JPS61161416A - Index signal detector - Google Patents

Abstract

PURPOSE:To record a magnetic signal correctly and magnetically and to detect a reference position precisely by adjacently opposing magneto-resistance elements to an index track on which constant wavelength signal parts and index parts are alternately continued. CONSTITUTION:Repeated magnetic signals having a fixed wavelength lambda are magnetically recorded on the same periphery to form an encoder track 2 and constant wavelength signal parts 31 magnetically recorded with the wavelength lambdaand index parts 32 magnetically recorded with 2lambda are alternately and continuously formed on the same periphery to form the index track 3. In each magneto- resistance element 4, an encoder part 41 opposed to the track 2 and an index part 42 opposed to the track 3 have respective current paths R1-R4. The current paths R3, R4 have the phase difference corresponding to 180 deg. electric angle for a magnetic signal of the index part 32 and the phase difference corresponding to 90 deg. electric angle for a magnetic signal of the constant wavelength signal part 31. Since the constant wavelength signal parts 31 and the index parts 32 are alternately and continuously formed, signals are precisely detected and the reference position is precisely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an index signal detection device used in rotary encoders, near scales, and the like.

(Prior art) As an index signal detection device, for example, in a rotary encoder that detects repeated magnetic signals and index signals of a certain wavelength using magnetoresistive elements from an encoder track and an index track formed in a rotating part, the index track has a reference Japanese Patent Laid-Open No. 5 (1973) discloses an index signal recorded by magnetizing a pair of N and S poles at certain positions and detecting this with a magnetoresistive element.
It is known from the publication No. 9-5914.

(Problems to be Solved by the Invention) In the above index signal detection device, when an index signal is recorded by magnetizing a pair of N and S poles at the reference position of the index track, this index signal is As shown in the figure, both ends of the S/N pole spread, or as shown in Figure 6, multiple N and S poles are formed, making it impossible to record correctly. Therefore, the standard is determined by detecting the index signal. Even if the index track is provided on a member that performs linear motion with respect to the magnetoresistive element instead of the rotating part, where the position cannot be detected accurately, the reference position can be detected accurately as well. I can't.

(Means for Solving the Problems) The present invention continuously comprises a constant wavelength signal section in which a magnetic signal of a constant wavelength is repeatedly magnetized and recorded, and an index section in which a magnetic signal is magnetized and recorded at a wavelength different from this constant wavelength signal section. A magnetoresistive element having a plurality of current paths is closely opposed to the index track, and the pitch between the current paths is adjusted electrically to the wavelength of the constant wavelength signal section or the index section. They are arranged so that there is a phase difference of approximately 180 degrees at the corners.

(Function) A magnetoresistive element detects a signal from an index track, and since the index track is provided with a constant wavelength signal section and an index section in succession, the magnetic signal can be magnetized and recorded correctly, so signal detection can be performed accurately. Therefore, the reference position can be accurately detected.

(Embodiment) FIG. 1 shows an embodiment of a rotary encoder to which the present invention is applied.

The magnetic body 1 is provided in a rotating part that is attached concentrically to the rotating shaft of a rotating body, and rotates with the rotation of the rotating body. This magnetic body 1 is created by magnetizing and recording magnetic signals of a constant wavelength λ repeatedly on the same circumference, that is, by magnetizing and recording magnetic signals of a constant wavelength λ,
The encoder track 2 is formed by magnetizing the poles repeatedly.

