Abstract:
A torque sensor includes a torsion bar, a first shaft connected to one end of the torsion bar, a second shaft connected to the other end of the torsion bar, first through third magnetic bodies, and two coils. The first magnetic body is fixed to the first shaft and has an annular shape so as to surround the torsion bar. The first magnetic body is composed of two magnetically separated magnetic portions and has a first projection on an outer circumference thereof. The second magnetic body is fixed to the second shaft and has an annular shape so as to surround the first magnetic body. The second magnetic body has on an inner circumference thereof a second projection which radially faces the first projection. The coils are disposed at respective axial positions corresponding to the magnetic portions of the first magnetic body and surround the second magnetic body. The third magnetic body is composed of two magnetically separated magnetic portions, each being disposed to surround the corresponding coil and forming, in cooperation with the first and second magnetic bodies, a closed magnetic circuit around the corresponding coil. The first and second projections are configured and arranged in such a manner that when a facing area through which the first and second projections face each other varies due to torsion of the torsion bar, inductances of the coils change in accordance with the variation in the facing area.

Description:
INCORPORATION BY REFERENCE  
         [0001]    The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2000-368240, filed on Dec. 4, 2000. The contents of that application are incorporated herein by reference in its entirety.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a torque sensor usable in, for example, a motor-driven power steering apparatus.  
           [0004]    2. Description of the Related Art  
           [0005]    Japanese Patent Application Laid-Open (kokai) No. 2000-146722 discloses a conventional torque sensor as shown in FIG. 7. In the torque sensor, a torsion bar  90  extends axially; and a hollow input shaft  91  serving as a first shaft is disposed coaxially with the torsion bar  90  and connected to an upper end of the torsion bar  90  via a pin  96 . An unillustrated steering wheel of a vehicle is connected to an upper portion of the input shaft  91 .  
           [0006]    A hollow output shaft  92  serving as a second shaft is disposed coaxially with the torsion bar  90  and the input shaft  91 , and connected to a lower end of the torsion bar  90  by means of spline-engagement and press-fitting; and a pinion  92   a  is formed on a lower portion of the output shaft  92 .  
           [0007]    An upper housing  93  and a lower housing  94  are provided so as to surround the input shaft  91  and the output shaft  92 , respectively, and to support the same via bearings  95   a  and  95   b , respectively. A rack  81  is supported by the lower housing  94  and is in meshing-engagement with the pinion  92   a  of the output shaft  92 . An unillustrated motor for assisting driver&#39;s steering operation is operatively coupled with the rack  81 .  
           [0008]    A first sensor ring  97  made of a magnetic material and serving as a first magnetic body is disposed within the upper housing  93  and fixed to the input shaft  91 . As shown in FIG. 8, the first sensor ring  97  assumes an annular shape in order to surround the torsion bar  90  circumferentially; and a large number of rectangular teeth  97   a  serving as a first protrusion are formed on a lower end surface of the first sensor ring  97 .  
           [0009]    As shown in FIG. 7, a second sensor ring  98  made of a magnetic material and serving as a second magnetic body is disposed within the upper housing  93  and fixed to the output shaft  92 . As shown in FIG. 8, the second sensor ring  98  assumes an annular shape in order to surround the torsion bar  90  circumferentially; and a large number of rectangular teeth  98   a  serving as a second protrusion are formed on an upper end surface of the second sensor ring  98 . The teeth  98   a  face the teeth  97   a  with an axial clearance and a phase shift provided therebetween.  
           [0010]    As shown in FIG. 7, a coil  99  is fixedly disposed within the upper housing  93  so as to surround the first and second sensor rings  97  and  98 , while facing their outer circumferences. Further, a guide  85  and a spacer  86  serving as a third magnetic body are fixedly disposed so as to surround the coil  99  and to form a magnetic circuit in cooperation with the first and second sensor rings  97  and  98 . The coil  99  is connected to an interface circuit (hereinafter referred to as an “I/F circuit”)  80 , which is connected to an unillustrated microcomputer.  
           [0011]    The above-described torque sensor operates as follows. When a torque is transmitted from the steering wheel to the input shaft  91  upon operation of the steering wheel, the torsion bar  90  is twisted with resultant generation of a relative displacement between the input shaft  91  and the output shaft  92 . As a result, an area through which the teeth  97   a  of the first sensor ring  97  face the teeth  98   a  of the second sensor ring  98  changes, and thus, the inductance of the coil  99  changes. This change in inductance is input to the microcomputer via the I/F circuit  80 . Therefore, in a motor-driven power steering apparatus which employs the above-described torque sensor, an assisting force proportional to the torque input to the input shaft  91  is imparted to the rack  81 .  
