JPH0462444A - Torque transducer - Google Patents

Abstract

PURPOSE:To enable highly accurate detection and prevent an electromagnetic shield means and a fixed housing from being shielded electrically by holding a rotary shaft, equipped with a ferromagnetic magnetostrictive means which varies magnetic permeability according to torque, on a fixed housing member through a bearing means, and providing an electromagnetic shield means with a ground connection projection part for rotation prevention. CONSTITUTION:When the torque operates on the rotary shaft 10, annular belts 12 and 14 of the ferromagnetic magnetostrictive means vary in magnetic permeability and a magnetic field varies, so that the magnitude of the torque is detected. Ball bearings 30 and 32 are interposed between the shaft 10 and fixed housing member 26 to prevent relative deflection substantially. An electromagnetic shield case 44, on the other hand, is held on the member 26 fixedly in the axial direction and radial direction and a rotation stop projection part 86 connects the case 44 to an earth wire and also prevent the case 44 from rotating in the circumferential direction. This constitution enables the highly accurate torque detection and prevent the electromagnetic shield case and fixed housing member from being shielded electrically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to improvements in non-contact magnetoelastic torque transducers that provide measurements of torque acting on a rotating shaft.

[Prior Art] As an example of a non-contact magnetoelastic torque transducer that provides a measured value of torque acting on a rotating shaft, Japanese Patent Laid-Open No. 6
Examples include those disclosed in Japanese Patent No. 3-252487.

To explain this with reference to FIG. 9, which is a longitudinal cross-sectional view of the central part, and FIG. 10, which is a circuit diagram, a and b are annular bands having mutually symmetrical magnetic anisotropy in the spiral direction. They are provided on the surface of the rotating shaft C so as to be spaced apart in the axial direction.

This annular band is surrounded by bobbins d and e coaxial with the rotation axis C, and a pair of coils fg and i are attached to the bobbins d and e.
is installed. Of these, f and h are exciting coils connected in series and driven by alternating current, and g and i are
These are sensing coils connected in opposite directions that sense the difference in magnetic flux between two annular bands. Also, j is a ferrite material core.

Excitation coils f and h are supplied with power from AC power source k, and the electromotive force induced in sensing coils g and i connected in opposite directions is:
It is phase-sensitively rectified by a rectifier m and displayed on a voltage display n. The black dots in FIG. 10 indicate the polarity of the coil.

When no torque is applied to the rotating shaft C, the stresses in the annular bands a and b are symmetrical and equal, so even if an alternating current is applied to the excitation coils f and h, the output signal of the rectifier m is substantially the same. Does not occur.

However, when torque is applied to the rotation axis C,
The annular bands a, b are subjected to tensile and compressive stresses, respectively, so that the magnetic permeability in one annular band increases and in the other it decreases. Therefore, the magnetic flux through one annular band increases and decreases in the other, and the voltage induced in one sensing coil exceeds the induced voltage in the other. As a result, an output signal corresponding to the induced voltage difference, ie proportional to the applied torque, is obtained, which is converted by the rectifier m into a DC voltage corresponding to the torque value. The polarity of this rectifier output determines the direction of the applied torque.

[Problem to be Solved by the Invention 1] Since the torque transducer described above detects the torque value in a non-contact state with respect to the rotating shaft, it is possible to accurately detect the torque value acting on the rotating shaft. In addition, it is necessary to keep the vibration of the rotating shaft relative to the excitation coil and sensing coil to a sufficiently small level. In addition, if the excitation coil or sensing coil is subjected to thermal stress due to temperature changes or due to the accumulation of tolerances of each component, fitting stress exceeding a certain level may occur, or if the rotating shaft is affected by deformation, displacement, vibration, etc. Exceeding a certain level will have a negative effect on the accuracy of torque value detection.

However, in the past, sufficient solutions have not always been provided for this problem.

The present invention has been made in view of the above-mentioned problems existing in the prior art, and its purpose is to keep the vibration of the rotating shaft relative to the excitation coil and the sensing coil to a sufficiently small level, and to This prevents thermal stress due to temperature changes and fitting stress due to accumulation of tolerances of each part from exceeding a certain degree, or from being affected by deformation, displacement, vibration, etc. of the rotating shaft beyond a certain degree. An object of the present invention is to provide a torque transducer that can accurately detect a torque value acting on a rotating shaft.

