JP2005321361A - Torque detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detector capable of reducing a detection error caused by an external magnetic field, and capable of reducing a magnetic shielding area. <P>SOLUTION: This torque detector has two magnetism collecting rings 5, 5 juxtaposed around an outer circumference of a magnetic circuit forming member provided in a rotor, with a separate space along an axial direction, and for collecting a magnetic flux generated by the magnetic circuit forming member, and a detecting part 7 for detecting a torque applied onto the rotor, based on density of the magnetic flux collected by the magnetism collecting rings 5, 5. The magnetism collecting rings 5, 5 are formed into a cylindrical shape having protruded pieces 51, 51 extended radial-directionally outside from radial-directional one portion, and has magnetic shielding layers 6, 6 for shielding magnetically outer circumferential sides and end faces of the magnetism collecting rings 5, 5 from one-portions of the protruded pieces 51, 51. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a torque detection device that detects torque applied to a rotating body.

  As a torque detection apparatus, it describes in patent document 1, for example. The torque detection device of Patent Document 1 is arranged in parallel in the axial direction so as to be spaced apart from the outer periphery of a magnetic circuit forming member provided in a rotating body having an input shaft and an output shaft connected by a torsion bar. Are provided with two magnetic flux collecting rings for collecting the generated magnetic flux, and a detection unit for detecting the torque applied to the rotating body based on the density of the magnetic flux collected by the magnetic flux collecting rings.

  The torque detection device configured as described above is incorporated in an electric power steering device for a vehicle. The electric power steering apparatus includes the rotating body in which the input shaft is connected to a steering wheel, a housing that accommodates and supports the rotating body, an electric motor that is connected to the output shaft via a speed reduction mechanism, a drive circuit for the electric motor, and the And a control unit using a microprocessor connected to the detection unit, and the detection unit detects the rotational torque applied to the input shaft by steering the steering wheel by the torsion generated in the torsion bar. Based on this, the electric motor is driven and controlled.

By the way, since the torque detection device is arranged around the magnetic circuit forming member, when a vehicle mounted speaker or the like having a permanent magnet is disposed near the torque detection device, the torque detection device is generated from the permanent magnet such as the vehicle mounted speaker or the like. For example, a detection error may occur due to the influence of an external magnetic field. For example, the entire torque detection device may be covered with a magnetic shielding member, or the housing that houses and supports the rotating body may be covered with a magnetic shielding member. It is conceivable to eliminate the detection error.
JP 2003-149062 A

  However, when the entire torque detection device is covered with a magnetic shielding member, or the housing that accommodates and supports the rotating body is covered with a magnetic shielding member, the magnetic shielding area covered by the magnetic shielding member is relatively large, which increases costs. There is a problem of becoming.

  The present invention has been made in view of such circumstances, and a main object of the present invention is to provide a torque detection device capable of reducing detection errors due to an external magnetic field and reducing the magnetic shielding area. Another object is to provide a torque detection device that can reduce the cost of the magnetism collecting ring itself. Another object of the present invention is to provide a torque detector that can improve the workability of assembling the magnetism collecting ring and the magnetic shielding member.

  A torque detector according to a first aspect of the present invention is arranged around the outer periphery of a magnetic circuit forming member provided on a rotating body, and a magnetic flux collecting ring for collecting magnetic flux generated by the magnetic circuit forming member, and the magnetic collecting ring collected A torque detection device comprising a detection unit that detects a torque applied to the rotating body based on a magnetic flux density, wherein the magnetism collection ring has a magnetic shielding layer on an outer peripheral side.

  In the first invention, since the magnetic shielding layer is provided on the outer peripheral side of the magnetic flux collecting ring for collecting the magnetic flux generated by the magnetic circuit forming member, the influence of the external magnetic field on the magnetic flux collecting of the magnetic flux collecting ring is reduced. And detection errors due to an external magnetic field can be reduced. Moreover, since the magnetic shielding layer covers the outer peripheral side of the magnetism collecting ring, the magnetic shielding area of the magnetic shielding layer can be reduced.

  In the torque detector according to a second aspect of the present invention, the magnetic shielding layer is externally fitted to the magnetism collecting ring, has an annular shape with one circumferential opening, and extends radially outward from the middle in the circumferential direction. It is characterized by comprising a non-magnetic plate having an extended portion.

