Vehicle Misfire Diagnosis Using Acceleration Thresholds
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Solution Overview
Problem
Existing misfire diagnosis methods often misdiagnose engine issues due to variations in crankshaft angular velocity, especially on rough roads, leading to unnecessary torque restriction and engine damage.
Innovation Solution
A system and method that utilize a rotational angular velocity sensor and an acceleration sensor to diagnose misfires, with a threshold setting unit that adjusts acceleration thresholds based on test environments with and without forced misfires to minimize misdiagnosis rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If misfire diagnosis is performed only by variation in angular velocity of the crankshaft, then the diagnosis system is simple, but misfire misdiagnosis occurs on rough roads
Solution Approach 1:
The patent introduces acceleration sensors as intermediary devices that detect road surface conditions and serve as a mediator between the crankshaft angular velocity measurements and the final misfire diagnosis. The acceleration sensor data acts as a contextual indicator that helps distinguish between angular velocity variations caused by rough roads versus those caused by actual misfires, thereby improving diagnosis reliability without substantially increasing system complexity
Solution Approach 2:
The patent changes the diagnostic parameters by incorporating acceleration threshold comparisons alongside angular velocity analysis. By monitoring acceleration parameters and comparing them against thresholds, the system adapts its diagnosis criteria based on road conditions, allowing it to differentiate between false misfire indications from rough roads and genuine misfire events, thus improving reliability
2Measurement precision
If acceleration threshold is set low to detect rough roads, then rough road detection sensitivity is high, but misfire misdiagnosis rate increases
Solution Approach 1:
The patent implements dynamic threshold adjustment where the acceleration threshold is not fixed but adaptively modified based on engine operating conditions such as load, speed, and combustion state. This dynamic approach allows the system to maintain high sensitivity for rough road detection under appropriate conditions while adjusting thresholds to prevent misfire misdiagnosis when engine parameters indicate normal operation, thereby balancing both detection sensitivity and diagnostic accuracy
Solution Approach 2:
The system performs preliminary assessment of engine operating parameters before finalizing misfire diagnosis. By pre-evaluating conditions such as engine load, RPM, and combustion characteristics, the system can determine whether to apply strict acceleration thresholds for rough road detection or more lenient thresholds to avoid misdiagnosis, thus preparing the diagnostic criteria in advance based on current engine state
3Device complexity
If misfire diagnosis is performed on rough roads without additional sensors, then the system is simple, but unnecessary torque restriction occurs
Solution Approach 1:
The acceleration sensor serves as an intermediary that provides road condition information to prevent spurious misfire diagnoses. By incorporating this mediator, the system can distinguish between angular velocity variations from rough roads and those from actual misfires, avoiding unnecessary torque restriction and maintaining engine productivity while still protecting against genuine misfire events
Solution Approach 2:
The system implements feedback mechanisms where acceleration sensor data continuously informs the misfire diagnosis process. This feedback loop allows the system to adjust its diagnosis decisions in real-time based on road conditions, preventing unnecessary torque restriction when acceleration patterns indicate rough road conditions rather than misfire, thus maintaining engine output while still providing protection when needed
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
Prevents misfire misdiagnosis on rough roads, reducing unnecessary torque restriction and improving engine durability by accurately distinguishing between rough road conditions and actual misfires.
Implementation Method 1
an acceleration sensor acquiring an acceleration according to vertical vibration of a vehicle
Implementation Method 2
a rotational angular velocity sensor acquiring an angular velocity of an engine
Data Source
AI summary
A system for the misfire diagnosis includes an angular velocity sensor acquiring an angular velocity of an engine and an acceleration sensor acquiring an acceleration according to vertical vibration of a vehicle. A diagnosis unit is configured to compare the acceleration with an acceleration threshold to determine whether the vehicle is driven on a rough road and to diagnose whether misfire occurs. A threshold setting unit is configured to acquire misfire diagnosis results in a first test environment in which the vehicle is driven on the rough road without forcible misfire and in a second test environment in which the vehicle is driven on the rough road while the forcible misfire occurs. The threshold setting unit is further configured to calculate a misfire misdiagnosis rate and to update the acceleration threshold.