US4424709A — Frequency domain engine defect signal analysis

Claim 1

Independent Claim 187 words

A signal analyzer for detecting engine defects including: an engine speed sensor means for detecting engine speed and generating an electrical engine speed signal; an exhaust pressure sensor means for detecting engine exhaust pressure and generating an electrical exhaust pressure signal; an intake manifold vacuum sensor means for detecting engine intake manifold vacuum and generating an electrical intake manifold vacuum signal; a crankcase pressure sensor means for detecting blowby gas pressure in the engine crankcase and generating an electrical crankcase pressure signal; an oil pressure sensor means for detecting engine oil pressure and generating an electrical oil pressure signal; a frequency domain analyzer circuit means coupled to said engine speed sensor means exhaust pressure sensor means, intake manifold vacuum sensor means, crankcase pressure sensor means and oil pressure sensor means for generating a frequency domain spectrum signal from the outputs of said coupled sensor means; and a comparison means coupled to said frequency domain analyzer circuit means for comparing said frequency domain spectrum signal to a normal engine signal thereby determining at what frequencies differences between the two signals exist, such differences being indicative of engine defects.

Claim 2

Dependent Claim 187 words

A signal analyzer for detecting engine defects including: an engine speed sensor means for detecting engine speed and generating an electrical engine speed signal; an exhaust pressure sensor means for detecting engine exhaust pressure and generating an electrical exhaust pressure signal; an intake manifold vacuum sensor means for detecting engine intake manifold vacuum and generating an electrical intake manifold vacuum signal; a crankcase pressure sensor means for detecting blowby gas pressure in the engine crankcase and generating an electrical crankcase pressure signal; an oil pressure sensor means for detecting engine oil pressure and generating an electrical oil pressure signal; a frequency domain analyzer circuit means coupled to said engine speed sensor means exhaust pressure sensor means, intake manifold vacuum sensor means, crankcase pressure sensor means and oil pressure sensor means for generating a frequency domain spectrum signal from the outputs of said coupled sensor means; and a comparison means coupled to said frequency domain analyzer circuit means for comparing said frequency domain spectrum signal to a normal engine signal thereby determining at what frequencies differences between the two signals exist, such differences being indicative of engine defects.

Claim 3

Dependent Claim 33 words

A signal analyzer as recited in claim 1 further comprising a frequency classifier means for associating an engine defect with any variations in said frequency domain spectrum signal from said normal engine signal.

Claim 4

Dependent Claim 130 words

A signal analyzer for detecting engine defects including: a plurality of sensing means coupled to the engine for detecting at least two engine operating parameters from the following group: engine speed, engine exhaust manifold pressure, intake manifold vacuum, crankcase gas pressure, and oil pressure; a frequency domain analyzer circuit means coupled to receive said at least two engine operating parameters for generating a frequency domain spectrum signal as a function of said at least two engine operating parameters; and a comparison means coupled to said frequency domain analyzer circuit means for comparing said frequency domain spectrum signal to a normal engine signal thereby determining at what frequencies differences between the two signals exist, such differences being indicative of particular types of engine defect depending upon the pattern of such differences.

Claim 5

Dependent Claim 130 words

A signal analyzer for detecting engine defects including: a plurality of sensing means coupled to the engine for detecting at least two engine operating parameters from the following group: engine speed, engine exhaust manifold pressure, intake manifold vacuum, crankcase gas pressure, and oil pressure; a frequency domain analyzer circuit means coupled to receive said at least two engine operating parameters for generating a frequency domain spectrum signal as a function of said at least two engine operating parameters; and a comparison means coupled to said frequency domain analyzer circuit means for comparing said frequency domain spectrum signal to a normal engine signal thereby determining at what frequencies differences between the two signals exist, such differences being indicative of particular types of engine defect depending upon the pattern of such differences.

Claim 6

Dependent Claim 81 words

A signal analyzer as recited in claim 3 wherein said frequency domain analyzer circuit includes: a buffer means coupled to said sensing means for filtering undesired noise; a channel selection switch means coupled to said buffer means for selecting one of a plurality of outputs associated with one of said sensing means, said channel selection switch having one output; and a selectable bandpass filter means coupled to said channel selection switch for processing information associated with one of said sensing means.

