JP2007057311A - Compound magnetic head and torque detection device for rotary shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for a torque detection device of a magnetostriction type for a rotary shaft capable of making the additional work to the shaft unnecessary, and capable of making the excitation/detection coils of the magnetic head high sensitivity depending on the number of turns of the coils while simplifying the coil winding method of the coils. <P>SOLUTION: The compound magnetic head core 20 is formed such that the rotary shaft 2 having magnetostrictive performance, the soft magnetism part 10 and the non-magnetism part 11 are arranged alternatively while intervening the air gap in between. By twisting the soft magnetism parts 10 to the shaft by approximately 45° while winding the coil in a solenoid shape to the head core 20, the twisting stress of the rotary shaft is detected precisely. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for detecting the axial torque of a rotating shaft in a non-contact manner using magnetostrictive characteristics, and is particularly applicable to the automobile field, industrial machine field, and the like.

  In the power steering mechanism, engine control mechanism, power transmission mechanism, and the like of automobiles, means for accurately detecting shaft torque has long been desired. Various techniques have been proposed so far because precise control and efficiency can be improved by increasing detection accuracy. In particular, the non-contact method of detecting shaft torque using the magnetostriction characteristics of the rotating shaft is excellent in responsiveness, is relatively easy to increase sensitivity, and has a large overload capability. Therefore, it is attracting attention as an alternative to the conventional method for detecting torque.

  For example, Patent Document 1 proposes a technique in which a magnetic film 115 having an inclination angle is fixed to a rotating shaft and excitation and detection are performed by a solenoid coil on the outer periphery of the rotating shaft, as shown in FIG. However, since this method requires additional processing on the rotating shaft, there is a risk that reliability such as peeling of the magnetic film may be impaired. Furthermore, since it is essential to specialize the shaft and increase the diameter, it is considered that the wearability is poor.

  Further, in Patent Document 2, as shown in FIG. 7B, a method is proposed in which torque is detected in the same manner as in Patent Document 1 by disposing the rotating shaft and arranging the loop coil while maintaining a constant inclination angle. Has been. Although this method does not require any additional work on the shaft, it is necessary to detect a wide area in the longitudinal direction of the shaft in order to increase sensitivity, and there is a concern that the size of the apparatus will increase.

  Further, in Patent Document 3, as shown in FIG. 7 (c), a structure for greatly reducing the coil portion is proposed to overcome the problem of Patent Document 2, but since the coil structure is complicated, a large number of windings are required. It is difficult to achieve high sensitivity depending on the number of turns of the coil.

  In addition, the above three types of structures all have a high risk of disconnection of the coil due to the influence of rotational runout of the shaft and contamination of foreign matter because the coil is adjacent to the rotation shaft. In order to ensure reliability, it may be necessary to take measures such as covering and reinforcing the coil part with resin or the like, or enlarging the gap between the shaft and the coil to sacrifice sensitivity.

  Moreover, in patent document 4, as shown in FIG.7 (d), the structure which provides a U-shaped iron core in the outer periphery of a rotating shaft is described. However, if a plurality of U-shaped iron cores are arranged on the outer periphery of the rotating shaft, the structure becomes complicated and it becomes difficult to downsize, the productivity is poor, and it is difficult to increase the working area of the magnetic poles. It appears to be.

JP-A-1-94230 JP-A-6-273247 JP-A-6-194239 Japanese Patent No. 2905561

  The present invention is to solve the problems related to the mounting property, reliability, downsizing, high sensitivity, and productivity related to the conventional magnetostriction detection type torque detection device described above.

  The present invention forms a composite magnetic head core in which soft magnetic portions and nonmagnetic portions are alternately arranged in the circumferential direction with a gap on a rotating shaft having magnetostrictive characteristics, and the soft magnetic portion is rotated. The coil is inclined with respect to the axis, and an excitation / detection coil is wound around the composite magnetic head core.

