Valve device

Abstract

A housing (42) is provided with a main spool hole (50), a pump passage (53), cylinder passages (55, 56), and an accumulator passage (54). The pump passage (53) and one cylinder passage (55) are provided at positions facing each other across the accumulator passage (54) in the direction in which a main spool (62) moves through the main spool hole (50). In addition, the main spool (62) is provided with a first land (62A) that blocks between the accumulator passage (54) and the one cylinder passage (55) when the main spool (62) is at a first position, and blocks between the pump passage (53) and the accumulator passage (54) when the main spool (62) is at a second position.

Description

Valve device

[0001] The present disclosure relates to, for example, a valve device incorporated in a hydraulic circuit of a vehicle (work vehicle) such as a wheel loader or a wheel excavator.

[0002] Work vehicles such as wheel loaders often travel with excavated material loaded in a bucket. However, when material is loaded in the bucket, the overall weight of the vehicle increases. Therefore, vibration generated during traveling of the vehicle causes pitching of the front working implement, which may result in spillage of the load in the bucket or deterioration of the ride comfort of the vehicle. Accordingly, some work vehicles are provided with a function (ride control function) for suppressing pitching of the front working implement during loaded traveling.

[0003] More specifically, a work vehicle includes a traveling vibration suppression device that suppresses pitching of a front working implement during loaded traveling. The traveling vibration suppression device connects a bottom chamber of a hydraulic cylinder, to which pressure oil is supplied when raising the front working implement, to an accumulator. That is, in order to suppress swinging of the bucket during traveling of the vehicle, the accumulator, which has accumulated pressure during work, is connected to the hydraulic cylinder, thereby absorbing vibration.

[0004] Here, for example, Patent Document 1 describes a hydraulic control device in which an operating valve is used to enable connection between the bottom chamber of a hydraulic cylinder, the oil chamber of the accumulator, the hydraulic pump, and the tank. The hydraulic control device of Patent Document 1 communicates and blocks the operating valve to supply pressure oil from the hydraulic pump to the hydraulic cylinder, thereby raising or lowering the working device (front working implement). In addition, when the vehicle is traveling, in order to suppress swinging of the bucket, the opening / closing valve is communicated to connect the accumulator and the bottom chamber of the hydraulic cylinder, thereby absorbing vibration.

[0005] In the case of the hydraulic control device described in Patent Document 1, if the on-off valve is opened when the differential pressure between the hydraulic cylinder and the accumulator is large, the flow of oil from one to the other due to the differential pressure may cause a shock to the vehicle body. In contrast, Patent Document 2 describes a control device for work vehicles that suppresses the generation of differential pressure between the hydraulic cylinder and the accumulator by providing a supply passage (branch passage) connecting the hydraulic pump and the accumulator. The control device for work vehicles in Patent Document 2 is equipped with a switching valve (charge switching valve) that shuts off the supply passage (branch passage) when the on-off valve is opened.

[0006] Japanese Patent Publication No. 2005-249039 Japanese Patent Publication No. 2000-309953

[0007] Let's consider integrating the on-off valve and the switching valve (charge switching valve) described in Patent Document 2 into a single unit, that is, configuring these valves as a single valve device. In this case, if the valve bodies (spools) of each valve and the signal lines (oil passages) that operate them are integrated into a single housing, the valve device becomes complex and large.

[0008] The objective of the present invention is to provide a valve device for a vehicle vibration suppression device that can suppress complexity and size.

[0009] The present invention preferably relates to a valve device comprising a housing provided with a spool hole, a pump passage connecting a hydraulic pump to the spool hole, a cylinder passage connecting a hydraulic cylinder to the spool hole, and an accumulator passage connecting an accumulator to the spool hole, and a spool slidably mounted in the spool hole and moving between a first position and a second position in response to pilot pressure acting on one end thereof, wherein the pump passage and the cylinder passage are connected to the accumulator in the direction in which the spool moves through the spool hole. The spool is provided in positions opposite each other across the road, and the spool is provided with a first annular groove that connects the pump passage and the accumulator passage when the spool is in the first position, a second annular groove that connects the accumulator passage and the cylinder passage when the spool is in the second position, and a land that blocks the space between the accumulator passage and the cylinder passage when the spool is in the first position, and blocks the space between the pump passage and the accumulator passage when the spool is in the second position.

[0010] According to the present invention, it is possible to suppress the complexity and size increase of the valve device for constituting the driving vibration suppression device.

[0011] This is a left side view showing a wheel loader equipped with a valve device according to an embodiment. This is a circuit diagram showing the hydraulic and electrical circuits of the wheel loader in Figure 1. This is a cross-sectional view showing the valve device in Figure 2. This is an enlarged cross-sectional view of section (IV) in Figure 3. This is an enlarged cross-sectional view of section (V) in Figure 3. This is a flowchart showing the control processing performed by the control unit (C / U) in Figure 2.

[0012] The following will provide a detailed explanation, with reference to the attached drawings, using the valve device according to the embodiment as an example of a device for suppressing travel vibrations of a wheel loader. Each step in the flowchart shown in Figure 6 will be denoted as "S" (for example, step 1 = "S1").

[0013] Furthermore, in the following explanation, the front-to-back direction of the wheel loader 1 is defined as the side with the work implement 11 being the front, and the side with the counterweight 10, which is opposite the work implement 11, being the rear. The left-to-right direction of the wheel loader 1 is defined as being perpendicular to the front-to-back direction. That is, the side with the work implement 11 on the left side of Figure 1 is the front of the wheel loader 1, and the side with the counterweight 10 on the right side of Figure 1 is the rear of the wheel loader 1. The left-to-right direction of the wheel loader 1 also corresponds to the front-to-back direction of Figure 1. That is, the front side (foreground) of Figure 1 is the left side of the wheel loader 1, and the back side (back) of Figure 1 is the right side of the wheel loader 1. In addition, the up-to-down direction of the wheel loader 1 corresponds to the up-to-down direction of Figure 1.

[0014] In Figure 1, the wheel loader 1, as a vehicle (work vehicle), is configured as an articulated work vehicle in which a front body 3, equipped with left and right front wheels 2, and a rear body 5, equipped with left and right rear wheels 4, are connected in a manner that allows them to bend in the left and right direction. That is, the front body 3 and the rear body 5 constitute the body of the wheel loader 1. The front body 3 and the rear body 5 are connected by a connecting shaft 6 so that they can rotate freely in the left and right direction.

[0015] Furthermore, a steering cylinder 7 is provided between the front body 3 and the rear body 5. The front body 3 and the rear body 5 bend in the left-right direction by extending and contracting the steering cylinder 7. That is, the front body 3 bends in the left-right direction relative to the rear body 5 by extending and contracting the steering cylinder 7. This allows the wheel loader 1 to be steered while in motion.

