JPS63206613A - Absolute magnetic encoder - Google Patents

Abstract

PURPOSE:To obtain an encoder having a stable spacing characteristic by a method wherein the stripe length direction of a magnetoresistance (MR) element is made perpendicular substantially to the surface of a magnetic recording medium while the strip width direction thereof is made parallel to the direction of a magnetized pattern array. CONSTITUTION:A magnetic recording medium 1 is formed on the outer peripheral part of a drum 4 fixed to a rotating shaft 3, while an MR element 2 and a terminal 6 are formed on a glass substrate 5 and connected to a drive detector circuit 8 through a lead wire 7. The stripe length direction of the element 2 is made perpendicular substantially to the surface of the recording medium 1, while the stripe width direction thereof is made parallel to a magnetized pattern array of the recording medium 1. Arrows marked on the recording medium 1 represent the degree of intensity of magnetization and are magnetized by means of a ring head. On the occasion, the distribution of the intensity of magnetization shows a triangular shape in one magnetized pattern array, and a phase difference between first and second arrays is 90 deg.. Thus, a change in the resistance of the element 2 occurs in accordance with the intensity of magnetic field leaking from the recording medium 1. An output signal of this change is inputted to the circuit 8, and the position of a motor can be detected from the amplitude of the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an absolute position detector for drive and control motors in products such as robots and manipulators.

(Prior Art) There is a need for a detector that is built into a robot or manipulator and can instantaneously and accurately measure the absolute position of an actuator that performs rotational or linear motion. It is desirable that the encoder be large and have a full circumference.Therefore, photoelectric encoders have conventionally been used as suitable for such applications.This photoelectric encoder is made by photolithography of a metal film deposited on a glass disc. Since it consists of an optical slit, a light emitting diode, and a photodiode, the glass disk is vulnerable to shock, and since it uses diodes, it cannot be used at high temperatures, and the layout of the diodes makes it impossible to miniaturize. In order to eliminate these drawbacks, an absolute position detector was invented that combined a magnetic drum and a magnetoresistive element (hereinafter abbreviated as MR element) (Japanese Patent Application Laid-Open No. 118259/1982).
. However, even with this detector, it is difficult to miniaturize it, there are problems in terms of accuracy, and the number of lead wires from the MR element becomes very large, which causes wiring problems. On the other hand, the same M
A compact and lightweight encoder with fewer lead wires was developed using an R element (M&E).

6 (1985) P38).

[Problem that the invention seeks to solve]

As shown in FIG. 6, this encoder consists of a curved rotating yoke-shaped magnetic body 11 and an MR element 2 arranged at a constant distance along its circumference, and the magnetic field entering the MRR element 12 is applied to the rotational position. This takes advantage of the fact that the output value changes due to the change in the output value (because the magnetic body 11 has a curved shape). The stripe length direction of the MRR element 12 is aligned with the rotation direction of the magnetic body 11, and the MRR element surface is arranged parallel to the surface of the magnetic body. In such a structure, the distance between all the MR elements 12 and the rotating yoke-shaped magnetic body 11 must be kept constant, which requires precision in parts processing and assembly, resulting in high costs.Furthermore, since the MRR elements 12 are arranged on a curved surface, the diameter is small. As the technology grows, production becomes more difficult. The rotating yoke-shaped magnetic body 11 having a curved shape is similarly difficult to manufacture because its shape accuracy is related to the output accuracy of the MRR element 12. Also, in terms of characteristics, it is susceptible to spacing variations.

An object of the present invention is to provide a compact, lightweight, high-resolution magnetic encoder that is easy to manufacture and is less susceptible to spacing variations.

[Means for solving problems]

The absolute magnetic encoder of the present invention detects a magnetic field from a magnetic recording medium on which at least one magnetization pattern array having a magnetization gradient is written, using at least one striped MR element close to the recording medium, In an absolute magnetic encoder that detects the absolute position of a detected object based on the magnitude of its output value, the MR element stripe flame length direction is approximately perpendicular to the magnetic recording medium surface, and the stripe width direction is parallel to the magnetization pattern row direction, It is characterized in that a magnetic field from a magnetization pattern is applied in the stripe width direction.

