JP5633471B2 - Torque detector and electric power steering device - Google Patents

Description

  The present invention relates to a torque detector and an electric power steering system (EPS).

  Conventionally, various types of torque detectors (torque sensors) have been proposed for use in electric power steering devices mounted on automobiles and the like. For example, in Patent Document 1, a pair of ring-shaped sensor members (a sensor yoke and a collector) are arranged so as to face one surface or the outer peripheral surface of a ring-shaped magnetic member (permanent magnet) magnetized in the circumferential direction. There has been proposed a torque detector that provides a magnetic yoke) and detects torque generated on the magnetic member side or the sensor member side based on the magnetic flux detected by the magnetic flux detector disposed between the sensor members.

And although the torque detection principle is different from the torque detector described in Patent Document 1, it is possible to increase the coupling strength of the magnetic member to the input shaft or the output shaft, and thus to increase the accuracy of torque detection. For example, what is shown in FIG. 11 is known (refer patent document 2). FIG. 11 is an exploded perspective view of a magnetic member and an output shaft in a conventional torque detector.
In FIG. 11, the output shaft 101 includes a round bar-shaped main body portion 102 and a cylindrical small-diameter portion 103 that is provided at the upper end of the main body portion 102 and has a smaller diameter than the main body portion 102.

  The magnetic member 110 is formed in a substantially disc shape having a press-fitting hole 111 for press-fitting and fixing to the small-diameter portion 103 at the center. A plurality of notched portions 113 are formed on the outer peripheral portion of the magnetic member 110 so as to leave the plurality of notched portions 112 and penetrate in the axial direction at predetermined intervals in the circumferential direction.

Three axially extending grooves 114 are formed at predetermined intervals on the inner peripheral surface of the press-fitting hole 111 in the magnetic member 110. On the other hand, on the outer peripheral surface of the small-diameter portion 103 of the output shaft 101, a plurality of protrusions 104 extending in the axial direction that engage with the grooves 114 are provided.
Here, the magnetic member 110 is fixed by press-fitting the press-fitting hole 102 into the small-diameter portion 103 of the output shaft 101. At this time, the protrusion 104 on the outer periphery of the small-diameter portion 103 is engaged with the groove 114 of the magnetic member 110, and the rotation of the magnetic member 110 is prevented.

JP 2009-271055 A JP 2003-185510 A

However, the method of fixing the magnetic member 110 to the output shaft 101 in the torque detector shown in FIG. 11 has the following problems.
That is, the magnetic member 110 is press-fitted and fixed to the small-diameter portion 103 of the output shaft 101, and rotation is prevented by engaging the protrusion 104 with the groove 114, but the fixing is limited only to the holding force by press-fitting. Therefore, when the press-fit holding force decreases, the magnetic member 110 may come out in the direction opposite to the press-fit direction.

  Accordingly, the present invention has been made to solve this problem. The purpose of the present invention is to prevent rotation of the magnetic member, and even when the press-fitting holding force is reduced, the magnetic member comes out in the direction opposite to the press-fitting direction. It is an object of the present invention to provide a torque detector and an electric power steering device that can avoid such a situation.

In order to solve the above-described problems, a torque detector according to claim 1 of the present invention includes an elastic body that connects the first rotating shaft and the second rotating shaft, and a magnetic member fixed to the first rotating shaft. A plurality of magnetic bodies fixed to the second rotating shaft and disposed in the magnetic field of the magnetic member, forming a magnetic circuit of the magnetic member, and disposed in the magnetic field of the magnetic member; A torque detector comprising: an auxiliary magnetic body that forms a circuit; and a magnetic flux detector that detects the magnetic body and a magnetic flux induced by the auxiliary magnetic body, wherein the magnetic member is an outer periphery of the first rotating shaft. A press-fitting hole that is press-fitted into the press-fitting, and a protrusion that is formed on an inner peripheral surface of the press-fitting hole and protrudes inward in the radial direction of the first rotary shaft, and the first rotary shaft includes the first rotation It is formed on the outer peripheral surface of the shaft, and has a groove into which the protrusion enters when press-fitting, A recess is formed on the bottom surface of the groove. The recess is recessed inward in the radial direction of the first rotating shaft. The protrusion and the recess slide on the recess when the magnetic member is pressed. In a direction opposite to the direction, the tip of the protrusion is engaged with the recess, so that the magnetic member can be prevented from coming out in the direction opposite to the press-fitting direction. Yes.

