Casting mould for casting complex-shaped castings and use of such a casting mould

Abstract

A casting mould for casting complex-shaped castings from a molten metal. The casting mould has a mould cavity forming the casting and a delivery system that delivers molten metal into the mould cavity. The delivery system includes a sprue, a runner connected to the sprue and a feeder system connected to the runner. The mould cavity is connected to the feeder system or the runner via connections. When seen in the flow direction of the molten metal flowing from the sprue into the runner during the casting operation, the runner has a branch directed away from the sprue along the feeder system and has a directed-back branch adjoining the directed-away branch and guided along the feeder system in the opposite direction to the directed-away branch. The feeder system is connected to both the directed-away branch and the directed-back branch via two or more gates distributed along the respective branch.

Claims

1. A casting mould for casting a complex-shaped casting from a molten metal, the casting mould comprising: a mould cavity forming the casting; and a delivery system for delivery of the molten metal, which is to be cast into the casting, into the mould cavity, wherein the delivery system comprises a sprue, a runner connected to the sprue and a feeder system connected to the runner, and the mould cavity is connected to the feeder system and/or the runner via connections, wherein when seen in a flow direction of the molten metal flowing from the sprue into the runner during a casting operation, the runner has a directed-away branch directed away from the sprue along the feeder system and has a directed-back branch adjoining the directed-away branch, the directed-back branch guided along the feeder system in an opposite direction to the directed-away branch, and the feeder system is connected to both the directed-away branch and the directed-back branch via two or more gates distributed along a respective branch.

2. The casting mould according to claim 1, wherein a number of gates assigned to the directed-away branch is equal to a number of gates assigned to the directed-back branch.

3. The casting mould according to claim 1, wherein one of the gates, via which the directed-back branch is connected to the feeder system, is arranged opposite to a corresponding gate, via which the directed-away branch of the runner is connected to the feeder system.

4. The casting mould according to claim 1, wherein a size of the gates assigned to the directed-away branch is the same size as the gates assigned to the directed-back branch.

5. The casting mould according to claim 1, wherein the feeder system comprises at least one feeder chamber, which is connected via respectively at least one gate to both the directed-away branch and the directed-back branch of the runner.

6. The casting mould according to claim 5, wherein the feeder system comprises more than one feeder chamber, and the feeder chambers are connected to one another via a gate.

7. The casting mould according to claim 6, wherein the feeder system comprises at least two adjacent feeder chambers, and either the directed-away branch is arranged in an intermediate space between the feeder chambers and along a side of each of the feeder chambers runs a directed-back branch branching off from the directed-away branch, said side being outwardly disposed with respect to the intermediate space, or the runner is divided into two directed-away branches, one of which runs respectively along a side of the feeder chambers, said side being outwardly disposed with respect to the intermediate space, and at least one directed-back branch connected to the directed-away branches runs in an intermediate space between the feeder chambers.

8. The casting mould according to claim 7, wherein the runner is branched into two directed-away branches adjacent a connection to the sprue, and at least one directed-back branch is connected to the directed-away branches.

9. The casting mould according to claim 1, wherein the branches of the runner are arranged in a plane.

10. The casting mould according to claim 1, wherein the casting mould is composed as a core stack of a plurality of cores, of which certain cores form an outer shape and other cores form recesses, cavities, and/or channels in the casting to be produced.

11. The casting mould according to claim 10, wherein at least the casting cores surrounding the connections at least in sections are held in an outer shell of the casting mould.

12. The casting mould according to claim 11, wherein the outer shell is designed as a permanent mould part, which is preserved after demoulding the casting, and the casting cores, which are destroyed as lost casting mould parts during demoulding, are made of a moulding material based on casting sand.

13. The casting mould according to claim 1, wherein at least one connection leading from the feeder system and/or from the runner to the mould cavity is only guided outside of a volume of the casting mould occupied by the mould cavity.

14. The casting mould according to claim 13, wherein a plurality of connections, leading from the feeder system are provided, and inlet openings of the connections are arranged together in a plane.

15. The casting mould according to claim 1, wherein the directed-back branch has a first end connected to the directed-away branch and a second end connected only to the feeder system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will subsequently be explained in more detail with reference to a drawing depicting exemplary embodiments. The figures thereof show schematically and not to scale:

(2) FIG. 1 a casting mould for casting a cylinder crankcase for an internal combustion engine in a cross-section;

(3) FIG. 2 a cylinder crankcase which has been cast in the casting mould 1 after demoulding in the un-cleaned state, in a view from above;

(4) FIG. 3 the cylinder crankcase according to FIG. 2 in a frontal view of its one end face;

(5) FIG. 4 the cylinder crankcase according to FIGS. 2 and 3 in a side view.

(6) FIG. 5 a further casting mould for casting a cylinder crankcase for an internal combustion engine in a cross-section;

(7) FIGS. 6-9 the casting mould according to FIG. 5 during the filling with melt;

(8) FIG. 10 the casting mould according to FIG. 5 in the post-filling position rotated for solidification.

DESCRIPTION OF THE INVENTION

(9) The casting mould 1 shown in FIG. 1 is used for casting the cylinder crankcase Z shown in FIGS. 2-4, often also called cylinder blocks, for an internal combustion engine made of an AlCu alloy.

(10) FIG. 1 shows schematically a section transverse to the longitudinal extension of the cylinder crankcase Z.

(11) The casting mould 1 designed as a core stack comprises two outer shells 2,3 formed as permanent mould parts, between which are arranged a larger number of lost casting cores 4 formed in the conventional manner from moulding sand. The outer shells 2, 3 and the casting cores 4 surround a mould cavity 5, which forms the cylinder crankcase Z to be cast with its four cylinder openings ZÖ arranged in a row and the design features usually provided for such internal combustion engine cylinder crankcases.

(12) Furthermore, the casting cores 4 surround a sprue, not visible in FIG. 1, leading downwards perpendicularly from the side 6 of the casting mould 1 arranged at the top in FIG. 1, a runner 7 connected to the sprue, a feeder system 8 connected to the runner 7 and the casting cavity 5, as well as connections 9a, 9b provided for connecting the mould cavity 5 to the runner 7 or the feeder system 8.

(13) The casting mould 1 is shown in FIG. 1 in the position shown for filling with melt, in which the opening of the sprue faces up and the feeder system 8 is arranged at the bottom of the casting mould 1.

(14) After filling the melt, the casting mould 1 is closed in a conventional manner and is rotated, for example, 180° in a known manner, about a pivot axis aligned parallel to the longitudinal extension of the casting mould 1, until the feeder system 8 is arranged above. In this way, a uniform solidification of the melt filled into the casting mould 1 is favoured, which solidification takes place in the direction of the feeder system 8.

(15) During solidification, not only does the cylinder crankcase Z to be produced form as a solid cast body, but after demoulding, these originally hollow mould elements of the casting mould 1 are formed contiguous with the cylinder crankcase Z as a consequence of the melt solidifying in the sprue 10, in the runner 7, in the feeder system 8 and in the connections 9a, 9b.

(16) During cleaning following demoulding, the relevant mould elements are separated from the cylinder crankcase Z in a conventional manner, and sent for recycling.

(17) The special features of a casting mould 1 according to the invention can thus be illustrated most simply on the demoulded and not-yet-cleaned cylinder crankcase Z, as shown in FIGS. 2-4.

(18) The feeder system 8 accordingly comprises two rows arranged side by side and extending in the longitudinal direction L of the cylinder crankcase Z, each having five pot-type feeder chambers 11, 12. Adjacent feeder chambers 11, 12 of each row are connected by gates 13, 14. The rows of feeder chambers 11, 12 delimit a gap 15 between them.

(19) The feeder chambers 11, 12 are arranged above the top surface ZD of the cylinder crankcase Z provided for mounting a cylinder head (not shown here) and have identical shapes and volumes. The bases of the feeder 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.

(20) The runner 7 is also arranged in a horizontal plane H2, aligned parallel to the top surface ZD, in which the top of the feeder chambers 11, 12 also ends.

(21) Starting from the head 17 of the sprue 10 shown on the demoulded cylinder crankcase Z as a sprue rod running slightly conical in the direction of the runner 7, the runner 7 is divided into two branches 18, 19, said branches 18, 19 being directed away from the sprue 10, seen in the flow direction S of the melt filled into the casting mould 1 during the casting operation.

(22) The branches 18, 19 directed away from the sprue 10, mirror-symmetrically formed with respect to the longitudinal axis L of the cylinder crankcase Z when viewed in plan view (FIG. 2), first emanate respectively from the sprue head 17 transverse to the longitudinal axis L, in order then to transition in a curve and via a filter F in each case into a section which extends at a small distance along the outer side of the respective row of the feeder chambers 11, 12, said side facing away from the intermediate space 15.

