Exhaust aftertreatment device and method

Abstract

Exhaust gas aftertreatment device with a control unit (53) for controlling a pump (2) in two opposite directions, wherein the pump (2) conveys a liquid (HWL) from a tank (1) through a liquid (HWL) channel (57) to a nozzle (70) in the first direction (20), which injects the liquid (HWL) into an exhaust gas stream (18), wherein at least one gas collection pocket (56, 75, 76, 78, 79) is provided in the liquid (HWL) channel (57) between the nozzle (70) and the pump (2), in which a gas is pressurized by the pump (2) conveying in the first direction (20), and wherein the gas is sucked into the liquid (HWL) channel (57) by the pump (2) conveying in the second direction (19) during an operating start phase.

Description

[0001] The invention relates to an exhaust gas aftertreatment device according to the one-part patent claim 1. According to the independent method claim 14, the invention relates to a method for an exhaust gas aftertreatment device.

[0002] In the following, urea-water solution is referred to as HWL.

[0003] WO 2009 / 010 569 A1 and DE 10 2009 037 564 A1 each disclose an exhaust gas aftertreatment device with a pump that can pump in two directions. In the first direction, the pump conveys a UWL from a tank through a UWL channel to a nozzle, which injects the UWL into an exhaust stream. In the second direction, the UWL is conveyed back into the tank. WO 2009 / 010 569 A1 addresses the problem that UWL tends to freeze quickly. With this freezing, the pressure of the UWL, which transforms into the solid state, increases. In order to reduce the pressure in a timely manner, a pressure relief device is proposed that includes a 2 / 2-way valve leading from the UWL channel.

[0004] US 2009 / 0 205 316 A1 discloses an exhaust aftertreatment system with a pump. This pump conveys a urea solution from a tank through a urea solution channel to a nozzle, which injects the urea solution into an exhaust stream. A calibrated check valve extends from the urea solution channel, which acts as a control valve and controls the spray pressure in the urea solution channel.

[0005] The unpublished DE 10 2011 053 742 A1 relates to a heat exchanger for a dosing unit of an exhaust gas aftertreatment system.

[0006] DE 10 2009 032 489 A1 discloses an exhaust aftertreatment system that, in addition to a feed pump for conveying the urea to an injector, has a secondary pump driven by the pressure fluctuations caused by the feed pump to feed ambient air into a pressure accumulator. When the feed pump is switched off, the injector is ventilated by the stored air.

[0007] From DE 198 19 579 C1, another exhaust gas aftertreatment device is known in which a pressure accumulator serves to provide pressurized UWL and thus to enable the pump required to generate the injection pressure to be operated only temporarily.

[0008] The object of the invention is to provide an exhaust gas aftertreatment device which is reliably protected against freezing even without a power supply.

[0009] This object is achieved according to the invention with the features of patent claims 1 and 14.

[0010] The invention can be used in both passenger cars and commercial vehicles, since the exhaust aftertreatment system according to the invention does not require compressed air. Other "air-assisted systems" with compressed air are used in commercially available commercial vehicles to inject the urea into the exhaust system.

[0011] Commercial vehicles are often sold with the "emergency stop switch" required for hazardous goods transport, which disconnects the entire electrical system from the power supply. Without a power supply, however, the problem arises that the exhaust aftertreatment system can no longer be pumped dry by the pump, so that the waste water that freezes in cold weather destroys the exhaust aftertreatment system more and more with each freezing cycle.

