Patent Document

CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on Japanese Patent Application No. 2000-384831, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to improvement of a small-sized motor used for lens drive of a camera. 
     2. Description of Related Art 
     FIG. 2 is a sectional view of a small-sized motor with a lead screw, which is used for purposes of lens drive of a camera and the like. As shown in FIG. 2, in this motor, a metal frame  3  having a C-shaped section is fixed to one axial end of a stator  2  opposed to a rotor  1 . Further, a bearing  4   a  is fitted into the other axial end of the stator  2 , and one end of a rotary shaft  11  inserted and fixed into the rotor  1  is rotatably supported by this bearing  4   a.    
     In this rotary shaft  11 , its other end side protrudes from the stator  2 , and its leading end is rotatably supported by a bearing  4   b  fitted into the metal frame  3 . The portion of the rotary shaft  11  protruding from the stator  2 , that is, the portion arranged in the metal frame  3  having the C-shaped section functions as an output portion  11   a , at which a lead screw is formed. By rotation of the rotary shaft  11 , this lead screw feeds axially an operation member (not shown) for operating a lens, whereby the lens is moved. 
     Such a conventional small-sized motor with a lead screw for driving a lens, since the metal frame  3  is attached to one end of the stator  2  as described above, has problems that an attaching method of the motor to another member is limited and that space-saving is difficult. Further, since the bearings  4   a  and  4   b  receiving each end of the rotary shaft  11  are supported respectively by the stator  2  and the metal frame  3  which are different members, shaft accuracy is not easy to obtain. Further, since the number of parts is large, assembly efficiency is bad, which makes it more difficult to obtain the shaft accuracy. 
     The inventors thought that the metal frame  3  was removed from one end of the stator  2  in consideration of the space saving and the assembly efficiency. In this case, it is necessary to fit a metal bearing for rotate-supporting a portion in the middle of the output shaft  11  to one end of the stator  2 , that is, onto the attaching surface of the metal frame  3  in the above-mentioned example. However, regarding fitting of this metal bearing, the workability is bad. In case that the stator  2  and the metal bearing are integrally manufactured by insert molding in consideration of the work performance, a molding die is so complicated so that a problem of high cost is caused. 
     SUMMARY OF THE INVENTION 
     An object of the invention, in view of the above-mentioned problems, is to provide, in a small-sized motor used for lens drive, the motor which is easy to attach to another member and gives space saving. Further, another object of the invention is to provide a motor in which the number of parts is reduced thereby to improve assembly efficiency and shaft accuracy is good. 
     In order to achieve such the objects, a motor of the invention comprises a rotor; a rotary shaft inserted and fixed into the rotor; a stator core constituting a stator opposed to the rotor; an output side bearing provided on an output side of the rotary shaft, and supporting a portion near an output portion of the rotary shaft; and an opposite side bearing holding portion for holding an opposite side bearing supporting an opposite side to the output side of the rotary shaft; wherein the stator core, the output side bearing and the opposite side bearing holding portion are integrally formed by insert molding, and the output side bearing and the opposite side bearing holding portion are made of resin. 
     According to the invention, since the output side bearing and the opposite output side bearing holding portion, which were conventionally constituted by a different member from the stator, are formed integrally with the stator cores by insert molding, the number of parts can be reduced and position accuracy can be improved. 
     Further, the invention is characterized in that in the above-mentioned motor, a lead screw is formed at the output portion and a rotation of the lead screw directly affects an operated member. 
     Further, the invention is characterized in that in the above-mentioned motor, the opposite side bearing, which is urged to the output side and comprises an axially movable slide bearing, is arranged in a hole of the opposite output side bearing holding portion, and that an end of the rotary shaft is supported by this opposite output side bearing. Therefore, the rotary shaft can be exactly rotated axially in the more stable position, so that rotational position accuracy can be heightened. 
     Further, the invention is characterized in that in the above-mentioned motor, a hole having an inner diameter larger than an outer diameter of the rotor is formed in the opposite side bearing holding portion. 
     Further, in order to achieve the objects, a motor of the invention comprises a rotor, and a stator opposed to the rotor and constituted by stator cores, wherein the stator cores, and an output side bearing that rotates and supports a side, near an output portion for operating an operated member, of a rotary shaft inserted and fixed into the rotor are formed integrally by insert molding; the output side bearing is made of a resin; a lead screw is formed from the output portion of the rotary shaft to a portion thereof opposed to an inner surface of the output side bearing; and lubricant is filled in an opposed gap between the lead screw and the output side bearing. 
     According to the invention, since the output side bearing, which was conventionally constituted by a different member from the stator, is formed integrally with the stator cores by insert molding, the number of parts can be reduced and the position accuracy can be improved. Further, according to the invention, the lead screw is formed up to the portion of the rotary shaft opposed to the inner surface of the output side bearing, and the lubricant is filled in its portion. Therefore, though the metal frame that has been used in the related art is removed and the portion in the middle of the rotary shaft is held by the bearing, the rotating operation of the lead screw is smooth and run-out of the shaft is not produced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view showing the whole constitution of a motor in a mode for carrying out the invention; and 
     FIG. 2 is a sectional view showing the whole constitution of a conventional motor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A mode for carrying out the invention will be described below. FIG. 1 is a sectional view showing the whole of a motor in this mode. 
