DE102009032489A1 - Ventilation device for injection nozzle of internal combustion engine of commercial motor vehicle, has pumping device with drive provided with line element, and displacement element deviated dependent on liquid pressure in line element - Google Patents

Abstract

The device has a pressure accumulator (6) connected with an outlet of a pumping device (4). A valve is arranged in a liquid line connection between the pressure accumulator and an injector (5) i.e. injection nozzle. The valve is formed such that the valve opens with a differential pressure. A hydraulic drive of the pumping device includes a line element, and a displacement element i.e. diaphragm (45), is arranged at the line element, where the displacement element is deviated dependent on liquid pressure prevailing in the line element. Independent claims are also included for the following: (1) an emission control device (2) a method for ventilating an injector of an emission control device.

Description

The The present invention relates to an exhaust gas purification device for vehicles, in the exhaust gas purification a fluid and in particular a liquid reducing agent is used.

In the thermal utilization of solid, gaseous and liquid natural and fossil fuels such as coal, gas, oil and wood, there is usually the formation of nitrogen oxides NO _X. The exhaust gases of internal combustion engines for motor vehicles and commercial vehicles contain nitrogen oxides. The proportion of nitrogen oxides in exhaust gases from diesel-powered internal combustion engines is particularly high.

Nitrogen oxides and in particular nitrogen dioxide NO ₂ are suspected of irritating or damaging the human respiratory system. In addition, nitric oxides due to the formation of nitric acid (HNO ₃ ) by reaction with water (H ₂ O) (2NO ₂ + H ₂ O → HNO ₃ + HNO ₂ ) or by incorporation of N ₂ O ₅ in aerosol particles and subsequent formation of NO ₃ ^- in the liquid phase associated with the formation of "acid rain". Furthermore, nitrogen oxides are also involved in the formation of smog and (under the influence of UV radiation) also in the formation of ozone (O ₃ ).

Efforts are therefore increasingly being made to reduce the content of nitrogen oxides in the exhaust gas. For this purpose, it was proposed to inject a non-toxic fluid reducing agent of water (H ₂ O) and urea (CH ₄ N ₂ O) precisely metered into the (still hot) exhaust stream. The resulting ammonia (NH ₃ ) reacts with the nitrogen oxides of the exhaust gas in a downstream of the injection along the exhaust stream SCR catalyst (SCR = Selective Catalytic Reduction, to German: Selective catalytic reduction) to the environment harmless nitrogen and water. As the liquid reducing agent, for example, urea mixed with water may be used. A 32.5% aqueous urea solution is available, for example under the brand name AdBlue ^® commercially. The injection of the reducing agent can be mixed with compressed air or carried out directly in liquid form. In principle, it would also be possible to use ammonia instead of urea as a reducing agent, but due to the corrosive, environmentally hazardous and toxic property of ammonia, this is extremely problematic.

The Use of fluid and in particular of liquid reducing agents for Purification of exhaust gases from a combustion device is eliminated from the fact that to the operation of the respective combustion device additionally to the fuel also reducing agent must be provided the disadvantage that the reducing agent at low temperatures solidify, wherein the volume change of the reducing agent in Freezing not just to the detriment but also to damage can lead from in contact with him components.

The freezing point of AdBlue ^® is, for example, at -11 ° C, a temperature that is often undershot even in the winters of temperate zones. In the case of aqueous reducing agents, the volume occupied by them during freezing increases. For example, with AdBlue ^® , about 11% of the volume in the liquid state. If there is no corresponding space available for the expansion of the freezing reducing agent, the pressure in the reducing agent and, associated therewith, also increases in the components in contact with it.

To the Injection of the reducing agent into the exhaust stream is referred to as injection or injector referred device used, which is usually movable components for active or passive control of injection timing and injection quantity of the reducing agent. The one with one Freezing of reducing agent in the device connected volume or pressure change can to leaks of the device and damage possibly existing movable components of the device with the result of functional impairment to lead, which expand until failure or destruction of the device can.

