JP2008180517A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor which is easy to assemble while making the length in the sensor axis direction short. <P>SOLUTION: The torque sensor comprises: a connection rod 14 for connecting a first shaft 12 and a second shaft 16; a permanent magnet 20 fixed on the first shaft 12; a plurality of magnetic substances 22, 24 and auxiliary magnetic substances 30, 32 fixed to the connection rod 14 for forming the magnetic circuit of the permanent magnet 20; and a magnetic flux detector 38 for detecting the flux introduced by the magnetic substances 22, 24 and the auxiliary magnetic substances 30, 32. The torque sensor detects the torque based on the output of detection of the magnetic flux detector 38, when the torque acted on the first shaft 12 or the second shaft 16. The permanent magnet 20 is formed in flat annular shape and different magnetic poles are magnetized in multiple poles in the axial direction, and facing opposite to the magnetic substances 22, 24 in the axial direction of the first shaft 12. The magnetic substances 22, 24 and the auxiliary magnetic substances 30, 32 are partially facing opposite to each other in the radial direction of the first shaft 12. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a torque sensor, for example, a torque sensor for measuring a torsion torque generated on a rotating shaft of a steering device of an automobile or the like.

  Conventionally, for measuring torsional torque generated on a rotating shaft, for example, a ring-shaped sensor member that acts as a magnetic collector (see Patent Document 1), or an arc-shaped magnetic collector is provided. Two magnetic detection elements for detecting a magnetic flux change (see Patent Documents 2 and 3), and a magnetic detection element disposed between magnetic bodies provided in a magnetic circuit to detect a magnetic flux change (Patent Documents) 4), a magnetic body and a magnetic collector in a magnetic circuit are formed of an iron plate, a magnetic flux is collected by a ring-shaped magnetic collector, and the magnetic flux is detected by one or two magnetic detection elements (see Patent Document 5) Etc. have been proposed.

  However, since what is described in Patent Documents 1 to 5 is composed of a circumferentially opposed sensor, the magnetic yoke must be able to receive a certain amount of magnetic flux from the permanent magnet. It is necessary to ensure a certain area where the magnetic poles of the permanent magnets face each other. Therefore, the permanent magnet requires a certain length (height) in the axial direction of the input shaft, and the torque detector cannot be shortened in the axial length direction of the input shaft, so that it is difficult to reduce the size.

In order to reduce the size, a permanent magnet composed of a conical multipolar magnet has been proposed (see Patent Document 6).
JP-A-2-162221 Japanese Utility Model Publication No. 3-48714 JP-A-2-141616 Japanese Patent Laid-Open No. 2-93321 JP 2003-149062 A JP 2006-20527 A

  However, the one described in Patent Document 6 uses a ring magnet and is sandwiched between magnetic yokes. However, since the magnetic yokes are arranged on both sides of the magnet, it is not sufficient to shorten the axial dimension. In addition, processing is difficult and the assembly cost is high.

  The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a torque sensor in which the axial length of the sensor is shortened to facilitate assembly.

  In order to achieve the above object, the present invention provides a first shaft body, a second shaft body, a connecting rod that connects the first shaft body and the second shaft body, and the first shaft body. A permanent magnet solidified at one end of the shaft body or the connecting rod, and fixed to the other end of the second shaft body or the connecting rod and disposed in the magnetic field of the permanent magnet, and the magnet of the permanent magnet A plurality of magnetic bodies and auxiliary magnetic bodies that form a circuit; and a magnetic flux detector that detects a magnetic flux induced by the magnetic bodies and the auxiliary magnetic bodies, and torque is applied to the first shaft body or the second shaft body. In the torque sensor for detecting the torque based on the detection output of the magnetic flux detector, the permanent magnet is formed as a planar annular body surrounding the connecting rod, and different magnetic poles are alternately arranged. In the axial direction of the magnetic body and the first shaft body. There was a surface facing, and the magnetic body and the auxiliary magnetic body, is characterized in that at least a part is made to face in the radial direction of the first shaft.

