Engine Spark Plug Pipe Sealing with Annular Projection
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Solution Overview
Problem
Existing engine designs for straddle-type vehicles, such as motorcycles, require complex arrangements for sealing around the spark plug, including concave grooves and O-rings, which complicate the sealing process.
Innovation Solution
The engine incorporates a pipe surrounding the spark plug with an annular projection that divides the space between the pipe and the surrounding wall into subspaces, using a liquid gasket in one subspace to enhance sealing, and a tapered inner periphery to improve seal quality, along with a seal member between the head cover and pipe to prevent movement and ensure a secure seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a concave groove and O-ring are provided to seal between the plug tube and support cylindrical part, then sealing is achieved, but the arrangement becomes complicated
Solution Approach 1:
The invention extracts the sealing function from the mechanical groove-O-ring arrangement and transfers it to a liquid gasket contained in the pipe. The liquid gasket is introduced into the space between the pipe outer periphery and surrounding wall inner periphery, eliminating the need for concave grooves and O-rings while maintaining reliable sealing.
Solution Approach 2:
The invention replaces the mechanical sealing system (groove and O-ring) with a liquid-based sealing system. The liquid gasket flows into and fills the sealing space, creating an effective seal without requiring mechanical grooves or elastomeric O-rings, thereby simplifying the overall arrangement.
2Ease of manufacture
If the pipe is pressed against the first surrounding wall portion, then sealing is provided, but additional seal structures are needed to ensure reliability
Solution Approach 1:
The invention employs a composite sealing approach combining mechanical pressing of the pipe against the first surrounding wall portion with a liquid gasket in the sealing space. This composite sealing system leverages both mechanical contact and liquid filling to achieve reliable sealing while maintaining ease of manufacture.
Solution Approach 2:
The liquid gasket acts as a cushioning element that compensates for any gaps or irregularities in the mechanical pressing arrangement. By introducing the liquid gasket beforehand into the sealing space, the system ensures reliable sealing even if the mechanical pressing alone is insufficient.
3Reliability
If the annular projection divides the space into subspaces, then the liquid gasket is contained and sealing is improved, but the pipe structure becomes more complex
Solution Approach 1:
The annular projection segments the space between the pipe and surrounding wall into distinct subspaces. This segmentation contains the liquid gasket within specific regions, preventing its migration and ensuring it remains positioned to provide effective sealing at critical interfaces.
Solution Approach 2:
The annular projection acts as an intermediary structure within the pipe that facilitates the containment and positioning of the liquid gasket. By introducing this intermediate element, the system achieves reliable liquid gasket containment with minimal additional complexity.
Data Source
AI summary
An engine of a straddle-type vehicle includes a seal between a surrounding wall and a pipe. A cylinder head includes a first surrounding wall portion and a second surrounding wall portion. One end of the pipe is pressed in against the first surrounding wall portion. The second surrounding wall portion is located more distant from an attachment portion than the first surrounding wall portion is, and has an inner diameter larger than that of the first surrounding wall portion. The pipe includes an annular projection. The annular projection projects from the outer periphery of the pipe, and divides a space defined by the outer periphery of the pipe and the inner periphery of the second surrounding wall portion into subspaces arranged in an axial direction of the pipe when the one end of the pipe is pressed in against the first surrounding wall portion.