Two-Stroke Exhaust Valve Cleaning via Decompression Passage
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Solution Overview
Problem
Two-stroke engines face challenges in reducing compression during start-up, leading to increased engine starting difficulty and operational inefficiency, while existing decompression systems add cost and complexity, and there is a need for a method to clean exhaust valves during engine operation to prevent coke buildup and sticking issues.
Innovation Solution
A method for cleaning the exhaust valve of a two-stroke internal combustion engine that initiates a cleaning cycle based on predetermined conditions such as time since last cleaning, valve opening rate, throttle valve closure, and engine speed, involving moving the exhaust valve between fully lowered and fully opened positions, and adjusting oil pump supply rates to facilitate cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a decompression system is provided to reduce compression during start-up, then engine starting difficulty is reduced, but cost and complexity of the engine increases
Solution Approach 1:
The exhaust valve utilizes its own operational movements and the existing decompression passage to clean itself during normal engine operation. The valve cycles between opened and closed positions, allowing decompression passage to flush coke deposits away during the opened position, eliminating the need for separate cleaning mechanisms or additional components.
Solution Approach 2:
The decompression passage serves dual functions: it reduces compression during start-up (original function) and simultaneously acts as a cleaning mechanism for the exhaust valve during operation (additional function). The existing decompression system is repurposed to perform both decompression and valve cleaning without requiring separate dedicated systems.
2Reliability
If the exhaust valve is cleaned by cycling it rapidly through various positions, then coke buildup is prevented, but engine efficiency is reduced during cleaning cycles
Solution Approach 1:
The exhaust valve undergoes periodic cycling between opened and closed positions during normal operation. This periodic movement creates intermittent flushing action through the decompression passage that gradually removes coke deposits over time, rather than requiring continuous or rapid cycling that would significantly impact engine efficiency.
Solution Approach 2:
The valve cleaning function is integrated into the continuous normal operation of the engine. The exhaust valve cycles as part of regular engine operation rather than being separated into dedicated cleaning cycles, ensuring that the cleaning action occurs continuously alongside useful engine work without interrupting productivity.
3Ease of operation
If the decompression passage is kept open during operating conditions, then engine starting is facilitated, but operational efficiency is reduced
Solution Approach 1:
The decompression passage dynamically switches between open and closed states based on engine operating conditions. During start-up, the passage remains open to facilitate starting. During normal operation, the passage closes to maintain compression and efficiency, while still allowing periodic valve cleaning through the valve's own cycling movements.
Data Source
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AI summary
A method for cleaning an exhaust valve (100) of a two-stroke internal combustion engine (10) comprising: requesting (206) an exhaust valve cleaning cycle if at least one of a first condition and a second condition is satisfied; initiating (212) the exhaust valve cleaning cycle if at least one of a third condition and a fourth condition is satisfied; and aborting (218) the exhaust valve cleaning cycle if at least one of the at least one of the third and fourth conditions is no longer satisfied; the first condition (202) being a time elapsed since a previous cleaning cycle has been completed being greated than a predetermined time; the second condition (204) being a rate of opening of the exhaust valve being less than predetermined rate; the third condition (208,214) being a throttle valve being closed; and the fourth condition (210,216) being an engine speed being less than a predetermined engine speed.