JP3504573B2 - Work vehicle steering system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering apparatus for a work vehicle that steers the vehicle body by changing the mounting direction of the left and right wheels with respect to the vehicle body.

[0002]

2. Description of the Related Art In an agricultural tractor, for example, when the headland is turned with a small turning radius, the headland becomes smaller, and the headland can be moved quickly, so that the head can be moved efficiently and work can be performed efficiently. For this reason, in the past, for example
There was a steering technique shown in Japanese Patent Publication No. 36574 and USP 5046577. This steering technology uses an axle member that supports the wheels on both ends so that it can swing around a vertical steering axis of the vehicle body, and is rotated around the vertical axis of the vehicle body at the center of the vehicle body in the left-right direction. By freely supporting and changing the mounting direction of the axle member with respect to the vehicle body and the mounting direction of the left and right wheels with respect to the axle member, the mounting direction of the left and right wheels with respect to the vehicle body is changed for steering the vehicle body. Then, by changing the orientation of the wheels with respect to the vehicle body both by changing the orientation of the wheels with respect to the axle member and by changing the orientation of the axle member with respect to the vehicle body, it is possible to divide the tread more than by simply changing the orientation of the wheels with respect to the axle member. The maximum turning angle of the wheel is large and the turning radius is small.

[0003]

In the case of the above-described conventional steering technique, when the steering operation is performed, the left and right wheels change direction with respect to the vehicle body while largely sliding on the running ground. An object of the present invention is to increase the turning angle of a wheel relative to the tread and to control the vehicle body while suppressing side slippage of the wheel, and to drive the wheel with a relatively simple transmission structure. (EN) Provided is a steering device for a work vehicle capable of performing the work.

[0004]

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

[Structure] In the steering apparatus for a working vehicle according to the present invention, the left and right ends support wheels, and the left and right wheels drive power for traveling.
And a pair of left and right wheels which are swingably supported around a first steering axis in the vertical direction of the vehicle body separately on the vehicle body side case supported on the vehicle body and on the left and right ends of the vehicle body side case. Of the intermediate case, an axle case that is swingably supported on the free end side of the left intermediate case around a second steering axis that is vertically oriented in the vehicle body, and rotatably supports the left wheel, and the right side And an axle case rotatably supported on the free end side of the intermediate case around a second steering axis extending in the vertical direction of the vehicle body and rotatably supporting the right wheel. A steering operation device for performing a swing operation of the case around the first steering axis and a swing operation of the left and right axle cases around the second steering axis for steering the left and right wheels; The first steering axis and the second steering axis With parallel arrangement, movement of the traveling on the wheel through the axle case from the vehicle body case
The power transmission mechanism is provided with a gear transmission unit having a spur gear having the first steering axis as a rotation axis and a spur gear having the second steering axis as a rotation axis. .

[Operation] When the steering operation device is operated, the left and right intermediate cases are oscillated around the first steering axis with respect to the vehicle body side case, and the left and right axle cases with respect to the intermediate case. By swinging around the second steering axis, the left and right wheels are mounted in a desired mounting direction with respect to the vehicle body, and the vehicle body is steered. As a result, by steering the wheel with respect to the vehicle body with only one steering axis, the mounting direction of the wheel with respect to the vehicle body is set to a desired mounting direction, and the axles supporting the wheel at both left and right end sides with respect to the vehicle body. By swinging and swinging the wheel with respect to this axle, the wheel can be steered to a desired maximum turning angle as compared with the conventional one in which the mounting direction of the wheel with respect to the vehicle body is a desired mounting direction. The distance between the wheel and the vehicle body needs to be small, and when the wheel is steered to a desired maximum turning angle, the wheel is displaced laterally with respect to the vehicle body due to steering. The vehicle can be steered by steering the wheels to a desired maximum turning angle while reducing the maximum stroke of the vehicle to a small stroke.

