Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
1999-04-19
2001-01-16
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C310S030000, C310S035000, C310S034000, C310S012060, C310S014000, C310S015000, C310S051000, C310S043000, C310S045000
Reexamination Certificate
active
06175168
ABSTRACT:
FIELD OF THE INVENTION
The present relates to solenoid-type fuel metering devices such as those used on diesel and other direct fuel injection internal combustion engines, and more particularly to an improved stator for use in such a solenoid.
BACKGROUND OF THE INVENTION
In modern direct fuel injection engines, such as diesels, it is known to use one or more solenoid actuated devices to control the volume and timing of the fuel supplied to the fuel injectors associated with each combustion chamber. Such solenoid fuel metering devices are preferably electronically controlled and allow the extremely precise metering of fuel necessary to achieve optimum engine performance and low emissions. Fuel metering solenoids must be extremely rugged in order to function properly in the engine environment over a long service life, and they must be able to operate at relatively high fuel pressures.
In order to ensure the factory-set performance characteristics of the engine are not altered by a mechanic or operator after the engine is sold, it is desirable to construct the fuel metering devices to prevent or discourage any tampering therewith.
A prior art fuel metering solenoid stator, as seen in
FIG. 1
, comprises two large metal components: a casing
100
which houses a solenoid bobbin assembly, and a tubular metal plunger guide
102
with an integral top plate
104
. The stator is assembled by inserting the bobbin assembly into a cavity formed in the lower surface of the casing
100
, placing mold cores in alignment with three apertures
106
,
108
in the top of the casing, and pouring or injecting a liquid plastic into the cavity to surround the bobbin assembly and mold cores. The mold cores are removed to leave three holes
110
,
112
passing completely through the casing
100
, and the plunger guide
102
is inserted downwardly through the large, center hole
110
so that it passes through the center of the bobbin assembly. Bolts are inserted upwardly through the two smaller holes
112
passing adjacent the outside of the bobbin and engage threaded holes
114
in the top plate
104
to secure the top plate to the casing and the entire assembly to an engine (not shown). An electrical connector
116
for supplying current to the bobbin wire exits the side of the casing.
A metering plunger (not shown) is inserted upwardly into the bore
118
of the plunger guide
102
from below and a spring (not shown) is disposed in the upper end of the guide
102
to bias the plunger downwardly. When the solenoid stator is energized, the magnetic field generated thereby draws the plunger upward to alternatively open and close a metering orifice below the stator assembly.
This prior art stator assembly requires a significant amount of precision machining and assembly, and therefore is relatively expensive to produce.
SUMMARY OF THE INVENTION
It is an objective of this invention to provide a stator for a liquid metering solenoid that is less costly to produce than prior art stators. It is a further objective of this invention to provide a stator assembly that is substantially encapsulated within a plastic material and so is rugged and tamper resistant.
According to the invention, an encapsulated stator comprises a bobbin assembly and a plunger guide which are substantially surrounded by a plastic overmold to hold the assembly together and provide a protective housing. Upper and lower ends of the plunger guide are not covered by the overmold, but rather are left exposed so that additional manufacturing and assembly steps may be performed on the stator. An electrical conductor is connected to the coil and passes through the overmold so that electrical power may be supplied to the coil.
According to another feature of this invention, the encapsulated stator further includes at least one threaded body having a threaded hole for receiving a fastener such as a bolt. In the preferred embodiment, two threaded bodies are utilized and are positioned on opposite sides of the bobbin assembly with the threaded holes parallel to a longitudinal axis of the plunger guide. The threaded bodies are substantially surrounded by the overmold with the holes exposed at the lower surface of the stator and are used to fasten the stator in its operating position.
According to a further feature of the invention, the plunger guide and the threaded body are connected with one another by a support plate which extends substantially normal to the longitudinal axis of the plunger guide and is disposed above the bobbin assembly. The support plate serves to positively position the threaded bodies relative to the plunger guide so as to ensure dimensional accuracy of the finished part. In a preferred embodiment of the invention, the support plate, plunger guide and threaded bodies are formed as an integral unit by casting.
According to yet another feature of this invention, a cap is secured to the bobbin assembly adjacent its upper end such that the plunger guide projects through a hole in the cap. The engagement between the cap and the bobbin retains the core and plunger guide in proper positions relative to the bobbin prior to the assembly being encased in the overmold. In a preferred embodiment of the invention, the cap comprises an electrical connector housing for mating engagement with the electrical power supply which powers the solenoid.
The present invention also provides a method of manufacturing an encapsulated stator having the structure described above. In the invention method, a plunger guide is inserted through a center passage of a bobbin assembly to form a stator assembly, and a plastic material is molded over and around the stator assembly.
REFERENCES:
patent: 4010390 (1977-03-01), Stampfli
patent: 4259653 (1981-03-01), McGonigal
patent: 4295066 (1981-10-01), Lloyd et al.
patent: 4342443 (1982-08-01), Wakeman
patent: 4358691 (1982-11-01), Nayler
patent: 4368446 (1983-01-01), Araki et al.
patent: 4643653 (1987-02-01), Masaka et al.
patent: 4661048 (1987-04-01), Masaka et al.
patent: 4725208 (1988-02-01), Brown
patent: 4840163 (1989-06-01), Alsobrooks et al.
patent: 4845392 (1989-07-01), Mumbower
patent: 5000421 (1991-03-01), Hendrixon et al.
patent: 5051631 (1991-09-01), Anderson
patent: 5075584 (1991-12-01), Hendrixon et al.
Budd Walter
Hojnacki Steve R.
Dougherty Thomas M.
Ghahramani Saeed
Pontiac Coil Inc.
Young & Basile P.C.
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