WO2004090297A2 - Internal combustion engine comprising an exhaust gas aftertreatment device in the exhaust tract - Google Patents

Abstract

Disclosed is an internal combustion engine comprising an exhaust system (102) with at least one exhaust tract (105) which is connected to the internal combustion engine (101) via an exhaust manifold (103). At least one exhaust gas aftertreatment device (104) is disposed downstream of the exhaust manifold (103). The exhaust gas aftertreatment device (104) and/or the exhaust tract (105) located upstream of the exhaust gas aftertreatment device (104) is/are embodied at least in part with a double wall.

Description

Internal combustion engine

The invention relates to an internal combustion engine with an exhaust system with at least one exhaust line, which is connected to the internal combustion engine via an exhaust manifold.

Various exhaust gas aftertreatment devices, such as catalytic converters or the like, are state of the art for meeting the legally required emission levels at the exhaust end of an internal combustion engine. The function of such exhaust gas aftertreatment devices is generally dependent on the operating temperature. There is a lower limit from which the pollutant reduction begins (e.g. in the catalytic converter the "light off") and an upper limit from which secondary emissions are formed (the diesel oxidation catalytic converter forms sulfates from approx. 400 ° C) or from which the Exhaust gas treatment device would be damaged (an Otto three-way catalytic converter is damaged approximately above 950 ° C). The rapid reaching of this temperature range or staying within it can generally be largely ensured by manipulating the mixture composition, ignition and position of the components within the exhaust system, although this ultimately has a disadvantageous effect on fuel consumption.

Various measures for cooling the exhaust line and the exhaust gas aftertreatment device are known in order to avoid exceeding the maximum permissible temperature.

US 3,747,346 A describes a temperature control system for a catalyst of an internal combustion engine. Upstream of a catalytic converter, an exhaust pipe is surrounded by a housing structure, an air gap for a cooling channel being formed between the housing structure and the exhaust pipe. The cooling channel has an air inlet in the start area of the housing structure and an air outlet in the end area of the housing structure. The housing structure and the cooling channel end upstream of the catalytic converter. Control flaps which are mechanically connected to one another are arranged in the region of the air inlet and the air outlet. The control flaps are actuated via a solenoid valve depending on the catalyst temperature. Air inlet and outlet are directly connected to the environment. Since a separate housing structure is required for cooling the exhaust pipe, the temperature control device is relatively complex. A similar exhaust system is known from DE 22 40 681 A.

EP 0 928 885 A2 shows an exhaust device with an exhaust manifold encased in a housing. US 3,820,327 A describes a temperature control device for a catalyst. Part of the exhaust pipe and the catalytic converter are surrounded by a separate cooling housing, the cooling air inlet of which is connected to the radiator fan chamber. By means of a changeover flap, the cooling air can optionally be conducted into the cooling housing for cooling the catalytic converter or around the cooling housing. This cooling device is also relatively complex, since a separate cooling housing is required.

From Japanese published patent application JP 09-133 019 A, an air-gap-insulated cup manifold for an exhaust gas system of an internal combustion engine is known, which has an inner tube carrying the exhaust gas and an outer shell. An air gap is formed between the inner tube and the outer shell. The outer shell has a plurality of openings through which an external air flow is blown into the air gap due to the wind. The cooling air leaves the air gap in the end area of the manifold. Control of the cooling is not provided. An exhaust manifold formed by a double pipe construction is also known from EP 0 622 531 AI.

The publications US 5,983,628 A and US 5,987,885 A show exhaust systems for internal combustion engines with a catalytic converter in the exhaust line, a heat exchanger being arranged upstream of the catalytic converter, in which cooling air is blown cold via a blower across the exhaust stream to cool the hot exhaust gas. In addition, an electrical heating device is provided in the area of the heat exchanger in the exhaust line in order to reduce the light-off time of the catalytic converter on cold start. Both cooling and heating of the exhaust gas are, however, associated with a very high level of design and manufacturing complexity. Electrical resources are used to heat the exhaust gas, which places an additional load on the vehicle battery during start-up and warm-up operation of the internal combustion engine.

In particular with liquid-cooled diesel internal combustion engines with direct injection, there is the problem of an unsatisfactory heating output since not enough heat is introduced into the coolant. Exhaust ducts up to a connection flange surface for an exhaust pipe work are usually designed separately, the union of the exhaust ducts often only taking place in the exhaust pipe work designed as an exhaust manifold. Although such constructions enable a compact cylinder head, they have the disadvantageous effect that the surfaces of the exhaust ports wetted by the coolant are relatively small.

Cylinder heads are known from US Pat. No. 6,513,506 and US Pat. No. 4,329,843 A, in which the exhaust ports are connected to the flow within the cylinder head and the exhaust manifold is thus integrated into the cylinder head. such However, cylinder heads require a relatively high level of production expenditure and also have a disadvantageous effect on the size of the cylinder head.

