Steering system and work vehicle

Abstract

To provide a steering device allowing a comfortable steering operation and a work vehicle.SOLUTION: A base member 43 supports an operation lever 41. A transmission mechanism 45 rotates the base member 43 around a shaft 45n for the base member by transmitting rotation of a front frame 2a relative to a rear frame 2b to the base member 43. The shaft 45n for the base member is arranged to be inclined so as to be located downward toward the front from the rear.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a steering device and a work vehicle.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2020-26230 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2020-26233 (Patent Document 2) disclose a steering device in an articulated work vehicle in which a front frame and a rear frame are connected. In this steering device, rotation based on the rotation angle of the front frame with respect to the rear frame is transmitted to a base member that supports a joystick lever for steering operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] ]] In the steering devices described in these publications, when an operator sitting in the driver's seat tries to perform a steering operation while placing an elbow on the armrest and gripping the joystick lever, the twisting motion of the elbow and wrist becomes an unnatural motion, which may cause fatigue to the operator.

[0005] An object of the present disclosure is to provide a steering device and a work vehicle capable of comfortable steering operation.

Means for Solving the Problems

[0006] One steering device of this disclosure is a steering device for a work vehicle having a rear frame and a front frame connected to the rear frame so as to be articulate. The steering device comprises an operating lever, a base member, and a transmission mechanism. The base member supports the operating lever. The transmission mechanism rotates the base member about a central axis by transmitting the rotation of the front frame relative to the rear frame to the base member. The central axis is inclined to be located downward as it is viewed from rear to front.

[0007] Another steering device of the present disclosure is a steering device for a work vehicle having a rear frame and a front frame connected to articulate with respect to the rear frame. This steering device comprises an armrest, an operating lever, and a base member. The base member supports the operating lever and rotates about a central axis in conjunction with the rotation of the front frame relative to the rear frame. The base member is inclined such that, in a side view, the extension of the central axis intersects with the armrest.

[0008] A work vehicle according to this disclosure comprises a rear frame, a front frame, an operating lever, a base member, and a transmission mechanism. The front frame is connected to the rear frame so as to be articulate. The base member supports the operating lever. The transmission mechanism rotates the base member about a central axis by transmitting the rotation of the front frame relative to the rear frame to the base member. The central axis is inclined so as to be located downward from rear to front.

[0009] Other work vehicles in this disclosure include a rear frame, a front frame, an armrest, an operating lever, and a base member. The front frame is connected to the rear frame so as to be articulate. The base member supports the operating lever and rotates about a central axis in conjunction with the rotation of the front frame relative to the rear frame. The base member is inclined so that, in a side view, the extension of the central axis intersects with the armrest. [Effects of the Invention]

[0010] According to this disclosure, a steering system and work vehicle that enable comfortable steering operation can be realized. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view of a wheel loader, an example of a work vehicle. [Figure 2] This figure shows the internal configuration of the cab in the wheel loader shown in Figure 1. [Figure 3] This figure shows the steering system in the wheel loader shown in Figure 1. [Figure 4] This is a perspective view showing the configuration of the transmission mechanism that transmits information about the actual vehicle frame angle θs_real to the base member of the lever unit. [Figure 5] Figure 4 shows a side view (A) and a top view (B) illustrating the configuration of the transmission mechanism. [Figure 6] This is a side view illustrating the inclination of the base member. [Figure 7] Figures (A) to (F) show the operation of the steering device and the state of the vehicle frame in the wheel loader shown in Figure 1. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described below with reference to the drawings.

[0013] In the specification and drawings, the same reference numerals are used for identical or corresponding components, and redundant descriptions are avoided. Furthermore, in the drawings, components may be omitted or simplified for the sake of clarity. Also, at least some of the embodiments and modifications may be combined in any way.

[0014] <Overall configuration of wheel loader 1> In an embodiment, a wheel loader 1 will be described as an example of a working machine. FIG. 1 is a side view of a wheel loader as an example of a working machine. FIG. 2 is a diagram showing the configuration inside the cab of the wheel loader shown in FIG. 1.

[0015] As shown in FIG. 1, the wheel loader 1 includes a vehicle body frame 2, a working machine 3, a traveling device 4, and a cab 5. The vehicle body of the wheel loader 1 is composed of the vehicle body frame 2, the cab 5, etc. The working machine 3 and the traveling device 4 are attached to the vehicle body of the wheel loader 1. The main body of the wheel loader 1 has a vehicle body and a traveling device 4.

[0016] The traveling device 4 is for traveling the vehicle body of the wheel loader 1 and includes traveling wheels 4a, 4b. The wheel loader 1 is a wheeled vehicle provided with traveling wheels 4a, 4b as traveling rotors on both sides in the left-right direction of the vehicle body. The wheel loader 1 can travel by itself when the traveling wheels 4a, 4b are rotationally driven, and can perform a desired operation using the working machine 3.

[0017] In this specification, the direction in which the wheel loader 1 travels straight is referred to as the front-rear direction of the wheel loader 1. In the front-rear direction of the wheel loader 1, the side where the working machine 3 is arranged with respect to the vehicle body frame 2 is defined as the front direction, and the side opposite to the front direction is defined as the rear direction. The left-right direction of the wheel loader 1 is a direction orthogonal to the front-rear direction when the wheel loader 1 on a flat ground is viewed in plan view. The right side and the left side in the left-right direction when looking in the front direction are the right direction and the left direction, respectively. The up-down direction of the wheel loader 1 is a direction orthogonal to the plane defined by the front-rear direction and the left-right direction. The side with the ground is the lower side and the side with air is the upper side in the up-down direction.

