An interfitting groove is disposed in a bottom portion of a trough portion so as to have a groove direction that is axial and so as to extend axially outward from axially inside, and a rotation arresting portion housing recess portion is recessed into an axially inner opening edge portion of the interfitting groove on a first yoke portion. A magnet holding seat that holds a permanent magnet is disposed in the trough portion by an interfitting portion being fitted into the interfitting groove such that radial movement is restricted. A rotation arresting portion that is disposed so as to project axially outward from a flange portion of the bobbin is housed inside a space that is constituted by the rotation arresting portion housing recess portion and an external shape reduced portion that extends axially inward from the interfitting groove such that rotation of the bobbin around the shaft is restricted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dynamoelectric machine such as an automotive alternator, etc., and particularly relates to a permanent magnet holding construction in a Lundell rotor.

2. Description of the Related Art

Automotive alternators that use Lundell rotors have been used in automobiles for decades. Loads from electrical equipment that is mounted due to environmental issues have been increasing rapidly in recent years, and further increases in generated power are being sought from Lundell rotors.

In view of these conditions, generated power has conventionally been increased by disposing permanent magnets on yoke portions of a Lundell rotor so as to face claw-shaped magnetic poles to alleviate magnetic saturation of the pole core (See Patent Literature 1 through 3, for example).Patent Literature 1: WO/2008/044347 (Pamphlet: FIG. 14)Patent Literature 2: Japanese Patent Laid-Open No. 2003-244875 (Gazette: FIG. 8)Patent Literature 3: Japanese Patent Laid-Open No. HEI 10-136623 (Gazette: FIG. 3)

SUMMARY OF THE INVENTION

However, in conventional automotive alternators such as those described in Patent Literature 1 through 3, generated power can be increased by alleviating magnetic saturation of the pole core by disposing permanent magnets, but no consideration has been given to preventing rotation of a bobbin onto which a field coil is wound that is mounted onto a boss portion between the yoke portions. Thus, one disadvantage has been that when conventional automotive alternators are rotated at high speed and a high angular speed is applied to the bobbin, the bobbin may rotate around the axis of the boss portion, causing breakages in output wires of the field coil.

The present invention aims to solve the above problems and an object of the present invention is to provide a dynamoelectric machine that can increase reliability and durability and improve output characteristics by enabling a permanent magnet to be held while preventing rotation of a bobbin onto which a field coil is wound to suppress occurrences of breakages of output wires of the field coil, etc.

In order to achieve the above object, according to one aspect of the present invention, there is provided a dynamoelectric machine including: a rotor including: a pole core including: a boss portion; a pair of yoke portions that are disposed so as to extend radially outward from two axial end edge portions of the boss portion; and a plurality of claw-shaped magnetic pole portions that are disposed so as to extend in an axial direction alternately from each of the pair of yoke portions, and that are arranged circumferentially so as to intermesh with each other, a trough portion that curves radially inward being formed on a portion of each of the yoke portions between circumferentially adjacent claw-shaped magnetic pole portions, and the pole core being fixed to a shaft that is inserted through a central axial position of the boss portion; and a field coil that is wound onto a bobbin that is mounted to the boss portion, and that is housed inside a space that is surrounded by the boss portion, the pair of yoke portions, and the plurality of claw-shaped magnetic pole portions; a stator that is disposed so as to surround an outer circumference of the rotor; and a permanent magnet that is disposed in the trough portion so as to face an inner circumferential surface near a tip end of the claw-shaped magnetic pole portions. The dynamoelectric machine includes: an interfitting groove that is disposed in a bottom portion of the trough portion so as to have a groove direction that is axial and so as to extend axially outward from axially inside; a rotation arresting portion housing recess portion that is recessed into an axially inner opening edge portion of the interfitting groove on the yoke portions; a magnet holding seat that is disposed in the trough portion by being fitted into the interfitting groove such that radial movement is restricted, and that holds the permanent magnet; and a rotation arresting portion that is disposed so as to project axially outward from a flange portion of the bobbin, the rotation arresting portion being housed inside a space that is constituted by the rotation arresting portion housing recess portion and the magnet holding seat such that rotation of the bobbin around the shaft is restricted.

According to the present invention, because a rotation arresting portion of a bobbin is housed inside a space that is constituted by a rotation arresting portion housing recess portion that is recessed into an axially inner opening edge portion of an interfitting groove of a yoke portion and a magnet holding seat that is fitted into the interfitting groove, rotation of a bobbin onto which a field coil is wound can be prevented, and the magnet holding seat, which holds a permanent magnet, can also be mounted to a trough portion so as to avoid interference with the rotation arresting portion. Thus, occurrences such as breakages of output wires of the field coil, etc., can be suppressed, increasing reliability and durability, and also improving output characteristics.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross section that schematically shows an automotive alternator according to Embodiment 1 of the present invention,FIG. 2is a perspective of a rotor that can be used in the automotive alternator according to Embodiment 1 of the present invention,FIG. 3is a cross section of the rotor that can be used in the automotive alternator according to Embodiment 1 of the present invention,FIG. 4is a perspective of a field coil assembly that can be installed in the rotor that can be used in the automotive alternator according to Embodiment 1 of the present invention, andFIG. 5is a side elevation of part of a bobbin of the field coil assembly that can be installed in the rotor that can be used in the automotive alternator according to Embodiment 1 of the present invention.FIGS. 6A and 6Bare diagrams that explain a configuration of a permanent magnet assembly that can be mounted to the rotor that can be used in the automotive alternator according to Embodiment 1 of the present invention,FIG. 6Ashowing a step of mounting the permanent magnet, andFIG. 6Bshowing a mounted state of the permanent magnet.FIG. 7is a perspective that explains a construction of a trough portion of a pole core in the rotor that can be used in the automotive alternator according to Embodiment 1 of the present invention, andFIG. 8is a perspective that explains a method for mounting the permanent magnet assembly to the pole core in the automotive alternator according to Embodiment 1 of the present invention.FIGS. 9A and 9Bare diagrams that explain a configuration of a magnet holding seat of the permanent magnet assembly in the automotive alternator according to Embodiment 1 of the present invention,FIG. 9Ashowing a cross section thereof andFIG. 9Bshowing a front elevation.FIGS. 10A and 10Bare diagrams that explain the configuration of the magnet holding seat of the permanent magnet assembly in the automotive alternator according to Embodiment 1 of the present invention,FIG. 10Ashowing a cross section thereof andFIG. 10Bshowing a front elevation.FIGS. 11A and 11Bare diagrams that explain the configuration of the magnet holding seat of the permanent magnet assembly in the automotive alternator according to Embodiment 1 of the present invention,FIG. 11Ashowing a cross section thereof andFIG. 11Bshowing a front elevation.FIGS. 12A and 12Bare diagrams that explain a relationship between the magnet holding seat and a rotation arresting portion of the bobbin in the automotive alternator according to Embodiment 1 of the present invention,FIG. 12Ashowing a cross section thereof andFIG. 12Bshowing a front elevation.

InFIGS. 1 through 5, an automotive alternator1that functions as a dynamoelectric machine includes: a case4that is constituted by a front bracket2and a rear bracket3that are each made of aluminum so as to have an approximate cup shape; a rotor15that is rotatably disposed inside the case4such that a shaft16is supported by means of bearings5in the case4; a pulley6that is fixed to an end portion of the shaft16that extends outward at a front end of the case4; fans7that are fixed to two axial end surfaces of the rotor15; a stator10that is fixed to the case4so as to surround an outer circumference of the rotor15so as to have a constant air gap relative to the rotor15; a pair of slip rings8that are fixed to a rear end of the shaft16, and that supply current to the rotor15; a pair of brushes9that are disposed inside the case4so as to slide on the respective slip rings8; a rectifier13that rectifies an alternating current that is generated in the stator10into direct current; and a voltage regulator14that adjusts magnitude of an alternating voltage that is generated in the stator10.

The stator10includes: a cylindrical stator core11; and a stator coil12that is mounted to the stator core11, and in which an alternating current arises due to changes in magnetic flux from a field coil17(described below) that accompany rotation of the rotor15.

The rotor15includes: a field coil17that generates magnetic flux on passage of an excitation current; a pole core18that is disposed so as to cover the field coil17and in which magnetic poles are formed by that magnetic flux; and the shaft16, which is fitted through a central axial position of the pole core18.

The pole core18is configured so as to be divided into first and second pole core bodies19and23that are each prepared by a cold forging manufacturing method using a low carbon steel such as S10C, for example.

The first pole core body19has: a first boss portion20that has an outer circumferential surface that has a cylindrical shape, and in which a shaft insertion aperture is formed so as to pass through at a central axial position; a thick ring-shaped first yoke portion21that is disposed so as to extend radially outward from a first end edge portion of the first boss portion20; and first claw-shaped magnetic pole portions22that are disposed so as to extend toward a second axial end from outer circumferential portions of the first yoke portion21. Eight, for example, first claw-shaped magnetic pole portions22are formed so as to have a tapered shape in which a radially-outermost surface shape is an approximately trapezoidal shape, a circumferential width gradually becomes narrower toward a tip end, and a radial thickness gradually becomes thinner toward the tip end, and are arranged on the outer circumferential portions of the first yoke portion21at a uniform angular pitch circumferentially.

The second pole core body23has: a second boss portion24that has an outer circumferential surface that has a cylindrical shape, and in which a shaft insertion aperture is formed so as to pass through at a central axial position; a thick ring-shaped second yoke portion25that is disposed so as to extend radially outward from a second end edge portion of the second boss portion24; and second claw-shaped magnetic pole portions26that are disposed so as to extend toward a first axial end from outer circumferential portions of the second yoke portion25. Eight, for example, second claw-shaped magnetic pole portions26are formed so as to have a tapered shape in which a radially-outermost surface shape is an approximately trapezoidal shape, a circumferential width gradually becomes narrower toward a tip end, and a radial thickness gradually becomes thinner toward the tip end, and are arranged on the outer circumferential portions of the second yoke portion25at a uniform angular pitch circumferentially.

