JP2009020943A - Magnetic tape, magnetic tape cartridge, magnetic tape drive, magnetic head tracking control method, and servo writer - Google Patents

Abstract

In a magnetic tape, a high-speed response is enabled, and a large storage capacity can be achieved by effectively using a recording surface of the magnetic tape.
A magnetic tape MT is configured by including at least one servo track ST having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape T. For example, the servo track ST is configured such that one magnetic moment 41 directed in the width direction is arranged. A servo signal is read from the servo track ST by inductive servo signal reading elements SRa and SRb having a reading width smaller than the width of the servo track ST, and the magnetic head H is tracking-controlled according to the output of the servo signal.
[Selection] Figure 1

Description

  The present invention relates to a magnetic tape, a magnetic tape cartridge, a magnetic tape drive, a tracking control method for a magnetic head, and a servo writer.

In recent years, the width of a data track on a magnetic tape has become extremely narrow as the recording density increases. In order to cause the recording or reproducing element of the magnetic head to accurately follow the narrow data track, a servo signal indicating the reference position of the data track is written in advance on the magnetic tape.
The servo signal is written in a servo track set on the magnetic tape. For example, as disclosed in Patent Document 1, a C-shaped magnetic pattern (hereinafter referred to as “servo pattern”) is repeatedly written in the longitudinal direction of the magnetic tape in the servo track.

  The servo pattern described in Patent Document 1 is intermittently generated in a magnetic tape drive by being read by a magnetic head having a servo signal reading element having a width smaller than the width of the letter C. The tracking position of the magnetic head (position in the width direction of the magnetic tape) is calculated based on the time interval of the generated pulse signal, and the position of the magnetic head is controlled.

  As another magnetic tape tracking control method, as in Patent Document 2, two servo tracks are provided, and two servo signal reading heads are provided corresponding to the two servo tracks. One that tracks a magnetic head according to the intensity of a servo signal read by a signal reading head is known.

  In the servo pattern of the prior art, the direction of the magnetic moment is formed along the longitudinal direction of the magnetic tape.

JP 2003-168269 A JP-A-5-46961

  However, in the case of a so-called timing-based servo system as disclosed in Patent Document 1, the tracking position of the magnetic head cannot be obtained (calculated) unless a plurality of servo patterns separated in the longitudinal direction of the magnetic tape are read. . Therefore, when the magnetic tape fluctuates at a high frequency in the width direction, there is a problem that the magnetic head cannot follow the movement of the magnetic tape.

  In the tracking servo system described in Patent Document 2, only one position information of the magnetic head can be obtained from two servo tracks. Further, as shown in FIG. 2 of Patent Document 2, a non-recording portion equivalent to the servo track must be provided on both sides of the servo track. For this reason, there is a problem that the surface area of the magnetic tape cannot be sufficiently utilized for increasing the recording capacity.

  The present invention has been made in view of the background as described above. A magnetic tape and a magnetic tape cartridge capable of high-speed response and capable of increasing the storage capacity by effectively using the recording surface of the magnetic tape. An object of the present invention is to provide a magnetic tape drive, a tracking control method for a magnetic head, and a servo writer.

  The present invention that has solved the above-described problems is characterized by comprising at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape.

  According to such a magnetic tape, when servo signals are read by a magnetic head provided with at least two servo signal reading elements having a reading width smaller than the width of the servo track within the width of one servo track, each servo signal is read. The intensity of the read signal varies depending on the position of the signal reading element in the servo track. Therefore, for example, by adjusting the position of the magnetic head so that the signals read by the two servo signal reading elements have the same intensity, the magnetic head can be tracked. In this case, the magnetic head is controlled so that the center of the servo track is traced between the two servo signal reading elements.

  When such tracking control is performed, if one servo signal (servo pattern) is read, the intensity of the servo signal read by the two servo signal reading elements is compared to obtain the tracking position of the magnetic head at that time. be able to. Therefore, the magnetic head can be made to follow with high response to the fluctuation of the magnetic tape.

  Also, by reducing the reading width of the two servo signal reading elements compared to the width of the servo track, there is no need to provide a non-recorded portion corresponding to the servo track around the servo track, and the data track (data band ) Close to the servo track. Therefore, it is possible to effectively use the recording surface of the magnetic tape and realize a large recording capacity.

  Furthermore, since the intensity of the servo signal arranged in the servo track has a mountain-shaped or valley-shaped distribution in the width direction, the positions where the two servo signal reading elements are shifted from the center in the width direction of the servo track are traced. The position can be controlled as described above, and one type of magnetic tape can be used for a recording format having a plurality of types of data track widths.

  The servo track can be configured by arranging a servo pattern having one magnetic moment directed in the width direction of the tape in the entire width of one servo track.

  When the servo signal of such a servo track is read with an induction type magnetic head having a magnetic gap smaller than the servo track width and oriented in the width direction of the tape, the magnetic moment of the magnetic moment is determined by the characteristics of the magnetic field formed by the magnetic moment. A strong magnetic force enters the magnetic gap near the center, and a weak magnetic force enters the magnetic gap near both ends of the magnetic moment. Therefore, the intensity of the servo signal that can be read by the servo signal reading element is strong near the center of the magnetic moment, that is, near the center of the servo track, and is weak near both ends of the magnetic moment, that is, near both ends of the servo track in the width direction. The signal is read as having a chevron or trough intensity distribution. Note that whether the servo signal intensity distribution is mountain-shaped or valley-shaped is a matter of whether the signal is positive or negative. For example, if the winding direction of the coils constituting the magnetic head is reversed, The valley is reversed.

