JP2978048B2 - Apparatus and method for magnetizing a signal magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal magnet magnetizing device and a magnetizing method which can be used for a magnetic drum of a magnetic encoder, for example.

[0002]

2. Description of the Related Art A signal magnet of a rotation detecting device applied to a magnetic encoder or the like is formed by applying a magnetizing voltage to the outer peripheral surface of a cylindrical signal magnet with a magnetizing head. The signal magnet is held on a rotatable support, and the outer peripheral surface is magnetized while being rotated by the support.

However, it is difficult to make the center of the signal magnet coincide with the center of rotation, and the center positions of the magnets are often shifted. Due to this deviation, the signal magnet rotates while swinging, so that the gap between the outer peripheral surface of the signal magnet to be magnetized and the magnetization head always fluctuates with one rotation of the signal magnet as one cycle. It is impossible to uniformly magnetize the magnet for use, and the detection output of the magnetic sensor for detecting the magnetization of the magnet for signal fluctuates.

Therefore, a magnetizing device has been proposed which aims at uniformly magnetizing the outer peripheral surface of the signal magnet. For example, one described in Japanese Patent Application Laid-Open No. 1-160001 is known. This magnetizing device detects the position of the magnetized surface of the signal magnet with a touch sensor, and drives the magnetized head with a motor in accordance with the detected position of the magnetized surface of the signal magnet,
By keeping the position of the magnetizing head closer to the peripheral surface of the signal magnet or away from the outer peripheral surface of the signal magnet to keep the gap constant, uniform magnetization is performed.

[0005]

However, according to the above-mentioned conventional magnetizing device, the position of the outer peripheral surface of the signal magnet is detected by a mechanical sensor, and the magnetizing head is operated mechanically according to the detection result. Magnetization is performed while keeping the gap constant, which complicates the configuration and increases costs.Also, due to mechanical delays, the magnetization speed must be reduced, resulting in production. Sex had declined. Further, since the touch sensor position and the magnetic head position are displaced in the circumferential direction, the position of the signal magnet outer peripheral surface detected by the touch sensor and the position of the signal magnet outer peripheral surface at the position where the magnetized head is opposed are different. There was a drawback that the gaps could not be kept constant theoretically.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to make the detection output of a magnetic sensor for detecting a recording signal of a signal magnet low-cost and uniform. An object of the present invention is to provide a magnetizing device for a signal magnet and a magnetizing method thereof.

[0007]

According to the first aspect of the present invention,
A support base for rotating the signal magnet to be magnetized, a magnetizing head for applying a voltage opposite to the signal magnet for magnetizing, and a magnetizing power supply for supplying a magnetizing voltage to the magnetizing head. The magnetizing head is provided with a voltage from a magnetizing power supply to magnetize the signal magnet, and a signal is generated from a signal generation source different from the magnetizing power supply. It is characterized by being superposed and magnetized so as to be supplied and demagnetized to a desired output value.

According to a second aspect of the present invention, there is provided a signal magnet which rotates a signal magnet to be magnetized, applies a voltage to a magnetizing head facing the signal magnet, and magnetizes the signal magnet. After the signal magnet is magnetized, a voltage is applied to the magnetizing head to demagnetize it to a desired output value .
It is characterized by being superposed and magnetized as described above .

According to a third aspect of the present invention, the overlapping magnetizing means includes:
A DC voltage is applied to the magnetizing head to demagnetize it to a desired output value.

According to a fourth aspect of the present invention, the superposition magnetizing means comprises:
It is a means for applying an AC voltage to the magnetizing head to demagnetize it to a desired output value.

According to a fifth aspect of the present invention, the overlapping magnetizing means comprises:
It is a means for applying a voltage to the magnetizing head so as to reverse the phase magnetized to the signal magnet to demagnetize it to a desired output value.

[0012]

After magnetizing the outer peripheral surface while rotating the signal magnet, a DC or AC voltage is applied to demagnetize the signal. If the center of rotation of the signal magnet and the center of the signal magnet are displaced and the gap between the signal magnet and the magnetizing head fluctuates, the portion with a small gap is magnetized greatly, but the amount of demagnetization is also large. In addition, the portion where the gap is large is magnetized small, but the amount of demagnetization is also small, so that the final output of the magnetic sensor is substantially uniform over the entire circumference.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A signal magnet magnetizing apparatus and a magnetizing method according to the present invention will be described below with reference to the drawings. 1 (a) and 1 (b), the signal magnet 1 to be magnetized has a cylindrical shape and has a shaft 7 at the center, and the shaft 7 is held by a support (not shown). A magnetizing head 2 is mounted at a position adjacent to the outer periphery of the signal magnet 1.
The magnetized portion 2 a at the tip of the magnetized head 2 faces the outer peripheral surface of the signal magnet 1. Further, the magnetized portion 2a is brought close to the outer peripheral surface of the signal magnet 1 to such an extent that it does not contact the outer peripheral surface of the signal magnet 1. Therefore, a small gap H is provided between the outer peripheral surface of the signal magnet 1 and the magnetized portion 2a. doing. MR sensor 3 is arranged to face the outer periphery of the signal magnet 1.