[Means for Solving the Problems] In order to achieve the above object, the torque transducer of the present invention is provided with a ferromagnetic material that is provided on a rotating shaft and whose magnetic permeability changes in response to the torque acting on the rotating shaft. a magnetostrictive means; a magnetic field applying means for applying a magnetic field to the ferromagnetic magnetostrictive means; and a magnetic field applying means that senses a change in permeability caused by a torque acting on the rotating shaft and converts it into an electric signal corresponding to the magnitude of the torque. and a sensing means for rotating the rotating shaft via a bearing means so as to substantially prevent relative wobbling of at least a portion of the rotating shaft where the sensing means senses a change in magnetic permeability of the ferromagnetic magnetostrictive means. A fixed housing member that freely holds the magnetic field applying means and the sensing means, and an electric Fin shielding means that securely holds the magnetic field applying means and the sensing means inside and shielding the electric field Ii3, and the magnetic field applying means and the sensing means are attached to the side wall part of the fixed housing member. A through hole is provided for leading out a conducting wire connected to the electromagnetic shielding means, and the electromagnetic shielding means is fixed via a relatively elastic holding member while the magnetic field applying means and sensing means are not in contact with the rotating shaft. The electromagnetic shielding means is provided with a protrusion that is held fixedly in the axial and radial directions by the housing member and protrudes into the through hole to prevent rotation of the electromagnetic shielding means in the circumferential direction with respect to the fixed housing member. It is assumed that the shielding means and the ground wire are connected through the protrusion.

[Function] When torque acts on the rotating shaft, the magnetic permeability of the ferromagnetic magnetostrictive means changes, and its influence extends to the magnetic field applied by the magnetic field applying means. From the change in the magnetic field, a sensing means senses the change in magnetic permeability and converts it into an electrical signal corresponding to the magnitude of the torque acting on the rotating shaft.

Of the ferromagnetic magnetostrictive means that changes the magnetic permeability in response to the torque acting on the rotating shaft, the relative position of the rotating shaft with respect to the fixed housing member, in which at least a portion that detects the change in magnetic permeability by the sensing means is provided. blurring is substantially prevented by interposing the bearing means between the rotary shaft and the fixed housing member, and the electromagnetic shielding means is held fixed in the axial and radial direction by the fixed housing member. The portion of the rotating shaft is substantially prevented from wobbling relative to the electromagnetic shielding means and the magnetic field applying means and sensing means fixedly held inside the electromagnetic shielding means.

The protrusion connects the electromagnetic shielding means and the ground wire, and prevents the 1i magnetic shielding means from rotating in the circumferential direction with respect to the fixed housing member, thereby making the detection of the torque value acting on the rotating shaft more stable. This also prevents damage to conductors and ground wires.

In addition, since the electromagnetic shielding means is fixedly held in the axial and radial directions by the fixed housing member via the relatively elastic holding member, thermal stress caused by temperature changes and tolerances caused by assembling each part are accumulated. The fitting stress due to si
(i) that the effects of deformation, displacement, vibration, etc. of the rotating shaft occurring on the shielding means, the magnetic field applying means and the sensing means are transmitted to the electromagnetic shielding means, the magnetic field applying means and the sensing means via the bearing and the fixed housing member; This will be suppressed by the holding member.

[Example] An example of the present invention will be described with reference to FIGS. 1 to 8.

Figures 1 to 6 show one of the torque transducers of the present invention.
1 is a vertical cross-sectional view of the central part, and FIG. 2 is an assembled view of the whole.

10 is a rotating shaft to which torque is applied. This axis of rotation lO is made of nickel maraging steel, that is, a ferromagnetic magnetostrictive material. Reference numerals 12 and 14 indicate annular bands that are spaced apart in the axial direction and have magnetic anisotropy in a spiral direction that is axially symmetrical to each other. The annular bands 12 and 14 having magnetic anisotropy in the helical direction are formed by a large number of spiral bands 12 and 14 formed on the side circumferential surface of the center of the rotating shaft 10 at an angle of +45 degrees and -45 degrees, respectively, with respect to the axis. This is done by forming a knurling which creates a residual stress. The strength of the magnetic anisotropy is sufficiently stronger than the disordered magnetic anisotropy that may exist in other parts of the rotation axis lO, so that the magnetic anisotropy in the other parts can be ignored. and each annular band 12 and 14 has at least 50% (preferably 80%) of its circumferential length in a peripheral area free of residual stress zones (the line of intersection of the plane perpendicular to the axis of the member and the surface of the member). In this embodiment, the magnetic permeability of the annular bands 12 and 14 that changes in response to the torque acting on the rotating shaft 10 is sensed. Further, this rotating shaft 10i is provided with a hollow portion 18 that penetrates in the axial direction.
Six radial oil supply holes 24 are provided in the axially outer annular portions 20 and 22 of each of the annular bands 12 and 14, respectively, to communicate the hollow portion 18 with the outside.

