JPH01185414A - Magnetic type rotary encoder - Google Patents

Abstract

PURPOSE:To reduce the variation of an output waveform and to enhance resolving power, by arranging at least three sets of magnetic sensors to one magnetic rotary body and connecting the MR elements of said magnetic sensors in series. CONSTITUTION:When a magnetic rotary body 1 is rotated, respective MR elements 21a-24b generate a change in a resistance value due to a change in the intensity of the magnetic field of said rotary body and AC waveforms appear at output terminals. At this time, the variation of the change in the resistance value of a magnetic sensor 2a is low with respect to magnetic sensors 2b, 2d and the variation of the change in the resistance value of a magnetic sensor 2c is large corresponding thereto. That is, AC outputs are varied with the rotation of the magnetic rotary body 1 but averaged as a whole to obtain stable output. By this method, the variation of an output waveform is reduced to make it possible to impart excellent resolving power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic rotary encoder (hereinafter simply referred to as an encoder) that detects the rotation angle of a rotating body in information equipment, automation equipment, etc.

[Conventional technology]

Conventional examples of encoders are shown in FIGS. 3 to 6. Third
In the figure, the encoder is composed of two main elements: a magnetic drum 1 and a magnetic sensor 2, which are attached to the shaft of a rotating body, and the magnetic drum 1 and the magnetic sensor 2 are opposed to each other with a distance apart. The magnetic drum 1 has north and south poles alternately magnetized at a constant pitch λ on the circumferential surface of a rotating drum attached to the shaft of a rotating body, and the pitch λ is an electrical angle π.

As shown in FIG. 5, the magnetic sensor 2 has a glass substrate 3 coated with an alloy having a magnetoresistive effect such as permalloy at λ/2.
Both magnetoresistive elements (
(hereinafter referred to as MR element) 21a.

21b are connected in series. In Fig. 4, a magnetic disk 4 is used instead of the magnetic drum 1, and N and S poles are alternately magnetized at a constant pitch λ on the circumference of the rotating disk, and the magnetic sensor 2 has already been magnetized. It is similar to that shown in FIG. 5 mentioned above. Since the operation of the magnetic disk 4 is almost the same as that of the magnetic drum 1, the magnetic drum 1 or the magnetic disk 4 is referred to as a magnetic rotating body.

The magnetic sensor 2 includes MR elements 21a, 2 as shown in FIG.
1b are connected in series and a DC voltage Vd is applied to both ends thereof, and the magnetic pole of the magnetic rotating body 1 is connected to both MR elements 21a and 2.
1b changes the resistance values of both MR elements 21a and 21b, so when the magnetic rotating body 1 rotates, an alternating current voltage Va is generated between the connection point of both MR elements 21a and 21b and one end of element 21b. .

By counting the frequency of this AC voltage, the rotation angle of the magnetic rotating body 1 can be detected. Generally, as shown in FIG. 6, in addition to both MR elements 21a and 21b, this MR element 21
a, shifted from 21b by λ/4 (electrical angle π/4) -
A set of MR elements 21c and 21d is provided, and by combining them, a two-phase alternating current consisting of A phase and B phase is obtained, and the A phase is λ/
The direction of rotation can be detected based on whether the phase B is advanced by 4 or whether the B phase is advanced by λ/4. Note that by doing so, it is also possible to increase the detection signal and improve the resolution of the encoder.

[Problem to be solved by the invention]

In recent years, encoders have been required to be compact and have high resolution. One way to obtain high resolution is to reduce the magnetization pitch λ of the magnetic rotating body and increase the frequency of the output voltage. However, if the magnetization pitch λ is made smaller, one magnetic pole becomes smaller, and the magnetic field acting on the magnetic sensor becomes weaker. Therefore, in order to increase the sensitivity, it is necessary to bring the magnetic sensor closer to the magnetic rotating body. In this case, there is a problem that the output fluctuates due to a change in the strength of the magnetic field due to slight eccentricity of the magnetic rotating body, or that the magnetic rotating body and the magnetic sensor come into contact with each other. Another method is to provide a plurality of magnetic sensors at intervals of λ/4 around the magnetic rotating body to increase the number of signals and obtain high resolution. However, this method assumes that the fluctuation of the output waveform due to the rotation of the magnetic rotating body is small, but in the case of a magnetic drum as the magnetic rotating body, there is eccentricity,
In the case of a magnetic disk, there is surface runout, and in either case, there is a problem in that the output waveform fluctuates and adjustment requires a large number of man-hours.

An object of the present invention is to provide an encoder that reduces fluctuations in output waveform and has excellent resolution.

