CA1049609A - Ignition systems for internal combustion engines - Google Patents
Ignition systems for internal combustion enginesInfo
- Publication number
- CA1049609A CA1049609A CA226,349A CA226349A CA1049609A CA 1049609 A CA1049609 A CA 1049609A CA 226349 A CA226349 A CA 226349A CA 1049609 A CA1049609 A CA 1049609A
- Authority
- CA
- Canada
- Prior art keywords
- ignition system
- stage
- electronic ignition
- combustion
- engine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P5/00—Advancing or retarding ignition; Control therefor
- F02P5/04—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions
- F02P5/05—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using mechanical means
- F02P5/10—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using mechanical means dependent on fluid pressure in engine, e.g. combustion-air pressure
- F02P5/103—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using mechanical means dependent on fluid pressure in engine, e.g. combustion-air pressure dependent on the combustion-air pressure in engine
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P5/00—Advancing or retarding ignition; Control therefor
- F02P5/04—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions
- F02P5/145—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using electrical means
- F02P5/1455—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using electrical means by using a second control of the closed loop type
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
- Electrical Control Of Ignition Timing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A closed loop electronic ignition system for internal combustion engines, in which a comparison is made between a signal derived from a fixed predetermined crank-shaft angle, and a signal derived from the commencement of the second stage of combustion within a cylinder of the engine, and if non-coincidence is detected between the two signals, the ignition timing is either advanced or retarded so as to maintain coincidence between the signals, so that the second stage of combustion always occurs at the fixed predetermined crank angle, the spark then being extinguished by switching the ignition coil "on" at this predetermined crank-shaft angle, irrespective of the speed and load on the engine, as well as all other parameters which can affect the ignition timing.
A closed loop electronic ignition system for internal combustion engines, in which a comparison is made between a signal derived from a fixed predetermined crank-shaft angle, and a signal derived from the commencement of the second stage of combustion within a cylinder of the engine, and if non-coincidence is detected between the two signals, the ignition timing is either advanced or retarded so as to maintain coincidence between the signals, so that the second stage of combustion always occurs at the fixed predetermined crank angle, the spark then being extinguished by switching the ignition coil "on" at this predetermined crank-shaft angle, irrespective of the speed and load on the engine, as well as all other parameters which can affect the ignition timing.
Description
960~
The present invention relates to an igni~ion system for internal combustion engines~ and more particularly to the timing of the switching on and off of the spark.
A known type of ignition system for an internal combustion engine employs contact breaker points operated by a cam driven via suitable gearing from the engine crank-shaft. In this system the contacts are closed and thus the battery is connected across the ignition ; coil for a fixed number of degrees of crank-shaft rotation irrespective of engine speed. The duration of the spark~
which commences when the contact breaker points are openedg is a function of the electrical parameters of the system, and is substantially independent of engine speed.
Another known type of ignition system for internal combustion engines employs a magnetic trigger to switch - off the current to the ignition coil, so initiating a spark, the current being switched on again a suitable time before another spark is required. The period of time between switch off of the ignition coil, and switch on of the ignition coil is related by suitable control means to the speed of therengine such that the coil has sufficient 'ton'' time for its magnetic field to accumulate sufficient energy to pr~duce the spark.
A further known type of ignition system is triggered by opto-electronic means at appropriate crank shaft positions~ the triggering switching off the current to 1~49~09 the ignition coil, the coil being reconnected to the battery a fixed period after switch off. In such a system the crank-shaft position at which a spark is `
initiated is precisely defined. The spark duration depends on the electrical parameters of the system, -switch on of the coil being a fixed time after switch off rather than a particular number of crank-shaft degrees later. This system is effectively monostable, since the spark is produced by an electronic circuit which has a stable state in which the coil is "on"
and is triggered to the unstable state to interrupt the current in the primary winding, and thus initiate the necessary secondary voltage to produce the spark, the circuit returning to the stable state a fixed time ~
thereafter. :
A known improvement upon the above monosta~le opto-electronically controlled system is a bistable sys-tem as disclosed in our Canadian Patents Nos. 879,285 ~
and 932,382, whereby the crank-shaft angles between the `
switch on and off of the coil are fixed.
In our copending Canadian Application No.
195,002, we have disclosed an ignition system for an in-ternal combustion engine in which not only the timing of the spark is controlled in accordance with the speed ;
and load on the engine, but the duration of the spark is controlled relative to the angular position of the crank-shaft such that the spark at the spark plug is extinguished .
at a predetermined crank-shaft angle irrespective of tl~e crank-shaft angle at which the spark is initiated.
In the preferred embodiment disclosed, this position is in the range of from 0 to 5 after top dead centre (A.T.D.C.) The system disclosed in Canadian Application ~O. 195JOO2 utilizes the basic principle disclosed in our Canadian Patent Application No. 160,849 concerning the automatic computerized advance and retard of spark la~ter ~ ignition. In this/Application, the advance and retard of the spark ignition of an internal combustion engine is achieved electronically by generating two series of pulses in synchronism with the engineJ using one series as a reference for maximum advance and "coil on", and the other series to operate a counter to count down the requisite number of pulses beyond the maximum advance point before the spark is initiated, the count of the counter being varied from a computer in accordance with speed and/or load on the engine.
In addition to the speed and/or load of the engine there are a numlber of other factors which to a ; greater or less extent affect the spark timing of an in-ternal combustion engine.
The principal factors are: fuel octane rating, air temperature, humidity and air pressure.
It has been general practice to establish ad-vance curve requirements for both speed and load changes on .~ ... .
:
11~)4~609 the particular engine concerned by dynometer testing using simulated conditions in the laboratory. ~laving obtained the advance curves -Eor speed and load, mechanical mcans are constructed in order to reproduce these curves representing the required timing of the ignition by means of physical movcment of the ignition system components relative to the engine's crank position, i.e. top dead centre ~T.D.C.) It has further been proposed to use mechanical means to achieve advance or retard of the ignition timing, which takes into account the other factors noted above, such as fuel octane rating, air temperature, humidity and air ;
pressure. Such systems are, of course, mechanically complic-ated and are liable to error and failure. -Studies of the combustion process within an internal combustion engine have shown that the combustion process has two distinct stages. Firstly, after the initiation of the ;
.
spark, there is a low pressure stage wherein the mixture is igniting and a flame is starting to propogate within the `~
combustion chamber. At some subsequent point in time a sudden rise in both the pressure and temperature within the cylinder is observed, which marks the commencement of the second explosive stage of combustion. During the initial stage of combustion temperatures and pressures within the combustion -chamber are low compared with the temperatures, and pressures within the combustion chamber during the second stage of ',: .
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1(~4~ 9 combustion.
~ y the commencement of the second stage of combus-tion the mixture in the cylinder is well alight, and the presence of any spark at the spark plug is irrelevant to the following process of combustion within the cylinder. It is the timing of the commencement of this second stage which is extremely important. Tests have shown that for best engine efficiency this sudden pressure and temperature rise should always occur at one fixed crank-shaft angle) regardless of all the variables which influence the spark timing require-ment.
It is therefore an object of the present invention to provide a closed loop ignition system in which a predeter-mined pressure on the pressure rise curve occurring during the second stage of combustion can be accurately sensed in , relation to a given fixed angular position, and maintained at this position under all engine conditions.
: ::
`~ According to the present invention there is provided an electronic ignition system for an internal combustion engineJ including: means for sensing a pre-determined pressure on the pressure rise curve occurring during the second :::
stage of combustion in a cylinder of an engine at each firing cycle; means for comparing the crank-shaft position at said pre-determined pressure with a fixed pre-determined crank-: ;
shaft position; and digital means for advancing or retarding .
~- the ignition by one step at a time so as to maintain this pre-determined crank-shaft position at said pre-determined pressure on the pressure rise curve occurring during the second stage of combustion, irrespective of engine requirements.
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Preferably, the predetermined crank-shaft angle at which the commencement of the second stage of combustion ~ :
occurs is ideally 10 A.T.D.C., but this may vary according to certain engine characteristics, more particularly those relating to the design of the cylinder heads.
