EP0816666A2 - Exhaust gas recirculation device - Google Patents

Abstract

The metallic exhaust gas pipe is for feeding gas between an exhaust gas recirculation valve and the intake manifold, which in its area sealing in relation to the intake manifold wall is enclosed by a heat insulation layer. The heat insulation layer is formed by a hardenable, high temperature-proof binder, particles of a material containing pores together with a fibre or needle-shaped reinforcement component, all of which constitute a casing-shaped form part (24). This form part on the one hand is fitted in a sealed manner in the opening (18) of the intake manifold wall (16) and on the other hand locates with at least one axial section of its inner wall surface against the outer periphery of the exhaust gas pipe (12,12A).

Description

The invention relates to a device for controlled feedback of exhaust gases to the intake manifold of an internal combustion engine, with one in an opening of the intake manifold wall usable, metallic exhaust pipe for exhaust gas routing between an EGR valve (Exhaust Gas Recirculation Valve) and the intake manifold, which is in its opposite the intake manifold wall area to be sealed by a thermal barrier coating is included.

In modern gasoline and diesel engines, part of the exhaust gases the intake side of the engine fed to contained in the exhaust gas unburned hydrocarbons and possibly soot particles to burn. The one returned to the intake side of the engine Exhaust gas volume is determined using a so-called EGR valve controlled depending on the load.

Exhaust gas recirculation takes place at the current state of the art only during certain engine operating conditions, i.e. H. the EGR valve is often closed. However, to the from 1998 To comply with the more stringent exhaust gas standards, that must EGR valve is always in operation, i. H. it must be constantly Exhaust gas can be returned to the engine intake side, even if the amount of exhaust gas returned is regulated depending on the load.

Until a while ago, the intake manifold was a light metal casting; for cost reasons and to save weight are used as intake manifolds in modern engines however, injection molded plastic parts used.

A metallic exhaust pipe leads from the EGR valve to the intake manifold and protrudes into an opening of the intake manifold wall into it, this opening being larger than the outside diameter of the exhaust pipe, so that the latter the intake manifold wall not touched. Because the recirculated exhaust gases in the area temperatures of the exhaust pipe leading away from the EGR valve from 350 to 400 ° C, compared to which the plastic of Intake manifold is not stable, takes place at the state of the Technique to fix the exhaust pipe leading away from the EGR valve in the intake manifold and its seal against the Intake manifold as follows: is on the metallic exhaust pipe a metallic sleeve is welded to the tube at a distance surrounds, so that between the latter and the sleeve annular air gap, which gives the thermal insulation serves; so that the metallic sleeve is welded to the exhaust pipe it has on the EGR valve End a cone-shaped area with its small Diameter bears against the outer circumference of the exhaust pipe and is welded there while the intake manifold-side end the sleeve is open. The intake manifold now has one said opening in the short, surrounding the intake manifold wall Pipe socket-shaped approach in which the metallic sleeve is inserted together with the exhaust pipe and against its inner wall the outer circumference of the sleeve by means of an O-ring is sealed.

A similar exhaust gas recirculation device results from the EP-A-0 647 779; in this device is on the exhaust gas recirculation serving metallic exhaust pipe also a attached approximately conical metal sleeve, namely e.g. B. by soldering, the attachment point not the EGR valve, but facing the plastic intake manifold is. In addition, the seal is not made using a O-ring, but by means of a flexible plastic sleeve, which on the one hand on the intake manifold and on the other hand with her, facing away from the latter, the metallic one End region comprising sleeve is fixed to this sleeve, namely on the sleeve area with the largest diameter by means of a clamping ring.

This way of introducing the metallic exhaust pipe into A plastic intake manifold is sufficient if the exhaust gas recirculation only for a short time, but it is unsuitable, if exhaust gas is constantly returned to the intake side of the engine because then the one adjacent to the metallic sleeve Areas of the plastic intake manifold would get hot.

