DE102016223150B3 - Method for determining an ignition point and control device for an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating a control device and such a control device, wherein at least one boundary condition for combustion of a fuel-air mixture in a combustion chamber of the internal combustion engine is determined, based on a first predefined parameter and the boundary condition, a burning time and based on a second predetermined parameter ignition delay of combustion of a fuel-air mixture in a combustion chamber of the internal combustion engine are determined, based on a desired predefined efficiency of the internal combustion engine, a desired combustion focus of the combustion is determined, based on the burning time, the ignition delay, the desired focus of combustion and a third predefined parameter, the desired ignition timing for ignition of the fuel-air mixture is determined, based on the determined desired ignition timing of an ignition of the Brenns Toff-air mixture is introduced.

Description

The invention relates to a method according to claim 1 and a control device according to claim 9.

It is a drive system consisting of an internal combustion engine and a control unit known, wherein the control unit controls the internal combustion engine.

In the US 2016/0290307 A1 a control unit for an internal combustion engine is described which comprises a crank angle detector and an ECU. The ECU is configured to: a) calculate a mass fraction burned; b) detecting the crank angle detected by the crank angle detector when the burned mass fraction reaches a predetermined burned mass fraction as a specific crank angle, and c) controlling at least one of an injected fuel amount, an intake air amount, and an ignition energy based on a first one Difference. The first difference is a difference between a first parameter and a second parameter. The first parameter is a crank angle period from an ignition timing to a specified crank angle or a correlation of the crank angle period. The second parameter is a target value of the crank angle period or a target value of the correlation value.

In the US 2005/0229903 A1 a control method for a diesel engine is described. The cylinders of the diesel engine are provided with cylinder pressure sensors for detecting combustion chamber pressures. An electronic control unit of the engine selects optimal combustion parameters in accordance with a fuel injection mode and fuel injection valves of the engine and a combustion mode determined by the amount of EGR gas supplied from the EGR valve among a plurality of types of combustion parameters expressing the combustion state of the engine. is calculated based on the output of the cylinder pressure sensor, and the feedback controls the fuel injection amount and the fuel injection timing such that the values of the combustion parameters match target values of the engine operating conditions. Due to this, the engine combustion state is controlled to the optimum state at any time regardless of the fuel injection mode or the combustion mode.

It is an object of the invention to provide an improved method for determining a desired ignition timing of an internal combustion engine and an improved control unit.

This object is achieved by means of a method according to claim 1 and by means of a control device according to claim 8. Advantageous embodiments are given in the dependent claims.

It has been recognized that an improved method and apparatus may be provided by determining at least one constraint for combustion of a fuel-air mixture in a combustion chamber of the internal combustion engine, based on a first predefined parameter and the constraint, a spark duration and based on a second predefined parameter and the boundary condition, an ignition delay of a combustion of a fuel-air mixture in a combustion chamber of the internal combustion engine are determined, based on a desired predefined desired efficiency of the internal combustion engine, a desired combustion focus of the combustion is determined, based on the burning time , the ignition delay, the desired combustion center and a third predefined parameter, the desired ignition timing for ignition of the fuel-air mixture is determined, based on the determined ignition ignition of the fuel-air mixture is controlled. The burning time is determined on the basis of a first laminar fraction and a second turbulent fraction, the first laminar fraction preferably being determined on the basis of an ethanol content of the fuel.

This refinement has the advantage that the desired ignition point can be determined particularly quickly and simply and the internal combustion engine can be controlled.

In a preferred embodiment, the second fraction is determined based on a fourth parameter and the first fraction, wherein the fourth predefined parameter accounts for turbulent kinetic energy of the fuel-air mixture in an ignition window in which the fuel-air mixture is ignitable ,

In a further embodiment, an actuator position of at least one actuator of the internal combustion engine, in particular an actuator of an intake tract and / or an injection system for injecting fuel into the combustion chamber, is determined, wherein a rotational speed of the internal combustion engine is determined, wherein the turbulent kinetic energy based on the actuator position and the speed is determined.

