DE19644687A1 - Gas routing system of an internal combustion engine - Google Patents

Abstract

Air is fed through an auxiliary port of an internal combustion chamber at a high velocity of flow in a turbulence system. This enables mixture formation to be improved. Air flowing through the auxiliary port must be controlled. In the inventive gas flow control system, the main port gas flow (31) which circulates through the gas throttle port (34c) and the auxiliary port gas flow (12) are jointly regulated by the gas throttle (40). The gas flow control system is especially designed for automotive internal combustion engines.

Description

State of the art

The invention relates to a gas routing system Internal combustion engine according to the preamble of claim 1.

In internal combustion engines, it is usually via a channel a gas stream is supplied to the combustion chamber or combustion chambers. The channel has a relatively large cross section, so at Requires a large gas flow without excessive flow losses can be supplied to the combustion chamber or combustion chambers. in the There is an adjustable throttle element along the channel, with which the gas flow is controlled. The throttle body will adjusted with the help of an actuator. The throttle body is usually a throttle valve. The gas flow is flowing air, which, depending on the type of internal combustion engine Course of the channel fuel is supplied or Fuel is fed directly into the combustion chamber or into the Injected combustion chambers.

Because the cross-section of the channel is relatively large, it is Flow rate of the in the combustion chamber or in the Combustion chamber inflowing gas flow is quite small. Because of this especially in the idle range of the internal combustion engine  Problems with mixture formation and thus with The course of combustion in the combustion chamber can result in a secondary channel a secondary gas flow into the combustion chamber or in the combustion chambers is fed. Because the cross section of the Secondary duct is quite small, the secondary gas flow has in the A secondary duct is also a large one with a relatively small secondary gas flow Flow velocity in the area of the inlet duct in the Combustion chamber, which causes the mixture formation and thus the Course of combustion in the combustion chamber or in the combustion chambers improved.

To control the bypass gas flow in the bypass is So far, another throttle element in the course of the secondary duct intended. Both throttling organs are created with the help of one Actuator adjusted. The further throttle body and the additional actuators require a considerable total Effort, and the resulting additional costs at Manufacture of the gas routing system are significant Disadvantage.

Advantages of the invention

The gas routing system designed according to the invention Internal combustion engine with the characteristic features of the Claim 1 has the advantage that the Manufacturing effort is significantly reduced.

By the measures listed in the subclaims advantageous developments and improvements in Main claim specified gas routing system Internal combustion engine possible.

Is the throttle body in the form of a throttle valve and in addition becomes the sub-channel inlet of the sub-channel of controlled a flat side of the throttle valve, so this offers  the advantage that even with a slight adjustment of the Throttle valve the free cross section in the secondary duct can be opened or closed.

The sub-duct inlet acts as a stop for the throttle valve used, then the manufacturing cost is reduced advantageously in addition, and the assignment of Throttle valve to the sub-duct inlet is easily possible.

Is the throttle body designed so that when the Throttle valve closes the channel by slight Adjustment of the throttle valve the free cross section of the Channel is changed only slightly, then this has considerable advantages in the assignment of the throttle valve the secondary duct inlet.

If the secondary duct inlet is deformable during manufacture, then this facilitates the manufacture of the gas routing system advantageously additionally.

drawing

Preferred selected, particularly advantageous embodiment examples of the invention are shown in simplified form in the drawing and he explains in more detail in the following description. They show: Fig. 1 is a schematic illustration of a gas delivery system embodying the present invention and FIGS. 2, 3 and 4 show details of different embodiments of executed.

Description of the embodiments

The gas routing system designed according to the invention Internal combustion engine can be used with any internal combustion engine be used in a combustion chamber via a channel  a main channel gas flow and via a secondary channel Secondary gas flow is to be supplied. The internal combustion engine can only have one combustion chamber, for example. The The internal combustion engine can also have multiple combustion chambers include. For example, the channel can be reached before Combustion chambers can be divided into several individual channels. Of the Channel with the adjustable throttle body can be designed in this way be that the adjustable throttle body for the gas flow controls all combustion chambers of the internal combustion engine. The Gas routing system can also be designed so that for example, each combustion chamber of the internal combustion engine separate channel with a separate throttle element assigned is. At least one of these throttling organs then also serves for adjusting the secondary gas flow in the secondary channel. It can but also be provided that each of the adjustable Throttling devices for controlling the main duct gas flow in the Channel and also for controlling the secondary gas flow in the Secondary channel serves.

