JPH0565952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a magnetic disk head drive device, 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 drive device.

[Prior art and its problems]

In hard magnetic disks, optical disks, etc., tracking servo technology is generally used to track the detection head, and recently this technology has also been adopted in magnetic disks with high TPI. It's coming.

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.

Therefore, there is a device that uses a bimorph piezoelectric element to expand and contract in proportion to the applied voltage to perform fine feeding, but this bimorph piezoelectric element has a slow response speed, poor conversion efficiency with respect to the applied voltage, and hysteresis. Since the magnetic head is large, accurate fine feeding cannot be performed, and therefore accurate positioning of the magnetic head cannot be performed.

[Purpose of the Invention] Therefore, the present invention solves the problems of the conventional ones as described above, and has a fast response speed, accurate fine feeding, and accurate positioning of the magnetic head. An object of the present invention is to provide a magnetic disk head drive device capable of performing the following steps.

[Summary of the invention]

The above-mentioned objects of the present invention are 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 first electric actuator including an electrostrictive element installed at one end of the screw shaft to move the screw shaft a predetermined amount in the axial direction; a second electric actuator that is an electrostrictive element that moves the head in a direction opposite to the direction in which the screw shaft is moved by the first electric actuator; and control that controls driving of at least the motor and the first and second electric actuators. the control circuit drives the motor for coarse feeding of the head carriage at least during playback, and then drives the first motor for coarse feeding of the magnetic head in one direction by minute feeding of the head carriage. When the electric actuator is driven and the magnetic head is located at the optimum position, the magnetic head is stopped in that state, and when the magnetic head cannot be placed at the optimum position by driving the first electric actuator, the first electric actuator is stopped. This is generally achieved by a magnetic disk head drive which stops and drives a second electric actuator to move the magnetic head in the opposite direction to the optimum position.

[Embodiments of the invention]

Embodiments of the 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;
Reference numeral 5 denotes a screw shaft which is supported between the support plates 1 and 2 and is held so as to be movable by a predetermined amount in the axial direction.
The rotation is transmitted by gears 7 and 8.

Reference numeral 9 denotes a head carriage, and a fixing member 13 is provided on the upper surface of the head carriage 9. A laminated piezoelectric ceramic (actuator) 14 is provided on the side surface of the fixing member 13 in the moving direction of the head carriage 9, that is, on the upper side in the figure. A magnetic head 10 is attached.

Further, the head carriage 9 is guided and held by the guide shafts 3 and 4, and its pin (screw engaging portion) 11 engages with the wall surface of the threaded portion 5a of the screw shaft 5,
The rotation of the screw shaft 5 causes the magnetic disk (not shown) to be transported along the radial direction.

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 as shown in the second figure.

Further, one end of the screw shaft 5 is formed with a small diameter portion 5b, and the end of the small diameter portion 5b is fitted into the hole of the support plate 2, and there is no space between the screw shaft 5 and the support plate 2. A spring 15 is wound around the spring 15 and urges the screw shaft 5 upward in the drawing.

On the other hand, a small diameter portion 5c is also formed at the other end of the screw shaft 5, and the end of the small diameter portion 5c is inserted into the hole of the support plate 1, and a laminated piezoelectric ceramic is formed so as to cover the small diameter portion 5c. (actuator)
16 is located.

In addition, the control circuit is shown in FIG. 3, and in the upper part of FIG. A start signal circuit that changes from level to H level; 42 is a clock oscillator that generates pulses to move the seeking stepping motor; this clock oscillator 4;
2 and the start signal circuit 41 are connected to an input terminal of an ant gate 43, and a digital comparator 45, which will be described later, is further connected to an input terminal of the AND gate 43 via an inverter 44.

