DE102021205170A1 - Internal combustion engine with a secondary air line branching off downstream of a fresh gas compressor - Google Patents

Abstract

Internal combustion engine with an internal combustion engine (1), a fresh gas line (5) in which a fresh gas compressor (13) is integrated, an exhaust line (9) in which an exhaust gas aftertreatment component is integrated, and a secondary air line (19) in which a secondary air blower (21 ) is integrated and which branches off from the fresh gas line (5) downstream of the fresh gas compressor (13) and opens into the exhaust line (9) upstream of the exhaust gas aftertreatment component.

Description

The invention relates to an internal combustion engine with an internal combustion engine, a fresh-gas line in which a fresh-gas compressor is integrated, an exhaust line in which an exhaust gas after-treatment component is integrated, and a secondary air line in which a secondary air fan is integrated and which branches off from the fresh-gas line and upstream of the exhaust gas after-treatment component in the exhaust line opens.

The use of secondary air systems for secondary air injection is known from internal combustion engines with spark-ignited internal combustion engines. In such a secondary air injection, after a cold start of the internal combustion engine, air is usually introduced via a secondary air line, which branches off from a fresh gas branch supplying the internal combustion engine with fresh gas, into a section of an exhaust branch located upstream of an exhaust gas aftertreatment device. At the same time, the combustion air ratio of the internal combustion engine is adjusted sub-stoichiometrically. This secondary air in conjunction with an increased exhaust gas temperature, which can be achieved, for example, by temporarily retarding the ignition angle, leads to the oxidation of unburned fuel components contained in the exhaust gas in an exothermic reaction within the exhaust system. The exothermic reaction accelerates the heating of the exhaust aftertreatment device.

Secondary air is usually conveyed as required by means of a secondary air blower integrated into the secondary air line. According to the DE 10 2007 057 603 A1 However, such a secondary air blower can be dispensed with if the secondary air line branches off from the fresh gas line downstream instead of upstream of a fresh gas compressor integrated in the fresh gas line, because a charge pressure generated by the fresh gas compressor can ensure a sufficient pressure drop across the secondary air line.

the DE 10 2018 209 698 A1 also discloses an internal combustion engine with a secondary air line which branches off from a fresh-gas branch downstream of a fresh-gas compressor.

The invention is based on the object of improving heating of an exhaust gas aftertreatment component integrated into an exhaust system of an internal combustion engine in conjunction with secondary air injection during a warm-up operating phase of the internal combustion engine.

This problem is solved in an internal combustion engine according to patent claim 1 . A method for operating such an internal combustion engine is the subject of patent claim 7. Advantageous configurations of the internal combustion engine according to the invention and preferred embodiments of the method according to the invention are the subject of the further patent claims and result from the following description of the invention.

An internal combustion engine according to the invention comprises an internal combustion engine, in particular an internal combustion engine operated at least temporarily with spark ignition, and a fresh gas line for supplying fresh gas to the internal combustion engine, a fresh gas compressor, which is preferably part of an exhaust gas turbocharger, being integrated in the fresh gas line. Furthermore, an internal combustion engine according to the invention comprises an exhaust line in which at least one exhaust gas aftertreatment component, in particular a three-way catalytic converter, and preferably also an exhaust gas turbine of the exhaust gas turbocharger are integrated. In addition, an internal combustion engine according to the invention comprises a secondary air line, in which a secondary air fan is integrated and which branches off from the fresh gas line downstream (with respect to the flow direction of fresh gas in the direction of the internal combustion engine) of the fresh gas compressor and upstream (with respect to the flow direction of exhaust gas starting from the internal combustion engine) of the exhaust gas aftertreatment component flows into the exhaust system.

An opening into the exhaust line is also understood to mean an opening into one or more outlet ducts of the internal combustion engine, which may be provided as a gas-carrying connection between a combustion chamber or several combustion chambers of the internal combustion engine and an exhaust manifold (as the section connected to a housing of the internal combustion engine) of the exhaust line .

