Sequential Wiper Heating Control to Limit Inrush Current
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Solution Overview
Problem
The high initial inrush current caused by heating elements with increasing electrical resistivity can damage the protection fuse and deteriorate the electric circuit in wiper systems, leading to inoperative heating modules, especially when multiple heating elements are used in motor vehicle windscreen wiper systems.
Innovation Solution
A control module is implemented to delay the electricity supply to the second heating element compared to the first, using a single electric circuit with heating elements made of materials with increasing resistivity, ensuring that the combined current intensity does not exceed a predetermined limit, thereby preventing fuse damage and allowing safe activation of both heating elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple heating elements are supplied with electricity simultaneously, then the heating function is provided, but the high initial inrush current destroys the protection fuse and deteriorates the electric circuit
Solution Approach 1:
The control module activates heating elements sequentially rather than simultaneously. The first heating element is activated initially, and only after its current stabilizes (when temperature rises and resistivity increases) is the second heating element activated. This preliminary activation sequence prevents the sum of inrush currents from exceeding the fuse rating.
Solution Approach 2:
The heating function is divided into separate activation stages for different heating elements. Instead of treating all heating elements as a single group activated together, the system segments them into individual activation sequences, with each element activated only when previous elements have stabilized their current draw.
2Temperature
If the heating elements are made of metal material with increasing electrical resistivity, then the heating effect is achieved, but the initial electrical resistivity is low causing very high initial current intensity
Solution Approach 1:
The control module waits for the first heating element to undergo its initial temperature rise and resistivity increase before activating the second heating element. This preliminary action allows the system to naturally transition from high current (low temperature) to lower current (high temperature) state before adding the next heating element to the circuit.
3Reliability
If a protection fuse is used to protect the electric circuit, then the components are protected from excessive current, but the fuse is destroyed by the combined initial currents of multiple heating elements
Solution Approach 1:
The control module performs preliminary activation of heating elements one at a time, allowing each element's current to stabilize before activating the next. This sequential preliminary action ensures that the total current never exceeds the fuse's rated capacity, preserving fuse durability while maintaining circuit protection.
4Loss of time
If the heating elements are activated simultaneously, then the heating time is reduced, but the electric circuit is damaged due to excessive current
Solution Approach 1:
The control module implements preliminary sequential activation where each heating element is activated only after the previous one has stabilized. This approach accepts a longer total heating time as a necessary preliminary step to ensure circuit integrity, preventing damage before the full heating function operates.
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 effectively manages the initial high current intensity, preventing damage to the electric circuit and ensuring both heating elements can operate without compromising the protection fuse, thus maintaining the functionality of the wiper system by controlling the activation timing based on measured and predetermined intensity levels.
Implementation Method 1
Each one of the heating elements is designed to heat one of the windscreen wipers... heating modules are generally made of a metal material whose electrical resistivity, and therefore electrical resistance, increase with temperature
Data Source
AI summary
The invention relates to a motor vehicle wiper system comprising:at least two windscreen wipers 12, 22, including a first windscreen wiper 12 and a second windscreen wiper 22, a heating device comprising a first heating element 14 designed to heat the first windscreen wiper 12 and a second heating element 24 designed to heat the second windscreen wiper 22, an electrical supply device designed to supply electricity to the first 14 and second 24 heating elements, anda control module,the wiper system being characterized in that the control module is designed so as to delay, when the heating device is activated, the electricity supply to the second heating element 24 compared to the electricity supply to the first heating element 14, by a pause duration Δt.