Induction Control Unit for Engine Stop-Start Torque Fluctuation
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Solution Overview
Problem
In automatic stop-and-restart vehicles with variable valve mechanisms, the high actual compression ratio setting increases startability but leads to significant torque fluctuations and noise during engine stop and restart, causing discomfort to occupants due to unstable engine speed and torque.
Innovation Solution
A control unit that adjusts the lift amount of the inlet valve and throttle valve opening to manage the engine's induction state, ensuring stable automatic stop and restart by maintaining a predetermined intake air amount, using a negative pressure detector to prevent engine stop until sufficient brake pressure is reached, and advancing the valve closing timing to reduce compression ratio and pumping loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the actual compression ratio is increased to improve startability, then the engine can be started more reliably, but torque fluctuation increases causing large vibrations and striking noise during engine stop and restart
Solution Approach 1:
The patent applies dynamics by making the valve lift amount adjustable based on operating conditions. The ECU controls the variable valve mechanism to set the inlet valve lift amount to a smaller value during automatic stop/restart operations, while allowing larger lift amounts during normal operation. This dynamic adjustment resolves the contradiction by optimizing valve lift for different operational states.
Solution Approach 2:
The patent changes the parameter of valve lift amount based on operating conditions. By controlling the ECU to set a smaller inlet valve lift amount during automatic stop/restart, the actual compression ratio is reduced, which suppresses torque fluctuation and noise while maintaining sufficient startability. This parameter change resolves the technical contradiction.
2Object-generated harmful factors
If the inlet valve lift amount is increased to reduce actual compression ratio and suppress noise, then vibrations are reduced, but the amount of intake air is affected largely by negative pressure causing unstable engine speed and torque
Solution Approach 1:
The patent merges the control of multiple parameters (valve lift amount and throttle valve opening) to achieve stable engine operation. The ECU simultaneously controls both parameters during automatic stop/restart, combining their effects to maintain stable intake air amount despite negative pressure variations. This merged control approach resolves the contradiction between noise suppression and stability.
Solution Approach 2:
The patent implements feedback control where the ECU monitors engine operating conditions and adjusts the inlet valve lift amount and throttle valve opening accordingly. This feedback mechanism ensures that intake air amount remains stable despite changes in negative pressure, resolving the contradiction while maintaining low noise levels.
3Use of energy by moving object
If the engine is automatically stopped to improve fuel economy, then fuel consumption is reduced, but torque fluctuation and noise increase during restart
Solution Approach 1:
The patent applies preliminary action by pre-setting the inlet valve lift amount to a smaller value before engine restart. The ECU controls the variable valve mechanism in advance to optimize valve timing and lift, ensuring that when the engine restarts after automatic stop, torque fluctuation and noise are minimized while fuel economy benefits are maintained.
Data Source
AI summary
A controller puts an internal combustion engine in a first induction control state in which a lift amount of an inlet valve is equal to or smaller than a predetermined amount and an opening of a throttle valve is larger than a predetermined opening with respect to a predetermined running state. The controller puts the internal combustion engine in a second induction control state in which the lift amount of the inlet valve is larger than the predetermined amount and the opening of the throttle valve is equal to or smaller than the predetermined opening with respect to the predetermined running state. An automatic stopper automatically stops the internal combustion engine in when the lift amount of the inlet valve is equal to or smaller than the predetermined amount, when a stopping condition of the internal combustion engine is met under which a predetermined vehicle state is produced.