JPS6262215A - Encoder apparatus - Google Patents

Abstract

PURPOSE:To minimize a detection error with narrowed expanse of magnetic flux for the reference position detection, by installing, before and behind a magnetized range for the reference position detection, a magnetized range of shorter recording wave length than this magnetized range. CONSTITUTION:An incremental phase 7 of a rotor is provided with the usual magnetized pattern 5, and the magnetized pattern 5 as a index phase 6 is provided with magnetized range 12 of a single magnetic field given the same recording wave length as the phase 7 in the reference position and with a magnetized range 13 given a shorter recording wave length before and after of it. As the same poles of each range 13 are arranged before and behind N and S poles of the range 12, a magnetic flux 14 of the range 12 becomes a distribution of small expanses in the same order as the magnetic flux of the phase 7. Consequently, a detecting output wave length of the phase 6 becomes of the same order of the pulse width as the output wave length of the phase 7 thus preventing the reference position 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 that detects a reference position of a detected object using a magnetic sensor.

[Prior Art] A magnetoresistive element (hereinafter referred to as an MR element) detects a change in an applied magnetic field based on a change in resistance of the element.

Therefore, when used as a detection means for various encoders, a magnetic field generating means such as a permanent magnet may be used as the object to be detected.

On the other hand, in the so-called optical encoder device, L
A power source is required for a light source such as an ED, and a photosensor or the like that requires a consumable light source is used as a detection means. Therefore, a magnetic encoder using an MR element has a simpler structure and superior durability than an optical encoder.

FIG. 4 shows a rotary encoder using a conventional MR element. In FIG. 4, reference numeral 1 denotes a rotor having a magnetization pattern 5 formed on its circumferential surface. This magnetization pattern 5 forms an incremental phase 7 for detecting the rotor's rotation direction, rotation angle, rotation speed, etc., and an index phase 6 for detecting a reference position of the rotor accompanying the detection. A rotary encoder is constructed by arranging MR elements 3.4 formed on the substrate 2 close to each phase and facing each other.

Here, the operating principle of the MR element 3 (4) will be explained.

The MR element has a striped number plate on the substrate 2 made of Fe-Ni, N
It is constructed by forming a thin film of an alloy such as i-Co.

In general, the resistance change rate of an MR element is expressed as a function of resistance Ra when a magnetic field is applied parallel to the current flowing through the element, and resistance Rh when a magnetic field is applied perpendicular to the current, and is a function of the actual magnetization direction and current. When the angle formed by
It is denoted as os 2θ.

For encoders, the MR element is made to have l-axis anisotropy, and a magnetic field H is applied in a direction perpendicular to the current I flowing through the element.
The strength of the magnetic field is extracted as a resistance change of the element 3.

[Problems to be Solved by the Invention] On the other hand, index phase 6 in FIG. The distribution of magnetic flux in the incremental phase 7 is as shown in FIG.

In the incremental phase 7, since the magnetization is continuously reversed, there are the same poles right next to each other, and the magnetic flux 10 is narrowed due to mutual repulsion, but in the index phase 6, only one magnetization pattern of S and N poles is provided. Since the magnetic flux is not 1
1 will spread.

Therefore, the detection signal obtained using the MR element 3.4 having the above-mentioned configuration is as shown in FIG.

In FIG. 6, symbol A is a detection signal based on the reproduced output of the MR element 4, and symbol C is a detection signal based on the reproduced output of the MR element 3. If the detection signal waveform C by the MR element 3 for the index phase is thus wide, there is a problem that an error occurs in the detection timing of the index pulse depending on the rotational direction of the rotor l.

It is preferable that the output waveform of the index phase is a pulse having a resolution similar to that of the incremental phase, or even narrower than that of the incremental phase, as shown by reference numeral B in FIG.

[Means for Solving the Problems] In order to solve the above problems, the present invention employs a configuration in which magnetized regions having a recording wavelength shorter than that of the magnetized regions are provided before and after the magnetized region for detecting the reference position.

