APPARATUS AND METHOD FOR LAMBDA CONTROL OF SPARK-IGNITION ENGINES, AND MOTOR VEHICLE

Abstract

A device for lambda control of a gasoline engine includes a first three-way catalytic converter, a second three-way catalytic converter, a linear lambda sensor, a binary lambda sensor and an NOx sensor. The first three-way catalytic converter is arranged upstream of the second three-way catalytic converter. The linear lambda sensor is arranged upstream of the first three-way catalytic converter. The binary lambda sensor is arranged downstream of the first three-way catalytic converter or the binary lambda sensor is arranged in the first three-way catalytic converter or in the second three-way catalytic converter and is arranged upstream of the second three-way catalytic converter. The NOx sensor is arranged downstream of the second three-way catalytic converter, and the linear lambda sensor, the binary lambda sensor and the NOx sensor are connected to a control device for lambda control.

Claims

1. A device for lambda control of a gasoline engine, having a first three-way catalytic converter, having a second three-way catalytic converter, having a linear lambda sensor, having a binary lambda sensor and having an NOx sensor, wherein the first three-way catalytic converter is arranged upstream of the second three-way catalytic converter, wherein the linear lambda sensor is arranged upstream of the first three-way catalytic converter, wherein the binary lambda sensor is arranged downstream of the first three-way catalytic converter and upstream of the second three-way catalytic converter, or wherein the binary lambda sensor is arranged in the first three-way catalytic converter or in the second three-way catalytic converter, wherein the NOx sensor is arranged downstream of the second three-way catalytic converter and wherein the linear lambda sensor, the binary lambda sensor and the NOx sensor are connected to a control device for lambda control.

2. The device according to claim 1, wherein the control device has a cascade control with a first controller (42), a second controller and a third controller, wherein the first controller is set up for mixture control using a setpoint value of the linear lambda sensor, wherein the second controller is set up for trim control of the setpoint value of the linear lambda sensor using a setpoint value of the binary lambda sensor, and wherein the third controller is set up for trim control of the setpoint value of the binary lambda sensor using at least one setpoint value and/or using at least one measured value of the NOx sensor.

3. The device according to claim 2, wherein the third controller has a measured value of the NOx sensor as an input value and a trim value of the second controller as an output value, the second controller has a measured value of the binary lambda sensor and the trim value of the second controller as input values and a trim value of the first controller as output value, and the first controller has a measured value of the linear lambda sensor and the trim value of the first controller as input values and a fuel quantity to be injected as output value.

4. The device according to claim 1, wherein the control device has a cascade control with a first controller, a second controller and a third controller, wherein the first controller is set up for mixture control using a setpoint value of the linear lambda sensor, wherein the third controller is set up for trim control of the setpoint value of the linear lambda sensor using at least one setpoint value and/or using at least one measured value of the NOx sensor.

5. The device according to claim 4, wherein the third controller has a measured value of the NOx sensor as an input value and a trim value of the first controller as an output value and/or wherein the second controller is set up for trim control of the setpoint value of the linear lambda sensor using a setpoint value of the binary lambda sensor and the second controller has a measured value of the binary lambda sensor as an input value and a trim value of the first controller as an output value.

6. The device according to claim 5, wherein a setpoint/actual deviation of the second controller is an input value of the third controller and/or a measured value of the binary lambda sensor is an input value of the third controller and/or a measured value of a mass air flow is an input value of the third controller.

7. The device according to claim 1, wherein the third controller is assigned at least one characteristic map which has data on the relationship between NH3 emission, NOx emission and optimum conversion of the three-way catalytic converters, and/or the third controller is assigned at least one characteristic curve which has data on the relationship between NH3 emission and an optimum conversion of the three-way catalysts, and/or the third controller is assigned at least one characteristic curve which has data on the relationship between NOx emission and optimum conversion of the three-way catalytic converters, and/or a binary and/or linear signal from the NOx sensor is assigned to the third controller as an input value.

8. The device according to claim 1, wherein a particulate filter is arranged upstream of the second three-way catalytic converter and downstream of the first three-way catalytic converter, which is coated with a catalytically active component and/or no further catalytically active components are arranged downstream of the NOx sensor.

9. A method for lambda control of a gasoline engine, the method having the following steps: providing a device according to claim 2, mixture control of the gasoline engine using the setpoint value of the linear lambda sensor; trim control of the setpoint value of the linear lambda sensor using the setpoint value of the binary lambda sensor; trim control of the setpoint value of the binary lambda sensor using measured values from the NOx sensor; or having the method steps of: providing the device wherein the control device has a cascade control with a first controller, a second controller and a third controller, the first controller is set up for mixture control using a setpoint value of the linear lambda sensor, the third controller is set up for trim control of the setpoint value of the linear lambda sensor using at least one setpoint value and/or using at least one measured value of the NOx sensor, mixture control using the setpoint value of the linear lambda sensor, trim control of the setpoint value of the linear lambda sensor using measured values of the NOx sensor and/or trim control of the setpoint value of the linear lambda sensor using a setpoint value of the binary lambda sensor.

10. A motor vehicle, having a gasoline engine and having a device for lambda control of a gasoline engine, having a first three-way catalytic converter, having a second three-way catalytic converter, having a linear lambda sensor, having a binary lambda sensor and having an NOx sensor, wherein the first three-way catalytic converter is arranged upstream of the second three-way catalytic converter, wherein the linear lambda sensor is arranged upstream of the first three-way catalytic converter, wherein the binary lambda sensor is arranged downstream of the first three-way catalytic converter and upstream of the second three-way catalytic converter, or wherein the binary lambda sensor is arranged in the first three-way catalytic converter or in the second three-way catalytic converter, wherein the NOx sensor is arranged downstream of the second three-way catalytic converter and wherein the linear lambda sensor, the binary lambda sensor and the NOx sensor are connected to a control device for lambda control or adapted to carry out the method according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The disclosure is described in more detail below with reference to a drawing illustrating exemplary embodiments. It shows schematically in each case:

[0045] FIG. 1 shows a first device according to the disclosure;

[0046] FIG. 2 shows characteristic curves of the linear and binary lambda sensor and the NOx sensor;

[0047] FIG. 3 shows a further illustration of the first device according to the disclosure;

[0048] FIG. 4 shows a second device according to the disclosure;

[0049] FIG. 5 shows method steps of a first method according to the disclosure;

[0050] FIG. 6 shows method steps of a second method according to the disclosure; and

[0051] FIG. 7 shows a motor vehicle according to the disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 shows a first device 10 according to the disclosure for lambda control of a gasoline engine 12. The first device 10 has a first three-way catalytic converter 14, a second three-way catalytic converter 16, a linear lambda sensor 18, a binary lambda sensor 20 and an NOx sensor 22.

[0053] The first three-way catalytic converter 14 is arranged upstream of the second three-way catalytic converter 16. The linear lambda sensor 18 is arranged upstream of the first three-way catalytic converter 14. The binary lambda sensor 20 is arranged downstream of the first three-way catalytic converter 14 and upstream of the second three-way catalytic converter 16. According to alternative exemplary embodiments, the binary lambda sensor can be arranged in the first three-way catalytic converter or in the second three-way catalytic converter 16. The NOx sensor 22 is arranged downstream of the second three-way catalytic converter 16. The linear lambda sensor 18, the binary lambda sensor 20 and the NOx sensor 22 are connected to a control device 24 for lambda control.

[0054] A mixture of air 26 and fuel 28 is fed to the gasoline engine 12 in a known manner and burned in cylinders 30 of the gasoline engine 12 to generate drive power. Exhaust gas 32 flowing out of the cylinders 30 is subjected to exhaust gas aftertreatment by means of the three-way catalytic converters 14 and 16 and then discharged into an environment U. A direction of flow of the exhaust gas 32 is indicated by the direction of the arrows designated by the reference sign 32.

[0055] Further components 34, 36 can be arranged upstream and downstream of the linear lambda sensor 18 in the exhaust system. The component 34 can, for example, be a turbine of an exhaust gas turbocharger. The component 36 can be, for example, a turbine of a further exhaust gas turbocharger or an exhaust gas recirculation system.

[0056] A particulate filter 38 coated with a catalytically active component is arranged upstream of the second three-way catalytic converter 16 and downstream of the binary lambda sensor 20.

[0057] The first three-way catalytic converter 14 is an electrically heatable catalytic converter 14.

[0058] The control device 24 has a cascade control 40, having a first controller 42, a second controller 44 and a third controller 46.

[0059] The first controller 42 is set up for mixture control using a setpoint value S1 of the linear lambda sensor 18. The second controller 44 is set up for the trim control of the setpoint value S1 of the linear lambda sensor 18 using a setpoint value S2 of the binary lambda sensor 20. The third controller 46 is set up for the trim control of the setpoint value S2 of the binary lambda sensor 20 using at least one setpoint value S3 of the NOx sensor 22.

[0060] The third controller 46 has a measured value M3 of the NOx sensor 42 as an input value and a trim value K2 of the second controller 44 as an output value. The second controller 44 has a measured value M2 of the binary lambda sensor 20 and the trim value K2 of the second controller 44 as input values and a trim value K1 of the first controller 42 as output value. The first controller 42 has a measured value M1 of the linear lambda sensor 18 and the trim value K1 of the first controller 42 as input values and a fuel quantity G to be injected as output value.

[0061] The trim value K2 is offset against the setpoint value S2 of the second controller 44 to form a corrected setpoint value SK2. For example, the setpoint value S2 can be increased or decreased by the amount of the trim value K2. Alternatively, the trim value K2 can represent a correction factor and can be multiplied by the setpoint value S2 to form the corrected setpoint value SK2. Similarly, the trim value K1 is offset against the setpoint value S1 of the first controller 42 to form a corrected setpoint value SK1.

[0062] FIG. 2 schematically shows a characteristic curve KB of the binary lambda sensor 20, a characteristic curve KL of the linear lambda sensor 18, and a characteristic map KN for the NOx and NH3 emissions, each plotted against the lambda value. According to the known definition, a stoichiometric combustion air ratio =1.0 applies.

[0063] The NH3 and NOx emissions are measured in ppm (parts per million), for example, and the lambda sensors 18, 20 output measured values in mV (millivolts). It is understood that the NH3 and NOx emissions can also be indicated in milligrams per kilometer or in another standardized or cumulative manner or represented in characteristic diagrams.

[0064] If a lambda of exactly 1.0, for example, is to be adjusted in the present case, the measured NH3 and NOx emissions can be used to determine whether the gasoline engine 12 is actually being operated at lambda equal to 1.0. This is because the NH3 and NOx emissions have a minimum at lambda equal to 1.0, so that an excessively high NOx emission indicates that the gasoline engine 12 is operating too leanly and an excessively high NH3 emission indicates that the gasoline engine 12 is operating too richly.

[0065] For example, it can happen that the characteristic curve KB of the binary lambda sensor 20 changes over the course of the operating time, so that a setpoint value S2 originally specified correctly for lambda equal to 1.0, which is specified in millivolts, now causes an incorrect trim control of the first controller 42 away from lambda equal to 1.0. Based on the measurement of the NH3 and NOx emissions, the incorrect setpoint value S2 due to the shift in the characteristic curve can be corrected by means of the correction value K2, so that the corrected setpoint value SK2 again results in correct trim control of the first controller 42 by the second controller 44 for lambda equal to 1.0.

[0066] The third controller 46 can therefore be assigned characteristic curves and/or characteristic maps F1, F2 and F3, which contain data on the relationship between NH3 emission, NOx emission and an optimum conversion of the three-way catalytic converters 14, 16. Using the measured NH3 and NOx emissions, the trim value K2 can be determined using the characteristic curves and/or maps F1, F2 and F3.

[0067] For example, emission values NOx [mg/km] and NH3 [mg/km] can be evaluated according to the first characteristic map F1. For example, emission values NOx [ppm] and NH3 [ppm] can be evaluated according to the second characteristic curve F2. For example, a binary signal from the NOx sensor can be taken into account according to the characteristic curve F3. Alternatively or additionally, a linear signal from the NOx sensor can be taken into account.

[0068] No other catalytically active components are arranged downstream of the NOx sensor 22, so that the NOx sensor 22 can be used to measure the emissions actually released into the environment U and the exhaust gas aftertreatment can thus be optimally controlled.

[0069] The fuel quantity G to be injected is calculated on the basis of a basic fuel quantity GB, wherein a factor GK for adjusting the fuel quantity GB is calculated using a deviation of the measured value M1 from the corrected setpoint value SK1.

