Rotary drum and magnetic tape recording/reproducing apparatus using the same

There is provided a rotary drum which is capable of increasing recording density of a magnetic tape by changing tape/head relative speed and by solving problems which occur in increasing the tape/head relative speed. The inventive rotary drum includes a pair of recording heads having different azimuth angles and disposed separately with 180&deg; of central angle and a second recording head disposed at the same position in the circumferential direction with one recording head among the pair of recording heads while separating by 5.5 &mgr;m in the direction of height of the rotary drum and having a different azimuth angle from the one recording head. A first mode is created by the pair of recording heads separated by 180&deg; of central angle and a second mode is created by the two recording heads at the same position in the circumferential position.

RELATED APPLICATION DATA

The present application claims priority to Japanese Application No. P11-312306 filed Nov. 2, 1999, which application is incorporated herein by reference to the extent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary drum and a magnetic tape recording/reproducing apparatus using the same or more specifically to technology which allows recording density of a magnetic tape to be changed by changing tape/head relative speed and recording density to be increased by solving problems which have occurred in increasing the tape/head relative speed.

2. Related Art Statement

Among magnetic tape recording/reproducing apparatuses, there has been one which reproduces information by means of reproducing heads while recording information on a tape recording medium by means of recording heads.

For instance, a magnetic tape streamer drive unit known as a computer data recording apparatus reproduces information while recording the information to a tape recording medium to check whether or not the information has been correctly recorded. Such function is called as RAW (Read after Write) function. In order to realize such function, a rotary drum is provided with recording heads and reproducing heads and a rotary transformer is provided with recording system channels and reproducing system channels for transmitting signals to the recording heads and for transmitting signals from the reproducing heads.

FIGS. 9 through 11 show one example of a prior art rotary drum for realizing such RAW function, wherein FIG. 9 is a schematic plan view for explaining the positional relationship of the respective heads and FIG. 10 is a schematic side view of the rotary drum.

The rotary drum a is provided with the two recording heads bA and bB and two reproducing heads cA and cB separately with 180 of central angle as shown in FIG. 9 . The recording head bA has an azimuth angle A and the recording head bB has an azimuth angle B. The reproducing head cA has an azimuth angle A and the reproducing head cB has an azimuth angle B.

The recording heads bA and bB are disposed with a certain gap, e.g., 11 m, in the direction of a rotary shaft (in the direction of height) of the rotary drum a and the reproducing heads cA and cB are also disposed with a certain gap, e.g., 11 m, in the same manner with the recording heads bA and bB as shown in FIG. 10 . It is noted that FIG. 9 shows the recording heads bA and bB and the reproducing heads cA and cB by arranging in the circumferencial direction in order to represent the respective heads on a plan view.

Thereby, recording tracks Ta having the azimuth angle A and recording tracks Tb having the azimuth angle B are recorded on the magnetic tape d separately with the gap between the recording head bA and recording head bB (gap in the direction of height of the drum, e.g., 11 m) as shown in FIG. 11 .

However, because the track pitch Tp of the recording tracks recorded on the magnetic tape d by the prior art rotary drum a as described above is equal to the gap between the recording heads bA and bB (gap in the direction of height of the drum, e.g., 11 m) and is constant, it is unable to change the recording density of the magnetic tape d (see FIG. 11 ).

Then, it is conceivable to dispose two recording heads eA and eB and two reproducing heads cA and cB by separating them by 180 of central angle as shown in FIG. 12 .

Thereby, the track pitch Tp may be changed by changing tape/head relative speed.

That is, the distance between the recording track Ta and the recording track Tb (track pitch Tp) is determined by the tape/head relative speed. The track pitch Tp increases as the tape/head relative speed increases and the pitch decreases as the speed decreases. Thereby, the recording density of the magnetic tape d may be changed by changing the tape/head relative speed.

However, when the tape/head relative speed is increased to increase the recording density by disposing the two recording heads 6 A and 6 B by separating by 180 of central angle as described above, there has been a problem that the neighboring recording tracks Ta and Tb are liable to overlap.