[0016] The front body 3 is equipped with a pair of front wheels 2, one on the left and one on the right. The rear body 5 is equipped with a pair of rear wheels 4, one on the left and one on the right. In Figure 1, only the left front wheel 2 and the left rear wheel 4 of the pair of front wheels 2 and rear wheels 4 are shown. A work implement 11, also called a front work implement, front device, or work device, is mounted on the front side of the front body 3 so as to be able to rotate in the vertical direction.

[0017] In contrast, the rear body 5 is equipped with a cab 8, which serves as the driver's compartment. Although not shown in the illustration, the cab 8 contains a driver's seat where the operator sits, a steering wheel operated by the operator, driving pedals, and control levers for the work equipment 11. The rear body 5 also includes a machine room 9 that houses various equipment such as the engine, hydraulic pump 22 (see Figures 2 to 5), and cooler, as well as a counterweight 10 to balance the weight with the work equipment 11 on the front body 3.

[0018] The work machine 11 includes a lift arm 12 that can rotate vertically, a pair of lift arm cylinders 13, 13 that drive the lift arm 12 by extending and retracting, a bucket 14 attached to the tip of the lift arm 12, a bucket cylinder 15 that rotates the bucket 14 vertically relative to the lift arm 12 by extending and retracting, a bell crank 16 that is rotatably connected to the lift arm 12 and forms a link mechanism between the bucket 14 and the bucket cylinder 15, pipelines 27A, 27B (see Figure 2) that guide pressurized oil (hydraulic oil) to the pair of lift arm cylinders 13, 13, and a pipeline (not shown) that guides pressurized oil (hydraulic oil) to the bucket cylinder 15.

[0019] In Figure 1, only the left-hand lift arm cylinder 13 of the pair of lift arm cylinders 13, 13 is shown with a dashed line. Also, in Figures 3 and 4, the pair of lift arm cylinders 13, 13 are simply represented as a single cylinder to avoid complexity in the drawings.

[0020] As shown in Figures 1 to 4, the lift arm cylinders 13, 13 are hydraulic cylinders. Each lift arm cylinder 13, 13 comprises a tube 13A, a piston 13D slidably inserted into the tube 13A and dividing the inside of the tube 13A into a bottom-side oil chamber 13B and a rod-side oil chamber 13C, and a rod 13E whose base end is fixed to the piston 13D and whose tip end protrudes outside the tube 13A. Also, as shown in Figure 1, the bucket cylinder 15 is a hydraulic cylinder. The bucket cylinder 15 comprises a tube 15A, a piston (neither shown) slidably inserted into the tube 15A and dividing the inside of the tube 15A into a bottom-side oil chamber and a rod-side oil chamber, and a rod 15B whose base end is fixed to the piston and whose tip end protrudes outside the tube 15A.

[0021] The lift arm 12 rotates upward as the rods 13E, 13E of the pair of lift arm cylinders 13, 13 extend from the tube 13A, and rotates downward as the rods 13E, 13E retract into the tube 13A. The bucket 14 rotates upward relative to the lift arm 12 as the rod 15B of the bucket cylinder 15 extends from the tube 15A, and rotates downward relative to the lift arm 12 as the rod 15B retracts into the tube 15A.

[0022] Next, the hydraulic drive circuit 21 of the wheel loader 1, including the travel vibration suppression device 31, will be explained with reference to Figure 2. Note that Figure 2 mainly shows the hydraulic circuits of the lift arm cylinders 13, 13 and the electrical circuit of the electromagnetic control valve 71 of the travel vibration suppression device 31, while the hydraulic circuits of the bucket cylinder 15, steering cylinder 7, and other electrical circuits are omitted.

[0023] The hydraulic drive circuit 21 of the wheel loader 1 includes lift arm cylinders 13, 13 as hydraulic cylinders, a hydraulic pump 22, a tank 23, a control valve device 24, and a travel vibration suppression device 31. The lift arm cylinders 13, 13 extend or retract by the supply of pressurized oil from the hydraulic pump 22. The hydraulic pump 22, together with the tank 23, constitutes a hydraulic power source. The hydraulic pump 22 is rotationally driven by the engine (prime mover such as a diesel engine) in the machine room 9. The hydraulic pump 22 draws in hydraulic oil from the tank 23 and discharges (supplies) pressurized oil toward the pump pipeline 25.

[0024] The pressurized oil discharged into the pump pipeline 25 is supplied to the lift arm cylinders 13, 13 via the control valve device 24 (more specifically, the lift arm directional control valve 24A). A tank pipeline 26 is also provided between the control valve device 24 (more specifically, the lift arm directional control valve 24A) and the tank 23 to return the oil from the lift arm cylinders 13, 13 back to the tank 23.

[0025] As will be described later, a branch pipeline 36 of the running vibration suppression device 31 is connected to the pump pipeline 25. The pressurized oil discharged into the pump pipeline 25 is supplied to the accumulator 32 via the branch pipeline 36 and the valve device 41 (shut-off valve 81 and on / off switching valve 61).

[0026] The control valve device 24 is a group of control valves consisting of multiple directional control valves 24A. Note that the control valve device 24 shown in Figure 2 mainly shows the lift arm directional control valves 24A, which are directional control valves for the lift arm cylinders 13, 13. In other words, the control valve device 24 shown in Figure 2 omits other directional control valves, such as the bucket directional control valve, which is the directional control valve for the bucket cylinder 15.

[0027] The control valve device 24 distributes the pressurized oil discharged from the hydraulic pump 22 to the lift arm cylinders 13, 13 and the bucket cylinder 15, which act as hydraulic actuators. Specifically, the control valve device 24 controls the direction of the pressurized oil supplied from the hydraulic pump 22 to the lift arm cylinders 13, 13 and the bucket cylinder 15 in response to a switching signal (operating pilot pressure) based on the operation of an operating lever located inside the cab 8. As a result, the lift arm cylinders 13, 13 and the bucket cylinder 15 are driven by the pressurized oil (hydraulic fluid) supplied (discharged) from the hydraulic pump 22.

[0028] The lift arm directional control valve 24A of the control valve device 24 has hydraulic pilot sections (not shown) on both axial sides of the spool 24A1 and is normally held in a neutral position (A). The lift arm directional control valve 24A is switched from the neutral position (A) to the switching positions (B) and (C) by supplying pilot pressure (operating pilot pressure) to the hydraulic pilot section.

