Patent ID: 12209527

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG.1schematically shows an internal combustion engine40with an air supply with a first air duct1and a second air duct2. The air duct1is connected to an air filter31via a third air duct3. The air duct2is likewise connected to the air filter31via the air duct3. The air filter31filters ambient air and provides the filtered ambient air for the operation of the internal combustion engine40, not only for the cylinders10but also for the heater15.

Starting from the air duct3, a throttle valve21and then at least one cylinder10are arranged in the first air duct1. Starting from the air duct3, an air pump14, a shut-off valve22and then a heater15are arranged in the second air duct2.

A sensor element11, which has a mass flow sensor, is provided in the air duct3. The mass flow sensor measures the mass of air that flows through the air duct3. Furthermore, a pressure sensor and a temperature sensor can each additionally be provided in the sensor element11. The pressure in the air duct3is measured by the pressure sensor. The temperature of the air flowing through the air duct3is measured by the temperature sensor. The air flowing through the air duct3can flow further to the cylinder10or the heater15corresponding to the actuation of the control elements, i.e., the throttle valve21and the air pump14and shut-off valve22.

The mass which flows through the air duct1is controlled by the throttle valve21. For this purpose, a valve flap33is actuated in such a way that it controls the air flow.FIG.1schematically shows a position of the valve flap33transverse to the air flow, which represents a closed valve flap33and thus no flow through the air duct1. However, the valve flap33can also assume intermediate positions between open and closed, by means of which the amount of air that is sucked in by the cylinders10of the internal combustion engine is controlled.

The amount of air flowing through the air duct2is determined by the air pump14and the shut-off valve22. Only when the air pump14is switched on is a negative pressure generated which leads to a flow in the second air duct2. Furthermore, the amount of air flowing through the air duct2can be influenced as a function of the position of a valve flap34of the shut-off valve22. The amount of air can be influenced by the delivery rate of the air pump14and the position of the valve flap34. In a particularly simple embodiment, the valve flap34can only assume the completely open position or the completely closed position, and the air quantity is controlled only by the delivery rate or rotational speed of the air pump14. In the representation inFIG.1, the valve flap34is arranged longitudinally or in a laminar manner relative to the air flow, which corresponds to a fully open shut-off valve22. In the representation inFIG.1, an air flow through the air duct2toward the heater15is thus provided.

The cylinders10and the heater15are each connected to an exhaust system35so that the exhaust gases of the cylinders10and of the heater15are routed through the exhaust system35. Catalytic converters13and at least one lambda sensor19are provided in the exhaust system35. The catalytic converters13may have a plurality of partial catalytic converters, for example a first and a second three-way catalytic converter, a particle filter, and a catalytic converter for NOx reduction. The precise function and arrangement of the partial catalytic converters is not important for understanding the present invention. The residual oxygen content in the exhaust gas of the cylinder10is determined by the lambda sensor19. It can thus be ensured that the total quantity of fuel introduced into the cylinders10is in a stoichiometric ratio to the introduced air, since only in such an operating range is good cleaning of the exhaust gas ensured.

The heater15comprises a fuel injector16and an igniter17. The fuel injector16is designed as a conventional fuel injection valve and allows a precisely defined quantity of fuel to be introduced into the heater15for a heating operation. The igniter17is typically designed as a spark plug or as a glow plug for igniting a fuel/air mixture. A further lambda sensor18can optionally also be arranged in the connecting pipe between the heater15and the exhaust system35, by means of which further lambda sensor it can be ensured that the quantity ratios of air and fuel in the heater15also correspond to a desired setpoint value.

Typically, the heater15is switched on before the internal combustion engine40is started or during an early operating phase of the internal combustion engine. For example, the start of an internal combustion engine can be delayed and initially only an operation of the heater15take place. A heating of the exhaust system35is thus already achieved before the start of an internal combustion engine. As a result of this measure, cleaning of the exhaust gas is already allowed in early operation of the internal combustion engine, since it is not necessary to wait until the exhaust gases of the cylinders10reach the operating temperature of the catalytic converters13for converting the exhaust gases in the exhaust system35. A start of the internal combustion engine is therefore delayed for a short time (for example 1 to 10 seconds) in order to ensure a minimum temperature of the exhaust system at start-up of the internal combustion engine. Typically, a second operating phase is then carried out in which the internal combustion engine is already being operated by combustion processes in the cylinders10and, at the same time, heating by the heater15is also taking place. A further rapid heating of the exhaust system35up to an optimal operating temperature of the catalytic converters13is thereby ensured. In a third continuous operation of the combustion in the cylinders10, it is possible for the heater15then not to be operated further. If operating phases occur with insufficient heat introduction into the exhaust system35during further operation of the internal combustion engine, the heater15can be activated again.

For controlling and diagnosing the device according toFIG.1, a control device32is provided which (via lines not shown here) receives signals from all sensors and sends signals for controlling all control elements. The control device32processes the sensor signals and calculates control signals for the control elements. Accordingly, the diagnostic functions described below are executed by the control device32. The control device32can also be a part of a large control device which can be a wide variety of control tasks for the operation of the internal combustion engine or of a vehicle in which the internal combustion engine is installed.

InFIG.1, the throttle valve21is closed and the air pump14is activated, and the shut-off valve22is open.FIG.1thus shows an operating state in which the cylinder10(or the plurality of cylinders, if a plurality of cylinders is provided) of the internal combustion engine are not in operation and thus no air is flowing through the air duct1to the cylinder10. The shut-off valve22is open and the air pump14is activated. This operating state thus corresponds to a heating of the exhaust system35with no combustion taking place in the cylinders10. This is the case, for example, in an upstream heating operation of the exhaust system35before the internal combustion engine is started, for example during a cold start.

Since no air is flowing through the air duct1, in the case of correct operation, the mass flow through the sensor element11corresponds to the mass flow through the second air duct. The measurement signal of the mass flow sensor in the sensor element11can therefore be used for regulating the operation of the heater15. In particular, in a dynamic first operating phase, for example when the rotational speed of the air pump14changes dynamically, it is therefore possible to regulate the operation of the heater15using the measured signal of the mass flow sensor. Accordingly, in this operating phase, for example the quantity of fuel injected into the heater15can be adjusted in accordance with the measured air quantity.

If the flow conditions in the second air duct have stabilized such that a dynamic operating phase, i.e., a run-up of the air pump14, is no longer present, the measured signal of the mass flow sensor in the sensor element11can also be used for a precise regulation of the rotational speed of the air pump14or the position of the shut-off valve34. Small changes in the air pump14, the air duct2, or the shut-off valve34can be compensated in this way.

The operation with stabilized flow in the second air duct2also enables a diagnosis of the second air duct2. For this purpose, the measured mass flow through the air duct3, i.e. corresponding to the mass flow through the air duct2, is compared to an expected value which arises from the controlling of the air pump14and, if applicable, the opening of the valve22or the position of the valve flap34. If the flow through the air duct2is controlled not only by the operating data of the air pump14but also by the position of the valve flap34, both values will have to be taken into account for the formation of an expected value. If the flow through the air duct2is defined only by the operating data of the air pump14, in particular a delivery rate or rotational speed, then only the operating data of the air pump will have to be taken into account for the formation of an expected value. If it is then determined that the mass flow through the air duct2does not correspond to the expected value or the deviation from the expected value is too large, a fault in the air duct2will be detected. Such a fault can be, for example, a leak of the air duct2toward the ambient air, a fault in the pump14or a malfunction in the valve22. If a pressure sensor is also provided in the sensor element12, a pressure signal can alternatively also be used for this diagnosis.

The operation of the internal combustion engine40, as shown inFIG.1, also makes possible a further diagnosis using the lambda sensor18. A disturbance of the ratio of air and fuel in the heater15has a direct effect on the oxygen content of the exhaust gas of the heater15. The aim is an operation in which air and fuel are introduced into the heater15in a stoichiometric ratio, i.e., the same amount of oxygen is available as is required for the combustion of the introduced fuel. A deviation from this can in particular give an indication of a leak in the air duct2or an insufficient amount of fuel that has been injected into the heater15. In the same way, deviations from desired sub-and superstoichiometric operating phases can also be diagnosed.

FIG.2shows an internal combustion engine40with all elements, as has already been described forFIG.1. In contrast toFIG.1, however, the valve plate33of the throttle valve21is shown open and the valve plate34of the shut-off valve22is also shown open. This is therefore a second operating state of the internal combustion engine40in which the cylinders10and the heater15are simultaneously supplied with air. Such an operating state is useful for achieving a further heating of the exhaust system35up to an optimal operating temperature for the catalytic converters13. After a first heating of the exhaust system35to a minimum temperature from which the catalytic converters13operate (emissions already converted to parts) , a further heating up to the optimal temperature is effected by a simultaneous heating with exhaust gases of the cylinders10and of the heater15. Furthermore, such an operating state can make sense if only a small amount of heat is introduced by the cylinders10into the exhaust system35during normal operation. This can be the case, for example, in the case of longer overrun phases (for example, driving downhill, no heat release into the exhaust system35, resulting in rapid cooling) or even in lower partial-load operation (for example, stop-and-go operation, start-stop operation, idling operation) if only small amounts of fuel are introduced into the cylinders10, which results in reduced heat release/exhaust gas temperatures of the internal combustion engine40.

In this second operating state, the amount of air flowing through the air duct3is divided between the first air duct1and the second air duct2. The air flow through the first air duct1was used to supply the at least one cylinder10with air for combustion in the cylinder10. The air flowing through the second air duct2is used to supply the heater15. During normal operation, the amount of air flowing through the second air duct2can also be determined with good reliability based on the operating data of the air pump14and the shut-off valve34. This reliability is also achieved in that, in the first operating phase, a diagnosis of the flow through the second air duct2has already taken place, as has already been described forFIG.1. Since the second operating phase takes place after the first operating phase, it can therefore be assumed that the flow through the second air duct2can be reliably determined based on the operating conditions of the air pump14or of the shut-off valve (s)34. The flow thus determined through the second air duct2is therefore subtracted from the measured signal of the mass flow sensor in the sensor element11in order to obtain the amount of air flowing through the first air duct. In this second operating state, a regulation of the amount of air flowing through the first air duct1to the at least one cylinder10can therefore take place based on the thus determined flow through the first air duct1.

Furthermore, in this second operating state a diagnosis can also take place in which the amount of air which flows through the third air duct3is compared with expected values which result from operating data of the at least one cylinder10and the control elements in the first and second air ducts1,2. The expected value for the mass flow through the air duct1results from the operating parameters of the at least one cylinder10, for example the rotational speed of the internal combustion engine and load, and from the control of the throttle valve21, for example the position of the valve plate33in the throttle valve21. The expected value for the mass flow through the air duct2results from the operating parameters of the air pump14and the valve22. Here again, a diagnosis of the flow through the second air duct2has already taken place through a diagnosis in the first operating state. Since in this way a good reliability of the air flow through the second air duct2is ensured, possible deviations of the measured amount of air flowing through the third air duct3can be associated with deviations in the first air duct1. Such deviations can be associated, for example, through the throttle flap21or through the operating states of the at least one cylinder10or actuators of the cylinder10or sensors of the cylinder10.

In this diagnosis, the oxygen content in the exhaust gas of the heater15can additionally also be measured and compared with expected values which result from the operating data of the control elements in the second air duct2, i.e., the air pump14and the shut-off valve34. This check additionally ensures that the flow of air through the second air duct2corresponds to the planned expected value. It is thus additionally ensured that a found deviation of the measured mass flow of air through the third air duct3is to be associated with a deviation of the flow through the first air duct1.

FIG.3shows an internal combustion engine40with all elements, as has already been described forFIG.1or2. In contrast toFIG.1, however, the valve plate33of the throttle valve21is shown open and the valve plate34of the shut-off valve22is shown closed. This is therefore a third operating state of the internal combustion engine40in which the cylinders10are supplied with air and the heater15is not in operation. This is therefore a normal operation of the internal combustion engine40, without additional heating provided by the heater15. Since during fault-free operation there is no air flowing through the air duct2, the mass flow sensor11measures the air flow which is supplied to the cylinders10for combustion. A simple diagnosis can thus take place in that this measurement signal of the air mass sensor11is compared to an expected value which results from the operating data of the cylinders10, in particular rotational speed or load, and from the operating data of the throttle valve21, in particular the position of the valve plate33.