JP3594519B2 - Work vehicle steering system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steering device for a work vehicle that performs a steering operation of a vehicle body by changing a mounting direction of right and left wheels with respect to the vehicle body.
[0002]
[Prior art]
For example, in an agricultural tractor, when the headland is turned with a small turning radius, the headland can be advantageously moved such that the headland becomes smaller or 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 No. 56-36574 and US Pat. No. 5,046,577. In this steering technology, an axle member that supports wheels on both ends so as to be swingable around a vertical steering axis is rotated around a vertical axis of the vehicle body in the center of the vehicle body in the left-right direction. The steering direction of the vehicle body is changed by changing the mounting direction of the right and left 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 wheel with respect to the vehicle body by performing both the direction change of the wheel with respect to the axle member and the direction change of the axle member with respect to the vehicle body, the maximum change of the wheel can be achieved as compared with the case where the wheel is only changed with respect to the axle member. The turning angle becomes large and the turning radius becomes small.
[0003]
[Problems to be solved by the invention]
In the case of the above-described conventional steering technology, when the 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 a wheel, and enable relatively inexpensive and lightweight rolling of the wheel. Is to provide.
[0004]
[Means for Solving the Problems]
The configuration, operation and effect of the invention according to claim 1 are as follows.
[0005]
〔Constitution〕
A pair of left and right intermediate supports respectively supported on left and right wheel support portions of the vehicle body so as to be swingable around a first steering axis in a vertical direction of the vehicle body; It is supported so as to be swingable around a second steering axis centered vertically. Wheel support When, A left wheel rotatably supported by the left wheel support around an axle axis and swingable with respect to the left intermediate support integrally with the left wheel support around the second steering axis. With wheels A free end of the intermediate support on the right side, which is swingably supported around a second steering axis, which is vertically directed to the vehicle body. Wheel support When, The right wheel support is rotatably supported on the right wheel support around an axle axis and is swingable with respect to the right intermediate support integrally with the right wheel support around the second steering axis. With wheels With
The left and right intermediate supports around the first steering axis For the wheel support While swinging, the left and right wheel supports are moved around the second steering axis. For the intermediate support A steering device for a work vehicle including a steering operation mechanism that swings and steers left and right wheels.
[0006]
[Action]
When the steering operation is performed, the steering operation mechanism swings each of the left and right intermediate supports around the first steering axis with respect to the wheel supporting unit, and moves each of the left and right wheel supports on the second steering axis. The mounting direction of the left and right wheels with respect to the vehicle body changes by swinging the intermediate support around the core and changing both the direction of the intermediate support relative to the vehicle body and the direction of the wheels relative to the intermediate support. . 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.
[0007]
Further, since the intermediate support is swingably supported by a wheel support located on the left or right side of the vehicle body, the second steering axis is the wheel swing axis, and the wheel swing axis is The first steering axis is at a fulcrum when the vehicle moves back and forth with respect to the vehicle body. That is, the distance from the moving fulcrum to the wheel swinging axis is shorter than the distance from the swinging axis of the axle member, which is the conventional moving fulcrum, to the wheel swinging 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.
[0008]
The vehicle body is provided with an axle member that is swingably supported around a longitudinal axis of the vehicle body, and a left wheel support portion is formed at one end of the axle member, and a right wheel support portion is formed at the other end. Then, while the axle member is merely connected to the vehicle body at the intermediate portion so as to be rotatable around the longitudinal axis of the vehicle body, the left and right wheels are rotated around the second steering axis of the wheel support. The direction is changed by the swing and the swing of the intermediate support around the first steering axis, and the rolling is performed on the vehicle body via the wheel support, the intermediate support, and the axle member.
[0009]
〔effect〕
By changing the direction of the left and right wheels with respect to the vehicle body by steering the left and right wheels to a larger turning angle than by only swinging the wheels around the second steering axis, the vehicle can turn on the headland with a small turning radius. Work can be performed while traveling advantageously, such as making 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 wheels change direction less than in the conventional case where the axle member swings at the left and right center parts 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.
