US2842956A - Apparatus for detecting uncontrolled combustion within internal combustion engines - Google Patents

Description

y 1958 o. A. UYEHARA ET AL 2,842,956

APPARATUSYFOR DETECTING UNCONTROLLED COMBUSTION WITHIN INTERNAL COMBUSTION ENGINES Filed Dec. 28, 1955 INVENTORS. arm A. UYEHARA PHILLIP s. MYERS ATTORNEY 2,842,956 Patented July 15, 1958 APPARATUS'FOR DETEQTING UNCONTRDLLED COMBUSTION -WITHFN IN'IERNAL CGMEUS- TION ENGINES ottoA Uyehara and Philip-S. Myers, tatiison, Wis,

assignors to .The 'Pure, Oil Company, Chicago, Ill a corporation of Ohio Application December 28, 1953, Serial No. 400,510

5 Claims. ((11; 73-35) The-present invention. relates to an apparatus for detecting autoignition ,within internal combustion engines and, more particularly, to means for interrupting *the spark cycle' inrelation to .the detecting cycle or :cycles so .that preignition before or after sparking can bewdetected, studied, andrecorded.

Changes in design and increases in engine compression ratios have allowed the niore efficient consumption ;.of motor fuels inthe :modern internal combustion en- .gines. However, during actual road operation of these engines .there occurs an increased tendency for preigni- "IlOH. within the combustion chamber with attendant high rates of pressure increase, knocking, severe wear, and

it is advisable to set forth at least in part the definitions intended to. apply herein.'

; The combustion occurring within a combustion chambervmay be sparkinducedor may be a combination of combustions causedbyother sources of ignition. These latter combustions, are .termed broadly uncontrolled combustion since-thegtime sequence of their occurrence is not directly within the control of the mechanical features of :the engine. This uncontrolled combustion may be due to many conditions existing during the compression and firing cycle of. the engine and is logically divided into (1) those conditions of temperature and pressure which causes ignition which is not a direct .resultof the spark and (2) those conditions other than temperature and pressure. which cause a form of igni- :tionnot induced .by. spark. Within the meaning of this specification, uncontrolled ignition caused by conditions of temperature and pressure will be called autoignition and the balance of the conditions which cause uncontrolledjgnition will be termed hot spot ignition. Thus knock,-whichhas been ,gdefined. by others as. the spontaneous ignition of a portion of the end gas as a result of its temperatureandv pressure, is included within the term autoignition. That type of preignition (ignition occurring before spark) caused by hot surfaces, which is primarily associated with aircraft engines, is necessarily excluded from within the definition of autoignition and falls within the term hot spot ignition. Those conditions which cause hot spot ignition may include --anyexternal means (except spark) that fires off the charge of combustion mixture or portions thereof by catalytic action, glow phenomenon, hot surfaces, or pieces of .loose flakes of deposit; or broadly, deposit-induced aignition. *Preignition includes any hot spot ignition previous to .spark. 'Those' phenomena termed after-firing ,,and. .af ter-runningare included in hot spot ignition.

; Prior investigators have used various means for study- 2 ing uncontrolled ignition. For example, studies have been made in an L-head single cylinder engine wherein a number of ionization gaps are placed .within the combustion chamber. These ionization gaps have two electrodes spaced several thousandths of an inch-apart which detect. the presence of ignited gases therebetween by the change in conductivity caused by the ionization present in the flame. The gap devices are connected to an electronic apparatus designed to establish the point of time in the engine cycle at which the combustion appeared at a given gap. In another apparatus, a single ionization gap is located some distance from the spark plug at a point near the center of theaarea above the piston for the purpose of giving a reliable indication of the degree of deposit-induced ignition at some time interval after spark ignition. The voltage change across a resistor due to the change in. conductivity of the gap on arrival of the flame is transmitted through a cathode follower to a gating device, amplifier, and pulse generator to a recorder or electromechanical counter.

Under certain conditions, namely, that the flame from the hotspot ignition reach the ionization gap before the flame from the sparkfinduced ignition, detection, of

deposit-induced ignition, occurringafter spark, is possible. The purpose of the gating device or circuit is to permit only the deposit-induced flames to actuate the counter or recorder by rendering the recorder nonoperative, previous to the arrival of the flame front from the spark-induced ignition. However, even with the gating device or circuit, uncertainties in the count of depositinduced flames is introduced because of cycle-to-cycle variations .in the speed of travel in the spark-induced flame and accurate and reliable detection can be accomcut off actually a few degrees Ibefore spark. The principal disadvantage to these prior devices .is that they require-many hoursof engine operation and requirethat preignition occurs before spark.

