JP5814443B2 - Torque sensor - Google Patents

Description

  The present invention relates to a torque sensor that detects an axial torque applied to a rotating shaft as a change in magnetic flux density (magnetic field strength).

  Conventionally, a torque sensor for detecting shaft torque in an electric power steering device or the like is known. For example, in the torque sensor described in Patent Document 1, when a torsion bar that connects an input shaft and an output shaft is twisted, a magnetic flux generated by a change in relative position in the circumferential direction between the multipolar magnet and the yoke is generated. The shaft torque is detected by detecting the fixed magnetic sensor. Here, in the multipolar magnet, the N pole and the S pole are alternately magnetized at a constant magnetization angle in the circumferential direction. For example, the torque sensor of Patent Document 1 is provided with 24 poles in total, 12 poles each for N poles and S poles.

JP 2003-149062 A

  Since the torque sensor detects the relative position in the circumferential direction between the multipolar magnet and the yoke, when the multipolar magnet and the yoke rotate integrally with respect to the magnetic sensor, that is, the multipolar magnet and the yoke When the relative position in the circumferential direction does not change, the output of the magnetic sensor is preferably constant.

  However, in reality, when the multipolar magnet and the yoke are rotated together with the torque sensor described in Patent Document 1, the output varies according to the rotation angle. For example, when the N pole and the S pole of the multipolar magnet are each 12 poles, output fluctuation of 12 cycles occurs per rotation. This output fluctuation causes a decrease in the detection accuracy of the rotation angle.

The present inventor has clarified that this output fluctuation is caused by magnetic flux that directly reaches the magnetic sensor from the multipolar magnet through the space without passing through the yoke.
The present invention has been made in view of the above-described problems, and its purpose is to produce output fluctuations caused by magnetic flux that directly reaches the magnetic sensing portion from the multipolar magnet when the multipolar magnet and the yoke are rotated together. It is an object of the present invention to provide a torque sensor that reduces the noise.

The torque sensor according to the present invention includes a torsion bar, a multipole magnet, a set of yokes that form a magnetic circuit on the outer diameter of the multipole magnet, and a set of collectors that collect magnetic flux from the set of yokes to the magnetic flux collector. A torque sensor including a magnetic body and a magnetic sensor having a magnetic sensing portion for detecting a magnetic flux density generated in a magnetic circuit further includes a spacer. The spacer adjusts the distance between the pair of magnetic collectors and the magnetic sensor so that the magnetic sensing part of the magnetic sensor is disposed at an equal distance from the magnetic collectors of the pair of magnetic collectors. The magnetic sensing part is provided at a position shifted from the center of the magnetic sensor in the thickness direction, and the spacer and the mold part of the magnetic sensor have the same magnetic characteristics.
The output fluctuation due to the magnetic flux directly reaching the magnetic sensor through the space without passing through the yoke from the multipolar magnet tends to be zero at the intermediate position in the axial direction of the magnetism collecting portion. Therefore, the output fluctuation can be reduced by arranging the magnetic sensing portion at the intermediate position in the axial direction of the magnetic collecting portion by the spacer.

1 is an exploded perspective view of a torque sensor according to a first embodiment of the present invention. 1 is a schematic configuration diagram of an electric power steering apparatus to which a torque sensor according to a first embodiment of the present invention is applied. It is (a): sectional drawing of the torque sensor by 1st Embodiment of this invention, (b): The b direction arrow line view of (a). It is a front view (IV direction arrow view of FIG. 3) which shows the neutral state of the torque sensor by 1st Embodiment of this invention. In the torque sensor by a 1st embodiment of the present invention, it is a front view showing the state where a multipolar magnet rotated to the left (a): the state rotated to the right (b). It is a disassembled perspective view of the torque sensor by 15th Embodiment of this invention. It is (a): sectional drawing of the torque sensor by 15th Embodiment of this invention, (b) It is a b direction arrow directional view of (a). (A): Front view showing a neutral state (viewed in the direction of arrow VIIIa in FIG. 7) of the torque sensor according to the fifteenth embodiment of the present invention, (b): Enlarged view of part b of (a). It is an output characteristic figure of a torque sensor by a 15th embodiment of the present invention. It is an enlarged view of the torque sensor by 16th Embodiment of this invention. It is a front view which shows the neutral state of the torque sensor by 17th Embodiment of this invention.

