Abstract: This invention provides a hydrocarbon concentration measuring apparatus, which, even when the concentration and composition of hydrocarbons contained in an object gas to be measured vary, can measure the concentration of the hydrocarbons with good response and good accuracy, and a hydrocarbon measuring method. Light with a waveband including a common absorption region, which is absorbed by a single or a plurality of chemical species, is applied to the object gas by an infrared irradiation equipment. The light applied to the object gas is detected with a line sensor. The absorbance in the common absorption region of the object gas is computed with an analyzer based on the detected light. The sum of concentrations of chemical species, which absorb light in the waveband in the common absorption region, in the single or plurality of chemical species contained in the object gas, is computed with the analyzer based on the absorbance.

Abstract: A direct fuel injection-type spark-ignition internal combustion engine is disclosed. The engine comprises a spark plug, a fuel injector and a cavity formed on the top surface of the piston. The cavity has a bottom wall, a spark plug side wall and a fuel injector side wall. The fuel injector injects fuel toward the bottom wall of the cavity in stratified charge combustion. The fuel mainly proceeds toward the spark plug side wall of the cavity along the bottom wall, is deflected by the spark plug side wall and is led to the vicinity of the spark plug. In the engine, the fuel injector side wall of the cavity is provided with a deflecting portion. If a part of the injected fuel proceeds toward the fuel injector side wall along the bottom wall of the cavity, that part of the fuel is led to the vicinity of the spark plug by the deflecting portion.

Abstract: An aspherical lens for use in optical equipment is made of a transparent lens material and rotationally symmetrical around a Z-axis of an XYZ three-dimensional coordinate system. The aspherical lens has a surface on which incident light falls and another surface from which light emerges. Either one of the surfaces comprises a spherical surface and the other surfaces comprises an aspherical surface to allow a lens to singly diverge and converge parallel rays of light. The coordinates in three-dimensional coordinate system of points on the spherical and aspherical surfaces are given using as parameters an angle (-90.degree..ltoreq..theta..ltoreq.90.degree.) formed in a plane containing the Z-axis and normal to an X-Y plane and between the Z-axis and a line connecting the point and the origin of the coordinate system, and an angle (0.degree..ltoreq..phi..ltoreq.180.degree.) formed in a plane parallel to the X-Y plane and between an X-axis and a line connecting the point and the Z-axis.