SE510448C2 - Fuel regulating system for IC engine - Google Patents

Abstract

An ion flow sensor (5) detects ionisation in the cylinder during combustion and, dependent of the extent of ionisation, produces an ion flow signal for an ion flow signal receiving device (40-44) and from which a first crankshaft angle in connection with top dead centre (TDC) forward to another crankshaft angle at least 40 degrees later than the first, with integration in an integrator of the ion flow signal produced during combustion and which produces an integrated actual value of the ion flow signal from each combustion. A pinking sensor detects pinking from the combustion process and in proportion to the pinking intensity produces an actual pinking signal from each combustion event. A signal correcting circuit reduces the integrated actual value of the ion flow signals dependent upon the intensity of the pinking signal. A control unit (10) continuously varies at least one regulating parameter in accordance with a regulating algorithm stored in a memory. This algorithm maximises the corrected integrated actual value of the ion flow signals.

Description

510 448 ii l2 The object of the invention is to optimize the combustion in an internal combustion engine without risking regulation against a knocking condition where the engine risks overheating and breakdown. Another object is to regulate against an optimal lean fuel-air mixture which does not cause leakage, or is as close to the border as possible to unacceptable knocking. Yet another object of an advantageous embodiment is that control depending on detected knocking and combustion quality can take place without sensors in the combustion chamber other than the spark plug arranged therein, over which spark plug ionization degree in the combustion chamber is detected to determine both knocking and combustion quality.

BRIEF DESCRIPTION OF THE INVENTION The inventive method is characterized by the characterizing part of claim 1 and the system for carrying out the inventive method is characterized by the characterizing part of claim 7.

Through the inventive method and system, the internal combustion engine can be regulated in an optimal way with low fuel consumption and low emissions, without the internal combustion engine risking failure. With the method and control system, an optimal power output can be obtained especially for high-speed two-stroke engines, even in those operating cases where the engine easily starts to knock. The other features and advantages of the invention appear from the subscribing parts of the other claims and the following description of an embodiment. The description is made with reference to fi guras specified in the following fi gurförteclming.

LIST OF FIGURES Figure 1 schematically shows an arrangement for controlling an internal combustion engine and detecting the degree of ionization in the combustion chamber, Figure 2 schematically shows an inventive controller in a first embodiment; Figure 3 shows the pressure in the combustion medium during a normal combustion and during a combustion with ignition, Figure 4 shows how the integrated value of the ion current signal increases during a normal combustion and during a combustion with knocking, Figure 5 shows how the integrated value of the ion current signal varies at a emaciated control of the fuel during a normal combustion and during a combustion with knocking, Figure 6 shows a principal control algorithm which maximizes the reduced value of the ion current integral depending on the knocking 3 510 448 Figure 7 which shows a typical ion current signal, detected with an arrangement according to fi gur 1 .

DESCRIPTION OF EXECUTIVE EXEWEL Figure 1 shows an arrangement for regulating an internal combustion engine 1. Figure 1 shows an all-electronic control system for both the fuel supply and ignition of the internal combustion engine. With a microcomputer 10 which detects at least engine speed, engine temperature and engine load, via the sensors 11, 12 and 13, respectively, the ignition time is controlled as well as the amount of fuel supplied. The sensor 11 is preferably a conventional pulse sensor arranged to detect teeth on the periphery of the flywheel, where position determination can also be obtained by one or more of the members having different tooth gap / tooth width at a certain crankshaft position.

The microcomputer 10 usually contains an arithmetic unit 15 and the required memories 14, where control algorithms, fuel matrices and ignition matrices are stored.

In each cylinder 4 at least one spark plug 5 is arranged, only the spark plug in a cylinder shown in Figure 1. The ignition voltage is generated in an ignition coil 32 with a primary winding 33 and a secondary winding 34.

