DE102013008835B4 - Motor vehicle with an additive container, in particular for an SCR reducing agent - Google Patents

Abstract

Motor vehicle (300), comprising - an exhaust pipe (150), - a container (100) for holding a liquid additive, - a conveying unit (120) for conveying the liquid additive into the exhaust pipe (150) and - a plurality of wheel arches (200) , characterized in that the container (100) is arranged in one of the wheel housings (200) of the motor vehicle and is fastened by means of a fastening device (104) arranged in the wheel housing (200), which is designed to selectively fasten the container or an activated carbon filter .

Description

The invention relates to a motor vehicle with an exhaust pipe, a container for holding a liquid additive, a conveying unit which is capable of conveying the liquid additive into the exhaust pipe, and a plurality of wheel arches.

Internal combustion engines that operate temporarily or predominantly with a lean air-fuel mixture produce nitrogen oxides NO _x (mainly NO ₂ and NO), which require NO _x -reducing measures. An engine measure to reduce raw NO _x emissions in the exhaust gas is exhaust gas recirculation, in which part of the exhaust gas from the internal combustion engine is returned to the combustion air, thereby lowering the combustion temperatures and thus reducing NO _x production. However, exhaust gas recirculation is not always sufficient to comply with legal NO _x limits, which is why additional active exhaust gas aftertreatment is required, which reduces the final NO _x emissions. A known NO _x exhaust gas aftertreatment involves the use of discontinuously operated NO _x storage catalysts, which store nitrogen oxides in the form of nitrates in lean operation (at λ > 1) and the stored nitrogen oxides in short intervals with a rich exhaust gas atmosphere (λ < 1). desorb and reduce to nitrogen N ₂ in the presence of the reducing agents HC and H ₂ present in the rich exhaust gas.

Another approach to converting nitrogen oxides in exhaust gases from lean-burn combustion engines is the use of catalyst systems that work according to the principle of selective catalytic reduction (SCR). These systems include at least one SCR catalytic converter (also referred to as a DeNOx catalytic converter), which converts the nitrogen oxides of the exhaust gas into nitrogen and water in the presence of a reducing agent, usually ammonia NH ₃ , which is continuously supplied to the exhaust gas. The ammonia can be metered into the exhaust gas stream in gaseous form or as an aqueous ammonia solution. Alternatively, an NH ₃ -releasing precursor compound is often used, from which ammonia is obtained by thermolysis and hydrolysis. The most common precursor compound for ammonia is currently urea, which is used in the form of solid urea pellets or an aqueous urea solution.

Regardless of the type of reducing agent used, it must be stored and carried in the vehicle. In the case of liquid reducing agents or reducing agent solutions, reducing agent containers are provided for this purpose, which are filled via a filling line. Space constraints sometimes make it necessary for the filling line to open into a lower region of the reducing agent container, which in turn can result in problems with the escape of the air displaced by the inflowing reducing agent while the container is being filled. In order to effectively use the available installation space, it is often necessary to adapt the shape of the container to the installation space. This results in unfavorable container shapes, such as flat and/or irregular shapes (e.g. L-shape), which in turn have an unfavorable effect on level and temperature measurement. In addition, limited ice strength can occur, as the freezing point of the urea solution commonly used as a reducing agent carrier is -11 °C. In order to solve the problems underlying the container shape, the use of baffles to reduce sloshing noises and the use of heating mats installed in addition to the heating element of the conveyor unit are known. The latter is intended to ensure sustainable dosing readiness for frozen reducing agents.

In order to ensure the supply of the liquid reducing agent into the exhaust line, a delivery unit is usually provided, which includes a delivery pump and a filter unit. In addition, the containers are typically equipped with an integrated level and temperature sensor as well as a heating element. This equipment significantly increases the space requirement of the entire unit, which is problematic given the limited number of possible installation locations in the motor vehicle.

Stricter legal requirements for exhaust gas composition, as well as efforts to significantly reduce the size of the container, mean that in the future the reducing agent supply in passenger cars can no longer be filled exclusively within the service interval. Constructions in which the container is difficult to access, such as in the subfloor ( DE 10 2007 019 912 A1 ) are therefore no longer useful.

Also trying to divide the supply between a harder to access large container in the trunk and an easier to access smaller container in the engine compartment, as in DE 10 2007 005 006 A1 described are insufficient. Rather, it must be possible for the driver of the vehicle to fill the container quickly and easily. In order to improve accessibility when filling, it is also known to mount the container near a wheel house in such a way that the filler neck protrudes into the wheel house ( DE 10 2008 020 213 A1 ).

