Ball Engine Brake Mechanism for Heavy-Duty Diesel Valvetrains
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Solution Overview
Problem
Heavy-duty diesel engines with single overhead cam valvetrains require high braking power at low engine speeds, but existing valve train assemblies face challenges in providing this power without excessive load on the camshaft, particularly when using compression engine brakes.
Innovation Solution
A rocker arm assembly with a ball engine brake mechanism that includes a capsule assembly, a biasing member, and a ball, which selectively actuates a valve plunger to open exhaust valves during engine braking, reducing the input load by acting on one exhaust valve instead of two, and can be hydraulically, mechanically, or electrically actuated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a compression engine brake is used to provide high braking power at low engine speeds, then braking performance is improved, but the load on the camshaft and valvetrain increases excessively
Solution Approach 1:
The invention divides the exhaust valve control into separate mechanisms: a cam-driven rocker arm for normal operation and a ball mechanism for engine braking. This segmentation allows the braking function to be isolated from the camshaft, reducing the load on the camshaft while maintaining high braking power through direct ball-to-valve plunger action.
Solution Approach 2:
The ball mechanism acts as an intermediary between the rocker arm and the valve plunger during engine braking. The ball transfers force directly to the valve plunger, bypassing the camshaft and reducing its load while still enabling effective exhaust valve opening for compression braking.
2Power
If both exhaust valves are actuated during engine braking, then braking effectiveness is maximized, but the complexity of the valve train assembly increases
Solution Approach 1:
The invention applies engine braking action to only one exhaust valve rather than both, creating a localized braking effect. This local quality approach reduces the complexity of the valve train assembly while still providing sufficient braking effectiveness, as the single valve opening is adequate for compression braking without requiring dual valve actuation.
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 solution provides high braking power with reduced load on the valvetrain, allowing for efficient engine braking without overloading the camshaft, and can be adapted for various engine configurations, including six-cylinder engines.
Implementation Method 1
The biasing member biases the capsule toward the unactuated position
Implementation Method 2
The capsule and the ball move as a unit from an unactuated position to an actuated position
Data Source
AI summary
An exhaust valve rocker arm assembly operable in a combustion engine mode and an engine braking mode, the exhaust valve rocker arm assembly selectively opening first and second exhaust valves and including a rocker shaft, exhaust valve rocker arm assembly and a ball engine brake mechanism. The exhaust valve rocker arm assembly has an exhaust rocker arm that receives the rocker shaft and is configured to rotate around the rocker shaft. The ball engine brake mechanism is configured on the exhaust rocker arm and selectively actuates a valve plunger causing an exhaust valve to perform engine braking. The ball engine brake mechanism includes a capsule assembly having a capsule, a biasing member and a ball. The capsule has a cylindrical body that extends between a first end having an actuation face and a second end having a spring return face.