Casting tool for producing a rotor of an electric motor

Abstract

Casting tool (10) for producing a rotor of an electric motor, comprising a first mold part (1) which has a first sprue cavity (11) and a feed region (12) for casting material, a second mold part (2) which has a second sprue cavity (21), and a third mold part (3) which has a cavity (31) for receiving a laminated core (33), wherein the mold parts (1, 2, 3) are designed to jointly form a casting cavity (20) when the mold parts (1, 2, 3) bear against each other along a mold axis (15), wherein the first sprue cavity (11) has an annular cross-section in a plane orthogonal to the mold axis (15), and wherein the feed region (12) opens tangentially into the first sprue cavity (11).

Description

[0001] The present invention relates to a casting tool for producing a rotor of an electric motor. Furthermore, the invention relates to a method for producing a rotor of an electric motor.

[0002] Electric motors, in particular asynchronous motors, are known which have rotors comprising a plurality of rotor laminations stacked to form a laminated core. Such a laminated core is usually penetrated in the axial direction by solid, electrically highly conductive rods, which are connected to one another at both end faces of the laminated core by means of a short-circuit ring. It is known that the rods and short-circuit rings are formed by die casting. A known device for vertical die casting of a rotor for an asynchronous motor and a corresponding method for vertical die casting are shown in DE 10 2020 211 765 A1. With known casting tools and casting processes, the problem of uneven mold filling often arises, which can lead to air inclusions and thus deterioration in material quality.

[0003] It is therefore an object of the present invention to provide a casting tool for producing a rotor of an electric motor, with which rotors with improved material properties can be produced efficiently and cost-effectively. Furthermore, it is an object of the invention to provide a method for producing a rotor of an electric motor, with which rotors with optimal material properties can be produced.

[0004] The object is achieved by a casting tool according to claim 1 and by a method according to claim 11.

[0005] The casting tool according to the invention comprises a first mold part, which has a first sprue cavity and a feed region by means of which casting material can be fed. The casting tool further comprises a second mold part, which has a second sprue cavity, and a third mold part, which has a cavity for receiving a laminated core. The three mold parts are designed to jointly form a casting cavity when the mold parts abut one another along a mold axis. The first sprue cavity has an annular cross-section in a plane orthogonal to the mold axis, and the feed region opens tangentially into the first sprue cavity.

[0006] Preferably, the three mold parts are each substantially plate-shaped. In particular, the casting tool is thus a three-plate casting tool.

[0007] Preferably, in the abutting state, which is also referred to below as the casting configuration, the second mold part is arranged along the mold axis between the first mold part and the third mold part.

[0008] In other words, a casting tool is provided which has the three mold parts. The first mold part and the second mold part together form a sprue for the component to be produced. The cavity in the third component can have the laminated core on and around which rods and short-circuit rings are to be cast. In particular, the cavity of the third mold part, together with the laminated core and preferably with the second mold part, shapes the component to be cast. For example, a first short-circuit ring can be formed by an axial end of the cavity in the first mold part. Preferably, a second axially opposite short-circuit ring can be formed by an end face of the first mold part facing the second mold part, together with the second mold part.The first sprue cavity in the first mold part, through which the casting material flows into the sprue cavity, has an annular cross-section in the plane orthogonal to the mold axis. The feed area, through which the casting material can flow into the first sprue cavity, opens tangentially into the first sprue cavity. An annular cross-section is considered to be, in particular, a ring that is completely closed at least in the plane. This means that there are no interruptions in the annular cross-section that would impede a completely circular flow of the liquid material along the ring in the circumferential direction.

[0009] The casting tool according to the invention offers the advantage that the tangential inflow of the material into the first sprue cavity enables particularly targeted, uniform filling of the casting cavity. The tangential inflow of the casting material into the first sprue cavity by means of the special design of the first mold part makes it possible to provide a circular inflow of the melt with respect to the mold axis, which can also be referred to, for example, as cyclone-shaped filling of the runner. In this case, the radially outer region of the sprue is filled first due to centrifugal force. Preferably, if the casting tool is arranged during casting, i.e. during mold filling, such that the first mold part is positioned at the bottom in the direction of gravity, the melt then continues to rise to the second mold part and finally into the third mold part.The rotating motion of the melt enables a particularly uniform, gradual mold filling along the mold axis. This allows the casting cavity to be filled particularly evenly in terms of time and volume flow. This allows, for example, the ribs and recesses within the laminated core to be flowed through more evenly and reliably, resulting in fewer air pockets and thus a particularly uniform material quality for the entire component.

