CN111350568A

CN111350568A - Internal combustion engine with air injection before particle filter

Info

Publication number: CN111350568A
Application number: CN201911316646.XA
Authority: CN
Inventors: M.德伦格; C.施魏策; 孙飞; M.海因克勒; O.克兰尼希; R.迈尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-12-20
Filing date: 2019-12-19
Publication date: 2020-06-30
Also published as: DE102018222587A1

Abstract

An internal combustion engine (10) is proposed, comprising an intake system (12) and an exhaust system (14) having a three-way catalyst (16) and a particle filter (18) arranged downstream of the three-way catalyst (16). The internal combustion engine (10) is characterized in that the exhaust system (14) has a device (42) for introducing air into the exhaust system (14) between the three-way catalyst (16) and the particle filter (18). The independent claim relates to a method for controlling an internal combustion engine (10).

Description

Internal combustion engine with air injection before particle filter

Technical Field

The invention relates to an internal combustion engine according to the preamble of the claims and to a method according to the independent method claims. Such an internal combustion engine has an intake system and an exhaust system having a three-way catalyst and a particulate filter arranged downstream of the three-way catalyst. The preamble of the method claim relates to the control of such an internal combustion engine. Such an internal combustion engine and such a method are known per se.

Background

Such exhaust systems are used in particular in conjunction with modern internal combustion engines which operate on gasoline. For effective regeneration of the particle filter, the temperature thereof is increased by means of motor-driven measures, for example, by late ignition of a gasoline-operated internal combustion engine, which increases the exhaust gas temperature. If the ignition temperature of the soot deposited in the particle filter in the presence of oxygen is exceeded, the deposited soot burns, as a result of which the particle filter is in turn receptive and is thus regenerated. The temperature level required for the ignition of the regeneration can also be achieved by operating the internal combustion engine in the range close to full load when a correspondingly high torque demand is present. Regeneration in the particle filter can then be triggered by the fuel supply being switched off in coasting mode. In the case of ignition operation, i.e., operation of the internal combustion engine operated on gasoline by fuel injection and generating torque, no regeneration takes place, since the exhaust gas cleaning of the internal combustion engine operated on gasoline in the three-way catalyst requires a stoichiometric composition of the fuel-air mixture. Due to the stoichiometry, there is no longer free oxygen in the particle filter arranged downstream of the three-way catalyst for the combustion of the soot deposited in the particle filter. Regeneration of the particle filter is therefore limited to the coasting phase of fuel cut-off.

Disclosure of Invention

The invention differs from the prior art mentioned at the outset with regard to its device in that the exhaust system has a device for introducing air into the exhaust system between the three-way catalyst and the particle filter. In its method aspect, the present invention differs from the prior art in that the introduction of air into the exhaust system between the three-way catalyst and the particulate filter is controlled.

The invention thus allows the provision of oxygen for the effective regeneration of the particle filter outside the coasting operating phase of the fuel cut. The elimination of active regeneration is thus limited to the coasting operating phase of the fuel cut. It is thus possible to use the thermal phase following the acceleration process to trigger regeneration, even if a coasting operation without a fuel cut then takes place. Since the ignition temperature is already reached in some cases by a large heat flow in the exhaust gas during acceleration, heating which would otherwise occur by measures within the motor can not occur. Measures within the motor, such as lambda splitting (Split), with late injection or inefficient combustion for triggering an exothermic reaction in the exhaust gas and thus with hot exhaust gas and a large exhaust gas mass flow (for example by late ignition), involve additional fuel consumption and are disadvantageous in this respect. Furthermore, the particle filter temperature does not have to be kept high by motor-driven measures until it is sufficient for a plurality of and long coasting operating phases to occur. In modern internal combustion engines operated on gasoline, the coasting operating phases occur only less and less, since these internal combustion engines are usually operated at low rotational speed levels.

A preferred embodiment of the internal combustion engine is characterized in that the air-side end is connected to a secondary air pump, which can be used to pump air into the supply line, in a gas-conducting manner.

