Abstract:
In a magnetic tape apparatus for controlling a running of a magnetic tape to stop at a reference stop position, a control part controls the feed reel shaft and the take-up reel shaft to reel the magnetic tape and a stop position control part displaces a stop position of the magnetic tape from the reference position wherein the control part activates the stop position control part to displace the stop position when the control part stops running the magnetic tape.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to magnetic tape apparatuses and methods for controlling the running of a magnetic tape so as to stop at a stop position, and more particularly to a magnetic tape apparatus and a method for controlling the running of a magnetic tape for writing or reading data so as to stop at a stop position.  
           [0003]    2. Description of the Related Art  
           [0004]    In a conventional magnetic tape apparatus controlling the running of a magnetic tape, the magnetic tape is stopped with a predetermined timing when data on the magnetic tape is read, when data is written on the magnetic tape, or when an EOT (end of tape) mark is detected, or when the magnetic tape is reeled from one stop position to another stop position after being stationary for a predetermined time interval, for avoiding adhering of dust (hereinafter, this operation is called a patrol reposition). In a case of running a cleaning medium to clean a magnetic head, a predetermined section of the cleaning medium is always used for the magnetic head cleaning operation.  
           [0005]    In the conventional magnetic tape apparatus, as mentioned above, the magnetic tape is always stopped with a predetermined timing. Thus, the magnetic tape is abraded at the same position or the same section. Further, dust tends to adhere on the same position or the same section of the magnetic tape surface. As a result, recording of data on the magnetic tape or reading of data from the magnetic tape may not be carried out optimally.  
           [0006]    In addition, in the conventional magnetic tape apparatus, one predetermined section on the cleaning medium may be used heavily in the cleaning operation. Thus, in the conventional magnetic tape apparatus, even if an entire area of the cleaning medium is two times longer than an area required for one cleaning operation, the cleaning medium is not effectively utilized, that is, only one section of the cleaning medium is frequently used. Accordingly, the cleaning effect of the cleaning medium is quickly degraded.  
         SUMMARY OF THE INVENTION  
         [0007]    It is a general object of the present invention to provide a magnetic tape apparatus in which the above-mentioned problems are eliminated.  
           [0008]    A more specific first object of the present invention is to provide a magnetic tape apparatus and a method for controlling the running of a magnetic tape so as to stop at controlled stop positions so that the magnetic tape can be prevented from being abraded or from collecting dust on the magnetic tape surface.  
           [0009]    A second specific object of the present invention is to provide a magnetic tape apparatus and a method for controlling the running of a magnetic tape so as to stop at controlled stop positions controlled so as to evenly utilize the entire area of a cleaning medium.  
           [0010]    The above first object of the present invention is achieved by a magnetic tape apparatus for controlling the running of a magnetic tape so as to stop at a reference stop position, including: a feed reel shaft and a take-up reel shaft respectively adapted to hold a feed reel and a take-up reel of the magnetic tape; a magnetic head; a control part controlling the feed reel shaft and the take-up reel shaft so as to reel the magnetic tape; and a stop position control part displacing a stop position of the magnetic tape from the reference position, wherein said control part activates the stop position control part so as to displace the stop position each time said control part stops running of the magnetic tape.  
           [0011]    According to the present invention, the stop position is displaced each time the magnetic tape is stopped. Therefore, it is possible to prevent the magnetic tape from being severely abraded at the specific position and prevent dust from adhering on specific areas of the magnetic tape surface.  
           [0012]    Also, the above first object of the present invention is achieved by a method for controlling a running of a magnetic tape so as to stop at a stop reference position, including the steps of: (a) controlling a feed reel shaft and a take-up reel shaft so as to reel the magnetic tape; and (b) displacing a stop position of the magnetic tape from the reference position, wherein the step (a) activates the step (b) so as to displace the stop position each time said control part stops running of the magnetic tape.  
           [0013]    According to the present invention, the stop position is displaced each time the magnetic tape is stopped. Therefore, the magnetic tape can be prevented from being severely abraded at the specific position and from collecting dust on specific areas of the magnetic tape surface.  
           [0014]    Furthermore, the above second object of the present invention is achieved by a magnetic tape apparatus for controlling the running of a magnetic tape, the magnetic tape apparatus controlling a cleaning medium so as to clean a magnetic head, including: a feed reel shaft and a take-up reel shaft respectively adapted to hold a feed reel and a take-up reel of the cleaning medium; a magnetic head; a control part controlling the feed reel shaft and the take-up reel shaft so as to reel the cleaning medium; and a cleaning section determining part determining a cleaning section on the cleaning medium that is used for a single cleaning step of the magnetic head, wherein said control part controls the feed reel shaft and the take-up reel shaft to clean the magnetic head for the cleaning section by the cleaning medium.  
           [0015]    According to the present invention, the cleaning section on the cleaning medium is shifted each time the magnetic head is cleaned. Thus, it is possible to prevent from starting the cleaning step from the beginning of the cleaning medium every time. The entire cleaning medium can be evenly utilized. Consequently, the endurance of the cleaning medium can be improved.  
