EP3570992B1 - Casting mould for casting complexly shaped cast parts and use of such a casting mould - Google Patents

Description

The invention relates to a casting mold for casting complex-shaped, large-volume cast parts from a metal melt. Such casting molds usually have a mold cavity that reproduces the cast part and a feed system for feeding the molten metal to be poured into the cast part into the mold cavity. The feed system comprises a sprue, a pouring runner connected to the pouring runner and a feeder system which is connected to the pouring runner, the cavity of the casting mold being connected to the feeder system or the pouring runner via connections

The invention also relates to a practical use of such a casting mold.

When casting cast parts with casting molds of the type under discussion here, the feeder system serves on the one hand to control the solidification direction of the poured melt, which is optimally directed towards the feeder. On the other hand, the melt volume stored in the feeder system compensates for the reduction in the specific volume of the melt poured during the liquid / solid phase transition. The feeder system represents an additional melt reservoir from which melt can flow into the cast part while it is cooling.

The casting of modern cylinder crankcases and comparable filigree cast parts made of light metal alloys, which can develop high mechanical properties or high thermal load capacity, represent a particular challenge. Such light metal alloys include, for example, hardenable AlCu alloys.

The high property potential of such light metal alloys is offset in practice by problems in the reliable production of high-quality cast parts on an industrial scale. For example, it is difficult to produce complex-shaped cast parts from AlCu alloys that are free of voids and hot cracks. It was found that the quality of the cast part obtained depends crucially on the uniformity of the filling of the casting mold cavity and on the homogeneity of the temperature distribution in the melt.

In the case of alloys with a non-shell-like, pulpy and / or sponge-like solidification morphology, mass accumulations are to be avoided, since sinkholes arise and the replenishment is made more difficult by the subsequent flow of the melt within the solidifying casting itself.

A large number of proposals for casting molds which are intended to meet these requirements are known from the prior art.

So is from the DE 42 44 789 A1 a casting mold for casting a cylinder crankcase for an internal combustion engine is known, in which two separate filling funnels are provided, via which the melt is poured into the casting mold. The melt flows from the filling funnels via a pouring runner into the mold cavity delimited by the casting mold. The runners are guided through a crankcase block core. Of the Runners branch off casting channels that lead to the lower casting contours of the casting mold. The pouring channels are each aligned so that their mouths lie on a horizontal plane.

A low-pressure permanent mold casting process for casting metal cast parts, such as cylinder heads or engine blocks of internal combustion engines, is known from US Pat DE 39 24 742 A1 known. The complexity of the cast parts to be cast with this method results from the fact that they have thinner walls in at least one area than in another area. In the known method, liquid metal is pressed from a melting container through a riser pipe into the mold by means of gas pressure. The mold is arranged in such a way that the thicker walls of the cast part are located on top and thus far from the sprue, via which the metal reaches the cavity of the casting mold that depicts the component. At the same time, the liquid metal at or near the area of the mold that is located at the bottom near the gate is directed into the sections that form the thinner wall of the casting mold. In this case, the liquid metal can be fed via a bottom run at several sprue points to the area of the mold that is near the bottom of the sprue and introduced into the sections of the mold cavity that form the thinner wall of the casting.

From the WO 2014/111573 A1 Finally, a method for casting cast parts is known in which a metal melt is poured via a feeder or separate pouring runners or pouring channels into a mold cavity that is delimited by a casting mold and depicting the cast part. The casting mold includes molded parts that determine the shape of the casting to be cast. The melt is passed through at least two connections, at least one of which is designed as an additional channel leading through one of the molded parts and independent of the contour of the cast part to be cast, into at least two sections of the mold cavity that are assigned to different levels of the cast part to be cast . Documents EP2352608B1 , DE4103802A1 and CN205008543U are further examples of known casting molds in the technical field.

For the casting of cast parts of the type considered here, casting molds that are completely or partially designed as core packages are particularly suitable. With such a core package, the casting mold is composed of a large number of cores that determine the inner and outer contour of the cast part to be produced. The casting cores are usually made of a molding material or an easily destructible material as so-called "lost cores" which are destroyed when the casting is removed from the mold. However, mixed forms of core packages are also known in which, for example, the molded parts that determine the outer contour are designed as reusable permanent molded parts, while the recesses, cavities, channels, lines, etc. to be depicted on the inside in the cast part are depicted by lost cores.

Core package casting molds of the type explained above are mainly used in gravity casting processes or in low-pressure casting processes, whereby these processes can also include a rotation of the casting mold after it has been filled with the melt in order to optimize the solidification process and, consequently, an optimal structure of the cast part achieve.

Against the background of the prior art explained above, the object of the invention was to create a casting mold that reliably allows highly complex-shaped cast parts to be produced from alloys that are difficult to use conventionally and are uncertain in terms of the quality of the casting result let shed.

In addition, a particularly advantageous use of such a casting mold should be specified.

