JPH0132209Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an index pulse generator for a floppy disk.

(Background of the Idea) The recording format on a magnetic disk employed in a conventional mini-floppy disk will be explained based on FIGS. 1 and 2. Reference numeral 1 denotes a disk, and on its upper surface, a plurality of concentric tracks TR, for example 40, are formed around the spindle hole 2 (inside the track TR, there are a plurality of tracks TR, for example 16).
The head of one track TR or head PH is a detection signal (index pulse) generated by the index mechanism.
determined by. A first gap Gap1 is formed as a preamble from this front end position PH,
Thereafter, the first sector sec1, the second sector sec2, and so on up to the 16th sector sec16 are formed, and after passing through the post ampoule, they reach the front end position PH again.

Furthermore, within one sector sec, as shown in Figure 2, there is a second index field (1D Field).
Gap2, data field (Data
Field) and the third gap Gap3. Also, the above index field is sync,
Consists of index mark 1D, error correction code CRC, and the above data field is synchronized.
sync, data mark DM, data error correction code
It is made up of each area of the CRC. However, regarding the generation timing of the index pulse, it is necessary to generate the index pulse with sufficient margin for the first gap Gap1 as a preamble.

Now, regarding a floppy disk, etc., if we assume the following conditions: index cycle 200μsec data transfer time 250KB/s = 32μsec/ByTe number of tracks 80 outermost track diameter φ79 innermost track diameter φ49 track interval 0.1875mm motor speed fluctuation α Minimum length per 1Byte l _BMIN = Lmin / 200 × 10 ^-3 (1 - α / 100) / 32 × 10 ^-6 = Lmin / 6250 (1 - α / 100) When α = 3% l _BMIN = It becomes 0.0239mm/Byte.

In the example of the format shown in Figure 1, Gap
Since Gap 1 is 32 Bytes and Gap 4 is 266 Bytes, the lengths of each are as follows.

L _Bnio 32 = 0.7648mm L _Bnio 266 = 6.35mm Therefore, the index generation timing is 0.7648mm on the innermost circumference φ49, and if converted to time,
It needs to occur within 993 μsec.

(Prior Art) A conventional index pulse generator was constructed as shown in FIGS. 7 and 8. That is, a unipolar magnetic pole of an indexing magnet 6 is protruded and fixed to the outer periphery of a rotor 4 of a motor that drives a floppy disk, and a Hall IC 12 is attached to a holder 10 so as to closely oppose the unipolar magnetic pole of the magnet 6. It is provided through. 5 is a support member, 7 is a rotor 4
The shaft portions of each are shown.

As the rotor 4 rotates, the unipolar magnetic pole of the magnet 6 and the Hall IC 12 face each other every rotation, and the Hall IC 1
2 is applied with a magnetic field having the magnetic flux density shown in FIG. 9a, and the Hall IC 12 shapes the waveform of this at a predetermined threshold level to generate an index pulse shown in FIG. 9b.

However, the magnet 6 has temperature characteristics, and as the temperature changes, the magnetic flux density changes as shown by the broken line in FIG. 9a, and the generation timing of the index pulse output from the Hall IC 12 changes as shown in FIG. 9b. There were defects that varied as shown by the broken line.

(Purpose of the invention) The present invention has been made in view of the above, and aims to provide an index pulse generator for a floppy disk that eliminates the above-mentioned drawbacks.
A Hall element is installed in the magnetic field of the magnet, and the zero cross of the output voltage from the Hall element is detected and used as an index pulse, providing a configuration in which the timing of index pulse generation does not change even depending on the temperature characteristics of the magnet. It is something to do.

(Example of idea) The present invention will be explained below with reference to examples.

FIG. 3 is a plan view showing an embodiment of the present invention.

In one embodiment of the present invention, a magnet 1 is attached to the rotor 4.
4 are fixedly protruding from each other, and the magnets 6 are arranged, for example, at south poles and north poles along the rotational direction of the rotor 4. The Hall element 15 is fixed to the holder 10 so as to face the magnet 14 closely, and the Hall element 1
The output of the Hall element 15 is supplied to a zero cross detection circuit 16, which detects the zero cross of the output of the Hall element 15. The zero cross detection circuit 16 is configured to have hysteresis.

Now, as the rotor 4 rotates in the direction of the arrow, a magnetic field with a magnetic flux density shown in FIG.
The output of 5 has the waveform shown in FIG. 4b. Hall element 1
5 is different from the conventional Hall IC 12,
It has the same shape as the magnetic field of the applied magnetic flux density.

