JPS5856408Y2 - Dashing prevention device on tractor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic actuation device used for raising and lowering a working machine of a tractor.

Conventionally, in tractors, especially small tractors, the rotary work equipment descended at a nearly constant speed, so the rotary blade touched the ground with considerable force and the tractor was driven by the rotational force of the rotary blade, a so-called darting phenomenon. was occurring.

Therefore, a hydraulic actuator has been proposed in which the descending speed of the rotary work machine is reduced by constricting the oil drain path in the final stroke of the piston of a hydraulic actuator consisting of a piston and a cylinder. Since a fine gap on the order of /100 (mm) is required, it has been difficult to improve the processing accuracy due to its structure.

Therefore, in the present invention, the oil passage and the cylinder are communicated through a free valve, and just before the work equipment touches the ground, the piston comes into contact with the free valve, and its expanded diameter part fits into the opening with a minute gap. To provide a douching prevention device for a tractor, which is configured to reduce the descending speed of the working machine by applying a squeezing action, thereby making it possible to obtain minute gaps without requiring high machining accuracy. It is intended to do.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

The tractor 1 has front wheels 2 and rear wheels 3 as shown in FIG.
The engine 6 is mounted on the front part of the fuselage 5, and the driver's seat 7 is arranged at the rear of the fuselage 5.

Furthermore, a rotary work machine 8 is installed at the rear of the machine body 5.
and is supported by a lift arm 12 via a lift rod 11 so as to be freely raised and lowered, and the lift arm 12 is rotatably supported by a hydraulic case 15 disposed above a mission case 13 at the rear of the fuselage 5. ing.

The hydraulic case 15 includes a piston 16 as shown in FIG.
The piston 16 is connected to the lift arm 12 via a piston rod 20 and a lift fork 21.

One side of the cylinder 17 is closed by a cylinder head 22, and the cylinder head 22 is provided with an oil passage 23.

The oil passage 23 communicates with the cylinder 17 through a check valve 27 consisting of a ball 25 and a spring 26 provided at the center of the cylinder head 22. The check valve 27 allows oil to flow into the cylinder 17, but does not Outflow from oil passage 17 to oil passage 23 is prevented.

In addition, a head 28 is located in the center of the cylinder head 22.
A bolt 28 is screwed in so that a protrudes outward, and the tip of the bolt 28 is arranged so as to be able to abut against the ball 25.

Furthermore, the oil passage 23 communicates with the cylinder 17 through an aperture 30, and a free valve 31 made of a solid body is provided in the aperture 30.
are pressed and fitted by the spring 32.

As shown in detail in FIG. 3, the opening 30 and the free valve 31 have a diameter of the cavity 33 Dl and a flange 31 H of the free valve 31.
The diameter of the small diameter part 31 b is d2, the diameter of the wide diameter part 3 is
When the diameter of 1 C is d2 and the diameter of the opening 30 is D2, the relationship is as follows: Dl>dl>D2>d3>d2.

That is, when the small diameter portion 31b of the free valve 31 is located in the opening 30 as shown in the figure, the oil in the cylinder 17 freely flows out due to the fitting portion having a large gap, but When the expanded diameter portion 31C of the free valve is located at 1/
The fitting gap becomes 100 [mm] mm, resulting in a narrowed state.

In addition, the length 1 of the expanded diameter portion 31C is the length 1 of the piston 1 corresponding to the maximum plowing depth from just before the rotary work machine 8 touches the field.
The length corresponds to the amount of movement of 6.

On the other hand, the oil passage 23 is an oil passage 32 bored in the hydraulic case 15.
It communicates with the hydraulic control valve 33 via the valve 3.
3, the spool 33a is operated by a work equipment lifting lever 35 provided on the driver's seat 7.

Since the present invention has the above configuration, as shown in FIG. 2, when the rotary work machine 8 is lifted to the raised position, the spool 33a of the control valve 33 is lifted by operating the work machine lift lever 35. When the valve is moved to the open position, the oil in the cylinder 11 is moved to the narrow diameter portion 31 of the free valve 31 due to the pressing force of the piston 16 based on the weight of the work implement 8.
After passing through the fitting portion with a large gap between b and the opening 30, the flange portion 31a is further moved slightly against the spring 32, and is discharged into the oil path 23, and the work implement 8 is rapidly lowered.

