JPH0484712A - Magnetism sensor - Google Patents

Abstract

PURPOSE:To make the detected output large and to make it possible to form a sensor in a compact size by arranging the magnetoresistance stripes of magnetism detecting ements in the respective sets in close proximity in the turning direction of a rotor magnet so that the stripes are deviated by 45 degrees to each other. CONSTITUTION:This sensor has first-fourth magnetoresistance elements 3, 7, 4, 8, 5, 9, 6 and 10. The mutual magnetoresistance stripes of the first elements 3 and 7 and the second elements 4 and 8, the mutual magnetoresistance stripes of the third elements 5 and 9 and the fourth elements 6 and 10, the mutual magnetoresistance stripes of the elements 3 and 7 and the elements 5 and 9 and the mutual magnetic stripes of the elements 4 and 8 and the elements 6 and 10 are arranged at the positions which are intersected approximagely orthogonally. The elements 3, 7, 4 and 8 are connected in series, and the connecting point is made to be a first output terminal (a). The elements 5, 9, 6 and 10 are connected in series, and the connecting point is made to be a second output terminal (b). The differential output between the output terminals (a) and (b) is made to be the output in one set of the magnetism detecting elements 1. The two sets of the magnetism detecting elements are provided. The stripes of the detecting elements 1 and 2 in the respective set are arranged in close proximity in the turning direction of a rotor magnet 42 so that the stripes are deviated by 45 degress to each other.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a magnetic sensor using a magnetoresistive element.

(Prior Art) In order to detect the rotation of a rotating body, there is one in which a rotor magnet is provided integrally with a rotating body, and a magnetic sensor is arranged near the rotor magnet. The flowmeter described in Japanese Utility Model Application No. 61-8820 is one such example, in which N magnetic poles and S magnetic poles are arranged alternately at equal angles on a circumference that rotates in accordance with the flow rate and flow direction of the fluid to be measured. The rotor magnet includes an arranged rotor magnet and a magnetic sensor arranged near the rotor magnet. FIG. 10 shows a detection circuit using the magnetic sensor.

In FIG. 10, inside the magnetic sensor 51, there are first and second magnetoresistive elements 52.53 connected in series with each other, and the first and second magnetoresistive elements 52.53 are positioned relative to each other. Third and fourth magnetoresistive elements 54,55 are provided which are spaced apart and connected in series with each other. The first and second magnetoresistive elements 52 and 53 constitute a first resistance bridge circuit, and the first and second
The series connection point of the magnetoresistive elements 52 and 53 serves as one output terminal 56. Third and fourth magnetoresistive elements 5
4.55 constitutes a second resistance bridge circuit, and the series connection point of the third and fourth magnetoresistive elements 54.55 serves as another output terminal 57. A constant voltage is supplied from a power supply 62 to both ends of the first resistance bridge circuit and the second resistance bridge circuit. Further, dividing resistors 60 and 61 are respectively connected in parallel with the power supply 62, and a signal Va is obtained between the dividing terminal 58 of the one-dividing resistor 60 and the output terminal 56,
A signal vb is obtained between the dividing terminal 59 of the dividing resistor 61 and the output terminal 57.

Now, when the rotor magnet rotates, along with this rotation, a sinusoidal signal Va as shown in FIG. 11 is obtained from between terminals 56 and 58, and a sinusoidal signal Vb is obtained from between terminals 57 and 59. Since the magnetoresistive elements 52 and 53 forming the first resistance bridge circuit and the magnetoresistive elements 54 and 55 forming the second resistance bridge circuit are installed apart from each other, there is a phase difference between the signals Va and vb. arise. Depending on the direction of this phase shift, the direction of rotation of the rotating body, that is, the direction of fluid flow, can be determined, and the signal Va.

The rotational speed of the rotating body can be measured by the period of vb, and thereby the flow rate and current of the fluid can be measured.

(Problems to be Solved by the Invention) According to the conventional magnetic sensor described above, since each of the first resistance bridge circuit and the second resistance bridge circuit is a group of two elements, the output is small. In addition, in order to obtain two signals with one phase difference, a first resistor bridge circuit and a second resistor bridge circuit are used.
The resistive bridge circuit must be installed at a distance, resulting in a large magnetic sensor.

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a magnetic sensor that can increase the detection output and can be made compact.