  The inclination angle of the soft magnetic part with respect to the rotation axis is preferably 35 to 55 degrees.

  It is preferable that the inclination directions of the soft magnetic portions are all clockwise or all counterclockwise.

  The soft magnetic part may be arranged so that the inclination direction of the soft magnetic part repeats clockwise and counterclockwise alternately.

  The minimum width in the circumferential direction of the nonmagnetic part is preferably 0.5 to 1.5 times the length of the soft magnetic part in the inclination angle direction.

  It is preferable that the composite magnetic head core is formed integrally or divided into two so as to surround the outer periphery of the rotating shaft.

  It is preferable that a composite magnetic head having a tilt angle in the clockwise direction and a composite magnetic head having a tilt angle in the counterclockwise direction are used in combination.

  It is preferable that both end portions in the axial direction of the soft magnetic portion protrude toward the inner diameter side.

  A rotary shaft torque detecting device can be formed by combining the composite magnetic head of the present invention and a signal processing circuit that outputs a signal by applying circuit processing to a signal obtained therefrom.

  The features of the present invention will be described below while explaining the principle of the magnetostrictive detection type rotating shaft torque detection device. When a current is passed through the excitation coil provided in the sensor, a magnetic flux 201 as shown in FIG. 8A is generated around the coil. The magnetic flux 201 generated by the coil forms a closed loop according to the right-handed screw rule in a plane orthogonal to the coil. In many cases, a plurality of closed magnetic paths are formed by devising a magnetic circuit such as a coil winding method. Even if the relative position of the sensor changes due to the rotation of the shaft, the magnetic permeability does not change unless a rotational torque is applied to the shaft to cause distortion, so that the coil inductance does not change.

  When rotational torque is applied to the shaft as shown in FIG. 8B from the no-load state in FIG. 8A, tensile stress (−σ in the directions inclined by + 45 ° and −45 ° with respect to the longitudinal direction of the shaft. ) And compressive stress (+ σ) are simultaneously generated while being orthogonal to each other. Here, it is possible to use magnetostriction characteristics in which the permeability increases when a tensile stress is applied to the soft magnetic material and conversely the permeability decreases when a compressive stress is applied.

  In other words, the magnetic flux generated by the exciting coil is easy to flow in the direction in which tensile stress is applied, and on the other hand, it is difficult to flow in the direction in which compressive stress is applied. The amount can be estimated. For example, as shown in FIG. 8, it is assumed that there is a spiral exciting coil in a direction inclined by + 45 ° with respect to the axis. Since the magnetic flux generated in the coil forms a closed magnetic circuit according to the right-handed screw law, the magnetic flux is greatly affected by the permeability change in the −45 ° direction perpendicular to the coil. Here, assuming that a tensile stress is applied in the −45 ° direction, the magnetic flux flows more easily than when there is no load, so the coil inductance increases compared to when there is no load. Conversely, when compressive stress is applied, the inductance decreases.

  As described above, when rotational torque is applied to the shaft, stresses having different directions are generated simultaneously in both directions of + 45 ° and −45 °. Therefore, in the method of estimating the torque from the amount of change in inductance with respect to no load, + 45 ° Or a change in magnetic permeability in one direction of −45 ° may be detected. Further, by detecting both the + 45 ° and −45 ° directions at the same time and detecting the difference amount, it is possible to estimate the torque with higher accuracy. As means for simultaneously detecting both + 45 ° and −45 ° directions, as shown in FIG. 2 (b), a combination of a clockwise tilt angle and a counterclockwise tilt angle as shown in FIG. This can be realized by using a pair. Alternatively, as shown in FIG. 3 (b), the inclination direction of the soft magnetic part repeats alternately clockwise and counterclockwise, and the winding method is in the axial direction shown in FIG. 4 (b). The winding may be divided into two for each inclination direction of the soft magnetic part.

