JPH08329596A - Index detecting mechanism - Google Patents

Abstract

PURPOSE: To prevent the occurrence of an error pulse due to leakage magnetic flux of a permanent magnet by disposing the end of one magnetic pole side of a magnetized part of the permanent magnet on the opposite side to the rotating direction of a rotor yoke and the end of a window hole part to be put aside in contiguity with each other. CONSTITUTION: The end of an N-pole side of an index magnetized part on the opposite side to the rotating direction of the rotor yoke 2a and the end of the window part 3a of the rotor yoke 2a are disposed to be put aside in contiguity with each other. Consequently, when the rotor yoke 2a is rotated, a change in magnetic flux of the index magnetized part 9a is detected by a Hall element 7, and when it is inputted as an index output waveform signal to a packaged circuit on a driving circuit board, the occurrence of leakage magnetic flux to be generated between the N-pole side of rotational driving magnetization 10 and index magnetization 9a and the rotor yoke 2a in the window hole part 3a is suppressed. Therefore, a normal index pulse signal is only generated without generating an error pulse caused by malfunction of a time constant circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an index detecting mechanism, and more particularly to an index detecting mechanism used in a flexible disk drive.

[0002]

2. Description of the Related Art FIG. 1 is an exploded perspective view showing a medium drive section of a flexible disk device. Further, FIG. 5 is a diagram showing an example of a rotor including an index magnetizing portion of a conventional index detecting mechanism, and FIGS. 5 (a) and 5 (b).
FIG. 3 is a configuration diagram and a perspective view, respectively. Furthermore, FIG.
FIG. 6 is a waveform diagram illustrating the principle of generating an index signal by a conventional index detection mechanism.

As shown in FIGS. 1 and 5, a conventional index detecting mechanism has a rotor composed of a rotor yoke 2 in which a permanent magnet 1 is fixed to a magnetic yoke, a drive pin (not shown) and a flexible disk. A drive coil portion 6 which generates a magnetic flux between the hub 4 having a medium receiving surface and a bearing for axially supporting the rotor to rotate the rotor yoke 2; And a drive circuit board 5 on which a circuit for controlling the rotation of the rotor yoke 2 and calculating the output signal of the Hall element 7 is mounted.

The permanent magnet 1 is provided with a drive magnetizing portion 10 and an index magnetizing portion 9, and the index magnetizing portion 9 is provided at the center of the window hole portion 3 provided on the outer periphery of the rotor yoke 2. And the rotor provided with the index magnetized portion 9 is fixed at a mechanical angle. The Hall element 7 is mounted on the drive circuit board 5 so as to have a positional relationship of traversing the index magnetized portion 9 when the drive pin is at the reference position.

When the rotor yoke 2 rotates and the index magnetized portion 9 crosses just in front of the hall element 7, the hall element 7 detects the leakage magnetic flux 8 leaking from the window hole 3 as a change in the magnetic flux and drives it. It is input as a detection signal to the circuit mounted on the circuit board 5. The waveform of this detection signal is
For example, when the index output waveform 21 as shown in FIG. 7 reaches a predetermined threshold value 23 and a zero-cross point 22 intersecting the threshold value 23 is detected, the index output waveform 21 shown in FIG. The time constant circuits A and B that do not operate generate the output waveform 24 of the time constant circuit A and the output waveform 25 of the time constant circuit B, respectively, and output the index signal 26 from them.

[0006]

As shown in FIG. 5, the conventional index detecting mechanism as described above is magnetized at the same time as the rotational drive magnetizing 10 at the center of the window hole 3 on the outer periphery of the rotor yoke. Since the index magnetized portion 9 composed of NS poles is installed on the outer periphery of the permanent magnet, a leakage magnetic flux 8 is generated between the N pole side of the index magnetized portion 9 and the rotor yoke 2, and the rotor yoke 2 rotates. When the index magnetized portion 9 traverses the Hall element 7, and when the Hall element 7 detects the magnetic flux of the index magnetized portion 9, the leakage magnetic flux 8 is also detected.

Therefore, the index output waveform 21 is
As shown in FIG. 7, for example, due to the leakage flux on the N pole side,
A convex portion bias waveform 27 that exceeds the threshold value 23 in the positive direction is generated again. Therefore, in the conventional index detection mechanism, the time constant circuits A and B (not shown) are activated to output the normal index signal 26, and then the threshold value 23 is reached again at the convex bias waveform 27, and the zero cross point 2 is reached.
There is a problem that the false pulse 28 is generated by detecting 2.

