JPH01145519A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To enable the suppression of effect of adjacent magnetic poles, by arranging material having a magnetic shielding effect at a position separated by a width (t) or 3p/4 (p: pitch of magnetic pole) of an amorphous magnetic body before and after thereof across the width thereof. CONSTITUTION:This apparatus comprises a magnetizing member 1 with numerous magnetic poles so magnetized as to be inverted alternately in the direction of a magnetic field arranged on the surface of a moving object, a magnetic body comprising an amorphous wire 5 disposed in proximity to the magnetization member 1 and a detection winding 4 wound on the magnetic body. Then, the direction of magnetizing a magnetic pole formed on the magnetization member 1 is made at the right angle to the movement of the moving object and the width of the amorphous magnetic body along the movement of the magnetic pole is represented by (t) and the pitch of the magnetic pole (p), a material 7 is arranged having an effect of shielding magnetism caused by a magnetic recording medium other than a magnetization pattern to be detected partially or wholly at a position separated by (t) or 3p/4 before or after an amorphous magnetic body across the width (t) thereof. This can suppress a drop in an output signal due to the effect of adjacent magnetic poles.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to driving equipment such as robots and machine tools;
The present invention relates to a magnetic encoder for detecting the speed and position of a control motor.

[Conventional technology]

In order to improve the control accuracy of motors that perform rotational or linear motion built into robots and machine tools, there is a need for a detector that can instantaneously and accurately measure the position and speed of these motors.

As such a detector, there are a type using a magnetoresistive element and a photoelectric type.

The former method is a method in which the strength of a periodic magnetic field from a moving magnetized member subjected to multipolar magnetization is detected as a voltage change using a magnetoresistive element.

However, in the case of this method, when the magnetic pole pitch becomes smaller due to higher resolution, the change in the strength of the magnetic field becomes smaller, so the output voltage is low and there is a problem that it is easily affected by noise. Furthermore, since current must always flow through the magnetoresistive element, there is also the problem of power consumption.

In response, a system has been proposed that generates high output even with small changes in magnetic field and consumes zero power (Japanese Patent Laid-Open No. 61-266914). This system includes a magnetized member that generates a periodic magnetic field, an amorphous magnetic material located close to the magnetized member, and a pickup coil wound around the amorphous magnetic material.

In this method, as the magnetization member rotates, the magnetic field acting on the amorphous wire reverses, so a pick-up coil extracts the magnetic flux change as a voltage change, and the signal is used to detect the position.

On the other hand, a photoelectric detector consists of a metal film deposited on a glass disk, an optical slit made by photophosphorography, a light emitting diode, and a photodiode bud as a light receiving element. However, this photoelectric detector has the drawbacks that the glass disk is susceptible to impact, that it is impossible to make it thin due to the arrangement of the light emitting and light receiving elements, and that it cannot be used at high temperatures of 80° C. or higher.

In recent years, with the miniaturization of robots and manipulators, there has been an increasing need for detectors to have improved heat resistance and smaller size and higher resolution. To meet these demands, we developed a drum with a magnetization pattern written on it and an amorphous wire.

Mouri Yoshino proposed a magnetic encoder that combines a multivibrator and a pickup coil.

Okuda: Summary of the 10th Japanese Society of Applied Magnetics Academic Lectures.

11 (1986), 57).

In this detector, changes in the magnetic field of each magnetic pole will be detected by each amorphous wire connected in parallel.

Therefore, output fluctuations corresponding to changes in the magnetic field caused by vibration of the shaft or eccentricity of the rotating drum are canceled out, and a high-resolution output signal can be obtained. Also, this detector
Since the amorphous wire used has good heat resistance, it can be used in high-temperature atmospheres, for example up to 200°C.

[Problem that the invention seeks to solve]

By the way, when trying to achieve high resolution with the magnetic encoder of the method proposed in the above-mentioned Japanese Patent Application Laid-open No. 61-266914,
As the pitch p of the magnetic poles decreases, the magnetic flux passing through the amorphous wire decreases in proportion to e x /p as the spacing, that is, the distance iX between the rotating disk and the amorphous wire increases. Therefore, variations in output voltage occur due to variations in spacing, leading to reading errors, which has been a major problem in achieving high resolution.

This spacing problem also occurs in the magnetic encoder proposed by Yoshino et al. That is, when increasing the resolution of the magnetic encoder, twice as many amorphous wires as the number of magnetic poles are required, and they must be arranged around the rotating drum. This is necessary to prevent output fluctuations in response to changes in the magnetic field caused by shaft wobbling or eccentricity of the rotating drum. Conversely, the higher the resolution, the greater the number of magnetic poles. Therefore, if the number of magnetic poles is increased, this problem becomes even more serious. For example, if 400 magnetic poles are installed on a rotating body with a diameter of 60, each magnetic pole will be 470-, so the diameter will be 2.
It is necessary to prepare 800 0[1-'r amorphous wires and arrange them around the rotating drum.

The present inventor has proposed a method in which the magnetization direction of the magnetization member is formed perpendicular to the moving direction of the magnetization member, with the aim of suppressing the variation □ in the output voltage due to such spacing variation and achieving high resolution. was proposed first.

