoid drive unit having a first movable element connected to or integrally formed with a first end of the spool valve to drive the spool valve; and a second solenoid drive unit having a second movable element connected to or integrally formed with a second end of the spool valve to drive the spool valve. The directional switching valve is characterized by having a pressure equalization circuit that applies pressure equally to both the first end side and the second end side of the spool valve.

[0015] Furthermore, the housing is characterized in that it has a first discharge flow path and a second discharge flow path, wherein the fluid discharged by the movement of the piston in the working cylinder flows to either the first discharge flow path or the second discharge flow path according to the direction of piston movement. As a pressure homogenization circuit, a connecting flow path connecting the first discharge flow path and the second discharge flow path is provided in one or both of the housing and the outlet connected to the housing in a stacked state, and a first pressure homogenization circuit is connected to the connecting flow path. The valve has a first pressure homogenization chamber and a second pressure homogenization chamber. The first pressure homogenization chamber is disposed on the first end side of the valve and communicates with the first pressure homogenization flow path to apply the pressure of the fluid in the connecting flow path to the first end side of the valve. The second pressure homogenization chamber is disposed on the second end side of the valve and communicates with the second pressure homogenization flow path to apply the pressure of the fluid in the connecting flow path to the second end side of the valve.

[0016] In addition, the first pressure homogenization chamber and the second pressure homogenization chamber are characterized in that the circumferential grooves provided through the inner circumferential surface of the valve hole are shaped to correspond to the circumferential protrusions provided on the outer circumferential surface of the core used in the casting process of forming the valve hole.

[0017] In addition, the housing is characterized by having: a first stacking flow path that communicates with the first pressure homogenization chamber and a first stacking opening formed on the side of the housing opposite to the side where the opening of the end portion of the first pressure homogenization flow path is provided; and a second stacking flow path that communicates with the second pressure homogenization chamber and a second stacking opening formed on the side of the housing opposite to the side where the opening of the end portion of the second pressure homogenization flow path is provided.

[0018] In addition, the fluid supplied from the external source is characterized by having a maximum pressure of 10 MPa or more and a maximum flow rate of 60 liters / min or more.

[0019] Invention Effects

[0020] According to the disclosed directional switching valve, in a configuration where the spool valve is directly driven by a solenoid drive unit, the pressure and flow rate of the fluid controlled by the spool valve can be set to be large. Furthermore, when driving the spool valve, stable fluid control can be achieved by preventing unstable spool valve operation. Attached Figure Description

[0021] Figure 1This is a front view illustrating an example of a directional switching valve according to an embodiment of the present invention.

[0022] Figure 2 yes Figure 1 Sectional view of line II-II.

[0023] Figure 3 yes Figure 2 Enlarged view of Part III.

[0024] Figure 4 It is shown Figure 1 A perspective view of an example housing of a directional switching valve.

[0025] Figure 5 yes Figure 4 Enlarged cross-sectional view of the V section.

[0026] Figure 6 This is a front view illustrating another example of a directional switching valve according to an embodiment of the present invention. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 This is a front view (or schematic view) showing an example of the direction switching valve 1 of this embodiment. Additionally, Figure 2 yes Figure 1 The diagram shows the cross-sectional view of line II-II, but additional peripheral equipment and circuits have been included for illustrative purposes. Furthermore, Figure 3 yes Figure 2 A magnified view of Part III. Additionally... Figure 4 This is a perspective view (sketching) of the casing 10. Figure 5 yes Figure 4 Enlarged cross-sectional view of the V section (and) Figure 4 (Perspective view from the same angle). Furthermore, in all the accompanying drawings used to illustrate the embodiments, components having the same function are labeled with the same reference numerals, and sometimes repeated descriptions are omitted.

[0028] In this embodiment, the direction switching valve 1 controls the operation of the working cylinder of the external working device (for example, the working device of a working vehicle), that is, switches or stops the flow direction of the fluid used to operate the working cylinder.