The output voltage from the Hall element 15 having the waveform shown in FIG. 4b is supplied to the zero cross detection circuit 16,
When a zero cross is detected, an index pulse is obtained which rises at the zero cross point and falls when the output of the Hall element 15 exceeds "A" as shown in FIG. 4c. "A" is hysteresis.

Further, when the strength of the magnetic pole of the magnet 14 changes due to a temperature change and the magnetic flux density applied to the Hall element 15 changes as shown in FIG. 4a, the Hall element 1
The output voltage of the zero-cross detection circuit 16 changes as shown by the broken line in FIG. However, the zero-crossing point of the output of the Hall element 15 does not change. As a result, the timing of index pulse generation does not deviate.

As shown in FIG. 5, an example of the zero-cross detection circuit 16 includes transistors Tr ₁ , Tr ₂ , Tr ₆ , Tr ₇ forming a differential amplifier circuit, and a current mirror circuit.
Tr ₃ , Tr ₄ , Tr ₈ , Tr ₉ , Tr ₁₅ , Tr ₁₆ transistor
It includes transistors Tr ₅ , Tr ₁₀ , Tr ₁₁ and a resistor R _Hys that generates hysteresis, as well as transistors Tr ₁₃ and Tr ₁₄ that form a constant current source. Now AB
In between, the output of the Hall element 15 is supplied. The output of the supplied coil 15 is as shown in FIG. 6a, and FIG. 6b is a reproduction of FIG. 4b. The output of the coil 15 is the transistor Tr ₁ , Tr ₂
The output of transistor Tr ₁ is amplified by transistor Tr ₅ and output to point D. The output waveform at point D is a waveform obtained by amplifying the input voltage between A and B, as shown in FIG. 6b. When the potential at point E via the resistor R _Hys falls below the potential at point F, transistor Tr ₆ of the differential amplifier formed by transistors Tr ₆ and Tr ₇ is turned on, and the output of transistor Tr ₆ turns on the transistor.
Tr ₁₀ is turned on, transistor Tr ₁₁ is turned off, and the outputs of transistors Tr ₁₀ and Tr ₁₁ , that is, the outputs of points G and H, become as shown in FIG. 6d and e. On the other hand, a part of the current from the output of the transistor Tr ₆ flows into the transistor Tr ₁₅ , so the transistor Tr ₁₆ forming a current mirror circuit with the transistor Tr ₁₅ sucks the current from the point E, resulting in a positive feedback state. Therefore, if the potential at point E is shown based on the potential at point F, it will be as shown in Figure 6c, and the product of the resistor R _HYS and the current I flowing through the resistor R _HYS will be as shown by the solid line from the wiring, and the zero cross will be reached. At times, sharp pulses are output. This state is maintained until the potential at point D reaches a predetermined value A of (+).

Therefore, an output as shown in FIG. 4c is obtained,
There is no malfunction caused by drift of the zero cross detection circuit 16 or the like.

(Effects of the invention) As explained above, according to the invention, a Hall element is provided in the magnetic field of the magnet, and the zero cross of the output voltage from the Hall element is detected and used as an index pulse. Even if the index pulse is generated, the timing at which the index pulse is generated will not change.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing the format in a floppy disk. FIG. 2 is a diagram showing an example of the format for one track. FIG. 3 is a plan view showing an embodiment of the present invention. FIG. 4 is a waveform diagram for explaining the operation of an embodiment of the present invention. FIG. 5 is a circuit diagram showing an example of a zero-cross detection circuit used in an embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the operation of the zero-cross detection circuit shown in FIG. 5. FIG. 7 is a plan view showing the configuration of a conventional index generation circuit. FIG. 8 is a side view of FIG. 7. FIG. 9 is a waveform diagram for explaining the operation of the conventional example shown in FIG. 4... Rotor, 14... Magnet, 15... Hall element, 16... Zero cross detection circuit.

Claims (1)

[Scope of utility model registration request] A magnet with both NS and NS poles is fixed to the outer circumference of the rotor that rotates the disk, and a Hall element is provided close to and opposite the magnet.The output of the Hall element is supplied to a zero-cross detection circuit, and the zero-cross detection output is used as an index pulse. An index pulse generator for a floppy disk, characterized in that: