JP2003028736A - Magnetostrictive torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance precision of a magnetostrictive sensor formed with a magnetic-anisotropic part in a sensor shaft, provided with a coil to surround the magnetic-anisotropic part, and constituted to detect by the coil a change of magnetic permeability in the magnetic-anisotropic part generated by torque applied to the sensor shaft. SOLUTION: This sensor is provided with a cylindrical shield yoke 6 for fitting a cylindrical coil bobbin 3 for winding coils 4A, 4B, 5A, 5B, to the sensor shaft 2 to be supported relatively rotatably to the sensor shaft 2, and for covering an outer circumferential side of the coils 4A, 4B, 5A, 5B, and provided with a radial-directionally extended flange 34 over the whole circumference of an axial-center-directional end of the shield yoke 6. Supports 45 are provided to be arranged in circumferential-directional multiple portions in an outer circumferential side of the coil bobbin 3, the each support 45 is formed of a rubberlike elastomer, and the flange 34 of the shield yoke 6 is supported by the supports 45 to generate a space between the flange 34 and the coil bobbin 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor.

[0002]

2. Description of the Related Art As a magnetostrictive torque sensor, a pair of magnetic anisotropies in the axial direction are formed on the outer circumference of a sensor shaft, which include knurling grooves which are inclined at angles of ± 45 ° with respect to the axial direction and are inclined in mutually opposite directions. There is a coil provided with a pair of coils in the axial direction so as to surround each magnetic anisotropy portion. In this magnetostrictive torque sensor, a current is passed through the coil to generate a magnetic flux and apply a magnetic field to the sensor shaft,
When torque is applied to the sensor shaft in this state, tensile stress acts selectively on one side of the magnetic anisotropy part and compressive stress acts on the other side, and as a result, due to the inverse magnetostriction effect, the magnetic stress exerted by the tensile stress acts. The magnetic permeability of the anisotropic part increases, the magnetic permeability of the magnetic anisotropy part on which compressive stress acts decreases, and a change in permeability due to this inverse magnetostriction effect is generated in each coil as an induced electromotive voltage, and this is converted to DC. After that, by differential amplification, a voltage output (sensor output) proportional to the torque applied to the sensor shaft can be obtained.

As this type of magnetostrictive torque sensor, there is one disclosed in Japanese Patent Application Laid-Open No. 9-89691. In this magnetostrictive torque sensor, as shown in FIG. 18, both magnetic anisotropy parts 6 formed on the sensor shaft 60.
A cylindrical coil bobbin 62 fitted over the sensor shaft 60 is provided so as to cover the 1A and 61B.
The coils 64A and 64B are housed in the coil housing grooves 63A and 63B in the circumferential direction formed corresponding to the magnetic anisotropic portions 61A and 61B on the outer periphery of the coil 2, and both coils 64A and 6B are provided.
A cylindrical shield yoke fitted over the coil bobbin 62 is provided so as to cover 4B.

Both ends of the coil bobbin 62 in the axial direction are directly (or via bearings) to the outer peripheral step portion 66 of the sensor shaft 60.
The coil bobbin 6 is supported so as to be rotatable about its axis.
Circumferential grooves 67 are formed on the outer peripheral side of 2 on the axially outer sides of the coil housing grooves 63A and 63B, respectively. The shield yoke 65 is provided with a cylindrical portion 65A, and a flange portion 65B extending inward in the radial direction is provided at the end of the cylindrical portion 65A in the axial direction over the entire circumference.

Further, the inner peripheral side edge of the collar portion 65B is formed in a circular shape, and the shield yoke 65 is divided into two by a dividing surface along the axial direction and the radial direction. So that the collar portion of the shield bobbin 62 is inserted into the circumferential groove 67 of the coil bobbin 62.
The shield yoke 65 is fixed to the coil bobbin 62 by abutting the two constituents of the above-mentioned structure on the dividing surfaces and injecting an adhesive into the peripheral groove 67 to bond and fix the flange portion 65B to the peripheral groove 67.

[0006]

In the magnetostrictive torque sensor shown in FIG. 18, the shield yoke 65 is made of a magnetic material and concentrates the magnetic flux generated from the coils 64A and 64B. Although it prevents the leakage of magnetic flux and increases the sensor sensitivity, the shield yoke 6
When the end portion of the collar portion 65B of No. 5 and the bottom portion of the circumferential groove 67 are in contact with each other, the shield yoke 65 is made of metal and the coil bobbin 62
Is formed of resin, so that when a temperature change occurs, stress acts on the shield yoke 65 due to the difference in linear expansion coefficient (thermal expansion) between the shield yoke 65 and the coil bobbin 62.
Therefore, there is a problem that the magnetic permeability of the shield yoke 65 changes and the sensor output fluctuates, which affects the sensor accuracy.

