Small Vehicle Engine Lubrication System Narrow Crankcase Design
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Solution Overview
Problem
The existing lubrication systems for small vehicle engines require a wider lower case to accommodate oil passages, limiting the degree of freedom in arranging the body frame and exhaust system, and making it difficult to secure a suitable bank angle.
Innovation Solution
The lubrication system design includes a crankcase with an upper case coupled to a cylinder barrel and a lower case that supports a crankshaft, featuring a supply source side oil passage extended parallel to the crankshaft axis, a branched oil passage guiding oil upwardly, and an upper case side oil passage communicating with the head side oil passage. This configuration allows for a narrower lower case width by offsetting the oil passage and using a communication passage between the upper and lower cases, with a wider portion and a groove to enhance liquid sealability and prevent gasket entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lower case width is increased to accommodate the oil passage arrangement, then the oil passage can be properly connected to the head side oil passage, but the degree of freedom in arranging the body frame and exhaust system is reduced and the bank angle becomes difficult to secure
Solution Approach 1:
The oil passage is arranged in a three-dimensional configuration rather than a simple linear planar arrangement. The branched oil passage extends upwardly from the lower case, connects to the upper case side oil passage through a communication passage, and then connects to the head side oil passage. This vertical and lateral routing in multiple dimensions allows the oil passage to fit within a narrower lower case width while maintaining proper connectivity.
Solution Approach 2:
The communication passage is formed within the coupled surfaces of the upper case and lower case, utilizing the existing structural space between the two cases. The groove and liquid gasket arrangement nests the sealing mechanism within the coupled surface geometry, preventing gasket entry while maintaining the passage function without requiring additional external space.
2Adaptability or versatility
If the lower case width is reduced to increase arrangement freedom, then the bank angle can be secured and body frame arrangement is improved, but the oil passage connection becomes difficult to maintain
Solution Approach 1:
The oil passage utilizes vertical and lateral routing in three dimensions rather than requiring horizontal space in a single plane. The branched oil passage extends upwardly from the lower case, connects to the upper case side oil passage through a communication passage, and then connects to the head side oil passage. This multi-dimensional routing enables proper oil passage connection within a narrower lower case width.
Solution Approach 2:
The oil passage is divided into multiple segments: the supply source side oil passage in the lower case, the branched oil passage extending upwardly, the communication passage through the coupled surfaces, and the upper case side oil passage connecting to the head side oil passage. This segmentation allows each segment to be optimized for its specific spatial requirements, enabling the overall system to fit within a narrower case width while maintaining proper connectivity.
3Length of moving object
If a communication passage is formed between upper and lower cases, then the oil passage can be offset to reduce lower case width, but liquid sealability must be maintained and gasket entry prevented
Solution Approach 1:
The coupled surfaces of the upper case and lower case are designed with different local properties: a wider portion containing the communication passage for oil flow, and a groove structure for sealing. The liquid gasket is applied specifically to the groove portion, creating a seal that prevents gasket entry into the communication passage while allowing the passage itself to function for oil communication. This local differentiation of structure and function resolves the contradiction between passage formation and sealability.
Solution Approach 2:
The groove structure acts as an intermediary element between the communication passage and the liquid gasket. The groove receives and contains the liquid gasket, preventing it from entering the communication passage while still allowing the passage to function for oil communication. This intermediary groove structure maintains liquid sealability without compromising the passage function or requiring increased case width.
Data Source
AI summary
A lubrication system of a vehicle engine wherein a cylinder head has a head side oil passage disposed at one end thereof along the axis of a crankshaft. A lower case of a crankcase is provided with a supply source side oil passage communicating with an oil supply source and extending parallel to the axis of the crankshaft and a branched oil passage guiding oil to the head side oil passage which branches from the supply source side oil passage and extends upwardly. An upper case side oil passage extending vertically to communicate with a head side oil passage is provided at one end of an upper case along the axis of the crankshaft. A communication passage communicating the upper end of a branched oil passage is provided in a lower case in a position inwardly from the upper case side oil passage along the axis of the crankshaft.