The ferromagnetic magnetostrictive material may be, for example, an iron-nickel martensitic hardenable steel such as a nickel maraging steel, or a material characterized by a substantially isotropic magnetostriction with an absolute value of at least 5 ppm and between 0.05 and 0. ,75% by weight
of carbon, and the magnetostriction of the alloy is at least 5 ppm in absolute value.
sufficient amounts of nickel, chromium, cobalt,
Mention may be made, for example, of thermally hardened steel alloys containing one or more elements selected from titanium, aluminum, manganese, molybdenum, copper and boron.

Note that the rotating shaft 10 does not necessarily need to be entirely made of ferromagnetic magnetostrictive material. For example, only the portion near the surface where the annular bands 12 and 14 are provided may be made of a ferromagnetic magnetostrictive material (or a ferromagnetic magnetostrictive material may be bonded to the surface in a band shape).

The residual stress inducing method for providing magnetic anisotropy may be mechanical, thermal, or any other suitable method. Methods for imparting magnetic directional characteristics induced by residual stress to desired locations on the rotating shaft include, for example, excessive torsional strain, knurling, grinding, mechanical scribing, directional or masked shot peening, or sanding. - Blasting, roll crushing, suitable chemical means, selective trajectory treatment, etc. may be mentioned. It is particularly desirable that the stress applied to induce residual stress be greater than the maximum stress expected to be applied to the part during use. This is to ensure that the residual window cover turn does not change due to the torque applied to the rotating shaft during use, and the magnetic anisotropy within the annular band does not change with it.

The orientation of the residual stress and the resulting easy axis of magnetization relative to the axis of the axis of rotation is symmetrical in both apex bands 12 and 14. The absolute value thereof is larger than 0 degrees (it can be in a range smaller than 90 degrees, but it is preferably 10 to 80 degrees. More preferably, it is 20 to 60 degrees. The annular bands 12 and 14
are preferably placed on a member of the same diameter and sufficiently close to each other to apply the same torque.

26 is a fixed housing member made of metal. This fixed housing member 26 has a substantially cylindrical shape, and has a through hole 28 provided in its side wall. A portion of the rotating shaft 10 that includes both apex bands 12 and 14 and both annular portions 20 and 22 provided with an oil supply hole 24 is inserted into the fixed housing member 26 . , the annular portions 20 and 22 are rotatably held by a fixed housing member 26 via ball bearings 30 and 32 in the axially separated state. 34 and 36 are outer rings of the ball bearing, 38 and 40 are inner rings, and 42 is a transfer sphere.

44 is an electromagnetic shielding case made of permalloy, ie, a high magnetic permeability material. 46 and 47 are bobbins for exciting coils, 48 are bobbin terminals for exciting coils, 50 are protrusions on which the bobbin terminals 48 for exciting coils are provided, 52 and 5
3 is a bobbin for a sensing coil, 54 is a bobbin terminal for a sensing fill, 56 is a notch, and 58 is a flexible circuit board. FIG. 3 shows an assembled drawing of these parts, and FIG. 4 shows a completed drawing thereof. The electromagnetic shielding case 44 is formed into two halves, and a pair of sensing coil bobbins 52 and 53 are adhesively fixed to the inside of the case while being spaced apart in the axial direction. 46
and 47 are adhesively fixed in a fitted state. Then, by fitting the protrusion 50 into the notch 56, the exciting coil bobbin terminal 48 and the sensing coil bobbin terminal 54 are arranged substantially in a straight line. In addition, the excitation coil bobbin 4
Excitation coils 60 and 61 are wound around the bobbins 6 and 47, respectively, and sensing coils 62 and 63 are wound around the sensing coil bobbins 52 and 53, respectively.

