Circular Wedge Rotor Shaft Connection for Pump Assemblies
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Solution Overview
Problem
Existing pump unit designs face challenges with the attachment of the rotor stack to the rotor shaft, including sensitivity to manufacturing tolerances, temperature variations, and mechanical torque, as well as high production costs and material limitations with conventional press fits, screws, and welding methods.
Innovation Solution
A circular wedge connection is used between the rotor shaft and rotor core, allowing for higher manufacturing tolerances, reduced production costs, and a self-locking torque transmission mechanism, with the option for easy assembly and maintenance, and the ability to handle different materials, including ceramics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a press fit connection is used between rotor shaft and rotor core, then the rotor core can be fixed on the rotor shaft, but small tolerances must be maintained during manufacturing and the connection is sensitive to temperature and mechanical torque
Solution Approach 1:
The connection interface is segmented into a rotor shaft with an outer circular wedge profile and a rotor core with a complementary inner circular wedge profile. This segmentation allows independent manufacturing of each component with relaxed tolerances, as the wedge geometry provides self-aligning and self-compensating features that eliminate the need for tight press-fit tolerances.
Solution Approach 2:
The connection transitions from a rigid press-fit geometry to a wedge-shaped geometry with specific angular parameters. The wedge profiles are designed with angles between 5-15 degrees, creating a mechanical advantage that converts axial insertion force into radial clamping force, thereby compensating for tolerance variations and temperature-induced expansion.
2Reliability
If additional fixing means such as spring washers or cotter pins are used, then the rotor stack can be axially fixed, but production costs increase and additional wearing parts are introduced
Solution Approach 1:
The fixing function is merged into the basic structural components themselves. The rotor shaft and rotor core are each given a wedge profile as an integral feature, eliminating the need for separate fixing elements like spring washers, cotter pins, or keyways. This reduces part count, manufacturing steps, and associated costs while eliminating wearing parts.
Solution Approach 2:
The circular wedge connection is self-fixing through its geometric design. When the rotor core is inserted onto the rotor shaft, the wedge profiles automatically engage and lock, providing axial fixation without requiring additional components. The self-locking nature of the wedge geometry ensures reliable fixing through the operational lifetime.
3Reliability
If a welded connection is used to fix the rotor stack on the rotor shaft, then secure fixing is achieved, but material choice is limited to weldable materials
Solution Approach 1:
The connection replaces thermal welding processes with a mechanical wedge-based system. This substitution allows the use of diverse materials including ceramics, which cannot be welded, alongside metals and other materials. The mechanical wedge profile provides secure fixing through geometric interlocking and friction, independent of material weldability.
4Strength
If a conventional press fit is used, then the rotor core can be attached to the rotor shaft, but the connection area is small and surface pressure is non-uniform due to deformation
Solution Approach 1:
The connection interface utilizes circular curved wedge profiles instead of straight cylindrical surfaces. The curved geometry distributes contact pressure uniformly around the entire circumference, preventing localized stress concentrations and deformation. The circular symmetry ensures homogeneous load distribution and uniform surface pressure across the connection interface.
5Reliability
If the rotor core is designed for secure fixing, then reliable torque transmission is achieved, but assembly and maintenance become more complex
Solution Approach 1:
Instead of using complex multi-component fixing systems that secure the rotor core, the design inverts the approach by making the basic cylindrical components and adding simple wedge profiles. This inverted simplicity achieves secure torque transmission through the wedge's mechanical advantage while maintaining straightforward assembly - the rotor core is simply inserted onto the rotor shaft, where the wedges self-lock.
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 circular wedge connection ensures precise and constant positioning, effective torque transmission, and simplified assembly and maintenance, while accommodating various materials and reducing the risk of wear and tear, and allows for optimal liquid flow and heat transport in wet-running motors.
Implementation Method 1
The circular wedge connection ensures effective torque transmission and a constant press connection over the service life, as it is self-locking when twisted in the clamping direction
Implementation Method 2
a circular wedge connection comprises a wedge-shaped outer circumferential surface of the rotor shaft and a complementary wedge-shaped inner peripheral surface of the rotor core
Implementation Method 3
The use of a circular wedge connection enables tolerances to be compensated for, so that the components can be manufactured with higher tolerances
Implementation Method 4
a circular wedge connection has the advantage over conventional press connections that the connection partners touch over a large area, which is not the case with a press fit due to the deformation that results in non-round connections. Furthermore, a uniform surface pressure along the circumference of the connection is achieved
Data Source
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AI summary
The invention relates to a pump assembly comprising a pump unit and an electric motor driving said pump unit and comprising a rotor (1) having a rotor shaft (2, 3) and a rotor stack (3) fastened thereon. The fastening of the rotor stack (3) on the rotor shaft (2, 3) is performed by means of a circular key joint (5, 6) comprising at least one circular key (5) on the side of the rotor shaft (2, 3) and a complementary circular key (6) on the side of the rotor stack (3).