GB2279800A

GB2279800A - Magnetic head apparatus

Info

Publication number: GB2279800A
Application number: GB9417710A
Authority: GB
Inventors: Masaru Nishimura
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1991-04-25
Filing date: 1992-04-16
Publication date: 1995-01-11
Anticipated expiration: 2012-04-16
Also published as: GB9417710D0; GB2279800B; GB2279801A; GB9417711D0

Abstract

In a magnetic head apparatus, having a high density magnetic head (2) and a low density magnetic head (3) for reading/reproducing selectively tracks at different track densities of a disc, the effective width TWL of the low density magnetic head (3) is set to be an even number multiple of the track pitch TPU of the high density tracks to minimise the effects of cross-talk. The heads may be on a single slider, or on two sliders on opposite sides of a disc. They may be arranged side-by-side or one-behind-the-other in the track direction, to which they may be inclined. <IMAGE>

Description

MAGNETIC HEAD APPARATUS The invention relates to a magnetic head apparatus used for magnetic disc apparatus or flexible disc apparatus.

FIG. 7 of the accompanying drawings is a general construction diagram of a conventional magnetic head apparatus disclosed in the laidopen Japanese patent publication No. 62-28913. In the figure, 1 is a slider, which mounts a high density magnetic head 2 and a low density magnetic head 3. Either a recording medium 4A for low density or a recording medium 4B for high density is arranged under the slider 1. A low track 5 is arranged on the surface of the low density recording medium 4A, and a high track 6 is arranged on the surface of the high density recording medium 4B. 7 is representative of magnetic interference (crosstalk) between the high density magnetic head 2 and the low density magnetic head 3. TWU is a track width of the high density magnetic head 2. Two is a track width of the low density magnetic head 3. Tpu is a track pitch between the tracks on the high density recording medium 4B. TpL is a track pitch between the tracks on the low density recording medium 4A. T, is a distance between the high density magnetic head 2 and the low density magnetic head 3. TWA is a distance between the low tracks 5 on the low density recording medium 4A.

The operation of the conventional magnetic head apparatus is explained hereinafter. The conventional slider 1 has a plurality of heads for different densities, such as the high density magnetic head 2 and the low density magnetic head 3, in order to record and reproduce the data in a plurality of the different density recording mediums 4A and 4B. The plurality of magnetic heads operate independently according to each standard.

A mechanical feeding stepping motor is used for positioning the Jer 1 to an arbitrary position. The high density magnetic head 2 is iven to the arbitrary position at the high density track 6 for every one ?ulse, and the low density magnetic head 3 is driven to the arbitrary position at the low density track 5, for example, for every two pulses.

The positions at the low density track 5 and the high density. track 6 on the respective recording mediums 4A and 4B are deEmed by the apparatus standard. Therefore, not only the low density magnetic head 3 but also the high density magnetic head 2 may be positioned over the low density track 5 ,while the low density magnetic head 3 is operated by the feeding pitch of the stepping motor.

Since the conventional magnetic head apparatus is constructed as described above, if the high density magnetic head 2 is positioned over another bw density track SB ,while the low density magnetic head 3 is recording or reproducing the recording signal, when a recording signal is applied to the low density magnetic head 3, a part of the recording signal leaks to the high density magnetic head 2 by the influence of the crosstalk 7 between the high density magnetic head 2 and the low density magnetic head 3.

The recording signal to be recorded onto the low density track 5A is also recorded into another low density track SB by the influence of the above mentioned crosstalk. When the low density magnetic head 3 reproduces the data on the low density track SA, the high density magnetic head 2 reproduces the data on the low density track SB at the same time, and a part of the reproduced data by the high density magnetic head 2 leaks to the low density magnetic head 3 by the influence of the crosstalk 7.

Accordingly, there occur error problems, since the data reproduced by the high density magnetic head 2 are superimposed over the data reproduced from the low density track 5A by the low density magnetic head 3.

FIG. 8 and FIG. 9 of the accompanying drawings are respectively, an enlarged diagram and a diagram for enplaning the operation of the conventional magnetic head apparatus disclosed in the laid-open Japanese patent publication No. 62-28913. In FIG. 8, 1 is a slider, 2 is a magnetic head having narrower track width (having high density ) , referred as a high density magnetic head in the following. 3 is a magnetic head having wider track width (having low density ), referred as a low density magnetic head in the following. 4 is a recording medium. 5 is a signal track recorded on the recording medium. 6 shows magnetic interference between the low density magnetic head and the high magnetic head, referred as crosstalk in the following. Twu is a track width of the high density magnetic head 2. T,is a track width of the low density magnetic head 3. Tpu is a track pitch between the signal tracks of the high density magnetic head. S1 to Slo, A and B are the servo signals recorded on the signal track.

