Exhaust Gas After Treatment System

Abstract

The invention relates to an exhaust gas aftertreatment system for delivering a reducing agent (15) into the exhaust gas stream of an internal combustion engine for selective catalytic reduction, the system having a reducing agent tank (1) and a pump (3) for delivering the reducing agent from the tank (1) to an injection unit, the tank (1) having at least one opening, the pump (3) being made as an integrated unit (2) and being plugged into the opening of the tank, the integrated unit (2) forming a tank closure and sealing the tank.

Description

The invention relates to an exhaust gas aftertreatment system for delivering a reducing agent into the exhaust gas stream of an internal combustion engine for selective catalytic reduction, the system having a reducing agent tank and a pump for delivering the reducing agent from the tank to an injection unit.

These exhaust gas aftertreatment systems are known and are used to reduce nitrogen oxides in exhaust gases from internal combustion engines, injection of a reducing agent, such as a urea solution, especially according to DIN 70070, into the exhaust gas stream of the internal combustion engine taking place. Exhaust gas aftertreatment systems with delivery of a reducing agent into the exhaust gas stream for selective catalytic reduction of nitrogen oxides (SCR) are used to minimize nitrogen oxide emissions from internal combustion engines. To do this, a reducing agent is injected into the exhaust gas system with a metering and injection device. Ammonia is the reducing agent. In this sense a reducing agent or urea solution is to be understood as ammonia and also urea solution or another reductively acting agent and especially so-called AdBlue, i.e. a urea solution according to DIN 70070.

In these exhaust gas systems a reducing agent such as for example urea solution is injected by means of compressed air into the exhaust gas stream and atomized in order to form an aerosol which is as fine and uniformly distributed as possible. The reducing agent is used for selective catalytic reduction (SCR) in so-called SCR catalytic converters for reduction of nitrogen oxide emissions from diesel engines.

The disadvantage in known exhaust gas aftertreatment systems is their complex structure of a plurality of units and modules; this entails very high production and installation effort and requires a large installation space; this is especially disadvantageous in applications in the domain of passenger cars since the available installation space is very limited.

Proceeding from this prior art, the object of the invention is to reduce the installation effort of the components which are to be installed in the exhaust gas aftertreatment system and thus to cut production costs. Another object is that in the production of the exhaust gas aftertreatment system fewer parts need be installed and the installation space is optimized.

This object is achieved as claimed in the invention by an exhaust gas aftertreatment system as claimed in Claim 1. Advantageous developments of the invention are given in the dependent claims.

In the exhaust gas aftertreatment system for delivering a reducing agent into the exhaust gas stream of an internal combustion engine for selective catalytic reduction, the system having a reducing agent tank and a pump for delivering the reducing agent from the tank to an injection unit, it is especially advantageous for the tank to have at least one opening, the pump being made as an integrated unit and being plugged into the opening of the tank, the unit forming a tank closure and sealing the tank.

The reducing agent which is to be delivered is preferably a urea solution especially according to DIN 70070 for selective catalytic reduction. The term reducing agent encompasses however any suitable liquid substance. But preferably a urea solution is used. The tank is accordingly made diffusion-tight and consists preferably of plastic.

The pump for delivery of the reducing agent from the tank to the injection unit thus forms an integrated unit which is plugged into the tank so that the tank more or less forms the pump housing. The pump unit thus closes the tank and seals it.

The opening of the tank into which the pump as an integrated unit is plugged is preferably located on the bottom of the tank or in a lower region of one side wall of the tank so that the intake fitting of the pump is also covered at a low level of the reducing agent and delivery of the reducing agent from the tank is possible.

The pump as an integrated unit for this purpose has an intake fitting whose intake opening is located at the geodetically lowest point of the tank.

Alternatively the pump unit can be plugged into an opening on the top of the tank or in the upper region of one side wall of the tank and can seal the tank. In this case the pump also has a suction fitting which, optionally provided with an extension, discharges at the geodetically lowest point of the tank so that the intake fitting of the pump or the open end of the pipeline or hose line connected upstream of the suction fitting is covered even at a low level of the reducing agent and delivery of the reducing agent from the tank is possible.

It is advantageous here that the tank cannot become leaky toward the bottom if for example a seal between the pump unit and the tank opening has not been correctly installed.

