JPH0332508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a control system of a power steering device (power steering) for a vehicle.

FIG. 1 shows an example of a power steering device, in which reference numeral 1 is a constant flow pump, the discharge side of which communicates with the suction side of the control valve 3 via the supply pipe 2. The connected supply/discharge pipe 4 is connected to a power cylinder 5, and the power pistons 5a of the power cylinder 5 are connected to left and right steering wheels (not shown), respectively. Also control valve 3
The discharge side of is connected to a reservoir tank 7 via a return pipe 6.
The suction side of the constant flow pump 1 communicates with the reservoir tank 7 via a pipe 8. Reference numeral 9 denotes a bypass line that communicates between the supply line 2 and the return line 6;
A part of the working fluid passing through the pipe is diverted and discharged to the return pipe 6. Therefore, this bypass pipe line 9
There is a variable aperture section 10 in the middle, and a variable aperture section 1.
A flow rate control valve 12 composed of a pressure compensating valve section 11 for keeping constant the differential pressure between the hydraulic pressures before and after zero is provided, and controls the amount of oil supplied to the control valve 3.

That is, the bypass flow rate flowing through the bypass pipe line 9 is controlled by the drive current value applied to the solenoid 11a, which is a component of the flow control valve 12. Further, the drive current value is determined by a control circuit 14 comprising a microprocessor, an arithmetic processing unit, and a memory, which are controlled by signals from the vehicle speed sensor 13 and the like. FIG. 2 is a flowchart of this control circuit 14.

That is, in block 15, the target bypass flow rate Q _B is determined from the vehicle speed V, and in block 16, the target drive current value i is determined from the target bypass flow rate Q _B.
had decided.

However, such conventional power steering devices are structured so that when there is a sudden change in vehicle speed due to sudden braking, etc., the bypass flow rate changes suddenly. There was a problem in that the steering assist force suddenly changed in such a case, making the steering unstable.

The present invention has been made to solve these conventional problems, and it sets the maximum value of the bypass flow rate that changes within a certain period of time within a certain range, and prevents the bypass flow rate from changing due to a sudden change in vehicle speed. It is an object of this invention to solve the above-mentioned problem by configuring a control circuit so that the bypass flow rate does not exceed a set change range even when the bypass flow rate changes.

Hereinafter, the present invention will be explained with reference to the drawings. The components of the power steering device of the present invention are similar to those in FIG. 1, and the difference is in the configuration of the control circuit 14 that determines the drive current value of the solenoid 11a, and FIG. 3 shows a flowchart thereof. It is something.

To explain the operation of this control circuit, first, in block 15, a bypass flow rate _QB is determined according to a predetermined vehicle speed signal V using the vehicle speed signal V from the vehicle speed sensor 13, and then in block 16, a bypass flow rate _QB is determined. The drive current value i required for the bypass signal according to is determined.

In the present invention, in a newly provided block 17, the target drive current value io from a certain time ago is stored, and the range of change Δi between this io and i is determined.

Next, in decision block 18, Δi is compared with a preset maximum drive current change range ΔiMAX, and when Δi≦ΔiMAX, the drive current value of the solenoid 11a is set to the previously determined i.

Also, when Δi>ΔiMAX, i and io are compared in decision block 19, and when i≧io, i=io+ΔiMAX is set in block 20, and in the comparison in decision block 19, when i<io, In block 21, i=io-ΔiMAX.

According to the invention, therefore, the solenoid 11a
The drive current value does not change by more than ΔiMAX within a certain period of time. Furthermore, like the blocks 20 and 21 of the embodiment, the solenoid 11a
By controlling the drive current value, the drive current value is changed within the allowable variation range of the bypass flow rate, so that responsiveness is not unduly sacrificed.

As explained above, in the present invention,
According to the present invention, the maximum value of the bypass flow rate that changes within a certain period of time is set, and the control circuit is configured so that the width of change of the bypass flow rate that changes within a certain period of time does not exceed the set maximum value. It is possible to keep the range of change in the steering assist force within a certain range. Therefore, even if there is a sudden change in vehicle speed due to sudden braking or the like, the range of change in the steering assist force will not exceed the set value, so there is no risk of unstable steering.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a power steering device for a vehicle, FIG. 2 is a flowchart showing a control circuit of a conventional power steering device, and FIG. 3 is a control circuit of a power steering device of the present invention. This is a flowchart. 1... constant flow pump, 3... control valve,
5...Power cylinder, 7...Reservoir tank,
10...Variable throttle section, 11...Pressure compensation valve section, 1
2...Flow control valve, 13...Vehicle speed sensor, 14...
...Control circuit, 15-21...Various blocks, V...
...Vehicle speed, Q _B ...Target bypass flow rate, i...Target drive current value, io...Target drive current value a certain period of time ago, Δi...|i-io|, ΔiMAX...Set maximum drive current change range.

Claims (1)

[Claims] 1. A power cylinder that connects the left and right steering wheels to a power piston, a constant flow pump that discharges working fluid to the power cylinder side, and a control that selectively supplies working fluid to the power cylinder in response to steering operations. and a flow rate control valve that controls the flow rate of working fluid supplied to the control valve based on an input signal of vehicle speed, so as to produce an appropriate steering force assisting effect in response to a steering operation. , in a power steering device including an assistance control circuit that controls the relationship between the input signal and the flow rate of the working fluid, an upper limit value of a change in the flow rate of the working fluid over a certain period of time is set within a certain range; Features a power steering device.