[0010]
Furthermore, when the left and right wheels can be rolled so that the vehicle can run while keeping the vehicle level or almost horizontal regardless of the unevenness or inclination of the running ground, the axle member forming the left and right wheel support portions is replaced with an axle member of the axle member. A structure that only allows vertical swinging with respect to the vehicle body. The structure may be connected to the vehicle body by a simple mounting structure, and it is inexpensive and lightweight.
[0011]
The configuration, operation and effect of the invention according to claim 2 are as follows.
[0012]
〔Constitution〕
In the configuration of the invention according to claim 1, the second steering axis is larger than the first steering axis in a state where the left and right wheels are in a straight running direction. Body front direction Is misaligned.
[0013]
[Action]
When the mounting direction of the wheel is changed to the outward direction, as the wheel swings around the second steering axis, one of the front and rear ends of the wheel approaches an inner member such as a vehicle body located inside the wheel. Corresponds to the 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, when the wheels are steered from straight ahead to outward, the ground contact point of the wheels always becomes the second steering axis. It penetrates the inside of the car body around the counter axis. Therefore, the angle at which the intermediate support can be swung around the first steering axis from the position where the wheel is directed straight to the time when the wheel hits the inner member becomes larger in the former case. You. This Thereby, the second steering axis is larger than the first steering axis when the wheels are in the straight running direction. Body front direction The left and right wheels can be steered so that the maximum turning angle becomes larger when the vehicle is displaced in the lateral direction than when the vehicle is aligned in the lateral direction of the vehicle body.
[0014]
〔effect〕
The turning angle of the left and right wheels is also increased in view of the arrangement of the first steering axis and the second steering axis, so that the vehicle travels with a smaller turning radius and advantageously travels with a smaller headland. it can.
[0015]
The configuration, operation and effect of the invention according to claim 3 are as follows.
[0016]
〔Constitution〕
In the configuration of the invention according to claim 1 or 2, The intermediate support An operating mechanism linked to the steering wheel; The wheel support to the operating mechanism An interlocking mechanism that is interlocked is provided in the steering operation mechanism.
[0017]
[Action]
Stay Ants When the operating handle is operated, The intermediate support Swing and interlock by interlock mechanism The wheel support is the intermediate support The right and left wheels can be steered by swinging in conjunction with the swing. In other words, while the steering operation mechanism is simplified in terms of structure and control as compared with the case where the intermediate support and the wheel support are separately linked 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.
[0018]
〔effect〕
What can be steered by increasing the maximum turning angle of the left and right wheels can be obtained simply and inexpensively in terms of the steering operation mechanism.
[0019]
The configuration, operation and effect of the invention according to claim 4 are as follows.
[0020]
〔Constitution〕
In the configuration of the invention according to claim 3, the interlocking mechanism includes: The wheel support and It is a link type including a swing link attached to the wheel support portion.
[0021]
[Action]
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 as the intermediate support swings the unit angle, The intermediate support and the wheel support are interlocked so that the angle at which the wheel support swings depends on the swing position of the intermediate support. The wheel can be steered in a state in which the angle of swinging around the axis and changing direction is different between a range where the turning angle of the wheel is small and a range where the turning angle is large.
[0022]
〔effect〕
Depending on the amount of operation of the steering wheel, a state where the change in the wheel direction becomes large or small can be obtained by the link, and a slight operation of the steering wheel will change the wheel direction greatly and make a small turn, A simple operation of the steering wheel makes it possible to easily obtain a state in which the wheel direction does not change much and the wheel does not meander easily.
[0023]
The structure, operation and effect of the invention according to claim 5 are as follows.
[0024]
〔Constitution〕
In the configuration of the invention according to claim 3, the interlocking mechanism includes: The wheel support is This is a gear type including a gear rotatably provided integrally and a gear fixed to the wheel supporting portion in a state of meshing with the gear.
[0025]
[Action]
For example, the intermediate support is configured so that 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. The angle at which the wheel swings around the second steering axis and changes direction according to the operation of the unit angle of the steering handle is adjusted to any range, regardless of the turning angle of the wheel. In The steering operation of the wheels can be performed in a state in which the vehicle speed is also constant.
