Rotor for an electrical machine, motor vehicle and method for producing a rotor

Abstract

The invention relates to a rotor (10) for an electrical machine, which is designed to be rotated during operation about an axis of rotation (16) extending in the axial direction (A), having a rotor lamination stack (14) comprising a plurality of rotor laminations lying against one another in the axial direction (A), having at least one sleeve (24) which extends in the axial direction (A) through an opening (22) of the rotor lamination stack (14) and rests with its outer wall circumferentially against a wall of the rotor lamination stack (14) delimiting the opening (22), having at least one tie rod (26) which is inserted through the sleeve (24) in the axial direction (A) and clamps the rotor laminations together in the axial direction (A), wherein the tie rod (26) together with the sleeve (24) delimits at least one cooling channel (36) extending within the sleeve (24),which extends in the axial direction (A) through the rotor core (14) and through which a cooling fluid can flow.,

Description

[0001] The invention relates to a rotor for an electrical machine, a motor vehicle and a method for producing a rotor.

[0002] DE 10 2018 215 734 A1 discloses a modular system for producing different designs of a rotor for an electric motor of a motor vehicle, comprising a rotor shaft that is compatible with all designs and a laminated core that is compatible with all designs, can be arranged on the rotor shaft and connected to the rotor shaft in a rotationally fixed manner. The modular system comprises at least one clamping device formed separately from the rotor shaft and separately from the laminated core, by means of which laminated core layers of the laminated core arranged successively in the axial direction of the rotor shaft can be clamped together in the axial direction of the rotor shaft. The clamping device comprises at least two clamping plates spaced apart from one another in the axial direction and at least one tension rod connected to the clamping plates and capable of tensile loading.Furthermore, a cooling channel is provided which is directly delimited by the laminated core and / or at least partially by the clamping device, in particular by the tie rod.

[0003] The object of the present invention is to provide a solution which enables particularly secure clamping of a large number of rotor laminations of a rotor lamination stack and, at the same time, particularly efficient cooling of the rotor lamination stack.

[0004] This object is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented 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 any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0005] The invention relates to a rotor for an electrical machine, in particular a traction machine of a motor vehicle. The rotor is designed to be rotated about an axis of rotation running in the axial direction during operation. In particular, the rotor is designed to be rotated about the axis of rotation relative to a stator of the electrical machine during operation in the electrical machine. The electrical machine is in particular a radial flux machine. The rotor comprises a rotor lamination stack which comprises a plurality of rotor laminations lying adjacent to one another in the axial direction. This means that the rotor laminations are stacked on top of one another in the axial direction and thereby form the rotor lamination stack.The rotor further comprises at least one sleeve which extends in the axial direction through an opening in the rotor laminated core and whose outer wall rests circumferentially against a wall of the rotor laminated core that delimits the opening. This means that the opening in the rotor laminated core is lined by the sleeve over its entire axial length. In particular, the sleeve is made of aluminum, which allows particularly good heat transfer between the sleeve and the rotor laminated core. The rotor further comprises at least one tie rod which is inserted axially through the sleeve and clamps the rotor laminations together in the axial direction. The tie rod can be inserted into the sleeve, in particular with radial play relative to the sleeve, which enables particularly simple and low-force insertion of the tie rod into the sleeve.By axially applying pressure to the sleeve, in particular when clamping the rotor laminations of the rotor laminated core, the sleeve can be pressed against the wall of the rotor laminated core that defines the opening by means of the tie rod. This means that when the rotor laminations of the rotor laminated core are clamped by means of the tie rod, the clamping sleeve is subjected to pressure in the axial direction, in particular is compressed, whereby the radial diameter of the sleeve increases. As a result of the enlargement of the radial diameter of the sleeve, a secure application of the sleeve to the wall of the rotor laminated core that defines the opening can be ensured. The radial direction of the sleeve is perpendicular to the axial direction of the rotor. The tie rod can comprise a clamping screw and a nut clamped onto a free end of the clamping screw or, alternatively, comprise a threaded rod with a nut screwed onto each end of each of the rods.By screwing the at least one nut onto the free end of the clamping screw or onto the associated end of the threaded rod, respective rotor laminations of the rotor lamination stack that are outermost along the axial direction can be pressed towards one another in the axial direction, whereby all rotor laminations of the rotor lamination stack arranged between these rotor laminations are pressed together in the axial direction.

