JP2001086803A - Steering apparatus for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the maximum steering angle of a working vehicle having a steering apparatus for steering the body by changing the attaching direction of the right and left wheels relative the body while suppressing the lateral slip of the wheel on the ground. SOLUTION: The objective steering apparatus is provided with a pair of right and left intermediate supporting members 14, 14 supported by the right and left wheel-supporting parts 16, 16 of the body of the working vehicle in a state swivelable around the vertical 1st steering shaft P1. The apparatus is further provided with a wheel-supporting member 15 supported on the free end of the left intermediate supporting member 14 in a state freely swivelable around the 2nd vertical steering shaft P2 and supporting the left wheel 1 in a state rotatable on the wheel shaft and with a wheel-supporting member 15 supported on the free end of the right intermediate supporting member 14 in a state freely swivelable around the 2nd vertical steering shaft P2 and supporting the right wheel 1 in a state rotatable on the wheel shaft.

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 working vehicle that performs a steering operation of a vehicle body by changing the mounting directions of right and left wheels with respect to the vehicle body.

[0002]

2. Description of the Related Art In an agricultural tractor, for example, when a headland is turned with a small turning radius, the headland becomes smaller,
It can run advantageously, for example, the headland can be moved quickly. For this reason, conventionally, there has been a steering technique disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 56-36574 and US Pat. No. 5,046,577. In this steering technology, an axle member that supports the wheels at both ends so as to be swingable around a vertical steering axis of the vehicle body is rotated around a vertical axis of the vehicle body at the center in the left-right direction of the vehicle body. The steering direction of the vehicle body is changed by changing the mounting direction of the left and right wheels to the vehicle body by changing the mounting direction of the axle member to the vehicle body and changing the mounting direction of the left and right wheels to the axle member. is there. By changing the direction of the wheels with respect to the vehicle body by performing both the direction change of the wheels with respect to the axle member and the direction change of the axle members with respect to the vehicle body, the maximum change of the wheels can be achieved rather than performing the direction change of the wheels only with respect to the axle members. The turning angle becomes large and the turning radius becomes small.

[0003]

In the conventional steering technique described above, when a steering operation is performed, the left and right wheels change directions with respect to the vehicle body while sliding largely on the running ground. Also, in order to enable the left and right wheels to roll with respect to the vehicle body, it is necessary to support the axle member on the vehicle body so as to swing also around the longitudinal axis of the vehicle body. The mounting structure has become complicated, and the mounting structure has to be provided with high supporting strength, which is disadvantageous in terms of cost and weight. SUMMARY OF THE INVENTION An object of the present invention is to provide a steering apparatus for a working vehicle that can not only increase the turning angle of a wheel, but also reduce the side slip of the wheel, and enable relatively inexpensive and lightweight rolling of the wheel. Is to provide.

[0004]

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

[Structure] A pair of left and right intermediate supports respectively supported by left and right wheel support portions of a vehicle body so as to be swingable around a first steering axis centering vertically on the vehicle body, and the left intermediate support member A wheel supporter rotatably supported on a free end side of the vehicle body around a second steering axis centering vertically and supporting the left wheel rotatably around the axle axis; A wheel support that is supported on the free end side of the support so as to be swingable around a second steering axis centering vertically on the vehicle body and that supports the right wheel so as to be rotatable around the axle axis; A swing operation of the left and right intermediate supports around the first steering axis and a swing operation of the left and right wheel supports around the second steering axis to steer the left and right wheels; A steering device for a work vehicle provided with a steering operation mechanism.

[Operation] When the steering operation is performed, the steering operation mechanism swings the left and right intermediate supports around the first steering axis with respect to the wheel supporting portions, and simultaneously operates the left and right wheel supports. Is pivoted about the second steering axis with respect to the intermediate support, and both the change of the orientation of the intermediate support with respect to the vehicle body and the change of the orientation of the wheels with respect to the intermediate support allow the left and right wheels to rotate. The mounting direction with respect to changes. Thus, when the left and right wheels are steered, the steering operation can be performed such that the maximum turning angle becomes larger than that when the steering operation is performed only by changing the direction around the second steering axis.

