JPS61226362A - Steering torque detector in power steering gear device - Google Patents

Abstract

PURPOSE:To obtain a highly accurate steering torque detector, by enabling a steering torque exerted to a steering wheel to be delivered as an electrostatic capacity. CONSTITUTION:A ball screw 20a is formed in an input shaft 20, and balls 30 fitted in the ball screw 20 are prevented from coming off by means of a movable member 31. A movable electrode plate 40 is fastened to one end of the movable member 31, and further, these are pressed by a movable electrode pressing spring 33 which is secured at the bearing 22 side. Further, a stationary electrode plate 41 is fixed to an upper housing 3 through the intermediary of a stationary electrode base plate 42, being opposed to one surface of the movable electrode plate 40. The electrostatic capacity between the stationary electrode plate 41 and the movable electrode plate 40 is changed in association with the movement of the movable electrode plate 40, and the torque of the steering wheel may be detected in accordance with variations in this electrostatic capacity.

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, it converts twist of a torsion bar mechanism etc. into a change in capacitance to detect non-zero The present invention relates to a steering torque detector for a power steering device that detects torque by contact.

[Prior Art] As a conventional steering torque detector for this type of power steering device, there is a technique disclosed in Japanese Patent Application Laid-Open No. 57-47251.

The technique disclosed in the above publication converts the relative rotation between the input shaft and the output shaft into angular displacement by a torsion bar, and further converts the angular displacement into a spiral cam groove formed on the outer circumferential surface of the input shaft by fitting a ball into it. This is converted into axial displacement of the input shaft, and this axial movement is converted into an electrical signal using a magnetic scale.

[Problems to be Solved by the Invention] However, in order to increase the detection accuracy with the magnetic scale, as shown in the principle diagram of FIG.
It is necessary to shorten the length of a single pole in which the length of the north pole in the axial direction is LH and the length of the south pole is LS in the magnetization composed of Mn. Further, the thickness t also needs to be made thin. Naturally, if this is done in a cumulative manner, the magnetization becomes weaker, resulting in electromagnetic problems such as a decrease in detection output and deterioration of temperature characteristics.

Also, mechanically, the gap G between the detection part SE and the magnetic scale is
has always had to be uniformly and minutely controlled. Furthermore, since the magnetic detection means and the processing of the digital waveform of its detection output are special, there is a problem with the signal processing circuit that the digital waveform processing circuit must be expensive.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned problems and provide a steering torque detector for a power steering device that can obtain a highly accurate analog output, has a simple detector structure, and is inexpensive. It is something.

[Means for Solving the Problems] A steering torque detector for a power steering device according to the present invention is provided in addition to a steering wheel, which is disposed between an input shaft such as a steering shaft and an output shaft such as a binion shaft. A torsional angular displacement generating member such as a torsion bar that converts the generated steering torque into angular displacement is fitted to a ball screw that converts the torsional angular displacement into axial movement, and the rotation is transferred to a sliding guide. It consists of a movable member that is regulated and moves along the axial direction, a movable electrode plate that converts the movement of the movable member into a change in capacitance, and a fixed electrode plate that is arranged in parallel to the movable electrode plate. .

According to the present invention, the steering torque applied to the steering wheel is generated by the torsional angular displacement generating member disposed between the steering shaft of the input shaft and the binion of the rack-and-binion type steering of the output shaft. A certain torsion
converted into angular displacement by the bar. The converted angular displacement is fitted into a ball screw provided on the input shaft, and rotation is regulated by a sliding guide provided on the output shaft, resulting in axial movement of the movable member that moves along the axial direction. is converted to

A movable electrode plate is attached to the movable member, and movement of the movable member in the axial direction causes a change in capacitance between the movable electrode plate and a fixed electrode plate arranged in parallel.

At this time, if two fixed electrode plates are provided by placing fixed electrode plates parallel to a movable electrode plate on both sides of the movable electrode plate, the movable electrode plate has two fixed electrode plates. Because it is located between the plates, when the capacitance formed by one fixed electrode plate increases in inverse proportion to the gap, the capacitance formed by the other fixed electrode plate decreases in inverse proportion to the gap. It turns out.

Therefore, by using the torsional angular displacement generating member and the movable member that converts the torsional angular displacement into axial movement, the steering torque applied to the steering wheel can be output as a change in capacitance, and both capacitances can be changed. can be used as a differential detection output.

[Embodiment] FIG. 1 is a sectional view of an embodiment of a steering torque detector of a power steering device of the present invention, and FIG. 2 is a diagram showing the overall configuration of the power steering device.

