Patent Publication Number: US-10781823-B2

Title: Impeller and supercharger

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of International Application No. PCT/JP2016/078660, filed on Sep. 28, 2016, which claims priority to Japanese Patent Application No. 2015-196472, filed on Oct. 2, 2015, the entire contents of which are incorporated by reference herein. 
    
    
     BACKGROUND ART 
     Technical Field 
     The present disclosure relates to an impeller, which includes a main body portion and a plurality of blades formed on an outer circumferential surface of the main body portion, and to a supercharger. 
     Related Art 
     There has been known an electric supercharger that includes a rotor provided to a shaft and a stator provided on a housing side. In the electric supercharger, the shaft is driven to rotate by a magnetic force generated between the rotor and the stator. The electric supercharger is one type of superchargers. An impeller is provided to the shaft of the electric supercharger. When the shaft is rotated by the electric motor, the impeller is rotated together with the shaft. The electric supercharger compresses air along with the rotation of the impeller and delivers the compressed air to an engine. 
     The impeller of the supercharger includes a main body portion. The main body portion is increased in diameter from one side to another side in a rotation axis direction. A plurality of blades are formed on an outer circumferential surface of the main body portion. In an impeller described in Patent Literature 1, a thinned portion which is recessed toward one side in a rotation axis direction is formed in a back surface of a main body portion. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Laid-Open No. 2-132820 
     SUMMARY 
     Technical Problem 
     As described in Patent Literature 1 mentioned above, the impeller is downweighted through the formation of the thinned portion in the back surface of the main body portion of the impeller. In such a manner, inertia of the impeller is reduced. A response performance of the impeller is improved. However, when the thinned portion is simply formed, the strength of the impeller is reduced. Therefore, a rib is formed at the thinned portion of the impeller described in Patent Literature 1 to improve the strength. The rib extends in a radial direction. However, when such a rib is formed, the rib receives air resistance. As a result, efficiency is degraded. 
     It is an object of the present disclosure to provide an impeller and a supercharger which are capable of achieving downweighting and securing the strength while suppressing degradation in efficiency. 
     Solution to Problem 
     In order to solve the above-mentioned problem, according to one embodiment of the present disclosure, there is provided an impeller, including: a main body portion which is increased in diameter from one side to another side in a rotation axis direction; a thinned portion, which is formed in a back surface of the main body portion so as to be oriented toward the another side in the rotation axis direction, and is recessed toward the one side in the rotation axis direction; a plurality of full blades which are formed on an outer circumferential surface of the main body portion so as to be oriented toward the one side in the rotation axis direction; and a plurality of splitter blades, which are formed on the outer circumferential surface, and have end portions being located on the one side in the rotation axis direction and being positioned on the another side in the rotation axis direction with respect to the full blades. 
     The thinned portion may have a deepest portion, which is located at a position being the same as positions of the end portions of the splitter blades or may reach a position deeper than the end portions. 
     The impeller may further include: a cylindrical portion, which is formed on a back surface side of the main body portion, and protrudes toward the another side in the rotation axis direction with respect to the deepest portion of the thinned portion to serve as an outer wall of an insertion hole for receiving a shaft inserted to the insertion hole; and a rib, which is arranged apart from the cylindrical portion in a radial direction of the shaft, and protrudes from the back surface of the main body portion toward the another side in the rotation axis direction and extends in a circumferential direction of the shaft. 
     In order to solve the above-mentioned problem, according to another embodiment of the present disclosure, there is provided an impeller, including: a main body portion which is increased in diameter from one side to another side in a rotation axis direction; a plurality of blades which are formed on an outer circumferential surface of the main body portion so as to be oriented toward the one side in the rotation axis direction; and a thinned portion, which is formed in a back surface of the main body portion so as to be oriented toward the another side in the rotation axis direction, and is recessed toward the one side in the rotation axis direction; a cylindrical portion, which is formed on a back surface side of the main body portion, and protrudes toward the another side in the rotation axis direction with respect to a deepest portion of the thinned portion to serve as an outer wall of an insertion hole for receiving a shaft inserted to the insertion hole; and a rib, which is arranged apart from the cylindrical portion in a radial direction of the shaft, and protrudes from the back surface of the main body portion toward the another side in the rotation axis direction and extends in a circumferential direction of the shaft. 
