JP2006162460A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily carry out miniaturization of a torque sensor while securing detection accuracy of a magnetic flux density in regard to a torque sensor provided with a ring like magnet body attached to a one end side of a torsion bar, a set of magnetic yokes attached to another end side of the torsion bar, and a magnetic sensor detecting a magnetic flux density generated between the magnetic yokes. <P>SOLUTION: In the magnet body 13, magnetic poles of an outer circumference and an inner circumference are different in each area 13a divided at even intervals in a circumferential direction, and polarization is carried out such that the magnetic poles exist alternately in the circumferential direction. The set of magnetic yokes 14 is comprised of an outer ring 14a and an inner ring 14b facing each other via a predetermined interval in a radial direction, and it is provided with a plurality of protruding parts 15a arranged at even intervals in a circumferential direction and facing the outer circumference of the magnet body 13 to compose magnetic protruding and recessed ends in the outer ring 14a, and a plurality of protruding parts 15b arranged at even intervals in the circumferential direction and facing the inner circumference of the magnet body body 13 to compose magnetic protruding and recessed ends in the inner ring 14b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-contact type torque sensor that detects torque from torsion of a rotating shaft.

  As a non-contact type torque sensor used for a vehicle steering system or the like, those disclosed in Patent Document 1 and Patent Document 2 are known. A ring-shaped magnet is attached to one end of the torsion bar, and a set of magnetic yokes is attached to the other end of the torsion bar. The magnet body is magnetized so that S poles and N poles appear alternately in the circumferential direction. Each yoke has a plurality of protrusions (magnetic path pieces or claws) formed at equal intervals in the circumferential direction. These protrusions are set so as to protrude alternately along a magnetic pole surface (one end surface or outer peripheral surface of the magnet body) where the S pole and N pole of the magnet body appear alternately in the circumferential direction between a pair of magnetic yokes. The

Each protrusion is configured such that the center of the protrusion coincides with the boundary between the S pole and the N pole of the magnet body in a neutral state where the torsion bar twist is zero. When the torsion bar is twisted, relative rotation occurs between the magnet body and the pair of magnetic yokes, so that each projection of one magnetic yoke overlaps the S pole or N pole of the magnet body in a larger area, The projection of the other magnetic yoke overlaps with the north or south pole more in area, and a magnetic field is generated between the pair of magnetic yokes. The torsional torque of the torsion bar is obtained by detecting this magnetic field change with a magnetic sensor (Hall element).
Patent No. 3094049 JP2003-149062

  By the way, in such a conventional torque sensor, only the magnetic pole surface on one side of the magnet body is used (the projections of one set of magnetic yokes appear alternately in the circumferential direction of the S pole and N pole of the magnet body). If the diameter of the magnet body is reduced to reduce the size of the torque sensor, the distance (interval) between the protrusions will be reduced and the amount of magnetic flux leakage will increase. This can easily affect the detection accuracy of the magnetic flux density.

  In electric power steering and the like, in order to improve the steering feeling of the vehicle, there is a tendency to set the maximum value of the torsion bar torsion angle (torsion amount) small. This is likely to increase, which may lead to a decrease in magnetic flux density detection accuracy.

  It is an object of the present invention to provide a torque sensor that can improve such problems.

  The present invention relates to a ring-shaped magnet body attached to one end side of a torsion bar, a set of magnetic yokes attached to the other end side of the torsion bar, and a magnetic sensor for detecting a magnetic flux density generated between the set of magnetic yokes. And the magnet body is magnetized so that the magnetic poles of the outer periphery and the inner periphery are different for each region divided at equal intervals in the circumferential direction, and these magnetic poles appear alternately in the circumferential direction, A set of magnetic yokes comprises an outer ring and an inner ring that are opposed to each other at a predetermined interval in the radial direction, and are arranged at equal intervals in the circumferential direction so as to form a magnetic input / output end portion on the outer ring. A plurality of convex portions facing the outer periphery of the magnet body, and a plurality of convex portions facing the inner periphery of the magnet body arranged at equal intervals in the circumferential direction so as to form a magnetic input / output end portion in the inner ring. Features.

  According to the present invention, the plurality of convex portions constituting the magnetic input / output end portion of the set of magnetic yokes are not disposed only on the magnetic pole surface on one side of the magnet body, but are disposed on the magnetic pole surfaces on both sides of the magnet body. Therefore, the magnetic flux enters and exits from the magnetic pole surfaces on both sides of the magnet body through a plurality of convex portions, and there is a margin between the convex portions. Therefore, while ensuring the accuracy of detecting the magnetic flux density, the torque sensor Miniaturization can be easily achieved.

  A torque sensor according to an embodiment of the present invention will be described based on the drawings.

