Exhaust-responsive engine speed and condition indicator

Claim 2

Apparatus responsive to the exhaust from an internal combustion engine having x ignitions per second depending on engine speed, and having y ignitions per revolution of the crankshaft depending on number of cylinders and whether twostroke or four-stroke cycle, and having an engine speed in rpm equal to x times the constant 60/y, comprising means to project a light beam from a source through the exhaust gas exiting from the engine to a photodetector to produce an electrical signal having a frequency x Hz which varies directly with the operating speed of the engine, frequency detector means translating the varying frequency of said electrical signal to a corresponding amplitude varying signal, and an electrical meter receptive to said amplitude varying signal and calibrated to indicate engine speed in revolutions per minute.

Claim 3

Apparatus as defined in claim 1 wherein said frequency detector means comprises a phase locked oscillator.

Claim 4

Apparatus as defined in claim 1, and in addition, a band pass filter coupling said frequency varying electrical signal to said frequency detector means and having a passband to limit the frequencies passed to frequencies in the range determined by the operating speed range of the engine.

Claim 5

Apparatus as defined in claim 2, and in addition, a band pass filter coupling said frequency varying electrical signal to said phase locked oscillator and having a passband to limit the frequencies passed to frequencies in the range determined by the operating speed range of the engine.

Claim 6

Apparatus as defined in claim 1, and in addition, an elapsed time counter, and logic means responsive to operation of the accelerator on said engine to start said elapsed time counter, and responsive to an attained predetermined amplitude signal from said frequency detector means to stop said elapsed time counter, whereby the elapsed time is a measure of the condition of said engine.

Claim 7

Apparatus as defined in claim 1, and in addition, an elapsed time counter, and logic means operating following a maximum acceleration of said engine and responsive to a signal from said frequency detector means corresponding to a predetermined low speed to start said elapsed time counter, and responsive to a signal from said frequency detector means corresponding to a predetermined high speed to stop said elapsed time counter, whereby to automatically record the results of an acceleration burst test.

Claim 8

Apparatus responsive to the exhaust from an internal combustion engine having x ignitions per second depending on engine speed, and having y ignitions per revolution of the crankshaft depending on number of cylinders and whether two-stroke or four-stroke engine, and having an engine speed in rpm equal to x times the constant 60/y, comprising means to project a light beam from a source through the exhaust gas exiting from the engine to a photodetector to produce a periodically-varying electrical signal having a fundamental frequency component x Hz and harmonic frequency components which vary over a predetermined range determined by the operating speed range of the engine, a band pass filter receptive to said electrical signal and being operative to pass said fundamental and harmonic frequency components in said predetermined range, a phase-locked oscillator responsive to the output of said band pass filter and including a comparator comparing the frequency of the output of the oscillator with one of said fundamental and harmonic frequency components of the electrical signal and producing an error signal applied to the oscillator to make it track said one of the fundamental and harmonic frequency components, whereby said error signal varies in accordance with engine speed, and an electrical meter receptive also to said error signal and calibrated to indicate engine speed in revolutions per minute for the conditions when the oscillator is locked onto any one of said fundamental or harmonic frequency components of the electrical signal.

Claim 9

Apparatus responsive to the exhaust from an internal combustion engine having x ignitions per second depending on engine speed, and having y ignitions per revolution of the crankshaft depending on number of cylinders and whether two-stroke or four-stroke engine, and having an engine speed in rpm equal to x times the constant 60/y, comprising means to project a light beam from a source through the exhaust gas exiting from the engine to a photodetector to produce a periodically-varying electrical signal having a fundamental frequency component x Hz and harmonic frequency components which vary over a predetermined range determined by the operating speed range of the engine, a band pass filter receptive to said electrical signal and being operative to pass said fundamental and harmonic frequency components in said predetermined range, a phase-locked oscillator responsive to the output of said band pass filter and including a comparator comparing the frequency of the output of the oscillator with one of said fundamental and harmonic frequency components of the electrical signal and producing an error signal applied to the oscillator to make it track said one of the fundamental and harmonic frequency components, whereby said error signal varies in accordance with engine speed, and an electrical meter receptive also to said error signal and calibrated to indicate engine speed in revolutions per minute for the conditions when the oscillator is locked onto any one of said fundamental or harmonic frequency components of the electrical signal.

Claim 10

Apparatus as defined in claim 7, and in addition, an elapsed time counter, and logic means responsive to operation of the accelerator on said engine to start said elapsed time counter, and responsive to an attained predetermined amplitude of the error signal from said phase locked oscillator to stop said elapsed time counter, whereby the elapsed time is a measure of the condition of said engine.

Claim 11

Apparatus as defined in claim 7, and in addition, an elapsed time counter, and logic means operating following a maximum acceleration of said engine and responsive to said error signal corresponding to a predetermined low speed to start said elapsed time counter, and responsive to said error signal corresponding to a predetermined high speed to stop said elapsed time counter, whereby to automatically record the results of an acceleration burst test.