Abstract:
A pillow for holding a bearing comprises an outer circumferential sidewall having a radially inner side and an inner circumferential sidewall for holding the bearing. The inner circumferential sidewall has a first end connected with the radially inner side of the outer circumferential sidewall and a second end opposite to the first end. The outer circumferential sidewall and the inner circumferential sidewall are spaced apart except at the first end.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a motor structure, and more particularly, to a pillow having vibration-absorbing means and heat insulating means of a motor structure. 
     2. Description of the Related Art 
     In rotation, the temperature of the stator of a common motor rises and its heat is transferred to its surroundings. The heat transferred to the bearing adversely affects its life. In a common fan motor, e.g. a fan motor disclosed in U.S. Pat. No. 5,343,104, a pillow is provided between a bearing and the stator of the motor. The heat generated in the stator of the motor transfers to the bearing through the pillow. A conventional fan motor similar to the fan motor disclosed in U.S. Pat. No. 5,343,104 will be described in the following. 
     FIG. 1 shows a conventional fan motor structure. It comprises an upper casing  101 ; a lower casing  102  having a base portion  102   a  and a pillow portion  102   b;  a bearing  103  accommodated in the pillow portion  102   b;  a rotation shaft  104  supported by the bearing  103 ; a C-ring  105  snap engaged with the rotation shaft  104  for fixing the bearing  103  at an axial location; an impeller  106 ; a coil unit  107 , and a printed circuit board  108 . The impeller  106  consists of a plurality of blades  106   a,  a yoke  106   b,  a ring-shaped magnet  106   c,  and a hub portion  106   d.  The coil unit  107  consists of an upper cover  107   a,  a lower cover  107   b,  and a stator core  107   c.    
     When the impeller rotates, the heat generated in the coil unit  107  transfers to the bearing  103  through the pillow portion  102   b  and causes an adverse effect. Generally speaking, the pillow portion  102   b  can be made of plastic or copper. 
     Although the pillow portion  102   b  made of plastic can achieve a certain degree of insulation, most of the heat rapidly transfers to the bearing  103  through the thin sidewall of the pillow portion  102   b.  The pillow portion  102   b  made of copper can rapidly transfers heat to the bearing  103  because it can achieve a good heat conduction effect. Therefore, the pillow portion  102   b  cannot insulate the bearing  103  from the heat generated in the coil unit  107  to avoid the adverse effect on the bearing  103 . 
     Moreover, when the fan motor operates, the vibration of the impeller  106  transmits to the bearing  103  through the rotation shaft  104  and then transmits to the coil unit  107  and the printed circuit board  108  through the pillow portion  102   b.  The slight transmission of the vibration can result in the vibration and noises of the system in which the fan motor is mounted and serious transmission of the vibration can result in the disengagement between the coil unit  107  and the printed circuit board  108  or even the disengagement of the electronic elements (not shown) from the printed circuit board  108 . Therefore, if the vibration can be absorbed more effectively then the life of all the elements of the fan motor can be prolonged. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a pillow having vibration absorbing and heat insulating features. More specifically, the pillow can absorb the vibration generated when the motor operates and can prevent the heat generated in the motor from transmitting to the bearing in the motor. 
     In accordance with the first aspect of the invention, a pillow for holding a bearing comprises an outer circumferential sidewall having a radially inner side; an inner circumferential sidewall for holding the bearing, the inner circumferential sidewall having a first end connected with the radially inner side of the outer circumferential sidewall and a second end opposite to the first end, and the outer circumferential sidewall and the inner circumferential sidewall being spaced apart except at the first end. 
     The outer circumferential sidewall and the inner circumferential sidewall are integrally formed. 
     The pillow further comprises an inner bottom portion connected with the second end of the inner circumferential sidewall for closing the second end of the inner circumferential sidewall. The outer circumferential sidewall, the inner circumferential sidewall, and the inner bottom portion are integrally formed. The pillow is made of plastic material. 
     In accordance with the second aspect of the invention, a pillow for holding a bearing comprises a base portion; an outer circumferential sidewall vertically provided on said base portion and having a radially inner side; and an inner circumferential sidewall for holding said bearing, the inner circumferential sidewall having a first end connected with the radially inner side of said outer circumferential sidewall and a second end opposite to said first end, and said outer circumferential sidewall and said inner circumferential sidewall being spaced apart except at said first end. 
     The outer circumferential sidewall and the inner circumferential sidewall are integrally formed. 
