DE102017211998A1 - Injection device for an exhaust aftertreatment system, exhaust aftertreatment system - Google Patents

Abstract

The invention relates to an injection device (3) for an exhaust gas aftertreatment system (1) of an internal combustion engine, in particular of a motor vehicle, with a tank (8) for storing a particularly liquid exhaust aftertreatment agent, with a metering module (2) for metered emission of the exhaust aftertreatment agent and with a conveyor ( 4) for outputting the exhaust aftertreatment agent from the tank (8) to the metering module (2), wherein the conveyor (4) at least one drivable pump (6) and at least one 4/2-way valve (7). It is envisaged that the 4/2-way valve (7) is connected to the tank (8), the metering module (2) and the pump (6), that in a first switching position the tank (8) a suction side of the pump (6) and the metering module (2) with a pressure side of the pump (6) connects, and in a second switching position the metering module (2) with the suction side and the tank (8) with the pressure side of the pump (6) combines.

Description

The invention relates to an injection device for an exhaust aftertreatment system of an internal combustion engine, in particular of a motor vehicle, with a tank for storing and providing a particular liquid exhaust aftertreatment agent, with a metering module for metered output of the exhaust aftertreatment agent and with a conveyor for conveying the exhaust aftertreatment agent from the tank to the metering module, wherein the conveyor has at least one drivable pump and at least one 4/2-way valve.

Furthermore, the invention relates to an exhaust aftertreatment system with such an injector.

State of the art

Injection devices and exhaust aftertreatment systems of the type mentioned are already known from the prior art. Thus, the published patent application DE 10 2014 010 119 A1 an injection device for providing a liquid under pressure of a predeterminable exhaust gas aftertreatment agent. The injector has a 4/2-way valve connected between a first pressure generator and a second pressure generator, wherein the 4/2-way valve is actuated by a pressure existing in the second pressure generator. The second pressure generator is a piston pump having two pumping diaphragms, which are alternately pressurized by the 4/2-way valve from one side or the other side with a hydraulic pressure, whereby a reciprocating motion is generated, the 5/2-way valve moves, of which at least two ports are connected to the 4/2-way valve to its operation. As a result, a self-contained pressure generating system is bound.

Due to legal requirements, the exhaust gas of internal combustion engines of passenger cars and trucks must comply with certain limits. To meet these limits exhaust gas aftertreatment systems are used downstream of the engine, the aim of which is to reduce in particular particulate and nitrogen oxide concentrations in the exhaust gas. For this purpose, filters and catalysts are used downstream of the engine, which are flowed through by the exhaust gas. Moreover, it is known to introduce an exhaust gas aftertreatment agent, in particular oxidation-reducing agent, into the exhaust gas train by means of an injection device, which then reacts reducing emissions together with the exhaust gas in a catalytic converter. This is used, for example, to regenerate a diesel particulate filter or a NOx storage catalyst or perform a selective catalytic reduction in an SCR catalyst.

By this injection device, the exhaust aftertreatment agent is conveyed from the tank to the dosing and mixed as needed with the exhaust gas.

Disclosure of the invention

The injection device according to the invention with the features of claim 1 has the advantage that the ice pressure resistance of the exhaust aftertreatment system is improved by a simple change in the use of the 4/2-way valve. The inventive design of the injector allows that the exhaust gas aftertreatment agent can be brought back into the tank in a simple manner from the metering module without the operation of the pump having to be changed for this purpose. In particular, an operating direction of the pump can be maintained, so that, for example, a pump driving the electric motor for sucking back the exhaust aftertreatment agent does not have to perform a change of direction. According to the invention this is achieved in that 4/2-way valve is connected to the tank, the metering module and the pump so that it connects the tank with a suction side of the pump and the metering module with a pressure side of the pump in a first switching position and in a second switching position, the metering module with the suction side and the tank with the pressure side of the pump. By a simple adjustment of the 4/2-way valve from the first to the second switching position or vice versa is thus interchangeable between a delivery operation and a Rücksaugbetrieb the exhaust aftertreatment system or the injection device.

Furthermore, it is preferably provided that the 4/2-way valve has a cylindrical housing, in the jacket wall connections for the pump, the tank and the metering module are formed, and an axially displaceable in the housing, the connections releasing or occluding valve element, wherein the housing and the valve element are made of metal. The 4/2-way valve is thus designed as a slide valve whose connections are closed or released by the axially displaceable valve element as a function of the position of the valve element. Depending on the position of the valve element while the connections are separated or connected to each other to obtain the above-described connection between the pump, tank and dosing. The advantageous embodiment of the housing and the valve element made of metal has the advantage that reduces wear of the relatively movable parts and thereby the life of the 4/2-way valve and in particular the injector as a whole is increased.

According to a preferred embodiment of the invention it is provided that the suction side and the pressure side of the pump is associated with a respective check valve. The check valves are in each case acted upon counter to the conveying direction or flow direction of the fluid with a spring force of a return spring. Thereby, a malfunction of the injector is reliably prevented.

Furthermore, it is preferably provided that between the valve element and the housing a plurality of radial seals are formed by a respective fit of valve element and housing. The valve element expediently has a plurality of radial sealing rings arranged axially spaced from one another, which are configured so wide and spaced from one another that the aforementioned switching positions of the 4/2-way valve are made possible. Due to the radial distance from the valve element to the housing inner wall while the fits are formed, which terminals separate from each other, close or form annular chambers between them, through which, for example, adjacent terminals are connected together. By forming the radial seals by fits a simple and wear-free variant of the valve is required.

Particularly preferably, one of the fits is designed as an overflow fit, by means of which an overflow quantity can be returned to the tank. In particular, one of the fits has a slightly greater distance to the inner wall of the housing in comparison to the other fits, whereby a desired leakage is achieved, which allows overflow quantities to be reliably removed from the valve and, in particular, to the tank. The remaining fits are expediently chosen such that sets only a negligible small leak rate. The advantageous overflow adjustment eliminates a division of dosing and overflow on the metering valve, so that a return line from the metering valve to the tank is no longer necessary and is preferably avoided. Instead, the return line is now assigned to the 4/2-way valve, resulting in a particularly compact design of the injector, which has particularly short lines and thus a particularly small located in the lines volume of exhaust aftertreatment agent. This simplifies the re-sucking process for producing ice crush resistance.

Alternatively or additionally, at least one of the radial seals has an elastically deformable sealing ring, in particular with a sealing lip. The sealing ring is in particular in operative contact with the housing inner wall of the housing, so that a particularly dense radial seal is ensured. By the optional sealing lip, the sealing performance of the sealing ring is improved and in particular a leakage at this point completely or at least largely prevented.

Furthermore, it is preferably provided that the valve element is assigned at one end a controllable actuator and the other end a return spring. By the actuator so that the valve element against the spring force of the return spring is movable, and the return spring moves the valve element in the direction of the actuator when it is no longer actuated. As a result, a particularly simple operation of the 4/2-way valve is achieved. In particular, the actuator is designed as an electromagnetic actuator, which can efficiently move the valve element against the return spring.

Particularly preferably, it is provided that the valve element made of metal forms an armature of the electromagnetically operating actuator. This anchor and valve element are integrally formed and offered a particularly compact embodiment of the injector. Due to the one-piece design can be dispensed with a sealing membrane between the armature and valve element. According to an alternative embodiment of the invention, it is preferably provided that armature and valve element are formed separately from each other and separated from each other by a flexible membrane media-tight. For example, the membrane lies between the armature and the valve element, so that it is acted on by both with a biasing force and moved by armature and valve element.

Furthermore, it is preferably provided that the return spring is arranged in a compensation space of the housing for Eisdruckbildung. The housing thus has a compensation space in which liquid can expand when frozen, without causing damage. By arranging the return spring in this compensation space a multiple use of the space is achieved and ensures a compact embodiment of the 4/2-way valve.

Furthermore, it is preferably provided that leads from the 4/2-way valve at least one pressure relief line to the tank, which in particular has a throttle device. Preferably, the pressure relief line is connected to the 4/2-way valve so that it opens into the space which is arranged downstream of the overflow, so that the overflowing medium can be discharged through the pressure relief line to the tank. For this the valve expediently on the other end on a connection, which is not switchable by the valve element and acts only as a leakage line or pressure relief line. By the pressure relief line and in particular the overflow is also achieved that damage to the 4/2-way valve is prevented due to an excessive hydraulic pressure.

The exhaust aftertreatment system according to the invention with the features of claim 11 is characterized by the inventive design of the injector. This results in the already mentioned advantages. Further advantages and preferred features emerge in particular from the previously described and from the claims.

• 1 ein Abgasnachbehandlungssystem in einer vereinfachten Darstellung,
• 2A und 2B einen Teil einer Einspritzeinrichtung des Abgasnachbehandlungssystem in unterschiedlichen Schaltzuständen,
• 3A und 3B die Einspritzeinrichtung gemäß einem weiteren Ausführungsbeispiel in unterschiedlichen Schaltzuständen.

In the following, the invention will be explained in more detail with reference to the drawing. Show this

• 1 an exhaust aftertreatment system in a simplified representation,
• 2A and 2 B a part of an injection device of the exhaust aftertreatment system in different switching states,
• 3A and 3B the injection device according to a further embodiment in different switching states.

1 shows a simplified illustration of an exhaust aftertreatment system 1 for an internal combustion engine, not shown here, of a motor vehicle. The exhaust aftertreatment system 1 has a dosing module 2 on, which is associated with an exhaust line of the internal combustion engine, in particular upstream of a catalyst to inject if necessary liquid exhaust aftertreatment agent in the exhaust line or admix the exhaust, so that this together with the exhaust in the downstream catalyst pollutant reducing or catalyst regenerating cooperates.

The dosing module 2 is part of an injection device 3 which also has a conveyor 4 with a controllable electric motor 5 and one by the electric motor 5 drivable pump 6 , as well as a 4/2-way valve 7 and the liquid exhaust aftertreatment agent storing and providing tank 8th having.

The 4/2-way valve 7 has four connections 9 . 10 . 11 . 12 in a housing 13 on, by an axially displaceable in the housing valve element 14 are released or closed depending on a position. This will be discussed later. The housing 13 and the valve element 14 In particular, both are made of metal, so that the 4/2-way valve 7 has a long service life.

The connection 9 is with a suction side 15 or a suction port of the pump 6 connected. The connection 10 is with a print page 16 or with a pressure connection of the pump 6 connected. In the two connections between the 4/2-way valve 7 and the pump 6 is each a check valve 17 respectively 18 arranged, each having a flow direction of a fluid urged by a spring element valve element, to prevent inadvertent backflow of medium or exhaust aftertreatment agent. The pump 6 is presently designed as a diaphragm pump, which sucks at the suction port exhaust aftertreatment agent and promotes the exhaust gas aftertreatment agent with a predetermined hydraulic pressure in the direction of the 4/2-way valve 7 at the pressure port. Optionally, the check valves 17 . 18 but also omitted, for example, when the pump is designed as a rotary pump.

The connection 11 of the 4/2-way valve 7 is with the tank 8th connected to suck exhaust aftertreatment means, and the connection 12 with the dosing module 2 to inject the delivered exhaust aftertreatment agent at the predetermined pressure into the exhaust gas of the internal combustion engine.

In a first switching position, as in 1 shown are the connections 11 and 9 as well as the connections 10 and 12 fluidly connected to each other, so sucked exhaust aftertreatment agent and the dosing 2 is supplied. In a second switching position, the 4/2-way valve 7 connects the connections 11 and 10 as well as the connections 9 and 12 with each other, causing the pump 6 now exhaust aftertreatment agent from the connecting lines between the 4/2-way valve 7 and the metering module 2 sucks and towards the tank 8th promotes. By simply switching the 4/2-way valve 7 Thus, a recirculation mode is set by which located in the connecting lines exhaust aftertreatment agent back into the tank 8th is conveyed, so that the freezing resistance of the dosing particular 2 even at low temperatures below the freezing point of the exhaust aftertreatment agent is secured.

2A and 2 B each show in a simplified representation of a part of the injector 3 , being out 1 already known elements are provided with the same reference numerals and insofar reference is made to the above description.

