Patent Publication Number: US-2023133593-A1

Title: Grounding structure for motor stator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 110140348, filed on Oct. 29, 2021. 
     FIELD 
     The disclosure relates to a grounding structure, particularly to a grounding structure for a motor stator that does not compromise the structure of a silicon steel sheet unit of the motor stator. 
     BACKGROUND 
     Designing electronic products that are Electromagnetic Compatibility (EMC) compliant is an important objective pursued by manufacturers of electronic products. EMC is defined as operating without creating electromagnetic interference to other equipment while preserving the original performance even though electromagnetic interference from other equipment is present. The electronic product must reduce electromagnetic interference (EMI) and not have excessive electromagnetic susceptibility (EMS) when encountering electromagnetic interference in order to achieve electromagnetic compatibility. Conventional electric motors are prone to causing electromagnetic interference to nearby equipment or are sensitive to electromagnetic interference from other equipment, due to the influence of their electromagnetic field, current, and voltage. Such electromagnetic interference may adversely affect performance or even cause operational failure in the conventional motors or the nearby equipment. In order to solve the problems as mentioned, anti-interference electronic components or conductive materials are conventionally inserted in the motor&#39;s circuit board to eliminate electromagnetic interference or improve electromagnetic tolerance. However, these electronic components or conductive materials only have a limited effect on improving EMC, while conversely, they may have an unfavorable influence on the characteristics of the motor. 
     As shown in FIG. 1, Taiwanese Utility Model Patent No. M598562 discloses an anti-interference structure for a motor stator, which includes two insulating frames  11  spaced apart from each other along an axis of the anti-interference structure, a silicon steel sheet unit  13  positioned between the two insulating frames  11  and having a slit  131  extending in an axial direction, a connector member  14  extending in the axial direction and embedded in the slit  131 , and a circuit board  12  disposed at an outer side of and connected to one of the insulating frames  11 . The connector member  14  protrudes out of the one of the insulating frames  11 , and is connected to a ground contact of the circuit board  12  to achieve grounding, so that electromagnetic interference during motor operation can be avoided and electromagnetic compatibility can be enhanced. 
     However, the anti-interference structure of the motor stator requires a slit  131  to be formed in the silicon steel sheet unit  13 , which will damage the structure of the silicon steel sheet unit  13 . In addition, the binding between the connector member  14  and the silicon steel sheet unit  13  may not be strong enough due to the manufacturing tolerances of the slit  13 . So there is still room for improvement. 
     SUMMARY 
     Therefore, the object of the disclosure is to provide a grounding structure for a motor stator without detracting from the structural integrity of the silicon steel sheet unit thereof. 
     According to the disclosure, a grounding structure for a motor stator includes a silicon steel sheet unit, an upper insulating frame, and a lower insulating frame. The upper insulating frame is disposed at an upper side of the silicon steel sheet unit along an axis. The lower insulating frame is disposed at a lower side of the silicon steel sheet unit along the axis, and cooperates with the upper insulating frame to clamp the silicon steel sheet unit therebetween. 
     The grounding structure further includes a conductive member and a circuit board. The conductive member is clamped between the silicon steel sheet unit and the lower insulating frame, and protrudes from a lower end of the lower insulating frame. The circuit board is disposed at a lower side of the lower insulating frame, and includes a negative contact that is connected to a lower edge of the conductive member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
       FIG. 1 is an exploded perspective view of the conventional anti-interference structure for a motor stator, which is disclosed in Taiwanese Utility Model Patent No. M598562; 
         FIG.  2    is a fragmentary exploded perspective view of an embodiment of the grounding structure for a motor stator according to the disclosure with a circuit board and coils thereof being omitted; 
         FIG.  3    is a vertical cross-sectional view illustrating the embodiment; and 
         FIG.  4    is a top view of the circuit board of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS.  2  and  3   , the embodiment of the grounding structure for a motor stator according to the disclosure includes a silicon steel sheet unit  21 , an upper insulating frame  22  disposed at an upper side of the silicon steel sheet unit  21  along an axis, a lower insulating frame  23  disposed at a lower side of the silicon steel sheet unit  21  along the axis and cooperating with the upper insulating frame  22  to clamp the silicon steel sheet unit  21  therebetween, a conductive member  24  confined between the silicon steel sheet unit  21  and the lower insulating frame  23 , a circuit board  25  disposed on a lower side of the lower insulating frame  23  and connected to the conductive member  24 , and a plurality of coils  26  wound on the upper insulating frame  22  and the lower insulating frame  23 . The silicon steel sheet unit  21  may be composed of a plurality of silicon steel sheets  211  stacked along the axis, but should not be limited to the above. It should be particularly noted that the upper and lower sides mentioned in this embodiment are relative to each other in the direction of the axis. This is only to facilitate the description of the relationship between the elements of this embodiment and should not limit the disposition direction of the present embodiment in actual use. 
     Referring to  FIGS.  2 ,  3 , and  4   , the lower insulating frame  23  surrounds to define an axial hole  231  that extends along the axis through upper and lower ends thereof, and a positioning groove  232  that extends transversely and outwardly from the axial hole  231  and that is adjacent to the silicon steel sheet unit  21 . The conductive member  24  includes a rim portion  241  confined in the positioning groove  232 , and a tubular portion  242  extending downwardly from an inner end of the rim portion  241  along the axis, passing through the axial hole  231 , and protruding from the lower end of the lower insulating frame  23 . In this embodiment, the conductive member  24  is made of copper, but it may also be made of other materials that have a grounding effect. The rim portion  241  is clamped between the silicon steel sheet unit  21  and the lower insulating frame  23 . The circuit board  25  includes a negative contact  251  connected to a lower edge of the tubular portion  242  of the conductive member  24 . In this embodiment, the negative contact  251  is substantially ring-shaped, as shown in  FIG.  4   . The top surface of the rim portion  241  and the lower edge of the tubular portion  242  are connected respectively to the silicon steel sheet unit  21  and the negative contact  251  to achieve a grounding effect to eliminate electromagnetic interference and increase electromagnetic tolerance. The coils  26  secure the upper insulating frame  22  and the lower insulating frame  23  to the silicon steel sheet unit  21 , such that the conductive member  24  is tightly clamped between the silicon steel sheet unit  21  and the lower insulating frame  23 . In other words, the coils  26  can ensure that the conductive member  24  is fixed between the silicon steel sheet unit  21  and the lower insulating frame  23 . This arrangement prevents the problem of poor contact after installation of the connector member  14 . 
     In summary, the disclosure achieves a secure installation of the conductive member  24  by positioning it between the silicon steel sheet unit  21  and the lower insulating frame  23 , without cutting grooves on the silicon steel sheet unit  21  to avoid damaging the structural strength of the silicon steel sheet unit  21 . 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.