The primary winding 33 is connected at one end to a voltage source, battery 6, and in its ground connection is arranged an electrically controlled switch 35. By the microcomputer on the trigger output 50 making the switch 35 conductive, a current surface begins through the primary winding 33, and when the current is cut off. as usual, an up-transformed ignition voltage is induced in the secondary winding 34 of the ignition coil 32 and an ignition spark is generated in the spark plug gap 5. When the current is to be released and when the current is to be interrupted by the switch 35, so-called dwell-time control, is controlled in accordance with ignition angle mouse stored in the microcomputer memory 14, so that the required primary current has time to develop and that the ignition spark is generated at the ignition time required for the current load case. One end of the secondary is connected to the spark plug 5 and in the combustion chamber. The detection layer comprises a voltage accumulator, here in the form of a rechargeable capacitor 40, which energizes the spark gap of the spark plug with a substantially constant measuring voltage. The capacitor corresponds to an equivalent solution to the embodiment shown in EP, C, 18818 where the voltage accumulator is an elevated / uptransformed voltage from the charging circuit in a capacitive ignition system. In the embodiment shown in fi, the capacitor 40 is charged to a voltage level given by the breakdown voltage of the zener diode 41 when the ignition voltage pulse is induced in the secondary winding 34. This breakdown voltage can be anywhere between 80-400 volts. When the up-transformed ignition voltage around about 30-40 kVolts is generated in the sectar winding, the zener diode 41 opens and ensures that the capacitor 40 is not charged to a higher voltage level than the breakdown voltage of the zener diode. In parallel with the measuring resistor 42, a second reverse protection diode 43 is arranged which correspondingly protects against voltages of reversed polarity. 510 448 4 Over the measuring resistor 42, the current flowing in the circuit 5-34-40 / 4042 earth can then be detected, which current is dependent on the conductivity of the gases in the combustion chamber, which conductivity is dependent on the degree of ionization in the combustion chamber. connected closest to earth, only a connection is required in the measuring point 45 to a detection layer 44, which detection circuit measures the voltage across the resistor 42 and in the measuring point 45 relative to ground. By analyzing the current, or the voltage, through the measuring notch, knock and preignition can be detected. and as disclosed in US, A, 4535740, in certain operating cases the actual mixture dehumidifying air-fuel could be detected by measuring how long the ionization current is above a certain level, Through a lambda probe 31 in the earmuff motor gas exhaust collector 3, seen in the exhaust direction arranged before a catalyst 30 arranged in the exhaust system, the residual amount of oxygen in the exhaust gases can be present is detected, and thereby the current mixture-containing air-fuel is detected. With a conventional narrowband lambda probe, the output of which has a distinct turning point just below a stoichiometric mixing ratio, the amount of fuel specified from a stored fuel matrix can be corrected so that the ideal mixture of air fuel for the catalyst 30 function is contained. The output signal A of the lambda probe provides a feedback corrective control of the amount of fuel specified from the fuel matrix, which control is performed so that the output of the lambda probe lies and oscillates between high and low output signal up to a few times per second. The combustion engine fuel system conventionally contains a fuel tank 21. pump unit 22 arranged in the fuel tank. From the pump unit 22 the pressurized fuel is then fed on to a pressure equalizer, on to a fuel element 24 and on to other containers / volumes 2.5 including the fuel distribution pipe. In some cases a pressure regulator 26 is arranged at the end of the fuel distribution pipe, which in case of overpressure opens for a return i in the return line 27 back to the fuel tank 21 or the pump unit 22. An alternative to a pressure regulator 26 which opens at overpressure may be a pressure control of the fuel pump 22. 27 can be dispensed with. The volume of the fuel pump unit 22, the pressure equalizer 23, the fuel belt 24 and other cavities or containers 25 is so large that a couple of minutes of operation can take place before a fuel refueled in the fuel tank 21 reaches the injectors 20. The fuel injectors 20 are preferably arranged in the respective cylinders. preferably sequentially in synchronism with the opening of the respective cylinder inlet valve. The amount of fuel injected is determined by the length of the control pulse that the microcomputer applies to each injector. The amount of fuel, as well as the ignition timing, is controlled depending on current engine parameters in accordance with a fuel or ignition manis stored in the memory of the 510 448 microcomputer 14, and where the amount of fuel given by the matrix is possibly corrected by the lambda probe. the fuel supply system. With a fuel quality sensor 28, the fuel control can be adapted to the octane number of the fuel in question or the mixing ratio of, for example, methanol and petrol. The control unit 10 receives an input signal K from the fuel quality sensor indicating the current fuel quality. Figure 2 shows a signal processing circuit suitable for detection in the detection circuit 44.

