JPH0347231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that adjusts steering force according to vehicle speed.

(Conventional device) Conventional power steering devices adjust the steering force according to the speed of the vehicle;
It was detected from the rotation speed of the engine's crankshaft or drive shaft.

However, during sudden braking, the wheels lock, so a vehicle speed signal lower than the actual vehicle speed (ground speed) is detected, and the steering force control circuit operates in accordance with the detected signal. For this,
When braking suddenly, the steering force is controlled in a manner similar to stationary steering, so the steering wheel suddenly becomes lighter.

Therefore, if you operated the steering wheel during sudden braking using the conventional steering sensation, there was a risk that you would turn the steering wheel too much and cause a serious accident. In addition, even if it did not directly lead to an accident, there were problems that caused a great deal of anxiety to the driver.

This also applies during sudden acceleration.
Drivers felt very anxious.

(Objective of the present invention) This invention maintains the previous steering force during sudden braking or sudden acceleration, and after the sudden braking or sudden acceleration is completed, a steering force corresponding to the vehicle speed can be obtained. The aim is to provide a power steering device with improved safety.

(Embodiment of the present invention) This embodiment consists of a circuit unit whose main elements are a control valve V and a pressure control valve S.

In other words, the control valve V has a main body 3 that forms a pump port 1 and a tank port 2.
A spool hole 4 is formed in the spool hole 4, and a spool 5 is slidably provided in the spool hole 4.

This spool 5 has both ends facing reaction force chambers 6 and 7, and springs 8 and 9 are provided in these reaction force chambers 6 and 7.
By this action, the spool 5 is held at the neutral position shown.

This spool 5 has annular grooves 10 and 1.
1, and annular recesses 12 and 13 are formed on the inner peripheral surface of the spool hole 4.

In the control valve V thus constructed, when the spool 5 is in the neutral position shown in the figure, the annular grooves 10, 11 of the spool 5 and the annular recesses 12, 13 of the spool hole 4 are different from each other. In this neutral position, a slight gap is created between the annular groove 10, the annular recess 13, and the annular groove 11, and the pump port 1 and the tank port 2 are communicated through this gap.

When the spool 5 is switched from the neutral position to the left or right, the oil discharged from the pump P is supplied to one chamber of a power cylinder (not shown), and the oil is returned to the other chamber of the power cylinder. The oil is allowed to flow out from tank port 2.

The control valve V is a known one used in rack-and-pinion power steering, and the spool 5 is switched in the following manner.

That is, the input rotation from the handle is transmitted to the pinion shaft 14. As a result, the yoke 15 connected to the pinion shaft 14 swings, and the drive lever 16 moves left and right along with this swing.

Since the drive lever 16 is connected to the spool 5, the spool 5 is switched as the drive lever 16 reciprocates.

The tank port 2 of the control valve V communicates with the import 17 of the pressure control valve S, and the configuration of the pressure control valve S is as follows.

That is, this pressure control valve S has the above-mentioned import 17 formed in its main body 18, and
An output port 19 communicating with the reaction chambers 6 and 7 of the control valve V and a return port 20 communicating with the tank T are formed.

Furthermore, this pressure control valve S has a poppet 21 installed therein, and a control hole 22 is formed at a position opposite to this poppet 21.

The poppet 21 has a spring 23
Normally, it is held in the position shown by the action of
When the solenoid 24 is energized, the spring 23
move against. However, the amount of movement is proportional to the amount of current applied to the solenoid 24.

In the pressure control valve S thus constructed, the import 17 and the output port 19 are always in communication, but the return port 20 is configured to communicate with the import 17 and the output port 19 via the control hole 22. .

Therefore, when the solenoid 24 is energized now, the poppet 21 moves against the spring 23.
The amount of thrust of the tip of the poppet 21 into the control hole 22 differs depending on the amount of movement of the poppet 21, but the greater the amount of thrust, the more
The opening area of this control hole 22 becomes smaller. In other words, the poppet 21 and the control hole 22 together constitute a variable orifice.

Therefore, when the poppet 21 is in the state shown, the control hole 22 is fully opened. When the control hole 22 is fully open, oil flowing from the on port 17 passes through the control hole 22 and the return port 20,
Returning to the full tank T, no pressure is supplied to the reaction force chambers 6, 7, so the reaction force chambers 6, 7 are at tank pressure.

When the reaction force chambers 6 and 7 reach tank pressure, the spool 5
Only the spring force of the springs 8 and 9 acts on both ends of the . Therefore, the spool moves with a force that resists the spring, and its steering reaction force becomes small.

Then, when the solenoid 24 is energized and the poppet 21 is moved against the spring 23, the opening area of the control hole 22 becomes smaller. Therefore,
A differential pressure is generated before and after the control hole 22, and the pressure on the upstream side is transmitted through the output port 19 to the reaction chambers 6 and 7.
flows into. When pressure flows into the reaction chambers 6 and 7,
This pressure acts as resistance against the movement of the spool 5, so the pressure in the reaction chambers 6 and 7 is
Steering reaction force increases.

