Abstract:
A magnetic recording and reproduction apparatus for recording and reproducing a signal to and from a magnetic tape includes a substrate having first and second positioning engagement holes; a rotation head cylinder provided on the substrate and having the magnetic tape wound therearound over a prescribed angle and having first and second female screws; a first attaching screw having a first cylindrical section for insertion into the first positioning engagement hole and engagement with the first female screw; and a second attaching screw having a second cylindrical section for insertion into the second positioning engagement hole and engagement with the second female screw. Diameters A 1  and A 2  of the first and second cylindrical sections and diameters B 1  and B 2  of the first and second positioning engagement holes fulfill the following relationships: 
     
       
         0.0002 mm&lt;B 1 -A 1 &lt;0.1 mm, 
       
     
     and 
     
       
         0.0002 mm&lt;B 2 -A 2 &lt;0.1 mm.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a magnetic recording and reproduction apparatus for performing recording and reproduction of signals to or from a magnetic tape which is wound around a rotation head cylinder of the magnetic recording and reproduction apparatus. 
     2. Description of the Related Art 
     FIG. 11 is a plan view of a conventional magnetic recording and reproduction apparatus  100 . As shown in. FIG. 11, the magnetic recording and reproduction apparatus  100  includes a substrate  1  and a rotation head cylinder  2  attached to a cylinder attachment section  3  of the substrate  1 . 
     FIG. 12 is a plan view of the substrate  1 . The substrate  1  has a first through-hole  4  having a diameter C 1 , a second through-hole  5  having a diameter C 2 , a first positioning pin  6  having a diameter D 1  and pressure-inserted into the substrate  1 , and a second positioning pin  7  having a diameter D 2  and pressure-inserted into the substrate  1 . 
     FIG. 13 is a bottom view of the rotation head cylinder  2 . The cylinder  2  has a first female screw  8 , a second female screw  9 , a first positioning hole  10  and a second positioning hole  11 . The first positioning hole  10  is circular and has a diameter E 1 . The second positioning hole is substantially slot-shaped and has a width E 2 . 
     FIG. 16 is a cross-sectional view of the conventional magnetic recording and reproduction apparatus  100  taken along line H—H in FIG.  11 . As shown in FIG.  16 , the rotation head cylinder  2  is attached to the substrate  1  via a first attaching screw  22  inserted Into the through-hole  4  of the substrate  1  and a second attaching screw  25  inserted into the through-hole  5  of the substrate  1 . 
     FIG. 14 is a side view of the first attaching screw  22 . The first attaching screw  22  includes a (first) cylindrical section  23  having a diameter A 1  and a (first) male screw  24  projecting from the first cylindrical section  23 . FIG. 15 is a side view of the second attaching screw  25 . The second attaching screw  25  includes a (second) cylindrical section  26  having a diameter A 2  and a (second) male screw  27  protecting from the second cylindrical section  26 . 
     Returning to FIG. 16, the first attaching screw  22  is inserted into the through-hole  4  of the substrate  1 , so that the first male screw  24  is engaged with the first female screw  8  of the rotation head cylinder  2 . A coil spring  14   a , interposed between a head of the first attaching screw  22  and the substrate  1 , loads the first attaching screw  22  in such a direction as to pressure-contact the rotation head cylinder  2  to the substrate  1 . Likewise, the second attaching screw  25  is inserted into the through-hole  5  of the substrate  1 , so that the second male screw  27  is engaged with the second female screw  9  of the rotation head cylinder  2 . A coil spring  14   b , interposed between a head of the second attaching screw  25  and the substrate  1 , loads the second attaching screw  25  in such a direction as to pressure-contact the rotation cylinder  2  to the substrate  1 . 
     FIG. 17 is a cross-sectional view of the conventional magnetic recording and reproduction apparatus  100  taken along line I—I in FIG.  11 . The first positioning pin  6  is engaged with the first positioning hole  10 , and the second positioning pin  7  is engaged with the second positioning hole  11 . In general, relationships of the sizes of the pins, screws and holes are set as follows. 
     
