JP2005140593A - Angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle sensor capable of improving linearity of an detection output, capable of widening an electric effective angle, and capable of eliminating irregular rotation of a magnet. <P>SOLUTION: In this angle sensor, a Hall element 20 is arranged opposedly to a neutral detection position C with respect to the magnet 15 attached to a shaft 10, and a rotation angle of the magnet 15 is detected based on an output from the Hall element 20. The magnet 15 is formed into a crescent shape, and a rotation axis O is arranged to be conformed on a line passing through the gravity center position P of the magnet 15. Tip protrusions 15a, 15b of the magnet 15 is preferably set in a position rotated by ±130°±5° along a direction separated from the neutral detection position C, using a straight line CO connecting the neutral detection position C of the Hall element 20 and the rotation axis O, as a reference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an angle sensor, and more particularly, to an angle sensor in which a magnet and a magnetic sensing element are arranged to face each other and a relative rotation angle between them is detected based on the output of the magnetic sensing element.

  Conventionally, as an angle sensor, as shown in FIG. 11, a rectangular parallelepiped magnet 1 and a magnetic detection element 2 are arranged to face each other, and the rotation angle of the magnet 1 attached to a rotation shaft (not shown) is determined by the magnetic detection element 2. Something to detect based on the output was provided.

  The magnetic sensing element is a Hall element or a magnetoresistive element, and is an element that generates an output voltage proportional to the magnitude of the magnetic flux density passing through these elements vertically or changes its resistance value. For example, in the case of a Hall element, when the circumferential position relative to the magnet 1 changes from A to E, the output voltage changes as shown in FIG.

  In this type of angle sensor, it is preferable that the angle and the output have a linear relationship (linear relationship) over the entire range of angles to be detected in order to improve detection accuracy, and improvement in linearity is required. Yes. Further, it is preferable that the detectable angle range is wide, and there is a demand for expansion of the electrical effective angle.

  Here, the linearity of the output of the magnetic sensing element and the electrical effective angle will be described in more detail. Since the S pole of the magnet 1 is closest to the position A of the magnetic sensing element 2, when the magnetic flux from the N pole is positive, the magnetic sensing element 2 has the maximum magnetic flux density in the negative direction, and the output voltage is the minimum value. Become. Since the N pole of the magnet 1 is closest to the position E, the output voltage becomes the maximum value. Further, since the magnetic flux perpendicular to the magnetic sensing element 2 is zero at the position C, the output voltage is zero, and this position C is referred to as a neutral detection position in this specification.

  The ideal output characteristic is a straight line X shown in FIG. 12, and FIG. 13 shows the amount of deviation of the output voltage from the straight line X, the maximum variable voltage value (here 0.15V) in the detection range (± 60 ° here). It is expressed as a ratio to. In order for the angle and the output to have a linear relationship (linear relationship), the smaller the shift amount, the better.

  The electrical effective angle is an angle at which the output can be detected with guaranteed linearity. This effective angle varies depending on the purpose of use of the sensor, and a wide angle is not required for all applications. However, it is easy to use a sensor having a wide effective angle in a narrow range, but the reverse use is impossible, and a wider electrical effective angle is beneficial. Incidentally, the effective angle of the conventional angle sensor whose characteristics are shown in FIG. 12 is ± 60 °.

  Conventionally, a magnet is a rectangular parallelepiped in view of ease of manufacture, and magnetic flux is generated in such a rectangular parallelepiped magnet 1 as shown in FIG. When the magnet 1 is rotated about the center O as shown in FIG. 11, the slope of the output voltage between the positions B and D is determined by the length L of the magnet 1. The output voltage of the S pole maximum magnetic flux density portion at position A and the N pole maximum magnetic flux density portion at position E is determined by the distance (radius r) between the magnetic pole and the magnetic sensing element 2, and the output level (magnetic flux density) becomes closer to this distance. ) Will grow.

  However, the output characteristics of the positions A and E are rounded, and the effective angle with good linearity is at most about ± 60 °.