Preferably, the electronic ignition system for an internal combustion engine includes means for generating a first series of square wave voltage pulses in synchronism with the engine revolutions to provide a series of alternate highs and lows; means for generating a second series of square wave voltage pulses at a frequency greatly in excess ~ `
of the first series; means for counting a given number o~
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the second series of voltage pulses from a given point in relation to the first series of voltage pulses; cmd means for producing an output of a give~ level from said counting means after said count has been completed, means for detecting the presence of both a signal at said given level from the first pulse generating means and the counting means, in order to bring about the initiation of the spark, the extinguishing-of the spark being effected when the signal from the first generating means changes to the opposite level; and means for varying the count of the counting means in accordance with the position of the commencement of the second stage in the combustion process if this deviates from the predetermined crank-shaft position.
Preferably, in one form the electronic device controls the advance and retard of the ignition, the counting means starting to count near the position of maximum advance.
Alternatively, the count may be started from the fixed coil turn on signal. Thus a signal at said given level from the first trigger initiates the count of the counting means, which then counts down the number it has been set to before giving a signal at said given level to cause the initiation of the spark, and then to permit the spark to continue until the pressure rise point is reached, and the coil is turned on~
The counting means is preferably a frequency divider whose count can be increased or reduced by a single step -8- ;
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at each cycle of ignition.
The present invention will now be described in greater detai]. by way of examples, with reference to the accompanying drawings, wherein:-Figure 1 is a diagram (partly in block form) ofone form of spark control device for use with a spark ignition system of an internal combustion engine;
Figure 2 is a front view of the disc shown in Figure l;
Figure 3 is a set of waveforms which assist in explaining the operatisn of the circuit shown in Figure 1;
Figure 4 is a diagram (partly in block form) of an alternative form of spa~k control device to that shown in Figure 1.
Figure 5 is a set of waveforms which assist in ~
explaining the operation of the circuit shown in Figure 4; :
Figure 6 is a cross sectional view through a cylinder : ~
... .
showing a second method of detecting the commencement of the second stage of the combustion process in the cylinder using a second spark plug;
Figure 7 is a circuit diagram illustrating this second method; ~-Figure 8 is a cross sectional view through a cylinder ;
showing a third method of detecting the commencement of the second stage of the combustion process in the cylinder by means of a fibre-optic cable and a translucent window in the upper part of the cylinder;
_9_ .
60g Figure 9 is a circuit diagram illustrating this third method;
Figure 10 is a circuit diagram showing an alter-native form of combining the logical signals from the first and third triggers;
Figure 11 is a part cross sectional view through .,.
the inlet manifold of the engine, showing a second embodi-ment of the invention, utilizing the vacuum in the inlet manifold;
Figure 12 is a view of the chopper disc for this second embodiment; and :~
Figure 13 is a circuit diagram of the circuit .
which energizes the solenoid shown in Fi.gure 11.
The ignition control system according to the present invention will now be described with reference to a four cylinder internal combustion engine.
Referring to Figures 1 and 2, the device achieves electronic control of the advance and retard of the initia-.
: tion of the spark through the detection of the crank-shaft : 20 position of the commencement of the second stage of the combustion within the cylinders. The device includes a radiation chopper device generally designated l; a first fast inverse switching trigger circuit 11; a second fast ~.
inverse switching trigger circuit 12; a counter 1~; a pressure detector stage 16; an AND gate 19; and a power tran--sistor stage 18.
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: ~" : ' ," '' ~ ' ,: . . . , : , ' Circuit details of the two inverse fast switching triggers 11 and 12 and the power transistors stage 18 have been disclosed in our Canadian Patent No. 98~,935 which issued on March 2, 1976. Each trigger 11 and 12 comprises two transistors arranged to switch in inverse relation to each other, the first transistor also switching in inverse relation to its respective associated photo-transistor 7 and 8 to which its base electrode is connected. The power transistor stage 18 comprises a Darlington pair.
The radiation chopper device 1 consists of a housing 2; a disc 3;
a shaft ~ carrying the disc 3, infra-red radaition sources 5 and 6; and radiation detectors 7 and 8. The infra-red radiation sources 5 and 6 are preferably gallium arsenide lamps, and the radiation detectors are prefer-ably photo-transistors, all these elements being fixed to the housing 2. The shaft 4 is journalled in bearings ~not shown) in the housing 2, and is driven at cam shaft speed o~ the engine.
The chopper disc 3 comprises two series of concentric apertures 9 and 10. There are four large apertures 9 in equi-spaced relation, and a large number of small apertures of slits 10 ~e.g. sixty eight). The aper-tures 9 permit infra-red radiation from the lamp ~ to reach the photo-tran-sistor 7, and the slits 10 permit infra-red radiation from the lamp 6 to reach the photo-transistor 8. The lamps 5 and 6 are energized through a common stabilized voltage source 20.
The output from the respective phototransistors 7 and 8 is fed to the inputs of respective fast inverse switching triggers 11 and 12. The output from the first trigger 11 is applied firstly to the power transistor stage 18, and seeondly to a first input of the AND gate 19. The output of the second trigger 12 is fed to the counter 1~, which normally gives a -11 - , ~ ' .
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3La~'~.9~ 9 "0" output, but which on completion of the count down set therein through the operatlon of the AND gate 17 gives a "1"
output. The pressure detector stage 16 is preferably a piezo-electric detector, and is designed to give an output when the pressure exceeds a predetermined value. The piezo-electric detector is housed either in the wall of the cylinder above the piston when located at T.D.C., or in the upper cylinder head on the opposite side from the spark plug. The output from the piczo-electric detector is applied to a third trigger 13, which squares the output pulse, and applies it to a second input of the AND gate 19. The AND gate 19 detects whether or not there is a simultaneous coincidence of "1" on both its inputs and in the event there is coincidence, it provides an output to adjust the count of the counter 14 by one step at a time to advance the ignition by a few degrees, in order to ensure that the pressure peak occurs at a predetermined crank-shaft angle, which is preferably 10 A.T.D.C. ~e power transistor stage 18 controls the current flow through the primary winding of the ignition coil 26. When the outputs from the stages 11 and 14 are either "0" and "1" or "1' and "0" or "0" and "0" current flows through the primary winding of the ignition coil 26, but when both outputs are at the high level "1", then the current through the coil is inter-rupted, producing the collapse of the magnetic field and the resultant high secondary voltage necessary for the spark.
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The operation of the electronic spark control device will now be described in greater detail with the aid of the waveforms shown in Figure 3. As the disc 3 is rotated at crank-shaf~ speed of the engine, the infra-red radiation from the lamps 5 and 6 impinges on the respective photo-transistors 7 and 8 through the apertures 9 and slits 10. Accordingly, the photo-transistor 7 produces four current pulses per revolution of the disc 3, whilst -the photo-transistor 8 produces a large number (e.g. sixty eight) of pulses per revolution. The two triggers 11 and 12 fast switch and amplify these pulses to produce the waveforms (a) and (b) ~-~
respectively. ~uring the interval between crank-shaft positions tO and tl the photo-transistor 7 is energized by infra-red radiation, and is therefore conductive. The out-. .
put from the first trigger is at the low level representing a "0". At the position tl, the infra-red radiation is cut off and the output of the first trigger becomes high repre-senting a "1". This output is applied to both the counter 14 and the first transistor of the power transistor stage 18.
The counter 14 now counts the pulses from the second trigger 12 according to the number set therein. The output of the counter 14 is at the low level "0" from crank-shaft position tO up to and beyond the crank-shaft position tl. Therefore, when the trigger 11 produces a high level output, the power transistor stage is not switched because of the continued presence of a low level output from the counter 14. In the . ,.~ . ,: . .
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example illustrated, the counter 14 is set to count down a total of six pulscs before its output switches to the high level. Therefore, at crank-shaft position t2, when the count of six has been completed, the output becom0s high at the seventh pulse, and the power transistor stage switches off the flow of current in the primary winding of the ignition coil 26, and thus initiates the spark through the high induced secondary voltage on the collapse of the field in the primary winding of the coil. At crank-shaft position t3 which is the idealized crank-shaft position at which the commencement of the second stage of the combustion should occur, the output of the first trigger reverts to the low level, thus extinguish-ing the spark, and resetting the frequency divider, which also reverts to the low level, as shown by waveform ~c), these events both happening when the photo-transistor 7 is again energized by infra-red radiation.
Waveform ~d) shows the "1" output from the third trigger 13 when the combustion within the cyli.nder has reached its second stage, and has been detected by the piezo-electric detector 16.
The circuit is designed to operate about the ideal position when the leading edge of the waveform (d) coincides with the crank-shaft position t3, this leading edge represent-ing the commencement of the second stage of combustion. If, as shown in waveform ~e), the leading ',' .
