Abstract:
A method for assembling a head-drum assembly for a magnetic recording/reproducing apparatus is provided. The head-drum assembly is assembled by inserting a shaft to a fixed drum first, setting up a motor stator in the fixed drum, and putting a rotary drum assembly and drum cover assembly into the shaft sequentially. The method can reduce the number of part to be abandoned due to a defect caused in the assembly process by performing a process of assembling the shaft and the fixed drum first, an area in which most defects are caused, and then proceeding to the subsequent assembly processes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. 119(a) of Korean Patent Application No. 2004-48811 filed Jun. 28, 2004, in the Korean Intellectual Property Office, the entire contents of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention:  
         [0003]     The present invention relates to a head-drum assembly for a magnetic recording/reproducing apparatus. More particularly, the present invention relates to a method for assembling a head-drum assembly which is used for a magnetic recording/reproducing apparatus such as a small-sized camcorder including a digital video camera (DVC).  
         [0004]     2. Description of the Related Art:  
         [0005]     Generally, a magnetic recording/reproducing apparatus such as a small-sized camcorder including a digital video camera (DVC), and a videocassette recorder (VCR) comprises a head-drum assembly in the deck. The head-drum assembly includes a magnetic head that is formed to be rotatable at a high-rate and records/reproduces video data by scanning magnetic tape.  
         [0006]      FIG. 1  is a cross-sectional view illustrating a head-drum assembly which is set up in a deck of a magnetic recording/reproducing apparatus, i.e., a small-sized camcorder.  
         [0007]     As shown in the drawing figure, the head-drum assembly  100  comprises a rotary drum  110 , a fixed drum  120 , and a drum cover  130 .  
         [0008]     The rotary drum  110  is set up in a shaft  140  to be rotatable and support a magnetic head (h) for recording/reproducing video data by scanning magnetic tape (not shown) that runs on the rotary drum  110 .  
         [0009]     The fixed drum  120  and the drum cover  130  are press-fitted over the lower and upper parts of the shaft  140  respectively with the rotary drum  110  placed therebetween.  
         [0010]     The drum cover  130  is disposed in the upper part of the rotary drum  110 , which is shown in  FIG. 2 . The drum cover  130  includes a conductive bush unit  131 , a cover unit  132 , and a grounding plate  133 .  
         [0011]     The bush unit  131  is shaped in a flange to which the shaft  140  is press-fitted. The cover unit  132  is formed using a resin molding method to be connected with the bush unit  131  by a pair of screws S. Then, the grounding plate  133  is supported by any one of the screws (S) to be exposable on the top surface of the cover unit  132 , and it is electrically connected to a sub-circuit substrate  153 .  
         [0012]     Between the rotary drum  110  and the drum cover  130 , a pair of rotation transformers  151  and  152  are formed proximately to each other to communicate signals with the magnetic head (h) and the sub-circuit substrate  153 , individually.  
         [0013]     A motor rotor  160  including a doughnut-shaped magnet  162  in an annular rotor case  161  is disposed on the bottom surface of the rotary drum  110 , and a motor stator  170  is disposed on the top surface of the fixed drum  120 . The motor stator  170  is fabricated by forming a three-layer fine pattern (FP) coil in a disk shape and placing the disk in close proximity to the doughnut-shaped magnet  162 . Reference numerals ‘ 140   a ’ and ‘ 140   b ’ denote upper and lower bearings, respectively, and a reference numeral ‘ 141 ’ denotes a preload spring.  
         [0014]     The conventional head-drum assembly  100  with the above-described structure is assembled by putting together the shaft  140  and the rotary drum  110  first, inserting the rotary drum  110  with the shaft  140  to the fixed drum  120 , and then putting the drum cover  130  on the top surface of the rotary drum  110  with the fixed drum  120 .  
