JP2013002835A - Rotation angle detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detecting device having a magnetoelectric transducer, capable of suppressing angular errors resulting from displacement of a rotation axis or eccentricity of a magnet.SOLUTION: A rotation angle detecting device 400 includes a sensor package 6 having first and second magnetoelectric transducers on a sensor mounting board 7, and a magnet 5 which rotates around a predetermined rotation axis 8. The first and second magnetoelectric transducers of the sensor package 6 are arranged in a sensor chip, for example as shown in Figure 2, so as to detect a magnet field horizontal with the surface of the sensor chip. The rotation axis 8 of the magnet is arranged in the direction vertical to the surface of the sensor chip. The magnet 5 used for the rotation angle detecting device 400 has a magnetization direction in parallel with the surface of the sensor chip. The magnet 5 has a maximum length in the magnetization direction shorter than the maximum length in the direction vertical to the magnetization direction and the rotation axis.

Description

  The present invention relates to a rotation angle detection device, and more particularly to a rotation angle detection device including a magnetoelectric conversion element.

  As a conventional method for detecting a rotation angle, there is a method in which a magnetic field horizontal to the surface of a sensor chip provided with a magnetoelectric conversion element is applied by a magnet and the absolute angle around the rotation axis of the magnet is detected. Examples of the magnetoelectric conversion element include a Hall element, a Hall element using a magnetic converging plate (see Patent Document 1), a vertical Hall element (see Patent Document 2), a magnetoresistive element, and the like.

  As an example using a Hall element, at least two Hall elements are installed in a state in which each magnetosensitive surface faces a different direction with respect to the magnetic field. At this time, the absolute angle can be calculated using sine waves of different phases output from the Hall element.

  The vertical Hall element described in Patent Document 2 is a Hall element that can apply a current perpendicular to the surface of the sensor chip and detect a magnetic field in a uniaxial direction that is horizontal to the surface. This vertical Hall element can be installed in at least two different directions, and the absolute angle can be calculated using sine waves of different phases output from these elements.

  Further, in the configuration in which the Hall element 16 is provided in the vicinity of the magnetic converging plate 14 of the soft magnetic thin film as shown in FIGS. 2A and 2B, FIG. 2C shows a horizontal magnetic field applied in the x direction. Represents the magnetic field lines when The magnetic field in the horizontal direction is converted into a magnetic field perpendicular to the Hall element magnetosensitive surface that can be felt by the Hall element 16 by the magnetic focusing plate 14. When a magnetic field as shown in FIG. 2D is applied, the output differential voltage V (16 (x +) from each Hall element 16 (x +), 16 (x−), 16 (y +), 16 (y−). )), V (16 (x−)), V (16 (y +)), and V (16 (y−)) are a sine wave voltage and a cosine wave voltage according to the following equation (1).

V (16 (x +)) = A × cos θ
V (16 (x −)) = − A × cos θ (1)
V (16 (y +)) = A × sin θ
V (16 (y −)) = − A × sin θ
Here, A is a proportionality constant, and θ is the magnetic field application angle shown in FIG. By taking the difference between these output voltages as shown in the following equation (2), X-side and Y-side signals Vx and Vy are generated.

Vx = V (16 (x +)) − V (16 (x −)) = 2A × cos θ (2)
Vy = V (16 (y +)) − V (16 (y −)) = 2A × sin θ
The absolute angle is calculated using the signals Vx and Vy generated here.

  In addition, an anisotropic magnetoresistive element (AMR), a giant magnetoresistive element (GMR), and a tunnel magnetoresistive element (TMR) that detect a magnetic field horizontal to the surface of the sensor chip. Even when such a magnetoresistive element is used as a magnetoelectric conversion element, it can be rotated by arranging at least two elements having different detection directions and using sinusoidal voltages having different phases as in the Hall element and the vertical Hall element described above. The angle can be calculated.

  In signal processing, two magnetoelectric transducers detect magnetic fields with two axes orthogonal to each other about the rotation axis, and two types of sine wave signals with different phases output from these magnetoelectric transducers have a relationship between sine and cosine. In this case, the absolute angle can be calculated by dividing the following equation (3) and taking the arc tangent.