  In the second invention, since it is possible to obtain two magnetic shielding layers from the strip-shaped nonmagnetic plate, the removal area of the nonmagnetic plate can be reduced compared to the case where the nonmagnetic plate is formed into an annular shape. Can be reduced.

  A torque detector according to a third aspect of the present invention includes two magnetic flux collecting rings that are arranged in parallel in the axial direction so as to be separated from each other in the axial direction on the outer periphery of a magnetic circuit forming member provided on a rotating body, and collect magnetic flux generated by the magnetic circuit forming member. And a detecting unit that detects torque applied to the rotating body based on the density of magnetic flux collected by each magnetism collecting ring, wherein the magnetism collecting ring extends radially outward from one place in the radial direction. It has a cylindrical shape with protruding convex pieces, and has a magnetic shielding layer that magnetically shields the outer peripheral side and end face of the magnetism collecting ring and a part of the convex pieces.

  In the third aspect of the invention, the outer peripheral side of the magnetic flux collecting ring for collecting the magnetic flux generated by the magnetic circuit forming member and the outer end face in the axial direction, and a part of the convex piece (in the axial direction on the side where the detection unit is not arranged) Since the magnetic shielding layer is provided on the outer surface), the influence of the external magnetic field on the magnetic flux collection of the magnetic flux collecting ring can be reduced, and the detection error due to the external magnetic field can be reduced. In addition, the magnetic shielding layer covers the outer peripheral side of the magnetism collecting ring and the end surface on the outer side in the axial direction, and part of the convex piece (the surface on the outer side in the axial direction on the side where the detection unit is not disposed). The magnetic shielding area of the magnetic shielding layer can be reduced.

  The torque detector according to a fourth aspect of the invention is characterized in that the magnetism collecting ring and the magnetic shielding layer are molded of a synthetic resin material.

  In the fourth invention, since the magnetism collecting ring and the magnetic shielding layer are molded, the number of parts can be reduced and the number of assembly work steps can be reduced.

  According to the first and third inventions, it is possible to reduce the influence of an external magnetic field on the magnetic flux collection of the magnetic flux collecting ring, to reduce detection errors due to the external magnetic field, and to reduce the magnetic shielding area of the magnetic shielding layer. Thus, the cost of the torque detection device can be reduced.

  According to the second invention, since it is possible to obtain two magnetic shielding layers from a strip-shaped nonmagnetic plate, the removal area of the nonmagnetic plate can be reduced compared to the case where the nonmagnetic plate is formed into an annular shape. This can reduce the cost of the magnetic shielding layer itself, and thus the cost of the torque detector.

  According to the fourth invention, since the magnetism collecting ring and the magnetic shielding layer are molded, the number of parts can be reduced, and the number of assembly work steps can be reduced.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a cross-sectional view showing a configuration of a torque detection device according to the present invention, FIG. 2 is a schematic exploded perspective view, and FIG. 3 is an explanatory diagram of a magnetic circuit generated when a rotating body rotates in one direction.

  The torque detection device A is arranged in the axial direction so as to be separated from the outer periphery of the magnetic circuit forming member 4 included in the first rotating body 2 and the second rotating body 3 that are coaxially connected by the torsion bar 1. Two magnetic flux collecting rings 5 and 5 that collect magnetic flux generated by the magnetic circuit forming member 4, magnetic shielding layers 6 and 6 that magnetically shield the magnetic flux collecting rings 5 and 5 from an external magnetic field, and each magnetic flux collecting ring 5 , 5 is provided with a detection unit 7 for detecting the torque applied to the first rotating body 2 based on the density of the magnetic flux collected, and a detection circuit board 9 connected to the detection unit 7 by a conductor 8. The magnetic circuit forming member 4 is disposed around the outer periphery of the first rotating body 2, the plurality of permanent magnets 41 and the outer periphery of the permanent magnet 41, and is fitted on the second rotating body 3. It consists of two fixed magnetic rings 42 and 42.

  The permanent magnet 41 is a multipolar magnetized ring in which N poles and S poles are alternately magnetized at a plurality of circumferential positions, and is externally fixed to the outer peripheral portion of the first rotating body 2. .

