Camshaft Rotation State Detection Using Adaptive Time Frames
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Solution Overview
Problem
Current methods for determining the state of rotation of a camshaft in a vehicle engine are inefficient, particularly at low engine speeds, leading to prolonged time in determining if the camshaft has stopped rotating, which affects engine synchronization and management.
Innovation Solution
A method that defines a shorter time frame (Tcam_cal) for determining the state of rotation of the camshaft by considering a rotational speed higher than the minimum engine speed, allowing for quicker identification of 'rotating', 'stopped', or 'in the process of stalling' states, using a sensor to detect camshaft wheel tooth-fronts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the minimum engine speed is used to calculate the time frame for determining camshaft rotation state, then the determination is conservative and reliable, but the time required for determination is excessively long
Solution Approach 1:
The patent applies dynamics by making the time frame calculation adaptive rather than static. The ECU dynamically selects between two different time frame calculations: Tcam (using minimum engine speed for reliability) and Tcam_cal (using a higher predetermined low speed for speed). This dynamic adaptation allows the system to optimize between reliability and speed based on operational context, resolving the contradiction between conservative reliability and fast determination.
Solution Approach 2:
The patent changes the parameter of engine speed used in the time frame calculation. Instead of always using the minimum engine speed, the system introduces a second speed parameter (predetermined low speed higher than minimum) and selects between them. This parameter change enables the time frame to be shortened when appropriate, reducing the determination time while maintaining reliability through selective parameter application.
2Reliability
If a longer time frame is used to account for minimum engine speed variations, then all possible rotation states are covered, but engine synchronization and management efficiency deteriorate
Solution Approach 1:
The patent segments the determination process into two distinct time frame calculations: Tcam for comprehensive state coverage and Tcam_cal for rapid determination. By dividing the single determination process into two segmented approaches, the system can apply the appropriate segment based on conditions, thereby maintaining comprehensive coverage while improving management efficiency through faster operation when using Tcam_cal.
Solution Approach 2:
The patent applies partial action by using Tcam_cal (which provides faster but less conservative determination) in specific contexts where full comprehensiveness is not required. This partial application of the faster time frame calculation improves efficiency without completely sacrificing reliability, as Tcam remains available when full state coverage is needed.
3Measurement precision
If the determination method accounts for low engine speed variations, then accuracy is maintained, but the response speed of engine management system decreases
Solution Approach 1:
The patent makes the determination method dynamic by allowing the ECU to switch between two accuracy-speed profiles: Tcam for high accuracy at low speed and Tcam_cal for faster response. This dynamic switching enables the system to maintain measurement precision when needed while improving response speed when using the calibrated time frame, resolving the contradiction between accuracy and response speed.
Solution Approach 2:
The patent changes the speed parameter used in time frame calculation from minimum engine speed to a higher predetermined low speed, thereby changing the characteristics of the determination process. This parameter change allows the system to achieve faster response while maintaining acceptable accuracy through selective application of different speed parameters.
Data Source
AI summary
Disclosed is a method for determining the state of rotation of a camshaft of a vehicle engine, notable in that the method for determining the state of rotation of the camshaft determines that the state of rotation of the camshaft is “in the process of stalling”, corresponding to an intermediate state of rotation, when the time elapsed since the last detection of a camshaft wheel tooth-front by the sensor exceeds Tcam_cal, Tcam_cal being defined as the theoretical length of time needed for the camshaft wheel to cover an angular distance equal to the maximum angular distance separating two successive camshaft wheel tooth-fronts at a camshaft rotational speed corresponding to a predetermined low engine speed higher than the minimum engine speed tolerated by the engine.