JPH0599688A - Magnetic encode - Google Patents

Abstract

PURPOSE:To provide a compact magnetic encoder at a low cost. CONSTITUTION:The structure in which f1-fn are assigned to the frequency of magnetizing pitch in conformation to signals S1-Sn by magnetizing method of absolute signal is provided. Thus, the output from the element 5 of one MR sensor 3 of absolute which was a two-value signal can be changed to a multiple value signal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to magnetic encoders.

[0002]

2. Description of the Related Art A conventional magnetic encoder is constructed, for example, as shown in FIG. In this figure, 101 is a rotating drum, which can freely rotate around the axis of 102, and is surrounded by γ around the rotating drum 101.
A magnetic material such as —Fe ₂ O ₃ is provided and magnetized like the magnetization pattern 104. The magnetization pattern 10
4 is magnetized so that the magnetic poles NS alternate in the circumferential direction, and the respective patterns are recorded on a plurality of tracks. Reference numeral 103 denotes an MR (magnetoresistive element) sensor, which senses a change in magnetization of a magnetization pattern 104 formed around the rotary drum 101. Magnetoresistive element (hereinafter referred to as MR element) group 105
Permalloy or the like having a magnetoresistive effect is used as the material of (1) and is formed on the surface of the glass substrate 106 by a method such as vapor deposition. On the surface of the MR element 105, a film such as SiO ₂ is formed as a protective film. MR sensor 1
Reference numeral 03 is fixed in parallel to the side surface of the magnetic drum 101 with a distance of about 0.1 mm. The encoder type is a type that detects the position by an incremental signal and an absolute position signal (hereinafter referred to as an absolute signal).
There are three types, one with and one with both. As for the incremental signal, the number of rotations and the position can be known by counting the number of the same signal by repeating the same signal. On the other hand, the absolute signal reads the position information written on multiple tracks as a signal,
The position can be known without counting the signal. However, as shown in FIG.
In the case of an n-bit signal of a base number, one track requires one track, and therefore n tracks require n tracks. Therefore, a high resolution encoder requires many tracks and many MR elements 105.

FIG. 7 shows the arrangement of the magnetization pattern 104 and the MR element 105. Magnetization pattern 10
4 is divided into 110 to 122 tracks. The track 110 is an incremental signal track, and the tracks 111 to 122 are absolute tracks. 1
The signals of the tracks 10 to 122 are M of 130 to 142.
It can be read by the R element. Reference numeral 130 is an incremental pattern for each MR element of the MR element 105. The left and right sides of the figure are the circumferential directions of the rotary drum 101. The magnetization pattern 110 has a magnetic pole NS in the circumferential direction.
Are arranged alternately. The distance from the change N of the magnetic pole to the change S is defined as the magnetizing pitch M. The MR sensor is composed of rectangular MR elements, the long sides of the MR elements being arranged at right angles to the circumferential direction and arranged in the circumferential direction. Eight arrays are arranged at a pitch of M / 4 with respect to the magnetizing pitch M, and lead wires are connected to both ends of the MR element. A phase from output terminal,
Output phase B.

The magnetization pattern 111 has a magnetic pole NS in the circumferential direction.
There are places where are alternately arranged and places where are not magnetized. The distance from the change N of the magnetic pole to the magnetism pitch M
And The MR sensor is composed of rectangular MR elements, the long sides of the MR elements being arranged at right angles to the circumferential direction and arranged in the circumferential direction. Two arrays are arranged at a pitch of M / 2 with respect to the magnetizing pitch M, and lead wires are connected to both ends of the MR element. Since a large number of absolute tracks are required, a plurality of tracks are arranged in the axial direction. This number of tracks increases as the resolution increases.

The above magnetic encoder applies a rated voltage to the power supply terminal of the MR sensor. The shaft 102 is connected to another rotating body, and the rotating drum 101 rotates freely. Due to this rotation, the strength of the magnetic field that each MR element of the MR sensor receives in the in-plane direction changes in a pseudo sine wave shape. The change changes into a change in the resistance of each MR element of the MR sensor, and the incremental signal is output from the output terminal as a signal of A phase and B phase.

The absolute code is mainly a binary code and a Gray code. (Table 1) and (Table 2) show the above binary code and Gray code. The binary code is a conversion of the decimal numbers of the position signals 0, 1, 2, ... 6, 7 into binary numbers. The Gray code is a rearrangement of the above binary code, and the number forming the code changes only by one in accordance with the change of the position signal. In the binary code and the Gray code, the numbers forming the code change randomly, so that the number of tracks is as many as the numbers forming the code.

[0007]

[Table 1]

[0008]

[Table 2]

The magnetic drum 101 is manufactured by a magnetic material γ-Fe ₂ which is a coating type magnetic film on the circumference of cylindrical aluminum.
Apply a mixture of O ₃ and binder. Then, the magnetic drum 101 is rotated around the shaft 102 and magnetized as a magnetized pattern 104 by the ring head. The MR sensor forms permalloy (Ni-Fe) on a cleaned glass substrate by a method such as vapor deposition. After that, etching is performed according to the pattern of each MR sensor. Si on the protective film
O ₂ is deposited by a method such as vapor deposition. The MR sensor and the magnetic drum created as described above are assembled in the arrangement as shown in FIG.

