EP0958076B1 - Method and core for moulding an internal combustion engine cylinder head - Google Patents

Description

The present invention relates to a process for the production of foundry parts and aims more particularly a process for casting a cylinder head for internal combustion engine as well that a nucleus for the implementation of this process, to improve accuracy dimensions of all the bedrooms combustion, intake ducts, ducts exhaust.

Conventionally the production of a cylinder head of internal combustion engine is performed in a mold comprising at least one core for each combustion chamber, duct sub-assemblies intake and exhaust pipes. The core defining the shapes of the combustion chambers often being produced by an integrated footprint the sole (metal bottom) of the mold.

Such devices have the disadvantage of being sensitive to deviations from positioning of the nuclei with respect to others, these positioning differences coming from either inaccuracies when installing cores in the mold, or movements of the nuclei during of the metal casting caused by the difference density between the cores and the cast metal.

These differences in the positioning of the nuclei making the intake and exhaust ducts generally causes a shift between the position valve seat connected to the combustion chamber and the end of the intake duct or exhaust which disrupts air flow and deteriorates engine performance.

It is known to remedy this disadvantage of performing calibration machining of the connection between the ducts and the seats of valves. This machining, carried out for example by milling, allows alignment of valve seat with the conduit but most often leads to creation of a spoiler, corresponding to a discontinuity in the slope of the conduit at the intersection of the latter with the trajectory of the strawberry, which disrupts the flow of the air.

This disturbance caused by the spoiler is less important than the one previously created by the offset of the end of the duct with the valve seat but is nevertheless penalizing in the case of weak pipes and valves diameter.

The object of the present invention is therefore to propose a method for casting a cylinder head as well that a nucleus allowing to directly obtain a good location of the valve seats by relative to intake and exhaust ducts so as to eliminate the calibration machining and get better gas flow. The realization of this process and its associated core remaining simple and economical to make.

The method according to the invention relates to molding of a combustion engine cylinder head internal, of the type by which an alloy is poured metal in a mold containing non-nucleus fuses corresponding in particular to the parts hollowed out from the cylinder head such as the chambers of combustion, intake ducts, ducts exhaust and water or oil chambers.

According to the invention the process is characterized in that it comprises a step of placing in the mold of a monobloc core integrating the shapes defining both the chambers of combustion and the intake ducts, and supporting rings making up the valve seats.

According to another characteristic of the process of production by molding of a cylinder head according to the invention, the monobloc core also incorporates the shapes defining the exhaust pipes.

According to another characteristic of the process of production by molding of a cylinder head according to the invention, the cylinder head valve seats are made by added and inserted rings during casting, said rings being supported by the monobloc core.

According to another characteristic of the process of production by molding of a cylinder head according to the invention, the monobloc core also incorporates the adapted forms defining the gross repository used for machining starts.

The invention also relates to a core intended for be used for the implementation of the process defined above and characterized in that it is monobloc type and integrates the forms defining both the combustion chambers and the ducts of admission, and in that it supports rings serving valve seats.

Advantageously, the monobloc core integrates also the shapes defining the conduits exhaust and supports the rings serving as valve seat.

According to another characteristic of the invention, the monobloc core also incorporates the adapted forms defining the gross repository used for machining starts.

According to yet another characteristic of the invention, said one-piece core is made in a core box and is made of sand compressed and agglomerated with a binder such as resin.

• la figure 1 représente une vue schématique, en perspective, d'un mode de réalisation particulier d'un noyau monobloc servant au moulage d'une culasse de moteur à combustion interne selon l'invention ;
• la figure 2 est une vue de dessus du noyau monobloc représenté à la figure 1 ;
• la figure 3 est une vue de côté du noyau monobloc représenté sur la figure 1 ;
• la figure 4 est une vue de dessus d'un dispositif de moulage utilisé pour la mise en oeuvre du procédé ;
• la figure 5 représente une section transversale suivant la ligne V-V du dispositif de moulage représenté à la figure 4 ;
• la figure 6 représente une vue partielle en coupe longitudinale du dispositif de moulage suivant la ligne VI-VI de la figure 4.