An annular holding member 64 made of polytetrafluoroethylene resin, which has more elasticity than the materials of the ILT&R shielding case 44 and the fixed housing member 26, is provided on the outer circumference of both axial ends of the electromagnetic shielding case 44 inside the fixed housing member 26.
It is held fixed in the axial and radial directions via. Further, the rotation of the electromagnetic shielding case 44 with respect to the fixed housing member 26 about the axis of the rotating shaft 10 is also controlled by the holding member 6.
This is temporarily prevented by the friction between 4 and 4. This holding member 6
4, the excitation coil 60 and sensing coil 62 and the excitation coil 61 and sensing coil 63 surround each of the annular bands 12 and 14 in a non-contact manner coaxially with the rotation axis lO. The cross-sectional shape of the holding member 64 is approximately hook-shaped, but by cutting out a part of the cross-section to reduce the cross-sectional area near the axial and radial contact portion, It is configured to be easily elastically deformed in the direction. The material of the holding member 64 must be able to absorb differences in expansion coefficients of each part due to temperature changes and tolerances of each part to some extent, and should be made in accordance with the purpose and location of use of this torque transducer. In order to avoid restrictions as much as possible, it is desirable that the material can withstand a certain degree of high temperature and have oil resistance.

It is also desirable that the material be insulating. In this embodiment, the cross-sectional shape of the holding member 64 is approximately hook-shaped as described above, but it has an annular flat plate-shaped portion along a plane perpendicular to the rotation axis and a cylindrical shape along the circumferential surface parallel to the rotation axis. Of course, there is no problem even if it is separated into two parts.

Fixed annular plates 66 and 67 made of a sintered metal, which is one of the porous materials, are fixed to the axially outer sides of the outer rings 34 and 36 of the double positive bearings 30 and 32, and a rotating shaft is fixed to the outer sides of these plates. The same rotating annular plates 68 and 69 made of sintered metal rotate integrally with the fixed annular plates 66 and 67.
It is provided so that it overlaps and slides in an annular shape. These rotating annular plate portions 68 and 69 and fixed annular plate portions 66 and 67 allow oil (liquid lubricant) supplied from the oil supply hole 24 to be delivered while preventing foreign matter from entering the ball bearings 30 and 32 from the outside. This constitutes seal devices 70 and 72 that prevent intrusion. On the axially outer side of the rotary annular plate portion 68 in one (left side in FIG. 1) of the sealing device 70, an annular retainer 74 with a hook-shaped cross section fixed to the rotary shaft 10 provides an elastic force such as a disc spring 76. Means is retained, thereby elastically pressing the inner side of the outer circumference of the rotating annular plate part 68 against the outer side of the inner circumference of the fixed annular plate part 66, thereby creating a gap so that the annular overlapping part 78 does not open too much. Adjustments are made. It is also possible at the same time to preload the ball bearings 30, 32 by means of this elastic means. Although the sealing device 72 on the right side of FIG. 1 is not provided with elastic means, it is of course possible to provide it on both sides.

In this embodiment, the gap adjustment of the annular overlapping portion 78 is performed under constant pressure preload. For example, as shown in FIG. The gap may be adjusted in this state. Alternatively, as shown in FIG. 8, for example, the rotating annular plate part 68 may be fixed to the ball bearing 30 side, and the fixed annular plate part 66 may be fixed to the fixed housing member 26 so as to overlap in an annular manner outward in the axial direction. Of course you can.

82 is a C ring fitted into the groove of the rotary shaft]O located on the axially outer side of the ball bearings 30 and 32; 84 is a C ring inserted between the left ball bearing 30 and the holding member 64 in FIG. This is an annular spacer.

86 is a detent made of a conductive material and has a screw hole passing through it. The flexible circuit board 58 is sandwiched between the detent 86 and the electromagnetic shielding case 44, and they are fixed by screws 88 made of a conductive material. As shown in the fifth section showing the overall plan view, each detent 86 is disposed so as to protrude into the through hole 28 and contact both ends of the through hole 28 in the circumferential direction. Circumferential rotation of the electromagnetic shielding case 44 with respect to the housing member 26 is prevented. 90 is a shielded cable, 92 is a lead wire, and 94 is a ground wire. The ground wire 94 is connected to the detent 86 and the screw 8
The lead wire 92 is electrically connected to the electromagnetic shielding case 44 through the cable 8, and the lead wire 92 is connected to key points on the flexible circuit board 58, and the shield cable 90 is led out through the through hole 28. There is. This shielded cable 90 is held by the fixed housing member 26 via a cable presser 96 fixed to the fixed housing member 26, and at the same time, the folded portion 97 of the shield in the shielded cable 90 and the fixed housing member 26 are held together by the cable presser 96. It is electrically connected via 96. 98 is a screw for tightening the cable holder 96; 100;
is a connector provided at the other end of the shielded cable 90. In addition, in FIG. 5, a shielded cable 90, a lead wire 92, a ground wire 94, a cable holder 96
The tightening screw 98 is omitted.

