JP2007093532A - Magnetic sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic sensor device that detects polarization of a magnetic pole by using a detection signal from a Hall element, to detect a rotation position device. <P>SOLUTION: With rotation of a rotary table, where at least a pair of magnetic poles facing each other, the magnetic sensor device detects magnetic fields from respective poles by magnetoresistive elements provided, at places facing to the center of the rotary table to determine rotation positions. In the device, two Hall elements are provided at a crosses axes angle of 90° of the magnetoresistive elements. Based on the output signals from the Hall elements, a region of respective rotation angles of 180° in a sine waveform at an electrical angle 720°, that is outputted from the magnetoresistive elements per rotation of the rotary table can be specified. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic sensor device such as a magnetic rotary encoder or a magnetic linear scale that detects a position (angle) by detecting a magnetic field from a magnetic pole by a magnetoresistive element.

  For example, the magnetism for detecting the rotation position (including the rotation amount or rotation angle, and hereinafter simply referred to as the rotation position) of a rotating disk in which magnetic poles having different N and S poles are magnetized at 0 ° and 180 ° positions. In a magnetic rotary encoder as a sensor device, a sine wave waveform (cosine wave waveform) output by detecting a magnetic pole of a rotating disk by a magnetic sensor such as a Hall element or a magnetoresistive element (hereinafter referred to as an MR element). ) Is divided based on the desired detection resolution to detect the rotational position of the turntable.

  In the magnetic rotary encoder described above, when the magnetic sensor is a Hall element, the detection signal from the Hall element outputs a signal corresponding to the magnetism of the magnetic pole, but the magnetic field detection sensitivity is poor, and therefore the output voltage is low, If this is divided according to the desired detection resolution, there is a problem that the rotational position detection accuracy deteriorates.

  On the other hand, when an MR element is used as a magnetic sensor, an output signal with a high voltage ratio can be obtained by a large change in the magnetic resistance corresponding to the change in the magnetic field strength, thereby enabling position detection with high accuracy. However, since the output signal is the same regardless of whether the magnetic field is positive or negative, there is a problem that it is impossible to determine which magnetic pole corresponds to the signal and position detection cannot be performed accurately.

  That is, in a magnetic sensor using MR elements, in order to obtain a high rate of change in magnetoresistance, four MR elements obtained by processing metal magnetic materials into stripes are arranged so that the stripes cross each other at 90 °. An MR sensor chip is used by being arranged and bridge-connected, and a detection signal having a sine wave waveform with an electrical angle of 720 ° (4π) is output per rotation of the rotating disk. However, since the MR element itself outputs the same signal regardless of the polarity of the magnetic pole, as described above, the above-described sinusoidal waveform signal with an electrical angle of 720 ° has a relative rotation angle of 180 °. It was not possible to determine which magnetic pole was located, and the rotational position could not be detected accurately.

The disadvantage of using the MR element described above is that a bias permanent magnet is provided on the MR element and magnetically biased so that the sensitivity width is halved, and output from the MR element per rotation of the rotating disk. There is a method in which the sine wave output is corrected so that the electrical angle is 360 °, and it is possible to determine which magnetic pole corresponds to the 180 ° portion. However, it is extremely difficult to magnetically bias the MR element so that the sensitivity width is halved. Also, since the sensitivity width is halved, an output signal with a high voltage ratio cannot be obtained. As in the case of using the element, the rotational position could not be detected with high accuracy.
JP-A

The problem to be solved is that the MR element outputs a detection signal regardless of the polarity of the magnetic pole, so it cannot be determined which 180 ° region of the detection signal is located, and the rotation amount detection accuracy is poor. In the point.

According to the first aspect of the present invention, a magnetic field from each magnetic pole is detected by a magnetoresistive element provided at a position facing the center of the rotating disk as the rotating disk provided with at least a pair of opposing magnetic poles rotates. In the magnetic sensor device for detecting the rotational position, two Hall elements are arranged with a crossing angle of 90 ° with respect to the magnetoresistive element, and the electric power output from the magnetoresistive element per rotation of the rotating disk. It is characterized in that each rotation angle 180 ° region in a sine wave waveform signal having an angle of 720 ° can be specified based on an output signal from the Hall element.

