DE2601871A1 - METHOD FOR CONTROLLING THE COMBUSTION PROCESS OF AN EXTERNAL IGNITION COMBUSTION ENGINE - Google Patents

Description

Z / DR-2 Sp uk

P atent registration

Method for controlling the combustion process of a spark-ignited

Internal combustion engine

The invention relates to a method for controlling the combustion sequence of an externally ignited internal combustion engine.

So far it was known to use an ionization probe to investigate combustion sabl to use e in internal combustion engines. The ones in such investigations The combustion processes identified were systematically recorded in their effects are studied and in the subsequent determination of a parameter of an internal combustion engine are taken into account accordingly.

The parameters established in this way for an internal combustion engine presented here with regard to the different operating conditions an internal combustion engine is always a more or less happy compromise.

The present invention has set itself the task of using an ionization probe combustion processes determined in an internal combustion engine

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to register, relate and compare immediately with the engine running and to draw from this information on the appropriate change in the parameters of the internal combustion engine while the engine is running.

According to the invention, this object is achieved by in an internal combustion engine the process steps indicated in the claims carried out will.

The inventive arrangement of an ionization probe in the combustion chamber of an internal combustion engine at a point furthest away from the spark plug, in such a way that the ionization probe generates a signal as soon as it comes from the Flame front of a combustion process is achieved, connecting the ionization probe to an electronic counter circuit in such a way that during a certain number of work cycles or during a certain period of time by a first counter the angle sector within a first crankshaft detected flame fronts reaching the ionization probe are counted and then by a second counter that determined within a second crankshaft angle sector, the ionization probe reaching flame fronts are counted, the connection of the electronic counter circuit with an electronic divider circuit in which the Counting result of the first counter is divided by the counting result of the second counter and a signal proportional to this ratio is generated which represents a measure of the combustion quality and the connecting of the electronic Divider circuit with an electronic comparison feedback circuit, in which the signal for the combustion quality is compared with a preselectable target value and, depending on the deviation from it, the corresponding one Control signals for influencing the air-fuel ratio, the ignition or the turbulence of the mixture of the internal combustion engine are generated, an optimal control of the internal combustion engine is either in view of achieved for maximum performance or minimum exhaust emissions.

The invention is illustrated by means of one in the accompanying drawings Tax system explained in more detail.

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Fig. 1 shows a view of a cylinder head of an internal combustion engine from below showing the arrangement of the ionization probe.

FIG. 2 shows an ionization probe as used in FIG. FIG. 3 shows a section along the line AA in FIG. 1.

Fig. 4 shows an electronic circuit diagram for a in connection with the Ionization probe in Fig. 1 control system to be used.

5 A to 5 D show diagrams from which the different degrees of flame front propagation emerge under different test conditions.

6 shows a diagram of the specific fuel consumption of an internal combustion engine in relation to the combustion quality according to the invention - Relationship.

Fig. 7 shows a diagram of the flame front propagation degrees with different combustion s-quality ratio.

A spark ignition internal combustion engine 10 of the conventional reciprocating piston type has a cylinder head 19 with a combustion chamber 11 in which inlet and outlet valves 12 and 13 are arranged. The spark plug is located at 14. An ionization probe 15 extends through a bore 16 in the cylinder head 19 to the combustion chamber 11, namely at one of the Spark plug 14 furthest away point. The passage of the ionization probe 15 through the bore 16 can, for. B. be sealed with an adhesive 25.

The ionization probe 15 consists of two electrodes in a ceramic

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Tubes of 2.5 mm in diameter are arranged. A voltage potential of about 300 volts is applied across conductors 17 and 18 and across a 10 MSi resistor. The signal of the ionization probe 15 is here from removed from the junction of the resistor with one of the conductors. Normally there is no current flow in the ionization β probe 15. However, as soon as a flame front reaches the ionization probe 15, the resistance between the two electrodes drops as a result of the ionization of the gases and a current flows through the ionization probe, as a result of which the voltage potential drops from about 300 volts to a lower value.

Preferably there is a multi-cylinder in the combustion chamber of each cylinder Internal combustion engine an ionization probe 15 as in FIG. 1 to 3 shown, arranged.

4 shows the connection of the ionization probe with the one according to the invention Control system shown. The signal from the ionization probe 15 is fed to an input 1 and an input 2 via a line 20. With an internal combustion engine with a plurality of cylinders, the ionization probes arranged in each case in the cylinders are connected in parallel with the line 20, so that the inputs 1 and 2 all signals of the flame front propagation degree of received all cylinders.

