Abstract:
Drum type washing machine including a tub having a wall for mounting a driving unit, a drum installed within the tub, a shaft passed through the tub and coupled to the drum, for transmission of driving force from a motor to the drum, at least one bearing for supporting the shaft, a bearing housing secured to a wall of the tub, a stator; and a rotor around the stator which forms the motor, wherein the stator includes an annular helical type core having multiple layers, an insulator enclosing the helical type core, and fastening portions formed integrally with the insulator which has a fastening hole at a center for fastening the stator to the wall of the tub, thereby providing a drum type washing machine of a direct coupling type of a new structure having employed a motor for reducing factors of noise, faults, energy waste, and improving washing performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of parent application Ser. No. 10/981,481, filed Nov. 5, 2004, now U.S. Pat. No. 7,520,148, and claims the benefit of Korean Patent Application No. P-2003-78481, filed on Nov. 6, 2003, each of which are hereby incorporated by reference for all purposes as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to drum type washing machines, and more particularly, to a structure of driving part of a direct coupling type drum type washing machine. 
     2. Discussion of the Related Art 
     In general, in a drum type washing, the washing is performed by using friction between a drum rotated by driving force of a motor and laundry in a state detergent, washing water, and the laundry are introduced into the drum, and gives almost no damage to the laundry, has no entangling of the laundry, and can provide a pounding, and rubbing washing effect. 
     A related art drum type washing machine will be described briefly with reference to  FIG. 1 . 
       FIG. 1  illustrates a longitudinal section of a related art drum type washing machine, provided with a tub  2  on an inside of a cabinet  1 , a drum  3  rotatably mounted at a center of an inside of the tub  2 . 
     Under the tub  2 , there is a motor  5   a  coupled to a motor pulley  18  with a shaft. There is a drum shaft connected to a rear of the drum  3 , having a drum pulley  19  mounted thereon. The drum pulley  19  on the drum shaft and the motor pulley  18  coupled to the motor  5   a  are coupled with a belt  20 , a power transmission element. 
     There is a door on a front of the cabinet  1 , with a gasket  22  between the door  21  and the tub  2 . 
     In the meantime, between the cabinet  1  at an inside of an upper portion thereof and the tub  2  at an upper side of an outside circumference thereof, there are hanging springs  23  for hanging the tub  2 , and between the cabinet  1  at an inside of a lower portion thereof and the tub  2  at an lower side of an outside circumference thereof, there are friction dampers  24  for attenuating vibration of the tub  2  occurred at the time of spinning. 
     However, the related art drum type washing machine, transmitting driving force from the motor  5   a  to the drum  3  through the motor pulley  18 , the drum pulley  19 , and the belt  20  coupling the motor pulley  18  and the drum pulley  19 , has the following disadvantages. 
     Because the driving force is transmitted to the drum  3  from the motor  5   a , not directly, but through the motor pulley  18 , the drum pulley  19 , and the belt  20 , there is an energy loss occurred in a process of driving force transmission. 
     Moreover, because the driving force is transmitted to the drum  3  from the motor  5   a , not directly, but through many components, such as the motor pulley  18 , the drum pulley  19 , and the belt  20 , there is much noise occurred in the process of power transmission. 
     Because many components, such as the motor pulley  18 , the drum pulley  19 , and the belt  20 , for transmission of the driving force from the motor  5   a  to the drum  3 , many assembly man-hours are required. 
     In proportion to a number of components required for transmission of the driving force from the motor  5   a  to the drum  3 , number and frequency of fault occurrences become greater. 
     In summary, transmitting driving force from the motor  5   a  to the drum  3  through the motor pulley, the drum pulley, and the belt indirectly, the related art drum type washing machine is liable to cause faults, and noise, has many energy wasting factors, and results in poor washing performance. 
     Along with this, because of the tub  2  formed of stainless steel, the related art drum type washing machine is expensive, has a poor formability, and is heavy. 
     Consequently, in order to solve the problems of the related art drum type washing machine, a direct coupling type drum type washing machine with a BLDC motor is suggested. 
     However, since the direct coupling type drum type washing machines with BLDC motors developed up to the present time still has various disadvantages and problems in view of structures, process lines, or operations, there are requirements for direct coupling type drum type washing machines of new structures. 
     That is, the related art drum type washing machine has much waste of materials, such as core, and so on, in fabrication of the motor, or has a problem of complicate fabrication process, and strengths of the tub or the stator mounted thereon are weak for mounting the motor on the tub, to fail in attenuating vibration and noise, effectively. 
     Particularly, the washing machine which rotates the drum directly with the BLDC motor has the stator mounted on a rear side of the tub, directly. In a case of the motor for a large capacity drum type washing machine, with weight of the stator only being 1.5 kg or more, and a spinning speed of 600˜2000 RPM, a joining portion of the stator and the tub is broken due to weight of the stator, and vibration, shake, and deformation of the rotor  5  at the time of spinning. 
     That is, in a case of a drum type washing machine which employs a BLDC motor with a stator secured to a rear wall of the tub, since an axis direction of the stator is substantially parallel to a floor, vibration caused at the time of operation of the washing machine causes heavy damage at the joining portion of the stator with the tub rear wall. 