That is, the rotary drum a sometimes causes precession which bends slightly and helically the recording tracks Ta and Tb formed on the magnetic tape d when spread in plan as shown in FIG. 13 .

As it is apparent from FIG. 13 , when the rotary drum a causes precession, a locus of an arbitrary point thereof is S-shaped in one turn (360 ) when spread in plan and a locus which bends upward or downward is formed in a half turn (180 ).

Then, when the two recording heads bA and bB create such S-shaped locus by semicircle each (180 each), two recording tracks are formed abreast. The locus of one recording head bA becomes the recording track Ta which bulges upward and the locus of the other recording head bB becomes the recording track Tb which bulges downward. Thus, the bulged parts become closer to each other as compared to the other parts and the two recording tracks Ta and Tb overlap each other in some cases.

Accordingly, there has been a problem that even if the track pitch is reduced by disposing the two recording heads bA and bB separately with 180 of central angle and by increasing the tape/head relative speed, the track pitch cannot be reduced so much and the increase of the recording density is limited.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a rotary drum which realizes a plurality of modes with regard to recording density of a magnetic tape by changing tape/head relative speed and increases the recording density by solving the limit of the increase of recording density implemented by increasing the tape/head relative speed.

It is another object of the invention to provide a magnetic tape recording/reproducing apparatus which realizes a plurality of modes with regard to recording density of a magnetic tape corresponding to different tape/head relative speeds and increases the recording density by solving the limit of the increase of recording density implemented by increasing the tape/head relative speed.

In order to achieve the above-mentioned objects, an inventive rotary drum comprises a pair of recording heads having different azimuth angles and disposed separately with 180 of central angle and a second recording head disposed at the same position in the circumferential direction with at least one recording head among the pair of recording heads while leaving a predetermined gap in the direction of height of the rotary drum and having a different azimuth angle from the one recording head.

Accordingly, because the pair of recording heads are disposed separately with 180 of central angle on the inventive rotary drum, the plurality of modes may be realized with regard to the recording density of the magnetic tape by varying the tape/head relative speed. Further, because the second recording head is disposed by leaving the certain gap (gap in height) in the direction of height from one recording head, the parallel of the two recording tracks created by such gap in height may be maintained. Therefore, the recording density may be increased by setting a mode so that such gap in height becomes the smallest track pitch.

According to a second aspect of the invention, the drum further comprises a dummy head having almost the same mass with the second recording head at the position separated from the second recording head by 180 of central angle, so that it is possible to eliminate the weightwise eccentricity of the rotary drum and to prevent nonuniformity of rotation in rotating the drum.

An inventive magnetic tape recording/reproducing apparatus has a rotary drum comprising a pair of recording heads having different azimuth angles and disposed separately with 180 of central angle and a second recording head disposed at the same position in the circumferential direction with at least one recording head among the pair of recording heads while leaving a predetermined gap in the direction of height of the rotary drum and having a different azimuth angle from one recording head. The apparatus has two or more modes with regard to tape/head relative speed of tape recording medium.

Accordingly, because the pair of recording heads are disposed separately with 180 of central angle in the inventive magnetic tape recording/reproducing apparatus, the plurality of modes may be realized with regard to the recording density of the magnetic tape by varying the tape/head relative speed. Further, because the second recording head is disposed by leaving the certain gap (gap in height) in the direction of height from one recording head, the parallel of the two recording tracks created by such gap in height may be maintained. Therefore, the recording density may be increased by setting a mode so that such gap in height becomes the smallest track pitch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An inventive rotary drum and a magnetic tape recording/reproducing apparatus using the same will be explained below in detail in accordance to preferred embodiments shown in the appended drawings.

