JP4249053B2 - Rotation angle detector - Google Patents

Description

  The present invention relates to a rotation angle detection device that detects a rotation angle of a rotation shaft.

FIG. 8A shows an axial sectional view of the rotation angle detecting device, and FIG. 8B shows a top view. As shown in the figure, the rotation angle detection device 100 includes a magnet 101, a yoke 102, and a Hall IC 103. The magnet 101 is mounted on the rotating shaft 104. The magnet 101 can rotate together with the rotating shaft 104. The yoke 102 is fixed to the inner peripheral surface of the housing (not shown). The yoke 102 and the magnet 101 are arranged coaxially. In the yoke 102, a pair of gaps 102a and 102b are disposed. The Hall IC 103 is disposed in the gap 102a. When the magnet 101 rotates together with the rotating shaft 104, the magnetic flux density in the gaps 102a and 102b changes. The Hall IC 103 outputs a voltage corresponding to the magnetic flux density. The rotation angle of the rotating shaft 104 is detected from this voltage.
Japanese Patent No. 2842482 (column 5, lines 43 to 46)

  By the way, in order to increase the rotation angle detection accuracy, the change of the magnetic flux with respect to the rotation angle of the rotation shaft 104 may be made linear. However, in the case of the conventional rotation angle detection device, the linearity of the magnetic flux change with respect to the rotation angle is not always satisfactory.

  FIG. 9 shows the circumferential magnetic flux distribution on the inner circumferential surface of the yoke. As shown in FIG. 8B, the position of the Hall IC 103 is the θ = 0 ° position with the central axis of the rotation shaft 104 as the center. As shown in the figure, the circumferential magnetic flux distribution on the inner peripheral surface of the yoke 102 has a substantially sine curve shape. In other words, there is no angle section where the magnetic flux amount φ is flat. That is, the magnetic flux change with respect to the rotation angle is not linear.

  Note that Patent Document 1 describes that a change in magnetic flux with respect to a rotation angle can be made linear by making the shape of a magnet an ellipse or the like. However, the document does not specifically explain or illustrate the shape.

  The rotation angle detection device of the present invention has been completed in view of the above problems. Therefore, an object of the present invention is to provide a rotation angle detection device capable of improving the linearity of magnetic flux change with respect to the rotation angle.

(1) In order to solve the above-mentioned problem, a rotation angle detection device according to the present invention is arranged in a ring-shaped magnet connected to a rotation shaft to form a magnetic field, and a magnetic field on the outer peripheral side of the magnet. A ring-shaped yoke having a pair of gaps arranged so as to change a magnetic flux density when a relative angle with respect to the magnet is changed by rotation of the rotary shaft, and one of the pair of gaps And a magnetic angle detector for detecting the magnetic flux density, wherein an inner peripheral surface of the yoke is on a circumference around the rotation axis, and The magnetic flux distribution curve having a constant cross-sectional shape except for the gap, and having a flat angle section in which the magnetic flux amount is substantially constant has at least one section, and the N pole side of the magnetic flux distribution curve. N-pole angle section that is part Section and length, and the section length of the S-pole-side angle section is S-pole side portion of the magnetic flux distribution curve, characterized by different.

  A flat angle section appears in the magnetic flux distribution curve indicating the entire magnetic flux distribution on the inner circumferential surface of the yoke of the rotation angle detection device of the present invention. In addition, the section length of the N pole side angle section (corresponding to section X in FIG. 9) and the section length of the S pole side angle section (corresponding to section Y in FIG. 9) are inconsistent. According to the rotation angle detection device of the present invention, the amount of magnetic flux in the flat angle section is substantially constant. For this reason, the linearity of the magnetic flux change with respect to a rotation angle improves. That is, the rotation angle detection accuracy can be improved.

  (2) Preferably, when a straight line connecting a pair of magnetization boundaries on the outer peripheral surface of the magnet is defined as a magnetization boundary line, when the rotation angle of the magnet is 0 degree, the magnetization of the outer peripheral surface of the magnet The magnetic detector side with respect to the boundary line has a short axis radius a, a long axis radius b, a short axis direction displacement y, and a long axis direction displacement x, with the middle point of the magnetization boundary line as the center. It has a shape that satisfies the following formula,

  Out of the outer peripheral surface of the magnet, the side opposite to the magnetic detector with respect to the magnetization boundary line has an angle with respect to a straight line connecting the midpoint and the magnetization boundary with the center point as the center and a short axis It is better to have a configuration satisfying the following formula, where the radius is a ′, the major axis radius is b, and the radius of curvature is R.