     In order to prevent this, in fabrication of a stator core in the related art, a metal sheet is pressed, to form Ts and base portion, and, at the same time with this, projections  500  are formed on an opposite side of the Ts for joining, and a plurality of which are stacked, to form a stator core as shown in  FIG. 2 . 
     However, fabrication of above SC (Sectional type core) of the stator, not only is complicate, but also has waste of much material. 
     For reducing waste of material, and simplifying the fabrication process, though so called helical type core is favorable, in which a steel plate having the Ts and the base is stacked while turning the steel plate in an helix, the helical type core has disadvantage in that the projections  500  can not be formed toward an inner side of the core for joining the stator to the tub because a steel plate punched in a form of a stripe is required to be bent in a helix in fabrication of the helical type core. 
     This is because the projections  500  formed toward an inner side of the core make the stacking of the core by the turning the core in a helix impossible due to too great width of the core. 
     Consequently, a stator structure is required, in which a function identical to the projections of the sectional core SC is made to be performed, not by the core itself, but by other part, for enabling application of the helical type core HC. 
     For reference, the reason that securing of an adequate rigidity of the projections each having a fastening hole for fastening the stator to the tub is important is as follows. 
     The washing machine which rotates the drum directly with the BLDC motor has the stator mounted on a rear side of the tub, directly. In a case of the motor for a large capacity drum type washing machine, with weight of the stator only being 1.5 kg or more, and a spinning speed of 600˜2000 RPM, a joining portion of the stator and the tub is broken due to weight of the stator, and vibration, shake, and deformation of the rotor  5  at the time of spinning. 
     That is, in a case of a drum type washing machine which employs a BLDC motor with a stator secured to a rear wall of the tub, since an axis direction of the stator is substantially parallel to a floor, vibration caused at the time of operation of the washing machine causes heavy damage at the joining portion of the stator  6  with the tub rear wall. 
     Thus, securing of an adequate rigidity of the projections each having a fastening hole for fastening the stator  6  to the tub is very important. 
     Moreover, when an axis direction of the stator is parallel to the ground, with a heavy stator over 1.5 kg overhung therefrom, there has been breakage of a portion of the tub the stator is fastened thereto caused by the vibration. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a drum type washing machine that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a stator structure which can reduce material and weight required in fabrication of a stator of a BLDC motor, simplifies a fabrication process, and enables secure mounting of the stator to a mating part, such as a tub. 
     Another object of the present invention is to provide a structure which can sustain weight and vibration of a motor from a side of the tub in a case a washing machine BLDC motor is attached to a wall surface of the tub directly, which BLDC motor has 1.5 kg or more stator weight, and rotates at a speed varied in a range of 600˜2,000 RPM. 
     Another object of the present invention is to provide a structure which enables easy assembly when a stator and the tub are assembled in an assembly line. 
     Another object of the present invention is to provide a driving unit structure which enables a service man to make easier service at a time of maintenance and replacement of a product. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a drum washing machine includes a tub of plastic for holding washing water, the tub having a wall for mounting a driving unit thereto, a drum mounted on an inside of the tub, a shaft passed through the tub and coupled to the drum mounted inside of the tub, for transmission of driving force from a motor to the drum, at least one bearing for supporting the shaft, a bearing housing insert molded in the plastic tub for supporting the bearing, a stator to form the motor with a rotor, the rotor around the stator, and a tub supporter of metal between the wall of the tub and the stator, wherein the stator includes an annular helical type core having multiple layers formed by winding a steel plate having Ts and a base portion in a helix starting from a bottom layer to a top layer, an insulator insert molded with the helical type core to cover an outside surface of the helical type core for electrical insulation of the helical type core, and three fastening portions formed as a unit with the insulator projected from an inside circumferential surface of the helical type core toward a center of the stator, for fastening the stator to the tub supporter, wherein the fastening portion has a fastening hole at a center for fastening the stator to the wall of the tub with screws. 
     In another aspect of the present invention, a drum type washing machine includes a tub for holding washing water, the tub having a wall for mounting a driving unit thereto, a drum mounted on an inside of the tub, a shaft passed through the tub and coupled to the drum mounted inside of the tub, for transmission of driving force from a motor to the drum, at least one bearing for supporting the shaft, a bearing housing mounted to the tub for supporting the bearing, a stator to form the motor with a rotor, and the rotor around the stator, wherein the stator includes an annular helical type core having multiple layers formed by winding a steel plate having Ts and a base portion in a helix starting from a bottom layer to a top layer, an insulator insert molded with the helical type core to cover an outside surface of the helical type core for electrical insulation of the helical type core, and three fastening portions formed as a unit with the insulator projected from an inside circumferential surface of the helical type core toward a center of the stator, for fastening the stator to the bearing housing, wherein the fastening portion has a fastening hole at a center for fastening the stator to the wall of the tub with screws. 