[0029] A pair of actuator lines 27A and 27B are provided between the lift arm cylinders 13, 13 and the lift arm directional control valve 24A. One actuator line 27A connects the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 to one of the pressurized oil inlet / outlet ports of the lift arm directional control valve 24A. The other actuator line 27B connects the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 to the other pressurized oil inlet / outlet port of the lift arm directional control valve 24A.

[0030] As will be described later, the actuator lines 27A and 27B are connected to the connecting lines 35A and 35B of the travel vibration suppression device 31, respectively. As a result, the bottom oil chambers 13B, 13B and rod oil chambers 13C, 13C of the lift arm cylinders 13, 13 can be connected to the accumulator 32 and tank 23 via the valve device 41 (on / off switching valve 61).

[0031] The travel vibration suppression device 31 suppresses the shaking of the work equipment 11 during travel by connecting the accumulator 32, which is a pressure accumulation device, to the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13, which are hydraulic cylinders, when the wheel loader 1, which is a vehicle, is traveling. The travel vibration suppression device 31 comprises the accumulator 32, the accumulator pipeline 33, the tank pipeline 34, a pair of connecting pipelines 35A, 35B, a branch pipeline 36, a valve device 41, and a control unit 101.

[0032] The valve device 41 comprises an on / off switching valve 61, an electromagnetic control valve 71, and a shut-off valve 81. The valve device 41 has a single housing 42, and is constructed by assembling the on / off switching valve 61, the electromagnetic control valve 71, and the shut-off valve 81 into this single housing 42. In other words, the on / off switching valve 61, the electromagnetic control valve 71, and the shut-off valve 81 are integrated as a single unitized valve device 41.

[0033] In this embodiment, a valve device 41 is shown in which the switching valve 61, the electromagnetic control valve 71, and the shut-off valve 81 are integrated into a single unit. However, the invention is not limited to this configuration. For example, the switching valve and the electromagnetic control valve may be integrated into a single unit, while the shut-off valve is a separate valve device. Alternatively, the switching valve, the electromagnetic control valve, and the shut-off valve may each be separate valve devices. In other words, the valve device can be configured to include at least a switching valve.

[0034] The accumulator 32 of the running vibration suppression device 31 is a pressure accumulator that stores pressurized oil. The accumulator 32 is connected to the valve device 41 (more specifically, the on / off switching valve 61) via the accumulator pipeline 33. The running vibration suppression device 31 is constructed by connecting the housing 42 of the valve device 41 and the accumulator 32 with the accumulator pipeline 33.

[0035] Pressurized oil discharged from the hydraulic pump 22 flows into the accumulator 32 via the branch pipeline 36, valve device 41, and accumulator pipeline 33. This allows the accumulator 32 to store pressurized oil. When the wheel loader 1 is in motion, the accumulator 32, which is filled with pressurized oil, is connected to the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 via the accumulator pipeline 33, valve device 41, and connecting pipeline 35A. At this time, the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 are connected to the tank 23 via the connecting pipeline 35B, valve device 41, and tank pipeline 34.

[0036] The accumulator conduit 33 is provided between the accumulator 32 and the valve device 41. The accumulator conduit 33 connects the accumulator 32 and the valve device 41 (more specifically, the on / off switching valve 61). The tank conduit 34 is provided between the tank 23 and the valve device 41. The tank conduit 34 connects the tank 23 and the valve device 41 (more specifically, the on / off switching valve 61). A pair of connecting conduits 35A and 35B are provided between the lift arm cylinders 13 and 13 and the valve device 41.

[0037] One connecting pipe 35A is connected to one actuator pipe 27A. Thus, one connecting pipe 35A, together with one actuator pipe 27A, connects the valve device 41 (more specifically, the switching valve 61) to the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13. The other connecting pipe 35B is connected to the other actuator pipe 27B. Thus, the other connecting pipe 35B, together with the other actuator pipe 27B, connects the valve device 41 (more specifically, the switching valve 61) to the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13.

[0038] The branch pipeline 36 is located between the hydraulic pump 22 and the valve device 41. The branch pipeline 36 is connected to the pump pipeline 25. That is, the branch pipeline 36 branches off from the pump pipeline 25 and connects the hydraulic pump 22 to the valve device 41 (more specifically, the shut-off valve 81). As a result, the pressurized oil from the hydraulic pump 22 can be supplied to the accumulator 32 via the pump pipeline 25, the branch pipeline 36, the valve device 41 (shut-off valve 81 and switching valve 61), and the accumulator pipeline 33.

[0039] The valve device 41 is a spool valve device that constitutes the running vibration suppression device 31. Specifically, the valve device 41 is equipped with an on / off switching valve 61 which serves as the main valve. The valve device 41 is also equipped with an electromagnetic control valve 71 that controls the pilot pressure supplied to the hydraulic pilot section 63 of the on / off switching valve 61. Furthermore, the valve device 41 is also equipped with a shut-off valve 81 that disconnects the connection between the hydraulic pump 22 and the accumulator 32 when a predetermined pressure is reached. Therefore, the valve device 41 is equipped with a housing 42 common to the on / off switching valve 61, the electromagnetic control valve 71, and the shut-off valve 81.

[0040] The switching valve 61 switches between connecting and disconnecting the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 to the accumulator 32, connecting and disconnecting the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 to the tank 23, and connecting and disconnecting the hydraulic pump 22 to the accumulator 32. The switching valve 61 comprises a housing 42, a main spool 62 as a spool, a hydraulic pilot unit 63, and a spring 64. The main spool 62 is held in a first position (A) by the spring 64. The main spool 62 moves from position (A) to a second position (B) when pilot pressure is supplied to the hydraulic pilot unit 63 via the electromagnetic control valve 71.

[0041] When the main spool 62 is at position (A), the open / close switching valve 61 connects the hydraulic pump 22 and the accumulator 32. Also, when the main spool 62 is at position (A), the open / close switching valve 61 disconnects the bottom-side oil chambers 13B, 13B of the lift arm cylinders 13, 13 from the accumulator 32, and disconnects the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 from the tank 23.

[0042] In contrast, when the main spool 62 is at position (B), the open / close switching valve 61 disconnects the hydraulic pump 22 from the accumulator 32. Also, when the main spool 62 is at position (B), the open / close switching valve 61 connects the bottom-side oil chambers 13B, 13B of the lift arm cylinders 13, 13 to the accumulator 32, and connects the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 to the tank 23.

[0043] The electromagnetic control valve 71 controls the pilot pressure supplied to the hydraulic pilot portion 63 of the open / close switching valve 61 to switch the main spool 62, which is the spool of the open / close switching valve 61. The electromagnetic control valve 71 is, for example, a 3-port 2-position electromagnetic switching valve (electromagnetic proportional control valve) configured as a proportional solenoid valve. The electromagnetic control valve 71 includes a housing 42, a control spool 72 (Fig. 2), a sleeve 73 (Fig. 3) having a spool hole (not shown) in which the control spool 72 slides, a solenoid 74 serving as an electromagnetic pilot portion, and a spring 75. The solenoid 74 is connected to the control unit 101.