[0008]

The structure of the index permanent magnet of the present invention is an annular permanent magnet that rotates integrally with a rotating shaft and has a magnetized portion on the outer peripheral portion for detecting an index.
A rotor yoke in which the permanent magnet is fixed to a yoke made of a magnetic material, and a window hole portion provided on an outer peripheral portion of the rotor yoke so that a magnetized portion of the permanent magnet is located,
An index detection mechanism including a magnetic flux detection sensor that is disposed near the outer circumference of the rotor yoke and that detects a magnetic flux generated from the permanent magnet, wherein one of the magnetized portions of the permanent magnet that is on the opposite side of the rotation direction of the rotor yoke. It is arranged such that the end on the magnetic pole side and the end of the window hole portion are arranged so as to be in contact with each other.

Further, the end of the magnetized portion of the permanent magnet on the side of the one magnetic pole may be formed to extend to the end of the window hole portion of the rotor yoke, or the end of the window hole portion of the rotor yoke may be formed. The window hole portion may be formed so as to be in contact with the end of the magnetized portion of the permanent magnet on the one magnetic pole side.

[0010]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is an exploded perspective view showing a medium drive section of a flexible disk device. FIG. 2 is a diagram showing an example of a rotor including an index magnetizing portion according to the first embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are a structural view and a perspective view, respectively. Is. Further, FIG. 6 is a waveform diagram for explaining the principle of generating an index signal by the index detecting mechanism of the present invention.

As shown in FIGS. 1 and 2, the index detecting mechanism of this embodiment has a rotor yoke 2a in which a permanent magnet 1 is fixed to a yoke of a magnetic material, as in the conventional example.
And a rotor 4 including a drive pin (not shown) and a hub 4 having a receiving surface for a flexible disk medium, and a bearing (not shown) for axially supporting the rotor to generate a magnetic flux. Drive coil section 6 that rotates by rotating
And a drive circuit board 5 on which a circuit for energizing the drive coil portion 6 to generate magnetic flux and controlling the rotation of the rotor yoke 2a and calculating the output signal of the Hall element 7 is mounted.

The permanent magnet 1 is provided with a drive magnetizing portion 10 and an index magnetizing portion 9a. The index magnetizing portion 9a is provided at the center of the window hole portion 3 provided on the outer periphery of the rotor yoke 2a. The dove pin provided on the hub 4 and the rotor provided with the index magnetized portion 9a are fixed while being mechanically positioned. The Hall element 7 is mounted on the drive circuit board 5 so as to have a positional relationship of traversing the index magnetized portion 9a when the drive pin is at the reference position.

When the rotor yoke 2 rotates and the index magnetized portion 9 crosses just before the hall element 7, the hall element 7 detects the leakage magnetic flux 8 leaking from the window hole 3 as a change in the magnetic flux and drives it. It is input as a detection signal to the circuit mounted on the circuit board 5. The waveform of this detection signal is
For example, when the index output waveform 11 as shown in FIG. 6 reaches a predetermined threshold value 13 and a zero cross point 12 intersecting the threshold value 13 is detected, the index output waveform 11 shown in FIG. The time constant circuits A and B that do not operate generate the output waveform 14 of the time constant circuit A and the output waveform 15 of the time constant circuit B, respectively, and output the index signal 16 from them.

In the index detecting mechanism of the present embodiment, the window driving portion 3a is provided between the rotor driving magnetizing portion 10 and the index magnetizing portion 9a between one magnetic pole side (in this embodiment, the N pole side is shown) and the rotor yoke 2a. In order to suppress the generation of the leakage magnetic flux generated in the above, the N pole side end of the index magnetized portion 9a, which is the opposite side to the rotation direction of the rotor yoke 2a, and the end of the window hole portion 3a of the rotor yoke 2a are brought close to each other. It is installed.

As a result, in the index detecting mechanism of the present embodiment, when the rotor yoke 2a rotates, the Hall element 7 detects the change in the magnetic flux of the index magnetized portion 9a, which is used as the index output waveform signal 11 for the drive circuit board 5. When input to the circuit mounted on the above, it is possible to prevent the generation of the convex bias waveform which is the component of the leakage magnetic flux as in the conventional case, so that the time constant circuit does not malfunction and no false pulse occurs, Only normal index pulse signals can be generated.

