Variable Valve Timing Actuator Overheating Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Variable valve timing systems using electric motors face challenges in accurately controlling valve timing, especially in cold environments or during engine starting, due to insufficient hydraulic pressure and slow camshaft response, leading to potential overheating issues that can result in malfunctions or reduced efficiency.
Innovation Solution
A variable valve timing system that employs an electric motor as an actuator, incorporating a changing mechanism, command value preparation unit, electric motor drive unit, reference value setting unit, overheating determination unit, and command value restriction unit to adjust the electric power supply based on the rotational speed of the electric motor and engine, thereby preventing overheating and ensuring efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electric motor is used to drive the camshaft in a variable valve timing system, then the valve timing control accuracy is improved and hydraulic pressure dependency is reduced, but the risk of overheating in the motor coil and drive unit increases
Solution Approach 1:
The control device calculates the accumulated value of electric power supply before overheating occurs, and proactively restricts power supply when the accumulated value reaches a threshold. This preliminary action prevents overheating before it damages the motor coil or drive unit, resolving the contradiction between improved control accuracy and overheating risk.
Solution Approach 2:
The control device continuously monitors the electric power supply to the motor, calculates the accumulated value, and adjusts the power supply based on this feedback. When the accumulated value exceeds a threshold, the control device restricts further power supply, creating a closed-loop feedback system that prevents overheating while maintaining optimal valve timing control.
2Reliability
If the reference value for overheating protection is set too low, then the motor is protected from overheating, but the valve timing control efficiency is reduced due to excessive restriction
Solution Approach 1:
Instead of using a fixed reference value that restricts operation unnecessarily, the control device dynamically calculates the accumulated value of electric power supply and compares it against a threshold. This dynamic approach allows the system to maintain high control efficiency during normal operation while providing reliable protection when the accumulated power supply indicates potential overheating.
Solution Approach 2:
The control device changes the parameter being monitored from instantaneous power supply to the accumulated value of electric power supply over time. This parameter change allows for a more accurate assessment of thermal buildup, enabling reliable motor protection without unnecessarily restricting valve timing control efficiency during brief high-power operations.
3Productivity
If the reference value for overheating protection is set too high, then the valve timing control efficiency is maintained, but the motor may overheat and cause malfunctions
Solution Approach 1:
The control device calculates the accumulated value of electric power supply in advance and restricts power supply before overheating damages occur. This preliminary action ensures motor reliability is maintained while allowing the reference value to be set at a level that does not unnecessarily restrict valve timing control efficiency.
Solution Approach 2:
The control device uses feedback from the calculated accumulated power supply value to adjust the reference value dynamically. This feedback mechanism ensures that the reference value is appropriately set to maintain both valve timing control efficiency and motor reliability, preventing malfunctions while avoiding excessive restriction.
4Device complexity
If a fixed reference value is used for overheating protection, then the control system is simple, but it cannot adapt to varying operating conditions leading to either excessive restriction or insufficient protection
Solution Approach 1:
The control device dynamically adjusts the reference value based on the calculated accumulated value of electric power supply and current operating conditions. This dynamic adjustment allows the system to adapt to varying operating conditions such as different engine speeds and loads, providing appropriate protection without excessive restriction while maintaining reasonable control system complexity.
Solution Approach 2:
The control device changes the reference value parameter based on operating conditions and the accumulated power supply value. This parameter change enables the system to adapt to different operating scenarios, providing reliable motor protection during high-stress conditions while allowing efficient valve timing control during normal operation.
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 effectively protects the electric motor and drive unit from overheating by dynamically adjusting the reference values based on operating conditions, maintaining efficient valve timing control while preventing excessive protection that could reduce efficiency.
Implementation Method 1
a variable valve timing system that uses an electric motor as an actuator
Implementation Method 2
the passage of electric current through the electric motor causes a motor coil or a drive unit (a power converter circuit) of the electric motor to heat up
Data Source
AI summary
An actuator operation amount setting unit prepares the rotational speed command value for an electric motor such that the phase of an intake valve changes in accordance with the target phase. An electric-motor EDU controls the motor supply electric power such that the electric motor operates in accordance with the rotational speed command value. An overheating determination unit determines whether at least one of the electric motor and the electric-motor EDU needs to be restricted from heating up based on a result of comparison between the information indicating the motor supply electric power and the reference value. A rotational speed command value restriction unit restricts the rotational speed command value provided to the electric-motor EDU to a value within a predetermined range, when it is determined that the at least one of the electric motor and the electric-motor EDU needs to be restricted from heating up. A reference value setting unit variably sets the reference value based on the rotational speed of the electric motor.