JPS6262213A - Encoder apparatus - Google Patents

Abstract

PURPOSE:To achieve pronounced improvement of detecting accuracy, by installing a track on a spcimen arranged with No.1 magnetizing pattern and No.2 magnetizing pattern differentiated by the specified angle as to the magnetized direction from said pattern in the relative displacing direction of a detecting means and the specimen. CONSTITUTION:Magnetized pattern of azimuth angle theta are formed all along the periphery to a track 3 of a magnetic drum. theta is determined by an equation of track width W, number of stripes n of MR element and arrangement pitch of MR elements P. Next, a signal range 14 is installed in an overlapped manner on this azimuth range 13 on each track. By this arrangement, width of magnetic flux 15 take convergent aspect at the border 9 of signal range 14 and azimuth range 13 showing the approximately the same width as the signal range 14 outside the border range. Consequently, an output signal from the MR element is raised in approximate correspondence with partitioned passage of the border 9 and wave formation allows the signal to correspond accurately to a position of the boarder 9 without a detecting error.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an encoder device, and particularly to an encoder device using a magnetoresistive element (hereinafter referred to as an MR element).

[Prior Art] Recently, office equipment such as printers and magnetic disk drives have become widespread, and with this, demand for rotary encoder devices used for rotation control, position detection, etc. is rapidly increasing. Currently, most rotary encoders are optical, but magnetic rotary encoders are increasingly being used to improve resolution, response speed, reliability against dust and condensation, or to lower prices.

It was said that it was difficult to manufacture so-called absolute type encoders that can directly detect the absolute position of the detected object as a multi-bit address, especially when the detected object is stopped, but recently A rotary encoder as shown in the figure has been proposed.

In FIG. 4, reference numeral 1 denotes a motor whose rotation is controlled, and a magnetic drum 2 whose circumferential surface is made of a magnetic material is directly connected to the shaft of this motor 1. A plurality of tracks 3 provided on the magnetic drum 2 form a predetermined gray code pattern by magnetized areas and erased areas, and 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 thus obtained.

FIG. 5(A) shows an example of a 4-bit gray code recorded on the magnetic drum 2 in FIG. 4. When this gray code is recorded on the magnetic drum 2, the developed view of the surface of the magnetic drum 2 becomes The result will be as shown in Figure 5 (B). The shaded area in FIG. 5(B) is an area where a pattern of repeatedly reversed magnetization at a certain frequency is recorded, and the white area is an area where a1(
(or erased) state.

On the other hand, the MR element 5 provided on the substrate of the MR sensor 4 is
It is composed of n MR elements folded back at a pitch P of the magnetization pattern (n=an integer).

MR elements as shown in FIG. 6 are arranged in tracks 3 in FIG. 4 with a clearance of about 0.1 mm between them.

The MR element shown in Fig. 6 has multiple MR elements made of Fe-Ni, N
Alloys with magnetoresistive effects such as 1-Go and 0.03p
The film is deposited to a thickness of 0.1 pm to 0.1 pm by a so-called thin film forming method such as vacuum evaporation or sputtering, and then etched to form an integral structure. When forming this pattern, a thin film is formed and etched so that each element has uniaxial anisotropy in the longitudinal direction.

The magnetic drum 2 is controlled by the MR sensor configured as described above.
When the magnetic field of each track is detected, a detected waveform as shown in FIG. 7 is obtained. In FIG. 7, numerals 71 to 74 are waveforms output by each strip of the MR element 5 in FIG.
These combined outputs look like 76 in the magnetized region.

By shaping this output signal through a waveform processing circuit using a comparator or the like, it is possible to obtain an ON output in any part of the magnetized region of track 3 and an OFF output in the non-magnetized region. The combination of ON and OFF of the detection signal makes it possible to detect the absolute address corresponding to the gray code. The optimum value can be determined based on the resolution or the distance between the magnetized drum and the MR sensor.

