Variable Lift Valve Cam Transitional Shape Control
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Solution Overview
Problem
The existing cam switching type valve train mechanisms in internal combustion engines experience significant changes in engine power during switching between different valve lift characteristics, leading to discomfort in vehicle operation due to wide differences in cam profiles.
Innovation Solution
A control device that smoothly and continuously changes engine power by controlling the ignition timing and valve lift characteristics using a three-dimensional cam with transitional shape portions, allowing for seamless switching between plane cam shape portions through advanced engine control modules and sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a cam switching type valve train mechanism switches between different cam profiles to change valve lift characteristics, then the engine can adapt to different operating conditions, but the engine power changes significantly causing discomfort in vehicle operation
Solution Approach 1:
The patent introduces an intermediary transitional cam shape portion between different plane cam shape portions. This transitional portion has a curved cam face that continuously connects the cam faces of adjacent plane cam shape portions, serving as a mediator that enables smooth power transition during cam switching while maintaining the adaptability benefits of multiple cam profiles.
Solution Approach 2:
The patent changes the cam profile parameters continuously through the transitional shape portion rather than switching abruptly between discrete cam profiles. By varying the cam face curvature and geometry along the rotational direction, the system achieves gradual parameter changes that modulate engine power smoothly, resolving the contradiction between adaptability and operational comfort.
2Productivity
If plane cam shape portions have widely different cam profiles to provide distinct valve lift characteristics, then the engine can achieve different performance levels, but the torque curves do not cross and cause significant power changes during switching
Solution Approach 1:
The transitional cam shape portion acts as an intermediary that bridges widely different plane cam shape portions. Its curved cam face continuously connects the disparate cam profiles, enabling gradual transition between them and stabilizing engine power during switching while preserving the wide performance range provided by the different plane cam shapes.
Solution Approach 2:
The patent applies curvature to the cam face in the transitional shape portion, creating a curved surface that continuously connects the flat cam faces of adjacent plane cam shape portions. This spherical/curved geometry enables smooth interpolation between different cam profiles, allowing the engine to maintain stable power output while accessing a wide performance range.
3Adaptability or versatility
If the cam switching mechanism switches from one cam to another to change valve lift characteristics, then the engine can optimize for different intake negative pressures, but the ignition timing must be switched simultaneously causing complex control requirements
Solution Approach 1:
The transitional cam shape portion serves as an intermediary that enables gradual valve lift characteristic changes during switching. This continuous transition allows the control system to modulate ignition timing more smoothly alongside the cam switching, reducing the abrupt control actions needed and simplifying the overall control complexity while maintaining adaptability to different intake negative pressures.
Data Source
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AI summary
A control device for an internal combustion engine includes: a camshaft of the internal combustion engine; a plurality of plane cam shape portions; at least one transitional shape portion; a cam switching mechanism; a cam position sensor; and a control section. The plurality of plane cam shape portions are provided at the camshaft, have valve lift characteristics different from each other. During transition from a valve lift to another, the engine control modifies the ignition timing, the fuel injection time and the duty ratio of the sub-throttle valve drive motor for smoothing the transition.