Patent Publication Number: US-6713914-B2

Title: Motor assembled by using motor-base-holder and method of assembling the same motor

Description:
This application is a Divisional of U.S. patent application Ser. No. 09/672,216, filed Sept. 28, 2000. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a construction of a mini-motor and a method of assembling the mini-motor at high productivity. More particularly, the present invention relates to a micro-motor producing vibration sensible to a human body. This micro-motor is employed in a cellular-phone to notify a user of a call with the vibration. 
     BACKGROUND ART 
     A motor used in information devices comprises the following elements: 
     a metal base; 
     a bearing, a printed circuit board, and a stator mounted to the metal base; 
     a cylindrical rotor magnet mounted on an outer or inner wall of the stator core, thereby facing the magnet to the stator core. 
     When a motor has a certain size, this structure is easy to assemble; however, downsizing the motor increases difficulties of assembling and lowers the productivity, because assembling machines or operators&#39; finger-tips cannot access to inside or even cannot access close to the motor. 
     The Japanese Patent Application Non-Examined Publication No. H10-127031 addresses the problem discussed above. FIG. 10 illustrates the motor of this prior art. 
     In FIG. 10, metal wired-board  14  is buried in base  24  made of synthetic resin with maintaining the insulation. A first end of board  14  extends over an upper end of base  24  as riser  40 , and a second end is exposed as a connector terminal. 
     This structure allows terminal  42  of winding  18  coiled on stator core  20  to be coupled to riser  40  with ease. 
     However, downsizing the motor reveals a problem, i.e. elements of the motor are hard to handle by operators. For instance, a motor of 10 mm across gives us a difficulty to handle its components quickly. Further downsizing of the motor requires severer mating allowances between the components. This increases the difficulty of assembling the components into a motor. As such, the productivity is traded off for downsizing the motor. A breakthrough method of this problem has been enthusiastically demanded. 
     A section bonded with another section or a section undergone resin-welding needs time before it is fixed to. Shortening this waiting time has been also demanded. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the problems discussed above, and aims to provide a motor having a structure allowing high productivity as well as a method of assembling the same motor by solving problems such as difficulty of handling, severity of mating, time-consuming of bonding or welding. 
     A motor-base-holder of the present invention comprises the following elements: 
     (a) a motor base including; 
     (a-1) a base; 
     (a-2) a bearing supporter protruded vertically from the base for supporting a bearing; 
     (a-3) a stator supporter concentric with the bearing supporter for being mounted with a stator; 
     (a-4) a terminal made of metal plate and insert-molded around the bearing supporter; 
     (b) a frame made of the same metal as the terminal and linked with fringe section of the motor base 
     A motor of the present invention comprises the following elements: 
     (a) a motor base including; 
     (a-1) a base; 
     (a-2) a bearing supporter protruded vertically from the base for supporting a bearing; 
     (a-3) a stator supporter concentric with the bearing supporter; 
     (a-4) a terminal made of metal plate and insert-molded around the bearing supporter; 
     The motor base is formed by cutting off bridges linking between the motor base and the frame around the motor base. 
     (b) a stator mounted to the stator supporter; and 
     (c) a rotor supported by the bearing which is supported by the bearing supporter. 
     Another motor of the present invention comprises the following elements: 
     (a) a stator having a stator core; 
     (b) a motor base including: 
     (b-1) a base; 
     (b-2) a bearing supporter protruded vertically from the base for supporting a bearing; 
     (b-3) a stator supporter concentric with the bearing supporter; 
     (b-4) a stator fixer extending from the stator supporter; and 
     (c) a rotor supported by the bearing supported by the bearing supporter. 
     After the stator core is inserted into the stator supporter, a bushing is press-fitted into the stator fixer, thereby fixing the stator. 
     Still another motor of the present invention comprises the following elements: 
     (a) a motor base including: 
     (a-1) a base; 
     (a-2) a bearing supporter protruded vertically from the base for supporting a bearing; 
     (a-3) a stator supporter; 
     (a-4) a terminal made of metal plate and disposed around the bearing supporter; 
     (a-5) a metal tip extended outside of the motor base; 
     (b) a stator mounted to the stator supporter; 
     (c) a rotor supported by the bearing which is supported by the bearing supporter; and 
     (d) a metal cover of which terminal is fixed to the metal tip, for covering the rotor. 