           [0016]    Also, the above second object of the present invention is achieved by a method for controlling a running of a magnetic tape, the method controllable of a cleaning medium to clean a magnetic head, comprising the steps of: (a) controlling the feed reel shaft and the take-up reel shaft so as to reel the cleaning medium; and (b) determining a cleaning section on the cleaning medium that is used for a single cleaning step of the magnetic head, wherein said step (a) controls the feed reel shaft and the take-up reel shaft to clean the magnetic head for the cleaning section by the cleaning medium.  
           [0017]    According to the present invention, the cleaning section on the cleaning medium is shifted each time the magnetic head is cleaned. Thus, it is possible to prevent from starting the cleaning step from the beginning of the cleaning medium every time. The entire cleaning medium can be evenly utilized. Consequently, the method can improve the endurance of the cleaning medium. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:  
         [0019]    [0019]FIG. 1A is a diagram showing a forward running operation of a magnetic tape apparatus from the related art and FIG. 1B is a diagram showing a backward running operation of a magnetic tape apparatus from the related art;  
         [0020]    [0020]FIG. 2 is a diagram showing a configuration of a magnetic tape apparatus  20  according to a first embodiment of the present invention;  
         [0021]    [0021]FIG. 3A is a diagram showing a forward running operation of a magnetic tape according to the first embodiment of the present invention and FIG. 3B is a diagram showing a backward running operation of a magnetic tape according to the first embodiment of the present invention;  
         [0022]    [0022]FIG. 4 is a flow chart for explaining a control routine executed by the processor part after a read/write process to the magnetic tape is completed, according to the first embodiment of the present invention;  
         [0023]    [0023]FIG. 5 is a flow chart for explaining another control routine executed by the processor part when the patrol reposition is carried out, according to the first embodiment of the present invention;  
         [0024]    [0024]FIG. 6 is a schematic diagram showing a running control of the magnetic tape apparatus to clean the magnetic head in a magnetic tape apparatus from the related art;  
         [0025]    [0025]FIG. 7 is a schematic diagram showing a running control of the magnetic tape apparatus to clean the magnetic head according to the second embodiment of the present invention; and  
         [0026]    [0026]FIG. 8 is a flow chart for explaining a control routine executed by the processor part when the magnetic head is cleaned, according to the second embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    A related art magnetic tape operation will now be described with reference to FIG. 1A and FIG. 1B. FIG. 1A is a diagram showing a forward running operation of a magnetic tape from the related art and FIG. 1B is a diagram showing a backward running operation of a magnetic tape from the related art.  
         [0028]    As shown in FIG. 1A and FIG. 1B, in the magnetic tape operation, when data stored on the magnetic tape is read, a tape running is stopped or turned over (rewound) by predetermined timing or when data is written to the magnetic tape, or when the EOT is detected, or when the patrol reposition is carried out. In this case, a specific position of the magnetic tape is easily abraded and also dusts tend to adhere on the specific area of the magnetic tape surface. Therefore, in order to prevent the magnetic tape from being abraded or contaminated by dust, it is desired to avoid turning over and stopping the magnetic tape at the same position repeatedly.  
         [0029]    [0029]FIG. 2 is a diagram showing a configuration of a magnetic tape apparatus  20  according to a first embodiment of the present invention. The magnetic tape apparatus  20  writes data to a magnetic tape  22  or reads data from the magnetic tape  22  by reeling the magnetic tape  22  accommodated in a tape cassette (not shown). Data is recorded in data blocks on the tape while a predetermined interval is provided between data blocks such that a running operation of the magnetic tape is stopped after or started before a data block.  
         [0030]    As shown in FIG. 2, the magnetic tape apparatus  20  includes a feed reel  24  and a take-up reel  26 . A feed reel  28  and a take-up reel  30  are provided in the tape cassette to reel the magnetic tape  22 . The tape cassette is mounted on the magnetic tape apparatus  20  such that the feed reel  28  and the take-up reel  30  are brought into engagement with a feed reel shaft  24  and a take-up reel shaft  26 , respectively. The magnetic tape apparatus  20  further includes a magnetic head  32  that makes contact with a surface of the magnetic tape  22  when the tape cassette is mounted. The magnetic apparatus  20  records data on the magnetic tape  22  or reads data from the magnetic tape  22  by using the magnetic head  32 .  
         [0031]    In the magnetic tape apparatus  20 , tape cleaners  34  and  36  are provided at both sides of the magnetic head  32 . The tape cleaners  34  and  36  remove dust from the surface of the magnetic tape  22  by making a contact engagement with the surface of the magnetic tape  22 . In order to prevent dust from adhering on the surface of the magnetic tape  22 , the running operation of magnetic tape  22  is controlled so as to move compulsorily to another stop position when the running has stopped for a predetermined time interval. In this case, the magnetic tape  22  is controlled to run for a distance such that a facing area  39  of the magnetic tape  22  facing the magnetic head  32  can pass over the tape cleaner  34  or  36 .  
         [0032]    The magnetic tape apparatus  20  includes a processor  40 , an I/O address recorder/register  42 , a tacho pulse detecting circuit  46 , a digital analog converter (DAC) unit  48 , a read/write circuit  50 , a pulse speed meter circuit  52 , a power monitoring circuit  54 , a nonvolatile memory  56 , ROM  58 , and RAM  60 , which are mutually connected by a bus  62 . The magnetic tape apparatus  20  is connected to a host system via the bus  62 .  