In addition, the sensor output may fluctuate due to external force such as vibration or impact force acting on the shield yoke 65 from the coil bobbin 62. Incidentally, JP-A-9-896
No. 91 discloses that the flange portion 65B of the shield yoke 65 is bonded and fixed to the circumferential groove 67 with an elastic adhesive such as a rubber adhesive. However, the flange portion of the shield yoke 65 is disclosed. The above problem cannot be solved only by fixing 65B to the circumferential groove 67 with an adhesive having high elasticity.
Further, in the magnetostrictive torque sensor, by providing the flange portion 65B at the end portion of the shield yoke 65, the end portion of the shield yoke 65 is brought closer to the sensor shaft 60, and the flange portion 6 is provided.
A large amount of magnetic flux is taken into the shield yoke 65 from 5B to prevent the magnetic flux from leaking.
Is misaligned with respect to the sensor shaft 60 (when the shield yoke 65 and the sensor shaft 60 do not have the same axial center), the gap between the shield yoke 65 and the sensor shaft 60 differs in the circumferential direction. Therefore, the shield yoke 65
Where the gap between the sensor axis 60 and
A large amount of magnetic flux is taken into a large gap, and an output fluctuation occurs due to a change in magnetic flux density of the shield yoke 65, which affects the sensor accuracy.

For this reason, the shield yoke 65 and the sensor shaft 60 must be arranged concentrically, but the end portion of the flange portion 65B of the shield yoke 65 is brought into contact with the bottom portion of the circumferential groove 67 over the entire circumference. If so, there is a problem that it is difficult to align the shield yoke 65 and the sensor shaft 60 with each other. That is, the flange portion 65B of the shield yoke 65
In the case where the entire circumference is brought into contact with the bottom portion of the circumferential groove 67 of the coil bobbin 62, in order to make the shield yoke 65 and the sensor shaft 60 concentric, the bottom surface of the circumferential groove 67 of the coil bobbin 62 is the sensor shaft. Although it is necessary to form an arc centering on the shaft center of 60 and an inner peripheral surface of the collar portion 65B of the shield yoke 65 centering on the shaft center of the sensor shaft 60, both of them are formed in the circumferential direction in manufacturing. Since it is difficult to form an arc centered on the axis of the sensor shaft 60 over the entire circumference, a manufacturing error occurs, and the shield yoke 65 has no position restriction in the circumferential direction with respect to the coil bobbin 62. When the two are in contact with each other at a large error, a relatively large misalignment occurs between the shield yoke 65 and the sensor shaft 60 for the magnetostrictive torque sensor.

In particular, if the shield yoke 65 is formed of a thin press-molded product in order to save space, reduce costs, and reduce weight, it is difficult to form the inner peripheral side of the flange portion 65B into an arc. When the coil bobbin 62 is supported on the sensor shaft 60 via the bearing, the shield yoke 65 is provided with the flange portion 65B so that a large amount of magnetic flux is taken in by the shield yoke 65, but the coil bobbin 62 is supported. If the bearing is made of a copper-based material having a high conductivity, the bearing absorbs leakage magnetic flux, which lowers the sensor output and affects the sensor accuracy.

Further, if the directions of the magnetic fluxes generated in the coils 64A and 64B are the same, the output will be reduced and the accuracy of the sensor will be affected. The present invention is
In view of the above problems, it is an object of the present invention to solve the above problems and provide a magnetostrictive torque sensor intended to improve the accuracy of the sensor.

[0011]

The technical means taken by the present invention to solve the technical problem is to form a magnetic anisotropic portion on the outer circumference of the sensor shaft and to surround the magnetic anisotropic portion. A magnetostrictive torque sensor having a coil arranged in such a manner that the change in the magnetic permeability of the magnetic anisotropy part caused by the torque applied to the sensor shaft is detected by the coil. -Shaped coil bobbin is fitted onto the sensor shaft and supported rotatably relative to the sensor shaft, and a cylindrical shield yoke that covers the outer peripheral side of the coil is provided, and a radial direction is provided at the axial center end of the shield yoke. An inwardly extending flange portion is provided over substantially the entire circumference, and a support body arranged at a plurality of circumferential positions is provided on the outer peripheral side of the coil bobbin. The support body is formed of a rubber-like elastic body and By the body The flange portion of the shield yoke Te, characterized in that the support such that the interval is generated between the flange portion and the coil bobbin.

Further, the shield yoke is divided by a dividing surface extending in the axial direction and the radial direction, and a cylindrical shield yoke is constituted by bringing the dividing surfaces of the constituent members constituting the shield yoke into contact with each other, and the supporting member is It is preferable to support the abutting portion of the shield yoke structure and to provide the support with a partition wall located between the shield yoke structures.
Further, it is preferable that the support body is arranged at a radial symmetrical position of the coil bobbin. Further, it is preferable that the coil bobbin is rotatably supported by the sensor shaft via a bearing in the vicinity of the flange portion of the shield yoke, and the bearing is made of a material having a low conductivity.