With regard to the casting mold, the invention has achieved this object in that such a casting mold is designed according to claim 1.

A casting mold designed according to the invention is particularly suitable for use when casting a cylinder crankcase for an internal combustion engine from a light metal melt, in particular an AlCu melt.

Advantageous embodiments of the invention are specified in the dependent claims and are explained in detail below, like the general inventive concept.

A casting mold according to the invention for casting complex-shaped, large-volume cast parts from a metal melt has a mold cavity which depicts the cast part and a feed system for feeding the metal melt to be cast into the cast part into the mold cavity, the feed system having a sprue, a pouring runner connected to the sprue and comprises a feeder system which is connected to the runner, the mold cavity being connected to the feeder system or the runner via connections.

According to the invention - as seen in the flow direction of the molten metal flowing from the sprue into the sprue during casting - the sprue with a branch facing away from the sprue along the feeder system and with a branch directed backwards, which connects to the branch facing away, along in the opposite direction to the branch directed away of the feeder system, wherein the feeder system is connected to both the branch directed away and with the branch directed back via two or more gates distributed along the respective branch.

With the design of a casting mold according to the invention, it is possible to equalize the temperature of the melt provided in the feeder system and guided into the casting mold cavity so that an equally uniform temperature distribution is established in the cast part. This Even in the case of metal melts that are difficult to cast, in particular for light metal melts that are difficult to cast, such as AlCu melts, after the casting mold has been filled, this leads to a uniform solidification process, during which an equally uniform replenishment from the feeder system is ensured. Local temperature differences and the associated non-uniform solidification in the various planes of the cast part, which entails the risk of cavity formation, are avoided in this way. Instead, a solidification front is reliably formed in the melt filled into a casting mold according to the invention, which, starting from the point furthest away from the feeder system, progresses continuously in the direction of the feeder system.

At this point it goes without saying that the terms "uniform temperature distribution", "average temperature", "homogenization of the temperature distribution", "equal temperatures", "uniform temperature" and the like used here are to be understood in the technical sense, i.e. within the scope of the technical possibilities with the tolerances regarded as usual by the person skilled in the art.

The homogenization of the temperature of the melt flow fed to the casting mold cavity is achieved according to the invention in that the melt flow fed via the sprue is first guided along the feeder system in a "directed branch" leading away from the sprue, already through the gates provided along the directed branch into the feeder system runs and is then guided again in the direction of the sprue in a "backward-directed branch" running opposite to the branch directed away from the sprue. However, there is no direct connection between the sprue and the branch that has been directed back. Rather, only melt runs from the branch facing away from the pouring runner into its branch facing back.

The temperature of the melt flowing through the runner when pouring into the casting mold decreases with increasing distance from the gate. Accordingly, in a casting mold according to the invention, maximum hot melt reaches the feeder system via the gate of the branch directed away from the gate next to the sprue, whereas the melt that runs into the riser system via the last gate of the back-directed branch in the flow direction that is furthest away from the gate is cooled to the maximum . There is therefore a maximum temperature difference between the melt reaching the feeder system via the first cut of the branch directed away and the last cut of the back cut. As the maximum hot and the maximum cooled melt are fed to the same area of the casting mold, the differently tempered melt streams mix and a mixing temperature is established in the melt contained in this area which, with appropriate coordination of the melt volume flows entering the area concerned, for example corresponds to the mean temperature of the maximum hot and maximum cooled melt streams flowing into this area.

Between the melt that entered the feeder system through the last cut of the turned away branch provided in the direction of flow at the end of the branch pointing away and cooled down via the path along the feeder system, and the melt that enters the feeder system through the first cut of the backwards directed branch and if only slightly cooled over a comparatively short distance between the last cut of the branch directed away and the first cut of the branch directed back, there is only a correspondingly small temperature difference. Since these melt streams with comparably slightly different temperatures are also fed to the same area of the feeder system, there is also a mixed temperature there. This can in turn by a suitable setting of the gates in the Melt volume flows entering the feeder system can be set so that the mixing temperature that is established in the relevant area is equal to the mixing temperature that is established by mixing the maximum hot and maximum cooled melt in the area of the feeder system next to the pouring.

The same applies to the melt streams, which are passed into the feeder system via those optionally available further gates, which run along the away and the backward branch of the runner between the - seen in the flow direction of the melt - at the end and at the beginning of the away and of the backward branch are provided.

As a result, the design of the runner provided in a casting mold according to the invention and its special connection to the feeder system result in a homogeneous temperature distribution over the entire volume of the feeder system. As a result, the melt reaching the casting mold cavity via the feeder system also has a uniform temperature distribution, which means that even with a filigree shape of the design elements to be reproduced on the cast part, such as thin walls and fine webs or ribs, not only an optimal mold filling, but an equally uniform one Solidification of the melt is achieved. With the invention, it is consequently possible to cast components that are difficult to control in terms of casting technology, such as cylinder crankcases for internal combustion engines, even from metal melts, which are known for their poor mold filling and feeding capacity, but can develop high mechanical or thermal properties.