In the magnetizing device for the signal magnet 1 having the above-described configuration, the center of rotation 5 and the center 6 of the signal magnet 1 rarely coincide completely with each other. When the signal magnet 1 is rotated, as shown in FIG. Accordingly, the gap H between the signal magnet 1 and the magnetized head 2 shown in FIG. 2B becomes smaller when the signal magnet 1 swings toward the magnetized head 2, and the signal magnet 1 is moved to the magnetized head 2. It becomes larger when swinging away from the two sides.

A voltage is supplied from a magnetizing power supply to the coil of the magnetizing head 2 in a state where the signal magnet 1 held on the support rotates while swinging, and the outer peripheral surface of the signal magnet 1 is magnetized. . In this case, the signal magnet 1 is magnetized quite strongly so that an output larger than the desired output is finally obtained.

Since the magnetized signal magnet 1 is eccentric, as shown in FIG. 2 (c), the intensity of the applied magnetic field is large where the gap H between the magnetized head 2 is small,
Conversely, the intensity of the applied magnetic field is small where the gap H with the magnetizing head 2 is large. Further, since the signal magnet 1 is magnetized so strongly that an output larger than a desired output is obtained, the output signal of the MR sensor 3 for detecting the magnetized signal of the signal magnet 1 is shown in FIG. 3
As shown in the figure, both the portion where the gap H is large and the portion where the gap H is small greatly exceed the output range that is ultimately obtained as indicated by the symbol A.

After the first magnetizing, a voltage is applied to the coil of the magnetizing head 2 from a signal source other than the first magnetizing power source while rotating the signal magnet 1. Then, the magnetization of the signal magnet 1 in the previous step is demagnetized by the overlapping magnetization so that the output level of the MR sensor 3 becomes a desired output level. .
As shown in FIG. 2 (c), a portion where the dimension of the gap H is small and the strength of the applied magnetic field is large also has a large strength of the applied demagnetizing field as shown in FIG. 2 (d). FIG.
As shown in FIG. 2C, the portion where the dimension of the gap H is large and the intensity of the applied magnetic field is small has a small intensity of the applied demagnetizing field as shown in FIG. .

After the first magnetization, demagnetization is performed by overlapping magnetization, so that the intensity of the demagnetizing field shown in FIG. 2D is subtracted from the intensity of the demagnetizing field shown in FIG. Figure 2
The final magnetized surface magnetic flux as shown in (e) is obtained. FIG.
The graph of the final magnetized surface magnetic flux of (e) has a shape conforming to the graph showing the gap H shown in FIG.
A portion where the gap H is large has a large surface magnetic flux, and a portion where the gap H is small has a small surface magnetic flux. When this magnetized signal is detected by the MR sensor 3, the gap between the outer peripheral surface and the MR sensor 3 fluctuates with the deflection of the signal magnet 1, but ( b ) and (e) of FIG.
As is clear from the comparison, the magnetic flux on the final magnetized surface is small in the portion where the gap is small, and the magnetic flux on the final magnetized surface is also large in the portion where the gap is large.
As shown in (1), the MR output is substantially constant without fluctuation.

The voltage applied for the superposed magnetization may be DC or AC. For example, the signal magnet 1 is shown in FIG.
4A, even if the output of the MR signal per rotation fluctuates greatly as shown in FIG. 4B, the DC signal as shown in FIG. When applied after the first magnetization, as shown in FIG.
The R signal can be made substantially uniform overall. Similar results can be obtained by applying an AC signal after the first magnetization. The frequency of the AC signal is arbitrary, and can be used from a low frequency to a high frequency. FIG. 6A,
As means for the superposition magnetization for obtaining a desired output after the first magnetization by the strong magnetic field as shown in FIG. 6B, a reverse phase as shown in FIGS. 6C and 6D is used. The demagnetization may be performed by applying an AC signal. Also in this case, FIG.
As shown in (e), the MR output signal can be made substantially uniform overall.

In the above description, the object of magnetization is assumed to be, for example, an incremental signal magnet of a magnetic encoder. However, the magnetizing device and the magnetizing method of the signal magnet as described above are based on the index signal magnet. It is also applicable to magnetization. When forming the magnet for the index signal, FIG.
As shown in (a), one pulse of the magnetized signal is used to magnetize one location on the outer peripheral surface of the signal magnet, but pulsed magnetization is performed so that an output larger than a desired output is obtained. As shown in FIG. 7 (b), two peaks having different levels occur at two places. If this is sliced at a constant level and converted into a rectangular wave, two pulses are generated. Therefore, after the index signal magnet is subjected to index magnetization, a DC current as shown in FIG. 8A is applied as a demagnetizing current. By applying a DC current, as shown in FIG. 8B, the level of an unnecessary peak is lower than a certain slice level, and one pulse can be obtained. Further, if the level of the applied DC current is further increased as shown in FIG. 9A, unnecessary peaks can be further reduced as shown in FIG. 9B.