       
         0.0002 mm&lt;E 1 -D 1 &lt;0.1 mm 
       
     
     
       
         0.0002 mm&lt;E 2 -D 2 &lt;0.1 mm 
       
     
     
       
         0.1 mm≦C 1 -A 1   
       
     
     
       
         0.1 mm≦C 2 -A 2   
       
     
     Therefore, the positioning precision of the rotation head cylinder  2  on the substrate  1  required for reliable operation of the conventional magnetic recording and reproduction apparatus is determined by the relationship in size between the first positioning pin  6  and the first positioning hole  10 , and the relationship in size between the second positioning pin  7  and the second positioning hole  11 . The first cylindrical section  23  and the first through-hole  4  have a gap therebetween, and the second cylindrical section  25  and the second through-hole  5  have a gap therebetween. Therefore, the first and second attaching screws  22  and  25  and the first and second through-holes  4  and  5  do not influence the positioning precision. 
     As described above, the conventional magnetic recording and reproduction apparatus  100  requires two positioning pins  6  and  7  in correspondence with two positioning holes  10  and  12  in order to provide a positioning precision of the rotation head cylinder  2  to the substrate  1 . Such an arrangement undesirably complicates the structure of the magnetic recording and reproduction apparatus. Furthermore, since a large number of elements are required to be precisely positioned relative to each other, there is a high possibility of imprecise positioning of the rotation head cylinder  2 . 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a magnetic recording and reproduction apparatus for recording and reproducing a signal to and from a magnetic tape includes a substrate having a first positioning engagement hole and a second positioning engagement hole; a rotation head cylinder provided on the substrate and having the magnetic tape wound therearound over a prescribed angle, the rotation head cylinder having a first female screw and a second female screw; a first attaching screw having a first cylindrical section for insertion into the first positioning engagement hole and engagement with the first female screw; and a second attaching screw having a second cylindrical section for insertion into the second positioning engagement hole and engagement with the second female screw. The first cylindrical section has a diameter A 1 , the first positioning engagement hole has a diameter B 1 , the second cylindrical section has a diameter A 2 , and the second positioning engagement hole has a width B 2 , and A 1 , A 2 , B 1  and B 2  fulfill the following relationships: 
     
       
         0.0002 mm&lt;B 1 -A 1 &lt;0.1 mm, 
       
     
     and 
     
       
         0.0002 mm&lt;B 2 -A 2 &lt;0.1 mm. 
       
     
     According to another aspect of the invention, a magnetic recording and reproduction apparatus for recording and reproducing a signal to and from a magnetic tape includes a substrate having a first positioning engagement hole and a second positioning engagement hole; a rotation head cylinder provided on the substrate and having the magnetic tape wound therearound over a prescribed angle, the rotation head cylinder having a first female screw and a second female screw; a first attaching screw having a first male screw for insertion into the first positioning engagement hole and engagement with the first female screw; and a second attaching screw having a second male screw for insertion into the second positioning engagement hole and engagement with the second female screw. The first male screw has a diameter A 1 , the first positioning engagement hole has a diameter B 1 , the male screw has a diameter A 2 , and the second positioning engagement hole has a width B 2 , and A 1 , A 2 , B 1  and B 2  fulfill the following relationships: 
     
       
         0.0002 mm&lt;B 1 -A 1 &lt;0.1 mm, 
       
     
     and 
     
       
         0.0002 mm&lt;B 2 -A 2 &lt;0.1 mm. 
       
