Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Patent
1995-06-12
1998-09-22
Denion, Thomas E.
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
92140, 92 76, 123 533, F01B 702
Patent
active
058098640
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to opposed piston engines. Particularly, but not exclusively, the invention relates to opposed piston internal combustion engines, but the invention may be applicable to engines powered by a source of pressurised gas or vapour.
BACKGROUND INFORMATION
An important aspect of the invention relates to opposed piston diesel engines, but the invention is not restricted thereto. The use of opposed pistons in a diesel engine enables two-stroke operation to be obtained, whereby the output power of the engine is significantly increased, thereby off-setting to some extent the inherent weight disadvantage of a diesel engine.
However, certain previous proposals in relation to opposed piston two-stroke engines have suffered from significant disadvantages, notably their complexity, weight, and inability in some cases to operate at reasonably high rates of rotation. Accordingly, such engines are inherently unsuitable for application to propeller-driven aircraft, and indeed to outboard motor uses. Other prior proposals are subject to limitations in the sequence of events during use, as explained below.
Examples of prior patents disclosing the concepts discussed above include the following:
While these prior proposals disclose the overall general disposition of pistons and connecting levers, it is found when a study is made of the geometries of the prior disclosures, that important operating problems arise. For example, we have discovered that as a consequence of the crankshaft axis passing through the centre line between the upper and lower cylinders, (see GB 539,231 FIG. 3), it is impossible to obtain symmetrical events between the cylinders, in terms of the cylinder charging and firing sequence.
Additionally, the geometry of this prior proposal leads to the fact that the accuracy of the top dead centre position relates to the length of the connecting rods. Also, if both big-ends are on one crank pin the resulting diagonal connection arrangement leads to rocking couples applied thereto and strange angular accelerations, which are disadvantages. Likewise, we have established that you cannot obtain symmetrical events in the two cylinders with the previously proposed crankshaft disposition. Broadly speaking, this is due to the fact that the acceleration of the pistons varies between the two cylinders, due to the angularity of the connecting rods, and this is very critical to engine operation, particularly for a two-stroke engine.
Arising from this, we have established that with the general engine layout and disposition of the prior proposals, it is relatively straightforward to arrange that the sequence of events for one cylinder is satisfactory, but that for the other it is not. When an attempt is made to compromise, this can only be done, we have found, at the expense of altering the angular accelerations of the relevant components, thereby resulting in unsatisfactory operating sequences.
There is disclosed in GB 165,861 (Vickers) mentioned above an engine in accordance with the pre-characterising portion of claim 1 hereof in which the rockers are connected to the crankshaft by diagonal links D. In the embodiment of FIGS. 2 and 3, connecting rods are attached to one side of the links D and the crankshaft E is correspondingly displaced from the centre line of the engine for this reason.
There is disclosed in U.S. Pat. No. 2,561,261 (Zecher) also an engine in accordance with the pre-characterising portion of claim 1 hereof wherein the rockers interconnecting the pistons have so-called third arms 15 disposed generally inwardly of the engine and coupled to the crankshaft 18 by connecting rods 16. The axis of crankshaft 18 is offset from the central region of the engine in order to accommodate the crankshaft throw within the available space between the water jackets enclosing the pairs of upper and lower cylinders, as can be seen from FIGS. 4 and 5 of the drawings.
We have discovered that if the geometry of the engine layout is altered so that the centre line of the crankshaft i
REFERENCES:
patent: 2561261 (1951-07-01), Zecher
patent: 2653484 (1953-09-01), Zecher
patent: 3474768 (1969-10-01), Anesetti
International Search Report Jan. 14, 1994.
Denion Thomas E.
JMA Propulsion Ltd.
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