JPH076062Y2 - Hydraulic power steering relief valve structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a relief valve structure of a hydraulic power steering in a riding type traveling vehicle such as a riding type rice transplanter and an agricultural tractor.

[Problems to be Solved by Prior Art and Invention] Generally, in this type of passenger vehicle, a hydraulic power steering having a steering shaft as an input shaft and a hydraulic operating portion such as a torque generator provided below the steering shaft. There is one that adopts a system to perform steering. In this case, a relief valve is provided in the hydraulic circuit for the hydraulic actuating unit as a safety measure when the steering load increases.

However, in the past, this relief valve was built in the hydraulic pump or a dedicated one was installed in the hydraulic circuit.
As a result, the structure is complicated and the cost is inevitably high.Because the piping from the relief valve to the hydraulic operating part is long, piping resistance due to these acts and the desired relief pressure is obtained. It cannot be ensured, and as a result, there are drawbacks such as lack of stability and reliability, which is a problem.

[Means for Solving Problems] In view of the above-mentioned circumstances, the present invention was devised with the object of providing a relief valve structure for a hydraulic power steering that can eliminate these drawbacks. , The port block for connecting the pressure pipe and the return pipe to the outer peripheral surface of the hydraulic operating part provided in the shaft part of the hydraulic power steering with the steering shaft as the input shaft, rather than the outer peripheral rear end edge of the hydraulic operating part. The port block is mounted so as to be positioned in the front, and a relief valve having a valve seat is formed on the port block between the pressure port and the return port.

According to the present invention, a stable and highly reliable relief valve can be provided by this structure while having a simple structure and a low cost.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a traveling machine body of a riding type rice transplanter, a torque generator 3 is provided at a lower end portion of a steering shaft 2 of the traveling machine body 1, and steering is performed based on a turning steering operation of a steering wheel 4. The shaft 2 is connected to the input shaft to switch the steering control valve 3a provided on the torque generator 3 which is a hydraulically operated portion,
Steering wheels (front wheels) that are connected to the front axle 8 by controlling the pressure oil from the hydraulic pump 5 to the gerotor 3b and acting on the pitman arm 7 side through the gear transmission mechanism provided in the transmission case 6. The steering operation of No. 9 and the like are the same as conventional ones.

A hydraulic pump 5 is provided on the outer peripheral surface of the torque generator 3.
The front block is so positioned that the port block 12 for connecting and attaching the compression pipe 10 from 10 to the return pipe 11 to the transmission case (oil tank) 6 is located in front of the rear end edge of the torque generator 3. The port block 12 is formed to have a direct acting relief valve 13 built therein. That is, the port block 12 is formed with a compression port 12a to which the compression pipe 10 is connected and a return port 12b to which the return pipe 11 is connected. Hole 13
a has been drilled. The tip end guide 14a of the valve body 14 is movably fitted into the relief hole 13a so as to be guided by a guide hole 12d provided outside the pressure port 12a.

On the other hand, reference numeral 15 is an adjuster bolt, which is fitted from the outside of the return port 12b and screwed and fixed to the port block 12, and one end of the adjuster bolt 15 is elastically attached to the adjuster bolt 15. Due to the spring 16 held, the seat receiving surface 14b of the valve body 14 is fixed to both ports 12 of the port block 12.
The valve seat 12c formed between a and 12b is abutted against the valve seat 12c in an elastic manner, thereby restricting the flow of pressure oil from the pressure port 12a to the return port 12b.
When the pressure on the a side overcomes the biasing force of the spring 16, the valve element 14 moves to the return port 12b side, whereby the pressure oil is relieved to the return port 12b side.

On the other hand, the transmission case 6 has an engine 17
The shafts such as the input shaft 18, the intermediate shaft 19, and the traveling output shaft 20 that receive the power from the shaft are supported respectively, but the traveling output shaft 20 is directed rearward from the output chamber 6a arranged on the lower side of the case. Is projected. An output shaft 21 for planting projects from the output chamber 6b toward the rear at the upper part of the transmission case 6, and the output chamber 6b is transmitted from the gear chamber of the transmission case 6 via the bearing 21a. Although it is incomplete, it is isolated, and a breather 6c for the transmission case 6 is formed on the upper surface of the output chamber 6b.

In the embodiment of the present invention constructed as described above, the steering wheel 9 is steered by the operation of the torque generator 3 based on the rotation of the steering wheel 4, but at this time, the steering load is increased. Press port
When the pressure on the 12a side becomes higher than the relief pressure (cracking pressure), the valve body 14 moves to the return port 12b side against the urging force of the spring 16, which causes the pressure oil to flow from the pressure port 12a side to the return port 12b side. It will flow to the side.