[0010] The first sprue cavity preferably has a spirally tapered cross-section, particularly in a circumferential direction relative to the mold axis. This allows for a constant flow velocity of the melt during and after flowing into the first sprue cavity. In particular, this allows for particularly simple and reliable mold filling due to the centrifugal force of the melt during flow.

[0011] Particularly preferably, the first sprue cavity is tapered in the shape of an Archimedean spiral, particularly in a circumferential direction relative to the mold axis. This allows the advantageous, uniform mold filling to be achieved in a particularly simple, targeted and reliable manner through a uniform flow in the circumferential direction within the first sprue cavity.

[0012] Preferably, the second sprue cavity is arranged in a radially inner region of the first sprue cavity. This ensures that the melt overflows later, particularly after the first sprue cavity has been largely filled. This allows the sprue cavity to be gradually filled with the inflowing melt in a particularly uniform manner, thereby ensuring optimal material quality.

[0013] Further preferably, the second sprue cavity is designed such that the second sprue cavity tapers radially in a plane parallel to the mold axis in the direction of the third mold part. The second sprue cavity is preferably designed to taper conically in the plane parallel to the mold axis. In other words, a radially outer circumferential surface and a radially inner circumferential surface, which delimit the second sprue cavity, are each designed to taper, in particular conically, in the direction of the third mold part. Particularly preferably, the cross-section of the second sprue cavity is additionally designed to taper in the direction of the third mold part, i.e. the cross-sectional area of ​​the second sprue cavity decreases along the direction of the mold axis. This makes it particularly reliable to ensure that the cavity is gradually and evenly filled with the melt.

[0014] Preferably, the second sprue cavity is formed jointly by the first mold part and the second mold part when the mold parts are in contact, i.e., in the casting configuration. In other words, a portion of the boundary of the second sprue cavity is formed by both the first mold part and the second mold part. This makes it possible to provide a particularly advantageous design of the casting tool, which, for example, enables at least partial engagement of the first mold part and the second mold part in the axial direction. This makes it possible to simplify the design of the two mold parts, and also to simplify the assembly of the casting tool for the casting process.

[0015] Particularly preferably, the second mold part has a recess, which is preferably designed as a through-opening that is in particular substantially circular. In addition, the first mold part has a protruding mandrel, which is in particular substantially cylindrical. When the two mold parts are in contact, that is to say in particular in the casting configuration, the mandrel is arranged within the recess, so that the second sprue cavity is arranged in the radial direction between the mandrel and an inner wall of the recess or is delimited thereby. In this way, for example, the annular second sprue cavity, which extends completely through the second mold part along the mold axis, can be formed in a simple manner. Furthermore, further advantageous properties of the tool can be enabled.For example, the mandrel can enable simpler and more effective cooling in the area of ​​the second sprue cavity. It can also simplify the design and assembly of the molded parts, as they can be designed in such a way that the sheet stack is pressed into the cavity of the third molded part by the mandrel of the first molded part, ensuring precise positioning during casting.

[0016] The casting tool preferably further comprises a cooling device arranged at least within the first mold part. The cooling device extends at least partially into the mandrel. This allows for effective cooling of the casting tool in the region of the sprue. Furthermore, the cooling device can be provided in a particularly simple and cost-effective manner. For example, in the case of fluid-conducting cooling, fluid lines can thus be easily arranged exclusively within the first mold part.

[0017] The mold parts are preferably designed to jointly form at least two casting cavities. The first mold part preferably has a common feed area, with which each of the at least two feed areas is fluidly connected. This means that at least two, preferably exactly two, alternatively preferably exactly four, components to be cast can be produced simultaneously in a single three-plate casting tool using a single common feed area into which the casting material is poured. This enables particularly simple and efficient production of rotors for electric motors.

