Die-casting tool and die-casting method for producing a raw cast wheel

Abstract

The invention relates to a die-casting tool for manufacturing a raw cast wheel (1), in which the mold is filled by means of a central sprue in a filling direction from a wheel hub (3) via spokes (7) radially outwards to a front horn (9) and from there axially via a rim bed (11) to a rear horn (13). According to the invention, the die-casting tool has at least one, and in particular a number, of secondary compactors (37, 39) distributed in the circumferential direction of the wheel in the region of the rear horn (13), which compact the casting material (42) in the region of the rear horn (13) during the casting process.

Description

[0001] The invention relates to a die-casting tool according to the preamble of claim 1 and a die-casting method according to the preamble of claim 10.

[0002] A raw cast wheel can be manufactured using a die-casting process. After production, the raw cast wheel is further processed into a vehicle wheel. In the die-casting process, the mold is filled via a central sprue, with the molten metal flowing radially outwards from the wheel hub, through the spokes, to a front rim, and then axially across a rim well to a rear rim. The advantage of die-casting lies in the ability to cast thin walls with very close contours. This minimizes material usage, conserves resources, and reduces manufacturing effort by requiring less machining of the raw cast wheel. Ideally, in die-casting, the molten metal should flow from thicker to thinner wall thicknesses. In this case, the molten metal accelerates progressively, thus preventing casting defects such as pre-solidification, solidification shrinkage cavities, and porosity.

[0003] The following problem arises during the die casting of a raw cast wheel: During the filling process, the flow front moves from the thin-walled rim bed to the thick-walled rear rim. With this flow direction from the thin-walled rim bed to the thick-walled rear rim, solidification cavities form in the rear rim. A holding pressure phase carried out during the casting process cannot have an effect in the thick-walled rear rim because the molten metal in the thin-walled rim bed has already solidified, and therefore compaction in the rear rim area is no longer possible. For this reason, it is not possible with current technology to produce a porosity-free vehicle wheel in the rear rim area.

[0004] DE 10 2020 100 702 A1 discloses a generic method for manufacturing an aluminum rim for a motor vehicle wheel. DE 10 2016 104 019 B3 discloses a device for manufacturing a casting, in particular a wheel rim, by means of a die-casting process. The device has a lower base plate, an upper vertically movable plate, and four horizontally movable side parts or side slides. DE 10 2017 125 634 A1 discloses a casting device for manufacturing a light alloy rim. The casting device has a base plate, a punch, and side slides. During a casting process, post-compaction is carried out via the punch to prevent blowholes. US 2016 368 043 A1 discloses a device for die-casting a wheel. The device has a tool with a lower part, an upper part, and four side parts.

[0005] The object of the invention is to provide a die-casting tool and a die-casting process for producing a raw cast wheel in which, compared to the prior art, solidification cavities in the raw cast wheel can be avoided in a simple manner.

[0006] The problem is solved by the features of claim 1 or 10. Preferred embodiments of the invention are disclosed in the dependent claims.

[0007] The invention relates to a die-casting tool for producing a raw cast wheel. In the die-casting process, the mold is filled via a central sprue with a filling direction from a wheel hub, radially outwards through spokes to a front rim, and from there axially via a rim bed to a rear rim. According to the characterizing part of claim 1, solidification cavities in the raw cast wheel are avoided as follows: The die-casting tool has a number of secondary compactors distributed in the circumferential direction of the wheel in the area of ​​the rear rim. These compactors can locally compress the casting material in the area of ​​the rear rim during the casting process. Through this local compression, the still unsolidified casting material in the rear rim cavity is displaced along a flow path in the circumferential direction of the wheel. This results in the casting material being distributed evenly and without cavities in the circumferential direction of the wheel.

[0008] In a technical implementation, the recompressor can be a recompressor piston. During a recompression phase in the casting process, the recompressor piston can extend in a recompressor stroke into a displacement chamber of a rear horn partial cavity of the die-casting tool, creating local pressure.

[0009] Preferably, a number of secondary compressors are positioned evenly distributed around the circumference of the wheel. The secondary compressors comprise a group of radial secondary compressors and a group of axial secondary compressors. The radial secondary compressors are arranged radially outside the rear horn partial cavity of the die-casting tool. In this case, the radial secondary compressors can act on the rear horn partial cavity via a radial secondary compressor piston stroke. In contrast, the axial secondary compressors are arranged axially adjacent to the rear horn partial cavity of the die-casting tool, that is, preferably at right angles to the radial secondary compressors. The axial secondary compressors can act on the rear horn partial cavity of the die-casting tool via an axial secondary compressor piston stroke.Due to the different points of attack of the axial and radial after-compressors, a void-free material condition in the area of ​​the rear horn can be ensured in a process-technically advantageous manner.

