Relative compression of an internal combustion engine

• US 4,050,296 A
• Filed: 05/07/1976
• Issued: 09/27/1977
• Est. Priority Date: 05/07/1976
• Status: Expired due to Term

• Current Assignee: Clean Air Technologies Inc.
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Benedict, Richard S.
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US05/684,038
• Time in Patent Office: 508 Days
• Field of Search: 73/116, 73/117.2, 73/115, 73/117.3
• US Class Current: 73/114.22
• 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 compression of each cylinder of a reciprocating, internal combustion engine, expressed in a relative fashion as compared with the compression of another of the cylinders of the engine, is determined by sensing the peaks and valleys in an engine parameter which fluctuates commensurately with fluctuations in engine operating condition while cranking, such as starter current or voltage or instantaneous, subcyclic speed. The difference (D) between each peak and the preceding valley is measured, and these are filtered by averaging them with eight-tenths of the maximum difference, and each is expressed as a percentage of the maximum filtered difference. The time from one peak to the next is compared against some percentage of the average or expected peak to peak time (such as 130%), and if a peak is detected after the maximum allowed time, it is taken as being indicative of one peak being totally missing due to a very weak cylinder, so the difference value for the cylinder which was being looked for is taken to be zero, and the difference value for the cylinder whose peak actually was found is taken to be some fraction (such as 0.7) of the valley to peak difference actually calculated. Whenever the time out test does not indicate a failure, every difference measured is compared against three-tenths of the maximum difference which is expected, and if the difference is below that, the peak measured is used for the following valley, and the processing switches to look for a peak of the following cylinder.

Claims

1. In a method for providing an indication of relative cylinder compression of a reciprocating internal combustion engine, the steps of:

determining in turn the maxima and minima in the speed of a rotating engine from excursions in magnitude of a signal derived from an engine parameter, the magnitude of which follows excursions in engine speed as a consequence of successive cylinder-related compression strokes, and providing successive manifestations thereof referred to hereinafter as "max" and "min", respectively;

providing the difference between the magnitudes of each max and the next succeeding min after sensing each min and before sensing the next max; and

comparing each provided difference with a predetermined difference to thereby determine when the speed excursions are sufficiently small that detection of the next succeeding max may be impaired, and in response thereto, utilizing the last min sensed as the next succeeding max and next sensing thereafter the next succeeding min.

2. In a method for providing an indication of relative cylinder compression of a reciprocating internal combustion engine, the steps of:

determining in turn the maxima and minima in the speed of a rotating engine from excursions in magnitude of a signal derived from an engine parameter, the magnitude of which follows excursions in engine speed as a consequence of successive cylinder-related compression strokes, and providing successive manifestations thereof in pairs;

providing a manifestation of the difference between the magnitudes of each pair sensed;

comparing the time interval between sensing of adjacent pairs with a predetermined time interval to determine if the second one of said manifestations in a pair relates to the same cylinder as the preceeding one of said manifestations in said pair; and

providing for each cylinder a result manifestation indicative of the measured relative compression for that cylinder in response to the difference manifestation provided for each pair related to a corresponding cylinder, and when said time interval exceeds said predetermined time interval, providing for the cylinder related to the first manifestation of the pair sensed during the excessive interval, a predetermined result manifestation related to minimal compression, and providing for the cylinder related to the second manifestation of the pair sensed during the excessive interval a result manifestation related to the difference manifestation provided for the pair in said excessive interval.

3. A method according to claim 2 wherein the result manifestation provided to the cylinder related to the second one of said manifestation of the pair sensed during the excessive interval is a fraction of the difference manifestation for the pair in said excessive interval.

4. In a method of providing an indication of relative cylinder compression of a reciprocating internal combustion engine, the steps of:

sensing, in an expected order, extremes in magnitude representing successive, alternate maxima and minima in a signal derived from an engine parameter having excursions in magnitude which indicate the excursions in speed of a rotating engine on a cylinder-by-cylinder basis due to the compression stroke of each cylinder in turn, said expected order comprising sensing a magnitude indicating maximum speed followed by sensing a magnitude indicating minimum speed, as a pair, respectively;

providing a manifestation of the difference between the magnitudes of each pair sensed;

comparing the time interval between adjacent minimum speed magnitudes against a predetermined time interval to determine if the second one of said minimum speed signals relates to the same cylinder as the preceeding one of said maximum speed signals;

comparing the difference manifestation for each of said pairs relating to a predetermined difference manifestation to thereby determine when the excursions are too small to permit detection of the maximum speed magnitude next following said pair, and utilizing the minimum speed magnitude of said pair as the maximum speed magnitude of the next pair in said order in response thereto; and

providing for each cylinder a data manifestation indicative of the measured relative compression for that cylinder in response to the difference manifestation for each pair related to a corresponding cylinder, or when said time interval exceeds said predetermined time interval, providing for the cylinder related to the maximum speed magnitude of the pair sensed during the excessive interval a predetermined data manifestation related to minimal compression, and providing for the cylinder related to the minimum speed magnitude of the pair sensed during the excessive interval a data manifestation related to the difference manifestation for the pair in said excessive interval.

5. A method according to claim 4 wherein the data manifestation provided to the cylinder related to the minimum speed magnitude of the pair sensed during the excessive interval is a fraction of the difference manifestation for the pair in said excessive interval.

6. Apparatus for providing an indication of relative compression of a reciprocating internal combustion engine, comprising:

sensing means adapted to be disposed for a response to the magnitude of an engine parameter, the magnitude of which fluctuates in conjunction with the cylinder-related, sub-cyclic excursions in engine speed as a consequence of the compression strokes of the individual cylinders, said sensing means providing a corresponding compression signal; and

processing apparatus, responsive to said sensing means, comprising means for determining successive magnitudes in the excursions of said compression signal respectively relating to maximum engine speed and to minimum engine speed, providing max signals and min signals corresponding thereto, providing a difference manifestation related to the difference in magnitude between each min signal and the next succeeding one of said max signals and comparing it against a predetermined difference, and when the difference is less than said predetermined difference, utilizing the related min signal as the next max signal and thereafter next sensing the next succeeding magnitude related to minimum engine speed.

7. Apparatus according to claim 6 wherein said processing apparatus also comprises means for:

comparing the time interval between sensing of adjacent pairs of max and min signals with a predetermined time interval to determine if the min signal of the pair relates to the same cylinder as the max signal of said pair, and providing for each cylinder a result manifestation indicative of the measured relative compression for that cylinder in response to the difference manifestation for each pair related to a corresponding cylinder, and when said time interval exceeds said predetermined time interval, providing for the cylinder related to the max signal of the pair sensed during the excessive interval, a predetermined result manifestation related to minimal compression, and providing for the cylinder related to the min signal of the pair sensed during the excessive interval a result manifestation related to the difference manifestation provided for the pair in said excessive interval.

8. A method according to claim 7 wherein the result manifestation provided to the cylinder related to the min signal of the pair sensed during the excessive interval is a fraction of the difference manifestation provided for the pair in said excessive interval.

9. Apparatus according to claim 6 wherein said processing apparatus also comprises means for:

averaging the difference determined for each of said cylinders with a fraction of the maximum difference determined for any of said cylinders to provide a manifestation of a filtered difference for each of said cylinders.

10. Apparatus according to claim 9 wherein said processing apparatus also comprises means for:

expressing the average difference represented by the filtered difference manifestation for each of said cylinders as a percentage of the averaged difference expressed by the filtered difference manifestation for the one of said cylinders having the maximum difference.