JPH0413791Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a head drive device for a magnetic disk, and in particular to a magnetic disk drive device that can improve the positioning accuracy of a magnetic head in a 2-inch magnetic disk used in an electronic still camera. This invention relates to a disk head adjustment device.

[Prior art and its problems]

For hard disks, optical disks, etc.
In general, tracking servo technology is used to perform tracking of the detection head, and recently this technology is also being adopted in magnetic disks with high TPI.

However, in most of the above cases, a voice coil type actuator capable of fine feeding is used, but since voice coil type actuators are relatively expensive, small magnetic disk drives are required to reduce the price. It is difficult to apply to devices.

On the other hand, in consideration of the above points, Japanese Patent Application Laid-Open No. 52 (1972) developed a system in which the main feed of the head carriage that is transferred along the magnetic disk is performed by a motor, etc., and the fine servo feed control is performed by a piezoelectric actuator.
Publication No. 36010 of 1980, Japanese Patent Publication No. 10384 of 1988, Special Publication No. 10385 of 1988, and Special Publication No. 10386 of 1988
There is something shown in the publication No. The devices shown in these patents are designed to reduce costs while performing tracking servo, but in all of these earlier applications, the head assembly is moved relative to the head carriage, and therefore, the head assembly is moved relative to the head carriage, so the head assembly is moved relative to the head carriage. Therefore, there is a problem that there is a concern about fluctuations and deterioration of the so-called head touch.The magnetic head is generally fixed in position with precision adjustment to the head carriage, and as the two move relative to each other, the magnetic head may change. There are concerns about changes in tilt and azimuth angle. Furthermore, since a relatively high voltage of several hundred volts is applied to the piezoelectric actuator in the vicinity of the head, there is a concern that the electric field may have an adverse effect.

[Purpose of invention]

Therefore, this invention makes it possible to fine-tune the stop position of the head carriage at least during playback using a tracking servo using a piezoelectric actuator to ensure that the magnetic head is at the desired track position, and to prevent fluctuations such as head touch. It is an object of the present invention to provide a magnetic disk head drive device that is free from danger.

[Summary of the idea]

The above object of this invention is to provide a head carriage which carries a magnetic head and is transported along the radial direction of a magnetic disk, a guide shaft for guiding the head carriage, and a motor installed substantially parallel to the guide shaft. The screw shaft is rotated by the screw shaft, the screw engaging portion of the head carriage engages with the screw shaft, and the head carriage is rotated in one direction in order to bring the screw engaging portion into contact with the threaded portion of the screw shaft. a biasing spring; and an electric actuator installed on at least one end of the screw shaft to move the screw shaft a predetermined direction in a direction substantially orthogonal to the direction of movement of the head carriage, the screw shaft being moved in the direction. As a result of the movement, the contact point between the screw shaft wall surface and the screw shaft engaging portion changes, so that the head carriage can be slightly fed in the transport direction, and at least during playback, the head carriage can be coarsely fed. This is generally achieved by a magnetic disk head drive device which is driven by the motor, and the small amount of movement of the head carriage is driven by the electric actuator based on a servo signal.

[Example of idea]

Embodiments of this invention shown in the drawings will be described below.

In FIG. 1, 1 and 2 are support plates provided in parallel at a predetermined interval, and 3 and 4 are the support plates 1,
a guide shaft installed parallel to each other between the two;
A screw shaft 5 is rotatably supported between the support plates 1 and 2, and the rotation of the stepping motor 6 is transmitted through gears 7 and 8.

Reference numeral 9 denotes a head carriage, on the upper surface of which is fixed a magnetic head 10 that is accurately positioned and adjusted, and is guided and guided by the guide shafts 3 and 4.
At the same time, the pin (screw engaging portion) 11 engages with the threaded portion 5a of the screw shaft 5, and the rotation of the screw shaft 5 causes the magnetic disk (not shown) to be transported along the radial direction. It's becoming like that.

Incidentally, reference numerals 12 and 12 are springs for pressing the pin 11 of the head carriage 9 against one of the walls of the threaded portion 5a.

Moreover, as shown in FIG.
(The same applies to the support plate 2).The support plate 2 is installed so that it can only move up and down.

Further, the bearing 13 is attached to an adjustment plate 20 which is pivotally attached to one end of the support plates 1 and 2 at a position approximately the same size and height as the motor shaft, and is swingable in the vertical direction. This adjusting plate 20 is connected to the substrate 2.
It is supported on the upper surface of a laminated piezoelectric ceramic (actuator) 21 provided on the upper surface of 3, and
It is biased downward by a spring 22 provided between the base plate 23 and the base plate 23 .