, . . , . , ~ : , . . .
:
~9~(39 edge of the pulse from the trigger 13 occurs after the position t3, the AN~ gate 19 does not detect any coincidence between the "1" outputs from the first trigger 11 and the third trigger 13, as shown in waveform tf). Under these conditions the count of the counter 14 is reduced by one step at a time until coincidence is detected. I9 on the other hand, as shown in waveform (g), the leading edge of the pulse from the trigger 13 occurs before the crank-shaft position t3~ the AN~ gate detects coincidence as shown in its output waveform (h). Under these conditions the count of the counter 14 is increased by one step at a time until coincidence is no longer detected. Thus, under normal running conditions, the count of the counter is adjusted by increments so as to maintain the leading ~-edge of the waveform (d) at the crank-shaft position of t3-An alternative embodiment also using a piezo-electric detector is shown in Figurès 4 and 5. In this form, the AND gate 19 is replaced by a comparator 17. A differentiating circuit 21, a limiter 22, an inverter 24 and a frequency divider circuit 25 are connec~ed in series between the output of the first trigger 11 and one input of the comparator 17. The frequency divider circuit in this example performs a division by four and is synchronized from the third trigger 13.
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The output of the first trigger 11 which is applied to the differentiator 21 is the square waveform (a). The differentiator 21 provides an alternate series of positive and negative going spikes as shown in waveform (_), the positive spikes being clipped off by means of the limiter circuit 22 to provide waveform (_). The negative going spikes of waveform (k) are then inverted and shaped in the circuit 24 as shown in waveform (1). The frequency divider 25 allows only one pulse in four to be applied to the compar-ator 17, such a pulse being shown by waveform (_). In order to ensure that this selected pulse passed by the frequency divider 24 corresponds to the firing of the cylinder associated with the piezo-electric detector 16, a synchroniz-ation link is provided between the third trigger 13, and the frequency divider 25 to ensure that the latter remains syn-chronized at all times.
The comparator 17 thus compares the position of the pulse output from the third trigger 13 (waveform d) with that of the pulse output from the frequency divider 25 (waveform m).
If the two pulses are coincident then there is no output from the comparator 17 to the counter 14, and its count remains unaltered. On the other hand, if the pulse of waveform (d) occurs before the pulse of waveform ~_), then there is a negative output from the comparator, which effects a one step increase in the count of the counter 14, in order to re~ard the point at which the spark is induced. Likewise, if the pulse of waveform ~d) occurs after the pulse of waveform ~m), ~`
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16J 4~:i09 then there is a positive output from the comparator 17 which effects a one step decrease in the count of the counter 14 in order to advance the point at which the spark is induced.
The increase or decrease oE the count of the frequency divider 14 will continue until the pulse of waveform (d) is coincident with the pulse of waveform (m).
In the above described alternative embodiment of Figures 4 and 5, the detection of the second stage of the combustion process is confined to one cylinder only, but a separate piezo-electric detector can be provided for each cylinder, in which case the frequency divider 25 is removed from the circuit. Such a multi-detector system has the dis- ~ .
advantage that if there are slightly different firing character- ~ ;
istics between cylinders, the co~mt of the frequency 14 will tend to hunt instead of remaining fixed under constant speed and/or load conditions.
~` Instead of using an electro-mechanical transducer device to detect the commencement of the second stage of com-bustion, in a second preferred form it is possible to utilize -` 20 a second spark plug as shown in Figure 6, which is a cross sectional view through one cylinder of the four cylinder -~ engine. As conventional, a piston 30 reciprocates within the cylinder wall 32, a connecting rod 34 being connected to the piston 30 by the little end 36. At the upper end of the cylinder head 38, there is provided - ' '' ~ , . ~
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as conven-tional~ a spark plug 40 and inlet valve 42 ~the outlet valve not being shown in the drawing as it is positioned behind the inlet valve.) A second spark plug 44 is provided on the other side of the cylinder head from the ~ain spark! plug 40. This second spark plug is utilized to detect the second stage of combustion within the cylinder when the main spark plug has ignited the compressed combustible mixture within the cylinder.
In order not to interfere with the flame front, which propagates through the cylinder when the discharge across the points of the main spark plug 40 occurs, it is desirable ;
that the second spark plug 44 is located as far away as possible from the main spark plug ~0. In this particular design of cylinder, having overhead valves, the second spark plug 44 is conveniently located diametrically opposite to the main spark plug 40. In order to fit the second spark plug 44, it is desirable to slightly modify the position ~f the inlet and/or outlet manifolds from the cylinder head.
Referring now to Figure 7, one simple circuit for detecting the second stage in the combustion process by means of the second spark plug, includes a resistor 46, a voltage detector 48, a 30 volt battery 50 and a pulse ~-shaper 52. The resist~r 46 is connected in series with the points of the second spark plug 44 across the battery 50. ~hen there is no combustion in the cylinder no current flows in the resistor 46 because the spark plug , ~gO 496(~
44 presents an open circuit. The voltage detector thus produces zero output. When the combustible mixture within the cylinder becomes compressed, and is ignited by the main spark plug 40, as soon as the gap across the seconcl spark plug has become fully ionized upon the pressure wave front reaching the second spark plug at the commence-ment of the second stage of combustion, the spark plug presents a short circuit and current flows through the resistor 46. The voltage across this resistor rises, and is detected by theevoltage detector 48. The resultant output pulse produced by the voltage detector during the brief instant that the spark plug 44 is short-circuited by the ionization of the gas within the cylinder, is shaped by the pulse shaper 52 to produce a square wave output. This positive going pulse is applied to either the AND gate 19 of the first embodiment, or the comparator ; 17 of the alternative -~mbodiment.
In the third way of detecting the commencement of the second stage of combustion, use is made of a fibre-
The present invention relates to an igni~ion system for internal combustion engines~ and more particularly to the timing of the switching on and off of the spark.
A known type of ignition system for an internal combustion engine employs contact breaker points operated by a cam driven via suitable gearing from the engine crank-shaft. In this system the contacts are closed and thus the battery is connected across the ignition ; coil for a fixed number of degrees of crank-shaft rotation irrespective of engine speed. The duration of the spark~
which commences when the contact breaker points are openedg is a function of the electrical parameters of the system, and is substantially independent of engine speed.
Another known type of ignition system for internal combustion engines employs a magnetic trigger to switch - off the current to the ignition coil, so initiating a spark, the current being switched on again a suitable time before another spark is required. The period of time between switch off of the ignition coil, and switch on of the ignition coil is related by suitable control means to the speed of therengine such that the coil has sufficient 'ton'' time for its magnetic field to accumulate sufficient energy to pr~duce the spark.
A further known type of ignition system is triggered by opto-electronic means at appropriate crank shaft positions~ the triggering switching off the current to 1~49~09 the ignition coil, the coil being reconnected to the battery a fixed period after switch off. In such a system the crank-shaft position at which a spark is `
initiated is precisely defined. The spark duration depends on the electrical parameters of the system, -switch on of the coil being a fixed time after switch off rather than a particular number of crank-shaft degrees later. This system is effectively monostable, since the spark is produced by an electronic circuit which has a stable state in which the coil is "on"
and is triggered to the unstable state to interrupt the current in the primary winding, and thus initiate the necessary secondary voltage to produce the spark, the circuit returning to the stable state a fixed time ~
thereafter. :
A known improvement upon the above monosta~le opto-electronically controlled system is a bistable sys-tem as disclosed in our Canadian Patents Nos. 879,285 ~
and 932,382, whereby the crank-shaft angles between the `
switch on and off of the coil are fixed.
In our copending Canadian Application No.
195,002, we have disclosed an ignition system for an in-ternal combustion engine in which not only the timing of the spark is controlled in accordance with the speed ;
and load on the engine, but the duration of the spark is controlled relative to the angular position of the crank-shaft such that the spark at the spark plug is extinguished .
at a predetermined crank-shaft angle irrespective of tl~e crank-shaft angle at which the spark is initiated.
In the preferred embodiment disclosed, this position is in the range of from 0 to 5 after top dead centre (A.T.D.C.) The system disclosed in Canadian Application ~O. 195JOO2 utilizes the basic principle disclosed in our Canadian Patent Application No. 160,849 concerning the automatic computerized advance and retard of spark la~ter ~ ignition. In this/Application, the advance and retard of the spark ignition of an internal combustion engine is achieved electronically by generating two series of pulses in synchronism with the engineJ using one series as a reference for maximum advance and "coil on", and the other series to operate a counter to count down the requisite number of pulses beyond the maximum advance point before the spark is initiated, the count of the counter being varied from a computer in accordance with speed and/or load on the engine.