[0012] The exhaust gas aftertreatment device according to the invention avoids the problem by - when switching on the vehicle electrical system via the ignition key or - when switching on the vehicle electrical system using a keyless access card or - when the engine is started - i.e. during the start-up phase - gas is sucked into the UHT channel by the pump running in reverse. This happens for a limited time, for example 10 seconds. The pump then operates in the normal - i.e. first - direction again. Gas collection pockets are provided in the UHT channel from the pump to the nozzle. As a result, the gas compressed by the pump under an operating pressure of, for example, 14 bar is collected in the gas collection pockets and takes up a minimized volume. If the power supply fails, the pump also fails and the operating pressure drops. The gas compressed in the gas collection pockets expands and forces the UHT out of the components at risk of freezing and at least partially out of the UHT channel. The escaping UHT can be released, for example, via leaks in the pump and / or the nozzle.If an injection valve is provided on the nozzle, it may have leaks to reduce pressure or it may even be designed to be “normally open”.

[0013] The components at risk of freezing can include, for example, the injection valve, the nozzle, various filters, various sensors, especially pressure / temperature sensors, a pressure accumulator, rigid pipe sections of the urinary sanitation duct, or hose couplings of the urinary sanitation duct. The component at risk of freezing can also be a supply unit to which the pump belongs.

[0014] In one embodiment, several gas traps are provided so that each endangered component is protected individually and / or the gas volume for expelling the UWL is particularly large.

[0015] In a further embodiment, the gas is sucked in through an open valve through a separate intake channel when the pump is running "backwards" - i.e. in the second direction. This intake channel leads to gas that has been cleaned of dirt particles. This prevents dirt particles from penetrating the UWL channel and clogging the nozzle or one of the filters. Sensitive sensors or the injection valve are also protected from dirt particles. The cleaned gas can, for example, come from the UWL tank. The intake channel can also lead to a filter. Accordingly, the gas can be air or a gas mixture that forms in the tank.

[0016] The valve for the separate intake channel can, in particular, be a check valve. This is then arranged such that it closes when the pump is pumping in the first direction and opens when the pump is pumping in the second direction. Such a check valve is particularly cost-effective and lightweight, as no electrical components are required. An example of a check valve is the ball check valve. However, it is also possible to design the valve as an electromagnetic valve that is both normally open and normally closed.

[0017] A pressure accumulator with a gas trap can branch off from the UWL channel. This pressure accumulator can also be arranged in-line. The pressure accumulator compensates for pressure fluctuations, enables intermittent pump operation, and forms a very large gas trap.

[0018] The gas collection pockets are designed in such a way that they are located above the UWL channel when installed, so that the gas collects there and the UWL flows past them.

[0019] The pump can be designed to also pump the gas. This makes it possible to pump the gas all the way to the tank during the start-up phase, so that after the subsequent reversal of direction, large quantities of gas can be pumped into the UWL channel.

[0020] In an advantageous embodiment of the invention, a gear pump is used to pump the urea. In a particularly advantageous embodiment, this gear pump can be designed as an external gear pump. The profile of the gears can, in particular, be designed with an involute. The urea is pumped from an inlet to an outlet in spaces between the teeth and a housing. Due to its simple design, this pump is cost-effective, durable, and resistant to freezing urea.

[0021] The pump can be particularly advantageously arranged in a supply unit. This supply unit then also contains a device for introducing the gas for antifreeze protection of the components. These components include, for example, the central unit and the dosing unit. The supply unit can also be connected to the diesel engine coolant circuit, so that the supply unit performs the defrosting function for the tank and the pump. Thus, the coolant and the coolant pump of the diesel engine are used. A solenoid valve is provided in / on the supply unit to control / regulate the coolant.

[0022] A brushless DC motor can be used to drive one of the gears. This eliminates the need for wear-prone brushes or graphite rods to convert the current. Instead, an electronic circuit is used. Such a brushless DC motor has an external rotor and is easy to control.

[0023] According to a further advantage of the invention, the dosing unit for atomizing the urea solution in the exhaust stream has a nozzle designed as an atomizing nozzle. Compared to spraying a barely distributed urea solution jet onto a hot surface of the exhaust pipe, atomization has the advantage of significantly better distribution, resulting in a correspondingly large reactive surface of the urea solution. This allows a very high proportion of the urea solution to be fully converted, resulting in particularly good exhaust emissions with low urea solution consumption. Furthermore, no hot surface is required, which would have to be additionally heated during the start-up process or warm-up phase.