[0010] For this purpose, it is preferred if the axial and radial secondary compressors are arranged alternately in series in the circumferential direction of the wheel and offset from each other by pitch intervals. For example, at least one secondary compressor of the second group (for example, an axial secondary compressor) can be arranged centrally between two adjacent secondary compressors (for example, radial secondary compressors).

[0011] In one specific design variant, the rear horn, with its outer flank, forms the rear of the wheel, while its inner flank, together with the rim bed, creates an inner corner area. In this case, the radial compression element can act directly on the inner corner area between the inner flank of the rear horn and the rim bed. Conversely, the axial compression element can act on the outer flank of the rear horn.

[0012] The casting process according to the invention can be divided into the following casting phases: In a build-up phase, a casting piston in the gating area of ​​the die-casting tool is first moved by one build-up stroke to fill the gating channel of the die-casting tool with casting material. After the build-up phase, a mold-filling phase takes place. In the mold-filling phase, the casting piston of the die-casting tool is moved by one filling stroke so that the cavity of the die-casting tool can be filled with liquid casting material. The filling process can be completed in a few milliseconds. After the filling process, a holding-pressure phase begins, in which the casting piston is moved by one holding-pressure stroke so that the casting material in the cavity, which has not yet solidified, is compacted to prevent solidification shrinkage cavities. The holding-pressure phase cannot take effect in the thick-walled rear horn, as the melt has already solidified in the area of ​​the thin-walled rim bed.Against this background, the casting process according to the invention includes a post-compaction phase. In the post-compaction phase, post-compactors are used to compact the casting material, which has not yet solidified, located in the rear horn partial cavity. The post-compaction phase can be carried out simultaneously with the holding pressure phase or with a time delay.

[0013] The die-casting process according to the invention can preferably be carried out using a three-plate die-casting tool. This tool consists of a fixed mold half, a movable mold half, and an intermediate floating mold half. The fixed mold half and the floating mold half form a central gating area through which the molten metal is poured into the cavity. The cavity is formed between the floating mold half and the movable mold half.

[0014] The movable mold half is divided into a base body and radially outer slides. The base body of the movable mold half has a rotationally symmetrical, radially inner mold surface that defines the cavity from the inside. In contrast, the radially outer slides together form a rotationally symmetrical, radially outer mold surface that defines the cavity from the outside. The secondary compressors are integrated into the mold halves in a space-saving manner as follows: the radial secondary compressors can be guided in the radially outer slides with adjustable stroke. The axial secondary compressors, on the other hand, can be guided in the base body of the movable mold half with adjustable stroke.

[0015] An embodiment of the invention is described below with reference to the accompanying figures.

[0016] They show: Figures 1 to 7 show different views, which describe the structure of the die-casting tool and the die-casting process.

[0017] In the Figure 1 Figure 1 shows a raw cast wheel 1 produced in a die-casting process according to the invention, which was manufactured in the die-casting tool described with reference to the following figures. The raw cast wheel 1 has a central hub 3, which is closed by a hub cap 5. Spokes 7 are formed on the central wheel hub 3, which terminate radially on the outside at a front rim 9. The front rim 9 transitions axially into a thin-walled rim bed 11, which extends to a thick-walled rear rim 13.

[0018] The raw cast wheel 1 has on a rear horn outer flank 15 forming the rear side of the wheel ( Figure 2) an axially projecting, sleeve-shaped material dome 19. Similarly, another radially outwardly projecting, sleeve-shaped material dome 17 is formed at the inner corner area between the inner flank 14 of the rear horn and the rim bed 11. The material domes 17, 19 were produced during a post-casting process according to the invention. In a post-processing step (not shown), both the material domes 17, 19 and the hub cap 5 are removed from the raw cast wheel 1.

[0019] The die-casting tool for producing the raw cast wheel 1 is in the Figure 3with a closed mold cavity 20, indicated to the extent necessary for understanding the invention. Accordingly, the die-casting tool is realized as a three-plate die-casting tool, consisting of a fixed mold half 21, a movable mold half 23, and a floating mold half 25 arranged axially between them. The fixed mold half 21 and the floating mold half 25 form a gating area with a vertical sprue 27, a horizontal sprue 28, and a filling chamber 29. This chamber is bounded by a horizontally adjustable injection piston 31. The horizontal sprue 28 opens into the mold cavity 20. This cavity is located in the Figure 2 formed between the floating mold half 25 and the movable mold half 23.

