JPS6239684B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method of repeating magnetization having bit lengths P equally spaced along the circumference on one surface of a rotating body such as a disk or drum that is attached to a rotating shaft and has a magnetic storage medium. The magnetic signals recorded in the form of
The present invention relates to an angle detector that detects the rotation angle of the rotating body by reading it with a magnetic sensor comprising:

Conventionally, the magnetic sensor of this kind of angle detector is
A predetermined interval corresponding to the bit length P (for example, 1/
4P), formed in parallel on a flat substrate,
It consists of a plurality of strip-shaped MR elements, which are arranged parallel to the magnetic storage medium surface with a predetermined spacing so that the component parallel to the substrate of the signal magnetic field emitted from the magnetic storage medium can be detected. The rotation angle and rotation direction of the rotation shaft are detected by processing the resistance change of each MR element using a magnetic signal in a reproducing circuit.

Here, as shown in FIG. 1, a strip-shaped MR element 1
The relationship between the width direction magnetic field Hx and the resistivity ρ is usually a bimodal curve consisting of two curves 2 and 3 due to anisotropic dispersion. Which curve the resistance changes according to the signal magnetic field varies depending on the history of the MR element. For example, if the periodic signal magnetic field 4 from the magnetic medium follows curve 2, the resistance change of the MR element will be a distorted waveform of every other element as shown in 5, so the signal output of the magnetic sensor and The correspondence with the signal magnetic field 4 deteriorates. As a result, correct angle detection becomes difficult. The same applies to the case where curve 3 is followed.

Furthermore, this tendency increases as the distance between the magnetic medium and the MR element, that is, the spacing, increases.
The spacing cannot be made too large because it becomes more noticeable as the signal magnetic field strength applied to the element becomes smaller. This means that a high degree of precision is required when assembling the angle detector, which means that the angle detector is expensive.

On the other hand, it is well known that the above-mentioned bimodal curves 2 and 3 can be corrected as shown in Figure 6, since the dispersion becomes smaller when a weak DC bias magnetic field is applied in the longitudinal direction of the MR element. There is. the result
The distortion caused by the resistance change of the MR element is also corrected, and as shown in 7, it becomes suitable for the signal magnetic field 4.

An object of the present invention is to solve the above-mentioned drawbacks by providing such a DC bias magnetic field by a simple means, and to provide a low-cost and highly reliable angle detector.

The configuration of the angle detector of the present invention has a magnetic storage medium on one surface in which a magnetic signal is recorded in the form of repeated magnetization along the circumference, and a magnetic storage medium on the other surface in a fixed direction orthogonal to the magnetic signal. a rotating body, such as a disk or a drum, which has a magnetic storage medium magnetized with a predetermined width and is attached to a rotating shaft;
The present invention is characterized in that the angle detection section is constituted by a magnetic sensor made of a ferromagnetic magnetoresistive element that senses changes in the magnetic field generated from two magnetic storage media as changes in electrical resistance.

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

FIG. 2a shows an embodiment of the present invention. On one side of the disk 9 attached to the rotating shaft 8, magnetic signals are distributed along the circumference at equal intervals of bit length P.
A magnetic storage medium 10 is formed in which magnetization 11 is repeatedly recorded, and as shown in FIG. A magnetic storage medium 12 is formed. The magnetic storage medium 1 is configured to detect a signal magnetic field emitted from the magnetic storage medium 10.
A magnetic sensor 14 is arranged parallel to the 0 plane.

Here, in order to make the operation of the present invention easier to understand,
An example of a magnetic sensor 14 in which four strip-shaped MR elements are formed at a pitch of 1/4P on a flat substrate will be explained using FIGS. 3 to 5.

FIG. 3 shows the positional relationship between the MR elements 17 to 20 and the magnetic storage media 10 and 12. Four strip-shaped MR elements 17 to 20 transmit signals to the magnetic storage medium 10. They are arranged in parallel with a spacing D in between so as to detect the horizontal component of the magnetic field 15. A feature of the present invention is that, in addition to the signal magnetic field applied in the width direction, the MR elements 17 to 20 also receive a magnetic game storage medium on the back surface of the disk 9 in the approximately longitudinal direction (y direction). Bias magnetic field 1 emanating from radial magnetization 13 in 12
6 is applied to the MR element 1.
The reason is that the anisotropic dispersion of 7 to 20 is reduced. Therefore, the resistance change of each MR element 17 to 20 with respect to the signal magnetic field follows the characteristic curve shown in FIG. As a result, the angle detector can be made inexpensive.