  In any case, in the magnetostrictive rotating shaft torque detection device, it is important to read the change in permeability in the direction of inclination of + 45 ° and −45 ° with respect to the shaft. Instead of winding in the form of a solenoid with no inclination angle, a magnetic film is provided in a direction inclined by ± 45 ° on the rotating shaft so that the magnetic flux flows only in the inclination direction. Moreover, in patent document 2 and patent document 3, axial torque can be detected by giving the coil an inclination angle.

  Although the structure of Patent Document 1 has a great feature that a coil is a simple solenoid and can be easily wound in a large number and is easy to achieve high sensitivity, the need for machining on the shaft deteriorates reliability and mountability. It was.

  Therefore, in this method, the rotating shaft is not processed, and a plurality of magnetic pole portions are formed in which the soft magnetic portions and the nonmagnetic portions are alternately arranged in the circumferential direction through gaps with respect to the rotating shaft, and the soft magnetic portions rotate. The main structural features are that the coil has an inclination angle with respect to the shaft and the coil for exciting the magnetic pole portion is a simple solenoid.

  By eliminating the need for complicated machining on the shaft, it is possible to significantly improve the mounting ability. Even if the rotating shaft does not have magnetostriction characteristics such as non-magnetic SUS, it is only necessary to cover the outer peripheral portion of the shaft with a ring having magnetostriction characteristics. There is nothing. Further, since the coil can be formed in a solenoid shape, high sensitivity depending on the number of turns is facilitated. Furthermore, since the coil can be arranged on the outer peripheral surface of the magnetic head, it is possible to avoid the risk of the coil being disconnected. Furthermore, it is easy to increase the sensitivity by greatly reducing the gap between the rotating shaft and the magnetic head.

  As the structure of the magnetic head, it is preferable that the soft magnetic portion has an inclination angle of 35 to 55 ° in absolute value with respect to the rotation axis. The inclination angle of the soft magnetic part is most preferably set to 45 °, which is the direction in which the torsional stress of the rotating shaft is generated. However, the direction in which the magnetic flux flows slightly changes depending on the gap between the rotating shaft and the composite magnetic head, so that the tilt angle of the soft magnetic part of the composite magnetic head is within ± 10 ° with respect to the ideal value of 45 °. Even if it deviates, there is no significant difference in detection accuracy.

  The circumferential width of the non-magnetic portion is 0.5 to 1.5 times the inclination angle direction length of the soft magnetic portion, and a plurality of closed magnetic paths that are generated in the same number as the number of soft magnetic portions. Since magnetic interference hardly occurs, it is possible to efficiently detect a magnetic permeability change in a direction inclined by 45 ° with respect to the rotation axis. The magnetic flux generated by the excitation / detection coil flows along the tilt direction while being divided for each soft magnetic piece of the composite magnetic head, and flows into the rotating shaft from the vicinity of one end through a gap. If the magnetic circuit is configured so that the magnetic flux flowing into the rotating shaft returns to the vicinity of the other end of the same soft magnetic piece, the magnetic path length, that is, the magnetic resistance is minimized, so that the detection sensitivity is increased. As a means for this, it is preferable to widen the circumferential width of the nonmagnetic portion located between adjacent poles. If the circumferential width of the non-magnetic portion is less than 0.5 times the length of the soft magnetic portion in the inclination angle direction, the magnetic flux flowing out from the rotating shaft will flow to other adjacent soft magnetic pieces. In addition, the magnetic path length, that is, the magnetic resistance is increased, and the detection sensitivity is relatively lowered. In addition, when the circumferential width of the nonmagnetic portion greatly exceeds 1.5 times the inclination angle direction length of the soft magnetic portion, the effective area of the soft magnetic portion that can act as a magnetic pole surface by facing the rotating shaft Decreases relatively, and the detection sensitivity decreases.