  That is, this structure improves the linearity of the magnetic flux change with respect to a rotation angle by making the outer peripheral surface of the magnet into a shape that matches the above three formulas. According to the rotation angle detection device of the present invention, an angular interval in which the amount of magnetic flux is flat is generated in the circumferential magnetic flux distribution on the inner circumferential surface of the yoke. For this reason, the linearity of the magnetic flux change with respect to a rotation angle can be improved. Therefore, the rotation angle detection accuracy can be improved.

  According to the present invention, the linearity of magnetic flux change with respect to the rotation angle can be improved.

  Hereinafter, an embodiment in which the rotation angle detection device of the present invention is used for detection of an operation amount of an accelerator pedal will be described.

  First, the configuration of the rotation angle detection device of the present embodiment will be described. FIG. 1A shows an axial sectional view of the rotation angle detection device of the present embodiment, and FIG. As shown in the figure, the rotation angle detection device 1 includes a magnet 2, a yoke 3, and a Hall IC 4. The Hall IC 4 is included in the magnetic detector of the present invention.

  The magnet 2 is made of ferrite and has a ring shape. The magnet 2 is fixed to the rotating shaft 5 made of SUS304. The rotating shaft 5 rotates forward / reversely within a predetermined angle range in response to depression of an accelerator pedal (not shown) and return. Therefore, the magnet 2 also rotates forward / reversely with the rotary shaft 5.

  The yoke 3 is formed by arranging a pair of half-ring members 30a and 30b to face each other. A pair of gaps 31 and 32 are disposed between the half ring-shaped members 30a and 30b so as to be separated from each other by 180 °. The yoke 3 is made of SPCC-SD (heat treated) and has a concentric ring shape as a whole. The yoke 3 is fixed to the inner peripheral surface of the housing (not shown). The yoke 3 is disposed on the outer peripheral side of the magnet 2. The yoke 3 is disposed in the magnetic field of the magnet 2. A magnetic circuit is formed between the yoke 3 and the magnet 2.

  The Hall IC 4 is disposed only in the gap 31 of the pair of gaps 31 and 32. The Hall IC 4 includes a Hall element and an operational amplifier (not shown). The magnetic flux density is magnetoelectrically converted into a voltage by the Hall IC 4.

  Next, the movement of the rotation angle detection device of this embodiment will be described. When the rotation shaft 5 is rotated by the accelerator pedal operation, the magnet 2 fixed to the rotation shaft 5 is also rotated. For this reason, the magnetic flux density in the gaps 31 and 32 changes. The magnetic flux density is converted into a voltage by the Hall element of the Hall IC 4. The converted voltage is amplified by an operational amplifier. Based on the amplified voltage, the rotation angle of the rotating shaft 5, that is, the depression amount of the accelerator pedal is detected.

Next, the dimensions of the rotation angle detection device of this embodiment will be described. The diameter D1 of the rotary shaft 5 is 4 mm, the thickness L1 of the magnet 2 is 6 mm, the inner diameter D3 of the yoke 3 is 15 mm, the outer diameter D4 of the yoke 3 is 18 mm, the thickness L2 of the yoke 3 is 5 mm, and the gaps 31 and 32 are spaced. G was set to 1.5 mm. The interval A between the central axis A _S of the rotating shaft 5 and the magnetization boundary line BL connecting the magnetization boundaries α and α ′ between the N pole and the S pole was set to 1.0 mm.

  In FIG. 2, the top view of the magnet of the rotation angle detection apparatus of this invention is shown. The straight line l is a midpoint O of the magnetization boundaries α and α ′ and is orthogonal to the magnetization boundary line BL. The distance a between the midpoint O on the straight line l and the N pole outer peripheral surface was set to 5 mm. Further, the distance a ′ between the midpoint O on the straight line l and the S pole outer peripheral surface was set to 5.8 mm. Further, the interval b between the midpoint O on the magnetization boundary line BL and the magnetization boundary α or the magnetization boundary α ′ was set to 6.8 mm.

Here, the interval a corresponds to the minor axis radius of [Equation 1] of claim 2 . The interval a ′ corresponds to the minor axis radius of [Equation 2] and [Equation 3] of claim 2 . The interval b corresponds to the long axis radius of the Equation 1 according to claim 2 [Formula 2] [Formula 3].

