Patent Publication Number: US-2023154493-A1

Title: Magnetic tape device and method of operating magnetic tape device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of International Application No. PCT/JP2021/015582 filed on Apr. 15, 2021, the disclosure of which is incorporated herein by reference in its entirety. Further, this application claims priority from Japanese Patent Application No. 2020-123830 filed on Jul. 20, 2020, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The technology of the present disclosure relates to a magnetic tape device and a method of operating a magnetic tape device. 
     2. Description of the Related Art 
     Various magnetic tape devices that cause a magnetic element of a magnetic head to act on a magnetic layer of a magnetic tape to record data on the magnetic layer and/or read data recorded on the magnetic layer have been proposed. As the magnetic tape device, there is a magnetic tape device equipped with a small magnetic head used for a hard disk drive, which records and/or reads data in a state in which a gap (called a spacing) of several nm to several tens of nm is provided between the magnetic layer and the magnetic element. 
     Meanwhile, there is known a problem of so-called entrained air in which air is entrained between the magnetic tape and a support member, such as a support roller, in a case where the magnetic tape is caused to run while being pressed against the support member. The entrained air causes a variation on the order of several hundred nm in a thickness direction of the running magnetic tape. For this reason, the variation in spacing due to the entrained air is fatal in a magnetic head that records and/or reads data with a spacing of several nm to several tens of nm between the above-described magnetic layer and the above-described magnetic element. 
     Conventionally, as a measure against entrained air, a method of forming grooves for removing air in the support member has been employed. The grooves are formed along a running direction of the magnetic tape. In particular, a roller in which grooves are formed is called a microgroove roller. For example, U.S. Pat. No. 7,609,475B discloses that grooves are formed uniformly or non-uniformly in a support roller disposed at a position facing the magnetic head. 
     SUMMARY 
     However, in a case where the support member in which the grooves are formed is used, there arises a new problem that the spacing may vary because of the magnetic tape entering the groove. 
     One embodiment according to the technology of the present disclosure provides a magnetic tape device and a method of operating a magnetic tape device capable of reducing a variation in spacing. 
     According to the present disclosure, there is provided a magnetic tape device comprising: a magnetic head having a magnetic element that acts in proximity to a magnetic layer formed on a front surface of a magnetic tape; and a support member which is disposed at a position facing the magnetic head and against which a back surface of the magnetic tape provided on a side opposite to the front surface is pressed, in which the support member has a groove formed along a running direction of the magnetic tape only in a region corresponding to a non-acting region except for a region of the magnetic layer on which the magnetic element acts. 
     It is preferable that a width of the magnetic head is smaller than a width of the magnetic tape. 
     It is preferable that the support member is a roller. 
     It is preferable that the groove has a V-shaped cross-section. 
     It is preferable that a plurality of sets of the magnetic heads and the support members are provided. 
     It is preferable that the magnetic head includes a feed head that operates in a case where the magnetic tape is fed out from a feed reel on which the magnetic tape is wound, and a rewind head that operates in a case where the magnetic tape is rewound on the feed reel, and the support member includes a feed support member disposed at a position facing the feed head, and a rewind support member disposed at a position facing the rewind head. 
     It is preferable that the magnetic layer has a first region and a second region that are divided with respect to a width direction of the magnetic tape, a magnetic element of the feed head acts on the first region, a magnetic element of the rewind head acts on the second region, the feed support member has the groove formed only in a region corresponding to the non-acting region except for the first region, and the rewind support member has the groove formed only in a region corresponding to the non-acting region except for the second region. 
     It is preferable that a plurality of data bands on which data is recorded are arranged in the magnetic layer along the width direction of the magnetic tape, the first region includes data bands of one half out of the plurality of data bands, and the second region includes data bands of the other half. 
     It is preferable that the first region includes data bands of one party of odd-numbered data bands or even-numbered data bands out of the plurality of data bands, and the second region includes data bands of the other party of the odd-numbered data bands or the even-numbered data bands. 
     It is preferable that a plurality of data bands on which data is recorded, and a plurality of servo bands on which a plurality of servo patterns used for servo control to move the magnetic head in a width direction of the magnetic tape are recorded are formed in the magnetic layer, and the data band and the servo band are alternately arranged along the width direction of the magnetic tape. 
     It is preferable that the magnetic head has, as the magnetic element, two servo pattern reading elements corresponding to two servo bands that sandwich one data band, and a data element provided between two servo pattern reading elements. 
     It is preferable that the data element includes a data recording element that records the data on the magnetic layer, and a data reading element that reads the data recorded on the magnetic layer. 
     According to the present disclosure, there is provided a method of operating a magnetic tape device, comprising: causing a magnetic tape to run while pressing a back surface of the magnetic tape provided on a side opposite to a front surface on which a magnetic layer is formed against a support member disposed at a position facing a magnetic head, the support member having a groove formed along a running direction of the magnetic tape only in a region corresponding to a non-acting region except for a region of the magnetic layer of the magnetic tape on which a magnetic element of the magnetic head acts; and causing the magnetic element to act in proximity to the magnetic layer of the magnetic tape in a state in which the back surface is pressed against the support member. 
