Classifications

• • 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
  • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
  • F02D41/0047—Controlling exhaust gas recirculation [EGR]
  • F02D41/0065—Specific aspects of external EGR control
  • F02D41/0072—Estimating, calculating or determining the EGR rate, amount or flow
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/04—Engine intake system parameters
  • F02D2200/0402—Engine intake system parameters the parameter being determined by using a model of the engine intake or its components
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/04—Engine intake system parameters
  • F02D2200/0406—Intake manifold pressure
  • F02D2200/0408—Estimation of intake manifold pressure
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/40—Engine management systems

Definitions

• the present invention relates to a method and a device for determining a mass flow via a control valve and for determining a modeled intake manifold pressure in an internal combustion engine with exhaust gas recirculation, the sum being formed from the partial pressure of the fresh gas and the partial pressure of the recirculated exhaust gas.
• An external exhaust gas recirculation system is particularly necessary for Otto engines with gasoline direct injection in order to comply with the legally required limit values for NOx emissions in the exhaust gas.
• Increased raw NOx emissions in the exhaust gas occur predominantly in stratified engine operation with an air / fuel ratio ⁇ > 1.
• the exhaust gas recirculation in which an exhaust gas mass flow is removed from the exhaust system and fed back to the internal combustion engine in metered quantities via an exhaust gas recirculation valve, reduces the peak temperature of the combustion process and thus reduces the raw NOx emission.
• the partial pressure of the recirculated exhaust gas cannot be measured in the exhaust gas recirculation line. Therefore, only a model of the recirculated exhaust gas can be determined. In order to be able to implement a robust intake manifold pressure model which is as error-free as possible and which depends on the partial pressure of the recirculated exhaust gas, it is crucial to form a model for the partial pressure of the recirculated exhaust gas which is as free from errors as possible.
• the valve flow characteristic from which the mass flow over the valve is determined as a function of the valve position, is adapted to improve accuracy by means of an offset value which is related to the valve position of the valve.
• This offset value is constant over the valve position with different degrees of contamination of the valve.
• an offset value related to the mass flow on the other hand, a decrease in the offset value for a certain degree of contamination can be observed as the valve opening becomes smaller.
• a modeled partial pressure of the recirculated exhaust gas is derived from a flow characteristic of a valve located in an exhaust gas recirculation line depending on the valve position and that the modeled partial pressure of the recirculated exhaust gas derived from the flow characteristic is adaptive, depending on the difference from the modeled intake manifold pressure and a measured intake manifold pressure is corrected.
• the mass flow via the exhaust gas recirculation valve is determined as a function of the flow characteristic of the exhaust gas recirculation valve, that a relative charge in the intake manifold is then calculated from the mass flow by dividing it by the engine speed, and finally from the relative one Filling in the intake pipe the partial pressure of the recirculated exhaust gas is derived.
• Fresh air filling the partial pressure of the fresh gas is derived.
• FIG. 1 shows a schematic illustration of an internal combustion engine with exhaust gas recirculation
• FIG. 2 shows a functional diagram for calculating a modeled intake manifold pressure
• FIG. 3 shows a detail from the functional diagram of FIG. 2 for adaptively adapting the flow characteristic of the exhaust gas recirculation valve
• FIG. 4 shows a flow chart for the offset correction of the flow characteristic with an offset value related to the valve position.
• FIG. 1 schematically shows an internal combustion engine 1 with an exhaust gas duct 2 and an intake manifold 3.
• An exhaust gas recirculation line 4 branches off from the exhaust gas duct 2 and opens into the intake manifold 3.
• a valve 5 is located in the exhaust gas recirculation line 4. Via this exhaust gas recirculation valve 5, the recirculated exhaust gas mass or the partial pressure pagr of the recirculated exhaust gas can be controlled.
• Behind the mouth of the exhaust gas recirculation line 4, a pressure sensor 6 is arranged in the intake manifold 3, which measures the intake manifold pressure psaug.
