Crank Member Assembly Fixation via Axial Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for assembling crankshafts and crank members often require fixing halves in the circumferential direction at bearing and toothed surfaces, leading to potential deviations and the need for mechanical after-treatment, whereas the proposed method allows for axial and radial fixation without circumferential fixation, ensuring accurate assembly and reducing the need for such treatments.
Innovation Solution
The method involves fixing crank member halves in axial and/or radial directions using centring elements and locking members, such as I-shaped locking members inserted into recesses, allowing for precise alignment and assembly without circumferential fixation, and optionally using welding or shrinkage fits for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If halves are fixed in circumferential direction at bearing portion and toothed surface, then assembly stability is improved, but manufacturing precision deteriorates due to undesired deviations requiring mechanical after treatment
Solution Approach 1:
The fixation method is segmented into three independent directional components: axial fixation (preventing separation), radial fixation (preventing displacement), and circumferential alignment (ensuring rotational position). This segmentation allows each direction to be optimized independently, with circumferential fixation omitted at sensitive surfaces while maintaining overall assembly stability.
Solution Approach 2:
Different fixation strategies are applied to different locations: at the bearing portion and toothed surfaces, only axial and radial fixation are applied to preserve surface accuracy, while circumferential alignment is achieved through localized features such as keyways or splines at non-critical locations. This local differentiation eliminates the need for mechanical after-treatment at precision surfaces.
2Ease of manufacture
If crank member is composed of two halves, then ease of manufacture is improved, but device complexity increases due to additional fixation requirements
Solution Approach 1:
Multiple fixation functions are merged into integrated features: the same axial slots and locking members that provide axial fixation also contribute to radial positioning, while circumferential alignment is achieved through combined keyway-spline features. This merging reduces the total number of separate components and simplifies the assembly process despite the crank member being split into two halves.
Solution Approach 2:
The locking members and centring elements are designed with multi-functionality: they simultaneously provide axial positioning, radial constraint, and circumferential alignment in certain configurations. This universality reduces the number of separate fixation components needed, thereby reducing assembly complexity while maintaining the manufacturability benefits of the two-half construction.
3Ease of operation
If fixing place is located at axial outer side, then ease of operation is improved by facilitating access, but manufacturing precision may be affected by additional drilling operations
Solution Approach 1:
The axial slots and locking member recesses are pre-formed during the manufacturing process using precision machining or additive manufacturing techniques. This preliminary action ensures that the fixing places are accurately positioned before assembly, eliminating the need for field drilling operations that would compromise precision. The pre-formed features then facilitate easy access during assembly without sacrificing manufacturing accuracy.
Solution Approach 2:
Traditional drilling and tapping operations for creating fixation holes are replaced with pre-formed axial slots and recesses that can be directly received by locking members. This substitution eliminates complex drilling operations at the fixing places, maintaining manufacturing precision while greatly facilitating access during assembly. The locking members themselves may be inserted through simple axial movement rather than requiring precision drilling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures accurate fitting of the crank member halves, eliminating the need for mechanical after-treatment and allowing for easy access and assembly, while accommodating manufacturing tolerances through the selection of appropriate locking members, resulting in a robust and efficient crankshaft assembly suitable for reciprocating piston mechanisms.
Implementation Method 1
The locking member and the recesses may be shaped such that the locking member is inserted by means of pressing, causing the halves to be pressed to each other at the same time
Implementation Method 2
Alternatively, the locking member is inserted into the recesses and shrinked, for example in case of a heat assembly
Implementation Method 3
The applied fixation may comprise welding of the halves at the fixing place
Data Source
AI summary
A method of assembling a crankshaft and a crank member comprises supplying a crankshaft including a crankpin which extends between crank arms, supplying two halves of a crank member, which are fixed to each other about the crankpin such that in assembled condition the crank member is rotatable about the crankpin and comprises a bearing portion having an outer circumferential wall for bearing a big end of a connecting rod and an external crank member gear for driving the crank member about the crankpin, wherein the halves are fitted about the crankpin, hence creating two contact faces at opposite sides of the crankpin, after which both halves are fixed to each other in circumferential direction by means of applying at least a fixation at a fixing place located remote from the bearing portion and the toothed surface of the crank member gear.