[0018] The vehicle body frame 2 includes a front frame 2a and a rear frame 2b. The front frame 2a is arranged in front of the rear frame 2b. The front frame 2a and the rear frame 2b are connected to each other so as to be rotatable (articulate) in the left-right direction by a connecting shaft 2c (FIG. 3).

[0019] A pair of steering cylinders 11a and 11b are attached across the front frame 2a and the rear frame 2b. Each of the steering cylinders 11a and 11b is a hydraulic cylinder. As the steering cylinders 11a and 11b expand and contract by the hydraulic oil from the steering pump, the traveling direction of the wheel loader 1 is changed left and right.

[0020] The front frame 2a and the rear frame 2b constitute a vehicle body frame 2 of an articulated structure. The wheel loader 1 is an articulated working machine in which the front frame 2a and the rear frame 2b are connected so as to be capable of bending operation.

[0021] The working machine 3 and a pair of traveling wheels (front wheels) 4a are attached to the front frame 2a. The working machine 3 is attached in front of the main body of the wheel loader 1. The working machine 3 is supported by the vehicle body of the wheel loader 1. The working machine 3 includes a boom 14 and a bucket 6. The bucket 6 is disposed at the tip of the working machine 3. The bucket 6 is a working tool for excavation and loading.

[0022] The base end portion of the boom 14 is rotatably attached to the front frame 2a by a boom pin 9. The bucket 6 is rotatably attached to the boom 14 by a bucket pin 17 located at the tip of the boom 14.

[0023] The working machine 3 further includes a bell crank 18 and a link 15. The bell crank 18 is rotatably supported by the boom 14 by a support pin 18a located approximately at the center of the boom 14. The link 15 is connected to a connection pin 18c provided at the tip end portion of the bell crank 18. The link 15 connects the bell crank 18 and the bucket 6.

[0024] The front frame 2a and the boom 14 are connected by a pair of boom cylinders 16. The boom cylinders 16 are hydraulic cylinders. The boom cylinders 16 rotate the boom 14 up and down around the boom pin 9. The base end of the boom cylinder 16 is attached to the front frame 2a. The tip of the boom cylinder 16 is attached to the boom 14.

[0025] The bucket cylinder 19 connects the bell crank 18 and the front frame 2a. The base end of the bucket cylinder 19 is attached to the front frame 2a. The tip of the bucket cylinder 19 is attached to a connecting pin 18b provided at the base end of the bell crank 18. The bucket cylinder 19 is a hydraulic actuator that rotates the bucket 6 up and down relative to the boom 14.

[0026] The rear frame 2b is fitted with the cab 5 where the operator sits, and a pair of running wheels (rear wheels) 4b. The box-shaped cab 5 is located behind the boom 14. The cab 5 is mounted on the vehicle frame 2. The cab 5 is mounted on the rear frame 2b.

[0027] As shown in Figure 2, the cab 5 contains a driver's seat 7 where the wheel loader operator sits. To the side of the driver's seat 7 are an operating lever 41, a console box 12, and an armrest 13.

[0028] The operating lever 41 is, for example, an operating lever for steering, and is operated by the operator. The operating lever 41 is positioned to extend upward from the front end of the console box 12.

[0029] The armrest 13 is the part on which the operator seated in the driver's seat 7 rests their elbow. The armrest 13 is located behind the control lever 41 and above the console box 12. This arrangement allows the operator seated in the driver's seat 7 to, for example, rest their left elbow on the armrest 13 while gripping and operating the control lever 41 with their left hand.

[0030] <Steering System 10> Next, the steering system 10 in the wheel loader shown in Figure 1 will be explained using Figure 3.

[0031] Figure 3 shows the steering system in the wheel loader shown in Figure 1. As shown in Figure 3, the steering system 10 of this embodiment includes an adjustment mechanism 21, a steering device 22, a controller 23, and a vehicle speed sensor 24.

[0032] The adjustment mechanism 21 adjusts the drive output of the steering cylinders 11a and 11b. The steering device 22 has an operating lever 41, etc., and the operator inputs the steering rotation instruction angle of the wheel loader 1. Based on the steering rotation instruction angle input to the steering device 22, the controller 23 instructs the adjustment mechanism 21 to adjust the drive output of the steering cylinders 11a and 11b. The vehicle speed sensor 24 detects the vehicle speed V of the wheel loader 1 and transmits it to the controller 23 as a detection signal.

[0033] In Figure 3, electrical signal transmission is shown with dotted lines, hydraulic transmission with solid lines, and sensor detection with dashed lines.

[0034] (Adjustment mechanism 21) As shown in Figure 3, the adjustment mechanism 21 adjusts the flow rate of oil supplied to the steering cylinders 11a and 11b. The adjustment mechanism 21 includes a hydraulic valve 31, a main pump 32, an electromagnetic pilot valve 33, and a pilot pump 34.

[0035] The hydraulic valve 31 is a flow control valve that adjusts the flow rate of oil supplied to the steering cylinders 11a and 11b in accordance with the input pilot pressure. For example, a spool valve is used for the hydraulic valve 31. The main pump 32 supplies the hydraulic fluid that operates the steering cylinders 11a and 11b to the hydraulic valve 31.

[0036] The hydraulic valve 31 has a valve body (not shown) that can move to the left steering position, the neutral position, and the right steering position. When the valve body in the hydraulic valve 31 is positioned in the left steering position, the steering cylinder 11a retracts and the steering cylinder 11b extends, reducing the actual vehicle frame angle θs_real and causing the vehicle to turn to the left.

[0037] When the valve body of the hydraulic valve 31 is positioned in the right steering position, the steering cylinder 11b contracts and the steering cylinder 11a extends, increasing the actual vehicle frame angle θs_real and causing the vehicle to turn to the right. When the valve body of the hydraulic valve 31 is positioned in the neutral position, the actual vehicle frame angle θs_real does not change.