Further, since the intermediate support is swingably supported by a wheel support portion located on the left or right side of the vehicle body, the second steering axis becomes a swing axis of the wheel. The fulcrum when the moving shaft center moves back and forth with respect to the body
The steering axis becomes. That is, the distance from the moving fulcrum to the wheel oscillating axis is shorter than the distance from the oscillating axis of the axle member, which is a conventional moving fulcrum, to the wheel oscillating axis, and the left and right wheels change directions. In this case, the left and right wheels can be steered while the length of the side slip on the traveling ground is shorter than before.

An axle member is provided on the vehicle body so as to be swingable about a longitudinal axis of the vehicle body, and a left wheel support portion is provided at one end of the axle member and a right wheel support portion is provided at the other end. Form. Then, while the axle member is merely connected to the vehicle body at an intermediate portion so as to be rotatable around a longitudinal axis of the vehicle body, the left and right wheels are the second members of the wheel support.
The direction is changed by the swing around the steering axis and the swing of the intermediate support around the first steering axis, and the body is changed with respect to the vehicle body via the wheel support, the intermediate support and the axle member. Rolling.

[Effect] The left and right wheels can be steered to a larger turning angle than when the directions of the left and right wheels with respect to the vehicle body are changed only by swinging of the wheels around the second steering axis. It is possible to work while traveling advantageously, such as turning around the radius to make the headland smaller, or moving quickly from the previous work end point to the next work start point. In addition, steering is performed while the axle member suppresses side slip on the running ground when the direction of the wheels changes, as compared with the conventional case where the axle member swings at the left and right center of the body, and steering and running defects due to the side slip occur. It can run in a stable state with little or no difficulty.

Further, when rolling of the left and right wheels is enabled so that the vehicle can run while keeping the vehicle body horizontal or substantially horizontal regardless of the unevenness or inclination of the running ground, an axle member forming left and right wheel support portions is provided. A structure that allows the axle member to swing up and down with respect to the vehicle body can be connected to the vehicle body by a simple mounting structure, and it is inexpensive and lightweight.

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

In the configuration according to the first aspect of the present invention, the second steering axis is displaced in the longitudinal direction of the vehicle body from the first steering axis in a state where the left and right wheels are in the straight traveling direction. I have.

[Operation] When the mounting direction of the wheels is changed to the outward direction, as the wheels swing around the second steering axis, the front and rear ends of the wheels are located inside the wheels. And eventually hit its inner member. When the wheel is a front wheel, if the second steering axis is displaced to the front side of the vehicle body with respect to the first steering axis in a state where the wheel is in the straight traveling direction, the wheel is moved outward from the straight traveling direction. When the steering operation is performed, the ground contact point of the wheel initially goes out of the vehicle body around the second steering axis. On the other hand, when the second steering axis is aligned with the first steering axis in the lateral direction of the vehicle body, the ground contact point of the wheel always moves to the second steering point when the wheel is steered from straight ahead to outward. It penetrates the inside of the car body around the opposing axis. For this reason, the angle at which the intermediate support body can swing around the first steering axis from the position where the wheel moves straight ahead to the inner member becomes larger in the former case. And
When the wheel is the rear wheel, if the second steering axis is displaced to the rear side of the vehicle body with respect to the first steering axis in a state where the wheel is in the straight traveling direction, the wheel is moved outward from the straight traveling direction. When the steering operation is performed, the ground contact point of the wheel initially goes out of the vehicle body around the second steering axis. On the other hand, when the second steering axis is aligned with the first steering axis in the lateral direction of the vehicle body, the ground contact point of the wheel always moves to the second steering point when the wheel is steered from straight ahead to outward. It penetrates the inside of the car body around the opposing axis. For this reason, the angle at which the intermediate support body can swing around the first steering axis from the position where the wheel moves straight ahead to the inner member becomes larger in the former case. Accordingly, when the second steering axis is displaced in the front-rear direction of the vehicle body with respect to the first steering axis in a state where the wheels are in the straight traveling direction, the maximum is larger than when the wheels are aligned in the lateral direction of the vehicle body. The left and right wheels can be steered so that the turning angle is large.

