JPH11118627A - Magnetostriction type torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain change of detection sensitivity and detection precision which is caused by expansion and contraction of each yoke forming member which is caused by temperature change. SOLUTION: A yoke 15 is formed by using a plurality of yoke forming member 20 linked in the circumferential direction of a shaft. The yoke forming member 20 are linked together by welding parts 22 which joint outer circumferential surfaces 20b of the members 20 together. On the inner circumferential surface of the yoke 15, circumferential trenches 18, 19 are formed, in which a primary coil and a secondary coil 12 are accommodated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor for detecting a magnitude of a torque applied to a detected shaft, and more particularly, to a torque sensor based on a magnetostrictive effect corresponding to a twist of the detected shaft according to the magnitude of the torque. And a magnetostrictive torque sensor that detects the magnitude of torque.

[0002]

2. Description of the Related Art FIG. 8 shows a cross section of a magnetostrictive sensor 41 of this type provided on a shaft 40, which is a shaft to be detected, along the central axis of the shaft 40. The magnetostrictive sensor 41 includes a detection target 4 provided on the outer peripheral surface of the shaft 40.
2 and the shaft 4 on the same rotation axis as the shaft 40.
And a detection unit 43 supported so as to be able to rotate relative to zero. A pair of magnetostrictive regions 44 and 45 are provided on the outer peripheral surface of the detected portion 42 along the central axis thereof. The detection unit 43 includes a pair of primary coils 46 provided at positions opposed to the respective magnetostrictive regions 44 and 45, and a secondary coil 47 provided as a pair with each of the primary coils 46. Each primary coil 46 and secondary coil 47 are supported by a cylindrical yoke 48 made of a magnetic material such as permalloy. The yoke 48 is connected to the shaft 40.
Are supported so as to be relatively rotatable with respect to. The magnetostrictive torque sensor 41 includes a primary coil 46 and a secondary coil 47.
Have a mutual inductance with the magnetic permeability of each of the magnetostrictive regions 44 and 45 as a factor.

An AC current is supplied from an oscillator to each of the primary coils 46, and an induced electromotive force is excited in each of the secondary coils 47 through the respective magnetostrictive regions 44 and 45. Shaft 4
When no torque is applied to zero and the shaft 40 is not twisted, the difference between the two output voltages output from the secondary coils 47 is zero. When torque is applied to the shaft 40 and the shaft 40 is twisted,
The difference between the two output voltages is a magnitude corresponding to the amount of twist of the shaft 40, that is, the magnitude of the torque applied to the shaft 40.

[0004] The magnitude of the induced electromotive force excited in each secondary coil 47 increases as the mutual inductance between the primary coil 46 and the secondary coil 47 increases. Therefore, to increase the detection sensitivity of the magnetostrictive torque sensor 41, it is necessary to increase the mutual inductance. For this reason, the yoke 48 is arranged such that its inner peripheral surface is close to each of the magnetostrictive regions 44 and 45 and each primary coil 46 so as to minimize the air gap between the detected portion 42 and the detecting portion 43. The secondary coil 47 is housed in a circumferential groove 49 provided on the inner peripheral surface of the yoke 48 at a position facing each of the magnetostrictive regions 44 and 45.

FIG. 9 shows a cross section perpendicular to the center axis of the yoke 48. As described above, the circumferential groove 4 in which the primary coil 46 and the secondary coil 47 are formed on the inner circumferential surface of the yoke 48
9, the yoke 48 is formed by combining a semi-cylindrical yoke forming member 50. Then, at the time of assembling the yoke forming member 50, the primary coil 46 and the secondary coil 47 are assembled into the circumferential grooves 49 formed.

Further, the two yoke forming members 50 are connected to the yoke 4
In order to fix and hold the yoke 48 in the state where the yoke 48 is formed,
A cylindrical fixed holding member 51 is fitted to the outside. The fixed holding member 51 is formed of a synthetic resin having flexibility so as to be easily fitted to the yoke 48, for example, a fluorine resin or the like. Since the yoke 48 is formed by connecting the pair of yoke forming members 50 in the circumferential direction, a magnetic flux from the primary coil 46 is generated in the yoke 48 between the circumferentially opposite end surfaces of the respective yoke forming members 50. An insulating member 52 for reducing eddy current is interposed.