  The magnetic rings 42, 42 extend from the two annular plate portions 42 a, 42 a facing each other in the axial direction of the second rotating body 3 and the inner peripheral portions of the annular plate portions 42 a, 42 a so as to approach each other. Comb teeth 42b and 42b, and the magnetic flux density between the magnetic rings 42 and 42 is changed by rotating relative to the permanent magnet 41. The comb teeth 42b and 42b are arranged at equal intervals so as to alternately mesh with each other in the circumferential direction, and the magnetic rings 42 and 42 are molded with a synthetic resin material in a state where the comb teeth 42b and 42b alternately mesh with each other. 43.

4 is an enlarged sectional view of the magnetism collecting ring portion, FIG. 5 is a side view of the magnetism collecting ring portion, and FIG. 6 is an exploded perspective view of the magnetism collecting ring portion.
The magnetism collecting rings 5, 5 extend radially outward from one place in the circumferential direction and have a cylindrical shape having convex pieces 51, 51 disposed on both sides of the detection unit 7. The magnetic flux collects in The magnetism collecting rings 5 and 5 are formed by molding a magnetic plate such as an iron plate.

  The magnetic shielding layers 6 and 6 include cylindrical covering portions 61 and 61 that cover the outer peripheral sides of the magnetic flux collecting rings 5 and 5, annular covering portions 62 and 62 that cover one end face of the magnetic flux collecting rings 5, 5, The ring bodies 64 and 64 have plate-shaped covering portions 63 that cover the outer surface portions of the pieces 51 and 51, and the ring bodies 64 and 64 are externally fitted to the magnetism collecting rings 5 and 5. The magnetism collecting rings 5 and 5 to which the rings 64 and 64 are fitted are supported by a synthetic resin case 10 as a support member. The magnetic shielding layers 6 and 6 are made of a nonmagnetic material such as a silicon steel plate, but the material is not particularly limited.

  The case 10 has a ring portion 10b having a through hole 10a corresponding to the inner peripheral surfaces of the magnetism collecting rings 5 and 5, and a bottomed portion extending radially outward from the outer periphery of the ring portion 10b and having a receiving portion 10c. And the ring portion 10b and the accommodating portion 10c communicate with each other through the communication hole 10e. The magnetism collecting rings 5 and 5 are fitted and fixed to the ring portion 10b, and the convex pieces 51 and 51 of the magnetism collecting rings 5 and 5 are arranged in the communication hole 10e. In addition, the detection circuit board 9 is attached to the housing portion 10c with a small screw. A lid 11 is attached to the open end of the rectangular tube portion 10d to the outside with a small screw or the like.

  The detection unit 7 is composed of a Hall element whose electrical characteristics (resistance) change due to the action of a magnetic field, so that the detection signal changes according to the change in magnetic flux density generated between the convex pieces 51 and 51 of the magnetism collecting rings 5 and 5. The detection signal is given to the detection circuit board 9. The detection unit 7 is not limited to a Hall element, but may be any magnetosensitive element whose electrical characteristics (resistance) are changed by the action of a magnetic field, such as a magnetoresistive effect element (MR element).

  The torque detection device configured as described above includes cylindrical covering portions 61 and 61 that cover the outer peripheral sides of the magnetic flux collecting rings 5 and 5 that collect magnetic flux generated by the magnetic circuit forming member 4, and the magnetic flux collecting rings 5 and 5. Ring-shaped covering portions 62 and 62 that cover one end surface of the slab, and a plate-shaped covering portion 63 that covers a part of the convex pieces 51 and 51 (a surface on the outer side in the axial direction on the side where the detection portion is not disposed). Since the magnetic shielding layers 6 and 6 are provided, it is possible to reduce the influence of the external magnetic field on the magnetic flux collection of the magnetic flux collecting rings 5 and 5, and to reduce the detection error due to the external magnetic field. Further, since the magnetic shielding layers 6 and 6 do not cover the entire surfaces of the magnetism collecting rings 5 and 5 but cover a part of the magnetism collecting rings 5 and 5, the magnetic shielding areas of the magnetic shielding layers 6 and 6 are reduced. This can reduce the cost of the magnetic shielding layers 6 and 6, and thus the cost of the torque detector.