According to a sixth aspect of the present invention, a magnetic field from each magnetic pole is provided by a magnetoresistive element provided on a movable body that reciprocates relative to a magnetic scale in which different magnetic poles having a width corresponding to a desired detection resolution are alternately provided in the longitudinal direction. In the magnetic sensor device that detects the moving position of the movable body by detecting the magnetoresistive element, the magnetoresistive element outputs at least a sinusoidal waveform signal by a magnetic field from different magnetic poles, and two Hall elements in the vicinity of the magnetoresistive element, A magnetic angle is provided so as to be detected every 180 °.

  According to the present invention, the MR element capable of detecting the magnetic field from the magnetic pole with high sensitivity can detect the point where the polarity of the magnetic pole cannot be detected by the detection signal from the Hall element, and can detect the rotational position with high accuracy.

In the present invention, two Hall elements are arranged with a 90 ° crossing angle with respect to the magnetoresistive element, and a sine wave signal of 720 ° in electrical angle output from the magnetoresistive element per rotation of the rotating disk. The best mode is that each rotation angle region of 180 ° can be specified based on the output signal from the Hall element.

The present invention will be described below with reference to the drawings showing embodiments.
1 and 2 (A) and 2 (B), the magnetic sensor device 1 includes a rotating disk 3 fixed to a rotating shaft 2 of an electric motor such as a servo motor, and a central portion of one surface of the rotating disk 3. The sensor chip 5 is fixed. On one surface of the rotating disk 3, an N-pole first magnetic pole 7a, for example, is magnetized at the 0 ° position, and an S-pole second magnetic pole 7b is magnetized at the 180 ° position.

  The sensor chip 5 is formed by, for example, four MR elements 5a to 5d in which magnetic metal materials such as permalloy are arranged in a stripe shape and arranged so that each stripe intersects at 90 degrees and bridge-connected. A control voltage Vcc is applied to the connection between the MR elements 5a and 5b, and the connection between the MR elements 5c and 5d is grounded. Then, a detection signal is taken out from a connection portion between the MR elements 5a and 5d and the MR elements 5b and 5c. The sensor chip 5 outputs a sine wave waveform signal having an electrical angle of 720 ° per one rotation of the turntable 3.

  Note that the sensor chip 5 obtains a cosine waveform signal as the turntable 3 rotates and performs comparison processing with the sine waveform, or the waveform curve becomes gentle at the peak portion of the sine waveform. If the difference is reduced, the rotational position detection becomes inaccurate. In this case, it is necessary to detect the rotational position with high accuracy using the steep part of the cosine wave waveform corresponding to the peak part of the sine wave waveform. The other four MR elements (not shown) are provided with a 45 ° crossing angle (90 ° in electrical angle) with respect to each of the MR elements 5a to 5d. These four cosine wave MR elements may be provided on the same substrate as the sine wave MR elements 5a to 5d or on a separate substrate.

  In addition, around the sensor chip 5, two Hall elements 9 a and 9 b are arranged with an intersection angle of 90 ° with respect to the center of the rotating disk 3. The hall elements 9a and 9b output positive and negative electrical signals corresponding to the polarities of the magnetic poles. The electrical signals output from the Hall elements 9a and 9b corresponding to the polarities of the magnetic poles become maximum voltages when opposed to the respective magnetic poles.

