JP2003307460A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor which is lightweight and whose reliability of a torque signal is ensured sufficiently with respect to a magnetic flux noise. <P>SOLUTION: The torque sensor comprises an iron-based metal upper housing 93 used to house a torsion bar 90, an input shaft 91, an inner ring 2, an outer ring 6, guides 12, 15, spacers 13, 16 and coils 14, 17; and an aluminum-based metal under housing 22 used to house an output shaft 92. A spacer 21 by which the magnetic flux noise to be input from a side of the under housing 22 is guided to the upper housing 93 from the output shaft 92 and which is composed of a magnetic material is installed between the upper housing 93 and the under housing 22. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor applicable to electric power steering and the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
A torque sensor disclosed in Japanese Patent Publication No. 146722 is known. In this torque sensor, a torsion bar 90 extends in the axial direction, and a hollow input shaft 91 as a first shaft coaxial with the torsion bar 90 is connected to the upper end of the torsion bar 90 by a pin 96. There is.
A steering wheel (not shown) of the vehicle is connected to the upper portion of the input shaft 91.

At the lower end of the torsion bar 90, there is provided a second shaft coaxial with the torsion bar 90 and the input shaft 91.
A hollow output shaft 92 as a shaft is connected by spline fitting and press fitting, and a pinion 92a is integrally formed at a lower portion of the output shaft 92.

An upper housing 93 and an under housing 94 are provided on the outer circumferences of the input shaft 91 and the output shaft 92 via bearings 95a and 95b. The rack 81 that meshes with the pinion 92a of the output shaft 92 is provided in the under housing 94.
Is held. This rack 81 is provided with a motor (not shown) that assists the steering force.

In the upper housing 93, a first sensor ring 97 as a first magnetic body made of a magnetic material is fixed to the input shaft 91. The first sensor ring 97 has an annular shape that surrounds the torsion bar 90 and extends in the circumferential direction, and a large number of comb-shaped rectangular tooth portions 97a are formed on the lower end surface of the first sensor ring 97. Has been done.

In the upper housing 93, the second sensor ring 9 as a second magnetic body made of a magnetic material is used.
8 is fixed to the output shaft 92. The second sensor ring 98 also has an annular shape that extends in the circumferential direction surrounding the torsion bar 90, and a large number of comb-shaped rectangular tooth portions 98a are formed on the upper end surface of the second sensor ring 98. Has been done. Each tooth portion 98a faces each tooth portion 97a with a phase shift while having a gap in the axial direction.

Further, in the upper housing 93,
A coil 99 that faces the first and second sensor rings 97 and 98 from the outer peripheral side is fixed. Further, a guide 85 and a spacer 86 as a third magnetic body are fixed so as to surround the coil 99 and form a magnetic circuit with the first and second sensor rings 97 and 98. The coil 99 is an interface circuit (hereinafter referred to as an I / F circuit) 8
0, and the I / F circuit 80 is connected to a microcomputer (not shown) (not shown).

In this torque sensor, when the coil 99 is energized by the I / F circuit 80, one magnetic path indicated by an arrow is formed as shown in FIG. When torque is transmitted to the input shaft 91 by operating the steering wheel of the vehicle, the torsion bar 90 is twisted,
A relative displacement occurs between the input shaft 91 and the output shaft 92. Thereby, the first and second sensor rings 97, 9
8, the facing area of the tooth portions 97a and 98a changes, and the coil 9
The inductance of 9 changes. This change in inductance is reflected in the output signal of the coil 99, and the I / F circuit 8
A torque signal is input to the microcomputer via 0. Therefore, in the electric power steering employing this torque sensor, the steering force corresponding to the torque is assisted by the motor to the rack 81.

Here, in this torque sensor, since the toughness and rigidity are desired, the torsion bar 90, the input shaft 91 and the output shaft 92 are generally made of an iron-based metal which is a magnetic material. The upper housing 93 and the under housing 94 are also generally made of iron-based metal which is a magnetic material.