:In accordance with the present invention, adevice and method is provided to detect uncontrolled ignition caused by hot spots or other conditions in the combustion chamber besides normal spark, including presignition, without the disadvantages -of previous devices.

,More particularly, the present invention comprises a design of switcharrangements and associated circuits .which periodically interrupts the spark for a single cycle or cycles and also provides a 1 means for detecting "whetheror. notcombustion occurred during this nonsparking'cycle or cycles. If combustion occurs during this non-sparking cycle or cycles it is clearly the result of uncontrolled. combustion.

Accordingly, a primary object of the invention is to provide a method and apparatus for detecting and re- -mentto detect any combustionother than an intentionallyfired and de'sired combustion during either an unfired or fired cycle.

Other objects and advantages of the invention will in part be obvious and in part appear hereinafter.

In the drawing, one embodiment of the invention is shown diagrammatically.

The description of the apparatus and tracing of associated circuits may be as follows, referring to the drawing wherein single cylinder, 2 or 4 cycle engine has cylinder 11 andcombustion chamber 12., Piston 13 operates within cylinder 11 rotating fly wheel 14 through connecting rod 15 and crankshaft 16. Spark plug 17 is supplied current through line 18 from a suitable voltage source (not shown). A spark grounding or interrupting switch arrangement is shown comprising drive connection 19 connected to reduction gear 20, which rotates disc 21 through drive connection 22. Disc 21 has raised portion 23 which intermittently raises contact 24 of wire 18 against grounded contact 25, during the rotation of disc 21. Reduction gear has drive connection 26 leading to rotating disc 27 having raised portion 28. Cathode ray oscilloscope tube 29 of the electrostatic deflection type connected to a suitable power supply (not shown) is altered by a circuit adapted to brighten the cathode ray 30 impinging on fluorescent screen 31. At desired periodic intervals, to be described subsequently, regulated either manually or by reduction gear 20 and the resultant speed of rotation of disc 27, the raised portion 28 closes contact 32 against contact 33. This completes the circuit consisting of a battery 36, wire 37, relay 38, wire 39, contact points 32 and 33, wire 35, and actuates the relay 38. The closing of contacts 32 and 33 is regulated to occur simultaneously with the spark interruption by contacts 24 and 25 as will be described. Relay 38 serves as a double throw switch 40 making and breaking the connection between movable contact 41 and fixed contacts 42 and 43. The movable contacts of potentiometers 44 and 45 are connected to the intensity grid of the cathode ray tube via the contact points of relay 38 and wire 46.

Wire 48 is connected to the negative voltage of the oscilloscope power supply (not shown). The cathode ray oscilloscope has the usual form of electron emitting cathode 52, heater 53 (which is heated by transformer 51), and control grid 54. The focusing is accomplished by the second anode 60 and by the first focusing anode 55 which is supplied with the proper voltage through wire 56, resistance 57, potentiometer 58, and wire 59. The deflection area of the cathode ray tube 29 is represented by deflection plates 63 and 64 with connecting wires 65 and 66 and deflecting plates 67 and 68 with connecting wires 69 and 70.

It is seen that closing of contacts 32 and 33 actuates relay 38, closing contacts 41 and 42 which increases the flow of electrons from cathode 52 through grid 54.