[Effect] The turning angle of the left and right wheels is increased from the plane of the arrangement of the first steering axis and the second steering axis, and the vehicle turns with a smaller turning radius, and the headland is further reduced. It is possible to run advantageously.

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

[0016] [Constitution] In the constitution of the invention according to claim 1 or 2, an operation mechanism for linking one of the wheel support and the intermediate support to a steering handle, and an operation mechanism for the wheel support and the intermediate support. An interlocking mechanism that interlocks the other with the operation mechanism is provided in the steering operation mechanism.

[Operation] When the steering ring handle is operated, one of the wheel support and the intermediate support swings by the linkage of the operating mechanism, and the other swings with one of the swings due to the linkage by the linkage mechanism. To swing and steer the left and right wheels. In other words, while the steering operation mechanism is simpler in terms of structure and control compared to separately linking the intermediate support and the wheel support to the steering handle, the wheel support and the intermediate support are formed by the steering handle. Can be operated in conjunction with the body.

[Effect] A steering device capable of increasing the maximum turning angle of the left and right wheels and performing the steering operation can be obtained with a simple structure at a low cost in terms of the steering operation mechanism.

The structure, operation and effect of the invention according to claim 4 are as follows.

[Structure] In the structure of the invention according to claim 3, the interlocking mechanism is a link type having a swing link attached to the other of the wheel support and the intermediate support and the wheel support. .

[Operation] When the length and the mounting angle of the swing link are appropriately set, for example, the wheel support swings in conjunction with the swing of the intermediate support, and the intermediate support is rotated by a unit angle. The intermediate support and the wheel support are interlocked so that the angle at which the wheel support swings with the swing of the intermediate support depends on the swing position of the intermediate support. It is possible to steer the wheel in a state where the angle at which the wheel swings around the second steering axis and changes its direction is different between a range where the turning angle of the wheel is small and a range where the turning angle is large. .

[Effect] A state in which the change of the wheel direction becomes large or small is obtained by the link in the division of the operation amount of the steering wheel, and the wheel direction changes greatly by slightly operating the steering wheel. It is possible to easily obtain a state in which a small turning operation or a slight operation of the steering wheel does not change the direction of the wheels so much that it is difficult to meander.

The structure, operation and effect of the invention according to claim 5 are as follows.

In the structure according to the third aspect of the present invention, the interlocking mechanism includes a gear provided with the other of the wheel support and the intermediate support so as to be rotatable integrally with the wheel support. And a gear fixed to the section.

[Operation] For example, the wheel support swings in conjunction with the swing of the intermediate support, and the interlocking ratio between the intermediate support and the wheel support does not change depending on the swing position of the intermediate support. In this way, the intermediate support and the wheel support are interlocked, and the angle at which the wheel swings around the second steering axis and changes direction with the operation of the unit angle of the steering handle is determined by the turning angle of the wheel. The steering operation of the wheels can be performed in a state where the wheel is constant regardless of the size of the vehicle.

[Effect] A state in which the relationship between the amount of operation of the steering wheel and the amount of change in the wheel direction is constant is obtained by gear interlocking. When the steering wheel is largely operated, the wheel direction changes greatly and the vehicle turns slightly. A simple operation of the steering handle can easily obtain a state in which the wheel direction does not change much and the vehicle does not meander easily.

The structure, operation and effect of the invention according to claim 6 are as follows.

[Configuration] In the configuration of the invention according to any one of claims 1 to 5, the left and right wheel support portions, the intermediate support and the wheel support are separated by a wheel drive case for transmitting a driving force to the left and right wheels. And a drive shaft provided in a drive case section constituting a wheel support section, and a transmission shaft provided in a drive case section constituting an intermediate support body, and connected around the same axis as the first steering axis. It has a universal joint that bends.