In a further embodiment, the boundary condition comprises at least one of the following Quantities on: amount of air, residual gas quantity, fuel injection quantity, fuel injection pattern.

In a further embodiment, the ignition delay is determined on the basis of at least one mixture property of the fuel-air mixture in the combustion chamber and of the optimum combustion center of gravity.

In another embodiment, based on the boundary condition and a fifth predefined parameter, an optimal combustion center of gravity of the fuel-air mixture in the combustion chamber is determined.

In another embodiment, based on the optimum focus of combustion, an optimal efficiency is determined, wherein a difference between the optimum efficiency and the desired efficiency is determined, based on the difference, a correction factor is determined, wherein a product of the correction factor and the burning time and / or the ignition delay is considered in the determination of the ignition timing.

In another embodiment, the ignition timing is determined on the basis of a symmetrical combustion curve of the fuel-air mixture in the combustion chamber.

• 1 eine schematische Darstellung eines Antriebssystems,
• 2 eine schematische Darstellung eines in 1 gezeigten Steuergeräts,
• 3 ein Ablaufdiagramm eines Verfahrens zum Betrieb des in 1 gezeigten Antriebssystems,
• 4 ein Diagramm einer turbulenten kinetischen Energie auftragen über einen Kurbelwellenwinkel,
• 5 ein Diagramm einer Umsetzungsrate aufgetragen über dem Kurbelwellenwinkel

zeigen.The above-described characteristics, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments which will be described in connection with the drawings

• 1 a schematic representation of a drive system,
• 2 a schematic representation of an in 1 shown control unit,
• 3 a flowchart of a method for operating the in 1 shown drive system,
• 4 apply a graph of turbulent kinetic energy over a crankshaft angle,
• 5 a plot of a conversion rate plotted against the crankshaft angle

demonstrate.

1 shows a schematic representation of a drive system 100 , The drive system 100 has an internal combustion engine 105 and a controller 110 on.

The internal combustion engine 105 includes an example of an intake tract 130 , an engine block 135 , a cylinder head 140 and an exhaust tract 145 , The intake tract 130 includes a throttle 150 , a suction pipe 155 and a collector 160 , The engine block 135 has at least one cylinder with a combustion chamber 165 on. The combustion chamber 165 is through the cylinder head 140 and a piston 170 limited. The cylinder head 140 includes a Ve.ntiltrieb with an inlet valve 185 , an exhaust valve 190 and an inlet valve 185 associated first valve drive 195 and one the exhaust valve 190 associated second valve drive 200 ,

Furthermore, the cylinder head 140 a spark plug 210 and / or an injector 205 an injection system 206 exhibit. Alternatively, the injector 205 in the intake manifold 155 be arranged. Also can on the spark plug 210 be waived. This may be the case in particular when the internal combustion engine 105 is designed as a diesel engine.

By way of example, the injection system 206 a high pressure pump 211 and a high-pressure accumulator 212 on. The high-pressure accumulator 212 is fluidic with the high pressure pump 211 and the injector 205 connected.

The internal combustion engine 105 exemplifies a speed sensor 207 , an air mass sensor 208 , a lambda sensor 209 and a high pressure sensor 213 on. The air mass sensor 208 is in the intake tract 130 and the lambda sensor 209 in the exhaust tract 145 arranged. The high pressure sensor 213 is with the high-pressure accumulator 212 fluidly connected.

2 shows a schematic representation of the in 1 shown control unit 110 ,

The control unit 110 has an observation device 214 with a first observation module 215 and a second observation module 220 , a computing device 225 , an efficiency determining device 235 and a data store 240 on.

In the data store 240 a first to seventh parameter is stored. The first to seventh parameters may be formed as a data processing program and / or map and / or mathematical algorithm and / or mathematical formula and / or tabular assignment. Of particular advantage is when one of the parameters, for example, as a polynomial, preferably second or fourth degree, is formed.

Of course, other embodiments of the first to seventh parameters are conceivable. The first to seventh parameters may have been determined based on pre-measured values. Also, the first to seventh parameters may additionally or alternatively have been calculated model-based or determined during operation of the drive system 10.

It should be noted that the first observation module 215 and / or the second observation module 220 may also be formed as a data processing algorithm by the computing device 225 is performed. Also, the first observation module 215 and the second observation module 220 be formed together.

The data store 240 is with the computing device 225 by means of a first connection 245 and by means of a second connection 250 with the first observation module 215 and by means of a third connection 255 with the second observation module 220 connected.

The second observation module 220 is by means of a fourth connection 260 with the computing device 225 connected. By means of a fifth connection 265 is the first observation module 215 with the second observation module 220 connected. By means of a sixth connection 270 is the computing device 225 with the efficiency determining device 235 connected.

The first observation module 215 is by means of a seventh connection 275 with the computing device 225 connected. By means of an eighth connection 280 is the first observation module 215 with the air mass sensor 208 connected. Additionally, via a ninth connection 285 the first observation module 215 with the throttle 150 and / or by means of a tenth connection 290 with the speed sensor 207 be connected. Of course, the first observation module 215 also with other and / or other sensors and / or actuators of the internal combustion engine 105 be connected.

The second observation module 220 is by means of an eleventh connection 295 with the lambda sensor 209 and by means of a twelfth connection 300 with the high pressure sensor 213 connected.

3 shows a flowchart of a method for operating the in 1 shown drive system 100 ,

In a first process step 400 is using at least one sensor, such as the air mass sensor 208 and / or the speed sensor 207 , at least one operating state of the internal combustion engine 105 determined. The operating state of the sensor is the first observation module 215 ready. The first observation module 215 detects the operating state.

Furthermore, advantageously, an actuator position of at least one actuator, in particular an actuator in the intake tract 130 , for example, the throttle valve 150 , through the first observation module 215 detected.

In a second process step 405 be a lambda value and an information of the injector 205 and / or the pressure in the high-pressure accumulator 212 determined. In the embodiment, the lambda sensor measures 209 the lambda value of the exhaust gas and the high pressure sensor 213 measures the pressure of the fuel in the high-pressure accumulator 212 and sets the pressure reading to the second observation module 220 ready. However, the values can also be calculated at least partially and / or completely.

In a third process step 410 determines the first observation module 215 on the basis of the determined operating state, for example based on the information of the air mass sensor 208 and the speed, and the first predefined parameter, a first boundary condition about the combustion of a fuel-air mixture in the combustion chamber 165 the internal combustion engine 105 ,

The first observation module 215 represents the determined first boundary condition over the fourth connection 260 the second observation module 220 and / or the computing device 225 ready.

In a fourth process step 415 determines the second observation module 220 a second boundary condition for the combustion of the fuel-air mixture in the combustion chamber 165 the internal combustion engine 105 , In this case, the second observation module 220 consider the first boundary condition when determining the second boundary condition. The second boundary condition is based, for example, on the lambda value, pressure and / or other operating parameters of the internal combustion engine 105 and determined based on the second predefined parameter. In this case, it is of particular advantage if the second boundary condition comprises at least one of the following variables: an air quantity, a residual gas quantity, an injection quantity of fuel into the combustion chamber 165 , an injection pattern of fuel into the combustion chamber 165 ,

In a fifth process step 420 determines the second observation module 220 based on a mixture property, such as an ignitability, of the fuel-air mixture in combustion chamber 165 and the third parameter an ignition delay 530 ,

This is under a Zündverzzug 530 a time period between a spark generated by the spark plug 210 , and a predefined mass conversion point, for example, at a combustion of 5% to 10% of the fuel in the combustion chamber 165 , Understood. In addition, while the second observation module 220 in addition a composition and / or a charge dynamics of the fuel-air mixture in the combustion chamber 165 in the determination of the ignition delay 530 consider.

