Low noise, vibration and harshness solutions for in-line three-cylinder range extender and hybrid electric vehicles

Consideration of internal combustion engine formats suitable for hybrid or range extender electric vehicles usually focuses on selecting a power plant, which is as compact as possible to meet the demands and constraints of the installation. In-line three-cylinder engines often provide an attractive solution for such vehicles. This article presents a low emission two-stroke engine of in-line three-cylinder format and draws a comparison with an equivalent four-stroke engine. The particular focus of the analysis is on strategies for minimization of noise, vibration and harshness with significant reduction in piston lateral force compared with the four-stroke unit. The design also considers a balance shaft arrangement to further assist with noise, vibration and harshness reduction. The presented arrangement demonstrates an integrated induction control/balance shaft arrangement, which erodes the usual cost penalties typical of balance shaft consideration in three-cylinder engines.

Location of unbalance mass and supporting bearing for different type of balance shaft module

The dynamic characteristics of balance shaft module is controlled by the design of rotating parts as how to allocate both a unbalance mass and a supporting bearing so that the concept design of a rotor structure is the key issue on determining the overall quality of dynamic performance as well as fatigue resistance. Even the design on balance shaft has some limitation from the lay-out of a vehicle engine system, there is still chance to enhance the reliability of the balance shaft module by the promising design model of the rotor structure including support bearing locations. In this paper, an optimal location of unbalance mass and supporting bearing is proposed to make an efficient conceptual design using an objective function to minimize a bending deformation of rotor as well as a reaction force at supporting bearing. In addition, the application of design optimization of a balance shaft model is explained using an in-house program for inline 3-cylinder and inline 4-cylinder engine, respectively.