[0029] First, in order to solve the above-mentioned problems, the inventors of this application studied a directional switching valve as a comparative example, which employs a direct-acting switching valve, that is, a switching valve having a solenoid drive unit that directly moves the spool valve. This is because, with this configuration, the pressure reducing valve and its control proportional solenoid can be omitted, thus achieving miniaturization, weight reduction, and structural simplification. Furthermore, fuel efficiency performance can be improved by reducing the pilot pressure (standby pressure) used to drive the spool valve.

[0030] The results of research through trial production and experiments yielded the following insights: Direct-acting switching valves can stably move the spool valve under relatively low fluid pressure and flow rates (the so-called low-flow and medium-flow conditions refer to a maximum fluid pressure below 10 MPa and a maximum flow rate below 50 L / min). However, under relatively high fluid pressure and flow rates (the so-called high-flow conditions refer to a maximum fluid pressure above 10 MPa and a maximum flow rate above 60 L / min), the instability of the spool valve's movement becomes apparent.

[0031] Further research revealed that the aforementioned problem stems from the fact that, in the case of a direct-acting switching valve, the solenoid drive unit directly drives (moves) the spool valve. Therefore, compared to conventional electromagnetic proportional pressure reducing valves, the driving force generated is significantly smaller. Specifically, it was found that the smaller the force driving the spool valve, the more significant the influence of the fluid pressure flowing through the spool valve orifice, controlled by the spool valve, as a force driving the spool valve. Even extremely low pressures, such as the pressure of the fluid discharged from the working cylinder (for example, a low pressure around 0.1 MPa), cannot be ignored as a force driving the spool valve. As a result, the spool valve's operation becomes unstable (specifically, phenomena such as inaccurate execution of actions following control signals occur), which is the cause of unstable fluid control.

[0032] As a solution to this problem, increasing the size of the solenoid drive unit (for example, setting it to a diameter of 80 mm or more) to increase the thrust of the movable element would allow the effect of the pressure of the fluid discharged from the working cylinder as a force to move the spool valve to be ignored. However, this would result in a larger overall size.

[0033] Therefore, the directional switching valve 1 of this embodiment can solve the complex problems described above by having the following configuration.

[0034] First, the overall structure of the directional switching valve 1 in this embodiment will be explained. For example... Figure 1 , Figure 2 As shown, the directional switching valve 1 is located between the main hydraulic pump 2, which supplies fluid (in this case, pressurized oil) at a specified pressure, and the working cylinder 4, which operates the forks, bucket, and other working devices. It controls the flow path and flow rate of the fluid supplied to / discharged from the working cylinder 4. This allows the setting of the working direction, workload, and working speed of the working device.

[0035] The direction switching valve 1 includes a housing 10 and solenoid drive units 30 disposed on the left and right sides of the housing 10 (hereinafter, the configuration of the housing 10 and the solenoid drive unit 30 is sometimes referred to as the "main body 100"). Furthermore, in this embodiment, it includes a side connected to the housing 10 in a stacked state (for convenience, according to...). Figure 1 The configuration is described as the "upper surface" (the inlet 102) and the other side of the housing 10 is connected in a stacked state (for convenience, according to...). Figure 1 The outlet 104 (described as the "lower surface") is provided at the inlet 102. As an example, an inlet port 16 is provided at the inlet 102 for fluid supplied from an external source (main hydraulic pump) 2 to flow in. Additionally, outlet ports 18A and 18B are provided on the main body 100 (here, the housing 10) for fluid to flow out to the working cylinder 4. Furthermore, these outlet ports 18A and 18B also serve as ports for fluid discharged from the working cylinder 4 to flow in. Additionally, a tank port 19 is provided at the outlet 104 for fluid discharged from the working cylinder 4 to flow into the tank 3. However, this configuration is not limited to this; a configuration without an inlet and outlet, where the inlet port and tank port are directly provided on the housing 10 (not shown), is also possible.