  The servo track can be configured by arranging a servo pattern having one magnetic moment in the thickness direction of the tape in the entire width of one servo track. Alternatively, in the servo track, a servo pattern having a plurality of magnetic moments oriented in the thickness direction of the tape in the entire width of one servo track is arranged, and the magnetic moment closer to the center in the width direction of the one servo track The size can be increased.

  If a servo signal of such a servo track is read by an MR (Magneto Resistive) head having a reading width smaller than the servo track width, the magnetic moment formed by the magnetic moment causes the vicinity of the center of the magnetic moment. A strong magnetic force is generated, and a weak magnetic force is generated near both sides of the magnetic moment around it. Therefore, the intensity of the servo signal that can be read by the servo signal reading element is strong near the center of the magnetic moment, that is, near the center of the servo track, and weak near both ends of the magnetic moment, that is, near both ends of the servo track in the width direction. The signal is read as having a chevron or trough intensity distribution.

The servo track can be configured by changing the magnitude of the magnetic moment continuously or intermittently in the longitudinal direction of the tape.
The magnetic moment can also reverse the direction of the magnetic moment in the longitudinal direction of the tape.

  The servo track is preferably recorded with information encoded by a change in the magnitude of the magnetic moment. Further, it is desirable that information encoded by the interval of arrangement of the magnetic moment in the longitudinal direction of the tape is recorded on the servo track. Examples of such information include the position in the longitudinal direction of the magnetic tape.

  Each magnetic tape described above can be accommodated in a cartridge case to constitute a magnetic tape cartridge.

  The present invention for solving the above-described problems is a magnetic tape drive for recording or reproducing information on a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the tape width direction. A magnetic head in which at least two servo signal reading elements having a reading width smaller than the width of the servo track are provided within one servo track, and the magnetic head is moved in the width direction of the magnetic tape. And a control device that performs tracking control of the magnetic head by operating the actuator based on a signal read by the servo signal reading element, and the control device includes the two servo signal reading elements. The actuator is operated so that the difference in the intensity of each servo signal read by the controller becomes a predetermined value. And wherein the door.

  According to such a magnetic tape drive, when the two servo signal reading elements read the servo signal, the intensity of the obtained signal changes according to the position of each servo signal reading element in the servo track. Therefore, the magnetic head can be tracked by adjusting the position of the magnetic head so that the difference in intensity between the signals read by the two servo signal reading elements approaches a predetermined value. According to such tracking, high-speed response is good and it is possible to cope with an increase in the storage capacity of the magnetic tape.

By controlling the position of the magnetic head so that the difference in the intensity of the signals read by the two servo signal reading elements becomes zero, the center of the servo track is traced between the two servo signal reading elements. Controlled. On the other hand, by controlling the position of the magnetic head so that the difference between the signals read by the two servo signal reading elements becomes a value deviated from 0, the two servo signal reading elements are displaced from the center of the servo track. It is controlled to trace the position.
Thus, by performing tracking control at a position deviated from the center of the servo track, even when the same type of magnetic tape is used, recording / reproducing can be performed in a plurality of formats having different data track widths.

  In order to perform such position control, as another configuration, the control device corrects each servo signal read by the two servo signal reading elements so that the strength of one servo signal is greater than the other. Thus, tracking control can be performed so that the two servo signal reading elements are shifted from the center of the servo track.

  The servo track can be configured by arranging one magnetic moment directed in the width direction of the tape in the entire width of one servo track. For the magnetic tape, the two servo signal reading elements are the It can be configured to be an inductive magnetic head having a magnetic gap oriented in the width direction of the tape.

  The servo track can be configured by arranging one or a plurality of magnetic moments oriented in the thickness direction of the tape in the entire width of one servo track. For the magnetic tape, the two servo signal reading elements are The MR head can be used.

  The present invention for solving the above-mentioned problems has a reading width smaller than the width of the servo track with respect to a magnetic tape having at least one servo track having a peak-shaped or valley-shaped signal intensity distribution in the tape width direction. A method for tracking control of a magnetic head in which at least two servo signal reading elements are provided within the width of one servo track, wherein the two servo signal reading elements read and read servo signals from the servo track. The magnetic head is moved in the width direction of the tape so that the two servo signals have the same intensity.

  According to such a tracking method of the magnetic head, like the above-described magnetic tape drive, high-speed response of tracking is good, and it is possible to cope with a large storage capacity of the magnetic tape.

  The present invention for solving the above-mentioned problems is a servo writer for manufacturing a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape. A magnetic tape transport device that feeds and travels a magnetic tape material on which no signal is recorded; a servo signal writing head that is in sliding contact with the traveling magnetic tape material and records a servo signal on the servo track; A control device for inputting a signal to the servo signal write head, wherein the servo signal write head has one magnetic gap in the width direction of the magnetic tape material corresponding to one servo track. It is formed.

  According to such a servo writer, the above-described tracking with excellent high-speed response is possible, and a magnetic tape corresponding to a large storage capacity can be manufactured.

  The present invention for solving the above-mentioned problems is a servo writer for manufacturing a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape. A magnetic tape transport device that feeds and travels a magnetic tape material on which no signal is recorded; a servo signal writing head that is in sliding contact with the traveling magnetic tape material and records a servo signal on the servo track; And a control device for inputting a signal to the servo signal write head, the servo signal write head corresponding to one servo track and facing in the thickness direction of the tape within the width of the servo track. It is an induction type magnetic head that forms one magnetic moment.