This digital comparator 45 compares the track number setting value A by the track number setting circuit 47 and the value B of the up-down counter 46 indicating the current track position of the magnetic head 10, and determines whether they match or not. It is determined whether the stepping motor 6 is moved in the direction of increasing or decreasing the track number, and when both values A and B match, the output is sent to the AND gate 43 via the inverter 44, which will be described later. When the stepping motor 6 is to be moved in the direction of increasing the track number, the output is input to the up side of the up-down counter 46 and the stepping motor drive circuit 48, and further, When moving in the direction of decreasing the track number, the output is input to the down side of the up-down counter 46 and the stepping motor drive circuit 48.

The track number setting circuit 47 automatically increments the track number by one when shooting (recording) is completed, and when playing back, manually switches a dial switch (not shown) or the like to output the track number to be played. It's becoming like that.

The up-down counter 46 is
AND gate 43 is digital comparator 4
The track number is increased/decreased by receiving the output pulse of the clock oscillator 42 through the L level output of the clock oscillator 41 and the H level output of the start signal circuit 41.

The same pulse as the input pulse to the up-down counter 46 is input to the stepping motor drive circuit 48 via the AND gate 43, and the stepping motor drive circuit 48 receives the output instruction of the digital comparator 45 and the input pulse. The stepping motor 6 is moved in a direction in which the track number increases or is driven in a direction in which the track number is decreased.

In the control circuit part as mentioned above, first,
First, the case where recording is performed on a magnetic disk (not shown) using the magnetic head 10 by moving the head carriage 9 in the vertical direction in FIG. 1 will be described.

In this case, the track number setting circuit 47 recognizes that recording is in progress and automatically specifies the next track number.

Therefore, when the shutter button is pressed, the output of the start signal circuit 41 becomes H level, and the clock oscillator 42 also outputs a pulse. On the other hand, since A>B (B+1>B), the output of the digital comparator 45 becomes high. The output is input as an H level to an AND gate 43 via an inverter 44, and the gate of the AND gate 43 is opened and the clock pulse of the clock oscillator 42 is input to the stepping motor drive circuit 48.

The stepping motor drive circuit 48 recognizes that the stepping motor 6 is to be driven in the direction of increasing the number of tracks based on the output of the digital comparator 45, and drives the stepping motor 6 in the direction of increasing the number of tracks according to this direction instruction and the clock pulse. to drive.

The pulses of the clock oscillator 43 are also input to an up-down counter 46.

Since the up-down counter 46 receives the output from the digital comparator 45 that indicates A>B, it becomes an up-count and when the stepping motor 6 is driven by a predetermined amount, A=B. The digital comparator 45 outputs an H level signal from the output terminal indicating A=B, closes the gate of the AND gate 43, and enters a state of waiting for the next input of a start signal from the start signal circuit 41.

In this way, by pressing the shutter button, the stepping motor 6 is driven, and the head carriage 9 and the magnetic head 10 above it move at a track pitch of 100 μm, for example, to sequentially take pictures (record).

In addition, when reproducing (reading) the contents of each recorded track, when track number A is set, a predetermined pulse drive signal is input to the stepping motor 6 as described above, and this input causes the stepping motor to step. The head carriage 9 is moved by the motor 6 to position the magnetic head 10 on a desired track, and at the same time as this is completed, the tracking servo is activated.

The lower part of the control circuit in FIG. 3 shows a control circuit portion for this tracking servo.

In this section, 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 synchronization signal Vsync 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 is also input to the voltage comparator 3.
A signal V2 is supplied to one input terminal of the 5.

Further, the peak hold circuit 34 supplies the (peak) signal V1 held every rotation of the magnetic disk to the other input terminal of the voltage comparator 35.

The output of the voltage comparator 35 is:
The output of the charging control circuit 36 is input to the analog switch 37A, 37 whose one end is connected to the high voltage power supply 39.
B and the bases of switching transistors T1 and T2.

The charging control circuit 36 turns on and off two switching transistors T1 and T2 and two analog switches 37A and 37B based on the outputs of the voltage comparator 35 and the digital comparator 45 described above. This charging control circuit 36 is ON only during playback.
A playback switch 38 is connected.

