JPH0711430B2 - Encoder device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an encoder device, particularly a magnetoresistive effect element (hereinafter
MR device) is used for the encoder device.

[Prior Art] The spread of office equipment such as a printer or a magnetic disk device has been remarkable recently, and accordingly, the demand for a rotary encoder device used for rotation control, position detection and the like is rapidly increasing. Currently, most rotary encoder devices are optical encoders, but magnetic rotary encoders are increasing in order to improve resolution, response speed, reliability against dust and dew condensation, or cost reduction.

In particular, it has been said that it is difficult to manufacture a so-called absolute type encoder that can directly detect the absolute position of the detected object as a multi-bit address when the detected object is stopped. A rotary encoder as shown is proposed.

In FIG. 4, reference numeral 1 is a motor whose rotation is controlled, and a shaft of the motor 1 is directly connected to a magnetic drum 2 having a circumferential surface formed of a magnetic material. A plurality of tracks 3 provided on the magnetic drum 2 form a predetermined gray code pattern by a magnetized area and an erased area. This pattern is detected by an MR sensor 4 arranged along the drum 2, The rotation of the motor 1 is detected by the electric signal obtained by.

FIG. 5 (A) shows an example of a 4-bit gray code recorded on the magnetic drum 2 of FIG. 4, and when this gray code is recorded on the magnetic drum 2, a developed view of the surface of the magnetic drum 2 shows It becomes like FIG. 5 (B). The shaded area in FIG. 5 (B) is an area in which a pattern repeatedly magnetized at a certain frequency is recorded, and the white background area is an unmagnetized (or erased) area.

On the other hand, the MR element 5 provided on the substrate of the MR sensor 4 is composed of n MR elements folded at a pitch p (n = an integer) of the pitch P of the magnetization pattern. MR elements such as those shown in Fig. 6 are each installed in track 3 of Fig. 4 by about 0.1 m.
Place through a clearance of m.

The MR element shown in FIG. 6 is obtained by depositing a multi-row MR element with an alloy having a magnetoresistive effect such as Fe-Ni, Ni-Co to a thickness of 0.03 μm to 0.1 μm by a so-called thin film forming method such as vacuum deposition or sputtering. After that, it is integrally formed by etching. When forming this pattern, thin film formation and etching are performed so that each element has uniaxial anisotropy in the longitudinal direction.

When the magnetic field of each track of the magnetic drum 2 is detected by the MR sensor configured as described above, a detection waveform as shown in FIG. 7 is obtained. In FIG. 7, reference numerals 71 to 74 are waveforms output by the strips of the MR element 5 in FIG. 6, respectively.

If this output signal is shaped through a waveform processing circuit using a comparator or the like, an ON output can be obtained in any part of the magnetized area of the track 3 and an OFF output can be obtained in the non-magnetized area. O of detection signal
The combination of N and OFF makes it possible to detect the absolute address corresponding to the gray code. The magnetizing pitch in the magnetizing area and the number of MR sensor patterns of the MR element are the motor 1
Rotation speed, required resolution, or magnetizing drum and MR
The optimum value can be determined by the distance of the sensor.

[Problems to be Solved by the Invention] However, in the above-described conventional example, the magnetized region 7 and the non-magnetized region 8 are provided as shown in FIG. 8 (A).
Therefore, at the boundary between these regions, the distribution of the magnetic flux at the end of the magnetized region is wider than the distribution 10 of the magnetic flux at the continuously magnetized part as indicated by reference numeral 11. Therefore, the eighth
When scanning is performed from left to right in the track diagram of FIG. 8A, the detected waveform is as shown in FIG. 8B. When the waveform is shaped by comparing this waveform with a predetermined threshold value and its t _V using a comparator or the like, a detection output as shown in FIG. 8C is obtained. That is, as shown in FIG. 8, there is a detection error of ΔT in the detection signal at the time when the boundary 9 actually passes in front of the MR sensor. This error also occurs when the rotating direction of the magnetic drum is reversed. Therefore, it is difficult to obtain good detection accuracy with the conventional configuration.

Further, as shown in FIG. 5 (B), in order to form a gray code, it is sometimes necessary to arrange an unmagnetized region and a magnetized region in adjacent tracks, and in order to avoid interference of magnetic fields at this time, It was difficult to reduce the size of the magnetic drum because the tracks had to be separated by a certain distance.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, there is provided an encoder device including a detection unit including a magnetoresistive effect element and a detection target, wherein the detection target is: A first magnetization pattern and a second magnetization pattern having a magnetization direction different from that of the first magnetization pattern;
Of the second magnetization pattern is arranged in a predetermined direction with respect to the relative movement direction. We adopted a configuration with a tilted angle.

[Operation] According to the configuration as described above, the change of the magnetic field with a phase shift is applied to the detecting means by the second magnetization pattern, so that the output of the detecting means becomes 0 in this region, and
At the boundary between the first and second magnetization patterns, the spread of the magnetic flux generated by the first magnetization pattern becomes small, and a detection signal with a sharp rise (fall) can be obtained.

[Examples] The present invention will be described in detail below based on examples shown in the drawings.

It is assumed that the encoder device according to the present invention comprises a magnetic drum 2 and an MR sensor 4 which are almost the same as those of the conventional example shown in FIG. However, as shown in FIG.
A magnetization pattern is formed by the method shown in FIG.

FIG. 1A shows two tracks 3 of the magnetic drum 2. First, an inclined magnetization pattern as shown in the figure is formed over the entire circumference of the magnetic drum 2 with an azimuth angle of θ with respect to the track 3. The tilt angle θ is determined by the following formula.

Here, w is the width of the track 3, n is the number of MR elements, and p is MR.
The element pitch. The region in which such a magnetization pattern is formed is called an azimuth region (13) here.

