JPH0725351A - Turning operation structure for work vehicle - Google Patents

Abstract

PURPOSE:To make a side brake at the turning center side operate to the braking side, and thereby make a small turn even if no side brake pedal is depressed at the time of turning in a work vehicle equipped with paired right and left side brakes capable of being independently applied to each of a right and a left rear wheel. CONSTITUTION:A right and a left side brake 27 and a cam mechanism 23 provided for a power steering mechanism 21 for each front wheel 1 are mechanically connected by paired linkage mechanisms 29 and 41 so as to be interlocked with each other, and when each front wheel 1 is turned to the right or the left with a steering angle greater than a specified one by the power steering mechanism 21, the side brake at the turning center side is so constituted as to be automatically operated to the braking side by the cam mechanism 23. Beside, the side brake 27 at the turning center side is set to be in a week braking condition at the time of turning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking structure for rear wheels of a work vehicle during turning.

[0002]

2. Description of the Related Art An agricultural tractor, which is an example of a work vehicle as described above, is provided with a pair of left and right side brakes capable of independently braking left and right rear wheels, and a pair of left and right side brakes provided in a driving section. Each of the side brake pedal and the side brake is mechanically interlocked by a connecting rod, a wire, or the like. As a result, a small turn can be made by stepping on one of the side brake pedals when turning and braking the rear wheel on the turning center side.

[0003]

When making a small turn by using one of the side brakes as described above, the operator of the driving section simultaneously operates the steering wheel to steer the front wheels.
Since the side brake pedal on the turning center side must be depressed, there is room for improvement in terms of simplifying the turning operation. It is an object of the present invention to make a small turning operation using a side brake easy and smooth, and to make the structure simple.

[0004]

A feature of the present invention resides in the following structure in the turning operation structure of a work vehicle as described above. That is, [1] a pair of left and right side brakes capable of independently braking the left and right rear wheels and a cam mechanism provided in the power steering mechanism for the front wheels are mechanically interlocked by a pair of linkage mechanisms. When the front steering wheel is steered from the straight ahead position to the right or left by the power steering mechanism at a set angle or more, the side brake on the turning center side is configured to be operated on the braking side by the cam mechanism. The operation amount to the braking side of the side brake on the turning center side by the cam mechanism and the linkage mechanism is set so that the side brake is in a weak braking state.

[2] In the configuration of [1] above, a change mechanism capable of changing the operation amount of the side brake on the turning center side to the braking side by the cam mechanism and the linkage mechanism, and the rotational states of the left and right rear wheels are detected. When the side brake on the turning center side is operated toward the braking side by the power steering mechanism and the cam mechanism, the rear wheel on the turning center side does not stop rotating based on the detection of the rotation sensor. The change mechanism is provided with control means for changing the operation amount of the side brake on the turning center side to the braking side.

[0006]

[Action]

[I] According to the constitution described in [1], if the front steering wheel is steered by the power steering mechanism from the straight ahead position to the right, for example, by a set angle or more, the right side brake is automatically operated by the action of the cam mechanism and the linkage mechanism. It is operated to the braking side. In this way, the side brake on the side of the turning center is operated toward the braking side by simply manipulating the front wheels with the steering wheel. do not have to.

The power steering mechanism of the existing structure is simply added with a cam mechanism and a linkage mechanism for interlocking connection of the cam mechanism and the side brakes. The structure of the invention is obtained. Further, if a power steering mechanism having a sufficient operation force is provided, even if the side steering operation is performed by the power steering mechanism as in the present invention, the operation of the steering handle does not become heavy, There is no decrease in sex.

In this case, when the side brake on the turning center side is strongly operated to the braking side, the rear wheel on the turning center side is dragged on the ground during turning, and the rear wheel on the turning center side roughens the ground. Sometimes. On the other hand, in the present invention, the side brake on the turning center side is set to the weak braking state by the power steering mechanism during turning, so that the rear wheel on the turning center side can be dragged during turning. In this state, the braking force of the side brakes is lost in this state, and the rear wheel on the turning center side rotates, and the rear wheel on the turning center side does not roughen the ground.

