Patent Publication Number: US-2013229076-A1

Title: Miniature Motor and Bearing Arrangement

Description:
FIELD OF THE INVENTION 
     The present invention relates to electric miniature motors and a bearing arrangement for those. 
     State of the art 
     Nowadays, miniature motors are used in various applications. Those include drives in home appliances, hand tools, actuators in motor vehicles and the like. The demands upon the motors are steadily increasing, including a lower noise generation besides a higher performance. 
     A major noise source can be the mounting of the rotor of the motor if axial and/or radial relative movements of the motor shaft can occur in the mounting positions for mounting the same. These movements are enabled by the tolerances required for fabricating the components of the motor, the reduction of which can only be obtained with a considerable cost effort. 
     Therefore, efforts have been made to minimize the mentioned relative movements without reducing the free movability of the shaft. Measures for achieving this object are described in EP 1 041 303 A1, DE 195 37 503 A1, DE 40 10 564 A1 and DE 10 2008 027 841 A1, for example. The solutions shown in these documents are still accompanied by a considerable effort regarding the components or the process. 
     The object of the present invention is thus to provide an electric miniature motor with a bearing system in which the bearing clearance of the shaft can be adjusted within narrow limits without the requirement that the individual components have to have narrow axial and radial tolerances. 
     It has now been found that this object can be achieved by fixing the bearing by welding, e.g. laser welding, in the bearing seat. 
     SHORT DESCRIPTION OF THE INVENTION 
     The object of the present invention is an electric miniature motor, wherein metallic configurations for seating the bearings are formed at the end faces of the stationary assemblies and wherein at least one of the bearings is a roller bearing, e.g. a ball bearing, which is connected by welding, e.g. laser welding, to the configuration. 
    
    
     
       SHORT DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates a longitudinal section of a miniature motor including the common assemblies according to an embodiment of the present invention; 
         FIG. 2  is a detailed view of the mounting according to  FIG. 1  with the welded joint  2 . 3 ; 
         FIG. 3  illustrates a top view of the configuration  2 . 1  for receiving the ball bearing  2 . 2  with a point-like welded joint  2 . 3 ; 
         FIG. 4  is a view similar to  FIG. 3  with an axially positioned corrugated welded joint  2 . 3 ; 
         FIG. 5  is a view similar to  FIG. 3  with a corrugated welded joint  2 . 3  positioned at the circumference of the configuration  2 . 1 ; 
         FIG. 6  illustrates in a longitudinal section similar to  FIG. 2  another embodiment of the invention with a front-sided welding between the ball bearing  2 . 2  and the configuration  2 . 1 ; 
         FIG. 7  illustrates in a longitudinal section similar to  FIG. 2  another embodiment of the invention with a welding between the ball bearing  2 . 2  and the configuration  2 . 1  if the ball bearing  2 . 2  axially protrudes over the configuration  2 . 1 ; 
         FIG. 8  illustrates in a longitudinal section similar to  FIG. 2  another embodiment of the invention with a welding between the ball bearing  2 . 2  and the configuration  2 . 1  if the ball bearing  2 . 2  is axially recessed behind the configuration  2 . 1 ; 
         FIG. 9  illustrates a top view according to  FIGS. 6 to 8  with three welded joints  2 . 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A miniature motor according to the present invention substantially comprises a rotor assembly  1 , a housing assembly  2  and a power transmission assembly  3 . The components of these assemblies are sufficiently known from conventional motors and are thus only described here insofar as required for understanding the invention. 
     The housing assembly  2  and the power transmission assembly  3  have cylindrical configurations  2 . 1  and  3 . 1 , respectively, receiving the bearings  2 . 2  and  3 . 2 , respectively, in which in turn the shaft  1 . 1  of the rotor assembly  1  is mounted. 
     In the further description, it is exemplarily assumed that the bearing  3 . 2  is fixed in the cylindrical seat  3 . 1  and that the shaft  1 . 1  is axially displaceable in this bearing. Further, it is assumed that the bearing  2 . 2  is a ball bearing, and that it is to be positioned so that the axial movement of the rotor assembly  1  can be adjusted to a desired amount. For achieving this characteristic, the bearing  2 . 2  is fixed undisplaceably on the shaft  1 . 1  which can be achieved by a press fit, for example. 
     The inner diameter of the configuration  2 . 1  is larger than the outer diameter of the bearing  2 . 2 , whereby it is possible that the rotor assembly  1  is still moveable in a mounted motor in which the housing assembly  2  is already fixedly connected to the power transmission assembly  3 . This movement is possible axially and, in the limits of the diameter difference of the configuration  2 . 1  and the bearing  2 . 2 , also radially. 
     Using suitable means and devices, respectively, the rotor assembly  1  is brought into the desired position with respect to the housing assembly  2 , and the outer ring of the ball bearing  2 . 2  is then welded to the configuration  2 . 1 , e.g. by a laser beam. The welding  2 . 3  can occur both at the outer diameter of the outer ring of the ball bearing  2 . 2  through the configuration  2 . 1 , i.e. in radial direction ( FIGS. 2 to 5 ), and in axial direction at the contact edge between the outer ring and the configuration  2 . 1  ( FIGS. 6 to 9 ). A combination of both welding directions is also possible. Each welded joint  2 . 3  can be point-like or corrugated, and it can be made at one or several positions or through a closed path. 
     Each individual welded joint  2 . 3  reaches a specific resistance against axial and radial forces acting upon the bearing  2 . 2 . It is thus also possible to satisfy different requirements regarding these forces depending upon the use conditions of the motor by the number of welded joints  2 . 3  and their configuration or combination.