JPH01153003A - Agricultural tractor lift arm drive device - Google Patents

Abstract

PURPOSE:To provide the above drive where an oil amount-regulating mechanism to change flow channel area is connected to a lift arm in a specified state and a valve to open or shut a channel arranged in parallel with the oil channel to be reduced in the area is opened or shut through a hydraulic pressure for raising the lift arm, thus decreasing the landing speed of the working machine. CONSTITUTION:A hydraulic pressure for raising is applied on an oil-charging or discharging channel to allow a valve 18 to be opened, and a hydraulic cylinder is fed with a large amount of hydraulic fluid to raise a lift arm in high speed. During the lift arm is made to descend to a prescribed position, said lift arm is lowered in high speed with an oil amount-regulating mechanism 15 extending the channel, and when said lift arm is lowered below the prescribed position, said mechanism 15 then reduces the channel area through the mechanical connection. At this time, the valve 18 is kept shut, therefore, the amount of the oil to be discharged from the hydraulic cylinder is decreased, thus the lift arm descends at low speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lift arm drive device for an agricultural tractor.

[Conventional technology]

In the conventional drive device, for example,
As shown in Publication No. 152212, when adjusting the descending speed of a lift arm that is raised and lowered by a single-acting hydraulic cylinder, a screw-turning manual control valve is used to control the oil drainage path from the hydraulic cylinder. The structure was designed to accommodate this by changing the flow path area.

[Problems to be Solved by the Invention] In general, in agricultural tractors, when working by connecting a rotary tiller as a working device, for example, when turning a headland, the tiller is rotated while turning the machine. If the tiller is then lowered at a high speed to resume work, problems such as the tiller sinking into the soil, causing the front of the machine to lift up, or causing the engine to stall due to a sudden increase in the tilling load. Therefore, in order to avoid such a situation, the descending speed of the working device is changed and adjusted by the above-mentioned manual control valve.
Since the Jgff valve is adjusted over a minute range, it is configured with a screw rotation type, and the adjustment work is time-consuming and troublesome.

Moreover, in order to eliminate the troublesome work described above, if the work equipment is always set to descend at a low speed, it takes time to descend from the raised position to the normal work position, reducing work efficiency. This has the disadvantage of doing so.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to make it possible to lower the landing speed of a working device without bothersome effort and without reducing work efficiency.

[Means for solving problems]

A feature of the present invention is that an oil amount adjustment mechanism that changes the flow path area is provided in the oil supply and drainage path to the single-acting hydraulic cylinder for driving the lift arm up and down, and the oil amount adjustment mechanism and the lift arm are connected mechanically. The flow path area of the oil amount adjustment mechanism is reduced in a region on the lowering side than the set position of the lift arm, and the oil 111M node mechanism is connected to A valve body is provided which opens a flow path parallel to the oil path and closes the flow path when the application of hydraulic pressure is removed, and its functions and effects are as follows.

[For production]

In other words, when raising the lift arm, the lifting hydraulic pressure is applied to the oil supply and drainage path, the valve body is opened, and a large amount of hydraulic oil is supplied to the hydraulic cylinder, so that the entire stroke The lift arm rises at high speed. When lowering the lift arm, the oil amount adjustment mechanism expands the flow path while the lift arm is lowered to the set position, so the lift arm is lowered at high speed, but when lowered below the set position, , the oil amount adjustment mechanism reduces the flow path area through mechanical interlock. At this time, since the valve body is in a closed state, the amount of oil discharged from the hydraulic cylinder is restricted, and the lift arm descends at a low speed.

[Problem that the invention seeks to solve]

Therefore, when turning a headland in which the rotary tiller connected to the lift arm is raised and lowered while being rotated, it is necessary to drive it downward at high speed when raising it and while lowering it close to the ground. When the tiller lands on the ground, it is driven downward at low speed, so waiting time is short, work efficiency is not reduced, and problems such as lifting of the front part of the machine and engine stalling can be prevented.

〔Example〕

As shown in Fig. 5, a pair of left and right lift arms (3), (3), which are vertically swung by a medium-acting hydraulic cylinder (2), are installed at the rear of the body (1) of an agricultural tractor. (3) A three-point linkage mechanism (4) is provided that is driven and swung up and down in conjunction with (3), and a rotary tiller (5) is detachably connected to the three-point linkage mechanism (4). be.

The three-point linkage mechanism (4) includes a pair of left and right lower links (6), (6) that connect the machine body (1) and the rotary tiller (5), and a pair of left and right lower links (6) that connect the machine body (1) and the rotary tiller (5). 5) A pair of left and right lower links (6) connecting
, (6), the top link support (7) attached to the rear upper side of the fuselage (1), and the rotary tilling device (5).
) and a top link (9) that connects the attached top mass 1-(8).

Then, the lift arms (3), (3) and the lower links (6), (6) are connected to the lift arms (10).
) and (10), and the three-point N structure (4) can be driven and moved by the telescopic operation of the single-acting hydraulic cylinder (2).

The input shaft (not shown) of the rotary tiller (5) and the power take-off shaft (12) protruding from the rear of the body (1) are interlocked and connected by a connecting shaft (13) so as to be flexible. ) is configured to rotate.