When power is transmitted to the wheels using a gear having the first steering axis and the second steering axis as the rotation axes, the intermediate case and the axle case are swung smoothly, and the unequal speed is achieved. It is possible to transmit power while preventing transmission failures such as transmission.
In this case, if both steering axes are arranged non-parallel, it is necessary to adopt a bevel gear as a gear with the steering axis as the rotation axis. A gear is transmitted while adopting a spur gear as a gear having an axis as a rotation axis.

[Effect] When turning at the end of the field, etc., the left and right wheels are steered to a large turning angle to travel with a small turning radius, and quickly move from the previous work end point to the next work start point. You can work efficiently by doing. Its split less lateral slip of the wheels with tread is small, and further, between the case and the second steering axis in shall be the rotational axis of the first and second steering axis
The axle case with the rotation axis as the center of rotation smoothly oscillates, and the spur gear with the first and second steering axes as the rotation axis
The power can be smoothly transmitted to the wheels via the wheel, and the wheel can be obtained in an advantageous state so that it can be easily maneuvered, run, or stowed, and can be obtained at a relatively low cost by using a spur gear.

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

[Structure] In the structure of the invention according to claim 1, the gear transmission is a deceleration transmission.

[Operation] The gear transmission portion is easily manufactured with a spur gear and is provided with a speed reduction function. By this reduction, the reduction ratio of the reduction portion in the axle or the like is made relatively small, while the transmission reduction ratio for the wheels is reduced. As a result, power can be transmitted with a desired reduction ratio.

[Effect] The reduction gear portion such as the axle is made compact with a small reduction ratio, and the gear transmission portion is provided with the reduction gear function at a low cost, so that the entire wheel drive case can be obtained compactly and at a low cost.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION 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 unsteered rear wheels 2, 2, an engine 3, and an engine. A lift cylinder (not shown) rocks up and down on the rear part of the mission case 7 forming the rear part of the vehicle body including the driving part having the bonnet 4, the steering wheel 5 and the driving part having the driver's seat 6. An agricultural tractor is constructed by providing a lift arm 8 and a power take-out shaft 9 which can be freely operated. In this tractor, various working devices such as a rotary cultivating device are connected to a rear part of a vehicle body so that they can be moved up and down by the lift arm 8, and a rotational driving force is transmitted to the connected working device by the power take-off shaft 9. .

As shown in FIGS. 3 to 5, the front portion of the vehicle body is formed by an intermediate portion in the longitudinal direction of the wheel drive case 10 which is also used as a front axle member which supports the front wheel 1 on both left and right sides. It is attached to the front body frame 20. That is,
A pair of front and rear cylindrical shaft type connecting shafts 11 and 12 are provided at an intermediate portion in the longitudinal direction of the wheel drive case 10, and the front connecting shaft 1
1 is fitted into a boss portion 21a of a front side support body 21 supported by the front end sides of a pair of left and right support portions 20a provided in the front vehicle body frame 20 so as to be rotatable about an axis X in the longitudinal direction of the vehicle body. The rear connecting shaft 12 is fitted into the boss portion 22a of the rear support 22 supported by the rear end sides of the pair of left and right supporting portions 20a so as to be rotatable around the same axis as the axis X. I am allowed. That is, the left and right front wheels 1 and 1 are arranged such that when one front wheel 1 descends with respect to the vehicle body around the axis X, the other front wheel 1 rises with respect to the vehicle body around the axis X. It is supported by the vehicle body so that it can be rolled freely with X as the rolling axis. As a result, even if one of the left and right front wheels 1, 1 enters a recessed portion of the traveling ground or rides on a convex portion, or even if the traveling ground is inclined in the lateral direction of the vehicle body, the left and right front wheels 1, 1 roll and The attitude in the left-right direction is maintained horizontal or close to it.

The wheel drive case 10 is separately connected to the vehicle body side case 13 supported by the front vehicle body frame 20 by the pair of front and rear connecting shafts 11 and 12, and both ends of the vehicle body side case 13. A pair of left and right intermediate cases 14,
Axle case 15 connected to the left middle case 14
And the axle case 1 connected to the intermediate case 14 on the right side.
It is configured by 5 cases of 5 and 5. A pair of tie rods 3 respectively connected to the left and right intermediate cases 14, 14.
Steering mechanism 30 having 1, 31; 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
Thus, the steering device is configured. This steering apparatus operates the steering operation device S by the steering handle 5 to steer the left and right front wheels 1 and 1 to perform steering operation of the vehicle body. There is.

