Method and device for lambda control

Abstract

Method for lambda control in an internal combustion engine (10), wherein a residual oxygen content in the exhaust gas is determined by means of at least one exhaust gas sensor (15) which is arranged in the exhaust gas channel (18) of the internal combustion engine (10) and a specific air-fuel ratio is set by means of lambda control by adjusting a fuel quantity by means of a fuel metering device (13) on the internal combustion engine (10), wherein the residual oxygen values ​​determined with the exhaust gas sensor (15) are temporarily compared against an atmospheric oxygen content, characterized in that ahead sections of the route which have an atmospheric oxygen content deviating from the normal atmospheric oxygen content are detected by means of a navigation preview, and forecast data for the expected atmospheric oxygen content are determined from this, which are used to adapt the lambda control.

Description

State of the art

[0001] The invention relates to a method for lambda control in an internal combustion engine, wherein a residual oxygen content in the exhaust gas is determined with at least one exhaust gas probe which is arranged in the exhaust gas channel of the internal combustion engine and a specific air-fuel ratio is set by means of lambda control by adjusting a fuel quantity by means of a fuel metering device on the internal combustion engine, wherein the residual oxygen values ​​determined with the exhaust gas probe are temporarily compared against an air oxygen content.

[0002] The invention further relates to a device for carrying out the method.

[0003] To reduce emissions in gasoline-powered passenger cars, three-way catalytic converters are typically used as exhaust gas purification systems. These systems only convert sufficient exhaust gases if the air-fuel ratio (λ) is precisely controlled. For this purpose, the air-fuel ratio (λ) is measured by an exhaust gas sensor located upstream of the exhaust gas purification system. The oxygen storage capacity of such a system is utilized to absorb oxygen during lean phases and release it again during rich phases. This allows oxidizable pollutant components in the exhaust gas to be converted. An exhaust gas sensor downstream of the exhaust gas purification system monitors its oxygen storage capacity. This oxygen storage capacity must be monitored as part of the on-board diagnostics (OBD) system, as it is a measure of the exhaust gas purification system's conversion efficiency.To determine the oxygen storage capacity, the exhaust gas purification system is either first supplied with oxygen in a lean phase and then emptied in a rich phase with a lambda value known in the exhaust gas, taking into account the volume of exhaust gas passing through, or the exhaust gas purification system is first emptied of oxygen in a rich phase and then refilled in a lean phase with a lambda value known in the exhaust gas, taking into account the volume of exhaust gas passing through. The lean phase ends when the exhaust gas probe downstream of the exhaust gas purification system detects the oxygen that can no longer be stored by the system. Similarly, a rich phase ends when the exhaust gas probe detects the passage of rich exhaust gas. The oxygen storage capacity of the exhaust gas purification system corresponds to the amount of reducing agent supplied during the rich phase for emptying.The amount of oxygen supplied for replenishment during the lean phase. The exact amounts are calculated from the signal of the upstream exhaust gas sensor and the exhaust gas mass flow determined from other sensor signals.

[0004] Lambda sensors are used as exhaust gas sensors in modern engine control systems. A distinction is made between a continuous sensor, also known as a wideband lambda sensor, and a two-point lambda sensor, also known as a switching sensor. A lambda sensor is based on a galvanic oxygen concentration cell with a solid electrolyte. The solid electrolyte typically becomes conductive for oxygen ions at an activation temperature of approximately 350°C. The nominal temperature of the sensor is usually significantly higher, typically between 650°C and 850°C. The temperature at which the lambda sensor becomes operational and meets the requirements of an engine control system lies between the activation temperature and the nominal temperature of the sensor. A wideband lambda sensor, representing the state of the art and its construction, is described, for example, in DE 10 2008 042 268 A1.

[0005] In summary, lambda sensors measure the residual oxygen content in the exhaust gas and use this information, compared to the atmospheric oxygen content, to optimize combustion by adjusting the fuel quantity. However, if the atmospheric oxygen content changes abruptly, this lambda control no longer functions optimally. In particular, situations where the atmospheric oxygen content is lower than the usual 21% are not taken into account. As a result, this can lead to a misadaptation, which negatively affects the accuracy of the lambda control.

[0006] Newer vehicle management systems utilize a navigation preview that, among other things, integrates into driver assistance systems (DAS) and energy management in modern vehicles. Driver assistance systems are electronic add-ons in motor vehicles designed to support the driver in specific driving situations. Safety aspects are often paramount, but increasing driving comfort is also a key consideration. Improved fuel economy is another important aspect.