A torque detector according to a second aspect of the present invention is the torque detector according to the first aspect, wherein the magnetic member is a permanent magnet formed as a plate-like annular body surrounding the first rotating shaft. And an annular back yoke made of metal for housing the permanent magnet, and the inner peripheral surface of the annular back yoke is the press-fitting hole.
According to a third aspect of the present invention, an electric power steering apparatus according to a third aspect of the present invention is an electric motor that generates auxiliary steering torque from an electric motor and transmits it to an output shaft of a steering mechanism in response to steering torque applied to a steering wheel. It is a power steering apparatus, Comprising: The torque detector of Claim 1 or 2 is provided, It is characterized by the above-mentioned.

  According to the torque detector according to claim 1 and the electric power steering apparatus according to claim 3 of the present invention, the magnetic member includes a press-fitting hole that is press-fitted and fixed to the outer periphery of the first rotating shaft, and a press-fitting hole. A projection formed on the inner circumferential surface and projecting radially inward of the first rotation shaft. The first rotation shaft is formed on the outer circumferential surface of the first rotation shaft, and has a groove into which the projection enters during press-fitting. Since the magnetic member can be press-fitted and fixed to the first rotation shaft, the protrusion can enter the groove during press-fitting so that the rotational phase of the magnetic member can be easily positioned during press-fitting, and the magnetic member can be fixed even after press-fitting. It is possible to prevent rotation. In addition, a recess that is recessed inward in the radial direction of the first rotating shaft is formed on the bottom surface of the groove. The protrusion and the recess slide in the recess when the magnetic member is pressed, and in a direction opposite to the press-fitting direction of the magnetic member. Since the tip of the protrusion is configured to engage with the recess, even when the press-fitting holding force is reduced, the protrusion of the protrusion engages with the recess, so that the magnetic member comes out in the direction opposite to the press-fitting direction. Thus, a torque detector and an electric power steering device can be provided.

  According to the torque detector according to claim 2 and the electric power steering apparatus according to claim 3 of the present invention, the magnetic member is a permanent plate formed as a plate-shaped annular body surrounding the first rotating shaft. It consists of a magnet and a metal annular back yoke that houses the permanent magnet, and the inner peripheral surface of the annular back yoke is the press-fitting hole, so that the magnetic members are all made of permanent magnets. Further, the weight can be reduced by using a metal annular back yoke. Further, since the protrusion formed on the inner peripheral surface of the press-fitting hole is formed on the inner peripheral surface of the metal annular back yoke, the protrusion can be easily formed.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a disassembled perspective view for demonstrating the main components of the electric power steering apparatus shown in FIG. FIG. 2 is a cross-sectional view around a torque detector of the electric power steering apparatus shown in FIG. 1. The magnetic member which comprises the torque detector shown in FIG. 3 is shown, (A) is a top view, (B) is sectional drawing which follows the 4B-4B line | wire in (A). The output shaft of the electric power steering apparatus shown in FIG. 1 is shown, (A) is a top view, (B) is sectional drawing which follows the 5B-5B line | wire in (A). 4A and 4B show a state where the magnetic member shown in FIG. 4 is press-fitted and fixed to the output shaft, where FIG. 5A is a schematic cross-sectional view, and FIG. 3A and 3B show a sensor yoke assembly constituting the torque detector shown in FIG. 3, wherein FIG. 3A is a perspective view, and FIG. 3A and 3B show a combination of a magnetic member, a sensor yoke, and a magnetism collecting yoke that constitute the torque detector shown in FIG. 3, and FIG. 3B is a perspective view when a modification of the magnetism collecting yoke is adopted. FIG. The state which combined the magnetic member which comprises the torque detector shown in FIG. 3, the sensor yoke, and the magnetism collection yoke is shown, (A) is a partial cross section figure, (B)-(D) shows the modification. FIG. It is explanatory drawing for demonstrating the torque detection principle by the torque detector shown in FIG. It is a disassembled perspective view of the magnetic member and output shaft in the torque detector of a prior art example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The electric power steering apparatus shown in FIG. 1 detects a steering torque generated in the steering shaft 2 by the operation of the steering wheel 1 by a torque detector 3, and the control unit 13 drives and controls the electric motor 12 based on the detection signal. Thus, auxiliary steering torque is generated to assist the steering force of the steering wheel 1.

  A steering shaft 2 connected to the steering wheel 1 has an input shaft (second rotating shaft) 2a and an output shaft (first rotating shaft) 2b on which a driver's steering force acts, and the input shaft 2a and the output shaft. Between 2b, the torque detector 3 and the reduction gear box 11 are interposed. The steering force transmitted to the output shaft 2b of the steering shaft 2 is transmitted to the steering mechanism. Specifically, the steering force is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6, and the steering force transmitted to the pinion shaft 7 is transmitted to the steering gear 8. Is transmitted to the tie rod 9 to steer a steered wheel (not shown). The steering gear 8 is configured as a rack-and-pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is converted into a rectilinear motion by the rack 8b. It has been converted.

