JP2010181196A - Magnetostrictive device for detecting torque and rotation angle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting a torque and rotation angle, which is miniaturized with a simple structure. <P>SOLUTION: A magnetostrictive device for detecting the torque and rotation angle 20 includes: a rotating shaft 16; a first magnetostrictive film 27, which covers the rotating shaft 16, and which includes magnetic anisotropy; a second magnetostrictive film 28 which includes magnetic anisotropy opposite to that of the first magnetostrictive film 27; a third magnetic film 29 of which the axial film width changes and which does not exhibit magnetostrictive characteristics; a first detection coil 31 which is arranged facing the first magnetostrictive film 27; a second detection coil 32 which is arranged facing the second magnetostrictive film 28; and a third detection coil 33 which is arranged facing the third magnetic film 29. The small parts count and well-organized arrangement can provide the detection apparatus miniaturized with a simple structure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetostrictive torque / rotation angle detection device capable of collectively detecting a torque and a rotation angle of a rotating shaft.

  For example, an electric power steering of an automobile is provided with various detection devices in order to control an auxiliary motor that assists the steering force (see, for example, Patent Document 1 (FIG. 2)).

The technique of this patent document 1 is demonstrated below based on drawing.
As shown in FIG. 13, the steering shaft 101 is provided with a torque detection device 102 that detects torque on the steering shaft 101 and a rotation angle detection device 103 that detects a rotation angle on the steering shaft 101.

  In the torque detection device 102, when the steering shaft 101 is rotated as shown by an arrow, the torsion bar 104 is twisted by the action of torque, and a displacement occurs in the rotation angle between the steering shaft 101 and the output shaft 105. Due to this displacement, the positional relationship between the magnet 106 provided on the steering shaft 101 and the yoke 107 provided on the output shaft 105 also changes. Then, magnetic flux is generated in the yoke 107 and detected by the magnetic sensor 109 via the magnetism collecting ring 108. Torque can be detected based on this detection information.

  In the rotation angle detection device 103, when the internal gear 111 is rotated integrally with the steering shaft 101, the external gear 112 meshed with the internal gear 111 rotates. The magnet 113 also rotates integrally with the external gear 112. Then, a change in magnetic characteristics is detected by the magnetic sensor 115 provided in the housing 114. Based on the detection information, the rotation angle can be detected.

  However, in the technique according to Patent Document 1, since the torque detection device 102 and the rotation angle detection device 103 are separately arranged at different positions, the number of parts increases and a space is also required. That is, there is a demand for a torque / rotation angle detection device that can be reduced in size with a simple structure.

JP 2007-269281 A

  It is an object of the present invention to provide a torque / rotation angle detection device that can be reduced in size with a simple structure.

  The invention according to claim 1 is a rotating shaft, a first magnetostrictive film portion coated on the rotating shaft and provided with magnetic anisotropy, and a magnetic anisotropy covered on the rotating shaft and having the first magnetic anisotropy. A second magnetostrictive film portion provided in a direction opposite to the magnetostrictive film portion, a third magnetic film portion that is covered with the rotating shaft in a form in which the film thickness changes in a direction perpendicular to the axis and does not exhibit magnetostriction, A first detection coil that is arranged facing the first magnetostrictive film part and detects a change in magnetic characteristics at the first magnetostrictive film part, and a magnetic characteristic at the second magnetostrictive film part arranged facing the second magnetostrictive film part. A second detection coil for detecting the change of the first detection coil, a torque calculation unit for calculating a torque applied to the rotating shaft from detection information of the second detection coil and detection information of the first detection coil, and the third magnetism A third detection coil arranged facing the film part for detecting a change in magnetic characteristics in the third magnetic film part; A rotation angle calculation unit for calculating a rotation angle of the rotary shaft from the detection information of the third detection coil consists, characterized in that it is possible to detect at once and torque and rotation angle of the rotary shaft.

  The invention according to claim 2 is characterized in that the third magnetic film portion is coated on the rotating shaft in such a manner that the film thickness in the direction perpendicular to the axis changes in a cycle of 180 °.

  The invention according to claim 3 is characterized in that the third magnetic film portion is a film having a characteristic that does not cause a change in magnetic field with respect to torsional torque.

  The invention according to claim 4 is characterized in that the third detection coil includes a yoke having a period of magnetic collection.

  The invention according to claim 5 is characterized in that at least two detection coils each having a yoke having a period of magnetic collection are arranged in the third magnetic film portion with a phase shift of ¼ period. .

