EP0974001B1 - Internal combustion engine exhaust device and method for making same - Google Patents

Description

The subject of the present invention is a exhaust system for combustion engine internal and its production process. The current invention relates more particularly to a conduit exhaust having a suitable housing for the mounting of a measurement probe and the method of realization of such housing.

Internal combustion engines fitted motor vehicles are today equipped an electronic control system which adjusts to from preprogrammed strategies and following engine operating conditions, the quantity fuel injected, the amount of gas recirculated exhaust, etc.

Among the information required by electronic control systems to determine operating conditions and adapt in consequently the quantity of fuel injected (the degree of opening of the EGR valve, etc.), are shown those relating to the composition and / or the exhaust temperature and more particularly the residual oxygen level. These exhaust gas information is delivered by appropriate measurement probes which are arranged in the exhaust gas path.

Conventionally, the measurement probes coming equip the exhaust line are screwed in threaded housings crossing the wall of exhaust pipes, so as to bring the analysis cells in contact with the gas flow exhaust.

Given the thinness of the walls of the exhaust pipes currently used (between 1.5 and 2 mm on average) compared the diameters of the holes to be made (more than 20 mm), the tapped holes are conventionally formed by appropriate rings which are reported by welding in openings made through the exhaust pipes (SEFG welding or welding by resistance).

It appeared to the Applicant that the use of welded rings presents disadvantages and in particular a significant rate of mounting and sealing faults (see document FR-A-2 586 753). Indeed, when from welding, heating tends to deform the inner threads of the rings, which sometimes either to prevent the screwing of the probe or, on the contrary, to prevent the unscrewing of this last. Furthermore, these deformations affect the tightness of the assembly and therefore cause leaks of burnt gases or even aspirations air depending on the engine operating point, which is particularly damaging to the quality of the measurements, especially when the probe is an oxygen sensor.

The subject of the present invention is therefore a exhaust pipe with a tapped hole to house a probe used to analyze the gas composition, this hole being made directly through the very wall of the duct without welded attached threaded ring.

The exhaust system for internal combustion according to the invention, comprises a conduit element inside which flow exhaust gases, this duct element comprising a housing allowing the mounting of a measurement sensor such as an oxygen sensor.

According to the invention, the device exhaust is characterized in that the housing intended for mounting the probe is formed by a hole extended by a socket made directly through the wall of the conduit element.

According to another characteristic of the exhaust device object of the invention, the conduit element where the extended hole is formed through a socket, has a thick wall substantially uniform between 1 and 3 mm.

According to another characteristic of the exhaust device which is the subject of the invention, the duct element where the hole extended by a socket is formed, is made of stainless metal alloy.
The present invention also relates to a method of producing such a housing. According to the invention the housing produced through the same wall of the duct element is obtained from a first drilling operation consisting of drilling through the wall with a tool, a speed and a penetration force adapted to cause the fusion and the discharge of the material around the tool as the latter advances until a bush of required height and diameter is obtained.

According to another characteristic of the process object of the invention, the tool used for the drilling operation is constituted by an ogival mandrel.

According to another characteristic of the process of realization object of the invention, the first flow drilling operation is then followed by a second tapping operation by deformation.

la figure 1 est une vue en coupe axiale partielle d'un conduit d'échappement selon l'invention équipé d'une sonde de mesure ;

les figures 2 et 3 sont des vues de détail du conduit selon la figure 1, précisant le procédé de réalisation du logement de la sonde.

The aims, aspects and advantages of the present invention will be better understood from the description given below of an embodiment of the invention, given by way of non-limiting example, with reference to the accompanying drawings, wherein :

Figure 1 is a partial axial sectional view of an exhaust duct according to the invention equipped with a measurement probe;

Figures 2 and 3 are detail views of the conduit according to Figure 1, detailing the method of producing the housing of the probe.

According to the figures, only the constituent parts necessary for the understanding of the invention have been shown. In addition, to simplify the reading of the drawings, the same elements have the same references from one figure to another.