  An auxiliary steering mechanism 10 that transmits auxiliary steering torque to the output shaft 2 b is connected to the output shaft 2 b of the steering shaft 2. The auxiliary steering mechanism 10 includes a reduction gear box 11 connected to the output shaft 2b, and an electric motor 12 connected to the reduction gear box 11 and generating auxiliary steering torque. The steering shaft 2, the torque detector 3 and the reduction gear box 11 constitute a column, and the electric motor 12 applies auxiliary steering torque to the output shaft 2b of the column. That is, the electric power steering apparatus in this embodiment is a column assist type.

  The torque detector 3 detects the steering force transmitted to the input shaft 2a via the steering wheel 1 as a steering torque. The configuration of the torque detector 3 will be described in detail later. The control unit 13 that controls the driving of the electric motor 12 is supplied with electric power from the battery 15 with the ignition switch 14 turned on. The control unit 13 calculates an assist steering command value of the assist command based on the steering torque T detected by the torque detector 3 and the traveling speed V detected by the vehicle speed sensor 16, and the calculated assist steering command value is calculated. Based on this, the supply current value to the electric motor 12 is controlled.

  Next, as shown in FIGS. 2 and 3, the torque detector 3 includes a torsion bar (elastic body) 2c that connects the input shaft (second rotating shaft) 2a and the output shaft (first rotating shaft) 2b, Magnetic member 31 including permanent magnet 31a, sensor yoke assembly (plural magnetic bodies) 32 and magnetic collecting yoke assembly (auxiliary magnetic body) 33 forming magnetic circuit, magnetic flux detected by induction of sensor yoke 32a and magnetic collecting yoke 33a And a detector assembly 34 including a magnetic flux detector 34a for detecting the torque based on the detection output of the magnetic flux detector 34a when torque is applied to the input shaft 2a.

  The torsion bar 2c is a connecting shaft that connects one axial end of the input shaft 2a and one axial end of the output shaft 2b. A steering wheel 1 (see FIG. 1) is attached to the other axial end of the input shaft 2a. As shown in FIGS. 2 and 3, the input shaft 2a is covered with a hollow shaft 2d. The gear cover 2e connected to the hollow shaft 2d is attached to the reduction gear box 11, so that the structure (the reduction gear and the torque detector 3) in the reduction gear box 11 is protected. The output shaft 2b is rotatably supported by the reduction gear box 11 by a bearing 30. A steered wheel (not shown) is attached to the other axial end of the output shaft 2b via a universal joint 4 or the like.

  As shown in FIGS. 3 and 4, the magnetic member 31 includes a permanent magnet 31a formed as a flat annular body surrounding the output shaft 2b (and the torsion bar 2c), and a metal member that houses the permanent magnet 31a. And an annular back yoke 31b. The permanent magnet 31a is configured by alternately magnetizing different magnetic poles (N pole and S pole) in the circumferential direction, and is fixed to the annular back yoke 31b by adhesion.

  The annular back yoke 31b is press-fitted and fixed to the outer periphery of the output shaft 2b. As shown in FIGS. 4A and 4B, the annular back yoke 31b includes an inner peripheral side wall 31c that rises from the inner peripheral edge of the bottom wall to which the permanent magnet 31a is bonded. The inner peripheral surface 31d of the inner peripheral side wall 31c constitutes a press-fitting hole that is press-fitted and fixed to the outer periphery of the output shaft 2b, and has a circular shape when viewed from above so as to contact the outer peripheral surface of the output shaft 2b. . On the other hand, a gap is formed between the inner peripheral side wall 31c of the annular back yoke 31b and the permanent magnet 31a, as shown in FIGS. For this reason, it becomes possible to press-fit the annular back yoke 31b into the output shaft 2b without applying stress to the permanent magnet 31a. The use of a ferromagnetic material as the material of the annular back yoke 31b is preferable because the magnetic force of the permanent magnet 31a can be used efficiently.

  Further, on the inner peripheral surface 31d of the inner peripheral side wall 31c of the annular back yoke 31b, as shown in FIGS. 4 (A) and 4 (B), a plurality of (this book) projecting inward in the radial direction of the output shaft 2b. In the embodiment, three projections 31e are provided. The plurality of protrusions 31e are arranged at an equal pitch in the circumferential direction on the inner peripheral surface 31d of the inner peripheral side wall 31c. Each protrusion 31e is cut and raised from the side opposite to the press-fitting direction of the inner peripheral surface 31d of the inner peripheral side wall 31c (the lower side in FIGS. 4B, 6A, and B) to output shaft 2b. It extends diagonally inward in the radial direction. As shown in FIG. 6A, each protrusion 31e is formed so that the width is gradually narrowed from the root toward the tip.

