JP2006242915A - Potentiometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a potentiometer for obtaining stable detection sensitivity. <P>SOLUTION: The potentiometer 1 changes the thickness of a magnet facing a Hall element 10 accompanying rotation of a shaft 3, since the shape of the magnet 13 is a substantially columnar shape whose thickness in a circumferential direction is changed. Thus, the output voltage from the Hall element 10 is changed to detect the rotation position of the shaft 3 on the basis of the voltage change. In the potentiometer 1, since the Hall element 10 is arranged, in facing the outer peripheral face 13c of the magnet outward of a radial direction of the magnet 13; even if the shaft 3 is shifted toward the direction of the axial line L, gap fluctuations between the magnet 13 and the Hall element 10 are suppressed. As a result, the output voltage from the Hall element 10 is stabilized, to stabilize detection sensitivity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-contact magnetic potentiometer incorporated in an electric device or the like and used for detecting a rotational position.

Conventionally, as a technology in this type of field, for example, there is a non-contact type potentiometer described in Patent Document 1. This conventional potentiometer is a Hall element that senses the magnetic flux density of a magnetic field formed by a disc-shaped magnet fixed to a shaft as a rotating shaft and outputs a voltage corresponding to the magnetic flux density. And. In this potentiometer, when the output voltage from the Hall element changes due to the rotation of the shaft, the rotational position of the shaft is detected based on this voltage change.
JP 57-27081 A JP-A-7-243804 JP 2001-091298 A JP 2001-041768 A

  However, in the above-described conventional potentiometer, since the Hall element is disposed to face the magnetized surface of the magnet, the gap between the magnet and the Hall element is likely to fluctuate due to the axial displacement of the shaft. . Such a variation in the gap tends to cause a variation in the output voltage from the Hall element, and instability of the detection sensitivity.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a potentiometer capable of obtaining stable detection sensitivity.

  In order to solve the above-mentioned problems, a potentiometer according to the present invention is fixed to a shaft, and is sensitive to a magnet magnetized with N and S poles in the thickness direction, and a magnetic flux density of a magnetic field formed by the magnets. And a Hall element that outputs a voltage corresponding to the magnetic flux density sensed by the magnetosensitive surface, and the magnet is formed in a substantially cylindrical shape whose thickness varies in the circumferential direction. It is characterized in that it is arranged on the outer side in the radial direction of the magnet so as to face the outer peripheral surface of the magnet.

  In this potentiometer, since the magnet has a substantially cylindrical shape whose thickness changes in the circumferential direction, the thickness of the magnet facing the Hall element changes as the shaft rotates. As a result, the output voltage from the Hall element changes, and the rotational position of the shaft can be detected based on this voltage change. In this potentiometer, since the Hall element is arranged on the outer side in the radial direction of the magnet and opposed to the outer peripheral surface of the magnet, even if the shaft is displaced in the axial direction, the Hall element is located between the magnet and the Hall element. Gap fluctuation is suppressed. Thereby, the output voltage from the Hall element is stabilized, and the detection sensitivity can be stabilized.

  Moreover, it is preferable that the thickness of the magnet is continuously changing linearly or curvedly over the entire circumference in the circumferential direction. In this case, in such a magnet configuration, the magnetic flux density continuously changes over the entire circumference of the magnet, so that the detectable range (effective electrical angle) of the rotational position of the shaft can be widened.

  Moreover, it is preferable that the magnetic sensitive surface of the Hall element extends in the axial direction of the shaft. In this way, the magnetic flux density of the magnetic field formed by the magnet can be accurately sensed by the magnetic sensing surface of the Hall element, so that the accuracy of detecting the rotational position of the shaft can be improved.

  Moreover, it is preferable that the magnetic sensitive surface of the Hall element is arranged unevenly on either the N pole side or the S pole side of the magnet. This makes it possible to perform magnetic sensing of the magnetic flux density with higher accuracy, thereby further improving the accuracy of detecting the rotational position of the shaft.

  Moreover, it is preferable that the magnetic sensitive surface of the Hall element extends in a direction orthogonal to the axial direction of the shaft. Even with such an arrangement of the Hall elements, it is possible to accurately sense the magnetic flux density of the magnetic field formed by the magnet, thereby improving the accuracy of detecting the rotational position of the shaft.

  Further, it is preferable that a yoke made of a magnetic material or a permanent magnet is disposed on the opposite side of the Hall element from the magnetically sensitive surface. In this case, the magnetic flux can be reliably passed through the Hall element, and leakage of the magnetic flux can be suppressed.

  As described above, according to the potentiometer according to the present invention, stable detection sensitivity can be obtained. Further, the rotation position of the shaft can be detected over a wide range.