[0006] The tie rod, together with the sleeve, defines at least one cooling channel running inside the sleeve, which extends axially through the rotor lamination stack and through which a cooling fluid can flow. The cooling fluid flowing through the cooling channel can carry away heat conducted away from the rotor lamination stack via the sleeve, allowing the rotor lamination stack to be cooled particularly effectively. Because both the tie rod is located in the opening of the rotor lamination stack and the cooling channel runs through it, particularly efficient cooling of the rotor lamination stack can be achieved in the area of ​​the tie rod, particularly secure clamping of the rotor laminations of the rotor lamination stack by means of the tie rod, and moreover, a particularly high fill level of the rotor lamination stack can be achieved, since only the volume predetermined by the opening is required for both cooling and clamping.Furthermore, the sleeve enables particularly good heat transfer from the laminated core to the cooling fluid flowing in the cooling channel. Inserting the sleeve into the opening of the rotor laminated core also reliably prevents any rotation of the rotor laminations of the rotor laminated core relative to one another about the rotor's axis of rotation. This ensures that the cooling channel's cross-section is defined by the sleeve and / or the tie rod over its entire axial length. The sleeve is particularly effective in preventing any undesired cross-sectional narrowing of the cooling channel due to rotation of adjacent rotor laminated cores relative to one another about the axis of rotation.

[0007] In one possible development of the invention, it is provided that the rotor has a hollow rotor shaft on which the rotor laminated core is seated in a rotationally fixed manner. It is further provided that the rotor comprises two clamping plates, each arranged on the end face of the rotor laminated core. This means that the clamping plates rest on opposite end faces of the rotor laminated core. The rotor laminated core is thus arranged between the two clamping plates in the axial direction. It is provided that the clamping plates are pressed against the respective end faces of the rotor laminated core by means of the at least one tie rod. At least one of the clamping plates has at least one cooling fluid supply channel, via which cooling fluid emerging from the hollow rotor shaft via a rotor shaft opening can be guided in a radial direction to the at least one cooling channel.In particular, it is provided that the tie rod is pushed through respective clamping openings in the clamping plates and engages behind respective walls of the clamping plates that delimit the clamping openings. This means that the tie rod rests on respective outer sides of the clamping plates facing away from the rotor laminated core, is pushed through the clamping openings in the clamping plates and extends through the opening in the rotor laminated core. Because the tie rod engages behind the clamping openings in the clamping plates from the outside, the clamping plates are pressed from the outside onto the rotor laminated core, in particular onto the respective end faces against which the clamping plates rest. In particular, it is provided that the sleeve does not extend through the clamping openings in the clamping plates, but merely through the opening in the rotor laminated core.The at least one cooling fluid supply channel in the at least one clamping plate extends at least partially in the radial direction, whereby the cooling fluid flowing radially out of the rotor shaft via the rotor shaft opening of the rotor shaft can be guided to the cooling channel by means of the cooling fluid supply channel. The clamping plates thus enable, on the one hand, a particularly uniform application of the axially acting force to the respective end faces of the rotor lamination stack, thereby enabling a particularly uniform pressing of the rotor laminations of the rotor lamination stack together, and, furthermore, a reliable guidance of the cooling fluid from the hollow rotor shaft to the at least one cooling channel.

[0008] In this context, it can be provided, in particular, that at least one of the clamping plates has a cooling fluid guide channel, via which cooling fluid emerging from the cooling channel can be guided radially outwards away from the cooling channel. The cooling fluid guide channel thus serves to guide the cooling fluid out of the cooling channel after the cooling fluid has flowed through the cooling channel. For example, the cooling fluid guide channel can be configured to propel the cooling fluid received from the cooling channel towards a stator of the electrical machine during operation, whereby the stator can be cooled by means of the cooling fluid after the rotor core has already been cooled by means of the cooling fluid. As a result, the electrical machine can be cooled particularly efficiently by means of the cooling fluid.The clamping plates thus enable a reliable guiding of the cooling fluid from the hollow rotor shaft to the cooling channel and via the at least one cooling fluid guide channel away from the cooling channel, in particular out of the rotor.