As mentioned, the mixing temperature established in the feeder system can be adjusted by coordinating the melt volume flows entering the individual areas of the feeder system via the gates provided there can be set. For this purpose, the position on the respective branch of the pouring runner, the number or the geometry, in particular the diameter, of the gates can be adapted so that the desired volume of the total melt contained in the feeder system results from the proportions of the melt streams reaching the feeder system at different temperatures Mixing temperature in the feeder system results.

The arrangement of the gates assigned to the away and backward branches can directly influence the mixing of the gates into the feeder system and the associated equalization of the temperature of the melt contained in the feeder system.

The inventive design of a casting mold proves to be advantageous for all casting tasks in which a particularly homogeneous temperature distribution in the melt to be cast and a uniform supply of the melt into the casting mold cavity depicting the casting are important for casting success. Thus, the invention can be used for cast parts with an elongated, block-like basic shape, such as engine blocks, as well as for cast parts that have a cylindrical basic shape characterized by an ellipsoidal or circular cross-section.

With regard to an optimized homogeneity of the temperature distribution, it has proven to be advantageous if one of the gates, via which the backward branch is connected to the feeder system, is arranged opposite each gate via which the branch of the pouring runner facing away is connected to the feeder system . This is particularly favorable in the case of a feeder system whose length is significantly greater than its width, that is to say for example a feeder system that has a rectangular basic shape in plan view.

It also helps to equalize the temperature distribution of the melt contained in the feeder system during the casting operation if the number of gates assigned to the branch directed away is equal to the number of gates assigned to the backward branch.

The latter applies in particular if the size of the gates assigned to the branch directed away is the same as the size of the gates assigned to the backward branch, i.e. if the gates are dimensioned in such a way that the same volume flows into the feeder system via the gates of the branches of the pouring runner assigned to one another reach.

Depending on the way in which the feeder system is connected to the casting mold cavity or the melt volume required for replenishing the casting mold cavity during the solidification of the melt in the feeder system, it can be useful to provide a single, sufficiently large feeder chamber in the feeder system, which in the manner according to the invention is connected to the facing away and the backward branch of the pouring runner is connected. The feeder chamber then serves as a mixing area for the melt reaching it via the outward and backward branch and thus contributes to the homogenization of the melt reaching the casting mold cavity. In addition, such a feed chamber can take on a feed function in the sense of replenishing melt into the cavity of the casting mold.

If the intermixing and the associated equalization of the temperature distribution of the melt contained in the feeder system is to be further optimized, it can be useful to provide two or more feeder chambers in the feeder system, each of which has at least one gate with both the branch pointing away and the backward branch of the pouring runner is connected. With two or more Feeder chambers, the individual chambers each contain only a partial volume of the total melt volume required for replenishing the casting mold cavity. The correspondingly smaller volume of the individual feeder chambers results in a particularly intensive mixing of the melt streams of different temperatures entering them via the branches of the pouring runner. In this way, it can be ensured with comparably little effort that the melt volumes present in the respective melt chamber have the desired mixing temperature overall, and that local temperature differences are avoided. It proves to be particularly favorable in this respect if the volumes enclosed by the feeder chambers are the same.

In order to ensure in a feeder system with two or more feeder chambers that the feeder volumes contained in the individual chambers assume a common mixed temperature, the feeder chambers can be connected to one another via additionally provided gates directly connecting the feeder chambers. Via these additional gates, the melt volumes contained in the feeder chambers are exchanged and, as a result, the possibly different temperatures of the melt portions contained in the chambers are balanced.

A variant of the invention which is particularly suitable for casting cylinder crankcases for internal combustion engines with cylinder openings arranged in a row is characterized in that the feeder system comprises at least one, in particular at least two feed chambers arranged side by side, and either the branch facing away is arranged in the space between the feed chambers and along the side of each of the feeder chambers that is on the outer side of the intermediate space is in each case a back-directed branch branching off from the branch directed away or the The branch facing away is divided into two branches facing away, one of which runs along the outer side of the supply chambers in relation to the space between the feeder chambers, whereas at least one branch that is connected to the branches facing away runs in the space between the feeder chambers. The even distribution of the melt to the feeder chambers can be supported by the fact that the pouring runner is branched into two outgoing branches immediately following the sprue, to each of which a returning branch is connected.

It has proven to be particularly advantageous with regard to the distribution of the melt over the branches of the pouring runner of a casting mold according to the invention if the branches of the pouring runner are arranged together in one plane. This level is optimally aligned horizontally in the casting operation, so that a gradient and the associated different flow velocities in the branches of the runner are avoided.

In the case of such a common plane for the branches of the pouring runner, it has proven to be advantageous if the gates of the incoming and returning branch each have their own level so that the melt is layered when converging and does not collide with one another.

