JPS6182374A - Index pulse generator of floppy disk - Google Patents

Abstract

PURPOSE:To prevent the timing shift of the index pulse generation by providing a magnet in the outer periphery of a rotor and setting the zero cross detection output of a coil disposed opposite to the single magnetic pole of the magnet to an index pulse. CONSTITUTION:The single magnetic pole of a magnet is provided on a rotor 4 so as to project, and a coil 15 is disposed opposite to the pole. Whenever the rotor 4 makes one turn in the direction of an arrow, an induced voltage arises at the coil 14. Its output is inputted to a zero cross detection circuit 16, and an index pulse is outputted. Even if the intensity of the magnetic pole of a magnet 6 varies due to a change in temperature, etc., a zero cross point will not change; therefore the generation timing of the index pulse will not shift.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an index pulse generator for a floppy disk.

(Background of the Invention) 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 there is a concentric track TR centered around the spindle hole 2.
For example, a plurality of sectors Sec, for example 40, are formed, and within one track IR, several sectors Sec, for example 16, are sequentially arranged, and the head or head PH of one track T is detected by the index mechanism. determined by the signal (index pulse). A first gap G ap 1 is formed as a preamble from this front end position p r-r, and then the first sector 5 ecl and the second sector 5 e c are sequentially formed.
2, up to the 16th sector 5ecl 6 is formed and reaches the front end position PH again through the postamble.

Furthermore, within one sector Sec, as shown in FIG.
d) It is divided into a third gap Gap3. The above index field consists of synchronous 5 ync, index mark ID, and error correction code ORO areas, and the above data field is synchronous 5 ync.

It consists of each area of data mark DM and data error correction code CRC. However, regarding the generation timing of the index pulse, it is necessary to generate the index pulse with a sufficient margin with respect to the first gap Gapl as a preamble.

Currently, the following conditions apply regarding floppy disks, etc.

Index period 2'OO/7sec Data transfer time 250 KB/S= 32 μsec/Byte
Number of tracks: 80 Outermost track diameter: φ79 Innermost track diameter: φ49 Track spacing: 0.1875mm Motor speed fluctuation α:

Minimum length per IByte When it comes to α-3 tBMIN”0.0239mm/Byte.

In the format example shown in Figure 1, Gapl is 3.
Since 2 Bytes and Gap 4 are 266 Bytes, their respective lengths are as follows.

LBmin 32=0.7648 mmL13m+
n 266 ” 6.35 mm Therefore, the index generation timing is 0.7648 on the innermost circumference φ49
If we correct it to 91 hours in m, it needs to occur within 993 psec with a margin.

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

As the rotor 4 rotates, the single magnetic pole of the magnet 6 and the hole ] C12 are opposed to each other every rotation, and the hall IC 12 is arranged as shown in FIG.
A magnetic field with a magnetic flux density of a) is applied, and the hole 10 ],
The index pulse shown in FIG. 9(b) is generated by shaping the waveform at a predetermined threshold level.

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. 9(a).
Since the generation timing of the index pulse ξ output from the Hall IC 12 changes as shown by the broken line in FIG. 9(b), there is a drawback that the timing of the index pulse generation is shifted.

(Object of the Invention) The present invention has been made in view of the above, and an object of the present invention is to provide an index pulse generator for a floppy disk which eliminates the above-mentioned drawbacks.

In place of the conventional Hall IC, a coil wound around a ferrite core is provided, and a zero cross of the induced voltage of the coil is detected to thereby prevent a timing shift in index pulse generation.

(Embodiments of the invention) 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 single pole of a magnet 6 is fixed to the rotor 4 in a protruding manner, and a coil 15 wound around a ferrite core 14, for example, is mounted on a holder 10 so as to closely oppose the single pole of the magnet 6. The output of the coil 15 is supplied to a zero cross detection circuit 16 to detect the zero cross of the output of the coil 15. The zero cross detection circuit 16 is left open to have hysteresis.

That is, in place of the conventional hole 1C12.

A coil 15 wound around a ferrite core 14 is provided to detect the zero cross of the induced voltage in the coil.