     In order to solve the above-mentioned problem, according to one embodiment of the present disclosure, there is provided a supercharger, including the above-mentioned impeller. 
     Effects of Disclosure 
     With the impeller and the supercharger according to the present disclosure, downweighting can be achieved, and the strength can be secured without degrading the efficiency. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic sectional view of an electric supercharger (supercharger). 
         FIG. 2A  is an external appearance perspective view of a compressor impeller. 
         FIG. 2B  is a view as seen from the direction indicated by the arrow IIb of  FIG. 2A . 
         FIG. 3  is a sectional view taken along a plane including a rotation axis of the compressor impeller. 
         FIG. 4  is an extraction view of the two-dot chain line portion of  FIG. 3 . 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Now, with reference to the attached drawings, an embodiment of the present disclosure is described in detail. The dimensions, materials, and other specific numerical values represented in the embodiment are merely examples used for facilitating the understanding of the disclosure, and do not limit the present disclosure otherwise particularly noted. Elements having substantially the same functions and configurations herein and in the drawings are denoted by the same reference symbols to omit redundant description thereof. Further, illustration of elements with no direct relationship to the present disclosure is omitted. 
       FIG. 1  is a schematic sectional view of an electric supercharger C (supercharger). In the following description, the direction indicated by the arrow L illustrated in  FIG. 1  corresponds to a left side of the electric supercharger C, and the direction indicated by the arrow R illustrated in  FIG. 1  corresponds to a right side of the electric supercharger C. As illustrated in  FIG. 1 , the electric supercharger C includes a supercharger main body  1 . The supercharger main body  1  includes a motor housing  2 . A compressor housing  4  is coupled to the left side of the motor housing  2  by a fastening bolt  3 . A plate member  6  is coupled to the right side of the motor housing  2  by a fastening bolt  5 . A cord housing  8  is coupled to the right side of the plate member  6  by a fastening bolt  7 . The motor housing  2 , the compressor housing  4 , the plate member  6 , and the cord housing  8  are integrated. 
     In the motor housing  2 , there is formed a motor hole  2   a  that is opened on the right side in  FIG. 1 . In the motor hole  2   a , an electric motor  9  is received. The electric motor  9  includes a stator  10  and a rotor  11 . The stator  10  is formed by winding coils  13  on a stator core  12 . The stator core  12  has a cylindrical shape. 
     A plurality of coils  13  are arranged in a circumferential direction of the stator core  12 . The coils  13  are arranged in the order of U-phase, V-phase, and W-phase being phases of supplied alternate-current power. Lead wires  14  are provided to the U-phase, the V-phase, and the W-phase, respectively. One end of each of the lead wires  14  is coupled to each of the coils  13  of the U-phase, the V-phase, and the W-phase. The lead wires  14  supply the alternate-current power to the coils  13 . 
     Further, the stator core  12  is inserted to the motor hole  2   a  from an opening side of the motor hole  2   a . The stator core  12  is mounted in the motor hole  2   a . An opening of the motor hole  2   a  on the right side is closed by the plate member  6 . The cord housing  8  coupled to the plate member  6  has a cord hole  8   a . The cord hole  8   a  penetrates in a right-and-left direction in  FIG. 1 . One end of the cord hole  8   a  is closed by the plate member  6 . A plate hole  6   a  is formed in the plate member  6 . The motor hole  2   a  and the cord hole  8   a  communicate with each other through the plate hole  6   a . The lead wires  14  extend from the coils  13  to the cord hole  8   a  through the plate hole  6   a.    
