JPH1081255A - Turning drive structure of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turning drive structure having a structure capable of restraining a field from being roughened as well as to achieve simplification of the turning operation in the turning drive structure of a working vehicle provided with a pair of right and left side brakes. SOLUTION: A pair of side brakes 8R, 8L capable of independently braking right and left rear wheels 3 into the locking state are provided, an operating means for operating the side brakes 8R, 8L inside turning to the braking side when the right or left steering angle of front wheels 5 becomes the set angle or more is provided, and the braking action of the operating means is set to the weak braking state so that the side brakes 8R, 8L inside turning may brake the rear wheels 3 by such operating force that the rear wheels 3 may not be in the locking state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turning drive structure for a four-wheel drive agricultural tractor, and more particularly, to a turning drive structure for a left and right rear wheel, which is provided with side brakes which can be braked independently. This relates to a sharp turn with the rear wheel braked.

[0002]

2. Description of the Related Art In a tractor of this type, conventionally,
As disclosed in JP-A-2-175331, a hydraulic actuator is interposed in the operation system of each of the side brakes, and a solenoid valve is provided in an oil passage branched from a hydraulic supply passage in the front wheel speed increasing mechanism. A solenoid valve that switches and controls a solenoid valve based on the detection operation of a detection switch that detects that a left-right steering operation beyond a set angle has been performed, and drives a hydraulic actuator corresponding to a side brake inside the turn. was there.

[0003]

The above conventional structure enables a sharp turn by turning the front wheel speed increasing mechanism and braking the rear wheel inside the turn at the time of turning in a field. The present invention is designed to eliminate the troublesome operation of depressing the brake pedal for one-side braking operation, and to perform the above-described operation only by the sterling operation. However, the sharp turning travel is performed by locking the rear wheel on the inside of the turn, that is, the so-called pivot turn state in which the rear wheel on the inside of the turn is off-axis at the stop position. There was a possibility that the field was roughened due to the formation of a shaft (corresponding to a rut) due to the rotation. An object of the present invention is to make it possible to make a brake turn according to the geological condition of a field, and to eliminate the possibility of damaging the field.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a front steering wheel and a rear driving wheel, and a left and a right rear wheel having respective side brakes which can be braked independently. In the turning drive structure of the agricultural tractor, a hydraulic actuator for braking operation is provided in the operation system of each side brake, and when the right steering angle of the front wheel is equal to or larger than a set value, the hydraulic actuator for right side brake operation is operated, and
When the left steering angle of the front wheel is equal to or larger than a set value, a switching valve that can be switched in accordance with the steering operation of the front wheel is provided in a state where the hydraulic actuator for the left side brake operation is operated, and a hydraulic circuit for the hydraulic actuator is provided. A variable relief valve capable of changing and setting the maximum pressure is provided. In addition, when the steering angle of the front wheels exceeds a set value, a hydraulically driven front wheel speed increasing mechanism that switches the driving rotational peripheral speed of the front wheels to a state faster than the driving rotational peripheral speed of the rear wheels is connected to the hydraulic circuit. It is convenient if the hydraulic pressure required for operating the front wheel speed increasing mechanism is set to be lower than the hydraulic pressure required for operating the brake operating hydraulic actuator.

[0005]

According to the first aspect of the invention, in order to turn the vehicle body, for example, when the front wheels are steered to the right by a predetermined angle or more, the switching valve is accordingly operated to drive the right hydraulic actuator to drive the right side wheel. A sudden turning state due to the brake turning after the brake is actuated automatically appears. Therefore, when making a small turn on a headland or the like, the pilot only needs to perform a steering operation without braking operation and suddenly. Can turn. In addition, since the above-described sharp turning state is one in which the front wheels are steered to appear at a set angle or more, the hydraulic switching valve maintains a neutral state during straight running or a gentle turning operation. No braking force acts on the rear wheels. Since the maximum pressure of the hydraulic circuit can be changed and set by the variable relief valve, for example, in a hard field, the circuit pressure is set to a higher value, and the brake turning state in which the rear wheel inside the turning is completely locked is displayed. In a soft field, the circuit pressure is set to a low value, and the rear turning wheel inside the turning is brought into a semi-braking state (a state in which the rear wheel rotates while being braked) to appear in the brake turning state. For example, it is possible to make the brake turning state suitable for the geological state of the field, for example, in such a way that it is difficult for the dust to occur. In the configuration of claim 2, when the front wheel is steered by a set angle or more, the front wheel speed increasing mechanism and the hydraulic actuator for the side brake are both driven, so that both the small turning action by the brake turning and the small turning action by the front wheel speed increasing are performed. A steeper turning state after the addition can be quickly revealed. The circuit pressure can be set to a state in which the front wheel speed increasing mechanism is operated but the hydraulic brake actuator for side brake operation is not operated by adjusting the variable relief valve. In the case of a very soft field where axle can be formed even if the braking force applied to the rear wheel inside the turn is extremely small, this increase It is possible to perform a sharp turn with a small turning radius as much as possible within a range where the shaft cannot be driven by the fast turning state.