[0010]

However, in order to realize the weight reduction of the torque sensor and the fuel economy due to the weight reduction of the vehicle, the upper housing 93 having a relatively small volume is made of iron-based metal, It has been considered to use the aluminum-based metal which is a non-magnetic material for the under housing 94 having a relatively large volume.

In this case, as shown in FIG. 5, after magnetic flux noise from a road heater or the like buried in the road surface is input to the output shaft 92 via the rack 81, this is output to the second sensor ring 98 and the first sensor. There is a risk of flowing in the ring 97, the coil 99, the guide 85, and the spacer 86. When such a situation occurs, the inductance of the coil 99 is affected by the magnetic flux noise, and the reliability of the torque signal deteriorates.

The present invention has been made in view of the above-mentioned conventional circumstances, and provides a torque sensor which is lightweight and which can sufficiently secure the reliability of a torque signal against magnetic flux noise. Is a problem to be solved.

[0013]

A torque sensor according to the present invention comprises a torsion bar made of a magnetic material extending in the axial direction and a magnetic material connected to one end of the torsion bar and coaxial with the torsion bar. A first shaft, a second shaft connected to the other end of the torsion bar and made of a magnetic material coaxial with the torsion bar and the first shaft, and a first magnetic body fixed to the first shaft, Second fixed to the second shaft
A magnetic body, a coil facing the first magnetic body and the second magnetic body, and a third magnetic body that surrounds the coil and forms a magnetic circuit with the first magnetic body and the second magnetic body. , The torsion bar, the first shaft, the first magnetic body, the second magnetic body,
The first magnetic body and the second magnetic body, the first magnetic body and the second magnetic body having a first housing that houses the third magnetic body and the coil, and a second housing that is fastened to the first housing and that houses the second shaft. The bodies face each other, the coil changes the inductance in accordance with the relative displacement between the first magnetic body and the second magnetic body due to the twist acting on the torsion bar, and the torque is generated by the output signal based on the inductance. In the torque sensor to detect,

The first housing is made of a magnetic material,
The second housing is made of a non-magnetic material, and the magnetic flux noise input from the second housing side is guided from the second shaft to the first housing between the first housing and the second housing. It is characterized in that a spacer made of a magnetic material is provided.

In the torque sensor of the present invention, the first housing having a relatively small volume is made of a magnetic material, and the second housing having a relatively large volume is made of a non-magnetic material. For this reason, it is possible to reduce the weight of the torque sensor, which in turn reduces the fuel consumption of the vehicle.

Further, in this torque sensor, even if the magnetic flux noise from the road heater or the like buried in the road surface is input to the second shaft, the torque sensor uses the magnetic material provided between the first housing and the second housing. Since the spacers guide the magnetic flux noise from the second shaft to the first housing, the magnetic flux noise is less likely to flow in the second magnetic body, the first magnetic body, the coil, and the third magnetic body. Therefore, the inductance of the coil is less likely to be affected by the magnetic flux noise, and the reliability of the torque signal is improved.

Therefore, the torque sensor of the present invention is lightweight and can sufficiently secure the reliability of the torque signal against magnetic flux noise.

A bearing device made of a magnetic material for supporting the second shaft in the first housing and the second housing may be provided between the first housing and the second housing. In this case, the spacer preferably receives the outer ring of the bearing device. In this case, the bearing device can be firmly supported by the spacer made of a magnetic material.

In this case, the outer ring is preferably surrounded by the spacer in the second housing. In this case, the second shaft and the first housing come into contact with each other over a large area via the bearing device and the spacer, and the magnetic flux noise input from the second housing side is easily guided to the first housing.

It is preferable that the spacer secures a minute gap between the spacer and the circlip made of a magnetic material that locks the bearing device to the second shaft. Thereby, the magnetic flux noise input to the second shaft easily passes through the circlip and passes through the minute gap, and is easily guided to the first housing through the spacer.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Among the main mechanical constitutions of the torque sensor of the embodiment, as shown in FIG. 1, the same constitutions as the conventional mechanical constitution shown in FIG. Is omitted.

