JPH02296109A - Angle detecting device - Google Patents

Abstract

PURPOSE:To detect the rotary angle of a drum by providing a drum having at least one of first magnetoreistance element for detecting the rotary angle at every constant pitch and at least one of second magnetoresistance element for detecting the passage at a divided pitch. CONSTITUTION:Only the parts of reference points are magnetized at a more dense pitch on a magnetic recording medium 1 which is alternately magnetized on a cylinder at an equal pitch. Magnetoresistance elements of ferromagnetic thin films are formed on the outer surface of a drum 2 which forms a concentric circle with the recording medium. The drum 2 is rotatably provided around a central shaft 3. The medium 1 is fixed so as to surround the outer surface. When the drum 2 is rotated, the resistance values of the magnetoresistance elements are changed in response to the change in magnetic field. When the change is detected, the rotary angle of the drum 2 can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an angle detection device, and particularly to a device for detecting the relative rotation angle of a cylindrical multi-pole magnetic recording medium using a ferromagnetic magnetoresistive element. The present invention relates to an angle detection device.

[Conventional technology]

Conventional angle detection devices of this type have a magnetic sensor with a magnetoresistive element formed on a flat substrate mounted on the outer circumferential surface of a rotating drum that is the object of angle detection, and fixed in close proximity to a multi-pole magnetized magnetic recording medium. The rotation angle of the drum is detected by detecting the change in the resistance value of the magnetoresistive element according to the rotation of the drum.

[Problem to be solved by the invention]

Since the above-mentioned conventional angle detection device has a structure in which the magnetic sensor and the magnetic recording medium are individually assembled, it is difficult to adjust the gap between them according to the designed value.
It is necessary to allow for an error of about 30%, and it is necessary to add a circuit to correct this error. Furthermore, since magnetic recording media are magnetized with multiple poles at a constant pitch, it is impossible to perform both reference point detection and angle detection at the same time. There are problems such as the need to provide an extra magnetic recording medium.

[Means to solve the problem]

The angle detection device of the present invention uses a magnetic recording medium which is alternately magnetized at a fixed pitch in the circumferential direction of the inner surface of a fixed cylinder, and is alternately magnetized at a pitch that is further subdivided from the fixed pitch at a portion indicating a reference point. , a first magnetoresistive element that is rotatably provided around the central axis of the magnetic recording medium and detects rotation angles for each of the predetermined pitches at a location on the outer circumferential surface facing the magnetic recording medium; and and a cylindrical drum provided with at least one second magnetoresistive element for detecting passage.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view of one embodiment of the present invention.

The magnetic recording medium 1, which is alternately magnetized on a cylinder at equal pitches, is magnetized at even finer pitches only at the reference points.

A magnetoresistive element made of a ferromagnetic thin film is formed on the outer peripheral surface of the drum 2 concentrically with this. The drum 2 is rotatably provided around a central axis 3, and the magnetic recording medium 1 is fixed so as to surround the outer periphery of the drum 2. When the drum 2 rotates, the magnetic resistance element changes its resistance value in response to changes in the magnetic field, and by detecting this, the rotation angle of the drum 2 can be detected.

FIGS. 2(a) and 2(b) are partial side views of this embodiment. The magnetic recording medium 1 is alternately magnetized with a pitch λ, and the pitch λ is further subdivided (λ/4.λ/2) only at the reference point.
．． λ/4) and are alternately magnetized. A pair of magnetoresistive elements 7 arranged at an interval of λ/4 and connected in series are used for detecting the reference point pitch (λ/2), and a pair of magnetoresistive elements 7 arranged at an interval of λ/2 and connected in series The magnetoresistive element 6 is for detecting the pitch λ similar to the conventional device.

FIG. 3 is a signal waveform diagram illustrating the operation of this embodiment.

The detection signals a1 and bl are output signals obtained when the drum 2 rotates when the three pairs of magnetoresistive elements 6 and 7 are connected to a bridge circuit as in the conventional device, and are converted into pulses. are pulses a2 and b2
It is. The detection signal a1 becomes an alternating current that is synchronized with the passing timing of the alternating magnetization with the pitch λ, but a slight waveform distortion occurs when passing through the magnetized location for reference point detection. However, the magnitude of the waveform distortion can be ignored during waveform processing for pulse conversion. On the other hand, the detection signal b1 has a pitch of λ/2
This is an alternating current that appears only near the timing of passage of the magnetized point, and the magnitude can be ignored during waveform processing during other periods.

In this embodiment, if the cylinder on which the magnetic recording medium 1 is disposed and the drum 2 on which the magnetoresistive elements 6 and 7 are disposed can be assembled while sharing the central axis 3, the assembly can be carried out as in the conventional case. There is no need for complicated gap adjustment, and by magnetically recording only one track on the magnetic recording medium 1, both reference point detection and angle detection can be performed simultaneously.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to easily and reliably set the gap between the magnetic recording medium and the magnetoresistive element, and also to perform both reference point detection and angle detection just by magnetically recording on one track. I can do it.

[Brief explanation of drawings]

FIG. 1 and FIGS. 2(a) and 2(b) are a cross-sectional view and a partial sectional view of the present invention, respectively, and FIG. 3 is a signal waveform diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Magnetic recording medium, 2... Drum, 3... Central shaft, 6.7... Magnetoresistive element.

Claims (1)

[Claims] A magnetic recording medium that is alternately magnetized at a fixed pitch in the circumferential direction of a fixed cylindrical inner surface, and alternately magnetized at a pitch that is further subdivided only at the fixed pitch at a portion indicating a reference point, and a central axis of the magnetic recording medium. A first magnetoresistive element rotatably provided around the outer circumferential surface of the magnetic recording medium at a location facing the magnetic recording medium for detecting rotation angles for each of the predetermined pitches, and a second magnetoresistive element for detecting passage of the subdivided pitches. An angle detection device comprising: a cylindrical drum provided with at least one resistance element.