JPS60136972A - Magnetic disc device - Google Patents

Abstract

PURPOSE:To shorten the access time and to improve the tracking accuracy of following by providing additionally an acceleration sensor to a magnetic head of a magnetic disc device and using a detection signal as one of feedback signals of an access control circuit. CONSTITUTION:A position control loop consists of a position signal generating circuit 17, a position control feedback circuit 24, a power amplifier 23, a voice coil motor 2, a carriage of the access device 4, and a slider 9 provided with the magnetic head 3. A detection signal from the acceleration sensor 11 is amplified or filtered by an acceleration generating circuit 19 and fed to a position control feedback circuit 24. The position control feedback circuit 24 uses a speed signal and a position signal in addition to the acceleration signal to generate a position feedback signal. The position control feedback circuit 24 improve the tracking accuracy to a track while suppressing the actual vibrating state of the magnetic head based thereupon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic disk device, and particularly to a magnetic disk device suitable for track positioning.

[Background of the invention]

A servo magnetic head in a conventional magnetic disk device has a function of reading servo signals written on servo tracks of a servo magnetic disk. The access control circuit calculates the position and speed of the head from this servo signal, and performs a seek operation in which the head moves from one track to another, and a following operation in which the head follows that track and performs reading and writing with a magnetic recording ped. It has the function of controlling operations. The speed of this seek operation, that is, the access time, and the accuracy of the four-ink operation, that is, the tracking error, are important because they determine the storage capacity and reliability of the magnetic disk device.

A voice coil motor is usually used as a drive source to determine the position of the head. This voice coil motor and head are coupled by a carriage. This carriage is a structure made of a combination of members made of a metal material such as aluminum, and has a unique vibration mode. When the voice coil motor is driven at high speed in order to shorten access time, the vibration mode of this carriage is excited, causing minute vibrations in the head attached to the tip of the carriage, which deteriorates positioning accuracy. It was the cause.

For this reason, there are problems in that the speed of the seek operation is limited and that reading and 1:in cannot be performed immediately after the seek operation is completed, requiring a long settling time. Furthermore, if the response frequency of the voice coil motor is increased in order to reduce the tracking error, the vibration mode of the carriage will also be excited, which will generate minute vibrations in the head attached to the tip of the carriage, and will instead cause the 7. There was a problem in that the accuracy, that is, the tracking error increased.

[Object of the Invention] An object of the present invention is to shorten the access time without limiting the speed of the seek operation or lengthen the settling time after the seek operation is completed, and to improve the tracking accuracy of 7-orowing. The objective is to provide a magnetic disk device that can perform

[1g of the Invention] A feature of the present invention is that in a magnetic disk device, an acceleration sensor is attached to the magnetic head of the magnetic disk device, and this detection signal is used as one of the feedback signals of the access control circuit. It's what I did.

[Embodiment J of the invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of an example of an access mechanism section in a magnetic disk device of the present invention. In this figure, 1 is a voice coil motor, and magnet 2 is a voice coil bobbin. Numeral 3 is a magnetic head, one of which is generally a servo magnetic head 3S, and the remaining 9 are magnetic heads for reading and loading information from and to the magnetic disk. These magnetic heads 3 and voice coil bopi 72 are mounted on the carriage 4.
The carriage 4 connected by the carriage support 5
It is rotatably supported by a rotation bearing 6 (ear). By applying a current to the voice coil bobbin 2, the magnetic head 3 is positioned at an arbitrary track on the magnetic disk.

FIG. 2 is an enlarged view of the head portion shown in FIG. 1. Each magnetic head is supported on a carriage by a leaf spring-like gimbal 7, and the flying height is adjusted in response to changes in the flying height of the head. Keep it constant.

FIG. 3 is an external view of a magnetic head 3S used in the apparatus of the present invention. Reference numeral 8 denotes a coil and a core for reading servo signals from a servo track of a magnetic disk j for servo. 9 is a slider for stably floating the head above the disk.

A portion of the slider 9 designated by reference numeral 10 forms an air bearing as the disk rotates, and the head flies to a constant height above the disk. 11 is an acceleration sensor,
It is attached to the slider 9 at a position and direction where the acceleration in the moving direction A of the head can be detected. B indicates the direction of rotation of the disk.

FIGS. 4 and 5 show an example of the acceleration sensor 11 used in the present invention, which is of a semiconductor type. 12
is a cantilever-shaped silicon beam, with a weight 13 attached to the lower surface of the free end and a resistor element 14 attached to the upper surface. 015 is a cover for the acceleration sensor 11, and 16 is a signal output terminal. . If the mouth speed changes when the acceleration sensor 11 moves in the direction of the arrow α, the silicon beam 12 is bent, so the resistance value of the resistance element 14 changes. Acceleration can be detected by amplifying this. For magnetic disks, the acceleration detection range is ±20 to ±5 (approximately
001h, and the attenuation coefficient is about 0.01 to 0.001, so the main body 13, cover 15, and silicon beam tz,! : It can be adjusted by changing the substance that fills the space between O.

FIG. 6 is a block diagram of the access control circuit in the device of the present invention. In this figure, parts with the same reference numerals as in FIGS. 1 to 3 are the same parts. Track positioning control is divided into a seek operation in which the head is moved from the current track to a target track, and a following operation in which the head is subsequently caused to follow that track.

Generally, seek operations are performed using a speed control method that controls the head speed to match a predetermined target speed depending on the position, and following operations are performed using a speed control method that controls the head speed to match a predetermined target speed depending on the position. This is done using a position control method based on signals. The speed control loop includes a position signal generation circuit 17. Target speed generation circuit 2
1. Speed control compensation circuit 22. Seeking operation-7 Orrowing operation changeover switch 25. Bakamp 23. Voice coil motor 2. and access mechanism carriage 4. It is composed of a slider 9. In order to improve the control performance of this speed control and obtain the desired control characteristics, a minor speed feedback loop is required. The speed deviation is determined by a comparing subtraction circuit 26, and control is performed accordingly.

The access mechanism is a structure that combines metal material members.
Since it has a unique vibration mode, it cannot be regarded as a completely rigid body; for example, it has an inertial mass M・n, a damping coefficient B, b,
If you try to model it using a spring constant, etc., it will swing like the area surrounded by the dotted line in Figure 6. Therefore, voice coil motor 2 can be controlled simply by slider 9 speed feedback.
It is not possible to directly control the speed of the slider 9 with high precision even if force is applied to the carriage 4 from A slight vibration is generated in the head 3 through the attached slider 9, which actually worsens the positioning accuracy. To avoid this, magnetic head 3
It is effective to directly detect the vibration state, especially its acceleration, and use it for feedback control. For this purpose, the present invention uses a detection signal from an acceleration sensor 11 attached to the slider 9. The detection signal from the acceleration sensor 11 is amplified or converted into three waves by the acceleration signal generation circuit 19 and is applied to the speed control feedback circuit 20 .

The speed control 11 feedback circuit 20 generates a speed feedback signal using the above-mentioned speed signal in addition to this acceleration signal. This speed control feedback circuit 20
Accordingly, based on the actual vibration state of the magnetic head, it is possible to suppress the vibration while increasing the moving speed and shortening the access time.

The position control loop includes a position signal generation circuit 17, a position control feedback circuit 24. Puff-amplifier 23 voice coil motor 2 and access mechanism carriage 4. It consists of a slider 9 equipped with a magnetic head 3. In order to improve the control product of this position control and obtain the desired control characteristics, it is necessary to avoid exciting the vibration mode of the access mechanism mentioned above. Simply provide position feedback of the position signal corresponding to the position deviation of the magnetic head. Even if force is applied to the carriage 4 from the voice coil motor 2, it is not possible to directly control the magnetic head with high accuracy, and instead the vibration mode of the access mechanism is excited, causing the carriage 4 to A slight vibration occurs in the head 3 attached to the tip, which actually worsens the positioning accuracy. In order to avoid this, it is effective to directly detect the vibration state of the magnetic head 3, and sometimes its acceleration, and use it for feedback control. For this purpose, a detection signal from an acceleration sensor 11 attached to the slider 9 is used.

The detection signal from the acceleration sensor 11 is amplified or filtered by the acceleration signal generation circuit 19 and applied to the position control feedback circuit 24 . The position control feedback circuit 24 generates a position feedback signal using the above-mentioned velocity signal and position signal in addition to this acceleration signal. This position control feedback circuit 24 makes it possible to suppress vibrations based on the actual vibration state of the magnetic head and improve tracking accuracy.

〔Effect of the invention〕

According to the present invention, it is possible to directly detect the acceleration of the magnetic head, which is the original control target, and use this as one of the feedback signals of the access control circuit. It is possible to control the speed or position of the attached magnetic head with high accuracy, that is, to prevent unnecessary vibrations from occurring.

[Brief explanation of drawings]

FIG. 1 is an external view of an example of an access mechanism in a magnetic disk device of the present invention, the second cause is an external view of a magnetic head portion that constitutes the device of the present invention, and FIG. 3 is an external view of the magnetic head portion shown in FIG. 4 is a vertical cross-sectional plan view of the acceleration sensor used in the device of the present invention, FIG. 5 is a cross-sectional view taken along the ■-■ arrow in FIG. 4, and FIG. 6 is a cross-sectional view of the device of the present invention. 2 is a block diagram of the access control circuit that constitutes the circuit. 1... Voice coil motor magnet, 2... Voice coil bobbin, 3, 3i9... Magnetic head, 41
1. Carriage, 5... Carriage support part, 6... Rotating bearing, 7... Gimbal, 8... Magnetic coil and core, 9... Slider, 10... Air bearing, 1
1... Acceleration sensor, 12... Silicon beam, 1
3...Oh too! l), 14... resistance element, 15.
...Cover, 16...Terminal, 17...Position signal generation circuit, 18...Speed signal generation circuit, 19-...
Acceleration signal generation circuit, 20... Speed control feedback circuit, 21... Target speed generation circuit, 22... Speed control compensation circuit, 23... Power amplifier, 24... Position control feedback circuit, 25.・Seek operation-7
Orrowing operation changeover switch, 26...subtraction circuit. Sai 1 Flash Oz 1! ] Figure 4: 5.

Claims (1)

[Scope of Claims] 1. In a magnetic disk device that uses a magnetic head to write information onto a magnetic disk or read information from a magnetic disk, an acceleration sensor is attached to the head, and this configuration signal is transmitted to an access control circuit. A magnetic disk device characterized in that it is used as one of the feedback signals. 2. The magnetic disk device according to claim 1, wherein the blade edge speed sensor is attached to the magnetic head in a direction for detecting acceleration in the direction of movement of the head. 3. A magnetic disk drive according to claim 1, wherein a plurality of acceleration sensors are attached to the magnetic head so as to be able to calculate the acceleration in the traveling direction of the head. 4. The magnetic disk device according to claim 2 or 3, wherein the acceleration sensor is of a semiconductor type.