In the figure, a pinion gear 2 is attached to the rotating shaft of a motor 1. A case of the motor 1 is fixed to an upper housing 3. The binion gear 2 meshes with a reduction gear 5a that is pivotally supported between a bearing 7 of the upper housing 3 and a bearing 8 of the lower housing 4.

The rotation of the reduction gear 5a is transmitted to the output gear port via the reduction gear 5b connected thereto by a fastening member. The output gear port is fixed by a key to an output shaft 9 having a binion portion 9a that meshes with a rack 10 of a rack-and-binion type steering. The output shaft 9 is supported by a bearing 14 and a bearing 15 provided in the lower housing 4. And the output shaft 9
The bearings 14 and 15 are firmly fixed to the lower housing 4 by providing a bolt at the end and engaging the nut 16 with the bolt, and the nut 16 is sealed to the lower housing 4 by a cap screw 1.7. be done. The rack 10 that meshes with the binion portion 9a of the output shaft 9 is
As shown in the overall configuration diagram of power steering in Figure 2,
Rack 1 installed inside steering housing 100
0 moves left and right, the link rods 101 and 102 attached to both ends move,
The wheels 103 and 104, that is, the left and right wheels are steered by moving the knuckle arms (not shown) on both the left and right wheels.

The rack 10 is maintained in mesh with the binion portion 9a of the output shaft 9 by a sliding support member 11.

That is, a pressing force is applied to the sliding support member 11 on the rack 10 via a spring 12 and a pressing screw 13 screwed into the lower housing 4.

The output shaft 9 and the input shaft 20 connected to the steering shaft 110 by serrations are connected by locking one end of the torsion bar 19 with a pin 21 and the other end with a pin 18. And input shaft 2
0 is supported by a bearing 22 via a fixed electrode support member 23 inserted into the upper housing 3, and is fitted to the output shaft 9. Therefore, the input shaft 20
The applied torque is transmitted to the output shaft 9 via the torsion bar 19.

That is, the torsion bar 19 is connected to the input shaft 20 and the output shaft 9.
The torque applied to the input shaft 20 causes a relative angular displacement between the input shaft 20 and the output shaft 9, and functions as a torsional angular displacement generating member that generates a torsional angular displacement. do.

The steering shaft 110 side of the input shaft 20 is pivotally supported by the bearing 22, and a seal member 24 is provided on the outside of the bearing 22 to fix the bearing 22 and seal between the input shaft 20 and the fixed electrode support member 23. is being stopped. The fixed electrode support member 23 is inserted into the upper housing 3, sealed with an O-ring, and fixed to the upper housing 3 with a snap ring 25. The outside of these fixed electrode support member 23, seal member 24, and snap ring 25 is surrounded by a dust cover 26 to prevent dust from entering.

The input shaft 20 has a ball screw 20a carved on its outer circumferential surface, as shown in detail in the sectional view of the main part of the angular displacement-electrical displacement converter in FIG. A ball 30 is fitted into the ball screw 20a, and a movable member 31 prevents the ball 30 from coming off the ball screw 20a.

That is, the ball 30 is attached to the ball screw 20 together with the movable member 31.
It is attached movably in the circumferential direction of a. The rotation of the movable member 31 is restricted by the fitting hole 31a that fits into the sliding guide 32, and only movement in the axial direction is possible.

Since the sliding guide 32 is fixed to the output shaft 9,
Due to the relative angular displacement between the input shaft 20 and the output shaft 9, the position of the ball screw 20a that fits into the ball 30 changes, and this change causes a change in the movable member 31. Therefore, the movable member 31 can convert the relative angular displacement between the input shaft 20 and the output shaft 9 into an axial displacement.

A movable electrode plate 40 is screwed to one end of the movable member 31 whose displacement in the axial direction is converted, and is further pressed by a movable electrode pressing spring 33. 33 is bearing 2
It is fixed on two sides.

A fixed electrode plate 41 is fixed to the upper housing 3 via a fixed electrode substrate 42 made of an insulating material, corresponding to one surface of the movable electrode plate 40. Corresponding to the other surface of the movable electrode plate 40, a fixed electrode plate 43 is fixed to the fixed electrode support member 23 inserted into the upper housing 3 via a fixed electrode substrate 44 made of an insulating material. That is, as shown in the front view of the electrode plate in FIG. 4, the fixed electrode plates 41 and 43 are formed of metal, such as copper foil, on the surface of a fixed electrode substrate 42 or 44 made of an insulating material such as epoxy. It is. Therefore, the movable electrode plate 40
is a movable electrode plate between the fixed electrode plate 41 on the upper housing 3 side and the fixed electrode plate 43 on the fixed electrode support member 23 side, while maintaining a state parallel to the surfaces of both electrode plates 41 and the electrode plate 43. 40 moves.

