EP3017164B1 - Metal part produced by moulding comprising inner recesses, method for producing same and internal combustion engine comprising such a part - Google Patents

Description

The invention relates to metal parts made by molding comprising at least two internal recesses.

Metal parts of this type comprising internal recesses comprise, for example, cylinder heads of an internal combustion engine, in particular for a motor vehicle. An internal combustion engine conventionally comprises a cylinder head mounted on a crankcase, these two parts being cooled and lubricated by coolant and oil circulations, respectively. In general, the coolant circulates in the cylinder block, feeds the cylinder head and leaves the engine. For this purpose, the cylinder head and the cylinder block each comprise an internal chamber (or recess), usually called a water core, for the circulation of the cooling liquid, these water nuclei communicating with each other. In some engines, to improve the performance of the engine, the coolant flows separately in the cylinder head and the cylinder block: the water cores of the cylinder head and the cylinder block must not communicate with each other.

To produce metal parts comprising internal recesses, a sand mold is made comprising a lower part, an upper part and one or more cores, each core being a positive of an internal recess. This sand mold can be made by cold box molding, by hot box molding or by the so-called "croning" process. The cores obtained by the Croning process are more rigid and therefore more difficult to destroy, which increases the cost of producing a part. In this way, cold or hot box molding processes are generally preferred to reduce costs. However, these latter processes produce nuclei with limited stiffness. When producing a part comprising a plurality of internal recesses, it may then happen that the lower core rises during the casting of the metal. In order to avoid this rise, surfaces of contact between the two cores are allowed, so that the upper water core prevents the water core lower to go up. These contact surfaces between the cores create internal orifices between the internal recesses of the finished part: there is no fluid tightness between these recesses.

In order to seal between the recesses obtained, one solution is to close the existing openings between the recesses by positioning a shutter in each inner orifice, this shutter being for example fixed by screwing or shrunk. This solution, however, requires the passage of a tool, which can be difficult or impossible, depending on the configuration of the room. In addition, the shutters used exert constraints on the wall separating the internal recesses, constraints that can lead to the formation of cracks and a rupture of this wall. Finally, there is a risk of losing the shutter inside the metal part.

The document DE10312086-A1 discloses a machine body having an internal void space for the flow of fluids formed by molding, resulting in the formation of an opening closed by a cover. The lid is extended into the void space by a fluid directional member that deflects the fluid or accelerates the fluid.

There is therefore a need for the inexpensive production of metal parts including internal recesses, in which a fluid communication between the internal recesses resulting from the manufacture of the part is rendered null or virtually zero without exerting stress on the walls separating internal recesses.

• au moins un orifice interne traversant ladite paroi interne et reliant lesdits évidements et,
• un orifice externe associé à chaque orifice interne et traversant ladite paroi externe, les axes respectifs de l'orifice interne et de l'orifice externe associé étant confondus,
• un obturateur associé à chaque couple d'orifices interne et externe et comprenant :
  • une partie de fixation fixée de manière étanche à l'intérieur de l'orifice externe,
  • une partie d'ajustement coaxiale avec la partie de fixation et insérée à l'intérieur de l'orifice interne associé audit orifice externe, la partie d'ajustement étant configurée de manière à obturer la plus grande partie de la section de passage dudit orifice interne sans entrer en contact avec une paroi dudit orifice interne.

To this end, the subject of the invention relates to a metal part comprising an outer wall delimiting at least two internal recesses separated by an inner wall, said metal part further comprising:

• at least one internal orifice passing through said inner wall and connecting said recesses and,
• an external orifice associated with each internal orifice and passing through said outer wall, the respective axes of the internal orifice and the associated external orifice being merged,
• a shutter associated with each pair of internal and external ports and comprising:
  • an attachment portion sealingly secured within the outer port,
  • an adjustment portion coaxial with the attachment portion and inserted within the inner port associated with said outer port, the adjusting portion being configured to close most of the passage section of said inner port without coming into contact with a wall of said internal orifice.

