Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-09-20
2001-10-23
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S496000, C239S096000
Reexamination Certificate
active
06305359
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to a fuel injection valve for internal combustion engines.
2. Description of the Prior Art
In a fuel injection valve of the type with which is invention is concerned, which is known from DE 39 00 763, a valve member is guided so that it can move axially in a guide bore of a valve body. With its end oriented toward the combustion chamber, the valve member controls a through flow cross section to at least one injection opening into the combustion chamber of the engine to be supplied. With its end remote from the combustion chamber, the valve member protrudes at least indirectly into a fuel-filled spring chamber in which a valve spring is clamped that acts on the valve member in the closing direction of the through flow cross section. This valve spring is supported with its end remote from the valve member against a deflecting piston which, during the supply of high fuel pressure to the fuel injection valve, can be moved a certain distance into the spring chamber and by means of this insertion, increases the initial stress force of the valve spring. The preinjection in the fuel injection valve is controlled by means of this increase in the initial stress force of the valve spring during the injection phase. The spring chamber containing the valve spring has a connecting conduit to a low pressure fuel chamber encompassing the valve body of the fuel injection valve. This low pressure fuel chamber is embodied as an intake chamber for a high pressure fuel pump which, together with the fuel injection valve, constitutes a component and is connected to the fuel injection valve by means of a clamping nut. This component is then inserted into a corresponding receiving opening of the housing of the engine to be supplied, wherein the control of the high pressure delivery to the high pressure fuel pump and consequently the high pressure fuel injection at the fuel injection valve takes place by means of an electric control valve, preferably a solenoid valve, which is connected laterally to the housing of the high pressure fuel pump.
In this connection, however, the fuel injection valve has the disadvantage that the closing force of the valve spring is not enough to also produce very high injection opening pressures in the fuel injection valve. Furthermore, with the known fuel injection valve, when the valve member is opened rapidly, an oscillation of the valve spring and consequently also of the components connected to it—particularly of the valve member—can occur, which has a disadvantageous effect on the actually prevailing injection opening pressure and as a result, on the metering precision of the injection quantity in the fuel injection valve.
SUMMARY OF THE INVENTION
The fuel injection valve for internal combustion engines according to the invention, has the advantage over the prior art that the closing forces acting on the valve member during the main injection phase can be sharply increased while the structural dimensions remain the same. This increase in the closing forces acting on the valve member is achieved through the advantageous provision of a throttle between the spring chamber and a low pressure fuel chamber, which limits the escape of the fuel disposed in the spring chamber. In this manner, in addition to the increase of the initial spring stress of the valve spring when the deflecting piston is inserted into the spring chamber also produces an increase in the hydraulic closing force, wherein the additional hydraulic closing force approximately corresponds to the closing force of the valve spring. Consequently, the closing force can be increased approximately by a factor of 2 in comparison to conventional fuel injection valves. The increased closing forces on the valve member thereby produce a significant increase in the necessary injection opening pressure in the fuel injection valve so that an improved fuel injection characteristic curve can be produced in the injection valve, which has a positive influence on the fuel preparation and combustion in the combustion chamber of the engine to be supplied, particularly in the engine map region that is sensitive to emissions and consumption. The magnitude of the additional hydraulic closing force is thereby influenced by the throttle diameter, the total stroke of the deflecting piston, and the shaft diameter of the nozzle needle, wherein the increase in the injection opening pressure and the maximal injection pressure during the main injection phase becomes apparent particularly at low and medium engine speeds. The intensified increase thereby occurs with the small injection quantities, which are important for emissions measurements and in which the peak pressures of the high pressure delivery pump are hardly ever greater than the injection opening pressures. At the nominal speed and maximal quantity, however, due to the short cycle times, there is advantageously no significant increase in the maximal injection opening pressure.
Another advantage of providing a throttle opening between the spring chamber and the low pressure fuel chamber encompassing the valve holding body is the damping effect of the hydraulic pressure in the spring chamber, which suppresses oscillations of the valve spring and consequently fluctuations of the injection opening pressure.
The pressure in the spring chamber, which only decreases slowly due to the throttle action, furthermore advantageously encourages the closing of the valve member with increasing force as the speed increases, which is particularly advantageous due to the short diversion times at high speeds. In addition, less cavitation is produced in the high pressure region after the closing of the valve member, which reduces the subsequent filling stroke in it. This permits the reduction of noise emission and the risk of an undesirable reopening of the valve member.
The provision, according to the invention, of a throttle relief bore of the spring chamber in connection with a deflecting piston that reduces the volume of the spring chamber is shown in the exemplary embodiment of a so-called unit fuel injector, but can also be used in other injection systems which provide a deflecting piston in the spring chamber of the fuel injection valve.
REFERENCES:
patent: 4546739 (1985-10-01), Nakajima et al.
patent: 4928886 (1990-05-01), Kronberger
patent: 5984200 (1999-11-01), Augustin
patent: 5984201 (1999-11-01), Hofmann et al.
patent: 6024298 (2000-02-01), Kelly
Kronberger Maximilian
Strahberger Herbert
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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