JPH0569752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a rack-and-pinion type power steering device having electric driving force or hydraulic driving force as power assist.

[Prior art]

Generally, in a power steering device, a steering wheel steering torque is detected as a signal by some kind of detection means, and a power assist is generated for the steering wheel steering torque by a control means such as a power steering valve or a controller.

For example, in a hydraulic power steering device, the steering torque is mechanically detected using a torsion bar, etc., and the displacement of the spool valve or rotary valve, which is the control means, is controlled to generate power assist. .

On the other hand, in an electric or electrohydraulic power steering device, steering torque is detected as some kind of electric signal, and this signal is sent to a predetermined control device to generate power assist.

As a steering torque detection means in this latter case,
Conventionally, the following two examples are given.

One of them is that, as shown in FIG. 6, the steering torque is proportional to the torsion angle of the torsion bar 62 that rotates together with the steering shaft 61. This method uses direct detection. That is, when the steering wheel is rotated, the torsion bar 62 is twisted, the relative angle between the magnet 64 and the guide 63 changes, and the magnetic flux passing through the magnetic sensor 65 changes. A magnetic sensor 65 detects this change in magnetic flux, converts it into an electrical signal such as voltage, and inputs it to an electronic control unit 67. Then, for a predetermined input steering torque, the electric signal amplified in the electronic control circuit 67 is
The electric motor 68 is operated, and the necessary steering torque is transmitted through the reducer 68A, clutch 68B, and gear 68C.
is applied to the steering shaft 61.

In other examples, as shown in FIGS. 7 and 8 (A-A cross section in FIG. 7), since the steering torque has a constant relationship with the torsion angle connected to the input shaft 71, this The displacement of the torsion angle of the torsion bar 81 connected to the input shaft 71 is measured by the planetary gear mechanism 8.
3, 83A, 83B, and 83C, it is converted into a linear displacement amount of the spool 82, and this displacement amount is used as an electric signal for detecting the steering torque by a potentiometer,
It is extracted by a detection device 84 such as a differential transformer (details are shown in Japanese Patent Laid-Open No. 59-11965).

However, since the magnetic sensor (optical sensor) used in the first steering torque detection means shown in FIG. 6 is a semiconductor, its temperature characteristics are not good, and it is detected as the torsion angle of the torsion bar and the steering torque conversion amount. It is not necessarily proportional to the amount of electricity that should be
In order to establish a proportional relationship, an electronic circuit unit is required, which increases the number of parts and complicates the system, which also has the disadvantage of being more prone to failure. Furthermore, magnetic sensors (optical sensors), which are semiconductors, are easily affected by dust and dirt, and have the disadvantage of requiring countermeasures against such disturbances.

Further, although the steering torque detection means using the planetary gear mechanism shown in FIGS. 7 and 8 has a proven track record, it has the disadvantage that the structure is extremely complicated and expensive.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide a rack-and-pinion type power steering device having a steering torque detecting device with a simple structure.

[Summary of the invention]

A rack-and-pinion power steering device according to the present invention is intended to achieve the above object by providing a steering torque detection means in a bearing portion that supports a pinion shaft.

That is, the pinion shaft receives a force in a direction opposite to the sliding direction of the rack, which acts on the bearing portion. This force is detected by a detection means such as a piezoelectric element or a resistance wire strain gauge, and power assist is generated based on the detected force.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1, FIG. 2, and FIG. 3 are diagrams showing a first embodiment of the present invention.

Figure 1 is a schematic diagram of a rack-and-pinion type power steering device that uses electric driving force as power assist, Figure 2 is a vertical cross-sectional view of the gearbox showing the meshing state of the rack and pinion, and Figure 3 is the same as Figure 2. It is a BB sectional view showing a steering torque detection means.

In FIG. 1, a wheel 1 is connected to a steering link 3 via a knuckle arm 2. In FIG. A rack 4 formed integrally with the steering link 3 and a pinion 7 connected from the handle 5 via an input shaft 6 are engaged in a gear box 7B.

The rack and pinion steering device is
The rotation of the handle 5 is transmitted to the steering link 3 via a mechanism consisting of a pinion 7 and a rack 4, thereby changing the direction of the left and right wheels 1.

A motor 9 is installed to assist the steering force of this rack-and-pinion steering device.
Pinion 9 attached to the output shaft end of motor 9
A is designed to mesh with the rack 4 and cause the rack 4 to slide, thereby producing power assist. The forward/reverse rotation and output control of the motor 9 are performed by the controller 8 processing an electric signal detected by the steering torque detection device 7A.

In Figure 2, 4 is a rack, 7 is a pinion,
7B is the gear box, 21 and 22 are the bearing parts, 21A and 22A are the outer races of the bearing parts 21 and 22, and 21B and 22B are the bearing 2.
It is fitted onto the pinion shaft 7C through inner races 1 and 22.

A pinion 7 that engages with the rack 4 is formed integrally with a pinion shaft 7C, and is supported by a gear box 7B via bearings 21 provided before and after the pinion 7.

In FIG. 3, a pair of piezoelectric elements 31, 31R, and 31L, which are steering torque detection means, are clamped between the outer race 21A of the bearing part 21 and the gearbox B, and the piezoelectric elements 31 (31
The surface that receives the pressure of R, 31L) is the pinion shaft 7
A line 10A passing through the axis 10 of C and parallel to the rack 4
It is in an orthogonal state.

Next, the operation of steering torque detection will be explained. The steering torque is proportional to the force that the pinion 7 receives from the rack 4, and this force is
Since the voltage detected by 31R and 31L is approximately proportional to the voltage detected by the piezoelectric elements 31 and 3, which are steering torque detection means, the voltage approximately proportional to the steering torque is
1R, 31L.

That is, when the handle 5 is rotated clockwise (in the direction of arrow a in FIG. 3), the loaded wheels 1, knuckle arm 2, steering link 3, and rack 4 are in one fixed state, so the pinion 7 is rotated to the rack 4. 3, the pinion shaft 7C, which is integrated with the pinion 7, presses the bearing portion 21 in the right direction in FIG. 3. Then, the piezoelectric element 31R is compressed by the outer race 21B of the bearing part 21, and a voltage change due to this compressive force is detected to determine the rotation direction of the motor 9 and to generate power assist for rightward steering.

On the other hand, when the steering wheel 5 is rotated counterclockwise, the piezoelectric element 31L is compressed to provide power assist for leftward steering.

FIG. 4 is a sectional view showing essential parts of a second embodiment of the present invention. This is the piezoelectric element 31 of the first embodiment,
31R, 31L, a pair of resistance wire strain gauges 41, 41R,
41L is provided, and its mounting position is along a line 10 that passes through the axis 10 of the pinion shaft 7C and is parallel to the rack.
It's on A.

In FIG. 4, when the steering wheel is rotated and the tire is under load, the pressing force of the pinion shaft 7C is applied to the resistance wire strain gauge 41 attached to the outer surface of the gearbox 7B via the bearing parts 21 and 22. , 41R, and 41L, the steering torque can be detected as a resistance change.

Note that in the first and second embodiments, a pair of piezoelectric elements 3
1, 31R, 31L or resistance wire strain gauge 41, 4
1R and 41L is shown, but a single piezoelectric element or strain gauge may be provided, and in that case, it is necessary to apply an initial stress to the piezoelectric element or strain gauge in advance.

Note that in the first and second embodiments, the piezoelectric elements 31, 3
1R, 31L, resistance wire strain gauge 41, 41R, 4
Although the steering torque detection means such as 1L is shown as being provided in the bearing portion 21 shown in FIG. 2, it may be provided in another bearing portion 22 that supports the pinion shaft 7C.

FIG. 5 is a schematic diagram of a rack-and-pinion type power steering device in which hydraulic driving force is used as power assist instead of electric driving force in the first embodiment in which electric driving force is used as power assist, and the means for power assisting. This embodiment is different from the first to second embodiments (FIGS. 1 to 4) in that they are different from each other.

In FIG. 5, an electric signal detected by a steering torque detecting means 7A such as a piezoelectric element or a strain gauge is input to a controller 8, and is processed by a control valve 5.
1, the pipe line 5 is connected to the cylinder 55.
Pressure oil is supplied through link 4 to generate power assist to link 3. (Note that 52 indicates a hydraulic pump, and 53 indicates an oil tank.) [Effect] As is clear from the above explanation, it is possible to obtain a rack-and-pinion type power steering device having a steering torque detection device with a simple structure. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a rack-and-pinion power steering device according to a first embodiment of the present invention, FIG. 2 is a vertical sectional view of its gearbox, FIG. 3 is a sectional view of its essential parts, and FIG. 4 5 is a schematic view of another embodiment, FIG. 6 is a sectional view showing a conventional first steering torque detection means, and FIG. 7 is a sectional view of a conventional first steering torque detection means. A schematic diagram of a power steering device having another steering torque detection means,
FIG. 8 is a sectional view of a main part of the steering torque detection means. DESCRIPTION OF SYMBOLS 1... Wheel, 3... Steering link, 4... Rack, 5... Handle, 6... Input shaft, 7... Pinion, 7A... Steering torque detection means, 7B... Gear box, 7C... Pinion Axis, 21, 22
...bearing part, 21A, 22A...bearing part outer race, 21B, 22B...bearing part inner race, 31R, 31L...piezoelectric element, 41R, 41L...resistance wire strain gauge.

Claims (1)

[Claims] 1. A rack-and-pinion power steering device that includes a torque detection means for detecting steering torque as an input signal, and generates power assist based on the detected signal,
A rack-and-pinion power steering device characterized in that the torque detection means is provided in a bearing portion that supports a pinion shaft. 2. The rack-and-pinion power steering device according to claim 1, wherein the torque detection means is a piezoelectric element. 3. The rack-and-pinion type power steering device according to claim 1, wherein the torque detecting means is a resistance wire strain gauge.