(Means for Solving the Problems) The present invention provides a magnetic sensor that is arranged near a rotor magnet in which N magnetic poles and S magnetic poles are alternately arranged at equal angles in the circumferential direction, and detects the magnetic field of the rotor magnet. It has first, second, third and fourth magnetoresistive elements, the first magnetoresistive element and the second magnetoresistive element have mutually different magnetoresistive stripes, and the third magnetoresistive element and the fourth magnetoresistive element have mutually arranged magnetoresistive stripes. Positions where the magnetoresistive stripes of the element, the magnetoresistive stripes of the first magnetoresistive element and the third magnetoresistive element, and the magnetoresistive stripes of the second magnetoresistive element and the fourth magnetoresistive element are substantially perpendicular to each other. 1st,
The second magnetoresistive elements are connected in series and the connection point is set as the first output terminal, the third and fourth magnetoresistive elements are connected in series and the connection point is set as the second output terminal, and the first 1 whose output is a differential output between the output of the output terminal and the output of the second output terminal
The present invention is characterized in that two sets of magnetic detecting elements are provided, and the magnetic resistance stripes of the magnetic detecting elements of each set are arranged close to each other and shifted by 45 degrees in the rotational direction of the rotor magnet.

(Function) When the rotor magnet rotates, the magnetic field rotates for each set of magnetic detection elements, and accordingly, the first output terminal and second output terminal of each set of magnetic detection elements alternately A varying output signal is obtained. Take out the differential output of the signals obtained from the first output terminal and the second output terminal,
This is taken as the output of one set of magnetic detection elements. Since the magnetic resistance stripes of these two sets of magnetic sensing elements are arranged with a 45° shift from each other with respect to the rotational direction of the rotor magnet, the outputs of the two sets of magnetic sensing elements have a phase difference of 45'' with respect to each other. The direction of rotation of the rotor magnet can be detected based on the direction of this phase shift, and the rotational position and speed can be detected from the output of each magnetic detection element.

(Example) Hereinafter, an example of the magnetic sensor according to the present invention will be described with reference to the drawings.

The embodiment shown in FIG. 1 has two sets of magnetic detection elements 1 and 2 arranged close to each other. The first set of magnetic detection elements 1 consists of first, second, . third and fourth magnetoresistive elements 3,
4, 5.6, and the second set of magnetic detection elements 2 also have first, second, .
It has third and fourth magnetoresistive elements 7, 8, 9.10. The magnetoresistive stripes of the first magnetoresistive element 3 and the second magnetoresistive element 4 in the first set of magnetic sensing elements 1 are mutual, and the magnetoresistive stripes of the third magnetoresistive element 5 and the fourth magnetoresistive element 6 are mutual. , the magnetoresistive stripes of the first magnetoresistive element 3 and the third magnetoresistive element 5 and the magnetoresistive stripes of the second magnetoresistive element 4 and the fourth magnetoresistive element 6 are arranged to be substantially perpendicular to each other. has been done.

First magnetoresistive element 7 in second set of magnetic sensing elements 2
and the magnetoresistive stripes of the second magnetoresistive element 8, the magnetoresistive stripes of the third magnetoresistive element 9 and the fourth magnetoresistive element 10, and the magnetoresistive stripes of the first magnetoresistive element 7 and the third magnetoresistive element 9. The magnetoresistive stripes of the second magnetoresistive element 8 and the fourth magnetoresistive element 10 are arranged to be substantially perpendicular to each other.

The first and second magnetoresistive elements 3.4 in the first set of magnetic detection elements 1 are connected in series, and their connection point is the first output terminal a, and the third. Fourth magnetoresistive element 5, 6
are connected in series, and the connection point serves as the second output terminal. Further, the other ends of the first and third magnetoresistive elements 3 and 5 are connected to form a power supply terminal Vcc, and the second
, the other ends of the fourth magnetoresistive elements 4 and 6 are connected to form a ground terminal. Similarly, the first and second magnetoresistive elements 7 and 8 in the second set of magnetic detection elements 2 are connected in series, and their connection point is the first output terminal C, and the third
, the fourth magnetoresistive elements 9 and 10 are connected in series, and their connection point is the second output terminal d. Also, the first
The other end of the third magnetoresistive element 7.9 is connected to serve as a power supply terminal Vcc, and the second. Fourth magnetoresistive element 8,1
The other end of 0 is connected and serves as a ground terminal.

It is assumed that the first set of magnetic detection elements 1 and the second set of magnetic detection elements 2 are formed on one common substrate. The four magnetoresistive stripes that make up the first set of magnetic detection elements 1 and the four magnetoresistive stripes that make up the second set of magnetic detection elements 2 are arranged close to each other and shifted by 45 degrees.

