JP3242367B2 - Tractor turning control - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tractor turning control device. 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 peripheral speed of the front and rear wheels is substantially equal when traveling straight, and the peripheral speed of the front wheels is changed to that of the rear wheels when turning. There is known a configuration in which a high-speed state is created by approximately twice as high. 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 tilling work or the like using a tractor having a high-low speed switching device, if it is desired to turn the body with a minimum turning radius, the front wheel drive system is driven at a high speed. In addition to the state, the brake device must also be operated by depressing the brake pedal inside the turn, and such operation is complicated because it involves operating the steering handle and the hydraulic lever when turning at the edge of the field. It is a burden for the driver to turn while continuing to depress the brake pedal when turning at the ridge. [0005] The present invention proposes to solve the above-mentioned disadvantages, and has taken 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 rear wheel braking devices for independently braking left and right rear wheels. in tractor and a pressure control valve for adjusting the brake pressure of the rear wheel brake device, the steering angle state steering angle approaches the minimum turning radius
When the direction detection device detects, the rear wheel brake
Brakes the pressure at the pressure set by the pressure control valve.
The tractor turning control device further comprises control means for setting the high / low speed switching device to a high speed state. Further, 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. An embodiment of the present invention will be described below based on an embodiment 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 rearward direction. 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 front wheel drive system clutch (hereinafter referred to as a front wheel clutch) 10 are mounted. 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 hydraulic switching valve 25 and a pressure control valve 26 to transmit the transmission gear 1.
1 is configured to be switched to three stages, namely, a low speed at which the clutch gear 20 is engaged, a high speed at which the transmission gear 12 and the clutch gear 23 are engaged, 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. As described above, the present invention provides 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 left and right rear wheel. In a tractor including a pair of left and right rear wheel brake devices that independently brake and a pressure control valve that adjusts a braking pressure of the rear wheel brake device, an angle state in which a steering angle approaches a minimum turning radius.
When the steering angle detection device detects
Braking the rake device with the pressure set by the pressure control valve
In addition, since the control means for setting the high-low speed switching device to the high-speed side state is provided, at the time of turning, the high-low speed switching device is automatically switched to the high-speed side to brake the rear wheel inside the turning. The device also operates automatically, and the turning operation is easier and easier than in the conventional device. In particular, in the present invention, since the braking pressure of the rear wheel brake device can be changed by the pressure control valve, a smooth turning according to the hardness of the field can be performed more smoothly than in the case of uniformly applying the braking pressure. It becomes possible. Further, in the case where the pressure oil passed through 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 further improved. Make it 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] 1 tractor 2 Engine 3 Mission case 10 Front wheel clutch 37 Brake equipment 44 Steering control device 50 control means (controller)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 11/08 B60K 41/26 B60T 8/24 F16H 61/16

Claims (1)

(57) [Claims] 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, a pair of left and right rear wheel braking devices for independently braking left and right rear wheels , In a tractor having a pressure control valve for adjusting a braking pressure of a rear wheel brake device, a steering angle is a minimum turning half.
The steering angle detection device detects an angle state approaching the diameter
And the rear wheel brake device inside the turn is operated by the pressure control valve.
A turning control device for a tractor, further comprising control means for braking at a set pressure and for setting the high / low speed switching device to a high speed state. 2. The turning control device for a tractor according to claim 1, wherein the pressure oil adjusted 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.