It is preferable that the coil bobbin is rotatably supported by the sensor shaft via a bearing in the vicinity of the flange portion of the shield yoke, and the bearing is composed of a winding bush. Another technical means is to form a pair of magnetic anisotropy portions in the axial direction on the outer periphery of the sensor shaft, and to provide a pair of coils arranged so as to surround each magnetic anisotropy portion,
A magnetostrictive torque sensor in which a coil detects changes in magnetic permeability of a magnetic anisotropy portion caused by torque applied to the sensor shaft, and a tubular coil bobbin for winding the coil is fitted onto the sensor shaft. A cylindrical shield yoke that supports the sensor shaft so as to be rotatable relative to the sensor shaft and covers the outer peripheral side of the coil, and applies a current to each coil so that the magnetic flux generated by each coil faces the opposite direction of the coil. It is characterized by having done.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a magnetostrictive torque sensor 1, and the magnetostrictive torque sensor 1 is
Sensor shaft 2 for transmitting torque by being inserted in a power transmission system
A coil bobbin 3 fitted over the sensor shaft 2, and coils 4A, 4B, 5 wound around the coil bobbin 3.
A, 5B, a shield yoke 6 for covering the outer peripheral sides of the coils 4A, 4B, 5A, 5B, and an amplifier substrate 7.

The sensor shaft 2 is a hollow shaft made of a magnetostrictive material such as nickel or cobalt or a material containing the magnetostrictive material. A pair of magnetic anisotropic portions 8A and 8B are provided on the outer peripheral surface of the sensor shaft 2 in the axial direction, and the magnetic anisotropic portions 8A and 8B are provided on the outer peripheral surface of the sensor shaft 2 with a large number of grooves. Are processed in parallel (rolled), the groove of one magnetic anisotropy portion 8A is formed in the direction of + 45 ° with respect to the axis of the sensor shaft 2, and the magnetic anisotropy of the other is formed. The groove of the portion 8B is − with respect to the axis of the sensor shaft 2.
It is formed in the direction of 45 °.

Therefore, when a magnetic field is applied to the sensor shaft 2 and torque is applied to the sensor shaft 2 in this state, a tensile stress is selectively applied to one of the magnetic anisotropic portions 8A and 8B and a compressive stress is selectively applied to the other. As a result, due to the inverse magnetostrictive effect, the magnetic permeability of the magnetic anisotropic portions 8A, 8B on which the tensile stress acts increases, and the magnetic permeability of the magnetic anisotropic portions 8A, 8B on which the compressive stress acts decreases. It has become. Also, of the sensor shaft 2,
Bearing seats 9 and 1 for externally fitting the bearings 16 and 17 to the outer and outer sides in the axial direction of the magnetic anisotropic portions 8A and 8B, respectively.
0 is formed, a step portion 11 having a diameter larger than that of the bearing seat 9 is formed on the outer side in the axial direction of the sensor shaft 2 of one bearing seat 9, and the axial center of the sensor shaft 2 of the other bearing seat 10 is formed. A circumferential groove 13 is formed on the outer side in the direction for fitting the retaining ring 12 for preventing the bearing 17 from coming off.

A power transmission portion (spline fitting portion) 14 is formed on the outer peripheral side of the sensor shaft 2 on the outer side in the axial direction of the sensor shaft 2 of the step portion 11, and the sensor groove 2 shaft of the peripheral groove 13 is formed. A power transmission portion (spline fitting portion) 15 is formed on the inner peripheral side of the sensor shaft 2 on the outer side in the axial direction.
Is interposed in the power transmission system such that rotational power is input from one of the power transmission units 14 and 15 and rotational power is output from the other of the power transmission units 14 and 15. Coil bobbin 3
As shown in FIGS. 1 to 5, is formed in a tubular shape from a resin material, and is fitted onto the sensor shaft 2 so as to cover both magnetic anisotropic portions 8A and 8B.

On both sides of the coil bobbin 3 in the axial direction,
Bearing fitting portions 18 and 19 which are fitted on the bearings 16 and 17 are formed, and the coil bobbin 3 is supported by the sensor shaft 2 via the bearings 16 and 17 so as to be relatively rotatable about the axis. An engaging portion 20 is provided on the lower side of the coil bobbin 3 to prevent the coil bobbin 3 from rotating along with the fixed side of the housing of the power transmission system in which the torque sensor 1 is provided. There is. In addition, the bearing 1
Between 6 and the step portion 11 and between the bearing 17 and the retaining ring 12,
Thrust washers 21 are provided respectively, and the bearings 16 and 17 receive a radial load and the thrust washers 21 receive a thrust load to reduce uneven rotation and torque cross of the sensor shaft 2.