As described above, the amount of current applied to the solenoid 24 that controls the pressure control valve S is controlled in accordance with the electric signal output from the steering force control circuit D, and this steering force control circuit D is connected to the arithmetic processing circuit 25, It consists of a storage circuit 26 connected to this arithmetic processing circuit 25, and an interface 27 is connected to the arithmetic processing circuit 25. This interface 27 is connected to a vehicle speed sensor 2 provided on the crankshaft or drive shaft of the engine 28.
9 is connected to an acceleration sensor 30 that detects acceleration G in the longitudinal direction of the vehicle.

The steering force control circuit D thus configured operates as follows to control the pressure control valve S.

That is, in normal driving conditions, the vehicle speed sensor 2
The amount of current applied to the pressure control valve S is adjusted in accordance with the signal from 9, and the amount of current applied is proportional to the vehicle speed.

Therefore, in the low speed range, the pressure control valve S is maintained in a non-excited state, and the steering force is the lightest. As the vehicle speed increases, the amount of current applied to the pressure control valve S increases, and accordingly, the steering force also increases. The bluff in FIG. 2 shows the relationship between vehicle speed and steering force.

When sudden braking is applied from the above-mentioned normal running state, the speed suddenly decreases, so the acceleration G changes greatly. If this acceleration change exceeds a certain value, the steering force control circuit D determines that it is sudden braking, and the pressure control valve S is activated so that the steering force before sudden braking can be maintained. The amount of current applied to the solenoid 24 is controlled.

When the sudden braking is completed and a certain period of time has elapsed, the normal running state is restored and a steering force proportional to the vehicle speed is obtained. The graph in FIG. 3 shows this relationship. In this graph, sudden braking is initiated at point a, and the steering force before the sudden braking is maintained until time f has elapsed from the sudden braking time a. After this time f has elapsed, the steering force is again proportional to the vehicle speed.

If only the steering force control during sudden braking is considered, in addition to the acceleration sensor 30, a pressure sensor 32 that detects the pressure of the brake master cylinder 31 and a reaction force sensor 34 that detects the reaction force of the brake pedal 33 are used. Alternatively, a stroke sensor 35 or the like that detects the depression stroke of the brake pedal 33 may be used.

(Structure of the present invention) The structure of the present invention has a reaction force chamber in the control valve part, and communicates a hydraulic oil supply source to the reaction force chamber through the import and output ports provided in the pressure control valve. On the other hand, the import and output ports are connected to the return port via a variable orifice provided in the pressure control valve, and the opening area of the variable orifice is adjusted by the amount of current applied to the solenoid. A power steering device that obtains a steering reaction force is equipped with a sensor that detects driving conditions such as sudden braking or sudden acceleration, and maintains the steering force before sudden braking or sudden acceleration for the required time according to the signal from this sensor. The steering force control circuit is characterized in that a steering force control circuit is provided for inputting an electric signal to the pressure control valve.

(Effects of the present invention) This invention can detect sudden braking or sudden acceleration of the vehicle and maintain the steering force before the sudden braking or sudden acceleration, so the steering force changes suddenly during sudden braking or sudden acceleration. do not. Since the steering force does not change, the driver can turn the steering wheel based on the previous feeling of operation, which reduces the chances of steering errors.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is a cross-sectional circuit diagram of a control valve and a pressure control valve, and Fig. 2 shows the relationship between vehicle speed and steering force under normal driving conditions. The graph shown in FIG. 3 is a graph showing the relationship between vehicle speed and steering force during sudden braking. V...control valve, S...pressure control valve, 5...spool, 6, 7...reaction force chamber, 17...import, 19...output port, 20...return port,
21... Poppet, 22... Control hole, 24... Solenoid, D... Steering force control circuit, 29... Vehicle speed sensor, 3
0... Acceleration sensor, 32... Pressure sensor, 34... Reaction force sensor, 35... Stroke sensor.

Claims (1)

[Claims] 1 The control valve part has a reaction force chamber, and a hydraulic oil supply source is communicated with the reaction force chamber through the import and output ports provided in the pressure control valve, while the variable orifice provided in the pressure control valve A power steering device in which the import and output ports are connected to the return port through the power steering device, and the opening area of the variable orifice is adjusted by the amount of current applied to the solenoid, thereby obtaining a steering reaction force proportional to the vehicle speed. A sensor is provided to detect the driving state of sudden braking or sudden acceleration, and in response to the signal from this sensor, an electric signal is sent to the pressure control valve to maintain the steering force for the required time during sudden braking or sudden acceleration. A power steering device equipped with a steering force control circuit that inputs to the