  In the first aspect of the invention, the rotating shaft, the first and second magnetostrictive film portions and the third magnetic film portion covered by the rotating shaft, and the first and second magnetostrictive film portions and the third magnetic film thereof. The first to third detection coils arranged facing the unit, a torque calculation unit, and a rotation angle calculation unit. According to the prior art, since the torque detection device and the rotation angle detection device are separately arranged at different positions, the number of parts increases and a space is also required. Compared to this, in the present invention, the number of components is small and the arrangement is uniform, so that the detection device can be simplified in structure and reduced in size.

  In the invention which concerns on Claim 2, the 3rd magnetic film part is coat | covered by the rotating shaft in the form from which the film thickness in an axis perpendicular direction changes with a period of 180 degrees. Since a magnetic film having a portion with different magnetoresistance can be manufactured only by changing the film thickness, the manufacturing cost can be reduced.

  In the invention according to claim 3, the third magnetic film portion is a film having a characteristic that does not cause a change in the magnetic field with respect to the torsional torque. Even if the third magnetic film portion is disposed in the vicinity of the first and second magnetostrictive film portions that cause a change in the magnetic field with respect to the torsion torque, the third magnetic film portion is not affected by the torsion torque. The second magnetostrictive film portion and the third magnetic film portion can be arranged together to achieve a compact size.

  In the invention which concerns on Claim 4, the 3rd detection coil is provided with the yoke with a period in magnetism collection. Since it is possible to manufacture a yoke having a portion with a large magnetic flux collecting effect by simply changing the shape of the yoke, the manufacturing cost can be reduced.

  In the invention according to claim 5, at least two detection coils each having a yoke having a period of magnetic collection are arranged in the third magnetic film portion with a ¼ period phase shifted. In order to detect the absolute angle and the rotation direction of the rotating shaft, it is only necessary to shift the arrangement of the detection coils, so that the structure can be made compact with a simple structure.

It is a figure explaining the usage example of the magnetostriction type torque and rotation angle detection apparatus which concerns on this invention. It is sectional drawing of the electric power steering which concerns on embodiment of this invention. 1 is a cross-sectional view of a magnetostrictive torque / rotation angle detection device according to the present invention. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 1 is a configuration diagram of a magnetostrictive torque / rotation angle detection device according to the present invention. FIG. It is a figure explaining the basic principle of the output change in a 3rd detection coil. It is a figure explaining arrangement | positioning of the rotating shaft and detection coil in a 3rd magnetic film part. It is a figure explaining the process of detecting the rotation angle of a rotating shaft. It is a figure explaining the relationship between the magnetic characteristic detected with the 3rd detection coil corresponding to FIG. 8, and a rotation angle. It is a figure explaining the relationship between the output characteristic of a detection coil, and a torque. It is a figure explaining the manufacturing method of a magnetostriction film. It is a figure explaining another Example which concerns on this invention. It is a figure explaining the basic principle of the prior art.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.

First, Embodiment 1 of the present invention will be described with reference to the drawings.
As shown in FIG. 1, when the steering handle 11 is turned in the vehicle 10, this rotational force is transmitted to the electric power steering mechanism 13 (detailed structure will be described later) via the steering shaft 12. Torque corresponding to the rotational force is applied by the electric power steering mechanism 13. The rack shaft 14 is moved horizontally with the increased torque, and the wheels 15 are steered.

  As shown in FIG. 2, the electric power steering mechanism 13 transmits auxiliary power to a rotating shaft 16, a magnetostrictive torque / rotation angle detecting device 20 that collectively detects a torque and a rotating angle of the rotating shaft 16, and the auxiliary power. The auxiliary power transmission mechanism 21 that rotates, the pinion rack mechanism 22 that converts the rotary motion of the rotary shaft 16 into a reciprocating motion, and the housing 23 and the lid 24 that surround the outside thereof. The rotary shaft 16 is rotatably supported by the housing 23 using bearings 25 and 26.

  The magnetostrictive torque / rotation angle detection device 20 includes a first magnetostrictive film portion 27, a second magnetostrictive film portion 28, a third magnetic film portion 29 provided on the rotating shaft 16, and the first and second magnetostrictive films. The first detection coil 31, the second detection coil 32, and the third detection coil 33 are provided on the lid 24 so as to face the portions 27 and 28 and the third magnetic film portion 29.

  The auxiliary power transmission mechanism 21 includes an auxiliary motor 34 that is provided in the housing 23 and generates auxiliary power, a transmission shaft 35 that is provided in the auxiliary motor 34 and transmits a rotational force, and a worm gear 36 that is provided in the transmission shaft 35. And a worm wheel 37 that is provided on the rotary shaft 16 so as to mesh with the worm gear 36 and transmits auxiliary power.