  In Patent Document 1, in order to improve the linearity of the output of the magnetic detection element, as shown in FIG. 15, the magnet 5 is formed in a semicircular shape and fitted in the side groove of the rotating shaft 6, and the Hall element 7 is attached to the magnet 5. An angle sensor is disclosed in which the position of the magnet 5 is fixed and the center P of the magnet 5 is decentered with respect to the center O of the rotating shaft 6.

The angle sensor disclosed in Patent Document 1 improves the linearity in the effective angle range by biasing the magnetic flux distribution toward the rotation axis O side by making the magnet 5 into a semicircular shape (see FIG. 16). is there. However, the effective angle is at most about ± 60 °, and the effective angle cannot be further increased. Further, since the center of gravity of the magnet 5 and the center of rotation are deviated, the rotating body (rotating shaft and magnet) is likely to have uneven rotation.
JP 2000-121309 A

  Therefore, an object of the present invention is to provide an angle sensor that not only improves the linearity of the detection output but also increases the electrical effective angle and does not cause uneven rotation of the magnet.

  In order to achieve the above object, according to the present invention, there is provided an angle sensor in which a magnet and a magnetic sensing element are arranged so as to face each other, and a relative rotation angle of both is detected based on an output of the magnetic sensing element. Is formed in a crescent shape on the rotation plane of the magnet, and the rotation axis of the magnet is arranged so as to substantially coincide with a line passing through the center of gravity of the magnet.

  In the angle sensor according to the present invention, since the shape of the magnet is a crescent shape, the pole portion (maximum magnetic flux portion) of the magnet is far from the neutral detection position of the magnetic sensing element, and the electrical effective angle is expanded. In addition, the linearity of the detection output is improved by setting the distance of the detection element so that the point A or the point E comes to an extended portion of the substantially straight line between the BCDs of the output characteristics shown in FIG. Further, since the rotation axis of the magnet is arranged so as to substantially coincide with the line passing through the position of the center of gravity of the magnet, that is, the center of the magnet and the rotation axis are substantially coincided with each other. Is eliminated, and the occurrence of detection errors can be eliminated.

  In the angle sensor according to the present invention, a Hall element or a magnetoresistive element can be used as the magnetic sensing element. Also, the position where the tip of the crescent-shaped magnet rotates ± (130 ° ± 5 °) in the direction away from the neutral detection position with reference to the straight line connecting the neutral detection position of the magnetic detection element and the rotation axis It is preferable that it is set to.

  The linearity of the output is guaranteed when the crescent-shaped magnet apex is set to a position rotated ± 130 ° in the direction away from the neutral detection position with reference to the straight line connecting the neutral detection position of the magnetic detection element and the rotation axis. The possible electrical effective angle is expanded to ± 90 ° or more. In order to obtain an effective angle of ± 90 °, it is necessary to set the cusp at a position rotated at least ± 125 ° in a direction away from the neutral detection position with reference to a straight line connecting the neutral detection position and the rotation axis. is there. On the other hand, if the apex exceeds the position rotated ± 135 ° in the direction away from the neutral detection position with respect to the straight line connecting the neutral detection position and the rotation axis, the magnetic field lines are less likely to pass through the magnetic detection element. However, both the linearity and accuracy of the detection output are deteriorated.

  Embodiments of an angle sensor according to the present invention will be described below with reference to the accompanying drawings.

(Configuration of one embodiment, see FIGS. 1 to 3)
An embodiment of an angle sensor according to the present invention is shown in FIGS. In this angle sensor, a magnet 15 is fixed to an arrow a and an end surface of a shaft 10 that is rotatable in the opposite direction, and a Hall element 20 is fixedly disposed at a neutral detection position C facing the magnet 15. .

  The magnet 15 has a crescent moon shape in its rotation plane (xy plane orthogonal to the rotation axis O of the shaft 10), and the rotation axis O is arranged on a line passing through the center of gravity P of the magnet 15. Here, the center-of-gravity position P is the intersection of the midpoint of the crescent-shaped x-direction height H, the midpoint of the y-direction width W, and the midpoint of the z-direction thickness T.

