Pumping device for supplying an exhaust gas aftertreatment system of an internal combustion engine with a reductant, and method
The invention relates to a pumping device ( 20 ) for supplying an exhaust gas aftertreament system ( 10 ) of an internal combustion engine with a reductant ( 14 ), in particular with a urea-water solution, in order to reduce nitrogen oxides (NOx) in the exhaust gas flow of the internal combustion engine, comprising a motor ( 32 ) for driving two pumps ( 22, 24 ). According to the invention, the first pump ( 22 ) is connected to the motor ( 32 ) by means of a first coupling, and the second pump ( 24 ) is connected to the motor by means of a second coupling. In a preferred embodiment, the couplings are designed as freewheel couplings ( 26, 28 ) acting in opposite directions, so that a switch between a “pumping state” and a “suck-back state” can be made by simply reversing the direction of rotation of the motor ( 32 ).
1. An exhaust gas aftertreatment system ( 10 ) of an internal combustion engine comprising a pumping device ( 20 ) for supplying exhaust gas of the internal combustion engine with a reductant ( 14 ) in order to reduce nitrogen oxides in the exhaust gas flow of the internal combustion engine, the pumping device ( 20 ) having a motor ( 32 ) for driving two pumps ( 22 , 24 ), characterized in that the first pump ( 22 ) is connected to the motor by a first freewheel coupling ( 26 ), and the second pump ( 24 ) is connected to the motor by a second freewheel coupling ( 28 ), wherein the motor ( 32 ) is operable to rotate in a first direction and a second direction, and wherein the first pump ( 22 ) is driven by the motor ( 32 ) via the first coupling ( 26 ) when the motor ( 32 ) is rotating in the first direction and is not driven by the motor ( 32 ) via the first coupling ( 26 ) when the motor ( 32 ) is rotating in the second direction, and the second pump ( 24 ) is driven by the motor ( 32 ) via the second coupling ( 28 ) when the motor ( 32 ) is rotating in the second direction and is not driven by the motor ( 32 ) via the second coupling ( 28 ) when the motor ( 32 ) is rotating in the first direction.
2. The pumping device ( 20 ) as claimed in claim 1 , wherein a metering module ( 18 ) of the exhaust gas aftertreatment system ( 10 ) is connected to a discharge line ( 34 ) of the second pump ( 24 ) and to a suction line ( 38 ) of the first pump ( 22 ) by a shuttle valve ( 36 ).
3. The pumping device ( 20 ) as claimed in claim 1 , wherein a suction line ( 40 ) of the second pump ( 24 ) and a discharge line ( 42 ) of the first pump ( 22 ) are connected to a storage tank ( 12 ) for the reductant ( 14 ).
4. The pumping device ( 20 ) as claimed in claim 1 , wherein the pumps ( 22 , 24 ) are diaphragm pumps.
5. The pumping device ( 20 ) as claimed in claim 1 , wherein the motor ( 32 ) is an electric motor.
6. The pumping device ( 20 ) as claimed in claim 2 , wherein at least one return flow restrictor ( 50 is provided.
7. The pumping device ( 20 ) as claimed in claim 6 , wherein the return flow restrictor ( 50 ) is arranged between the second pump ( 24 ) and the shuttle valve ( 36 ) and is connected to the storage tank ( 12 ) by a return flow line ( 52 ).
8. The pumping device ( 20 ) as claimed in claim 6 , wherein the return flow restrictor is integrated into the shuttle valve ( 36 ) and is connected to a storage tank ( 12 ) for the reductant.