As shown in FIGS. 4 and 5, the vehicle body side case 13 includes a case body made of a pipe material having the pair of front and rear connecting shafts 11 and 12, and connecting bolts at both ends of the case body. It is formed by a cast end case 13a connected by 50.

The left and right intermediate cases 14 are the case 1 on the vehicle body side.
3, the input cylinder portion 14a is inserted into the support portion 13b provided on the upper end side of the end case 13a, and the bearing 51 is arranged so as to rotate about the first steering axis P1 which is oriented vertically in the vehicle body.
The input case 14b made of casting which is supported through
And a cast output side case 14c connected to the end of the input side case 14b opposite to the side where the input tube portion 14a is located. The connecting portion 14 is formed so as to extend from the intermediate portion of the output side case 14c in the vertical direction of the vehicle body and is cast as an integral part with the output side case 14c when the output side case 14c is cast.
The extended end side of d is the end case 1 of the vehicle body side case 13.
It is externally fitted to a support shaft portion 13c projecting to the lower end side of 3a and supported via a bearing 52 so as to rotate around the first steering axis P1. As a result, the left middle case 14 swings around the first steering axis P1 at the left end of the vehicle body side case 13 and the right middle case 14 at the right side end of the vehicle body side case 13, respectively. Is supported as.

The left and right axle cases 15 are the intermediate cases 14
Support portion 14 provided on the lower end side of the output side case 14c
The input side case 15a supported by a bearing 53 so as to be fitted around the second steering axis P2 and fitted around the second steering axis P2 which is parallel to the first steering axis P1 and which extends vertically to the vehicle body.
And an axle support case 15b whose side end is connected to one side of the input side case 15a.
The axle 1a is rotatably attached via a bearing 54 across the axle support case 15b and the input side case 15a. As a result, the left axle case 15 is supported by the free end side of the left intermediate case 14 so as to swing around the second steering axis P2 having the kingpin angle, and via the axle 1a. The left wheel 1 is rotatably supported. The right axle case 15 is supported by the free end side of the right intermediate case 14 so as to swing around the second steering axis P2 having a kingpin angle, and the right wheel 1 via the axle 1a. Is rotatably supported.

That is, in both the left front wheel 1 and the right front wheel 1, the intermediate case 14 swings in the vehicle body front-rear direction with respect to the vehicle body side case 13 around the first steering axis P1, and the axle case 15 moves to the first axle. 2 Intermediate case 14 around the steering axis P2
On the other hand, by swinging in the front-back direction of the vehicle body, the mounting direction of the wheel 1 with respect to the vehicle body becomes a straight-ahead direction, or a sideways direction toward the left or right side of the straight-ahead direction.

As shown in FIGS. 2 and 3, the steering operation mechanism 30 includes a knuckle arm 32 extending from the upper ends of the left and right intermediate cases 14 to the front side of the vehicle body.
The pair of tie rods 3 each having one end connected to
1, a pair of left and right tie rods 31, 31, the other end side of which is rotatably connected to the free end side, and the pitman arm 33 is swingably operated around a vertical axis 33a of the vehicle body. It is constituted by a hydraulic power steering device 34 which is freely provided. The control valve of the hydraulic power steering device 34 is interlocked with the steering wheel support shaft 5a that is integrally rotatably connected to the steering handle 5 and is operated by 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, and when the steering handle 5 is rotated, the pitman arm 33 is swung accordingly. ,
The pitman arm 33 moves the left and right intermediate cases 14, 14 through the tie rods 31 in a direction corresponding to the rotation direction of the steering wheel 5 by an angle corresponding to the rotation operation angle of the steering wheel 5.
Swing with respect to.

