DIESEL VCR (VARIABLE COMPRESSION RATIO) ENGINE DEVELOPMENT USING MULTI-LINK MECHANISM

摘要

A variable compression ratio (VCR) technology, that has a new piston-crankshaft mechanism with multi links, has been patented by Nissan. This technology has been developed inside Nissan for some years and has been shown in previous papers. This proposed paper will present the use of the VCR technology for Diesel engine. The objectives set with the use of VCR for Diesel engine are both: 1) To reduce as much as possible engine out emission to prepare long-term more severe emission standard. 2) To reach increased specific power output while limiting maximal cylinder pressure. This paper will explain how a variable compression ratio technology could contribute to such objectives. This study was conducted as an Alliance research activity between Renault and Nissan based on the VCR mechanism originally developed by Nissan (SAE Paper 2003-01-0921, 2005-01- 1134) and based on Renault expertise on Diesel engines. The VCR engine is based on Renault M9R 2.0 liter Diesel engine. With 130 kW et 360 N.m, the M9R 2.0 liter Diesel engine is today's best-in-class regarding specific output values. Activities will be detailed in this paper including the design of VCR mechanism adapted to Diesel constraints (e.g. high cylinder combustion pressure) and EHL studies realized to verify the good behaviour of the bearings of the mechanism under high loads. A completely new Diesel engine adapted to VCR mechanism has been drawn. Lower engine parts include the integration of VCR actuator.