JPH10274660A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the moving direction of a part to be detected with one output signal by separately arranging a plurality of magnetic resistor elements with different sensitivities along the moving direction of the part to be detected. SOLUTION: Magnetic resistor elements 15 to 17 with different sensitivities constituted by using different numbers of magnetic resistor elements 15a, 16a, 16b, 17a-17c are arranged with intervals along the moving direction (the direction of the arrow a) of a part to be detected 11 placed projected out of the outer surface 10a of a rotor 10. When the part to be detected 11 rotating with the rotor 10 passes the position corresponding to the elements 15 to 17, the magnetic field at the elements 15 to 17 varies clue to the part to be detected 11. By this magnetic field variation, the electric resistances of the elements 15 to 17 vary and the electric potential at the middle point varies. In this case, as the sensitivities of the elements 15 to 17 are made different, the output waveforms of the middle point electric potential become different for the moving direction of the detecting part 11. By discriminating the waveforms of the middle point electric potentials, the moving direction of the detecting part 11 (rotor 10) is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor.

[0002]

2. Description of the Related Art As is well known, in a vehicle such as an automobile, it is common practice to control the vehicle by measuring the number of revolutions, the direction of rotation, the angle of rotation, etc. of an axle. 2. Description of the Related Art Conventionally, magnetic sensors are often used to measure the number of revolutions of an axle of this type.

FIG. 5 shows an example of a magnetic rotation detecting system using this magnetic sensor. In the drawing, reference numeral 1 denotes a rotating shaft, 2 denotes a rotating body, and 3 denotes a magnetic sensor. The rotation axis 1 is
It is rotatably supported and is rotated by driving means (not shown).

[0004] The rotating body 2 is formed of a magnetic material and is fixed to the rotating shaft 1. The peripheral surface of the rotating body 2 has a gear-shaped rotation angle detecting section 2a having peaks and valleys formed at regular intervals over the entire circumference, and a rotational speed detection section having only one peak formed over the entire circumference. A portion 2b is formed.

[0005] The magnetic sensor 3 is arranged opposite to the peripheral surface of the rotating body 2. This magnetic sensor 3 has a first magnetoresistive element section 6 and a second magnetoresistive element section 7. These magnetoresistive element sections 6 and 7 have I
A magnetoresistive element formed of n-Sb, In-NiSb, InAs, or the like is used, and detects a magnetoresistance corresponding to a peak or a valley formed on a rotating body 2 made of a magnetic material. .

[0006] The first magnetoresistive element section 6 includes the rotating body 2.
The rotation angle detection unit 2a is disposed to face the rotation angle detection unit 2a.
It is configured to output signals A-phase and B-phase whose phases are shifted from each other by 90 ° according to the cycle of the peaks and valleys of a (see FIG. 6). The first magnetoresistive element 6
Are of a differential type for improving the S / N ratio, and as shown in FIG. 6, signals A-bar phase and B-bar phase which are opposite phases of A-phase and B-phase are obtained. Therefore, as shown in FIG. 7, the first magnetoresistive element section 6 is composed of eight magnetoresistive elements 6a, 6a,.

As shown in FIG. 5, the second magnetoresistive element section 7 is disposed opposite to the rotation number detecting section 2b of the rotator 2, and each time the rotator 2 makes one rotation, a signal, that is, Z It is configured to output a phase (see FIG. 6).

The magnetic rotation detecting system configured as described above detects a change in magnetic resistance generated in accordance with the rotation of the rotating body 2 with the magnetic sensor 3 as follows. Rotating body 2
Rotates with the rotation of the rotating shaft 1. Since the first magnetoresistive element section 6 is arranged to face the rotation angle detection section 2a of the rotating body 2, it outputs output signals A-phase and B-phase corresponding to the peaks and valleys of the rotation angle detection section 2a ( See FIG. 6). In this case, the A phase and the B phase become sine waves corresponding to peaks and valleys formed at regular intervals in the rotation angle detection unit 2a, and the rotation angles of the rotating shaft 1 and the rotating body 2 are determined by the phases of the sine waves. Can be detected. Further, since the A-phase and the B-phase are configured to be output signals shifted by 90 °, the rotation direction can be detected by comparing the A-phase and the B-phase. Since the second magnetoresistive element unit 7 is arranged to face the rotation speed detection unit 2b of the rotating body 2, it outputs a Z phase corresponding to the peak of the rotation speed detection unit 2b (see FIG. 6). In this case, the peak of the rotation speed detecting unit 2b is
Are formed around the entire circumference of the rotating shaft 1, so that the rotation speeds of the rotating shaft 1 and the rotating body 2 can be detected.

