EP2689118A1

EP2689118A1 - Exhaust gas post treatment system

Info

Publication number: EP2689118A1
Application number: EP12702185.5A
Authority: EP
Inventors: Werner Overhoff; Sascha Dolenec; Sebastian Mühlenbrock
Original assignee: Albonair GmbH
Current assignee: Albonair GmbH
Priority date: 2011-03-21
Filing date: 2012-01-27
Publication date: 2014-01-29
Also published as: US20140065022A1; DE102011014634A1; WO2012126548A1

Abstract

The invention relates to an exhaust gas post treatment system for introducing a reducing agent (15) into the exhaust gas stream of an internal combustion engine for the purpose of selective catalytic conversion, wherein the system has a reducing agent tank (1) and a pump (3) for delivering the reducing agent out of the tank (1) to an injection unit, wherein the tank (1) has at least one opening, wherein the pump (3) is designed as an integrated unit (2) and is plugged into the opening in the tank, wherein the integrated unit (2) forms a tank closure and closes the tank in a sealing manner.

Description

aftertreatment system

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

Such exhaust aftertreatment systems are known and are used for the reduction of nitrogen oxides in exhaust gases of internal combustion engines, wherein an injection of a reducing agent, such as a urea solution, in particular according to DIN 70070, takes place in the exhaust stream of the internal combustion engine. Exhaust aftertreatment systems with a contribution of a reducing agent into the exhaust gas stream for the selective catalytic reduction of nitrogen oxides (SCR) are used to minimize the nitrogen oxide emissions of internal combustion engines. For this purpose, a reducing agent is injected into the exhaust system with a metering and injection device. The reducing agent is ammonia. In this sense, the term reducing agent or urea solution is intended to include both ammonia and urea solution or another reducing agent and in particular the so-called AdBlue, i. a urea solution according to DIN 70070 are understood.

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

A disadvantage of the known exhaust aftertreatment systems whose complex structure of a plurality of units and assemblies, which involves a very high manufacturing and assembly costs and requires a large amount of space, which is particularly disadvantageous especially in applications in the field of passenger cars, as the available standing space is very limited.

Based on this prior art, the present invention seeks to reduce the assembly costs of the components to be mounted in the exhaust aftertreatment system and thus to reduce the manufacturing cost. Another object is that in the production of the exhaust aftertreatment system fewer parts are to be mounted and a space optimization is achieved. This object is achieved by an exhaust aftertreatment system according to claim 1. Advantageous developments of the invention are specified in the subclaims.

Particularly advantageous in the exhaust aftertreatment system for introducing a reducing agent into the exhaust stream of a selective catalytic reduction internal combustion engine, the system comprising a reducing agent tank and a pump for conveying the reducing agent from the tank to an injection unit, it is that the tank has at least one opening, wherein the pump is formed as an integrated unit and is inserted into the opening of the tank, wherein the assembly forms a tank closure and sealingly closes the tank.

As a reducing agent to be introduced is preferably urea solution in particular according to DIN 70070 for selective catalytic reduction Commitment. However, the term reducing agent includes any suitable liquid substance. Preferably, however, a urea solution is used. The tank is accordingly formed diffusion-tight and is preferably made of plastic.

The pump for conveying the reducing agent from the tank to the injection unit thus forms an integrated structural unit which is inserted into the tank so that the tank virtually forms the pump housing. The pump unit thus closes the tank and seals it off.

The opening of the tank, in which the pump is inserted as an integrated unit, is preferably arranged on the underside of the tank or in a lower region of a side wall of the tank, so that the suction nozzle of the pump is covered even at a low level of reducing agent and a Promotion of the reducing agent from the tank is possible.

The pump as an integrated unit has for this purpose an intake, whose intake is located in the geodesic lowest point of the tank. Alternatively, the pump assembly may be plugged into an opening at the top of the tank or at the top of a side wall of the tank to seal the tank. Also in this case, the pump has a suction nozzle, which optionally provided with an extension in the geodesic lowest point of the tank opens, so that the intake of the pump or the open end of the suction pipe upstream pipe or hose even at a low level of reducing agent is covered and a promotion of the reducing agent from the tank is possible. It is advantageous that the tank can not leak downwards, for example, if a seal between the pump unit and tank opening was not mounted correctly. If it requires the design of the tank due to the given installation situation, the tank can have any of a shape which is approximately cuboid in shape, as is customary in tanks installed in motor vehicles. In such a case, the pump assembly can also be used in a deviating from a vertical or horizontal position diagonal position in the tank and seal it sealed. In principle, the position of the pump assembly in the mounted position and its arrangement in the tank, ie, the arrangement of the tank opening into which the pump unit is inserted, arbitrary. Therefore, the pump assembly can be arranged vertically, horizontally or diagonally in their installation situation.

