FR2891206A1 - EXHAUST DEVICE FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

An exhaust system for an internal combustion engine comprising an exhaust manifold (1) secured by a flange (2) to the engine cylinder head, primary exhaust tubes (3) connecting the manifold (1) to a first system purification device (4), and a leakage tube (6) towards a second purification system, characterized in that the first purification system (4) has fixing means ( 7) on the motor supporting its own mass, as well as that of the primary tubes (3).

Description

EXHAUST DEVICE FOR INTERNAL COMBUSTION ENGINE

  The present invention relates to an exhaust system for an internal combustion engine comprising an exhaust manifold fixed by a flange to the cylinder head of the engine, primary exhaust tubes connecting the manifold to a first gas cleaning system. exhaust, and a leakage tube to a second purification system.

  Such a device is intended to be mounted at the outlet of the exhaust pipes of each cylinder, and lead into a downstream part of the exhaust line, including in particular the second purification system mentioned.

  The catalytic function of an exhaust line, intended to ensure the purification of the exhaust gases, in particular HC hydrocarbons, and NOx nitrogen oxides, is often distributed between two subsets, including a pre-catalytic converter relocated upstream. of the exhaust line, and a main catalyst. The precatalyst, which is placed near the exhaust manifold, is intended primarily to retain hydrocarbons and nitrogen oxides. Generally, it is more loaded with precious metals than the main catalyst, or downstream catalyst, intended primarily to retain nitrogen oxides.

  To meet the new standards of pollution control, the trend is to lighten the exhaust manifolds, so as to accelerate their rise in temperature when starting the engine, and reduce the catalyst boot time. The collectors can thus be made of very thin stainless steel sheet, about two millimeters thick. Another measure to reduce the priming time of the precatalyst, is to place the latter as close as possible to the engine, which amounts to reducing the length of the primary tubes, by which it is connected to the exhaust manifold. This arrangement, however, goes against the acoustic performance of the exhaust line, which require relatively long primary tube lengths, and equal to each other.

  Furthermore, in known exhaust devices, the collector itself supports the exhaust line through the primary tubes. For this reason, the primary tubes are relatively thick.

  Thus, when the precatalyst is connected to the collector by relatively short and thick primary tubes, the performance of the exhaust system, in terms of acoustic treatment pollution abatement of the exhaust gases remain poor.

  The present invention aims to ensure the desired acoustic agreement in an exhaust system, to reduce engine noise, while limiting the pollutant emissions of the engine.

  For this purpose, it proposes that the first purification system has fixing means on the engine, supporting its own mass, as well as that of the primary tubes.

  Preferably, the attachment means include at least one rigid support leg on the flange of the exhaust manifold and on the cylinder head of the engine.

  Other characteristics and advantages of the invention will become clear from reading the following description of a non-limiting embodiment thereof, with reference to the accompanying drawings, in which FIG. 1 is an overall view. in perspective, of this embodiment.

  This device has an exhaust manifold 1 fixed by a flange 2 on the cylinder head (not shown) of an internal combustion engine. Primary exhaust pipes 3 connect the manifold 1 to a first exhaust gas cleaning system 4, such as a precatalyst. The latter comprises a leakage tube 6, in the direction of a second purification system, not shown, such as an oxidation catalyst, or trap nitrogen oxides (Noxtrap).

  In the diagram, we see two crutches 7, ensuring the attachment of the precatalyst 4 on the engine. The crutches support the mass of the precatalyst 4, including the leakage tube 6. In accordance with the invention, the precatalyst can thus support, thanks to its crutches, the entire exhaust line, from the primary tubes, to the second purification system. In all cases, the first purification system 4 has fastening means on the engine supporting its own mass, as well as that of the primary tubes 3. These means include at least one rigid support leg 7, on the flange of the collector or, on the cylinder head of the engine, exhaust, preferably two crutches, as in the embodiment described.

  Thanks to these provisions, the primary tubes can be made of thin sheet metal, because it is not they who carry the exhaust line, but the precatalyst, their function being essentially limited to guiding the exhaust gas between the engine and the input of the precatalyst. They may in particular be made of stainless sheet less than one millimeter thick.

  The advantages of the invention are numerous. Among these, it can be noted: the possibility of increasing the length of the primary tubes, so as to optimize the filling of the precatalyst, and to optimize the torque delivered by the engine, by obtaining the acoustic agreement of the four primary tubes, - a very fast priming of the precatalyst, thanks to the thinness of the primary tubes, which reduces their thermal inertia and accelerates their rise in temperature, - a decrease in the risk of breakage in the primary tubes, the fact that they do not support the weight of the exhaust line.

2891206 -5-

Claims (7)

  An exhaust system for an internal combustion engine comprising an exhaust manifold (1) secured by a flange (2) to the engine cylinder head, primary exhaust tubes (3) connecting the manifold (1) to a first exhaust gas purification system (4), and a leakage tube (6) towards a second purification system, characterized in that the first purification system (4) has means for fixing (7) on the motor supporting its own mass, as well as that of the primary tubes (3).   2. Exhaust device according to claim 1, characterized in that the fastening means include at least one rigid support leg (7) on the engine.   3. Exhaust device according to claim 1 or 2, characterized in that the fastening means include a rigid mounting bracket (7) on the flange (2) of the exhaust manifold (1).   4. Exhaust device according to claim 1, 2 or 3, characterized in that the fastening means include a rigid mounting bracket (7) on the cylinder head of the engine.   5. Exhaust device according to one of the preceding claims, characterized in that the first purification system (4) supports the entire exhaust line to the second purification system.   6. Exhaust device according to one of the preceding claims, characterized in that the primary tubes (3) are made of thin sheet metal.   7. Exhaust device according to claim 6, characterized in that the primary tubes (3) are made of stainless sheet less than one millimeter thick.