     According to the technology of the present disclosure, it is possible to provide a magnetic tape device and a method of operating a magnetic tape device capable of reducing a variation in spacing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments according to the technique of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG.  1    is a diagram showing an example of a magnetic tape device; 
         FIG.  2    is an enlarged view of vicinities of a feed head and of a rewind head; 
         FIG.  3    is a plan view of a feed support roller and a rewind support roller as viewed from sides of the feed head and of the rewind head; 
         FIG.  4    is a diagram showing a table showing an operating position and an acting region of the feed head, a non-acting region of the feed head, and a region of the feed support roller where a groove is formed; 
         FIG.  5    is a plan view showing the feed support roller; 
         FIG.  6    is a diagram showing a table showing an operating position and an acting region of the rewind head, a non-acting region of the rewind head, and a region of the rewind support roller where a groove is formed; 
         FIG.  7    is a plan view showing the rewind support roller; 
         FIG.  8    is an enlarged view of a vicinity of the feed head at an F1 position; 
         FIG.  9    is a diagram showing a correspondence relationship between a data element and a data track; 
         FIG.  10    is an enlarged view of the data element; 
         FIG.  11    is a block diagram of a control unit; 
         FIG.  12    is a flowchart showing an operation procedure of the magnetic tape device; 
         FIG.  13    is a graph showing a simulation result of an amount of variation in spacing due to entrained air with respect to the number of grooves; 
         FIG.  14    is a diagram showing another example of the table showing the operating position and the acting region of the feed head, the non-acting region of the feed head, and the region of the feed support roller where the groove is formed; 
         FIG.  15    is a plan view showing the feed support roller in the example of  FIG.  14   ; 
         FIG.  16    is a diagram showing another example of the table showing the operating position and the acting region of the rewind head, the non-acting region of the rewind head, and the region of the rewind support roller where the groove is formed; 
         FIG.  17    is a plan view showing the rewind support roller in the example of  FIG.  16   ; and 
         FIG.  18    is a diagram showing another example of a support member. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG.  1   , a cartridge  11  is loaded into a magnetic tape device  10 . A cartridge reel  13  on which a magnetic tape  12  is wound is accommodated in the cartridge  11 . The magnetic tape device  10  records data on the magnetic tape  12  fed out from the cartridge reel  13 . Further, the magnetic tape device  10  reads data recorded on the magnetic tape  12 . The cartridge reel  13  is an example of the “feed reel” according to the technology of the present disclosure. 
     The magnetic tape  12  has, for example, a configuration in which a magnetic layer  16  and a back coating layer  17  are formed on a base film  15 . In the magnetic tape  12 , a surface on which the magnetic layer  16  is formed is a front surface  18  of the magnetic tape  12 . On the other hand, a surface on which the back coating layer  17  is formed is a back surface  19  of the magnetic tape  12 . Data is recorded on the magnetic layer  16 . The magnetic layer  16  contains ferromagnetic powder. As the ferromagnetic powder, ferromagnetic powder generally used in the magnetic layer of various magnetic recording media can be used. Preferable specific examples of the ferromagnetic powder can include hexagonal ferrite powder. As the hexagonal ferrite powder, for example, hexagonal strontium ferrite powder or hexagonal barium ferrite powder can be used. The back coating layer  17  contains, for example, non-magnetic powder, such as carbon black. The base film  15  is also called a support and is formed of, for example, polyethylene terephthalate, polyethylene naphthalate, or polyamide. A non-magnetic layer may be formed between the base film  15  and the magnetic layer  16 . 
     The magnetic tape device  10  comprises a feeding motor  25 , a winding motor  26 , a winding reel  27 , a feed head  28 , a rewind head  29 , a feed support roller  30 , a rewind support roller  31 , a control unit  32 , and the like. The feed head  28  and the rewind head  29  are an example of the “magnetic head” according to the technology of the present disclosure. The feed support roller  30  and the rewind support roller  31  are an example of the “support member” according to the technology of the present disclosure. Further, the feed support roller  30  is an example of the “feed support member” according to the technology of the present disclosure, and the rewind support roller  31  is an example of the “rewind support member” according to the technology of the present disclosure. Hereinafter, the feed head  28  and the rewind head  29  may be collectively denoted as a magnetic head. Similarly, the feed support roller  30  and the rewind support roller  31  may be collectively denoted as a support roller. 
     The feeding motor  25  rotates the cartridge reel  13  provided in the cartridge  11  under the control of the control unit  32 . The magnetic tape  12  fed out from the cartridge reel  13  is wound on the winding reel  27 . Further, the magnetic tape  12  wound up on the winding reel  27  is rewound on the cartridge reel  13 . The winding motor  26  rotates the winding reel  27  under the control of the control unit  32 . 
     The magnetic tape  12  runs in a feed direction FWD or a rewind direction BWD while being guided by the feed support roller  30 , the rewind support roller  31 , and a plurality of guide rollers  33  with the drive of the feeding motor  25  and the winding motor  26 . The feed direction FWD is a direction from the cartridge reel  13  toward the winding reel  27 . The rewind direction BWD is, on the contrary, a direction from the winding reel  27  toward the cartridge reel  13 . The feed direction FWD and the rewind direction BWD are an example of the “running direction” according to the technology of the present disclosure. Further, in the magnetic tape  12 , the rotational speed and the rotational torque of the feeding motor  25  and the winding motor  26  are adjusted so that the tension during running and the running speed are adjusted to appropriate values. 
     The feed head  28  and the rewind head  29  are disposed on the front surface  18  side of the magnetic tape  12  in order to access the magnetic layer  16 . The feed head  28  and the rewind head  29  record data on the magnetic layer  16 . Further, the feed head  28  and the rewind head  29  read data recorded on the magnetic layer  16 . 
     The feed head  28  operates in a case where the magnetic tape  12  is running in the feed direction FWD. In other words, the feed head  28  operates in a case where the magnetic tape  12  is fed out from the cartridge reel  13 . On the other hand, the rewind head  29  operates in a case where the magnetic tape  12  is running in the rewind direction BWD. In other words, the rewind head  29  operates in a case where the magnetic tape  12  is rewound on the cartridge reel  13 . 
     The feed head  28  and the rewind head  29  have the same structure except that operating timings are different from each other. The feed head  28  and the rewind head  29  are small magnetic heads, such as a magnetic head used for a hard disk drive. The feed head  28  and the rewind head  29  are provided at distal ends of suspensions  35  and  36  (see  FIG.  2    and the like), respectively. Proximal ends of the suspensions  35  and  36  are movably attached to a frame of the magnetic tape device  10  via, for example, an arm. The feed head  28  and the rewind head  29  may be retracted to a standby position separated from the magnetic tape  12  during non-operation. 
     The feed support roller  30  and the rewind support roller  31  are disposed on the back surface  19  side of the magnetic tape  12  facing the feed head  28  and the rewind head  29 . The feed support roller  30  and the rewind support roller  31  guide the magnetic tape  12  to the feed head  28  and the rewind head  29 . 
