Abstract:
Disclosed herein is a step motor, including a lead screw, a rotor fixed to an outer surface of the lead screw, a fixture containing a stator disposed to face the rotor and a housing whose one side end part is open to insert the stator and wrap the stator, and a bracket having a bracket body of a plate shape on which the housing is disposed and a bending part bent towards the one side end part of the housing from the bracket body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119 of Korean Application No. 10-2009-0095435, filed Oct. 8, 2009, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention is directed to a step motor. 
     2. Description of the Related Art 
     An ODD (Optical Disk Driver) includes a step motor. The step motor is installed inside the optical disk driver to drive an optical pick-up. The optical pick-up travels along in a radial direction of an optical disk by means of a step motor whilst reading a data recorded in a disk or recording data into a disk. 
     In general, a step motor encompasses a bracket and a housing. The bracket and housing rotatably supports one end and the other end of a lead screw. One pair of bobbins may be installed at the inner part of a housing. A coil winds on the outer surface of a bobbin, and a tooth yoke is coupled at the inner surface of a bobbin. Around an outer surface of a lead screw positioned inside the housing is fixed a rotor. 
     In a case the housing is welded to a bracket, a coupling intensity between the housing and the bracket turns lowered. Thus, by an external force from outside, a warping of the bracket and/or housing may be easily observed. 
     When the housing and/or the bracket may be bent by the external force, a gap formed between the rotor formed on the lead screw and the stator is changed so that noise during the rotation of the lead screw may be generated or a torque of a step motor may be decreased. 
     BRIEF SUMMARY 
     The present invention provides a step motor having an enhanced coupling intensity between a housing and a bracket by improving a coupling structure of the housing and the bracket. 
     A step motor of the present invention includes a lead screw; a rotor fixed to an outer surface of the lead screw; a fixture containing a stator disposed to face the rotor and a housing whose one side end part is open to insert the stator and wrap the stator and; and a bracket having a bracket body of a plate shape on which the housing is disposed and a bending part bent towards the one side end part of the housing from the bracket body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an upper surface of a step motor of the present invention; 
         FIG. 2  is a perspective view showing a rear surface of a step motor of the present invention; and 
         FIG. 3  is a floor cross-sectional view of a cut plane ‘A’ in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective view showing an upper surface of a step motor of the present invention,  FIG. 2  is a perspective view showing a rear surface of a step motor of the present invention, and  FIG. 3  is a floor cross-sectional view of a cut plane ‘A’ in  FIG. 1 . 
     Hereinafter, a step motor and an assembling method thereof of the present invention will be described in detail with reference to  FIG. 1  and  FIG. 3  together. 
     The depicted step motor  100  includes a lead screw  130 , a rotor  150 , a stator  140 , a housing  120  and a bracket  110 . 
     The stator  140  is formed of cylindrical shape for inserting the rotor  150 , the stator  140  has wired on its surface by a coil  142  producing a magnetic field, and the stator  140  is fixed within the cylindrical housing  120 . 
     By means of an electric power applied to the coil  142  winded into the stator  140 , a magnetic field from the coil  142  is produced, and on the strength of a repulsion force from the magnetic field from the coil  142  and a magnetic field produced by a magnet  152  included in the rotor  150 , the rotor  150  rotates. 
     The lead screw  130  may be coupled to the inner surface of the rotor  150  formed with a pipe shape, the lead screw  130  rotates together with the rotor  150 . 
     The stator  140  includes a bobbin  141  disposed inside the housing  120 , a coil  142  winded on an outer surface of the bobbin  141 , and a tooth yoke  143  coupled at the inner side of the bobbin  141 . 
     One end part of a lead screw  130  disposed outside the housing  120  is supported by a ball bearing (not shown) coupled to one side of the bracket  110  and a ball sheet (not shown) supportive of this. 
     The one end part and the other opposite part of a lead screw  130  coupled to the bracket  110  is supported by a thrust holder  170  coupled into the housing  120 . 
     While a ball bearing is not interposed between the other end part of a lead screw and a thrust holder  170 , it is also allowable to interpose any ball bearing between the other end part of the lead screw  130  and the thrust holder  170 . 
     On the one hand, in order to give pressure to the thrust holder  170  in an axial direction of the lead screw  130 , a plate spring  210  is coupled to a later-described bending part  110   b  formed perpendicularly to the bracket  110 . 
     The plate spring  210  gives pressure by a predetermined force to the lead screw  130  contacting with the thrust holder  170 , to improve a rotation torque of a motor and realize low-level noise. 
     The housing  120  is formed of cylindrical shape being one side open, and the housing  120  includes a body part  120   a  and a lateral surface part  120   b.    
     The body part  120   a  may be formed of cylindrical shape, and the body part  120   a  extends to an axial direction of the lead screw  130 . On the lower surface of the body part  120   a  among the body part  120   a  facing a later-described bracket  110 , a coupling part  127  protruded from the lower surface of the body part  120   a  is formed as shown in  FIG. 2 . 
     The body part  120   a  has a stator insertion groove  126  inserting the stator  140 . 
     The lateral surface part  120   b  may be formed at one end part of the body part  120   a , and the lateral surface part  120   b  has a through hole  124  running through the lead screw  130 . 
     The other end part  120   c  opposite to the one end part of the body part  120   a  that forms the lateral surface part  120   b  may be open, and a stator  140  wrapping out the rotor  150  disposed at the outer surface of the lead screw  130  inserts into the other part  120   c.    
     To reduce rotating noise of the lead screw  130  and also prohibit rocking of the housing  120 , a step motor  100  may include a guide member  200 . One side of the guide member  200  adheres to the stator  140 , and another side opposing said one side of the guide member  200  is disposed at the bending part  110   b  of a later described bracket  110 . 
     The housing  120  may be disposed on the bracket  110 . One side of the bracket  110  at which the housing  120  is disposed rotatively supports an end part of the lead screw  130  protruded from the housing  120 , the other side opposite to said one side of the bracket  110  is bent in a housing  120  destined direction, and the other end part  120   c  of the body part  120   a  of a housing  120  is fixed to the bent other side in a bracket  110 . 
     The bracket  110  includes a bracket body  110   a  fixing the body part  120   a  of a housing  120 , and a bending part  110   b  bent from the bracket  110  and having an opening formed to fix the other end part  120   c  of the housing  120 . 
     A bracket body  110   a  of the bracket  110  fixed to the body part  120   a  of the housing  120  is provided with an opening part  110   c  inserting at least one of the body part  120   a  of the housing  120 . 
     A portion of contacting the body part  120   a  of the housing  120  with the bracket body  110   a  of the bracket  110  has a first welding part W 1 , a portion of contacting the other end part  120   c  of the body part  120   a  of the housing  120  with the bending part  110   b  of the bracket  110  has a second welding part W 2 , and a portion of contacting the body part  120   a  of the housing  120  with an opening part  110   c  of the bracket  110  forms a third welding part W 3 . 
     At least one of the first through third welding part W 1 , W 2 , W 3  may be welded, and as a result, the housing  120  is firmly coupled to the bracket  110 . 
     Hereinafter, a description will be provided with regard to an assembling method of the step motor  100  of the present invention. When the housing  120  is fixed to the bracket in accordance with the present invention, the housing  120  is disposed on the bracket  110  and the other end part  120   c  of the body part  120   a  of the housing  120  is fixed to the bending part  110   b  of the bracket  110  so that an entire housing  120  can be supported by the bracket  110 . Therefore, a warp occurrence of the housing  120  can be prohibited and a change to a coaxial state of the lead screw  130  can be prevented. 
     The stator  140  may be inserted inside the housing  120  through the other end part  120   c  of the body part  120   a  of the housing  120 . Successively, the lead screw  130  may be inserted from the other end part  120   c  of the body part  120   a  of the housing  120  towards a through hole  124 . 
     Successively, at least one of a thrust holder  170  supporting one side of the lead screw  130  and a guide member  200  adhering to the stator  140  may be inserted inside the housing  120  from the other end part  120   c  of the body part  120   a  of the housing  120 . Accordingly, the rocking and rotating noise of a motor can be reduced. 
     The other end part  120   c  of the body part  120   a  of the housing  120  is fixed to one side of the bending part  110   b  of the bracket  110 , and a plate spring  210  is fastened to outside of the bending part  110   b  of the bracket  110 . Accordingly, the thrust holder  170  may be given pressure by the plate spring  210  in an axial direction of the lead screw  130 , and resultantly, uniform pressure may be applied to the lead screw  130 . 
     The bracket  110  and the housing  120  are fastened using at least one of the first welding part W 1 , the second welding part W 2  and the third welding W 3 . By doing this, the bracket  110  can support the entire part of the housing  120 , and a warp occurrence of the housing  120  or a coaxial twisting of the lead screw  130  will be prohibited. 
     While embodiments according to the present invention have been described above, these are only by way of example and it would be understood by those skilled in the art that any embodiment of various modifications and equivalents can be made thereto. Thus, the genuine technical scope of the present invention should be defined from the accompanying claims.