  According to the present invention, when a torsional torque is input between the first shaft body and the second shaft body and the connecting rod is twisted, the relative position between the permanent magnet and each magnetic body changes, and the magnetic The magnetic flux density distribution in the circuit changes. By detecting this change in the magnetic flux density distribution with a magnetic flux detector, it is possible to obtain a change in the relative position between the permanent magnet and each magnetic body, and finally to obtain a torque. Further, since the permanent magnet and the magnetic body are disposed so as to face each other in the axial direction of the first shaft body, the length of the sensor in the axial direction can be shortened, and the sensor can be downsized and the assembly cost can be reduced. Can contribute. Further, since a part of each magnetic body and a part of each auxiliary magnetic body are opposed to each other in the radial direction of the first axis, there is an advantage that it is difficult to be affected by the axial variation.

  In constructing the torque sensor, the following elements can be added. The plurality of magnetic bodies are formed in an annular shape and are arranged in one of the regions on both sides centered on the permanent magnet, and face the permanent magnet. By configuring in this way, each magnetic body does not sandwich the permanent magnet in the axial direction, so that it is possible to reduce the size and facilitate assembly.

  One of the plurality of magnetic bodies has a small diameter cylindrical portion, and the other magnetic body has a large diameter cylindrical portion having a diameter larger than that of the small diameter cylindrical portion. Each has a plurality of claw portions facing the permanent magnet, and the plurality of claw portions are the same in the number of the small diameter cylindrical portion and the large diameter cylindrical portion, and are arranged at equal intervals over the entire circumference.

  By configuring in this way, it is not necessary to divide and arrange each magnetic body in the axial direction, so that downsizing is possible. Furthermore, since the number of the claw parts is the same in the small diameter cylindrical part (inner side) and the large diameter cylindrical part (outer side) and is arranged at equal intervals over the entire circumference, the leakage magnetic flux is reduced and the permanent magnet The magnetic flux from can be effectively induced.

  The claw portions in the small-diameter cylindrical portion and the large-diameter cylindrical portion are formed corresponding to the number equal to the number of poles of the permanent magnet. With this configuration, it is possible to make maximum use of the boundary between the magnetic poles of the permanent magnet necessary for detecting the torque.

  The plurality of magnetic bodies and the plurality of auxiliary magnetic bodies are formed as annular bodies having different diameters, and at least some of them are opposed to each other in the radial direction of the first shaft body. The opposing portion is formed over the entire circumference.

With this configuration, it is possible to always induce a constant magnetic flux from the magnetic body to the auxiliary magnetic body regardless of the rotation angles of the first shaft body and the second shaft body.
The length in the axial direction of the facing portion between each magnetic body and each auxiliary magnetic body is longer for each magnetic body than for each auxiliary magnetic body. With this configuration, even if the relative position in the axial direction of the magnetic body and the auxiliary magnetic body changes, it is possible to eliminate fluctuations in the amount of magnetic flux induced to the magnetic flux detector.

  One of the plurality of magnetic bodies has a small-diameter cylindrical portion, the other magnetic body has a large-diameter cylindrical portion, and one of the plurality of auxiliary magnetic bodies has the auxiliary magnetic body A small-diameter cylindrical portion having a diameter different from that of the small-diameter cylindrical portion of the body, and the other auxiliary magnetic body has a large-diameter cylindrical portion having a diameter different from that of the large-diameter cylindrical portion of the magnetic body. Form the small-diameter cylindrical facing portion by opposing each other in the radial direction of the first shaft body, and the large-diameter cylindrical portions are respectively opposed by opposing each other in the radial direction of the first shaft body. A large-diameter cylindrical facing portion is formed, and the small-diameter cylindrical facing portion and the large-diameter cylindrical facing portion are arranged to be shifted in the axial direction.

  By configuring in this way, the permeance between the facing portion (inner facing portion) in each small-diameter cylindrical portion and the facing portion (outer facing portion) in each large-diameter cylindrical portion can be lowered, and leakage flux can be reduced. Can be reduced.

  The plurality of auxiliary magnetic bodies are magnetically coupled to each magnetic body to induce the magnetic flux from each magnetic body and have a magnetic flux concentrating portion for collecting the induced magnetic flux, and the magnetic flux detector is provided in the magnetic flux concentrating portion. The collected magnetic flux is detected.

  With this configuration, the magnetic flux induced from the magnetic body to the auxiliary magnetic body can be concentrated on the magnetic flux detector, and the magnetic flux detector can be fixed.

  In addition, since two magnetic flux detectors are provided and the two magnetic flux detectors constitute a differential output, a double system is obtained, and the dynamic range is widened with the differential output. The temperature drift of the magnetic flux detector can be canceled.

