JPH0450230B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a steering torque detector for a power steering device, and in particular, detects the magnitude of the steering torque of a power steering device, and detects the magnitude of the steering torque of the power steering device according to the detected output. The present invention relates to a steering torque detector for an electric power steering device that controls the driving force of an electric motor of the power steering device.

[Prior Art] As a conventional steering torque detector for this type of electric power steering device, there is a technique disclosed in Japanese Patent Application Laid-open No. 59-209964.

The above technology includes an input shaft connected to a steering shaft of a vehicle, an output shaft connected to a steering gear box of a vehicle, a torsion member connecting the input shaft and the output shaft to each other, and the input shaft and the output shaft. a torque sensor that generates a torque signal representing the torque applied between A power steering device comprising a gear train for assisting a driver, a first signal representing the magnitude of torque applied between the input shaft and the output shaft, and a second signal representing the direction in which the torque is applied. sensor means for generating an amplified signal responsive to said first and second signals, having a magnitude that varies as a function of said first signal and having a polarity representative of said second signal; The present invention is characterized by comprising an amplifier, a low-speed, high-torque reversible electric motor that generates a rotational output having a magnitude and direction representing the amplified signal, and a gear train that transmits the rotational torque output of the electric motor to an output shaft. .

[Problems to be Solved by the Invention] Specifically, the above-mentioned torque sensor has a pair of resistance bridge strain gauges attached to the center of a steel plate, and the stability of the attachment of the strain gauges can be achieved. However, when pulling out the lead wires from the strain gauge, it is necessary to wrap the lead wires around the steel plate in advance, or
Alternatively, it is necessary to use a slip ring or the like to transmit and receive electrical signals, which poses reliability problems with repeated use.

Another option is to attach the strain gauge directly to the steering shaft, but if the steel plate to which the strain gauge is attached is made of a round bar such as a torsion bar, the attached strain gauge itself will be strained in its initial state. , there was a problem with the output. In particular, strain gauges are attached to small diameter torsion bars to increase strain output.
Since the strain gauges are not attached uniformly, distortion occurs in the initial state, the bridges of the strain gauges are not balanced, and the reliability of the detection output becomes a problem.

SUMMARY OF THE INVENTION Therefore, the present invention solves the above problems and provides a steering torque detector for an electric power steering device that can obtain a highly reliable electrical signal from a torque sensor and that can be easily converted into a torque sensor. The challenge is to provide this information.

[Problems to be Solved by the Invention] The steering torque detector of the electric power steering device according to the present invention includes an input shaft such as a steering shaft, an output shaft such as a shaft connected to a steering gear box, a torque balance detection unit and an axial direction conversion means constituting a torque-axial displacement conversion mechanism that converts the force direction and force magnitude of the steering torque into axial displacement between the input shaft and the output shaft; a sliding member displaceable in the axial direction constituting a torque-axial displacement conversion mechanism; a housing housing the torque-axial displacement conversion mechanism; one end fixed to the housing and the other end attached to the sliding member; It consists of a cantilever that is supported and fitted with a strain gauge.

[Operation] A sliding member displaceable in the axial direction that constitutes a torque-axial displacement conversion mechanism that converts the direction and force of steering torque applied to the steering shaft into axial displacement of the input shaft or output shaft. Then, the direction and magnitude of the steering torque on one end of the cantilever are converted into axial displacement, and the strain of the cantilever between the other end of the cantilever and the fixed housing is detected using a strain gauge. The detection output of the gauge is used to rotate the electric motor in a predetermined direction and apply the necessary rotational force to the output shaft.

[Embodiment] FIG. 1 is a sectional view of a first embodiment of a steering torque detector for an electric power steering device of the present invention. FIG. 2 is a cross-sectional view of a main part of a torque balance detection section used in an embodiment of the present invention, and FIG. 3 is a cross-sectional view of a main part of an axial direction converting means used in an embodiment of the present invention.

In FIG. 1, the housing 11 is fixed to the vehicle, and has divided parts 11a, 11.
parts 11a, 11b, 11 formed by connecting b, 11c, 11d with bolts etc. or dividing them
c and 11d are integrally formed by welding or the like.

The input shaft 12 in the housing 11 includes a hollow shaft body 13 having a flange 13a on the outer periphery of its lower end;
The connecting shaft body 15 is fitted into the hole of the hollow shaft body 13 and integrally connected with a connecting pin 14 extending in the radial direction. The upper end of the hollow shaft body 13 is rotatably supported by the housing 11 via a needle bearing 16. A spline 13b is formed on the upper part of the inner wall of the hollow shaft body 13 for connection to a steering shaft (not shown).