[Operation] The intermediate support and the wheel support portion are
The left and right wheels are used as drive wheels while the portion rotatably connected around the steering axis is made relatively compact enough to accommodate a universal joint therein.

[Effects] When the left and right wheels are steered to a range where the turning angle is large, the wheels are driven at a peripheral speed higher than that of the other non-steered driving wheels. ,
When turning with a small turning radius, it is possible to make a smaller turn by both the magnitude of the turning angle of the left and right wheels and the high-speed driving of the left and right wheels. For that reason, the part where the intermediate support and the wheel support part are connected is made compact, and this connected part becomes high above the ground and runs advantageously to make it difficult to touch the ground, Advantageously obtained in terms of cost.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pair of left and right drivable front wheels 1, 1, a pair of left and right drivable non-steering rear wheels 2, 2, an engine 3 and an engine hood 4 are shown. A lift cylinder (not shown) is used to freely swing up and down by a lift cylinder (not shown) at a rear portion of a transmission case 7 forming a rear portion of a vehicle body having a driving unit having a steering handle 5 and a driving seat 6. An agricultural tractor is provided by providing a simple lift arm 8 and a power take-out shaft 9. 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 rotating power is transmitted to the connected working device by the power take-out shaft 9.

As shown in FIGS. 2 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 left and right front wheels 1, 1 at both ends, is a front portion of the vehicle body. It is attached to. That is, a pair of front and rear cylindrical shaft type connecting shafts 11 are provided at an intermediate portion in the longitudinal direction of the wheel drive case 10.
And a boss portion 21a of a front support 21 supported by a front vehicle body frame 20 forming a front portion of the vehicle body, and the front connection shaft 11 is rotatable around an axis X in the vehicle front-rear direction. And a boss portion 22a of a rear support 22 that supports the rear connecting shaft 12 with the front body frame 20.
Is rotatably fitted around the same axis as the axis X. 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 provided with a base drive case 13 having the front and rear connecting shafts 11 and 12 at an intermediate portion.
An intermediate drive case part forming a pair of left and right intermediate supports 14 respectively connected to both ends of the base end drive case part 13; and a wheel support 15 connected to the left intermediate support 14
And the right intermediate support 14
The steering device is constituted by five cases including a front end drive case forming a wheel support 15 connected to the steering wheel. The steering device comprises left and right intermediate supports 14, 1
4, an operating mechanism 30 having a pair of tie rods 31, 31 connected separately to each other, and an interlocking mechanism 40 having swing links 41, 41 respectively connected to the left and right wheel supports 15, 15.
The left and right front wheels 1 and 1 are steered by a steering operation mechanism S having the following. The steering operation of the vehicle body is performed, and is configured in detail as follows.

[0034] At both ends of the base drive case 13, joint members constituting a wheel support 16 of the vehicle body are provided. Base end 14a of each of left and right intermediate drive case parts
Is a convex spherical joint 1 slidably fitted in the concave spherical joint 16a of the joint member of the base end drive case 13.
4b, and is rotatably connected to the joint member. As a result, the left intermediate support 14 is supported by the wheel support 16 on the left side of the vehicle body so as to be swingable around the first steering axis P1 in the vertical direction of the vehicle body, and the right intermediate support 14 is The vehicle is supported by a wheel support portion 16 on the right side of the vehicle body so as to be swingable about a first steering axis P1 that is vertically directed to the vehicle body.
The base ends of the left and right distal drive case portions are respectively connected to the upper support portion 14c and the lower support portion 14 of the free end portion of the intermediate drive case portion.
and d. This allows
The left wheel support 15 is supported on the free end side of the left intermediate support 14 so as to be swingable around a second steering axis P2 that is vertically directed to the vehicle body, and the left front wheel 1 is axle-mounted at the free end side. The right wheel support 15 is rotatably supported around the center.
Is supported on the free end side of the right intermediate support member 14 so as to be swingable about a second steering axis P2 that is vertically directed to the vehicle body, and the right front wheel 1 is freely rotatable around the axle center on the free end side. I support it.

