FR2900063A1 - Pollution e.g. nitrogen oxide, reduction device for internal combustion heat engine of e.g. car, has pipe including inner tube compressible based on rate adapted to compensate fluid dilatation and with heating element to heat fluid - Google Patents

Abstract

The device has a reservoir (105) connected by a pipe (10) to a fluid injection unit emerging into a catalyst, where the reservoir comprises a ADBLUE(RTM: cleaning fluid) comprising a mixture of water and urea. The pipe has an inner tube (2) coaxially extending into an outer tube (1) and compressible according to a rate adapted to compensate a fluid dilatation, where the tubes are made of thermoplastic materials. The inner tube has a heating element (6) e.g. metal wire, connected to a power supply source for heating the fluid circulating in the pipe. An independent claim is also included for a pipe comprising an outer tube receiving a compressible part.

Description

The present invention relates to a pollution reduction device

  for a motor vehicle, a motor vehicle comprising such a device and a pipe for transporting a corresponding depollution fluid.

  The invention is applicable to any type of auto-mobile vehicle including trucks, passenger cars and others. BACKGROUND OF THE INVENTION Anti-pollution systems have greatly developed on motor vehicles with a view to reducing their polluting emissions. Among these anti-pollution systems, there is the catalytic converter that has prevailed on most vehicles. However, environmental standards have lowered the maximum allowable emission level of nitrogen compounds (NOx). The catalytic converter alone was then insufficient to obtain such a reduction in emissions of these compounds. It has therefore been imagined to inject, in the catalytic converter, a solution resulting from a mixture of urea and water in order to create in the catalytic converter redox chemical reactions with the nitrogen compounds. This technology is implemented in the so-called SCR (Selective Catalyst Reduction) reduction devices. The transport of the solution in the motor vehicle is delicate because of the sensitivity of the solution to temperature: the solution decomposes from 70 C by releasing ammonia and freezes from -7 C, solidification of the solution causing its volume expansion. The pipes used for the transport of this solution must therefore be chemically resistant and able to withstand strong dimensional variations. The tubes currently used comprise fluorinated materials in an inner layer to be in contact with the solution and integrate heating systems to prevent the solution from freezing or to liquefy the solution if it has frozen. The tubes are further reinforced in order to resist dilation of the solution which can result in particular from the gel thereof. These pipes are very expensive, not flexible and bulky. This has the consequence of increasing the cost and the size of the pollution reduction devices themselves. OBJECT OF THE INVENTION It would therefore be advantageous to have a means to reduce the cost of such a pollution reduction device. SUMMARY OF THE INVENTION For this purpose, according to the invention, a pollution reduction device is provided, comprising a depollution fluid reservoir connected by a pipe to a fluid injection member in a catalyst of a line. exhaust gas exhaust system, characterized in that the pipe comprises an outer tube receiving a compressible member at a rate adapted to compensate for an increase in pressure exerted by the fluid on the pipe. Thus, when the fluid pressure increases, the fluid will cause a decrease in the volume of the compressible member so that the pressure exerted on the outer tube will be relatively limited, allowing the outer tube to maintain substantially identical dimensions. The compressible member also allows damping pulsations of the fluid, the. deformation of the compressible member reducing the amplitude of the pressure wave resulting from a peak pressure. According to a particular embodiment, the pipe comprises an inner tube extending coaxially in the outer tube, the inner and outer tubes having diameters such that a space for circulation of the fluid is left between them, the inner tube having an outer surface compatible with the transported fluid and the inner tube being more flexible than the outer tube to deform by compensating for expansion of the fluid.

  The inner tube constitutes a compressible member extending over the entire length of the outer tube, so that it does not disturb the circulation of the fluid and may have a relatively small section, the volume reduction caused by the expansion of the fluid being translated. by a reduction of section distributed over the entire length of the inner tube. According to various embodiments: the inner tube is made of thermoplastic material comprising, for example, polypropylene and ethylene propylene diene monomer; the inner tube is made of elastomer material, for example silicone-based; deformation of the inner tube is thus obtained.