         [0033]    The tacho pulse detecting circuit  46  detects rotation amounts of the feed reel shaft  24  and the take-up reel shaft  26  based on output signals from sensors provided at the outsides of the feed reel shaft  24  and take-up reel shaft  26 . The read/write circuit  50  is connected to the magnetic head  32  and supplies the magnetic head  32  with signals corresponding to data to be recorded on the magnetic tape  22  or receives signals corresponding to data being recorded on the magnetic tape  22  and read by the magnetic head  32 . The pulse speed meter circuit  52  measures the running speed of the magnetic tape  22  based on output signals from the read/write circuit  50  each time the magnetic head  32  reads a predetermined signal recorded on the magnetic tape  22  at a predetermined interval. When the condition to stop the magnetic tape  22  is satisfied, the timer counter  44  counts time that is used to stop the magnetic tape  22 .  
         [0034]    The magnetic tape apparatus  20  further includes a feed reel motor  70  and a take-up reel motor  72  that drive the feed reel shaft  24  and the take-up reel shaft  26 , respectively. The feed reel motor  70  and the take-up reel motor  72  are connected to the processor  40  via an amplifier unit  74  and the DAC unit  48 . The processor  40  calculates a motor current that is supplied to the motors  70  and  72  such that the magnetic tape  22  runs at speed based on a calculation result and then outputs a signal corresponding to the motor current to the amplifier unit  74 . The motors  70  and  72  rotate the feed reel shaft  24  and the take-up reel shaft  26  based on an instruction signal supplied from the processor  40 . In the above configuration, the magnetic tape apparatus  20  runs the magnetic tape  22 , which is accommodated in the tape cassette, by the feed reel motor  70  and the take-up reel motor  72  controlled by the processor  40 .  
         [0035]    In addition, the magnetic tape apparatus  20  includes a motor  76  that moves the magnetic head  32  in a width direction across the magnetic tape  22 . The motor  76  is also connected to the processor  40  via the amplifier unit  74  and the DAC unit  48 . When a cleaning tape instead of the magnetic tape  22  is used to clean the magnetic head  32 , the processor  40  calculates the motor current to supply the motor  76  such that the magnetic head  32  moves in the width direction across the cleaning tape and then outputs a signal corresponding to the motor current to the amplifier unit  74 . The motor  76  moves the magnetic head  32  in the width direction across the cleaning tape based on the instruction signal supplied by the processor  40 .  
         [0036]    The power monitoring circuit  54  detects an abnormal condition of a power source supplied to the magnetic tape apparatus  20 . The ROM  58  stores programs to be executed by the processor  40 . The RAM  60  stores current programs executed by the processor  40 . Also, the cleaning number of cleaning the magnetic head  32 , that is, a cleaning frequency M of the cleaning tape is stored in the nonvolatile memory  56 . When the cleaning tape for the magnetic tape  22  is used, the processor  40  determines a cleaning position for the cleaning tape to clean the magnetic head  32  based on the cleaning frequency M stored in the nonvolatile memory  56  (described later). Accordingly, the instruction signal is supplied to the feed reel motor  70  and the take-up reel motor  72  in order to clean the magnetic head  32  at normal speed after the cleaning tape is reeled to the determined cleaning position.  
         [0037]    In the magnetic tape apparatus  20  according to the present invention, in order to avoid turning over or stopping at the same position, the timing for a turnover instruction signal or stop instruction signal, which is supplied the feed reel motor  70  and the take-up reel motor  72 , is changed each time the magnetic tape  22  is turned over or stopped. Thus, the turnover position and the stop position on the magnetic tape  22  can be displaced. Advantageously, the magnetic tape apparatus  20  according to the present invention has a feature that changes the timing of the instruction signal for the feed reel motor  70  and the take-up reel motor  72  as mentioned above.  
         [0038]    An operation of the magnetic tape  22  after a read/write operation is completed will be now described according to the present invention. FIG. 3A is a diagram showing a forward running operation of a magnetic tape  22  according to the first embodiment of the present invention and FIG. 3B is a diagram showing a backward running operation of a magnetic tape according to the first embodiment of the present invention. As shown in FIG. 3A and FIG. 3B, the magnetic tape apparatus  20  in this embodiment displaces the turnover position or stop position on the magnetic tape  22  at every turnover or stop. Hence, when data recorded on the magnetic tape  22  is read or data is written on the magnetic tape  22 , or when the EOT is detected, or when the patrol reposition is carried out, the apparatus can avoid the problem of magnetic tape  22  turned over or stopped at the same position. Accordingly, it is possible to prevent specific positions on the magnetic tape  22  from being severely abraded. Further, deposition of dust on the magnetic tape  22  is also prevented.  
         [0039]    [0039]FIG. 4 is a flow chart for explaining a control routine executed by the processor  40  when a read/write process to the magnetic tape  22  is completed. The control routine shown in FIG. 4 is executed each time the control routine is completed. With the start of the routine shown in FIG. 4, the process in a step  100  is processed.  
         [0040]    In the step  100 , it is determined whether or not the read/write process is completed. The process in the step  100  is repeated until the read/write process is completed. As a result, when the condition is satisfied, the process in a step  102  is processed next.  
