Low emission vehicle

Abstract

A low emission vehicle operates an internal combustion engine with lean air fuel ratios over at least a portion of its operating load range. The vehicle satisfies EURO IV emission requirements with just a three way catalyst and without any NOX storage capability in the exhaust after treatment system. An electronic control unit is programmed to operate the engine such that 80% or less of any tail pipe NOX mass emitted by the vehicle is generated during lean operation of the engine whereby the vehicle satisfies the EURO IV emission requirements.

Description

[0001] This invention relates to internal combustion engines and emissions standards for internal combustion engines, and more particularly, to the calibration, control and operation of direct injection engines and lean burn stratified charge engines so as to comply with certain emissions standards.[0002] The recent and future introduction of increasingly stringent internal combustion engine emissions legislation around the world, such as the proposed US ULEV II & SULEV emissions regulations and European Euro IV regulations, has resulted in increasing pressure on engine and vehicle manufacturers to reduce engine emissions.[0003] In meeting these stringent emissions standards, most MPI (manifold port injected) vehicles suffer a fuel consumption penalty even though overall tail pipe emission levels decrease. This increase in fuel consumption arises for various reasons including increased engine hardware requirements that serve to increase the level of parasitic loading on the engine, ...

AI Technical Summary

Benefits of technology

0017] There is further provided according to the present invention a vehicle having an internal combustion engine with a direct injection fuel system and an electronic control unit and an exhaust system with a three way catalyst wherein the electronic control unit is programmed to operate the engine with at least lean and stoichiometric air fuel ratios and wherein engine out NOx mass for lean air fuel ratios over the Euro IV drive cycle is 80% or less of the Euro IV standard whereby said vehicle has tail pipe emissions over the Euro IV drive cycle that satisfy the Euro IV requirement.

0018] Preferably, said catalyst has a volume of 85% or less engine swept volume (ESV). Preferably, said vehicle is operated with a stoichiometric air fuel ratio for engine loads equivalent to 50 km/h cruise on the vehicle's road load curve.

0019] There is further provided according to the present invention a vehicle having a lean bum internal combustion engine, an electronic control unit and an exhaust system with a three way

Problems solved by technology

In meeting these stringent emissions standards, most MPI (manifold port injected) vehicles suffer a fuel consumption penalty even though overall tail pipe emission levels decrease.

This increase in fuel consumption arises for various reasons including increased engine hardware requirements that serve to increase the level of parasitic loading on the engine, increased fuel consumption due to the catalyst light-off strategies used and an increase in fuel consumption that arises when the engine is calibrated to produce reduced levels of hydrocarbon emissions and NOx emissions.

However, they also present certain challenges in that conventional three-way catalytic converters (TWC's) have been found to be unsatisfactory for efficiently treating NOx emissions produced during lean burn operation.

This requirement for rich operation reduces the fuel consumption benefit that is available from direct injection engines.

There have also been found to exist certain other issues with the use of LNTs.

Due to the precious metal loadings necessary on such LNTs, significant cost increases are likely to be incurred for any DI engine incorporating such an LNT.

Furthermore and equally prohibitive is the sensitivity of an LNT to sulphur.

Currently available fuels typically contain a significant proportion of sulphur which has been found to effectively "poison" an LNT such that after a certain period of time it is no longer effective in trapping and treating NOx.

In many countries including the United States of America, low sulphur content fuel is still not readily available.

It is therefore not possible at present to effectively use an LNT on vehicles to be driven in the U.S. and other such countries where the emission regulations require strict control of NOx emissions.

At the time, the vehicle discussed in this paper was unable to satisfy Euro IV requirements without a NOx storage and reduction catalyst.

Images