Rail Vehicle Drive Train Grounding Device Input Side Current Diversion
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Solution Overview
Problem
Bearing damage in the transmission units of rail vehicle drive trains due to undesired current flow caused by variable-frequency controls in electric drive machines, which existing grounding devices fail to adequately protect.
Innovation Solution
A drive train design with a grounding device positioned on the input side of the transmission unit, ahead of the first bearing arrangement, to divert harmful currents into the transmission housing, where they can be safely discharged through an electrical coupling with the bogie or chassis frame, thereby preventing damage to the bearing arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grounding device is arranged on the output side of the transmission unit, then the bearing arrangements are protected from current damage, but the housing design becomes more complex requiring labyrinth covers
Solution Approach 1:
The patent inverts the conventional grounding device arrangement by placing it on the input side of the transmission unit instead of the output side. This reversal allows the grounding device to intercept harmful currents before they reach the bearing arrangements, eliminating the need for complex labyrinth covers while maintaining bearing protection.
Solution Approach 2:
The grounding device is positioned upstream (on the input side) to perform preliminary current diversion before the currents can cause damage to the bearing arrangements. This preliminary action prevents the harmful effects from occurring in the first place, rather than attempting to protect the bearings after exposure.
2Reliability
If a grounding ring is fixed on the transmission housing, then current diversion is achieved, but the housing cover requires more complex design
Solution Approach 1:
The grounding device is extracted from the conventional output-side position and relocated to the input side of the transmission unit. This extraction changes the functional architecture, allowing current diversion to occur earlier in the power flow path without requiring modifications to the housing cover design.
3Strength
If metal coupling is used between rotor shaft and input shaft, then torsional stiffness is achieved, but spark erosion and bearing damage occur
Solution Approach 1:
The grounding device acts as an intermediary element that provides a controlled electrical path for harmful currents. It mediates between the metal coupling (which provides torsional stiffness) and the bearing arrangements (which would otherwise suffer from spark erosion), allowing the metal coupling to maintain its mechanical function while the grounding device handles the electrical harmful effects.
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 design effectively prevents bearing damage by diverting interference currents away from the first bearing arrangement, ensuring reliable operation and extending the lifespan of the transmission unit components.
Implementation Method 1
the grounding device is arranged on the input side of the input shaft into the transmission housing in the direction of power flow from the prime mover to the output of the transmission unit in front of the first bearing arrangement
Implementation Method 2
Means for connecting a device for electrical coupling with a spaced-apart connection area
Data Source
Figure 1~3b
Figure 4a~4b
AI summary
The invention relates to a transmission unit and to a drive train (20) for driving a wheel drive shaft or wheel set shaft (26) which is coupled to at least one drive wheel (R) and has a transmission unit of this kind, furthermore has a chassis frame or bogie (21) on which the at least one drive wheel (R)/the drive wheels (R) are mounted, and at least one electrical drive machine (2), wherein the transmission unit (3) is arranged between the drive machine (2) and the drive wheels (21) in the drive power flow. An earthing device (22) is provided between chassis frame or bogie (21) and the wheel drive or wheel set shaft (26). The transmission housing is electrically coupled to the chassis frame or bogie (21) and/or to the drive machine (2) so as to form at least one electrically conductive connection (23, 24).