Temperature-sensitive variation of the compression ratio in pistons having variable compression height

US4979427A · kind A · utility

Assignee

• Daimler-Benz AG · DE

Inventors

• Viktor Pfeffer · Esslingen am Neckar, DE
• Friedrich Wirbeleit · Eßlingen, DE
• Klaus Binder · Munich, DE

Key dates

• Filing date: Mar 3, 1989
• Grant date: Dec 25, 1990
• Expiry date: Mar 3, 2009

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F05C2251/042
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

The invention relates to a piston having a variable compression height and two control chambers connected to each other through a hydraulic system. In order to achieve better cold-start and warm-up behavior, an oil discharge bore from the upper control chamber into the crankcase is closed by a control slide valve in the cold operating state of the engine. The blockage of the oil discharge produces a great compression height and therefore high compression. The control slide valve is connected to an expansible element which maintains it in this closed position when the engine is cold. As the engine warms up, the expansible element, due to its thermal expansion, pushes the control slide valve out of its closed position, so that the discharge of oil can occur progressively more unthrottled with rising temperature. In the warm operating state of the engine the control slide valve clears the oil discharge duct completely, and an unobstructed discharge of oil is ensured.