The objects, aspects and advantages of the present invention will be better understood from the description given below of various embodiments of the invention, presented by way of non-limiting examples, with reference to the accompanying drawings, in which :

• FIG. 1 represents a schematic perspective view of a particular embodiment of a monobloc core used for molding an cylinder head of an internal combustion engine according to the invention;
• Figure 2 is a top view of the one-piece core shown in Figure 1;
• Figure 3 is a side view of the one-piece core shown in Figure 1;
• Figure 4 is a top view of a molding device used for the implementation of the method;
• Figure 5 shows a cross section along line VV of the molding device shown in Figure 4;
• FIG. 6 represents a partial view in longitudinal section of the molding device along line VI-VI of FIG. 4.

To make the drawings easier to read, the same parts have the same references of a figure to another. Furthermore, only the elements necessary for understanding the invention have been figured.

Figure 1 shows an embodiment particular of a core 1 for the realization by molding of a combustion engine cylinder head internal according to the invention.

Referring to Figures 1 to 3, we see a core 1 of one-piece type used for molding an internal combustion engine cylinder head type with four in-line cylinders and four valves per cylinder.

The monobloc core 1 of FIGS. 1 to 3 has four identical parts 4 regularly spaced, arranged in the same alignment, and defining the four combustion chambers of the cylinder head to be molded. Each combustion chamber 4 of the monobloc core 1 is connected in its part greater than two arms 2 and an arm 3 defining the two intake ducts and the two Siamese cylinder head exhaust pipes to mold.

As we can see more precisely on FIG. 3, rings 7, not shown on the Figures 1 and 2, are arranged around the conduits intake 2 and exhaust 3, against combustion chambers 4 of the monobloc core 1. These rings 7 are made of material suitable for the valve seat and allow inserting valve seats when pouring of the cylinder head molding.

In accordance with Figures 1 to 3, the core monoblock 1 comprises a part 5 arranged under the combustion chambers 4. This part 5 extends mainly towards the rooms of combustion 4 neighbors to form a base 5 supporting the combustion chambers 4 to one adapted distance.

The base 5 also extends transversely to form arms 6 whose ends 8 define the raw repository used for machining starts. The thickness of the base 5 is chosen according to the rigidity and holding the desired monobloc core 1.

The core 1 as shown in the Figures 1 to 3 can be carried out in a known manner in a core box with compressed sand and agglomerated with a binder.

Figures 4 to 6 show a mode particular realization of a device molding using the monobloc core 1 for setting in the process of molding a cylinder head according to the invention.

Figure 4 presents more particularly a mold seen from above when only the core monobloc 1 is put in place. This mold has four movable lateral mold elements 11, 12, 16 and 17 can be moved apart to facilitate the demolding of the cylinder head and a mold element lower or sole 10 having a surface plane 15 producing the underside of the cylinder head to mold.

Figure 5 shows a section of the mold of figure 4 when the different nuclei classics needed to mold the chamber water from the cylinder head are in place. The mold comprises a movable upper mold element 13, not shown in Figure 4, closing the mold to define the thickness of the walls of the cylinder head to mold and the volume of the chamber oil. Filling holes, not shown in the figure, are arranged through the upper mold element to allow the casting operation.

The movable side mold element 11 has a cavity for maintaining position of the free end of the arms 2 realizing the intake ducts when the mold is closed. Likewise, the side mold element 12 mobile has a cavity allowing the holding the free end of the arms in position 3 making the exhaust pipes.

As can be seen in Figures 5 and 6, the sole 10 has a cavity 14 intended to receive the monobloc core 1 before closing the mold and the casting operation. The shape and volume of the cavity 14 are adapted and adjusted to base 5 and arms 6 of the monobloc core 1 such that shown in Figures 1 to 3, so that the base 5 and the arms 6 are integrally disposed in the cavity 14 of the sole 10 when the one-piece core 1 is arranged in the mold.

Thus, only the elements of the monobloc core 1 defining particular cavities of the molding cylinder head such as intake ducts 2, the exhaust pipes 3, the combustion 4 and the ends 8 of the arms 6 are arranged above the flat surface 15 of the sole 10 defining the underside of the cylinder head.

