JPH07385Y2 - Power steering device for work vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a power steering device for a work vehicle such as a work tractor.

<Prior Art> As a power steering device for a conventional work vehicle, there is an all-hydraulic power steering device in which a metering pump interlocked with a steering wheel operation operates a hydraulic switching valve to perform steering operation by a power cylinder. Further, it is known that the oil of the main circuit for operating the power cylinder is supplied by a steering pump driven by an engine and the main circuit is connected to a transmission to utilize the lubricating oil of the transmission as oil for power steering.

<Problems to be solved by the invention> However, in the conventional full hydraulic power steering device as described above, the steering pump is stopped when the engine is stopped, so that the steering cannot be operated or the metering linked to the steering wheel operation. There are some pumps that manually operate the power cylinder to enable steering, but even in the latter case, the return pipe of the main circuit must always be immersed below the oil surface of the transmission in order to suck the oil. However, in the case of a transmission that is long in the front and rear, there is a drawback that the return pipe end is exposed from the oil surface due to the fluctuation of the oil surface when the machine body is tilted, the oil in the pipe is discharged and air is sucked, and the steering becomes uncontrollable.

<Means for Solving Problems> The device of the present invention for solving the above problems is
A steering pump 11 and a switching valve 7 are provided in a main circuit 8 composed of a delivery pipe 9 and a return pipe 13, and the switching valve 7 is controlled by a metering pump 6 operated by a steering wheel operation to operate a power cylinder 25,
In the mechanism in which the main circuit end is connected to the inside of the transmission 1 and the lubricating oil for transmission is used as oil for power steering, the return pipe 13
Is connected to the lubrication portion 15 above the transmission 1 by opening the end portion thereof between the tank port 18 side and the pump port 17 side at the connection portion between the main circuit 8 and the switching valve 7 side. From the pump port 17 side is provided with a bypass circuit in parallel with a check valve 22 that allows oil suction, and at a position higher than the tank port 18 of the return pipe 13 when the steering pump 11 is not operating. Oil sump that supplies oil to the metering pump 6
It is characterized by the provision of 19.

<Operation> When the steering wheel 11 is operated while the steering wheel 4 is switched to the left or right, the metering pump 6 operates and the switching valve 7
Is switched to the left or right switching position, the oil enters through the delivery pipe 9 and is discharged through the return pipe 13, and the power cylinder 25 is operated leftward or rightward to be steered.

If the steering wheel 4 is switched to the left or right while the steering pump 11 is stopped, the hydraulic pressure by the metering pump 6 will be the check valve 22.
Through the tank port 18 side to the pump port 17 side, and the power cylinder 25 is driven leftward or rightward. At this time, the oil in the oil sump 19 is replenished to the circuit of the metering pump 6 to prevent troubles due to air intake.

<Embodiment> The embodiment illustrated below will be described in detail. FIGS. 2 and 3 are a side view and a rear view of the device of the present invention, in which a steering unit 2 is mounted on a transmission 1 mounted on a frame of a traveling vehicle body. The steering unit 2 is projected.
A base end portion of a column 3 is attached to the column 3, and a handle shaft 5 having a handle 4 at its upper end is inserted into the column 3. As shown in FIG. 1, the steering unit 2 accommodates a metering pump 6 and a switching valve 7 which are operated by rotating the handle shaft 5.

A main circuit 8 is connected to the switching valve 7, and an end portion of a delivery pipe 9 which constitutes the main circuit 8 is inserted and opened below the oil surface in the transmission 1 which also serves as an oil tank, and a filter 10 is provided in the middle thereof. , The steering pump 11 is provided. The other end of the main circuit 8 constitutes a return pipe 13, and the end of the main circuit 8 is connected and opened via a return port 14 to a lubrication-needed portion 15 such as a gear meshing portion on the upper portion of the transmission 1. Reference numeral 16 denotes a hydraulic pump for raising and lowering the working machine, which is branched from the delivery pipe 8.

Delivery circuit 9 and return circuit 13 of the main circuit 8
Are connected to the switching valve 7 at the pump port 17 and the tank port 18, respectively, and a relief valve 21 and a tank port are provided between the pump port 17 side and the tank port 18 side of both pipes.
A check valve 22 that allows oil to flow only from the 18 side to the pump port 17 side is interposed. Return pipe 13
An oil sump 19 for storing oil is provided at a position higher than the tank port 18 of.

The metering pump 6 is connected to the switching valve 7 by a switching circuit 23 for switching operation of the switching valve 7, and further the pump circuit 24
It is connected to the switching valve 7 by a and 24b. The switching valve 7
Cylinder circuits 26a and 26b for operating the power cylinder 25 for steering operation are connected to the left and right cut ports 27 and 28, respectively.

