Abstract:
A method and a device for controlling a gas flow over a throttle valve in an internal combustion engine. The method and device can be used in particular in internal combustion engines in motor vehicles and allow for fast and accurate control of a gas flow while minimizing apparatus and control costs. A method is provided for controlling a gas flow over a throttle valve in a combustion over the throttle valve and the actual gas flow; and taking into account the determined difference when calculating the throttle setting.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and a device for controlling a gas flow over a throttle valve in an internal combustion engine. The present invention concerns, in particular, a method and a device for use in automotive engineering. 
     BACKGROUND INFORMATION 
     An air/fuel mixture is ignited in the combustion chamber of an internal combustion engine to generate an engine torque. The gas mass filling the combustion chamber must be controlled and detected as accurately as possible because it determines, among other things, the engine torque, the fuel volume to be injected, and the ignition point. 
     Using an “electronic gas pedal” in modern engine control systems, the pedal position is interpreted as a torque request. This torque request is converted to a setpoint for the air mass flow. A “charge control” function calculates a setpoint air mass flow from the torque request and generates from this value a setpoint for controlling the throttle plate. A control element adjusts the throttle plate to the setpoint. A downstream hot-film air mass sensor measures the actual air mass flow. Based on tolerances in the hot-film air mass sensor and in the calculation path of the calculation of air mass flow over the throttle valve, a difference is produced between the actual value and the setpoint of the air mass flow and between the actual torque and the torque request. 
     To correct these inaccuracies, an adjustment system that has not only one adjustment unit, but two adjustment units, is described in European Patent No. 575710. In a convention device, the first adjustment unit sends the actuating signal to the adjustment path, while the second adjusting unit is used to calibrate the first adjusting unit. In the known device, a throttle-plate-based charge signal is used to control injection, with this relatively fast adjusting signal being calibrated by an air mass meter in the stationary state. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a method and a device for controlling a gas flow over a throttle valve in an internal combustion engine, thereby adjusting the gas flow quickly and precisely. In addition, it must be possible to carry out the method as well as produce and operate the device economically. 
     The object is achieved, in particular, by providing a method for controlling a gas flow over a throttle valve in a combustion chamber of an internal combustion engine having the following steps: calculation of a throttle setpoint setting from the setpoint gas flow, activation of the throttle valve using the throttle setpoint setting, and determination of an actual gas flow, characterized by the following steps: calculation of a gas flow over the throttle valve on the basis of an actual throttle setting, determination of a difference between the calculated gas flow over the throttle valve and the actual gas flow, and taking into account the determined difference when calculating the throttle setpoint setting, in particular by adjusting the setpoint gas flow. In doing this, the setpoint air mass in the combustion chamber is advantageously converted in one step to a throttle valve setpoint at which an actual air mass begins to form with the accuracy of the sensor used to determine the actual gas flow. A hot-film air mass sensor can be used, in particular, as the sensor for determining the actual gas flow. A further advantage lies in the fact that, unlike the related art, an additional charge controller, which subsequently adjusts the setpoint and actual mass, is not used. This reduces the production, maintenance, and operating costs. A further advantage lies in the fact that the single-step control stabilizes the throttle plate characteristic, thereby improving the operation of the entire internal combustion engine unit. A further advantage lies in the fact that the method makes it possible to adjust the desired air mass flow very quickly and precisely. In the steady state, in particular, there is no difference between the setpoint charge and the actual charge measured by the hot-film air mass sensor. 
     In one particular embodiment of the present invention, the method is characterized by a determination of at least two correction quantities when taking into account the difference between the gas flow over the throttle plate of the throttle valve and the actual gas flow. This has the advantage that the determination of at least two correction quantities makes it possible to achieve faster and more precise control. An additional advantage lies in the fact that the determination of at least two correction quantities provides for the separate treatment of and compensation for different error quantities and disturbances, thus further improving control accuracy and speed. 
     In a further embodiment of the present invention, the method is characterized by additively taking into account at least one first correction quantity and multiplicatively taking into account at least one second correction quantity, with the first and second correction quantities being taken into account simultaneously or alternately, in particular the first correction quantity being taken into account, i.e., being relevant, primarily in the case of small gas flows and the second correction quantity being taken into account, i.e., being relevant, primarily in the case of large gas flows over the throttle valve. In a further embodiment of this design, the first correction quantity corrects an error caused by leakage air over the throttle valve, and the second correction quantity corrects an error caused by an incorrect detection of a pressure upstream from the throttle valve. This is advantageous because it allows the two errors to be handled according to their specific error characteristics, thus increasing control accuracy. One advantage lies in the fact that an error caused by leakage air, which is made noticeable by an additive error in any operating state, but is not relevant especially with small gas flows, can be treated accordingly. Likewise, an error caused by erroneous pressure detection, which is noticeable in any operating state and is relevant, in particular, with large gas flows, can also be treated accordingly. The two correction quantities can be preferably taken into account simultaneously, thus achieving a high control accuracy. Overall, an embodiment of this type provides very fast and yet highly accurate and reliable control, at the same time lowering costs of both equipment and computer-supported control. 
