U.S. patent number 3,694,661 [Application Number 04/867,299] was granted by the patent office on 1972-09-26 for ac generator directly coupled to an internal combustion engine.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Tsutomu Minowa.
United States Patent |
3,694,661 |
Minowa |
September 26, 1972 |
AC GENERATOR DIRECTLY COUPLED TO AN INTERNAL COMBUSTION ENGINE
Abstract
An AC generator directly coupled to an engine wherein a
cup-shaped rotor having a pair of claw pole pieces is mounted on an
extension of the engine crankshaft which is projected to the
outside of the engine block on the side reverse to the engine
output such that an opening is provided on the side opposite to the
engine, an armature core with an armature coil and a field core
with a field coil are respectively disposed, being separated by a
small air gap, at the radially outer and inner sides of the
interposed claw pole pieces, and said armature core and said field
core are securely mounted on the inside of a non-magnetic cover
which is fastened to the engine block to cover said armature and
field cores.
Inventors: |
Minowa; Tsutomu (Hitachi-shi,
JA) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JA)
|
Family
ID: |
13592356 |
Appl.
No.: |
04/867,299 |
Filed: |
October 17, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Oct 18, 1968 [JA] |
|
|
43/7599 |
|
Current U.S.
Class: |
290/1R; 310/60R;
310/168 |
Current CPC
Class: |
H02K
7/1815 (20130101); H02K 19/24 (20130101) |
Current International
Class: |
H02K
7/18 (20060101); H02K 19/24 (20060101); H02K
19/16 (20060101); H02k 019/20 () |
Field of
Search: |
;240/1
;310/168,263,60,62 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simmons; G. R.
Claims
What is claimed is:
1. An AC generator directly coupled to an internal combustion
engine comprising an armature unit and a field unit which are
disposed concentrically with the crankshaft of an engine such that
a magnetic flux applied to the armature unit is varied by a rotor
unit mounted on the crankshaft and adapted to rotate between the
units, characterized in that a cup-shaped claw rotor is provided
wherein a first magnetic path is formed radially extending from the
end of an extension of the engine crankshaft reverse to the engine
which projects outside the engine block, a plurality of first claw
pole pieces of the same polarity are formed axially extending from
the end portion of said first magnetic path and disposed equally
spaced from one another, a plurality of second claw pole pieces of
the other same polarity are formed, said second pole pieces being
mechanically coupled so that said second pole pieces are arranged
between said first claw pole pieces and form a second magnetic path
with a ring-shaped portion at the other end thereof, and said pole
pieces of the respective polarities are mechanically interconnected
by a non-magnetic material on the inside thereof; an armature core
with an armature coil is disposed with a small air gap with respect
to and outside of the outer periphery of said claw pole pieces; a
field coil is formed, said field coil being wound on a cylindrical
field core having a L-shaped cross section; said field core is
disposed on the inner side of said claw rotor such that one side of
the L-shaped cross section of said field core is opposed to the
boss of said rotor connected to said first claw pole pieces and
another side of said L-shaped cross section is opposed to said
ring-shaped portion of said second claw pole pieces with a small
air gap being interposed therebetween, respectively; and said
armature core and said field core are securely supported on the
inside of a non-magnetic supporting member extending from the
engine block to cover said cores.
Description
The present invention relates to a brushless AC generator provided
with a rotor directly coupled to the crankshaft of an engine for
vehicles.
The AC generator installed in a vehicle is usually driven by the
engine which drives the vehicle. Ordinary vehicles employ an
arrangement whereby the crankshaft of an engine is extended to the
outside of the engine block and a pulley is mounted on this
extension of the crankshaft so that the generator, together with a
cooling fan and the like, is driven by means of a belt. However,
this belt-driven system is extremely disadvantageous from the
aspect of the miniaturization of engine assemblies, and moreover
the belt-driven type is impracticable as the AC generator for small
motor vehicles such as a motorcycle. Such being the case, a
flywheel magneto or a starter dynamo was used in a motorcycle, both
of which were, in fact, disadvantageous from the aspects of
maintenance, inspection and life because the flywheel magneto could
not generally produce a large power and the starter dynamo included
brushes and a commutator.
To eliminate these drawbacks, a form of drive was developed whereby
an AC generator was directly coupled to the crankshaft of an
engine, and moreover brushless-type AC generators were proposed to
solve the problem of maintenance due to the brushes and others.
Their examples were described in the specifications of U.S. Pats.
Nos. 3,215,877 and 2,928,963, but both of them still involved
serious drawbacks structurally from the aspect of temperature rise
in the AC generator. First, in the case of the former the armature
and the field cores were subjected to the heat from the engine
since they were mounted on the engine block and moreover the
temperature of the armature and the field windings tended to become
exceedingly high due to the generation of heat in these windings.
In the latter case, the AC generator had its armature and field
cores supported on the side reverse to the engine so that the
direct thermal effect due to the heat generated by the engine was
not great. However, since this AC generator was mounted between the
engine block and the transmission case, its construction was not
convenient for the dissipation of the heat generated by the current
in the armature and field coils themselves. In other words, besides
the fact that the transmission case was usually coupled to the
engine block mechanically, thus being subject to the heat from the
engine, its temperature was caused to increase considerably by the
heat generation due to the transmission gears and lubricating oil
and therefore the heat dissipation, particularly the dissipation of
heat generated in the field coil mounted on the inner side thereof
was difficult. Thus, a considerable temperature rise was
unavoidable in this AC generator.
In this type of AC generators, the effect of the temperature rise
would have a deteriorating effect on the electrical insulation of
the two coils and result in a decrease in the electrical output due
to an increase in the electric resistance. In particular, a
decreased current flow due to an increase in the resistance of the
field coil would reduce the intensity of a magnetic field produced
thus becoming a major factor of a decrease in the electrical
output.
It is therefore a primary object of the present invention to
provide a brushless-type AC generator directly coupled to an
engine.
Another object of the present invention is to provide a
brushless-type AC generator directly coupled to an engine, whose
temperature rise is low and which is compact, yet produces a
relatively large electrical output.
Further object of the present invention is to provide an AC
generator which can be assembled or disassembled easily and whose
assembly, inspection or later adjustment operation is simple and
easy.
Still further object of the present invention is to provide an AC
generator consisting of a smaller number of component parts.
Still further objects of the present invention will be apparent
from the following description of the embodiments when read in
conjunction with the accompanying drawings, in which:
FIG. 1 is a general view of an engine assembly on which is mounted
an AC generator directly coupled to an engine according to the
present invention;
FIG. 2 is a longitudinal sectional side view of an AC generator
directly coupled to an engine according to the present
invention;
FIG. 3 is a longitudinal sectional side view of another embodiment
of the AC generator directly coupled to an engine;
FIG. 4 is a longitudinal sectional side view of a further
embodiment of the AC generator directly coupled to an engine;
FIG. 5 is a perspective view of a rotor used in the AC generator of
the present invention; and
FIG. 6 is an output characteristic diagram of the AC generator
according to the present invention.
Referring to FIG. 1, numeral 1 designates an AC generator directly
coupled to an engine, the subject matter of the present invention,
which is mounted on the side of an engine block 2 reverse to the
clutch of an ordinary engine assembly comprising, in addition to
said engine block 2, a clutch 3, a transmission 4 and a gear shift
lever 6 for adjusting the number of revolutions of a driving shaft
5, and the AC generator is driven by the rotation of the engine.
This generator 1 is constructed as shown in FIG. 2. That is, in
FIG. 2, 7 designates a cup-shaped rotor having separate claw pole
pieces 8 and 81 interconnected by means of a non-magnetic ring 9
and it has an external appearance as shown separately in FIG. 5.
This rotor 7 has its boss 10 mounted on an extended portion 13 of
the crankshaft 12 journaled in the engine block 2 by means of
roller bearings 11 and the rotor is then securely fixed by a
locking bolt 14. Numeral 15 designates a generator cover made of a
non-magnetic material such as aluminum, the cover being securely
fixed on the side of the engine block 2 by a plurality of bolts 16
and having an armature core 19 with an armature coil 18 mounted on
its inner periphery by means of a stepped surface 17 and secured by
fastening bolts 20. Numeral 21 designates a cylindrical field core
having a field coil 22 wound concentrically thereon and fitted in
the hollow portion of the cup-shaped rotor 7 with an air gap
interposed therebetween, and this field core is attached to the
inner wall of the generator cover 15 by means of fastening screws
23 so that, together with the armature core 19, it is located
concentrically with the crankshaft 12. Numeral 24 designates a lead
wire brought out through an attaching side 25 of the field core 21,
through the clearance provided between the attaching side 25 and
the generator cover 15 and through a guide slot 26 formed in the
armature core 19, whereby both the lead wire 24 and an output lead
wire 27 are brought out of the generator for external connection.
Here, the outlet hole is usually provided with a rubber bushing 28
for insulating purpose.
With an arrangement as described above, it is a well known fact
that as the engine is operated and the crankshaft 12 rotates to
turn the rotor 7, the claw pole pieces 8 and 81 produce a rotating
field and an AC current is induced in the armature coil 18 and that
the generator output decreases in proportion to the internal
temperature rise. According to the construction of the present
invention, however, the field core 21 with the field coil 22 is
directly fitted to the generator cover 15 provided on the side
reverse to the engine and exposed to the atmosphere so that it does
not conduct the large quantity of heat on the side of the engine
and the heat generated by itself is conducted to the aluminum
generator cover 15 which is a good heat radiator, whereby an
excellent cooling effect is attained with a considerable
improvement in the generator performance. In addition, as the field
core 21 used here has a L-shaped cross section and can be
threadedly secured by means of the locking screws 23 from the
exterior of the generator cover 15, there is no need to provide a
mounting base exclusively for the field core 21 with a resultant
reduction in size and moreover, since the armature coil 18 and the
field coil 22 can be removed together with the generator cover 15
by unfastening the bolts 16 when the maintenance, inspection or
later adjustment operation of these coils is required, a
considerable improvement in the operating efficiency is
ensured.
Referring now to FIG. 3 showing another embodiment of the present
invention, a boss 10 of a rotor 7 is axially extended to project
through an opening 50 of a generator cover 15 and a propeller fan
29 is mounted at the end of the extended boss 10 at the same time
that a locking bolt 14 is fastened, with a screw 30 securing the
fan 29 to prevent slipping thereof, whereby, by providing an
effective fan performance by the rotation of the rotor 7, the
generator cover 15 is positively cooled to attain an improved heat
dissipation of the generator. In the figure, 31 designates radially
disposed fins and the cooling performance can be improved by these
fins. constantly apply a the end In addition, ventilation holes may
be formed in the generator cover 15 at any desired places thereof,
if needed, to thereby provide an improved cooling efficiency.
Further embodiment of the present invention will be explained with
reference to FIG. 4 in which 32 designates an auxiliary cover
formed by extending the periphery of the generator cover 15 outward
from a partition wall 33. Numeral 34 designates a camshaft
extending through an opening 35 of the partition wall 33 and
secured to the rotor boss 10 by the locking bolt 14 and a breaker
36 is operatively associated with this camshaft. The breaker 36 is
adjustably mounted on a base 38 secured to the partition wall by
means of screws 37 so that a breaker cam follower 39 contacts the
periphery of the camshaft 34. Numeral 40 designates a lubricating
felt carried by a supporting bracket 41 projected to the base 38 to
constantly apply a lubricant to the cam surface to prevent the wear
of the breaker cam follower 39. Numeral 42 designates a dust cover
located to cover an open end of the auxiliary cover 32 and it is
fixed to the end portion of the auxiliary cover 32 by screws 43 to
protect the breaker 36. In this embodiment wherein the breaker 36
is mounted near the end portion of the same shaft, the heat
generated by the breaker is nevertheless negligibly small so that
an improved generator performance is attained as the heat can be
effectively radiated through the generator cover 15 provided with
the auxiliary cover 32.
According to the embodiments of the present invention described
above, the temperature rise of the armature unit and the field unit
may be held between 60.degree. C and 80.degree. C. If the
temperature rise is limited within this range, the ordinary class F
insulation will be sufficient as the electrical insulation for the
respective coils. With the conventional direct-coupled AC
generators, however, particularly the temperature of the field unit
frequently rose to as high as 100.degree. C to 150.degree. C, and
at 150.degree. C, for example, the class F insulation would reach
the allowable limit and thus it could not withstand a long service.
In addition, since the temperature rise of the field coil would
result in an increased electrical resistance of the field coil
preventing the flowing of the field current, it tended to reduce
the produced magnetic flux decreasing the electrical output of the
armature coil. FIG. 6 shows the relationship between the rpm N and
the output current I of an AC generator with the field coil
temperature T being 80.degree. C, 100.degree. C and 150.degree. C,
respectively. According to the figure, at N = 2,000 rpm and T =
80.degree. C, the output current I was 13 amperes, whereas at T =
100.degree. C, the I was 11.5 amperes, and at T = 150.degree. C, it
still dropped to 8 amperes. Then, the output current I which was 17
amperes at N = 6,000 rpm and T = 80.degree. C dropped to 15.5
amperes at T = 100.degree. C and it further dropped to 12 amperes
at T = 150.degree. C. It will be apparent from the foregoing that
the temperature rise of the field coil has an important effect on
the magnitude of the output current, and the superiority of the AC
generator of the present invention will be understood even from
this fact.
* * * * *