If the configuration of the tank due to the given installation situation requires, the tank can have any shape which differs from a roughly cuboidal shape, as is conventional in tanks installed in motor vehicles. In this case the pump unit can also be inserted into the tank in a diagonal position which differs from a vertical or horizontal position and can seal it. Fundamentally the location of the pump unit in the installed position and its arrangement in the tank, i.e. also the arrangement of the tank opening into which the pump unit is plugged, are optional. Therefore the pump unit in its installation situation can be located vertically, horizontally or diagonally.

The tank and pump as an integrated unit thus form a compact unit which can be installed premounted into the vehicle. The required installation space within the motor vehicle is minimized and optimally used by the tank and pump forming a compact unit.

Since the tank can preferably be a plastic tank, it can be optimally adapted in its geometry to the existing installation space. The tank is preferably a diffusion-tight plastic tank.

The pump as an integrated unit is inserted like a cartridge into the opening of the tank intended for installation of the pump. Preferably the pump unit is screwed into a thread in the opening of the tank, forming a seal. Alternatively or cumulatively the pump unit can be inserted into the tank opening by means of a quarter-turn fastener, forming a seal.

The unit is preferably made such that one bottom plate bears the pump and other components so that the bottom plate forms a somewhat smooth-surfaced tank closure and the components of the pump unit in the installed state lie within the tank. The tank then more or less forms the pump housing.

Preferably the opening is located on the bottom of the tank or in the lower region of one side wall of the tank and the pump unit or bottom plate of the unit seals the tank downward.

Alternatively or cumulatively the border of the tank opening can be made stepped so that a bottom plate of the pump unit is inserted into one step and is braced against the tank and seals it by means of clamps which are located on the tank and which reach behind corresponding undercuts on the bottom plate.

On the top of the tank there is preferably a refill fitting for delivering the required reducing agent solution into the reducing agent tank. The terms reducing agent or reducing agent solution are used synonymously in this sense and encompass any suitable reducing agent for selective catalytic reduction.

The pump as an integrated unit can be inserted into the tank and mounted from the bottom, like an oil filter or like a cartridge which is inserted and attached.

In one especially preferred configuration of the exhaust gas aftertreatment system the system has a reducing agent filter and/or a heating apparatus for heating of the reducing agent and/or a temperature sensor for detecting the reducing agent temperature and/or pure power electronics for triggering the pump and/or a communications interface, especially a standardized communications interface, especially a CAN bus interface and/or a LIN bus interface.

Especially preferably the pump as an integrated unit has a reducing agent filter and/or a heating apparatus for heating of the reducing agent and/or a temperature sensor for detecting the reducing agent temperature and/or power electronics for triggering the pump and/or a communications interface, especially a standardized communications interface, especially a CAN bus interface and/or a LIN bus interface.

Integrating other components into the integrated unit with the pump yields an especially compact embodiment which can be advantageously installed. Insertion of this integrated unit with pump and other components into the tank yields a compact unit which can be installed completely premounted into the vehicle, especially a passenger car, and to which then only the delivery line for delivery of the reducing agent to the injection unit is connected. This reducing agent line is preferably heated. Likewise there is preferably a heating apparatus for heating of the reducing agent. The reducing agent solution according to DIN 70070 freezes at −11° C. so that for especially low outside temperatures at least in the region of the intake fitting of the pump there is a heating apparatus in order to enable delivery of the reducing agent from the tank by means of the pump even at low outside temperatures in order to thaw the reducing agent in the tank if it should be frozen.

The arrangement of an interface, especially a standardized communications interface, such as for example a CAN bus interface and/or a LIN bus interface makes it possible to incorporate the pump unit into the control system of the vehicle. This so-called CAN bus is an asynchronous serial bus system. A so-called LIN bus is a serial communications system.

In one preferred embodiment the pump as an integrated unit has a sensor for detecting a physical property of the reducing agent, especially for detection of the electrical conductivity and/or for detection of the speed of sound in the reducing agent.

By means of this sensor permanent detection and monitoring of the quality of the reducing agent are possible so that any manipulations, for example of filling of the tank with water, can be effectively prevented in order to ensure proper operation of the exhaust gas aftertreatment system. Thus, by this reducing agent quality sensor by means of which a physical property of the delivered reducing agent is detected it can be ascertained whether the correct reducing agent is being used and injected into the exhaust gas line for exhaust gas aftertreatment.