[0018] Furthermore, the invention leads to a method for producing a rotor of an electric motor, comprising the steps: - Providing the described casting tool, - Filling the casting cavity with casting material, in particular with liquid metal such as aluminum, and - Demolding of the cast component.

[0019] Demolding is considered to be, in particular, disassembling the casting tool, in particular separating all mold parts, in order to be able to remove the cast component. Demolding may preferably also include removing a sprue.

[0020] Demolding preferably comprises tearing off the sprue directly at the component by removing the first molded part from the second molded part. This means that after the casting process, and in particular after the melt has solidified, the first molded part is removed from the second molded part, preferably along the direction of the mold axis, which preferably initially remains adjacent to the first molded part. In particular, due to the tapered geometry of the second sprue cavity, the sprue is completely torn off together with the first molded part and directly at the component itself. The sprue further shrinks onto the mandrel of the first molded part, whereby the tear-off forces at the gate are increased or concentrated, and uncontrolled tearing can be avoided.Furthermore, difficult-to-demolish contours in the second molded part, in which adhesives or melt residues could become trapped, are eliminated, as the contour is geometrically formed as a single large through-hole through the second molded part. This ensures a cleaner tear-off of the sprue at the tip of the mandrel and clean demolding from the second molded part. This provides a particularly simple and time-efficient manufacturing process for rotors.

[0021] The invention is explained in more detail below using exemplary embodiments. These show: Fig. 1 a highly simplified schematic view of a casting tool according to a first embodiment of the invention, Fig. 2 a highly simplified schematic view of a casting tool according to a second embodiment of the invention, Fig. 3 a perspective view of a casting cavity of the casting tool of the Fig. 1, Fig. 4 a partial sectional side view of the casting cavity of the Fig. 3, and Fig. 5 highly simplified schematic views of a sprue tearing off after casting.

[0022] In the following, preferred embodiments of casting tools 10 for producing a rotor of an electric motor are explained. Fig. 1 to 5. Identical or functionally identical components are always provided with the same reference numerals.

[0023] Rotors for asynchronous motors can be manufactured using the casting tool 10 according to the invention. Such rotors comprise a laminated core 33, which has a plurality of laminations stacked along a laminated core axis. This laminated core 33 has a plurality of axial grooves and / or through-holes into which a highly electrically conductive metal is to be introduced in order to form axial rods 41 through the laminated core 33. A short-circuit ring 42 is also provided on each of the two axial end faces of the laminated core 33, which extends in the circumferential direction and connects all of the rods 41 to one another.

[0024] By means of the casting tool 10, the bars 41 and the short-circuit rings 42 can be cast directly into or onto the laminated core 33 as a single, one-piece component and in one step. The rotor thus finished is shown, for example, in a simplified schematic still within the casting tool 10 in the Fig. 1. In the Fig. 3 and Fig. 4 also shows a casting cavity 20, by means of which the geometry of the components to be cast, in particular rods 41 and short-circuit rings 42, can be seen, in particular the Fig. 3 and Fig. 4, the reference numerals 4, 41, 42 contained in FIG. 4 are used only for illustration purposes and do not represent the actual cast component 4.

[0025] In the Fig. Figure 1 shows a highly simplified schematic sectional view of a casting tool 10 according to a first embodiment of the invention. The casting tool 10 comprises a first mold part 1, a second mold part 2, and a third mold part 3. The three mold parts 1, 2, and 3 are each essentially plate-shaped, so that the casting tool 10 can also be referred to as a three-plate tool.

[0026] In the Fig. In the casting configuration shown in Figure 1, the three mold parts 1, 2, 3 are pressed together along a mold axis 15, for example, by means of a clamping device (not shown). In the casting configuration, the mold parts 1, 2, 3 together form a casting cavity 20, in which the laminated core 33 is arranged, and into which the casting material, in particular a liquid molten metal, such as aluminum, is poured to form the component 4 to be produced.

[0027] Preferably, the casting material is filled by means of pressure, so that it is particularly a die casting process.