The coils 4A, 4 are provided at the outer peripheral side of the coil bobbin 3 corresponding to the magnetic anisotropic portions 8A, 8B.
The coil housing grooves 22A and 22B formed in the circumferential direction so as to wind B, 5A and 5B have a pair of magnetic anisotropic portions 8
A pair of circumferential grooves 23 are formed on the outer sides in the axial direction of the coil housing grooves 22A and 22B, respectively. 1, 2, and 13 to 1
As shown in FIG. 5, in each coil accommodation groove 22A, 22B,
On the inner peripheral side, detection coils 4A and 4B (which are referred to as detection coils) that detect changes in magnetic permeability of the magnetic anisotropic portions 8A and 8B when torque is applied to the sensor shaft 2 are provided. Excitation coils 5A and 5B (which are referred to as excitation coils) for applying a magnetic field to the sensor shaft 2 are provided on the outer peripheral side, and a polyester film is provided between the detection coils 4A and 4B and the excitation coils 5A and 5B. Insulation layer 14
Is provided.

A terminal mounting portion 29 for vertically fixing the connection terminals 25a to 25h is provided between the coil housing grooves 22A and 22B on the outer peripheral side of the coil bobbin 3.
The coils 4A, 4B, 5A,
The ends of the winding wire 5B are wound and connected by soldering. The right connection terminals 25a to 25d are for the right coils 4A and 5A, and the left connection terminals 25e to 25h.
Are for the left coils 4B and 5B. One end of the detection coil 4A on the right side is connected to the connection terminal 25a,
The winding of the detection coil 4A is wound from the connection terminal 25a in the direction of arrow A in FIG. 13 and is also wound outward in the axial direction in order to reach the end of the coil housing groove 22A. Then, it is folded back and wound on the first layer winding inward in the axial direction.

By repeating this, the winding of the detection coil 4A on the right side is wound in four layers, and the other end side of the winding is connected to the connection terminal 25b. On the other hand, the detection coil 4B on the left side is wound from the connection terminal 25e in the direction of the arrow B in FIG. 13 and is sequentially wound outward in the axial direction (opposite to the detection coil 4A on the right side). When it reaches the end of the coil housing groove 22B, it is folded back and wound on the first layer winding inward in the axial direction. Similarly to the detection coil 4A on the right side, the detection coil 4B on the left side is wound in four layers, and the winding end side of the winding is connected to the connection terminal 25f.

The right exciting coil 5A is wound two layers on the right detecting coil 4A via the insulating layer 24 in the same manner as the coil 4A. It is connected to the connection terminal 25d. Further, the left side excitation coil 5B is provided on the left side detection coil 4B via the insulating layer 24 in the same manner as the coil 4B.
The layers are wound, and the winding end side is connected to the connection terminal 25h for the first time from the connection terminal 25g. The number of turns (the number of turns) of the detection coils 4A and 4B is 240 (6).
0 × 4 layers), and the number of turns of the exciting coils 5A and 5B is
The number is 80 (40 × 2 layers).

Further, each coil 4A, 4B, 5A, 5B
Is an ultra-super-aligned winding in which the winding of the upper layer (for example, the second layer) is accurately stacked and wound on the winding of the lower layer (the first layer). From the viewpoint of the sensor output of the torque sensor 1, it is preferable to provide the excitation coils 5A and 5B on the inner peripheral side and the detection coils 4A and 4B on the outer peripheral side, but in the present embodiment, the detection is performed on the inner peripheral side. The coils 4A and 4B are provided with exciting coils 5A and 5B on the outer peripheral side.

This is because, in the present embodiment, the detection coils 4A and 4B and the excitation coils 5A and 5B are provided in the same coil accommodating grooves 22A and 22B, and these coils 4A and 4B are provided.
A, 4B, 5A and 5B are ultra-super-aligned windings, and the windings of the detection coils 4A and 4B have a smaller wire diameter and a larger number of turns than the windings of the excitation coils 5A and 5B (excitation coil 5A). , 3 times that of 5B), so that the exciting coils 5A, 5
This is because if B is provided and the detection coils 4A and 4B are wound around the outer circumference of the B, there is a fear that the detection coils 4A and 4B cannot be accurately wound, and if not correctly wound, the sensor accuracy will be affected.