The switching transistors T1, T are connected between the analog switches 37A, 37B and the ground.
2 and capacitors C1 and C2 are connected in parallel, and these switching transistors T1 and T2
Buffer amplifiers 40A and 40B, which are direct current amplifiers, amplify the charging voltage of the capacitors C1 and C2 to a voltage that can sufficiently drive the electrostrictive element, respectively, at the connection points between the analog switches 37A and 37B and the capacitors C1 and C2. Laminated piezoelectric ceramics 14 and 16, which are electrostrictive elements, are connected to buffer amplifiers 40A and 40B, respectively.

During recording, the playback switch 38 is
Since the charging control circuit 36 is turned off, the analog switches 37A and 37B are turned off during recording.
Since the switching transistors T1 and T2 are turned OFF and the switching transistors T1 and T2 are turned ON, the capacitors C1 and C2 are not charged, so that the laminated piezoelectric ceramics 14 and 16 are not deformed.

In the above circuit configuration, when the playback switch 38 is turned on during playback, the analog switches 37A, 37B and the switching transistors T1, T2 are connected to the voltage comparator 35.
It is controlled by the charging control circuit 36 which is controlled by the output of the digital comparator 45. When the track number A to be played is set in the track number setting circuit 47, the track number A to be played and the current track number are set. The track number position, that is, the value B of the up-down counter 46 is determined by the digital comparator 45
The value B of the up-down counter 46 is compared with
When the track number A is smaller than the track number A to be reproduced, only the output terminal indicating A>B among the outputs of the digital comparator 45 becomes H level.
An up-count instruction is given to the up-down counter 46, and a direction instruction is input to the stepping motor drive circuit 48 to seek in a direction in which the track number increases.

In this state, when the access start button (not shown) is pressed and turned ON to output a start signal from the start signal circuit 41, the output of the digital comparator 45 is input to the AND gate 43 via the inverter 44 as an H level signal. Therefore, the AND gate 43 is opened, and the clock pulse of the clock oscillator 42 is output from the AND gate 4.
3 to an up-down counter 46 and a stepping motor drive circuit 48.

As a result, the stepping motor drive circuit 48 drives the stepping motor 6, and an up-count is started. When the value B of the up-down counter 46 and the set value A of the track number setting circuit 47 match, the digital Only the output of the output terminal of the comparator 45 indicating A=B becomes H level, the AND gate 43 is closed, and the clock pulses to the up-down counter 46 and the stepping motor drive circuit 48 are blocked.

In this way, the digital comparator 45
At the same time, only the output of A=B becomes H level,
Upon receiving this signal, the charging control circuit 36 immediately turns off the switching transistor T1 and turns on the analog switch 37A, so that constant current charging of the capacitor C1 by the high voltage power supply is started, and the voltage corresponding to the charging voltage of the capacitor C1 is started. A voltage is applied to the laminated piezoelectric ceramic 16.

On the other hand, the reproduction output of the magnetic head 10 is transmitted to the detection circuit 3.
2. The signal V2 is input to the peak hold circuit 34 via the integrating circuit 33, and is also input to one input terminal of the voltage comparator 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 voltage comparator 35.

Therefore, in the process of applying a voltage to the laminated piezoelectric ceramic 16 and moving the magnetic head 10 in one direction (the direction of the arrow A in FIG. 1), when the magnetic head 10 is moving in a direction approaching the center of the track, the signal V1 and V2 is VI<V2, and magnetic head 1
0 moves so that V2<V1, the output of the voltage comparator 35 is inverted, and the charging control circuit 36 switches the analog switch 37A.
When set to OFF, charging is stopped and the position of the magnetic head 10 is maintained.

That is, after the magnetic head 10 reaches the optimum position on the target track and the signal V1 shows the highest value,
Very small amount of magnetic head 10 passes the proper position and V2
<V1, the charging control circuit 36 turns off the analog switch 37A to stop the servo drive of the magnetic head 10. For this operation, please refer to the timing chart shown in FIG.