     In a further embodiment of the present invention, at least one of the correction quantities is stored at the end of operation of the internal combustion engine. This advantageously provides full control accuracy as soon as the internal combustion engine resumes operation. The correction quantities can be advantageously stored by appropriate electronic components, for example by an SRAM component or a magnetic storage device. 
     In a further embodiment of the present invention, a predetermined value is used as a starting value for at least one of the correction values when operation of the internal combustion engine resumes. This is advantageous because it allows a selected cold-start value to be easily determined for specific correction quantities. The provision of predetermined values is also advantageous because it maintains secure control even if the internal combustion engine is idle for an extended period of time or if data or information relating to the predetermined correction quantities is lost. 
     In a further embodiment of the present invention, the setpoint gas flow is determined on the basis of at least one request for the torque of the internal combustion engine. This is advantageous because, in a motor vehicle with an internal combustion engine, not only can the torque request via the gas pedal be taken into account, but also torque requests that are produced by an automatic transmission of the motor vehicle or by an anti-spin control system of the motor vehicle. 
     The object of the present invention is also achieved by providing a device for controlling a gas flow over a throttle valve in a combustion chamber of an internal combustion engine including a throttle valve controller having an input signal for a setpoint gas flow and an output signal for a valve position, and a measuring sensor for determining an actual gas flow, characterized in that the throttle valve controller has a computing device which calculate a gas flow over the throttle valve on the basis of the throttle setting, and which further determines a difference between the calculated gas flow over the throttle valve and the actual gas flow, with this difference being taken into account when calculating the output signal, in particular by adjusting the setpoint gas flow. A device of this type according to the present invention has the same advantages mentioned above in connection with the method according to the present invention. In particular, a device of this type is advantageous because it ensures fast and precise control, at the same time reducing the apparatus and computing requirements so that a device of this type can be produced, maintained, and operated economically. 
     In one embodiment of the present invention, at least two correction quantities are determined when determining the difference. This has the advantage that even complex error quantities and disturbances can be detected quickly and with relatively little effort, achieving stable and precise control. This is particularly true when the at least two correction quantities separately detect error sources with additive and multiplicative error characteristics and preferably take them into account simultaneously. 
     The subject matter of the present invention also includes a device that carries out one of the above-mentioned control methods according to the present invention. This combines the advantages of fast and accurate control with an economical implementation by a device according to the present invention. 
     The subject matter of the present invention also concerns a motor vehicle that has a device like the one described above. 
     The present invention also relates to data media which contain a control program for carrying out one of the above-mentioned control methods according to the present invention, or which contain the parameters that are necessary or advantageous for carrying out one of the above-mentioned methods according to the present invention. The data media can store the information in any form, in particular in mechanical, magnetic, optical or electronic form. In particular, electronic data media are advantageous, for example a ROM, PROM, EPROM or EEPROM device that can be advantageously inserted into corresponding control units. Data media of this type can be used to easily exchange control parameters and control programs, thus making it possible, for example, to configure a standard control unit for different vehicle types simply by inserting the corresponding data medium. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a block diagram for detecting a charge using a hot-film air mass sensor, and for determining two correction quantities. 
     FIG. 2 shows a block diagram for determining a gas flow over a throttle valve. 
     FIG. 3 shows a block diagram for controlling the charge according to the present invention as well as for calculating the throttle valve angle. 
     FIG. 4 shows a device according to the present invention for controlling a gas flow over a throttle valve. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a block diagram for the charge detection system, including a hot-film air mass sensor, and for determining two correction quantities msndko and fkmsdk. In the upper signal path of FIG. 1, an air mass flow mshfm measured by the hot-film air mass sensor is converted to a corrected relative charge r 1  of a cylinder. To do this, air mass flow mshfm measured by the hot-film air mass sensor is first converted to an uncorrected relative charge rlroh of a cylinder. This is done through division  111  of air mass flow mshfm measured by the hot-film air mass sensor by a value that is derived from multiplication  112  of an engine-specific constant KUMSRL by engine speed nmot. Intake manifold pressure ps is derived from uncorrected relative charge rlroh by applying the gas equation and a corresponding integration  113 . Corrected relative charge r 1  of the cylinder is calculated from intake manifold pressure ps by the taking into account  114  of additional influencing quantities in relation to the flow rate ratios in the intake manifold. To convert the standard air mass flow to a mass flow at an instantaneous temperature, the air mass flowing over the throttle valve is calculated  115  from intake manifold pressure ps together with throttle plate angle wdkba of the throttle valve in relation to a stop and an intake-air temperature-compensation factor ftvdk. FIG. 2 shows a detailed illustration of the calculation of the air mass flowing over throttle valve msdk. Difference msdif is formed by a subtraction  116  from measured air mass flow mshfm and calculated air mass flow msdk. A first additive correction quantity msndko is derived by an integration  117  of difference value msdif. A second multiplicative correction quantity fkmsdk is calculated in the same manner by an integration  118  of difference value msdif. Integration operations  117 ,  118  also differ from each other, in particular, in terms of the integration constants, i.e., the resulting physical unit. Additive correction quantity msndko is returned directly to the calculation of throttle-valve gas flow  115 . Multiplicative correction quantity fkmsdk is also returned to the calculation of the throttle-valve gas flow by a multiplication  120  by an ambient pressure pvdkds measured by a pressure sensor, determining an effective pressure upstream from throttle valve pvdk. By taking into account correction factors msndko and fkmsdk when calculating the gas flow over the throttle valve, the calculated value for the gas flow over throttle valve msdk is brought into alignment with measured value mshfm. This improves the accuracy of this system in such a way that the calculation of relative charge r 1  can be based exclusively on calculated gas mass flow msdk if necessary, for example if the hot-film air mass sensor fails. This is done by flipping switch  119  according to a corresponding changeover signal B_ehfm. 
     In carrying out the multiplicative correction, for example, it is assumed that pressure value pvdk coming from the ambient pressure sensor lies within certain tolerances, producing a difference between calculated gas mass flow msdk and measured gas flow mshfm. The correction responds to this difference by adjusting multiplicative correction quantity fkmsdk until msdk is equal to mshfm. Following a steady-state adjustment, quantity pvdk is identical to the actual pressure upstream from the throttle plate, if the other influencing quantities do not lie within the tolerances. Normally, the adaptation quantities cover all tolerances that occur in the hot-film air mass sensor path and the throttle valve path, causing quantity pvdk to differ from the actual pressure upstream from the throttle valve. Nevertheless, the adjustment serves its purpose, which is to adjust the throttle-valve-based air mass flow calculation to the air mass flow calculation based on the hot-film air mass sensor. 
     In an induction engine, quantity pvdkds can be derived from an ambient pressure sensor and, in a pressure-charged engine, it can be derived from a charge-air pressure sensor upstream from the throttle valve. In an induction engine with a hot-film air mass sensor and a pressure sensor in the intake manifold, pressure pvdkds can be derived from the intake manifold pressure via a level adaptation. If a pressure sensor is not provided, value pvdkds is set to 1 and fkmsdk is set to the same value as pvdk, while in an induction engine, fkmsdk includes the ambient pressure information along with tolerance inaccuracies in the throttle valve and the hot-film air mass sensor system. 
     FIG. 2 shows a block diagram for determining gas mass flow msdk over the throttle valve according to calculation unit  115  in FIG.  1 . Setpoint angle wdkba of a throttle plate of the throttle valve is first available as the input signal. Setpoint angle wdkba is preferably related to the throttle plate stop. Using a transfer function MSNWDK  201  established in an air test bay, mass flow msndk is calculated downstream from the throttle valve. Additive correction quantity msndko, which preferably detects the leakage air over the throttle valve under normal conditions, is added  202  to mass flow msndk. The value resulting from this addition  202  is multiplied  203  by an intake-air temperature-compensation factor ftvdk for converting the standard air mass flow to an air mass flow at an instantaneous temperature. At the same time, a correction factor fpvdk is derived from a pressure value pvdk upstream from the throttle plate of the throttle valve by division  204  by nominal pressure value 1013 hPa to adjust the air mass flow at normal pressure upstream from the throttle valve to instantaneous conditions. Value pvdk is multiplicatively composed of an ambient pressure pvdkds measured by a pressure sensor and multiplicative correction factor fkmsdk, as shown in FIG.  1 . At the same time, a correction factor KLAF (ps/pvdk) is also derived, by quotient formation  205 , from intake manifold pressure ps and the pressure upstream from the throttle plate of throttle valve pvdk and a subsequent transfer function  206 , which is also known as the outflow characteristic and which adjusts the standard flow through the throttle valve measured at an above-critical flow rate to below-critical flow rates. The two derived correction factors fpvdk and KLAF (ps/pvdk) are each taken into account along with the mass flow by a multiplication  207 ,  208 . To summarize, air mass flow msdk is calculated as follows: 
     
       
           msdk=msndk×ftvdk×fpvdk×KLAF  ( ps/pvdk ). 
       
     
     FIG. 3 shows the charge control system according to the present invention by calculating the setpoint angle of the throttle plate of throttle valve wdks from the setpoint for air mass flow mssol. In this case, the setpoint for air mass flow mssol is first altered according to different correction quantities. Many of the components of the charge control system according to the present invention are constructed in an inverse relationship to the charge detection system illustrated in FIG.  1 . In particular, correction quantities msndko and fkmsdk determined during the course of charge detection are used in the charge control system according to the present invention. As shown in FIG. 1, the parameters of engine speed nmot and KUMSRL are first multiplied  112 . Setpoint mssol is divided by the resulting product, yielding a setpoint charge rlsol in the combustion chamber. Further division  302  of this value by a conversion factor fupsrl, “intake manifold pressure in relative charge” and a subsequent addition  303  to a correction factor pirg, which takes into account the partial pressure of the internal exhaust gas recirculation, yields setpoint pressure pssol in the intake manifold. This value pssol is altered by a division  304  by a pressure pvdk upstream from the throttle plate of the throttle valve and transferred to a transfer function  305 , which is also known as the “outflow characteristic” and adjusts the standard flow through the throttle valve measured at an above-critical flow rate to below-critical flow rates. Value pvdk is calculated by multiplication  306  from ambient pressure pvdkds measured by a pressure sensor and multiplicative correction factor fkmsdk, just like the calculation shown in FIG.  1 . The value derived from outflow characteristic  305  is subsequently adjusted by a multiplication  307  by an intake-air temperature-compensation factor ftvdk to convert the standard air mass flow to an air mass flow at an instantaneous temperature, and subsequently by a multiplication  308  by a correction factor fpvdk to adjust the air mass flow at normal pressure upstream from the throttle valve to instantaneous conditions for the instantaneous temperature and pressure ratios. Correction factor fpvdk is derived from pressure pvdk upstream from the throttle plate of the throttle valve by division  309  by a nominal pressure of 1013 hPa. The value resulting from the calculations described above is subjected to a division  310  together with setpoint mssol for the air mass flow. Additive correction value msndko, which takes into account the leakage air over the throttle valve under normal conditions, is subsequently subtracted from the value reached by division  310 . Resulting value msnwdks is transferred to a transfer function WDKMSN  311 , which yields the inverted characteristic of transfer function MSNWDK shown in FIG.  2  and thus a setpoint angle wdks for the throttle plate of the throttle valve derived from the corrected and adjusted setpoint for air mass flow msnwdks. FIG. 4 shows the device according to the present invention for controlling a gas flow over a throttle valve. Setpoint mssol for the air mass flow is determined from the position of a gas pedal  401 . As shown in FIG. 3, charge control system  402  derives a setpoint angle wdks of a throttle plate  403  from this value. Actual angle wdkba of the throttle plate is detected and serves as an input quantity for charge detection system  404 . As shown in FIG. 1, charge detection system  404  derives mass flow msdk over the throttle valve from value wdkba. A hot-film air mass sensor  405  connected downstream in intake manifold  400  determines air mass flow mshfm. As shown in FIG. 1, an additive correction value msndko and a multiplicative correction value fkmsdk are derived from values msdk and mshfm in a comparator and integrator module  405 . The two correction values are output to both charge control system  402  and charge detection system  404 , where they serve as input quantities. The advantage of this device according to the present invention is not only that charge control system  402  can set a throttle plate angle at which the setpoint matches the value measured by the hot-film air mass sensor without any subsequent correction by a relatively slow controller, but also that, in an injection system located upstream from the intake valve in which the air mass flow at the time the intake valve closes should be known, the throttle plate angle achieved at this later point in time is easier to estimate than a future air mass flow based on the hot-film air mass sensor signal. The future air mass flow can be calculated on the basis of this future throttle plate angle, and thus the instantaneous injection time advantageously corrected, with the correction factors making this prediction just as accurate as the hot-film air mass sensor. 
     Abbreviations 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 B_ehfm 
                 Error signal, changeover signal. 
               
