JPH02198007A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To eliminate the magnetical and electrical influences of the writing current of a data head on a servo head by simple means by controlling the writing current value of the data head in accordance with the distance from the servo head. CONSTITUTION:A write driver 3 converts write data 5 to the inversion current of the current value determined by a writing current setting circuit 4 and supplies the same to a head selecting circuit 2 at the time of data writing. The head is selected by the circuit 2 and the writing current is caused to flow. The writing current value for each of the heads set in this circuit 4 is so set as to decrease the current for the data heads nearer the servo head and to increase the current as the heads are parted from the servo head. The writing current of the magnitude corresponding to the head selected by a head select signal is transmitted to the driver 3. The magnetical and electrical influences of the writing current on the servo head is eliminated in this way by the simple means.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic disk device, and particularly to a magnetic disk device that performs recording current control suitable for making a magnetic head follow a track stably. Regarding.

[Prior Art] Generally, positional information (servo information) on a magnetic disk is read by a magnetic head for reading positional information (hereinafter referred to as "servo head"), and based on the read positional information,
A magnetic disk device is known that performs track positioning of a data recording/reproducing magnetic head that moves together with the servo head.

In this device, the write current during data recording affects the position information signal read by the servo head.

Therefore, a malfunction may occur in the track positioning operation.

In order to deal with this problem, conventionally, for example, Japanese Patent Laid-Open No. 60-1
As described in Japanese Patent No. 11318, a magnetic shield material is provided between the servo head and the magnetic head for data recording/reproduction (hereinafter referred to as "data head"), so that the write current during recording is directed to the read position of the servo head. There are things that reduce the impact on information signals.

[Problems to be Solved by the Invention] When writing data with a data head, there are two types of paths that influence the positional information read by the servo head: magnetic and electrical. As for magnetic,
When writing data, the alternating magnetic field generated in the data head by the recording current wraps around the servo head and is superimposed as noise on the servo information read by the servo head, so it is thought that accurate servo information cannot be obtained. Also.

Electrically, it is thought that the write current leaks through the narrow circuit pattern into the read position signal of the servo head circuit.

According to the technique disclosed in the above-mentioned publication, the influence due to magnetic causes may be reduced to some extent, but the influence due to electrical causes cannot be eliminated. Furthermore, in order to effectively magnetically shield the gap between the servo head and the data head, a large magnetic shielding member is required, which poses a problem of increasing the size of the magnetic head device.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to eliminate the electrical and magnetic effects of the write current of the data head on the servo head.
Enables stable track control by eliminating the influence of noise on servo information (position information) when writing data.
It is an object of the present invention to provide a magnetic disk device which can record and reproduce data with high accuracy and can eliminate such magnetic and electrical influences by simple means without increasing the size of the magnetic head device.

[Means for Solving the Problems] In order to achieve the above object, the magnetic disk device of the present invention has the following features: , the recording current flowing through the data recording/reproducing magnetic head near the positional information reading magnetic head is set to a relatively low value, and the further the data recording/reproducing magnetic head is from the positional information reading magnetic head, the more the recording current is applied to it. Equipped with a data recording circuit for setting a high value.

[Effect] The operation based on the above configuration will be explained.

The causes of superimposition of noise on servo information during data writing include magnetic coupling due to the magnetic field generated by the head, as well as electrical coupling due to the pattern of the signal line wiring.

The noise caused by these couplings depends on the positional relationship between the servo head and the data head, and when a write current is applied to the data head close to the servo head (for example, when both heads are located on the front and back sides of the magnetic disk), This has a large effect, but no effect appears if the write current is applied to a data head that is separate from the servo head. It also depends on the write current value; when a large current flows, the influence of noise is large, and when a small current flows, the effect is small. Therefore, if a data head close to the servo head is selected, the write current should be reduced as much as possible to ensure sufficient recording on the medium, and if a data head located far from the servo head is selected, the write current should be reduced. By controlling the write current for each head so that the data head is increased, even if this data head is selected and the write current is flowing, noise due to electrical and magnetic leakage is eliminated and servo information can be read accurately. This makes it possible to stably perform track following control.

In this case, it should be noted that for conventional coating-type magnetic disks with a relatively thick magnetic layer, there is a write current value that gives the maximum playback output, and if the write current value is higher than that, the playback output will actually decrease. It has been found that in thin film type magnetic disks produced by sputtering, vapor deposition, etc., the reproduction output for a write current of a certain value or more remains almost constant even if the current value increases. Therefore, as in the present invention, even if the current values of the head closer to the servo head and the head farther from the servo head are different, a constant reproduction output can be obtained.

Furthermore, by passing a relatively small current through the data head that is relatively close to the servo head and has a small tracking deviation (off-track), the effective track width is made relatively narrow, and when the data head is relatively far from the servo head, the effective track width is made relatively narrow. By passing a relatively large current through a data head with a large tracking deviation, a relatively wide effective track width can be provided. As a result, it is possible to form a data track with substantially no tracking deviation using either the near or far data head.

[Example 1] An example of the present invention will be described below with reference to FIG. Here, it is assumed that data head 1 is the closest to the servo head, data head 2 is the next closest, and data head n is the furthest from the servo head. Note that these data heads 1,
2. It is assumed that the relative positional relationship between n and the servo head does not change even during the seek movement operation. When the data write state is entered, the write driver 3 writes write data 5 (voltage waveform) using an inverted current (for example, NRZ) having a current value determined by the write current setting circuit 4.
etc.) and supplies it to the head selection circuit 2. The head selection circuit 2 selects the desired head,
A write current based on the reversal current flows through the head. At this time, a write current value for each head is preset in the write current setting circuit 4, and a write current of a magnitude corresponding to the head selected by the head select signal 6 is transmitted to the write driver 3.

FIG. 2 shows the relationship between the write current flowing through the data head and the read voltage of the data head. The medium is sufficiently magnetized on the right side of line A in the figure. The write current value of each head is set in the write current setting circuit 4 so that the write current corresponding to data head 1 is A, the current is gradually increased as the distance from the servo head increases, and the write current corresponding to data head n is B. By setting this in advance, accurate servo information can be read even when writing data.

FIG. 3 shows an example of a write current setting circuit. When the base potential of the transistor 7 is set to a certain reference voltage, the collector current can be controlled by the value of the emitter resistor 8 (R, , R, , R, , R4). The level of the output of the decoder 10 changes depending on the content of the head select signal 6. 9 is an open collector output buffer 6. For example, when data head 1 is selected, all the outputs of decoder 10 are set to high level, so that the output of buffer 9 becomes high impedance and the collector current is determined only by the R circuit. The collector current at this time is set to the value A in FIG. When data head n is selected, all outputs of the decoder 10 are set to low level.
The output of buffer 9 is almost at ground level, R□,
Collector 1 due to the parallel combined resistance value of R2, R, and R4.
The style is decided.

The current I at this time is set to the value B in FIG. If another head is selected, the collector current will take a value between A and B if the decoder is configured so that some of the outputs of the decoder 10 are at a low level depending on the head number.

Additionally, positioning errors due to thermal off-track, etc. generally increase as the distance from the servo head increases, but in this case, the head farther away from the servo head sends a large write current, magnetizing the medium beyond the data track width. This has the effect that even if thermal off-track occurs, write data can be read accurately.

Note that leakage can be further reduced by changing the write current depending on the distance between the servo head and the data head and by using a conventional shield member. Even in this case, the shield member can be small.

Furthermore, in the case of a magnetic disk, the write current value may change between the outer circumference where the speed is faster and the inner circumference where the speed is slower, and this may be added to the above embodiment.

Furthermore, in the embodiment shown in FIG. 3, a plurality of resistors selected according to the head select signal are connected in parallel to the emitter of the transistor serving as the write current source, but the present invention is not limited to this, and various A modified circuit is possible. For example, a plurality of selected resistors may be connected in series,
Alternatively, the emitter resistance value may be kept constant and the base voltage applied to the transistor 7 may be varied. Also, the first
In the figure, the write current value is switched and set by the write driver at the front stage of the head selection circuit 2, but the optimum current value for each data head can also be set by the head selection circuit 2 itself or at a stage after it. good.

[Effects of the Invention] As explained in detail above, according to the present invention, when the data recording/reproducing magnetic head is close to the one-position information reading magnetic head, the current value flowing through the data recording/reproducing magnetic head is lowered. , the write current value applied to the data recording/reproducing magnetic head was increased as the data recording/reproducing magnetic head was separated from the position information magnetic head. With a simple means, leakage from any data recording/reproducing magnetic head to the positional information reading head can be eliminated, and the influence of noise from the positional information reading head during data writing can be eliminated. Also,
This provides excellent effects such as minimizing the substantial amount of off-track by any data recording/reproducing magnetic head.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a magnetic head device of the present invention;
FIG. 2 is a diagram showing the relationship between write current and read voltage of a magnetic head for data recording and reproducing, and FIG. 3 is a circuit diagram showing a specific example of a write current setting circuit. 1...Data head, 2...Head selection circuit.

Claims (1)

[Claims] 1. In a magnetic disk device that positions a data recording/reproducing magnetic head based on positional information reproduced from a positional information reading magnetic head, a data recording/reproducing device near the positional information reading magnetic head. The data recording circuit is characterized in that the recording current flowing through the magnetic head is set to a relatively low value, and the farther the magnetic head for data recording/reproduction is from the magnetic head for reading position information, the higher the value of the recording current flowing through the magnetic head is set. magnetic disk device. 2. The data recording circuit includes a recording drive circuit that generates a recording current based on data to be recorded, a head selection circuit that switches and supplies the recording current to a desired data recording/reproducing magnetic head, and the data recording/reproducing magnetic head. 2. The magnetic disk device according to claim 1, further comprising a recording current setting circuit that switches the value of the recording current to a predetermined value simultaneously with switching of the magnetic head. 3. The magnetic disk device according to claim 1 or 2, wherein the magnetic disk device is applied to a thin film type magnetic disk.