θ = arctan (sin θ / cos θ) (3)
In Expression (3), θ represents an angle counterclockwise from an arbitrary x axis.

  As described above, a plurality of rotation angle detection devices including a magnetoelectric conversion element are already known, but practically, when assembling the rotation angle detection device, not the ideal configuration state of FIG. An angle error occurs due to a relative shift between the center of the sensor package as shown in FIG. 1B and the rotation axis of the magnet, or due to the eccentricity of the magnet as shown in FIG. The center of the sensor package 1 having the magnetoelectric conversion element, the center 2 of the magnet 4 and the rotation shaft 3 of the magnet 4 may be arranged on a straight line, but the sensor package 1 may be displaced or the rotation shaft 3 may be displaced. Then an error is born.

  The configuration of the rotation angle sensor proposed in Patent Document 3 in the past is resistant to misalignment of the magnetoelectric conversion element, but tends to be expensive, such as using two magnets and sensors.

  In addition, a rotation angle detection method configured as in Patent Document 4 has been proposed. In this method, it is possible to skillfully change the thickness of the magnetic body so that a magnetic field can be uniformly applied to the magnetoelectric conversion element, and it is possible to reduce misalignment errors. However, this configuration requires a complicated magnetic circuit, and it is generally difficult to make the configuration inexpensive and highly versatile.

International Publication No. 2003/081182 JP 2006-32396 A JP 2006-47227 A JP 2005-3590 A

  The configurations of Patent Documents 3 and 4 described above become complicated when it is attempted to suppress the influence of the rotational axis deviation, and it is pointed out that the necessity of calibration and a large rotation angle detection device become necessary, and the cost is secondary. It is expected to be.

  Furthermore, in the conventional methods such as a magnetoresistive element that detects a horizontal magnetic field under a circular magnet, a vertical Hall element, and a Hall element using a magnetic converging plate, a large angular error appears with respect to rotational axis deviation and eccentricity. There's a problem. This configuration causes an angular error when the rotation axis of a radially magnetized cylindrical magnet with a small area on the surface facing the sensor is changed, or when the magnet is eccentric, and its size is small. Absent. For example, in the case of a radially magnetized cylindrical magnet having a diameter of 7 mm and a thickness of 2 mm, when the rotational axis shifts in the x direction, FIG. 3A, and when the center of eccentricity is rotated by -0.2 mm in the x direction, FIG. The angle error is as shown in (b).

  In the future, resource problems such as depletion of rare elements such as rare earth elements will be included, and miniaturization of the magnet in the rotation angle detection device is required.

  The present invention has been made in view of such a problem, and an object of the present invention is a rotation angle detection device including a magnetoelectric conversion element, which suppresses an angle error caused by a rotational axis deviation or a magnet eccentricity. An object of the present invention is to provide a rotation angle detection device capable of performing the above.

  In order to achieve such an object, according to a first aspect of the present invention, there are provided first and second magnetoelectric transducers provided in a sensor chip for detecting a magnetic field horizontal to the surface of the sensor chip, A magnet having a magnetization direction in a direction parallel to the surface of the sensor chip and rotating about a rotation axis in a direction perpendicular to the surface of the sensor chip, the first and second magnetoelectric conversions The rotation angle of the magnet is calculated using sinusoidal signals with different phases output from the element, and the magnet has a maximum length in the magnetization direction in the direction perpendicular to the magnetization direction and the rotation axis. The rotation angle detection device is characterized by being shorter than the maximum length.

  A second aspect of the present invention is the first aspect, wherein the magnet is a dipole cuboid magnet, and has a short side in the magnetization direction, a long side in the magnetization direction and a direction perpendicular to the rotation axis. It is characterized by having.

  According to a third aspect of the present invention, in the second aspect, the length of the long side with respect to the length of the short side is 2 or more and 10 or less.

