Variable Valve Actuator Overheat Prevention via Controlled Power Interruption
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Solution Overview
Problem
Existing control devices for variable valve mechanisms in internal combustion engines fail to prevent actuator overheating and associated torque shocks, which affect drivability by suddenly changing engine torque.
Innovation Solution
A control device that includes a sensor to detect actuator overheating, interrupting power supply to maintain the drive element in a fixed position, and restarting power when the actuator cools down, allowing for gradual resumption of variable valve control based on engine conditions, such as driver requests for acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the valve lift is fixed at the maximum value when the actuator overheats, then the actuator overheating is prevented, but the amount of intake air suddenly increases causing torque shock
Solution Approach 1:
The control device predicts future actuator temperature based on current operating conditions (intake air amount, engine speed, actuator duty cycle) before overheating occurs. This preliminary prediction allows the system to take preventive action by gradually adjusting the valve lift or reducing intake air amount, rather than suddenly fixing the valve lift at maximum value, thereby avoiding torque shock while preventing overheating.
Solution Approach 2:
Instead of fixing the valve lift at a static maximum value, the control device dynamically adjusts the valve lift or intake air amount based on real-time predicted temperature and operating conditions. This dynamic adjustment allows the system to maintain optimal performance while preventing overheating, avoiding the sudden changes that cause torque shock.
2Productivity
If the valve lift is suddenly set to an optimum value when normal control is resumed, then the actuator can operate efficiently, but the driver may feel torque shock
Solution Approach 1:
Before fully resuming normal variable valve control, the control device gradually transitions from the restricted mode (fixed valve lift or reduced intake air) back to optimal control. This gradual transition allows the valve lift to smoothly return to its optimum value, preventing sudden changes that would cause torque shock while still allowing the actuator to operate efficiently.
3Productivity
If the variable valve control is continuously operated to maintain optimal performance, then the engine efficiency is improved, but the actuator overheats
Solution Approach 1:
The control device operates the variable valve mechanism at a restricted level (partial action) when actuator temperature is high or predicted to become high, rather than continuously maintaining optimal performance. This partial operation reduces the actuator duty cycle and prevents overheating, while the system gradually returns to full optimal operation when temperature conditions permit, thereby balancing engine efficiency with actuator temperature management.
Data Source
AI summary
A control device for a variable valve mechanism that avoids the overheating an actuator while reducing adverse effects on the driveability of a vehicle. The actuator adjusts the lift of an intake valve by moving a drive element, and a sensor is used to determine whether the actuator will overheat. A control unit stops the drive element if the lift adjusted by the actuator is equal to or larger than a first predetermined value, when the control unit determines that the actuator will overheat. The actuator may be an electric actuator. In this case, the actuator maintains the drive element in a fixed position when supply of electric power to the actuator is interrupted. The control unit stops the drive element, and interrupts the supply of electric power to the actuator.