JPH049613A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To obtain an index pulse at an optional position and to compactly constitute the whole device by writing an index mark on an optional position of a magnetic recording medium. CONSTITUTION:The index mark IM is written on an optional position on the outer periphery of the magnetic recording medium 2 with black paint. When the medium 2 is rotated, an index pulse is outputted from a reflection type photosensor 3 at every arrival of the mark IM. An angle counting circuit is constituted of waveform shaping circuits 7 to 9, a direction deciding circuit 10 and an up/down counter 11. The counter 11 is reset at every arrival of the origin of the medium 2 at the set position of a magnetic sensor 4. Even in a state obtained before resetting the counter 11 by an origin signal at the time of power ON or the like, an index pulse is outputted from the sensor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a magnetic encoder that detects rotational angles and linear displacements.

``Prior Art'' As is well known, a magnetic rotary encoder for detecting a rotation angle has an origin track and a pitch signal track along the circumference of a disc-shaped magnetic recording medium fixed to a rotating shaft. An origin signal is recorded at a specific location on the origin track, and pitch signals are recorded at regular intervals on the pitch signal track. A counter is provided that counts pulses obtained based on a pitch signal detected by a magnetic sensor from a pitch signal track, and is reset by an origin signal detected by another magnetic sensor from an origin track. The value is output as angle data corresponding to the rotation angle of the rotation axis.

"Problems to be Solved by the Invention" By the way, when the above-mentioned magnetic rotary encoder is incorporated into an industrial robot to detect the operating angle of the arm, in addition to simply detecting the operating angle of the arm,
There is a desire to obtain an index pulse every time the arm reaches a predetermined rotation angle.Therefore, conventionally, a digital comparator is used to detect when the count value of a counter or a predetermined value has been reached. However, in the state before the counter is reset by the origin signal, such as when the power is turned on, the counter is reset and the index pulse is set to the predetermined value. Since the index pulse is not output until after the count has been reached, the arm must be returned to the home position and then moved to the position where the index pulse can be obtained, which poses the problem of not being able to obtain the index pulse immediately. In this case, it is conceivable to provide a new track for the index pulse on the magnetic recording medium ζ, but the problem arises that the entire apparatus becomes a doll.

This invention was made in view of the above-mentioned circumstances, and it is possible to generate an index pulse at any position related to the operation of a counter for detecting the displacement of a magnetic recording medium. Δ
The purpose is to provide a magnetic encoder that: 1. I'm here.

``Means for Solving the Problems 1 This invention includes a magnetic recording medium supported rotatably and linearly movably, and magnetic information recorded on the magnetic recording medium is read out and the magnetic information is a displacement detection means for detecting displacement of a recording medium; an index mark recorded at an arbitrary location on the magnetic recording medium by varying the reflectance of light; and an index mark for optically detecting the index mark. The present invention is characterized in that it includes an index mark detection means 4'.

"Operation" According to the above-mentioned configuration ζζ, each time an index mark is written at an arbitrary location on the magnetic recording medium, an index mark is created at an arbitrary position regardless of the operation of the displacement detection means that detects the displacement of the magnetic recording medium. A pulse is obtained.

[Example] Hereinafter, with reference to the drawings, the present invention will be described in detail. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.

In this figure, the symbol (■) is a shaft that is rotatably supported by a bearing (not shown) in the direction of arrow M shown in the figure, and a cylindrical magnetic recording medium 2 is attached to this shaft 1. As shown in FIG. 2, this magnetic recording medium 2 includes a cylindrical base 2a, a magnetic layer 2b formed on the outer peripheral surface of this base 2a, and a non-magnetic layer 2b formed on the surface of this magnetic layer 2b. It is composed of a layer 2c. In this case, the nonmagnetic layer 2c is formed by vapor depositing a metal such as Af2 or Cr, or by coating holes with white synthetic resin.

This non-magnetic layer 2c is provided for the purpose of increasing the reflectance of the surface of the magnetic layer 2b, and the magnetic layer 2b is made of an alloy magnet (F
If it is made of a material with a high reflectance of .5, such as e-Cr-Go alloy, there is no need to form the non-magnetic layer 2c.

On the outer peripheral surface of this magnetic recording medium 2, over the entire circumference,
An origin track Tz and a pitch signal track TP are installed. The magnetic recording medium 2 is placed at the origin l and the rack Tz.
At the origin of ,! 4' One cycle of sinusoidal magnetic information is recorded as an origin signal, and on pitch signal track 7p, sinusoidal magnetic information with a constant wavelength λ is repeatedly recorded as a bitch signal. has been done.

Furthermore, an index mark IM is written with black paint at an arbitrary location on the outer peripheral surface of the magnetic recording medium 2.

Reference numeral 3 denotes a reflective photosensor, which is placed opposite to the outer peripheral surface of the magnetic recording medium 2 with a certain gap in between. and,
Each time the magnetic recording medium 2 rotates and the index mark IM reaches the sensor 2, an index pulse is generated.