Such an internal combustion engine according to the invention can advantageously be used to accelerate heating of the exhaust gas aftertreatment component during a warm-up operating phase of the internal combustion engine, in particular immediately after a cold start of the internal combustion engine, by the secondary air fan being operated at least temporarily, preferably permanently or always during the warm-up operating phase and thereby fresh gas is transferred to the exhaust line as secondary air. This secondary air (which, like the fresh gas, can consist primarily or entirely of air that was previously sucked in from the environment) or the oxygen contained therein is then burned with hydrocarbons contained in the exhaust gas to heat energy release, through which the heating of the exhaust aftertreatment component is accelerated. Against this background, it can make sense for the secondary air fan to be operated until the end of the warm-up operating phase.

The hydrocarbons can in particular already be contained in the raw exhaust gas generated by the internal combustion engine, for which purpose it can be provided within the scope of a method according to the invention that the internal combustion engine is substoichiometric at least temporarily, possibly permanently or always during the warm-up operating phase (λ < 1, for example in a range between λ =0.65 and λ = 0.95 in the combustion chamber) in order to ensure that the raw exhaust gas specifically includes relevant quantities of unburned hydrocarbons. In addition or as an alternative to this, however, provision can also be made for hydrocarbons to be introduced separately into the exhaust line in the form of fuel.

An operation of the internal combustion engine in which at least the exhaust gas aftertreatment component has an operating temperature that is below the associated light-off temperature (light-off temperature), from which it can be assumed that the exhaust gas aftertreatment component is sufficiently effective with regard to exhaust gas aftertreatment, is considered a "warm-up operating phase". A "cold start" is a start-up of the internal combustion engine in which at least the exhaust gas aftertreatment component has an operating temperature that corresponds approximately (i.e. with a deviation of up to 10 K, 20 K or 30 K) to the ambient temperature. A warm-up operating phase does not always have to follow a cold start or a start-up of the internal combustion engine with an operating temperature of the exhaust gas aftertreatment component that is below the light-off temperature; Rather, a warm-up operating phase can also begin with the internal combustion engine and in particular the internal combustion engine being previously operated in such a way that the previously exceeded light-off temperature is again undershot by a defined extent, as may be the case when the internal combustion engine is idling or overrun for a longer period of time can.

By contrast, normal operation of the internal combustion engine can be provided if at least the exhaust gas aftertreatment component has an operating temperature that corresponds to or is greater than the light-off temperature. In operation of an internal combustion engine according to the invention, a normal operating phase of the internal combustion engine can consequently follow the warm-up operating phase. In this normal operating phase it can be provided that the secondary air fan is not or never operated. In addition, it can be provided that the internal combustion engine is then not operated sub-stoichiometrically but, particularly preferably, stoichiometrically or with a stoichiometric combustion air ratio (λ≈1).

Stoichiometric operation of the internal combustion engine is also understood to mean operation in which the actual combustion air ratio fluctuates in a usually relatively narrow range of, for example, ± 1% or ± 3% or ± 5% around the exactly stoichiometric combustion air ratio (λ = 1), if this a stoichiometric combustion air ratio is or should be achieved on average over time. Such a fluctuation in the actual combustion air ratio can be a consequence of a reactive control and in particular a regulation of the combustion air ratio depending on the composition of the exhaust gas, as is fundamentally known, in particular using one or more lambda probes, which is/are arranged in the exhaust line. A so-called natural frequency control for the combustion air ratio can be implemented, in which the combustion engine is alternately operated in a defined way slightly rich, i.e. with a slightly sub-stoichiometric combustion air ratio (Ä < 1), and slightly lean, i.e. with a slightly super-stoichiometric combustion air ratio (Ä > 1). , whereby the desired stoichiometric operation occurs on average over time. Switching between rich and lean operation can take place when there are defined deviations from the stoichiometric combustion air ratio.

According to the invention, a “three-way catalytic converter” is understood to mean an exhaust gas aftertreatment component that at least converts carbon monoxide (CO), nitrogen oxides (NOx) and unburned hydrocarbons (HC) in the exhaust gas to carbon dioxide (CO ₂ ), nitrogen (N ₂ ) and water (H ₂ O ) can support catalytically.