Claim 7

Dependent Claim 26 words

A signal analyzer as recited in claim 4 wherein said comparison means includes stored information for comparison with the output of said selectable bandpass filter means.

Claim 8

Dependent Claim 85 words

A signal analyzer as recited in claim 5 further comprising: an ignition sensor means for sensing engine ignition pulses and the firing of a particular engine cylinder; an engine event generator means coupled to said ignition sensing means for generating signals indicative of the firing of each one of the engine cylinders; and a cylinder isolator means coupled to said engine event generator means and to said frequency domain analyzer circuit means for providing an indication of the engine cylinder associated with a particular fault.

Claim 9

Dependent Claim 86 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, and intake manifold vacuum; said frequency domain analyzer circuit means passes frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.50, 0.75, 1.25, 1.75, 2.0 and 2.25 and said comparison means including means for classifying the defect as an engine misfire upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 10

Dependent Claim 89 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.0625, 0.125, 0.1875, 0.25, 0.3125, 0.375, 0.4375, 0.5625, 0.625, 0.6875, 0.75, 0.8125, 0.875 and 0.9375; and said comparison means including means for classifying the defect as an intake manifold leak upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 11

Dependent Claim 116 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum and oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25 and 0.75 for engine exhaust manifold pressure; 0.035 0.25, 0.50 and 0.75 for engine speed; 0.25, 0.50 and 0.75 for intake manifold vacuum; and 0.375, 0.50, 1.75 and 2.0 for oil pressure; and said comparison means including means for classifying the defect as a collapsed exhaust valve tappet upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 12

Dependent Claim 117 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum, and oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.75, and 1.0 for engine exhaust manifold pressure; 0.0625, 0.125, 0.25 and 0.75 for engine speed; 0.25, 0.50, and 0.75 for intake manifold vacuum and 0.25, 1.0, 1.75, 2.0 and 2.25 for oil pressure; and said comparison means including means for classifying the defect as collapsed intake valve tappets upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 13

Dependent Claim 105 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, and intake manifold vacuum; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.50 and 0.75 for engine exhaust manifold pressure; 0.0625, 0.125, 0.1875 and 0.25 for engine speed; 0.25 and 0.75 for intake manifold vacuum; and said comparison means including means for classifying the defect as exhaust gas recirculation valve leaks upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 14

Dependent Claim 87 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of intake manifold vacuum and oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 2 for intake manifold vacuum; and 0.75 and 1.95 for oil pressure; and said comparison means including means for classifying the defect as improper camshaft timing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 15

Dependent Claim 91 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine speed, intake manifold vacuum and oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.360 for engine speed; 0.0625 for intake manifold vacuum; and 0.75 for oil pressure; and said comparison means including means for classifying the defect as improper camshaft timing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 16

Dependent Claim 108 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum and oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.360 and 0.75 for engine exhaust manifold pressure; 0.125, 0.360 and 0.50 for engine speed; 0.078 for intake manifold vacuum and 0.638 and 2.04 for oil pressure; and said comparison means including means for classifying the defect as improper camshaft timing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 17

Dependent Claim 110 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum, and oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.201, 0.402, 0.603 and 0.804 for engine exhaust manifold pressure; 0.377 and 0.75 for engine speed; 0.089, 0.801, 0.890 for intake manifold vacuum; 0.383 and 0.801 for oil pressure; and said comparison means including means for classifying the defect as improper camshaft timing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 18

Dependent Claim 76 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.045, 0.090, 0.50 and 1.0; and said comparison means including means for classifying the defect as missing main bearings upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 19

Dependent Claim 74 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine speed; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25; and said comparison means including means for classifying the defect as top compression piston ring missing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 20

Dependent Claim 76 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 2.10 and 3.0; and said comparison means including means for classifying the defect as incorrect spark timing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 21

Dependent Claim 113 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum and crankcase pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.083, 0.1662, 0.25 0.332, 0.415, 0.50, 0.664, and 0.75 for engine exhaust manifold pressure; 0.25, 0.50, and 0.75 for engine speed; 0.50 for intake manifold vacuum and 0.75 for crankcase pressure; and said comparison means including means for classifying the defect as a scored intake valve upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 22