     The motor discussed above may be assembled through the following steps: 
     (a) positioning and supporting the motor base at a given place by the frame; 
     (b) assembling the stator and the rotor to the motor base; and 
     (c) detaching the motor base from the frame. 
     The present invention discussed above can solve the problems particularly in mini-motors such as difficulties in handling the parts of the motor, difficulties in mating the respective components, time-consuming of bonding or welding. As a result, a motor of high productivity and a method of assembling the motor can be obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross section illustrating a structure of a motor in accordance with a first exemplary embodiment of the present invention. 
     FIG. 2A is a top view of the same motor as shown in FIG.  1 . 
     FIG. 2B is a side view of the same motor as shown in FIG.  1 . 
     FIG. 2C is a bottom view of the same motor as shown in FIG.  1 . 
     FIG. 3A is a plan view of a motor base of the motor shown in FIG.  1 . 
     FIG. 3B is a side view of the motor base of the motor shown in FIG.  1 . 
     FIG. 4 is a plan view of a motor-base-holder. 
     FIG. 5 is an exploded lateral view of the motor shown in FIG.  1 . 
     FIG. 6 illustrates a motor-base-holder in accordance with a second exemplary embodiment of the present invention. 
     FIG. 7 illustrates a motor-base-holder in accordance with a third exemplary embodiment of the present invention. 
     FIG. 8 illustrates a motor-base-holder in accordance with a fourth exemplary embodiment of the present invention. 
     FIG. 9 is a partial lateral view illustrating how a motor cover is fixed to the motor base in accordance with a fifth exemplary embodiment of the present invention. 
     FIG. 10 is a cross section illustrating a structure of a conventional motor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention are demonstrated hereinafter with reference to the attached drawings. 
     Exemplary Embodiment 1 
     FIG. 1 is a cross section illustrating a structure of a motor in accordance with the first exemplary embodiment of the present invention. FIG. 2A is a top view, FIG. 2B is a side view and FIG. 2C is a bottom view of the same motor. FIG. 3A is a plan view of a motor base of the motor shown in FIG.  1 . FIG. 3B is a side view of the same motor base. FIG. 4 is a plan view of a motor-base-holder. FIG. 5 is an exploded lateral view of the motor shown in FIG.  1 . 
     In FIG. 1, the motor comprises a stator, a rotor and a cover. The rotor includes rotor frame  1100  and ring-shaped magnet  1200  mounted to an inner wall of rotor frame  1100 , and revolves on shaft  1400  mounted at the center thereof. Further, eccentric weight  1300  is mounted to frame  1100 , thereby producing vibration when the motor spins. 
     Stator  2000  is mounted to motor base  3101 , and a bearing, i.e. metal  3200 , is mounted to the center of base  3101 . Stator  2000  includes stator core  2100 , wire terminating member  2200 , and winding  2300 . Terminal  3111  of base  3101  is coupled to winding&#39;s terminal  2310 . Shaft  1400  is jounaled by metal  3200 , and cover  3401  covers the rotor. 
     An appearance of the motor used in this first embodiment shows, as illustrated in FIG. 2A, circular cover  3401  on polygonal motor-base  3101 . As shown in FIG. 2B, cover  3401  has some protrusions  3411  and  3421  extended to base  3101 . Some of the protrusions extend to as deep as a lower end of base  3101 , and the other are coupled with metal tip  3121  extended from a side face of base  3101 . On the bottom face of base  3101 , six terminals  3111  are exposed as shown in FIG.  2 C. These exposed terminals can be coupled with a base board (not shown) of a device, e.g. a cellular phone, on which the motor is mounted by re-flow soldering. This coupling allows terminals  3111  to carry electric current from the device board to the stator windings, thereby spinning the rotor. Then weight  1300  produces vibrations to make the device vibrate, and this notifies a device user of a calling. 
     The motor-base of motor by the present invention is detailed hereinafter. 