  The pinion rack mechanism 22 includes a pinion 40 provided on the rotary shaft 16, a rack 41 provided so as to mesh with the pinion 40, and a housing 41 slidably provided toward the rack 41. And a compression spring 44 which is provided on the housing 23 via a cap 43 and urges the rack guide 42 to be pressed against the pinion 40.

As shown in FIG. 3, the magnetostrictive torque / rotation angle detection device 20 includes a rotating shaft 16, a first magnetostrictive film portion 27 that is covered with the rotating shaft 16 and has magnetic anisotropy, and a rotating shaft. 16 and the second magnetostrictive film part 28 to which the magnetic anisotropy is applied in the direction opposite to that of the first magnetostrictive film part 27, and the rotating shaft 16 in a form in which the film thickness changes in the direction perpendicular to the axis. A third magnetic film portion 29 that does not exhibit magnetostriction, a first detection coil 31 that is disposed facing the first magnetostrictive film portion 27 and detects a change in magnetic characteristics in the first magnetostrictive film portion 27, and a second magnetostriction A second detection coil 32 arranged facing the film portion 28 to detect a change in magnetic characteristics in the second magnetostrictive film portion 28, and a magnetism in the third magnetic film portion 29 arranged facing the third magnetic film portion 29. A third detection coil 33 that detects a change in characteristics and one excitation core disposed around the rotary shaft 16. And Le 47, consisting of.
The direction of magnetic anisotropy is indicated by A and B.

The sectional structure of the third magnetic film portion 29 will be described with reference to the next drawing.
As shown in FIG. 4, the third magnetic film portion 29 is covered with the rotating shaft 16 in such a manner that the film thickness t in the direction perpendicular to the axis changes at a cycle of 180 °. The third detection coil 33 includes a yoke 48 having a period of magnetic collection.

The magnetic resistance of the third magnetic film unit 29 varies depending on the size of the air gap. In the third magnetic film portion 29, the air gap is reduced in the portion where the film thickness t is thick, and the magnetic resistance is reduced. On the contrary, in the portion where the film thickness t is thin, the air gap is increased and the magnetic resistance is increased.
Further, by making the yoke 48 a half-cracked structure, it is possible to give a period to the magnetic collection. A region of the yoke 48 where the magnetism collecting effect is large is R, and a region where the magnetism collecting effect is small is S.
The periodicity of the film thickness is not limited to 180 °, and the rotating shaft 16 may be covered in a form in which the film thickness changes in the direction perpendicular to the axis at a cycle of 360 ° / n. The yoke 48 has a cycle of 180 °, but is not limited to this, and may have a cycle of 360 ° or the like, and may be changed according to the film thickness of the third magnetic film portion 29 that changes in the direction perpendicular to the axis at a cycle of 360 ° / n. There is no problem. The number of regions R having a large magnetic flux collection effect or the number of regions S having a small magnetic flux collection effect is N. When n = 1, N ≧ 1 may be satisfied, and when n ≧ 2, N = 1 or N = n. If it is. However, n = 1, 2,..., N = 1, 2,..., And the positions of the region R and the region S are 360 ° / N intervals. For example, if N = 2, the interval is 180 °, and if N = 3, the interval is 120 °.

Next, the calculating part which concerns on the 1st-3rd detection coils 31, 32, and 33 shown in FIG. 3 is demonstrated.
As shown in FIG. 5, the exciting coil 47 arranged with respect to the first and second magnetostrictive film portions 27 and 28 and the third magnetic film portion 29 and the first to third detection coils 31, 32 and 33. Is conceptually shown as an electrical relationship. An AC power supply 51 that always supplies an AC current for excitation is connected to the excitation coil 47 that is arranged in common to the first and second magnetostrictive film portions 27 and 28 and the third magnetic film portion 29. The first to third detection coils 31, 32, 33 are arranged in two pieces, each divided into an upper stage and a lower stage. Inductive voltages V _A and V _B corresponding to the torque are output from the output terminals of the upper and lower first detection coils 31 and 31. Induced voltages V _C and V _D corresponding to torque are output from the output terminals of the upper and lower second detection coils 32 and 32. The induction voltages V _E and V _F corresponding to the rotation angle are output from the output terminals of the upper and lower third detection coils 33 and 33.

