JP2001270457A - Steering device for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate by means of a simple steering operation device a steering device for a working vehicle such that each wheel is steered about two steering axes P1 and P2. SOLUTION: The end case 13a of a wheel drive case 13 supports an intermediate case 14 in such a manner that the intermediate case is free to oscillate about the first steering axis P1 and the intermediate case 14 supports an axle case 15 in such a manner that the axle case is free to oscillate about the second steering axis P2. A pitman arm oscillates the intermediate case 14. For a link mechanism 40 comprising a movable link 43 which the axle case 15 includes, a fixed link 42 which the end case 13c includes, and a connecting link 41 extending between both links 42 and 43, the axle case 15 oscillates as the intermediate case 14 oscillates. The fixed link 42 is connected to the portion 13e of the pivot part 13c of the end case 13 which protrudes from a connection 14d which the axle case 15 includes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle in which left and right wheel support portions of a vehicle body support an intermediate support so as to be swingable around a first steering shaft centering vertically, and the left wheel is rotatably supported. A wheel supporting the right wheel so as to be rotatable around a second steering axis centering vertically on the vehicle body at the free end side of the left intermediate support. The present invention relates to a work vehicle steering device in which a support is swingably supported on a free end side of the right intermediate support around a second vertical steering axis of the vehicle body.

[0002]

2. Description of the Related Art For example, in a farm tractor, when the headland is turned with a small turning radius, the headland becomes smaller or the headland can be moved quickly so that the headland can run advantageously and work efficiently. For this reason, the working vehicle is configured to swing the intermediate support relative to the vehicle body around the first steering axis, and to move the wheel support relative to the intermediate support around the second steering axis. A configuration in which the mounting direction of the wheel with respect to the vehicle body is changed by both swinging and swinging, and the mounting direction of the wheel with respect to the vehicle body is changed by steering the wheel with only one steering axis. In comparison, the distance between the wheel and the vehicle body must be small so that the wheel can be steered to the desired maximum turning angle, and the tread is reduced, while the wheel is moved to the desired maximum turning angle. It is possible to steer the vehicle body.
For example, Japanese Utility Model Application Laid-Open No. 56-36574 and USP
As shown in 5046577, an axle supporting the wheels so as to be steerable at both left and right ends is swingably supported on the vehicle body at an intermediate portion, and the axle is swung with respect to the vehicle body, and the wheels are mounted on the axle. When the wheel is steered to a desired maximum turning angle, the wheel is moved sideways with respect to the vehicle body in order to steer the wheel to the desired maximum turning angle, as compared to a configuration in which the mounting direction of the wheel with respect to the vehicle body is changed by swinging the wheel. While the maximum stroke displaced in the direction is set to a small stroke, the vehicle can be steered by steering the wheels to a desired maximum turning angle.

[0003]

SUMMARY OF THE INVENTION As described above, the first and the second
2) The steering system with both steering axes is equipped with a pitman arm interlocked with tie rods on the left and right intermediate supports, and a hydraulic system for operating this pitman arm. When the intermediate handle is linked to the steering handle and the steering handle is rotated, the left and right intermediate supports are configured to swing with respect to the wheel support of the vehicle body. Then, a link mechanism for connecting the wheel support to the wheel support of the vehicle body is provided, and when the intermediate support is swingingly operated with respect to the wheel support, the wheel support is operated by the action of the link mechanism in conjunction with this. It is advantageous that the left and right wheels can be steered by a relatively simple steering operation device if the intermediate support is configured to swing in a predetermined direction.

In this case, as the wheels are steered, if the tire seat portion of the rim or the tire hits the link mechanism,
The maximum turning angle of the wheel cannot be made sufficiently large. However, so that the link mechanism is not likely to hinder wheel steering,
If the link constituting the link mechanism is made long or has a complicated shape, the link mechanism becomes complicated. Also, if the link or the like becomes long or complicated, it is necessary to increase the size so as to have a predetermined strength regardless of the shape, and the link mechanism becomes larger and heavier. Also, for example, when the fixed link provided in the wheel support and the movable link provided in the wheel support are located apart from each other in the up-down direction of the vehicle body, the link connecting the two links becomes longer and has a complicated shape, A similar problem occurs. An object of the present invention is to steer a work vehicle that can steer by adopting a relatively simple structure or a light and small steering operation device while steering wheels around two steering axes. To provide an orientation device.

