JPS6111814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is configured to drive a pair of left and right front wheels by a pair of hydraulic motors provided separately for each of the front wheels. A switching valve is provided for two hydraulic pumps that can be freely switched between a series connection state and a parallel connection state, and one hydraulic pump for rear wheel drive is provided separately from the front wheel drive hydraulic pump. A hydraulic motor is connected, a rear wheel is interlocked with the hydraulic motor via a mechanical transmission, and further,
A control device is provided for detecting the rotation speed of the output shaft side of the front wheel drive hydraulic motor and controlling the drive speed of the rear wheel drive hydraulic pump so that the front wheels and the rear wheels are driven in synchronism. Relating to wheel drive tractors.

The above-mentioned four-wheel drive tractor can easily obtain greater propulsive force than a two-wheel drive tractor.
Furthermore, when traveling uphill or during work requiring horsepower such as in wet fields, by switching between high and low speeds, it is possible to create a travel mode that corresponds to various conditions.

In a vehicle that uses hydraulic pressure to drive four wheels, it is easier to create a structure for matching the circumferential speeds of the front and rear wheels, which have different diameters, than in a vehicle that uses a mechanical gear transmission.

However, since it is a four-wheel drive type, when driving on flat roads with little road resistance, there was a waste of having to continue driving the front wheels when they were not needed.

Therefore, when driving on the road, which requires speed rather than torque, there is a desire to switch to two wheels and drive at high speed.In order to achieve two-wheel drive, a steering clutch is installed on the lower side of the drive motor. Although this is possible, it has the disadvantage of complicating the structure.

Furthermore, in systems where the steering clutch is manually operated to switch to two-wheel drive, the operator must judge this and switch to four-wheel drive when torque is required due to uneven road surfaces. However, there is a drawback that problems such as engine stalling occur due to delays in switching timing.

The present invention enables automatic switching to two-wheel drive without complicating the structure.
Moreover, it is an object of the present invention to automatically switch to four-wheel drive as the load increases during two-wheel driving.

The characteristic configuration of the present invention for achieving the above object is that, in the four-wheel drive tractor, the switching valves are connected in series, in parallel, and in all flow paths connected to each switching valve. A control mechanism is provided for selectively switching control between opening the front wheel drive hydraulic motor and causing the front wheel drive hydraulic motor to operate under no load. A speed detecting device is provided, and the detecting device and the control mechanism are connected to each other when the actual rotational speed detected by the detecting device exceeds a set value.
All of the switching valves are linked so that they are automatically switched to the flow path open state, and this configuration provides the following effects.

That is, when driving on the road, the actual rotational speed of the rear wheel axle or the shaft linked thereto is detected by increasing the traveling speed of the entire aircraft by operating the speed change operation tool for the front wheel drive pump. If the detection result is greater than or equal to the set value, all of the switching valves are connected to each other through a linkage mechanism that links the detection device and each switching valve that switches the front wheel drive motor to a series connection state. By switching the flow path to the open state, the power spent on front wheel drive can be concentrated on rear wheel drive, allowing efficient two-wheel drive driving.

When two wheels are running at high speed and the load increases due to uneven road surfaces, etc., and torque is required,
A detection device detects a decrease in the speed of the aircraft, and based on the detection result, the connection mechanism releases the flow path open state of each switching valve that is in the flow path open state, automatically switching to four-wheel driving mode. This allows smooth running without causing engine stalling.

When switching to two-wheel drive, we used switching valves to connect the front wheel drive motors in series, which made the structure simpler than when a steering clutch was installed to free the front wheels. Ivy.

Embodiments of the present invention will be described below with reference to the drawings. 1 and 1 are a pair of left and right front steering wheels arranged at the front of the aircraft; 2 and 2 are a pair of left and right rear wheels arranged at the rear of the aircraft; 3 is a steering handle for the front steering wheels 1 and 1; The steering front wheels 1, 1 are pivoted to the aircraft body so as to be swingable around vertical axes 4, 4 with respective hydraulic motors _M1 , _M1 , and knuckle arms 5, 5 linked thereto. The two are connected by a tie rod 6, and a drag rod 7 extending from one knuckle arm 5 is linked to a pitman arm 8 that is linked to the handle 3. On the other hand, the rear wheels 2, 2 are linked via a differential mechanism 9.

The hydraulic motors M ₁ , M ₁ are connected in parallel to a common variable displacement hydraulic pump P ₁ , and the differential mechanism 9 includes:
It is linked to one hydraulic motor _M2 , and furthermore, one variable displacement hydraulic pump _P2 is connected to this motor _M2 .
is connected. The pump P ₁ on the front wheel side and the pump P ₂ on the rear wheel side are interlocked with the engine E via a suitable interlocking mechanism.

Reference numeral 10 denotes an operating device that can change the traveling speed of the entire aircraft, and includes a speed change operation lever 12 for adjusting the oil discharge amount of the front wheel pump P ₁ and a swash plate 11 for adjusting the oil output amount of the rear wheel pump P ₂ . The output shafts 1 of the front wheel motors M ₁ , M ₁ are connected to the plate 13 via a linkage mechanism 14 having a certain small range of linkage flexibility.
Output rotation speed detection device 16, 1 provided at 5, 15
6 and a drive mechanism 17 linked to the swash plate 13 on the rear wheel side.
are linked via the control device 18.

