Patent Application
20070246411
Reference is made to the accompanying drawings, in which:
With reference to the figures, the vehicle in accordance with the invention (represented diagrammatically in chain-dotted lines) comprises in conventional manner an internal combustion engine 100 having an admission line 101 and an exhaust line 102 provided with a catalyst 103 operating using selective catalyst reduction (SCR) in known manner.
A pollution-reducer device 104 is fitted to the exhaust line 102. The pollution-reducer device 104 comprises a tank 105 connected by a first pipe 10 to a metering member 106, itself connected by a second pipe 10 to an injector member 107 delivering in conventional manner into the catalyst 103.
The tank 105 contains a depollution fluid here comprising a mixture of urea and water respectively in proportions of about 30% and 70%. By way of example, such a fluid is sold under the trademark Adblue by the supplier Greenchem.
The metering member 106 controls delivery of the necessary quantity of depollution fluid to the injector. The metering member is itself known and in particular it incorporates a metering pump and a control unit.
The injector member 107 of conventional structure serves to introduce the depollution fluid into the catalyst 103, possibly together with air, in quantities determined by the metering member 106.
Each pipe 10 is rigid and shaped by thermoforming to have a shape that enables it to be installed in the pollution-reducer device 104.
Each pipe 10 comprises an outer tube 1 and an inner tube 2, here extending coaxially within the outer tube 1. The outer tube 1 and the inner tube 2 have respective inside and outside diameters so as to leave a fluid flow space 7 between them.
The outer tube 1 is a multilayer tube comprising an inner layer 3 of high density polyethylene, an intermediate layer 4 of maleic anhydride grafted polyethylene, and an outer layer 5 of polyamide. The outer tube 1 could be of a different structure, and for example it could be a single layer tube comprising a layer of a thermoplastic material such as a polyamide, a polyethylene, or a mixture of polypropylene and ethylene-propylene-diene monomer.
In this example, the inner tube 2 is a single layer tube made of a thermoplastic material, more particularly a mixture of polypropylene and ethylene-propylene-diene monomer. The inner tube 2 may also be made of elastomer, and more particularly of an elastomer that incorporates silicone.
The inner tube 2 is more flexible than the outer tube 1. The flexibility and the thermal behavior of the inner tube 2 are such that the inner tube 2 is deformable at low temperature. The inner tube 2 must thus retain its flexibility at temperatures lower than −7° C.
The materials used present the advantage of being inexpensive. The material of the inner tube 2 and of the inner layer 3 are compatible with the transported fluid, i.e. they withstand it chemically.
In its thickness, the inner tube 2 also incorporates a heater element 6, in this example a metal wire extending helically in the material of the inner tube 2, and suitable for being connected to an electrical power supply so as to heat the fluid flowing in the pipe 10. In a variant, the heater element 6 could be a braid or a tape or any other resistive element made of a material that is suitable for heating on being subjected to a voltage.
The pipe 10 of the invention is made by coextrusion.
The first pipe 10 is connected to the tank 105 and to the metering member 106 (forming elements of the depollution fluid transport circuit) via couplings secured to the ends of the pipe 10 and given overall reference 20.
Each coupling 20 comprises a tubular body 21 having one end 21.1 closed by a radial partition 22, and an opposite end 21.2 arranged to be engaged in the corresponding end of the outer tube 1.
A bushing 23 extends coaxially inside the body 21. The bushing 23, likewise of tubular shape, has one end 23.1 connected to the body 21 by the partition 22, and an opposite end 23.2 arranged to be engaged in the corresponding end of the inner tube 2. The end 23.1 is open to the outside of the coupling 20. The bushing 23 incorporates an electrical conductor 27 leading to the outside at the end 23.2 so as to be put into contact with one element of the heater element, and at the end 23.1 so as to be connected to an electrical power supply 28 of conventional kind. On a motor vehicle, the power supply 28 may be the battery of the vehicle. The heater element 6 may alternatively be connected to the power supply 28 by using any type of electrical connection.
The bushing 23 and the body 21 define an annular space 24 in communication with the space 7 when the pipe 10 is connected to the coupling 20.
The coupling 20 includes an endpiece 25 that projects radially from the body 21 and defines a channel 26 in communication with the annular space 24. The endpiece 25, of conventional shape, is engaged in the circuit element 105, 106. The endpiece 25 may be in the form of a serrated spigot, or a teat, or it may be smooth, or fitted with screw/nut type connection means.
The connection of the second tube to the metering member 106 and to the injector member 107 is likewise provided by couplings 20.
When the temperature drops below the temperature at which the fluid solidifies, the fluid freezes and its volumes increases. The expansion of the fluid exerts pressure on the outer tube 1 and on the inner tube 2. because of its flexibility, the inner tube 2 deforms by being compressed, and possibly even by collapsing so as to absorb the expansion of the fluid without leading to excessive pressure on the outer tube 1. The air contained in the inner tube 2 can be evacuated through the end 23.1 thereof which is open. Specifically, the end 23.1 allows air to pass freely from the outside to the inside, and vice versa. Thus, the outside diameter of the tube does not vary, thus making it easier to put into place and to hold in position in the vehicle. The heater element 6 serves to liquefy the fluid while consuming relatively little energy, given its disposition inside the pipe and very close to the fluid.
By way of example, it is assumed that the pipe must be capable of accommodating an expansion of 20% by the fluid. For a flow space 7 having a section of 100 square millimeters (mm2) (referred to as the hydraulic section or the flow section of the pipe), the hydraulic section must be capable of increasing up to 120 mm2. The inner tube then has a hydraulic section of 40 mm2, for example: the necessary increase in the hydraulic section of the pipe can be achieved with the inner tube having a compressibility ratio of 50%. It would also be possible to accommodate the fluid expanding by 40%, since a corresponding increase in the hydraulic section of the pipe would result in the inner tube collapsing completely. Naturally, the pipe could be dimensioned in some other way.
In a particular embodiment, the outer tube has a thickness lying in the range 1 millimeter (mm) to 1.4 mm, approximately, and the inner tube has a thickness lying in the range 0.4 mm to 0.6 mm, approximately.
Naturally, the invention is not limited to the embodiment described, and variants can be applied thereto without going beyond the ambit of the invention as defined by the claims.
In particular, at its ends, the pipe may include spacers holding the inner and outer tubes apart. The inner tube may be closed at its ends. The inner tube need not be coaxial with the outer tube. The compressible member may be of a shape different from that of a tube, and it could comprise a cylinder of cellular material. It is possible to act on the compressibility of a gas contained in the cells.
The shape of the ends 21.1 and 23.2 could be corrugated, serrated, teat-shaped, . . . .
Although the pipe is shown having its ends fitted with couplings 20 that are identical, air may flow in and out of the inner tube 2 via one end only, and the same can apply to the electrical connection with the heater element 6 if the ends thereof can be brought out at a single end of the inner tube 1.
The heater element incorporated in the inner tube 2 may also be backed up by a heater element incorporated in the outer tube 1, or it could be omitted if the outer tube has a heater element. The heater element could be provided around the outer tube 1. The heater element is optional.
The coupling 20 could be of a structure different from that described, and for example it could be arranged to engage on the inner and outer tubes instead of in them.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06 03653 | Apr 2006 | FR | national |
