Eccentric Slot Valve Train for Variable Lift
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Solution Overview
Problem
Existing continuously variable valve lift (CVVL) systems often introduce delays in valve opening or result in lost motion, which can be undesirable in certain engine operating conditions.
Innovation Solution
A valve train system that includes a camshaft, a control shaft with an eccentric slot, and rocker assemblies that allow for variable valve opening without lost motion, ensuring all rotational motion is transferred to the combustion valve, allowing for continuous variation of valve lift without delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a lost motion arrangement is used to vary valve lift, then valve lift can be continuously varied, but the timing of valve opening is delayed
Solution Approach 1:
A control shaft with an eccentric control shaft slot acts as an intermediary mechanism between the camshaft and the rocker pivot shaft. The eccentric slot translates camshaft rotation into controlled angular displacement of the rocker pivot shaft, enabling continuous valve lift variation without delaying valve opening timing.
Solution Approach 2:
The invention introduces a new degree of freedom by allowing the rocker pivot shaft axis to change position in space through the eccentric control shaft slot. This dimensional change enables continuous variation of the rocker arm's pivot point, achieving variable valve lift without the timing delays associated with traditional lost motion arrangements.
2Adaptability or versatility
If a lost motion arrangement is used to vary valve lift, then valve lift can be continuously varied, but motion is lost in the mechanism
Solution Approach 1:
The control shaft with eccentric slot serves as a motion-transferring intermediary that efficiently transmits rotational motion from the camshaft to the rocker pivot shaft. The eccentric mechanism ensures that motion is transferred without loss, as the changing position of the rocker pivot shaft axis directly controls the rocker arm's angular displacement throughout the entire camshaft rotation cycle.
3Device complexity
If the rocker pivot shaft axis position is fixed, then the mechanism is simple, but valve lift cannot be continuously varied
Solution Approach 1:
The invention makes the rocker pivot shaft axis dynamic by allowing its position to change continuously through the eccentric control shaft slot. As the control shaft rotates, the rocker pivot shaft axis moves to different positions, enabling continuous valve lift variation. This dynamic element is controlled through the geometric relationship of the eccentric slot, maintaining mechanism simplicity while achieving variable valve lift.
Solution Approach 2:
By introducing the ability of the rocker pivot shaft axis to change position in space through the eccentric control shaft slot, the invention adds a new dimension of control. This spatial variation of the pivot point enables continuous valve lift adjustment without significantly increasing overall mechanism complexity.
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
The system enables continuous variation of valve lift without introducing delays, ensuring efficient engine operation and minimizing lost motion, thereby improving engine performance and reducing emissions.
Implementation Method 1
a control shaft that is rotatable about a control shaft axis and includes a control shaft slot eccentric to the control shaft axis
Data Source
AI summary
A valve train system includes a camshaft with a camshaft lobe that is rotatable about a camshaft axis. A control shaft is rotatable about a control shaft axis and includes an eccentric control shaft slot. An input rocker engages the camshaft lobe and has a rocker slot. An output rocker engages a valve actuation member which is engaged with a combustion valve. A rocker pivot shaft has a rocker pivot shaft axis and is fixed to the output rocker and extends through both the control shaft slot and the rocker slot. Rotation of the camshaft causes the input rocker and the output rocker to pivot about the rocker pivot shaft axis and rotation of the control shaft changes the magnitude that the input rocker and the output rocker pivot about the rocker pivot shaft axis and also changes the magnitude of opening the combustion valve.