Fluid sprinkling – spraying – and diffusing – Including valve means in flow line – Reciprocating
Reexamination Certificate
1998-05-21
2001-06-12
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Including valve means in flow line
Reciprocating
Reexamination Certificate
active
06244526
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a fuel injection valve according to the definition of the species of claim
1
and claim
2
.
Fuel injection valves are already known that can be operated electromagnetically and thus have a magnetic circuit comprising at least a magnet coil, a core an armature and a stationary pole. Such fuel injection valves are presented and described, for example, in such publications as German DE-OS 30 16 993, DE-PS 32 30 844, DE-PS 37 33 809, DE-PS 40 03 227 and DE-OS 195 03 821. Ferromagnetic (magnetically soft) materials are usually used for the solid core with a compact one-piece design (and for the movable armature). Ferritic chromium steel, a 13% chromium steel, for example, has proven to be an especially suitable material for cores in fuel injection valves. Such a ferritic chromium steel is a good compromise, because although it has somewhat less favorable magnetic properties in comparison with ferritic soft iron, for example, it is very suitable for use in a compact and highly structured fuel injection valve due to its good machinability and handling. If there is a change in magnetic flux density in the core carrying a magnetic flux due to the electric current flowing in the magnet coil, stresses are induced in the flux field perpendicular to the direction of flux, resulting in eddy currents. These eddy currents weaken the effective magnetic field, because they create an opposing field. The result is a magnetic circuit with a reduced efficacy which is to be improved according to this invention.
ADVANTAGES OF THE INVENTION
The fuel injection valve according to this invention with the characterizing features of claim
1
and claim
2
has the advantage that a magnetic circuit that minimizes eddy currents is created by simple and inexpensive use of materials having a lower eddy current tendency for the core. The execution of selected partial volumes of the internal pole of the magnetic circuit, in particular the core, with a material having a low tendency to eddy currents yields an advantageous shortening of switching times (pickup time, closing time) of the valve in comparison with known magnetic circuits having the same geometry, and does so without any mentionable reduction in the maximum force level of the magnetic circuit. The shortening of switching time in comparison with comparable known injection valves amounts to 15% to 50%. Magnetically soft powder composite materials have proven especially advantageous as low-eddy-current materials.
It is also advantageous to manufacture part of the core forming the magnetic circuit from a pure ferritic material, with the core being composed of several sectors forming an annulus and the individual sectors electrically insulated from one another. Such a design of the core also has a lower tendency to eddy currents than known compact cores of ferritic chromium steel, so that even in this case, the switching time of the valve is shortened while the quality of the magnetic properties is the same.
According to this invention, the switching times are shortened and thus the linearity of the fuel injection valve is improved without any sacrifices in terms of the magnetic force at the same time. Furthermore, utilization of power is improved, which thus yields lower heating of the magnet coil and the possibility of utilizing the magnetic circuit energy in shutdown for the next energizing phase. This in turn makes it possible to implement a simple and inexpensive layout of the output stage to be driven.
Encapsulation of the low-eddy-current material, which is mechanically more susceptible and is not necessarily completely resistant to fuel (especially when gasoline is the fuel) prevents contamination problems with the fuel injection valves and guarantees the required functional reliability and endurance. The means for encapsulation of the core ensure that there is a tight seal to the fuel flow path and thus wetting by the fuel is ruled out.
Through the measures characterized in the subclaims, advantageous refinements and improvements of the fuel injection valve characterized in claim
1
and claim
2
are possible.
It is especially advantageous to use as the powder composite material an iron powder containing a polymer additive, where the individual particles of iron are coated with electrically insulating layers (phosphate layers). Due to the high electric resistance between the powder particles, hardly any eddy currents can develop there. Although phosphating the particles of iron ensures insulation of the particles, the polymer additive serves both to insulate the particles and to bind the individual particles together. This material structure permits the above-mentioned low-eddy-current effect and the resulting very good switching dynamics of the injection valve.
A sleeve which extends through a longitudinal opening in the core and encapsulates it toward the inside is designed in an advantageous manner of a very thin wall of stainless austenitic steel (e.g., V2A steel) which is largely free of magnetic flux and eddy currents. The efficacy of the magnetic circuit is affected only very slightly by the thin-walled nonmagnetic sleeve, so that the positive magnetic properties of the low-eddy-current materials are definitely predominant. The core is encapsulated on its lower end face with an adjacent pole part made of a ferritic material. It is advantageous if both the sleeve and the pole part are designed as thin as possible, with the sleeve being made of a material having a higher magnetic resistance than the core and also having a higher magnetic resistance than the pole part.
REFERENCES:
patent: 4262877 (1981-04-01), Lang
patent: 4875658 (1989-10-01), Asai
patent: 4958771 (1990-09-01), Klomp
patent: 4984549 (1991-01-01), Mesenich
patent: 5247918 (1993-09-01), Wakeman
patent: 30 16 993 (1980-11-01), None
patent: 32 30 844 (1984-02-01), None
patent: 37 33 809 (1988-04-01), None
patent: 40 03 227 (1991-01-01), None
patent: 195 03 821 (1996-08-01), None
patent: 196 01 019 (1997-07-01), None
Eichendorf Andreas
Glumann Christiane
Keim Norbert
Martin Ottmar
Mueller Martin
Kenyon & Kenyon
Kim Christopher S.
Robert & Bosch GmbH
Scherbel David A.
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