Cooling structure for alternator rectifier

Briefly, the invention comprises an improved cooling fin arrangement for a triphasic bridge rectifier used in conjunction with a three phase alternator in an automotive vehicle. The heat transfer ability of a metallic air core heat sink and radiator is more than doubled by increasing its thickness (and thus its exposed surface area) and by providing a cutout groove allowing the air to flow in two directions thus reducing the air flow resistance. An improved cover plate cooperates with the newly provided air flow paths and also provides simplified connectors for the electrical elements.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to improved cooling structure for a triphasic 
alternator rectifier such as commonly used on automotive vehicles. More 
specifically, it relates to an improved air cooled heat sink device which 
provides more surface area and better air flow on such an alternator. More 
generally it relates to a heat sink device which is well adapted to 
partially encircle any rotary electromotive machine in close proximity to 
the rotors of that machine. As such it is particularly well adapted to 
provide cooling for the control circuitry of any modern motor, generator, 
or alternator, used in a setting where fluid flow is available for 
cooling. The cooling fluid may be a gas or liquid or both. 
Fields most likely to benefit from the advantages of the instant invention 
include the transportation, manufacturing, and home appliance industries, 
as well as any industry dependent on electromotive machinery for power 
generation. Examples include electric lawn mowers, heating ventilation and 
air conditioning motors, mixing and blending machinery, and auxiliary 
power generation on all sorts of vehicles. These are but several examples 
of possible applications. 
Thus it can be seen that the potential fields of use for this invention are 
myriad and the particular preferred embodiment described herein is in no 
way meant to limit the use of the invention to the particular field chosen 
for exposition of the details of the invention. 
A comprehensive listing of all the possible fields to which this invention 
may be applied is limited only by the imagination and is therefore not 
provided herein. Some of the more obvious applications are mentioned 
herein in the interest of providing a full and complete disclosure of the 
unique properties of this previously unknown general purpose article of 
manufacture. It is to be understood from the outset that the scope of this 
invention is not limited to these fields or to the specific examples of 
potential uses presented hereinafter. 
2. Description of the Prior Art 
The use of semiconductor devices in control circuitry for large 
electromotive machinery is becoming more and more common. The precision of 
control and generally light weight and small size of the semiconductor 
devices are advantages which are difficult to ignore. However, there 
remains a crucial problem with semiconductor devices which has yet to be 
overcome and that is their sensitivity to heat. Therefore, certain 
electromotive devices that are required to operate in high temperature 
areas are prone to premature failure if they use semiconductor control 
devices. 
A common example of this occurs in automotive alternators which are used to 
generate electrical power for recharging batteries which supply auxiliary 
electrical power for the vehicle for such devices as lights, windshield 
wiper motors, radios, etc. The alternator is located in close proximity to 
the massive heat source of a high powered internal combustion engine. 
Conventional alternators naturally generate a cyclic alternating current 
as they are turned by the engine. A steady direct current is required to 
recharge the conventional wet cell chemical batteries in common use. A 
rectifier device is needed to convert the alternating current provided by 
the alternator to the direct current required by the batteries. One such 
common and inexpensive rectifier can be constructed from six semiconductor 
diodes and a suitable capacitor connected in a bridge circuit so as to 
rectify three phase alternating current produced by an alternator. The 
prior art has disclosed such devices. However problems continue to exist 
relative to breakdown of the semiconductor diodes due to the excessive 
heat in the automotive underhood environment. My invention represents a 
simple and effective means of overcoming these problems with the prior 
art. 
Searches were conducted at the United States Patent and Trademark Office 
for related inventions and the prior art discovered is discussed herein. 
As will be seen, the simplicity and effectiveness of my invention is not 
rivaled in the prior art. 
