Variable Valve Timing Controller for Engine Stop Phase Control
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Solution Overview
Problem
Existing electric variable valve timing apparatuses face challenges in controlling valve timing accurately at low engine speeds and during engine stop conditions, leading to difficulties in restarting the engine from an arbitrary phase due to rough sensor signal detection and inability to maintain precise phase control.
Innovation Solution
A controller device that adjusts motor speed to change the relative rotational phase of the camshaft to the most advanced or retarded position before engine stop and maintains this phase during low-speed conditions by fixing motor current or voltage, allowing precise control until the engine completely stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If normal control is used to adjust motor current/voltage according to crankshaft rotational speed, then valve timing can be controlled at higher speeds, but control accuracy deteriorates at low speeds below the first threshold
Solution Approach 1:
The control system dynamically switches between two control modes based on crankshaft rotational speed. When speed is above the first threshold, normal control adjusts motor current/voltage according to speed. When speed drops below the first threshold, the system transitions to low-speed control mode where motor current or voltage is fixed at a predetermined value to maintain accurate valve timing control despite rough sensor signals.
Solution Approach 2:
The control method changes the motor control parameter from speed-proportional adjustment to fixed value based on the detected crankshaft rotational speed. This parameter change occurs when the crankshaft speed falls below the first threshold, allowing the system to maintain reliable control accuracy in the low-speed region where sensor signal roughness would otherwise cause control errors.
2Use of energy by moving object
If the engine stops completely, then energy consumption is reduced, but the ability to restart from an arbitrary phase is lost
Solution Approach 1:
The control system performs preliminary action by maintaining the camshaft phase at a predetermined position (most advanced or most retarded) during the stopping process. By fixing the motor current or voltage when crankshaft speed falls below the first threshold, the system ensures the camshaft reaches and holds a known phase position before complete stop, enabling flexible restart from arbitrary phase while minimizing energy consumption during the stopped state.
3Stability of the object's composition
If duty control is performed in small increments to prevent overshoot, then control stability improves near target phase, but control speed decreases
Solution Approach 1:
The control system applies partial action by using fixed motor current/voltage values that are sufficient to maintain phase position without excessive force. This prevents overshoot while achieving the target phase efficiently. The fixed values are chosen to provide just enough control authority to maintain position against mechanical forces without causing oscillation or overshoot, balancing control speed and stability.
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
Enables accurate control of valve timing at arbitrary positions before and after engine stop, reducing engine speed variation and noise at restart, and suppressing pumping loss and NVH by maintaining the phase at the most advanced or retarded position.
Implementation Method 1
a variable valve timing apparatus that changes a relative rotational phase of a camshaft with respect to a crankshaft of the internal combustion engine by adjusting a motor speed of a motor connected to the camshaft
Implementation Method 2
the rotational speed of the crankshaft is equal to or higher than a first threshold... during a period from when the rotational speed of the crankshaft becomes lower than the first threshold to when the rotational speed becomes zero
Data Source
AI summary
An object of the present invention is to obtain a controller device for a variable valve timing apparatus capable of controlling a phase to an arbitrary fixed valve timing from immediately before an internal combustion engine stops until after the internal combustion engine has stopped. The controller device for the variable valve timing apparatus according to the present invention performs, during engine stop processing of the internal combustion engine, normal control of changing the relative rotational phase of a camshaft to a most advanced position or a most retarded position when the rotational speed of a crankshaft is equal to or more than a first threshold, and low-speed control of fixing a current or a voltage supplied to the motor to be constant to maintain the relative rotational phase of the camshaft at the most advanced position or the most retarded position in a period from when the rotational speed of the crankshaft is lower than the first threshold until the rotational speed becomes zero.