Valve Timing Adjustment Device Signal Correction for Hysteresis
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Solution Overview
Problem
Existing valve timing adjustment devices for internal combustion engines face issues with accurately recognizing the rotation position of electric motors due to hysteresis effects in Hall sensors, especially when the engine is stopped and the power source is repeatedly turned on/off, leading to erroneous control signals.
Innovation Solution
A valve timing adjustment device that includes a rotation signal generator, a control circuit, and a signal corrector to correct excess or shortage edges in the rotation speed and direction signals based on voltage levels and rotation direction at power on/off states, ensuring accurate control signals even during repeated power cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensors are used to detect rotation position, then rotation position detection is enabled, but hysteresis effects cause inaccurate recognition especially during repeated power on/off cycles
Solution Approach 1:
The control device performs preliminary actions by storing the voltage level of the rotation speed signal at the time of power source turn-off, and upon turn-on, compares the current voltage level with the stored value to determine and correct any edge excess or shortage before normal operation begins. This preliminary correction prevents inaccurate rotation position recognition from occurring during the critical startup phase.
Solution Approach 2:
The control device implements feedback by continuously monitoring the voltage level of the rotation speed signal at power on/off transitions, comparing it with previously stored values, and using this feedback information to determine whether edge correction is needed. This closed-loop approach ensures that hysteresis-induced errors are detected and corrected based on actual signal behavior.
2Adaptability or versatility
If the power source is repeatedly turned on/off while the engine is stopped, then operational flexibility is improved, but signal errors occur due to hysteresis in Hall sensors
Solution Approach 1:
Before normal control operations begin after a power cycle, the control device performs preliminary correction by storing the voltage level at turn-off, comparing it with the turn-on voltage level, and adjusting the rotation speed signal edges accordingly. This preliminary action ensures that the system is ready for accurate operation regardless of how many times the power has been cycled.
Solution Approach 2:
The control device converts the harmful hysteresis effect into a detectable pattern by storing the voltage level at power turn-off and comparing it with the turn-on level. By recognizing the specific voltage level changes caused by hysteresis, the system can identify when edge correction is needed and apply the appropriate correction, thereby converting the hysteresis-induced error into a correctable signal characteristic.
3Measurement precision
If edge correction is performed based on voltage levels at power on/off, then signal accuracy is improved, but additional processing steps are required
Solution Approach 1:
The control device integrates multiple functions into a unified correction process: it stores voltage levels, compares current and stored values, determines edge excess or shortage, and performs correction all within the same control circuit. This multi-functional approach achieves accurate signal correction without requiring separate dedicated components for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The control device performs self-correction by using its own stored voltage level information to identify and correct errors in the rotation speed signal. The system serves itself by automatically detecting when correction is needed through voltage level comparison and executing the appropriate edge correction without external intervention, thereby managing the added processing complexity through automated self-service mechanisms.
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 device effectively corrects signal errors caused by hysteresis, allowing for precise recognition of the electric motor's rotation position and accurate control signal generation, even when the engine is stopped and the power source is turned on/off, thereby maintaining proper valve timing adjustments.
Implementation Method 1
a plurality of Hall elements (also referred to as Hall effect elements) that respectively output a rotation signal of the electric motor
Data Source
AI summary
Hall sensors respectively output a measurement signal, a voltage level of which changes according to a rotation position of an electric motor. A rotation signal generator of a drive circuit generates a rotation speed signal and a rotation direction signal of the electric motor based on the measurement signals. A control circuit generates control signals of the electric motor according to edges of output signals of the rotation signal generator. A signal corrector corrects an excess or a shortage of the edge of the signal at the time of starting the electric motor based on: the voltage levels of the rotation speed signal and the rotation direction signal at the time of turning off and the time of turning on of an electric power source; and a rotation direction of the electric motor at the time of starting thereof.