Another embodiment of the invention that is particularly important for practice consists in the fact that the connection leading from the feeder system or from the pouring runner to the casting mold cavity is guided exclusively outside the volume of the casting mold occupied by the casting mold cavity. Since in a casting mold according to the invention the melt is conducted into the casting mold cavity exclusively via connections which are formed on the outside in the area of the walls of the casting mold bounding the casting mold cavity, the uniformity of the Temperature distribution of the melt flowing into the mold cavity during casting and the uniformity of the mold filling optimized.

As a result of the connection that takes place exclusively outside the casting mold cavity, temperature differences in the melt introduced into the casting mold cavity are avoided during the casting operation. These can occur when melt is also conducted into the mold cavity via internal cores heated by the melt flowing into the casting mold cavity, which form recesses, cavities, channels and the like in the casting. Due to the heating of the internal cores, the melt flowing through them would cool down less than the melt fed in via the external connections. Since the melt is only fed into the mold cavity via external connections, this ensures that the melt cools evenly on its way from the feeder system or from the pouring runner into the mold cavity and thus enters the mold cavity at a uniform temperature.

It has proven to be particularly advantageous in this respect if, in the event that the feeder system is connected to the casting mold cavity via several connections, the inflow openings of the connections assigned to the feeder system are arranged together in one plane. In this way, the melt is in each case discharged from the feeder system at the same level at which there is a uniform temperature of the melt contained in the possibly several chambers. This also contributes to the fact that the melt entering the casting mold cavity has a uniform temperature in the technical sense.

The casting mold according to the invention is suitable for gravity casting processes or low-pressure casting processes. In particular, casting molds according to the invention can be used to produce cast parts in tilt casting or rotation casting processes, in which the casting mold according to or is moved during the filling from a filling position into a solidification position. A comprehensive explanation of these procedures can be found in EP 2 352 608 B1 and the prior art cited therein.

In order to be able to depict the filigree design features of cast parts to be cast by means of casting molds according to the invention, the casting mold according to the invention can be composed as a core package from a large number of cores, of which certain cores represent the outer shape and other cores in the cast part to be made recesses, cavities, channels and the like depict. The cores of the core package can be designed as lost cores that are destroyed when the casting is removed from the mold, or some of the cores can be designed as permanent molded parts that can be used repeatedly.

For example, in the case that is particularly advantageous in practice, that the connection of the feeder system to the casting mold cavity is implemented exclusively via connections that are outside the casting mold cavity, it can be useful, for example, to provide an outer shell designed as a permanent molded part on the casting mold according to the invention, on which at least the casting cores delimiting the connections at least in sections are held. This proves to be particularly advantageous if the casting cores which at least partially delimit the connections are designed as lost casting cores.

With the invention, a cylinder crankcase can thus be represented in the core package process with a feed system in which the melt is divided into two pouring runner branches, so that the feeder system connected to it, ideally comprising pot-like feeder chambers, for homogenizing the temperature distribution in the feeder system and subsequently in the component represented by the casting mold serves. in the In the casting operation, the feeder system is filled with melt at different temperatures through its two or more gates on the branches of the runner. By adapting the geometries and the position of the gates, the melt in the feeder system is mixed in such a way that overall a homogeneous temperature distribution results in the feeder system. The correspondingly homogeneously tempered melt is fed to the casting mold cavity depicting the cast part.

The casting process made possible by the design according to the invention allows it, in particular in combination with the optionally exclusively external supply of the casting mold cavity and the associated avoidance of "internal" supply paths, light metal melts that are difficult to cast, such as Al-Cu-based alloys, despite their generally poor filling and pouring power free from macroscopic defects. The feeder and external connections that are present on the cast part after it has been demolded can easily be made weight-neutral using common processing methods, such as e.g. Drill to be removed. Mass accumulations on the cast part, which in the prior art are intended to avoid premature local solidification of the melt, but do not serve any other technical purpose, can be avoided in a casting mold according to the invention, as can complex channel guides when connecting the feeder system to the casting mold cavity in order to avoid the appearance of freezing .

In a casting mold according to the invention, chill molds can of course also be arranged in the region of the casting mold cavity in order to bring about locally accelerated solidification there in a manner known per se for the purpose of forming a locally particularly pronounced structure. In particular, if the casting mold cavity is filled and topped up with melt exclusively via external connections, these chill molds do not hinder the casting operation either the uniform filling process ensured by the design according to the invention.

Fig.1

eine Gießform zum Gießen eines Zylinderkurbelgehäuses für einen Verbrennungsmotor in einem Querschnitt;

Fig. 2

ein in der Gießform 1 gegossenes Zylinderkurbelgehäuse nach dem Entformen im ungeputztem Zustand in einer Ansicht von oben;

Fig. 3

das Zylinderkurbelgehäuse gemäß Fig. 2 in einer frontalen Sicht auf seine eine Stirnseite;

Fig. 4

das Zylinderkurbelgehäuse gemäß Fig. 2 und 3 in einer seitlichen Ansicht.

