BACKGROUND OF THE INVENTION -

1. Field of Invention -

This invention relates to the field of engine analyzing devices for spark plug ignited combustion engines.

2. Description of the Previous Art -

The purpose here is to analyze an engine's operation by an analysis of the voltage produced by a spark plug.

In ordinary operation, the magnitude of a spark plug's voltage is determined by the spark plug itself and not by the ignition system. The spark plug determines the spark size by its gap size and by the m Lcrial within the gap. The gap of a spark plug changes only slightly with the miles of operation of a motor vehicle engine. Voltage however changes rapidly from one burn cycle to the next. These changes are due possibly to the material changes within the gap of the spark plug from one burn cycle to the next.

Λs a cylinder in a motor vehicle burns its fuel, it produces ionized gases and the more gases there are in the spark plug gap from burning, the lower the electrical resistance across that gap will be. This lower resistance will reduce Llio magnitude of the voltages across the spark plug gap.

Current engine analysis devices may have the ability to display a particular characteristic of a spark voltage that is processed by the apparatus of this invention. Those devices may also function to determine an average value for that charac¬ teristic. However no current engine analysis devices can process a voltage to produce an output that is an instantaneous running average of that characteristic. Further the device herein provides information about the burning process inside an engine that no other device is known to provide.

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SUMMARY OF THE INVENTION -

This invention relates to an analyzing device for a spark plug ignited internal combustion engine. Λ means for sensing generated sparks is coupled to a spark plug to transmit spark signals proportional to each of the generated sparks. Each sensing means is connected to a circuit of the analyzing device which is capable of analyzing the spark and of producing an output that will enable either the user or an attached computing device to evaluate the function of the engine based on the analysis of one or more of sensed spark voltages.

The apparatus of this invention is particularly adapted for processing the voltage produced in the gap of a spark plug in order to identify problems with the operation of an internal combustion engine.

Λ particular disclosing and reliable feature of the invention herein is that its analysis of spark plug voltage is that it produces an instantaneous and continuous running average reading of one or more features of the voltage in the gap of a spark plug.

Λ unique aspect of the engine performance analysis of the device comprising the invention herein is that the analysis gathers information from a number of spark plug firings which is used to calculate readings from which qualities of a spark wave form can be analyzed. This calculation may be derived from either the breakdown voltage, the collapsing field voltage or from the spark voltage pulse duration or from a combination of two or more of Lliese. This is contrasted to the prior art which only displays spark voltages generally.

The calculation derived from a number of spark plug firings may be referred to as an averaged reading or voltage value. This averaged reading is important in providing significant information about the operation of an engine which any single reading of a spark plug firing would not supply. The reason why one reading does not supply sufficiently useful information is the great

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,„., _« PCTΛJS95/14129 6/15366 _d isparity in such readings from one spark plug firing to the next in engines that are operating properly. The averaged reading obtained evens out the natural variations of the engine and creates an output which reflects the actual ongoing operation of an engine.

The engine analysis device in processing the voltage of spark plug firings discloses features which relate to the proper operation of an engine and particularly invaluable is the fact that the analysis of the engine's operation is observed during the time that incidents interfering with the proper operation of the engine are actually occurring.

Further, the present invention can determine the effective¬ ness of the voltage of sparks that have been delivered to an engine. If an engine is not burning fuel properly, the invention will point out any and all cylinders not functioning properly and also a variety of engine problems such as clogged fuel injectors, bad exhaust systems, bad valves, incorrect timing and other problems which may cause poor combustion, improper cylinder operation and other problems. Thus with the invention herein, the spark plug acts as if it were a sensing probe within the engine.

BRIEF DESCRIPTION OF THE DRAWINGS -

Fig. 1 is a flow 'chart of the basic operation of steps of the invention herein;

Fig. 2 is a partial flow chart combined with an enlarged schematic showing of a circuit;

Fig. 3 is a schematic diagram of the circuitry of the invention herein;

Fig. 4 is a diagrammatic view of an output display;

Fig. 5 is a view similar to that of Fig. 4;

Fig. 6 is a view similar to that of Fig. 5 showing a problem condition; and

Fig. 7 is a diagrammatic view of a spark plug wave form.

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D _ESCR IPTION OF Λ PREFERRED EMBODIMENT -

_Λ preferred embodiment of the circuitry of the device comprising the invention herein is shown in Fig. 3 and is indicated generally by the reference numeral 50.

A unique aspect of engine analysis from spark plug firings is the information derived from the breakdown voltage, collapsing field voltage or the voltage pulse duration thereof or a combination thereof and Fig. 7 provides a diagrammatic illustration of the voltage wave forms.