A timing disc 21 is connected to the crankshaft of the internal combustion engine and delivers via a corresponding converter a timing signal over a line 22 to the inlet 1 to this inlet 45 before the upper Open dead center and close 45 after top dead center ·.

In a similar manner, a timing signal is fed via a line 23 to the inlet to this in
Close dead center.

guided to open this at top dead center and 90 to the top

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The signals of the flame front propagation that pass input 1 are counted by a counter 1 and the signals of the flame front propagation, that pass input 2 are counted by a counter 2. After a certain number of work cycles, e.g. B. 100 work cycles, the Status of counter 1 and the status of counter 2 in a divider circuit 26 introduced, which sets the status of counter 1 to the status of counter 2 in relation.

The result of this calculation is a number between 0 and 1, which is used as Combustion quality ratio (VQV) is designated and the representative for the degree of flame front propagation during the determined time

from sections s from top dead center to 90 after top dead center.

The counters 1 and 2 are each after completion of the z. B. 100 work cycles reset to 0 and start counting again. The divider circuit 26 supplies meanwhile, a signal corresponding to the combustion quality ratio is sent to a comparison feedback circuit 24.

The burn quality ratio cannot only be in relation to a specific one Number of work cycles can be determined but can also be recorded over a predetermined period of time.

FIGS. 5 A to 5 D show the degrees of flame front propagation of various tests under different operating conditions. The designation of the curves provides information on the operating conditions. The designation D 40-16 means that the Verbrennungemotor was operated with a conventional throttle valve, that the ignition timing was at 40 before top dead center and that the air-blowing cloth ratio 16: 1. The letter C, on the other hand, means that an additional turbulence has been generated. The various tests were all carried out at 3000 rpm and with a constant air flow that was about half full load. The degree of flame front propagation

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indicates the proportion of work cycles in which the flame front is within a predetermined crankshaft angle sector on the ionization probe has arrived.

To classify the various work cycles with regard to the arrival the flame front on the ionization probe was classified as follows:

- 45 working cycles that burn early to top dead center

Top dead center up to 45 rapidly burning work cycles

45 after top dead center

up to 90 ° after top dead center .... slowly burning work cycles 90 after top dead center up to

bottom dead center .... work cycles burning late

lower dead center to upper

Dead center ... delays burning work cycles

No arrival of a flame front detected ... intermittent or incompletely burning work cycles.

The curves of the tests carried out are shown in FIG. 5A no early burning work cycles were found. Work cycles in which the flame front reaches the ionization probe before top dead center, are generally undesirable and are usually only caused by detonation or causing burns too fast. The work cycles make the maximum contribution to the performance of an internal combustion engine. where the flame front is shortly after top dead center at the ionization probe entry. These are the fast-burning work cycles. To achieve maximum performance, all work cycles should be fast-burning work cycles be.

The combustion quality ratio, as it is in connection with the in GB-187 / January 13, 1976 609832/0260 -7-

4 may be defined as follows will:

early burning work cycles in % + fast burning work cycles in%

VQV =::: ■ ^:

fast-burning work cycles in% + long-burning work cycles in %

_ intensely burning work cycles in %
normal burning work cycles in%

In Fig. 6 is the specific fuel consumption of an internal combustion engine shown under different operating conditions. The air-fuel ratio was changed between 12: 1 and 20: 1, the ignition point was changed between 30 and 50 before top dead center and in addition, the conventional throttle valve was provided with an additional turbulence generating device replaced. The under the different operating conditions measured combustion quality ratios as well as the related determined specific fuel consumption showed that the combustion quality ratio gives a reliable statement about the economical combustion process of the internal combustion engine.

If the combustion quality ratio is 1.0, the result is a maximum Economy, d. H. when all work cycles are fast-burning work cycles. If the combustion quality ratio is less than 1.0, i.e. some of the work cycles are slow burning work cycles, so deteriorated profitability. In exceptional cases it can it can happen that the combustion quality ratio is one number larger than 1, this occurs when working cycles burn early as a result of detonation-like or knocking burns occur.

Having now established that the combustion quality ratio (VQV) a reliable statement about the economic process of a

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Combustion s before gange s delivers, the next step is that of the signal for the combustion quality ratio of an electronic comparison

Feedback circuit is fed to the respective incoming signal compares with a preselectable target value and, depending on the deviations, corresponding control signals to influence the air-fuel ratio, generated by the ignition or the swirling of the mixture of the internal combustion engine.