         [0041]    In the step  102 , data D 1  is converted to a random value X 1 . The random X 1  is obtained from a predetermined random table.  
         [0042]    In the step  104 , a remainder R 1  is obtained from the expression data D 1  divided by 5. Subsequently, a supply timing T 11  for turnover instruction signals to the feed reel motor  70  and the take-up reel motor  72  is set to be a value resulting from adding a time f(R 1 ), which is proportional to the remainder R 1 , to a reference time T 10 . The reference time T 10  is a minimum time until a decelerating process of the magnetic tape  22  is started after the read/write process is completed.  
         [0043]    In the first embodiment, when the read/write process to the magnetic tape  22  is completed, the supply timing for the turnover instruction signal or the stop instruction signal to the feed reel motor  70  and the take-up reel motor  72  is selected from five timing options. Each timing option is determined based on a time difference that is required to pass over at least a length of a contact area  39  between the magnetic tape  22  and the magnetic head  32  at a constant speed.  
         [0044]    In a step  106 , it is determined whether or not a time T 12  after the read/write process is completed reaches the value of the supply timing T 11  set in the step  104 . The determining process in the step  106  is repeated until T 12 &gt;=T 11 =T 10 +f(R 1 ) is satisfied. As a result, when it is determined that T 12 &gt;=T 11  is satisfied, a process in step  108  is processed next.  
         [0045]    In a step  108 , in order to decelerate the running speed of the magnetic tape  22 , a process to reduce the motor current for the feed reel motor  70  and the take-up reel motor  72  is started.  
         [0046]    In a step  110 , it is determined whether or not a time T 21  after the process in step  108  is executed reaches the value of a predetermined time T 20 . The predetermined time T 20  is the time to continue to decelerate the running speed of magnetic tape  22  and is determined as a constant time value beforehand. The determining process in the step  110  is repeated until T 21 &gt;=T 20  is satisfied. As a result, when it is determined that T 21 &gt;=T 20  is satisfied, a process in step  112  is processed next.  
         [0047]    In a step  112 , in order to stop the running of the magnetic tape  22 , a process to stop each of the motors  70  and  72  is executed.  
         [0048]    In a step  114 , in order to turn over the magnetic tape  22 , a process to supply motor current appropriate to each of the motors  70  and  72  is executed so that the motors  70  and  72  are reversed. When the process in the step  114  is executed, the running of the magnetic tape  22  is accelerated in a backward direction.  
         [0049]    In a step  116 , it is determined whether or not a time T 31  after the step  114  is executed reaches the value of a predetermined time T 30 . The predetermined time T 30  is a time to continue to accelerate the speed of the magnetic tape  22  in the backward direction and is determined as a constant time value beforehand. The process in the step  110  is repeated until it is determined that T 31 &gt;=T 30  is satisfied. As a result, when it is determined that T 31 &gt;=T 30  is satisfied, a step  118  is processed next.  
         [0050]    In the step  118 , in order to maintain the constant speed of the magnetic tape  22 , a process to maintain the motor current at a constant current level is executed.  
         [0051]    In the step  120 , a process to convert data D 2  to a random value X 2  is executed. The random X 2  is obtained from the predetermined random table.  
         [0052]    In a step  122 , a remainder R 2  is obtained from data D 2  divided by 5. Subsequently, a supply timing T 41  of the stop instruction signal to the feed reel motor  70  and the take-up reel motor  72  is set to be a value resulted from adding a time f(R 2 ) , which is proportional to the remainder R 2 , to a reference time T 40 . The reference time T 40  is the minimum time until the decelerating process of the magnetic tape  22  is started after the constant running process of the magnetic tape  22  in the backward direction is started.  
         [0053]    In a step  124 , it is determined whether or not a time T 42  after the constant running process for the magnetic tape  22  in the reverse direction is started is equal to or greater than the supply timing determined in step  122 . The process in the step  124  is repeated until it is determined that T 42 &gt;=T 41  is satisfied. As a result, when it is determined that T 42 &gt;=T 41  is satisfied, a process in step  126  is processed next.  
         [0054]    In the step  126 , in order to decelerate the running speed of the magnetic tape  22  in the reverse direction, a process to reduce the motor current for the feed reel motor  70  and the take-up reel motor  72  is started.  
         [0055]    In a step  128 , it is determined whether or not a time T 51  after the process in the step  126  is executed reaches the value of a predetermined time T 50 . The predetermined time T 50  is the time to continue to decelerate the running speed of the magnetic tape  22  in the backward direction and is determined as a constant time value beforehand. The determining process in the step  128  is repeated until it is determined that T 51 &gt;=T 50  is satisfied. As a result, when it is determined that T 51 &gt;=T 50  is satisfied, a process in a step  130  is processed next.  
         [0056]    In the step  130 , in order to stop the running of the magnetic tape  22 , a process to stop each of the motors  70  and  72  is executed. After the process in the step  130  is completed, this routine is terminated.  