In order that the screen 31 function to depict the piston position in relation to time and the pressure or rate of change of pressure with time, represented by the function where p equals pressure and 1 equals time, the motion of the cathode ray in one direction is influenced by a signal from sweep circuit 71 and the motion in the other direction is influenced by pick-up 72. Since the embodiments shown for these two respective means are the preferred species thereof and other means may be used for curved edge of the cams gradually allows the light to impinge with an increasing amount on one tube and with a decreasing amount on the other tube. Under the influence of the light source, the photo tubes send a signal through their respective circuits, indicated by wires and 81, and 82 and 83 with associated batteries 84 and 85 and variable resistors 86 and 87 to amplifier 88 wherein the signal is amplified to a suflicient voltage which is impressed across deflecting plates 67 and 68. This controls the magnitude of the sweep of the cathode ray 30 on screen 31 as a function of the piston (13) position Within cylinder 11. This is represented as the cycle between bottom center, top center, and back to bottom center during the compression and firing stroke if the drive 77 is connected to the crankshaft of the engine. To obtain this relationship, the rotation of drive connection '77 and shaft 76 is adjusted so that as the piston passes upwardly in the beginning of the compression stroke, one cam is just beginning to allow a small amount of light to impinge on one of the phototubes and the other cam is just beginning to decrease from the maximum amount of the light falling in the other phototube. This light change caused by the rotation of the cams produces voltages that gradually sweep the cathode ray 30 across the screen 31 and almost instantaneously returns it to the starting position for the next cycle. A suitable sweep circuit device for this purpose of influencing plates 67 and 68 comprises the Rowe Radio Research Laboratory Co.s Angular Sweep Potentiometer, type APZXB and type AP2.

In place of the sweep circuit 71 an oscillator adapted to give a saw-tooth voltage curve in relation to time may be used and its voltage signal may be impressed across the plates 67 and 68. Such an oscillator is built into many oscillographs and could be synchronized with the engine rotation either by internal synchronization which is customarily provided in the oscillograph or by an external synchronization signal provided cyclically from the engine.

A further expedient for impressing a voltage signal across plates 67 and 68 is by means of a potentiometer having a sweep contact rotated by the engine revolution which picks up and transmits a varying voltage to the plates influencing the movement of the cathode ray 30.

The movement of the cathode ray 30 perpendicular to the previously described sweep movement on screen 31 is proportional to the pressure directly or to the rate of change of pressure in relationship to time,

l (it and is accomplished by placing a voltage signal across plates 63 and 64 through pick-up 72. This is accomplished by pick-up device 72 which generates a voltage proportional to One such instrument is manufactured by the Phillips Petroleum Company and is used for other purposes such as fuel rating. This voltage passes through wire 89 to amplifier 90 and thence to the pair of deflection plates 63 and 64 via wires 65 and 66. Thus the movement of the cathode ray 30 along one axis is a function of and the movement along the other axis is a function of piston position.

In place of the rate-of-change-of-pressure pick-up, a

pick-up that is directly responsive to pressure may be employed to detect if hot spot ignition occurred. For this purpose, the Li pick-up as manufactured by Control Engineering Corporation is'suitable. This pressure pick-up comprises essentially a flexible diaphragm directchanges.

assesses 1y under influence of pressure within the combustion zone. The diaphragm is associated with and impinges upon a small cylinder in direct contact with the diaphragm. The cylinder is tightly wrapped with strained gage wire in the form of two separate coils, one coiled around the circumference of the cylinder and the other coiled in loops, the planes of which lie against the first coil and parallel with the axis of the cylinder. Under influence of pressure the cylinder is compressed slightly and as a consequence its cross-sectional area increases. This expansion causes a change in the cross-sectional area of the respective coils and, as a result, the amount of current flowing therethrough per unit of time also This change is picked up by an appropriate circuit (not shown) and sent to the plates 63 and 64.

A third means for changing the path of cathode ray '30 when combustion occurs within the combustion zone 12 comprises a quartz window set within the cylinder Wall 11 with an associated flame radiation detector such as a photoelectric cell. Such an arrangement would give an indication or signal proportional to the change in relative illumination occurring within the combustion zone. In using such devices, however, adjustment should be made so that illumination due to cool flame combustion is eliminated.

In operation, the reduction gear 20 and drive con nections 26, 22, and 77 are adjusted so that at the moment piston 13 is at the bottom center. position and about to begin the upward compression stroke, disc 27 closes contacts 32 and 33 to brighten the scope, rotating disc 21 closes contacts 24 and 25 to ground out the spark, and sweep circuit 71 causes the spot or cathode ray 30 to travel across the face of screen 31. Ifdesired, the picture produced on the screen may be photographed .through the use of a camera focused thereon, the shutter of which is either operated manually or opened and closed by the completion of the cycle as through a mechanism (not shown) connected to reduction gear 20. In place of or in conjunction with photographingthe results, it is often desirable to employ a counter, again connected through the reduction gear, to count only the number of uncontrolled combustions occurring in nonfired cycles or times of interrupted spark. Also, it is expedient to use two counters, one to record the number of spark interruptions and a second torecord the number:

of times the spark was interrupted but combustion occurred. For this purpose,a Veeder-Root counter manu- Efactured by Veeder-Root Inc., Hartford, Connecticut,

erating temperature, including a 105 F. inlet mixture temperature, a coolant temperature of 212 F., etc. The

fuel under investigation was carbureted and admitted to the combustion chamber. As the engine operated, the spark was interrupted by the described apparatus every 56 engine revolutions, and the resultant oscillographs were observed and photographed on a single-frame for 25 non-fired cycles in cases with relatively few hot spot ignitions, and on a double frame for 12 and 13 non-fired cycles where hot spot ignition was frequent. The developed films were then analyzed on an arbitrary basis of the number of hot spot ignitions per 100 non-fired cycles in order to compare and evaluate the fuel. The method is useful not only for evaluating various fuels and mixtures thereof, but also for evaluating the effects of oils and fuel or oil additives upon fuel combustion.

The invention, accordingly, comprises apparatus for detecting uncontrolled ignition or combustion within the combustion chamber of an internal combustion engine. Either a 2-cycle or 4-cycle engine may be used and the engine may have any number of cylinders. Single cylinthese physical changes.

. tions, i. e., no load. Particular features of the apparatus include the means for grounding out the sparking device and means for brightening the oscilloscope during the detection steps. The features of the method includethe step of grounding out the spark so that uncontrolled ignition can be detected during the entire compression and what would normally be the fired cycle. ,The method also includes the step of brightening the scope during the detection of piston position and detecting a change in a physical property within the combustion chamber simultaneously therewith.

Also, with the method and apparatus of this invention, a new combustion phenomenon has been detected which produces on the oscilloscope screen a sharp peak in opposite direction to and immediately preceding, or within the area of, the usual dip observed on the screen when an uncontrolled combustion occurs. The ordinary dip represents a voltage drop arising from passage of current from a battery and a resistor by virtue of ions in the flame front. The new phenomenon observed therefore appears to be an actual voltage generation across the gap, and is believed to indicate a type of hot spot ignition which occurs only when said hot spot ignition terminal is grounded, the peak appears as before but I the usual dip is, of course, missing. These observations show the consistency of the new phenomenon, which is considered to be of fundamental significance, and the discovery of the same was made possible by the invention described herein.

The change in physical property detected within the combustion chamber in accordance lit-h this invention includes rate of change of pressure with time, pressure per se, ionization, light radiation, temperature, sound waves, vibration, or combinations of two or more of Ionization is detected by means of an ionization gap device located within the combustion chamber wherein the appearance of the flame between spaced electrodes allows the passage of current therebetween in proportion to the flameintensity or de gree and kind of ionization. For this purpose, a spark plug or other insulated gap suitable for detecting ionization in series with a battery or power supply and a resistor is used. Light radiation is detected by means of a quartz window in the cylinder wall or head adjacent thecombustion chamber through which a photocell detects the appearance of flame therein and transmits a signal tothe oscilloscope. Temperature is detected by means of one or more sensitive thermocouples located within the combustion chamber. Sound waves may be detected by means of an acoustical device similar to a microphone or stethoscope aflixed or located near the combustion chamber whereby the sound received may be detected orally or converted to voltage and observed on the screen or counted by a counter. Vibration may be detected by a vibration pick-up such as is made by the Sperry Company and used in engine knock indicators. In this case the pick-up must be attached to the engine cylinder.

The preferred physical property detected within the combustion chamber is rate of change of pressure because it provides the greatest differential indications between hot spot combustion and normal dead cycle operation. Where two or more physical changes are measured it is preferred that ate of change of pressure and ionization be used in combination, or pressure change and light radiation, since one may supplement the other. in making such combination measurements, it is advantageous to make the determinations using one physical property and then check the results by repeating the experiments using another physical property. In this way the course of the complicated reactions and phenomena occurring in the combustion chamber may be more completely investigated.

Although the invention has been described using specific embodiments, the only limitations thereon appear in the appended claims.