Known internal and external outlet collectors have a closed design and require a considerable amount of casting technology.

Exhaust gas recirculation systems in certain classes of commercial vehicle and industrial engines should be as simple, robust and cost-effective as possible and should therefore be able to operate without complex actuation mechanisms (e.g. without variable valve train or electronic map control or the like). On the one hand, these exhaust gas recirculation systems should keep the exhaust gas recirculation rate as low as possible at a low engine speed in order not to deteriorate the response behavior and the starting torque of the engine. On the other hand, the exhaust gas recirculation rates in the relevant operating points of the emission cycle (e.g. at medium and high engine speed / high load) should be kept as large as possible in order to achieve the required NOx reduction in the emission cycle.

A diesel internal combustion engine with a cam-controlled internal exhaust gas recirculation is known from WO 03/040540 AI. Cam-controlled internal exhaust gas recirculation systems deliver relatively constant exhaust gas recirculation rates in the entire map area, but cannot be switched off due to their simple, inexpensive design. The course of the exhaust gas recirculation quantity over the speed can be influenced favorably by a suitable shape and position of the pre-lift cam, however, the influence on the exhaust gas recirculation rates is limited and compromises have to be made.

Simple, external exhaust gas recirculation systems, in turn, can only recirculate exhaust gas if the exhaust gas back pressure in front of the exhaust gas turbine is higher than the boost pressure in the intake manifold of the internal combustion engine. For commercial vehicles, however, with medium engine speed and high engine load, the problem arises that no exhaust gas can be recirculated due to the prevailing pressure conditions.

From JP 03-085362 A a diesel internal combustion engine with an internal and an external exhaust gas recirculation system is known. A shut-off flap is provided in the exhaust tract as well as in the intake tract to carry out the internal exhaust gas recirculation, so that the internal exhaust gas recirculation can take place by contraction of the intake air or the exhaust gases. The flaps and the exhaust gas recirculation valve in the exhaust gas recirculation line are controlled such that internal exhaust gas recirculation at low speed and low load and external exhaust gas recirculation in the other operating areas of the internal combustion engine leads. However, this type of control of the exhaust gas recirculation requires a considerable amount of control engineering.

Regeneration of exhaust gas aftertreatment systems in high-speed, direct-injection diesel engines is initiated by increasing the exhaust gas temperature using internal engine measures, such as by intake air throttling, if necessary by lowering the boost pressure, and in particular by one or more so-called post-injections of the fuel, that is to say by adding fuel after the actual main injection. This post-injection of the fuel usually takes place after the top dead center of the ignition has been exceeded.

To ensure the exhaust gas temperature required for regeneration at low load and speed, high post-injection quantities are required at very late times. This leads to drastically worsened exhaust emissions, severe fuel consumption disadvantages, as well as considerable entry of fuel into the engine oil. Furthermore, strong throttling or lowering of the boost pressure in turbo engines leads to poor responsiveness and reduced driving dynamics.

US Pat. No. 6,412,276 B1 discloses a system for regenerating a particle filter of a diesel internal combustion engine, which provides that fuel is injected into at least one cylinder during an expansion stroke in order to achieve an increase in the exhaust gas temperature.

US 2003/0056498 AI also describes a method for the regeneration of a particle filter of a diesel internal combustion engine, in which the temperature increase of the exhaust line is achieved by post-injection of fuel. An additional post-injection to increase the temperature of the exhaust gas for the initiation of the regeneration of a particle filter of a diesel engine is also known from WO 96/03571 AI.

The object of the invention is to avoid these disadvantages and to enable the exhaust gas temperature to be controlled in the simplest possible manner in order to improve the emissions with the lowest possible fuel consumption.

Another object of the invention is to reduce the manufacturing outlay for an outlet duct arrangement. Another object of the invention is to increase the heating power.

Furthermore, sufficiently high exhaust gas recirculation rates should be ensured in all engine load and speed ranges and smoke emission peaks should be avoided in particular in acceleration operation. Furthermore, it is an object of the invention to propose a method for the regeneration of exhaust gas aftertreatment systems with which fuel consumption disadvantages and an entry of fuel into the engine oil can be largely avoided.

According to the invention it is provided that at least one exhaust gas aftertreatment device is arranged downstream of the exhaust manifold, the exhaust gas aftertreatment device and / or the exhaust gas line upstream of the exhaust gas aftertreatment device being at least partially double-walled, at least one gap forming a channel being formed between an exhaust gas-carrying inner wall and an outer wall a heat-transferring medium can be flowed through, and the channel preferably has an inlet in an initial region of the exhaust manifold and an outlet preferably in the end region of the exhaust gas aftertreatment device. It can be provided that the channel can be heated by a heat source preferably formed by an additional heating device, it being particularly advantageous if the additional heating device is a calorific heating device and has an exhaust gas line for the burner exhaust gas, which can be connected to the entry of the channel.