In the following description of the exemplary embodiments For reasons of simplification, it is assumed that the Internal combustion engine has four combustion chambers and the throttle body the gas flow, the main duct gas flow and the secondary gas flow controls for the four combustion chambers.

Fig. 1 is a preferably selected exemplary embodiment in symbolic form.

Fig. 1 shows schematically an internal combustion engine 2 and a belonging to the internal combustion engine 2 gas guide Appendix 4. Within the internal combustion engine 2 there are a first combustion chamber 6 , a second combustion chamber 6 ′, a third combustion chamber 6 ″ and a fourth combustion chamber 6 ″ ″. The gas routing system 4 comprises a channel 8 , a throttle element 10 and a secondary channel 12 . The channel 8 comprises a channel inlet side 14 , the throttle element 10 , a connection 15 and a collector 16th Viewed in the direction of flow, the parts of the channel 8 mentioned come in the order in which they were named. A first individual channel 18 , a second individual channel 18 ', a third individual channel 18 ''and a fourth individual channel 18 ''' branch off from the collector 16 in parallel. The individual channels 18 , 18 ′, 18 ″, 18 ″ ″ are designed, for example, as oscillating tubes in order to be able to achieve the greatest possible full load output in the internal combustion engine 2 .

At the transitions of the individual channels 18 , 18 ', 18 '', 18 ''' into the combustion chambers 6 , 6 ', 6 '', 6 ''' there are inlet valves which are not shown in the drawing for the sake of clarity. In the course of the channel 8 of the gas routing system 4, there is, for example, one injection valve or several injection valves. In the drawing, also for the sake of clarity, no injection valve is shown. The internal combustion engine 2 can be designed, for example, in such a way that a fuel injection valve is located in the region of the channel inlet side 14 in front of the throttle element 10 , or the internal combustion engine 2 can be constructed such that at the end of each of the individual channels 18 , 18 ', 18 '', 18 ''' One fuel injection valve is arranged, which either feeds the fuel into the individual channels 18 , 18 ', 18 '', 18 ''' upstream of the inlet valve or directly into the combustion chambers 6 , 6 ', 6 '', 6 ' behind the inlet valves. '' injected.

In the preferred embodiment selected, the secondary duct 12 comprises a secondary duct inlet 20 , a secondary duct guide 22 , a so-called turbulence collector 24 , a first turbulence air supply 26 , a second turbulence air supply 26 ', a third turbulence air supply 26 ''and a fourth turbulence air supply 26 '''. The secondary duct 12 branches off from the duct 8 in the region of the throttle element 10 . The secondary duct 12 begins with the secondary duct inlet 20 .

A gas stream 30 flows through the gas routing system 4 . The gas stream 30 is shown symbolically in the drawing with an arrow provided with the reference symbol 30 . Gas stream 30 is typically flowing air. The gas stream 30 can also be a fuel-air mixture, depending on whether one looks at the gas stream upstream or downstream of the fuel injection valve, where fuel is added to the flowing air. In the region of the throttle element 10 , the gas stream 30 is divided into a main channel gas stream 31 and a secondary gas stream 32 . The main channel gas stream 31 flows through the connection 15 , through the collector 16 and through the individual channels 18 , 18 ', 18 '', 18 ''' into the combustion chambers 6 , 6 ', 6 '', 6 '''. The secondary gas stream 32 flows through the secondary duct inlet 20 , then through the secondary duct guide 22 , through the turbulence collector 24 and through the turbulence air supply lines 26 , 26 ', 26 '', 26 ''', where the secondary gas stream 32 is preferably directly on the inlet valve or on the Inlet valves of the combustion chambers 6 , 6 ', 6 '', 6 ''' is directed. Because, apart from the relatively small gas flow 30 in the idling area of the internal combustion engine 2 , the secondary gas flow 32 is significantly smaller than the main duct gas flow 31 , the arrow 32 is shown thinner than the arrow 31 .

The throttle element 10 shown symbolically preferably comprises a throttle valve connector 34 . The throttle valve connector 34 has a tubular wall 36 and on the inside of the wall 36 a throttle valve channel 34 c. In the throttle valve channel 34 c there is a throttle valve 40, which is symbolically shown in FIG. 1 and is pivotably mounted with the aid of a throttle valve shaft 38 . The throttle valve shaft 38 is rotatably mounted in the wall 36 of the throttle valve connector 34 . The throttle valve 40 can be adjusted with a mechanically and / or electrically operating actuator 42, also shown symbolically. The actuator 42 comprises, for example, an electric motor with which the throttle valve shaft 38 and the throttle valve 40 fastened to the throttle valve shaft 38 can be adjusted via a gear, not shown.

The actuator 42 can adjust the throttle valve 40 so that the free cross section for the main channel gas flow 31 is completely or almost completely closed. The throttle valve 40 can also be adjusted so that the air or the fuel-air mixture can flow largely unthrottled through the throttle valve duct 34 c of the throttle valve connector 34 into the collector 16 . By adjusting the throttle valve 40 , the main duct gas flow 31 flowing through the duct 8 can be controlled.

In the embodiment shown in FIG. 1, the secondary duct inlet 20 is formed, for example, by a plurality of transverse bores leading through the wall 36 of the throttle valve connector 34 into the throttle valve duct 34 c. The transverse bores are arranged, for example, such that when the throttle valve duct 34 c of the duct 8 is closed by the throttle valve 40 , the transverse bores of the secondary duct inlet 20 are also closed. The transverse bores of the secondary duct inlet 20 can be closed by the peripheral surface of the disk-like throttle valve 40 . If the throttle valve 40 has opened the free cross section through the channel 8 , then the transverse bores of the secondary channel inlet 20 are also open, and the secondary gas flow 32 can flow through the secondary channel 12 into the combustion chambers 6 , 6 ′, 6 ″, 6 ″ ″ . In the exemplary embodiment shown symbolically in FIG. 1 and designed according to the invention, both the main channel gas flow 31 flowing through the channel 8 and the secondary gas flow 32 flowing through the secondary channel 12 can be controlled by adjusting the one throttle valve 40 . The control of the gas flow 30 or the main channel gas flow 31 and the secondary gas flow 32 is possible together with the adjustable throttle element 10 .

Because the transverse bores of the secondary duct inlet 20 leading through the wall 36 cannot be made arbitrarily large in the exemplary embodiment shown symbolically in FIG. 1, in particular because the throttle valve 40 is not as thick as desired, and because these transverse bores do not extend over the entire circumference of the throttle valve duct 34 c can be arranged, in the exemplary embodiment shown in FIG. 1 only a relatively small secondary gas flow 32 can be conducted through the secondary channel 12 . Because the secondary gas flow 32 is often intended to be larger than is possible in the exemplary embodiment shown in FIG. 1, exemplary embodiments are shown in the following figures in which the control of a larger secondary gas flow 32 is also possible.

FIG. 2 shows an alternative, particularly advantageous, preferably selected exemplary embodiment on a different scale, the clarity is shown for only the area of the throttle valve connector 34.

The same or equivalent parts are included in all the figures provided the same reference numerals. Unless nothing against it Part mentioned or shown in the drawing applies the one mentioned and represented with the help of one of the figures in the other embodiments. Provided that from the The explanations are otherwise, the details of the different embodiments with each other can be combined.

Roughly speaking, the throttle valve 40 has the shape of a flat, flat, approximately round disk. The throttle valve 40 has a first side surface 40 a facing the channel inlet side 14 and a second side surface 40 b facing the connection 15 or the combustion chambers 6 , 6 ′, 6 ″, 6 ″ ″. Between the two side surfaces 40 a, 40 b, the throttle valve 40 has a peripheral surface 40 c.

In the exemplary embodiment shown in FIG. 2, the secondary duct inlet 20 is essentially formed by a bypass tube 44 . The throttle valve connector 34 with the wall 36 is an injection molded part. The auxiliary duct guide 22 of the auxiliary duct 12 or a first part of the auxiliary duct guide 22 is cast as a cavity in the wall 36 of the throttle valve connector 34 . In the throttle valve connector 34 , a transverse mounting bore 46 is provided from the outside through the wall 36 into the channel inlet side 14 . To the outside, the mounting hole 46 is closed with a plug 46 a. The mounting hole 46 connects the secondary duct guide 22 to the duct inlet side 14 . The bypass pipe 44 is inserted on the channel inlet side 14 facing side of the wall 36 into the mounting hole 46, fixed therein and sealed. The bypass tube 44 has an end 48 facing the side surface 40 a of the throttle valve 40 . The bypass tube 44 is bent so that the end 48 extends approximately parallel to the longitudinal axis of the throttle valve connector 34 in the direction of the throttle valve 40 . In the end 48 of the bypass pipe 44, an end piece 50 is fitted, with respect to the bypass tube 44 is sealed and fixed. The end piece 50 of the secondary duct inlet 20 of the secondary duct 12 is tubular and has an end face 20 a facing the first side surface 40 a of the throttle valve 40 . Between the end face 20 a and the side surface 40 a, depending on the position of the throttle valve 40 , there is a more or less controllable secondary duct throttle cross section 52 . The secondary duct throttle cross section 52 depends on the position of the throttle valve 40 . Roughly viewed, the secondary duct throttle cross section 52 is determined from the circumference of the end face 20 a and from the distance from the end face 20 a to the side surface 40 a of the throttle valve 40 .

Providing the secondary channel guide 22 of the secondary channel 12 or the first part of the secondary channel guide 22 as a cavity in the wall 36 of the throttle valve connector 34 results in considerable advantages in terms of production costs, weight or material requirements and the space requirements of the gas routing system 4 .

The tubular throttle valve connector 34 has an inner lateral surface. This lateral surface forms the throttle valve duct 34 c. Depending on the position of the throttle valve 40 , there is a more or less large throttle cross section 55 between the throttle valve channel 34 c and the peripheral surface 40 c of the throttle valve 40 . The throttle valve 40 can be adjusted in the opening direction until the throttle valve 40 is parallel to the longitudinal direction of the throttle valve connector 34 . In the exemplary embodiment shown in FIG. 2, this is a counterclockwise rotation. In this position of the throttle valve 40 , the throttle cross section 55 is opened to the maximum. By turning the throttle valve 40 in the closing direction, ie in FIG. 2 by turning the throttle valve 40 clockwise, the throttle cross section 55 in the end position of the throttle valve 40 reaches its minimum or the throttle cross section 55 is completely closed. On the outside of the throttle valve connector 34 there is a closed position stop , not shown, against which the throttle valve shaft 38 comes to rest in the closed position. But it can also be provided that the throttle valve 40 strikes in the closed position on the throttle valve channel 34 c; ie the throttle valve channel 34 c serves as a closed position stop. So that the throttle valve 40 is not jammed with the throttle valve channel 34 c, the throttle valve 40 is set in the closed position, that is, the throttle valve 40 is not adjustable in the closed position until the throttle valve 40 is transverse to the longitudinal axis of the throttle valve body 34 , but the throttle valve 40 comes at an angle of less than 90 °, based on the longitudinal axis of the throttle valve connector 34 , at the closed position stop to the system.

In the drawing, the throttle valve 40 is shown in a position in which the throttle valve 40 is slightly adjusted in the opening direction, ie the throttle valve 40 is shown in a position in which the secondary duct throttle cross section 52 and the throttle cross section 55 are slightly open.

If the throttle valve 40 is in the closed position, ie if the throttle valve 40 or the throttle valve shaft 38 abuts the closed position stop, then the throttle cross section 55 is completely or almost completely closed, and also the secondary duct throttle cross section 52 is at least almost completely closed. If the throttle valve 40 is adjusted in the opening direction by the actuator 42 ( FIG. 1), starting from the closed position, that is to say in the embodiment shown in FIG. 2, rotation counterclockwise, then the auxiliary duct throttle cross-section is already at a slight rotation of the throttle valve 40 52 opened relatively wide, whereas the throttle cross section 55 is initially only opened relatively little. When the throttle valve 40 is rotated further in the opening direction, the secondary duct throttle cross section 52 is opened further, to such an extent that the throttling of the secondary gas flow 32 flowing through the secondary duct 12 essentially no longer takes place at the secondary duct throttle cross section 52 , but within the secondary duct guide 22 ; at the same time, the throttle cross section 55 is increasingly opened.

When the throttle valve 40 rotates relatively slightly from the closed position, the secondary duct throttle cross section 52 is first opened relatively strongly, and the throttle cross section 55 is opened relatively weakly in the process. A relatively wide rotation of the throttle valve 40 in the opening direction then has almost no influence on the secondary duct throttle cross-section 52 and thus on the size of the secondary gas flow 32 flowing through the secondary duct 12 , but by rotating the throttle valve 40 then essentially only the through the main channel gas flow 31, which flows relatively broadly opening throttle cross section 55, is controlled.