     The lead wires  14  are received in the cord hole  8   a . Another end of each of the lead wires  14  on a side opposite to each of the coils  13  is coupled to a connector  15 . The connector  15  has a flange portion  15   a . The flange portion  15   a  closes another end of the cord hole  8   a  of the cord housing  8 . The flange portion  15   a  is mounted to the cord housing  8  by a fastening bolt  16 . The alternate-current power is supplied to the coils  13  of the stator  10  through the connector  15  and the lead wires  14 . The stator  10  functions as an electromagnet. 
     Further, the rotor  11  is mounted to the shaft  17 . The rotor  11  is inserted to the stator core  12 . The rotor  11  has a gap with respect to the stator core  12  in a radial direction of the shaft  17 . Specifically, the rotor  11  includes a rotor core  18 . The rotor core  18  is a cylindrical member. The rotor core  18  has a hole penetrating in an axial direction of the shaft  17 . A magnet  19  (permanent magnet) is received in the hole of the rotor core  18 . The electric motor  9  generates a driving force in the rotation direction for the shaft  17  by a mutual force generated between the rotor  11  and the stator  10 . 
     The shaft  17  is inserted to a housing hole  2   b  of the motor housing  2 . The housing hole  2   b  penetrates in the axial direction of the shaft  17  through a wall portion  2   c  forming a bottom surface of the motor hole  2   a . A ball bearing  20  is arranged in the housing hole  2   b . The shaft  17  is axially supported by the ball bearing  20 . 
     One end of the shaft  17 , which protrudes toward the plate member  6  side with respect to the rotor  11 , is inserted to a boss hole  6   b . The boss hole  6   b  is formed in the plate member  6 . An annular protrusion  6   c  is formed on the plate member  6 . The annular protrusion  6   c  protrudes into the motor hole  2   a . The annular protrusion  6   c  forms a part of an outer wall forming the boss hole  6   b . A ball bearing  21  is arranged in the boss hole  6   b . The shaft  17  is axially supported by the ball bearing  21 . 
     Another end side of the shaft  17  protrudes from the housing hole  2   b  into the compressor housing  4 . On a portion of the shaft  17 , which protrudes into the compressor housing  4 , a compressor impeller  22  (impeller) is provided. The compressor impeller  22  is received in the compressor housing  4  so as to be rotatable. 
     The compressor housing  4  has an intake port  23 . The intake port  23  is opened on the left side of the electric supercharger C. The intake port  23  is connected to an air cleaner (not shown). Further, under a state in which the motor housing  2  and the compressor housing  4  are coupled to each other by the fastening bolt  3 , a diffuser flow passage  24  is formed. The diffuser flow passage  24  is formed by opposed surfaces of the motor housing  2  and the compressor housing  4 . The diffuser flow passage  24  increases the air in pressure. The diffuser flow passage  24  is annularly formed so as to extend from a radially inner side to a radially outer side of the shaft  17 . On the above-mentioned radially inner side, the diffuser flow passage  24  communicates with the intake port  23  through intermediation of the compressor impeller  22 . 
     Further, an annular compressor scroll flow passage  25  is provided to the compressor housing  4 . The compressor scroll flow passage  25  is positioned on the radially outer side of the shaft  17  with respect to the diffuser flow passage  24 . The compressor scroll flow passage  25  communicates with an intake port of an engine (not shown). The compressor scroll flow passage  25  communicates also with the diffuser flow passage  24 . 
     The driving force generated by the electric motor  9  causes the compressor impeller  22  to rotate. The rotation of the compressor impeller  22  causes air to be sucked into the compressor housing  4 . The air is sucked through the intake port  23  in the axial direction of the shaft  17 . The sucked air is increased in speed by an action of a centrifugal force in the course of flowing through between blades of the compressor impeller  22  (through between a plurality of blades  27  described later). The air having been increased in speed is delivered to the diffuser flow passage  24  and the compressor scroll flow passage  25 , and is increased in pressure (compressed). The air having been increased in pressure is led to the intake port of the engine. 
       FIG. 2A  is an external appearance perspective view of the compressor impeller  22 .  FIG. 2B  is a view as seen from the direction indicated by the arrow IIb of  FIG. 2A . 