Tank and pump as an integrated unit thus form a compact unit that can be installed in the motor vehicle pre-assembled. Due to the fact that tank and pump form a compact unit, the required installation space within the motor vehicle is minimized and optimally utilized.

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

Into the provided for mounting the pump opening of the tank, the pump is used as an integrated unit similar to a cartridge. Preferably, the assembly of the pump is sealingly screwed into a thread in the opening of the tank. Alternatively or cumulatively, the structural unit of the pump can be sealingly inserted into the opening of the tank by means of a bayonet closure.

The assembly is preferably designed such that a bottom plate carries the pump and other components, so that the bottom plate forms an approximately smooth surface tank cap and the components of the pump assembly are in the mounted state within the tank. The tank then forms the pump housing. In this case, the opening is preferably arranged on the underside of the tank or in the lower region of a side wall of the tank, and the pump unit or a base plate of the structural unit seals the tank downwards.

Alternatively or cumulatively, the border of the tank opening may be formed stepwise, so that a bottom plate of the pump unit is inserted into a stage and clamped by means of clamps which are arranged on the tank and engage behind the corresponding undercuts on the bottom plate against the tank and sealingly closes this ,

At the top of the tank, a refilling nozzle is preferably provided for introducing the required reducing agent solution into the reducing agent tank. The terms reducing agent or reducing agent solution are used interchangeably in this sense and include any suitable reducing agent for selective catalytic reduction.

The pump as an integrated assembly can then be inserted and mounted from the bottom into the tank, much like an oil filter or a cartridge that is inserted and secured.

In a particularly preferred embodiment of the exhaust aftertreatment system, the system has a reducing agent filter and / or a heating device for heating the reducing agent and / or a temperature sensor for detecting the reducing agent temperature and / or pure power electronics for controlling the pump and / or a communication interface, in particular a standardized communication interface, in particular a CAN bus interface and / or a LIN bus interface.

Particularly preferably, the pump has as an integrated unit a reducing agent filter and / or a heating device for heating the reducing agent and / or a temperature sensor for detecting the reducing agent temperature and / or the power electronics for driving the pump and / or a communication interface, in particular a standardized communication interface, in particular a CAN bus interface and / or a LIN bus interface. By integrating further components into the integrated structural unit with the pump, a particularly compact and advantageously to be mounted embodiment is provided. With the onset of such an integrated unit with pump and other components in the tank a compact unit is created, which can be completely pre-assembled in the motor vehicle, especially a passenger car and then followed only the delivery line for conveying the reducing agent to the injection unit. This reducing agent line is preferably heated. Likewise, a heating device for heating the reducing agent is preferably provided. The reducing agent solution according to DIN 70070 freezes at -11 ° C, so that for particularly low outside temperatures, at least in the region of the intake of the pump, a heating device is arranged to allow a promotion of the reducing agent from the tank by means of the pump even at low ambient temperatures to the Thaw reducing agent in the tank if it should be frozen.

By arranging an interface, in particular a standardized communication interface such as a CAN bus interface and / or a LIN bus interface, it is possible to integrate the pump unit in the control system of the motor vehicle. Such a so-called CAN bus is an asynchronous, serial bus system. A so-called LIN bus is a serial communication system.

In a preferred embodiment, the pump has an integrated structural unit as a sensor for detecting a substance property of the reducing agent, in particular for detecting the electrical conductivity and / or for detecting the speed of sound in the reducing agent. By means of such a sensor, a permanent detection and monitoring of the reducing agent quality is possible, so that any manipulations, for example, the filling of the tank with water, can be effectively prevented in order to ensure proper functioning of the exhaust aftertreatment system. It can thus be determined by such a reducing agent quality sensor, by means of which a substance property of the conveyed reducing agent is detected, whether the correct reducing agent is used and injected into the exhaust tract for exhaust gas aftertreatment.

As a 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 a particularly preferred embodiment, the sensor for detecting a substance property of the reducing agent in the tank is arranged such that the signal of the sensor can be used simultaneously as a level indicator for detecting the undershooting of a minimum filling level in the tank.

The sensor for detecting a substance property of the reducing agent is accordingly positioned in the tank so that it also serves as a level indicator, so that a display can be activated when the tank reserve is reached. The sensor thus serves simultaneously as a level sensor or level sensor for the reserve display.

