Venturi Tube Probe for Engine Misfire Detection
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Solution Overview
Problem
Existing methods for detecting engine misfires in multi-cylinder engines are difficult to use and lack accuracy due to the interference of resonant frequency fluctuations in the exhaust system, making it hard to distinguish and amplify the negative pulses indicative of incomplete combustion.
Innovation Solution
A probe with a Venturi tube placed in the exhaust stream, coupled with a pressure sensor, generates a voltage signal that filters out unwanted fluctuations and amplifies the negative pulses, allowing for accurate detection of misfiring cylinders by creating a stable waveform readable on an oscilloscope or processed by a microprocessor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exhaust pulsations are detected directly, then misfire detection is possible, but resonant frequency fluctuations interfere with accurate detection
Solution Approach 1:
A Venturi tube is introduced as an intermediary device between the exhaust stream and the pressure sensor. The Venturi tube creates a controlled flow environment that converts exhaust pressure fluctuations into measurable pressure differential signals, while filtering out harmful resonant frequency interference from the exhaust system
Solution Approach 2:
The system changes the measurement parameter from direct exhaust pressure to pressure differential across the Venturi tube. This parameter transformation allows the sensor to detect misfire-related pressure changes while excluding resonant frequency fluctuations that occur at different pressure levels
2Loss of information
If pressure sensor monitors exhaust stream, then misfire signal is obtained, but unwanted exhaust pulsations are also detected
Solution Approach 1:
The Venturi tube extracts only the relevant pressure differential information from the exhaust stream while leaving the harmful pulsations behind. By measuring pressure difference between two points in the Venturi configuration, the system isolates the misfire signal from the noisy exhaust environment
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 solution effectively dampens unwanted exhaust pulsations and amplifies the negative pulses, providing a clear and accurate signal for misfire detection, enabling precise identification of misfiring cylinders, which improves the accuracy of engine diagnosis.
Implementation Method 1
The present invention comprises a probe and method for sensing pressure variations in the exhaust stream of an engine for detecting cylinder misfires. The probe includes a Venturi tube placed in the exhaust stream.
Data Source
AI summary
A probe and method for sensing pressure variations in the exhaust stream of an engine for detecting cylinder misfires. The probe includes a Venturi tube placed in the exhaust stream. The Venturi tube has a sensing tube with an aperture, and the sensing tube is coupled to a pressure sensor for monitoring the pressure of the exhaust stream within the Venturi tube at the point of the aperture. The pressure sensor then generates a voltage signal based on the pressure, and this voltage signal is viewed on an oscilloscope or processed by a microprocessor to generate a waveform readable by a technician. The waveform will indicate the presence of a misfiring cylinder(s), and more specifically, which cylinder(s) is misfiring.