  According to such a servo writer, a magnetic tape having one magnetic moment directed in the thickness direction within the width of one servo track can be manufactured. Therefore, if the servo signal reading element of the magnetic tape drive is an MR head, a mountain-shaped or valley-shaped signal intensity distribution can be obtained.

  Further, in order to obtain a similar signal intensity distribution, the servo signal writing head forms a plurality of magnetic moments corresponding to one servo track within the width of the servo track in the thickness direction of the tape. The magnetic core constituting the induction type magnetic head is magnetically divided into a plurality of parts in the width direction, and the magnetic permeability of each of the divided parts is outside from the center in the width direction. You may comprise so that it may become large gradually or gradually become small toward.

  According to the present invention, when tracking a magnetic tape, high-speed response can be improved, and a large storage capacity can be achieved.

[First Embodiment]
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
First, the magnetic tape according to the first embodiment of the present invention will be described. FIG. 1 is a perspective view of a magnetic tape and a magnetic head according to the first embodiment, FIG. 2 is a configuration diagram of a magnetic tape drive, and FIG. 3 is a plan view of the magnetic tape and the magnetic head. FIG. 4 is a block diagram of the control device.

  As shown in FIG. 1, in the magnetic tape MT according to the first embodiment, a magnetic layer M is formed on a tape T as a support, and a servo pattern SP is repeatedly written in the magnetic layer M along the longitudinal direction. Servo tracks ST are formed and configured. Although details of the layer configuration of the magnetic tape MT are omitted, a nonmagnetic layer and the like are included as necessary.

  Data is recorded on and reproduced from the magnetic tape MT by a magnetic tape drive 20 described later. Servo signal reading elements SRa and SRb (hereinafter simply referred to as “SR” if not specified) are arranged on the magnetic head H provided in the magnetic tape drive 20 approximately corresponding to the position of the servo track ST. ing. The width of the servo signal reading element SR (size in the width direction of the tape T) is formed smaller than the width of the servo track ST. Note that the servo signal reading element SR in FIG. 1 schematically shows an inductive magnetic head. Each element on the magnetic head H is actually formed by a thin film forming technique.

The servo pattern SP formed on the servo track ST is such that a signal output (referred to as “signal strength” in this specification) obtained by reading by the servo signal reading element SR has a mountain-shaped distribution in the width direction. Is formed. Whether or not the signal intensity has a mountain-shaped distribution depends on the configuration of the servo signal reading element SR. In the present embodiment, the servo pattern SP is configured to have one magnetic moment 41 directed in the width direction over the entire width of one servo track ST.
Further, as shown in FIGS. 1 and 3, the servo patterns SP are repeatedly arranged at a predetermined interval in the longitudinal direction of the magnetic tape MT.

One servo track ST is formed in the vicinity of both edges of the magnetic tape MT along the longitudinal direction (see FIG. 3). Of course, the number of servo tracks ST may be one or three or more.
A data band DB in which data is recorded is disposed between the servo tracks ST. In the data band DB, a data track DT having the same width as the servo track ST is arranged. The data track DT is conceptual before information is recorded, and the magnetic material of the magnetic layer M may be randomly arranged in the data track DT, or may be in one direction (for example, one in the longitudinal direction). Direction).
Such a magnetic tape MT is accommodated in a cartridge case 12 as shown in FIG.

Next, the configuration of the magnetic tape drive 20 that records and reproduces data on the magnetic tape MT configured as described above will be described.
As shown in FIG. 2, the magnetic tape drive 20 is a device that pulls out the magnetic tape MT from the magnetic tape cartridge 10 and records / reproduces data by the magnetic head H. Specifically, the magnetic tape drive 20 mainly includes a transport device 21, a magnetic head H, a rotation speed sensor 29, and a control device 27.

  The transport device 21 is a device that transports the magnetic tape MT in one direction or the other direction, and mainly includes a feed motor 25, a take-up reel 23, a take-up motor 26, and a plurality of guide rollers G. .

  The delivery motor 25 rotates the cartridge reel 11 in the magnetic tape cartridge 10, and its rotation direction, rotation speed, rotation torque, and the like are appropriately controlled by the control device 27. Specifically, when the magnetic tape MT is taken up by the take-up reel 23, the control device 27 causes the rotational speed and rotational torque of the delivery motor 25 to correspond to the speed of the magnetic tape MT taken up by the take-up reel 23. Thus, an appropriate tension is applied to the magnetic tape MT. In addition, when the magnetic tape MT is rewound (wound) onto the cartridge reel 11, the feeding motor 25 rotates in a direction to be rewound at a predetermined rotation speed according to an instruction from the control device 27.

  The take-up reel 23 is a reel that takes up the magnetic tape MT sent out from the cartridge reel 11.

The take-up motor 26 rotates the take-up reel 23, and the rotation direction, rotation speed, rotation torque, and the like thereof are appropriately controlled by the control device 27. Specifically, when the magnetic tape MT is rewound onto the cartridge reel 11, the rotational speed and rotational torque of the winding motor 26 are controlled by the control device 27 according to the speed of the magnetic tape MT rewound onto the cartridge reel 11. As a result of the adjustment, an appropriate tension is applied to the magnetic tape MT. When the magnetic tape MT is taken up by the take-up reel 23, the take-up motor 26 is rotated by a predetermined rotation according to an instruction from the control device 27. It rotates in the direction of winding at speed.

  In the present embodiment, the tension of the magnetic tape MT is controlled by controlling the rotational speed and rotational torque of the feed motor 25 or the take-up motor 26, but the tension may be adjusted using a dancer roller, The tension may be adjusted by appropriately pulling the magnetic tape into the vacuum chamber.