That is, in both the left front wheel 1 and the right front wheel 1, the intermediate support 14 is swung about the first steering axis P1 with respect to the wheel support 16 in the front-rear direction of the vehicle body. 15 around the second steering axis P2 to the intermediate support 1
By swinging the vehicle wheel 4 in the vehicle front-rear direction, 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.

The operating mechanism 30 includes a tie rod 31 whose one end is separately connected to a knuckle arm 14 e extending from the left and right intermediate supports 14, and the other end of each of the pair of tie rods 31, 31. The pitman arm 32 rotatably connected to the free end side
and a hydraulic power steering device 34 which is provided so as to be swingable around a and is operated by the steering handle 5. That is, the operating mechanism 30 connects the knuckle arms 14 e of the left and right intermediate supports 14, 14 to the steering handle 5.
The left and right intermediate supports 14 are linked to the steering handle 5 such that the left and right intermediate supports 14 can be pivotally operated around the first steering axis P1 by the turning operation thereof.

The interlocking mechanism 40 includes the left wheel support 1
5, a left-side interlocking mechanism including the swing link 41 having one end rotatably connected to an operation arm 15a extending so as to swing around the second steering axis P2. The swing link 41, one end of which is rotatably connected to an operation arm 15a extending from the right wheel support 15 so as to swing it around the second steering axis P2. And a right-side interlocking mechanism provided. Both the left and right interlocking mechanisms are mounted over the operation arm 15a of the wheel support 15, the arm 16b of the wheel support 16 of the vehicle body, and the two arms 15a, 16b. A link mechanism comprising the swing link 41 and
When the intermediate support 14 is rocked, the operating force causes the wheel support 15 to swing in the same direction as the rocking direction of the intermediate support 14 in conjunction with the rocking of the intermediate support 14. It is configured in. Accordingly, the interlocking mechanism 40 is interlocked with the operation mechanism 30 so that the left and right wheel supports 15 are swingably operated by the operation mechanism 30 in conjunction with the left and right intermediate supports 14.

Thus, the steering operation mechanism S causes the intermediate support 14 of the left and right intermediate supports 14 and the intermediate support 14 of the wheel supports 15 to be linked to the steering handle 5 by the operation mechanism 30 and to the left wheel support. The body 15 is interlocked with the left intermediate support 14 and the right wheel support 15 is interlocked with the right intermediate support 14 by an interlocking mechanism 40, and the left and right front wheels 1, 1 are steered by turning the steering handle 5. Operation is enabled.

Therefore, when the steering handle 5 is turned to perform the steering operation of the vehicle body, the left and right intermediate supports 14 are moved in the first steering direction due to the operating force and the operation of the steering operation mechanism S. The left and right wheel supports 15 swing about the axis P1 in the front-rear direction with respect to the vehicle body, and the left and right wheel supports 15 swing about the second steering axis P2 with respect to the intermediate support 14 in the front-rear direction of the vehicle body. , 1 with respect to the vehicle body corresponds to the operating position of the steering handle 5.

That is, when the steering handle 5 is turned to the straight running position, the left and right intermediate supports 1 are moved.
5, the shaft center 14f in the horizontal portion on the upper end side of the intermediate support body 14 is directed toward the front of the vehicle body at an inclination angle A of about 15 degrees with respect to the shaft center 13a of the base end drive case portion 13, as clearly shown in FIG. 6A, the left and right wheel supports 15, 15 are in a connected posture in which the axle 1a is in the lateral direction of the vehicle body as shown in FIG. become. At this time, since the intermediate support 14 is slightly forward facing the wheel support 16, the left and right second steering axes P2 are located 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. 6B, the left or right intermediate support 14, which is located on the inner side of the turn, is turned. The wheel support 15 swings toward the rear side of the vehicle body relative to the wheel support 16 with respect to the intermediate support 14 when the vehicle is traveling straight, and the intermediate support 14 located on the outer side of the turning is the wheel support. 16, the wheel support 15 swings forward relative to the intermediate support 14 compared to when the vehicle is traveling straight, and the left and right front wheels 1, 1 are equal to the operating direction of the steering handle 5 with respect to the vehicle body. It can be left or right sideways. At this time, as the operation angle of the steering wheel 5 increases, the turning angle of the left and right front wheels 1 and 1 from the straight running direction increases, and the maximum turning angle of the front wheel 1 located inside the turning from the straight running direction is about 90. Once again
The maximum turning angle of the front wheel 1 located outside the turning from the straight running direction is about 75 degrees.

