JPS61161417A - Index signal detector - Google Patents

Abstract

PURPOSE:To record a magnetic signal exactly and magnetically and to detect a reference position exactly by opposing magneto-resistance elements to an index track on which constant wavelength signal parts and index parts are alternately continued. CONSTITUTION:The index track on which the constant wavelength signal parts 12 recording repeated magnetic signals having a fixed wavelength lambda and the index parts 13 recording magnetic signals having a fixed wavelength 2lambda are alternately and continuously formed is formed on a magnetic recording medium. The recording medium is a member for detecting a reference position and formed unitedly with a unit executing rotational or straight motion or the like and the index track is formed along its moving direction theta. The current paths MR1, MR2 of each magneto-resistance element 14 are constituted of ferromagnetic magneto-resistance elements, arranged with the pitch lambda in the moving direction theta and connected to both the terminals of a DC power supply 15 in series. An output terminal 16 is connected to the node of the current paths MR1, MR2. Since the constant wavelength signal parts 12 and the index parts 13 are alternately and continuously formed and signal detection can be exactly executed, the reference position can be exactly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an index signal detection device used in rotation detectors, linear detectors, etc.

(Prior art) An example of an index signal detection device is a rotation detector that detects repeated magnetic signals and index signals of a fixed wavelength using magnetoresistive elements from an encoder track and an index track formed on a rotating part, respectively. JP-A-59-591 records an index signal by magnetizing a pair of N and S poles at a reference position and detects this with a magnetoresistive element.
It is known from Publication No. 4.

(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 18, multiple N and S poles are formed, making it impossible to record correctly. Position cannot be detected accurately. Even if the index track is provided on a member that moves linearly with respect to the magnetoresistive element instead of the rotating part, the reference position cannot be detected accurately.

(Means for Solving the Problems) The present invention provides a constant wavelength signal section in which a magnetic signal of a constant wavelength λ is repeatedly magnetized and recorded, and a
An index track is formed in which an index section magnetized and recorded at a wavelength of λ is continuously provided, a plurality of current paths are connected in series to this index track, and a magnetoresistive element to which a magnetic bias is applied is faced, and each of the above-mentioned The pitch between the current paths is made approximately equal to the wavelength λ.

(Function) A magnetic bias is applied to the magnetoresistive element and the signal is detected from the index track, but the index track is provided with a constant wavelength signal section and an index section in succession, so that the magnetic signal can be correctly magnetized and recorded. 6 (Embodiment) Magnetoresistive elements are roughly divided into two types: semiconductor magnetoresistive elements and ferromagnetic magnetoresistive elements. 9 The present invention Either can be used. In one embodiment of the present invention, a ferromagnetic magnetoresistive element is used, and this ferromagnetic magnetoresistive element
It has MR characteristics (change in resistance to external magnetic field) as shown in Figure 1. As shown in FIG. 12, when a ferromagnetic magnetoresistive element 1 is applied with a magnetic field of N/S polarity according to a recording signal from, for example, a magnetic recording medium 2 as it rotates, MR
The resistance value changes according to the characteristics. However, as can be seen from FIG. 11, the ferromagnetic magnetoresistive element cannot distinguish magnetic poles.

Therefore, the ferromagnetic magnetoresistive element 1 is connected to the magnet 3 from the outside.
By applying a magnetic bias, the polarity discrimination ability is obtained as shown in FIG. If the magnet 3 is not present, the output waveform of the magnetoresistive element 1 will have a wavelength of 1/2 and a frequency twice that of the magnetic field applied by the recording signal of the magnetic recording medium 2, as shown in FIG. Then, as shown in FIG. 13, the wavelength and frequency of the magnetic field applied by the recording signal of the magnetic recording medium 2 will be the same.

