Conveyor unit for a liquid additive

Abstract

Conveying unit (1) for a liquid additive, comprising a block (2) with channels (3) to which at least one active component (4) for conveying the liquid additive is mounted, wherein at least three channels (3) in the block (2) open into a cylindrical collecting chamber (5), and a deformable sleeve-shaped element (6) is arranged in the collecting chamber (5), wherein the sleeve-shaped element (6) has at least one sealing lip (26) which seals the collecting chamber against the surroundings of the block.

Description

The invention relates to a conveying unit for conveying a liquid additive. This delivery unit can be used, for example, in a motor vehicle in order to deliver a liquid additive to an exhaust gas treatment device.In particular in motor vehicles with diesel internal combustion engines, exhaust gas treatment devices are used to which a reducing agent is supplied as liquid additive for cleaning the exhaust gases of the internal combustion engine. An exhaust gas purification method which is particularly frequently used in exhaust gas treatment devices of this type is the selective catalytic reduction (SCR method, SCR=selective catalytic reduction) method. In this method, nitrogen oxide compounds in the exhaust gas of the internal combustion engine are reacted with ammonia to produce harmless substances such as water (H2O), nitrogen (N2) and CO2. Ammonia is normally not stored directly in motor vehicles, but rather in the form of a precursor solution which can be supplied to the exhaust gas treatment device as a liquid additive. A 32.5 percent urea-water solution, also available under the trade name AdBlue® can be used as the precursor solution.To provide a liquid additive in a motor vehicle, a delivery unit is provided, as described here. A problem with such a delivery unit is that typical liquid additives (such as the urea-water solution described, for example) freeze at low temperatures. AdBlue® freezes at about -11° C., for example. Such temperatures can occur during long pauses in the operation of the motor vehicle. When the liquid additive is frozen, a volume expansion occurs which can damage the conveying unit. A conveying unit should therefore be designed such that it is not damaged by liquid additive expanding during freezing.In addition, a delivery unit for liquid additive should be able to be produced as cost-effectively as possible and should have as high a dosing accuracy as possible and as long a service life as possible.DE 100 40 571 A1 discloses an apparatus which is part of a system for post-treatment of the exhaust gas of an auto-ignition internal combustion engine, wherein the effect of a reduction catalyst is improved by the reducing agent-air mixture generated by this apparatus. The device has a mixing chamber into which reducing agent can be introduced via a reducing agent feed controlled by a metering valve and air via an air feed. The mixing chamber is formed in a mixing chamber body to which a valve body of the metering valve is connected. The mixing chamber opens into a connecting piece towards the metering valve, and the metering valve has a valve member which, for controlling the supply of reducing agent into the mixing chamber, interacts at least indirectly with the end face of the connecting piece as a valve seat. The valve body is screwed into a bore of the mixing space body. This results in a simple construction of the device with few components which are simple to install.DE 10 2011 116 335 A1 discloses a conveying device for conveying reducing agent into an exhaust gas treatment device having at least one conveying channel with at least one flexible wall region. The flexible wall region may deform when reductant in the feed passage freezes. The flexible wall region delimits the conveying channel from a compressed air chamber which is connected to a compressed air source.Proceeding from this, it is the object of the present invention to solve the technical problems described in a particularly advantageous manner. In particular, a particularly cost-effective delivery unit for a liquid additive is to be disclosed, which is resistant to freezing liquid additive.These objects are achieved with a device according to the features of claim 1. The features listed individually in the patent claims can be combined with one another in any desired, technologically meaningful manner and can be supplemented by explanatory facts from the description, wherein further embodiment variants of the invention are shown.The conveying unit for a liquid additive has a block with channels, to which at least one active component for conveying the liquid additive is mounted, wherein at least three channels in the block open into a cylindrical collecting space, and a deformable sleeve-shaped element is arranged in the collecting space, wherein the sleeve-shaped element has at least one sealing lip, which seals the collecting space with respect to the surroundings of the block.The block preferably represents a type of (separate) basic structure on which all components of the conveying unit are mounted. The block has channels which connect the individual active components of the conveying unit in a