Marine Propulsion Device Electric Motor Cooling System
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Solution Overview
Problem
Existing marine propulsion devices using electric motors face challenges in cooling the electric motor effectively, especially when the engine is stopped, as the water pump is not driven, leading to delayed cooling of the electric motor components.
Innovation Solution
A marine propulsion device featuring a coolant circulation passage with a cooling passage, a heat exchange passage, and a pump that circulates coolant to immediately cool the electric motor, ensuring efficient heat exchange and rapid cooling upon startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a water pump driven by an engine is used to cool the engine, then the engine can be cooled during operation, but the engine cannot be cooled immediately when the engine is stopped because the water pump is not driven
Solution Approach 1:
The patent replaces the engine-driven water pump with an electric pump that is independently powered by a battery. This substitution allows the cooling system to operate independently of the engine's mechanical drive, enabling the pump to run even when the engine is stopped, thus eliminating the cooling delay.
Solution Approach 2:
The electric pump is designed to be self-driven by the battery, making the cooling system self-sufficient and not dependent on the engine's operation. This allows the cooling system to function autonomously, providing immediate cooling when needed regardless of engine status.
2Temperature
If water is taken from outside the marine propulsion device and pumped up to the engine, then the engine can be cooled, but it takes time for the engine to be cooled after the engine is started
Solution Approach 1:
The electric pump can be activated before the engine starts operation to pre-cool the engine. This preliminary cooling action ensures that the engine is already at an optimal temperature when started, reducing the overall cooling time and preventing overheating during initial operation.
Solution Approach 2:
By replacing the engine-driven pump with an electric pump, the system gains the ability to perform preliminary cooling actions independent of engine operation, directly addressing the time delay issue.
3Temperature
If an engine-driven water pump is used for cooling, then the cooling system can operate during engine operation, but the system cannot cool the electric motor when the engine is stopped
Solution Approach 1:
The patent replaces the engine-driven mechanical pump with an electric pump powered by a battery. This substitution fundamentally changes the power source from engine-dependent to independent, allowing the cooling system to operate in both engine-on and engine-off conditions, thereby improving adaptability.
Solution Approach 2:
The electric pump-based cooling system serves multiple functions: it can cool the engine during operation, cool the electric motor when the engine is stopped, and provide preliminary cooling before startup. This multi-functionality enhances the system's versatility across different operational states.
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
The solution enables immediate and effective cooling of the electric motor after startup, ensuring the motor is properly cooled and the coolant is efficiently cooled through the heat exchange passage, addressing the delayed cooling issue in electric motor propulsion systems.
Implementation Method 1
Coolant for cooling the electric motor flows through the coolant circulation passage. The cooling passage is disposed through the electric motor.
Implementation Method 2
The heat exchange passage is connected to the first connection passage and disposed through the lower case. The coolant is cooled in the heat exchange passage of the coolant circulation passage.
Data Source
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AI summary
A marine propulsion device includes an electric motor, a propeller shaft, a lower case, a coolant circulation passage, and a pump. The propeller shaft is driven by the electric motor. The lower case houses the propeller shaft. Coolant for cooling the electric motor flows through the coolant circulation passage. The coolant circulation passage includes a cooling passage, a first connection passage, a heat exchange passage, and a second connection passage. The cooling passage is arranged through the electric motor. The first connection passage is connected to the cooling passage and extends from the cooling passage toward the lower case. The heat exchange passage is connected to the first connection passage and arranged through the lower case. The second connection passage is connected to the heat exchange passage and extends from the heat exchange passage to the cooling passage. The pump circulates the coolant through the coolant circulation passage.