Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-08-30
2004-05-04
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S064000, C361S704000, C363S145000
Reexamination Certificate
active
06731030
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to bridge rectifiers for rectifying the current output of an alternating current generator. More specifically, the present invention relates to a high performance bridge rectifier which utilizes an improved first heat sink, an improved carrier plate second heat sink, an improved connection cover of the rectifier, improved first polarity and second polarity diodes, improved diode layout over the first and the second heat sinks, improved diode contact with the electrical contacts of the rectifier, and said rectifier is especially characterized by an improved B+ stud that more efficiently dissipates heat to properly cool the rectifier while providing current to various electrical loads such as, for example, a motor.
2. Background of the Related Art
Bridge rectifiers are used to rectify current output from alternative current sources, such as an alternating current generator. Bridge rectifiers for motor vehicle alternators are well known in the art and generally include two metal parts used as heat sinks that are electrically insulated from each other. As a result of the current that is transmitted therethrough, the bridge rectifier becomes heated due to the internal power loss on each individual diode. Thus, the bridge rectifier must be properly cooled in order to be able to handle the maximum required current, while still being tolerant to increased temperatures due to internal power losses.
Each of the metal parts or carrier plates includes semiconductor diodes that are arranged to polarize the two metal parts into respective positive and negative direct voltage output terminals. The diodes are then connected to respective phase windings of an output winding of the alternating current generator.
The rectifier diodes are connected to respective carrier plates, and these carrier plates are used as heat sinks for these diodes as well. The rectifier diodes are typically inserted by pressure in receiving bore holes of the carrier plate or heat sink, or are soldered to the carrier plate using appropriate solder alloys. The end wires connected to the rectifier diodes enable the rectifier diodes to be connected to external sources.
The heat sinks are typically constructed in the shape of a circle or crescent and are fastened in the same plane to the alternating current generator.
Various difficulties or problems have occurred using this standard diode rectifier. For example, since the diode rectifier is mounted to an alternating current generator that is used with a motor, there are space limitations within the motor, for example, which limit the size of the diode rectifier. One prior art solution to this problem is constructing or fabricating the carrier plates that are connected to the rectifier diodes into a shape that is more than a half circle approximating the circular shape of the alternating current generator. The carrier plates are constructed as a positive heat sink and a negative heat sink and the two heat sinks are arranged coaxially in separate planes spaced apart by an axial distance from one another. See, for example, U.S. Pat. No. 4,952,829 to Armbruster, et al., incorporated herein by reference.
Another problem experienced with diode rectifiers includes the need to carefully match the diode characteristics in order to avoid imbalance in the amount of current conducted by the individual diodes. If thermal imbalance is experienced, certain diodes will increase current flow that may result in thermal runaway. Thermal runaway involves a diode that is unable to regulate its current flow and temperature. In this situation, the diode conducts increased current and experiences increased temperature until the individual diode is no longer able to sustain the normal working reverse voltage, and the diode is destroyed. Frequently, thermal runaway results in the destruction of an individual diode, and the destroyed diode becomes short-circuited thereby rendering the entire bridge rectifier inoperative.
Another problem which has been encountered in bridge rectifiers is that the bridge rectifiers must not only be able to withstand normal battery charging current, but must also be able to supply current, perhaps as much as ten times the normal charging current. These increased current situations may occur, for example, when the motor vehicle is being started. Bridge rectifiers, as discussed, are typically unable to absorb or conduct these types of excess currents and are also unable to rapidly dissipate the resulting heat. Thus, the heat generated within the bridge rectifier may destroy the individual diodes. In order for bridge rectifiers to handle these types of excessive currents and heat, it becomes necessary to utilize a bridge rectifier, which has higher current handling capability. Due to the space limitations of the alternating current generator, it then becomes very difficult to provide such a bridge rectifier from a feasibility standpoint as well as at an economical cost.
A further attempt at increasing the current capacity and heat dissipating characteristics of the bridge rectifier includes the mounting of semiconductor diode chips onto first and second metallic heat sinks, which are electrically insulated from each other by a thin sheet of electrical insulating material. The diode chips are then covered by a protective insulating coating after connection to the respective heat sink. One of the metallic heat sinks includes a finned area, which is subjected to cooling air when the bridge rectifier is mounted to the generator. This type of bridge rectifier is shown in U.S. Pat. No. 4,606,000 to Steele, et al., and is incorporated herein by reference. The heat sink, with a plurality of fins, includes twelve air passages.
FIGS. 1
a
-
1
b
are prior art illustrations of a similar bridge rectifier as depicted in Steele et al. In
FIG. 1
a,
combined alternator cover and carrier plate
2
includes carrier plate or heat sink
4
connected to alternator cover
6
(only partially depicted to expose underlying plate
4
). Carrier plate
4
includes receiving bore holes
8
, which are formed for receiving the diodes. Carrier plate
4
includes alternator-mounting holes
10
for mounting carrier plate
4
to the alternator cover
6
via standard connection means, such as a stud or screw connection. Alternator cover
6
includes three main alternator air passages, which interact with the twelve air passages
14
in carrier plate
4
, thereby cooling radiating fins
13
. As depicted in
FIG. 1
b
(alternator cover
6
omitted for simplicity), carrier plate
4
is of a rectangular shape (in side view) having the air passages
14
going completely through carrier plate
4
.
FIG. 2
is a prior art illustration of the positioning of the bridge rectifier
1
within a standard alternating current generator. As depicted in
FIG. 2
, the completely assembled bridge rectifier
1
, which includes carrier plate and cover
1
a,
is connected to alternator cover
6
via any standard connection means, such as screws
7
. Reference numeral
3
denotes the bottom of carrier plate
4
, while reference numeral
5
denotes the top of carrier plate
4
. Bridge rectifier
1
is also connected to regulator
9
. As mentioned previously, the standard bridge rectifier shown in Steele et al. and
FIGS. 1
a
-
1
b
is well known in the art, and may also be purchased from Wetherill Associates Inc. of Royersford, Pa. as part no. 31-113, including cover part no. 46-1858.
FIGS. 3
a
-
3
b
illustrate a prior art solution presented by U.S. Pat. No. 5,646,838 to Integral Automotive S.A. of Luxemburg, and invented by 3 of the 4 inventors of the present invention, with a bridge rectifier using a first heat sink
84
, an insulator layer
80
, a second heat sink
4
, with heightened plateau area
18
over the base section area
16
, and an improved convection surface area over the base section, using ridges
54
for better cooling. Again shown are receiving bore holes
8
, alternator-mounting holes
10
, cooling radiating fins
Dobrinescu Sorin
Keidar Zvi
Popa Eugen
Turtudau Florian
Integral Ro Design Ltd.
Mayer Brown Rowe & Mawl LLP
Waks Joseph
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