[0006]

Therefore, in the turning drive structure according to the first aspect, a troublesome operation of using both the steering operation and the side brake operation is unnecessary, and a sharp turn can be realized by simple operation of only the steering operation. Thus, it is possible to provide a device capable of adjusting and setting a state in which a sharp turn can be performed while keeping the field from being roughened, in accordance with the geological condition of the field. In the turning drive structure according to the second aspect, in addition to the above-described effects, the addition of the front wheel speed increase enables a sharper and quicker turn in a hard field or the like, and a sharp turn by the speed increase turn in a very soft field or the like. Such as turning, the state that can make a sharp turn without breaking the field can be adjusted and set irrespective of the geological condition of the field, that is, the adaptation range of the field is expanded than that of claim 1, It was possible to realize something more convenient.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 shows an agricultural tractor. This agricultural tractor has the engine 1 mounted on the front of the fuselage,
A transmission system is configured to transmit the power of the engine 1 to the left and right rear wheels 3 and 3 via the transmission case 2 at the rear and to the left and right front wheels 5 and 5 via the transmission shaft 4. When the steering angle of the front wheels 5, 5 is equal to or greater than the set value, the driving rotational speed of the front wheels 5, 5 is changed to the rear wheel 3,
3 is provided with a hydraulically driven front wheel speed-up mechanism 6 for switching to a higher speed than the driving rotation peripheral speed of No. 3. The transmission systems to the left and right rear wheels 3, 3 are provided with side brakes 8R, 8L for respectively braking the left and right rear wheels 3, 3 by depressing the operation pedals 7R, 7L. As shown in FIGS. 4 and 5, the operation system of the side brakes 8R and 8L includes:
Hydraulic cylinders 9R and 9L (an example of a hydraulic actuator) that can freely perform a braking operation regardless of the depression operation of the operation pedals 7R and 7L are provided.

A hydraulic circuit Y for driving the front wheel speed-up mechanism 6 and the hydraulic cylinders 9R and 9L for the side brakes.
When the right-hand steering angle of the front wheels 5, 5 exceeds a set value, the hydraulic cylinder 9 for operating the right-hand side brake 8R is used.
R for switching the R and the front wheel speed-up mechanism 6 to a driving state.
A second state in which the hydraulic cylinder 9L for operating the left side brake 8L and the front wheel speed-up mechanism 6 are switched to a driving state when the left steering angles of the front wheels 5 and 5 are equal to or greater than a set value; When the steering angles 5 and 5 are within the set angle, each of the hydraulic cylinders 9R and 9L and the front wheel speed-up mechanism 6 is maintained in a non-driven state in a neutral state, respectively, in accordance with the steering operation. A switchable hydraulic switching valve 10 is provided. More specifically, as shown in FIG. 1, the hydraulic switching valve 10 is disposed near the base end of the pitman arm 12 in the operation system of the steering handle 11, and the cam 13 formed at the base end of the pitman arm 12 is Along with the steering operation, the spool 14 which is biased by the spring is pushed in to switch to each of the above states. The cam 13 is set at three levels, and is switched from the middle level L1 at the center to the high and low levels L2 and L3 on both sides by a steering operation beyond the set angle, so that the spool 14 can be switched to the three states. I have. In other words, the pressure oil is supplied to the hydraulic cylinder 9R for operating the right side brake 8R and the front wheel speed increasing mechanism 6 by the operation beyond the right set angle, and the left side brake is operated by the operation beyond the left set angle. An oil passage is formed so that pressure oil is supplied to the hydraulic cylinder 9L and the front wheel speed-up mechanism 6 for 8L operation. A switch valve 15 for turning on and off the front wheel speed-up operation is interposed on the upstream side of the hydraulic switching valve 10.

As shown in FIGS. 1 to 4, a variable relief valve 16 is provided which can change and set the maximum pressure of the hydraulic circuit Y with respect to the hydraulic cylinders 9L and 9R. It is integrated into the body 10A. That is, a variable relief valve 16 composed of a pivot 19, an urging spring 20, a stopper 21, and a cam cylinder 22 is formed in a lateral hole 18 communicating with the supply oil passage 17 to the spool 14, and the relief pressure is adjusted. Is
The rotation is performed by rotating the cam cylinder 22 that receives the stopper 21. That is, as shown in FIG.
A stopper 21 is formed on the eccentric cam 22a, and an operation groove 22b is formed in a protruding portion from the case body 10A. The operation groove 22b is formed with a minus screwdriver or the like to form the cam cylinder 22. Is rotated to change and adjust the position of the stopper 21 receiving portion. Reference numeral 23 denotes a drain oil passage, and reference numeral 24 denotes a ball type detent mechanism acting on the cam cylinder 22. By providing a plurality of recessed holes 22c of the cam cylinder 22, the relief pressure can be easily adjusted and set in multiple steps. It is.

