Star disk for a rotor of an electrically excited machine, rotor, motor vehicle and method for manufacturing a star disk

Abstract

The invention relates to a star disk (10) for a rotor of an electrically excited machine, with a separately manufactured switching ring (18) which comprises several contact elements (12, 14, 16) embedded in a first plastic material (20), which are arranged to be connected to respective rotor windings of the rotor or to a slip ring of the electrically excited machine, and which is held on a base body (22) of the star disk (10) by overmolding with a second plastic material (26).

Description

[0001] The invention relates to a star disk for a rotor of an electrically excited machine, a rotor, a motor vehicle with an electric traction machine and a method for manufacturing a star disk for a rotor.

[0002] From DE 10 2021 122 066 A1, a star disk for a rotor of a separately excited synchronous machine is known. At least the surface of the star disk consists of plastic in which busbars are embedded, each of which electrically connects a pole shoe or a groove of the star disk to an adjacent pole shoe or a corresponding groove of the star disk, and each of which has a contact element at both ends for receiving a winding wire that protrudes from the surface of the star disk.

[0003] The object of the present invention is to provide a solution which enables a particularly simple and precise positioning of the respective contact elements of a rotor to the rotor windings of the rotor to be contacted with the contact elements.

[0004] This problem is solved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0005] The invention relates to a star disk for the rotor of an electrically excited machine. The electrically excited machine is, in particular, a traction machine for a motor vehicle. The traction machine is designed to drive the motor vehicle using electrical energy. The electrically excited machine can also be referred to as a separately excited machine. In particular, the electrically excited machine is an electrically excited synchronous machine. The rotor of an electrically excited machine typically comprises a rotor body, which has several pole arms. Several rotor windings are wound around these pole arms of the rotor body. In order to make winding these rotor windings particularly easy and precise at the respective end faces of the rotor body, it is typically provided in electrically excited machines that a star disk is arranged at each end face of the rotor body.This star disc is designed to be particularly robust and features rounded edges, which makes it especially easy to wrap the rotor windings around the star disc during winding.

[0006] Furthermore, electrically excited machines typically include contact elements by which the rotor windings can be interconnected, and an electrically conductive contact between the rotor windings and a power source, usually via a slip ring, can be established. To enable particularly simple, reliable, and precise positioning of the contact elements relative to the rotor windings to be connected, the star disk incorporates a separately manufactured switching ring, which includes several contact elements embedded in a first plastic material. These contact elements are designed to be connected to the respective rotor windings or to a slip ring of the electrically excited machine. For example, crimp forks and / or solder tabs can be embedded in the first plastic material as contact elements.The crimp forks are designed to be connected to the respective rotor windings by crimping. The solder tabs are designed to be electrically connected to the slip ring by soldering. Alternatively, the respective contact elements can be designed to be connected to the rotor windings or the slip ring via a screw connection and / or a plug connection. The switching ring may, for example, be manufactured separately as a so-called pre-molded part. The switching ring may include conductors embedded in the first plastic material, by means of which at least some of the contact elements of the switching ring are electrically connected to each other for switching the rotor windings.

[0007] In the star disk design, the switching ring is held to the star disk's base body by overmolding it with a second plastic material. The separately manufactured switching ring can thus be integrated into the star disk's base body or attached to it by overmolding with the second plastic material. Because the contact elements are already fixed relative to each other within the separately manufactured switching ring, it is ensured that even when the switching ring is firmly connected to the base body by overmolding with the second plastic material, the contact elements integrated into the star disk remain precisely positioned relative to each other and firmly held to the star disk. This effectively prevents the risk of relative displacement of the contact elements to the star disk's base body within the electric machine, particularly during operation.If the contact elements were embedded directly into the second plastic material during the manufacturing of the star disk, without first being embedded in the first plastic material, they could tip over or shift relative to each other during the overmolding process, resulting in a misalignment. Because the switching ring is manufactured separately, the manufacturing process for the switching ring can be adapted to ensure that the contact elements remain precisely aligned when embedded in the first plastic material, preventing them from tipping over or shifting relative to each other.When overmolding the switching ring produced in this way with the second plastic material, this further process can be geared towards optimizing the production of the star disk, in particular the production of the base body or the overmolding of the base body with the second plastic material. With this step-by-step production of the star disk, the risk of the contact elements shifting relative to each other or to the base body of the star disk is particularly low, so that the contact elements are aligned with exceptional precision relative to each other within the star disk. Because the contact elements are aligned with exceptional precision relative to each other and relative to the base body of the star disk, they can be connected and electrically contacted with their respective assigned rotor windings particularly easily.The first plastic material can be different from the second plastic material, or the same plastic material can be used for both. The first and / or second plastic material is typically a thermoset or a thermoplastic.