In a sixth process step 425 determines the second observation module 220 based on the first and second boundary conditions and the fourth predefined parameter, an optimal combustion center of gravity 540 of the fuel-air mixture in the combustion chamber 165 , This is under an optimal combustion focus 540 the focus of combustion 540 understood that optimally one or more design criteria of the internal combustion engine 105 Fulfills. This is how the optimal combustion focus can be 540 for example, be chosen so that the internal combustion engine 105 provides a maximum torque.

In determining the optimal center of combustion 540 preferably takes into account the second observation module 220 In addition, the speed of the internal combustion engine 105 and / or a load of the internal combustion engine 105 , In addition, the second observation module 220 Furthermore, a wall temperature of the combustion chamber 165 take into account.

In a seventh process step 430 hands over the second observation module 220 the determined optimal combustion focus 540 and the ignition delay 530 to the computing device 225 , Furthermore, the second observation module passes 220 the boundary conditions to the computing device 225 ,

In an eighth process step 435 determines the computing device 225 a burning time BD the combustion of the fuel-air mixture in the combustion chamber 165 the internal combustion engine 105 based on the optimal combustion focus 540 , It is under the burning time BD understood that 5 to 95% of the fuel mass conversion or 10 to 90% of the mass conversion of the fuel in the combustion chamber 165 to be burned.

In 4 is a first graph 500 , a second graph 505 , a third graph 510 and a fourth graph 515 shown.

The first graph 500 shows a first course of the turbulent kinetic energy TKE at a first actuator position, such as a first throttle position of the throttle 150 , and by means of the second graph 505 is a second course of turbulent kinetic energy TKE over the crankshaft angle CRK at a second actuator position, for example, a second throttle position applied. The third graph 510 shows a first conversion rate during the combustion of the fuel-air mixture and the fourth graph 515 shows a second conversion rate.

Depending on the turbulent kinetic energy TKE is an example of ignition 520 at the optimal focus of combustion 540 of the first graph 500 before another ignition point 525 of the second graph 505 arranged, with a desired focus of combustion 540 correlated.

5 shows a diagram of a conversion rate plotted against the crankshaft angle CRK , The conversion rate of the fuel in the combustion chamber 165 begins with the ignition delay 530 , At the ignition delay 530 closes the burning time BD at. The ignition delay 530 is determined from the beginning of combustion at a conversion rate of 0% to, for example, a conversion rate of 5%. At a conversion rate of 5%, the burning time begins BD and ends at a conversion rate of 95%. Additionally is in 5 at the conversion rate of 50% the combustion focus 540 located. The firing curve in the embodiment is exemplary symmetrical to the conversion rate of 50%.

This is the burning time BD based on a first laminar fraction of the burning time BD the combustion of the fuel-air mixture and a second turbulent fraction of the burning time BD determined.

The first laminar fraction of the burning time BD is determined based on preferably an ethanol content of the fuel. The first laminar fraction can also be mapped as a function of a mean combustion chamber temperature of a fuel quantity, the lambda value and / or the residual gas content.

The second turbulent part of the burning time BD is based on a turbulent kinetic energy TKE the fuel-air mixture in the combustion chamber 165 determined. The turbulent kinetic energy TKE shows an asymptotic approach to a limit in the range of an ignition window for igniting the fuel-air mixture.

The turbulent kinetic energy TKE of the fuel-air mixture can be based on the actuator position, for example, an actuator of the internal combustion engine 105 , in particular an actuator in the intake tract 130 and / or the injection system 206 for injection of fuel into the combustion chamber 165 , and the speed of the internal combustion engine 105 be determined.

The turbulent kinetic energy TKE can empirically and / or semiempirisch and / or model-based prior to implementation of the method by the control unit 110 be determined. The turbulent kinetic energy TKE can also be the fifth predefined parameter in the data store 240 be filed.

