Engine Synchronization Wheel Decoding for Fast Position Detection
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Solution Overview
Problem
Existing engine synchronization methods in internal combustion engines with direct fuel injection systems face challenges in accurately determining the engine position, leading to delayed fuel injection timing, especially in stop-start systems, due to initial speed ambiguity and phase errors in tooth and gap detection.
Innovation Solution
A control method that includes re-casting steps for ambiguous tooth detection, phase error correction, and enhanced precision through De Bruijn decoding and edge counting, allowing for precise engine position determination using Manchester encoding and edge location tables, integrated into the engine control unit software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional toothed wheel decoding is used to determine engine position, then the system structure is simple, but the engine position determination is delayed until the double tooth has passed, requiring almost a complete camshaft revolution
Solution Approach 1:
The toothed wheel is segmented into two distinct types of teeth: normal teeth and reference teeth (double tooth or single tooth with different spacing). This segmentation allows the sensor to distinguish between regular position markers and synchronization markers, enabling the ECU to identify the start of a camshaft revolution and begin decoding immediately without waiting for the double tooth to pass.
Solution Approach 2:
The reference tooth is positioned in advance at a known location on the toothed wheel (either as a double tooth at a specific position or as a single tooth with different spacing). This preliminary positioning allows the ECU to anticipate the start of a revolution cycle and prepare for immediate decoding when the reference tooth is detected, eliminating the delay of waiting for the double tooth to pass.
2Measurement precision
If the engine starts from standstill with unknown position, then the system must handle initial speed ambiguity, but this increases the time required before fuel injection can be synchronized
Solution Approach 1:
The system uses feedback from the sensor detecting the reference tooth to immediately trigger the decoding process. When the reference tooth is detected, the ECU receives feedback that a new revolution cycle has started, allowing it to begin counting normal teeth and determining engine position without delay, even when starting from standstill with unknown position.
Solution Approach 2:
The system changes the parameter of tooth spacing by incorporating reference teeth with different spacing patterns (double tooth or single tooth with different interval) compared to normal teeth. This parameter change allows the ECU to distinguish the start of a revolution cycle and begin position determination immediately, resolving speed ambiguity faster than traditional methods.
3Reliability
If rapid deceleration of the wheel occurs, then phase errors appear in the Manchester code, but these errors disrupt the position decoding accuracy
Solution Approach 1:
The system takes preliminary anti-action by using the reference tooth to reset and synchronize the decoding process at the start of each revolution cycle. This preliminary synchronization prevents phase errors from accumulating during rapid deceleration, as each cycle begins with a known reference point that re-establishes the correct phase relationship between the sensor signal and the expected Manchester code pattern.
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
Enables precise engine position determination within 36° to 42° of crankshaft rotation, reducing the delay in fuel injection timing and improving synchronization accuracy, even under varying engine speeds.
Implementation Method 1
The sensors delivering said signals are variable reluctance (VR) sensors, detecting ferrous features at the periphery of a wheel associated to the crank-shaft
Data Source
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AI summary
An engine synchronisation means (12) of an internal combustion engine (10) having a crank-shaft and a camshaft geared together with a fixed rotation ratio, said means (12) comprising a crank-shaft wheel (18) cooperating with a first sensor (16) and, a camshaft wheel (22) cooperating with a second sensor (20), both wheels (18, 22) being provided with peripheral features (24, 26, 28, 30) and, both sensors (16, 20) being adapted to detect said features and to communicate to an ECU (14) binary signals (S16, S20). The features (24, 26) of the crank-shaft wheel (18) are arranged as per a sequential pattern and, a sliding window (W) of a specific width covers a unique set of features (24, 26) corresponding to a unique string of consecutive bits mapping to a unique angular position of the crank-shaft.