In addition to the speed and/or load of the engine there are a numlber of other factors which to a ; greater or less extent affect the spark timing of an in-ternal combustion engine.
The principal factors are: fuel octane rating, air temperature, humidity and air pressure.
It has been general practice to establish ad-vance curve requirements for both speed and load changes on .~ ... .
:
11~)4~609 the particular engine concerned by dynometer testing using simulated conditions in the laboratory. ~laving obtained the advance curves -Eor speed and load, mechanical mcans are constructed in order to reproduce these curves representing the required timing of the ignition by means of physical movcment of the ignition system components relative to the engine's crank position, i.e. top dead centre ~T.D.C.) It has further been proposed to use mechanical means to achieve advance or retard of the ignition timing, which takes into account the other factors noted above, such as fuel octane rating, air temperature, humidity and air ;
pressure. Such systems are, of course, mechanically complic-ated and are liable to error and failure. -Studies of the combustion process within an internal combustion engine have shown that the combustion process has two distinct stages. Firstly, after the initiation of the ;
.
spark, there is a low pressure stage wherein the mixture is igniting and a flame is starting to propogate within the `~
combustion chamber. At some subsequent point in time a sudden rise in both the pressure and temperature within the cylinder is observed, which marks the commencement of the second explosive stage of combustion. During the initial stage of combustion temperatures and pressures within the combustion -chamber are low compared with the temperatures, and pressures within the combustion chamber during the second stage of ',: .
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1(~4~ 9 combustion.
~ y the commencement of the second stage of combus-tion the mixture in the cylinder is well alight, and the presence of any spark at the spark plug is irrelevant to the following process of combustion within the cylinder. It is the timing of the commencement of this second stage which is extremely important. Tests have shown that for best engine efficiency this sudden pressure and temperature rise should always occur at one fixed crank-shaft angle) regardless of all the variables which influence the spark timing require-ment.
It is therefore an object of the present invention to provide a closed loop ignition system in which a predeter-mined pressure on the pressure rise curve occurring during the second stage of combustion can be accurately sensed in , relation to a given fixed angular position, and maintained at this position under all engine conditions.
: ::
`~ According to the present invention there is provided an electronic ignition system for an internal combustion engineJ including: means for sensing a pre-determined pressure on the pressure rise curve occurring during the second :::
stage of combustion in a cylinder of an engine at each firing cycle; means for comparing the crank-shaft position at said pre-determined pressure with a fixed pre-determined crank-: ;
shaft position; and digital means for advancing or retarding .
~- the ignition by one step at a time so as to maintain this pre-determined crank-shaft position at said pre-determined pressure on the pressure rise curve occurring during the second stage of combustion, irrespective of engine requirements.
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Preferably, the predetermined crank-shaft angle at which the commencement of the second stage of combustion ~ :
occurs is ideally 10 A.T.D.C., but this may vary according to certain engine characteristics, more particularly those relating to the design of the cylinder heads.
Preferably, the electronic ignition system for an internal combustion engine includes means for generating a first series of square wave voltage pulses in synchronism with the engine revolutions to provide a series of alternate highs and lows; means for generating a second series of square wave voltage pulses at a frequency greatly in excess ~ `
of the first series; means for counting a given number o~
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the second series of voltage pulses from a given point in relation to the first series of voltage pulses; cmd means for producing an output of a give~ level from said counting means after said count has been completed, means for detecting the presence of both a signal at said given level from the first pulse generating means and the counting means, in order to bring about the initiation of the spark, the extinguishing-of the spark being effected when the signal from the first generating means changes to the opposite level; and means for varying the count of the counting means in accordance with the position of the commencement of the second stage in the combustion process if this deviates from the predetermined crank-shaft position.
Preferably, in one form the electronic device controls the advance and retard of the ignition, the counting means starting to count near the position of maximum advance.
Alternatively, the count may be started from the fixed coil turn on signal. Thus a signal at said given level from the first trigger initiates the count of the counting means, which then counts down the number it has been set to before giving a signal at said given level to cause the initiation of the spark, and then to permit the spark to continue until the pressure rise point is reached, and the coil is turned on~
The counting means is preferably a frequency divider whose count can be increased or reduced by a single step -8- ;
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at each cycle of ignition.
The present invention will now be described in greater detai]. by way of examples, with reference to the accompanying drawings, wherein:-Figure 1 is a diagram (partly in block form) ofone form of spark control device for use with a spark ignition system of an internal combustion engine;
Figure 2 is a front view of the disc shown in Figure l;
Figure 3 is a set of waveforms which assist in explaining the operatisn of the circuit shown in Figure 1;
Figure 4 is a diagram (partly in block form) of an alternative form of spa~k control device to that shown in Figure 1.
Figure 5 is a set of waveforms which assist in ~
explaining the operation of the circuit shown in Figure 4; :
Figure 6 is a cross sectional view through a cylinder : ~
... .
showing a second method of detecting the commencement of the second stage of the combustion process in the cylinder using a second spark plug;
Figure 7 is a circuit diagram illustrating this second method; ~-Figure 8 is a cross sectional view through a cylinder ;
showing a third method of detecting the commencement of the second stage of the combustion process in the cylinder by means of a fibre-optic cable and a translucent window in the upper part of the cylinder;
_9_ .
60g Figure 9 is a circuit diagram illustrating this third method;
Figure 10 is a circuit diagram showing an alter-native form of combining the logical signals from the first and third triggers;
Figure 11 is a part cross sectional view through .,.
the inlet manifold of the engine, showing a second embodi-ment of the invention, utilizing the vacuum in the inlet manifold;
Figure 12 is a view of the chopper disc for this second embodiment; and :~
Figure 13 is a circuit diagram of the circuit .
which energizes the solenoid shown in Fi.gure 11.
The ignition control system according to the present invention will now be described with reference to a four cylinder internal combustion engine.
Referring to Figures 1 and 2, the device achieves electronic control of the advance and retard of the initia-.
: tion of the spark through the detection of the crank-shaft : 20 position of the commencement of the second stage of the combustion within the cylinders. The device includes a radiation chopper device generally designated l; a first fast inverse switching trigger circuit 11; a second fast ~.
inverse switching trigger circuit 12; a counter 1~; a pressure detector stage 16; an AND gate 19; and a power tran--sistor stage 18.
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: ~" : ' ," '' ~ ' ,: . . . , : , ' Circuit details of the two inverse fast switching triggers 11 and 12 and the power transistors stage 18 have been disclosed in our Canadian Patent No. 98~,935 which issued on March 2, 1976. Each trigger 11 and 12 comprises two transistors arranged to switch in inverse relation to each other, the first transistor also switching in inverse relation to its respective associated photo-transistor 7 and 8 to which its base electrode is connected. The power transistor stage 18 comprises a Darlington pair.
The radiation chopper device 1 consists of a housing 2; a disc 3;
a shaft ~ carrying the disc 3, infra-red radaition sources 5 and 6; and radiation detectors 7 and 8. The infra-red radiation sources 5 and 6 are preferably gallium arsenide lamps, and the radiation detectors are prefer-ably photo-transistors, all these elements being fixed to the housing 2. The shaft 4 is journalled in bearings ~not shown) in the housing 2, and is driven at cam shaft speed o~ the engine.
The chopper disc 3 comprises two series of concentric apertures 9 and 10. There are four large apertures 9 in equi-spaced relation, and a large number of small apertures of slits 10 ~e.g. sixty eight). The aper-tures 9 permit infra-red radiation from the lamp ~ to reach the photo-tran-sistor 7, and the slits 10 permit infra-red radiation from the lamp 6 to reach the photo-transistor 8. The lamps 5 and 6 are energized through a common stabilized voltage source 20.
The output from the respective phototransistors 7 and 8 is fed to the inputs of respective fast inverse switching triggers 11 and 12. The output from the first trigger 11 is applied firstly to the power transistor stage 18, and seeondly to a first input of the AND gate 19. The output of the second trigger 12 is fed to the counter 1~, which normally gives a -11 - , ~ ' .
