JPH0311143A - Variable compression ratio piston - Google Patents

Abstract

PURPOSE: To improve responsiveness by forming an upper part oil chamber into annular form and fitting an inner piston with an outer piston so that the relative revolution in the peripheral direction is regulated on an annular inner peripheral surface.

CONSTITUTION: When an internal combustion engine starts, lubricating oil is sent as pressurized oil into the hollow part 15a of a piston pin 15 from an oil passage 3, and the pressurized oil is introduced into an upper part oil chamber 45 through an outlet 15c and the oil feeding valve 51 of an inner piston 13, and the pressurized oil stays in the oil chamber 45 having the larger area than that of a lower part oil chamber 47, and a high compression ratio is obtained. When the engine is put into high load operation, and the internal pressure of the oil chamber 45 increases over a prescribed value by the increase of the gas pressure applied onto the upper surface of an outer piston 35, the pressurized oil pushing-opens an oil discharge valve 55, and the outside discharge of working oil is started, and the pressurized oil in the oil chamber 45 is introduced into an oil chamber 47 from a communication passage 596 through an orifice 62, forming the oil chamber 47, accompanied with the lowering of the piston 35. In this case, the oil chamber 45 is formed into an annular form, and the capacity is reduced, and the revolution in the peripheral direction of the piston 35 is regulated, and speedy switching from high compression ratio to low compression ratio is performed.

COPYRIGHT: (C)1991,JPO&Japio