Split Crankcase Central Support Torque Isolation
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Solution Overview
Problem
Internal combustion engines with split crankcases face challenges in supporting the central portion of the crankshaft while minimizing torque applied to the crankcase due to force transfer from the crankshaft, particularly in high-power engines.
Innovation Solution
The design includes a crankshaft support with apertures that are coaxial with the crankshaft axis, fastened to the cylinder block and cylinder head using fasteners perpendicular to the crankshaft axis, which reduces torque transmission by distributing the forces across multiple planes, thereby providing adequate support to the central crankshaft portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate central crankshaft support is fastened to one of the two crankcase portions using fasteners perpendicular to the split plane, then the central portion of the crankshaft is supported, but torques are applied to the crankcase due to force transfer from the crankshaft
Solution Approach 1:
The crankcase is divided into two separate portions (first and second crankcase portions) that are joined along a plane containing the crankshaft axis. This segmentation allows each portion to independently support end portions of the crankshaft, while the central support is provided separately, distributing the support functions and reducing torque transmission to the crankcase structure.
Solution Approach 2:
A crankshaft support component acts as an intermediary element between the crankshaft and the crankcase portions. This intermediate structure provides the necessary central support for the crankshaft while isolating the crankcase from direct torque forces, as the support can be designed to accommodate rotational forces without transmitting them to the crankcase walls.
2Ease of manufacture
If the crankcase is split along a plane perpendicular to the crankshaft axis between the two cylinders, then casting is facilitated, but the central portion of the crankshaft requires additional support in high power engines
Solution Approach 1:
The crankcase is segmented into two castable portions that can be manufactured separately and then joined. This segmentation facilitates the casting process by allowing each portion to be formed independently, while the joining plane is positioned to accommodate the crankshaft support structure, balancing manufacturing ease with structural requirements.
Solution Approach 2:
The crankshaft support structure serves multiple functions: it provides central support for the crankshaft, acts as a joining element between the two crankcase portions, and can incorporate bearing surfaces and alignment features. This multi-functionality reduces the need for additional separate components, simplifying the overall structure despite the split crankcase design.
Data Source
AI summary
An internal combustion engine has a crankcase having a first crankcase portion fastened to a second crankcase portion along a first plane, a crankshaft, a cylinder block defining two cylinders, two pistons, and a cylinder head. A crankshaft support defines a crankshaft support aperture. A central portion of the crankshaft is received in the crankshaft support aperture. At least one fastener fastens the crankshaft support to the cylinder block. The at least one fastener is perpendicular to a crankshaft axis and is disposed in a second plane. The crankshaft axis is normal to the first plane. The second plane is one of coplanar with and parallel to the first plane.