Rotor for automotive alternator having mechanism for positioning magnetic pole cores

Abstract

A rotor for an automotive alternator includes a rotary shaft, first and second magnetic pole cores each having a plurality of magnetic pole claws, a bobbin, a field coil, a plurality of permanent magnets, and a positioning mechanism. The magnetic pole claws of the first magnetic pole core are interleaved with those of the second magnetic pole core. The field coil is wound around the first and second magnetic pole cores via the bobbin. The permanent magnets are interposed between the first and second magnetic pole cores. The positioning mechanism, which is made up of at least one of the rotary shaft, the first and second magnetic pole cores, and the bobbin, functions to position the first and second magnetic pole cores in the circumferential direction of the rotary shaft with intervals between adjacent pairs of the magnetic pole claws of the first and second magnetic pole cores being even.

1 . A rotor for an automotive alternator, comprising:
 a rotary shaft;   a pair of first and second magnetic pole cores each of which includes a hollow cylindrical boss portion, a disc portion, and a plurality of magnetic pole claws, the boss portion being fit on the rotary shaft to rotate along with the rotary shaft, the disc portion extending radially outward from an axially outer part of the boss portion, each of the magnetic pole claws axially extending from a radially outer part of the disc portion, the magnetic pole claws of the first magnetic pole core being interleaved with the magnetic pole claws of the second magnetic pole core;   a bobbin fit on both the boss portions of the first and second magnetic pole cores;   a field coil wound around the bobbin;   a plurality of permanent magnets each of which is interposed between adjacent two of the magnetic pole claws of the first and second magnetic pole cores in a circumferential direction of the rotary shaft, so as to reduce magnetic flux leakage between the two magnetic pole claws; and   a positioning mechanism made up of at least one of the rotary shaft, the first and second magnetic pole cores, and the bobbin, the positioning mechanism functioning to position the first and second magnetic pole cores in the circumferential direction of the rotary shaft with intervals between adjacent pairs of the magnetic pole claws of the first and second magnetic pole cores being even.   
     
     
         2 . The rotor as set forth in  claim 1 , wherein the bobbin has at least one protrusion that is formed on a radially inner surface of the bobbin to extend in an axial direction of the rotary shaft,
 each of the boss portions of the first and second magnetic pole cores has at least one recess that is formed on a radially outer surface of the boss portion to engage with the at least one protrusion of the bobbin, and   the at least one protrusion of the bobbin, the at least one recess of the boss portion of the first magnetic pole core, and the at least one recess of the boss portion of the second magnetic pole core together make up the positioning mechanism.   
     
     
         3 . The rotor as set forth in  claim 2 , wherein the at least one protrusion of the bobbin comprises a protrusion that continuously extends over an entire axial length of the bobbin,
 the at least one recess of the boss portion of the first magnetic pole core comprises first and second recesses that are offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the first magnetic pole core,   the at least one recess of the boss portion of the second magnetic pole core comprises first and second recesses that are offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the second magnetic pole core, and   both the first recesses of the boss portions of the first and second magnetic pole cores engage with the protrusion of the bobbin, with the second recesses of the boss portions being respectively located on both sides of the protrusion of the bobbin in the circumferential direction of the rotary shaft.   
     
     
         4 . The rotor as set forth in  claim 2 , wherein the at least one protrusion of the bobbin comprises first and second protrusions that extend respectively from first and second axial ends of the bobbin for a given axial length of the bobbin, the first and second protrusions being offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the first magnetic pole core,
 the at least one recess of the boss portion of the first magnetic pole core comprises a recess that engages with the first protrusion of the bobbin,   the at least one recess of the boss portion of the second magnetic pole core comprises a recess that engages with the second protrusion of the bobbin, and   the relative position of the recess engaging with the first protrusion of the bobbin to the magnetic pole claws in the first magnetic pole core is identical to that of the recess engaging with the second protrusion of the bobbin to the magnetic pole claws in the second magnetic pole core.   
     
     
         5 . The rotor as set forth in  claim 2 , wherein the bobbin includes a magnetic member provided inside the at least one protrusion. 
     
     
         6 . The rotor as set forth in  claim 1 , wherein the bobbin has, on a radially inner surface thereof, at least one flat area that extends in an axial direction of the rotary shaft,
 each of the boss portions of the first and second magnetic pole cores has, on a radially outer surface thereof, at least one flat area that extends in the axial direction of the rotary shaft to engage with the at least one flat area of the bobbin, and   the at least one flat area of the bobbin, the at least one flat area of the boss portion of the first magnetic pole core, and the at least one flat area of the boss portion of the second magnetic pole core together make up the positioning mechanism.   
     
