EP0484197B1 - Cylinder head of an internal combustion engine with cast metallic insert - Google Patents

Description

The subject of the invention is an internal combustion engine cylinder head provided with a metal insert arranged for casting, in the zones subjected to strong temperature gradients, in particular between two valve seats.

To avoid the formation of cracks of thermal origin currently used in the cylinder heads of diesel engines inserts in pressed sheet metal embedded in the sand before casting which, after machining the surfaces of the valve seats, constitute two separate arcs joining these litters in the most vulnerable areas.

These inserts are generally of revolution with a cylindrical part, one end of which is arranged in the cylinder head opposite the hot surface has a folded collar intended to avoid the concentration of stresses. This type of insert has the disadvantage of being sometimes driven in rotation by the tool machining the seats of the valve seats, hence a large scrap of cylinder heads considerably increasing the manufacturing costs.

Document DE-A-1508934 shows a tubular insert of constant elliptical cross section arranged for pouring into the wall of a tube. This insert is used to modify the thermal expansion in a part of the tube.

The invention aims to eliminate this drawback while ensuring a good distribution of the stresses generated in operation.

To this end, a cylinder head according to the invention is provided with an insert of the type comprising a folded-down circular collar and is characterized in that the body of the insert, arranged in the hot zone of the cylinder head, is a cylinder of elliptical section. gradually connecting to the circular flange.

Preferably, the functional area of the elliptical body of the insert is located in the vicinity of the minor axis of the ellipse, the insert being arranged for casting so that the major axis of the ellipse is aligned with the right joining the centers of the seats of the valve seats between which the insert must establish a double junction.

According to another characteristic of the invention, the connection radius of the elliptical body and the circular flange is constant over the entire periphery of the latter.

According to another characteristic, the angle of folding of the fallen edge constituting the flange is greater than 90 °. Finally the angles of the edge of the collar will be cut down.

• la figure 1 représente une vue de l'insert coté collerette en projection parallèlement à son axe de symétrie ;
• la figure 2 montre une vue en coupe de l'insert selon le plan II - II passant par le petit axe de l'ellipse;
• la figure 3 est un détail agrandi de la section de la collerette dans la zone fonctionnelle;
• la figure 4 est une vue en coupe de l'insert selon le plan IV-IV passant par le grand axe de l'ellipse;
• la figure 5 montre de façon schématique la disposition de l'insert avant la coulée;
• la figure 6 montre la zone de la culasse où est disposée l'insert après l'usinage des portées des sièges de soupape ;
• la figure 7 est une coupe selon le plan VII-VII de la figure 6 montant l'insert noyé dans la culasse.

Other characteristics will appear on reading the following description of a nonlimiting exemplary embodiment illustrated by the appended drawing in which:

• FIG. 1 represents a view of the insert on the flange side in projection parallel to its axis of symmetry;
• Figure 2 shows a sectional view of the insert according to the plane II - II passing through the minor axis of the ellipse;
• Figure 3 is an enlarged detail of the section of the flange in the functional area;
• Figure 4 is a sectional view of the insert according to the plane IV-IV passing through the major axis of the ellipse;
• Figure 5 shows schematically the arrangement of the insert before casting;
• FIG. 6 shows the zone of the cylinder head where the insert is disposed after the machining of the seats of the valve seats;
• Figure 7 is a section along the plane VII-VII of Figure 6 mounting the insert embedded in the cylinder head.

As can be seen in Figures 1 to 4, the insert 1 made of stamped sheet metal has an axis of symmetry defined by two planes of symmetry II-II and in the plane IV-IV.
The body 2 of the insert is a cylinder of elliptical section. The minor axis of the base ellipse is located in the II-II plane and the major axis in the IV-IV plane.

The body 2 is connected to a circular collar 3 produced by a beaten collar or dropped edge. The radius R of connection of the dropped edge and the elliptical body is constant over the entire periphery.

The functional area is distributed symmetrically on either side of the minor axis of the ellipse.
In zone Z the folding angle α of the fallen edge is greater than 90 ° and the sharp angles are cut down. These precautions are important to avoid a concentration of stresses. Before casting the cylinder head (Figure 5) the insert 1 is partially embedded in the sand cores 4.5 intended to provide the intake and exhaust ducts, the major axis of the ellipse of the body 2 being positioned on the axis joining the centers of these conduits.

During the machining of the seats of the valve seats 6,7 (fig. 6) the parts of the insert outside the functional zone Z are removed by the tool and, thanks to the elliptical shape of the insert associated with the edge fallen circular, it avoids the rotational drive thereof.

In operation, the large radius of the fallen edge forming the flange 3 associated with a stamped angle greater than 90 ° makes it possible to avoid peak effects which can generate stresses detrimental to the holding of the cylinder head.

The fallen edge 3 is embedded in the metal of the cylinder head 8 opposite the face 9 subjected to the hot gases from the combustion chamber.

Claims (5)

1. A cylinder head for an internal combustion engine provided with a metal insert disposed during casting, comprising a flanged circular collar which, after machining of the mating surfaces of the valve seats, constitutes two distinct arcs joining these mating surfaces, characterised in that the body 2 of the insert 1, disposed in the hot zone of the cylinder head, is a cylinder with an elliptical section connecting progressively to the circular collar 3.
2. A cylinder head according to Claim 1, characterised in that the functional zone Z of the elliptical body of the insert is located in the vicinity of the minor axis of the ellipse, the insert being disposed during casting such that the major axis of the ellipse is aligned with the straight line joining the centres of the mating surfaces of the valve seats 6, 7 between which the insert has to establish a double junction.
3. A cylinder head according to Claims 1 or 2, characterised in that the radius R of connection between the elliptical body 2 and the circular collar 3 is constant over the whole periphery of the latter.
4. A cylinder head according to any one of the preceding claims, characterised in that the bending angle of the turned-up edge constituting the collar is greater than 90°.
5. A cylinder head according to Claim 4, characterised in that the angles of the edge of the collar are rounded.

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