5 to 7 show each side of the usage of the magnetic sensor configured as described above. In the example shown in FIG. 5, a magnetic sensor 41 formed by integrally forming two sets of magnetic detection elements 1 and 2 as described above is arranged at the inner center of a cylindrical rotor magnet 42. In the illustrated example, the rotor magnet 42 has N magnetic poles and S magnetic poles arranged at an angle of 180° in the circumferential direction. For boat fishing, N magnetic poles and S magnetic poles may be arranged alternately at equal angles in the circumferential direction of the rotor magnet 42. In addition, the magnetic sensor 41
are arranged so that the surface on which the magnetoresistive stripes are formed is parallel to the end surface of the rotor magnet 42. In the example shown in FIG. 6, the magnetic sensor 41 is placed close to and facing the end face of the rotor magnet 42. In the example shown in FIG. 7, the magnetic sensor 41 is arranged close to the outer circumferential side of the rotor magnet 42. In the example shown in FIG. In any case, the magnetic sensor 41 is arranged so that the surface on which the magnetic resistance stripes are formed is parallel to the end surface of the rotor magnet 42. The rotor magnet 42 may rotate by itself, or may be formed integrally with an appropriate rotating body.

With this arrangement, the rotating magnetic field of the rotor magnet passes parallel to the magnetic resistance stripe forming surface of the magnetic sensor, and this rotating magnetic field can be detected by the magnetic sensor.

Next, an example of connection between each magnetoresistive element constituting the two sets of magnetic detection elements 1 and 2 and an external circuit will be described. 8th
In the figure, first and second sets of magnetic sensing elements 1 and 2 are shown.
A constant voltage is applied from a power supply 45 between each power supply terminal Vcc and the ground terminal. The outputs of the first and second output terminals a and b of the first set of magnetoresistive elements 1 are input to the plus terminal and minus terminal of a differential amplifier 47, respectively, to output a differential output. This differential output becomes the A-phase output signal. The outputs of the first and second output terminals c and d of the second set of magnetic detection elements 2 are respectively input to the positive and negative terminals of a differential amplifier 48 to output a differential output, This differential output becomes the B-phase output signal.

FIG. 9 shows the output signal waveforms of the A phase and B phase.

As mentioned above, the first set and the second set of magnetic detection elements 1,
Since the two magnetoresistive stripes are arranged to be shifted from each other by 45 degrees with respect to the rotational direction of the rotor magnet, a phase difference of 45 degrees in electrical angle occurs between the output signals of the A phase and B phase. Which of the A-phase and B-phase output signals is leading is determined by the rotational direction of the rotor magnet, so the rotational direction of the rotor magnet is detected by detecting the phase relationship of the A-phase and B-phase output signals. be able to.

By the way, a conventional general magnetic sensor detects the alternating magnetic field of a magnet, and generates a digital signal of, for example, 100 pulses per rotation, and determines the rotation angle by the digital amount.

On the other hand, according to the embodiment of the present invention, as can be seen from the differential output signal waveforms of the magnetic detection elements 1.2 of each set shown in FIG. Since the magnetic field is output as a quantity, by detecting the analog quantity of the differential output of each set of magnetoresistive elements 1 and 2, the rotation angle of the magnetic field, that is, the rotation angle of the rotor magnet can be detected. In addition, each set of magnetoresistive elements 1 and 2
From the change in the differential output signal waveform of the N magnetic pole and S magnetic pole within a unit time
The rotation speed of the rotor magnet can also be detected by detecting the switching of the magnetic poles.

As is clear from the above description, according to one embodiment of the present invention, one set of magnetoresistive elements is configured with four elements as one group,
Two of these four elements are connected in series, their connection points are used as the first and second output terminals, and the differential output of these first and second output terminals is used as the output signal. The output is larger than that using two elements as one group, such as. Incidentally, the signal vb indicated by a broken line in FIG. 9 is a comparison of the output signal obtained by the conventional magnetic sensor shown in FIG. 10 with the output signal obtained by the embodiment of the present invention. It can be seen that the output signal obtained by the example is approximately twice as large as the conventional one. Increasing the output signal in this way has the effect of increasing the detection accuracy when trying to detect the rotation angle of the rotor magnet based on the analog quantity.

Next, various modified embodiments of the magnetic sensor according to the present invention will be described.

The embodiment shown in FIG. In arranging the second set of magnetic sensing elements 12 consisting of the third and fourth magnetoresistive elements 17, 18, 19°20 in close proximity, the formation area of the first set of magnetic sensing elements 11 and the second set of magnetic sensing elements 11 are Magnetic detection element 12
, and the four elements 17, 18, 19 .
The direction of the 20 magnetoresistive stripes is inclined by 45'' with respect to the direction of the magnetoresistive stripes of the four elements 13, 14.degree. 15.16 constituting the first set of magnetic sensing elements 11. The electrical connection relationship and operation and effect of each magnetoresistive element are the same as in the previous embodiment.

In the embodiment shown in FIG. 3, a second set of magnetic detecting elements 22 is arranged surrounded by a first set of magnetic detecting elements 21. In the embodiment shown in FIG. Four elements 23 forming the first set of magnetic detection elements 21
．． 24, 25, and 26 are formed in a triangular plane so as to occupy each corner of a square substrate, and these four elements 23
, 24, 25. Four elements 27, 28, 29 constituting the second set of magnetic detection elements 22 within a square plane surrounded by
°30 is formed. Each set of magnetic detection element 21゜2
The relative orientation of the magnetoresistive stripes of each of the four elements constituting the second embodiment, the electrical connections, and the effects are substantially the same as in the previous embodiment.

In the embodiment shown in FIG. 4, a first set of magnetic detection elements 31 and a second set of magnetic detection elements 32 are arranged three-dimensionally overlapping each other. Four elements 3 constituting the first set of magnetic detection elements 31
3, 34, 35, 36 and the four elements 37, 38, 39, and 40 constituting the second set of magnetic sensing elements 32. is virtually the same as This embodiment also provides the same effects as the previous embodiment.

(Effects of the Invention) According to the present invention, a set of magnetic detection elements is constructed with four elements as one group, two of these four elements are connected in series, and their connection points are connected to the first and second magnetic detection elements. Since the differential output of the outputs of these first and second output terminals is used as the output signal, the output is larger than the conventional one using two elements as a group, and the detection accuracy is improved. It has the effect of improving.

Furthermore, by arranging the magnetic resistance stripes of each set of magnetic detection elements close to each other and shifted by 45'' in the rotational direction of the rotor magnet, a compact magnetic sensor is provided that outputs two signals having a phase difference. be able to.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the magnetic sensor according to the present invention, FIG. 2 is a plan view showing another embodiment of the magnetic sensor according to the present invention, and FIG. 3 is a plan view showing another embodiment of the magnetic sensor according to the present invention. FIG. 4 is a plan view showing still another embodiment of the magnetic sensor according to the present invention; FIG. 4 is an exploded perspective view showing still another embodiment of the magnetic sensor according to the present invention;
The figure is a plan view showing an example of the arrangement of the magnetic sensor according to the present invention.
FIG. 6 is a perspective view showing another arrangement example of the magnetic sensor according to the invention, FIG. 7 is a perspective view showing still another arrangement example of the magnetic sensor according to the invention, and FIG. 8 is a perspective view showing another arrangement example of the magnetic sensor according to the invention. A circuit diagram showing an example of the circuit, FIG. 9 is a waveform diagram showing an example of an output signal obtained by the same example circuit, FIG. 10 is a circuit diagram showing an example of a circuit used in a conventional magnetic sensor, and FIG. 11 is a conventional example of the same as above. FIG. 3 is a waveform diagram showing an example of an output signal obtained by example. 1.2, 11, 12, 21, 22, 31. 32...1
Set of magnetic detection elements, 3, 7, 13, 17° 23.2
7,33,37...first magnetoresistive element, 4.8,1
4, 18, 24, 28, 34.38... second magnetoresistive element, 5, 9, 15, 19, 25.29, 35.3
9...Third magnetoresistive element, 6.10, 16, 20,
26, 30, 36.40... fourth magnetoresistive element,
41... Magnetic sensor, 42... Rotor magnet,
a: first output terminal, b: second output terminal. Fig. 3 Fig. 4 Funeral diagram Fig. 6 Fig. Fig. 1゜Replace “4” in line 14 of page 9 of the procedural amendment specification to “4 J.” Attached on December 6, 1990 Figure 2 in the drawings has been revised as shown in the attached sheet.

Claims (1)

[Scope of Claims] A magnetic sensor that is arranged near a rotor magnet in which N magnetic poles and S magnetic poles are arranged alternately at equal angles in the circumferential direction and detects the magnetic field of the rotor magnet, comprising: 3 and a fourth magnetoresistive element, the magnetoresistive stripes of the first magnetoresistive element and the second magnetoresistive element mutually, the magnetoresistive stripes of the third magnetoresistive element and the fourth magnetoresistive element mutually, The magnetoresistive stripes of the first magnetoresistive element and the third magnetoresistive element mutually and
The magnetoresistive stripes of the magnetoresistive element and the fourth magnetoresistive element are arranged at substantially orthogonal positions, and the first and second magnetoresistive elements are connected in series, with the connection point serving as the first output terminal. , the third and fourth magnetoresistive elements are connected in series, the connection point thereof is used as the second output terminal, and the differential output between the output of the first output terminal and the output of the second output terminal is output. A magnetic sensor characterized in that two sets of magnetic detecting elements are provided, and the magnetic resistance stripes of the magnetic detecting elements of each set are arranged close to each other and shifted by 45 degrees in the rotational direction of the rotor magnet.