  The guide roller G is a roller for guiding the magnetic tape MT, and a traveling path of the magnetic tape MT is determined by being appropriately disposed at a predetermined position in the magnetic tape drive 20.

  The rotational speed sensor 29 detects the rotational speed of the take-up reel 23 as speed information related to the traveling speed of the magnetic tape MT. Then, the rotation speed sensor 29 outputs the detected rotation speed to the control device 27.

  The magnetic head H is formed in a size that is in sliding contact with the entire width of the magnetic tape MT. As shown in FIG. 3, the servo signal reading element SR, the data recording elements W1, W2,... Wn (hereinafter referred to as “Wn” unless otherwise specified) are provided on the sliding contact surface with the magnetic tape MT. And data reproducing elements R1, R2,... Rn (hereinafter simply referred to as “Rn” if not specified).

  The servo signal reading element SR has magnetic gaps 65a and 65b facing in the width direction as shown in the figure. The width of the servo signal reading element SR is formed smaller (narrower) than the width of the servo track ST.

  Two servo signal reading elements SR are arranged corresponding to the upper and lower servo tracks ST in FIG. The servo signal reading elements SRa and SRb corresponding to the upper servo track ST are arranged at a predetermined distance from each other at an interval in which both are contained in the servo track ST. Similarly, the servo signal reading elements SRc and SRd corresponding to the lower servo track ST are also arranged at a predetermined distance from each other at an interval in which both are within the servo track ST.

The data recording elements Wn are arranged in a staggered manner near the center of the magnetic head H so that adjacent ones are displaced in the tape longitudinal direction.
The data reproducing elements Rn are also arranged in a staggered manner on the left side of the data recording elements Wn in FIG. 3 so that adjacent ones are displaced in the tape longitudinal direction.

  In the present embodiment, the width of the data recording element Wn and the data reproducing element Rn is formed to be equal to the servo track ST, but is not limited to such a size. Alternatively, a narrower data track may be formed by forming a smaller width. Further, as in Patent Document 2, the data recording element Wn and the data reproducing element Rn may be arranged at predetermined intervals in the width direction by using a serpentine type recording method.

  An actuator A is attached to the magnetic head H. The actuator A is a device that moves the magnetic head H in the width direction of the magnetic tape MT. For example, a piezoelectric element or the like can be used.

In addition to controlling the transport device 21 as described above, the control device 27 performs tracking control of the magnetic head H based on the servo signals read by the servo signal reading elements SRa and SRb of the magnetic head H.
As shown in FIG. 4, the control device 27 includes a preamplifier 27a, a correction circuit 27b, a differentiator 27c, a drive circuit 27d, a pulse generation circuit 27e, and a main control unit 27x.
Two preamplifiers 27a are provided so that the servo signals (Ia ′, Ib ′) respectively input from the servo signal reading elements SRa, SRb are input, and appropriately amplify the input signals.

  The correction circuit 27b is provided corresponding to each preamplifier 27a. The correction circuit 27b amplifies the signal output from the preamplifier 27a with an appropriate gain in accordance with an instruction from the main control unit 27x. As a result, variations in sensitivity of the servo signal reading element SR can be corrected. This correction value may be determined in a uniform magnetic field. If the correction value is set so that one of the two correction circuits 27b outputs a signal larger than the other, tracking control may be performed by shifting the center of the servo signal reading elements SRa and SRb from the center of the servo track ST. it can.

  The differencer 27c receives the servo signals (Ia, Ib) output from the correction circuit 27b and calculates the difference in intensity between these servo signals (Ia, Ib). This difference is output to the drive circuit 27d.

  The drive circuit 27d outputs a drive signal to the actuator A based on the signal input from the differentiator 27c. When the signal input from the differentiator 27c is 0, the drive circuit 27d does not move the actuator A and maintains the current position. As a result, the servo signal reading elements SRa and SRb are feedback-controlled to positions allocated with the center of the servo track ST as a reference.

  The pulse generation circuit 27e is a circuit that generates a pulse signal for writing digital data to the magnetic tape MT.

  The main control unit 27x outputs a signal to the pulse generation circuit 27e in accordance with data to be recorded on the magnetic tape MT input from the input / output interface (I / O). Further, the signal read from the data reproducing element Rn of the magnetic head H is converted into digital data and output to the input / output interface (I / O). Further, when changing the tracking position of the magnetic head H, a correction signal is output to the correction circuit 27b.

  The operation of the magnetic tape drive 20 configured as described above will be described. 5A is a diagram showing the relationship between the servo signal reading element and the servo pattern, and FIG. 5B is a diagram showing the intensity distribution of the signal read by the servo signal reading element. FIG. 6A is a diagram showing a temporal change in the relative position of the servo track and the magnetic head, and FIG. 6B is a diagram showing a change in the intensity of the servo signal read by one servo signal reading element. (C) is a diagram showing a change in the intensity of a servo signal read by another servo signal reading element, and (d) is a servo signal read by one servo signal reading element and another servo signal reading. It is a figure which shows the change of the difference of the servo signal read with the element.

