JP2006105757A - Magnetic detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic detection device having high angle detection accuracy, by providing a pseudo-sine wave waveform having a large output change by eliminating distortion of the waveform. <P>SOLUTION: This magnetic detection device is composed of a detecting object rotary body 4 having recess-projection parts 4a and 4b on a side surface; a magnetic detection part 1 oppositely arranged on the side surface of this detecting object rotary body 4; and a bias magnet 2 for applying a magnetic field to this magnetic detection part 1, and is formed by positioning the one side end of this bias magnet 2 on one side more than the axis in the radial direction of the detecting object rotary body 4, to be arranged at an interval from the magnetic detection part 1; and can output a pseudo-sine wave by eliminating distortion of the waveform by controlling a magnetic field vector of a magnetic detection element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic detection device that detects a rotation speed, a rotation angle, or torque by detecting a change in a magnetic field.

  FIGS. 8A and 8B are a top view and a front view showing a schematic configuration of a conventional magnetic detection device.

  In FIG. 8, the magnetic detection element 102 and the bias magnet 101 are disposed so as to oppose the concave and convex portions 108 a and 108 b of the detected rotating body 108 made of a magnetic material. The magnetic detection element 102 is provided between the bias magnet 101 and the detected rotating body 108 and is disposed without providing a gap with the bias magnet 101.

  As the detected rotating body 108 rotates, the convex portions 108 a and the concave portions 108 b of the detected rotating body 108 alternately face the bias magnet 101. As a result, the magnetic field applied to the magnetic detection element 102 increases or decreases as the detected rotating body 108 rotates. That is, the magnetic field applied to the magnetic detection elements 102a and 102b increases as the convex portion 108a approaches, and decreases as the convex portion 108a moves away.

  Due to the change in the magnetic flux on the magnetic sensing surfaces of the magnetic detection elements 102a and 102b, the resistance values of the magnetic detection elements 102a and 102b change according to the magnitude of the applied magnetic field. The analog signals output from the magnetic detection elements 102a and 102b are waveform-shaped by a signal processing circuit, and rectangular wave signals corresponding to the convex portions 108a and the concave portions 108b of the detected rotating body 108 are output.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP-A-9-311135

  However, the magnetic sensing element used in the conventional configuration is a ferromagnetic magnetoresistive element (MR element) or a giant magnetoresistive element (GMR element), and the positional relationship among the detected rotating body, the magnetoresistive element, and the magnet. Because the magnetic field change is large in this case, it is necessary to use the non-linear region of the magnetic field-resistance characteristic curve, or by crossing the zero point, the distortion of the waveform becomes large and it does not become a pseudo sine wave. When the gap between the detected rotating body and the magnetoresistive element is changed, there is a problem that the waveform does not change in a similar shape.

  The present invention solves the above-described conventional problems, and the bias magnet disposed opposite to the side surface of the detected rotating body has one end positioned on one side of the radial center axis of the detected rotating body. In addition, by arranging the magnetic detection unit so as to be spaced from the magnetic detection unit, it becomes easy to control the direction and the magnitude of the magnetic flux applied to the magnetic detection element, and the pseudo sine wave is obtained by eliminating waveform distortion. The object of the present invention is to provide a magnetic detection device with high angle detection accuracy by changing the waveform to a similar shape even when the gap is changed.

  In order to achieve the above object, the magnetic detection device of the present invention has the following configuration.

  According to a first aspect of the present invention, a detected rotating body having a concavo-convex portion on a side surface, a magnetic detection unit provided facing the side surface of the detected rotating body, and a magnetic field is applied to the magnetic detection unit The bias magnet is configured to be arranged so that one end of the bias magnet is located on one side with respect to the central axis in the radial direction of the rotation body to be detected and is spaced from the magnetic detection unit. As a result, the change in the magnetic field in the axial direction of the magnetic detection element changes in a substantially linear region (A region) on only one side of the magnetic field-resistance characteristic shown in FIG.

  The invention according to claim 2 of the present invention is configured such that each magnetic detection element is provided on an insulating substrate so that the magnetic detection unit is symmetric with respect to the central axis in the radial direction of the detected rotating body. By arranging the magnetic detection elements so as to be symmetric with respect to the central axis in the radial direction of the detection rotating body, it is possible to obtain the effect that the midpoint potential differences of the output waveforms output from the respective magnetic detection elements can be made uniform. .

  According to the third aspect of the present invention, two sets of magnetic detection elements are provided to form a full bridge circuit on the upper surface of the insulating substrate. The change in magnetoresistance of one magnetic detection element and the other magnetic detection Since the difference from the change in magnetoresistance of the element can be taken out as a signal output, the output amplitude can be increased compared to a circuit configuration using only one set, and the effect of improving detection accuracy can be obtained. . In addition, since the resistance temperature coefficients of the two sets of magnetic detection elements are substantially equal, the effect of improving the stability of the element output with respect to the temperature can be obtained.