[0024] A so-called swirl nozzle, also known as a “pressure swirl atomizer,” can be used particularly advantageously as an atomizer nozzle. Such a swirl nozzle is known, for example, from EP 1 698 768 A1 or WO 96 / 11335. In a swirl nozzle, several discs with openings are placed one above the other. These openings introduce a swirl into the UWL stream before it exits from an opening that preferably opens conically. With such a “pressure swirl atomizer,” a very specific distribution of different droplet sizes can be achieved at a relatively low pressure. With such a dimensioned distribution of droplet sizes, it is achieved that the droplets - on the one hand, they are so large and heavy that they are not carried along with the exhaust gas flow before they are chemically converted in front of the catalyst and - on the other hand, are so small that they can be completely chemically converted.

[0025] According to a further advantage of the invention, a fine pressure filter is provided as the main filter downstream of the pump, which protects the atomizer nozzle of the dosing unit from clogging. Accordingly, this fine pressure filter is arranged downstream of the pump in the urea flow. This means that the pressure loss at the fine pressure filter is less noticeable than if this pressure filter were arranged in the suction channel upstream of the pump. In an advantageous embodiment, the pump itself can be protected from coarse contamination by means of a coarse intake filter, with only a slight pressure loss occurring at this coarse intake filter. This also protects the pump from dirt particles. This ensures a particularly high degree of functional reliability of the pump.

[0026] In a particularly advantageous embodiment, the exhaust aftertreatment system can be designed to be freeze-proof after shutdown, even without power supply. Consequently, no draining or valve opening is necessary.

[0027] In a particularly advantageous embodiment of the invention, the temperature of the urea solution is measured directly in the vicinity of its injection into the exhaust stream. For this purpose, a temperature sensor is provided in the dosing unit.

[0028] Further advantages of the invention will become apparent from the further patent claims, the description and the drawings.

[0029] The invention is explained below using an embodiment.

[0030] The drawing shows: Fig. 1 schematically shows the hydraulic circuit of an exhaust gas aftertreatment device, Fig. 2 the components of the exhaust aftertreatment system Fig. 1, whereby a combination hose is provided, Fig. 3 a section of the combination hose from Fig. 2 in a section along its longitudinal axis, with spacers provided, Fig. 4 the combination hose Fig. 3 in a cross-section in front of the spacer, Fig. 5 the spacer from Fig. 4 in a perspective view, Fig. 6 the spacer from Fig. 4 and Fig. 5 as a single part in a different view, Fig. 7 simplifies the wiring of a control unit of the exhaust aftertreatment system, which also controls a pump, Fig. 8 as a single part in a perspective longitudinal section a supply unit to which the pump from Fig. 7 and Fig. 9 the central unit Fig. 7 in a cut perspective view.

[0031] Fig. Figure 1 shows the hydraulic circuit of an exhaust gas aftertreatment system. This system comprises a tank 1 filled with urea. From this tank 1, a pump 2 draws the urea through a pre-filter 3, which is designed as a coarse filter. The pump 2 is driven by a brushless DC motor 4. The pump 2 is associated with a supply unit 55, which also includes a motor control unit for the DC motor 4. The pump 2 is mounted on the tank 1. The supply unit 55 has a first gas collection pocket 79, which is also Fig. 8 is shown in more detail.

[0032] The pressurized UWL is conveyed in a first direction 20 via a line section 6 to a main filter 5. A pressure accumulator 7 branches off from the line section 6. This pressure accumulator 7 makes it possible to operate the pump 2 intermittently. Furthermore, pressure fluctuations can be compensated for with the pressure accumulator 7. Furthermore, a second gas trap pocket 56 is formed in the pressure accumulator 7. The pressure accumulator 7 can be designed, in particular, as a bladder accumulator.