Fig. 5

eine weitere Gießform zum Gießen eines Zylinderkurbelgehäuses für einen Verbrennungsmotor in einem Querschnitt;

Fig. 6 - 9

die Gießform gemäß Fig, 5 beim Befüllen mit Schmelze;

Fig. 10

die Gießform gemäß Fig. 5 in der nach dem Füllen zum Erstarren gedrehten Stellung.

The invention is explained in more detail below with the aid of a drawing showing exemplary embodiments. Their figures each show schematically and not to scale:

Fig.1

a mold for casting a cylinder crankcase for an internal combustion engine in a cross section;

Fig. 2

a cylinder crankcase cast in the casting mold 1 after demolding in the uncleaned state in a view from above;

Fig. 3

the cylinder crankcase according to Fig. 2 in a frontal view of its one end face;

Fig. 4

the cylinder crankcase according to Fig. 2 and 3 in a side view.

Fig. 5

a further casting mold for casting a cylinder crankcase for an internal combustion engine in a cross section;

Figs. 6-9

the mold according to Fig. 5 when filling with melt;

Fig. 10

the mold according to Fig. 5 in the position rotated to solidify after filling.

In the Fig. 1 Mold 1 shown is used to cast the in the Figures 2 - 4 cylinder crankcase Z shown, often also called cylinder blocks, for an internal combustion engine made of an AlCu alloy.

Fig. 1 shows a schematic section transverse to the longitudinal extension of the cylinder crankcase Z.

The casting mold 1 designed as a core package comprises two outer shells 2, 3 designed as permanent mold parts, between which a larger number of lost casting cores 4 formed from molding sand are arranged. The outer shells 2, 3 and the casting cores 4 delimit a casting mold cavity 5, which depicts the cylinder crankcase Z to be cast with its four cylinder openings ZÖ, which are arranged in series here, and the design features usually provided in such cylinder crankcases for internal combustion engines.

In addition, the casting cores 4 define an in Fig. 1 not visible, perpendicular to the in Fig. 1 the upper side 6 of the casting mold 1 leading downwards, a pouring runner 7 connected to the pouring sprue, a feeder system 8 connected to the pouring runner 7 and the casting mold cavity 5 and connections 9a provided for connecting the casting mold cavity 5 to the casting runner 7 or the feeder system 8, 9b.

The mold 1 is in Fig. 1 shown in the position shown for filling with melt, in which the opening of the sprue points upwards and the feeder system 8 is arranged on the underside of the casting mold 1.

After the melt has been poured in, the casting mold 1 is closed in a manner known per se and rotated in an equally known manner about a pivot axis parallel to the longitudinal extension of the casting mold 1, for example 180 °, until the feeder system 8 is arranged at the top. In this way, a uniform solidification of the melt filled into the casting mold 1 running in the direction of the feeder system 8 is promoted.

When solidifying, not only does the cylinder crankcase Z to be produced form as a solid cast body, but also these originally hollow molded elements after demolding as a result of the melt solidifying in the sprue 10, in the runner 7, in the feeder system 8 and in the connections 9a, 9b the casting mold 1 with the cylinder crankcase Z is shown coherently.

When cleaning following the removal from the mold, the relevant molded elements are separated from the cylinder crankcase Z in a manner known per se and sent for recycling.

The peculiarities of a casting mold 1 according to the invention can thus be explained most easily using the cylinder crankcase Z that has been removed from the mold and has not yet been cleaned, as shown in FIGS Figures 2 - 4 is shown.

The feeder system 8 accordingly comprises two rows arranged next to one another and extending in the longitudinal direction L of the cylinder crankcase Z, each with five pot-like feed chambers 11, 12. Feed chambers 11, 12 of each row arranged adjacent to one another are connected to one another by gates 13, 14. The rows of feed chambers 11, 12 delimit an intermediate space 15 between them.

The feed chambers 11, 12 are arranged above the cover surface ZD of the cylinder crankcase Z, which is provided for mounting a cylinder head (not shown here), and have identical shapes and volumes. The bottoms of the feed chambers 11, 12 are arranged together in a horizontal plane H1 which is aligned parallel to the top surface ZD of the cylinder crankcase Z.

The pouring runner 7 is also arranged in a horizontal plane H2 which is aligned parallel to the top surface ZD and in which the upper side of the feeder chambers 11, 12 also ends.

The pouring runner 7 is divided into two branches 18, 19 starting from the head 17 of the crankcase Z when the cylinder crankcase Z is demolded as a pouring rod tapering slightly conically in the direction of the pouring runner 7, which can be seen from the flow direction S of the melt poured into the casting mold 1 during the pouring operation Sprue 10 are directed away.

The relative to the longitudinal axis L of the cylinder crankcase Z seen in plan view ( Fig. 2 ) mirror-symmetrically shaped branches 18, 19 directed away from the sprue 10 initially each extend transversely to the longitudinal axis L from the sprue head 17, in order to then merge in a curve and via a filter F into a section which is at a small distance along the gap 15 facing away from the outer side of the respective row of feeder chambers 11,12.