Around To prevent this, the exhaust gas purification device with a External heating for provided the device or other parts of the reducing agent supply which are always above the temperature of the reducing agent whose freezing point holds. The energy demand of corresponding heaters is very high. In mobile incinerators, the energy needed for heating mostly over separate energy storage of limited capacity, for example by batteries or Accumulators, provided so that appropriate heating the reducing agent supply only over for a limited period of time. Especially for power and commercial vehicles result in this not insignificant restrictions in terms of their operational readiness. Furthermore means an external heating an additional technical effort, to a considerable increase in the price of the exhaust gas purification device and their maintenance leads.

In order to improve the operational readiness of the injector device at cold ambient temperatures even without heating, it is known to empty the injector when not using the incinerator. The emptying of the injector has also the advantage that the injector when restarting the combustion device does not have to be completely thawed first in order to be functional again. The emptying of the injector is done either actively by emptying or by displacing the reducing agent from the injector by blowing compressed air. However, technical equipment is required for this purpose, which must continue to be supplied with electricity or energy after switching off the incinerator. In addition, a large proportion of motor vehicle manufacturers are unwilling to bear the costs associated with these facilities.

outgoing of the above are embodiments The invention is directed to a reliable and inexpensive device with simple construction as well as a reliable and cost-effective Specify a method that is detrimental or damaging the Device for injecting the reducing agent by freezing Prevent reducing agents.

Appropriate embodiments are the subject of independent Claims.

A embodiment includes a ventilation device for one Injection device (eg injector or injector) for injecting a Reducing agent in the output from a combustion device Exhaust gas flow, wherein the ventilation device a pumping device, a pressure accumulator and a valve. The pumping device of the ventilation device has a hydraulic drive and is for promotion and for pressurizing one different from the reducing agent formed second fluid. The accumulator is with an outlet connected to the pumping device and for receiving the pressurized formed second fluid. The valve is in a fluid line connection between the pressure accumulator and the injector and is designed so that it opens at a differential pressure at which the pressure on the pressure vessel facing side of the valve is larger, as the pressure on the side of the valve, that of the injector is facing. The drive of the pumping means comprises one of a Fluid permeable Conduction element, on which at least one displacement element is arranged, that depends deflected by a prevailing in the line element fluid pressure becomes.

The permeable by a fluid Conduit element of the pumping device can be advantageous in the line be used over which the delivery pump the reducing agent pumps into the injector. The at the line element the pumping device arranged displacement element is over the Pressure fluctuations of the reducing agent in the supply to the injector actuated, so that the accumulator over the pressure fluctuations of the reducing agent automatically with a pressurized second fluid is filled. Once the pressure of the reducing agent in the injector to one over the Valve determinable value below the fluid pressure in the accumulator has fallen off, opens the valve and take care of it an automatic ventilation of the injector by displacing the therein Reducing agent.

A another embodiment relates to an exhaust gas purification device with a tank for a fluid Reducing agent, an injector, the one in the exhaust stream a combustion device opening Having nozzle opening, for injecting the reducing agent into the exhaust stream of the combustion device is formed, a feed pump, in a connecting the tank with the injector Fluid connection arranged and for pumping the reducing agent the tank formed in the injector under delivery pressure fluctuations is, and with a ventilation device as indicated above, wherein the not with the pressure vessel related side of the valve with that of the feed pump fillable with the reducing agent Interior of the injector is in communication, and wherein the Conduit element of the pumping device within the part of the fluid connection is arranged, which the feed pump connects to the injector.

A another embodiment relates to a method for venting an injection device of an exhaust device as indicated above with steps to promote a reducing agent of a reducing agent-containing Tank over one Fluid connection in the interior of an injection device such that the pressure of the reducing agent in the fluid connection in time varies, steps to detect the pressure fluctuations in the fluid connection for the Drive a pumping device for conveying and pressurizing a second fluid other than the reducing agent, steps for storing the second fluid in a pressure vessel, and Feeding steps the pressurized second fluid in the for recording the reducing agent provided in the injector interior dependent on from the difference between the pressure of the second fluid in the pressure vessel or on the side of the valve, which faces the pressure vessel, and the Pressure of the reducing agent in the injector.

In this context, it should be noted that the terms used in this specification and the claims for listing characteristics include "comprise", "comprise", "include", "contain" and "with", as well as their grammatical Modifications, generally as a non-exhaustive list of characteristics such. Process steps, facilities, areas, sizes and the like, and in no way preclude the presence of other or additional features or groupings of other or additional features.

further developments These embodiments are each subject of the dependent Claims.

According to one embodiment includes the displacement element the pumping means a diaphragm, whereby a good separation of the funded by the pumping device especially gaseous Fluids from the for obtained the drive of the pumping means used reducing agent becomes. Furthermore allows the use of a diaphragm a simple pump design with only very low maintenance requirements. Alternatively or in addition can the displacement element the pumping device also comprise a piston, in particular for Realization of larger pump strokes is suitable and can also be combined with a membrane.

When the funded by the pumping device second In particular, air can be used as fluid in the environment of combustion devices is generally commonly available and thus does not need to be separately provided or prepared.

In an embodiment if the reducing agent is formed by an aqueous urea solution, and in particular a 32.5% aqueous urea solution.

The feed pump for pumping the reducing agent into the injector in one embodiment be designed as a piston pump, but also as a diaphragm pump. In an embodiment includes the feed pump a membrane that is displaced by a fluid displaced by a piston pump is deflected. In this case, by the piston pump for Deflection of the membrane displaced Fluid the hydraulic drive of the pumping device to promote of the second fluid.

Further Features of the invention will become apparent from the following description of exemplary embodiments in connection with the claims as well the figures. The individual features may in one embodiment according to the invention ever for be realized or more than one. In the following explanation some embodiments the invention is referred to the attached figures, of which

1 illustrates a combustion device with an exhaust gas purification device, the reducing agent injector is automatically vented when not in use,

2 shows an embodiment of an electromechanically controllable injector in a schematic representation, and

3 Fig. 3 is a flow chart illustrating the essential steps for venting an injector for an exhaust purification device as described above.

The in the 1 The combustion device shown has a combustion device 8th , For example, an internal combustion engine of a motor vehicle, and an exhaust gas purification device 100 on. The exhaust gas purification device 100 includes an exhaust system 7 into which of the combustion device 8th initiated exhaust gases and in which they are cleaned before passing through the outlet 72 be delivered to the environment. In the exhaust system 7 is a catalyst 71 For example, an integrated as described above SCR catalyst. The exhaust gas purification device 100 further comprises a reducing agent supply with an injector in the form of an injector 5 , which is also referred to as an injection nozzle. The injector 5 is in between the combustion device 8th and the catalyst 71 arranged segment of the exhaust system 7 appropriate. The injector 5 serves to inject reducing agent into the exhaust stream 81 before feeding to the catalyst 71 , A pump 3 promotes the reducing agent 11 over the from the Saugleitungsabschnitten 21 and 22 and the intermediate filter 2 formed delivery line from the reducing agent tank 1 and guides it over the supply line sections 24 and 25 the injector 5 to.

Between the sections 24 and 25 the supply line is a secondary pumping element 4 arranged, which is driven by the pressure fluctuations in the supply line air into an accumulator 6 inflated. The air is from the pumping element 4 via an inlet valve 41 sucked in and over an exhaust valve 42 in a pressure line 44 fed via an accumulator port 61 with the accumulator 6 connected is. The accumulator 6 is also a vent line 51 with the injector 5 connected. A check valve 52 separates the interior of the ventilation duct 51 from the interior of the injector 5 , which is filled in the case of operation with the reducing agent.

At the in 1 embodiment shown sucks the secondary pumping element 4 the air is not directly from the environment of the inlet valve 41 but via one with the inlet valve 41 connected air intake line 43 , which preferably ei NEN (not shown in the figure) has filters. This can ensure that the function of the secondary pumping element 4 is not affected by sucked particles or liquids, such as dust, rainwater or the like. In a preferred embodiment, inlet valve 41 and exhaust valve 42 integral with the secondary pumping element 4 executed.