The 4 / 2-way valve 7 is designed as a slide valve, in which the housing 13 is at least substantially cylindrical, so that the connections 9 to 12 are formed in its jacket wall, and in which the valve element 14 axially displaceable in the cylindrical housing as a piston. It is in the valve element 14 one-stop an actuator 19 assigned, which is designed in this case as an electromagnetic actuator. Other end is the valve element 14 a return spring 20 associated with which the valve element 14 with a spring force in the direction of the actuator 19 applied. The actuator 19 is designed to the valve element 14 against the force of the spring element 20 to move from the first switching position to the second switching position. In this case, the valve element forms 14 with its end facing the actuator 19 the armature of the electromagnetically operating actuator, so that the armature 21 integral with the valve element 14 is trained. This is achieved by the manufacture of the valve element 14 made of metal.

The valve element 14 is also cylindrical, but has two recesses along its axial extent 22 . 23 in the form of Radialumfangsnuten. This results in areas of the valve element 14 that have a larger diameter and areas that have a smaller diameter. The sections with the larger diameter each form a radial seal 24 . 25 . 26 , whose outer diameter is chosen such that a minimal leakage between the inner wall of the housing 13 and valve element 14 he follows.

Through the areas of smaller diameter or through the wells 22 . 23 be in the case 13 Chambers formed by which, for example, the connections 9 and 11 as well as the connections 10 and 12 each hydraulically connected to each other, as in the first switching position in 2A shown.

Will the actuator 19 operated, so that the valve element 14 against the return spring 20 is moved, as in 2 B shown so that the valve element 14 reaches its second switching position, so are the connections 9 and 12 as well as the connections 10 and 11 connected to each other to activate the Rücksaugmodus the injector, without the conveying direction of the conveyor 4 must be changed.

Present is the connection 12 formed in two parts and has a shunt 12 ' so close to the port 9 - Seen axially - is formed, that in the second switching position connection 12 and 9 through the extension 12 ' be connected with each other, as in 2 B shown. Because the connections 12 and 12 ' in the present case, it is a 4/2-way valve, even though there are basically five separate switchable ports on the housing 18 having. Optionally, thus could the valve 7 Also referred to as 5/2-way valve, in which two connections, namely the connections 12 and 12 ' be merged so fluidically that the function of the valve assembly or the valve 7 which corresponds to a 4/2-way valve. Like, however 1 can be removed, also a 4/2-way valve can be used, which has only four separate switchable ports.

In the normal state, ie with no current supplied actuator 19 , the 4/2-way valve is thus in the first switching position, which is used for injection. Will the actuator 19 energized or driven, the valve element 14 moved to the second switching position for the Rücksaugbetrieb. Once the activation of the actuator 19 is terminated, urges the return spring 20 the valve element 14 back to the first switching position.

At least one of the fits is preferred 24 and or 26 designed as overcurrent, which offers a larger leakage cross-section compared to the other fits. For example, the fit is preferred 24 designed as Überstrompassung through which at high pressures medium or exhaust aftertreatment agent in the frontal chamber 27 of the housing 13 can flow, in which also the return spring 20 is arranged. From this chamber preferably performs a pressure relief line 28 as well as in 1 shown back to the tank 8th so that excess exhaust aftertreatment agent simply returns to the tank 8th to be led. As a result, an overpressure in the spring chamber is avoided, so that the valve element 14 , which represents a piston, at any time in the direction of the return spring 20 through the actuator 19 is movable.

In addition to the radial seals 24 . 25 . 26 coming directly from valve element 14 and housing 13 are optional, at the larger diameter portions of the valve element 14 one or more sealing rings 25 ' , preferably arranged with a rubber lip, which increase the sealing effect, such as in 2 shown. In addition, preferred are the connections 9 to 12 sealed with respect to the subsequent lines / flow channels and with respect to the environment of the 4/2-way valve, for example by O-rings or other sealing elements. The chamber 27 It also serves as a compensation space in the event that the ambient temperature falls below the freezing point of the exhaust aftertreatment agent and ice forms in the 4/2-way valve.

According to a specific embodiment, the stroke of the valve element 14 , So the distance between the two switch positions, 3 to 6 mm, preferably 4 mm. The largest diameter of the valve element 14 is preferably 3 to 8 mm, preferably 4 mm. Appropriately, valve element and housing 13 made of a stainless steel. Alternatively, however, combinations of metal and plastic are possible, in which case preferably the piston made of metal and the housing 13 are made of plastic.