[0007]

However, there is a large difference between the coefficient of thermal expansion of the synthetic resin forming the fixed holding member 51 and the coefficient of thermal expansion of the magnetic material forming the yoke 48. Therefore, when the ambient temperature rises beyond a certain limit, the combined yoke forming members 50 are not fixed and held in the cylindrical shape by the fixed holding member 51. The two yoke forming members 50 may be displaced in the radial direction of the shaft 40, or each yoke forming member 50 may be inclined with respect to the shaft 40. In such a case, the mutual inductance between each primary coil 46 and the secondary coil 47 changes from the initial value. Therefore, when the ambient temperature rises, there is a problem that the output voltage output from each secondary coil 47 includes an error based on the variation of the mutual inductance, and the detection sensitivity and the detection accuracy decrease.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a magnetostrictive torque sensor in which a yoke is formed by a plurality of yoke forming members. An object of the present invention is to suppress fluctuations in detection sensitivity and detection accuracy caused by expansion and contraction of a yoke forming member.

[0009]

According to a first aspect of the present invention, there is provided a magnetostrictive region closed in a circumferential direction along an outer peripheral surface of a shaft to be detected where torque is detected. A yoke formed by connecting a plurality of yoke forming members in the circumferential direction of the detected shaft so as to be rotatable relative to the detected shaft and not to be relatively movable in the direction of the central axis; In the magnetostrictive torque sensor in which a primary coil and a secondary coil which are fitted to the magnetostrictive region at positions opposite to the yoke are supported by the yoke, the respective yoke forming members are independent of expansion and contraction of the respective yoke forming members due to a temperature change. The yoke forming members are connected by fixed holding means for fixing and holding the yoke forming members so as not to be displaced from each other in the radial direction and the central axis direction of the detected shaft.

According to a second aspect of the present invention, in the first aspect, the fixing and holding means is a welded portion for joining the yoke forming members at their outer peripheral surfaces. The invention according to claim 3 is the invention according to claim 1,
The fixed holding member is formed of a metal having substantially the same thermal expansion coefficient as the yoke forming member in a cylindrical shape, and is fixedly fitted to each of the yoke forming members assembled in a cylindrical shape to form the yoke. It is.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the primary coil and the secondary coil are formed on a peripheral surface formed on an inner peripheral surface of the yoke. Supported in the groove.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the circumferentially opposed end faces between the respective yoke forming members connected in the circumferential direction. An insulating member was interposed between them.

(Operation) According to the first aspect of the present invention,
Even when the temperature of each of the plurality of yoke forming members forming the yoke fluctuates and each yoke forming member expands and contracts in the circumferential direction and the central axis direction of the yoke, each yoke forming member is moved around the detection shaft by the fixed holding means. It is fixed and held so as not to be displaced from each other in the direction and the central axis direction. Therefore, even if each yoke forming member expands and contracts in the circumferential direction and the central axis direction due to a temperature change, the form of the yoke formed by each yoke forming member is maintained.
As a result, the variation based on the temperature change of the mutual inductance between each primary coil and the secondary coil is suppressed.

According to the invention described in claim 2, according to claim 1,
In addition to the operation of the invention described in the above, the respective yoke forming members are fixed and held at the welded portions joining the outer peripheral surfaces of the respective yoke forming members so as not to shift in the circumferential direction and the axial direction.

According to the invention described in claim 3, according to claim 1 of the present invention,
In addition to the effects of the invention described in (1), each yoke forming member is fixed and held in a state where the yoke is formed by a cylindrical fixed holding member formed of a metal having substantially the same thermal expansion coefficient as the yoke forming member. Therefore, the assembly of the yoke and the yoke need only fit the fixed holding member outside. Here, the fact that the thermal expansion coefficients are substantially equal means that the thermal expansion coefficient of the yoke forming member is approximately 10 times or less than that of the fixed holding member, or approximately 1/10.