The detection circuit 44 receives the signal corresponding to the degree of ionization on the line 56.

This ion current signal is processed in two cascaded signal processing steps.

In one signal processing step, the ion current signal is integrated in an integrator 61. The integrated value is then averaged in an average value 62. In the second signal processing step, the high frequency content of the ion current signal is filtered out in a bandpass filter 63, preferably above 5 kHz. The frequency content representative of the knock is then processed in a converter 64 which converts the frequency content into an analog signal proportional to the intensity of the knock. The converter 64 may suitably contain, in a manner known per se, a rectifier which rectifies the AC voltage signal from the bandpass filter 63, and an integrator which integrates the rectified signal. The signal thus integrated then becomes proportional to the intensity of the fine sequence content superimposed on the ion current signal and representative of the knocking. Before making a more detailed description of the last steps 65-66 of the signal processing circuit, reference is made to Figures 3-6 which illustrate the effects on the ion current signal or its integrated value caused by a knocking condition.

Figure 3 shows in solid lines the pressure level P, detected via a pressure sensor arranged in the combustion pipe, which is relevant for different crankshaft angles CD ° during a combustion without knocking. The dashed curve shows the pressure level that is relevant for different crankshaft angles during a combustion with knocking, but with other parameters the same. What can be seen is that in the knocking state the amplitude of the pressure signal increases in Figure 4 shows how the integrated value of the ion current signal IINT grows at a normal combustion, solid curve, respectively in the case of a combustion with knocking, dashed lmrva. The integrated value of the ion tube integral is here calculated in a measuring pattern which opens at the upper dead center, ie at the crankshaft angle 0 °. The degree of ionization in the combustion chamber increases with both the pressure and the temperature. This means that the ion integral integral also increases upon tapping. 510 448 i 'v f A control in which the value of the integral is maximized then means that control measures which force knocking are strengthened and that the internal combustion engine risks being locked in a state with strong loosening.

Figure 5 shows an example where in the case of emaciated control of the fuel, to the right of the X-axis, one tries to find the operating point where the integrated value of the ion current signal IINT has its maximum.

When knocking does not occur, the optimal operating point can be at an amount of fuel where the weight loss has taken place with a corrective and reducing amount A. When increasing the fuel reduction as well as decreasing the fuel reduction, the integrated value of the ion current signal IINT decreases. If there should instead be knocking when regulating the fuel, the integrated value will receive a maximum at a completely different leaner fuel quantity, where the fuel redionion -AF is greater, ie at the reducing amount B in 5. gur 5. Knocking is a limiting condition when losing weight , which knocking is provoked by too lean fuel-air mixtures. If you use a regulator that optimizes the integrated value of the ionstrone integral, a very effective knock-up state will occur mainly at high speeds and loads where the knock-in state quickly causes overheating and engine failure.

A phenomenon that occurs during knocking is that the combustion chamber or exposed parts of the combustion chamber are heated by the knocking process, which results in subsequent burns giving a higher ion current signal and a higher integrated value even if knocking did not occur. The temperature of residual gases, obtained from natural EGR and / or incomplete flushing in two-strokes, can also be higher after a knock, which can increase the ion current signal. The degree of ionization increases depending on both the pressure and the temperature in the cylinder.

The normal control measure during knocking is to quickly delay, for example, the ignition, and to maintain this delayed ignition time point for a predetermined time or a time dependent on the engine speed, so that the knocking state can be lifted and the combustion time has time to return to normal temperature. Another alternative or complement is to grease the fuel-air mixture to the knocking cylinder, and correspondingly maintain this perception for a predetermined time or a time dependent on the engine speed, so that the knocking state has time to be lifted and the combustion chamber returns to normal temperature.

In engines with superchargers, the knock resistance can also be raised by reducing the charge air pressure, but this affects all cylinders equally, even the cylinders that do not knock, if conventional supercharger units are used. Even when regulating the charge pressure for lifting the knock condition, it is required that the reduced charge air pressure must act over a certain predetermined time or engine speed dependent time 27 510 448 ”The knock can also be lifted by injecting water into the combustion chamber, which is a method that also for preventive purposes applied at very extreme operating points, usually at maximum load and high speeds.

After this description of how the knock affects the ion current signal and its integrated value, reference is again made to Figure 2. The signal obtained from the transducer 64 and proportional to the intensity of the knock is then valued in an averaging alter 65. led attenuation alteri the last step 66 occurs after an attenuation of the from step 62 the averaged value of the ion current signal depending on the level of the averaged proportional level of the tapping intensity. The output signal from step 66 on line 54 then becomes a conjugated integrated value of the ion current signal.

The control unit 10 can, through a control algorithm stored in the memory 14, for example initiate a lean control of, for example, the fuel so that the signal on the line 54 is maximized, i.e. the integrated value of the ion current signal corrected depending on the intensity of the knock is maximized. Figure 6 shows such a principle control algorithm which maximizes the knock-down value of the ion current integral depending on the knock. A thinning can for instance be initiated by the control unit 10 at substantially constant load on the internal combustion engine and initiated by gradually reducing the amount of fuel given by the fuel matrix. After at least one combustion with the reduced amount of fuel, in a first step 90 the last conjugated integrated value of the ion current signal fmgw is read on line 54. In the next step 91 fNEw is compared with the corrected integrated value of the ion current signal low obtained from the previous combustion with original amount of fuel. If the control measure results in an increase in Iya-tv relatively low, the initiated weight loss continues with the same reducing amount of fuel. If, on the other hand, the control measure has resulted in INEW being lower than low, then the algorithm goes to step 92 in which the corrective amount of fuel changes characters, which means that a weight loss changes to a fat loss, alternatively that a fat loss changes to a lean weight. Before returning to the control unit's main program, Ilmv is read in as a new value for low, to be used in the next correction of the fuel initiated by the control unit.

Correspondingly, the control unit can correct the ignition timing step by step so that the corrected integrated value of the ion current signal is maximized. The ignition point can then be driven to an optimal ignition with a safe margin against knocking, as the integral is reduced depending on the intensity of the firing. The boost pressure can also be increased gradually in a corresponding way. 510448 i i V8 The averaging in step 62 is required for the controller to be more stable and not affected by the large cycle-to-cycle variations that occur between combustions.

The averaging takes place suitably as a rolling averaging where a part of the current value, ie the most recent integrated value, is averaged with the previously calculated averaging.

As a result, temporary disturbances or deviations cannot have a full effect on the averaged signal, which makes the controller more stable. The averaging filcret preferably gives an output signal y given by the following relationship; y (k) = Km-y (k-I) + (1-Km) -x (k) where Km is the mean value factor, which determines how much the previously formed value should affect the mean value, and x corresponds to the last value. In practical application, the mean value factor K ,,. is set to 0.95 in step 62, roughly corresponding to an average value formation over about 30 measured values, which for the pre-combustion engine takes place very quickly.

The averaging in step 65 is required for a reduction of the integrated value of the ion current signal to occur even in a subsequent combustion to compensate for the residual temperature raising effects after a knock in the previous combustion. How this average formation is to take place must be adapted to the propensity to knock of each engine type and how long the temperature-raising effects after a knock remain after a knocking combustion.

In some runs, the remaining temperature-raising effects after a knock, which increase the integrated value of the ion current signal, have already subsided after 1-2 subsequent burns without a knock. In other engine types, the temperature-raising effects can persist for more than a dozen combustions in a row.

Averaging in step 65 can for a particular engine type take place over a limited number of combustions where the new mean value Mn after the last combustion n takes place over, for example, the last 3 combustions and can be drawn as; Mn: (k1 ~ IONSign) + (k20M ,,,) + (kg .MQ), where, k] -kg are constants IONSign is the current signal from step 64, and MM and MH are the mean values from the previous combustion nl and nZ respectively. gradually decreasing the constants k; -k3 provides an attenuation of the ion current integral adapted to the residual temperature-raising effects from previous combustion with knocking. In some applications the effect of raising the temperature and increasing the degree of ionization is higher on the combustion which follows immediately after a combustion with knocking, which means that in some applications it is k; greater than kl. How the ratio is can differ between different engine types, and must be tested for each engine type in question. In the exemplary engine type, the remaining 29 mare 448 effects are gone after 3 burns, but additional terms (k., V MQ + ... etc.) Can be used if the effects remain more than 3 dry burns.