At the end of the respective row of feeder chambers 11, 12, seen in the direction of flow S, the branches 18, 19 facing away merge in a further curve into a section oriented towards the other branch 19, 18 facing away and extending over the width of the respective row of feeder chambers 11.12 extends.

At the end of this section, seen in the direction of flow S, the branches 18, 19 of the pouring runner 7 directed away from the runner open together in a branch 20 of the pouring runner directed back towards the pouring head 17. This backward branch 20 of the pouring runner 7 has a cross-sectional area which corresponds at least approximately to the sum of the cross-sectional areas of the branches 18, 19 directed away. In this way, the branch 20 that is directed back can safely absorb the melt volumes flowing into it via the branches 18, 19 directed away.

The backward branch 20 is arranged in the intermediate space 15 centrally between the rows of feed chambers 11, 12 and, viewed in the direction of flow S, runs opposite to that of the sprue 10 branches 18, 19 directed away towards the sprue 10. However, the branch 20 directed back ends in front of the pouring head 17, so that in the casting operation melt reaches the branch 20 directed back exclusively via the branches 18, 19 directed away.

Each of the feed chambers 11, which are evenly spaced along the longitudinal axis L, is connected to the branch 18 facing away via a respective cut 21, and each of the feed chambers 12, which are also equally spaced in the longitudinal direction L, is connected to the branch 19 directed away via a cut 22. In the same way, each of the feeder chambers 11 is connected to the branch 20 directed back via a respective cut 23 and each of the feeder chambers 12 via a respective cut 24. The gates 21-24 are also distributed at equal intervals along the longitudinal axis L, the gates 21, 22; respectively assigned to each feeder chamber 11, 12; 23,24 are positioned opposite one another and in the middle with respect to the respective wall of the feeder chambers 11,12.

The casting mold cavity 5 is connected directly to the runner 7 (connection 9a) or the feeder chambers 11, 12 (connections 9b) via connections 9a, 9b. The connections 9a, 9b are each formed exclusively outside the mold cavity 5, so that no melt reaches the mold cavity 5 via casting cores 4 placed in the mold cavity 5. According to the principle of communicating tubes, the melt has one level, consequently part of the melt also reaches the mold cavity 5 via the feeder chambers 11, 12. The solidification in the component then takes place very quickly over the thin walls and the feed only takes place via the locally large volumes in close proximity to the supply requirement. The mouth of the connections 9b connected to the feeder chambers 11, 12 are arranged on a common horizontal plane H3, so that in each case the melt of the same temperature from the feeder chambers 11, 12 into those connected to them Connections 9b reached. The supply of the melt to the mold cavity 5, on the other hand, can extend over a height range or be distributed over several levels.

With regard to the filling or the solidification behavior of particularly critical areas of the casting mold cavity 5, melt can be supplied in a targeted manner through a separate connection 9b in order to feed the respective problem area directly.

In the Fig. 5 The casting mold 31 shown, completely constructed as a core package of lost cores, is also provided for casting a cylinder block for an internal combustion engine. The casting mold 31 comprises a cover core 32, an outer core 33 carrying the cover core 32, a further outer core 34 carrying the outer core 33, two outer shell cores 35, 36 which form the outer end of the casting mold 31 in the region of the mold cavity of the casting mold 31 and on which the outer cores 33,34 and the cover core 32 are supported, a contouring core 37 which depicts the contour of the interior of the cast part, which forms the lower end of the casting mold and on which the shell cores 35,36 are supported, as well as laterally within the shell cores 35,36 Cores 38,39 arranged in a limited space, which determine the outer contour of the casting.

Outwardly extending branches 40, 41, which are directed away from the sprue, which is not visible here, and a centrally arranged, rear-directed branch 42 of the pouring runner, are formed in the cover core 32. A feeder pot 43, 44 is formed in the cover core 32 and the outer cores 33, 34 in the space between the branch 40, 41 facing away from the outside and the branch 42 facing back. The feeder pots 43, 44 accordingly sit directly on the top surface of the cast part (eg sealing surface to the oil pan or to the cylinder head). The feeder pots 43,44 thus feed all areas which are arranged in direct local proximity to them such as the cylinder head screw pipes. The branches 40, 41 facing away are connected to the respective associated feeder pot 43,44 via connections that are arranged close to the outer core 33, whereas the branch 42 directed back is connected via connections to the feeder pots 43, 44, which point towards the top of the Cover core 32 are offset.

The shell cores 35, 36 and the respectively assigned cores 38, 39, which determine the outer contour of the cast part, additionally limit external feed volumes 45, 46, which are each connected to one of the feed pots 43, 44 via an inlet 47, 48. The external feeder volumes 45, 46 are filled via the assigned inlet 47, 48, which is always connected to one of the feeder pots 43, 44. The external feeder volumes 45, 46 feed everything in their immediate vicinity, e.g. Mass accumulation through functional integration.

