Variable Valve Timing for Low-Speed Engine Vibration Reduction
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Solution Overview
Problem
Compression ignition four-stroke internal combustion engines experience excessive vibrations when operating at low rotational speeds, which can lead to engine damage, driver discomfort, and structural resonances.
Innovation Solution
A method involving a control arrangement that changes the timing of the exhaust camshaft to advance the closing of the exhaust valve and changes the timing of the intake camshaft to delay the opening of the intake valve when the engine operates below a threshold rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the compression ignition engine operates at low rotational speeds, then the engine produces sufficient power for low-speed applications, but excessive vibrations occur causing engine damage, driver discomfort, and structural resonances
Solution Approach 1:
The patent applies variable valve timing technology to dynamically adjust the timing of intake and exhaust valves based on engine operating conditions. At low rotational speeds, the system advances exhaust valve closing and delays intake valve opening to modify combustion characteristics and reduce vibrations. This dynamic adjustment allows the engine to adapt its valve timing strategy to different speed regimes, effectively suppressing vibrations at low speeds while maintaining optimal performance at higher speeds.
Solution Approach 2:
The patent changes the timing parameters of valve opening and closing events to alter combustion pressure characteristics. By advancing exhaust valve closing timing and delaying intake valve opening timing, the system modifies the pressure development during combustion, which reduces the amplitude of vibrations at low rotational speeds. This parameter change approach directly addresses the vibration problem by transforming the combustion pressure profile.
2Use of energy by moving object
If the compression ratio is increased to improve fuel efficiency and power output, then the engine achieves better thermal efficiency, but combustion pressure increases causing greater vibrations at low rotational speeds
Solution Approach 1:
The variable valve timing system dynamically adjusts valve timing parameters based on engine load and speed conditions. When operating at low rotational speeds with high compression ratio, the system advances exhaust valve closing and delays intake valve opening to reduce combustion pressure peaks, thereby mitigating vibrations while preserving the benefits of high compression ratio for fuel efficiency at other operating points.
Solution Approach 2:
The patent modifies combustion chamber pressure parameters through variable valve timing adjustments. By changing the timing of valve events, the system alters the pressure-time history of combustion, reducing peak pressures and their rate of rise at low speeds, which directly reduces vibration excitation while maintaining the thermodynamic efficiency benefits of the high compression ratio design.
3Object-affected harmful factors
If variable valve timing is implemented to reduce vibrations, then engine vibrations are reduced at low rotational speeds, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The variable valve timing system serves multiple functions: it reduces vibrations at low rotational speeds, optimizes power output across the operating range, improves fuel efficiency, and controls emissions. By integrating this single control system to achieve multiple objectives, the patent reduces the need for separate vibration suppression devices, thereby limiting the increase in overall device complexity while gaining comprehensive performance benefits.
Solution Approach 2:
The patent utilizes existing valve timing parameters, which are already part of the engine control system for optimizing performance and emissions. By repurposing and adjusting these existing parameters for vibration reduction, the system avoids adding entirely new control mechanisms. The same actuators and sensors used for performance optimization are leveraged for vibration suppression, minimizing the increase in device complexity.
Data Source
AI summary
The disclosure concerns a method for vibration reduction in a compression ignition four-stroke internal combustion engine. The internal combustion engine comprises exhaust and intake valves controlled by exhaust and intake camshafts. The method comprises, when operating the internal combustion engine below a threshold rotational speed, steps of: changing a timing of the exhaust camshaft to advance closing of the exhaust valve, and —changing a timing of the intake camshaft to delay opening of the intake valve.