     As shown in the enlarged view of  FIG.  2   , the back surface  19  of the magnetic tape  12  is pressed against the feed support roller  30  and the rewind support roller  31 . That is, the magnetic tape  12  runs while the back surface  19  is pressed against the feed support roller  30  and the rewind support roller  31 . The feed support roller  30  and the rewind support roller  31  each have an outer diameter Φ of, for example, 10 mm. The magnetic tape  12  runs such that the center of a width direction WD (refer to  FIG.  3    and the like, a direction perpendicular to a paper surface in  FIG.  2   ) thereof coincides with the centers of the feed support roller  30  and of the rewind support roller  31 . The feed head  28  and the rewind head  29  are disposed at positions facing portions where the back surface  19  of the magnetic tape  12  is pressed against the feed support roller  30  and the rewind support roller  31 . The term “coincide” as used herein indicates a coincidence in a sense including an error generally allowed in the technical field to which the technology of the present disclosure belongs, in addition to the complete coincidence. 
     A first moving mechanism  40  is connected to the suspension  35 , and a second moving mechanism  41  is connected to the suspension  36 . The first moving mechanism  40  moves the suspension  35 , that is, the feed head  28 , in the width direction WD of the magnetic tape  12 . Similarly, the second moving mechanism  41  also moves the suspension  36 , that is, the rewind head  29 , in the width direction WD of the magnetic tape  12 . The first moving mechanism  40  and the second moving mechanism  41  each include, for example, an actuator, such as a voice coil motor or a piezoelectric element. A reference numeral SP indicates a spacing which is a gap between the magnetic layer  16  of the magnetic tape  12  and the magnetic elements of the feed head  28  and of the rewind head  29 . 
     In  FIG.  3    in which the feed support roller  30  and the rewind support roller  31  are viewed from the sides of the feed head  28  and of the rewind head  29 , the feed head  28  and the rewind head  29  are disposed so as to be shifted from each other in the feed direction FWD and the rewind direction BWD (a length direction of the magnetic tape  12 ) such that the feed head  28  and the rewind head  29  do not interfere with each other. A width W_H of each of the feed head  28  and the rewind head  29  is smaller than a width W_T of the magnetic tape  12 . Specifically, the width W_H of each of the feed head  28  and the rewind head  29  is about ⅛ of the width W_T of the magnetic tape  12 . The width W_T of the magnetic tape  12  is, for example, 12.65 mm, and the width W_H of each of the feed head  28  and the rewind head  29  is, for example, 1.6 mm to 2.0 mm. Incidentally, other sizes such as the depth and the height of each of the feed head  28  and the rewind head  29  are also smaller than the width W_T of the magnetic tape  12  and are, for example, about several mm. 
     The magnetic layer  16  has eight data bands DB 1 , DB 2 , DB 3 , DB 4 , DB 5 , DB 6 , DB 7 , and DB 8  on which data is recorded, and nine servo bands SB 1 , SB 2 , SB 3 , SB 4 , SB 5 , SB 6 , SB 7 , SB 8 , and SB 9 . These data bands DB 1  to DB 8  and these servo bands SB 1  to SB 9  are formed along the feed direction FWD and the rewind direction BWD. The data bands DB 1  to DB 8  are arranged at equal intervals along the width direction WD of the magnetic tape  12 . The servo bands SB 1  to SB 9  are also arranged at equal intervals along the width direction WD of the magnetic tape  12 . A width W_DB of each of the data bands DB 1  to DB 8  is, for example, 1.58 mm, and a width W_SB of each of the servo bands SB 1  to SB 9  is, for example, 100 μm. 
     The data band DB 1  is disposed between the servo bands SB 1  and SB 2 , and the data band DB 2  is disposed between the servo bands SB 2  and SB 3 . The data band DB 3  is disposed between the servo bands SB 3  and SB 4 , and the data band DB 4  is disposed between the servo bands SB 4  and SB 5 . The data band DB 5  is disposed between the servo bands SB 5  and SB 6 , and the data band DB 6  is disposed between the servo bands SB 6  and SB 7 . The data band DB 7  is disposed between the servo bands SB 7  and SB 8 , and the data band DB 8  is disposed between the servo bands SB 8  and SB 9 . That is, the data bands DB 1  to DB 8  and the servo bands SB 1  to SB 9  are alternately arranged along the width direction WD of the magnetic tape  12 . 
     A servo pattern  50  is recorded on the servo bands SB 1  to SB 9 . A plurality of the servo patterns  50  are provided at equal intervals along, for example, the feed direction FWD and the rewind direction BWD. The servo pattern  50  is composed of a pair of linearly symmetric magnetization regions  51 A and  51 B that are non-parallel to each other and that form a predetermined angle. The magnetization region  51 A is tilted toward the rewind direction BWD side, and the magnetization region  51 B is tilted toward the feed direction FWD side. The servo pattern  50  is used for the servo control to move the feed head  28  and the rewind head  29  in the width direction WD of the magnetic tape  12  through the first moving mechanism  40  and the second moving mechanism  41 . 
     A plurality of grooves  52  are intermittently formed in the feed support roller  30  and the rewind support roller  31 . The grooves  52  are formed along the feed direction FWD and the rewind direction BWD at preset pitches P (see  FIG.  5   ) and sizes. The pitch P of the grooves  52  is, for example, 200 μm to 500 μm. A width W_G (see  FIG.  5   ), which is the size of the groove  52 , is, for example, 100 μm to 200 μm, and a depth D_G (see  FIG.  5   ) is, for example, 10 μm to 100 μm. 
     As shown in a table  55  of  FIG.  4   , the feed head  28  moves together with the suspension  35  to each operating position of an F1 position, an F2 position, an F3 position, and an F4 position. At each operating position, the feed head  28  records data on the data bands DB 1 , DB 3 , DB 5 , and DB 7  and reads data recorded on the data bands DB 1 , DB 3 , DB 5 , and DB 7 . In addition, at each operating position, the feed head  28  reads the servo patterns  50  recorded on the servo bands SB 1  and SB 2  that sandwich the data band DB 1 , the servo bands SB 3  and SB 4  that sandwich the data band DB 3 , the servo bands SB 5  and SB 6  that sandwich the data band DB 5 , and the servo bands SB 7  and SB 8  that sandwich the data band DB 7 . In summary, regions (hereinafter, referred to as acting regions) of the magnetic layer  16  on which the magnetic element of the feed head  28  acts are the data bands DB 1 , DB 3 , DB 5 , and DB 7  and the servo bands SB 1  to SB 8 . These data bands DB 1 , DB 3 , DB 5 , and DB 7  and these servo bands SB 1  to SB 8  are an example of the “first region” according to the technology of the present disclosure. Therefore, the first region includes the data bands DB 1 , DB 3 , DB 5 , and DB 7  of one half out of eight data bands DB 1  to DB 8 . Further, the first region includes the odd-numbered data bands DB 1 , DB 3 , DB 5 , and DB 7  out of eight data bands DB 1  to DB 8 . 