[0070] FIG. 3 shows a more detailed representation of the cascade control 40. The third controller 46 can evaluate measured values M3 of the NOx sensor using one, two or more characteristic maps F1 and/or F2 and/or F3 in order to detect operation that is too lean or too rich outside the specified lambda window and generate the trim value K2.

[0071] By means of the first and second controllers 42, 44, the first correction value K1 and the fuel quantity G to be injected can subsequently be generated, in which PID elements are used.

[0072] FIG. 4 shows a second device 10 according to the disclosure, wherein only the differences to the exemplary embodiment described above are discussed and the same reference signs are assigned to the same features.

[0073] The device 10 is distinguished by a cascade control 40 of a control device 24, which differs from the exemplary embodiment described above.

[0074] The cascade control 40 has a first controller 42, a second controller 44 and a third controller 46.

[0075] The first controller 42 is set up for mixture control using a setpoint value S1 of the linear lambda sensor 18. The third controller 46 is set up for the trim control of the setpoint value S1 of the linear lambda sensor 18. The second controller 44 can also be set up for the trim control of the setpoint value S1 of the linear lambda sensor 18.

[0076] The third controller 46 has a measured value M3 of the NOx sensor as an input value and a trim value K1 of the first controller 42 as an output value. The second controller 44 can also have a measured value M2 of the binary lambda sensor as an input value and a trim value K of the first controller 42 as an output value.

[0077] It is provided that NOx and NH3 emissions measured by the NOx sensor are evaluated using characteristic maps and/or characteristic curves F2, F3, F4, F5, which are assigned to the third controller 46. A measured air mass flow MAF can be evaluated using a characteristic curve F6.

[0078] For example, emission values NOx [ppm] and NH3 [ppm] can be evaluated according to the characteristic maps F2 and F4. For example, a binary signal from the NOx sensor can be taken into account in accordance with characteristic curve F3. Alternatively or additionally, a linear signal from the NOx sensor can be taken into account. Furthermore, a setpoint/actual deviation of the second controller 44 can be assigned to the third controller 46 as an input value.

[0079] The third controller 46 therefore has a measured value M3 of the NOx sensor 42, the measured air mass flow and the setpoint/actual deviation of the second controller 44 as input values and the trim value K1 of the first controller 42 as output value.

[0080] The second controller 44 has a measured value M2 of the binary lambda sensor 20 as an input value and the trim value K1 of the first controller 42 as an output value.

[0081] The first controller 42 has a measured value M1 of the linear lambda sensor 18 and the trim values K1, K1 of the first controller 42 as input values and a fuel quantity G to be injected as output value, wherein K1 is optional.

[0082] The trim values K1 and K1 are offset against the setpoint value S1 of the first controller 42 to form a corrected setpoint value SK1, wherein K1 is optional.

[0083] The fuel quantity G to be injected is calculated on the basis of a basic fuel quantity GB, wherein a factor GK for adjusting the fuel quantity GB is calculated on the basis of a deviation of the measured value M1 from the corrected setpoint value SK1.

[0084] Compared to device 10, device 10 enables more rapid correction of the lambda control in the event of a sudden increase in the emissions measured by the NOx sensor.

[0085] A method for lambda control of the gasoline engine 12 by means of the device 10 has the following method steps: (A) provision of the device 10; (B) mixture control of the gasoline engine 12 using the setpoint value S1 of the linear lambda sensor 18, trim control of the setpoint value S1 of the linear lambda sensor 18 using the setpoint value S2 of the binary lambda sensor 20 and trim control of the setpoint value S2 of the binary lambda sensor using measured values or using at least one setpoint of the NOx sensor 22 (FIG. 5).

[0086] A method for lambda control of the gasoline engine 12 by means of the device 10 has the following method steps: (A) provision of a device 10; (B) mixture control using the setpoint value S1 of the linear lambda sensor 18, with a trim control of the setpoint value S1 of the linear lambda sensor 18 using measured values or using at least one setpoint value of the NOx sensor 22 and/or a trim control of the setpoint value S1 of the linear lambda sensor 18 on the basis of a setpoint value of the binary lambda sensor 20 (FIG. 6).

[0087] FIG. 7 shows a motor vehicle 100 with a gasoline engine 12 and with a device 10 and/or 10, set up to carry out the methods according to FIG. 5 and/or FIG. 6.