JPH0158582B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for writing or reading signals onto or from a magnetic disk medium using a movable magnetic head. In general, in order to conduct experiments and evaluations of magnetic disk media and magnetic heads in detail, a drive mechanism that can drive the magnetic head over several tens of millimeters and position it with high precision is required. Conventionally, the drive and positioning mechanism for the magnetic head of this type of device uses a voice coil type linear motor, which uses a speed signal from a speed sensor attached to a part of the moving part and a position sensor attached to a part of the moving part. The method used was to build a servo loop that fed back the position signal from the sensor. However, in the servo loop configuration, when the total mass of the movable part changes or the detection sensitivity of the speed sensor or the position sensor changes, it is necessary to recalculate each constant in the loop to calculate the optimum value. Furthermore, when the load conditions change due to changes in the movable part over time, the servo loop characteristics change, causing loop oscillation, which often makes positioning impossible. On the other hand, an open-loop drive and positioning mechanism using a pulse motor and feed screw without using servo loop control has a simple configuration, but
It had the disadvantage that it could not perform highly accurate positioning of 1 μm or less and could not provide sufficient accuracy as a signal writing device for a magnetic disk. SUMMARY OF THE INVENTION An object of the present invention is to provide a signal writing device that eliminates the above-mentioned drawbacks, has a simple configuration, and is capable of positioning a magnetic head with high precision. In the signal writing device of the present invention, a magnetic head for recording signals on a magnetic disk medium is connected to a movable part, and the movable part is moved by repeating minute displacements caused by the electrostrictive effect of a piezoelectric element. A drive body, a position sensor that detects the amount of movement of the magnetic head, and a logic control unit that monitors an output signal of the position sensor and outputs a drive command to the drive body to position the magnetic head at a predetermined position. configured. Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention, in which 1 is a logic control section, 2 is a piezoelectric element drive voltage generation section, 3 is a driver incorporating a piezoelectric element, 4 is a magnetic head, and 5 is a A position sensor, 6 a data conversion circuit that converts the output signal of the position sensor into a digital quantity, and 7 a recording signal write/read circuit.
The logic control unit 1 reads the position signal of the magnetic head 4 detected by the position sensor 5 as a digital quantity through the data conversion circuit 6, and compares this value with the target position of the magnetic head 4 to be positioned next. For example, if the current position of the magnetic head is before the target position, the piezoelectric element drive voltage generator 2 issues a forward command, and conversely, if it is beyond the target position, it issues a backward command.
Output to. The piezoelectric element drive voltage generation section 2 applies a drive voltage to the piezoelectric element built into the drive body 3 based on a command from the logic control section 1 . An example of the driving principle of the driving body 3 is shown in FIG. 10 is a cylindrical movable part; 11 and 12 are ring-shaped piezoelectric elements that contract and grasp the movable part 10 by applied voltage; and 13 is connected to piezoelectric elements 11 and 12 to extend the distance between piezoelectric elements 11 and 12 by applied voltage. The center portion 14 of the ring-shaped piezoelectric element is connected to a fixed base 15. When voltages are applied to piezoelectric elements 11, 12, and 13 in the order shown in Table 1, piezoelectric element 11 moves to the movable part at No. 1.

[Table] Grasp 10, and in No. 2 the piezoelectric element 13 is in the center 14
It extends toward the piezoelectric elements 11 and 12 using the fulcrum as the fulcrum.
If the amount of expansion of the piezoelectric element 13 is d, then in the No. 2 state, the movable part 10 is displaced by d/2 in the A direction.
After the piezoelectric elements 11 and 12 grasp the movable part 10 at No. 3, the piezoelectric element 11 releases the movable part 10 at No. 4.
At No. 5, the piezoelectric element 13 contracts. At this time, movable part 1
0 is further displaced by d/2 in the A direction. Piezoelectric elements 11 and 12 grip movable part 10 at No. 6. The displacement of the movable part 10 is a minute amount equal to the extension amount d of the piezoelectric element 13 and less than 1 μm in one series of operations from No. 1 to No. 6, but by repeating this, it can be increased to several tens of mm. . Furthermore, by changing the order of voltage application to the piezoelectric elements 11, 12, and 13, the movable part 10 can also be moved in the B direction. When the movable part 10 of the drive body 3 is driven in this way and the magnetic head 4 connected to the movable part 10 moves and reaches the target position, the logic control part 1 stops issuing a drive command to the piezoelectric element drive voltage generation part 2, and writes. A write command is output to circuit 7. The signal writing device of the present invention uses a driving body that utilizes an electrostrictive effect in the driving section of the magnetic head, thereby achieving stable and highly accurate positioning without causing oscillation even when the load characteristics of the movable section change. It becomes possible. In addition, there is an effect that a speed sensor, a servo amplifier, etc. are not required, the configuration is simplified, and the control method is simplified because the processing of analog quantities is reduced and the processing of digital quantities becomes the main processing.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Logic control section, 2... Piezoelectric element drive voltage generation section, 3... Drive body, 4... Magnetic head, 5
...Position sensor, 6...Data conversion circuit, 7...
writing circuit. FIG. 2 shows an example of the driving principle of the driving body 3 shown in FIG.
Piezoelectric element, 14... center of piezoelectric element 13, 15
...Fixed stand.

Claims (1)

[Claims] 1. A magnetic head that records signals on a magnetic disk medium, a driving body that connects the magnetic head and a movable part and moves the movable part by repeating minute displacements caused by the electrostrictive effect of a piezoelectric element, and A signal book comprising: a position sensor that detects the amount of movement; and a logic control section that monitors the output signal of the position sensor and outputs a drive command to the drive body to position the magnetic head at a predetermined position. Including device.