Additional heating devices, for example based on a burner, are widely used today for comfort reasons for vehicle interior heating. In the case of efficient diesel vehicles in particular, short-term interior heating can only be achieved by means of additional heating devices. The fact that the hot burner exhaust gas from the additional heating device is used to heat the exhaust line upstream of the catalytic converter means that no additional energy resources of the vehicle are consumed. The design effort is extremely low if an additional heating device already provided in the vehicle area is used.

In order to be able to control the temperature of the exhaust gas aftertreatment device at both the lower and the upper limit, it is particularly advantageous if the inlet can be functionally connected to the heat source or a heat sink by a switching element. The design effort can be kept very low if the heat sink is formed by a cooling device working with air as the cooling medium, preferably having a blower. It is particularly advantageous if the heat sink is formed by a secondary air blower. Secondary air blowers are usually used for exhaust gas dilution during the start-up and warm-up phase of an internal combustion engine operated here in rich grease. As an additional function, the secondary air blower can act as a heat sink.

In a further embodiment of the invention it can also be provided that the heat sink and the heat source are formed by the same component. Beispiels- the burner of an additional heating device can be used as a heat sink in the deactivated state, that is to say when the fuel supply is switched off.

To simplify production, it is further provided according to the invention that in the cylinder head of the internal combustion engine, in particular liquid-cooled diesel internal combustion engine, at least one outlet channel per cylinder, which is at least partially surrounded by a cooling space, is arranged, at least one group of outlet channels being connected to one another in the area of the cylinder head are and leads to a common exhaust pipe work connected to a flange face of the cylinder head, and wherein the flow connection between the exhaust ports is formed by at least one connection channel molded into the cylinder head in the area of the flange face and having a cross section open to the flange face.

A particularly simple manufacture is possible if the connecting channel runs essentially parallel to the flange surface, it preferably being provided that the outlet channels open into the connecting channel transversely, preferably approximately at a right angle. This enables the cylinder head to be molded in easily. Because the connecting duct is partially formed in the cylinder head, the exhaust pipe work can be designed very simply and without a core. It can be provided that the connecting duct is partially formed by the exhaust pipe work, preferably at least half the cross section of the connecting duct being formed in the cylinder head. The outlet tube mill therefore only has to accommodate a part of the connecting channel and can be designed to be open.

The heating power can be increased in that the wall of the connecting duct borders a cooling space at least on the side of the cylinder head. The contact area between the exhaust system and the engine coolant can thus be significantly increased and thus the performance of the vehicle heating can be improved.

In a further embodiment of the invention, it is provided that at least two connecting channels with a cross section open to the flange surface are at least partially molded into the cylinder head, a group of outlet channels opening into each of the connecting channels. The exhaust ports can be grouped depending on the ignition sequence, so that mutual interference between the cylinders can be excluded. It can be provided that the connecting channels in the exhaust pipe work are arranged separately, preferably one above the other - in the cylinder axis direction. Cost-effective, accurate and reliable production is possible if the outlet tube works are free of undercuts and can be manufactured using the permanent mold casting process.

In order to ensure sufficiently high exhaust gas recirculation rates in all engine load and speed ranges, it is provided according to the invention that the internal combustion engine has an internal exhaust gas recirculation system that is controlled in particular independently of the load, preferably by means of a pre-lift cam, and that an external exhaust gas recirculation system is additionally provided with at least one exhaust gas recirculation valve that can be controlled via at least one control line is, preferably at least one delay element being arranged in the control line.

It is essential that the internal and external exhaust gas recirculation system uses the simplest control means. The purely mechanical internal exhaust gas recirculation system can be designed moderately, so that sufficiently high exhaust gas recirculation rates result in the medium speed range and almost no exhaust gas is recirculated at low speed.

The desired increasing exhaust gas recirculation rate at high engine speed results from a suitable selection of the exhaust pipe diameter of the external exhaust gas recirculation system in a wide operating range of the internal combustion engine due to the prevailing pressure conditions. Active control of the external exhaust gas recirculation rate is only required in low partial load operation and in transient operation.

Due to the time delay element in the control line, exhaust gas recirculation rates which are too high and which would generate soot emission peaks are avoided in transient operation.

The time delay element can be mechanical in nature, wherein it is preferably provided that the control line is a pneumatic control pressure line and the mechanical delay element has a pressure container. An orifice is provided at the inlet of the control pressure line. The control pressure line is either connected to the inlet manifold or to a vacuum pump. The tank is only slowly filled or slowly emptied through the orifice, which means that the switching pressure for the exhaust gas recirculation valve is only built up or reduced with a time delay. Smoke emissions in acceleration mode due to excessive exhaust gas recirculation quantities are thus effectively avoided.

The vacuum pump can be driven mechanically by the internal combustion engine or also electrically. In a particularly simple embodiment of the invention it is provided that the vacuum pump can be switched depending on the position of the injection pump. A mechanical switch on the injection pump switches vacuum to the control line of the exhaust gas recirculation valve depending on the injection pump position. The vacuum opens the exhaust gas recirculation valve. In order to delay the switching time of the exhaust gas recirculation system in the transient acceleration process, a pressure vessel is again provided as a mechanical delay element, the pressure vessel being brought to negative pressure by the vacuum pump.

As an alternative to this, it can also be provided that the exhaust gas recirculation valve is connected to an electronic control unit via an electrical control line and can be switched directly and electrically via this depending on the load. In this case, the time delay element is also of an electrical type and can be integrated directly into the electronic control unit.

For regeneration of the exhaust gas aftertreatment system for an internal combustion engine, in particular a diesel internal combustion engine with direct injection, it is further provided according to the invention that the regeneration is initiated by at least one internal measure depending on the temperatures of the exhaust gas aftertreatment system, preferably for initiating and carrying out the regeneration

a) the internal engine load is increased if the temperature of the exhaust gas aftertreatment system is lower than a defined regeneration temperature,

b) when the regeneration temperature of the exhaust gas aftertreatment system is reached, the injection timing and / or the control time of at least one gas exchange valve of at least one cylinder is adjusted such that ignition of the injected fuel is not possible, so that the unburned fuel is stored upstream of the exhaust gas aftertreatment system,

c) after the regeneration temperature of the exhaust gas aftertreatment system has been reached, the fuel injection is switched off in at least one cylinder and the cylinder is operated as an air delivery device for the exhaust gas aftertreatment system.

To increase the internal engine load in step a), the control of the gas exchange valves can be carried out in such a way that maximum compression work is generated. This can be achieved, for example, by temporarily not opening the exhaust valve or valves. It is preferably provided that the fuel injection is suspended in the cylinder performing the maximum compression work. This avoids increased fuel consumption. To increase To prevent the entry of fuel into the engine oil, it is particularly advantageous if one or more cylinders are operated alternately with normal and increased internal engine load.

To initiate regeneration, the internal engine load is increased, especially at low loads and in the low speed range. For this purpose, especially in less dynamic or stationary driving conditions, following an algorithm, the number of injections per cylinder is applied such that e.g. With a 4-cylinder four-stroke engine, not every 720 ° crank angle is injected, but depending on the map in even or odd multiples of 720 °. In order to maintain a certain engine load speed state, the injection mass required by the suspension of an injection is compensated. For this purpose, the correction injection masses are calculated using freely applicable maps. At the same time, the control time of the gas exchange valves is modified in such a cylinder in which no injection takes place in such a way that maximum compression work is generated. This is done, for example, by temporarily not opening at least one outlet valve. By compensating the injection mass after a previous suspension of the injection of the forerunner cylinder and by increasing the compression work, the indicated mean pressure is increased at the same effective mean pressure, whereby the exhaust gas temperature can be increased even without post-injection.

If the exhaust gas aftertreatment system has the desired regeneration temperature, fuel is injected into individual cylinders and / or individual cycles under such conditions that self-ignition can be ruled out. This can be achieved by appropriate selection of the control times or the injection timing, for example by injecting a small fuel mass below the auto-ignition conditions and at the same time opening at least one exhaust valve shortly after the top dead center of the ignition. This ensures that the injected fuel mass does not ignite and is available as an unburned hydrocarbon to the exhaust gas aftertreatment system to initiate an exothermic reaction. Due to the pressure drop, the fuel mass injected for hydrocarbon generation is discharged directly on the outlet side. The entry of fuel into the engine oil is significantly reduced with the same level of hydrocarbon availability compared to the conventional method by means of post-injection.

After the initiation of the exothermic reaction - after "ignition", for example, loading a particle filter - the addition of additional hydrocarbons to support regeneration is no longer necessary. To maintain the burning process, sufficient oxygen must be available for regeneration. To achieve this, according to method step c) at least one cylinder is operated temporarily as an air delivery device. The fuel injection and the control times are switched off in this cylinder adjusted at the same time so that after the hydrocarbon has been deposited after process step b), the oxygen required for the exothermic reaction is provided exactly. This is achieved in particular by optimizing the outlet opening times for air delivery. There is therefore no combustion in this cylinder, which means that the oxygen content in the cylinder filling is completely retained. Even in map areas with a conventionally low residual oxygen content, the amount of oxygen required to provide an optimal exothermic reaction can be measured. The exhaust gas temperature after the exhaust gas aftertreatment system is raised significantly, emission breakthroughs after the exhaust gas aftertreatment system are significantly minimized.

The method according to the invention is suitable for exhaust gas aftertreatment systems with catalysts and particle filters.

The invention is explained in more detail below with reference to the figures. Show it:

1 shows an outlet duct arrangement of an internal combustion engine according to the invention in a first embodiment variant,

2 shows this outlet duct arrangement in a section along the line II-II in FIG. 1,

3 shows the outlet duct arrangement in a section along the line III-III in FIG. 1,

4 shows an outlet duct arrangement according to the invention in a second embodiment variant,

5 shows this outlet duct arrangement in a section along the line V-V in FIG. 4,

6 shows this outlet duct arrangement in a section along the line VI-VI in FIG. 4,

7 an internal combustion engine in an embodiment variant according to the invention,

8 an internal combustion engine in a further embodiment variant according to the invention,

9 shows an internal combustion engine according to the invention in a schematic view,

10 shows the pressure conditions in the intake manifold and in front of the turbine, 11 shows the exhaust gas recirculation rates of the combined exhaust gas recirculation system according to the invention in comparison to internal exhaust gas recirculation systems and

Fig. 12 shows a compressor map with engine operating lines.

Parts with the same function are given the same reference numerals in the figures.

The exhaust port arrangement 1 has a plurality of exhaust ports 3a, 3b, 3c, 3d arranged in the cylinder head 2. In the area of a flange surface 4 for an exhaust pipe work 5 connected to the cylinder head 2, a connecting channel 6 is arranged, which is formed partly by the cylinder head 2 and partly by the exhaust pipe work 5. The connecting channel 6 has an open cross section both in the cylinder head 2 and in the exhaust pipe work 5 and is arranged approximately parallel to the flange surface 4. The outlet channels 3a, 3b, 3c, 3d open into the connecting channel 6 transversely, advantageously approximately at a right angle. Due to the position of the connecting channel 6, the outlet tube 5 can be produced without a core, that is to say, for example, using the mold casting process.

In the embodiment variant shown in FIGS. 1 to 3, the outlet channels 3a, 3b, 3c, 3d all open into a single connecting channel 6, from which a single outlet tube 7 extends.

In contrast, in the embodiment shown in FIGS. 4 to 6, two outlet channels 3a, 3d and 3b, 3c are combined to form a group A ', B', each group A ', B' of outlet channels 3a, 3d or 3b, 3c opens into a connecting channel 6a or 6b. Each of the connecting channels 6a, 6b opens into an outlet tube 7a, 7b of the outlet tube assembly 5, wherein connecting channels 6a, 6b and outlet tubes 7a, 7b are - at least partially - arranged one above the other.

In order to increase the heating power of the internal combustion engine, the walls 6 ', 6a', 6b 'of the connecting channels 6, 6a, 6b border on cooling rooms through which coolant flows. This significantly increases the contact area between the exhaust system and engine coolant and thus decisively improves the performance of the vehicle heating.

The internal combustion engine 101 shown in FIGS. 7 and 8 has an exhaust system 102 with an exhaust manifold 103, which is arranged upstream of an exhaust gas aftertreatment device 104 formed by a catalytic converter in the exhaust line 105. A silencer 106 is located in the exhaust line downstream of the exhaust gas aftertreatment device 104. The exhaust line 105 is configured between the exhaust manifold 103 and the exhaust gas aftertreatment device 104, wherein an air gap forming a channel 109 is formed between the inner wall 107 carrying the exhaust gas and the outer wall 108. The annular channel 109 has an inlet 110 at the beginning of the exhaust manifold 103 and an outlet 111 at the end of the exhaust gas aftertreatment device 104. In the area of the outlet 111, the channel 109 can open into the exhaust line 105 via a connecting line 112 at a point 113 downstream of the muffler 106. The inlet 110 can be connected to a heat source 115 via a switching element 114.

The heat source 115 is formed by a calorific additional heater 116, the exhaust pipe 117 of which can be brought into flow connection with the channel 109 by the switching element 114.

It is also possible for the additional heating device 116 to heat air and to supply it to the channel 109 instead of the burner exhaust gas.

If the temperature of the exhaust gas aftertreatment device 104 is below the target temperature range, the additional heating device 116 either heats up air or uses the hot burner exhaust gas directly and conducts it via line 117 into the channel 109, as a result of which the exhaust system 105 between the internal combustion engine 101 and the exhaust gas aftertreatment system 104 is heated.

In the embodiment variant shown in FIG. 8, the inlet 110 can optionally be connected to a heat source 115 or a heat sink 118. The heat source 115 is advantageously formed by a cooling device 119 with a fan 120 that works with air as the cooling medium. Via the switching element 114, the inlet 110 can optionally be flow-connected to the exhaust gas line 117, the additional heating device 116 or to the air line 121 of the air cooling system 119. Below the target temperature, the exhaust gas aftertreatment device 104 is heated by connecting the inlet 110 to the exhaust gas line 117. When the lower target temperature is reached, the connection to the inlet 110 can be disconnected via the switching element 114, so that there is neither additional heating nor cooling of the exhaust line 105. If the upper temperature limit of the exhaust gas aftertreatment device 104 is exceeded, the exhaust gas system 102 is connected to the heat sink 118 by establishing a flow connection between the inlet 110 and the air line 121 via the switching element 114. The fan 120 conveys cool ambient air through the channel 109 and cools the exhaust system 102 accordingly.

9 shows the internal combustion engine 201 according to the invention in a schematic block diagram. The diesel internal combustion engine 201 has at least one cylinder 202, an intake system 203, an exhaust system 204, an internal exhaust gas recirculation system 205 and an external exhaust gas recirculation system 206. With loading Zugszeichen 207 denotes an exhaust gas turbocharger with a compressor 208 in the intake line 209 and a turbine 210 in the exhaust line 211. The turbine 210 can be bypassed via a bypass line 212. The inlet air enters the inlet line 209 via the air filter 213, is compressed by the compressor 208 and is fed to an intercooler 214, via which the compressed inlet air flows into the inlet header 215. From the intake manifold 215, the charge air enters the cylinders 202 via intake channels 216 and intake valves (not shown).

The exhaust gas flows from the cylinders 202 into the exhaust line 211 via exhaust valves and exhaust channels 217, which are not shown. From the exhaust line 211, the exhaust gas recirculation line 218 of the external exhaust gas recirculation system 206 branches upstream of the turbine 210, wherein an exhaust gas recirculation cooler 219 can be arranged in the exhaust gas recirculation line 218.

To control the external exhaust gas recirculation, an exhaust gas recirculation valve 220 is arranged in the exhaust gas recirculation line 218. The exhaust gas recirculation valve 220 is advantageously actuated pneumatically via a control line 222 designed as a control pressure line 221. In the exemplary embodiment shown in FIG. 9, the control pressure line 221 is connected in terms of flow to the inlet header 215 and is therefore controlled by the boost pressure downstream of the compressor 208, specifically by the pressure in the inlet header 215. In order to delay the switching time of the external exhaust gas recirculation system 206 in the transient acceleration process, a mechanical delay element 223 is provided in the control pressure line 221, which is simply provided by a pressure container 224 of sufficient size and a throttle 225 designed as an orifice at the entry of the control pressure line 221 into the container 224 consists. The pressure vessel 224 is slowly filled by this throttle 225 and the switching pressure for the exhaust gas recirculation valve 220 is built up only with a time delay. This prevents smoke emissions during acceleration due to excessive exhaust gas recirculation quantities.

Alternatively, the exhaust gas recirculation valve 220 can also be switched by negative pressure, which is generated by a vacuum pump 226, as is arranged by dotted lines in FIG. 9. The vacuum pump 226 is switched either by an electronic control unit or - particularly simply - by a mechanical switch on the injection pump, which, depending on the injection pump position, switches vacuum to the control line of the exhaust gas recirculation valve. The negative pressure opens the exhaust gas recirculation valve 220. The vacuum pump 226 can either be driven by the internal combustion engine or electrically. In order to delay the switching time of the external exhaust gas recirculation system 206 in the transient acceleration process, a Mechanical delay element 223 is provided between the vacuum pump 226 and the exhaust gas recirculation valve 220, the pressure vessel 223 being used by the vacuum pump 226 for negative pressure.

As an alternative to a pneumatically operated exhaust gas recirculation valve 220, an electrically switched exhaust gas recirculation valve can also be used. The switching process and the time delay take place electrically via an electronic control unit.

The internal exhaust gas recirculation system 205 is cam-controlled, the course of the exhaust gas recirculation quantity over the rotational speed being optimized by a suitable shape and position of a pre-lift cam of the intake cam. Inlet cams and pre-lift cams are rigidly connected to the camshaft. In order to make the diesel engine as simple and robust as possible, no camshaft adjusting device is provided. Thus, during the exhaust stroke, regardless of the load and speed, at least one intake valve is opened by a constant value by the pre-lift cam. The internal exhaust gas recirculation system 205 can be designed to be moderate, so that sufficiently high exhaust gas recirculation rates result in the middle speed range and almost no exhaust gas is recirculated at low speed. In order to achieve a significant NOx reduction at medium and high engine speeds, additional exhaust gas is supplied by the external exhaust gas recirculation system 206 from a predefined engine speed, which is essentially defined by the pressure conditions in the intake manifold 215 and in front of the turbine 210. The desired increasing exhaust gas recirculation rate at high engine speed n results from the suitable selection of the diameter of the exhaust gas recirculation line 218 of the external exhaust gas recirculation system 206 in a wide operating range of the internal combustion engine 201 by the prevailing pressure conditions, as indicated in FIGS. 10 and 11.