[0020] In the Figure 3The movable mold half 23 is divided into a base body 33 and a total of four radially outer slides 35, two of which are shown opposite each other. The base body 33 of the movable mold half 23 forms a rotationally symmetrical, radially inner mold surface that bounds the cavity 20 from the inside. In contrast, the radially outer slides 35 together form a rotationally symmetrical, radially outer mold surface that bounds the cavity 20 from the outside.

[0021] A key aspect of the invention is that recompressor pistons 37, 39 are guided in a stroke-adjustable manner both in the slides 35 and in the base body 33 of the movable mold half 23. The recompressor pistons 37, 29 are grouped into radial recompressor pistons 39 and axial recompressor pistons 37. The radial recompressor pistons 39 are in the Figure 3The radial compression pistons 39 are guided in the slides 35 with adjustable stroke, while the axial compression pistons 37 are guided in the base body 33 with adjustable stroke. The radial compression pistons 39 can be moved into a displacement chamber 41 during the casting process ( Figure 4 ) of the rear horn partial cavity, under local pressure build-up. Accordingly, during the casting process, the axial post-compressor pistons 37 can enter a displacement chamber 43 ( Figure 4 ) of the posterior horn partial cavity under local pressure build-up. This creates the cells in the Figure 1 or 2 shown sleeve-like material domes 17, 19. By means of the adjusting movement of the secondary compressor pistons 37, 39, a local pressure build-up occurs in the rear horn partial cavity. The local pressure build-up causes the still unsolidified casting material 42 ( Figure 5 or 6) in the rear horn partial cavity via flow paths in the circumferential direction of the wheel, so that the casting material 42 is distributed evenly and without voids in the circumferential direction of the wheel.

[0022] The axial and radial secondary compressor pistons 37, 39 are each arranged in a series in the circumferential direction, spaced apart from one another by pitch intervals. For example, the axial secondary compressors 39 and the radial secondary compressors 37 can be arranged alternately one behind the other in the circumferential direction. In this way, at least one radial secondary compressor 39 can be positioned between two adjacent axial secondary compressors 37.

[0023] The following describes an example of a casting process for producing the raw cast wheel 1 shown in Figure 1. Accordingly, the casting process according to the invention is divided into the following four casting phases: In a build-up phase, the casting piston 31 is moved via a build-up stroke, whereby the liquid casting material 42 enters the vertical sprue 27 ( Figure 3 ) rises to an upper edge at the transition to the horizontal sprue 28. This is followed by a mold-filling phase in which the casting piston 31 is further adjusted via a mold-filling stroke to fill the cavity 20 with the liquid casting material 42. Subsequently, a holding-pressure phase is initiated in which the casting piston 31 is adjusted by a holding-pressure stroke to compensate for solidification shrinkage in the cavity 20.

[0024] However, the indentation phase does not act in the rear horn partial cavity, since in the area of ​​the thin-walled rim bed 11 there is already solidified casting material 44 ( Figure 5 or 6) is formed. To ensure compaction also occurs in the rear horn partial cavity, the post-compression phase according to the invention is carried out. In the post-compression phase, the axial and radial post-compressor pistons 37, 39 move into the displacement spaces 41, 43 of the rear horn partial cavity of the die-casting tool under local pressure build-up (Figure 6). This ensures that the raw cast wheel 1 is also produced without porosity in the rear horn area.

[0025] In the Figure 7An example of a raw cast wheel 1 is shown in a perspective view from the rear. Accordingly, a total of sixteen axially projecting material domes 19 are formed on the outer flank 15 of the rear horn, while a total of eight radially projecting material domes 17 are formed in the inner corner area between the inner flank 14 of the rear horn and the rim bed 11. With such a distribution of material domes 17, 19, the die-casting tool must have a total of sixteen axial recompressor pistons 37 and eight radial recompressor pistons 39. Two pairs of axial recompressor pistons 37 are positioned between each pair of adjacent radial recompressor pistons 39, as can be seen from the material dome arrangement of the Figure 7 This is evident. Therefore, each of the four slide valves 35 can contain two radial after-compressor pistons 39. REFERENCE MARK LIST:

[0026] 1 Raw cast wheel 3 Hub 5 Hub cap 7 Spokes 9 Front horn 11 Rim bed 13 Rear horn 14 Rear horn inner flank 15 Rear horn outer flank 17 Sleeve-shaped material dome 19 Sleeve-shaped material dome 20 Cavity 21 Fixed mold half 23 Moving mold half 25 Floating mold half 27 Vertical sprue 28 Horizontal sprue 29 Filling chamber 31 Piston 33 Base body 35 Slide 37 Axial recompressor piston 39 Radial recompressor piston 41 Displacement chamber 42 Liquid casting material or melt 43 Displacement chamber 44 Solidified casting material

Claims

1. Pressure die-casting tool for producing a raw cast wheel (1) in which a mold is filled by means of a central sprue in a filling direction from a wheel hub (3) via spokes (7) radially outwards to a front flange (9) and from there axially via a rim base (11) to a rear flange (13), wherein in order to avoid solidification cavities the pressure die-casting tool has in the region of the rear flange (13) a number of booster compressors (37, 39) which are distributed in the circumferential wheel direction and which during the casting process compress the casting material (42) in the region of the rear flange (13), and in that the number of booster compressors has a group of radial booster compressors (39) and a group of axial booster compressors (37).