The bobbin28is a resin-molded body that is made of an insulating resin, and includes: a drum portion29that is mounted so as to be fitted over the first and second boss portions20and24; a pair of flange portions30that are disposed so as to extend radially outward from two axial ends of the drum portion29; eight rotation arresting portions31that are disposed so as to project at a uniform angular pitch from each of the pair of flange portions30; and cover portions32that are disposed so as to extend from outer circumferential edge portions of the pair of flange portions30so as to cover the field coil17that is wound onto the drum portion29. Each of the rotation arresting portions31is configured so as to have a Y-shaped thick portion that is disposed so as to project axially outward from each of the flange portions30. A field coil assembly27is prepared by winding a conducting wire that constitutes the field coil17into multiple layers on the drum portion29of the bobbin28.

As shown inFIG. 7, trough portions35are recessed so as to have U-shaped walls that curve concavely radially inward at respective portions of the first yoke portion21between circumferentially adjacent first claw-shaped magnetic pole portions22. These trough portions35that are curved radially inward pass through the first yoke portion21axially such that circumferential widths thereof become gradually narrower toward a radially inner side. Rotation arresting portion housing recess portions36are recessed into (axially inner) edge portions of the trough portions35near the field coil17and into axially inner portions of the first yoke portion21at lower portions of the trough portions35so as to have axial depths that are equal to wall thicknesses of the rotation arresting portions31and internal shapes that conform to external shapes of the rotation arresting portions31. In addition, interfitting grooves37that have major arc cross sections are formed so as to expand near a floor portion of the trough portions35so as to have groove directions that are axial, and so as to have predetermined lengths outward from axially inside. Here, the interfitting grooves37do not pass through the trough portions35of the first yoke portion21axially, but have bottom surfaces37athat are perpendicular to an axial direction that function as stopping portions.

Moreover, although not explained, trough portions35, rotation arresting portion housing recess portions36, and interfitting grooves37are also formed on the second yoke portion25in a similar manner.

As shown inFIG. 6B, a permanent magnet assembly40includes: a permanent magnet41; and a magnet holding seat42that fits over and holds the permanent magnet41. The permanent magnet41is prepared into a columnar body that has a predetermined length that has a cross-sectional shape that is an isosceles trapezoid using a neodymium-iron-boron rare earth sintered magnet, for example.

The magnet holding seat42is configured using a magnetic material into a columnar body that has a composite cross-sectional shape that aligns an upper side (a short side) of an isosceles trapezoid with a chord of a major arc and that has a thickness that is approximately equal to the length of the permanent magnet41. A magnet holding portion43that is constituted by a columnar portion that has an isosceles trapezoidal cross section is prepared so as to have a shape that can be fitted between side surfaces of a trough portion35that face each other circumferentially when the permanent magnet assembly40is mounted to the trough portion35. A magnet interfitting groove44is recessed into a bottom surface of the magnet holding portion43that is constituted by a lower side (a long side) of an isosceles trapezoidal cross section so as to have a groove shape in which a groove direction is in a thickness direction and a groove width increases with depth. The groove shape of the magnet interfitting groove44matches approximately with a cross-sectional shape of a bottom surface of the permanent magnet41that is constituted by a lower side (a long side) of the isosceles trapezoidal cross section.

In addition, the magnet holding seat42includes: an external shape reduced portion45that is prepared by cutting away an outer circumferential edge portion of a first end in a thickness direction of the columnar portion that has a major arc cross section to a predetermined thickness, and in which a width gradually becomes thinner away from the chord of the major arc; and an interfitting portion46that is constituted by a remaining portion of the columnar portion that has a major arc cross section. The external shape of the external shape reduced portion45conforms to an internal shape of a forked portion of the rotation arresting portions31of the bobbin28. The interfitting portion46has a thickness that is approximately equal to a groove length of the interfitting groove37that is formed on the trough portion35, and an external shape thereof conforms to a groove shape of the interfitting groove37. Notches47that have a predetermined depth are disposed so as to extend from the first end in the thickness direction of the magnet holding seat42to a second end on two side surfaces of the magnet holding seat42at boundaries between the magnet holding portion43and the external shape reduced portion45and the interfitting portion46.

As shown inFIG. 6A, the permanent magnet assembly40is assembled by fitting the permanent magnet41into the magnet interfitting groove44from the first end in the thickness direction of the magnet holding seat42. Thus, the permanent magnet41is held in the magnet holding seat42so as to be connected magnetically by being fitted into the magnet interfitting groove44such that a bottom surface thereof faces a bottom surface of the magnet interfitting groove44in contact therewith or so as to leave a minute gap. Moreover, the permanent magnet41is held in the magnet holding seat42by the fitting force from the magnet interfitting groove44, but an adhesive may also be applied if required.

