JPH0616148A - Side brake operation structure for working vehicle - Google Patents

Abstract

PURPOSE:To prevent the sticking of mud while covering a control valve and the switching structure, and eliminate a side brake operation exclusive use pump by installing a side brake control valve in a hydraulic type power steering mechanism. CONSTITUTION:In a power steering mechanism 3, the movable member 22 is installed in the power steering mechanism 3, and a control valve 34 for side brakes 11R and 11L is formed between the movable member 22 and a fixed part 32. When steering operation is carried out on front wheels 1 by not less than a preset angle, switching operation is carried out on the control valve 34 in a case of the power steering mechanism 3, and operating oil is supplied to turning center side hydraulic actuators 13R and 13L from the control valve 34. In such constitution, since the whole control valve 34 and the switching structure are covered completely, the sticking of mud can be prevented. Since the operating oil being supplied to the power steering mechanism 3 from a pump 26 is constituted to be supplied the control valve 34 by passing through supply passages 22a and 33, a side brake exclusive use pump can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a side brake operating structure for a four-wheel type work vehicle equipped with side brakes capable of independently braking left and right rear wheels.

[0002]

2. Description of the Related Art In an agricultural tractor, which is an example of a four-wheel type work vehicle, as disclosed in, for example, Japanese Patent Laid-Open No. 3-243429, the left and right rear wheels can be independently braked. Some include a pair of side brakes (13R, 13L in FIG. 1 of the publication) and a hydraulic actuator (17 in FIG. 1 of the publication) capable of operating the side brakes on the braking side. . in this case,
When the front wheels are steered from the straight ahead position to the right or left beyond the set angle, the control valve (8, 22 in FIG. 1 of the above publication) is switched and hydraulic oil is supplied to the hydraulic actuator on the turning center side. The side brake on the turning center side is automatically operated to the braking side. This allows
The braking action on the rear wheel on the turning center side enables a small turn around the rear wheel on the turning center side.

In this case, as shown in FIG. 2 of the above publication, a cam plate is fixed to a pitman arm for steering operation of front wheels, and a spool of a side brake control valve is brought into contact with the cam plate. When the front wheel is steered by the pitman arm from the straight ahead position to the right or left over a set angle, the control valve is switched by the cam plate.
And it is equipped with a pump for the hydraulic actuator of the side brake.

[0004]

The pitman arm for steering operation of the front wheels as described above is generally mounted on the lower part of the machine body in many cases, and is often used in a work vehicle that travels on rough terrain such as a field. , A lot of mud etc. tend to adhere to the bottom of the machine. Therefore, if mud or the like adheres to the pitman arm, the cam plate, the spool of the control valve, etc., it may cause malfunction of the control valve. Therefore, it is necessary to sufficiently cover the pitman arm, the cam plate, the spool of the control valve, etc. . However, it is actually difficult to completely cover a member that is largely movable, such as a pitman arm, a cam plate, and a spool of a control valve, and there is room for improvement. Further, in the above-mentioned structure, since a dedicated pump for supplying hydraulic oil to the hydraulic actuator for the side brake is equipped, there is room for improvement in terms of simplification of the structure. The present invention can easily and reliably cover the vicinity of a control valve that supplies hydraulic oil to a hydraulic actuator for a side brake.
Another object of the present invention is to configure a pump for supplying hydraulic oil to a hydraulic actuator for a side brake so that a dedicated pump need not be provided.

[0005]

A feature of the present invention is that the side brake operation structure for a work vehicle as described above is configured as follows. That is, a pair of left and right side brakes that can independently brake a pair of left and right rear wheels, a pair of left and right hydraulic actuators that can operate each of the left and right side brakes on the braking side, and a hydraulic type for steering operation of the front wheels. In addition to the power steering mechanism, the power steering mechanism forms a control valve between a movable member that moves forward and backward in accordance with the steering operation of the front wheels and a fixed portion to supply hydraulic oil to the power steering mechanism. When the front steering wheel is steered from the straight-ahead position to the left or right by the power steering mechanism, the hydraulic oil from the control valve to the hydraulic actuator on the turning center side is provided. Is supplied and the side brake on the turning center side is operated to the braking side.