For the metered injection of the reducing agent 11 in the exhaust stream 81 sets the feed pump 3 that in the funding line 24 / 25 and in the interior of the injector 5 reducing agents present 11 vacuum. The injector has in the case presented an electromagnetically actuated valve 53 that the interior of the injector 5 with its nozzle opening 54 combines. With the valve open 53 can the reducing agent 11 thus over the nozzle opening 54 in the exhaust stream 81 be initiated. The amount of reducing agent injected into the exhaust stream is determined over the period of time during which the valve 53 is open. The control of the valve 53 takes place actively in this embodiment by means of a controller, not shown in the figures, which may also be the engine control of the combustion device.

In the cross-sectional view of 2 are the essential components of such an electromagnetically controlled injector 5 illustrated. The shape and construction of the injector shown are chosen with a view to a clear representation and may differ from those of an actual injector. The injector 5 has a housing 5a on, which encloses an interior, which extends to the nozzle opening 54 can rejuvenate. The nozzle opening 54 connects the tapered in the representation tapering of the interior with the interior of the exhaust system 7 ,

One inside the case 5a slidably arranged element 53b can be in the area around the nozzle opening 54 against the inner wall of the housing 5a be moved the way it is in 2 is shown, the nozzle opening with respect to the interior of the injection nozzle 5 to close. To open the nozzle opening 54 is the slidable element commonly referred to as a nozzle needle 53b from the housing wall 5a in the area of the nozzle opening 54 withdrawn, whereby the housing interior is again in communication with the interior of the exhaust line, and in the interior of the nozzle pressurized reducing agent 11 in the exhaust stream 81 can transgress. In the 2 Arrows indicated indicate the flow direction of the reducing agent within the injector interior during the injection process.

Moving the nozzle needle 53b is preferably via a (in the figure only schematically indicated) electric drive 53a For example, a plunger coil, a linear motor, a spindle motor or the like other drives. The adapted to the housing geometry, here conical shape of the nozzle needle tip allows a safe closing of the nozzle opening 54 ,

As already indicated above, the in 2 illustrated geometries of Injektorgehäuse 5a and nozzle needle 53b not mandatory. Rather, both can be distinguished from the presentation of the 2 have different shapes, wherein the shape of the nozzle needle tip for closing the nozzle opening 54 opposite the interior of the injector 5 is designed suitable.

When parking the exhaust gas purification device 100 puts the feed pump 3 the promotion of reducing agents 11 to the injector 5 and connects the funding line 22 and the supply line sections 24 and 25 with the return line 23 , Of course, the connection of the delivery line 22 and the supply line sections 24 / 25 with the return line 23 also by means of a separate from the pump 3 arranged valve can be realized. By connecting the return line 23 with the support line 22 and the supply line sections 24 / 25 the reductant pressure in the delivery line relaxes 22 and the supply line sections 24 / 25 and thus also inside the injector 5 on the tank 1 prevailing pressure, which usually corresponds to the ambient pressure. However, there is no further emptying of the delivery line except for the reductant return required for pressure reduction 22 or the supply line sections 24 / 25 instead, leaving the interior of the injector 5 continue with reducing agent 11 is filled, which expands when freezing while the injector 5 can damage.

To prevent this, in a preferred embodiment, the reducing agent 11 displaced from inside the injector with the aid of compressed air. Instead of air, other pressurized gases can be used. As an alternative, liquids are also available which neither solidify nor increase in volume at the expected low temperatures.

Preferably, the displacement of the reducing agent into the supply line sections takes place 24 / 25 into it. This is possible without additional effort, since the nozzle valve 53 usually self-closing is executed and the supply line sections 24 / 25 over the return line 23 an open, depressurised passage to the reducing agent tank 1 forms, which displaces the reducing agent 11 from the injector 5 not opposed to any great resistance.