In this torque sensor, the torsion bar 9
0, the input shaft 91 as the first shaft and the output shaft 92 as the second shaft are made of a ferrous metal which is a magnetic material. The upper housing 93 as the first housing is also made of an iron-based metal that is a magnetic material, and the under housing 22 that is the second housing is made of an aluminum-based metal that is a non-magnetic material.

As shown in FIG. 1, the upper housing 9
A bearing device 23 made of a magnetic material for supporting the output shaft 92 in the upper housing 93 and the under housing 22 is provided between the shaft 3 and the under housing 22. The bearing device 23 is locked by a circlip 24 provided on the output shaft 92 and made of a magnetic material. The outer ring of the bearing device 23 is received in the under housing 22 while being surrounded by the spacer 21 made of a magnetic material. Thus, the spacer 21 is provided between the upper housing 93 and the under housing 22.

The spacer 21 is provided so as to face the circlip 24 with a minute gap G. As shown in FIG. 2, the spacer 21 has an annular shape that extends in the circumferential direction and surrounds the torsion bar 90. The spacer 21 is provided with a fitting groove 21a on its axial surface for fitting with the outer ring of the bearing device 23, and the bottom surface of the fitting groove 21a is fitted to prevent contact with the inner ring of the bearing device 23. The groove 21b is recessed. In addition, a hole 21c facing the circlip 24 is formed through the bottom surface of the fitting groove 21b.

As shown in FIGS. 1 and 3, the ring 1 made of a non-magnetic material is fixed to the input shaft 91 in the upper housing 93, and the inner surface of the ring 1 serves as the first magnetic body. A ring 2 is provided. As a result, the inner ring 2 becomes the input shaft 9
It is magnetically divided with respect to 1. Inner ring 2
Is a first magnetic portion 3 made of a cylindrical magnetic material, and a first cylindrical non-magnetic material made from the input shaft 91 side.
It comprises a non-magnetic portion 4 and a second magnetic portion 5 made of a cylindrical magnetic material.

The first and second magnetic parts 3, 5 of the inner ring 2
Has a ring shape extending in the circumferential direction surrounding the torsion bar 90, and a large number of comb-shaped rectangular tooth portions 3a, 5a are formed on the outer peripheral surface thereof.

Further, in the upper housing 93, an outer ring 6 as a second magnetic body is provided above the output shaft 92. The outer ring 6 is, from the input shaft 91 side, a third magnetic portion 7 made of a tubular magnetic material, a third non-magnetic portion 8 made of a tubular non-magnetic material, and a fourth tubular magnetic material. The magnetic portion 9, the fourth non-magnetic portion 10 made of a tubular non-magnetic material, the fifth magnetic portion 11 made of a tubular magnetic material, and the fifth non-magnetic portion 20 made of a tubular non-magnetic material. Consists of.

The third magnetic part 7, the fourth magnetic part 9 and the fifth magnetic part 11 of the outer ring 6 are also annularly extending in the circumferential direction surrounding the torsion bar 90, and the third, fourth and fifth magnetic parts are formed. A large number of comb-shaped rectangular tooth portions 7a, 9a, 11a are formed on the inner peripheral surfaces of the portions 7, 9, 11.

Further, in the upper housing 93,
Two sets of guides 1 made of a magnetic material as the third magnetic body
2, 15 and spacers 13, 16 are separated by a separator 18 made of a non-magnetic material, and the circlip 1
It is fixed by 9. The guides 12, 15, the spacers 13, 16 and the separator 18 also have an annular shape that surrounds the torsion bar 90 and extends in the circumferential direction, and covers the outer peripheral surface of the outer ring 6.

Then, one magnetic circuit is formed by the first magnetic portion 3, the third magnetic portion 7, the guide 12, the spacer 13 and the fourth magnetic portion 9. Further, another magnetic circuit is formed by the second magnetic unit 5, the fifth magnetic unit 11, the guide 15, the spacer 16 and the fourth magnetic unit 9. Coils 14 and 17 are arranged in each magnetic circuit. Then, the I / F circuit 8
When the coil 99 is energized from 0, two opposite magnetic paths are formed as shown by the arrow.