[0044] The electromagnetic control valve 71 outputs pressure oil (pilot pressure P) having a pressure proportional to the electric power supplied from the control unit 101 to the hydraulic pilot portion 63 of the open / close switching valve 61. That is, the control spool 72 is held at position (A) by the spring 75. The control spool 72 moves from position (A) to position (B) when electric power W is supplied from the control unit 101 to the solenoid 74.

[0045] When the control spool 72 is at position (A), the electromagnetic control valve 71 connects the hydraulic pilot portion 63 of the on-off switching valve 61 to the tank 23 via the drain port 43 (Fig. 2) of the housing 42. In contrast, when the control spool 72 is at position (B), the electromagnetic control valve 71 connects the hydraulic pilot portion 63 of the on-off switching valve 61 to a pilot pump (not shown) via the pilot port 44 of the housing 42.

[0046] When the on-off switching valve 61 is at position (A) and the pressure of pressure oil supplied from the hydraulic pump 22 to the accumulator 32 reaches a predetermined pressure, that is, when the pressure of the accumulator 32 reaches the predetermined pressure, the shut-off valve 81 shuts off the connection between the accumulator 32 and the hydraulic pump 22. The shut-off valve 81 includes a shut-off spool 82 and a spring 83. The shut-off spool 82 is held at position (A) by the spring 83. The shut-off spool 82 moves from position (A) to position (B) when "the force (axial force) applied to the shut-off spool 82 based on the pressure oil supplied from the hydraulic pump 22" exceeds "the force (axial force) applied to the shut-off spool 82 by the spring 83".

[0047] When the shut-off spool 82 is at position (A), the shut-off valve 81 connects the hydraulic pump 22 and the accumulator 32. In contrast, when the shut-off spool 82 is at position (B), the shut-off valve 81 shuts off the connection between the hydraulic pump 22 and the accumulator 32. Further, a check valve 84 is provided on the shut-off spool 82. The check valve 84 allows pressure oil to flow from the hydraulic pump 22 toward the accumulator 32, and blocks pressure oil from flowing from the accumulator 32 toward the hydraulic pump 22.

[0048] That is, the check valve 84 suppresses backflow of pressure oil from the accumulator 32 to the hydraulic pump 22. Accordingly, the shut-off valve 81 provided with the check valve 84 suppresses backflow of pressure oil from the accumulator 32 to the hydraulic pump 22, and shuts off the connection between the accumulator 32 and the hydraulic pump 22 when the pressure on the upstream side of the shut-off valve 81 (the pressure of the accumulator 32) reaches a high pressure (predetermined pressure).

[0049] Furthermore, an orifice 91 is provided downstream of the shut-off valve 81, that is, between the hydraulic pump 22 and the shut-off valve 81, as a first flow rate control device that limits the flow rate of pressurized oil flowing from the hydraulic pump 22 toward the shut-off valve 81 to a constant level. By limiting the flow rate of pressurized oil flowing from the hydraulic pump 22 toward the shut-off valve 81 to a constant level, the orifice 91 can control the pressure rise time of the accumulator 32 and control the amount of pressure accumulated in the accumulator 32.

[0050] Next, the configuration of the valve device 41 will be explained in more detail with reference to Figures 2 to 5.

[0051] The valve device 41 includes a housing 42. The outer surface of the housing 42 has openings for a drain port 43 (Figure 2), a pilot port 44 (Figure 2), a pump port 45, an accumulator port 46, a pair of cylinder ports 47 and 48, and a tank port 49. The drain port 43 (Figure 2) is connected to the tank 23 via a return pipe (not shown).

[0052] The pilot port 44 (Figure 2) is connected to a pilot pump (not shown) via a pilot line (not shown). A branch line 36 is connected to the pump port 45. An accumulator line 33 is connected to the accumulator port 46. Connecting lines 35A and 35B are connected to a pair of cylinder ports 47 and 48. A tank line 34 is connected to the tank port 49.

[0053] Furthermore, the housing 42 is provided with a main spool hole 50, which is the spool hole for the switching valve 61. The housing 42 is provided with a solenoid valve insertion hole 51 into which the electromagnetic control valve 71 is installed. The housing 42 is provided with a shut-off spool hole 52, which is the spool hole for the shut-off valve 81. The housing 42 is also provided with a pump passage 53, an accumulator passage 54, a pair of cylinder passages 55 and 56, a tank passage 57, and a pilot passage 58.

[0054] As shown in Figures 3 and 4, the main spool 62 of the switching valve 61 is inserted into the main spool hole 50. The main spool hole 50 extends linearly through the housing 42 in the left-right direction (left-right direction in Figures 3 and 4, the axial direction in which the main spool 62 slides). A first annular recess 50A, a second annular recess 50B, a pair of third annular recesses 50C and 50D, and a fourth annular recess 50E are formed on the inner circumference of the main spool hole 50.

[0055] The first annular recess 50A is located in the axial middle of the main spool hole 50. The pump passage 53 is connected to the first annular recess 50A. The second annular recess 50B is located adjacent to the first annular recess 50A in the axial direction of the main spool hole 50. The accumulator passage 54 is connected to the second annular recess 50B.

[0056] The third annular recesses 50C and 50D are located axially outward from the main spool hole 50 and spaced apart from each other in the left-right direction compared to the first annular recess 50A and the second annular recess 50B. Cylinder passages 55 and 56 are connected to the third annular recesses 50C and 50D, respectively. Specifically, one cylinder passage 55, which leads to the bottom oil chambers 13B and 13B of the lift arm cylinders 13 and 13, is connected to one of the third annular recesses 50C. The other cylinder passage 56, which leads to the rod oil chambers 13C and 13C of the lift arm cylinders 13 and 13, is connected to the other third annular recess 50D.

[0057] The fourth annular recess 50E is located axially outward from the main spool hole 50 than the third annular recesses 50C and 50D, and is provided on the opposite side of the hydraulic pilot section 63 in the axial direction. The tank passage 57 is connected to the fourth annular recess 50E.

[0058] The first annular recess 50A communicates with the second annular recess 50B when the main spool 62 is in the position shown in Figure 3. This connects the pump passage 53 and the accumulator passage 54. Conversely, when the supply of pilot pressure to the hydraulic pilot unit 63 causes the main spool 62 to move to the right from the position shown in Figure 3 against the pressing force of the spring 64, the first annular recess 50A is blocked from the second annular recess 50B. This blocks the pump passage 53 and the accumulator passage 54.