[0006]

For example, as shown in FIGS. 1, 2 and 3, in the hydraulic power steering mechanism 3, the movable members (ball nut 19, sector shaft 22 and the like) are installed inside the case of the power steering mechanism 3. There is. Therefore,
If a control valve for a side brake is formed between the movable member and a fixed portion such as the case as in the present invention, the entire control valve and its switching structure (movable member) are inside the case of the power steering mechanism. Will be stored in. If the front steering wheel is steered to the left or right by the power steering mechanism at a set angle or more, the control valve is switched within the case of the power steering mechanism. Oil is supplied, and the side brake on the turning center side is operated to the braking side. As a result, the entire side brake control valve and its switching structure are completely covered by the case of the power steering mechanism or the like.

Further, in the present invention, as shown in FIGS. 1, 2 and 3, for example, the hydraulic oil supplied from the pump 26 to the power steering 3 mechanism is branched and supplied to the side brake control valve 34. ing. Therefore, since this pump is used for both the power steering mechanism and the side brake, it is not necessary to equip the pump exclusively for the hydraulic actuator of the side brake.

[0008]

As described above, by incorporating the control valve for the side brake in the power steering mechanism which is the existing structure, the entire control valve and its switching structure are covered almost completely. It has become possible to prevent the adherence of such matters, and it is possible to improve the reliability of the structure in which the side brake on the turning center side is automatically operated to the braking side when turning. Also, the pump dedicated to the automatic operation of the side brake can be omitted, and the structure can be simplified and an advantageous structure in terms of production cost can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of an agricultural tractor which is an example of a four-wheel type work vehicle. An engine (not shown) is provided at a front portion of a body supported by a pair of left and right front wheels 1 and a pair of left and right rear wheels 2. An agricultural tractor is provided with the mission case 4 at the rear. Power from the engine is transmitted from the rear wheel differential mechanism 5 to the left and right rear wheels 2 via a main transmission (not shown) and an auxiliary transmission (not shown) in the mission case 4. Then, the power branched from immediately before the rear wheel differential mechanism 5 is transmitted to the left and right front wheels 1 via the front wheel transmission 6, the front wheel output shaft 7, and the front wheel differential mechanism 8.

The front wheel transmission 6 shown in FIG. 1 has a normal state in which the front wheel 1 is driven at substantially the same speed as the rear wheel 2, and a state in which the front wheel 1 is driven at a higher speed than the rear wheel 2. It is possible to perform switching operation between two states, that is, a transmission speed increasing state. As shown in FIG. 1, the shift member 9 for two-state switching operation is a spring 10
Is urged toward the side of engagement with the standard gear 20, and the shift member 9 is normally engaged with the standard gear 20 to be in the standard state. Then, when hydraulic oil is supplied into an oil chamber (not shown) formed between the shift member 9 and the standard gear 20, the shift member 9 slides to the left side of the drawing and the friction clutch 21 is pressed and operated. A speed-up state can be obtained.

As shown in FIG. 1, with respect to the left and right rear wheels 2,
Side brakes 11 that can independently brake each rear wheel 2
R and 11L are provided. As shown in FIGS. 1 and 4, the side brake pedal 12 is provided on the right side of the floor of the control section.
A pair of left and right R and 12L are arranged. The left and right side brake pedals 12R and 12L and the side brake 11 are arranged.
R and 11L are interlockingly connected via cylinders 13R and 13L (corresponding to hydraulic actuators) and a linkage rod 14.

With the above structure, the left and right side brake pedals 12R and 12L can be independently operated by depressing the left and right side brake pedals 12R and 12L. As shown in FIG. 4, the cylinders 13R and 13L are urged toward the extension side by springs 13a. By supplying hydraulic oil to contract the cylinders 13R and 13L, the left and right side brakes 11R and 1L are released.
It is possible to operate 1L to the braking side.

Next, the power steering mechanism 3 for steering operation of the front wheels 1 will be described. As shown in FIGS. 2 and 1, a worm shaft 17 interlockingly connected to a steering handle 16 through an operating shaft 15, a ball nut 19 externally fitted to the worm shaft 17 through a ball 18, and an engagement with a ball nut 19 A sector shaft 22 (corresponding to a movable member of the power steering mechanism 3), a spool 23 and the like externally fitted to the worm shaft 17 are provided in the first case 24, and the integral type power steering mechanism 3 is provided. Is configured. A pitman arm 25 for steering operation of the front wheels 1 is fixed to the end of the sector shaft 22 protruding from the first case 24.

