Motor

Abstract

The electric machine (1) comprises: a drive shaft (11) rotatable about an axis of rotation (L), said drive shaft (11) having an axial bore (14); a rotor (4) non-rotatably fixed to the drive shaft (11), said rotor (4) having a rotor core (5) and at least one rotor ring (6, 7) axially supporting an end of the rotor core (5); and at least one cooling channel (12) for conveying coolant at least partially in the at least one rotor ring (6, 7), where the at least one cooling channel (12) extends from an inlet opening (13) fluidically connected to an axial bore (14) of the drive shaft (11) to a radially outward outlet opening (15), characterized in that the inlet opening (13) is fluidically connected to the axial bore (14) of the drive shaft (11) and the outlet opening (15) is fluidically connected to the outlet opening (15). The at least one cooling channel (12) extends at least partially along a path deviating from the straight radial direction.

Description

Technical Field

[0001] The invention relates to an electric machine, comprising a drive shaft rotatable about a rotation axis and a rotor non-rotatably fixed to the drive shaft. The drive shaft has an axial hole. The rotor has a rotor core and at least one rotor ring axially supporting the end of the rotor core. At least one cooling channel for conveying a coolant is at least partially arranged in the at least one rotor ring, wherein the at least one cooling channel extends from an inlet opening fluidically connected to the axial hole of the drive shaft to a radially outward outlet opening. Background Art

[0002] The performance of electric machines is thermally limited during operation. Intrinsic losses may occur in the copper, iron and magnets of the machine, where the material properties limit the temperature of the corresponding components and structures. In order to achieve adequate performance, effective cooling is necessary. Especially for induction machines with a cage rotor, such as asynchronous motors or generators, the hottest point is the cage of the rotor.

[0003] JP 2009-118686 A discloses a motor with a cooling structure as mentioned above. The motor includes a stator and a rotor. The rotor is provided with a permanent magnet, and the stator is provided with a winding. For cooling, the motor has a first flow path for a coolant for cooling the permanent magnet and the winding. The motor has a second flow path for a coolant only for cooling the winding. A flow switching unit is provided, which switches the flow state of the coolant to the first flow path and the second flow path based on one or both of the rotation speed and the output torque of the motor. Both flow paths supply coolant from a supply hole in the center of the drive shaft of the motor. The coolant is supplied to the flow path by the centrifugal force generated by the rotation of the drive shaft. Therefore, the first flow path and the second flow path are arranged to penetrate the hollow drive shaft linearly from the inner peripheral surface to the outer peripheral surface along the radial direction of the rotation axis. The first flow path continues into a rotor ring, which is mounted on the drive shaft and supports the rotor core in the axial direction. The first flow path terminates in axial outlets in the rotor annulus on axially opposite sides of the rotor annulus to provide coolant to the rotor core and windings of the stator.

[0004] US11018555 B2 discloses an induction motor including a motor shaft, a rotor and rotor conductor bars. The rotor has a first axial side and a second axial side and is non-rotatably fixed to the motor shaft. The rotor includes a rotor core having an inner surface defining a slot extending from the first axial side to the second axial side. The rotor conductor bars are arranged in the slots. The rotor conductor bars and the slots cooperate to define a channel configured to transfer a fluid from the first axial side to the second axial side through the rotor core while directly contacting the rotor conductor bars. An inlet pipe is coupled to the first axial side of the rotor and delivers the fluid to the channel. The outlet pipe is coupled to the second axial side of the rotor extending to the outside of the rotor core and is configured to guide the fluid to the windings of the stator. Summary of the invention

[0005] An object of the present invention is to enhance heat dissipation in an electric machine.

[0006] This object is achieved by an electric machine according to claim 1. Exemplary embodiments are described in the dependent claims.

[0007] According to the present invention, an electric machine comprises a drive shaft rotatable about a rotation axis, and a rotor non-rotatably fixed to the drive shaft. The drive shaft has an axial hole. The rotor has a rotor core and at least one rotor ring supporting the end of the rotor core in the axial direction. At least one cooling channel for conveying a coolant is at least partially arranged in the at least one rotor ring, wherein the at least one cooling channel extends from an inlet opening fluidically connected to the axial hole of the drive shaft to a radially outward discharge opening. The at least one cooling channel extends at least partially along a path deviating from a straight radial direction.

[0008] Thus, the path of the at least one cooling channel deviates from a line extending in a radial direction from the axis of rotation. Thus, the cooling channel is arranged along a longer path compared to a straight path in a radial direction. The longer path and the resulting increased heat exchange area enhance the heat dissipation from the at least one rotor ring to the coolant transported by centrifugal force.

[0009] In order to connect the axial bore of the drive shaft to the at least one cooling channel, at least one supply channel can be provided in the drive shaft.

[0010] According to an exemplary embodiment, the inlet opening and the outlet opening of the at least one cooling channel are arranged offset from each other in the circumferential direction. Thus, the cooling channel extends in the radial direction and in the circumferential direction. It is also conceivable that the inlet opening and the outlet opening are arranged on a radius, which is a line segment extending from the axis of rotation in a straight radial direction, and the cooling channel between the inlet opening and the outlet opening follows a path in the shape of a curve, for example in the form of a zigzag.

[0011] The circumferential offset of the inlet opening and the outlet opening may enclose an angle greater than 45 degrees, for example an angle of about 180 degrees. This means that a radius (i.e. a line segment) from the axis of rotation to the inlet opening and a radius from the axis of rotation to the outlet opening enclose an angle greater than 45 degrees. The angle of the circumferential offset may be defined by the offset of the center of the inlet opening from the center of the outlet opening.

[0012] The inlet opening and the outlet opening of the at least one cooling channel may be arranged offset from each other in the axial direction. Such an offset of the openings will result in a longer path of the at least one cooling channel. In combination with an offset of the openings in the circumferential direction, the length of the at least one cooling channel may even be further extended. The at least one cooling channel in this example will have a three-dimensional shape.

[0013] According to an exemplary embodiment, the discharge opening of the at least one cooling channel is arranged in the outer peripheral surface of the at least one rotor ring. Such a configuration has the advantage that the cooling channel extends as long as possible through the rotor ring in the outer region of the at least one rotor ring and that heat dissipation is enhanced. Furthermore, the coolant leaves the discharge opening in the radial direction and splashes onto radially outwardly arranged components of the electric machine, such as the windings of the stator.

[0014] In particular, the outer peripheral surface is an outer cylindrical or conical surface of the at least one rotor ring.

[0015] The at least one cooling channel may protrude out of the inner circumferential surface of the rotor ring towards the drive shaft.Alternatively, an entry opening of the at least one cooling channel may be arranged in the inner circumferential surface of the at least one rotor ring.

[0016] The at least one cooling channel may be at least partially formed in a curved shape about the rotation axis so as to extend the length of a path of the at least one cooling channel.

[0017] According to a specific embodiment, the at least one cooling channel is at least partially formed in a spiral shape around the rotation axis. The at least one cooling channel can be made of different segments. The radius of each individual segment can gradually increase in the direction towards the discharge opening to complete the packaging of the assembly in terms of filling the rotor annulus area and avoiding collisions between different cooling channels.

[0018] For example, at least one cooling channel may start with an entry opening in a first segment along a straight radial direction, followed by a second segment along a portion of a circle. The second segment merges into a third segment along a portion of a circle, wherein the radius of the second segment (i.e., the length of a line segment extending from the center of the circle to the circumference of the circle) is less than the radius of the third portion. The third segment may merge into a segment having a straight extension along a secant of the outer circumference of at least one rotor ring. Between the second segment and the third segment, any number of additional segments may be arranged, wherein the radius of the segments increases from the inside to the outside of the at least one rotor ring. In the context of the present invention, such a configuration is still considered to be spiral.

[0019] According to an exemplary embodiment, the at least one cooling channel is a tube. The cooling channel being a tube has the advantage that, for example, the at least one cooling channel can be produced in a simple manner in any conceivable shape. After the cooling channel has been formed into the desired shape, the base material of the at least one rotor ring can be at least partially molded onto the tube. The tube can have a circular, rectangular or any other possible contour in a cross-sectional view.

[0020] To facilitate the overmolding process, the tube may be made of a material having a higher melting temperature than the base material of the at least one rotor ring. For example, the base material of the at least one rotor ring may be aluminum and the tube may be made of copper.

[0021] The motor may further include a stator having a winding of conductive material, and the discharge opening of the at least one cooling channel may be arranged to overlap the axial end of the winding in the axial direction. Thus, not only the rotor is effectively cooled, but also the end of the stator winding is effectively cooled. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] These and other features and advantages of the present invention will become apparent from a further reading of the specification in light of the accompanying drawings.

[0023] Figure 1 is a schematic longitudinal cross-sectional view of the motor;

[0024] Figure 2 yes Figure 1 A perspective view of a motor;

[0025] Figure 3 yes Figure 1 A schematic front view of a rotor ring of an electric machine;

[0026] Figure 4 yes Figure 3 A side view of a rotor ring;

[0027] Figure 5 yes Figure 3 and Figure 4 A front view of a tubular object of one of the cooling channels of a rotor annulus;

[0028] Figure 6 yes Figure 5 A side view of a tubular object;

[0029] Figure 7 yes Figure 1 A cross-sectional view of the electric machine in the region of the rotor ring; and

[0030] Figure 8 yes Figure 7 An enlarged fragmentary view of a tube connected to the drive shaft of the motor. DETAILED DESCRIPTION

[0031] Figure 1 A schematic longitudinal section of an asynchronous electrical machine 1, in particular an asynchronous motor, is shown with a stator 2. The stator 2 has a winding 3 made of an electrically conductive material and connected to an alternating current to induce a magnetic field rotating around an axis L of rotation. Figure 2 A perspective view of the electric machine 1 is shown, but without the winding 3, but with the slots 16 accommodating the winding 3. The rotor 4 is arranged in a stator 2 rotatable about an axis of rotation L. The rotor 4 has a magnetically conductive rotor core 5, which is made as a laminated core or a sintered material. The rotor 4 has two rotor rings 6, 7, each of which axially supports one axial end of the rotor core 5, so that the rotor core 5 is sandwiched between the two rotor rings 6, 7. The rotor rings 6, 7 are configured as short-circuit rings of a cage 8 of the rotor 4. In addition to the rotor rings 6, 7, the cage 8 also includes several conductor bars 9, which are arranged in the slots 10 of the rotor core 5 and are connected to each of the rotor rings 6, 7. The cage 8 is made of an electrically conductive material, so that the rotating magnetic field generated by the stator 2 induces a current in the conductor bars 9, which short-circuits the conductor bars 9 through the rotor rings 6, 7. The induced current in the conductor bars 9 generates another magnetic field which causes the rotor to rotate about the rotation axis L. The cage 8 may be composed of separate rotor rings 6, 7 and separate conductor bars 9 which are interconnected by suitable mechanical means such as welding. Alternatively, the cage 8 may be die cast as one piece to the rotor core 5.

[0032] The rotor 4, in particular the rotor core 5, is fixed to the drive shaft 11 in a non-rotatable manner so that the torque generated by the rotating magnetic field is transmitted from the rotor 4 to the drive shaft 11. It is to be understood that the asynchronous machine 1 can also be operated as a generator so that by rotating the drive shaft 11, a rotating magnetic field is induced in the stator 2 for generating electrical power.

[0033] In the disclosed embodiment, the rotor rings 6, 7 are radially spaced apart from the drive shaft 11. However, it is also possible that the rotor rings 6, 7 are arranged in a non-rotatable manner on the drive shaft 11 in order to transmit torque.

[0034] Each of the rotor rings 6, 7 is provided with a plurality of cooling channels 12 for conveying a coolant. The coolant may be any fluid suitable for extracting heat energy, such as, for example, cooling oil. It is also possible that only one of the rotor rings 6, 7 is provided with such a cooling channel 12. The rotor rings 6, 7 may also be provided with only one cooling channel 12.

[0035] Each cooling channel 12 extends from an inlet opening 13, which is fluidly connected to an axial bore 14 in the drive shaft 11, to a radially outward outlet opening 15. Thus, when the drive shaft 11 and the rotor rings 6, 7 rotate about the rotation axis L, all cooling channels 12 are supplied with coolant from the axial bore 14 of the drive shaft 11 by centrifugal force.

[0036] The cooling channel 12 extends at least partially along a path that deviates from a straight radial direction. A radial direction means any direction along a radius starting from the rotation axis L and arranged perpendicular to the rotation axis L. The reason for this is that a greater length of cooling channel 12 is provided within the rotor ring 6, 7 than a cooling channel extending in a straight radial direction. This results in a greater heat exchange area between the cooling channel 12 and further material of the rotor ring 6, 7.

[0037] Figure 3 Depicted is a front view of one of the rotor rings 6 with schematically shown cooling channels 12. Despite the fact that a large portion of the cooling channels 12 is arranged within the surrounding base material 20 of the rotor ring 6, the cooling channels 12 are illustrated in solid lines.

[0038] The rotor ring 6 comprises five cooling channels 12 evenly distributed around the axis of rotation L, one of which is provided with a reference number and will be described below.

[0039] The cooling channel 12 is arranged over the maximum length of the base material 20. The cooling channel 12 extends from the inner peripheral surface 17 to the outer peripheral surface 18 of the rotor ring 6. By conveying the coolant through the cooling channel 12, the base material 20 and the entire rotor ring 6 can be effectively cooled. In order to enhance the cooling effect, the rotor ring 6 is provided with fins 19, which protrude in the axial direction on the side opposite to the rotor core 5, as can be seen in FIG. Figure 1 The fins 19 are optional and the rotor ring 6 can also be configured without fins 19.

[0040] The cooling channel 12 is provided in the form of an independent tubular object. Figure 5 and Figure 6 One of the separate tubes is depicted in . The cooling channel 12 in the form of a tube protrudes inwardly beyond the inner peripheral surface 17 . The inlet opening 13 of the cooling channel 12 is connected to the axial bore 14 of the drive shaft 11 .

[0041] In the disclosed embodiment, the outlet opening 15 of the cooling channel 12 is flush with the outer circumferential surface 18 of the rotor ring 6. However, it is also conceivable that the cooling channel 12 in the form of a tube protrudes outwardly beyond the outer circumferential surface 18.

[0042] In order to provide a long path of the cooling channel 12 in the base material 20 of the rotor ring 6, the inlet opening 13 and the outlet opening 15 of each cooling channel 12 are arranged offset from each other in the circumferential direction. In the disclosed embodiment, the circumferential offset angle α of the inlet opening 13 and the outlet opening 15 is almost 180 degrees. Therefore, the cooling channel 12 extends over almost half of the circumference of the rotor ring 6.

[0043] As can be seen in the side view of the rotor ring 6 shown in FIG. Figure 4 As can be seen in FIG. 1 , the inlet opening 13 and the outlet opening 15 of each cooling channel 12 are offset from each other in the axial direction. The reference symbol S is used to indicate this offset.

[0044] like Figure 1 As can be seen in FIG. 4 , the discharge opening 15 of the cooling channel 12 is arranged to overlap with the end of the winding 3 in the axial direction. In response to the centrifugal force acting on the coolant during the rotation of the rotor 4, the coolant is ejected from the cooling channel 12 and splashes onto the end of the winding 3. Therefore, the winding 3 is also cooled.

[0045] If you can Figure 5 As can be seen in FIG. 1 , the cooling channels 12 are formed in a curved shape (particularly in a spiral or spiral-like shape) around the rotation axis L. Each cooling channel 12 has different segments. The radius of each individual segment gradually increases in the direction toward the discharge opening 15 .

[0046] like Figure 5 The cooling channel 12 depicted in FIG. 1 starts from the entry opening 13 with a first segment 21 that follows a straight line. The first segment 21 merges into a second segment 22 that follows a portion of a circle with a first radius R1. A third segment 23 with a second radius R2 follows the second segment 22. The subsequent fourth segment 24 has a third radius R3. The final fifth segment 25 again follows a straight line.

[0047] The first radius R1 is smaller than the second radius R2, and the second radius R2 is smaller than the third radius R3. Between the different segments 21, 22, 23, 24, 25, further segments are arranged. The fifth segment 25 is arranged along the secant of the rotor ring 6. The rotor ring 6 is produced by an overmolding process of a base material 20 around the cooling channel 12 in the form of a tube. The melting temperature of the cooling channel 12 in the form of a tube is higher than the melting temperature of the base material 20, so that it is not affected during the overmolding process of the cooling channel 12. For example, the base material 20 can be aluminum, and the material of the cooling channel 12 in the form of a tube can be copper.

[0048] The cooling channel 12 is connected to a radially arranged supply channel 26 which leads from the axial bore 14 of the drive shaft 11 to the outer peripheral surface of the drive shaft 11. Figure 7 and Figure 8 ), the first segment 21 of the cooling channel 12 is arranged in the supply channel 26. It is also conceivable that the cooling channel 12 is only partially arranged in the supply channel 26, or is connected to the radially outer end of the supply channel 26.

[0049] List of reference numbers

[0050] 1 Motor

[0051] 2 Stator

[0052] 3 Winding

[0053] 4 Rotor

[0054] 5 Rotor core

[0055] 6 Rotor Ring

[0056] 7 Rotor Ring

[0057] 8 Rat Cage

[0058] 9 Conductor strips

[0059] 10 slots

[0060] 11 Drive shaft

[0061] 12 Cooling channels

[0062] 13 Enter the opening

[0063] 14 Axial hole

[0064] 15 Discharge opening

[0065] 16 slots

[0066] 17 Inner peripheral surface

[0067] 18 Peripheral surface

[0068] 19 Fins

[0069] 20 Basic Materials

[0070] 21 First Segment

[0071] 22 Second segment

[0072] 23. Section 3

[0073] 24 Fourth Segment

[0074] 25 Fifth Section

[0075] 26 Supply Channel

[0076] L Rotation axis

[0077] R1 First radius

[0078] R2 Second radius

[0079] R3 Third radius

[0080] S is the displacement in the axial direction.

[0081] α is the deviation along the circumferential direction.

Claims

1. The motor (1) comprises: a drive shaft (11) rotatable about a rotation axis (L), the drive shaft (11) having an axial hole (14); a rotor (4) non-rotatably fixed to the drive shaft (11), the rotor (4) having a rotor core (5) and at least one rotor ring (6, 7) axially supporting ends of the rotor core (5); and at least one cooling channel (12) for conveying a coolant at least partially in the at least one rotor ring (6, 7), wherein the at least one cooling channel (12) extends from an inlet opening (13) which is fluidically connected to an axial bore (14) of the drive shaft (11) to a radially outward outlet opening (15), It is characterized in that The at least one cooling channel (12) extends at least partially along a path that deviates from a straight radial direction.

2. The electric machine (1) according to claim 1, It is characterized in that The at least one supply channel (26) is disposed in the drive shaft (11), and the supply channel (26) fluidically connects an axial bore (14) of the drive shaft (11) with the at least one cooling channel (12).

3. The electric machine (1) according to claim 1 or 2, It is characterized in that The inlet opening (13) and the outlet opening (15) of the at least one cooling channel (12) are arranged offset from one another in the circumferential direction.

4. The electric machine (1) according to claim 3, It is characterized in that The circumferential offset of the inlet opening (13) and the outlet opening (15) encloses an angle (α) greater than 45 degrees.

5. The electric machine (1) according to one of claims 1 to 4, It is characterized in that The inlet opening (13) and the outlet opening (15) of the at least one cooling channel (12) are arranged offset from one another in the axial direction.

6. The electric machine (1) according to one of claims 1 to 5, It is characterized in that The outlet opening (15) of the at least one cooling channel (12) is arranged in the outer peripheral surface (18) of the at least one rotor ring (6, 7).

7. The electric machine (1) according to one of claims 1 to 6, It is characterized in that The at least one cooling channel (12) protrudes beyond the inner peripheral surface (17) of the rotor ring (6, 7) toward the drive shaft (11).

8. The electric machine (1) according to one of claims 1 to 7, It is characterized in that The at least one cooling channel (12) is at least partially formed in a curved shape around the rotation axis (L).

9. The electric machine (1) according to one of claims 1 to 8, It is characterized in that The at least one cooling channel (12) is at least partially formed in a helical shape around the rotation axis (L).

10. The electric machine (1) according to one of claims 1 to 9, It is characterized in that The at least one cooling channel (12) is a tube.

11. The electric machine (1) according to claim 10, It is characterized in that The at least one rotor ring (6, 7) comprises a base material (20) at least partially moulded onto the tube.

12. The electric machine (1) according to claim 11, It is characterized in that The tube is made of a material having a higher melting temperature than a base material (20) of the at least one rotor ring (6, 7).

13. The electric machine (1) according to claim 11 or 12, It is characterized in that The base material (20) of the at least one rotor ring (6, 7) is aluminum and the tube is made of copper.

14. The electric machine (1) according to one of claims 1 to 13, It is characterized in that The motor (1) further comprises a stator (2) having a winding (3) of a conductive material, and The outlet opening (15) of the at least one cooling channel (12) is arranged to overlap with an axial end of the winding (3) in the axial direction.

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