Variable Valve Actuation for Engine Braking Mode Transitions
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Solution Overview
Problem
Existing methods for actuating engine valves during transitions between positive power operation and engine braking impose undesirable loads on the engine valves and valve trains, leading to potential damage and failure, and there is a need for cost-efficient and effective variable valve actuation methods that can optimize engine performance across various operating conditions.
Innovation Solution
A method of variable valve actuation that includes transitioning between positive power and engine braking modes by actuating intake and exhaust valves with late intake valve opening, early intake valve closing, early exhaust valve closing, and enabling/disabling the brake valve, allowing for smooth transitions and optimized engine performance without excessive loads on the valve train.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional valve actuation methods are used during transitions between positive power and engine braking modes, then the engine can switch between operating modes, but undesirable loads are imposed on the engine valves and valve trains leading to potential damage and failure
Solution Approach 1:
The patent implements dynamic valve actuation by varying intake and exhaust valve timing and duration based on the current operating mode. During transition from positive power to engine braking, the system dynamically adjusts valve events to prevent excessive loads. The controller modifies valve actuation parameters in real-time to match the required operating mode, making the valve train adaptable while protecting against damage.
Solution Approach 2:
The patent applies preliminary action by preparing the valve train for mode transition before the actual switch occurs. The controller anticipates the transition requirement and pre-adjusts valve timing and duration to smooth the transition process. This prevents sudden load changes that would otherwise damage the valve train during mode switching.
2Power
If engine valves are actuated to provide compression-release braking, then engine braking power is generated, but the valve train experiences excessive wear and potential failure
Solution Approach 1:
The patent utilizes parameter changes by systematically varying valve timing parameters (intake valve opening/closing, exhaust valve opening/closing) and valve duration based on the desired braking power level. The controller adjusts these parameters to optimize engine braking power while keeping valve loads within safe limits. By changing timing and duration parameters rather than using fixed aggressive valve events, the system achieves high braking power without excessive wear.
3Productivity
If variable valve actuation is implemented to optimize engine performance across various operating conditions, then engine efficiency and emissions are improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies universality by designing a valve actuation system that performs multiple functions through a single integrated controller and valve train mechanism. The same intake and exhaust valves are used for both positive power operation and engine braking operation, with the controller switching between different valve timing strategies. This multi-functional approach eliminates the need for separate dedicated braking valves or complex additional mechanisms, reducing overall system complexity while maintaining optimization capabilities across all operating conditions.
Data Source
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AI summary
A control method for transitioning from positive power to engine braking (and vice-versa) is disclosed. This transition may be made using variable valve actuation and two-stroke braking. The process may involve three engine operation modes: positive power (i.e., firing or non-braking), engine braking, and transition between engine braking and positive power. The intake and exhaust valve actuations provided for each of the different modes of operation may be different from each other.