The invention was therefore based on the object of an exhaust gas recirculation device of the kind mentioned at the beginning, which is then combined with a plastic intake manifold when the EGR valve is in constant operation, and which enables long service life and low manufacturing costs.

The basic idea of the present invention is that at least that area of the metallic exhaust pipe which adjacent after installing the intake manifold wall is a shielding thermal insulation layer made of an easy to process high temperature resistant and good thermal insulation properties having to form, curable molding compound, which also as good as possible on the metallic exhaust pipe is liable, whereby, as will become clear from the following, such liability easily by other fastening and Sealing measures can be replaced.

A particularly suitable molding compound results from the in Form of the International published WO 95/26938 Patent application PCT / EP95 / 00561 by Elring Klinger GmbH, which is why it is proposed according to the present invention to design a device of the type mentioned in the introduction, that the thermal barrier coating is made from a curable, a high temperature resistant binder, particles of a porous Materials as well as a fibrous or needle-shaped reinforcement component containing molding compound produced, sleeve-shaped molded part is formed, which one hand gas-tight in the area of the opening of the intake manifold wall the latter definable and on the other hand with at least one axial portion of its inner wall surface against the outer circumference abuts the exhaust pipe, so as to the exhaust pipe with respect of the intake manifold and the molded part with respect to the exhaust pipe to position.

A molded part produced from such a molding compound is not only particularly temperature-resistant and heat-insulating, but it also has what is necessary for engine operation mechanical fatigue strength, so that even in engine operation constantly occurring vibrations do not cause cracks or permanent breaks to lead.

Basically, it would be enough if the inner wall surface of the molded part and the outer circumference of the exhaust pipe along one around the latter running line or in three on this Points lying against each other would line up to the Position the molded part on the metallic exhaust pipe or in the If the molded part is fixed on the intake manifold and / or the metallic exhaust pipe on the EGR valve with respect to the intake manifold to be determined. However, if the molding as one over their entire length against the outer circumference of the exhaust pipe adjacent sleeve is formed, the molded part in Form from the molding compound on the metallic exhaust pipe and harden, with the appropriate choice of the in the molding compound contained binder also a permanent connection can be achieved between molded part and exhaust pipe.

To in such an embodiment of the invention Device the gas pipe provided with the molded part gas-tight It is recommended to insert it into the intake manifold for sealing an annular, opposite the intake manifold wall with radial pressure against the outer circumference of the sleeve Seal made of elastic material, which then another thermal insulation element at the transition to the plastic wall of the intake manifold.

With the help of the molded part to be provided according to the invention but also the air gap thermal insulation realize the known device described at the outset, by designing the molded part so that it is only in its valve-side end area with its inner wall surface bears against the outer circumference of the exhaust pipe and otherwise runs at a radial distance from this outer circumference, so that between the inner wall surface of the molded part and the outer circumference of the exhaust pipe gives an annular space, which with air, exhaust gas or a mixture of these and an additional one Thermal insulation effect.

In the solution according to the invention, however, it can also be entirely based on this be dispensed with, the molding with the exhaust pipe firmly and connect permanently. For constructions without one Connection of the molded part is expediently carried out among other things, that the molded part with its valve-side end face in the axial direction against one with respect supports the solid end face of the exhaust pipe. On the on the other hand, you will design the molded part so that it (at an end face facing away from the EGR valve) has, which is in particular via a sealing ring supported on the intake manifold wall. In such a case the molded part can also be particularly easy in the direction fixed to the intake manifold transversely to the exhaust pipe axis, by pulling the molded part away from the EGR valve End area with a graduated outer diameter, so that it has an axial section of smaller diameter inserted into the opening of the intake manifold wall can be.

In particularly advantageous embodiments of the invention The molded part is one after a device or more of claims 2 to 16 in the form of International patent application published in WO 95/26938 PCT / EP95 / 00561.