           [0012]    However, in the above-described conventional torque sensor, since the teeth  97   a  and  98   a  of the first and second sensor rings  97  and  98  face each other in the axial direction, only the single coil  99  is provided for torque detection. Therefore, when the reliability of a signal obtained from the coil  99  decreases, provision of assist force by the motor must be stopped, for reasons of safety. Therefore, stable steering of the vehicle cannot be attained.  
           [0013]    The reliability of the torque sensor may be improved through formation of two or more magnetic circuits for provision of two or more torque detection coils. However, since the conventional torque sensor is configured such that the teeth  97   a  and  98   a  of the first and second sensor rings  97  and  98  face each other in the axial direction, formation of two or more magnetic circuits for provision of two or more torque detection coils results in a considerably complicated structure, thus making manufacture difficult.  
           [0014]    Further, in the conventional torque sensor, since the teeth  97   a  and  98   a  of the first and second sensor rings  97  and  98  face each other in the axial direction, the size of the gap between the teeth  97   a  and  98   a  may vary as a result of assembly errors. Therefore, inductance varies greatly among manufactured torque sensors, resulting in variation in quality.  
         SUMMARY OF THE INVENTION  
         [0015]    In view of the foregoing, an object of the present invention is to provide a torque sensor which can secure stable steering operation and which can be manufactured at a consistent level of quality.  
           [0016]    In order to solve the above-described problems in the related art, the present inventors have carried out earnest studies and have found that the problems can be solved through employment of an arrangement such that a first projection of a first magnetic body and a second projection of a second magnetic body radially face each other. The present invention has been completed on the basis of this finding.  
           [0017]    The present invention provides a torque sensor comprising: a torsion bar extending along an axial direction; a first shaft disposed coaxially with the torsion bar and connected to one end of the torsion bar; a second shaft disposed coaxially with the torsion bar and the first shaft and connected to the other end of the torsion bar; a first magnetic body fixed to the first shaft and having an annular shape so as to surround the torsion bar, the first magnetic body being composed of at least two magnetically separated magnetic portions and having a first projection on an outer circumference thereof; a second magnetic body fixed to the second shaft and having an annular shape so as to surround the first magnetic body, the second magnetic body having on an inner circumference thereof a second projection which radially faces the first projection; at least two coils disposed at respective axial positions corresponding to the magnetic portions of the first magnetic body and surrounding the second magnetic body; and a third magnetic body composed of at least two magnetically separated magnetic portions, each being disposed to surround the corresponding coil and forming, in cooperation with the first and second magnetic bodies, a closed magnetic circuit around the corresponding coil, wherein the first and second projections are configured and arranged in such a manner that when a facing area through which the first and second projections face each other varies due to torsion of the torsion bar, inductances of the coils change in accordance with the variation in the facing area.  
           [0018]    In the torque sensor according to the present invention, at least two closed magnetic circuits are formed, and a coil is provided for each of the magnetic circuits so as to detect torque individually. Therefore, even when the reliability of one magnetic circuit or coil decreases, torque can be detected by use of other coils. Thus, the torque sensor of the present invention can secure stable steering operation.  
           [0019]    Further, since the first projection of the first magnetic body radially faces the second projection of the second magnetic body, assembly errors do not cause variance in the radial size of the clearance between the first and second projections. Therefore, inductance does not vary among manufactured torque sensors, and variation in quality hardly occurs.  
           [0020]    Therefore, the torque sensor of the present invention can secure stable steering operation, and can be manufactured with consistent quality.  
           [0021]    In the torque sensor of the present invention, the first through third magnetic bodies may have the following structure. The first magnetic body is composed of at least two tubular magnetic portions fixed to the first shaft while being magnetically separated from the first shaft, and at least one nonmagnetic portion integrally disposed between the two tubular magnetic portions. The second magnetic body is composed of at least three tubular magnetic portions and at least two nonmagnetic portions, each being integrally disposed between the corresponding tubular magnetic portions. Two adjacent magnetic portions of the second magnetic body radially face the corresponding one of the magnetic portions of the first magnetic body. The third magnetic body is composed of at least two magnetic portions and at least one nonmagnetic portion integrally disposed between the magnetic portions. Each magnetic portion of the third magnetic body radially faces two corresponding adjacent magnetic portions of the second magnetic body.  
