FR2514414A1 - EXHAUST PUMPS AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

EXHAUST SYSTEM AND ITS MANUFACTURING PROCESS. THE EXHAUST SYSTEM ACCORDING TO THE PRESENT INVENTION INCLUDES AN EXTERNAL ENCLOSURE 1 IN SHEET. THE EXTERIOR CYLINDRICAL SURFACE OF AT LEAST ONE CERAMIC ELEMENT 6 IS IN CONTACT WITH THE INTERNAL CYLINDRICAL WALL OF THE ENVELOPE. TO PREVENT THE APPEARANCE OF GENERATING VIBRATIONS DUE TO THE RESONANCE AND TO OBTAIN A RIGID STRUCTURE, THE INTERNAL WALL OF THE ENVELOPE 1 IS FIRMLY ASSEMBLED WITH THE CYLINDRICAL EXTERIOR SURFACE OF THE CERAMIC ELEMENT 6, FOR EXAMPLE BY A CONTRACTION OF THE ENVELOPE AROUND THE CERAMIC ELEMENT.

Description

I

  Exhaust and its manufacturing process.

  The present invention relates to an exhaust pot

  having a good acoustic and mechanical property and comprising a preferably cylindrical sheet-metal casing, sheet-end walls attached to the casing and at least one porous ceramic sound-absorbing member traversed by at least one channel for exhaust, the element

  ceramic material disposed in said envelope comprising a

  outer cylindrical surface contiguous with the inner cylindrical wall of the casing and capable of absorbing the compressive forces The invention also relates to a method for

  make such a muffler.

  The exhaust pipes containing one or more porous acoustically sound-absorbing ceramic elements are described in the

  Swedish patent application 8203892-8.

  These exhausts proved extremely

  effective in terms of sound absorption with respect to

  conventional exhaust pipes which are entirely of sheet metal or which comprise a sound-absorbing fibrous material Furthermore, the sound-absorbing fibrous material is rapidly decomposed and expelled from the muffler The damping effect of the sounds is so

of course seriously reduced.

  On the other hand, the porous ceramic element remains entirely

intact.

  A common feature of conventional exhaust pipes previously known is that the envelope must be made of a relatively thick sheet, for example a stainless steel sheet of 1.5 mm thick, which is

  translated into a relatively large mass Another

  The reason is that the sheet-metal casing and possibly also the components in the casing are the seat of resonant vibrations. Therefore, the radiating sound of the outer surface is often more intense than the sound of the exhaust gas at the exit of the

exhaust pipe.

  The present invention relates to an improvement to the invention according to the Swedish patent application 8203892-8

  o the excellent mechanical properties of the ceramic elements

  porous issues described in this application are used to obtain a new structure of a muffler, this structure to use a much thinner sheet for the envelope without decreasing the mechanical strength of the muffler The new structure is also translated by

  total elimination or at least a reduction in

  Thus, according to the present invention, an exhaust muffler having good acoustic and mechanical properties is obtained. This muffler comprises a preferably cylindrical sheet-metal casing, end walls at 8 mm. connected to the casing and at least one porous ceramic sound-absorbing element, traversed by at least one channel for the exhaust gases, the ceramic element disposed in said

  envelope having a continuous cylindrical outer surface

  gu 8 to the inner cylindrical wall of the envelope and

  absorb compression efforts.

  This muffler is characterized by the fact that

  the envelope and the ceramic element together form a structure

  sandwich-type rigid structure in which the outer surface

  the cylindrical part of the ceramic element is firmly

  attached to the inner wall of the envelope.

  We get this firm association preferably

  by means of a contraction connection and / or an assembly

  It is also possible to combine the envelope and the ceramic element with an adhesive capable of withstanding the heat. Because of this firm connection between the envelope and the ceramic element, the pot can be considered. exhaust system such as a one-piece body or a sandwich structure having a

  large mass and a large wall thickness

  quent, we can reduce the thickness of the envelope It is not

  necessary that this thickness be greater than 0.3 0.5 mm.

  In addition, there is no risk that this muffler will emit

  troublesome vibrations resulting from the resonance.

  We obtain the greatest stability of this pot of escape.

  when compression efforts act between

  envelope and ceramic element and, therefore,

  use a contraction connection and / or

assembly to the press.

  The present invention will now be described with reference to the accompanying drawings, in which: FIG. 1 is a partially cutaway view of an exhaust pipe according to the present invention; and FIG. 2 is a partially cutaway view of a

  another exhaust pipe according to the present invention.

  Figure 1 shows in perspective a pot of escape

  according to the present invention and shows a casing 1 partially torn off, preferably consisting of a stainless steel sheet The casing has a cylindrical configuration of circular section and the thickness of the sheet

  in the illustrated embodiment is about 0.5 mm.

  At the open ends of the casing 1 are fixed the walls 2 and 3 from which exhaust pipes 4 and 5 extend. The walls are preferably formed.

  thicker metal sheet and welded to the inside.