What is claimed is:

1. An instrument to detect uncontrolled combustion with the combustion chamber of an internal combustion engine equipped with a sparking device comprising in combination, means for detecting a change in a physical property Within said combustion chamber in relation to piston position during a compression and combustion cycle, means including an oscillograph to depict said change in physical property graphically on a screen, an ignition grounding device connected to a rotating part of said engine through a reduction gear whereby at predetermined intervals the ignition impulse to the sparking device is grounded out so that a comparison of fired and unfired cycles may be made.

2. An instrument to detect uncontrolled combustion within the combustion chamber of an internal combustion engine equipped with a sparking device comprising, in combination, means for detecting a change in a physical property within said combustion chamber in relation to piston position during a compression and combustion cycle, means including an oscillograph to depict said change in physical property graphically on a screen, an ignition grounding device comprising a rotatable disc connected to a rotating part of said engine through a reduction gear, said disc having a raised portion on its peripheral surface, a spring-loaded member. in contact with the peripheral surface of said disc and connected between said sparking device and the electrical system of said engine, a grounded contact spaced from said spring-loaded member whereby said raised portion periodically moves said spring-loaded member against said grounded contact and shorts out the ignition of said sparking device.

3. An instrument to detect uncontrolled combustion within the combustion chamber of an internal combustion engine equipped with a sparking device comprising, in combination, means for detecting a change in a physical property within said combustion chamber in relation to piston position during a compression and combustion cycle, means including an oscillograph to depict and trace said change in physical property graphically on a screen, an ignition grounding device connected to a rotating part of said engine through a reduction gear, and means for simultaneously brightening said trace during the period of detecting said change in physical property at the time said ignition grounding device is actuated, whereby a comparison of fired and non-fired cycles within said combustion chamber may be made.

4. An instrument to detect uncontrolled combustion within the combustion chamber of an internal combustion engine equipped with an electrical system and a sparking device comprising, in combination, means for detecting a change in a physical property within said combustion chamber in relation to piston position during a compression and combustion cycle, means including an oscillograph to depict said change in physical property graphically on a screen, a power supply for said oscillograph, an ignition grounding device comprising a rotatable disc connected to a rotating part of said engine through a reduction gear, said disc having a raised portion on its circumference, a springloaded member in contact with the circumferential-surface of said disc and connected between said sparking device and the electrical system of said engine, a grounded contact spaced from said spring-loaded member whereby rotation of said disc causes said raised portion to periodically raise said spring-loaded member against said grounded contact to short out the ignition of said sparking device, means for simultaneously brightening said oscillograph screen including a second rotating disc connected to said reduction gear, said-second disc having a raised portion on its peripheral surface, a springloaded member in contact with the peripheral surface of said second disc and connected in series with a source of electrical current and a relay switch to a stationary contact whereby said raised portion periodically moves said spring-loaded member against said stationary con tact to actuate said relay, said relay having two terminals, said terminals being connected through variable resistances to said power source and to the cathode and control grid of said oscillograph whereby simultaneously with the grounding of said sparking device said second rotating disc causes said relay switch connect said cathode and control grid to a terminal of increased electrical power and brighten graphic indicia on said screen.

5. An instrument in accordance with claim 3 in which the means for brightening said oscilloscope trace include a rotating disc having a raised portion on its circumferential edge, a flexible conduit member incontact with said circumferential edge, said conduit being connected at its other end through a source of electrical energy to a relay type switch to a second spaced contact whereby said raised portion contacts said flexible conduit to raise same against said second contact or third contact operated by said relay, said third contact opening and closing the power supply circuit to said oscilloscope to brighten said trace.

References Cited in the file of this patent UNITED STATES PATENTS 1,914,496 Fernandez June 20, 1933 2,133,437 Dodds Oct. 18, 1938 2,355,363 Christaldi Aug. 8, 1944 2,414,457 Eldredge et a1. Jan. 21, 1947 2,445,245 Sexton July 13, 1948 2,518,427 Lindberg et al. Aug. 8, 1950 2,543,141 Vichnievsky Feb. 27, 1951 2,641,719 Adams June 9, 1953 2,660,883 Wyczalek Dec. 1, 1953 FOREIGN PATENTS 831,166 Germany Feb. 11, 1952 OTHER REFERENCES Socony-Vacuum Laboratories Instruction Manual for Engine Analyzer, Type 2517, Research and Dev. Dept., Paulsboro, New Jersey, September 1951, pages 7, 8, 9, 11, 12, 32, 39.

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