           [0022]    In this case, each of the first and third magnetic bodies may have two magnetic portions which sandwich a single nonmagnetic portion, and the second magnetic body may have three magnetic portions sandwiching two nonmagnetic portions.  
           [0023]    In the torque sensor of the present invention, alternatively, the first through third magnetic bodies may have the following structure. The first magnetic body is composed of two tubular magnetic portions fixed to the first shaft without being magnetically separated from the first shaft, and a nonmagnetic portion integrally disposed between the two tubular magnetic portions. The second magnetic body is composed of two tubular magnetic portions and a nonmagnetic portion integrally disposed between the tubular magnetic portions. Each magnetic portion of the second magnetic body radially faces the corresponding one of the magnetic portions of the first magnetic body. The third magnetic body is composed of at least two magnetic portions and a nonmagnetic portion integrally disposed between the magnetic portions. Each magnetic portion of the third magnetic body radially faces the corresponding one of the magnetic portions of the second magnetic body. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which:  
         [0025]    [0025]FIG. 1 is a longitudinal cross section of a torque sensor according to a first embodiment of the present invention;  
         [0026]    [0026]FIG. 2 is an enlarged longitudinal cross section of the torque sensor according to the first embodiment;  
         [0027]    [0027]FIG. 3 is a cross section taken along line III-III of FIG. 1;  
         [0028]    [0028]FIG. 4 is a cross section taken along line IV-IV of FIG. 1;  
         [0029]    [0029]FIG. 5 is a block diagram of an I/F circuit used in the torque sensor according to the first embodiment;  
         [0030]    [0030]FIG. 6 is a longitudinal cross section of a torque sensor according to a second embodiment of the present invention;  
         [0031]    [0031]FIG. 7 is a longitudinal cross section of a conventional torque sensor; and  
         [0032]    [0032]FIG. 8 is an enlarged longitudinal cross section of the conventional torque sensor. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Embodiments of the present will now be described with reference to the drawings.  
         [0034]    First Embodiment  
         [0035]    As shown in FIG. 1, the main mechanical structure of a torque sensor according to a first embodiment is identical with that of the conventional torque sensor shown in FIG. 7.  
         [0036]    Therefore, structural elements identical with those of the conventional torque sensor shown in FIG. 7 are denoted by the same reference numerals, and their repeated descriptions are omitted.  
         [0037]    As shown in FIGS. 1 and 2, in the torque sensor according to the present embodiment, a ring  1  made of a nonmagnetic material is disposed within the upper housing  93  and fixed to the input shaft  91 , which serves as a first shaft; and a first sensor ring  2  serving as a first magnetic body is fitted onto an outer circumferential surface of the ring  1 .  
         [0038]    Therefore, the first sensor ring  2  is magnetically separated from the input shaft  91 . The first sensor ring  2  is composed of a first tubular magnetic portion  3  made of a magnetic material, a first tubular nonmagnetic portion  4  made of a nonmagnetic material, and a second tubular magnetic portion  5  made of a magnetic material, which are arranged in this sequence from the side of the input shaft  91 .  
         [0039]    As shown in FIGS. 3 and 4, the first and second magnetic portions  3  and  5  of the first sensor ring  2  each assume an annular shape so as to surround the torsion bar  90 . A large number of rectangular teeth  3   a  are formed on outer circumferential surface of the first magnetic portion  3  at predetermined intervals in the circumferential direction, and a large number of rectangular teeth  5   a  are formed on the outer circumferential surface of the second magnetic portion  5  at predetermined intervals in the circumferential direction. The teeth  3   a  serve as a first projection, as do the teeth  5   a.    
         [0040]    Further, as shown in FIGS. 1 and 2, in the upper housing  93 , a second sensor ring  6  serving as a second magnetic body is fitted onto an upper portion of the output shaft  92 , which serves as a second shaft. The second sensor ring  6  is composed of a third tubular magnetic portion  7  made of a magnetic material, a third tubular nonmagnetic portion  8  made of a nonmagnetic material, a fourth tubular magnetic portion  9  made of a magnetic material, a fourth tubular nonmagnetic portion  10  made of a nonmagnetic material, and a fifth tubular magnetic portion  11  made of a magnetic material, which are arranged in this sequence from the side of the input shaft  91 .  