  Further, the magnet 15 is magnetized in the x direction, the tip apex 15a is magnetized to the S pole, and the tip apex 15b is magnetized to the N pole. However, this magnetization may be reversed. The apexes 15a and 15b extend in a direction away from the neutral detection position C of the Hall element 20, and the angle α from the rotation axis O is ± (130 with respect to a straight line CO connecting the position C and the rotation axis O. It is set at a position of (± 5 °).

  The magnet 15 has a crescent shape formed by overlapping circles with radii r1 and r2 at an interval M. The sizes of r1 are 3.5 to 4.5 mm, r2 is 4.0 to 5.5 mm, and the width W is Although 1 to 3 mm and thickness T are arbitrary, 2 mm is the limit. The center of gravity position P coincides with the rotational axis O, but it does not necessarily have to coincide exactly and may be shifted in any direction within a limit of 1 mm.

  The magnet 15 may be cut out from a rectangular parallelepiped, but can be manufactured at low cost by press molding, stamping from a rubber material, injection molding, or the like.

  As for the arrangement of the Hall elements 20, it is appropriate to set the distance r3 from the rotation axis O to 10 to 15 mm.

  The above arrangement relations and specific dimensions are merely examples, but as shown in Experimental Examples 2 to 4 below, arrangements and dimensions that can maintain the linearity (linearity) of the angle detection output at ± 1% or less are shown. Yes.

  In the above configuration, the magnetic flux distribution formed by the crescent-shaped magnet 15 is biased to the opposite side to the Hall element 20, as shown in FIG. That is, arrows A and B indicate the maximum magnetic flux density direction, and the maximum magnetic flux portion is away from the neutral detection position C of the Hall element 20 in the outer peripheral direction of the shaft 10. Incidentally, with respect to the maximum magnetic flux density directions A and B, the angle β from the rotation axis O is ± 100 ° with respect to the straight line CO connecting the position C and the rotation axis O.

(Output characteristics, see FIGS. 4-8)
In the angle sensor which is one embodiment having the above-described configuration, the inventors manufactured Experimental Examples 1 to 5 shown in Table 1 below and measured the characteristics thereof. As shown in Table 1, the angles α of the tip cusps 15a and 15b are ± 120.6 ° in Experimental Example 1, ± 125.0 ° in Experimental Example 2, ± 130.5 ° in Experimental Example 3, and Experimental Example 4 Was set at ± 135.0 °, and in Experimental Example 5 was set at ± 140.8 °. 4 to 8 show output characteristics corresponding to Experimental Examples 1 to 5, respectively.

  In each of Experimental Examples 1 to 5, the output characteristics of the Hall element 20 with respect to the rotation angle of the magnet 15 are as shown by a curve F in FIGS. As is apparent from this characteristic curve F, an output characteristic with good linearity was obtained over a wide range of at least ± 90 ° from the neutral detection position C (output zero). That is, the electrical effective angle is greatly expanded.

  In Experimental Examples 1 to 5, the deviation from the ideal output characteristic is shown by a curve G in FIGS. Comparing the deviation amount in each of the experimental examples 1 to 5 shown in the curve G and Table 1, in the experimental examples 2 to 4, the deviation amount is 1% or less in the range where the angle α is ± 90 °, It showed good characteristics.

  On the other hand, as in Experimental Examples 1 and 5, when the angle α exceeds ± (130 ° ± 5 °), the deviation amount also exceeds 1%, and satisfactory characteristics cannot always be obtained.

  In the experimental examples 2 to 4, the amount of deviation of the output is greatly improved as apparent from comparison with the amount of deviation of the conventional example shown in FIG. In combination with O, the detection accuracy has been improved.

  That is, in Experimental Examples 2 to 4, the direction in which the cusps 15a and 15b of the crescent-shaped magnet 15 are moved away from the neutral detection position C with reference to the straight line CO that connects the neutral detection position C of the hall element 20 and the rotation axis O. Thus, the effective electrical angle that can guarantee the linearity of the output voltage of the Hall element 20 could be expanded to ± 90 ° or more. In order to obtain an effective angle of at least ± 90 °, at least ± 125 ° in a direction away from the neutral detection position C with reference to a straight line CO connecting the cusps 15a and 15b to the neutral detection position C and the rotation axis O. It is necessary to set to the rotated position.