  As shown in FIG. 5A, when the servo signal reading element SR passes through the servo pattern SP of the servo track ST, the servo pattern SP is formed in the magnetic gaps 65a and 65b formed in the servo signal reading elements SRa and SRb, respectively. Part of the magnetic lines of force 41a formed around by the magnetic moment 41 enters. Since the magnetic gaps 65a and 65b are oriented in the width direction of the magnetic tape MT, the component of the magnetic force line 41a oriented in the width direction is the magnitude of the read signal output of the servo signal reading elements SRa and SRb. Therefore, the output of the signal read by the servo signal reading element SR from the servo pattern SP is as shown in FIG. 5B according to the position. The horizontal axis of the graph of FIG. 5B is approximately aligned with the position of the servo pattern SP of FIG. As shown in FIG. 5B, the distribution of the output of the signal read by the servo signal reading element SR, that is, the signal intensity distribution has a mountain-shaped distribution in the width direction due to the characteristics of the magnetic force lines 41a.

An operation for tracking control of the magnetic head H using a servo signal read from the servo pattern SP will be described. As shown in FIG. 6A, the signal intensity (plotted peak voltage of the pulse signal) when the magnetic head H is positioned at times t1, t2, t3, and t4 with respect to the servo track ST is a graph. If it becomes, it will become like FIG.6 (b), (c).
When the servo signal reading elements SRa and SRb are targeted with respect to the center line CL of the servo track ST at times t1 and t3 in FIG. 6A, the signals read by the servo signal reading element SRa and the servo signal reading element SRb The output will be the same.
When the servo signal reading element SR is shifted downward in the drawing relative to the servo track ST as at time t2 in FIG. 6A, the signal intensity Ia of the servo signal reading element SRa is increased. The signal intensity Ib of the servo signal reading element SRb becomes low (see FIGS. 6B and 6C).
On the other hand, when the servo signal reading element SR is shifted to the upper side in the figure relative to the servo track ST as at time t4 in FIG. 6A, the signal intensity Ia of the servo signal reading element SRa is low. The signal intensity Ib of the servo signal reading element SRb increases (see FIGS. 6B and 6C).

  When the difference Ia−Ib is obtained by the differentiator 27c for the signal intensities Ia and Ib obtained in this way, the result is as shown in FIG. Since the difference Ia-Ib indicates the amount of deviation of the servo signal reading elements SRa and SRb from the center line CL of the servo track ST, the servo signal reading is performed by driving the actuator A according to the difference signal. Tracking control can be performed so that the elements SRa and SRb trace the positions allocated with reference to the center of the servo track ST.

  Thus, since the signal intensity distribution of the servo signal of the magnetic tape MT of this embodiment is a mountain shape in the width direction, the signal intensity read by the magnetic tape drive 20 with each of the servo signal reading elements SRa and SRb. If the magnetic head H is controlled so as to be the same, the servo signal reading elements SRa and SRb can be controlled to be tracked to a position assigned with reference to the center of the servo track ST.

  According to such a tracking control method, unlike the conventional timing-based servo system, information on the position of the magnetic head H in the width direction of the magnetic tape MT can be obtained when the servo pattern SP is read. In particular, since the calculation performed by the control device 27 is only a process of calculating the difference between the servo signals read by the two servo signal reading elements SRa and SRb, the calculation load of the control device 27 is extremely light, and feedback control is performed. The sampling frequency can be increased. Therefore, the tracking error of the magnetic head H can be suppressed even if there is a sudden position change of the magnetic tape MT. Further, by arranging the servo pattern SP in a state of being packed in the longitudinal direction of the magnetic tape MT and acquiring a lot of position information of the magnetic head H within a unit time, the position accuracy of the magnetic head H can be further improved. it can. Alternatively, the transfer speed of the magnetic tape drive 20 can be increased by increasing the traveling speed of the magnetic tape MT.

Further, since the reading width of the servo signal reading element SR is formed to be smaller than the width of the servo track ST, it is not necessary to provide a large non-recorded portion of the data signal on both sides of the servo track ST. Therefore, it is possible to increase the storage capacity of the magnetic tape MT by effectively using the recording surface in the vicinity of the servo track ST.
In the first embodiment, the magnetic tape MT having a servo track having a mountain-shaped intensity distribution in the width direction is exemplified, but the mountain-shaped or valley-shaped is determined by the relationship with the servo signal reading element SR, and the servo signal The signal strength of the valley shape can be obtained by reversing the winding direction of the coil of the reading element SR, reversing the direction of the magnetic moment 41, or performing signal processing after reading the signal.

Next, a servo writer for manufacturing the magnetic tape MT as described above will be described. In the drawings to be referred to, FIG. 7 is a diagram showing the overall configuration of the servo writer, and FIG. 8 is a perspective view schematically showing the relationship between the servo signal write head and the magnetic tape.
As shown in FIG. 7, the servo writer 30 has a magnetic tape transport device 31 similar to the magnetic tape drive 20, while the magnetic tape material 51 on which no servo signal is written is caused to travel by the magnetic tape transport device 31. This is a device for writing a servo signal to the magnetic tape material 51 by the servo signal write head SWH. In the following description, the description of the same parts as the magnetic tape drive 20 will be omitted as appropriate.

  In the servo writer 30, a magnetic tape transport device 31 is disposed on a base plate 30a. The magnetic tape transport device 31 is a device for transporting the magnetic tape MT in one direction or the other direction, and mainly includes a feed motor 35, a feed reel 32, a take-up reel 33, a take-up motor 36, a plurality of guide rollers G, and the like. A head guide assembly 34 is provided.

  The control device 37 calculates the traveling speed of the magnetic tape material 51 based on the rotational speed of the take-up reel 33 detected by the rotational speed sensor 39, and controls the rotational speed and rotational torque of the feed motor 35 and the take-up motor 36. Thus, the magnetic tape material 51 is conveyed at a constant speed, and a constant tension is applied to the magnetic tape material 51. As is well known, the tension of the magnetic tape material 51 may be adjusted using a dancer roller or a vacuum chamber.