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3La~'~.9~ 9 "0" output, but which on completion of the count down set therein through the operatlon of the AND gate 17 gives a "1"
output. The pressure detector stage 16 is preferably a piezo-electric detector, and is designed to give an output when the pressure exceeds a predetermined value. The piezo-electric detector is housed either in the wall of the cylinder above the piston when located at T.D.C., or in the upper cylinder head on the opposite side from the spark plug. The output from the piczo-electric detector is applied to a third trigger 13, which squares the output pulse, and applies it to a second input of the AND gate 19. The AND gate 19 detects whether or not there is a simultaneous coincidence of "1" on both its inputs and in the event there is coincidence, it provides an output to adjust the count of the counter 14 by one step at a time to advance the ignition by a few degrees, in order to ensure that the pressure peak occurs at a predetermined crank-shaft angle, which is preferably 10 A.T.D.C. ~e power transistor stage 18 controls the current flow through the primary winding of the ignition coil 26. When the outputs from the stages 11 and 14 are either "0" and "1" or "1' and "0" or "0" and "0" current flows through the primary winding of the ignition coil 26, but when both outputs are at the high level "1", then the current through the coil is inter-rupted, producing the collapse of the magnetic field and the resultant high secondary voltage necessary for the spark.
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The operation of the electronic spark control device will now be described in greater detail with the aid of the waveforms shown in Figure 3. As the disc 3 is rotated at crank-shaf~ speed of the engine, the infra-red radiation from the lamps 5 and 6 impinges on the respective photo-transistors 7 and 8 through the apertures 9 and slits 10. Accordingly, the photo-transistor 7 produces four current pulses per revolution of the disc 3, whilst -the photo-transistor 8 produces a large number (e.g. sixty eight) of pulses per revolution. The two triggers 11 and 12 fast switch and amplify these pulses to produce the waveforms (a) and (b) ~-~
respectively. ~uring the interval between crank-shaft positions tO and tl the photo-transistor 7 is energized by infra-red radiation, and is therefore conductive. The out-. .
put from the first trigger is at the low level representing a "0". At the position tl, the infra-red radiation is cut off and the output of the first trigger becomes high repre-senting a "1". This output is applied to both the counter 14 and the first transistor of the power transistor stage 18.
The counter 14 now counts the pulses from the second trigger 12 according to the number set therein. The output of the counter 14 is at the low level "0" from crank-shaft position tO up to and beyond the crank-shaft position tl. Therefore, when the trigger 11 produces a high level output, the power transistor stage is not switched because of the continued presence of a low level output from the counter 14. In the . ,.~ . ,: . .
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example illustrated, the counter 14 is set to count down a total of six pulscs before its output switches to the high level. Therefore, at crank-shaft position t2, when the count of six has been completed, the output becom0s high at the seventh pulse, and the power transistor stage switches off the flow of current in the primary winding of the ignition coil 26, and thus initiates the spark through the high induced secondary voltage on the collapse of the field in the primary winding of the coil. At crank-shaft position t3 which is the idealized crank-shaft position at which the commencement of the second stage of the combustion should occur, the output of the first trigger reverts to the low level, thus extinguish-ing the spark, and resetting the frequency divider, which also reverts to the low level, as shown by waveform ~c), these events both happening when the photo-transistor 7 is again energized by infra-red radiation.
Waveform ~d) shows the "1" output from the third trigger 13 when the combustion within the cyli.nder has reached its second stage, and has been detected by the piezo-electric detector 16.
The circuit is designed to operate about the ideal position when the leading edge of the waveform (d) coincides with the crank-shaft position t3, this leading edge represent-ing the commencement of the second stage of combustion. If, as shown in waveform ~e), the leading ',' .
, . . , . , ~ : , . . .
:
~9~(39 edge of the pulse from the trigger 13 occurs after the position t3, the AN~ gate 19 does not detect any coincidence between the "1" outputs from the first trigger 11 and the third trigger 13, as shown in waveform tf). Under these conditions the count of the counter 14 is reduced by one step at a time until coincidence is detected. I9 on the other hand, as shown in waveform (g), the leading edge of the pulse from the trigger 13 occurs before the crank-shaft position t3~ the AN~ gate detects coincidence as shown in its output waveform (h). Under these conditions the count of the counter 14 is increased by one step at a time until coincidence is no longer detected. Thus, under normal running conditions, the count of the counter is adjusted by increments so as to maintain the leading ~-edge of the waveform (d) at the crank-shaft position of t3-An alternative embodiment also using a piezo-electric detector is shown in Figurès 4 and 5. In this form, the AND gate 19 is replaced by a comparator 17. A differentiating circuit 21, a limiter 22, an inverter 24 and a frequency divider circuit 25 are connec~ed in series between the output of the first trigger 11 and one input of the comparator 17. The frequency divider circuit in this example performs a division by four and is synchronized from the third trigger 13.
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The output of the first trigger 11 which is applied to the differentiator 21 is the square waveform (a). The differentiator 21 provides an alternate series of positive and negative going spikes as shown in waveform (_), the positive spikes being clipped off by means of the limiter circuit 22 to provide waveform (_). The negative going spikes of waveform (k) are then inverted and shaped in the circuit 24 as shown in waveform (1). The frequency divider 25 allows only one pulse in four to be applied to the compar-ator 17, such a pulse being shown by waveform (_). In order to ensure that this selected pulse passed by the frequency divider 24 corresponds to the firing of the cylinder associated with the piezo-electric detector 16, a synchroniz-ation link is provided between the third trigger 13, and the frequency divider 25 to ensure that the latter remains syn-chronized at all times.
The comparator 17 thus compares the position of the pulse output from the third trigger 13 (waveform d) with that of the pulse output from the frequency divider 25 (waveform m).
If the two pulses are coincident then there is no output from the comparator 17 to the counter 14, and its count remains unaltered. On the other hand, if the pulse of waveform (d) occurs before the pulse of waveform ~_), then there is a negative output from the comparator, which effects a one step increase in the count of the counter 14, in order to re~ard the point at which the spark is induced. Likewise, if the pulse of waveform ~d) occurs after the pulse of waveform ~m), ~`
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16J 4~:i09 then there is a positive output from the comparator 17 which effects a one step decrease in the count of the counter 14 in order to advance the point at which the spark is induced.
The increase or decrease oE the count of the frequency divider 14 will continue until the pulse of waveform (d) is coincident with the pulse of waveform (m).
In the above described alternative embodiment of Figures 4 and 5, the detection of the second stage of the combustion process is confined to one cylinder only, but a separate piezo-electric detector can be provided for each cylinder, in which case the frequency divider 25 is removed from the circuit. Such a multi-detector system has the dis- ~ .
advantage that if there are slightly different firing character- ~ ;
istics between cylinders, the co~mt of the frequency 14 will tend to hunt instead of remaining fixed under constant speed and/or load conditions.
~` Instead of using an electro-mechanical transducer device to detect the commencement of the second stage of com-bustion, in a second preferred form it is possible to utilize -` 20 a second spark plug as shown in Figure 6, which is a cross sectional view through one cylinder of the four cylinder -~ engine. As conventional, a piston 30 reciprocates within the cylinder wall 32, a connecting rod 34 being connected to the piston 30 by the little end 36. At the upper end of the cylinder head 38, there is provided - ' '' ~ , . ~
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as conven-tional~ a spark plug 40 and inlet valve 42 ~the outlet valve not being shown in the drawing as it is positioned behind the inlet valve.) A second spark plug 44 is provided on the other side of the cylinder head from the ~ain spark! plug 40. This second spark plug is utilized to detect the second stage of combustion within the cylinder when the main spark plug has ignited the compressed combustible mixture within the cylinder.
In order not to interfere with the flame front, which propagates through the cylinder when the discharge across the points of the main spark plug 40 occurs, it is desirable ;
that the second spark plug 44 is located as far away as possible from the main spark plug ~0. In this particular design of cylinder, having overhead valves, the second spark plug 44 is conveniently located diametrically opposite to the main spark plug 40. In order to fit the second spark plug 44, it is desirable to slightly modify the position ~f the inlet and/or outlet manifolds from the cylinder head.
