DE102006032454A1 - Exhaust system for an internal combustion engine - Google Patents

Abstract

In an exhaust system (10) for an internal combustion engine having at least one exhaust pipe (12) and a tank (14) for a urea solution (16), a portion of the exhaust pipe (12) through the tank (14).

Description

The Invention relates to an exhaust system for an internal combustion engine, with at least one exhaust pipe and a tank for a urea solution.

In order to comply with environmental regulations, the exhaust gases of internal combustion engines, in particular motor vehicles driven by internal combustion engines, must be subjected to a cleaning process. For nitrogen oxide reduction are increasingly called SCR catalysts (also known as denitration catalysts) are used, the nitrogen oxides (NO _x ) generated during combustion in the engine selectively reduced with the aid of cached in the SCR catalyst ammonia (NH ₃ ) to water and nitrogen. The provision of the ammonia required for the selective catalytic reduction takes place by hydrolysis of urea, which is added to the exhaust gas in dissolved form. For this purpose, a correspondingly arranged storage tank is required. Since urea solution freezes at -11 ° C, the storage tank must be insulated or heated, which requires additional electrical energy.

The Invention provides an exhaust system, in which a simple way Freeze the urea solution is prevented.

This is achieved in an exhaust system of the type mentioned, characterized the existence Section of the exhaust pipe is passed through the tank. Thus can on a additional Heating device, which would increase the (electrical) energy consumption omitted become. Naturally It is also conceivable, a section of the exhaust pipe so on Running along the tank that of Exhaust gas flow a sufficient amount of heat to the urea solution is delivered. Another advantage of the invention compared to about the use of existing coolant for heating the urea solution is that no long pipes needed are to coolant to the usual in the end of the exhaust system arranged tank for the urea solution Transport, as the engine and the radiator of the engine cooling circuit at most motor vehicles, especially cars and trucks, in the front Area of the vehicle are arranged. This results in a cost-effective solution that characterized by a minimum of energy consumption.

Preferably has the exhaust pipe to a plurality of branch lines, one of which passed through the tank is. The amount of heat provided by this branch is sufficient to prevent freezing of the urea solution.

According to the preferred Embodiment has the exhaust pipe upstream of the tank on a valve. This can be closed if necessary, overheating the urea solution to avoid. This can be a comparatively simple and thus inexpensive valve, such as a 2/2-way valve, find use, especially on the tightness no particularly high demands Need to become.

Especially is a control unit provided, which controls or regulates the valve. This can, depending on the valve, only one opening and closing of the valve or a stepless control or regulation of the flow cause.

Advantageous is the control unit coupled with a sensor that detects the temperature of the urea solution. The control unit then controls or regulates the valve in response to the detected temperature.

Preferably is the one led by the tank Branch line attached decoupled from the rest of the exhaust system, for example by so-called corrugated hoses.

Further Features and advantages of the invention will become apparent from the following Description of a preferred embodiment with reference to the accompanying drawings. In these show:

1 a plan view of an exhaust system according to the invention; and

2 a side view of the exhaust system 1 ,

The figures show a detail of an exhaust system 10 , which is downstream of an internal combustion engine, in particular a motor vehicle engine. The exhaust system 10 includes an exhaust pipe 12 , which is located upstream of a tank 14 for a urea solution 16 branched. While a first branch line 18 the exhaust pipe 12 around the tank 14 is at least a portion of a second branch line 20 through the tank 14 passed. This is the urea solution 16 through the exhaust gas flow in the second branch line 20 heated and thus prevented from freezing during operation even at low temperatures. Should the urea solution 16 Once frozen with the engine off, it thaws quickly due to the heat provided by the exhaust stream during operation.

The second branch line 20 can after the tank 14 again with the first branch line 18 be merged or serve as an exhaust gas recirculation line.

Immediately upstream of the tank 14 indicates the second branch line 20 a valve 22 on, here a 2/2-way valve. For controlling or regulating the valve 22 is a control unit 24 provided that with a sensor 26 for detecting the temperature of the urea solution 16 coupled and depending on the detected temperature, the valve 22 controls or regulates.

deviant Of course, the 2/2-way valve shown in the figures is also a proportional valve conceivable.

The branch line 20 is vibration-decoupled from the rest of the exhaust system 10 fastened, for example via metal bellows or world hoses made of metal (not shown).

10

exhaust system

12

exhaust pipe

14

tank

16

urea solution

18

first branch line

20

second branch line

22

Valve

24

control unit

26

sensor

Claims (6)

Exhaust system for an internal combustion engine, with at least one exhaust pipe ( 12 ) and a tank ( 14 ) for a urea solution ( 16 ), characterized in that a portion of the exhaust pipe ( 12 ) through the tank ( 14 ) is guided. Exhaust system according to claim 1, characterized in that the exhaust pipe ( 12 ) several branch lines ( 18 . 20 ), at least one of which through the tank ( 14 ) is guided. Exhaust system according to claim 1 or 2, characterized in that the exhaust pipe ( 12 ) upstream of the tank ( 14 ) a valve ( 22 ) having. Exhaust system according to claim 3, characterized in that a control unit ( 24 ) is provided, which the valve ( 22 ) controls. Exhaust system according to claim 4, characterized in that the control unit ( 24 ) with a sensor ( 26 ), which determines the temperature of the urea solution ( 16 ) detected. Exhaust system according to one of Claims 2 to 5, characterized in that the 14 ) guided branch line ( 20 ) decoupled from the rest of the exhaust system ( 10 ) is attached.