Internal-combustion engines – Two-cycle – Whirl through piston-controlled ports
Patent
1995-11-30
1998-01-20
McMahon, Marguerite
Internal-combustion engines
Two-cycle
Whirl through piston-controlled ports
F02D 904, F02D 908, F02D 1302
Patent
active
057091773
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the management of the operation of internal combustion engines, particularly two stroke cycle internal combustion engines having an exhaust valve associated with at least one of the exhaust ports of the combustion chambers of the engine.
It has been known to provide a valve in association with the exhaust port of each cylinder of a two stroke cycle engine for the purpose of varying the timing of the commencement of the exhausting of combustion gases from the engine cylinders. Such an exhaust valve can be operated to improve the engine operation over the normal range of speeds and loads. For example, in some applications, the exhaust valve can be operated to delay the timing of the opening of the exhaust port at low to medium engine loads and speeds in order to improve the stability of the operation of the engine, and at higher loads and speeds the timing of the opening of the exhaust port can be advanced so as to open earlier in the expansion stroke resulting in a higher torque output of the engine when coupled with an appropriately tuned exhaust system. When the exhaust valve is used solely for these purposes, it is commonly referred to as a "power valve", and such power valves have in the past been commonly used in two stroke cycle engines as installed in motorcycles.
More recently, it has been proposed in the applicant's U.S. Pat. No. 4920932 to provide an exhaust valve for the exhaust port of each cylinder of a multi-cylinder two stroke cycle engine, and by virtue of use of an electronic control unit (ECU), varying the relationship of the exhaust valve to the exhaust port for the purpose of controlling the combustion process in the respective cylinders of the engine to contribute to the control of contaminants in the exhaust gas released from the engine. In that proposal, the exhaust valve of each cylinder of the engine is coupled to a common control mechanism under the management of an ECU programmed to determine from the prevailing engine operating conditions the appropriate location for the exhaust valves with respect to the exhaust ports. This ability to control the position of the exhaust valve provides the scope for further improving the operation of two stroke cycle engines, and for the management of a range of problems which arise under particular operating conditions.
It has also been noted in regard to the operating of two stroke cycle engines that, while the engine is operating at a low fuelling rate, such as during or near idle operation at low load, the temperature of the combustion gases in the engine cylinders is relatively low. Hence the development of carbon build-up on the exposed surfaces in the combustion chamber, including surfaces of exhaust valves arranged in cylinder exhaust ports, is commonly experienced. Also, the low temperature of the exhaust gases in such circumstances can lead to a reduction in the temperature of a catalytic converter, which may be provided in the exhaust system, to below that necessary to maintain the catalyst operational, this temperature commonly being referred to as the "light-off" temperature.
It is therefore the object of the present invention to provide a method of using the exhaust valve provided at the exhaust port of an internal combustion engine to enhance the operation of the engine and/or control deterioration of the engine performance.
Accordingly, it is proposed by the present invention that there is provided, a method of operating an internal combustion engine having at least one combustion chamber having an exhaust port and a cooperating exhaust valve and means operable to vary the timing of the commencement of the opening of the exhaust port between preset limits, the method comprising advancing the timing of the opening of the exhaust port to the earliest timing within said limits in response to the engine operating at idle or low load conditions.
More specifically, there is provided a method of operating a two stroke cycle internal combustion engine having at least one exhaust port communicating with each combu
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patent: 4388894 (1983-06-01), Tanaka et al.
patent: 4920932 (1990-05-01), Schlunke
patent: 5410993 (1995-05-01), Masuda et al.
patent: 5537958 (1996-07-01), Nishimura
Patent Abstract of Japan, M-911, p. 41, JP,A, 1-244125.
Patent Abstract of Japan, M-927, p. 63, JP,A,1-277628.
Patent Abstract of Japan, M-659, p. 80, JP,A,62-174515.
Archer Mark Douglas
Fitzgerald Brian Anthony
Worth David Richard
McMahon Marguerite
Orbital Engine Company
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