EP3636365B1 - Casting mould for manufaturing a casting part by having at least one internal contour and the use of such mold - Google Patents

Description

The invention relates to a casting mold or a casting tool for the production of a metal cast part, which has a hollow-cylindrical area with a cylindrical inner contour. Furthermore, the invention relates to the use of such a casting mold.

A casting mold is a mostly metallic (reusable) permanent form for the production of cast (component) parts. For this purpose, a casting mold has a mold cavity that can be filled with melt or liquid metal and forms the cast part. Hollow or inner contours provided in the cast part can be mapped with the help of immovable cores or movable slides. In order to be able to demould the casting produced after the melt has solidified, a casting mold is constructed in several parts and consists, e.g. B. from a fixed and a movable mold half. Furthermore, so-called drafts are required in order to be able to lift the cast part. Such drafts should also be provided on cores (if they are reusable permanent cores) or on slides. Drafts, however, lead to allowances on the cast part. These oversizes then have to be removed during the post-processing of the cast part (this is usually done by machining), which is complex and involves high material consumption. Furthermore, such allowances can also lead to high wall thicknesses, so that there is an increased risk of defects (e.g. shrinkage cavities and gas pockets).

In the nearest DE 10 2015 220 980 A1 describes a mold for the production of metallic cast components. The mold has a mold cavity (cavity). The mold also has at least one multi-part slide for forming an inner contour (undercut) in the cast components. The slide is designed in two parts with a first partial slide and a second partial slide. When retracting, the partial slides can be moved separately, ie separately from one another, with opposite oblique directions, so that extraction bevels or bevels are not required. Furthermore, the first partial slide and the second partial slide are designed with corresponding inclined surfaces on which the partial slides can slide against one another when they are pulled back. Injection molding tools with multi-part cores for imaging inner contours or undercuts are known for plastic injection molding, which have a centrally arranged mandrel or the like and arranged around the mandrel core segments, wherein the core segments can be displaced transversely to the direction of movement of the mandrel by longitudinal displacement of the mandrel. The relevant prior art is on the US 4,541,605A ,

DE 10 2011 011 784 A1 , US 4,286,766A , US 5,403,179 A , US 4,362,291A , DE 26 19 064 A1 , and US 4,731,014A referred.

Starting from the DE 10 2015 220 980 A1 the invention is based on the object of specifying a further (ie alternative) advantageous casting mold for the production of a metal cast part, which has at least one core without the usual extraction bevels.

The object is achieved by the casting mold according to the invention of claim 1. That is, the invention now provides a further, particularly advantageous casting mold with the features mentioned in claim 1, which has at least one core without the otherwise usual drafts or drafts having. Advantageous developments of the casting mold according to the invention result from the dependent patent claims, the following description of the invention and also from the figures.

• einen Formhohlraum, der den Abmessungen des (herzustellenden) Gussteils entspricht; und
• wenigstens einen zumindest teilweise im Formhohlraum angeordneten bzw. in den Formhohlraum hineinreichenden Kern zur Abbildung der Innenkontur, wobei dieser Kern kein loser Kern, sondern ein (baulicher) Bestandteil bzw. Werkzeugteil der Gießform ist. Erfindungsgemäß ist vorgesehen, dass der Kern mehrteilig ausgebildet ist und mehrere bewegliche Kernsegmente sowie einen längsverschieblich zwischen den Kernsegmenten angeordneten Dorn aufweist, wobei die Kernsegmente beim Längsverschieben des Dorns quer zur Bewegungsrichtung des Dorns bewegt bzw. verschoben werden und durch Ausfahren des Dorns in eine Gießstellung bringbar sind und durch Einfahren des Dorns in eine Entformungsstellung bringbar sind.

The casting mold or casting mold according to the invention for the production of a metal casting, which has a hollow-cylindrical area with a cylindrical inner contour, comprises:

• a mold cavity corresponding to the dimensions of the casting (to be produced); and
• at least one core arranged at least partially in the mold cavity or extending into the mold cavity for imaging the inner contour, this core not being a loose core but a (structural) component or tool part of the casting mold. According to the invention, the core is designed in several parts and has a plurality of movable core segments and a mandrel that can be displaced longitudinally between the core segments, the core segments being moved or displaced transversely to the direction of movement of the mandrel when the mandrel is longitudinally displaced and can be brought into a casting position by extending the mandrel are and can be brought into a demolding position by retracting the mandrel.