[0009]

The conventional magnetic sensor 3 has the following problems. The first magnetoresistive element section 6 needs a B phase whose phase is shifted by 90 ° with respect to the A phase for detecting the rotation direction of the rotating body 2, so that a total of eight magnetoresistive elements 6 a, 6 a ... had to be provided. Therefore, the number of magnetic resistance elements cannot be reduced, and the cost of the magnetic sensor 3 cannot be reduced.

The present invention has been made in view of the above problems, and it is possible to detect the moving direction of a detection target with one output signal without using two output signals of A phase and B phase. It is an object of the present invention to provide a magnetic sensor.

[0011]

The magnetic sensor according to the present invention employs the following means in order to solve the above-mentioned problems.
The magnetic sensor according to claim 1, wherein a plurality of magnetoresistive element portions are arranged at positions separated from each other along the moving direction of the detected portion and in a state of being connected in series with each other, and both ends of each of the magnetoresistive element portions. A magnetic sensor that applies a voltage between the magnetic resistance elements and detects a change in a magnetic field accompanying the movement of the detected part based on any midpoint potential between the respective magnetic resistance element parts. Are different from each other in sensitivity.

A plurality of magnetoresistive elements are arranged along the direction of movement of the detected part, these magnetoresistive elements are connected in series, and a voltage is applied between both ends. Therefore, when the electric resistance of the magnetoresistive element changes, the midpoint potential between the magnetoresistive elements also changes. When the detected portion moves along the magnetoresistive element portion arranged in one direction, the detected portion approaches and separates from the magnetoresistive element portion. Changes. Due to this change in the magnetic field, the electric resistance of the magnetoresistive element changes,
The midpoint potential will fluctuate. In this case, since the sensitivities of the respective magnetoresistive element portions are different, the output waveform of the midpoint potential differs depending on the moving direction of the detected portion. Therefore, the moving direction of the detected portion is detected by determining the output waveform of the midpoint potential.

A magnetic sensor according to a second aspect of the present invention is the magnetic sensor according to the first aspect, wherein the magnetoresistive element includes a magnetoresistive element having a constant magnetoresistive effect. It is characterized by comprising different numbers of the magnetoresistive elements.

By providing a different number of magnetoresistive elements having a constant magnetoresistance effect in each magnetoresistive element section, the sensitivities of the respective magnetoresistive element sections are different from each other.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a perspective view showing an embodiment of the present invention, and shows a state in which a magnetic sensor is arranged so as to face a peripheral surface of a rotating body. In the figure, reference numeral 10 denotes a rotating body, 11 denotes a detected part, and 12 denotes a magnetic sensor.

The rotator 10 is driven to rotate about an axis (not shown) in the forward direction, which is the direction of arrow a shown in the figure, or in the reverse direction, which is the reverse direction of arrow a. This rotating body 10
The detected portion 11 is provided on the peripheral surface 10a of the first portion.

The detected part 11 is made of a magnetic material and is provided so as to protrude from the peripheral surface 10a of the rotating body 10.

The magnetic sensor 12 is disposed opposite to the rotating body 10 and the portion to be detected 11 at a position separated therefrom.
This magnetic sensor 12 includes a first magnetoresistive element section 15,
The second magnetoresistive element section 16 and the third magnetoresistive element section 1
7 are provided. The first magnetoresistive element section 15 includes one magnetoresistive element 15a. This magneto-resistive element 15a has a constant magneto-resistive effect in which the electric resistance changes due to a change in the magnetic field.
It is formed of iSb, InAs or the like. The second magnetoresistive element section 16 is located on the right side of the first magnetoresistive element section 15, and includes two magnetoresistive elements 16a and 16b similar to the aforementioned magnetoresistive element 15a. These magnetoresistive elements 16a and 16b are connected in series. The third magnetoresistive element section 17 is
And three magnetoresistive elements 17a, 17b, 17c similar to the magnetoresistive element 15a. These magnetoresistive elements 17a, 17b, 17c
They are connected in series.

As described above, each of the magnetoresistive element sections 15, 1
Reference numerals 6 and 17 are arranged at positions separated from each other along an arrow a, which is the moving direction of the detection target 11. In this case, it is desirable that the interval between the respective magnetoresistive element portions 15, 16, 17 is larger than the width W of the detected portion 11 in the direction of the arrow a. Further, each of the magnetoresistive element sections 15, 1
6, 17 are different numbers of magnetoresistive elements 15 respectively.
, 16a, 17a,..., the sensitivities of the magnetoresistive element sections 15, 16, 17 for detecting a change in the magnetic field are different.

These magnetoresistive element sections 15, 16, 17
Are connected in series, the terminal on the first magnetoresistive element section 15 side is connected to the constant potential Vcc, and the terminal on the third magnetoresistive element section 17 side is grounded. Thus, a voltage is applied between both ends of each of the magnetoresistive element sections 15, 16, and 17. Further, the second magneto-resistive element section 16 and the third magneto-resistive element section 17 are so detected as to detect the midpoint potential Vm between the second magneto-resistive element section 16 and the third magneto-resistive element section 17. Is connected to the signal processing unit 20.