liquid-conducting manner. The channels can be designed in the block as recesses and / or as bores. Active components are understood here to mean all components which assume an active function when the liquid additive is conveyed by the conveying unit. The most important active component of a delivery unit is typically a pump which delivers and / or meters the liquid additive. Further active components are, for example, valves which control the provision or the delivery of the liquid additive, sensors which monitor the operation of the delivery unit and / or the properties of the liquid additive, and / or ice pressure compensation elements which permit a defined deformation when the liquid additive solidifies in the delivery unit. The active components are preferably mounted to the block from the outside so as to be adjacent to the channels in the block and are interconnected via channels in the block.The channels (in particular all channels) in the block of the described conveying unit open into a substantially cylindrical collecting space. The collecting space is preferably designed as a recess or as a bore in the block, which extends from an outer side into the block. The collecting channel is distinguished in particular in that it has a significantly larger or widened cross section compared to the channels. Even if a cylindrical shape is specified here for describing the basic shape of the collecting space, a shape which deviates (slightly) therefrom and can have, for example, chamfers, grooves, local widenings / narrowings can also be selected. Preferably, the diameter of the plenum is at least twice, and more preferably at least three times, the average diameter of the channels in the block.On the surface of the block there is preferably a circular opening from which the collecting space extends into the block. In the collecting space there is a deformable sleeve-shaped element. In this case, the shapes of the collecting space and element preferably correspond such that a substantially uniform annular gap is formed between them. The deformable sleeve-shaped element is preferably inserted into the cylindrical collecting space starting from the described opening. The deformable sleeve-shaped element preferably has at least one sealing lip which seals the collecting space with respect to the surroundings of the block. Preferably, all the channels in the block open into the collecting space. Channels are preferably provided in the block connecting each individual active component on the block to the collection space. Preferably, no branches of the channels with each other are provided in the block, which are spaced apart from the collecting space. Preferably, all channels in the block are (only) connected to each other via the collecting space. Preferably, the plenum represents the central connection of all channels in the block. Therefore, at least three channels open into the collecting chamber. A channel is connected to a pump. A channel is connected to a line connection at which the delivery unit provides liquid additive (from a tank). A further channel is connected, for example, to a return valve or to a sensor. In a preferred embodiment variant, even at least four channels open into the collecting chamber.This design of a conveying unit makes it possible for a freezing-induced volume expansion of the liquid additive occurring in the channels in the block of the conveying unit to be conducted through the channels preferably or even always in the direction of the collecting chamber, starting from the active components. Liquid additive is thus present in the collecting chamber during freezing until the last time, and the volume expansion of the liquid additive can be effectively introduced into the sleeve-shaped element in the collecting chamber. This enables a particularly effective, reliable and cost-effective compensation of the ice pressure during freezing of the liquid additive in the conveying unit. In particular, dangerous pressure increases in this way in the region of the channels or near the active components are avoided.Furthermore, the conveying unit is advantageous if the sleeve-shaped element expands due to elastic stresses when the conveying unit is deactivated and the sleeve-shaped element thus displaces liquid additive from the collecting chamber.In the event of deactivation of the conveying unit, the pressure of the additive in the channels is reduced because the active components do not maintain the pressure in the channels. During the operation of the conveying unit, an operating pressure of, for example, between 3 bar and 9 bar is present in the channels. This operating pressure is generated by a pump (as an active component). The pressure drops, for example, because the pump ceases operation when the delivery unit is deactivated. It is also possible that during deactivation a valve is opened, which releases a flow path from the channels back into a tank. Such a valve is preferably a return valve which releases a return line. By opening such a valve, a pressure drop takes place in the delivery unit.A return line is typically a flow path through at least one channel, so that a circulation delivery of liquid additive from the