Testing compression in engines from starter motor current waveform

• US 4,062,232 A
• Filed: 10/12/1976
• Issued: 12/13/1977
• Est. Priority Date: 10/12/1976
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: RCA Corporation (General Electric Company)
• Inventors: Sutphin, Eldon Marvin Jr.
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US05/731,209
• Time in Patent Office: 427 Days
• Field of Search: 73/116, 73/117.2, 73/115
• US Class Current: 73/114.23
• CPC Class Codes: G01L 23/085 by measuring fluctuations of starter motor current or of battery voltage battery testing arrangements G01R31/36; testing of electrical installation on transport means G01R31/005; battery testing arrangements G01R31/36

Abstract

The relative compression in the cylinders of an internal combustion engine is tested by analyzing the starter motor current waveform when the engine is cranked with the ignition or the fuel inhibited. In asymmetrical engines, where the compression strokes of individual cylinders are unequally spaced in time, the starter current waveform may contain double-hump cycles. The area under each double-hump cycle is integrated, and the integration peaks are compared. The compression in one or more cylinders is deficient if the minimum integration peak is less than the maximum integration peak by a significant percentage such as 15 percent or more.

Claims

1. Apparatus to detect unsatisfactory compression in individual cylinders of an internal combustion engine having compression strokes, comprising

means for detecting the starter motor current waveform when the engine is cranked with the ignition or fuel inhibited, said waveform having cycles each corresponding with at least one compression stroke,

means for integrating the area under each of said cycles to produce corresponding integration signals, and

means for comparing the amplitudes of the smallest and largest integration signals and indicating when their ratio is less than a predetermined value, whereby to register unsatisfactory compression in at least one of the cylinders of the engine.

2. Apparatus defined in claim 1 wherein said engine is asymmetrical, and said cycles each correspond with a group of at least two compression strokes.

3. A method to detect unsatisfactory compression in individual cylinders of an internal combustion engine having compression strokes, comprising the steps of

detecting the starter motor current waveform when the engine is cranked with the ignition or fuel inhibited, said waveform having cycles each corresponding with at least one compression stroke,

integrating the area under each of said cycles to produce corresponding integration signals, and

comparing the amplitudes of the smallest and the largest integration signals and indicating when their ratio is less than a predetermined value, whereby to register unsatisfactory compression in at least one of the cylinders of the engine.

4. A method as defined in claim 3 wherein said engine is asymmetrical and said cycles each correspond with a group of at least two compression strokes.