[Effect]

Therefore, the MR element only needs to be made on a flat surface, and a curved magnetic recording medium is no longer necessary, making it possible to manufacture a magnetic encoder at low cost.Furthermore, by adopting this structure, it is possible to reduce spacing variations. Output fluctuation is no J)
Therefore, the encoder can be made smaller.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of the absolute magnetic encoder of the present invention, and FIG. 2 is a waveform diagram of an output signal of the embodiment of FIG.

In this embodiment, an aluminum alloy drum 4 fixed to a rotating shaft 3 and Go-γFe, 03i
A detection head consisting of a B air recording medium 1, an MRR element 2 formed of an 81Ni-Fe film on a glass substrate 5, and a terminal 6 formed of a Cu film, and a lead wire 7 connected to the terminal 6. It consists of a drive detection circuit 8, and the stripe length direction of the MRR element 2 is substantially perpendicular to the surface of the magnetic recording medium 1, and the stripe width direction is parallel to the magnetization pattern row of the magnetic recording medium 1. The arrows marked on the magnetic recording medium 1 indicate the strength of magnetization, and magnetization was performed using a ring head. In this case, the magnetization strength distribution has a triangular shape within one magnetization pattern row, with the first and second rows having a triangular shape.
The phase difference between the rows is 90°. In such a configuration, the resistance of the MRR element 2 changes depending on the strength of the magnetic field leaking from the magnetic recording medium 1, and an output signal as shown in FIG. 2 is obtained. The solid line portion of this signal is divided on the circuit, and the position of the motor can be detected from the size. Next, when the magnetization distribution within the magnetization pattern array was made sinusoidal and the signal was looked at, the same waveform as in FIG. 2 was obtained.

FIG. 3 shows the MRR element 2 and magnetic recording medium 1 in this embodiment.
FIG. 3 is a diagram illustrating the relationship between output voltage and spacing in comparison with a conventional example. It can be seen that the output fluctuation of this embodiment is smaller and more stable than that of the conventional example.

FIG. 4 and FIG. 5 show a drum 1 in another embodiment of the present invention.
FIG. 3 is a diagram showing the distribution of magnetization strength per rotation.

FIG. 5 shows the addition of signals from two rows of magnetization patterns on the disk, and FIG. 4 shows an example in which the strength of magnetization is changed continuously within one rotation.

〔Effect of the invention〕

As explained above, in the present invention, the length direction of the MR element stripe is substantially perpendicular to the surface of the magnetic recording medium, 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. By doing so, it is possible to manufacture an inexpensive, high-precision encoder with easy manufacture of MR elements and magnetic recording media, and stable spacing characteristics.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment of the absolute magnetic encoder of the present invention, Fig. 2 is a waveform diagram of an output signal of the embodiment of Fig. 1, and Fig. 3 is a spacing and output of the embodiment of Fig. 1. 4 and 5 are waveform diagrams of output signals of other embodiments of the present invention, and FIG. 6 is a sectional view showing the inside of the conventional example. 1... Magnetic recording medium, 2... MR element, 3... Rotating shaft, 4... Drum, 5... Substrate, 6...terminal, 7...lead wire, 8...drive detection circuit.

Claims (1)

[Claims] 1. A magnetic field from a magnetic recording medium on which at least one magnetization pattern array having a distribution of magnetization strength is written is applied to at least one striped magnetic resistor in close proximity to the recording medium. In an absolute magnetic encoder that uses an effect element to detect the absolute position of an object based on the magnitude of its output value, the length direction of the stripe of the magnetoresistive element is approximately perpendicular to the surface of the magnetic recording medium, and the width direction of the stripe is approximately perpendicular to the surface of the magnetic recording medium. An absolute position magnetic encoder characterized in that a magnetic field from the magnetization pattern is applied in the stripe width direction parallel to the magnetization pattern row direction. 2. The absolute magnetic encoder according to claim 1, wherein the magnetization pattern array has a triangular distribution of magnetization strength. 3. The absolute magnetic encoder according to claim 1, wherein the magnetization strength distribution of the magnetization pattern array is a sine wave.