Referring to Figure 1, we see a exhaust pipe element referenced 1 equipping an exhaust line with a internal combustion mounted for example on a motor vehicle. This conduit which is formed by a simple stainless steel alloy tube of thin (conventional steel or coated steel aluminum), between 1 and 3 mm, and which is intended, for example, to extend into the collector exhaust and catalytic converter not shown, has a housing 2 for a measurement probe 3 such as a lambda oxygen sensor.

Housing 2 is made directly at through the very wall of the tube, thanks to the process described in accordance with Figures 2 and 3.

According to Figure 2, the first operation consists in operating by drilling a hole 21 extended by a socket 22. This hole 21 and this socket 22 are obtained by the perforation of the wall of the tube by a mandrel or ogival punch 4, for example in tungsten carbide, turning at high speed, at over 500 rpm and preferably between 3000 and 5000 rpm, and pressed in the tube with a certain force of penetration.

The rapidly rotating tip contact locally causes a sharp rise in temperature which brings the metal to the plastic state. The push exerted by the punch by the system in advance makes it gradually penetrate the hole thus outlined by pushing the material around from him. Metal flowing in the direction of advance forms a collar and in reverse a bead. A collar 41 located at the part upper punch can fold metal full of the outside of the tube and give it a flat surface facilitating support and sealing of probe 3.

In a few seconds you get a calibrated hole 21 extended by a socket 22. In this socket 22, it is then possible to form a thread allowing the screwing of the probe 3. According to FIG. 3, this second operation setting up a net 23 is carried out by rolled thread.

this threadless tapping operation consists in obtaining the net by deformation of the sleeve material 22. To do this, a tool 5 having a screw-like active surface is used as a tap. The tap operates by rolling by deforming the material of the sleeve, the profile of the net 23 is then printed by moving the material from the bottom of the net to the crest. Speed of rotation and the penetration force of the tap are adapted to produce the desired resistance nets. You can choose a rotation speed tap preferably between 700 and 1500 rpm, this is not however limiting of the present invention.

So in two relatively small operations simple and quick to implement it is possible to make a threaded housing 2 directly in the wall of the duct exhaust 1, which is significantly more simple than the prior art which consists in effect, to pierce or cut the duct exhaust by stamping, deburring this orifice, to make a probe holder machined in stainless steel, to weld this support on the conduit, and finally to wash away metal particles generated by the previous operations.

So regardless of the advantages over the quality of the thread obtained thanks to the invention by compared to the prior art of the ring or the insert and welded insert, the present invention has the added benefit of being more economical and simpler to implement.

Of course, the invention is by no means limited to the embodiment described and illustrated which was only given as an example. At on the contrary, the invention includes all technical equivalents of the means described as well as their combinations if these are performed following his spirit.

Thus the present invention is not limited to only making a tapped hole for housing an oxygen sensor but can apply to the realization of all holes tapped on the exhaust line of a internal combustion engine required for setting in place of the various sensors or probes required for engine control and / or diagnostic of the or means for treating the gases burned by catalytic conversion fitted to the line exhaust. Likewise the present invention also applies to exhaust pipes comprising several concentric walls. In this case, the tapped hole necessary for the mounting of the sensor by operating the flow drilling at through the different walls.

Claims (3)

1. An exhaust arrangement for an internal combustion engine comprising a pipe element (1) in the interior of which the exhaust gases flow, said pipe element (1) comprising a housing (2) permitting the fitment of a measuring sensor such as an oxygen probe, characterised in that said housing (2) is formed by a hole prolonged by a sleeve (22) which is produced directly from the material constituting the wall of said pipe element (1), the housing (2) comprising a screwthread obtained by deformation and a bead on the edge of the hole, the bead being produced directly from the material constituting the wall.
2. An exhaust arrangement according to claim 1 characterised in that said pipe element (1) has a wall of a substantially uniform thickness of between 1 and 3 mm.
3. An exhaust arrangement according to either one of claims 1 and 2 characterised in that said pipe element (1) has a wall made of a non-oxidisable metal alloy.

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