     In another aspect of the present invention, a drum type washing machine includes a tub of plastic for holding washing water, the tub having a wall for mounting a driving unit thereto, a drum mounted on an inside of the tub, a shaft passed through the tub and coupled to the drum mounted inside of the tub, for transmission of driving force from a motor to the drum, at least one bearing for supporting the shaft, a bearing housing fixedly secured to a wall of the tub for supporting the bearing, a stator to form the motor with a rotor, and the rotor around the stator, wherein the stator includes an annular helical type core having multiple layers formed by winding a steel plate having Ts and a base portion in a helix starting from a bottom layer to a top layer, an insulator of an insulating material insert molded with the helical type core to cover an outside surface of the helical type core, and fastening portions formed as a unit with the insulator projected from an inside circumferential surface of the helical type core toward a center of the stator, for fastening the stator to the tub, wherein the fastening portion has a fastening hole at a center for fastening the stator to the wall of the tub with screws, wherein the insulator of the stator includes positioning projections, or holes, and the wall of the tub includes holes, or projections in complementary to the positioning projections, or holes of the insulator, and the wall of the tub includes fastening holes in correspondence to fastening holes in the insulator of the stator. 
     In another aspect of the present invention, an outer rotor type BLDC motor includes a stator including an annular helical type core having multiple layers formed by winding a steel plate having Ts and a base portion in a helix starting from a bottom layer to a top layer, an insulator formed by placing the helical type core in a mold for forming the insulator, and covering with an insulating material for insulation of the helical type core, three fastening portions formed as a unit with the insulator projected from an inside circumferential surface of the helical type core toward a center of the stator, and coils wound on the Ts of the helical type core respectively, and a rotor around the stator, having cooling fins and vent holes for cooling the stator. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; 
         FIG. 1  illustrates a longitudinal section of a related art drum type washing machine, schematically; 
         FIG. 2  illustrates a perspective view of a related art sectional core; 
         FIG. 3  illustrates a longitudinal section of a drum type washing machine in accordance with a preferred embodiment of the present invention; 
         FIG. 4  illustrates a longitudinal section of an “A” part in  FIG. 3 , showing a detail of a driving unit of a drum type washing machine in accordance with a preferred embodiment of the present invention; 
         FIG. 5  illustrates a perspective view of the stator in  FIG. 4 ; 
         FIGS. 6A and 6B  illustrate enlarged views of key parts of  FIG. 4 , wherein 
         FIG. 6A  illustrates a plan view of the key parts, and 
         FIG. 6B  illustrates a perspective view of the key parts; 
         FIG. 7  illustrates a perspective view of a helical type core applicable to a stator in accordance with a preferred embodiment of the present invention; 
         FIG. 8  illustrates a perspective view of the stator in  FIG. 5  in accordance with another preferred embodiment of the present invention; 
         FIG. 9  illustrates a longitudinal section of “A” part in  FIG. 3 , showing a detail of a driving unit in accordance with another preferred embodiment of the present invention; 
         FIG. 10  illustrates a longitudinal section of “A” part in  FIG. 3 , showing a detail of a driving unit in accordance with another preferred embodiment of the present invention; and 
         FIG. 11  illustrates a longitudinal section of “A” part in  FIG. 3 , showing a detail of a driving unit in accordance with another preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings  FIGS. 3˜11 . Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     A first preferred embodiment of the present invention will be described with reference to  FIGS. 3˜7 . 
       FIG. 3  illustrates a longitudinal section of a drum type washing machine in accordance with a preferred embodiment of the present invention, and  FIG. 4  illustrates a longitudinal section of an “A” part in  FIG. 3 , showing a detail of a driving unit of a drum type washing machine in accordance with a preferred embodiment of the present invention. 
       FIG. 5  illustrates a perspective view of the stator in  FIG. 4 ,  FIGS. 6A and 6B  illustrate enlarged views of key parts of  FIG. 4 , wherein  FIG. 6A  illustrates a plan view of the key parts, and  FIG. 6B  illustrates a perspective view of the key parts, and  FIG. 7  illustrates a perspective view of a helical type core applicable to a stator in accordance with a preferred embodiment of the present invention. 
     The drum type washing machine in accordance with a first preferred embodiment of the present invention includes a tub  2  of plastic having a wall portion for securing a driving unit thereto, for holding washing water, a drum  3  mounted on an inside of the tub  2 , a shaft  4  passed through the tub  2  and coupled to the drum  3  inside of the tub  2 , at least one bearings  6   a , and  6   b  for supporting the shaft  4 , a bearing housing  7  insert molded in the plastic tub  2  for supporting the bearings  6   a , and  6   b , a stator  14  of a motor, a rotor  13  of the motor surrounding an outside circumference of the stator  14 , a tub supporter  17  of metal between the wall of the tub  2  and the stator  14 . 
     The stator  14 , with a weight 1.5 kg or more, includes an annular helical type core HC having multiple layers formed by winding a steel plate having Ts  151  and a base portion  150  in a helix starting from a bottom layer to a top layer, an insulator  144  of an insulating material insert molded with the helical type core HC to cover an outside surface of the helical type core HC for electrical insulation of the helical type core HC, and at least three fastening portions  143  formed as a unit with the insulator  144  projected from an inside circumference of the helical type core HC toward a center of the stator  14 , for fastening the stator  14  to a tub supporter  17 . 
     The fastening portion  143  has a fastening hole  143   a  at a center for fastening the stator  14  to the wall of the tub with screws. 