     The compressor impeller  22  is made of, for example, carbon fiber reinforced plastic (CFRP). As illustrated in  FIG. 2A , the compressor impeller  22  includes a main body portion  26  and a plurality of blades  27 . The main body portion  26  is increased in diameter from one side (indicated by the broken line arrow on the left side in  FIG. 2A ) to another side (indicated by the one-dot chain line arrow on the right side in  FIG. 2A ) in a rotation axis direction. The main body portion  26  has an insertion hole  26   a . The insertion hole  26   a  penetrates through the main body portion  26  in an axis direction of a rotation axis (hereinafter referred to as “rotation axis direction”) about which the compressor impeller  22  rotates. That is, the insertion hole  26   a  penetrates through the main body portion  26  in an axial direction of the shaft  17 . The shaft  17  is inserted to the insertion hole  26   a  (see  FIG. 1 ). 
     The main body portion  26  has an outer circumferential surface  26   b  which is oriented toward the one side in the rotation axis direction. The main body portion  26  has a back surface  26   c  which is oriented toward the another side in the rotation axis direction. The outer circumferential surface  26   b  and the back surface  26   c  have a circular outer shape as seen from the rotation axis direction. 
     The outer circumferential surface  26   b  of the main body portion  26  is gradually increased in outer diameter toward the another side in the rotation axis direction. 
     The outer circumferential surface  26   b  has the plurality of blades  27 . The plurality of blades  27  are separated apart in a circumferential direction of the outer circumferential surface  26   b . The plurality of blades  27  protrude in a radial direction from the outer circumferential surface  26   b . The plurality of blades  27  extend in a direction of inclining in the circumferential direction of the outer circumferential surface  26   b  with respect to the rotation axis direction of the compressor impeller  22 . 
     The back surface  26   c  of the main body portion  26  has a thinned portion  26   e . The thinned portion  26   e  is a portion which is recessed toward a front end surface  26   d  side. The front end surface  26   d  is formed at a distal end of the main body portion  26  on the one side in the rotation axis direction. The back surface  26   c  is a part of an inner wall of the thinned portion  26   e . For example, the thinned portion  26   e  is formed so that the portion at which the back surface  26   c  is formed has a substantially constant thickness. 
     The thinned portion  26   e  has a cylindrical portion  26   f . The cylindrical portion  26   f  protrudes from an inner circumferential surface of the thinned portion  26   e  toward the back surface  26   c  side in the rotation axis direction of the compressor impeller  22  (another side of the rotation axis). The insertion hole  26   a  is formed on an inner circumference side of the cylindrical portion  26   f . That is, the cylindrical portion  26   f  serves as an outer wall of a portion of the insertion hole  26   a  on the back surface  26   c  side. 
     The thinned portion  26   e  has a rib  26   g  on a radially outer side of the main body portion  26  with respect to the cylindrical portion  26   f . As illustrated in  FIG. 2A  and  FIG. 2B , the rib  26   g  is formed into an annular shape. The rib  26   g  is arranged apart from the cylindrical portion  26   f  in the radial direction of the main body portion  26 . 
       FIG. 3  is a sectional view taken along a plane including the rotation axis of the compressor impeller  22 . In  FIG. 3 , the blades  27  are illustrated with respective shapes obtained as a result of projection in the rotation direction of the compressor impeller  22  (meridional shape). 
     As illustrated in  FIG. 3 , the cylindrical portion  26   f  protrudes from a deepest portion  26   h  of the thinned portion  26   e  toward the back surface  26   c  side along the rotation axis direction. 
     The plurality of blades  27  include full blades  28  (indicated by the one-dot chain lines in  FIG. 3 ) and splitter blades  29  (indicated by the broken lines in  FIG. 3 ). The full blades  28  and the splitter blades  29  protrude so as to approach a radially outer side from the outer peripheral surface  26   b  as extending from the one side (front end surface  26   d  side) toward the another side (back surface  26   c  side) in the rotation axis direction. End portions  29   a  of the splitter blades  29  on the one side in the rotation axis direction are located on the another side in the rotation axis direction with respect to end portions  28   a  of the full blades  28  on the one side in the rotation axis direction. The splitter blades  29  have smaller length in the rotation axis direction than the full blades  28 . The full blades  28  and the splitter blades  29  are arranged alternately in the circumferential direction (rotation direction) of the outer circumferential surface  26   b.    