Going now to Fig. 1, a flow diagram of the operating function of the invention herein is shown wherein a spark plug gap voltage 11 is conducted by a line 11a to the device comprising the invention herein for transmission to and through the device, first by the voltage transmission means 100a, 101 and 102 which reduce the voltage received to a value for processing through the device, then to detection of peaks of said voltage by means 113, 114 and 103, 104 and securing averaged peak voltage readings by means of the elements 115, 116, 117 and 105, 106 and 107, the same being arranged for display through the output element 9415. It is noted that the voltage, of a spark plug is in the thousands of volts whereas the device herein in operation requires only a few volts.

Λ detailed description will now be given particularly in connection with Figs. 2 and 3.

Referring to Fig. 3, the voltage transmission means in the present embodiment is shown as including an incoming or input line 100a of Fig. 3 which includes a very simple voltage divider comprising a pair of resistors such as 101 and 102. Resistor 101 feeds into and through the resistor 102, the resistors having a ratio on the order of 1000 to 1 which reduces the voltage accordingly to a useable value. This is all well known in the art and may be variously otherwise accomplished.

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The voltage thus having been reduced is fed into the processing of the circuitry of the device of the invention as shown and as described in connection with Figs. 2 and 3.

Fig. 3 in showing a preferred embodiment of the circuitry of the invention herein shows it adapted to analyze the voltage of an eight cylinder engine. The analysis being the same for each cylinder, the circuitry is described for one cylinder as in the enlarged showing of the circuitry 100 of Fig. 2 and the remaining circuits 200-800 are analyzed identically in sequence for the remaining cylinders, the same having applied thereto sequential numbers for reference as if the same were specifically described herein.

The specific elements comprising the invention and the specific elements of the circuitry and the connection thereof are not individually described as all are well known in the art. It is their unique combination which comprises the invention.

The reduced voltage or electrical signal, referring to Fig. 2, from the voltage transmission means 100a, 101 and 102 is conducted by conventional wiring to circuitry 100 of the first cylinder comprising circuit elements 103 and 113 which are operational amplifiers which are connected to diodes 104 and 114 which respectively detect peak negative and peak positive voltages while allowing said reduced voltage Lo pass through in one direction only. These circuit elements are referred to as peak voltage detectors because capacitors 106 and 116 to which said voltage passes will be charging while the device herein is in operation and only voltage with magnitude greater than that of the respective associated capacitor will pass through. Hence only the highest peaks of said reduced voltage will pass through.

Said capacitors 106 and 116 function as analog computers and perform this function either through their charging or discharging activity.

Resistors 105 and 11 ^r > '-ontrol the charging of said capacitors while resistors 107 and 117, as shown, control the discharging thereof. This limitation on the charging results in a number of spark plug firings being required to charge the capacitors rather than just one firing. Thus as an end result there is determined a running average or an averaged spark plug voltage reading which has occurred during the previous period, possibly being a five second period of engine operation.

For a description up to the output of the voltage display means of Fig. 1, reference is now had to Fig. 3.

Conductors 144 and 154 in connection with the capacitors 106 and 116 and the resistors 105 and 115 acting as analog computers conduct Lliπ output therefrom feeding the same to analog selector devices 931 and 932. The selector 931 will output the computed negative analog voltages at 931a and the selector 932 will output the computed positive analog voltages at 932a. The output of the analog voltages is sequentially outpufted by the action of binary counter 916 to be described. Since the output of said selectors is controlled by said counter, the output of said selectors will always be the negative and positive voltages of the same computed spark plug voltage or electrical signal output.

The outputs 931a and 932a of the selectors 931 and 932 are fed into differential amplifiers 941, 944 and 947, the output of which is the sum of the magnitude of the computed negative and positive weighted running average voltages calcu¬ lated by the previously described analog computers.

Λ reason why the output from the differential amplifier is better than the output from either selector individually is that the polarity of the spark electrical signal is different for different engines and sometimes different within a given engine. Therefore combining the polarities into one output removes the requirement that the device user know the polarity of the spark being analyzed and αcL accordingly.

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Another reason is that problems with an engine's -per¬ formance will generally have similar effects on the magnitude of both the positive and negative signals being analyzed. Hence the effect of a bad engine performance is normally in¬ creased and may be doubled by combining the two outputs for a better analysis.

Λ binary counter 925 is formed by the combination of an oscillator 915 driving a counter 916. The frequency of the oscillator is about 0 kilo hertz. Outputs 916a, 916b and 916c from said counter determine which two of the sixteen computed analog voltages (eight circuits) of the device 50 herein are selected by the selectors 931 and 932. When eight possible outputs have been cycled through by counter 916, an output trigger 917 from the counter provides a signal for an oscilloscope display through the outlet 948 of said amplifiers 94J, 944 ,-ιιιtl 947. The rosisl-nrs 942, 943, 945 find 946 drtprmi.no the gain for said amplifiers. This trigger signal insures that the user will always' see the computed output from the first spark plug wire at the far left of an oscilloscope screen and the other seven spark plug wires in this embodiment will be seen in order displayed from left to right on the screen. The reference numberals and/or characters within said counter and said selectors relate, to specific cylinders of the engine and to the specific circuits 100-800 for sequential output on a display. The counter and selectors are conventional elements.

The output of which examples are shown in Figs. 4-6 is designed Lo be displayed on any standard oscilloscope. When thus displayed, the user would see the sum of the magnitude of the negative and positive computed average peak voltages side by side on α screen in sequence througli the circuits 100-800 and repeating in the same pattern. In connection with said counter 91C, the diodes 921 and 922 flash to indicate the counter is operating. The capacitors 901 and 913 are by-passes and the resistors 911 and 912 determine the frequency of the output of said counter 925.

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This device processes its output from its analog computation from the capacitors 106, 116 and resistors 105, 115 so that a technician can easily see the problems with an engine by looking at a display on an oscilloscope. It is noted here that the information from the analog computers could be transmitted to a digital computer for analysis of which there is an instal¬ lation in the engines of many new vehicles.

Diagnosis whether by α computer or α technician involves comparing the output voltages with each other and with where it is known they should be under a variety of operating conditions.

Λ further description is given of the output voltage which comprises the breakdown voltage, collapsing field voltage and spark voltage pulse duration. The breakdown voltage reaches its greatest magnitude just before the current begins to flow in the spark plug and the collapsing fieldvoltage in an oscil¬ lation that occurs right after the current has stopped flowing in the spark plug (see Fig. 7) . The duration of the spark is the time that elapses from the peak of the breakdown voltage to the beginning of the collapsing field voltage.

With regard to ionized gases generated, a decrease in ionized gases results in an increase in breakdown voltage and a decrease in ionized g ses results in an increase in collapsing field voltage. Λ decrease in ionized gases also results in a shorter and more intense spark plug spark.

In result, analyses of breakdown voltages and spark duration provide information about previous engine cycles while an analysis of collapsing field voltage provides information about both previous and current engine cycles. Λ valid conclusion may be made that an analysis based on collapsing field voltage in combination with breakdown voltage and/or spark duration is more informative than an analysis based on only one of those factors.

The device described herein as the invention in its preferred embodiment can base its analysis of the breakdown voltage or

collapsing field voltage depending on the speed specification of the operational amplifiers in its output circuitry. The outputs can be combined in either an additive or subtractive manner. If the output is subtractive, then the effect of residual ionized gases would be erased and only newly created ionized gases would effect the output.

Figure 6 indicates a problem found by comparing cylinder 3 with the others. Cylinder 3 must have a problem because its voltage is so different than that of the other cylinders. The problem if unrelated to an operating condition may relate to a defective spark plug or spark plug wire or it may indicate failure of an engine to burn fuel properly under those particular conditions that exist when a different voltage is displayed. In contrast Figs. 4 and 5 show a fairly uniform cylinder display of a properly running engine, Fig. 5 showing an increase in volts generated relative to Fig. 4.

Problems can be seen by rcyarding a cylinder as of itself as improperly operating cylinders will often have an erratic element in their operation which will cause voltages to vary more than voltages of properly operating cylinders. By setting the oscilloscope sensitivity as high as possible and looking at the bounce of each cylinder's voltage, problems in a particular cylinder may be seen as in the case of the cylinder 3 in Fig. 6.

Tiie correct voltages for a particular engine varying under a variety of operating conditions could be determined. Once the acceptable range of voltages lias been determined, those outside of this range would indicate a problem with the engine. These readings could be used so that preventative maintenance may be performed before noticeable problems appear.

Λ power supply circuit 949 is an integral part of the circuitry 50 and the connection therewith although not here directly shown is conventional and well known in the art.

The elements 950 and 953 of the circuitry 949 provide terminals for a battery connection to power said circuitry.

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_Λ resistor 961 limits current so that a sudden burst of current when the device is operating will not damage any component.

Λ diode 963 prevents a reverse connected battery from damaging components. Resistors 963 and 964 create a reference voltage

V3. Capacitors 965 and 966 stabilize the reference voltage

V3 and the element 952 provides a ground for said voltage.

With the reference voltage established, deviations therefrom can be noted to provide preventative maintenance before a noticeable problem appears.

The contacts of the reference voltage V3 are clearly shown throughout the circuitry 50. The power supply V2 is adapted for the digital circuitry as shown in connection with the counter

'916 and the terminal VI provides a general power supply.

It will of course be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of the invention herein, which, generally stated, consists in a device capable of carrying out the objects above set forth, in the parts and combination of parts disclosed and defined in the appended claims.

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