The connection terminals 25a to 25h are connected to the amplifier board 7.
The amplifier board 7 is fixed to the board mounting portion 30 provided on the coil bobbin 3 by the positioning projection 31 formed on the board mounting portion 30 and the bolt 32 screwed into the screw hole 26. , Magnetic anisotropy parts 8A, 8B
Change in magnetic permeability is generated in each of the detection coils 5A and 5B as an induced electromotive voltage, which is converted into a direct current by the amplifier board 7.
It is configured to perform differential amplification and output a voltage proportional to torque. Further, as shown in FIG. 16, the right side coils 4A, 5A and the left side coils 4B, 5B are arranged such that the magnetic fluxes generated by the respective coils 4A, 4B, 5A, 5B are directed inward in the opposite direction. 4A, 4B, 5
An electric current is applied to A and 5B.

As a result, the magnetic flux collecting force of the shield yoke is increased to prevent the leakage magnetic flux from being unbalanced. In the figure, arrows C and D indicate the direction of magnetic flux, and arrows E and F indicate the direction of current. The amplifier board 7
Is connected to a power source and a measuring device, a control device, or the like by electric wiring. The shield yoke 6 is made of a thin press-molded product obtained by pressing a thin plate material made of a magnetic material, and is lightweight, compact, and inexpensive.

Further, the shield yoke 6 has the structure shown in FIGS.
As shown in FIGS. 6 to 8, the coil bobbin 3 is formed into a tubular shape and fitted over the coil bobbin 3.
And a flange portion 34 that extends radially inward from both axial end portions of the cylindrical portion 33 and that is inserted into the circumferential groove 23 of the coil bobbin 3. The flange portion 34 is provided over substantially the entire circumference of the cylindrical portion 33 in the circumferential direction. Further, the amplifier board 7 is arranged on the outer side in the radial direction of the shield yoke 6, and the cylindrical terminals 33 of the shield yoke 6 allow the connection terminals 25a to 25h to pass therethrough.
The insertion hole 35 is formed, and an opening 36 having the same size as the insertion hole 35 is formed at a position (radially symmetrical position) opposite to the insertion hole 35 in the radial direction.

The shield yoke 6 is divided into a plurality of structural members 6A along a dividing surface extending in the axial direction and the radial direction (in the present embodiment, the shield yoke 6 has the insertion hole 35 and the opening 36 in the circumferential direction). It is divided into two to divide into two). The structure 6A that constitutes the shield yoke 6 is
The rectangular flat plate 38 shown in FIG. 9 is pressed to be formed into a half-cylinder shape with a collar. By making the dividing surfaces of the half-cylinder-shaped component 6A into a butt shape, the shield is obtained. The yoke 6 is assembled into a tubular shape.

A notch 39 located at the center in the width direction orthogonal to the length direction is formed at both ends of the flat plate 38 in the length direction, and one notch 39 constitutes the insertion hole 35. The opening 36 is formed by the other notch 39. Also,
A plurality of flange pieces 42 are formed in the length direction on both sides of the flat plate 38 in the width direction, and these flange pieces 42 form the flange portion 34 of the shield yoke 6. The flat plate 38 is curved in an arc shape so that the lengthwise direction is the circumferential direction, and the collar pieces 42 are bent in the radial direction, whereby the structure 6A of the shield yoke 6 is formed. .

The edge 42a of the flat plate 38 in the width direction of each flange 42 is formed in an arc shape so that the edge of the flange 34 has an arc shape with the axial center of the shield yoke 6 as the center. There is. In addition, the structure 6A that constitutes the shield yoke 6,
The portion forming the collar portion 34 may be formed continuously. In addition, in the structure 6A that constitutes the shield yoke 6,
A pair of recesses 43 for maintaining the shape are formed in the circumferential direction in the portion forming the cylindrical portion 33.

On the other hand, in each circumferential groove 23 of the coil bobbin 3,
A pair of support bodies 45 for supporting the collar portion 34 of the shield yoke 6 are provided at radially symmetrical positions of the coil bobbin 3 so that a gap is formed between the collar portion 34 of the shield yoke 6 and the coil bobbin 3. There is. 3 to 5 and FIG.
~ As shown in FIG. 12, of the circumferential groove 23 of the coil bobbin 3,
The coil bobbin 3 is provided in the portion 44 where the support body 45 is arranged.
A recess 46 is formed in the wall on the outer side in the axial direction, and
At the bottom of the circumferential groove 23, a flat seat surface 47 reaching the recess 46 is formed.
Are formed.

The seat surface 47 does not have to be formed in particular. The support 45 is made of a rubber-like elastic material (for example,
The base portion 48 is made of NBR (rubber hardness JISA Hs70 ± 5) and is in contact with the seat surface 47 of the coil bobbin 3, and the recess portion 46 extends vertically from one end side of the base portion 48. The base 4 has a standing wall 49 and a partition wall 50 that extends vertically from the central portion of the coil bobbin 3 in the circumferential direction of the base portion 48.
By inserting the standing wall 49 of No. 5 into the recess 46, the support body 45 is positioned at the support body arrangement portion 44 of the coil bobbin 3.