[0033] The line section 6 belongs to a UWL channel 57, which leads from the pump 2 to a nozzle 70, which is designed as an atomizing nozzle in the form of a swirl nozzle.

[0034] The UWL channel 57 thus leads from the line section 6 to the aforementioned main filter 5 via a flexible hose 10, which is adapted to the specific requirements of the vehicle manufacturer. For this purpose, a hose coupling 11, 12 is provided at each end of the hose 10. The main filter 5 is designed as a pressure filter or fine filter. This main filter 5 is followed by a rigid line section 13, from which a pressure sensor 14 branches off. The rigid line section 13 is followed by a flexible UWL hose 15, which is also customer-specific. This UWL hose 15 leads to an electromagnetic injection valve 16, into which a temperature sensor 17 is integrated. This electromagnetic injection valve 16 injects the UWL via the nozzle 70 into an exhaust gas stream 18, which is passed through a catalytic converter 72. The solid arrows indicate the first direction 20 in which the UWL channel 57 guides the UWL from the tank 1 to the nozzle 70.

[0035] A valve 8, designed as a check valve, branches off from line section 6. This check valve blocks the flow towards an intake channel 9 leading to tank 1. For this purpose, intake channel 9 establishes a hydraulic connection between valve 8 and tank 1. Thus, pressure coming from pump 2 is blocked by the check valve. However, if DC motor 4 rotates backward, so that the pump delivers in the second direction 19, pump 2 briefly draws air into the HWL channel 57 until the check valve opens automatically due to the pressure drop to intake channel 9. The open check valve forms a small circuit. Gas - primarily air - is then pumped from tank 1 in the second direction 19 back into tank 1. This small circuit is in the Fig. 1 and is shown by the second direction 19, which is shown with hatched arrows.

[0036] To prevent urea from being pumped through the intake duct 9 during the approximately 10-second start-up phase, this intake duct 9 does not lead to the bottom of the tank 1, but rather to the area of ​​the tank 1 that is at the top in the installed position. Any urea present in the intake duct 9 can thus drip into the tank 1. However, urea cannot be sucked in.

[0037] Fig. 2 shows the components of the exhaust aftertreatment system from Fig. 1. It can be seen that the supply unit 55 with the pump 2 can be arranged both outside the tank 1 and inside the tank 1. The pump 2 is designed here as a gear pump. This gear pump is the Fig. 8. The pressure accumulator 7 is not shown here, as it is only an add-on module of the exhaust gas aftertreatment system that can be used additionally and is not necessary in every vehicle configuration. The supply unit 55 is followed by the central unit 21, in which the pressure sensor 14 and the main filter 5 (not shown in the drawing for clarity) are housed. Furthermore, a blower 22 is integrated into the central unit 21, which can blow hot air into a combination hose 30 so that the UWL located inside the UWL hose 15 can be preheated or thawed. Furthermore, it is possible to use this blower 22 to blow cool air into the hose 15 in order to cool the injection valve 16, which is associated with a metering unit 23. For this purpose, the dosing unit 23 with the injection valve 16 and the temperature sensor 17 is attached to the other end of the combination hose 15.Since the dosing unit 23 also has an electromagnet 24, an electrical line 25 also leads to the end 26 of the combination hose 15, which is connected to the central unit 21. The electrical line 25 exits at this end 26 and leads to a connection plug 27 on the central unit 21. Furthermore, a connection plug 28 for the blower 22 is also provided at this end 26 on the combination hose 15. The UWL hose 15 is provided radially within a jacket sleeve 31 for the blower air duct. This UWL hose 15 is plugged onto a connection plug 29 at the end 26. This connection plug 29 leads via the UWL channel 57, which runs partially within a housing part 33, to the main filter 5 (not shown in detail). This main filter 5 is also arranged within the housing part 33. The HWL channel 57 is drilled inside the housing part 33, which is coupled to the main filter 5, not visible here.The pressure sensor 14 is screwed to the housing part 33. Similar to the connection plug for the urea hose 15, another connection plug 35 extends from the housing part 33, onto which the flexible hose 10 is plugged, which then leads into the already existing . Fig. 1 leads to pump 2.