As shown inFIG. 8, a permanent magnet assembly40that has been assembled in this manner is mounted into each of the trough portions35of the first pole core body19from axially inside the first pole core body19by inserting the interfitting portion46into the interfitting groove37until comes into contact with the bottom surface37a. Here, radially outward movement of the permanent magnet assembly40is restricted by the groove shape of the interfitting groove37that has a major arc cross section, circumferential movement is restricted by the magnet holding portion43being inserted between the side surfaces of the trough portion35that face each other circumferentially, and axially outward movement is restricted by the interfitting portion46coming into contact with the bottom surface37aof the interfitting groove37.

The magnet holding seats42are held in each of the trough portions35of the first pole core body19so as to be connected magnetically by being fitted into the interfitting groove37such that an outer circumferential surface of the interfitting portion46faces an inner circumferential surface of the interfitting groove37in contact therewith or so as to leave a minute gap. Moreover, the magnet holding seats42are held in the trough portions35by the fitting force from the interfitting groove37, but an adhesive may also be applied if required. Drippings that are formed during formation of the interfitting groove37on opening edge portions that are constituted by two ends of the interfitting groove37that has a major arc cross section are housed inside the notches47when the interfitting portion46is inserted inside the interfitting groove37, and do not affect the mounting operation of the magnet holding seat42into the trough portions35. Moreover, permanent magnet assemblies40are also mounted to the trough portions35of the second pole core body23in a similar manner.

To assemble the rotor15, the first and second pole core bodies19and23in which a permanent magnet assembly40is mounted to each of the trough portions35are fixed to the shaft16that has been fitted through the shaft insertion apertures such that the first and second claw-shaped magnetic pole portions22and26alternately intermesh and a second end surface of the first boss portion20is abutted to a first end surface of the second boss portion24. Here, the first and second boss portions20and24and the first and second yoke portions21and25correspond to a boss portion and first and second yoke portions of the pole core18.

In a rotor15that has been assembled in this manner, the field coil assembly27is housed in a space that is surrounded by the first and second boss portions20and24, the first and second yoke portions21and25, and the first and second claw-shaped magnetic pole portions22and26by inserting the first and second boss portions20and24inside the drum portion29of the bobbin28. The cover portions32extend from outer circumferential edge portions of the pair of flange portions30so as to cover the field coil17that is wound onto the drum portion29, ensuring electrical insulation between the field coil17and the first and second claw-shaped magnetic pole portions22and26. The rotation arresting portions31of the bobbin28are housed inside spaces that are formed by the rotation arresting portion housing recess portions36that are formed on the first and second yoke portions21and25and the external shape reduced portions45that extend axially inward from the interfitting grooves37, restricting rotation of the bobbin28and also performing circumferential positioning of the bobbin28. In addition, end surfaces of the interfitting portions46come into contact with the rotation arresting portions31, restricting axially inward movement of the permanent magnet assemblies40.

Here, the permanent magnets41are disposed in the respective trough portions35so as to face inner circumferential surfaces near tip ends of the first and second claw-shaped magnetic pole portions22and26, and are magnetically oriented so as to be opposite to an orientation of a magnetic field that the field current that flows through the field coil17produces in a plane that is perpendicular to a central axis of the rotor15. Although not shown, output wires17aof the field coil17are led out through lead grooves that are recessed into floor portions of two trough portions35of the second pole core body23so as to extend outward from axially inside, and are connected to the slip rings8.

Next, operation of an automotive alternator1that has been configured in this manner will be explained.

First, electric current is supplied from a battery (not shown) to the field coil17of the rotor15by means of the brushes9and the slip rings8, generating magnetic flux. The first claw-shaped magnetic pole portions22of the first pole core body19are magnetized into North-seeking (N) poles by this magnetic flux, and the second claw-shaped magnetic pole portions26of the second pole core body23are magnetized into South-seeking (S) poles.

At the same time, rotational torque from an engine is transmitted to the shaft16by means of a belt (not shown) and the pulley6, rotating the rotor15. Thus, a rotating magnetic field is applied to the stator coil12of the stator10, generating electromotive forces in the stator coil12. These alternating-current electromotive forces are rectified into direct current by the rectifier13to charge the battery or to be supplied to electric loads, etc.

Magnetic flux is generated when an electric current is passed through the field coil17. This magnetic flux enters tooth portions of the stator core11by passing through the air gap from the first claw-shaped magnetic pole portions22. The magnetic flux then moves circumferentially through a core back portion from the tooth portions of the stator core11, and enters neighboring second claw-shaped magnetic pole portions26by passing through the air gap from the tooth portions that face those second claw-shaped magnetic pole portions26. Next, the magnetic flux that has entered the second claw-shaped magnetic pole portions26passes through the second yoke portion25, the second boss portion24, the first boss portion20, and the first yoke portion21, and reaches the first claw-shaped magnetic pole portions22. Now, in a conventional Lundell rotor, because the first and second pole core bodies are at their design limit, they are magnetically saturated by the magnetic field that is generated by the field coil, reducing magnetic flux that is generated by the rotor.