Therefore, the drive of the magnetic head 10 is stopped when the signal V2 has slightly passed its peak, in other words, when the magnetic head 10 has slightly passed the true proper value on the target track. According to the standard of the floating disk, the off-track is ±14μm.
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.

If the magnetic head 10 is moving away from the center of the track, the analog switch 37A is turned OFF, the switching transistor T1 is turned ON, and at the same time, the analog switch 37B is turned ON, and the switching transistor T2 is turned ON. When turned OFF, capacitor C
1 is discharged, and the laminated piezoelectric ceramic 1
Since the magnetic head 6 quickly returns to the reference displacement state (for example, displacement O), the magnetic head 10 is quickly returned to its original position.
Further, since constant current charging is started to the capacitor C2, a voltage corresponding to the charging voltage of the capacitor C2 is applied to the laminated piezoelectric ceramic 14, and the magnetic head 10 is moved in the opposite direction (in the direction of the arrow B in FIG. 1).
gradually displaced.

Then, in the same way as above, when V2<V1, the charging control circuit 36 turns off the analog switch 37B by reversing the output of the voltage comparator 35, stops charging, and maintains the position of the magnetic head. It's becoming like that. For the above-mentioned operation, please refer to the timing chart shown in FIG.

Due to the above operation, the mechanism operates as follows.

That is, during recording, the screw shaft 5 rotates in accordance with the driving of the stepping motor 6, and the pin (screw engaging portion) 11 of the head carriage 9 is attached to one wall surface of the threaded portion 5a of the screw shaft 5. Since the head carriage 9 is pressed by the spring 12, the head carriage 9 moves in the direction opposite to the direction of the arrow in FIG. It is now possible to take pictures (record) by positioning the camera.

Furthermore, during reproduction, as the servo operation starts, a voltage is first applied to one of the laminated piezoelectric ceramics 16, so that the laminated piezoelectric ceramic 16 changes its dimensions downward as shown in FIG.

Due to this change in the dimensions of the laminated piezoelectric ceramic 16, the screw shaft 5 is
5 in the downward direction of Fig. 1 (in the direction of arrow A)
Therefore, the head carriage 9 and the magnetic head 10 located above it move to the first position.
It moves downward in the diagram (in the direction of arrow A), and voltage application is performed until the aforementioned signals V1 and V2 become V2<V1.

In addition, if V2<V1 does not hold, that is,
When moving away from the center of the track, the laminated piezoelectric ceramic 16 is discharged;
At the same time, voltage application begins to be applied to the laminated piezoelectric ceramic 14, and therefore, the head carriage 9 does not move in its initial state, and only the magnetic head 10 above it moves in the opposite direction (in the direction of the arrow B in FIG. 1). gradually begin to move.

Then, as before, the above-mentioned signals V1 and V2
The voltage is applied until V2<V1, and the magnetic head 10 is slightly moved.

That is, in FIG. 6, during playback, the magnetic head 10 is set to the peak of the track by open control.
Assuming that it stops at point Po, which is before point PA, first, by applying a voltage to the laminated piezoelectric ceramic 16, the maximum displacement position P1 of the laminated piezoelectric ceramic 16 is reached.
Move up to.

When P2 decreases with respect to Po, the laminated piezoelectric ceramic 16 is short-circuited or the like to return to the initial state, that is, the magnetic head 10 is returned to the Po point.
At the same time, charging of the laminated piezoelectric ceramic 14 is started, so the magnetic head 10 moves from point Po toward point P2 and reaches the point where V2<V1 as described above, that is, the peak PA point of the reproduction output. The magnetic head 10 is stopped slightly after this point.

Furthermore, in FIG. 6, if the magnetic head 10 is stopped at point P3 under open control during playback, then
A voltage is applied to the laminated piezoelectric ceramic 16 to move the magnetic head 10, and when it slightly passes the peak PA point, V2<V1, and at this point, the voltage application to the laminated piezoelectric ceramic 16 is stopped and the magnetic head 10 is moved to that position. This is to stop the magnetic head 10, and even if one of the laminated piezoelectric ceramics 16 is activated or both laminated piezoelectric ceramics 14 and 16 are activated in sequence, the magnetic head 10 is stopped at the peak PA point of the track. Since the deviation is only a few μm at most, in practice (apparently) the magnetic head 10 is stopped at an appropriate position.