The operation of the conventional magnetic head apparatus is explained hereinafter. The conventional magnetic head apparatus has a plurality of magnetic heads for different densities as shown in FIG. 8, such as the high density magnetic head 2 and the low density magnetic head 3, in order to record and reproduce the data in a plurality of the different density recording mediums. The plurality of magnetic heads operate independently according to each standard. As shown in FIG. 8 , while the high density magnetic head 2 is recording and reproducing the data to the high track density on the recording medium 4, the low density magnetic head 3 is positioned over a plurality of signal track 5. Accordingly the low density magnetic head 3 reproduces the data signal and the servo signal, and some of the signals generated by the crosstalk 6 leak to the high density magnetic head 2 and are superposed on the signal reproduced by the high density magnetic head 2.

In order to position the high density magnetic head 2 to the desired signal track 5 on the recording medium 4, a sector servo system is generally used.

Figure 9 of the accompanying drawings shows an example of the sector servo system. In Figure 9, when the high density magnetic head 2 is going to be positioned relative to the signal track, for example 5g, the high density magnetic head 2 is moved to the near position 5g by detecting the servo signal S, which records the information such as the track number and the sector number. By detecting the difference of the servo signal A and B, the high density magnetic head 2 is positioned precisely over the position 5g.

Since the conventional magnetic head apparatus is constructed as described above, while the difference of the servo signals A and B is detected in order to position the high density magnetic head to the accurate position, the low density magnetic head also detects the servo signals A and B. The detected signal at the low density magnetic head is superposed on the high density magnetic head signal by the crosstalk. Therefore, the servo signals A and B to be detected at the high density magnetic head include error signals. Accordingly, it has been difficult to detect the accurate position of the magnetic head because the errors are increased for positioning.

According to the present invention, there is provided magnetic head apparatus for use with a recording medium of predetermined format comprising circumferential tracks of predetermined widths and pitches including a wide track width and a narrow track width, the apparatus comprising a plurality of magnetic heads having different effective widths corresponding to the predetermined widths, said heads being carried by at least one slider, herein the effective width of the magnetic head orresponding to the wide tracks is set to be an even number multiple of the predetermined track pitch of the narrow tracks.

Thus, the present invention can prevent tihe generation of an error servo signal by the crosstalk and provide for accurate positioning because of the small positioning error.

The invention will be further described by way I of non-limitative example, with reference to the accompanying drawings, in which: Figure 1 is an enlarged diagram of the head of the magnetic head apparatus of a first embodiment of the present invention.

Figure 2 is a diagram for explaining the operation of the first embodiment of the present invention.

Figure 3 is a general diagram of a second embodiment of the present invention.

Figure 4 is an enlarged diagram of a third embodiment of the present invention.

Figure 5 is a general diagram of a fourth embodiment of the present invention.

Figure 6 is a general diagram of a fifth embodiment of the present invention.

Figure 7 is a construction diagram of a conventional magnetic head apparatus.

Figure 8 is an enlarged diagram of a conventional magnetic head apparatus.

Figure 9 is a diagram for explaining the operation of the conventional magnetic head apparatus.

The first embodiment of the present invention is described hereinafter. Figure 1 of the accompanying drawings is an enlarged diagram of the head portion of the magnetic head apparatus of the present invention. Figure 2 of the accompanying drawings is a diagram for explaining the operation of the invention. The reference numbers in Figure 1 are the same as those used in Figure 8 for the same portions or the corresponding portions.

In the first embodiment of the present invention of Figure 1, high density magnetic head 2 is adjacent to the low density magnetic head 3 in slider 1 and the track width Tt of the low density magnetic head 3 is set to be an even number multiple of the track pitch TpU of the high density magnetic head 2.

The operation of the magnetic head apparatus is explained hereinafter. Since the track width Tt of the low density magnetic head 3 is set to be an even number multiple of the track pitch Tor of the high density magnetic head 2, when the high density magnetic head 2 is positioned to the signal track 5g in Figure 2, the low density magnetic head 3 is positioned over the tracks 5b - Se. Accordingly, the low density magnetic head 3 reproduces the servo signal A from the 7b and 7c and the servo signal B from the oblique line parts of Sa, 8b and 8c. Since the sunimation amount of the oblique line parts of 8a , 8b and Sc corresponds to one servo signal B, the ratio of the servo signal A and the servo signal B is always equal to 1:1.