     As shown in  FIG.  4   , non-acting regions except for the acting regions of the feed head  28  are the data bands DB 2 , DB 4 , DB 6 , and DB 8 . Therefore, in this example, as shown in  FIG.  5   , the grooves  52  are formed in the feed support roller  30  only in regions C_DB 2 , C_DB 4 , C_DB 6 , and C_DB 8  corresponding to the data bands DB 2 , DB 4 , DB 6 , and DB 8 . The groove  52  has a V-shaped cross-section. Strictly speaking, the servo band SB 9  is also included in the non-acting region of the feed head  28 , but is excluded in this example. Of course, the servo band SB 9  may be included in the non-acting region of the feed head  28 . 
     On the other hand, as shown in a table  58  of  FIG.  6   , the rewind head  29  moves together with the suspension  36  to each operating position of a B1 position, a B2 position, a B3 position, and a B4 position. At each operating position, the rewind head  29  records data on the data bands DB 8 , DB 6 , DB 4 , and DB 2  and reads data recorded on the data bands DB 8 , DB 6 , DB 4 , and DB 2 . In addition, at each operating position, the rewind head  29  reads the servo patterns  50  recorded on the servo bands SB 8  and SB 9  that sandwich the data band DB 8 , the servo bands SB 6  and SB 7  that sandwich the data band DB 6 , the servo bands SB 4  and SB 5  that sandwich the data band DB 4 , and the servo bands SB 2  and SB 3  that sandwich the data band DB 2 . In summary, the acting regions of the rewind head  29  are the data bands DB 2 , DB 4 , DB 6 , and DB 8  and the servo bands SB 2  to SB 9 . These data bands DB 2 , DB 4 , DB 6 , and DB 8  and these servo bands SB 2  to SB 9  are an example of the “second region” according to the technology of the present disclosure. Therefore, the second region includes the data bands DB 2 , DB 4 , DB 6 , and DB 8  of the other half out of eight data bands DB 1  to DB 8 . Further, the second region includes the even-numbered data bands DB 2 , DB 4 , DB 6 , and DB 8  out of eight data bands DB 1  to DB 8 . 
     As shown in  FIG.  6   , the non-acting regions except for the acting regions of the rewind head  29  are the data bands DB 1 , DB 3 , DB 5 , and DB 7 . Therefore, in this example, as shown in  FIG.  7   , the grooves  52  are formed in the rewind support roller  31  only in regions C_DB 1 , C_DB 3 , C_DB 5 , and C_DB 7  corresponding to the data bands DB 1 , DB 3 , DB 5 , and DB 7 . Strictly speaking, the servo band SB 1  is also included in the non-acting region of the rewind head  29 , but is excluded in this example. Of course, the servo band SB 1  may be included in the non-acting region of the rewind head  29 . 
     In  FIG.  8   , which is an enlarged view of the vicinity of the feed head at the F1 position, the feed head  28  has a plurality of magnetic elements that are provided on a surface facing the magnetic layer  16  and that act on the magnetic layer  16 . The feed head  28  causes the magnetic element to act on the magnetic layer  16  by bringing the magnetic element close to the magnetic layer  16  with the spacing SP on the order of several nm to several tens of nm therebetween. The magnetic element has two servo pattern reading elements SR 1  and SR 2 , and eight data elements DRW 1 , DRW 2 , DRW 3 , DRW 4 , DRWS, DRW 6 , DRW 7 , and DRW 8 . Hereinafter, in a case where there is no need to make a particular distinction, the servo pattern reading elements SR 1  and SR 2  are collectively denoted as a servo pattern reading element SR, and the data elements DRW 1  to DRW 8  are collectively denoted as a data element DRW. 
     The servo pattern reading elements SR 1  are provided at positions corresponding to the servo bands SB 1 , SB 3 , SB 5 , and SB 7 . Further, the servo pattern reading elements SR 2  are provided at positions corresponding to the servo bands SB 2 , SB 4 , SB 6 , and SB 8 . The data elements DRW 1  to DRW 8  are provided between the servo pattern reading elements SR 1  and SR 2 . The data elements DRW 1  to DRW 8  are arranged at equal intervals along the width direction WD of the magnetic tape  12 . The data elements DRW 1  to DRW 8  simultaneously record data and/or read data with respect to eight data tracks DT 1 , DT 2 , DT 3 , DT 4 , DT 5 , DT 6 , DT 7 , and DT 8 . 
     As shown in  FIG.  9    as an example, the data element DRW 1  is in charge of recording data on a data track group DTG 1  composed of a total of 12 data tracks DT, that is, data tracks DT 1 _ 1 , DT 1 _ 2 , DT 1 _ 3 , DT 1 _ 4 , . . . , DT 1 _ 11 , and DT 1 _ 12 . In addition, the data element DRW 1  is in charge of reading data recorded on the data track group DTG 1 . Similarly, the data element DRW 2  is in charge of recording data on a data track group DTG 2 , which is composed of data tracks DT 2 _ 1  to DT 2 _ 12 , and of reading data recorded on the data track group DTG 2 . Hereinafter, similarly, the data element DRW 8  is in charge of recording data on a data track group DTG 8 , which is composed of data tracks DT 8 _ 1  to DT 8 _ 12 , and of reading data recorded on the data track group DTG 8 . Twelve data tracks DT constituting each of the data track groups DTG 1  to DTG 8  are arranged at equal intervals along the width direction WD of the magnetic tape  12 . The number of data tracks DT included in one data band DB is 8×12=96. In a case where there is no need to make a particular distinction, the data tracks DT 1  to DT 8  are collectively denoted as a data track DT. 