FIG. 4 is an example of a reproducing circuit, and FIG. 5 is a diagram showing a reproducing process of the signal magnetic field 15. When the rotating shaft 8 rotates,
For example, when the magnetic storage media 10 and 12 move in the direction of the arrow 29 in FIG. 3, the repetition of the magnetic signal 15 accompanying this movement causes the MR element 17 to The output terminal of
A signal output as shown at 23 in FIG. 5b is produced. Similarly, a signal output 24 whose phase lags 23 by 1/2P is generated at the output terminal of the MR element 19 located 1/2P apart from the MR element 17. Here, the signal output waveforms 23 and 24 have good waveform distortion and are compatible with the signal field 15 due to the effect of reducing anisotropic dispersion of the MR element, which is a feature of the present invention. .

Further, these signals are converted into a signal output 25 (FIG. 5c) obtained through a differential amplifier 21, and pulsed by a comparator 22 using a comparison level (Vc) 26 as a reference.
It is possible to obtain an angle signal (A phase output) 27 (FIG. 5d) that accurately corresponds to each bit of . Similarly, MR elements 18 and 20 output 2 phase A outputs.
7, an angle signal (B phase output) 28 (FIG. 5e) whose phase is delayed by 1/4P can be obtained. Here, the phase relationship between the A-phase output 27 and the B-phase output 28 is reversed by J degrees when the rotation direction is reversed.

In this way, the rotation angle of the rotating shaft 8 can be determined by counting the A-phase output 27 or the B-phase output 28 or the signal pulses obtained by electrically processing them, and also by counting the rotation direction. A, A.
It can be detected based on the phase relationship of the B-phase output.

If there is no such bias magnetic field 16, the signal output waveform of the MR elements 17 and 19 will be the fifth
Distortions occur as shown at 29 and 30 in FIG. If this distortion becomes large, the phase relationship between the pulse outputs 32 and 33 will be disturbed as shown in FIG. 5h and i, making it impossible to accurately detect the rotation angle and rotation direction.

FIG. 6 shows a second embodiment of the invention. In this case, a magnetic recording medium 34 magnetized in the rotation axis direction (z direction) is formed on the end surface (drum surface) of the disk 9, and due to this magnetization 35,
A bias magnetic field is applied in the longitudinal direction (y direction) of the MR element, and it operates in the same manner as in the first embodiment.

FIG. 7 shows a third embodiment of the present invention. In this case, the drum 40 has a diaphragm shape.
A magnetic storage medium 36 in which a periodic signal magnetic field is recorded in the form of repeated magnetization 37 having a bit length P is formed on the front surface of the drum. The longitudinal direction of the magnetization 37 is arranged so as to be perpendicular to the magnetization 37. A magnetic storage medium 38 is magnetized in the rotation axis direction (y direction) on the inner surface of the drum 40.
is formed, and due to this magnetization 39, MR
A bias magnetic field is applied in the longitudinal direction (y direction) of the element, and the same operation as in the first and second embodiments is performed.

FIG. 8 shows a fourth embodiment of the present invention. In this case, as in the third embodiment, a magnetic storage medium 36 that generates a periodic signal magnetic field is formed on the end surface of the disk 9, and the MR sensor 14
The MR element is arranged parallel to the end surface of the disk so that the longitudinal direction of the MR element is orthogonal to the magnetization direction of the magnetic storage medium 36. A radially magnetized magnetic storage medium 41 is formed on the plane of the disk 9, and this magnetization 42 applies a bias magnetic field in the longitudinal direction (y direction) of the MR element. The operation is similar to that of the first to third embodiments.

FIG. 9 shows a fifth embodiment of the present invention. This is almost the same as the third embodiment, but
The magnetic medium 43 for generating a bias magnetic field is formed in a state that it is packed up to the rotation axis. This too,
The operation is similar to that of the first to fourth embodiments.