  In the present embodiment, the example in which the permanent magnet 31a is attached to the annular back yoke 31b in order to effectively use the magnetic flux has been described. However, the permanent magnet 31a can also be attached directly to the output shaft 2b. As a magnet material constituting the permanent magnet 31a, a ferrite magnet, a rare earth magnet (Nd—Fe—B magnet, Sm—Co magnet, etc.), a metal magnet, a sintered magnet, or the like can be employed. Moreover, you may employ | adopt as a permanent magnet the bond magnet (rubber magnet or plastic magnet) integrally molded with the cyclic | annular back yoke 31b. As described above, when the permanent magnet 31a is directly attached to the output shaft 2b, a press-fitting hole that is press-fitted and fixed to the outer periphery of the output shaft 2b is formed in the permanent magnet 31a, and the output shaft 2b is formed on the inner peripheral surface of the press-fitting hole. A plurality of projections (not shown) projecting radially inward are formed.

  When the permanent magnet 31a is attached to the annular back yoke 31b, the weight can be reduced by using the metallic annular back yoke 31b as compared with the case where the magnetic member 31 is entirely composed of the permanent magnet 31a. Further, since the protrusion 31e formed on the inner peripheral surface of the press-fitting hole is formed on the inner peripheral surface of the metal annular back yoke 31b, the protrusion 31e can be easily formed.

  Further, as shown in FIGS. 3 and 5A and 5B, the output shaft 2b has a shaft main body 2ba extending in the vertical direction (the vertical direction and the axial direction in FIG. 3), and the outer periphery of the shaft main body 2ba. The annular back yoke 31b of the magnetic member 31 is press-fitted and fixed. The shaft body 2ba is provided with an input shaft receiving recess 2bc into which one axial end of the input shaft 2a enters and a torsion bar receiving recess 2bb into which the torsion bar 2c enters. Here, the annular back yoke 31b of the magnetic member 31 is press-fitted and fixed to the outer peripheral surface of the shaft main body 2ba of the output shaft 2b. The press-fitting direction of the annular back yoke 31b is a direction from the top to the bottom as shown by the arrow in FIG. As shown in FIG. 3 and FIGS. 5A and 5B, a base step 2bd on which the press-fitted and fixed annular back yoke 31b is seated is formed on the outer peripheral surface of the shaft body 2ba. Has been.

  When the annular back yoke 31b of the magnetic member 31 is press-fitted into the outer peripheral surface of the shaft body 2ba as shown in FIGS. 5 (A), 5 (B) and 6 (A), (B). A plurality of (three in the present embodiment) grooves 2be into which the protrusions 31e formed on the back yoke 31b enter are formed. The plurality of grooves 2be are arranged at an equal pitch in the circumferential direction on the outer peripheral surface of the shaft body 2ba. And each groove | channel 2be is extended in the up-down direction from the upper end of shaft main body 2ba to the base part 2bd in the outer peripheral surface of shaft main body 2ba. The width of each groove 2be is substantially the same as the base of the protrusion 31e so that the protrusion 31e can enter and the rotation of the press-fitted annular back yoke 31b is prevented.

Further, on the bottom surface of each groove 2be, as shown in FIGS. 5 (B) and 6 (B), a plurality of (this book) is recessed inward in the radial direction of the output shaft 2b (rightward in FIG. 5 (B)). In the embodiment, three recesses 2bf are formed. The plurality of recesses 2bf are arranged at an equal pitch from top to bottom on the bottom surface of the groove 2be.
Here, the protrusions 31e and the recesses 2bf described above cause the protrusions 31e to slide on the recesses 2bf when the magnetic member 31 is pressed into the output shaft 2b of the annular back yoke 31b. In the direction opposite to the press-fitting direction, the tip of the protrusion 31e is configured to engage with the recess 2bf.

