Abstract:
A rotor. The rotor includes a case, a reinforcing part, a shaft and a connecting element. The reinforcing part is formed with the case and defines an opening. The shaft extends into the opening. The connecting element connects the case and the shaft, with the reinforcing part disposed inside.

Description:
BACKGROUND 
   The invention relates to a rotor, and in particular, to a rotor with enhanced mechanical strength to be used in the fan. 
   In a conventional rotor, the shaft and the case are connected as follows. 
     FIG. 1  depicts a rotor assembled by insert molding, wherein a shaft  20  is disposed in contact with a joining area  11  of a case  10 , and then a connecting material (e.g. plastic or soft metal)  30  is provided between the shaft  20  and the case  10  by insert molding. Thus, the shaft  20  is firmly connected to the case  11 . 
     FIG. 2  depicts another rotor assembled by fitting-and-riveting, wherein a shaft  20  is fitted into a copper cover  40 , and then the copper cover  40  and the case  10  are connected by riveting (i.e. the copper cover  40  is passed through an opening  12  of a case  10 , and the part of the copper cover  40  projecting from the opening  12  is flattened by pressing). 
   The described methods of assembling the rotor have their respective drawbacks; for insert molding, the parts of the case  10  and the shaft  20  embedded in the connecting material  30  are small. During rotation, therefore, the shaft  20  or/and the connecting material  30  may separate from the case  10  due to insufficient rigidity of the case  10 . Furthermore, connection via riveting has poor resistance to vibration. For fitting-and-riveting, therefore, the riveted part of the copper cover  40  may be broken during rotation so that the shaft  20  and the case  10  separate, particularly when the rotor is heavy or metal fatigue occurs. 
   In conclusion, the described methods of assembling the rotor fail to maintain the connection between the shaft and the case after long-term use. Thus, the application of the fan is limited. Frequent maintenance and replacement of parts of the rotor are unavoidable. The fans, produced by the described methods, fail to meet the demand of the manufacturing industry and the consumers for endurance of products. An improvement of the described rotors is necessary. 
   SUMMARY 
   To solve the described problems, the invention provides a rotor with the shaft and the case firmly connected, thereby promoting the reliability and endurance thereof. 
   A rotor in accordance with an exemplary of the invention includes a case, a reinforcing part, a shaft and a connecting element. The reinforcing part is formed with the case and defines an opening. The shaft extends into the opening. The connecting element connects the case and the shaft, with the reinforcing part disposed inside, whereby the connection between the shaft, the connecting element and the case is stronger, such that separation therebetween is less likely, and the reliability and endurance of the rotor is promoted. 
   Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is a sectional view of a rotor introduced in the background of the invention; 
       FIG. 2  is a sectional view of another rotor introduced in the background of the invention; 
       FIGS. 3A-3C  show the process of assembling a rotor which comprises a case and a shaft; 
       FIG. 4  is a sectional view of  FIG. 3C ; and 
       FIG. 5  shows another shape of the supporting part and the opening. 
   

   DETAILED DESCRIPTION 
   Please refer to  FIGS. 3A ,  3 B,  3 C and  4 , wherein  FIGS. 3A ,  3 B and  3 C show the process of assembling a rotor which comprises a case and a shaft, and  FIG. 4  is a sectional view of  FIG. 3C . 
   Referring to  FIG. 3A , the case  50  is the main part of the rotor. In this embodiment, the case  50  has a circular cross section. An opening  51  is provided in the center of the bottom of the case  50  for receiving the shaft  60 . 
   The case  50  has a recessed supporting part  52  near the opening  51 . The supporting part  52  is annular and has at least a hole  54 . A reinforcing part  53  extends from the supporting part  62  into the case  50 . 
   It is understood that the cross section of the case  50  can be circular, polygonal or similar. The opening  51  can be circular, polygonal or similar. The supporting part  52 , shaped to match the case  50  and the opening  51 , is correspondingly circular, polygonal or similar. As shown in  Fig.5 , the supporting part  52  of the case  50  is polygonal, and the shape of the opening  51  matches the supporting part  52 . 
   The case  50  is made of metal, plastic or alloy. Furthermore, the case  50  is formed by pressing or is integrally formed. 
   The reinforcing part  53  extends at a 90° angle ( FIG. 3A ) from the case  50 . The angle, however, can be 45° (not shown) or any other easily machined. 
   Referring again to  FIGS. 3B and 3C , the shaft  60  has an end in the opening  51  of the case  50 . A groove  61  is circumferentially provided on the end of the shaft  60 . A connecting element  70  is provided between the shaft  60  and the cast  50  by insert molding. The connecting element  70  comprises plastic or soft metal (e.g. aluminum, zinc or an alloy of aluminum and magnesium), so that the connecting element  70  can be forced into the hole  54  during insert molding to firmly connect the case  50  and the shaft  60 . 
   The end of the shaft  60  in the opening  51  can have a polygonal cross section, be cylindrical, or shaped like a pillar having concave/convex side surfaces for reinforcing the connection between the shaft  60  and the connecting element  70 . It is noted that any shape of the end is acceptable during the formation of the connecting element  70  by insert molding. 
   Referring to  FIG. 4 , the connecting element  70  completely covers the reinforcing part  53 , partially covers the supporting part  52 , and fully occupies the groove  61  of the shaft  60  and the gap between the reinforcing part  53  and the shaft  60 . 
   The invention provides a reinforcing part  53  to improve the mechanical strength of the connecting element  70 . In addition, the connecting element  70  is supported by both the reinforcing part  53  and the supporting part  52 . Therefore, separation of the connecting element  70  from the case  50  due to insufficient rigidity can be avoided. Furthermore, fixing of the shaft  60  by the connecting element  70  becomes stronger due to the reinforcing part  53 . Thus, the fan is more reliable during operation. 
   While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.