[Problems to be Solved by the Invention] However, in the conventional example described above, a magnetized region 7 and an unmagnetized region 8 are provided as shown in FIG. 8(A).

Therefore, at the boundary between these regions, the magnetic flux distribution at the end of the magnetized region is wider than the magnetic flux distribution 10 at the continuously magnetized portion, as indicated by reference numeral 11. Therefore, when scanning from left to right on the track diagram in Figure 8(A),
The detected waveform is as shown in FIG. 8(B). When this waveform is shaped by comparing its tv with a predetermined threshold value using a comparator or the like, a detection output as shown in FIG. 8(C) is obtained. That is, as shown in FIG. 8, a detection error of ΔT occurs in the detection signal with respect to the point in time when the boundary 9 actually passes in front of the MR sensor. This error similarly occurs even if the direction of rotation of the magnetic drum is reversed. Therefore, it is difficult to obtain good detection accuracy with the conventional configuration.

Furthermore, as shown in Fig. 5(B), in order to form a gray code, it is sometimes necessary to line up unmagnetized areas and magnetized areas on adjacent tracks, and in order to avoid magnetic field interference at this time, each It was difficult to miniaturize the magnetic drum because the tracks had to be spaced at a certain distance or more.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an encoder device comprising a detection means including a magnetoresistive element and an object to be detected, in which the first magnetization pattern and , the first magnetization pattern is a second magnetization pattern whose magnetization direction is at a predetermined angle, and the track formed by arranging the first magnetization pattern and the second magnetization pattern in a direction of relative movement between the detection means and the detection object, when the detection object We adopted a configuration with

[Function] According to the above configuration, since the first magnetization pattern applies a change in the magnetic field with a phase shift to each MR element, the output of the MR element becomes 0 in this region. At the boundary between the first magnetization pattern and the second magnetization pattern, the spread of the magnetic flux generated from the second magnetization pattern becomes smaller, making it possible to obtain a detection signal with a sharp rise (fall). Accuracy can be significantly improved.

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

The configuration of the encoder device according to the present invention includes a magnetic drum 2 and an MR sensor 4, which are almost the same as the conventional example shown in FIG. However, for track 3, there are
A magnetization pattern is formed by the method shown in B).

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

(n-1) θ=j a n ′ −p Here, W is the width of the track 3, n is the number of MR elements, and p is the pitch of the MR elements. The region in which such a magnetization pattern is formed is herein referred to as an azimuth region (13).

Thereafter, 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).

In order to distinguish this magnetized region from the conventional magnetized region 7, this magnetized region will be referred to as a signal region 14 below.

According to the above configuration, as shown in FIG. 2(A), the eighth
The spread of the magnetic flux 15 is smaller than that of the conventional example shown in the figure, and the spread is almost the same as that of the signal region 14 other than the boundary region.

Therefore, the signal output from the MR element rises approximately corresponding to the passage of the boundary 9 as shown in FIG. 2(B), and the output waveform-shaped using a comparator etc.
), the rise accurately corresponds to the position of the boundary 9. Therefore, detection errors do not occur as in the conventional case. Further, in the azimuth region 13, since the phase of the magnetic field input to the MR sensor is shifted, the magnetic field is exactly canceled at both ends of one MR element, and is not output as a magnetic field detection signal.

Furthermore, by installing the azimuth region, the spread of the magnetic field in the direction of adjacent tracks at the boundary 9 becomes smaller than before, so the distance between adjacent tracks and tracks can be reduced.
Therefore, it is possible to downsize the entire device.

In the above embodiment, the magnetization direction of the azimuth region is the same between adjacent tracks, but as shown in FIG. 3(A), the magnetization direction of the adjacent tracks is made symmetrical with respect to the magnetization direction of the signal region. Then, as shown in FIG. 3(B), the signal region 1 is formed in the same manner as described above.
If the configuration is such that 4 is formed, the interference between the traverse and the ac can be further reduced. Therefore, it is possible to further reduce the distance between the tractors and the axes, thereby achieving miniaturization of the device.