  1 to 3, reference numeral 10 denotes a torsion bar, which connects the first shaft (11) and the second shaft (12) coaxially. A magnet body 13 is attached to one end side of the torsion bar 10 via a nonmagnetic member, and a set of magnetic yokes 14 is attached to the other end side of the torsion bar 10 via a nonmagnetic member.

  The magnet body 13 is formed in a ring shape, and the outer and inner magnetic poles are different for each arc region 13a divided at equal angles in the circumferential direction, and these magnetic poles alternate in the circumferential direction of the ring. Magnetized to appear in

  The set of magnetic yokes 14 includes an outer ring 14a (outer cylinder) and an inner ring 14b (inner cylinder) that are opposed to each other at a predetermined interval in the radial direction. A plurality of convex portions 15a facing the outer periphery of the magnet body 13 are arranged at equal intervals in the circumferential direction so as to form a magnetic input / output end portion on the outer ring 14a. A plurality of convex portions 15b facing the inner periphery of the magnet body 13 are arranged at equal intervals in the circumferential direction so as to form a magnetic input / output end portion in the inner ring 14b.

  For each convex portion 15a facing the outer periphery of the magnet body 13 and each convex portion 15b facing the inner periphery of the magnet body 13, when the torsion bar 10 is in a neutral state of 0, the S pole and the N pole of the magnet body 13 It overlaps with the same area so as to cross the boundary.

  A pair of magnetism collecting rings 16 and 16b (annular bodies) are interposed in a non-contact manner between the ends of the rings 14a and 14b opposite to the convex portions 15a and 15b. The pair of magnetism collecting rings 16a and 16b are arranged concentrically with a predetermined gap (gap) between them, and a magnetic sensor 18 (Hall element) for detecting the magnetic flux density generated in these gaps is inserted (see FIG. 3, see).

  The magnetic sensor 18 and the pair of magnetism collecting rings 16a and 16b are fixed to the housing side via a nonmagnetic member that couples them. In the illustrated case, the two magnetic sensors 18 are arranged symmetrically about the axis, but this is to eliminate the influence of the eccentricity of the torsion bar and basically only one magnetic sensor 18 may be used.

  When the twist of the torsion bar 10 is in a neutral state, the convex portions 15a and 15b of the yokes 14a and 14b overlap with the same area so as to straddle the boundary between the S pole and the N pole of the magnet body 13. . In the adjacent arc region 13a of the magnet body 13, the magnetic flux between the arc regions 13a is closed by the convex portion 15a facing the outer periphery of the magnet body 13 and the convex portion 15b facing the inner periphery of the magnet body 13. Since no magnetic flux flows through the magnetic yoke 14 to the pair of magnetism collecting rings 16a and 16b, the magnetic flux density detected by the magnetic sensor 18 is zero (see FIG. 4-a).

  When the torsion bar 10 is twisted, relative rotation occurs between the magnet body 13 and the pair of magnetic yokes 14. FIG. 4B illustrates a case where the pair of magnetic yokes 14 are displaced counterclockwise by this relative rotation, and the convex portion 15a facing the outer periphery of the magnet body 13 has more area than the N pole. On the other hand, the convex portion 15b facing the inner periphery of the magnet body 13 overlaps with the south pole more in area. In the adjacent arc region 13a of the magnet body 13, magnetic flux that flows to the pair of magnetic flux collecting rings 16a and 16b via these convex portions 15a and 15b is generated. Therefore, the magnetic flux density between the magnetic flux collecting rings 16a and 16b is determined by the magnetic sensor 18. The torsional torque applied to the torsion bar 10 is obtained by detecting at.

  In this torque sensor, a plurality of convex portions 15 a and 15 b that constitute a magnetic input / output end portion of a set of magnetic yokes 14 are not arranged only on the magnetic pole surface on one side of the magnet body 13. Since the magnetic poles are arranged on the magnetic pole surfaces on both sides, the magnetic flux enters and exits from the magnetic pole surfaces on both sides of the magnet body 13 via the plurality of convex portions 15a and 15b, and there is a margin between the convex portions 15a and between the convex portions 15b. Therefore, the torque sensor can be easily downsized while ensuring the detection accuracy of the magnetic flux density.

  In the electric power steering, the maximum value of the torsion angle (twisting amount) of the torsion bar 10 is reduced in order to improve the steering feeling of the vehicle without excessively reducing the distance between the convex portions 15a and the convex portions 15b. It can be set.

  Since the magnetic sensor 18 and the pair of magnetism collecting rings 16a and 16b are fixed to the housing side via nonmagnetic members that couple them, the wiring of the magnetic sensor 18 seems to be entangled with the rotation of the torsion bar 10. There is nothing that can be done easily.

