Controllable Resistive Load for Relay Current Maintenance
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Solution Overview
Problem
In motor vehicle electrical architectures, the existing solutions for ensuring a minimum current in relays to prevent fouling of contact points are inefficient, leading to high power dissipation, increased costs, and heat management issues, particularly in the engine compartment.
Innovation Solution
A controllable resistive load is introduced in parallel with the relay, controlled by a computer to ensure a minimum current of at least 500 mA when the relay opens, using a switch in series with a resistor, activated only when the vehicle is stationary to minimize power dissipation and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistive load is added to ensure minimum current in the relay, then the relay contact fouling is prevented, but the power dissipation and heat generation increase
Solution Approach 1:
The patent applies dynamics by making the resistive load controllable rather than permanent. The load is activated only when the relay is about to open (when current drops below threshold) and deactivated when current is sufficient, creating a dynamic system that adapts to real-time conditions. This resolves the contradiction by providing relay protection only when needed, eliminating continuous power dissipation.
Solution Approach 2:
The system uses the relay's own current consumption characteristics to trigger the resistive load activation. When the relay current naturally drops below the threshold, the system automatically activates the load to restore minimum current, and when current is sufficient, it deactivates the load. This self-regulating mechanism prevents relay fouling without requiring external monitoring or continuous power consumption.
2Duration of action of stationary object
If a resistive load is continuously activated to maintain minimum relay current, then relay longevity is extended, but the heat management in the engine compartment becomes difficult
Solution Approach 1:
The patent implements periodic action by activating the resistive load only during specific periods when the relay current drops below the threshold and deactivating it when current is sufficient. This intermittent operation provides the necessary current for relay contact maintenance while significantly reducing overall heat generation compared to continuous operation, thus resolving the heat management issue in the confined engine compartment.
3Reliability
If a resistive load is added to the electrical architecture, then the minimum current threshold is maintained, but the device complexity and cost increase
Solution Approach 1:
The patent merges the resistive load control functionality with the existing computer (BSI/VSM/BCM) that already controls vehicle electrical systems. The computer monitors relay current and activates/deactivates the resistive load through existing control circuits, eliminating the need for separate dedicated control hardware. This integration maintains minimum current reliability while minimizing additional device complexity and cost.
4Loss of energy
If the resistive load is activated only when the vehicle is stationary, then the power dissipation is minimized, but the relay current may be insufficient during vehicle motion
Solution Approach 1:
The patent uses feedback by continuously monitoring the relay current and comparing it to a predetermined threshold. When the current drops below the threshold (regardless of vehicle motion state), the resistive load is activated to restore minimum current. When current is sufficient, the load is deactivated. This feedback mechanism ensures relay current sufficiency is maintained based on actual conditions rather than fixed vehicle state assumptions, resolving the contradiction between energy minimization and reliability.
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 extends the longevity of the relay, reduces power dissipation and CO2 emissions, and avoids excessive heating in the engine compartment, while maintaining system stability through hysteresis in the control logic.
Implementation Method 1
a controllable resistive load arranged in parallel with the relay and comprising a switch in series with a resistor, the switch being adapted to be controlled by the computer
Data Source
AI summary
Disclosed is a motor vehicle electrical architecture comprising a supply switched by a relay. The architecture comprises a controllable resistive load (60) ensuring a consumption of, for example at least 500 mA, connected at the output of said relay and controlled by a computer (30) according to a control law. The controlled resistive load is only activated when the speed of said vehicle is zero, or very close to 0. This makes it possible to limit the duration of supply of the resistive load, and consequently the heat dissipation, electrical consumption and CO2 emissions over the duration of travel, while ensuring consumption at the switched supply voltage in the phases where the driver is likely to cut the ignition and thus cause the relay to open.