[0036] In this embodiment, the housing 10 is provided with a slide valve hole 20, which serves as a cylindrical space communicating with the inlet port 16, the outlet ports 18A and 18B, and the tank port 19. Furthermore, a slide valve 22 is housed within the slide valve hole 20. The slide valve 22 is configured to move in the axial direction, thereby changing or stopping the flow rate of the fluid. As an example, both the slide valve 22 and the slide valve hole 20 are formed with a circular cross-sectional shape, and the slide valve hole 20 extends from one side of the housing 10 to the other side.

[0037] Furthermore, the solenoid drive unit 30 is a component that drives (moves) the slide valve 22. In this embodiment, two solenoid drive units (specifically, the first solenoid drive unit 30A and the second solenoid drive unit 30B) are symmetrically arranged on both sides of the housing 10. As an example, when the operator operates the operating lever 5, the corresponding drive signal is sent to the corresponding solenoid drive unit 30 via the control unit 6. The solenoid drive unit 30 drives the movable element to move, thereby actuating (moving) the slide valve 22 (details of the working principle will be described later).

[0038] Additionally, the housing 10 is provided with a supply flow path 11 communicating with the inlet port 16, a first working flow path 12A and a second working flow path 12B communicating with the outlet ports 18A and 18B respectively, and a first discharge flow path 13A and a second discharge flow path 13B communicating with the tank port 19. These flow paths are configured to communicate with the slide valve orifice 20. As an example, the supply flow path 11 is positioned between the first working flow path 12A and the second working flow path 12B. The first working flow path 12A is positioned between the supply flow path 11 and the first discharge flow path 13A. The second working flow path 12B is positioned between the supply flow path 11 and the second discharge flow path 13B.

[0039] Here, supply flow path 11 is a flow path connected to the main hydraulic pump 2 via inlet port 16 and used to supply fluid at a specified pressure (for example, a high pressure of 20 MPa) delivered from the main hydraulic pump 2. Additionally, the first working flow path 12A and the second working flow path 12B are flow paths connected to the working cylinder 4 via outlet ports 18A and 18B respectively, used to supply fluid at a specified pressure (for example, a high pressure of 20 MPa) to the working cylinder 4 and to return fluid at a specified pressure (for example, a low pressure of 2 MPa) discharged from the working cylinder 4. Furthermore, the first discharge flow path 13A and the second discharge flow path 13B are flow paths connected to the tank 3 via tank port 19 and used to discharge fluid at a specified pressure (for example, a low pressure of 0.1 MPa) flowing from the working cylinder 4 to the tank 3.

[0040] Furthermore, in this embodiment, the circuit configuration controlled by the slide valve orifice 20 and the slide valve 22 results in a configuration where the fluid discharged by the movement of the piston 4a in the working cylinder 4 is sent to either the first working flow path 12A or the second working flow path 12B according to the direction of movement of the piston 4a (for example, when the piston 4a moves towards...). Figure 2 When the piston moves upward, fluid is discharged from the working cylinder 4 to the first working flow path 12A; conversely, when the piston 4a moves upward... Figure 2 When the fluid moves downwards, it is discharged from the working cylinder 4 to the second working flow path 12B. Furthermore, the fluid supplied to the first working flow path 12A flows only to the first discharge flow path 13A (meaning it does not include the second discharge flow path 13B). Conversely, the fluid supplied to the second working flow path 12B flows only to the second discharge flow path 13B (meaning it does not include the first discharge flow path 13A).

[0041] Secondly, the slide valve 22 is formed with a circular cross-section, is housed in the slide valve hole 20 of the housing 10, and can move in the axial direction (more specifically, can slide with a specified fitting tolerance).

[0042] Although not specifically illustrated, the outer peripheral surface of the slide valve 22 is provided with a cut that connects the supply flow path 11 with the first working flow path 12A and the second working flow path 12B, a cut that connects the first working flow path 12A with the first discharge flow path 13A, and a cut that connects the second working flow path 12B with the second discharge flow path 13B.

[0043] In addition, sealing members 14 (for example, O-rings made of rubber, elastomers, etc.) are provided at the required locations.

