Internal-combustion engines – Charge forming device – With fuel pump
Patent
1985-03-29
1986-10-07
Miller, Carl Stuart
Internal-combustion engines
Charge forming device
With fuel pump
123508, 123470, F02M 3900
Patent
active
046153233
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention is directed to improvements in a pump
ozzle unit for use in internal combustion engine fuel injection systems. A pump
ozzle unit of this kind is already known (German laid-open patent application De-OS 32 26 238), in which the piston injection pump and injection nozzle are combined in a common pump housing to make a structrual unit installed on the cylinder head of the engine. Differing from the otherwise conventional coaxial, i.e., in-line, structure, in the known pump
ozzle unit the longitudinal axis of the pump piston, which is also designated as the line of action of the injection pump, and the longitudinal axis of the injection nozzle are preferably at right angles to one another. This provision was made in order to attain a more compact structure and in order to intercept the pumping forces at a cylinder head location remote from the injection nozzle receiving bore. This has the advantage that the injection nozzle diameter and structural shape, and the thicknesses of the cylinder head wall surrounding this nozzle, can be optimally designed. This is possible because the very strong pumping forces, which are on the order of magnitude of 2000N, are intercepted at a cylinder head location the dimensions of which can be made appropriately thick. To this end, the pump
ozzle unit described in FIG. 2 of the above German laid-open patent application is supported with a support face, on its end remote from the camshaft, on a corresponding face of the cylinder head. The injection nozzle disposed laterally at an angle with respect to the longitudinal axis of the pump piston is received by a receiving bore in the cylinder head and protrudes into the working cylinder of the engine; it does not have to transmit any pumping and clamping forces. However, the disadvantage of this arrangement is that the locational tolerances of the support faces, the laterally disposed injection nozzle and the receiving bore in the cylinder head must be kept extremely tight, to prevent tensing and clamping forces form acting on the injection nozzle. This is critical particularly because the cylinder head is subjected to very large temperature differences, and heat expansion of the cylinder head and pump housing, added to the manufacturing tolerances, results in deviations in the installation location. It is the object of the present invention to intercept the pumping forces in the cylinder head in such a manner that even with severe temperature fluctuations and the existing manufacturing tolerances, no forces that would strain the injection nozzle will be able to act upon it.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the pump
ozzle unit according to the invention that the pumping forces resulting from the injection pressure in the pump work chamber are transmitted directly into the cylinder head, without these forces being introduced into the pump housing, by the counterpart piston, which its outwardly pointing end face embodies the support face resting on the support bearing. Thus the injection nozzle, which is attached to the housing extension that protrudes at least approximately at right angles to the longitudinal axis of the pump piston, and the associated receiving bore are entirely relieved from the pumping forces. In the case of the counterpart piston according to FIG. 2, which is fitted, in the form of a floating piston, into a pump cylinder extension which is provided with a constant diameter until the end section of the pump housing, the pumping forces transmitted to the counterpart piston via the fuel, which is under pressure, are introduced entirely into the support bearing. However, it is also possible, by means of slight differences in the diameter of the pump piston and the counterpart piston and correspondingly embodied bores sections in the pump cylinder, to form a pressure shoulder which additionally compensates for drive forces, emanating for instance from the tappet spring.
It is another object of the invention that fuel leakage, which is unavoidable even given
REFERENCES:
patent: 1863232 (1932-06-01), Woolson
patent: 2354403 (1944-07-01), Reggio
patent: 2793078 (1957-05-01), Brill
patent: 3845748 (1974-11-01), Eisenberg
patent: 4522182 (1985-06-01), Mowbray
Leblanc Jean
Rossignol Francois
Greigg Edwin E.
Miller Carl Stuart
Robert & Bosch GmbH
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