Fuel injection device for internal combustion engines

Details Fuel injection device for internal combustion engines Fuel injection device for internal combustion engines

1991-08-19

1993-01-12

Kashnikow, Andres

Internal-combustion engines

Combustion chamber means having fuel injection only

Using multiple injectors or injections

417494, F02M 4506

Patent

active

051781107

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a fuel device for injection internal combustion engines, comprising a main plunger and a preinjection plunger, which is arranged coaxially with the latter and driven by the latter to make axial stroke movements, and has a smaller diameter, the main injection plunger being rotatable and fitted with a bevelled-edge control, and the preinjection plunger being held in contact with the main injection plunger by the force of one or more springs, and separate injection nozzles being provided for the main injection and preinjection. Known fuel injection devices of this type in which, however, the preinjection plunger is axially non-displaceably connected to the main injection plunger have become known, for example, from German Patent 577,288, Austrian Patent 227,479, German Patent 1,187,857 and German Patent 1,028,387.
In accordance with an unpublished proposal, it has already been suggested to construct the preinjection plunger separately and support it against the main injection plunger, the aim being for the preinjection plunger to be driven by the main injection plunger to make the compression stroke, and to be held by a spring, acting against the compression stroke of the preinjection plunger, so as to bear against the main injection plunger. The pressure in the working chamber of the main injection plunger now acts on the end face of the preinjection plunger facing the main injection plunger, and the preinjection plunger is to be pressed on the main injection plunger against this force by the spring. The force of the spring must therefore overcome the force exerted on the preinjection plunger by this pressure, with the result that the spring would have to be constructed greatly oversized. In modern injection pumps, the injection pressure in the working chamber of the main injection plunger is very high, and is up to 1200 bar, or even more. However, a spring which can over-come this force would have dimensions that make accommodating the spring in the pump impossible. This proposal therefore cannot be realised, particularly in the case of high injection pressures. Regardless of this, in the known designs only the annular surface between the outer circumference of the main injection plunger and the circumference of the preinjection plunger is available for the main injection. In order to achieve a sufficient main injection amount, it is therefore necessary for the main injection plunger to be constructed with a relatively large diameter, as a result of which the structural dimensions of the injection pump are enlarged.
The object of the invention is to improve, and reduce the structural dimensions of, an injection pump in which a preinjection plunger separated from the main injection plunger is held bearing against the main injection plunger by means of a spring force.
In order to achieve this object, the essence of the invention is that the preinjection plunger delivers a portion of the main injection amount after termination of the preinjection and the spray interval. Since, during the main injection, i.e. during the period in which the high injection pressure acts in the working chamber of the main injection plunger, the preinjection plunger also delivers fuel at the pressure occurring during the main injection in the working chamber of the main injection plunger, during this period the working chamber of the preinjection plunger is also at a pressure corresponding to the main injection pressure, and the preinjection plunger is loaded by the main injection pressure in the direction of the spring force acting on it. There is thus no need for the spring to overcome the pressure occurring in the working chamber of the main injection plunger, and a very weak design of this spring therefore suffices, so that this spring can easily be accommodated. Because the preinjection plunger now delivers a portion of the main injection amount during the main injection, the diameter of the main injection plunger can be constructed to be smaller, so that the structural dimensions of the injection pump

REFERENCES:
patent: 4426198 (1984-01-01), Bastenhof et al.
patent: 5074766 (1991-12-01), Kochanowski

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