     
     In one embodiment of the invention, one of the first and second positioning engagement holes is circular and the other of the first and second positioning engagement holes is substantially slot-shaped. 
     In one embodiment of the invention, the magnetic recording and reproduction apparatus further includes a third attaching screw for insertion into a third positioning engagement hole of the substrate. 
     In one embodiment of the invention, the third attaching screw has a clearance equal to or greater than 0.1 mm when inserted into the third positioning engagement hole. 
     In one embodiment of the invention, a first coil spring is provided between a head of the first attaching screw and the substrate and a second coil spring is provided between a head of the second attaching screw and the substrate, the first and second coil springs respectively loading the first and second attaching screws in a direction so as to pressure-contact the rotation head cylinder to the substrate. 
     In one embodiment of the invention, the substrate further has an assembly projection for insertion into an assembly hole of the rotation head cylinder. 
     In one embodiment of the invention, the assembly projection has a clearance equal to or greater than 0.1 mm when inserted into the assembly hole. 
     Thus, the invention described herein makes possible the advantages of providing a magnetic recording and reproduction apparatus in which the positioning of a rotation head cylinder on a substrate is achieved with a sufficiently high level of precision while providing a simple structure. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a magnetic recording and reproduction apparatus according to a first example of the present invention; 
     FIG. 2 is a plan view of a substrate of the magnetic recording and reproduction apparatus shown in FIG. 1; 
     FIG. 3 is a bottom view of a rotation head cylinder of the magnetic recording and reproduction apparatus shown in FIG. 1; 
     FIG. 4 is a side view of a first attaching screw used to attach the rotation head cylinder to the substrate of the magnetic recording and reproduction apparatus shown in FIG. 1; 
     FIG. 5 is a side view of a second attaching screw used to attach the rotation head cylinder to the substrate of the magnetic recording and reproduction apparatus shown in FIG. 1; 
     FIG. 6 is a cross-sectional view of the magnetic recording and reproduction apparatus taken along line F—F in FIG. 1; 
     FIG. 7 is a plan view of a magnetic recording and reproduction apparatus according to a second example of the present invention; 
     FIG. 8 is a side view of a first attaching screw used to attach a rotation head cylinder to a substrate of the magnetic recording and reproduction apparatus shown in FIG. 7; 
     FIG. 9 is a side view of a second attaching screw used to attach the rotation head cylinder to the substrate of the magnetic recording and reproduction apparatus shown in FIG. 7; 
     FIG. 10 is a cross-sectional view of the magnetic recording and reproduction apparatus taken along line G—G in FIG. 7; 
     FIG. 11 is a plan view of a conventional magnetic recording and reproduction apparatus; 
     FIG. 12 is a plan view of a substrate of the conventional magnetic recording and reproduction apparatus shown in FIG. 11; 
     FIG. 13 is a bottom view of a rotation head cylinder of the conventional magnetic recording and reproduction apparatus shown in FIG. 11; 
     FIG. 14 is a side view of a first attaching screw used to attach the rotation head cylinder to the substrate of the conventional magnetic recording and reproduction apparatus shown in FIG. 11; 
     FIG. 15 is a side view of a second attaching screw used to attach the rotation head cylinder to the substrate of the magnetic recording and reproduction apparatus shown in FIG. 11; 
     FIG. 16 is a cross-sectional view of the magnetic recording and reproduction apparatus taken along line H—H in FIG. 11; and 
     FIG. 17 is a cross-sectional view of the magnetic recording and reproduction apparatus taken along line I—I in FIG.  11 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the present invention will be described by way of illustrative examples with reference to the accompanying drawings. 
     EXAMPLE 1 
     FIG. 1 is a plan view of a magnetic recording and reproduction apparatus  200  according to a first example of the present invention. As shown in FIG. 1, the magnetic recording and reproduction apparatus  200  includes a substrate  1  and a rotation head cylinder  2  attached to a cylinder attachment section  3  of the substrate  1 . 
     FIG. 2 is a plan view of the substrate  1 . The substrate  1  has a first positioning engagement hole  20  and a second positioning engagement hole  21 . The first positioning engagement hole  20  is circular and has a diameter B 1 . The second positioning engagement hole  21  is substantially slot-shaped and has a width B 2 . 
     FIG. 3 is a bottom view of the rotation head cylinder  2 . The cylinder  2  has a first female screw  8  and a second female screw  9 . 
     FIG. 6 is a cross-sectional view of the magnetic recording and reproduction apparatus  200  taken along line F—F in FIG.  1 . As shown in FIG. 6, the rotation head cylinder  2  is attached to the substrate  1  via a first attaching screw  22  inserted into the first positioning engagement hole  20  of the substrate  1  and a second attaching screw  25  inserted into the second positioning engagement hole  21  of the substrate  1 . 
     FIG. 4 is a side view of the first attaching screw  22 . The first attaching screw  22  includes a (first) cylindrical section  23  having a diameter A 1  and a (first) male screw  24  projecting from the first cylindrical section  23 . FIG. 5 is a side view of the second attaching screw  25 . The second attaching screw  25  includes a (second) cylindrical section  26  having a diameter A 2  and a (second) male screw  27  projecting from the second cylindrical section  26 . 
     Returning to FIG. 6, the first attaching screw  22  is inserted through the first positioning engagement hole  20  of the substrate  1 , so that the first male screw  24  is engaged with the first female screw  8  of the rotation head cylinder  2 . A (first) coil spring  14   a , interposed between a head of the first attaching screw  22  and the substrate  1 , loads the first attaching screw  22  in such a direction as to pressure-contact the rotation head cylinder  2  to the substrate  1 . Likewise, the second attaching screw  25  is inserted through the second positioning engagement hole  21  of the substrate  1 , so that the second male screw  27  is engaged with the second female screw  9  of the rotation head cylinder  2 . A (second) coil spring  14   b , interposed between a head of the second attaching screw  25  and the substrate  1 , loads the second attaching screw  25  in such a direction to pressure-contact the rotation cylinder  2  to the substrate  1 . 
     Generally in a magnetic recording and reproduction apparatus, the rotation head cylinder needs to be positioned relative to the substrate in a predetermined position with a high level of precision so as to provide reliable operation of the apparatus. The DV (digital video) Standards are provided for magnetic recording and reproduction apparatuses of systems in which a rotatable head disposed on a rotation head cylinder helically scans a magnetic tape. According to the DV Standards, a magnetic tape having a width of 6.35 mm is wound around a rotation head cylinder having a diameter of 21.7 mm over 174 degrees. The rotation head cylinder is inclined at 9.15 degrees with respect to the substrate. When the rotation head cylinder rotates at 9000 rev/min and the magnetic tape runs at a speed of 18.83 mm/sec so as to record/reproduce a signal to/from the magnetic tape, the linearity of the running locus of a rotation head with respect to the magnetic tape needs to be within 0.003 mm. In the first example, the positioning precision of the rotation head cylinder  2  on the substrate  1  with respect to the above DV Standards is determined by the relationships between A 1 , A 2 , B 1  and B 2 . 
     Table 1 shows the relationship between A 1  and B 1 , and the evaluation of the linearity of the running locus of the rotation head with respect to the magnetic tape. Table 2 shows the relationship between A 2  and B 2 , and the evaluation of the linearity of the running locus of the rotation head with respect to the magnetic tape. 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Relationship between A1 and B1 
                 Evaluation 
               
               
                   
                   
               
             
             
               
                   
                    0 ≦ B1 − A1 ≦ 0.0002 
                 Poor 
               
               
                   
                 0.0002 &lt; B1 − A1 ≦ 0.01 
                 Good 
               
               
                   
                  0.01 &lt; B1 − A1 ≦ 0.05 
                 Good 
               
               
                   
                  0.05 &lt; B1 − A1 &lt; 0.1 
                 Good 
               
               
                   
                   0.1 ≦ B1 − A1 ≦ 0.2 
                 Poor 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Relationship between A2 and B2 
                 Evaluation 
               
               
                   
                   
               
             
             
               
                   
                    0 ≦ B2 − A2 ≦ 0.0002 
                 Poor 
               
               
                   
                 0.0002 &lt; B2 − A2 ≦ 0.01 
                 Good 
               
               
                   
                  0.01 &lt; B2 − A2 ≦ 0.05 
                 Good 
               
               
                   
                  0.05 &lt; B2 − A2 &lt; 0.1 
                 Good 
               
               
                   
                   0.1 ≦ B2 − A2 ≦ 0.2 
                 Poor 
               
               
                   
                   
               
             
          
         
       
     
     In Tables 1 and 2, the relationships of 0≦B 1 -A 1 ≦0.0002 and 0≦B 2 -A 2 ≦0.0002 result in the evaluation of “poor” linearity of the running locus. The reason is that the clearance between the first cylindrical section of the first attaching screw and the first positioning engagement hole, and the clearance between the second cylindrical section of the second attaching screw and the second positioning engagement hole, are each too small to allow the first and second cylindrical sections to respectively pass through the first and second positioning engagement holes. 
     The relationships of 0.1≦B 1 -A 1 ≦0.2 and 0.1≦B 2 -A 2 ≦0.2 also result in the evaluation of “poor” linearity of the running locus. The reason is that too high a positioning error of the rotation head cylinder on the substrate results, and as such, the linearity of the locus exceeds 0.003 mm as set by the DV Standards. Accordingly, A 1 , A 2 , B 1  and B 2  are set to have the following relationships. 
     
       
         0.0002 mm&lt;B 1 -A 1 &lt;0.1 mm 
       
     
     
       
         0.0002 mm&lt;B 2 -A 2 &lt;0.1 mm 
       
     
     Due to such relationships of A 1 , A 2 , B 1  and B 2 , the magnetic recording and reproduction apparatus  200  according to the first example of the present invention includes a rotation head cylinder which is positioned with respect to the substrate of the apparatus with a sufficiently high level of precision to provide reliable operation without requiring dedicated positioning pins or dedicated positioning holes as is conventional. 
     EXAMPLE 2 
     FIG. 7 is a plan view of a magnetic recording and reproduction apparatus  300  according to a second example of the present invention. As shown in FIG. 7, the magnetic recording and reproduction apparatus  300  includes a substrate  1  and a rotation head cylinder  2  attached to a cylinder attachment section  3  of the substrate  1 . 
     FIG. 10 is a cross-sectional view of the magnetic recording and reproduction apparatus  300  taken along line G—G in FIG.  7 . In FIGS. 7 and 10, identical elements previously discussed with respect to FIGS. 1,  2 ,  3  and  6  bear identical reference numerals thereto and the detailed descriptions thereof will be omitted. 
     As shown in FIG. 10, the rotation head cylinder  2  is attached to the substrate  1  via a first attaching screw  28  inserted into the first positioning engagement hole  20  of the substrate  1  and a second attaching screw  30  inserted into the second positioning engagement hole  21  of the substrate  1 . 
     FIG. 8 is a side view of the first attaching screw  28 . The first attaching screw  28  includes a (first) male screw  28  having a diameter A 1 . FIG. 9 is a side view of the second attaching screw  30 . The second attaching screw  30  includes a (second) male screw  31  having a diameter A 2 . The first and second male screws  29  and  31  respectively correspond to first and second cylindrical sections of the first and second attaching screws  28  and  30 . 
     Returning to FIG. 10, the first male screw  29  of the first attaching screw  28  is inserted into the first positioning engagement hole  20  of substrate  1  and is engaged with the first female screw  8  of the rotation head cylinder  2 . A coil spring  14   a , interposed between a head of the first attaching screw  28  and the substrate  1 , loads the first attaching screw  28  in such a direction as to pressure-contact the rotation head cylinder  2  to the substrate  1 . Likewise, the second male screw  31  of the second attaching screw  30  is inserted into the second positioning engagement hole  21  of the substrate  1  and is engaged with the second female screw  9  of the rotation head cylinder  2 . A coil spring  14   b , interposed between a head of the second attaching screw  30  and the substrate  1 , loads the second attaching screw  30  in such a direction as to pressure-contact the rotation cylinder  2  to the substrate  1 . 
     Tables 1 and 2 shown above regarding the magnetic recording and reproduction apparatus  200  in the first example are also applicable to the magnetic recording and reproduction apparatus  300  in the second example. 
     The relationships of 0≦B 1 -A 1 ≦0.0002 and 0≦B 2 -A 2 ≦0.0002 result in the evaluation of “poor” linearity of the running locus. The reason is that the clearance between the first male screw and the first positioning engagement hole, and the clearance between the second male screw and the second positioning engagement hole, are each too small to allow the first and second male screws to respectively pass through the positioning engagement holes. 
     The relationships of 0.1≦B 1 -A 1 ≦0.2 and 0.1≦B 2 -A 2 ≦0.2 also result in the evaluation of “poor” linearity of the running locus. The reason is that too high a positioning error of the rotation head cylinder on the substrate results, and as such, the linearity of the locus exceeds 0.003 mm as set by the DV Standards. Accordingly, A 1 , A 2 , B 1  and B 2  are set to have the following relationships. 
     
       
         0.0002 mm&lt;B 1 -A 1 &lt;0.1 mm 
       
     
     
       
         0.0002 mm&lt;B 2 -A 2 &lt;0.1 mm 
       
     
     Due to such relationships of A 1 , A 2 , B 1  and B 2 , the magnetic recording and reproduction apparatus  300  according to the second example of the present invention includes a rotation head cylinder which is positioned with respect to the substrate of the apparatus with a sufficiently high level of precision to provide reliable operation without requiring dedicated positioning pine or dedicated positioning holes as is conventional. 
     In the first and second examples, only two attaching members (e.g., the attaching screws) and only two holes (e.g., positioning engagement holes) are used for attaching the rotation head cylinder to the substrate. In addition to this, the substrate may have another (third) attaching hole into which another (third) attaching screw is inserted. In this case, a cylindrical section of the additional attaching screw and attaching hole need to have a clearance equal to or greater than 0.1 mm, so that the provision of the additional attaching screw and attaching hole does not influence the positioning precision of the rotation head cylinder to the substrate based on the diameter relationships of the other two attaching screws and attaching holes. 
     In the first and second examples, coil springs are used to attach the rotation head cylinder to the substrate via the first and second attaching screws. Alternatively, the rotation head cylinder may be attached to the substrate via the first and second attaching screws without using the coil springs. 
     The rotation head cylinder and the substrate may be easily assembled together by forming an assembly hole in a bottom surface of the rotation head cylinder and providing an assembly projection on the substrate which is inserted into the assembly hole. The assembly hole and the assembly projection need to have a clearance equal to or greater than 0.1 mm, so that the provision of the assembly hole and assembly protection does not influence the positioning precision of the rotation head cylinder to the substrate based on the diameter relationships of the two attaching screws and attaching holes. 
     As described above, according to the present invention, the relationship between the diameter of a first positioning engagement hole and the diameter of the cylindrical section of an attaching screw, which is to be engaged with the first positioning engagement hole, and the relationship between the width of a second positioning engagement hole and the diameter of the cylindrical section of an attaching screw, which is to be engaged with the second positioning engagement hole, are appropriately defined so as to provide precise positioning of the rotation head cylinder on the substrate for reliable operation. Therefore, the rotation head cylinder can be attached to the substrate with a high level of precision without providing dedicated positioning pine on the substrate or forming dedicated positioning holes in the rotation head cylinder. 
     Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.