DE19715939C1 - Eaxhaust for motor vehicle internal conmbustion engine - Google Patents

Abstract

The exhaust (1) has gas ducts (3,5) with a pre-silencer for cooling and silencing the exhaust gases. There is a catalyser (6) downstream from the silencer with a control (10) to regulate the exhaust gas stream and a bypass pipe (9) which extends from the exhast gas labyrinth (16) to the catalyser. The bypass pipe extends through the front exhaust piupe (3) the preseilencer, a connecting pipe (5) and a casing (11) for a positioning branch of the control regulator and opens downsteam behind the branch in the conencting pipe (5) or the catalyser.

Description

The invention relates to an exhaust system for an internal combustion engine Machine with the features according to the preamble of claim 1.

In exhaust systems with a catalyst, there is the problem that the catalyst depending on the distance from the internal combustion engine ne operating temperature of over 250 ° Celsius only after one to reached two minutes and becomes fully effective. Is the distance low, on the other hand there is a risk of overheating, because the durability increases with an excessive operating temperature maturity.

An exhaust system is known from DE 43 22 949 C2, at the hot combustion gases during a cold start via a rela tiv short and straight bypass line directly to the catalytic converter be directed while after reaching operating temperature a large part of the combustion gases via an exhaust pipe and a pre-sound that dampens and cools the combustion gases damper reaches the catalytic converter and there the hot burning Gases are added to an optimal operating temperature guarantee. An exhaust flap that goes downstream ter arranged the front silencer and therefore not immediately the amount is regulated by the hot combustion gases the added cooler combustion gases.  

In the known arrangement of front silencer, catalyst and the main silencer, the exhaust pipe initially runs par allel to the bypass line and then shows many pipe bends on. Because the exhaust pipe and the bypass pipe are in operation heating up and expanding differently, it comes down gas system to heat stresses, which are caused by the offset of the Bypass line to the exhaust line and through the pipe bends as Impact bending stresses. These can be influenced by Vibrations favored by the length of the exhaust pipe become, lead to pipe breaks or it would have to be expensive directions for expansion compensation are created. Furthermore be the exhaust system takes up a lot of space and shines because of its large surface area emits considerable sound and heat, which the bordering components, especially the underbody of a Vehicle.

An exhaust system is also known from DE 42 18 523 C1, which has largely straight pipe sections, and in which the Catalyst is arranged within the front silencer. There through results in a relatively voluminous front silencer a large diameter that is not always structurally simple is to be brought. If the front silencer is only on one side attached, it tends to vibrate; but it will be on both Tied to the sides, no thermal expansion can be absorbed the. Furthermore, the offset between the exhaust leads tion and the bypass line bending stresses at an angle part of the bypass line. Finally, the exhaust flap is on Inlet of the front muffler so that it burns hot is exposed to gases.

The invention has for its object to provide an exhaust system predominantly straight lines, a small construction volume and a low temperature and noise pollution of the environment to create exercise. Furthermore, the exhaust system should be as free as possible  of bending stresses and vibrations. This task will solved according to the invention with the features of the first claim.

Through the bypass line laid in the exhaust pipe, which then through the front silencer and the housing for an actuator the control device is guided, there are relatively small Expansion differences between the bypass line and the exhaust gas management. Since lever arms avoided by the coaxial arrangement are generated, in turn, at most pressure and tension which are mainly absorbed by the weld seams and are easier to control. Cracks no longer occur. Furthermore, the short, coaxially laid lines tend less to vibrations and radiate because of their small surface little noise and heat, so that the vehicle underbody and the neighboring components are less affected by heat be charged. In addition, the lower heat capacity the bypass line that the catalyst is either faster Operating temperature reached or a larger distance between an exhaust manifold and the catalytic converter can be approved, e.g. B. up to two meters, which makes a larger constructive Free movement results.

The bypass line with a small diameter changes that Volume of the exhaust pipe, the front silencer and the exhaust gas do not work well. Since it increases from the exhaust pipe other locations can be supported by the coaxial arrangement exposed to low mechanical loads and through ih Right position in the exhaust pipe from mechanical damage is protected, it can be made thin-walled. Usually wall thicknesses smaller than 0.7 mm are sufficient. The little wall reduce the thickness and the small diameter of the bypass line their weight and their heat capacity, whereby the exhaust gases hardly Heat is extracted and the catalyst is even faster most favorable operating temperature reached. This improves in the Sum also the exhaust gas quality. By eliminating Rohrbiegun  the exhaust pipe and the use of materials are shortened the weight of the exhaust system is further reduced. Furthermore be the straight lines appear subjectively more comfortable noise behavior of the exhaust system, since the so-called The "trickle noise" is less clearly perceptible due to Supersonic pressure surges from the internal combustion engine to the pipe bend conditions arises.