The operation of press-fitting the annular back yoke 31b of the magnetic member 31 into the shaft main body 2ba of the output shaft 2b will be described with reference to FIGS. 6 (A) and 6 (B).
When the annular back yoke 31b is press-fitted into the shaft main body 2ba, the annular back yoke 31b is inserted from above the shaft main body 2ba in the press-fitting direction indicated by the arrow in FIG. 6A (from the top to the bottom in FIG. 6A). The protrusion 31e enters the groove 2be into the shaft body 2ba, and is pushed in until the tip of the protrusion 31e slides over the desired recess 2bf. Then, the annular back yoke 31b is moved slightly in the direction opposite to the press-fitting direction. As a result, the tip of the protrusion 31e engages with the desired recess 2bf, and the press-fitting operation of the annular back yoke 31b into the shaft body 2ba is completed. Accordingly, the annular back yoke 31b of the magnetic member 31 can be press-fitted and fixed to the shaft main body 2ba of the output shaft 2b, and the protrusion 31e enters the groove 2be after the press-fitting, so that the rotation of the magnetic member 31 including the annular back yoke 31b is performed. Blocking can be done. Moreover, since the protrusion 31e enters the groove 2be at the time of press-fitting, the rotational phase of the magnetic member 31 at the time of press-fitting can be easily performed.

  A recess 2bf that is recessed radially inward of the output shaft 2b is formed on the bottom surface of the groove 2be. The protrusion 31e and the recess 2bf slide on the recess 2bf when the magnetic member 31 is press-fitted. The tip of the protrusion 31e is configured to engage with the recess 2bf in the direction opposite to the press-fitting direction. For this reason, even when the press-fit holding force is reduced, it is possible to prevent the magnetic member 31 from coming out in the direction opposite to the press-fit direction by engaging the protrusion 31e with the recess 2bf.

  Next, as shown in FIG. 3 and FIGS. 7A and 7B, the sensor yoke assembly 32 includes a sensor yoke 32a, a metal sleeve 32b inserted in the center of the sensor yoke 32a, and these sensor yokes. 32a and a resin molded body 32c formed outside the sleeve 32b. The sensor yoke 32a is an annular magnetic body formed by arranging two short cylindrical sensor yoke components (first sensor yoke component 32aA and second sensor yoke component 32aB) in the axial direction, and is a permanent magnet. The magnetic circuit of the permanent magnet 31a is formed in the magnetic field of the 31a. As shown in FIG. 7B, the first sensor yoke constituting portion 32aA includes a plurality of flat plate trapezoidal claw constituting portions 32dA constituting the claw portions 32d, a side wall portion 32eA constituting the outer peripheral portion 32e, have. The second sensor yoke constituting part 32aB has a plurality of flat plate-like claw constituting parts 32dB constituting the claw parts 32d and a side wall part 32eB constituting the outer peripheral part 32e.

  As shown in FIGS. 3, 7A, and 8A, the sensor yoke 32a is disposed on a substantially flat surface so as to face the one axial side of the permanent magnet 31a and surround the input shaft 2a. It has a plurality of flat plate-like claw portions 32d. These claw portions 32d are formed by combining the claw portion constituting portion 32dA of the first sensor yoke constituting portion 32aA and the claw portion constituting portion 32dB of the second sensor yoke constituting portion 32aB in the circumferential direction. They are arranged at equal intervals. The sensor yoke 32a has an outer peripheral portion 32e that is arranged in a non-contact state on the radially inner side of the magnetism collecting yoke 33a described later and extends in the axial direction. This outer peripheral part 32e is comprised from the side wall part 32eA of 1st sensor yoke structure part 32aA, and the side wall part 32eB of 2nd sensor yoke structure part 32aB.

  The side wall portion 32eB of the second sensor yoke constituting portion 32aB constituting the outer peripheral portion 32e of the sensor yoke 32a is disposed on the radially outer side of the permanent magnet assembly 31. In other words, the permanent magnet assembly 31 is housed in a cylindrical space composed of the side wall portion 32eB and the claw portion constituting portion 32dB of the second sensor yoke constituting portion 32aB. For this reason, the axial dimension of the structure which consists of the permanent magnet assembly 31 and the sensor yoke assembly 32 can be shortened, and by extension, the axial dimension of the torque detector 3 can be shortened.

  An integral sensor yoke assembly 32 is formed by covering the sleeve 32b and the sensor yoke 32a with a resin molding 32c provided on the outside thereof. The sleeve 32b is fixed to the input shaft 2a by caulking after being fitted to the input shaft 2a. By fixing the sleeve 32b to the input shaft 2a in this way, the phase of the sensor yoke 32a and the permanent magnet 31a can be adjusted with the sensor yoke assembly 32 inserted into the input shaft 2a. Can be improved. The sleeve 32b is preferably made of a non-magnetic material because leakage flux from the claw portion 32d of the sensor yoke 32a to the input shaft 2a can be reduced. If the sleeve 32b is made of a material softer than the input shaft 2a, the input shaft 2a is not deformed during caulking, so that positioning can be performed with high accuracy.

