JPH06189606A - Hydraulic pressure control unit for tractor - Google Patents

Abstract

PURPOSE:To provide a hydraulic pressure control unit for a tractor designed to electrically detect workload and improve the responsiveness of draft control by the resultant signal. CONSTITUTION:The control unit so designed that a tractor vehicle 21 is equipped with a hydraulic unit 23 bearing a lift arm 22 and a link-type attaching device 26 and the lift arm 22 is connected to the left and right lower links 25 at the attaching device 26 and the hydraulic unit 23 is put to vertical motion via a control valve 45 based on detecting workload F. The left and right sides of the tractor vehicle 21 are fitted with lower link attaching pins 29 for separately, respectively connecting the left and right lower links 25 thereto, and each of the pins 29 is equipped with (A) a strain gauge 41 to detect workload F as shear strain and (B) a feedback means 44 to give the detection signals from the strain gauge 41 to the control valve 45.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a hydraulic control device for a tractor, Japanese Patent Publication No.
There is a technique disclosed in Japanese Laid-Open Patent Publication No. 65121, and as a part of the control device, there is a top link sensing system and a lower link sensing system as a work load detection. The top link sensing method is one in which a load spring is interposed in the top link mounting base, and it is difficult to detect when the work load is light. Therefore, the lower link sensing method shown in FIG. 5 (A) (B) and FIG. 6 is adopted. ing.

In FIGS. 5 (A) and 5 (B), a hydraulic device (a cylinder and a piston rod are omitted and only the housing is shown) 3 having a pair of left and right lift arms 2 is provided on a rear upper surface of a tractor vehicle body 1. The lift arm 2 is mounted and lifted by operating the control valve 4. Tractor body 1
A lower link mounting rod 5 that penetrates left and right (vehicle width) and is elastically deformable is installed via a pair of left and right ball (spherical) bearing bodies 6, and a ball joint 7 is attached to a left and right protruding portion 5A of the rod 5. The left and right lower links 8 are connected via.

The top link 9 is pivotally supported by a top link mount 10 provided on the tractor body 1 via a pin 11.
The lift arm 2 and the left and right lower links 8 are lift rods 1.
It is connected by two. The work load F1 when a work machine such as a plow (not shown) is mounted via the link mounting device 13 including the top link 9 and the lower link 8 is caused by the elastic bending force F2 with respect to the rod 5. The displacement is transmitted to the control valve 4 by the feedback means by the link mechanism 14 as shown by the arrow in FIG.

In the conventional example shown in FIG. 6, the elastic bending force F2 is detected by the strain gauge 15, and this signal is fed back to the control valve by an electrical (electronic) method (others are shown in FIG. 5).
(B) is the same as that of (B), and therefore the common parts are indicated by common symbols).

[0006]

In the prior art shown in FIGS. 5A and 5B, the displacement amount of the rod 5 is determined by the link mechanism 14.
It is amplified by and transmitted to the switching of the control valve 4 (substantially spool), but since it is the link mechanism 14, rattling, play, etc. are unavoidable, and there was a problem in response (hysteresis). .

On the other hand, in the conventional technique shown in FIG.
Although the problem of the link mechanism described above is temporarily solved, a rod 5 is installed on a pair of left and right ball (spherical) bearing bodies 6 and a strain gauge 15 is provided at the center of the rod 5 in the longitudinal direction to detect a load. After hydraulic control (draft control), it was difficult for the rod 5 bent in a curved (bow) shape to return to a completely straight line even though the load was removed (erased).

In particular, since the bearing body 6 is near the ground, there are many occasions when mud is attached and hardened, and stones and the like are often bitten, so that the rod 5 is not completely restored. Therefore, the present invention is
By detecting the work load as shear strain and using the lower link mounting member as a short pin, it is possible to ensure a complete return after the load is removed, and to provide a hydraulic control device for a tractor with good responsiveness and accurate control. Is the purpose.

[0009]

According to the present invention, a tractor body 21 is provided with a hydraulic device 23 having a lift arm 22 and a link type mounting device 26, and the lift arm 22 and the left and right lower links 25 in the mounting device 26 are provided. In the hydraulic control device of the tractor, which connects the hydraulic pressure control device and the hydraulic control device 45 up and down via the control valve 45 based on the detection of the work load F, the following technical measures are taken to achieve the above object.

That is, the present invention relates to the tractor body 2
Lower link mounting pins 29 for separately connecting the left and right lower links 25 are provided on the left and right side portions of 1, and a strain gauge 41 for detecting the work load F as a shear strain is provided on each of the mounting pins 29. It is characterized in that a feedback means 44 for sending the detection signal of the gauge 41 to the control valve 45 is provided.

[0011]

As shown in FIG. 2, when the working machine (exemplified by plow) 27 is mounted on the tractor 20 via the link mounting device 26 to perform the plow work, the work load F thereof is larger than the set reference value. Since the traction force is sometimes too large, the work implement 27 is lifted and controlled via the hydraulic device 23 (that is, draft control).

This is because when the work load F acts on the left and right lower links 25 as shown in FIG. 1, shear strain occurs in the mounting pin 29, which is detected by the strain gauge 41 and the signal is fed back to the control valve 45. Lift the work implement 27 to reduce the traction force. The mounting pins 29 are left and right, and the shear strain is detected by the strain gauge 41. Therefore, the detection is reliable, and the axial length of the mounting pins 29 is short, so that the restoration after the load removal is also complete.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. Hydraulic device 23 having a pair of lift arms 22
Is installed. Central 1 at the rear of the tractor body 21
A three-point link type mounting device 26 including a book top link 24 and a pair of left and right lower links 25 is provided, and a plow 27 is mounted on the three-point link mounting device 26 to connect the left and right lift arms 22 and the lower link 25 with a lift rod 28. The plow 27 can be raised and lowered by being connected.

Hydraulic control, in the embodiment draft control, is shown in FIG.
It is configured as shown in. In the first embodiment shown in FIG. 1, short lower link attachment pins 29 are attached to the left and right side portions of the tractor vehicle body 21 so as to project outward, and a ball joint 25A is attached to each of the pins 29. One end of the lower link 25 is connected and is prevented from coming off by a nut 25B or the like.

Specifically, a fitting portion 30 formed by a hole or a recess is formed at a relative position on both lower sides of the vehicle body 21, and the fitting portion 3 is formed.
A holder 32 having an insertion fitting portion 31 for spigot fitting is provided, and the holder 32 is attached by fixing a flange 32A of the holder 32 with a bolt 32B. A small-diameter first pin fitting hole 31A is formed in the insertion portion 31 of the holder 32 in the axial direction, and a large-diameter second pin is inserted through the step portion.
The pin fitting hole 33 is continuously provided.

The mounting pin 29 has a shaft portion (body) of a small diameter first pin portion 34, a large diameter intermediate pin portion 35, and a small diameter mounting pin portion 36, which are connected in this order to form a first pin portion 34. Is fitted in the first pin fitting hole 31A by a spigot and is prevented from rotating by a flat surface (swirl) 37, and the intermediate pin portion 35 has a radial gap 38 in the second pin fitting hole 33. The spigot is fitted.

A female thread in the axial direction is formed on the axial center of the first pin portion 34, a bolt 39 is screwed onto this, and a retaining collar 40 is pressed against the end face of the insertion portion 31, so that the pin 29 is held by the holder 32. Assembled so that the holder 32, which is an assembly of the flange 32A, is bolted to the bolt 32B.
It is fastened at. The mounting pin 29 is elastically deformable in the radial direction within the range of the skimmer 38, and the strain gauge 41 for detecting the shear strain using the skimmer 38 or the like has an intermediate pin portion 3.
The detection signal is attached to the outer peripheral surface of No. 5, and the detection signal is transmitted to the electronic (electric) type control circuit 43 through the lead wire 42 and the like by the feedback means 44, and the circuit 43 detects the left and right strain gauges 41. The electromagnetic control valve 45 of the hydraulic device is controlled by summing the signals.

That is, the work load F during work is detected by the strain gauge 41, and the strain is converted into an electric resistance or the like to control the control valve 4.
4 can be controlled. The strain gauge 41 directly detects the shear strain when it is attached to the upper and lower sides a and b of the intermediate pin portion 35, and detects the shear strain through compression or tension due to bending when it is attached to the front and rear c and d. To do.

FIG. 3 shows a first pin portion 3 according to the second embodiment of the present invention.
The involute spline 46 is used as a fitting position determination (rotation stop) between the No. 4 and the first pin fitting hole 31A.
According to this, as compared with the flat surface 37 of the first embodiment, broaching is possible, mass production is possible, and accuracy is improved.
This is advantageous in that the occurrence of dripping due to the concentration of surface pressure is small and the backlash can be controlled.

Further, FIG. 4 shows a third embodiment in which a flat surface 37,
In place of the involute spline 46, a rotation stopping means 47 using a key and a groove is used. Since radial backlash can be eliminated, it is short but can support a load in a long span and has durability. improves. 3 and 4, the points other than those described above are common to the first embodiment, and common parts are denoted by common reference numerals.

Since the vehicle body 21 is usually cast, the holder 32 is made of an elastic metal material, and the holder 32 has a drawbar box mounting hole 48 formed therein. Further, when the rotary is mounted as the working machine, the direction of the work load F is opposite to that shown in the drawing.

[0022]

According to the present invention, it is possible to detect the work load with a strain gauge to eliminate hysteresis and to detect with good linearity. In addition, since it is electrically detected, it can be automatically controlled by a computer in combination with a control valve (electromagnetic valve).

Further, since the mounting pin is short, the restoring property after the load is removed is reliable and the responsiveness is good.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an overall side view of a plow attached to a tractor.

FIG. 3 is a cross-sectional view of essential parts of a second embodiment.

FIG. 4 is a cross-sectional view of an essential part of a third embodiment.

5A and 5B show a conventional example 1; FIG. 5A is a vertical sectional view, and FIG.

FIG. 6 is a plan sectional view showing a second example of the related art.

[Explanation of symbols]

 21 tractor vehicle body 22 lift arm 23 hydraulic device 25 lower link 26 mounting device 29 mounting pin 41 strain gauge 45 control valve

Claims (1)

[Claims] 1. A tractor vehicle body (21) is provided with a hydraulic device (23) having a lift arm (22) and a link type mounting device (26), and the left and right of the lift arm (22) and the mounting device (26). A hydraulic control device for a tractor, which is connected to a lower link (25) and moves up and down a hydraulic device (22) through a control valve (45) based on detection of a work load (F), comprising: A strain gauge for detecting the work load (F) as a shear strain is provided on each of the mounting pins (29) on the left and right sides, and a lower link mounting pin (29) for separately connecting the left and right lower links (25) is provided. (4
1) is provided and feedback means (44) for sending the detection signal of the strain gauge (41) to the control valve (45) is provided, and the hydraulic control device for the tractor.