WO2013087668A1

WO2013087668A1 - Pumping unit

Info

Publication number: WO2013087668A1
Application number: PCT/EP2012/075170
Authority: WO
Inventors: Uwe Hammer
Original assignee: Robert Bosch Gmbh
Priority date: 2011-12-15
Filing date: 2012-12-12
Publication date: 2013-06-20
Also published as: DE102011088679A1; EP2791509B1; EP2791509A1

Abstract

The invention relates to a pumping unit (14, 30) for conveying a reducing fluid, in particular for conveying a urea-water solution for reducing nitrogen oxides in an exhaust gas flow of an internal combustion engine, with a housing cover (32), a housing upper part (34) and a housing lower part (36), wherein a diaphragm (38) which is actuable by means of a drive unit (40) is accommodated between the housing cover (32) and the housing upper part (34), and a first and a second connection chamber (60, 62) are provided in the housing lower part (36). According to the invention, the conveying direction is reversible by means of an integrated valve unit (22), in particular by means of a 4/2-way valve. This reduces, inter alia, the number of components required for constructing an SCR system, thereby in particular reducing the outlay on installation and maintenance. At the same time, the availability of the SCR system is improved, in particular because of the reduced number of connecting lines. Furthermore, owing to the connecting lines no longer being necessary, the installation space which is to be kept ready and the weight are reduced.

Description

Description title

pump unit

State of the art

In motor vehicles with internal combustion engines, in particular with diesel engines, nitrogen oxides (NOx) must be reduced in the exhaust gas flow due to increasingly stringent exhaust gas limit values, among other things. A well-known process, which is widely used in this context, is the catalytic reduction ("Selective Catalytic

Reduction "), that is, the so-called SCR method.

In a special SCR catalytic converter, which is integrated into the exhaust pipe of the internal combustion engine, NOx is converted into N 2 and H 2 O with the aid of NH 3, the NH 3 preferably being in the form of an aqueous urea solution ("AdBlue®") via the SCR catalyst Injector is supplied. In many cases, electrical feed pumps, such as diaphragm pumps, are used to convey urea. A major problem of the watery

Urea solution is that it freezes at temperatures below about -12 ° C, which leads to an increase in volume of the urea-water solution. This can lead to frost-related burst damage to the SCR system. In order to achieve the necessary frost protection at temperatures below -12 ° C and to prevent damage to the SCR system by the increase in volume of the urea-water solution, these systems are usually equipped with a 4/2-way valve. After the vehicle has been switched off, it is actuated while the SCR pump is running, as a result of which the urea-water solution in the SCR system can be pumped out of the system back into the storage tank. In prior art SCR systems for motor vehicles with internal combustion engine, the SCR (diaphragm) pump and the 4/2-way valve are formed as two separate components, which are connected to each other via a complex line system. The line system leads in particular to increased installation and maintenance costs. At the same time, the availability of the entire SCR system is reduced due to the individual components to be coupled, whereby at the same time the total weight and the claimed installation space increase. Disclosure of the invention

It is a pump unit for conveying a reducing fluid, in particular for conveying a urea-water solution for reducing nitrogen oxides in an exhaust stream of an internal combustion engine, disclosed with a housing cover, an upper housing part and a lower housing part, wherein between the housing cover and the upper housing part operable by means of a drive unit membrane is included, and im

Housing lower part, a first and a second connection chamber are provided.

According to the invention the conveying direction by means of an integrated valve unit, in particular by means of a 4/2-way valve, reversible.

As a result of the directly integrated into the pump unit valve unit, the number of components to be coupled to the SCR system and the reliability increases considerably. In particular, eliminates the otherwise between the SCR pump unit and a separate 4/2 way valve necessary line connections. By means of

Valve unit can be the pump unit in a simple way to switch from normal delivery operation in the Rücksaugbetrieb after switching off the engine to

Avoid frost damage within the SCR system at temperatures in the range of -12 ° C or below. The pump unit itself can be designed, for example, as a diaphragm pump. The internal combustion engine is preferably a

Diesel engine.

A development of the pumping unit provides that a membrane chamber is separated from a pumping chamber by the membrane.

