JPH0240538B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device with excellent neutrality restorability.

In conventional power steering devices, power assist is performed during steering wheel operation, but power assist is not performed during return steering operation, and the power assist is not performed when the steering wheel is returned, but rather relies on self-alignment torque generated by front wheel alignment relative to the power cylinder and the return spring built into the control valve. The reaction force only cooperates with the return of the handle.

When the wheels are reversed by the self-alignment torque, the piston of the power cylinder is moved by discharging hydraulic fluid from the contraction side pressure chamber via the control valve via the sector gear. At this time, the hydraulic fluid encounters resistance from the narrow passage of the control valve, so the power steering system is generally inferior in steering wheel return compared to a manual steering system.

Especially near the neutral position, the steering angle is small, so the self-alignment torque is small, and the return spring is also close to its initial state, so the biasing force is small.
The return of the vehicle to straight-line driving is delayed.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a power steering device that improves neutral restorability by forcibly feeding pressure oil into a power cylinder when the steering wheel is returned.

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

In FIG. 1, the power steering device according to the present invention is composed of an output drive section 1, a steering state detection means 2, a control circuit 3, a control valve 4 as a control valve means, and the like.

As shown in FIG. 2, the power cylinder 5 of the output operating unit 1 has an input shaft 7 connected to a handle 6 rotatably attached to a housing 8.
A piston 9 is screwed into the piston 9 through a ball (not shown).
is slidably housed in a housing 8, and its piston 9 defines pressure chambers A and B. A rack 10 formed on the piston 9 is engaged with a sector gear 11, and this sector gear 11 is used as a steering link of a wheel. Connect.

The steering state detection means 2 includes a strain gauge 12 attached to the input shaft 7, and a steering force circuit 13 that outputs a signal indicating the presence or absence of steering force based on the output signal of the strain gauge 12.
and potentiometer 1 attached to input shaft 7.
4, a steering direction circuit 15 that outputs a steering direction signal based on the output signal thereof, and a link status circuit 16 that outputs a signal indicating whether the steering link is neutral or not based on the output of the potentiometer 14. ing.

The output signal of the steering force circuit 13 is outputted as an ON signal since the strain gauge 12 is distorted during steering/holding, and as an OFF signal while the steering wheel is being returned since the gauge 12 is not distorted.

Further, the steering direction circuit 15 outputs a signal indicating whether the steering wheel is turned to the right or to the left, and the link status circuit 16 outputs a signal indicating whether the steering link is neutral or non-neutral.

The control circuit 3 inputs the signals of the circuits 13, 15, and 16, and outputs left-turn and right-turn signals when the handle is turned, and outputs left-turn and right-turn signals when the handle is returned, as shown in FIG. Output.

The control valve 4 switches the signal output from the control circuit 3 by an electromagnetic solenoid 17 operated by a handle signal amplified by an amplifier 18 or a return handle signal. The direction of the pressure oil is reversed. In other words, the control valve 4 has three positions: a neutral position where pressure oil is returned to the tank side, a neutral position where pressure oil is sent to pressure chamber A and pressure chamber B is released to the tank, and a position where pressure oil is sent to pressure chamber B and pressure is It has a position that releases chamber A to the tank, and when driving on the left, pressurizes pressure chamber A at high pressure.
Conversely, when driving on the right, pressure chamber B is switched to high pressure, and in the neutral position both pressure chambers A and B are kept at the same pressure.
It is driven by the solenoid 17, and when the handle is returned, the power cylinder 5 is actively activated in the returning direction.
The switch is made so that pressure oil is sent to the

Next, the effect will be explained.

Now, for example, if you turn the steering wheel to the left, control circuit 3
In response to the left turn signal, the electromagnetic solenoid 18 is activated, and the control valve 4 supplies pressurized oil from the pump P to the pressure chamber A of the output drive unit 1, and the pressure chamber B to the tank T.
Since the piston 9 is lowered and the sector gear 11 is rotated counterclockwise, a leftward shift is performed.

When the steering wheel is returned from this turning state, that is, when the steering wheel is returned to the right, the strain gauge 12 is no longer strained, so the output of the steering force circuit 13 becomes an OFF signal, and the output of the link state circuit 16 by the potentiometer 14 is While the non-neutral signal is output, the steering direction circuit 15 outputs a left turn signal.

The control circuit 3 to which these signals are input is the third
A right return signal is output as shown in the thick frame in the figure.

This right return signal activates the electromagnetic solenoid 17, switches the control valve 4, supplies the pressure oil from the pump P to the pressure chamber B in the opposite direction, and connects the pressure chamber A to the tank T. For this reason, the piston 9
is raised and the sector gear 11 is rotated clockwise,
The power assist allows for quick right-hand return steering. In order to prevent the handle return action from being performed more rapidly than necessary, it is preferable that the stroke of the control valve 4 at the time of return is set smaller than that when the handle is turned.

Fig. 4 shows another embodiment of the present invention, which differs from Fig. 1 in that an auxiliary cylinder 5' dedicated to the return handle is attached to the output drive section 1, and together with the control valve 4 as control valve means. , an auxiliary control valve 4' for the auxiliary cylinder 5' is provided.
In this case, the capacity of the auxiliary cylinder 5' is set so as to provide optimum power assist upon return, and the auxiliary control valve 4' is in the neutral position during normal steering operation. Also,
When the handle is returned, the control valve 4 is maintained in a neutral state, and the main power cylinder 5 is not output.

As explained above, according to the present invention, the oil feeding direction at the time of the handle is reversed when the handle is returned, so power assist is performed even during the return handle, and therefore, the neutral restorability is greatly improved. effective.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is an explanatory sectional view of the output drive section of FIG. 1, FIG. 3 is an explanatory diagram of input/output signals of the control circuit of FIG. FIG. 4 is a schematic diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Output drive unit, 2... Steering state detection circuit, 3...
Control circuit, 4... Control valve, 5... Power cylinder,
12...Strain gauge, 13...Steering force circuit, 14
... Potentiometer, 15 ... Steering direction circuit, 16
...Link status circuit, 19...Switching valve.

Claims (1)

[Claims] 1. An output drive unit that transmits the input rotation from the steering wheel to the wheels via the power cylinder, means for detecting the steering state, and a steering wheel signal that is set to return when steering, based on the signal from the detection means. A control circuit that outputs a return handle signal when the handle is turned,
Based on the handle signal from this control circuit, pressure oil from the pump is selectively introduced into or discharged from the pressure chamber of the power cylinder so as to power assist the handle operation, and based on the return handle signal, the handle is returned to the neutral position. A power steering device comprising: a control valve means for reversing the direction of oil feeding. 2. The control valve means includes a control valve that selectively introduces or discharges pressure oil from a pump into a pressure chamber of the power cylinder so as to power-assist a steering wheel operation based on a steering wheel signal from the control circuit; The power steering device according to claim 1, further comprising an auxiliary control valve that reverses the direction in which pressure oil is fed from the pump in the direction of returning the handle to the neutral position based on a return handle signal from the pump. 3. The power steering device according to claim 2, wherein the output drive section includes a power cylinder that receives pressure oil from a control valve, and an auxiliary cylinder that receives pressure oil from an auxiliary control valve.