  Advantageously, the outer tube is made of thermoplastic material and, preferably, selected from the following materials: polyethylene, polyamide and a blend of polypropylene and ethylene propylene diene monomer; or the outer tube comprises an inner layer of high density polyethylene, an intermediate layer of maleic anhydride grafted polyethylene and an outer layer of polyamide. In the multilayer version, polyethylene forms a barrier to urea and ammonia resulting from the decomposition or degradation of urea, and chemically resists them. This prevents an odor of ammonia from the device and is noticeable by the user. In addition, it eliminates the risk of corrosion of the pipe. Polyamide gives the pipe its mechanical strength.

  According to a particular embodiment, the pipe has ends respectively connected to a fluid emitter element and a fluid receiving element so that the fluid circulates in the sponge extending between the tubes and that the tube inside either free exhaust. Thus, during the compression of the inner tube under the effect of the expansion of the fluid, the air contained in the inner tube can escape.

  Advantageously, at least one end of the pipe is provided with a coupling comprising a tubular body having an end arranged to cooperate with the corresponding end of the outer tube, and an opposite end closed by a radial partition, an inner fur extending coaxially in the body and having an end secured to the radial partition and opening outwardly of the connector and an oppositely disposed end arranged to cooperate with the corresponding end of the inner tube so as to bring into communication the space of circulation of the pipe with an annular space delimited by the body and the fur, the connection comprising means for connecting this annular space with the element. The connection of the pipe is then made simply and reliably by ensuring, on the one hand, the tightness of the fluid transfer and, on the other hand, the free escape of the air extending into the inner tube. The invention also relates to a motor vehicle with a combustion engine comprising a burnt gas exhaust line provided with a catalyst and a pollution reduction device having at least one of the above characteristics. The invention further relates to a pipe for dis-positive pollution reduction having at least one of the above characteristics.

  Preferably, the pipe is arranged to be rigid and conformable by thermoforming. This method of manufacture is inexpensive and simplifies the installation of the pipe under the body of a vehicle. Other features and. Advantages of the invention will become apparent on reading the following description of a particular non-limiting embodiment of the invention.

  BRIEF DESCRIPTION OF THE DRAWINGS Reference is made to the accompanying drawings, in which: FIG. 1 is a diagrammatic view of a motor vehicle according to the invention, FIG. 2 is a longitudinal sectional view of a section of FIG. circuit of the pollution reduction device according to the invention. DETAILED DESCRIPTION OF THE INVENTION With reference to the figures, the vehicle according to the invention (shown diagrammatically in double dashed line) comprises, in a manner known per se, an internal combustion engine 100 comprising an intake line 101 and a exhaust line 102 provided with a catalyst 103 operating according to the SCR (Selective Catalyst Reduction) technology known per se. A pollution reduction device 104 equips the exhaust line 102. The pollution reduction device 104 comprises a reservoir 105 connected by a first pipe 10 to a metering member 106 itself connected by a second pipe 10 to an organ injection device 107 opening in a manner known per se in the catalyst 103. The reservoir 105 comprises a pollution control fluid comprising here a mixture of urea and water in respective proportions of 30ô and 70ô approximately. Such a fluid is for example marketed under the trademark ADBLUE by the company GREENCHEM. The dosing member 106 controls delivery of the required amount of depollution fluid to be injected. This metering member is known in itself and incorporates in particular a metering pump and a control unit. The injection member 107, of conventional structure, ensures the introduction of the pollution control fluid into the catalyst 103 optionally with air in quantities determined by the metering member 106. Each pipe 10 is rigid and shaped by thermoforming according to a geometry allowing its implantation in the pollution reduction device 104.

  Each pipe 10 comprises an outer tube 1 and an inner tube 2 extending here coaxially in the outer tube 1. The outer tube 1 and the inner tube 2 respectively have internal diameters and ex-dull such that is left between them space 7 for circulating the fluid. The outer tube 1 is a multilayer tube comprising an inner layer 3 made of high density polyethylene, an intermediate layer 4 of grafted polyethylene maleic anhydride and an outer layer 5 of polyamide. The outer tube 1 may have a different structure and be for example a monolayer tube comprising a layer of a thermoplastic material such as a mixture of polypropylene and ethylene-propylene-diene monomer, a polyethylene or a polyamide.

