FR2858654A1 - Exhaust piping for motor vehicle, has outer tube enclosing inner tube, where tubes have different thermal dilations that are compensated and have space filled with insulating material that is sealed by sealing and compensation unit - Google Patents

Abstract

The piping (1) has an inner tube (8) in which exhaust gas passes, and an outer tube (9) that encloses the tube (8) up to a distance, where different thermal dilations in the tubes (8, 9) are compensated. The tubes have a space that is filled with a microporous insulating material (14) and is sealed by a sealing and compensation unit (13). An independent claim is also included for a process for fabrication of an insulated exhaust piping.

Description

DESCRIPTION

  The invention relates to an exhaust pipe for an internal combustion machine and a method for its manufacture. The exhaust pipe has an inner tube, through which the exhaust gas passes, and an outer tube, which sheaths the inner tube at a distance therefrom, with different thermal expansions in the inner tube and the outer tube being compensated. .

  In motor vehicle exhaust systems, exhaust from the engine is exhausted through an exhaust pipe and, usually, a catalytic converter that is disposed in the exhaust line. To comply with the legal emission requirements, the integrated catalytic converters must be brought as quickly as possible to the operating temperature. Apart from the measures, such as electric preheating as well as the use of a mixture of air and very rich fuel with associated afterburner associated with it in the exhaust system, it is known to use exhaust pipes isolated by an air space, as described, for example, in DE 101 05 841 A1, to obtain a rise in temperatures in the catalytic converter. With a double tube, the annular void space, formed between the inner tube and the outer tube, acts as an air insulator, so that the exhaust gas is less cooled during its transportation.

  To compensate for the differences in expansion of the inner tube and the outer tube due to the different temperatures acting on them, these two tubes are coupled by means of compensating elements, provided in particular in the form of wire mesh rings. Thanks to the compensating element, the mounting of the inner tube is flexible and flexible, i.e. that no significant resistance opposes the movement of the inner tube, under the effect of increasing temperatures, so that no cracking of the components is to be feared.

  These modular elements of known tubular construction have in addition to the shell construction modules the advantage of a reduced weight and replace for reasons of weight reduction and fuel economy more and more cast iron parts 35 in the engine compartment.

  Despite the use of such insulated exhaust piping with an air gap, it is not possible to completely avoid heat radiation from the hot exhaust gases in the engine compartment of the vehicle. The fact that the subgroups, due to their increasing number, are placed more and more tightly against each other in the engine compartment, prejudices the ventilation so that the temperature rises constantly in said engine compartment. This represents a danger for many plastic parts, the use of thermal protection sheets or known heat shields can not significantly improve the situation. Although the heat shields protect the sensitive elements in their direct vicinity from high temperatures, they can not prevent the general release of heat in the engine compartment. In addition, they represent an additional subgroup, requiring adequate fasteners, such as brackets and screws, which gives rise to new costs that must be avoided.

  To maintain the surface temperature of the exhaust pipes at a low level, DE 21 37 699 discloses an exhaust pipe provided with an insulating sheath. In this expensive arrangement, the inner wall of the tube is divided into sliding pipe sections on or in the other, and an insulating material is provided between the inner wall and the outer wall of the pipe, which insulation is limited to each end by the outer wall of the tube. Due to the sliding housings (sliding joint) of the inner tube, it is possible to compensate for the extremely different expansion behaviors of the inner structure and the outer structure, while the cooler outer sheath must, as a carrying element 25, transfer forces from one section of tube to another.

  From DE 42 10 691 A1, it is known to wrap exhaust pipes in an insulating material and then surround them with a lower half-shell and an upper semicoque. The half-shells are provided on both sides with folded, longitudinal edges which are connected in a compression tool. A well-insulated pipe is thus obtained, but the solution requires a massive supporting tubular structure capable of withstanding mechanical and thermal loads to which it is subjected in the tool. This massive tubular structure has the disadvantage of delaying the heating of the catalytic converter which must be fast.

  On this basis, the object of the invention is to provide an exhaust pipe and a method for its manufacture ensuring a low thermal radiation in the compartment, with a high degree of insulation, while continuing to compensate for optimal thermal dilations different from the inner structure and the outer structure.

  The solution to the problem lies in exhaust piping as well as in a process according to the invention.

  The basic idea of the invention, based on the known pipe, isolated by an air gap, is to fill the space formed between the inner tube and the outer tube with insulating material and to seal the ends at the end. using a sealing and compensation unit. This unit simultaneously performs the function of a compensation element and that of a sealing element. This results in an exhaust gas duct with particularly effective insulation ensuring low heat radiation in the surrounding area.

  The sealing and compensation unit (in the guiding or sliding unit direction) here combines properties optimally so that the unit provides the necessary air permeability and sealing of the material. insulating. Thus, on the one hand, the air, contained in space and expanding under the effect of temperature rises, can escape and, on the other hand, the exhaust stream can not drive the insulation out of the space. The insulating material is optimally protected against the direct attack of the exhaust gas and a drive due to the velocities and pulsating pressures of the exhaust gas is effectively prevented. This is particularly important when the insulating material is fiber-based.

  The insulating material is microporous and able to flow or be poured. It is preferably in powder form, the powdery particles being small enough to be introduced into space. Highly dispersed silicic acid materials are particularly suitable as microporous insulating materials. These materials contain additives, preferably infrared opacifying agents, which, moreover, prevent the heat conduction by radiation in the air still present in the insulating material. The microprocessor materials provide the best insulation in the temperature range of motor vehicle exhaust and provide maximum insulation to the compartment being used.

  In addition, artificial mineral fibers, based on calcium silicate or calcium silicate and magnesium or aluminum oxide, are particularly advantageous.

  The unit or sealing and compensation unit preferably comprises a separate compensation element and a sealing element which are arranged next to one another in the space between the tubes, the element sealing directly adjacent the insulating material.

  The arrangement in the space between the tubes is achieved in particular by means of a common support, as known in principle, from the compensation element of DE 101 05 841 A1. Here, a compensation element, in the form of a lattice of rectangular configuration, is clamped on three sides in the support which is formed by folding a piece of pipe which is attached to either the inner tube or the outer tube . The seal and compensation liner 15 may be disposed either in the inlet zone or in the exhaust gas outlet zone.

  The sealing and compensation lining consists of at least one metal interlacing which absorbs the major part of the mechanical loads between the inner structure and the outer structure. The sealing member or sealing zone between the metallic interlacing and the powdered insulating material is structured in accordance with the requirements imposed on the joint. It is advisable to design the sealing element in several pieces or in several layers. It is advantageous to provide a portion of fine fibers, directly adjacent the insulating material and a portion of coarse fibers adjacent to the metal interlacing. The fine fiber portion avoids a large amount of passage of the insulating material while the coarse fiber portion retains the insulating material having possibly penetrated into the fine fiber portion.

  Overall, the materials used for the sealing and compensation group are selected so that the sealing properties decrease as the distance of the insulating material increases, while the compensation property increases. . Wire interleaving essentially absorbs the mechanical loads while the fine fiber insulating material prevents the penetration of the pulverulent insulating material in the combined group.

  Because of their arrangement in the support, elements can cooperate in the compensation of thermal expansions.

  In a particularly preferred development of the invention for long length exhaust pipes, a pressure compensation chamber is provided, which is in the form of a sleeve which accommodates air escaping from the space. between the tubes and transmits it to the atmosphere or transfer in the channel through which the exhaust gas flows.

  The sealing and compensation unit can be fixed to the outer tube by means of the support and rest on the inner tube which is sliding or displaceable. A similar attachment, but to the outer tube with support against the outer tube, is also possible.

  For the realization of an isolated exhaust piping according to the invention, it is proposed to use a tubular tube construction, in particular a double tube, as they are used for the tubes isolated by air space, and to bend the end. To do this, the hydroforming technique, known from DE 40 19 899 C1, is particularly suitable, the tube remaining open on one side. The space between the inner tube and the outer tube is then filled with an insulating material, especially with a microporous pulverulent insulating material suitable for flowing or pouring. The sealing and compensation unit is then inserted into said space and assembled to the inner tube or the outer tube. In complicated geometries, it is advisable to move the tube back and forth to speed up filling. The method also makes exhaust pipes with complicated and large radii possible. When tube-tube tubing is first filled with the insulating material and subsequently subjected to forming, it may happen that the inner structure collapses rapidly, the insulating material not providing it with adequate support.

  Other details and advantages of the invention emerge from the following description of the embodiments of the invention shown in the figures.

  FIG. 1 is a longitudinal section of an isolated exhaust pipe which is arranged between the motor of a motor vehicle and a catalytic converter and equipped with a sealing and compensation unit installed in the exit zone of the gases. exhaust; FIG. 2 is a detailed view of the sealing and compensation group according to FIG. 1; FIG. 3 is a longitudinal section of an isolated exhaust pipe which is arranged between the engine of a motor vehicle and a catalytic converter and equipped with a sealing and compensation unit installed in the inlet zone. exhaust gases; Figure 4 is a longitudinal section of the end of an exhaust pipe which is provided with a pressure compensation sleeve; Figure 5 is a longitudinal section of an isolated exhaust piping, with a sealing and compensating unit which is attached to the outer tube.

  FIG. 1 shows an exhaust pipe 1 which is arranged as an exhaust pipe between a machine 2 or a combustion engine, in which, via an inlet pipe 3 and a an intake valve 4, air is introduced, and a catalytic converter 5. This exhaust pipe 1 is connected, at its first end, to the exhaust pipe 6 of the exhaust gas machine. 2, and, by a flange 7, the catalytic port 5. The exhaust pipe 1 is designed as a double tube, with an inner tube 8 (here, inner tube) and an outer tube 9 (here, outer tube) which sheaths the inner tube, said tubes having between them a radial distance A or forming between them a space 10 or an annular chamber. The result is an inner duct for the exhaust gases (AG) and an insulating annular space. While the outer tube 9 and the inner tube jacket 8 are welded together on the exhaust gas inlet side 11, a sealing and compensation unit or a sealing and compensation unit 13 is inserted. in the space on the outlet side of the exhaust gas 12. This group 13 seals against the pulverulent insulating material 14 which fills the space 10 and optimally isolates the exhaust pipework . In addition, it forms the expansion compensation zone for the inner structure and the outer structure of the exhaust pipe 1.

  FIG. 2 shows in detail the sealing and compensation group 13. The front portions of the inner tube and the outer tube extend on the same transverse plane QE, a flange 15 being fixed to the outer periphery of the outer tube by a cord The sealing and compensating unit 13 is disposed in the annular chamber or the space 10 by means of a support 17 or a sealing pack receptacle. This support 17 or gutter-shaped clamping surfaces 18, 19 are formed by suitable bends 20, 21 and an end tab 22 made of a piece of pipe. It is fixed, via a cylindrical longitudinal section 23 of the piece of pipe, to the inner tube 8 with the aid of a fastening element 24. The distance between the first fold 20 and the weld seam the flange 16 is designated by the reference 25.

  The sealing and compensation unit 13 is composed of a compensating element 26 in the form of a wire mesh ring and a sealing element 27 of fibrous material. The wire mesh ring 28 has a substantially rectangular cross-section. It leans with its free side 29 or sliding area against the inner surface of the outer tube 9, while its other three sides 30 to 32 are clamped in the first channel 18 of the support 17. The support 17 can also be attached to outer tube 9, the compensation element 26 then bearing against the inner tube 8, as shown in Figure 5.

  The sealing element 27 follows the compensation element 26. Said sealing element 27 consists of an insulating fabric. In the illustrated embodiment, a first portion 33 of the sealing member is also designed in the form of a ring as the interlacing of metal wires and is disposed in the second gutter-shaped clamping surface 19 of the support 17. This is an insulating material, compacted. Due to the arrangement in the support 17, this part of the sealing element 33 also performs compensation functions, besides the sealing functions. It is followed by the second part of the sealing element 34 which consists of a fibrous insulating material and is no longer clamped in the support 17. Said fibrous insulating material is directly adjacent to the pulverulent insulating material 14.

  In comparison with FIG. 1, FIG. 3 shows the arrangement of a sealing and compensation unit 13 in the exhaust gas inlet zone 11 of the exhaust pipe 1. While the wire mesh 28 essentially absorbs the mechanical loads, the fibrous insulating materials of the sealing member 27 seal the insulating, powdery material 14 in the space 10 and simultaneously prevent the insulating material 14 from being entrained by the exhaust gas.

  In the relatively long exhaust pipes 1, it is advisable to provide the air which is heated in the insulating space 10 a second possibility of expansion. Figure 4 shows an embodiment of such a sleeve-shaped pressure compensation chamber. Said pressure compensation chamber 35 is disposed where the inner tube 8 and the inner tube 9 are fixed relative to each other, i.e. on the side of the tube opposite the sealing and compensating unit 13, and is welded to the outer tube 10 sealingly on a side 37. As the hot air rises upward, the chamber should be arranged at a relatively Student. The outer tube 9 is connected to a flange 39 by a weld bead 38.

  In the outer tube 9, one or more perforations 40 are made in the surface covered by the sleeve 36 so that air can escape into said sleeve 36 which is filled with a fibrous insulating material 41. The sleeve 36 is itself provided with a perforation 43, made in its front surface 42 so that the air can be brought into contact with the atmosphere. In an embodiment not shown, this perforation can also be made in the walls of the inner tube and the outer tube 20 so that air can flow into the exhaust gas channel. The sleeve is then sealed to the outer structure as at its other end.

  With the proposed combination sealing and compensation system 13, an exhaust pipe is available which combines the following properties: On the one hand, an almost stress-free expansion of the inner structure or the inner pipe 8 is achieved by relative to the outer structure or the outer tube 9. The more effective the insulation is in the space 10 and above this is because the temperature differences between the inner structure and the outer structure increase depending on the quality of the interior. Insulation, that is, that the internal structure heats up while the external structure remains cold. And secondly, a minimum of air permeability dilating in the insulating material contained in the space, as well as effective retention of the powdery insulating material in said space are thus provided, without considerable contact with the gases exhaust. Finally, the proposed insulated exhaust pipe 1 can be manufactured at low cost.

  The proposed exhaust piping and process are not limited to the use of round tubes (circular cross section). The invention also extends, for example, to oval or angular sections, used in the case of a very narrow engine compartment. Exhaust piping may be used in all motor vehicle air ducts, for example in addition to the tubes here also shown the collectors installed downstream of the catalytic converter.

  List of references: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

18. 30 19. 20. 21. 22.

23. 35 24.

  Exhaust pipe or exhaust pipe Machine or combustion engine Inlet pipe Inlet valve Catalytic converter Exhaust pipe Flange Inner pipe (in case of double pipe) Outer pipe (in case of piping double) Space Exhaust gas inlet side Exhaust gas outlet Sealing or compensation unit or seal Insulating material, powdery Flange Welding wire Support Gutter-shaped clamping surface Gutter-shaped clamping surface Folding Fold End leg Longitudinal cylindrical section of pipe Attachment of receptacle 25. 26. 27.

28. 5 29. 30. 31. 32.

33. 10 34. 35. 36. 37.

38. 15 39. 40. 41.

42. 20 43.

  Space between wire mesh and weld seam of the flange Compensation element Sealing element Wire mesh Free side of compensating element or sliding sector Clamping side of compensating element Clamping side of compensating element Side of the compensating element First part of the sealing element made of insulating material, compacted Second part of the sealing element made of fibrous insulating material Pressure compensation chamber Sleeve Welded side of the sleeve Welding wire Flange Perforation in the outer tube or in the outer pipe of the exhaust gas Insulating material, fibrous resp. sealing pack in the sleeve Front side of the sleeve Second perforation QE Transverse plane AG Exhaust gas

Claims (12)

claims   An isolated exhaust pipe (1) for a combustion machine (2) having an inner pipe (8), in which an exhaust gas (AG) passes, and an outer pipe (9) which is remotely ducted. (A) said inner tube (8), different thermal expansions in the inner and outer tubes (8, 9) being compensated, characterized in that the space (10) between the inner tube (8) and the outer tube ( 9) is filled with an insulating material (14) which is sealed by a sealing and compensating unit (13).   2. isolated exhaust pipe according to claim 1, characterized in that the insulating material (14) is microporous and able to flow or be poured.   An insulated exhaust pipe according to claims 1 and 2, characterized in that the sealing and compensating unit (13) comprises a separate compensating element (26) and a separate sealing element (27). .   Insulated exhaust pipe according to one of claims 1 to 3, characterized in that the materials and the shut-off system of the elements of the sealing and compensating unit (13) are selected so that in different proportions, the compensating element (26) also has sealing properties and the sealing element (27) also has compensating properties.   5. insulated exhaust pipe according to one of claims 1 to 4, characterized in that the compensation element (26) and a portion (33) of the sealing element are held tight in a common support ( 17) which is disposed either in the inlet zone or in the exit zone of the exhaust gas (11, 12).   Insulated exhaust pipe according to one of claims 1 to 5, characterized in that the sealing and compensating unit (13) comprises a wire mesh body (28).   An insulated exhaust pipe according to one of claims 1 to 6, characterized in that the sealing and compensating unit (13) comprises, as a multi-piece sealing element, a portion of fine fibers (34), directly adjacent to the insulating material (14), and a portion of coarse fibers (33).   Isolated exhaust pipe according to one of Claims 1 to 7, characterized in that the sealing and compensating unit (13) is arranged in one end of the space (10) and that, in order to offer in the space-heated air (10) another possibility of expansion, a pressure compensation chamber (35) is provided at the other end of the space (10), at which end the inner tube ( 8) and the outer tube (9) are fixed relative to each other.   Insulated exhaust piping according to one of claims 1 to 8, characterized in that the pressure compensation chamber (35) is designed as a sleeve (36) which equips the outer tube (9). ) and that the surface of said outer tube covered by said sleeve (36) has at least one expanding air-permeable perforation (40), the sleeve (36), filled with fibrous filter material (41), being in contact with the atmosphere by at least one perforation (43) or being impervious to air with respect to the atmosphere and having a perforation towards the inner tube driving the exhaust gas.   Insulated exhaust pipe according to one of claims 1 to 9, characterized in that the sealing and compensating unit (13) is either fixed to the inner tube and bears against the outer tube (9), is attached to the outer tube (9) and bears against the inner tube (8).   Process for the manufacture of an isolated exhaust pipe (1) for a combustion machine (2) having an inner pipe (8) through which an exhaust gas (AG) and an outer pipe ( 9) which sheaths, at a distance (A), said inner tube 30 (8), different thermal expansions in the inner and outer tubes (8, 9) being compensated, in particular for the manufacture of an exhaust pipe according to the one of claims 1 to 10, characterized by the following steps - Common forming of the inner tube and the outer tube (8, 9), in particular by hydroforming, the two tubes being open on a front side after said forming, - Filling of the space (10) between the inner tube and the outer tube (8, 9) with an insulating material (14), - Sealing of the space (10) filled with insulating material (14) by means of a unit sealing and compensation (13).   12. Method according to claim 11, characterized in that the inner tube and the outer tube (8, 9) are subjected to vibrations to facilitate the filling operation of the insulating material (14) capable of flowing or to be paid.