According to the invention described in claim 4, according to claim 1 of the present invention,
In addition to the effects of the invention described in any one of claims 3 to 3, a magnetic path formed of a magnetic material having a high magnetic permeability is formed on both sides of each of the primary coil and the secondary coil in the central axis direction. . Therefore, the mutual inductance between each primary coil and the secondary coil increases.

According to the invention described in claim 5, according to claim 1,
5. In addition to the effect of the invention according to any one of claims 4 to 4, in the yoke formed by the yoke forming members, the inner peripheral side portion where the magnetic flux density is higher than the outer peripheral side is each of the yokes. It is circumferentially insulated between the forming members.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 3 shows a magnetostrictive torque sensor (hereinafter referred to as a torque sensor) 2 provided on a shaft 1 as a shaft to be detected.
2 shows a cross section of the shaft 1 along the central axis.
The shaft 1 is rotatable relative to the tube 3 in a cylindrical tube 3 fixed and held in a non-rotating state by a pair of bearings 4 supported on the inner peripheral surface of the tube 3. Supported. The torque sensor 2 includes a cylindrical detection part 5 fitted into the shaft 1 and the tube 3 at a position facing the detection part 5 in the tube 3.
And a detection unit 6 which is supported by a fixing means (not shown) so as not to rotate relatively.

The detected part 5 has a cylindrical core material 7 fitted on the shaft 1 and a magnetostrictive layer 8 is formed on the outer peripheral surface of the core material 7 by means such as thermal spraying in a state of being closed in the circumferential direction. Have been. The magnetostrictive layer 8 is provided with a pair of magnetostrictive regions 9 and 10 provided in a closed state in the circumferential direction of the shaft 1 and provided side by side in the central axis direction. A plurality of grooves 9a are formed in one magnetostrictive region 9 so as to form an angle of 45 ° in the direction of the central axis and impart magnetic anisotropy to the magnetostrictive region. Are formed in the magnetostrictive region 10 so as to provide magnetic anisotropy in a direction perpendicular to the magnetostrictive region 9. When the shaft 1 is twisted in one of the clockwise direction and the counterclockwise direction, each of the magnetostrictive regions 9 and 10 has a high magnetic permeability in one of the magnetostrictive regions 9 and a low magnetic permeability in the other magnetostrictive region 10. When the shaft 1 is twisted in either the clockwise direction or the counterclockwise direction, the magnetic permeability of one magnetic region 9 decreases and the other magnetostrictive region 1
0 is formed to have a high magnetic permeability.

The detecting section 6 includes a pair of primary coils 11 and 13 and secondary coils 12 and 14 which are externally fitted to the detected section 5 at positions corresponding to the magnetostrictive regions 9 and 10, respectively, at the same central axis as the shaft 1. A cylindrical yoke 15 is provided for support. The yoke 15 is supported by a pair of bearings 16 supported on the shaft 1 on both sides of the detected portion 5.
A pair of support members 17 supported so as to be relatively rotatable with respect to the center axis and relatively unmovable in the direction of the center axis are rotatable relative to the shaft 1 on the same center axis as the shaft 1 and the center axis. It is supported so that it cannot move relative to the direction.

On the inner peripheral surface of the yoke 15, a circumferential groove 18 is formed at a position facing the magnetostrictive region 9, and a circumferential groove 19 is formed at a position facing the magnetostrictive region 10. In the circumferential groove 18,
A secondary coil 12 is housed on the bottom side of the secondary coil 1.
The primary coil 11 is housed inside the 2. Circumferential groove 1
9, a secondary coil 14 is accommodated on the bottom side, and a primary coil 13 is accommodated inside the secondary coil 14.

FIG. 1 shows a perspective view of the detection unit 6, and FIG. 2 shows a cross section perpendicular to the center axis of the yoke 15. FIG.
As shown in FIG. 2, the yoke 15 includes a plurality of yoke forming members 2 connected in the circumferential direction of the shaft 1 and having the same shape.
0. In the present embodiment, the yoke 15 is formed by two yoke forming members 20. Between the circumferentially opposed end surfaces 20a of the two yoke forming members 20 connected in the circumferential direction, a film-shaped insulating member 2 is provided.
1 is interposed. The two yoke forming members 20 are connected by a plurality of welded portions 22 as fixed holding means for joining the outer peripheral surfaces 20b so as to connect the opposed end surfaces 20a.

