JPS6255264A - Steering torque sensor of electrical power steering device - Google Patents

Abstract

PURPOSE:To improve reliability by attaching a strain gauge on a cantilever fixed to a housing accommodating a torque to axial displacement conversion mechanism and by detecting the torque of a power steering from the strain gauge. CONSTITUTION:When steering torque is applied on an input shaft 12, relative angular displacement is produced between the input shaft 12 and an output shaft 17 according to the torque on the input shaft 12 due to resilient force of a spring 29 which is a part of a torque equilibrium sensor section 28A. This angular displacement is made into axial displacement of a sliding member 37 which constitutes an axial displacement conversion means 28B, and the displacement of the sliding member 37 is made into deflection of the free end of a cantilever 40. By means of signals from a strain gauge 41 attached on the cantilever 40, torque signals regarding the magnitude and direction of the torque applied on the input shaft 12 are obtained.

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. 1111 is applied to a steering torque detector of an electric power steering device that controls the driving force of the 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 Laid-Open No. 59-209964.

”-The above technology includes an input shaft connected to a steering shaft of a car, an output shaft connected to a city steering gear box, a torsion member connecting the input shaft and the output shaft with each other, the input shaft and the output shaft. A torque converter generates a torque signal representing the torque applied between the output shafts, a power amplifier responds to the torque signal to drive the electric motor, and connects the output of the electric motor to the output shaft to control the turning of the wheels. In a power steering device equipped with a gear train that assists a driver when driving, the power steering device includes 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 responsive to said first and second signals and having a polarization representative of said second signal having a magnitude that varies as a function of said first signal; a power amplifier that generates an amplified signal, a low-speed high I/L reversible electric current vJvs 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 the output shaft. It is characterized by having.

[Problems to be Solved by the Invention] Specifically, the above-mentioned torque sensor has a pair of low resistance bridge strain gauges attached to the center of a steel plate, which provides stability in attaching the strain gauges. Even if the lead wire is pulled out from the strain gauge, it is necessary to wrap the lead wire around the steel plate in advance or use a slip ring, etc. to send and receive electrical signals, and repeated use is required. There was a reliability problem.

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. However, there was a problem with the output.

In particular, in order to increase the strain output, strain gauges are pasted on torsion bars with a small diameter. The bridge is not balanced and the reliability of its detection output becomes a problem.

Therefore, the present invention solves the above problems and provides a torque sensor 1.
The object of the present invention is to provide a steering torque detector for an electric power steering device that can obtain a highly reliable electrical signal from J' and that can be easily converted into a torque sensor.

[Problems to be Solved by the Invention] A steering torque detector for an 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 that constitute a torque-axial displacement conversion mechanism that converts the force direction and force magnitude of the steering torque between the input shaft and the output shaft into an axial displacement;
A sliding member displaceable in the axial direction constituting the torque-axial displacement conversion mechanism, a housing housing the torque-axial displacement conversion mechanism, and a housing having one end fixed to the housing and the other end fixed to the sliding member. It consists of a cantilever supported by a moving member and equipped with a strain gauge.

[Action 1] By means of a sliding member displacing in the axial direction that constitutes a torque-axial displacement conversion mechanism that converts the direction and force of the steering torque applied to the steering shaft into axial displacement of the input shaft or output shaft. , one end of the cantilever is converted from the direction and magnitude of the steering torque into axial displacement, and the other end of the cantilever is detected by a strain gauge, and the strain between the cantilever and the fixed housing side is detected by a strain gauge. Using the detection output of Rotate the FJJ * 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 a vehicle, and has divided parts 11a and 11b.

11c and 11d are integrally formed by joining with bolts or the like, or the divided parts 11a, 11b, 11C, and 11d are integrally formed by welding or the like.

The input shaft 12 inside the housing 11 has a
A hollow shaft body 13 having a flange 13a, and this hollow shaft body 1
3 and a connecting shaft body 15 that is fitted into the hole of No. 3 and integrally connected with a connecting pin 14 that extends in the radial direction. Hollow shaft body 1
3 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 17a at its end into which the lower part of the connecting shaft 15 is loosely fitted, and its center and lower ends are connected via ball bearings 18 and 19, respectively. It is rotatably supported by the housings 111) and 11G.

Inside the housing 11c at the lower part of the housing 11, there is a reduction gear mechanism 21 that reduces the rotation of the motor 200 by a necessary number of gears to transmit the output of the motor 20 fixed to the housing 11C from the motor output shaft 20a to the output shaft 17. It is located. This reduction gear 1fi1421 includes a gear 21a coaxial with the motor output shaft 20a, and gears 25 and 26 attached to a shaft 24 rotatably supported by the housing 11[) and the housing 11C via ball bearings 22.23. , an output shaft 17 and a coaxial gear 27.