         [0057]    According to the above processes, after the read/write process is completed, when the running of the magnetic tape  22  is turned over, the running speed of the magnetic tape  22  may be decelerated based on the timing randomly selected from the five timing options. Also, when the running of the magnetic tape  22  stopped, the running speed of the magnetic tape  22  can be decelerated based on the timing randomly selected from the five timing options. That is, when the timing to decelerate the running speed of the magnetic tape  22  is changed the turnover position or the stop position is displaced by a difference proportional to the timing varied along the running direction. According to the first embodiment, it can be avoided to frequently turn over or stop the magnetic tape  22  at a specific position. Therefore, it is possible to prevent severe abrasion at a specific position on the magnetic tape  22  and prevent dust from adhering on specific areas of the surface of the magnetic tape  22 .  
         [0058]    In the first embodiment, as mentioned above, each timing option for the turnover instruction signal or the stop instruction signal to the feed reel motor  70  and the take-up reel motor  72  is determined based on a time difference that is required to pass over at least a length of one contact area  39  between the magnetic tape  22  and magnetic head  32  at constant speed. Thus, the timing for turning over or stopping the magnetic tape  22 , which is determined by the time difference according to the first embodiment, can prevent the contact area of the magnetic tape  22  contacting with the magnetic head  32  from being the same area. Therefore, according to the magnetic tape apparatus  20 , after the read/write process is completed, it is possible to prevent severe abrasion at a specific position on the magnetic tape  22  and prevent dust from adhering on specific areas of the surface of the magnetic tape  22 . Thus, advantageously, it is possible to improve the reliability of the read/write process to/from the magnetic tape  22 .  
         [0059]    In addition, in the first embodiment, the supply timing for the turnover instruction signal or the stop instruction signal to each of motors  70  and  72  is set based on a value randomly obtained each time the read/write process is completed. Since the position on the magnetic tape  22  where the read/write process is completed is detected, it is not required to count the executions of the read/write process at the position. The method according to the first embodiment of the present invention can be simplified more than a method in which the supply timing is determined based on the execution number of the read/write process at each position.  
         [0060]    The method for achieving the above function will now be described in detail. FIG. 5 is a flow chart for explaining another control routine executed by the processor  40  when the patrol reposition is carried out, according to the first embodiment of the present invention. The control routine shown in FIG. 5 is executed again each time the control routine is completed. When the routine shown in FIG. 5 is executed, the process in a step  140  is processed.  
         [0061]    In the step  140 , it is determined whether or not a time interval T 1  in which the magnetic tape  22  is stopped at the same position reaches to a predetermined time value T 0 . The predetermined time value T 0  is a time interval after the magnetic tape  22  is stopped and before the patrol reposition is carried out. The predetermined term T 0  is determined as a constant time interval beforehand. The process in the step  140  is repeated until it is determined that T 1 &gt;=T 0  is satisfied. As a result, when it is determined that T 1 &gt;=T 0  is satisfied, the process in a step  142  is executed next.  
         [0062]    In the step  142 , data D 5  is converted to a random value X 5  obtained from a predetermined random table.  
         [0063]    In a step  144 , a remainder R 5  is obtained from data D 5  divided by 5.  
         [0064]    In the step  146 , a stop state of the magnetic tape  22  is released and a process to supply the motor current to the feed reel motor  70  and the take-up reel motor  72  is started. That is, the magnetic tape  22  is operated to move the stop position to another position that has a constant remote distance from the stop position before the patrol reposition is carried out. In this case, the move distance for the patrol reposition is set as a distance such that a surface area of the magnetic tape  22  facing the magnetic head  32  in the stop status is passed over tape cleaners  34  and  36  shown in FIG. 2. When the process in the step  146  is executed, the running of the magnetic tape  22  is accelerated.  
         [0065]    In a step  148 , it is determined whether or not a time T 61  after the process in step  146  is executed reaches the value of a predetermined time T 60 . The predetermined time T 60  is a time to continue accelerating the magnetic tape  22  and is determined as a constant value beforehand. The process in the step  148  is repeated until it is determined that T 61 &gt;=T 60  is satisfied. As a result, then it is determined that T 61 &gt;=T 60  is satisfied, the process in a step  150  is processed next.  
         [0066]    In the step  150 , in order to maintain constant speed of the magnetic tape  22 , a process to maintain the motor current supplying each of motors  70  and  72  at a constant current level is started.  
         [0067]    In a step  152 , it is determined whether or not a time T 71  after the process to maintain the motor current constant is started reaches a value resulting from adding a time f(R 5 ), which is proportional to the remainder R 5 , to a reference time T 70 . The reference time T 70  is a minimum time after the process to maintain the motor current is started and before a decelerating process for the magnetic tape  22  is started. Also, the reference time T 70  is determined based on the move distance of the magnetic tape  22  by the patrol reposition. The process in the step  152  is repeated until it is determined that T 71 &gt;=T 70 +f(R 5 ) is satisfied. As a result, when it is determined that T 71 &gt;=T 70 +f(R 5 ) is satisfied, the process in a step  154  is processed next.  
         [0068]    In the step  154 , in order to decelerate the running speed of the magnetic tape  22 , a process to reduce a motor current for the feed reel motor  70  and the take-up reel motor  72  is started.  
