Integrated Gear Case Layout for Engine Crankshaft Twist Reduction
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Solution Overview
Problem
The arrangement of a flywheel and a gear train across a cylinder block in engine devices leads to twist in the crankshaft, causing increased torsional vibration and noise due to the distance between the flywheel's high moment of inertia and the crank gear's position.
Innovation Solution
Integrally forming housing bracket portions on the cylinder block to create a gear case that accommodates the gear train alongside the flywheel, reducing twist by aligning the flywheel and gear train on the same end portion of the crankshaft, and incorporating a weight-reduction space and ribs within the flywheel housing for strength and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the flywheel and gear train are arranged on opposite sides of the cylinder block, then the structural layout is simplified, but the crankshaft twist increases due to the large distance between the flywheel and crank gear
Solution Approach 1:
The patent transitions from a linear arrangement (flywheel and gear train on opposite sides along the crankshaft axial direction) to a spatial arrangement (both on the same side within a gear case). This dimensional reorganization reduces the axial distance between components while maintaining functional separation, thereby reducing crankshaft twist without significantly increasing overall structural complexity.
Solution Approach 2:
The gear train is nested within the gear case that is positioned on the same side as the flywheel. This nesting allows the gear train to be accommodated in the radial direction rather than requiring axial separation, thus reducing the distance between the crank gear and flywheel while keeping the structural layout manageable.
2Stability of the object's composition
If the flywheel and gear train are arranged on the same end portion of the crankshaft, then the crankshaft twist is reduced, but the gear case becomes more complex requiring additional housing bracket portions
Solution Approach 1:
The housing bracket portions are merged with the cylinder block to form an integrated structure. This combination eliminates the need for separate bracket components, simplifying the gear case structure while still providing the necessary support for the gear train on the same side as the flywheel.
Solution Approach 2:
The cylinder block is given multiple functions: it serves as both the main structural component and as the mounting base for the housing bracket portions that support the gear case. This multi-functionality reduces the number of separate components needed, simplifying the overall gear case structure.
3Strength
If the flywheel housing is made robust to accommodate the gear train, then the structural strength is improved, but the weight of the housing increases
Solution Approach 1:
The flywheel housing employs local quality by varying wall thickness in different regions: thicker walls in areas requiring high strength (such as mounting surfaces and load-bearing sections) and thinner walls in non-critical areas. This approach maintains necessary structural strength while minimizing overall weight.
Solution Approach 2:
The housing bracket portions are segmented and integrally formed with the cylinder block, allowing each segment to be optimized for its specific function. This segmentation enables the housing to achieve necessary strength through strategic material placement rather than uniform thickening, thus reducing overall weight.
Data Source
AI summary
An engine device having a flywheel housing (7) in which a flywheel that is rotated integrally with a crankshaft (5) is accommodated on one side portion (303) of a cylinder block (6), in which the cylinder block (6) is integrally formed with housing bracket portions (304) each protruding in a direction away from the crankshaft (5) from each of opposite side portions (301) of the cylinder block (6) extending along a crankshaft axial direction (300), the housing bracket portions (304) protruding from end portions of the opposite side portions (301) close to the one side portion (303) A space surrounded by the one side portion (303), the housing bracket portions (304), and the flywheel housing (7) constitutes a gear case (330) for accommodating therein a gear train.