10, the pressure p _A in the exhaust line 211 in front of the turbine 210 and the pressure p _E in the intake manifold 215 are plotted against the engine speed n. EGRext denotes the area of the external exhaust gas recirculation from the exhaust line 211 to the intake manifold 215. At high engine loads, compressed charge air can be conveyed via the activated external exhaust gas recirculation system 206 from the intake manifold 215 in front of the turbine 210 if the pressure p _{A in} front of the turbine 210 is lower than the pressure p _E in the intake manifold 215 (low and medium engine speed n depending on engine size). This area is represented by R in FIG. 10. This effect is quite desirable, since it shifts the operating points Pi, P ₂ in the compressor map shown in FIG. 12 at low and medium engine speed n in the direction of high mass flows M to the efficiency of the compressor 208. At high engine speed n, the operating points P ₃ , P ₄ , P ₅ in the compressor map in the direction of low mass flows M and are again close to the optimum efficiency OPT of the compressor 208. In the compressor similarity map shown in FIG. 12, the pressure ratio PR is plotted over the corrected delivery flow M. Reference symbol S denotes the surge limit, reference symbol OPT represents the area with the best efficiency. In the map, line A shows the operation without external exhaust gas recirculation, line B shows the operation with external exhaust gas recirculation. It can be clearly seen that the operating points Pi, P ₂ , P ₃ , P ₄ , Ps in the compressor map are always shifted in the direction of the optimum efficiency OPT.

Furthermore, the rapidly increasing exhaust gas recirculation quantity EGR over the speed n facilitates the use of uncontrolled turbines 210, since the mass flow through the turbine 210 is reduced by the exhaust gas recirculation quantity EGR.

11 shows the exhaust gas recirculation rates EGR over the engine speed n for differently designed internal exhaust gas recirculation systems, which are indicated by the lines C, D, E, F, and for combined internal and external exhaust gas recirculation G. Due to the position and the shape of the pre-lift cam, the intake cam, the course of the internal exhaust gas recirculation quantity can be shaped favorably over the speed n, but there are limits to the influence of the exhaust gas recirculation rates, especially at high speed. Even higher exhaust gas recirculation rates at high engine speeds can only be achieved with the combined internal and external exhaust gas recirculation indicated by curve G.

The patent claims submitted with the application are proposals for formulation without prejudice for the achievement of further patent protection. The applicant reserves the right to claim further features previously only disclosed in the description and / or drawings.

References used in the subclaims indicate the further development of the subject matter of the skin claim through the features of the respective subclaim; they are not to be understood as a waiver of the achievement of independent, objective protection for the characteristics of the related subclaims.

However, the subjects of these subclaims also form independent inventions which have a design which is independent of the subjects of the preceding subclaims.

The invention is also not restricted to the exemplary embodiment (s) of the description. Rather, numerous changes and modifications are possible within the scope of the invention, in particular such variants, elements and Combinations and / or materials that are inventive, for example, by combining or modifying individual elements in conjunction with the features or elements or method steps described in the general description of the embodiments and the claims and contained in the drawings and by combinable features to form a new object or lead to new process steps or process step sequences, also insofar as they relate to manufacturing, testing and working processes.

Claims

PATENT REQUEST E0. Internal combustion engine with an exhaust gas system with at least one exhaust gas line, which is connected to the internal combustion engine via an exhaust manifold, characterized in that at least one exhaust gas aftertreatment device is arranged downstream of the exhaust gas manifold, the exhaust gas aftertreatment device and / or the exhaust gas line upstream of the exhaust gas aftertreatment device being at least partially double-walled, wherein a gap, which forms at least one channel and through which a heat-transfer medium can flow, is formed between an exhaust-gas-carrying inner wall and an outer wall, and the channel preferably has an inlet in an initial region of the exhaust manifold and preferably an outlet in the end region of the exhaust gas aftertreatment device. 1. Internal combustion engine, in particular according to claim 1, characterized in that the channel can be heated by a heat source preferably formed by an additional heating device. 2. Internal combustion engine, in particular according to claim 1 or 2, characterized in that the additional heating device is a calorific heating device and has at least one exhaust gas line for the burner exhaust gas, which can be connected to the entrance of the channel. 3. Internal combustion engine, in particular according to one of claims 1 to 3, characterized in that the entry is at least one functionally connectable by at least one switching element with the heat source or at least one heat sink. 4. Internal combustion engine, in particular according to one of claims 1 to 4, characterized in that the heat sink is formed by at least one cooling device working with air as the cooling medium, preferably having a blower. 5. Internal combustion engine, in particular according to one of claims 1 to 5, characterized in that the heat sink is formed by at least one secondary fan. 6. Internal combustion engine, in particular according to one of claims 1 to 6, characterized in that the heat sink and the heat source are formed by the same component. 7. Internal combustion engine with an exhaust port arrangement, in particular for a liquid-cooled diesel internal combustion engine with direct injection, characterized in that at least one exhaust port per cylinder, which is at least partially surrounded by a cooling space, is arranged in the cylinder head, with at least one group of exhaust ports in the area of the cylinder head with one another are connected to the flow and leads to a common exhaust pipe work connected to a flange surface of the cylinder head, and wherein the flow connection between the exhaust ports is formed by at least one connecting channel molded into the cylinder head in the region of the flange surface and having a cross section open to the flange surface. 8. Internal combustion engine, in particular according to claim 8, characterized in that the connecting channel runs essentially parallel to the flange surface. 9. Internal combustion engine, in particular according to claim 8 or 9, characterized in that the outlet channels open transversely, preferably approximately at a right angle into the connecting channel. 10. Internal combustion engine, in particular according to one of claims 8 to 11, characterized in that the wall of the connecting channel borders at least on the side of the cylinder head to the cooling chamber. 11. Internal combustion engine, in particular according to one of claims 8 to 11, characterized in that the connecting channel is partly formed by the exhaust pipe work, preferably at least half the cross section of the connecting channel being formed in the cylinder head. 12. Internal combustion engine, in particular according to one of claims 8 to 12, characterized in that at least two connecting channels with a cross-section open to the flange surface are at least partially molded into the cylinder head, a group of outlet channels opening into each of the connecting channels. 13. Internal combustion engine, in particular according to claim 13, characterized in that the connecting channels in the exhaust pipe work are arranged separately, preferably one above the other - in the cylinder axis direction. 14. Internal combustion engine, in particular according to one of claims 8 to 14, characterized in that the outlet tube works are undercut-free and can be produced in the mold casting process. 15. Internal combustion engine, in particular a diesel internal combustion engine, characterized in that the internal combustion engine has an internal exhaust gas recirculation system that is controlled in particular independently of the load, preferably by a pre-lift cam, and that an external exhaust gas recirculation system is additionally provided with at least one exhaust gas recirculation valve that can be controlled via at least one control line, preferably in the control line is arranged at least one delay element. 16. Internal combustion engine, in particular according to claim 16, characterized in that the delay element is a mechanical delay element. 17. Internal combustion engine, in particular according to claim 16 or 17, characterized in that the control line is a pneumatic control pressure line and the mechanical delay element has at least one pressure vessel. 18. Internal combustion engine, in particular according to claim 18, characterized in that at least one throttle, preferably orifice, is arranged at the entry of the control pressure line into the pressure vessel. 19. Internal combustion engine, in particular according to claim 18 or 19, characterized in that the control pressure line is fluidly connected to at least one inlet manifold. 20. Internal combustion engine, in particular according to one of claims 18 to 20, characterized in that the control pressure line is connected to at least one vacuum pump which can be switched depending on the load of the diesel internal combustion engine. 21. Internal combustion engine, in particular according to claim 21, characterized in that the vacuum pump can be driven mechanically by the diesel internal combustion engine. 22. Internal combustion engine, in particular according to claim 21, characterized in that the vacuum pump is electrically driven. 23. Internal combustion engine, in particular according to one of claims 21 to 23, with an injection pump for fuel injection, characterized in that the vacuum pump is switchable depending on the position of the injection pump. 24. Internal combustion engine, in particular according to one of claims 16 to 24, characterized in that the time delay element is an electrical or electronic time delay element. 25. Internal combustion engine, in particular according to one of claims 16 to 25, characterized in that the exhaust gas recirculation valve is connected to an electronic control unit via at least one electrical control line and can be electrically switched directly via this in dependence on the load. 26. A method for the regeneration of an exhaust gas aftertreatment system for an internal combustion engine, in particular a diesel internal combustion engine with direct injection, characterized in that the regeneration is initiated by at least one internal measure depending on the temperatures of the exhaust gas aftertreatment system, preferably for initiating and carrying out the regeneration a) the internal engine load is increased if the temperature of the exhaust gas aftertreatment system is lower than a defined regeneration temperature, b) when the regeneration temperature of the exhaust gas aftertreatment system is reached, the injection timing and / or the control time of at least one gas exchange valve of at least one cylinder is adjusted such that ignition of the injected fuel is not possible, so that the unburned fuel is stored upstream of the exhaust gas aftertreatment system, c) after the regeneration temperature of the exhaust gas aftertreatment system has been reached, the fuel injection is switched off in at least one cylinder and the cylinder is operated as an air delivery device for the exhaust gas aftertreatment system. 27. The method, in particular according to claim 27, characterized in that in step a) to increase the internal engine load, the control time of at least one gas exchange valve of at least one cylinder is changed so that maximum compression work is performed. 28. The method, in particular according to claim 28, characterized in that the fuel injection is suspended in the cylinder performing the maximum compression work. 9. The method, in particular according to one of claims 27 to 30, characterized in that one or more cylinders are operated alternately with normal and increased internal engine load.