FIG. 1 is a schematic plan view of the rotary drum 1 for explaining the positional relationship of respective heads. The rotary drum 1 comprises a rotor side drum 2 and a stator side drum 3 . The rotor side drum 2 has a pair of recording heads 4 A and 4 B disposed separately with 180 of central angle, a second recording head 5 A disposed at the same position in the circumferential direction with one recording head 4 B among the pair of recording heads while leaving a certain gap (gap in height) in the direction of height of the rotary drum 1 and two reproducing heads 6 A and 6 B disposed separately from each other with 180 of central angle. The recording head 4 A, the reproducing head 6 A, the recording head 4 B (second recording head 5 A) and the reproducing head 6 B are disposed at equal intervals in the circumferential direction, i.e., separately with 90 of central angle, as shown in FIG. 1 . The respective heads 4 A, 4 B, 6 A and 6 B are disposed at the same position in terms of the direction of the rotary shaft (in the direction of height of the rotary drum 1 ) and the recording head 4 B and the second recording head 5 A are disposed separately by 5.5 m for example, in the direction of height. It is noted that MR heads are adopted for the reproducing heads 6 A and 6 B.

The recording head 4 A and the second recording head 5 A have an azimuth angle A, the recording head 4 B has an azimuth angle B, the reproducing head 6 A has an azimuth angle A and the reproducing head 6 B has an azimuth angle B.

A magnetic tape 7 is wrapped around to the rotary drum 1 aslant with an angle of 180 or more. Thereby, recording tracks Ta and Tb are formed aslant with a predetermined angle. The recording tracks Ta having the azimuth angle A and the recording tracks Tb having the azimuth angle B are formed adjacent to each other as shown in FIGS. 2 and 3 .

The rotary drum 1 described above has a first mode (see FIG. 2 ) of forming the first recording tracks T 1 a and T 1 b by the recording heads 4 A and 4 B and a second mode (see FIG. 3 ) of forming the second recording tracks T 2 b and T 2 a by the recording head 4 B and the second recording head 5 A.

In forming the recording tracks by the recording heads 4 A and 4 B separated from each other by 180 (first mode), the track pitch Tp 1 is determined by the tape/head relative speed as described above. The pitch increases as the tape/head relative speed increases and decreases as the speed decreases. Thus, the recording density of the magnetic tape 7 depends on the tape/head relative speed.

Then, the tape/head relative speed is controlled so that the track pitch Tp 1 is set at 11 m for example in the first mode.

Here, although there is a case when the recording tracks T 1 a and T 1 b are formed curvedly by the precession of the rotary drum 1 , the recording tracks T 1 a and T 1 b will not overlap each other because the track pitch Tp 1 is set at 11 m.

While it is necessary to read the recording tracks T 1 a and T 1 b by the reproducing heads 6 A and 6 B immediately after forming the tracks by the recording heads 4 A and 4 B in order to realize the RAW function described above, the recording tracks T 1 a and T 1 b are scanned with the same tape/head relative speed because the reproducing heads 6 A and 6 B are also separated from each other by 180 .

Next, in recording the recording tracks T 2 b and T 2 a in the second mode by the recording head 4 B and the second recording head 5 A, the tape/head relative speed must be set at twice of that of the first mode.

The two recording tracks T 2 b and T 2 a formed by the two recording heads 4 B and 5 A disposed at the same position in the circumferential direction while leaving an arbitrary gap (gap in height) in the direction of height do not depend on the tape/head relative speed. The gap in height 5.5 m between the recording heads 4 B and 5 A becomes a track pitch Tp 2 5.5 m in the second mode, so that the tape/head relative speed may be set at any speed.

However, the recording tracks T 2 a and T 2 b must be read almost in the same time by the reproducing heads 6 A and 6 B in order to realize the RAW function and the reproducing heads 6 A and 6 B must scan the recording tracks T 2 a and T 2 b by the same tape/head relative speed. Accordingly, the intervals of the loci scanned by the reproducing heads 6 A and 6 B must coincide with the track pitch Tp 2 5.5 m of the recording tracks T 2 a and T 2 b described above.

The recording tracks T 2 a and T 2 b formed by the recording heads 4 A and 5 A may be read by setting the tape/head relative speed at twice of that of the first mode.

While the track pitch Tp 2 has been set at 5.5 m in the second mode to set at a half of the track pitch Tp 1 11 m in the first mode, the both recording tracks T 2 a and T 2 b will not overlap each other even if the rotary drum 1 causes precession because the adjacent recording tracks T 2 a and T 2 b bend in the same direction.