So that the throttle valve 40 can properly reach its closed position stop, and in order to ensure that the end face 20 a of the secondary duct inlet 20 is correctly aligned with respect to the side surface 40 a, in particular in the closed position of the throttle valve 40 , it preferably being provided that the throttle valve 40 in its Closed position on the end face 20 a of the secondary duct inlet 20 and thus also the secondary duct throttle cross section 52 is closed in the closed position, it can be provided that the end piece 50 is an elastically resilient molded elastomer part, on which the throttle valve 40 comes into contact shortly before reaching its closed position and then pushes this elastomer part back until the throttle valve 40 reaches its closed position.

In a modification of the embodiment just described, the end piece 50 can also be a molded part which is plastically deformable during the assembly of the throttle valve connector 34 . The end piece 50 is, for example, a thermoplastic that is deformable by heating. The end piece 50 is installed in the longitudinal direction with oversize in the throttle valve connector 34 . After installation, the end piece 50 is heated and the throttle valve 40 is simultaneously pressed in the closing direction up to the closed position stop. Characterized in that the end piece 50 is deformed by the supply of heat, the end face 20 a is pushed back somewhat, so that the end face 20 a bears exactly against the side surface 40 a of the throttle valve 40 when the throttle valve 40 is in the closed position. The plastic reshaping of the end piece 50 also ensures that the end face 20 a extends somewhat obliquely and thus the angle of attack of the throttle valve 40 is also optimally adapted in terms of angle. After cooling the fitting 50 , the position of the end face 20 a is such that when the throttle valve 40 is in its closed position, the side surface 40 a of the throttle valve 40 just abuts the end face 20 a.

The embodiment just described can also be modified so that the end piece 50 is dispensed with, so that the end face 20 a is located directly on the bypass tube 44 . For the purpose of adapting the bypass tube 44 to the throttle valve 40 , the entire bypass tube 44 can be produced from a thermoplastic material which can be deformed by the supply of heat. By heating the bypass tube 44 while simultaneously pressing the throttle valve 40 , the bypass tube 44 is deformed somewhat, so that after the bypass tube 44 has cooled, it takes on the intended shape and length.

In order to produce a relatively large secondary channel throttle cross-section 52 with a moderate extent of the end face 20 a of the side channel inlet 20, the throttle valve 40 facing end has 48 of the bypass tube 44, viewed in the radial direction, a little distance preferably to the wall 36 of the throttle body 34, so that the entire The circumference of the end face 20 a can be available for the secondary duct throttle cross section 52 . The projecting into the throttle valve assembly 34 inwardly bypass pipe 44 can for reasons of stability over a narrow ridge 58 with the wall 36 of the throttle body 34 can be connected.

Fig. 3 shows a further preferably selected, especially advantageous exemplary embodiment.

In the embodiment shown in FIG. 3, the throttle valve 40 is installed in the throttle valve connector 34 so that the throttle valve 40 is not in its closed position, as shown in FIG. 2, but is located transversely to the longitudinal axis of the throttle valve connector 34 . In this closed position of the throttle valve 40 there is a narrow gap over the circumference of the throttle valve 40 between the circumferential surface 40 c of the throttle valve 40 and the throttle valve channel 34 c of the throttle valve connector 34 . It is preferably provided that the end face 20 a on the bypass tube 44 also serves as a closed position stop for the throttle valve 40 . In this embodiment, the throttle valve 40 comes into contact with the end face 20 a in its closed position. The end face 20 a determines the closed position of the throttle valve 40 .

When the throttle valve 40 is adjusted in the opening direction, as explained with reference to FIG. 2, the secondary duct throttle cross section 52 also opens relatively strongly in the exemplary embodiment according to FIG. 3. Because the throttle valve 40 in its closed position is essentially perpendicular to the longitudinal axis of the throttle valve connector 34 in FIG. 3, when the throttle valve 40 is actuated in the opening direction, the throttle cross-section 55 initially opens less strongly at a small adjustment angle than in the exemplary embodiment shown in FIG. 2 .

Because in the embodiment shown in FIG. 3 the closed position for the throttle valve 40 has to be set less precisely than in the embodiment shown in FIG. 2, the exact position of the end face 20 a in the embodiment according to FIG. 3 must also be less accurate can be set than in the exemplary embodiment according to FIG. 2. This facilitates the manufacture of the gas routing system 4 .