Referring now to Figure 7, one simple circuit for detecting the second stage in the combustion process by means of the second spark plug, includes a resistor 46, a voltage detector 48, a 30 volt battery 50 and a pulse ~-shaper 52. The resist~r 46 is connected in series with the points of the second spark plug 44 across the battery 50. ~hen there is no combustion in the cylinder no current flows in the resistor 46 because the spark plug , ~gO 496(~
44 presents an open circuit. The voltage detector thus produces zero output. When the combustible mixture within the cylinder becomes compressed, and is ignited by the main spark plug 40, as soon as the gap across the seconcl spark plug has become fully ionized upon the pressure wave front reaching the second spark plug at the commence-ment of the second stage of combustion, the spark plug presents a short circuit and current flows through the resistor 46. The voltage across this resistor rises, and is detected by theevoltage detector 48. The resultant output pulse produced by the voltage detector during the brief instant that the spark plug 44 is short-circuited by the ionization of the gas within the cylinder, is shaped by the pulse shaper 52 to produce a square wave output. This positive going pulse is applied to either the AND gate 19 of the first embodiment, or the comparator ; 17 of the alternative -~mbodiment.
In the third way of detecting the commencement of the second stage of combustion, use is made of a fibre-
2~ optic cable and translucent window as shown in Figure 8, which is a similar cross sectional view through one cylinder of the engine. In this embodiment the second spark plug is replaced by a quartz glass window 54. A
fibre-optic cable 56 has one end clamped to the window 54 by suitable clamping means 58.
Referring to Figure 9, the other end of the fibre-optic cable 56 is coupled to a photo-transistor 60, ~-: ' ', , . :
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which is mounted in the distributor of the engine along with the rest of the double-trigger integrated circuitry except Eor the power transistor stage 18. The photo-transistor 60 is connected in series with a resistor 62 across a battery 64.
A voltage detector 66 is connected across the resistor 62.
The radiation (whether visible and/or infra-red) from within the cylinder is transmitted through the quartz glass window ; 54, along the fibre-optic cable 56, to the photo-transistor 60.
When the level of radiation exceeds a given value as a result of the sudden temperature rise at the commencement of the second stage of combustion, the photo-transistor 60 is energized. The photo-transistor 60 conducts and current flows ;
from the battery 64 through the resistor 62. The rise in voltage across the resistor 62 is detected by the voltage detector 66. The resultant output pulse produced by the .
voltage detector during combustion is shaped by a pulse shaper :
68 to produce a square wave output. This positive going pulse ~ :
is applied to either the AND gate 19 of the first embodiment, or the comparator 17 of the alternative embodiment.
With any one of the described embodiments, the commence-; ment of the second stage of combustion is always maintained -at the same crank-shaft angle (e.g. 10 A.T.D.C.) irrespective of the speed of the engine, the load on the engine, air pressure, air temperature, humidity and other factors which can affect ~ the performance of an internal combustion engine.
; Instead of using an AND gate 19 in the embodiment shown in Figure 1, the output stages of the first and .
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third triggers could be connected as shown in Figure 10. An output transistor 70 of the first trigger 11 is effectively connected in parallel with an output transistor 72 of the third trigger 13, each transistor being in series with a resistor 74 across a 12 volt supply. The logical output at 76 is fed to the counter 14. When both transistors are conductive and when one or the other is conductive the output is a logical "0~'.
A logical 1l1" is produced when both are non~conductive simultaneously.
Whilst in the above described embodiments, the counting means starts to count near the positi0n of maximum advance, it would be well within the scope of the invention to start the count from the fixed c0il "on" position.
In all the above embodiments, use has~been made of the second trigger 12 and counter 14 in conjunction with the first trigger 11 and electro-mechanical transducer to determine the coil off position, i.e. the production of the spark such that the commencement of the second stage of combustion occurs at the precise crank-shaft position at which the~coil switches on to extinguish the spark. Instead of determining the requirediadvance and retard electronically~ it may be achieved by electro~
mechanical means. In a second preferred fo~ shQwn in Figures 11 to 13, the second trigger and frequency divider are omitted. This second distinct way of carrying out .
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the invention utilizes the vacuum manifold of the engine.
As shown in Figure It, a pipe 80 is connected to the engine inlet manifold of the carburetDrl 82 upstream of a throttle valve 84. The pipe 80 has a branch 86 connected to a chamber 88. The chamber 88 is provided with a diaphragm 90, to which is connected a rod 92 carrying a forked portion 94. The ends of the forked portion 94 carry the infra- red radiation source 5 and the detector 7 associated with the first trigger 11. A spring 96 is provided within the chamber 88 to urge the diaphragm 90 to its neutral position against the partial vacuum produced in the chamber 88. A solenoid valve 98 is provided to bleed air from the atmosphere into the chamber 88 from a pipe 99.
An apertured M isc 100 is rotated in synchronism with ~`
the crank-shaft of the engine, and is positioned as shown in Figures 11 and 12 between the infra-red source 5 and ~` detector 7. The disc 100 has four identical apertures 102 equi-spaced around the circumference of the disc. Each aperture 102 has arcua~ccouter and inner peripheries 104 and 106 respectively, a radial aligned edge 108 and a ~j straight radially inclined edge 110. The radial edge 108 -provides the constant coil "on~' position to extinguish the spark and the radially inclined edge 110 provides the ~ -necessary advance and retard of the production of the spark ~the coil "off" position) according to the distance of the infra-red source 5 and detector 7 from the centre :........ . . . . . . .
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of ~he disc 100. The output square waveform generated by the first trigger thus has a variable mark space ratio which is a function of the dis-tance of the elements 5 and 7 from the centre of the disc.
The logical outputs from the first trigger 11 and the third trigger 13 are combined as shown in Figure 10, the combined signal being available at the output 76.
As shown in Figure 13, the signal available at the output 76 is passed through three inverse switching stages 112, 114 and 116~ the last stage 116 being in series with the energizing coil 118 of the solenoid valve 980 ~ his second embodiment operates as follows. The system is designed so that~the vacuum of the inlet manifold of the engine pulls theediaphragm 90 against the action of the spring, so as to move the line of slght of the elements 5 and 7 radially outwards with respect to the disc 100~ thus tending to increase the mark-space ratio of the output of the first trigger in order to over advance the ignition timing. When the timing becomes over-advanced, i.e. the leading edge of the wave~form (d) is occur~ing before the crank-shaft position of t3, coincidence is detected at the output 76. This causes the transistor 112 to conduct, the transistor ll~ to become non-conductive~ and the transistor 116 to be conductive. When the transistor 116 becomes conductive, the solenoid 98 is energized to bleed in air ,~ into the chamber 88. This causes the diaphragm to relax slightly, and to move the line of sight of the elements , - .
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66~9 5 and 7 Fadially inwards, towards the centre of the disc 100~ so as to effect a retard of the ignition timing. As soon as coincidence at the terminal 76 ceases, the circuit of~-` the transistors 112 to 116 reverts to its other stable state to de-energi~e the solenoid ~8. The system thus hunts about the point where the leading edge of the waveform (d) is maintained at the crank-shaft position t3.
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fibre-optic cable 56 has one end clamped to the window 54 by suitable clamping means 58.
Referring to Figure 9, the other end of the fibre-optic cable 56 is coupled to a photo-transistor 60, ~-: ' ', , . :
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which is mounted in the distributor of the engine along with the rest of the double-trigger integrated circuitry except Eor the power transistor stage 18. The photo-transistor 60 is connected in series with a resistor 62 across a battery 64.
A voltage detector 66 is connected across the resistor 62.
The radiation (whether visible and/or infra-red) from within the cylinder is transmitted through the quartz glass window ; 54, along the fibre-optic cable 56, to the photo-transistor 60.
When the level of radiation exceeds a given value as a result of the sudden temperature rise at the commencement of the second stage of combustion, the photo-transistor 60 is energized. The photo-transistor 60 conducts and current flows ;
from the battery 64 through the resistor 62. The rise in voltage across the resistor 62 is detected by the voltage detector 66. The resultant output pulse produced by the .
voltage detector during combustion is shaped by a pulse shaper :
68 to produce a square wave output. This positive going pulse ~ :
is applied to either the AND gate 19 of the first embodiment, or the comparator 17 of the alternative embodiment.
With any one of the described embodiments, the commence-; ment of the second stage of combustion is always maintained -at the same crank-shaft angle (e.g. 10 A.T.D.C.) irrespective of the speed of the engine, the load on the engine, air pressure, air temperature, humidity and other factors which can affect ~ the performance of an internal combustion engine.
; Instead of using an AND gate 19 in the embodiment shown in Figure 1, the output stages of the first and .