Next, the operation of detecting the rotational position by the magnetic sensor device 1 will be described.
First, the outline of the rotational position detection action of the rotating disk 3 by the MR elements 5a to 5d will be described. When the rotating disk 3 is rotated with the rotation of the rotating shaft 2, the first and second magnetic poles 7a in the rotating disk 3 are rotated. The magnetic resistance of each MR element 5a-5d changes with the change in the direction of the magnetic lines of force between 7b and the direction of the stripes in each MR element 5a-5d. A detection signal of 720 ° in angle is output. (See Figs. 3 and 4)

The control means (not shown) detects the rotational position by dividing the input electric signal by the number of divisions set in advance according to the desired position detection resolution and counting the number of divided signals.
However, as described above, the rotation position detection operation outputs an electrical signal unrelated to the polarities of the MR elements 5a to 5d themselves and the first and second magnetic poles 7a and 7b. The rotation position of the board 3 cannot be determined in which region of the rotation angle 180 ° within the electrical angle 720 °, and the rotation position cannot be detected.

  In this embodiment, based on the signals from the Hall elements 9a and 9b, the rotational position of the rotating disk 3 is determined as to which rotational angle 180 ° region of the electrical angle 720 ° and the rotational position can be detected. .

  That is, as described above, from the MR elements 5a to 5d, an electrical signal having an electrical angle of 720 ° per rotation of the turntable 3, and accordingly, an electrical signal having an electrical angle of 180 ° for every 90 °. Output a signal. Now, for example, when the Hall element 9a is positioned relative to the MR element 5a, a positive (plus) maximum voltage detection signal is output from the Hall element 9a and the detection signal voltage from the Hall element 9b is zero. It has become. In this state, when the turntable 3 rotates clockwise and the rotation angle of the turntable 3 is located between 0 ° and 90 °, the voltage of the detection signal from the Hall element 9a gradually decreases. When the rotation angle of the turntable 3 is 90 °, it becomes zero and the detection signal from the Hall element 9b gradually increases at a positive voltage, and when the rotation angle of the turntable 3 is 90 °, the maximum positive voltage is obtained. Become.

When the turntable 3 further rotates and the first magnetic pole 7a is positioned between the rotation angle of the turntable 3 between 90 ° and 180 °, the Hall element 9a is gradually opposed to the second magnetic pole 7b. When a detection signal of a negative (minus) voltage is output from the hall element 9a and the rotation angle of the turntable 3 is 180 °, a detection signal of a negative maximum voltage is output and the detection signal voltage from the hall element 9b is positive. When the rotation angle of the turntable 3 is 180 °, the detection signal voltage becomes zero.

Further, when the turntable 3 is positioned between the regions of 180 ° to 270 ° in terms of its rotation angle, it is separated from the Hall element 9a by gradually separating from the second magnetic pole 7b that was opposed to the Hall element 9a. When a detection signal that returns to zero from the negative maximum voltage value is output and the rotation angle of the rotating disk 3 is 270 °, the detection value becomes a zero detection signal, and the second magnetic pole 7b gradually moves with respect to the Hall element 9b. A detection signal with a negative voltage value is output by approaching, and when the rotation angle of the turntable 3 is 270 °, a detection signal with a negative maximum voltage value is output.

Still further, when the turntable 3 is positioned between 270 ° and 360 ° in terms of its rotation angle, the first magnetic pole 7a gradually approaches the Hall element 9a, so that the Hall element 9a gradually moves away from the Hall element 9a. When a detection signal with a positive voltage value that increases to a maximum is output and the rotation angle of the turntable 3 is 360 °, the voltage value becomes the maximum positive value and the second magnetic pole 7b is gradually separated from the Hall element 9b. Then, a detection signal that returns from the negative maximum voltage value to zero is output, and when the rotation angle of the turntable 3 is 360 °, a detection signal that outputs a detection signal having a voltage value of zero is output. (See Figure 5)

Based on the change of the detection signals from the Hall elements 9a and 9b, the control means is in which 180 ° region of the detection signal of the electrical angle 720 ° output from the MR elements 5a to 5d the rotation position of the turntable 3 is. Is determined. That is, when the signal from the Hall element 9a is positively decreased and the signal from the Hall element 9b is positively increased, the electrical angle ranges from 0 ° to 180 ° (rotation from 0 ° to 90 ° on the rotating disk 3). Region), when the signal from the Hall element 9a is negatively increased and the signal from the Hall element 9b is positively decreased, the electrical angle ranges from 180 ° to 360 ° (90 ° to 180 ° on the turntable 3). In the case where the signal from the Hall element 9a is negatively decreased and the signal from the Hall element 9b is positively decreased, the electrical angle is 360 ° to 540 ° (180 ° to 270 ° on the rotary disk 3). In the case where the signal from the Hall element 9a is positively increased and the signal from the Hall element 9b is negatively increased, the electric angle is 540 ° to 360 ° (270 ° to 360 ° on the rotary disk 3). It is determined that the turntable 3 is rotating in the ° rotation area. To.