With the above structure, for example, when the steering handle 16 is operated to the right and the worm shaft 17 is started to be rotated rightward, the spool 23 is operated and the spool 23 is operated.
As shown in FIG.
It is supplied to the oil chamber 29 via the oil passage 27, the spool 23, and the oil passage 28 in the No. 4. Therefore, by turning the worm shaft 17 to the right turning side and supplying hydraulic oil to the oil chamber 29,
The ball nut 19 moves to the upper side of the drawing and moves to the sector shaft 2
2 is rotated counterclockwise in the drawing, and the front wheel 1 is steered rightward by the pitman arm 25.

On the contrary, when the steering handle 16 is operated to the left and the worm shaft 17 is started to be rotated to the left, the spool 23 is operated and the hydraulic oil from the pump 26 is discharged as shown in FIG. The oil is supplied to the oil chamber 31 via the oil passage 27, the spool 23, and the oil passage 30 in the first case 24.
Therefore, by rotating the worm shaft 17 to the left turning side and supplying hydraulic oil to the oil chamber 31, the ball nut 19 moves downward in the plane of the drawing, and the sector shaft 22 is rotated clockwise in the drawing, so that the pitman arm is rotated. The front wheel 1 is steered to the left by 25.

Next, when the front wheel 1 is steered to the right or left beyond the set angle from the straight ahead position to make a turn, the side brakes 11R and 11L on the turning center side are automatically operated to the braking side. Will be described. As shown in FIGS. 2 and 3, the sector shaft 22 extends from the first case 24 to the side opposite to the pitman arm 25, and the second case 32 covers the portion of the sector shaft 22 protruding to the opposite side. (Corresponding to the fixed part of the power steering mechanism 3)
The second case 32 is fixed to the first case 24. Further, one supply passage 22a is opened in the sector shaft 22, and the oil passage 2 on the pump 26 side is formed.
The oil passage 33 (corresponding to the supply passage) branched from 7 is the supply passage 2
2a. As shown in FIG. 3, a portion of the sector shaft 22 inside the second case 32 is formed into a spool shape of the rotary valve, and the first land portion 22 is formed.
A and the second land portion 22B are formed side by side, and the first and second land portions 22A, 22 of the sector shaft 22 are formed.
A control valve 34 is formed between B and the second case 32.

The first land portion 22A side and the right cylinder 13R in FIG. 1 are connected via an oil passage 35, and the second land portion 22B side and the left cylinder 13L in FIG. 1 are connected to the oil passage 36.
And the oil chambers between the shift member 9 and the standard gear 20 in the front wheel transmission 6 and the oil passages 35, 36.
And are connected via oil passages 37 and 38. The oil passages 37, 38 are provided with check valves 39, 40 which can be opened by pilot pressure.

The state shown in FIG. 3 is a state in which the front wheel 1 is operated to the straight traveling position, and the hydraulic oil from the pump 26 is supplied to the oil passage 3
3, supply path 22a and output ports 22b and 22c of the sector shaft 22, drain port 32 of the second case 32
It is discharged via a and 32b. In this state, the left and right cylinders 13R and 13L are connected to the oil passages 35 and 36,
Oil is drained through the drain portions 22d and 22e of the sector shaft 22, and the left and right side brakes 11R and 11
L is not operated to the braking side. Then, the check valves 39, 40 are opened by the pilot pressure from the drain ports 32a, 32b, and the oil chambers between the shift member 9 of the front wheel transmission 6 and the standard gear 20 also open the oil passages 37, 38. After that, the oil is drained and the front wheel transmission 6 is in the standard state.

When the front wheel 1 is steered to the right over the set angle from the above state, the sector shaft 22 shown in FIG. 3 is rotated counterclockwise in the drawing, and the side of the first land portion 22A of the sector shaft 22 is rotated. The output port 22b of is communicated with the oil passage 35. As a result, hydraulic oil is supplied to the right cylinder 13R, the right cylinder 13R contracts, and the right (turning center side) side brake 11R is operated to the braking side. In this case, on the side of the second land portion 22B of the sector shaft 22, the oil passage 36 and the drain portion 22e are still in communication with each other, so the left side brake 11L is not operated to the braking side.