A constant wavelength signal section 31 in which a magnetic signal of a constant wavelength λ is repeatedly magnetized and recorded, and an index section 32 in which a magnetic signal of a different wavelength, for example 2λ, is magnetized and recorded are placed on the same circumference. The index track 3 is formed by providing the index track 3 continuously. The encoder track 2 and the index track 3 are provided concentrically around the center of rotation of the magnetic body 1, and the magnetic signal magnetized and recorded on the index track 3 has a sine wave as shown in FIG. The index section 32 is provided at a reference position on the index track 3. Magnetoresistive element 4 has encoder track 2 and index track 3
The encoder section 41 facing the encoder track 2 and the index section 42 facing the index track 3 are arranged at fixed positions in close proximity to each other and have a plurality of current paths R1, R3, and R4, respectively. This current path R
1 to R4 are composed of ferromagnetic magnetoresistive elements (or Hall elements, etc.).1 As is well known, ferromagnetic magnetoresistive elements have a magnetoresistive effect in which the resistance value decreases when a magnetic field is applied, as shown in Figure 4. The ferromagnetic magnetoresistive elements R3 and R4 of the section 42 are arranged at a pitch of λ/2 in the rotation direction of the magnetic body 1 (magnetic signal recording direction) as shown in FIG. It is connected in series between both ends of the power supply E. Further, the ferromagnetic magnetoresistive element R1 of the encoder section 41,
R2 is (1/4 + 1/2)λ in the rotation direction of magnetic body 1
They are arranged at a pitch of , and are connected in series between both ends of the DC power supply. Therefore, the ferromagnetic magnetoresistive elements R3 and R4 have a phase difference of 90 degrees in electrical angle with respect to the magnetic signal of the index section 32, and a phase difference of 180 degrees in electrical angle with respect to the magnetic signal of the constant wavelength signal section 31. 1 ferromagnetic magnetoresistive element R3,
The detection signal obtained from the connection point 5 of R4 is determined by the resistance ratio of the ferromagnetic magnetoresistive elements R3 and R4, and as the magnetic body 1 rotates, it remains constant for the constant wavelength signal section 31 as shown in Figure 2 (■). level, and the index section 32 becomes an AC waveform.

The detection signal at the connection point 5 is kept constant by a comparator (not shown) and is compared with Beyle to form a pulse waveform as shown in FIG. That is, in the index section 31, a magnetic signal having a wavelength such that a detection signal can be obtained is magnetized and recorded, and in the constant wavelength signal section 31, a magnetic signal having a wavelength such that a detection signal cannot be obtained is magnetized and recorded. Furthermore, a detection signal is obtained at the connection point between the ferromagnetic magnetoresistive elements R1 and R2 in accordance with the magnetic signal recorded on the encoder track 2.

Further, in another embodiment of the present invention, the pitch of the ferromagnetic magnetoresistive elements R3 and R4 is set to inches in the above embodiment, and the pitch of the ferromagnetic magnetoresistive elements R3 and R4 is
For example, the wavelength of the index section 32 is arranged so as to have a phase difference of 180 degrees in electrical angle with respect to the wavelength of the index section 2, and a phase difference of 90 degrees in electrical angle with respect to the wavelength of the constant wavelength signal section 31. The pitch of the ferromagnetic magnetoresistive elements R3 and R4 is set to 1/2 of the wavelength of the portion 31 as described above. Therefore, contrary to the above embodiment, the detection signal at the connection point 5 is at a constant level for the index section 32, but the detection signal for the constant wavelength signal section 3 is at a constant level.
1 becomes an alternating current waveform, and its constant level is detected by a circuit (not shown).

Note that the present invention can also be used in a linear scale, etc., and an index track can be provided in a straight line, so that a detection signal can be obtained at the origin position.

(Effects of the Invention) As described above, according to the present invention, a constant wavelength signal section in which a magnetic signal of a constant wavelength is repeatedly magnetized and recorded, and an index section in which a magnetic signal is magnetized and recorded at a wavelength different from this constant wavelength signal section are provided. A continuous index track is formed, and the reference position is detected by detecting a magnetic signal from this index track using a magnetoresistive element, so it is possible to record the magnetic signal correctly on the index track. Therefore, the reference position can be detected accurately.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a rotary encoder to which the present invention is applied, FIG. 2 is an explanatory diagram of the embodiment, FIG. 4
The figure is a characteristic diagram of a ferromagnetic magnetoresistive element, and FIGS. 5 and 6 are diagrams showing signal recording waveforms of a conventional device. 3... Index track, 31... Index section, 32... Constant wavelength signal section, 4... Magnetoresistive element, R3, R4... Current path.

Claims (1)

[Scope of Claims] 1. An index in which a constant wavelength signal section in which a magnetic signal of a constant wavelength is repeatedly magnetized and recorded and an index section in which a magnetic signal is magnetized and recorded at a wavelength different from the constant wavelength signal section are successively provided. A track is formed, and a magnetoresistive element having a plurality of current paths is closely opposed to the index track, and the pitch between the current paths is approximately 180 degrees in electrical angle with respect to the wavelength of the constant wavelength signal section or index section. An index signal detection device arranged so as to have a phase difference. 2. When the wavelength of the constant wavelength signal section is λ, the wavelength of the index section is 2λ, and the pitch between each current path is λ/
2. An index signal detection device according to claim 1.