  Hereinafter, a preferred embodiment of a potentiometer according to the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the non-contact magnetic potentiometer 1 includes a housing 2 made of, for example, a magnetic metal, and a shaft 3 as a rotating shaft. The housing 2 includes a cap-shaped housing body 4 having a substantially cylindrical shape and a flat cover 6. The cover 6 is fixed to the bottom surface 4 a of the housing body 4, and the housing body 4 Is provided with a cylindrical accommodation space S. In addition, the wall 5 is formed thick on the top surface 4b side of the housing body 4, and a circular through hole 4c that communicates the housing space S with the outside is formed at the center of the wall 5. Is provided. The casing 2 is provided with a recess 2a that surrounds the back side of the Hall element 10 to be described later, and the casing 2 functions as a yoke for allowing the magnetic flux to pass through the Hall element 10 reliably.

  The shaft 3 is made of, for example, a nonmagnetic metal. The lower end 3 a of the shaft 3 is disposed in the accommodation space S, and the upper end 3 b projects from the through hole 4 c of the housing 2. The shaft 3 is rotatably supported by a pair of ball bearings 7 and 7 provided in the through hole 4c. Further, a groove portion 3c is formed in a substantially middle portion of the shaft 3, a flange portion 3d is formed on the lower end portion 3a side of the shaft 3, and a C-ring 8 is fitted in the groove portion 3c. As a result, by the cooperation of the C ring 8 and the flange portion 3d, it is possible to prevent the shaft 3 from being displaced in the thrust direction and to prevent the shaft 3 from coming off from the housing 2.

  Further, a rotary knob (not shown) as an operation unit is attached to the upper end portion 3 b of the shaft 3 protruding from the housing 2, and the magnet 13 is attached to the lower end portion 3 a of the shaft 3 accommodated in the accommodation space S. Is mounted so as to be concentric with the shaft 3. As shown in FIG. 3, the magnet 13 is formed in a substantially cylindrical shape whose thickness changes linearly and continuously over the entire circumference in the circumferential direction, and is magnetized into an N pole and an S pole in the thickness direction. ing. Moreover, in the magnetized surface 13a of the magnet 13, the joint part of the thinnest part and the thickest part is the step part 13b. In order to prevent the shaft 3 from being included in the magnetic path, the magnet 13 may be fixed to the lower end portion 3a of the shaft 3 via a resin member.

  Further, as shown in FIGS. 1 and 2, a circular circuit board 9 and a Hall element 10 are accommodated in the accommodation space S of the housing 2. The circuit board 9 is pressed against and fixed to a step portion 4 d provided on the inner wall of the housing body 4. A protruding portion 9 a that protrudes toward the concave portion 2 a of the housing 2 is formed on a part of the peripheral edge portion of the circuit board 9. The hall element 10 has three terminals 10a and is fixed to the overhanging portion 9a of the circuit board 9 through leg pieces 10b. Further, the Hall element 10 is disposed on the outer side in the radial direction of the magnet 13 so as to face the outer peripheral surface 13 c of the magnet 13. Further, in the Hall element 10, the magnetosensitive surface 10 c of the magnetosensitive film extends in the direction of the axis L of the shaft 3 and is unevenly arranged on the N pole side of the magnet 13. The Hall element 10 outputs a voltage corresponding to the magnetic flux density of the magnetic field sensed by the magnetic sensing surface 10c. The output voltage is amplified by a predetermined process in the circuit board 9, and then the lead wire 16 It is taken out through.

  In the potentiometer 1 having such a configuration, the shaft 3 and the magnet 13 attached to the lower end 3a of the shaft 3 are moved around the axis L by operation of a rotary knob (not shown) attached to the upper end 3b of the shaft 3. Rotate. At this time, as shown in FIG. 3, since the magnet 13 is formed in a substantially cylindrical shape whose thickness changes linearly and continuously over the entire circumference in the circumferential direction, it faces the magnetosensitive surface 10c of the Hall element 10. The thickness of the magnet 13 to be continuously changed as the shaft 3 rotates.

  Therefore, if the position at which the step 13b of the magnet 13 and the magnetosensitive surface 10c of the Hall element 10 face each other is defined as a reference position (rotation position 0 °), the potentiometer 1 causes the shaft 3 to move from the reference position to either the left or right If the rotation position is in the range of about 45 ° to about 315 °, the magnetic flux density at which the magnetic sensitive surface 10c is sensitive changes linearly in a directly proportional relationship. Further, in the vicinity of the reference position (about 40 ° and about 320 °), the magnetic flux density at which the magnetic sensitive surface 10c is sensitive becomes maximum and minimum. Therefore, the effective electrical angle of the potentiometer 1 is in the range of about 45 ° to about 315 ° at which the magnetic flux density changes linearly with respect to the change in the rotational position of the shaft 3. Within the range, the output voltage from the Hall element 10 with respect to the rotational position of the shaft 3 can be determined in a directly proportional relationship. The output voltage from the Hall element 10 is extracted to the outside through the lead wire 16, and the rotational position of the shaft 3 is detected based on this output voltage.

  Here, in the potentiometer 1, the Hall element 10 is disposed on the outer side in the radial direction of the magnet 13 so as to face the outer peripheral surface 13 c of the magnet 13. Therefore, even if the shaft 3 is displaced in the direction of the axis L, the gap variation between the outer peripheral surface 13c of the magnet 13 and the magnetic sensitive surface 10c of the Hall element 10 can be suppressed. Such suppression of gap fluctuation stabilizes the output voltage from the Hall element 10, and as a result, it is possible to stabilize the detection sensitivity.

