Freeze-resistant metering valve
View Patent ↗A freeze-resistant metering valve is provided that comprises a magnetic part and a hydraulic part. The magnetic part has an armature biased by a spring. The hydraulic part has an annular space for receiving and conveying a liquid as well as a tappet facing a valve seat. The valve seat comprises a nozzle opening on the side facing away from the tappet. In a currentless state, the tappet blocks the annular space in the direction of an opening (nozzle opening) until a freezing pressure exerted onto the armature generates a sufficient force by virtue of the solidifying liquid. This force is used to counteract the spring force until a freeze expansion space is created by way of a relieving motion.
1. An exhaust gas cleaning system, comprising:
a metering valve, said metering valve comprising:
a magnetic part and a hydraulic part, the magnetic part having an armature biased by a spring and the hydraulic part having an annular space for receiving and conveying a urea-water solution received from a liquid inlet, as well as a tappet facing a valve seat, and
the valve seat having a nozzle opening on a side facing away from the tappet, said tappet being connected to said armature, and
said metering valve being in fluidic communication with a motor vehicle exhaust gas system,
wherein:
in a currentless state, the tappet blocks the annular space in the direction of said nozzle opening until a freeze expansion space is created by means of a freezing pressure from solidification of the urea-water solution during freezing,
the urea-water solution is introduced into the exhaust gas system without use of compressed air;
the metering valve has a diaphragm in its interior; and
the diaphragm is provided on a side of the tappet facing away from the valve seat; and
said freezing pressure of the urea-water solution deforms the diaphragm, by way of a relieving motion of the solidifying urea-water solution, and the deformed diaphragm acts indirectly on the armature which lifts the tappet from the valve seat.
2. An exhaust gas cleaning system as claimed in claim 1 , wherein the annular space extends along a specific portion of the tappet.
3. An exhaust gas cleaning system as claimed in claim 1 , wherein a length of the annular space is created such that the magnetic part is positioned in a markedly lower temperature range than an end piece of the hydraulic part of the valve.
4. An exhaust gas cleaning system as claimed in claim 1 , wherein a diameter of the annular space is reduced to a minimum volume, without a noticeable pressure loss occurring along the annular space.
5. An exhaust gas cleaning system as claimed in claim 1 , wherein a diameter of the tappet is smaller than, or equal to, 2 mm and the annular space is 5/10 mm larger than the tappet.
6. An exhaust gas cleaning system as claimed in claim 1 , wherein the diaphragm is in sealing contact with a valve housing.
7. An exhaust gas cleaning system as claimed in claim 1 , wherein the spring is located in the urea-water solution during operation.
8. An exhaust gas cleaning system as claimed in claim 7 , wherein the spring is fixedly held by at least two projections as stop faces, and as a result no undercuts are formed which can hinder the flow of the urea-water solution.
9. An exhaust gas cleaning system as claimed in claim 1 , wherein a compensation connection is provided in the armature.
10. An exhaust gas cleaning system as claimed in claim 9 , wherein a pressure on two opposing sides of the armature is compensated for by a compensation bore in the armature.
11. An exhaust gas cleaning system as claimed in claim 1 , wherein the hydraulic part of the metering valve has a smaller diameter than the magnetic part of the metering valve.
12. An exhaust gas cleaning system as claimed in claim 1 , wherein one of a disc or a bearing is arranged in a vicinity of the valve seat.
13. An exhaust gas cleaning system as claimed in claim 12 , wherein the disc or the bearing is provided with at least one through-passage.
14. An exhaust gas cleaning system as claimed in claim 1 , wherein the valve is equipped with an axial connector for the urea-water solution.
15. An exhaust gas cleaning system as claimed in claim 1 , wherein a seal pot surrounds the armature as a friction bearing support.
16. An exhaust gas cleaning system as claimed in claim 1 , wherein a non-magnetic sealing ring is provided to deflect magnetic flux in a region of the armature.
17. An exhaust gas cleaning system as claimed in claim 1 , wherein a second outlet is provided as an opening in a vicinity of the nozzle opening.
18. An exhaust gas cleaning system as claimed in claim 1 , wherein the valve seat is covered by a nozzle plate.