[Function] With the above configuration, the magnetic flux of the magnetized region for reference position detection is prevented from spreading in the moving direction of the detected object due to the repulsion of the adjacent magnetized regions with short recording wavelengths, and the width of the detection pulse is made narrower. Therefore, the above-mentioned detection error can be reduced. Furthermore, since the magnetized portion with a short recording wavelength has a small amount of magnetic flux protruding due to its short wavelength, it is difficult to be detected by the magnetic sensor due to spacing loss with the magnetic sensor, and erroneous detection does not occur.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 shows the rotor portion of a rotary encoder according to the invention. In this embodiment, the incremental phase 7 of the rotor I has a magnetization pattern 5 similar to that of the conventional example shown in FIG. The magnetization pattern 5 as the index phase 4 includes a magnetization region 12 at a reference position caused by one magnetic field having the same recording wavelength as that of the incremental phase 7, and a magnetization region 13 having a smaller recording wavelength continuously provided before and after the magnetization region 12.
It consists of

Although illustration of the MR element section is omitted, it is assumed that the structure is similar to that of the conventional example shown in FIG.

According to the above configuration, the magnetic flux distribution due to the magnetization pattern of the index phase 6 is as shown in FIG. Since there are the same poles of the magnetized region 13 before and after the S and N poles of the magnetized region 12, the magnetic flux 14 of the magnetized region 12 due to this repulsion
becomes a distribution with a small spread narrowed to the same extent as the magnetic flux lO of the incremental phase 7.

Therefore, when a magnetic field is detected by the MR element, the detected output waveform of the index phase 6 has a pulse width comparable to the output waveform A of the incremental phase 7, as indicated by the symbol B in FIG. There is no reference position detection error caused by the rotational direction of the rotor.

On the other hand, since the recording wavelength of the magnetized region 13 is sufficiently small, the projection of magnetic flux from the rotor surface toward the MR element is small, so that it is difficult for the magnetic flux to reach the MR element due to spacing loss. The recording wavelength of the magnetized region 13 may be determined to be an optimum value depending on a combination of the distance between the MR element and the rotor, the element sensitivity, the wavelength of the magnetized region 12, and other factors. For example, it has been found that when the distance between the MR element and the rotor is 0.1 mm and the stripe width of the element is lOILm, the recording wavelength of the magnetized region 13 should be equal to or less than h of the magnetized region 12.

In Figure 1, the magnetized area 13 is one round before and after the magnetized area 12, but the same effect can be obtained by providing one short wavelength recording area before and after the reference position as shown in Figure 3. be able to.

Furthermore, although a rotary encoder has been exemplified above, the present invention can be similarly applied to a linear encoder in which tracks are arranged in a straight line. Furthermore, similar effects can be obtained when using an inductive magnetic sensor other than an MR element as the detection element.

[Effect] As is clear from the above explanation, according to the present invention, a configuration is adopted in which magnetized regions having a recording wavelength shorter than that of the magnetized region are provided before and after the magnetized region for detecting the reference position. It is possible to provide an excellent encoder device that can narrow the spread of magnetic flux for detection and reduce detection errors.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the rotor section of a rotary encoder according to the present invention, Fig. 2 is an explanatory diagram showing the magnetic flux distribution of the rotor in Fig. 1, and Fig. 3 shows a different embodiment of the invention. FIG. 4 is a waveform diagram showing a detection signal by the apparatus shown in FIG. l... Rotor 5... Magnetization pattern 6...
・Index phase 7...Incremental phase 12.13...Magnetization area 10.14...Magnetic flux person 5p

Claims (1)

[Claims] An encoder device that detects the reference position of a detected object using a magnetic sensor, characterized in that magnetized regions having a recording wavelength shorter than that of the magnetized region are provided before and after a magnetized region for detecting the reference position of the detected object. encoder device.