Rocker Arm Assembly With DLC Coating For Variable Valve Lift
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Solution Overview
Problem
Current rocker arm designs for variable valve actuation systems in internal combustion engines lack efficiency and durability, particularly in switching between low and high lift modes, leading to increased fuel consumption and emissions.
Innovation Solution
The development of a discrete variable valve lift (DVVL) system with a switching roller finger follower (SRFF) rocker arm configuration, utilizing a diamond-like carbon (DLC) coating on slider pads for reduced friction and increased durability, and a dual feed hydraulic lash adjuster (DFHLA) for optimized oil flow and side loading management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rocker arm designs are used for variable valve actuation, then structural simplicity is maintained, but durability and efficiency deteriorate due to increased wear and fuel consumption
Solution Approach 1:
The rocker arm is divided into two separate arms: a inner rocker arm and an outer rocker arm. The inner arm engages with the cam lobe while the outer arm connects to the valve mechanism. This segmentation allows each arm to be optimized for its specific function, with the inner arm featuring a roller follower for reduced wear and the outer arm providing structural support, thereby improving overall durability without excessive complexity
Solution Approach 2:
The roller follower surface is coated with diamond-like carbon (DLC) material, creating a composite structure that combines the mechanical strength of the metal rocker arm with the low-friction, high-wear-resistance properties of the DLC coating. This composite approach significantly extends component life and reduces wear-related failures
2Use of energy by moving object
If switching between low and high lift modes is implemented, then fuel consumption and emissions are reduced, but wear and durability issues arise at the switching interfaces
Solution Approach 1:
The traditional sliding contact interface between the rocker arm and cam lobe is replaced with a roller follower mechanism. This mechanical substitution converts sliding friction into rolling friction, dramatically reducing wear at the contact interface while enabling efficient switching between valve lift modes, thus improving both fuel economy and wear resistance
Solution Approach 2:
The roller follower is equipped with a diamond-like carbon (DLC) coating that provides exceptional wear resistance and low friction coefficients. This composite material approach protects the high-stress switching interface from wear while maintaining the efficiency benefits of the roller mechanism, allowing sustained fuel consumption reductions over the engine's operational life
3Ease of operation
If hydraulic lash adjusters are used, then valve train adjustment is automated, but side loading and oil flow management issues reduce efficiency
Solution Approach 1:
A dual feed hydraulic lash adjuster is introduced as an intermediary component between the cam lobe and rocker arm. This adjuster features two separate oil feed paths that independently control the adjustment mechanism, allowing precise hydraulic lash compensation while managing side loads through balanced oil pressure distribution, thus maintaining ease of operation without excessive energy loss
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
The DVVL system enables efficient switching between low and high lift modes within one cam revolution, reducing fuel consumption, emissions, and extending engine life by minimizing wear and maintaining hydraulic lash adjustment, while being compatible with existing engine designs.
Implementation Method 1
utilizing a diamond-like carbon (DLC) coating on slider pads for reduced friction and increased durability
Implementation Method 2
A high impact roller rides on the first crowned cam for operating the engine valves according to a first lift profile
Implementation Method 3
dual feed hydraulic lash adjuster (DFHLA) for optimized oil flow and side loading management
Data Source
AI summary
A durable system is disclosed for controlling variable valve actuation of an engine valve corresponding to a cylinder of an automobile engine. The system is designed to have a durability that exceeds the expected life of a conventional automobile engine. The system includes first crowned cam having a first lift profile, a second crowned cam having a second lift profile, and a rocker arm assembly. The rocker assembly includes a first arm having an end connected to said engine valve, having a high impact roller following the first crowned cam operating the engine valves according to a first lift profile. The rocker arm assembly also includes a second arm having slider pads riding on the second crowned cam to operate said engine valve according to a second lift profile. The slider pads have a sliding surface covered with an impact-resistant multilayer coating with its outermost coating being a wear-resistant coating. A latch having adjustable latch lash secures the second arm relative to the first arm when in a latched position causing the valve to operate according to a second lift profile when the latch is in a latched position, and the valve is operated according to a first lift profile when the latch is not in a latched position.