If a faster response is to be obtained due to a spontaneous knock, then the new average value M., under special conditions, can only or at least substantially only be formed on the current signal from step 64. A condition may preferably be that if the IONSign signal from the last combustion is greater than 20-40% of the previous IONSign, the new mean value Mn is drawn as; Mn = (K; 0 IONSign), where Kl> kl, k2 or kg.

For each subsequent combustion, an additional term is then added, k; 0 MM, to the successively updated mean. In an alternative embodiment not shown for conventional systems, with a separate lataclr control algorithm, knock control shall always be given higher priority than the algorithm which optimizes the value of the ion current integral when the knock intensity is above a dry minimum level. This lowest level can be a tolerably limited state of ignition for the engine, for example that only a few single burns knock at longer intervals between knocking burns and which in time do not risk destroying the engine. Alternatively, the knock-lifting control measures can be given a priority proportional to the knock-intensity over the control measures which strive to optimize the value of the ion tube integral.

As long as an acute knocking condition, which can be a knocking intensity above a certain minimum value, is detected, the control measures that are put in place to lift the knocking condition are always given priority over the control measures that seek to increase the ion beam integral value.

Corresponding priority is obtained in the reduction of the value of the ion current integral, in that the reduction of the integral takes place in proportion to the intensity of the leakage. A very limited ignition intensity can give a only marginal reduction of the ion tube integral, which practically means that a limited and non-harmful knocking can be allowed in the steady state. Figure 7 schematically shows the appearance of the ion current signal UION obtained on line 56 with a measuring arrangement 1 in accordance with measurement arrangement 1. The UIQN is indicated on the Y-axis and is here measured in volts, and can be between the output signal 0 volts to just over 2.5 volts. The X-axis indicates crankshaft degrees ° VC, where 0 ° indicates the upper dead center when the piston is in its uppermost position.

At the SP position, which is a position before the dead center, for example 15-20 crankshaft degrees before the dead center, the spark ignition is generated with the dry ignition ring that is relevant during the prevailing operating conditions, mainly depending on load and speed. The generation of the spark generates a high measuring pulse in the detection circuit, caused by the flash in the spark plug gap during the so-called break down phase, but this high measuring pulse is filtered out, and its measured value is not used in the preferred embodiment.

Suitably, the acquisition array of measurement signals is controlled by the microcomputer 10, so that the microcomputer only reads the input signal input 55 at certain determined motor positions or times, cLv.s in certain measuring windows. These measuring windows are preferably activated in dependence on the ignition time SP, so that these measuring windows are opened long enough after the flashover phase has ended.

After the flashover phase, a ame ionization phase (Flame ionization phase), in fi gur 7 called FLAME ION, starts, during which phase the measuring voltage is affected by the establishment of a burning core of the air-fuel mixture in or at the spark plug gap.

After the ionization phase, the ionization phase (Post ionization phase), called POST ION, starts in Figure 7, during which phase the measuring voltage is affected by the combustion in the combustion chamber as the number of ionizing particles increases with temperature and combustion pressure. Typically, POST ION reaches a maximum value, indicated by PP in fi clock 7, when the combustion accident has developed to its highest value and the fr amfront has reached the walls of the fox combustion chamber, which results in an increase in pressure.

The current network window under which the ion current signal is integrated must be made as large as possible for the greatest possible resolution, and at least cover the entire post-ionization phase, but preferably also all or parts of the jon ionization phase. The measuring window can be controlled depending on the ignition time, but should preferably be open in the range -5 crankshaft degrees before upper dead center to at least 40 crankshaft degrees after upper dead center. The measuring window can in some applications be open up to 180 crankshaft degrees after the upper dead center, ie to the lower dead center position of the piston, in order to detect very long deionization phases caused by poorer fuel qualities or too lean fuel-air mixtures which burn more slowly.

Within the framework of the patent claims, the invention can be modified in a number of ways. The knock detection does not necessarily have to take place over the spark plug of the internal combustion engine as shown in Figure 1.