When the sector shaft 22 rotates in this manner, the pilot pressure applied to the check valves 39 and 40 disappears and the check valves 39 and 40 close. In this case, oil passage 3
5 is supplied to the front wheel transmission 6 via the check valve 39 and the oil passage 37, and the shift member 9 shown in FIG. 1 presses and operates the friction clutch 21 to increase the front wheel 1. Driven fast. As described above, when the front wheel 1 is steered to the right over the set angle, the rear wheel 2 on the right side (center of turning) is automatically braked, and the front wheel 1 is driven at a higher speed than the rear wheel 2. Then, a small turn to the right can be made.

On the contrary, when the front wheel 1 is steered leftward from the straight traveling state shown in FIG. 3 by a set angle or more, the sector shaft 22 shown in FIG. 3 is rotated clockwise in the drawing to move the sector shaft 22 to the second position. The output port 22c on the side of the land portion 22B communicates with the oil passage 36. This allows the left cylinder 13
The hydraulic oil is supplied to L, the left cylinder 13L contracts, and the left (turning center side) side brake 11L is operated to the braking side. In this case, on the side of the first land portion 22A of the sector shaft 22, the oil passage 35 and the drain portion 2 are provided.
2d is still in communication, so the right side brake 1
1R is not operated on the braking side.

When the sector shaft 22 rotates in this manner, the pilot pressure applied to the check valves 39 and 40 disappears and the check valves 39 and 40 close. In this case, oil passage 3
6 is supplied to the front wheel transmission device 6 via the check valve 40 and the oil passage 38, and the shift member 9 shown in FIG. 1 presses and operates the friction clutch 21 to increase the front wheel 1. Driven fast. As described above, when the front wheel 1 is steered to the left over the set angle, the left rear wheel 2 (center of turning) is automatically braked and the front wheel 1 is driven at a higher speed than the rear wheel 2. Then, a small turn to the left can be made.

[Other Embodiment] Although the control valve 34 is formed between the sector shaft 22 and the second case 32 in the power steering mechanism 3 in the above embodiment, the ball nut 19 (power steering mechanism 3 shown in FIG. Corresponding to the movable member) and the first case 24 (power steering mechanism 3).
(Corresponding to the fixed portion of), a control valve may be formed.
Although the above-described embodiment is a four-wheel drive type equipped with the front wheel transmission 6, it is a four-wheel drive equipped with only the side brakes 11R and 11L for the rear wheels 2 without the front wheel transmission 6 as described above. The present invention may be applied to a type or two-wheel drive type work vehicle.

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 diagram showing a linked state of a transmission system for front and rear wheels, left and right side brakes and side brake pedals, a power steering mechanism for front wheels, and the like.

FIG. 2 is a vertical sectional side view of a power steering mechanism for front wheels.

FIG. 3 is a vertical sectional side view of the vicinity of a control valve in a power steering mechanism for front wheels.

FIG. 4 is a side view showing a connected state of a side brake pedal and a cylinder and a side brake.

[Explanation of symbols]

 1 Front Wheel 2 Rear Wheel 3 Power Steering Mechanism 11R, 11L Side Brake 13R, 13L Hydraulic Actuator 26 Pump 22 Power Steering Mechanism Movable Member 22a, 33 Supply Path 32 Power Steering Mechanism Fixed Part 34 Control Valve

Claims (1)

[Claims] 1. A pair of left and right side brakes (11R), (11) capable of independently braking a pair of left and right rear wheels (2).
L) and the left and right side brakes (11R), (11
L) is provided with a pair of left and right hydraulic actuators (13R), (13L) that can be operated on the braking side, and a hydraulic power steering mechanism (3) for steering operation of the front wheels (1). In the power steering mechanism (3), a control valve (34) is provided between a fixed member (32) and a movable member (22) that moves forward and backward in accordance with the steering operation of the front wheels (1).
And a supply passage (22a), (33) for branching hydraulic oil from a pump (26) for supplying hydraulic oil to the power steering mechanism (3) and supplying the hydraulic oil to the control valve (34). When the front steering wheel (1) is steered by the power steering mechanism (3) from the straight-ahead position to one of the left and right over a set angle, the control valve (34) shifts the hydraulic actuators (13R) and (13L) on the turning center side. The hydraulic oil is supplied to the side brakes (11R), (11R) on the turning center side.
L) is operated to the braking side, the control valve (34)
The side brake operation structure of the work vehicle that constitutes the.