  Furthermore, by providing the magnetic flux detector 3 or more, a failed magnetic flux detector can be specified, and the reliability of the torque sensor can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to shorten the axial length of a sensor, an assembly can be made easy and it can contribute to size reduction of a sensor and reduction of an assembly cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a sectional view of a torque sensor showing a first embodiment of the present invention, FIG. 2 is an exploded perspective view of the torque sensor, FIG. 3 is a sectional top perspective view of the torque sensor, and FIG. 4 is a torque sensor. FIG.

  1 to 4, the torque sensor 10 includes a first shaft body 12 formed in a substantially cylindrical shape, and a part of the first shaft body 12 is rotated by a bearing (not shown). It is supported freely. A steering wheel (not shown) of an electric power steering device (EPS) is connected to one axial end side of the first shaft body 12, and a second shaft is connected to the other axial end side via a connecting rod 14. The body 16 is connected. The connecting rod 14 is an elastic member of a torsion element and a connecting member that connects the first shaft body 12 and the second shaft body 16, and both axial ends thereof are the first shaft body 12 and the second shaft body, respectively. 16. A part of the second shaft body 16 is rotatably supported by a bearing (not shown).

  Around the connecting rod 14, a back yoke 18 formed in an annular shape and a permanent magnet 20 formed in an annular shape are arranged. The permanent magnet 20 is formed in a ring shape as a planar annular body, and is fixed directly or indirectly to the first shaft body 12, and magnetic poles (N pole and S pole) different in the axial direction are magnetized. It is configured as a multipole magnet.

  A pair of magnetic bodies (yokes) 22 and 24 having different diameters are provided in one of the axially opposite sides of the permanent magnet 20 in the axial direction of the first shaft 12. And are arranged so as to face each other. The large-diameter magnetic body 22 includes a large-diameter cylindrical portion 22a. A plurality of claw poles (claw portions) 26 projecting inward from the large-diameter cylindrical portion 22a are provided on the bottom side of the large-diameter cylindrical portion 22a. It is arranged at equal intervals along the direction. The small-diameter magnetic body 24 includes a small-diameter cylindrical portion 24a having a smaller diameter than the large-diameter cylindrical portion 22a. The small-diameter cylindrical portion 24a includes a claw pole (claw portion) 28 protruding outward from the bottom side of the small-diameter cylindrical portion 24a. Are arranged at equal intervals along the circumferential direction.

  The large-diameter cylindrical portion 22a and the small-diameter cylindrical portion 24a are disposed to face each other in the radial direction of the first shaft 12 as opposed portions. The claw poles 26 and 28 are each formed in a trapezoidal shape and are alternately fitted to each other so as to face each magnetic pole of the permanent magnet 20 and maintain a gap.

  The magnetic bodies 22 and 24 are arranged in the magnetic field of the permanent magnet 20 and are configured as an element of the magnetic circuit of the permanent magnet 20, and one claw pole 26 is opposed to, for example, the S pole of the permanent magnet 20. In this case, the other claw pole 28 faces the north pole of the permanent magnet 20. That is, when the torque is not input, the magnetic pole boundary line of the permanent magnet 20 and the center of the claw poles 26 and 28 are arranged to coincide. The claw poles 26 and 28 are not limited to a trapezoidal shape, but may be a triangular shape or a rectangular shape. Further, the back yoke 18 on the back surface of the permanent magnet 20 need not be provided, but it is preferable to provide the back yoke 18 because leakage of magnetic flux can be reduced.

  Adjacent to the magnetic bodies 22 and 24, the auxiliary magnetic bodies 30 and 32 are arranged with a certain gap therebetween. The auxiliary magnetic bodies 30 and 32 are formed in an annular shape and are disposed so as to surround the connecting rod 14 or the second shaft body 16. The auxiliary magnetic body 30 includes a large diameter cylindrical portion 30a, and a magnetic flux concentrating portion 34 protruding from the large diameter cylindrical portion 30a is formed in a part of the large diameter cylindrical portion 30a. The auxiliary magnetic body 32 includes a small-diameter cylindrical portion 32a having a smaller diameter than the large-diameter cylindrical portion 30a, and a magnetic flux concentrating portion 36 protruding from the small-diameter cylindrical portion 32a is formed in a part of the small-diameter cylindrical portion 32a.

