JPH01119715A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To increase magnetoresistance effect, by introducing much magnetic flux to the MR element stripe part more remote from a magnetic recording medium. CONSTITUTION:In this encoder, a magnetoresistance effect element 2 forms an angle of 90 deg. with respect to the surface tangential direction of a magnetic recording medium 7 and soft magnetic films 3 are applied from the vicinities of the N- and S-poles of the medium 7 to the vicinities of the stripes of the element. At this time, the trapezoidal magnetic films 3 are arranged along the outsides of two stripes of the element 2. In each these magnetic films 3, the relation of W2>W1 is provided between the width W1 of the side thereof near to the medium 7 and the width W2 of the side thereof remote from the medium 7 and the sides opposed to the stripes are made parallel to the stripes. In this case, the area on which interlinkage magnetic flux acts by a magnetized pattern becomes gradually wide from the part near to the medium 7 to the part remote therefrom and much magnetic flux is introduced to a part more remote from the medium 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic encoder that detects the speed and position of a drive or control motor in, for example, a robot or a manipulator.

[Conventional technology]

2. Description of the Related Art There has been a demand for a detector that can instantaneously and accurately measure the position and speed of an actuator that performs rotational or linear motion and is incorporated into a robot or manipulator.

Conventionally, photoelectric type detectors have often been used as such detectors. This photoelectric detector consists of a metal film deposited on a glass disk, an optical slit made by photolithography, a light emitting diode, and a photodiode as a light receiving element, so the glass disk is vulnerable to shock. , light emitting diode.

Due to the arrangement of the light receiving element, it is impossible to make it thinner, and the temperature at 80°C
The drawback was that it could not be used at higher temperatures.

In recent years, with the miniaturization of robots and manipulators, the need for improved heat resistance and smaller size and higher resolution detectors has increased. In response to such demands, a magnetic encoder was developed that combines a drum on which a magnetization pattern is written and a magnetoresistive element (hereinafter referred to as MR hydrogen element) (Japanese Patent Application Laid-Open No. 115257-1983).

The detector includes a rotating body that rotates in conjunction with a rotating shaft and has a magnetic recording medium on which a magnetization pattern is written at a pitch P;
It is composed of MR hydrogen elements that detect the periodic magnetic field distribution leaking from this magnetization pattern, and the actual length direction of the MR element stripe is perpendicular to the direction of the magnetic field, and the width direction of the stripe is parallel to the circumferential direction of the rotating body. ing. In such a configuration, when the magnetic field Hex from the magnetic recording medium is applied to MR hydrogen atoms, the magnetic field Herb' entering the MR hydrogen atoms becomes Herr -Hex-Hd, where Hd is the demagnetizing field (Japanese Patent Laid-Open No. 57-197885 ).

Here, the pattern width of the MR cord is W, and the film thickness is t.

When the MR hydrogen ion saturation magnetic field is Is, the demagnetizing field Hd is Hd-4πIs φ □, so the magnetic field Hef'f' becomes Hcff -Hex-4yr Is ·-. That is, as the pattern width W becomes smaller, the demagnetizing field Hd becomes larger and the magnetic field Hef'l' becomes smaller, resulting in a decrease in the MR hydrogen element output. Normally, twice the pattern width W can be considered as a position reading unit, so in such a structure, the MR pattern width is 10 μm as the limit, so 20 μm is the position reading unit. Since the required resolution is several μm, this is not possible with this structure. Furthermore, since the distance between the MR hydrogen magnetic recording media must be several tens of micrometers, the MR hydrogen magnetic recording media may come into contact with each other during assembly of the magnetic encoder, causing the MR hydrogen atoms to be destroyed.

Therefore, the present inventors first invented a magnetic encoder that can solve this problem (Japanese Patent Application No. 62-39180, Japanese Patent Application No. 62-39180,
-39178, hereinafter referred to as the "first precedent").

The main parts of the first prior example magnetic encoder are shown in a perspective view in FIG. 3, for example.

The periodic magnetic field from the magnetic recording medium 7 on which at least one magnetization pattern array is written with a pitch P is generated at least in the vicinity of the magnetic recording medium so as to generate a periodic magnetic field according to the required position reading accuracy. one striped M
In a magnetic encoder whose output is converted by an RR element 2,
The actual length of the MR element strip is g, and the magnetic recording medium and MR
When the closest distance of the R element 2 is g, the stripe length direction and the magnetic recording medium surface surface line direction at the closest point are 90°.
The stripe width direction is parallel to the magnetization pattern column direction, and the magnetic field from the magnetization pattern is applied in the stripe width direction. In FIG. 3, four striped MRR elements 2 are connected by forming three folded parts and output as one MRR element 2, and the arrow and length shown on the magnetic recording medium 7 are in the magnetization direction. (magnetization direction pattern) and size, and the curved dotted line represents the magnetic recording medium 7.
This shows the state in which the magnetic flux generated from the magnetic flux is interlinked with the MRR element 1.

