Induction system of internal combustion engines

Details Induction system of internal combustion engines Induction system of internal combustion engines

1995-10-13

1996-10-01

McMahon, Marguerite

Internal-combustion engines

Two-cycle

Rear compression

123195R, 123 73PP, F02F 122, F02F 114, F02M 3510

Patent

active

055603289

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the construction of the cylinder block and/or crankcase of a multi-cylinder internal combustion engine and particularly relates to the provision of appropriate passageways therein for the distribution of gas to or from respective cylinders of the engine at multiple locations. The present invention will be described in relation to the provision of appropriate passageways in the cylinder block and/or crankcase of a two-stroke multi-cylinder internal combustion engine to facilitate the distribution of incoming air from one side of a cylinder bank of the engine to the other. It is however to be appreciated that the invention is not limited to this application, and that other applications are also envisaged for both two and four stroke engines.
It is well appreciated particularly in the automotive engine industry that it is most important to miniraise engine size and weight as these lead directly to weight and space savings in the vehicle body, suspension and other areas. Such engine size and weight minimisations are also of benefit in other engine applications such as in marine and motorcycle applications, particularly with regard to the packaging and overall weight of the engine.
In order to obtain the desired gas flow within the cylinder of an engine to achieve the required power output, fuel efficiency, and exhaust gas emission control, the disposition of the exhaust port(s) and inlet or transfer port(s) is a critical factor. This is particularly so in an engine operating on the two-stroke cycle.
It is a common feature of engines operating on the two-stroke cycle that the transfer port(s) and the exhaust port(s) are open at the same time in the engine combustion cycle during at least part of the cycle. Accordingly, there is a potential for part of the fresh air charge entering the cylinder through the transfer port(s) to travel across the cylinder and escape through the exhaust port(s) during this period (commonly referred to as "short circuiting"). Modern two-stroke cycle engines normally use a configuration of transfer ports that establish a generally upwardly directed flow of the incoming fresh air charge within the engine cylinder which is then deflected downward by the cylinder head toward the exhaust port(s).
Such engines are generally referred to as loop-scavenged engines and in a typical modern example the cylinder has main transfer ports on either side of the exhaust port arranged to direct the incoming fresh air charge away from the exhaust port and towards the opposite side of the cylinder and auxiliary transfer port(s) located generally opposite the exhaust port. The combined effect of the auxiliary and main transfer ports is to create an upward flow of the incoming fresh air charge on the side of the cylinder opposite to the exhaust port, thereby avoiding short circuiting of the incoming charge to the exhaust port.
Although the above described transfer port arrangement is desirable to achieve effective scavenging of exhaust gases from the cylinder and the correct location of the fresh air charge within the cylinder, the necessity to provide transfer ports on the opposite sides of the cylinder presents a challenge in applying the loop scavenge configuration to a multi-cylinder in-line engine whilst minimising engine size and weight. One solution would be to provide passages from one side of the engine to the other side thereof located between the cylinder bores. This however would lead to a substantial increase in engine block length. This increase in engine block length typically results in a corresponding increase in engine weight, and in automotive applications, an increase in engine compartment size and hence overall vehicle size and weight.
Several prior art constructions to achieve air distribution from one side of an engine to the other are known and result from various different engine requirements and limitations. One such prior art construction is to duct air over the top of the engine, however this invariably leads to an increase in the overall height of the

REFERENCES:
patent: 3530841 (1970-09-01), Brookfield
patent: 3815558 (1974-06-01), Tenney
patent: 4190023 (1980-02-01), Fujikawa et al.
patent: 4242993 (1981-01-01), Onishi
patent: 4530313 (1985-07-01), Feichtinger
patent: 4879974 (1989-11-01), Alvers
Patent Abstracts of Japan, M-1516, p. 138, JP,A, 5-202802.

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