  Head guide assemblies 34 for accurately positioning the position of the magnetic tape material 51 in the width direction are arranged on the upstream and downstream sides of the servo signal writing head SWH in the traveling direction of the magnetic tape material 51.

  The control device 37 is provided with a pulse generation circuit 37a, and a pulse signal is output from the pulse generation circuit 37a to the servo signal writing head SWH, so that the magnetic tape material 51 has an interval corresponding to the pulse signal. The servo pattern SP is written.

  As shown in FIG. 8, the servo signal writing head SWH has servo signal writing elements SWE arranged corresponding to the positions of the servo tracks ST. The servo signal writing element SWE is an induction type magnetic head in which a magnetic gap 66 is formed in the width direction of the magnetic tape material 51. The width direction of the magnetic gap 66 is the same as the width of the servo pattern SP. By inputting a pulse signal to the servo signal writing element SWE, a leakage magnetic flux is generated from the magnetic gap 66 in the width direction of the magnetic tape material 51, and the servo pattern SP is recorded by the leakage magnetic flux.

  A servo pattern SP is formed in the magnetic layer M by outputting a pulse signal from the control device 37 to the servo signal writing head SWH at an appropriate timing while conveying the magnetic tape material 51 by such a servo writer 30. be able to.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the second embodiment, the servo signal writing method to the magnetic tape is changed. In the present embodiment, description will be made centering on differences from the first embodiment, and description of similar parts will be omitted as appropriate. In FIG. 9A, FIG. 9A is a diagram showing the relationship between the servo pattern written on the magnetic tape and the magnetic head according to the second embodiment, and FIG. 9B is a signal read by the servo signal reading element. FIG. 10 is a schematic perspective view for explaining a method of writing a servo signal with a servo writer for manufacturing the magnetic tape according to the second embodiment, and FIG. These are typical perspective views which show the modification of the method of writing a servo signal, and FIG.11 (b) is an enlarged view of (a).

  As shown in FIG. 9A, in the magnetic tape MT ′ according to the second embodiment, the magnetic moment 45 is perpendicular to the plane direction of the magnetic layer M, that is, in the thickness direction. In order to perform such perpendicular recording, a backing layer U may be optionally formed below the magnetic layer M (tape T side). The backing layer U is made of a soft magnetic material and is a film that passes through the back side of the magnetic layer M in order to pass the lines of magnetic force in the thickness direction of the magnetic layer M as is well known. As the magnetic layer M, for example, as disclosed in the example of Japanese Patent Application Laid-Open No. 2001-297423 (particularly Example 8), the plate-like ratio suitable for perpendicular recording in which the SQ of the magnetic layer M is about 0.83. It is preferable to use a material having Hc.

The magnetic tape MT ′ according to the second embodiment uses servo signal reading elements SRMa and SRMb configured by so-called MR heads. The reading width of the servo signal reading elements SRMa and SRMb is formed smaller than the width of the servo track ST ′ as in the first embodiment. Note that, as is well known, the MR head uses an element whose electric resistance changes according to the fluctuation of the external magnetic field.
When there is one magnetic moment 45 oriented in the thickness direction of the magnetic layer M, a strong magnetic field is generated around the center of the magnetic moment 45 in the width direction as shown in FIG. Magnetic field lines 45a that are weakened are formed. Therefore, when the servo signal is read by the servo signal reading elements SRMa and SRMb composed of the MR heads, as shown in FIG. An output I that becomes weaker as the distance from the center becomes smaller.

  As described above, according to the magnetic tape MT ′ including the servo track ST ′ having the servo pattern SP ′, the magnetic head H is replaced with the servo signal reading elements SRMa and SRMb including the MR head in the magnetic tape drive 20 of the first embodiment. By using the magnetic head H ′ provided with the magnetic head H ′, tracking control of the magnetic head H ′ can be performed just like the magnetic tape MT.

  As with the magnetic tape MT, the tracking control of the magnetic head H can be performed with an extremely light calculation load. Therefore, the responsiveness of the magnetic head H 'is improved, the magnetic head H' position accuracy is improved, the data transfer speed is improved An effect can be obtained. Further, since the reading width of the servo signal reading elements SRMa and SRMb is formed smaller than the width of the servo track ST, the large capacity of the magnetic tape MT can be obtained by effectively using the recording surface in the vicinity of the servo track ST. Can be achieved.

Next, a servo writer for manufacturing the magnetic tape MT ′ as described above will be described.
The servo writer for manufacturing the magnetic tape MT ′ of the second embodiment differs from the servo writer 30 of the first embodiment only in the servo signal writing element. As shown in FIG. 10, the servo signal writing element SWE2 provided in the servo signal writing head SWH2 of the servo writer according to the second embodiment includes a magnetic core 61 made of a U-shaped soft magnetic material and a coil 62. By winding and supplying a pulse signal to the coil 62, a magnetic flux penetrating the magnetic layer M in the thickness direction is generated, and the magnetic body in the magnetic layer M is magnetized in the thickness direction. On the downstream side (the right side in FIG. 10) of the running magnetic tape MT ′ of the magnetic core 61, the shape of the tip portion facing the magnetic layer M matches the shape of the servo pattern SP ′.

  According to such a servo writer, by supplying a pulse signal to the coil 62 of the servo signal writing element SWE2 at an appropriate timing, a servo pattern SP ′ having a magnetic moment in the thickness direction of the magnetic layer M is formed. be able to. FIG. 10 shows an example in which a servo pattern SP ′ is formed by repeatedly generating pulse signals in the forward direction and the reverse direction.

