Digital engine analyzer

• US 5,296,869 A
• Filed: 05/14/1993
• Issued: 03/22/1994
• Est. Priority Date: 09/24/1990
• Status: Expired due to Term

• Current Assignee: Snap-On Incorporated
• Original Assignee: Snap-On Tools Company LLC (Snap-On Incorporated)
• Inventors: Putrow, Michael C., Sniegowski, John C., Jonker, Gary D., Govekar, Craig F., Meeker, Michael B., Piehl, James R.
• Primary Examiner(s): HJERPE, RICHARD A
• Application Number:
  US08/062,145
• Time in Patent Office: 312 Days
• Field of Search: 340/720, 340/721, 340/722, 340/723, 340/747, 73/117.2, 73/117.3, 73/116, 324/378, 324/379, 324/384, 324/393, 324/394, 324/388, 324/391, 324/392, 324/399, 364/431.03, 364/431.04, 364/481, 364/483, 364/487, 345/24, 345/140
• US Class Current: 345/24
• CPC Class Codes: F02P 17/08 using a cathode-ray oscilloscope F02P17/06 takes precedence

Abstract

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed and calculates and display spark plug burn time information derived from a single analog input signal, the data being displayed in both numerical and bar graph form. The measured burn time is the time that the ignition voltage signal is above a predetermined threshold level which is greater than the amplitude of the ringing portion of the ignition voltage signal.

Claims

1. In a system for analyzing the operation of a multiple cylinder internal combustion engine having a spark plug for each cylinder and an ignition coil having a secondary winding for applying a firing voltage to each spark plug, with each cylinder having a cylinder time interval from the application of a firing voltage to the spark plug for that cylinder to the application of a firing voltage to the spark plug for the next cylinder and a spark plug burn time interval, including display means and sensing means coupled to the secondary winding for generating ignition voltage signals representative of the ignition characteristics of individual cylinders, the improvement comprising:

detection means coupled to the sensing means and responsive to only the ignition voltage signals from the secondary winding for determining spark plug burn time, said detection means including first and second comparison means for respectively comparing the voltage of the ignition voltage signals to predetermined first and second threshold voltage levels greater than zero and respectively generating first and second pulse signals each having a leading edge when the voltage of the ignition voltage signals rises above the corresponding threshold voltage level, said second pulse signal having a trailing edge when the voltage of the ignition voltage signals drops below the second threshold level, blanking means coupled to said first comparison means for disabling the output thereof an instant after the leading edge of said first pulse signal and maintaining said output disabled for the duration of the cylinder time interval to terminate said first pulse signal so that said first comparison means can produce only one first pulse signal during each cylinder time interval, processing means coupled to said detection means and responsive to said pulse signals for measuring the time between the leading edge of said first pulse signal and the trailing edge of said second pulse signal for determining the duration of burn time interval for each cylinder and generating duration data representative thereof, and display drive means coupled to said processing means and to the display means and responsive to the duration data for displaying on the display means a representation of the burn time interval for each cylinder.

2. The system of claim 1, wherein said display drive means includes means for displaying numerical indicia of the burn times for the several cylinders.

3. The system of claim 1, wherein the display means includes a cathode-ray tube monitor.

4. The system of claim 1, and further comprising means for capturing the maximum and minimum values of burn time interval for each cylinder over a plurality of engine cycles, and means for displaying said maximum and minimum values.

5. The system of claim 1, wherein said display drive means includes means for displaying on the display means a bar graph including a plurality of bars respectively indicating the burn times for the several cylinders.

6. The system of claim 5, wherein the bar graph has a horizontal time axis.

7. The system of claim 5, wherein the bar graph is repeatedly updated to display real time burn time information.

8. The system of claim 5, and further comprising means coupled to cylinder number 1 for generating a number 1 signal in response to ignition of cylinder number 1, said processing means being responsive to said number 1 signal for identifying the portion of the duration data which corresponds to cylinder number 1.

9. The system of claim 8, wherein said display drive means includes means for displaying next to each bar of the bar graph the number of the corresponding cylinder.