Internal-combustion engines – Poppet valve operating mechanism – Rocker
Patent
1987-12-17
1989-04-11
Nelli, Raymond A.
Internal-combustion engines
Poppet valve operating mechanism
Rocker
123 9027, 123 9022, 123 9016, 123 9023, 123 904, F01L 126
Patent
active
048195910
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a poppet valve assembly, for example for a piston-and-cylinder internal combustion engine, in which a plurality of poppet valves are required to be operated simultaneously.
There is now increasing interest in using more than one inlet valve, and sometimes more than one exhaust valve, per cylinder to increase the effective port window area during induction or exhaust of a charge of air or mixture, to a value greater than that available with the largest single poppet valve which can be accommodated in the required combustion chamber design.
According to the present invention there is provided a poppet valve assembly comprising a plurality of simultaneously operated poppet valve members slidably mounted for movement between their open and closed positions by their stems the axes of which are not all parallel, a rocker mounted for rocking movement about a rocking axis transverse to each valve stem axis, the rocker having a valve stem engaging tappet element for each valve for engaging an end face of the respective valve stem, the respective lengths of the valve stems, being such that the tapper elements are not all in the same plane through the rocker axis in such a manner that simultaneously for each valve, in an intermediate part of the valve lift travel, a line from the rocker axis to the point of engagement of the tappet element with the end face of the valve stem is perpendicular to the valve stem axis.
Also, according to the invention, there is provided a poppet valve assembly comprising a plurality of simultaneously operated poppet valve members slidably mounted for movement between their open and closed positions by their stems, the axes of which are not all parallel, a rocker mounted for rocking movement about a rocking axis transverse to each said valve stem, the rocker carrying a valve stem engaging tappet element for each valve member for engaging an end face of the respective valve stem, wherein the angular spacing of the valve stem engaging tappet elements around the rocker axis corresponds to the angles between the axes of the respective valve stems and the lengths of the valve stems are such that the tappet elements of the rocker engage the valve stems simultaneously.
The motions of the tappet elements relative to their respective valve stems are then identical and can thus be simultaneously optimised.
To obtain equal valve lift, the valve stem axes are made equidistant from the rocker axis.
If a greater lift is required for one valve than another, this is achieved by spacing the axis of the said one valve a proportionately greater distance from the rocker axis than the other valve.
The invention will now be further described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a top elevational view of the cylinder head of a single-cylinder internal combustion engine (or of one cylinder of a radial internal combustion engine),
FIG. 2 is a longitudinal section on the line II--II of FIG. 1,
FIG. 3 is a underplan view of the cylinder head as seem in the direction of the arrows III--III of FIG. 2,
FIG. 4 is a view of the inlet rocker shaft in the direction of the arrow IV of FIG. 2,
FIG. 5 shows a detail of FIG. 2 on an enlarged scale,
FIG. 6 shows diagramatically the valve layout in a cylinder head incorporating an overhead camshaft,
FIG. 7 is a view corresponding to portions of FIG. 2 with a modified valve gear incorporating hydraulic self-adjusting tappets and
FIG. 8 is a plan view of the rocker shaft of FIG. 7.
The cylinder head 1 shown in FIGS. 1 to 3 is formed by an aluminium alloy casting. The casting defines a combustion chamber 2 and inlet and exhaust ducts 3 and 4 which communicate with the combustion chamber 2 through inlet and exhaust ports defined by inlet and exhaust valve seat inserts 5 and 6 respectively.
The cylinder head casting 1 also defines coolant passages W which receive water-based coolant from a coolant jacket J (FIG. 2) in a cylinder block 7 to which the head is secured and convey the coolant to an outlet 8 (F
REFERENCES:
patent: 4624222 (1986-11-01), Yoshikawa
patent: 4637350 (1987-01-01), Kuroda
patent: 4638774 (1987-01-01), Aoi
patent: 4638779 (1985-03-01), Kitada
patent: 4660529 (1982-04-01), Yoshikawa
patent: 4679532 (1987-07-01), Aoi et al.
patent: 4697554 (1987-10-01), Bothwell
"Nur Ventile im Kopf", Motorrad, Nov. 1980, pp. 154-156.
Collins Motor Corporation Limited
Nelli Raymond A.
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