Electric Phaser Startup Control for Camshaft Phase Adjustment
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Solution Overview
Problem
Internal combustion engines face challenges in precisely controlling the phase of camshaft phasers during startup, as the angular position of the camshaft relative to the crankshaft may not be known, leading to inefficient engine operation.
Innovation Solution
A method and system that detect rotational movements of the electric motor output shaft controlling the camshaft phaser and the crankshaft, determining the relative difference in their rotational movements to determine if the camshaft phase is advancing, retarding, or remaining constant, and adjusting the phase using an electric phaser motor, without requiring precise initial angular positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional fixed relationship control is used between crankshaft and camshaft, then the system is simple, but the engine cannot achieve optimal valve timing during startup
Solution Approach 1:
The patent implements dynamic phase control of the camshaft relative to the crankshaft during startup. The camshaft phaser is actuated by an electric motor to dynamically adjust the camshaft phase angle, allowing the system to adapt valve timing to optimal values during engine startup and transition to a fixed relationship during normal operation.
Solution Approach 2:
The patent applies preliminary action by pre-positioning the camshaft phase during the startup period before the engine reaches normal operating conditions. The control system calculates and applies the appropriate phase adjustment in advance, ensuring optimal valve timing is established before combustion begins, rather than waiting for sensor feedback during operation.
2Measurement precision
If camshaft position is not precisely known during startup, then the control system is simpler, but the phase relationship between camshaft and crankshaft cannot be accurately maintained
Solution Approach 1:
The patent uses an intermediary approach by introducing a camshaft phase estimator that calculates the camshaft angular position based on available crankshaft position data and phaser motor position data, rather than directly measuring camshaft position. This intermediary calculation system maintains measurement precision without requiring additional complex sensors on the camshaft.
Solution Approach 2:
The patent replaces direct mechanical position sensing of the camshaft with an electronic estimation system. Instead of using mechanical sensors or encoders on the camshaft, the system substitutes a computational approach that estimates camshaft position based on crankshaft position and phaser motor commands, reducing mechanical complexity while maintaining precision.
3Speed
If camshaft rotation is too slow during startup, then the engine can be started more gently, but position updates from cam sensors are not timely
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual camshaft phase position through the phaser motor position sensor and comparing it with the target phase position. This feedback loop allows the control system to detect and correct any phase deviations in real-time, ensuring accurate phase maintenance even when camshaft rotation speed varies during startup.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining continuous phase control through the electric phaser motor during the entire startup period. Rather than relying on intermittent camshaft position samples that may be delayed, the system continuously adjusts the camshaft phase based on ongoing feedback, ensuring uninterrupted and timely position information is available for control decisions.
Data Source
AI summary
A system and method of controlling an angular position of a camshaft relative to an angular position of a crankshaft includes detecting rotational movement of an electric motor output shaft controlling a camshaft phaser; detecting rotational movement of the crankshaft; determining the relative difference between the rotational movement of the electric motor output shaft and the rotational movement of the crankshaft; and determining whether the angular position of the camshaft relative to the angular position of the crankshaft is advancing, retarding, or remaining constant.