Electric Machine Drive Train Assembly With Access-Window Bearing Fit
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Solution Overview
Problem
Conventional drive trains for electric machines, such as wind turbines, face challenges in achieving increased stiffness while maintaining cost-effectiveness, as single-piece housings require expensive tapered roller bearings for assembly.
Innovation Solution
A method and design for assembling a drive train using a single-piece housing with spherical roller bearings, employing a bolted joint connection and access window for maintainability, allowing the use of less expensive spherical rolling bodies and maintaining conventional bearing designs and assembly tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single-piece housing is used to improve stiffness, then the stiffness of the drive train is improved, but the cost increases due to the requirement of expensive tapered roller bearings
Solution Approach 1:
The patent changes the bearing type parameter from tapered roller bearings to spherical roller bearings, and modifies the assembly method by introducing thermal expansion parameters (heating the housing and bearing to enable assembly). This allows achieving the stiffness benefit of single-piece housing while using more cost-effective spherical roller bearings that can be assembled with the hot-fitting method
Solution Approach 2:
The patent segments the bearing assembly process into multiple steps: heating the housing, heating the bearing, assembling the bearing to the shaft, then cooling and contracting. This segmentation of the assembly process enables the use of spherical roller bearings with a single-piece housing, resolving the contradiction between stiffness and manufacturing cost
2Weight of stationary object
If a single-piece housing is used to reduce weight, then the weight of the main frame is reduced, but the manufacturing complexity increases due to assembly constraints
Solution Approach 1:
The patent utilizes thermal expansion parameters by heating both the housing and bearing to elevated temperatures, allowing the bearing to be fitted onto the shaft. After assembly, the components are cooled, causing thermal contraction that secures the bearing in place. This thermal parameter change enables simplified single-piece housing design without increasing assembly complexity
Solution Approach 2:
The patent applies preliminary heating action to both the housing and bearing before assembly. This preliminary thermal preparation creates the necessary clearance and fit conditions for easy assembly, then the reverse action (cooling) automatically secures the components, reducing overall assembly complexity despite the single-piece housing design
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
The solution enhances the stiffness of the drive train, reduces the weight of the main frame, and decreases the number of bolts in the housing/main frame interface, while maintaining cost-effectiveness and allowing for easy access and maintainability throughout the drive train's lifespan.
Implementation Method 1
mounting the front bearing to the shaft by temporarily heating the front bearing and shifting the same to a front position at the shaft
Data Source
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Figure 5
AI summary
It is described a drive train (1) for an electric machine (18). The drive train (1) comprises a shaft (2). The shaft (2) has a front end and a rear end and which is supported in a housing (3) via a front bearing (4) and a rear bearing (5), wherein the front bearing (4) comprising a front bearing outer ring (41) and a front bearing inner ring (42), and the rear bearing (5) comprising a rear bearing outer ring (51) and a rear bearing inner ring (52). The drive train (1) comprises a first cover (6) mounted to the housing (3) and being configured to seal a rear side of the front bearing (4), wherein the first cover (6) is mounted to the housing (3) by an auxiliary support (9) which connects the first cover (6) to the housing (3), a second cover (7) mounted to the housing (3) and being configured to seal a front side of the rear bearing (5), a third cover (8) mounted to the housing (3) and being configured to seal a rear side of the rear bearing (5), wherein the rear bearing outer ring (51) is compressed by the second and third covers (7, 8). The housing (3) is a single-piece housing and comprises an access window (15) between the first and second covers (6, 7).