FIGS. 10 and 11 are schematic diagrams thereof. In these examples, the direction of movement of the rotating body 10.20 and the direction of the magnetic field entering the amorphous wire 11.21.22 from the magnetization member are perpendicular. Note that 12, 23, and 24 are search coils, respectively.

However, as shown in Figure 10, 1
As the magnetic pole pitch in one magnetization pattern row is made smaller, magnetic fields from (b) and (C) in opposite directions enter part (a), so the magnetic field in part (a) becomes weaker and the magnetic field in part (d) becomes smaller. There was no difference, and there was a limit to higher resolution. This also applies to the example shown in FIG.

The present invention has been made in view of such conventional problems, and an object thereof is to suppress the influence of adjacent magnetic poles.

[Means for solving problems]

In order to achieve this object, the magnetic encoder of the first invention of the present application includes a magnetized member formed on the surface of a moving body and magnetized with a large number of magnetic poles so that the direction of the magnetic field is alternately reversed, and a magnetized part of the magnetized member. In a magnetic encoder that includes a magnetic body made of an amorphous wire disposed in close proximity to each other and a detection winding wound around the magnetic body, the magnetization direction of the magnetic pole formed on the magnetization member is determined by the magnetization direction of the magnetic pole formed on the magnetization member. The direction is perpendicular to the direction of movement,
When the width of the amorphous magnetic body along the moving direction of the magnetic pole is t1 and the pitch of the magnetic pole is p, a detection target is placed in part or all of the positions t to 3p/4 away from the front and back of the amorphous magnetic body in the width direction. It is characterized by disposing a material having a magnetic shielding effect that shields magnetism caused by a magnetic recording medium other than the magnetization pattern.

The second invention of the present application also provides a magnetic recording medium in which at least one magnetization (turn sequence) is written at a constant pitch while moving together with the moving body, and a winding arranged close to the magnetic recording medium. a multi-vibrator that converts a change in magnetic flux acting on the winding into a change in oscillation frequency; .

In a magnetic encoder that detects speed, the magnetization direction of the magnetic pole formed on the magnetic recording medium is parallel to the magnetization pattern row direction and perpendicular to the moving direction of the magnetic recording medium, and When the width of the amorphous magnetic material along the line is t, and the pitch of the magnetic poles is p, the front and rear of the amorphous magnetic material in the width direction is from t to p/2.
A material having a magnetic shielding effect that shields the magnetism caused by the magnetic recording medium other than the magnetization turn to be detected is disposed at a part or all of the position separated by the distance.

In either of the first and second inventions, a superconducting material can be used as the material having the magnetic shielding effect, and the Meissner effect can be used to perform the magnetic shielding.

〔Example〕

Hereinafter, the features and effects of the present invention will be explained in detail based on each embodiment shown in the drawings.

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a magnetic encoder corresponding to the first invention of the present application. In this figure, 1
For example, a resin 3 containing a magnetic material such as CO-γFe2O3 is placed on the surface of a drum 2 made of a non-magnetic material such as aluminum.
It is a magnetized member coated with 00 ts, and is magnetized in the direction of the arrow in the figure (the size represents the degree of magnetization strength).

The magnetization pitch p was set to 200 to 600p.

Near the magnetizing member 1, there are 130 wires (Pea, 5cOo, 5hss+) wound with copper wire of 51bcm in diameter.
A sensor section 6 is formed by arranging an amorphous wire 5 having a +o B+s composition. A magnetic shielding material 7 made of permalloy foil having a thickness of 30 IETI was placed on the outside of the winding 4 along the moving direction of the magnetized member 1. FIG. 2 shows a detailed sectional view. 8 in the figure is a molding material. In FIG. 2, a magnetic shielding material 7 with a height equal to the length of the amorphous wire 5 is installed. FIG. 3 shows an example in which the magnetic shielding material is provided only in the vicinity of the drum 2.

FIG. 4 shows the effect of the magnetization pitch p on the output during magnetization reversal for these magnetic encoders in comparison with a conventional example that does not use a shield. As shown in the figure, it was found that the output could be stably obtained even when the magnetization pitch was small. Next, the influence of the position of the shield material was investigated with the magnetization pitch p kept constant at 200-. Figure 5 shows the results.

3/4 of the magnetization pitch p from the same distance as the amorphous wire diameter
An output greater than the noise level was obtained between the two. This is thought to be because if the shielding material is too close to the amorphous wire, it will also shield the magnetic flux that should enter the amorphous wire, and if it is too far away from the amorphous wire, the shielding effect will be lost. No difference can be seen between the two embodiments shown in FIGS. 2 and 3.

FIG. 6 is a schematic diagram showing an embodiment of a magnetic encoder corresponding to the second invention of the present application. In this figure, l is a magnetized member in which a Co-P film is plated to a thickness of 15p as a magnetic film 9 on the surface of a drum 2 made of a non-magnetic material such as aluminum, and this magnetic film 9 is in a state in which the direction of the magnetic field is alternately reversed. Multipolar magnetization is applied. Magnetization width is 200 ts ~ 70
It was varied between 0-.