A known oscillator (not shown) for supplying an alternating current to each of the primary coils 11, 13 is connected to each of the primary coils 11, 13, and each of the secondary coils 12, 14 is provided with a magnetostrictive region 9, 10. A known output voltage processing circuit (not shown) for detecting the magnitude of the torque applied to the shaft 1 from the potential difference between each induced electromotive force excited in each of the secondary coils 12 and 14 is connected thereto.

Next, the operation of the magnetostrictive torque sensor configured as described above will be described. When an alternating current is supplied from the oscillator to each of the primary coils 11 and 13, a magnetic flux is generated from each of the primary coils 11 and 13. The magnetic flux generated from the primary coil 11 returns from the yoke 15 to the yoke 15 through the magnetostrictive region 9. An induced electromotive force is excited in each secondary coil 12 by this magnetic flux. The magnetic flux generated from the primary coil 13 passes from the yoke 15 through the magnetostrictive region 10 to the yoke 1
Return to 5. An induced electromotive force is excited in the secondary coil 14 by this magnetic flux.

When no torque is applied to the shaft 1, no distortion occurs in each of the magnetostrictive regions 9 and 10.
The magnetic permeability of each of the magnetostrictive regions 9 and 10 has not changed from the initial value. Therefore, the potential difference between the induced powers becomes zero, and it is detected that the torque applied to the shaft 1 is zero.

When a clockwise or counterclockwise torque is applied to the shaft 1, the shaft 1 twists clockwise or counterclockwise. Then, one of the two magnetostrictive regions 9 (10) has a higher magnetic permeability and the other magnetostrictive region 10 (or 9) has a lower magnetic permeability. Therefore, of the two secondary coils 12, 14, one of the secondary coils 12 (or 14) is excited with a larger induced electromotive force, and the other secondary coil 14 (or 12) is excited with a smaller induced electromotive force. Is excited.
Therefore, the output voltage processing circuit detects the direction and magnitude of the torque applied to the shaft 1 from the potential difference between the two induced electromotive forces.

When the ambient temperature rises, each yoke forming member 2
When the temperature of 0 rises, each yoke forming member 20 extends in the circumferential direction and the central axis direction. At this time, since the two yoke forming members 20 are connected by the plurality of welds 22 joining their outer peripheral surfaces, the two yoke forming members 20 are fixed and held without being shifted from each other in the circumferential direction and the central axis direction. You. Therefore, even if each yoke forming member 20 expands and contracts due to a temperature change due to a change in ambient temperature, each yoke forming member 2
The shape of the yoke 15 formed at 0 is maintained in a state that does not substantially change. For this reason, each mutual inductance between the primary coil 11 and the secondary coil 12 and between the primary coil 13 and the secondary coil 14 does not easily change.

When a magnetic flux is excited in the yoke 15 by each of the primary coils 11, 13, an eddy current flows in the yoke 15 in the circumferential direction. However, between the circumferential end surfaces 20a of the respective yoke forming members 20 is insulated by the insulating member 21 and the welded portions 22 are provided on the outer peripheral surface 20b of the respective yoke forming members 20 having a smaller magnetic flux density than the inner peripheral side. Therefore, the eddy current generated in the yoke 15 is reduced as compared with the yoke formed integrally. Therefore, the eddy current loss becomes equal to that of the conventional magnetostrictive torque sensor 41.

As described in detail above, according to the magnetostrictive torque sensor of the present embodiment, the following effects can be obtained. (A) Even if each yoke forming member 20 forming the yoke 15 expands and contracts in the circumferential direction and the central axis direction of the yoke 15 due to a temperature change, the respective yoke forming members 20 are fixed to each other by the fixing and holding means (welded portion 22). It is fixed and held so as not to shift in the direction and the center axis direction. Therefore, each yoke forming member 2
Even if the temperature of 0 changes, the shape of the yoke 15 is maintained in a state where it hardly changes, so that a change in each mutual inductance between each primary coil 11 (13) and the secondary coil 12 (14) is suppressed. You. As a result, fluctuations in detection sensitivity and detection accuracy due to temperature changes are suppressed.

