EP2646183B1 - Process for producing a cast wheel and casting mould - Google Patents

Description

The invention relates to a method for producing a cast wheel, wherein a core remaining in the casting wheel, which has a circumferential rim, is inserted into a casting tool having at least one lower mold part and one upper mold part, which are moved relative to each other for closing the casting mold, wherein the Core is positioned by means of at least one positioning element in a predetermined position in the casting mold, wherein an end portion of the positioning is frictionally locked in the circumferential ring of the core.

The invention further relates to a casting tool for producing a cast workpiece, in particular a cast wheel, with at least one lower molded part and one upper molded part, which are movable relative to each other for closing the casting tool.

From the AT 409 728 B For example, there is known a method for producing a wheel-cast rim, in which a preformed metal foam core part is inserted into a casting tool which has a mold top part, a mold bottom part and lateral core slides. The core part is fixed in position using positioning elements and then cast in a light metal. For discharging gases which escape during the casting over of the core part, the casting tool or the positioning element has a ventilation opening. The remaining in the casting wheel positioning are fixed to the core. For centering the core part in the casting tool, the positioning elements with the movable mold upper part enter into a self-clamping connection. For this purpose, the positioning element has a conical lateral surface, which causes the self-clamping effect by abutment on a shoulder forming a cross-sectional constriction in the vent opening of the mold upper part. This technique has proven to be particularly useful to keep the core part with positioning in the predetermined position, when the positioning can be attached to ribs of the core member, which protrude from an annular outer part radially inwardly. In this embodiment, the projecting in the axial direction of the ribs positioning can be clamped in the appropriate vent opening of Kokillenoberteils. In many cases, however, it is not possible to provide such a connection. This is especially the case when the core member has no radially inwardly projecting ribs to which the positioning elements could be attached. Accordingly, it would be particularly desirable to enable accurate positioning of the core even when the core has no ribs projecting into the wheel spokes.

From the WO 99/39923 A1 Another casting wheel is known in which the core is held by means of positioning elements in the intended position.

The DE 10 2007 046 124 A1 discloses a different type of mold for producing cast wheels. In this case, plate-shaped hollow body made of thin-walled material are introduced into the spoke spaces as mold cores. The hollow body can be held by means of a circumferential Fixierstegs in corresponding Fixieraufnahmen of the moldings.

The DE 20 2006 114 075 U1 describes a different type of casting technique, in which massive, reusable mandrels are used to produce undercuts in a cast wheel.

The EP 1 792 674 A1 discloses a technique for casting a different type of casting, namely a motorcycle frame, wherein a core is positioned by cotter pins in the mold.

From the DE 42 01 278 A1 Furthermore, a casting mold for casting a hollow camshaft is known. For this purpose, a casting core is arranged in the casting mold, which has a free end. To support the free end of the casting core a support is provided. The support has on both sides of the casting core anchoring sections, which are anchored between the lower part and upper part of the mold. Thus, the support extends between opposite sides of the casting tool. However, this embodiment is intended or suitable only for casting different types of molded parts.

WO 2006/042350 A1 and EP 1 792 674 A1 disclose other types of positioning devices.

In contrast, the object of the present invention is to provide a method and a casting tool for producing a cast wheel with a coronary core of the type mentioned, which ensures an exact positioning of the core in the casting tool with the greatest possible freedom for the design of the core.

This is achieved in the method of the initially mentioned type in that a free end portion of the positioning, which protrudes from the circumferential rim of the core is placed when positioning the core in the casting mold on a preferably horizontally arranged in operation bearing surface of the lower mold part of the casting tool, such that the core is positioned in the predetermined position under the action of gravity.

For positioning the core in the casting tool, therefore, the positioning element is placed on the corresponding bearing surface of the lower molding of the casting tool. In this position, the core is positioned under the action of gravity without contact with the mold parts of the casting tool. The holder of the core is thus carried out in particular on the weight of the core, so that a stable support on the support surface is achieved. Accordingly, it is not necessary to provide a clamping connection between the positioning element and the associated molded part of the casting tool for centering the core. Appropriately, the positioning is placed on a respect to its operating position horizontally arranged bearing surface; However, depending on the design, it would also be conceivable to provide a bearing surface that is inclined relative to the horizontal, but it should be ensured that the core is held by gravity in a stable position relative to the molded parts of the casting tool.

For precise positioning of the core, it is advantageous if the positioning element is clamped when closing the casting tool between the support surface of the lower mold part and a corresponding contact surface of the upper mold part. In the production of the cast workpiece, the core is first placed on the support surface of the lower mold part before the mold parts are moved towards each other for closing the casting tool, wherein the positioning element between the corresponding contact surfaces of the casting tool is clamped. As a result, the core is secured against slipping during the casting process, so that the core is arranged with high accuracy in the desired position in the finished casting workpiece.

In order to position the core in the predetermined position in the casting tool, it is favorable if a pin-shaped, bow-shaped or plate-shaped end region of the positioning element projecting from the core is placed on the bearing surface of the lower molding. The other end region of the positioning element is preferably fixed in the core in a friction-locked and / or force-locking manner. The shape of the end region projecting from the core determines the contact surface with the bearing surface of the lower molding. In the case of a pin-shaped end region of the positioning element, a comparatively small contact surface is provided; In contrast, the contact between the positioning element and the support surface can be increased by means of the plate-shaped end region.

In a particularly preferred embodiment of the invention, provision is made for an end region of the positioning element projecting radially inwardly from a circumferential rim of the core to be placed on the bearing surface of the lower molding. When casting around the core with a light metal, a cast workpiece is formed, which encloses the particular circular encircling ring. This method is particularly useful for producing a cast wheel, in which the core is arranged substantially completely in a circumferential rim flange. For the formation of the cast wheel, it is particularly advantageous if the ring has in particular radially inwardly projecting pockets, which may optionally extend into the spokes of the cast wheel.

For exact positioning of the core in the casting tool, it is advantageous if a plurality of circumferentially spaced at the circumferential rim of the core fixed positioning are placed on corresponding bearing surfaces of the lower mold part. In order to support the core evenly on the lower molded part, it is particularly favorable if the positioning elements are arranged at substantially regular angular intervals are arranged on the encircling wreath. Of course, however, the positioning elements can be positioned at arbitrary locations, ie without a necessarily predetermined uniform division, at the core. When inserting the core into the casting tool, the positioning elements are placed on the matching bearing surfaces of the lower molding.

In order to avoid adverse effects by the remaining in the casting workpiece positioning, it is advantageous if a protruding from the finished cast workpiece end of the positioning removed, in particular cut or -rotated.

To avoid corrosion, which could occur in earlier methods at the exit points of the positioning, it is advantageous if the cast workpiece is painted or powdered at least in the region of the cut end of the positioning. In a preferred embodiment, the entire cast workpiece is finally painted to eliminate the risk of corrosion as much as possible.

When casting tool of the initially mentioned type, the object underlying the invention is achieved in that the lower mold part has a circular encircling elevation with a support surface on which a free end portion of a connected to a circumferential ring of a core positioning element can be placed so that the core can be positioned without contact with the moldings in the casting mold. Accordingly, the same advantages can be achieved with the casting tool according to the invention as with the described method, so that in order to avoid repetition reference is made to the above statements.

To produce a cast workpiece with a circular circumferential section, in particular for producing a cast wheel, it is expedient for the circular peripheral elevation to be formed as a section of boundary surfaces enclosing a cavity. The shape of the finished casting workpiece is defined by the cavity enclosed by the boundary surfaces established.

For stable positioning of the core in the predetermined position, it is advantageous if the support surface is arranged horizontally in operation. The arrangement of the support surface ensures that the core is held without contact at least to the lower mold part under the action of gravity. This can be achieved in principle by a tilted at a shallow angle bearing surface depending on the version.

In order to secure the core in the predetermined position against lateral slippage, it is advantageous if the upper mold part and / or the lower mold part have a groove. Preferably, the shape of the groove corresponds to the outer contour of the positioning element inserted in the groove, so that the positioning element does not laterally encase the core with a light metal can dodge.

In order to prevent the core during casting with a light metal undesirable shift in any direction in space, it is advantageous if the groove (s) of the upper and lower mold part is formed in a closed position of the casting tool such that the Kern projecting positioning in which or in the groove (s) is clamped. The trapped in the groove positioning can not escape from the predetermined position even under high load, so that the core is arranged with high precision in the desired position in the cast workpiece.

In order to form a cavity in the casting mold which images the shape of the finished casting workpiece, it is advantageous if sealing surfaces are provided between the upper and lower shaped parts, wherein the bearing surface is formed as a section of the sealing surface of the lower molded part. Accordingly, the sealing surface of the lower molding on the especially in operation horizontally arranged bearing surface, whereby the positioning of the core is considerably facilitated in the casting tool.

• Fig. 1 einen Querschnitt eines Ausschnitts eines Gießwerkzeugs, das einen von einem Leichtmetall umgossenen Kern aufnimmt;
• Fig. 2a eine Frontansicht des Kerns, wobei an einem umlaufenden Kranz bügelförmige Positionierelemente befestigt sind;
• Fig. 2b das in Fig. 2a mit einem Kreis veranschaulichte Detail in demgegenüber vergrößertem Maßstab;
• Fig. 3 eine Schnittansicht des Kerns gemäß der Linie C-C in Fig. 2b;
• Fig. 4a eine Ansicht eines Teils des Kerns, der gemäß einer weiteren Ausführung mit einem einen plattenförmigen Endbereich aufweisenden Positionierelement verbunden ist;
• Fig. 4b das in Fig. 4a mit einem Kreis veranschaulichte Detail in demgegenüber vergrößertem Maßstab;
• Fig. 5a eine Ansicht eines Teils des Kerns, der gemäß einem weiteren Ausführungsbeispiel mit einem stiftförmigen Positionierelement verbunden ist; und
• Fig. 5b das in Fig. 5a mit einem Kreis veranschaulichte Detail in demgegenüber vergrößertem Maßstab.

The invention will be explained below with reference to exemplary embodiments shown in the figures, to which, however, it should not be limited. In detail, in the drawing:

• Fig. 1 a cross section of a section of a casting tool that receives a light-metal-encapsulated core;
• Fig. 2a a front view of the core, wherein on a circumferential ring bow-shaped positioning elements are attached;
• Fig. 2b this in Fig. 2a on the other hand, detail illustrated with a circle on an enlarged scale;
• Fig. 3 a sectional view of the core along the line CC in Fig. 2b ;
• Fig. 4a a view of a part of the core, according to another Execution is connected to a plate-shaped end portion having a positioning element;
• Fig. 4b this in Fig. 4a on the other hand, detail illustrated with a circle on an enlarged scale;
• Fig. 5a a view of a portion of the core, which is connected according to a further embodiment with a pin-shaped positioning member; and
• Fig. 5b this in Fig. 5a By contrast, detail illustrated with a circle is enlarged scale.

In Fig. 1 a section of a casting tool 1 for producing a cast workpiece 2 is shown. In the embodiment shown, a light metal rim or a cast wheel 2 'is produced for a motor vehicle. In the casting tool 1, a core 3 is accommodated, which has a lower density than a light metal alloy with which the core 3 is cast to form the cast wheel 2 '. The core 3 is preformed from a compact, for example of porous silicate material, in particular vermiculite; the core 3 may alternatively consist of a metal foam or any other material. By the inclusion of a comparatively low density core 3 in the cast wheel 2 ', a weight saving can be achieved. How out Fig. 1 can be seen, the casting tool 1 is designed as a mold with an upper mold part 4 and a lower mold part 5. In addition, the casting tool 1, for example, four circumferentially adjoining core slide 6. To close the casting tool 1, the upper mold part 4 is moved toward the lower mold part 5, wherein the lateral core slide 6 are moved radially inwardly until it rests against the lower mold part 5. In order to position the core 3 in a predetermined position in the casting tool 1, a positioning element 7 is provided, which is connected to the core 3. The positioning element 7 makes it possible to arrange the core 3 without contact with the mold parts 4, 5 when inserting it into the casting tool 1, before the core 3 is encapsulated with the light metal alloy. When introducing the light metal alloy, the core 3 is encapsulated on all sides by the light metal alloy.

In known processes for the production of cast wheels 2, a self-clamping connection between the positioning element 7 and the upper molded part 4 has often been made for centering the core 3 in the casting tool 1. However, the core 3 shown has a comparatively short extent in the axial direction, so that the core 3 does not extend below the upper molded part 4. Accordingly, it is not possible in this embodiment, make a positioning of the core 3 via a self-locking connection with the upper mold part 4.

In order to achieve an exact positioning of the core 3 shown here in the predetermined position, the positioning element 7 is placed during positioning of the core 3 in the casting mold 1 on a support surface 8 of the lower mold part 5. The core 3 is thus held under the action of gravity without contact to the mold parts 4, 5 in the predetermined position. The support surface 8 is arranged horizontally relative to an operating position of the casting tool 1. The lower mold part 5 has a circular circumferential elevation 9, the saddle surface of the support surface 8 includes. The elevation 9 has flanks 10, 11 which connect radially outwards or radially inwards to the horizontal support surface 8. The support surface 8 and seen in the radial direction inner edge 10 of the elevation 9 are formed as sections of sealing surfaces 12 between the correspondingly shaped mold parts 4, 5. The outer edge 11 seen in the radial direction is concavely curved according to the shape of the finished rim bed. The flank 11 thus forms a section of boundary surfaces 13 which enclose a cavity 14 which images the shape of the cast wheel 2 '. The support surface 8 of the lower mold part 5 has a groove 16 into which the positioning element 7 is inserted. When closing the casting tool 1, the positioning element 7 is clamped between the support surface 8 of the lower mold part 5 and a facing contact surface of the upper mold part 4, to secure the core 3 on all sides against slipping.

Out Fig. 1 is further seen that the resting on the support surface 8 end of the positioning 7 protrudes from the finished cast wheel 2 '. After the casting of the core 3 is the protruding end of the positioning 7 cut off. To avoid corrosion, the cast wheel 2 'is then painted at least in the region of the cut end of the positioning element 7; Expediently, the entire cast wheel 2 'is provided with a coating.

In the Fig. 2a and 2b an embodiment of the core 3 is shown, which provides a circular encircling ring 17 having radially inwardly projecting pockets 18. At the in Fig. 1 a total of four distributed over the circumference of the ring 3 positioning elements 7 are provided, which are fixed frictionally or non-positively on the rim 17. The free end portions of the positioning 7 are from the rim 17 radially inwardly from. When inserting the core 3 in the casting tool 1, the protruding from the core 3 end portions of the positioning elements 7 are each placed on a corresponding support surface 8 of the lower mold part 5. According to the Fig. 2a and 2b the positioning element 7 is bow-shaped bent, wherein the free ends of the legs of the bow-shaped positioning element 7 are fixed in the rim 17 of the core 3.

Fig. 4a and 4b shows an alternative embodiment of the positioning element 7, which has a plate-shaped end portion which is placed on the support surface 8.

At the in Fig. 5a and 5b As shown, a pin-shaped positioning element 7 is provided. The fixation of the positioning element 7 in the core 3 can be done in a known manner positive or non-positive. For a frictional connection, the positioning element 7 expediently has a pointed end, which is pushed into the preformed core 3.

Claims (13)

1. Method for producing a cast wheel (2'), a core (3) that remains in the cast wheel (2') and has a circumferential rim (17) being inserted into a casting mould (1) that comprises at least one lower mould part (5) and one upper mould part (4), which are moved relative to one another in order to close the casting mould (1), the core (3) being positioned in a predetermined position in the casting mould (1) by means of at least one positioning element (7), an end region of the positioning element (7) being fixed in the circumferential rim (17) of the core (3) in a force-locking or frictional manner, characterised in that a free end region of the positioning element (7), which end region protrudes from the circumferential rim (17) of the core (3), is placed on a contact surface (8) of the lower mould part (5) of the casting mould (1), which contact surface is preferably arranged horizontally during operation, when positioning the core (3) in the casting mould (1), such that the core (3) is positioned in the predetermined position under the action of gravity.
2. Method according to claim 1, characterised in that the positioning element (7) is clamped between the contact surface (8) of the lower mould part (5) and a corresponding contact surface of the upper mould part (4) when the casting mould (1) is closed.
3. Method according to either claim 1 or claim 2, characterised in that a pin-shaped, bow-shaped or planar end region of the positioning element (7), which end region projects out of the core (3), is placed on the contact surface (8) of the lower mould part (5).
4. Method according to any of claims 1 to 3, characterised in that an end region of the positioning element (7), which end region protrudes radially inwards from a circumferential rim (17) of the core (3), is placed on the contact surface (8) of the lower mould part (5).
5. Method according to claim 4, characterised in that a plurality of positioning elements (7), which are fixed so as to be spaced apart on the circumferential rim (17) of the core (3) in the circumferential direction, are placed on corresponding contact surfaces (8) of the lower mould part (5).
6. Method according to any of claims 1 to 5, characterised in that an end of the positioning element (7), which end projects from the completed cast part (2), is removed.
7. Method according to claim 6, characterised in that the cast part (2) is lacquered or powder-coated at least in the region of the cut-off end of the positioning element (7).
8. Casting mould (1) for producing a cast part (2), in particular a cast wheel, comprising at least one lower mould part (5) and one upper mould part (4), which are moved relative to one another in order to close the casting mould (1), characterised in that the lower mould part (5) has a circumferentially extending projection (9) having a contact surface (8), on which a free end region of a positioning element (7) connected to a circumferential rim (17) of a core (3) can be placed, such that the core (3) can be positioned relative to the mould parts (4, 5) in the casting mould (1) in a contact-free manner.
9. Casting mould (1) according to claim 8, characterised in that the circumferentially extending projection (9) is formed as a portion of a boundary surface (13) enclosing a cavity (14).
10. Casting mould (1) according to either claim 8 or claim 9, characterised in that the contact surface (8) is arranged horizontally during operation.
11. Casting mould (1) according to any of claims 8 to 10, characterised in that the upper mould part (4) and/or the lower mould part (5) comprise a groove (16).
12. Casting mould (1) according to claim 11, characterised in that the groove(s) (16) of the upper and lower mould part (4, 5) is or are formed such that the positioning element (7) protruding from the core (3) is clamped in the groove(s) (16) when the casting mould (1) is in a closed position.
13. Casting mould (1) according to any of claims 8 to 12, characterised in that sealing surfaces (12) are provided between the upper mould part (4) and lower mould part (5), the contact surface (8) being formed as a portion of the sealing surface (12) of the lower mould part (5).

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