JPH07198510A - Torque sensor - Google Patents

Abstract

PURPOSE:To provide a torque sensor that is provided with a slider that can be easily processed. CONSTITUTION:The torque sensor comprises an input shaft 31 and an output shaft 32 that are connected with each other coaxially and torsionally, a slider 351 made of an abrasive-resistant resin that is supported as to slide freely around the shaft 31 in an axial direction, a crank mechanism that converts a relative torsional angle between the shafts 31 and 32 into the sliding quantity in an axial direction of the slider 351, a bobbin 49 arranged coaxially around the slider 351, and a differential transformer that is formed by winding a coil 38 on the bobbin 49 and generates induction voltage based on the displacement quantity in an axial direction of the slider 351.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor, and more particularly to a torque sensor that senses the magnitude and direction of steering torque in an electric power steering system and converts these into a voltage signal for output.

[0002]

2. Description of the Related Art An electric power steering system is provided with a torque sensor for detecting a steering torque applied to a steering shaft and determining an assist amount of a steering force. FIG. 4 is a diagram for explaining a mechanical operating principle of a torque sensor in general, and FIG. 5 is a diagram for explaining an electrical operating principle thereof.

The pinion shaft 10 has a dual structure of an input shaft 31 and an output shaft 32, and the shafts 31 and 32 are internally connected via a torsion bar 34.

A slider 35 is fitted around the outer circumference of the pinion shaft 10 so as to be slidable only in the axial direction.
A guide pin 37 integral with the input shaft 31 is fitted in the spiral groove 36 of the slider 35. Further, as shown in FIG. 5, a differential transformer 40 including a primary coil 38a and secondary coils 38b and 38c is attached to the outside of the slider 35.

In such a structure, when a rotational phase is generated between the input shaft 31 and the output shaft 32, the guide pin 37 moves in the rotational direction, so the rotational phase is converted into vertical movement of the slider 35 by the spiral groove 36. To be done. Here, since an alternating current is supplied to the primary coil 38a of the differential transformer 40 and is in an excited state, an induced voltage is applied to each of the secondary coils 38b and 38c according to the position of the slider 35 that functions as a movable iron core. Occurs.

That is, when steering to the right [FIG. 4 (a)], the slider 35 moves upward, so that the upper secondary coil 38b is moved.
Becomes higher and the voltage of the lower secondary coil 38c becomes lower. Further, in the straight traveling state [Fig. 4 (b)], the voltages of the upper and lower secondary coils 38b and 38c become equal. Further, during left steering [FIG. 4 (c)], the slider 35 moves downward, so that the voltage of the upper secondary coil 38b becomes lower and the voltage of the lower secondary coil 38c becomes higher.

FIG. 6 is a partial sectional view showing the structure of a conventional torque sensor, which is constructed by covering the pinion shaft 10 described with reference to FIG. 6 with an aluminum upper housing 50a and a lower housing 50b. .

The input shaft 31 is rotatably supported by a bearing 39 press-fitted into the opening end of the upper housing 50a. A core member composed of a tubular slider 35 and a core 34 press fitted into both ends of the slider is provided on the outer peripheral portion of the output shaft 32. A Teflon ring 41 for keeping good slidability is attached.

The spiral groove 3 is formed on the side surface of the slider 35.
6 and the vertical guide groove 43 are formed, and the upper slider pin 37 is fitted in the spiral groove 36. A claw 35 a provided inside the slider 35 is engaged with the vertical guide groove 43. Around the slider 35, a differential transformer 40 configured by winding a coil 38 around a cylindrical bobbin 49 is arranged.

[0010]

In the above-mentioned conventional torque sensor, the core 34 and the slider 35 are made of a metal material, but since these have a sliding surface, they are carburized to increase the surface hardness. I had to give it. In addition, there is a problem that precise surface processing is required to increase the surface roughness, and the mechanical processing itself is difficult because the structure is complicated.