  In the present embodiment, the sleeve 32b is fixed to the input shaft 2a by caulking. However, the sleeve 32b may be fixed to the input shaft 2a by means of screwing, welding, adhesion, or the like from the lateral direction. it can. Further, in the present embodiment, an example in which the planar shape is the trapezoidal claw portion 32d (the claw portion constituting portions 32dA and 32dB) is shown, but the planar shape is a triangular shape or a rectangular shape. Also good.

  In the present embodiment, as shown in FIG. 9A (and FIG. 9D), an outer peripheral portion 32e (side wall portion 32eA, having an I-shaped cross section extending only in the axial direction from the claw portion 32d. 32eB) is provided on the sensor yoke 32a. However, as shown in FIGS. 9B and 9C, the cross-sectional core extending continuously outward in the axial direction and the radial direction from the claw portion 32d is shown. A character-shaped outer peripheral portion 32e can also be provided. Further, as shown in FIG. 9E, the side wall portion 32eA of the first sensor yoke constituting portion 32aA extends radially outward to be formed on the same plane as the claw portion 32d, while the second sensor yoke It is also possible to provide the outer peripheral portion 32e having an L-shaped cross section by extending the side wall portion 32eB of the component portion 32aB in the axial direction. When the first sensor yoke component 32aA opposite to the permanent magnet 31a is formed in a flat plate shape in this way, the axial dimension of the torque detector 3 can be further shortened.

  As shown in FIGS. 3 and 8A, the magnetic flux collecting yoke assembly 33 includes a magnetic flux collecting yoke 33a disposed in a non-contact state in the vicinity of the outer peripheral portion 32e of the sensor yoke 32a, and a magnetic flux collecting yoke holder 33b. Have. The magnetism collecting yoke holder 33b accommodates and fixes the magnetism collecting yoke 33a therein, is made of a non-magnetic material, and is fixed to the reduction gear box 11 as shown in FIG. The magnetism collecting yoke 33a includes two magnetism collecting yoke constituent parts (first sensor yoke constituent parts (first sensor yoke constituent part 32aA and second sensor yoke constituent part 32aB)) that constitute the sensor yoke 32a. 1 is an annular auxiliary magnetic body configured by arranging one magnetic flux collecting yoke component 33aA and second magnetic flux collecting yoke component 33aB) in the axial direction. Form.

  As shown in FIG. 8A, the first magnetism collecting yoke portion 33aA and the second magnetism collecting yoke constituting portion 33aB are respectively the first sensor yoke constituting portion 32aA and the second sensor yoke constituting portion 32aB. It arrange | positions so as to oppose the surface of the outer peripheral part 32e on the radial direction outer side. As shown in FIG. 8 (A), the first (second) magnetism collecting yoke component 33aA (33aB) includes a direction and radial direction of the second (first) magnetism collecting yoke component 33aB (33aA). Convex portions 33c formed so as to protrude outward are provided, and these convex portions 33c function as magnetic flux concentrating portions. The interval between the convex portions 33c in the axial direction is generated from the permanent magnet 31a because it is narrower than the interval in the axial direction between the first magnetic flux collecting yoke component 33aA and the second magnetic flux collecting yoke component 33aB. Magnetic flux can be concentrated. A magnetic detector 34a of a detector assembly 34 to be described later is disposed on the convex portion 33c as the magnetic flux concentrating portion.

  In the present embodiment, an example is shown in which an annular (circular planar shape) magnetic collecting yoke 33a is employed. However, as shown in FIG. 8B, the planar shape is a fan shape (or a semicircular shape). It is also possible to employ a magnetic collecting yoke 33d. When the magnetic flux collecting yoke 33d having a planar shape or a semicircular shape is employed in this way, the magnetic flux collecting yoke 33d can be assembled from the lateral direction (radial direction) of the sensor yoke 32a, and the magnetic flux collecting yoke 33d can be attached to the input shaft 2a. As a result, it is not necessary to penetrate through, so that the assembling work can be greatly facilitated.

  Further, in the present embodiment, as shown in FIG. 9A (and FIG. 9E), the magnetism collecting yoke 33a is arranged radially outside the outer peripheral portion 32e (side wall portions 32eA, 32eB) of the sensor yoke 32a. In the example shown in FIGS. 9B and 9C, the magnetism collecting yoke 33a is placed on the axial surface of the outer peripheral portion 32e of the sensor yoke 32a. It can also arrange so that it may counter. Further, as shown in FIG. 9D, the magnetism collecting yoke 33a may be disposed so as to face both the radially outer surface and the axial surface of the outer peripheral portion 32e of the sensor yoke 32a. As shown in FIGS. 9B to 9D, when the magnetism collecting yoke 33a is arranged so as to oppose the axial surface of the outer peripheral portion 32e of the sensor yoke 32a, the axis of the input shaft 2a with respect to the magnetism collecting yoke 33a. Even when shaking occurs, the amount of magnetic flux passing through the magnetism collecting yoke 33a is less likely to fluctuate.