[0038] Since the housing part 33 is rigid and carries the UWL channel 57, a third gas collection pocket in the housing part 33 leads off from the bores for the UWL channel 57. This third gas collection pocket is arranged in the housing part 33 and is therefore not visible in the drawing. The third gas collection pocket absorbs compressed gas during normal operation of the pump 2. This gas in the third gas collection pocket expands again when the pump 2 is switched off or in the second direction 19 of the pump 2. The bores in the housing part 33 are then freed of parts of the UWL, so that freezing of any UWL still present in the bores cannot lead to the destruction of the housing 33.

[0039] The perspective section over a section in Fig. The combination hose 30 shown in Figure 3 thus carries both the - Air flow from the fan 22 as well as - the HWL as well as - the electrical lines 25 for the electromagnet 24 as well as - in Fig. 4 and Fig. 7 visible signal lines 36 of the temperature sensor 17.

[0040] The urea is routed through the centrally located urea hose 15. The jacket 31 is held in place radially outside this urea hose 15 by spacers 37. The spacers 37 also guide both the electrical lines 25 and the signal lines 36 near the urea hose 15.

[0041] The outer casing 31 is designed with compressed folds. This allows the combination hose 30 to be installed relatively flexibly. This allows one hose type to be used for different vehicle types.

[0042] The spacer 37 has the shape of a spoked wheel. The rim 38 of the spoked wheel has a material weakening 39 located diametrically opposite a clip connection 40. This makes it possible to open the rim 38 in order to insert the urea-based water hose 15, the electrical signal lines 36, and the electrical lines 25. The electrical signal lines 36, the electrical lines 25, and the urea-based water hose 15 are inserted into a hub 41 of the spacer 37. This hub 41 is separated diametrically between the clip connection 40 and the material weakening 39. Each of the two resulting hub halves 42, 43 is connected to the rim 38 by two retainers 44, 45 and 46, 47, respectively. Thus, each hub half 42 or 43 has a rim half 48, 49 associated with it. The hub 41 has a recess on the inside for receiving the electrical signal line 36 or the electrical line 25.Between the reservoirs 44 to 47, four pie-shaped passages are formed for the air flow of the fan 22.

[0043] In Fig. 7 also shows that the central processing unit 21 has a control unit 50. The control unit 50 includes the central processing unit or ECU 53 and the 24V power supply 51 for the supply unit 55 and the vehicle ignition 58. Furthermore, the 24V power supply 51 provides a 5V line 54 that leads to the pressure sensor 14. This pressure sensor 14 outputs signals to the central processing unit or ECU 53. Furthermore, the 5V line 54 leads to the central processing unit or ECU 53.

[0044] The central processing unit (ECU) 53 receives a signal from a tank level sensor of tank 1. Furthermore, the central processing unit (ECU) 53 receives signals from the DC motor 4 of the pump 2. Furthermore, the central processing unit (ECU) 53 receives a signal from the memory module 52 of the dosing unit 23. The central processing unit (ECU) 53 directly controls the electromagnet 24 in the dosing unit 23. The central processing unit (ECU) 53 communicates with the motor control unit 59.

[0045] The metering unit 23 with the injection valve 16 is also visible. An annular channel 73 is provided. This annular channel 73 extends from a diameter-enlarged region 74 near the electromagnet 24 to a valve seat 77 near the nozzle 70. The nozzle 70 is arranged below the electromagnet 24 in the installed position. This creates a fourth gas trap pocket 75 in the diameter-enlarged region 74. This fourth gas trap pocket 75 protects, in particular, the metering unit 23 from freezing UWL.