As the physical quantity for detecting the reducing agent quality the electrical conductivity of the reducing agent and/or the speed of sound in the reducing agent can be measured by means of the sensor and transferred to an evaluation unit.

In one especially preferred embodiment the sensor for detecting a physical property of the reducing agent is arranged in the tank such that the signal of the sensor can be used at the same time as a liquid level indicator for ascertaining that a minimum level in the tank has not been reached.

The sensor for detecting a physical property of the reducing agent is accordingly positioned in the tank such that at the same time it is used as a liquid level indicator so that a display can be activated when the tank reserve is reached. The sensor is thus used at the same time as a liquid level sensor or liquid level transmitter for reserve display.

Preferably the system has a control device by means of which the pump is triggered depending on the measured values acquired by the sensors and/or depending on the current operating parameters of the internal combustion engine, in particular is triggered via a bus system.

This control unit can also be the central control device of the vehicle. In this case the triggering and operation monitoring of the exhaust gas aftertreatment system can be integrated into the central control device of the motor vehicle and implemented accordingly.

Preferably there is at least one seal, especially an O-ring seal, between the pump unit and the tank.

The arrangement of this seal ensures reliable sealing of the tank.

Preferably the system has an injection unit with at least one nozzle by which the reducing agent is injected into the exhaust gas stream and/or is atomized in the exhaust gas stream. In particular compressed air can be used for atomization in order to form a uniform, finely distributed aerosol and to achieve optimum and uniformly distributed droplet formation.

The exhaust gas aftertreatment system preferably has a SCR catalytic converter in which the reducing agent is delivered into the exhaust gas stream of the internal combustion engine for selective catalytic reduction, upstream and/or downstream of the SCR catalytic converter there being a sensor for detecting the nitrogen oxide concentration in the exhaust gas.

These NOx sensors enable online monitoring and diagnosis of the selective catalytic reduction in the SCR catalytic converter, i.e. the quality of the exhaust gas aftertreatment, and at the same time triggering of the pump to deliver the reducing agent from the tank to the injection unit depending on the values which have been ascertained by means of the NOx sensor or sensors is possible in order to trigger the exhaust gas aftertreatment system as required.

One exemplary embodiment of the invention is shown in the figures and is explained below.

FIG. 1 shows a schematic of a tank with an inserted pump unit.

FIG. 1 shows a schematic of a tank 1 in which the reducing agent solution 15 is stored. The tank 1 is preferably a diffusion-tight plastic tank.

In the lower region of the tank 1 a pump unit 2 which is made as an integrated unit is inserted into an opening of the tank 1.

The integrated unit 2 contains the pump 3 and the power electronics 4 for triggering the pump and other components which are explained below.

In the unit 2 there is furthermore a temperature sensor 5 such as for example an NTC temperature sensor for detecting the temperature of the reducing agent solution 15 in the tank 1. The temperature sensor 5 is used at the same time for heating control and for density compensation of the reducing agent via the temperature. The heating element can be a resistance element. In the illustrated exemplary embodiment the heating element 6 is a MOSFET transistor which is likewise triggered via the power electronics 4 of the integrated unit 2.

The integrated unit 2 has corresponding terminals for the liquid level sensor 8 and furthermore a standardized communications interface such as for example a CAN bus system, a power supply via the vehicle electrical system with a +12 volt terminal and a so-called ground terminal (0 volt).

The integrated module 2 is plugged into the opening of the tank 1 located in the lower region of the tank 1 and is sealed by means of O-ring seals 10. The suction fitting 11 is arranged such that it lies in the lower region of the tank 1 so that a residual amount of the reducing agent 15 located in the tank 1 can also be intaken via the pump 3 through the suction fitting 11. A filter 7 by which the reducing agent 15 is filtered is connected upstream of the suction fitting 11 on the pump 3.

In addition to the MOSFET transistor 6 which is used as the heating element, a heating element 9 is placed in the tank which in the illustrated exemplary embodiment is an aluminum rod which is used for heating of the tank contents 15 in order to thaw them at extremely low temperatures so that in the lower region of the tank 1 the reducing agent can be thawed in order to intake it via the suction fitting 11 by means of the pump 3 through the filter 7.