     The data element DRW is shifted to a position corresponding to one designated data track DT out of  12  data tracks with the movement of the feed head  28  in the width direction WD performed by the first moving mechanism  40 . The data element DRW stays at a position corresponding to one designated data track DT through the servo control using the servo pattern  50 . 
     As shown in the enlarged view of  FIG.  10   , the data element DRW includes a data recording element DW and a data reading element DR. The data recording element DW records data on the data track DT. The data reading element DR reads the data recorded on the data track DT. 
     The data recording element DW is disposed on an upstream side of the feed direction FWD, and the data reading element DR is disposed on a downstream side of the feed direction FWD. The reason for such a disposition is that the data reading element DR immediately reads the data recorded by the data recording element DW to check errors. 
     Although neither shown nor described in detail, the rewind head  29  also has two servo pattern reading elements SR corresponding to the servo bands SB 2  to SB 9  and eight data elements DRW provided between two servo pattern reading elements SR. The data element DRW of the rewind head  29  records data and/or reads data with respect to 96 data tracks DT of each of the data bands DB 2 , DB 4 , DB 6 , and DB 8 . The data element DRW of the rewind head  29  includes a data recording element DW disposed on an upstream side of the rewind direction BWD and a data reading element DR disposed on a downstream side of the rewind direction BWD. 
     The control unit  32  is realized by, for example, a computer including a central processing unit (CPU), a memory, and a storage. The memory is, for example, a random access memory (RAM) or the like and temporarily stores various types of information. The storage, which is a non-transitory storage medium, is, for example, a hard disk drive or a solid state drive and stores various parameters and various programs. The CPU loads the program stored in the storage into the memory and executes processing in accordance with the program, thereby controlling the operation of each unit of the magnetic tape device  10  in an integrated manner. 
     In  FIG.  11   , the control unit  32  functions as a running control unit  60 , a first position detection unit  61 , a first servo control unit  62 , a first data acquisition unit  63 , a first recording control unit  64 , a first read control unit  65 , a first data output unit  66 , a second position detection unit  67 , a second servo control unit  68 , a second data acquisition unit  69 , a second recording control unit  70 , a second read control unit  71 , and a second data output unit  72 . 
     The running control unit  60  controls the drive of the feeding motor  25  and the winding motor  26  to cause the magnetic tape  12  to run in the feed direction FWD or the rewind direction BWD. Further, the running control unit  60  adjusts the rotational speed and the rotational torque of the feeding motor  25  and the winding motor  26  to adjust the tension during running and the running speed of the magnetic tape  12  to appropriate values. 
     A servo signal based on the servo pattern  50  read by the servo pattern reading element SR of the feed head  28  is input to the first position detection unit  61 . The servo signal is intermittent pulses corresponding to the magnetization regions  51 A and  51 B. The first position detection unit  61  detects the position of the servo pattern reading element SR in the servo band SB in the width direction WD, that is, the position of the feed head  28  in the width direction WD with respect to the magnetic tape  12 , on the basis of a pulse interval of the servo signal. The first position detection unit  61  outputs the detection result of the position of the feed head  28  in the width direction WD to the first servo control unit  62 . 
     Two types of servo signals based on the servo patterns  50  read by two servo pattern reading elements SR are input to the first position detection unit  61 . The first position detection unit  61  calculates the average value of the pulse intervals of two types of servo signals. Then, the first position detection unit  61  detects the position of the feed head  28  in the width direction WD, on the basis of the calculated average value. 
     The first servo control unit  62  compares the detection result of the position of the feed head  28  from the first position detection unit  61  with a target position of the feed head  28 . In a case where the detection result is the same as the target position, the first servo control unit  62  does nothing. In a case where the detection result is displaced from the target position, the first servo control unit  62  outputs a servo control signal for making the position of the feed head  28  match the target position, to the first moving mechanism  40 . The first moving mechanism  40  operates so as to make the position of the feed head  28  match the target position according to the servo control signal. The target position is stored in the storage, for example, in the form of a data table in which the values corresponding to the respective data tracks DT 1  to DT 8  are registered. 
     The first data acquisition unit  63  reads out and acquires the data to be recorded on any one of the data bands DB 1 , DB 3 , DB 5 , or DB 7  by the feed head  28  from, for example, a host computer (not shown) connected to the magnetic tape device  10 . The first data acquisition unit  63  outputs the data to the first recording control unit  64 . 
     The first recording control unit  64  encodes the data output from the first data acquisition unit  63  into a digital signal for recording. Then, the first recording control unit  64  causes a pulse current corresponding to the digital signal to flow into the data recording element DW of the feed head  28  and causes the data recording element DW to record the data on the designated data track DT of any one of the data bands DB 1 , DB 3 , DB 5 , or DB 7 . 
     The first read control unit  65  controls the operation of the data reading element DR of the feed head  28  to cause the data reading element DR to read the data recorded on the designated data track DT of any one of the data bands DB 1 , DB 3 , DB 5 , or DB 7 . The data read by the data reading element DR is a pulse-shaped digital signal. The first read control unit  65  outputs this pulse-shaped digital signal to the first data output unit  66 . 
     The first data output unit  66  decodes the pulse-shaped digital signal output from the first read control unit  65  to obtain data. The first data output unit  66  outputs the data to, for example, the host computer. 
     The second position detection unit  67 , the second servo control unit  68 , the second data acquisition unit  69 , the second recording control unit  70 , the second read control unit  71 , and the second data output unit  72  have the same functions as the first position detection unit  61 , the first servo control unit  62 , the first data acquisition unit  63 , the first recording control unit  64 , the first read control unit  65 , and the first data output unit  66 , except that the above-described feed head  28  is replaced with the rewind head  29  and the data bands DB 1 , DB 3 , DB 5 , and DB 7  are replaced with the data bands DB 2 , DB 4 , DB 6 , and DB 8 . Therefore, detailed description thereof will be omitted. 