[0046] Fig. 8 shows supply unit 55 with - pump 2, - the first gas collection bag 79, - an inlet channel 62 for the HWL, - a drain channel 63 for the HWL, - a connection for the intake duct 9 with the check valve 8, - a coolant inlet 80, - a coolant outlet 81, - a solenoid valve 82 for controlling / regulating the coolant and - the DC motor 4, which is not shown in the drawing.

[0047] The DC motor 4 is connected to a gear 60 via a shaft (not shown in the drawing). This gear 60 meshes with another gear 61, which is arranged parallel to the first-mentioned gear 60. The two gears 60, 61 rotate in a pump housing 64, which has an inlet channel 62 and an outlet channel 63. The UWL is guided in the spaces between the teeth of the two gears 60, 61 along the inner walls of the pump housing 64, into which the gears 60, 61 are inserted. The pump builds up a pressure of approximately 14 bar.

[0048] The first gas collection pocket 79 is arranged in the installed position above a channel 68 leading from the pump 2 to the drain channel 63. This channel 68 is open to the gas collection pocket 79. The pump 2 adjacent to the gas collection pocket 79 is frost-protected. The gas collection pocket 79 is arranged in a supply unit housing 71 and closed with a cover 32, which is sealed with a sealing ring 69.

[0049] The solenoid valve 82 for controlling / regulating the coolant for cooling the diesel engine is screwed to the supply unit housing 71. The solenoid valve 82 controls the flow of cooling water through the supply unit housing 71 so that the UWL in the supply unit housing 71 can be thawed. The cooling water can also be used to thaw the UWL present in tank 1, which may have frozen. The solenoid valve 82 controls the flow of cooling water as needed.

[0050] Fig.Figure 9 shows the central unit 21 in a perspective view. The fan 22 and the control unit 50 extend perpendicular to each other. For heat dissipation, the control unit 50 has a screwed cover 65 with cooling fins 67.

[0051] The main filter 5 has a fifth gas trap 76. A sixth gas trap 78 is provided in the pressure sensor 14.

[0052] The described embodiments are merely exemplary configurations. A combination of the described features for different embodiments is also possible. Further features of the device components belonging to the invention, in particular those not described, can be found in the geometries of the device components shown in the drawings. List of reference symbols 1 tank 2 pump 3 pre-filters 4 DC motor 5 main filters 6 line section 7 pressure accumulators 8 Check valve 9 Intake duct 10 flexible hose 11 Hose coupling 12 hose coupling 13 line sections 14 Pressure sensor 15 HWL hose 16 Injector 17 Temperature sensor 18 Exhaust system 19 second direction 20 first direction 21 Central unit 22 blowers 23 Dosing unit 24 Electromagnet 25 electrical cable 26 End of the combination hose 27 Temperature sensor connector 17 28 Fan connector 22 29 Connector plug for HWL hose 15 30 combination hose 31 Coat shell 32 lids 33 Housing part 34 Connection coupling 35 Additional connector 36 Electrical signal cable 37 spacers 38 rim 39 Material weakening 40 clip connection 41 Hub 42 hub half 43 Hub half 44 spokes 45 spokes 46 spokes 47 spoke 48 rim half 49 rim half 50 control unit 51 24V power supply 52 memory module 53 ECU 54 5V line 55 supply unit 56 second gas catcher 57 HWL channel 58 Vehicle ignition 59 Engine control 60 gear 61 gear 62 inlet channel 63 Drain channel 64 pump housing 65 lids 66 ventilation recesses 67 cooling fins 68 channel 69 Sealing ring 70 nozzle 71 Supply unit housing 72 Catalyst 73 Ring Canal 74 diameter-extended area 75 fourth gas catcher pocket 76 fifth gas trap pocket 77 Valve seat 78 sixth gas trap pocket 79 first gas trap 80 Coolant inlet 81 Coolant outlet 82 Solenoid valve