  In addition, the magnetic sensing surface 10 c of the Hall element 10 extends in the direction of the axis L of the shaft 3 and is unevenly arranged on the N pole side of the magnet 13. As a result, as shown in FIG. 4, the magnetic flux density of the magnetic field from the N pole side of the magnet 13 toward the outside in the radial direction of the magnet 13 can be accurately sensed by the magnetosensitive surface 10 c of the Hall element 10. Therefore, the accuracy of detecting the rotational position of the shaft 3 can be improved. Further, since the housing 2 functioning as a yoke is located on the back side of the magnetically sensitive surface 10c of the Hall element 10, the magnetic flux can be surely passed through the Hall element 10, and the leakage of the magnetic flux Can be suppressed. This makes it possible to secure a sufficient amount of change in the magnetic flux density that the Hall element 10 senses, and to further improve the detection accuracy. Since the magnetic sensing surface 10c of the Hall element 10 faces the outer peripheral surface 13c of the magnet 13, the magnetic flux from the magnet 13 can be directly sensed without using a yoke or the like.

  The present invention is not limited to the above embodiment. For example, the shape of the magnet 13 may be a substantially cylindrical shape whose thickness changes in a curved shape (for example, a quadratic curve shape) continuously over the entire circumference in the circumferential direction. In this way, depending on the relationship between the dimensions of the magnet 13 and the position of the Hall element 10, the rotational position of the shaft 3 is compared with the case where the thickness changes linearly over the entire circumference in the circumferential direction as shown in FIG. The linearity of the change amount of the magnetic flux density with respect to the change amount of the magnetic field is improved, and a wide effective electrical angle can be obtained. Further, the magnetic sensitive surface 10 c of the Hall element 10 may be arranged unevenly on the S pole side of the magnet 13. In this case, the magnetic flux density of the magnetic field from the outside in the radial direction of the magnet 13 toward the S pole side of the magnet 13 can be accurately sensed by the magnetosensitive surface 10 c of the Hall element 10. Further, when the housing 2 is formed of a non-magnetic metal, the hall element 10 is provided with a yoke made of a metal piece or a permanent magnet piece on the back side of the magnetic sensitive surface 10c of the magnetic sensitive film. The magnetic flux can be surely passed through the element 10.

  Furthermore, as a modification of the arrangement of the Hall elements 10, as shown in FIGS. 5 and 6, the magnetic sensitive surface 10 c of the Hall elements 10 extends in a direction orthogonal to the axis L direction of the shaft 3. You may arrange in. In this case, as shown in FIG. 6, by arranging the magnetosensitive surface 10 c at the boundary between the north pole and the south pole of the magnet 13, the magnetic flux density of the magnetic field along the axis L direction of the shaft 3 is changed to the Hall element. Thus, it is possible to accurately sense the magnetism with the ten magnetosensitive surfaces 10c. In this modified example, since the housing 2 that functions as a yoke is located on the back side of the magnetically sensitive surface 10c of the Hall element 10, leakage of magnetic flux can be suppressed and detection accuracy can be improved. Is planned.

It is sectional drawing which shows one Embodiment of the potentiometer which concerns on this invention. It is the II-II sectional view taken on the line in FIG. It is the perspective view which showed the shape of the magnet. It is sectional drawing which showed the positional relationship of a magnet and a Hall element. It is sectional drawing which showed the potentiometer which concerns on a modification. It is the figure which showed the positional relationship of the magnet and Hall element in the potentiometer which concerns on a modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Potentiometer, 3 ... Shaft, 10 ... Hall element, 10c ... Magnetosensitive surface, 13 ... Magnet, 13c ... Outer peripheral surface, L ... Axis line.

Claims (6)

A magnet fixed to the shaft and magnetized in the thickness direction to N and S poles;
A magnetic sensing surface that senses the magnetic flux density of the magnetic field formed by the magnet, and a Hall element that outputs a voltage corresponding to the magnetic flux density sensed by the magnetic sensing surface,
The magnet is formed in a substantially cylindrical shape whose thickness changes in the circumferential direction,
The potentiometer, wherein the hall element is disposed on the outer side in the radial direction of the magnet so as to face the outer peripheral surface of the magnet.   The potentiometer according to claim 1, wherein the thickness of the magnet continuously changes linearly or curvedly over the entire circumference in the circumferential direction.   The potentiometer according to claim 1, wherein the magnetosensitive surface of the hall element extends in an axial direction of the shaft.   4. The potentiometer according to claim 3, wherein the magnetosensitive surface of the Hall element is unevenly arranged on either the N pole side or the S pole side of the magnet.   The potentiometer according to claim 1, wherein the magnetosensitive surface of the Hall element extends in a direction orthogonal to the axial direction of the shaft.   The potentiometer according to any one of claims 1 to 5, wherein a yoke made of a magnetic material or a permanent magnet is disposed on the opposite side of the Hall element to the magnetosensitive surface.

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