At this time, the capacitance ff1cx between the fixed electrode plate 41 and the movable electrode plate 40 and the capacitance Cy between the fixed electrode plate 43 and the movable electrode plate 40 are determined by the gap between the fixed electrode plate 41 and the fixed electrode plate 43. d1 displacement of movable electrode plate 40 Δx1 capacitance IC
Letting the gap between x be X, CX=εεoS/x cy−εεoS/ (d−x) However, ε. is the dielectric constant in vacuum, ε is the relative dielectric constant in air, and S is the effective area of the electrode plate.

Here, the movement of the movable electrode plate 40 is performed using a detection circuit that obtains a detection output E outl by the electrostatic capacitances ff1cx and Cy between the fixed electrode plates 41 and 43 and the movable electrode plate 40 shown in FIG. The relationship between Eout1 and the detection output Eout1 is as follows.

A voltage E from an externally connected oscillator is applied to the fixed electrode plate 41 and the fixed electrode plate 43 to form a parallel circuit consisting of capacitance Cx and capacitance Cy, and capacitor Cout and capacitance Cx and Cy are separated. If we detect a voltage drop that increases, then Then, equation (1) becomes...(2).

Here, if (d/2)>ΔX, then the equation (2) becomes: −8Δx −EH/d” However, in the above equation, EH=E/(Sinωt).

That is, as E outl, approximately -8Δx -EH/d2
The output is obtained.

Therefore, under the condition of (d/2>)ΔX, a linear output can be obtained. Also. In order to discharge the charges accumulated in the capacitances Cx and Cy in one cycle, the diodes D1 and D2 are configured to discharge the charges. Therefore, the circuit of FIG. 5 can operate continuously. Note that the operational amplifier OP is used as a buffer amplifier. In this way, changes in capacitance CX and capacitance Cy obtained by the torque detector can be detected as a voltage difference between them.

Therefore, the output E 0ut2 of the operational amplifier OP is determined by the position of the movable electrode plate 40 being between the fixed electrode plate 41 and the fixed electrode plate 43.
When the capacitance Cx between the fixed electrode plate 41 and the movable electrode plate 40 is larger than the capacitance Cy between the fixed electrode plate 43 and the movable electrode plate 40, it becomes zero. The output is When the opposite is true, a negative output is obtained. therefore,
Each electrostatic capacity ff1c constituted by this type of movable electrode plate 40, two fixed electrode plates 41, and fixed electrode plate 4'3.
If the changes in X and capacitance Cy are taken out as a differential detection output, the rotation direction can be detected based on the polarity, and the torque value can be detected based on the value.

As described above, in the steering torque detector of the power steering device of this embodiment, the steering force applied to the steering wheel 120 is transmitted to the input shaft 20 via the steering shaft 110. The steering force of the steering wheel 120 corresponding to the load required to move the binion portion 9a of the output shaft 9 to move the rack 10 and steer the left and right wheels is applied to the input shaft 2.
This appears as a torsional angular displacement of the torsion bar connected between the output shaft 9 and the output shaft 9.

A ball screw 20a is carved on the outer periphery of the input shaft 20, and a ball 30 attached to a movable member 31
The movable member 3 is fitted into the ball screw 20a.
Since the fitting hole 31a drilled in the axial direction of 1 is fitted with the sliding guide 32 fixed to the output shaft 9 and extending in the axial direction, the movable member 31 is obtained by a torsion bar. Convert twist angle change into axial movement. A movable electrode plate 40 is attached to the movable member 31 so as to be movable in the axial direction of the movable member 31, and the distance between the fixed electrode plates 41 and 44 arranged in parallel with the movable electrode plate 40 31 changes in the axial direction. At this time, either the capacitance Cx between the fixed electrode plate 41 and the movable electrode plate 40 that face each other or the capacitance ff1cy between the fixed/fixed electrode plate 43 and the movable electrode plate 40, or both, are By guiding and detecting the change, it is possible to output a change in capacitance according to the torque applied to the steering wheel 120.

Therefore, in response to the output of the steering torque detector TS of the power steering of this embodiment, the control circuit 1 shown in FIG.
30 can drive the motor 1 according to the detected torque to provide power. steering wheel 1
When the motor 20 is restored and no steering force is applied, the rotation of the motor 1 is stopped by the output of the steering torque detector TS.

In this embodiment, the movable member 31 is fitted into a ball screw 20a carved around the input shaft 20, and the rotation of the movable member 31 is restrained by a sliding guide 32 fixed to the output shaft 9. It allows movement only in the axial direction. However, since the movable member 31 only needs to convert the relative angular displacement between the input shaft 20 and the output shaft 9 into axial movement, the present invention is not limited to this embodiment. , a ball screw may be provided on the output shaft 9 side, and a sliding guide 32 may be provided on the input shaft 20 side. When the diameter of the input shaft 20 is smaller than that of the output shaft 9 as in this embodiment, it is possible to reduce the size by carving a ball screw on the input shaft 20 side.

Further, the ball screw 20a is arranged around the input shaft 20.
It is carved so that the axial movement changes linearly with respect to the angular displacement of the input shaft 20.

At this time, for example, the capacitance CX becomes an output that is inversely proportional to the electrode plate spacing X. Therefore, the axial movement is set to change according to a specific curve with respect to the angular displacement of the input shaft 20, and the change in the capacitance Cx of the input shaft 20 is
It may be made to change linearly with respect to the angular displacement of.

However, although the ball screw 20a of this embodiment can be machined using a general lathe, when changing the capacitance linearly with respect to angular displacement, the ball screw 20a carved on the input shaft 20 is It forms a curve with respect to its circumference, and requires cutting using an NG lathe or the like.

The ball 30 and the ball screw 20a attached to the movable member 31 are movable because all they have to do is convert the relative angular displacement between the input shaft 20 and the output shaft 9 into axial movement of the movable member 31. A ball screw is carved on the inner periphery of the member 31, and the ball 30 is attached to a hole drilled in the input shaft 20.
The ball 30 may be fitted into the ball screw. Alternatively, the movable member 31 may be directly screwed into a ball screw formed on the input shaft without using the ball 30.

Fixed electrode plates 41 and 43 that obtain the capacitance of this embodiment,
The movable electrode plate 40 disposed between these has a capacitance ff
1cx and Cy, however, when implementing the present invention, the present invention is not limited to this embodiment, and only one of the fixed electrode plate 41 and the fixed electrode plate 43 may be used.

Further, the fixed electrode plate 41 or 43 is connected to the fixed electrode substrate 42.
Or, as in the example of the other fixed electrode plate shown in FIG. When set, the capacitance between the electrodes fiCx and Cy
can reduce the influence of capacitance with other conductors.

Since the movable electrode plate 40 moves integrally with the movable member 31, the movable electrode plate 40 moves as one body with the movable member 31.
0 and the movable member 31 do not need to be formed separately, and may be formed integrally with the movable member and the movable electrode plate.

[Effects of the Invention] As described above, the present invention includes a torsional angular displacement generating member that converts steering torque into angular displacement, a movable member that converts the torsional angular displacement into axial movement, and a movable member that converts the torsional angular displacement into axial movement. It is composed of a movable electrode plate that converts the change in capacitance into a change in capacitance, and a fixed electrode plate that is arranged in parallel with the movable electrode plate. Since it fits into a carved ball screw and its rotation is regulated by a sliding guide, it has a simple structure and can be manufactured at low cost. Furthermore, the detection output can be determined only with mechanical accuracy, and a highly accurate analog output can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the steering torque detector of the power steering device of the present invention, FIG. 2 is an overall configuration diagram of the power steering, and FIG. 4 is a front view of the fixed electrode plate used in this example; FIG. 5 is a detection circuit diagram that obtains the detection output by capacitance between the fixed electrode plate and the movable electrode plate; FIG. 6 is a front view of another embodiment of the fixed electrode plate, and FIG. 7 is a principle diagram of an example of a magnetic scale used in a steering torque detector of a conventional power steering device. In the figure, 9... Output shaft, 19... Torsion bar, 20... Input shaft, 20a... Ball screw, 32... Sliding guide, 31... Movable member, 40...・Movable electrode plate, 41.43...Fixed electrode plate. In addition, in the figures, the same reference numerals and the same symbols indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A torsional angular displacement generating member disposed between the input shaft and the output shaft that converts steering torque into angular displacement, and a torsional angular displacement generating member that is fitted with a ball screw carved on the shaft and whose rotation is caused by sliding. a movable member that converts the torsional angular displacement regulated by a guide into axial movement; a movable electrode plate that converts the movement of the movable member into a change in capacitance; and a fixed electrode arranged in parallel with the movable electrode plate. A steering torque detector for a power steering device, characterized in that it is composed of a plate. (2) The fixed electrode plate arranged in parallel with the movable electrode plate is characterized in that two fixed electrode plates are arranged in parallel on each side corresponding to both sides of the movable electrode plate. A steering torque detector for a power steering device described in . (3) The power steering according to claim 2, characterized in that a change in capacitance of each of the movable electrode plate and the two fixed electrode plates is extracted as a differential detection output. Device steering torque detector. (4) The steering torque detector for a power steering device according to claim 1, wherein the shaft on which the ball screw is carved is used as an input shaft.