[0044] Secondly, at both ends of the slide valve 22, solenoid drive units 30 (first solenoid drive unit 30A and second solenoid drive unit 30B) are respectively provided to move the slide valve 22. The basic structure of the two solenoid drive units 30A and 30B is the same, so only one solenoid drive unit 30A is mentioned as an example ( Figure 2 The following will be explained in detail using Part III as an example. Furthermore, in this embodiment, the solenoid drive unit 30 will be described using a so-called "pull-type proportional solenoid" configuration as an example. However, "push-type" and "push-pull-type" configurations (not shown) can also be used. Moreover, in cases where it is sufficient to switch directions only and not adjust the flow rate, an "on-off solenoid" configuration (not shown) can be used instead of a "proportional solenoid".

[0045] like Figure 2 , Figure 3 As shown, the solenoid drive unit 30A of this embodiment includes, inside the housing 32: a coil 36, which is formed by insulating a long conductor member and winding it around a coil frame 34; a fixed iron core 38 through which magnetic flux lines generated by the excitation of the coil 36 pass; and a movable element 22A (first movable element), which allows the magnetic flux lines generated by the excitation of the coil 36 to pass through and move along the axial direction of the coil 36 (i.e., along the direction of the central axis of the coil 36 wound around the coil frame 34, hereinafter the same) by the attraction force generated by the magnetic flux lines. Furthermore, the movable element 22A of this embodiment is integrally formed with the slide valve 22 (formed as an integral structure machined from a single component). However, it is not limited to this; it may also be separately formed and connected to the first end 22a (the end on the solenoid drive unit 30A side) of the slide valve 22 (not shown).

[0046] The housing 32 is a cylindrical (here, cylindrical, but square) component that houses the coil 36, the fixed iron core 38, and the movable element 22A. As an example, it is formed using a soft magnetic material such as carbon steel or free-cutting steel. The housing 32 is fixed to the side of the housing 10 using bolts or the like (not shown).

[0047] The coil 36 is formed by winding an insulated strip of conductor member onto the coil frame 34. This conductor member is, for example, a wire made of copper alloy or the like with a cross-section shaped like a circle or square, but it can also be made of strip, sheet, or the like (not shown).

[0048] The fixed core 38 is a component that attracts the movable element 22A through magnetic flux lines generated by the excitation of the coil 36. For example, it is formed using a soft magnetic material such as carbon steel or free-cutting steel. In this embodiment, the fixed core 38 includes a base and a stator 38C arranged spaced apart from each other in the axial direction of the coil 36. The base includes a first base 38A with a radially extending flange at a first end 38a and a second base 38B embedded within the first base 38A; both the first base 38A and the second base 38B are cylindrical. The stator 38C is cylindrical and formed with a radially extending flange at a first end 38c.

[0049] In this embodiment, the first base 38A has a conical surface 38d at its second end 38b, the diameter of which expands toward the first end 38a. This allows for an increase in the magnetic flux density at the second end 38b and an attempt to maintain a constant attractive force regardless of the position of the movable element 22A.

[0050] Furthermore, inside the second base 38B, there is a transmission member (pin) 40 supported by a bushing 44 and movable in the axial direction, and a force-applying member 42 that applies force to the transmission member 40 toward the movable element 22A. As an example, both the transmission member 40 and the bushing 44 are made of non-magnetic materials (stainless steel alloy, resin material, etc.). In addition, the force-applying member 42 is, for example, a so-called return spring composed of a coil spring, which applies a force that moves the movable element 22A in the opposite direction to the direction in which the movable element 22A is attracted by the fixed iron core 38 when the coil 36 is energized.

[0051] The movable element 22A is a component through which the magnetic flux generated when the coil 36 is energized passes and moves along the axial direction of the coil 36 by means of the attractive force toward the fixed iron core 38 caused by the magnetic flux. As an example, it is formed using a soft magnetic material such as carbon steel or free-cutting steel.

[0052] According to the above configuration, by energizing the coil 36 of the solenoid drive unit 30A in this embodiment, a force is generated that attracts the movable element 22A from the fixed iron core 38, causing the movable element 22A to move in a predetermined direction (in this case, from the second end 38b of the first base 38A to the first end 38a). Furthermore, by demagnetizing the coil 36, the force attracting the movable element 22A from the fixed iron core 38 disappears, and the force exerted by the force-applying member 42 causes the movable element 22A to move in the direction of returning to the neutral position. In this embodiment, the force exerted by the force-applying member 42 is transmitted to the movable element 22A via the transmission member 40.

[0053] Furthermore, the solenoid drive unit 30A in this embodiment is a "proportional solenoid," thus generating a magnetic field of strength corresponding to the operating amount of the operating lever 5 (i.e., an attractive force on the movable element 22A). Therefore, the movable element 22A will move to a position where the attractive force and the force applied by the force-applying member 42 are balanced and stop. That is, the movement amount of the slide valve 22 is set according to the operator's operation, thereby setting the flow rate of the fluid in the direction switching valve 1 and controlling the working speed of the working cylinder 4.

[0054] On the other hand, regarding the solenoid drive section 30B equipped with the movable element 22B (the second movable element), since it has the same configuration as the solenoid drive section 30A equipped with the aforementioned movable element 22A (the first movable element), a repeated description is omitted. Furthermore, the movable element 22B, like the movable element 22A, is integrally formed with the slide valve 22. However, as a variation, it may be configured to connect to the second end 22b (the end on the solenoid drive section 30B side) of the slide valve 22 (not shown).

[0055] As mentioned above, the directional switching valve 1 in this embodiment is a direct-acting switching valve. Therefore, the driving force that can be generated is significantly smaller than that of conventional electromagnetic proportional pressure reducing valves, which may cause the spool valve 22 to operate unstably and the fluid control to become unstable.

[0056] To address this issue, the directional switching valve 1 of this embodiment is provided with a pressure equalization circuit that applies the same pressure (i.e., applies pressure equally) to the first end 22a side and the second end 22b side of the slide valve 22.

[0057] In this embodiment, the pressure homogenization circuit has the following configuration. Specifically, a connecting flow path 15 connecting the first discharge flow path 13A and the second discharge flow path 13B is provided in the outlet 104. Furthermore, a first pressure homogenization flow path 23A and a second pressure homogenization flow path 23B communicating with the connecting flow path 15 are continuously provided on both the outlet 104 and the housing 10. Moreover, a first pressure homogenization chamber 24A (see reference) is provided in the housing 10 (slide valve hole 20), disposed on the first end 22a side of the slide valve 22 and communicating with the first pressure homogenization flow path 23A. Figure 4 (etc.). The first pressure homogenizing chamber 24A serves to deliver fluid from the connecting flow path 15 to the first end 22a side of the slide valve 22. Therefore, the pressure of the fluid in the connecting flow path is applied to the first end 22a side of the slide valve 22 (i.e., applied to the slide valve 22 in the direction from the first end 22a to the second end 22b). Similarly, a second pressure homogenizing chamber 24B is provided on the second end 22b side of the slide valve 22 and communicates with the second pressure homogenizing flow path 23B (is connected to the second pressure homogenizing flow path 23B). Figure 4 The second pressure homogenizing chamber 24B is configured symmetrically with the first pressure homogenizing chamber 24A shown in the figure. This second pressure homogenizing chamber 24B serves to deliver fluid from the connecting flow path 15 to the second end 22b side of the slide valve 22. Therefore, the pressure of the fluid in the connecting flow path 15 is applied to the second end 22b side of the slide valve 22 (i.e., applied to the slide valve 22 in the direction from the second end 22b to the first end 22a). Furthermore, as an example, the first pressure homogenizing flow path 23A is provided as a separate, independent flow path within the housing 10 that is not directly connected to the first discharge flow path 13A, and the second pressure homogenizing flow path 23B is also provided as a separate, independent flow path within the housing 10 that is not directly connected to the second discharge flow path 13B. Furthermore, the first pressure homogenization flow path 23A and the second pressure homogenization flow path 23B have substantially the same structure (a structure that is linearly symmetrical within the housing 10 with reference to the axial center position of the slide valve orifice 20), and the first pressure homogenization chamber 24A and the second pressure homogenization chamber 24B have substantially the same structure (a structure that is linearly symmetrical within the housing 10 with reference to the axial center position of the slide valve orifice 20). However, this configuration is not the only limitation.