         [0069]    In a step  156 , it is determined whether a time T 81  after the process in the step  154  is executed reaches a predetermined time T 80 . The predetermined time T 80  is the time to continue to decelerate the running speed of magnetic tape  22  and is determined as a constant time value beforehand. The determining process in the step  154  is repeated until T 81 &gt;=T 80  is satisfied. As a result, when it is determined that T 81 &gt;=T 80  is satisfied, a step  158  is processed next.  
         [0070]    In the step  158 , in order to stop the running of the magnetic tape  22 , a process to stop each of the motors  70  and  72  is executed. When the process in the step  158  is completed, this routine is terminated.  
         [0071]    According to the above processes, the magnetic tape  22  is decelerated based on the timing randomly determined while the stop position is changed to another position by patrol reposition in order to avoid the state in which the magnetic tape  22  is stopped at the same position for a long time interval. According to the first embodiment, similarly to the case in which the read/write process to the magnetic tape  22  is completed, when the patrol reposition is carried out, it can be avoided to frequently turn over or stop the magnetic tape  22  at a specific position. Therefore, it is possible to prevent the magnetic tape  22  from being severely abraded at the specific position and to prevent dust from adhering on specific areas of the surface of the magnetic tape  22 .  
         [0072]    As mentioned above, in the first embodiment, the move distance for the patrol reposition is set as a distance such that a surface area of the magnetic tape  22  facing the magnetic head  32  in the stop status passes over tape cleaners  34  and  36  shown in FIG. 2. Therefore, in the magnetic tape apparatus  20  according to the first embodiment, it is possible to certainly remove dustadhered on the surface of the magnetic tape  22  during the running stop status before the patrol reposition when the patrol reposition is carried out.  
         [0073]    In the first embodiment, the turnover position and the stop position on the magnetic tape  22  are displaced by varying the supply timing of the turnover instruction signal or the stop instruction signal to the feed reel motor  70  and the take-up reel motor  72  after the read/write process is completed. Further, the turnover position and the stop position on the magnetic tape  22  may be displaced by varying rotation speed of each of motors  70  and  72 .  
         [0074]    Also, in the first embodiment, the time interval in which the magnetic tape is operated at constant speed is varied. But, the method for varying the supply timing for signals to each of motors  70  and  72  is not limited to this. It is noted that the supply timing may be changed by varying the duration for decelerating the magnetic tape  22  after the read/write process is completed.  
         [0075]    Moreover, in the first embodiment, the turnover position and the stop position on the magnetic tape  22  is displaced after the read/write process is completed. But the present invention is not limited this method. Another method, in which the turnover position and the stop position on the magnetic tape  22  are displaced after the EOT is detected, may be applied.  
         [0076]    Also, in the first embodiment, the supply timing of the turnover instruction signal or the stop instruction signal to the motors  70  and  72  are varied. But, the stop position can be displaced by changing the supply timing only for the turnover instruction signal while the distance between the turnover position and the stop position on the magnetic tape  22  is maintained.  
         [0077]    Furthermore, in the first embodiment, the supply timing for the turnover instruction signal or the stop instruction signal to the motors  70  and  72  is randomly varied. But, the present invention is not limited to this method. The supply timing may be increased or decreased in sequence.  
         [0078]    A second embodiment according to the present invention will now be described with reference to FIGS. 6, 7 and  8 . A magnetic tape apparatus  80  according to the second embodiment can be realized by the processor  40  in FIG. 2 executing a routine shown in FIG. 8 when the magnetic head  32  is cleaned. The magnetic tape apparatus  80  in the second embodiment includes the same configuration as the magnetic tape apparatus  20  shown in FIG. 2.  
         [0079]    [0079]FIG. 6 is a schematic diagram showing a running control of the magnetic tape  22  to clean the magnetic head  32  in a magnetic tape apparatus of the related art. In the magnetic tape apparatus of the related art, when a tape cassette accommodating a cleaning tape is loaded, the magnetic head  32  starts being cleaned from the beginning of the tape as shown in FIG. 6.  
         [0080]    In details in the cleaning process, after the cassette is loaded, (1) in a state in which the magnetic head  32  is moved to and positioned at the up side of the width of the cleaning tape, the cleaning tape is cycled a predetermined number of times by accelerating, maintaining a constant speed and decelerating in a forward direction, (2) in a state in which the magnetic head  32  is moved to and positioned at the down side of the width of the cleaning tape, the cleaning tape is cycled a predetermined number of times, in the same manner as (1) above, by accelerating, maintaining the constant speed and decelerating in a forward direction, (3) in a state in which the cleaning tape is running at the constant speed, the magnetic head  32  is moved periodically up and down a predetermined number of times in the width direction, (4) the running of the cleaning tape is turned over and the above (1) through (3) processes are executed again in a backward direction.  
         [0081]    In the above (1) and (2) in the cleaning process, tension is applied to the cleaning tape and then the entire surface of the magnetic head  32  is cleaned by acceleration and deceleration of the cleaning tape in the forward and backward directions. Also, in the above (3) in the cleaning process, the surface of the magnetic head  32  is cleaned in the width direction by the tension of the cleaning tape and the magnetic head  32  being accelerated or decelerated. Thus, according to the cleaning process, the surface of the magnetic head  32  is cleaned.  
