Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1996-11-12
1998-05-05
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Fuel injection system
F02M 5502
Patent
active
057461813
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection valve for internal combustion engines. In conventional fuel injection valves of this type, the fuel inlet conduit extends in the valve body obliquely to the center axis, next to the guide bore for the valve member (nozzle needle) extending coaxially with the center axis, and laterally intersects the pressure chamber, which is embodied as an undercut. Because of the slanting course of the inlet conduit, the wall of the valve body has only a slight thickness between the inlet conduit and the guide bore, near where the inlet conduit discharges into the pressure chamber. A further factor is that the wall of the valve body surrounding the pressure chamber, because of the width needed for distributing the fuel, has the least thickness and strength. At injection pressures of up to 400 bar, no significant damage occurs in known fuel injection valves. At higher injection pressures, which in modern direct-injection internal combustion engines have been increased to about 1800 bar, breakage at the end of the partition between the guide bore and the inlet conduit (that is, in the nip) of the pressure chamber can occur, which progresses over time and can lead to the destruction of the valve body of the injection valve. Such breaks are due especially to the high dynamic internal pressure load, compared with the static tension with which the valve body is pressed by the adjusting nut against the valve retaining body, and the injection valve itself is pressed by the adjusting nut against a counterpart stop in the engine housing. In fuel injection valves that are combined directly with a high-pressure pump, which are known as unit fuel injectors, a further factor is that in the pressure buildup, the axial housing pressure of the pump is transmitted to the valve member body via the retaining body.
To lessen the danger of breakage of the valve body in the region of the pressure chamber, it is known to weaken the wall surrounding the pressure chamber as little as possible. To that end, instead of the circular widening of the pressure chamber, an eccentric recess is disposed only at the discharge region of the fuel inlet conduit (U.S. Pat. No. 3,511,442), so that the inclined guidance of the fuel inlet conduit can be made as steep as possible. It is also known to guide the fuel inlet conduit parallel to the guide bore, up to the level of the pressure chamber, and from there on to connect it to the relatively closely guided pressure chamber through a radial, or only slightly steep, or curved connecting conduit (European patent disclosures EP-A 425 236 and EP-A 363 142). Producing such a connecting conduit, however, is complicated and very expensive.
From German Patent Disclosure DE-OS 41 42 430, a fuel injection valve is also known in which the annular shoulder of the adjusting nut that axially braces the valve body against the retaining body is embodied conically on the end of the nut remote from the retaining body. However, this known fuel injection valve also has the disadvantage that widening of the adjusting nut can occur from the axial strain caused when the entire fuel injection valve is fastened in the housing of the engine, so that the compressive force exerted by the adjusting nut in the direction of the pressure chamber cannot contribute substantially to stabilizing the valve body wall.
ADVANTAGES OF THE INVENTION
The fuel injection valve according to the invention for internal combustion engines has the advantage over the prior art that even at very high pressures (about 1800 bar) in the pressure chamber, breakage of the valve body can be reliably avoided.
This is advantageously achieved by the combination of the two conically embodied fuel introduction faces (two chamfers) between the adjusting nut and the valve body and the engine housing and the valve body; as a result, both the bracing force of the adjusting nut when the valve body is braced against the retaining body and the fastening force when the entire injection valve is fastened into the housing of t
REFERENCES:
patent: 5394850 (1995-03-01), Murphy et al.
patent: 5479900 (1996-01-01), Bodenhausen et al.
patent: 5499612 (1996-03-01), Haughney
patent: 5520151 (1996-05-01), Gras et al.
patent: 5575263 (1996-11-01), Pontoppidan et al.
patent: 5577480 (1996-11-01), Gmelin et al.
Boecking Friedrich
Haug Stefan
Greigg Edwin E.
Greigg Ronald E.
Nelli Raymond A.
Robert & Bosch GmbH
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