The metal part thus obtained has the advantage of having a reduced or zero fluid communication between its recesses without a constraint being exerted on the inner wall separating these recesses thanks to the particular configuration of the shutter, which is set up via an external orifice, each internal orifice being accessible via the associated external orifice.

In particular, the shutter attachment portion is sealingly secured within the outer port.

Advantageously, the fixing portion is configured to fit tightly within the external orifice, without play between the fixing portion and the external orifice. This lack of clearance ensures the seal between the recess and the outside of the metal part and can be obtained by a hoop between the fixing portion and the external orifice or by a screw connection or by a sealant .

Alternatively, the sealed fastening can be obtained by any other means, such as the presence of a seal.

The shutter adjustment portion is itself coaxial with the attachment portion and inserted within the internal port associated with said outer port. It is further configured to close most of the passage section of said internal port without coming into contact with said internal port. In other words, its dimensions and shape are chosen so as to close the maximum of the passage section of the internal orifice without coming into contact with this internal orifice. The clearance, perpendicular to the axis of the internal orifice, between the shutter adjustment portion and the internal orifice is thus always positive, the minimum dimension of the internal orifice being greater than the maximum dimension of the shutter adjustment part. This type of assembly is sometimes called sliding fit.

Advantageously and in a nonlimiting manner, the shutter adjustment portion is shaped so that a clearance, measured perpendicularly to the axis of the internal orifice, exists between the adjustment portion and the internal orifice, this clearance may be between a minimum clearance and a maximum clearance, the minimum clearance being defined so that the adjustment portion does not come into contact with the internal orifice, the maximum clearance resulting from manufacturing dispersions. In particular, the maximum clearance is the result of the dispersions of positioning and concentricity of the tools used to make the openings of the metal part and the shutter manufacturing dispersion.

The maximum clearance thus defines a section of free passage between the shutter adjustment portion and the internal orifice, namely a pressure drop when a fluid flows in the recesses and, ultimately, a leakage flow. If this leakage rate is too great compared to a maximum permissible leakage rate for the intended application, it is possible to reduce this leakage rate by reducing the number of internal orifices as much as possible according to the manufacturing constraints. recesses, either by reducing the manufacturing dispersions, in other words the dispersions of positioning and concentricity of the tools used to make the orifices of the metal part and to make the shutter. These dispersions can be calculated by the usual techniques known to those skilled in the art.

For example, for a metal part of an internal combustion engine cylinder head type, the maximum flow rate of fluid that can be allowed between the two recesses is, for example, less than 5% of the total fluid flow, preferably less than 1%. the total flow of fluid.

Advantageously and in a nonlimiting manner, for the sake of simplicity and efficiency of the closure, the shutter adjustment portion and the internal orifice may each have a cylindrical shape.

Similarly, the shutter attachment portion and the outer port may each have a cylindrical shape.

In particular, the fastener portion of the shutter may have a cylindrical shape of diameter greater than a cylindrical shape of the adjustment portion. The shutter can then be shaped so simple two cylindrical parts of different diameters, for example two full cylinders.

Advantageously and in a nonlimiting manner, the external orifice may have a shoulder at its end adjacent to a recess, shoulder against which is supported the fixing portion of the shutter parallel to the axis of the external orifice. In other words, the outer orifice has a reduced section on the end side adjacent to a recess. This prevents the shutter from falling inside the recess.

Advantageously and without limitation, the metal part may comprise at least two or at least three internal orifices passing through an inner wall separating two recesses. In particular, the minimum number of orifices may be chosen so as to ensure a smooth cold or hot box molding of the metal part, namely to avoid a relative displacement of the mold cores during molding. The maximum number of orifices may be chosen so as not to exceed a maximum fluid flow rate allowed between the recesses of the finished metal part, maximum flow determined according to the intended application.

The metal part according to the invention may more particularly be a cylinder head of an internal combustion engine, for example made of aluminum.