     The insulator  144  of the stator  14  has positioning projections  143   b , and the tub supporter  17  has holes in complementary to the positioning projections  143   b  on the insulator  144 , and the tub supporter  17  also has fastening holes in correspondence to the fastening holes  143   a  in the insulator  144  of the stator  14 . 
     In this instance, the positioning holes may be formed in the insulator  144  of the stator  14 , and the positioning projections may be formed on the tub supporter  17 . 
     The stator  14  further includes a cylindrical metal  143   p  inserted in the fastening hole  143   a  at the center of the fastening portion  143 . The cylindrical metal  143   p  may be, for an example, a spring pin with an incised portion for having elasticity, or a hollow pin for press inserted into the fastening hole  143   a.    
     In the meantime, it is required that the fastening portion  143  has a height 20% or more than 20% of a total height of the core, or more preferably 20%˜150%. 
     The fastening portion  143  is formed such that a≧b, where “a” denotes a length of the T  151  projected from an outside circumferential surface of the helical type core HC, and “b” denotes a distance from the inside surface of the helical type core HC to a center of the fastening hole  143   a  in the fastening portion  143 . 
     Together with this, the fastening portion  143  of the stator  14  has a hollow portion  143   c  for damping vibration during driving the motor. The helical type core HC is riveted with rivets  13  through pass through holes in the base portion  150  for holding the multiple layers together. Moreover, a winding starting portion, and a winding end portion of the helical type core HC may be welded to the base portion  150 , respectively. 
     In the meantime, the metallic bearing housing  7  has steps  8   a , and  8   b  for supporting a front bearing  6   a  and a rear bearing  6   b  on an inside circumferential surface for preventing the bearings  6   a , and  6   b  from breaking away from the bearing housing  7 . 
     The shaft  4  inside of the bearing housing  7  for transmitting a driving force from the motor  5  to the drum  3  has steps at a front and a rear of an outside circumference for positioning the front bearing  6   a  and the rear bearing  6   b  on the shaft  4 . 
     The shaft  4  has a front end fixedly secured to a spider  10  in the rear wall of the drum  3 , and a section from an exposed portion in rear of the spider  10  to the front bearing  6   a  with a brass bushing  11  press fit thereon for preventing the shaft  4  from rusting, with a sealing member  12  fitted on an outside surface of the bushing  11  for preventing infiltration of water toward the bearing. 
     The shaft  4  has the rotor  13  of the direct drive motor  5  mounted at a center of a rear end portion, on an inner side of which the stator  14  is positioned, that is mounted on the rear wall of the tub  2  to form the direct drive motor together with the rotor  13 . 
     Referring to  FIG. 4 , the rotor  13 , formed of a steel plate, has a circumferential bent portion with a seating surface  130  for seating magnets M placed on a front of an inside surface of a side wall  13   b  extended forward from an edge of a rear wall  13   a  of the rotor  13 , and a hub  132  in a center part of the rear wall  13   a  having a pass through hole  131  for passing fastening members  15   a , such as bolts, in mounting the rotor  13  on the shaft  4 . 
     It is preferable that the rotor  13  is formed by pressing. 
     The rotor  13  has a plurality of radial cooling fins  133  around the hub  132  for blowing air toward the stator  14  when the rotor  13  rotates, to cool down heat from the stator  14 . Each of the cooling fins  133  has a length in the radial direction. 
     The cooling fin  133  is formed by lancing to be bent at 90° from the rear wall to direct an opened side of the rotor  13 , and a through hole  134  formed in the lancing serves as a venting hole. 
     Together with this, the rotor  13  has embossing  135  between adjacent cooling fins  133  on the rear wall  13   a  for reinforcing the rotor  13 , and drain holes  136  in the embossing  135 . 
     The rotor  13  has fastening holes  137  for fastening a connector  16  engaged with a rear end portion of the shaft  4  in rear of the rear bearing  6   b  by means of serration, and positioning holes  138  for positioning the connector in mounting the connector on the shaft  4 , both of which fastening holes  137  and positioning holes  138  are formed around the pass through hole  131  in the hub  132  at regular intervals. 
     The connector  16  is formed of plastic having a vibration mode different from the rotor  5  of steel plate, and also serves as a bushing for the rotor. 
     The connector  16  has positioning projections  160  for automatic positioning of the fastening holes  162  in the connector  16  and the fastening holes  137  in the rotor  13 . 
     The connector  16  has a serration  164  on an inside circumferential surface complementary to the serration on the rear end portion of the shaft  4 , and reinforcing ribs  161  on a hub of the connector  16 , for reinforcing a strength of the connector  16 . 
     The wall  200  of the tub  2  has a hub  201  for placing the bearing housing  7  therein in the injection molding of the tub, and the hub  201  has fastening bosses  202  formed at an outside along a circumferential direction at regular intervals for fixedly securing the stator  14  on the rear wall of the tub  2  with fastening members  15   a.    
     Between the rear wall of the tub  2  and the stator  14 , there is a tub supporter  17  having a shape almost same with an outside shape of the rear wall of the tub fixedly secured to the rear wall of the tub at the time of mounting the stator  14  for supporting the stator  14 , and maintaining a concentricity of the stator  14 . 
