Synchronizing Internal Combustion Engine Piston Positions
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Solution Overview
Problem
Existing methods for determining the state of rotation of camshafts in internal combustion engines are inadequate for precise piston position detection, especially in four-stroke engines, as they fail to provide clear information about the intake and exhaust phases without ambiguity, leading to uncertainties in engine cycle synchronization.
Innovation Solution
A method utilizing two parallel coupled current source sensors to detect the passage of teeth on multiple targets secured to the crankshaft and camshafts, generating signals that allow for precise determination of piston positions by computing average angular positions and assigning edges to corresponding signals, with optional phase-shifting to improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor is used to detect camshaft position, then device complexity is reduced, but measurement precision is insufficient to distinguish between intake and exhaust phases
Solution Approach 1:
The patent combines two current source sensors into a single differential signal connection. The sensors are connected in parallel with opposite polarities, and their outputs are combined into a single differential signal that is processed by the control unit. This merging approach reduces wiring complexity while maintaining the ability to distinguish between intake and exhaust phases through the differential signal processing.
Solution Approach 2:
The differential signal connection serves multiple functions: it provides redundancy for fault detection, enables precise position measurement through differential processing, and reduces wiring requirements. The single differential connection handles both the sensing function and the diagnostic function, making the system more universal and efficient.
2Measurement precision
If three-pin voltage source sensor is used, then measurement precision is sufficient, but device complexity and wiring complexity increase
Solution Approach 1:
The patent merges two sensor functions into a single differential connection, eliminating the need for separate wiring for each sensor. The differential signal combines the outputs of both sensors into a single communication channel, significantly reducing wiring complexity compared to using three-pin voltage source sensors.
Solution Approach 2:
The patent replaces the traditional voltage source sensor system with a current source sensor system that uses differential signaling. This substitution changes the electrical architecture from voltage-based to current-based sensing, enabling more efficient signal transmission and reduced wiring requirements while maintaining measurement precision.
3Device complexity
If parallel coupled current source sensors are used, then wiring complexity is reduced, but difficulty of detecting and measuring increases due to signal differentiation
Solution Approach 1:
The control unit implements a feedback mechanism that analyzes the differential signal characteristics to determine which sensor is active. By monitoring the signal patterns and comparing them against expected patterns for intake and exhaust phases, the system can accurately identify the signal source and resolve the measurement ambiguity.
Solution Approach 2:
The patent introduces asymmetry in the sensor configuration by connecting the sensors with opposite polarities in the differential circuit. This asymmetric connection creates distinct signal characteristics for each sensor, enabling the control unit to differentiate between the two signal sources even though they are connected in parallel.
Data Source
AI summary
The aim of the present invention is a method for synchronizing an engine comprising at least one movable piston of a four-stroke internal combustion engine, said method comprising a first step (e1) involving initializing a second memory space, a second step (e2) involving waiting for an edge on a fourth signal (CAM_TOT), a fourth step (e4) involving testing the value of a counter (CPT), an eighth step (e8) involving selecting the theoretical angular positions of the slots of the second signal (CAM_IN) relative to the edges of a first signal (CRK) and of the slots of a third signal (CAM_EX) relative to the edges of the first signal (CRK).