  On the Hall IC 4 side (upward in FIG. 2) from the magnetization boundary line BL, the displacement in the direction toward the magnetization boundary α ′ in the magnetization boundary line BL is x, and the displacement in the direction toward the N pole on the straight line 1 is y. The shape satisfying the following formula was set.

  Further, on the side opposite to the Hall IC 4 side from the magnetization boundary line BL (lower side in FIG. 2), the radius of curvature is R, and the magnetization boundary α is θb = 0 deg with respect to the midpoint O, counterclockwise on the page. The shape satisfying the following formula was set.

Next, the magnetic flux distribution in the circumferential direction on the inner circumferential surface of the yoke of the rotation angle detection device of the present embodiment will be described. FIG. 3 shows a magnetic flux distribution in the circumferential direction on the inner circumferential surface of the yoke of the rotation angle detection device of the present embodiment. As shown in FIG. 1B, the position of the Hall IC 4 is the θ = 0 ° position with the central axis A _Y of the yoke 3 as the center. As shown in the figure, the magnetic flux distribution curve has a rectangular wave shape. In other words, the magnetic flux distribution curve has flat angle sections F _X and F _{Y in} which the magnetic flux amount φ is flat. Among these, the flat angle section F _X is arranged in the N pole side angle section X that occupies the N pole portion of the magnetic flux distribution curve. Further, the flat angle section F _Y is arranged in the S pole side angle section Y that occupies the S pole portion of the magnetic flux distribution curve. In the flat angle sections F _X and F _Y , the magnetic flux change with respect to the rotation angle is linear.

  In the case of FIG. 9, the ratio between the section length of the N pole side angle section X and the section length of the S pole side angle section Y was 1: 1. On the other hand, in the case of FIG. 3, when comparing the section length of the N pole side angle section X and the section length of the S pole side angle section Y, the S pole side angle section Y is longer. That is, in the magnetic flux distribution curve, the ratio of the S pole is larger than the ratio of the N pole.

  Next, the hysteresis in the Hall IC of the rotation angle detection device of the present embodiment will be described in comparison with the hysteresis in the Hall IC of the conventional rotation angle detection device. FIG. 4 shows changes in the magnetic flux density inside the yoke when the rotating shaft, that is, the magnet is reciprocally rotated within a range of ± 50 deg. FIG. 5 shows changes in magnetic flux density at each angular position of the yoke in this case.

  As a comparison object, FIG. 6 shows a change in magnetic flux density inside the yoke when the rotary shaft, that is, the magnet is reciprocally rotated within a range of ± 50 deg in the conventional rotation angle detection device shown in FIG. FIG. 7 shows changes in magnetic flux density at each angular position of the yoke in this case.

  For convenience of explanation, the angle of the magnet is represented as “deg”, and the angle of the yoke is represented as “°”. In FIG. 4 (FIG. 6), the horizontal axis magnet rotation angle indicates an angle when the magnet 2 (101) is reciprocally rotated with the Hall IC 4 (103) position set to 0 deg. In FIG. 1B (FIG. 8B), the counterclockwise direction is the plus direction and the clockwise direction is the minus direction. In FIG. 4 (FIG. 6), the solid line data indicates data when the magnet 2 (101) is rotated in the plus direction. The dotted line data indicates data when the magnet 2 (101) is rotated in the minus direction. As shown in FIG. 1B (FIG. 8B), the data is obtained by setting the position of the Hall IC 4 (103) to 0 °, and the yoke 3 (102) in the circumferential direction every 45 ° (that is, θ = 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, 315 °). In FIG. 4 (FIG. 6), regarding the direction of the magnetic flux density on the vertical axis, the clockwise direction is the positive direction and the counterclockwise direction is the negative direction on the paper surface of FIG. 1 (b) (FIG. 8 (b)). .

  First, the conventional rotation angle detection device shown in FIG. 8 will be described. As an example, the magnetic flux density change at the position of θ = 0 ° in the yoke 102 will be described. When the magnet 101 is rotated from 0 deg to +50 deg, the magnetic flux density (solid line data) at the position of θ = 0 ° of the yoke 102 gradually increases as indicated by the white arrow in FIG. The magnetic flux density is maximum at +50 deg.

  Subsequently, when the magnet 101 is restored and rotated from +50 deg to 0 deg, the magnetic flux density (dotted line data) at the position of θ = 0 ° of the yoke 102 gradually decreases as indicated by the white arrow in FIG. The magnetic flux density is minimum at 0 deg.