[0010]

In the conventional magnetic encoder, since the absolute signal whose absolute position is known is divided into a plurality of tracks and arranged, the number of MR elements of the MR sensor increases. However, as the number of MR elements increases, the manufacturing cost of the MR sensor increases. It is n
When one MR element is integrated, one MR
This is because it becomes the n-th power of the production yield of the element. Further, since the sensor becomes longer as the number of tracks increases, the displacement of the tracks easily occurs due to the mounting accuracy.

The present invention solves the above problems, and an object thereof is to provide a low-cost, compact magnetic encoder.

[0012]

In order to achieve the above object, the present invention provides a method of magnetizing an absolute signal by using S _{1 to} S _n.
In this configuration, frequencies f _{1 to} f _n are assigned to the frequencies of the magnetizing pitch in accordance with the signal of the above.

[0013]

According to the present invention, the output from the element of one absolute MR sensor can be changed from a binary signal to a multilevel signal.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic encoder according to an embodiment of the present invention is shown in FIG.
Is configured as shown in the perspective view of the main part of FIG. FIG. 2 shows the arrangement of the magnetization pattern. The track 10 is an incremental pattern, and the track 11 is an absolute pattern. The conventional absolute track has a plurality of tracks, but the absolute track has one track. FIG. 3 shows the arrangement of MR elements. The MR element 20 corresponds to the incremental track 10 and the track 21 corresponds to the absolute track 11. The left and right sides of the figure are the circumferential directions of the rotary drum 1. In the magnetization pattern 11, magnetic poles NS are alternately arranged in the circumferential direction, and the absolute signal is frequency-modulated and magnetized. FIG. 4 shows a case where n = 3 is obtained by magnetizing the above absolute and signal. One round of one track is divided into several areas and classified into three different areas. A number is assigned to this classified area. That number is the absolute signal. The above-mentioned one area of the magnetic drum 1 is magnetized by being modulated into three kinds of frequencies corresponding to three absolute signals. Since the absolute signal in the first area is "1" in decimal, the magnetizing frequency is 100 Hz. Since the absolute signal in the second area is "0" in decimal, the magnetizing frequency is 50 Hz. Absolute signal of the third area is 1
Since it is "2" in the 0-ary number, the magnetizing frequency is 150 Hz. The wavelength of the magnetization pattern changes according to these frequencies. Further, the strength of the magnetic field generated from the above-mentioned magnetization pattern changes in proportion to the wavelength of the magnetization pattern.

This magnetic encoder applies a rated voltage (5v) to the power supply terminal of the MR sensor. The shaft 2 is connected to another rotating body, and the rotating drum 1 freely rotates. This rotation changes the magnetic field received by each MR element 5 of the MR sensor. The change changes into a change in the resistance of each MR element 5 of the MR sensor, and the incremental signal is output as in the conventional example. In the absolute signal, as shown in FIG. 4, the change of the magnetic field changes in proportion to the wavelength of the magnetization pattern, so that the same change of magnetic field occurs in the MR element located at a certain distance. The output signal reflects the magnetization pattern. Therefore, multi-valued output is obtained using the method of the present invention.

As described above, according to the magnetic encoder of the embodiment of the present invention, the incremental track is magnetized at a constant wavelength (constant interval), and the absolute track is magnetized at a plurality of wavelengths to obtain a multilevel signal. Since they are arranged, a magnetic encoder showing an absolute position equivalent to that of the conventional multi-track magnetic encoder can be obtained with two tracks.

[0017]

As is apparent from the above embodiments, according to the present invention, the frequency of the magnetizing pitch is changed from f _{1 to} f _{n in accordance} with the method of magnetizing the absolute signal according to the signals of S _{1 to} S _n. By allocating a frequency modulation method, the output from one absolute MR sensor element can be changed from a binary signal to a multivalued signal, so that the number of absolute MR sensor elements and the magnetization can be magnetized. A magnetic encoder that can reduce the number of tracks can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a magnetic encoder according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a magnetization pattern of the encoder.

FIG. 3 is a layout diagram of MR elements of the encoder.

FIG. 4 is a schematic diagram showing the relationship between the magnetization and magnetic field of the encoder.

FIG. 5 is a perspective view of a main part of a conventional magnetic encoder.

FIG. 6 is a schematic diagram showing an encoder shape when a position resolution is increased by a conventional magnetic encoder.

FIG. 7 is a schematic diagram showing a magnetization pattern and an MR element of the encoder.

[Explanation of symbols]

 1 Magnetic drum 5 MR element

Claims (1)

[Claims] 1. A magnetic drum magnetized by assigning frequencies f _{1 to} f _n of a magnetizing signal in correspondence with absolute position signals S _{1 to} S _n , and a size corresponding to a magnetization pattern of the absolute position signal of said magnetic drum. Magnetic encoder with the magnetoresistive effect element of.