         [0015]     More specifically, the shaft  140  is press-fitted into the upper bearings  140   a  and the upper bearings  140   a  with the shaft  140  is housed by a bearing housing formed in the upper part of the rotary drum  110 . Then, the preload spring  141  and the lower bearings  140   b  are set up in the inside of the rotary drum  110  as shown in  FIGS. 1 and 2 . After the shaft  140  and the rotary drum  110  are assembled, the magnetic head (h) and the motor rotor  160  are set up in the bottom surface of the rotary drum  110  sequentially, and a rotation transformer  152  is placed on the top surface.  
         [0016]     Subsequently, the fixed drum  120  is assembled with the rotary drum  110  having the shaft  140  press-fitted by setting up the motor stator  170  at a position in confrontation with the motor rotor  160 . Herein, the rotary drum  110  and the fixed drum  120  are assembled by forcedly fitting the shaft  140  to the rotary drum  110  and the fixed drum  120 . Then, the drum cover  130  is joined with the bush member  131  in the upper part of the rotary drum  110  assembled with the fixed drum  120 .  
         [0017]     However, the process of inserting the shaft  140  to the fixed drum  120  is generally performed using a cold pressure insertion, which causes a high defect rate. Once a defect is caused during the insertion process, all the parts set up in the rotary drum  110  and the fixed drum  120  should be abandoned. Therefore, the economic loss due to the abandonment of defective parts is huge, and some improvement is required.  
       SUMMARY OF THE INVENTION  
       [0018]     It is, therefore, an object of the present invention to provide a method for assembling a head-drum assembly for a magnetic recording/reproducing apparatus. The method simplifies the assembly process and minimizes the number of parts that are abandoned when a defect is caused during an assembly process.  
         [0019]     In accordance with an aspect of the present invention, there is provided a method for assembling a head-drum assembly which includes a fixed drum assembly, a rotary drum assembly, and a shaft for supporting the rotary drum assembly to be rotatable with respect to the fixed drum assembly and used for a magnetic recording/reproducing apparatus. The method comprises assembling the fixed drum assembly with the shaft by press-fitting the shaft; and assembling the shaft with the rotary drum assembly by inserting bearings.  
         [0020]     The fixed drum assembly includes a fixed drum, a yoke which comprises a silicon steel plate set up in the fixed drum, and a two-layer fine pattern (FP) coil which is set up in the yoke and forms a motor stator.  
         [0021]     The rotary drum assembly comprises a rotary drum, upper and lower bearings press-fitted into the inner circumference of the rotary drum, a magnetic head, a rotation transformer which is connected with the magnetic head and set up in the top surface of the rotary drum, and a motor rotor which is formed proximately to the motor stator in the lower part of the rotary drum.  
         [0022]     Herein, the motor rotor comprises a rotor case fixed to the rotary drum; and a magnet fixed to the rotor case. The rotor case is a plane having a ring shape.  
         [0023]     In accordance with another aspect of the present invention, there is provided a method for assembling a head-drum assembly for a magnetic recording/reproducing apparatus. The method comprises assembling a fixed drum assembly and a rotary drum assembly; assembling a shaft with the fixed drum assembly; assembling the rotary drum assembly with the shaft to be rotatable; and assembling a drum cover assembly with the shaft protruding from the upper part of the rotary drum assembly.  
         [0024]     In the process of assembling the fixed drum assembly, the shaft is press-fitted into a fixed drum and a fine pattern (FP) coil which comprises two layers and forms a yoke. A motor stator is bonded to the fixed drum.  
         [0025]     Also, the process of assembling the rotary drum assembly comprises preparing a rotary drum; inserting upper and lower bearings to the inner circumference of the rotary drum; setting up a magnetic head in the rotary drum; setting up a first rotation transformer in the rotary drum and connecting the first rotary transformer set up in the rotary drum with the magnetic head; and setting up a motor rotor in the rotary drum.  
         [0026]     The motor rotor includes an annular rotor case having a plane structure, a magnet installed in the rotor case. The rotor case is bonded to the rotary drum while the magnet is bonded to the rotor case.  
         [0027]     The drum cover assembly includes a drum cover, a second rotation transformer proximate to the first rotation transformer, and a sub-circuit substrate, and the drum cover assembly is press-fitted into the shaft with a preload spring inserted between the upper bearing and the drum cover assembly.  
         [0028]     The aspects of the present invention described above can reduce the economic loss caused by a defective part by performing a process of assembling the fixed drum and the shaft, in which most defects are caused, first and, if a defect is generated during the assembling process, only abandoning the fixed drum and the shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The above aspects and features of the present invention will be more apparent by describing certain embodiments of the present invention with reference to the accompanying drawings, in which:  
         [0030]      FIG. 1  is a cross-sectional view illustrating a conventional head-drum assembly;  
         [0031]      FIG. 2  is an exploded perspective view illustrating the head-drum assembly of  FIG. 1 ;  
         [0032]      FIG. 3  is a cross-sectional view illustrating a head-drum assembly in accordance with an embodiment of present invention; and  
         [0033]      FIGS. 4A  to  4 C are cross-sectional views illustrating an example for assembling the head-drum assembly sequentially in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     Certain embodiments of the present invention will be described in greater detail with reference to the accompanying drawings.  
         [0035]     The matters defined in the description such as a detailed construction and elements are exemplary. Thus, it should be apparent that the present invention can be performed without the specific examples. Also, well-known functions or constructions are not described in detail for conciseness.  
         [0036]      FIG. 3  is a cross-sectional view illustrating a head-drum assembly  200  for a magnetic recording/reproducing apparatus in accordance with an embodiment of the present invention.  
         [0037]     As shown in the drawing, the head-drum assembly  200  comprises a shaft  210 , a rotary drum assembly  220  (see  FIG. 4B ), a fixed drum assembly  230  (see  FIG. 4A ), and a drum cover assembly  240  (see  FIG. 4C ).  
         [0038]     The shaft  210  supports the rotary drum assembly  220 , the fixed drum assembly  230 , and the drum cover assembly  240  by being in the rotational center of the rotary drum assembly  220 , the fixed drum assembly  230 , and the drum cover assembly  240 .  
         [0039]     The rotary drum assembly  220  includes a rotary drum  220   a , a magnetic head  221 , a first rotation transformer  223 , and a motor rotor  260 .  
         [0040]     The rotary drum  220   a  is set up to be rotatable by upper and lower bearings  211  and  212  with respect to the shaft  210 . Herein, it is preferred that the upper and lower bearings  211  and  212  have the same inner diameter.  
         [0041]     The magnetic head  221  reads video data by scanning a magnetic tape (not shown). The magnetic head  221  is connected to the first rotation transformer  223 .  
         [0042]     The first rotation transformer  223  communicates signals with a second rotation transformer  243  which is set up in a position corresponding to the drum cover assembly  240  to thereby transmit the signals from the magnetic head  221  to a sub-circuit substrate  250 , which will be described below.  
         [0043]     The motor rotor  260  includes an annular rotor case  261  and a magnet  262 . The annular rotor case  261  is a plane fabricated without requiring an additional process such as bending, and the magnet  262  is formed in the shape of a doughnut and bonded to the lower part of the annular rotor case  261 .  
         [0044]     The fixed drum assembly  230  includes a fixed drum  230   a  and a motor stator  270 . The fixed drum  230   a  is positioned under the rotary drum  220   a . The motor stator  270  is set up on the top surface of the fixed drum  230   a  and includes a fine pattern (FP) coil  271  and a yoke  272 .  
         [0045]     The FP coil  271  is formed in the shape of a disk having two layers and proximal to the doughnut-shaped magnet  262 . The yoke  272  is set up to prevent Eddy Current Loss phenomenon of a magnetic field that is formed in the bottom surface of the FP coil  271 . Preferably, the yoke  272  comprises a silicon steel plate.  
         [0046]     If the yoke  272  comprises a silicon steel plate, the material cost can be reduced while the same performance is achieved, compared to a conventional ferrite yoke. In the drawing, a reference numeral ‘ 280 ’ denotes a motor FPC that conveys a control signal to the motor stator  270 .  
         [0047]     The drum cover assembly  240  includes a drum cover  240   a , a second rotation transformer  243 , and a sub-circuit substrate  250 .  
         [0048]     As shown in  FIG. 2 , the drum cover  240   a  is positioned in and connected with the upper part of the rotary drum  220   a  by the shaft  210  press-fitted thereto. The sub-circuit substrate  250  in the inside of the drum cover  240   a  is positioned to be connected with the second rotation transformer  243 . Meanwhile, since the sub-circuit substrate  250  has a ground line positioned therein, it does not require an additional ground screw.  
         [0049]     Hereafter, a method for assembling a head-drum assembly for a magnetic recording/reproducing apparatus, which is suggested in an embodiment of the present invention, will be described with reference to  FIGS. 4A  to  4 C.  
         [0050]     The first step of the head-drum assembly assembling method, according to an embodiment of the present invention is to insert the shaft  210  to the fixed drum  230   a  by using a cold pressure insertion method, which is illustrated in  FIG. 4A . Herein, if a defect is caused during the process of inserting the shaft  210  to the fixed drum  230   a , the parts of the defect are abandoned. Only when the shaft  210  is connected with the fixed drum  230   a  normally, the motor stator  270  is positioned in the fixed drum  230   a  to thereby form a fixed drum assembly. Herein, the yoke  272  is bonded onto the fixed drum  230   a , and then the FP coil  271  is bonded onto the top surface of the yoke  272 .  
         [0051]     Subsequently, as shown in  FIG. 4B , the rotary drum assembly  220  is assembled. The upper and lower bearings  211  and  212  are press-fitted into the bearing housings  223  and  225  formed in the upper and lower part of the rotary drum  220   a , and the magnetic head  221  is formed at a predetermined position. Then, the first rotation transformer  223  is formed in the upper part of the rotary drum  220   a  to be connected with the magnetic head  221 , and the motor rotor  260  is positioned in proximity to the motor stator  270  in the lower part of the rotary drum  220   a.    
         [0052]     Subsequently, as illustrated in  FIG. 4C , the fixed drum  230   a  with the shaft  210  press-fitted thereto is connected with the rotary drum  220   a  which is prepared as shown in  FIG. 4B . Herein, the shaft  210  is inserted onto the upper and lower bearings  211  and  212  formed in the rotary drum  220   a  using the cold pressure insertion method.  
         [0053]     As shown in  FIG. 4C , the drum cover assembly  240  is set up in the upper part of the rotary drum  220   a  connected with the fixed drum  230   a . Herein, in the process of assembling the rotary drum assembly  220  with the fixed drum assembly  230 , pressure is applied to the inner hub of the upper and lower bearings  211  and  212  as the shaft  210  is press-fitted. Due to the pressure by the insertion of the shaft  210 , the inner and outer hubs of the bearings may deviate. In order to prevent the deviation, the preload spring  245  is inserted between the rotary drum  220   a  and the drum cover  240   a . The preload spring  245  pressures the inner hub in the direction of the arrow which is illustrated in  FIG. 4C  to thereby arrange the inner and outer hubs of the upper and lower bearings  211  and  212 .  
         [0054]     As described above, if the shaft  210  is inserted onto the fixed drum  230   a  without the motor stator  270  installed yet and if a defect is caused during the shaft insertion, only the shaft  210  and the fixed drum  230   a  need to be abandoned. Therefore, the number of parts to be abandoned is reduced, compared to the conventional head-drum assembly.  
         [0055]     In accordance with the embodiment of the present invention which is described above, the number of parts that are abandoned due to a defect caused in the process of assembling the shaft and the fixed drum is reduced. Therefore, less parts are wasted and the assembling cost can be reduced.  
         [0056]     The foregoing embodiment and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.