[0005]

The constitution, operation and effect of the invention according to claim 1 are as follows.

[Structure] An intermediate support is supported by left and right wheel support portions of a vehicle body so as to be swingable around a first steering shaft centering vertically, and a left wheel is rotatably supported. A wheel support for swingably supporting the body on the free end side of the intermediate support on the left side around a second steering axis centering vertically on the vehicle body and rotatably supporting the right wheel, In a steering apparatus for a working vehicle, the left and right intermediate supports are swingably supported on a free end side of a right intermediate support around a second steering axis in a vertical direction of the vehicle body, the left and right intermediate supports are rotated by a steering handle. A steering operation mechanism linked to the steering handle so as to be swingably operated around the first steering axis, and an intermediate support on both the left and right sides swings with respect to the wheel support. As the wheel support swings with respect to the intermediate support A link mechanism connecting the wheel support and the wheel support, wherein the wheel support is configured such that the connection of the intermediate support is rotatably connected about the first steering axis. And a projecting shaft portion penetrating the connecting portion of the intermediate support and projecting to the outer surface side of the connecting portion, and the link mechanism is connected to the projecting shaft portion. .

[Operation] When the steering handle is rotated, the steering operation mechanism swings the left and right intermediate supports around the first steering axis. Then, since the left and right wheel supports are connected to the vehicle body support portion by the link mechanism, the second support with respect to the intermediate support due to the swinging power of the intermediate support.
Swinging around the steering axis, the left and right wheels are oriented in a desired manner with respect to the vehicle body. Thus, the steering operation device that swings the wheel support by the swinging power of the intermediate support can be employed to steer the wheel to a large maximum turning angle, and the steering operation can be performed while reducing the lateral displacement of the wheel. .

[0008] Since the link mechanism is connected to the protruding shaft portion, the fixed link connected to the vehicle body support and the movable link provided on the wheel support are located at the same or similar arrangement level, and both links are provided. As the link to be connected, a simple link in which the end connected to the movable link and the end connected to the fixed link are located at the same or almost the same arrangement level can be adopted to constitute the link mechanism.
In addition, both the fixed link and the movable link are provided at the vehicle body support portion and the wheel support while being positioned at a lower level than the upper end of the vehicle body support, and the entire link mechanism is positioned at a lower level than the upper end of the wheel support. Then, when the wheel is largely steered, it will not easily become an obstacle to wheel steering by entering the ring of the tire seat of the wheel rim, and the movable link of the link mechanism will be relatively short or a simple shape While steering the wheel to a desired large maximum turning angle.

[Effect] Therefore, the wheel support can be swiveled by the swinging power of the intermediate support while the wheel can be turned slightly by steering operation to a large maximum turning angle while minimizing the side slip of the wheel as much as possible. In addition, the steering mechanism can be steered using a simple and lightweight steering operation device having a relatively small link mechanism and a simple structure.

The construction, operation and effect of the invention according to claim 2 are as follows.

In the structure according to the first aspect of the present invention, a fixed link that forms the link mechanism and is connected to the protruding shaft portion, and the wheel support that forms the link mechanism. Are located at the same arrangement level.

[Operation] Since the fixed link and the movable link are located at the same arrangement level, the link connecting the two links has the same end as the link connected to the movable link and the same end connected to the fixed link. The link mechanism can be configured while employing simple components located at substantially the same arrangement level.

[Effect] Therefore, the link mechanism can be further reduced by employing a small connecting link, and a simpler and more compact steering operation device can be employed.

The structure, operation and effect of the invention according to claim 3 are as follows.

[Structure] In the structure of the invention according to the second aspect, the projecting shaft portion projects below the connecting portion of the intermediate support.