[0008] In a possible further development of the invention, the base body of the star disc and the switching ring are overmolded or cast together with the second plastic material. For example, the base body of the star disc can be made of steel. This steel base body can, for example, be manufactured as a forging. The switching ring and the base body of the star disc can thus be overmolded or cast together with the second plastic material. This holds the base body and the switching ring together by means of the second plastic material. It is possible that the switching ring rests directly against the base body and that the base body and the switching ring are at least partially encased by the second plastic material, thereby holding the switching ring to the base body of the star disc.Because the base body and the switching ring are manufactured separately, they can be precisely aligned and fixed in this precisely aligned position by being at least partially encased in the second plastic material. This ensures a particularly secure hold of the switching ring to the base body of the star disc.

[0009] As an alternative to designing the star disc such that it comprises the separately manufactured base body, which, together with the switching ring, is overmolded or cast in the second plastic material, the base body of the star disc can be manufactured by injection molding or casting onto the switching ring. Thus, the respective pole arms of the star disc can be injection molded or cast onto the switching ring from the second plastic material. Additionally, a yoke of the base body of the star disc can be injection molded or cast onto the switching ring. This means that the base body can be manufactured entirely from the second plastic material by placing the switching ring in an injection mold or casting mold and injection molding or casting the base body onto the switching ring from the second plastic material.

[0010] The invention further relates to a rotor with a rotor body and at least one star disk arranged on the end face of the rotor body, as already described in connection with the star disk according to the invention. In particular, the rotor has a star disk on each end face of the rotor body. The rotor body can, in particular, be designed as a laminated core. Rotor windings of the rotor are wrapped around the respective star disk and wound around the rotor body. Furthermore, it is provided that the respective rotor windings of the rotor are connected to the contact elements embedded in the switching ring and are thereby electrically connected, thus electrically interconnecting the rotor windings.Because the contact elements are precisely aligned and positioned relative to the base of the star disk, the rotor windings can be connected to the contact elements particularly easily. Because the switching ring is precisely aligned relative to the base of the star disk, it is also precisely aligned with the rotor windings. This ensures that the rotor windings are electrically connected to each other via the switching ring with exceptional reliability, according to a predefined wiring configuration.

[0011] The invention further relates to a motor vehicle with an electric traction machine, which is in particular a current-excited synchronous machine comprising a stator and a rotor rotatable about an axis of rotation relative to the stator, wherein the rotor is designed according to the already described rotor according to the invention. Because the rotor comprises the already described star disk according to the invention, the risk of relative displacement of the switching ring of the rotor relative to the base body of the star disk is particularly low, thereby ensuring reliable switching of the rotor windings of the rotor of the electric traction machine by means of the switching ring.

[0012] The invention further relates to a method for manufacturing a star-shaped disk for a rotor, in particular a rotor of an electric traction motor of a motor vehicle. In this method, a switching ring is produced by embedding individual contact elements in a first plastic material. The contact elements can be embedded in the first plastic material by overmolding or casting them with the first plastic material. The switching ring thus produced is then attached to a base body of the star-shaped disk by overmolding it with a second plastic material. This integrates the switching ring into the star-shaped disk, thereby minimizing the risk of relative displacement of the individual contact elements to each other and to the base body of the star-shaped disk. The star-shaped disk is thus manufactured in a two-stage plastic casting or injection molding process.

[0013] In a possible further development of the invention, it is provided that, for the production of the switching ring, the contact elements are positioned relative to each other in a tool by means of at least one hold-down device, while the contact elements are overmolded or encased with the first plastic material. By means of the at least one hold-down device, the contact elements can be aligned particularly precisely relative to each other and prevented from moving or falling over relative to each other during the overmolding with the first plastic material. After the contact elements have been fixed relative to each other by means of the first plastic material, the at least one hold-down device can be released, and any openings in the switching ring that were held open by the hold-down device can be closed, for example, by potting them with the first plastic material.