     As shown in FIG. 3B, motor-base  3101  is made of resin molded, and comprises approx. flat base  3131 , bearing supporter  3141  protruding vertically from the center of base  3131  for supporting the bearing, and stator supporter  3151  concentric with the bearing supporter and for being mounted with the stator. On base  3131 , as shown in FIG. 3A, six terminals  3111  are disposed around bearing supporter  3141 . These terminals  3111  are made of metal plate and insert-molded into base  3131 . The upper face of terminals  3111  are coupled with the windings&#39; terminals of the stator, and the lower face thereof are coupled with the device board by re-flow soldering. 
     The motor-base detailed above is a part of a completed motor; however, the present invention preferably handles the motor-base including a metal frame outside thereof when the motor is assembled, to be more specific, motor-base  3101  with metal frame  4101  added to outside of base  3101  forms motor-base-holder  4001  as shown in FIG.  4 . 
     Now, motor-base-holder  4001  is detailed. 
     Metal frame  4101  shapes in a rectangle with fallen-out section in the center like a picture frame. Motor base  3101  is disposed at the center of holder  4001 . Frame  4101  has six bridges  4201  which are arranged in radial at approx. the same intervals around base  3101 . As such, frame  4101  surrounds and holds base  3101 . Base  3101  is separated off from frame  4101  at perforations  4211  indicated with broken lines. Six round-holes  4301  are punched through frame  4101  for positioning holder  4001 . 
     A process of assembling the motor using holder  4001  is demonstrated with reference to FIG.  5 . 
     First, place holder  4001  on an assembling machine by fitting round-holes  4301  to positioning pins  7101 . 
     Second, mate metal  3200 , i.e. the bearing, in bearing supporter  3141  of the motor-base. 
     Third, insert stator  2000  into stator supporter  3151 . 
     Then press-fit bushing  3300  into stator fixer  3161 . In this embodiment, the outer diameter of stator supporter  3151  is the same as that of stator fixer  3161 . Bushing  3300  and stator fixer  3161  are manufactured to be tightly mated each other. Stator  2000  can be thus fixed to stator supporter just by press-fitting bushing  3300  into stator fixer  3161 . 
     After that, weld the windings&#39; terminals of stator to the terminal of motor-base. A resistance-welding-machine may be used in this case. 
     On the other hand, the rotor has been assembled as shown in FIG. 5, and is supplied to the assembled body of motor-base-holder  4001  with stator  2000 . A motor assembling machine chucks rotor frame  1100 , and inserts shaft  1400  by centering metal  3200 . 
     Then cap the rotor with cup-shaped cover  3401 . At this time, protrusions  3411  and  3421  extended from the end of cover  3401  are positioned with corresponding places on the motor-base. 
     Protrusions  3421  is fixed to metal tip  3121  protruded from the motor-base by welding as shown in FIG. 2B. A laser-welding-machine may be used in this case. 
     Finally, base  3101  is cut off from frame  4101  at perforations  4211  shown in FIG.  4 . 
     The motor thus assembled is shipped to the market after inspection and packaging. Meanwhile, a performance inspection is carried out as follows: the electrical conductance between terminals and bridges of the motor base is cut off, or the bridge is kept as a common grounding terminal, then the motor being kept on the metal frame can be inspected. 
     The motor in accordance with the first embodiment uses motor-base-holder  4001  linked with metal frame  4101  made of the same material as terminal  3111 , and holder  4001  is disposed outside of motor base  3101 . Frame  4101  made by punching a piece of metal plate together with terminals  3111  positions base  3101  with respect to the assembling machine. The insert-mold into base  3101  is carried out with respect to round holes  4301  of frame  4101 , base  3101  can be thus positioned much more precisely than a conventional method which sets positioning reference on a resin-made motor-base. The method of the present invention thus can deal with a micro motor which requires a precise mating allowance, and can realize to assemble the micro motor at high productivity. 
     In the motor of this first embodiment, base  3101  is positioned together with base-holder  4001  and supported by bridges  4201 . Bearing supporter  3141  protrudes vertically from the base center, and metal  3200  is mounted to bearing supporter  3141 , therefore, metal  3200  also protrudes from base  3101  with a certain distance. Bridges  4201  supporting base  3101  is elastically deformed by lateral force. When shaft  1400  is inserted into metal  3200 , this structure produces centering action between them. This centering action contributes to high productivity of assembling the micro motor. 