     End portions  28   b  of the full blades  28  on the radially outer side of the outer circumferential surface  26   b  of the main body portion  26  and end portions  29   b  of the splitter blades  29  on the radially outer side of the outer circumferential surface  26   b  of the main body portion  26  extend to substantially the same positions in the radial direction and in the rotation axis direction. 
     Now, simple description is made of a flow of air around the compressor impeller  22 . Air having flowed in through the intake port  23  flows from the end portion  28   a  side of the full blades  28  through gaps between the plurality of full blades  28  adjacent to each other. The air having flowed through the gaps between the plurality of full blades  28  adjacent to each other flows from the end portion  29   a  side of the splitter blades  29  through gaps between the plurality of blades  27  adjacent to each other (full blades  28  and splitter blades  29 ). The air having flowed through the gaps between the plurality of blades  27  adjacent to each other is delivered to the radially outer side along the outer circumferential surface  26   b  of the main body portion  26  and the plurality of blades  27  while being directed toward the back surface  26   c  side. 
     That is, the end portions  28   a  of the full blades  28  are upstream ends of the full blades  28  in the flow direction of air. The end portions  29   a  of the splitter blades  29  are upstream ends of the splitter blades  29  in the flow direction of air. The end portions  28   b  of the full blades  28  are downstream ends of the full blades  28  in the flow direction of air. The end portions  29   b  of the splitter blades  29  are downstream ends of the splitter blades  29  in the flow direction of air. 
     At the upstream ends of the full blades  28  (end portions  28   a ), the short blade  29  is not present between the full blades  28 , and hence the flow passage is not divided by the short blade  29 . Therefore, a large amount of air flows into the gaps between the blades  27 . 
     Further, as described above, the compressor impeller  22  includes the splitter blades  29  and the thinned portion  26   e . Downweighting can be achieved by the thinned portion  26   e . The splitter blades  29  function as ribs. Therefore, the strength can be improved without increasing the air resistance in the thinned portion  26   e . 
       FIG. 4  is an extraction view of the two-dot chain line portion of  FIG. 3 . In  FIG. 4 , there is illustrated a draw-out line a which extends in a direction perpendicular to the rotation axis of the compressor impeller  22  from a portion  29   c  of the end portion  29   a  of the short blade  29  on the radially innermost side. As illustrated in  FIG. 4 , the end portion  29   a  of the short blade  29  is slightly inclined with respect to a direction of a plane perpendicular to the rotation axis of the compressor impeller  22 . The portion  29   c  of the short blade  29  on the radially innermost side is located on the most front end surface  26   d  side (left side in  FIG. 4 ) of the short blade  29 . 
     According to comparison between the draw-out line a and the thinned portion  26   e , a deepest portion  26   h  of the thinned portion  26   e  reaches a position deeper than the end portion  29   a  of the short blade  29  on the front end surface  26   d  side. In the deepest portion  26   h  of the thinned portion  26   e , a position in the rotation axis direction is located between the end portion  29   a  of the short blade  29  and the end portion  28   a  of the long blade  28 . That is, the thinned portion  26   e  extends in the rotation axis direction to a position between the end portion  29   a  of the short blade  29  and the end portion  28   a  of the long blade  28 . Herein, an example is given of a case in which the deepest portion  26   h  of the thinned portion  26   e  reaches a position deeper than the end portion  29   a  of the short blade  29  on the front end surface  26   d  side. However, the deepest portion  26   h  of the thinned portion  26   e  may extend to the position which is the same as the positions of the end portions  29   a  of the splitter blades  29  on the front end surface  26   d  side. 