The signal processing section 20 processes the output waveform of the midpoint potential Vm and detects the rotation direction, the rotation angle, and the like of the rotating body 10. The signal processing unit 20 includes a rising differentiating circuit 21 and a post-processing circuit 22. The rising differentiating circuit 21 is configured to output a differential value of the rising output of the midpoint potential Vm. Post-processing circuit 2
Numeral 2 is connected to the midpoint potential Vm and the output of the rising differentiating circuit 21 to process the midpoint potential Vm and the output waveform of the rising differentiating circuit 21.

Next, a method of detecting the direction of rotation of the rotating body 10 using the magnetic sensor 12 having the above configuration will be described. The detected portion 11 is rotated in the forward direction (the direction of arrow a) together with the rotating body 10 by a driving source (not shown). The detected portion 11 sequentially passes through positions corresponding to the first, second, and third magnetoresistive element portions 15, 16, and 17. When passing through each of the magnetoresistive element sections 15, 16, and 17, the detected section 11 changes the magnetic field, and the electric resistance of the magnetoresistive element sections 15, 16, and 17 also changes in accordance with the change. In this case, these magnetoresistive element sections 15, 1
Since a constant potential difference Vcc is applied between both ends of 6 and 17, the midpoint potential Vm between the second magnetoresistive element section 16 and the third magnetoresistive element section 17 also changes. FIG. 2A shows the change of the midpoint potential Vm.

In FIG. 2A, the horizontal axis represents time, and the vertical axis represents voltage. The midpoint potential Vm indicates the equilibrium potential V0 when the detected portion 11 does not pass through the magnetoresistive element portions 15, 16, and 17. The detected part 11 is the first magnetoresistive element part 15
, The midpoint potential Vm shows the first maximum value V1. Similarly, the second magnetoresistive element section 16
When passing through the position corresponding to, the second maximum value V2 is shown. On the other hand, the detection target 11 is the third magnetoresistance element 17.
When passing through the position corresponding to the minimum value V3.

In this case, the first and second magnetoresistive elements 1
5 and 16 show the maximum values V1 and V2, while passing through the third magnetoresistive element section 17 shows the minimum value V3 because the third magnetoresistive element section 17 has a medium value. This is because it is attached to the ground side with respect to the position from which the point potential Vm is taken out. Further, the first maximum value V1 indicates a value smaller than the second maximum value V2. This is because the sensitivity of the first magnetoresistive element section 15 is
This is because it is configured to be lower than the sensitivity. That is, the first magneto-resistive element section 15 is composed of one magneto-resistive element 15a, while the second magneto-resistive element section 16 is configured by connecting two magneto-resistive elements 16a and 16b in series. It is because it is constituted. Here, the low sensitivity of the magnetoresistive element means that the ratio of the change in the electric resistance of the magnetoresistive element to the change in the magnetic field around the magnetoresistive element is small.

The decrease of the midpoint potential Vm when passing through the third magnetoresistive element 17, ie, the absolute value of the difference between the equilibrium potential V0 and the minimum value V3, is determined by the first and second magnetoresistive elements. It is larger than the increment of the midpoint potential Vm when passing through the channels 15 and 16, that is, the absolute value of the difference between the first and second maximum values V1 and V2 and the equilibrium potential V0. This is because the third magnetoresistive element section 17 has three magnetoresistive elements 17a, 17b, 17c.
And the first and second magnetoresistive element portions 1
This is because the sensitivity is higher than 5 and 16.

When detecting the number of revolutions of the rotating body 10, a threshold value Vs1 is set between the equilibrium potential V0 and the minimum value V3, and the passage of the third magnetoresistive element 17 is detected by a comparator or the like. What should I do?

On the other hand, when the rotating body 10 rotates in the opposite direction, that is, in the direction opposite to the arrow b, the output waveform of the midpoint potential Vm is as shown in FIG. That is, when the rotating body 10 rotates in the reverse direction, the detection target 11 sequentially passes through the positions corresponding to the third, second, and first magnetoresistive element units 17, 16, and 15. Therefore, the minimum value V3 appears first, then the second maximum value V2, and then the first maximum value V1.
Appears. When the rotation speed of the rotating body 10 is detected, the threshold value Vs1 may be set to detect the passage of the third magnetic resistance unit 17, as in the case of FIG.