With the accommodation of washer fluid containers for windshield or headlight wiper systems genes deal with, for example DE 10 2011 118 929 A1 , JP S60 - 169 355 A and DE 199 44 881 A1 .

The invention is based on the object of providing a motor vehicle in which the reducing agent container is arranged in the vehicle in such a way that it can be filled in a simple and convenient manner by the driver at regular intervals, for example when refueling. Ideally, it should be ensured that all supply, exhaust and ventilation lines can be designed to be as short as possible and free of siphons.

This task is achieved by a motor vehicle with the features of claim 1.

The motor vehicle according to the invention comprises an exhaust pipe, a container for holding a liquid additive, a conveying unit for conveying the liquid additive into the exhaust pipe, and a plurality of wheel arches. According to the invention it is provided that the container is arranged in one of the wheelhouses of the motor vehicle and is fastened by means of a fastening device arranged in the wheelhouse, which is designed to selectively fasten the container or an activated carbon filter.

By arranging the container in the wheelhouse, it is possible to make the inlet and outlet lines very short. Due to the installation space, it is often unavoidable in known vehicles that the supply and discharge lines pass through local low points with regard to their line routes and thus form siphon sections, so to speak, for example in order to bypass the vehicle's supports. The positioning according to the invention in the wheel house, on the other hand, enables the discharge lines to be laid without a siphon due to the relative height to the exhaust pipe. In addition, the container is easily accessible. The accessible container ensures that refilling and/or replacing the container is possible without a visit to the workshop and can take place independently of a service interval. This makes it easy for the user to refill if necessary.

In gasoline vehicles, it is common practice to install an activated carbon filter to bind fuel vapors in a rear wheel arch. By coordinating the fastening of the activated carbon filter and the fastening of the container according to the invention, the same fastening device can be used on the body side. The advantage of this is that the same body type can be used for diesel vehicles that do not use an activated carbon filter and therefore no different processes are necessary for diesel or gasoline vehicles when producing the body.

In a preferred embodiment of the invention it is provided that the container is arranged in the wheel house which is located in the immediate vicinity of a filling device, in particular a tank trough, for filling a fuel tank of the motor vehicle. In particular, this is a wheel arch of the rear axle of the vehicle. This arrangement has the advantage that the installation space is already adapted to the requirements of pipe systems for liquid media, such as fuel, and can therefore ensure siphon-free installation.

The arrangement in the vicinity of the fuel filling device also makes it possible to arrange a filler neck for filling the container, preferably directly in the fuel filling device, in particular in a common tank trough. This advantageously enables the container to be filled during fuel filling intervals. Furthermore, no additional tools are required. Rather, the user is familiar with this process and can easily integrate the additional filling of the container into their usual routines.

To make this possible, the dimensions of the container are preferably chosen so that a volume can be stored that covers the need for the liquid additive during the consumption of a tank filling. A preferred range is between 6 and 12 liters. This volume is significantly lower than concepts currently used, in which the container volume is designed for filling or replacement only during service intervals.

In the described embodiment of the filler neck of the container in the immediate vicinity of the filler neck of the fuel system, the invention provides, in a preferred embodiment, a separation between the two filler necks, which prevents simultaneous filling. Rather, only one filler neck is always accessible. This prevents accidental contamination of each other's systems.

In a preferred embodiment of the invention it is provided that the discharge lines of the container open into an exhaust pipe of the motor vehicle. The mouth is preferably located upstream of a catalytic converter. An SCR catalytic converter for exhaust gas purification is particularly preferred. The advantage resulting from this arrangement is that the container is preferably filled with a liquid additive, which is necessary for the functional way of the SCR catalyst supplies the necessary reducing agents.

In a further preferred embodiment of the invention, the liquid additive is therefore a reducing agent. In the context of the present invention, the term “reducing agent” is also understood to mean a precursor compound (reducing agent carrier) which releases the actual reducing agent (in particular ammonia NH ₃ ) through further process steps. In particular, in the context of the present invention, the liquid reducing agent or the liquid reducing agent solution also includes solutions of urea or ammonia in a suitable solvent, in particular water.

Since chemical decomposition can occur when storing a liquid additive, especially when using a reducing agent, in particular the urea solution, and decomposition products of all aggregate states can occur, a preferred embodiment of the invention provides a closure for closing the filler neck before and after filling before. This can be either a manually lockable lid or a self-closing mechanism. Another advantage of closing the filler neck is preventing contamination from the fluid from the other system.