  However, even if the magnet 101 is restored and rotated, the magnetic flux density is not restored to the original state. That is, the magnetic flux density is increased by the arrow Y0. Similarly, at the position θ = 45 °, the magnetic flux density is increased by the arrow Y45. In addition, the magnetic flux density is increased by the amount of the arrow Y315 at the position θ = 315 °. On the other hand, at the positions θ = 135 °, 180 °, and 225 °, the magnetic flux densities are respectively reduced by the arrows Y135, Y180, and Y225. Note that the magnetic flux density does not change at the positions of θ = 90 ° and 270 °.

  As shown in FIG. 7, arrows Y45, Y0, and Y315 are pointing in the plus direction, and Y135, Y180, and Y225 are pointing in the minus direction. Changes in the magnetic flux density at each angular position of these yokes 102 affect each other magnetically. As a result, the magnetic flux density at the 0 ° position where the Hall IC 103 is disposed is in the positive direction. That is, the magnetic flux density at the 0 ° position increases when the magnet 101 is rotated forward / reversely from 0 deg → + 50 deg → 0 deg again. This means that even when the magnet 101 is at the same 0 deg position, the output of the Hall IC 103 during reverse rotation is larger than the output of the Hall IC 103 during forward rotation. That is, it means that hysteresis is generated in the output of the Hall IC 103.

  Secondly, the rotation angle detection device of this embodiment will be described. As shown in FIG. 4, at the positions θ = 0 °, 45 °, and 315 °, the magnetic flux density is increased by the amounts of arrows y0, y45, and y315, respectively. On the other hand, at θ = 90 °, 135 °, 180 °, 225 °, and 270 °, the magnetic flux density is decreased by the amounts of arrows y90, y135, y180, y225, and y270, respectively.

  In the case of FIG. 6, the magnetic flux density did not change at the positions of θ = 90 ° and 270 °. On the other hand, in the case of FIG. 4, as described above, the magnetic flux density is reduced by y90 at the position θ = 90 °. In addition, the magnetic flux density is reduced by y270 at the position θ = 270 °.

  As shown in FIG. 5, arrows y45, y0, and y315 are directed in the positive direction, and y90, y135, y180, y225, and y270 are directed in the negative direction. Changes in the magnetic flux density at each angular position of these yokes 3 affect each other magnetically. As a result, the magnetic flux density at the 0 ° position where the Hall IC 4 is arranged is in the plus direction as in FIG.

  However, in FIG. 5, y90 and y270 that are directed in the negative direction are generated. Further, assuming that the magnetic flux density change before and after rotation at an arbitrary angular position θ in FIG. 5 is Bhybθ and the magnetic flux density change before and after rotation at an arbitrary angular position θ in FIG. 7 is Bhycθ, ΣBhybθ <ΣBhycθ. That is, the amount of hysteresis of the magnetic flux density changes in the negative direction.

  For this reason, the magnetic flux density in the minus direction of the gap 32 becomes larger than that in the case of FIG. On the other hand, the magnetic flux density in the positive direction of the gap 31 in which the Hall IC 4 is disposed becomes smaller by y90 and y270 that are directed in the negative direction.

Next, the function and effect of the rotation angle detection device of this embodiment will be described. 5 and 7 show the magnetic flux density distribution of the yoke by hatching. Note that the smaller the hatch pitch, the higher the magnetic flux density. In the case of the conventional rotation angle detection device, as shown in FIG. 7, when the magnet 101 is in the 0 deg position, the Hall IC 103 position is 0 °, and the magnetic flux density distribution is a straight line L connecting the 270 ° position and the 90 ° position. Is symmetric. In other words, the arrangement of the maximum density portion B _max in the magnetic flux density distribution is symmetric with respect to the straight line L.

On the other hand, the magnet 2 of the rotation angle detection device 1 of the present embodiment has a characteristic shape as shown in [Expression 4], [Expression 5], and [Expression 6]. For this reason, when the rotation angle of the magnet 2 is 0 deg, the maximum density portion B _max of the magnetic flux density is unevenly distributed on the region side exceeding 270 ° and less than 90 ° with the position of the Hall IC 4 being 0 °. Due to this uneven distribution, negative magnetic flux densities y90 and y270 are generated at the θ = 90 ° position and the 270 ° position. For this reason, the positive direction magnetic flux density generated in the gap 31 can be offset. Therefore, according to the rotation angle detection device 1 of the present embodiment, hysteresis generated in the Hall IC 4 can be suppressed.

