Metering pump assembly

1. A metering pump assembly for admixing a fluid reduction agent into an exhaust gas flow, comprising:

a premixing device that includes:

a mixing chamber having:

a peripheral wall in which entry openings for pressurized gas are formed,

a mixing region in which the supplied reduction agent is mixed with the pressurized gas, and

an entry opening for the reduction agent, formed centrally in an end-side of the mixing chamber,

a first check valve arranged in the premixing device in a supply conduit for the reduction agent, in front of and directly adjacent the mixing region in the flow direction, and wherein the entry opening of the reduction agent is closed by the first check valve, and

wherein the entry openings for the pressurized gas are configured to supply a flow of the pressurized gas onto and over an outlet side of the first check valve.

2. A metering pump assembly according to claim 1 , wherein the first check valve is an integral component of the mixing chamber delimiting the mixing region.

3. A metering pump assembly according to claim 1 , further comprising a supply conduit for the pressurized gas that includes a second return valve upstream from a first return valve in the flow direction of the pressurized gas.

4. A metering pump assembly according to claim 3 , wherein the supply conduits of the reduction agent and of the pressurized gas to the mixing region are arranged concentrically to one another.

5. A metering pump assembly according to claim 4 , wherein an end-side of the mixing chamber is designed in a funnel-like manner, wherein a plate-like closure element of the first check valve is arranged in a funnel.

6. A metering pump assembly according to claim 4 , wherein a first return valve is held in a closed position by a spring element, and may be moved into an opened position by way of the fluid pressure of the reduction agent against the force of the spring element.

7. A metering pump assembly according to claim 3 , wherein a second check valve is formed by an elastic sealing element, which may be brought to sealingly bear on a wall of the supply conduit.

8. A metering pump assembly according to claim 7 , wherein the sealing element is sealingly held on the wall of the supply conduit by way of biasing, and may be moved into an opened position distanced to the wall by way of the pressure of the pressurized gas acting in the flow direction towards the mixing region, against the biasing.

9. A metering pump assembly according to claim 7 , wherein the wall is a generally cylindrical, outer wall of a component containing the mixing region and the first check valve.

10. A metering pump assembly according to claim 9 , wherein the sealing element of the second check valve is designed as an annular sleeve which extends in the flow direction of the pressurized gas inclined towards the wall.

11. A metering pump assembly according to claim 7 , wherein the second check includes a collar having a sleeve about an inner periphery of the collar that extends in the axial direction.

12. A metering pump assembly according to claim 11 , wherein the sleeve extends conically from the collar.

13. A metering pump assembly according to claim 7 , wherein the second check valve circumscribes the wall of the supply conduit.

14. A metering pump assembly for admixing a fluid reduction agent into an exhaust gas flow, comprising:

a premixing device that includes:

a mixing chamber having:

a peripheral wall in which entry openings are formed to direct a flow of pressurized gas radially inwardly onto and over an outlet side of a first check valve within the mixing chamber, and

a mixing region in which the supplied reduction agent is mixed with the pressurized gas, and

an entry opening for the reduction agent, formed centrally in an end-side of the mixing chamber,

wherein the first check valve is arranged in the premixing device in a supply conduit for the reduction agent, in front of and directly adjacent the mixing region in the flow direction, and wherein the entry opening of the reduction agent is closed by the first check valve, and

a supply conduit for the pressurized gas that includes a second check valve upstream from the first check valve in the flow direction of the pressurized gas and wherein the supply conduit is configured to supply the flow of the pressurized gas through the entry openings of the peripheral wall of the mixing chamber onto and over an outlet side of the first check valve.

15. A metering pump assembly for admixing a fluid reduction agent into an exhaust gas flow, comprising:

a central plate;

an end-plate having a surface; and

a premixing device positioned between the central plate and the end-plate, the premixing device including:

a mixing chamber having:

a mixing region in which the supplied reduction agent is mixed with a pressurized gas,

a peripheral wall in which entry openings for the pressurized gas are formed, the peripheral wall being adjacent the surface of the end-plate to direct a flow of the pressurized gas radially inwardly onto and over an outlet side of a first check valve, and

an entry opening for the reduction agent, formed centrally in an end-side of the mixing chamber,

wherein the first check valve is arranged in the premixing device in a supply conduit for the reduction agent, in front of and directly adjacent the mixing region in the flow direction, and wherein the entry opening of the reduction agent is closed by the first check valve, and

a supply conduit for the pressurized gas that includes a second return valve upstream from a first return valve in the flow direction of the pressurized gas and wherein the supply conduit is configured to supply a flow of the pressurized gas to the entry openings of the peripheral wall.