Next, FIG. 3 is a diagram showing a structure of a rotor including an index magnetizing portion according to a second embodiment of the present invention,
3A and 3B are a configuration diagram and a perspective view, respectively.

This embodiment is shown in FIGS. 3 (a) and 3 (b).
As shown in FIG. 7, the structure is the same as that of the first embodiment except that the N-pole side of the index magnetized portion 9b is formed so as to be in contact with the window hole portion 3b of the rotor yoke 2b. This prevents the generation of false pulses.

Further, FIG. 4 is a view showing the structure of a rotor including an index magnetizing portion according to a third embodiment of the present invention, and FIGS. 4 (a) and 4 (b) are a structural view and a perspective view, respectively. It is a figure.

This embodiment is shown in FIGS. 4 (a) and 4 (b).
As shown in, the end of the window hole portion 3c of the rotor yoke 2c is
The configuration is the same as that of the first and second embodiments except that the window hole portion 3c is formed so as to be in contact with the end of the index magnetized portion 9b on the N-pole side. It prevents the occurrence.

[0021]

As described above, according to the index detecting mechanism of the present invention, one end of the index detecting magnetized portion on the side opposite to the rotating direction of the rotor yoke is on the side of one magnetic pole and the end of the window hole portion. By arranging them so that they are in contact with each other, it is possible to prevent a convex portion bias waveform from being generated in the index output waveform, and thus it is possible to prevent an erroneous pulse signal from being generated.

The end on the one magnetic pole side of the magnetized portion for index detection may be formed large to the end of the window hole portion. The same effect can be obtained by forming the window hole narrow so that the end of the window hole is in contact with the end on the one magnetic pole side of the index magnetization.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a medium driving unit of a flexible disk device.

FIG. 2 is a diagram showing a configuration of a rotor including an index magnetizing portion according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a rotor including an index magnetizing portion according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a rotor including an index magnetizing portion according to a third embodiment of the present invention.

FIG. 5 is a diagram showing an example of a configuration of a rotor including an index magnetizing section of a conventional index detecting mechanism.

FIG. 6 is a waveform diagram illustrating the principle of generation of an index signal by the index detection mechanism of the present invention.

FIG. 7 is a waveform diagram illustrating a principle of generating an index signal by a conventional index detection mechanism.

[Explanation of symbols]

 1 Permanent Magnet 2, 2a, 2b, 2c Rotor Yoke 3, 3a, 3b, 3c Window Hole 4 Hub 5 Drive Circuit Board 6 Drive Coil 7 Hall Element 8 Leakage Flux 9, 9a, 9b, 9c Index Magnetized 10 Drive Magnetizing unit 11,21 Index output waveform 12,22 Zero cross point 13,23 Threshold 14,24 Time constant circuit A output waveform 15,25 Time constant circuit B output waveform 16,26 Index signal 27 Convex portion bias Waveform 28 False pulse

Claims (3)

[Claims] 1. A ring-shaped permanent magnet that rotates integrally with a rotary shaft and has a magnetized portion on the outer peripheral portion for index detection, a rotor yoke in which the permanent magnet is fixed to a yoke made of a magnetic material, and an outer periphery of the rotor yoke. And a window hole portion provided in a portion so that the magnetized portion of the permanent magnet is located, and a magnetic flux detection sensor that is disposed close to the outer periphery of the rotor yoke and detects the magnetic flux generated from the permanent magnet. In the index detection mechanism, one end of one side of the magnetized portion of the permanent magnet on the side opposite to the rotating direction of the rotor yoke on the magnetic pole side and the end of the window hole portion are arranged so as to be offset. An index detection mechanism characterized by the above. 2. The index detecting mechanism according to claim 1, wherein an end of the magnetized portion of the permanent magnet on the side of the one magnetic pole is formed to extend to an end of the window hole portion of the rotor yoke. 3. The end of the window hole portion of the rotor yoke is
2. The index detecting mechanism according to claim 1, wherein the window hole portion is formed so as to be in contact with an end of the magnetized portion of the permanent magnet on the one magnetic pole side.