               
                 fkmsdk 
                 Multiplicative correction quantity. 
               
               
                 fpvdk 
                 Correction factor for adjusting the air mass flow at normal 
               
               
                   
                 pressure upstream from the throttle valve to instantaneous 
               
               
                   
                 conditions = pvdk/1013 hPa. 
               
               
                 ftvdk 
                 Intake-air temperature-compensation factor for converting 
               
               
                   
                 the standard air mass flow to an air mass flow at an instant- 
               
               
                   
                 aneous temperature. 
               
               
                 fupsrl 
                 Conversion factor for the intake manifold pressure in a re- 
               
               
                   
                 lative charge. 
               
               
                 KLAF 
                 Outflow characteristic for adjusting the standard flow mea- 
               
               
                   
                 sured at an above-critical rate of flow to below-critical rates 
               
               
                   
                 of flow. 
               
               
                 KUMSRL 
                 Parameter for determining the relative cylinder charge from 
               
               
                   
                 the air mass flow and the engine speed, piston-swept 
               
               
                   
                 volume. 
               
               
                 msdif 
                 Difference between the calculated and measured gas mass 
               
               
                   
                 flow = mshfm - msdk. 
               
               
                 msdk 
                 Calculated air mass flow over the throttle valve. 
               
               
                 mshfm 
                 Air mass flow measured by the hot-film air mass sensor. 
               
               
                 msndk 
                 Mass flow downstream from the throttle valve. 
               
               
                 msndko 
                 Additive correction quantity, leakage air over the throttle 
               
               
                   
                 valve under normal conditions. 
               
               
                 msndks 
                 Setpoint for air mass flow under normal conditions. 
               
               
                 MSNWDK 
                 Standardized air mass flow over the throttle valve, 
               
               
                   
                 measured in an air 
               
               
                 (wdkba) 
                 test bay. 
               
               
                 msnwdks 
                 Adjusted setpoint gas flow over the throttle valve. 
               
               
                 mssol 
                 Setpoint for the air mass flow under instantaneous 
               
               
                   
                 conditions. 
               
               
                 nmot 
                 Engine speed. 
               
               
                 pirg 
                 Correction of the intake manifold pressure by exhaust gas 
               
               
                   
                 recirculation, partial pressure of internal exhaust gas 
               
               
                   
                 recirculation. 
               
               
                 ps 
                 Pressure in the intake manifold. 
               
               
                 pssol 
                 Setpoint pressure in the intake manifold. 
               
               
                 pvdk 
                 Pressure upstream from a throttle plate of the throttle 
               
               
                   
                 valve = pvdkds × fkmsdk. 
               
               
                 pvdkds 
                 Ambient pressure measured by a pressure sensor. 
               
               
                 rlroh 
                 Air mass flowing into the intake manifold, uncorrected 
               
               
                   
                 relative charge of a cylinder. 
               
               
                 rl 
                 Air mass flowing out of the intake manifold, corrected 
               
               
                   
                 relative charge of a cylinder. 
               
               
                 wdkba 
                 Actual angle of a throttle plate of the throttle valve in 
               
               
                   
                 relation to a stop. 
               
               
                 wdks 
                 Setpoint angle of a throttle plate of the throttle valve in 
               
               
                   
                 relation to a stop = WDKMSN (msnwdk). 
               
               
                 WDKMSN 
                 Inverted characteristic of MSNWDK.