In Embodiment 1, the permanent magnets41are magnetically oriented so as to be opposite to the orientation of the magnetic field that is generated by the field coil17. Thus, to interlink with the stator core11, it is necessary for the magnetic flux that originates from the permanent magnets41to make a round trip across the air gap, which has a large magnetic resistance. The permanent magnets41are disposed radially inside the first and second claw-shaped magnetic pole portions22and26, and are disposed so as to circuit in a shorter magnetic path length to the inner circumferential surface sides of the first and second claw-shaped magnetic pole portions22and26. Thus, a large portion of the magnetic flux that originates from the permanent magnets41forms a closed magnetic circuit inside the rotor15without going around through the stator core11.

In other words, the magnetic flux that originates from the permanent magnets41that are disposed in the trough portions35between the first claw-shaped magnetic pole portions22passes from the magnet holding seats42through the first yoke portion21, the first boss portion20, the second boss portion24, the second yoke portion25, and the second claw-shaped magnetic pole portions26, and returns to the permanent magnets41. The magnetic flux that originates from the permanent magnets41that are disposed in the trough portions35between the second claw-shaped magnetic pole portions26enters the first claw-shaped magnetic pole portions22by means of the gap, passes through the first yoke portion21, the first boss portion20, the second boss portion24, the second yoke portion25, and the magnet holding seats42, and returns to the permanent magnets41.

Thus, the magnetic flux that originates from the permanent magnets41is in a reverse direction from the magnetic flux34athat originates from the field coil17, enabling the magnetic flux density of the magnetic bodies that constitute the first and second pole core bodies19and23to be reduced significantly, thereby enabling magnetic saturation to be relieved.

According to Embodiment 1, interfitting grooves37that have major arc cross sections are formed on floor portions of each of the trough portions35of the first and second pole core bodies19and23outward from axially inside so as to have groove directions that are axial, and rotation arresting portion housing recess portions36are recessed into axially inner edge portions of the trough portions35of the first and second yoke portions21and25so as to have internal shapes that conform to the external shapes of the Y-shaped rotation arresting portions31. The magnet holding seats42include: interfitting portions46that have external shapes that conform to the groove shapes of the interfitting grooves37that have major arc cross sections; and external shape reduced portions45that have external shapes that conform to internal shapes of forked portions of the rotation arresting portions31on first ends in the thickness direction of the interfitting portions46.

Thus, the rotation arresting portions31can be housed inside spaces that are formed by the rotation arresting portion housing recess portions36and the external shape reduced portions45simply by mounting the field coil assembly27onto the first and second pole core bodies19and23in which the permanent magnet assemblies40have been mounted to the trough portions35by fitting the interfitting portions46of the magnet holding seats42into the interfitting grooves37, and integrating the first and second pole core bodies19and23. A rotor15in which rotation of the field coil assembly27around the shaft16is prevented can thereby be assembled easily. In addition, even if a high angular speed is applied to the bobbin28by operating the automotive alternator1at high speed, rotation of the field coil assembly27around the shaft16is prevented, enabling breakage of the output wires17aof the field coil17to be prevented.

Because external shape reduced portions45that extend axially inward from the interfitting grooves37can be prepared so as to have shapes that do not interfere with the rotation arresting portions31, conventional parts can be used for the bobbin28, enabling costs to be reduced. In addition, because axially inner positions of the magnet holding seats42can be disposed closer to the field coil17and overlap between the permanent magnets41and the first and second claw-shaped magnetic pole portions22and26can be increased in an axial direction, magnetic flux that originates from the permanent magnets41flows between the permanent magnets41and the first and second claw-shaped magnetic pole portions22and26efficiently.

Because the interfitting grooves37do not pass through the trough portions35axially but have crescent-shaped bottom surfaces37athat are perpendicular to an axial direction, axial positions of the magnet holding seats42can be positioned by fitting the interfitting portions46into the interfitting grooves37until end surfaces of the interfitting portions46come into contact with the bottom surfaces37a. In addition, because the rotation arresting portions31are positioned axially inside the interfitting portions46that are fitted into the interfitting grooves37, axial movement of the interfitting portions46is restricted by the bottom surfaces37aand the rotation arresting portions31.

Next, a specific construction of the magnet holding seats42will be explained with reference toFIGS. 9 through 12.

As shown inFIG. 9, a magnet holding seat42is prepared by laminating first and second thin plates50and55that are obtained by pressing and shaping magnetic steel plates.

As shown inFIGS. 10A and 10B, the first thin plates50are prepared so as to have a tapered shape in which a width becomes narrower toward a leading end, and a leading end portion thereof is a circular arc shape. Recessed grooves51in which a groove width becomes gradually wider toward the leading end are recessed into floor portions of the first thin plates50. Pairs of crimped portions52are disposed so as to project at central portions of the first thin plates50so as to be spaced apart in a width direction. In addition, notches53are recessed into longitudinally central portions of two side portions of the first thin plates50. Moreover, the recessed grooves51, the crimped portions52, and the notches53are formed simultaneously when the first thin plates50are pressed and shaped.

