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This application is a continuation application of international patent application PCT/EP 2007/051820, filed Feb. 27, 2007, designating the United States and claiming priority from German application 10 2006 017 414.3, filed Apr. 13, 2006, and the entire content of both applications is incorporated herein by reference.
The invention relates to a heated urea conduit arrangement for an exhaust-gas aftertreatment system of an internal combustion engine.
To reduce nitrogen oxide emissions of an internal combustion engine, it is known to convert nitrogen oxide into atmospheric nitrogen and water vapor by means of selective catalytic reduction (SCR) technology. As a reducing agent, use is made of an aqueous urea solution which is carried in a separate storage vessel.
The hose conduits between the storage vessel and the exhaust conduit must be heatable since there is the risk of the aqueous urea solution freezing below −11° C. It is known to use electrically heatable hoses.
It is an object of the invention to provide a heated urea conduit arrangement which acts satisfactorily and reliably without the use of electrical energy.
The object is achieved according to the invention in that a hose conduit, which conducts the aqueous urea solution, runs parallel to a hose conduit which conducts heating water, and in that the two hose conduits are tightly surrounded by a hose which shrinks when heated.
With the invention, the hose conduit which conducts the urea solution is positioned parallel to a hose conduit which conducts heating water and which comprises preferably a thermally conductive elastomer. The hose which shrinks when heated (shrink hose) presses the two hose conduits together and, as a result, a good transfer of heat is obtained.
In an advantageous embodiment of the invention, the shrink hose is a fabric shrink hose. The fabric can, for example, be polyester which is coated with a polyolefin.
The fabric shrink hose effects a close contact between the two hose conduits, which run parallel, and this ensures a good transfer of heat. The fabric shrink hose is sewn together parallel to the axis and has a satisfactory degree of design-related expansion. This leads to a degree of flexibility which is required for easy location of the hose pack within the engine compartment.
When heated, the fabric shrinks, such that the two hose conduits, which form the hose pack, run so as to bear constantly against one another, with the linear contact being reliably maintained.
In a further advantageous embodiment of the invention, the hose conduit pair, which is held together by the shrink hose, is surrounded by an insulating foam hose. The heat which comes from the heating water is thus supplied in a targeted manner to the hose which conducts the urea solution.
The invention will now be described with reference to the drawings wherein:
FIG. 1 is a perspective view of the hose conduit pair which is held together by a fabric shrink hose; and,
FIG. 2 shows a cross section of the arrangement shown in FIG. 1.
A hose conduit 3 which conducts aqueous urea solution is arranged adjacent, and parallel, to a hose conduit 4 which conducts heating water. The two hose conduits 3 and 4 are surrounded by a fabric shrink hose 5 which has shrinkage properties when heated. The two media-conducting hose conduits 3 and 4, which are surrounded by the fabric shrink hose 5, are pressed against one another with linear contact. This generates a type of heat-exchanger effect. The heat which is present in the heating water of the one hose conduit 4 is supplied to the hose conduit 3 which conducts the urea solution. The heat transfer is sufficient to prevent the urea solution from freezing.
The hose conduit pair 3 and 4, which is surrounded by the fabric shrink hose 5, runs in an insulating foam hose 7.
It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.