In the device in which the present invention is implemented in this way, the relief valve 13 can reliably prevent damage to the hydraulic circuit. However, the relief valve 13 prevents the torque generator 3 from hydraulic pressure. It is provided by effectively utilizing the port block 12 necessary for connecting the circuit. Therefore, the relief valve 13 is arranged in a state of being almost directly connected to the torque generator 3, and the piping distance from the relief valve 13 to the torque generator 3 is remarkably short, so that there is almost no pressure loss due to piping resistance. Moreover, the pipes for that amount are also unnecessary, and the pressure loss due to the pipe resistance makes it impossible to secure the desired relief pressure due to the pressure loss due to pipe resistance, resulting in an unstable and unreliable relief action. It is possible to reliably prevent such problems. Moreover, this relief valve 13
It is formed by effectively using the port block 12 required for piping to the torque generator 3 without providing a dedicated member, so the structure is not allowed to be simplified, and a separate mounting space is secured. There is no need to do this, and the assembly is easy, and the cost can be reduced and the size can be reduced.

In addition, since the guide portion of the valve element 14 is formed by utilizing the outside of the pressure port 12a, the length of the relief valve direction can be shortened and a compact port block unit can be obtained, and the valve seat 12c can be formed. The distance L from the guide portion to the guide portion can be secured long even when the set length of the spring 16 is short, and accordingly, an unpleasant relief sound such as a tapping sound or a chattering sound of the valve body 14 against the valve seat 12c is effective. Can be reduced to.

In addition, the port block 12 is the torque generator 3
Since it is provided at the front position so as to be located in front of the rear edge, the port block 12 is attached to the outer peripheral surface of the torque generator 3 while the port block 12 is located behind the torque generator 3. It is possible to prevent the space under the driver's feet from becoming narrower by projecting rearward from the end edge, which may be an obstacle to driving.

In addition, this is the transmission case 6,
The breather 6c is provided in the output chamber 6b of the planting output shaft 21 arranged at the top of the case, but it is separated from the chamber containing oil by the case partition and the bearing, and only the air in and out is between the balls of the bearing. Since there is no oil spouting, the amount of oil that enters the room is saved, and oil leakage from the breather 6c can be effectively prevented. Moreover, since the breather 6c is formed so as to face the inner side of the center of the case, it is convenient because the intrusion of water from the outside can be effectively prevented.

It is needless to say that the present invention is not limited to the above-mentioned embodiment, but can be applied to the all-hydraulic power steering.

[Advantages] In short, since the present invention is configured as described above, it is provided in the hydraulic circuit of this hydraulic actuation unit even though it is a hydraulic power steering in which the hydraulic actuation unit is provided in the shaft portion. Since the relief valve is formed in the port block for pipe piping that is attached to the outer circumference of the hydraulic operating part, it can be configured so that it is almost directly connected to the hydraulic operating part, and there is no pressure loss due to piping resistance and the desired relief. It will be possible to secure pressure and make it stable and highly reliable.

Moreover, since the relief valve is formed by effectively utilizing the port block required for piping to the hydraulic operating portion without providing a dedicated member, the relief valve is built in the hydraulic operating portion. As described above, the structure of the hydraulic operating unit does not become complicated and large, and a relief valve function comparable to that of a relief valve built into the hydraulic operating unit using a small general-purpose hydraulic operating unit without a relief valve. This means that the port block can be effectively used, and the assembly is easy, the cost can be reduced, and the size can be reduced.

In addition, since the port block is provided so as to be located in front of the rear end edge of the hydraulically actuated portion, a port block having a relief valve is separately attached to the outer peripheral surface of the hydraulically actuated portion. Thus, the port block is projected rearward from the rear end edge of the torque generator to narrow the foot space of the driver, effectively avoiding the obstacle of driving.

[Brief description of drawings]

FIG. 1 shows an embodiment of a relief valve structure for a hydraulic power steering according to the present invention. FIG. 1 is a schematic side view of a traveling airframe of a riding type rice transplanter, and FIG. 2 is a power steering section. Left side view of the main part, FIG. 3 is a right side view of the main part of the same as above, FIG. 4 is a plan view of the main part of the same as above, and FIGS. 5A and 5B are front views, side views, and partially cutaway views of the port block. Is a hydraulic circuit diagram, FIG. 7 is a vertical sectional view of the machine body frame, FIG. 8 is a side view showing a state in which a half case of the transmission case is removed, and FIG. 9 is a sectional view taken along line AA of FIG. FIG. 10 is a rear view of the main part of the power steering unit. In the figure, 2 is a steering shaft, 3 is a torque generator, 10 is a pressure pipe, 11 is a return pipe, and 12 is a return pipe.
Is a port block, 12a is a pressure port, 12b is a return port, 12c is a valve seat, and 14 is a valve body.

Claims (2)

[Scope of utility model registration request] 1. A port block for connecting a pressure pipe and a return pipe to an outer peripheral surface of a hydraulic operating portion provided in a shaft portion of a hydraulic power steering having a steering shaft as an input shaft. The port block is mounted so as to be located in front of the edge, and a relief valve having a valve seat is formed between the pressure port and the return port in the port block. Relief valve structure. 2. The relief valve according to claim 1, wherein a guide portion for guiding the valve element is formed outside the valve seat via a compression port. Relief valve structure for hydraulic power steering.