         [0041]    As shown in FIGS. 3 and 4, the third, fourth, and fifth magnetic portions  7 ,  9 , and  11  of the second sensor ring  6  each assume an annular shape so as to surround the first sensor ring  2 . A large number of rectangular teeth  7   a ,  9   a , and  11   a  are formed on respective inner circumferential surfaces of the third, fourth, and fifth magnetic portions  7 ,  9 , and  11  at predetermined intervals in the circumferential direction. The teeth  7   a ,  9   a , and  11   a  serve as a second projection.  
         [0042]    The teeth  3   a  and  5   a  of the first and second magnetic portions  3  and  5  and the teeth  7   a ,  9   a , and  11   a  of the third, fourth, and fifth magnetic portions  7 ,  9 , and  11  share a common center O. The teeth  3   a  and  5   a  of the first and second magnetic portions  3  and  5  face the teeth  7   a ,  9   a , and  11   a  of the third, fourth, and fifth magnetic portions  7 ,  9 , and  11  with a radial clearance of dimension  1 .  
         [0043]    In the neutral condition, a center line L 0  of each tooth  7   a  ( 9   a ,  11   a ) passing through the center O and a center line L 1  of each tooth  3   a  passing through the center O form an angle θ therebetween; and the center line L 0  of each tooth  7   a  ( 9   a ,  11   a ) passing through the center O and a center line L 2  of each tooth  5   a  passing through the center O form an angle θ therebetween in the direction opposite the direction in which the center lines L 0  and L 1  form the angle θ.  
         [0044]    As shown in FIGS. 1 and 2, two guides  12  and  15  and two spacers  13  and  16  made of a magnetic material and serving as a third magnetic body are provided within the upper housing  93 . The pair including the guide  12  and the spacer  13  and the pair including the guide  15  and the spacer  16  are separated from each other by means of a separator  18  made of a nonmagnetic material, and are fixed by means of a circlip  19 . Each of the guides  12  and  15 , the spacers  13  and  16 , and the separator  18  assumes an annular shape so as to surround the second sensor ring  6 .  
         [0045]    The first magnetic portion  3 , the third magnetic portion  7 , the guide  12 , the spacer  13 , and the fourth magnetic portion  9  form a closed magnetic circuit. The second magnetic portion  5 , the fifth magnetic portion  11 , the guide  15 , the spacer  16 , and the fourth magnetic portion  9  form another closed magnetic circuit. Coils  14  and  17  are disposed within the respective magnetic circuits.  
         [0046]    As shown in FIG. 5, the coils  14  and  17  are connected to an I/F circuit  20 , which includes a base oscillation circuit  21 ; a first oscillation circuit  22  connected between the base oscillation circuit  21  and the coil  14 ; a second oscillation circuit  24  connected between the base oscillation circuit  21  and the coil  17 ; a torque detection-processing circuit  23  connected to the coil  14 ; and a torque detection-processing circuit  25  connected to the coil  17 .  
         [0047]    The torque sensor of the present embodiment having the above-described structure is manufactured in the following manner.  
         [0048]    The second sensor ring  6  can be manufactured through a process of bonding, by use of adhesive, the third magnetic portion  7 , the third nonmagnetic portion  8 , the fourth magnetic portion  9 , the fourth nonmagnetic portion  10 , and the fifth magnetic portion  11 . Alternatively, the second sensor ring  6  can be manufactured through a process of placing the third magnetic portion  7 , the fourth magnetic portion  9 , and the fifth magnetic portion  11  in a cavity of a mold for injection molding and then injecting a nonmagnetic resin into the cavity to thereby integrally form the third nonmagnetic portion  8  and the fourth nonmagnetic portion  10 . Alternatively, the second sensor ring  6  can be manufactured through a process of alternately placing, in a cavity of a mold, magnetic powder for forming the third magnetic portion  7 , the fourth magnetic portion  9 , and the fifth magnetic portion  11  and a nonmagnetic powder for forming the third nonmagnetic portion  8  and the fourth nonmagnetic portion  10 , forming them into a green body, and sintering the green body. The first sensor ring  2  can be manufactured through a similar process.  