Hereinafter, torque sensors according to a plurality of embodiments of the present invention will be described with reference to the drawings. In a plurality of embodiments, substantially the same configuration is denoted by the same reference numeral, and description thereof is omitted.
Note that the first embodiment is a reference form for explaining a common configuration. The second to fourteenth embodiments are omitted.
[Overall configuration of torque sensor applied to electric power steering device]
First, a configuration common to the torque sensors of the embodiments of the present invention will be described. Note that the torque sensor 101 of the first embodiment is used as a representative for the reference numeral of the torque sensor.
As shown in FIG. 2, the torque sensor 101 according to the embodiment of the present invention is applied to an electric power steering apparatus for assisting a steering operation of a vehicle.

  FIG. 2 shows an overall configuration of a steering system including the electric power steering device 90. A steering shaft 94 connected to the handle 93 is provided with a torque sensor 101 for detecting steering torque. A pinion gear 96 is provided at the tip of the steering shaft 94, and the pinion gear 96 meshes with the rack shaft 97. A pair of wheels 98 are rotatably connected to both ends of the rack shaft 97 via tie rods or the like. The rotational motion of the steering shaft 94 is converted into a linear motion of the rack shaft 97 by the pinion gear 96, and the pair of wheels 98 are steered.

  The torque sensor 101 is provided between the input shaft 11 and the output shaft 12 constituting the steering shaft 94, detects the steering torque applied to the steering shaft 94, and outputs it to the ECU 91. The ECU 91 controls the output of the motor 92 according to the detected steering torque. The steering assist torque generated by the motor 92 is decelerated via the reduction gear 95 and transmitted to the steering shaft 94.

Next, a configuration common to the torque sensors of the embodiments will be described with reference to FIGS. 1 and 3 to 5 of the first embodiment.
As shown in FIG. 1, the torque sensor (101) includes a torsion bar 13, a multipolar magnet 14, a set of yokes 31, 32, a set of magnetism collecting rings (502), a magnetic sensor 41, and the like. . Since the reference numerals of the torque sensor and the pair of magnetism collecting rings are different for each embodiment, the reference numerals are shown here in parentheses.

One end side of the torsion bar 13 is fixed to the input shaft 11 as a “first axis”, and the other end side is fixed to an output shaft 12 as a “second axis” by a fixing pin 15. 12 are connected on the same axis as the rotation axis O. The torsion bar 13 is a rod-like elastic member, and converts the steering torque applied to the steering shaft 94 into a torsional displacement.
The cylindrical multipolar magnet 14 is fixed to the input shaft 11 and N and S poles are alternately magnetized in the circumferential direction. For example, in this embodiment, the number of N poles and S poles is 12 pole pairs, for a total of 24 poles.

  The pair of yokes 31 and 32 are annular bodies made of a soft magnetic material, and are fixed to the output shaft 12 on the outer side of the multipolar magnet 14. In the yokes 31 and 32, the same number (12 in this embodiment) of claws 315 and 325 as the north and south poles of the multipolar magnet 14 are provided at equal intervals along the inner edge of the ring. The claws 315 of one yoke 31 and the claws 325 of the other yoke 32 are alternately arranged with a shift in the circumferential direction. Thus, one yoke 31 and the other yoke 32 are opposed to each other via the air gap in the axial direction. The pair of yokes 31 and 32 form a magnetic circuit in the magnetic field generated by the multipolar magnet 14.

  Here, when the multipolar magnet 14 and the pair of yokes 31 and 32 are not twisted and displaced in the torsion bar 13, that is, when steering torque is not applied between the input shaft 11 and the output shaft 12. The centers of the claws 315 and 325 of the yokes 31 and 32 and the boundary between the north and south poles of the multipolar magnet 14 are arranged so as to coincide with each other.

  The pair of magnetic flux collecting rings (502) is formed of a soft magnetic material and includes a main body portion (56), a connecting portion (57), and magnetic flux collecting portions (521, 522). The pair of magnetic flux collecting rings (502) are provided so as to face each other in the axial direction of the torsion bar 13 which is the vertical direction in FIG. 1, and the magnetic flux collecting portions (521, 522).

At least one magnetic sensor 41 is provided between the magnetic flux collectors (521, 522). The magnetic sensor 41 converts the magnetic flux density passing through the magnetic sensing unit 410 into a voltage signal and outputs it to the lead wire 49. Specifically, a Hall element, a magnetoresistive element, or the like can be used as the magnetic sensor 41.
Hereinafter, for each of the embodiments, a specific configuration of a set of magnetism collecting rings, a magnetic sensor, and the like, and operational effects derived from the configuration will be described.

[Embodiment for Reducing Output Fluctuation Using Spacer]
Next, fifteenth to seventeenth embodiments of the present invention in which output fluctuation is reduced using a spacer will be described with reference to FIGS.
(Fifteenth embodiment)
First, a fifteenth embodiment will be described with reference to FIGS. In the torque sensor 205 shown in FIG. 6, the magnetism collecting ring 507 on the input shaft 11 side shown on the upper side of the figure includes a main body part 561, a connecting part 571, and a magnetism collecting part 511, and the output shaft 12 shown on the lower side of the figure. The side magnetic flux collecting ring 507 includes a main body portion 562, a connecting portion 572, and a magnetic flux collecting portion 512. Hereinafter, the magnetic flux collector 511 is distinguished from the “first magnetic flux collector”, and the magnetic flux collector 512 is distinguished from the “second magnetic flux collector”.
The set of magnetism collecting rings 507 corresponds to a “set of magnetism collectors” recited in the claims.

  As shown in FIGS. 6 to 8, a spacer 81 is interposed between the first magnetic flux collector 511 and the second magnetic flux collector 512 in addition to the magnetic sensor 41. In the present embodiment, the spacer 81 is provided between the first magnetic flux collector 511 and the magnetic sensor 41. The spacer 81 is made of a nonmagnetic material such as resin.

The magnetic sensor 41 is configured in the form of a flat plate IC package in which the magnetic sensing part 410 is molded with resin, and specifically, is an IC package of a Hall element or a magnetoresistive element. Here, in general, in a commercially available magnetic sensor, a magnetic sensitive part is provided at a position shifted from the center in the thickness direction of the IC package. For example, in this embodiment, as shown in FIG. 7B and FIG. 8, the magnetic sensing part 410 is displaced from the center of the magnetic sensor 41 in the thickness direction toward the first magnetic flux collecting part 511.
Therefore, by providing a spacer 81 having an appropriate thickness between the first magnetism collecting portion 511 and the magnetic sensor 41, the magnetism sensing portion 410 is separated from the first magnetism collecting portion 511 and the second magnetism collecting portion 512. Arrange them at equidistant positions. That is, in FIG. 7B and FIG. 8, the distance d1 from the first magnetic flux collector 511 to the magnetic sensitive portion 410 and the distance d2 from the second magnetic flux collector 512 to the magnetic sensitive portion 410 are equal. adjust.

  The spacer 81 is made of a nonmagnetic material such as resin, and has the same magnetic characteristics as the resin mold portion of the IC package of the magnetic sensor 41. Therefore, if the distance d1 and the distance d2 are equal, the magnetic relationship between the first magnetism collecting part 511 and the magnetism sensing part 410 and the magnetic relation between the second magnetism collecting part 512 and the magnetism sensing part 410 are obtained. Are equivalent.

  As shown in FIG. 9, when the distance d1 and the distance d2 are different, the rotation angle when the magnet 14 and the yokes 31 and 32 are rotated integrally is determined depending on which of the distance d1 and the distance d2 is larger. On the other hand, output fluctuations in opposite directions occur. On the other hand, in this embodiment, output fluctuation can be reduced by adjusting the distance d1 and the distance d2 equally by using the spacer 81.

  As shown in FIG. 8, when a virtual plane D including the magnetic sensing part 410 and orthogonal to the axis of the torque sensor 205 is defined, the magnetic flux collecting ring 507 includes not only the magnetic flux collecting parts 511 and 512 but also the main body parts 561 and 562. Since they are formed symmetrically with the virtual plane D, the distances e1 and e2 from the two main body portions 561 and 562 to the virtual plane D are equal. In addition, since the multipolar magnet 14 is also symmetrically located in the virtual plane D, the distances f1 and f2 from the both end portions of the multipolar magnet 14 in the axial direction to the magnetic sensing portion 410 are equal.

  However, the effect of suppressing the output fluctuation is realized only by a configuration in which “the magnetic sensing unit 410 is located at an equal distance from the first magnetic collecting unit 511 and the second magnetic collecting unit 512”. The symmetry of the main body portions 561 and 562 and the multipolar magnet 14 has no significant meaning. Therefore, the following sixteenth and seventeenth embodiments may be employed instead of the fifteenth embodiment.

(Sixteenth and seventeenth embodiments)
As shown in FIG. 10, in the torque sensor 206 of the sixteenth embodiment, the main body portions 563 and 564 of the magnetism collecting ring 508 are asymmetric with respect to the virtual plane D. That is, the distance e1 from the upper main body portion 563 to the virtual plane D and the distance e3 from the lower main body portion 564 to the virtual plane D are different.

As shown in FIG. 11, in the torque sensor 207 of the seventeenth embodiment, the multipolar magnet 14 is asymmetric with respect to the virtual plane D. That is, the distance f1 from the upper end of the multipolar magnet 14 to the virtual plane D is different from the distance f3 from the lower end of the multipolar magnet 14 to the virtual plane D.
However, in both the sixteenth and seventeenth embodiments, the distance d1 from the first magnetism collecting portion 511 to the magnetism sensing portion 410 is equal to the distance d2 from the second magnetism collecting portion 512 to the magnetism sensing portion 410. Therefore, the output fluctuation can be reduced as in the fifteenth embodiment.

(Modification of Embodiment Using Spacer)
The number of spacers is not limited to one, and a plurality of spacers may be combined. For example, spacers having different thicknesses may be interposed between the first magnetic flux collector 511 and the magnetic sensor 41 and between the second magnetic flux collector 512 and the magnetic sensor 41, respectively. In that case, the magnetic sensitive part 410 can be arranged at the center of the magnetic flux collecting parts 511 and 512 by utilizing the difference in thickness between the two spacers.
Alternatively, an IC package in which the magnetism collecting portion is arranged at the center in the thickness direction may be specially manufactured. In this case, it can be considered that a part of the resin mold part of the IC package includes the spacer of the present invention.

[Other Embodiments of Torque Sensor for Reducing Output Fluctuation According to the Present Invention]
(A) The number of magnetic poles of a multipolar magnet is not limited to 12 pole pairs and 24 poles. In addition, the number of claws 315 and 325 of the yokes 31 and 32 corresponding to this is not limited to twelve.
(A) The N pole and the S pole in the above description may be reversed.

  (C) In the above embodiment, “a magnet and a set of magnet end yokes” are fixed to the input shaft 11 side of the torsion bar 13, and “a set of intermediate yokes” are fixed to the output shaft 12 of the torsion bar 13. . Conversely, the “magnet and the set of magnet end yokes” may be fixed to the output shaft 12, and the “set of intermediate yokes” may be fixed to the input shaft 11.

  As mentioned above, this invention is not limited to such embodiment, In the range which does not deviate from the meaning of invention, it can implement with a various form. For example, the present invention can be applied not only to an electric power steering device but also to various devices that detect shaft torque.

205-207 ... torque sensor,
11 ... input shaft (first axis), 12 ... output shaft (second axis),
13 ... Torsion bar, 14 ... Multipole magnet,
31, 32 ... a set of yokes,
41 ... Magnetic sensor,
410 ... magnetic sensitive part,
507, 508 ... a set of magnetism collecting rings (a set of magnetism collectors),
81: Spacer.

Claims (2)

A torsion bar (13) which connects the first shaft (11) and the second shaft (12) coaxially and converts torque applied between the first shaft and the second shaft into a torsional displacement. )When,
A multi-pole magnet (14) fixed to one end of the first shaft or the torsion bar and having N and S poles alternately magnetized in the circumferential direction;
A magnetic circuit is formed in the magnetic field generated by the multipolar magnet, fixed to the second shaft or the other end of the torsion bar outside the diameter of the multipolar magnet, and opposed in the axial direction through a gap. A set of yokes (31, 32)
It is composed of a main body part (561, 562, 563, 564) and a magnetic flux collecting part (511, 512) formed so as to protrude in the radially outward direction of the main body part, and a magnetic flux from the set of yokes to the magnetic flux collecting part. A set of current collectors (507, 508),
A plate-like magnetic sensor (41) provided between the magnetism collectors of the pair of magnetism collectors and having a magnetism sensing part (410) for detecting a magnetic flux density generated in the magnetic circuit;
A spacer (81) for adjusting a distance between the magnetic flux collector and the magnetic sensor so that the magnetically sensitive portion in the magnetic sensor is disposed at an equal distance from the magnetic flux collector of the set of magnetic collectors. When,
Equipped with a,
The magnetic sensing part is provided at a position shifted from the center in the thickness direction of the magnetic sensor,
It said spacer and the mold portion of the magnetic sensor, torque sensor magnetic properties characterized equivalent der Rukoto (205, 206, 207). The torque sensor according to claim 1, wherein the spacer and the mold portion of the magnetic sensor are formed of a non-magnetic material.

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