[0026]
〔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, and when the steering wheel is operated large, the wheel direction changes greatly and turns slightly, and the steering wheel is slightly operated By simply doing this, it is possible to easily obtain a state in which the wheel direction does not change much and the wheel does not meander easily.
[0027]
The configuration, operation and effect of the invention according to claim 6 are as follows.
[0028]
〔Constitution〕
6. The invention according to claim 1, wherein the left and right wheel support, the intermediate support and the wheel support are formed by a wheel drive case for transmitting a driving force to the left and right wheels. And a universal joint that connects the transmission shaft of the drive case section and the transmission shaft of the drive case section of the intermediate support and that bends around the same axis as the first steering axis. It is.
[0029]
[Action]
The left and right wheels are used as drive wheels while the portion where the intermediate support and the wheel support are rotatably connected around the second steering axis is relatively compact enough to accommodate a universal joint therein. Things.
[0030]
〔effect〕
When the left and right wheels are steered to a range with a large turning angle, they are configured to be driven at a higher peripheral speed than other non-steered driving wheels, and turn with a small turning radius When traveling, both the turning angle of the left and right wheels and the high speed driving of the left and right wheels make a smaller turn Turn be able to. 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]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 1, a pair of left and right drivable front wheels 1 and 1, a pair of left and right drivable non-steering rear wheels 2 and 2, a driving unit including an engine 3 and an engine hood 4, and a steering handle 5. A lift arm 8 that can swing up and down by a lift cylinder (not shown) is provided at a rear portion of a transmission case 7 that forms a rear portion of a vehicle body having a driving unit having a driver seat 6 and a power take-out. The shaft 9 is 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 the vehicle body by a lift arm 8 so as to be able to move up and down freely, and a rotating power is transmitted to the connected working device by the power take-out shaft 9.
[0032]
As shown in FIG. 2 to FIG. 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 attached to a front portion of the vehicle body. is there. 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, and the front connecting shaft 11 is connected to a front vehicle body frame forming a front portion of the vehicle body. A rear support member supported by the front body frame 20 supports a rear connection shaft 12 on a boss portion 21a of a front support member 21 supported by the front body frame 20 so as to be rotatable around an axis X in the front-rear direction of the vehicle body. The boss 22a is rotatably fitted inside the boss 22a 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 of the front wheels 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 and 1 enters the recessed portion of the running ground or rides on the convex portion, or the running ground is inclined in the left and right direction of the vehicle body, the left and right front wheels 1 and 1 roll, The posture in the left-right direction is kept horizontal or close to it.
[0033]
A base end drive case section 13 having the front and rear connection shafts 11 and 12 at an intermediate portion thereof, and a pair of left and right intermediate supports 14 respectively connecting both end sides of the base end drive case section 13 to each other. , A tip drive case part forming a wheel support 15 connected to the left intermediate support 14, and a tip drive case forming the wheel support 15 connected to the right intermediate support 14. The steering device is constituted by five case sections including the section. The steering device includes an operating mechanism 30 having a pair of tie rods 31, 31 respectively connected to the left and right intermediate supports 14, 14, and a swing link 41, separately connected to the left and right wheel supports 15, 15, respectively. The left and right front wheels 1 and 1 are steered by a steering operation mechanism S including an interlocking mechanism 40 having a steering mechanism 41, and the steering operation of the vehicle body is performed.
[0034]
At both ends of the base drive case portion 13, joint members forming a wheel support portion 16 of the vehicle body are provided. The base end portion 14a of each of the left and right intermediate drive case portions includes a convex spherical joint portion 14b that is slidably fitted inside the concave spherical joint portion 16a of the joint member of the base drive case portion 13. , Are rotatably connected to the joint member. As a result, the left intermediate support 14 is swingably supported by the wheel support portion 16 on the left side of the vehicle body around the first steering axis P1 facing the vehicle body up and down, 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 around a first steering axis P1 that is vertically directed to the vehicle body. The base ends of the left and right front drive case portions are rotatably connected to each other over the upper support portion 14c and the lower support portion 14d of the free end portion of the intermediate drive case portion. As a result, the left wheel support 15 is swingably supported on the free end side of the left intermediate support 14 around the second steering axis P2, which is vertically directed to the vehicle body, and the left front wheel is positioned at the free end side. 1 is rotatably supported around the axle center, and the right wheel support 15 is swingable about the second steering shaft center P2 facing the vehicle body vertically on the free end side of the right intermediate support 14. The right front wheel 1 is rotatably supported around the axle axis at the free end side.