         [0082]    The cleaning tape has a tape length of about two times longer than that required for one cleaning process. However, the beginning of the cleaning tape is always used for the cleaning process of the magnetic head. Disadvantageously, the cleaning tape is not effectively used in the conventional construction and the cleaning effect of the cleaning tape is quickly degraded. Thus, it is effective to properly change the cleaning section of the cleaning tape in the cleaning process. Consequently, in the second embodiment, the cleaning section of the cleaning tape is properly changed each time the cleaning process is executed.  
         [0083]    [0083]FIG. 7 is a schematic diagram showing a running control for the magnetic tape  22  to clean the magnetic head  32  according to the second embodiment of the present invention. A cassette tape, which is to be loaded into the magnetic tape apparatus  80  according to the second embodiment, accommodates a cleaning tape about five times longer than that required for one cleaning process for the magnetic head  32 . In this embodiment, the cleaning section of the cleaning tape, which is used for the cleaning process of the magnetic head  32 , is determined. As shown in FIG. 7, the cleaning tape is run until the selected cleaning start point of the cleaning section is properly positioned and then the above (1) through (4) in the cleaning process are executed from the cleaning start point. According to the cleaning process, using the same specific section every time the cleaning process is executed can be avoided. Therefore, it is possible to effectively use the cleaning tape.  
         [0084]    [0084]FIG. 8 is a flow chart for realizing the above function. More specifically, FIG. 8 is a flow chart for explaining a control routine executed by the processor  40  when the magnetic head  22  is cleaned, according to the second embodiment of the present invention. The control routine shown in FIG. 8 is executed again each time the control routine itself is completed. When the control routine shown in FIG. 8 is started, the process in a step  200  is executed.  
         [0085]    In the step  200 , it is determined whether or not a special cleaning tape is used in the magnetic tape apparatus  80  according to the second embodiment. When it is determined that the special cleaning tape is not used, that is, a cleaning tape used for other magnetic tape apparatuses is used or many cleaning tapes are used for the magnetic tape apparatus  80 , a use frequency of the cleaning tape is not counted. Thus, in this embodiment, when the special cleaning tape is not used, the process in a step  202  is executed next.  
         [0086]    In the step  202 , data D 10  is converted to a random value X 10  obtained from a predetermined random table. After step  202  is completed, a process in step  210  is executed.  
         [0087]    When it is indicated in the step  200  that the special cleaning tape is used, the use frequency of the cleaning tape can be properly counted. That is, it is possible to use the cleaning tape from the beginning consecutively. Accordingly, when the special cleaning tape is used in the second embodiment, the process in a step  204  is executed next.  
         [0088]    In the step  204 , the cleaning frequency of the cleaning tape stored in the nonvolatile memory  56  in FIG. 2 is set to data D 10 .  
         [0089]    In a step  206 , data D 10  set in the step  204  is incremented by 1.  
         [0090]    In a step  208 , data D 10  incremented in the step  206  is stored in the nonvolatile memory  56  in FIG. 2.  
         [0091]    In a step  210 , a remainder R 10  is obtained by dividing data D 10 , which is processed in the step  202  or the step  208 , by 5. In this embodiment, since the cleaning tape has a tape length enough to execute the cleaning process for the magnetic head  32  five times, data D 10  is divided by 5.  
         [0092]    In the step  212 , it is determined whether or not the remainder R 10  is 0 (zero). When R 10 =0 is not satisfied, the cleaning process of the magnetic head  32  starts from the middle of the cleaning tape because it is determined that the current cleaning section is not the beginning. In this case, it is needed to reel the cleaning tape at high speed until reaching the start point of another cleaning section. Then, when it is determined that the remainder R 10  is not 0 (zero), the process in a step  214  is executed next.  
         [0093]    In the step  214 , a ratio of rotation of the feed reel shaft  24  to that of the take-up reel shaft  26  is set such that the tension F applied to the cleaning tape in the running state is suppressed more than that in the normal state.  
         [0094]    In a step  216 , while the rotation ratio set in the step  214  is maintained, a process to supply a motor current to the feed reel motor  70  and the take-up reel motor  72  is executed so that the cleaning tape runs from the beginning of the cleaning tape to the cleaning start point in the forward direction at high speed.  
         [0095]    In a step  218 , it is determined whether a time T 92  after the cleaning tape runs at the high speed reaches the value of a time f(R 10 ) corresponding to the remainder R 10  obtained in the step  210 . The determining process in the step  218  is repeated until it is determined that T 92 &gt;=f(R 10 ) is satisfied. As a result, when it is determined that T 92 &gt;=f(R 10 ) is satisfied, the process in a step  220  is executed next.  
         [0096]    In this embodiment, the time f(R 10 ) is increased by time required for the cleaning tape to run a distance needed for a single cleaning step for the magnetic head  32 , each time the remainder R 10  is incremented by 1 while the cleaning tape runs at high speed. That is, the cleaning start point on the cleaning tape becomes farther from the beginning of the cleaning tape and nearer to the end of the cleaning tape each time the remainder R 10  is incremented.  
         [0097]    In the step  220 , in order to stop the cleaning tape after the high speed running, a process to stop the rotation of the feed reel motor  70  and the take-up reel motor  72  is executed. When the process in the step  220  is completed, the process in a step  222  is executed.  
