The present invention relates to a method of, and an apparatus for, fuel-saving travel of an internal combustion engine-driven vehicle.
In the range of the revolution often selected for use in a usual case for a conventional internal combustion engine to be mounted on an automobile, efficiency is high enough and fuel consumption (g/Ps.h) is favorable enough in the case of high load in general; however, in the case of low load, to the contrary, efficiency is low and fuel consumption (g/Ps.h) is unfavorable. Now that an automobile conventionally has the transmission gear ratio thereof so set as to be capable of a wide range of use, including acceleration and traveling up a slope, a range of low load is usually selected at the time of traveling at constant speed on a flat and smooth road at either intermediate or low speed, which results in that an engine is low in efficiency and selection of a range of unfavorable fuel consumption becomes imperative. Furthermore, the engine is kept in an operating state even at the time of traveling up a slope, drifting, and stoppage, to put it otherwise, the engine itself remains running even in case the engine is not required to be thus kept in an operating state, hence a fairly great deal of fuel is consumed. For instance, even at the time of stoppage, drifting, or traveling down on such a comparatively gentle slope as enables an automobile to travel without employing an engine brake, the automobile has the engine put in an operating state with an accelerator kept totally or nearly closed, and in the case of a gasoline engine, 10-50 cc/minute (0.6 l/hour-3 l/hour) of fuel is thus consumed unnecessarily, although the correct quantity of the fuel thus wasted depends on the displacement of the automobile. Even in the case of traveling at constant speed on a flat and smooth road, the load to be applied on an engine mounted on automobiles other than those of small displacement, including a light car, is rather small in the range of the ordinary car speed of 100km or less for use, and the said load is especially small in the case of traveling at low speed, which has thus far resulted in that a range of quite low efficiency has to be selected in terms of the characteristics of an internal combustion engine, thus involving such a defect that the fuel cost becomes high and hence unfavorable.