JPH0222510A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To nearly eliminate variation in the amplitude of an output signal and to improve the stability of the output signal by arranging magnetism sensing parts at constant intervals to the entire periphery radially from a center of rotation. CONSTITUTION:The distance between the surface of a sensor element 1 and the surface of a disk 2 varies owing to the play of the disk surface in the direction of the rotary shaft 3 as the disk rotates. For example, when the disk approaches magnetism sensing parts 9a and 9h, their resistance values vary by DELTAr+DELTAR. (DELTAr is the quantity of resistance abnormal variation due to the approach of the disk and DELTAR is the quantity of resistance value variation due to normal magneto-resistance effect). Further, resistances 9d and 9e which are at positions of point symmetry about the rotary shaft 3 vary in resistance value by -DELTAr+DELTAR. Then the total of the resistance value variation of the magnetism sensing part resistances 8 and 9 is overall resistance value variation. The output of the element 1 is determined depending upon only DELTAR, so a signal with a constant amplitude is obtained finally.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable magnetoresistive magnetic sensor among magnetic sensors used in magnetic encoders and tacho generators.

[Conventional technology]

A magnetoresistive magnetic sensor (hereinafter abbreviated as magnetic sensor) is an element that converts periodic changes in magnetic field into changes in output voltage by utilizing changes in resistance due to changes in external magnetic field. 48-79655). As a rotating body that generates periodic magnetic field changes, for example, a magnetic drum as shown in FIG. 9 or a magnetic disk as shown in FIG. 8 are known. A magnetic drum type rotating body increases the thickness in the direction of the rotating shaft and is not suitable for miniaturization, so a magnetic disk type rotating body is preferable. In magnetic sensors using magnetic disks, a method was used in which a sensor element was fixed opposite a part of the disk surface to detect changes in the magnetic field from the disk surface (factor 8)0. Problems to be Solved] In the magnetic sensor having the above structure, the disk surface fluctuates in the direction of the rotation axis as the disk rotates due to misalignment between the rotating magnetic disk and the rotation axis. Therefore, the distance between the magnetic sensor element and the disk surface constantly changes. In FIG. 6, the distance between the disk surface and the sensor is small, and the sensor element outputs a signal with a large amplitude. In FIG. 7, the distance between the disk surface and the sensor element is large and the magnetic field received by the sensor element is weak, so the output signal amplitude is small. As the disk rotates, the cases shown in FIG. 6 and FIG. 7 occur alternately, and the signal output from the sensor element has a large amplitude fluctuation, and there is a problem that an output signal with a constant amplitude cannot be obtained. The object of the present invention is to provide a magnetic sensor that does not have the above-mentioned output amplitude fluctuations and can generate an output signal that always has a constant amplitude.

[Means to solve the problem]

The present invention is a magnetic sensor characterized in that the magnetically sensitive parts of the sensor element are arranged radially at a predetermined pitch with respect to the center of rotation over the entire circumference of a support facing the disk surface. In the case of a magnetoresistive magnetic sensor, a magnetically sensitive portion resistance is provided within the sensor element, and the value of this resistance changes with changes in the external magnetic field p1. By dividing one resistor and placing it around the entire circumference of the support facing the disk surface, even if one end of the disk approaches the sensor element during rotation, the end that is symmetrical to that On the contrary, they drift apart in the club. The magnitude of the magnetic field received by the sensor element is proportional to the distance from the disk surface to the sensor element, and the change in resistance value is also proportional to the magnitude of the magnetic field. Therefore, the change in resistance value is small where the distance between the disk and the sensor is large, and the change is large where the distance is small. However, since these resistors are formed as part of one long resistor, the change in resistance value of this long resistor as a whole always remains constant. Therefore, the magnetoresistance change resulting from this entire long resistance remains constant and the output amplitude is always constant.

〔Example〕

FIG. 1 shows an embodiment of the present invention. 8a to 8h and 9a
to 9h are magnetoresistive magnetic sensing parts, which are formed using thin films or thin wires. Between the voltage application terminal 4 and the grounding terminal 5, from 8a to 8h and from 9a to 9h
The magnetic sensing parts of each are connected in series as a resistor. These wirings are usually formed on a support 26 made of glass, organic resin, or ceramic, but when metal is used as the support 26, an insulator is interposed between the wiring and the support 260. . A signal output terminal 6 is provided at an intermediate point between the wirings 4 and 5. On the other hand, as shown in 2 in Figure 2, the rotating disc-shaped rotating plate has N and S poles alternately magnetized along the local direction with a constant track width. The number is a predetermined number of poles ranging from 2 to 5000 poles. If the distance between the north pole and the south pole is the magnetized pitch, the pitch of the magnetically sensitive part resistors 8a to 8h is an integral multiple of the magnetized pitch, and the pitch of the magnetically sensitive part resistors 9a to 9hk is also similar to each other. It has to do with placement.

However, one of the magnetic sensing part resistances from 8a to 8h and one of the resistances from 9a to 9h are always mutually (η+η)λ
The positional relationship is (η: integer, λ: magnetization pitch). When rotating a magnetized disk plate to extract a signal, the disk plate and sensor element are placed opposite each other as shown in Figure 2.
3′x from 10μm.

Install them at a specified distance from each other. As the disk plate rotates, as shown in FIG. 5, the distance between the sensor element surface and the disk surface changes due to play in the direction of the rotation axis of the disk surface. For example, when the disk plate approaches the magnetically sensitive resistors 9a and 9h as shown in Figure 5, these resistance values are △r + △R.
only changes.

