Valve Bridge Movable Lever Engine Braking
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Solution Overview
Problem
Existing valve train assemblies with compression engine brakes face issues with unintended extension of hydraulic lash adjusters during engine braking, leading to potential loss of compression and piston-to-valve contact due to the cocking of the valve bridge, which increases actuation force requirements.
Innovation Solution
The integration of a movable lever assembly within the valve bridge that passes some valve actuation force back to the hydraulic lash adjuster, preventing unintended extension and reducing the actuation force needed for engine braking, while maintaining dynamic stability through constant contact with the engine brake rocker arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional valve bridge is used during engine braking, then the exhaust valve can be actuated, but the valve bridge cocks and causes unintended extension of the hydraulic lash adjuster, leading to loss of compression and piston-to-valve contact
Solution Approach 1:
The valve bridge is segmented into a fixed main body and a movable lever assembly. The lever can rotate independently relative to the main body about a pivot axis, allowing the lever to accommodate the engine brake rocker arm actuation without causing the entire valve bridge to cock. This segmentation isolates the movement to a localized component while maintaining the stability of the main valve bridge structure.
Solution Approach 2:
The lever assembly is designed to be dynamic rather than fixed. The lever rotates about a pivot axis during engine braking to maintain contact with the engine brake rocker arm, and returns to its original position when the brake is released. This dynamic movement prevents the valve bridge from cocking while still enabling effective engine brake actuation.
2Stability of the object's composition
If the valve bridge is designed to prevent cocking, then stability is improved, but the actuation force required for engine braking increases
Solution Approach 1:
By segmenting the valve bridge into a stable main body and a movable lever, the main body remains stationary and stable while the lever absorbs the actuation forces through rotation. This segmentation allows the stable main body to provide a firm mounting surface for the exhaust valve while the lever handles the dynamic forces of engine braking.
Solution Approach 2:
The lever acts as an intermediary between the engine brake rocker arm and the exhaust valve. It transfers the actuation force from the rocker arm to the valve while rotating to accommodate the force application, thereby reducing the force required compared to a fully rigid connection that would resist rotation.
3Stability of the object's composition
If the lever is allowed to rotate freely, then dynamic stability is improved, but contact with the engine brake rocker arm may be lost
Solution Approach 1:
The lever assembly incorporates a spring that provides continuous contact force between the lever and the engine brake rocker arm. The spring acts as a feedback mechanism that maintains the lever in contact with the rocker arm during rotation, ensuring that the actuation force is consistently transmitted while allowing the lever to rotate freely to maintain dynamic stability.
Solution Approach 2:
The spring provides a counteracting force that balances the lever during rotation. This counterforce ensures that the lever remains in contact with the engine brake rocker arm throughout its rotation range, preventing loss of contact while allowing the lever to move dynamically to maintain stability.
Data Source
AI summary
A rocker arm assembly selectively opening first and second engine valves. The assembly includes a rocker arm and a valve bridge operably associated with the rocker arm and including a main body and a lever rotatably coupled to the main body. The main body is configured to engage the first engine valve, and the lever is configured to engage the second engine valve.