Valves and valve actuation – Electrically actuated valve – Including solenoid
Utility Patent
1998-05-15
2001-01-02
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Electrically actuated valve
Including solenoid
C251S129210
Utility Patent
active
06168135
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a solenoid actuated fuel injector for internal combustion engines and, in particular, to a fuel injector having a slotted housing that decreases the closing time of the fuel injection valve by reducing motion-retarding eddy currents produced during field decay upon deenergizing of the solenoid.
BACKGROUND OF THE INVENTION
The ability of a fuel injector to open and close rapidly is a significant factor in determining the amount of fuel that is injected into an internal combustion engine. The fuel injector is opened by applying a voltage to a magnetic circuit of a solenoid located within the injector. The magnetic circuit generates a magnetic force. The magnetic force draws upward a valve and armature assembly, thereby opening the injection valve against the force of a return spring and allowing fuel to flow.
Closing of the injection valve by the return spring occurs upon demagnetization of the magnetic circuit of the solenoid. Demagnetization begins upon removal of the power source. As a result, magnetic flux lines decay rapidly. This rapid decay creates undesirable eddy currents which form perpendicular to the magnetic flux lines and are carried by any electrically conductive material in the magnetic field. These eddy currents resist and slow the decay of the flux, causing a slower than desired closing time of the fuel injection valve.
In the past, eddy current loss was largely overcome by making the magnetic material of the solenoid pole or housing of very thin laminations. Each lamination was coated on each side with an insulating material so that no current could flow between the laminations. However, a laminated housing is costly to manufacture.
U.S. Pat. No. 5,207,410, issued May 4, 1993 to the assignee of the present invention, provides grooves or surface slots in the magnetic poles which increase surface area and decrease eddy currents by increasing the length and resistance of the flow path.
SUMMARY OF THE INVENTION
The present invention provides a fuel injector having a solenoid actuated injection valve used to control the injection of fuel into an internal combustion engine. The fuel injector housing is provided with slots through the housing which extend longitudinally and radially in the direction of the lines of magnetic flux and, thus, perpendicular to the direction of flow of eddy currents formed upon decay of the flux field when the solenoid coil is deenergized. These slots significantly reduce the circumferential flow path area of the housing, thus reducing the flow of eddy currents in that direction. However, the saturation strength of the magnetic circuit is not greatly reduced because the slots are relatively narrow and are aligned with the direction of flux lines in the housing.
These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.
REFERENCES:
patent: 3633139 (1972-01-01), Thompson
patent: 4474332 (1984-10-01), Kaska
patent: 4812884 (1989-03-01), Mohler
patent: 5544816 (1996-08-01), Nally et al.
patent: 39 33 758 (1991-04-01), None
Keasel Eric
Shaver Kevin
Siemens Automotive Corporation
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