The track length was kept constant at 700p. The size of the arrow indicates the strength of magnetization. Near the magnetization member 10 is a coil with a diameter of 200p (:07oFt:ssI) with a winding 4 attached.
t.

BI! Two amorphous wires 5 of the same composition are arranged, and a magnetic shielding material 7 is provided on the outer side of the winding in the moving direction of the magnetized member 1. FIG. 7 shows a detailed sectional view of the sensor section 6. 7(a) and 7(a) respectively show a case where the length of the magnetic shielding material 7 is made equal to the entire length of the amorphous wire 5, and a case where it is made only near the drum 2. Magnetic shielding material 7
20-2 permalloy foil was used, and the entire sensor portion was hardened with molding material 8.

FIG. 8 shows a comparison of the magnetization pitch p which affects the output value of these magnetic encoders with that of a conventional example without a shield. As shown in the figure, it was found that a high output signal could be obtained even at a small magnetization pitch p.

Next, the influence of the position of the shielding material was investigated by keeping the magnetization pitch p constant at 600 tones. The results are shown in Figure 9. An output greater than the noise level was obtained from the same distance as the amorphous wire diameter to 1/2 of the young pitch p. This is thought to be because if the shielding material is too close to the amorphous wire, the shielding material will also shield the magnetic flux that should enter the amorphous wire, and if it is too far away from the amorphous wire, the shielding effect will be lost.

Although permalloy is used as the magnetic shielding material 6 in the embodiment, it is clear that other soft magnetic materials or superconducting materials may be used. That is, since superconducting materials have the Meissner effect, it is possible to achieve complete magnetic shielding.

In this case, the distance between the MR film and the magnetic shielding material is t~3/
If it is within 4P, the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As explained above, the magnetic encoder of the present invention includes a material that shields the magnetic flux from the magnetic recording medium adjacent to the magnetic pole of the magnetic field to be detected, near the amorphous wire that detects the magnetic field leaking from the magnetic recording medium. We are planning to establish a Therefore, it is possible to suppress a decrease in the output signal due to the influence of adjacent magnetic poles. Therefore, it is possible to obtain a large output signal, and high resolution can be achieved. Further, by using a superconducting material as a shielding material, complete magnetic shielding can be achieved due to its Meissner effect.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a magnetic encoder showing an embodiment of the first invention of the present application, FIGS. 2 and 3 are sectional views thereof, FIGS. 4 and 5 are views showing its effects, and FIG. 6 is a perspective view of a magnetic encoder showing an embodiment of the second invention of the present application, FIG. 7 is a sectional view of the sensor section, FIGS. 8 and 9 are views showing the effects of the present invention, and FIGS. 10 and 11. is a schematic diagram of a magnetic encoder previously proposed by the present inventor. 1: Magnetizing member 2 Drum 3: Resin containing magnetic material 4: Winding wire 5: Amorphous wire 6: Sensor section 7: Magnetic shielding material 8: Mold material 9: Magnetic film Patent applicant Anyo Electric Manufacturing Co., Ltd. Agent
Masu Kobori (and 2 others) Fig. 10 Fig. 11, Fig. 1
) Figure 6 Figure 7 (a) (b) Figure 8 0 200 400 600
Bo. Magnetizing pitch + (μm) Figure 9

Claims (1)

[Claims] 1. A magnetized member that is formed on the surface of a moving body and has a large number of magnetic poles magnetized so that the direction of the magnetic field is alternately reversed, and an amorphous wire that is disposed close to the magnetized portion. In a magnetic encoder comprising a magnetic body and a detection winding wound around the magnetic body, the magnetization direction of the magnetic pole formed in the magnetized member is perpendicular to the moving direction of the moving body, and the magnetic pole The width of the amorphous magnetic material along the circumferential direction is t,
When the pitch of the magnetic poles is p, a magnetic field that shields magnetism caused by a magnetic recording medium other than the magnetization pattern to be detected is applied to a part or all of the amorphous magnetic body at positions spaced from front and back t to 3p/4 in the width direction of the amorphous magnetic body. A magnetic encoder characterized by arranging a material that has a shielding effect. 2. The magnetic encoder according to claim 1, wherein the material having a magnetic shielding effect is a superconducting material. 3. Moves together with the moving object and at least once at a constant pitch
a magnetic recording medium on which a magnetization pattern row is written; at least one amorphous magnetic material wound with a wire disposed close to the magnetic recording medium; and a multivibrator that detects the position and speed of the moving body by changing the oscillation frequency of the multivibrator, the magnetization direction of the magnetic pole formed on the magnetic recording medium is set in the direction of the magnetization pattern column. is parallel to and perpendicular to the moving direction of the magnetic recording medium, the width of the amorphous magnetic material along the moving direction of the magnetic pole is t, and the pitch of the magnetic pole is p. A material having a magnetic shielding effect that shields magnetism caused by a magnetic recording medium other than the magnetization pattern to be detected is arranged in part or all of the positions spaced apart from each other by t or p/2 in the width direction. magnetic encoder. 4. The magnetic encoder according to claim 3, wherein the material having a magnetic shielding effect is a superconducting material.