  As a means for obtaining a composite magnetic head in which soft magnetic portions and nonmagnetic portions are alternately arranged in the circumferential direction, for example, as shown in FIG. 1, the soft magnetic yoke 10 and the nonmagnetic spacer 11 are individually cut, forged, cast, etc. After manufacturing, a method of assembling by bonding or screwing can be selected. In addition, after manufacturing only the soft magnetic parts individually, a technique of insert molding a plurality of soft magnetic pieces with a non-magnetic resin or the like, or a technique of casting with a non-magnetic aluminum die-casting can be selected.

  In addition, as shown in FIG. 6, by dividing the magnetic head into two in the circumferential direction, the magnetic head can be mounted so as to sandwich the shaft, and the mounting property to the rotating shaft can be improved. Further, a part of the magnetic head can be cut out to facilitate attachment to and removal from the rotating shaft.

  As the winding method of the excitation / detection coil, in addition to the method of winding it in the form of a solenoid around each of the soft magnetic material pieces as described in Patent Document 4 of FIG. 7 (d), FIGS. 4 (a) to 4 (c). As described, the magnetic head can be uniformly wound so as to surround the whole. In the method shown in FIG. 4A, the ring-shaped composite magnetic head core 20 is wound in the circumferential direction on the outer peripheral surface. The winding work is the easiest, and furthermore, no coil exists on the inner peripheral surface side of the magnetic head into which the rotating shaft is inserted, so that higher structural reliability can be obtained. 4B, the ring-shaped composite magnetic head core 20 is wound in the axial direction. In the composite magnetic head that alternately repeats clockwise and counterclockwise rotation as shown in FIG. 3 (b), the winding is divided into two according to the inclination direction of the soft magnetic portion, or as shown in FIG. This is effective when the winding is divided into two in the circumferential direction and the windings are applied independently to each of them. In the winding method shown in FIG. 4C, the winding density in the circumferential direction is made non-uniform so that the winding mainly crosses the soft magnetic piece. Although the winding work is complicated, there is an advantage that a coil can be arranged in a direction orthogonal to a soft magnetic piece having an inclination angle, which leads to an improvement in detection efficiency.

  Further, as shown in FIG. 5, it is also preferable that both end portions in the axial direction of the soft magnetic portion protrude toward the inside where the rotation shaft is located (FIG. 5A). When the non-magnetic portion that fills the space between the soft magnetic portions is formed in the same manner as the soft magnetic portion, a composite magnetic head core 20 having a flange protruding toward the inner peripheral side is formed (FIG. 5B). As described above, in the vicinity of both end portions in the axial direction of the soft magnetic portion of the composite magnetic head, the magnetic flux is bent at a right angle toward the inner peripheral surface, and enters and exits the rotating shaft through the air gap. For this reason, it becomes easy to increase the sensitivity by reducing the gap amount and reducing the magnetic resistance by bringing the vicinity of both ends of the soft magnetic portion as close as possible to the rotation axis.

  Further, as shown in FIG. 5 (c), the coil for excitation / detection is simultaneously disposed in each of the outer peripheral side surface and the concave portion on the inner peripheral side surface of the magnetic head, thereby simultaneously realizing a large number of coils and a reduction in size. It is also possible.

  The present invention eliminates the need for complicated additional work on the rotating shaft that detects torque. In addition, the structural reliability of the magnetic head portion is improved, and compactness is facilitated. Further, since the winding process of the excitation / detection coil is easy, the productivity of the entire apparatus is improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(overall structure)
1A to 1C show an embodiment of a magnetostrictive torque detection device of the present invention. FIG. 1A is a perspective view showing an exploded core portion of a composite magnetic head. The iron core of the magnetic head is composed of four soft magnetic yokes 10 having an inclination angle of 45 degrees, four nonmagnetic spacers 11 disposed between them, and an outer peripheral reinforcing ring 12 that reinforces both ends of the outer periphery. Has been. Sintered ferrite was used for the soft magnetic yoke 10, and aluminum was used for the nonmagnetic spacer 11 and the outer peripheral reinforcing ring 12, and the respective members were bonded and fixed. FIG. 1B shows a perspective view of the composite magnetic head core 20 after being bonded and fixed. FIG. 1 (c) shows a composite magnetic head 1 formed by winding an excitation / detection coil around the outer periphery of the composite magnetic head core 20 and inserting a rotating shaft 2 as a test object into the inner periphery thereof. It is the perspective view which showed a mode that the alternating current 13 is applied to the both ends. The rotating shaft used was nickel-molybdenum steel that was carburized.

