Switchable Valve Train for Engine Braking
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Solution Overview
Problem
Internal combustion engines lack an efficient mechanism to selectively convey inputs from multiple camshaft lobes to engine valves, particularly for transitioning between power and braking modes, which limits their ability to effectively implement compression release engine braking.
Innovation Solution
A rocker arm assembly that can operate in multiple modes, selectively transmitting inputs from two or more camshaft lobes to an exhaust valve, allowing for seamless transition between power and braking operations by adjusting a locking mechanism to pivot the subframe relative to the body, enabling the valve to open and close based on different camshaft lift profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single camshaft lobe is used to control the exhaust valve, then the valve timing is simple, but the engine cannot switch between power and braking modes
Solution Approach 1:
The exhaust valve is designed to serve multiple functions by being controllable by different camshaft lobes. The same valve structure can be actuated by a first camshaft lobe for normal power operation and by a second camshaft lobe for braking mode, eliminating the need for separate valve mechanisms for each function.
Solution Approach 2:
The system dynamically switches between different camshaft lobes based on operational mode. The ability to selectively engage either the first or second camshaft lobe allows the valve timing mechanism to adapt its behavior in real-time, transitioning between power and braking functions as needed.
2Reliability
If multiple camshaft lobes are used to control the exhaust valve, then the engine braking capability is enhanced, but the valve timing control becomes complex
Solution Approach 1:
A switching mechanism acts as an intermediary to manage the complexity of controlling the exhaust valve from multiple camshaft lobes. This intermediary component selectively connects either the first or second camshaft lobe to the exhaust valve, simplifying the control architecture while maintaining the ability to provide both power and braking functions.
3Force
If the valve timing is adjusted for compression release braking, then the braking force is increased, but the normal power operation is affected
Solution Approach 1:
The camshaft lobe configuration is segmented into distinct functional zones. The first camshaft lobe is optimized for power mode with specific lift profiles that maximize engine power output, while the second camshaft lobe is designed for braking mode with lift profiles that enable compression release. This segmentation allows each mode to operate optimally without interfering with the other.
Data Source
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AI summary
An internal combustion engine (10) defining at least one cylinder (26), the internal combustion engine including a first camshaft lobe (100a), a second camshaft lobe (108a), a valve (40b) in fluid communication with the at least one cylinder, a pivot (116), and a follower (120) in contact with and operatively engages the pivot, the valve, the first camshaft lobe, and the second camshaft lobe. During use, the follower (102) is operable in a first mode, in which the follower is configured to transmit motion between the first camshaft lobe (100a) and the valve (40b), and a second mode, in which the follower is configured to transmit motion between the first camshaft lobe (100a) and the valve and the second camshaft lobe (100b) and the valve (40b).