Automotive rotary electric machine

First side surfaces 22bb of first magnetic pole portions 22b and second side surfaces 23bb of second magnetic pole portions 23b that face each other in a circumferential direction are configured into parallel flat surfaces, first circumferentially tapered portions 25b are formed on circumferential shoulder portions of the first magnetic pole portions 22b, second circumferentially tapered portions 26b are formed on circumferential shoulder portions of the second magnetic pole portions 23b, and portions of the first and second circumferentially tapered portions 25b and 26b enter a region 24 in which the first side surfaces 22bb and the second side surfaces 23bb that face each other in the circumferential direction overlap when viewed from a direction that is perpendicular to the first side surfaces 22bb and the second side surfaces 23bb.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automotive rotary electric machine that includes a Lundell rotor.

2. Description of the Related Art

In conventional automotive dynamoelectric machines that have a Lundell rotor, circumferentially tapered portions are formed on shoulder portions of magnetic pole portions of claw-shaped magnetic poles that are positioned forward in a direction of rotation to reduce unpleasant wind noise that has high-order harmonic components (see Patent Literature 1, for example).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

In automotive rotary electric machines of this kind, in order to achieve compactness and high output, it is important to improve the amount of effective magnetic flux, which is the amount of magnetic flux that interlinks with a stator coil among the magnetic flux that is generated by a rotor. In order to improve this amount of effective magnetic flux, it is important to suppress magnetic leakage flux that arises between the magnetic pole portions of circumferentially adjacent claw-shaped magnetic poles. However, in conventional automotive rotary electric machines, no consideration has been given to suppressing magnetic leakage flux that arises between the circumferentially adjacent magnetic pole portions.

The present invention aims to solve problems such as that mentioned above and an object of the present invention is to provide a compact automotive rotary electric machine that can improve output.

An automotive alternator according to the present invention includes: a rotor including: a pole core that is fixed to a rotating shaft that is rotatably supported by a case, the pole core being disposed inside the case; and a field coil that is mounted to the pole core; and a stator including: a stator core; and a stator coil that is mounted to the stator core, the stator being disposed inside the case so as to be coaxial to the rotor so as to surround the rotor. The pole core includes a first pole core and a second pole core, the first pole core includes: a disk-shaped first main body portion; a first yoke that protrudes axially from a central portion of the first main body portion; and a plurality of first claw-shaped magnetic poles that are disposed on an outer circumferential portion of the first main body portion at a uniform angular pitch in a circumferential direction, the first claw-shaped magnetic pole portions each include: a first root portion that protrudes radially outward from the outer circumferential portion of the first main body portion; and a first magnetic pole portion that protrudes axially from an upper end of the first root portion, the second pole core includes: a disk-shaped second main body portion; a second yoke that protrudes axially from a central portion of the second main body portion; and second claw-shaped magnetic poles that are equal in number to the first claw-shaped magnetic pole portions, the second claw-shaped magnetic poles being disposed on an outer circumferential portion of the second main body portion at a uniform angular pitch in a circumferential direction, and the second claw-shaped magnetic pole portions each include: a second root portion that protrudes radially outward from the outer circumferential portion of the second main body portion; and a second magnetic pole portion that protrudes axially from an upper end of the second root portion. The first pole core and the second pole core are fixed to the rotating shaft in a state in which a protruding end of the first yoke and a protruding end of the second yoke are butted together, and in which the first magnetic pole portions and the second magnetic pole portions are arranged alternately, and a first side surface of the first magnetic pole portions and a second side surface of the second magnetic pole portions that face each other in a circumferential direction are configured into parallel flat surfaces. A circumferentially tapered portion is formed on a circumferential shoulder portion of at least one magnetic pole portion of the first magnetic pole portions and the second magnetic pole portions that face each other in the circumferential direction, and a portion of the circumferentially tapered portion enters a region in which the second side surface and the first side surface that face each other in the circumferential direction overlap when viewed from a direction that is perpendicular to the first side surface and the second side surface.

