Engine misfire detection probe

• US 8,020,434 B1
• Filed: 06/05/2009
• Issued: 09/20/2011
• Est. Priority Date: 07/17/2007
• Status: Active Grant

• Current Assignee: Bernie C. Thompson
• Original Assignee: Bernie C. Thompson
• Inventors: Thompson, Bernie C.
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US12/455,829
• Time in Patent Office: 837 Days
• Field of Search: 731/140.2, 731/140.6, 731/140.8
• US Class Current: 73/114.02
• CPC Class Codes: G01M 15/11 by detecting misfire

Abstract

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.

Claims

1. A method of detecting a misfire in an engine comprising the steps of:

(a) placing a Venturi tube at least partially in an exhaust stream of said engine;

(b) sensing exhaust pulsations in said exhaust stream;

(c) generating a first voltage signal from said exhaust pulsations;

(d) generating a second voltage signal from an ignition discharge in said engine;

(e) synchronizing said first and second voltage signals to detect a misfire in said engine.

2. The method of detecting a misfire in an engine of claim 1 further comprising the step of dampening unwanted exhaust pulsations.

3. The method of detecting a misfire in an engine of claim 1 further comprising the step of amplifying negative exhaust pulsations.

4. The method of detecting a misfire in an engine of claim 1 further comprising the step of generating a first and a second waveform from said first and second voltage signals.

5. The method of detecting a misfire in an engine of claim 4 further comprising the step of processing said waveforms with one or more statistical filters.

6. The method of detecting a misfire in an engine of claim 5 further comprising the step of compensating said synchronizing for a delay between a spark plug firing and an exhaust stroke in said engine as part of said second waveform.

7. The method of detecting a misfire in an engine of claim 1 further comprising the step of identifying an action occurring in the course of operation of said engine as a trigger for use in identifying the misfire source.

8. The method of detecting a misfire in an engine of claim 7 wherein said step of identifying further comprises assigning ignition of a cylinder in said engine as said trigger.

9. A method of detecting a misfire in an engine comprising the steps of:

(a) placing a Venturi tube at least partially in an exhaust stream of said engine;

(b) sensing exhaust pulsations in said exhaust stream;

(c) dampening unwanted exhaust pulsations;

(d) amplifying negative exhaust pulsations;

(e) generating a voltage signal from said exhaust pulsations;

(f) generating a voltage signal from an ignition discharge;

(g) generating waveforms from said voltage signals;

(h) processing said waveforms with statistical filters; and

(i) identifying an action occurring in the course of operation of said engine as a trigger for use in identifying the misfire source; and

(j) compensating for a delay between a spark plug firing and an exhaust stroke in said engine; and

(k) synchronizing said waveforms to determine the location of said misfire in said engine.