The container must be designed so that it is suitable for storing the reducing agent described above. In addition to suitable materials, this also includes the shape of the container. The container in the motor vehicle according to the invention is preferably designed in a tall shape. This means a ratio of height to length of the base area in the case of a rectangular container or a ratio of height to diameter of the base area of a cylindrical container, which is greater than one. The design of the container in a high shape offers the advantage that the functional requirements for the container can be implemented without complex additional measures. Specifically, this means that, for example, a sensor system installed to transmit the level to a display panel can detect the level with a significantly higher level of accuracy than with a flat version of the container. In addition, the use of baffles is not necessary since the liquid surge is greatly reduced in a tall container shape, especially a cylindrical one, due to the smaller moving masses. In order to ensure sustainable readiness for dosing, it is often necessary to install specific heating mats in flat and/or irregularly designed containers in order to thaw the frozen reducing agent and make it ready for dosing, particularly in the case of filling with urea solution. In the case of frozen liquid, the tall shape is still preferred because, particularly in the case of irregular containers, the expansion in the frozen state can lead to the container walls being subjected to excessive stress. In particular, with the L-shape typical of known reducing agent containers, an expansion volume of approximately 10% cannot be maintained everywhere in the container, since this is physically only possible at the top of the container.

A preferred embodiment of the container provides for the attachment of at least one temperature sensor and/or fill level sensor and/or at least one heating element. The sensor system enables the liquid additive to be monitored in such a way that, on the one hand, notification is made in a display field about the need for refilling. On the other hand, when using a temperature sensor in the case of solid or solidifying additive, a sensible connection to the heating element triggers the activation of the same and thus restores the ability to meter the additive.

The liquid additive is preferably metered in by means of a delivery unit, in particular comprising a delivery pump, a pump sump, and also a filtering unit, which is designed, for example, as a sieve. Both a flexible arrangement of the feed pump on the container and a separate external feed pump are preferred. In a preferred embodiment of a firmly connected pump, a recess is provided on the container, which is adapted in shape and size to the delivery unit. This means that the space next to the conveyor unit can also be used as a container volume. The advantage of using an external pump is that the preferred volumes of up to 10 liters can be achieved even when the container is installed in the wheel house. The overall package consisting of a container and a permanently integrated conveyor unit previously made it difficult to arrange sensible container sizes in the wheelhouse. Furthermore, standardized container shapes can be used.

• 1 eine schematische Darstellung eines Kraftfahrzeugs mit einem Behälter und einer Abgasleitung nach einer ersten Ausgestaltung der Erfindung,
• 2 eine schematische Darstellung eines Behälters zur Bevorratung eines flüssigen Additivs mit Fördereinheit nach einer bevorzugten Ausgestaltung; a) Seitenansicht; b) Ansicht von der Unterseite des Behälters, und
• 3 eine schematische Darstellung der Anordnung einer Befülleinrichtung nach einer ersten Ausgestaltung der Erfindung.

The invention is explained below in exemplary embodiments using the associated drawings. Show it:

• 1 a schematic representation of a motor vehicle with a container and an exhaust pipe according to a first embodiment of the invention,
• 2 a schematic representation of a container for storing a liquid additive with a delivery unit according to a preferred embodiment; a) side view; b) View from the bottom of the container, and
• 3 a schematic representation of the arrangement of a filling device according to a first embodiment of the invention.

1 shows a motor vehicle marked 300 in total. The side of the motor vehicle 300 is shown, on which a filling device of a fuel tank, not shown here, is arranged. The motor vehicle 300 has four wheel arches 200, two of which are visible here.

The vehicle has an internal combustion engine (not shown here) as a drive source in the front engine compartment, which is in particular a diesel engine. A fuel tank of the internal combustion engine, also not shown, is refueled via a filling device 180 designed here as a tank trough.

The internal combustion engine is fluidly connected to an exhaust pipe 150, which houses an SCR catalytic converter 151. This is designed to selectively catalytically convert nitrogen oxides from the exhaust gas of the internal combustion engine in the presence of a reducing agent. In the present example, an aqueous urea solution, which is stored in a storage container 100, is used as the reducing agent. The urea solution is conveyed by means of a conveying unit 120 from the container 100 via a line 140 to a controllable metering device 141, which meters the urea solution into the exhaust line 150 upstream of the SCR catalytic converter 151. The urea decomposes through hydrolysis and thermolysis to form ammonia, which acts as the actual reducing agent in the catalyst 151.

According to the invention, the storage container 100 is arranged in one of the wheel arches 200. As shown here, the wheel house 200 that is in the immediate vicinity of the tank trough 180 is preferred. The container is filled via a filler neck 110. The filler neck is located in the tank well, as is a fuel filler neck. When filling the container, the reducing agent enters the container 100 via a filling pipe 111 connected to the filler neck 110. The level of the reducing agent in the container is monitored with a level sensor 102 in the lower area of the container. In addition, a temperature sensor 103 is attached near the level sensor 102. A heating element 101, which can also be activated and is also mounted in the container, serves to heat and thaw the solution if the temperature drops below the freezing point of the solution, which is reached at -11 ° C for urea solution. The heating element ensures that dosing can be achieved at any ambient temperature.

