DE102008042987A1 - Dosing device for use in exhaust gas duct of e.g. diesel engine of passenger car, has valve stem with opening e.g. rectangular running slot, for discharging liquid into gap, where gap is limited by compressible wall - Google Patents

Abstract

The device (10) has a nozzle (26) leading into a discharge area (28), and a dosing unit (20) provided with a dosing valve with a filling material e.g. PTFE. A valve stem of the dosing unit is guided by forming a gap in a valve body of the dosing valve. The valve stem includes an opening e.g. rectangular running slot, borehole and oval opening, to discharge liquid into the gap, where the gap is limited by a compressible wall. The nozzle is formed as a pressure controlled nozzle that brings a reducing agent i.e. urea, in an aqueous solution and in the form of jets (32) into the discharge area.

Description

State of the art

One established process for nitrogen oxide reduction in exhaust gas lean operation An internal combustion engine is Selective Catalytic Reduction (SCR). In the ammonia-SCR process, ammonia is used as the reducing agent needed in the exhaust gas before a corresponding reducing agent catalyst. there is often in current methods by blowing an aqueous Urea-air aerosols in the engine exhaust by thermolysis and subsequent (catalyzed) hydrolysis, the actual reducing agent ammonia released. This procedure is immediate in the commercial vehicle sector before the series use.

in the With regard to a possible car use is this procedure with air injection due to the high system complexity in terms of cost, space and compressed air supply as little market classified. Another method for compressed air independence sees the injection of the pressurized by means of a pump Urea solution with self-processing valves. Valves, such as those from gasoline injection, are often used are known. Difficulties here are among others the Necessity of cooling such an electric valve, which is attached directly to the hot exhaust system. Furthermore, the winter suitability is to be regarded as problematic. At temperatures below -11 ° C freezes the usual Water-urea solution and therefore expands. Thus, to achieve winter suitability of such a valve and other affected system components, such as a pump and pressure control, a considerable constructive and thus system complexity increasing effort to accept. So is a ice-resistant Construction, a heating option and a Rücksaugende Pump required. For use in passenger cars thus arises the question of one in system complexity simple and therefore cost and customer acceptance realistic concept point. Opened with a simple concept the possibility of a widespread use of urea SCR technology for denitrification of leaner, for example, diesel engine Abga se and thus the possibility of fulfilling it in the future Expected nitrogen oxide emission limits.

DE 196 46 643 C1 refers to a nitrogen oxide reductant injection in an exhaust stream. In this case, the reducing agent is injected through a plurality of fine nozzle openings through in the form of finest rays controllable by local clocked pressure generation in the exhaust gas stream. The nozzles used herein are piezoelectrically controlled nozzles, similar to the nozzles used in piezoelectric ink jet printheads or nozzles with clocked heating resistor elements, similar to known bubble jet inkjet printheads. From DE 196 46 643 C1 However, the arrangement described is quite complex in terms of apparatus and, in particular with regard to the aggressive fluids, is susceptible to failure and expensive and thus appears unsuitable for applications in the automotive sector.

DE 10 2006 012 855 A1 relates to a method and a dosing system for pollutant reduction in automotive exhaust gases. Out DE 10 2006 012 855 A1 is a method for dosing a fluid pollutant-reducing medium, in particular an aqueous urea solution known. This aqueous urea solution is introduced into a motor vehicle exhaust system, wherein the fluid medium is conveyed to a nozzle module, in particular a nozzle or a valve and introduced into the exhaust system by means of the nozzle module. An upstream of the nozzle module transport is controlled pulse width modulated. The method and the associated dosing ensure a precise and relative to degrees of frost relatively robust arrangement or dosage, in particular a reducing agent using fewer components, which can be used in motor vehicles.

