JPS59218677A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To control a magnetic head so as to reduce the off-track factor by dividing plural magnetic heads provided to an arm into plural groups to have a simultaneous access among these groups and at the same time constituting the groups with heads which receive the offsets of the similar levels due to temperatures. CONSTITUTION:It is possible to recognize the off-track state of each magnetic head by an experiment, etc. When a temperature change occurs under the con ditions where the selection of plural magnetic heads is inhibited from each arm in the same pair among 20 magnetic heads and the selection is inhibited for the magnetic heads that correspond to the magnetic disks. Therefore four units of H0 are collected in a set, and a set consists of H1-H4. Then the simultaneous read/write is carried out for each set. Thus the magnetic heads of the same set have the similar thermal off-track factors even if the magnetic head has an off-track. Therefore all heads of the corresponding set can be corrected with the same offset factor to give offset to those magnetic heads of the same set. Thus the on-track control is possible with all magnetic heads.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is directed to a magnetic disk device in which a plurality of heads with different arms are used to read and write data from 11 spindles in parallel. When configured to read and write from the head at the same time,
The present invention relates to a magnetic disk device in which disks having substantially the same degree of influence are defined as a group so that the influence of thermal off-track can be recovered, and the state of thermal off-track can be corrected for each group.

[Technological background and its problems]

In a magnetic disk drive, a plurality of magnetic disks are attached to a spindle and rotated simultaneously. By the way, Sanfu 1
To serve as a samurai. At this time, for example, four heads are attached to one arm.

Six magnetic disks are mounted on the same spindle, and one arm is placed between each magnetic disk.

If each arm is provided with four magnetic heads, five arms will be used, so a total of 20 magnetic heads will be provided per spindle.

However, in conventional magnetic disk drives, it has been desired to configure one magnetic head per spindle so that only one magnetic head can perform read/write operations.

For this reason, a magnetic disk device has been developed in which reading and writing can be performed simultaneously using four magnetic heads per spindle, although one magnetic head per arm.

By the way, in a magnetic disk drive, there is a data disk for recording data, and a servo mounted on the same spindle as the data disk to control the positioning of the magnetic head.
It includes a disk and a servo head that moves together with the magnetic head, and the position of the magnetic head is controlled by controlling the positioning of the servo head with respect to the servo track on the servo disk.

However, even if the positioning of the servo head with respect to the servo track is accurately controlled, the magnetic head may deviate from the center of the data track due to thermal expansion of the arm or other parts of the magnetic disk, resulting in a reduction in reading output. Data may be read incorrectly.

Furthermore, in magnetic disk drives, the pitch of data tracks is being reduced in order to increase storage capacity, but as a result, the above-mentioned reading errors are more likely to occur, and their removal has therefore become an important technical issue. ing.

The operation of moving the magnetic head in order to eliminate the reading error caused between the data track and the magnetic head by this thermal expansion table is usually called offset.
In particular, the amount of thermal off-track increases in a magnetic head that is far from the servo surface. In this case, offset has conventionally been performed by performing the following control by a controller via a magnetic head positioning control circuit.

That is, when a reading error as described above occurs, the reading output decreases, and a data reading error occurs.

First, the controller moves the magnetic head to a predetermined amount.

For example, data is read by moving 1 μm toward the inner circumference. If a data reading error occurs even in this manner, the primary step is to move 2 μm toward the outer circumference from this position. Similarly, if an error occurs in reading the data, it is further moved 3 μm toward the inner circumference from this position.

Thereafter, in the same manner, the magnetic head is moved until normal reading is achieved, and a predetermined number of trials, for example, six, are performed. That is, the data is read by moving from the initial position to the inner circumference and the outer circumference at a pitch of 1 μm at a maximum of 3 μm.

However, as mentioned above, in the case where, for example, four magnetic heads read and write at the same time, when the above positional deviation occurs in one magnetic head and this positional deviation is corrected, the other three Misalignment may occur between the individual pieces. In other words, if the thermal expansion characteristics of magnetic heads that can read and write at the same time are uneven, a positional deviation occurs in one of the magnetic heads, and four of them will be driven to correct the positional deviation at the same time. There is a problem in that even if one magnetic head can be brought on-track, the other magnetic heads are likely to be misaligned.

[Purpose of the invention]

An object of the present invention is to reduce the off-track rate when simultaneously reading and writing data from a plurality of magnetic heads, in order to solve the above-mentioned problem that exists when the structure is configured so that it can be accessed simultaneously by a plurality of magnetic heads. An object of the present invention is to provide a magnetic disk device in which a magnetic head can be controlled in this manner.

[Structure of the invention]

In order to achieve this object, the magnetic disk drive of the present invention supports a plurality of magnetic disk disks on one spindle, and provides an arm with a plurality of magnetic heads for accessing the surface of the magnetic disk. In addition, in a magnetic disk drive equipped with a plurality of actuators that control the arms, the plurality of magnetic heads provided on the arms are divided into groups, each group accesses simultaneously, and the groups are offset by temperature. The present invention is characterized in that it is constructed with a head that receives the same amount of damage.

[Embodiments of the invention]

An embodiment of the present invention will be described based on FIGS. 1 to 3.

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a magnetic head that cannot be collected as a set, and FIG. 3 is a configuration diagram of a magnetic head position control system.

As shown in Figure 1, magnetic disks DO to D5 are attached to the spindle SP, and the lower surface of the magnetic disk DO is used as a servo disk. The other side of the magnetic disk is then used as a data disk.

Arms AO to A4 are arranged between the magnetic disks, and each arm is provided with four magnetic heads H. For example, arm AO has magnetic heads HO, H1, H2.
, H4 (The meaning of the number after H will be explained later)
are provided on arm A1, and magnetic heads HO, H1, H
2, H3 are provided. And the first one on the other arm as well.
A magnetic head as shown in the figure is provided. In this way, each arm is equipped with four magnetic heads,
It is not possible to use multiple magnetic heads on one arm at the same time, and only one magnetic head can be used. And also, the magnetic heads HM and HN and Hm and H shown in Figure 2.
If magnetic heads facing the magnetic disk D, such as rL, write at the same time, magnetic interference will occur through the magnetic disk D, so such a thing should not be done. And in this example, there are 4 magnetic heads, 4
The structure is such that each arm can read and write to one magnetic head.

In the present invention, under the above-mentioned constraints, heads that receive the same off-track tm are collected and read/written as one set even if there is a temperature effect.

That is, among the 20 magnetic heads in FIG.
Taking the above-mentioned restrictions into consideration, for example, four magnetic heads that are subject to the same degree of off-track are collected into one set, and this single magnetic head performs reading and writing simultaneously.

In Figure 1, out of 20 magnetic heads, there are restrictions such as not selecting more than one magnetic head from each arm in the same line, and not selecting one facing the magnetic disk as described above. Under.

The off-track state of each magnetic head, that is, the degree of misalignment that occurs when a temperature change occurs, can be recognized through experiments. , H2°H3, and H4 each form one set.

The configuration is such that each line is read and written simultaneously.

In other words, in Fig. 1, 20
The off-track rates of each magnetic head were determined through many years of experimentation, and calculations were made based on the off-track rates to find those in a similar range, and the magnetic heads were divided into five groups of four each. By doing this, even if the magnetic head goes off track,
Since the thermal off-track rates of magnetic heads in the same group are about the same, when offset, all heads in the group can be corrected with the same offset rate, and all magnetic heads can be controlled on-track. be able to.

The means for offsetting and on-tracking the magnetic head when it goes off-track is not particularly limited; for example, a control circuit as shown in FIG. 3 can be used.

In Fig. 3, 1 is an offset control circuit which inputs the offset amount given from the controller 13 and obtains an offset signal S to be given to a positioning control circuit (described later) in order to eliminate a positional error of the magnetic head; A variable gain amplifier amplifies the read signal obtained by reading from the data disk DD; 3 is an AGO circuit that generates an AGO signal to be applied to the variable gain amplifier 2; 4 demodulates the output of the variable gain amplifier 2 and converts it to binary coding. Ichiban-1 [4P fist-1 fist q demodulation circuit, 5 is a magnetic disk, 6 is a magnetic helad carriage, 7 is a near motor that drives the magnetic helad carriage, 8, 9, 10, 11, and 12
8 constitutes a positioning control circuit, and 8 controls the servo disk SD and magnetism provided at the bottom of the magnetic disk 5, and the servo head SH provided at the bottom of the γ doper carriage 6 controls the magnetic head carriage 6 for the magnetic disk 5. 9 is a current detector that detects the acceleration of the magnetic heliad carriage 6 from the drive current generated by the power amplifier described later; 10 is a power amplifier that generates a drive current to be applied to the linear motor 7; 11 12 is a speed detector that detects the speed of the magnetic head carriage 6 from the output keel of the position detector 8 and the output signal of the current detector 9 and generates a damping signal to be applied to an error amplifier described later; 12 is a signal generated by the offset control circuit 1; This is an error amplifier that generates a position control signal to be given to the power amplifier 10 based on the offset signal S and the output of the position detector 8. Nah, 3rd e”c
C. 5. For simplicity, only two magnetic heads are shown on each arm.

In the above configuration, first, the magnetic and y-dog gear carriage 6 is connected to the power amplifier 1 from another control system (not shown).
0, the servo head S
H is moved to a position where the target servo track on the servo disk SD is selected.

Subsequently, the servo head SH is controlled so that the center of the servo head SH is located on the boundary between two adjacent servo tracks.

After this, the magnetic head will read the data on the data disk DD.

1 specified in this specification, for example, by moving 1 μm to the inner circumferential side.
Offset control can also be performed using a conventional method such as moving outward by 2 .mu.m and further moving 3 .mu.m inward.

〔Effect of the invention〕

According to the present invention, when a magnetic disk can be read and written simultaneously by a plurality of channels.

When configuring a set of multiple magnetic heads that can be accessed at the same time, the heads that receive the same amount of off-track are collected into one set, so when offset, all the magnetic heads of all sets are offset at the same offset rate. Can be on-track. Therefore, even if the configuration is such that multiple channels can be accessed at the same time, only a specific magnetic head will not be on-track.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 'A-2 is an explanatory diagram of a magnetic head that cannot be grouped into one set, and Fig. 3 is a block diagram of a magnetic head position control system. In the figure, 1 is an offset control circuit, 2 is a variable gain amplifier, 3 is an AGO circuit, 4 is a demodulation circuit, 5 is a magnetic disk,
6 is a magnetic herad carriage, 7 is an IJ near motor, 8
9 is a position detector, and 9 is a current detector. 10 is a power amplifier, 11 is a speed detector, 12 is an error amplifier, and 13 is a controller. Patent applicant Fujitsu Ltd. agent Patent attorney Akira Yamatani

Claims (1)

[Claims] One spindle supports a plurality of magnetic disk disks, an arm is provided with a plurality of magnetic heads for accessing the surface of the magnetic disk, a plurality of these arms are provided, and an actuator is provided to control the arm. A magnetic disk in a disk device, characterized in that a plurality of magnetic heads provided on the arm are divided into a plurality of groups, each group accesses simultaneously, and each group is composed of heads that are subjected to offsets due to temperature to the same extent. Device.