The casting mold (casting tool) according to the invention is in particular a chill mold for chill casting or a die-casting or die-casting mold for die-casting metals, in particular light metals. However, the invention is also suitable for other metal casting processes in which permanent molds are used.

Both the mandrel and the core segments are part of the mold and form a permanent core. The mandrel can be moved in its longitudinal or axial direction and can use a suitable drive can be extended and retracted, which is comparatively easy to do. As it extends, the mandrel is advanced or pushed toward the mold cavity. During retraction, the mandrel is moved back or withdrawn in the opposite direction (ie, out of the mold cavity). When the mandrel is extended, the core segments are moved outwards transversely, in particular essentially perpendicularly, to the direction of movement of the mandrel and assume a casting position. The core is quasi expanded and takes on the shape of the inner contour to be imaged. When the mandrel is retracted, the core segments are moved inwards transversely to the direction of movement of the mandrel and assume a demoulding position, whereby the cross-section of the core is reduced or narrowed, so to speak, and demoulding of the cast part produced is made possible without drafts or draft angles. Only small machining allowances are therefore required for the inner contour, which on the one hand reduces the post-processing effort and material consumption and on the other hand reduces the risk of defects.

The mandrel is centrally located and the core segments are arranged around the mandrel. This enables a compact core structure and ensures effective function.

The mandrel and core segments are formed with complementary ramps that form a wedge slide mechanism. Wedge slide mechanisms are known in various designs from toolmaking. The mandrel can, for example, have a conical or frustoconical section, on which the core segments formed with corresponding complementary surfaces can slide and are thereby displaced transversely to the direction of movement of the mandrel. The core segments can be spring-loaded against the mandrel. The springs, which are in particular compression springs (coil springs), ensure physical contact between the core segments and the mandrel and can also cause the return (return) of the core segments (to the demoulding position). The reset can also be hydraulic, pneumatic or mechanical (e.g. by means of an umbrella mechanism or other suitable linkage system).

The movement of the core segments is preferably guided by means of slot guides or the like. The core segments can, for example, be mounted in grooves provided for this purpose by means of one or more sliding blocks. The groove guides can also be designed with end stops that limit the movements of the core segments.

The core segments can have shape elements that enable the depiction of an undercut inner contour. This means that undercuts can already be created during casting on the inner contour of the cast part, which would no longer be demouldable with conventional permanent cores or slides.

It is envisaged that the cast part to be produced has a hollow-cylindrical area, the cylindrical inner contour of which is reproduced with the multi-part core, this core having three or more movable core segments and the mandrel being designed with three or more pockets in which these core segments can be moved transversely are arranged. In addition, the mandrel has three or more radially extending ridges extending (longitudinally and radially) between the pockets, the outer (radial) surfaces of these radial ridges together with the outer (radial) surfaces of those in the pouring position Core segments specify or define the inner contour to be mapped. The (radial) outer surfaces of the radial webs are preferably designed with draft bevels so that the mandrel can be inserted or withdrawn more easily.

The casting mold according to the invention is preferably used to produce a stator pot for an electric machine, for which purpose a cast aluminum or magnesium alloy is used in particular. However, the invention is not limited to this.

Fig. 1

zeigt in einer Schnittdarstellung eine erfindungsgemäße Druckgießform mit einem mehrteiligen Kern, dessen Kernsegmente sich in ihren Gießstellungen befinden.

Fig. 2

zeigt eine Querschnittsdarstellung des zur Druckgießform der Fig. 1 gehörenden Kerns.

Fig. 3

zeigt die Druckgießform aus Fig. 1, wobei sich die Kernsegmente nun in ihren Entformungsstellungen befinden.

Fig. 4

zeigt in einer perspektivischen Darstellung den zum Kern der Fig. 2 gehörenden Dorn.

