Internal-combustion engines – Two-cycle – Whirl through piston-controlled ports
Patent
1993-12-02
1995-01-10
Okonsky, David A.
Internal-combustion engines
Two-cycle
Whirl through piston-controlled ports
123 65V, F02B 7502
Patent
active
053797310
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a two stroke cycle multi-cylinder internal combustion engine, wherein pivotally mounted valves are provided in the exhaust passage of each cylinder for controlling the engine performance.
The design of the mounting of these valves in the respective exhaust passage, and the interconnecting thereof to operate in unison, does present some manufacturing problems, particularly in relation to high volume production of components.
Further, valves located in exhaust passages are subject to an aggressive environment and thus the design of such valves must take account of this factor. The prior art does not disclose an engine provided with a valve having such design characteristics and indeed German Patent No. 3833846 addresses itself only to the location of a pivotally mounted valve on the induction side of the engine where the environment is much less hostile than on the exhaust side.
In particular, it is to be noted that where, as with the present invention, the valve bearings are located on the exhaust side they are subject to higher temperatures and higher velocity gases than exist on the induction side. This invariably leads to a higher deterioration rate of materials and the formation of undesirable leakage paths.
Thus, it is evident that if a prior an construction, having a cylindrical bush located within a supporting body with parallel straight sides, clear leakage paths through the body being evident, were employed there would be a high rate of leakage. Also, as there is a relatively small area of contact between the bush, engine block and exhaust manifold to reduce heat transfer from the bush there would be little prospect of cooling the bush by leading heat away from the bush by conduction. This would inevitably lead to problems in valve performance and potentially, valve failure.
It is also to be noted that having regard to the function of the power valve located in the exhaust port it is subject to more frequent movement with resulting hammer loads on the bearings. Thus a valve mounted on the exhaust side requires more rigid and stable support for the bush than disclosed in the prior art.
Further, the gasket between the exhaust manifold and the engine block needs protection from high point loadings and exposure to hot gases. In such an environment, it is desirable for gaskets to be clamped into position over their full area.
Thus it can be seen that there are numerous problems in applying a prior art valve construction, designed for use on the induction side of an engine to the exhaust side.
It is therefore the object of the present invention to provide an engine of the above type having mountings for the exhaust passage valves that are comparatively simple to manufacture, which is effective in operation and tolerant to interchangeability of components.
With this object in view there is provided in a two stroke cycle internal combustion engine having a cylinder block with one or more cylinders and having a respective exhaust passage communicating with the or each cylinder, a valve member associated with each exhaust passage, said valve members being supported for pivotal movement relative to the respective passage about a common axis extending longitudinally of the block, each said exhaust passage extending to a surface on one side of the cylinder block, and an exhaust manifold having a complementary surface detachably secured to the cylinder block with said surfaces in abutting relation, characterised in that said surface of the cylinder block has a plurality of aligned recesses therein with at least one recess between each two adjacent exhaust passages, a bearing member received in each recess, each bearing member having an aperture therethrough preferably of circular cross section, said recesses and bearing members being configured so that the bearing members are immobilely retained in the recess by the exhaust manifold with the apertures of the bearing members co-axial when the exhaust manifold is secured to the cylinder block, with the respective surfaces in abutting rela
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Okonsky David A.
Orbital Engine Company (Australia) Pty. Limited
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