  The outer diameter of the rotating shaft was Φ20 mm, the inner diameter of the composite magnetic head was Φ20.6 mm, and the outer diameter was Φ25 mm. The excitation / detection coil used was an enameled wire with a diameter of 0.5 mm, wound 120 turns around the outer periphery of the composite magnetic head core, and the frequency of the alternating current was 100 kHz.

  FIG. 9 shows the measured changes in the inductance of the coil when a torque of −200 to +200 Nm is applied to the rotating shaft. Torque was measured with a torque meter connected to the rotating shaft, and coil inductance was measured with an LCR meter. From FIG. 9, it can be seen that the inductance change when torque is applied exhibits good linearity. Therefore, if circuit processing is added to the signal obtained from the composite magnetic head of the present invention, an output signal with extremely good linearity can be obtained.

It is a schematic diagram of the torque detection apparatus concerning one Example of this invention. It is a schematic diagram which shows the attachment method of the apparatus concerning one Example of this invention. It is a schematic diagram which shows the magnetic pole pattern concerning one Example of this invention. It is a schematic diagram which shows the coil winding method concerning one Example of this invention. It is a schematic diagram which shows the other structure in connection with one Example of this invention. It is a schematic diagram which shows the other apparatus attachment method in connection with one Example of this invention. It is a schematic diagram which shows another Example. It is a schematic diagram which shows the principle of the torque detection in connection with one Example of this invention. It is a graph which shows the experimental result regarding one Example of this invention.

Explanation of symbols

1: Composite magnetic head 2: Rotating shaft
10: Soft magnetic yoke
11: Nonmagnetic spacer
12: Peripheral reinforcement ring
13: Excitation / detection coil
20: Composite magnetic head core
102: Rotation axis
110: Soft magnetic yoke
113: Excitation / detection coil
115: Soft magnetic piece
201: Magnetic flux

Claims (9)

A composite magnetic head core in which soft magnetic parts and nonmagnetic parts are alternately arranged in the circumferential direction through a gap with respect to a rotational axis having magnetostrictive characteristics is formed, and the soft magnetic part is arranged with respect to the rotational axis. A composite magnetic head, wherein the magnetic head is tilted and an excitation / detection coil is wound around the composite magnetic head core. 2. The composite magnetic head according to claim 1, wherein an inclination angle of the soft magnetic portion with respect to a rotation axis is 35 to 55 degrees. 3. The composite magnetic head according to claim 1, wherein the inclination directions of the soft magnetic parts are all clockwise or all counterclockwise. 4. 3. The composite magnetic head according to claim 1, wherein an inclination direction of the soft magnetic portion alternately repeats clockwise and counterclockwise. 5. The composite according to claim 3, wherein a minimum width in the circumferential direction of the nonmagnetic part is 0.5 to 1.5 times a length in a tilt angle direction of the soft magnetic part. Magnetic head. 6. The composite magnetic head according to claim 3, wherein the magnetic pole portion is formed integrally or divided into two so as to surround the outer periphery of the rotating shaft. 7. The composite magnetic head according to claim 3, wherein the head having an inclination angle clockwise and the one having an inclination angle counterclockwise are used as a pair. Characteristic composite magnetic head. 8. The composite magnetic head according to claim 3, wherein both ends of the soft magnetic portion in the axial direction protrude toward an inner diameter side. 9. 9. A rotary shaft torque detecting device that outputs a signal by subjecting the signal obtained from the composite magnetic head according to claim 1 to circuit processing.

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