  On the other hand, when the cusps 15a and 15b exceed the position rotated ± 135 ° in the direction away from the neutral detection position C with reference to the straight line CO connecting the neutral detection position C and the rotation axis O, the magnetic lines of force pass through the Hall element 20. Although the effective angle does not narrow as shown by the curve F in FIG. 8, it has been confirmed that both the linearity and accuracy of the detection output deteriorate as shown by the curve G in FIG. 8.

(Refer to other shapes of magnet, FIGS. 9 and 10)
9 and 10 show other shapes of magnets that can be used in the angle sensor according to the present invention.

  The crescent-shaped magnet 16 shown in FIG. 9 (A) has a circular central portion with radii r1 and r2, and has no significant change in output characteristics as compared with the magnet 15.

  The crescent-shaped magnet 17 shown in FIG. 9B is obtained by overlapping two ellipses j at intervals K, and the tip cusps 17a and 17b at which the magnetic flux density is maximized are located further away from the neutral detection position C. Is set. Even in the magnet 17, the output characteristics are not significantly changed as compared with the magnet 15, and the electrical effective angle can be made larger than ± 90 °.

  In addition to the shapes shown in FIGS. 9A and 9B, magnets 18A, 18B, and 18C configured by straight lines shown in FIGS. 10A, 10B, and 10C may be used. The tip of each magnet 18A, 18B, 18C is denoted by reference numerals 18Aa, 18Ab, 18Ba, 18Bb, 18Ca, 18Cb, respectively.

(Other examples)
The angle sensor according to the present invention is not limited to the above-described embodiment, and can be changed to various configurations within the scope of the gist.

  For example, the shape of the details of the crescent-shaped magnet is arbitrary, and other shapes than those shown in FIGS. 9 and 10 can be used.

It is a perspective view which shows one Example of the angle sensor which concerns on this invention. It is a front view which shows the said angle sensor. It is a chart figure showing magnetic flux distribution formed with a magnet in the angle sensor. It is a graph which shows the output characteristic and the deviation | shift amount in Experimental example 1 in the said angle sensor. It is a graph which shows the output characteristic and the deviation | shift amount in Experimental example 2 in the said angle sensor. It is a graph which shows the output characteristic and the deviation | shift amount in Experimental example 3 in the said angle sensor. It is a graph which shows the output characteristic and the deviation | shift amount in Experimental example 4 in the said angle sensor. It is a graph which shows the output characteristic and the deviation | shift amount in Experimental example 5 in the said angle sensor. It is a front view which shows the other example of a magnet. It is a front view which shows the other example of a magnet. It is explanatory drawing which shows the arrangement | positioning relationship between the magnet and magnetic detection element in the conventional angle sensor. It is a graph which shows the output characteristic in the conventional angle sensor. It is a graph which shows the deviation | shift amount of the output in the conventional angle sensor. It is explanatory drawing which shows magnetic flux distribution formed with a rectangular parallelepiped magnet. The shape of the magnet improved in the conventional angle sensor is shown, (A) is a front view, (B) is a perspective view. It is explanatory drawing which shows magnetic flux distribution formed with the semicircle-shaped magnet shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Shaft 15, 16, 17 ... Magnet 15a, 15b ... Point tip 20 ... Hall element C ... Neutral detection position P ... Center of gravity position O ... Rotation axis CO ... Straight line which connects neutral detection position and rotation axis

Claims (3)

In the angle sensor that arranges the magnet and the magnetic sensing element to face each other and detects the relative rotation angle of both based on the output of the magnetic sensing element,
The shape of the magnet is a crescent shape in the plane of rotation of the magnet,
The rotational axis of the magnet is arranged substantially on a line passing through the center of gravity of the magnet,
An angle sensor characterized by.   The tip of the crescent-shaped magnet is set to a position rotated ± (130 ° ± 5 °) in the direction away from the neutral detection position with reference to the straight line connecting the neutral detection position of the magnetic sensor and the rotation axis. The angle sensor according to claim 1, wherein the angle sensor is provided.   The angle sensor according to claim 1, wherein the magnetic sensing element is a Hall element or a magnetoresistive element.

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