Diagnosing Relay-Controlled Fan Degradation via Current Differential
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Solution Overview
Problem
Existing methods for diagnosing multiple-speed engine cooling fan systems, particularly relay-controlled and variable speed systems, face limitations due to lack of smart controllers and interference from other electrical loads, leading to inaccurate fan degradation detection.
Innovation Solution
A diagnostic method that measures the change in current drawn from the battery-alternator system during stable vehicle conditions, comparing the difference in current before and after fan speed modifications to an expected change, and indicating degradation if the absolute error exceeds a threshold, without requiring additional hardware or sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If current measurement is performed to diagnose fan degradation, then diagnostic capability is improved, but measurement precision deteriorates due to interference from other electrical loads
Solution Approach 1:
The patent extracts the fan current measurement from the total system current by using differential measurement. It measures the current before and after fan activation, then calculates the difference to isolate the fan's current consumption, thereby eliminating interference from other electrical loads.
Solution Approach 2:
The patent performs preliminary current measurement before activating the fan to establish a baseline. This preliminary action allows the system to later compare the baseline with post-activation current to determine fan degradation, separating the measurement process from the interference of other loads.
2Adaptability or versatility
If multiple relays are used to control fan speeds, then fan speed control capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing relays serve dual purposes: their primary function of controlling fan speeds and their secondary function as diagnostic indicators. By monitoring the current draw through these existing relays, the system performs self-diagnosis without requiring additional sensors or controllers, thereby maintaining versatility while reducing complexity.
3Measurement precision
If additional sensors or hardware are added to improve diagnostic accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent enables the existing battery-alternator system and current draw measurements to serve diagnostic purposes. By analyzing the current consumption patterns of existing components, the system achieves accurate fan degradation detection without requiring additional sensors, maintaining measurement precision while avoiding increased hardware complexity.
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
Enables accurate diagnosis of cooling fan degradation in multiple-speed systems operated by relay-controlled motors, minimizing costs and reducing errors by stabilizing other electrical loads during diagnosis, thus ensuring reliable detection of fan malfunctions.
Implementation Method 1
measuring the change in current drawn from a battery-alternator system as fan speeds are varied
Implementation Method 2
multiple speed relay-controlled electric fan
Data Source
AI summary
Methods and systems are described for diagnosing a multiple speed, relay controlled engine cooling fan system. One method includes measuring the change in current drawn from a battery-alternator system when fan speed is modified. A degradation in cooling fan operation is flagged when measured current change differs from an expected change.