Thus, it is necessary to set the track pitch Tp 1 to the degree by which the adjacent recording tracks T 1 a and T 1 b do not overlap by the precession of the rotary drum 1 because the recording tracks T 1 a and T 1 b are formed by the two recording heads 4 A and 4 B separated by 180 of central angle in the first mode as described above. Accordingly, the track pitch Tp 1 may be able to set the smaller track pitch T by lowering an allowance of axial deviation of the rotary drum 1 caused by the precession.

Then, it is preferable to decide the second track pitch Tp 2 after setting the track pitch Tp 1 in the first mode because the track pitch Tp 2 in the second mode may be reduced as compared to the track pitch Tp 1 in the first mode.

By the way, it is conceivable that crosstalk between respective channels in a rotary transformer 8 for transmitting signals to those recording heads 4 A and 4 B or to the stator side from the reproducing heads 6 A and 6 B may cause a problem because the two recording heads 4 A and 4 B and the reproducing heads 6 A and 6 B are disposed separately with 180 of central angle.

Then, it is effective to arrange the rotary transformer 8 as described below to carry out the invention (see FIGS. 4 and 5 ).

The rotary transformer 8 comprises channels 9 a, 9 b, 10 a and 11 respectively corresponding to the heads 4 A, 4 B, 5 A, 6 A and 6 B, a power system channel 12 for transmitting power to amplifiers described below for the reproducing heads 6 A and 6 B and a short ring 13 as a shield channel for preventing crosstalk from the power system channel 12 . It is noted that there is provided only one reproducing system channel 11 to reduce a number of channels by selectively connecting the reproducing heads 6 A and 6 B to the reproducing system channel 11 by a switch described later. It is noted that reproducing system channels may be provided respectively for the reproducing heads 6 A and 6 B.

Each of the channels 9 , 10 , 11 , 12 and 13 comprises a rotor side element r and a stator side element s. Each of these elements r and s, i.e., coils wound in ring, is stored within a ringed groove so as to face to each other.

Then, the respective channels are arrayed in order of the reproducing system channel 11 , a short ring 13 , the power system channel 12 , the short ring 13 , the recording system channel 9 b, the recording system channel 9 a and the recording system channel 10 a from the center of rotation of the rotary transformer 8 as shown in FIG. 4 .

A stator side element 12 s of the power system channel 12 of the rotary transformer 8 is connected to a power drive amplifier 14 and to an oscillating circuit 15 to transmit a power signal to a rotor side element 12 r.

The power signal transmitted to the rotor side element 12 r of the power system channel 12 is supplied to amplifiers 18 A and 18 B for the reproducing heads 6 A and 6 B via a rectifying and smoothing circuit 16 and a regulator 17 as shown in FIG. 5 .

Reproduced signals reproduced by the reproducing heads 6 A and 6 B are amplified by the amplifiers 18 A and 18 B, respectively, and are supplied to the rotor side element 11 r of the reproducing system channel 11 after being switched by a switch 19 . It is then transmitted to the stator side element 11 s of the reproducing system channel 11 to be outputted via a reproducing amplifier 20 and an equalizer 21 as shown in FIG. 5 .

It is noted that the reproducing heads 6 A and 6 B read the recording signals both in the first and second modes in the same manner.

The recording signal is recorded to the magnetic tape 7 as follows. It is noted that this will be explained separately in the first and second modes.

In case of the first mode, the recording signals are amplified, respectively, by recording amplifiers 22 A and 22 B disposed at the stator side and are supplied to stator side elements 9 as and 9 bs of the recording system channels 9 a and 9 b. Then, they are transmitted to rotor side elements 9 ar and 9 br of the recording system channels 9 a and 9 b and are supplied respectively to the recording heads 4 A and 4 B to be recorded to the magnetic tape 7 .

Next, in case of the second mode, the recording signals are amplified respectively by the recording amplifiers 22 B and 22 A 2 disposed on the stator side and are supplied to the stator side elements 9 bs and 10 as of the recording system channels 9 b and 10 a. Then, they are transmitted to the rotor side elements 9 br and 10 ar of the recording system channels 9 b and 10 a and are supplied respectively to the recording heads 4 B and 5 A to be recorded to the magnetic tape 7 .