Disclosure of the invention

According to the invention proposed, thereby form the metering unit ice-proof that a shaft of the metering valve of the metering unit with openings is provided and the body in which the with breakthroughs provided shaft is guided, having flexible walls. The body with flexible walls is outward sealed off. Thus, the reducing agent in which it is preferably urea in aqueous solution, at sinking temperature from the shaft with breakthroughs emerge. Due to the expansion of the flexible body can be additional Volume may be provided, whereby the metering unit may be destructive pressures due to the expansion of the freezing aqueous solution can be avoided. The invention has the advantage of being chemically resistant to the reducing agent resistant metering valves that already exist through the inven tion according to modification to improve their ice crushing strength and thereby consuming To avoid new developments.

The metering unit is preferably installed between the pressure and suction sides of the reducing agent-conveying pump with the interposition of a metering valve, whereby a connection is made, which is closed if necessary. As long as the metering valve of the metering unit is open, the pump circulates. Thus, can itself build up pressure on the pressure side, which is above the opening pressure of the nozzle, via which the reducing agent is metered into the exhaust pipe and the exhaust gas flow past there. Due to this circumstance, the nozzle remains closed and it is not metered.

As soon as from the control unit of the dosing requested a dosage is done, there is a closing of the metering valve of the metering unit. Consequently, a pressure build-up takes place on the pressure side of the pump, whereby the nozzle opens after exceeding the opening pressure and thus reducing agent, which is preferably urea in aqueous solution, is supplied to the exhaust gas stream becomes. Since, according to this application, the metering valve no spray mist generated, may be due to the installation of a spray perforated disk completely dispensed with. This will also be sufficient large cross section for the implementation of the reducing agent provided by the metering valve. The spray perforated disk stops a significant cost factor of the metering valve, by the elimination of the spray perforated disk can now be significantly reduced. The corrosion resistance of the metering valve and the receiving this Metering unit is given by the choice of materials. The freezing resistance (Ice pressure resistance) is in the upper part of the metering valve by compressible reached trained filling body. The mode of action compressible filler offers the possibility when freezing the urea-water solution additional Provide volume and component destructive pressures to avoid. The freezing resistance (or ice pressure resistance) in bottom of the metering valve is through openings in the valve stem and through the surrounding body compressible, an additional volume providing walls reached.

The openings can be in any geometry, such as rectangular trained slots, holes or oval openings be executed. The one with the openings of any Geometry provided valve stem is in a valve body guided, the compressible, this means elastic walls having. As a material from which the valve body made especially PTFE (Teflon) is recommended. The valve body can also be multi-part to facilitate the assembly of the valve stem be executed; as well is a one-part feasibility the valve body possible. To a simpler Assembly of sealing elements, which are preferably designed as O-rings are to realize, the valve body can be made in two parts be executed. Between the valve body and the valve stem remains filled with reducing agent Gap. At the ends of this space are seals, which may be formed, for example, as an O-ring.

comes it to a temperature drop, so that the reducing agent begins to freeze and consequently expands, the reducing agent passes through the openings of any geometry in the valve stem in the space between the apertured Valve stem and this receiving valve body. Due to the fact that the walls of the body are designed to be compressible and thus deformable, stretch These turn outward and thus form for the reducing agent an additional volume for expansion. Due to this circumstance, the pressure increases upon freezing of the reducing agent not over impermissibly high values and the components stay undamaged.

As soon as the temperature rises again and the reducing agent thaws, Reducing agent reduces its volume, eliminating the previously increased pressure drops and the valve stem with openings any geometry receiving valve body of the metering valve returns to its original form.

Brief description of the drawings

Based In the drawings, the invention will be described below in more detail.

It shows:

1 a schematic overall view of the dosing system for pollutant reduction in automotive exhaust gases by means of a reducing agent,

2 a sectional view of the inventively proposed metering valve for use in a metering unit of in 1 dosing shown for dosing a reducing agent in the exhaust stream of an internal combustion engine.

embodiments

The representation according to 1 is a metering, especially for dosing a reducing agent in the exhaust stream of the internal combustion engine of a motor vehicle refer.

In the schematic representation according to 1 , which are just the most important components of a dosing system 10 for a reducing agent in the exhaust gas stream of an internal combustion engine, reference numeral denotes 10 the dosing system. The dosing system 10 includes a dosing pump module 12 , which in the illustration according to 1 a delivery unit 14 and a metering unit 20 having. In real installation cases, the delivery unit 14 and the metering unit 20 constitute a structural unit; However, it is also a structural separation of the two components of the Dosierpumpenmoduls mentioned 12 possible. A suction side of the delivery unit 14 is by reference numerals 16 identified while a pressure side of the delivery unit 14 by reference numerals 18 indicated. Through the delivery unit 14 is a reducing agent, which is in particular urea in aqueous solution for nitrogen oxide reduction, from a reducing agent tank 22 promoted and reaches the suction side 16 in the delivery unit 14 of the dosing pump module 12 , From the pressure side 18 this will be out of the reducing agent tank 22 promoted reducing agent via the metering unit 20 a dosing line 24 fed, and a trained example as a pressure-controlled nozzle nozzle 26 in the form of rays 32 introduced into an exit space. At the in 1 indicated exit space is an exhaust pipe 28 , in which, for example, designed as a pressure-controlled nozzle nozzle 26 the reducing agent in the form of rays 32 injects. Instead of discrete rays 32 can also be a spray, depending on the configuration of the nozzle 26 , in the exit room 28 , which is an exhaust pipe here 28 be introduced. At the nozzle 26 , which may for example be designed as a pressure-controlled nozzle, it may also be a nozzle with variable cross-section, the nozzle 26 has no spray perforated disk in comparison to the solutions of the prior art, so that their production costs, their installation size and the space required are much lower. Depending on the configuration of the nozzle 26 , about which in the dosing line 24 flowing reducing agent in the outlet space 28 is introduced, an outlet of the reducing agent in the form of jets 32 or as a spray or in droplet form in an exhaust stream 30 , for example, a procured exhaust pipe as exit space 28 flows through, enter. From the illustration according to 1 also shows that the exhaust pipe 28 symmetrical to the axis of symmetry 34 is formed and the nozzle 26 on the outside of a coat 36 of the outlet space performing exhaust pipe 28 is attached.

The representation according to 2 is a sectional view of the metering unit in the metering according to 1 refer to.

As the perspective view according to 2 shows comprises a metering valve 48 the metering unit 20 a valve body 40 to which, for example, as retaining rings 42 . 44 . 46 trained holder are formed. These can be the metering valve 48 between that of the reducing agent tank 22 to the suction side 16 of the delivery unit 14 extending line on the one hand and on the other hand between the pressure side 18 of the delivery unit 14 to the nozzle 26 extending dosing 24 Fasten. The metering unit 20 includes the metering valve 48 which is a filler 50 contains, which is preferably made of PTFE. The filler 50 is located in the upper area of the metering valve 48 and serves, made for. B. as a hollow cylinder, to provide an additional volume to lower the freezing pressure in a possible freezing of the urea-water solution at low ambient temperatures.

As shown in the reproduced in perspective sectional view according to 2 shows, the metering valve acts 48 the metering unit 20 on a valve stem 52 , The valve stem has at least one opening 62 on, about which reducing agent from the valve stem 52 in a gap 56 to be able to withdraw. The openings 62 in the valve stem 52 For example - as in 2 shown - as rectangular slots in the valve stem 52 be formed and in a circumferential pitch of 180 °, 90 ° or 60 ° on the circumference of the valve stem 52 , also vertically offset from each other, be formed. Furthermore, there is the possibility of the openings 62 in manufacturing technology particularly simple way to form holes or as slots or as oval openings in the valve stem 52 train. The at least one in the valve stem 52 trained opening 62 ensures the ice pressure resistance of the metering valve 48 in that, during freezing, the reducing agent, preferably as urea-water solution, from the valve stem 52 can escape. Furthermore, the valve body 40 such that this a compressible, deformable coat 54 has, for example made of PTFE. Occurs the freezing reducing agent from the at least one opening 62 on the circumference of the valve stem 52 in a gap 76 a through the lateral surface of the valve stem 52 and the compressible coat 54 of the valve body 40 is formed, there is an expansion of the made of compressible material shell 54 in the radial direction to the outside, so that additional volume is created. This is the valve body 40 from a free space 74 surrounded, as shown in 2 for example, between the second retaining ring 44 and the third retaining ring 46 runs. In the radial direction is an unobstructed expansion of the shell 54 of the valve body 40 of the metering valve 48 guaranteed. As a result, component-destructive pressures are excluded by the freezing of the reducing agent.