Claims

[1] Exhaust gas aftertreatment device with a control unit (53) for controlling a pump (2) in two opposite directions, wherein the pump (2) conveys a UWL in the first direction (20) from a tank (1) through a UWL channel (57) to a nozzle (70) which injects the UWL into an exhaust gas flow (18), wherein in the UWL channel (57) between the nozzle (70) and the pump (2) at least one gas trap pocket (56, 75, 76, 78, 79) is provided, in which a gas is pressurized by the pump (2) conveying in the first direction (20), wherein the gas is sucked into the UWL channel (57) by the pump (2) conveying in the second direction (19) in an operating start-up phase. [2] Exhaust gas aftertreatment device according to claim 1, characterized by that several gas collection pockets (56, 75, 76, 78, 79) are provided. [3] Exhaust gas aftertreatment device according to one of the preceding claims, characterized bythat when the pump (2) is conveying in the second direction (19), the gas is sucked in via an open valve (8) through a separate intake channel (9), which leads to gas cleaned of dirt particles. [4] Exhaust gas aftertreatment device according to claim 3, characterized by that the separate intake duct (9) leads to the tank (1) in the installation position above a surface of HWL. [5] Exhaust gas aftertreatment device according to claim 3 or 4, characterized by that the valve (8) is a check valve which is arranged in such a way that it closes when the pump is delivering in the first direction (20) and opens when the pump (2) is delivering in the second direction (19). [6] Exhaust gas aftertreatment device according to one of the preceding claims, characterized by that the pump (2) is a gear pump. [7] Exhaust gas aftertreatment device according to one of the preceding claims, characterized bythat a pressure accumulator 7, which has a gas trap pocket (56), branches off from the HWL channel (57). [8] Exhaust gas aftertreatment device according to one of the preceding claims, characterized by that a filter (5) having a gas trap pocket (76) is provided in the HWL channel (57). [9] Exhaust gas aftertreatment device according to one of the preceding claims, characterized by that the nozzle (70) is associated with a metering unit (23) which has an injection valve (16) actuated by an electromagnet (24), wherein an annular channel (73) runs from a diameter-enlarged region (74) near the electromagnet (24) to a valve seat (77) near the nozzle (70), which in the installed position is arranged below the electromagnet (24), so that a gas trap pocket (75) is formed in the diameter-enlarged region (74). [10] Exhaust gas aftertreatment device according to one of the preceding claims, characterized bythat the nozzle (70) belongs to a metering unit (23) which has an injection valve (16) actuated by an electromagnet (24) which is closed in the start-up phase. [11] Exhaust gas aftertreatment device according to one of the preceding claims, characterized by that a gas trap pocket (78) is provided in a sensor (14). [12] Exhaust gas aftertreatment device according to one of the preceding claims, characterized by that the pump (2) belongs to a supply unit (55) with a supply unit housing (71) which has a gas collecting pocket (79). [13] Exhaust gas aftertreatment device according to claim 12, characterized by that the supply unit housing (71) has a coolant inlet (80) and a coolant outlet (81) for coolant of a diesel engine. [14] Exhaust gas aftertreatment processes, characterized by , that - in a first method step, in response to a signal to start operation, a pump (2) conveys a gas via a valve (8) in a second direction (19) which is opposite to a first direction (20), - in a second method step, the pump (2) conveys a UWL and the gas in the first direction (20) along a UWL channel (57) with at least one gas trap pocket (56 or 75 or 76 or 78 or 79), so that the gas is trapped in the gas trap pocket (56 or 75 or 76 or 78 or 79), - in a subsequent operating phase, the UWL is conveyed past the gas collection pocket (56 or 75 or 76 or 78 or 79) and injected into an exhaust gas stream (18) via a nozzle (70). [15] Method according to claim 14, characterized by that the gas expands when the pump (2) is stopped and conveys HWL at least partially out of the HWL channel (57).

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