While the feeder pots 43, 44 in the casting mold 31 intended for casting cylinder crankcases ZK are always on the same level, the external feeder volumes 45, 46 are at different heights.

For filling with melt, the casting mold 31 is rotated, for example, by 180 ° transversely to the longitudinal extension of the cylinder crankcase ZK to be cast, so that the cover core 32 with the branches 40, 41 facing away and the branch 42 facing back is on the underside. Hot melt M is passed through the sprue into the branches 40, 41 facing away. From the branches 40, 41 facing away, the melt M, which has cooled down on the way through the branches 40, 41 facing away, reaches the branch 42 facing backwards and into the feeder pots 43, 44 ( Fig. 6 ).

With increasing filling of the branches 40, 41 directed away, hot melt M also reaches the corresponding connections from the branches 40, 41 facing away into the feeder pots 43, 44 so that hot melt M and cooled melt M mix in feeder pots 43, 44 and melt M is present in feeder pots 43, 44, which has a homogeneously distributed mixing temperature ( Fig. 7 ).

The correspondingly tempered melt M rises via the inlets 47, 48, on the one hand, into the external feeder volumes 45, 46 and, on the other hand, over the gates, via which the feeder pots 43, 44 are connected directly to the casting mold cavity depicting the casting, into the casting mold cavity ( Fig. 8 ).

After completely filling ( Fig. 9 ) the casting mold 31 is closed in a manner known per se and rotated transversely to its longitudinal extension by 180 ° into the solidification position ( Fig. 10 ).

In the exemplary embodiments of a casting mold according to the invention described here, the melt is thus filled into the casting mold via at least one sprue. The melt is then divided into two separate branches facing away from the sprue, which, given a corresponding basic shape of the feeder system, are preferably aligned such that they run parallel at least in sections. The melt, which is divided into branches of the pouring runner directed away, is returned to the pot-like feeder chambers via a deflector. In this case, a curve can be provided in the area of the deflection, which leads out of the main plane in which the pouring runner mainly lies in order to slow down the flow speed of the melt flowing through the respective branch directed away. The section of the respective branch adjoining the curve in question is then again in the main plane of the pouring runner. Following the branches pointing away, the melt is carried on into at least one central, backward-directed casting branch. Of course, it is also possible to have a separate, directed back, on each branch of the runner that is directed away. also to be connected in the space between the rows of feeder chambers.

The early separation of the runner system and supply of the melt to several feeder volumes provided by the feeder chambers results in optimized filling conditions. The configuration according to the invention guarantees a rapid, uniform inflow of the molten metal and, as a result, a homogeneous temperature distribution in the feeder system and in the component. For this purpose, the runners are connected to the feeder chambers via gates. The connection of the feeder chambers is selected in such a way that the penetrating melt is optimally mixed in the chambers. For this purpose, it can also be useful, for example, not to connect all of the feeder chambers directly to the runner, as in the exemplary embodiment explained here, but to connect individual feeder chambers only to the immediately adjacent feeder chamber, which is then connected to the runner. To support mixing and temperature equalization, the feeder chambers are connected to one another via gates. By varying the gate cross-sections and the feeder chamber volumes, the melt flow and the achieved temperature distribution can be adapted to the particular casting task. Because the feeder system is arranged above the mold cavity during the solidification, solidification in the direction of the feeder system is achieved. This means that the component cools down and solidifies, starting from the point furthest away from the feeder system, while the melt contained in the feeder system and finally filled into the mold remains hot for longer. If the mold is gravity cast without rotation, i.e. filled with the feeder system at the top, the mold cavity representing the cast part is filled first, and only finally the feeder system is filled.

The simple removal of the feeder system, the pouring runner, the sprue and the connections can be supported by the Connections are connected to the component contour over a small area. The connection points preferably go to existing slugs and sit on surfaces that are part of the standard post-processing. The feeder system can be easily removed during the pre- and post-processing of the respective component (cylinder crankcase Z), for example by drilling.

REFERENCE MARK

1

Mold

2.3

Outer shells

4th

Casting cores

5

Mold cavity

6th

Side of the mold 1

7th

Pouring runner

8th

Feeder system

9a, 9b

Connections

10

Sprue

11.12

Pantries

13.14

Cuts

15th

Space delimited by feeder chambers 11, 12

17th

Sprue head

18.19

branches of the runner facing away 7

20th

backward branch of the runner 7

21-24

Cuts

L.

Longitudinal axis

F.

filter

H1-H3

Horizontal planes, aligned parallel to the top surface ZD of the cylinder crankcase Z.

S.

Flow direction of the melt

Z

Cylinder crankcase

ZD

Top surface of the cylinder crankcase Z

ZÖ

Cylinder openings

31

Mold

32

Cover core

33.34

Outer cores

35.36

outer shell kernels

37

the core that determines the inner contour of the casting ZK

38.39

Cores that determine the outer contour of the casting.