As shown in FIGS. 2 and 5, the left and right link mechanisms 40 include the upper support portion 13b and the lower support shaft portion 13c of the end case 13a of the vehicle body side case 13.
When the end case 13a is formed so as to extend laterally outward from the space between and between the end case 13a and the end case 13a, the end case 13a is integrally formed with the end case 13a. When the input side case 15a is formed by extending the link 42 and the input side case 15a of the axle case 15, the axle case 15 is formed by casting the link side 42 and the input side case 15a as an integral part. Together with the movable link 43 provided so as to swing with respect to the intermediate case 14, one end of the movable link 43 is rotatably and swingably connected to the free end side of the movable link 43 by the ball joint 44, and the other end side is the above-mentioned. The fixed link 42 is connected to the extended end side of the fixed link 42 by the ball joint 44 so as to be rotatable and swingable. As a result, when the intermediate case 14 swings around the first steering axis P1, the left and right link mechanisms 40 have 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 swinging force of the intermediate case 14 causes the axle case 15 to move to the intermediate case 14 around the second steering axis P2 as the intermediate case 14 swings. Swing against. Further, in the link mechanism 40, the connection relationship between the connection point where the connection link 41 of the fixed link 42 is connected, the connection point where the connection link 41 of the movable link 43 is connected, and the second steering axis P2. With this setting, if the intermediate case 14 swings to the front side of the vehicle body, the axle case 15 also swings to the front side of the vehicle body, and if the intermediate case 14 swings to the rear side of the vehicle body, the axle case 15 also moves. Axle case 1 so that it swings to the rear side of the vehicle body
5 is connected to the vehicle body side case 13.

Thus, when the steering operation device S rotates the steering handle 5, the steering operation device S is linked to the steering handle 5 to move the left and right intermediate cases 14, 14 around the first steering axis P1 and the left and right axle cases 15 respectively. , 15 are swung around the second steering axis P2 in the 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, when carrying out the steering operation of the vehicle body, the steering handle 5 is rotated. Then,
The steering operation device S links the left and right intermediate cases 14, 14 with the first steering axis P in association with the rotation of the steering wheel 5.
1, the left and right axle cases 15, 15 are swung around the second steering axis P2 in the 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. , Front left and right wheels 1,1
Steering handle 5 is attached to the car body
The turning angle of the left and right front wheels 1, 1 becomes an angle corresponding to the rotational operation angle of the steering handle 5.

That is, when the steering handle 5 is turned to the straight-ahead position, the left and right intermediate cases 1 are moved.
4, 14 are the first 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 in a connecting posture in which the axis 14f inclines forward with respect to the axis 13d of the vehicle body case 13 at an inclination angle A of about 15 degrees. The left and right axle cases 15, 15 are in a connecting posture in which the axle 1a is laterally oriented as shown in FIG.
1 goes straight to the car body. At this time, since the intermediate case 14 faces slightly forward with respect to the vehicle body-side case 13, the left and right second steering axis cores P2 are located slightly forward of the vehicle body with respect to the first steering axis core P1.

When the steering handle 5 is rotated leftward or rightward from the straight-ahead position, as shown in FIG. 7B, the intermediate case 14 of the left and right intermediate cases 14, 14 which is located on the inside of the turn is on the vehicle body side. With respect to the case 13, the axle case 15 swings rearward of the vehicle body relative to the intermediate case 14 when traveling straight ahead, and the intermediate case 14 located on the outside of the turn turns with respect to the vehicle body side case 13. The axle case 15 swings toward the front of the vehicle body relative to the intermediate case 14 when traveling straight ahead, and the left and right front wheels 1 and 1 face leftward or rightward with respect to the vehicle body in the same direction as the steering wheel 5 is operated. . At this time, the larger the operating angle of the steering handle 5 is, the more the left and right front wheels 1,
1, the maximum turning angle of the front wheel 1 located inside the turning is about 90 degrees, and the maximum turning angle of the front wheel 1 located outside of the turning is from the straight running direction. Is about 75 degrees.

