JPS61247572A - Power steering device - Google Patents

Abstract

PURPOSE:To obtain optimum performance in various working operations, by providing a mechanism for changing over the operating force performance and/or responsiveness of a power steering device in a construction machine vehicle, etc. to a control circuit for the power steering. CONSTITUTION:When a steering wheel 2 is rotated, oil discharged from a steering unit 1 is fed into the pilot pressure actuating section of a control valve 3 through a pilot circuit 1a or 1b, and therefore, the control valve 3 is changed over. Then, pressure oil from a variable displacement pump 4 is fed into a left or right chamber in a steering cylinder device 5 to turn the vehicle. In this arrangement external signal receiving sections 7a, 8a, 11 are provided, respectively to a pressure control valve 7, a differential pressure actuating valve 8 and a shockless valve 10 disposed in a circuit bypassing a check valve 6. A pilot pressure may be introduced into these receiving sections 7a, 8a, 11 by way of an external signal change-over device 13 which may by changed over between its working position 13a and its running position 13b.

Description

[Detailed description of the invention] Industrial field of application The present invention relates to a construction machine having a steering mechanism, and which is suitable for excavating,
The present invention relates to a power steering device used in a vehicle such as a wheel loader that is used for both loading and other operations and transportation and other driving.

BACKGROUND OF THE INVENTION Construction machines as described above are generally required to have the following steering performance.

(1) Performance during operation The steering force is light, and the operator does not feel any shock that could lead to fatigue due to the shock caused by the inertia of the vehicle body during operation, when stopping the steering wheel, or when turning the steering wheel, or Prevent dirt, etc. from spilling from the work packet.

(2) Driving performance (1) The vehicle must be able to run stably in a straight line without meandering or other irregularities; (1) The vehicle must be able to smoothly change course when avoiding obstacles, etc.

Conventionally, in response to the above-mentioned steering performance requirement (υ), the response is somewhat sacrificed to give a dull feeling and reduce shock.

In addition, for (2) and (1), K is generally used to increase the steering force to improve steering stability, and for (2) and (1) K, there is no response delay. , the steering device has a dull feeling.

As mentioned above, work performance and driving performance are required to have contradictory performance, and the steering performance of such a vehicle is designed to balance both performances.

Problems to be Solved by the Invention As mentioned above, the conventional design that balances both work performance and driving performance cannot be said to be an optimal design for both performances from another perspective. This problem has come up as complaints from users who rely mainly on work performance, such as ``the operating force is a little heavy'' or ``it gives me a shock.''

Means and Effects for Solving the Problems The present invention was conceived in view of the above-mentioned problems, and includes a control circuit for a power steering device that is designed to improve the performance of either one of the steering force performance and response. A mechanism is provided for switching between the two, and this switching mechanism is operated by an external signal, so that the working performance and the driving performance can be switched by the external signal.

Example Embodiments of the present invention will be described based on the drawings.

In the figure, reference numeral 1 denotes a steering unit for pilot operation that is directly connected to the steering wheel 2, and this steering unit 1 is equipped with an amount of oil proportional to the number of rotations of the steering wheel.The left and right pilot circuits 1 ( !, is designed to be discharged to IA. 3 is a control pulp whose stroke position is set according to the flow rate from the steering unit 1, and this control pulp 3
has a neutral position 3α and a left position 3b.

It has right position 3C. 4 is a variable pump with a position control device located upstream of the control pulp 3; 5
is a steering cylinder device located downstream of the control knob (lube 3).

The left and right pilot circuits 1α and IA each include a check valve 6 that prevents the steering unit from returning in the direction of the steering unit 1, and a pressure control valve 7 that is pushed open and communicated with the flow K in the return direction against the spring force. It is an intervention. Both positive force control valves 7 are provided with an external signal receiving section 7α for changing the push-opening force in the direction of increasing it.

The variable pump 4 equipped with a position control device is configured such that the differential pressure caused by the control pulp 3 is detected by the differential pressure operating valve 8, and the discharge amount can be automatically adjusted so that this differential pressure becomes constant. The differential pressure operated valve 8 is provided with an external signal receiving section 8b into which an external signal is input in addition to a receiving section gα into which the differential pressure signal from the control pulp 3 is input.

Left and right pressure chambers 5α and 5b of the steering cylinder device 5
Between the left and right circuits qa and qb connected to the control pulp 3, when the steering is turned back by switching K, both circuits 9α and 9b are temporarily short-circuited via a throttle to absorb the shock when the steering is turned back. Suru Shockless Pulp 10
is an intermediary. At both ends of this shockless pulp 10, there is a ninth pilot circuit that urges this shockless pulp 10 toward the operating side. A, 9bK are connected. At one end of this shockless pulp 10, an external signal receiving section 11 for receiving external signals is provided separately from the pilot circuit.

The power steering device with the above configuration has performance suitable for work without inputting external signals, that is,
The structure is such that the steering force is light, and the shock is small when working, stopping the steering wheel, or turning the steering wheel around.

External signal receiving section 7a of the pressure control valve 7, external signal receiving section 8 of the differential pressure operated valve 8 of the variable pump 4 with position control device
A signal circuit 12 is connected to each of the shockless pulp 10 and the external signal receiving section 11 of the shockless pulp 10, and an external signal receiving section [13 is connected to this signal circuit 12. This external signal switching device 13 has a working device 13α that turns off the signal, and a travel position 13A that gives the signal.

In the above configuration, during work, the external signal switching device 13 is set to the work position 13g. In this state, the external signal receiving sections 7α of the pressure control valve 7, the variable pump 4, and the shockless pulp 10.

Since there is no external signal input to 11.11, the pressure control valve 7 communicates with a light push-opening force, and the variable pump 4 with a position control device controls the amount according to the differential pressure caused by the control valve 3. By discharging pressurized oil and also performing the normal operation of the shockless pulp 10, the steering wheel can be operated with light steering force and dull feeling, and with a small shock.

When traveling, the external signal switching device 13 is set to the traveling device 13A. In this state, an external signal is sent to each external signal receiving section 7α, HA, and II, and the force required to push the pressure control valve 7 open increases first. Further, in the variable pump 4 equipped with a position control device, the gain of the differential pressure operating valve 8 can be changed, and furthermore, the operating range of the shockless pulp 10 can be changed.

In this state, the steering force becomes heavier and the stability of the steering wheel improves, allowing stable straight-line driving. In addition, the steering has a dull feel, so there is no delay in response, allowing for smooth course changes.

Note that each part signal in the above embodiment uses pilot pressure, and this pilot pressure is turned on by the external signal switching device 13.
, it is turned off.

Further, this external signal may be generated by using a vehicle speed sensing type external signal generating device in which the pilot pressure changes depending on the vehicle as shown in FIG. 2, instead of using the external signal switching device 13. Furthermore, as shown in FIG. Alternatively, the signal may be transmitted when the gear shift lever 15 of the control switch 14 of the transmission is set to the third or fourth gear, which is used for land transport or the like.

Note that each external signal receiving section 7 may individually input external signals from separate external signal switching devices.

Effects of the Invention According to the present invention, in terms of steering performance, by switching between work performance and driving performance, it is possible to exhibit optimal steering performance in each work.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a circuit diagram;
FIG. 2 is a diagram showing an example of an external signal pattern, and FIG. 3 is a circuit diagram showing the other side of the external signal switching device. 1 is the steering unit, 2 is the handle, 3 is the control pulp, 4 is the variable pump, 5 is the steering cylinder device% 7g, 8AI11 is the external signal receiver, 1
3 is an external signal switching device.

Claims (1)

[Claims] In power steering devices for construction machinery that are used for both excavation, loading, etc. work and transportation, etc., there is a control circuit that switches the performance of steering force performance and/or response. 1. A power steering device comprising a mechanism, and the switching mechanism is activated by an external signal.