tank through the delivery unit and back into the tank is possible. Such a circulation conveying is particularly advantageous in order to convey air bubbles in the liquid additive out of the conveying unit. The return line preferably branches off from a conveying path for the liquid additive behind the pump. The delivery path typically denotes the path of the liquid additive from a withdrawal point on the tank to a consumer, such as a supply device for supplying the additive to an exhaust gas treatment device. The return line can be opened and / or closed by the described return valve in order to optionally enable or prevent circulation through the return line.Due to the decreasing pressure in the conveying unit or in the channels and in the collecting space in the event of deactivation, the sleeve-shaped element can thus preferably expand or expand. The sleeve-shaped element is accordingly preferably compressed during operation of the conveying unit or pressed against a surface in order to be able to expand (automatically) when the conveying unit is deactivated. When the sleeve-shaped element expands, the sleeve-shaped element preferably displaces liquid additive from the collecting space. The liquid additive is preferably forced back into the tank through a described return line. It is additionally or alternatively possible for the liquid additive to be forced against the normal conveying direction back into the tank.By pushing the liquid additive out of the collecting chamber, space is created in the collecting chamber when the conveying unit is deactivated, which space can be used in the event of freezing to absorb an expansion of the liquid additive during freezing. The space is in particular a space assigned to the sleeve-shaped element, preferably an inner cavity.The conveying unit is particularly advantageous if the block consists of a plastic material. A block made of a plastic material is particularly cost-effective and can be produced particularly easily in the desired shape with the cylindrical collecting space and the various channels. The block of the plastic material is preferably produced by an injection molding process. An injection molding method enables particularly cost-effective production of the block.Furthermore, the conveying unit is advantageous if, during operation of the conveying unit, at least one tubular first connecting space exists in the collecting space between the block and the sleeve-shaped element, which first connecting space is filled with liquid additive.The operation of the conveying unit here means an operating mode in which the liquid additive is under pressure in the collecting space and in the channels. The collecting chamber preferably has a first diameter. The sleeve-shaped element preferably has a second diameter which represents an outer diameter of the sleeve-shaped element. The second diameter is preferably smaller than the first diameter and the sleeve-shaped element is preferably arranged concentrically in the collecting space. Between the sleeve-shaped element and the wall of the collecting chamber, a tubular connecting chamber (in the manner of an annular gap) is thus produced, which forms the tubular first connecting chamber. The various channels in the block open at openings into this collecting chamber and thus into the tubular first connecting chamber.The tubular first connecting space, which is bounded by the collecting space and the sleeve-shaped element, realizes the fluidic connection between the individual channels in the block. It is possible that not only a tubular first connecting space exists in the collecting space. It is also possible that an additional tubular second connecting space exists. This tubular second connecting space can be delimited from the first connecting space by a sealing lip on the sleeve-shaped element. The first connection space can then establish a fluidic connection between a first group of channels in the block, while the second connection space establishes a fluidic connection between a second group of channels in the block. The first connecting space and the second connecting space can be fluidically separated from one another by a substantially annular sealing lip arranged on the sleeve-shaped element. The outer diameter of the sealing lip preferably corresponds to the diameter of the cylindrical collecting space, so that the sealing lip seals the first connecting space with respect to the second connecting space within the cylindrical collecting space. If a plurality of connecting spaces are formed with the collecting space and the sleeve-shaped element, these are arranged adjacent to one another in particular in the direction of the axial extent of the collecting space or sleeve-shaped element and are separated from separating webs on the inner wall of the collecting space and / or sealing lips on the outer surface of the sleeve-shaped element. The plurality of connecting spaces can differ from one another in particular with regard to their dimensions (inner diameter, outer diameter, axial length) and can thus accommodate different volumes of the liquid additive.The sleeve-shaped element is preferably made of an elastic plastic.The sleeve-shaped element is