2. Pressure die-casting tool according to claim 1, characterized in that each of the booster compressors (37, 39) is a booster compressor piston and in that the booster compressor piston (37, 39) during a booster compression phase which takes place in the casting process moves into a compression space (41, 43) of a rear flange part-cavity of the pressure die-casting tool with local pressure build-up in the melt (42) which is located in the rear flange part-cavity.

3. Pressure die-casting tool according to claim 2, characterized in that the group of radial booster compressors (39) is arranged radially outside the rear flange part-cavity of the pressure die-casting tool, and in that the radial booster compressors (39) act with a radial booster compressor piston stroke on the rear flange part-cavity, and in that the group of axial booster compressors (37) is arranged axially beside the rear flange part-cavity of the pressure die-casting tool, that is to say at right-angles with respect to the radial booster compressors (37), and in that the axial booster compressors (39) act with an axial booster compressor piston stroke on the rear flange part-cavity of the pressure die-casting tool.

4. Pressure die-casting tool according to claim 3, characterized in that the axial booster compressors (37) and the radial booster compressors (39) are arranged in series alternating one behind the other in the circumferential wheel direction and are offset from each other by means of division spacings so that at least one booster compressor (39) of the second group is arranged centrally between two adjacent booster compressors (37) of the first group.

5. Pressure die-casting tool according to claim 4 or 5, characterized in that the rear flange (13) forms with its outer flank (15) a wheel rear side and defines with its inner flank (14), together with the rim base (11) an inner corner region, and in that the radial booster compressor (39) acts on the inner corner region between the rear flange inner flank (17) and rim base (11), and in that the axial booster compressor (37) acts on the rear flange outer flank (15).

6. Pressure die-casting tool according to any one of the preceding claims, characterized in that the casting process has a mold filling phase in which a casting piston (31) in the sprue region of the pressure die-casting tool can be adjusted by a filling stroke in order to fill the cavity (20) of the pressure die-casting tool completely with liquid casting material (42), and in that the casting process has a holding pressure phase in which the casting piston (31) is adjusted by a holding pressure stroke in order to compact the casting material which is located in the cavity and which has not yet solidified, and in that the redensification phase is carried out at the same time as the holding pressure phase or with a time delay with respect to the holding pressure phase.

7. Pressure die-casting tool according to any one of the preceding claims, characterized in that the pressure die-casting tool is a three-plate pressure die-casting tool which is formed from a fixed mold half (21) and a movable mold half (23) and a floating mold half (25) which is arranged therebetween, and in that the fixed mold half (21) and the floating mold half (25) form a sprue region via which the liquid casting material (42) is poured into the cavity (20), and in that the cavity (20) is formed between the floating mold half (25) and the movable mold half (23).

8. Pressure die-casting tool according to claim 7, characterized in that the movable mold half (23) is sub-divided into a base body (33) which has a rotationally symmetrical, radially inner mold face which delimits the cavity (20) internally, and in particular four radially outer sliding members (35) which together form a rotationally symmetrical, radially outer mold face which delimits the cavity (20) externally.

9. Pressure die-casting tool according to claim 8, characterized in that the radial booster compressors (39) are guided so as to be able to be adjusted in terms of stroke in the radially outer sliding members (35), in particular two radial booster compressors (39) per sliding member (35), and / or in that the axial booster compressors (37) are guided so as to be able to be adjusted in terms of stroke in the base body (33) of the movable mold half (23).

10. Method for producing a raw cast wheel (1) in a pressure die-casting tool according to any one of the preceding claims, in which a mold is filled by means of a central sprue in a filling direction from a wheel hub (3) via spokes (7) radially outwards to a front flange (9) and from there axially via a rim base (11) to a rear flange (13), wherein in order to avoid solidification cavities the pressure die-casting tool has in the region of the rear flange (13) a number of booster compressors (37, 39) which are distributed in the circumferential wheel direction and which during the casting process compress the casting material (42) in the region of the rear flange (13), and in that the number of booster compressors has a group of radial booster compressors (39) and a group of axial booster compressors (37).

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