  The inner tube 2 is here a monolayer tube made of thermoplastic material, more particularly here a mixture of polypropylene and ethylenepropylene-diene monomer. The inner tube 2 may also be made of elastomer and more particularly of an elastomer incorporating 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 below -7 C. The materials employed have the advantage of being inexpensive. The material of the inner tube 2 and the inner layer 3 are compatible with the transported fluid, namely that they are chemically resistant to it. The inner tube 2 further incorporates in its thickness a heating element 6, here a wire extending helically in the material of the inner tube 2, which can be connected to a source of electric power supply for heating the fluid. As a variant, the heating element 6 may be a braid or a ribbon or any resistive element made of a material that can be heated when it is subjected to an electrical voltage. The pipe 10 according to the invention is produced by coextrusion. The first pipe 10 is connected to the reservoir 105 and to the metering member 106 (forming elements of the transport circuit of the pollution control fluid) via connections fixed to the ends of the pipe 10 and generally designated 20. Each connection 20 comprises a tubular body 21 having an 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 fur 23 extends coaxially inside the body 21. The fur 23, also of tubular shape, has an 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 opens out of the 20. The fur 23 incorporates an electrical conductor 27 opening outward at the end 23.2 to be in contact with one end. of the heating element and at the end 23.1 to be connected to a power supply 28 known in itself. On a motor vehicle, the power supply 28 may be the battery of the vehicle. The connection of the heating element 6 to the power supply 28 can furthermore be achieved by any type of electrical connection. The fur 23 and the body 21 define an annular space 24 in communication with the space 7 when the pipe 10 is connected to the fitting 20.

  The connector 20 comprises a tip 25 projecting radially from the body 21 and delimiting a channel 26 in communication with the annular space 24. The tip 25, of known shape in itself, is engaged in the element of circuit 105, 106. The tip 25 may have a shape of fir-tree tooth or nipple, be smooth or be equipped with screw-type connection means. The connection of the second tube to the metering member 106 and to the injection member 107 is also performed by connectors 20.

  When the temperature falls below the solidification temperature of the fluid, the fluid freezes and its volume increases. The expansion of the fluid exerts a pressure on the outer tube 1 and on the inner tube 2. Because of its flexibility, the inner tube 2 deforms by compressing or even crashing: to absorb the expansion of the fluid without generating an excessive pressure on the outer tube 1. The air contained in the inner tube 2 can be exhausted by the end 23.1 of the latter which is free exhaust. In this case, the end 23.1 allows free passage of air from the outside to the inside and vice versa. Thus, the outer diameter of the pipe does not vary, which facilitates its implementation and its position in the vehicle. The heating element 6 makes it possible to liquefy the fluid while consuming relatively little energy because of its arrangement inside the pipe as close as possible to the fluid. For example, it is considered that the pipe must be able to withstand an expansion of 20% of the fluid. For a circulation space 7 having a section of 100 mm 2 (referred to as hydraulic section or section of passage of the pipe), the hydraulic section must be able to grow up to 120 mm 2. The inner tube then has for example a 40rmn2 hydraulic section: the necessary increase in the hydraulic section of the pipe resulting from a compressibility rate of 50% of the inner tube. A 40% fluid expansion would also be bearable, since a corresponding increase in the hydraulic section of the pipe would result from the total crushing of the inner pipe. A different dimensioning of the pipe is obviously possible. In a particular embodiment, the outer tube has a thickness of between about 1 mm and 1.4 mm and the inner tube has a thickness between about 0.4 mm and 0.6 mm.

  Of course, the invention is not limited to the embodiment described and it can provide variations of embodiment without departing from the scope of the invention as defined by the claims. In particular, the pipe may comprise, at its ends, spacers now spaced the inner and outer tubes. The inner tube can be closed at its ends. The inner tube may not be coaxial with the outer tube. The compressible member may have a different shape than a tube and carry a cylinder of cellular material. It is possible to play on the compressibility of a gas enclosed in the cells. The ends 21.1 and 23.2 may have a ringed shape, fir-tooth, nipple ...

