JPS6230939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tractor, and more particularly to a front and rear wheel hydraulic drive type tractor in which a front wheel drive hydraulic motor and a rear wheel drive hydraulic motor are each independently connected to a variable displacement hydraulic pump. Regarding.

Conventionally, in the above-mentioned tractor, as described in Japanese Patent Application Laid-open No. 56-57521, for example,
One hydraulic pump is provided with an operating tool for changing and adjusting its swash plate angle by manual operation force, and the other hydraulic pump is provided with a drive device for changing and adjusting its swash plate angle. A device for detecting the rotation speed of a wheel driven by a hydraulic pump is provided, the drive device is operated based on the detection result of the detection device, and the swash plate angle of the other hydraulic pump is determined according to the detected rotation speed. The configuration was such that the rotational speed ratio of the front and rear wheels was adjusted to the set value by changing the angle to the set value, but the actual wheel drive by the hydraulic pump on the side that was manually operated was not correct. Since the swash plate angle of the other hydraulic pump is changed and adjusted after the rotation speed of the other hydraulic pump is detected, there is a time lag until the change and adjustment of the swash plate angle of the other hydraulic pump is completed. It takes a certain amount of time after the operating tool is operated until the wheel connected to the other hydraulic pump starts rotating at a predetermined rotational speed ratio, which has the drawback that slips are likely to occur.

Therefore, it may be possible to mechanically connect the swash plates of both pumps using a link with a flexible mechanism so that the swash plate angles of both pumps can be changed and adjusted using a single manual operating tool, but in this case, the operating force is reduced. There is a big drawback.

In addition, only the rotational speed of the wheel driven by the hydraulic pump on the side that is manually operated is detected, and the swash plate angle of the other hydraulic pump is adjusted to the angle set according to the detected rotational speed. Therefore, even under normal running conditions, it is impossible to detect the occurrence of slip and adjust the running speed, resulting in the disadvantage that efficient speed control cannot be performed.

Focusing on this point, the present invention suppresses the occurrence of time lag by changing and adjusting the swash plate angles of both hydraulic pumps almost simultaneously with a small operation, and makes it possible to start running smoothly, and to maintain normal running. The purpose of this invention is to enable speed control to be performed efficiently even in the state of the vehicle.

Next, embodiments of the present invention will be described based on the drawings.

An engine 3 is mounted on the front part of a traveling vehicle body that supports front wheels 1 and rear wheels 2 for steering, and transmits power to a lift arm 4 and attached work equipment that suspends an attachment work equipment at the rear so that it can be driven up and down. A power take-off shaft 5 is provided, and the front wheel 1
An agricultural tractor is constructed by disposing a steering handle 6, a driver's seat 7, a control section 8 consisting of various operating levers, etc. on the upper part of the vehicle body.

As shown in FIGS. 2 and 3, the drive structure for the steering front wheels 1 and rear wheels 2 includes two variable displacement pumps connected in conjunction with an engine 3.
One of P ₁ and P ₂ is connected to hydraulic motors M ₁ and M 1 interlocked with the left and right steering front wheels 1 _{and 1} , respectively, through an electromagnetic flow rate regulating valve mechanism V, and the other The pump P ₂ is connected to a hydraulic motor M 2 which is interlocked and connected to an input shaft 10 of a transmission case 9 on which the left and right rear wheels 2, ₂ are mounted.

Based on the detection results of the rotational speed detection mechanisms 11, 11 provided on the left and right front wheels 1, 1, respectively, and the steering angle detection mechanism 12 of the front wheels 1 provided on the steering handle 6, the left and right front wheels 1 are detected. , 1 in accordance with the steering angle, an electric control circuit 13 for automatically operating the flow rate regulating valve mechanism V is connected to the flow rate regulating valve mechanism V.
A differential mechanism for left and right front wheels 1 is configured.

A swash plate angle detection mechanism 1 is provided for each of the pumps P ₁ and P ₂ .
4 and 17, one pump _P1 is provided with an artificial operating tool 15 for changing and adjusting its swash plate angle, and this operating tool 15 has a friction mechanism for holding it at an arbitrary operating position. 16 is attached. In order to match the swash plate angle of _the other pump P ₂ with _{the swash plate angle of one pump P 1 ,} as shown in FIG.
The detection results output from 4 and 17 are sent to the first comparator 1.
The swash plate angle is controlled by inputting the angle ratio output from the first comparator 18 to the control mechanism 20 that operates the hydraulic cylinder 19 that changes and adjusts the swash plate angle of the other pump _P2 . A mechanism is constituted, and the front wheel hydraulic motors M ₁ , M ₁ and the rear wheel hydraulic motor M ₂ are activated by the swinging operation of the human operating tool 15.
It is constructed so that forward and reverse rotation, drive stop, and speed change operations can be performed. Further, a mechanism 21 is provided which calculates the average rotational speed of the left and right front wheels 1 from the rotational speed detection mechanisms 11, 11 of the left and right front wheels 1, and this detection result and the rotation of the rear wheel 2 attached to the input shaft 10 are provided. The detection result of the speed detection mechanism 22 and the second comparator 23
By inputting the speed ratio output from the second comparator 23 to the control mechanism 20, the cylinder 19 is operated so that the rotational speed ratio of the front wheels 1 and the rear wheels 2 becomes the set value. A rotation speed control mechanism is configured to The rotational speed ratio of the front and rear wheels 1 and 2 is set to 1:1, or so that the front wheel 1 is slightly faster.