Dependent Claim 90 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure and intake manifold vacuum; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 3.57 for engine exhaust manifold pressure and 0.50 for intake manifold vacuum; and said comparison means including means for classifying the defect as a scored exhaust valve upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 23

Dependent Claim 98 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, intake manifold vacuum and crankcase pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.50 for engine exhaust manifold pressure, 0.50 for intake manifold vacuum and 0.25 and 0.50 for crankcase pressure; and said comparison means including means for classifying the defect as hole in piston dome upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 24

Dependent Claim 120 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum and crankcase pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.50, 0.75, 1.25 1.5, and 1.75 for engine exhaust manifold pressure; 0.25, 0.50 and 0.75 for engine speed; 0.0432, 0.0864, 0.25, 0.50 and 0.75 for intake manifold vacuum and 0.25, 0.50 and 0.75 for crankcase pressure; and said comparison means including means for classifying the defect as two top compression rings missing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 25

Dependent Claim 106 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed and intake manifold vacuum; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.50, 0.75, 1.25, 1.5 and 1.75 for exhaust pressure; 0.29, 0.50 and 0.75 for engine speed; 0.0432, 0.25, 0.50 and 0.75 for intake manifold vacuum; and said comparison means including means for classifying the defect as weak intake valve springs upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 26

Dependent Claim 104 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed and intake manifold vacuum; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.50 and 0.75 for engine exhaust manifold pressure, 0.25, 0.50 and 0.75 for engine speed; 0.25, 0.50 and 0.75 for intake manifold vacuum and said comparison means including means for classifying the defect as weak exhaust valve springs upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 27

Dependent Claim 118 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of engine exhaust manifold pressure, engine speed, intake manifold vacuum and crankcase pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25, 0.50, 0.75, 1.25 and 1.75 for engine exhaust manifold pressure, 0.25, 0.50 and 0.75 for engine speed; 0.25, 0.50, 0.75 and 1.25 for intake manifold vacuum and 0.25, 0.75 and 1.35 for crankcase pressure; and said comparison means including means for classifying the defect as a cylinder head gasket leak upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 28

Dependent Claim 76 words

A signal analyzer as recited in claim 5 wherein: said plurality of sensing means detects the engine parameters of oil pressure; said frequency domain analyzer circuit means passes the frequencies of the engine firing frequency multiplied by the factors of 0.25 and 1.0; and said comparison means including means for classifying the defect as a missing connecting rod bearing upon detection of predetermined signal amplitudes at the frequencies passed by said frequency domain analyzer circuit means.

Claim 29

Dependent Claim 64 words

A signal analyzer for detecting defects in a multi-cylinder engine including: a plurality of sensing means coupled to the engine for detecting engine operating parameters including engine exhaust manifold pressure, intake manifold vacuum, crankcase gas pressure and oil pressure; and a bandpass filter associated with at least one of said sensing means for passing a band of frequencies including the frequency of cylinder firings.

Claim 30

Dependent Claim 64 words

A signal analyzer for detecting defects in a multi-cylinder engine including: a plurality of sensing means coupled to the engine for detecting engine operating parameters including engine exhaust manifold pressure, intake manifold vacuum, crankcase gas pressure and oil pressure; and a bandpass filter associated with at least one of said sensing means for passing a band of frequencies including the frequency of cylinder firings.

Claim 31

Dependent Claim 46 words

A signal analyzer as recited in claim 27 further comprising: a plurality of bandpass filters, one coupled with each of said sensing means; and a classification means associated with each of said bandpass filters for associating particular engine defects with the outputs of said bandpass filters.

Claim 32

Dependent Claim 31 words

A signal analyzer as recited in claim 27 wherein the engine has four cylinders and at least one of said bandpass filters passes a band of frequencies centered at 8.3 Hz.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-01-09	1987-07-11	1988-01-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-01-09	1991-07-11	1992-01-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-01-09	1995-07-11	1996-01-10	$7700.00	Window Closed / Lapsed

Frequency domain engine defect signal analysis

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