  The large-diameter cylindrical portion 30a and the small-diameter cylindrical portion 32a are arranged to face each other in the radial direction of the first shaft 12, and the large-diameter cylindrical portion 30a serves as the outer-facing portion as the large-diameter cylindrical portion of the magnetic body 22. 22a and the first shaft 12 are arranged opposite to each other in the radial direction, and the small diameter cylindrical portion 32a is opposed to the small diameter cylindrical portion 24a of the magnetic body 24 in the radial direction of the first shaft 12 as an inner facing portion. Are arranged.

  The opposing portions of the magnetic bodies 22, 24 and the auxiliary magnetic bodies 30, 32 are axially displaced because the magnetic bodies 22, 24 are longer in the axial direction than the auxiliary magnetic bodies 30, 32. You can cancel the effect.

  A linear type magnetic flux detector (magnetic detection element) 38 whose output voltage changes according to the amount of magnetic flux is inserted between the magnetic flux concentrating portion 34 and the magnetic flux concentrating portion 36. The magnetic flux detector 38 can measure the magnetic flux density of the magnetic flux that passes through the axial gap between the magnetic flux concentrating portions 34 and 36.

  The auxiliary magnetic bodies 30 and 32 are arranged to face the magnetic bodies 22 and 24 in a magnetic field of the permanent magnet 20 while maintaining a certain gap to constitute a magnetic circuit, and the auxiliary magnetic bodies 30 and 32 have a magnetic flux. By narrowing the gap in the axial direction between the concentrated portions 34 and 36 smaller than the other portions, the magnetic flux generated from the permanent magnet 20 can be concentrated in the magnetic flux concentrated portions 34 and 36. In this case, the magnetic bodies 22 and 24 are molded with the resin 40 and are integrally molded and fixed to the connecting rod 14, and the auxiliary magnetic bodies 30 and 32 are molded with the resin 42 and integrally molded. 40, both of which constitute a magnetic circuit in a state where they face each other, even if the magnetic bodies 22, 24 and the auxiliary magnetic bodies 30, 32 rotate, the total amount of magnetic flux passing through both of them Will not fluctuate. As the molding method, insert molding, potting, or the like can be used.

  Further, by inserting the magnetic flux detector 38 into the gap in the axial direction of the magnetic flux concentrating parts 34 and 36 in the auxiliary magnetic bodies 30 and 32, the amount of magnetic flux passing through the gap in the axial direction of the magnetic flux concentrating parts 34 and 36 can be reduced. The magnetic flux detector 38 can reliably measure.

  The magnetic flux detector 38 may be any device that can measure the amount of magnetic flux, such as a Hall element, MR element, or MI element.

  Further, although one magnetic flux detector 38 is sufficient, the reliability of the apparatus can be improved by using two or more magnetic flux detectors. When two or more magnetic flux detectors 38 are used, if the magnetic flux detection direction of each magnetic flux detector 38 is changed and the magnetic flux is measured using the output difference of each magnetic flux detector 38 as a differential output, the fluctuation of the zero point is cancelled. can do. Further, when two magnetic flux detectors 38 are used, a double system is used, and a dynamic range is widened with a differential output, which is less susceptible to external noise, and cancels temperature drift of the magnetic flux detector 38. You can also. At this time, the magnetic flux concentrating portions 34 and 36 may be provided only once for each auxiliary magnetic body 30 and 32. However, if two or more magnetic concentrating portions 34 and 36 are provided, the areas of the magnetic flux concentrating portions 34 and 36 can be managed. preferable.

  Further, when three or more magnetic flux detectors are used, even if one of the magnetic flux detectors fails, two or more normal detectors remain, so that highly reliable data by majority vote can be obtained.

  Note that the magnetic flux detector 38 is generally housed in a plastic package, and the detector (element) itself is smaller than the outer dimensions of the package. Therefore, the areas of the parallel portions of the magnetic flux concentrating portions 34 and 36 that are parallel to each other may be matched to the size of the detector (element) itself, instead of matching the size of the package.

  However, if it is too small, the saturation magnetic flux density of the material of the magnetic flux concentrating portions 34 and 36 will be exceeded, so it is preferable to make the area where magnetic saturation does not occur.