  The invention according to claim 4 of the present invention has a configuration in which the magnetic detection element is a magnetoresistive element or a giant magnetoresistive element, and only the vector component of the magnetic field applied to the magnetosensitive surface is taken out as a change in resistance value. Therefore, the effect of being able to detect with high accuracy is obtained.

  The invention according to claim 5 of the present invention is such that the insulating substrate has an alumina substrate and a glass glaze layer provided on the upper surface thereof, and is strong in mechanical strength and smoothes the substrate surface by the glass glaze layer. Therefore, a magnetic sensing element having a good film quality is formed, and an effect of obtaining a magnetic sensing element having high magnetic sensitivity and improved reliability can be obtained.

  According to the sixth aspect of the present invention, a metal plate made of a magnetic material is interposed between the magnetic detection element and the bias magnet, and the magnitude of the magnetic field of the bias magnet applied to the magnetic detection element. The effect that the sheath direction can be controlled is obtained.

  As described above, according to the present invention, the detected rotating body having the concavo-convex portion on the side surface, the magnetic detection unit provided facing the side surface of the detected rotating body, and the bias magnet that applies a magnetic field to the magnetic detection unit The bias magnet is arranged such that one end thereof is located on one side of the center axis in the radial direction of the detected rotating body and is spaced from the magnetic detection unit. When the distortion is eliminated and a pseudo sine wave is used and the gap is changed, the waveform changes to a similar shape, thereby realizing a magnetic detection device with high angle detection accuracy.

  Hereinafter, a magnetic detection device according to an embodiment of the present invention will be described with reference to the drawings.

  1A and 1B are a top view and a front view showing the positional relationship between the configuration of the magnetic detection device and the detected rotating body in the embodiment of the present invention, and FIG. 2 is a configuration diagram illustrating the magnetic detection unit. 3 is a diagram showing the connection of the magnetic detection element, FIG. 4 is a sectional view of the magnetic detection unit, FIG. 5 is a characteristic diagram showing a change in resistance value with respect to the magnetic field of the magnetic detection element, and FIG. FIG. 7 is a Lissajous figure of the output analog signal, showing the output waveform at the midpoint potential of the bridge circuit of the corresponding magnetic detection element.

  In FIG. 1, the magnetic detection device 6 is disposed so as to face the side surface having the concavo-convex portions 4a and 4b of the detected rotating body 4 through a predetermined gap (gap). The magnetic detection device 6 includes a magnetic detection unit 1, a bias magnet 2, a metal plate 5, and a magnetic circuit (not shown). The magnetic sensing surfaces of the magnetic sensing elements 1 a, 1 b, 1 c, and 1 d, which are composed of the magnetoresistive element and the giant magnetoresistive element shown in FIG. The magnetic detection element 1a and the magnetic detection element 1b form one bridge, and the magnetic detection element 1c and the magnetic detection element 1d form another bridge. Further, the magnetic detection element 1a and the magnetic detection element 1c are arranged so as to have a phase of 90 degrees. The bias magnet 2 is a magnet that generates a strong magnetic field, such as a rare earth magnet or a neodymium bond magnet. The bias magnet 2 is spaced from the magnetic detection unit 1 so that the magnetization direction is the radial direction of the detected rotating body 4. The one end is arranged so as to be on one side with respect to the central axis in the radial direction of the detected rotating body, and a bias magnetic field is applied to the magnetic detection unit 1.

  The case where a giant magnetoresistive element (hereinafter referred to as a GMR element) is used for the magnetic detection elements 1a, 1b, 1c, and 1d will be described for the magnetic detection unit 1. In FIG. 2, the magnetic detection unit 1 includes four line-shaped GMR elements 1 a, 1 b, 1 c, and 1 d formed on an insulating substrate 20 in order to improve magnetic detection sensitivity. The GMR elements 1a, 1b, 1c, and 1d are arranged perpendicular to the rotation direction of the detected rotating body 4. FIG. 3 is a circuit connection diagram of the GMR elements 1a, 1b, 1c, and 1d constituting the magnetic detection unit 1. The GMR elements 1a, 1b, 1c, and 1d are connected in series between the power supply Vcc and the ground GND to constitute a full bridge circuit 11. From the midpoints 12 a and 12 b of the full bridge circuit 11, analog signals accompanying the rotation of the concave and convex portions 4 a and 4 b of the detected rotating body 4 are output.

