基于二自由度可调机构的新型VCR发动机运动方案设计方法的研究

Design Study of a New VCR Engine Motion Scheme Based on a Two-Degree-of-Freedom Adjustable Mechanism

针对现阶段VCR发动机的设计方法存在不完整、不透明的问题,本文提出一种基于二自由度可调机构的新型VCR发动机方案的设计方法。首先使用拓扑缩图插点法对二自由度9杆及构件数低于9的机构进行型综合,并系统地为新型VCR发动机进行机构选型。其次,根据给定的设计指标,对新型VCR发动机机构进行尺度综合,提出能同时满足机构传动角和机构整周转需求的几何计算方法,确定了二自由度可调构件位置变化与压缩比变化的函数关系,实现了压缩比范围的精确控制,为VCR发动机的创新设计提供了相应的理论依据,同时还拟定出完整的设计流程。

Since the present design method of VCR engine is incomplete and opaque,this paper proposes a design method of a new VCR engine scheme based on a two-degree-of-freedom adjustable mechanism.Firstly,type synthesis of two-degree-of-freedom nine-bar mechanisms and mechanisms with components fewer than nine is carried out,using the topological thumbnail interpolation point method.The mechanism selection for the new VCR engine is conducted systematically.Secondly,according to the given design index,the scale synthesis of the new VCR engine mechanism is carried out and a geometric calculation method is proposed,which meets the requirements of both the mechanism drive angle and the mechanism turnaround.The function relationship between the position of the two-degree-of-freedom adjustable members and the compression ratio is determined to realize the accurate control of the compression ratio range.The study provides theoretical basis for the innovative design of VCR engines.Finally,a complete design process is also developed.