The invention is explained in more detail below by way of example and in a non-limiting manner with reference to the figures. The features shown in the schematic figures that are not true to scale and/or explained below can also be general features of the invention, independently of specific combinations of features, and develop the invention accordingly.

1

shows a sectional view of a die-casting mold according to the invention with a multi-part core, the core segments of which are in their casting positions.

2

shows a cross-sectional view of the die for the 1 belonging core.

3

shows the die 1 , with the core segments now in their demoulding positions.

4

shows a perspective view of the core of 2 belonging thorn.

In the 1 Die casting mold 100 shown has a lower, fixed mold half 110 and an upper, movable mold half 120 . The lower mold half 110 is formed with a mold cavity 130 for the production of a ring-cylindrical die-cast part 200 . The hollow-cylindrical inner contour is reproduced with the aid of a core 140, which will be explained in more detail below, and which is intended to keep the cavity free of melt during die-casting. That is to say, the mold cavity 130 is formed by an outer cavity wall of the lower mold half 110 and an inner cavity wall of the core 140, which together with the end cavity walls define the shape or form of the die-cast part 200 to be produced. The standing orientation is only an example. Likewise, the mold halves 110, 120 can also be formed with a vertical division as right and left mold halves.

The die-cast part 200 is z. B. a thin-walled stator for receiving stator cores in an electric machine for the traction drive (electric drive) of a motor vehicle. On the one hand, the die-cast part 200 is comparatively thin-walled (e.g. <5 mm) in relation to its diameter (e.g. >200 mm). On the other hand, high mechanical demands are placed on the die-cast part 200 . Depending on the angle of inclination, the draft angles that usually have to be provided on the outer cavity wall and on the inner cavity wall result in high and unequal wall thicknesses, which means there is an increased risk of defects.

In the case of the die-casting mold 100 according to the invention, the core 140 is of multi-part design and has a plurality of transversely movable core segments 146 and a mandrel 141 which is arranged between these core segments 146 and can be displaced longitudinally or axially. The 141 mandrel is how out 2 and 4 as seen, is formed with three uniform pockets 145 in which the identically shaped core segments 146 are located. The mandrel 141 is also formed with a central cone or truncated cone 142 and three radial webs 143 which protrude in the radial direction R and extend like wings at an angular distance of approximately 120° between the pockets 145 . The mandrel 141 is preferably manufactured in one piece, as in 4 shown. The core segments 146 rest on their radial inner surfaces in a form-fitting manner on the cone 142 and are designed for this purpose with complementary partial cone surfaces.

When the mandrel 141 is extended, for which purpose this is done as in 1 is moved upwards, the core segments 146 are moved radially outwards transversely to the direction of movement of the mandrel 141 by means of a wedge slide mechanism (the cone 142 acts like a driving wedge) (the displacement path and a Transmission ratio can be set) and assume a casting position, the radial outer surfaces 144 of the radial webs 143 together with the radial outer surfaces 147 of the core segments 146 defining the cylindrical inner contour to be imaged. Furthermore, the core segments 146 have shaped elements 148 on their outer surfaces 147 (see 1 ) for forming undercut geometries on the inner contour. This allows undercut geometries such. B. an inner ring groove for a retaining ring or the like, at least be pre-cast.

After the mold cavity 130 has been filled with melt, the mandrel 141 is retracted before the die-cast part 200 has reached its demoulding temperature (in order to keep the shrinkage forces small), for which purpose it is shown in 3 illustrated, is moved back or withdrawn downwards. The core segments 146 are moved radially inwards transversely to the direction of movement of the mandrel 141 and assume their demolding position, with a circumferential gap S forming between the radial outer surfaces 147 and the inner contour of the die-cast part 200 (the core 200 is therefore no longer in contact with the die-cast part 200), which allows easy lifting of the die-cast part 200. (The die-cast part 200 is removed from the mold upwards.) The outer surfaces 144 of the radial webs 143 are designed with draft bevels (e.g. 1° to 3°), preferably over their entire length, so that they become detached from the die-cast part 200 when the mandrel 141 is pulled back be able. (The outer surfaces 147 of the core segments 146 are formed without drafts.) Conventional drafts may be present on the outer cavity wall of the lower mold half 110 . The lower mold half 110 can also be designed with a vertical split for demoulding, so that no drafts are required at all. The ring-cylindrical die-cast part 200 can thus be die-cast with a uniformly thin wall thickness and only small machining allowances (e.g. <1.5 mm).

As previously explained, the core segments 146 are displaced transversely to the movement axis L of the mandrel 140 by extending the mandrel 141 and brought into a casting position, as in FIG 1 illustrated with arrows. By retracting the mandrel 141, the core segments 146 are brought into a demolding position or reset, as in 3 illustrated with arrows. In this case, the core segments 146 are only displaced in radial directions R (in contrast to a slider which is moved back and forth by extending and retracting). A radial movement guidance of the core segments 146 takes place both through the radial webs 143 and with the aid of slot guides. For this purpose, the lower mold half 110 is formed with grooves 119 or the like, in which the core segments 146 are fastened by means of sliding blocks 149 or The like are movably mounted in the radial direction R and held in place in the circumferential direction and in the axial direction and secured against twisting and tilting. The sliding blocks 149 can be screwed onto the core segments 146 or can also be designed in one piece with the core segments 146 . Also arranged in the grooves 119 are springs 150 which bias the core segments 146 against the mandrel 141 and enable resetting.

Reference List

100

mold

110

mold half

119

groove

120

mold half

130

mold cavity

140

core

141

mandrel

142

cone

143

radial bar

144

Outer surface (at the radial web)

145

pocket

146

core segment

147

Outer surface (on the core segment)

148

feature

149

slot nut

150

Feather

200

casting

L

longitudinal direction

R

radial direction

S

gap

Claims (7)

1. Casting mould (100) for producing a metallic cast part (200) which has a hollow-cylindrical region with a cylindrical inner contour, comprising:

   - a mould cavity (130) which corresponds to the dimensions of the cast part (200); and

   - at least one core (140), which is arranged in the mould cavity (130), for mapping of the inner contour, wherein this core (140) is a constituent part of the casting mould (100);

   wherein the core (140) is of multi-part form and has a plurality of movable core segments (146) and a mandrel (141) which is arranged so as to be longitudinally displaceable between the core segments (146),

   wherein the mandrel (141) is arranged centrally and the core segments (146) are arranged around the mandrel (141),

   wherein the mandrel (141) and the core segments (146) are formed with complementary oblique surfaces which form a wedge-type slide mechanism,

   wherein, during the longitudinal displacement of the mandrel (141), the core segments (146) are displaced transversely with respect to the movement direction of the mandrel (141) and can be brought into a casting position by extending of the mandrel (141) and can be brought into a demoulding position by retracting of the mandrel (141),

   wherein the multi-part core (140), with which the inner contour is mapped, has three or more movable core segments (146) and the mandrel (141) is formed with three or more pockets (145) in which these core segments (146) are arranged in a transversely movable manner,

   wherein the mandrel (141) also has three or more radial webs (143) which extend between the pockets (145), wherein the outer surfaces (144) of these radial webs (143) predefine, together with the outer surfaces (147) of the core segments (146) in the casting position, the inner contour to be mapped.
2. Casting mould (100) according to Claim 1, characterized in that
   the core segments (146) are preloaded against the mandrel (141) by means of springs (150).
3. Casting mould (100) according to either of the preceding claims,
   characterized in that
   the core segments (146) are guided in movement by means of groove guides (119, 149).
4. Casting mould (100) according to one of the preceding claims,
   characterized in that
   the core segments (146) are formed with mould elements (148) which allow an undercut inner contour to be mapped.
5. Casting mould (100) according to one of the preceding claims,
   characterized in that
   the outer surfaces (144) of the radial webs (143) are formed with pull slopes.
6. Casting mould (100) according to one of the preceding claims,
   characterized in that
   the mandrel (141) is manufactured in one piece.
7. Use of a casting mould (100) according to one of the preceding claims for production of a stator pot for an electric machine.

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