Variable Valve Timing Control with Sensorless Motor Angle Estimation
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Solution Overview
Problem
Existing variable valve timing (VTC) systems face accuracy issues in phase angle interpolation due to the use of torque-current (T-I) and torque-speed (T-N) characteristics, which are stationary and influenced by factors other than motor torque, leading to inaccuracies in phase angle changes.
Innovation Solution
A control device and method that calculates motor torque and rotation angle based on motor current, engine operating state, and oil temperature to interpolate cam phase angle without a motor rotation angle sensor, considering factors like engine speed and oil temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phase angle interpolation is performed using torque-current (T-I) characteristics and torque-speed (T-N) characteristics, then the cost is reduced by removing the motor rotation angle sensor, but the measurement precision of cam phase angle deteriorates
Solution Approach 1:
The patent changes the parameters used for interpolation from stationary T-I and T-N characteristics to dynamic parameters including real-time motor torque, engine speed, engine rotation angle, and engine oil temperature. This allows the interpolation to adapt to changing operating conditions, resolving the accuracy problem while maintaining cost reduction by not using a motor rotation angle sensor
Solution Approach 2:
The patent introduces feedback mechanisms by continuously monitoring engine oil temperature and engine operating state, and using this information to correct and update the motor rotation angle calculation. This feedback loop compensates for the lack of direct motor rotation angle sensing, maintaining accuracy while reducing cost
2Device complexity
If stationary T-I characteristics and T-N characteristics are used for interpolation, then the device complexity is reduced, but the measurement precision deteriorates due to rapid phase angle changes
Solution Approach 1:
The patent transitions from static T-I and T-N characteristics to a dynamic calculation system that continuously updates motor torque and rotation angle based on real-time engine conditions. The system dynamically adjusts the interpolation parameters according to changing engine speed, load, and oil temperature, enabling accurate tracking of rapid phase angle changes without increasing device complexity
3Device complexity
If T-I characteristics and T-N characteristics of the motor alone are used, then the device complexity is reduced, but the measurement precision deteriorates due to external factors affecting VTC
Solution Approach 1:
The patent creates a universal calculation model that integrates multiple influencing factors (motor torque, engine speed, engine rotation angle, engine oil temperature) into a single comprehensive system. This multi-functional approach accounts for various external factors affecting VTC performance, providing accurate phase angle measurement without requiring separate compensation systems for each factor
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
Achieves high accuracy in cam phase angle interpolation, reducing costs by eliminating the need for a motor rotation angle sensor and improving phase angle detection precision.
Implementation Method 1
a brushed DC motor is used and a voltage is applied to the motor only during phase conversion so as to rotate a motor shaft part relative to a sprocket part and convert the phase of a cam shaft part
Data Source
AI summary
A control device and a control method for a variable valve timing mechanism are provided so as to improve the accuracy of cam phase angle interpolation without using a motor rotation angle sensor. The control device for the variable valve timing mechanism includes a controller configured to detect a phase angle of a cam based on a cam signal and control the phase angle of the cam by using an electric motor. The controller is configured such that a motor torque estimation unit calculates a motor torque from a motor current based on motor characteristics, a motor rotation-angle estimation unit calculates a motor rotation angle at least based on the motor torque and an engine operating state, and a conversion unit and a feedback control unit interpolate the cam phase angle of the variable valve timing mechanism from the motor rotation angle.