Electric supercharger

Abstract

An electric supercharger includes: a compressor impeller; a motor configured to transmit a driving force to the compressor impeller via a rotational shaft; a back-surface side casing facing a back surface of the compressor impeller via a gap and surrounding the rotational shaft; a bearing disposed between the back-surface side casing and the rotational shaft so as to support the rotational shaft rotatably; and a mechanical seal positioned between the back surface of the compressor impeller and the bearing in an axial direction of the compressor impeller and configured to seal a gap between the rotational shaft and the back-surface side casing.

1 . An electric supercharger, comprising:
 a compressor impeller;   a motor configured to transmit a driving force to the compressor impeller via a rotational shaft;   a back-surface side casing facing a back surface of the compressor impeller via a gap and surrounding the rotational shaft;   a bearing disposed between the back-surface side casing and the rotational shaft so as to support the rotational shaft rotatably; and   a mechanical seal positioned between the back surface of the compressor impeller and the bearing in an axial direction of the compressor impeller and configured to seal a gap between the rotational shaft and the back-surface side casing,   wherein the mechanical seal includes:
 a stationary ring supported on the back-surface side casing; 
 a rotary ring protruding from the rotational shaft toward an outer side in a radial direction of the compressor impeller and facing the stationary ring so as to be capable of being in contact with the stationary ring in the axial direction of the compressor impeller, the rotary ring being configured to rotate with the rotational shaft; and 
 a biasing member configured to bias one of the rotary ring or the stationary ring toward the other one of the rotary ring or the stationary ring, and 
   wherein a groove is formed on a facing surface which is one of a surface of the rotary ring which faces the stationary ring or a surface of the stationary ring which faces the rotary ring.   
     
     
         2 . (canceled) 
     
     
         3 . The electric supercharger according to  claim 1 ,
 wherein the back surface of the compressor impeller has a plurality of ribs disposed on the back surface at intervals in a circumferential direction of the compressor impeller.   
     
     
         4 . The electric supercharger according to  claim 3 ,
 wherein each of the ribs is disposed to so as to extend along a direction which intersects with the circumferential direction of the compressor impeller.   
     
     
         5 . The electric supercharger according to  claim 3 ,
 wherein each of the ribs has an airfoil shape.   
     
     
         6 . The electric supercharger according to  claim 3 ,
 wherein each of the ribs is disposed so as to extend in a direction inclined from a radial direction of the compressor impeller such that a radially outer end of the rib is positioned on an upstream side of a radially inner end of the rib with respect to a rotational direction of the compressor impeller.   
     
     
         7 . An electric supercharger, comprising:
 a compressor impeller;   a motor configured to transmit a driving force to the compressor impeller via a rotational shaft;   a back-surface side casing facing a back surface of the compressor impeller via a gap and surrounding the rotational shaft;   a bearing disposed between the back-surface side casing and the rotational shaft so as to support the rotational shaft rotatably;   a mechanical seal positioned between the back surface of the compressor impeller and the bearing in an axial direction of the compressor impeller and configured to seal a gap between the rotational shaft and the back-surface side casing; and   between the mechanical seal and the back surface of the compressor impeller, a rotary part protruding from the rotational shaft toward an outer side in a radial direction of the compressor impeller, the rotary part being configured to rotate together with the rotational shaft.   
     
     
         8 . The electric supercharger according to  claim 1 , further comprising an abradable coating layer formed on at least a part of the back surface of the compressor impeller, or at least a part of a surface of the back-surface side casing which faces the back surface of the compressor impeller. 
     
     
         9 . The electric supercharger according to  claim 8 ,
 wherein a ratio G/R of a size G of a gap between the back surface of the compressor impeller and the back-surface side casing to an outer diameter R of the compressor impeller is less than 0.5%.   
     
     
         10 . The electric supercharger according to  claim 1 , further comprising an internal-pressure adjustment mechanism configured to adjust a pressure inside the back-surface side casing by bringing into communication an inside and an outside of the back-surface side casing. 
     
     
         11 . The electric supercharger according to  claim 7 , further comprising an abradable coating layer formed on at least a part of the back surface of the compressor impeller, or at least a part of a surface of the back-surface side casing which faces the back surface of the compressor impeller. 
     
     
         12 . The electric supercharger according to  claim 11 ,
 wherein a ratio G/R of a size G of a gap between the back surface of the compressor impeller and the back-surface side casing to an outer diameter R of the compressor impeller is less than 0.5%.   
     
     
         13 . The electric supercharger according to  claim 7 , further comprising an internal-pressure adjustment mechanism configured to adjust a pressure inside the back-surface side casing by bringing into communication an inside and an outside of the back-surface side casing.