Further, in the above-mentioned prior art, since the lower housing 50b covering the differential transformer 40 is made of metal such as aluminum, when an AC voltage is applied to the differential transformer 40, an eddy current is generated in the aluminum housing 50b. Will end up. When an eddy current is generated, the coil 38
Since the magnetic flux generated in the core decreases, the magnetic flux passing through the core decreases. Therefore, there is a problem that an amplifier with a high amplification degree must be connected to the output stage in order to compensate for the decrease in output sensitivity due to the eddy current.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a torque sensor using a slider that can be easily processed.

Another object of the present invention is to provide a torque sensor which can prevent generation of an eddy current and can obtain high detection sensitivity.

[0014]

In order to achieve the above object, according to the present invention, there is provided a crank mechanism for converting a relative twist angle between an input shaft and an output shaft into an axial sliding amount of a slider, and a shaft of the slider. A torque sensor including a differential transformer that generates an induced voltage according to the amount of directional displacement, a housing that covers at least the differential transformer, and a bearing that rotatably supports the input shaft with respect to the housing. It is characterized in that it took measures. (1) The slider is made of wear resistant resin. (2) The housing that covers the differential transformer is made of a dielectric material. (3) One end of the bobbin constituting the differential transformer is extended to form a tubular rib, and the bearing is inserted into the tubular rib for positioning.

[0015]

According to the above-mentioned structure (1), the carburizing process, the surface process, and the complicated machining which are necessary when the slider is formed by machining the metal material are not necessary.

According to the above configuration (2), it is possible to prevent the generation of an eddy current in the housing when an AC voltage is applied to the differential transformer.

According to the above configuration (3), since the bearing is accurately positioned with respect to the bobbin, even when the bearing or the differential transformer is insert-molded in resin, the bearing is highly coaxial with each shaft. It becomes possible to hold it with accuracy.

[0018]

1 is a cross-sectional view showing the structure of a main portion of a torque sensor according to a first embodiment of the present invention, and the same reference numerals as those used above denote the same or equivalent portions.

In this embodiment, the core 341 and the slider 351 are molded of abrasion resistant resin. Further, at least the slider 351 functioning as a movable iron core is made a magnetic material by taking appropriate means such as mixing a metal filler.
A voltage is induced in the differential transformer 40 by the fluctuation of the slider 351.

According to the present embodiment, since the core 341 and the slider 351 are molded from the abrasion resistant resin, the carburization of the surface, which is indispensable when these are formed by machining the metal material. Eliminates machining, surface machining, and complex machining.

FIG. 2 is a sectional view showing the structure of the main part of a torque sensor according to a second embodiment of the present invention, and the same reference numerals as those used above represent the same or equivalent parts.

As is clear from a comparison with the first embodiment of the present invention described with reference to FIG. 1, in this embodiment, the metal upper housing 50a is eliminated and the periphery of the differential transformer 40 is made of resin or the like. It is characterized in that it is covered with the dielectric material 51.

According to the present embodiment, even if an AC voltage is applied to the differential transformer 40, no eddy current is generated in the surrounding housing, so that the output sensitivity of the differential transformer 40 can be prevented from lowering. it can.

By the way, when the upper housing portion 51 is made of resin as in the second embodiment, it is necessary to previously insert the bearing 39 at a predetermined position in the upper housing portion 51 by insert molding.

However, as is well known, it is difficult to perform the alignment by insert molding, and it is difficult to accurately position the bearing 39 at a desired position due to heat shrinkage of the resin at the time of molding, resulting in high coaxial accuracy. There is a new problem that you cannot get it.

Therefore, in the third embodiment of the present invention described below, even if a resin is used for the upper housing portion 51, the bearing 39 can be accurately positioned so that high coaxial accuracy can be obtained.

FIGS. 3 (b) and 3 (c) are enlarged views showing the structure in the vicinity of the upper housing portion 51 of the torque sensor of the third embodiment of the present invention, and FIG. 3 (a) shows the structure of the prior art. It is the enlarged view shown, and the same code | symbol as the above represents the same or equivalent part.

In this embodiment, a cylindrical coil bobbin 491 is used.
Is formed by coaxially connecting two cylindrical bodies 491a and 491b having different radii with a tapered portion 491c. A coil 38 is wound around the outer side surface of the cylindrical body 491b having a large radius. In addition, the cylindrical body 4 having a small radius
As shown in FIG. 9B, a tubular rib 491d is formed at one end of 91a at a height corresponding to the thickness of the bearing 39, and the bearing 39 is press-fitted inside thereof. Further, the dust seal 33 is press-fitted into the bearing-side opening of the upper housing part 51.

Then, the coil 38 and the bearing 39
The coil bobbin 491 to which is fixed is integrally molded with a resin that covers the outer peripheral portion of the coil bobbin 491 to form the upper housing portion 51.

According to this embodiment, the bearing 39 is prepositioned at one end of the coil bobbin 491, so that the bearing 39 can be held with high coaxial accuracy.

In the above embodiment, the tubular rib 49
Although 1d is formed to have a height corresponding to the thickness of the bearing 39, as shown in FIG. 3 (c), if the bearing 39 can be positioned, the cylindrical rib 491 can be formed.
The height of d is not necessarily as thick as the thickness of the bearing 39.

[0032]

As described above, according to the present invention, the following effects can be achieved. (1) Since the slider functioning as the movable iron core of the differential transformer is molded of wear-resistant resin, carburizing and surface processing of the surface are not required, and the molding is extremely easy. (2) Since the upper housing that covers the differential transformer is made of resin, even if an AC voltage is applied to the differential transformer, no eddy current is generated in the surrounding housing, and the output sensitivity of the differential transformer decreases. Can be prevented. (3) When molding the upper housing with resin, provide a cylindrical rib on one end of the bobbin that constitutes the differential transformer,
Since the bearing is press-fitted into the inner side and then insert-molded to integrally mold them, the bearing can be held with high coaxial accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a main part of a torque sensor that is a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a main part of a torque sensor that is a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a main part of a torque sensor which is a third embodiment of the present invention in comparison with a conventional technique.

FIG. 4 is a diagram for explaining the mechanical operating principle of the torque sensor.

FIG. 5 is a diagram for explaining the electrical operating principle of the torque sensor.

FIG. 6 is a partial cross-sectional view of the prior art.

[Explanation of symbols]

101 ... Pinion shaft, 31 ... Input shaft, 32 ... Output shaft, 34 ... Torsion bar, 35, 351 ... Slider, 36 ... Spiral groove, 3
7 ... Guide pin, 38 ... Coil, 39 ... Bearing, 4
0 ... Differential transformer, 50a ... Upper housing, 51
... Upper housing part, 341 ... Core, 491 ... Coil bobbin, 491d ... Cylindrical rib

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Hyakunan 1-4-1 Chuo 1-4, Wako-shi, Saitama Stock Research Institute Honda Research Institute

Claims (3)

[Claims] 1. An input shaft and an output shaft, which are coaxially and twistably connected to each other, and axially slidably supported around the input shaft,
A slider made of wear-resistant resin, a crank mechanism for converting a relative twist angle between an input shaft and an output shaft into an axial sliding amount of the slider, and a bobbin arranged around the slider and coaxially therewith. A differential transformer that is formed by winding a coil around the bobbin and that generates an induced voltage according to the amount of axial displacement of the slider; a housing that covers at least the differential transformer; and an input shaft with respect to the housing. A torque sensor comprising: a rotation bearing member that rotatably supports the torque sensor. 2. The torque sensor according to claim 1, wherein the housing is made of a dielectric material. 3. The bobbin includes a tubular rib formed by extending one end thereof, and the rotary bearing member is inserted into the tubular rib and positioned coaxially with the input shaft. The torque sensor according to claim 2, wherein: