The present application relates to a rotor for an electrical machine and to an electrical machine.
Typically, electrical machines comprise a stator and a rotor movable relative thereto. Electrical machines can be operated as a motor or as a generator, converting electrical energy into kinetic energy or vice versa. In operation, a magnetic field of the rotor interacts with a magnetic field of the stator.
The stator may have a distributed winding type. Electric machines with distributed windings are widely used in electric vehicles as prime movers. However, distributed windings have the disadvantage that the winding heads take up a lot of space along the axial machine length. This leaves less space along the axial machine length for the active length. This refers to the area that can be used to generate torque and power.
This inevitably means that this machine type is to be evaluated as inefficient, at least with regard to the utilization of the available installation space.
One task to be solved is to provide a rotor for an electrical machine, which can be operated efficiently. A further task to be solved is to provide an electrical machine which can be operated efficiently.
The tasks are solved by the objects of the independent claims. Advantageous designs and further developments are indicated in the subclaims.
According to at least one embodiment of the rotor for an electrical machine, the rotor comprises a main rotor which is rotatable around a longitudinal axis. The main rotor may have the shape of a cylinder. Furthermore, the main rotor may be arranged on a shaft of the electrical machine. The main rotor may be a claw pole type rotor with an excitation coil.
Furthermore, the rotor comprises at least one auxiliary rotor, which is an axial flux rotor. The auxiliary rotor may be in direct contact with the main rotor. The auxiliary rotor may be firmly connected to the main rotor. Thus, the main rotor and the auxiliary rotor always run at the same speed of rotation and have the same angle to each other. For example, the auxiliary rotor is glued to the main rotor.
The auxiliary rotor is also rotatable around the longitudinal axis and is arranged along the longitudinal axis so as to be adjacent to the main rotor.
The auxiliary rotor comprises at least one permanent magnet. The permanent magnet has a magnetic axis. The magnetic axis is parallel to the magnetization direction of the permanent magnet. This means that the magnetic axis connects the two poles of the permanent magnet. The permanent magnet may include rare earths or ferrite magnets. While rare earths enable a very high power density, ferrite magnets offer the advantage of lower costs.
The permanent magnet has the shape of a ring at least in parts. This may mean that at least a part of the permanent magnet has the shape of a ring. Furthermore, the permanent magnet may have further parts that do not have the shape of a ring. In other words, the permanent magnet may have different areas of which at least one has the shape of a ring. The different areas of the permanent magnet are connected to each other. For example, the different areas of the permanent magnet are connected by an adhesive. The permanent magnet may be formed in one piece. In this case, the permanent magnet has a particularly high mechanical strength. It is also possible that the permanent magnet has the shape of a ring. The diameter of the ring may be smaller than the diameter of the main rotor. The ring can be arranged around the shaft of the electric machine.
The rotor described here may be used in an electric machine comprising a stator with a distributed winding. In this case, the stator has an active length which is the area that may be used to generate torque and power. The winding heads of the distributed winding are arranged along the longitudinal axis besides the active length. The length of the main rotor along the longitudinal axis can be equal to the active length. The auxiliary rotor is thus arranged adjacent to the winding heads. This means that the auxiliary rotor is arranged around the longitudinal axis and the winding heads are arranged around the auxiliary rotor.
In this configuration of the electrical machine, the auxiliary rotor increases the magnetic flux density of the main rotor. This means that the magnetic flux density generated by the main rotor is amplified. During operation of the electric machine, the magnetic flux passes through the main rotor and the auxiliary rotor. Especially if the main rotor is a claw pole rotor, the flux density of the main rotor is increased by the arrangement of the auxiliary rotor next to the main rotor.
The effect of the auxiliary rotor may be increased by increasing the surface area of the permanent magnet of the auxiliary rotor in a cross-section through the rotor, with the longitudinal axis extending perpendicular to the cross-section through the rotor. This is achieved by the permanent magnet having the shape of a ring at least in parts. This allows the permanent magnet to cover a large surface area in the cross-section through the rotor. The permanent magnet may have further areas so that the surface area of the permanent magnet in the cross section through the rotor is further increased. In total, the volume of the permanent magnet is thus increased, which leads to an increased effect on the flux density of the main rotor. This means that the larger the volume of the permanent magnet, the more the flux density of the main rotor is increased. This leads to a higher torque and a higher power density of the electric machine. Thus, the electrical machine can be operated more efficiently.
According to at least one embodiment of the rotor, the main rotor is formed as a claw pole type rotor. The claw pole rotor may have an excitation coil. In a claw pole rotor, claws of two rotor halves alternately engage into each other. The two rotor halves are arranged in such a way that along the circumference of the claw pole type rotor a respective claw, which is designed as south pole, is arranged between two claws, which are designed as north pole. Thus, the north and south poles alternate along the circumference of the claw pole type rotor. The claws are arranged around the excitation coil. This means that the claws are arranged around the excitation coil in a cross-section through the main rotor. The excitation coil may have the shape of a ring. Advantageously, the at least one auxiliary rotor can increase the flux density of the claw pole type rotor.
According to at least one embodiment of the rotor, the rotor comprises a further auxiliary rotor, with the main rotor being arranged along the longitudinal axis between the auxiliary rotor and the further auxiliary rotor. The further auxiliary rotor may have the same structure as the auxiliary rotor. Along the longitudinal axis, the further auxiliary rotor may be arranged in the opposite direction to the auxiliary rotor. This means that, concerning the auxiliary rotor and the further auxiliary rotor, the permanent magnet faces the main rotor. By using the auxiliary rotor and the further auxiliary rotor, the flux density of the main rotor can be further increased. Advantageously, an auxiliary rotor is arranged on both sides of the main rotor along the longitudinal axis. Thus, the flux density of the main rotor may be increased more than with only one auxiliary rotor. The installation space in which the auxiliary rotor and the further auxiliary rotor are arranged is usually not intended for other parts of the rotor or of the electrical machine. Therefore, no further space is required to mount the auxiliary rotor and the further auxiliary rotor to the main rotor. This means that the efficiency of the electrical machine including the rotor can be increased without requiring more installation space.
According to at least one embodiment of the rotor, the magnetic axis of the permanent magnet extends parallel to the longitudinal axis. This means that the magnetic axis of the permanent magnet points either towards the main rotor or away from the main rotor. The magnetic axis of the permanent magnet of the auxiliary rotor may point in the same direction as the magnetic axis of the permanent magnet of the further auxiliary rotor. In this way, the flux density of the main rotor can be increased.
According to at least one embodiment of the rotor, the auxiliary rotor has a rotor core which has the shape of a ring at least in parts. The rotor core contains iron, for example. Thus, the rotor core serves as a rotor yoke. The permanent magnet is attached to the rotor core. The rotor core and the permanent magnet may be in direct contact. The fact that the rotor core has the shape of a ring at least in parts means that at least a part of the rotor core has the shape of a ring. Furthermore, the rotor core may have further parts that do not have the shape of a ring. In other words, the rotor core may have various areas of which at least one has the shape of a ring. The different areas of the rotor core are connected to each other. The rotor core may be formed in one piece. The diameter of the ring of the rotor core may be the same as the diameter of the main rotor. Since the auxiliary rotor has the permanent magnet and the rotor core, the flux density of the main rotor may be increased by the auxiliary rotor.
According to at least one embodiment of the rotor, the rotor core has teeth which extend toward the main rotor and are arranged to be spaced from each other. The teeth may also contain iron. The teeth are arranged along the circumference of the ring of the rotor core. Here, the teeth extend from the ring of the rotor core toward the main rotor. Along the longitudinal axis, the teeth of the rotor core extend further toward the main rotor than the permanent magnet. The teeth may be attached to the ring of the rotor core or they may be integral with it. The teeth of the rotor core are each assigned to a claw of the main rotor. Furthermore, the teeth of the rotor core may each be flush with a respective claw of the main rotor. Thus, the teeth of the rotor core may be connected to the main rotor. Advantageously, the teeth of the rotor core represent a path for the magnetic flux passing through the teeth of the rotor core into the main rotor. Thus, the flux density of the main rotor can be increased.
According to at least one embodiment of the rotor, the permanent magnet is arranged at least in parts along the longitudinal axis between the rotor core and the main rotor. The permanent magnet may be arranged along the longitudinal axis between the ring of the rotor core and the main rotor. The teeth of the rotor core may be in direct contact with the main rotor, so that the permanent magnet along the longitudinal axis is not arranged between the rotor core and the main rotor. The flux density of the main rotor can be increased by this design.
According to at least one embodiment of the rotor, the permanent magnet has recesses along its outer circumference which extend in the direction of the longitudinal axis partially through the permanent magnet. This means that the recesses extend from the outer circumference of the permanent magnet partially in the direction of the longitudinal axis. Thus, the recesses extend from the outer circumference of the permanent magnet in a radial direction partially in the direction of the longitudinal axis. The radial directions each extend perpendicular to the longitudinal axis. The teeth of the rotor core may be arranged in the recesses. This means that the rotor core and the permanent magnet may be flush with each other except for the areas of the recesses and the teeth. This shape of the permanent magnet maximizes the surface area of the permanent magnet in the cross-section through the rotor. This maximizes the volume of the permanent magnet and thus the flux density of the main rotor. This is why the electrical machine can be operated more efficiently. Furthermore, the shape of the auxiliary rotor may be adapted to the shape of the main rotor. To this end, the number of the recesses may be equal to the number of the pole pairs of the main rotor.
According to at least one embodiment of the rotor, the recesses are equal in size and have equal distances to each other. This means that the recesses along the circumference of the auxiliary rotor may be equal in size. Furthermore, the distances between the recesses along the circumference of the auxiliary rotor may be the same. Thus, the permanent magnet and the teeth of the rotor core may be adapted to the shape of the main rotor. This increases the flux density of the main rotor.
According to at least one embodiment of the rotor, further permanent magnets are connected to the permanent magnet, the further permanent magnets being arranged along the outer circumference of the permanent magnet so as to be spaced from each other. In this case, the permanent magnet has the shape of a ring. The further permanent magnets are arranged along the outer circumference of the ring. Thus, the further permanent magnets are attached to the permanent magnet. The permanent magnet with the further permanent magnets thus forms a ring, which has recesses along its outer circumference. These recesses extend from the outer circumference partially in the direction of the longitudinal axis. The further permanent magnets may be of the same size and have the same distances relative to each other. This means that the distances between the further permanent magnets along the circumference of the auxiliary rotor may be equal in size. This shape of the permanent magnet with the further permanent magnets maximizes the surface area, covered by permanent magnets, in the cross-section through the rotor. This maximizes the volume of the permanent magnet and thus the flux density of the main rotor. Therefore, the electrical machine may be operated more efficiently.
According to at least one embodiment of the rotor, the magnetic axes of the further permanent magnets extend parallel to the magnetic axis of the permanent magnet. Thus, the further permanent magnets also contribute to the amplification of the magnetic flux of the main rotor.
According to at least one embodiment of the rotor, the number of the further permanent magnets is equal to the number of the pole pairs of the main rotor. This is why the shape of the auxiliary rotor can be adapted to the shape of the main rotor. Each of the further permanent magnets may end flush with a claw of the claw pole type rotor. The flux density of the main rotor can be increased by this design.
Furthermore, an electrical machine is provided. According to at least one embodiment of the electrical machine, the electrical machine comprises the rotor. Thus, all features of the described rotor are also disclosed for the electrical machine, and vice versa. The electrical machine also has a stator. The rotor may be an internal rotor or an external rotor. If the rotor is an internal rotor, an outer side of the rotor faces the stator. The rotor may be arranged on a shaft of the electric machine. An air gap may be arranged between the stator and the rotor. The stator has a distributed winding or a concentrated winding.
According to at least one embodiment of the electrical machine, the stator has a winding with winding heads, with the main rotor extending as far as the area of the stator between the winding heads along the longitudinal axis. The winding including the winding heads is a distributed winding. The stator therefore has an active length that extends in the area between the winding heads. The active length is the area that may be used to generate torque and power. Along the longitudinal axis, the length of the main rotor thus corresponds to the active length. This means that the auxiliary rotor is arranged along the longitudinal axis outside the active length. Thus, the auxiliary rotor is arranged adjacent to the winding heads. In a cross-section through the electrical machine, which is parallel to the longitudinal axis, the auxiliary rotor is arranged between the winding heads. Along the longitudinal axis, the auxiliary rotor may extend approximately as far as the winding heads on one side of the stator. It is also possible that the auxiliary rotor extends along the longitudinal axis as far as the winding heads on one side of the stator. Without the use of the auxiliary rotor, the space in which the auxiliary rotor is arranged would not be used for torque generation. However, the auxiliary rotor contributes to an increase in the flux density of the main rotor. Thus, the electrical machine can be operated more efficiently.
In the following, the rotor described here and the electrical machine are explained in more detail in conjunction with exemplary embodiments and the corresponding Figures.
The rotor 20 has a main rotor 22 which is rotatable around a longitudinal axis z. The longitudinal axis z extends through the rotor 20. The main rotor 22 is a claw pole type rotor. The main rotor 22 has several claws 32 which are distributed along the circumference of the main rotor 22. Furthermore, the main rotor 22 has an excitation coil 39. The claws 32 are arranged around the excitation coil 39. The main rotor 22 has approximately the shape of a cylinder. The claws 32 each have a base area in the shape of a trapezoid. The base area extends along the circumference of the main rotor 22. The main rotor 22 has two end faces 33, which form the base areas of the cylinder. The claws 32 are arranged in such a way that one half of the claws 32 has the longer base of the base area of the trapezoid pointing toward one of the end faces 33 and the other half of the claws 32 has the shorter base of the base area pointing toward this end face 33. Thus, the claws 32 are alternately distributed along the circumference of the main rotor 22.
Moreover, the rotor 20 has an auxiliary rotor 23 and a further auxiliary rotor 25. The auxiliary rotor 23 is an axial flow rotor. In addition, the auxiliary rotor 23 can also be rotated about the longitudinal axis Z and is arranged along the longitudinal axis Z adjacent to the main rotor 22. The auxiliary rotor 23 comprises a permanent magnet 24 and a further permanent magnets 29. The permanent magnet 24 has the shape of a ring. The ring is arranged around the longitudinal axis z. Thus, the center of the ring lies on the longitudinal axis z.
The further permanent magnets 29 are connected to the permanent magnet 24. In this arrangement, the further permanent magnets 29 are arranged along the outer circumference of the permanent magnet 24 so as to be spaced from each other. The permanent magnet 24 with the further permanent magnets 29 thus form a ring which has recesses 28 along its outer circumference. The further permanent magnets 29 each have the same size and are arranged at equal distances from each other along the circumference of the permanent magnet 24. In addition, the magnetic axes of the further permanent magnets 29 extend parallel to the magnetic axis of the permanent magnet 24. The magnetic axis of the permanent magnet 24 is parallel to the longitudinal axis z. The permanent magnet 24 has a smaller extension along the longitudinal axis z than along a radial direction r, which is perpendicular to the longitudinal axis z. The further permanent magnets 29 also have a smaller extension along the longitudinal axis z than along a radial direction r.
The auxiliary rotor 23 also comprises a rotor core 26, which has the shape of a ring at least in parts. The rotor core 26 may contain iron and serve as a rotor yoke. The rotor core 26 also has teeth 27, which extend toward the main rotor 22 and are arranged to be spaced from each other. The teeth 27 are arranged on the outside of the rotor core 26. Furthermore, the teeth 27 are equally spaced along the circumference of the rotor core 26. The remaining part of the rotor core 26, apart from the teeth 27, has the shape of a ring. The ring of rotor core 26 has a smaller extension along the longitudinal axis z than along a radial direction r.
The permanent magnet 24 is arranged along the longitudinal axis z between the rotor core 26 and the main rotor 22. The teeth 27 of the rotor core 26 are in direct contact with the main rotor 22. This means that the permanent magnet 24 is not arranged between the teeth 27 of the rotor core 26 and the main rotor 22. In the assembled state, the teeth 27 extend through the gaps between the further permanent magnets 29 toward the main rotor 22. In addition, the permanent magnet 24 with the further permanent magnets 29 is in direct contact with the main rotor 22 in the assembled state. The individual components of the rotor 20 may be joined together by adhesive bonding.
When assembled, the further permanent magnets 29 are each flush with a longer base of the base area of a claw 32 of the main rotor 22. In the assembled state, the teeth 27 are also in direct contact with a shorter base of the base area of a claw 32. This is why the number of the further permanent magnets 29 is equal to the number of the pole pairs of the main rotor 22. Thus, during operation of the electric machine 21, the magnetic flux through claws 32 may extend further through the teeth 27 and the rotor core 26. This increases the magnetic flux density of the rotor 20.
The further auxiliary rotor 25 has the same structure as the auxiliary rotor 23 and is mounted on the main rotor 22 in the opposite direction as compared to the auxiliary rotor 23. The main rotor 22 is arranged along the longitudinal axis z between the auxiliary rotor 23 and the further auxiliary rotor 25. Thus, the permanent magnet 24 of the further auxiliary rotor 25 is arranged between the rotor core 26 of the further auxiliary rotor 25 and the main rotor 22. The auxiliary rotor 23 and the further auxiliary rotor 25 are arranged at opposite end faces 33 of the main rotor 22. Since the further permanent magnets 29 of the further auxiliary rotor 25 are also adapted to the claws 32 of the main rotor 22, the further auxiliary rotor 25 is turned around the longitudinal axis z by an angle relative to the auxiliary rotor 23.
The exemplary embodiment shown in
Compared to the exemplary embodiment shown in
In this exemplary embodiment, the permanent magnet 24 also exhibits high mechanical stability. It can also be easily manufactured.
Number | Date | Country | Kind |
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10 2019 130 358.3 | Nov 2019 | DE | national |