The control device 18 includes the detection devices 16, 16.
Drive mechanism 1 according to the average value of rotational speed detected by
7, and the swash plate 13 of the rear wheel pump P ₂ , which has been roughly adjusted in accordance with the speed change operation of the speed change operation lever 12 of the front wheel pump P ₁ , is adjusted to the traveling speed of the front wheels 1, 1 when the aircraft is traveling straight. and that of the rear wheels 2, 2 are corrected so that there is a one-to-one relationship.

Reference numeral 19 denotes a gear type transmission as a mechanical transmission which is installed in the transmission system between the motor M ₂ on the rear wheel side and the differential mechanism 9 and can freely switch between high and low speeds.
The high speed output rotation speed is set to twice the low speed output rotation speed.

20 is a switching mechanism for freely switching between a four-wheel drive running state and a two-wheel drive running state with only the rear wheels 2, ₂ ;
Flow rate regulating valves 21, 21 interposed in the parallel supply oil passages with the pump _P1 for each _M1 , and a directional switching valve 23 interposed in the middle of the bypass oil passage 22 that directly connects the parallel supply oil passages. By opening these valves 21, 21, and 23, the vehicle is switched to the two-wheel drive state.

24, in conjunction with the high-low switching of the gear type transmission 19, changes the rotational speed of both the front wheel motors _M1 , _M1 such that the speed ratio of the front and rear wheels 1, 1, 2, 2 is 1:1. In addition, when the speed of the rear wheels 2, 2 is equal to or higher than a preset value, all flow paths connected to the valves 21, 21, 23 are opened. , is a control mechanism for creating a two-wheel drive state by driving only the rear wheels 2, 2,
This electrically connects the actuators of each of the valves 21, 21, and 23 to a switch 26 that detects that the operating lever 25 of the gear type transmission 19 is in the high-speed operating position via a control circuit 27, and A detection device 28 detects the speed of the drive system on the rear wheels 2, 2 side using the output shaft 29 of the gear type transmission 19, and when the detection result of the detection device 28 is equal to or higher than a set value, the switching mechanism 20 is activated. Automatically operate each valve 2
Control circuit 3 that puts 1, 21, 23 in the flow path open state
It is composed of 0. That is, when the gear type transmission 19 is in a low speed state, the flow rate regulating valve 21,
21 is open, and the directional control valve 23 is closed, so that both the motors M ₁ and M ₁ are connected in parallel to the pump P ₁ , and the pressure oil discharged from the pump P ₁ is transferred to each motor M ₁ and M ₁ .
The running speed of the front wheels 1, 1 is kept the same as that of the rear wheels 2, 2, which are in a low speed state. Further, when the gear type transmission 19 is in a high speed state and the running speed of the rear wheels 2, 2 is twice the above-mentioned speed, the flow rate regulating valves 21, 21 are closed, and the direction switching valve 2 is closed.
3 opens and connects both motors M ₁ and M ₁ to pump P ₁ in series, and supplies the entire amount of pressure oil discharged from pump P ₁ to each motor M ₁ and M ₁ , respectively. , 1 is doubled, and the front and rear wheels 1, 1, 2, 2 are kept at the same speed.

Further, when the actual rotational speed of the rear wheels 2, 2 side detected by the detection device 28 is equal to or higher than the set value set by the control circuit 30, priority is given to the control signal of the control circuit 27. Each of the valves 21 and 2 is controlled by a control signal from the latter control circuit 30.
1 and 23 are set in an open state and set in a two-wheel drive state. Conversely, if the actual rotational speed falls below the set value, the control signal from the control circuit 30 is stopped and the The configuration is such that control by the control circuit 27 is continued.

[Brief explanation of the drawing]

The drawings show an embodiment of a four-wheel drive tractor according to the present invention, with FIG. 1 being a plan view and FIG. 2 being a control system diagram. 1...front wheel, 2...rear wheel, 18...control device,
19... Mechanical transmission, 21, 23... Switching valve, 24... Control mechanism, 28... Detection device, P ₁ ,
P ₂ ... Hydraulic pump, M ₁ , M ₂ ... Hydraulic motor.

Claims (1)

[Claims] 1 A pair of hydraulic motors M ₁ , M ₁ provided separately for the left and right front wheels 1 , 1 are configured to drive the front wheels 1 , 1 , and the hydraulic motors M ₁ , M ₁ are For one hydraulic pump P ₁ for front wheel drive, switching valves 21, 21, 23 that can be freely switched between a series connection state and a parallel connection state are provided, and separately from the front wheel drive hydraulic pump P ₁ . One hydraulic motor M ₂ is connected to the rear wheel drive hydraulic pump P ₂ provided, and the rear wheels _2, 2 are interlocked with the hydraulic motor M 2 via a mechanical transmission 19. , the hydraulic motor M ₁ for front wheel drive,
Detects the rotational speed of the output shaft side of M ₁ and rotates the front wheels 1, 1.
In the four-wheel drive tractor, the four-wheel drive tractor is provided with a control device 18 for controlling the driving speed of the rear wheel drive hydraulic pump P2 so that the rear wheels _{2 and 2} are driven in synchronism. 23 in the series connection state, the parallel connection state, and each of the switching valves 2.
A control mechanism 24 is provided for selectively switching and controlling the front wheel drive hydraulic motors M ₁ , M ₁ to a state in which they are operated under no load by opening all flow passages connected to the hydraulic motors M 1 , 23 , and 23 . The mechanical transmission 19
A device 28 for detecting the actual rotational speed of the rear wheels 2, 2 is provided on the downstream side of the transmission. A four-wheel drive tractor, characterized in that all of the switching valves 21, 21, 23 are linked so that they are automatically switched to a flow path open state when the temperature is reduced.