Engine Crankcase Partition Wall for Oil Aeration Control
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Solution Overview
Problem
In engines with a lowered cylinder position, the reduced distance between the cylinder's lower end and the oil pan leads to increased oil level variations due to piston movement, causing lubrication failures, increased friction, and reduced fuel efficiency, as air is mixed with oil, resulting in inadequate lubrication performance.
Innovation Solution
The engine design incorporates a crankcase with a partition wall and a communicating hole on the cylinder's side surface, allowing air displaced by the piston to be discharged from the crank chamber through openings in the partition wall, preventing oil level fluctuations and ensuring proper lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the cylinder position is lowered to reduce engine height, then the overall engine height is reduced, but the distance between the cylinder lower end and oil pan decreases causing increased oil level variations and aeration
Solution Approach 1:
The crankcase is divided into a crank chamber and an air discharge chamber by a partition wall. The partition wall includes a first portion and a second portion positioned at different heights, creating segmented spaces that allow air to be discharged separately from the oil pan, preventing aeration while maintaining the lowered cylinder position for reduced engine height.
Solution Approach 2:
The partition wall acts as an intermediary structure between the crank chamber and the air discharge chamber. It includes a first opening for air discharge and a second opening positioned higher than the first opening, mediating the separation of air and oil paths to prevent oil aeration while allowing air to escape from the lowered cylinder configuration.
2Length of stationary object
If the cylinder lower end protrudes into the crank chamber, then engine height is reduced, but air displaced by piston movement mixes with oil in the oil pan causing lubrication failure
Solution Approach 1:
The crankcase is segmented into distinct chambers by a partition wall with different height portions. The first portion of the partition wall allows air discharge at a lower level, while the second portion at a higher level prevents oil from being drawn into the air discharge path, thereby segmenting the air and oil flow paths to eliminate aeration.
Solution Approach 2:
Air is extracted and discharged from the crank chamber through openings in the partition wall before it can mix with oil in the oil pan. The air discharge chamber and openings provide a separate extraction path for air, removing the harmful aeration effect that would otherwise occur with the lowered cylinder configuration.
3Device complexity
If the distance between cylinder lower end and oil pan is reduced, then engine compactness is improved, but pumping loss increases due to air mixing with oil
Solution Approach 1:
The crankcase is segmented into a crank chamber and an air discharge chamber by a partition wall with first and second portions at different heights. This segmentation creates separate flow paths that allow air to be discharged through the first opening while preventing it from mixing with oil, reducing pumping loss in the compact engine design.
Solution Approach 2:
The partition wall serves as an intermediary structure that mediates between the need for compactness (lowered cylinder) and the need to prevent energy loss (air-oil mixing). By providing separate discharge paths at different heights, it enables compact design without the penalty of increased pumping loss.
Data Source
AI summary
An engine includes a crankcase in which a crank chamber that houses a crankshaft is formed, a cylinder block that is attached to the crankcase, and a cylinder that is formed with a sliding surface with respect to a piston. The crankcase includes a partition wall that forms the crank chamber. A lower end of the cylinder protrudes into the crank chamber from a lower end of the cylinder block, and a communicating hole that connects inside and outside of the cylinder is formed on a side surface of the cylinder as viewed in an axial direction of the crankshaft. The partition wall is formed with an opening that is communicated with the communicating hole.