Preferably, the system has a control unit, by means of which the pump is actuated as a function of the measured values detected by sensors and / or as a function of current operating parameters of the internal combustion engine, in particular via a bus system.

This control unit may also be the central control unit of the motor vehicle. In this case, the control and Operating monitoring of the exhaust aftertreatment system integrated into the central control unit of the motor vehicle and implemented accordingly.

Preferably, at least one seal, in particular an O-ring seal, is arranged between the pump unit and the tank.

By arranging such a seal a reliable sealing of the tank is ensured. The system preferably has an injection unit with at least one nozzle, through which the reducing agent is injected into the exhaust gas stream and / or 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 uniform droplet formation.

The exhaust gas aftertreatment system preferably has an SCR catalytic converter in which the reducing agent is introduced into the exhaust gas stream of the internal combustion engine for selective catalytic reduction, wherein a sensor for detecting the concentration of nitrogen oxide in the exhaust gas is arranged in front of and / or behind the SCR catalytic converter.

Such NOx sensors provide on-line monitoring and diagnosis of selective catalytic reduction in the SCR catalyst, i. H. the quality of the exhaust aftertreatment possible and it is at the same time a control of the pump for conveying the reducing agent from the tank to the injection unit in dependence of the detected by means of the NOx sensors or values possible to control the exhaust aftertreatment system as needed.

An embodiment of the invention is shown in the figure and will be explained below. It shows:

1 shows a schematic representation of a tank with a pump assembly used. Figure 1 shows a schematic representation 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 part of the tank 1 is inserted into an opening of the tank 1, a pump assembly 2, which is designed as an integrated unit.

The integrated unit 2 includes the pump 3 and the power electronics 4 for controlling the pump and other components, which are explained below.

In the assembly 2 is further arranged a temperature sensor 5 such as an NTC temperature sensor for detecting the temperature of the reducing agent solution 15 in the tank 1. The temperature sensor 5 serves both the heating control and the Reduktionsmitteldichtekompensation over the temperature. As a heating element, a resistance element can be used. In the illustrated embodiment, the heating element 6 is a MOSFET transistor, which is also driven via the power electronics 4 of the integrated module 2.

The integrated module 2 has corresponding connections for the level sensor 8 and also for a standardized communication interface such as a CAN bus system, a power supply via the electrical system with a +12 volt connection and a so-called ground connection (0 V).

The integrated assembly 2 is inserted into the arranged in the lower region of the tank 1 opening of the tank 1 and sealed by means of O-ring seals 10. The suction nozzle 1 is arranged so that it is located in the lower region of the tank 1, so that a residual amount of the reducing agent 15 located in the tank 1 can be sucked through the suction nozzle 11 via the pump 3. The suction nozzle 11 on the pump 3 is preceded by a filter 7 through which the reducing agent 15 is filtered. In addition to the serving as a heating element MOSFET transistor 6 is introduced into the tank, a heating element 9, in which it is an aluminum rod in the illustrated embodiment, which serves to heat the tank contents 15 to thaw at extremely low temperatures, thus in the lower Area of the tank 1, the reducing agent can be thawed to suck it via the suction port 1 by means of the pump 3 through the filter 7.

Integrated into the assembly 2 is the pressure port 12 of the pump, to which a heated reducing agent line connects and opens into an injection unit for injecting the reducing agent into the exhaust gas stream of the internal combustion engine.

Further, in the tank 1 is arranged a level sensor 8, which is also wired to the power electronics 4, as indicated in FIG. 1. By means of the sensor 8, a fill level control within the tank 1 takes place inasmuch as via the filled into the tank 1 reducing agent 15 of the circuit between the level sensor 8 and the aluminum rod 9 and / or the aluminum tube 11 is closed. Once this circuit is interrupted, the reserve area of the tank 1 is reached and it is turned on a reserve lamp as an indication to the driver. A refilling of reducing agent 15 in the tank 1 is possible via the arranged at the top of the tank 1 refill 13. The entire assembly 2 is inserted as an integrated assembly in the arranged in the lower region of the tank 1 opening and sealed by means of the O-ring seals 10. For complete assembly of the entire arrangement, only the assembly 2 is to be mounted in the tank 1 and there are the connectors for power electronics 4, which serve to control heating element and pump and the monitoring of the level sensor or level sensor 8 to connect.