By using secondary air blowing, disturbances in the charging pressure generated in the intake system, which disturbances may occur as a result of the extraction of air from the intake system, can be avoided. A further advantage of this configuration is that a controlled continuous regeneration can be achieved, since the particulate filter can be kept in regeneration operation at low load (and therefore low boost pressure) during the ignition phase.

It is also preferred that the air-side end is connected to the intake system between an air compressor and a throttle valve of the intake system in a manner that allows air to be conducted. This design has the following advantages: an additional pump, for example an additional secondary air pump, can be dispensed with.

In addition, it is preferred that a controllable valve is arranged in the supply line between the secondary air pump or air compressor and the first exhaust-side end of the supply line in a gas-conducting manner. This design allows for controlled air delivery to the particulate filter as desired.

A further preferred embodiment of the internal combustion engine is characterized in that the device for introducing air has, in addition to the first exhaust-gas-side end, a second exhaust-gas-side end, and the second exhaust-gas-side end is connected upstream of the three-way catalyst in a gas-conducting manner to the exhaust system.

With this design, a three-way catalyst arranged upstream of the particulate filter can be used to heat the particulate filter. It is thus possible, when the internal combustion engine is operated with an air ratio λ of less than 1 and when the air supply is adjusted such that an air ratio of 1 is produced in the three-way catalytic converter, to initiate an exothermic reaction in the three-way catalytic converter, which enables heating of the particulate filter without having to endure the risk of overheating of components close to the motor, such as the turbine of the exhaust gas turbocharger.

In terms of method, it is preferred that the control of the intake air is carried out as a function of the temperature of the particle filter, wherein the intake air is provided that the temperature of the particle filter is above the ignition temperature of soot particles stored in the particle filter.

It is also preferable that, when extracting air to be introduced into the exhaust system from the intake system, such extraction is controlled so as not to fall below the boost pressure required to generate the required torque of the internal combustion engine.

It is also preferred for an internal combustion engine equipped with an electric additional compressor to be switched on if air for introduction into the exhaust system is taken from the intake system and the boost pressure is less than the boost pressure required to produce the required torque. This makes it possible to compensate for the fact that the exhaust gas turbocharger cannot absorb sufficient exhaust gas energy for the build-up of charging pressure under certain operating conditions.

A further preferred embodiment of the method is characterized in that the air is introduced during the ignition operation when the torque requirement is less than a predetermined torque threshold value.

It is also preferred that the air is introduced when the internal combustion engine is switched off.

After the acceleration phase, after the motor has been switched off, the exhaust system, and therefore the hot particle filter, which is still hot, can be regenerated when stationary, which can damage the components and possibly also parts of the exhaust system, since a temperature level critical for the components is reached. Blowing in (cold) fresh air may be used to reduce the temperature level on the particle filter in order to avoid critical temperatures after shutdown. Critical states can thus be avoided if air is blown in after the warm phase of the particle filter, depending on the load state. Such blowing-in can be effected, for example, by means of a secondary air pump or an electrical additional compressor when the motor is at rest. The heat removal from the particle filter can be improved by the material flow.

It is also preferred that the introduction of air into the exhaust system takes place additionally directly upstream of the three-way catalyst, and that the lambda value of the fuel-air mixture combusted in the combustion chamber of the internal combustion engine is adjusted in such a way that the exhaust gas produced thereby, together with the air introduced upstream of the three-way catalyst, results in a lambda value of 1.

This makes it possible to achieve targeted heating when controlling with rich λ and/or when controlling the blown-in air mass flow to exhaust gas λ =1, without damaging components in the vicinity of the motor, for example the turbine of the compressor.

By making full use of the hot phase of the particle filter, fuel savings can be achieved by, for example, an acceleration phase and a permanently achievable regeneration.

Other advantages can be derived from the description and the accompanying drawings.

It goes without saying that the features mentioned above and those yet to be described below can be used not only in the respectively indicated combination but also in other combinations or alone without departing from the scope of the invention.