By the way, the side brakes 8L and 8R are
The pressure value of the pressure oil acting on the hydraulic cylinders 9L and 9R is 3kg
/ cm start effectiveness and ² to increase, together with the pressure value is set so as to completely locked the rear wheel 3 to reach 8 kg / cm ^2, the pressure oil required for the front-wheel speed increasing mechanism 6 is operated Is set to 2 kg / cm ² . Incidentally, the recessed hole 22c is set at a speed increasing turning position at which the relief pressure, that is, the hydraulic circuit Y pressure is set to 2 or more and less than 3 (for example, 2.5 kg / cm ² ), and 10 kg / cm ^2. Lock rotation position, and a value that is 3 or more and less than 8 (for example, 4 kg / cm ² or 6 kg
/ cm ² ) at at least three of the gentle braking turning positions set at one or more locations. Therefore, by adjusting the variable relief valve 16, a speed-up turning state in which only the front wheel speed-up mechanism 6 is operated, a slow braking turning state in which the front wheel speed-up mechanism 6 is operated and the side brakes 8L and 8R are half-braked, When the front wheel speed-up mechanism 6 is activated, the rear wheel 3 inside the turning
Each of the sharp turning states of the locked turning state in which is locked can be obtained, such as a speed-up turning state in a super soft field, a slow braking turning state in a soft field, and a locking turning state in a hard field. As described above, it is possible to select and set an appropriate rapid turning mode according to the condition of the field.

Here, the structure of the front wheel speed-up mechanism 6 will be briefly described. As shown in FIG.
A speed increasing drive gear 28 and a constant speed driving gear 29 are idlely supported on a speed changing shaft 26 which is gear-linked with the transmission shaft 4, and a speed increasing passive gear 30 and a constant speed passive gear are linked on a speed increasing shaft 27 which is linked with the transmission shaft 4. 31 and a speed-increasing drive gear 28 and a constant-speed drive gear 29
A speed-increasing clutch 32 for selecting one of the above and rotating integrally with the speed-change shaft 26 is provided on the speed-change shaft 26.
The hydraulically operated speed increasing clutch 32 is usually provided with an urging spring 33.
The operation pin 3 penetrates the clutch body 32A
4, a constant speed driving state in which the shift rotating tool 35 is engaged with the constant speed driving gear 29 is shown. Then, when hydraulic pressure is supplied and the piston 36 moves rightward in the drawing, the bite between the shift rotating tool 35 and the constant speed drive gear 29 is released, and the clutch body is formed as a clutch and fitted outside the spline to the speed change shaft 26. 32A and the speed-up drive gear 28 rotate integrally, and the speed-up drive state appears. A clutch is interposed on the side of the speed increasing drive state in order to reduce the shift shock.

In the claims, reference numerals are provided to facilitate comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a sectional view of a hydraulic switching valve.

FIG. 2 is a sectional view showing the structure of a variable relief valve.

FIG. 3 is a perspective view showing the shape of a cam cylinder.

FIG. 4 is a hydraulic drive system diagram

FIG. 5 is a sectional view of a hydraulic cylinder.

FIG. 6 is an overall side view of the agricultural tractor.

FIG. 7 is a sectional view showing the structure of the front wheel speed increasing mechanism.

[Explanation of symbols]

 Reference Signs List 3 rear wheel 5 front wheel 6 front wheel speed-up mechanism 8L, 8R side brake 9L, 9R hydraulic actuator 10 switching valve 16 variable relief valve Y hydraulic circuit

Claims (2)

[Claims] 1. A pair of left and right side brakes capable of independently braking left and right rear wheels in a locked state, and when the right or left steering angle of a front wheel exceeds a set angle, the side brakes inside the turning are braked. And a braking action of the operating means is set to a weak braking state so that the side brake on the inside of the turn brakes with an operating force that does not lock the rear wheel. The turning drive structure of the working vehicle. 2. A front wheel speed-up mechanism capable of switching operation to a speed-up driving state in which front wheels are driven at a higher speed than rear wheels, and a pair of left and right side brakes capable of independently braking left and right rear wheels in a locked state. When the right or left steering angle of the front wheels is equal to or greater than a set angle, an operating means for switching the front wheel speed increasing mechanism to a speed-up driving state and operating the side brake inside the turning to the braking side. The braking action of the operating means is such that the side brake on the inside of the turning brakes the work vehicle set in the weak braking state so as to brake the rear wheel with an operating force that does not lock the rear wheel. Drive structure.