A combustion quality ratio is used here for economy and performance of 1.0, while a combustion quality ratio of 0.8 should be aimed for for economy and low exhaust emissions.

7 shows a diagram of the degree of flame front propagation at different levels Combustion quality ratios. This diagram was compiled from the tests shown in FIGS. 5 to 5D. If the combustion quality ratio is below 1.0, it can be replaced by a richer one Air-fuel ratio, by advancing the ignition point or by Increasing the turbulence of the mixture delivered into the combustion chamber increase.

In order to reduce exhaust emissions, it is desirable to use the internal combustion engine operate with a lean air-to-fuel ratio. By Continuous measurement of the combustion quality ratio while the engine is running and the corresponding setting of the air-fuel ratio as well as other variable quantities, it is possible to make the internal combustion engine much closer to those required for low exhaust emissions Conditions to operate. These ratios are roughly equivalent to a combustion quality ratio of 0.8, with no significant impairment of the operating behavior despite the optimally emaciated mixture of the internal combustion engine occurs.

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260 1

The information given above for dividing the work cycles into intensely burning work cycles and normally burning work cycles can be changed within the following limits:

Inlet 1 (intensely burning work cycles)

open between 45 before top dead center and top dead center Closing at 45 after top dead center - 15

Inlet 2 (normally burning work cycles)

opening between top dead center - 5 closing at 90 after top dead center - 30.

The crankshaft angles specified for the timing signals for inlets 1 and 2 Sectors are essentially dependent on the arrangement of the ionization probe 15. The information given in Fig. 4 is only applicable here, when the ionization probe is at a point furthest away from the spark plug is arranged. If such an arrangement of the ionization probe is not possible, the time control signals must be within the above specified Boundaries are changed.

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Claims (6)

1. Method for controlling the combustion process of a spark-ignited Combustion engine, characterized by the following process steps: a) Arranging an ionization probe (15) in the combustion chamber (11) of a Internal combustion engine (10) at a point furthest away from the spark plug (14), in such a way that the isonization probe (15) a signal is generated as soon as it is reached by the flame front of a combustion process. b) connecting the ionization probe to an electronic counter circuit in such a way that during a certain number of work cycles or during a certain period of time by a first counter 1 within a first crankshaft angle sector detected, the ionization probe (15) reaching flame fronts counted and then by a second counter 2 the detected within a second crankshaft angular sector, the flame fronts reaching the ionization probe (15) are counted. c) connecting the electronic counter circuit with an electronic Divider circuit (26) in which the count result of the first counter 1 is divided by the count result of the second counter 2 and generate a signal proportional to this ratio! will, which is a measure of the combustion quality ratio (VQV). GB-187 / January 13, 1976 609832/0260 -Z - d) connecting the electronic divider circuit to an electronic one Comparison feedback circuit (24) in which the signal for the combustion quality ratio (VQV) with a preselectable setpoint is compared and, depending on the deviation, corresponding control signals to influence the air-fuel ratio, the ignition or the swirling of the mixture of the internal combustion engine can be generated. 2. The method according to claim 1, characterized in that the counter of the counter circuit via a timing disc connected to the crankshaft (21) are switched on and off, such that the counter 1 , the fast-burning work cycles and detected within a first crankshaft angle sector the counter 2 counts the normally burning working cycles within a subsequent second crankshaft angle sector. 3. The method according to claims 1 and 2, characterized in that the first crankshaft · angular sector, which detects the rapidly burning work cycles, lies between top dead center + or - 5 and 45 after top dead center ί 15 °. 4. The method according to claim 1, characterized in that the Counter of the counter circuit can be switched on and off via a timing disc (21) connected to the crankshaft, in such a way that the Counter 1 is within an extended first crankshaft angle sector recorded, intensely burning work cycles and the counter 2 within a second crankshaft angle sector partially overlapping the first sector recorded, normally burning work cycles counts. GB-187 / January 13, 1976 - 3 - 60 9 8 32/0260 5. The method according to claim 4, characterized in that the the First crankshaft angle sector that captures intensely burning work cycles does not begin before 45 before top dead center and not later than top dead center. 6. The method according to claims 4 and 5, characterized in that that the second crankshaft angle which detects the normally burning work cycles ector ends at 90 after top dead center + possibly 30. GB-187 / January 13, 1976 609832/0260