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third triggers could be connected as shown in Figure 10. An output transistor 70 of the first trigger 11 is effectively connected in parallel with an output transistor 72 of the third trigger 13, each transistor being in series with a resistor 74 across a 12 volt supply. The logical output at 76 is fed to the counter 14. When both transistors are conductive and when one or the other is conductive the output is a logical "0~'.
A logical 1l1" is produced when both are non~conductive simultaneously.
Whilst in the above described embodiments, the counting means starts to count near the positi0n of maximum advance, it would be well within the scope of the invention to start the count from the fixed c0il "on" position.
In all the above embodiments, use has~been made of the second trigger 12 and counter 14 in conjunction with the first trigger 11 and electro-mechanical transducer to determine the coil off position, i.e. the production of the spark such that the commencement of the second stage of combustion occurs at the precise crank-shaft position at which the~coil switches on to extinguish the spark. Instead of determining the requirediadvance and retard electronically~ it may be achieved by electro~
mechanical means. In a second preferred fo~ shQwn in Figures 11 to 13, the second trigger and frequency divider are omitted. This second distinct way of carrying out .
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the invention utilizes the vacuum manifold of the engine.
As shown in Figure It, a pipe 80 is connected to the engine inlet manifold of the carburetDrl 82 upstream of a throttle valve 84. The pipe 80 has a branch 86 connected to a chamber 88. The chamber 88 is provided with a diaphragm 90, to which is connected a rod 92 carrying a forked portion 94. The ends of the forked portion 94 carry the infra- red radiation source 5 and the detector 7 associated with the first trigger 11. A spring 96 is provided within the chamber 88 to urge the diaphragm 90 to its neutral position against the partial vacuum produced in the chamber 88. A solenoid valve 98 is provided to bleed air from the atmosphere into the chamber 88 from a pipe 99.
An apertured M isc 100 is rotated in synchronism with ~`
the crank-shaft of the engine, and is positioned as shown in Figures 11 and 12 between the infra-red source 5 and ~` detector 7. The disc 100 has four identical apertures 102 equi-spaced around the circumference of the disc. Each aperture 102 has arcua~ccouter and inner peripheries 104 and 106 respectively, a radial aligned edge 108 and a ~j straight radially inclined edge 110. The radial edge 108 -provides the constant coil "on~' position to extinguish the spark and the radially inclined edge 110 provides the ~ -necessary advance and retard of the production of the spark ~the coil "off" position) according to the distance of the infra-red source 5 and detector 7 from the centre :........ . . . . . . .
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of ~he disc 100. The output square waveform generated by the first trigger thus has a variable mark space ratio which is a function of the dis-tance of the elements 5 and 7 from the centre of the disc.
The logical outputs from the first trigger 11 and the third trigger 13 are combined as shown in Figure 10, the combined signal being available at the output 76.
As shown in Figure 13, the signal available at the output 76 is passed through three inverse switching stages 112, 114 and 116~ the last stage 116 being in series with the energizing coil 118 of the solenoid valve 980 ~ his second embodiment operates as follows. The system is designed so that~the vacuum of the inlet manifold of the engine pulls theediaphragm 90 against the action of the spring, so as to move the line of slght of the elements 5 and 7 radially outwards with respect to the disc 100~ thus tending to increase the mark-space ratio of the output of the first trigger in order to over advance the ignition timing. When the timing becomes over-advanced, i.e. the leading edge of the wave~form (d) is occur~ing before the crank-shaft position of t3, coincidence is detected at the output 76. This causes the transistor 112 to conduct, the transistor ll~ to become non-conductive~ and the transistor 116 to be conductive. When the transistor 116 becomes conductive, the solenoid 98 is energized to bleed in air ,~ into the chamber 88. This causes the diaphragm to relax slightly, and to move the line of sight of the elements , - .
,,. ~,.
~i ' . .
66~9 5 and 7 Fadially inwards, towards the centre of the disc 100~ so as to effect a retard of the ignition timing. As soon as coincidence at the terminal 76 ceases, the circuit of~-` the transistors 112 to 116 reverts to its other stable state to de-energi~e the solenoid ~8. The system thus hunts about the point where the leading edge of the waveform (d) is maintained at the crank-shaft position t3.
' "-,, .
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Claims (22)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electronic ignition system for an internal com-bustion engine, including: means for sensing a pre-determined pressure on the pressure rise curve occurring during the second stage of combustion in a cylinder of an engine at each firing cycle; means for comparing the crank-shaft position at said pre-determined pressure with a fixed pre-determined crank-shaft position; and digital means for advancing or retarding the ignition by one step at a time so as to maintain this pre-determined crank-shaft position at said pre-determined pressure on the pressure rise curve occurring during the second stage of combustion, irrespective of engine require-ments.
2. An electronic ignition system according to claim 1, wherein the means for sensing the pre-determined pressure on the pressure rise curve occurring during the second stage of the combustion process in the cylinder is an electro-mechanical transducer device, which is located in the wall of the cylinder, above the level of the top of the piston at T.D.C.
3. An electronic ignition system according to claim 2, wherein said electro-mechanical transducer device is a piezo-electric detector.
4. An electronic ignition system according to claim 1, wherein the means for sensing the pre-determined pressure on the pressure rise curve occurring during the second stage of the combustion process in the cylinder is an additional spark plug across which a low voltage supply is applied, means being provided for detecting the current flow across the gap of the spark plug, due to ionization of the fuel mixture on combustion.
5. An electronic ignition system according to claim 1, wherein said means for sensing the pre-determined pressure is means for sensing the commencement of the second stage of the combustion process in the cylinder, said means for sensing the commencement of the second stage of the combustion process in the cylinder being the combination of a translucent window located in the wall of the cylinder above the level of the top of the piston at T.D.C., a radiation sensitive device, and a fibre optic cable interconnecting the window and the radiation sensitive device, so as to sense the commence-ment of the second stage of combustion and, consequently, the pre-determined pressure occurring at the commencement of the second stage of combustion.
6. An electronic ignition system according to claim 5, wherein said translucent window is made of quartz glass.
7. An electronic ignition system according to claim 5, wherein said radiation sensitive device is a photo-transistor.
8. An electronic ignition system according to claim 1, additionally including means for generating a first series of square wave voltage pulses in synchronism with the engine revolutions, to provide a series of alternate first and second pre-determined voltage levels; means for generating a second series of square wave voltage pulses at a frequency greatly in excess of the first series; means for counting a given number of the second series of voltage pulses from a given point in relation to the first series of voltage pulses; means for producing an output at said first voltage level from said counting means after said count has been completed; means for detecting the presence of both a signal at said first level from the first pulse generating means, and the counting means, in order to bring about the initiation of the spark, the extinguishing of the spark being effected when the signal from the first generating means changes to the opposite level; and means for varying the count of the counting means in accordance with the crank-shaft position of the sensed pre-determined pressure on the pressure rise curve if this deviates from the pre-determined crank-shaft position.
9. An electronic ignition system according to claim 81 wherein the counting means starts to count from a point near the position of maximum advance.
10. An electronic ignition system according to claim 8, wherein the counting means is an electronic counter.
11. An electronic ignition system according to claim 8, additionally including an AND gate receiving a signal derived from the means for sensing the pre-determined pressure on the pressure rise curve occuring during the second stage of the combustion process, and the output from the means for generating the first series of square wave voltage pulses, said AND gate providing a logical output to either increase or decrease the count of the counting means.
12. An electronic ignition system according to claim 8, additionally including a comparator receiving a signal derived from the means for sensing the pre-determined pressure on the pressure rise curve occuring during the second stage of the combustion process, and a signal derived from one edge of the square waveform generated by the first generating means, said comparator comparing the relative positions of said two signals and effecting either an increase or decrease in the count of the counting means if the two signals are not coincident.
13. An electronic ignition system according to claim 12, additionally including the series combination of: a differentiator; a limiter circuit;
an inverter; and a frequency divider located between the output of the first square waveform voltage generating means and the comparator in order to generate said signal derived from one edge of the square waveform of the first generating means.
an inverter; and a frequency divider located between the output of the first square waveform voltage generating means and the comparator in order to generate said signal derived from one edge of the square waveform of the first generating means.
14. An electronic ignition system according to claim 13, wherein the frequency divider is synchronized with the output from the output of the means for sensing the pre-determined pressure on the pressure rise curve occuring during the second stage of combustion.