Furthermore, the reason why both the laminated piezoelectric ceramics 14 and 16 are always displaced in only one direction to perform servo is that the influence of hysteresis in the reciprocating displacement of the laminated piezoelectric ceramics 14 and 16 can be ignored.

Furthermore, since the two laminated piezoelectric ceramics 14 and 16 are arranged so that their displacement directions are opposite to each other as described above, the expansion due to temperature changes cancels each other out, making it possible to obtain a high accuracy guarantee. Furthermore, in the floppy disk drive device for an electronic still camera according to the embodiment, the head carriage 9 is extremely small and lightweight, and the screw shaft is lightweight, so the laminated piezoelectric ceramic is also small and consumes little power. It is of course possible to use electrical actuators other than laminated piezoelectric ceramics, which are advantageous.

〔Effect of the invention〕

As described above, this invention uses two electrostrictive elements arranged so that their displacement directions are opposite to each other, so that even if the amount of displacement of one electrostrictive element is small, the adjustment range of the head is sufficient. In addition, the response speed is increased, and as the element itself becomes smaller, the entire element can be made smaller.Moreover, the displacement directions are opposite to each other, so even if the element itself expands due to a change in ambient temperature. Since the two magnetic heads cancel each other out, the initial position of the magnetic head is guaranteed even when the ambient temperature changes, and high positional accuracy can be obtained.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a plan view of the feeding mechanism of the head carriage, FIG. 2 is a schematic diagram showing the state of engagement between the threaded portion of the screw shaft and the pin, and FIG. 3 is a diagram showing the control circuit. Figures 4 and 5 are timing charts, and Figure 6 is a timing chart.
The figure shows the relationship between the reproduction output and the stop position of the magnetic head. DESCRIPTION OF SYMBOLS 1, 2... Support plate, 3, 4... Guide shaft, 5... Screw shaft, 6... Stepping motor, 7, 8... Gear, 9... Head carriage, 10... Magnetic head, 11... ...Pin, 1
2,15...Spring, 13...Fixing member, 14,1
6... Multilayer piezoelectric ceramic, 30... Preamplifier, 31... FM demodulation/synchronization signal separation circuit, 32
...Detection circuit, 33 ... Integration circuit, 34 ... Peak hold circuit, 35 ... Voltage comparator, 36 ... Constant current source, 37A, 37B ... Analog switch, 38 ... Regeneration switch, 39 ...
...High voltage power supply, 40...Buffer amplifier, 41...
...Start signal circuit, 42...Clock oscillator,
43...and gate, 44...inverter,
45... Digital comparator, 46... Up-down counter, 47... Track number setting circuit, 48... Stepping motor drive circuit, T1, T2... Transistor, C1, C2
……condenser.

Claims (1)

[Claims] 1. 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, and a screw installed substantially parallel to the guide shaft and rotated by a motor. a shaft; a screw engaging portion of the head carriage that engages with the screw shaft; a spring that biases the head carriage in one direction to bring the screw engaging portion into contact with a threaded portion of the screw shaft; a first electric actuator, which is an electrostrictive element installed at one end of the screw shaft and moves the screw shaft in a predetermined direction in the axial direction; a second electric actuator made of an electrostrictive element that moves the screw shaft in a direction opposite to the direction of movement of the screw shaft by the actuator; and a control circuit that controls driving of at least the motor and the first and second electric actuators; The control circuit drives the motor to coarsely feed the head carriage at least during playback, and then drives the first electric actuator to finely feed the magnetic head in one direction by finely feeding the head carriage; Alternatively, the magnetic disk head drive device is characterized in that the second electric actuator is driven after stopping the driving of the first electric actuator.