[Operation] Since the protruding shaft portion protrudes below the connecting portion, the movable link and the fixed link are located at the same or similar arrangement level, and both ends are used as links for connecting both links. In addition to being able to configure the link mechanism while employing a simple one located at the same or almost the same placement level, the entire link mechanism is located at a placement level lower than the upper end of the wheel support, and the wheels are When the steering operation is largely performed, the link mechanism can be configured while being hardly hindered by the wheel rim entering the annular shape of the tire seat portion of the wheel rim.

[Effect] Accordingly, the link mechanism is made lighter by a lighter connecting link, and furthermore, it is made lighter while making it less likely to hinder the wheel steering. The steering operation can be performed up to a large maximum turning angle by employing a simple steering operation device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, a pair of left and right drivable front wheels 1, 1, a pair of left and right drivable non-steerable rear wheels 2, 2, an engine 3 and an engine are shown. A lift cylinder (not shown) swings up and down a rear portion of a transmission case 7 forming a rear portion of a vehicle body including a driving portion having a hood 4 and a driving portion having a steering handle 5 and a driving seat 6. A lift tractor 8 and a power take-out shaft 9 that can be moved freely are provided to constitute an agricultural tractor. In this tractor, various working devices such as a rotary tilling device are connected to a rear portion of a vehicle body by a lift arm 8 so as to be able to move up and down freely, and rotational driving force is transmitted to the connected working device by the power take-out shaft 9. .

As shown in FIGS. 3 to 5, an intermediate portion in the longitudinal direction of the wheel drive case 10 which is also used as a front axle member for supporting the front wheel 1 at both left and right ends is formed as a front portion of the vehicle body. Attached to the front vehicle body frame 20. That is,
A pair of front and rear cylindrical shafts 11 and 12 are provided at an intermediate portion of the wheel drive case 10 in the longitudinal direction.
1 is rotatably fitted inside a boss portion 21a of a front support 21 supported by the front end sides of a pair of left and right support portions 20a provided on the front body frame 20 so as to be rotatable around a longitudinal axis X of the vehicle body. The rear connecting shaft 12 is rotatably fitted inside the boss portion 22a of the rear support member 22 supported by the rear end sides of the pair of left and right support portions 20a around the same axis as the axis X. Let me do it. In other words, the left and right front wheels 1 and 1 are arranged such that when one front wheel 1 descends around the axis X with respect to the vehicle body, the other front wheel 1 rises around the axis X with respect to the vehicle body. X is the rolling axis and is supported on the vehicle body in a freely rolling manner. Thereby, even if one of the left and right front wheels 1, 1 enters into the recessed portion of the running ground or rides on the convex portion, or if the running ground is inclined in the lateral direction of the vehicle body, the left and right front wheels 1, 1 roll, and The posture in the left-right direction is kept horizontal or close to it.

The wheel drive case 10 is separately connected to a vehicle body-side case 13 supported on the front vehicle body frame 20 by the pair of front and rear connection shafts 11 and 12, and to both ends of the vehicle-body-side case 13. A pair of left and right intermediate cases 14,
Axle case 15 connected to left intermediate case 14
And the axle case 1 connected to the right intermediate case 14
5 and 5 cases. A pair of tie rods 3 respectively connected to the left and right intermediate cases 14, 14
1, a link mechanism 40 having a connecting link 41 connected to the left axle case 15, and a link mechanism 40 having a connecting link 41 connected to the right axle case 15. And the steering operation device S
And thus a steering device. This steering device performs a steering operation of a vehicle body by operating a steering operation device S with the steering handle 5 to steer the left and right front wheels 1 and 1. More specifically, the steering device is configured as follows. It is.

As shown in FIG. 4 and FIG.
Reference numeral 3 denotes a case body made of a pipe material having the pair of front and rear connection shafts 11 and 12, and a cast end case 13a connected to both ends of the case body by connection bolts 50. It is.

