Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/0004—Gaseous mixtures, e.g. polluted air
  • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
  • G01N33/0073—Control unit therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
  • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
  • F02D41/2425—Particular ways of programming the data
  • F02D41/2429—Methods of calibrating or learning
  • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
  • F02D41/2474—Characteristics of sensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M15/00—Testing of engines
  • G01M15/04—Testing internal-combustion engines
  • G01M15/10—Testing internal-combustion engines by monitoring exhaust gases or combustion flame
  • G01M15/102—Testing internal-combustion engines by monitoring exhaust gases or combustion flame by monitoring exhaust gases
  • G01M15/104—Testing internal-combustion engines by monitoring exhaust gases or combustion flame by monitoring exhaust gases using oxygen or lambda-sensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/0004—Gaseous mixtures, e.g. polluted air
  • G01N33/0006—Calibrating gas analysers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/04—Introducing corrections for particular operating conditions
  • F02D41/12—Introducing corrections for particular operating conditions for deceleration
  • F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
  • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
  • F02D41/2425—Particular ways of programming the data
  • F02D41/2429—Methods of calibrating or learning
  • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
  • F02D41/2454—Learning of the air-fuel ratio control

Definitions

• the invention relates to a method for compensating for a voltage offset in a voltage lambda characteristic curve with respect to a reference voltage lambda characteristic curve of the two-point lambda probe, wherein the two-point lambda probe is arranged in the exhaust gas of an internal combustion engine.
• the invention further relates to a control unit for carrying out the method.
• lambda probes are used in modern internal combustion engines for determining the composition of the exhaust gas and for controlling the internal combustion engine.
• Lambda sensors determine the oxygen content of the exhaust gas, which is used to control the internal combustion engine supplied air-fuel mixture and thus the exhaust lambda before a catalyst.
• the air and fuel supply of the internal combustion engine is controlled via a lambda control circuit in such a way that optimum catalytic converter composition of the exhaust gas is achieved for exhaust gas aftertreatment by catalysts provided in the exhaust duct of the internal combustion engine.
• gasoline engines is usually on a lambda of 1, ie a stoichiometric ratio of air to fuel regulated. The pollutant emission of the internal combustion engine can be minimized.
• lambda probes there are various forms of lambda probes in use.
• a two-point lambda probe also referred to as a jump probe or Nernst probe
• the chip lambda characteristic curve at Lambda 1 to a sudden drop. It therefore essentially allows the distinction between rich exhaust gas ( ⁇ ⁇ 1) when operating the internal combustion engine with excess fuel and lean exhaust gas ( ⁇ > 1) when operating with excess air and allows control of the exhaust gas to a lambda of 1.
• an internal combustion engine can also be regulated to a lean operation with excess air.
• Two-point lambda probe are present, otherwise the accuracy of the control is not sufficient and impermissibly high emissions may occur. Due to manufacturing tolerances and aging effects of the two-point lambda probe this condition is not met.
• the document DE 10 2010 027 984 A1 describes a method for operating an exhaust system of an internal combustion engine, in which at least one parameter of the exhaust gas flowing in an exhaust gas channel is detected by an exhaust gas probe. It is envisaged that during an operating condition of the internal combustion engine, in which an injection and combustion of fuel does not take place, the exhaust duct upstream of the exhaust gas probe by means of a fresh air supply associated with the fresh air supply fresh air is supplied, and during and / or after the exhaust gas probe is adjusted.
• a sufficiently good compensation of the voltage offset is only possible if it is equally pronounced not only at overrun fuel cut with corresponding oxygen-containing exhaust gas, but in the entire lambda.
• two-point lambda probes before catalyst are usually used with a two-point control.
• This has the disadvantage that in operating modes for which a lean or rich air-fuel mixture is necessary, for example, for catalyst diagnosis or component protection, the target lambda set only pilot-operated, but can not be controlled.
• the object of the invention relating to the method is achieved by determining the slope or a measure of the slope of the voltage-lambda characteristic curve for an output voltage of the two-point lambda probe and determining it with the slope or Measure for the slope of the reference voltage-lambda characteristic at the same output voltage and that from a deviation of the determined slope or the measure of the slope of the voltage-lambda curve from the slope or the measure for the slope of the reference Voltage lambda characteristic of the voltage offset is determined.
• the reference voltage lambda characteristic corresponds to the voltage lambda characteristic of an unaged two-point lambda probe.
• the determination of the voltage offset is thus not bound to operating parameters of the internal combustion engine, which result in a particular exhaust gas composition, such as the rarely occurring in modern engine concepts overrun phases.
• a simple determination of the slope of the voltage-lambda characteristic and thus of a voltage offset can be achieved by starting from an output voltage of the two-point lambda probe a measured voltage change AUmess the two-point lambda probe after a predetermined lambda change ⁇ with a reference voltage change AU Ref the Reference voltage lambda characteristic is compared at an equal lambda change ⁇ and that from a Deviation of the measured voltage change AU meS s from the reference voltage change AU Ref the voltage offset is determined.
• AU meS s AA represents the slope of the voltage lambda curve
• AU Ref / AA the slope of the reference voltage lambda curve.
• the voltage change AU is a measure of the slope and can therefore be used directly for the determination of the voltage offset.
• the output voltage of the two-point lambda probe in which the slope of the voltage-lambda characteristic curve is determined, it can be determined in which lambda range the voltage offset is to be determined.
• the lambda change ⁇ can be achieved by a targeted change of the internal combustion engine supplied air-fuel mixture. Since the output voltage of the two-point lambda probe before the catalyst reacts very quickly to lambda changes, the lambda changes must be impressed only briefly. The method therefore allows a very fast determination of the voltage offset.
• the voltage offset is determined for the entire lambda range of the two-point lambda probe or that values of the voltage offset for different lambda ranges, in particular for a rich and a lean lambda range, are determined.
• the voltage offset for different lambda ranges may vary. Due to the possibility of separately determining the voltage offset for different lambda ranges, the voltage offset can be compensated for as a function of the lambda range. Many causes of a voltage offset have different effects in the lean and in the rich lambda range. This can be compensated for by a separate measurement and compensation of the voltage offset in the case of lean and rich exhaust gas mixtures.
• the predefinable lambda change ⁇ is set in a targeted manner and / or that the determination of the voltage offset takes place with a system-dependent lambda change ⁇ .
• an active, specifically predetermined lambda change ⁇ the voltage change AU at a predetermined output voltage of the two-point lambda probe can be determined.
• System-related active lambda changes such as those for catalytic converter diagnostics, probe dynamic diagnostics or phases with two-point lambda can be used to obtain additional measurements for voltage changes, if necessary, without making an active lambda change for this purpose.
• the compensation of a voltage offset can be improved by repeatedly determining the measured voltage change AU meS s starting from an output voltage of the two-point lambda probe and / or by determining the measured voltage change AU meS s with positive and negative predefinable lambda changes ⁇ and the determination of the voltage offset from the averaged or filtered measured voltage changes AU meS s takes place.
• a further improvement in the determination of a voltage offset can be achieved by determining measured voltage changes AU meS s on the basis of different output voltages of the two-point lambda probe and checking the voltage offsets determined therefrom by comparison for plausibility.
• the amount and / or the type and / or duration of the predefinable lambda change ⁇ can be selected as a function of exhaust gas conditions or operating conditions of the internal combustion engine.
• the lambda change ⁇ can be effected, for example, by a jump, a ramp, by wobble, by positive or negative lambda changes ⁇ or by any desired combinations thereof.
• the amount and / or the type and / or the duration of the predefinable lambda change ⁇ can be predefined as a function of the exhaust gas conditions or the operating conditions of the internal combustion engine such that a clear and reliable evaluation of the specific slope or the specific voltage change AUmeas is performed can.
• the determined voltage offset is made plausible by a comparison of the measured output voltage of the two-point lambda probe with the reference voltage lambda characteristic at a fuel cut of the internal combustion engine. This is advantageous, in particular, if the active lambda change ⁇ itself is subject to tolerances.
• the specific voltage offset of the voltage-lambda characteristic curve is completely or partially compensated and / or that the voltage offset is compensated as a function of the lambda region of the voltage-lambda characteristic curve.
• causes of the voltage offset are determined from the course of the voltage offset as a function of lambda and / or that measures are taken to avoid or reduce the causes of the voltage offset.