Moreover, 4, 5a, and 5b are magnetic sensors formed by forming a magnetoresistive element on the glass substrate 1-, and are arranged opposite to the outer peripheral surface of the magnetic recording medium 2 with a certain gap in between. , L magnetoresistive element is a phenomenon in which, when placed in a magnetic field, the specific resistance changes depending on the strength of the magnetic field,
The element material is composed of J, which produces a so-called magnetoresistive effect, and by utilizing this magnetoresistive effect, the pitch recorded on the origin track Tz (recorded origin signal and pitch signal track TI) is The signal can now be read. Further, the magnetic sensors 58 and 5b are aligned with each other (m±174)λ along the moving direction M of the magnetic recording medium 2.
(However, m is an integer) They are arranged opposite to the pitch signal track Tp with a distance therebetween. The resistance value of the magnetoresistive element patterns of the magnetic sensors 5a and 5b changes depending on the magnetic field received from the pitch signal track Tp, and as a result, the magnetic sensors 5a and 5b output a level corresponding to the positional relationship with the pitch signal track Tp. signal can be obtained. That is, the section of one period of sinusoidal magnetic information on the pitch signal track Tp is set to θ=0.
˜2π, a level signal of sin θ is obtained from the magnetic sensor 5a and a level signal of eO8θ is obtained from the magnetic sensor 5b.

Then, when the pitch signal track Tp moves relative to the magnetic sensors 5a and 5b, the magnetic sensor 5
Two-phase detection signal s whose phase is shifted by π/2 from a and 5b
inθ (A phase) and Cogθ (B phase) are obtained.

6 is an angle counting circuit, and waveform shaping circuits 7.8 and 9
, direction discrimination circuit IO, and up/down counter 11
It is composed of. In the waveform shaping circuits 7 and 8,
The A-phase and B-phase detection signals are waveform-shaped and output. In this case, the A-phase pulse Pa and the B-phase pulse Pb output from the waveform shaping circuits 7 and 8 respectively become rectangular waves whose phases are shifted by π/2, and when the rotation direction of the magnetic recording medium 2 is in the positive direction, , the A-phase pulse Pa has an advanced phase, and in the case of a negative direction, the B-phase pulse Pb has an advanced phase. Then, in the direction discrimination circuit 10, for example,
The direction of rotation is determined depending on whether the level of the B-phase pulse Pb is 'H' or 'L' at the rise of the A-phase pulse Pa.

The output signal Sv of this direction discrimination circuit 1O is outputted by the counter 11.
is supplied to the up/down switching terminal U/f5. Then, the counter 11 receives the A-phase pulse P while the count mode is switched up or down by the signal Sv.
a is counted. In this case, up-counting is performed when the magnetic recording medium 2 is rotating in the positive direction, and down-counting is performed when it is rotating in the negative direction.

On the other hand, every time the origin of the magnetic recording medium 2 passes through the installation location of the magnetic sensor 4, the origin signal recorded at the origin is detected by the magnetic sensor 4, and this is transmitted via the waveform shaping circuit 9 to the origin pulse Pz. and is supplied to the reset terminal R of the counter 11. As a result,
The counter 11 is reset each time the origin of the magnetic recording medium 2 reaches the location where the magnetic sensor 4 is installed. Therefore,
The count value of the counter 11 is the pitch signal track TI that has passed over the magnetic sensor 5 as 5b from the time when the origin of the magnetic recording medium 2 passed through the installation location of the magnetic sensor 4 until the present time. The value corresponds to the number of magnetization sections, that is, the value corresponds to the rotation angle of the magnetic recording medium 2. Then, the count value of the counter 11 is output as angle data D corresponding to the rotation angle of the shaft 2.

As described above, according to the embodiment described above, an index mark IM is written with black paint at an arbitrary location on the magnetic recording medium 2, and a reflective photosensor 3 is provided to optically detect the index mark IM. Therefore, even in a state before the counter 11 is reset by the origin signal, such as when the power is turned on, the index pulse is output from the reflective photosensor 3. Further, the index mark IM can be easily erased by wiping it with a suitable solvent, and can also be written in another location.

Next, FIG. 3 is a diagram showing the configuration of another embodiment of the present invention. In this embodiment, a disk-shaped magnetic recording medium 1
2, an origin track Tz and a pitch signal track τp are provided on the upper surface thereof, and an index mark IM is further written along the radial direction. Magnetic sensors 4 and 5a are spaced apart from the upper surface of the magnetic recording medium 12 by a certain gap.

A magnetic sensor unit 13 including a magnetic sensor unit 5b and a reflective photosensor 3 are respectively arranged.

In addition, in the above-mentioned embodiment, the index mark IM may be written with black paint, or may be pasted with black tape, in short, to avoid light reflection from other parts. All you have to do is make the rates different. Also,
Magnetic 1iii-Tally encoder that detects rotation angle has been explained as an example, but what about magnetic linear J encoder that detects linear displacement? , 2 can of course also be applied to 4'.

"Effects of the Invention" As explained above, according to the present invention, by writing an index mark at an arbitrary location on a magnetic recording medium, the operation of the displacement detecting means for detecting the displacement of the magnetic recording medium is completely controlled. Regardless, the index pulse can be obtained at any position, and since there is no need to separately install an index track, the entire device can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the structure of the magnetic recording medium of the same example;
FIG. 3 is a perspective view showing the structure of another embodiment of the present invention. 1. Magnetic recording medium; 2a... base; magnetic layer;
2c - Non-magnetic layer 1, index mark, reflective type sensor, (index mark detection means), Tz...origin track, Tp...pitch signal track, 4.5a, 5b . . . Magnetic sensor, 6. . . Angle counting circuit (hereinafter referred to as displacement detection means). 2 ・・ 21)・iM・・ 3 ・

Claims (1)

[Scope of Claims] A magnetic recording medium supported rotatably or linearly; displacement detecting means for reading magnetic information recorded on the magnetic recording medium and detecting displacement of the magnetic recording medium; and the magnetic recording medium. A magnetic encoder comprising: index marks recorded at arbitrary locations on a recording medium by varying the reflectance of light; and index mark detection means for optically detecting the index marks. .