[Means to solve the problem]

In order to solve the above-mentioned problem, the present invention provides a large number of magnetic poles at a constant pitch on the circumferential surface of a rotating drum or the circumferential edge of a rotating disk.
A magnetic rotary encoder is equipped with a magnetic rotary encoder that is a combination of a magnetic rotary body and a plurality of magnetoresistive elements installed around the magnetic rotary body and whose resistance value changes due to changes in the magnetic field caused by the rotation of the magnetic rotary body. In, there are few (
In each case, three sets of magnetic sensors are arranged around the magnetic rotating body at equal intervals at integral multiples of the magnetic pole pitch, and the magnetoresistive elements of each magnetic sensor are connected in series.

[Effect]

Changes in the output of the magnetic sensor are caused by the rotation of the eccentric magnetic rotating body, which changes the distance between the magnetic rotating body and the magnetic sensor installed around the magnetic rotating body, and the strength of the magnetic field acting on the magnetic sensor changes. So it happens. Therefore, if at least three sets of magnetic sensors are arranged around a magnetic rotating body at equal intervals at integral multiples of the magnetic pole pitch, and the MR elements of these magnetic sensors are connected in series, the output of each magnetic sensor will correspond to the rotation of the magnetic rotating body. However, the sum of these outputs remains constant, making it possible to obtain a high-resolution encoder.

〔Example〕

1 and 2 show an embodiment of the encoder according to the present invention, and the same parts as in FIGS. 3 to 6 are given the same reference numerals as in FIGS. 3 to 6. In Figure 1,
Around the magnetic rotating body 1, there is a magnetic sensor 2a consisting of MR elements 21a and 21b, a magnetic sensor 2b consisting of MR elements 22a and 22b, a magnetic sensor 2C consisting of MR elements 23a and 23b, and a magnetic sensor 24a and 24b. The magnetic sensors 2d are arranged at equal intervals of 90 degrees mechanical angle (an integral number n times the magnetic pole pitch λ), and the magnetic rotating body 1 has its magnetic poles separated from the magnetic sensor 2a due to eccentricity, and the magnetic sensor 2C
It shows a state close to . The MR elements 21a to 24b of each of the magnetic sensors 2a to 2d are connected in series as shown in FIG.
is applied. Further, the connection point between the MR element 24a and the element 24b is an output end of the AC voltage Va.

When the magnetic rotating body 1 rotates, each MR element 21a to 24b causes a change in resistance value due to a change in the strength of the magnetic field, and an alternating current waveform appears at the output end. At this time, sensors 2b and 2d
On the other hand, the variation in the resistance value change of the sensor 2a is small, and the variation in the resistance value change of the sensor 2C is correspondingly large. That is, if we focus on one sensor, the AC output will fluctuate as the magnetic rotating body 1 rotates, but as a whole, this is averaged out to obtain a stable output. Therefore, from the point of view of output stability, it is desirable to have a large number of sensors, but a minimum of three will provide considerable stability.

In this embodiment, each magnetic sensor 2a, 2b.

2c and 2d are each made up of two MR elements spaced apart by λ/2 for simplicity, but each of these magnetic sensors 2a, 2b, 2c, and 2d is composed of four magnetic sensors shown in FIG. By arranging magnetic sensors consisting of two MR elements at equal intervals and connecting them according to FIG. 2, high resolution can be obtained and the direction of rotation can also be detected.

〔Effect of the invention〕

According to the present invention, at least three sets of magnetic sensors are arranged for one magnetic rotating body, and the MR elements of the magnetic sensors are connected in series to combine their outputs. Even if the output of each magnetic sensor fluctuates as the drum or disk rotates due to eccentricity or surface runout of the magnetic disk, a stable output can be obtained as a whole. Therefore, it is possible to arrange a plurality of sets of each MR element of the magnetic sensor, increase the number of signals, and configure a high-resolution encoder.

In addition to the eccentricity of the drum and the surface runout of the disk, the causes of output instability include magnetization unevenness between each magnetic pole, but the present invention has the advantage that output instability due to magnetization unevenness can also be reduced. There is.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the encoder according to the present invention, FIG. 1 is a plan view showing its outline, FIG. 2 is a wiring diagram of the magnetic sensor shown in FIG. 1, and FIGS. The figures show an example of a conventional encoder, Fig. 3 is a perspective view showing an outline of an encoder using a magnetic drum, Fig. 4 is a perspective view showing an outline of an encoder using a magnetic disc, Figs. 6
The figures are plan views of different magnetic sensors. 1 Magnetic rotating body, 2 Magnetic sensor, 21a, 21b~2
4 a, 24 b MR element. Figure 1 Figure 2

Claims (1)

[Claims] 1) A magnetic rotating body with a large number of magnetic poles arranged at a constant pitch on the circumferential surface of a rotating drum or the periphery of a rotating disk, and a resistance value that is set around this magnetic rotating body and changes in the magnetic field due to the rotation of this magnetic rotating body. In the magnetic rotary encoder, at least three sets of magnetic sensors are arranged around the magnetic rotating body at equal intervals at integral multiples of the magnetic pole pitch. , a magnetic rotary encoder characterized in that the magnetoresistive elements of each magnetic sensor are connected in series.