U.S. patent application number 09/839173 was filed with the patent office on 2002-04-18 for automotive alternator.
Invention is credited to Adachi, Katsumi, Asao, Yoshihito.
Application Number | 20020043885 09/839173 |
Document ID | / |
Family ID | 18795449 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020043885 |
Kind Code |
A1 |
Asao, Yoshihito ; et
al. |
April 18, 2002 |
Automotive alternator
Abstract
An outboard bearing is constituted by a multi-row bearing having
one inner ring and one outer ring, a plurality of ball tracks
disposed axially between the inner ring and the outer ring, and a
plurality of balls disposed in each of the ball tracks. A rectifier
is disposed in an outboard bracket on an outer circumferential side
of an outboard bearing box, and a ventilation aperture is bored
through the outboard bracket on an outer circumferential side of
the outboard bearing box.
Inventors: |
Asao, Yoshihito; (Tokyo,
JP) ; Adachi, Katsumi; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037
US
|
Family ID: |
18795449 |
Appl. No.: |
09/839173 |
Filed: |
April 23, 2001 |
Current U.S.
Class: |
310/90 ;
310/68D |
Current CPC
Class: |
H02K 7/083 20130101;
F16C 19/08 20130101; F16C 19/18 20130101; F16C 35/067 20130101;
H02K 5/141 20130101; F16C 2380/26 20130101 |
Class at
Publication: |
310/90 ;
310/68.00D |
International
Class: |
H02K 005/16; H02K
007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2000 |
JP |
2000-316514 |
Claims
What is claimed is:
1. An automotive alternator comprising: an inboard bracket formed
in a bowl shape having a cylindrical inboard bearing box in a
central portion of an end surface, and an outboard bracket formed
in a bowl shape having a cylindrical outboard bearing box in a
central portion of an end surface, said brackets being joined with
open portions of said bowl shapes facing each other; a shaft
rotatably supported in said inboard and outboard brackets by means
of inboard and outboard bearings disposed inside said inboard and
outboard bearing boxes; a pulley fixed to an inboard end portion of
said shaft; a stator disposed such that first and second ends
thereof are supported in said inboard and outboard brackets; a
rotor fixed to said shaft, said rotor being disposed radially
inside said stator; a rectifier disposed in said outboard bracket
on an outer circumferential side of said outboard bearing box; and
a heat exchange portion for dissipating heat generated in said
rectifier, wherein said outboard bearing is constituted by a
multi-row bearing having one inner ring and one outer ring, a
plurality of ball tracks disposed axially between said inner ring
and said outer ring, and a plurality of balls disposed in each of
said ball tracks.
2. The automotive alternator according to claim 1, further
comprising slip rings for supplying a field current to a field
winding in said rotor disposed at an outboard end of said shaft,
wherein a diameter of said multi-row bearing and a diameter of said
slip rings are constructed so as to be substantially equal.
3. The automotive alternator according to claim 1 wherein said
shaft is supported in said multi-row bearing such that an outboard
end surface of said shaft is positioned between an outboard end
surface of said multi-row bearing and a center line of an outermost
ball track at said outboard end.
4. The automotive alternator according to claim 1, further
comprising a creep-preventing member disposed on an outer
circumferential surface of said outer ring of said multi-row
bearing facing said ball tracks.
5. The automotive alternator according to claim 4 wherein: said
multi-row bearing has two ball tracks; and said creep-preventing
member is formed into ring-shaped bodies having a width which is
less than or equal to a diameter of said balls disposed in said
ball tracks, said ring-shaped bodies being disposed on an outer
circumferential surface of said outer ring facing each of said ball
tracks such that width-direction center lines of said ring-shaped
bodies are offset towards end surfaces of said multi-row bearing
relative to center lines of said ball tracks.
6. The automotive alternator according to claim 4 wherein: said
outboard bracket is made of a metal; and said creep-preventing
member is made of a resin.
7. The automotive alternator according to claim 1 wherein a heat
dissipation means is disposed in said outboard bracket.
8. An automotive alternator comprising: an inboard bracket formed
in a bowl shape having a cylindrical inboard bearing box in a
central portion of an end surface, and an outboard bracket formed
in a bowl shape having a cylindrical outboard bearing box in a
central portion of an end surface, said brackets being joined with
open portions of said bowl shapes facing each other; a shaft
rotatably supported in said inboard and outboard brackets by means
of inboard and outboard bearings disposed inside said inboard and
outboard bearing boxes; a pulley fixed to an inboard end portion of
said shaft; a stator disposed such that first and second ends
thereof are supported in said inboard and outboard brackets; a
rotor fixed to said shaft, said rotor being disposed radially
inside said stator; a rectifier disposed in said outboard bracket
on an outer circumferential side of said outboard bearing box; and
a ventilation aperture bored through said outboard bracket on an
outer circumferential side of said outboard bearing box, said
automotive alternator being constructed such that said rectifier is
cooled by allowing air to flow through said ventilation aperture,
wherein said outboard bearing is constituted by a multi-row bearing
having one inner ring and one outer ring, a plurality of ball
tracks disposed axially between said inner ring and said outer
ring, and a plurality of balls disposed in each of said ball
tracks.
9. The automotive alternator according to claim 8 wherein: said
rectifier is constructed in an arc shape having a central angle of
180 degrees or more and is disposed on a common axis with said
outboard bearing so as to overlap said outboard bearing in a radial
direction; and said ventilation aperture is bored through said
outboard bracket so as to open in an arc shape for half a
circumference or more in a circumferential direction facing said
rectifier.
10. The automotive alternator according to claim 8, further
comprising slip rings for supplying a field current to a field
winding in said rotor disposed at an outboard end of said shaft,
wherein a diameter of said multi-row bearing and a diameter of said
slip rings are constructed so as to be substantially equal.
11. The automotive alternator according to claim 8 wherein said
shaft is supported in said multi-row bearing such that an outboard
end surface of said shaft is positioned between an outboard end
surface of said multi-row bearing and a center line of an outermost
ball track at said outboard end.
