Split Crankcase Engine with Integrated Transmission Case
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Solution Overview
Problem
Conventional engine units with split crankcases for enhanced rigidity are complex in structure, and there is a need for a simpler design that maintains or improves rigidity while allowing for easier assembly and disassembly.
Innovation Solution
A split crankcase engine design where the crankcase is divided into two parts along the crankshaft axis, with a transmission case that can also be split, allowing for unitary members to support both the driving and driven pulley shafts, providing enhanced rigidity without a complicated structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional engine unit uses a split crankcase with multiple bearing bosses and a rear case bracket to enhance rigidity, then the rigidity of the engine unit is improved, but the structural complexity increases
Solution Approach 1:
The patent combines the transmission case and rear case into a single integrated rear case assembly. The transmission case houses both the driving pulley shaft and driven pulley shaft, eliminating the need for separate rear case brackets and multiple bearing bosses. This merging of components maintains engine unit rigidity while significantly simplifying the overall structure.
Solution Approach 2:
The integrated rear case serves multiple functions: it acts as the transmission case housing, provides bearing supports for both driving and driven pulley shafts, and functions as the rear case structure. This multi-functional design replaces the conventional separate components (rear case bracket, transmission case, multiple bearing bosses), reducing structural complexity while maintaining rigidity.
2Ease of manufacture
If the crankcase is split into two parts along the crankshaft axis for assembly purposes, then the ease of assembly is improved, but the rigidity of the engine unit deteriorates
Solution Approach 1:
By merging the transmission case and rear case into a single integrated assembly, the patent creates a more rigid structure that spans across the crankcase splitting plane. This integrated assembly acts as a unifying element that connects the left and right crankcase halves, providing structural reinforcement that compensates for the crack introduced by the split crankcase design.
Solution Approach 2:
The integrated rear case assembly extends in multiple dimensions, creating a three-dimensional structural framework that reinforces the engine unit. The assembly includes vertical walls, horizontal floors, and side panels that work together to provide rigidity in multiple directions, counteracting the potential weakness from the crankcase split.
Data Source
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AI summary
An engine (2) includes a crankshaft (40), and a speed changer (60) having a driving pulley shaft (62) and a driven pulley shaft (64) includes a crankcase (20) which can be split on a splitting plane passing along an axis (P1) of the crankshaft (40), and a transmission case (30). In the engine (2), the transmission case (30) has members (30a) and (30b) unitarily formed while including a driving-side pivot supports (33a) and (33b) for pivotally supporting the driving pulley shaft (62) and a driven-side pivot supports (34a) and (34b) for pivotally supporting the driven pulley shaft (64). One part 20a of the crankcase (20) from the splitting plane is combined with a section among the members (30a) and (30b) of the transmission case (30). The other part (20b) of the crankcase from the splitting surface is combined with another section among the members (30a) and (30b) of the transmission case.