The suction nozzle 11 of the pump 3 is arranged in the lower region of the tank 1, so that even when the area of the reserve tank is reached, that is, when the level sensor 8 is exceeded by the filling height forth and no longer responds, continued operation of the exhaust aftertreatment system for a certain time is possible until the tank 1 is filled via the refill 13 with reductant 15 again.

At the same time, the electrical conductivity of the reducing agent 15 between the lower end of the level sensor 8 and the heating element 9 is monitored by measuring the electrical resistance between the sensor 8 and the heating element 9 to perform quality control of the reducing agent 15 introduced into the tank 1. In this way it can be ascertained, for example, if water was introduced instead of a reducing agent in accordance with DIN 70070. The sensor 8 thus simultaneously serves to monitor the quality of the filled reducing agent 15 and the fill level control in the tank 1.

In the pump housing used in the tank of the level sensor 8 is formed in an alternative embodiment with multiple contact surfaces above the filling level of the tank 1 to realize a more accurate and detailed level indicator with multiple intermediate steps for more accurate display of the remaining tank contents.

In an alternative, not shown, the integrated module is inserted as an integrated module in a arranged in the upper region of the tank opening from above and sealed by means of O-ring seals. The tank then has at the bottom of a continuous diffusion-tight plastic tub. Any leaks in the tank in case of incorrect assembly of the O-ring seals are excluded.

In this case, a heating element is integrated into the assembly and is thus also inserted from above into the tank, so that can be dispensed with the additional Aluminiumheizstab.

Claims

claims

An exhaust aftertreatment system for introducing a reducing agent into the exhaust stream of a selective catalytic reduction internal combustion engine, the system comprising a reducing agent tank and a pump for conveying the reducing agent from the tank to an injection unit characterized in that the tank (1) has at least one opening, wherein the pump (3) is formed as an integrated unit (2) and is inserted into the opening of the tank, wherein the integrated unit (2) forms a tank closure and sealing the tank closes.

2. exhaust aftertreatment system according to claim 1, characterized in that the structural unit (2) in a thread in the opening of the tank (1) is screwed sealingly or that the assembly (2) by means of a bayonet fitting sealingly inserted into the opening of the tank (1) is.

3. exhaust aftertreatment system according to claim 1 or 2, characterized in that the opening at the bottom and / or in the lower region of the tank (1) is arranged and the assembly (2) the tank (1) seals down.

4. exhaust aftertreatment system according to one of the preceding claims, characterized in that the system comprises a reducing agent filter (7) and / or a heating device (6, 9) for heating the reducing agent (15) and / or a temperature sensor (5) for detecting the reducing agent temperature and / or a power electronics (4) for controlling the pump (3) and / or a communication interface, in particular a standardized communication interface, in particular a CAN bus interface.

5. exhaust aftertreatment system according to one of the preceding claims, characterized in that the pump (3) as an integrated unit (2) a reducing agent filter (7) and / or a heating device (6) for heating the reducing agent (15) and / or a temperature sensor ( 5) for detecting the reducing agent temperature and / or the power electronics (4) for controlling the pump (3) and / or an interface, in particular a CAN bus interface.

6. exhaust aftertreatment system according to one of the preceding claims, characterized in that the pump (3) as an integrated unit (2) has a sensor (8) for detecting a substance property of the reducing agent, in particular for detecting the electrical conductivity and / or for detecting the speed of sound in the reducing agent.

7. exhaust aftertreatment system according to claim 6, characterized in that the sensor (8) for detecting a substance property of the reducing agent is arranged such that the signal of the sensor (8) at the same time used as a level indicator for detecting the undershooting a Mindestfüllhöhe in the tank (1) can be.

8. exhaust aftertreatment system according to one of the preceding claims, characterized in that the system comprises a control device by means of which the pump (3) is controlled in dependence of the measured values detected by sensors and / or in dependence of current operating parameters of the internal combustion engine, in particular controlled by a bus system becomes.

9. exhaust aftertreatment system according to one of the preceding claims, characterized in that between the assembly (2) and the tank (1) at least one seal, in particular an O-ring seal (10) is arranged.

10. exhaust aftertreatment system according to any one of the preceding claims, characterized in that the system comprises an injection unit with at least one nozzle through which the reducing agent (15) injected into the exhaust stream and / or is atomized in the exhaust stream.

11. exhaust aftertreatment system according to one of the preceding claims, characterized in that the system comprises an SCR catalyst, in which the reducing agent (15) is introduced into the exhaust gas stream of the internal combustion engine for selective catalytic reduction, wherein before and / or behind the SCR catalyst a sensor for detecting the nitrogen oxide concentration in the exhaust gas is arranged.