As shown in FIG. 6, which shows an example of a torque detection circuit diagram using the torque transducer of the present invention, the excitation coil 6
0 and 61 are connected in series in the same direction and driven by the alternating current fi 102, and the sensing coils 62 and 63 sense the difference in magnetic flux between the two annular bands 12 and 14.
They are connected in series in opposite directions. Excitation coil 60
and 61 are supplied with AC power #102, and the electromotive force induced in the sensing coils 62 and 63 connected in opposite directions is phase-sensitively rectified by the rectifier 104, and the voltage indicator 10
6. 108, rain sensing coils 62 and 63;
This is an adjustment line derived from between. The black dots indicate the polarity of the coil.

When no torque is applied to the rotation axis lO, the stresses in the annular bands 12 and 14 are symmetrical and equal, so even if an alternating current is applied to the excitation coils 60 and 61, the output signal of the rectifier 104 is substantially the same. Does not occur. In this case, the magnetic permeability in both the annular bands 12 and 14 is equal, and the voltages induced in the rain sensing coils 62 and 63 are equal in magnitude and opposite in polarity, and cancel each other out.

However, when torque is applied to the rotating shaft 10, the annular bands 12 and 14 are subjected to tensile and compressive stresses, respectively, so that the magnetic permeability in one of the annular bands 12 and 14 increases while the other annular band It decreases in the band. Therefore, the magnetic flux through one annular band increases and decreases in the other, and the voltage induced in one sensing coil exceeds the induced voltage in the other sensing coil. As a result, an output signal corresponding to that induced voltage difference,
That is, an output signal is obtained that is proportional to the applied torque. The output signal is converted by the rectifier lO4 into a DC voltage corresponding to the torque value. This rectifier 104
The polarity of the output determines the direction of the applied torque, i.e. clockwise or counterclockwise.

The rotary shaft 10 is rotatably held by the fixed housing member 26 via ball bearings 30 and 32 at both axially outer portions of the apex portions 20 and 22, so that at least the annular portion of the rotary shaft 10 Relative wobbling of the portions provided with the bands 12 and 14 with respect to the fixed housing member 26 is substantially prevented, and the electromagnetic shielding case 44 is held fixedly in the axial and radial direction by the fixed housing member 26. Therefore, the portion of the rotating shaft 10 is substantially prevented from wobbling relative to the electromagnetic shielding case 44 and the excitation coils 60 and 61 and the sensing coils 62 and 63 that are fixedly held inside the case.

The ball bearings 30 and 32 are lubricated from the oil supply hole 24 through the hollow part 18 of the rotating shaft 10 to the fixed housing member 2.
6, and the oil is passed through the raceways of the rolling balls 42 of the ball bearings 30 and 32, and then to the rotating annular plates 68, 69 made of sintered metal in the sealing devices 70 and 72 and/or This is ensured by passing the fixed annular plates 66, 67 made of bonded metal by penetration or by passing them through their annular overlap 78 and out of the fixed housing part 26. Furthermore, the seal devices 70 and 72 prevent foreign matter from entering the ball bearings 30 and 32 from the outside. Prevention of foreign matter intrusion is achieved by the annular polymerization part 78.
The gap adjustment can be made more reliable by performing the adjustment under constant pressure preload by the elastic means or under constant position preload by the annular holder.

Then, the electromagnetic shielding case 44 and the ground wire 94 are connected to each other by the detent 86 fixed in the through hole 28 by the nephew 88.
and the electromagnetic shielding case 44 is prevented from circumferentially rotating relative to the fixed housing member 26, thereby making the detection of the torque value acting on the rotating shaft 10 more stable, and also connecting the lead wire 92 and the ground. Damage to wire 94 is prevented.

Furthermore, as described above, the electromagnetic shielding case 44 is fixedly held in the axial and radial directions by the fixed housing member 26 via the relatively elastic holding member 64, so that it is free from thermal stress due to temperature changes and Fitting stress due to accumulation of tolerances caused by assembling parts may occur in the electromagnetic shielding case 44, excitation coils 60 and 61, and sensing coils 62 and 63, and effects of deformation, displacement, vibration, etc. of the rotating shaft 10 may occur on the ball bearings 30 and 32 and the fixed housing member 26 to the electromagnetic shielding case 44, the excitation coils 60 and 61, and the sensing coils 62 and 63.