     In this instance, the tub supporter  17  has a front portion in close contact with an inner side surface of the rib  203  on one side of the rear wall of the tub, and a rear end portion in close contact with an outside circumferential surface of the rear end portion of the bearing housing  7 , not covered with the hub  132  at a center of the rear wall of the tub, but exposed. 
     In the meantime, referring to  FIG. 4 , the stator  14  of the motor  5  includes a helical type core HC, an insulator  144  of an insulating material insert molded with the helical type core HC to cover an outside surface of the helical type core HC, coils  142  wound on the Ts  151  of the helical type core HC respectively, and at least three fastening portions  143  formed as a unit with the insulator  144  projected from an inside of the helical type core HC. 
     The helical type core HC has multiple layers formed by winding a steel plate in a helix starting from a bottom layer to a top layer. There are Ts  151  projected outwardly in a radial direction from a base portion  150  of the helical type core HC, and the base portion  150  of the helical type core HC has grooves  152  for reducing stress at the time of winding the core. 
     The helical type core HC is riveted with rivets  13  through pass through holes in the base portion  150  for holding the multiple layers together. Moreover, a winding staring portion, and a winding end portion of the helical type core HC may be welded to the base portion  150 , respectively. 
     The groove  152  in the base portion  150  of the helical type core HC may be rectangular or trapezoidal, or an arc. 
     Referring to  FIG. 5 , the fastening portion  143  is formed such that a≧b, where “a” denotes a length of the T  151  projected from an outside circumferential surface of the helical type core HC, and “b” denotes a distance from the inside surface of the helical type core HC to a center of the fastening hole  143   a  in the fastening portion  143 . 
     The fastening portion  143  has a height one fifths or more of a total height of the core, or, the same with the total height of the core. 
     The fastening portion  143  has at least one hollow portion  143   c  for damping vibration during driving the motor, and a positioning projection  143   b  complementary to the positioning hole in the rear wall of the tub  2 . 
     In the meantime, of course, the positioning projections  143   b  may be formed on the rear wall of the tub  2 , and the positioning holes complementary to the positioning projections on the rear wall of the tub  2  may be formed in the fastening portion  143 . 
     The operation of the drum type washing machine in accordance with a first preferred embodiment of the present invention will be described. 
     When rotation of the rotor  13  is started by a current flowing through the coils  142  of the stator  14  in succession under the control of a motor driving controller (not shown) attached to a control panel, the shaft  4  engaged with the connector  16  secured to the rotor with a serration rotates. According to this, power is transmitted to the drum  3  through the shaft  4 , to rotate the drum  3 . 
     The working of the drum type washing machine having the driving unit of the present invention applied thereto will be described. 
     Fabrication of the drum type washing machine becomes easy, because the tub  2  is formed of plastic having a good heat resistance, and light by injection molding. 
     The drum type washing machine of the present invention is applicable even to a drum type washing machine having a spinning cycle, because the bearing housing  7 , bearing supporting means, of a metal, such as aluminum, has no thermal deformation even at an elevated temperature. 
     Since the metal bearing housing  7  is inserted molded with the hub  201  of the rear wall of the tub at the time of injection molding of the tub  2  of plastic, to form one unit with the tub  2 , omitting the step of assembling the bearing housing  7  to the rear wall of the tub, an assembly process can be simplified to reduce assembly man-hours. 
     Especially, referring to  FIG. 4 , since the stator  14  of the motor  5  has the groove  152  in the base portion  150  of the helical type core HC, to reduce stress caused by core winding, the winding can be made with a force smaller than the related art. 
     Taking a matter into account, in which even if positioning of the fastening hole  143   a  closer to a point of action of a load the more favorable in view of torque, if the fastening hole  143   a  is positioned too close to the point of action of the load, excessively small diametered bolts are required, to require excessively many number of bolts, the relation of the a≧b of fastening portion  143  is determined, where “a” denotes a length of the T  151  projected from an outside circumferential surface of the helical type core HC, and “b” denotes a distance from the inside surface of the helical type core HC to a center of the fastening hole  143   a  in the fastening portion  143 . 
     The fastening portion  143  has a height 20%˜150% of the total height of the core, for preventing the fastening portion  143  from breaking when the fastening portion  143  has a height below 20% of the total core height. 
     Though the higher the total height of the fastening portion  143 , the better the rigidity of the fastening portion  143 , because excessive height of the fastening portion  143  can increase a total width of the driving unit of the washing machine, resulting in a washing capacity of the washing machine, the total height of the fastening portion is set to be less than 150% of the total height of the core. 
     The hollow  143   c  in the fastening portion  143  buffers and dampens vibration occurred at the time of driving the motor, to improve mechanical reliability of the stator  14 . 
     The positioning projection  143   b  on the fastening portion  143  fits into the positioning hole in the tub  2 , enabling easy fastening of the stator  14 . 
     Of course, the positioning projection may be on the tub  2 , while the positioning hole is formed in the fastening portion  143 . 
     The “           ” shaped step  8   a  on the front of the inside circumferential surface, and the “         ” shaped step  8   b  on the rear of the inside circumferential surface of the bearing housing  7  of the present invention enable to support a rear end of the front bearing  6   a  and a front end of the rear bearing  6   b  mounted on an outside circumferential surface of both end portions of the shaft  4 .