[II] Even when the side brakes on the turning center side are set to be in the weak braking state as in the above [1], the turning center side is changed due to the size of the turning radius and changes in the ground condition. The rear wheels may stop and damage the ground.

Therefore, with the construction of the above [2], the rotation state of the rear wheels on the turning center side is detected during turning, and the side brakes on the turning center side are controlled so that the rear wheels on the turning center side do not stop. The power (the operation amount by which the cam mechanism operates the side brake on the turning center side to the braking side) is automatically and strongly changed. As a result, the braking force of the side brakes on the turning center side is maintained to such an extent that the rear wheels on the turning center side do not stop, regardless of the size of the turning radius and changes in the ground conditions, etc. The risk of damaging the ground with is further reduced.

[0011]

As described in claim 1, since the operation of the side brake on the turning center side to the braking side is automatically performed only by operating the steering handle, it is not necessary to step on the side brake pedal during turning. As a result, the turning operation can be simplified and the turning operability can be improved. In this case, by using the power steering mechanism having the existing structure for operating the side brake, the configuration of the present invention can be easily obtained with a slight addition or modification, which is advantageous in terms of manufacturing cost. Become. Since the side brake on the turning center side is set to be in the weak braking state,
It is less likely that the rear wheels on the center side of the turn will stop and the ground will be roughened during turning, and the turning performance can be improved. If the braking force of the side brake on the turning center side is automatically changed and adjusted as in claim 2, the rear wheel on the turning center side may stop and the ground may be roughened during turning. Therefore, the turning performance of the work vehicle can be further improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (1) An example of a four-wheel drive type work vehicle in which an engine 3 is mounted on the front part of a machine body supported by front wheels 1 and rear wheels 2 and a mission case 4 is mounted on the rear part of the machine body as shown in FIG. It constitutes an agricultural tractor. As shown in FIG. 1, motive power from the engine 3 is transmitted to a traveling transmission (not shown) in the transmission case 4 to perform a speed change operation, and is transmitted from the rear wheel differential mechanism 5 to the left and right rear wheels 2. The power branched from the rear wheel differential mechanism 5 is transmitted from the front wheel transmission 7 to the left and right front wheels 1 via the front wheel transmission shaft 8 and the front wheel differential mechanism 6.

(2) Next, the front wheel transmission 7 will be described. As shown in FIG. 10, the power branched from just before the rear wheel differential mechanism 5 is transmitted from the transmission gear 16 to the first standard gear 12, and the first speed increasing gear 12 is transmitted via the first standard gear 12 and the transmission shaft 11. 13 has been transmitted. A second standard gear 9 and a second speed-increasing gear 10 are fitted on the front wheel transmission shaft 8 to the front wheel 1 so as to be rotatable relative to each other, and the first and second standard gears 12,
9, the first and second speed increasing gears 13 and 10 are in mesh with each other.

When the shift member 14 slidably attached to the front wheel transmission shaft 8 by the spline structure is engaged with the second standard gear 9, the power is transmitted while the front wheel 1 is driven at substantially the same speed as the rear wheel 2. It is done (standard condition). Conversely, the second
When the friction clutch 15 formed between the speed increasing gear 10 and the front wheel transmission shaft 8 is pressed and operated by the shift member 14, the power is transmitted in a state in which the front wheel 1 is driven at a higher speed than the rear wheel 2 ( Acceleration state).