  In the interior of the casing 1 is disposed a ceramic body 6 having a cylindrical outer surface with circular section, this body being preferably rectified; This ceramic body 6, which forms a sound-absorbing element, is

  provided with a central through channel 7 for exhaust gas

  The ceramic element 6 comprises an expanded ceramic material and has been molded into a mold to obtain a high dimensional accuracy and, as mentioned

  previously, the cylindrical surface of the element is pre-

  to correct dimensions so that optimal contact with the inner wall is achieved

of the envelope 1.

  The ceramic element, which is extremely porous and has a compressive strength of at least 4 Ω N / m, and preferably at least 400 k N / m 2, has an outside diameter which, at room temperature, is larger than the inner diameter of the casing 1 The casing 1 is then heated up to a temperature, for example 400-6000 C, sufficiently high that the ceramic element 6 can be pressed into the press 1 envelope 1, said element being maintained,

  for example, at room temperature.

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  The envelope 1 is preferably brought to a temperature of

  of course, the casing can be heated to much higher temperatures than those mentioned if it is desired to obtain very high pressure stresses between the inner wall of the casing 1 and the surface exterior of ceramic element 6 When placed

  the ceramic element 6 in a desired position in the casing

  heated pe 1, this envelope is allowed to cool, which in turn contracts on the element 6.

  the end walls 2 and 3 to the envelope The result set

  both, comprising the envelope 1 and the element 6, becomes

  ticu 1 rigidly rigid, which prevents the envelope from generating oscillations and, as mentioned previously,

  the envelope can also be very thin.

  above has been given by way of example and may vary depending on the coefficient of expansion of the sheet and the ceramic material respectively or as a function of

  the temperature of the ceramic when the element 6 is

  in the envelope 1 The method of assembly

  described in which the ceramic element is press-fitted to the

  in the heated envelope, which creates a combination of contraction and press assembly, can naturally be replaced by a simple contraction assembly in which the casing 1 is heated so that it expands to such an extent that the ceramic element 6 can be inserted without having to resort to a large force, or simply by assembling it to the press in which the element is pressed down ceramic in the envelope without heating

prior to the latter.

  Whatever the process used, an important criterion

  as long as we obtain an assembly such as the contrain-

  pressure zones are confined between the cylindrical outer surface of the ceramic body 6 and the inner wall of the casing 1, even at maximum operating temperatures, for example operating temperatures of

6000 C.

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  FIG. 2 represents an exhaust pipe comprising

  a plurality of ceramic elements, for example elements 8, 9 and 10, all of which have been assembled by an assembly

  by contraction in the metal casing 1.

  Each cylindrical element 6, 8, 9 and 10 is rectified to an outside diameter which, at the low temperatures by which is meant here the normal ambient temperature, i.e., about 20 ° C, is greater than the

  inner diameter of the casing 1 at the same temperature.

  In some cases, the cylindrical elements can be molded to sufficiently precise dimensions so that it

  It is not necessary to machine external surfaces separately.

res of said elements.

  The contraction and / or press assembly described above can be replaced by an assembly using an adhesive for obtaining a thin

  continuous adhesive coating to the entire cylindrical surface

  external drique of the ceramic element The element has a

  diameter adapted to the inside diameter of the envelope of

  However, at least some force is required to press the element into the envelope. Any suitable heat-resistant bonding agent can be used, such as an aluminum phosphate binder. . The present invention is not limited to the embodiments described since it is possible to make modifications or variants in the case of the present invention. Thus, it is not essential for the envelope to be cylindrical because that one can also use an envelope having another geometric shape Of course, the outer surface of the ceramic element must always have

  the same shape as the inner wall of the envelope.

Claims (5)

  Exhaust having good acoustic and mechanical properties, comprising a preferably cylindrical sheet-metal casing, t-end walls connected to the casing and at least one sound-absorbing porous ceramic element comprising at least one through channel for the exhaust gases, the ceramic element   said casing having a cylindrical outer surface   contiguous with the inner cylindrical wall of the casing and capable of absorbing compressive forces, characterized in that the casing (1) and the ceramic element (6)   together form a rigid sandwich structure in which   the cylindrical outer surface of the ceramic element   is firmly attached to the inside wall of the envelope.   2 exhaust pipe according to claim 1, characterized in that the envelope contracts and / or   is pressed on the ceramic element.   Exhaust pipe according to Claim 1, characterized in that the casing (1) is assembled to the ceramic element (6) by means of an adhesive forming a   continuous layer between the ceramic element and the wall the envelope.   4 Process for making a muffler   according to claim 1, characterized by the fact that   to provide at least one porous ceramic element (6) of a   preferably cylindrical outer surface with circular section   having a diameter which, at a first low temperature 1 exceeds the diameter of the cylindrical inner wall of a casing (1) sheet, to heat the casing (1) to   a high temperature as it expands and then introduces   re the element (6) in the envelope (1), the envelope (1) contracting fermementur the element (6) when-the temperature   of the envelope decreases and becomes again equal to the first first low temperature.   Process according to Claim 4, characterized in that the element (6) is assembled in the press the heated envelope (1).