[0059] The third annular recesses 50C and 50D are blocked from the second annular recess 50B and the fourth annular recess 50E when the main spool 62 is in the position shown in Figure 3. This blocks the cylinder passages 55 and 56 from the accumulator passage 54 and the tank passage 57. However, when the main spool 62 moves to the right from the position shown in Figure 3, one of the third annular recesses 50C communicates with the second annular recess 50B, and the other third annular recess 50D communicates with the fourth annular recess 50E. As a result, one cylinder passage 55 leading to the bottom oil chambers 13B and 13B of the lift arm cylinders 13 and 13 communicates with the accumulator passage 54, and the other cylinder passage 56 leading to the rod oil chambers 13C and 13C of the lift arm cylinders 13 and 13 communicates with the tank passage 57.

[0060] The main spool 62 slides and displaces axially (left-right direction in Figure 3) within the main spool hole 50 according to the pilot pressure supplied to the hydraulic pilot section 63 via the electromagnetic control valve 71. The main spool 62 has a first land 62A that selectively connects or disconnects the second annular recess 50B to either the first annular recess 50A or one of the third annular recesses 50C.

[0061] A notch 62A1 for fine-tuning the flow rate of pressurized oil is provided in the first land 62A at a position corresponding to the space between the second annular recess 50B and one of the third annular recesses 50C. The main spool 62 also has a second land 62B that separates the space between the first annular recess 50A and the other third annular recess 50D, a third land 62C that connects or blocks the space between the other third annular recess 50D and the fourth annular recess 50E, and a fourth land 62D that separates the space between one of the third annular recesses 50C and the hydraulic pilot section 63.

[0062] A first annular groove 62E is formed between the first land 62A and the second land 62B. A second annular groove 62F is formed between the first land 62A and the fourth land 62D. In other words, the outer circumferential surface of the main spool 62 is provided with a first annular groove 62E, which forms the first constriction, and a second annular groove 62F, which forms the second constriction. The first annular groove 62E connects the pump passage 53 and the accumulator passage 54 when the main spool 62 is in the first position shown in Figure 3 (position (A) in Figure 2). The second annular groove 62F connects the accumulator passage 54 and one of the cylinder passages 55 when the main spool 62 is in the second position (position (B) in Figure 2), which is to the right of the position shown in Figure 3. The first land 62A, acting as a land, blocks the accumulator passage 54 from one of the cylinder passages 55 when the main spool 62 is in the first position (position (A) in Figure 2). The first land 62A also blocks the pump passage 53 from the accumulator passage 54 when the main spool 62 is in the second position (position (B) in Figure 2).

[0063] The pump passage 53 connects the pump port 45 and the first annular recess 50A. Thus, the pump passage 53 connects the hydraulic pump 22 and the main spool hole 50. A shut-off valve 81 and an orifice 91 are provided in the middle of the pump passage 53. The accumulator passage 54 connects the accumulator port 46 and the second annular recess 50B. Thus, the accumulator passage 54 connects the accumulator 32 and the main spool hole 50.

[0064] One cylinder passage 55 connects one cylinder port 47 to one third annular recess 50C. The other cylinder passage 56 connects the other cylinder port 48 to the other third annular recess 50D. Thus, the cylinder passages 55 and 56 connect the lift arm cylinders 13, 13 to the main spool hole 50.

[0065] In this case, one cylinder passage 55 connects the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 to the main spool hole 50. The other cylinder passage 56 connects the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 to the main spool hole 50. Furthermore, the pump passage 53 and one cylinder passage 55 are positioned opposite each other across the accumulator passage 54 in the direction in which the main spool 62 moves through the main spool hole 50. That is, the accumulator passage 54 is located between the pump passage 53 and one cylinder passage 55 in the axial direction of the main spool 62.

[0066] The tank passage 57 connects the tank port 49 and the fourth annular recess 50E. Thus, the tank passage 57 connects the tank 23 and the main spool hole 50. The pilot passage 58 connects the solenoid valve insertion hole 51 and the hydraulic pilot section 63. Thus, the pilot passage 58 connects the solenoid control valve 71 and the on / off switching valve 61 (hydraulic pilot section 63).

[0067] As shown in Figure 3, the electromagnetic control valve 71 is mounted on the housing 42. In this case, the electromagnetic control valve 71 is mounted on the housing 42 with the sleeve 73 of the electromagnetic control valve 71 inserted into the electromagnetic valve insertion hole 51. As shown in Figure 2, the housing 42 is provided with a pilot supply passage 59, a drain passage 60, and a pilot passage 58. The pilot supply passage 59 connects a pilot port 44 opening on the outer surface of the housing 42 to a supply port 76 of the electromagnetic control valve 71.

[0068] The drain passage 60 connects the drain port 43, which opens to the outer surface of the housing 42, to the discharge port 77 of the electromagnetic control valve 71. The pilot passage 58 connects the supply / discharge port 78 of the electromagnetic control valve 71 to the hydraulic pilot section 63 of the switching valve 61. The pilot port 44 is connected to a pilot pump (not shown). The drain port 43 is connected to the tank 23.

[0069] As shown in Figures 3 and 5, the shut-off spool 82 of the shut-off valve 81 is inserted into the shut-off spool hole 52. The shut-off spool hole 52 extends linearly in the left-right direction of the housing 42 (left-right direction in Figures 3 and 5, the axial direction in which the shut-off spool 82 slides). A pair of annular recesses 52A and 52B are formed on the inner circumference of the shut-off spool hole 52. The pair of annular recesses 52A and 52B are adjacent to each other in the axial direction of the shut-off spool hole 52.

[0070] One annular recess 52A is located in a position corresponding to the axial direction of the first annular recess 50A of the main spool hole 50. The annular recess 52A and the first annular recess 50A are connected by a pump passage 53, more specifically, a downstream pump passage 53A that connects the switching valve 61 and the shut-off valve 81. The other annular recess 52B and the pump port 45 are also connected by a pump passage 53, more specifically, an upstream pump passage 53B that connects the pump port 45 and the shut-off valve 81.

[0071] The control unit 101 controls the valve device 41 of the travel vibration suppression device 31, more specifically, the electromagnetic control valve 71. The control unit 101 is a control device comprising a microcomputer, a power supply circuit, and a drive circuit. The control unit 101 includes a control unit that performs calculations such as a CPU (processing unit), and a storage unit consisting of memory such as ROM, RAM, and non-volatile memory. The storage unit (memory) of the control unit 101 stores processing programs and the like that perform the processing shown in Figure 6, which will be described later.