U.S. Pat. No. 4,606,000, issued to Steele et al. on Aug. 12, 1986, shows a 
bridge rectifier for a diode-rectified alternating current generator. It 
is comprised of two metallic heat sinks formed respectively of copper and 
aluminum that are separated by an electrical insulator. Each heat sink 
carries a plurality of semiconductor diode chips. The diode chips are 
electrically connected to electrical connectors that are inserted molded 
to insulator blocks that are supported by one of the heat sinks. The 
electrical connectors are adapted to be connected to the phase windings of 
an alternating current generator. The aluminum heat sink has a finned area 
which is adapted to be contacted by cooling air when the bridge rectifier 
is mounted in the generator. The structure of this patent forms the basis 
upon which the improvement of the present invention is predicated. 
Therefore, U.S. Pat. No. 4,606,000 is hereby incorporated by reference. By 
contrast, the device of the instant invention has a thicker finned 
aluminum heat sink portion so as to present approximately twice the 
surface area to the air flow and thus effectively double the convective 
heat transfer. In addition, an undercut circumferential groove has been 
incorporated into the wall forming the major diameter of the finned 
aluminum heat sink. This groove is deep enough to intersect the air flow 
path through the finned aluminum heat sink and provide an additional air 
flow in the radial direction an provide further improved cooling of the 
sensitive semiconductor diodes. Also, the additional embodiment of my 
invention showing separate radial cooling fins in place of multiple 
apertures through the aluminum heat sink is not shown by Steele et al. 
U.S. Pat. No. 4,604,538, issued to Merrill et al. on Aug. 5, 1986, shows an 
air cooled diode-rectified alternating current generator for use on motor 
vehicles. The generator has an internal fan located within the slip ring 
end frame and an external fan located adjacent the outer wall of the drive 
end frame. The internal fan cooperates with a baffle having a central 
opening and forces cooling air between air inlet openings and air outlet 
openings formed on the slip ring end frame. The air that traverses this 
path cools one end of a stator winding and a bridge rectifier. The 
external fan causes a flow of air between air inlet openings and air 
outlet openings formed in the drive end frame and this air contacts an 
opposite end of the stator winding. The cooling arrangement also provides 
for a flow of cooling air from the air inlet openings in the slip ring end 
frame to the air outlet openings in the drive end frame. The patent 
basically discloses the same dual heat sinks described in the Steele et 
al. patent above and the instant invention presents the same differences. 
U.S. Pat. No. 4,286,186, issued to Hagenlocher et al. on Aug. 25, 1981, 
shows a vehicular alternator end shield construction. The patent is to 
facilitate manufacture and provide readily accessible insertion openings 
for rectifier diodes in automotive alternators. The end covers or end 
shields are made as sheet metal elements with radially extending arms, 
leaving space for ventilating openings therebetween, extending from the 
center of rotation of the alternator, and form with bearing retaining 
means at the center, for example in the form of a punch or drawn bushing 
extension extending in an axial direction and at right angles to the major 
plane of the sheet metal element which, preferably, is also formed with 
stiffening ribs or beads at the lateral edges thereof. Preferably, the 
alternator is, in cross section, hexagonal and three arms, extending at 
120 degrees with respect to each other, the hexagonal outer end portions, 
are provided to permit universal fitting of the electrical connections 
with respect to the rotary position of the alternator shell and thus 
permit matching of the position of electrical connection to various 
attachment positions of the shell on a internal combustion engine. By 
contrast the cover or shell of the instant invention is designed to 
provide passage of the diode connections through in the radial direction. 
U.S. Pat. No. 4,680,495, issued to Chiampas et al. on Jul. 14, 1987, shows 
a spark protected alternator. It has an external cavity on an end plate of 
the alternator housing with commutating (slip) rings on an alternator 
shaft extension and mating metal brushes positioned within the external 
cavity. The external cavity is effectively sealed from ambient atmosphere 
surrounding the alternator, to provide protection from sparks generated 
between the brushes and commutating rings wherein a minimum area of the 
housing end plate is utilized. Integral extensions of the end plate form 
side walls of the external cavity that partially radially surround the 
shaft extension and commutating rings. A brush holder in which the brushes 
are attached has projections which mate with slots in the side walls to 
radially close the external cavity, and an end cap (including a gasket) 
closes an open end of the external cavity, while the end plate effectively 
closes the other end of the external cavity. The brush holder forms part 
of the walls that close the external cavity, and this minimizes the size 
of the external cavity required to seal the commutating rings and brushes 
from the ambient atmosphere. By contrast, the cover or shell of the 
instant invention is designed to provide passage of the diode connections 
through in the radial direction and no particular provision has been made 
for sealing or spark proofing. 
U.S. Pat. No. 5,043,614, issued to Yockey on Aug. 27, 1991, shows an 
alternator rectifier bridge assembly. An alternator rectifier bridge is 
incorporated into an alternator housing by inserting half of the diodes of 
the bridge into apertures formed into an alternator housing end plate 
which then serves as one output for the alternator and also as a massive 
heat sink to dissipate heat generated in the diodes. The other half of the 
diodes of the bridge are inserted into apertures formed in a radiator 
plate which is embedded into a plastic circuit member together with 
conductor members which interconnect electrodes of the diodes to stator 
windings of the alternator and also perform other electrical connections 
required for efficient manufacture and proper operation of the alternator. 
The radiator plate serves as the other output for the alternator and also 
as a heat sink. The plastic circuit member is coupled to the alternator 
housing end plate such that the electrodes of the diodes embedded therein 
pass through the plastic circuit member to engage corresponding ones of 
the conductor members resulting in a compact, highly efficient bridge 
which is readily assembled, preferably in an automated manner, using a 
limited number of component parts. A crescent shaped plastic end plate is 
molded so as to embed several of the electrical components of the 
rectifier bridge and make the appropriate connections when the plate is 
fastened to an end wall of the alternator which serves as a heat sink. By 
contrast, the instant invention has a cover plate which attaches to a 
separate dual metallic heat sink which does not form an integral part of 
the alternator. Also, the cooling air ports of the instant invention are 
provided with side ports, provided by a special undercut groove, which 
allow air flow in both the longitudinal and radial directions. 
U.S. Pat. No. 4,162,419, issued to DeAngelis on Jul. 24, 1979, shows an 
alternator having improved rectifier cooling. The rectifier assembly of an 
alternator is provided with improved cooling by improved air flow directed 
over the semiconductor elements of the rectifier assembly. Improved flow 
of air is provided by an auxiliary fan blade that is attached to a 
rotating member in the alternator structure. The fan blade is in proximity 
to the semiconductor rectifier elements of the rectifier assembly. Air 
ports are provided in the alternator housing to accommodate this 
longitudinal air flow and to improve the distribution of cooling air. By 
contrast, the cooling air ports of the instant invention are provided with 
side ports, provided by a special undercut groove, which allow air flow in 
both the longitudinal and radial directions. 
U.S. Pat. No. 4,419,597, issued to Shiga et al. on Dec. 6, 1983, shows an 
alternator assembly having a rectifier device in thermal contact with case 
and cover. The patent shows; an alternator assembly for an automotive 
vehicle including a rectifier device composed of a plurality of diodes 
supported on a negative-side cooling fin of semi-circular shape, a 
plurality of diodes supported on a positive-side cooling fin of 
semi-circular arc shape, and a terminal board supporting a plurality of 
terminals connected to the diodes. The rectifier device is assembled and 
held in a unitary structure by a plurality of metal members, and arranged 
in a space defined by an end frame and a rear cover of the alternator 
assembly in such a manner that the metal members are in contact at one end 
thereof with the rear cover and at the other end thereof with the end 
frame. By contrast, the cooling air ports of the instant invention are 
provided with side ports, provided by a special undercut groove, which 
allow air flow in both the longitudinal and radial directions. 
It will be noted that all the prior art devices provide for air cooling by 
the flow of air in a single direction regardless of the type of air flow 
ports or fins, etc. provided. This uni-directional air flow makes these 
devices inefficient as convective heat transfer devices and thus leads to 
the aforementioned overheating and semiconductor failures discussed above. 
None of the above inventions and patents, taken either singly or in 
combination, is seen to describe the instant invention as claimed. 
SUMMARY OF THE INVENTION 
Briefly, the invention comprises an improved cooling fin arrangement for a 
triphasic bridge rectifier used in conjunction with a three phase 
alternator in an automotive vehicle. The heat transfer ability of a 
metallic air core heat sink and radiator is more than doubled by 
increasing its thickness (and thus its exposed surface area) and by 
providing a cutout groove allowing the air to flow in two directions thus 
reducing the air flow resistance. An improved cover plate cooperates with 
the newly provided air flow paths and also provides simplified connectors 
for the electrical elements. 
Accordingly, it is a principal object of the invention to provide a new and 
improved cooling structure for a triphasic alternator rectifier which 
overcomes the disadvantages of the prior art in a simple but effective 
manner. 
It is a major object of this invention to provide a new and improved 
cooling structure for a triphasic alternator rectifier which is easily 
adapted to be provided as a kit for mounting to a presently mass produced 
alternator as an improvement thereof. 
It is another object of the invention to provide such a new and improved 
cooling structure for a triphasic alternator rectifier which is at least 
twice as effective in removing heat from the area of the sensitive 
semiconductor diodes as anything disclosed by the prior art. 
It is another object of the invention to provide such a new and improved 
cooling structure for a triphasic alternator rectifier which-achieves its 
advantages by extending the dimension of a radiator device in the 
direction of air flow so as to present more convective surface area to the 
flow of air past the device. 
It is another object of the invention to provide such a new and improved 
cooling structure for a triphasic alternator rectifier which achieves its 
advantages by the provision of an undercut groove which allows additional 
air flow and wherein the additional air flow is diverted directly across 
some of the semiconductor diodes of the rectifier. 
It is another object of the invention to provide such a new and improved 
cooling structure for a triphasic alternator rectifier with cooling fins 
in place of the conventional cooling ports so as to enhance the radiant 
heat transfer in addition to the convective heat transfer of the device. 
It is another object of the invention to provide such a new and improved 
cooling structure for a triphasic alternator rectifier with an improved 
cover arrangement which provides both protection from the elements as well 
as integral provision of some of the required electrical connection 
elements between diodes. 
Finally, it is a general goal of the invention to provide improved elements 
and arrangements thereof in an apparatus for the purposes described which 
is inexpensive, dependable and fully effective in accomplishing its 
intended purposes. 
These and other objects of the present invention will become readily 
apparent upon further review of the following specification and drawings. 
The present invention meets or exceeds all the above objects and goals. 
Upon further study of the specification and appended claims, further 
objects and advantages of this invention will become apparent to those 
skilled in the art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates generally at 10 the overall environment in which the 
invention is likely to be used. High powered internal combustion engine E 
of a standard automotive vehicle is illustrated with alternator A near the 
front thereof driven by belt drive B. It is obvious that the alternator A 
is located in a high heat location since at least 60% of the fuel energy 
burned by an internal combustion engine is wasted as heat. The high 
temperatures caused by the heat of the engine in the confined quarters of 
the engine compartment are cause for considerable concern when 
semiconductor electronic control elements are used in this area. 
FIG. 2 illustrates a closer view of alternator A and the relative location 
of the triphasic rectifier bridge B of which this invention forms an 
improvement. Belt drive B provides rotary energy through pulley P to 
alternator A. Rectifier bridge B is generally arcuate in shape and is 
mounted near the rear (with respect to the vehicle) plate of alternator A. 
FIG. 3 shows the rectifier bridge assembly B as it appears when removed 
from alternator A. Cover portion 153 is made of plastic material for 
protection of the internal components of the rectifier from the elements. 
Seen on the outer portion of the cover 153 are three are three slots S 
(see also FIG. 4). The slots S each contain and embedded conductor to 
connect outer and inner wires 22 and 24 which each lead to an appropriate 
side of an internal diode. The diodes are thus connected together in 
pairs. The cover 153 used is not the same as cover 53 in the Steele et al. 
Patent, incorporated by reference, but is a commercially available 
replacement cover which is manufactured by Transpo Electronics 
Incorporated. The general layout of the rectifier bridge is well 
documented in U.S. Pat. No. 4,606,000 which is incorporated by reference. 
In general the positioning of the diodes and other electronic components 
is identical in my invention as described in Steele et al. Three diodes D 
are mounted on the copper heat sink plate 202 and three are mounted on the 
aluminum heat sink plate 204. The diodes are connected to the phase 
windings of the alternating current generator as shown in the circuit 
diagram of FIG. 13 of the Steele Patent. Note in particular that the 
diodes are connected together in pairs. These pair connections are made in 
the cover 153 of this invention, described earlier. 
Particular attention is drawn to FIGS. 9-13 of that Patent in which the 
dual heat sink concept is illustrated. The instant invention also 
incorporates the dual heat sink concept with copper heat sink 202 and 
aluminum heat sink 204 visible in FIG. 3. The copper heat sink 202 is 
electrically insulated from the aluminum heat sink 204 by a thin 
interposed membrane 206 best visible in FIG. 7 and well described in the 
incorporated Patent. 
Aluminum heat sink 204 is similar but not identical to the heat sink 
described in the Steele et al. Patent incorporated herein. A major 
difference and improvement of this patent is that arcuate portion 204A 
including radially extending passages 204C separated by fins 204B are 
twice as thick (in the longitudinal direction of the passages) as the 
corresponding portions 104A, 104B, and 104C of the prior art patent. The 
thicker arcuate radiator portion of the aluminum heat sink presents 
approximately twice the surface area for convective heat transfer to the 
cooling air. 
Another major difference is the undercut groove 200 which extends all the 
way around the larger diameter portion of the arcuate portion 204A of the 
aluminum heat sink at a position approximately half way along the 
longitudinal thickness. The depth of the groove 200 is such that its back 
face intersects the outer radial tip of each of the radially extending air 
passages 204C. The edge of rectangular groove 200 may clearly be seen in 
FIG. 3. In FIG. 4 the depth of rectangular grove 200 may be seen in the 
hidden line arc as being just sufficient to open into the outer end of 
each of the radially extending air passages 204C. Air is forced through 
the air passages 204C in the manner well described in the Steele et al. 
Patent, incorporated by reference. The effect of undercut groove is to 
give the air in passages 204C another exit path into the undercut groove 
200. FIG. 10 clearly illustrates with arrows the newly provided pathway 
for the air. This additional exit path reduces the flow resistance of the 
air passageways and will lead to increased flow volume for the same 
pressure differential. As is well known to those skilled in the art, the 
increased flow volume will significantly increase the convective heat 
transfer of the "radiator". Thus the improved aluminum heat sink 204A of 
the instant invention is much better at providing cooling for the 
semiconductor diodes than is the incorporated prior art version. 
In FIG. 10 it also can be seen that diode support cup D' is directly in 
line with the diverted air flow passing into groove 200. This means that 
the diodes supported in cup D' are also subjected to direct convective 
cooling from the air flow as well as the conductive cooling afforded by 
the aluminum heat sink 204A. This direct convective cooling of the diodes 
mounted on the aluminum heat sink is not shown or made possible by the 
prior art. 
A variant of the improved aluminum heat sink is shown as 204' in FIGS. 
11-13. In this embodiment the air passageways 204C of the prior embodiment 
have been extended inwardly in the radial direction until they actually 
break the inner radial surface 300 of arcuate aluminum heat sink 204. Thus 
formed are full fins or fingers 302 which provide excellent radiant heat 
transfer capabilities as well as the previously described convective and 
conductive advantages. Inner groove 200' is undercut in the same manner as 
in the previous embodiment. 
It is to be understood that the provided illustrative examples are by no 
means exhaustive of the many possible uses for my invention. 
From the foregoing description, one skilled in the art can easily ascertain 
the essential characteristics of this invention and, without departing 
from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages and 
conditions. For example, the artisan could easily ascertain that the 
undercut groove need not be rectangular in cross section but could be 
circular or any other convenient shape. 
It is to be understood that the present invention is not limited to the 
sole embodiment described above, but encompasses any and all embodiments 
within the scope of the following claims: