DE2443413A1 - PROCEDURE AND EQUIPMENT FOR CONTROLLING THE OPERATING BEHAVIOR OF AN COMBUSTION ENGINE - Google Patents

Description

August 15, 1974 Ka / Thu

Attachment to
Patent application

ROBERT BOSCH GMBH, 7 Stuttgart 1

Method and device for regulating the operating behavior of an internal combustion engine

The invention relates to a method for regulating the operating behavior of an internal combustion engine in a predetermined one Operating range, with its operating behavior as a function of fluctuations in operating parameters of the internal combustion engine is changed.

As a result of stricter emissions regulations and due to the general Solutions to fuel shortages are sought which internal combustion engines can be operated in an operating range in which the harmful components of the exhaust gas are " reduced to a minimum ΐ / can ground and / or in which the consumed Fuel is a minimum.

In order to meet such a requirement, it is obvious at first glance to equip the internal combustion engine with a to operate a lean fuel-air mixture, i.e. at the so-called

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called the lean running limit of the internal combustion engine. Relatively low-emission exhaust gas and low fuel consumption can be expected in this operating range. The fluctuation in the pressure curve in the cylinders is the characteristic variable for the lean running limit an internal combustion engine.

On closer inspection of the problem described, however, it turns out that the individual pressure curves of not controllable operating parameters of the internal combustion engine are determined, for example by air ratio, filling and Turbulence fluctuations. If the combustion chamber pressure is determined by the instantaneous values of the angular velocity on the crankshaft measured, further disruptive influences occur, for example due to the oscillating masses of the crank drive, Unevenness in the road surface of the motor vehicle or any forces on the engine block of the internal combustion engine. The fluctuations described, which are superimposed on the normal pressure curve in a cylinder of the internal combustion engine, and that are expressed in fluctuations in the angular velocity of the crankshaft, could indeed be filtered out with low-pass filters are, however, the use of such filters is extremely problematic because the internal combustion engine 'in should be operated over a wide speed range. This makes it difficult at low speeds (frequencies) and to find suitable filters equally at high speeds.

Proceeding from the problems outlined, the object of the invention is to find a method with which Help the control of the internal combustion engine in a certain operating range is possible without the mentioned Difficulties or disadvantages arise.

This object is achieved according to the invention in that ion currents in the combustion chamber of the internal combustion engine are used for identification the actual value for the operating behavior of the internal combustion engine can be detected and compared with a setpoint value

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and that as a function of the control deviation via an actuator, the operating behavior of the internal combustion engine will be changed.

A further object of the invention is to provide a device to create the implementation of the method, with the help of which the regulation is carried out easily and reliably can be. Particular attention must be paid to ensuring that the control device is also used in the rough operation of a motor vehicle works reliably and that possibly also uses existing transducers in the motor vehicle can be. After all, the facility should be designed to save costs.

This object is achieved according to the invention in that an ion current sensor arranged in the combustion chamber of the internal combustion engine which is in operative connection with a comparison device to which a setpoint value signal is also applied is, wherein the output of the comparison device with a control device in particular exhibiting integral behavior to influence the mixing ratio of the fuel-air mixture and / or the exhaust gas recirculation rate is in operative connection.

Further advantageous refinements and expedient developments of the invention emerge in connection with the subclaims from the following description of exemplary embodiments and from the accompanying drawings. Show it:

Fig. 1 shows the course of ion currents over time, the ion current curves of different Cylinders of an internal combustion engine are applied,

2 shows a diagram in which the mean relative fluctuation of the ion currents is plotted against the air ratio is,

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Pig. 3 the combustion chamber of an engine in which a spark plug and an ion current probe are arranged,

4 is a diagram in which the frequency distribution H for the ignition time (angle) at the Spark plug and for the arrival time (angle) at the ion current probe of the arrangement according to FIG. 3 are plotted over time.

5 shows a diagram in which the mean relative fluctuation of flame run times in the combustion chamber of an internal combustion engine is plotted against the air ratio λ,

6 shows the combination of a spark plug and an ion current probe,

7 shows a device for regulating the operating behavior of an internal combustion engine as a function of the Flame runtime between the spark plug and the ion current probe,

8 shows the part of a device for generating setpoint values for the device according to FIGS. 7 and

9 shows a pulse diagram for explaining the exemplary embodiments according to FIG. 7 and FIG. 8.

In the following, devices and method steps are to be described with which an internal combustion engine is to be at least partially in its operating range located at the lean operating limit. The so-called lean running limit should be understood to mean an operating range in which the first protracted burns occur. Combustion failure only occurs when the air ratio is 5 to 10% higher, ie when the mixture is significantly leaner. In an area of a running limit defined in this way, the fuel consumption is generally significantly lower than in an operating area of the internal combustion engine in which a stoichiometric fuel-air mixture (air ratio λ = 1) is supplied.

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If two electrodes are attached to the combustion chamber of an internal combustion engine, during the combustion process, when flames reach the two electrodes, an ion current flows between them. This ion current can do this can be used to identify the operating range in which the internal combustion engine is operating. Here is the ion current depending on the air ratio Λ of the internal combustion engine supplied Fuel-air mixture. Both the absolute value of the ion current can be used for the regulation as this decreases with increasing λ. However, the relative fluctuations of the integral values can also be affected the ion currents in one working cycle of a piston an internal combustion engine can be determined. These relative Fluctuations increase with the air ratio λ. In Pig. I are plotted in a diagram of ion current curves over time t. The first curve is a first cylinder, the second curve is a second cylinder, and the third curve is a cylinder third cylinder and the fourth curve assigned to a fourth cylinder. If one integrates the ion currents over one each A certain time range, expediently over a working cycle of a piston of the internal combustion engine, is then obtained electrical signals that change with the air ratio ^.

In Fig. 2, the relative fluctuations in the ion current are plotted against the air ratio Λ. ^ - thereby rises with increasing air speed, so that one can take advantage of the corresponding electrical signals for influencing the operating behavior of the internal combustion engine by at the supplied to the internal combustion engine fuel-air mixture is easily made rich for example for large \ the mixture ratio or the recirculated exhaust gas amount is reduced will.

The ion current can, for example, with an ion current probe 10 can be determined, which is shown in FIG. 3. The ion current probe is in the cylinder head 11 of an internal combustion engine arranged, in which a spark plug 12 is attached. The ion current probe 10 does not have to be a separate one The spark plug 12 itself can, for example, also serve as an ion current probe, if

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the ion current flowing during the combustion process is determined between the two electrodes.

The arrangement of ion current probe 10 and spark plug 12 shown in FIG. 3 in cylinder head 11 of an internal combustion engine can also be used to determine the running time of a flame front that emanates from the spark plug 12 and after the ion current probe 10 reaches a certain time. In Fig. 4 is the frequency distribution of the time of ignition at the spark plug 12 and the frequency distribution of the arrival time of the flame front at the ion current probe 10 applied over time t. The time between the frequency focus of ignition triggering shown at 13 is here and the center of frequency of the arrival time at the ion current probe shown at 14 equal to the mean transit time T- the flame front. The running time of the flame front TV also changes in absolute terms with the air ratio / \. In addition, fluctuations in the transit time Tr over the air ratio λ change. This relationship is shown in FIG. 5 shown. Here, in a diagram on the ordinate, the mean value of the runtime changes is related to plotted the mean value of the running time. The air ratio λ is plotted on the abscissa. From the diagram recognize that the relative fluctuations in the running time with increasing air number, λ increase. This signal can in turn to influence the operating behavior of an internal combustion engine be exploited.

In Fig. 6 an arrangement is shown for the transit time measurement of flame fronts is particularly useful, since with this arrangement an additional hole in the cylinder head the internal combustion engine for the ion current probe is avoided. In Fig. 6 the base 15 of a spark plug is shown, which has two ignition electrodes 16 and 17. In addition, two further electrodes 18 and 19 are attached to the base 15, through which an ion current can flow. The distance between the two pairs of electrodes 16, 17 and 18, 19 is only slightly ge mm. This distance is sufficient to be able to carry out time of flight measurements.

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Another possibility is that of dispersing time between the increase in the ignition voltage and the increase in the ionic current at the spark plug itself (so-called ignition delay time) use.