One embodiment of the present invention adopts a method of applying a magnetic bias to a ferromagnetic magnetoresistive element as described above, and the first embodiment
As shown in the figure, the magnetic recording medium 11 includes a constant wavelength signal section 12 in which a magnetic signal of a constant wavelength λ is recorded repeatedly by magnetizing N and S poles repeatedly at regular intervals, and a pair of N and S poles. By magnetizing the poles, an index track is formed in which an index portion 13 on which a magnetic signal (index signal) with a wavelength of 2λ is recorded is continuously provided. This magnetic recording medium 11 is provided integrally with a member that is to detect a reference position and performs rotational or linear motion.
The index track is formed along the moving direction θ of this member. The magnetoresistive element 14 is placed close to and facing the index track in a stereotactic manner. Note that the magnetoresistive element 14 may be attached to the moving member and moved on the index track.The index portion 13 is provided at a position (reference position) on the index track where it is desired to obtain an index signal, and A constant wavelength signal section 12 is provided elsewhere on the top. The magnetoresistive element 14 has a plurality of current paths MHI
, MRZ, and the current paths MHI and NR2 are composed of ferromagnetic magnetoresistive elements and are arranged at a pitch of λ in the moving direction θ. Current path! 'fR1 and R2 are connected in series between both ends of the DC power supply 15, and the current path is 1°MR.
An output terminal 16 is provided at the connection point of 2. Current path MH
I, MR2 are provided with a constant magnetic field (
(magnetic bias) is applied and has a magnetic pole discrimination function.1
The operating points of the MR characteristics are set as shown in FIGS. 2 and 3, respectively. Therefore, when the magnetic recording medium 11 moves relative to the magnetoresistive element 14 and a magnetic field is applied to the current paths MHI and MR2 by a recording signal recorded on the index track as shown in FIG. The output waveforms are as shown in FIGS. 4 and 5, and the output signal of the output terminal 16 is at a constant level for the constant wavelength signal section 12 and is an AC waveform for the index section 13, as shown in FIG. 6. becomes.

The output signal from the output terminal 16 is compared with a constant level by a comparator (not shown), and becomes a pulse signal that is generated in the index section 13 in one narrow pulse. Figure 9 and 1
Figure 0 shows the output waveforms of the current path Ayu, MR2, and the output terminal 16 when the moving direction θ is reversed.

By appropriately providing the magnetic bias for the current paths MHI and MR2, the gap between the current paths MHI and MR2 and the magnetic recording medium 11, and the recording signal pattern of the index track, the output waveform of the output terminal 16 can be obtained as shown in FIG. It can also be done.

FIG. 15 shows an embodiment of a rotation detector to which the present invention is applied. The magnetic recording medium 11 and the magnetoresistive element 14 are substantially the same as in the above embodiment. It is provided. The disk 18 is provided on the same axis as the disk 17 and is driven to rotate, and a magnetic recording medium 19 is attached to the outer circumference of the disk 18. The magnetic recording medium 19 receives a repetitive magnetic signal of a constant wavelength λ in the direction of rotation. The signal is magnetically recorded, and this magnetic signal is detected by the magnetoresistive element 20. The magnetoresistive element 20 consists of A-phase and B-phase magnetoresistive elements arranged at a pitch of λ/4 in the rotation direction, and each output is the first
It will look like Figure 6. The pulse signal obtained from the output of the magnetoresistive element 14 (output of the comparator) is ANDed with the output of the A-phase magnetoresistive element to produce an index signal as shown in FIG.

(Effects of the Invention) As described above, according to the present invention, since magnetic signals are continuously magnetized and recorded on the index track, it is possible to record the magnetic signals in the correct magnetized manner, and the reference position can be detected accurately. can be done.

Further, since a magnetic signal is detected by applying a magnetic bias to the magnetoresistive element, it is possible to detect the reference position minutely.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIGS. 2 and 3 are MR characteristic diagrams of current paths in the same embodiment. 4 and 5 are waveform diagrams showing the resistance change of the current path in the same example, FIG. 6 is a waveform diagram showing the magnetoresistive element output in the same example, and FIG. 7 is a waveform diagram showing the index track arrival in the same example. A waveform diagram showing the magnetic pattern, FIG. 8 is a waveform diagram showing the index signal output of the same example, FIGS. 9 and 10 are waveform diagrams showing the waveforms of each part of the same example, and FIG. 11 is a waveform diagram showing the index signal output of the same example. Figure 12 is a perspective view showing an example of a method for detecting a magnetic signal by applying a magnetic bias to a magnetoresistive element, Figure 13 is a diagram explaining the characteristics of the same method, and Figure 14 is a diagram showing the above implementation. Figure 15 is a perspective view showing an embodiment of a rotation detector to which the present invention is applied, Figure 16 is a timing chart of the same embodiment, and Figures 17 and 18 are conventional devices. FIG. 3 is a waveform diagram showing an index signal recording pattern of FIG. 11... Magnetic recording medium, 12... Constant wavelength signal section, 1
3... Index portion, 14... Magnetoresistive element,
MRI, MR2...Current path.

Claims (1)

[Claims] An index track is formed in which a constant wavelength signal section is magnetized and recorded with a repeated magnetic signal of a constant wavelength λ, and an index section is magnetized and recorded at a wavelength of 2λ with respect to the wavelength λ of this constant wavelength signal section. An index signal characterized in that a plurality of current paths are connected in series and a magnetoresistive element to which a magnetic bias is applied is faced to the index track, and the pitch between the current paths is made to substantially match the wavelength λ. Detection device.