40.41

outwardly directed branches of the pouring runner

42

centrally arranged backward branch of the pouring runner

43.44

Food pots

45.46

external food volumes

47.48

Inlets

ZK

Cylinder crankcase (cast part)

M.

melt

Claims (15)

1. Casting mould for casting complex-shaped, large-volume castings (Z) from a molten metal, wherein the casting mould (1) has a mould cavity (5) forming the casting (Z) and a delivery system for delivery of the molten metal, which is to be cast into the casting (Z), into the mould cavity (5), wherein the delivery system comprises a sprue (10), a runner (7) connected to the sprue and a feeder system (8) connected to the runner (7), and wherein the mould cavity (5) is connected to the feeder system (8) or the runner (7) via connections (9a, 9b), characterised in that when seen in the flow direction (S) of the molten metal flowing from the sprue (10) into the runner (7) during the casting operation, the runner (7), having a branch (18, 19) directed away from the sprue (10) along the feeder system (8) and having a directed-back branch (20) adjoining the directed-away branch (18, 19), is guided along the feeder system (8) in the opposite direction to the directed-away branch (18, 19), and in that the feeder system (8) is connected to both the directed-away branch (18, 19) and the directed-back branch (20) via two or more gates (21, 24) distributed along the respective branch (18, 19, 20).
2. Casting mould according to Claim 1, characterised in that the number of gates (21, 23) assigned to the directed-away branch (18, 19) is equal to the number of gates (22, 24) assigned to the directed-back branch (20).
3. Casting mould according to any one of the preceding claims, characterised in that one of the gates (22, 24), via which the directed-back branch (20) is connected to the feeder system (8), is arranged opposite to each gate (21, 23), via which the directed-away branch (18, 19) of the runner (7) is connected to the feeder system (8).
4. Casting mould according to any one of the preceding claims, characterised in that the size of the gates (21, 23) assigned to the directed-away branch (18, 19) is the same size as the gates (22, 24) assigned to the directed-back branch (20).
5. Casting mould according to any one of the preceding claims, characterised in that the feeder system (8) comprises at least one, two or more feeder chambers (11, 12), each of which is connected via respectively at least one gate (21-24) to both the directed-away branch (18, 19) and the directed-back branch (20) of the runner (7).
6. Casting mould according to claim 5, characterised in that the feeder chambers (11, 12) are connected to one another via a gate (13, 14).
7. Casting mould according to any one of claims 5 or 6, characterised in that

   - the feeder system (8) comprises at least two adjacent feeder chambers (11, 12), and

   - in that

   - either the directed-away branch (18, 19) is arranged in the intermediate space (15) between the feeder chambers (11, 12) and along the side of each of the feeder chambers (11, 12) runs a directed-back branch (20) branching off from the directed-away branch (18, 19), said side being outwardly disposed with respect to the intermediate space (15)

   - or the runner (7) is divided into two directed-away branches (18, 19), one of which runs respectively along the side of the feeder chambers (11, 12) between the feeder chambers (11, 12), said side being outwardly disposed with respect to the intermediate space (15), whereas at least one directed-back branch (20) connected to the directed-away branches (18, 19) runs in the intermediate space (15) between the feeder chambers (11, 12).
8. Casting mould according to claim 7, characterised in that the runner (7) is branched into two directed-away branches (18, 19) in the immediate connection to the sprue (10), to which branches at least one directed-back branch (20) is connected.
9. Casting mould according to any one of the preceding claims, characterised in that the branches (18, 19, 20) of the runner (7) are arranged in a plane (H2).
10. Casting mould according to any one of the preceding claims, characterised in that the casting mould is composed as a core stack of a plurality of cores (2, 3, 4), of which certain cores (2, 3, 4) form the outer shape and other cores (4) form recesses, cavities, channels and the like in the casting to be produced.
11. Casting mould according to any one of the preceding claims, characterised in that the connection (9a, 9b) leading from the feeder system (8) or from the runner (7) to the mould cavity (5) is guided only outside of the volume of the casting mould (1) occupied by the mould cavity (5).
12. Casting mould according to claim 11, characterised in that, in the case of a plurality of connections (9a, 9b), the inlet openings of the connections (9a, 9b) assigned to the feeder system (8) are arranged together in a plane (H3).
13. Casting mould according to any one of claims 10 to 12, characterised in that at least the casting cores (4) surrounding the connections (9a, 9b) at least in sections are held in an outer shell (2, 3) of the casting mould (1).
14. Casting mould according to claim 13, characterised in that the outer shell (2, 3) is designed as a permanent mould part, which is preserved after demoulding the casting (Z), whereas the casting cores (4), which are destroyed as lost casting mould parts during demoulding, are made of a moulding material based on casting sand.
15. Use of a casting mould (1) designed according to any one of the preceding claims for casting a cylinder crankcase (Z) for a combustion engine from a light metal melt.

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