Each component 6A constituting the shield yoke 6
The radial end of the shield yoke 6 of the collar 34 is the support 4
5, the division surface side of the collar portion 34 abuts on the partition wall 50 of the support body 45, and the outer end surface of the collar portion 34 in the axial direction of the shield yoke 6 abuts on the standing wall 49 of the support body 45. Then, the inner end surface of the flange portion 34 in the axial direction of the shield yoke 6 is assembled so as to have a space from the wall portion of the circumferential groove 13 on the inner side in the axial direction of the shield yoke 6. After that, the circumferential groove 13 is filled with a rubber adhesive (for example, silicon rubber) to bond and fix the shield yoke 6 and the support body 45 to the coil bobbin 3.

As a result, the shield yoke 6 is elastically supported while being separated from the coil bobbin 3, and is based on the difference in the linear expansion coefficient between the shield yoke 6 and the coil bobbin 3 when the temperature changes. The stress acting on the shield yoke 6 is absorbed by the elastic deformation of the support body 45, the fluctuation of the sensor output due to the difference in thermal expansion between the shield yoke 6 and the coil bobbin 3 can be prevented, and the sensor accuracy can be improved. . When the collar portion 34 of the shield yoke 6 is supported by an elastic body so that a gap is formed between the collar portion 34 and the coil bobbin 3, the collar portion 34 of the shield yoke 6 is formed by an elastic body over the entire circumference. If supported, the shield yoke 6
It is difficult to match the shaft center of the shield yoke 6 with the shaft center of the sensor shaft 2 due to the manufacturing error of the coil bobbin 3, but in the present embodiment, the collar portion of the shield yoke 6 is arranged. Since 34 is supported by the support members 45 arranged at a plurality of positions (two positions in the present embodiment) in the circumferential direction of the coil bobbin 3, the support member 4 of the coil bobbin 6 is provided.
5 and the flange portion 3 of the shield yoke 6
If the precision of the portion of the No. 4 contacting the support body 45 is provided, the shield yoke 6 and the sensor shaft 2 can be arranged concentrically, and the concentricity between the shield yoke 6 and the sensor shaft 2 can be easily improved. It is possible to improve the sensor accuracy.

When the flange portions 34 of the structural body 6A forming the shield yoke 6 are in contact with each other, stress is generated in the shield yoke 6 due to thermal expansion, but the partition wall 50 of the support body 45 causes the flange of the structural body 6A. The contact between the parts 34 is surely prevented, and the shield yoke 6 is positioned. Further, when the shield yoke 6 is assembled, the flange portion 34 is slightly pressed against the support body 45 and abuts on the support body 45, so that a portion of the flange portion 34 abuts on the support body 45 is slightly stressed. Although this has an effect on the sensor output, the support body 45 is provided at radially symmetrical positions of the coil bobbin 3 and the shield yoke 6, and by this, the support is balanced and the output fluctuation is prevented.

The shield yoke 6 comprises coils 4A, 4
The magnetic fluxes generated from B, 5A and 5B are caused to flow in a concentrated manner to prevent leakage of the magnetic flux and increase the sensor sensitivity, and the flange 34 provided at the end of the shield yoke 6 allows the shield to be shielded. Although the end of the yoke 6 is brought close to the sensor shaft 2 and a large amount of magnetic flux is taken into the shield yoke 6 from the collar portion 34 to prevent leakage of magnetic flux, the bearings 16 and 17 supporting the coil bobbin 3 have high conductivity. If the bearings 16 and 17 are made of a copper-based material, the bearings 16 and 17 absorb the leakage magnetic flux, the sensor output is reduced, and the sensor accuracy is affected. Therefore, the bearings 16 and 17 have low conductivity (0 Including)
It is preferably formed of a material, and in the present embodiment, it is formed of a material such as an iron-based material or a stainless steel-based material (for example, NTN Bare Fight F material). It doesn't matter).

As the bearings 16 and 17, bushes (oil-impregnated bushes) or small bearings are used, but the bushes are preferable because the cost can be reduced. Further, when the bearings 16 and 17 are made of bushes, the bearings 16 and 17 can be made thin so that the absorption of leakage magnetic flux can be suppressed even if the bearings 16 and 17 are made of a material having high conductivity such as copper. it can. Further, when the bearing supporting the coil bobbin 3 is formed of a material having a high conductivity such as a copper-based material, the bearing may be configured by a thin cylindrical bush, but as shown in FIG. A thin-walled cylindrical portion (radial receiving portion) 51A externally fitted to and abutted on the bearing seat 9 of the coil bobbin 3, and a bearing 51 that supports the bearing 51 and extends radially outward from one end side of the cylindrical portion 51A. By forming the flange portion (thrust receiving portion) 51B contacting the step portion 11 with an L-shaped cross section, the radial load and the thrust load can be received even if the thickness of the cylindrical portion 51A is thin. By reducing the thickness of the cylindrical portion 51A, absorption of leakage magnetic flux can be suppressed.