The delivery end 12 of the pump is integrated into the module 2; a heated reducing agent line is connected to that end and discharges into an injection unit for injecting the reducing agent into the exhaust gas stream of the internal combustion engine.

Furthermore in the tank 1 there is a liquid level sensor 8 which is likewise wired to the power electronics 4, as is suggested in FIG. 1. By means of the sensor 8 the liquid level within the tank 1 is monitored in that via the reducing agent 15 added to the tank 1 the circuit between the liquid level sensor 8 and the aluminum rod 9 and/or the aluminum pipe 11 is closed. As soon as this circuit is broken, the reserve region of the tank 1 is reached and a reserve lamp is turned on as a display for the driver. Refilling of the tank 1 with the reducing agent 15 is possible via the refill fitting 13 which is located on the top of the tank 1.

The entire module 2 as an integrated module is plugged into the opening located in the lower region of the tank 1 and is sealed by means of the O-ring seals 10. For complete installation of the entire arrangement only the module 2 need be installed in the tank 1 and the plug-and-socket connections to the power electronics 4 which are used for triggering of the heating element and pump and also monitoring of the liquid level sensor or liquid level transmitter 8 need be coupled.

The suction fitting 11 of the pump 3 is located in the lower region of the tank 1 so that even when the region of the reserve tank is reached, i.e. when the liquid level sensor 8 is not reached in terms of the liquid level and no longer responds, further operation of the exhaust gas aftertreatment system for a certain time is possible until the tank 1 is filled again with the reducing agent 15 via the refill fitting 13.

At the same time, the electrical conductivity of the reducing agent 15 between the lower end of the liquid level sensor 8 and the heating element 9 is monitored by a measurement of the electrical resistance between the sensor 8 and the heating rod 9 in order to perform quality control of the reducing agent 15 which has been added to the tank 1. In this way it can be ascertained if for example water instead of a reducing agent according to DIN 70070 has been added. The sensor 8 is thus used at the same time for monitoring the quality of the added reducing agent 15 and for monitoring of the liquid level in the tank 1.

On the pump housing inserted into the tank the liquid level sensor 8 in one alternative embodiment is made with several contact surfaces over the height of the tank 1 in order to implement a more accurate and detailed liquid level display with several intermediate steps for more exact indication of the remaining tank contents.

In one alternative which is not shown, the integrated module as an integrated module is plugged into an opening located in the upper region of the tank from overhead and is sealed by means of O-ring seals. The tank in the lower region then has a continuous, diffusion-tight plastic trough. Possible tank leaks for faulty installation of the O-ring seals are thus eliminated.

In this case a heating element is integrated into the module and is thus likewise pushed from overhead into the tank so that the additional aluminum heating rod can be omitted.

Claims

1. An exhaust gas after treatment system for delivering a reducing agent into the exhaust gas stream of an internal combustion engine for selective catalytic reduction, the system comprising a reducing agent tank, an injection unit and a pump for delivering the reducing agent from the said reducing agent tank to said injection unit, characterized in that said reducing agent tank has at least one opening, the pump being made as an integrated unit and being plugged into the opening of the tank, the integrated unit forming a tank closure and sealing said tank, wherein the injection unit comprises at least one nozzle by which the reducing agent is injected into the exhaust gas stream and/or is atomized in the exhaust gas stream, wherein compressed air is used for atomization in order to form a uniform, finely distributed aerosol.

2. The exhaust gas after treatment system as claimed in claim 1, wherein the integrated unit is screwed into a thread in the opening of said tank, forming a seal or wherein the unit is inserted into the opening of the tank by means of a quarter-turn fastener, forming a seal.

3. The exhaust gas after treatment system as claimed in claim 1 wherein the at least one opening is located at or near the bottom and/or in the lower region of said tank and the unit (2) seals said tank at said at least one opening.

4. The exhaust gas after treatment system as claimed in claim 1 wherein the system at least on member selected from the group consisting of reducing agent filters filter and/or a heating apparatuses for heating of the reducing agent, temperature sensors for detecting the reducing agent temperature, power electronics for triggering the pump and/ communications interfaces, especially a standardized communications interface, including a CAN bus interface.