Therefore, first, by moving the head carriage 9 in the vertical direction in FIG.
When recording on a magnetic disk (not shown) by, for example, the stepping motor 6
By inputting a drive signal of 8 pulses times the number of tracks to be recorded from a control circuit (not shown), the head carriage 9 and the magnetic head 10 above it move at a track pitch of 100 μm to perform recording (writing).

Further, when reproducing (reading) the contents of each recorded track, a drive signal of (number of tracks x 8) - 1 pulse is inputted to the stepping motor 6 from the control circuit.

By inputting this number of pulses, the head carriage 9 is moved via the stepping motor 6, and the magnetic head 10 is moved to the desired track position by 12.5 μm.
(This value is a theoretical value and actually varies)
It is located in the front, and the tracking servo is activated after this.

FIG. 4 shows a control circuit for this tracking servo. In the figure, reference numeral 10 denotes the magnetic head, and the reproduced output of the magnetic head 10 is supplied to an FM demodulation/synchronization signal separation circuit 31 and a detection circuit 32 via a preamplifier 30.

The output of the FM demodulation/synchronization signal separation circuit 31 is sent to a known video reproduction circuit at a subsequent stage (not shown) for desired video reproduction.
The vertical synchronizing signal V _syoc discriminated by is sent to the peak hold circuit 34 as a reset signal every rotation of the disk.

On the other hand, the detection output of the detection circuit 32 is input to the peak hold circuit 34 via the integration circuit 33, and the signal V2 is supplied to one input terminal of the comparison circuit 35. Further, the peak hold circuit 34 supplies the (peak) signal V1 held every rotation of the disk to the other input terminal of the comparison circuit 35.

The output of the comparator circuit 35 controls an analog switch 37 whose one end is connected to a constant current source 36, and the output of the comparator circuit 35 controls an analog switch 37 whose one end is connected to a constant current source 36.
When V2<V1, analog switch 37 is
It is designed to be turned off. That is, as will be described later, after the magnetic head 10 reaches the proper position on the target track and the signal V1 shows the highest value, the very small amount of the magnetic head 10 passes the proper position and V2<V.
When it becomes 1, turn off analog switch 37.
Then, the servo drive of the magnetic head 10 is stopped.

Therefore, the drive of the magnetic head 10 is stopped when the signal diagram V2 has slightly passed its peak, in other words, the magnetic head 10 has slightly passed the true proper value on the target track. According to the standard of floppy disk, the off-track is ±14μ.
m, and the magnetic head 10 has a track width
The magnetic head 10 is stopped on the target track 60 μm above the target track, which is a moderate deviation of at most several μm from the true proper value on the track, so in practice (apparently) the magnetic head 10 is stopped at the proper position. I can do it.

A switch 38 and a capacitor 39 are connected in parallel between the other end of the analog switch 37 and the ground, and the piezoelectric ceramic 21 is connected to the connection point of these three, 37, 38, and 39 via a buffer amplifier 40. The other end of the piezoelectric ceramic 21 is grounded.

The switch 38 is turned OFF by the final drive pulse from the drive circuit of the stepping motor 6 [the above-mentioned {(number of tracks x 8) - 1}th pulse], and is turned off based on a new track search command. It is designed to be turned on by the first drive pulse to the stepping motor 6.

When the switch 38 is turned off at the above timing, the magnetic head 10 is at this point approximately 12.5 μm before the calculated appropriate position on the target track.
Naturally, the relationship between the signals V1 and V2 is V2>V1, so the analog switch 37 is ON and the switch 38 is OFF, so the capacitor 39 starts charging and the piezoelectric ceramic 21 is also driven. , the magnetic head 10 starts to be displaced in one direction (in the embodiment, in the direction of increasing displacement), and the magnetic head 10 is displaced as will be described later.

Then, after this, the signals V1 and V2 become V2<V1
The piezoelectric ceramic 21 is driven (the amount of displacement is increased) until V2<V1, the analog switch 37 is turned off, and the piezoelectric ceramic 21 is maintained in this state.

When the image reproduction of the desired track is completed and a new track search command is input, the first drive pulse to the stepping motor 6 based on this command activates the switch 38 as described above.
When turned on, the capacitor 39 is discharged and the piezoelectric ceramic 21 is returned to a reference displacement state (for example, displacement 0).For the above-mentioned operation, please refer to the timing chart shown in FIG.

The reason why the servo drive as described above, that is, the servo is performed by always displacing the piezoelectric ceramic 21 in one direction, is that the influence of hysteresis of the reciprocating displacement of the piezoelectric ceramic 21 can be ignored, and the control circuit has an extremely simple configuration. This is because of this.