The input shaft 1 is located inside the housing 11 at the upper part of the housing 11.
A torque-to-axial displacement converter 1128 is arranged to generate a torsional angular displacement between both shafts according to 201 Herc. This torque-axial displacement conversion mechanism 28 includes a torque balance detection section 28A (see FIG. 2) and an axial direction conversion means 28B (
(see Figure 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 pin 30 inserted between mutually parallel ends 29a and 29b of the distal end thereof, and a groove 32a into which a pin 31 fixed to the output shaft 17 is fitted so as to be slidable in the vertical direction, The pin 33 is fixed to a play 1-32 that rotates together with the output shaft 17, and is inserted between both ends 29a and 29b of a spring 29. The plate 32 has a boss portion 32b that is guided by an arcuate portion 29G between both ends of the spring 290. 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 returns to the state in which both ends thereof are closest to each other by pinching the pins 30 and 33, and the input shaft 12 and the output shaft 17 are brought into contact with zero torsional angular displacement. It becomes a neutral positional relationship. Further, when torque is applied to the input shaft 12, this acts to separate both ends 29a and 29b of the spring 29, and due to the elastic deformation of the spring 29, the input shaft 12 is placed between the input shaft 12 and the output shaft 17. A torsional angular displacement occurs depending on the torque.

Below the torque balance detection section 28A, an axial direction conversion means 2 is provided.
8B is placed. This axial direction conversion means 28B is
As shown in FIGS. 1 and 3, a pin 36 is fixed to the lower end of the connecting shaft 15 of the input shaft 12 and extends in the radial direction through the relief hole 17b provided in the output shaft 17. , a sliding member 37 that is slidably fitted to the upper end of the output shaft 17 and has an elongated hole 37a into which the bottle 36 is slidably inserted; Ta-1 Partial flange 37b and lower part 7
The flange 37G and a bin 43 fixed to the output shaft 17 and extending in the radial direction are fitted in a movable manner, and the sliding member 37 has a slot 37d extending in the direction of the output shaft 17.

Although the sliding member 37 can be displaced vertically with respect to the output shaft 17 by the pin 43 and the slot 37d, it is not allowed to rotate. Then, a cylindrical body 44 for preventing the pin 43 from being removed is fitted into the sliding member 37.

The elongated hole 37a1 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 closed, the pin 36 is located at the center between both ends of the elongated hole 37a. When a torsional angular displacement occurs between the input shaft 12 and the output shaft 17, the contact between the peripheral surface of the bottle 36 and the side surface of the elongated hole 37a causes the sliding member 37 to respond to the torsional angular displacement due to cam action. Output shaft 1
7, the upper flange 37b and the lower flange 37C are displaced by 1 in the axial direction.

A cylindrical shaft 39 provided at one free end of the cantilever 40 is sandwiched between the upper flange 37b and the lower 7 flange 37c. The other end of the cantilever 40 is firmly screwed with a bolt 42 to a mounting base 45 fixed to the housing 11d. The mounting base 45 seals the housing 11d with an O-ring or the like, and the cantilever 40 can be firmly and accurately positioned and mounted by screwing the bolt 42 with a washer or the like. . This cantilever 40 has strain gauges 41a, 41b, 41c which are configured with resistance bridges on both sides of the cantilever 40 on the side of the bolt 42 mounting hole from the center, as shown in the perspective view of FIG. 4 showing the relationship between the cantilever and the cylindrical shaft. , 41d, and when no displacement is applied to the free end of the cantilever 40, the strain gauge 41a forms a resistance bridge.
41b.

Minimize the output of 410.416, and use the cantilever 4
When the maximum displacement is applied to the free end of 0, the strain gauges 41a and 41b constitute a resistance bridge.

This maximizes the outputs of 41c and 41d.

Note that the cylindrical shaft 3 attached to the free end of the cantilever 40
9 reduces the contact resistance against displacement of the lower flange 37C such as the partial flange 37b of the sliding member 37. In addition, in this example, the cantilever 400IFI
is made of phosphor refined copper, its surface is coated with an insulating layer,
Strain gauges 41a, 41b are formed with thin film circuits on the insulating layer.
41c and 41d are formed by sputtering or the like, and connected to the fixed end wire to the fixed end. The strain gauge 41a
.

The surfaces of 41b, 41c, and 41d are coated with a moisture-proof coating to eliminate the influence of oil and humidity, and are further coated with silicone rubber or the like.

Further, 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 41a is provided on the opposite side.

41b and 410.41d are attached using an adhesive such as a thermosetting adhesive. Strain gauges 41a, 41b, 41c
, 41d are treated in the same manner as in the case of FIG.

In the width direction of the cantilever 40 shown in FIG.
Since it has a structure that is balanced by the cylindrical shaft 39, the strain gauges 41a, 41b, 41 constituting the bridge
It is possible to equalize the distortions of c and 41d. Since the cantilever 40 shown in FIG. 4 has a steel ball 39a sandwiched between the -1 part flange 37b and the lower flange 37G,
The contact resistance can be minimized.