[0038] The actual vehicle frame angle θs_real is 0° when wheel loader 1 is moving straight, a positive value when moving to the right, and a negative value when moving to the left.

[0039] The electromagnetic pilot valve 33 is a flow control valve that adjusts the flow rate or pressure of pilot oil supplied to the hydraulic valve 31 in response to a command from the controller 23. The pilot pump 34 supplies hydraulic fluid to the electromagnetic pilot valve 33 to operate the hydraulic valve 31. The electromagnetic pilot valve 33 is, for example, a spool valve and is controlled according to a command from the controller 23.

[0040] The electromagnetic pilot valve 33 has a valve body (not shown) that is movable to a left pilot position, a neutral position, and a right pilot position. When the valve body of the electromagnetic pilot valve 33 is positioned in the left pilot position, the hydraulic valve 31 is in the left steering position. When the valve body of the electromagnetic pilot valve 33 is positioned in the right pilot position, the hydraulic valve 31 is in the right steering position. When the valve body of the electromagnetic pilot valve 33 is positioned in the neutral position, the hydraulic valve 31 is in the neutral position.

[0041] As described above, the hydraulic valve 31 is controlled by controlling the pilot pressure or pilot flow rate from the electromagnetic pilot valve 33 in response to a command from the controller 23, thereby controlling the steering cylinders 11a and 11b.

[0042] (Controller 23) As shown in Figure 3, the controller 23 includes a processor and memory (not shown). The following processes are performed using the processor.

[0043] The controller 23 receives the detected value θi_detect from the lever angle sensor 46, the detected value θs_detect from the vehicle frame angle sensor 47, and the vehicle speed V_detect detected by the vehicle speed sensor 24. Based on these values, the controller 23 outputs an electromagnetic pilot valve control current output i to control the electromagnetic pilot valve 33.

[0044] The controller 23 determines the electromagnetic pilot valve control current output i based on the detected lever angle value θi_detect, the detected vehicle frame angle value θs_detect, and the detection signal V_detect from the vehicle speed sensor 24. Based on the determined electromagnetic pilot valve control current output i, the controller 23 issues a command to the electromagnetic pilot valve 33.

[0045] (Steering device 22) As shown in Figure 3, the steering device 22 includes a lever unit 25, a transmission mechanism 45, a lever angle sensor 46, and a vehicle body frame angle sensor 47.

[0046] [Lever Unit 25] The lever unit 25 includes an operating lever 41, a support portion 42, a base member 43, a biasing member 44, and a regulating portion 48.

[0047] The support portion 42 is fixed to the frame 12f of the console box 12. The support portion 42 may also be part of the frame of the console box 12.

[0048] The base member 43 is rotatably supported by the support portion 42. The base member 43 has an axis 43a. The axis 43a is rotatably supported by the support portion 42. This allows the base member 43 to rotate relative to the support portion 42 around the axis 43a. Alternatively, the base member 43 can also be configured to rotate relative to the support portion 42 by having an axis in the support portion 42, a through hole in the base member 43, and the axis of the support portion 42 passing through the through hole in the base member 43.

[0049] The operating lever 41 is rotatably positioned relative to the base member 43 or the support portion 42. For example, the operating lever 41 is configured to be rotatable relative to the base member 43 by forming a through hole at its base end and inserting the shaft 43a into the through hole. Alternatively, the support portion 42 may have a shaft, and the shaft may pass through the through hole at the base end of the operating lever 41, thereby configuring the operating lever 41 to be rotatable relative to the support portion 42.

[0050] The biasing member 44 is, for example, a spring member, and is interposed between the operating lever 41 and the base member 43. The biasing member 44 biases the operating lever 41 relative to the base member 43 to the base reference position 43b. The operating lever 41 is subjected to a reaction force in both cases: when it is rotated to the right from the base reference position 43b and when it is rotated to the left from the base reference position 43b. When the operator is not gripping the operating lever 41, the operating lever 41 is positioned at the base reference position 43b by biasing forces from the left and right rotation directions.

[0051] The restricting portion 48 is provided on the base member 43. The restricting portion 48 has contact portions 481 and 482. The contact portions 481 and 482 restrict the rotation range of the operating lever 41 relative to the base member 43 to within a predetermined angular range. The state in which the longitudinal direction of the operating lever 41 is positioned at the base reference position 43b is considered to be the state in which the rotation angle of the operating lever 41 relative to the base member 43 is zero. When the operating lever 41 is rotated to the right relative to the base member 43, the rotation angle of the operating lever 41 relative to the base member 43 is represented as positive. When the operating lever 41 is rotated to the left relative to the base member 43, the rotation angle of the operating lever 41 relative to the base member 43 is represented as negative. The actual relative angle of the operating lever 41 relative to the base member 43 is indicated by θr_real.

[0052] When the operating lever 41 is rotated to the right Yr relative to the base member 43, and the actual relative angle θr_real of the operating lever 41 with respect to the base member 43 reaches θ1 (a positive value), the operating lever 41 comes into contact with the contact portion 481 of the base member 43 and can no longer be rotated to the right. Similarly, when the operating lever 41 is rotated to the left Yl relative to the base member 43, and the relative angle θr_real reaches θ1' (a negative value), the operating lever 41 comes into contact with the contact portion 482 of the base member 43 and can no longer be rotated to the left. In other words, the operating lever 41 is set to be rotatable within the range of angles θ1' to θ1 relative to the base member 43. The predetermined angles θ1' and θ1 are set to, for example, -10 degrees and 10 degrees. The absolute values ​​of the predetermined angle θ1 and the predetermined angle θ1' may be the same or different.

[0053] Furthermore, the operating lever 41 is restricted not only by the base member 43 but also by the support portion 42. The support portion 42 has a contact portion 49 against which the operating lever 41 abuts. The contact portion 49 has a right contact portion 491 and a left contact portion 492. The support portion 42 restricts the base member 43 within a predetermined angle range of θ2' (negative value) to θ2 (positive value) with respect to the support reference position 42b. The predetermined angles θ2' and θ2 are set to, for example, -20 degrees and 20 degrees. The absolute values ​​of the predetermined angle θ2 and the predetermined angle θ2' may be the same or different.

[0054] The front frame 2a and the base member 43 are connected by a transmission mechanism 45. Through this, information about the actual vehicle frame angle θs_real, which is the rotation angle of the front frame 2a relative to the rear frame 2b, is mechanically input to the base member 43 via the transmission mechanism 45. As a result, the rotation angle based on the actual vehicle frame angle θs_real is transmitted to the base member 43.

[0055] [Lever Angle Sensor 46] The lever angle sensor 46 is configured, for example, by a potentiometer. The lever angle sensor 46 detects the actual lever angle θi_real of the operating lever 41 relative to the support part 42 as the detected lever angle value θi_detect.

[0056] When the longitudinal direction of the operating lever 41 is maintained at the support reference position 42b, the adjustment mechanism 21 controls the actual vehicle frame angle θs_real to be 0°. In this state, the front frame 2a is positioned along the front-rear direction relative to the rear frame 2b.

[0057] When the operating lever 41 is positioned at the support reference position 42b, the rotation angle of the operating lever 41 relative to the support portion 42 is considered to be zero. When the operating lever 41 is rotated to the right relative to the support portion 42, the rotation angle of the operating lever 41 relative to the support portion 42 is represented as positive. When the operating lever 41 is rotated to the left relative to the support portion 42, the rotation angle of the operating lever 41 relative to the support portion 42 is represented as negative.

[0058] The controller 23 controls the vehicle frame so that the actual vehicle frame angle θs_real corresponds to the actual lever angle θi_real of the operating lever 41 from the support reference position 42b. The actual base angle of the base member 43 with respect to the support part 42 is θb_real. The actual base angle θb_real corresponds to the rotation angle of the base reference position 43b of the base member 43 from the support reference position 42b.

[0059] Furthermore, when the base reference position 43b is positioned at the support reference position 42b, the rotation angle of the base member 43 relative to the support portion 42 is considered to be zero. When the base member 43 is rotated to the right relative to the support portion 42, the rotation angle of the base member 43 relative to the support portion 42 is represented as positive. When the base member 43 is rotated to the left relative to the support portion 42, the rotation angle of the base member 43 relative to the support portion 42 is represented as negative.

[0060] [Vehicle frame angle sensor 47] The vehicle frame angle sensor 47 detects the actual vehicle frame angle θs_real as the detected value θs_detect of the vehicle frame angle. The vehicle frame angle sensor 47 is located near the connecting shaft 2c, which is positioned between the steering cylinders 11a and 11b, or on the shaft 45n for the base member of the base member 43, which is included in the transmission mechanism 45 described later. The vehicle frame angle sensor 47 is configured, for example, by a potentiometer. The vehicle frame angle sensor 47 sends the detected value θs_detect of the vehicle frame angle as a detection signal to the controller 23.

[0061] Furthermore, each of the steering cylinders 11a and 11b may be provided with a cylinder stroke sensor for detecting the cylinder stroke. The detected values ​​from these cylinder stroke sensors may be sent to the controller 23, thereby detecting the vehicle frame angle θs_detect.

[0062] Furthermore, the transmission mechanism 45, described later, ensures that the vehicle frame angle θs_real and the base angle θb_real, which is the rotation angle of the base member 43 relative to the support portion 42, are in a corresponding positional relationship. For this reason, a vehicle frame angle sensor 47 may be provided on the shaft 43a of the base member 43. This is because the vehicle frame angle can be detected by detecting the rotation angle of the base member 43 relative to the support portion 42.

[0063] [Transmission mechanism 45] Figure 4 is a perspective view showing the configuration of the transmission mechanism that transmits information of the actual vehicle frame angle θs_real to the base member of the lever unit. Figure 5 is a side view (A) and a top view (B) showing the configuration of the transmission mechanism shown in Figure 4.

[0064] As shown in Figure 4, the transmission mechanism 45 transmits information about the actual vehicle frame angle θs_real to the base member 43, and rotates the base member 43 to a position corresponding to the actual vehicle frame angle θs_real.

[0065] The transmission mechanism 45 is a mechanism that includes a link. The transmission mechanism 45 has a rotating shaft 45b, a rod 45c, a connecting part 45d, a link member 45e, a rotating shaft 45f, and a transmission member TM.

[0066] Bracket 45a is attached to the front frame 2a, for example, by bolts. The position of bracket 45a is fixed to the front frame 2a. Bracket 45a rises upward from the top surface of the front frame 2a.

[0067] The rod 45c is a push-pull rod. The rod 45c is connected to the bracket 45a via a pivot shaft 45b. This makes the rod 45c rotatably connected to the bracket 45a. The pivot shaft 45b extends, for example, in the vertical direction. This makes the rod 45c rotatable relative to the front frame 2a, for example, in the front-rear, left-right, and right-hand planes.

[0068] The link member 45e is made of, for example, a flat plate. The link member 45e has a first end 45e1 and a second end 45e2 that face each other in its longitudinal direction. The link member 45e is connected to the rod 45c at the first end 45e1 via a connecting portion 45d. The connecting portion 45d is made of, for example, a ball joint. As a result, the link member 45e is rotatable relative to the rod 45c.

[0069] The link member 45e has a pivot shaft 45f at its second end 45e2. The pivot shaft 45f extends upward from the link member 45e. The pivot shaft 45f is attached and fixed to the link member 45e, and its position is fixed relative to the link member 45e. Therefore, when the link member 45e rotates, the pivot shaft 45f also rotates together with the link member 45e.

[0070] The transmission member TM transmits rotational force to the base member 43 while maintaining the rotational direction of the rotating shaft 45f when the link member 45e rotates. The transmission member TM includes a first shaft 45h, a rotating part 45j, a second shaft 45l (connecting shaft), a shaft for the base member 45n, and universal joints 45g, 45i, 45k, and 45m.

[0071] The first shaft 45h is connected to the second end 45e2 of the link member 45e via a rotating shaft 45f and a universal joint 45g. The universal joint 45g is connected between the rotating shaft 45f and the first shaft 45h. This allows the first shaft 45h to rotate together with the rotating shaft 45f, and the joint angle between the first shaft 45h and the rotating shaft 45f can be changed. The first shaft 45h has, for example, a telescopic structure. This allows the first shaft 45h to extend and retract in the axial direction.

[0072] The rotating part 45j is connected to the first shaft 45h via a universal joint 45i. As a result, the rotating part 45j can rotate together with the first shaft 45h, and the joint angle between the rotating part 45j and the first shaft 45h can be changed.

[0073] The second shaft 45l is connected to the rotating part 45j via a universal joint 45k. This allows the second shaft 45l to rotate together with the rotating part 45j, and the joint angle between the rotating part 45j and the second shaft 45l can be changed. The second shaft 45l has, for example, a telescopic structure. This allows the second shaft 45l to extend and retract in the axial direction.

[0074] The shaft 45n for the base member is connected to the second shaft 45l via a universal joint 45m. This allows the shaft 45n to rotate together with the second shaft 45l, and the joint angle between the second shaft 45l and the shaft 45n can be changed. The shaft 45n for the base member is fixed to the base member 43. This allows the base member 43 to rotate together with the shaft 45n for the base member. The shaft 45n for the base member may be integrated with the shaft 43a (Figure 3), or it may be a separate component. The shaft 45n for the base member or the shaft 43a corresponds to the "central shaft".

[0075] As shown in Figure 5(A), the transmission mechanism 45 has a portion located outside the cab 5 and a portion located inside the cab 5. The rotating shaft 45b, rod 45c, connecting portion 45d, and link member 45e of the transmission mechanism 45 are located outside the cab 5 and below the cab 5.

[0076] The rotating shaft 45f is positioned both externally and internally to the cab 5. The rotating shaft 45f is inserted into a through-hole in the floor 5F of the cab 5. The rotating shaft 45f is attached to the floor 5F of the cab 5 via a bearing. This allows the rotating shaft 45f to rotate relative to the floor 5F of the cab 5.

[0077] The transmission member TM of the transmission mechanism 45 is located inside the cab 5. The universal joint 45g of the transmission mechanism 45 is connected to the end (upper end) of the rotating shaft 45f, which is located inside the cab 5. The universal joint 45k, the second shaft 45l, the universal joint 45m, and the shaft 45n for the base member of the transmission mechanism 45 are located inside the console box 12.

[0078] The console box 12 is rotatable around axis BC. This allows the console box 12 to rotate between an operating state, where the operator can operate the control levers, and an upright state, where the console box is flipped up.

[0079] As shown in Figure 5(B), in a top view, the first direction in which the front frame 2a rotates relative to the rear frame 2b due to articulation is opposite to the second direction in which the link member 45e rotates around the rotation axis 45f. In a top view, if the front frame 2a rotates around the connecting axis 2c relative to the rear frame 2b by, for example, counterclockwise R1, the link member 45e rotates clockwise R3 around the rotation axis 45f. Also in a top view, if the front frame 2a rotates around the connecting axis 2c relative to the rear frame 2b by, for example, clockwise R2, the link member 45e rotates counterclockwise R4 around the rotation axis 45f.

[0080] In a top view, the rotation axis 45f is located on the opposite side of the articulation center AC between the rear frame 2b and the front frame 2a relative to the rod 45c. Here, the articulation center AC refers to the axis center of the connecting shaft 2c. In this embodiment, the rotation axis 45f is located to the left of the rod 45c (lower side in Figure 5(B)), and the articulation center AC is located to the right of the rod 45c (upper side in Figure 5(B)).

[0081] In a top view, the distance LB from the connection point 45d between the rod 45c and the link member 45e to the rotation axis 45f is greater than the distance LA from the articulation center AC to the connection point (rotation axis 45b) between the rod 45c and the front frame 2a (bracket 45a).

[0082] As described above, the transmission member TM transmits rotational force to the base member 43 (Figure 3) while maintaining the rotational direction of the rotation axis 45f when the link member 45e rotates. Here, "rotational direction" refers to the rotational direction when viewed from the end of the rotating member to which the rotational force is transmitted (transmission destination) to the end of the rotating member to which the rotational force is transmitted (transmission source).

[0083] For example, in the state shown in Figure 5(B), when viewed from above, if the front frame 2a rotates to the left (counterclockwise R1) relative to the rear frame 2b, and the link member 45e rotates clockwise R3, then the first shaft 45h also rotates clockwise when viewed from above, and the second shaft 45l and the shaft for the base member 45n also rotate clockwise when viewed from the front. As a result, the base member 43 also rotates clockwise (to the left in Figure 3) when viewed from the front.