  According to a fourth aspect of the present invention, in the third aspect, the length of the long side with respect to the length of the short side is 4 or more and 10 or less.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the first and second magnetoelectric transducers detect the magnetic field with two axes perpendicular to the rotation axis. It is arranged to be.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the first and second magnetoelectric transducers are arranged in the vicinity of a magnetic flux concentrating plate made of a soft magnetic material. It is characterized by being a Hall element made.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the sensor chip is a silicon substrate, and the Hall element is integrated with the other arithmetic circuit on the sensor chip. It is characterized by that.

  According to the present invention, a rotation angle detection device including a magnetoelectric conversion element by using a magnet having a maximum length in the magnetization direction shorter than the maximum length in the magnetization direction and the direction perpendicular to the rotation axis, Angular errors due to rotational axis deviation and magnet eccentricity can be suppressed.

It is a figure which shows the ideal structure state at the time of assembling a rotation angle detection apparatus, (a-1) is a top view, (a-2) is a side view. It is a figure which shows the state which produced the rotation-axis shift | offset | difference at the time of assembling a rotation angle detection apparatus, (b-1) is a top view, (b-2) is a side view. It is a figure which shows the state in which the rotating shaft is decentered when assembling a rotation angle detection apparatus, (c-1) is a top view, (c-2) is a side view. It is a figure for demonstrating the rotation angle detection apparatus using the conventional magnetic convergence board and Hall element. It is a figure for demonstrating the rotation angle detection apparatus using the conventional magnetic convergence board and Hall element. It is a figure for demonstrating the rotation angle detection apparatus using the conventional magnetic convergence board and Hall element. It is a figure for demonstrating the rotation angle detection apparatus using the conventional magnetic convergence board and Hall element. It is a figure which shows the angle error by the rotation axis offset in the conventional rotation angle detection apparatus. It is a figure which shows the angle error by eccentricity in the conventional rotation angle detection apparatus. It is a figure which shows the rotation angle detection apparatus which concerns on one Embodiment of this invention from one direction. It is a figure which shows the rotation angle detection apparatus which concerns on one Embodiment of this invention from the direction orthogonal to Fig.4 (a). It is a figure which shows the specific example of the magnet 5 of Fig.4 (a) and 4 (b). It is a figure which shows the result of having evaluated the relationship between aspect ratio a / b and an angle error, changing the kind of magnet. It is a figure for demonstrating the influence which acts on the angle error of eccentricity, (a-1) is a top view, (a-2) is a side view. It is a figure which shows the relationship between eccentricity and an angle error about the conventional cylindrical magnet and the rectangular parallelepiped magnet used by this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
4 (a) and 4 (b) show a rotation angle detection device according to an embodiment of the present invention. The rotation angle detection device 400 includes a sensor package 6 including first and second magnetoelectric conversion elements on the sensor mounting substrate 7 and a magnet 5 that rotates with respect to a predetermined rotation shaft 8.

  The first and second magnetoelectric transducers included in the sensor package 6 are provided in the sensor chip as shown in FIG. 2, for example, and can detect a magnetic field horizontal to the surface of the sensor chip. The rotating shaft 8 of the magnet is arranged in a direction perpendicular to the surface of the sensor chip. As described above, the rotation angle of the magnet 5 is calculated using sine wave signals with different phases output from the first and second magnetoelectric transducers.

  In the rotation angle detection device 400 according to the present embodiment, the magnet 5 has a magnetization direction in a direction parallel to the surface of the sensor chip (direction in the XY plane in FIGS. 4A and 4B). Use. The magnet 5 further has a maximum length in the magnetization direction (X direction in FIG. 4A) greater than the maximum length in the magnetization direction and the direction perpendicular to the rotation axis (Y direction in FIG. 4B). It is short. By using such a magnet 5, it is possible to create a horizontal magnetic field in the same direction with respect to a wide range of the surface of the sensor chip, such as a wide vector, and the rotational axis deviation and the angle of eccentricity of the magnet The influence on the error can be significantly reduced.

  In the present embodiment, the “rotary axis” refers to a straight line that passes through the vicinity of the center of gravity of the magnet 5 and is perpendicular to the surface of the sensor chip. Since it includes not only an accurate geometric center of gravity point but also its vicinity, it is assumed that an angular error due to a rotational axis deviation or the like may occur.