Fig. 1

einen Längsschnitt durch eine erste Ausführungsform, wobei in Fig. 1 links auch noch das EGR-Ventil in Seitenansicht und rechts ein Teil der Ansaugkrümmerwandung im Schnitt dargestellt wurden;

Fig. 2

einen Ausschnitt aus Fig. 1, nämlich das der Wärmedämmung dienende Formteil wiederum im Längsschnitt, jedoch in größerem Maßstab als in Fig. 1, und

Fig. 3

eine der Fig. 1 entsprechende Darstellung einer zweiten Ausführungsform, jedoch ohne EGR-Ventil.

Further features, advantages and details of the invention result from the appended claims and / or from the attached drawing and the following description of two particularly advantageous embodiments of the exhaust gas recirculation device according to the invention; show in the drawing:

Fig. 1

a longitudinal section through a first embodiment, wherein in Fig. 1, the EGR valve was also shown in side view on the left and part of the intake manifold wall in section on the right;

Fig. 2

a section of Fig. 1, namely the molded part serving thermal insulation again in longitudinal section, but on a larger scale than in Fig. 1, and

Fig. 3

1 corresponding representation of a second embodiment, but without EGR valve.

1 shows an EGR valve 10 in a side view, from which a metallic exhaust pipe serving for exhaust gas recirculation 12 to an intake manifold designated as a whole by 14 leads. Only the area of the latter became a manifold wall 16 shown, in which the latter a Opening 18 for the entry of the exhaust pipe 12 into the interior of the intake manifold 14.

On the end region of the exhaust pipe facing the EGR valve 10 12 is a cuff 20 attached, which a 1 right end face 20a, which is vertical runs to the axis 12a of the exhaust pipe 12 and, as is the following will result, a stop and sealing surface forms. It is preferably the cuff 20 around a part made of a material which is at least approximately the same coefficient of thermal expansion how the metal of the exhaust pipe 12 has; in addition, the Sleeve 20 gas-tight on the outer peripheral surface of the exhaust pipe 12 sit.

However, the end face 20a could also have a circumferential one Shoulder, a collar of the metallic exhaust pipe 12 or an end face of the EGR valve 10 is formed.

Runs between the end face 20a and the manifold wall 16 a sleeve-shaped molded part 24, which consists of a molding compound was produced as in the publication WO 95/26938 has been described and claimed. The molding 24 is rotationally symmetrical to the axis 12a according to the invention 1 and has an approximately conical shape on the left axial section, to the right a whole roughly circular cylindrical section connects so that a gas-filled between the exhaust pipe 12 and the molded part 24 Annulus 26 results. According to the invention, the smallest inside diameter of the molded part 24 the same or only very slightly larger than the outside diameter of the exhaust pipe 12 (At least on that surrounded by the left end region of the molded part 24 Body), so that the molded part 24 when pushed on the exhaust pipe 12 is centered on the latter.

As can be seen in FIGS. 1 and 2, the molded part 24 a graded one at its right end according to the drawing figures Outside diameter and thus forms a perpendicular to End surface 30 extending along axis 12a and a shoulder 32 with a smaller outside diameter. The latter is now in accordance with the invention the same or slightly smaller than that Diameter of the opening 18 in the manifold wall 16 so that the molded part 24 with the projection 32 also with respect to the opening 18 of the intake manifold 14 can be centered.

In the end face 30 and one opposite the latter End face 34 of the molded part 24 is located in each case an annular groove 36 and 38, in each of which a not shown O-ring can be inserted so that the joint between the Intake manifold wall 16 and the molded part 24 or between the Seal cuff 20 and the molded part 24 when the invention Device is mounted on the intake manifold 14 - The molded part 24 is in the axial direction between the Cuff 20 and the intake manifold wall 16 clamped.

In Fig. 3 were the first embodiment corresponding Parts with the same reference numerals as in Figures 1 and 2 provided, but with the addition of an A.