The left and right intermediate cases 14 are the case 1 on the vehicle body side.
The bearing 51 is provided so that the input cylinder portion 14a enters the support portion 13b provided on the upper end side of the end case 13a of the end portion 13a and rotates around the first steering shaft center P1 in the vehicle body vertical direction.
Input side case 14b supported via
And a cast output side case 14c connected to an end of the input side case 14b opposite to the side where the input cylinder portion 14a is located. When the output side case 14c is cast by forming the output side case 14c so as to extend from a middle portion of the output side case 14c in the vertical direction of the vehicle body, the connecting portion 14 cast as an integral part with the output side case 14c.
d to the end case 1 of the vehicle body side case 13.
The shaft 3c is externally fitted to a support shaft 13c protruding from the lower end of the shaft 3a, and is supported via a bearing 52 so as to rotate around the first steering axis P1. As a result, the left intermediate case 14 swings around the left end of the vehicle body side case 13 and the right intermediate case 14 swings around the first steering axis P1 at the right end of the vehicle body side case 13, respectively. It is supported.

The left and right axle cases 15 are connected to the intermediate case 14.
Support portion 14 provided on the lower end side of the output side case 14c.
e, the input side being supported via a metal 58a and a bearing 53a so as to rotate around a second steering axis P2 that is vertically oriented parallel to the first steering axis P1 and that is vertically oriented to the vehicle body. It is formed by a case 15a and an axle support case 15b having one end connected to one side of the input side case 15a by a connection bolt 59. One end of the axle 1a is rotatably supported by the axle support case 15b via a bearing 54, and the other end of the axle 1a is rotatably supported by the input side case 15a via the bearing 1a. A connecting portion 15d on the upper end side of the axle case 15, which is a connecting arm whose base end is connected to an upper end portion of the input side case 15a by a connecting bolt 59b, is connected to a supporting shaft portion 14g of the intermediate case 14 via a metal 58b. And the second
It is supported rotatably around the steering axis P2. As a result, the left axle case 15 has a kingpin angle due to the free end side of the left intermediate case 14.
The left wheel 1 is rotatably supported via the axle 1a while being supported so as to swing around the steering axis P2. The right axle case 15 is the right intermediate case 1
4 supports the right wheel 1 rotatably via an axle 1a while swinging around the second steering axis P2 having a kingpin angle by the free end side of the wheel.

That is, in both the left front wheel 1 and the right front wheel 1, the intermediate case 14 swings around the first steering axis P1 with respect to the vehicle body side case 13 in the vehicle longitudinal direction, and the axle case 15 Intermediate case 14 around 2 steering axis P2
By swinging the vehicle 1 in the front-rear direction with respect to the vehicle body, the mounting direction of the wheel 1 with respect to the vehicle body becomes a straight-ahead direction, or a lateral direction that is more leftward or rightward than the straight-ahead direction.

As shown in FIGS. 2 and 3, the steering operation mechanism 30 includes a knuckle arm 32 extending forward from the upper end of each of the left and right intermediate cases 14 toward the front of the vehicle body.
A pair of tie rods 3 having one end connected to each other
1, a pitman arm 33 in which the other end sides of the pair of left and right tie rods 31, 31 are rotatably connected to the free end side, and swing operation of the pitman arm 33 around a vertical axis 33a of the vehicle body. It comprises a hydraulic power steering device 34 provided freely. The control valve of the hydraulic power steering device 34 is operated by the steering handle 5 in conjunction with a handle support shaft 5a integrally and rotatably connected to the steering handle 5.

As a result, the steering operation mechanism 30 links the left and right intermediate cases 14, 14 to the steering handle 5. When the steering handle 5 is rotated, the pitman arm 33 is swung accordingly. ,
The pitman arm 33 causes the left and right intermediate cases 14, 14 via the tie rods 31 to move in the direction corresponding to the rotation direction of the steering handle 5 by an angle corresponding to the rotation operation angle of the steering handle 5.
Rocking operation.

As shown in FIGS. 5, 6 and the like, the support shaft 13c is provided so as to penetrate the connection portion 14d of the intermediate case 14 and protrude outward on the lower surface side of the connection portion 14d. A fixed link 42 whose base end is fitted to the protruding shaft portion 13e and which is fixed to the vehicle body side case 13 by being prevented from coming off and rotating by the connecting bolt 57;
A movable link 43 which is integrally formed with the case part at a portion rotatably connected to the movable member 4 so as to be integrally swingable with the axle case 15; The link 42 connects the link 42 with the link 42.