Drawings

Embodiments of the invention are illustrated in the drawings and will be described in detail in the following description. The same reference numbers in different figures denote identical or at least functionally comparable components. In schematic form:

FIG. 1 shows a first embodiment of a device according to the invention, which operates as an air compressor with a secondary air pump;

fig. 2 shows a second embodiment of the device according to the invention, which operates with the compressor of an exhaust-gas turbocharger as an air compressor;

FIG. 3 shows a design of the apparatus of FIGS. 1 and 2; and

fig. 4 shows a flow chart as an embodiment of the method according to the invention.

Detailed Description

Specifically, FIG. 1 shows an internal combustion engine 10 with an intake system 12 and an exhaust apparatus 14 having a three-way catalyst 16 and a particulate filter 18 disposed downstream of the three-way catalyst 16. The internal combustion engine 10 is preferably an internal combustion engine that can be operated using gasoline as a fuel.

In the illustrated design, the intake system 12 has an air filter, an air mass meter 22, an air compressor 24, and an air mass regulator 26. The air mass adjusting element 26 is, for example, a controllable throttle valve.

The internal combustion engine 10 has at least one combustion chamber 28 that is repeatedly filled with air from the intake system 12. The fuel injection valve 30 is used to inject gasoline into at least one combustion chamber 28. The charge of fuel-air mixture obtained in the at least one combustion chamber 28 is ignited by means of an ignition device 32, for example a spark plug. Exhaust gas 34 resulting from the subsequent combustion of the combustion chamber charge is discharged into the exhaust apparatus 14.

In the example shown, the exhaust apparatus 14 has a turbine 36 of an exhaust gas turbocharger 38. The turbine 36 is driven by the exhaust gas stream and itself drives the compressor of the air compressor 24. Instead of or in addition to the compressor of the exhaust-gas turbocharger 38, the air compressor 24 can also be realized as an electrically driven compressor or as an additional compressor 40, or as a mechanically driven compressor. In the exhaust gas mass flow, a three-way catalyst 16 is arranged downstream of the turbine 36. In the exhaust gas stream, downstream of the three-way catalyst 16, a particulate filter 18 is arranged. The particulate filter 18 filters soot particles from the exhaust gas stream. The soot filtered off is deposited in the particulate filter 18 and increases its flow resistance, which increases fuel consumption. Furthermore, as the soot deposit increases, the filtering effect decreases. For this reason, the particulate filter 18 must be repeatedly regenerated. The regeneration is carried out by burning carbon black in an exhaust gas atmosphere containing free oxygen under the condition that the exhaust gas temperature is high.

The exhaust system 14 has a device 42 for introducing air into the exhaust system 14 between the three-way catalyst 16 and the particle filter 18. With this arrangement 42, air may be introduced into the exhaust stream flowing into the particulate filter 18 as desired. In order to optimize exhaust gas cleaning in the three-way catalytic converter 16, internal combustion engines which are operated on gasoline are usually operated with a stoichiometric composition of the fuel-air mixture. The exhaust gas stream then contains virtually no free oxygen downstream of the three-way catalyst 16. The device 42 for introducing air has an inlet line 44 with at least one first exhaust-side end 46 which is connected to the exhaust system 14 in a gas-conducting manner and has an air-side end 48 via which air can be introduced into the inlet line 44 and the exhaust system 14. Via this supply line 44, the oxygen required for the regeneration of the particle filter 18 can be supplied to the exhaust gas stream as a constituent of the intake air.

In the embodiment shown in fig. 1, the air-side end 48 of the supply line 44 can be connected to a secondary air pump 50 as an air compressor, by means of which air can be pumped into the exhaust gas mass flow before the particle filter 18.

An air valve 52 is arranged in the air flow downstream of the secondary air pump 50, which, in parallel with the switching on of the secondary air pump 50, can be opened for supplying air to the exhaust gas and can be closed for preventing the supply of air to the exhaust gas. In this design, the air to be introduced is not taken from the intake system 12, but from the surroundings of the internal combustion engine 10.

Fig. 2 shows a design in which an air-side end 48 is connected to the intake system 12 so as to be able to conduct air between the air compressor 24 and the throttle 26 of the intake system 12. A controllable valve 54 is arranged in the supply line 44 between the air compressor 24 and the first exhaust-side end 46 of the supply line 44 in a gas-conducting manner. The controllable valve 54 can be opened for delivering air to the exhaust gas and can be closed for preventing air from being delivered to the exhaust gas. In this design, the air to be introduced is extracted from the air intake system 12. Instead of or in addition to the compressor of the exhaust-gas turbocharger 38, the air compressor 24 can also be realized as an electrically driven compressor or as an additional compressor 40, or as a mechanically driven compressor.

Fig. 3 shows a design that is compatible with both extracting air from the ambient to be delivered to the exhaust gas stream and extracting air from the air induction system 12 to be delivered to the exhaust gas stream. The feature of this embodiment is that the means for introducing air have a second exhaust-side end 47 in addition to the first exhaust-side end 46, and the second exhaust-side end 47 is connected to the exhaust system 14 upstream of the three-way catalyst 16 in a gas-conducting manner.

The controller 56 shown in fig. 1 to 3 controls the internal combustion engine 10 and for this purpose processes signals from sensors of the internal combustion engine 10 and outputs control signals for controlling the internal combustion engine 10 to a control unit of the internal combustion engine. In the illustrated design, these sensors include the air mass meter 22, a rotational speed sensor 58 that detects the rotational speed of the internal combustion engine 10, and a driver intent transmitter 60 that detects the driver's torque request. This list is not exhaustive. The internal combustion engine 10 may have further sensors, in particular sensors for detecting pressure and temperature. The differential pressure generated between the inlet and the outlet of the particle filter 18 can then be analyzed, for example, as a measure of the load state of the particle filter 18. The differential pressure increases as the load increases. The exhaust gas temperature measured at the inlet of the particulate filter 18 or in the particulate filter 18 may be used to determine whether the temperature is high enough to initiate ignition of the deposited soot. Alternatively or additionally, however, the temperature and/or pressure can also be modeled by the controller 56 using a computational model based on signals from other sensors.

In the illustrated embodiment, the control device comprises in particular gas-conducting

valves

52, 54 for controlling the introduction of air into the exhaust gas stream, a secondary air pump 50 which is present in one embodiment, and an electrically driven supplementary compressor 40 which is present in another embodiment, as well as an electrically controllable coupling of the mechanically driven compressor. Furthermore, the air mass regulator 26, the injection valve 30 and the ignition device 32 belong to the regulators which can be controlled by the controller 56. This list is also not exhaustive.

Fig. 4 shows a flow chart as an embodiment of the method according to the invention. From main routine 100 for controlling the internal combustion engine, step 102 is reached, in which it is checked whether the conditions under which the introduction of air into the exhaust gas stream flowing into the particle filter is to take place are met. The presence of these conditions is based, in particular, on the assumption that the measured or modeled temperature of the particle filter is at the ignition temperature of the soot particles stored in the particle filter.

In an alternative or additional embodiment, the spark operation is carried out with torque requests which are less than a predetermined torque threshold.

In another alternative or additional embodiment, it is provided that the internal combustion engine is switched off and it is desired to introduce air in order to cool the particle filter.

When the conditions are met, the process moves to step 104 where the introduction of air into the exhaust gas stream is initiated or maintained and controlled. Depending on the design, this triggering takes place by switching on the secondary air pump or by opening one or all of the valves which can conduct the gas, if appropriate additionally by switching on an electrically operated additional compressor or compressor.

The control performed in step 104 is performed in such a way that the boost pressure required to generate the required torque of the internal combustion engine is not lower for a device having an exhaust gas turbocharger as an air compressor. If there is a risk of the air being drawn being below the charging pressure of the exhaust gas turbocharger required to generate the required torque, and if an electric additional compressor is present, it is switched on. This prevents or reduces an undesirable drop in the boost pressure. When there is no longer a danger, the additional compressor is switched off again. The boost pressure is known in modern motor control by measurement or modeling within the controller.

In one embodiment of the device, in addition to the introduction of air into the exhaust gas mass flow between the three-way catalyst and the particle filter, the introduction of air into the exhaust system takes place directly upstream of the three-way catalyst, and in this embodiment, the lambda value of the fuel-air mixture combusted in the combustion chamber of the internal combustion engine is set in such a way that the resulting exhaust gas, together with the air introduced upstream of the three-way catalyst, yields a lambda value of 1. This produces an exhaust gas atmosphere which reacts exothermically in the three-way catalytic converter, the heat of reaction of which heats the downstream particle filter in order to reach or maintain the ignition temperature.

In step 106, it is repeatedly checked during the introduction of air whether another introduction of air is to be performed. If this is not the case, the introduction of air is ended in step 108 and the method returns to the main routine executed in step 100.

Claims

1. An internal combustion engine (10) having an intake system (12) and an exhaust system (14) with a three-way catalyst (16) and a particle filter (18) arranged downstream of the three-way catalyst (16), characterized in that the exhaust system (14) has a device (42) for introducing air into the exhaust system (14) between the three-way catalyst (16) and the particle filter (18).

2. Internal combustion engine (10) according to claim 1, characterised in that the device (42) for introducing air has an inlet line (44) with at least one first exhaust-side end (46) which is connected to the exhaust system (14) in a gas-conducting manner and with an air-side end (48) via which air can be introduced into the inlet line (44) and into the exhaust system (14).

3. Internal combustion engine (10) according to claim 2, characterised in that the air-side end (48) is connected in a gas-conducting manner to a secondary air pump (50) with which air can be pumped into the supply line (44).

4. Internal combustion engine (10) according to claim 2, characterized in that the air-side end (46) is connected to the air intake system (12) in a gas-conducting manner between an air compressor (24) of the air intake system (12) and an air mass regulator (26).

5. Internal combustion engine (10) according to claim 3 or 4, characterized in that a controllable valve (52; 54) is arranged in the supply line (44) in a gas-conducting manner between the secondary air pump (50) or the air compressor (24) and the first exhaust-side end (46) of the supply line (44).

6. An internal combustion engine (10) according to any one of claims 2 to 5, characterized in that the means (42) for introducing air has a second exhaust-side end (47) in addition to the first exhaust-side end (46), and the second exhaust-side end (47) is connected to the exhaust apparatus (14) upstream of the three-way catalyst (16).

7. A method for controlling an internal combustion engine (10) having an intake system (12) and an exhaust apparatus (14) with a three-way catalyst (16) and a particulate filter (18) arranged downstream of the three-way catalyst (16), characterized by controlling the introduction of air into the exhaust apparatus (14) between the three-way catalyst (16) and the particulate filter (18).

8. The method according to claim 7, characterized in that the introduction of air is controlled as a function of the temperature of the particle filter (18), wherein the introduction of air is provided on the premise that the temperature of the particle filter (18) is above the ignition temperature of soot particles stored in the particle filter (18).

9. A method according to claim 8, characterised in that when extracting air from the intake system (12) to be introduced into the exhaust equipment (14), this extraction is controlled so as not to fall below the boost pressure required in order to produce the required torque of the internal combustion engine (10).

10. A method according to claim 9, characterized in that for an internal combustion engine (10) equipped with an electric additional compressor (40), the electric additional compressor (40) is switched on if air for introduction into the exhaust apparatus (14) is taken from the intake system (12) and the boost pressure is less than the boost pressure required to produce the required torque.

11. A method according to any one of claims 7 to 10, wherein the introduction of air is carried out during ignition operation when the torque requirement is less than a predetermined torque threshold.

12. The method as claimed in claim 7, characterized in that the introduction of air takes place when the internal combustion engine (10) is switched off.

13. A method as claimed in any one of claims 7 to 11, characterized in that the introduction of air into the exhaust system (14) takes place additionally directly upstream of the three-way catalyst (26), and the lambda value of the fuel-air mixture combusted in the combustion chamber (28) of the internal combustion engine (10) is adjusted in such a way that the exhaust gases produced in this way, together with the air introduced before the three-way catalyst (16), result in a lambda value of 1.