  As shown in FIG. 3, the detector assembly 34 is attached to the magnetic flux collecting yoke assembly 33, and is inserted into the gap in the axial direction of the convex portion 33c as a magnetic flux concentrating portion provided in the magnetic flux collecting yoke 33a. A magnetic flux detector 34a is provided. The magnetic flux detector 34a is arranged in the vicinity of the outer peripheral portion 32e of the sensor yoke 32a in a non-contact state with the sensor yoke 32a, and detects the amount of magnetic flux passing through the gap in the axial direction of the magnetic flux concentrating portion (convex portion 33c). . The magnetic flux detector 34a may be any device that can measure the amount of magnetic flux, such as a Hall element, MR element, MI element, or the like.

  If an alloy containing nickel is used as the material for the sensor yoke 32a and the magnetism collecting yoke 33a, the magnetic characteristics (output hysteresis) can be improved and good performance as the torque detector 3 can be obtained. It becomes. If hysteresis is not a problem, the sensor yoke 32a and the magnetism collecting yoke 33a are configured using other magnetic metal (for example, a silicon steel plate or a rolled steel plate such as SPCC generally used as a material for a motor or the like). can do. Further, either one of the sensor yoke 32a and the magnetism collecting yoke 33a may be configured using an alloy containing nickel.

  Next, the principle of torque detection of the torque detector 3 according to this embodiment will be described with reference to FIG. FIG. 10 shows the permanent magnet 31 a and the sensor yoke 32 a that constitute the torque detector 3. In FIG. 10, in order to clarify the positional relationship between the claw portion 32d of the sensor yoke 32a and the permanent magnet 31a, the second sensor yoke constituting portion 32aB constituting the sensor yoke 32a is not shown. However, in actuality, the claw portion constituting portion 32dB of the second sensor yoke constituting portion 32aB is disposed between the claw portion constituting portions 32dA of the first sensor yoke constituting portion 32aA, and a plurality of claw portions 32d are formed.

  When there is no torque input, each of the claw portions 32d of the sensor yoke 32a is located on the boundary between the magnetic poles (N pole and S pole) constituting the permanent magnet 31a, and the permanent magnet 31a viewed from each claw portion 32d. Since the permeance (reciprocal of the magnetic resistance) with respect to the N pole and the S pole is equal, the magnetic flux flows as shown in FIG. Specifically, the magnetic flux generated from the N pole of the permanent magnet 31a enters the claw portion 32d of the sensor yoke 32a and enters the S pole of the permanent magnet 31a as it is. Therefore, the magnetic flux does not flow through the magnetic flux detector 34a.

  When torque is input to the input shaft 2a by the driver rotating the steering wheel 1, the input side of the torsion bar 2c rotates in the same manner as the steering wheel 1 and the torsion bar 2c itself is twisted according to the input torque. Will occur. This twist causes a relative angular displacement between the input side and the output side of the torsion bar 2c. The relative angular displacement generated between the input side and the output side of the torsion bar 2c appears as a relative angular displacement between the permanent magnet 31a of the torque detector 3 and the sensor yoke 32a.

  When relative angular displacement occurs between the permanent magnet 31a and the sensor yoke 32a, the balance of permeance as shown in FIG. 10 is lost, and the magnetic circuit including the magnetic flux detector 34a (that is, the magnetic flux generated from the N pole of the permanent magnet 31a). Flows to the claw portion constituting portion 32dA of the first sensor yoke constituting portion 32aA, and the magnetic flux detector 34a is passed from the first sensor yoke constituting portion 32a via the first magnetic flux collecting yoke constituting portion 33aA and the convex portion 33c. The magnetic flux passes through the second magnetic flux collecting yoke component 33aB through the claw component component 32dB and returns to the S pole of the permanent magnet 31a. By detecting the magnetic flux generated in the magnetic circuit including the magnetic flux detector 34a by the magnetic flux detector 34a, the relative angular displacement can be measured, and the torque applied to the torsion bar 2c can be detected.