     
         7 . The rotor as set forth in  claim 6 , wherein the at least one flat area of the bobbin comprises a flat area that continuously extends over an entire axial length of the bobbin,
 the at least one flat area of the boss portion of the first magnetic pole core comprises first and second flat areas that are offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the first magnetic pole core,   the at least one flat area of the boss portion of the second magnetic pole core comprises first and second flat areas that are offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the second magnetic pole core, and   both the first flat areas of the boss portions of the first and second magnetic pole cores engage with the flat area of the bobbin, with the second flat areas of the boss portions being respectively located on both sides of the flat area of the bobbin in the circumferential direction of the rotary shaft.   
     
     
         8 . The rotor as set forth in  claim 6 , wherein the at least one flat area of the bobbin comprises first and second flat areas that extend respectively from first and second axial ends of the bobbin for a given axial length of the bobbin, the first and second flat areas being offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the first magnetic pole core,
 the at least one flat area of the boss portion of the first magnetic pole core comprises a flat area that engages with the first flat area of the bobbin,   the at least one flat area of the boss portion of the second magnetic pole core comprises a flat area that engages with the second flat area of the bobbin, and   the relative position of the flat area engaging with the first flat area of the bobbin to the magnetic pole claws in the first magnetic pole core is identical to that of the flat area engaging with the second flat area of the bobbin to the magnetic pole claws in the second magnetic pole core.   
     
     
         9 . The rotor as set forth in  claim 1 , wherein the bobbin has, on a radially inner surface thereof, at least one curved area that extends in an axial direction of the rotary shaft and has a diffident curvature from the other area of the radially inner surface,
 each of the boss portions of the first and second magnetic pole cores has, on a radially outer surface thereof, at least one curved area that extends in the axial direction of the rotary shaft, with a diffident curvature from the other area of the radially outer surface, to engage with the at least one curved area of the bobbin, and   the at least one curved area of the bobbin, the at least one curved area of the boss portion of the first magnetic pole core, and the at least one curved area of the boss portion of the second magnetic pole core together make up the positioning mechanism.   
     
     
         10 . The rotor as set forth in  claim 9 , wherein the at least one curved area of the bobbin comprises a curved area that continuously extends over an entire axial length of the bobbin,
 the at least one curved area of the boss portion of the first magnetic pole core comprises first and second curved areas that are offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the first magnetic pole core,   the at least one curved area of the boss portion of the second magnetic pole core comprises first and second curved areas that are offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the second magnetic pole core, and   both the first curved areas of the boss portions of the first and second magnetic pole cores engage with the curved area of the bobbin, with the second curved areas of the boss portions being respectively located on both sides of the curved area of the bobbin in the circumferential direction of the rotary shaft.   
     
     
         11 . The rotor as set forth in  claim 9 , wherein the at least one curved area of the bobbin comprises first and second curved areas that extend respectively from first and second axial ends of the bobbin for a given axial length of the bobbin, the first and second curved areas being offset from one another in the circumferential direction of the rotary shaft by one half of the pitch of the magnetic pole claws of the first magnetic pole core,
 the at least one curved area of the boss portion of the first magnetic pole core comprises a curved area that engages with the first curved area of the bobbin,   the at least one curved area of the boss portion of the second magnetic pole core comprises a curved area that engages with the second curved area of the bobbin, and   the relative position of the curved area engaging with the first curved area of the bobbin to the magnetic pole claws in the first magnetic pole core is identical to that of the curved area engaging with the second curved area of the bobbin to the magnetic pole claws in the second magnetic pole core.   
     
     
         12 . The rotor as set forth in  claim 1 , wherein the first magnetic pole core has a protrusion that protrudes from an axial end face of the boss portion facing the second magnetic pole core,
 the second magnetic pole core has a recess that is recessed from an axial end face of the boss portion facing the first magnetic pole core, to engage with the protrusion of the first magnetic pole core, and   the protrusion of the first magnetic pole core and the recess of the second magnetic pole core together make up the positioning mechanism.   
     
     
         13 . The rotor as set forth in  claim 12 , wherein the first magnetic pole core further has a recess that is recessed from the axial end face of the boss portion, and offset from the protrusion of the first magnetic pole core in the circumferential direction by one half of the pitch of the magnetic pole claws of the first magnetic pole core,
 the second magnetic pole core further has a protrusion that protrudes from the axial end face of the boss portion to engage with the recess of the first magnetic pole core, and is offset from the recess of the second magnetic pole core in the circumferential direction by one half of the pitch of the magnetic pole claws of the second magnetic pole core, and   the engaged pairs of the protrusions and recesses of the first and second magnetic pole cores together make up the positioning mechanism.   
     
     
         14 . The rotor as set forth in  claim 12 , wherein the first magnetic pole core further has two recesses that are recessed from the axial end face of the boss portion, and respectively positioned on both sides of the protrusion of the first magnetic pole core in the circumferential direction, each of the recesses of the first magnetic pole core being offset from the protrusion of the first magnetic pole core in the circumferential direction by one half of the pitch of the magnetic pole claws of the first magnetic pole core,
 the second magnetic pole core further has a recess, which is recessed from the axial end face of the boss portion, and a protrusion that protrudes from the axial end face of the boss portion to engage with either of the two recesses of the first magnetic pole core, each of the recesses of the second magnetic pole core being offset from the protrusion of the second magnetic pole core in the circumferential direction by one half of the pitch of the magnetic pole claws of the second magnetic pole core, and   a set of the protrusion and recesses of the first magnetic pole core and a set of the protrusion and recesses of the second magnetic pole core together make up the positioning mechanism.   
     