1. (i) réaliser un moule en sable comprenant au moins deux noyaux, deux noyaux adjacents étant reliés par au moins un plot de liaison qui formera un orifice interne entre les évidements de la pièce métallique finie ;
2. (ii) injecter le métal fondu à l'intérieur du moule en sable,
3. (iii) après refroidissement du métal, éliminer le moule en sable et extraire les noyaux en sable des évidements,
4. (iv) réaliser au moins un orifice externe dans la paroi externe d'axe confondu avec l'axe d'un orifice interne laissé par le plot, cet orifice externe étant obtenu en réalisant de manière adaptée le moule de l'étape (i) et/ou étant obtenu par usinage,
5. (v) insérer à l'intérieur de l'orifice externe un obturateur comprenant une partie de fixation et une partie d'ajustement coaxiale avec la partie de fixation, la partie d'ajustement étant configurée de manière à obturer la plus grande partie de la section de passage dudit orifice interne sans entrer en contact avec une paroi dudit orifice interne ;
6. (vi) fixer la partie de fixation de manière étanche à l'intérieur de l'orifice externe, la partie d'ajustement étant insérée à l'intérieur de l'orifice interne associé audit orifice externe, sans entrer en contact avec une paroi dudit orifice interne.

The invention also relates to a method of manufacturing a metal part comprising an outer wall delimiting at least two internal recesses separated by an inner wall, comprising the following steps:

1. (i) providing a sand mold comprising at least two cores, two adjacent cores being connected by at least one bonding pad which will form an internal hole between the recesses of the finished metal piece;
2. (ii) injecting the molten metal into the sand mold,
3. (iii) after cooling the metal, removing the sand mold and extracting the sand cores from the recesses,
4. (iv) making at least one external orifice in the outer wall of axis coinciding with the axis of an internal orifice left by the stud, this external orifice being obtained by correspondingly producing the mold of step (i) and / or being obtained by machining,
5. (v) inserting inside the outer orifice a shutter comprising a fastening portion and an adjusting portion coaxial with the fastening portion, the adjusting portion being configured to close off most of the fastening portion; passage section of said inner port without contacting a wall of said inner port;
6. (vi) securing the securing portion within the outer port, the fitting portion being inserted into the internal port associated with said outer port, without contacting a wall of said internal orifice.

In particular, in step (i) of producing the mold, a cold box or hot box molding process may be used, which will facilitate the extraction of the mold in step (iii).

This method is particularly intended for the manufacture of the metal part according to the invention and in particular adapted to the manufacture of an internal combustion engine cylinder head.

The invention thus also relates to an internal combustion engine comprising a metal part, in particular a cylinder head, according to the invention or obtained by the method according to the invention.

• la figure 1 est une vue en coupe d'une pièce métallique selon un mode de réalisation de l'invention ;
• la figure 2 est un agrandissement de la vue en coupe de la figure 1 ;
• la figure 3 est une représentation partielle en perspective des noyaux d'un moule utilisé pour réaliser une pièce métallique selon un mode de réalisation de l'invention.

The invention is now described with reference to the appended non-limiting drawings, in which:

• the figure 1 is a sectional view of a metal part according to one embodiment of the invention;
• the figure 2 is an enlargement of the sectional view of the figure 1 ;
• the figure 3 is a partial perspective representation of the cores of a mold used to make a metal part according to one embodiment of the invention.

The figure 1 schematically represents a metal part 10 comprising an outer wall 12 delimiting at least two internal recesses 14, 16 separated by an inner wall 18.

• au moins un orifice interne 20 traversant la paroi interne 18 et reliant les évidements 14, 16 et,
• un orifice externe 22 associé à chaque orifice interne 20 et traversant la paroi externe 12, les axes 20a, 22a respectivement de l'orifice interne 20 et de l'orifice externe 22 associé étant confondus.

The metal part 10 further comprising:

• at least one internal orifice 20 passing through the inner wall 18 and connecting the recesses 14, 16 and,
• an external orifice 22 associated with each internal orifice 20 and passing through the outer wall 12, the axes 20a, 22a respectively of the inner orifice 20 and the associated external orifice 22 being merged.