When the steering pump 11 is operated by the engine operation, when the handle 4 is rotated from the neutral position to the left or right, the switching valve 7 is switched by the operation of the metering pump 6, and the delivery pipe 9 is displaced from the pump circuit 24a or 24b. And the return pipe 13 communicates with either one of the cylinder circuits 26a or 26b and the power cylinder.
Left and right steering is performed by moving 25 right and left. The state of FIG. 1 shows a straight-ahead steering state in which the handle 4 does not rotate to the left and right, and the delivery pipe 9 and the return pipe 13 of the main circuit 8 communicate with each other in the switching valve 7.

During such normal operation, the return oil from the return pipe 13 is returned to the inside of the transmission 1 through the return port 14 at the upper portion of the transmission 1, so that the oil level fluctuation may occur when the work vehicle climbs up and lubrication is required. Even if the internal lubricating oil does not reach the portion 15, the lubricating oil is continuously supplied by the return oil.

On the other hand, when the steering pump 11 does not operate due to engine stop or the like and the handle 4 is rotated from the neutral position to the left or right, the switching valve 7 is switched to either the left or right switching position, and the pipes on the pump port 17 side and the tank port 18 side are connected. Is connected by a bypass circuit with a check valve 22 that allows oil flow only from the tank port 18 side to the pump port 17 side, so the oil supplied with hydraulic pressure by the metering pump 11 is a check valve. Pump circuit 24a, 24b through 22
Also, the power cylinder 25 is circulated through the cylinder circuits 26a and 26b and driven in either the left or right direction to be steered.

During this manual operation, the oil from the oil sump 19 flows into the operating circuit of the metering pump 6 from a high position, so that the metering pump 6 is replenished with oil and the metering by air suction or the like is performed. Problems such as inoperability of the pump 6 are prevented, and the return pipe 13 does not necessarily have to be inserted below the oil level in the transmission 1. 29 and 30 are relief valves provided between the cylinder circuits 26a and 26b.

FIG. 4 is a plan view of an essential part showing the mounting state of the power cylinder 25, and the knuckle arms at both ends of the front axle case 31.
A power cylinder 25 is fixed in the left-right direction in front of the front axle case 31 between the two 32, 32. Is connected with. In this example, the delivery pipe 9'and the return pipe 13 'are connected to both ends of the front axle case 31 and communicate with each other through the inside thereof, so that effects such as cooling of oil, prevention of dirt, and shortening of the pipe can be expected.

<Effect of Device> According to the device of the present invention configured as described above, since the oil sump for constantly storing oil is provided at a position higher than the tank port in the return pipe, the steering pump is not operated when the engine is stopped or otherwise. By operating the handle even when stopped, the metering pump operates without sucking air by sucking oil from the oil sump, and a check valve provided between the pump port side and the tank port side. Since the operation circuit of the power cylinder is formed by this, the work vehicle can be steered by the power cylinder.

Also, since air is not sucked into the metering pump,
It is not necessary to extend the return pipe to the bottom of the transmission and keep it immersed in the oil surface at all times, and troubles due to air intake due to oil surface fluctuations such as when climbing the vehicle body can be prevented. The return oil can be effectively used as a lubricating oil at an appropriate position by opening it in a lubrication required portion, and it is particularly useful for eliminating a poor lubrication due to a change in the oil level when climbing or descending a vehicle body.

[Brief description of drawings]

1 to 3 are a piping view, a side view and a rear view of a main part of a power steering device showing an embodiment of the present invention, and FIG. 4 is a plan view of the main part showing a mounting state of a power cylinder. 1: Transmission 6: Metering pump 7: Switching valve, 8: Main circuit 9: Delivery pipe, 13: Return pipe 17: Pump port, 18: Tank port 19: Oil sump, 22: Check valve 25: Power cylinder

Claims (1)

[Scope of utility model registration request] A steering pump (11) and a switching valve (7) are provided in a main circuit (8) consisting of a delivery pipe (9) and a return pipe (13), and the switching valve (7) is operated by a handle. In the mechanism for controlling the power cylinder (25) by controlling the metering pump (6) operated by the above, connecting the main circuit end to the inside of the transmission (1) and utilizing the lubricating oil for transmission as the oil for power steering, The end portion of the return pipe (13) is opened and connected to the lubricated portion (15) above the transmission (1), and the main circuit (8) is connected.
Port (18) at the connection between the switch and the switching valve (7)
Tank port (18) between the side and the pump port (17) side
Side of the return pipe (13) is installed higher than the tank port (18) of the return pipe (13), with a bypass circuit installed side by side with a check valve (22) that allows the intake of oil only from the pump side (17) to the pump port (17). , The steering pump (11)
Power steering device for a work vehicle, which is provided with an oil sump (19) for supplying oil to the metering pump (6) when the engine is not operating.