Relay Contact Oxide Layer Removal via High Voltage Arcing
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Solution Overview
Problem
Existing electromotive adjusting devices in motor vehicles face issues with relay contact wear and overheating due to arc formation and oxide layer buildup, leading to reduced reliability and increased material costs.
Innovation Solution
A method for operating an electromotive adjusting device that switches relays based on specific conditions to prevent arc formation and oxide layer buildup, using semiconductor switches to manage current flow and voltage, and employing silver tin oxide contacts to reduce material costs while maintaining reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver contacts are used to maintain low contact resistance, then electrical conductivity is improved, but oxide layer formation increases due to chemical reaction with ambient air
Solution Approach 1:
The patent converts the harmful oxide layer formation into a beneficial cleaning mechanism. By periodically applying high voltage across the contacts, the oxide layers are burned off through arc discharge, transforming the harmful oxidation process into a useful self-cleaning function that restores low contact resistance.
Solution Approach 2:
The patent implements periodic cleaning cycles where high voltage is applied across the contacts at predetermined intervals. This periodic action prevents permanent oxide buildup by regularly removing it, maintaining reliable electrical connection without requiring expensive alternative materials.
2Ease of operation
If relay switching is performed with current flow across contacts, then circuit control is achieved, but arc formation occurs causing contact burn-up and reduced service life
Solution Approach 1:
The patent applies preliminary action by performing contact cleaning before the oxide layer becomes too thick to affect performance. The control unit monitors operating conditions and triggers cleaning cycles proactively, preventing the accumulation of harmful oxide layers before they cause significant resistance increases.
Solution Approach 2:
The patent implements feedback control where the control unit monitors various parameters (operating time, switching frequency, current load) and adjusts the cleaning cycle timing accordingly. This feedback mechanism optimizes the balance between maintaining contact quality and minimizing unnecessary cleaning operations.
3Reliability
If gold contacts are used to prevent chemical reaction with ambient air, then reliability is improved, but material costs increase significantly
Solution Approach 1:
The patent uses inexpensive silver contacts instead of expensive gold contacts, accepting that the contacts will degrade over time through oxidation. However, the periodic cleaning mechanism effectively resets the contact condition, extending the functional life of the cheap contacts to match or exceed that of expensive gold contacts.
Solution Approach 2:
The patent changes the electrical parameters during operation by switching between normal operating voltage and high cleaning voltage. This parameter change enables the same silver contacts to serve dual functions: efficient power transmission during normal operation and self-cleaning during maintenance cycles, eliminating the need for expensive gold plating.
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 method extends the service life of relays, reduces burn-up, and allows the use of cost-effective materials by effectively managing contact interactions and preventing arc formation and oxide layer growth, thereby improving the reliability and reducing production costs of electromotive adjusting devices.
Implementation Method 1
the electric motor is operated by pulse width modulation (PWM), and therefore sets the supplied electrical energy
Implementation Method 2
an electrical output of the electric motor can be routed either to ground or to the potential of the on-board electrical system, usually 12 volts, by a relay
Implementation Method 3
If the relay is opened in the event of an electric current flow across its contacts, it is possible for an arc to form between the two contacts
Implementation Method 4
This leads to heating of the relay when the contacts are closed, on account of the increased electrical resistance
Data Source
AI summary
A method operates an electromotive adjusting device of a motor vehicle. The adjusting device contains a relay which has two contacts. The relay is switched by an electric current flow across the contacts or by an electrical voltage drop between the contacts given a first condition. The relay is switched without an electric current flow across the contacts or without an electrical voltage drop between the contacts given a second condition. An electromotive adjusting device of a motor vehicle, in particular an electromotively operated tailgate, contains such a relay which has two contacts.