[0009] In a further possible embodiment of the invention, the rotor is provided with an annular channel which extends in the circumferential direction of the tie rod around the tie rod and is fluidically connected to the cooling channel. As a result, cooling fluid to be supplied to the cooling channel can be collected before being supplied to the cooling channel, or cooling fluid flowing out of the cooling channel can be collected before being led away from the cooling channel. The annular channel can be provided, in particular, by a notch in the tie rod which runs around the circumference of the tie rod. The annular channel is delimited at least in regions by the notch in the tie rod and in regions by one of the clamping plates. Depending on whether the annular channel is located upstream or downstream of the cooling channel, the annular channel is provided to collect the cooling fluid to be supplied to the cooling channel before it is supplied, or to collect the cooling fluid flowing out of the cooling channel after it has flowed out.The annular channel thus enables the cooling fluid to be supplied to the cooling channel or removed from the cooling channel reliably and with particularly low leakage at the transition between the cooling channel and the cooling fluid removal channel or the cooling channel to the cooling fluid supply channel.

[0010] In a further possible embodiment of the invention, it is provided that the sleeve and the opening in the rotor laminated core have corresponding cross-sections whose respective shapes deviate from a circular ring and a circle. For example, the sleeve and the opening with their outer circumference of the cross-section can have the shape of a trapezoid or a triangle with rounded corners or a circular sector shape. By correspondingly shaping the cross-section of the sleeve with the cross-section of the opening, reliable application of the sleeve with its entire outer circumference to the wall of the rotor laminated core delimiting the opening can be ensured. If the sleeve has a cross-section that deviates from a circular ring and the opening has a cross-section that deviates from a circle, then the sleeve is secured against rotation about the axial direction in the opening.The risk of the sleeve twisting around the axial direction in the opening is thus particularly low. Furthermore, the cross-section of the opening and the sleeve can be selected depending on a specified cross-section to be achieved for the cooling channel. In other words, the cross-section of the sleeve and the opening can be selected depending on the cooling requirements to be met for the cooling channel. This allows for particularly efficient cooling of the rotor core by means of the cooling fluid flowing through the cooling channel.

[0011] In a further possible embodiment of the invention, the tie rod has a centering section in at least one longitudinal region along the axial direction, in which the tie rod rests against the inside of the sleeve at several points. Because the tie rod rests against the inside of the sleeve at several points, a relative position between the tie rod and the sleeve is precisely defined. This ensures that the cooling channel, which is defined by the tie rod and / or the sleeve, has a precisely defined cross-section.

[0012] In this context, it can be provided in particular that the tie rod in the centering section has a plurality of axially extending ribs which are arranged distributed over the circumference of the tie rod in the centering section and which each bear against the inside of the sleeve. These plurality of axially extending ribs enable the tie rod in the centering section to be designed to be particularly lightweight, since the tie rod does not bear against the sleeve over its entire circumferential outer side, but only with the ribs on the inside. Furthermore, the ribs, provided their longitudinal extent runs in the axial direction, can keep certain areas between the inside of the sleeve and the tie rod free, through which the cooling fluid can flow in the axial direction between the sleeve and the tie rod.In other words, the tie rod has respective recesses between ribs adjacent to one another in the circumferential direction of the tie rod, which recesses can extend through the centering section over an entire axial length of the centering section and through which the cooling fluid can flow. This enables, on the one hand, the tie rod to be centered in the centering section relative to the sleeve through direct contact with the sleeve, and at the same time, due to the recess between respective ribs, the cooling fluid can flow in the axial direction along the centering section of the tie rod or in the axial direction through the centering section of the tie rod, in that the cooling fluid flows through the respective recesses of the tie rod between ribs adjacent to one another in the circumferential direction.

[0013] In a further possible embodiment of the invention, it can be provided that the tie rod has a circumferential collar in the centering section, which rests on the inside of the sleeve. Furthermore, this collar has at least one through-opening running in the axial direction, through which cooling fluid can flow to the at least one cooling channel or away from the at least one cooling channel. In particular, a fluidic connection between the cooling channel and the cooling fluid supply channel or the cooling fluid removal channel is provided via the at least one through-opening running in the axial direction. This enables, on the one hand, reliable, precise centering of the tie rod via the centering section relative to the sleeve and, furthermore, ensures that the cooling fluid can flow into the cooling channel or flow out of the cooling channel.

[0014] The invention further relates to a motor vehicle having an electric traction machine. The electric traction machine is configured to drive the motor vehicle using electrical energy. The electric traction machine comprises a stator and a rotor rotatable about a rotational axis relative to the stator, as already described in connection with the rotor according to the invention. Because the rotor has the cooling channel extending axially through the rotor core, by means of which the rotor core can be cooled particularly efficiently using cooling fluid, the electric traction machine can be operated particularly efficiently. As a result, the motor vehicle can in turn be driven particularly efficiently by means of the electric traction machine.

