Rotor and method for manufacturing a rotor

Abstract

Rotor of an electric machine, with a rotor body (30), several permanent magnets (46) distributed around the circumference, and at least one balancing disc (60) which is arranged on an end face of the rotor base body (30), wherein the balancing disc (60) is designed such that the balancing disc (60) is reworked in certain sections by removing or adding material so that the imbalance is at least partially compensated during rotation of the rotor, and wherein the balancing disc (60) has at least one recess (62) on an end face facing away from the rotor base body (30), characterized by the fact that the recess (62) is filled by a plastic material (70).

Description

[0001] The invention relates to a rotor of an electric machine, comprising a rotor body, several permanent magnets distributed around the circumference, and at least one balancing disc arranged on an end face of the rotor body, wherein the balancing disc has at least one recess on an end face facing away from the rotor body.

[0002] Such rotors are generally known from the prior art. The balancing discs serve to balance the rotor. This is usually achieved by reworking the balancing disc in specific sections by removing or adding material, so that the imbalance is at least partially compensated for when the rotor rotates. In particular, material is removed from the balancing disc at an end face facing away from the rotor body, thereby balancing the rotor.

[0003] A disadvantage of this rotor design with at least one recess on the balancing disk is that the recess causes air to be drawn in, creating air turbulence. This, in turn, reduces the cooling of the electric machine, as the cooling air flowing along the rotor and / or stator is obstructed by the air turbulence, thus reducing the cooling capacity of the electric machine. Reduced cooling leads to a decrease in the drive power output of the electric machine, as the machine heats up and the drive power must be throttled.

[0004] From CN 1 11 786 484 B, a rotor of an electric machine is known, which has a rotor core with several permanent magnets, wherein the rotor core is received by a structural element. The structural element is non-rotatably connected to a transmission element via two vibration dampers made of a plastic. The transmission elements are in turn non-rotatably connected to a rotor shaft. Thus, the rotor core is connected to the rotor shaft via the structural element, the vibration dampers, and the transmission elements in a torque-transmitting manner. Furthermore, DE 10 2021 133 460 A1 discloses a rotor of an electric machine, wherein an end disk is arranged at each of the end faces of a rotor body. One of the two end disks has coolant outlet openings.

[0005] The object of the invention is to provide a rotor with the highest possible efficiency, which can be balanced by a balancing disc, and yet reliably ensures air cooling of the rotor.

[0006] The problem is solved by the features of claim 1.

[0007] According to the invention, the recess of the balancing disc is filled with a plastic material. The recess is filled with the plastic material in such a way that no surface defining the recess acts on the air during rotation of the rotor in a manner that would cause the air to be entrained. In other words, there is no surface defining the recess that acts on the air in the manner of a wing. This prevents unwanted air currents and turbulence, thus ensuring that the cooling of the electric machine is not negatively affected by the recess and that reliable cooling of the electric machine is guaranteed.

[0008] Preferably, the recess is arranged circumferentially in the area of ​​at least one permanent magnet. This leaves the balancing disc recessed in the area of ​​the permanent magnets, so that the magnetic flux caused by the permanent magnets is not negatively affected by the magnetic or magnetizable balancing disc, thereby increasing the efficiency of the electric machine.

[0009] Preferably, several groups of permanent magnets are provided, each with a circumferential recess in the area of ​​the groups of permanent magnets, and each recess being filled with the plastic material. Each group has at least two permanent magnets, which are arranged, for example, in a V-shape. In a preferred embodiment, the permanent magnets of each group are arranged in two radially offset planes. For example, each group has four permanent magnets, with two permanent magnets arranged in each plane in a V-shape. In another embodiment, for example, three permanent magnets are arranged in each plane, with the permanent magnets of one plane arranged in a U-shape.

[0010] Preferably, the balancing disc has a star-shaped cross-section. The permanent magnets or groups of permanent magnets are arranged uniformly around the circumference, which also results in the recesses located in the area of ​​the permanent magnets or groups of permanent magnets being uniformly distributed around the circumference, thus creating a star-shaped balance disc. Filling the recesses of the balance disc restores a circular cross-section.

[0011] In a preferred embodiment, the permanent magnets are arranged in individual magnet receiving openings of the rotor body, with a cavity between each permanent magnet and a wall defining the magnet receiving opening being filled with a plastic material, such that the cavities between the permanent magnets and the walls defining the magnet receiving opening, as well as the filling of the recess, are achieved through a single plastic filling process. During the manufacture of the rotor, particularly for positioning the permanent magnets in the magnet receiving openings, the cavities of the magnet receiving openings are filled with the plastic material while the permanent magnets are already mounted. This is done, in particular, by an injection molding process.By appropriately modifying the injection mold, the recesses of the balancing disc already mounted on the rotor body can also be filled with the plastic material.

[0012] Preferably, the balancing disc for balancing the rotor is machined. This allows the rotor to be reliably balanced, whereby the rotor with all mounted components is first rotated at a predefined speed and the existing imbalance is determined. Subsequently, the balancing disc is machined at the relevant points, in particular by a drilling process using a milling cutter on the end face facing away from the rotor body, thus balancing the rotor.

[0013] The problem is further solved by a method for manufacturing a rotor according to any one of claims 1 to 7, wherein several permanent magnets are inserted into magnet receiving openings provided on a rotor base body, the balancing disc is arranged on the rotor base body, and finally the recess of the balancing disc and cavities between the permanent magnets and the walls delimiting the magnet receiving opening are filled with a plastic material. In a preferred embodiment, the fully assembled rotor is balanced by mechanically removing a section of the balancing disc.

[0014] The advantages of the procedure are described in the preceding paragraphs.

[0015] This provides a rotor with high efficiency, which can be balanced by a balancing disc, while still reliably ensuring air cooling of the rotor.

[0016] An embodiment of the invention is explained in more detail with reference to the drawing.

[0017] The figure schematically depicts a rotor in a perspective view.

[0018] The figure shows a rotor 10 of an electric machine, whereby only the rotor 10 is shown in the figure and the stator of the electric machine has been omitted.

[0019] The rotor 10 comprises a rotor shaft 20 and a rotor body 30. The rotor shaft 20 has a receiving section 22 for receiving the rotor body 30 and a drive section 24 with helical teeth. The drive section 24 serves to transmit the drive power of the electric machine to another component, the other component having teeth that mesh with the helical teeth of the drive section 24. The rotor body 30 is arranged on the receiving section 22, i.e., on the outer circumferential surface of the rotor shaft 20 in the region of the receiving section 22. The rotor shaft 20 with the receiving section 22 is inserted into a through-opening in the rotor body 30 and is connected to the rotor body 30 by friction and / or positive locking. Thus, the rotor shaft 20 and the rotor body 30 rotate together.

[0020] The rotor body 30 is designed as a laminated core 32 with several rotor laminations, the laminated core comprising several partial laminated cores 34 stacked axially. All partial laminated cores 34 have a plurality of magnet receiving openings 48 distributed around the circumference and open at their ends, each containing a permanent magnet 46. The magnet receiving openings 48 and the permanent magnets 46 are configured such that several permanent magnets 46, in this case six permanent magnets 46, form a group 40, each group 40 having two radially spaced planes 42, 44, in each of which three permanent magnets 46 are arranged. The rotor 10 has six groups 40 evenly distributed around its circumference.

[0021] To balance the rotor 10, a balancing disk 60 is arranged on one end face of the rotor body 30, the balancing disk 60 being attached to the rotor body 30 and / or to the rotor shaft 20. To increase the efficiency of the electric machine, the balancing disk 60 has a recess 62 in the circumferential region of each group 40 of permanent magnets 46. This recess is located at the edge of the balancing disk 60 and extends axially from one end face of the balancing disk 60 to the other end face. The six groups 40 of permanent magnets 46, evenly distributed around the circumference, also provide six recesses 62, giving the balancing disk 60 a star-shaped cross-section.

[0022] Due to the star-shaped design of the balancing disc 60, the radially projecting sections cause, during operation of the electric machine, i.e., during rotation of the rotor 10, both an airflow in the direction of rotation and turbulence at the balancing disc 60. This means that the necessary air cooling of the rotor 10 and, if applicable, other components of the rotor 10, is no longer provided or only partially provided, since the airflow required for cooling is negatively affected by the turbulence and the airflow in the direction of rotation. To prevent this, the recesses 62 are filled with a plastic material 70 such that the balancing disc 60, including the plastic material, has a substantially circular cross-section. The same plastic material 70 is also used to fill cavities 50 between the permanent magnets 46 and the walls 49 that define the magnet mounting openings 48.

[0023] The balancing of the rotor 10 is carried out by mechanically machining the balancing disc 60, whereby at least one recess 64 is made in the balancing disc 60.

[0024] In the manufacture of the rotor 10, the permanent magnets 46 are first inserted into magnet receiving openings 48 provided on the rotor body 30. The star-shaped balancing disc 60 with its six recesses 62 is then attached to the rotor body 30 and / or the rotor shaft 20. In the next step, the recesses 62 and the cavities 50 between the permanent magnets 46 and the walls 49 are filled with the plastic material 70. This is done, in particular, by placing the rotor 10 in an injection mold and filling the corresponding areas of the rotor 10 with the plastic material 70. Finally, the fully assembled rotor 10 is balanced by machining the balancing disc 60.In this process, an imbalance is determined by rotating the rotor 10 at predefined speeds and the recess 64 is incorporated at a point on the balancing disc 60 that compensates for the imbalance, in particular by a milling process.

[0025] By filling the recesses 62 with the plastic material 70, there are no surfaces bounding the recesses 62 that could cause undesirable air currents and turbulence. Therefore, the cooling of the electric machine through the recesses 62 is not negatively affected, thus ensuring reliable cooling of the electric machine.

Claims

[1] Rotor of an electric machine, with a rotor body (30), several permanent magnets (46) distributed around the circumference, and at least one balancing disc (60) which is arranged on an end face of the rotor base body (30), wherein the balancing disc (60) is designed such that the balancing disc (60) is reworked in certain sections by removing or adding material so that the imbalance is at least partially compensated during rotation of the rotor, and wherein the balancing disc (60) has at least one recess (62) on an end face facing away from the rotor base body (30), characterized by , that the recess (62) is filled by a plastic material (70). [2] Rotor according to claim 1, characterized by , that the recess (62) is arranged in the circumferential direction in the area of ​​at least one permanent magnet (46). [3] Rotor according to claim 2, characterized by , that several groups (40) of permanent magnets (46) are provided, wherein a recess (62) is arranged in the circumferential direction in the area of ​​the groups (40) of permanent magnets (46), and wherein all recesses (62) are filled by the plastic material (70). [4] Rotor according to claim 3, characterized by , that the permanent magnets (46) of each group (40) are arranged in two radially offset planes (42, 44). [5] Rotor according to claim 3 or 4, characterized by , that the balancing disc (62) has a star-shaped cross-section. [6] Rotor according to any one of the preceding claims, characterized by, that the permanent magnets (46) are arranged in each a magnet receiving opening (48) of the rotor base body (30), wherein a cavity (50) between each permanent magnet (46) and a wall (49) defining the magnet receiving opening (48) is filled by the plastic material (70), such that the cavities (50) between the permanent magnets (46) and the walls (49) defining the magnet receiving opening (48) and the filling of the recess (62) are carried out by a common plastic filling process. [7] Rotor according to any one of the preceding claims, characterized by , that the balancing disc (60) for balancing the rotor (10) can be machined by mechanical means. [8] Method for manufacturing a rotor (10) according to one of claims 1 to 7, wherein several permanent magnets (46) are inserted into each of a magnet receiving opening (48) provided on a rotor base body (30), the balancing disk (60) is arranged on the rotor base body (30), and finally the recess (62) of the balancing disk (60) and cavities (50) between the permanent magnets (46) and the walls (49) defining the magnet receiving opening (48) are filled with a plastic material (70). [9] Method according to claim 8, wherein the fully assembled rotor (10) is balanced by mechanically removing a section of the balancing disc (60).

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