A vent 130 is arranged above the maximum fill level of the container. The ventilation is led into the tank trough 180.

A possible design of the container 100 with integrated conveyor unit 120 is explained in more detail below.

2 shows, in a preferred embodiment of the invention, the container 100 with a permanently integrated conveyor unit 120. A tall form of a rectangular container is shown. This means that the ratio between the height h of the container and the length l or width b of the base area is greater than one.

The container can be attached to a body of the vehicle or to a fastening device by means of several fastening tabs 104.

For optimal use of installation space, a recess 124 is embedded in the container, the shape and size of which is designed so that it can accommodate the conveyor unit 120. The conveyor unit is arranged within this recess.

In addition to a pump, the delivery unit includes a heating element, not shown, and a temperature sensor, also not shown, in order to monitor and prevent freezing of the reducing agent in the pump. The reducing agent is sucked out of a pump sump 122 through a suction line 125. The pump sump 122 is designed as a depression of the container 100 at its lowest point. In order to retain solid components, a filter unit 123, which can be designed in the form of a sieve, is arranged in the pump sump 122 in front of the suction line 125. An upper output of the delivery unit includes a connection for the discharge, not shown. The reducing agent is conveyed via the discharge line into the exhaust pipe using the metering device.

3 shows a section 1 . As in 1 shown, the container 100 is arranged in the wheel house 200 of the motor vehicle which is in close proximity to the filling device designed as a tank trough.

A detailed design of the tank trough 180 is shown. The tank trough 180 can be closed by a flap, not shown here, which is pivotally articulated on the side of the tank trough shown here on the right. The fuel filler neck 160 is arranged in the tank trough and is connected to the fuel tank, not shown, via a filler pipe 161. The filler neck 110 for the tank is also located in the tank trough Container 100. The filler neck for the container is designed differently than the fuel filler neck 160, in particular significantly smaller than this, so that a fuel nozzle cannot be inserted into the filler neck 110. A preferably screwable lid closes the filler neck 110 in order to prevent additional contamination by fuel.

The reducing agent enters the container through the filler neck 110 via a filling pipe 111. The vent 130 returns gases above the reducing agent into the tank cavity to avoid the formation of excess pressure. The filling pipe 111 as well as the vent 130 are arranged in such a way that no local low points (siphons) arise in which liquid can collect and filling and/or venting is hindered.

Reference symbol list

100

container

101

Heating element

102

Level sensor

103

Temperature sensor

104

Fastening tabs

110

Filler neck

111

Filling pipe

120

conveyor unit

121

Connection

122

pump sump

123

Filter unit

124

recess

130

Venting

140

heated line

141

Dosing device

150

Exhaust pipe

151

SCR catalyst

160

Fuel filler neck

161

Fuel filler pipe

180

Filling device (tank trough)

200

Wheelhouse

300

motor vehicle

Claims (8)

Motor vehicle (300), comprising - an exhaust pipe (150), - a container (100) for holding a liquid additive, - a conveying unit (120) for conveying the liquid additive into the exhaust pipe (150) and - a plurality of wheel arches (200) , characterized in that the container (100) is arranged in one of the wheel housings (200) of the motor vehicle and is fastened by means of a fastening device (104) arranged in the wheel housing (200), which is designed to selectively fasten the container or an activated carbon filter . motor vehicle Claim 1 , characterized in that the container is mounted in the wheel house which is arranged in the vicinity of a filling device (180), in particular a tank trough, for filling a fuel tank of the motor vehicle. motor vehicle Claim 2 , characterized in that a filler neck (110) for filling the container is arranged in the filling device (180) for the fuel of the motor vehicle. Motor vehicle according to one of the preceding claims, characterized in that the exhaust pipe comprises an SCR catalytic converter (151) and a feed of the additive opens into the exhaust pipe upstream of the SCR catalytic converter. Motor vehicle according to one of the preceding claims, characterized in that the additive is a reducing agent, preferably comprising urea in solution. Motor vehicle according to one of the preceding claims, characterized in that the container (100) is designed such that its height is greater than the length of a rectangular base or the diameter of a round base. Motor vehicle according to one of the preceding claims, characterized in that the container (100) is equipped with at least one element selected from the group of temperature sensor (103), fill level sensor (102) and/or heating element (101). Motor vehicle according to one of the preceding claims, characterized in that the conveying unit (120) is attached to the container, in particular in a recess (124) in the container.

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