Next, the structure of the operation system of the shift member 14 of the front wheel transmission 7 will be described. As shown in FIG.
The shift fork 17 for the shift member 14 is externally fitted to the operation shaft 18 that is slidable in the axial direction via a spring 19 for accommodation, and the spring 20 having a weaker biasing force than the spring 19 causes the shift fork 17 to move. It is urged toward the side of engagement with the second standard gear 9 (standard state side). On the other hand, as shown in FIGS. 2 and 1, the power steering mechanism 21 supports the pitman arm 22 for steering operation of the front wheels 1, and the cam plate 23 (corresponding to the cam mechanism) is fixed to the pitman arm 22. The pin 24a of the cam arm 24, which is swingably supported around the vertical axis P1 of the machine body fixing portion, is attached to the cam plate 2
3 is engaged with the cam hole 23a. And wire 2
5 is connected across the tip of the cam arm 24 and the operating shaft 18.

With the above-described structure, when the steering wheel 26 shown in FIG. 11 is operated and the power steering mechanism 21 swings the pitman arm 22 from the straight-ahead position to the right or left over the set angle, that is, the front wheel 1 When the steering wheel is steered to the right or left from the straight-ahead position over the set angle, the cam arm 24 is swung to the left side of the drawing by the cam action of the cam hole 23a and the pin 24a as shown in FIG.
The wire 25 is pulled to the cam arm 24 side. As a result, the operation shaft 18 and the shift fork 17 in FIG. 10 are slid to the left in the drawing, the shift member 14 presses the friction clutch 15, and the front wheel 1 is accelerated.

(3) As shown in FIG. 1, a pair of left and right side brakes 27 that can independently brake the left and right rear wheels 2 are provided. Next, the operation structure of the left and right side brakes 27 will be described. As shown in FIG. 1, a pair of brake operating mechanisms 33 are provided for the pair of left and right side brakes 27. As shown in FIGS. 5 and 6, an L-shaped brake arm 28 is swingably supported around the axis P2 in the brake operating mechanism 33, and the lower end of the brake arm 28 on the paper surface and the side brake 27 are connected to each other. Are linked together by link rods 29 (corresponding to link mechanisms). As shown in FIGS. 1 and 6, a pair of left and right side brake pedals 30 is provided on the right side of the control section of the aircraft, and as shown in FIGS. 1, 5 and 6, one end of the side brake pedal 30 and one end of the brake arm 28 are provided. Are linked and linked by a linking rod 31 and a connecting pin 32.

With the above structure, when the left side brake pedal 30 is depressed, for example, as shown in FIG. 7, the link rod 31 is pulled upward and the brake arm 28 swings counterclockwise in the plane of the drawing. The left side brake 27 is operated to the braking side by the link rod 29.

(4) Next, the linkage between the left and right side brakes 27 and the power steering mechanism 21 for the front wheels 1 will be described. As shown in FIGS. 5 and 6, the operation arm 34 is swingably supported independently of the brake arm 28 around the axis P2 of the brake operation mechanism 33.
A link arm 36 is swingably supported around a support pin 35 at the tip of the operation arm 34. As shown in FIG. 6, a spring 37 that urges the linkage arm 36 clockwise in the plane of the drawing.
Is attached to the support pin 35, and the linkage arm 36
A vertically long concave portion 36a is formed on the left side of the paper.
As a result, the connecting pin 32 of the brake arm 28 is inserted into the recess 36a of the linking arm 36 by the urging force of the spring 37.

As shown in FIGS. 1, 2, and 4, a right operation arm 39 is swingably supported around a vertical axis P3 of a right frame 38 at the front of the machine body, and a right brake operation mechanism 33 is provided.
The support pin 35 of the operation arm 34 and the right operation arm 39 are interlockingly connected by a spring 40 and a wire 41 (corresponding to a linkage mechanism). The support shaft 42 is rotatably supported around the vertical axis P4 of the left frame 38.
The left first operation arm 43 is fixed to the upper end of 2, and the left second operation arm 44 is fixed to the lower end. The support pin 35 of the operation arm 34 of the left brake operation mechanism 33 and the left second operation arm 44 are interlockingly connected by a spring 40 and a wire 41 (corresponding to a linkage mechanism). Right operation arm 39
A stopper 46 for stopping the left second operation arm 44 in the posture shown in FIG. 2 is fixed to the left and right frames 38. Further, as shown in FIGS. 2 and 5, the operation arm 3 is attached to the support pin 35 of the operation arm 34 of the brake operation mechanism 33.
A spring 45 for urging 4 in the clockwise direction of the drawing is attached.