  FIG. 7 is an explanatory view showing a molding process of the magnetic shielding layer of the torque detector. The magnetic shielding layers 6 and 6 are formed of a nonmagnetic plate such as a silicon steel plate. This molding includes, for example, FIG. 7 (a) and FIG. 7 (b). (a) is a punching of the center part of a rectangular non-magnetic plate into a ring plate shape (c), one punched ring plate 6a is formed (d), and this punched ring plate 6a is formed into a cylindrical shape. (e).

  (b) is a strip-shaped nonmagnetic plate having both sides in the width direction punched into a strip shape (f), two punched strip plates 6b, 6b are formed (g), and each punched strip plate 6b, 6b is It has an annular shape (cylindrical covering portion 61) in which one circumferential position is opened by bending, and has an extending portion (plate-shaped covering portion 63) extending radially outward from the middle in the circumferential direction. It is molded into a shape (h). In this way, (b) can form the two magnetic shielding layers 6 and 6 with a strip-shaped non-magnetic plate, so that the case where the rectangular non-magnetic plate is formed into an annular shape as shown in (a). In comparison with the above, it is possible to reduce the removal area of the non-magnetic plate, and it is possible to easily perform the bending of the non-magnetic plate, thereby reducing the cost of the magnetic shielding layers 6 and 6 themselves.

When the magnetic shielding layers 6 and 6 are formed of a strip-like nonmagnetic plate as shown in FIG. 7 (b), the punched strip plates 6b and 6b are made flat, as shown in (i). It is good also as a corrugated plate shape which makes an uneven | corrugated strip.
Thus, by making the punched strips 6b and 6b corrugated, the absorbability of the external magnetic field can be enhanced. In other words, the magnetic shielding effect can be enhanced because the magnetic flux has a property of gathering at the convex portion.

  FIG. 8 is an enlarged cross-sectional view showing an example in which the magnetism collecting rings 5 and 5 and the magnetic shielding layers 6 and 6 of the torque detecting device are molded by a synthetic resin material. The magnetic shield layers 5 and 5 shown in FIGS. 4 to 6 are held on the magnetic flux collecting rings 5 and 5 by external fitting, and the magnetic flux collecting rings 5 and 5 provided with the magnetic shield layers 6 and 6 are formed. The magnetism collecting rings 5, 5 and the magnetic shielding layers 6, 6 are molded by the mold layer 20 by injecting a synthetic resin material of the same system as the synthetic resin of the case into the cavity in a state of being placed in the mold cavity. This mold makes the magnetism collecting rings 5 and 5 and the magnetic shielding layers 6 and 6 into one component, so that the number of assembling steps during assembling work can be reduced, the assembling workability can be improved, and work mistakes such as assembling leakage And, in turn, the cost of the torque detector can be reduced.

  FIG. 9 is an enlarged cross-sectional view showing an example in which the torque detection device is used in an electric power steering device. The torque detection device A manufactured as described above is used, for example, in an electric power steering device for a vehicle. This electric power steering apparatus includes an input shaft 20 (first rotating body 2) connected to a steering wheel, and an output shaft 21 (second rotating body 3) coaxially connected to the input shaft 20 by a torsion bar 1. The housing 25 surrounds the input shaft 20 and the output shaft 21 and rotatably supports the input shaft 20 and the output shaft 21 by the three bearings 22, 23, 24, and the steering assist electric motor attached to the housing 25. The motor 26, a speed reduction mechanism 27 that transmits the rotational force of the drive shaft of the electric motor 26 to the output shaft 21, the torque detection device A, the detection circuit board 9 of the torque detection device A, and the drive circuit of the electric motor 26 And a control unit (not shown) using a connected microprocessor. Then, the detection unit 7 detects the rotational torque applied to the input shaft 20 by steering the steering wheel, and the detection circuit board 9 converts the detected torque into a voltage signal by the twist generated in the torsion bar 1. In addition, the electric motor 26 is driven and controlled by the instruction signal output from the control unit, and the output shaft 21 rotates through the speed reduction mechanism 27.