[0015] The invention further relates to a method for producing a rotor, as already described in connection with the rotor according to the invention. In the method, the sleeve is inserted into an associated opening in the rotor laminated core in the axial direction with some play. Furthermore, the tie rod is inserted through the sleeve in the axial direction. The rotor laminated core is then clamped by means of the tie rod, wherein the sleeve is subjected to axial pressure by means of the tie rod, whereby the sleeve is pressed with its outer wall against the wall of the rotor laminated core delimiting the opening and is thereby pressed onto the rotor laminate. The rotor laminated core can have a plurality of openings, which can be arranged on the rotor laminate in particular distributed around the axis of rotation of the rotor. In particular, it is provided that a sleeve and a tie rod are inserted into each of these openings in the rotor laminated core.This allows several cooling channels running in the axial direction to be provided in the rotor laminated core. In addition, the multiple tie rods enable particularly secure and even pressing of the rotor laminations of the rotor laminated core. When inserted into the associated opening in the rotor laminated core, the sleeve has, in particular, radial play with respect to the opening. This makes it particularly easy to insert the sleeve into the associated opening in the rotor laminated core in the axial direction. The sleeve is then pressed into the associated opening by the tie rod, by means of which the rotor laminations are simultaneously clamped together in the axial direction and the sleeve is subjected to a force along the axial direction at each of its axial ends, by means of which the sleeve is compressed in the axial direction.This allows the sleeve to rest on the outer circumference against the wall of the rotor core that defines the opening, thus achieving particularly good heat transfer from the rotor core to the sleeve. This allows for particularly efficient heat transfer from the rotor core via the sleeve to the cooling fluid flowing through the cooling channel.

[0016] Further features of the invention may emerge 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 alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0017] The drawing shows in the only figure ( Fig. 1) a schematic sectional view of a section of a rotor for an electric traction machine of a motor vehicle.

[0018] In Fig. 1 shows a rotor 10 for an electric traction machine of a motor vehicle. In this case, the rotor 10 comprises a rotor shaft 12 and a rotor laminated core 14 mounted in a rotationally fixed manner on the rotor shaft 12. During operation, the rotor 10 is rotatable about a rotation axis 16 running in the axial direction A of the rotor 10. The rotor laminated core 14 comprises a plurality of rotor laminations stacked on top of one another in the axial direction A. In this case, the rotor 10 further comprises two clamping plates 18, which are arranged on opposite end faces 20 of the rotor laminated core 14. In this case, it is provided that the clamping plates 18 are also mounted in a rotationally fixed manner on the rotor shaft 12. The rotor laminated core 14 has a plurality of openings 22 running in the axial direction A. A sleeve 24 is inserted into each of these openings 22 in the axial direction A. In this case, the respective sleeve 24 has a hollow cylindrical shape.In this case, the sleeve 24 is designed as an aluminum tube with a diameter of ten millimeters.

[0019] In this case, the rotor 10 has a plurality of tie rods 26. In this case, a tie rod 26 is inserted into each sleeve 24 in the axial direction A, in particular pushed through the respectively assigned sleeve 24. In this case, each of the tie rods 26 comprises a clamping screw 28 and a nut 30. The nut 30 is screwed onto a free end of the clamping screw 28. The tie rod 26 is pushed through respective clamping openings 32 of the clamping plates 18, whereby a screw head 34 of the clamping screw 28 is arranged on the outer side of the assigned clamping plate 18 facing away from the rotor laminated core 14. Furthermore, the nut 30 assigned to this clamping screw 28 is arranged on the outer side of the other clamping plate 18 facing away from the rotor laminated core 14 in the axial direction A.If the nut 30 is now screwed further onto the free end of the clamping screw 28, the clamping plates 18 are pressed towards one another in the axial direction by means of the screw head 34 and the nut 30, whereby the rotor laminated core 14 arranged between the clamping plates 18 in the axial direction A is pressed in the axial direction A. The tie rods 26 thus enable the rotor laminations of the rotor laminated core 14 to be pressed in the axial direction A via the clamping plates 18. The clamping plates 18 enable a force applied by the tie rods 26 in the axial direction A to be distributed over a particularly large area and thus evenly across the end faces 20 of the rotor laminated core 14. As an alternative to the design of the respective tie rods 26 with the clamping screw 28 and the nut 30, each of the tie rods 26 can have a threaded rod, to the respective axial ends of which a nut 30 is screwed.In this case, the clamping screw 28 and the nut 30 each have an M5 thread.