According to the present invention, a circumferentially tapered portion is formed on a circumferential shoulder portion of at least one magnetic pole portion of first magnetic pole portions and second magnetic pole portions that face each other in a circumferential direction, and a portion of the circumferentially tapered portion enters a region in which a second side surface and a first side surface that face each other in the circumferential direction overlap when viewed from a direction that is perpendicular to the first side surface and the second side surface. Thus, magnetic leakage flux that flows between the first magnetic pole portions and the second magnetic pole portions that face each other in the circumferential direction is reduced, increasing the amount of effective magnetic flux such that output is improved. In addition, because the magnetic leakage flux that flows between the first magnetic pole portions and the second magnetic pole portions can be reduced without widening spacing between the first magnetic pole portions and the second magnetic pole portions that face each other in the circumferential direction, axial lengths of a first root portion and a second root portion can be made shorter, enabling radial dimensions of a rotor to be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross section that shows an automotive alternator according to Embodiment 1 of the present invention, andFIG. 2is an oblique projection that shows a rotor of the automotive alternator according to Embodiment 1 of the present invention. Moreover, to facilitate explanation, “an axial direction” is an axial direction of the rotating shaft, “a radial direction” is a radial direction of the rotating shaft, and “a circumferential direction” is a direction of rotation of the rotating shaft.

InFIGS. 1 and 2, an automotive alternator100that constitutes an automotive rotary electric machine includes: a case3that is constituted by a front bracket1and a rear bracket2that are made of aluminum; a Lundell rotor7that is housed inside the case3so as to be fixed to a rotating shaft6that is supported in the front bracket1and the rear bracket2by means of bearings5; and a stator8that has an annular stator core9and a stator coil10that is mounted to the stator core9, the stator8being held so as to be coaxial to the rotor7to the case3so as to surround the rotor7so as to ensure an extremely small air gap from the rotor7.

A pulley4is fixed to a first end of the rotating shaft6such that rotational torque from an engine can be transmitted to the rotating shaft6by means of a belt (not shown). A pair of slip rings11that supply electric current to the rotor7are fixed to a second end portion of the rotating shaft6that protrudes outward from the rear bracket2. A brush holder13is disposed axially outside the rear bracket2. A pair of brushes12are housed in the brush holder13so as to slide on each of the slip rings11. A regulator14that adjusts magnitude of an alternating-current voltage that arises in the stator8is held so as to be fixed by adhesive to a heat sink15that is fitted onto the brush holder13. A rectifier16that is electrically connected to the stator8and that rectifies alternating current that is generated in the stator8into direct current is disposed axially outside the rear bracket2. A rear cover17is mounted to the rear bracket2so as to cover the brush holder13, the regulator14, and the rectifier16, etc.

The rotor7is constituted by: a field coil18that generates magnetic flux on passage of electric current; and a pole core19that is disposed so as to cover the field coil18, and in which magnetic poles are formed by the magnetic flux that is generated by the field coil18. The pole core19includes a first pole core20and a second pole core21. Fans30are fixed to two axial end surfaces of the pole core19.

Next, a shape of the second pole core21will be explained with reference toFIGS. 3 through 6.FIG. 3is an oblique projection that shows a second pole core in the rotor of the automotive alternator according to Embodiment 1 of the present invention,FIG. 4is a diagram that explains a relationship between adjacent first pole cores and second pole cores in a circumferential direction of claw-shaped magnetic poles in the rotor of the automotive alternator according to Embodiment 1 of the present invention,FIG. 5is a plan that shows the adjacent first pole cores and second pole cores in the rotor of the automotive alternator according to Embodiment 1 of the present invention when viewed from radially outside, andFIG. 6is an end elevation of a claw-shaped magnetic pole of the second pole core inFIG. 5from Direction A.

The second pole core21is produced by forging a low carbon steel, for example, and has: a disk-shaped second main body portion21a; a cylindrical second yoke21bthat is disposed so as to protrude in a first axial end direction from a central portion of this second main body portion21a; and second claw-shaped magnetic poles23that are formed so as to protrude radially outward from an outer circumference of the second main body portion21a, and then be bent in a first axial end direction. Portions of the second claw-shaped magnetic poles23that protrude radially outward from the outer circumference of the second main body portion21aconstitute second root portions23a, and portions thereof that protrude in the first axial end direction from the second root portions23aconstitute second magnetic pole portions23b. In this case, eight second claw-shaped magnetic poles23are disposed on an outer circumferential edge portion of the second main body portion21aat a uniform angular pitch circumferentially.