  The housing 25 projects from a cylindrical portion 25a that surrounds the input shaft 20 and the output shaft 21, a mounting seat 25b for mounting the case 10, and a radial mounting plate 25b. A through hole 25c for penetrating in the direction and arranging the magnetism collecting rings 5 and 5 in the cylindrical part 25a, and a fitting groove 25d connected to the through hole 25c and curved corresponding to the ring part 10b of the case 10. The case 10 is attached to the attachment seat 25b.

  In this case 10, the ring-shaped portion 10b is inserted into the cylindrical portion 25a from the through-hole 25c that opens in the radial direction of the housing 25, and the ring-shaped portion 10b is engaged with the fitting groove 25d. The position in the tube portion 25a is determined, and the square tube portion 10d of the case 10 is attached to the attachment seat 25b. After attaching the case 10, the input shaft 20 and the output shaft 21 are inserted into the cylindrical portion 25 a from the axial direction of the housing 25, and the permanent magnet 41 and the magnetic ring 42 are disposed inside the magnetism collecting rings 5 and 5. The

  In the embodiment described above, the magnetic shielding layers 6 and 6 are formed of a non-magnetic plate such as a silicon steel plate. In addition, the magnetic shielding layers 6 and 6 coat the magnetic collecting rings 5 and 5 with a non-magnetic material. Alternatively, it may be formed by sticking a non-magnetic plate formed in a shape corresponding to the magnetism collecting rings 5 and 5 to the magnetism collecting rings 5 and 5.

  Further, the torque detection device A according to the present invention may be used for devices other than the electric power steering device in addition to the electric power steering device.

It is sectional drawing which shows the structure of the torque detection apparatus which concerns on this invention. It is a typical exploded perspective view of the torque detector concerning the present invention. It is explanatory drawing of the magnetic circuit which generate | occur | produces when a rotary body rotates to one direction. It is an expanded sectional view of the magnetism collection ring part of the torque detector concerning the present invention. It is a side view of the magnetism collection ring part of the torque detector concerning the present invention. It is a disassembled perspective view of the magnetism collection ring part of the torque detector which concerns on this invention. It is explanatory drawing which shows the formation process of the magnetic shielding layer of the torque detection apparatus which concerns on this invention. It is an expanded sectional view which shows the example by which the magnetism collection ring and magnetic shielding layer of the torque detection apparatus which concern on this invention were molded by the synthetic resin material. It is an expanded sectional view showing the example which used the torque detection device concerning the present invention for the electric power steering device.

Explanation of symbols

A Torque detection device 2 First rotating body (rotating body)
3 Second rotating body (rotating body)
Reference Signs List 4 Magnetic circuit forming member 5 Current collecting ring 51 Convex piece 6 Magnetic shielding layer 7 Detector 63 Extending part (plate-shaped covering part)

Claims (4)

  A magnetic flux collecting ring arranged around the outer periphery of the magnetic circuit forming member provided in the rotating body and collecting the magnetic flux generated by the magnetic circuit forming member, and the rotating body based on the density of the magnetic flux collected by the magnetic collecting ring A torque detection apparatus comprising: a detection unit that detects applied torque, wherein the magnetism collecting ring has a magnetic shielding layer on an outer peripheral side.   The magnetic shield layer is a non-magnetic plate that is externally fitted to the magnetism collecting ring, has an annular shape in which one circumferential direction is opened, and has an extending portion that extends radially outward from the middle in the circumferential direction. The torque detection device according to claim 1, comprising:   Two magnetic flux collecting rings that are separated from each other in the axial direction on the outer periphery of the magnetic circuit forming member provided on the rotating body and collect the magnetic flux generated by the magnetic circuit forming member, and the magnetic flux collected by each magnetic collecting ring And a detecting unit that detects a torque applied to the rotating body based on density, wherein the magnetism collecting ring has a cylindrical shape having a convex piece extending radially outward from one place in the circumferential direction. None, a torque detection device comprising a magnetic shielding layer that magnetically shields the outer peripheral side and end face of the magnetism collecting ring and a part of the convex piece. The torque detection device according to any one of claims 1 to 3, wherein the magnetism collecting ring and the magnetic shielding layer are molded of a synthetic resin material.

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