As shown in FIGS. 3 to 5, the shaft center X is provided inside the rear connecting shaft 12 of the wheel drive case 10.
An input shaft 50 is provided concentrically with the input shaft 50, and a wheel drive mechanism 51 for transmitting the rotational power of the input shaft 50 to the left and right front wheels 1, 1 is provided inside the wheel drive case 10.
The input shaft 50 is connected to a rotating shaft 7 a extending forward from the transmission case 7, thereby introducing rotational power for front wheels from a traveling mission (not shown) located inside the transmission case 7. It is configured as follows.

The drive mechanism for the left front wheel 1 and the drive mechanism for the right front wheel 1 of the wheel drive mechanism 51 are:
The base drive case portion 13 of the wheel drive case 10
, A transmission cylinder shaft 53, a distribution transmission shaft 53, a front wheel clutch 54, and a transmission shaft 55, and an input-side horizontal direction provided inside an intermediate drive case portion forming the intermediate support 14. Transmission shaft 56, output-side vertical transmission shaft 5
7 and an axle drive gear 58 provided inside a front end drive case part constituting the wheel support 15.

The transmission cylinder shaft 52 has a bevel gear 52a provided at one end of the transmission cylinder shaft 52 so as to rotate integrally by spline engagement, and a portion located inside the base end drive case portion 13 of the input shaft 50. The gear is interlocked with the input shaft 50 by meshing with the bevel gear portion 50a provided for the motor. The distribution transmission shaft 53 is internally fitted to the transmission cylinder shaft 52 and is spline-engaged to rotate integrally with the transmission cylinder shaft 52. The end of the distribution transmission shaft 53 is fitted inside the input cylinder shaft 54a of the front wheel clutch 54 and connected so as to rotate integrally by spline engagement, and the output body 54b of the front wheel clutch 54 is connected to the transmission shaft 55. Of the distribution transmission shaft 53 is transmitted to the transmission shaft 55 via the front wheel clutch 54 by being externally fitted to the end of the transmission shaft 55 and connected so as to rotate integrally by spline engagement. The other end of the transmission shaft 55 is connected to a universal joint 59 provided at an end of the lateral transmission shaft 56 on the input side of the intermediate drive case.
Thus, it is connected to the lateral transmission shaft 56 so as to rotate integrally. The lateral transmission shaft 56 of the intermediate drive case portion is
A bevel gear 56a which is externally fitted to the end of the shaft and which is integrally rotatably connected by spline engagement, and which is externally fitted to the upper end of the vertical transmission shaft 57 and integrally rotated by spline engagement. By meshing with a bevel gear 57a provided so as to be movably connected, it is interlocked with the vertical transmission shaft 57. A bevel gear 57b which is fitted to the lower end of the vertical transmission shaft 57 and is integrally rotated by spline engagement is meshed with the axle drive gear 58. The left and right universal joints 59 are connected to the first steering axis P1.
And a ball-type universal joint that bends around the same axis.

Thus, the wheel drive mechanism 51 allows the universal joint 59 to allow the intermediate support 14 to swing about the first steering axis P1 with respect to the wheel support 16, while supporting the intermediate support 14 with the intermediate support 14. Second steering axis P for body 14
The rotation of the input shaft 50 is transmitted to the left and right front wheels 1 and 1 while allowing the swinging motion around the second 2 by the bevel gears 56a and 57a. Therefore, the left and right front wheels 1 and 1 are drivable wheels.