FIG. 10 shows an example in which one servo moment has one magnetic moment 45 in the width direction, but a plurality of magnetic moments may be formed in the width direction.
For example, in the servo signal writing element SWE3 of the servo signal writing head SWH3 according to the modification shown in FIG. 11B, the downstream side of the magnetic core 71 in the running direction of the magnetic tape MT ′ is divided into three sections. These three sections are separated by a nonmagnetic material 71p. And the front-end | tip parts 71a-71c are comprised with the material from which magnetic permeability differs. For example, the tip part 71a and the tip part 71c on both sides are made of a material with low magnetic permeability, and the tip part 71b at the center is made of a material with high magnetic permeability.

When the servo signal writing element SWE3 configured as described above is used, when a pulse signal is input to the coil 62, a strong magnetic flux is emitted from the central tip 71b and weak from the tips 71a and 71c on both sides. Magnetic flux comes out. Therefore, as shown in FIG. 11A, a strong magnetic moment 75b is formed in the center of the servo track ST ″, and weak magnetic moments 75a and 75c are formed on both sides. When the servo signal is read using the servo signal reading elements SRMa and SRMb composed of MR heads, a chevron-shaped intensity distribution is more clearly obtained in the width direction.
In this modification, if the magnetic core 71 of the servo signal writing element SWE3 has a magnetic permeability that increases toward the center and gradually decreases toward the outside, the magnetic moment at the center decreases, and the width increases. Servo tracks having a trough-shaped intensity distribution in the direction can be formed.

[Servo pattern layout example]
FIG. 12 is a diagram showing an arrangement example of servo patterns in the longitudinal direction of the magnetic tape.
In FIG. 12, the case where the magnetic moment in the planar direction as described in the first embodiment is described will be described. However, the same application is possible even in the case where the magnetic moment is in the vertical direction.

As a basic form, the servo pattern SP can arrange magnetic moments 41 in the same direction at regular intervals, as shown in FIG.
And as shown in FIG.12 (b), the magnitude | size of the magnetic moment 41 is gradually changed in the magnetic tape longitudinal direction, and it can also be set as the aspect changed continuously. Moreover, in FIG.12 (b), it is good also as an aspect which changes the magnitude | size of a magnetic moment intermittently.
In addition, as shown in FIG. 12C, the direction of the magnetic moment may be reversed from a certain position in the longitudinal direction of the magnetic tape.
Further, as shown in FIG. 12D, two types of servo patterns having different sizes in the width direction may be mixed and arranged. In such a case, for example, it is possible to embed information by codes of 1 and 0, with a wide servo pattern SP corresponding to 1 and a narrow servo pattern SP corresponding to 0.

  Such information embedding is also possible in the case where the magnitude of the magnetic moment is continuously changed as shown in FIG. 12B. For example, the information can be changed by changing the magnitude or period of the change in the magnetic moment. Can be encoded and embedded. Even in the arrangement pattern as shown in FIG. 12C, information can be embedded by encoding with the number of magnetic moments directed in one direction.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented.
For example, in the embodiments, for the sake of convenience of explanation, the servo track width and the magnetic moment width have been described as being the same, but the magnetic moment width may be larger or smaller than the servo track width. In FIG. 1 and the like, no magnetic moment is shown around the servo track in the width direction, but the periphery may be in a state where the magnetic moment is not oriented, or in the opposite direction to the servo track, for example, FIG. In FIG. 4, the servo track ST may be aligned with a rightward magnetic moment.

  In the present invention, the recording method of the data track DT is not particularly limited, and may be a vertical recording method or a flat recording method.

  In the embodiment, the example in which the tracking control of the magnetic head H is performed so as to distribute the servo signal reading elements SRa and SRb with reference to the center line CL of the servo track ST has been described, but the present invention is not limited to such a control method. It is also possible to perform tracking control so that the servo signal reading elements SRa and SRb are traced at positions shifted from the center of the servo track ST by setting different gains in the two correction circuits 27b shown in FIG. By using such tracking control, the next generation recording method for forming a narrow data track and the past generation recording method for forming a wide data track can be applied to the same magnetic tape MT. Can be applied.

1 is a perspective view of a magnetic tape and a magnetic head according to a first embodiment. It is a block diagram of a magnetic tape drive. It is a top view of a magnetic tape and a magnetic head. It is a block diagram of a control apparatus. FIG. 5A is a diagram showing the relationship between the servo signal reading element and the servo pattern, and FIG. 5B is a diagram showing the intensity distribution of the signal read by the servo signal reading element. (A) is a figure which showed the time change of the relative position of a servo track and a magnetic head, (b) is a figure which shows the change of the intensity | strength of the servo signal read with the one servo signal reading element. (C) is a figure which shows the change of the intensity | strength of the servo signal read with the other servo signal reading element, (d) is the servo signal read with one servo signal reading element, and another servo signal reading element. It is a figure which shows the change of the difference of the servo signal read by (1). It is a figure which shows the whole structure of a servo writer. It is a perspective view which shows typically the relationship between a servo signal write head and a magnetic tape. (A) is a figure which shows the relationship between the servo pattern written in the magnetic tape which concerns on 2nd Embodiment, and a magnetic head, (b) is a figure which shows intensity distribution of the signal read by a servo signal reading element. is there. It is a typical perspective view explaining the method to write a servo signal with a servo writer for manufacture of the magnetic tape which concerns on 2nd Embodiment. (A) is a typical perspective view which shows the modification of the method of writing a servo signal, (b) is an enlarged view of (a). It is the figure which showed the example of arrangement | positioning in the magnetic tape longitudinal direction of a servo pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic tape cartridge 11 Cartridge reel 12 Cartridge case 20 Magnetic tape drive 21 Conveyance apparatus 27 Control apparatus 30 Servo writer 31 Magnetic tape conveyance apparatus 37 Control apparatus 41 Magnetic moment 65a Magnetic gap 66 Magnetic gap 45 Magnetic moment 51 Magnetic tape material A Actuator DB Data band DT Data track H Magnetic head M Magnetic layer MT Magnetic tape SP Servo pattern SR (SRa, SRb) Servo signal reading element ST Servo track SWE Servo signal writing element SWH Servo signal writing head T Tape

Claims (17)

  A magnetic tape comprising at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape.   2. The magnetic tape according to claim 1, wherein the servo track is provided with a servo pattern having one magnetic moment in the width direction of the tape in the entire width of one servo track.   2. The magnetic tape according to claim 1, wherein the servo track is provided with a servo pattern having one magnetic moment in the thickness direction of the tape in the entire width of one servo track.   The servo track is arranged with a servo pattern having a plurality of magnetic moments oriented in the thickness direction of the tape in the entire width of one servo track, and the magnitude of the magnetic moment closer to the center in the width direction of the one servo track is larger. The magnetic tape according to claim 1, wherein the magnetic tape is large.   5. The servo track according to claim 2, wherein the magnitude of the magnetic moment of the servo track changes continuously or intermittently in the longitudinal direction of the tape. 6. Magnetic tape.   5. The magnetic tape according to claim 2, wherein a direction of the magnetic moment is reversed in a longitudinal direction of the tape.   5. The magnetic tape according to claim 2, wherein information encoded by a change in the magnitude of the magnetic moment is recorded on the servo track. 6.   5. The magnetism according to claim 2, wherein information encoded by an interval of arrangement of the magnetic moment in the longitudinal direction of the tape is recorded on the servo track. 6. tape.   9. A magnetic tape cartridge, wherein the magnetic tape according to claim 1 is accommodated in a cartridge case. A magnetic tape drive for recording or reproducing information with respect to a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape,
A magnetic head in which at least two servo signal reading elements having a reading width smaller than the width of the servo track are provided within one servo track;
An actuator for moving the magnetic head in the width direction of the magnetic tape;
A control device that performs tracking control of the magnetic head by operating the actuator based on a signal read by the servo signal reading element;
The magnetic tape drive, wherein the control device operates the actuator so that a difference in intensity between the servo signals read by the two servo signal reading elements approaches a predetermined value.   The control device corrects each servo signal read by the two servo signal reading elements so that the intensity of one servo signal is larger than the other, so that the two servo signal reading elements are centered on the servo track. The magnetic tape drive according to claim 10, wherein tracking control is performed so that the position is shifted from the position.   In the servo track, one magnetic moment in the width direction of the tape is arranged in the entire width of one servo track, and the two servo signal reading elements have a magnetic gap in the width direction of the tape. 12. The magnetic tape drive according to claim 10, wherein the magnetic tape drive is an induction type magnetic head having a magnetic field.   In the servo track, one or a plurality of magnetic moments in the thickness direction of the tape are arranged in the entire width of one servo track, and the two servo signal reading elements are MR heads. 12. A magnetic tape drive according to claim 10 or claim 11. The servo track having one servo signal reading element having a reading width smaller than the width of the servo track with respect to a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the tape width direction. A method for tracking control of at least two magnetic heads within a width of
A servo signal is read from the servo track by the two servo signal reading elements, and the magnetic head is moved in the tape width direction so that the intensity of the two read servo signals approaches a predetermined value. Head tracking control method. A servo writer for manufacturing a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape,
A magnetic tape transport device that feeds and runs a magnetic tape material on which no signal is recorded on the servo track; and
A servo signal writing head that is in sliding contact with the traveling magnetic tape material and records a servo signal on the servo track;
A controller for inputting a signal to the servo signal writing head,
The servo writer is characterized in that one magnetic gap facing the width direction of the magnetic tape material is formed corresponding to one servo track. A servo writer for manufacturing a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape,
A magnetic tape transport device that feeds and runs a magnetic tape material on which no signal is recorded on the servo track; and
A servo signal writing head that is in sliding contact with the traveling magnetic tape material and records a servo signal on the servo track;
A controller for inputting a signal to the servo signal writing head,
The servo signal writing head is an induction type magnetic head corresponding to one servo track and forming one magnetic moment in the thickness direction of the tape within the width of the servo track. Servo writer. A servo writer for manufacturing a magnetic tape having at least one servo track having a mountain-shaped or valley-shaped signal intensity distribution in the width direction of the tape,
A magnetic tape transport device that feeds and runs a magnetic tape material on which no signal is recorded on the servo track; and
A servo signal writing head that is in sliding contact with the traveling magnetic tape material and records a servo signal on the servo track;
A controller for inputting a signal to the servo signal writing head,
The servo signal writing head is an induction type magnetic head that forms a plurality of magnetic moments in the width direction of the servo track in the width direction of the tape corresponding to the one servo track. The magnetic core constituting the magnetic head is magnetically divided into a plurality of parts in the width direction, and the magnitude of the magnetic permeability of each of the divided parts gradually increases or decreases gradually from the center in the width direction toward the outside. Servo writer characterized by

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