  The plurality of convex portions 15a and 15b constituting the magnetic input / output end portions of the set of magnetic yokes 14 are formed as shown in FIG. 5 so that the convex portion 15a has an area of a surface facing the outer periphery of the magnet body. The areas of the surfaces of the convex portions 15b facing the inner circumference of the magnet body are preferably set to be equal. Thereby, the area (magnetic flux) of the magnetic path on both sides sandwiching the magnet body 13 is made uniform between the convex portions 15a and 15b, and the change in the magnetic field due to the twisting of the torsion bar 10 can be detected with higher accuracy.

  In the embodiment shown in FIGS. 1 to 3, the magnetic flux collecting convex portions 20a and 20b are integrally formed with the magnetic flux collecting rings 16a and 16b, but the magnetic flux collecting convex portions 20a and 20b are formed as shown in FIG. It is also conceivable to separately form 16a and 16b separately. In this case, the magnetic flux collecting rings 16a and 16b and the magnetic yokes 14 (outer ring 14a and inner ring 14b) are coupled by a nonmagnetic member, while the magnetic flux collecting convex portions 20a and 20b and between them (gap). Only the intervening magnetic sensor 18 can be coupled by a non-magnetic member and fixed to the housing side.

  FIG. 7 illustrates another embodiment, in which the magnetism collecting rings 16a and 16b are omitted, and the magnetism collecting convex portions 20a and 20b are provided in a non-contact manner between the outer ring 14a and the inner ring 14b. The magnetic flux collecting convex portions 20a and 20b and the magnetic sensor 18 interposed between them (gap) are coupled to each other by a nonmagnetic member and fixed to the housing side.

It is a principal part exploded view of the torque sensor which concerns on embodiment of this invention. It is the same partial assembly drawing and its sectional drawing. It is the same partial assembly drawing and its sectional drawing. It is explanatory drawing which similarly concerns on a neutral state (a) and a twist state (b). It is explanatory drawing which concerns on the neutral state (a) and the twisted state (b) showing the modification of a convex part. It is a partial assembly figure explaining the modification of a magnetism collection ring. It is a partial assembly drawing concerning another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Torsion bar 11 1st axis | shaft 12 2nd axis | shaft 13 Magnet body 13a Arc region of magnet body 14 1 set of magnetic yoke 14a Outer ring 14b Inner ring 15a, 15b Convex part 16a, 16b Magnetic flux collection ring 18 Magnetic sensor 20a, 20b Collection Magnetic convex part

Claims (7)

  A ring-shaped magnet body attached to one end of the torsion bar, a pair of magnetic yokes attached to the other end of the torsion bar, and a magnetic sensor for detecting a magnetic flux density generated between the pair of magnetic yokes. In the torque sensor, the magnet body is magnetized so that the magnetic poles of the outer periphery and the inner periphery are different for each region divided at equal intervals in the circumferential direction, and these magnetic poles appear alternately in the circumferential direction, while one set of magnets The yoke is composed of an outer ring and an inner ring that are opposed to each other at a predetermined interval in the radial direction. The yoke is arranged at equal intervals in the circumferential direction so as to form a magnetic input / output end portion and faces the outer periphery of the magnet body. And a plurality of convex portions arranged at equal intervals in the circumferential direction so as to form a magnetic input / output end portion on the inner ring and facing the inner circumference of the magnet body. Sensor.   In one set of magnetic yokes, when the torsion bar is in a neutral state where the torsion bar is zero, the convex portions facing the outer periphery of the magnet body and the convex portions facing the inner periphery of the magnet body are the S pole and N pole of the magnet body. The torque sensor according to claim 1, wherein the torque sensor is set so as to overlap with the same area in such a manner as to straddle the boundary between the two.   One set of magnetic yokes is set so that the area where each convex part of the outer ring faces the outer circumference of the magnet body is equal to the area where each convex part of the inner ring faces the inner circumference of the magnet body. The torque sensor according to claim 1.   In one set of magnetic yokes, a pair of magnetism collecting rings are provided in a non-contact manner between an inner ring and an outer ring, and the magnetic sensor is interposed between the pair of magnetism collecting rings. Item 2. The torque sensor according to Item 1.   4. The torque sensor according to claim 3, wherein the magnetic sensor and the pair of magnetism collecting rings are fixed to the housing side via a nonmagnetic member that couples the magnetic sensor and the pair of magnetism collecting rings.   In one set of magnetic yokes, a pair of magnetic flux collecting convex portions are provided in a non-contact manner between the inner ring and the outer ring, and the magnetic sensor is interposed between the pair of magnetic flux collecting convex portions. The torque sensor according to claim 1.   6. The torque sensor according to claim 5, wherein the magnetic sensor and the pair of magnetic flux collecting convex portions are fixed to the housing side via a non-magnetic material that couples the magnetic sensor and the pair of magnetic flux collecting convex portions.

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