[0084] Furthermore, for example, in the state shown in Figure 5(B), when the front frame 2a rotates to the right (clockwise R2) relative to the rear frame 2b in a top view, and the link member 45e rotates counterclockwise R3, the first shaft 45h also rotates counterclockwise in a top view, and the second shaft 45l and the shaft for the base member 45n also rotate counterclockwise in a front view. As a result, the base member 43 also rotates counterclockwise (to the right in Figure 3) in a front view.

[0085] In the above, "top view" refers to a viewpoint looking down from above the wheel loader 1. Also, in the above, "front view" refers to a viewpoint looking at the wheel loader 1 from the front to the rear.

[0086] <Inclination of base member 43> Next, the inclination of the base member 43 will be explained using Figure 6.

[0087] Figure 6 is a side view illustrating the inclination of the base member. As shown in Figure 6, the shaft 45n for the base member is inclined so that it is located downward as it is viewed from the rear to the front in a side view. Specifically, the axis AX1 of the shaft 45n for the base member is inclined so that it is located downward as it is viewed from the rear to the front in a side view. Therefore, the front end of the shaft 45n for the base member is located lower than the rear end.

[0088] Furthermore, the shaft 45n for the base member is inclined with respect to the second shaft 45l in a side view. Specifically, the axis AX1 of the shaft 45n for the base member is inclined with respect to the axis AX2 of the second shaft 45l in a side view. The axis AX1 of the shaft 45n for the base member slopes downward from the point of intersection with the axis AX2 of the second shaft 45l. In other words, the axis AX1 of the shaft 45n for the base member is inclined to be located downward as it extends forward from the point of intersection with the axis AX2 of the second shaft 45l. The axis AX1 of the shaft 45n for the base member is located below the height of the axis AX2 of the second shaft 45l. Also, the axis AX2 of the second shaft 45l extends approximately parallel to the top surface of the console box 12.

[0089] Furthermore, the base member 43 is positioned at an angle so that, in a side view, the extension of the base member shaft 45n intersects with the armrest 13. The extension of the base member shaft 45n refers to a hypothetical straight line extending from the base member shaft 45n, where the axis AX1 of the base member shaft 45n is located. The side view refers to a viewpoint seen from the left or right direction (view from right to left or left to right), as shown in Figure 6.

[0090] In a side view, the base member 43 is positioned at an angle such that the extension of the shaft 45n for the base member intersects with the upper surface US of the armrest 13. The upper surface US of the armrest 13 is the surface on which an operator seated in the driver's seat 7 can rest their elbow. In a side view, the extension of the shaft 45n for the base member also intersects with the upper surface of the console box 12 located directly below the armrest 13.

[0091] In this embodiment, the transmission mechanism 45 has been described as a mechanical link mechanism including a rod 45c, but the transmission mechanism 45 is not limited to a mechanical link mechanism. The transmission mechanism 45 in this embodiment may have a drive source such as a motor. The base member 43 may be rotated by this drive source such as a motor by a base angle θb_real corresponding to the vehicle frame angle θs_real detected by the vehicle frame angle sensor 47.

[0092] <Control operation of wheel loader 1> Next, the control operation of the wheel loader 1 in this embodiment will be described.

[0093] Figures 7(A) to 7(F) show the operation of the steering system and the state of the vehicle frame.

[0094] As shown in Figure 7(A), the base reference position 43b of the base member 43 coincides with the support reference position 42b of the support portion 42. The longitudinal direction of the operating lever 41 also coincides with the support reference position 42b.

[0095] As shown in Figure 3, in this state (also called the initial position), the actual lever angle θi_real caused by the operating lever 41 is zero. At this time, the electromagnetic pilot valve 33 is in the neutral position. The hydraulic valve 31 is also in the neutral position. Therefore, oil is not supplied to or discharged from the left and right steering cylinders 11a and 11b, and the actual vehicle frame angle θs_real is maintained at zero. Thus, since the actual vehicle frame angle θs_real is also zero, the base member 43 is also in the initial position.

[0096] Then, the operator applies an operating force to rotate the operating lever 41 from the support reference position 42b, for example, to the right. When this operating force exceeds the initial biasing force of the biasing member 44, the operating lever 41 rotates to the right, as shown in Figure 7(B), and the actual lever angle θi_real increases. As the lever moves to the right, the relative angle θr_real with the base member 43 increases, so the reaction force applied to the operating lever 41 by the biasing member 44 becomes larger.

[0097] The lever angle sensor 46 (Figure 3) detects the actual lever angle θi_real of the operating lever 41 operated by the operator as the detected lever angle value θi_detect. Next, the vehicle frame angle sensor 47 (Figure 3) detects the actual vehicle frame angle θs_real as the detected vehicle frame angle value θs_detect.

[0098] At this time, due to the delay in the response of the left and right steering cylinders 11a and 11b, the actual vehicle frame angle θs_real is zero. Therefore, the detected value of the vehicle frame angle θs_detect, which is the value detected by the vehicle frame angle sensor 47, is zero. Since the actual vehicle frame angle θs_real is almost zero, the base member 43 is also not rotating. Therefore, as shown in Figure 7(B), when the operating lever 41 is rotated to the right, the operating lever 41 is rotated to the right with respect to the base reference position 43b of the base member 43. In addition, the biasing member 44 biases the operating lever 41 to return to the base reference position 43b (which can also be called the support reference position 42b in the state shown in Figure 7(B)).

[0099] Next, the controller 23 (Figure 3) determines the electromagnetic pilot valve control current output i based on the detected lever angle value θi_detect, the detected vehicle frame angle value θs_detect, and the detection signal V_detect from the vehicle speed sensor 24. Based on the determined electromagnetic pilot valve control current output i, the controller 23 issues a command to the electromagnetic pilot valve 33.