• the voltage lambda characteristic of the two-point lambda probe is increasingly shifted in the rich lambda range by a fixed amount to lower output voltages, since the
• Probe is operated too hot.
• the heating power of the probe heater can be reduced, thereby at least reducing the voltage offset.
• the determination of the voltage offset at a predetermined output voltage and thus in a predetermined lambda range can be achieved by actively setting a predetermined output voltage of the two-point lambda probe to determine the voltage offset, or by determining the voltage offset when the predetermined output voltage due to desired operating conditions of the internal combustion engine is set.
• To actively approach the desired output voltage is particularly useful, if there is no offset compensation from previous operating cycles of the internal combustion engine. If, on the other hand, a compensation of the voltage offset has already been carried out in a preceding operating cycle and the data is present in a corresponding manner, a renewed adjustment can be carried out passively if the desired output voltage is more straightforward in the regular operation of the internal combustion engine.
• the object of the invention relating to the control unit is achieved in that the control unit is designed to set a predefinable lambda change ⁇ of the exhaust gas so that the control unit has measuring means for determining a voltage change AUmess of the two-point lambda probe in response to the defined lambda change ⁇ , in that a reference voltage-lambda characteristic curve of the two-point lambda probe is stored in the control unit, that the control unit executes a program sequence for comparing the measured voltage change AU meS s of the two-point lambda probe after the predefinable lambda change ⁇ with a reference voltage change AU Ref of the reference Voltage lambda characteristic with an identical lambda change ⁇ and that the control unit has a program sequence for determining a voltage offset of the present voltage lambda curve of the two-point lambda probe with respect to the reference voltage lambda curve from a deviation the measured voltage change AU meS s from the reference voltage change AU Ref has.
• the control unit makes it possible to determine a voltage offset of a two-point lambda probe as a function of the prevailing lambda range.
• the voltage offset can be compensated, whereby a use of the two-point lambda probe is enabled for a continuous Lambdarege- ment.
• FIG. 1 shows voltage-lambda characteristic curves of a two-point lambda probe with constant voltage offsets in relation to a reference voltage-lambda characteristic
• FIG. 2 shows a third voltage-lambda characteristic curve of a two-point lambda probe with a lambda-dependent voltage offset with respect to a reference voltage-lambda characteristic curve.
• FIG. 1 shows voltage lambda characteristic curves 10.1, 10.3 of a two-point lambda probe with constant voltage offsets 16, 17 with respect to a reference voltage lambda characteristic curve 10.2.
• the characteristic curves 10.1, 10.2, 10.3 are plotted against an axis probe voltage 20 and with respect to an axis lambda 21.
• a first voltage lambda characteristic 10. 1 is shifted by a negative voltage offset 17 and a second voltage lambda characteristic 10. 3 by a positive voltage offset 17 with respect to the reference voltage lambda characteristic 10.
• a first voltage value 22 of the two-point lambda probe are in the rich lambda range 1 1 at the first voltage lambda characteristic
• the first voltage lambda characteristic curve 10.1 results in the case of a negative voltage offset 17
• the second voltage lambda characteristic curve 10.3 results in a positive voltage offset 16.
• the gradient triangles 14.1, 14.2, 14.3, 14.4, 14.5, 14.6 each show a voltage change AU, which at a given, for all gradient triangles 14.1, 14.2, 14.3, 14.4, 14.5, 14.6 equal lambda change ⁇ , starting from the respective voltage value 22, 23 of the probe voltage yields. They thus represent the slopes of the respective voltage-lambda characteristic 10.1, 10.3 or of the reference voltage-lambda characteristic 10.2 at the respective voltage values 22, 23.
• the method according to the invention makes use of the fact that in the case of the reference
• Voltage lambda characteristic curve 10.2 not only between the output voltage U of the two-point lambda probe and lambda ⁇ a clear relationship exists, but also between the output voltage U and the slope of the characteristic curve AU / ⁇ . If there is a voltage offset 16, 17, the assignment between the output voltage and the slope of the characteristic is no longer correct.
• FIG. 2 shows a third voltage-lambda characteristic curve 10.4 of a two-point lambda probe with a voltage offset dependent on lambda in relation to the reference voltage-lambda characteristic curve 10.3 shown in FIG.