When the direction of rotation of the rotating body 10 is determined, that is, when the direction of movement of the portion to be detected 11 is determined, the rising differentiation circuit 21 is used to make the following determination. FIG.
FIG. 9A is an output waveform after the midpoint potential Vm has passed through the rising differentiating circuit 21. FIG.
Indicates a reverse rotation. When rotating in the forward direction, the first, second,
An increase rate of the voltage corresponding to the passage through the third magnetoresistive element sections 15, 16, 17 is output (see FIG. 3A). On the other hand, at the time of reverse rotation, the rate of increase of the voltage when shifting from the minimum value V3 in FIG. 2B to the second maximum value V2 is large, so that as shown in FIG. A maximum value V4 larger than that at the time of rotation in the direction appears. Therefore, if the threshold value Vs2 is set so as to detect only the local maximum value V4, the rotation direction can be determined.

As described above, the magnetoresistive element sections 15, 16,
17 are spaced apart from each other so that their sensitivities are different, so that the output waveform of the midpoint potential Vm when the rotating body 10 rotates in the forward direction and in the reverse direction can be made different. Therefore, it is possible to detect the rotation direction of the rotating body 10, that is, the moving direction of the detection target 11, with one output signal.

As shown in FIG. 4, the first magnetoresistive element 15 and the second magnetoresistive element 16 are connected in parallel, and the magnetoresistive elements 17 of the third magnetoresistive element 17 are connected.
a, 17b, 17c may be connected in parallel. Further, although the number of the magneto-resistive element portions 15, 16, 17 is three, the number is not limited thereto, and may be two, or four or more. Further, the detection position of the midpoint potential Vm may be any position of each of the magnetoresistive element sections, and is not limited to the position of the present embodiment. In addition, this embodiment,
The determination of the rotation direction of the rotating body has been described as an example. However, the present invention is not limited to this, and may be used, for example, when determining the moving direction of a detected portion that reciprocates linearly. In addition, the sensitivity of the magnetoresistive element portion is made different depending on the number of magnetoresistive elements having the same magnetoresistive property. However, the present invention is not limited to this, and one or more magnetoresistive elements having different magnetoresistive properties are used. The sensitivities of the magnetoresistive elements may be different. Further, the detected portion 11 is projected from the rotating body 10, but may be any as long as it changes the magnetic field around the magnetoresistive element when passing through a position corresponding to the magnetoresistive element. A portion in which a concave portion is formed on the peripheral surface 10a of the rotor 10 or a portion where a magnetic tape is stuck on the peripheral surface of the rotating body 10 may be the detected portion. In addition, the configuration using the differentiating circuit 21 is used to determine the difference between the output waveforms of the midpoint potential Vm during the forward rotation and the reverse rotation. However, the present invention is not limited to this. I just need.

[0031]

As described above, according to the magnetic sensor of the present invention, the following effects can be obtained. A plurality of magneto-resistive elements are arranged along the direction of movement of the part to be detected, and the sensitivity of each magneto-resistive element is made different, so the direction of movement of the part to be detected is determined by the output waveform of the midpoint potential. It is possible to do. Therefore, it is possible to determine the moving direction of the detected portion from one output signal, and it is possible to reduce the number of the magnetoresistive elements used. Therefore, the magnetic sensor can be configured with a simpler configuration, and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment in which a magnetic sensor according to the present invention is used to detect a rotation direction of a rotating body.

2A and 2B are output waveforms of the midpoint potential of the magnetic sensor of FIG. 1, wherein FIG. 2A shows a case where the rotating body is rotating in a forward direction, and FIG. Indicates when

3A and 3B are output waveforms after passing through the differentiating circuit of FIG. 1, wherein FIG.
Indicates the case of rotation in the opposite direction.

FIG. 4 is a perspective view showing a modification of the magnetic sensor of FIG. 1;

FIG. 5 is a front view showing a magnetic rotation detection system using a magnetic sensor according to the related art.

FIG. 6 is a diagram showing a detection output of the magnetic sensor of FIG. 7;

FIG. 7 is a plan view showing an arrangement state of magnetoresistive elements of the magnetic sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Detected part 12 Magnetic sensor 15 Magnetic resistance element part 16 Magnetic resistance element part 17 Magnetic resistance element part Vm Midpoint potential

Claims (2)

[Claims] A plurality of magnetoresistive element sections are arranged at positions separated from each other along the direction of movement of a detected section and connected in series with each other, and a voltage is applied between both ends of each of the magnetoresistive element sections. A magnetic sensor that detects a change in a magnetic field accompanying the movement of the detected part based on any midpoint potential between the respective magnetoresistive element parts. A magnetic sensor characterized by being different. 2. The magnetic sensor according to claim 1, wherein the magnetoresistive element section includes a magnetoresistive element having a constant magnetoresistive effect, and each magnetoresistive element section has a different number of the magnetoresistive elements. A magnetic sensor comprising an element.