With the above structure, when the front wheel 1 is steered to the left by more than the set angle, as shown in FIG. 3, the pitman arm 22 swings downward and the cam plate 23 moves to the left first operation. The left first and left second operation arms 43, 44 are brought into contact with the arm 43, and the left first and second left operation arms 43, 44 are oscillated in the clockwise direction of the drawing. As a result, the left wire 41 is pulled toward the first left and second left operation arms 43 and 44, and the operation arm 34 of the left brake operation mechanism 33 swings counterclockwise in the drawing.
In this case, as shown in FIG.
Since the connecting pin 32 of the brake arm 28 is inserted in a, the linkage arm 36 is moved along with the swing of the operation arm 34.
Is pulled upward in the drawing, the brake arm 28 is also swung counterclockwise in the drawing due to the engagement between the recess 36a and the connecting pin 32, and the left side brake 27 is operated in a weak braking state as described later. It is.

As described above, when one of the side brakes 27 is operated in the weak braking state by the steering operation of the front wheels 1, the wire 25 is pulled by the action of the cam plate 23 and the cam arm 24 shown in FIG. As described above, the front wheel transmission 7 is switched from the standard state to the speed increasing state. As a result, when the front wheels 1 are steered by a set angle or more, the front wheel transmission 7 is switched to a speed-up state and the front wheels 1 are driven to speed up. The side brake 27 of the rear wheel 2 on the side is operated to the weak braking state.

As shown in FIGS. 5 and 6, the link rod 31 on the side brake pedal 30 side is provided with a long hole 31a, and the connecting pin 32 is inserted into this long hole 31a. As a result, even if the front wheel 1 is steered over the set angle as described above and the operation arm 34 and the brake arm 28 swing counterclockwise in the drawing as shown in FIG.
The side brake pedal 30 is not operated, only the connecting pin 32 moves upward in the drawing.

The state shown in FIG. 2 (the wire 4
1 in a state where the pulling operation is not performed), when the side rod pedal 30 is stepped on and the linking rod 31 is moved upward in the drawing, as shown in FIG.
8 swings counterclockwise in the drawing, the connecting pin 32 only moves upward in the recess 36a of the linking arm 36 in the drawing, and the operating arm 34 and the linking arm 36 are not shown in FIGS.
It does not move in the posture shown in.

(5) Next, when the front wheel 1 is steered to the right or left over the set angle, the side brake 27 on the turning center side is automatically set to the weak braking state. explain. As shown in FIG. 12, the left and right wires 4
Both ends of one outer 41a are fixed to a fixed bracket 54 by a pair of nuts 47, respectively, so that the fixing position of the outer 41a can be adjusted.

As a result, as shown in FIG.
In a state in which 1 is removed from the support pin 35, the front handle 1 is steered by the steering handle 26 and the power steering mechanism 21 to the left, for example, at a set angle or more, and the connecting portion 41b of the wire 41 is separated from the support pin 35. In this state (the operation arm 34 and the left side brake 27 are completely returned to the braking release side), the support pin 3
The adjustment jig 55 is attached to 5. Next, the connecting portion 41b of the wire 41 is attached to the adjusting jig 55, and in this state, the fixing position of the outer 41a is adjusted by the nut 47 and the wire 41 is operated to move back and forth. The spring 40 is set in the free length state while eliminating mechanical backlash. Then, the adjusting jig 55 is removed, and the connecting portion 41b of the wire 41 is attached to the support pin 35 again.