The respective channels 9 a, 9 b, 10 a, 11 and 12 (except of the short rings 13 ) operate as follows. It is noted that the operation of the respective channels in the first and second modes will be explained, respectively.

FIG. 6 is a timing chart showing the operations (transmitting state) of the respective channels 9 a, 9 b, 11 and 12 (except of the short rings 13 ) of the rotary transformer 8 in the first mode.

As it is apparent from FIG. 6 , because the two recording heads 4 A and 4 B are disposed separately with 180 of central angle in the circumferential direction of the rotary drum 1 , the recording system channel 9 a or 9 b operates while the recording head 4 A or 4 B contacts with the magnetic tape 7 , i.e., by semicircle of the rotary drum 1 , and the other recording system channel 9 b or 9 a operates in the next semicircle because the recording head 4 B or 4 A contacts with the magnetic tape 7 .

Thereby, the other one of the two recording system channels 9 a and 9 b does not operate when one of them operates, so that they do not overlap temporally and no crosstalk occurs between them. It is noted that either one of the recording system channels 9 a and 9 b always thus operates.

The two reproducing heads 6 A and 6 B are disposed separately with 180 of central angle in the circumferential direction of the rotary drum 1 as described above. The reproduced signals read by those reproducing heads 6 A and 6 B are amplified respectively by the amplifiers 18 A and 18 B and are supplied to the rotor side element 11 r of one reproducing system channel 11 to be transmitted to the stator side element 11 s. Therefore, the reproducing system channel 11 always operates.

Then, although either one of the recording system channel 9 a or 9 b and the reproducing system channel 11 always operate in the same timing, no crosstalk occurs between the reproducing system channel 11 and the recording system channel 9 a or 9 b because the short ring 13 and the power system channel 12 interposed between the reproducing system channel 11 and the recording system channel 9 a or 9 b as described above function as shield channels.

FIG. 7 is a timing chart showing the operations (transmitting state) of the respective channels 9 b, 10 a, 11 and 12 (except of the short rings 13 ) of the rotary transformer 8 in the second mode.

As it is apparent from FIG. 7 , because the two recording heads 4 A and 4 B are disposed at the same position in the circumferential direction of the rotary drum 1 , the recording system channel 9 a or 10 a operates in the same timing and the operating time overlap temporally. Then, although crosstalk between both channels 9 b and 10 a is questioned, no crosstalk occurs between the two channels 9 b and 10 a because the recording system channel 9 a is disposed between the both channels 9 b and 10 a and it functions as a shield channel.

Further, although the reproducing system channel 11 overlaps temporally with the recording system channels 9 b and 10 a while they operate because the reproducing system channel 11 operates in the same manner with the first mode, no crosstalk occurs between the reproducing system channel 11 and the recording system channels 9 b and 10 a as described above.

It is noted that although the power system channel 12 must be always operated because it drives the amplifiers 18 A and 18 B of the reproducing heads 6 A and 6 B when the reproducing heads 6 A and 6 B read the recording signals of the magnetic tape 7 and crosstalk between the power system channel 12 and the recording system channel 9 a and the reproducing system channel 11 b is questioned, no crosstalk occurs between them because their short rings 13 , 13 r 1 and 13 s 1 or 13 r 2 and 13 s 2 are interposed.

Thus, the first mode in which the recording track Tp 1 11 m may be formed by operating the recording heads 4 A and 4 B and the recording system channels 9 a and 9 b respectively connected thereto or the second mode in which the recording track Tp 2 5.5 m may be formed by operating the recording heads 4 B and 5 A and the recording system channels 9 b and 10 a respectively connected thereto on the rotary drum 1 . In particular, the recording tracks T will not overlap because the recording tracks T formed by the recording heads 4 B and 5 A bend in the same direction in the mode in which the recording track T is small even if the rotary drum 1 causes precession. Still more, no crosstalk between the respective channels occurs in the rotary transformer 8 in the both modes. It is noted that although the crosstalk between the respective channels in the rotary transformer 8 may be prevented by disposing the respective channels as described above, the present invention is not limited to that and the short ring may be disposed per channels which operate in the same timing for example.

