Switchable Swing Arm Reducing Friction in Engine Valve Drive
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Solution Overview
Problem
Existing switchable rocker arms in internal combustion engines experience high friction losses, which affect the efficiency and service life of the valve drive.
Innovation Solution
A switchable rocker arm design featuring two lever parts with their own pivot bearings and rollers to counteract cams, along with a coupling device that allows controlled coupling and uncoupling, reducing friction and enabling simpler mounting and preassembly with non-switchable rocker arms on a common axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single lever design is used with a slide mechanism for switching between cam profiles, then the valve lift can be varied, but friction losses increase due to sliding contacts and complex mechanical interaction
Solution Approach 1:
The single lever is divided into two separate levers (first lever and second lever), each with its own pivot bearing and roller. This segmentation allows each lever to independently engage with cam profiles through rolling contacts, eliminating the sliding friction inherent in the single-lever slide mechanism while maintaining the ability to switch between different valve lift characteristics.
Solution Approach 2:
The sliding contact mechanism is replaced with rolling contact mechanisms. Each lever has a roller that rotates on the lever body, providing rolling friction instead of sliding friction at the cam contact points. This substitution significantly reduces energy losses while preserving the switchable valve lift function.
2Loss of energy
If two separate levers are used with independent pivot bearings, then friction losses are reduced through rolling contacts, but the device complexity increases
Solution Approach 1:
The two separate levers are merged into a single integrated rocker arm assembly that functions as one unit. Both levers share common mounting features and can be preassembled together with non-switchable rocker arms on a common axis, reducing the overall complexity despite having two independent pivoting elements.
Solution Approach 2:
The pivot bearings are designed with through-passages that can accommodate shaft sections from a common axis, allowing the same bearing structure to serve multiple rocker arms. This universal design reduces the number of separate components needed and simplifies manufacturing and assembly.
3Ease of manufacture
If multiple rocker arms are preassembled on a common axis, then space and costs are saved, but the manufacturing precision requirements increase
Solution Approach 1:
The rocker arms are preassembled on a common axis during manufacturing, allowing for quality control and alignment verification before installation in the engine. The through-passages in the pivot bearings are designed to receive shaft sections that form the common axis, enabling precise alignment to be established during preassembly rather than during engine assembly.
Solution Approach 2:
The pivot bearing design with aligned through-passages provides a standardized interface that can be replicated across multiple rocker arms. This standardization ensures that when multiple rocker arms are mounted on a common axis, the alignment requirements are met through consistent manufacturing features rather than requiring high-precision individual alignment.
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
Significantly reduces friction losses and tilting moments, increasing the service life of pivot bearings and allowing for efficient preassembly and mounting of multiple rocker arms on a common axis, thereby enhancing engine efficiency and reducing costs.
Implementation Method 1
at least one roller, which can rotate on the first lever part and has a lateral surface for contrasting a first cam of the valve drive to produce a pivoting movement of the first lever part about the first axis of rotation
Implementation Method 2
the friction losses caused by the rocker arm in the valve drive are significantly reduced
Implementation Method 3
a first lever part with a first pivot bearing, via which the first lever part can be supported on a housing of the internal combustion engine so as to be pivotable about a first axis of rotation
Data Source
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AI summary
The oscillating lever (10) has roller which is rotatably mounted on lateral surface of first lever. A second lever is arranged adjacent to the first lever. A roller is rotatably mounted on lateral surface of the second lever. The cams of valve drive are provided to generate pivotal movement of the first and second lever about first and second axis of rotation respectively. An actuating section for actuating gas exchange valve of internal combustion engine (1), is provided on one of the first and second lever.