As shown in FIG. 4, the vehicle body side case 13
The input shaft 60 inside the connecting shaft 12 on the rear side.
Is provided so as to rotate about the same axis as the axis X, and the input shaft 60 is connected to a rotary shaft 7a extending forward from the mission case 7 and is located inside the mission case 7. The rotational driving force for the front wheels is input from a traveling mission (not shown) to a ring gear 61a of a differential mechanism 61 provided inside the 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;
The transmission mechanism for transmitting the driving force of the right side gear 61b to the right front wheel 1 is configured as shown in FIGS. That is, the rotational driving force of the side gear 61b is transmitted to the transmission mechanism 65 provided inside the vehicle body-side case 13 and the intermediate case 1.
4 through an electric power transmission mechanism 70 provided inside the shaft case 15 to the input bevel gear 80 provided inside the axle case 15 so as to rotate about the same axis as the second steering axis P2, It engages with this input gear 80 and the axle 1a
The transmission is transmitted from the input gear 80 to the axle 1a by an axle drive gear 81 that is rotatably connected to the axle 1a by spline engagement.

The transmission mechanism 65 provided inside the vehicle body side case 13 is configured so that one end of the transmission mechanism 65 is connected to the side gear 61b of the differential mechanism 61 by spline engagement so as to be integrally rotatable. And a bevel gear 67 that is integrally rotatably connected to the other end of the rotary shaft 66 by spline engagement.
The end case 1 engages with the bevel gear 67.
3a and a bevel gear 68 provided inside the end case 13a such that the lower end of the bevel gear 68 is integrally rotatably connected by spline engagement.
The steering shaft core P1 and the output shaft 69 provided so as to rotate around the same shaft core.

The transmission mechanism 70 provided inside the intermediate case 14 is connected to the upper end side of the output shaft 69 by spline engagement so as to rotate integrally, so that the first steering shaft core P1 is connected. An input gear 71 formed of a spur gear that rotates as a rotary shaft core, an intermediate gear 72 that meshes with the input gear 71, and a mesh with the intermediate gear 72 while rotating with the second steering shaft core P2 as the rotary shaft core. An output shaft gear 73 made of a flat gear is connected to the output shaft gear 73 so that the upper end side integrally rotates by spline engagement, and the lower end side integrally rotates with the input gear 80 of the axle case 15 by spline engagement. Output shaft 74 connected
It is composed of and. Thereby, the transmission mechanism 70
Is the driving force of the output shaft 69 of the vehicle body side case 13
The transmission is transmitted to the output shaft 74 by a gear transmission unit composed of individual spur gears 71, 72, 73, and the output shaft 74 is used to transmit the axle case 1
5 to the input gear 80.

The connecting link 41 is constructed as shown in FIGS. That is, one end side is located on the lower surface side of the fixed link 42 and the other end side is located on the upper surface side of the movable link 43, and the intermediate case 14 swings around the first steering axis P1. However, the link body 41a is formed by bending so that the intermediate portion does not hit the connecting portion 14d, and the link body 41a is formed of a bent rod having the ball joints 44 on both end sides, and the bent portion of the link body 41a is reinforced. As described above, the link body 41a is constituted by the reinforcing plates 41b and 41c attached to the intermediate portion.

As shown in FIG. 5 and the like, the link mechanism 4
The fixed link 42 and the connection link 4 which form 0.
1. If the cutting angle of the front wheel 1 increases, the movable link 43 and the movable link 43 enter the ring of the tire seat portion 1b of the rim to prevent obstacles when the front wheel 1 is steered. It is arranged so as to be located at a level lower than the level at which the upper end portion 15c is located.

As shown in FIG. 5, at the ends of the left and right end cases 13a of the vehicle body-side case 13, the internal space of the vehicle body-side case 13 and the power transmission side where the differential mechanism 61 is present are provided. An oil seal mechanism 55 is provided which partitions the output shaft 69 from the transmission lower side and oil-seals the transmission lower side with respect to the transmission upper side, and supplies lubricating oil for the transmission mechanism 70 of the intermediate case 14. The oil level is stored inside the intermediate case 14 so that the oil level is at the arrangement level of the gears 71, 72, 73 and does not flow out from the end case 13a toward the vehicle body side case body. .