     The motor in accordance with this first embodiment is a micro-flat-motor of 10 mm across. The shaft of the motor is 0.8 mm across and a clearance between the shaft and the metal (bearing) is max. several μm. This precision is not only required by these elements but also by other elements. Automatic machines assemble those elements into a micro-motor at a high speed. Such an ultra-micro motor owes the high-speed assembly to the assembling method of the present invention, which allows quick handling of elements, highly precise positioning, and automatic centering action. 
     In the first embodiment, trim  4401  is disposed between bridge  4201  and picture-frame type frame  4101 . This trim  4401  functions as follows: Terminals  3111  made of metal plate are disposed on the bottom face of the motor so that the device board can be soldered with the motor by re-flow soldering. However, the metal plate should be insulated and yet held, thus the metal plate must be insert-molded in the resin of base  3101 . Therefore, the metal plate is inevitably shaped in a step-like form. In this case, trim  4401  allows less stress to remain in the metal plate, thus sections around the terminals and the metal frame are free from being abnormally deformed. 
     In the first embodiment, a plurality of perforations  4211  are disposed around base  3101 , and frame  4101  is separated from base  3101  at perforations  4211  which are, more particularly, arranged at the same intervals around base  3101 . This structure prevents base  3101  from being supported unbalancedly, therefore, when a vertical external forces is applied, it directs the displacement in vertical direction. This does not lower the positioning precision for assembly. When a radial external force is applied to metal  3200 , it causes uniform elastic deformation in all directions. This does not adversely affect the centering action. As a result, an ultra-micro-motor can be assembled with high productivity. 
     A plurality of perforations are arranged on both sides of a center line of base  3101  so that the effect discussed above can be obtained with ease. As will be discussed in a third embodiment, perforations cannot be arranged uniformly in all directions for some reason; and yet, the perforations are preferably arranged around the motor-base to be symmetric with respect to a point. 
     As FIG.  1  and FIG. 5 illustrate, stator core  2100  is inserted into stator supporter  3151 , then bushing  3300  is press-fitted into stator fixer  3161 , thereby fixing stator  2000  to stator supporter  3151 . Since only press-fitting of bushing  3300  can fix stator  2000 , the waiting-time after bonding or welding the stator can be saved. As a result, total assembly time can be shortened. 
     Protrusions  3421  extended from fringe of cover  3401  are fixed to metal tips  3121  extended from base  3101 . This structure, i.e. connection between metals, yields a strong bonding force per unit area. Thus the bonding can be completed with a small area, and this is preferable for an ultra-micro-motor. The structure discussed above also allows the fringe of cover  3401  to be electrically coupled with metal tips  3121 . Accordingly, while metal tip  3121  is electrically coupled to terminal  3111 , metal tip  3121  is grounded to the device, thereby shielding electromagnetic noises produced by the motor. 
     In the first embodiment, protrusions  3421  are welded to tips  3121 , so that coagulating time of the welding is shorter than that for resin. As a result, the total assembly time of the motor can be shortened. A protruded amount to outside the motor is less than that by engaging-deformation-fixing method which is discussed in a fifth embodiment. Thus the first embodiment is more advantageously for downsizing the motor over the fifth embodiment. 
     Exemplary Embodiment 2 
     FIG. 6 illustrates a motor-base-holder in accordance with the second exemplary embodiment of the present invention. 
     In FIG. 6, rectangular metal frame  4102  of motor-base-holder  4002  is formed by linking the metal frames shown in FIG.  4  and used in the first embodiment. Metal frame  4102  includes four pieces of motor-bases  3101 . Six bridges  4202  are provided to each base  3101  and they are arranged in radial at approx. the same intervals. Round holes  4302  for positioning are provided in total 18 on frame  4102 . 
     In the second embodiment, a plurality of motor-bases are linked to form a rectangle. Since this holder holds a plurality of motor-bases, better handling can be expected than holding a single base, and ultra-micro-motors can be handled with much ease. A positioning time at each step as well as an assembling time decreases at greater numbers of motor-base held by the holder. In this second embodiment, a rectangle containing several motor-bases or maximum not more than 20 motor-bases is handled, i.e. as far as the rectangle keeps a plate and not shapes in a hoop, so that bending stress is not applied to this size of rectangle in storage. As a result, the motor-bases are not deformed by creep. This is different from a third embodiment discussed later because the third embodiment addresses a belt-like holder. 
     Exemplary Embodiment 3 
     FIG. 7 illustrates a motor-base-holder in accordance with the third exemplary embodiment of the present invention. 
     Metal frame  4103  of motor-base-holder  4003  extends long and forms a belt. Frame  4103  contains numbers of motor-bases  3101 . Four bridges  4203  (two bridges per side) are provided to each base  3101 , this is different from that of the second embodiment. Bases  3101  are linked to frame  4103  by bridges  4203  at both the sides of the frame in width direction of the belt. Round holes  4303  for positioning are sequentially provided on frame  4103 . 
     In the third embodiment, as discussed above, fringes of plurality of motor-bases are linked by the metal frame, thereby forming a belt. This structure allows the motor-base to be transferred with the metal frame in sequence, so that the motors can be continuously assembled. This structure thus can simplify a transferring mechanism, and allows assembly equipment to be compact and inexpensive. As a result, an inexpensive motor can be manufactured at high productivity. 
     Adjacent motor-bases in the holder of this third embodiment are separated in the longitudinal direction of the belt. When the belt-like holder is wound on a reel, the motor-base which is insert molded is free from bending stress. Thus creep is prevented to occur on the resin in storage of the motor-bases, resin-mold products are not degraded their precision in shape. 
     A number of bridges is preferably not more than three on one side. If more than two bridges are provided on one side, bending stress tends to occur in the motor-base when the metal frame warps. 
     Exemplary Embodiment 4 
     FIG. 8 illustrates a motor-base-holder in accordance with the fourth exemplary embodiment of the present invention. 
     Metal frames  4104  of motor-base-holders  4004  are linked with each other to form a belt. However, the metal frame used in the first embodiment is not just linked in the longitudinal direction, but the metal frame is linked with the sections forming both sides of the belt (these sections may be part of metal frame  4104 ). Six bridges  4204  are provided to each base  3101  as same as the first embodiment and support the base evenly. 
     The motor-bases held by this holder are separated in the longitudinal direction. The resin-made motor bases are thus prevented from creep in storage, and resin-mold products are not degraded precision in shape. Further, each motor base is supported its surrounding evenly, so that the uniform centering action in all directions is obtainable. 
     Exemplary Embodiment 5 
     FIG. 9 is a partial lateral view illustrating how a motor cover is fixed to the motor base in accordance with the fifth exemplary embodiment of the present invention. 
     In FIG. 9, protrusions  3422  extended from end of cover  3402  extends their tips outwardly in radial direction. Metal tips  3122  extended from a motor base are folded so that the tips can clip protrusions  3422 . 
     In this fifth embodiment, the end of cover and the metal tips of motor base are engaged and deformed to fix each other. Metal is easy to deform flexibly and it maintains the strength after deformation. Therefore, the metal can be bonded with a small area, and this is preferably to an ultra-micro-motor. The fixation by this engaging-deformation needs not the time before solidification, while heat-resin-bonding requires some time for solidification. As a result, assembly time of the motor can be shortened. 
     Several exemplary embodiments of the present invention have been demonstrated; however, the present invention is not limited to these embodiments but various applications are available within the scope of the invention. The present invention is good for ultra-micro-motors as discussed in the embodiments; however, it is also applicable to various kinds of motors. Round holes for positioning are disposed on the metal frame on both sides; however, the round holes may be disposed on one side. 
     As discussed above, the present invention solves the difficulty of handling motors, difficulty of mating elements of the motors, time-consuming bonding, and provides a motor allowing high productivity as well as a method of assembling the same motor. 
     Industrial Applicability 
     The present invention provides a structure best-suited to a mini motor and a method of assembling the same motor at high productivity. A motor of the present invention comprises: a motor-base-holder including (a) a base, (b) a bearing supporter vertically protruding from the base for supporting a bearing, (c) a stator supporter concentric with the bearing supporter for being mounted with a stator, (d) a motor base made of metal plate and having a terminal insert molded around the bearing supporter, and (e) a frame made of the same metal as the terminal and linked to fringe of the motor base. The present invention also provides a method of assembling the same motor. The present invention is best-suited to an ultra-micro-motor for producing vibration to notify a user of a calling. Such a motor is employed in, e.g. cellular phone.