9. A method for operating a pumping device ( 20 ) as claimed in claim 1 , for supplying an exhaust gas aftertreatment system ( 10 ) of an internal combustion engine with a reductant ( 14 ) in order to reduce nitrogen oxides in the exhaust gas flow of the internal combustion engine, having a motor ( 32 ) for driving two pumps ( 22 , 24 ), characterized in that a switch is made between a delivery state and a suck-back state by reversing the direction of rotation of the motor ( 32 )between a first direction and a second direction, wherein, in the delivery state, the reductant ( 14 ) is pumped out of a storage tank ( 12 ) for the reductant ( 14 ), via a shuttle valve ( 36 ), as far as a metering module ( 18 ) by means of the second pump ( 24 ) and, in the suck-back state, the reductant ( 14 ) is sucked back out of the metering module ( 18 ), via the shuttle valve ( 36 ), into the storage tank ( 12 ) by means of the first pump ( 22 ), wherein the first pump ( 22 ) is driven by the motor ( 32 ) when the motor ( 32 ) is rotating in the first direction and is not driven by the motor ( 32 ) when the motor ( 32 ) is rotating in the second direction, and the second pump ( 24 ) is driven by the motor ( 32 ) when the motor ( 32 ) is rotating in the second direction and is not driven by the motor ( 32 ) when the motor ( 32 ) is rotating in the first direction.
10. The pumping device ( 20 ) as claimed in claim 1 , wherein the motor ( 32 ) is an external rotor motor.
11. The pumping device ( 20 ) as claimed in claim 2 , wherein a suction line ( 40 ) of the second pump ( 24 ) and a discharge line ( 42 ) of the first pump ( 22 ) are connected to a storage tank ( 12 ) for the reductant ( 14 ).
12. The pumping device ( 20 ) as claimed in claim 11 , wherein at least one return flow restrictor ( 50 ) is provided.
13. The pumping device ( 20 ) as claimed in claim 12 , wherein the return flow restrictor ( 50 ) is arranged between the second pump ( 24 ) and the shuttle valve ( 36 ) and is connected to the storage tank ( 12 ) by a return flow line ( 52 ).
14. The pumping device ( 20 ) as claimed in claim 13 , wherein the return flow restrictor is integrated into the shuttle valve ( 36 ) and is connected to the storage tank ( 12 ).
15. The pumping device ( 20 ) as claimed in claim 1 , wherein the first pump ( 22 ) is connected to a reductant storage tank ( 12 ) via a discharge line ( 42 ) and a shuttle valve ( 36 ) via a suction line ( 38 ) and the second pump ( 24 ) is connected to the reductant storage tank ( 12 ) via a suction line ( 40 ) and the shuttle valve ( 36 ) via a discharge line ( 34 ), wherein the second pump ( 24 ) supplies reductant ( 14 ) to the shuttle valve ( 36 ) from the storage tank ( 12 ) when driven by the motor ( 32 ) and the first pump ( 22 ) supplies reductant ( 14 ) to the storage tank ( 12 ) from the shuttle valve ( 36 ) when driven by the motor ( 32 ).
16. The pumping device ( 20 ) as claimed in claim 15 , wherein a metering module ( 18 ) of the exhaust gas aftertreatment system ( 10 ) is connected to the discharge line ( 34 ) of the second pump ( 24 ) and to the suction line ( 38 ) of the first pump ( 22 ) via the shuttle valve ( 36 ) and is configured to receive a particularly uniform supply of reductant ( 14 ) from the shuttle valve ( 36 ) and is further configured to deliver the supply of reductant ( 14 ) to the exhaust gas flow of the internal combustion engine.
17. The pumping device ( 10 ) as claimed in claim 16 , wherein the metering module ( 18 ) delivers the supply of reductant ( 14 ) to the exhaust gas flow of the internal combustion engine when the second pump ( 24 ) is supplying reductant ( 14 ) to the shuttle valve ( 36 ) and does not deliver the supply of reductant ( 14 ) to the exhaust gas flow of the internal combustion engine when the second pump ( 24 ) is not supplying reductant ( 14 ) to the shuttle valve ( 36 ).
18. The pumping device ( 10 ) as claimed in claim 15 , wherein at least one return flow restrictor ( 50 ) is provided, and wherein the return flow restrictor ( 50 ) is arranged between the second pump ( 24 ) and the shuttle valve ( 36 ) and is connected to the storage tank ( 12 ) by a return flow line ( 52 ).