In this case, when the front wheel 1 is steered to the left over a set angle, the length of the spring 41 is adjusted to such an extent that the left side brake 27 is operated in a weak braking state. The length of the tool 55 is set. As a result, when the front wheel 1 is steered to the left over the set angle, the left side brake 27 is automatically operated in the weak braking state. Then, the above operation is similarly performed on the right side brake 27.

(6) Next, when the front wheel 1 is steered by a set angle or more, the side brake 27 on the turning center side is automatically operated in the weak braking state and is not operated as described above. The structure for switching between states will be described. As shown in FIGS. 8 and 9, around the horizontal axis P5 of the control section of the aircraft,
An operation plate 48 having an L shape in a side view is swingably supported, and an operation lever 50 is fixed to a position of a horizontal axis P5 on the operation plate 48. As shown in FIGS. 1, 2, and 8, a pair of wires 51 are connected across each of the linkage arms 36 of the left and right brake operating mechanisms 33 and the operation plate 48, and the operation plate 48 and the operation lever 50 are connected to each other. ON shown in FIG.
A toggle spring 52 and a stopper 49 for holding the position and the OFF position are provided.

In the state shown in FIG. 8, the operating lever 50 and the operating plate 48 are operated to the ON position, and as shown in FIG. 2, the linkage arms 36 of the left and right brake operating mechanisms 33 move clockwise in the plane of the drawing. This is a state in which the connecting pin 32 on the brake arm 28 side is inserted into the recess 36a of the linking arm 36 by being rocked.

In this state, for example, when the front wheel 1 is steered to the left over a set angle, the operating arm 34 of the left brake operating mechanism 33 swings counterclockwise on the paper surface as shown in FIG. The brake arm 28 is oscillated counterclockwise in the drawing by the engagement of the connection pin 32 with the connection pin 32, and the left side brake 27 is operated in a weak braking state. In this case, as shown in FIGS. 8 and 9, a limit switch 53 for detecting a state where the operation lever 50 and the operation plate 48 are operated to the ON position is provided, and a lamp that lights up in accordance with this detection (see FIG. (Not shown). Thereby, the operator can recognize that the side brake 27 on the turning center side is automatically operated in the weak braking state when the front wheel 1 is steered over the set angle.

Then, when the operation lever 50 and the operation plate 48 are operated to the OFF position, the pair of wires 51 move the operation plate 4
8 and the linkage arms 36 of the left and right brake operating mechanisms 33 are oscillated counterclockwise in the drawing as shown by the chain double-dashed line in FIG. 6, so that the recess 36a of the linkage arm 36 moves toward the brake arm 28 side. The connecting pin 32 is moved to the right side of the drawing. In this state, for example, even if the front wheel 1 is steered to the left by a set angle or more, the operation arm 34 of the left brake operating mechanism 33 only swings counterclockwise on the paper surface, and the brake arm 28 rotates counterclockwise on the paper surface. The left side brake 27 is not operated in a weak braking state.

[Other Embodiments] The present invention may be configured as shown in FIGS. 13 and 14. In the configuration shown in FIG. 1 described above, as shown in FIGS. 13 and 14, a pair of rotation sensors 56 for detecting the number of rotations of the left and right rear wheels 2 are provided between the rear wheel differential mechanism 5 and the left and right rear wheels 2. Provided, brake operation mechanism 33
To the linkage rod 29 that connects the side brake 27 with the
A double-acting operation cylinder 57 (corresponding to a changing mechanism) is provided, and the hydraulic cylinder 57 expands and contracts by supplying / discharging operation oil from a control valve 58 of a three-position switching type and an electromagnetic operation type.

With the above configuration, for example, it is assumed that the front wheel 1 is steered leftward over a set angle and the left side brake 27 is weakly braked by the wire 41 and the linkage rod 29. In this case, the control device 59 (corresponding to the control unit) is based on the difference between the detection values of the left and right rotation sensors 56 (the detection value of the left rotation sensor 27 is small) and the signal from the limit switch 60 to the operation arm 34. , It is determined that the left side brake 27 has been operated in the weak braking state and the aircraft has begun to turn to the left.