  FIG. 4 shows a cross-sectional view of the magnetic detection unit 1. The GMR elements 1a, 1b, 1c, and 1d are formed on an insulating substrate 20, and an alumina substrate 21 is usually used as the substrate. However, by providing a glass glaze layer 22 on the alumina substrate 21, further mechanical properties are obtained. Strength can be increased. Further, since the surface of the insulating substrate 20 can be smoothed by the glass glaze layer 22, the GMR elements 1a, 1b, 1c, and 1d having good film quality are easily formed, and the magnetic detection unit 1 having high magnetic sensitivity and improved reliability is manufactured. be able to. The GMR elements 1a, 1b, 1c, and 1d have magnetic field-resistance characteristics as shown in FIG. The resistance values of the GMR elements 1a, 1b, 1c, and 1d have characteristics that the resistance value changes greatly when the applied magnetic field fluctuates. If the magnetic sensitivity of the MR element, which is a normal magnetic detection element, is about 4%, the GMR element has a magnetic sensitivity of about 20%.

  The metal plate 5 is provided to control the magnetic field applied to the magnetic detection unit 1, and the bias in the rotation direction of the detected rotating body 4 of the metal plate 5 is made larger than the width of the bias magnet 2. The magnetic flux 42 generated on the opposite side of the magnet 2 from the central axis of the detected rotating body 4 constitutes the magnetic field closed loop 41, thereby suppressing the application of the magnetic flux 42 to the gear and applying only the magnetic flux 43 to the magnetic detection unit 1. . Thereby, the magnetic field 43 applied to the magnetic detection unit 1 can be freely controlled by the size of the metal plate 5.

  Next, the operation of the magnetic detection device 6 will be described.

  As shown in FIG. 1, the convex portions 4 a and the concave portions 4 b of the detected rotating body 4 alternately face the magnetic detecting unit 1 as the detected rotating body 4 rotates. At this time, the magnetic field applied to the magnetic detection unit 1 is only the magnetic flux 43 because the magnetic flux 42 forms a magnetic field closed loop 41 with the bias magnet 2 due to the influence of the metal plate 5. The magnetic flux 43 is changed by the convex portion 4a and the concave portion 4b of the detected rotating body 4. At this time, the magnetic field change 44 of the magnetic flux 43 changes in the area A of the magnetic field-resistance characteristic, that is, the substantially linear area, as shown in FIG. An output waveform 45 can be obtained. In this way, the output waveform of the analog signal as shown in FIG. 6 is output from the midpoint potentials 12a and 12b of the full bridge circuit 11 shown in FIG.

  The Lissajous figures of the analog signals 12a and 12b are as shown in FIG. 7A, and there is no distortion in the waveform even when compared with the Lissajous figure of FIG. It is clear.

  The magnetic detection device of the present invention can increase the angle detection accuracy by eliminating the waveform distortion and outputting a pseudo sine wave, and is useful as a magnetic detection device for detecting the rotation speed and the rotation angle.

(A) Top view showing the positional relationship between the configuration of the magnetic detection device and the detected rotating body in the embodiment of the present invention, (b) Front view showing the positional relationship between the configuration of the magnetic detection device and the detected rotating body. Figure Configuration diagram explaining the magnetic detector Circuit diagram showing connection of magnetic detection element Cross section of magnetic detector Characteristic diagram showing change in resistance value against magnetic field of magnetic sensing element The figure which shows the output waveform of the shape of the rotation object to be detected and the corresponding midpoint potential Diagram showing Lissajous figure of output analog signal Configuration diagram for explaining a conventional magnetic detection device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic detection part 1a, 1b, 1c, 1d Magnetic detection element (SMR element)
2 Bias magnet 4 Rotating body to be detected 4a Convex 4b Concave 5 Metal plate 6 Magnetic detector 11 Full bridge circuit 12a, 12b Midpoint potential 20 Insulating substrate 21 Alumina substrate 22 Glass glaze layer 41 Magnetic field closed loop 42, 43 Magnetic flux 44 Magnetic flux 43 Magnetic field change of 45 Output waveform

Claims (6)

A rotating body to be detected having a concavo-convex portion on a side surface, a magnetic detecting unit provided opposite to the side surface of the rotating body to be detected, and a bias magnet for applying a magnetic field to the magnetic detecting unit. Is a magnetic detection device configured to be positioned on one side of the center axis in the radial direction of the detected rotating body and to be spaced from the magnetic detection unit. The magnetic detection device according to claim 1, wherein each magnetic detection element is provided on an insulating substrate so that the magnetic detection unit is symmetric with respect to a central axis in a radial direction of the detected rotating body. The magnetic detection device according to claim 2, wherein the magnetic detection unit has a full bridge circuit configuration of two sets of magnetic detection elements. The magnetic detection device according to claim 1, wherein the magnetic detection element is a magnetoresistive element or a giant magnetoresistive element. The magnetic detection device according to claim 1, wherein the insulating substrate is configured by providing a glass glaze layer on an alumina substrate. The magnetic detection device according to claim 1, wherein a metal plate made of a magnetic material is interposed between the magnetic detection element and the bias magnet.

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