JPS6340718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering system, and particularly to a system for controlling the operation of a hydraulic control valve thereof.

The valve sensitivity characteristics of a power steering system, which generally determines its characteristics, are determined by the channel shape of the valve part and the strength of the torsion bar, and are determined by various combinations depending on the car model. The same valve cannot be used for both.

With integral power steering, the control valve is assembled integrally with the power steering, so a seal is required to isolate the hydraulic chamber, and the frictional force of this seal adversely affects the restorability of the power steering, impairing its smoothness. It will be done.

Since the rigidity of the torsion bar that connects the worm and the input shaft is much lower than that of a general manual steering device, it is not possible to prevent the steering wheel from wobbling when driving at high speed.

There were other problems.

On the other hand, as shown in Japanese Patent Publication No. 45-21767, for example, it has been proposed to make it possible to use the same valve for each car model, but this involves manufacturing various valve channels and replacing them. However, no improvements have been made in the problems of sealing and torsion bar rigidity in integral power steering.

There are also attempts to solve the problem of seals in integral power steering;
This does not allow the use of the same valve for different vehicles, and does not solve the problem of torsion bar rigidity.

Further, a power steering device as shown in Japanese Patent Application Laid-Open No. 112325/1983 has been proposed.

This detects the steering angle of the steering wheel using a steering angle detector, drives the pulse motor by an angle corresponding to this, and uses the pulse motor to displace the valve spool of the control valve, supplying hydraulic pressure to the rack cylinder. It is designed to provide power assistance. Then, the rotation angle of the pulse motor detected by the pulse motor rotation angle detector is fed back and compared with the steering wheel steering angle to obtain the actual steering angle of the vehicle corresponding to the steering wheel rotation angle (steering angle). The purpose is to optimize the relationship between the steering wheel rotation angle and the actual steering angle under the driving conditions of the vehicle.

Therefore, in such a power steering device, since the operation of the valve spool is controlled only by the rotation angle of the steering wheel, the driver does not have a steering sensation when operating the steering wheel.

Since the steering wheel and gear part are separate, there is no fail-safe function like integral power steering. (In order to make the gear ratio a variable gear ratio, the gear section has to be separated.) Since the feedback signal of the pulse motor rotation angle detector is controlled by the movement of the valve spool, it is fed back as the actual steering angle, and the feedback signal from the pulse motor rotation angle detector is There is no direct relationship with the steering angle.

If you turn the steering wheel, the vehicle will be steered suddenly, creating a danger.

There are drawbacks such as.

The present invention aims to eliminate all of the drawbacks of the prior art as described above.

To explain the embodiment, a wormshaft 2 is interlocked with a cross shaft gear (not shown) through a well-known mechanism (not shown) in a gear box 1, and an input shaft 3 is rotated by a handle operation. The input shaft 3 and the wormshaft 2 are connected by a torsion bar 4, and are configured to allow relative rotational angular displacement between the input shaft 3 and the wormshaft 2 within a range of torsion angles allowed by the torsion bar 4.

Provide a screw 5 at the shaft end of the wormshaft 2,
The nut plate 6 is screwed together, and the pin 7 protruding from the input shaft 3 is engaged with the axial groove 8 of the nut plate 6, so that the input shaft 3 and the nut plate 6 rotate together. The torsion angle detecting means for the torsion bar 4 is configured so that the nut plate 6 can move in the axial direction when a rotational angular displacement occurs between the worm shaft 2 and the input shaft 3.

On the other hand, the potentiometer 10 is attached to the housing 9, and the outer peripheral edge of the nut plate 6 is engaged with the auxiliary ring 12 fixed to the operating shaft 11 of the potentiometer 10, so that the axial displacement of the nut plate 6, that is, the torsion bar 4 The potentiometer 10 is actuated in response to the displacement of the torsion angle.

A control valve 1 is installed at an appropriate location in the gearbox 1 to distribute the hydraulic pressure supplied from the hydraulic pump 13 to each chamber of the rack cylinder and to generate pressure.
4, and at the tip of the valve spool 15,
Screw into the valve housing and attach the valve spool 15.
a screw 16 that displaces the spool 15 in the axial direction by rotation of the screw 16, and a rotation shaft 1 of the servo motor 17.
A gear 20 that meshes with a gear 19 provided at
It can be formed integrally or manufactured separately and fixed.

The servo motor 17 is provided with a position sensor 21 that detects its rotation angle (number). This position sensor 21 may be attached to the valve spool.

The potentiometer 10 is as shown in FIG.
A resistor is incorporated, and the voltage (or current) between the terminals changes depending on the amount of movement of the operating shaft 11. At the center position where the handle does not rotate (a state where no torsion angle is generated in the torsion bar), the terminal voltage Vo is set to 1/2V, and the axis 11 moves as shown by the broken line in the figure according to the torsion angle displacement of the torsion bar 4. As you move to the right as shown in
Vo is 1/2V - ΔVx, 1/2V when moving to the left
+ΔVx.

The operation of this invention will be explained below. Even if rotational torque is generated in the input shaft 3 by steering wheel operation, at the initial stage, the rotation of the wormshaft 2 is prevented by the road resistance transmitted through the steering wheel and the well-known steering device, and the torsion bar 4 is prevented from rotating. Twisted. When the input shaft 3 rotates and the wormshaft 2 remains stationary, the nut plate 6, which rotates together with the input shaft 3, moves in the axial direction on the wormshaft 2, increasing the potential by an amount corresponding to the torsion angle of the torsion bar 4. The operating shaft 11 of the yometer 10 is moved. Therefore, an output signal of voltage e is generated at potentiometer 10.

By subtracting the reference voltage 1/2V from this output signal (voltage e) in the amplification calculation circuit 22 as shown in FIG. 3, the change in +ΔVx or -ΔVx corresponding to the torsion angle of the torsion bar 4 can be can get.
By determining + and - here, the rotational direction of the servo motor 17, which will be described later, can be detected.

This change, ie, the output of the amplification calculation circuit 22, is guided to the variable gain amplifier 23. The amplifier 23 is
The output signal voltage is changed in response to a signal from a driving condition detection section such as the vehicle speed sensor 24 or another crosswind sensor that operates in response to a crosswind during high-speed driving, and an output signal from the width arithmetic circuit 22. (The gain is changed.) When the rotational position of the servo motor 17 is controlled via the servo amplifier 25 using the output signal obtained in this way, the rotation position of the servo motor 17 is adjusted according to the amount by which the torsion bar 4 is twisted and the change in vehicle speed. Rotational position is obtained. When the servo motor 17 rotates, the valve spool 15 is rotated by the gears 19 and 20 and displaced in the axial direction by the screw 16, distributing the hydraulic pressure supplied from the hydraulic pump 13 and generating a pressure change in the rack cylinder 26. let Due to this distributed flow rate and pressure change, as is well known, the wormshaft 2
rotates to provide power assistance. 27 is a detection means for detecting the torsion angle of the torsion bar 4 described above.

That is, the torsion bar 4 generates a torsional angle proportional to the road resistance, and this torsional rigidity gives the driver a sense of load, eliminating the conventional inconvenience of turning the steering wheel too much.
Furthermore, with the amplification calculation circuit, the output signal voltage (or current) necessary to sufficiently change the rotational position of the servo motor can be obtained even with a small torsion angle of the torsion bar. There is no need to use a torsion bar, and the torsion bar can have sufficient rigidity to provide the driver with an appropriate steering sensation, that is, the torsion bar has as strong a rigidity as possible.

In addition, since the rotational position of the servo motor can be controlled by obtaining an output signal from a vehicle speed sensor, etc., the valve sensitivity characteristics are shown in Figure 4, where the hydraulic pressure P is taken on the vertical axis and the handle torque T is taken on the horizontal axis. can be set arbitrarily, and the power steering device can be a vehicle speed responsive type.

In addition, in conventional power steering devices, the basic discharge amount of the pump has been determined from the opening area of the valve, the supply and discharge flow rate to the power steering device, and the torsion rigidity of the torsion bar. Since the valve sensitivity characteristics can be freely adjusted depending on the rotational position of the hydraulic pump, it is possible to provide sufficient power assistance with a discharge volume that is even smaller than the basic discharge volume of the pump that was previously required. It is also possible to reduce energy consumption and achieve energy saving effects.

Furthermore, since a servo motor is used as the drive control means for the hydraulic control valve, the hydraulic control valve can be continuously and steplessly controlled in accordance with (proportional to) the rotation amount and rotation angle of the servo motor. Smooth steering is possible according to vehicle speed.

Therefore, for example, even when slowing down from a high speed range to make a curve, the steering wheel will not suddenly become lighter, which will prevent the steering wheel from turning too much and even causing the car to spin. There is no risk of connection, making it extremely safe.

Furthermore, according to this invention, the control valve can be set in any position that can be reached by electrical wiring, so it is possible to design the control valve freely according to the space for installing the steering wheel of the automobile, etc. Since the valve can be separated from the rotating position of the steering gear, it is possible to eliminate most of the hydraulic seals, which not only reduces the number of parts but also prevents failures caused by frictional forces generated in the seal sliding parts. By eliminating this, it is possible to obtain a power steering device with good restorability.

Furthermore, the fact that the valve sensitivity characteristics can be freely obtained means that one power steering system can be used for different types of vehicles, resulting in great effects such as mass production effects and cost reduction effects.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing the main parts of the embodiment, Fig. 2 is an explanatory diagram of the potentiometer, Fig. 3 is a flowchart to explain the operation, and Fig. 4 is a diagram showing the valve sensitivity characteristics. be. 2...Wormshaft, 3...Input shaft, 4...Torsion bar, 5...Screw, 6
... Nut plate, 7 ... Pin, 8 ... Axial groove, 1
0... Potentiometer, 11... Operating axis, 13
... Hydraulic pump, 14 ... Control valve,
15... Valve spool, 16... Screw, 17...
...Servo motor, 19,20...Gear, 22...
Amplification calculation circuit, 23... Variable gain amplifier, 24...
... Vehicle speed sensor, 27 ... Torsion angle detection means.

Claims (1)

[Scope of Claims] 1. A torsion bar that connects a wormshaft and an input shaft; a screw member screwed into the end of the wormshaft on the input shaft side; and a protrusion provided on an input shaft that engages with the member to permit axial displacement, and the torsion angle of the torsion bar is determined from the relative displacement between the wormshaft and the input shaft relative to the axis of the threaded member. a torsion angle detection means for detecting directional displacement; a potentiometer driven by the torsion angle detection means to output the axial displacement of the screw member as an electric signal as a change in voltage between terminals; a calculation means for calculating a change in the output signal of the potentiometer by comparing the output signal with a reference signal; a servo motor whose rotation is controlled by the output signal from the calculation means; and a servo motor controlled by the servo motor; 1. A power steering device comprising: a hydraulic control valve for controlling hydraulic pressure distribution to rack cylinders. 2. Claim 1, characterized in that the rotational position of the servo motor is controlled by calculating the output signal of the potentiometer and the output signal from a vehicle running condition detection unit such as a vehicle speed sensor or a crosswind sensor. The power steering device described.