[0028] The laminated core 33 is arranged in a cavity 31 of the third molded part 3 and preferably partially projects into the second molded part 2 in the axial direction.

[0029] The first mold part 1 and the second mold part 2 have a sprue for the component 4 to be cast. In detail, the second mold part 2 has a second sprue cavity 21, which completely penetrates the second mold part 2 and connects the first mold part 1 to the third mold part 3.

[0030] In addition, the first molded part 1 has a first sprue cavity 11 and a feed area 12 and a feed area 17. At the feed area 17, the melt is filled, preferably under pressure, into the casting tool 10 and then passes via the feed area 12, the first sprue cavity 11, and the second sprue cavity 12 to the first molded part with the cavity 31 and the laminated core 33. All these cavities together form the casting cavity 20, which is Fig. 3 and Fig. 4 is shown.

[0031] The casting tool 10 with the mold parts 1, 2, 3 is designed to jointly form at least two casting cavities 20. Preferably, the first mold part 1 has a single common feed area 17, with which each of the at least two feed areas 12 is fluidly connected. This means that in a single three-plate casting tool 10, at least two, preferably exactly two, alternatively preferably exactly four, components 4 to be cast can be produced simultaneously and by means of a single common feed area 17, into which the casting material is poured.

[0032] The first sprue cavity 11 is configured such that, in a plane orthogonal to the mold axis 15, it is formed as a completely circumferential ring that tapers spirally in the shape of an Archimedean spiral. The feed area 12 is arranged such that it opens tangentially into the first sprue cavity 11.

[0033] In addition, the second sprue cavity 21 is designed such that it is formed as a completely circumferential ring in a plane orthogonal to the mold axis 15. The second sprue cavity 21 is arranged in a radially inner region of the first sprue cavity 11 (cf. Fig. 4).

[0034] In addition, the second sprue cavity 21 is designed to taper conically toward the molded part 3. In detail, an outer geometry of the second sprue cavity 21 tapers radially. Preferably, a cross-sectional area of ​​the second sprue cavity can also be designed to taper toward the third molded part. Alternatively, the cross-sectional area of ​​the second sprue cavity 21 can preferably be constant in the axial direction.

[0035] The special design of the sprue with the annular first sprue cavity 11 and second sprue cavity 21 and the tangential feed of the casting material by means of the feed area 12 causes a cyclone-shaped inflow of the melt into the sprue cavity 20. The centrifugal force fills the radially outer region of the sprue first, and the filling of the casting cavity 20 takes place in a particularly targeted and continuous manner along the axial direction of the mold axis 15. This enables a particularly uniform filling of the casting cavity 20 in terms of time and volume flow. This allows the ribs within the laminated core 33 to be flowed through particularly evenly in order to enable fewer air inclusions and thus a particularly good and uniform material quality of the component 4 to be produced.

[0036] Furthermore, the first mold part 1 and the second mold part 2 are designed such that the boundaries of the second sprue cavity 21 are formed jointly by the first mold part 1 and the second mold part 2. In detail, the second mold part 2 has a recess 24 that completely penetrates the second mold part 2 in the axial direction. An inner wall 24a of the recess 24 delimits the second sprue cavity 21 in the radial outward direction.

[0037] In addition, the first mold part has a mandrel 14 which, in the casting configuration, extends into the recess 24 and forms a radially inner boundary of the second sprue cavity 21.

[0038] The molded parts 1, 2, 3 are further designed such that in the casting configuration the mandrel 14 of the first molded part 1 presses against the laminated core 33 and clamps it in the axial direction in the cavity 31 of the first molded part 1.

[0039] By designing the first mold part 1 with a mandrel 14, in addition to simple manufacture and assembly of the casting tool 10, it is also possible to achieve particularly effective cooling in the region of the first mold part 1 and, at the same time, the second mold part 2. For this purpose, a cooling device 5 can be provided, which is arranged within the first mold part 1 and extends into the mandrel 14.