very particularly preferably made of a rubber material. Such a material is particularly suitable for absorbing expansions of the liquid additive in the event of freezing by a deformation. Of course, a material is to be selected which is correspondingly stiff / deformable at the applied pressures and is also resistant to the liquid additive.The conveying unit is particularly preferred if a stiffening structure is arranged in an interior space of the sleeve-shaped element, against which a wall of the sleeve-shaped element abuts during operation, so that the sleeve-shaped element is stiffened during operation.The term "operation" is understood here in particular to mean a mode in which a delivery of liquid additive takes place with the delivery unit and the operating pressure described further above is present in the channels in the block or in the cylindrical collecting space. This pressure compresses the sleeve-shaped element. Since the sleeve-shaped element is preferably made of an elastic plastic material or even of a rubber material, the sleeve-shaped element would be compressed further and further with increasing pressure in the collecting space and in the channels. A stiffening structure within an interior space of the sleeve-shaped element can ensure that the sleeve-shaped element is pressed (finally after a desired shrinkage / compression) against this stiffening structure when the pressure in the collecting space reaches a limit pressure. As a result, the sleeve-shaped element is deformed only very little or no longer any further by further increasing pressure.This makes it possible for the sleeve-shaped element to behave substantially rigidly in the region of the operating pressure. A deformation of the sleeve-shaped element in the range of the operating pressure could interfere with the metering accuracy of the delivery unit. This could lead to it not being possible to detect exactly whether the liquid additive has actually been discharged / conveyed at the line connection or has merely led to a deformation of the sleeve-shaped element. This can be prevented precisely by the described stiffening structure.The sleeve-shaped element is preferably designed in the manner of a pipe socket or a cap made of rubber and closed on one side. This sleeve-shaped element thus has an opening opposite the described closed side. The sleeve-shaped element is preferably arranged in the collecting space such that the opening extends towards an outer side of the block. Through this opening, the stiffening structure can be inserted into the sleeve-shaped element.The conveying unit is particularly preferred if the stiffening structure is designed as a slotted sleeve which is inserted into the interior of the sleeve-shaped element. The stiffening structure can additionally have a structure by means of which the stiffening structure is fixed in the sleeve-shaped element. The stiffening structure can thus optionally also be deformed to a certain extent, for example until the slot has closed, and then behave rigidly. Such a slotted sleeve can be gripped and compressed with a tool (for example a pliers tool) and introduced into the interior of the sleeve-shaped element. The stiffening structure prevents, in particular, the sleeve-shaped element from collapsing or pressing flat under high pressure in the collecting space or in the channels.Furthermore, the conveying unit is advantageous if grooves are formed on the outer side of the sleeve-shaped element, wherein the grooves can form a fluidic connection between the channels in the block.Preferably, the grooves are not the only fluidic connection between the channels in the block. Preferably, there is additionally the at least one described tubular connecting space which connects channels to one another. The grooves represent, for example, a section-wise enlargement of the tubular connecting space, which specifically enables an improved flow of liquid additive between the individual channels. The grooves therefore preferably run only within an individual connecting space or they are interrupted by the separating webs / sealing lips. Preferably, only a small number of such grooves are provided, such as 2, 3, 4 or 5.Furthermore, the conveying unit is advantageous if the at least one active component is braced in a receptacle of the block with a clamping plate, wherein the block has a slot through which the clamping plate is pushed laterally into the receptacle and engages in a groove on the active component.Here, a connection concept is described, with which active components can be connected to a block of a conveying unit, wherein this connection concept is particularly advantageous for conveying units with a block made of plastic.The groove represents in particular a tapering of a connection of the active component. By inserting the clamping plate, a constriction is formed in the receptacle, so that the connection of the active component is held in the receptacle. Preferably, the clamping plate has a curvature such that it is under tension in the slot on the block and in the groove of the active component and clamps the active component in the receptacle. Such a conveying unit with an active component coupled via a