In order to ensure oxidation of the oxygen introduced into the exhaust system via the secondary air with hydrocarbons, provision can furthermore preferably be made for targeted measures to be taken to produce relatively hot exhaust gas. These measures can aim in particular at the fact that the internal combustion engine already emits relatively hot (raw) exhaust gas, which can be achieved, for example, by deliberately retarding the ignition angle in the case of a spark-ignited configuration of the internal combustion engine. Additionally or alternatively However, other measures to achieve relatively hot exhaust gas, such as heating the exhaust gas by means of a heating device, and/or initial ignition of the mixture of hydrocarbons and oxygen in the exhaust gas by means of an ignition device, can also be provided.

Compared to the secondary air system, which is also most common in supercharged internal combustion engines, in which the secondary air line branches off upstream of the fresh gas compressor and in which a secondary air fan is provided and operated to ensure a sufficient mass flow of the secondary air routed via the secondary air line, an internal combustion engine according to the invention has the advantage that in addition to the secondary air blower, a boost pressure generated by the fresh gas compressor can be used to ensure fresh gas is conveyed as secondary air via the secondary air line. This allows, with a still relatively underperforming
(e.g. with an outlet pressure of 100 mbar) and thus cost-effectively dimensioned secondary air blower to transfer secondary air into the exhaust system even when the combustion engine is running at a load above the no-load load, in particular at a load that is 10% or 30% or 50% of the full load can be, is operated. This has the advantage that secondary air injection and the resulting heating of the exhaust gas aftertreatment component can also continue to be carried out, for example, when the internal combustion engine is essentially immediately after a cold start with a relatively high load and not only for a few seconds, as is often the case, when idling is operated. This can have an advantageous effect on the pollutant emission behavior of the internal combustion engine.

Compared to the secondary air systems, as from the DE 10 2007 057 603 A1 and the DE 10 2018 209 698 A1 are known, an internal combustion engine according to the invention has the advantage that due to the integration of the secondary air blower in the secondary air line, a sufficient mass flow of secondary air can also be guaranteed if no or only a relatively small compression of the fresh gas is effected by means of the fresh gas compressor, as is the case in particular may be the case during idling operation of the internal combustion engine.

As an alternative or in addition to the preferred design of an internal combustion engine, in which the fresh gas compressor is part of an exhaust gas turbocharger and can therefore be driven by means of an exhaust gas turbine, another drive for the fresh gas compressor can also be used, in particular by means of an electric motor (preferably as the sole drive or in one design as a exhaust gas turbocharger supported by an electric motor) and/or by the internal combustion engine itself.

According to a preferred embodiment of an internal combustion engine according to the invention, it can be provided that the secondary air line branches off from the fresh gas line immediately downstream of the fresh gas compressor, so that at least no functional component of the fresh gas line, in particular no throttle valve and no charge air cooler, is arranged between the fresh gas compressor and the branch of the secondary air line. In particular, only a branch-free section of the fresh-gas line can be arranged between the fresh-gas compressor and the branch of the secondary air line. A branch of the secondary air line directly from an outlet duct of the fresh gas compressor should also fall under this. In this way it can be ensured that in the area of the branch of the secondary air line there is the highest possible boost pressure and accordingly a correspondingly high pressure drop across the secondary air line, which has a positive effect on the conveying of secondary air via the secondary air line.

A secondary air valve is preferably integrated into the secondary air line. This can advantageously prevent exhaust gas, particularly when the secondary air fan is not in operation, from flowing unintentionally from the exhaust line via the secondary air line into the fresh gas line, which could have a negative effect on the operating behavior of the internal combustion engine. The secondary air valve can preferably be designed to be actively controllable. A configuration as a passive secondary air valve, for example as a non-return valve, which closes automatically in the event of excess pressure on the part of the exhaust line, can also be advantageously implemented.

Provision can then also preferably be made for the secondary air valve to be arranged in the secondary air line between the secondary air fan and the opening of the secondary air line in the exhaust line. As a result, the secondary air fan can be protected by the secondary air valve from being acted upon by hot exhaust gas originating from the exhaust line, which can have an advantageous effect with regard to the service life of the secondary air fan and/or allows the secondary air fan to be of relatively simple design.

In particular, if the secondary air fan is designed in such a way that it prevents gas from flowing through when not in operation, and it can also withstand sufficient thermal loads, a secondary air valve can also be dispensed with.

According to a further preferred embodiment of an internal combustion engine according to the invention, it can be provided that a throttle valve is integrated in the fresh gas line between the fresh gas compressor and the internal combustion engine. This throttle valve can basically be provided for a power control of the internal combustion engine, in that the mass flow of the fresh gas that is supplied to the internal combustion engine can be controlled and in particular regulated by this due to a needs-based throttling of the fresh gas flow. If, in such an internal combustion engine, the secondary air line between the fresh-gas compressor and the throttle valve branches off from the fresh-gas line, as is preferably provided, operation of such an internal combustion engine according to the invention can provide that the throttle valve is at least partially and in particular relatively largely, i.e. is closed to a greater extent than during normal operation, as a result of which a particularly high pressure of the fresh gas can be achieved in the area of the branching off of the secondary air line.

The internal combustion engine of an internal combustion engine according to the invention can be operated both with liquid fuel (ie in particular gasoline) and with a gaseous fuel (in particular natural gas, LNG or LPG).

The invention also relates to a motor vehicle, in particular a wheel-based and non-rail-bound motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention. The internal combustion engine of the internal combustion engine can be provided in particular for the (direct or indirect) provision of the driving power for the motor vehicle.

• 1: eine erfindungsgemäße Brennkraftmaschine in vereinfachter Darstellung.

The invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawings. In the drawing shows:

• 1 : an internal combustion engine according to the invention in a simplified representation.

the 1 shows an internal combustion engine according to the invention for a motor vehicle. This comprises an internal combustion engine 1, which is designed, for example, in the form of a reciprocating piston engine with four cylinder openings 2 arranged in a row. The cylinder openings 2 delimit a combustion chamber 4 with reciprocating pistons 3 and a cylinder head movably guided therein. During operation of the internal combustion engine 1 and thus the internal combustion engine, fresh gas is supplied to these combustion chambers 4 via a fresh gas line 5, with the fresh gas being supplied by means of inlet valves 6, which are connected to the individual Combustion chambers 4 are assigned, is controlled. The fresh gas is exclusively or mainly air that has been sucked in from the environment and cleaned by means of an air filter 7 . Exhaust gas that is produced during the combustion of mixture quantities, which consists of the fresh gas and fuel injected directly into the combustion chambers 4 via fuel injectors 8, is discharged via an exhaust system 9 of the internal combustion engine, with the exhaust gas being discharged by means of outlet valves 10, which also are assigned to individual combustion chambers 4, is controlled. The exhaust gas flows through an exhaust gas after-treatment device 11, which is intended to remove components of the exhaust gas that are regarded as pollutants from the exhaust gas or to convert them into harmless components.

The quantities of mixture in the combustion chambers 4 are ignited by means of electrical ignition devices 12 which, for example, generate ignition sparks (spark plugs).

The internal combustion engine is supercharged, for which purpose a fresh-gas compressor 13 is integrated into the fresh-gas line 5 . The fresh gas compressor 13 is part of an exhaust gas turbocharger, which also includes an exhaust gas turbine 14 that is integrated into the exhaust line 9 . Exhaust gas that flows through the exhaust gas turbine 14 leads to a rotating drive of a turbine impeller, which is connected to a compressor impeller of the fresh gas compressor 13 via a shaft 15 in a rotationally driving manner, so that the result is that the fresh gas compressor 13 is driven by the exhaust gas turbine 14. A charge air cooler 16 is integrated into the fresh gas line 5 downstream of the fresh gas compressor 13, through which the fresh gas (so-called charge air) compressed by means of the fresh gas compressor 13 and thereby heated is cooled as required.

The exhaust gas aftertreatment device 12 comprises at least one exhaust gas aftertreatment component in the form of a three-way catalytic converter 17, which can also be configured integrally with a particle filter (i.e. as a four-way catalytic converter).

