Stepped Bore Drive Piston Assembly for Camless Valve Actuation
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Solution Overview
Problem
Existing valve train systems for internal combustion engines, particularly camless designs, face challenges in efficiently controlling valve lift profiles and fluid pressure distribution to optimize engine performance, leading to suboptimal engine efficiency and performance variability.
Innovation Solution
A drive piston assembly with a stepped bore and a boost sleeve, along with feedback chambers and on/off valves, is used to selectively open a poppet valve by varying fluid pressure, allowing for precise control of valve actuation and reduced energy consumption through unitary movement and direct acting mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a camless valve train is used to provide tailored valve lift profiles, then engine performance is improved, but device complexity increases
Solution Approach 1:
The valve actuator is segmented into distinct functional components: a drive piston for primary actuation, a boost sleeve for enhanced lift, and separate feedback chambers for precise control. This segmentation allows each component to perform its specific function efficiently while maintaining overall system performance
Solution Approach 2:
The boost sleeve is nested within the drive piston assembly, with the boost sleeve coaxially disposed about the drive piston. This nested configuration allows the boost mechanism to be integrated within the existing actuator structure, adding functionality without proportionally increasing overall device complexity
2Measurement precision
If feedback chambers are added to control fluid pressure, then valve control precision is improved, but device complexity increases
Solution Approach 1:
The first and second feedback chambers are merged into a single integrated fluid communication system that controls both the drive piston and boost sleeve. This combined feedback mechanism allows precise control of valve lift profiles through unified fluid pressure management, reducing the need for separate control systems
Solution Approach 2:
The feedback chambers automatically regulate fluid pressure through their inherent design, where pressure changes in the chambers directly influence the position of the drive piston and boost sleeve without requiring external control intervention. This self-regulating mechanism improves precision while minimizing additional control complexity
3Use of energy by moving object
If unitary movement between drive piston and boost sleeve is implemented, then energy efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
A shouldered portion on the drive piston serves as an intermediary engagement feature with the boost sleeve, enabling controlled unitary movement between the two components. This intermediary interface allows the components to move together as a unit during actuation while maintaining manufacturability through standard machining features
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables precise control of valve opening and closing, optimizing engine performance by reducing energy requirements and improving valve control, leading to enhanced engine efficiency and stability.
Implementation Method 1
the drive piston and the boost sleeve are sufficiently configured to move within the generally stepped bore in response to fluid pressure within the main fluid chamber to selectively open the poppet valve
Implementation Method 2
The first and second feedback chambers may be in fluid communication with the valve and may operate to vary the fluid pressure communicated to the main fluid chamber
Data Source
AI summary
A drive piston assembly is provided that is operable to selectively open a poppet valve. The drive piston assembly includes a cartridge defining a generally stepped bore. A drive piston is movable within the generally stepped bore and a boost sleeve is coaxially disposed with respect to the drive piston. A main fluid chamber is at least partially defined by the generally stepped bore, drive piston, and boost sleeve. First and second feedback chambers are at least partially defined by the drive piston and each are disposed at opposite ends of the drive piston. At least one of the drive piston and the boost sleeve is sufficiently configured to move within the generally stepped bore in response to fluid pressure within the main fluid chamber to selectively open the poppet valve. A valve actuator assembly and engine are also provided incorporating the disclosed drive piston assembly.