Δr is the amount of abnormal change in resistance due to the approach of the disk plate, and ΔR is the amount of change in resistance value due to the normal magnetoresistive effect. ΔR takes a positive or negative value depending on the physical properties of the material constituting the magnetically sensitive part. On the other hand, the resistance values of the resistors 9d and 9e, which are located point-symmetrically to these with respect to the rotation axis, change by -Δr+ΔR. Between the terminal 5 and the terminal 6, the sum of the resistance value changes of the respective magnetically sensitive portion resistances appears as the overall resistance value change. This total is as follows.

2 (△r + △R) + 2 (-△r + △R) + 4 △R = 88R In other words, the influence of resistance change △r due to the backlash during rotation of the disk plate is due to the influence of △r on points symmetrical to each other with respect to the center. This is not included in the overall resistance value change because the abnormal change in resistance cancels it out. Only a constant variation ΔR determined by the physical properties of the material appears. Since the output from the sensor element ultimately depends only on this ΔR, a signal with a constant amplitude is finally obtained. A similar effect also occurs for the magnetically sensitive resistors 8a to 8h located between the terminals 4 and 6. Therefore, for signal output, resistor 8a-8h and resistor 9
Only the phase difference between a and 9h appears and the amplitude is constant, resulting in a sufficiently stable signal as an output.

Figure 3 is 2a! This is an example of a magnetic sensor element that can extract similar signals (A-phase output and B-phase output).

Inside the element, there are resistors 14a to 14h and 15 as magnetically sensitive parts.
There are four types: a to 15h, 16a to 16h, and 17a to 17h, and the physiognomic output is resistor 16a to 16h and 17a to 17h.
In the series connection of
When a to 15h are connected in series, it can be taken out from the signal terminal 19 as a three-terminal output. The A-phase and B-phase signals have a phase difference of 90 degrees in electrical angle. The mechanism for generating signals for the human phase or B phase, respectively, is the same as in the embodiment shown in FIG.

FIG. 4 shows an example of a magnetic sensor incorporating a bridge circuit. The arrangement of the magnetic sensing part resistors is resistors 20a to 20h.
The phase difference between and 21a to 21h is (η+1/12)λ(
η: integer, λ: Jf magnetic pitch), and the resistance is 22
The relationship between a to 22h and resistors 23a to 23h is also the same.

On the other hand, the resistors 20a to 20h and the resistors 23a to 23h are arranged so as to obtain signals of exactly the same phase, and the resistors 21a to 20h are arranged so as to obtain signals of exactly the same phase.
The relationship between 21h and resistors 22a to 22h is also the same.

By using the bridge circuit, it is possible to improve the stability of the element with respect to the ambient temperature, and moreover, the amplitude of the output signal can be doubled compared to the case of the embodiments shown in FIGS. 1 and 3. Figure 1.

In either of the embodiments shown in FIGS. 6 and 4, since the magnetically sensitive resistors are arranged around the entire circumference of the rotating disk plate, stable signal output without amplitude fluctuations can be obtained. In the embodiment shown in FIG. 4, when taking out the A-phase and B-phase signal outputs, 32 g'g1 part resistors are added in total, and the phase relationship between them is the same as in the embodiment shown in FIGS. 1 and 3. This can be obtained by arranging a configuration that satisfies the following conditions. Figures 1 and 6.

In the case of the embodiment shown in FIG. 4, one magnetically sensitive portion resistance is divided into eight parts. For example, in FIG. 1, it is divided into eight parts 8a to 8h. The larger the number of divisions, the more stable the amplitude of the output signal can be obtained, and the greater the overall resistance value, making it possible to realize a magnetic sensor with low oil *'nt and force. Effects] According to the present invention, in a magnetic sensor using a rotating magnetic disk, it is possible to reduce the amplitude fluctuation of the output coefficient to almost zero, which could not be achieved in the past, and the stability of the output signal is significantly improved. It can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the magnetic sensor element according to the present invention, FIG. 2 is an assembled diagram of the magnetic sensor element and rotating magnetic disk according to the present invention, and FIG. 6 is a plan view showing another embodiment of the magnetic sensor element according to the present invention. 4 is a plan view of another embodiment of the invention, FIG. 5 is an explanatory diagram for the embodiment of the present invention, and FIGS. 6 and 7 show problems with conventional sensors. Explanatory diagram, No. 8
9 and 9 are configuration diagrams of a conventional magnetic sensor. 1: Magnetic sensor element 2: Rotating magnetic disk 3: Rotating shaft 4: N, source terminal 5: Ground terminal
6: Signal output terminal 7: Rotating magnetic drum 8.9.14~17.20~26: Magnetic sensing part resistance 10~1
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Claims (1)

[Claims] 1. A rotating magnetic disk having a magnetic layer on the disk surface and magnetized at a constant pitch, and a magnetically sensitive disk placed opposite to this disk. In a magnetic rotation sensor in which the magnetic sensing part is formed on the surface of a plate-shaped support using a metal thin film pattern, a thin conductor wire, or both, the magnetic sensing part is radially spaced from the center of rotation and at constant intervals over the entire circumference. A magnetic sensor characterized by being arranged in. 2. A magnetic rotation sensor according to claim 1, characterized in that the detection circuit from the magnetic sensing part to the signal output terminal has a three-terminal configuration. 3. A magnetic rotation sensor according to claim 1, characterized in that the detection circuit from the magnetic sensing part to the signal output terminal is a bridge type circuit.