     That is, the metallic bearing housing  7  can support the bearings  6   a , and  6   b  to prevent the bearings  6   a , and  6   b  from breaking away from the bearing housing  7  owing to the steps  8   a , and  8   b  on opposite sides of the inside circumferential surface of the bearing housing  7 . 
     Moreover, the positioning steps on an outside circumferential surface of front and rear sides of the shaft  4  inside of the bearing housing  7  for transmitting driving force from the motor  5  to the drum  3  enable easy positioning of the front bearing  6   a  and the rear bearing  6   b  with respect to the shaft  4 . 
     In the meantime, since the shaft  4  has a front end fixedly secured to a spider  10  in the rear wall of the drum  3 , and a section from an exposed portion in rear of the spider  10  to the front bearing  6   a  with a brass bushing  11  press fit thereon, rusting of the shaft  4  can be prevented. 
     The sealing member  12  fitted on the outside surface of the bushing  11  prevents infiltration of water toward the bearing. 
     In the meantime, the rotor  13  is mounted on a center of the rear end portion of the shaft  4 , and the stator  14  is positioned on an inside of the rotor  13 , wherein the circumferential bent portion having magnet seating surfaces  130  extended forward from an edge of the rear wall  13   a  of the rotor  13  supports the magnets M at the magnet seating surfaces  130  when the magnets M are attached to the inside surface of the rotor  13 , fabrication of the rotor is easy. 
     Moreover, the pass through hole  131  in the hub  132  at the center of the rear wall  13   a  of the rotor  13  enables pass of the fastening members  15   b , such as bolts, for fastening the rotor  13  to the shaft, and the plurality of radial cooling fins  133  around the hub  132  of the rotor  13  each with a predetermined length blow air toward the Stator  14  when the rotor  13  rotates, to cool down the heat from the stator  14 . 
     The cooling fin  133  is formed to direct an opened side of the rotor  13  by lancing, and a through hole  134  formed in the lancing serves as a venting hole. 
     The rotor  13  formed of steel plate by pressing reduces a fabrication time period, to improve productivity of the rotor. 
     Together with this, the rotor  13  has embossing  135  between adjacent cooling fins  133  on the rear wall  13   a  for reinforcing the rotor  13 , and drain holes  136  in the embossing  135  for draining water therethrough. 
     The rotor  13  has fastening holes  137  for fastening a connector  16 , and positioning holes  138  for positioning the connector in mounting the connector, both of which fastening holes  137  and positioning holes  138  are formed around the pass through hole  131  in the hub  132  of the rotor  13 . 
     That is, upon positioning the positioning projections  160  on the connector  16  at the positioning holes  138  in the rotor  13 , the fastening holes  137  and  162  in the rotor  13  and the connector  16  are aligned automatically, to make fastening of the fastening members  15   c  easy. 
     Since the connector  16  is formed of plastic having a vibration mode different from the rotor  5  of steel plate, the connector dampens vibration from the rotor  13  before the vibration is transmitted to the shaft  4 . 
     The serration  164  on the inside circumferential surface of the hub  201  of the connector  16  engaged with the serration  400  on the rear end portion of the shaft  4  enables transmission of the rotating force from the rotor  13  to the shaft  4  through the connector  16 . The reinforcing ribs  161  on the outside of the hub  201  of the connector  16  reinforce strength of the hub  201 . 
     The fastening bosses  202  on the outside of the hub  201  on the rear wall of the tub  2  along a circumferential direction at regular intervals enable to mount the stator  14  on the rear wall of the tub, securely. 
     The tub supporter  17 , having almost the same outside shape with the rear wall fixedly secured to the rear wall of the tub  2 , between the rear wall of the tub  2  and the stator  14  enables to support the stator  14  and maintains concentricity of the stator  14 . 
     That is, once the tub supporter  17  is fastened to the supporter fastening bosses  204  on the rear wall of the tub, the front end portion of the tub supporter  17  is brought into close contact with an inside surface of the ribs  203  on one side of the rear wall of the tub, and the rear end portion of the tub supporter  17  is brought into close contact with the outside circumferential surface of the rear end portion of the bearing housing  7  not surrounded by the hub  132 , but exposed, to support the stator  14  and to maintain the concentricity of the stator. 
       FIG. 8  illustrates a perspective view of the stator in  FIG. 5  in accordance with another preferred embodiment of the present invention. 
     Referring to  FIG. 8 , the stator  14  of this embodiment includes an annular helical type core HC having multiple layers formed by winding a steel plate with Ts  151  and base portion  150  in a helix starting from a bottom layer to a top layer, an insulator  144  of an insulating material insert molded with the helical type core HC to cover an outside surface of the helical type core HC, and fastening portions  143  projected from an inside circumferential surface of the helical type core HC projected toward a center of the stator  14  formed as one unit with the insulator  144 , for fixedly securing the stator  14  to the tub  2 . 
     The fastening portion  143  has a fastening hole  143   a  at a center for fastening the stator  14  to the wall of the tub with screws. 
     The insulator  144  of the stator  14  has positioning holes  143   g , and the rear wall  200  of the tub has projections complementary to the positioning holes  143   g . The insulator  144  of the stator  14  has fastening holes  143   a , and the tub  2  has fastening holes complementary to the fastening holes  143   a.    