(23) At the end of the respective row of feeder chambers 11, 12, seen in the flow direction S, the directed-away branches 18, 19 transition in a further curve into a section oriented opposite the other directed-away branches 19, 18, which section extends over the width of the respective row of feeder chambers 11, 12.

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

(25) The directed-back branch 20 is arranged centrally in the intermediate space 15 between the rows of feeder chambers 11, 12 and runs towards the sprue 10 opposite to the branches 18, 19 directed away from the sprue 10, viewed in the flow direction S. However, the directed-back branch 20 terminates in front of the sprue head 17, so that in the casting operation, melt enters into the directed-back branch 20 exclusively via the directed-away branches 18, 19.

(26) Each of the feeder chambers 11 arranged at equal intervals along the longitudinal axis L is connected to the directed-away branch 18 via a respective gate 21 and each of the feeder chambers 12 also arranged at equal intervals in the longitudinal direction L is connected to the directed-away branch 19 via a respective gate 22. Similarly, each of the feeder chambers 11 is connected to the directed-back branch 20 via a respective gate 23 and each of the feeder chambers 12 is connected to the directed-back branch 20 via a respective gate 24. The gates 21-24 are also distributed at equal intervals along the longitudinal axis L, wherein the gates 21, 22; 23, 24 respectively assigned to each feeder chamber 11, 12 are positioned opposite to each other and centrally relative to the respective wall of the feeder chambers 11, 12.

(27) The mould cavity 5 is connected via connections 9a, 9b directly to the runner 7 (connection 9a) or the feeder chambers 11, 12 (connections 9b). The connections 9a, 9b are respectively exclusively formed outside the mould cavity 5, so that no melt passes into the mould cavity 5 via casting cores 4 placed in the mould cavity 5. According to the principle of communicating vessels, the melt has a level, and consequently a part of the melt also reaches the mould cavity 5 via the feeder chambers 11, 12. The solidification in the component then takes place very quickly via the thin walls and the feeding is achieved only via the locally large volume in direct proximity to the feed supply. The mouth of the connections 9b connected to the feeder chambers 11, 12 is in this case arranged on a common horizontal plane H3, so that in each case melt which has an equal temperature passes from the feeder chambers 11, 12 into the connections 9b connected to them. The supply of the melt to the mould cavity 5, however, can extend over a height range or be distributed over several planes.

(28) With regard to the filling or the solidification behaviour of particularly critical regions of the mould cavity 5, it is possible to selectively supply melt through a dedicated connection 9b in order to feed the respective problem location directly.

(29) The casting mould 31 shown in FIG. 5, which is constructed entirely as a core stack of lost cores, is also provided for casting a cylinder block for an internal combustion engine. The mould 31 comprises a cover core 32, an outer core 33 bearing the cover core 32, a further outer core 34 bearing the outer core 33, two outer shell cores 35, 36 forming the outer end of the casting mould 31 in the region of the mould cavity of the casting mould 31, on which the outer cores 33, 34 and the cover core 32 are supported, a contouring core 37 forming the contour of the interior of the casting, which contouring core 37 forms the lower end of the casting mould and on which the shell cores 35, 36 are supported, and cores 38, 39 arranged within the space laterally bounded by the shell cores 35, 36, which cores 38, 39 determine the outer contour of the casting.

(30) Branches 40, 41 running on the outside, directed away from the sprue (not shown here), are moulded into the cover core 32, as is a centrally arranged directed-back branch 42 of the runner. In the intermediate space between the directed-away branch 40, 41 respectively arranged outside, and the directed-back branch 42, a feeder pot 43, 44 is respectively moulded into the cover core 32 and the outer cores 33, 34. The feeder pots 43, 44 accordingly sit directly on the top surface of the casting (e.g. sealing surface for an oil sump or cylinder head). The feeder pots 43, 44 thus feed all regions located in direct local proximity to them, such as the cylinder head screw pipes. The directed-away branches 40, 41 are connected via connections, which are arranged close to the outer core 33, to the respectively assigned feeder pot 43, 44, whereas the directed-back branch 42 is connected via connections to the feeder pots 43, 44, which are offset towards the top of the cover core 32.

(31) The shell cores 35, 36 and the respectively assigned cores 38, 39 that determine the outer contour of the casting also additionally delimit respectively external feed volumes 45, 46, which are connected to one of the feeder pots 43, 44 via one inlet 47, 48 in each case. The external feed 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 feed volumes 45, 46 feed everything in their immediate vicinity, e.g. mass accumulations through functional integration.

(32) While the feeder pots 43, 44 are always in the same plane in the casting mould 31 intended for casting cylinder crankcases ZK, the external feed volumes 45, 46 are at different levels.