As already stated above, the compressed air from a compressed air reservoir 6 provided by a check valve 52 with the interior of the injector 5 connected is. If the reducing agent pressure in the injector interior falls below a certain value, or reaches the pressure difference between the compressed air at the inlet of the check valve 52 and the reducing agent inside the injector 5 one about the characteristic (eg bias) of the check valve 52 certain value, so opens the check valve 52 and allows the compressed air to flow into the injector interior, whereby the reducing agent 11 and optionally also from the supply line sections 24 / 25 and the support line 22 is displaced.

The compressed air reservoir is filled 6 with the help of one between the segments 24 and 25 the delivery line attached secondary pumping element 4 , which is formed in a preferred embodiment as a diaphragm pump. A first side of the membrane 45 of the pumping element 4 stands with the through the supply line sections 24 / 25 subsidized reducing agent 11 in direct contact.

As can be seen from the flowchart of 3 it can be seen, the filling of the pressure vessel begins 6 with the start of the exhaust gas purification device in step S0 of the exhaust gas purification process carried out by it, followed by step S1, ie, the conveyance of the reducing agent 11 through the feed pump 3 ,

Because the feed pump 3 builds a continuous, but a temporally oscillating pressure, the membrane is 45 during operation of the exhaust gas purification device 100 in time with the feed pump 3 deflected. This deflection reduces the volume in the second side of the membrane 45 limited pumping chamber 46 the secondary pumping element 4 , which increases the pressure in the pumping chamber 46 elevated. After a certain pressure, the outlet valve opens 42 and the compressed air thus generated is in the compressed air reservoir 6 promoted. At subsequently decreasing pressure of the promoted reducing agent 11 takes the deflection of the membrane 45 , whereby the pressure in the pumping chamber decreases and the outlet valve decreases 42 closes. From a certain negative pressure finally opens the inlet valve 41 and creates a pressure equalization. The secondary pumping element 4 thus grips the pressure fluctuations in the supply line sections 24 / 25 and sets them for conveying and compressing a second fluid, in the present case of air. In other words, the secondary pumping element performs 4 Step S2 of the in 3 illustrated method.

Repeated deflection of the membrane 45 leads to a progressive filling of the pressure accumulator 6 with compressed air in the sense of step S3 of the exhaust gas purification device 100 executed emission control method.

When parking the exhaust gas purification device 100 drops the pressure of the reducing agent 11 in injector inside as described above. Once the pressure of the compressed air is greater than the sum of reductant pressure in the injector 5 and a possible bias of the valve 52 (Step S4), the compressed air automatically urges over the check valve at Step S5 of the exhaust gas purification process 52 into the now "depressurized" interior of the injector 5 and displaces the reducing agent 11 out of this. By "depressurized" is meant here that the pressure of the reducing agent 11 In the injector the penetration of the compressed air does not oppose any appreciable resistance. Finally, is the pressure in the accumulator 6 dropped below a certain value, the check valve closes in step S6 and the vent of the injector is completed.

According to an alternative embodiment not specifically shown, this is the membrane 45 for filling the pressure accumulator 6 actuating fluid not as in 1 shown that from the feed pump 3 pumped reducing agents 11 , Rather, in this alternative embodiment, the feed pump comprises a membrane which is displaced by a fluid displaced by a piston pump in the interior of the feed pump for pumping the reducing agent 11 is deflected. In this case, this can be done by the piston pump to deflect the diaphragm for pumping the reducing agent 11 displaced fluid by operating the membrane 45 the hydraulic drive of the secondary pumping element 4 for conveying the air for filling the pressure accumulator 6 provide. It is obvious that the pumping chamber 46 the secondary pumping element 4 not like in this case 1 shown between the supply line sections 24 / 25 is arranged, but with an interior of the feed pump 3 connected is.

The presented ventilation device allows automatic emptying of the reducing agent 11 from the injector 5 , wherein for generating the compressed air, the pressure fluctuations of the reducing agent in the delivery line 24 / 25 be used and so costly and expensive compressors and control devices omitted.