In the method of the first prior example, since the actual length direction of the MR element stripe is perpendicular to the surface of the magnetic recording medium, the magnetic field applied to the MRR element stripe portion located far from the medium surface becomes weaker. The entire MRR element could not be used effectively, and the output signal was insufficient.

Therefore, the larger the output signal is, the more reliable the magnetic encoder becomes, which is more resistant to noise.

Therefore, as shown in a perspective view of the main part in FIG. 4, the present inventors guided magnetic flux from the vicinity of the N and S poles of the magnetic recording medium to the vicinity of the MRR element 2 with a soft magnetic film 3, The MRR element 2 is configured so that a magnetic field is applied uniformly in the width direction of the stripe pattern, and the magnetic field from the magnetic recording medium 7 is received by the entire MRR element stripe and used effectively (Japanese Patent Application No. 62-42908 , Japanese Patent Application No. 62-42910 (hereinafter referred to as "second precedent example") (Problem to be solved by the invention) However, in the method of this second cited example, the soft magnetic film 3 that induces the magnetic field One end and the other end of the MR element near the MRR element 2 in the same direction as the strike flame length direction are respectively MRR
Since they correspond to one end and the other end in the length direction of the child stripe, the magnetic field induced by the soft magnetic film 3 was almost the same in both the near and far parts of the MRR child stripe from the magnetic recording medium 7.

Therefore, the magnetic field from the magnetic recording medium was still insufficient in the part of the MRR element stripe far from the magnetic recording medium 7, and the output of the MRR element as a whole was not sufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the drawbacks of the prior art and its predecessors and to provide a magnetic encoder with increased magnetoresistive effect.

[Means for solving problems]

The present invention applies a periodic magnetic field from a magnetic recording medium in which at least one magnetization pattern array is written at a pitch P to the magnetic recording medium so as to generate a periodic magnetic field in accordance with the required position reading accuracy. In a magnetic encoder that converts output using at least one striped magnetoresistive element, the length direction of the stripe of the magnetoresistive element and the linear direction of the surface surface of the magnetic recording medium at the closest point between the magnetoresistive element and the magnetic recording medium. The angle formed by the magnetic recording medium is approximately 90@, and the stripe width direction is parallel to the magnetization pattern column direction, and the magnetic field from the magnetization pattern is applied in the stripe width direction, and the magnetic field is applied from the vicinity of the N and S poles of the magnetic recording medium. A soft magnetic film is applied to the vicinity of the stripe of the resistive effect element, and this soft magnetic film has a shape in which the width of the soft magnetic film in the stripe width direction increases from the side closer to the magnetic recording medium along the stripe length direction. It is an encoder.

[For production]

Since the MRR child stripe portion far from the magnetic recording medium induces more magnetic flux, the magnetoresistive effect increases and the output of the magnetic encoder increases.

〔Example〕

FIG. 1 is a perspective view showing the configuration of essential parts in an embodiment of the present invention.

A magnetic recording medium 7 is formed by uniformly applying CO-γFe2O3 on the outer peripheral surface of a cylindrical aluminum alloy drum 8 that is fitted and fixed to a shaft 9 of a rotating body whose speed and position are detected. At least one magnetization pattern array 6 is written on the magnetic recording medium 7 at a pitch P (not shown) so as to generate a periodic magnetic field according to the required position reading accuracy.

The MRR element 2 has a striped circuit pattern on the surface of the glass substrate 1 as shown in the figure, and the two stripes are folded back near the magnetic recording medium 7 to form a U-shape. A lead portion 4 is provided to lead out the wire.

Then, along the outside of the two MRR child stripes 2,
A trapezoidal soft magnetic film (induction film) 3 is provided.

This induction film 3 has a characteristic in its shape and position, and the width W1 of the side near the magnetic recording medium 7 and the width W2 of the side far from the magnetic recording medium 7 are Wl>W
The side that satisfies the relationship 1 and runs opposite to the MRR element stripe 2 is parallel to the MR element stripe 2 in this embodiment.

In such an induction film 3, the area on which the magnetic flux linkage due to the magnetization pattern 6 acts gradually increases from the area closer to the magnetic recording medium 7 to the farther from the magnetic recording medium 7.
The R stripe 2 portion is designed to induce more magnetic flux.

A perspective view showing a partial configuration of another embodiment of the present invention is shown in FIG. 1(b).

In this other embodiment, the same shaft 9 is used in two sets of detection mechanisms.
The form of the magnetization pattern 6 magnetized on the two magnetic recording media 7 is different from that shown in FIG. 1(a). Although the width of each dielectric film 3 is W1 and W2, in this other embodiment, the side facing and running along the MRR stripe 2 is inclined, and the opposite side is MR
It is parallel to the elementary stripe 2.

The effect is the same as that shown in FIG. 1(a).

FIG. 1(c) is a perspective view showing the configuration of essential parts of another embodiment of the present invention.

In this other embodiment, information is written in sections with magnetization patterns (sections with arrows) and sections without magnetization patterns (sections with no arrows), and the direction of the arrow represents the direction of the magnetic field, and each The shape of the guiding film 3 is the same as that shown in FIG. 1(a).

The effect of the induction film 3 on the MRR child pattern 2 is as described above.

By the way, the MRR element 2 is made by forming an 81.7% Ni-Fe alloy film to a thickness of 600 mm on the glass substrate 1 by sputtering, and then patterning the 8941 portion 2 dielectric film 3 on the MR element by photolithography. Furthermore, the lead portion 4
was formed from a Cu film.

The ends of the induction film 3 are placed near the north and south poles of the magnetization pattern 6 recorded on the magnetic recording medium 5, and the other end is placed near the 8941 portion 2 on the MR element to form a trapezoidal shape. is as described above. The lines of magnetic force coming out from the north pole of the magnetization pattern 6 pass through the induction film 3 and enter the south pole of the magnetization pattern 6.

In the present invention, the width of the guiding film 3 near the magnetization pattern 6 along the stripe width direction is Wl, and the width of the opposite end is W
Regarding, Fig. 1(a) shows W1=20μm, W2-4
0μm, Figure 1(b) is W -20μm, W2-60
μm, Figure 1(c) is W -20μm, W2-80μ
m, and as a conventional example, wl-w for FIG. 1(a),
, -40 μm, Figure 1(b), for wl-wl-6
In contrast to 0 μm and FIG. 1(C), a wl-wl-80 μm one was prepared and the two were compared.

FIG. 2 shows a characteristic diagram comparing the output of the magnetic encoder of the present invention shown in FIGS. 1(a), 1(b), and 1(c) with the conventional example and under the conditions described above. a/ on the horizontal axis in the figure,
b/ and c/ are respectively shown in Fig. 1 (a), (b),
It is an example of the output characteristic of the magnetic encoder corresponding to (c).

As described above, the output of the magnetic encoder of the present invention is larger than that of the conventional example.

In each embodiment, the material of the MRR element 2 and the dielectric film 3 is the same N.
Although an i-Fe alloy film is used, the induction film 3 is a soft magnetic film such as Ni-Co, Co-Zr-Nb, Co-Zr-
It is clear that Mo, Fe, Co, Ni, etc. may also be used. The same applies to insulating magnetic films.

〔Effect of the invention〕

As explained above, it is clear that the magnetic encoder having the structure according to the present invention has a large output, is resistant to noise, and is advantageous even when the output value is electrically divided to achieve high resolution. A significant effect can be achieved in that the reliability as a magnetic encoder is significantly improved.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are perspective views showing the configuration of essential parts of one embodiment, another embodiment, and another embodiment of the present invention, and FIG. Output characteristic diagrams for each embodiment of the invention compared to the conventional example, and FIGS. 3 and 4 are explanatory diagrams of the conventional example. 1... Glass substrate, 2... Magnetoresistive element (MR
element, MRR element stripe), 3... soft magnetic film (induced film), 4... lead part, 6... magnetization pattern, 7.
... Magnetic recording medium, 8... Aluminum alloy drum, 9... Shaft. Applicant's representative Mr. Sato (b) Figure 1 (C,) Figure 1 Figure 2

Claims (1)

[Claims] 1. Magnetic recording of a periodic magnetic field from a magnetic recording medium on which at least one magnetization pattern array is written at a pitch P so as to generate a periodic magnetic field according to the required position reading accuracy. In a magnetic encoder that converts output using at least one striped magnetoresistive element close to a medium, the length direction of the stripe of the magnetoresistive element, the magnetic recording medium, and the magnetic recording medium at the closest portion of the magnetoresistive element. The angle formed with the surface line direction is approximately 90 degrees, the stripe width direction is parallel to the magnetization pattern column direction, the magnetic field from the magnetization pattern is applied in the stripe width direction, and the N and S poles of the magnetic recording medium A soft magnetic film is applied from the vicinity of the magnetoresistive element to the vicinity of the stripe of the magnetoresistive element, and the width of the soft magnetic film in the stripe width direction increases from the side closer to the magnetic recording medium along the length direction of the stripe. A magnetic encoder characterized by its shape.