The turbulent kinetic energy TKE can be determined, for example, in a CFD simulation and includes a relevant effect of speed and position of a charge cycle actuator for the burn time BD ,

In addition, for the burning time BD Also, a weighted sum of the first portion BD _stat and the second portion BD _turb the burning time are determined. In this case, a first weighting factor a is provided for the first component BDstat and a second weighting factor b is provided for the second component BD _turb . Where: BD = a BDstat + b · BD _turb = (a + b F _turb ) · BD _stat , where BDstat = g (m _fuel , lambda, fac _EGR , T _engine ) and F _dyn = f (turbulent kinetic energy), with the in the combustion chamber 165 located fuel mass m _fuel , with the lambda value of the combustion chamber 165 located fuel-air mixture, an exhaust gas recirculation rate fac _EGR , and a mean wall temperature T _{engine of} the combustion chamber 165 , The weighting factors a and b may be adapted to an engine configuration. The functions f and g can either be map-based or empirically determined.

4 shows a diagram of a course of the turbulent kinetic energy TKE applied over a crankshaft angle CRK ,

The burning process 510 . 515 in the embodiment is exemplarily symmetrical to the conversion rate of 50%. If the combustion is unbalanced, then the focal point of combustion 540 shifted from the in 5 shown illustration.

In a ninth procedural step 440 determines the efficiency determination device 235 a desired efficiency of the internal combustion engine 105 based on an operating condition of the drive system 100 , The desired efficiency of the internal combustion engine 105 can be less than an optimal efficiency of the internal combustion engine 105 , The desired efficiency can also be preset predefined. By means of the desired efficiency, for example, predefined, usually legally prescribed emission limits of the internal combustion engine 105 be maintained or, for example, an exhaust gas purification device heated or cleaned.

The efficiency determination device 235 provides the desired efficiency of the computing device 225 ready.

In a tenth procedural step 445 determines the computing device 225 based on the desired efficiency and the predefined sixth parameter a desired combustion focus 540 , The desired combustion focus 540 For example, it may be determined based on a difference between the optimum efficiency and the desired efficiency and the predefined sixth parameter based on the optimal combustion center 540 the desired combustion focus 540 is determined.

In an eleventh process step 450 determines the computing device 225 based on the desired combustion focus 540 that determined burning time BD , the determined ignition delay 530 and the seventh parameter a desired ignition timing. Optionally, the computing device 225 for the determined burning time BD and / or the determined ignition delay 530 consider a correction factor.

Additionally or alternatively, it is also conceivable that in the tenth method step 445 In addition, a transfer function is taken into account, wherein the computing device 225 based on the transfer function of the desired efficiency, the desired combustion focus 540 determined.

The desired additional ignition point 525 can be determined, for example, that the desired additional ignition 525 equal to the optimal combustion focus 540 and the desired combustion focus 540 minus 0.5 times the burning time BD minus the ignition delay 530 is.

Based on the determined further ignition timing 525 controls the computing device 225 the internal combustion engine 105 in a twelfth process step 455 at.

By the method described above, a precise control of the ignition timing due to the determined burning time BD be determined so that other necessary duplications of the empirical map based on different actuator settings reliably avoided become. By using the turbulent kinetic energy TKE the ignition timing can be set precisely. Furthermore, about the turbulent kinetic energy TKE an influence of other actuators, especially in the intake system 130 , be taken into account on the combustion.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

