Reagent injector

1. An injector for injecting a reagent into an exhaust stream, comprising:

an electromagnet;

an inner tube;

an outer tube extending through the electromagnet and surrounding the inner tube, a first end of the inner tube being circumferentially sealingly fixed to an inner surface of the outer tube;

a guide member and an orifice plate each being sealingly fixed to the inner surface of the outer tube, wherein a second end of the inner tube is aligned by the guide member; and

a moveable valve member including a pintle head guided by the inner surface of the outer tube to align the valve member with an orifice extending through the orifice plate.

2. The injector of claim 1 , further including a pole piece positioned adjacent to the pintle head and fixed to the inner surface of the outer tube.

3. The injector of claim 2 , wherein the pole piece includes a bore in receipt of a spring biasing the pintle head away from the pole piece.

4. The injector of claim 1 , wherein the electromagnet includes a coil of wire wrapped around a bobbin, a flux frame surrounding the wire and a plastic housing encapsulating the wire, bobbin and flux frame.

5. The injector of claim 1 , wherein the outer tube includes an aperture in receipt of the reagent, the aperture being axially located between the electromagnet and the orifice.

6. The injector of claim 5 , wherein the inner tube and the outer tube at least partially define a supply passage through which reagent flows.

7. The injector of claim 6 , further including a return passage extending through the pintle head and the pole piece to allow recirculation of the reagent.

8. The injector of claim 7 , further including a slot disc positioned between the orifice plate and the guide member, the slot disc including a swirl port extending therethrough, wherein the guide member includes an inlet port aligned with the swirl port to provide fluid communication between the supply passage and the orifice.

9. The injector of claim 8 , wherein the guide member includes a bypass port providing fluid communication between the supply passage and the return passage.

10. The injector of claim 9 , wherein the slot disc includes a plurality of circumferentially spaced apart swirl ports and a corresponding plurality of swirl slots extending from the swirl ports and terminating at a swirl chamber.

11. The injector of claim 10 , wherein each swirl slot includes a substantially linear portion and a circular portion, the circular portions defining an outer diameter of the swirl chamber.

12. The injector of claim 1 , further including a mount positioned on a first side of the electromagnet and an outlet tube positioned on an opposite second side of the electromagnet, the mount and the outlet tube being fixed to the outer tube to retain the electromagnet between the mount and the outlet tube.

13. The injector of claim 12 , wherein the outer tube and the mount are sealingly fixed to each other at separate axially spaced apart locations to restrict pressurized reagent from leaking from the injector.

14. The injector of claim 13 , wherein the mount forms a portion of a flux frame surrounding the electromagnet.

15. An injector for injecting a reagent into an exhaust stream, comprising:

a housing;

an electromagnet coupled to the housing;

a slot disc including a plurality of circumferentially spaced apart swirl ports extending therethrough, the slot disc also including a swirl slot extending between each swirl port and terminating at a swirl chamber, wherein each swirl slot includes a substantially linear portion and a circular portion, the circular portions defining an outer diameter of the swirl chamber;

an orifice plate including an orifice and being fixed to the slot disc;

a valve member moveable within the housing between a closed position where reagent is restricted from exiting the orifice and an open position where reagent is allowed to pass through the orifice based on an energization of the electromagnet, wherein reagent is pumped through the swirl ports, the swirl slots and the swirl chamber when the valve member is in the open position, wherein the housing includes an outer tube extending through the electromagnet and an inner tube positioned inside the outer tube; and

a mount positioned on a first side of the electromagnet and an outlet tube positioned on an opposite second side of the electromagnet, the mount including a radially outwardly extending flange and an integrally formed inlet passage, the injector including an aperture extending through the outer tube positioned in fluid communication with the inlet passage.

16. The injector of claim 15 , wherein a first portion of the inner tube is fixed to the outer tube and a second portion of the inner tube is spaced apart from the outer tube defining a reagent supply passage.

17. The injector of claim 16 , wherein the electromagnet includes a coil of wire wrapped around a bobbin, a flux frame surrounding the wire and a plastic housing encapsulating the wire, bobbin and flux frame.

18. The injector of claim 17 , wherein the mount and the outlet tube are fixed to the outer tube to retain the electromagnet between the mount and the outlet tube.

19. The injector of claim 15 , further including a pole piece positioned adjacent to the valve member and fixed to the outer tube, and a return passage extending through the valve member and the pole piece to allow recirculation of the reagent.

20. The injector of claim 19 , further including a guide member including a bypass port providing fluid communication between the supply passage and the return passage.

21. The injector of claim 20 , wherein the outer tube and the mount are sealingly fixed to each other at separate axially spaced apart locations to restrict pressurized reagent from leaking from the injector.