The induced voltages V _A , V _B , V _C and V _D output from the output terminals of the first and second detection coils 31, 31, 32 and 32 are input to the torque calculation unit 52. The torque calculator 52 calculates the torque applied to the rotating shaft 16 based on the induced voltages V _A , V _B , V _C , and V _D.
In addition, by combining the induction voltages V _A , V _B , V _C , and V _D output from each of these four detection coils 31, 31, 32, and 32 based on a predetermined relationship, the first, first, If a failure occurs in either of the two magnetostrictive film portions 27 and 28, failure detection can also be performed.

The induced voltages V _E and V _F output from the output terminals of the third detection coils 33 and 33 are input to the rotation angle calculation unit 53. The rotation angle calculation unit 53 calculates the rotation angle of the rotary shaft 16 based on the induced voltages V _E and V _F.
The torque calculation unit 52 and the rotation angle calculation unit 53 are configured by calculation means such as a microcomputer or an electric circuit for calculation.

As shown in FIG. 6, the rotation angle of the rotating shaft 16 from the reference line 54 is θ.
As shown in (a), when θ = 0 °, the thickest portion of the third magnetic film portion 29 faces the region R.
As shown in (b), when the rotary shaft 16 is rotated in the direction of the arrow (1) and θ = 45 °, the portion where the film thickness of the third magnetic film portion 29 is slightly reduced is in the region R. I'm here.
As shown in (c), when the rotary shaft 16 is rotated in the direction of the arrow (2) and θ = 90 °, the thinnest portion of the third magnetic film portion 29 faces the region R. Yes.
(D) is a graph showing the relationship between the rotation angle of the steering shaft and the detected impedance (magnetic characteristics), and the third detection coil 33 produces a result like a COS curve. In the first and second detection coils (FIG. 5, reference numerals 31 and 32), there is no change due to the rotation of the rotating shaft 16.

As shown in FIG. 7A, in the third magnetic film portion 29, two third detection coils 33, 33 each having a yoke 48 having a period of magnetic collection are arranged in an upper stage and a lower stage. Yes.
(B) is a diagram showing the arrangement of the upper third detection coil 33, and the region R of the third detection coil 33 is located on the reference line 54.
(C) is a diagram showing the arrangement of the third detection coil 33 in the lower stage, and the region R of the third detection coil 33 is positioned by shifting the phase from the reference line 54 by a quarter cycle (45 ° in the first embodiment). is doing.
Note that the number of the third detection coils is not limited to two, and at least two such as three or four may be arranged.

The operation of the magnetostrictive torque / rotation angle detector described above will be described next.
As shown in FIG. 8, the upper third detection coil 33 portion at the rotation angle θ = 0 ° is shown in (a), and the lower third detection coil 33 portion is shown in (b).
When the rotary shaft 16 is rotated and the rotation angle θ is 45 °, the upper third detection coil 33 portion is as shown in (c) and the lower third detection coil 33 portion is as shown in (d).
When the rotation shaft 16 is further rotated and the rotation angle θ is 90 °, the upper third detection coil 33 portion becomes (e), and the lower third detection coil 33 portion becomes (f). .

  As shown in FIG. 9A, the upper third detection coil (FIG. 5, reference numeral 33) obtains a result like a COS curve. On the other hand, the third detection coil 33 in the lower stage obtains a waveform with a quarter cycle phase shifted. From the waveform of the upper third detection coil and the waveform of the lower third coil, the absolute angle and the rotation direction of the rotary shaft 16 can be detected through the rotation angle calculator 53. As a result, as shown in (b), the relationship between the detected magnetic characteristic and the steering angle is obtained.

As shown in FIG. 10, the third magnetic film portion (FIG. 3, reference numeral 29) is a film having a characteristic that does not cause a change in magnetism with respect to torsional torque. The output characteristic of 33) does not change with respect to the torsional torque.
On the other hand, the first and second magnetostrictive film portions (FIG. 3, reference numerals 27 and 28) exhibit magnetostrictive characteristics, and therefore cause a change in magnetism with respect to torsional torque.

As shown in FIG. 11A, the Ni—Fe alloy material is electroplated on the outer peripheral surface of the rotating shaft 16 while rotating the rotating shaft 16 as indicated by an arrow (3), for example. Since the electric field density in the vicinity of the plating electrode is high, the rotation speed is slowed and the plating is thickened at the P1 and P3 portions. In P2 and P4, the rotational speed is increased and the plating is made thinner.
Then, as shown in (b), the third magnetic film portion 29 can be formed on the rotating shaft 16 in such a form that the film thickness in the direction perpendicular to the axis changes at a cycle of 180 °.