When the rotary working machine 8 descends to a position slightly higher than the field, the head of the piston 16 comes into contact with the tip of the free valve 31.

As a result, the free valve 31 is moved against the spring 32, and its expanded diameter portion 31C fits into the opening 30.

The fitting gap between the expanded diameter portion 31C and the opening 30 is 1/100 (
Since the gap is minute on the order of mm), the cylinder 17
The oil inside is greatly constricted by this gap and flows into oil passage 2 with a small flow rate.
It is discharged at 3.

Therefore, the rotary work machine 8 slowly touches the ground on the field and slowly descends to a predetermined plowing depth without causing the dabbing phenomenon.

Next, in order to raise the rotary working machine 8, the spool 33a of the control valve 33 is operated by the working machine lifting lever 35, and pressure oil from the hydraulic pump is introduced into the oil passage 23.

As a result, the hole 25 of the check valve 27 is connected to the spring 26.
Pressure oil is supplied into the cylinder 17 at a large flow rate and moves the piston 16.

The movement of the piston 16 is transmitted to the lift arm 12 via the piston rod 20 and the lift fork 21, and the work implement 8 rises rapidly.

In addition, when the work equipment needs to fall rapidly, such as during plow work, the bolt 28 can be screwed in and the tip of the bolt 28 can be used to secure the ball 2.
5 is moved against the spring 26.

As a result, there is always a gap between the ball 25 and the valve seat, so when the work machine is lowered, the screw I/N 16 is attached to the foot valve 31.
Even if the expanded diameter portion 31C of the free valve 31 fits into the opening 30 and is in a constricted state, the oil freely flows out from the gap between the ball 25 and the valve seat, and the work machine descend rapidly.

As explained above, according to the present invention, just before the rotary work machine 8 touches the ground, the piston 16 comes into contact with the free valve 31, and its expanded diameter portion 31C fits into the opening 30, and due to the throttling action. Since the descending speed of the working machine is reduced, the dumping phenomenon can be prevented.

In addition, in order to prevent dazzling, a narrowing action is required by a minute gap, and the circumference is proportional to π times the diameter, so in order to obtain this minute fitting gap, the diameter is as small as possible. However, the free valve 31, which is a solid body, can be manufactured to a small diameter by separate processing, and the opening 30 can also be made by separate processing, so a small diameter can be obtained. , a fine fitting gap can be obtained without requiring much machining accuracy.

Furthermore, in the conventional type, only a part of the cylinder head 22 needs to be improved, so it can be manufactured at low cost, and it can be easily installed on a conventional tractor by simply replacing the cylinder head.

[Brief explanation of the drawing]

Figure 1 is a side view of a tractor to which the present invention can be applied;
The figure is a side sectional view showing the hydraulic actuating device according to the present invention, and FIG. 3 is an enlarged sectional view showing the free valve. 1...l.Rafter 8...Work equipment, 12...Lift arm, 16...Piston, 17...Cylinder, 18...Hydraulic actuation device, 22...Cylinder head, 23... ...Oil passage, 27...Check valve, 30...
Opening hole, 31... Free valve, 31 C... Expanded diameter part, 2
8...Bolt (release device).

Claims (2)

[Scope of utility model registration request] (1) In a hydraulically actuated device consisting of a piston and a cylinder connected to a lift arm, an oil passage is provided in the cylinder head that closes one side of the cylinder, and the oil passage and the cylinder are reversed to prevent oil from flowing out of the cylinder. In addition to communicating through a stop valve, the oil passage and the cylinder are communicated through a free valve, and the free valve has an expanded diameter portion, and the piston contacts the free valve just before the work equipment touches the ground. A douching prevention device for a tractor, in which the swollen diameter portion fits into the opening with a minute gap to provide a throttling effect and reduce the descending speed of the working machine. (2) A douching prevention device for a tractor according to claim 1, which is configured to be able to release the action of the check valve.