[0058] According to the above configuration, pressure can be applied equally to both the first end 22a and the second end 22b of the slide valve 22. More specifically, the fluid discharged from the working cylinder 4 controlled by the slide valve 22 acts as a force to move the slide valve 22 (in the direction from the first end 22a to the second end 22b) when it flows from the first working flow path 12A through the slide valve hole 20 to the first discharge flow path 13A. Similarly, the fluid discharged from the working cylinder 4 controlled by the slide valve 22 acts as a force to move the slide valve 22 (in the direction from the second end 22b to the first end 22a) when it flows from the second working flow path 12B through the slide valve hole 20 to the second discharge flow path 13B. At any given time, this fluid can simultaneously apply the pressure generated by the fluid in the connecting flow path 15 to both the first end 22a and the second end 22b of the slide valve 22. Here, the pressure is the same as the pressure of the fluid flowing into the connecting flow path 15 from the first discharge flow path 13A and the second discharge flow path 13B (for example, a low pressure of about 0.1 MPa) (containing negligible minor differences).

[0059] Therefore, the effect of the fluid flowing through the valve orifice 20 as a force that moves the valve 22 can be eliminated or reduced to a negligible level, thus preventing unstable operation of the valve 22 and stabilizing fluid control.

[0060] As a result, even when the fluid pressure and flow rate are set to a large level (assuming the maximum fluid pressure is above 10 MPa and the maximum flow rate is around 60 to 160 liters / min), the configuration that allows the slide valve 22 to move directly and stably can be achieved without relying on a solution that enlarges the solenoid drive unit 30.

[0061] Furthermore, as a variation of the pressure homogenization circuit, configurations such as continuously providing the connecting flow path 15 on both the outlet 104 and the housing 10, or providing the connecting flow path 15, the first pressure homogenization flow path 23A, and the second pressure homogenization flow path 23B on the housing 10 (not shown) are also possible.

[0062] Furthermore, as a characteristic feature of the directional switching valve 1 in this embodiment, the first pressure homogenization chamber 24A and the second pressure homogenization chamber 24B have circumferential grooves that penetrate the inner circumferential surface of the slide valve hole 20, corresponding to the circumferential protrusions that protrude from the outer circumferential surface of the core (not shown) used in the casting process of forming the slide valve hole 20.

[0063] Accordingly, when the slide valve orifice 20 is formed by casting, the first pressure homogenization chamber 24A and the second pressure homogenization chamber 24B can be formed simultaneously. That is, no other machining (cutting) is required to form them, thus reducing machining time and cycle time.

[0064] Furthermore, the housing 10 includes: a first stacking flow path 27A, which communicates with the first pressure homogenization chamber 24A and a first stacking opening 26A formed by opening a surface on the side of the housing 10 opposite to the surface where the opening (first opening 25A) that serves as the end of the first pressure homogenization flow path 23A is provided; and a second stacking flow path 27B, which communicates with the second pressure homogenization chamber 24B and a second stacking opening 26B formed by opening a surface on the side of the housing 10 opposite to the surface where the opening (second opening 25B) that serves as the end of the second pressure homogenization flow path 23B is provided. In this case, when viewed from above, it is more preferable that the first opening 25A and the first stacking opening 26A are located in the same position, and the second opening 25B and the second stacking opening 26B are located in the same position.

[0065] Accordingly, Figure 6 As shown in another embodiment, a configuration in which multiple main body sections 100 are stacked between the inlet 102 and the outlet 104 can be achieved. Therefore, a direction switching valve 1 can be easily constructed where the number of stacked main body sections 100 is increased or decreased depending on the number of working cylinders 4 that are being controlled. Furthermore, Figure 6 The configuration shown is an example of having two layers, 100A and 100B, but it is not limited to two layers. It can also be configured with three or more layers depending on the number of working cylinders 4 (not shown).