The knock detection can also take place by ionization detection over a measuring gap separated from the spark plug. The knock detection can also take place by means of a conventional knock sensor of the accelerometer type mounted on the motor block, which detects the frequencies typical of the knock which are propagated in the motor block.

Claims (8)

10 20 25 30 211 sto 448 PATENTKRAV 1. l. Method for regulating a two-stroke or four-stroke internal combustion engine of Ottotype for optimal combustion where the ionization in the combustion chamber during combustion is detected and an ion current signal corresponding to the ionization can be obtained and where a knock from the combustion is detected and a knock signal intensity corresponding to by - that the signal corresponding to the ionization is integrated over a measuring window which is kept open after spark ignition adjacent to the upper dead center of the piston and at least 40 crankshaft degrees after the upper dead center, whereby an integrated value of the ion current signal is obtained from each combustion, an engine fuel is adjusted so that the integrated value of the ion current signal is maximized when a substantially knock-free state prevails, and that knocking with a knocking intensity exceeding at least one dry-determined minimum intensity takes place, a regulation of a motor takes place. influencing control parameters in order to cancel the knocking process with priority before a control of a motor influencing control parameters in order to maximize the integrated value of the ion current integral Method according to claim 1, characterized in that the integrated value of the ion current signal is reduced in dependence on the knock signal to form a corrected integrated value of the ion current signal, where the reduction of the ion current signal takes place in proportion to the intensity of the knock. corrected integrated value of the ion current signal is maximized even at knock. Method according to claim 2, characterized in that the knock signal from each combustion and combustion chamber to a predetermined part corrects the integrated value of the ion current integral in the reducing direction for a predetermined number of successive subsequent combustions in the combustion chamber or after combustion. Method according to claim 3, characterized in that at least from and with the second subsequent combustion in the actual combustion chamber after a first knocking combustion in this combustion chamber, the integrated value of the ion current integral is reduced depending on the intensity of the first knocking in successively decreasing extent for each subsequent combustion. 510448 i i 112 10 15 20 25 30 5. A method according to claim 3, characterized in that the knock signal from each combustion is averaged with knock signals from previous combustions, preferably through a rolling averaging where the knock signal obtained from the last combustion is averaged with the previous cracked average, and that the mean signal is integrated. the value of the ion current signal Method according to any one of claims 2-5, characterized in that the integrated value of the ion current signal from each combustion is averaged with integrated values from previous combustions, suitably by a rolling averaging where the integrated value of the ion current signal obtained from the most recent combustion is averaged integral mean value obtained from previous combustions, and that the mean value-formed integrated value of the ion current signal is reduced in dependence on the knock signal for the formation of the conjugated integrated value against which the maximization takes place in the control of the control parameter Fuel control system for an internal combustion engine with at least one cylinder (4) comprising, - a position sensor (1 1) which generates at least one reference position corresponding to a determined crankshaft angle for a cylinder in the internal combustion engine, - an ion current sensor (5) arranged in the cylinder which detects the ionization in the cylinder during combustion and which, depending on the degree of ionization, produces an ion current signal, an ion current signal receiving device (40-44) which from a first crankshaft angle in connection with the upper dead center to a second crankshaft angle at least 40 degrees later than the first crankshaft angle in an integrator ( 61) integrates the ion current signal generated during combustion and which produces a current value of the ion current signal integrated from each combustion, and - a knock sensor which detects knocks from the combustion and which in proportion to the intensity of the knock produces a knock signal current from each combustion. in that the fuel control system comprises - a signal correcting circuit (66) which reduces the integrated current value of the ion current signal depending on the intensity of the knock signal, - a control unit (10) which continuously varies at least one control parameter according to a control algorithm stored in the control unit memory. the value of the ion current signal 13 S10 44 8 Fuel control system according to claim 7, characterized in that the sensor element of the ion current sensor and the ignition sensor consists of a spark plug (5) arranged in the combustion chamber, where a signal proportional to the ionization chamber in the dry combustion chamber is output via a measuring circuit (40-43). the ignition coil (32) connected to the spark plug, where the signal obtained from the measuring circuit via a frequency terlter (63) filters out the frequency content representative of the knock and via integrating means (61) obtains a value of the signal obtained from the measuring circuit via the combustion means