A traveling transmission (not shown) located inside the transmission case 7 is provided with a front wheel transmission 60 that can be switched between a constant speed side and a speed increasing side. When switched to the constant speed side, the front wheel transmission 60 drives the left and right front wheels 1, 1 in a state where the average peripheral speed of the left and right front wheels 1, 1 is substantially equal to the average peripheral speed of the left and right rear wheels 2, 2. When switching to the high speed side, the left and right front wheels 1, 1 are driven in a state where the average peripheral speed of the left and right front wheels 1, 1 is about twice as high as the average peripheral speed of the left and right rear wheels 2, 2. Thus, when the left and right front wheels 1 and 1 are steered to the left and to the right, and the turning angle is increased and the vehicle is turned with a small turning radius, the shift speed control automatically operated based on the detection of the steering angle of the front wheels 1. By turning the front wheel transmission 60 automatically to the speed increasing side by means or by manually switching the front wheel transmission 60 to the speed increasing side to drive the left and right front wheels 1 and 1 to perform further small turning. You can make a turn with a radius.

[Other Embodiment] FIG. 7 shows a steering device and a wheel drive mechanism 51 according to another embodiment. A case part constituting the support part 16 is provided. The base end portion 14a of each of the intermediate drive case portions forming the left and right intermediate support members 14 is vertically oriented across the upper support portion 13b, the middle support portion 13c, and the lower support portion 13d of the base drive case portion 13. The first steering axis P1 is connected so as to rotate around the first steering axis P1.

The interlocking mechanism 40 of the operation mechanism 30 and the interlocking mechanism 40 of the steering operation mechanism S is provided at the upper end of the tip end drive case constituting the wheel support 14 as shown in FIGS. The gear type is constituted by a gear 42 and a gear 43 provided at the upper end of the wheel support 16. The gear 42 on the support side is arranged so as to rotate with the wheel support 15 around the second steering axis P2 with respect to the intermediate support 14 and is fixed to the wheel support 15 so as not to rotate. . The gear 43 on the vehicle body side is fixed to the wheel support 16 so as not to rotate. When the intermediate support 14 is swung by the operating mechanism 30 around the first steering axis P1 with respect to the wheel support 16 in the vehicle longitudinal direction, the two gears 42, 43
Are meshed with each other, so that the gear 4 on the support body side
2 revolves around the first steering axis P1 along the gear 43 on the vehicle body side, and due to this rotation, the wheel support 15 is rotated around the second steering axis P2 by the intermediate support. It swings in the longitudinal direction of the vehicle body with respect to 14. Accordingly, when the intermediate support 14 is rocked, the interlocking mechanism 40 causes the wheel support 15 to interlock with the rocking of the intermediate support 14 by this operating force, thereby changing the rocking direction of the intermediate support 14. Swing in the same direction. The angle at which the intermediate support 14 swings and the wheel support 1
The swing operation is performed in a state where the ratio of the swing angle of the gear 5 to the swing angle of the intermediate support 14 changes to a constant ratio determined by the interlocking ratio of the two gears 42 and 43 even when the swing position of the intermediate support 14 changes.

The drive mechanism for the left front wheel 1 and the drive mechanism for the right front wheel 1 of the wheel drive mechanism 51 include a differential mechanism in which the input gear meshes with the bevel gear section 50a of the input shaft 50; A transmission shaft 62 whose one end is interlocked with the output gear of the differential mechanism; a vehicle-body vertical transmission shaft 64 whose lower end is interlocked with the other end of the transmission shaft 62 by a bevel gear mechanism 63; A lateral transmission shaft 66 whose one end is interlocked by a bevel gear mechanism 65 on the upper end side of the transmission shaft 64, and a bevel gear mechanism 6 on the other end side of the transmission shaft 66.
The transmission shaft 68 is vertically connected to the axle 1a in a state in which the transmission shaft 68 is vertically engaged with the transmission shaft 68 whose upper end is interlocked with the bevel gear 69 provided on the lower end of the transmission shaft 68 so as to be integrally rotatable. And an axle drive gear 58 that is provided.

