JPS6355156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an emergency evacuation circuit for a magnetic disk device, and more particularly to an emergency evacuation circuit that is reliable and inexpensive and consists of a switching circuit using a relay.

FIG. 1 shows a block diagram of an example of a positioning mechanism using a voice coil motor (shown in sectional view) of a magnetic disk device, which is the object of the present invention. The servo control circuit 2 in the figure receives a positioning target input signal 1 from a control device (not shown), and based on this signal 1, the voice coil 8 is sent in the forward direction (when the head is at the center of the disk) through the voice coil power supply line 3. By supplying the forward direction drive current 4 or the backward direction drive current 5, it is possible to position the data head 10 at a desired track (on the surface of the magnetic disk 11) at high speed and precision.

At this time, the position detection signal 6 read from the servo head 9 is finally fed back to the servo control circuit 2 and compared with the positioning target input signal 1. The servo control circuit 2 includes a logic circuit, an arithmetic circuit, a power amplifier for driving the voice coil, etc. for carrying out the above operations, and also includes a circuit for escaping the head from above the magnetic disk surface in the event of an emergency such as a power outage. It also includes emergency evacuation circuits and switching circuits.

FIG. 2 shows a circuit diagram of the emergency evacuation circuit and switching circuit portion of the prior art. While the rotational speed of the magnetic disk 11 is within a specified range and is operating normally, the relay 16 of the switching circuit is in contact with the normally open contact 17 side, and the power amplifier 13 is connected to the voice coil 8 via the voice coil feeder line 3. and positioning control is performed as described above. During this normal operation, the emergency evacuation capacitor 20 is placed at a negative potential (normally -3V to -
(approximately 15V).

When an emergency situation such as a power outage occurs, the relay 16 switches to the normally closed contact 18 side, and the emergency evacuation discharge current 21 flows from the capacitor 20, causing the head 1
0 is removed from the surface of the magnetic disk 11. Here, the magnitude of the load potential of the capacitor 20 is proportional to the magnitude of the retraction speed of the head. The upper limit value of the load potential is determined to be the above-mentioned relatively small voltage value because of the need to suppress the retraction speed and the acceleration when colliding with the mechanical stop position. On the other hand relay 16
When contacting the normally open contact 17 side and operating the voice coil by the power amplifier, the drive voltage of the power amplifier is about ±30V to ±50V, the drive currents 14 and 15 are about 10A, and the relay 16 becomes a power relay. is normal. relay 1
Since 6 is a power relay and the contact 18 is not normally used, an oxide film is likely to be formed thereon, and since only a relatively small voltage is applied during an emergency evacuation operation, a contact failure is likely to occur at the normally closed contact 18. Therefore, the emergency evacuation discharge current 2
1 could not flow sufficiently, and the reliability of the emergency evacuation operation was low.

[Purpose of the invention]

To relatively easily realize a method of eliminating poor contact of the normally closed contact 18 of the relay 20, which is a drawback of the prior art.

An object of the present invention is to eliminate the problems of the prior art, and to provide an emergency evacuation circuit that can prevent contact failure of relay contacts.

[Summary of the invention]

In order to achieve the above object, the emergency evacuation circuit according to the present invention is characterized in that a high voltage is applied instantaneously when the relay contacts are switched to refresh the contacts.

[Embodiments of the invention]

FIG. 3 shows a circuit diagram of an emergency evacuation circuit according to an embodiment of the present invention (the power amplifier side is the same as that in FIG. 2 and is omitted). An additional part according to the present invention is shown by a relay contact refresh circuit 22 framed by a broken line. During normal operation, while the normally closed contact 18 of the relay 16 is open, the capacitor 20 is charged to a relatively small voltage as described above, but the refresh capacitor 25 is charged to a negative potential through the resistor 24.
Negative power supply voltage V (usually -30V to -50V) has been reached. At this time, diode 23 is reverse biased, and current from capacitor 20 to capacitor 25 is blocked. In an emergency, when the normally closed contact 18 closes as shown in Figure 3, the capacitor 2
A discharge current 26 flows instantaneously (approximately 0.1 ms to 5 ms) from 5 to destroy the oxide film, and the contact 18
After the refresh is performed, the emergency evacuation discharge current 21 of the capacitor 20 flows, causing the head to perform an evacuation operation. By implementing this relatively simple method, the emergency evacuation operation becomes reliable.

〔Effect of the invention〕

According to the present invention, poor contact of the emergency evacuation circuit side contact (normally closed contact) of the switching relay can be prevented, and the reliability of operation can be improved.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of an example of a positioning mechanism for a magnetic disk device using a voice coil motor. FIG. 2 is a diagram showing a circuit diagram of the emergency evacuation circuit and switching circuit portion of the prior art. Further, FIG. 3 is a diagram showing a circuit diagram of an emergency evacuation circuit according to an embodiment of the present invention. Explanation of symbols, 1...Positioning target input signal, 2
... Servo control circuit (including power amplifier, emergency evacuation circuit, and their switching circuit), 3 ... Voice coil power supply line, 4 ... Forward direction (direction in which the head moves toward the center of the disk surface) drive current, 5 ... Reverse drive current, 6...Position detection signal, 7...Voice coil motor magnet, 8...Voice coil, 9...Servo head (head dedicated to reading position detection signal), 10...Data head (information recording) (for reproduction), 11...Magnetic disk, 12...Power amplifier control input signal, 13...Power amplifier, 14...Forward drive current, 15...Backward drive current, 16...Relay, 17...Normal Open contact, 18... Normally closed contact,
19...Power supply circuit for capacitor charge, 20...
... Capacitor (for emergency evacuation), 21 ... Emergency evacuation discharge current, 22 ... Relay contact refresh circuit, 23 ... Diode, 24 ... Resistor, 25
...Capacitor (for refresh), 26...Discharge current (for refresh).

Claims (1)

[Claims] 1. A power amplifier that supplies head positioning drive current to the voice coil motor, a head emergency evacuation circuit including a capacitor charging/discharging circuit for evacuation of the head from the disk surface in an emergency such as a power outage, and the power amplifier and emergency evacuation circuit. In an emergency evacuation circuit of a magnetic disk device including a switching circuit for mutually switching circuits, a first capacitor that instantaneously applies a high voltage to a relay contact of the switching circuit between a relay in the switching circuit and the emergency evacuation circuit. An emergency evacuation circuit for a magnetic disk device, comprising: a second capacitor that applies a voltage that maintains switching of the relay contact.