Liquid cooled reductant dosing unit

1. A liquid cooled reduction unit, the unit comprising:

a diesel exhaust fluid (DEF) injection valve, the valve having an end portion extending to a distal end, the valve configured to receive a DEF and force the DEF to exit at the distal end, the DEF then being directed and applied to an exhaust stream of a vehicle engine; and

a coolant jacket selectively filled with a coolant, the coolant jacket having an outer side and an inner side, the inner side of the jacket facing a length of the end portion and being separated from the length of the end portion by an air gap, the air gap being closed at or near the distal end of the valve such that the air gap is not in fluid communication with a DEF fluid exit path of the valve.

2. The unit of claim 1 , further comprising a coolant inlet to deliver coolant to the coolant jacket.

3. The unit of claim 2 , further comprising a coolant outlet to allow the coolant to exit the coolant jacket.

4. The unit of claim 1 , further comprising a DEF inlet providing DEF into the DEF valve.

5. The unit of claim 1 , wherein the DEF is a reductant.

6. The unit of claim 1 , further comprising:

exactly two fluid inlets, the two fluid inlets consisting of a DEF fluid inlet providing DEF to the valve and a coolant inlet providing coolant to the coolant jacket; and

exactly two fluid outlets, the two fluid outlets consisting of a coolant outlet providing a coolant exit from the coolant jacket, and a DEF outlet disposed at the distal end of the valve to deliver the DEF into the exhaust stream of the vehicle.

7. An emission system in a vehicle:

an engine that creates an exhaust stream;

a liquid cooled reduction unit, the unit comprising:

a diesel exhaust fluid (DEF) injection valve, the valve having an end portion extending to a distal end, the valve configured to receive a DEF and force the DEF to exit at the distal end, the DEF then being directed and applied to the exhaust stream of a vehicle engine; and

a coolant jacket selectively filled with a coolant, the coolant jacket having an outer side and an inner side, the inner side of the jacket facing a length of the end portion and being separated from the length of the end portion by an air gap, the air gap being closed at or near the distal end of the valve such that the air gap is not in fluid communication with a DEF flow path exiting the valve; and

an exhaust pipe that receives the exhaust stream after the DEF has been injected to the stream, the injection of the DEF into the stream forming a modified exhaust stream that meets at least one government emission regulation.

8. The emission system of claim 7 , further comprising a coolant inlet to deliver coolant to the coolant jacket.

9. The emission system of claim 8 , further comprising a coolant outlet to allow the coolant to exit the coolant jacket.

10. The emission system of claim 7 , further comprising a DEF inlet providing DEF into the DEF valve.

11. The emission system of claim 7 , wherein the DEF is a reductant.

12. The emission system of claim 7 , wherein the reduction unit has exactly two fluid inlets, the two fluid inlets consisting of a coolant inlet to deliver coolant to the coolant jacket and a DEF inlet providing DEF into the DEF valve.

13. The emission system of claim 7 , wherein the reduction unit has exactly two fluid outlets, the two fluid outlets consisting of a coolant outlet to exit coolant from the coolant jacket and a DEF outlet at the distal end of the valve to deliver DEF into exhaust pipe.

14. The emission system of claim 7 , wherein air in the air gap is unable to exit the reduction unit at or near the distal end of the valve.