     Hereinafter, the action of the above-described configuration will be described with reference to the flowchart of  FIG.  12   . First, under the control of the running control unit  60 , the feeding motor  25  and the winding motor  26  are operated, and the magnetic tape  12  runs in the feed direction FWD or the rewind direction BWD. With this, as shown in  FIG.  3    and the like, the magnetic tape  12  runs while the back surface  19  of the magnetic tape  12  is pressed against the feed support roller  30  in which the grooves  52  are formed only in the regions C_DB 2 , C_DB 4 , C_DB 6 , and C_DB 8  corresponding to the data bands DB 2 , DB 4 , DB 6 , and DB 8 , which are the non-acting regions of the feed head  28 , or against the rewind support roller  31  in which the grooves  52  are formed only in the regions C_DB 1 , C_DB 3 , C_DB 5 , and C_DB 7  corresponding to the data bands DB 1 , DB 3 , DB 5 , and DB 7 , which are the non-acting regions of the rewind head  29  (step ST 100 ). 
     Then, the magnetic element of the feed head  28  or the magnetic element of the rewind head  29  is caused to act in proximity to the magnetic layer  16  of the magnetic tape  12  in a state in which the back surface  19  is pressed against the feed support roller  30  or the rewind support roller  31  (Step ST 110 ). Specifically, the servo pattern  50  is read by the servo pattern reading element SR. Further, the data is recorded on the data track DT by the data recording element DW under the control of the first recording control unit  64  or the second recording control unit  70 . Furthermore, the data recorded on the data track DT is read by the data reading element DR under the control of the first read control unit  65  or the second read control unit  71 . 
     The first position detection unit  61  or the second position detection unit  67  detects the position of the feed head  28  in the width direction WD or the position of the rewind head  29  in the width direction WD, from the interval of the servo signals based on the servo patterns  50 . The first servo control unit  62  or the second servo control unit  68  compares the detection result of the position of the first position detection unit  61  or the second position detection unit  67  with the target position, and performs the servo control for making the position of the feed head  28  or the rewind head  29  match the target position. 
     As described above, the magnetic tape device  10  comprises the feed head  28  and the rewind head  29  as magnetic heads, and the feed support roller  30  and the rewind support roller  31  as support members. The feed head  28  and the rewind head  29  each have the magnetic element that acts in proximity to the magnetic layer  16  formed on the front surface  18  of the magnetic tape  12 . The back surface  19  of the magnetic tape  12  provided on the side opposite to the front surface  18  is pressed against the feed support roller  30  and the rewind support roller  31 . In the feed support roller  30  and the rewind support roller  31 , the grooves  52  are formed along the running direction (the feed direction FWD and the rewind direction BWD) of the magnetic tape  12  only in the region corresponding to the non-acting region except for the region of the magnetic layer  16  on which the magnetic element acts. 
     Specifically, in the feed support roller  30 , the grooves  52  are formed only in the regions C_DB 2 , C_DB 4 , C_DB 6 , and C_DB 8  corresponding to the data bands DB 2 , DB 4 , DB 6 , and DB 8 , which are the non-acting regions of the feed head  28 . Further, in the rewind support roller  31 , the grooves  52  are formed only in the regions C_DB 1 , C_DB 3 , C_DB 5 , and C_DB 7  corresponding to the data bands DB 1 , DB 3 , DB 5 , and DB 7 , which are the non-acting regions of the rewind head  29 . Therefore, it is possible to reduce the variation in spacing SP due to the entrained air. Further, the spacing SP may vary because of the magnetic tape  12  entering the groove  52  in a case where the grooves  52  are formed in the region corresponding to the acting region. However, the grooves  52  are not formed in the region corresponding to the acting region, so that it is possible to reduce the variation in spacing SP due to the magnetic tape  12  entering the groove  52 . 
     As shown in  FIG.  3   , the width W_H of each of the feed head  28  and the rewind head  29  is smaller than the width W_T of the magnetic tape  12 . Since the weight is lighter than that of a magnetic head having a width W_H equal to or more than the width W_T, the response speed of the movement in the width direction WD in the servo control is high. Therefore, good followability can be obtained in the servo control. 
     As the support member, the feed support roller  30  and the rewind support roller  31  are used. Therefore, a contact area with the back surface  19  of the magnetic tape  12  can be reduced, and a probability that the magnetic tape  12  is displaced from a regular running position in the width direction WD because of vibration caused by friction can be reduced. In addition, an amount of foreign matter generated by being scraped off from the back surface  19  of the magnetic tape  12  because of friction can be reduced. 
     As shown in  FIG.  5   , the groove  52  has a V-shaped cross-section. Therefore, it is easier to process the groove  52  than a groove having a U-shaped cross-section. Further, since an angle of an upper opening edge of the groove  52  to the back surface  19  of the magnetic tape  12  is an obtuse angle, the back surface  19  of the magnetic tape  12  is less likely to be scratched as compared with the groove having a U-shaped cross-section in which the angle of the upper opening edge is 90°. 
     As shown in  FIG.  1    and the like, a plurality of sets of the magnetic heads and the support rollers are provided. Specifically, the magnetic head is composed of the feed head  28  that operates in a case where the magnetic tape  12  is fed out from the cartridge reel  13  of the cartridge  11  in which the magnetic tape  12  is accommodated, and the rewind head  29  that operates in a case where the magnetic tape  12  is rewound on the cartridge reel  13 . The support roller is composed of the feed support roller  30  disposed at a position facing the feed head  28  and the rewind support roller  31  disposed at a position facing the rewind head  29 . Therefore, data can be recorded and/or read by using the magnetic head and the support roller that are suitable for each of the case where the magnetic tape  12  is fed out and the case where the magnetic tape  12  is rewound. 
     As shown in  FIG.  3    and the like, the magnetic element of the feed head  28  acts on the first region of the magnetic tape  12 , and the magnetic element of the rewind head  29  acts on the second region of the magnetic tape  12 . The feed support roller  30  has the grooves  52  formed only in the region corresponding to the non-acting region except for the first region, and the rewind support roller  31  has the grooves formed only in the region corresponding to the non-acting region except for the second region. Therefore, it is possible to improve the efficiency of recording and/or reading data. 