During operation of the internal combustion engine 1, the fresh gas to be supplied to it and the quantities of fuel to be introduced into the individual combustion chambers 4 by means of the fuel injectors 8 per working cycle are targeted as a function of the specific operating state of the internal combustion engine 1, which is defined in particular by the required load and the operating speed set. For this purpose, with regard to the fresh gas, the operating position of a downstream of the intercooler 16 integrated into the fresh gas line 5 throttle valve 18 can be changed in a targeted manner.

During normal operation of the internal combustion engine, all of the combustion chambers 4 of the internal combustion engine 1 are supplied with the fuel and the fresh gas in such a way that a stoichiometric combustion air ratio is established. The setting of the combustion air ratio can be controlled in particular as a function of a measurement of the oxygen content in the exhaust gas, which can be determined using at least one lambda probe (not shown).

The internal combustion engine also includes a secondary air line 19 via which fresh gas can be branched off from the fresh gas line 5 as required and transferred to the exhaust line 9 as secondary air. The secondary air line 19 preferably branches off from the fresh gas line 5 in that section of the fresh gas line 5 which is located between the fresh gas compressor 13 and the charge air cooler 16 . Alternatively, however, provision can also be made for the secondary air line 19 to branch off from one of the sections that are located between the charge air cooler 16 and the throttle valve 18 or else downstream of the throttle valve 18, as is shown in FIG 1 is shown with dashed lines.

The secondary air line 19 opens directly downstream of the internal combustion engine 1 and thus both upstream of the exhaust gas after-treatment device 11 and the exhaust gas turbine 14 in an exhaust manifold 20 of the exhaust line 9, with one opening of the secondary air line 19 in each of the individual channels of the exhaust manifold 20, each with one or more outlet channels of a combustion chamber 4 of the internal combustion engine 1 is connected in a gas-carrying manner. These individual channels open into a collecting channel of the exhaust manifold 20 in which the raw exhaust gas originating from the individual combustion chambers 4 is collected and mixed.

In the secondary air line 19, starting from the branch from the fresh gas line 5, first an electric motor-driven secondary air fan 21 and then a secondary air valve 22 is integrated.

During a warm-up operating phase and in particular immediately after a cold start of the internal combustion engine, it is provided that the internal combustion engine 1 is operated with a sub-stoichiometric combustion air ratio. As a result, the raw exhaust gas generated by the internal combustion engine 1 contains relatively large amounts of unburned hydrocarbons. At the same time, a relatively high temperature of the exhaust gas is achieved by retarding the ignition angle at which ignition of the fuel/fresh gas mixture amounts in the individual combustion chambers 4 takes place by means of the ignition devices 12 . And again at the same time, the secondary air fan 21 is operated and the secondary air valve 22 is opened (in the case of an actively controllable configuration of the secondary air fan 21) or this opens automatically (in the case of a passive configuration), as a result of which secondary air is guided via the secondary air line 19 and introduced into the exhaust line 9. The oxygen contained in the secondary air then oxidizes with the hydrocarbons in the exhaust gas, with the relatively high temperature of the exhaust gas ensuring that this oxidation process takes place.

The thermal energy released by the oxidation of the oxygen with the hydrocarbons is used in particular to heat up the exhaust gas aftertreatment device 11 as quickly as possible until the light-off temperature of at least the three-way catalytic converter 17 contained in it is reached. It is provided that the corresponding operation of the internal combustion engine, i.e. the sub-stoichiometric operation of the internal combustion engine 1 in combination with the retarding of the ignition angle and the introduction of secondary air into the exhaust system 9, be carried out with as little interruption as possible until at least the three-way catalytic converter 17 has reached its light-off temperature. Until this is the case, the internal combustion engine 1 may already be or may have been operated with a load that is above, in particular also significantly above, the idling load. This can be the case, for example, when the internal combustion engine is used immediately after a cold start for a strongly accelerating drive of the motor vehicle driven by it. Operating the internal combustion engine 1 with a relatively high load leads to a relatively high pressure of the exhaust gas in the area of the openings of the secondary air line 19. In a conventional internal combustion engine, in which the secondary air line 19 consists of a section of the fresh-gas line 5 that is located upstream of the fresh-gas compressor 13 branched off, the introduction of secondary air into exhaust gas rank 9 would either have to be interrupted, because the intended secondary air blower 21 is not powerful enough to promote secondary air against exhaust gas pressure in exhaust gas rank 9, or the secondary air blower 21 should be designed accordingly in order to be powerful in order to to enable this, which would, however, be associated with correspondingly high costs and also a correspondingly large space requirement for the secondary air fan 21 .

The inventively provided branching of the secondary air line 19 downstream of the fresh gas compressor 13 avoids these disadvantages by an increase in pressure of the fresh gas generated by the fresh gas compressor 13 in the area of the branching off of the secondary air line 19 supports the (relatively small dimensioned) secondary air blower 21 in introducing secondary air into the exhaust system 9 even when the internal combustion engine 1 is operated at a relatively high load and thus a relatively high exhaust gas pressure in the area of the mouths of the secondary air line 19 is present. This support of the secondary air fan 21 by the fresh gas compressor 13 tends to be higher, the higher the load with which the internal combustion engine 1 is operated, because then, due to the correspondingly increasing exhaust gas enthalpy, the drive power generated by the exhaust gas turbine 14 for the fresh gas compressor 13 and thus the compression power of the fresh gas compressor 13 becomes larger. The support of the secondary air blower 21 by the fresh gas compressor 13 thus tends to be automatically adapted to the need for support.

reference list

1

combustion engine

2

cylinder opening

3

reciprocating

4

combustion chamber

5

fresh gas line

6

intake valve

7

air filter

8th

fuel injector

9

exhaust line

10

outlet valve

11

exhaust aftertreatment device

12

ignition device

13

fresh gas compressor

14

exhaust turbine

15

Wave

16

intercooler

17

three-way catalytic converter

18

throttle valve

19

secondary air line

20

exhaust manifold

21

secondary air blower

22

secondary air valve

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102007057603 A1 [0003, 0017]
• DE 102018209698 A1 [0004, 0017]

Claims (10)

Internal combustion engine with an internal combustion engine (1), a fresh gas line (5) in which a fresh gas compressor (13) is integrated, an exhaust line (9) in which an exhaust gas aftertreatment component is integrated, and a secondary air line (19) in which a secondary air fan (21 ) is integrated and which branches off from the fresh gas line (5) and opens into the exhaust line (9) upstream of the exhaust gas aftertreatment component, characterized in that the secondary air line (21) branches off from the fresh gas line (5) downstream of the fresh gas compressor (13). Internal combustion engine according claim 1 , characterized in that the secondary air line (19) branches off from the fresh gas line (5) immediately downstream of the fresh gas compressor (13). Internal combustion engine according claim 1 or 2 , characterized in that a secondary air valve (22) is integrated into the secondary air line (19). Internal combustion engine according claim 3 , characterized in that the secondary air valve (22) is arranged between the secondary air fan (21) and the mouth of the secondary air line (19) in the exhaust system (9). Internal combustion engine according to one of the preceding claims, characterized in that a throttle valve (18) is integrated in the fresh gas line (5) between the fresh gas compressor (13) and the internal combustion engine (1). Internal combustion engine according claim 5 , characterized in that the secondary air line (19) branches off from the fresh gas line (5) between the fresh gas compressor (13) and the throttle valve (18). Method for operating an internal combustion engine according to one of the preceding claims, characterized in that the internal combustion engine (1) is operated substoichiometrically at least temporarily during a warm-up operating phase of the internal combustion engine and the secondary air fan (21) is also operated. procedure according to claim 7 , characterized in that the secondary air fan (21) is also operated further when the internal combustion engine (1) is operated during the warm-up operating phase with a load lying above the idling load. procedure according to claim 7 or 8th , characterized in that the secondary air fan (21) is operated until the end of the warm-up operating phase. Method according to one of Claims 7 until 9 for operating an internal combustion engine according to claim 6 , characterized in that the throttle valve (18) is at least partially closed at least temporarily during the operation of the secondary air fan (21).

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