Claims (10)

Ventilation device for an injection device ( 5 ) for injecting a reducing agent ( 11 ) in the of a combustion device ( 8th ) emitted exhaust stream ( 61 ), with a pumping device ( 4 ), an accumulator ( 6 ) and a valve ( 52 ), in which - the pumping device ( 4 ) has a hydraulic drive and for the promotion and to pressurize a different from the reducing agent second fluid is formed, - the pressure accumulator ( 6 ) with an outlet of the pumping device ( 4 ) and adapted to receive the pressurized second fluid, and - the valve ( 52 ) in a fluid line connection between the accumulator ( 6 ) and the injection device ( 5 ) is arranged and is formed so that it opens at a differential pressure at which the pressure at the pressure vessel ( 6 ) facing side of the valve ( 52 ) is greater than the pressure on the side of the valve, that of the injector ( 5 ), and wherein the drive of the pumping device ( 4 ) comprises a fluid-flow-through conduit element, on which at least one displacement element ( 45 ) is arranged, which is deflected depending on a prevailing in the line element fluid pressure. Aeration device according to claim 1, wherein the displacement element ( 45 ) of the pumping device ( 4 ) comprises a membrane. Ventilation device according to claim 1 or 2, wherein the displacement element ( 45 ) of the pumping device ( 4 ) comprises a piston. Ventilation device according to claim 1, 2 or 3, wherein the pump device ( 4 ) conveyed and pressurized second fluid is air. Exhaust gas purification device with - a tank ( 1 ) for a fluid reducing agent ( 11 ), - an injector ( 5 ), one in the exhaust gas flow ( 81 ) a combustion device ( 8th ) opening nozzle ( 54 ) for injecting the reducing agent ( 11 ) in the exhaust stream ( 81 ) of the combustion device ( 8th ), - a feed pump ( 3 ) in a tank ( 1 ) with the injector ( 5 ) connecting fluid connection ( 21 . 2 . 22 . 24 . 25 ) and for pumping the reducing agent ( 11 ) from the tank ( 1 ) in the injector ( 5 ) is formed under delivery pressure fluctuations, and - a ventilation device according to one of the preceding claims, wherein the not with the pressure vessel ( 6 ) associated side of the valve ( 52 ) with that of the feed pump ( 3 ) with the reducing agent ( 11 ) fillable interior of the injector ( 5 ), and wherein the line element of the pumping device ( 4 ) is disposed within the part of the fluid connection, which the feed pump ( 3 ) with the injector ( 5 ) connects. Exhaust gas purification device according to claim 5, wherein the reducing agent is an aqueous Solution of Contains urea. Exhaust gas purification device according to claim 5 or 6, wherein the feed pump ( 3 ) is designed as a piston pump. Exhaust gas purification device according to claim 5 or 6, wherein the feed pump ( 3 ) is designed as a diaphragm pump and in particular as a piston-actuated diaphragm pump. Exhaust gas purification device according to claim 7 or 8, wherein the hydraulic drive of the pump device ( 4 ) is provided by a fluid displaced by a piston pump. Method for ventilating an injector ( 5 ) of an exhaust gas purification device ( 100 ) comprising the following steps: - conveying (S1) a reducing agent ( 1 ) from a tank containing the reducing agent ( 1 ) via a fluid connection ( 24 . 25 ) into the interior of an injector ( 5 ) such that the pressure of the reducing agent ( 11 ) in the fluid connection ( 24 . 25 ) varies over time, - tapping (S2) the pressure fluctuations in the fluid connection ( 24 . 25 ) for driving a pumping device ( 4 ) for pumping and pressurizing one of the reducing agent ( 11 ) different second fluid, - storing (S3) of the second fluid in a pressure vessel ( 6 ), and - feeding (S5) the pressurized second fluid into the space for receiving the reducing agent ( 11 ) in the injector ( 5 ) provided in dependence (S4) on the difference between the pressure of the second fluid in the pressure vessel ( 6 ) and the pressure of the reducing agent ( 11 ) in the injector ( 5 ).

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