     As shown in FIG. 1, the motor in this mode (herein simply referred to as a motor though the motor in this mode is constituted by a stepping motor) includes a stator  2  and a rotor  1  opposed to this stator  2 . The rotor  1  rotates in a state where it has received the urging force in the axial direction (more specifically, in the direction of an arrow X in FIG. 1) by an urging member  7  which will be described later. 
     In the center of the rotor  1 , a rotary shaft  11  is inserted and fixed so that one side protrudes greatly from the rotor  1 . A base portion of the protruding portion of the rotary shaft  11  is supported by an output portion side bearing  41  formed integrally with the stator  2 . The output shaft  11  passes through this output portion side bearing  41  and the leading end of the shaft further protrudes from the output portion side bearing  41 . The protruding portion of the rotary shaft  11  from the output portion side bearing  41  functions as an output portion  11   a  for operating a head member (not shown) that is an operated member for driving a lens. 
     In the rotary shaft, a lead screw is continuously formed from this output portion  11   a  to a portion opposed to an inner surface  41   a  of the output portion side bearing  41  arranged near the output portion  11   a . By this constitution, a head member fitted to the lead screw of the portion which functions as the output portion  11   a  is operated directly by the lead screw. 
     The stator  2  comprises two sets of metal-made stator cores  21  and  22 , which are axially superimposed, and the rotor  1  is rotatably arranged in this stator  2 . Each of the stator cores  21  and  22  has an outer yoke  23  arranged on the axial outside in the state where the stator cores  21  and  22  are superimposed, and an inner yoke  24  arranged adjacently in the superimposed state. These both yokes  23  and  24  are made of a magnetic metal member. Inside of their yokes, polar teeth  25  opposed to the outer surface of a magnet portion  1   a  of the rotor  1  are provided. 
     The two sets of outer yoke  23  and inner yoke  24  are formed integrally with a resin coil bobbin  28  for winding coil wires  26  and  27  thereon by insert-molding, and between a pair of the corresponding inner yoke  24  and the outer yoke  23 , there is a coil wire space for winding the coil wire  26  or  27 . The coil bobbin  28  has coil wire built-in portions  29  and  30  for winding each of the coil wires  26  and  27 , and a hole portion  28   a  that surrounds the rotor  1  at its inner surrounding portion. The surface of the polar teeth  25  is, in this hole portion  28   a , exposed inside the hole, and opposed to a magnet portion  1   a  of the rotor  1  which will be described later. 
     Winding start portions and winding end portions of the coil wires  26  and  27  wound on the coil wire built-in portions  29  and  30  of the coil bobbin  28  are respectively tied on a terminal pin  32   a  erected on a terminal portion  32 . This terminal portion  32  is formed integrally with the coil bobbin  28 , and protruded outward in the radial direction from an opening portion of a metal-made case member  38 . 
     Further, the stator  2 , in FIG. 1, has a cap portion  35  protruded axially from the axial opening portion of the case member  38 . This cap portion  35  is arranged on a rear end side of the rotor  1 , and has a circular hole  35   a  for holding movably in the axial direction the opposite output portion side bearing  42  constituted by a slide bearing that supports the rear end of the rotary shaft  11  of the rotor  1  after the rotor  1  was inserted into the stator  2 . 
     At the assembly, this hole  35   a  functions as an inlet for inserting the rotor  1  into the stator  2 . Therefore, an inner diameter of this hole  35   a  is formed larger than an outer diameter of the magnet portion  1   a  of the rotor  1 . The thus constructed cap portion  35  is formed integrally with the coil bobbin  28  that integrates the stator cores  21  and  22  by the insert molding, and the hole  35   a  of this cap portion  35  becomes a communication hole communicating with the hole portion  28   a.    
     After the opposite output portion side bearing  42  has been fitted into the hole  35   a  of the cap portion  35 , an urging member  7  having a leaf spring  7   a  that comes into contact with the rear end of the opposite output portion side bearing  42  and urges the opposite output portion side bearing  42  onto the output portion side bearing  41  is fitted into the hole  35   a  thereby to be held. Namely, the opposite output portion side bearing  42  that supports the rear end of the rotary shaft  11  of the rotor  1  is located between the urging member  7  and the rotary shaft  11 . The urging member  7  gives always the urging force to the opposite output portion side bearing  42  in the direction toward the output portion side bearing  41 , whereby it urges the rotor  1  onto the output portion side bearing  41  and presses the rotary shaft  11  against the output portion side bearing  41 , so that the rotation of the rotor  1  is stabilized. Namely, the cap portion  35  functions as an opposite output portion side bearing holding portion for holding the urging member  7  and the opposite output portion side bearing  42  that comes into contact with this urging member  7 . 
     Further, onto the end surface of one of the outer yokes  23  of the stator  2 , an attaching plate  41   b  is fixed. In the center of this attaching plate  41   b , the output portion side bearing  41  is fitted. Namely, the output portion side bearing  41  is formed of a resin integrally with the resin cap portion  35  and coil bobbin  28 . The attaching plate  41   b  is fixed to the coil bobbin  28  so as to fit this output portion side bearing  41  into its center hole. 
     To the inner surface  41   a  of the output portion side bearing  41 , the extension portion of the lead screw of the rotary shaft  11  is opposed. In a gap formed by this opposed arrangement, lubricant (not shown) is filled. Therefore, the rotation of the lead screw becomes smooth by this lubricant. 
     The thus constructed output portion bearing  41  functions as a radial bearing that supports the rotary shaft  11  of the rotor  1  rotatably, and as a position control portion that performs position control of the rotor  1  to the thrust position upon reception of the urging force given by the urging member  7 . 
     Therefore, when the rotor  1  is urged by the urging force of the urging member  7  in the direction of an arrow X in FIG. 1, a resin C-shaped washer  11   b  fitted into a narrow part  11   a  of the rotary shaft  11  of the rotor  1  is pressed against the end surface of the output portion side bearing  41 . Namely, the outer diameter of the C-shaped washer  11   b  is formed larger than the hole diameter of the output portion side bearing  41 , and by the movement of the rotor  1  in the direction of the arrow X, the end surface of the C-shaped washer  11   b  is pressed against the end surface of the output portion side bearing  41 . 
     The thus constructed output portion side bearing  41  is made of the resin in which the stator cores  21  and  22  are insert-molded together with the cap portion  35  functioning as the opposite output portion side bearing holding portion. In the hole portion  28   a  of the stator  2 , the rotor  1  is arranged rotatably. 
     The rotor  1  includes the magnet portion  1   a  opposed to the polar teeth  25  of the stator  2 , and the metal-made rotary shaft  11  inserted and fixed into the rotary center hole of this magnet portion  1   a  with adhesive so that its one side protrudes from the axial end surface of the magnet portion  1   a . In a portion of the rotary shaft  11  where is located inside the magnet portion  1   a , an adhesive staying groove  11   d  is formed. 
     Between the portion of the rotary shaft  11  inside the magnet portion  1   a  and the portion of the shaft in which the lead screw is formed, as described above, the narrow part  11   c  is formed, and the resin C-shaped washer  11   b  is fitted to this narrow part  11   c . Further, at the portion of the rotary shaft  11  protruding from the magnet portion  1   a  and at the outer surrounding on the leading end side of the rotary shaft  11  from the narrow part  11   c , the lead screw is formed. 
     This rotor  1  is inserted into the hole portion  28   a  from the cap portion  35  side of the stator  2  with the side where the lead screw is formed at the head, thereby to be built in the stator  2 . Namely, the leading end on the lead screw side of the rotary shaft  11  of the rotor  1  is firstly inserted into the hole  35   a  of the cap portion  35 , and then the leading end side of the lead screw passes through the hole portion  28   a  and the hole of the output portion side bearing  41 . Next, most of the lead screw is protruded from the output portion side bearing  41 . 
     Thereafter, in this state, the opposite output portion side bearing  42  comprising the slide bearing is inserted into the hole  35   a  of the cap portion  35 , and while the leaf spring  7   a  is being brought into contact with the rear end side of this opposite output portion side bearing  42 , the cap portion  35  is covered with the urging member  7 , whereby the motor is assembled. In the thus assembled motor, when the electric current is supplied to the coil wires  26  and  27  of the stator  2 , the rotor  1  is rotated about the rotary shaft  11 , urged onto the output portion side bearing  41  side and supported by the both bearings  41  and  42 . 
     The above-mentioned embodiment is an example of the preferred embodiment of the invention, the invention is not limited to this embodiment, and it is to be understood that various changes and variations may be made without departing from the spirit or scope of the invention. For example, in this embodiment, the lead screw is formed not only at the output portion  11   a  but also up to the position opposed to the inner surface of the output portion side bearing  41 . However, this constitution is not adopted but the lead screw may be formed only at the output portion  11 . 
     Further, in the embodiment, the lead screw is formed on the output portion  11   a  side of the rotary shaft  11 , however the lead screw may not be particularly formed. For example, the lead screw is not formed at the rotary shaft  11  but the rotary shaft may be constituted by only the shaft. Further, a gear may be held at the output portion  11   a  of the rotary shaft  11  in order to transmit the rotational force through the gear to the operated member. 
     As described above, in the invention, the two stator cores arranged, superimposed axially are formed by the insert-molding integrally with the coil bobbin, the output portion side bearing and the opposite output portion side bearing holding portion. Namely, the output portion side bearing and the opposite output portion side bearing holding portion which were constituted by the different member from the stator in the related art are integrated with the stator core by the resin-molding in the invention. Therefore, since assembly error of each member (stator portion and the both bearing) is not produced compared with the related art, shaft accuracy can be improved. Further, the number of parts can be reduced greatly.

Technology Category: 5