(B) Outer peripheral surface 2 of each yoke forming member 20
0b are joined together at the welded portion 22 to form the yoke 15. Therefore, since a member for fixing and holding each yoke forming member 20 is not required, the number of components can be reduced.

(C) Since the primary coil 11 (13) and the secondary coil 12 (14) are supported in the circumferential grooves 18 and 19 formed on the inner peripheral surface of the yoke 15, the yoke 1
5 is supported at a position close to the detected shaft (shaft 1). Therefore, the primary coil 11 (13) and the secondary coil 12
Since the mutual inductance between (14) and (14) increases, the detection sensitivity is improved.

(D) Each of the yoke forming members 20 is insulated between the end surfaces 20a facing each other in the circumferential direction, and the welded portion 22 is provided on the outer peripheral surface 20b having a relatively small magnetic flux density. Therefore, the eddy current loss generated in the yoke 15 can be suppressed to be equal to that of the conventional magnetostrictive torque sensor 41, and the detection sensitivity can be prevented from lowering.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the present embodiment is different from the first embodiment in that the welding portion 22 is replaced with a fixed holding member 30 in the first embodiment. Therefore, the same reference numerals are used for the other same components, and the description is omitted.

FIG. 4 shows a perspective view of the detector 6, and FIG. 5 shows a cross section perpendicular to the central axis. The two yoke forming members 20 are formed between the end surfaces 20a of the respective yoke forming members 20 facing each other in the circumferential direction.
In this state, a fixed holding member 30 as a fixed holding means formed of metal and having the same length as each yoke forming member 20 in a cylindrical shape is externally fitted. This fixed holding member 30
Is formed of a metal having a coefficient of thermal expansion substantially equal to that of each yoke forming member 20, for example, a metal material such as stainless steel. Here, that the thermal expansion coefficients are substantially equal means that the yoke forming member 20 has a thermal expansion coefficient
Is about 10 times or less than about one tenth of the thermal expansion coefficient.

According to this embodiment, when the temperature of each yoke forming member 20 rises and each yoke forming member 20 expands and contracts in the circumferential direction and the contact direction, the coefficient of thermal expansion is equal to that of each yoke forming member 20. The fixed holding member 30 extends and contracts with each yoke forming member 20. Then, each yoke forming member 2
0 are fixedly held by the fixed holding member 30 without being shifted from each other in the circumferential direction and the central axis direction. Therefore, even if each yoke forming member 20 expands and contracts due to a temperature change, the yoke 15
Is maintained in a state in which the shape of is substantially unchanged. For this reason,
Variations in the mutual inductance between each primary coil 11 (13) and secondary coil 12 (14) are suppressed.

Further, both end surfaces 20a of the two yoke forming members 20 facing each other in the circumferential direction are insulated by an insulating member 21, and the fixed holding member 30 is fitted on the outer peripheral surface 20b having a small magnetic flux density. . For this reason, the eddy current generated in the yoke 15 is reduced as compared with the yoke formed integrally, and the eddy current loss is reduced.
It is equivalent to 1.

As described in detail above, according to the magnetostrictive torque sensor of this embodiment, (a) and (b) of the first embodiment
The following effects can be obtained in addition to the effects described in (c) and (d).

(A) A fixed holding member 30 formed of a metal having substantially the same thermal expansion coefficient as that of each yoke forming member 20 in a cylindrical shape is externally fitted to each of the yoke forming members 20 combined in a cylindrical shape. Is formed. Therefore, assemblability can be improved as compared with the case where the yoke forming members 20 are welded to each other.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. Note that the present embodiment is different from the first embodiment in that the welded portion 22 is replaced with a connection by a ridge 32 provided on each yoke forming member 31 in the first embodiment. Accordingly, the same reference numerals are used for the other same components, and the description is omitted.

