Variable Valve Timing Control Unit for Engine Stop Phase
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Solution Overview
Problem
Existing variable valve timing mechanisms struggle to effectively change the valve phase after an engine stops, limiting the amount of change and potentially resulting in poor engine startability due to the valve phase not reaching a suitable position for next engine start.
Innovation Solution
A control unit that includes an actuator control unit, stop-time position setting unit, combustion stop processing unit, and motoring command unit, which controls the actuator to change the valve phase towards a target phase by rotating the internal combustion engine using a rotary electric machine after fuel combustion has stopped, ensuring the valve phase is suitable for engine starting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the valve phase is changed only during the period from engine stop command to actual engine stop, then the control system is simple, but the amount of valve phase change is limited and the valve phase may not reach the suitable position for engine starting
Solution Approach 1:
The invention performs preliminary action by rotating the engine using the rotary electric machine before the engine stop command is issued. This allows the valve phase to be advanced in advance so that when the engine actually stops, the valve phase has already reached or approached the suitable position for engine starting. The control unit calculates the required rotation amount based on the deviation between current and target valve phases, and executes the rotation before combustion stops.
2Manufacturing precision
If the valve phase change period is extended by rotating the engine after stop command, then the valve phase can reach suitable position, but power consumption increases and overheating risk arises
Solution Approach 1:
The invention applies partial action by rotating the engine only for the necessary duration and amount to achieve the target valve phase position, not continuously after the stop command. The control unit monitors the valve phase change and stops the rotation when the target is reached or when a predetermined time elapses, whichever comes first. This prevents excessive power consumption and overheating while still achieving sufficient valve phase adjustment.
3Manufacturing precision
If the valve phase change period is extended by rotating the engine after stop command, then the valve phase can reach suitable position, but the system becomes more complex with additional control units
Solution Approach 1:
The invention applies multi-functionality by making the existing rotary electric machine serve dual purposes: both as a starting motor for engine startup and as a rotation mechanism for valve phase adjustment during engine stop. The control unit integrates multiple functions including actuator control, stop-time position setting, combustion stop processing, and motoring command issuance, allowing a single control unit to manage all valve phase adjustment operations without requiring separate dedicated hardware.
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 solution allows for a greater amount of valve phase change after the engine stop command is issued, reliably bringing the valve phase to a suitable position for engine starting, thereby enhancing engine startability and minimizing power consumption and overheating.
Implementation Method 1
a vehicle that is provided with a rotary electric machine having an output shaft that is connected to an output shaft of the internal combustion engine via a gear
Data Source
AI summary
A stop-time target phase setting unit sets a target phase CAr for an intake valve to a target phase, which is used when an engine is stopped, in response to issuance of an engine stop command. An engine stop control unit generates a series of control commands for an engine stop process in response to issuance of the engine stop command. A motoring command unit generates a first MG control command for rotating the engine using a motor for a predetermined period Tm that is counted by a timer in response to issuance of the engine stop command. Thus, the engine idles even after fuel combustion stops. In this way, the period in which the valve phase can be changed by a VVT mechanism is increased. As a result, a valve phase when the engine stops is reliably brought to the target phase that is suitable for next engine starting.