         [0098]    On the other hand, when R 10 =0 is satisfied in the step  212 , it is determined that the cleaning process of the magnetic tape  32  will start from the beginning of the cleaning tape. In this case, it is not required to run the cleaning tape at high speed. Thus, when it is determined that R 10 =0 is satisfied, the processes in step  214  through  220  are not executed but the control routine jumps to a step  222  and then the process in the step  222  is executed.  
         [0099]    In the step  222 , a process to supply an appropriate motor current to the feed reel motor  70 , the take-up motor  72  and motor  76  to clean the magnetic head  32  is executed.  
         [0100]    In detail, in a state in which the magnetic head  32  is moved to and positioned at the up side of the width of the cleaning tape in a running process in the forward direction, the motor current is supplied to the motors  70 ,  72  and  76  such that the running of the cleaning tape is cycled to accelerate, maintain the constant speed and decelerate a predetermined number of times. Subsequently, in a state in which the magnetic head  32  is moved to and positioned at the down side of the width of the cleaning tape, the motor current is supplied to the motors  70 ,  72  and  76  such that the running of the cleaning tape is cycled to accelerate, maintain the constant speed, and decelerate a predetermined number of times. Also, in the running process of the cleaning tape in the backward direction, the motor current is supplied to the motors  70 , 72  and  76  in the same manner as in the forward direction.  
         [0101]    In a step  224 , it is determined whether the cleaning process to the magnetic head  32  is completed. The process in the step  224  is repeated until it is determined that the cleaning process to the magnetic head  32  is completed. As a result, when it is determined that the cleaning process is completed, the process in a step  226  is executed.  
         [0102]    In the step  226 , in the same manner as in the step  214 , the ratio of rotation of the feed reel shaft  24  to that of the take-up reel shaft  26  is set such that the tension F applied to the cleaning tape in the running state is suppressed more than that in the normal state.  
         [0103]    In a step  228 , while the rotation ratio set in the step  226  is maintained, a process to supply a motor current to the feed reel motor  70  and the take-up reel motor  72  is executed so that the cleaning tape runs from the beginning of the cleaning tape to the cleaning start point in the forward direction at high speed.  
         [0104]    In a step  230 , it is determined whether or not the BOT (Begin Of Tape) written at the beginning of the cleaning tape is detected. As a result, when the BOT is not detected, the high speed running of the cleaning tape is continued. On the other hand, when the BOT is detected, a process in step  232  is executed next.  
         [0105]    In a step  232 , in order to stop the high speed running of the cleaning tape, the process to stop the rotation of the feed reel motor  70  and the take-up reel motor  72  is executed. When the process in step  232  is completed, this control routine is terminated.  
         [0106]    In the second embodiment, two DACs in the DAC unit  48  and two AMPs in the AMP unit  74  in the configuration in FIG. 2 may be provided for the feed reel motor  70  and the take-up motor  72 , respectively. Therefore, it can be realized that the feed reel motor  70  and the take-up reel motor  72  are independently rotated based on the rotation ratio set in step  214  or step  226  by the processor  40 .  
         [0107]    According to the routine mentioned above, the cleaning start point on the cleaning tape is changed each time the magnetic head  32  is cleaned. Thus, in this embodiment, since using only the beginning of the cleaning tape can be avoided, the entire cleaning tape can be evenly utilized. Consequently, according to the magnetic tape apparatus  80 , the endurance of the cleaning tape can be improved.  
         [0108]    Moreover, according to the control routine in the second embodiment, when the cleaning tape runs from the beginning to the cleaning start point at high speed or from the ending point to the beginning of the cleaning tape, the tension applied to the cleaning tape can be suppressed. Since the tension applied to the cleaning tape is suppressed in this approach, even when the cleaning tape runs at high speed, it is possible to prevent the cleaning tape from being deteriorated by an increased abrasion between the magnetic head  32  and the cleaning tape and also it is possible to prevent from impairing the surface of the cleaning tape. Therefore, according to the second embodiment, it is possible to prevent from degrading the endurance of the cleaning tape caused by high speed running.  
         [0109]    In FIG. 8 in the second embodiment, the cleaning section is selected in an orderly manner when the special cleaning tape is used. But alternatively, the steps  200 ,  204 ,  206  and  208  in FIG. 8 may be omitted so as to always randomly set the cleaning section, instead of being concerned with only the special cleaning tape.  
         [0110]    In the present invention, when the magnetic tape is operated, the stop position is displaced each time the magnetic tape is stopped. Therefore, it is possible to prevent the magnetic tape from being severely abraded at the specific position and to prevent dust from adhering on specific areas of the surface of the magnetic tape.  
         [0111]    In addition, in the present invention, when the cleaning medium is operated, the cleaning section on the cleaning medium is determined each time the magnetic head is cleaned. Thus, since it using only the beginning of the cleaning medium can be avoided, the entire cleaning medium can be evenly utilized. Consequently, the endurance of the cleaning medium can be improved.  
         [0112]    The present invention is not limited to the specifically disclosed embodiments, variations and modifications, and other variations and modifications may be made without departing from the scope of the present invention.  
         [0113]    The present application is based on Japanese Priority Application No. 11-230585 filed on Aug. 17, 1999, the entire contents of which are hereby incorporated by reference.