As a result of the design of the pump unit as a diaphragm pump results in particular a structurally simple and at the same time reliable construction of the pump unit.

In accordance with a further advantageous embodiment, it is provided that the

Valve unit is formed, inter alia, with a rotary valve.

As a result, the valve unit within the pump unit reaches a high reliability and it is a fast switching of the pump unit between conveyor and

Recirculation mode possible.

According to a further embodiment of the invention, the rotary valve is pivotally received between the upper housing part and the lower housing part.

The bearing of the pivotable rotary valve can be done for example by means of a ball which is received in a ball socket with slight press-fit. alternative it is possible to form the pivotable rotary valve as an elastomeric component, in which a metal insert part is embedded. As a result, there is advantageously the possibility to jam the elastomer of the pivotable rotary valve in the housing and thus to achieve a sealing effect. The pivoting movement is due to the elastic deformability of the elastomer, so that an arrangement ball / ball socket, as described above, could be dispensed with. To the

Pivoting the rotary valve has this over an extension, which is led out laterally for example from the upper housing part or the lower housing part and which is actuated by means of an actuator for changing between the first and the second angular position of the rotary valve. Other than a rotary valve

Shut-off valves are used to realize the operation of a conventional 4/2-way valve.

In a further development of the pump unit is provided in a first

Angle position of the rotary valve, the reducing liquid is conveyed in the conveying operation of the first connection chamber into the second connection chamber.

In this way, in the normal operation of the internal combustion engine, the reducing agent can be conveyed with the aid of the pumping unit from a storage tank to an injector in the region of the SCR catalytic converter within the exhaust gas line of the internal combustion engine.

According to a further embodiment, it is provided that in a second angular position of the rotary valve, the reducing liquid in the Rücksaugbetrieb of the second

Connection chamber is conveyed into the first connection chamber.

This makes it possible, after long-term shutdown of the internal combustion engine by reversing the conveying direction of the pump unit, the reducing liquid or the urea water solution completely sucked out of the SCR system to prevent damage thereof at temperatures of -12 ° C or below.

In accordance with a further embodiment, at least two check valves and the lower housing part at least two check valves are arranged in the upper housing part, wherein the check valves in the upper housing part opposite acting to the

Check valves are arranged in the lower housing part.

As a result, the pumping operation and in conjunction with the rotary valve a quick change between the delivery mode and the Rücksaugbetrieb is possible. In one embodiment, the rotary valve in the first angular position closes a first

Pumping chamber bore and a second connection chamber bore and gives a first

Connection chamber bore and a second pump chamber bore free.

As a result, the normal conveying operation of the pump unit in the first angular position of

Rotary slide set during operation of the internal combustion engine.

Accordingly, the rotary valve in the second angular position, the first

Pumping chamber bore and the second connection chamber bore free and closes the first connection chamber bore and the second pumping chamber bore.

As a result, the Rücksaugbetrieb the pump unit in the second angular position of the

Rotary valve causes in the case of longer periods of inactivity of the internal combustion engine.

Brief description of the drawings

With reference to the drawing, the invention will be described below in more detail. Show it:

Figure 1 is a schematic diagram of an SCR system with an inventive

Pump unit; and

Figure 2 is a simplified cross-sectional view of a pump unit with integrated

Valve unit;

embodiments

1 shows the basic structure of an SCR system with a pump unit according to the invention.

An SCR system 10 for the catalytic reduction of NOx in an exhaust gas stream of an internal combustion engine, not shown, in particular a diesel engine, inter alia, a storage tank 12 for the unnamed reducing liquid, in particular a urea-water solution (sg "AdBlue®"), a pump unit according to the invention 14 and an injector 16 for injecting the reducing liquid in the likewise not shown exhaust gas line of the internal combustion engine. The pump unit 14 includes, for example, a diaphragm pump 18, a drive unit 20 for the Diaphragm pump and an inventively integrated valve unit 22, which is exemplified here as a 4/2-way valve. The drive unit 20 can

For example, be realized with an electric motor, with a periodically controlled by a control unit, not shown electromagnet or the like.