In the above embodiment, the magnetization direction of the signal region 14 is formed without being inclined with respect to the transfer direction of the MR sensor, but the signal region may also be provided with an inclination with respect to the rotation axis of the magnetic drum. By changing the magnetization direction between adjacent tracks, crosstalk between adjacent tracks in the signal region can be reduced and the track spacing can be made smaller.

[Effects] As is clear from the above description, according to the present invention, in an encoder device including a detection means including a magnetoresistive element and a detected object, a first magnetization pattern and a first magnetization pattern are provided. A configuration is adopted in which the detected object is provided with a track in which a second magnetized pattern whose magnetization direction differs by a predetermined angle from the magnetization pattern is arranged in a direction of relative movement between the detection means and the detected object. As a result, detection accuracy can be greatly improved without complicating the configuration, and the entire device can be made smaller.

[Brief explanation of the drawing]

Figures 1 to 3 are for explaining the present invention, and Figure 1 (A
) and (B) are explanatory diagrams showing the configuration of the magnetization pattern in the present invention, and Figures 2 (A) to (C) are the spread of magnetic flux due to the magnetization pattern of the encoder, the output signal of the MR element, and the output after waveform shaping. An explanatory diagram showing each direction signal, Fig. 3 (
A) and (B) are explanatory diagrams showing the configuration of other magnetization patterns according to the present invention, FIG. 4 is a perspective view showing the configuration of a conventional rotary encoder, and FIGS. 5 (A) and (B) are respectively An explanatory diagram of the gray code recorded on the magnetic drum and the corresponding magnetic recording pattern, Fig. 6 is an explanatory diagram showing the configuration of the MR element, Fig. 7 is a waveform diagram showing the output of the MR element, and Fig. 8 is an explanatory diagram showing the configuration of the MR element. FIG. 3 is an explanatory diagram showing the spread of magnetic flux, the direction of the MR element, and the detected output after waveform shaping in a conventional device. 3... Track 13... Azimuth area 14
...Signal area patent applicant Canon Electronics Co., Ltd. (A) Toku, 1. Absence of wealth tRm Absence of wealth tRm Absence of east spread and output 〉 form of deformation M2 Diagram De-Bn Garden Figure 5 MR Element Control, Mei Garden Figure 6 MR Flea Output 1) ΣBoss'', lY/Fast 7ffl MR element. Explanation port showing D output 1 Figure 8 Cn-

Claims (1)

[Claims] 1) An encoder device comprising a detection means including a magnetoresistive element and a detected object, the encoder device comprising a first magnetization pattern;
The object to be detected has a track in which a second magnetization pattern whose magnetization direction differs by a predetermined angle from the first magnetization pattern is arranged in a direction of relative movement between the detection means and the object to be detected. An encoder device characterized by: 2) The encoder device according to claim 1, wherein the detection means includes a plurality of magnetoresistive elements arranged and connected in series so as to each extend in the width direction of the track. . 3) Magnetization of the second magnetization pattern with respect to the magnetization direction of the first magnetization pattern, where the track width is W, and the arrangement pitch and number of arrangement strips of the plurality of magnetoresistive elements are p and n, respectively. 3. The encoder device according to claim 2, wherein the inclination angle θ of the direction is θ=tan^-^1[(n-1)/W]p. 4) The object to be detected has a plurality of tracks arranged in parallel, and the magnetization direction of the second magnetization pattern is made to match in adjacent tracks, and the magnetization direction of the second magnetization pattern is made to match the magnetization direction of the second magnetization pattern. 4. The encoder device according to claim 2, wherein the inclination angles of the magnetization directions of the first magnetization patterns are opposite to each other. 5) According to any one of claims 1 to 4, the magnetization direction of the second magnetization pattern is inclined at a predetermined angle with respect to the relative movement direction. encoder device.