The second claw-shaped magnetic poles23are formed so as to have a tapered shape in which a radially outermost surface shape thereof is an approximately trapezoidal shape, a circumferential width gradually becomes narrower toward a vicinity of a tip, and a radial thickness gradually becomes thinner toward the vicinity of the tip. Radially outermost surfaces of the second magnetic pole portions23bare constituted by portions of a cylindrical surface that has a central axis of the rotating shaft6as a central axis. Two edge portions in a circumferential direction of the radially outermost surfaces of the second magnetic pole portions23bare beveled to form second tapered surfaces23ba. Second side surfaces23bbthat are positioned on two circumferential sides of the second magnetic pole portions23bare formed into flat surfaces.

Shoulder portions that are positioned in a vicinity of second axial ends on radially outer sides of the second magnetic pole portions23bare beveled to constitute second shoulder portion tapered portions26a. The second shoulder portion tapered portions26aare formed so as to have inclined surfaces in which radial positions reduce gradually toward an end surface from outer circumferential surfaces of the second magnetic pole portions23b.

Shoulder portions that are positioned in a vicinity of second axial ends on radially outer sides on two circumferential sides of the second magnetic pole portions23bare beveled to constitute second circumferentially tapered portions26b. The second circumferentially tapered portions26bare formed so as to have inclined surfaces in which radial positions reduce gradually toward side surfaces that face in a circumferential direction of the second root portions23from outer circumferential surfaces of the second magnetic pole portions23b. Lower sides26baof the second circumferentially tapered portions26bare parallel to an axial direction, and intersect with lower sides of the second shoulder portion tapered portions26aat the second axial end.

Moreover, the first pole core20has a shape that is similar or identical to that of the second pole core21. Specifically, the first pole core20has a first main body portion20a, a first yoke20b, and first claw-shaped magnetic poles22. The first claw-shaped magnetic poles22are constituted by first root portions22aand first magnetic pole portions22b. Two edge portions in a circumferential direction of the radially outermost surfaces of the first magnetic pole portions22bare beveled to form first tapered surfaces22ba. First side surfaces22bbthat are positioned on two circumferential sides of the first magnetic pole portions22bare formed into flat surfaces. Shoulder portions that are positioned in a vicinity of first axial ends on radially outer sides of the first magnetic pole portions22bare beveled to constitute first shoulder portion tapered portions25a. Shoulder portions that are positioned in a vicinity of first axial ends on radially outer sides on two circumferential sides of the first magnetic pole portions22bare beveled to constitute first circumferentially tapered portions25b. Lower sides of the first circumferentially tapered portions25bare parallel to an axial direction, and intersect with lower sides of the first shoulder portion tapered portions25aat the first axial end.

As shown inFIG. 2, the first pole core20and the second pole core21that are configured in this manner are fixed to the rotating shaft6, which is press-fitted into rotating shaft insertion apertures that are formed at central axial positions of the first and second yokes20band21bso as to butt together the second axial end surface of the first yoke20band the first axial end surface of the second yoke21band so as to intermesh the first and second magnetic pole portions22band23balternately, to constitute the pole core19. The pole core19that is configured in this manner has an outer circumferential surface that is formed into a cylindrical surface, and circumferential positions of the first and second pole cores20and21are adjusted such that circumferential spacing between each of the first and second magnetic pole portions22band23bis equal. The field coil18is disposed inside a space that is surrounded by the first and second yokes20band21band the first and second claw-shaped magnetic poles22and23.

Here, as shown inFIG. 5, the facing first and second side surfaces22bband23bbof the circumferentially adjacent first and second magnetic pole portions22band23bare approximately parallel, and are spaced apart by a distance W3. A region24in which the first and second side surfaces22bband23bboverlap when the first magnetic pole portion22bis projected onto the second magnetic pole portion23bin a direction that is perpendicular to the facing second side surface23bbis a region that is indicated by hatching inFIG. 4. As shown inFIG. 4, portions of the second circumferentially tapered portions26bthat are formed on the second magnetic pole portion23benter the region24. As shown inFIG. 6, spacing W1′ between upper ends of the second circumferentially tapered portions26bthat are formed on two circumferential shoulder portions of the second magnetic pole portion23bis shorter than a circumferential width W1of the second root portion23aof the second magnetic pole portion23b. Although not shown, portions of the first circumferentially tapered portions25bthat are formed on the first magnetic pole portion22balso enter the region24. Spacing W1′ between upper ends of the first circumferentially tapered portions25bthat are formed on two circumferential shoulder portions of the first magnetic pole portion22bis shorter than a circumferential width W1of the first root portion22aof the first magnetic pole portion22b. Thus, as shown inFIG. 5, a distance W3′ between the first and second magnetic pole portions22band23bis longer than a distance W3in the portions of the region24where the first and second circumferentially tapered portions25band26benter.

When the automotive alternator100is operating, magnetic flux that is generated on passage of electric current to the field coil18enters the teeth of the stator core9across the air gap from the first magnetic pole portions22bof the first pole core20, flows through the core back to other teeth, enters the second magnetic pole portions23bof the second pole core21across the air gap, and returns to the field coil18. The magnetic flux that flows through this magnetic path constitutes magnetic flux that contributes to electric power generation, that is, effective magnetic flux that interlinks with the stator coil10. A portion of the magnetic flux that is generated on passage of electric current to the field coil18flows from the first magnetic pole portions22bof the first pole core20to the second magnetic pole portions23bof the second pole core21. The magnetic flux that flows through this magnetic path constitutes magnetic leakage flux that does not contribute to electric power generation. This magnetic leakage flux flows through the region24that is shown inFIG. 4.

According to Embodiment 1, first circumferentially tapered portions25bare formed on two circumferential sides at first axial ends on radially outer sides of first magnetic pole portions22b. Second circumferentially tapered portions26bare formed on two circumferential sides at second axial ends on radially outer sides of second magnetic pole portions22b. Portions of the first and second circumferentially tapered portions25band26benter the region24. Because a distance W3′ between the first and second magnetic pole portions22band23bis longer than a distance W3in the portions of the region24where the first and second circumferentially tapered portions25band26benter, magnetic flux is less likely to flow from the first magnetic pole portions22bto the second magnetic pole portions23bin the portions in question, reducing the amount of magnetic leakage flux. The amount of effective magnetic flux is thereby increased, enabling output to be improved.

The first and second circumferentially tapered portions25band26bthat are formed on all of the first and second magnetic pole portions22band23bof the first and second pole cores20and21are identically shaped. In other words, the areas of the first and second circumferentially tapered portions25band26bare equal. The taper angles of the first and second circumferentially tapered portions25band26bare also equal. Thus, the magnetomotive force between respective pairs of first and second magnetic pole portions22band23bis uniform, enabling output performance of the automotive alternator100to be improved. Moreover, the “taper angle” of the first circumferentially tapered portions25bis an angle that is formed between the first circumferentially tapered portions25band a plane that contacts an intersecting portion between the first circumferentially tapered portions25band the outer circumferential surfaces of the first magnetic pole portions22b.

Now, results of measuring generated electric current in the automotive alternator100while varying rotational frequency are shown inFIG. 8.FIG. 7is a plan that shows adjacent first pole cores and second pole cores in a comparative rotor when viewed from radially outside, andFIG. 8is a graph that shows a relationship between rotational frequency and generated electric current in the automotive alternator according to Embodiment 1 of the present invention. Moreover, inFIG. 8, a solid line represents the automotive alternator100according to the present invention, and a broken line represents a comparative automotive alternator. The comparative automotive alternator is configured in a similar or identical manner to that of the automotive alternator100except that a rotor has been used from which the first and second circumferentially tapered portions25band26bare omitted.