The output shaft 17 in the housing 11 has a fitting hole 1 at its upper end into which the lower part of the connecting shaft 15 is loosely fitted.
7a, whose central and lower end portions are rotatably supported by housings 11b and 11c via ball bearings 18 and 19, respectively.

Inside the housing 11c at the bottom of the housing 11 is an electric motor 20 fixed to the housing 11c.
A reduction gear mechanism 21 is arranged to reduce the rotation of the electric motor 20 using a necessary number of gears to transmit the output from the motor output shaft 20a to the output shaft 17. This reduction gear mechanism 21 includes a gear 21a coaxial with the motor output shaft 20a, a housing 11b, and a housing 11.
a gear 25 attached to a shaft 24 rotatably supported via ball bearings 22 and 23;
and 26, and a gear 27 coaxial with the output shaft 17.

Inside the housing 11a at the upper part of the housing 11 is a torque uniaxial displacement conversion mechanism 2 that generates a torsional angular displacement between both shafts according to the torque of the input shaft 12.
8 is placed. The torque uniaxial displacement converting mechanism 28 is composed of a torque balance detecting section 28A (see FIG. 2) and an axial direction converting means 28B (see FIG. 3).

The torque balance detection unit 28A is basically fixed to a spring 29 formed by molding a spring wire into a substantially C-shape as shown in FIG.
It has a groove 32a into which a pin 30 inserted between mutually parallel ends 29a and 29b of the distal end of the output shaft 17 and a pin 31 fixed to the output shaft 17 are slidably fitted in the vertical direction, is fixed to a plate 32 configured to rotate together with the output shaft 17, and
It consists of a pin 33 inserted between both ends 29a and 29b of the spring 29. The plate 32 has a boss portion 32b guided by an arcuate portion 29c between both ends of the spring 29. A washer 34 is interposed between the spring 29 and the lower end surface of the hollow shaft body 13.

In the torque balance detection section 28A having such a configuration, when no torque is applied to the input shaft 12, the spring 29 has both ends connected to the pin 30,
33 is sandwiched between them, and the input shaft 12 and the output shaft 17 are restored to the state where they are closest to each other, and the input shaft 12 and the output shaft 17 become in a neutral positional relationship with zero torsional angular displacement. Also, when torque is applied to the input shaft 12, this causes the force on both ends 2 of the spring 29.
The elastic deformation of the spring 29 causes a torsional angular displacement between the input shaft 12 and the output shaft 17 in accordance with the torque of the input shaft 12 .

An axial direction conversion means 28B is arranged below the torque balance detection section 28A. This axial direction conversion means 28B, as shown in FIGS. 1 and 3,
A pin 36 is fixed to the lower end of the connecting shaft body 15 of the input shaft 12 and extends radially through a relief hole 17b provided in the output shaft 17, and a pin 36 is slidably fitted to the upper end of the output shaft 17. a sliding member 37 having a long hole 37a into which a pin 36 is slidably inserted;
An upper flange 37b and a lower flange 37c provided at the lower end of this sliding member 37, and an output shaft 17
A pin 43 fixed to and extending in the radial direction is slidably fitted into the slot 37d in the direction of the output shaft 17.
It is composed of a sliding member 37 having a.

Note that the sliding member 37 has a pin 43 and a slot 37.
d, it can be displaced vertically with respect to the output shaft 17, but cannot be rotated. A pin 44 is fitted into the sliding member 37 to prevent the pin 36 and the pin 43 from coming off.

The long hole 37a of the sliding member 37 is provided in a spiral direction, and when the torsional angular displacement between the input shaft 12 and the output shaft 17 is zero, the pin 36 is located in the center between both ends of the long hole 37a, and the input When a torsional angular displacement occurs between the shaft 12 and the output shaft 17, the circumferential surface of the pin 36 and the elongated hole 3
Due to the contact with the side surface of 7a, the sliding member 37 is displaced in the axial direction on the output shaft 17 according to the amount of torsional angular displacement due to the cam action, and the upper flange 37b and lower flange 37c are displaced. There is.

A cylindrical shaft 39 provided at one free end of the cantilever 40 is sandwiched between the upper flange 37b and the lower flange 37c. The other end of the cantilever 40 is connected to the housing 1 with a bolt 42.
It is firmly screwed into the mounting base 45 fixed to 1d. Note that the mounting base 45 seals the housing 11d with an O-ring or the like, and the cantilever 4
0 can be firmly and accurately positioned and mounted by screwing with a bolt 42 using a washer or the like. As shown in the perspective view of FIG. 4 showing the relationship between the cantilever and the cylindrical shaft, this cantilever 40 has a strain gauge 4 with resistance bridges formed on both sides of the bolt 42 mounting hole at its center.
1a, 41b, 41c, 41d are formed,
When no displacement is applied to the free end of the cantilever 40, the strain gauge 41 constitutes a resistance bridge.
Minimize the outputs of a, 41b, 41c, and 41d,
When the maximum displacement is applied to the free end of the cantilever 40, the outputs of the strain gauges 41a, 41b, 41c, and 41d forming the resistance bridge are maximized. The cylindrical shaft 39 attached to the free end of the cantilever 40 reduces the contact resistance against displacement of the upper flange 37b and lower flange 37c of the sliding member 37. In addition,
In this embodiment, the material of the cantilever 40 is phosphor refined copper, its surface is coated with an insulating layer, and the strain gauges 41a, 41 are formed with thin film circuits on the insulating layer.
b, 41c, and 41d are formed by sputtering or the like, and connected to the lead wire at the fixed end side.
The surfaces of the strain gauges 41a, 41b, 41c, and 41d are coated with moisture-proof coating to eliminate the influence of oil and humidity, and are further coated with silicone rubber or the like.

FIG. 5 shows a perspective view of another embodiment of the cantilever, in which a steel ball 39a is provided at the free end of the cantilever 40, and a strain gauge 41 is provided on the opposite side.
a, 41b, 41c, and 41d are attached using an adhesive such as a thermosetting adhesive. Strain gauge 41
The surfaces of a, 41b, 41c, and 41d are treated in the same manner as in the case of FIG.

Since the cantilever 40 shown in FIG. 4 has a structure in which it is balanced in the width direction by the cylindrical shaft 39, the strain of the strain gauges 41a, 41b, 41c, and 41d forming the bridge is made uniform. can do. Cantilever 40 shown in FIG.
Since the steel ball 39a is held between the upper flange 37b and the lower flange 37c, the contact resistance thereof can be minimized.

In addition, strain gauges 41a, 41b, 41c, 41
FIG. 6 shows a well-known distortion detection circuit in which d is a bridge circuit and its output is taken out.

In FIG. 6, E is a constant voltage power supply and AMP is an amplifier circuit. FIG. 7 shows the relationship between the torque detection output voltage of the input shaft 12 and the amount of vertical displacement of the sliding member 37. Note that the amount of vertical displacement of the sliding member 37 and the torque detection output voltage are
It can be arbitrarily set by the amplification factor or bias voltage of the AMP, the resistance value of the strain gauge, etc.

In the above embodiment, the gap between the outer circumference of the pin 36 fixed to the input shaft 12 and the side surface of the long hole 37a of the sliding member 37 corresponds to the torsional angular displacement between the input shaft 12 and the output shaft 17. In order to eliminate this effect on the correspondence relationship with the axial displacement of the sliding member 37, a compression spring 60 is interposed between the upper flange 37b of the sliding member 37 and the plate 32. It is preferable that the compression spring 60 urges the sliding member 37 downward so that the outer periphery of the pin 36 contacts only the upper surface of the elongated hole 37a.

Then, the relative vertical displacement (backlash) between the input shaft 12 and the output shaft 17 is eliminated, and both shafts 1
Due to the gap between the fitting portions 2 and 17, twisting may occur between these axes, resulting in poor sliding performance between the pin 36 and the elongated hole 37a, or the upper flange 37 of the sliding member 37.
b and the lower flange 37c and its upper flange 3
7b and the lower flange 37c, the input shaft 1 is fixed as shown in FIG.
Tapered recess 1 in the center of the lower end surface of the connecting shaft 15 of 2
5a and a tapered recess 17c at the center of the bottom of the hole 17a of the output shaft 17, a steel ball 46 is interposed between the tapered recess 15a and the tapered recess 17c, and a hollow shaft of the input shaft 12 is provided. body 1
A compression spring 48 is provided above the flange 13a of No. 3, the upper end of which is received on the inner surface of the housing 11a via a needle bearing (thrust bearing) 47, and the lower end of which is received by the flange 13a. The input shaft 12 is pressed against the output shaft 17 via the steel balls 46.
This makes it possible to prevent relative vertical displacement and twisting between the shafts 12 and 17.

In addition, in FIG. 1, 50 indicates the housing 1.
The retaining rings 51, 52, and 53 screwed onto 1 are snap rings.

The operation of the embodiment of the steering torque detector of the electric power steering device of the present invention configured as described above will be explained.