Will on the overflow socket 24 omitted, so the injector 3 preferably in the line between the 4/2-way valve 7 and the dosing module 2 a compensation volume 29 on that through a return line 30 with optional throttle with the tank 8th is connected, as in 1 shown by dashed lines. This can excess exhaust aftertreatment even before the dosing 2 to the tank 8th be dissipated.

Alternatively to the embodiment described above, in which the valve element 14 or the piston the anchor 21 mitbildet is, according to another embodiment, as in 3A and 3B is shown, provided that valve element 14 and anchor 21 are formed separately from each other. It extends between the valve element 14 and anchor 21 a flexible membrane 31 that come with valve element 14 and anchor 21 upon actuation by the actuator 19 moved as in 3B shown. The membrane 31 is clamped between the valve element 14 and anchor 21 held so that it moves in both directions of movement of the valve element 14 moved and always a media separation of actuator 19 and 4 / 2-way valve 7 guaranteed.

Optionally, there is another pressure relief line 32 at the of the pressure relief line 28 opposite end of the housing 13 formed, which also leads back to the tank, as shown by way of example in the figures. Both the pressure relief line 28 as well as the pressure relief line 32 can optionally have a throttle device 33 be assigned to the speed of movement of the valve element 14 to influence, for example, movement noise or impact noise of the valve element 14 to reduce. Accordingly, by the respective fit a throttle effect between the valve element 14 and housing 13 be generated.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014010119 A1 [0003]

Claims (11)

Injection device (3) for an exhaust aftertreatment system (1) of an internal combustion engine, in particular of a motor vehicle, with a tank (8) for storing a particular liquid exhaust aftertreatment agent, with a metering module (2) for metered output of the exhaust aftertreatment agent and with a conveyor (4) for dispensing the exhaust aftertreatment agent from the tank (8) to the metering module (2), wherein the conveyor (4) at least one drivable pump (6) and at least one 4/2-way valve (7), characterized in that the 4 / 2-way valve (7) is connected to the tank (8), the metering module (2) and the pump (6), that in a first switching position the tank (8) with a suction side of the pump (6) and the metering module (2) with a pressure side of the pump (6) connects, and in a second switching position, the dosing module (2) with the suction side and the tank (8) with the pressure side of the pump (6) connects. Injection device according to Claim 1 , characterized in that the 4/2-way valve (7) has a cylindrical housing (13), in the jacket wall connections for the pump (6), the tank (8) and the metering module (2) are formed, and a axially in the housing (13) displaceable, the terminals (9-12) releasing or occluding valve element (14), wherein the housing (13) and the valve element (14) are made of metal. Injection device according to one of the preceding claims, characterized in that the suction side (15) and the pressure side (16) of the pump (6) in each case a non-return valve (17,18) is associated. Injection device according to one of the preceding claims, characterized in that between the valve element (14) and the housing (13) a plurality of radial seals (24-26) are formed by a respective fit of valve element (14) and housing (13). Injection device according to one of the preceding claims, characterized in that one of the fits (24) is designed as an overflow fit, by means of which an overflow quantity can be returned to the tank (8). Injection device according to one of the preceding claims, characterized in that at least one of the radial seals (24-26) has an elastically deformable sealing ring (25 '), in particular with a sealing lip. Injection device according to one of the preceding claims, characterized in that the valve element (14) is assigned at one end a controllable actuator (19) and at the other end a return spring (20). Injection device according to one of the preceding claims, characterized in that the valve element (14) made of metal forms an armature (21) of the electromagnetically operating actuator (19) at the end. Injection device according to one of the preceding claims, characterized in that the return spring (20) in a compensation chamber (27) of the housing (13) is arranged for Eisdruckbildung. Injection device according to one of the preceding claims, characterized in that from the 4/2-way valve (7) at least one pressure relief line (28,32) leads to the tank (8), which in particular has a throttle device (33). Exhaust after-treatment system (1) for an internal combustion engine of a motor vehicle, with at least one downstream of the internal combustion engine downstream / nachschaltbaren catalyst, and with at least one injector (3) for metered injection of a particular liquid exhaust aftertreatment agent in the exhaust gas of the internal combustion engine upstream of the catalyst, characterized by the formation of Injection device (3) according to one or more of Claims 1 to 10 ,

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