  Next, the operation of the torque sensor 10 configured as described above will be described. As shown in FIG. 5, in the state where there is no torque input, the circumferential center of the claw poles 26 and 28 is located on the pole boundary of the permanent magnet 20, and the permanent magnet 20 viewed from the claw poles 26 and 28. Since the permeance with respect to the N pole and the S pole is the same, the magnetic flux flows as shown by the arrows in FIG. Specifically, the magnetic flux generated from the N pole of the permanent magnet 20 in FIGS. 2 and 3 enters the claw pole 28 of the magnetic body 24 and enters the S pole of the permanent magnet 20 as it is. Therefore, since the magnetic flux does not flow through the magnetic flux detector 38, the magnetic flux detector 38 outputs an intermediate voltage.

  When torque is input by the driver rotating the steering wheel, the input side of the connecting rod 14 rotates in the same manner as the steering wheel, and the connecting rod 14 itself is twisted according to the input torque. This twist causes a relative angular displacement between the input side and the output side of the connecting rod 14. The relative angular displacement generated between the input side and the output side of the connecting rod 14 appears as a relative angular displacement between the claw poles 26 and 28 of the torque sensor of the present invention and the permanent magnet 20. When relative angular displacement occurs between the claw poles 26 and 28 and the permanent magnet 20, the balance of permeance is lost as shown in FIG. 6, and the magnetic circuit including the magnetic flux detector 38 in FIGS. Magnetic flux generated from the N pole flows to the claw pole 28 of the magnetic body 24, passes through the auxiliary magnetic body 30 and the magnetic flux concentrating portion 34 from the magnetic body 24, and is detected between the magnetic flux concentrating portion 34 and the magnetic flux concentrating portion 36. Magnetic flux flows through a magnetic circuit that passes through the container 38 and returns to the south pole of the permanent magnet 20 via the magnetic flux concentrating portion 36, the auxiliary magnetic body 32, the magnetic body 22, and the claw pole 26. By detecting the magnetic flux generated in the magnetic circuit including the magnetic flux detector 38 with the magnetic flux detector 38, the relative angular displacement can be measured, and the torque applied to the connecting rod 14 can be detected.

  According to the present embodiment, since the permanent magnet 20 and the magnetic bodies 22 and 24 are disposed so as to face each other in the axial direction of the first shaft body 12, the length in the axial direction can be shortened. Can contribute to downsizing and cost reduction. Furthermore, since part of the magnetic bodies 22 and 24 and part of the auxiliary magnetic bodies 30 and 32 are opposed to each other in the radial direction of the first shaft 12, it is not easily affected by fluctuations in the axial direction, and reliability is improved. Can contribute.

Further, according to the present embodiment, the following effects can be obtained.
The magnetic bodies 22 and 24 are formed in an annular shape and are disposed in one of the areas on both sides centering on the permanent magnet 20 and face the permanent magnet 20, so that the magnetic bodies 22 and 24 are permanent magnets. 20 is not sandwiched, miniaturization is possible, and assembly becomes easy.

  The claw poles 26 and 28 have the same number of small-diameter cylindrical portions 24a and large-diameter cylindrical portions 22a and are arranged at equal intervals over the entire circumference. Therefore, the magnetic bodies 22 and 24 are arranged in the axial direction. Therefore, the size can be reduced, the leakage magnetic flux can be reduced, and the magnetic flux from the permanent magnet 20 can be effectively guided to the magnetic flux detector 38. Further, since the claw poles 26 and 28 are formed corresponding to the number equal to the number of poles of the permanent magnet 20, the boundary between the magnetic poles of the permanent magnet 20 necessary for detecting the torque can be utilized to the maximum.

  The magnetic bodies 22, 24 and the auxiliary magnetic bodies 30, 32 are formed as annular bodies having different diameters, and at least a part thereof is opposed to each other in the radial direction of the first shaft body 12. Since the portion facing the auxiliary magnetic bodies 30 and 32 is formed over the entire circumference, a constant magnetic flux is always applied regardless of the rotation angle of the first shaft body 12 and the second shaft body 16. 24 can be guided to the auxiliary magnetic bodies 30 and 32.

  The axial lengths of the opposing portions of the magnetic bodies 22 and 24 and the auxiliary magnetic bodies 30 and 32 are longer in the magnetic bodies 22 and 24 than in the auxiliary magnetic bodies 30 and 32. Even if the relative positions of the magnetic bodies 30 and 32 in the axial direction change, fluctuations in the amount of magnetic flux induced to the magnetic flux detector 38 can be eliminated. In other words, even if the axial direction variation occurs, the facing area does not change, so that the influence of the axial direction variation can be reduced.