[0035]
That is, in both the left front wheel 1 and the right front wheel 1, the intermediate support 14 is swung in the vehicle front-rear direction with respect to the wheel support 16 around the first steering axis P1, and the wheel support 15 is moved to the second position. By swinging the intermediate support body 14 in the vehicle longitudinal direction around the second steering axis P2, the mounting direction of the wheel 1 with respect to the vehicle body becomes a straight-ahead direction, or a lateral direction in which the wheel 1 is directed to the left or right side of the straight-ahead direction. become.
[0036]
The operating mechanism 30 includes a tie rod 31 having one end 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, the free end being A pitman arm 32 rotatably connected to the shaft is provided so as to be swingable around an axis 32a, and is constituted by a hydraulic power steering device 34 operated by the steering handle 5. That is, the operating mechanism 30 links the left and right intermediate supports 14 to the steering handle 5 by rotating the knuckle arms 14 e of the left and right intermediate supports 14, 14 with the steering handle 5, thereby performing the first operation. They are linked so as to be able to swing around the center axis P1.
[0037]
The interlocking mechanism 40 has one end rotatably connected to an operation arm 15a extending from the left wheel support 15 so as to swing it around the second steering axis P2. One end is freely rotatable to a left-side interlocking mechanism provided with a swing link 41 and 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 with the swing link 41 connected to the control unit. 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 and 16b. When the intermediate support 14 is rocked, the wheel support 15 is interlocked with the swing of the intermediate support 14 by the operating force. The swing operation is performed in the same direction as the swing direction of the body 14. Thereby, the interlocking mechanism 40 is interlocked with the operating mechanism 30 such that the left and right wheel supports 15 are swingably operated by the operating mechanism 30 in conjunction with the left and right intermediate supports 14.
[0038]
Accordingly, the steering operation mechanism S causes the intermediate support 14 of the left and right side support members 14 and the intermediate support member 14 of the wheel support members 15 to be linked to the steering handle 5 by the operation mechanism 30, and the left wheel support member 15 is The left intermediate support 14 and the right wheel support 15 are interlocked with the right intermediate support 14 by an interlocking mechanism 40, so that the steering operation of the left and right front wheels 1 and 1 can be performed by turning the steering handle 5. I have to.
[0039]
Therefore, in performing the steering operation of the vehicle body, when the steering handle 5 is rotated, the left and right intermediate supports 14 are moved to the first steering axis P1 due to the operation force and the action of the steering operation mechanism S. Around the second steering axis P2, 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 and rear direction of the vehicle body. The mounting direction with respect to the vehicle body is the mounting direction corresponding to the operation position of the steering handle 5.
[0040]
That is, when the steering handle 5 is rotated to the straight-ahead position, the left and right intermediate supports 14, 14 are aligned with the shaft center 14f in the horizontal portion on the upper end side of the intermediate support 14, as clearly shown in FIG. As shown in FIG. 6A, the left and right wheel supports 15, 15 are connected to each other in such a manner that they are inclined forward with respect to the shaft center 13a of the drive case portion 13 at an inclination angle A of about 15 degrees. Is in the connecting posture in which the vehicle body is in the lateral direction, and the left and right front wheels 1, 1 are in the straight traveling direction with respect to the vehicle body. At this time, since the intermediate support 14 is slightly forward with respect to the wheel support portion 16, the left and right second steering axes P2 are positioned slightly forward of the first steering axis P1 with respect to the vehicle body.
[0041]
When the steering handle 5 is rotated leftward or rightward 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 to the wheel support. On the other hand, the wheel support 15 swings more toward the rear of the vehicle than the intermediate support 14 when traveling straight, and the intermediate support 14 located on the outer side of the turn with respect to the wheel support 16. As a result, the wheel support 15 swings forward relative to the intermediate support 14 more than when the vehicle is running straight, and the left and right front wheels 1 and 1 face the left or right with respect to the vehicle body in the direction of operation of the steering handle 5. Be turned 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 positioned inside the turning from the straight running direction is about 90. And the maximum turning angle of the front wheel 1 located outside the turning from the straight running direction is about 75 degrees.
[0042]
As shown in FIGS. 3 to 5, an input shaft 50 arranged concentrically with the axis X is provided inside the rear connection shaft 12 of the wheel drive case 10. A wheel drive mechanism 51 for transmitting rotational power to the left and right front wheels 1 and 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 to thereby introduce rotational power for a front wheel from a traveling mission (not shown) located inside the transmission case 7. It is configured as follows.
[0043]
A transmission mechanism provided inside the base drive case 13 of the wheel drive case 10 for both the drive mechanism for the front left wheel 1 and the drive mechanism for the front right wheel 1 of the wheel drive mechanism 51. Each of the cylindrical shaft 52, the distribution transmission shaft 53, the front wheel clutch 54, and the transmission shaft 55, and the input-side lateral transmission shaft 56 provided inside the intermediate drive case that forms the intermediate support 14, the output side , And an axle drive gear 58 provided inside a front end drive case portion constituting the wheel support 15.
[0044]
The transmission cylinder shaft 52 has a bevel gear 52a provided on one end side 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. It is linked with the input shaft 50 by meshing with a certain bevel gear portion 50a. The distribution transmission shaft 53 rotates integrally with the transmission cylinder shaft 52 by being fitted inside the transmission cylinder shaft 52 and being in spline engagement. 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 distributing 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 the lateral transmission shaft 56 by a universal joint 59 provided at an end of the input-side lateral transmission shaft 56 of the intermediate drive case portion so as to rotate integrally therewith. The lateral transmission shaft 56 of the intermediate drive case portion is externally fitted to the end thereof and is provided so as to be integrally rotatably connected by spline engagement, and the upper end of the vertical transmission shaft 57 It is interlocked with the vertical transmission shaft 57 by meshing with a bevel gear 57a which is fitted on the side and is provided so as to be integrally rotatable by spline engagement. A bevel gear 57b, which is fitted to the lower end of the vertical transmission shaft 57 and is integrally rotated by spline engagement, meshes with the axle drive gear 58. The left and right universal joints 59 are configured as ball-type universal joints that bend around the same axis as the first steering axis P1.
[0045]
Thus, the wheel drive mechanism 51 allows the universal support 59 to allow the intermediate support 14 to swing about the first steering axis P1 with respect to the wheel support 16 by the universal joint 59, while allowing the wheel support 15 to rotate with respect to the intermediate support 14. The turning power of the input shaft 50 is transmitted to the left and right front wheels 1, 1 while bevel gears 56a, 57a allow swinging around the second steering axis P2. Therefore, the left and right front wheels 1 and 1 are drivable wheels.
[0046]
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 velocity 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. Accordingly, 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. For example, the front wheel transmission 60 is automatically switched to the speed increasing side by means, or the front wheel transmission 60 is switched to the speed increasing side by manual operation to drive the left and right front wheels 1 and 1 to perform a further small turning. You can turn around the radius.
[0047]
[Another embodiment]
FIG. 7 shows a steering device and a wheel drive mechanism 51 according to another embodiment. In this steering device, a case portion forming a wheel support portion 16 of a vehicle body is provided at both ends of a base drive case portion 13. 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 extended across the upper support portion 13b, the middle support portion 13c, and the lower support portion 13d of the base drive case portion 13. It is connected so as to rotate around the first steering axis P1.
[0048]
The interlocking mechanism 40 of the operation mechanism 30 and the interlocking mechanism 40 of the steering operation mechanism S is attached to the upper end portion of the tip drive case constituting the wheel support 14 as shown in FIGS. Gi set up The gear type is composed of 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 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 in the vehicle front-rear direction with respect to the wheel support 16 around the first steering axis P1 by the operating mechanism 30, the two gears 42 and 43 mesh with each other. The gear 42 on the support side revolves around the first steering axis P1 along the gear 43 on the vehicle body side and revolves, and for this rotation, the wheel support 15 moves the second steering axis P2 of the second steering axis P2. It swings around the intermediate support 14 in the vehicle longitudinal direction.
Thus, 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 swing direction of the intermediate support 14. Perform swing operation in the same direction. The ratio between the angle at which the intermediate support 14 swings and the angle at which the wheel support 15 swings is constant even when the swing position of the intermediate support 14 changes, which is determined by the interlocking ratio of the two gears 42 and 43. Perform the swing operation in the state where the ratio is reached.
[0049]
Both 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 an 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 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, and an upper end of the transmission shaft 64 A transmission shaft 66 whose one end is interlocked by a bevel gear mechanism 65 on the side, a vehicle-body vertical transmission shaft 68 whose upper end is interlocked by a bevel gear mechanism 67 on the other end of the transmission shaft 66, and this transmission shaft An axle drive gear 58 is rotatably connected to the axle 1a so as to mesh with a bevel gear 69 provided integrally rotatably at the lower end of the axle 68.
[0050]
[0051]
Further, as the operation mechanism 30 of the steering operation mechanism S, left and right The intermediate support 14 In addition to the hydraulic power steering device 34 linked to the steering handle 5, a mechanical steering device or a means linked with an electric power steering device may be employed.
[0052]
INDUSTRIAL APPLICABILITY 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 cross-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]
1 wheel
5 Steering handle
14 Intermediate support
15 Wheel support
16 Wheel support
30 Operation mechanism
40 Interlocking mechanism
41 Swing link
42, 43 gear
55, 56 transmission shaft
59 Universal joint
P1 First steering axis
P2 2nd steering axis
S steering operation mechanism

Claims (6)

A pair of left and right intermediate supports respectively supported on left and right wheel support portions of the vehicle body so as to be swingable around a first steering axis in a vertical direction of the vehicle body; a wheel support member in the second steering axis about vertical direction that is swingably supported, it said together is rotatably supported by the axle core around the wheel supports of the left second steering shaft A left wheel swingable with respect to the left intermediate support integrally with the left wheel support around the center, and a second steering axis centered vertically on the free end side of the right intermediate support toward the vehicle body. a wheel support member that is swingably supported, together with the right side of the wheel support with the second steering axis around with and is rotatably supported around the axle center to the wheel support of the right A right wheel swingable with respect to the right intermediate support ,
The left and right intermediate supports are swung about the first steering axis with respect to the wheel support, and the left and right wheel supports are rotated with respect to the intermediate support about the second steering axis. work vehicle steering apparatus of the left and right wheels pivoted are provided with a steering operation mechanism for steering operation Te. The steering device for a work vehicle according to claim 1, wherein the second steering axis is displaced in a forward direction of the vehicle body with respect to the first steering axis in a state where the left and right wheels are in the straight traveling direction. 3. The steering operation mechanism according to claim 1, wherein the steering operation mechanism includes an operation mechanism that links the intermediate support to a steering handle, and a link mechanism that links the wheel support with the operation mechanism . 4. Work vehicle steering system. The steering device for a work vehicle according to claim 3, wherein the interlocking mechanism is a link type including a swing link attached to the wheel support and the wheel support. The interlocking mechanism, a gear provided freely the wheel support is integral rotation, the work vehicle of claim 3, wherein a gear type and a gear which is fixed to the wheel support portion in a state engaged with the gear Steering device. The left and right wheel support portions, the intermediate support and the wheel support are configured by a wheel drive case that transmits driving force to the left and right wheels, and a transmission shaft provided in a drive case portion forming the wheel support portion, and the intermediate support. The work according to any one of claims 1 to 5, further comprising a universal joint that connects a transmission shaft provided in a driving case portion to be configured and that is bent around the same axis as the first steering axis. Car steering system.

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