The valve body 40 can be carried out in one or more parts. In the illustration according to 2 this is for easier installation of sealing elements 56 . 58 formed in two parts. Between the inner wall of the coat 54 and the lateral surface of the valve stem 52 remains filled with reducing agent gap 76 , At the in the axial direction the gap 76 is limited! ends are the sealing elements 56 . 58 , which are made for example of embrittlement resistant material.

From the illustration according to 2 further states that the metering unit 20 with a nozzle-side connection 64 and a tank-side connection 66 is provided. These connections 64 . 66 are each aligned with holes 70 respectively 68 executed to a flow of the reducing agent through the metering valve 48 to enable. From the perspective view according to 2 it can be seen that the nozzle-side connection 64 into the dosing line 24 between the print side 18 of the delivery unit 14 and the nozzle 26 opens, while the tank-side connection 66 into the from the reducing agent tank 22 to the suction side 16 of the delivery unit 14 running line opens. position 72 designates the electrical connection of the metering valve 48 the metering unit 20 , The electrical connection 72 is formed so that this laterally between the first retaining ring 42 and the second retaining ring 44 runs and is accessible from the side. This allows between the second retaining ring 44 and the third retaining ring 46 the free space 74 be reached, which a radial extent of the compressible shell 54 of the valve body 40 serves and with freezing reducing agent whose radial expansion. From the sectional view according to 2 it also follows that the metering valve 48 via a magnet armature 80 and a magnetic coil 82 verfingt. By energizing the solenoid coil 82 there is a lifting movement of the valve stem 52 to release the by reference numerals 78 indicated valve seat of the metering valve 48 , The sectional view according to 2 It can also be seen that between the compressible coat 54 and the valve stem 52 a compressible body 86 is made of PTFE, for example. This compressible body 86 serves to provide an additional volume when freezing the reducing agent. This additional volume allows a considerable improvement in the ice pressure resistance of the metering valve 48 , The compressible body 86 is formed, for example, as a hollow cylinder. In the in 2 Representation shown are the compressible coat 54 and the compressible body 86 two separate components. It is also conceivable the parts 54 and 86 as a single component. In the in 2 illustrated variant, these are the components 86 . 54 designed as separate components, so that the second sealing element 58 can be easily mounted.

With reference number 84 is the flow path of the reducing agent inside the metering valve 48 designated. The reducing agent flows through from the nozzle-side port 64 over the hole 70 by the preferably designed as a hollow cylinder packing 50 , then through the interior of the valve stem 52 to the valve seat 78 at the lower end of the valve stem 52 , When closed, the sealing seat is 78 closed by a ball-shaped closing element, for example, in the opened state of the metering valve 48 is the valve stem 52 or the closing element of the valve seat 78 lifted. The representation according to 2 In addition, it can be seen that according to the fluid flow path 84 the reducing agent on the procured here as holes openings 62 from the valve stem 52 exit and the compressible body 86 compressed, indicated by the bulge.

The function of the metering unit 20 is represented as follows: In the metering unit 20 is between the print side 18 and the suction side 16 of the delivery unit 14 by means of the metering valve 48 made a connection, which is closed if necessary. As long as the metering valve 48 is open, promotes the delivery unit 14 in the circle, so that the reducing agent in a circuit, formed by the nozzle-side connection 64 and the tank side connection 66 , is promoted and on the print side 18 does not build up pressure above the opening pressure of the nozzle, for example designed as a pressure-controlled nozzle 26 lies. This leaves the pressure-controlled nozzle 26 closed and there is no metering of the reducing agent on this in the outlet space 28 , given here by the exhaust pipe 28 that from the exhaust stream 30 the internal combustion engine is flowed through.