  The small-diameter cylindrical portions 24 a and 32 a are arranged opposite to each other in the radial direction of the first shaft body 12, and the large-diameter cylindrical portions 22 a and 30 a are arranged opposite to each other in the radial direction of the first shaft body 12. Therefore, the permeance between the facing portion (inner facing portion) in the small diameter cylindrical portions 24a, 32a and the facing portion (outer facing portion) in the large diameter cylindrical portions 22a, 30a can be lowered, and the leakage magnetic flux can be reduced. Can be reduced.

  Since the magnetic bodies 22 and 24 and the auxiliary magnetic bodies 34 and 36 have a planar shape, they can be processed by a plane press or the like, so that the cost can be reduced and the axial dimension can be shortened.

  Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the worm wheel 44 of the electric power steering apparatus (EPS) is used as a first shaft body, the permanent magnet 20 is fixed to the side surface of the worm wheel 44, and the overall axial dimension is further shortened. Other configurations are the same as those of the first embodiment.

  When the permanent magnet 20 is fixed to the side surface of the worm wheel 44, the axial dimension of the entire sensor can be further shortened.

  According to the present embodiment, the same effects as those of the embodiment can be obtained, and the axial dimension of the entire sensor can be further shortened than that of the embodiment.

  When the material of the worm wheel 44 is iron, the back yoke 18 can be omitted. On the other hand, when the material of the worm wheel 44 is plastic, the back yoke 18 is preferable because the magnetic flux does not leak.

  In each of the above embodiments, as the material of the permanent magnet 20, a ferrite magnet or a rare earth magnet (Nd—Fe—B magnet, Sm—Co magnet, etc.) can be used. Further, a metal magnet or a sintered magnet may be used, but a plastic magnet or a rubber magnet may be used.

  Further, the radial dimension of the permanent magnet 20 may be longer than the length of the claw poles 26 and 28 of the magnetic bodies 22 and 24, but the direction of the claw poles 26 and 28 of the magnetic bodies 22 and 24 is longer. Most of the magnetic flux of the permanent magnet 20 can be guided to the magnetic bodies 22 and 24, and the magnetic flux leaking to other than the magnetic bodies 22 and 24 can be reduced, which is preferable.

  The opposing portions of the magnetic bodies 22 and 24 and the auxiliary magnetic bodies 30 and 32 are longer in the axial direction of the magnetic bodies 22 and 24 than in the auxiliary magnetic bodies 30 and 32. You can cancel the effect. In addition, it is preferable that the material of a magnetic body and an auxiliary | assistant magnetic body is an alloy containing nickel.

  When structural steel is used for the magnetic body and the auxiliary magnetic body, there is hysteresis in the output of the magnetic detection element, and it is difficult to accurately measure the angle from the output value. This is due to the magnetic properties of the material used for the magnetic holiday and the auxiliary magnetic material. Therefore, it is desirable to use an alloy containing nickel in order to improve the magnetic properties of the magnetic body and the auxiliary magnetic body.

  When an alloy containing about 40% or more of nickel (eg containing 45%) is used for the magnetic material and auxiliary magnetic material, the output hysteresis can be significantly reduced compared to the case of using structural steel. Torque detection accuracy could be improved.

  However, the hysteresis remains slightly and cannot be applied when high-precision detection is required. In such a case, it is necessary to further improve the characteristics. Therefore, in order to further improve the magnetic characteristics, it is more desirable to use an alloy containing about 70% or more of nickel (for example, containing 75%). Using an alloy containing 75% nickel, the hysteresis could be almost zero.

  However, since nickel is an expensive metal, it is preferable that the amount used is as small as possible. The content of nickel is preferably selected according to the required performance.