In this embodiment, high-sensitivity MR elements 5a to 5d are used as members for detecting the rotational position of the turntable 3, and a detection signal with a high voltage ratio can be obtained, and the MR elements 5a to 5d are used. In order to detect the rotational position of the rotating disk 3 with high accuracy, it is possible to determine the defect that cannot be determined in which region of 180 ° in electrical angle by the signals from the Hall elements 9a and 9b. Can do.

  In the above description, the magnetic sensor device 1 is used as a rotary encoder to detect the rotational position of the turntable 3. However, in the second embodiment, the N pole and the S pole are different magnetic poles, and a desired width and The present invention relates to a magnetic sensor device 51 applied to a magnetic scale magnetized alternately in the longitudinal direction at a pitch.

  When a magnetic scale is formed by magnetizing long N poles and S poles made of ferrite or the like, the magnetic strength may be different between the N pole and the S pole. In this way, when detecting the magnetic pole of the magnetic scale by the MR sensor, the MR sensor outputs an electrical signal that alternately repeats a signal having a high amplitude and a signal having a low amplitude, resulting in poor position detection accuracy. Have the problem.

This disadvantage is that a desired position detection accuracy is obtained by arranging a plurality of MR sensors composed of one pitch of magnetic poles having different longitudinal widths of the magnetic scale and averaging the electric signals output from the respective MR sensors. Trying to get. However, an MR sensor chip provided with a plurality of MR sensors actually uses a plurality of MR sensors arranged on a single substrate. High cost was inevitable.

In order to obtain high position detection accuracy while reducing the size of the MR sensor chip, the polarity of the magnetic pole having a weak magnetic strength and the magnetic strength difference are confirmed in advance, and a correction data table corresponding to the magnetic strength difference is obtained from the detection signal from the MR sensor. Store it as complementary data. The detection signal from the MR sensor can be complemented based on the complement data so that the amplitudes are substantially the same. In order to realize this, it is necessary to detect which magnetic pole side the MR sensor is located on the magnetic scale.

The present embodiment relates to a magnetic sensor device that realizes the above-described matters, and details thereof will be described below.
As shown in FIGS. 6 and 7, the magnetic sensor device 51 according to this embodiment includes a magnetic scale 53 and a sensor chip 55 provided on a movable body 52 that reciprocates in the longitudinal direction relative to the magnetic scale 53. Consists of The magnetic scale 53 has a required length in the longitudinal direction, and magnetic poles 53a and 53b having different N and S poles having a width corresponding to a required detection resolution are arranged in a longitudinal direction with a gap between the magnetic poles 53a and 53b. Are alternately magnetized. On the other hand, the sensor chip 55 includes an adjacent MR sensor 57 having different magnetic poles 53a and 53b and two Hall elements 59a and 59b.

Similar to the sensor chip 5 of the first embodiment, the MR sensor 57 includes two MR elements 57a and 57b connected in series with a magnetic metal material such as permalloy arranged in a stripe pattern on a substrate, and the MR sensor 57. Two MR elements 57c and 57d connected in series with the widths of the magnetic poles 53a and 53b are bridge-connected to the elements 57a and 57b, and a control voltage Vcc is applied to the connection portion of the MR elements 57a and 57b. At the same time, the connection between the MR elements 57c and 57d is grounded, and the detection signal is taken out from the connection between the MR elements 57a and 57d and the MR elements 57b and 57c. The MR sensor 57 outputs a sine wave signal having an electrical angle of 720 ° as the magnetic scale 53 moves.