A lift control mechanism 56 comprising a microcomputer linked to a control valve of a lift cylinder for lifting and lowering the lift arm 8 is provided in the operating section. The lift control mechanism 56 detects information from the steering angle sensor that detects the steering angle of the front wheel 1 to the left or right based on the swing position of the pitman arm 33, and determines whether the connected working device is operated from the working level. The lift arm 8 is automatically moved up and down by operating the lift cylinder based on information from a setter that sets the steering angle of the front wheels 1 when the work arm is lifted. As a result, when the front wheel 1 is steered leftward or rightward when turning around on a headland, and the cutting angle becomes a desired setting cutting angle preset by the setting device, the lifting control mechanism 56 is operated. The work device is automatically lifted to a non-working level for automatic control of the lift arm 8 by the operation, and the work device is lifted to the non-working level and traveled without any special labor for raising the work device. it can.

[Other Embodiments] FIGS. 9 and 10 show a steering apparatus having another embodiment. In this steering apparatus, the upper side of the end case 13a of the vehicle body side case 13 is provided. A fixed link 42 fixed to the vehicle body side case 13 by casting as an integral part of the end case 13a between the support portion 13b and the lower support shaft portion 13c,
A movable link 43 provided on the axle case 15 so as to swing with respect to the intermediate case 14 together with the axle case 15 by casting the front end portion of the input case 15a of the axle case 15 as an integral part with the input case 15a.
The link mechanism 40 is composed of the movable link 43 and the connection link 41 connecting the fixed link 42. In this case, since the movable link 43 extends from the front end side of the portion of the axle case 15 in which the axle drive gear 81 is housed, the link mechanism 40 is moved to a level higher than the level at which the uppermost end portion 15c of the axle case 15 is positioned. While arranging at a low level, the portion of the movable link 43 to which the connecting link 41 is connected and the portion of the fixed link 42 to which the connecting link 41 is connected are positioned at the same or almost the same arrangement level, and the connecting link 41 is moved to the next position. Can be formed as follows. That is, there is no level difference between the end portion on the side connected to the movable link 43 and the end portion on the side connected to the fixed link 42, and there is not much difference, and the structure is simple and advantageous in terms of strength.

11 and 12 show a steering apparatus according to another embodiment. In this steering apparatus, the driving force from the output shaft 69 of the vehicle body case 13 is transferred to the intermediate case 14. Of the three spur gears 71, 72, provided inside the
The transmission mechanism 70 including 73 transmits the input gear 80 to the input gear 80 of the axle case 15.

The transmission mechanism 70 provided in the intermediate case 14 is connected to the upper end side of the output shaft 69 so as to rotate integrally by spline engagement, whereby the first steering shaft core P1 is rotated. The input gear 71 formed of a spur gear that rotates as a core, the intermediate gear 72 that meshes with the input gear 71, and the intermediate gear 72 that meshes with the intermediate gear 72 and rotates with the second steering axis P2 as a rotation axis. The output shaft gear 73 formed of a flat gear is connected to the output shaft gear 73 so that the upper end side is integrally rotated by spline engagement, and the lower end side is integrally rotated by the spline engagement with the input gear 80 of the axle case 15. And an output shaft 74 connected to the. A pitch circle diameter of the input gear 71, a pitch circle diameter of the intermediate gear 72,
The relationship between the output shaft gear 73 and the pitch circle diameter is set as follows. Pitch circle diameter of input gear 71 <
The pitch circle diameter of the intermediate gear 72 is set to be smaller than the pitch circle diameter of the output shaft gear 73.

As a result, the transmission mechanism 70 applies the driving force of the output shaft 69 of the vehicle body side case 13 to the three spur gears 7.
It is transmitted to the output shaft 74 by the gear transmission portion composed of 1, 72 and 73, and is transmitted from the output shaft 74 to the input gear 80 of the axle case 15. The gear transmission section decelerates the rotational driving force of the output shaft 69 of the vehicle body side case 13 to reduce the rotational speed of the output shaft 7.
It is a deceleration transmission section that transmits to 4.

The base end portion is externally fitted to the protruding shaft portion 13e provided on the support shaft portion 13e so as to penetrate the connecting portion 14d of the intermediate case 14 and to project to the outside on the lower surface side of the connecting portion 14d. The fixed link 42 fixed to the vehicle body side case 13 by being prevented from coming off and rotating by the connecting bolt 57 and the portion of the axle case 15 rotatably connected to the intermediate case 14. A movable link 43 that is integrally swingably provided on the axle case 15 by being cast as an integral part with this case portion, the movable link 43 and the fixed link 4
The link mechanism 40 is configured by a connecting link 41 connecting the two. In this case, fixed link 4
2 extends from the projecting shaft portion 13e, so that the link mechanism 40 is mounted on the uppermost end portion 15c of the axle case 15.
While arranging it at a level lower than the level at which is located, position the portion of the movable link 43 to which the connecting link 41 connects and the portion of the fixed link 42 to which the connecting link 41 connects to the same or substantially the same arrangement level. The connecting link 41 can be formed as follows. That is, there is no level difference between the end portion on the side connected to the movable link 43 and the end portion on the side connected to the fixed link 42, and there is not much difference, and the structure is simple and advantageous in terms of strength.

The present invention can be applied to various work vehicles such as lawn mowers and rice transplanters as well as agricultural tractors. Further, the present invention can be applied to the case where the front wheels 1 are steering wheels and the rear wheels are steering wheels.

[Brief description of drawings]

[Figure 1] Side view of the entire 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 portion where a wheel drive case is attached to a vehicle body.

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

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

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

FIG. 8 is an overall perspective view of a connecting link.

FIG. 9 is a vertical cross-sectional view of a front wheel mounting portion of a wheel drive case including another embodiment.

FIG. 10 is a plan view of a front wheel mounting portion of a wheel drive case including another embodiment.

FIG. 11 is a vertical sectional view of a front wheel mounting portion of a wheel drive case including another embodiment.

FIG. 12 is a plan view of a front wheel mounting portion of a wheel drive case including another embodiment.

[Explanation of symbols]

1 wheel 10 wheel drive case 13 Body side case 14 Intermediate case 15 axle case 70 Transmission mechanism 71,73 spur gear P1 First steering axis P2 Second steering axis S steering operation device

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B62D ^7/ 00-7/20

Claims (2)

(57) [Claims] 1. A wheel drive case (10) for supporting wheels (1) (1) on both left and right sides and transmitting traveling power to the left and right wheels (1) (1), The vehicle body side case (13) supported by the vehicle body side case (13), and the first steering axis (P1) vertically oriented to the vehicle body at the left and right ends of the vehicle body side case (13).
A pair of left and right intermediate cases (14) (14) swingably supported around the left and right left intermediate cases (14) around the second steering axis (P2) vertically oriented on the free end side of the vehicle. An axle case (15) that is swingably supported and rotatably supports the left wheel (1), and a second steering axis that vertically extends toward the vehicle body on the free end side of the right intermediate case (14). (P
2) It is constituted by an axle case (15) that is swingably supported around and also supports the right wheel (1) rotatably, and the pair of left and right intermediate cases (1).
4) Swing the (14) around the first steering axis (P1), and move the left and right axle cases (15) (1).
5) A steering operation device (S) for operating the left and right wheels (1) (1) by swinging the second steering axis (P2) around the first steering axis. (P1) and the second steering axis (P2)
And are arranged in parallel with each other, and the vehicle body side case (1
3) From the axle case (15) (15) through wheels
(1) A transmission mechanism (7 ) for transmitting driving power to (1)
0) a spur gear (71) having the first steering axis (P1) as a rotation axis and a spur gear (73) having the second steering axis (P2) as a rotation axis. A steering device for a work vehicle, which is provided with a gear transmission part thereof. 2. The steering apparatus for a work vehicle according to claim 1, wherein the gear transmission is a deceleration transmission.