[0072] The running vibration suppression device 31 has two functions. The first function of the running vibration suppression device 31 is the pressure accumulation function of the accumulator 32. As shown in Figure 2, hydraulic fluid is supplied from the hydraulic pump 22 to the accumulator 32. At this time, the hydraulic fluid passes through the branch pipeline 36 that constitutes the pressure accumulation circuit, and the flow rate is controlled by the orifice 91 which acts as the first flow rate control device. In addition, the shut-off valve 81 prevents backflow of hydraulic fluid from the accumulator 32 and also shuts off the supply of hydraulic fluid through the branch pipeline 36 when the pressure in the accumulator 32 reaches a certain high pressure. The switching valve 61 can also supply and shut off hydraulic fluid through the branch pipeline 36, that is, it can open and close the branch pipeline 36.

[0073] The second function of the driving vibration suppression device 31 is a ride control function (driving vibration suppression function) that connects the accumulator 32 with the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13. Specifically, the electromagnetic control valve 71 controls the on / off switching valve 61 to connect the accumulator 32 with the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13. This makes it possible to suppress the pressure pulsation of the lift arm cylinders 13, 13 that occurs in response to vibrations during driving.

[0074] The orifice 91, acting as the first flow rate control device, is arranged adjacent to the hydraulic pump 22 on the pressure accumulation circuit. In this embodiment, the orifice 91 is located in the middle of the pump passage 53 of the valve device 41 (i.e., the pump passage 53 that constitutes the pressure accumulation circuit). The orifice 91 maintains a constant flow rate of the hydraulic fluid discharged from the hydraulic pump 22. As a result, the orifice 91 can control the pressure rise time of the accumulator 32 and control the amount of pressure accumulated in the accumulator 32.

[0075] The shut-off valve 81 is located in the middle of the pump passage 53, between the orifice 91 and the switching valve 61. In addition to preventing backflow from the accumulator 32, the shut-off valve 81 also shuts off the pressure accumulation circuit (pump passage 53) when the pressure in the accumulator 32 reaches a certain high pressure.

[0076] The switching valve 61 is located in the middle of the pressure accumulation circuit, specifically between the orifice 91 and the accumulator 32. The switching valve 61 is also located in the middle of the ride control circuit, specifically between the lift arm cylinders 13, 13 and the accumulator 32. The switching valve 61 is controlled by an electromagnetic control valve 71 within the housing 42 of the valve device 41.

[0077] The switching valve 61 is equipped with a second flow control device. Specifically, the main spool 62, which is the spool of the switching valve 61, is provided with a notch 62A1 that serves as the second flow control device. When the ride control function is activated, the notch 62A1 controls the flow path diameter between the lift arm cylinders 13, 13 and the accumulator 32, and slows down the flow of oil from one to the other when there is a pressure difference between the lift arm cylinders 13, 13 and the accumulator 32.

[0078] When the ride control function is activated, that is, when the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 are connected to the accumulator 32, the switching valve 61 connects the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 to the tank 23. This allows the hydraulic fluid to be discharged.

[0079] The electromagnetic control valve 71 controls the external pilot pressure for controlling the switching valve 61. Specifically, the electromagnetic control valve 71 connects the pilot pump and the hydraulic pilot section 63 of the switching valve 61 within the housing 42 of the valve device 41. When the ride control function is activated, the control unit 101 controls the current to operate the electromagnetic control valve 71. At this time, the control unit 101 slows down the switching speed of the switching valve 61, thereby slowing down the flow of oil from one to the other when there is a pressure difference between the lift arm cylinders 13, 13 and the accumulator 32.

[0080] Figure 6 shows the control process performed by the control unit 101 that controls the electromagnetic control valve 71. The process in Figure 6 is repeatedly executed at a predetermined control cycle.

[0081] The control process shown in Figure 6 is initiated, for example, by supplying power to the control unit 101. In S1, the control unit 101 determines whether the indicator switch for the ride control function is ON or OFF. The indicator switch is located, for example, inside the cab 8. The operator of the wheel loader 1 turns the indicator switch ON when they want to activate the ride control function. If the result in S1 is "NO," that is, if the ride control indicator switch is not ON, the process proceeds to S2.

[0082] In S2, no control current is supplied to the solenoid 74 of the electromagnetic control valve 71. That is, in this case, the main spool 62, which is the spool of the switching valve 61, is set to the position shown in Figure 3. That is, the main spool 62 of the switching valve 61 is set to the position shown in Figure 2 (A). This prevents communication between the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 and the accumulator 32. If no control current is supplied to the electromagnetic control valve 71 (solenoid 74) in S2, the system returns. That is, it returns to the start via the return process and repeats the processing from S1 onwards.

[0083] In response to this, if the answer in S1 is "YES," meaning the ride control instruction switch is ON, the process proceeds to S3. In S3, it is determined whether the vehicle speed is above a predetermined value. That is, in S3, it is determined whether the vehicle speed of the wheel loader 1 has reached the speed at which the ride control function should be activated. The predetermined value of the vehicle speed can be, for example, about 5 km / h. The vehicle speed of the wheel loader 1 is detected, for example, by a rotation speed sensor provided on the axle of the wheel loader 1. If the answer in S3 is "NO," meaning the vehicle speed of the wheel loader 1 is below the predetermined value, the process returns via S2. That is, in this case as well, similar to the case where "NO" is determined in S1, the process returns in S2 without supplying control current to the solenoid 74 of the electromagnetic control valve 71.

[0084] In response to this, if the answer in S3 is "YES," that is, if it is determined that the vehicle speed of the wheel loader 1 is equal to or greater than a predetermined value, the process proceeds to S4. In S4, a control current is supplied to the solenoid 74 of the electromagnetic control valve 71. In this case, the main spool 62, which is the spool of the switching valve 61, is moved to the right from the position shown in Figure 3. That is, the main spool 62 is moved to the position shown in Figure 2 (B). This connects the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 with the accumulator 32. After supplying the control current to the electromagnetic control valve 71 (solenoid 74) in S4, the process returns.

[0085] Thus, the control unit 101 determines whether to supply current to the electromagnetic control valve 71 (solenoid 74) based on whether the ride control indicator switch is ON or OFF. In this case, if the ride control indicator switch is OFF, no current is supplied to the electromagnetic control valve 71 (solenoid 74). On the other hand, if the ride control indicator switch is ON, and the speed of the wheel loader 1 is above a predetermined value, current is supplied to the electromagnetic control valve 71 (solenoid 74).

[0086] Next, we will explain the switching valve 61.

