Double-Concentric Cam Variable Valve Actuation
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Solution Overview
Problem
Fully mechanical variable valve actuation systems in internal combustion engines are limited by their large physical size, which poses challenges in packaging due to height and width constraints, especially in advanced engines with increasing fuel system space requirements.
Innovation Solution
A double-concentric complex cam system is used to provide both intake and exhaust variable actuation, packaging on one side of the cylinder head, utilizing a center shaft with two tubes and variable lobes on both the intermediate and outer tubes, along with a rocker assembly and energy storage device to control valve motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fully mechanical variable valve actuation systems are used, then valve lift and duration control is achieved, but device size becomes large
Solution Approach 1:
The patent employs a double-concentric cam arrangement where an inner cam is nested within an outer cam, both sharing a common center shaft. This nesting configuration allows two independent valve actuation systems (intake and exhaust) to occupy overlapping spatial volumes, dramatically reducing the overall device footprint while maintaining full variable lift and duration control capabilities for both valve types.
Solution Approach 2:
The invention transitions from traditional side-by-side cam positioning to a concentric radial arrangement, utilizing the radial dimension around the center shaft. By positioning cam lobes at different radial distances and angular positions on the inner and outer cams, the system achieves independent valve control without increasing axial or lateral dimensions, effectively solving the packaging constraint.
2Ease of operation
If traditional fully mechanical VVA systems are used, then valve actuation control is provided, but package space requirements increase
Solution Approach 1:
The patent merges the intake and exhaust cam systems into a single integrated double-concentric assembly sharing a common center shaft and housing. This consolidation combines previously separate mechanical subsystems into one unified structure, reducing the total package area occupied while maintaining independent actuation control for both intake and exhaust valves through differently positioned cam lobes.
Solution Approach 2:
The center shaft serves multiple functions simultaneously: it supports both the inner and outer cams, provides the rotational reference for both valve trains, and enables independent phase control for both intake and exhaust. This multi-functionality reduces the need for separate support structures and reduces overall package space requirements.
Data Source
AI summary
A variable valve actuation system in one form includes a rocker coupled with a valve stem at one end and a cam follower at the other end. The rocker is operable to rotate about a fixed axis and the cam follower includes a set of lower rollers operable to follow one cam lobe and an upper roller operable to follow another cam lobe. A leaf spring can be used to couple the cam follower with the rocker. A cam shaft can have a nested configuration that includes an inner shaft, an intermediate tube, and an outer tube. Cam lobes can be fastened to the cam shaft by fastening through each of the inner shaft, intermediate tube, and outer tube. The cam lobes can be attached by at least two devices inserted from either side of the cam shaft and that are not inserted at least through the inner shaft.