In Fig. 7 a device is shown with the help of the transit time of a flame front between a spark plug and an ion current probe to influence the operating behavior an internal combustion engine can be used. With the device described, the runtime is between the initiation of ignition and the arrival of the flame front at the ion current probe. Thereby a target value given. If the flame runtime is longer than the specified one The setpoint value means that the value supplied to the internal combustion engine The fuel-air mixture must be made leaner or the amount of recirculated exhaust gas must be reduced. On the other hand· an actual value below the target value means that the fuel-air mixture has become emaciated or the exhaust gas recirculation rate must be increased. In Fig. 7, an ignition distributor 20 is shown, from which pulses are taken can mark the initiation of the ignition process. These pulses are applied to a pulse shaping circuit 21, the square-wave pulses shown in FIG. 9a appear at the output of this pulse shaping circuit 21. Of the Output of the pulse shaping circuit 21 is with a first monostable multivibrator 22 connected, which with each pulse that appears at the output of the pulse shaper circuit 21 in their unstable switching position tilts. The duration of the unstable switching position can be dependent on various operating parameters of the internal combustion engine, in particular as a function varies from the speed η and the intake manifold pressure ρ

will. This enables the setpoint value for the control device can be made dependent on the speed or intake manifold pressure. At the output of the first monostable trigger stage 22 occur in Fig. 9b shown pulses. These impulses are on a second monostable multivibrator 23 is applied, which each time the first monostable multivibrator is tilted back is switched to its unstable switching state. The one at the output of the second monostable multivibrator 23

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appearing pulse, which is plotted in Fig. 9c represents the target value for the control device. The output of the second monostable multivibrator 23 is with the second input of an RS flip-flop 26 connected, which operates as a comparison switching device. With the first entrance 27 of the flip-flop 26 is the ion current probe via a pulse shaper 28 10 connected. The pulse shaper 28 delivers a in Fig. 9t> The signal shown when an ion current flows through the ion current probe 10, i.e. when that from the spark plug 12 outgoing flame front arrives at the ion current probe. With the help of the RS flip-flop 26 it is now compared whether the The actual value is greater or less than the setpoint value, i.e. whether the pulse applied to the first input 27 is earlier or less later than the pulse occurring at the second input 25 is present. The output signal of the flip-flop is L when there is a zero signal at the first input and a zero signal at the second Input an L signal is present. The output signal of the flip-flop 26 is zero when the first input 27 has an L signal and a zero signal is present at the second input 25. That The output signal of the flip-flop 26 is equal to the previous output signal when both inputs 25 and 27 have an L signal is present. From this it can be seen that with the help of the RS flip-flop 26 it can be determined whether the actual value is greater than that Target value is. The output signal of the flip-flop 26 changes accordingly. This output signal is via a resistor 29 is applied to an integrator which has an operational amplifier 3o. It is between the output of the Operational amplifier 30 and its inverting input an integrating capacitor 31 is connected. The tap is connected to the non-inverting input of the operational amplifier 30 a voltage divider made up of resistors 32 and 33 is connected. It is also connected to the inverting input of the operational amplifier 30 the resistor 29 is connected. Depending on the output signal of the flip-flop 26, the output voltage rises or falls at an output terminal of the integrator. This output signal can now be used, for example, in a fuel processing device are intervened and the mixing ratio of the fuel-air mixture supplied to the internal combustion engine to be changed. This can happen, for example, that the injection time of an injection injection

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direction depending on the output signal at the terminal 34 is extended or shortened.

The output signal at terminal 34 can also be used for this purpose be a solenoid valve in an exhaust gas recirculation line an internal combustion engine to open or close more or less and thereby the amount of recirculated exhaust gas to change.

Another possibility of using the arrival of a flame front at the ion current probe to regulate the operating behavior of an internal combustion engine is to use the time interval between a fixed angle of rotation of the crankshaft of the internal combustion engine and the arrival of the flame front on the ion current probe as a control variable. In this case, the target value is not formed by picking up an electrical signal at ignition distributor 20, but rather by picking up an electrical signal that is triggered by markings on the crankshaft of an internal combustion engine. Such an embodiment is shown in FIG. In Fig. 8, a disk 35 is shown which is firmly attached to the crankshaft of an internal combustion engine. The disk 35 has two lugs 36 and 37 which, when moving past an inductive sensor 38, induce a voltage in the latter. The signal that is induced in the inductive transmitter 38 is applied to the pulse shaping circuit 21, which is connected to the first monostable multivibrator 22. The first monostable multivibrator 22 is connected to the second monostable multivibrator 23, the output of the second monostable multivibrator 23 being applied to the comparison device 26. The mode of operation of the circuit branch described is exactly the same as that of the circuit branch in FIG. 7; in order to avoid repetition, the mode of operation should therefore not be repeated again. In this exemplary embodiment, too, the comparison device 26 now determines whether the actual value, namely “the signal triggered by the ion current at the ion current probe 10

arrives before or after the impulse serving as the target value. Changes depending on the determined control deviation

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the integrator 30, 31 its output voltage, this signal for influencing the fuel-air mixture or the EGR rate is used.