As shown inFIGS. 11A and 11B, the second thin plates55are prepared so as to have a composite shape that includes: a tapered shape in which a width becomes narrower toward a leading end; and a major arc shape that is linked to a leading end portion of the tapered shape. Recessed grooves56in which a groove width becomes gradually wider toward the leading end are recessed into floor portions of the second thin plates55. Pairs of crimped portions57are disposed so as to project at central portions of the second thin plates55so as to be spaced apart in a width direction. In addition, notches58are recessed into two side portions of the second thin plates55at linking portions between the tapered shape and the major arc shape. Moreover, the recessed grooves56, the crimped portions57, and the notches58are formed simultaneously when the second thin plates55are pressed and shaped.

Here, the first and second thin plates50and55are prepared so as to have identical shapes except for portions near the leading ends from the notches53and58. Portions of the second thin plates55near the leading ends from the notches58are prepared so as to be larger than the portions of the first thin plates50near the leading ends from the notches53.

Respective predetermined numbers of first and second thin plates50and55are stacked together such that press punch directions are aligned. Here, the first and second thin plates50and55are laminated so as to be positioned by fitting protruding portions of the crimped portions52(57) into recess portions on rear surfaces of neighboring crimped portions52(57). The magnet holding seats42are then prepared by pressing the laminated body of first and second thin plates50and55from two sides in a direction of lamination so as to integrate the laminated body of first and second thin plates50and55by plastically deforming, crimping, and fixing the crimped portions52(57).

The recessed grooves51and56line up in the direction of lamination to constitute the magnet interfitting groove44, and the notches53and58line up in the direction of lamination to constitute the notches47. Portions of the first and second thin plates50and55that have been laminated near root ends from the notches53and58constitute the magnet holding portion43. In addition, portions of the first thin plates50that have been laminated near the leading ends from the notches52constitute the external shape reduced portion45, and portions of the second thin plates55that have been laminated near the leading ends from the notches58constitute the interfitting portion46.

As shown inFIGS. 12A and 12B, external shape reduced portions45of magnet holding seats42that have been prepared in this manner are inserted inside the forked portions of the Y-shaped rotation arresting portions31of the bobbin28, restricting circumferential rotation of the bobbin28.

According to Embodiment 1, magnet holding seats42are prepared by laminating first and second thin plates50and55that are obtained by pressing and shaping magnetic steel plates. Thus, the magnet holding seats42can be prepared inexpensively compared to when prepared by molding. Modifications to the shape of the magnet holding seats42can also be accommodated easily, enabling manufacturing costs to be reduced.

Because the crimped portions52and57are respectively formed on the first and second thin plates50and55, the laminated body of first and second thin plates50and55can be integrated simply by pressing from two sides in the direction of lamination. Thus, need for a welding step, etc., to integrate the laminated body of first and second thin plates50and55is eliminated, enabling manufacturing costs to be reduced. In addition, because two crimped portions52and57are respectively formed on the first and second thin plates50and55, occurrence of misalignment in the step of stacking the first and second thin plates50and55is suppressed, enabling magnet holding seats42that have high dimensional precision to be prepared inexpensively.

Plate thickness of the first and second thin plates50and55will now considered.

There may be thickness irregularities in the magnetic steel plates that constitute the material for the first and second thin plates50and55that are unavoidable due to the manufacturing processes. Thus, the thickness irregularities are superimposed when the first and second thin plates50and55are laminated, making dimensional precision deteriorate. Moreover, because sixteen magnet holding seats42are mounted to the rotor15, deterioration in the dimensional precision of individual magnet holding seats42may lower the overall power generating performance of the automotive alternator1.

Steel plates that have a plate thickness less than 0.3 mm have increased thickness irregularities and also require a larger number of stacked plates. Increasing the number of stacked first and second thin plates50and55makes dimensional precision poor and also lowers workability. Steel plates that have a plate thickness greater than 2.0 mm, on the other hand, have reduced thickness irregularities and also enable the number of stacked plates to be reduced. However, if steel plates that have a plate thickness greater than 2.0 mm are used, it becomes impossible to match the thicknesses of the magnet holding seats42, the external shape reduced portions45, and the interfitting portions46to the groove length of the interfitting grooves37of the trough portions35and the shape of the rotation arresting portions31of the bobbin28with high precision. In particular, the shape of the rotation arresting portions31of the bobbin28is set so as to have a desired resistance against centrifugal forces, requiring dimension matching from the magnet holding seats42. From the above, it is desirable for the plate thickness of the first and second thin plates50and55to be set to greater than or equal to 0.3 mm and less than or equal to 2.0 mm.

