JPH1191616A - Turning controller for tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a tractor to be turned at the minimum turning angle. SOLUTION: A tractor comprising a steer angle detection device for detecting the steer angle of front wheels, a speed switching device for switching the driving state of the front wheels between high and low speeds, a pair of braking device which brakes the right and left wheels independently, and a pressure control valve for adjusting the braking pressure of the braking device, is provided with control means for braking the rear wheel braking device on the inner side of turning at a pressure set by a switch valve 40 and a pressure control valve 41 when the steer angle detection device detects that the steer angle of the front wheel is operated more than the specified value, thereby switching the speed switching device from low speed to high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tractor turning control device.

[0002]

2. Description of the Related Art In recent years, a high / low speed switching device has been incorporated in a front wheel drive system of a tractor so that the front and rear wheels have substantially the same peripheral speed when traveling straight, and when turning, the peripheral speed of the front wheels is approximately two times that of the rear wheels. It is known to increase the speed by about twice to create a high-speed state. Also, in tractors and the like, braking devices for braking the rear wheels are independently provided on the left and right, and these operate a pair of left and right brake pedals provided at the feet of the driver to simultaneously operate the left and right brake pedals.
Alternatively, it can be braked individually.

[0003] Except for traveling on a road moving at a high speed, the left and right brake pedals are not connected, and during general tilling work, the rear wheel inside the turning is braked to turn the body with a small turning radius.

[0004]

In the case of performing tilling work or the like using a tractor having a high / low speed switching device, if the aircraft is to be turned with a minimum turning radius, the front wheel drive system is set to a high speed state. At the same time, the brake device must be operated by depressing the brake pedal inside the turn, and such operation is complicated because it involves the operation of the steering handle and the hydraulic lever when turning at the edge of the field. It is also a burden for the driver to turn while continuing to depress the brake pedal when turning with the vehicle.

[0005]

SUMMARY OF THE INVENTION The present invention proposes to solve the above-mentioned problems, and employs the following technical means. A steering angle detecting device for detecting a steering angle of a front wheel, a high / low speed switching device for switching a driving state of a front wheel between high and low speeds, and a pair of left and right brake devices for independently braking left and right rear wheels; In a tractor having a pressure control valve for adjusting a braking pressure of a brake device, when the steering angle detection device detects that the steering angle of the front wheel has been operated to a predetermined angle or more, the high / low speed switching device is shifted to the high speed side. The tractor turning control device is characterized in that control means is provided for switching and braking the rear wheel brake device inside the turning with the pressure set by the pressure control valve.

In addition, the pressure oil set by the pressure control valve is switched by a switching valve and supplied to a brake cylinder of a left rear wheel or a right rear wheel.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on embodiments shown in the drawings. First, a description will be given of the structure. Reference numeral 1 denotes a tractor, which has an engine 2 mounted on a front portion of a machine frame, and has a rear wheel mounted on a rear end of a transmission shaft 5 which is mounted in a transmission case 3 in a transmission case. A bevel pinion 8 meshing with the bevel gear 7 of the differential device 6 is attached. A pair of transmission gears 11 and 12 having different numbers of teeth for transmission to a clutch (hereinafter referred to as a front wheel clutch) 10 of a front wheel drive system are attached.

As the front wheel clutch 10, a two-speed wet multi-plate clutch is adopted. A low-speed passive plate 15,... And a high-speed passive plate 16 are provided on both sides of a clutch shaft 14 parallel to the transmission shaft 5. , A driving plate 19 corresponding to the low-speed passive plate 15, a low-speed clutch gear 20, and a driving plate 22 corresponding to the high-speed passive plate 16, , A high-speed clutch gear 23 is provided.

The clutch gears 20 and 23 are
With respect to the transmission gears 11, 1
2 meshes with each other. The front wheel clutch 10 is driven by a transmission gear 1 by a hydraulic switching valve 25 and a pressure control valve 26.
1 is switched to a low speed at which the clutch gear 20 is meshed, a high speed at which the transmission gear 12 is meshed with the clutch gear 23, and a neutral stage in which all are disconnected.

The clutch shaft 14 is connected to a joint 28
Drive shaft 3 that transmits rotational power to the front wheels via the
Connected to 0. The shaft 32 (L,
R), a wheel pinion 35 (L, R) meshing with the wheel gears 33 (L, R) of the left and right rear wheels, and a brake plate 38 (L, R) of a brake device 37 (L, R) are attached. I have. The brake shoes 39 (L, R) can be individually driven by brake cylinders 42 (L, R) operated under the control of the switching valve 40 and the pressure control valve 41, and the rear wheels on any side can be used as necessary. You can put a brake on

The tractor 1 is provided with a steering control device 44 for controlling the steering of the traveling device. The steering control device 44 is configured as shown in FIG. 3, and detects a steering angle of the front wheels, that is, a steering angle by a steering sensor 47 provided below the intermediate shaft 46 connected to the steering shaft 45. This is processed by the controller 50, and an output signal is output to the switching valve 40 and the pressure control valve 41.

Referring specifically to FIG. 4, A and B are rotation centers at the time of a weak turn and a sharp turn, respectively, C and D are center points of a rear axle and a front axle, respectively, and angles θ1, θ2, θ3.
Is a set angle serving as a control reference. When the detected steering angle detected by the steering sensor 47 is within the range of θ1, the front wheel clutch 10 is kept neutral, and the vehicle travels by driving only the rear wheels. When the detected steering angle is in the range from θ1 to θ2, the clutch 10 is engaged at a low speed. At this time, the rotation ratio of the front and rear wheels is R1: R
2, the front wheels rotate slightly faster than the rear wheels.

When the detected steering angle is in the range from θ2 to θ3, the front wheel clutch 10 is switched at high speed.
At this time, the rotation ratio of the front wheel and the rear wheel is R3: R4, and the front wheel rotates considerably faster than the rear wheel. Therefore, even if the vehicle turns sharply, the rear wheel does not slip and the vehicle runs stably. Can be. Θ3 is the steering angle when turning with the minimum turning radius. When the detected steering angle approaches this, the brake device inside the turn is activated to apply a brake on that side to assist a sharp turn. . In this case, since the front wheel clutch 10 is switched to the high speed side, the front wheel does not act as a brake for the rear wheel, and the vehicle can turn quickly.

[0014]

According to the present invention, as described above, the steering angle detecting device for detecting the steering angle of the front wheel, the high / low speed switching device for switching the driving state of the front wheel between high speed and low speed, and the left and right rear wheels are independently provided. In a tractor having a pair of left and right brake devices for braking and a pressure control valve for adjusting the braking pressure of the brake devices, when the steering angle detection device detects that the steering angle of the front wheels has been operated to a predetermined angle or more. A control means for switching the high / low speed switching device to a high speed side and braking the rear wheel brake device on the inside of the turn with the pressure set by the pressure control valve. Is automatically switched to the high-speed side, and the brake device for braking the rear wheel inside the turn is also automatically operated, so that the turning operation is simpler and easier than the conventional device.

In particular, in the present invention, since the braking pressure of the brake device can be changed by the pressure control valve, the pressure can be set according to the hardness of the field, and the turning area can be smoothly changed without roughening the turning area. Becomes possible. In the case where the pressure oil set by the pressure control valve is switched by the switching valve and supplied to the brake cylinder of the left rear wheel or the right rear wheel, the supply pressure to the brake cylinder is stabilized, and the turning is performed. Make it more smooth.

[Brief description of the drawings]

FIG. 1 is a side view of a tractor.

FIG. 2 is an explanatory diagram of a main part.

FIG. 3 is a block diagram of a steering control device.

FIG. 4 is an explanatory diagram of steering control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tractor 2 Engine 3 Transmission case 10 Front wheel clutch 37 Braking device 44 Steering control device 50 Control means (controller)

Claims (2)

[Claims] 1. A steering angle detecting device for detecting a steering angle of a front wheel, a high / low speed switching device for switching a driving state of a front wheel between high and low speeds, and a pair of left and right brake devices for independently braking left and right rear wheels. And a pressure control valve for adjusting the braking pressure of the brake device, when the steering angle detection device detects that the steering angle of the front wheels has been operated to a predetermined angle or more, the high / low speed switching device is activated. A turning control device for a tractor, further comprising control means for switching to a high speed side and braking a rear wheel brake device inside the turning with a pressure set by the pressure control valve. 2. The tractor turning control device according to claim 1, wherein the pressure oil set by the pressure control valve is switched by a switching valve and supplied to a brake cylinder of a left rear wheel or a right rear wheel.