Variable Displacement Engine Cam Lobe Profiles
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Solution Overview
Problem
Existing engine systems with variable displacement capabilities face challenges in maintaining combustion stability and efficiency due to differences in valve lift and timing between deactivatable and non-deactivatable cylinders, leading to increased noise, vibration, and harshness (NVH) issues, particularly at idling speeds.
Innovation Solution
The implementation of a camshaft system with distinct cam lobe profiles for deactivatable and non-deactivatable cylinders, where deactivatable cylinders are driven by cams with a third cam lobe profile and non-deactivatable cylinders by cams with a second cam lobe profile, ensuring synchronized valve opening and closing rates and overlap, thereby reducing differences in valve lift and timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cam lobe profile is used for both deactivatable and non-deactivatable cylinders, then the device complexity is reduced, but combustion stability deteriorates due to differences in valve lift and timing characteristics
Solution Approach 1:
The camshaft incorporates different cam lobe profiles at different locations: a first cam lobe profile for deactivatable cylinders and a second cam lobe profile for non-deactivatable cylinders. This local differentiation allows each cylinder type to receive optimized valve actuation characteristics, ensuring consistent valve lift and timing across all cylinders while maintaining combustion stability.
2Use of energy by moving object
If deactivatable cylinders use different valve timing characteristics, then fuel economy is improved through variable displacement operation, but NVH issues worsen due to imbalance between activated and deactivated cylinders
Solution Approach 1:
The invention changes the cam lobe profile parameter between deactivatable and non-deactivatable cylinders. The first cam lobe profile is designed with specific geometric characteristics that, when used with deactivatable cylinders, produce valve lift and timing characteristics matching those of non-deactivatable cylinders. This parameter differentiation enables the engine to maintain balance among all cylinders during variable displacement operation, reducing NVH while improving fuel economy.
3Ease of manufacture
If valve lift and timing differences between deactivatable and non-deactivatable cylinders are not addressed, then manufacturing simplicity is maintained, but engine efficiency deteriorates due to combustion instability
Solution Approach 1:
The camshaft is manufactured with distinct cam lobe profiles at different locations along its length. The first cam lobe profile serves deactivatable cylinders while the second cam lobe profile serves non-deactivatable cylinders. This local quality approach allows the engine to achieve consistent valve operation characteristics across all cylinders, improving combustion stability and engine efficiency without significantly complicating the manufacturing process.
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 configuration enhances combustion stability, reduces NVH, and improves fuel efficiency by ensuring consistent valve operation across all cylinders, thereby balancing torque and minimizing residual gases post-combustion.
Implementation Method 1
a camshaft including first and second pluralities of cams, each cam of the first plurality of cams having a first cam lobe profile, and each cam of the second plurality of cams having a different, second cam lobe profile
Data Source
AI summary
Methods and systems are provided for an engine including cams having different lobe profiles. In one example, cams of a first cam group drive a plurality of deactivatable cylinder valves and cams of a second cam group drive a plurality of non-deactivatable cylinder valves. The cams of the first cam group include a different lobe profile relative to cams of the second cam group.