FIG. 6 shows a well-known strain detection circuit in which the strain gauges 41a, 41b, 41c, and 41d are used as a bridge circuit and the output thereof 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 −L downward displacement ω of the sliding member 37. The vertical displacement of the sliding member 37 and the torque detection output voltage can be arbitrarily set by adjusting the amplification factor or bias voltage of the amplifier circuit 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 370 is
This will affect the correspondence between the torsional angular displacement between the input shaft 12 and the output shaft 17 and the axial displacement of the sliding member 37, but in order to eliminate this, it is necessary to 7 A compression spring 6 is installed between the flange 37b and the plate 32.
0, the compression spring 60 urges the sliding member 37 downward, and the outer periphery of the pin 36 is inserted into the elongated hole 37.
It is preferable to make contact only with the upper surface of ``a''.

Then, the relative vertical displacement (backlash) between the input shaft 12 and the output shaft 17 is eliminated, and the gap between the fitting portions of both shafts 12 and 17 is distorted.
6 and the elongated hole 37a may deteriorate, or the sliding member 3
7' between the partial flange 37b and the lower flange 37G and the upper flange 37b and the lower 7 flange 37C,
In order to prevent the balance □□□ with the h-edge lever 40 supporting the free end from worsening, a tapered recess 15a is provided in the center of the lower end surface of the connecting shaft body 15 of the input shaft 12, as shown in FIG.
In addition, a tapered recess 17c is provided at the center of the bottom surface of the hole 17a of the output shaft 17, and these tapered recesses 15
A steel ball 46 is interposed between a and the tapered recess 17C, and
A compression spring 48 is placed above the flange 13a of the hollow shaft body 13 of the input shaft 12, and has an upper end received on the inner surface of the housing 11a via a needle bearing (thrust bearing) 47, and a lower end received on the 7 flange 13a. The compression spring 48 presses the input shaft 12 against the output shaft 17 via the steel ball 46.

This makes it possible to prevent relative vertical displacement and twisting between the two wheels 12 and 17.

In FIG. 1, 50 is a first ring screwed onto the housing 11, and 51, 52, and 53 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 steering torque to the input shaft 12, the elasticity of the spring 29 constituting the torque balance detection section 28A causes a relative angular displacement between the input shaft 12 and the output shaft 17 according to the torque of the input shaft 12. This angular displacement causes the sliding member 37 constituting the first axial direction conversion stage 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. Strain gauge 41
Accordingly, it is possible to obtain a torque detection signal output based on the magnitude and direction of the torque applied to the input shaft 12.

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

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

When carrying out the present invention described above, 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 the torque in the axial direction, that is, -F
However, when implementing the present invention, the present invention is not limited to the above embodiment, and the torque is converted into a downward displacement, preferably an axial displacement proportional to the torque. Any means that converts into displacement may be used.

Further, the sliding member constituting the torque-axial displacement conversion mechanism is the means for converting the torque into axial displacement (7).　　　　　　
It also moves in the axial direction. So. When the input shaft or the output shaft is a ball screw, and a torque-axial displacement conversion mechanism is configured in which the ball screw moves according to the torque, the sliding member is a nut-shaped member that screws with the ball screw. It can be used as a member. Alternatively, it may be a member that engages with the ball screw portion.

Further, although the housing in this embodiment is divided into four parts, the present invention is not necessarily limited to this. In particular, the opening of the housing lld is designed so that the cantilever can be freely removed, but if the cantilever can be freely removed or attached, it can be integrated with other halo zincs. It's okay.

[Effects of the Invention] As described above, the steering torque detector of the electric power steering device of the present invention converts the steering torque disposed between the human power shaft and the output shaft into axial displacement. 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; Since the device consists of a cantilever, it is only necessary to form the strain gauge on a flat cantilever, and the number of resistance bridges is 18.
- It can be easily formed uniformly by adhering each strain gauge used as a path, or by sputtering, vapor deposition, etc. of each strain gauge. 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. Furthermore, the cantilever to which the strain gauge is attached can be easily replaced, and the steering torque detector of the electric power steering device can be easily repaired.

[Brief explanation of the drawing]

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-torque detection output voltage characteristic. In the figure, 11, lla, llb, 11c, lld: housing, 12: input shaft, 17: output shaft, 28: torque-axial displacement conversion mechanism, 28A: torque balance detection section, 28B biaxial direction conversion means, 37 : sliding member, 40: cantilever, 41a
, 41b, 41c, 41d: strain gauges. In addition, in the figures, the same reference numerals and the same symbols indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A torque-axial displacement conversion mechanism disposed between an input shaft and an output shaft that converts steering torque into axial displacement; and a shaft constituting the torque-axial displacement conversion mechanism. a cantilever that has one end fixed to the housing, the other end supported by the sliding member, and a strain gauge attached thereto. A steering torque detector for an electric power steering device.