clamping plate can be combined as desired with all other features disclosed in this document.The ideas presented here are used in particular in a motor vehicle, having an internal combustion engine, an exhaust gas treatment device for cleaning the exhaust gases of the internal combustion engine, a tank for storing a liquid additive, and a described delivery unit for delivering the liquid additive from the tank into the exhaust gas treatment device. The exhaust gas treatment device preferably includes an SCR catalyst in which the SCR process may be performed to reduce nitrogen oxide compounds in the exhaust gas. The liquid additive conveyed by the conveying unit is added to the exhaust gas treatment device preferably in metered fashion via an injector.The invention and the technical field are explained in more detail below with reference to the figures. The figures show particularly preferred exemplary embodiments, to which the invention is, however, not limited. In particular, it should be pointed out that the figures and in particular the size relationships illustrated are only schematic. The following are shown:FIG. Ref. 1: a conveying unit described above,FIG. Ref. 2: a sleeve-shaped element for a described conveying unit,FIG. Ref. 3: a reinforcing structure for a sleeve-shaped element,FIG. Ref. 4: a section through a sleeve-shaped element with an inserted stiffening structure,FIG. Ref. 5: a tank for a liquid additive, into which a described conveying unit is inserted,FIG. Ref. 6: a motor vehicle having a described conveying unit,FIG. Ref. 7: a connection of an active component to a block, andFIG. Ref. 8: a clamping plate for the Ref shown in Figure. The connection shown in FIG. 7 is shown.In Figure Ref. The block 2 of a conveying unit 1 is shown in FIG. 1, channels 3 are arranged in the block 2, which open into a collecting space 5 in the block 2. The channels 3 each connect a receptacle 10 for an active component 4 to the collecting chamber 5. In total, three channels 3 are shown here, each of which opens into the collecting chamber 5 at a separate opening 25. A sleeve-shaped element 6 is arranged in the collecting chamber 5, which is reinforced with a reinforcing structure 7. The sleeve-shaped element 6 has an interior 29 in which the stiffening structure 7 is arranged. The sleeve-shaped element 6 is fixed to the block 2 by a securing pin 11.In Figure Ref. Figure 2 is a sleeve-shaped element 6 for the conveying unit according to Figure Ref. The embodiment of the embodiment is illustrated in FIG. 1. The sleeve-shaped element 6 has a groove 9 on its outer side 8. This groove can allow an improved flow path within the collecting space between two ports of channels in the block, because the space available for the fluid flow in the collecting space is locally increased by the groove 9.FIG. Ref. FIG. 3 shows a stiffening structure 7, which can be inserted into a sleeve-shaped element. The stiffening structure 7 is designed here as a slotted sleeve or insert, which can be inserted through an opening of the sleeve-shaped element into an interior space of the sleeve-shaped element. The stiffening structure 7 has a wall 30 or a surface against which the sleeve-shaped element abuts when an operating pressure is present in the collecting space during operation of the conveying unit. As a result, the stiffening structure 7 stiffens the sleeve-shaped element during operation. If the pressure in the collecting chamber decreases after deactivation of the conveying unit, the sleeve-shaped element expands and, if appropriate, only rests loosely against the wall 30.FIG. Ref. FIG. 4 shows a cross section through a sleeve-shaped element 6 with an inserted stiffening structure 7. During operation of the conveying unit, the sleeve-shaped element 6 rests with its inner side against the wall 30 of the stiffening structure 7. The sleeve-shaped element 6 has sealing lips 26 which can abut the block of a conveying unit when the sleeve-shaped element 6 is inserted into the collecting space in the block. The sealing lips 26 are configured to seal against a surface of the collecting space. In this case, a first connecting space 27 and a second connecting space 28 are delimited from one another by the sealing lips 26. Channels in the block can open into the collecting space either in the region of the first connecting space 27 or in the region of the second connecting space 28. The first connecting space 27 and the second connecting space 28 are separated from one another by a sealing lip 26. Channels which open into the first connecting space 27 are therefore only connected to channels which likewise open into the first connecting space 27. Channels which only open into the second connecting space 28 are accordingly only connected to channels which likewise open into the second connecting space 28.FIG. Ref. FIG. 5 shows a tank 20 in which a conveying unit 1 is arranged. The conveying unit 1 has a housing 13 which is inserted into the bottom of the tank 20. The liquid level 31 in the tank can be seen. The block with channels 3 and the collecting chamber 5 is located inside the housing 13, and a pump 12 is shown here as an active component 4 on the block 2. The pump 12 takes liquid