     The pillow further comprises an inner bottom portion connected with the second end of the inner circumferential sidewall for closing the second end of the inner circumferential sidewall. The outer circumferential sidewall, the inner circumferential sidewall, and the inner bottom portion are integrally formed. The pillow is made of plastic material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and the features and effects of the present invention can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein: 
     FIG. 1 is a schematic sectional view of a conventional fan motor structure; 
     FIG. 2 is a schematic sectional view of a fan motor structure in accordance with a preferred embodiment of the invention; and 
     FIG. 3 is a schematic sectional view of a fan motor structure in accordance with another preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 2, a fan motor in accordance with a preferred embodiment of the invention comprises: an upper casing  101 ; a lower casing  102  having a base portion  102   a  and a pillow portion  102   b  (consisting of an outer circumferential sidewall  102   b ′, an inner circumferential sidewall  102   c ′, and an inner bottom portion  102   d ′); a bearing  103  received in the pillow portion  102   b;  a rotation axis  104  supported by the bearing  103 ; a C-ring  105  snap engaged with the rotational axis  104  for securing the bearing  103  at an axial location; an impeller  106 ; a coil unit  107 ; and a printed circuit board  108 . The impeller  106  consists of a plurality of blades  106   a,  a yoke  106   b , a ring-shaped magnet  106   c,  and a hub portion  106   d.  The coil unit  107  consists of an upper cover  107   a,  a lower cover  107   b,  and a stator core  107   c.    
     For convenience of explanation, the pillow portion  102   b  is divided into an outer circumferential sidewall  102   b ′ in contact with the coil unit  107 , an inner circumferential sidewall  102   c ′ in contact with the bearing  103 , and an inner bottom portion  102   d ′ at the lower end of the inner circumferential sidewall  102   c ′. The upper end (the first end) of the inner circumferential sidewall  102   c ′ is connected with the upper end of the outer circumferential sidewall  102   b ′ and the lower end (the second end) of the inner circumferential sidewall  102   c ′ is connected with the circumference of the inner bottom portion  102   d′.    
     By comparing FIGS. 2 and 1, it can be known that the preferred embodiment is characterized in that there is a space  110  formed between the outer circumferential sidewall  102   b ′ and the inner circumferential sidewall  102   c′.    
     The space  110  is filled with air. Due to that the heat conductivity of air is smaller than that of any solid material, the space  110  can insulate the heat generated in the coil unit  107  from being transmitted to the bearing  103 . Thereby, the life of the bearing  103  can be prolonged. 
     In another aspect, the base portion  102   a,  the outer circumferential sidewall  102   b ′, the inner circumferential sidewall  102   c ′, and the inner bottom portion  102   d ′ can be integrally formed from plastic material. Due to that plastic material has elastic and vibration absorbing features and the free degrees provided by the joint between the outer circumferential sidewall  102   b ′ and the inner circumferential sidewall  102   c ′, the pillow portion  102   b  allows the inner circumferential sidewall  102   c ′ to vibrate in the horizontal direction in FIG.  2  and can absorb the vibration. Thereby, the vibration cannot transmit to the outer circumferential sidewall  102   b ′ and the coil unit  107 . 
     Furthermore, the inner bottom portion  102   d ′ encloses the bottom end of the inner circumferential sidewall  102   c ′ so that the lubricant leaking from the bearing  103  can be held by the inner bottom portion  102   d ′. In addition, a wear liner  109  is provided on the inner bottom portion  102   d ′ to aid the C-ring  105  to rotatably support the rotation axis  104 . 
     Although a preferred embodiment of the invention has been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the scope and spirit of the invention defined by the appended claims. For example, in the fan motor shown in FIG. 3 (in which elements similar to those shown in FIG. 2 are designated by the same numerals as in FIG.  2 ), the inner bottom portion  102   d ′ as shown in FIG. 2 is omitted so that the lower end of the inner circumferential sidewall  102   c ′ is not closed. This design, similar to the above-mentioned embodiment, can provide vibration absorbing and heat insulating effects. Additionally, the outer circumferential sidewall  102   b ′, the inner circumferential sidewall  102   c ′, the inner bottom portion  102   d ′, and the base portion  102   a  can integrally form a pillow having the feature of a base. 
     The present invention is by no means restricted to the above-described preferred embodiments, but covers all variations that might be implemented by using equivalent functional elements or devices that would be apparent to a person skilled in the art, or modifications that fall within the spirit and scope of the appended claims.