Turbocharged Engine Valve Timing and Compression Ratio for Turbo Lag
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Solution Overview
Problem
Internal combustion engines with turbochargers experience turbo lag due to delayed intake pressure increase during sharp load changes, leading to reduced fuel efficiency and increased risk of knocking when attempting to reduce turbo lag through ignition timing retardation.
Innovation Solution
An internal combustion engine equipped with a turbocharger, variable valve timing mechanism, and variable compression ratio mechanism, controlled by an electronic unit to adjust valve closing timing and compression ratio dynamically, bringing the valve closing timing closer to the intake bottom dead center and lowering the mechanical compression ratio in transient states to rapidly increase intake air and prevent knocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the valve closing timing of the intake valve is brought close to the intake bottom dead center to increase intake air amount in transient state, then the turbo lag is reduced, but the compression ratio becomes high and knocking is likely to occur
Solution Approach 1:
The invention changes the compression ratio parameter dynamically based on engine operating conditions. Specifically, the compression ratio is lowered when the intake valve closes near bottom dead center during transient states to prevent knocking, while allowing higher compression ratios during steady states for improved efficiency. This parameter change resolves the contradiction by adapting the compression ratio to the specific operating phase.
Solution Approach 2:
The invention implements dynamic control of the compression ratio mechanism in response to changing engine conditions. The system transitions between different compression ratio settings based on whether the engine is in a transient or steady state, allowing the compression ratio to adapt dynamically rather than remaining fixed. This dynamic adjustment prevents knocking during transient operations while maintaining optimal efficiency during steady operations.
2Object-affected harmful factors
If the ignition timing is retarded to prevent knocking when valve closing timing is brought close to intake bottom dead center, then knocking is prevented, but thermal efficiency decreases and fuel efficiency degrades
Solution Approach 1:
Instead of changing ignition timing, the invention changes the compression ratio parameter to prevent knocking. By lowering the compression ratio when the intake valve closes near bottom dead center, the system prevents knocking without retarding ignition timing, thereby avoiding the associated loss of thermal efficiency and fuel economy.
Solution Approach 2:
The invention replaces the traditional method of preventing knocking through ignition timing retardation with a mechanical approach - adjusting the compression ratio. This substitution allows knock prevention while maintaining optimal ignition timing for fuel efficiency, as the mechanical compression ratio adjustment addresses the root cause rather than using ignition timing as a compensatory measure.
3Object-affected harmful factors
If the mechanical compression ratio is made low in transient state, then knocking is prevented, but the intake pressure increase may be delayed
Solution Approach 1:
The invention dynamically adjusts the compression ratio parameter based on the engine's operational state. During transient states, the compression ratio is lowered to prevent knocking, while during steady states, the compression ratio is increased to optimize performance and pressure buildup. This parameter change strategy balances knock prevention with maintaining adequate intake pressure increase speed.
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
This solution effectively reduces turbo lag while minimizing fuel efficiency degradation and preventing knocking, maintaining thermal efficiency by dynamically adjusting valve timing and compression ratio in response to changing engine loads.
Implementation Method 1
a turbocharger (101) configured to be driven by exhaust gas to increase intake pressure
Data Source
Figure 1
Figure 2~3B
Figure 4A~4B
AI summary
An internal combustion engine (100) includes a turbocharger (101), a variable valve timing mechanism (B), a variable compression ratio mechanism (A), and an electronic control unit (31) that controls the variable compression ratio mechanism (A) such that the mechanical compression ratio becomes a target mechanical compression ratio and controls the variable valve timing mechanism (B) such that the valve closing timing of the intake valve (6) becomes a target valve closing timing. The electronic control unit (31) brings the target valve closing timing close to an intake bottom dead center and make the target mechanical compression ratio low, compared to a steady state after the intake pressure reaches a target pressure, in a transient state before the intake pressure reaches the target pressure in a case where the intake pressure is increased to the target pressure higher than an atmospheric pressure by the turbocharger (101).