     As described above, the strength of the compressor impeller  22  is improved by the splitter blades  29  and the rib  26   g . Therefore, the deepest portion  26   h  of the thinned portion  26   e  can be extended to the position which is deeper than the end portion  29   a  of the short blade  29  on the front end surface  26   d  side. Alternatively, the deepest portion  26   h  of the thinned portion  26   e  can be extended to the position which is the same as the positions of the end portions  29   a  of the splitter blades  29  on the front end surface  26   d  side. In such a manner, further downweighting can be achieved. 
     The embodiment has been described above with reference to the attached drawings, but, needless to say, the present disclosure is not limited to the above-mentioned embodiment. It is apparent that those skilled in the art may arrive at various alternations and modifications within the scope of claims, and those examples are understood as naturally falling within the technical scope of the present disclosure. 
     For example, in the above-mentioned embodiment, description is made of the case in which the rib  26   g  is formed. However, the rib  26   g  may be omitted as long as at least the full blades  28  and the splitter blades  29  are formed. In the case in which the rib  26   g  is formed, for example, as compared to the case in which the rib extends in the radial direction, the air resistance in the thinned portion  26   e  can be suppressed when the compressor impeller  22  is rotated. That is, the degradation in efficiency can be suppressed while improving the strength. 
     Further, in the above-mentioned embodiment, description is made of the case in which the plurality of blades  27  include the full blades  28  and the splitter blades  29 . However, the splitter blades  29  may be omitted as long as at least the rib  26   g  is formed. In this case, all of the blades  27  are the full blades  28 . For example, in order to secure the amount of inflow air, the number of blades is reduced to a half by the omission of the splitter blades  29 . However, the rib  26   g  is formed, and hence, as described above, the strength can be improved by the rib  26   g , and the reduction in efficiency due to the air resistance of the rib  26   g  can be suppressed. 
     Further, in the above-mentioned embodiment, description is made of the case in which the thinned portion  26   e  is formed so that the thickness of the portion at which the back surface  26   c  is formed is substantially constant. However, the thickness of the portion at which the back surface  26   c  is formed is not always substantially constant. When the thinned portion  26   e  is formed so that the thickness of the portion at which the back surface  26   c  is formed is substantially constant, the following effect is attained. That is, for example, when the compressor impeller  22  is manufactured by, for example, injection molding, flowability during molding is improved. 
     Further, in the above-mentioned embodiment, description is made of the case in which the deepest portion  26   h  of the thinned portion  26   e  is located at the position which is the same as the positions of the end portions  29   a  of the splitter blades  29  on the front end surface  26   d  side. Description is also made of the case in which the deepest portion  26   h  of the thinned portion  26   e  reaches the position deeper than the end portions  29   a . However, the deepest portion  26   h  of the thinned portion  26   e  may be shallower than the end portions  29   a  of the splitter blades  29  on the front end surface  26   d  side. 
     Further, in the above-mentioned embodiment, description is made of the electric supercharger C as an example. However, the above-mentioned configuration may be applied to a supercharger other than the electric supercharger C. Further, the above-mentioned configuration may be applied not only to the supercharger but also to, for example, an impeller for a centrifugal compressor. When the above-mentioned configuration is applied to the compressor impeller  22  of the electric supercharger C, further downweighting can be achieved by increasing the size of the thinned portion  26   e . This is because the rotation speed of the compressor impeller  22  during use is relatively low, and hence the requested strength is not excessively high. 
     Further, in the above-mentioned embodiment, description is made of the compressor impeller  22  as an example. However, the above-mentioned configuration may be applied to a turbine impeller of a turobcharger. 
     In the above-mentioned embodiment, description is made of the case in which the compressor impeller  22  is made of CFRP. However, the compressor impeller  22  may be made of other materials such as aluminum alloy. When the compressor impeller  22  is made of CFRP, together with the above-mentioned configuration, further downweighting can be achieved, and the strength can be synergistically improved. This is because CFRP is light and has high strength. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure can be used for an impeller having a plurality of blades on an outer circumferential surface of a main body portion, and for a supercharger.