         [0049]    The torque sensor is assembled by use of the above-described first and second sensor rings  2  and  6 . First, the second ring  6  is press-fitted to the output shaft  92 . Subsequently, the torsion bar  90  is fixed to the output shaft  92 .  
         [0050]    Meanwhile, after press-fitting of the ring  1  onto the input shaft  91 , the first sensor ring  2  is fitted onto the first ring  1 . Subsequently, after the upper housing  93  is fitted onto the input shaft  91  via the bearing  95   a , the guide  12  and the spacer  13 , after having been assembled with the coil  14  inserted into the guide  12 , are inserted into the upper housing  93 . Subsequently, after insertion of the separator  18 , the guide  15  and the spacer  16 , after having been assembled with the coil  17  inserted into the guide  15 , are inserted into the upper housing  93 . Subsequently, the guide  15  is fixed to the upper housing  93  by means of the circlip  19 .  
         [0051]    Subsequently, the upper housing  93  is mounted on the lower housing  94  in such a manner that the torsion bar  90  is axially inserted into the input shaft  91 . Subsequently, the input shaft  91  is connected to the torsion bar  90  by means of a pin as in the case of the conventional torque sensor shown in FIG. 7. Thus, the torque sensor according to the first embodiment is completed.  
         [0052]    As shown in FIG. 5, an oscillation signal output from the base oscillation circuit  21  of the I/F circuit  20  is supplied to the first and second oscillation circuits  22  and  24 , whereby properly synchronized signals are supplied from the first and second oscillation circuits  22  and  24  to the coils  14  and  17  of the torque sensor. Consequently, as shown in FIG. 2, two magnetic paths are formed, through which magnetic fluxes flow in opposite directions as indicated by arrows. The above-described torque sensor operates as follows. When a torque is input to the input shaft  91  upon operation of the steering wheel, the torsion bar  90  is twisted with a resultant generation of relative displacement between the input shaft  91  and the output shaft  92 . As a result, an area through which the teeth  3   a  and  5   a  of the first and second magnetic portions  3  and  5  face the teeth  7   a ,  9   a , and  11   a  of the third, fourth, and fifth magnetic portions  7 ,  9 , and  11  changes, and thus, the densities of magnetic fluxes flowing through the magnetic paths change, so that the inductance of the coil  14  and that of the coil  17  change. The torque detection-processing circuits  23  and  25  detect the inductances of the coils  14  and  17  and output corresponding torque signals T 1  and T 2 , which are then input to an unillustrated microcomputer.  
         [0053]    In the torque sensor, since variations in inductances of the coils  14  and  17  are detected individually, even when one of detection signals output from the coils  14  and  17  becomes unreliable, input torque can be determined on the basis of other detection signal. Therefore, even in such a case, the steering assist provided by the motor can be continued.  
         [0054]    Further, since the teeth  3   a  and  5   a  of the first and second magnetic portions  3  and  5  radially face the teeth  7   a ,  9   a , and  11   a  of the first, fourth, and fifth magnetic portions  7 ,  9 , and  11 , assembly errors do not cause variance in the radial dimension  1  of the clearance between the teeth  3   a  and  5   a , and the teeth  7   a ,  9   a , and  11   a . Therefore, inductance does not vary among manufactured torque sensors, and variation in quality hardly occurs.  
         [0055]    Therefore, the torque sensor of the first embodiment can secure stable steering operation, and can be manufactured with consistent quality.  
         [0056]    Further, variation in magnetic characteristics due to, for example, temperature can be compensated for on the basis of the difference between the detection signals output from the coils  14  and  17 .  
         [0057]    Moreover, the positional relation between the teeth  3   a  and  5   a  with respect to the teeth  7   a ,  9   a ,  11   a  enables doubling sensor sensitivity through employment of an inductance bridge circuit. That is, the center line L 0  of each tooth  7   a  ( 9   a ,  11   a ) and the center line L 1  of a corresponding tooth  3   a  form an angle θ in the direction opposite the direction in which an angle θ is formed by the center line L 0  of each tooth  7   a  ( 9   a ,  11   a ) and the center line L 2  of a corresponding tooth  5   a . Therefore, when a relative displacement is produced between the input shaft  91  and the output shaft  92  with a resultant increase in the facing area between the teeth  7   a  and  9   a , and the teeth  3   a , the facing area between the teeth  9   a  and  11   a  and the teeth  5   a  decreases. By contrast, when the facing area between the teeth  7   a  and  9   a , and the teeth  3   a  decreases, the facing area between the teeth  9   a  and  11   a  and the teeth  5   a  increases. Thus, the inductance of the coil  14  and the inductance of the coil  17  change in opposite directions, thereby doubling the sensitivity of the sensor.  