  FIG. 5 shows a specific example of the magnet 5. As shown in FIG. 5, a dipole cuboid magnet having a high aspect ratio (a> b) can be used. Here, the magnetization direction is the X direction, and the maximum length b in the magnetization direction X is shorter than the maximum length a in the magnetization direction X and the direction Y perpendicular to the rotation axis Z. In other words, it is magnetized in the direction of the short side, not the long side. It should be understood that the term “cuboid magnet” is not limited to a complete rectangular parallelepiped, but includes a shape in which the vertex of the rectangular parallelepiped is rounded.

  FIG. 6 shows the result of measuring the relationship between the aspect ratio a / b and the angle error with different types of magnets. All the results are obtained under the condition that the rotational axis deviation of the magnet 5 is 0.5 mm. As the magnetoelectric conversion element in the sensor package 6, an element having a Hall element formed on the lower side of the magnetic flux converging plate shown in FIG. 2 was used.

  Point H is a case of using a dipole cylindrical magnet subjected to conventional radial magnetization, and has a diameter of 5 mm and a thickness of 2 mm. In the notation of FIG. 6, in order to compare with other data, the point of a / b = 1 was set as the x coordinate. Point I was plotted in the same manner as point H with a diameter of 7 mm and point J with a diameter of 10 mm.

  Point K is the aspect ratio (a / b) of the rectangular parallelepiped magnet according to the present invention that gives an angular error substantially equal to that of a radially magnetized dipole cylindrical magnet having a diameter of 10 mm and a thickness of 2 mm used at point J. = 7).

  Point L shows the angle error of the rectangular magnet having the same volume at the aspect ratio a / b = 5 and the radial magnetized dipole cylindrical magnet having a diameter of 5 mm and a thickness of 2 mm used at point H. Point M represents the angular error of the rectangular magnet having the same volume at the aspect ratio a / b = 5 and the radially magnetized dipole cylindrical magnet having a diameter of 7 mm and a thickness of 2 mm used at point I. These show the angle error of the rectangular magnet of the present invention having the same volume at the aspect ratio a / b = 5 and the radially magnetized dipole cylindrical magnet having a diameter of 10 mm and a thickness of 2 mm used at point J.

  Line 9 relates to a rectangular magnet having the same volume at c = 2 and a radial magnetized dipole cylindrical magnet having a diameter of 5 mm and a thickness of 2 mm used at point H, and shows an angular error when the aspect ratio a / b is changed. Represent. The line 10 relates to a rectangular magnet with a diameter of 7 mm and a thickness of 2 mm used at point I and a rectangular parallelepiped magnet having the same volume at c = 2, and shows an angular error when the aspect ratio a / b is changed. Represent. The line 11 relates to a rectangular magnet having a diameter of 10 mm and a thickness of 2 mm used at the point J and a rectangular parallelepiped magnet having the same volume at c = 2, and shows an angle error when the aspect ratio a / b is changed. Represent.

  From FIG. 6, it is possible to reduce the angle error to 1/6 or less by setting the aspect ratio to 10 for a rectangular magnet having a diameter of 5 mm and a thickness of 2 mm and a rectangular parallelepiped magnet having the same volume at c = 2. I understand. Points L, M, and N using parameters with an aspect ratio of a / b = 5 are rectangular parallelepiped magnets having the same volume as the cylindrical magnets used at points H, I, and J, respectively. Compared with cylindrical magnets H, I, and J of the same volume, the angle error is reduced to about 1/3, M is about 1 / 3.3, and N is about 1 / 3.5. .

  In particular, when the aspect ratio a / b is 2 or more, there is an advantageous effect as compared with a conventional cylindrical magnet, and it is more preferably 4 or more. However, in view of the demand for downsizing, it is preferable that the aspect ratio a / b is 10 or less as a practical size.