     As shown in  FIG.  3    and the like, in the magnetic layer  16 , eight data bands DB 1  to DB 8  on which data is recorded are arranged along the width direction WD of the magnetic tape  12 . The first region includes the data bands DB 1 , DB 3 , DB 5 , and DB 7  of one half out of the eight data bands DB 1  to DB 8 , and the second region includes the data bands DB 2 , DB 4 , DB 6 , and DB 8  of the other half. Therefore, the feed head  28  and the rewind head  29  can have the same configuration, and various control methods, such as data recording control, need not be significantly changed. Further, the feed support roller  30  and the rewind support roller  31  may have substantially the same configuration. 
     As shown in  FIGS.  4  and  6   , the first region includes the odd-numbered data bands DB 1 , DB 3 , DB 5 , and DB 7  out of the plurality of data bands DB 1  to DB 8 , and the second region includes the even-numbered data bands DB 2 , DB 4 , DB 6 , and DB 8 . Therefore, the grooves  52  can be formed in the feed support roller  30  and the rewind support roller  31  without any bias in position. As a result, the discharge bias of the entrained air in the feed support roller  30  and the rewind support roller  31  is less likely to occur. 
     As shown in  FIG.  3   , the servo band SB on which the servo pattern  50  used for the servo control to move the feed head  28  or the rewind head  29  in the width direction WD is recorded is formed in the magnetic layer  16 , in addition to the data band DB. The servo band SB and the data band DB are alternately arranged along the width direction WD of the magnetic tape  12 . Therefore, the servo control to make the position of the feed head  28  or the rewind head  29  match the target position can be performed. 
     As shown in  FIG.  8   , the feed head  28  and the rewind head  29  each include two servo pattern reading elements SR corresponding to two servo bands SB that sandwich one data band DB and the data element DRW provided between two servo pattern reading elements SR, as the magnetic elements. Therefore, more accurate servo control based on the servo patterns  50  read by two servo pattern reading elements SR can be performed. 
     The data element DRW includes the data recording element DW that records data on the magnetic layer  16  and the data reading element DR that reads the data recorded on the magnetic layer  16 . Therefore, data recording and data reading can be smoothly performed. The data element DRW may be any one of the data recording element DW or the data reading element DR. 
     A graph  80  shown in  FIG.  13    as an example shows a simulation result of the amount of variation in spacing SP due to the entrained air with respect to the number of grooves  52 . The conditions of simulation are such that the width W_T of the magnetic tape  12  is 12.65 mm, the outer diameter  1  of each of the feed support roller  30  and the rewind support roller  31  is 10 mm, the running speed of the magnetic tape  12  is 6 m/s, and the tension of the magnetic tape  12  during running is 0.55 N. Further, the grooves  52  have a pitch P=500 μm and a cross-sectional shape is V-shaped. A mark ♦ indicates a case where the cross-sectional area of the groove  52  is 1000 μm 2  (for example, the width W_G of the groove  52 =100 μm and the depth D_G=10 μm), and a mark ▪ indicates a case where the cross-sectional area of the groove  52  is 2000 μm 2  (for example, the width W_G of the groove  52 =100 μm and the depth D_G=20 μm, or the width W_G of the groove  52 =200 μm and the depth D_G=10 m). 
     In the case of the cross-sectional area of 1000 μm 2  marked with ♦, the amount of variation in spacing SP due to the entrained air is estimated to be 2 μm in a case where the number of grooves  52  is zero, that is, the grooves  52  are not formed. On the other hand, in a case where the number of grooves  52  is 24, that is, the grooves  52  are formed over the entire regions of the feed support roller  30  and of the rewind support roller  31  without the limitation to the region corresponding to the non-acting region, the amount of variation in spacing SP due to the entrained air can be made zero. 
     In this example, the grooves  52  are formed only in the region corresponding to the non-acting region. Therefore, the number of grooves  52  is halved to 12 from 24 in a case where the grooves  52  are formed over the entire region. In the case of the cross-sectional area of 1000 μm 2  marked with ♦, the amount of variation in spacing SP due to the entrained air is estimated to be 1 μm in a case where the number of grooves  52  is 12. However, in a case where the cross-sectional area is doubled to 2000 μm 2  by widening the width W_G and/or increasing the depth D_G of the groove  52 , the amount of variation in spacing SP due to the entrained air can be made zero as in the case where the grooves  52  are formed over the entire region with a cross-section area of 1000 μm 2 . As described above, it is confirmed that the technology of the present disclosure can reduce the variation in spacing SP due to the entrained air. 
     As a variation that is likely to affect the spacing SP other than the entrained air, there is a variation due to eccentricity of the feed support roller  30 , the rewind support roller  31 , and the like. However, such a variation due to eccentricity of the roller can be suppressed to a period of about 0.2 kHz. Further, in a small magnetic head such as a magnetic head used for the hard disk drive illustrated above, variations in a period of about 20 kHz can be followed without any particular control. Therefore, it may be considered that the variation due to the eccentricity of the roller does not affect the spacing SP. 
     The distribution of the data band DB and the servo band SB to the first region and the second region is not limited to the above-described example. For example, distribution may be performed as shown in  FIGS.  14  to  17   . 
     As shown in a table  85  of  FIG.  14   , the feed head  28  records data on the data bands DB 1 , DB 2 , DB 3 , and DB 4  and reads data recorded on the data bands DB 1  to DB 4 , at each operating position of the F1 position, the F2 position, the F3 position, and the F4 position. In addition, the feed head  28  reads the servo patterns  50  recorded on the servo bands SB 1  and SB 2  that sandwich the data band DB 1 , the servo bands SB 2  and SB 3  that sandwich the data band DB 2 , the servo bands SB 3  and SB 4  that sandwich the data band DB 3 , and the servo bands SB 4  and SB 5  that sandwich the data band DB 4 , at each operating position. In summary, the acting regions of the feed head  28  in this case are the data bands DB 1  to DB 4  and the servo bands SB 1  to SB 5 . These data bands DB 1  to DB 4  and these servo bands SB 1  to SB 5  are an example of the “first region” according to the technology of the present disclosure. Therefore, the first region includes the data bands DB 1  to DB 4  of one half out of eight data bands DB 1  to DB 8 . 