In the state illustrated in FIG. 1, the pump unit 14 is in the so-called "conveying mode", that is to say the reducing liquid is sucked out of the storage tank 12 and conveyed as far as the injector 16. By horizontally displacing the valve unit 22 against the action of the unsigned spring in the direction of the white arrow, the pumping unit 14 can be switched from the conveying operation into a so-called "suck-back operation". In Rücksaugbetrieb the conveying direction of the pump unit 14 is reversed and the reducing agent is - as indicated by the small dashed black arrows in the

Valve unit 22 indicated - starting from the injector 16, via the diaphragm pump 18 to the storage tank 12 promoted back.

FIG. 2 illustrates a possible cross-sectional illustration

Embodiment of a pump unit according to the invention.

The pump unit 30 includes, inter alia, a housing cover 32, an upper housing part 34 and a lower housing part 36, which are connected to each other pressure-tight. Between the housing cover 32 and the housing upper part 34 is an elastic membrane 38th

clamped. By means of a drive unit 40, not shown, the

Move membrane 38 into vertical oscillating motion. Through the membrane 38, a diaphragm chamber 42 is separated from a pumping chamber 44. The drive unit 40 may be, for example, a periodically energized electromagnet or an eccentric driven by an electric motor. As a result of the periodically oscillating up and down movement of the diaphragm 38, an unnamed volume of the pumping chamber 44 decreases and increases, which results in the desired pumping action. Between the upper housing part 34 and the lower housing part 36, a rotary valve 46 is pivotally received. The bearing of the rotary valve 46, for example, by means of a non-designated ball, which is received in a likewise not designated calotte under preferably slight press-fit, be realized. In addition, it is possible to form the pivotable rotary valve 46 as an elastomeric part, which is provided with a metal insert. This makes it possible to clamp the elastomer of the rotary valve 46 in the housing 32, 34, 36 and thus a To achieve sealing effect. A pivoting movement is given by the elastic properties of the elastomeric material in this embodiment.

The rotary valve 46 is in the state shown in Figure 1 of the pump unit 30 in a first angular position, which allows the normal conveying operation in which the reducing liquid sucked during operation of the internal combustion engine from the storage tank and by means of the pumping unit 30 to the injector in the Exhaust line or the SCR catalyst is promoted. Through the upper housing part 34, the lower housing part 36 and the rotary valve 46, a first and a second intermediate chamber 48, 50 are limited, which are separated from each other pressure-tight. In a second, indicated by a dashed line angle position of the rotary valve 46, the pump unit 30 is in the Rücksaugbetrieb. In the suck-back operation, the conveying direction of the pump unit 30 is reversed, so that the reducing liquid, starting from the injector via the pump unit 30, can be conveyed back into the storage tank. This will be at longer

Downtime of the internal combustion engine avoided damage to the SCR system by the freezing of the reducing fluid at temperatures in the range of -12 ° C or below. The switching between the conveying operation and the suck-back operation takes place by the pivoting of the rotary valve 46 in the direction of the non-designated black, arcuate double arrow or by a change between the first and second angular position. Here is an unspecified tilt angle α of

Rotary valve 46 in the range of ± 10 °.

The rotary valve 46 has an axial extension, not shown, which protrudes from the upper housing part 34 and the lower housing part 36 so that in a simple manner between the first and second angular position of the rotary valve 46, for example by means of an actuator, and thus between the Delivery and return suction operation of

Pump unit can be switched. In the upper housing part 34 are also a first upper and a second upper check valve 52, 54 in not designated

Holes. Corresponding to this, in the lower housing part 36, a first and second, lower check valve 56, 58 added in likewise not designated holes. In the illustrated embodiment of Figure 2, the check valves 52, 54 and 56, 58 act respectively opposite. This means that the two lower check valves 56, 58 in the lower housing part 36 each block a bottom-up flow of the reducing liquid, while the two upper check valves 52, 54 act blocking in the opposite flow direction. In the lower housing part 36 are also a first and a second connection chamber 60, 62, each in Depending on the current operating state (angular position of the rotary valve) of the pump unit 30 can serve both for the supply and for the derivation of the reducing liquid (bidirectional connections).