  Further, the yoke 3 of the rotation angle detection device 1 of the present embodiment is made of SPCC-SD (heat treated). For this reason, compared with the case where expensive permalloy etc. are used in order to suppress a hysteresis, manufacturing cost can be reduced.

  In addition, according to the rotation angle detection device 1 of the present embodiment, as shown in FIG. 3, the circumferential magnetic flux distribution on the inner peripheral surface of the yoke 3 has a rectangular wave shape. In other words, there is an angle section where the magnetic flux amount φ is flat. That is, there exists an angle section in which the magnetic flux change is linear with respect to the rotation angle. Therefore, the rotation angle detection accuracy with respect to the rotation shaft 5 is high.

<Others>
The embodiment of the rotation angle detection device of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  For example, in the above embodiment, the magnet 2 is made of ferrite, but may be made of another hard magnetic material. In the above embodiment, the yoke 3 is made of SPCC-SD (heat treated), but may be made of other soft magnetic material. The magnet 2 may be used in combination with an auxiliary yoke made of a soft magnetic material.

  In the above embodiment, the Hall IC is used as the magnetic detector. However, for example, a magnetic detector having a magnetoresistive element whose resistance value changes according to the strength of the magnetic field may be used.

(A) is an axial sectional view of a rotation angle detection device according to an embodiment of the rotation angle detection device of the present invention, and (b) is a top view of the rotation angle detection device. It is a top view of the magnet of the rotation angle detection apparatus. It is a graph which shows the circumferential direction magnetic flux distribution in the yoke internal peripheral surface of the rotation angle detection apparatus. It is a graph which shows the change of the magnetic flux density in the yoke when a magnet is reciprocatingly rotated in the range of ± 50 deg in the same rotation angle detection device. It is a schematic diagram which shows the change of the magnetic flux density in each angular position of the yoke of the same rotation angle detection apparatus. It is a graph which shows the change of the magnetic flux density in the yoke at the time of rotating a magnet reciprocatingly in the range of +/- 50deg in the conventional rotation angle detection apparatus. It is a schematic diagram which shows the change of the magnetic flux density in each angular position of the yoke of the same rotation angle detection apparatus. (A) is an axial sectional view of a conventional rotation angle detection device, and (b) is a top view of the rotation angle detection device. It is a graph which shows the circumferential direction magnetic flux distribution in the yoke internal peripheral surface of the rotation angle detection apparatus.

Explanation of symbols

1: rotation angle detector, 2: magnet, 3: yoke, 30a: semi-ring member, 30b: semi-ring member, 31: gap, 32: gap, 4: Hall IC (magnetic detector), 5: rotation Axis, X: N pole side angle section, Y: S pole side angle section, F _X : flat angle section, F _Y : flat angle section.

Claims (2)

A ring-shaped magnet connected to the rotating shaft to form a magnetic field;
A pair arranged in a magnetic field on the outer peripheral side of the magnet, forming a magnetic circuit with the magnet, and arranged so that the magnetic flux density changes when the relative angle to the magnet changes due to the rotation of the rotating shaft. A ring-shaped yoke with a gap of
A magnetic detector disposed in one of the pair of gaps for detecting the magnetic flux density;
A rotation angle detection device comprising:
The inner peripheral surface of the yoke is on a circumference around the rotation axis, and has a constant cross-sectional shape excluding the gap,
The magnetic flux distribution curve over the entire circumference of the yoke inner peripheral surface has at least one flat angle section in which the amount of magnetic flux is substantially constant, and the section length of the N pole side angle section that is the N pole side portion of the magnetic flux distribution curve. And the section length of the S pole side angle section, which is the S pole side portion of the magnetic flux distribution curve, are different from each other. Assuming that a straight line connecting a pair of magnetization boundaries on the outer peripheral surface of the magnet is a magnetization boundary line, when the rotation angle of the magnet is 0 degree, the magnetism is greater than the magnetization boundary line on the outer peripheral surface of the magnet. The detector side has a shape satisfying the following equation, with the short axis radius a, the long axis radius b, the short axis direction displacement y, and the long axis direction displacement x with the center point of the magnetization boundary line as the center. Presents

Out of the outer peripheral surface of the magnet, the side opposite to the magnetic detector with respect to the magnetization boundary line has an angle with respect to a straight line connecting the midpoint and the magnetization boundary with the center point as the center and a short axis The rotation angle detection device according to claim 1, wherein the rotation angle detection device has a shape satisfying the following expression, where a ′ is a radius, b is a major axis radius, and R is a curvature radius.

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