Preloaded Shaft Grounding Ring for Low-Resistance Drive Units
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Solution Overview
Problem
Existing shaft grounding devices in motor vehicle electrified drive trains face challenges in maintaining low electrical resistance between rotating shafts and stationary housings, often requiring large contact areas and additional sealing elements, which can increase complexity and cost.
Innovation Solution
A shaft grounding device utilizing an electrically conductive rectangular ring with a wedge-shaped piston and radially preloaded spring to ensure consistent preloading and low contact resistance, integrated into a rectangular groove, allowing for efficient current dissipation between the shaft, sleeve, and housing, with the option of silver coating for reduced resistance and dual functionality as an oil sealing ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger contact area of the contacting on the shaft is used to keep contact resistance low, then electrical grounding effectiveness is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the grounding function and sealing function into a single integrated rectangular ring component. The rectangular ring serves dual purposes: providing electrical grounding through its conductive material and sealing the interface between the shaft and housing. This merging eliminates the need for separate grounding brushes and sealing elements, reducing device complexity while maintaining effective grounding through the ring's substantial contact area with the shaft groove.
2Reliability
If additional sealing elements are added to ensure grounding, then grounding reliability is improved, but manufacturing cost and assembly complexity increase
Solution Approach 1:
The rectangular ring is designed as a multi-functional component that simultaneously performs grounding and sealing functions. The conductive material of the rectangular ring ensures electrical grounding, while its geometric design and interaction with the shaft groove and housing create an effective seal. This universal design eliminates the need for additional sealing elements, reducing manufacturing cost and assembly complexity while maintaining grounding reliability.
3Reliability
If a rectangular ring with preloading device is used to ensure consistent contact, then contact resistance is reduced, but installation space requirement increases
Solution Approach 1:
The preloading device components (piston and base spring) are nested within the rectangular ring groove structure. The piston is positioned within the groove, and the base spring is arranged in the same groove space, creating a compact nested arrangement. This nesting allows the preloading mechanism to be integrated into the existing groove geometry without requiring significant additional installation space, while still providing consistent contact pressure to maintain low contact resistance.
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 solution provides effective electrical grounding with reduced manufacturing and assembly costs, minimal installation space, and dual functionality as an oil sealing ring, ensuring efficient current dissipation and low contact resistance while simplifying the grounding process.
Implementation Method 1
a spring element, in particular a radially preloaded base spring, which are arranged in the rectangular ring groove. The base spring presses the piston against the rectangular ring
Implementation Method 2
the rectangular ring, at rest, axially against the rectangular ring groove and, due to the wedge shape, radially outward against the sealing sleeve and the bearing
Implementation Method 3
an electrically conductive rectangular ring, which is arranged in a rectangular groove formed in the shaft, is provided for establishing an electrical contact to the shaft. The rectangular ring is in electrically conductive contact with the housing via a metallic sleeve
Implementation Method 4
the preloading device includes a piston designed to be wedge-shaped and a spring element. The base spring presses the piston against the rectangular ring, which, in turn, presses the rectangular ring, at rest, axially against the rectangular ring groove and, due to the wedge shape, radially outward against the sealing sleeve and the bearing
Data Source
AI summary
A shaft grounding device (X) for the electrical grounding of a shaft (1) with respect to a housing (2) includes an electrically conductive rectangular ring (4) arranged in a rectangular groove (3) formed in the shaft (1). The rectangular ring (4) is in electrically conductive contact with the housing (2) via a metallic sleeve (5). A preloading device presses the rectangular ring (4) axially against the rectangular ring groove (3) and radially outward against the sleeve (5).