5. The exhaust gas after treatment system as claimed in claim 1 wherein the pump as an integrated unit has at least one member selected from the group consisting of reducing agent filters heating apparatuses for heating of the reducing agent, temperature sensors for detecting the reducing agent temperature, power electronics for triggering the pump and communication interfaces, especially CAN bus interfaces.

6. The exhaust gas after treatment system as claimed in claim 1 wherein the pump as an integrated unit has a sensor for detecting a physical property of the reducing agent, especially for detection of the electrical conductivity and/or for detection of the speed of sound in the reducing agent.

7. The exhaust gas after treatment system as claimed in claim 6, wherein the sensor for detecting a physical property of the reducing agent is arranged in the tank such that the signal of the sensor can be used at the same time as a liquid level indicator for ascertaining that a minimum level in the tank has not been reached.

8. The exhaust gas after treatment system as claimed in claim 1 wherein the system has a control device by means of which the pump is triggered depending on the measured values acquired by the sensors and/or depending on the current operating parameters of the internal combustion engine, in particular is triggered via a bus system.

9. The exhaust gas after treatment system as claimed in claim 1 wherein there is at least one seal, especially an O-ring seal between the unit and the tank.

10. The exhaust gas after treatment system as claimed in claim 1 wherein the system has an injection unit with at least one nozzle by which the reducing agent is injected into the exhaust gas stream and/or is atomized in the exhaust gas stream.

11. The exhaust gas after treatment system as claimed in claim 2 wherein the system has an SCR catalytic converter in which the reducing agent is delivered into the exhaust gas stream of the internal combustion engine for selective catalytic reduction, upstream and/or downstream of the SCR catalytic converter there being a sensor for detecting the nitrogen oxide concentration in the exhaust gas.

12. The exhaust gas after treatment system as claimed in claim 2 wherein the integrated unit is screwed into a thread in the opening of the reducing agent tank forming a seal or wherein the integrated unit is inserted into the opening of the reducing agent tank by means of a quarter-turn fastener, forming a seal.

13. The exhaust gas after treatment system as claimed in claim 2 wherein the at least one opening is located on the bottom and/or in the lower region of the reducing agent tank and the integrated unit seals the reducing agent tank at said at least one opening.

14. The exhaust gas after treatment system as claimed in claim 2 wherein the system has at least one member selected from the group consisting of reducing agent filters, heating apparatuses for heating of the reducing agent, temperature sensors for detecting the reducing agent temperature, power electronics for triggering the pump and communications interfaces, especially a standardized communications interface, particularly a CAN bus interface.

15. The exhaust gas after treatment system as claimed in claim 2 wherein the pump as an integrated unit has at least one member selected from the group consisting of reducing agent filters, heating apparatuses for heating of the reducing agent, temperature sensors for detecting the reducing agent temperature, power electronics for triggering the pump and interfaces, especially a CAN bus interface.

16. The exhaust gas after treatment system as claimed in claim 2 wherein the pump is an integrated unit having a sensor for detecting a physical property of the reducing agent, especially for detection of the electrical conductivity and/or for detection of the speed of sound in the reducing agent.

17. The exhaust gas after treatment system as claimed in claim 16, wherein the sensor for detecting a physical property of the reducing agent is arranged in the reducing agent tank such that the signal of the sensor can be used at the same time as a liquid level indicator for ascertaining that a minimum level in the reducing agent tank has not been reached.

18. The exhaust gas after treatment system as claimed in claim 2 wherein the system has a control device by means of which the pump is triggered depending on the measured values acquired by the sensors and/or depending on the current operating parameters of the internal combustion engine, in particular is triggered via a bus system.

19. The exhaust gas after treatment system as claimed in claim 2 wherein there is at least one seal, especially an O-ring seal between the integrated unit and the reducing agent tank.

20. The exhaust gas after treatment system as claimed in claim 2 wherein the system has an injection unit with at least one nozzle by which the reducing agent is injected into the exhaust gas stream and/or is atomized in the exhaust gas stream and further comprising an SCR catalytic converter in which the reducing agent is delivered into the exhaust gas stream of the internal combustion engine for selective catalytic reduction, upstream and/or downstream of the SCR catalytic converter there being a sensor for detecting the nitrogen oxide concentration in the exhaust gas.