The sensor chip 57 obtains a cosine wave waveform signal as the movable body 52 moves and compares it with the sine wave waveform, or the waveform curve becomes gentle at the peak portion of the sine wave waveform, resulting in a voltage difference. Since the detection accuracy of the moving position deteriorates when the number of the moving parts decreases, it is necessary to detect the moving position with high accuracy using the steep part of the cosine wave waveform corresponding to the peak part. The four MR elements (not shown) are arranged with a 45 ° crossing angle with respect to each of the MR elements 57a to 57d for the sine wave waveform. The four MR elements for cosine waves may be provided on the same substrate as the MR elements 57a to 57d for sine waves or on a separate substrate.

Further, on the substrate of the MR sensor 57, two Hall elements 59a and 59b are spaced apart from each other by one magnetic pole 53a / 53b and a gap between them, and are close to the MR sensor 57 at a required distance. Installed on. In the example shown in FIG. 7, one Hall element 59a coincides with one MR element 57a and 57b connected in series, and the other Hall element 59b coincides with the other MR element 57c and 57d. Arranged. The hall elements 59a and 59b output positive and negative electrical signals corresponding to the polarities of the magnetic poles 53a and 53b. The positive and negative electrical signals output from the Hall elements 59a and 59b in accordance with the polarities of the magnetic poles 53a and 53b have a characteristic that the maximum amplitude voltage is obtained when facing the magnetic poles 53a and 53b. Yes.

Next, the operation of the magnetic sensor device 51 configured as described above will be described.
First, the outline of the position detecting action of the movable body 52 by the MR sensor 57 will be described. When the movable body 52 is moved along with the driving of the electric motor, the magnetic intensity change of the magnetic field between the magnetic poles 53a and 53b in the magnetic scale 53 is explained. As a result, the magnetic resistance of each of the MR elements 57a to 57d changes, and the sensor chip 55 outputs a position detection signal having a sine wave waveform having an electrical angle of 720 °. The control means divides the input detection signal by a number corresponding to a desired detection resolution, counts the number of divided signals, and detects the moving position of the movable body 52.

As described above, the magnetic strengths of the magnetic poles 53a and 53b in the magnetic scale 53 may be different. In that case, electrical signals having different amplitudes (voltages are different) are alternately output from the sensor chip 55, and the detection signal of a portion having a narrow amplitude is divided by a required number. At this time, the number of divided signals cannot be measured accurately, and the position detection accuracy is deteriorated. However, as described above, the signal from the sensor chip 55 cannot determine the polarities (N pole, S pole) of the magnetic poles 53a and 53b with which the sensor chip 55 is opposed and the positional deviation amount of the sensor chip 55 with respect to the magnetic poles 53a and 53b. .

In this embodiment, in order to solve the above problems, Hall elements 59a and 59b are provided in the vicinity of the magnetic scale 53, and the MR sensor 57 is relative to which magnetic poles 53a and 53b based on signals from the Hall elements 59a and 59b. It is determined whether it is doing. That is, as the movable body 52 moves, the respective hall elements 59a and 59b output signals corresponding to the polarities and magnetic strengths of the opposing magnetic poles 53a and 53b. (See FIG. 8, FIG. 8 shows an example in which the magnetic strength of the S pole is weaker than that of the N pole.)

Based on the signals from the Hall elements 59a and 59b, the control means discriminates whether the magnetic poles 53a and 53b opposed to the sensor chip 55 are N poles or S poles, that is, every 180 ° of the magnetic angle. The positional deviation amount of the sensor chip 55 with respect to the magnetic poles 53a and 53b is determined based on the voltage difference between the two. If the magnetic strength of the magnetic poles 53a and 53b of the magnetic scale 53 is, for example, that the magnetic strength of the S pole is weaker than that of the N pole, for example, the control means detects that the sensor chip 55 The position detection signal output from the sensor chip 55 by accessing the complementary data stored in the storage means in advance according to the positional deviation amount of the sensor chip 55 with respect to the S-pole side is approximately equal in voltage. Correct so that

