Abstract: An internal combustion engine according to this invention is provided with intake ports each of which is formed to guide a flow of inducted air in a particular direction. Each intake port includes, in the vicinity of its corresponding intake opening to a combustion chamber, a bent port portion bent at a greater curvature than a port portion on a side upstream of the bent port portion. The bent port portion has a greater inner diameter than the inner diameter of the corresponding intake opening, whereby air can be inducted in a sufficient amount without deterioration to the directing function for air to be inducted into the combustion chamber.

Abstract: A stratified burning internal combustion engine according to this invention is equipped with an intake port and a fuel feed device so that stratified tumble flows of different fuel concentrations can be formed in a combustion chamber. An ignition device is provided in the combustion chamber to ignite at least one of the tumble flows, said at least one tumble flow being rich in fuel. To promote the stratified tumble flows, a top wall of a piston has an inclined wall. This makes it possible to strengthen the tumble flows, whereby the stratification of an air-fuel mixture in the combustion chamber can be improved further to permit lean burn at a larger air/fuel ratio.

Abstract: An internal combustion engine according to this invention is provided with intake ports and an injector. The intake ports are designed to form stratified tumble flows of different fuel concentrations in a combustion chamber. A spark plug is arranged in the combustion chamber to ignite one of the tumble flows, which one tumble flow is rich in fuel. Each intake port is provided with a longitudinal partition which divides an interior of the intake port into two passages. These longitudinal partitions are formed in such a way that, of the air-fuel tumble flows formed around the spark plug, the tumble flow closest to the spark plug is formed of a richer air-fuel mixture. Each longitudinal partition is arranged only on a side upstream of a valve stem of an intake valve in the corresponding intake port, so that a sufficient amount of intake air can be obtained while extremely minimizing a reduction in the actual cross-sectional flow area.

Abstract: This invention relates to an intake port structure for an internal combustion engine. It is an object of the present invention to increase the strength of tumbling without lowering the maximum flow rate. An intake port (44) is constructed broader in a tumble-flow-side half (44a) than in the other half (44b) to have an intake air flow through the intake port (44) off-centered toward the side of a tumble flow, whereby an intake air flow from the intake port (44) promotes the tumble flow.