     The positioning projection may be formed on the insulator  144  of the stator  14 , and the positioning holes may be formed in the rear wall of the tub. 
     In this case too, the fastening portion  143  is formed such that a≧b, where “a” denotes a length of the T  151  projected from an outside circumferential surface of the helical type core HC, and “b” denotes a distance from the inside surface of the helical type core HC to a center of the fastening hole  143   a  in the fastening portion  143 , under the same reason described before. 
     In the meantime,  FIG. 9  illustrates a longitudinal section of “A” part in  FIG. 3 , showing a detail of a driving unit in accordance with another preferred embodiment of the present invention. 
     Referring to  FIG. 9 , the drum type washing machine includes a tub  2  of metal, a drum  3  rotatably mounted on an inside of the tub  2 , a shaft  4  passed through the tub  2  and coupled to the drum mounted on the inside of the tub  2 , for transmission of driving force from a motor to the drum  3 , bearings  6   b  and  6   b  mounted to support the shaft, a bearing housing  7  mounted to a rear wall of the tub  2  to support the bearings, a rotor  13  fixedly secured to a rear end portion of the shaft, to form the motor together with a stator  14 , and the stator  14  on an inside of the rotor  13  secured to the rear wall of the tub to form the motor together with the rotor  13 , wherein the stator  14  includes a helical type core HC, an insulator  144  of an insulating material insert molded with the helical type core HC to cover an outside surface of the helical type core HC, coils  142  wound on the Ts  151  of the helical type core HC respectively, and at least three fastening portions  143  formed as one unit with the insulator  144  and projected toward an inside of the core. 
     Alike the foregoing embodiment, the helical type core HC has multiple layers formed by winding a steel plate in a helix starting from a bottom layer to a top layer. There are a plurality of Ts  151  projected outwardly in a radial direction from a base portion  150 , and the base portion  150  has grooves  152  for reducing stress when the core is wound. 
     Elements and functions thereof described in the foregoing embodiment, but not this embodiment are the same with the foregoing embodiment, and description of which will be omitted, for avoiding repetition. 
       FIG. 10  illustrates a longitudinal section of “A” part in  FIG. 3 , showing a detail of a driving unit in accordance with another preferred embodiment of the present invention. 
     Referring to  FIG. 10 , the drum type washing machine includes a tub  2  for holding washing water, having a wall for mounting a driving unit thereto, a drum mounted on an inside of the tub  2 , a shaft  4  passed through the tub  2  and coupled to the drum  3  mounted inside of the tub, for transmission of driving force from a motor to the drum  3 , at least one bearing  6   a , and  6   b  for supporting the shaft  4 , a bearing housing  7  secured to the tub  2  for supporting the bearing  6   a , and  6   b , a stator  14  with weight 1.5 kg or more, and a rotor  13  around the stator  14 , wherein the stator  14  includes an annular helical type core HC having multiple layers formed by winding a steel plate having Ts  151  and a base portion  150  in a helix starting from a bottom layer to a top layer, an insulator  144  of an insulating material insert molded with the helical type core HC to cover an outside surface of the helical type core HC for electrical insulation of the helical type core HC, and at least three fastening portions  143  formed as a unit with the insulator  144  projected from an inside circumferential surface of the helical type core HC toward a center of the stator  14 , for fastening the stator  14  to bearing housing  7 . The fastening portion  143  has a fastening hole  143   a  for fastening the stator  14  to the bearing housing  7  with screws. 
     The tub  2  is formed of plastic, the bearing housing  7  is formed of an aluminum alloy, the bearing housing  7  is insert molded as one unit with the tub  2 , and the stator  14  is attached to the bearing housing  7 . 
     The stator  14  further includes a cylindrical metal  143   p  inserted in the fastening hole  143   a  at the center of the fastening portion  143 . As described before, the cylindrical metal  143   p  may be, for an example, a spring pin with an incised portion for having elasticity, or a hollow pin for press inserting into the fastening hole  143   a.    
     In the meantime, it is required that the fastening portion  143  has a height 20% or more than 20% of a total height of the core, or more preferably 20%˜150%. 
     The fastening portion  143  is formed such that a≧b, where “a” denotes a length of the T  151  projected from an outside circumferential surface of the helical type core HC, and “b” denotes a distance from the inside surface of the helical type core HC to a center of the fastening hole  143   a  in the fastening portion  143 . 
     Together with this, the fastening portion  143  of the stator  14  has a hollow portion  143   c  for damping vibration during driving the motor. The helical type core HC is riveted with rivets  13  through pass through holes in the base portion  150  for holding the multiple layers together. Moreover, a winding starting portion, and a winding end portion of the helical type core HC may be welded to the base portion  150 , respectively. 
     In the meantime, the insulator  144  of the stator  14  has the positioning projections  143   b  formed thereon, the bearing housing  7  having the stator  14  directly mounted thereon has holes complementary to the positioning projections  143   b , and the bearing housing  7  has fastening holes in correspondence to the fastening holes  143   a  in the insulator  144  of the stator  14 . 
     Of course, positions of the projections and the holes in the insulator  144  and the bearing housing  7  may be exchanged. 