  Although the pipe has been shown with its ends equipped with identical fittings, the passage of air from the inner pipe 2 may be provided at one end only as is the electrical connection of the heating element 6 if the ends of the latter can be brought to one end of the inner tube 1. The heating element integrated in the inner tube 2 can also be supported by a heating element integrated in the outer tube 1, or omitted if a heating element equip the outer tube. The heating element may be provided around the outer tube 1. The heating element is optional. The connector 20 may have a structure different from that described and for example be arranged to engage the inner and outer tubes and not in them.

Claims (19)

  1. A pollution reduction device, comprising a reservoir (105) of pollution control fluid connected by a pipe (10) to an injection member (107) of the fluid in a catalyst (103) of a line of exhaust (102) of burnt gases, characterized in that the pipe (10) comprises an outer tube (1) receiving a compressible member (2) at a rate adapted to compensate for an increase in pressure exerted by the fluid on this pipe.   2. Device according to claim 1, wherein the compressibility ratio is adapted to compensate for a dilatation of the fluid.   3. Device according to claim 1, in which the pipe (10) comprises an inner tube (2) extending coaxially in the outer tube (1), the inner and outer tubes having such diameters is left between they a circulation space (7) of the fluid, the inner tube having an outer surface compatible with the transported fluid and the inner tube being more flexible than the outer tube to deform in compensation of the pressure increase of the fluid.   4. Device according to claim 3, wherein the inner tube (2) is of thermoplastic material.   5. Device according to claim 4, in which the thermoplastic material of the inner tube (2) comprises polypropylene and ethylene propylene diene monomer.   6. Device according to claim 3, wherein the inner tube (2) is elastomeric material.   7. Device according to claim 6, in which the elastomer of the inner tube (2) is based on silicone. k- 12   8. Device according to claim 1, in which the outer tube (1) is made of thermoplastic material.   9. Device according to claim 8, wherein the thermoplastic material of the outer tube (1) is selected from the following materials. polyethylene, polyamide and blend of polypropylene and ethylene propylene diene monomer.   10. Device according to claim 8, wherein the outer tube (1) comprises an inner layer (3) of high density polyethylene, an intermediate layer (4) maleic anhydride grafted polyethylene and a polyamide outer layer (5). .   11. Device according to claim 1, wherein the pipe (10) comprises a resistive heating element (6).   12. Device according to claim 1, wherein the compressible member (2) is arranged to absorb an expansion resulting from solidification of the fluid at low temperature.   13. Device according to claim 1, in which the fluid comprises urea and the pipe (10) is made of a thermoplastic material forming a barrier to urea and at least one product resulting from a decomposition of the urea, and has an inner surface chemically resistant to urea and at least one product resulting from decomposition of urea.   14. Device according to any one of claims 3 to 7, having ends connected to circuit elements (101, 102) so that the fluid circulates in the circulation space (7) extending between the tubes (1, 2) and that the inner tube (2) is free exhaust.   15. Device according to claim 14, wherein at least one of the ends of the pipe (10) is equipped with a connector (20) comprising a tubular body (21) having an end (21.2) arranged to cooperate with the end corresponding outer tube (1), and an opposite end (21.1) closed by a radial partition (22), a fur (23) extending coaxially in the body and having an end (23.1) integral with the partition (23.2) and opening outwardly of the fitting and an opposite end arranged to cooperate with the corresponding end of the inner tube (2) so as to place the circulation space (7) of the hose in communication with a delimited annular space (24) by the body and the fur, the connection comprising connecting means (25, 26) of this annular space with the element.   16. Device according to claim 15, characterized in that the connecting means comprise a tip (25) extending radially projecting from the body (21).   A motor vehicle with a heat engine (100) having an exhaust gas exhaust line (102) provided with a catalyst (103) and a pollution abatement device (104) according to any of the claims. preceding. Pipe (10) comprising an outer tube (1) receiving a compressible member (2) at a rate adapted to compensate for a pressure increase exerted by the fluid on this pollution reduction device pipe according to any one of the claims 1 to 16. 19. Pipe (10) according to claim 18, arranged to be rigid and conformable by thermoforming.