Thereafter, the control device 59 switches the control valve 58 for the left side brake 27 and expands and contracts the left operating cylinder 57 based on the detection of the left rotation sensor 56, and the left side brake 27. The braking force of is adjusted to be strong or weak within the range of the weak braking state so that the left rear wheel 2 does not stop.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a plan view showing a linked state of a front wheel power steering mechanism, a front wheel transmission, and left and right side brakes.

[FIG. 2] In a state where the front wheels are operated in a straight ahead position,
A plan view and a side view showing a state in which the power steering mechanism for the front wheels and the left and right brake operating mechanisms are linked to each other.

FIG. 3 is a plan view and a side view showing a state in which the power steering mechanism for the front wheels and the left and right brake operating mechanisms are linked to each other when the front wheels are steered to the left over a set angle.

FIG. 4 is a rear view of the vicinity of the front wheel power steering mechanism in FIG. 2 as viewed from the right side of the paper surface of FIG.

5 is a rear view of the vicinity of the brake operation mechanism in FIG. 2 as viewed from the right side of the paper surface of FIG.

FIG. 6 is a side view showing a state in which the left and right brake operation mechanisms are linked with the left and right side brakes and side brake pedals.

7 is a side view showing a state in which the side brake pedal is stepped on from the state shown in FIG.

FIG. 8 is a side view of the vicinity of an operation lever for performing a switching operation between a state where a side brake on a turning center side is automatically operated to a weak braking state and a state where the side brake is not operated during turning.

9 is a view of the vicinity of the operation lever in FIG. 8 viewed from the lower side of the paper surface.

FIG. 10 is a vertical sectional side view of the front wheel transmission.

FIG. 11 is an overall side view of an agricultural tractor.

FIG. 12 is a diagram showing a setting state of an extension amount of a spring for a side brake in a state where a side brake on a turning center side is automatically operated to a weak braking state during turning.

FIG. 13 is a plan view showing a linked state of a front wheel power steering mechanism, a front wheel transmission, and left and right side brakes in another embodiment.

FIG. 14 is an operation circuit diagram in another embodiment.

[Explanation of symbols]

 1 Front Wheel 2 Rear Wheel 21 Power Steering Mechanism 23 Cam Mechanism 27 Side Brake 29, 41 Linkage Mechanism 56 Rotation Sensor 57 Change Mechanism 59 Control Means

Claims (2)

[Claims] 1. A pair of left and right side brakes (27) capable of independently braking the left and right rear wheels (2), and a cam mechanism (23) provided in a power steering mechanism (21) for the front wheels (1). Are mechanically interlocked by a pair of linkage mechanisms (29) and (41), and the power steering mechanism (21) steers the front wheel (1) from the straight-ahead position to the right or left at a set angle or more. When operated, the cam mechanism (2
3) The side brake (27) on the turning center side is configured to be operated to the braking side, and the cam mechanism (23) is arranged so that the side brake (27) on the turning center side is in a weak braking state. And linkage mechanism (2
9), (41) side brake (2)
7) A turning operation structure of a work vehicle in which the operation amount to the braking side of 7) is set. 2. The cam mechanism (23) and the linkage mechanism (2)
9), (41) side brake (2)
Change mechanism (57) that can change the operation amount to the braking side of 7)
And a rotation sensor (56) for detecting the rotation states of the left and right rear wheels, and the side brake (27) on the turning center side is braked by the power steering mechanism (21) and the cam mechanism (23). When it is operated to, the change mechanism (57) prevents the rear wheel (2) on the turning center side from stopping rotation based on the detection of the rotation sensor (56) by the side brake (27) on the turning center side. 2. The turning operation structure for a work vehicle according to claim 1, further comprising control means (59) for changing an operation amount of the vehicle to the braking side.