Method and apparatus for generating and identifying misfires

• US 6,216,678 B1
• Filed: 01/19/2000
• Issued: 04/17/2001
• Est. Priority Date: 01/19/2000
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: James, John Victor, Baker, Ryan Lee, Krzyske, Dennis Carl
• Primary Examiner(s): SOLIS, ERICK R
• Application Number:
  US09/488,065
• Time in Patent Office: 454 Days
• Field of Search: 123/594, 123/624, 123/629, 123/649, 731/173
• US Class Current: 123/594
• CPC Class Codes: F02P 17/00 Testing of ignition installations, e.g. in combination with adjusting testing fuel injection apparatus F02M65/00; testing ignition installations in general F23Q23/00; Testing of ignition timing in compression-ignition engines
• CPC Class Codes: F02P 17/12 Testing characteristics of the spark, ignition voltage or current testing of sparking plugs H01T13/60
• CPC Class Codes: F02P 3/05 for control of the magnitude of the current in the ignition coil during starting F02P15/12
• CPC Class Codes: G01M 15/11 by detecting misfire

Abstract

An engine cylinder firing event is intentionally defeated by clipping the flyback voltage of the ignition system primary coil winding under the control of a misfire generator that develops a misfire logic signal from ignition dwell events and user inputs and also develops a signal indicative of which cylinder firing event was defeated.

Claims

1. Apparatus for connection with an engine ignition system for causing an engine cylinder to misfire, said ignition system including a coil having a primary winding and a secondary winding and further including a coil driver connected with said primary winding for controlling current flow in said primary winding;

said apparatus comprising;

a series network comprising a voltage breakdown device and a switching device, said network connected in parallel with said coil driver;

a signal generator for generating a misfire signal for controlling the state of said switching device to selectively initiate a misfire.

2. The apparatus of claim 1 wherein the timing of said misfire signal is based on logic signals derived from ignition primary signals.

3. The apparatus of claim 2 wherein said signal generator provides a signal indicative of which cylinder firing event was intentionally defeated.

4. The apparatus of claim 1 wherein said voltage breakdown device is a zener diode.

5. The apparatus of claim 1 wherein said switching device is a MOSFET transistor.

6. The apparatus of claim 1 wherein said voltage breakdown device is a zener diode and said switching device is a MOSFET transistor.

7. The apparatus of claim 1 further comprising a diode having an anode connected to a junction between said voltage breakdown device and one side of said primary winding and a cathode connected with said coil driver, an inductor connected between the cathode of said diode and the other side of said primary winding for causing a voltage spike to appear at said coil driver when a misfire is initiated.

8. The apparatus of claim 1 wherein said signal generator is responsive to said ignition primary signals for developing a non-overlapping dwell signal representing a single dwell period per combustion event, and includes means for generating a pulse at the beginning of each dwell period, and for creating said misfire signal based on counting said pulses.

9. A method of inducing cylinder misfire comprising a sequence of the following steps:

sensing the voltage at a point of connection between a primary coil winding and a primary coil winding driver of an engine ignition system;

detecting the beginning of an ignition dwell period and in response to said detection;

providing a current path in parallel with said coil driver for a period greater than said dwell period to gradually lower the current flowing in said primary coil winding at the termination of said dwell period.

10. The method of claim 9 further comprising the step of:

generating a voltage spike comparable to the flyback voltage normally expected from the coil primary winding at the termination of said dwell period for ignition diagnostic purposes.