In the above embodiments, the shape of the rotating body supporting the magnetic storage medium is described as a disk and a drum, but the shape is not limited to these. For example, the shape is a disk and a drum. Of course, a combination of shapes, ie, an inner plate with a wider end face width, may also be used.

Next, an example of the material, shape, structure, etc. of the present invention will be shown. An aluminum alloy plate with a thickness of several millimeters and a diameter of several tens of millimeters is used for the disk 9 or the drum 40, and the surface of this aluminum alloy plate has
A magnetic storage medium with a saturation magnetization of 500 to 2000 Gauss and a coercive force of 200 Oersted or more is formed to a thickness of several to several hundred microns. This magnetic storage medium is Co-
A metal ferromagnetic material such as Ni or r-Fe ₂ O ₃ is used. The medium thickness, bit length P, and magnetization length L for generating a bias magnetic field are selected to range from several hundred microns to several millimeters depending on the application. Especially magnetic storage media 12, 34, 38, 4 for bias generation
The thickness of 1,43 and the magnetization length L are selected so that a bias magnetic field of several oersteds is applied in the longitudinal direction of the MR element.

The MR element is made of a metal ferromagnetic alloy whose main components are Fe, Ni, Co, etc., on a substrate with a smooth surface such as silicon single crystal, glass, or ceramic, with a thickness of several hundred angstroms and a width of several tens of microns. It is manufactured using thin film technology with electrical terminals on both ends so that it has a length of several millimeters.

Also, as a disk 9 or drum 40,
Using an isotropic magnetic material with excellent workability, such as FeCrCo rolled magnet material, repetitive magnetization 11 for signal magnetic field generation and magnetization 13 for bias are directly written on the upper surface, lower surface, or measurement surface, respectively. It's good to wear. In this case, it is possible to save the effort of forming a new magnetic storage medium, so it is suitable for an angle detector aiming at lower cost.

As described above, according to the present invention, it is possible to reduce the dispersion of the MR element by a simple means, thereby making it possible to reduce the price and improve the performance of the angle detector.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the characteristics of the MR element, Figure 2 a, b, Figure 3, Figure 6, Figure 7, Figure 8, Figure 9.
Figures a and b are diagrams showing an embodiment of the present invention, Figure 4 is a circuit diagram showing a reproduction circuit, Figure 5 is a diagram showing the reproduction process, a is a schematic diagram of a magnetic storage medium, and b to i are waveform diagrams. It is. 1, 17, 18, 19, 20...MR element,
2, 3... Relationship between MR resistance and horizontal magnetic field when there is anisotropic dispersion, 4, 15... Periodic signal magnetic field, 5, 7... MR resistance change in response to periodic signal magnetic field, 6 ...Relationship between MR resistance change and horizontal magnetic field when there is no anisotropic dispersion, 8...Rotation axis, 9...
...Disk, 10, 12, 34, 36, 38, 41,
43...magnetic storage medium, 11, 13, 35, 3
7, 39, 42, 44... Magnetization, 14... Magnetic sensor, 16... Bias magnetic field, 21... Differential amplifier, 22... Comparator, 23, 24, 2
9, 30... Signal output of MR element for periodic signal magnetic field, 25, 31... Differential amplifier output, 26
... Comparison level, 27, 32 ... A phase output, 2
8, 33...B phase output, 40...Drum.

Claims (1)

[Scope of Claims] 1. A magnetic storage medium in which a magnetic signal is recorded in the form of repeating magnetization along the circumference on one surface, and a magnetic storage medium on the other surface in a predetermined direction orthogonal to the magnetic signal. a rotating body having a magnetic storage medium magnetized with a width of , and attached to a rotating shaft;
1. An angle detector comprising an angle detector comprising a magnetic sensor made of a ferromagnetic magnetoresistive element that senses changes in the magnetic field generated by two magnetic storage media as changes in electrical resistance. 2. The angle detector according to claim 1, wherein the rotating body is made of rolled magnetic material and also serves as a magnetic storage medium. 3. According to claim 1 or 2, the magnetic field generated by the magnetic storage medium is magnetized in a certain direction perpendicular to the magnetic signal, and is configured so that the magnetic field generated by the magnetic storage medium acts substantially in the longitudinal direction of the ferromagnetic magnetoresistive element. Angle detector as described.