100

drive system

105

Internal combustion engine

110

control unit

130

intake system

135

block

140

cylinder head

145

exhaust tract

150

throttle

155

suction tube

160

collector

165

combustion chamber

170

piston

185

intake valve

190

outlet valve

195

first valve drive

200

second valve drive

205

injector

206

injection

207

Speed sensor

208

Air mass sensor

209

lambda sensor

210

spark plug

211

high pressure pump

212

High-pressure accumulator

213

High pressure sensor

214

observer

215

first observation module

220

second observation module

225

computing device

235

Efficiency detection device

240

data storage

245

first connection

250

second connection

255

third connection

260

fourth connection

265

fifth connection

270

sixth connection

275

seventh connection

280

Eighth connection

285

ninth connection

290

tenth connection

295

Eleventh connection

300

twelfth connection

305

thirteenth connection

400

first process step

405

second process step

410

third process step

415

fourth process step

420

fifth process step

425

sixth process step

430

seventh process step

435

eighth process step

440

ninth process step

445

tenth process step

450

Eleventh process step

455

twelfth process step

500

first graph

505

second graph

510

third graph, first firing history

515

fourth graph, second firing curve

520

ignition timing

525

another ignition point

530

ignition delay

540

Combustion center

BD

burning time

TKE

turbulent kinetic energy

CRK

crankshaft angle

Claims (8)

Method for determining a desired ignition point (520, 525) of an internal combustion engine (105), wherein at least one boundary condition for combustion of a fuel-air mixture in a combustion chamber (165) of the internal combustion engine (105) is determined, wherein, based on the boundary condition and a first predefined parameter and the boundary condition, a burning duration (BD) and on the basis of a second predefined parameter an ignition delay (530) of a combustion of a fuel-air mixture in a combustion chamber (165) of the internal combustion engine (105) be determined, wherein a desired combustion center of gravity (540) of the combustion is determined on the basis of a desired predefined efficiency of the internal combustion engine (105), wherein the desired ignition timing (520, 525) for igniting the fuel-air mixture is determined on the basis of the combustion duration (BD), the ignition delay (530) and the desired combustion center (540) and a third predefined parameter, wherein an ignition of the fuel-air mixture is controlled on the basis of the determined desired ignition timing (520, 525), wherein the burning time (BD) is determined on the basis of a first laminar component and a second turbulent component, wherein the first laminar fraction is preferably determined on the basis of an ethanol content of the fuel, Method according to Claim 1 , wherein the second component is determined on the basis of a fourth parameter and the first component, wherein the fourth predefined parameter takes into account a turbulent kinetic energy (TKE) of the fuel-air mixture in an ignition window. Method according to Claim 2 - wherein an actuator position of at least one actuator of the internal combustion engine (105), in particular an actuator of an intake tract (130) and / or an injection system (206) for injecting fuel into the combustion chamber (165) is determined, - wherein a rotational speed of the internal combustion engine (105) is determined, - wherein the turbulent kinetic energy (TEK) is determined based on the actuator position and the speed. Method according to one of the preceding claims, - Wherein the boundary condition for the combustion of the fuel-air mixture in a combustion chamber (165) of the internal combustion engine (105) is determined, - wherein the boundary condition comprises at least one of the following variables: - amount of air, - residual gas quantity, Injection quantity of fuel, - Injection pattern of fuel. Method according to one of the preceding claims, wherein an optimum combustion center (540) of the fuel-air mixture in the combustion chamber (165) is determined on the basis of the boundary condition and a fifth predefined parameter, wherein the optimal combustion centroid (540) is determined based on a second parameter and the constraint condition, - wherein the ignition delay (530) is determined on the basis of at least one mixture property of the fuel-air mixture in the combustion chamber (165) and the optimal combustion center of gravity (540). Method according to Claim 5 in which an optimum efficiency is determined on the basis of the optimal combustion center of gravity (540), wherein a difference between the optimum efficiency and the desired efficiency is determined, wherein a correction factor is determined on the basis of the difference, wherein a product of the correction factor and the burn duration (BD) and / or the ignition delay (530) is taken into account in the determination of the ignition timing (520, 525). Method according to one of the preceding claims, - Wherein the ignition timing (520, 525) based on a symmetrical combustion curve (510, 515) of the fuel-air mixture in the combustion chamber (165) is determined. Control unit (110) for an internal combustion engine (105), - wherein the control device (110) is designed to carry out a method according to one of the preceding claims.

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