This invention relates to a burning control system for an engine and more particularly to an improved internal combustion engine construction and method of operating such an engine.
Various engine constructions and engine operating methods have been proposed to improve fuel economy and exhaust gas emission control. One of the ways in which these goals have been sought, is through the use of a so called "lean burn" type of engine and engine operation. With such arrangements, the combustion chamber is provided with a mixture that is leaner than stoichiometric and some method is employed for insuring that there will be a stoichiometric mixture present at the spark plug at the time of firing. This can be accomplished through the use of various methods for increasing turbulence and/or directing the charge in the combustion chamber toward the spark plug at the time immediately prior to firing of the spark plug.
Although these arrangements have been quite effective in reducing fuel consumption and improving exhaust emission control, they are basically effective only under steady state running conditions. Most internal combustion engines, particularly those employed for automotive or vehicular applications, however, do not run at steady state conditions. When accelerating and/or operating at high load conditions, the conventional lean burn engines do not provide good performance. In order to offset this deficiency, it is the normal practice to run the lean burn engine at a stoichiometric or even richer condition under acceleration or at maximum load. Although this improves the running of the engine, it deteriorates both fuel economy and exhaust emission control.
It is, therefore, a principal object to this invention to provide an improved internal combustion engine and method of operating it which will permit operation under lean burn (less than stoichiometric) conditions under substantially all running conditions of the engine.
It is a further object to this invention to provide an improved engine and method of operating it so that the engine can operate at leaner than stoichiometric mixtures under all running conditions without deteriorating engine performance.
In order to insure optimum engine performance, good fuel economy and smooth running, it is desirable that all components of the engine and all running characteristics be adjusted for a particular type of optimum fuel which is used in the engine. However, frequently the optimum fuel may not be available or may not be used and performance can become degraded unless some corrective measure is taken.
For example, if an engine is designed to run on fuel of a certain octane and a lower octane fuel is substituted, poor performance and knocking can occur. Many engine control systems include an arrangement which sense a knocking condition and in response to that condition retard the spark timing to reduce the likelihood of knocking. At the same time, these systems generally enrich the air/fuel mixture so as to further insure against a knocking condition. However, when this is done fuel consumption will significantly increase and exhaust emission control may deteriorate.
It is, therefore, a still further object to this invention to provide an improved arrangement for adjusting the running condition of an engine when a knocking condition is detected so as to preclude knocking without increasing fuel consumption.