[0020] In order to enable particularly efficient cooling of the rotor laminated core 14, it is provided that a cooling fluid flows in the respective openings 22 of the rotor laminated core 14. For this purpose, the respective tie rods 26, together with the respectively associated sleeves 24, each delimit a cooling channel 36 running in the axial direction A. These cooling channels 36 running in the respective openings 22 run in the axial direction A through the rotor laminated core 14 and are designed to be flowed through by the cooling fluid. In the present case, the respective cooling channels 36 are delimited on the outer circumference by the sleeve 24. Due to the fact that the tie rod 26 extends in the axial direction A through the respectively associated sleeve 24, the respective cooling channels 36 have an annular cross-section at least in a longitudinal region along the axial direction A.The cooling fluid is thus guided in these cooling channels 36 along an inner side of the respective sleeves 24, whereby the sleeves 24 can be cooled particularly efficiently by means of the cooling fluid. Due to the aluminum design of the respective sleeves 24, heat is dissipated particularly efficiently from the rotor core 14 via the sleeves 24. The outer surface of the sleeves 24 rests flatly over their entire circumference against a wall of the rotor core 14 that delimits the respective associated opening 22 of the rotor core 14.

[0021] The cooling fluid flows within the respective cooling channels 36 along the axial direction A in a respective predetermined flow direction, wherein the cooling fluid flows in at least one of the cooling channels 36 in a first flow direction 38 and in at least a second of the cooling channels 36 in a second flow direction 40 opposite the first flow direction 38 along the axial direction A. Due to the opposite flow directions 38, 40 of the cooling fluid in the different cooling channels 36, a particularly uniform cooling of the rotor core 14 can be achieved by means of the cooling fluid flowing in the cooling channels 36.

[0022] In particular, respective cooling channels 36 arranged directly adjacent to one another in the circumferential direction around the axis of rotation 16 of the rotor 10 can each have different flow directions 38, 40 from one another.

[0023] In the present case, it is provided that the cooling fluid is guided within the hollow rotor shaft 12. The hollow rotor shaft 12 has a plurality of rotor shaft openings 42 designed as radial bores, through which cooling fluid flowing in the hollow rotor shaft 12 can flow out of the rotor shaft 12. In order to be able to guide the cooling fluid flowing out of the rotor shaft 12 via the rotor shaft openings 42 to the respective cooling channels 36, it is provided that one of the clamping plates 18 has a cooling fluid supply channel 44 for each of the cooling channels 36. This cooling fluid supply channel 44 is fluidically connected at one end to an associated rotor shaft opening 42 of the rotor shaft 12 and at the other end to the associated cooling channel 36. Furthermore, a cooling fluid removal channel 46 is provided for each cooling channel 36, which is provided by one of the clamping plates 18.The cooling fluid guide channel 46 in this case runs with its longitudinal extension in the radial direction R. The cooling fluid supply channel 44 in this case runs with its longitudinal extension in the radial direction R. The radial direction R is perpendicular to the axial direction A. The cooling fluid guide channel 46 is fluidly connected at one end to the associated cooling channel 36 and ends at the other end in the vicinity of the rotor 10. Thus, the cooling fluid flowing out of the associated cooling channel 36 can be guided away from the cooling channel 36 via the cooling fluid guide channel 46 and, in particular, guided, in particular, projected, into the vicinity of the rotor 10. In particular, the cooling fluid flowing out of the cooling fluid guide channel 46 can be projected onto a stator of the electric traction machine having the rotor 10 due to centrifugal forces acting on the cooling fluid.As a result, the stator can be additionally cooled at least in part by means of the cooling fluid after cooling the rotor 10.