Each internal orifice 20 is thus accessible via the associated external orifice 22.

• une partie de fixation 24a fixée de manière étanche à l'intérieur de l'orifice externe 22,
• une partie d'ajustement 24b coaxiale avec la partie de fixation 24a et insérée à l'intérieur de l'orifice interne 20 associé à l'orifice externe 22.

The metal part 10 also comprises a shutter 24, shown only figure 2 associated with each pair of internal and external ports 22 and comprising:

• a fastening portion 24a sealingly secured within the outer orifice 22,
• an adjustment portion 24b coaxial with the fixing portion 24a and inserted within the internal orifice 20 associated with the external orifice 22.

This adjustment portion 24b is configured to close most of the passage section of said inner port 20 without coming into contact with a wall 20b of said inner port 20. Thus, a game J is constantly observed between the portion 24b and the internal orifice 20, perpendicular to the axis 20a of the internal orifice 20 ( figure 2 ). For a metal part made of aluminum by cold or hot box molding, the clearance J can be of the order of 40 to 100 μm.

The passage section is defined as the surface perpendicular to the axis 20a of the internal orifice 20. The adjustment portion 24b is thus configured so as to close off this passage section as far as possible without coming into contact with the wall 20b of the orifice.

In particular, the adjustment portion 24b is long enough to close the internal orifice 20 over its entire length (measured parallel to its axis 20a).

In the embodiment shown, the internal and external orifices 20 and 22 are cylindrical and the shutter 24 consists of an upper part forming the fixing portion 24a in the form of a hollow cylinder and a lower part forming the part of fit 24b cylinder-shaped full of diameter less than the fixing portion 24a.

The external orifice 22 further comprises a shoulder 23 at its end adjacent to the recess 14, shoulder 23 against which is supported the fixing portion 24a of the shutter 24 parallel to the axis 20a.

In general, the shutter 24 is made of metal, for example steel, preferably stainless steel, or any other metal or alloy suitable for the intended application.

The fastening portion 24a of the illustrated example is configured to be shrunk into the outer hole 22. When the shutter is secured via its fastening portion 24a to the outer wall 12, its adjustment portion 24b is inserted inside the internal orifice 20, over the entire length of the latter along its axis 20a, as in the example shown in FIG. figure 2 .

Alternatively, the fixing portion 24a could be formed of a solid cylinder. In addition, the attachment can be obtained by any other means usually used (screwing or otherwise).

The metal part 10 described above can be obtained by a manufacturing method comprising the steps described hereinafter.

During a first step (i), a sand mold 30 is formed comprising at least two cores 32, 34, two adjacent cores being connected by at least one bonding pad 36 which will form an internal orifice between the recesses of the finished metal part. The figure 3 represents only the cores 32 and 34 of this sand mold 30, cores connected by two pads 36. The cores 32 and 34 will form after molding the recesses 14 and 16 of the metal part 10 respectively.

The molten metal is then injected into the sand mold 30 in a second step (ii).

During a step (iii), after cooling the metal, the sand mold 30 is removed and the sand cores 32, 34 are extracted from the recesses formed.
During a step (iv), then at least one external orifice 22 is produced in the outer wall 12, of axis 22a coinciding with the axis 20a of an internal orifice 20 left by a stud 36, this external orifice 22 being obtained by suitably producing the mold of step (i) and / or being obtained by machining (the positioning of the external orifice being for example determined by a string of dimensions).

During a step (v), inside the external orifice 22 is inserted a shutter 24 comprising a fastening portion 24a and an adjustment portion 24b that is coaxial with the fixing portion, the adjustment portion being configured to close most of the passage section of said inner port without contacting the wall 20b of said inner port 20.

Finally, during step (vi), the fixing part 20a is fixed in a sealed manner inside the external orifice 22, the part 24b being inserted inside the internal orifice 20 associated with said external orifice, without coming into contact with the wall 20b of said internal orifice 20.

A metal part having recesses whose internal orifices are almost closed can thus be achieved by an inexpensive method, such as cold-box or hot-box molding, the closure not applying any mechanical stress detrimental to the holding of the inner wall separating the recesses.

Claims (9)

1. Metal part (10) comprising an outer wall (22) delimiting at least two internal cavities (14, 16) separated by an internal wall (18), said metal part further comprising:

   - at least one internal orifice (20) passing through said internal wall (18) and connecting said cavities (14, 16),

   - an external orifice (22) associated with each internal orifice (20) and passing through said outer wall (12), the respective axes (20a, 22a) of the internal orifice (20) and of the associated external orifice (22) being coincident,

   - an obturator (24) that is associated with each pair of internal (20) and external (20) orifices and comprises:

   - a securing part (24a) secured in a sealing manner to the interior of the external orifice (22),

   - an adjustment part (24b) that is coaxial with the securing part (20a) and is inserted into the internal orifice (20) associated with said external orifice (22) over the entire length of said internal orifice, the adjustment part (24b) being formed such that a clearance (J), measured perpendicular to the axis (20a) of the internal orifice (20), exists between the adjustment part (24b) and the internal orifice (20), this clearance (J) being between a minimum clearance and a maximum clearance, the minimum clearance being defined such that the adjustment part does not come into contact with the internal orifice, the maximum clearance being a result of manufacturing tolerances, such that there is no or almost no fluidic communication between the internal cavities (14, 16) of the part.
2. Metal part (10) according to Claim 1, characterized in that the adjustment part (24b) of the obturator and the internal orifice (20) are each cylindrical in shape.
3. Metal part (10) according to either of Claims 1 and 2, characterized in that the securing part (24a) of the obturator and the external orifice (22) are each cylindrical in shape.
4. Metal part (10) according to Claim 3, characterized in that the securing part (24a) of the obturator is cylindrical in shape, with a diameter greater than a cylindrical shape of the adjustment part (24b).
5. Metal part according to one of Claims 1 to 4, characterized in that the external orifice (22) has a shoulder (23) at its end adjacent to a cavity (14), against which shoulder (23) the securing part (24a) of the obturator presses parallel to the axis (20a) of the external orifice (20).
6. Metal part (10) according to any one of Claims 1 to 5, characterized in that it comprises at least two or at least three internal orifices (20) passing through an internal wall separating two cavities.
7. Metal part (10) according to any one of Claims 1 to 6, characterized in that it forms a cylinder head for an internal combustion engine.
8. Method for manufacturing a metal part (10) comprising an outer wall (12) delimiting at least two internal cavities (14, 16) separated by an internal wall (18), comprising the following steps:

   (i) making a sand mould (30) comprising at least two cores (32, 34), two adjacent cores (32, 34) being connected by at least one connecting stub (36) which will form an internal orifice (20) between the cavities (14, 16) of the finished metal part,

   (ii) injecting the molten metal into the sand mould (30),

   (iii) once the metal has cooled, removing the sand mould (30) and extracting the sand cores (32, 34) from the cavities (14, 16),

   (iv) creating at least one external orifice (22) in the outer wall (12), the axis (22a) of which coincides with the axis (20a) of an internal orifice (20) left by the stub (36), this external orifice (22) being obtained by making the mould in a suitable manner in step (i), and/or by machining,

   (v) inserting, into the outer orifice (22), an obturator (24) comprising a securing part (24a) and an adjustment part (24b) that is coaxial with the securing part (24a), the adjustment part (24b) being configured to block the majority of the passage section of said internal orifice (20) without coming into contact with a wall (20b) of said internal orifice (20),

   (vi) securing the securing part (24a) in a sealing manner inside the external orifice (22), the adjustment part (24b) being inserted into the internal orifice (20) associated with said external orifice (22) without coming into contact with a wall (20b) of said internal orifice (20).
9. Internal combustion engine comprising a metal part (10), in particular a cylinder head, according to one of Claims 1 to 7 or obtained by the method of Claim 8 .

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