As the thin-walled cylindrical bush, a wound bush formed by curling a flat plate material into a cylindrical shape is usually adopted.
The flanged bush (bearing 51) is usually a wound bush formed by curling a flat plate material into a cylindrical shape and bending the flange portion 51B. In the present embodiment, the sensor shaft 2 is a hollow shaft, but it may be a hollow shaft. In addition, the power transmission portion is formed on the outer peripheral side of the step portion 11 and the power transmission portion is formed on the inner peripheral side of the bearing seat 10 forming portion of the sensor shaft 2, whereby the sensor shaft 2 (magnetostrictive torque sensor 1) is formed. Can be formed compactly and can be provided at low cost.

Further, the sensor shaft 2 may be of a coupling type by forming a power transmission portion on the inner peripheral side of the sensor shaft 2 where the bearing seats 9 and 10 are formed.

[0040]

According to the present invention, on the outer peripheral side of the coil bobbin, a support body made of rubber-like elastic material arranged at a plurality of circumferential positions is provided, and the collar portion of the shield yoke is secured by the support body. Since it is supported so that there is a gap between the coil portion and the coil bobbin, it is based on the difference in the linear expansion coefficient between the shield yoke and the coil bobbin when the temperature changes.
The stress acting on the shield yoke is absorbed by the elastic deformation of the support, and the fluctuation of the sensor output due to the difference in thermal expansion between the shield yoke and the coil bobbin can be prevented and the sensor accuracy can be improved.

Further, since the support made of a rubber-like elastic body absorbs external force such as vibration or impact force acting from the coil bobbin to the shield yoke, it is caused by external force such as vibration or impact force acting from the coil bobbin to the shield yoke. It is possible to prevent fluctuations in the sensor output that occur, and improve the sensor accuracy. Further, when the collar portion of the shield yoke is supported by the elastic body so that a gap is generated between the collar portion and the coil bobbin, when the collar portion of the shield yoke is supported by the elastic body over the entire circumference, Due to an error in manufacturing the shield yoke and the coil bobbin, it is difficult to match the axis of the shield yoke with the axis of the sensor shaft. However, in the present invention, the flange portion of the shield yoke is provided at a plurality of circumferential positions of the coil bobbin. Since it is supported by the support placed, the shield yoke and the sensor shaft can be concentric with each other if the accuracy of the part where the support of the coil bobbin is provided and the part that contacts the support of the collar part of the shield yoke is obtained. , The concentricity between the shield yoke and the sensor shaft can be easily improved, and the sensor accuracy can be improved.

Further, in some cases, the shield yoke is divided by a division surface along the axial direction and the radial direction, and the cylindrical shield yoke is constructed by abutting the division surfaces of the constituent members constituting this shield yoke. As a result, when the flanges of the components that form the shield yoke are in contact with each other, thermal expansion causes stress in the shield yoke.
By supporting the abutting part of the shield yoke structure and providing the support with a partition wall located between the structures forming the shield yoke, it is possible to reliably prevent the flange portions of the shield yoke structure from contacting each other. Along with
Positioning of the shield yoke is also performed.

When assembling the shield yoke,
Since the collar part is slightly pressed against the support and abuts on it, a slight stress is generated at the part of the collar part that abuts the support, which affects the sensor output. By arranging them at positions symmetrical with respect to the radial direction, they are balanced and output fluctuations are prevented. In addition, the shield yoke concentrates the magnetic flux generated from the coil to prevent leakage of the magnetic flux and increases the sensor sensitivity, and a collar portion provided at the end of the shield yoke allows the shield yoke to The end of the yoke is moved closer to the sensor shaft, and a large amount of magnetic flux is taken into the shield yoke from the collar to prevent leakage of the magnetic flux.However, the coil bobbin faces the sensor shaft via a bearing near the collar of the shield yoke. If the bearing that supports the coil bobbin is made of a material with high electrical conductivity, the bearing absorbs the leakage magnetic flux and reduces the sensor output, affecting the sensor accuracy. Exert. Therefore, by configuring this bearing with a material having a low electric conductivity, it is possible to suppress the absorption of leakage magnetic flux.

Further, by constructing the bearing for supporting the coil bobbin with the winding bush, even if the bearing is made of a material having high conductivity, since the bearing is thin, absorption of leakage magnetic flux can be suppressed. In addition, a pair of magnetic anisotropic portions are formed on the outer circumference of the sensor shaft in the axial direction, and a pair of coils are arranged so as to surround each magnetic anisotropic portion. A magnetostrictive torque sensor in which a change in magnetic permeability of a magnetic anisotropy portion that occurs is detected by a coil, and a tubular coil bobbin for winding the coil is fitted onto the sensor shaft and is rotated relative to the sensor shaft. In the one that is provided with a cylindrical shield yoke that freely supports and covers the outer peripheral side of the coil, so that the magnetic flux generated by each coil faces the opposite direction of the coil,
By causing a current to flow through each coil, it is possible to increase the magnetic flux collecting force of the shield yoke, prevent imbalance of leakage magnetic flux, and improve sensor accuracy.

