Electromagnetically actuable fuel injection valve

Fluid sprinkling – spraying – and diffusing – Distributor having thermal expansion joint – differentially...

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2395854, 239900, F02M 5100

Patent

active

059214694

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to an electromagnetically actuated valve, particularly to a fuel injection valve.


BACKGROUND INFORMATION

German Published Patent Application No. 38 31 196 A1 describes an electromagnetically actuated injection valve for fuel injection systems of mixture-compressing, spark-ignition internal combustion engines, in which injection valve a valve seat carrier and a valve needle are produced from the same material, for example chrome steel.
As the temperature of the fuel and of the interior of the internal combustion engine rises, the valve components, including the valve seat carrier and valve needle, assume an approximately equally high temperature. Since the valve seat carrier and the valve needle are produced from the same material, both valve components also have similar coefficients of thermal expansion; for example, the value .alpha. for chrome steel is approximately 16.times.10.sup.-6 K.sup.-1. As a result, during heating of the valve the longitudinal changes of the valve seat carrier and of the valve needle are similar. Consequently, the travel of the valve needle remains largely constant when temperature fluctuations occur in the internal combustion engine. When the valve is heated, a two-phase flow consisting of fuel and bubbles of gas is formed in the interior of the valve. This two-phase flow is disadvantageous to the extent that a reduction of the metered fuel inevitably occurs and thus a so-called leaning of the fuel/air mixture fed to the internal combustion engine occurs. A temperature increase in the interior of the internal combustion engine therefore has the consequence that when the same materials with identical coefficients of thermal expansion are used for the valve seat carrier and valve needle in the injection valve a reduction of the quantity of fuel delivered takes place.


SUMMARY OF THE INVENTION

In contrast to known valves, the electromagnetically actuated valve of the present invention has the advantage that by means of a suitable selection of material the reduction in through-flow of the metered fuel as a result of the formation of gas bubbles in the hot fuel is reduced and partially compensated. For the valve needle, it is expedient to use a material with a very low coefficient of thermal expansion, for example invar steel. The material invar steel is characterized by its nickel content of 36% and has the extremely small coefficient of thermal expansion .alpha.=0.9 . . . 1.5.times.10.sup.-6 K.sup.-1. When the temperature of the injection valve increases, the valve needle consisting of invar steel expands less as a result of the small coefficient of thermal expansion in comparison with the valve seat carrier consisting of chrome steel. Thus, in the case of heating by means of this material pairing, an increase in travel of the valve needle with respect to the valve seat occurs. As a result of this increase in travel of the valve needle, the travel damping component of the valve seat is reduced. With increasing temperature, the rate of through-flow of the fuel in comparison with the known valves therefore increases. Here, a 10 .mu.m travel increase of the valve needle provides an increase in through-flow of approximately 2 to 4%. The reduction of the metered fuel by the formation of gas bubbles in the hot fuel in injection valves in which the valve seat carrier and valve needle are manufactured from the same material is reduced or partially compensated in the injection valve according to the present invention by the selection of different materials with coefficients of thermal expansion which differ greatly from one another.
It is particularly advantageous to achieve a further increase in travel by the use of a material with a larger coefficient of thermal expansion than that of chrome steel for the valve seat carrier. For this purpose, the valve seat carrier is formed from two valve seat carrier sections: the valve seat carrier section which is directed to one magnetic coil being produced, as already known, from a magnetic

REFERENCES:
patent: 3604632 (1971-09-01), Eichelman
patent: 4116389 (1978-09-01), Furtah
patent: 4152903 (1979-05-01), Longsworth
patent: 4158442 (1979-06-01), Rathmayr
patent: 4284263 (1981-08-01), Newcomb
patent: 4483485 (1984-11-01), Kamiya
patent: 4798329 (1989-01-01), Mesenich
patent: 5156341 (1992-10-01), Terakado et al.
patent: 5405085 (1995-04-01), White

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