First, when the driver applies a steering torque to the input shaft 12, the relative angular displacement between the input shaft 12 and the output shaft 12 according to the torque of the input shaft 12 is caused by the elastic force of the spring 29 that constitutes the torque balance detection section 28A. This angular displacement causes the sliding member 37 constituting the axial direction conversion means 28B to be displaced in the axial direction, and the displacement of the sliding member 37 is the displacement of the free end of the cantilever 40, so that the cantilever 40 is strained. With the gauge 41, the magnitude of the torque applied to the input shaft 12 and the torque detection signal output in the direction thereof can be obtained.

Therefore, by using this torque detection signal output, it is input to the controller of the electric power steering device, the output is used to supply electric power to the electric motor 20, and the rotational force of the electric motor 20 is transmitted through the reduction gear mechanism 21. rotational force can be applied to the output shaft 17.

As described above, the present invention provides a torque-axial displacement conversion mechanism disposed between an input shaft and an output shaft that converts steering torque into an axial displacement, and a torque-axial displacement conversion mechanism disposed between an input shaft and an output shaft. A sliding member displaceable in the axial direction constituting a displacement converting mechanism, a housing housing the torque-axial displacement converting mechanism, one end fixed to the housing, the other end supported by the sliding member, It consists of a cantilever with a gauge attached.

When implementing the above-mentioned invention, in this embodiment, a torque balance detection section and an axial direction conversion means are used as a torque-axial displacement conversion mechanism to convert torque into displacement in the axial direction, that is, in the vertical direction. However, when carrying out the present invention, the present invention is not limited to the above embodiments, and any means that converts torque into a reciprocating displacement, preferably an axial displacement proportional to the torque, may be used. good.

Further, since the sliding member constituting the torque-axial displacement conversion mechanism moves in the axial direction in accordance with the torque of the means for converting into axial displacement,
When the input shaft or output shaft is a ball screw, and a torque-axial displacement conversion mechanism consisting of a mechanism in which the ball screw rotates according to torque is configured, the sliding member is a nut-shaped member that is screwed into the ball screw. be able to. Alternatively, it may be a member that engages with the ball screw portion.

Furthermore, although the housing in this embodiment is divided into four parts, when implementing the present invention,
It is not limited to that. In particular, the opening of the housing 11d is designed so that the cantilever can be freely removed, but it may be constructed integrally with another housing as long as the cantilever can be freely removed or attached.

[Effects of the Invention] As described above, the steering torque detector of the electric power steering device of the present invention detects the torque that converts the steering torque into axial displacement, which is arranged between the input shaft and the output shaft. a sliding member displaceable in the axial direction constituting an axial displacement converting mechanism; a housing housing the torque-axial displacement converting mechanism; one end fixed to the housing and the other end supported by the sliding member; Since it is composed of a cantilever with a strain gauge attached, it is sufficient to form the strain gauge on a flat cantilever, and the attached state of each strain gauge used as a resistance bridge circuit, or
Each strain gauge can be easily formed uniformly by sputtering, vapor deposition, or the like. Therefore, the conditions for forming each strain gauge can be made uniform, and the bridges of the strain gauges can be easily balanced, so that the reliability of the output obtained from the strain gauges can be improved. Moreover,
The cantilever with the strain gauge attached can be easily replaced, and the steering torque detector of the electric power steering device can be easily repaired.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a steering torque detector for an electric power steering device of the present invention, FIG. The figure is a sectional view of a main part of the axial direction conversion means used in the embodiment of the present invention, FIG. 4 is a perspective view showing an embodiment of the cantilever used in the embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. FIG. 6 is a perspective view showing another embodiment of a cantilever that can be used in
The figure is a diagram of a well-known strain detection circuit that takes out an output using a strain gauge as a bridge circuit, and FIG. 7 is a characteristic diagram showing the sliding member displacement amount vs. torque detection output voltage characteristic. In the figure, 11, 11a, 11b, 11c,
11d: Housing, 12: Input shaft, 17: Output shaft, 28: Torque-axial displacement conversion mechanism, 28
A: Torque balance detection section, 28B: Axial direction conversion means, 37: Sliding member, 40: Cantilever, 41
a, 41b, 41c, 41d: strain gauges. In addition, in the figures, the same reference numerals and symbols indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A torque-axial displacement conversion mechanism disposed between an input shaft and an output shaft that converts steering torque into axial displacement; and the torque-axial displacement conversion mechanism configured. A cantilever comprising: a sliding member that is displaced in the axial direction; a housing housing the torque-to-axial displacement conversion mechanism; one end fixed to the housing, the other end supported by the sliding member, and a strain gauge attached to the cantilever. A steering torque detector for an electric power steering device, characterized in that: