Variable Valve System Absolute Angle Sensor Startup Control
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Solution Overview
Problem
In variable valve systems for internal combustion engines, existing sensors struggle to accurately measure absolute camshaft angles immediately after startup, leading to potential measurement errors and inefficiencies in controlling valve opening and closing timings.
Innovation Solution
Incorporating an absolute angle sensor to measure the absolute rotation angle of the camshaft or crankshaft, with a controller performing correction operations based on voltage signals to account for environmental and operational factors, thereby reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse-counting sensors are used to measure camshaft angle, then the system structure remains simple, but measurement precision is insufficient during startup phase
Solution Approach 1:
The measurement system is segmented into two distinct sensor types: pulse-counting sensors for normal operation and absolute angle sensors for startup phase. This segmentation allows each sensor type to be optimized for its specific function, with absolute angle sensors providing precise absolute position measurement during startup without requiring pulse counting initialization.
Solution Approach 2:
Absolute angle sensors are activated preliminarily during the startup phase to establish accurate camshaft angle measurement before the engine reaches steady operation. This preliminary action ensures that valve timing control can begin immediately with accurate absolute position data, avoiding the waiting period required by pulse-counting sensors to reach a reference position.
2Productivity
If pulse-counting sensors are used, then device complexity is low, but loss of time occurs during startup before absolute angle can be determined
Solution Approach 1:
Absolute angle sensors provide camshaft angle information from the very beginning of startup, eliminating the need to wait for the crankshaft to reach a reference position. This preliminary availability of absolute angle data allows valve timing control to start immediately, significantly reducing startup time and improving productivity.
Solution Approach 2:
The absolute angle sensor acts as an intermediary that bridges the gap during startup phase, providing accurate camshaft position information without requiring the engine to complete a full rotation or reach a specific reference state. This intermediary measurement method enables immediate control action during the critical startup period.
3Measurement precision
If absolute angle sensors are used to measure absolute rotation angle, then measurement precision improves and startup waiting time is reduced, but device complexity increases
Solution Approach 1:
The sensor system is segmented so that absolute angle sensors are used only during the startup phase when precise absolute position measurement is critical, while pulse-counting sensors handle normal operation. This segmentation minimizes the overall complexity by limiting the use of complex sensors to only when necessary.
Solution Approach 2:
Absolute angle sensors are deployed preliminarily during startup to establish accurate baseline measurements, after which the system can transition to simpler pulse-counting methods for routine operation. This preliminary use of advanced sensors ensures accurate initialization without requiring them to operate continuously, thereby reducing overall system complexity.
4Productivity
If absolute angle sensors are used, then productivity during startup improves, but manufacturing precision requirements increase
Solution Approach 1:
The controller continuously monitors and corrects measurement values from absolute angle sensors, comparing them against expected ranges and making real-time adjustments. This feedback mechanism compensates for minor installation variations and manufacturing tolerances, ensuring accurate measurements even when perfect installation precision is difficult to achieve.
Solution Approach 2:
The system dynamically adjusts measurement and control parameters based on the operational phase. During startup, absolute angle measurements are used with specific correction algorithms, while during normal operation, the system switches to pulse-counting parameters. This parameter adaptation reduces the stringency of manufacturing precision requirements by optimizing measurement approaches for each operational condition.
Data Source
AI summary
A variable valve system including a crank angle sensor that measures a rotation angle of a crankshaft, a cam angle sensor that measures a rotation angle of a camshaft coupled to the crankshaft and which opens and closes valves, and a controller that controls the internal combustion engine. At least one of the crank angle sensor or the cam angle sensor is configured as an absolute angle sensor that measures an absolute rotation angle and outputs a voltage signal corresponding to this rotation angle. The controller is configured to perform a correction operation that corrects a rotation angle value calculated based on the voltage signal.