As a result, when the intermediate case 14 swings around the first steering axis P1, the left and right link mechanisms 40
Since the second steering axis P2, which is the axis connected to the intermediate case 14 of the axle case 15, moves in the front-rear direction with respect to the end case 13a, the intermediate case 14 swings with the intermediate case 14 swinging. The axle case 15 is swung about the second steering axis P2 with respect to the intermediate case 14 by the swinging power of 14. The link mechanism 40 includes a connection point of the fixed link 42 to which the connection link 41 is connected, and a movable link 43.
When the intermediate case 14 swings toward the front of the vehicle body by setting the arrangement relationship between the connection point to which the connection link 41 is connected and the second steering axis P2, the axle case 15 also swings toward the front of the vehicle body. The axle case 15 is connected to the vehicle body side case 13 such that the axle case 15 swings toward the rear of the vehicle body when the intermediate case 14 swings toward the rear of the vehicle body. Further, when the link mechanism 40 is located at a level lower than the level at which the uppermost end 15c of the axle case 15 is located, and the cutting angle of the front wheel 1 is increased, the link mechanism 40 enters the annular shape of the tire seat portion 1b of the rim to move the front wheel 1 Less likely to become an obstacle when steering.

The movable link 43 and the fixed link 42 are arranged at the same or almost the same arrangement level so that the connecting link 41 can be formed as follows. That is, there is little or no level difference between the end of the connecting link 41 connected to the movable link 43 and the end of the connecting link 41 connected to the fixed link 42, which is simple and advantageous in strength. It can be formed into something.

Thus, when the steering operation device S rotates the steering handle 5, the left and right intermediate cases 14, 14 are linked with the steering handle 5 around the first steering axis P1, and the left and right axle cases 15 are rotated. , 15 are pivoted about the second steering axis P2 in directions corresponding to the rotation direction of the steering handle 5 by an angle corresponding to the rotation operation angle of the steering handle 5.

Therefore, in performing the steering operation of the vehicle body, the steering handle 5 is rotated. Then
The steering operation device S moves the left and right intermediate cases 14 and 14 to the first steering axis P in association with the rotation of the steering handle 5.
1, the left and right axle cases 15, 15 are pivoted around the second steering axis P2 in directions corresponding to the rotational direction of the steering handle 5 by an angle corresponding to the rotational operation angle of the steering handle 5, respectively. , Left and right front wheels 1,1
Of the steering wheel 5
And the turning angles of the left and right front wheels 1 and 1 are angles corresponding to the rotation operation angle of the steering wheel 5.

That is, when the steering handle 5 is turned to the straight traveling position, the left and right intermediate cases 1 are moved.
4 and 14 are the first cases of the intermediate case 14 as clearly shown in FIG.
An axis 14f passing through the steering axis P1 and the second steering axis P2 is inclined so as to be inclined toward the front of the vehicle body at an inclination angle A of about 15 degrees with respect to the axis 13d of the vehicle body side case case 13. 7A, the left and right axle cases 15, 15 are in a connected posture in which the axle 1a is in the lateral direction of the vehicle body, and the left and right front wheels 1, 1 are in the straight traveling direction with respect to the vehicle body. At this time,
When the intermediate case 14 faces slightly forward with respect to the vehicle body side case 13, the left and right second steering axes P2 are positioned slightly forward of the first steering axis P1 with respect to the vehicle body.

When the steering handle 5 is rotated left or right from the straight traveling position, as shown in FIG. 7 (b), one of the left and right intermediate cases 14, 14, which is located on the inner side of the turn, is turned on the vehicle body side. With respect to the case 13, the axle case 15 swings more rearward of the vehicle than the intermediate case 14 when traveling straight, and the intermediate case 14 located on the outer side of the turn is The axle case 15 swings forward relative to the intermediate case 14 more than when traveling straight ahead, and the left and right front wheels 1, 1 are oriented leftward or rightward with respect to the vehicle body in the same direction as the operation direction of the steering handle 5. . At this time, as the operation angle of the steering handle 5 is increased, the left and right front wheels 1,
1 from the straight running direction, the maximum turning angle of the front wheel 1 positioned inside the turning from the straight running direction becomes about 90 degrees, and the maximum turning angle of the front wheel 1 positioned outside the turning from the straight running direction. Is about 75 degrees.