FIG. 8 shows a modified example related to the disposition of the respective heads. It is different from the embodiment described above in that it is provided with a dummy head.

The dummy head 23 is provided at the same position in the circumferential direction with the recording head 4 A and separately in the direction of the rotary shaft of the rotary drum 1 A (in the direction of height of the rotary drum 1 A) by 5.5 m. It allows eccentricity of weight of the drum 1 A to be eliminated.

That is, although there has been a possibility that the rotary drum 1 is put into the eccentric condition weightwise and causes nonuniformity of rotation when the recording heads 4 A, 4 B and 5 A are disposed as described above in the embodiment described above, the modified example can prevent the nonuniformity of rotation because the respective recording heads 4 A, 4 B, 5 A and the dummy head 23 are disposed symmetrically about the axis centering on the center of rotation.

It is noted that although the embodiment described above has been explained about the rotary drum 1 provided with the three recording heads 4 A, 4 B and SA and the two reproducing heads 6 A and 6 B, the invention is not limited to such a case and may be carried out by providing four recording heads and four reproducing heads, for example. In such a case, a pair of reproducing heads having different azimuth angles, disposed in the same position in the circumferential direction and separated appropriately in the direction of height are disposed separately with 180 of central angle from each other and by having a gap in the direction of height. Thereby, two kinds of modes of operating the recording heads disposed in the same position in the circumferential direction and a mode of operating the recording heads at the position separated by 180 of central angle may be realized. When the recording heads at the position separated by 180 of central angle from each other are operated, a plurality of kinds of modes may be realized by changing the tape/head relative speed.

It is noted that the invention may be applied not only to a magnetic tape streamer drive unit known as a data recording apparatus for computer but also widely to ones having the function (RAW function) of checking recorded information while recording the information to a magnetic tape.

Still more, the concrete shape or structure of each part shown in the embodiments described above is merely a part of exemplary case in carrying out the invention and the technological scope of the invention should not be construed by them.

As described above, the inventive rotary drum comprises a pair of recording heads having different azimuth angles and disposed separately with 180 of central angle and a second recording head disposed at the same position in the circumferential direction with at least one recording head among the pair of recording heads while leaving a predetermined gap in the direction of height of the rotary drum and having a different azimuth angle from one recording head.

Accordingly, because the pair of recording heads are disposed separately with 180 of central angle on the inventive rotary drum, the plurality of modes may be realized with regard to the recording density of the magnetic tape by varying the tape/head relative speed. Further, because the second recording head is disposed by leaving the certain gap (gap in height) in the direction of height from one recording head, the parallel of the two recording tracks created by such gap in height may be maintained. Therefore, the recording density may be increased by setting a mode so that such gap in height becomes the smallest track pitch.

According to a second aspect of the invention, the drum further comprises a dummy head having almost the same mass with the second recording head at the position separated from the second recording head by 180 of central angle, so that it is possible to eliminate the weightwise eccentricity of the rotary drum and to prevent nonuniformity of rotation in rotating the drum.

The inventive magnetic tape recording/reproducing apparatus has a rotary drum comprising a pair of recording heads having different azimuth angles and disposed separately with 180 of central angle and a second recording head disposed at the same position in the circumferential direction with at least one recording head among the pair of recording heads while leaving a predetermined gap in the direction of height of the rotary drum and having a different azimuth angle from one recording head and two or more modes with regard to tape/head relative speed of tape recording medium.

Accordingly, because the pair of recording heads are disposed separately with 180 of central angle in the inventive magnetic tape recording/reproducing apparatus, the plurality of modes may be realized with regard to the recording density of the magnetic tape by varying the tape/head relative speed. Further, because the second recording head is disposed by leaving the certain gap (gap in height) in the direction of height from one recording head, the parallel of the two recording tracks created by such gap in height may be maintained. Therefore, the recording density may be increased by setting a mode so that such gap in height becomes the smallest track pitch.