[Brief description of drawings]

FIG. 1 is a partial side sectional view of a main part of a magnetostrictive torque sensor.

FIG. 2 is a partial side sectional view showing the overall configuration of a magnetostrictive torque sensor.

FIG. 3 is a plan view of a coil bobbin.

FIG. 4 is a side sectional view of a coil bobbin.

FIG. 5 is a front view cross section of a coil bobbin.

FIG. 6 is a plan view of a structure of a shield yoke.

FIG. 7 is a side view of the structure of the shield yoke.

FIG. 8 is a front view of a structure forming a shield yoke.

FIG. 9 is a plan view of a flat plate forming a shield yoke structure.

FIG. 10 is a side sectional view of a supporting portion of a shield yoke and a coil bobbin.

FIG. 11 is a plan view of a shield yoke supporting portion.

FIG. 12 is a front view of a shield yoke supporting portion.

FIG. 13 is a plan view of the coil bobbin with the coil wound.

FIG. 14 is a plan view of a mounting portion for mounting a connection terminal that connects coil ends.

FIG. 15 is a side sectional view of the coil bobbin with the coil wound.

FIG. 16 is a conceptual diagram of a coil.

FIG. 17 is a side sectional view showing another example of the support portion of the coil bobbin.

FIG. 18 is a side sectional view of a conventional magnetostrictive torque sensor.

[Explanation of symbols]

1 Magnetostrictive torque sensor 2 sensor axes 3 coil bobbins 4A detection coil 4B detection coil 5A excitation coil 5B excitation coil 6 Shield yoke 8A magnetic anisotropy part 8B Magnetic anisotropy part 16 bearings 17 Bearing 34 Collar 45 Support 50 partitions

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Kurita             2-35 Jimmucho, Yabu City, Osaka Prefecture             Bota Kyuhoji Factory

Claims (6)

[Claims] 1. A magnetic anisotropy portion is formed on the outer periphery of a sensor shaft, and a coil arranged so as to surround the magnetic anisotropy portion is provided, and the magnetic anisotropy is generated by a torque applied to the sensor shaft. A magnetostrictive torque sensor configured to detect a change in magnetic permeability of a portion by a coil, wherein a tubular coil bobbin for winding the coil is fitted onto the sensor shaft and supported rotatably relative to the sensor shaft. A cylindrical shield yoke that covers the outer peripheral side of the coil is provided, and at the axial end of the shield yoke, a flange portion that extends radially inward is provided over substantially the entire circumference, and on the outer peripheral side of the coil bobbin, A support body is provided at a plurality of positions in the circumferential direction, and the support body is formed of a rubber-like elastic body, and the support body forms a collar portion of the shield yoke between the collar portion and the coil bobbin. A magnetostrictive torque sensor, characterized in that supported on. 2. A shield yoke is divided by a dividing surface extending in the axial direction and a radial direction, and a cylindrical shielding yoke is constituted by bringing the dividing surfaces of the constituent elements constituting the shield yoke into contact with each other, and the support is The magnetostrictive torque sensor according to claim 1, further comprising: a partition wall provided between the shield yoke components and supporting the abutting portions of the shield yoke components. 3. The magnetostrictive torque sensor according to claim 1, wherein the support body is arranged at radial symmetrical positions of the coil bobbin. 4. The coil bobbin is rotatably supported on the sensor shaft via a bearing near the collar portion of the shield yoke, and the bearing is made of a material having a low electrical conductivity. The magnetostrictive torque sensor according to any one of to 3. 5. The coil bobbin is rotatably supported by a sensor shaft via a bearing in the vicinity of the flange portion of the shield yoke, and the bearing is constituted by a winding bush. The magnetostrictive torque sensor according to any one. 6. A pair of magnetic anisotropy portions are formed on the outer periphery of the sensor shaft in the axial direction, and a pair of coils are arranged so as to surround each magnetic anisotropy portion. A magnetostrictive torque sensor in which a change in magnetic permeability of a magnetic anisotropy portion caused by a torque is detected by a coil, wherein a tubular coil bobbin for winding the coil is fitted onto the sensor shaft, Is equipped with a cylindrical shield yoke that rotatably supports the coil and covers the outer peripheral side of the coil, and a current is passed through each coil so that the magnetic flux generated by each coil faces the opposite direction of the coil. And a magnetostrictive torque sensor.