Electricity: measuring and testing – Internal-combustion engine ignition system or device
Patent
1990-05-17
1992-02-11
Strecker, Gerard R.
Electricity: measuring and testing
Internal-combustion engine ignition system or device
731173, 324379, 324402, F02P 1700
Patent
active
050878816
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to power measurement apparatus and more particularly to power measurement apparatus for use as a diagnostic aid in maintenance of internal combustion engines.
2. Description of Related Art
Some known apparatus for measuring the comparative power output of each cylinder of an internal combustion engine of the kind having two or more cylinders requires measurement to be effected on the output shaft of the engine. Such apparatus is not usually suitable for use with an engine in situ in a motor vehicle for example and may require use of purpose built testing rigs. Thus the performance of an engine under its normal working conditions is not practical.
SUMMARY OF THE INVENTION
Accordingly it is an object of the present invention to provide power measurement apparatus for use in measuring the comparative power outputs of the cylinders of an internal combustion engine, the apparatus being capable of use without affecting the working conditions of such an engine.
Acoording to the present invention there is provided power measurement apparatus for measuring the comparative output power of each cylinder of an internal combustion engine of the kind having at least two cylinders, the apparatus comprising first pick-up means for detecting current flow in an output lead of an electrical generator, second pick-up means for detecting engine timing pulses and, comparison means to compare the level of current flows in respect of each power stroke of the engine whereby the comparative power output of each cylinder of the engine may be determined.
Preferably the first pick-up means is a current transformer adapted for releasable attachment to an alternator output lead.
The second pick-up means may be a current transformer for attachment to a spark plug lead or injection control lead for example, or may be an electrically conducting clip for attachment to a timing pulse output.
BRIEF DESCRIPTION OF THE DRAWINGS
Power measurement apparatus in accordance with the invention will now be described by way of example only with reference to the accompanying drawings in which:
FIG. 1 is a block schematic diagram of the apparatus.
FIG. 2 is a waveform diagram showing the instantaneous speed effects;
FIG. 3 is a stabilised waveform showing certain power variation effects;
FIG. 4 is a stabilised waveform showing other power variation effects;
FIG. 5 is a circuit diagram of the phase locked loop detector current of FIG. 1, and,
FIG. 6 is a diagrammatic illustration showing the apparatus of FIG. 1, in use.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG. 1, the apparatus comprises a digital signal processor 1, for example an eight bit microprocessor which receives a signal indicative of instaneous engine speed from a phase locked loop circuit 2.
The phase locked loop circuit 2 is connected by way of inputs 3 and 4 to a current transformer of the kind detachably connectable to an alternator lead of a vehicle engine in a non-intrusive manner. The current transformer (not shown) detects the high frequency component of the alternator output. This signal is directly related to the instantaneous speed of the engine main shaft by a factor determined by the gearing between the main shaft and the alternator shaft and the number of poles and phases which the alternator has.
It will be appreciated that any engine running at an apparently constant speed (say 1500 revolutions per minute) is in practice running faster and slower than the nominal speed at any particular instant of time. This variation is dependant on the position in the engine cycle at the instant of measurement. Thus immediately after firing of a cylinder, the instantaneous power increase results in an instantaneous acceleration followed by a deceleration until the next power stroke of another cylinder.
Since the instantaneous acceleration provided is dependent upon the power input, each cylinder of a multi-cylinder engine will have an instantaneous effect dependant upon
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patent: 4417467 (1983-11-01), Higgs et al.
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patent: 4812979 (1989-03-01), Hermann et al.
patent: 4932379 (1990-06-01), Tang et al.
Patent Abstract of Japan, vol. 10, No. 41, p. 429 (2098), Feb. 18, 1986, and JP, 60-188826, Sep. 26, 1985.
Mueller Robert W.
Strecker Gerard R.
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