As soon as a metering of reducing agent is requested by a control unit, not shown, the metering valve is closed 48 , Well found on the print page 18 of the delivery unit 14 a pressure build-up instead, so that pressurized reducing agent in the dosing 24 pending. Due to the pressure generated opens the preferred pressure-controlled nozzle 26 after exceeding the opening pressure, so that reducing agent, urea in aqueous solution, the exhaust stream 30 in the form of rays 32 - as in 1 indicated - is supplied. In this application generates the metering valve 48 or preferably designed as a pressure-controlled nozzle nozzle 26 no spray, but rays 32 to the penetration depth of the reducing agent in the exhaust stream 30 increase, so that can be completely dispensed with the installation of an otherwise required spray perforated disc. This results in a sufficiently large cross-section for the passage of the reducing agent through the metering valve 48 provided. Since the spray orifice plate is a considerable cost factor of the metering valve 48 represents, can now be dispensed with, the production costs of the metering valve by eliminating the spray perforated disk 48 that in the metering 20 of the dosing module 12 is used, significantly lowered.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19646643 C1 [0003, 0003]
• - DE 102006012855 A1 [0004, 0004]

Claims (11)

Dosing device ( 10 ) for introducing liquids into an exit space ( 28 ), wherein the metering device ( 10 ) one in the exit space ( 28 ) nozzle ( 26 ) and a metering unit ( 20 ) with a metering valve ( 48 ) whose valve stem ( 52 ) forming a gap ( 76 ) in the valve body ( 40 ) of the metering valve ( 48 ), characterized in that the valve stem ( 52 ) at least one of the exit of the liquid in the space ( 76 ) enabling opening ( 62 ), wherein the intermediate space ( 76 ) of a compressible wall ( 54 ) is limited. Dosing device ( 10 ) according to claim 1, characterized in that it comprises a nozzle preferably designed as a pressure-controlled nozzle ( 26 ), which contains a reducing agent, preferably urea in aqueous solution, in the form of jets ( 32 ) in the exit space ( 28 ). Dosing device ( 10 ) according to claim 1, characterized in that the metering valve ( 48 ) of the metering unit ( 20 ) a filling body ( 50 ), which is compressed upon freezing of the reducing agent and releases additional expansion volume for the reducing agent. Dosing device ( 10 ) according to claim 1, characterized in that around the flexible wall ( 54 ) a free space ( 74 ) remains. Dosing device ( 10 ) according to claim 4, characterized in that the metering unit ( 20 ) Holder ( 43 . 44 . 46 ), which are preferably formed in a ring shape. Dosing device ( 10 ) according to claim 4, characterized in that a lateral surface of the valve body ( 40 ) as a deformable in the radial direction, flexible wall ( 54 ) is executed. Dosing device ( 10 ) according to claim 4, characterized in that between the flexible wall ( 54 ) and the peripheral surface of the valve stem ( 52 ) an annular space ( 76 ) is formed, which is filled with reducing agent. Dosing device ( 10 ) according to claim 7, characterized in that the gap ( 76 ) by sealing elements ( 56 . 58 . 60 ) in the axial direction in the valve body ( 40 ) is sealed. Dosing device ( 10 ) according to claim 1, characterized in that the at least one opening ( 62 ) of the valve stem ( 52 ) is formed as a substantially rectangular extending slot, as a bore, as an oval opening or stamped in star shape. Dosing device ( 10 ) according to claim 9, characterized in that the valve stem ( 52 ) a number of openings ( 62 ), which in the circumferential direction with respect to the lateral surface of the valve stem ( 52 ) are arranged in a 60 °, 90 °, 120 ° or 180 ° division. Dosing device ( 10 ) according to one or more of the preceding claims, characterized in that it is used in the exhaust tract of internal combustion engines, in particular self-igniting internal combustion engines, and in particular as urea in aqueous solution procured reducing agent in the exhaust gas stream ( 30 ) introduces the internal combustion engine.