     The non-acting regions except for the acting regions of the feed head  28  are the data bands DBS, DB 6 , DB 7 , and DB 8  and the servo bands SB 6 , SB 7 , SB 8 , and SB 9 . Therefore, in this example, as shown in  FIG.  15   , the grooves  52  are formed in a feed support roller  86  only in regions C_DB 5  to DB 8 SB 6  to SB 9  corresponding to the data bands DB 5  to DB 8  and the servo bands SB 6  to SB 9 . 
     On the other hand, as shown in a table  90  of  FIG.  16   , the rewind head  29  records data on the data bands DB 8 , DB 7 , DB 6 , and DB 5  and reads data recorded on the data bands DB 5  to DB 8 , at each operating position of the B1 position, the B2 position, the B3 position, and the B4 position. In addition, at each operating position, the rewind head  29  reads the servo patterns  50  recorded on the servo bands SB 8  and SB 9  that sandwich the data band DB 8 , the servo bands SB 7  and SB 8  that sandwich the data band DB 7 , the servo bands SB 6  and SB 7  that sandwich the data band DB 6 , and the servo bands SB 5  and SB 6  that sandwich the data band DB 5 . In summary, the acting regions of the rewind head  29  in this case are the data bands DB 5  to DB 8  and the servo bands SB 5  to SB 9 . These data bands DB 5  to DB 8  and these servo bands SB 5  to SB 9  are an example of the “second region” according to the technology of the present disclosure. Therefore, the second region includes the data bands DB 5  to DB 8  of the other half out of eight data bands DB 1  to DB 8 . 
     The non-acting regions except for the acting regions of the rewind head  29  are the data bands DB 1 , DB 2 , DB 3 , and DB 4  and the servo bands SB 1 , SB 2 , SB 3 , and SB 4 . Therefore, in this example, as shown in  FIG.  17   , the grooves  52  are formed in a rewind support roller  91  only in the regions C_DB 1  to DB 4 SB 1  to SB 4  corresponding to the data bands DB 1  to DB 4  and the servo bands SB 1  to SB 4 . According to this aspect, the grooves  52  can be collectively formed on one side of each of the feed support roller  86  and the rewind support roller  91  in the width direction. 
     The support member is not limited to the roller. For example, a rectangular support member, such as a feed support member  95  shown in  FIG.  18   , may be used. 
     The feed support member  95  has a sliding surface  96  on which the back surface  19  of the magnetic tape  12  is slid. The grooves  52  are formed in the sliding surface  96  only in the region corresponding to the non-acting regions of the feed head  28 . Even with such a configuration, it is possible to obtain an effect that variations in spacing SP can be reduced. 
     Although not shown, a support member with a half moon-shaped cross-section having a curved surface that is convex toward the magnetic head may be used. 
     The number of servo bands SB, the number of data bands DB, the number of data elements DRW, the number of data tracks DT that one data element DRW is in charge of, and the like shown above are merely an example, and the technology of the present disclosure is not particularly limited thereto. 
     For example, a magnetic tape in which five servo bands and four data bands are alternately arranged along the width direction WD may be used. Alternatively, a magnetic tape in which three servo bands SB and two data bands DB are alternately arranged along the width direction WD may be used. Alternatively, a magnetic tape in which 13 servo bands SB and 12 data bands DB are alternately arranged along the width direction WD may be used. 
     One magnetic head may be shared for feed/rewind without separating the feed head and the rewind head from each other. Further, the number of servo pattern reading elements SR disposed in one magnetic head may be one. Similarly, the number of data elements DRW disposed in one magnetic head may be one. 
     The number of data elements DRW disposed in one magnetic head may be, for example, 16, 32, or 64. Further, the number of data tracks DT that one data element DRW is in charge of for data recording and/or data reading is not limited to 12 illustrated above. The number of data tracks DT may be 1 or, for example, 4, 16, 32, or 64. 
     For example, in the above-described aspect in which the magnetic tape  12  has eight data bands DB, four feed heads  28  and four rewind heads  29  may be provided in conformity with four data bands DB that are in charge of recording and/or reading. That is, the same number of magnetic heads as the number of data bands DB may be provided. 
     The magnetic tape device  10  in which the cartridge  11  is loaded has been illustrated, but the technology of the present disclosure is not limited thereto. The magnetic tape  12  as it is in which the cartridge  11  is not accommodated may be a magnetic tape device wound on a feed reel, that is, a magnetic tape device in which the magnetic tape  12  is irreplaceably installed. 
     The magnetic tape  12  is not limited to the magnetic tape having the magnetic layer  16  containing ferromagnetic powder illustrated above. A magnetic tape in which a ferromagnetic thin film is formed by vacuum deposition, such as sputtering, may be used. 
     The computer constituting the control unit  32  may include, for example, a programmable logic device (PLD) which is a processor whose circuit configuration is changeable after manufacture, such as a field-programmable gate array (FPGA), and/or a dedicated electrical circuit which is a processor having a dedicated circuit configuration designed to execute specific processing, such as an application specific integrated circuit (ASIC), in place of or in addition to the CPU. 
     The technology of the present disclosure can also appropriately combine the above-mentioned various embodiments and/or various modification examples. In addition, it goes without saying that the technology of the present disclosure is not limited to the above embodiments and various configurations may be employed without departing from the gist thereof. 
     The contents described and shown above are detailed descriptions of the parts related to the technology of the present disclosure, and are merely an example of the technology of the present disclosure. For example, the descriptions of the above configurations, functions, actions, and effects are the descriptions of an example of the configurations, functions, actions, and effects of the parts related to the technology of the present disclosure. Accordingly, it is needless to say that unnecessary parts may be deleted, new elements may be added, or replacements may be made with respect to the contents described and shown above, without departing from the gist of the technology of the present disclosure. Further, in order to avoid complications and facilitate understanding of the parts related to the technology of the present disclosure, descriptions of common general knowledge and the like that do not require special descriptions for enabling the implementation of the technology of the present disclosure are omitted, in the contents described and shown above. 
     In the present specification, “A and/or B” has the same meaning as “at least one of A or B”. That is, “A and/or B” means that only A may be used, only B may be used, or a combination of A and B may be used. In addition, in the present specification, the same concept as “A and/or B” is also applied to a case where three or more matters are expressed by “and/or”. 
     All documents, patent applications, and technical standards described in the present specification are incorporated in the present specification by reference to the same extent as in a case where the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference.