CVVT Oil Control Valve Current Locking for Cam Phase Stability
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Solution Overview
Problem
Current continuously variable valve timing (CVVT) systems face challenges in optimally controlling valve timing according to engine speed and load, particularly at low and high speed regions, leading to inefficiencies in fuel consumption and increased hydrocarbon emissions.
Innovation Solution
A method of controlling a continuously variable valve timing apparatus using current control of an oil control valve, which involves checking predetermined times, locking/unlocking actuators with specific driving currents, and maintaining or adjusting the control cam phase to optimize valve timing, allowing for phase changes in the camshaft to match engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed valve overlap period is set for the camshaft, then the engine can operate stably under normal conditions, but the volume efficiency decreases at low speed and hydrocarbon emissions increase due to inability to adapt to varying engine loads and speeds
Solution Approach 1:
The patent implements dynamic valve timing control by enabling the camshaft phase to be continuously adjusted based on engine operating conditions. The ECU receives signals from sensors (crank angle sensor, cam angle sensor, throttle position sensor, etc.) and dynamically changes the intake cam phase to optimize valve timing for different engine loads and speeds, resolving the contradiction between fixed timing stability and adaptive performance
Solution Approach 2:
The system changes the phase angle parameter of the camshaft dynamically. By adjusting the camshaft phase angle based on engine operating conditions (speed, load, temperature), the valve timing is optimized for different scenarios, allowing the system to adapt to varying conditions while maintaining operational stability through controlled parameter variation
2Productivity
If the intake valve is opened in advance to increase valve overlap period, then volume efficiency increases at high speed, but volume efficiency decreases and hydrocarbon discharge increases at low speed
Solution Approach 1:
The patent applies different valve timing strategies for different engine operating conditions. By locally optimizing the intake cam phase for specific operating regions (high speed, low speed, idle, etc.), the system achieves high volume efficiency at high speeds while preventing excessive hydrocarbon emissions at low speeds, rather than using a single global timing setting
Solution Approach 2:
The system dynamically adjusts the intake cam phase based on real-time engine operating conditions. At high speeds, the cam phase is advanced to increase valve overlap and improve volumetric efficiency, while at low speeds and idle conditions, the cam phase is retarded to prevent excessive hydrocarbon emissions, allowing the system to optimize performance across different operating regimes
3Use of energy by moving object
If CVVT control is implemented to optimize valve timing according to engine load, then fuel efficiency and performance improve, but the control system complexity and oil control requirements increase
Solution Approach 1:
The patent implements a feedback control system where the ECU continuously monitors engine operating parameters (intake manifold pressure, throttle position, engine speed, cam/crank angles) and adjusts the oil control valve accordingly. This feedback mechanism allows the system to optimize fuel efficiency through adaptive valve timing while managing oil control complexity through intelligent control algorithms
Solution Approach 2:
The oil control valve acts as an intermediary between the ECU and the camshaft phasing mechanism. By using engine oil as the working fluid and the OCV to precisely control oil flow to the camshaft phasing mechanism, the system achieves fine-grained control of valve timing without requiring complex mechanical linkages, simplifying the overall control architecture while maintaining high fuel efficiency
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 approach enables optimal control of advance and retard angles for the intake valve, improving fuel efficiency, engine performance, and reducing exhaust gas emissions by adapting valve timing to various driving conditions.
Implementation Method 1
The OCV is a core part of a CVVT apparatus and controls the valve opening/closing time by changing the passage of engine oil supplied from an oil pump and flowing to the continuously variable valve timing unit
Implementation Method 2
The density of engine oil, which is a working fluid of the continuously variable valve timing unit, change in accordance with temperature
Implementation Method 3
the OTS, a sensor that compensates for the amount of change according to temperature, measures the temperature before the engine oil flows into an OCV and sends it to the ECU
Implementation Method 4
the oil valve control filter filters impurities in the engine oil flowing to the OCV and the oil tensioner
Data Source
AI summary
A method of controlling a CVVT may include a) checking whether a predetermined time has passed, after engine starts. b) locking an actuator by driving oil control valve with different driving currents in accordance with whether a predetermined time has passed after the engine starts. c) unlocking the actuator or feed-backing control cam phase in accordance with whether the actuator is unlocked. d) feed-backing control cam phase or locking the actuator by driving oil control valve with predetermined current in accordance with whether control cam phase is not reached before the actuator is locked. e) driving the oil control valve with predetermined current to maintain the control cam phase or turning off the oil control valve, after feed-backing control cam phase or locking the actuator by driving the oil control valve with predetermined current in accordance with whether the control cam phase is not reached before the actuator is locked.