[0024] In order to enable a reliable fluidic transition from the cooling fluid supply channel 44 to the associated cooling channel 36 and from the cooling channel 36 to the associated cooling fluid removal channel 46, two annular channels 48 are provided per cooling channel 36. The respective annular channels 48 extend in a ring shape around a circumference of the tie rod 26 associated with this cooling channel 36. The respective annular channels 48 are arranged in end regions of the tie rod 26 that are opposite one another in the axial direction A. As shown in Fig. 1, the respective annular channels 48 are delimited with regard to their inner radius by the associated tie rod 26 and with regard to their outer radius by one of the clamping plates 18. In the present case, each of the annular channels 48 is arranged in one of the clamping plates 18. A contour of the respective annular channels 48 can be predetermined by a notch running annularly around the tie rod 26. The respective cooling fluid supply channels 44 each open into an annular channel 48, whereby the cooling fluid flowing out of the cooling fluid supply channels 44 can be collected in these annular channels 48 and guided to the associated cooling channel 36. The cooling fluid flowing out of the respective cooling channels 36 can be collected in the respective annular channels 48 arranged downstream of the cooling channel 36 and made available for the respective cooling fluid removal channels 46.The respective annular channels 48 ensure that, regardless of a rotational position of the tie rod 26 about its longitudinal extension direction running in the axial direction A, a fluidic connection between the cooling channel 36 and the respectively associated cooling fluid supply channel 44 as well as the associated cooling fluid removal channel 46 is ensured.

[0025] In order to ensure precise alignment of the tie rod 26 relative to the sleeve 24, it is provided that the tie rod 26 has at least one centering section 50. In the present case, the tie rod 26 has two centering sections 50. A first of the centering sections 50 is arranged in the region of a first end of the cooling channel 36 and the further centering section 50 is arranged in the region of the second end of the cooling channel 36 opposite the first end in the axial direction A. In the respective centering sections 50, the tie rod 26 rests against the sleeve 24 at several points on the inside over its circumference. As a result, the tie rod 26 is precisely centered relative to the sleeve 24. In the respective centering sections 50, the tie rod 26 can have several ribs running in the axial direction, via which ribs the tie rod 26 rests against the inside of the sleeve 24.These ribs can be arranged in the respective centering section 50, evenly distributed over the circumference of the tie rod 26. In the present case, however, it is provided that the tie rod 26 has a circumferential collar 52 in each of the centering sections 50, via which the tie rod 26 rests on the inside of the sleeve 24. This collar 52 is penetrated in the present case by at least one through-opening 54 running in the axial direction A, through which the cooling fluid can flow. Via this through-opening 54, the cooling fluid can flow from the annular channel 48 arranged upstream of the cooling channel 36 into the cooling channel 36 or from the cooling channel 36 into the annular channel 48 arranged downstream of the cooling channel 36. In the present case, it is provided that the nut 30 of the respective tie rods 26 provides the circumferential collar 52 with the through opening 54 at one end of the tie rod 26.The circumferential collar 52 at the other end of the tension rod 26 is provided in this case by the clamping screw 28.

[0026] It is possible for the sleeve 24 and the opening 22 in the rotor core 14 to have respective cross-sections whose shapes deviate from a circular ring and a circle, wherein the cross-sections of the sleeve 24 and the opening 22 correspond to one another.

[0027] The invention described is based on the knowledge that when cooling a rotor 10 with a tie rod, the problem of heat transfer from the tie rod 26 to the rotor lamination stack 14 can arise. This can be solved by a dimensional overlap between the tie rod 26 and the rotor lamination stack 14. The dimensional overlap is to be understood as an excess of the tie rod 26 relative to the opening 22 of the rotor lamination stack 14. However, this overlap can lead to increased expenditure in the assembly of the rotor 10. In addition, when bracing the tie rod 26, a transverse contraction would result in a reduction of the overlap, which could lead to poorer heat transfer between the tie rod 26 and the rotor lamination stack 14. In order to overcome these disadvantages, it is necessary in the case of the Fig.1, it is provided that the rotor 10 has sleeves 24 which are inserted into the associated openings 22 of the rotor laminated core 14 and through which a respective associated tie rod 26 is inserted. When the respective clamping screws 28 of the tie rods 26 are tightened, the outer diameter of the associated sleeve 24 increases because the sleeve 24 is subjected to pressure in the axial direction A by means of the tie rod 26. By enlarging the outer diameter of the respective sleeves 24, particularly good heat transfer between the rotor laminated core 14 and the respective sleeves 24 can be achieved. Since the outer diameter of the sleeves 24 only increases when the tie rods 26 are tightened, the respective sleeves 24 can be inserted into the respective associated openings 22 of the rotor laminated core 14 in the axial direction A without excess size and in particular with play. This makes it particularly easy to assemble the rotor 10. List of reference symbols 10 Rotor 12 Rotor shaft 14 Rotor lamination package 16 axis of rotation 18 clamping plate 20 front side 22 Opening 24 sleeve 26 tie rods 28 clamping screw 30 mother 32 clamping opening 34 screw head 36 cooling channel 38 first flow direction 40 second flow direction 42 Rotor shaft opening 44 Cooling fluid supply channel 46 Cooling fluid channel 48 Ring Canal 50 centering section 52 collars 54 passage opening A axial direction R radial direction 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 2018 215 734 A1