         [0058]    Second Embodiment  
         [0059]    As shown in FIG. 6, the main mechanical structure of a torque sensor according to a second embodiment is identical with that of the conventional torque sensor shown in FIG. 7. Therefore, structural elements identical with those of the conventional torque sensor shown in FIG. 7 are denoted by the same reference numerals, and their repeated descriptions are omitted.  
         [0060]    As shown in FIG. 6, in the torque sensor according to the present embodiment, a first sensor ring  32  serving as a first magnetic body is press-fitted onto the input shaft  91 . Therefore, the first sensor ring  32  is not magnetically separated from the input shaft  91 . The first sensor ring  32  is composed of a first tubular magnetic portion  33  made of a magnetic material, a first tubular nonmagnetic portion  34  made of a nonmagnetic material, and a second tubular magnetic portion  35  made of a magnetic material, which are arranged in this sequence from the input shaft  91  side. A large number of rectangular teeth  33   a  and  35   a  are formed on outer circumferential surfaces of the first and second magnetic portions  33  and  35 , respectively. The teeth  33   a  serve as a first projection, as do the teeth  35   a.    
         [0061]    A holder  50  made of a magnetic material is press fitted on the output shaft  92 ; and a second sensor ring  36  formed of a magnetic material and serving as a second magnetic body is press-fitted onto an upper portion of the holder  50 . The second sensor ring  36  is composed of a third tubular magnetic portion  37  made of a magnetic material, a third tubular nonmagnetic portion  38  made of a nonmagnetic material, and a fourth tubular magnetic portion  39  made of a magnetic material, which are arranged in this sequence from the input shaft  91  side. A large number of rectangular teeth  37   a  and  39   a  are formed on inner circumferential surfaces of the third and fourth magnetic portions  37  and  39 , respectively. The teeth  37   a  and  39   a  serve as a second projection. The teeth  33   a  and  35   a  of the first and second magnetic portions  33  and  35  and the teeth  37   a  and  39   a  of the third and fourth magnetic portions  37  and  39  have the same angular relationship therebetween as in the first embodiment.  
         [0062]    Two guides  42  and  45  made of a magnetic material are disposed while being separated from each other by means of a separator  48 . Coils  44  and  47  are provided within the guides  42  and  45 , respectively. The guides  42  and  45  and the separator  48  each assume an annular shape so as to surround the torsion bar  90  and cover an outer circumferential surface of the second sensor ring  36 .  
         [0063]    The first magnetic portion  33 , the third magnetic portion  37 , the guide  42 , and the input shaft  91  form a closed magnetic circuit. The second magnetic portion  35 , the fourth magnetic portion  39 , the guide  45 , the output shaft  92 , and the input shaft  91  form another closed magnetic circuit. The remaining structure is the same as in the first embodiment.  
         [0064]    In the torque sensor of the second embodiment as well, as shown in FIG. 6, two magnetic paths are formed. The torque sensor of the second embodiment provides the same operation and effects as those of the torque sensor of the first embodiment.  
         [0065]    In the torque sensor of the first embodiment, the first sensor ring  2  serving as a first magnetic body is composed of two magnetic portions  3  and  5  and one nonmagnetic portion  4 ; the second sensor ring  6  serving as a second magnetic body is composed of three magnetic portions  7 ,  9 , and  11  and two nonmagnetic portions  8  and  10 ; two guides  12  and  15  and two spacers  13  and  16  are provided as a third magnetic body; a single separator  18  is provided as a nonmagnetic portion; and two coils  14  and  17  are provided. In the torque sensor of the second embodiment, the first sensor ring  32  serving as a first magnetic body is composed of two magnetic portions  33  and  35  and one nonmagnetic portion  34 ; the second sensor ring  36  serving as a second magnetic body is composed of two magnetic portions  37  and  39  and one nonmagnetic portion  38 ; two guides  42  and  45  are provided as a third magnetic body; a single separator  48  is provided as a nonmagnetic portion; and two coils  44  and  47  are provided. However, the above-described embodiments are mere examples, and the present invention can be practiced while being modified in various manners without departing from the scope thereof.