[0066] Furthermore, the first opening 25A, the first pressure homogenizing flow path 23A (a component within the housing 10), the first stacking flow path 27A, and the first stacking opening 26A can be formed simultaneously in a single drilling operation. Similarly, the second opening 25B, the second pressure homogenizing flow path 23B (a component within the housing 10), the second stacking flow path 27B, and the second stacking opening 26B can be formed simultaneously in a single drilling operation. Therefore, it is possible to reduce machining time and shorten cycle time.

[0067] As explained above, according to the disclosed directional switching valve, in a configuration where the spool valve is directly driven by a solenoid drive unit, the pressure and flow rate of the fluid controlled by the spool valve can be set to a large value without relying on enlarging the solenoid drive unit. Furthermore, stable fluid control can be achieved by preventing unstable spool valve operation during actuation.

[0068] Furthermore, by implementing a configuration without an electromagnetic proportional pressure reducing valve, it not only becomes a small, lightweight, and simple configuration, but also eliminates the need for standby pressure for control, thereby improving the fuel efficiency (including electrical efficiency) performance of the vehicle.

[0069] Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the present invention.

Claims

1. A directional switching valve comprising: a housing having a cylindrical spool valve orifice communicating with an inlet port for allowing fluid supplied from an external source at a predetermined pressure to flow in and an outlet port for allowing the fluid to flow out to a working cylinder driving an external operating device; a spool valve configured to move axially within the spool valve orifice to vary the outflow rate of the fluid; a first solenoid drive unit having a first movable element connected to or integrally formed with a first end of the spool valve to drive the spool valve; and a second solenoid drive unit having a second movable element connected to or integrally formed with a second end of the spool valve to drive the spool valve, characterized in that... A pressure equalization circuit is provided to apply pressure equally to the first end side and the second end side of the slide valve. The aforementioned housing has a first discharge flow path and a second discharge flow path, wherein the fluid discharged by the movement of the piston in the aforementioned working cylinder flows to either the first discharge flow path or the second discharge flow path according to the direction of piston movement. As the aforementioned pressure homogenization circuit, a connecting flow path is provided in one or both of the housing and the outlet connected to the housing in a stacked state, connecting the first discharge flow path and the second discharge flow path, and a first pressure homogenization flow path and a second pressure homogenization flow path communicating with the connecting flow path. Furthermore, a first pressure homogenization chamber and a second pressure homogenization chamber are provided in the slide valve orifice. The first pressure homogenization chamber is disposed on the first end side of the slide valve and communicates with the first pressure homogenization flow path, applying the pressure of the fluid in the connecting flow path to the first end side of the slide valve. The second pressure homogenization chamber is disposed on the second end side of the slide valve and communicates with the second pressure homogenization flow path, applying the pressure of the fluid in the connecting flow path to the second end side of the slide valve. The aforementioned housing has: a first stacking flow path that communicates with the aforementioned first pressure homogenization chamber and a first stacking opening formed on the side of the housing opposite to the side where the opening of the end portion of the first pressure homogenization flow path is provided; and a second stacking flow path that communicates with the aforementioned second pressure homogenization chamber and a second stacking opening formed on the side of the housing opposite to the side where the opening of the end portion of the second pressure homogenization flow path is provided.

2. The directional switching valve according to claim 1, characterized in that, The first pressure homogenization chamber and the second pressure homogenization chamber have circumferential grooves that penetrate the inner circumferential surface of the valve hole, corresponding to the circumferential protrusions that protrude from the outer circumferential surface of the core used in the casting process of forming the valve hole.

3. The directional switching valve according to claim 1 or 2, characterized in that, The fluid supplied from the aforementioned external source is configured to have a maximum pressure of 10 MPa or higher and a maximum flow rate of 60 liters / min or higher.

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