12. The automotive alternator according to claim 8, further
comprising a creep-preventing member disposed on an outer
circumferential surface of said outer ring of said multi-row
bearing facing said ball tracks.
13. The automotive alternator according to claim 12 wherein: said
multi-row bearing has two ball tracks; and said creep-preventing
member is formed into ring-shaped bodies having a width which is
less than or equal to a diameter of said balls disposed in said
ball tracks, said ring-shaped bodies being disposed on an outer
circumferential surface of said outer ring facing each of said ball
tracks such that width-direction center lines of said ring-shaped
bodies are offset towards end surfaces of said multi-row bearing
relative to center lines of said ball tracks.
14. The automotive alternator according to claim 12 wherein: said
outboard bracket is made of a metal; and said creep-preventing
member is made of a resin.
15. The automotive alternator according to claim 8 wherein a heat
dissipation means is disposed in said outboard bracket.
Description
[0001] This application is based on Application No. 2000-316514,
filed in Japan on Oct. 17, 2000, the contents of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an automotive alternator,
and in particular, relates to an outboard bearing construction for
supporting a rotor.
[0004] 2. Description of the Related Art
[0005] As the output of automotive alternators has increased,
enlargement of rotors and increases in interior temperature have
been promoted, requiring size reductions and high bearing
reliability.
[0006] FIG. 13 is a longitudinal section of a conventional
automotive alternator.
[0007] In FIG. 13, an inboard bracket 1 and an outboard bracket 2
are made of aluminum, formed into bowl shapes, and are fastened
together by fastening bolts and nuts (not shown) with open portions
of the bowl shapes facing each other. Cylindrical inboard and
outboard bearing boxes 1a and 2a are formed integrally in central
portions of end surfaces of the brackets 1 and 2. In addition,
inboard and outboard ventilation apertures 1b and 2b are bored
through the brackets 1 and 2 at outer circumferential portions of
the bearing boxes 1a and 2a.
[0008] A shaft 3 is rotatably supported in the brackets 1 and 2 by
means of inboard and outboard bearings 4 and 5 disposed inside the
bearing boxes 1a and 2a. A Lundell-type rotor 6 is fixed to the
shaft 3 and disposed rotatably inside the brackets 1 and 2. In
addition, a stator 7 is disposed with a first and second end
thereof supported by the brackets 1 and 2 so as to surround the
rotor 6.
[0009] Slip rings 8 for supplying field current to a field winding
in the rotor 6 are fixed to an outboard end of the shaft 3, and a
pair of brushes 9 are housed inside a brush holder 10 disposed
inside the brackets 1 and 2 so as to slide in contact with the slip
rings 8.
[0010] A pulley 11 and an external fan 12 are fixed to an inboard
end portion of the shaft 3, and in addition, a rectifier 13
electrically connected to the stator 7 for converting alternating
current generated in the stator 7 into direct current is mounted
inside the outboard bracket 2.
[0011] In conventional automotive alternators constructed in this
manner, an electric current is supplied from a battery (not shown)
through the brushes 9 and the slip rings 8 to the field winding in
the rotor 6, generating magnetic flux. Magnetic poles are generated
by this magnetic flux in claw-shaped magnetic poles on the rotor 6.
At the same time, rotational torque from an engine is transmitted
through a belt (not shown) and the pulley 11 to the shaft 3,
rotating the rotor 6. Thus, a rotating magnetic field is applied to
a stator winding 7a, generating an electromotive force in the
stator winding 7a. This alternating-current electromotive force
passes through the rectifier 13 and is converted into direct
current, charging the battery.
[0012] The external fan 2 is rotated and driven together with the
rotation of the shaft 3, forming a cooling air flow in which
external air flows in through the outboard ventilation apertures
2b, flows through the inside of the brackets 1 and 2, and is
expelled through the inboard ventilation aperture 1b, cooling
heat-generating parts such as the stator 7, the rotor 6, the
rectifier 13, and a voltage regulator (not shown).
[0013] Now, as shown in FIG. 14, the outboard bearing 5 is
constituted by a single-row bearing having a cylindrical inner ring
15 and a cylindrical outer ring 16, a ball track 17 disposed
between the inner ring 15 and the outer ring 16, and a plurality of
balls 18 disposed in the ball track 17. The inner ring 15 is fixed
to the shaft 3, and the outer ring 16 is fixed to the outboard
bearing box 2a.
[0014] Thus, rotational torque from the engine is transmitted
through the belt and the pulley 11 to the shaft 3, and the inner
ring 15, which is fixed to the shaft 3, is rotated and driven with
the shaft 3. A radial load due to tension applied to the belt is
transmitted through the plurality of balls 18 to the outer ring 16.
A load due to the weight of the rotor 6 is also transmitted through
the plurality of balls 18 to the outer ring 16. By passing through
the balls 18, these loads are applied to the outer ring 16 as
vibrating loads, repeatedly giving rise to warping in the outer
ring 16. Thus, one problem has been that fatigue failure occurs in
the inner ring 15, the outer ring 16, and the balls 18, reducing
the life of the outboard bearing 5.
[0015] In order to solve this problem, countermeasures have been
taken to raise outer-ring rigidity by increasing the diameter of
the bearing, substituting a bearing having a large load capacity,
or thickening the wall of the outer ring. However, these
countermeasures involve increasing the diameter of the outboard
bearing 5, in other words, increasing the diameter of the outboard
bearing box 2a, thereby reducing the size of the outboard
ventilation apertures 2b. Similarly, the size of the rectifier 13
is also be reduced due to a necessity to ensure electrical
insulation distance between the outboard bearing box 2a and the
rectifier 13.
[0016] If the size of the outboard ventilation apertures 2b is
reduced, the cooling air flow rate cannot be ensured, making the
cooling of heat-generating parts such as the rotor 6, the stator 7,
and the rectifier 13 insufficient, and if the size of the rectifier
13 is reduced, the area of a heat sink on the rectifier is reduced,
making the cooling of the rectifier 13 insufficient, and as a
result, the temperature of the automotive alternator rises, giving
rise to reduced output and a deterioration in the life of component
parts due to heat degradation.
[0017] Another countermeasure has been proposed in which the
outboard bearing is constructed by lining up two single-row
bearings, preventing fatigue failure by dividing the load in two.
However, in that case, radial clearance in the two single-row
bearings may differ, making the shared load in the two single-row
bearings unbalanced, and a problem has been that bearing life is
reduced.
[0018] Moreover, the inboard bearing 4 is constituted by a
single-row bearing in a similar manner to the outboard bearing 5,
but because the heat-generating parts such as the rectifier 13 and
the voltage regulator are disposed at the outboard bracket 2 end,
there is ample clear space on the outer circumferential side of the
inboard bearing 4, and it is not necessary to ensure electrical
insulation distance between a bearing box and a rectifier. Thus, it
is possible to adopt a bearing having enlarged outside diameter,
load capacity, or outer-ring wall thickness for the inboard bearing
4. Consequently, in an automotive alternator, countermeasures
against fatigue failure are more important in the outboard bearing
5, which is where the heat-generating parts such as the rectifier
13 and the voltage regulator are disposed.
[0019] In conventional automotive alternators, because the outboard
bearing 5 is constituted by a single-row bearing, one problem has
been that warping is applied repeatedly, giving rise to fatigue
failure in the outboard bearing 5, thereby reducing bearing
life.
[0020] Fatigue failure in the outboard bearing 5 can be suppressed
by adopting countermeasures in which rigidity is raised by
increasing the diameter or the load capacity of the outboard
bearing 5, or by thickening the wall of the outer ring. However,
such countermeasures lead to reductions in the size of the outboard
ventilation apertures 2b and the rectifier 13, increasing the
temperature of the automotive alternator, and another problem has
been that these countermeasures give rise to reduced output and a
deterioration in the life of component parts due to heat
degradation.
SUMMARY OF THE INVENTION
[0021] The present invention aims to solve the above problems and
an object of the present invention is to provide an automotive
alternator enabling the suppression of reductions in output and
deterioration in working life as a result of temperature increases
in the alternator by constituting an outboard bearing by a
multi-row bearing having one inner ring and one outer ring, a
plurality of ball tracks disposed axially between the inner ring
and the outer ring, and a plurality of balls disposed in each of
the ball tracks, thereby distributing the load bearing on the outer
ring plurally in an axial direction, improving load-bearing
properties without increasing the size of the outboard bearing, and
enabling the size of the outboard bearing to be reduced while
ensuring the durability thereof.
[0022] In order to achieve the above object, according to one
aspect of the present invention, there is provided an automotive
alternator including:
[0023] an inboard bracket formed in a bowl shape having a
cylindrical inboard bearing box in a central portion of an end
surface, and an outboard bracket formed in a bowl shape having a
cylindrical outboard bearing box in a central portion of an end
surface, the brackets being joined with open portions of the bowl
shapes facing each other;
[0024] a shaft rotatably supported in the inboard and outboard
brackets by means of inboard and outboard bearings disposed inside
the inboard and outboard bearing boxes;
[0025] a pulley fixed to an inboard end portion of the shaft;
[0026] a stator disposed such that first and second ends thereof
are supported in the inboard and outboard brackets;
[0027] a rotor fixed to the shaft, the rotor being disposed
radially inside the stator;
[0028] a rectifier disposed in the outboard bracket on an outer
circumferential side of the outboard bearing box; and
[0029] a heat exchange portion for dissipating heat generated in
the rectifier,
[0030] wherein the outboard bearing is constituted by a multi-row
bearing having one inner ring and one outer ring, a plurality of
ball tracks disposed axially between the inner ring and the outer
ring, and a plurality of balls disposed in each of the ball
tracks.
[0031] According to another aspect of the present invention, there
is provided an automotive alternator including:
[0032] an inboard bracket formed in a bowl shape having a
cylindrical inboard bearing box in a central portion of an end
surface, and an outboard bracket formed in a bowl shape having a
cylindrical outboard bearing box in a central portion of an end
surface, the brackets being joined with open portions of the bowl
shapes facing each other;
[0033] a shaft rotatably supported in the inboard and outboard
brackets by means of inboard and outboard bearings disposed inside
the inboard and outboard bearing boxes;
[0034] a pulley fixed to an inboard end portion of the shaft;
[0035] a stator disposed such that first and second ends thereof
are supported in the inboard and outboard brackets;
[0036] a rotor fixed to the shaft, the rotor being disposed
radially inside the stator;
[0037] a rectifier disposed in the outboard bracket on an outer
circumferential side of the outboard bearing box; and
[0038] a ventilation aperture bored through the outboard bracket on
an outer circumferential side of the outboard bearing box,
[0039] the automotive alternator being constructed such that the
rectifier is cooled by allowing air to flow through the ventilation
aperture,
[0040] wherein the outboard bearing is constituted by a multi-row
bearing having one inner ring and one outer ring, a plurality of
ball tracks disposed axially between the inner ring and the outer
ring, and a plurality of balls disposed in each of the ball
tracks.
[0041] The rectifier may be constructed in an arc shape having a
central angle of 180 degrees or more and may be disposed on a
common axis with the outboard bearing so as to overlap the outboard
bearing in a radial direction, and the ventilation aperture may be
bored through the outboard bracket so as to open in an arc shape
for half a circumference or more in a circumferential direction
facing the rectifier.
[0042] Slip rings for supplying a field current to a field winding
in the rotor may be disposed at an outboard end of the shaft, a
diameter of the multi-row bearing and a diameter of the slip rings
being constructed so as to be substantially equal.
[0043] The shaft may be supported in the multi-row bearing such
that an outboard end surface of the shaft is positioned between an
outboard end surface of the multi-row bearing and a center line of
an outermost ball track at the outboard end.
[0044] A creep-preventing member may be disposed on an outer
circumferential surface of the outer ring of the multi-row bearing
facing the ball tracks.
[0045] The multi-row bearing may have two ball tracks, and the
creep-preventing member may be formed into ring-shaped bodies
having a width which is less than or equal to a diameter of the
balls disposed in the ball tracks, the ring-shaped bodies being
disposed on an outer circumferential surface of the outer ring
facing each of the ball tracks such that width-direction center
lines of the ring-shaped bodies are offset towards end surfaces of
the multi-row bearing relative to center lines of the ball
tracks.
[0046] The outboard bracket may be made of a metal, and the
creep-preventing member may be made of a resin.
[0047] A heat dissipation means may be disposed in the outboard
bracket.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 is a longitudinal section of an automotive alternator
according to Embodiment 1 of the present invention;
[0049] FIG. 2 is a longitudinal section of an outboard bearing in
the automotive alternator according to Embodiment 1 of the present
invention;
[0050] FIG. 3 is an outboard end elevation of the automotive
alternator according to Embodiment 1 of the present invention;
[0051] FIG. 4 is an interior view of an outboard end of the
automotive alternator according to Embodiment 1 of the present
invention;
[0052] FIG. 5 is a perspective of a rectifier used in the
automotive alternator according to Embodiment 1 of the present
invention;
[0053] FIG. 6 is a longitudinal section of a construction of an
outboard bearing in an automotive alternator according to
Embodiment 2 of the present invention;
[0054] FIG. 7 is a longitudinal section of a construction of an
outboard bearing in an automotive alternator according to
Embodiment 3 of the present invention;
[0055] FIG. 8 is a perspective of an outboard bearing in an
automotive alternator according to Embodiment 4 of the present
invention;
[0056] FIG. 9 is an outboard end elevation of an automotive
alternator according to Embodiment 5 of the present invention;
[0057] FIG. 10 is an interior view of an outboard end of the
automotive alternator according to Embodiment 5 of the present
invention;
[0058] FIG. 11 is a longitudinal section of an automotive
alternator according to Embodiment 6 of the present invention;
[0059] FIG. 12 is a longitudinal section of an automotive
alternator according to Embodiment 7 of the present invention;
[0060] FIG. 13 is a longitudinal section of a conventional
automotive alternator; and
[0061] FIG. 14 is a partial cross section of a construction of an
outboard bearing used in a conventional automotive alternator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] The preferred embodiments of the present invention will now
be explained with reference to the drawings.
Embodiment 1
[0063] FIG. 1 is a longitudinal section of an automotive
alternator, FIG. 2 is a longitudinal section of an outboard bearing
in the automotive alternator shown in FIG. 1, FIG. 3 is an outboard
end elevation of the automotive alternator shown in FIG. 1, FIG. 4
is an interior view of an outboard end of the automotive alternator
shown in FIG. 1, and FIG. 5 is a perspective of a rectifier used in
the automotive alternator shown in FIG. 1.
[0064] In FIG. 1, an inboard bracket 1 and an outboard bracket 2
are made of aluminum, formed into bowl shapes, and are fastened
together by fastening bolts 14 with open portions of the bowl
shapes facing each other. Cylindrical inboard and outboard bearing
boxes 1a and 2a are formed integrally in central portions of end
surfaces of the brackets 1 and 2. First inboard and outboard
ventilation apertures 1b and 2b are bored through the brackets 1
and 2 at outer circumferential portions of the bearing boxes 1a and
2a, second inboard and outboard ventilation apertures 1c and 2c are
bored through side surface edge portions of the brackets 1 and 2,
and in addition, heat-dissipating ribs 2d functioning as a heat
dissipation means are disposed on the side surface edge portions of
the brackets 1 and 2.
[0065] A shaft 3 is rotatably supported in the brackets 1 and 2 by
means of inboard and outboard bearings 4 and 30 disposed inside the
bearing boxes 1a and 2a. A Lundell-type rotor 6 is fixed to the
shaft 3 and disposed rotatably inside the brackets 1 and 2. In
addition, a stator 7 is disposed with a first and second end of a
stator core 7b supported by the brackets 1 and 2 so as to surround
the rotor 6.
[0066] Slip rings 8 for supplying field current to a field winding
22 in the rotor 6 are fixed to an outboard end of the shaft 3, and
a pair of brushes 9 are housed inside a brush holder 10 disposed
inside the brackets 1 and 2 so as to slide in contact with the slip
rings 8.
[0067] A pulley 11 is fixed to an inboard end portion of the shaft
3, enabling rotational torque from an engine to be transmitted to
the shaft 3 through a belt (not shown).
[0068] A voltage regulator 20 for adjusting the magnitude of an
alternating voltage generated in the stator 7 is fixed by adhesive
to a regulator heat sink 21 functioning as a heat exchange portion
fitted onto the brush holder 10. In addition, a rectifier 13 which
is electrically connected to the stator 7 and converts the
alternating current generated in the stator 7 into direct current
is mounted inside the outboard bracket 2.
[0069] The rotor 6 is constituted by: a field winding 22, which
generates magnetic flux when a current is passed therethrough; and
a pair of first and second pole cores 23 and 24 disposed so as to
cover the field winding 22, magnetic poles being formed in the pair
of first and second pole cores 23 and 24 by the magnetic flux
generated in the field winding 22. The pair of first and second
pole cores 23 and 24 are made of iron, a plurality of first and
second claw-shaped magnetic poles 23a and 24a are disposed on outer
circumferential edge portions thereof at even pitch in a
circumferential direction so as to project axially, and the pair of
first and second pole cores 23 and 24 are fixed to the shaft 3
facing each other such that the first and second claw-shaped
magnetic poles 23a and 24a intermesh. In addition, internal fans 25
are fixed to first and second axial ends of the rotor 6.
[0070] The outboard bearing 30 is constituted by a multi-row
bearing having: a cylindrical inner ring 31 and a cylindrical outer
ring 32 forming a pair composed of carbon steel; two ball tracks 33
disposed axially between the inner ring 31 and the outer ring 32;
and a plurality of balls 34 disposed in each of the ball tracks 33.
Seals 35 are disposed at first and second ends of a space between
the inner ring 31 and the outer ring 32, and lubricating oil is
sealed in between the seals 35. The inner ring 31 is fixed to the
shaft 3, and the outer ring 32 is fixed to the outboard bearing box
2a. At this time, an outboard end surface 3a of the shaft 3 is
positioned between an outboard end surface 30a of the outboard
bearing 30 and a center line 33a of an outermost ball track 33 at
the outboard end. A diameter A of the outer ring 32 of the outboard
bearing 30 generally matches a diameter B of the slip rings 8.
[0071] As shown in FIG. 5, the rectifier 13 is constructed by
disposing arc-shaped positive- and negative-side heat sinks 40 and
41 concentrically such that main surfaces thereof are positioned in
a common plane, disposing positive- and negative-side diodes 43 and
44 on the main surfaces of the positive- and negative-side heat
sinks 40 and 41 so as to align with each other, and additionally
disposing an arc-shaped circuit board 42 on top of the positive-
and negative-side heat sinks 40 and 41 so as to sandwich the
positive- and negative-side diodes 43 and 44. The rectifier 13 is
disposed on a common axis with the shaft 3, and is secured to the
outboard bracket 2 such that a back surface (a surface on the
opposite side from a main surface) of the heat sink 41 is in close
contact with an inner wall surface of the outboard bracket 2.
[0072] Here, the main surfaces of the positive- and negative-side
heat sinks 40 and 41 are perpendicular to the axis of the shaft 3.
Heat-dissipating fins 40a are disposed so as to stand in a radial
pattern on a back surface of the positive-side heat sink 40.
Moreover, the positive- and negative-side heat sinks 40 and 41
constitute a heat exchange portion for dissipating heat generated
in the diodes 43 and 44.
[0073] Moreover, as shown in FIG. 4, the brush holder 10 and the
rectifier 13 are disposed inside the outboard bracket 2 so as to
surround the shaft 3, and the voltage regulator 20, the regulator
heat sink 21, and the rectifier 13 overlap the outboard bearing 30
in a radial direction. Furthermore, as shown in FIG. 3, a portion
of the first outboard ventilation apertures 2b is bored through the
outboard bracket 2 so as to face the regulator heat sink 21 and the
positive-side heat sink 40.
[0074] In the automotive alternator constructed in this manner,
electric current is supplied from a battery (not shown) through the
brushes 9 and the slip rings 8 to the field coil 22 of the rotor 6,
generating magnetic flux. The claw-shaped magnetic poles 23a of the
first pole core 23 are magnetized with south-seeking (S) poles by
this magnetic flux, and the claw-shaped magnetic poles 24a of the
second pole core 24 are magnetized with north-seeking (N) poles. At
the same time, the rotational torque from the engine is transmitted
through the belt (not shown) and the pulley 11 to the shaft 3,
rotating the rotor 6. Thus, a rotating magnetic field is applied to
a stator winding 7a, generating electromotive force in the stator
winding 7a. This alternating electromotive force passes through the
rectifier 13 and is converted into direct current, the output
voltage thereof is adjusted by the voltage regulator 20, and the
battery is recharged.
[0075] At the inboard end, the internal fan 25 is rotated and
driven together with the rotation of the shaft 3, and external air
flows into the inboard bracket 1 through the first inboard
ventilation apertures 1b, is deflected centrifugally by the
internal fan 25, cools first coil end of the stator winding 7a, and
is then expelled through the second inboard ventilation apertures
1c.
[0076] At the same time, as shown in FIG. 3, at the outboard end,
the internal fan 25 is rotated and driven together with the
rotation of the shaft 3, and external air flows into the outboard
bracket 2 through the first outboard ventilation apertures 2b, and
flows radially inwards along the positive-side heat sink 40 of the
rectifier 13 and the regulator heat sink 21 on the voltage
regulator 20. Thus, the heat generated in the positive-side diodes
43 and the voltage regulator 20 is dissipated from the
positive-side heat sink 40 and the regulator heat sink 21. The air
then flows between the brush holder 10 and the shaft 3 and between
the rectifier 13 and the shaft 3 towards the rotor 6, and a portion
of the heat generated in the outboard bearing 30 is dissipated from
the outboard bearing box 2a. Then, the air is deflected
centrifugally by the internal fan 25, cools second coil ends of the
stator winding 7a, and is then expelled through the second outboard
ventilation apertures 2c.
[0077] Moreover, heat generated in the negative-side diodes 44 is
transferred from the negative-side heat sink 41 to the outboard
bracket 2, and heat generated in the outboard bearing 30 is also
transferred to the outboard bracket 2. The heat transferred to the
outboard bracket 2 is dissipated from a surface of the outboard
bracket 2, and is also exchanged between the heat-dissipating ribs
2d and the cooling air flow expelled through the second outboard
ventilation apertures 2c.
[0078] In addition, a cooling air flow flows from the inboard side
to the outboard side as a result of pressure differences inside the
brackets 1 and 2, cooling the field coil 22 of the rotor 6.
[0079] Heat-generating parts such as the stator 7, the rotor 6, the
rectifier 13, and the voltage regulator 20 are cooled by these
cooling air flows. The inboard and outboard bearings 4 and 30 are
also cooled by these cooling air flows.
[0080] According to Embodiment 1 of the present invention, the
outboard bearing 30 is constituted by a multi-row bearing having
the cylindrical inner ring 31 and the cylindrical outer ring 32
forming a pair, two ball tracks 33 disposed axially between the
inner ring 31 and the outer ring 32, and a plurality of balls 34
disposed in each of the ball tracks 33.
[0081] Thus, the radial load due to the tension applied to the belt
and the load due to the weight of the rotor 6 applied to the outer
ring 32 is divided equally among the ball tracks. Thus, the
concentrated load is reduced, suppressing the occurrence of fatigue
failure in the inner ring 31, the outer ring 32, and the balls 34,
thereby enabling bearing life to be extended.
[0082] Because the concentrated load applied to the outer ring 32
is reduced, the outboard bearing 30 can be reduced in size,
ensuring insulation distance between the rectifier 13 and the
outboard bearing box 2a without increasing the size of the
alternator, and enabling the sizes of the first outboard
ventilation apertures 2b, the rectifier 13, and the voltage
regulator 20 to be increased. If the first outboard ventilation
apertures 2b are enlarged, the cooling air flow rate is increased,
enabling the cooling performance of the alternator to be raised. If
the sizes of the rectifier 13 and the voltage regulator 20 are
increased, the surface area (heat-dissipating area) of the heat
sinks 40, 41, and 21, which are heat exchange portions, can be
increased, enabling temperature increases in the rectifier 13 and
the voltage regulator 20 to be suppressed. As a result, because
temperature increases are suppressed in the alternator, output can
be improved, and deterioration in the life of component parts due
to heat degradation can be suppressed.
[0083] The outboard bearing 30 is constituted by a multi-row
bearing having two ball tracks 33. Thus, because the ball tracks
can be simultaneously machined, precision such as the coaxiality of
the two ball tracks can be improved, and the balls 34 can be
selected and incorporated in advance so as to minimize differences
in radial clearance between the rows. As a result, because
imbalances in the load shared between the rows can be reduced,
bearing life can be lengthened significantly compared to when two
single-row bearings are lined up.
[0084] When two single-row bearings are lined up, the space
contained between the seals between the bearings is unusable, but
in a multi-row bearing, since all of the space between the tracks
can be used as a grease trap, axial length can be shortened
compared to when two single-row bearings are lined up.
[0085] In addition, because the seals 35 are disposed at first and
second ends of the space between the inner ring 31 and the outer
ring 32, and lubricating oil is sealed in between the seals 35,
sticking due to depletion of the lubricating oil is eliminated,
enabling bearing life to be lengthened in this way also.
[0086] Because the outboard end surface 3a of the shaft 3 is
positioned between the outboard end surface 30a of the outboard
bearing 30 and the center line 33a of an outermost ball track 33 at
the outboard end, the load is applied uniformly to the balls 34 in
both rows, reducing imbalances in the load shared between the rows.
Because the shaft 3 does not project outwards from the outboard
bearing 30, assembly is improved.
[0087] Because the diameter A of the outer ring 32 of the outboard
bearing 30 generally matches the diameter B of the slip rings 8,
accidents can be prevented such the brush holder 10 being damaged
by the outboard bearing 30 catching on the brushes 9 when the shaft
3 is pulled out of the outboard bearing box 2a together with the
outboard bearing 30 in order to change worn brushes 9.
Embodiment 2
[0088] As shown in FIG. 6, in an outboard bearing 30A according to
Embodiment 2, ring-shaped recessed grooves 32a are disposed in an
outer circumferential surface of the outer ring 32 so as to face
each of the ball tracks 33, and resin bands 36 collectively
functioning as a creep-preventing member are mounted into each of
the recessed grooves 32a. A width w of the resin bands 36 is formed
so as to be less than or equal to a diameter R of the balls 34, and
outer circumferential surfaces of the resin bands 36 are positioned
on a common plane with the outer circumferential surface of the
outer ring 32. Here, a polybutylene terephthalate (PBT) resin, or a
polyamide resin, etc., is used in the resin bands 36. Moreover, the
rest of the construction is constructed in a similar manner to
Embodiment 1 above.
[0089] In Embodiment 1 above, the outboard bearing box 2a is heated
by the heat generated during operation of the automotive
alternator, and the outboard bearing box 2a and the outboard
bearing 30 expand due to the heat. Because the outboard bearing box
2a is composed of aluminum and the outboard bearing 30 is composed
of carbon steel, the outboard bearing box 2a and the outboard
bearing 30 expand in such a way that a gap arises between the
outboard bearing box 2a and the outer ring 32 of the outboard
bearing 30 as a result of a difference between the coefficients of
thermal expansion of the two. Thus, the bonding strength between
the outboard bearing box 2a and the outboard bearing 30 weakens,
and eventually there is a risk that the outer ring 32 of the
outboard bearing 30 will rotate together with the shaft, leading to
a state in which the outboard bearing box 2a is excessively heated
by friction between the outboard bearing box 2a and the outer ring
32, and the outer ring 32 slips (or creeps). Slippage of the outer
ring 32 results in variations in the rotational axis of the rotor
6, giving rise to damaging accidents due to the rotor 6 striking
the stator 7.
[0090] In Embodiment 2, because the resin bands 36 are disposed in
the outer circumferential surface of the outer ring 32 so as to
face and radially overlap each of the ball tracks 33, if the
outboard bearing box 2a is heated by the heat generated during
operation of the automotive alternator, the resin bands 36 expand
more than the outboard bearing box 2a, ensuring good bonding
strength between the outboard bearing box 2a and the outboard
bearing 30A. Thus, the outboard bearing box 2a is prevented in
advance from being excessively heated by friction between the
outboard bearing box 2a and the outer ring 32 due to the outer ring
32 of the outboard bearing 30A rotating together with the shaft,
thereby preventing collisions between the rotor 6 and the stator
7.
[0091] Because the resin bands 36 are disposed in the outer
circumferential surface of the outer ring 32 so as to face and
radially overlap each of the ball tracks 33, the resin bands 36
expand above a contact portion between the balls 34 and the outer
ring 32, reliably ensuring good bonding strength between the
outboard bearing box 2a and the outboard bearing 30A.
[0092] Because the creep-preventing member is composed of the resin
bands 36, manufacturing is easy and inexpensive.
Embodiment 3
[0093] As shown in FIG. 7, in Embodiment 3, the resin bands 36 are
disposed so as to radially overlap the corresponding ball tracks 33
such that width-direction center lines 36a of the resin bands 36
are offset (.delta.>0) towards end surfaces of an outboard
bearing 30B relative to their respective ball track center lines
33a. Moreover, the rest of the construction is constructed in a
similar manner to Embodiment 2 above.
[0094] According to Embodiment 3, because the width-direction
center lines 36a of the resin bands 36 are offset towards the end
surfaces of the outboard bearing 30B relative to the ball track
center lines 33a, good bonding strength between the outboard
bearing box 2a and the outboard bearing 30B is reliably ensured,
preventing slippage of the outboard bearing 30B.
Embodiment 4
[0095] As shown in FIG. 8, in Embodiment 4, metal rings 37
collectively functioning as a creep-preventing member are mounted
into the recessed grooves 32a. These metal rings 37 are prepared
from a spring material, are formed into a C shape having an inside
diameter greater than an outside diameter of the recessed grooves
32a, and when an outboard bearing 30C is mounted in the outboard
bearing box 2a, the metal rings 37 deform elastically so as to lie
along bottom surfaces of the recessed grooves 32a, and are disposed
in a compressed state between the outboard bearing box 2a and the
recessed grooves 32a of the outer ring 32. Moreover, the rest of
the construction is constructed in a similar manner to Embodiment 2
above.
[0096] In Embodiment 4, if the outboard bearing box 2a is heated by
the heat generated during operation of the automotive alternator,
the metal rings 37 return to their original state following the
thermal expansion of the outboard bearing box 2a, in other words,
so as to fit the gap arising between the outboard bearing box 2a
and the outer ring 32, and the compressed state of the metal rings
37 between the outboard bearing box 2a and the outer ring 32 is
maintained. Thus, because good bonding strength between the
outboard bearing box 2a and the outboard bearing 30 is ensured,
similar effects to those in Embodiment 2 above can also be achieved
in Embodiment 4.
Embodiment 5
[0097] As shown in FIGS. 9 and 10, in Embodiment 5, a rectifier 13A
is constructed in an arc shape having a central angle .theta. of
180 degrees or more and is disposed on a common axis with the
outboard bearing 30, and first outboard ventilation apertures 2b
are bored through the outboard bracket 2 so as to open in an arc
shape for half a circumference or more in a circumferential
direction facing the rectifier 13A. Except for the fact that the
central angle .theta. of the arc shape is 180 degrees or more, this
rectifier 13A is constructed in a similar manner to the rectifier
13 in Embodiment 1 above, and is disposed so as to overlap the
outboard bearing 30 in a radial direction. Moreover, the rest of
the construction is constructed in a similar manner to Embodiment 1
above.
[0098] In Embodiment 5, because the size of the rectifier 13A is
enlarged, the surface area (heat-dissipating area) of the
positive-side heat sink 40 is increased, efficiently dissipating
heat generated in the rectifier 13A. Because the size of the first
outboard ventilation apertures 2b is also enlarged, the flow rate
of the cooling air is increased, further improving cooling of the
automotive alternator. As a result, because temperature increases
are suppressed in the alternator, output can be improved, and
deterioration in the life of component parts due to heat
degradation can be suppressed.
[0099] In a construction like this, because the rectifier is
disposed to surround a larger portion of the outer circumferential
side of the outboard bearing, mutual thermal influence is great,
and it is ideal for the above-mentioned multi-row bearings of the
present invention.
Embodiment 6
[0100] As shown in FIG. 11, in Embodiment 6, an outboard end
portion of the shaft 3 is extended outwards from the outboard
bearing 30, and the slip rings 8 are mounted to the extended
portion of the shaft 3. The rectifier 13 and the voltage regulator
20 are disposed outside the outboard bracket 2 and around an outer
circumference of the outboard bearing 30. In addition, a bracket
cover 50 is mounted to the outboard bracket 2 so as to cover the
brush holder 10, the rectifier 13, and the voltage regulator 20.
Moreover, the rest of the construction is constructed in a similar
manner to Embodiment 1 above.
[0101] In Embodiment 6, when the outboard internal fans 25 are
rotated and driven together with the rotation of the shaft 3, at
the outboard end, external air flows into the bracket cover 50
through ventilation apertures 50a of the bracket cover 50 and flows
radially inwards along the positive-side heat sink 40 of the
rectifier 13 and the regulator heat sink 21 on the voltage
regulator 20. Thus, the heat generated in the positive-side diodes
43 and the voltage regulator 20 is dissipated from the
positive-side heat sink 40 and the regulator heat sink 21. The
cooling air then flows into the outboard bracket 2 through the
first outboard ventilation apertures 2b, which are disposed around
the outer circumference of the outboard bearing box 2a, towards the
rotor 6, and a portion of the heat generated in the outboard
bearing 30 is dissipated from the outboard bearing box 2a. Then,
the air is deflected centrifugally by the internal fans 25, cools
the second coil end of the stator winding 7a, and is then expelled
through the second outboard ventilation apertures 2c.
[0102] Moreover, the cooling air flow at the inboard end is similar
to that in Embodiment 1 above.
[0103] Heat-generating parts such as the stator 7, the rotor 6, the
rectifier 13, and the voltage regulator 20, and the inboard and
outboard bearings 4 and 30 are cooled by these cooling air
flows.
[0104] Thus, similar effects to those in Embodiment 1 above can
also be achieved in Embodiment 6.
Embodiment 7
[0105] As shown in FIG. 12, in Embodiment 7, a distribution channel
51 for distributing cooling water 52 is disposed in a fluid-tight
state inside an outboard bracket 2A. Here, the distribution channel
51 and the cooling water 52 constitute a heat dissipation means.
Moreover, the rest of the construction is constructed in a similar
manner to Embodiment 1 above.
[0106] In Embodiment 7, because the distribution channel 51 for the
cooling water 52 is disposed in the outboard bracket 2A, heat
generated in the negative-side diodes 44 is transferred from the
negative-side heat sink 41 to the outboard bracket 2A, and heat
generated in the voltage regulator and heat generated in the
outboard bearing 30 are also transferred to the outboard bracket
2A, and this heat is absorbed into the cooling water 52 flowing
through the distribution channel 51.
[0107] Consequently, according to Embodiment 7, temperature
increases in the rectifier 13, the voltage regulator 20, and the
outboard bearing 30 are suppressed.
[0108] Since the distribution channel is formed so as to cover an
outer circumference of the outboard bearing, the multi-row bearings
of the present invention are ideal because the distribution channel
can be made larger.
[0109] Moreover, in each of the above embodiments, the present
invention has been explained assuming that a multi-row bearing
having two ball tracks is used for the outboard bearing, but the
multi-row bearing is not limited to having two ball tracks; it may
be a multi-row bearing having three or more ball tracks.
[0110] In each of the above embodiments, the present invention has
been assumed to apply to an automotive alternator of a type in
which the rotor has a field winding, but similar effects can be
achieved even if the present invention is applied to a brushless
type automotive alternator in which a field winding is secured to a
bracket and a rotating magnetic field is supplied through an air
gap to a stator.
[0111] The present invention is constructed in the above manner and
exhibits the effects described below.
[0112] According to one aspect of the present invention, there is
provided an automotive alternator including:
[0113] an inboard bracket formed in a bowl shape having a
cylindrical inboard bearing box in a central portion of an end
surface, and an outboard bracket formed in a bowl shape having a
cylindrical outboard bearing box in a central portion of an end
surface, the brackets being joined with open portions of the bowl
shapes facing each other;
[0114] a shaft rotatably supported in the inboard and outboard
brackets by means of inboard and outboard bearings disposed inside
the inboard and outboard bearing boxes;
[0115] a pulley fixed to an inboard end portion of the shaft;
[0116] a stator disposed such that first and second ends thereof
are supported in the inboard and outboard brackets;
[0117] a rotor fixed to the shaft, the rotor being disposed
radially inside the stator;
[0118] a rectifier disposed in the outboard bracket on an outer
circumferential side of the outboard bearing box; and
[0119] a heat exchange portion for dissipating heat generated in
the rectifier,
[0120] wherein the outboard bearing is constituted by a multi-row
bearing having one inner ring and one outer ring, a plurality of
ball tracks disposed axially between the inner ring and the outer
ring, and a plurality of balls disposed in each of the ball
tracks,
[0121] whereby the load bearing on the outer ring is distributed
plurally in an axial direction, improving load-bearing properties
without increasing the size of the outboard bearing. As a result,
because the size of the outboard bearing can be reduced while
ensuring the durability thereof, the area of the heat exchange
portion can be increased. Thus, because cooling efficiency is
improved and temperature increases in the outboard bearing and the
rectifier are suppressed, an automotive alternator can be provided
which enables the suppression of reductions in output and
deterioration in working life as a result of temperature increases
in the alternator.
[0122] According to another aspect of the present invention, there
is provided an automotive alternator including:
[0123] an inboard bracket formed in a bowl shape having a
cylindrical inboard bearing box in a central portion of an end
surface, and an outboard bracket formed in a bowl shape having a
cylindrical outboard bearing box in a central portion of an end
surface, the brackets being joined with open portions of the bowl
shapes facing each other;
[0124] a shaft rotatably supported in the inboard and outboard
brackets by means of inboard and outboard bearings disposed inside
the inboard and outboard bearing boxes;
[0125] a pulley fixed to an inboard end portion of the shaft;
[0126] a stator disposed such that first and second ends thereof
are supported in the inboard and outboard brackets;
[0127] a rotor fixed to the shaft, the rotor being disposed
radially inside the stator;
[0128] a rectifier disposed in the outboard bracket on an outer
circumferential side of the outboard bearing box; and
[0129] a ventilation aperture bored through the outboard bracket on
an outer circumferential side of the outboard bearing box,
[0130] the automotive alternator being constructed such that the
rectifier is cooled by allowing air to flow through the ventilation
aperture,
[0131] wherein the outboard bearing is constituted by a multi-row
bearing having one inner ring and one outer ring, a plurality of
ball tracks disposed axially between the inner ring and the outer
ring, and a plurality of balls disposed in each of the ball
tracks,
[0132] whereby the load bearing on the outer ring is distributed
plurally in an axial direction, improving load-bearing properties
without increasing the size of the outboard bearing. As a result,
because the size of the outboard bearing can be reduced while
ensuring the durability thereof, the area of the rectifier and the
ventilation aperture can be increased. Thus, because cooling
efficiency is improved and temperature increases in the outboard
bearing and the rectifier are suppressed, an automotive alternator
can be provided which enables the suppression of reductions in
output and deterioration in working life as a result of temperature
increases in the alternator.
[0133] The rectifier may be constructed in an arc shape having a
central angle of 180 degrees or more and may be disposed on a
common axis with the outboard bearing so as to overlap the outboard
bearing in a radial direction, and the ventilation aperture may be
bored through the outboard bracket so as to open in an arc shape
for half a circumference or more in a circumferential direction
facing the rectifier, increasing the heat dissipation area of the
rectifier and the flow rate of the cooling air flowing in through
the ventilation aperture, thereby effectively cooling the rectifier
and the outboard bearing.
[0134] Slip rings for supplying a field current to a field winding
in the rotor may be disposed at an outboard end of the shaft, a
diameter of the multi-row bearing and a diameter of the slip rings
being constructed so as to be substantially equal, whereby the
outboard bearing no longer catches on the brushes during the
operation of changing worn brushes, thereby suppressing accidents
which damage the brush holder.
[0135] The shaft may be supported in the multi-row bearing such
that an outboard end surface of the shaft is positioned between an
outboard end surface of the multi-row bearing and a center line of
an outermost ball track at the outboard end, whereby load is
applied uniformly to each row of balls, reducing imbalances in the
load shared among the rows.
[0136] A creep-preventing member may be disposed on an outer
circumferential surface of the outer ring of the multi-row bearing
facing the ball tracks, improving creep resistance.
[0137] The multi-row bearing may have two ball tracks, and the
creep-preventing member may be formed into ring-shaped bodies
having a width which is less than or equal to a diameter of the
balls disposed in the ball tracks, the ring-shaped bodies being
disposed on an outer circumferential surface of the outer ring
facing each of the ball tracks such that width-direction center
lines of the ring-shaped bodies are offset towards end surfaces of
the multi-row bearing relative to center lines of the ball tracks,
improving the creep-preventing effect.
[0138] The outboard bracket may be made of a metal, and the
creep-preventing member may be made of a resin, increasing the
creep-preventing effect and improving productivity.
[0139] A heat dissipation means may be disposed in the outboard
bracket, whereby heat generated in the outboard bearing is
efficiently dissipated, suppressing temperature increases in the
outboard bearing.
* * * * *