When the tracking servo operates as described above, the mechanism operates as follows. That is, since a voltage is applied to the laminated piezoelectric ceramic 21 with the start of the servo operation, the laminated piezoelectric ceramic 21
The dimensions change upward as shown in the figure, that is, in a direction substantially perpendicular to the moving direction of the head carriage 9 and the magnetic head 10 above it, and the adjustment plate 20 is moved against the biasing force of the spring 22 to move the head carriage 9 and its upper part. The screw shaft 5 is raised in a direction substantially perpendicular to the moving direction of the magnetic head 10, and both ends 5c of the screw shaft 5 are raised accordingly, so that the screw shaft 5 is raised in that direction.

As the screw shaft 5 rises, the head carriage 9 and the magnetic head 10 above it are lifted up.
Since the screw shaft 5 is positioned in the height direction, the screw shaft 5 rises as shown in FIG. 3 and reaches the state shown by the broken line.
The pin 11, which is located in the threaded part 5a and is pressed against one of the walls of the threaded part 5a by the springs 12, 12, is restricted from moving in the height direction as described above. The head carriage 9 and the magnetic head 10 above are moved in the direction of resisting the biasing force of the head carriage 9 and the magnetic head 10 on the desired track.
That is, by moving FIG. 1 in the direction of the arrow, the 12.5 μm
The magnetic head 1 moves in the direction in which the difference between
A minute feed of 0 will be performed.

Since the magnetic head 10 is servo-fed without changing its relative position with respect to the head carriage 9, the touch between the magnetic head 10 and the disk does not change and playback is performed with the head touch adjusted as desired. It will be done.

In addition, in the video floppy disk drive device for electronic still cameras in this embodiment, the head carriage 9 is extremely small and lightweight, and the screw shaft 5 is also lightweight, so the piezoelectric ceramic 2 is used.
1 is also advantageous in that it is small in size and consumes little power.

Further, in the embodiment described above, a case was explained in which adjustment was made by raising both ends 5c of the screw shaft 5 at the same time, but the invention is not limited to this.
Only one end may be raised, and although a laminated piezoelectric ceramic is used as the member for raising, it is of course possible to use an electric actuator other than the laminated piezoelectric ceramic.

[Effect of idea]

By configuring this idea as described above,
During playback, after stopping the head carriage slightly before the desired track position, the tracking servo displaces the screw shaft in a direction approximately perpendicular to the axis, thereby moving the head carriage and the magnetic head above it by a small amount, making it possible to perform head touch, etc. The magnetic head can be reliably stopped at a desired position without being moved, and its practical value is great.

[Brief explanation of drawings]

The drawings show an embodiment of this invention, with Fig. 1 being a plan view of the head carriage feeding mechanism, Fig. 2 being a side view of the screw shaft adjustment section, and Fig. 3 showing the engagement between the threaded portion of the screw shaft and the pin. FIG. 4 is a circuit diagram showing an embodiment of a control circuit for tracking servo, and FIG. 5 is a timing chart based on FIG. 4. 1, 2... Support plate, 3, 4... Guide shaft, 5... Screw shaft, 5a... Threaded portion, 5c... End portion, 6... Stepping motor,
7, 8...Gear, 9...Head carriage, 10
... Magnetic head, 11 ... Pin (screw engagement part), 12, 22 ... Spring, 13 ... Bearing, 20
... Adjustment plate, 21 ... Laminated piezoelectric ceramic, 23
... Board, 30 ... Preamplifier, 31 ... FM demodulation/synchronization signal separation circuit, 32 ... Detection circuit, 33
...Integrator circuit, 34...Peak hold circuit, 3
5... Comparison circuit, 36... Constant current source, 37... Analog switch, 38... Switch, 39... Capacitor.

Claims (1)

[Scope of utility model registration request] a head carriage loaded with a magnetic head and transported along the radial direction of the magnetic disk; a guide shaft for guiding the head carriage;
a screw shaft installed substantially parallel to the guide shaft and rotated by a motor, a screw engaging portion of the head carriage that engages with the screw shaft, and a screw engaging portion of the screw shaft that is connected to the screw shaft. a spring that urges the head carriage in one direction to come into contact with the screw shaft; and a spring that is installed on at least one end side of the screw shaft to move the screw shaft a predetermined direction in a direction substantially perpendicular to the direction of movement of the head carriage. An electric actuator is provided, and as the screw shaft is moved in the aforementioned direction, the contact point between the screw shaft engaging portion and the screw shaft engaging portion changes, and the head carriage is moved by a small amount in the transport direction. A head drive for a magnetic disk, characterized in that, at least during playback, coarse feeding of the head carriage is performed by the motor, and minute feeding of the head carriage is performed by driving the electric actuator based on a servo signal. Device.