(33) For filling with melt, the casting mould 31 is rotated for example by 180° about a pivot axis transverse to the longitudinal extension of the cylinder crankcase ZK to be cast, so that the cover core 32 is located with the directed-away branches 40, 41 and the directed-back branch 42 at the bottom. Hot melt M is directed into the directed-away branches 40, 41 via the sprue. From the directed-away branches 40, 41, the melt M cooled on the way through the directed-away branches 40, 41 enters into the directed-back branch 42 and into the feeder pots 43, 44 (FIG. 6).

(34) As the directed-away branches 40, 41 become more full, hot melt M also passes via the corresponding connections of the directed-away branches 40, 41 into the feeder pots 43, 44, so that in the feeder pots 43, 44 hot melt M and cooled melt M mix and in the feeder pots 43, 44 melt M is present which has a homogeneously distributed mix temperature (FIG. 7).

(35) The melt M, which has an appropriate temperature, rises on the one hand via the inlets 47, 48 into the external feed volumes 45, 46 and on the other hand via the gates into the casting mould cavity (FIG. 8), via which gates the feeder pots 43, 44 are connected directly to the casting mould cavity forming the casting.

(36) After complete filling (FIG. 9), the casting mould 31 is closed in a conventional manner and rotated through 180° transverse to its longitudinal extension into the solidification position (FIG. 10).

(37) In the embodiments of a casting mould according to the invention described here, the melt is thus filled via at least one sprue into the casting mould. The melt is then divided into two separate branches directed away from the sprue, which, given a corresponding basic shape of the feeder system, are preferably aligned so that they are parallel at least in sections. The melt, which is divided into the directed-away branches of the runner, is returned to the pot-like feeder chambers via a diversion. In this case, in the region of the diversion, a curve can be provided which leads out of the main plane, in which the runner is mainly located, in order to decelerate the flow velocity of the melt flowing through the respective directed-away branch. The section of the respective branch adjoining the relevant curve then lies again in the main plane of the runner. In connection to the directed-away branches, the melt is led further into at least one central directed-back runner branch. Of course, it is also possible to connect to each directed-away branch of the runner a dedicated directed-back branch also extending in the intermediate space between the rows of feeder chambers.

(38) Early separation of the runner system and delivery of the melt to multiple feeder volumes provided by the feeder chambers results in optimised filling conditions. Thus, the embodiment according to the invention guarantees a rapid, uniform inflow of the molten metal and, consequently, 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 chosen so as to enable optimal mixing of the melt entering the chambers. For this purpose, it may for example also be useful not to connect all the feeder chambers directly to the runner as in the exemplary embodiment described here, but to connect individual feeder chambers only to the immediately adjacent feeder chamber, which is then connected to the runner. To support the mixing and the temperature equalisation, the feeder chambers are connected to each other 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 respective casting task. Due to the fact that the feeder system is arranged during the solidification above the mould cavity, a solidification is achieved in the direction of the feeder system. That is, the component cools and solidifies starting from the location farthest away from the feeder system, whereas the melt contained in the feeder system and finally filled into the mould remains hot for a longer time. If the casting mould is gravity-cast without rotation, i.e. filled with an overhead feeder system, then the mould cavity forming the casting is filled first and the feeder system is filled last.

(39) Easy removal of the feeder system, the runner, the sprue and the connections can be supported by the fact that the connections are connected to the component contour over a small area. The connection points preferably go onto existing slugs and sit on surfaces which are part of the standard post-processing. The feeder system can be easily removed, e.g. by means of bores, during pre-processing and post-processing of the component obtained (cylinder crankcase Z).

REFERENCE SIGNS

(40) 1 casting mould 2, 3 outer shells 4 casting cores 5 mould cavity 6 side of the casting mould 1 7 runner 8 feeder system 9a, 9b connections 10 sprue 11, 12 feeder chambers 13, 14 gates 15 intermediate space delimited by feeder chambers 11, 12 17 sprue head 18, 19 directed-away branches of the runner 7 30 directed-back branch of the runner 7 21-24 gates 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 casting mould 32 cover core 33, 34 outer cores 35, 36 outer shell cores 37 core determining the inner contour of the casting ZK 38, 39 cores that determine the outer contour of the casting 40, 41 directed-away branches of the runner running on the outside 42 centrally arranged directed-back branch of the runner 43, 44 feeder pots 45, 46 external feed volumes 47, 48 feeds ZK cylinder crankcase (casting) M melt