Lower Link Bolt Fastening Without Crankshaft Rotation
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Solution Overview
Problem
The complex and time-consuming process of fastening bolts for lower links in a multi-link-type piston crank mechanism requires multiple rotations of the crankshaft and precise axial force control, making the assembly of the multi-link-type piston crank mechanism inefficient.
Innovation Solution
A method involving holding the cylinder block in an inverted position, lifting the crankshaft, and using nut runners to fasten bolts from opposite directions without rotating the crankshaft, allowing for efficient assembly by centering the crank pins and maintaining the bolts' heads in a right and left direction, eliminating the need for crankshaft rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the crankshaft is rotated multiple times to fasten bolts for lower links in different cylinder sections, then all crank pins can be positioned for fastening, but the number of operations increases significantly and assembly time is extended
Solution Approach 1:
The lower links are preliminarily positioned on the crank pins before the crankshaft rotation, and the cylinder block is inverted to bring all crank pins to accessible positions. This preliminary arrangement allows all bolts to be fastened without rotating the crankshaft during the fastening process, thereby reducing the number of rotation operations from tens of times to essentially zero times during bolt fastening.
Solution Approach 2:
Instead of rotating the crankshaft to bring different crank pins to the fastening position, the cylinder block is inverted so that all crank pins are already in accessible positions from the start. This inversion approach reverses the conventional sequence of operations, allowing parallel access to all crank pins simultaneously and eliminating the need for repeated crankshaft rotations.
2Productivity
If multiple rotation operations are performed to position crank pins for fastening, then all lower links can be assembled, but the operational complexity and number of steps increase
Solution Approach 1:
The lower links are preliminarily positioned on the crank pins and the cylinder block is inverted before the fastening operation begins. This preliminary setup ensures that all crank pins are in accessible positions and all lower links are correctly oriented, allowing the fastening process to proceed in a single sequence without intermediate rotation steps, thereby simplifying the overall process complexity.
3Manufacturing precision
If the crankshaft is rotated to position each crank pin for fastening, then proper alignment is achieved, but the number of rotation operations reaches a few tens of times
Solution Approach 1:
The lower links are preliminarily positioned on the crank pins with proper alignment before the fastening operation. The preliminary positioning ensures that the crank pins are correctly aligned with the lower links, eliminating the need for repeated rotation operations to achieve proper alignment during fastening. This maintains manufacturing precision while dramatically simplifying the operation.
Data Source
AI summary
A jig (31) is placed on a cylinder block (11) set in an inverted position, and a crankshaft (5) is lifted upward from a main bearing part (17) and held at a predetermined height position. A lower link (7) temporarily fitted to a crank pin (6) in the previous step is rotated about the crank pin (6) as a center by a robot hand, and held in a predetermined inclined position in which a dividing surface (28) becomes vertical. In this state, a pair of bolts (29) is horizontally fastened from the right and the left by using a nut runner (55).