According to the signal magnet magnetizing apparatus and the magnetizing method having the above-described configuration, the magnetizing head 2 can use the magnetizing power supply to obtain an output larger than a desired output by the magnetizing power supply. And a signal is supplied from a signal source different from the magnetizing power supply to overlap and magnetize a desired output value. By the way, the magnetic field is greatly demagnetized, and the output of the sensor for detecting the magnetization signal of the signal magnet becomes uniform. Further, since there is no operation such as adjusting the gap by mechanically moving the magnetization head 2, the configuration is simple, and it is possible to sufficiently cope with a high speed magnetization. Also,
By applying demagnetization by overlapping magnetization after the first magnetization, the magnetization can be erased to such a degree that there is no problem in practical use. Therefore, it can be reused without discarding failed products and the like. .

In the above embodiment, the demagnetization is performed by the magnetization head 2 used for the magnetization. However, the demagnetization may be performed by a head different from the magnetization head. The apparatus and method according to the present invention are also applicable to FG magnetization of a capstan motor. Further, the description has been given of the cylindrical signal magnet, but as shown in FIG. 10, a disk-shaped signal magnet 1 ′ is used, and the magnetized head 2 is attached to the outer peripheral portion of the upper end surface or the lower end surface. It may be configured to apply magnetism.

[0023]

According to the present invention, a voltage is supplied from a magnetizing power supply to a magnetizing head so that a signal larger than a desired output can be obtained. Since the magnet is overlapped so as to demagnetize it to a desired output value by applying a voltage, even if the center of the signal magnet and the center of rotation are eccentric and the signal magnet swings, the magnetization signal of the signal magnet is magnetized. The output of the sensor for detecting is substantially uniform, so that a mechanism for uniformly magnetizing the outer peripheral surface of the signal magnet as in the related art is not required, the configuration is simplified, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows a magnetizing device for a signal magnet according to the present invention.
(A) is a top view which shows an Example, (b) is a perspective view which shows an Example.

FIG. 2 is a waveform chart showing various characteristics of a signal magnet formed by the signal magnet magnetizing device of the first embodiment;

FIG. 3 is a waveform diagram showing a sensor output by a first magnetizing of the signal magnet formed by the signal magnet magnetizing device of the first embodiment;

FIGS. 4A and 4B are graphs showing eccentricity of a signal magnet formed by the apparatus for magnetizing a signal magnet and the method of manufacturing the same according to the present invention, and FIG. FIG. 4 is a waveform diagram showing a signal.

5A is a waveform diagram showing a DC signal used for demagnetization, and FIG. 5B is a waveform diagram showing a sensor output signal after demagnetization. FIG.

6 (a) and 6 (b) are waveform diagrams showing an example of a first magnetized signal, and FIGS. 6 (c) and 6 (d) are waveforms showing examples of signals used for demagnetization. FIG. 3E is a waveform chart showing a sensor output signal after demagnetization.

FIG. 7 is a waveform diagram showing an example in which the signal magnet magnetizing apparatus and the manufacturing method according to the present invention are used for index magnetizing.

FIG. 8A shows a case where the apparatus for magnetizing a signal magnet and the method of manufacturing the same according to the present invention are used for index magnetization.
7A is a waveform diagram showing a signal used for demagnetization, and FIG. 7B is a waveform diagram showing an index output after demagnetization.

FIG. 9 also shows a case where the magnet is used for index magnetization.
(A) is a waveform diagram showing a larger demagnetization signal, and (b) is a waveform diagram showing an index signal after demagnetization.

FIG. 10 is a perspective view showing still another example of a signal magnet magnetizing apparatus and a method of manufacturing the same according to the present invention.

[Explanation of symbols]

 1 signal magnet 2 magnetizing head

Claims (5)

(57) [Claims] 1. A support for rotating a signal magnet to be magnetized, a magnetizing head for applying a voltage opposite to the signal magnet to magnetize the magnet, and applying a magnetizing voltage to the magnetizing head. A magnetizing device for a signal magnet, comprising: a magnetizing power supply that supplies a voltage from the magnetizing power source to magnetize the signal magnet; power supply and to the desired output value signal is supplied from a separate signal generating source
A magnetizing device for a signal magnet, which performs overlapping magnetization so as to be demagnetized . 2. A signal magnet magnetizing method comprising: rotating a signal magnet to be magnetized, applying a voltage to a magnetizing head facing the signal magnet, and magnetizing the signal magnet. Then, after magnetizing the signal magnet, a voltage is applied to the magnetizing head to perform overlapping magnetization so as to demagnetize it to a desired output value. Magnetic method. 3. The magnetizing apparatus according to claim 2, wherein said superimposing magnetizing means is means for applying a DC voltage to a magnetizing head to demagnetize the magnetized head to a desired output value. Method. 4. The magnetizing apparatus according to claim 2, wherein said superimposing magnetizing means is a means for applying an AC voltage to the magnetizing head to demagnetize the magnetized head to a desired output value. Method. 5. The overlapping magnetizing means applies a voltage to a magnetizing head so as to reverse the phase magnetized to a signal magnet,
3. The method according to claim 2, wherein the means is a means for demagnetizing to a desired output value.