• a throttle valve 7 Before the opening of the exhaust gas recirculation line 4 there is a throttle valve 7 with a potentiometer 8 which detects the throttle valve position wdk.
• an air mass sensor 9 is arranged in the intake manifold 3, which measures the air mass flow msdk via the throttle valve 7. Furthermore, are in the intake manifold 3 in front of the throttle valve 7, a pressure sensor 10, which measures the pressure pvdk in the intake manifold in front of the throttle valve, and a temperature sensor 11, which measures the intake air temperature TANS.
• a pressure sensor 12, which measures the exhaust gas pressure pvagr upstream of the exhaust gas recirculation valve 5, and a temperature sensor 13, which detects the temperature Tabg of the exhaust gas upstream of the exhaust gas recirculation valve 5, are arranged in the exhaust gas recirculation line 4 upstream of the exhaust gas recirculation valve.
• a control unit 14 is supplied with all of the sensed quantities mentioned. These include the measured intake manifold pressure psaug, the throttle valve position wdk, the air mass flow msdk in front of the throttle valve, the pressure pvdk in front of the throttle valve, the intake air temperature Tans, the position vs the exhaust gas recirculation valve 5, the engine speed nmot detected by a sensor 15, and the exhaust gas pressure pvagr in front of the exhaust gas recirculation valve and the temperature tab of the exhaust gas in front of the exhaust gas recirculation valve.
• the sizes pvdk, Tabg and pvagr can also be determined by model calculations from other operating sizes of the engine.
• the control unit 14 determines, among other things, the partial pressure pfg of the fresh gas and the partial pressure pagr of the recirculated exhaust gas from the input variables mentioned.
• the desired modeled intake manifold pressure psaugm arises from an additive combination 16 of the partial pressure pfg of the fresh gas and the modeled partial pressure pagr of the recirculated exhaust gas. It is described below how the control unit 14 derives the partial pressure pfg of the fresh gas and the partial pressure pagr of the recirculated exhaust gas.
• the mass flow msagr is first calculated via the exhaust gas recirculation valve according to equation (1).
• msagr fkmsag ⁇ - ⁇ [msnagr (vs) + msnagr o] ⁇ pvagr / 1013 bR ⁇ • -273 / Tagr ⁇ KLAF (psaug I pvagr) (1)
• This standard mass flow msnagr corresponds to the flow characteristic of the exhaust gas recirculation valve 5, which is usually provided by the valve manufacturer and is stored in the function block 17 (see FIG. 2).
• This standard mass flow msnagr (vs) is therefore a variable derived from the flow characteristic as a function of the valve position vs.
• the flow characteristic only takes into account the function of the exhaust gas recirculation valve 5, but not flow changes due to manufacturing tolerances and aging and also not the flow properties of the exhaust gas recirculation line 4. For this reason, in the equation (1) for the mass flow msagr via the exhaust gas recirculation valve, corrective heat fkmsagr and msnagro are provided, which can be changed adaptively.
• the correction term msnagro takes into account an offset of the flow characteristic.
• KLAF is a value taken from a characteristic curve, which shows the flow velocity over the exhaust gas recirculation valve in relation to the speed of sound as a function of the pressure ratio between the pressure psaug after the exhaust gas recirculation valve and the pressure pvagr upstream of the exhaust gas recirculation valve. If psaug / pvagr ⁇ 0.52 the speed of sound is set and if psaug / pvagr> 0.52 the flow speed drops below the speed of sound.
• the constant K depends on the cylinder stroke volume and the standard density of the air.
• the partial pressure pagr is calculated according to equation (3) from the relative filling rfagr resulting from the recirculated exhaust gas in the intake manifold on the basis of the recirculated exhaust gas.
• the map size KFURL indicates the ratio of the effective cylinder stroke volume to the cylinder stroke volume.
• the size ftsr reflects the temperature ratio of 273K to the gas temperature in the combustion chamber.
• a relative fresh air charge rlfg in the intake manifold is first determined in accordance with equation (4).
• the relative fresh air charge rlfg in the intake manifold can be calculated from the air mass flow msdk upstream of the throttle valve by division by the engine speed nrnot and the constant K (see equation (2)).
• the partial pressure pfg of the fresh gas is derived therefrom in function block 18 according to equation (5).
• the air mass flow msdk upstream of the throttle valve can either be measured with the sensor 9 or can be derived from other operating variables in accordance with equation (6).