• ouverture du moule par l'écartement des éléments de moule latéraux 11, 12, 16 et 17 et de l'élément de moule supérieur 13;
• mise en place du noyau monobloc 1 sur la semelle 10;
• mise en place des noyaux définissant la chambre d'eau et les passages d'huile;
• fermeture des éléments de moule latéraux 11, 12, 16 et 17 permettant l'immobilisation des noyaux présents dans le moule;
• fermeture de l'élément de moule supérieur 13 et réalisation d'une opération de coulée classique;
• démoulage après un certain temps variable suivant le mode refroidissement choisi.

In accordance with the foregoing description and in FIGS. 4 to 6, the process for producing the cylinder head by molding comprises the following operations:

• opening of the mold by the spacing of the lateral mold elements 11, 12, 16 and 17 and of the upper mold element 13;
• placing the one-piece core 1 on the sole 10;
• installation of cores defining the water chamber and the oil passages;
• closing the lateral mold elements 11, 12, 16 and 17 allowing the immobilization of the cores present in the mold;
• closing the upper mold member 13 and performing a conventional casting operation;
• demoulding after a certain variable time depending on the cooling mode chosen.

The molding process thus carried out allows obtain a cylinder head with excellent location of the rings 7 forming the seats of valve in relation to the intake ducts 2 and exhaust 3. Indeed, the latter being molded directly by the monobloc core 1 and the rings 7, inserted during casting, being supported by this same monobloc core 1, the precision dimensional of the whole bedroom combustion, valve seats, ducts intake, exhaust pipes is independent of the location of the different nuclei present in the mold and depends only on the quality of construction of the monobloc core 1.

This molding process using the core monobloc 1 therefore eliminates machining usually required with the conventional cylinder head molding processes using several cores for the conduits and the chamber combustion.

The use of the monobloc core 1 allows also to make a connection between the conduits and the combustion chamber including aerodynamics is optimized so as to offer very little resistance to air flow.

Minimizing pressure losses obtained by this process is particularly important for improving the performance of engine. Thus, the reduction in pressure losses at the connection between the intake duct and the combustion chamber helps to improve noticeably filling the engine and reducing the pollution resulting from combustion.

Furthermore, the monobloc core 1 defines also the raw repository used for machining starts which eliminates the location uncertainties related to use of different nuclei and get better location of all machining.

Of course, the invention is by no means limited to the embodiment described and illustrated which was only given as an example.

So the process of using a kernel monobloc integrating the forms defining both combustion chambers, ducts intake and exhaust pipes can be used in other types of molds such as die casting or squeeze-casting molds or sand mussels (green or self-hardening).

Claims (8)

1. Method for forming a cylinder head for an internal combustion engine by moulding, of the type wherein a metallic alloy is cast into a mould (11, 12, 13, 16, 17) enclosing refractory mould cores corresponding in particular to the hollow parts of the cylinder head, such as the combustion chambers (4), the intake manifolds (2), the exhaust manifolds (3) and the water or oil chambers, characterised in that it comprises a step of placing in the mould a one-piece mould core integrating the shapes defining both the combustion chambers (4) and the intake manifolds, and supporting rings (7) forming the valve seats.
2. Method for forming a cylinder head for an internal combustion engine by moulding according to claim 1, characterised in that said one-piece mould core (1) also integrates the shapes defining the exhaust manifolds (3).
3. Method for forming a cylinder head for an internal combustion engine by moulding according to one of claims 1 to 2, characterised in that the rings (7) are inserted when casting takes place.
4. Method for forming a cylinder head for an internal combustion engine by moulding according to one of claims 1 to 3, characterised in that said one-piece mould core (1) also integrates the suitable shapes defining the coarse reference frame (8) used for initiating machining.
5. Mould core (1) integrating the shapes defining particular cavities of a cylinder head for an internal combustion engine for the moulding thereof, characterised in that said mould core (1) is in one piece, in that it integrates the shapes defining both the combustion chambers (4) and the intake manifolds (2) and in that it supports rings (7) acting as valve seats.
6. Mould core according to claim 5, characterised in that said one-piece mould core (1) also integrates the shapes defining the exhaust manifolds (3).
7. Mould core according to claim 5 or 6, characterised in that said one-piece mould core (1) also integrates the suitable shapes (8) defining the coarse reference frame used for initiating machining.
8. Mould core according to claim 6 or 7, characterised in that said one-piece mould core (1) is formed in a core moulding box and is constituted of sand compressed and aggregated with a binding agent such as resin.

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