[0014] In a further possible embodiment of the invention, the switching ring is positioned against the base body of the star disk and, together with the star disk, is overmolded or cast in the second plastic material. The base body of the star disk can, for example, be made of a metallic material. To attach the switching ring to the base body of the star disk, the base body of the star disk and the switching ring are thus at least partially overmolded or cast in the second plastic material, whereby, after the second plastic material has hardened, the switching ring is held to the base body of the star disk by means of the second plastic material.

[0015] Due to the overmolding of the switching ring and the base body with the second plastic material, the second plastic material can form an undercut, via which the base body of the star disk and the switching ring are fixed in their position relative to each other.

[0016] In a further embodiment of the invention, the base body of the star disk may have a central opening into which an axially projecting collar of the switching ring is inserted. This allows the switching ring to be radially centered relative to the base body. The axially projecting collar can thus be pressed against an inner wall of the base body, which radially defines the opening of the star disk, with its radially outer surface, and in particular, can be pressed against the entire circumference. The switching ring is thus aligned with particular precision relative to the base body and can subsequently be held in this position on the base body by overmolding or overmolding with the second plastic material.Inserting the switching ring with the collar into the opening of the base body ensures that the switching ring is precisely positioned in a predetermined position relative to the base body before the switching ring is attached to the base body by overmolding or overmolding with the second plastic material.

[0017] In another possible embodiment of the invention, the base body of the star disk is forged from the metallic material. The metallic material is, in particular, steel. Forging the base body allows for a particularly simple and quick production of the base body with a precise contour.

[0018] Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0019] The drawing shows in: Fig. 1 a schematic perspective view of a switching ring; Fig. 2 a schematic top view of the switching ring which is attached to a base body of a star disk; and Fig. 3 A schematic top view of the switching ring and the base body of the star disc, which are overmolded or cast together with a plastic material.

[0020] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0021] In Fig. Figure 3 shows a star disk 10 for a rotor of an electrically excited machine of a motor vehicle. In the Fig. 1 and Fig. Figure 2 shows the respective intermediate stages in the manufacture of the star disk 10. The star disk 10 is designed to be placed against an end face of a rotor body. This allows the respective rotor windings of the rotor, which are wound around the respective pole legs of the rotor body, to be wrapped around the star disk 10 located on the end face of the rotor body. The respective rotor windings of the rotor are to be electrically interconnected and electrically contacted with a slip ring of the electric machine to energize the respective rotor windings. For this purpose, the star disk 10 has several contact elements 12, some of which are designed as crimp forks 14 and others as solder tabs 16. The crimp forks 14 are designed to be crimped to the respective rotor windings of the rotor, thereby allowing the rotor windings to be interconnected.In particular, the crimp forks 14 are connected to each other by means of electrically conductive connections for connecting the rotor windings. The crimp forks 14 may be tinned. The solder tabs 16 are designed to be electrically contacted with a slip ring of the rotor. The solder tabs 16 may be provided with a small piece of solder, in particular hard solder or soft solder.

[0022] For the production of the star disc 10, it is planned that first a Fig. The switching ring 18 shown in Figure 1 is manufactured. To manufacture the switching ring 18, the contact elements 12 are aligned relative to each other, for example by means of at least one hold-down device, and then the contact elements 12 are partially embedded in a first plastic material 20. For this purpose, the contact elements 12 can be overmolded or overmolded with the first plastic material 20. The switching ring 18 thus produced, which is a pre-molded part, is then placed against a base body 22 of the star disk 10, as shown in Figure 1. Fig. Figure 2 shows that the base body 22 is manufactured as a forged part from a metallic material. The base body 22 has a centrally located annular opening 24 into which a collar projecting axially from the switching ring 18 is inserted, at least partially. This centers the switching ring 18 radially relative to the base body 22 by ensuring that a circumferential outer surface of the switching ring 18, which radially outwards defines the collar, bears against an inner wall of the base body 22, which radially inwards defines the opening 24 of the base body 22, over its entire circumference. Subsequently, the switching ring 18 and the base body 22 are overmolded or cast together with a second plastic material 26, thereby forming the star disk 10 as shown in Figure 2. Fig.Figure 3 shows how the star disk 10 is manufactured. In particular, it is provided that the base body 22 of the star disk 10 is completely enclosed by the switching ring 18 and the second plastic material 26. At least the contact elements 12 of the switching ring 18 are at least partially free of the plastic materials to enable particularly simple and reliable electrical contact between the contact elements 12 and the rotor windings or the slip ring. The star disk 10 thus comprises the base body 22 and the switching ring 18, which is manufactured separately from the base body 22. These are molded or overmolded together with the second plastic material 26. After the second plastic material 26 has solidified, the switching ring 18 is held to the base body 22 by means of this second plastic material 26 and fixed in its relative position to the base body 22.The star disk 10 is designed to contact the poles of the rotor with each other and with the slip ring via the switching ring 18.