Therefore, even if some of the signals reproduced by the low density magnetic head 3 leak to the high density magnetic head 2 by the crosstalk between the heads, the difference signal of the servo signals A and B for positioning the high density magnetic head 2 is detected accurately. Because the difference signal of the servo signal A and the servo signal B influences to the high density magnetic head 2 with a small amount.

That is, even if the servo signals A and B reproduced by the low density magnetic head 3 leak to the high density magnetic head 2 by the crosstalk between the heads, the high density magnetic head 2 is not influenced by the crosstalk. Therefore the high density magnetic head 2 can be positioned accurately to the track 5g.

In the first embodiment of the present invention, the high density magnetic head 2 is arranged adjacent to the low density magnetic head 3. But, in FIG. 3, the high density magnetic head 2 is arranged far from the low density magnetic head 3. In this second embodiment of the present invention shown in FIG. 3, the same effect is obtained as that of the first embodiment of the present invention.

In the first embodiment and the second embodiment of the present invention, the effects of the crosstalk are explained. FIG. 4 of the accompanying drawings shows the crosstalk 6 generated between the slider la and the slider ib which are arranged at the opposite side of the recording medium 4. Therefore, if the track width TWL of the low density magnetic head 3 is set to be an even number multiple of the track pitch Tpu of the high density magnetic head 2 arranged at opposite side'for the recording medium 4, the same effect is obtained as that of the first embodiment of the present invention.

In the above embodiment 1, 2 and 3, the high density magnetic head 2 and the low density magnetic head 3 are arranged in parallel along the running direction. In FIG. 5 (a) and (b), the high density magnetic head 2 and the low density magnetic head 3 are arranged in series along the running direction. In this case, if the track width TWL of the low density magnetic head is set to be an even number multiple of the track pitch Tpu of the high density magnetic head 2, the same effect is obtained as that of the first embodiment of the third present invention. In the figure 5 (a) and (b), 13 is a coil for the high density magnetic head 2 and 15 is a coil for the low density magnetic head 3. 33 is a gap of the high density magnetic head 2 and 35 is a gap of the low density magnetic head 3. 41 is an erasing core.

In the fourth embodiment, it is better to set the distance L between the high density magnetic head 2 and low density magnetic head 3 to be smaller. In other words, when the high density magnetic head 2 is reproducing the servo signal A, the low density magnetic head 3 is preferable to reproduce the servo signal A for a long time. Therefore, as shown in FIG, 5 (b), the length Ls of the servo signal A along the track direction is preferable to be set such as L < Ls.

In Figure 6, the high density magnetic head 2 and the low density magnetic head 3 are formed by the core 31 and core 32 arranged oblique along the running direction. In this case, if the track width Tt of the low density magnetic head is set to be an even number multiple of the track pitch TpU of the high density magnetic head 2, the same effect is obtained as that of the first embodiment of the present invention.

The above shows the design of the magnetic head apparatus in which the track width is set to be an even number multiple in the case where the track pitch is constant. The invention may be applied though to a design in which the track width is constant. The track pitch is not decided by the track width of the head but also decided by the feeding pitch of the drive. The track pitch becomes large and the track density becomes small when the feeding amount becomes large even if the head having narrow track width is used. That is, the magnetic disc apparatus having the different pitch can be designed if the same magnetic head is used. Thus, in the invention, the track pitch can be designed so that the influence of the crosstalk may be maximally decreased by the same principle as that explained above.

This application was divided from copending application number 92 08410.2 which relates to spacing the heads by an odd number multiple of half the low density track pitch. A related divisional application is copending application number 94 which relates to spacing the heads by an integer multiple of the low density track width.

Claims

1. Magnetic head apparatus for use with a recording medium of predetermined format comprising circumferential tracks of predetermined widths. and pitches including a wide track width and a narrow track width, the apparatus comprising a plurality of magnetic heads having different effective widths corresponding to the predetermined widths, said heads being carried by at least one slider, wherein the effective width of the magnetic head corresponding to the wide tracks is set to be an even number multiple of the predetermined track pitch of the narrow tracks.

2. Magnetic head apparatus according to claim 1, wherein the heads are positioned to face opposite sides of the recording medium.

3. Magnetic head apparatus according to claim 1, wherein the heads are arranged sequentially in the tracking direction.

4. Magnetic head apparatus according to claim 1, wherein the heads are formed in cores arranged obliquely to the tracking direction.

5. Magnetic head apparatus constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.