The operation mechanism 30 of the operation mechanism 30 of the steering operation mechanism S and the interlocking mechanism 40 is configured such that the left and right intermediate supports 14 are linked to the steering handle 5 as shown in the above embodiment. In addition to the above, a configuration in which the left and right wheel supports 15 are linked to the steering handle 5 may be employed. In this case, as the interlocking mechanism 40, a mechanism configured to swing the intermediate support 14 in conjunction with the swing of the wheel support 15 is adopted.

As the operation mechanism 30 of the steering operation mechanism S, one of the left and right intermediate supports 14 and the wheel support 15 is linked to the steering handle 5 by a hydraulic power steering device 34, and the other is a mechanical type. The present invention may be implemented by adopting a steering device of the type described above or a unit linked by an electric power steering device.

The present invention can be applied to various work vehicles such as lawn mowers in addition to agricultural tractors.

[Brief description of the drawings]

FIG. 1 is a side view of an entire agricultural tractor.

FIG. 2 is a plan view of a front wheel mounting structure.

FIG. 3 is a sectional view of a front wheel drive case supporting portion.

FIG. 4 is a longitudinal sectional view of a support portion of an intermediate support and a wheel support.

FIG. 5 is a cross-sectional view of a support portion of the intermediate support.

FIG. 6 is an explanatory diagram of a front wheel steering state.

FIG. 7 is a longitudinal sectional view of an intermediate support and a wheel support according to another embodiment.

FIG. 8 is a plan view of a gear-type interlocking mechanism.

[Explanation of symbols]

 Reference Signs List 1 wheel 5 steering handle 14 intermediate support 15 wheel support 16 wheel support 30 operating mechanism 40 interlocking mechanism 41 swing link 42, 43 gear 55, 56 transmission shaft 59 universal joint P1 first steering axis P2 second operation Direction axis S Steering operation mechanism

Claims (6)

[Claims] 1. A pair of left and right intermediate supports respectively supported on left and right wheel support portions of a vehicle body so as to be swingable around a first steering axis centering vertically on the vehicle body, and a pair of left and right intermediate support members. A wheel support that is supported at the free end side so as to be swingable about a second steering axis centering vertically on the vehicle body and that supports the left wheel rotatably around the axle axis; A wheel supporter which is supported on the free end side of the body so as to be swingable around a second steering axis centering vertically on the vehicle body and which supports the right wheel rotatably around the axle axis; Steering for swinging left and right intermediate supports around the first steering axis and swinging the left and right wheel supports around the second steering axis to steer left and right wheels. A steering device for a work vehicle equipped with an operation mechanism. 2. The operation of a work vehicle according to claim 1, wherein the second steering axis is displaced in the vehicle longitudinal direction from the first steering axis when the left and right wheels are in the straight traveling direction. Equipment. 3. An operating mechanism that links one of the wheel support and the intermediate support to a steering handle;
The steering device for a work vehicle according to claim 1 or 2, wherein the steering operation mechanism includes an interlocking mechanism that interlocks the other of the wheel support and the intermediate support with the operation mechanism. 4. The steering of a work vehicle according to claim 3, wherein the interlocking mechanism is a link type including a swing link attached to the other of the wheel support and the intermediate support and the wheel support. apparatus. 5. The interlocking mechanism includes a gear provided with the other of the wheel support and the intermediate support so as to be rotatable integrally with the wheel support, and a gear fixed to the wheel support in a state of meshing with the gear. The steering device for a working vehicle according to claim 3, wherein the steering device is a gear type. 6. The drive shaft, wherein the left and right wheel support portions, the intermediate support member, and the wheel support member are configured by a wheel drive case that transmits a driving force to the left and right wheels, and a transmission shaft provided in a drive case portion that configures the wheel support portion. 6. A universal joint which connects a transmission shaft provided in a drive case part constituting an intermediate support and is bent about the same axis as the first steering axis. The steering device for a working vehicle according to item 7.