Further advantages and details emerge from the following the description of the drawing. In the drawing are execution illustrated examples of the invention. In the description and in the claims are numerous features related Darge represents and described. Those skilled in the art will find the features useful Usually also look at them individually and make sensible combinations summarize the ions.

Show it:

Fig. 1 shows schematically an exhaust system with a bypass line according to the invention,

Fig. 2 shows a cross section through a housing corresponding to the Li never II-II in Fig. 1 and

Fig. 3 shows a longitudinal section through the housing.

An exhaust system 1 for an internal combustion engine 2 comprises an exhaust pipe, consisting of a front exhaust pipe 3 , egg ner connecting line 5 and a rear exhaust pipe 7 , egg nem front silencer 4 , a downstream of this angeord designated catalyst 6 and a main silencer 8th Before muffler 4 is expediently double-walled for sound emission reasons. The two walls lie close together so that the sound is dampened by friction between the walls. Since the exhaust pipe of the exhaust system 1 according to the invention is short and thus the heat radiation is low, a larger amount of heat must be dissipated in the cooling and front silencer 4 . This is advantageously done with a low noise emission.

In the front exhaust pipe 3 , in the front silencer 4 and through a housing 11 for an actuator, for. B. an exhaust valve 12 or a not shown, pneumatically acting control mechanism of a control device 10 , a bypass line 9 is laid. It begins behind an exhaust manifold 16 of the internal combustion engine 2 and opens behind the housing 11 in the connec tion line 5 or in the catalyst 6th So that the combus- tion gases flow through the exhaust system 1 better, the mouth of the bypass line 9 can be ejector-shaped and thus produce a promotional effect.

The exhaust system 1 contains essentially straight lines which are aligned in the longitudinal direction of a vehicle, not shown. As a result, it takes up little installation space, requires little material and is light in weight. The protected bypass line 9 is expediently designed with thin walls, preferably with a wall thickness of less than 0.7 mm. Due to its short length, its small wall thickness and its small diameter, it has a low heat capacity, so that little heat is removed from the exhaust gas and the catalyst 6 very quickly reaches its optimal operating temperature.

The bypass pipe 9 is guided by the housing 11 and is surrounded in the region of an exhaust flap 12 of a closest tend connected to the housing 11 carrying the fourteenth As a result, the bypass line 9 is easy to assemble and does not interfere with the function of the exhaust flap 12 . This is pivoted in the housing 11 gela gert. An adjusting device 13 adjusts it as a function of the temperature in the catalytic converter 6 or as a function of other suitable operating parameters. It has a recess 15 which connects to the bushing 14 with little play. Since the bushing 14 is fixed in the housing 11 , the gas flap 12 closes off the bypass line 9 regardless of the manufacturing tolerances and is easy to regulate.

The housing 11 is used as a separate component downstream of the front silencer 4 in the connecting line 5 of the exhaust pipe, but it can also be integrated in the front silencer 4 or the catalyst 6 .

Claims (7)

1. Exhaust system ( 1 ) for an internal combustion engine ( 2 ), in the ei ne exhaust pipe ( 3 , 5 ) a combustion gas damping and cooling front silencer ( 4 ) and a downstream upstream of this arranged catalyst ( 6 ) and a control device ( 10 ) Contains control of the exhaust gas flow and a bypass line ( 9 ) from an exhaust manifold ( 16 ) to the catalyst ( 6 ), where the diameter of the bypass line ( 9 ) is smaller than the diameter of the exhaust line ( 3 , 5 ), characterized in that the bypass line ( 9 ) through the front exhaust line ( 3 ), the front silencer ( 4 ), a connecting line ( 5 ) and a Ge housing ( 11 ) for an actuator of the control device is laid and downstream downstream of the actuator in the connecting line ( 5 ) or the catalyst ( 6 ) opens. 2. Exhaust system ( 1 ) according to claim 1, characterized in that the housing ( 11 ) in the front silencer ( 4 ) is integrated. 3. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the housing ( 11 ) in the region of the gas flap ( 12 ) has a housing ( 11 ) sealingly connected bushing ( 14 ) for the bypass line ( 9 ) . 4. Exhaust system ( 1 ) according to claim 3, characterized in that the exhaust flap ( 12 ) has a passage ( 14 ) corresponding contour. 5. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the mouth of the bypass line ( 9 ) narrows ejector-shaped. 6. exhaust system ( 1 ) according to any one of the preceding claims, characterized in that the bypass line ( 9 ) up to two Me ter long and its wall thickness is less than 0.7 mm. 7. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the front silencer ( 4 ) is double-walled.