The first and second magnetostrictive film portions (FIG. 3, reference numerals 27 and 28) are sprayed or plated with a Ni—Fe alloy having a composition ratio showing magnetostrictive characteristics. Furthermore, magnetic anisotropy can be applied by high-frequency heating or the like while torque is applied to the rotating shaft 16.
The first and second magnetostrictive film portions 27 and 28 are not limited to Ni—Fe alloy materials, and other materials may be used as long as the materials exhibit magnetostrictive characteristics. The third magnetic film portion 29 is not limited to a Ni—Fe alloy material having a composition ratio that does not exhibit magnetostriction characteristics, and other materials may be used as long as they exhibit magnetism. Each film forming method is not limited to thermal spraying and plating.
In addition, in order to give a period to the film thickness, the manufacturing method is not limited to the above-described manufacturing method, and other manufacturing methods may be used as long as the film thickness can have a period, such as a polishing method after film formation. .

Next, a second embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 12A, grooves 55 and 55 are provided in the yokes 48 and 48. Thereby, the magnetic path length by a fringing magnetic flux can be changed, and a period can be given to magnetism collection. A region of the yoke 48 where the magnetism collecting effect is large is R, and a region where the magnetism collecting effect is small is S.

Next, Embodiment 3 of the present invention will be described with reference to the drawings.
As shown in FIG. 12B, the inner side 56 of the yoke 48 is elliptical. In the portion where the third magnetic film portion and the inner side 56 of the yoke 48 are close to each other, the air gap becomes small, and a region R having a large magnetism collecting effect is obtained. In a portion where the air gap is large, a region S having a small magnetism collecting effect is obtained.

  Although the magnetostrictive torque / rotation angle detection device according to the present invention is applied to the steering shaft of an automobile in the embodiment, it can also be applied to a rudder of a ship and detects torque and rotation angle of the rotation shaft. If so, it can be applied to general machine parts.

  The magnetostrictive torque / rotation angle detection device of the present invention is suitable for a steering shaft of an automobile.

  DESCRIPTION OF SYMBOLS 16 ... Rotating shaft, 20 ... Magnetostrictive torque / rotation angle detector, 27 ... First magnetostrictive film part, 28 ... Second magnetostrictive film part, 29 ... Third magnetic film part, 31 ... First detection coil, 32 ... First 2 detection coils, 33 ... third detection coil, 48 ... yoke, 52 ... torque calculation unit, 53 ... rotation angle calculation unit, A, B ... magnetic anisotropy, θ ... rotation angle.

Claims (5)

A rotating shaft, a first magnetostrictive film portion coated on the rotating shaft and provided with magnetic anisotropy, and a magnetic anisotropy coated on the rotating shaft and in a direction opposite to the first magnetostrictive film portion The second magnetostrictive film portion provided, the third magnetic film portion covered with the rotating shaft in a form in which the film thickness changes in the direction perpendicular to the axis and not exhibiting magnetostriction, and the first magnetostrictive film portion. A first detection coil that is arranged and detects a change in magnetic characteristics in the first magnetostrictive film part, and a second detection that is arranged facing the second magnetostrictive film part and detects a change in magnetic characteristics in the second magnetostrictive film part. A coil, a torque calculation unit for calculating a torque applied to the rotating shaft from the detection information of the second detection coil and the detection information of the first detection coil, and a first magnetic film unit disposed facing the third magnetic film unit. A third detection coil for detecting a change in magnetic characteristics in the three magnetic film portions; A rotation angle calculation unit for calculating a rotation angle from left information the rotary shaft consists of,
2. A magnetostrictive torque / rotation angle detecting device characterized in that a torque and a rotation angle of the rotation shaft can be detected at once.   2. The magnetostrictive torque / rotation angle according to claim 1, wherein the third magnetic film portion is coated on the rotation shaft in a form in which a film thickness in a direction perpendicular to the axis changes at a cycle of 360 ° / n. 3. Detection device.   3. The magnetostrictive torque / rotation angle detecting device according to claim 1, wherein the third magnetic film portion is a film having a characteristic that does not cause a change in magnetic field with respect to torsional torque.   4. The magnetostrictive torque / rotation angle detection device according to claim 1, wherein the third detection coil includes a yoke having a period of magnetic collection.   The at least 2 detection coil provided with the yoke with a period for magnetism collection is shifted in said 3rd magnetic film part, and the phase of 1/4 period is shifted, The any one of Claims 1-4 characterized by the above-mentioned. A magnetostrictive torque / rotation angle detecting device according to claim 1.

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