[0087] As shown in Figures 2 to 4, the switching valve 61 pressurizes the accumulator 32 by supplying pressurized oil discharged from the hydraulic pump 22 to the accumulator 32. At this time, the switching valve 61 connects the first annular recess 50A and the second annular recess 50B by the first annular groove 62E of the main spool 62. As a result, the pressurized oil supplied from the hydraulic pump 22 to the first annular recess 50A via the orifice 91, which is the first flow control device, and the shut-off valve 81 is supplied to the accumulator 32 via the first annular groove 62E and the second annular recess 50B.

[0088] Furthermore, when pilot pressure is supplied to the hydraulic pilot section 63 via the electromagnetic control valve 71, the switching valve 61 connects the pressurized accumulator 32 with the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13. This suppresses vibrations during the travel of the wheel loader 1. At this time, the switching valve 61 connects the second annular recess 50B and one of the third annular recesses 50C by the second annular groove 62F of the main spool 62.

[0089] Furthermore, when pilot pressure is supplied to the hydraulic pilot section 63 via the electromagnetic control valve 71, the switching valve 61 disconnects the connection between the first annular recess 50A and the second annular recess 50B with the first land 62A of the main spool 62. This cuts off the supply of pressurized oil from the hydraulic pump 22 to the accumulator 32, suppressing the pressure rise in the accumulator 32 and the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13.

[0090] In this embodiment, to satisfy these functions, a first annular recess 50A (pump passage 53) and one third annular recess 50C (one cylinder passage 55) are provided on both sides of the second annular recess 50B (accumulator passage 54) with respect to the axial direction of the main spool hole 50 (main spool 62). That is, the second annular recess 50B (accumulator passage 54) is adjacent to the first annular recess 50A (pump passage 53) in the axial direction.

[0091] Furthermore, the second annular recess 50B (accumulator passage 54) is adjacent in the axial direction to one of the third annular recesses 50C (one of the cylinder passages 55). In addition, the first annular recess 50A (pump passage 53) is adjacent in the axial direction to the other third annular recess 50D (the other cylinder passage 56).

[0092] Next, the orifice 91 and shut-off valve 81, which constitute the first flow rate control device, will be described.

[0093] The orifice 91 restricts the flow rate of pressurized oil supplied from the hydraulic pump 22 to the accumulator 32 via the shut-off valve 81 and the switching valve 61. This suppresses a rapid increase in the pressure of the accumulator 32. The shut-off valve 81 incorporates a check valve 84. This prevents the shut-off valve 81 from backflowing hydraulic fluid from the accumulator 32 to the hydraulic pump 22. The shut-off valve 81 also shuts off the connection between the hydraulic pump 22 and the accumulator 32 when a predetermined pressure is reached.

[0094] To summarize, the valve device 41 is composed of an on / off switching valve 61. The valve device 41, that is, the on / off switching valve 61, has a housing 42 and a main spool 62 as a spool. The housing 42 is provided with a main spool hole 50 as a spool hole, a pump passage 53, cylinder passages 55, 56 and an accumulator passage 54. The main spool hole 50 is through which the main spool 62 slides.

[0095] The pump passage 53 connects the hydraulic pump 22 to the main spool hole 50. The cylinder passages 55 and 56 connect the lift arm cylinders 13, 13, which function as hydraulic cylinders, to the main spool hole 50. In this case, one cylinder passage 55 connects the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 to the main spool hole 50. The other cylinder passage 56 connects the rod-side oil chambers 13C, 13C of the lift arm cylinders 13, 13 to the main spool hole 50.

[0096] The accumulator passage 54 connects the accumulator 32 and the main spool hole 50. The main spool 62 is slidably mounted in the main spool hole 50. The main spool 62 moves between a first position (A) and a second position (B) in response to the pilot pressure acting on one end thereof. That is, the main spool 62 moves between position (A) and position (B) in response to the pilot pressure supplied to the hydraulic pilot unit 63.

[0097] In this configuration, the pump passage 53 and the cylinder passages 55 and 56, more specifically the pump passage 53 and one of the cylinder passages 55, are positioned opposite each other across the accumulator passage 54 in the direction in which the main spool 62 moves through the main spool hole 50. That is, the accumulator passage 54 is located between the pump passage 53 and one of the cylinder passages 55 in the axial direction of the main spool 62.

[0098] The main spool 62 is also provided with a first annular groove 62E, a second annular groove 62F, and a first land 62A as a land. The first annular groove 62E connects the pump passage 53 and the accumulator passage 54 when the main spool 62 is in position (A). The second annular groove 62F connects the accumulator passage 54 and one of the cylinder passages 55 when the main spool 62 is in position (B). The first land 62A blocks the connection between the accumulator passage 54 and one of the cylinder passages 55 when the main spool 62 is in position (A), and blocks the connection between the pump passage 53 and the accumulator passage 54 when the main spool 62 is in position (B).

[0099] As a result, when the pilot pressure is below a predetermined pressure, the main spool 62 connects the pump passage 53 and the accumulator passage 54, while blocking the connection between the accumulator passage 54 and one of the cylinder passages 55. Also, when the pilot pressure is above a predetermined pressure, the main spool 62 connects the accumulator passage 54 and one of the cylinder passages 55, while blocking the connection between the pump passage 53 and the accumulator passage 54. The predetermined pressure corresponds, for example, to the pressure required to move the main spool 62 against the pressing force of the spring 64.

[0100] Furthermore, the pump passage 53 is provided with a shut-off valve 81 that shuts off the pump passage 53 when the pressure in the pump passage 53 exceeds a predetermined pressure. The predetermined pressure corresponds, for example, to the pressure to be accumulated in the accumulator 32. The shut-off valve 81 is provided with a check valve 84 that allows flow only from the hydraulic pump 22 to the accumulator 32. Pilot pressure is supplied to the hydraulic pilot section 63, which is one end of the main spool 62, via an electromagnetic control valve 71. The first land 62A of the main spool 62 is provided with a notch 62A1 at a position corresponding to the space between one cylinder passage 55 and the accumulator passage 54.

[0101] The wheel loader 1, the travel vibration suppression device 31, and the valve device 41 according to this embodiment have the configuration described above, and their operation will now be explained.

[0102] The operator of the wheel loader 1 boards the cab 8 and sits in the driver's seat. The operator can move the wheel loader 1 by operating the steering wheel, driving pedals, etc., and can operate the work equipment 11 by operating the control levers. As a result, the wheel loader 1 can use the bucket 14 of the work equipment 11 to perform tasks such as excavating, scooping, transporting, and loading (soil removal) soil onto dump trucks.

[0103] Furthermore, when the operator activates the ride control function of the driving vibration suppression device 31, they turn on the indicator switch, which is the ON / OFF switch for this function. As a result, the control unit 101 of the driving vibration suppression device 31 supplies a control current to the electromagnetic control valve 71 (solenoid 74) of the valve device 41 when the vehicle speed of the wheel loader 1 exceeds a predetermined value, for example, 5 km / h or more.