  In the torque detector 3 according to the above-described embodiment, the claw portion 32d of the sensor yoke 32a is arranged on a substantially flat surface so as to face the axial direction one side of the permanent magnet 31a formed as a flat annular body. Then, a part of the outer peripheral portion 32e of the sensor yoke 32a (the side wall portion 32eB of the second sensor yoke constituting portion 32aB) can be disposed on the radially outer side of the permanent magnet 31a. Therefore, the axial dimension of the torque detector 3 can be shortened, and the torque detector 3 can be downsized.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change and improvement can be performed.
For example, the magnetic member 31 is press-fitted and fixed to the output shaft 2b, but may be press-fitted and fixed to the input shaft 2a.
In addition, the protrusion 31e and the groove 2be into which the protrusion 31e enters are provided in plural (three in number), but may be provided in a single number.

Further, the shape of the protrusion 31e and the recess 2bf is such that the protrusion 31e slides on the recess 2bf when the magnetic member 31 is press-fitted, and the tip of the protrusion 31e engages with the recess 2bf in the direction opposite to the press-fitting direction of the magnetic member 31. It only has to be configured, and the shape is not limited to that shown in FIGS.
The sensor yoke assembly 32 is not limited to the illustrated example as long as the sensor yoke assembly 32 is fixed to the input shaft 2 a and disposed in the magnetic field of the magnetic member 31 to form the magnetic circuit of the magnetic member 31.
Further, the magnetic collecting yoke assembly 33 is not limited to the illustrated example as long as it is disposed in the magnetic field of the magnetic member 31 and forms the magnetic circuit of the magnetic member 31.

1 Steering wheel 2 Steering shaft 2a Input shaft (second rotating shaft)
2b Output shaft (first rotating shaft)
2ba shaft body 2bb torsion bar receiving recess 2bc input shaft receiving recess 2bd pedestal step 2be groove 2bf recess 2c torsion bar (elastic body)
2d hollow shaft 2e gear cover 3 torque detector 4 universal joint 5 lower shaft 6 universal joint 7 pinion shaft 8 steering gear 8a pinion 8b rack 9 tie rod 10 auxiliary steering mechanism 11 gear box 12 electric motor 13 control unit 14 ignition switch 15 battery 16 vehicle speed Sensor 31 Magnetic member 31a Permanent magnet 31b Annular back yoke 31c Inner peripheral side wall 31d Inner peripheral surface (press-fit hole)
31e Protrusion 32 Sensor yoke assembly 32a Sensor yoke 32aA First sensor yoke component 32aB Second sensor yoke component 32b Sleeve 32c Molded resin 32d Claw 32dA Claw component 32dB Claw component 32e Outer peripheral 32eA Side wall 32eB Side wall 33 Magnetic flux collecting yoke assembly 33a Magnetic flux collecting yoke 33aA First magnetic flux collecting yoke component 33aB Second magnetic flux collecting yoke component 33b Magnetic flux collecting yoke holder 33c Convex portion 33d Magnetic flux collecting yoke 34 Detector assembly 34a Magnetic flux detector

Claims (3)

An elastic body connecting the first rotating shaft and the second rotating shaft, a magnetic member fixed to the first rotating shaft, a magnetic member fixed to the second rotating shaft and disposed in the magnetic field of the magnetic member, A plurality of magnetic bodies forming a magnetic circuit of the magnetic member; an auxiliary magnetic body disposed in the magnetic field of the magnetic member; forming a magnetic circuit of the magnetic member; and a magnetic flux induced by the magnetic body and the auxiliary magnetic body A torque detector comprising a magnetic flux detector for detecting
The magnetic member includes a press-fitting hole that is press-fitted and fixed to the outer periphery of the first rotation shaft, and a protrusion that is formed on an inner peripheral surface of the press-fitting hole and projects radially inward of the first rotation shaft. The first rotating shaft is formed on the outer peripheral surface of the first rotating shaft, and includes a groove into which the protrusion is inserted during press-fitting. The bottom surface of the groove is radially inward of the first rotating shaft. A concave portion is formed, and the protrusion and the concave portion are configured such that the protrusion slides on the concave portion when the magnetic member is press-fitted, and the tip end portion of the protrusion is engaged with the concave portion in a direction opposite to the press-fitting direction of the magnetic member. By doing so, the torque detector is configured to avoid the magnetic member from slipping out in the direction opposite to the press-fitting direction .   The magnetic member includes a permanent magnet formed as a plate-shaped annular body surrounding the first rotating shaft, and a metal annular back yoke that houses the permanent magnet, and an inner peripheral surface of the annular back yoke is The torque detector according to claim 1, wherein the press-fitting hole is used.   The torque detector according to claim 1 or 2, wherein the electric power steering device generates an auxiliary steering torque from an electric motor and transmits the auxiliary steering torque to an output shaft of a steering mechanism in response to a steering torque applied to a steering wheel. An electric power steering apparatus comprising:

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