Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-23
2003-09-23
Pononarenke, Nicholas (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S089000
Reexamination Certificate
active
06624543
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an apparatus and method for concentrically aligning parts. More specifically, it relates to an engine powered generator having a stator concentrically aligned with a rotor.
BACKGROUND OF THE INVENTION
It is well known to power an electric generator using an engine. The flywheel of the engine is attached to the rotor of the generator. The rotor spins inside of a stator. The stator is held stationary inside of a housing. The stator housing assembly in turn is mounted to an adapter plate or fly wheel housing which is fixed to the engine behind the flywheel.
There is generally a small air gap between the rotor and the stator. The quality of the electric output of the generator is dependent upon the air gap having a constant size as the rotor spins. The rotor and the stator must be concentrically aligned with each other to achieve the desired constant size or dimensional uniformity.
Prior art attempts to achieve the required degree of concentricity involve tightly controlling the alignment of the stator housing assembly with the adapter plate. In one prior art method, the surface of the adapter plate is machined to form a circular pilot ring on its surface. The adaptor plate is fixedly mounted to the engine at a predetermined and known location behind the flywheel (which has the rotor attached to it). The stator is secured inside of the cylindrical housing, also at a predetermined and known location within the housing. The diameter of the end of the cylindrical stator housing assembly is slightly larger or slightly smaller than the diameter of the pilot ring on the adapter plate. The stator housing assembly, when placed over the rotor and aligned with the pilot ring, fits snugly onto the pilot ring. By tightly controlling the location and alignment of the stator housing assembly with respect to the pilot ring, therefore, the axis of the stator is indirectly forced into concentric alignment with the axis of the rotor.
This prior art method of alignment requires several expensive manufacturing steps to insure that the desired concentricity is obtained. For instance, the adaptor plate surface must be accurately machined to form and locate the pilot ring. This machining step is expensive. It is therefore desirable to have an adapter plate that does not require any machining.
One prior art housing is made from a relatively thin steel plate that is rolled into a cylinder and welded along the seam. A steel end ring is welded to each end of the housing to provide a proper surface for alignment with the continuous pilot ring. The end rings are made from relatively thick steel bar stock that is rolled into a ring and welded to the end of the housing. A gap is left between the ends of the rolled steel bar stock to accommodate the starter motor that extends out over the flywheel.
Different engine manufacturers locate the starter motor at different locations around the circumference of the flywheel. As a result, the location of the gap in the housing end ring that accommodates the starter motor is different for different engines and a different housing configuration must be provided for each different engine type. It is desirable therefore to have a single housing configuration that accommodates more than one type of engine.
The stator is press fit into the housing. A tight fit results when the stator contacts the inner surface of the housing at many points. The end rings are added to the housing assembly to provide a surface for alignment with the continuous pilot ring. These end rings add rigidity to the housing assembly and in the process may change the roundness of the housing. This results in the stator having too little contact to be securely held in place. It is necessary to drill through the housing into the stator and to weld the stator in place in these situations. The drilling process damages the painted outer surface of the housing and the housing must later be repainted to prevent corrosion from occurring. All of these additional steps to secure the stator in place add extra cost to the generator. It is therefore desirable to have a stator housing assembly without end rings wherein the stator is adequately secured in place by simply press fitting the stator into the housing without any further processing required.
The prior art cylindrical stator housing assembly also requires machining of the end rings to provide for proper and accurate alignment with the circular pilot ring. The stator housing assembly, which can weigh in excess of 200 pounds, is typically mounted on a lathe and the end rings are accurately machined thereon. This machining step is not only expensive, but in many cases dangerous due to the large weight of the spinning stator housing assembly on the lathe.
Another problem is that sharp metal chips produced during the machining operation can inadvertently land inside of the stator housing assembly. The stator is made up largely of copper wire that is insulated with, and sealed in, varnish. If left undetected, these stray metal chips can damage the insulation surrounding the copper wires. This can result in a shorted winding during operation of the generator. It is desirable therefore to entirely eliminate the machining operations applied to the stator assembly.
FIG. 1
shows a prior art generator
101
using a pilot ring to align the stator and rotor. Engine/rotor assembly
100
includes an engine (not shown), a flywheel
102
, a starter motor (not shown), and a rotor
104
. Rotor
104
is mounted to flywheel
102
at a predetermined and known location and spins with flywheel
102
. The starter motor is used to start flywheel
102
spinning and typically protrudes outward from the side of flywheel
102
. The location of the starter motor varies from engine manufacturer to engine manufacturer.
An adapter plate
105
is mounted to the engine block behind flywheel
102
. Adapter plate
105
is also mounted at a predetermined and known location. Prior art adapter plate
105
includes a circular pilot ring
106
and mounting holes
107
. Pilot ring
106
is created by machining the surface of adaptor plate
105
, and has a mostly continuous outside pilot ring surface
109
. Pilot ring
106
provides for alignment of a stator with rotor
104
as will be explained later.
A prior art stator housing assembly
200
is also shown in FIG.
1
. Stator housing assembly
200
includes a stator
201
and a housing
202
. Housing
202
typically is made by rolling a steel plate into a cylinder and then welding or otherwise joining the edges of the steel plate together. A steel end ring
203
is welded to each end of housing
202
. Stator
201
is then press fit into housing
202
. The location of stator
201
inside of housing
202
is also predetermined and known. One end of housing
202
is adapted for attachment to engine/rotor assembly
100
. The other end of housing
202
is adapted for attachment to a bearing assembly or other device in a similar manner.
Steel end ring
203
is generally included to provide a surface on the end of stator housing assembly
200
that can be accurately machined. This insures that stator
201
will be concentrically aligned with rotor
104
when stator housing assembly
200
is attached to engine/rotor assembly
100
. End ring
203
is typically formed from steel bar stock that is also rolled into shape. Unlike the steel plate used to make housing
202
, however, the ends of the steel bar used to make end ring
203
are not brought together. Rather, the ends are left separated to form a starter motor gap (not shown) in end ring
203
. The starter motor gap is located to accommodate the protruding starter motor when stator housing assembly
200
is mounted to engine/rotor assembly
100
. Different engine manufacturers locate their starter motors at different locations around the flywheel. The starter motor gap must therefore be located at a different location for different engine types. Different stator housing assemblies are therefore needed for different engine types.
End ring
20
Illinois Tool Works Inc.
Pononarenke Nicholas
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