Another possibility to take advantage of the arrival of a plasma front at an ion current probe is that the Arrival of the flame at the ion current probe is connected with the arrival of a signal that is given in a fixed manner Angular position of the crankshaft is triggered. Does the signal triggered by the ion current probe come sooner or later? when the electrical signal triggered at the specific angle of rotation of the crankshaft, the output voltage changes of the integrator 30, 31 and in the manner described, the mixing ratio of the fuel-air mixture or the exhaust gas recirculation rate is changed. The method described last is particularly useful when the ignition adjustment of an ignition system of the internal combustion engine is chosen so that a flame arrives at the ion current probe with a fixed angle of rotation of the crankshaft leads to minimal fuel consumption.

Should the fluctuations of the ion currents be used instead of the absolute values or the fluctuations in the flame transit times are determined, a sample and hold circuit known per se provide, with the help of which at least two successive measured values can be stored. By forming the difference fluctuations can be determined between the two values, which are then described in FIG Way can be compared with a target value. Depending on the system deviation determined, this can then Mass ratio of the fuel-air mixture or the exhaust gas recirculation rate can be influenced.

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Claims (1)

- Xl - Claims ? 2 g 7 experienced for regulating the operating behavior of an internal combustion engine in a predetermined operating range, depending on fluctuations in operating parameters the internal combustion engine changes its operating behavior is, characterized in that ion currents in the combustion chamber of the internal combustion engine to identify the actual value are detected for the operating behavior of the internal combustion engine and compared with a target value and that in The operating behavior of the internal combustion engine is changed as a function of the control deviation via an actuator. 2. The method according to claim 1, characterized in that the ion current in an ion current probe to determine the transit time a flame front is used in the combustion chamber of the internal combustion engine and that depending on changes in the Running time of the plasma front the operating behavior of the internal combustion engine is changed. ^. Method according to claim 2, characterized in that the Time of flight of the plasma front measured from the ignition electrodes of a spark plug (12) to the ion current probe (10) is and is compared with a target running time and that depending on the control deviation determined Operating behavior of the internal combustion engine by changing the mixing ratio of the internal combustion engine 609813/0112 supplied fuel-air mixture and / or the amount ^ influenced by recirculated exhaust gas from the internal combustion engine •will. 4. The method according to claim 2, characterized in that the spread of the transit time of the plasma front from the ignition electrodes of a spark plug to the ion current probe is measured and is compared with a setpoint value and that the operating behavior is dependent on the control deviation determined of the internal combustion engine by changing the mixing ratio of the fuel-air mixture supplied to the internal combustion engine and / or the amount of recirculated exhaust gas from the internal combustion engine is influenced. 5. The method according to claim 2, characterized in that the spread of the time between the ignition voltage rise and The increase in ion current at the spark plug or the ion current probe is determined and compared with a target value and that in Dependence on the determined control deviation of the operating behavior of the internal combustion engine by changing the Mixing ratio of that supplied to the internal combustion engine Fuel-air mixture and / or the amount of recirculated exhaust gas from the internal combustion engine is influenced. 6. The method according to claim 1, characterized in that a target crankshaft rotation angle is predetermined, in which one The plasma front in the combustion chamber of the internal combustion engine is to arrive at an ion current probe (10) and that the setpoint value is compared with the actual value of that crankshaft rotation angle at which the flame front at the ion 609813/0112 - 13 - - 13 - Y 2 9 / current probe arrives and that depending on "control deviations the operating behavior of the internal combustion engine by changing the mixing ratio of the internal combustion engine supplied fuel-air mixture and / or the amount of recirculated exhaust gas from the internal combustion engine being affected. 7. The method according to claim 1, characterized in that the Scatter of ionic ions integrated within at least one working cycle of a piston of the internal combustion engine • flow to an ion current probe it is determined that the The determined actual values are compared with a nominal value and that the mixing ratio is dependent on the control deviation of the fuel-air mixture supplied to the internal combustion engine and / or the amount of recirculated exhaust gas is influenced. 8. The method according to claim 1, characterized in that the scatter from within at least one work cycle of a piston of the internal combustion engine integrated ionic currents it is determined at a spark plug (12) of the internal combustion engine that the determined actual values are associated with a Setpoint values are compared and that, depending on the control deviation, the mixing ratio of the internal combustion engine supplied fuel-air mixture and / or the amount of recirculated exhaust gas is influenced. 9. The method according to claim 7 or 8, characterized in that that the changes in the ion currents are related to the absolute value of the ion currents (relative spread of the , integrated ion currents). 6G9813 / 0112 lh - in - 2 2 9 lo. Method according to one of Claims 3 to 6, characterized in that that the setpoint as a function of operating parameters of the internal combustion engine, in particular as a function of the speed and the intake manifold pressure is changed. ¹¹ · Device for carrying out the method according to one of Claims 1 to Io, characterized in that an ion current sensor. (10, 18, 19) is arranged in the combustion chamber of the internal combustion engine, which is in operative connection with a comparison device (26) to which a setpoint signal is also applied, the output of the comparison device (26) being connected to an adjusting device (30, 30, 31) is in operative connection with influencing the mixing ratio of the fuel-air mixture and / or the exhaust gas recirculation rate. 12. Device according to claim 11, characterized in that at least one spark plug of the internal combustion engine is provided as an ion current sensor. 13. Device according to claim 11, characterized in that as an ion current sensor, one mounted separately from the spark plug (12) in the cylinder head of the internal combustion engine Ion current probe (10) is provided. 14. Device according to claim 11, characterized in that the ion current sensor is combined with the spark plug, two electrodes (18, 19) of the ion current probe and 609813/0112 " ¹⁵ " two electrodes (16, 17) of the spark plug on a 2 2 9 -, common base (I5) are applied, which can be screwed into the cylinder head of the internal combustion engine. 15. Device according to claim 13 or 14, characterized in that the supplying the actual value for the control Ion current probe. (10, 18, 19) is connected to the first input of the comparison device (26) and that a the initiation of the ignition process in the combustion chamber of the internal combustion engine characterizing signal, in particular is applied via a pulse shaper (21) to a first monstable flip-flop (22), the flip-over time of which the setpoint forms, and that the first monostable flip-flop (22) is connected to a second monostable flip-flop (23), the output of which is connected to a second input (25) of the comparison device (26). 16. Device according to claim 13 or 14, characterized in that the supplying the actual value for the control device Ion current probe (12, 18, 19) is connected to the first input (27) of the comparison device (26) and that a signal characterizing a certain rotational angle position of the crankshaft, in particular via a pulse shaper (21) is in operative connection with the second input (25) of the comparison device (26). · 17. The device according to claim 16, characterized in that the • characterizing a certain angle of rotation position of the crankshaft electrical signal is applied to a first monostable multivibrator (22), the tilting time of which forms the setpoint, and 609813/01 12 - 16 - that the first monostable multivibrator (22) is connected to a second monostable multivibrator (23), the output of which is on a second input (25) of the comparison device is connected. 18. Device according to one of claims 15 or 17, characterized in that that the duration of the unstable switching state of the first monostable multivibrator (22) as a function of operating parameters of the internal combustion engine, in particular as a function of the speed and the intake manifold pressure is changeable. 19. Device according to one of claims 11 to l8, characterized in that that the comparison device (26) is designed as an RS flip-plop. 20. Device according to one of claims 11 to 19, characterized characterized in that the comparison device (26) has a fuel processing device in particular via an integrator (30, 31) influenced to change the fuel-air mixture ratio. 21. Device according to one of claims 11 to 19, characterized in that that the comparison device (26), in particular via an integrator (30, 31), has a valve in an exhaust gas recirculation line influenced to change the exhaust gas recirculation rate. 22. Device according to claim 11, characterized in that 609813/0112 - 17 - the electrical signals characterizing the ion currents in successive work cycles to a sample and Hold switching device applied to generate signals are which the fluctuations or the relative fluctuations of the ion currents and that this actual value signal is applied to a comparison device for comparison with a nominal value, depending on the determined Control device, in particular a fuel processing system via an actuating device exhibiting integral behavior to change the fuel-air mixture ratio and / or an actuator for changing the exhaust gas recirculation rate can be influenced. $ 09813/0112 Le e rs e11 e