In the second embodiment shown in FIG. 3 the plastic wall 16A of the intake manifold around its opening 18A a tubular socket Approach 50A through which the metallic exhaust pipe 12A a heat-insulating surrounding the exhaust pipe Form part 24A protrudes. In this second embodiment the molded part 24A is firmly connected to the exhaust pipe 12A, what z. B. can be achieved in that the molded part 24A is formed in situ on the exhaust pipe 12A. As in Fig. 3 indicated, it may recommend the exhaust pipe 12A on his To provide outer circumference with an annular groove 52A, so that the Molding compound enters this ring groove when the molded part 24A in is formed in situ on the exhaust pipe 12A. Furthermore forms an annular collar 54A of the exhaust pipe 12A an axial stop and Sealing surface for the molded part 24A.

So that the exhaust pipe 12A together with the molded part 24A in the opening 18A the intake manifold wall 16A centered and kept gas-tight is between the neck 50A of the manifold wall 16A and an annular seal on the outer periphery of the molded part 24A 60A made of an elastic and temperature-resistant material arranged, which is annular and an approximately L-shaped Cross section has and is dimensioned so that it with radial Pressing is held on the one hand on the molded part 24A and on the other hand abuts against the inner wall surface of the projection 50A.

As can be seen in FIGS. 1 and 3, the exhaust pipe is 12 or 12A in the axial direction Preferably so dimensioned that it protrudes a bit into the interior of the intake manifold, d. H. protrudes over the manifold wall 16 or 16A.

Claims (10)

Device for the controlled return of exhaust gases to the intake manifold of an internal combustion engine, with an insertable into an opening of the plastic intake manifold wall, a metallic exhaust pipe for exhaust gas routing between an EGR valve and the intake manifold, which is enclosed in its area to be sealed against the intake manifold wall by a thermal barrier coating , characterized in that the thermal barrier coating is formed by a sleeve-shaped molded part (24; 24A) made of a curable molding compound containing a high-temperature-resistant binder, particles of a porous material and a fibrous or needle-shaped reinforcing component, which is formed on the one hand in the opening (18; 18A) of the intake manifold wall (16; 16A) and can be fixed in a sealed manner with respect to the latter and, on the other hand, rests with at least one axial section of its inner wall surface against the outer circumference of the exhaust pipe (12; 12A). Device according to claim 1, characterized in that the molded part (24A) as one along its entire length the outer circumference of the exhaust pipe (12A) is trained. Device according to claim 2, characterized in that for sealing against the intake manifold wall (16A) an annular, with radial pressure against the outer circumference the sleeve (24A) provided seal (60A) provided is. Device according to claim 1, characterized in that the molded part (24) only in its valve side End area with its inner wall surface against the outer circumference of the exhaust pipe (12) and with the rest radial distance from this outer circumference. Device according to one or more of the preceding Claims, characterized in that the molded part (24; 24A) with its valve-side end face in axial Direction against a with respect to the exhaust pipe (12; 12A) supports a fixed end face (20a; 54A). Device according to claim 5, characterized by a sealing ring arranged between the two end faces. Device according to one or more of the preceding Claims, characterized in that the molded part (24) at its end area facing away from the EGR valve (10) has an end face (30) which has a sealing ring for Sealing against the outer surface of the intake manifold wall (16) is assigned. Device according to claim 6 or 7, characterized in that that the sealing ring in an annular groove (36, 38) of the Molding (24) is inserted. Device according to one or more of claims 4 to 8, characterized in that the molded part (24) on its a stepped end area facing away from the EGR valve (10) Has outside diameter and with an axial Section (32) of smaller diameter in the opening (18) of the intake manifold wall (16) can be used appropriately is. Device according to one or more of the preceding Claims, characterized in that the molded part (24; 24A) one according to one or more of the claims 2 to 16 of International Application PCT / EP95 / 00561 is.

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