In this torque sensor, the upper housing 93 having a relatively small volume is made of iron-based metal, and the under housing 22 having a relatively large volume is made of aluminum-based metal. For this reason, it is possible to reduce the weight of the torque sensor, which in turn reduces the fuel consumption of the vehicle.

Further, in this torque sensor, even if the magnetic flux noise from the road heater or the like buried in the road surface is input to the output shaft 92, the output shaft 92 and the upper housing 93 pass through the bearing device 23 and the spacer 21. Since they are in contact with each other over a large area, magnetic flux noise in the output shaft 92 is easily guided to the upper housing 93. Further, since the spacer 21 secures a minute gap with the circlip 24, the output shaft 9
The magnetic flux noise in 2 passes through the circlip 24, passes through a minute gap, and is easily guided to the upper housing 93 via the spacer 21. Therefore, magnetic flux noise is generated by the inner ring 2, the outer ring 6, the coils 14, 17, and the guide 1.
2 and 15 and spacers 13 and 16 are less likely to flow. Therefore, the inductance of the coils 14 and 17 is less likely to be affected by the magnetic flux noise, and the reliability of the torque signal is improved.

Therefore, according to the torque sensor of the embodiment, while being lightweight, it is possible to sufficiently secure the reliability of the torque signal against the magnetic flux noise.

In this torque sensor, the bearing device 23 is provided between the upper housing 93 and the under housing 22, and the spacer 21 receives the outer ring of the bearing device 23. 23 can be firmly supported.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a torque sensor according to an embodiment.

FIG. 2 is an enlarged vertical sectional view of a spacer according to the torque sensor of the embodiment.

FIG. 3 is an enlarged vertical sectional view of the torque sensor of the embodiment.

FIG. 4 is a vertical sectional view of a conventional torque sensor.

FIG. 5 is an enlarged vertical sectional view of a conventional torque sensor.

[Explanation of symbols]

90 ... Torsion bar 91 ... 1st shaft (input shaft) 92 ... 2nd shaft (output shaft) 2 ... 1st magnetic body (inner ring) 6 ... 2nd magnetic body (outer ring) 14, 17 ... Coil 12, 13 , 15, 16 ... Third magnetic body (12, 15 ... Guide, 13, 16 ... Spacer) 93 ... First housing (upper housing) 22 ... Second housing (under housing) 21 ... Spacer 23 ... Bearing device 24 ... Ser clip

Claims (4)

[Claims] 1. A torsion bar made of a magnetic material that extends in the axial direction, and a first shaft made of a magnetic material that is connected to one end of the torsion bar and is coaxial with the torsion bar.
A second shaft made of a magnetic material that is connected to the other end of the torsion bar and is coaxial with the torsion bar and the first shaft;
A first magnetic body fixed to the first shaft, a second magnetic body fixed to the second shaft, a coil facing the first magnetic body and the second magnetic body, and a coil surrounding the coil. A third magnetic body that forms a magnetic circuit together with the first magnetic body and the second magnetic body, the torsion bar, the first shaft, the first magnetic body, the second magnetic body, and the third magnetic body. A first housing that houses the body and the coil, and a second housing that is fastened to the first housing and houses the second shaft, and the first magnetic body and the second magnetic body face each other. A torque sensor for detecting a torque by an output signal based on the inductance, the inductance of the coil changing in response to relative displacement between the first magnetic body and the second magnetic body based on a twist acting on the torsion bar. The first housing is made of a magnetic material, and the second housing is And a magnetic material that guides magnetic flux noise input from the second housing side from the second shaft to the first housing between the first housing and the second housing. A torque sensor characterized in that a spacer is provided. 2. A bearing device made of a magnetic material for supporting a second shaft in the first housing and the second housing is provided between the first housing and the second housing, and the spacer is the bearing device. The torque sensor according to claim 1, wherein the outer ring of the torque sensor is received. 3. The torque sensor according to claim 2, wherein the outer ring is surrounded by a spacer in the second housing. 4. The torque sensor according to claim 1, wherein the spacer secures a minute gap between the spacer and the second shaft.