As shown in FIGS. 1 to 3, the hydraulic cylinder (
The cap portion (14) of 2) is formed with an oil supply and drainage passage ((,) that communicates with the oil chamber (R) of the hydraulic cylinder (2), and this oil supply and drainage passage (L) is connected to the oil chamber (R) of the hydraulic cylinder (2). (2) is communicatively connected to a control valve (not shown) that controls the supply and discharge of hydraulic oil to and from the oil supply and discharge passage (l,). A plunger (
15) is provided. This plunger (15) is provided so as to be slidable within a certain range in the axial direction, and an oil passage hole (17) having a small diameter in the radial direction is formed in the cylindrical part (15a) on the inner side of the cap part (14). It is. The plunger (I
5) Inside the cap part (14), 1ldJ 'tB
A valve body (18) is provided that opens and closes the flow path (8) by supplying or canceling the supply of pressure oil for lifting the lift arm (3), (3) from the pulp. More specifically, the plunger (15) is fitted and supported by a support member (19) which is screwed and fixed to the cap portion (14) so as to be able to slide inward and outward, and is supported by the support member (19) on the inner side of the support member (19). A locking protrusion (22) abuts and locks the stepped portion (21) of the thin-walled cylindrical portion (20) to prevent it from slipping outward. As will be described later, when the plunger (15) slides inwardly, it comes into contact with the valve body (18) and is biased in the opposite direction by the coil spring (23).
8) is configured to slide and displace against the spring force. Further, the thin-walled cylindrical portion (20) of the support member (19)
) is formed with a large-diameter oil passage hole (24) that can be used as a hydraulic oil passage.

and a linking rod (25) that mechanically links these (3) and (15) to the swing gap portion (14) of the one lift arm (3) near the plunger (15). has been extended. That is, as shown in FIG. 4, the rear end of the linking rod (25) is attached to a bracket (26) that is rotatably supported on the lift arm (3) around the horizontal axis (P). A guide member (19) is fitted on the support member (19) on the front side and is rotatably fitted on the support member (19).
It is loosely inserted and supported in the bent part (27a) of 27),
The linking rod (25) is arranged to move in the front-rear direction in conjunction with the vertical swinging of the lift arm (3).

The linking rod (25) is provided facing the outer end of the plunger (15), and has a recess (28) formed at a predetermined portion to allow the plunger (15) to move outward. When the lift arm (3) is in the range from the upper limit position to the lower predetermined setting position (the lift arm position where the lower end of the rotary tiller (5) is located near the ground surface), As shown, the plunger (15) is located in the recess (28) and protrudes outward, and the oil supply/drainage W (L) is set to the open state, causing the lift arm (3) to rise and The descent takes place at high speed. Further, when the lift arm (3) is in a region below the set position, the plunger (15) is moved into contact with and retracted from the inner body side by the linking rod (25), as shown in Fig. 1. The flow path of the oil supply and drainage path (L) is reduced at the portion of the small diameter oil passage hole (17). However, even in this state, when the lift arm (3) is raised, the valve body (18) is moved inward against the spring force of the coil spring (23) due to the dynamic pressure of the supplied pressure oil. As it moves to the side and opens the flow path, the lift arm (3) rises at high speed, and when it descends, the flow rate is restricted and it descends at low speed.

Note that the guide member (2) supporting the linking rod (25)
7) in a clockwise direction by operating a switching lever (27b) connected thereto, and retracting the linking rod (25) above the plunger (I5).
The plunger (15) is always maintained in an outwardly protruding state, and can be switched to a state in which raising and lowering are performed at high speed throughout the entire stroke.

[Another example]

As shown in FIG. 6, if the valve body (18) is equipped with a biasing coil spring (23) and a drain oil passage (29) is formed from the spring installation chamber (Q), During the upward movement with the plunger (15) pushed in, the hydraulic pressure supplied to the hydraulic cylinder (2) causes the valve body (18) to be reliably pressed against the spring (23) by static pressure.
It can be made to move backwards and rise at high speed.

Further, as shown in FIG. 7, there is a valve body (18) which is opened only by the plunger (15) and the application of upward pressure oil.
and may be arranged in parallel on separate paths.

Furthermore, the oil N adjustment mechanism may be of a rotary type instead of the linear sliding type as described above.

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 the lift arm drive device for an agricultural tractor according to the present invention, in which FIG. 1 is a sectional view of the main part with the adjustment member retracted, and FIG. 2 is a sectional view of the main part with the adjustment member protruded. Figure 3 is a plan view showing the connection with the lift arm, Figure 4 is a side view showing the connection with the lift tome, Figure 5 is a side view of the rear section of the tractor, and Figures 6 and 7 are Separate implementation
FIG.
Faction (2)...Hydraulic cylinder, (3)...
... Lift arm, (15) ... Oil amount adjustment mechanism, (18) ... Valve body, -(i!,) ...
・Flow path.

Claims (1)

[Claims] An oil amount adjustment mechanism (15) that changes the flow path area is provided in the oil supply and drainage path to the single-acting hydraulic cylinder (2) for driving the lift arm (3) up and down, and this oil amount adjustment mechanism (15) and The lift arm (3) is mechanically linked to the lift arm (3).
The flow path area of the oil amount adjustment mechanism (15) is reduced in a region on the lowering side than the set position of the oil amount adjustment mechanism (15), and the oil amount adjustment mechanism is A lift arm drive device for an agricultural tractor, which is provided with a valve body (18) that opens a flow path (1) parallel to the area-reduced oil path according to (15) and closes the flow path (1) when hydraulic pressure is removed.