     In the meantime, in  FIG. 10  of this embodiment, parts the same with the first embodiment will be given the same reference numerals, and description of names will be omitted. This is applicable to description of an embodiment described with reference to  FIG. 11 . 
     A driving unit for a drum type washing machine in accordance with another preferred embodiment of the present invention will be described with reference to  FIG. 11 . 
       FIG. 11  illustrates a longitudinal section of “A” part in  FIG. 3 , showing a detail of a driving unit in accordance with another preferred embodiment of the present invention. 
     Referring to  FIG. 11 , the drum type washing machine includes a tub  2  of plastic for holding washing water, having a wall for mounting a driving unit thereto, a drum  3  mounted on an inside of the tub  2 , a shaft  4  passed through the tub  2  and coupled to the drum  3  mounted inside of the tub, for transmission of driving force from a motor to the drum  3 , at least one bearing  6   a , and  6   b  for supporting the shaft  4 , a bearing housing  7  secured to a wall of the tub  2  for supporting the bearing  6   a , and  6   b , a stator  14  with weight 1.5 kg or more, and a rotor  13  around the stator  14 , wherein the stator  14  includes an annular helical type core HC having multiple layers formed by winding a steel plate having Ts  151  and a base portion  150  in a helix starting from a bottom layer to a top layer, an insulator  144  of an insulating material insert molded with the helical type core HC to cover an outside surface of the helical type core HC, and fastening portions  143  formed as a unit with the insulator  144  projected from an inside circumferential surface of the helical type core HC toward a center of the stator  14 , for fastening the stator  14  to the tub  2 . 
     The fastening portion  143  has a fastening hole  143   a  at a center for fastening the stator  14  to the wall of the tub  2  with screws. 
     Together with this, the insulator  144  of the stator  14  has positioning projections  143   b  or holes, the wall of the tub  2  has holes or projection complementary to the projections or holes of the insulator  144 , the tub  2  has fastening holes in correspondence to the fastening holes  143   a  in the insulator  144  of the stator  14 . 
     At least three of the fastening portions  143  are projected toward the center of the stator  14  at regular intervals. 
     The fastening portion  143  is formed such that a≧b, where “a” denotes a length of the T  151  projected from an outside circumferential surface of the helical type core HC, and “b” denotes a distance from the inside surface of the helical type core HC to a center of the fastening hole  143   a  in the fastening portion  143 . 
     Thus, in fabrication of the stator  14  of the BLDC motor, the drum type washing machine of the present invention according to above embodiments can reduce required material and weight, simplify a fabrication process, and mount the stator  14  to a mating side, such as the tub  2 , securely. 
     Moreover, the present invention can provide a structure which can sustain weight and vibration of a motor from a side of the tub  2  in a case a washing machine BLDC motor is attached to a wall surface of the tub directly, which BLDC motor has 1.5 kg or more stator weight, and rotates at a speed varied in a range of 0˜2,000 RPM or more. 
     The drum type washing machine of the present invention enables easy assembly of the stator  14  with the tub  2  on an assembly line, and, according to this, service by a service man can be made easily at the time of after service. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. 
     That is, the tub  2  of the present invention may have any shape as far as the shape has the rear wall of plastic for mounting the driving unit thereon. That is, even if the tub is not formed of plastic wholly, the tub is acceptable. For an example, a structure is acceptable, in which, while the rear wall for mounting the driving unit thereto is formed of plastic, a circumferential surface around an outside circumferential surface of the drum may be formed of metal, such as stainless steel. 
     Of course, the stator  14  illustrated in  FIG. 8  is applicable to the drum type washing machine illustrated in  FIG. 10  or  11 . 
     The present invention has the following advantages. 
     The drum type washing machine of the present invention, of a direct motor coupling type, can reduce noise, faults, and power loss. 
     In fabricating the stator of a BLDC motor for a drum type washing machine, the present invention can reduce material, and weight, and simplify a fabrication process, and permits secure mounting of the stator to a mating part, such as the tub. 
     The present invention can provide a structure which can sustain weight and vibration of a motor from a side of the tub  2  in a case a washing machine BLDC motor is attached to a wall surface of the tub directly, which BLDC motor has 1.5 kg or more stator weight, and rotates at a speed varied in a range of 0˜2,000 RPM or more. 
     The drum type washing machine of the present invention enables easy assembly of the stator  14  with the tub  2  on an assembly line, and, according to this, service by a service man can be made easily at the time of after service. 
     The formation of the rotor of the drum type washing machine of the present by pressing, with a good formability, permits to reduce a time period required for fabrication of the rotor, which improves productivity. 
     The employment of the helical type core of which winding is easy permits to prevent material from wasting, fabricate the core easily, and enhance rigidity of the fastening portions of the stator, to reduce noise and vibration, to improve mechanical reliability and elongate a lifetime. 
     The provision of the connector having a vibration mode different from the rotor permits to reduce transmission of vibration from the rotor to the shaft, and to support the stator, and maintain concentricity of the stator, effectively. 
     Thus, the present invention improves a structure of the driving unit of the drum type washing machine, to reduce noise and faults, and improve product reliability, and to improve productivity as productivity of components of the driving unit is improved.