FIG. 6 shows a perspective view of the detector 6, and FIG. 7 shows a cross section perpendicular to the central axis. The outer peripheral surface of each yoke forming member 31 has an end surface 31a in its circumferential direction.
Is provided along the center axis direction of the ridge portion 32. The two yoke forming members 31 are connected to each other by a fixing screw 33 that penetrates both insertion holes (not shown) provided in each of the protrusions 32 and a nut 34 that is screwed to the fixing screw 33. A film-shaped insulating member 35 is interposed between the end faces 31a of the two yoke forming members 31 that are opposed to each other in the circumferential direction. In the present embodiment, the fixing and holding means is constituted by the ridge 32, the fixing screw 33 and the nut 34.

According to this embodiment, even if the temperature of each yoke forming member 31 rises and each yoke forming member 31 expands and contracts in the circumferential direction and the center axis direction, each yoke forming member 31 does not expand.
Are connected, the respective yoke forming members 31 are fixed and held without shifting in the circumferential direction and the central axis direction. Therefore, even if each of the yoke forming members 31 expands and contracts due to a temperature change, the shape of the yoke 15 is maintained in a state where it is substantially unchanged. Therefore, each primary coil 11 (1
The change in mutual inductance between 3) and the secondary coil 12 (14) is suppressed.

Further, the end faces 31a of the two yoke forming members 31 which are opposed to each other in the circumferential direction are insulated by the insulating member 35, and the fixing screw 33 and the nut 34 are provided on the outer peripheral surface having a small magnetic flux density. The eddy current generated in the yoke 15 is smaller than that of the yoke formed integrally, and the eddy current loss becomes equal to that of the magnetostrictive torque sensor 41 of the conventional example.

As described in detail above, according to the magnetostrictive torque sensor of this embodiment, (a) and (b) of the first embodiment are used.
The following effects can be obtained in addition to the effects described in (c) and (d).

(A) By connecting the ridges 32 provided so that the respective yoke forming members 31 extend along the circumferential end surfaces 31a of the respective yoke forming members 31 by means of fixing screws 33 and nuts 34, Be linked. As a result, fluctuations in detection sensitivity and detection accuracy due to temperature changes are suppressed.

(B) A ridge 3 provided on the outer peripheral surface of the yoke 15 on the inner peripheral surface of the shaft support member to be detected such as the tube 1.
2 is provided with an engaging portion which can be engaged, and by engaging the ridge portion 32 with the engaging portion, the detecting portion 6 can be fixed to the detected shaft support member so as not to be relatively rotatable. Therefore, it is not necessary to newly provide a component for restricting the relative rotation of the detector 6 in the detector 6.

The embodiment is not limited to the above embodiment, but may be modified as follows. In the first embodiment, the number of the welded portions 22 connecting the two yoke forming members 20 at one joint of the both yoke forming members 20 is not limited to two, and may be one or three or more. .

Further, both yoke forming members 20 may be welded to both outer peripheral surfaces 20b over the entire end surface 20a. In this case, the strength of the weld is improved, and the fixing reliability over a long period is improved.

The welding portion 22 is formed of the two yoke forming members 20.
May be fused to the outer peripheral surface 20b of each yoke forming member 20, or may be a brazing portion made of a brazing material.

In the first embodiment, the insulating member 21 is provided between the end faces 20a of the yoke forming members 20 facing each other.
The outer peripheral surfaces 20b of the yoke forming member 20 may be welded to each other in a state where only a gap is provided without interposing a gap. In this case, while the eddy current loss in the yoke 15 is equal to that of the conventional example, the number of parts can be reduced by the amount of the two insulating members 21.

In the second embodiment, the yoke 1 is fixed by the fixed holding member 30 that fits over the entirety of the two yoke forming members 20.
The yoke forming member 20 may be fixedly held by externally fitting a plurality of fixed holding members having a shorter length in the central axis direction than the respective yoke forming members 20. . Also in this case, each effect of the second embodiment can be obtained, and the outer fitting to the yoke 15 becomes easy.

In the third embodiment, instead of the ridge 32 extending along the end face 31a in the circumferential direction of each yoke forming member 31, a ridge formed only along a part of the end face 31a. May be provided to connect the corresponding ridges of both yoke forming members 31 to each other.

In the third embodiment, the ridges 32 formed on the circumferential end surfaces of the respective yoke forming members 31
As in the embodiment, each yoke forming member is not limited to a ridge formed to protrude radially from the outer circumferential surface of each yoke forming member 31 forming the cylindrical outer circumferential surface of the yoke 15. A protrusion formed along the end surface 31a by a groove formed so as to extend in parallel with the end surface 31a at a position retracted from the end surface 31a of the base 31 may be used.
In this case, by accommodating the fixing screw 33 and the nut 34 in the groove, the connecting portion can be prevented from protruding from the outer peripheral surface of the yoke 15.

In the third embodiment, the method of connecting and fixing the protruding portions 32 is not limited to the method using the fixing screw 33 and the nut 34, but may be a method of connecting and fixing using rivets, caulking, bonding or the like. .

In each embodiment, both yoke forming members 2
The two yoke forming members 20 (3) are in a state in which the end surfaces 20a (31a) are directly in contact with each other without interposing the insulating member 21 (34) between the opposing end surfaces 20a (31a) of the pair 0 (31).
1) may be combined.

In each embodiment, the yoke 15 is not directly rotatably supported on the detected shaft by the bearing 16 supported on the detected shaft (shaft 1), but is supported on the detected shaft. A magnetostrictive torque sensor configured to be supported by a support member such as the tube 3 may be used. Also according to this configuration, each effect described in each embodiment can be obtained.

In each embodiment, the yoke may be formed by three or more yoke forming members. At this time, each yoke forming member does not have to have the same shape.

In each embodiment, a magnetostrictive layer may be formed directly on the outer peripheral surface of the shaft to be detected by means such as thermal spraying, and a magnetostrictive region may be formed in the magnetostrictive layer. In this case, the size of the magnetostrictive torque sensor can be reduced in the radial direction of the detected shaft.

In each embodiment, the primary coil 11 (1
3) and the secondary coil 12 (14) are mounted in the yoke from one opening of the yoke formed by the two yoke forming members, and abut on a step formed on the inner peripheral surface of the yoke. Thus, the magnetostrictive torque sensor may be configured to be positioned. Also in this case, each effect in each embodiment can be obtained, and the assemblability is improved.

Each of the magnetostrictive regions is a smooth magnetostrictive region having no groove for forming magnetic anisotropy on its surface, and a crosshead type pickup detects a torque applied to a detected shaft based on the magnetic permeability of each magnetostrictive region. The present invention may be applied to a magnetostrictive torque sensor having such a configuration.

Hereinafter, in addition to the technical idea described in the claims, the technical idea grasped from each of the above embodiments will be described together with its effects. (1) In the magnetostrictive torque sensor according to any one of claims 1 to 5, the yoke is supported to be relatively rotatable with respect to the detected shaft via a bearing. According to such a configuration, the detection accuracy is improved as compared with the case where the yoke is directly supported by the detected shaft support member such as a tube.

(2) In a yoke for a magnetostrictive torque sensor formed by connecting a plurality of yoke forming members in a circumferential direction of a center axis, each of the yoke forming members expands and contracts due to a temperature change. Irrespective of the above, the respective yoke forming members are connected by fixed holding means for fixing and holding the respective yoke forming members so as not to be shifted from each other in the central axis direction and the radial direction. According to such a configuration, a change in the form of the yoke due to expansion and contraction of each yoke forming member due to a temperature change is suppressed.

(3) In the yoke for a magnetostrictive torque sensor according to the above (2), the fixed holding means is a welded portion for joining the yoke forming members at their outer peripheral surfaces. According to such a configuration, one component forming the yoke is unnecessary, and the number of components is reduced.

(4) In the magnetostrictive torque sensor according to the above (2), the fixed holding means is formed in a cylindrical shape with a metal having substantially the same coefficient of thermal expansion as the yoke forming member, and is assembled in a cylindrical shape. And a fixed holding member which is fitted to each of said yoke forming members. According to such a configuration,
The assemblability can be improved as compared with the case where the yoke forming member is welded.

In this specification, means and members according to the present invention are defined as follows. (1) The magnetostrictive region is formed in a state of being closed in the circumferential direction along the outer peripheral surface of the detected shaft from which the torque is detected, and the magnetostrictive effect in which the magnetic permeability changes according to the twist of the detected shaft. As long as the magnetostrictive layer is formed so as to have a magnetic layer directly formed on the outer peripheral surface of the shaft to be detected by means such as thermal spraying, or a cylindrical core externally fitted to the shaft to be detected. It may be composed of a magnetic layer formed on the outer peripheral surface of the material.

[0066]

According to the first to fifth aspects of the present invention, in the magnetostrictive torque sensor in which the yoke is formed by a plurality of yoke forming members, the expansion and contraction of each yoke forming member due to a temperature change. The resulting fluctuations in detection sensitivity and detection accuracy are suppressed.

According to the second aspect of the present invention, no component for fixing and holding each yoke forming member is required, and the number of components is reduced. According to the third aspect of the present invention, assemblability can be improved as compared with the case where each yoke forming member is welded.

According to the present invention, the mutual inductance between the primary coil and the secondary coil can be increased to improve the detection sensitivity. According to the fifth aspect of the present invention, the eddy current loss in the yoke can be suppressed to the same level as in the conventional example, thereby preventing the detection sensitivity from lowering.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a yoke according to a first embodiment.

FIG. 2 is a sectional view of a yoke.

FIG. 3 is a sectional view of a magnetostrictive torque sensor.

FIG. 4 is a perspective view showing a yoke according to a second embodiment.

FIG. 5 is a sectional view of a yoke.

FIG. 6 is a perspective view showing a yoke according to a third embodiment.

FIG. 7 is a sectional view of a yoke.

FIG. 8 is a sectional view showing a conventional magnetostrictive torque sensor.

FIG. 9 is a sectional view of a yoke.

[Explanation of symbols]

Reference numeral 1 denotes a shaft as a detected shaft; 6 denotes a detection unit;
... Magnetostrictive region, 11, 13 ... Primary coil, 12, 14 ... Secondary coil, 15 ... Yoke, 20 ... Yoke forming member, 20
a ... end face, 21 ... insulating member, 22 ... welded part as fixed holding means, 30 ... fixed holding member as fixed holding means,
Reference numeral 32 denotes a ridge forming a fixing and holding means, 33 denotes a fixing screw, 34 denotes a nut, and 35 denotes an insulating member.

Claims (5)

[Claims] 1. A magnetostrictive region closed in a circumferential direction is provided along an outer peripheral surface of a shaft to be detected from which torque is detected, and a plurality of yoke forming members are connected in a circumferential direction of the shaft to be detected. The yoke includes a primary coil and a secondary coil which are rotatably supported with respect to the detected shaft and which are not movable relative to the center axis direction, and which are fitted to the magnetostrictive region at positions corresponding to the magnetostrictive region. In the magnetostrictive torque sensor supported by the above, the respective yoke forming members are not displaced from each other in the radial direction and the center axis direction of the detected shaft regardless of expansion and contraction of the respective yoke forming members due to a temperature change. A magnetostrictive torque sensor connected by fixed holding means for fixedly holding the respective yoke forming members. 2. The fixing and holding means is a welded portion for joining the respective yoke forming members at their outer peripheral surfaces.
3. The magnetostrictive torque sensor according to claim 1. 3. The fixing and holding means is formed in a cylindrical shape with a metal having substantially the same thermal expansion coefficient as the yoke forming member,
The magnetostrictive torque sensor according to claim 1, wherein the magnetostrictive torque sensor is a fixed holding member externally fitted to each of the yoke forming members assembled in a cylindrical shape. 4. The magnetostrictive torque sensor according to claim 1, wherein the primary coil and the secondary coil are supported in a circumferential groove formed on an inner peripheral surface of the yoke. . 5. The insulating member according to claim 1, wherein an insulating member is interposed between the circumferentially opposed end faces of the yoke forming members connected in the circumferential direction. Magnetostrictive torque sensor.