Then, a magnetized region corresponding to a predetermined gray code similar to the magnetized region 7 of the conventional example is formed on each track so as to overlap the azimuth region 13 as shown in FIG. 1 (B). This magnetized region is hereinafter referred to as a signal region 14 in order to distinguish it from the conventional magnetized region 7.

According to the above configuration, as shown in FIG. 2 (A), the spread of the magnetic flux 15 becomes smaller at the boundary 9 between the signal area 14 and the azimuth area 13 than in the conventional example shown in FIG. The signal area 14 is substantially the same as the signal area 14. Therefore MR
The signal output from the element rises almost corresponding to the passage of the boundary 9 section as shown in FIG. 2 (B), and the waveform-shaped output using a comparator or the like shows the boundary 9 as shown in FIG. 2 (C). The rise corresponds to the position of. Therefore, a detection error does not occur unlike the conventional case. Further, in the azimuth region 13, the magnetic field input to the MR sensor is out of phase, so that the magnetic field is just canceled at both ends of one MR element and is not output as a magnetic field detection signal.

Furthermore, since the azimuth region is provided, the boundary at the boundary 9 in the direction of the adjacent track becomes smaller than before, so that the distance between the adjacent tracks can be reduced.
Therefore, the size of the entire device can be reduced.

In the above embodiment, the magnetization directions of the azimuth regions are the same between the adjacent tracks, but the magnetization directions of the adjacent tracks are symmetrical with respect to the magnetization direction of the signal region as shown in FIG. 3 (A). The azimuth area is formed as shown in FIG. 3B, and then the signal area 14 is formed as shown in FIG.
With such a structure, the interference between the tracks can be further reduced. Therefore, the distance between the tracks can be made smaller, and the size of the device can be reduced.

In the above embodiment, the magnetization direction of the signal region 14 is formed without being inclined with respect to the transition direction of the MR sensor, but the signal region may be provided so as to be inclined with respect to the rotation axis of the magnetic drum. At this time, if the magnetization direction is changed between the adjacent tracks, crosstalk with the adjacent tracks in the signal area can be reduced and the track interval can be made smaller.

[Effect] As is apparent from the above description, according to the present invention, the detection target includes the first magnetization pattern and the second magnetization pattern having a magnetization direction different from that of the first magnetization pattern. A configuration is adopted in which tracks are arranged in the relative movement direction of the detection means and the detection target, and the magnetization direction of the second magnetization pattern is inclined at a predetermined angle with respect to the relative movement direction. Since the change of the magnetic field with a phase shift is applied to the detecting means by the second magnetization pattern, in this region,
The output of the detection means becomes 0, and the spread of the magnetic flux generated by the first magnetization pattern becomes small at the boundary between the first and second magnetization patterns, so that a detection signal with a sharp rise (fall) can be obtained. There is an excellent effect that the detection accuracy can be greatly improved by the simple and inexpensive configuration.

[Brief description of drawings]

1 to 3 are for explaining the present invention, and FIGS. 1 (A) and 1 (B) are explanatory views showing the constitution of a magnetization pattern in the present invention, and FIGS. 2 (A) to 2 (C). Is an explanatory view showing the spread of magnetic flux due to the magnetization pattern of the encoder, the output signal of the MR element, and the output signal after waveform shaping, and FIGS. 3 (A) and 3 (B) show configurations of other magnetization patterns according to the present invention. FIG. 4 is a perspective view showing the structure of a conventional rotary encoder, and FIGS. 5 (A) and 5 (B) are explanatory views of a gray code recorded on a magnetic drum and a magnetic recording pattern corresponding thereto. , FIG. 6 is an explanatory diagram showing the structure of the MR element, FIG. 7 is a waveform diagram showing the output of the MR element,
FIG. 8 is an explanatory diagram showing the spread of magnetic flux, the output of the MR element, and the detection output after waveform shaping in the conventional device. 3 …… Track, 13 …… Azimuth area 14 …… Signal area

(72) Inventor Hideto Sano, 1248 Shimokagemori, Chichibu, Saitama Prefecture, within Canon Electronics Co., Ltd. 72) Inventor Takeshi Osato 1248 Shimokagemori, Chichibu, Saitama Prefecture, within Canon Electronics Co., Ltd. (56) References JP-A-59-189500 (JP, A) JP-A-58-158017 (JP, A)

Claims (4)

[Claims] 1. An encoder device comprising a detection means including a magnetoresistive effect element and an object to be detected, wherein the object to be detected has a first magnetization pattern, and the first magnetization pattern has a magnetization direction. And a track formed by arranging different second magnetization patterns in the relative movement direction of the detection means and the detection target, and the magnetization direction of the second magnetization pattern is the relative movement direction. An encoder device which is inclined at a predetermined angle with respect to. 2. The detection means includes a plurality of magnetoresistive effect elements arranged and connected in series so as to extend in the width direction of the track.
The encoder device according to the item. 3. The second magnetization with respect to the magnetization direction of the first magnetization pattern, wherein W is the track width, p is the arrangement pitch of the plurality of magnetoresistive effect elements, and p is the number of arrangements, respectively. The inclination angle θ of the magnetization direction of the pattern The encoder device according to claim 2, wherein: 4. The object to be detected has a plurality of the tracks arranged in parallel, and in the tracks adjacent to each other, the magnetization directions of the first magnetization patterns of the tracks adjacent to each other are made to coincide with each other, and the tracks are adjacent to each other. The inclination angle of the magnetization direction of the second magnetization pattern with respect to the magnetization direction of the first magnetization pattern between the respective tracks is symmetrical with respect to the relative movement direction. Item 3. The encoder device according to item 3.