Oil pan structure for internal combustion engine

An oil pan for an internal combustion engine having a crankshaft, comprising:

• a shallow bottom section fixedly disposed under a cylinder block of the engine, said shallow bottom section having a bottom surface, said bottom surface defining thereover a space in which the crankshaft is disposed, said bottom surface being formed to allow oil to flow in a direction generally perpendicular to a vertical plane which passes through an axis of rotation of the crankshaft;
• a sump section defining a sump, located under said cylinder block, said sump being in communication with said shallow bottom section space, said sump having a lower part which is lower in level than said bottom surface;
• means for causing oil flow on said bottom surface of said shallow bottom section, said means for causing oil flow being in a direction generally perpendicular to said vertical plane, and including a means for directly applying kinetic energy to the oil on said bottom surface, wherein said kinetic energy is created by a rotation of said crankshaft;
• and
• means for defining an oil return path at least a part of which is formed in said shallow bottom section and which is located on a side of the shallow bottom section located downstream of the oil flow produced by said means for causing oil flow, said oil return path being located generally parallel with the axis of rotation of the crankshaft, said oil return path having an inlet which is opened opposite to the oil flow and having an outlet which is in communication with said sump.