In addition, instead of providing two annular bands as described above on the rotating shaft, for example, magnetic anisotropy generated by residual stress in the helical direction is imparted to at least a portion of the surface of the rotating shaft, and a small amount of ( Both of the peripheral regions have a small peripheral length (both of which have no residual stress-free region in 50%), and the magnetic field applying means is configured to connect the magnetic anisotropy portion and the rotating shaft to such a region. A magnetic field is applied to the area to which magnetic anisotropy is not imparted, and the sensing means detects the area to which magnetic anisotropy is imparted and the area of the rotating shaft to which such magnetic anisotropy is not imparted. It is also possible to sense the difference in magnetic permeability between said areas where there is no magnetic field.

Further, the magnetic field applying means and the sensing means are not limited to the excitation coil and sensing coil as described above. For example, it is possible to replace the magnetic field applying means and the sensing means by arranging one magnetic head on the outside of each of the above-mentioned apical bands.

In the above embodiment, sealing devices 70 and 72 are provided on the outside of the ball bearings 30 and 32, but if there is no problem with foreign matter entering from the outside of the ball bearings 30 and 321\, it is recommended to provide a sealing device. Not needed.

[Effects of the Invention] In the torque transducer of the present invention, at least the portion of the rotating shaft where the sensing means senses the change in magnetic permeability of the ferromagnetic magnetostrictive means, relative to the electromagnetic shielding means, the magnetic field applying means, and the sensing means. Shaking is virtually prevented. The protrusion connects the electromagnetic shielding means and the ground wire, and prevents the electromagnetic shielding means from rotating in the circumferential direction with respect to the fixed housing member, thereby making the detection of the torque value acting on the rotating shaft more stable. At the same time, damage to the conductor and ground wire is prevented.

However, since the electromagnetic shielding means is fixedly held by the fixed housing member via the holding member, thermal stress or fitting stress may occur in the electromagnetic shielding means, the magnetic field applying means, and the sensing means, or deformation of the rotating shaft may occur. , displacement, vibration, etc., are suppressed from being transmitted. Therefore, the torque value acting on the rotating shaft can be detected with higher accuracy by the sensing means.

[Brief explanation of the drawing]

Sections 1 to 6 show one part of the torque transducer of the present invention.
5. Figure 1 is a vertical sectional view of the central part, Figure 2 is an overall assembly diagram, and Figure 3 is a partial assembly diagram.
FIG. 4 is a partially completed diagram, FIG. 5 is an overall plan view, and FIG. 6 is a circuit diagram. FIGS. 7 and 8 are sectional views of main parts of different embodiments, respectively. FIG. 9 is a longitudinal cross-sectional view of a central portion of a conventional torque transducer, and FIG. 10 is a circuit diagram. In the drawing, 10 is a rotating shaft, 12 and 14 are annular bands 26 are fixed housing members, 28 is a through hole, 30 and 32 are ball bearings, 44 is an electromagnetic shielding case, 60 and 61 are excitation coils,
62 and 63 are sensing coils 564 are holding members, 66 and 67 are fixed annular plate parts, 68 and 69 are rotating annular plate parts, 8
6 is a rotation stopper.

Claims (1)

[Scope of Claims] Ferromagnetic magnetostrictive means that is provided on a rotating shaft and changes magnetic permeability in response to torque acting on the rotating shaft; and magnetic field applying means that applies a magnetic field to the ferromagnetic magnetostrictive means; sensing means for sensing a change in magnetic permeability caused by a torque acting on the rotating shaft and converting it into an electrical signal corresponding to the magnitude of the torque; A fixed housing member rotatably holds the rotating shaft via bearing means, and the magnetic field applying means and the sensing means are fixedly held inside so as to substantially prevent relative wobbling of the change sensing portion. and an electromagnetic shielding means for electromagnetic shielding, a through hole for leading out a conductor connected to the magnetic field applying means and the sensing means in the side wall of the fixed housing member, and the magnetic field applying means and the sensing means are rotated. The electromagnetic shielding means is held fixedly in the axial and radial directions on the fixed housing member via a relatively elastic holding member without contacting the shaft, and the electromagnetic shielding means is circumferentially rotated with respect to the fixed housing member. A protrusion for preventing motion is provided on the electromagnetic shielding means so as to protrude into the through hole, and the electromagnetic shielding means and the ground wire are connected through the protrusion. torque transducer.