Vessel Propulsion Reverse Rotation Detection via Intake Pressure
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Solution Overview
Problem
Conventional vessel propulsion systems face challenges in accurately detecting reverse rotation of the engine due to issues like noise in sensor signals, defective wiring, battery voltage fluctuations, and manufacturing tolerances, leading to erroneous detection and potential engine damage.
Innovation Solution
A vessel propulsion apparatus equipped with a rotation speed detector, shift state detector, intake pressure sensor, and a controller that uses specific conditions such as intake pressure thresholds and pulse output patterns to reliably detect reverse rotation, preventing engine damage by switching the shift position to neutral.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reverse rotation detection is performed using pulse signals from crankshaft rotation, then reverse rotation can be detected, but erroneous detection occurs due to noise, defective wiring, and voltage fluctuations
Solution Approach 1:
The patent introduces an intermediary variable (intake pressure) to detect reverse rotation. Instead of directly detecting crankshaft rotation pulses which are susceptible to noise and wiring issues, the system uses intake pressure as an indirect indicator. When the engine rotates in reverse, the intake pressure changes in a characteristic pattern that can be reliably detected, thus solving the problem of erroneous detection while maintaining detection capability.
Solution Approach 2:
The patent replaces the mechanical/electrical detection system (pulse signals from crankshaft rotation sensors) with a pressure-based detection system. By substituting the direct mechanical rotation detection with pressure field measurement, the system eliminates vulnerabilities to electrical noise, defective wiring, and voltage fluctuations while still achieving reverse rotation detection.
2Reliability
If reverse rotation is detected and the shift position is forcibly switched to neutral, then engine protection is achieved, but the operation is delayed and vessel maneuverability is affected
Solution Approach 1:
The patent performs preliminary detection of reverse rotation conditions by monitoring intake pressure changes before they can cause engine damage. By detecting the reverse rotation state early through pressure variations, the system can prepare for protective actions in advance, reducing the delay between actual reverse rotation occurrence and protective measure implementation.
Solution Approach 2:
The system continuously monitors intake pressure and provides real-time feedback about engine rotation state. This feedback mechanism allows the control system to immediately respond to reverse rotation conditions by switching the shift position to neutral, achieving rapid engine protection while minimizing impact on vessel maneuverability through precise, condition-based control.
3Reliability
If multiple detection methods are used to improve detection accuracy, then detection reliability improves, but device complexity increases
Solution Approach 1:
The patent makes the intake pressure sensor serve multiple functions: it detects both normal engine operation parameters and reverse rotation conditions. By using the same pressure sensor for both purposes, the system achieves reliable reverse rotation detection without adding separate dedicated sensors or detection systems, thus avoiding increased device complexity while maintaining high detection reliability.
Data Source
AI summary
A vessel propulsion apparatus includes an engine that rotates a crankshaft in a forward rotation direction, a rotation speed detector that detects a rotation speed of the crankshaft, a propeller shaft coupled to a propeller, a shift switch that switches between a shift-in state and a neutral state, a shift state detector, an intake passage, a throttle valve, an intake pressure sensor, and a controller. The controller determines that the crankshaft is reversely rotating by an external force input from the propeller shaft when a predetermined reverse rotation recording condition is satisfied, and stores reverse rotation information. The reverse rotation recording condition includes a condition that an intake pressure after the shift switch switches from a neutral state to a shift-in state while the crankshaft rotates in the forward rotation direction is larger than a value equal to or higher than atmospheric pressure.