• msdk msndk (wdk) ⁇ pvdk / 1013hPa A / 273 / Tans • KLAF (psaug I pvdk) (6)
• the KLAF value comes from a characteristic curve and provides the flow velocity over the throttle valve in relation to the speed of sound as a function of the pressure ratio psaug / pvdk at the throttle valve. If psaug / pvdk ⁇ 0.52 the speed of sound is set and if psaug / pvdk> 0.52 the flow rate drops below the speed of sound.
• the partial pressure pagr of the recirculated exhaust gas derived from the flow characteristic in function block 17 is subject to errors, because this throughflow characteristic of the exhaust gas recirculation valve 5 does not take into account manufacturing tolerances, flow changes due to aging and also the flow properties of the exhaust gas recirculation line 4.
• a function block 19 is provided, in which the partial pressure pagr of the recirculated exhaust gas is corrected.
• the aim is that the modeled partial pressure pagr of the recirculated exhaust gas that is available after the correction is corresponds exactly to the real partial pressure in the exhaust gas recirculation line, so that the modeled intake manifold pressure psaugm resulting from the sum of the partial pressure pfg of the fresh gas and the partial pressure pagr of the recirculated exhaust gas is as unadulterated as possible.
• a correction variable ⁇ ps is formed by forming the difference 20 from the modeled intake manifold pressure psaugm and the intake manifold pressure psaug measured by the pressure sensor 6, which is fed to a function block 19.
• the correction variable ⁇ ps is fed via a switch 21 to either an integrator 22 or an integrator 23.
• the integrator 22 provides the correction term fkmsagr occurring in equation (1)
• the integrator 23 provides the offset correction term msnagro.
• the integrators 22 and 23 increase the correction terms fkmsagr and msnagro to the extent that the correction variable ⁇ ps specifies.
• the partial pressure pagr of the recirculated exhaust gas is thus adaptively changed in function block 20 until the deviation between the measured intake manifold pressure psaug and the modeled intake manifold pressure psaugm becomes minimal.
• a threshold value decision takes place in switching block 21, which determines whether the measured intake manifold pressure psaug exceeds the threshold of 400 hPa. At a measured intake manifold pressure psaug that lies above the threshold of 400 hPa, only the integrator 23 for the correction term msnagro is controlled by the correction variable ⁇ ps. If the measured intake manifold pressure psaug is below the threshold of 400hPa, the correction variable ⁇ ps is switched over to the integrator 22 for the correction term fkmsagr.
• the mass flow via the valve is required to determine the partial pressure. This is based on an adap- animal characteristic is determined depending on the valve position. Such a characteristic curve can also be essential in connection with other applications, so that the characteristic curve adaptation described cannot only be used in exhaust gas recirculation.
• the air mass flow via a throttle valve is also determined in accordance with a flow characteristic, which can also be changed by valve contamination.
• the offset value is formed from the deviation of a value calculated using the characteristic curve with a measured value, for example by integration.
• FIG. 4 shows a flow chart for the adaptation of such a flow characteristic.
• the input variable is the valve position vp.
• the determined offset value off in the exemplary embodiment of an EGR valve ofvpagr, see e.g. FIG. 3, offset value msnagro
• the result is used to address the flow characteristic MSNTAG 26, the output variable of which is the standard mass flow msnv (in the exemplary embodiment of an EGR valve msnagrv) via the control valve, which if necessary by linking 27 (division) with a slope adaptation factor to the standard mass flow msn (in the exemplary embodiment of an EGR - valve msnagr) is linked.
• the offset value is related to the mass flow as described in equation 1. It is cheaper to refer to the valve position here as well.
• the following calculation equation for the mass flow then results:

Applications Claiming Priority (5)

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• 2001
  • 2001-01-18 EP EP01913510A patent/EP1264227A1/de not_active Ceased
  • 2001-01-18 WO PCT/DE2001/000200 patent/WO2001059536A1/de not_active Application Discontinuation
  • 2001-01-18 JP JP2001558803A patent/JP2003522888A/ja active Pending
  • 2001-01-18 CN CN01804767A patent/CN1416541A/zh active Pending
  • 2001-01-18 US US10/203,593 patent/US20030075158A1/en not_active Abandoned

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