[0007] Interventions in engine control systems for lambda control and exhaust aftertreatment, taking into account forecasts of the future operating phase of the internal combustion engine based on route data from GPS receivers or navigation receivers, are at least partially known from the state of the art.

[0008] DE 10 2008 045 067 A1, for example, relates to a method for operating a vehicle subsystem, whereby data on the vehicle's position, weather, and / or weather forecast are received and, in addition to vehicle-internal sensor signals, this data is used to modify the subsystem's control system. The method relates to air dryers or compressed air supplies for compressed air-operated systems, such as compressed air brake systems. The document also suggests the possibility of adjusting the lambda control to achieve optimized fuel consumption and emissions values ​​as needed, thereby enabling lower-emission operation in particularly polluted areas and fuel-efficient operation in less polluted areas. Specific examples of this implementation are not provided.

[0009] Another example of intervention in a motor vehicle subsystem using a future forecast from a route preview is described in DE 10 2008 025 569 A1. It describes a method for regulating and / or controlling a motor vehicle's functional system, which includes the steps of creating a forecast of a future operating mode of the internal combustion engine and predictively regulating and / or controlling a state of the functional system by taking the forecast into account. This involves a functional system whose state is controlled and / or regulated depending on the operating mode of the internal combustion engine. Specifically, the method relates to the operation of particulate filters, NOₓ. x- Storage catalysts, diesel oxidation catalysts, devices for adapting a lambda sensor, devices for tank venting diagnostics, an air conditioning system or a thermal storage unit. It is intended that data on route planning and vehicle positions via GPS navigation will be evaluated for predictive purposes.

[0010] German patent DE 10 2004 005 072 A1 describes a method for regenerating an exhaust gas purification system, in particular a particulate filter, whereby the regeneration cycle is controlled taking into account information about the driving route. The integration of GPS or position data from navigation systems is provided for in order to enable an optimal operating phase for regeneration. For example, the regeneration process can be aborted or not even started in a tunnel to avoid poor emissions.

[0011] DE 198 42 425 C2 describes a method for correcting the characteristic curve of a linear lambda sensor that is arranged upstream of a catalyst in an exhaust gas purification system for an internal combustion engine.

[0012] The task is therefore to provide a method that enables a prediction of the atmospheric oxygen concentration for future driving operations with a view to adapting a lambda control system.

[0013] It is also an object of the invention to provide a suitable device for carrying out the method. Disclosure of the invention

[0014] The problem concerning the procedure is solved by using a navigation preview to detect upcoming route sections that have an oxygen content that deviates from the normal atmospheric oxygen content of 21%, and from this, forecast data for the expected oxygen content are determined, which are used to adapt the lambda control.

[0015] This proactive approach allows for improvements in lambda control compared to current technology. It prevents incorrect adaptations based on erroneous assumptions about the atmospheric oxygen level. For example, exhaust gas sensors are typically calibrated against a standard oxygen content of 21% during overrun. However, if the oxygen content in the air deviates from this value, it leads to the aforementioned incorrect adaptations in lambda control. Furthermore, this method can increase the accuracy of the lambda control.

[0016] As one advantageous variant of the method provides, route information obtained from navigation data can be used to identify sections of the route with reduced oxygen levels compared to normal atmospheric oxygen, and a correction value for the oxygen level can be calculated from this. Particularly in situations with lower oxygen levels, this navigation preview can therefore optimize lambda control and fuel injection.

[0017] One preferred method involves calculating the expected oxygen content for an upcoming section of the route based on information about the density of buildings in the preceding section or about tunnel or enclosure sections ahead. Particularly in densely built-up areas, such as urban high-rise canyons, or in tunnel sections, the oxygen content can be lower than normal atmospheric oxygen levels. Such data on building density is typically available in the navigation data of modern navigation devices. The calculation can be performed using a model, for example, by assuming a deviation from normal atmospheric oxygen levels for the upcoming section based on building density, building height, road width, or the length of tunnels or enclosures.

[0018] Furthermore, data on traffic congestion or traffic density from radio-based systems, such as TMC, can be considered when forecasting the expected atmospheric oxygen content. High traffic volumes, especially in tunnel sections, can further reduce the oxygen content in the air. Using appropriate models, an atmospheric oxygen value can then be assumed, depending on the building density and / or existing tunnel sections or enclosures along the upcoming route, which may deviate from the normal atmospheric oxygen content.

[0019] If, as another variant of the procedure provides, additional emission requirements and / or speed limits for the upcoming section of road, derived from the navigation data, are taken into account during adaptation, the lambda control can be adjusted to avoid unnecessary pollutant emissions in such sections of road, or diagnoses regarding the functionality of the exhaust gas sensors, as provided for by the on-board diagnostics (OBD) system mentioned at the beginning, can be prevented, since otherwise the diagnosis would be faulty due to the rather unfavorable operating conditions in such sections of road.

[0020] Exhaust gas sensors include wideband lambda sensors, two-point lambda sensors, or other exhaust gas sensors or gas sensors, e.g., NO. xSensors are used to determine the residual oxygen content in the exhaust gas, either directly or indirectly. These sensors, however, must be checked and calibrated at regular intervals, usually against the reference value of the oxygen content of ambient air. If this value is known, depending on the route and / or traffic volume, the accuracy of the diagnostics provided by such exhaust gas sensors can be improved.

[0021] A preferred application of the method described above is its use to control the regeneration of an exhaust aftertreatment system in the exhaust manifold of an internal combustion engine or to specify a start time for the regeneration of the exhaust aftertreatment system. Exhaust aftertreatment systems typically contain a catalyst whose oxygen storage capacity must be checked by means of lambda adaptation, as mentioned earlier. For regeneration, a specific lambda value is pre-controlled in the exhaust manifold of the internal combustion engine. The type of pre-control and the start time of the regeneration can be adapted to the driving situation using the method described above. In particular, for example, in situations with reduced oxygen content in the air, a "rich" combustion can be used to regenerate NO. x -Catalytic converters are avoided, which would otherwise lead to increased emissions of pollutants.

[0022] The problem concerning the device is solved by the fact that the engine control unit includes calculation units and map storage units for carrying out the method with its aforementioned method variants, and that signal input data for a route prediction and, derived from this, data for a prediction of the atmospheric oxygen content in this upcoming route segment can be connected to the calculation unit as a corrective intervention in the lambda control. The functionality of the method can be implemented at least partially in software within this unit.

[0023] In a preferred embodiment, the route prediction and / or the prediction of the atmospheric oxygen content in the upcoming section of the route can be determined from stored navigation data in a navigation unit or in a special forecasting unit. This can be implemented, for example, in a so-called head unit with positioning and a digital map. Furthermore, traffic information for the upcoming section of the route can also be processed.

[0024] The invention is explained in more detail below with reference to an embodiment shown in the figure. It shows: Fig. 1 schematically represents the technical environment in which the method according to the invention can be applied.

[0025] Fig.Figure 1 schematically illustrates, using the example of a gasoline engine, the technical environment in which the inventive method for lambda control of an internal combustion engine 10 can be used. Air is supplied to the internal combustion engine 10 via an air inlet 11, and its mass is determined by an air mass meter 12. The air mass meter 12 can be designed as a hot-film air mass meter. The exhaust gas of the internal combustion engine 10 is discharged via an exhaust gas channel 18, with an exhaust gas purification system 16 being provided downstream of the internal combustion engine 10 in the direction of exhaust gas flow. The exhaust gas purification system 16 typically includes at least one catalyst.

[0026] For controlling the internal combustion engine 10, an engine control unit 14 is provided, which, on the one hand, supplies fuel to the internal combustion engine 10 via a fuel metering unit 13 and, on the other hand, receives the signals from the air mass meter 12 and the exhaust gas sensor 15 arranged in the exhaust duct 18, as well as from another exhaust gas sensor 17 arranged in the exhaust outlet 18. In the example shown, the exhaust gas sensor 15 determines an actual lambda value of a fuel-air mixture supplied to the internal combustion engine 10. It can be designed as a wideband lambda sensor or a continuous lambda sensor. The exhaust gas sensor 17 determines the exhaust gas composition after the exhaust gas purification system 16. The exhaust gas sensor 17 can be designed as a switching sensor or a two-point lambda sensor.

[0027] In the example shown, the engine control unit 14 has at least one map storage unit 14.1 in which target values ​​for lambda control are stored based on input variables such as residual oxygen content, exhaust gas temperature, exhaust gas mass flow, and other engine characteristics such as speed, injection quantity, etc. Based on this data, a situation-optimized fuel injection is determined in a corresponding processing unit.

[0028] According to the invention, it is provided that preview data for an upcoming route segment, including information on route segments with a reduced oxygen content compared to the normal atmospheric oxygen content of 21%, are determined from a navigation unit 20 in the vehicle and supplied as correction data to the engine control unit 14. This correction data is taken into account when calculating the fuel injection, thus enabling an adaptation of the lambda control.

[0029] The navigation unit 20 receives its position data from a GPS receiver 30, which receives radio signals from a network of satellites 40 spanning the Earth for position determination. The route forecast and / or the forecast of the atmospheric oxygen content in this upcoming section of the route can be determined in the navigation unit 20 or in a special forecasting unit (not shown here) from stored navigation data. Furthermore, it is possible to connect to information about the current traffic situation on the upcoming section of the route, which is available, for example, via a traffic message channel (TMC).

[0030] This allows for the proactive consideration of route sections with lower atmospheric oxygen content, e.g., when driving through tunnels or high-rise canyons. A correspondingly lower atmospheric oxygen content during this route section can be taken into account in the lambda control, in the regeneration of the exhaust gas purification system 16, or in diagnostics of the exhaust gas sensors 15, 17.

Claims

[1] Method for lambda control in an internal combustion engine (10), wherein at least one exhaust gas probe (15) arranged in the exhaust gas duct (18) of the internal combustion engine (10) determines a residual oxygen content in the exhaust gas and by means of the lambda control a specific air-fuel ratio is set by adjusting a fuel quantity by means of a fuel metering device (13) on the internal combustion engine (10), wherein the residual oxygen values ​​determined by the exhaust gas probe (15) are temporarily compared with an atmospheric oxygen content, characterized by that, by means of a navigation preview, sections of the route ahead are detected which have an atmospheric oxygen content which deviates from the normal atmospheric oxygen content, and from this, forecast data for the expected atmospheric oxygen content is determined, which is used to adapt the lambda control. [2] Method according to claim 1, characterized bythat, based on information on the route, which is determined from navigation data, in particular route sections with a reduced atmospheric oxygen content compared to the normal atmospheric oxygen content are determined and a correction value for the atmospheric oxygen content is calculated from this. [3] Method according to claim 1 or 2, characterized by that an expected atmospheric oxygen content for this section of the route is calculated using a model based on information on the density of development in the section of the route ahead or on information on tunnel or enclosure sections that lie ahead on the route. [4] Method according to claim 3, characterized by that information on traffic density is taken into account when forecasting the expected atmospheric oxygen content. [5] Method according to one of claims 1 to 4, characterized bythat additional emission specifications and / or speed limits for the route section ahead, which are derived from the navigation data, are taken into account during adaptation. [6] Method according to one of claims 1 to 5, characterized by that a broadband lambda probe, a two-point lambda probe or another exhaust gas probe or a gas sensor is used as the exhaust gas probe (15). [7] Use of the method according to claims 1 to 6 for controlling the regeneration of an exhaust gas purification layer (16) in the exhaust duct (18) of the internal combustion engine or for specifying a starting time for the regeneration of the exhaust gas purification system (16). [8] Device for lambda control in an internal combustion engine (10), which has at least one exhaust gas probe (15) which is arranged in the exhaust gas duct (18) of the internal combustion engine (10), with which a residual oxygen content in the exhaust gas can be determined and by means of an engine control (14) within the framework of the lambda control a certain air-fuel ratio can be set by adjusting a fuel quantity by means of a fuel metering (13) on the internal combustion engine (10), and wherein the residual oxygen values ​​determined by the exhaust gas probe (15) are temporarily compared with an atmospheric oxygen content, characterized bythat the engine control (14) has calculation units and characteristic map storage units (14.1) for carrying out the method according to method claims 1 to 6 and, on the signal input side, data for a route course forecast and, derived therefrom, data for a forecast of the atmospheric oxygen content in this upcoming route section can be applied to the calculation unit as a corrective intervention in the lambda control. [9] Device according to claim 8, characterized by that the route forecast and / or the forecast of the atmospheric oxygen content in this upcoming route section can be determined in a navigation unit (20) or in a special forecast determination unit from stored navigation data.

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