[0100] When the operating lever 41 is rotated to the right, the electromagnetic pilot valve 33 takes the right pilot position, and pilot pressure controlled by the electromagnetic pilot valve 33 is supplied to the hydraulic valve 31. Due to the supply of pilot pressure, the hydraulic valve 31 takes the right steering position, and main hydraulic pressure is supplied to the steering cylinders 11a and 11b so as to extend the steering cylinder 11a and retract the steering cylinder 11b.

[0101] As a result, the actual vehicle frame angle θs_real gradually increases, and the front frame 2a rotates to the right relative to the rear frame 2b. This change in the actual vehicle frame angle θs_real is reflected in the angle of the base member 43 via the transmission mechanism 45.

[0102] In other words, as shown in Figure 7(C), the angle of the base member 43 also rotates to a position corresponding to the vehicle frame angle θs_real. As the base member 43 rotates toward the rotation position of the operating lever 41 in this way, the deviation angle θr_real between the actual lever angle θi_real and the actual base angle θb_real becomes smaller, and therefore the biasing force of the biasing member 44 decreases.

[0103] As shown in Figure 7(D), when the operator stops the control lever 41 at a predetermined actual lever angle θi_real = θa, the actual vehicle frame angle θs_real gradually increases, so the difference angle θdiff becomes smaller.

[0104] Then, as shown in Figure 7(E), when the actual vehicle frame angle θs_real moves and the base angle θb_real becomes θa, the difference angle θdiff becomes zero. At this time, the electromagnetic pilot valve 33 takes the neutral position, and the hydraulic valve 31 also takes the neutral position. For this reason, no oil is supplied to or discharged from the left and right steering cylinders 11a and 11b. Also, since the base angle θb_real is proportional to the vehicle frame angle θs_real, the actual vehicle frame angle θs_real is maintained at θc, which is obtained by converting the rotation angle θa based on this proportional relationship. Furthermore, as shown in Figure 7(E), the base member 43 also rotates to the right by θa relative to the support part 42, and the operating lever 41 is positioned at the base reference position 43b of the base member 43.

[0105] Next, the operator returns the operating lever 41 from the right-side position (θi_real=θa) towards the support reference position 42b (θi_real=zero). As shown in Figure 7(F), the operating lever 41 is rotated counterclockwise so that it is positioned at the support reference position 42b.

[0106] Before returning the operating lever 41 to the support reference position 42b relative to the support part 42 (the state shown in Figure 7(E)), the positional relationship between the operating lever 41 and the base member 43 is the same as that shown in Figure 7(A). Therefore, when moving the operating lever 41, the reaction force at the start of movement is the same as the reaction force at the start of movement from the initial position. In other words, in this embodiment, since the base member 43 rotates to a position corresponding to the actual vehicle frame angle θs_real, the reaction force applied to the operation is determined according to the state of the electromagnetic pilot valve 33 (intermediate position, right pilot position, left pilot position), regardless of the position of the operating lever 41.

[0107] When the operating lever 41 is rotated counterclockwise to the support reference position 42b, the actual vehicle frame angle θs_real is θc due to the delay in response of the left and right steering cylinders 11a and 11b. Also, since the actual base angle θb_real is θa, similar to the actual vehicle frame angle θs_real, the biasing member 44 biases the operating lever 41 relative to the base member 43 to the state shown in Figure 7(F).

[0108] As described above, the actual vehicle frame angle θs_real is at state θc, so the difference angle θdiff decreases from zero to negative. Then the electromagnetic pilot valve 33 takes the left pilot position, pilot pressure is supplied to the hydraulic valve 31, and the hydraulic valve 31 takes the left steering position. As a result, hydraulic pressure is supplied so that the steering cylinder 11b extends and the steering cylinder 11a contracts.

[0109] This hydraulic pressure supply causes the actual vehicle frame angle θs_real to gradually decrease from the rotation angle θc. This change in the actual vehicle frame angle θs_real is reflected in the base member 43 via the transmission mechanism 45, and the base member 43 rotates in accordance with the change in the actual vehicle frame angle θs_real.

[0110] Then, when the actual vehicle frame angle θs_real becomes zero, the difference with the actual lever angle θi_real (=0) becomes zero. At this time, the electromagnetic pilot valve 33 takes the neutral position, and the hydraulic valve 31 is also in the neutral position. As a result, no oil is supplied to or discharged from the left and right steering cylinders 11a and 11b, and the actual vehicle frame angle θs_real returns to and is maintained at zero. As a result, the front frame 2a returns to an orientation aligned with the front-to-rear direction relative to the rear frame 2b.

[0111] Furthermore, as the actual vehicle frame angle θs_real decreases, the base member 43 rotates so that the actual base angle θb_real also becomes zero, returning to the initial position (θb_real=0) as shown in Figure 7(A).

[0112] Note that the procedure for rotating the operating lever 41 to the left is the same as described above, so it is omitted here.

[0113] <Effects> Next, the effects of this embodiment will be described.

[0114] In Figure 6, the operator, seated in the driver's seat 7, rests their elbow on the armrest 13 and grips the control lever 41 to operate the steering wheel. In this case, the operator operates the control lever 41 by moving their arm around the elbow resting on the armrest 13.

[0115] If the axis AX1 of the shaft 45n for the base member extends horizontally, rotating the operating lever 41, for example, left or right, would result in an unnatural twisting motion of the elbow or wrist, potentially causing fatigue in the operator.

[0116] In contrast, in this embodiment, as shown in Figure 6, the shaft 45n for the base member is inclined and positioned so that it is located downward as it moves from rear to front. As a result, the extension of the axis AX1 of the shaft 45n for the base member passes near the elbow resting on the armrest 13. Therefore, it becomes ergonomically easier for the operator to operate the control lever 41 by moving their arm around the elbow resting on the armrest 13, enabling comfortable steering operation.

[0117] Furthermore, in this embodiment, as shown in Figure 6, the shaft 45n for the base member is inclined so as to be located below the axis AX2 of the second shaft 45l, with the universal joint 45m as the fulcrum. This allows the extension of the axis AX1 of the shaft 45n for the base member to pass near the elbow resting on the armrest 13. Also, since the shaft 45n for the base member is connected to the second shaft 45l via the universal joint 45m, it becomes easy to position the base member 43 in the console box 12 at an appropriate inclination angle with respect to the second shaft 45l.

[0118] In this embodiment, as shown in Figure 4, the transmission mechanism 45 includes a rod 45c rotatably connected to the front frame 2a and a link member 45e rotatably connected to the rod 45c. The rotation axis 45f of the link member 45e is connected to the first axis 45h. This allows the transmission mechanism 45 to transmit the rotation of the front frame 2a relative to the rear frame 2b to the base member 43.

[0119] Furthermore, in this embodiment, as shown in Figure 6, the base member 43 is positioned at an angle such that, in a side view, the extension of the axis AX1 of the base member shaft 45n intersects with the armrest 13. As a result, the extension of the axis AX1 of the base member shaft 45n passes near the elbow resting on the armrest 13. Therefore, it becomes ergonomically easier for the operator to operate the control lever 41 by moving their arm around the elbow resting on the armrest 13, enabling comfortable steering operation.

[0120] Furthermore, in this embodiment, as shown in Figure 6, the base member 43 is positioned at an angle such that, in a side view, the extension of the axis AX1 of the base member shaft 45n intersects with the upper surface US of the armrest 13. This causes the extension of the axis AX1 of the base member shaft 45n to pass even closer to the elbow resting on the armrest 13. As a result, it becomes ergonomically easier for the operator to operate the control lever 41 by moving their arm around the elbow resting on the armrest 13, enabling comfortable steering operation.

[0121] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0122] 1 Wheel loader, 2 Body frame, 2a Front frame, 2b Rear frame, 2c Connecting axle, 3 Work equipment, 4 Running gear, 4a,4b Driving wheels, 5 Cab, 5F Floor, 6 Bucket, 7 Driver's seat, 9 Boom pin, 11a,11b Steering cylinder, 10 Steering system, 12 Console box, 12f Frame, 13 Armrest, 14 Boom, 15 Link, 16 Boom cylinder, 17 Bucket pin, 18 Bell crank, 18a Support pin, 18b,18c Connecting pin, 19 Bucket cylinder, 21 Adjustment mechanism, 22 Steering device, 23 Controller, 24 Vehicle speed sensor, 25 Lever unit, 31 Hydraulic valve, 32 Main pump, 33 Solenoid pilot valve, 34 Pilot pump, 41 Operating lever, 42 Support part, 43 Base member, 43a Axle, 44 45 biasing member, 45 transmission mechanism, 45a bracket, 45b, 45f rotating shaft, 45c rod, 45d connection part, 45e link member, 45e1 first end, 45e2 second end, 45g, 45i, 45k, 45m universal joint, 45h first shaft, 45j rotating part, 45l second shaft, 45n shaft for base member, 46 lever angle sensor, 47 body frame angle sensor, 48 regulating part, 49, 481, 482 contact part, 491, 492 contact portion, AC articulated center, BC rotating center, TM transmission member.

Claims

1. A steering system for a work vehicle having a rear frame and a front frame connected to the rear frame so as to be articulate, Operating lever and A base member that supports the aforementioned operating lever, The system includes a transmission mechanism that transmits the rotation of the front frame relative to the rear frame to the base member, thereby causing the base member to rotate around its central axis. A steering device in which the aforementioned central axis is inclined and positioned so as it moves from rear to front.

2. The aforementioned transmission mechanism is The first axis and, A rotating part connected to the first shaft, It has a second shaft connected to the aforementioned rotating part, The second shaft is connected to the central shaft via a joint, The steering device according to claim 1, wherein the central axis is inclined to be located below the axis of the second axis with the joint as a fulcrum.

3. The aforementioned transmission mechanism is A rod rotatably connected to the front frame, The device further comprises a link member having a first end and a second end, the first end being rotatably connected to the rod, and the second end having a pivot axis, The steering device according to claim 2, wherein the rotating shaft of the link member is connected to the first shaft.

4. A steering system for a work vehicle having a rear frame and a front frame connected to the rear frame so as to be articulate, Armrest and, Operating lever and The system includes a base member that supports the operating lever and rotates about a central axis in conjunction with the rotation of the front frame relative to the rear frame, A steering device in which the base member is inclined and positioned such that, in a side view, the extension of the central axis intersects with the armrest.

5. The steering device according to claim 4, wherein the base member is inclined and positioned such that, in a side view, the extension of the central axis intersects with the upper surface of the armrest.

6. Rear frame and A front frame is connected to the rear frame so as to be articulated with respect to the rear frame, Operating lever and A base member that supports the aforementioned operating lever, The system includes a transmission mechanism that transmits the rotation of the front frame relative to the rear frame to the base member, thereby causing the base member to rotate around its central axis. A work vehicle in which the aforementioned central axis is positioned at an angle so that it is located downwards as it is viewed from the rear to the front.

7. Rear frame and A front frame is connected to the rear frame so as to be articulated with respect to the rear frame, Armrest and, Operating lever and The system includes a base member that supports the operating lever and rotates about a central axis in conjunction with the rotation of the front frame relative to the rear frame, A work vehicle in which the base member is inclined and positioned such that, in a side view, the extension of the central axis intersects with the armrest.

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