In the case where the swash plate angle of one pump P ₁ is changed or adjusted by operating the human operating tool 15, the control mechanism 20 cuts off the input signal from the second comparator 23 and controls the cylinder 19. When the swash plate angles of both pumps P ₁ and P ₂ match due to the operation of
A control operation switching circuit is incorporated in which the cylinder 19 is actuated by the input signal of P3, and when the swash plate angle of one pump _P1 is changed by the manual operation tool 15 at the time of starting, first The hydraulic cylinder 19 is operated so that the swash plate angle of the other pump P ₂ matches the swash plate angle of one pump P ₁ , and when the swash plate angles of both pumps P ₁ and P ₂ match, then the front and rear wheels The cylinder 19 is operated according to a rotational speed ratio of 1 and 2 to obtain a set rotational speed ratio.

Note that a hydraulic motor, an electric motor, or the like may be used in place of the hydraulic cylinder 19, and these are collectively referred to as a drive device.

In summary, in the tractor according to the present invention, the hydraulic motor M ₁ for driving the front wheels 1 and the hydraulic motor M ₂ for driving the rear wheels 2 are each independently connected to variable displacement hydraulic pumps P ₁ and P ₂ , and one While changing and adjusting the swash plate angle of the hydraulic pump _P1 using the human operating tool 15,
The drive device 19 is configured to change and adjust the swash plate angle of the other hydraulic pump P _{2 .}
Based on the detection results of the swash plate angle detection mechanisms 14 and 17, which detect the swash plate angles of both hydraulic pumps P ₁ and P ₂ so that the swash plate angle of the hydraulic pump P ₁ matches the swash plate angle of one hydraulic pump P 1 , The front wheel 1 is adjusted based on the detection results of the swash plate angle control mechanism that operates the drive device 19 and the detection mechanisms 11 and 22 that detect the rotational speed of the front wheel 1 and the rear wheel 2, respectively.
and a rotation speed control mechanism that operates the drive device 19 so that the rotation speed ratio of the rear wheels 2 becomes a set value, and after the operation of the drive device 19 by the swash plate angle control mechanism is completed, the rotation speed It is characterized in that it is configured to start the operation of the drive device 19 by the control mechanism.

That is, only the swash plate angle of one pump P ₁ is changed and adjusted by the human operating tool 15, and the swash plate angle of the other pump P ₂ is changed based on the detection effect of the swash plate angle detection devices 14 and 17 of both pumps P _{1 and} P ₂ . Since the swash plate angle can be changed and adjusted by the drive device 19, both hydraulic motors
Although it is easy to perform forward/reverse rotation, drive stop, and speed change operations of M ₁ and M ₂ with little operating force, there is a time lag until the completion of changing the swash plate angle adjustment of the other pump P ₂ as mentioned above. By driving and rotating the front and rear wheels 1 and 2 almost simultaneously, it is now possible to start running smoothly with less slippage. Moreover, both pumps P ₁ and P ₂
When the swash plate angles of wheels 1 and 2 become approximately equal, both wheels 1 and 2
Since the swash plate angle of the other pump _P2 is changed based on the detection results of the rotational speed detection devices 22, 22 installed in the If it deviates from the value, the rotational speed of wheel 2 driven by the other pump _P2 is immediately adjusted, and the rotational speed ratio of front wheel 1 and rear wheel 2 is set even when driving on uneven ground where slips are likely to occur. We have now been able to provide a tractor that can be maintained at the same value and run well, and has excellent overall operability.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of a tractor according to the invention,
1 is an overall side view, FIG. 2 is a plan view of the wheel mounting structure, FIG. 3 is a wheel drive system diagram, and FIG. 4 is a block diagram showing the control system. 1...Front wheel, 2...Rear wheel, 11, 22...
Rotational speed detection mechanism, 14, 17... Swash plate angle detection mechanism, 15... Human operating tool, 19... Drive device,
P ₁ , P ₂ ... Variable displacement hydraulic pump, M ₁ , M ₂ ...
hydraulic motor.

Claims (1)

[Claims] 1 The hydraulic motor M 1 for driving the front wheel ₁ and the hydraulic motor M ₂ for driving the rear wheel 2 are each independently connected to variable displacement hydraulic pumps P ₁ and P ₂ , and one hydraulic pump
The swash plate angle of the other hydraulic pump P ₂ is changed and adjusted by the drive device _{19, and the swash plate angle of the other hydraulic pump P 2 is} changed and adjusted by the human operating tool 15. The drive device detects the swash plate angles of both hydraulic pumps P _{1 and} P ₂ based on the detection results of the swash plate angle detection mechanisms 14 and 17 so that the plate angle matches the swash plate angle of one hydraulic pump P 1 . The rotational speed ratio of the front wheel 1 and the rear wheel 2 becomes a set value based on the detection results of the swash plate angle control mechanism that operates the swash plate angle control mechanism 19 and the detection mechanisms 11 and 22 that detect the rotational speed of the front wheel 1 and the rear wheel 2, respectively. A rotational speed control mechanism for operating the drive device 19 is provided, and after the operation of the drive device 19 by the swash plate angle control mechanism is completed, the operation of the drive device 19 by the rotational speed control mechanism is started. A configured tractor.