In the upper housing part 34, a first pumping chamber bore 64 and a second pumping chamber bore 66 are introduced, while in the lower housing part 36, a first

Terminal chamber bore 68 and a second connection chamber bore 70 are provided. In addition, the upper housing part 34 has an approximately frustoconical sealing surface 72 in the area of the rotary valve 46, while the lower housing part 36 has a sealing surface 74 designed to be complementary thereto. The sealing surfaces 72, 74 form in cooperation with the rotary valve 46 a pressure-tight closure of the upper housing part 34 and the lower housing part 36. When pivoting the

Rotary valve 46, the first pumping chamber bore 64 and the second connection chamber bore 70 and the second pumping chamber bore 66 and the first connecting bore 68 are each pressure-tight manner.

In particular, the membrane 38, the diaphragm chamber 42, the pumping chamber 44 and the two upper check valves 52, 54 together with the housing cover 32, the upper housing part 34 and the lower housing part 36, a diaphragm pump initially fixed conveying direction. Among other things, the rotary valve 46, the sealing surfaces 72,74, the two lower check valves 56, 58 and the pumping chamber and

Connection chamber bores 64 to 70 represent the valve unit 22 and the 4/2 way valve, respectively, by means of which the functionality of the diaphragm pump is extended by the possibility of switching over the conveying direction.

In the further course of the description, the mode of operation of the pump unit 30 in the conveying mode, as shown in FIG. 2, will first be explained in more detail.

In the angular position shown, that is in the conveying operation of the pump unit, the rotary valve 46 closes the first pumping chamber bore 64 and the second

Terminal chamber bore 70, while the first connection chamber bore 68 and the second pumping chamber bore 66 are released from the rotary valve. The pressure-tight completion of the holes is carried out by appropriately machined, not designated upper sides and lower sides of the rotary valve 46 in cooperation with the two sealing surfaces 72, 74. A pressure-tight termination can also be achieved by means of elastic attached to the rotary valve 46 contours. As a result of the oscillating up and down movement of the diaphragm 38, the reducing fluid initially moves in the direction of a white arrow 76 into the first connecting chamber 60

sucked from there through the open first connection chamber bore 68 and, since the check valve 56 blocks in this flow direction, into the first intermediate chamber 48. From there, the reducing liquid passes through the permeable in this flow direction first upper check valve 52 into the pumping chamber 44. By the first

Pumping chamber bore 64, the reducing liquid can not flow because of the

Rotary slide 46 is pressure-tight manner in the illustrated first angular position.

Starting from the pumping chamber 44, the reducing fluid due to the pulsating effect of the membrane through the second pumping chamber bore 66, which is released in this angular position of the rotary valve 46, promoted to the second intermediate chamber 50 inside. The reducing fluid can not do anything about this in this case

Flow direction blocking second, upper check valve 54 in the upper housing 34 flow. From the second intermediate chamber 50, the reducing fluid passes via the second non-return valve 58 in the housing lower part 36 into the second connecting chamber 62, from where the reducing fluid in the direction of the white arrow 78 to the injector of the SCR system not shown here to be led. If the rotary valve 46 is pivoted counterclockwise in the direction indicated by a dashed line second angular position, the conveying direction of the

Pump unit 30 um, so that the reducing liquid can be completely sucked out of the SCR system.

In this second angular position, the first connection chamber bore 68 and the second pumping chamber bore 66 through the rotary valve 46 in cooperation with the

Sealing surfaces 72, 74 closed pressure-tight and the pump unit 30 is in the Rücksaugbetrieb. As a result of the pulsating upward and downward movement of the elastic membrane 38, the reducing liquid, starting from the injector not shown here in the direction of a dashed arrow 80, is now sucked into the second connecting chamber 62. From there, the reduction liquid passes through the second, released by the rotary valve 46 connection chamber bore 70 into the intermediate chamber 50. The reducing liquid can not flow through the second, lower check valve 58 in the lower housing part 36, since this is acted upon by the reducing liquid in the reverse direction. Starting from the second intermediate chamber 50, the reducing liquid flows through the in this