[0023] If the switching ring 18 were not held to the base body 22 of the star disk 10 by the second plastic material 26, the sliding motion of the switching ring 18 relative to the star disk, which is formed separately from the switching ring 18, could lead to a high positional tolerance of the crimp forks to the contacts of the rotor windings and of the solder tabs 16 to the slip ring. This would be counterproductive to high process reliability during contacting. If the contact elements 12 were integrated directly into the insulation of a star disk and thus into the second plastic material 26, these contact elements 12 could not be held in place during an overmolding process, or only with a very high level of technical effort. One risk during overmolding would be that the contact elements 12 would be dislodged by the injection pressure and thereby not maintain their minimum distance to the base body 22, which is relevant for electrical dielectric strength.To overcome these disadvantages, the contact elements 12, which are primarily designed as copper contact bridges, are integrated into the pre-molded part, which is the switching ring 18, in the star disk 10 shown in the figure. This switching ring 18, together with the base body 22 of the star disk 10, is overmolded with the electrically insulating second plastic material 26. This stepwise production of the star disk 10 prevents the contact elements 12 from shifting during the overmolding of the switching ring 18 with the second plastic material 26. Nevertheless, a rotationally secure and fixed positioning of the contact elements 12 relative to the rotor windings can be ensured. This results in particularly high process reliability when connecting the crimp forks 14 to the rotor windings.

[0024] Overall, the invention shows how the star disk 10 can be provided with the firmly cast switching ring 18. Reference symbol list 10 Star disc 12 Contact element 14 crimping fork 16 plumb bobs 18 shift ring 20 first plastic material 22 Basic body of the star disk 24-hour opening 26 second plastic material QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2021 122 066 A1

[0002]

Claims

[1] Star disk (10) for a rotor of an electrically excited machine, with a separately manufactured switching ring (18) comprising several contact elements (12, 14, 16) embedded in a first plastic material (20), which are designed to be connected to respective rotor windings of the rotor or to a slip ring of the electrically excited machine, and which is held on a base body (22) of the star disk (10) by overmolding with a second plastic material (26). [2] Star disk (10) according to claim 1, characterized by , that the base body (22) of the star disk (10) and the switching ring (18) are overmolded or cast together with the second plastic material (26). [3] Rotor with a rotor base body and at least one star disk (10) arranged at the end face of the rotor base body according to one of the preceding claims, around which rotor windings of the rotor which are wound around the rotor base body are wrapped. [4] Motor vehicle with an electric traction machine comprising a stator and a rotor rotatable about an axis of rotation relative to the stator according to claim 3. [5] Method for manufacturing a star disk (10) for a rotor, in which a switching ring (18) is manufactured by embedding respective contact elements (12, 14, 16) in a first plastic material (20) and subsequently the switching ring (18) is attached to a base body (22) of the star disk (10) by overmolding with a second plastic material (26). [6] Method according to claim 5, characterized by , that for the manufacture of the switching ring (18) the contact elements (12, 14, 16) are positioned relative to each other in a tool by means of at least one hold-down device, while the contact elements (12, 14, 16) are overmolded or overmolded with the first plastic material (20). [7] Method according to claim 5 or 6, characterized by, that the switching ring (18) is placed against the base body (22) of the star disk (10) and is overmolded or cast together with the star disk (10) by the second plastic material (26). [8] Method according to claim 7, characterized by , that the base body (22) of the star disk (10) has a central opening (24) into which an axially projecting collar of the switching ring (18) is inserted, thereby centering the switching ring (18) radially relative to the base body (22). [9] Method according to claim 7 or 8, characterized by , that the base body (22) of the star disk (10) is forged from a metallic material.

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