15. An electronic ignition system according to claim 1, additionally including: means for generating a series of square wave voltage pulses whose mark space ratio is variable for the purpose of advancing or retarding the ignition; means for varying the mark space ratio of the generated square wave voltage pulses in response to engine requirements; means for deriving a signal from said sensed pre-determined pressure; and means operative from a digital timing comparison between the occurrence of said derived signal and said fixed predetermined crank-shaft position as determined by an edge of the square voltage pulses to vary the mark space ratio of said voltage pulses and hence the ignition timing so maintaining coincidence between said derived signal and said edge of the square wave voltage pulses.
16. An electronic ignition system according to claim 15, wherein the means for varying the mark-space ratio include an apertured disc driven in synchronism with the crank-shaft of the engine, said apertures being equi-spaced around the disc, an infra-red radiation source and a detector mounted on either side of the disc for movement relative thereto, a first operative edge of each aperture being aligned in the direction of movement of said radiation source and detector, whilst a second operative edge is inclined relative thereto in order to achieve said advance or retard of the ignition timing, and mechanical means for moving said radiation source and detector in accordance with engine requirements.
17. An electronic ignition system according to claim 16, wherein said mechanical means includes a diaphragm actuated from the partial vacuum in the inlet manifold of the engine against the action of a spring, said diaphragm being coupled to said radiation source and detector for movement thereof relative to the disc, and a solenoid actuated from the result of said timing comparison for bleeding in air to partially relax said diaphragm against the pull of the partial vacuum.
18. An electronic ignition system according to claim 15 wherein the means for deriving a signal from the second stage of combustion is an electro-mechanical transducer device which is located in the wall of the cylinder, above the level of the top of the piston at top dead centre.
19. An electronic ignition system according to claim 18, wherein said electro-mechanical transducer device is a piezo-electric detector.
20. An electronic, ignition system according to claim 16, wherein said first operative edge of each aperture is radial with respect to the centre of the disc, whilst the second operator edge is inclined to the radial direction of the disc, the infra-red radiation source and detector being coupled to said mechanical means so as to be movable in a radial direction with respect to the centre of the disc.
21. An electronic ignition system according to claim 16, wherein said mechanical means includes an engine vacuum device coupled to said radiation source and detector, the movement of said engine vacuum device being controlled by a solenoid which on operation from the result of the timing comparison bleeds in air to maintain the desired timing position.
22. An electronic ignition system according to claim 15, wherein the signal derived from the second stage of combustion is a digital signal which is fed to the same input of an electronic device controlling said operative means as the said square wave voltage pulses, thereby performing said timing comparison digitally.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB20148/74A GB1483611A (en) | 1974-05-07 | 1974-05-07 | Ignition systems for internal combustion engines |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1049609A true CA1049609A (en) | 1979-02-27 |
Family
ID=10141173
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA226,349A Expired CA1049609A (en) | 1974-05-07 | 1975-05-06 | Ignition systems for internal combustion engines |
Country Status (10)
| Country | Link |
|---|---|
| JP (2) | JPS5636303B2 (en) |
| BR (1) | BR7502796A (en) |
| CA (1) | CA1049609A (en) |
| DE (2) | DE2520325C3 (en) |
| ES (1) | ES437877A1 (en) |
| FR (1) | FR2270454B1 (en) |
| GB (1) | GB1483611A (en) |
| IT (1) | IT1045543B (en) |
| SE (2) | SE406213B (en) |
| ZA (1) | ZA752795B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1483611A (en) | 1974-05-07 | 1977-08-24 | Lumenition Ltd | Ignition systems for internal combustion engines |
| DE2554988C2 (en) * | 1975-12-06 | 1985-01-10 | Robert Bosch Gmbh, 7000 Stuttgart | Method for determining the composition of the operating mixture fed to an internal combustion engine or the combustion sequence of the operating mixture and device for carrying out the method |
| FR2475640A2 (en) * | 1980-02-11 | 1981-08-14 | Inst Francais Du Petrole | METHOD AND DEVICE FOR AUTOMATICALLY ADJUSTING THE IGNITION OF A CONTROLLED IGNITION ENGINE |
| FR2432097A1 (en) * | 1978-07-26 | 1980-02-22 | Inst Francais Du Petrole | METHOD AND DEVICE FOR AUTOMATICALLY ADJUSTING THE IGNITION OF A CONTROLLED IGNITION ENGINE |
| DE2939690A1 (en) * | 1979-09-29 | 1981-04-16 | Robert Bosch Gmbh, 7000 Stuttgart | IGNITION TIMING METHOD |
| DE3111135A1 (en) * | 1980-06-20 | 1982-03-11 | Robert Bosch Gmbh, 7000 Stuttgart | METHOD FOR CONTROLLING THE COMBUSTION IN THE COMBUSTION ROOMS OF AN INTERNAL COMBUSTION ENGINE |
| US4483293A (en) * | 1982-04-06 | 1984-11-20 | Mitsubishi Denki Kabushiki Kaisha | Ignition time control device |
| JPS59168270A (en) * | 1983-03-12 | 1984-09-21 | Fuji Heavy Ind Ltd | Ignition timing control device |
| GB2142086A (en) * | 1983-06-23 | 1985-01-09 | Ford Motor Co | Engine control systems |
| DE3410067C2 (en) * | 1984-03-20 | 1996-07-18 | Bosch Gmbh Robert | Method for controlling an internal combustion engine with detection of the course of the light intensity |
| CA1331778C (en) * | 1988-07-01 | 1994-08-30 | Hideaki Arai | Abnormal combustion-detecting device and combustion control device for internal combustion engines |
| JPH02104978A (en) * | 1988-10-13 | 1990-04-17 | Mitsubishi Electric Corp | Misfire detector for internal combustion engine |
| JPH0715279B2 (en) * | 1988-10-14 | 1995-02-22 | 三菱電機株式会社 | Ignition timing control device |
| CN102699845A (en) * | 2012-06-11 | 2012-10-03 | 卓越（苏州）自动化设备有限公司 | Simple divider |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2109698A5 (en) | 1970-08-18 | 1972-05-26 | Bullo Aurelio | |
| GB1410782A (en) | 1972-01-18 | 1975-10-22 | Lumenition Ltd | Ingition systems and fuel injection system for internal combustion engines |
| GB1483611A (en) | 1974-05-07 | 1977-08-24 | Lumenition Ltd | Ignition systems for internal combustion engines |
-
1974
- 1974-05-07 GB GB20148/74A patent/GB1483611A/en not_active Expired
-
1975
- 1975-04-30 ZA ZA00752795A patent/ZA752795B/en unknown
- 1975-05-06 FR FR7514190A patent/FR2270454B1/fr not_active Expired
- 1975-05-06 IT IT7549475A patent/IT1045543B/en active
- 1975-05-06 SE SE7505270A patent/SE406213B/en unknown
- 1975-05-06 CA CA226,349A patent/CA1049609A/en not_active Expired
- 1975-05-06 JP JP5416875A patent/JPS5636303B2/ja not_active Expired
- 1975-05-07 BR BR3566/75A patent/BR7502796A/en unknown
- 1975-05-07 DE DE2520325A patent/DE2520325C3/en not_active Expired
- 1975-05-07 DE DE2559938A patent/DE2559938C2/en not_active Expired
- 1975-05-07 ES ES437877A patent/ES437877A1/en not_active Expired
-
1978
- 1978-02-21 SE SE7801999A patent/SE417125B/en unknown
-
1980
- 1980-04-21 JP JP5280180A patent/JPS55160164A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS55160164A (en) | 1980-12-12 |
| ES437877A1 (en) | 1977-01-01 |
| ZA752795B (en) | 1976-04-28 |
| SE7505270L (en) | 1975-11-10 |
| JPS50153137A (en) | 1975-12-09 |
| DE2559938C2 (en) | 1982-12-16 |
| SE7801999L (en) | 1978-02-21 |
| DE2520325A1 (en) | 1975-11-20 |
| SE406213B (en) | 1979-01-29 |
| DE2520325C3 (en) | 1979-04-12 |
| BR7502796A (en) | 1976-03-16 |
| FR2270454A1 (en) | 1975-12-05 |
| IT1045543B (en) | 1980-05-10 |
| DE2520325B2 (en) | 1978-07-27 |
| AU8078075A (en) | 1976-11-04 |
| FR2270454B1 (en) | 1983-01-28 |
| SE417125B (en) | 1981-02-23 |
| JPS5636303B2 (en) | 1981-08-22 |
| GB1483611A (en) | 1977-08-24 |
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