FromFIG. 8, it was confirmed that a higher generated electric current is achieved in the automotive alternator100than in the comparative example in a low rotational frequency region that is less than or equal to 3,500 rpm. This is because the distance between the first and second magnetic pole portions22band23bis W3throughout the region24in the comparative rotor, as shown inFIG. 7. Thus, in the comparative example, the magnetic leakage flux that flows through the region24is not reduced, reducing the amount of effective magnetic flux. In contrast to that, in the automotive alternator100, because a distance W3′ between the first and second magnetic pole portions22band23bis longer than a distance W3in the portions of the region24where the first and second circumferentially tapered portions25band26benter, making magnetic flux less likely to flow from the first magnetic pole portions22bto the second magnetic pole portions23bin the portions in question, the amount of magnetic leakage flux is reduced. Thus, it can be inferred that the amount of effective magnetic flux is increased in the automotive alternator100, achieving higher generated electric currents.

Next, effects due to being able to reduce the amount of magnetic leakage flux will be explained usingFIG. 9.FIG. 9is a half section that shows the second pole core in the automotive alternator according to Embodiment 1 of the present invention. InFIG. 9, O is a central axis of the second pole core, W2is an axial length of the second root portion23aof the second claw-shaped magnetic poles23, D1is a radius of the second yoke21b, and D2is a radial distance from the central axis of the rotating shaft6to the bending boundary between the second root portions23aand the second magnetic pole portions23b. Moreover, W1is a circumferential length of the second root portion23a.

Because the first and second root portions22aand23aof the first and second claw-shaped magnetic poles22and23constitute magnetic paths when the automotive alternator100is operating, it is necessary to ensure cross-sectional area (W1×W2) in the first and second root portions22aand23asuch that the first and second root portions22aand23aare not magnetically saturated. Similarly, because the first and second yokes20band21bconstitute magnetic paths, it is necessary to ensure cross-sectional area in the first and second yokes20band21bsuch that the first and second yokes20band21bare not magnetically saturated, the radius D1of the first and second yokes20band21bbeing set to a predetermined value.

In the above-mentioned comparative example, the circumferential length W1of the first and second root portions22aand23ais made shorter, and spacing W3between the first and second magnetic pole portions22band23bis widened, in order to reduce the magnetic leakage flux between the first and second magnetic pole portions22band23b. Thus, it is necessary to extend the axial length W2of the first and second root portions22aand23ain order to ensure the cross-sectional area of the first and second root portions22aand23a. As a result thereof, it is necessary to increase D2to ensure space for housing the field coil18, leading to an increase in the diameter of the rotor7.

In Embodiment 1, because the first and second circumferentially tapered portions25band26bare included, magnetic leakage flux between the first and second magnetic pole portions22band23bcan be reduced without widening the spacing W3between the first and second magnetic pole portions22band23b. Thus, the circumferential length W1of the first and second root portions22aand23acan be lengthened. The cross-sectional area of the first and second root portions22aand23acan thereby be ensured even if the axial length W2of the first and second root portions22aand23ais made shorter. As a result thereof, because D2is reduced, and space for housing the field coil18can be ensured, radial dimensions of the rotor7can be reduced, enabling the automotive alternator100to be reduced in size.

Next, results of measuring generated electric current in the automotive alternator100while varying Hcf/Dro and Lcf/Lp are shown inFIG. 11.FIG. 10is a half section that shows the pole cores of the rotor in the automotive alternator according to Embodiment 1 of the present invention, andFIG. 11is a graph that shows electric power generating characteristics of the automotive alternator according to Embodiment 1 of the present invention.

InFIG. 10, Lp is a total sum of axial lengths of the first and second pole cores20and21, that is, a total axial length of the pole core19. Dro is the diameter of the first and second pole cores20and21, that is, the diameter of the pole core19. Hcf is a radial length between an outer circumferential surface of the first and second yokes20band21band a bending boundary between the first and second root portions22aand23aand the first and second magnetic pole portions22band23b, that is, the radial length between the outer circumferential surface of the yoke of the pole core19and the bending boundary between the root portions and the magnetic pole portions in the claw-shaped magnetic pole. Lcf is a total sum of the axial lengths of the first and second yokes20band21b, that is, a total axial length of the yoke of the pole core19.

FIG. 11shows results of measuring generated electric current when operating the automotive alternator100at 1,800 rpm while varying Lcf/Lp and Hcf/Dro. InFIG. 11, B is a plot of Lcf/Lp and Hcf/Dro when the generated electric current is 100 A, and C is a plot of Lcf/Lp and Hcf/Dro when the generated electric current is 95 A.

FromFIG. 11, it can be seen that an automotive alternator100that can generate high electric current that is greater than or equal to 100 A can be achieved by setting Hcf, Lcf, Dro, and Lp so as to satisfy 0.05<Hcf/Dro<0.10, and 0.35<Lcf/Lp<0.42. Moreover, the above-mentioned automotive alternator100is rated at 190 A.

Here, in Embodiment 1, because first and second circumferentially tapered portions25band26bare also formed on shoulder portions of the first and second magnetic pole portions22band23bthat are positioned forward in the direction of rotation of the rotor7, wind noise that has unpleasant high-order harmonic components, which constitutes a noise problem in conventional vehicles, can be reduced in a high-speed rotational region that is greater than or equal to 12,000 rpm, in a similar or identical manner to Patent Literature 1. Moreover, “forward in the direction of rotation of the rotor7” means forward in the direction of rotation of the rotor7when the vehicle is moving forward.

FIG. 12is a diagram that explains a relationship between adjacent first pole cores and second pole cores in a circumferential direction of claw-shaped magnetic poles in a rotor of an automotive alternator according to Embodiment 2 of the present invention.

InFIG. 12, first axial ends of lower sides26baof second circumferentially tapered portions26bare positioned so as to be radially level with lower sides of second shoulder portion tapered portions26a, and second axial ends of the lower sides26bathereof intersect with the second shoulder portion tapered portions26aso as to be further radially outward than the lower sides of the second shoulder portion tapered portions26a. Although not depicted, second axial ends of lower sides of first circumferentially tapered portions25bare positioned so as to be radially level with lower sides of first shoulder portion tapered portions25a, and first axial ends of the lower sides thereof intersect with the first shoulder portion tapered portions25aso as to be further radially outward than the lower sides of the first shoulder portion tapered portions25a.

Moreover, a remainder of the configuration is configured in a similar or identical manner to that of Embodiment 1 above.

In Embodiment 2, because portions of the first and second circumferentially tapered portions25band26balso enter the region24, the amount of effective magnetic flux is increased, enabling output to be improved.

In Embodiment 2, first axial ends of lower sides26baof second circumferentially tapered portions26bare positioned so as to be radially level with lower sides of second shoulder portion tapered portions26a, and second axial ends of the lower sides26bathereof intersect with the second shoulder portion tapered portions26aso as to be further radially outward than the lower sides of the second shoulder portion tapered portions26a. Thus, taper angles of the second circumferentially tapered portions26bare smaller than the taper angles of the second circumferentially tapered portions26bin Embodiment 1. Similarly, taper angles of the first circumferentially tapered portions25bare smaller than the taper angles of the first circumferentially tapered portions25bin Embodiment 1. Because the amount of chamfering for forming the first and second circumferentially tapered portions25band26bis thereby reduced, the amount of iron in the first and second pole cores20and21is increased, enabling output to be improved.

Moreover, each of the above embodiments has been explained using an automotive alternator, but the automotive rotary electric machine is not limited to an automotive alternator, and an automotive alternating-current motor, or an automotive alternator-motor can be used.

In each of the above embodiments, the number of poles in the rotor7is the sixteen poles, but similar or identical effects can also be achieved if the number of rotor poles is four poles or greater.

In each of the above embodiments, the first and second circumferentially tapered portions25band26bare formed on the shoulder portions on two circumferential sides of all of the first and second magnetic pole portions22band23b, but it is not necessary for the first and second circumferentially tapered portions25band26bto be formed on the shoulder portions on two circumferential sides of all of the first and second magnetic pole portions22band23b. For example, the first circumferentially tapered portions25bmay be formed on the shoulder portions on two circumferential sides of all of the first magnetic pole portions22b, and the second circumferentially tapered portions26bomitted. Alternatively, the first and second circumferentially tapered portions25band26bmay be formed only on shoulder portions that are forward in the direction of rotation on all of the first and second magnetic pole portions22band23b.