Flow direction opening second upper check valve 54 in the upper housing part 34 into the Pumping chamber 44 into it. The reduction fluid can not flow through the second pumping chamber bore 66, since this is closed by the rotary valve 46. From the pumping chamber 44, the reducing fluid flows through the first pump chamber bore 64 also released from the rotary valve 46 into the first intermediate chamber 48. The passage of the first, upper non-return valve 52 in the upper housing part 34 is also not possible, since this is flowed in the reverse direction. Starting from the first intermediate chamber 48, the reducing liquid passes through the first lower check valve 56 in the lower housing part 36 into the first connecting chamber 60 in the flow direction. From the first connecting chamber 60, the reducing fluid finally flows in the direction of the dashed white arrow 82 in the here Not shown storage tank for the reducing fluid.

The pump unit 30 according to the invention enables a complete emptying of the SCR system, in particular in preparation for longer downtimes of the

Internal combustion engine. Any bursting damage due to the freezing at temperatures of -12 ° C or below reducing fluid can be avoided. Due to the integral design of the pump and 4/2-valve unit, which together form the pump unit 30, simplify the assembly and maintenance, which at the same time

Failure probability of the SCR system due to the lower number of

necessary connecting lines reduced. In addition, due to the unnecessary connection lines between the (diaphragm) pump and the 4/2-way valve, the installation space for the SCR system to be kept is reduced, which is of particular importance in applications in the field of automotive engineering. In addition, results from no longer necessary connecting lines, fasteners, etc., a weight reduction.

In this case, the design of the valve unit by means of a pivotable allows

Rotary valve 46 the fast switching between the delivery mode and the

Rücksaugbetrieb the pump unit 30, wherein the actuation of the rotary valve by means of an axial extension, not shown, which by means of an actuator, such as an electromagnet, a pneumatic or hydraulic cylinder, a motor

Eccentric drive or the like is operated.

Claims

Claims 1. Pump unit (14, 30) for conveying a reducing fluid, in particular for

Conveying a urea-water solution for the reduction of nitrogen oxides in an exhaust stream of an internal combustion engine, with a housing cover (32), a housing upper part (34) and a housing lower part (36), wherein between the housing cover (32) and the

Housing upper part (34) by means of a drive unit (40) operable membrane (38) is received, and in the housing lower part (36) has a first and a second

Connection chamber (60, 62) are provided, characterized in that by means of an integrated valve unit (22), in particular by means of a 4/2-way valve, the

Conveying direction is reversible.

2. pump unit (14, 30) according to claim 1, characterized in that a

Diaphragm chamber (42) from a pumping chamber (44) through the membrane (38) is separated.

3. pump unit (14, 30) according to claim 1 or 2, characterized in that the valve unit (22) is formed, inter alia, with a rotary valve (46).

4. pump unit (14, 30) according to any one of claims 1 to 3, characterized in that the rotary valve (46) is pivotally received between the upper housing part (34) and the lower housing part (36).

5. pump unit (14, 30) according to one of claims 1 to 4, characterized in that in a first angular position of the rotary valve (46) the reduction liquid in

Delivery operation of the first connection chamber (60) in the second connection chamber (62) is conveyed.

6. pump unit (14, 30) according to one of claims 1 to 4, characterized in that in a second angular position of the rotary valve (46), the reduction liquid in

Return suction from the second connection chamber (62) in the first connection chamber (60) is conveyed.

7. pump unit (14, 30) according to one of claims 1 to 6, characterized in that in the upper housing part (34) at least two check valves (52, 54) and in

Housing lower part (36) at least two check valves (56, 58) are arranged, wherein the check valves (52, 54) in the upper housing part (34) opposite to the non-return valves (56, 58) in the lower housing part (36) are arranged.

8. pump unit (14, 30) according to one of claims 1 to 7, characterized in that the rotary valve (46) in the first angular position a first pumping chamber bore (64) and a second connection chamber bore (70) closes and a first

Connection chamber bore (68) and a second pumping chamber bore (66) releases.

9. Pump unit according to one of claims 1 to 7, characterized in that the rotary slide (46) in the second angular position, the first pumping chamber bore (64) and the second connection chamber bore (70) releases and the first connection chamber bore (68) and the second pumping chamber bore ( 66) closes.