• the same identifiers are used as introduced for Figure 1.
• the reference voltage-lambda characteristic curve 10.2 is assigned a seventh gradient triangle 15.1 and the third voltage-lambda characteristic curve 10.4 is assigned an eighth gradient triangle 15.2.
• the reference voltage / lambda characteristic curve 10.2 is assigned a ninth gradient triangle 15.3 and the third voltage lambda characteristic curve 10.4 is assigned a tenth gradient triangle 15.4.
• the gradient triangles 15.1, 15.2, 15.3, 15.4 describe a voltage change in the third voltage-lambda characteristic 10.4 or the reference voltage-lambda characteristic 10.2 for a given lambda change ⁇ and thus the slope of the respective characteristic curves 10.2. 10.4.
• the third voltage-lambda characteristic 10.4 is shifted in the entire lambda range by a fixed amount towards higher voltages.
• this first effect may occur with pumped oxygen reference two-point lambda probes due to manufacturing tolerances.
• the third voltage lambda characteristic 10.4 is additionally shifted in the rich lambda range 1 1 by a fixed amount to lower voltages. This second effect can occur if the two-point lambda probe is operated too hot.
• the first effect is more pronounced than the second effect, so that in total the third voltage-lambda characteristic 10.4 is shifted toward higher voltages even in the rich lambda range 1 1, but less than in the lean lambda range 13.
• the output voltage of the two-point lambda probe is adjusted to the fourth voltage value 25.
• a voltage change AU.sub.mS.sup.S.sub.S of the output voltage is determined corresponding to the tenth gradient triangle 15.4, which is smaller than the expected chip change on the basis of the reference voltage lambda characteristic curve 10. change of order AU Re f. From this deviation, a compensation of the voltage offset necessary for the entire lambda range is performed and the fourth voltage lambda characteristic 10.4 is corrected accordingly.
• the output voltage of the two-point lambda probe is adjusted to the third voltage value 24.
• a now taking place predetermined lambda change ⁇ results in accordance with the eighth slope triangle 15.2 a voltage change AU meS s the output voltage, which is greater than the expected based on the reference voltage lambda curve 10.2 voltage change AU Re f. From this deviation, the remaining, for the rich lambda 1 1 1 necessary compensation of the voltage offset is performed for the rich lambda range.
• the voltage lambda characteristic curve thus obtained is now adapted to the reference voltage lambda characteristic curves 10. 2 in the entire lambda range.
• the cause of a voltage offset can also be detected from the course of the voltage offset as a function of lambda and then terminated or at least reduced. In the exemplary embodiment shown in FIG. 2, for example, the power of an electric heater of the two-point lambda probe can be reduced in order to reduce the second effect.
• the voltage offset can be determined separately for different lambda ranges and corrected accordingly.
• the determined offset compensation can be made plausible by repeating the measurement at the same point or at other points of the voltage-lambda characteristic 10.1, 10.3, 10.4. By averaging or filtering the measurement results, the compensation can be improved.
• the determined compensation of the voltage offset can also be plausibilized by a thrust balance.
• the offset compensation determined in the preceding drive cycle can be used to check the plausibility of offset measurements in the current drive cycle.
• the voltage values 22, 23, 24, 25 can be set active. This is advantageous if there is no offset compensation from an earlier driving cycle. If an offset compensation is already present, the adjustment can take place passively if a required voltage value 22, 23, 24, 25 is present in the regular operation of the internal combustion engine.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
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• General Engineering & Computer Science (AREA)
• Emergency Medicine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

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• 2012
  • 2012-05-15 DE DE102012208092.9A patent/DE102012208092B4/de not_active Expired - Fee Related
• 2013
  • 2013-04-17 JP JP2015510707A patent/JP6025970B2/ja active Active
  • 2013-04-17 US US14/401,483 patent/US9696289B2/en active Active
  • 2013-04-17 WO PCT/EP2013/057954 patent/WO2013171015A1/de active Application Filing
  • 2013-04-17 CN CN201380025319.3A patent/CN104271927B/zh active Active
  • 2013-04-17 EP EP13717488.4A patent/EP2850304A1/de not_active Withdrawn

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