In this embodiment, when the magnetic strengths of the magnetic poles 53a and 53b are different from each other, the magnetic poles 53a and 53b to which the sensor chip 55 that detects the position based on the change in the magnetic resistance of the MR elements 57a to 57d is opposed to each other. The polarity and position shift amount of the MR sensor 57 with respect to each and the magnetic poles 53a and 53b are discriminated based on the signals from the hall elements 59a and 59b, and the position detection signal from the sensor chip 55 is set so that the output voltage becomes substantially constant. It is possible to improve the position detection accuracy by correcting to the above. The magnetic scale 53 itself can be downsized to reduce the manufacturing cost.

It is explanatory drawing which shows the outline of a magnetic sensor apparatus. It is explanatory drawing which shows the outline of a sensor chip. It is explanatory drawing which shows the positional relationship of the magnetic pole position in a turntable, and a sensor chip. It is a wave form diagram which shows the rotational position detection signal output from MR element. It is a wave form diagram of the signal output from each Hall element. It is a perspective view which shows the magnetic sensor apparatus of a magnetic scale structure. It is explanatory drawing which shows the positional relationship of a magnetic scale and a sensor chip. It is a wave form diagram which shows the signal from a sensor chip and each Hall element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic sensor apparatus 3 Turntable 5 Sensor chip 5a-5d MR element 7a * 7b Magnetic pole 9a * 9b Hall element

Claims (10)

A magnet that detects a rotational position by detecting a magnetic field from each magnetic pole by a magnetoresistive element provided at a location opposite to the center of the rotating disk as the rotating disk provided with at least a pair of opposing magnetic poles rotates. In the sensor device, two Hall elements are arranged with a 90 ° crossing angle with respect to the magnetoresistive element, and a sine wave waveform of 720 ° in electrical angle output from the magnetoresistive element per rotation of the rotating disk. The magnetic sensor device that can specify each rotation angle 180 ° region in the signal of 1 based on the output signal from the Hall element. 2. The magnetic sensor device according to claim 1, wherein four magnetoresistive elements are bridge-connected at a crossing angle of 90 [deg.]. 4. The four magnetoresistive elements connected to each other in four bridge-connected magnetoresistive elements that output a sinusoidal waveform signal are bridge-connected at a crossing angle of 45 °, and a cosine waveform signal is output. Magnetic sensor device to output. 4. The magnetic sensor device according to claim 3, wherein the four magnetoresistive elements that output a sinusoidal waveform signal and the four magnetoresistive elements that output a cosine waveform signal are provided on the same substrate or different substrates. The magnetic sensor device according to claim 1, wherein the electric signal output from the magnetoresistive element is divided into a number corresponding to a desired detection resolution to detect a rotational position. Movable by detecting the magnetic field from each magnetic pole by a magnetoresistive element provided on a movable body that reciprocates relative to a magnetic scale in which different magnetic poles with widths corresponding to the desired detection resolution are alternately provided in the longitudinal direction. In a magnetic sensor device for detecting a moving position of a body, the magnetoresistive element outputs at least a sinusoidal waveform signal by a magnetic field from different magnetic poles, and two Hall elements in the vicinity of the magnetoresistive element are 180 degrees in magnetic angle. Magnetic sensor device provided to detect every time. 7. The magnetic sensor device according to claim 6, wherein four magnetoresistive elements are bridge-connected at a crossing angle of 90 [deg.]. 8. The bridge-connected four magnetoresistive elements at a crossing angle of 45 ° with respect to each of the four bridge-connected magnetoresistive elements that output a sinusoidal waveform signal, Magnetic sensor device to output. 9. The magnetic sensor device according to claim 8, wherein the four magnetoresistive elements that output a sinusoidal waveform signal and the four magnetoresistive elements that output a cosine waveform signal are provided on the same substrate or different substrates. The magnetic sensor device according to claim 6, wherein the electric signal output from the magnetoresistive element is divided into a number corresponding to a desired detection resolution to detect a moving position.

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