additive from the tank at the intake point 23 and conveys the liquid additive through the channels 3 in the block 2 to a line connection 24, to which a fluid line for conducting the liquid additive to a consumer can be connected. FIG. Ref. FIG. 6 shows a motor vehicle 17 having an internal combustion engine 18 and an exhaust gas treatment device 19 for cleaning the exhaust gases of the internal combustion engine 18. For this purpose, liquid additive can be supplied to the exhaust gas treatment device 19 with the aid of an injector 33. The injector 33 is supplied with liquid additive by a delivery unit 1 via a supply line 32, wherein the liquid additive is removed from a tank 20 by the delivery unit 1.FIG. Ref. FIG. 7 shows a possibility of connecting an active component 4 to a channel 3 in a block 2 of a conveying unit. Only a portion of block 2 is shown here. The block 2 has a receptacle 10 in which the channel 3 opens out and into which a connection 22 of the active component 4 can be inserted. The active component 4 or the connection 22 of the active component 4 has a groove 16. A clamping plate 14 can be inserted through a slot 15 on the block 2, which engages in the groove 16 of the active component 4 and thus fixes the active component 4 to the block on the receptacle 10.The clamping plate 14 from FIGS. Ref. 8 is Ref in Figure. This is shown in detail in FIG. 9. It can be seen that it has two arms, between which the groove of the active component is seated with its connection in the receptacle and the clamping plate 14 is inserted into the slot or the block.The conveying unit described here is particularly stable and durable, in particular even if the liquid additive to be conveyed regularly freezes in the conveying unit.List of reference characters1 Delivery unit 2 Block 3 Channel 4 Active component 5 Collecting chamber 6 Sleeve-shaped element 7 Stiffening structure 8 Outer side 9 Groove 10 Receptacle 11 Securing pin 12 Pump 13 Housing 14 Clamping plate 15 Slot 16 Groove 17 Motor vehicle 18 Internal combustion engine 19 Exhaust gas treatment device 20 Tank 21 SCR catalytic converter 22 Connection 23 Intake point 24 Line connection 25 Opening 26 Sealing lip 27 First connecting chamber 28 Second connecting chamber 29 Interior 30 Wall 31 Liquid level 32 Supply line 33 Injector

Claims

A delivery unit (1) for a liquid additive, comprising a block (2) with channels (3) to which at least one active component (4) for delivering the liquid additive is mounted, wherein at least three channels (3) in the block (2) open into a cylindrical collecting space (5), and a deformable sleeve-shaped element (6) is arranged in the collecting space (5), wherein the sleeve-shaped element (6) comprises at least one sealing lip (26), which seals the collecting space with respect to the surroundings of the block.Conveying unit (1) according to claim 1, wherein the sleeve-shaped element (6) expands due to elastic stresses when the conveying unit (1) is deactivated and the sleeve-shaped element (6) thus displaces liquid additive from the collecting space (5).A conveyor unit (1) according to any one of the preceding claims, wherein the block (2) is made of a plastics material.Conveying unit (1) according to one of the preceding patent claims, wherein, during operation of the conveying unit (1), at least one tubular first connecting space (27), which is filled with liquid additive, exists in the collecting space (5) between the block (2) and the sleeve-shaped element (6).Conveying unit (1) according to one of the preceding patent claims, wherein the sleeve-shaped element (6) is made of an elastic plastic.Conveying unit (1) according to one of the preceding patent claims, wherein an inserted stiffening structure (7) is arranged in an interior space (29) of the sleeve-shaped element (6), against which stiffening structure a wall (30) of the sleeve-shaped element (6) bears during operation, such that the sleeve-shaped element (6) is stiffened during operation.Conveying unit (1) according to claim 6, wherein the stiffening structure (7) is designed as a slotted sleeve which is inserted into the interior space (29) of the sleeve-shaped element (6).Conveying unit (1) according to one of the preceding patent claims, wherein grooves (9) are formed on the outer side (8) of the sleeve-shaped element (6), wherein the grooves (9) form fluidic connections between the channels (3) in the block (2).Conveying unit (1) according to one of the preceding patent claims, wherein the at least one active component (4) is braced in a receptacle (10) of the block with a clamping plate (14), wherein the block (2) has a slot (15), through which the clamping plate (14) is pushed laterally into the receptacle (10) and engages in a groove (16) of the active component (4).Motor vehicle (17) having an internal combustion engine (18), an exhaust gas treatment device (19) for cleaning the exhaust gases of the internal combustion engine (18), a tank (20) for storing a liquid additive and a delivery unit (1) according to one of the preceding patent claims for delivering the liquid additive from the tank (20) into the exhaust gas treatment device (19).

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