  Further, according to the present invention, it is possible to realize a rotation angle sensor system with a rectangular parallelepiped magnet having a mass smaller than that of a cylindrical magnet and lower in cost. In the current market, it is generally known that a rectangular parallelepiped magnet is cheaper than a cylindrical magnet and is less wasteful in production. For example, when looking at the point K, by setting the aspect ratio a / b = 7, it is possible to provide the same or better performance with respect to the rotational axis deviation despite the volume being 1/4. In this way, even if the volume of the magnet to be used is reduced, the angle error due to the rotational axis deviation does not increase, so the size of the magnet used can be reduced, and the cost of the rotation angle detection device is secondarily reduced. Become. As the magnet material, a neodymium magnet using an expensive rare earth element or a rare metal, a samarium cobalt magnet, an alnico magnet, or the like is used. Significance is great.

  In addition, according to the present invention, it is possible to easily determine the direction by using a rectangular parallelepiped magnet because it is difficult to distinguish the magnetization direction unless a cylindrical magnet is processed such as D-cut.

  FIG. 7B shows the influence of the eccentricity on the angular error. The line 12 is a cylindrical magnet having a diameter of 7 mm and a thickness of 2 mm, the line 13 is an aspect ratio a / b = 3.5, a = 11.6, It is a rectangular parallelepiped magnet with b = 3.3 and c = 2. The horizontal axis in FIG. 7 is the displacement of the center of gravity of the magnet and the rotation axis in the X-axis direction (see FIG. 7A). As is clear from this figure, magnets having the same volume are used, but the rectangular parallelepiped magnet clearly realized higher resistance against eccentricity.

  In the above description, a Hall element is used as a specific example of the magnetoelectric conversion element. However, it should be noted that this is also effective for a vertical Hall element, AMR, GMR, TMR, and the like.

  Moreover, even if the magnet shape is an ellipsoid or the like, it is sufficient if the maximum length in the magnetization direction is shorter than the maximum length perpendicular to the direction.

  The angle calculation method is the same for a CORDIC (Coordinate Rotational Digital Computer) algorithm used for an electronic computer, an algorithm used for an RD conversion IC that converts a signal from a resolver into a rotation angle, and the like. The sensor chip may be formed of a silicon substrate, and a magnetoelectric conversion element such as a Hall element and another arithmetic circuit for angle calculation may be integrated on the sensor chip.

  This method realized a low-cost, small-sized, and easy-to-install / direction-detection configuration of a non-contact rotation angle sensor using a rotating shaft end type horizontal magnetic field detection. The sensor configuration in this form is very simple and low cost, and can be used for, for example, a rotation switch, a potentiometer, an input device, and the like.

DESCRIPTION OF SYMBOLS 5 Magnet 6 Sensor package 7 Sensor mounting board 8 Rotating shaft 14 Magnetic converging plate 15 Sensor chip 16 Hall element 400 Rotation angle detection apparatus

Claims (7)

First and second magnetoelectric transducers provided on the sensor chip for detecting a magnetic field horizontal to the surface of the sensor chip;
A magnet having a magnetization direction in a direction parallel to the surface of the sensor chip and rotating about a rotation axis in a direction perpendicular to the surface of the sensor chip;
The rotation angle of the magnet is calculated using sinusoidal signals with different phases output from the first and second magnetoelectric transducers,
The rotation angle detection device according to claim 1, wherein the magnet has a maximum length in the magnetization direction shorter than a maximum length in the magnetization direction and a direction perpendicular to the rotation axis.   The rotation angle detection device according to claim 1, wherein the magnet is a dipole cuboid magnet, and has a short side in the magnetization direction and a long side in the magnetization direction and a direction perpendicular to the rotation axis. .   The rotation angle detection device according to claim 2, wherein the length of the long side with respect to the length of the short side is 2 or more and 10 or less.   The rotation angle detection device according to claim 3, wherein the length of the long side with respect to the length of the short side is 4 or more and 10 or less.   5. The rotation according to claim 1, wherein the first and second magnetoelectric transducers are arranged to detect the magnetic field with two axes orthogonal to each other about the rotation axis. Angle detection device.   The rotation according to any one of claims 1 to 5, wherein the first and second magnetoelectric transducers are Hall elements arranged in the vicinity of a magnetic flux concentrating plate made of a soft magnetic material. Angle detection device.   The rotation angle detection device according to claim 1, wherein the sensor chip is a silicon substrate, and the Hall element is integrated with the other arithmetic circuit on the sensor chip.

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