FIG. 4 shows a further preferably selected, especially advantageous exemplary embodiment.

In order to achieve a smaller opening of the throttle cross-section 55 compared to FIG. 3 when adjusting the throttle valve 40 in the opening direction with a small adjustment angle, the throttle valve channel 34 c in FIG. 4 is not cylindrical as in FIG. 3, but in FIG. 4 the throttle valve duct 34 c is approximately dome-shaped. As a result, the opening of the throttle cross-section 55 can be further delayed when the throttle valve 40 is adjusted in the opening direction, which facilitates the coordination of the throttle cross-section 55 and the secondary duct throttle cross-section 52 with one another and also the combustion process in the combustion chambers 6 , 6 ', 6 '', 6 '''' Favorably influenced in the lower idling range of the internal combustion engine 2 because, due to the spherical shape of the throttle valve duct 34 c, with a small adjustment angle of the throttle valve 40 in the lower idling range, a relatively large amount of air with a high flow rate through the relatively small cross section of the secondary duct 12 into the combustion chambers 6 , 6 ', 6 '', 6 ''' flows, while no or almost no air flows in through the relatively large cross section of the channel 8 . Because of the desired high flow velocity when the secondary gas flow 32 flows into the combustion chambers 6 , 6 ', 6 '', 6 ''', the cross section of the secondary channel 12 is particularly at the transitions into the combustion chambers 6 , 6 ', 6 '', 6 ''', especially small.

The idling of the internal combustion engine 2 is regulated both by the opening or closing throttle cross section 55 between the throttle valve duct 34 c and the throttle valve 40 and also by the simultaneously opening or closing secondary duct throttle cross section 52 between the end face 20 a of the secondary duct 12 and the side face 40 a of the throttle valve 40 . The throttle cross section 55 and the secondary duct throttle cross section 52 together contribute to controlling the power of the internal combustion engine 2 . The sum of the throttle cross section 55 and the secondary duct throttle cross section 52 together, but depending on the position of the throttle valve 40 with different proportions, determine the power of the internal combustion engine 2 .

Claims (10)

1. Gas routing system of an internal combustion engine with at least one combustion chamber, with a channel ( 8 ) for supplying a main channel gas flow into the combustion chamber, with an adjustable throttle element ( 10 , 40 ) in the channel ( 8 ) for controlling the main channel gas flow and with a secondary channel ( 12 ) for supplying a secondary gas flow into the combustion chamber, characterized in that the adjustable throttle member ( 10 , 40 ) is provided for controlling the secondary gas flow ( 32 ). 2. Gas routing system according to claim 1, characterized in that the secondary gas stream ( 32 ) is a secondary air stream. 3. Gas routing system according to one of the preceding claims, characterized in that the secondary duct ( 12 , 26 , 26 ', 26 '', 26 ''') for supplying the secondary gas stream ( 32 ) into the combustion chamber ( 6 , 6 ', 6 '', 6 ''') with high flow velocity. 4. Gas supply system according to one of claims 1 to 3, characterized in that the throttle member ( 10 , 40 ) in a throttle valve channel ( 34 c) is pivotally mounted throttle valve ( 40 ). 5. Gas routing system according to claim 4, characterized in that the secondary duct ( 12 ) branches off from the throttle valve duct ( 34 c). 6. Gas routing system according to claim 4 or 5, characterized in that the secondary duct ( 12 ) at one of the throttle valve ( 40 ) at least partially closable secondary duct inlet ( 20 , 20 a) begins. 7. Gas routing system according to claim 6, characterized in that the secondary duct inlet ( 20 , 20 a) from a side surface ( 40 a) of the throttle valve ( 40 ) is at least partially closable. 8. Gas routing system according to claim 6 or 7, characterized in that the secondary duct inlet ( 20 , 20 a) forms a closed position stop ( 20 a) for the throttle valve ( 40 ). 9. Gas routing system according to one of claims 4 to 8, characterized in that the throttle valve channel ( 34 c) in the region of the throttle valve ( 40 ) is dome-shaped. 10. Gas routing system according to one of claims 6 to 8, characterized in that at least a portion of the secondary duct inlet ( 20 , 44 , 50 ) is plastically deformable for reasons of adjustment.