[0104] When a control current is supplied to the electromagnetic control valve 71, pilot pressure is supplied to the on / off switching valve 61 (hydraulic pilot section 63) of the valve device 41 via the electromagnetic control valve 71. When pilot pressure is supplied to the on / off switching valve 61, the main spool 62 moves from position (A) to position (B) in Figure 2, connecting the bottom oil chambers 13B, 13B of the lift arm cylinders 13, 13 with the accumulator 32. This suppresses the vertical swaying of the work equipment 11 when the wheel loader 1 is traveling with a load.

[0105] In this embodiment, the housing 42 of the valve device 41 (on / off switching valve 61) is provided with a main spool hole 50 as a spool hole, a pump passage 53, cylinder passages 55, 56 and an accumulator passage 54. In this case, the pump passage 53 and one of the cylinder passages 55 are located opposite each other with the accumulator passage 54 in between. Furthermore, the main spool 62, which is slidably provided in the main spool hole 50, is provided with a first annular groove 62E that connects the pump passage 53 and the accumulator passage 54 when the main spool 62 is in a first position (position (A) in Figure 2, position in Figure 3).

[0106] Furthermore, the main spool 62 is provided with a second annular groove 62F that connects the accumulator passage 54 and one of the cylinder passages 55 when the main spool 62 is in the second position (position (B) in Figure 2). The main spool 62 is also provided with a first land 62A that blocks the connection between the accumulator passage 54 and one of the cylinder passages 55 when the main spool 62 is in the first position (position (A) in Figure 2, position in Figure 3), and blocks the connection between the pump passage 53 and the accumulator passage 54 when the main spool 62 is in the second position (position (B) in Figure 2).

[0107] Therefore, the main spool 62, which is a single spool, can switch between connecting and disconnecting the pump passage 53, one cylinder passage 55, and the accumulator passage 54. This makes it possible to suppress the complexity and size increase of the valve device 41 (on / off switching valve 61), more specifically the valve device 41 (on / off switching valve 61) that constitutes the running vibration suppression device 31, which is required to switch between connecting and disconnecting the pump passage 53, one cylinder passage 55, and the accumulator passage 54.

[0108] According to this embodiment, a shut-off valve 81 is provided in the pump passage 53. A check valve 84 is also provided in the shut-off valve 81. Therefore, the shut-off valve 81 can prevent the pressure in the accumulator 32 from becoming excessively high. In addition, the check valve 84 can prevent pressurized oil from flowing back from the accumulator 32 to the hydraulic pump 22.

[0109] According to this embodiment, pilot pressure is supplied to one end of the main spool 62 via an electromagnetic control valve 71. Therefore, the electromagnetic control valve 71 not only allows for automatic control of the movement of the main spool 62, but also enables stable movement.

[0110] According to the embodiment, a notch 62A1 is provided in the first land 62A of the main spool 62 at a position corresponding to the space between one cylinder passage 55 and the accumulator passage 54. Therefore, the notch 62A1 can mitigate the shock when the differential pressure between one cylinder passage 55 and the accumulator passage 54 is large (i.e., the sudden fluctuation of the lift arm cylinders 13, 13 due to the rapid flow of pressurized oil between one cylinder passage 55 and the accumulator passage 54).

[0111] In this embodiment, a valve device 41 in which an on / off switching valve 61, an electromagnetic control valve 71, and a shut-off valve 81 are integrated into a single unit was used as an example. However, the valve device is not limited to this, and may consist of, for example, only an on / off switching valve, which is a spool valve (switching valve). Alternatively, the valve device may consist of an on / off switching valve and an electromagnetic control valve. That is, the valve device can be configured as a spool valve having at least one spool hole in its housing.

[0112] In this embodiment, the example of using the travel vibration suppression device 31 on a wheel loader 1, which is a vehicle (work vehicle), was used. However, the travel vibration suppression device 31 is not limited to this and may also be used on vehicles other than wheel loaders, such as wheel shovels (work vehicles).

[0113] In the embodiment, the case where the hydraulic cylinder is a pair of lift arm cylinders 13, 13 was described as an example. However, the hydraulic cylinder is not limited to this, and may be a single lift arm cylinder, or it may be a cylinder other than a lift arm cylinder.

[0114] In this embodiment, the case in which the valve device 41 (on / off switching valve 61) is used in the running vibration suppression device 31 was described as an example. However, the valve device (spool valve) is not limited to this and can be widely used as a valve device (spool valve) incorporated into various machines such as industrial machinery and general machinery, or more specifically, as a valve device (spool valve) that provides communication and blockage between the pump passage, cylinder passage and accumulator passage.

[0115] 1 Wheel loader (vehicle, work vehicle) 13 Lift arm cylinder (hydraulic cylinder) 22 Hydraulic pump 31 Travel vibration suppression device 32 Accumulator 41 Valve device 42 Housing 50 Main spool hole (spool hole) 53 Pump passage 54 Accumulator passage 55 One cylinder passage (cylinder passage) 61 Switching valve 62 Main spool (spool) 62A First land (land) 62A1 Notch 62E First annular groove 62F Second annular groove 71 Solenoid control valve 81 Shut-off valve 84 Check valve

Claims

1. A housing provided with a spool hole, a pump passage connecting a hydraulic pump to the spool hole, a cylinder passage connecting a hydraulic cylinder to the spool hole, and an accumulator passage connecting an accumulator to the spool hole; a spool slidably mounted in the spool hole and moving between a first position and a second position in accordance with pilot pressure acting on one end thereof; the pump passage and the cylinder passage are positioned opposite each other across the accumulator passage in the direction in which the spool moves through the spool hole; the spool has a first annular groove that connects the pump passage and the accumulator passage when the spool is in the first position; and a second annular groove that connects the accumulator passage and the cylinder passage when the spool is in the second position. A valve device characterized by having a land provided that blocks the space between the accumulator passage and the cylinder passage when the spool is in the first position, and blocks the space between the pump passage and the accumulator passage when the spool is in the second position.

2. The valve device according to claim 1, characterized in that the pump passage is provided with a shut-off valve that shuts off the pump passage when the pressure in the pump passage exceeds a predetermined pressure, and the shut-off valve is provided with a check valve that allows flow only from the hydraulic pump to the accumulator.

3. The valve device according to claim 1, characterized in that the pilot pressure is supplied to one end of the spool via an electromagnetic control valve.

4. The valve device according to claim 1, characterized in that the land of the spool is provided with a notch at a position corresponding to the space between the cylinder passage and the accumulator passage.

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