[0002]

Claims

[1] Rotor (10) for an electrical machine, which is designed to be rotated during operation about an axis of rotation (16) extending in the axial direction (A), with a rotor lamination stack (14) comprising a plurality of rotor laminations lying against one another in the axial direction (A), with at least one sleeve (24) which extends in the axial direction (A) through an opening (22) of the rotor lamination stack (14) and rests with its outer wall circumferentially against a wall of the rotor lamination stack (14) delimiting the opening (22), with at least one tie rod (26) which is inserted through the sleeve (24) in the axial direction (A) and clamps the rotor laminations together in the axial direction (A), wherein the tie rod (26) together with the sleeve (24) delimits at least one cooling channel (36) running within the sleeve (24), which extends in the axial direction (A) through the rotor lamination stack (14) and which is supplied with a cooling fluid can be flowed through. [2] Rotor (10) according to claim 1, characterized by in that the rotor (10) has a hollow rotor shaft (12) on which the rotor laminated core (14) is seated in a rotationally fixed manner, and comprises two clamping plates (18), which are each arranged on the end face of the rotor laminated core (14) and are pressed onto the respective end faces (20) of the rotor laminated core (14) by means of the tie rod (26), wherein at least one of the clamping plates (18) has at least one cooling fluid supply channel (44), via which cooling fluid emerging from the hollow rotor shaft (12) via a rotor shaft opening (42) can be guided in the radial direction (R) to the at least one cooling channel (36). [3] Rotor (10) according to claim 2, characterized by that at least one of the clamping plates (18) has a cooling fluid guide channel (46) via which cooling fluid emerging from the cooling channel (36) can be guided radially outwards away from the cooling channel (36). [4] Rotor (10) according to one of the preceding claims, characterized by that an annular channel (48) is provided which extends in the circumferential direction of the tie rod (26) around the tie rod (26) and is fluidically connected to the cooling channel (36), whereby cooling fluid to be supplied to the cooling channel (36) can be collected before being supplied to the cooling channel (36) or whereby cooling fluid flowing out of the cooling channel (36) can be collected before being carried away from the cooling channel (36). [5] Rotor (10) according to one of the preceding claims, characterized by that the sleeve (24) and the opening (22) in the rotor laminated core (14) have mutually corresponding cross-sections, the respective shapes of which deviate from a circular ring and a circle. [6] Rotor (10) according to one of the preceding claims, characterized bythat the tie rod (26) has a centering section (50) in at least one length region along the axial direction (A), in which the tie rod (26) rests against the sleeve (24) at several points on the inside. [7] Rotor (10) according to claim 6, characterized by that the tie rod (26) in the centering section (50) has a plurality of axially extending ribs which are arranged distributed over the circumference of the tie rod (26) in the centering section (50) and which each bear against the inside of the sleeve (24). [8] Rotor (10) according to claim 6 or 7, characterized by in that the tie rod (26) in the centering section (50) has a circumferential collar (52) which rests on the inside of the sleeve (24) and which has at least one through-opening (54) running in the axial direction (A), via which cooling fluid can flow to the at least one cooling channel (36) or flow away from the at least one cooling channel (36). [9] Motor vehicle, with an electric traction machine which comprises a stator and a rotor (10) rotatable relative to the stator about an axis of rotation according to one of the preceding claims. [10] Method for producing a rotor (10) according to one of claims 1 to 8, in which the sleeve (24) is inserted into an associated opening (22) of the rotor laminated core (14) in the axial direction (A) with a clearance, the tie rod (26) is inserted through the sleeve (24) in the axial direction (A) and the rotor laminated core (14) is clamped by means of the tie rod (26), wherein the sleeve (24) is subjected to axial pressure by means of the tie rod (26), whereby the sleeve (24) is pressed with its outer wall against the wall of the rotor laminated core (14) delimiting the opening (22) and is thereby pressed against the rotor laminated core (14).

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