     
         15 . The rotor as set forth in  claim 14 , wherein each of the first and second magnetic pole cores further includes one or more sets of protrusion and recesses identical to the set of the protrusion and recesses thereof,
 all the sets of the protrusion and recesses of the first magnetic pole core are symmetrically located with respect to the rotary shaft, and offset from one another in the circumferential direction by an integral multiple of the pitch of the magnetic pole claws of the first magnetic pole core,   all the sets of the protrusion and recesses of the second magnetic pole core are symmetrically located with respect to the rotary shaft, and offset from one another by an integral multiple of the pitch of the magnetic pole claws of the second magnetic pole core, and   all the sets of the protrusion and recesses of the first magnetic pole core and all the sets of the protrusion and recesses of the second magnetic pole core together make up the positioning mechanism.   
     
     
         16 . The rotor as set forth in  claim 12 , further comprising a magnetic member that is provided in a gap between the protrusion of the first magnetic pole core and the recess of the second magnetic pole core. 
     
     
         17 . The rotor as set forth in  claim 1 , wherein both the boss portions of the first and second magnetic pole cores are integrated into a common boss portion to the first and second magnetic pole cores,
 the common boss portion has two first engaging portions that are respectively provided on both axial end faces of the common boss portion,   each of the disc portions of the first and second magnetic pole cores has a second engaging portion that is provided on an axial end face of the disc portion to engage with a corresponding one of the first engaging portions of the common boss portion, and   the first engaging portions of the common boss portion and the second engaging portions of the disc portions of the first and second magnetic pole cores together make up the positioning mechanism.   
     
     
         18 . The rotor as set forth in  claim 17 , wherein the two first engaging portions of the common boss portion are offset from one another in the circumferential direction by an odd multiple of one half of the pitch of the magnetic pole claws of the first magnetic pole core. 
     
     
         19 . The rotor as set forth in  claim 17 , further comprising a magnetic member that is provided inside at least one of the first engaging portions of the common boss portion and the second engaging portions of the disc portions of the first and second magnetic pole cores. 
     
     
         20 . The rotor as set forth in  claim 1 , wherein each of the first and second magnetic pole cores has a recess that is formed in a radially inner surface of the boss portion to extend in the axial direction of the rotary shaft,
 the rotary shaft has two protrusions that are formed on the outer surface of the rotary shaft to respectively engage with the recesses of the first and second magnetic pole cores, and   the recesses of the first and second magnetic pole cores and the protrusions of the rotary shaft together make up the positioning mechanism.   
     
     
         21 . The rotor as set forth in  claim 20 , wherein the relative circumferential position of the recess to the magnetic pole claws in the first magnetic pole core is identical to that in the second magnetic pole core, and
 the protrusions of the rotary shaft are offset from one another in the circumferential direction by one half of the pitch of the magnetic pole claws of the first magnetic pole core.   
     
     
         22 . A method of manufacturing a rotor for an automotive alternator, the method comprising the steps of:
 (a) preparing a rotary shaft, a pair of first and second magnetic pole cores, a bobbin, a field coil, and a plurality of permanent magnets,   the first and second magnetic pole cores each including a hollow cylindrical boss portion, a disc portion, and a plurality of magnetic pole claws, the disc portion extending radially outward from part of the boss portion, each of the magnetic pole claws axially extending from a radially outer part of the disc portion,   wherein at least one of the rotary shaft, the first and second magnetic pole cores, and the bobbin makes up a positioning mechanism;   (b) assembling together the rotary shaft, the first and second magnetic pole cores, the bobbin, and the field coil so that: the boss portion of each of the first and second pole cores is fitted on the rotary shaft to rotate along with the rotary shaft, the magnetic pole claws of the first magnetic pole core are interleaved with the magnetic pole claws of the second magnetic pole core, the bobbin is fitted on both the boss portions of the first and second magnetic pole cores, and the field coil is wound around the bobbin,   wherein the first and second magnetic pole cores are positioned, by means of the positioning mechanism, in a circumferential direction of the rotary shaft so that intervals between adjacent pairs of the magnetic pole claws of the first and second magnetic pole cores are made even;   (c) machining the first and second magnetic pole cores to tailor them for insertion of the permanent magnets therebetween; and   (d) inserting the permanent magnets between the first and second magnetic pole cores, so that each of the permanent magnets is interposed between adjacent two of the magnetic pole claws of the first and second magnetic pole cores in the circumferential direction of the rotary shaft so as to reduce magnetic flux leakage between the two magnetic pole claws.