With each rotation of the shunting rotor 4 in the direction of the arrow ＼,
The coil 15 crosses a magnetic field with a magnetic flux density shown in Fig. 4(a), and the output of the coil 15 generates an output with the waveform shown in Fig. 4(b), which is obtained by differentiating the waveform shown in Fig. 4(a). do. The output of the coil 15 having the waveform shown in FIG. 4(b) is supplied to the zero cross detection circuit 16, and the zero cross is detected and rises at the zero cross point as shown in FIG. 4(c).
The index flag ξ that falls when the output of 5 exceeds “N”
Lus is obtained. "A"' is hysteresis.

Further, even if the strength of the magnetic pole of the magnet 6 changes due to temperature changes and the strength of the magnetic field across the coil 15 becomes as shown by the broken line, the zero-crossing point of the output of the coil 15 does not change. As a result, the timing of index pulse generation does not shift.

An example of the zero cross detection circuit 16 is as shown in FIG. 5, which includes transistors Tr1. T
r2, TrB, Tr7, current mirror circuit Tr3゜Tr4, TrB, Trg, T
r15, TrH6+) transistor Tr5°Trl
o, TrH and the resistance T that generates hysteresis (
It has transistors Tr13 + Tr14 that form a constant power supply as well as I(ys).The output of the coil 15 is now supplied between AB.The output of the supplied coil 15 is shown in FIG. 6(a). As shown in Figure 6 (
b) is a reprint of FIG. 4(b). coil 15
The output of the transistor "I + Tr2 is amplified by a differential amplifier, and the output of the transistor Trl is amplified by the transistor Tr5 and output to point D.D
The output waveform at the point is a waveform obtained by amplifying the input voltage between AB as shown in FIG. 6(b). When the potential at point E via resistor RHys falls below the potential at point F, transistor Tr6
, Tr7 of the differential amplifier) The star Tr6 is turned on, and the output of the transistor Tr6 turns the transistor T r 1 o on, and the transistor Tr11 turns off, and the transistor Tr6 turns on.
The outputs of lQ + Trll, that is, the outputs at point G and point H, are as shown in FIGS. 6(d) and (e). On the other hand, part of the current due to the output of the transistor Tr6 is transferred to the transistor T
r (5), the transistor Tr16 forming a current mirror circuit with the transistor T r 15 sucks the current from the point E, resulting in a positive feedback state.

Therefore, the potential at point E can be expressed based on the potential at point F as shown in Figure 6 (
As shown in c), the product of the resistor RH7S and the current {circle around (2)} flowing through the resistor RHys is changed from the broken line to the solid line, and a sharp noise ξ is output at zero crossing from positive to negative. In this state, the potential at point D is maintained at a predetermined value Aj of (+).

Therefore, an output as shown in FIG. 4(c) can be obtained, and malfunctions will not occur even due to drift of the zero-cross detection circuit 16.

(Effects of the Invention) As explained above, according to the present invention, a coil is provided in the magnetic field of a magnet, and the zero crossing of the voltage induced in the coil is detected and used as an index pulse. The timing of occurrence often changes.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing the format of 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...mouth to evening, 6 river Fm stone, 14-ferrite core. 15...Coil, 1G...Zero cross detection circuit. Applicant Copal Electronics Co., Ltd. Agent Patent Attorney Sakae Kobayashi
^ l-\0
, Ω 0 Figure 7 Figure 8 Procedural amendment (4 issues) Date of July 3, 1980 Director General of the Japan Patent Office' Mr.
, Indication of the case Patent Application No. 203811 of 1983 2, Title of the invention Inodex pulse generator for floppy disk 3, Person making the amendment Relationship with the case Patent applicant 4/Agent Jinkan 60 5 Order for amendment Date 6, number of inventions increased by amendment 7, person subject to amendment II!

Claims (1)

[Claims] A single magnetic pole of a magnet is protruded and fixed to the outer circumference of a rotor that rotationally drives a disk, a coil is provided closely facing the single magnetic pole of the magnet, and the output of the coil is supplied to a zero-cross detection circuit to generate a zero-cross detection output. A floppy disk index pulse generator characterized by generating an index pulse.