As shown in FIG.
The input shaft 60 is provided inside the rear connecting shaft 12 provided in
Is provided so as to rotate around the same axis as the axis X, and the input shaft 60 is connected to a rotation shaft 7 a extending forward from the transmission case 7, and is located inside the transmission case 7. A rotational driving force for the front wheels is input from a traveling mission (not shown) to a ring gear 61 a of a differential mechanism 61 provided inside a central portion of the vehicle body side case 13. A transmission mechanism for transmitting the driving force of the left side gear 61b of the differential mechanism 61 to the left front wheel 1;
And a transmission mechanism for transmitting the driving force of the right side gear 61b to the right front wheel 1 as shown in FIGS. That is, the rotational driving force of the side gear 61b is
3 and a transmission mechanism 65 provided inside the intermediate case 14.
The transmission is transmitted to an input bevel gear 80 provided inside the axle case 15 so as to rotate around the same axis as the second steering axis P2 via a transmission mechanism 70 provided inside the axis. The transmission is transmitted from the input gear 80 to the axle 1a by an axle drive gear 81 which meshes with the input gear 80 and is integrally rotatably connected to the axle 1a by spline engagement.

The transmission mechanism 65 provided inside the vehicle body side case 13 is connected to the side gear 61b of the differential mechanism 61 at one end so as to be integrally rotatable by spline engagement. A bevel gear 67 that is rotatably connected to the other end of the rotating shaft 66 by spline engagement.
The end case 1 is engaged with the bevel gear 67.
The first bevel gear 68 provided in the inside of the end case 13a is connected to the bevel gear 68 by a spline engagement so that the lower end thereof can be integrally rotated.
The steering shaft center P1 and the output shaft 69 provided to rotate around the same shaft center are constituted.

The transmission mechanism 70 provided inside the intermediate case 14 is connected to the upper end side of the output shaft 69 so as to rotate integrally by spline engagement, so that the first steering axis P1 is connected. An input gear 71 composed of a spur gear rotating as a rotation axis, an intermediate gear 72 meshing with the input gear 71, and meshing with the intermediate gear 72 and rotating with the second steering axis P2 as a rotation axis. An output shaft gear 73 composed of a spur gear is connected to the output shaft gear 73 such that an upper end thereof is integrally rotated by spline engagement, and a lower end thereof is integrally rotated by the spline engagement with the input gear 80 of the axle case 15. Output shaft 74 connected
It is constituted by and. Thereby, the transmission mechanism 70
Indicates that the driving force of the output shaft 69 of the vehicle body side case 13 is 3
The transmission is transmitted to an output shaft 74 by a gear transmission composed of a plurality of spur gears 71, 72, 73.
5 to the input gear 80.

The relationship between the pitch circle diameter of the input gear 71, the pitch circle diameter of the intermediate gear 72, and the pitch circle diameter of the output shaft gear 73 is set as follows. The pitch diameter of the input gear 71 <the pitch diameter of the intermediate gear 72 <the pitch diameter of the output shaft gear 73 is set. Thereby, the three spur gears 71, 7 of the transmission mechanism 70
The gear transmissions 2 and 73 are deceleration transmissions that reduce the rotational driving force of the output shaft 69 of the vehicle body side case 13 and transmit it to the output shaft 74.

As shown in FIG. 5, the inner space of the vehicle body side case 13 is provided at the end of each of the left and right end cases 13a of the vehicle body side case 13 with the transmission upper side where the differential mechanism 61 exists, and An oil seal mechanism 55 for partitioning the output shaft 69 with the lower transmission side and oil-sealing the lower transmission side to the upper transmission side is provided, and lubricating oil for the transmission mechanism 70 of the intermediate case 14 is provided. The oil level is stored in the intermediate case 14 so that the oil level is at the arrangement level of the respective gears 71, 72, 73 and is prevented from flowing out of the end case 13a toward the vehicle body side case body. .

A lift control mechanism 56 composed of a microcomputer linked to a control valve of a lift cylinder for raising and lowering the lift arm 8 is provided in the operation unit. The elevation control mechanism 56 is configured to detect the steering angle of the front wheel 1 to the left or right based on the swing position of the pitman arm 33 and information from the steering angle sensor, and to change the connected working device from the working level. The lift arm 8 is automatically moved up and down by operating the lift cylinder based on information from a setting device for setting the steering angle of the front wheel 1 when the work level is controlled to be elevated. Thus, for example, when turning on a headland, the front wheel 1 is steered to the left or right, and when the turning angle reaches a desired setting turning angle set in advance by the setting device, the elevation control mechanism 56 The working device is automatically raised to the non-working level due to the automatic control of the lift arm 8 by the operator, and the working device is lifted to the non-working level and traveled without any extra work for raising the working device. it can.

[Other Embodiments] The present invention relates to the left and right front wheels 1, 1
The present invention can be applied to a case where non-driving wheels which are freely rotatably supported are employed, and a case where left and right front wheels are supported so as to be unable to roll. Therefore, the left and right end cases 13a of the vehicle body side case 13 are referred to as left and right wheel support portions 13a of the vehicle body, and the left and right intermediate cases 14 are referred to as intermediate support members 14.
The left and right axle cases 15 are referred to as wheel supports 15.

The present invention is applicable not only to agricultural tractors but also to various work vehicles such as lawn mowers and rice transplanters. Further, the present invention can be applied to a case where the front wheels 1 are steered wheels and the rear wheels are steered wheels.

[Brief description of the drawings]

Fig. 1 Side view of the whole agricultural tractor

FIG. 2 is a front view of a front wheel mounting portion.

FIG. 3 is a plan view of a front wheel mounting portion.

FIG. 4 is a sectional view of a mounting portion of a wheel drive case to a vehicle body.

FIG. 5 is a longitudinal sectional view of a wheel drive case at a front wheel mounting portion.

FIG. 6 is a plan view of a front wheel mounting portion of the wheel drive case.

FIG. 7 is an explanatory diagram of front wheel steering.

[Description of Signs] 1 Wheel 5 Steering handle 13a Wheel support 13c Support shaft 13e Projection shaft portion 14 Intermediate support 14d Intermediate support connection 15 Wheel support 30 Steering operation mechanism 40 Link mechanism 42 Fixed link 43 Movable Link P1 First steering axis P2 Second steering axis

Claims (3)

[Claims] 1. A wheel support that supports an intermediate support at left and right wheel support portions of a vehicle body around a first steering axis centering vertically on the vehicle body, and rotatably supports a left wheel. Is supported on the free end side of the intermediate support member on the left side so as to be swingable around a second steering axis centering vertically on the vehicle body, and the wheel support member rotatably supporting the right wheel is mounted on the right side. A steering device for a working vehicle, which is supported on the free end side of the intermediate support member so as to be swingable around a second steering axis in the vertical direction of the vehicle body, wherein the left and right intermediate support members are rotated by a steering handle. A steering operation mechanism associated with the steering handle so as to be operated to swing around the first steering axis, and an intermediate support swinging with respect to the wheel support on both left and right sides. Wheel support so that the wheel support swings relative to the intermediate support And a link mechanism connecting the wheel support and the wheel support. The wheel support is provided so that the connection of the intermediate support is rotatably connected around the first steering axis. A working shaft having a supporting shaft portion having a projecting shaft portion penetrating the connecting portion of the intermediate support and projecting to the outer surface side of the connecting portion, and the link mechanism being connected to the projecting shaft portion. Steering device. 2. A fixed link forming the link mechanism and connected to the protruding shaft portion is the same as a movable link forming the link mechanism and connected to the wheel support. 2. The steering device for a working vehicle according to claim 1, wherein the steering device is located at a placement level. 3. The steering apparatus for a working vehicle according to claim 2, wherein the projecting shaft portion projects below the connecting portion of the intermediate support.