Moreover, in Embodiment 1 above, permanent magnets are disposed in all of the trough portions, but permanent magnets may also be disposed in selected trough portions. In that case, it is desirable to dispose the permanent magnets in a well-balanced manner circumferentially. For example, permanent magnets may also be disposed in all of the trough portions of the second pole core body while not disposing any permanent magnets in the first pole core body. Permanent magnets may also be disposed in every second trough portion in a circumferential direction in both the first and second pole core bodies. Alternatively, permanent magnet assemblies may also be disposed in every second trough portion in a circumferential direction in both the first and second pole core bodies, and only magnet holding seats disposed in remaining trough portions. Although adopting this kind of configuration reduces output slightly compared to when the permanent magnets are disposed in all of the trough portions, the number of parts can be reduced, enabling output to be increased using an inexpensive configuration.

FIG. 13is a perspective of a field coil assembly that can be installed in a rotor that can be used in the automotive alternator according to Embodiment 2 of the present invention, andFIG. 14is a side elevation of part of a bobbin of a field coil assembly that can be installed in the rotor that can be used in the automotive alternator according to Embodiment 2 of the present invention.FIGS. 15A and 15Bare diagrams that explain a configuration of a magnet holding seat of a permanent magnet assembly in the automotive alternator according to Embodiment 2 of the present invention,FIG. 15Ashowing a cross section thereof andFIG. 15Bshowing a front elevation.FIGS. 16A and 16Bare diagrams that explain the configuration of the magnet holding seat of the permanent magnet assembly in the automotive alternator according to Embodiment 2 of the present invention,FIG. 16Ashowing a cross section thereof andFIG. 16Bshowing a front elevation.FIGS. 17A and 17Bare diagrams that explain the configuration of the magnet holding seat of the permanent magnet assembly in the automotive alternator according to Embodiment 2 of the present invention,FIG. 17Ashowing a cross section thereof andFIG. 17Bshowing a front elevation.FIGS. 18A and 18Bare diagrams that explain a relationship between the magnet holding seat and a rotation arresting portion of the bobbin in the automotive alternator according to Embodiment 2 of the present invention,FIG. 18Ashowing a cross section thereof andFIG. 18Bshowing a front elevation.

InFIGS. 13 and 14, a bobbin28A is a resin-molded body that is made of an insulating resin, and includes: a drum portion29that is mounted so as to be fitted over first and second boss portions20and24; a pair of flange portions30that are disposed so as to extend radially outward from two axial ends of the drum portion29; six rotation arresting portions31A and two output wire securing portions33that are disposed so as to project at a uniform angular pitch from each of the pair of flange portions30; and cover portions32that are disposed so as to extend from outer circumferential edge portions of the pair of flange portions30so as to cover a field coil17that is wound onto the drum portion29.

The output wire securing portions33are configured so as to have T-shaped thick portions that are disposed so as to project axially outward from each of the flange portions30, and are disposed so as to be offset by 180 degrees. The rotation arresting portions31A are constituted by: base portions34athat are constituted by Y-shaped thick portions that are disposed so as to project axially outward from the respective flange portions30; and U-shaped assembly positioning guides34bthat are disposed so as to protrude from forked portions of the base portions34a, two sets of three rotation arresting portions31A being disposed at a uniform angular pitch between the output wire securing portions33. A field coil assembly27A is prepared by winding a conducting wire that constitutes the field coil17into multiple layers on the drum portion29of the bobbin28A.

As shown inFIGS. 15A and 15B, a magnet holding seat42A is configured using a magnetic material into a columnar body that has a composite cross-sectional shape that aligns an upper side (a short side) of an isosceles trapezoid with a chord of a major arc and that has a thickness that is approximately equal to a length of a permanent magnet41. A magnet holding portion43A that is constituted by the columnar portion that has an isosceles trapezoidal cross section, is prepared so as to have a shape that can be fitted between side surfaces of a trough portion35that face each other circumferentially when the magnet holding seat42A is mounted to the trough portion35. A magnet interfitting groove44is recessed into a bottom surface of the magnet holding portion43A that is constituted by a lower side (a long side) of an isosceles trapezoidal cross section.

In addition, the magnet holding seat42A includes: an external shape reduced portion45A that is prepared by cutting away an outer circumferential edge portion of a first end in a thickness direction of a columnar portion that has a major arc cross section to a predetermined thickness; and an interfitting portion46A that is constituted by a remaining portion of the columnar portion that has a major arc cross section. The external shape of the external shape reduced portion45A conforms to an internal shape of a forked portion of the rotation arresting portions31A of the bobbin28A. The interfitting portion46A has a thickness that is approximately equal to a groove length of an interfitting groove37that is formed on the trough portion35, and an external shape thereof conforms to a groove shape of the interfitting groove37. Notches47A that have a predetermined depth are disposed so as to extend from the first end in the thickness direction of the magnet holding seat42A to a second end at positions on two side surfaces of the magnet holding seat42A that are constituted by two end portions of the interfitting portion46A that has a major arc cross section.

A magnet holding seat42A that is configured in this manner is prepared by laminating first and second thin plates50A and55A that are obtained by pressing and shaping magnetic steel plates.