It is sectional drawing of the torque sensor which shows 1st Example of this invention. It is a disassembled perspective view of a torque sensor. It is a principal part cross-section top perspective view of a torque sensor. It is a principal part sectional bottom perspective view of a torque sensor. It is the schematic for demonstrating operation | movement of a torque sensor when there is no torque input. It is the schematic for demonstrating operation | movement of a torque sensor when the input of torque is the maximum. (A) is sectional drawing of the torque sensor which shows 2nd Example of this invention, (b) is a principal part enlarged view of a magnetic body, (c) is a principal part enlarged view of an auxiliary | assistant magnetic body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Torque sensor 12 1st shaft body 14 Connecting rod 16 2nd shaft body 20 Permanent magnet 22, 24 Magnetic body 26, 28 Claw pole 30, 32 Auxiliary magnetic body 34, 36 Magnetic flux concentration part 38 Magnetic flux detector

Claims (11)

  Solidified at one end of the first shaft body, the second shaft body, a connecting rod for connecting the first shaft body and the second shaft body, and the first shaft body or the connecting rod. A plurality of magnetic bodies and auxiliary magnetic bodies that are fixed to the other end of the second shaft body or the connecting rod and are arranged in the magnetic field of the permanent magnet to form a magnetic circuit of the permanent magnet. And a magnetic flux detector for detecting magnetic flux induced by the magnetic body and the auxiliary magnetic body, and when the torque acts on the first shaft body or the second shaft body, the magnetic flux detector detects In the torque sensor for detecting the torque based on the output, the permanent magnet is formed as a planar annular body surrounding the connecting rod, and different magnetic poles are alternately magnetized in the axial direction, The surfaces of the first shaft body face each other in the axial direction, and the magnetic body and the Co magnetic body, the torque sensor, characterized in that at least a part is made to face in the radial direction of the first shaft.   The plurality of magnetic bodies are formed in an annular shape, arranged in one of the areas on both sides in the axial direction centering on the permanent magnet, and face-to-face with the permanent magnet. The torque sensor according to 1.   One of the plurality of magnetic bodies has a small-diameter cylindrical portion, and the other magnetic body has a large-diameter cylindrical portion having a diameter larger than that of the small-diameter cylindrical portion. A plurality of claw portions that are opposed to the permanent magnet are respectively formed in the diameter cylindrical portion, and the plurality of claw portions are equal in number in the small diameter cylindrical portion and the large diameter cylindrical portion, and are equally spaced over the entire circumference. The torque sensor according to claim 1, wherein the torque sensor is arranged as follows.   4. The torque sensor according to claim 3, wherein the claw portions in the small-diameter cylindrical portion and the large-diameter cylindrical portion are formed so as to correspond to the number of poles of the permanent magnet.   The plurality of magnetic bodies and the plurality of auxiliary magnetic bodies are formed as annular bodies having different diameters, and at least a part of the plurality of magnetic bodies is opposed to each other in the radial direction of the first shaft body, The torque sensor according to any one of claims 1 to 4, wherein a portion facing each auxiliary magnetic body is formed over the entire circumference.   6. The torque sensor according to claim 5, wherein an axial length of a facing portion between each magnetic body and each auxiliary magnetic body is longer in each magnetic body than each auxiliary magnetic body. .   One of the plurality of magnetic bodies has a small-diameter cylindrical portion, the other magnetic body has a large-diameter cylindrical portion, and one of the plurality of auxiliary magnetic bodies has the auxiliary magnetic body The small-diameter cylindrical portion having a diameter different from that of the small-diameter cylindrical portion of the magnetic body, and the other auxiliary magnetic body has a large-diameter cylindrical portion having a diameter different from that of the large-diameter cylindrical portion of the magnetic body. The portions are opposed to each other in the radial direction of the first shaft body to form the small diameter cylindrical facing portion, and the large diameter cylindrical portions are opposed to each other in the radial direction of the first shaft body. The torque sensor according to claim 5 or 6, wherein the large-diameter cylindrical facing portion is formed, and the small-diameter cylindrical facing portion and the large-diameter cylindrical facing portion are arranged so as to be shifted in the axial direction.   The plurality of auxiliary magnetic bodies are magnetically coupled to the magnetic bodies to induce magnetic flux from the magnetic bodies, respectively, and have a magnetic flux concentrating portion for collecting the induced magnetic flux. The torque sensor according to any one of claims 1 to 7, wherein a magnetic flux collected in the magnetic flux concentrating portion is detected.   The torque sensor according to any one of claims 1 to 8, wherein two of the magnetic flux detectors are provided, and the two magnetic flux detectors constitute a differential output.   The torque sensor according to any one of claims 1 to 8, comprising three or more magnetic flux detectors.   The torque sensor according to any one of claims 1 to 10, wherein the magnetic flux detector is mounted on an electric power steering device and detects a steering torque acting on a steering shaft.

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