[0040] The special design of the mold parts 1, 2, 3 of the casting tool 10 also offers the advantage of improved demolding after casting. This is shown schematically in the Fig. 5 shown. Fig. Figure 5 above shows the casting configuration in which the three mold parts 1, 2, 3 are adjacent to each other. After casting, the movable plates, namely the second mold part 2 and the third mold part 3, are removed axially from the first mold part 1 (see Figure 5). Fig. 5 Middle of first demolding (arrow A). This causes the sprue to break off directly at component 4. The second molded part 2 can then be removed from the first molded part 1 (see Fig. 5 below second demoulding (arrow B).

[0041] In Fig.2 shows a highly simplified schematic sectional view of a casting tool 10 according to a second exemplary embodiment of the invention. The second exemplary embodiment essentially corresponds to the first exemplary embodiment with the difference of an alternative configuration of the first mold part 1 and the second mold part 2. In detail, the first mold part 1 in the second exemplary embodiment does not have a protruding mandrel. Instead, the first mold part 1 and the second mold part 2 are also designed as flat plates. The second sprue cavity 21 is formed by the second mold part 2 alone. The second sprue cavity 21 can not be completely annular in this case, but rather can be designed with interruptions which, in particular, hold a part of the second mold part 2 located radially inside the second sprue cavity 21 in order to enable simple production of the geometry of the second mold part 2.Thus, an alternative design of the casting tool 10 can be provided. List of reference symbols 1 first molded part 2 second molded part 3 third molded part 4 component 5 Cooling device 10 casting tools 11 first sprue cavity 12 Feeding area 15 Form axis 17 Dining area 20 casting cavity 21 second sprue cavity 24 recess 24a interior wall 31 Cavity 33 sheet package 41 bars 42 short-circuit rings A first demolding B second demolding QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 211 765 A1

[0002]

Claims

[1] Casting tool for producing a rotor of an electric motor, comprising: - a first molded part (1) having a first sprue cavity (11) and a feed area (12) for casting material, - a second molded part (2) having a second sprue cavity (21), and - a third molded part (3) having a cavity (31) for receiving a laminated core (33), - wherein the mold parts (1, 2, 3) are designed to jointly form a casting cavity (20) when the mold parts (1, 2, 3) lie along a mold axis (15), - wherein the first sprue cavity (11) has an annular cross-section in a plane orthogonal to the mold axis (15), and - wherein the feed area (12) opens tangentially into the first sprue cavity (11). [2] Casting tool according to claim 1, wherein the first sprue cavity (11) has a spirally tapered cross-section. [3] Casting tool according to claim 2, wherein the first sprue cavity (11) tapers in the form of an Archimedean spiral. [4] Casting tool according to one of the preceding claims, wherein the second sprue cavity (21) has an annular cross-section in a plane orthogonal to the mold axis (15). [5] Casting tool according to one of the preceding claims, wherein the second sprue cavity (21) is arranged at a radially inner region of the first sprue cavity (11). [6] Casting tool according to one of the preceding claims, wherein the second sprue cavity (21) is formed to taper radially in a plane parallel to the mold axis (15) in the direction of the third mold part (3). [7] Casting tool according to one of claims 4 to 6, wherein the second sprue cavity (21) is formed jointly by the first mold part (1) and the second mold part (2). [8] Casting tool according to claim 7, wherein the second mold part (2) has a recess (24), wherein the first mold part (1) has a mandrel (14), wherein in the abutting state of the mold part (1, 2) the mandrel (14) is arranged within the recess (24) so ​​that the second sprue cavity (21) is arranged radially between the mandrel (14) and an inner wall (24a) of the recess (24). [9] Casting tool according to claim 8, further comprising a cooling device (5) which is arranged at least partially within the mandrel (14). [10] Casting tool according to one of the preceding claims, wherein the mold parts (1, 2, 3) are designed to form at least two casting cavities (20), in particular wherein the first mold part (1) has a common feed area (17) to which each feed area (12) is connected. [11] A method for manufacturing a rotor of an electric motor, comprising the steps of: - Providing a casting tool (10) according to one of the preceding claims, - Filling the casting cavity (20) with casting material, and - Demolding of the cast component. [12] Method according to claim 11, wherein demoulding comprises: tearing off the sprue directly on the component by removing the first mould part (1) from the second mould part (2).

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