As shown inFIGS. 16A and 16B, the first thin plates50A are prepared so as to have a composite shape that includes: an isosceles trapezoidal shape; and a tapered shape that is linked to a leading end portion of the isosceles trapezoidal shape. Recessed grooves51in which a groove width becomes gradually wider toward a leading end are recessed into floor portions of the first thin plates50A. Pairs of crimped portions52are disposed so as to project at central portions of the first thin plates50A so as to be spaced apart in a width direction. Moreover, the recessed grooves51and the crimped portions52are formed simultaneously when the first thin plates50A are pressed and shaped.

As shown inFIGS. 17A and 17B, the second thin plates55A are prepared so as to have a composite shape that includes: an isosceles trapezoidal shape and a major arc shape that is linked to a leading end portion of the isosceles trapezoidal shape. Recessed grooves56in which a groove width becomes gradually wider toward a leading end are recessed into floor portions of the second thin plates55A. Pairs of crimped portions57are disposed so as to project at central portions of the second thin plates55A so as to be spaced apart in a width direction. In addition, notches58are recessed into two side portions of the second thin plates55A at linking portions between the isosceles trapezoidal shape and the major arc shape. Moreover, the recessed grooves56, the crimped portions57, and the notches58are formed simultaneously when the second thin plates55A are pressed and shaped.

Respective predetermined numbers of first and second thin plates50A and55A are stacked together such that press punch directions are aligned. Here, the first and second thin plates50A and55A are laminated so as to be positioned by fitting protruding portions of the crimped portions52(57) into recess portions on rear surfaces of neighboring crimped portions52(57). The magnet holding seats42are then prepared by pressing the laminated body of first and second thin plates50A and55A from two sides in the direction of lamination so as to integrate the laminated body of first and second thin plates50A and55A by plastically deforming, crimping, and fixing the crimped portions52(57).

The recessed grooves51and56line up in the direction of lamination to constitute the magnet interfitting groove44, and the notches58line up in the direction of lamination to constitute the notches47. An isosceles trapezoidal shape laminated portion of the first and second thin plates50A and55A that have been laminated constitutes the magnet holding portion43A. In addition, a tapered shape laminated portion of the first thin plates50A that have been laminated constitutes the external shape reduced portion45A, and a major arc-shaped laminated portion of the second thin plates55A that have been laminated constitutes the interfitting portion46A.

As shown inFIGS. 18A and 18B, external shape reduced portions45A of magnet holding seats42A that have been prepared in this manner are inserted inside the forked portions of the Y-shaped rotation arresting portions31A of the bobbin28A, restricting circumferential rotation of the bobbin28A.

In Embodiment 2, magnet holding seats42A in which permanent magnets41are held are mounted to six trough portions35on respective first and second pole core bodies19and23that do not include two other trough portions35that face each other radially. A field coil assembly27A is installed in the first and second pole core bodies19and23such that output wire securing portions33are housed inside the trough portions35to which the magnet holding seats42A are not mounted. Rotation arresting portions31A are housed inside spaces that are formed by rotation arresting portion housing recess portions36that are recessed into axially inner edge portions of the trough portions35and external shape reduced portions45A that extend axially inward from interfitting grooves37. In addition, output wires17aof the field coil17are wound onto the output wire securing portions33, are extended outward from the trough portions35, and are connected to slip rings8.

Similar effects to those in Embodiment 1 above can also be achieved in Embodiment 2.

In Embodiment 2, because assembly positioning guides34bare disposed so as to project in a U shape in forked portions of Y-shaped base portions34aof the rotation arresting portions31A, it is possible to increase positioning accuracy during coupling between the field coil assembly27A and the first and second pole core bodies19and23by inserting assembly positioning guides34binto the external shape reduced portions45A of the magnet holding seats42A, enabling the number of assembly defects to be reduced, and increasing productivity. In addition, mechanical strength of the rotation arresting portions31A is increased by disposing the assembly positioning guides34bso as to protrude from the base portions34a, increasing reliability.

Because the magnet holding seats42A are configured by laminating first and second thin plates50A and55A, interference with the assembly positioning guides34bcan be avoided simply by changing the number of stacked first and second thin plates50A and55A.

Moreover, in each of the above embodiments, two crimped portions are formed on the first and second thin plates, but the number of crimped portions is not limited to two. In particular, from the viewpoint of suppressing occurrences of misalignment in the step of laminating the first and second thin plates, it is preferable for the number of the crimped portions to be set to greater than or equal to two.

In each of the above embodiments, the magnet holding seats are prepared by laminating magnetic steel plates, but the magnet holding seats may be prepared by molding, etc.

In each of the above embodiments, the interfitting grooves are formed so as to have major arc cross sections, but it is only necessary for the cross-sectional shape of the interfitting grooves to be able to restrict circumferential and radial motion of the interfitting portions of the magnet holding seats that are fitted together with the interfitting grooves, and is not limited to a major arc.

In each of the above embodiments, explanations are given for automotive alternators, but the present invention is not limited to automotive alternators, and similar effects are also exhibited if the present invention is applied to other dynamoelectric machines such as automotive electric motors, automotive generator-motors, etc.