Variable Valve Timing for Hybrid Engine Torque and NVH
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Solution Overview
Problem
Atkinson-cycle engines suffer from poor torque at low to medium engine speeds, leading to issues with noise, vibration, and harshness (NVH) as well as reduced fuel efficiency, due to the need for higher engine speeds to produce sufficient power in real-world driving conditions.
Innovation Solution
Implementing a system with adjustable intake and exhaust valve timing, allowing for dual retard operation to reduce oxygen flow to the exhaust catalyst during engine shutdown and cranking, thereby improving torque output and fuel efficiency, and reducing NVH by utilizing both intake and exhaust valve timing retard.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Atkinson-cycle engine operation is used, then fuel efficiency is improved, but torque output at low to medium engine speeds deteriorates
Solution Approach 1:
The patent applies variable valve timing mechanisms that dynamically adjust intake and exhaust valve opening/closing timings based on engine operating conditions. The system can switch between Atkinson cycle mode (late intake valve closing) for fuel efficiency and modes with advanced valve timings for improved torque output, allowing the engine to adapt to different driving requirements.
Solution Approach 2:
The patent changes key thermodynamic parameters by adjusting valve timing events. By retarding or advancing intake and exhaust valve timings, the system modifies the effective compression ratio and expansion ratio, enabling the engine to operate in different cycles (Atkinson, Otto, or hybrid modes) to optimize the balance between fuel efficiency and torque output.
2Power
If higher engine speeds are used to compensate for poor torque, then sufficient power is achieved, but noise, vibration, and harshness increase
Solution Approach 1:
The variable valve timing system dynamically adjusts valve events to optimize torque delivery across the engine speed range. By improving low-speed torque through appropriate valve timing, the engine can operate at lower RPMs for a given power demand, thereby reducing NVH while maintaining sufficient power output.
3Stability of the object's composition
If late intake valve closing is used during shutdown and cranking, then engine vibration is reduced, but oxygen flow to the catalyst increases
Solution Approach 1:
The patent adjusts valve timing parameters specifically during shutdown and cranking operations. By coordinating intake and exhaust valve timing retardation, the system reduces the amount of fresh air (oxygen) pumped through the engine during these operations, thereby protecting the catalyst while also reducing vibration through optimized valve events.
4Adaptability or versatility
If variable cam timing is used, then engine operation is improved over various speed/load conditions, but device complexity increases
Solution Approach 1:
The patent employs separate variable timing mechanisms for intake and exhaust valves, allowing independent control of each valve train. This segmentation enables precise optimization of valve timing events for different operating conditions while using proven, modular timing mechanism designs that manage complexity through established engineering approaches.
Data Source
AI summary
A method for operating a vehicle, the vehicle including an internal combustion engine coupled in the vehicle, the engine having at least one cylinder with an intake and an exhaust valve, where the opening and closing timing of the intake valve is adjustably retardable and the opening and closing timing of the exhaust valve is adjustably retardable via camshaft adjustments, during engine operation, an energy conversion device coupled in the vehicle capable of selectively supplying and absorbing torque during vehicle operation, and a transmission, the method comprising: adjustably retarding intake valve opening timing and intake valve closing timing from piston top dead center; and adjusting operation of the transmission and the energy conversion device to maintain engine speed sufficient to enable adjustment of said intake and exhaust valve timing.