Patent Publication Number: US-2022231558-A1

Title: Rotor with an optimized rotor laminate geometry for fluid guidance

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2020/100308, filed Apr. 16, 2020, which claims priority from German Patent Application No. 10 2019 113 456.0, filed May 21, 2019, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a rotor for an electrical machine, having a rotor laminated core, which has a plurality of axially layered rotor laminates, each of which are arranged at a predetermined rotation angle to an axially adjacent rotor laminate, and having a rotor shaft on which the rotor laminates are fitted, wherein the rotor shaft forms a torque-transmitting connection with slots formed in the rotor laminates. 
     Rotors for electrical machines which are composed of laminated cores, what are termed “rotor stacks” or “stacks”, are already known from the prior art. These laminated cores are usually connected to a shaft with a positive fit via a tongue and slot connection or with a friction fit via a press connection. If the electrical machine is arranged in the oil chamber, the oil/hydraulic medium/fluid/coolant can be used, among other things, to cool the rotor. For this purpose, an oil guide is required in the rotor shaft, through which the oil is conveyed radially through the rotor shaft to the rotor laminated core or the rotor laminated cores. 
     However, the prior art always has the disadvantage that an opening or a duct is required in the rotor laminates to lead the oil axially outwards. For this purpose, an additional opening is usually provided in the rotor core. In particular if the rotor laminates need to be staggered and therefore a large number of slots for torque transmission must be formed in the rotor laminates via a tongue and slot connection, the slots and/or the tongue are arranged differently in each rotor laminate, so that often no installation space for an oil guide opening is available through the many offset slots. 
     SUMMARY 
     It is therefore the object of the disclosure to avoid or at least to mitigate the disadvantages of the prior art. In particular, a rotor is to be provided which, on the one hand, is simple and inexpensive to manufacture and which provides, in a particularly simple manner, for example, a coolant guide which axially distributes coolant that is passed through the rotor shaft. 
     This object is achieved according to the disclosure in a device of the generic type in that the rotation angle and the width of the slots are matched to one another in such a way that a duct extending axially through the rotor for fluid guidance, in particular cooling (oil) guidance, is formed. This means that the slots of axially adjacent rotor laminates are arranged at least partially overlapping, so that the slots are axially connected to one another. This has the advantage that the slots in the rotor laminates, which must be provided for torque transmission, also serve as oil guide slots. As a result, it is advantageous to not need to keep an additional, specially defined opening in the laminated core. 
     Advantageous embodiments are explained below. 
     According to an advantageous embodiment, a plurality of slots can be formed in each rotor laminate, at least one of the slots serving for torque transmission and at least one other of the slots serving for fluid guidance. This ensures the torque transmission and the fluid guidance at the same time. 
     It is also expedient if the rotor shaft is designed as a hollow shaft in which at least one radially continuously extending fluid duct which opens into the slots is formed. As a result, the interior of the rotor shaft is connected to the slots so that the coolant/fluid can be conveyed to the slots and can be further distributed axially from there. 
     Furthermore, it is preferred if at least as many slots are formed in each rotor laminate as the rotor laminates forming a rotor laminated core, with another of the slots forming the torque-transmitting connection depending on the axial position in the rotor laminated core. This enables the staggering of the rotor laminates to be achieved in a particularly simple manner by selecting a specific slot in the rotor laminate. In other words, for example, the second slot has a different rotation angle to the first rotor laminate in the axial direction than does the third slot, so that the second rotor laminate in the axial direction is connected to the rotor shaft via the second slot. 
     In addition, it is preferred if the slots that do not form the torque-transmitting connection are used for fluid guidance. Since several slots are formed in each rotor laminate, but only one of the slots (with a tongue and slot connection) is connected to the rotor shaft via a tongue, the other slots that are used in the rotor laminated core for torque transmission to the other rotor laminates, are available in the one rotor plate for the coolant supply. 
     According to a particularly preferred embodiment, the rotation angle can be selected in such a way that it provides for a staggering of the rotor laminates. This means that the rotation angle is different from a pole angle with which the poles of the rotor are arranged to be spaced apart in the circumferential direction, specifically in particular different from the pole angle by the rotational staggering angle. The staggering of the rotor is thus implemented in a particularly simple manner. 
     In an advantageous development, one of the slots that forms the torque-transmitting connection between the rotor shaft and a first rotor laminate can be combined with another of the slots that forms the torque-transmitting connection between the rotor shaft and a rotor laminate that is axially adjacent to the first rotor laminate, being arranged to be offset by the rotation angle. As a result, the rotational staggering of the rotor laminates described above is implemented. 
     It is also preferred if one of the slots that forms the torque-transmitting connection between the rotor shaft and a first rotor laminate to another of the slots that forms the torque-transmitting connection between the rotor shaft and a rotor laminate that is axially spaced apart from the first rotor laminate, is arranged to be offset by an angle different from the rotation angle. This is due in particular to the fact that the rotation angle is different from the pole angle so that the slots cannot be arranged to be evenly distributed. In particular, the slot which is assigned to the first rotor laminate in the axial direction for torque transmission is rotated by the angle different from the rotation angle to the slot which is assigned to the last rotor laminate in the axial direction for torque transmission. 
     It is also advantageous if the rotor shaft is connected to the slots for torque transmission formed in the rotor laminates by one or more tongue and slot connections. This can also influence the arrangement of the slots. In addition, the force distribution is improved. 
     It is particularly advantageous when the rotor laminates are designed as identical parts. As a result, the rotor laminates can be produced with the same tool, for example with a punching tool. The rotor can thus be manufactured inexpensively. In addition, the fact that only one type of rotor laminate is required prevents a certain type of rotor laminate from being missing in the assembly, for example due to a mix-up. 
     In other words, the disclosure relates to a laminated rotor core having a plurality of slots which are arranged with different spacings in the circumferential direction. The slots that are not used for torque transmission through a tongue and slot connection to a rotor shaft are arranged to be axially connected so that they can serve for fluid guidance. For fluid guidance, the rotor shaft has radial through holes to form a fluid duct from the holes to the slots, which are not used for torque transmission. 
     In addition, it is advantageous if the torque-transmitting connection is formed by slots formed in the rotor laminates and a coupling element which is constructed separately from the rotor laminates and which is connected to the rotor shaft in a rotationally fixed manner. In other words, in contrast to a classic tongue and slot connection for connecting the rotor laminates, the coupling element, such as the tongue, is formed separately. As a result, instead of a projection forming the coupling element, a slot into which the coupling element engages must be provided on the rotor laminate geometry. This advantageously results in greater design options for the rotor laminates, since several slots can also be provided and it is only necessary during assembly to select which slot is connected to the coupling element to achieve a specific orientation in the circumferential direction. 
     According to a preferred embodiment, the torque-transmitting connection can be designed as a tongue and slot connection, wherein the coupling element is designed separately from the rotor shaft. The coupling element is preferably designed as a tongue, for example in the manner of a parallel key. By designing the tongue as a separate component, the structural design of the rotor shaft does not need to be changed. In addition, a separate tongue can be produced in a particularly simple and cost-effective manner. Alternatively, it is also possible to form the coupling element integrally with the rotor shaft. 
     In particular, it is preferred if the rotor laminates are each arranged to be rotated by a predetermined angle with respect to an axially adjacent rotor laminate. As a result, a staggering of the rotor can advantageously be kept, which has a positive effect on the noise behavior. According to an advantageous embodiment, the rotor laminates are rotated with respect to one another by a constant angle. 
     In addition, it is advantageous if a plurality of slots are formed in each rotor laminate, which are arranged to be offset from one another by the predetermined angle. This makes it possible to implement the staggering of the rotor in that the slot into which the coupling element is inserted can be selected depending on the desired offset relative to the rotor shaft and thus relative to the other rotor laminates. This allows the rotation of the rotor laminates to be determined when the rotor laminates are installed. In addition, this makes it possible for the same rotor laminate to be used at different positions in the rotor laminated core, i.e., with different rotations relative to the rotor shaft. In other words, the “correct” slot for the torque-transmitting connection must be selected during assembly to realize the staggering. 
     It is also expedient if the rotor has a plurality of poles which are arranged to be uniformly distributed in the circumferential direction, the predetermined angle being selected such that the poles of the rotor are staggered. That is, the predetermined angle is different from a pole angle at which the poles are arranged to be in the circumferential direction. The staggering of the poles is thereby achieved via the axial direction of the laminated rotor core. 
     It is also preferred if each of the plurality of slots is assigned to a position of the rotor laminate in the rotor laminated core. This means that, depending on the intended position of the respective rotor laminate in the rotor laminated core, a different slot is used for the connection to the rotor shaft. In other words, each of the slots in the rotor laminate is assigned to exactly one position in the rotor laminated core. 
     In a preferred embodiment, the predetermined angle by which the slots are offset from one another in a rotor laminate can be the sum of a pole angle corresponding to an angular distance between the poles of the rotor, or a multiple of the pole angle and a rotational staggering angle by which the poles are rotationally staggered. The slots can thus be suitably distributed over the inner circumference of the rotor laminate so that they do not overlap one another. 
     It is particularly preferred if the rotor laminates are connected to the rotor shaft via several torque-transmitting connections. As a result, the force can be better transmitted between the rotor shaft and the rotor core. Correspondingly, for example, two slots per rotor laminate are connected to two slots in the rotor shaft via two coupling elements. 
     According to an advantageous development, the plurality of torque-transmitting connections can be arranged to be uniformly distributed in the circumferential direction. As a result, the power transmission is evenly distributed over the rotor laminates or evenly over the circumference of the rotor shaft. 
     In other words, the disclosure also relates to a rotor having a laminated core, wherein different slots are formed in the rotor laminates of the laminated core, having a shaft with a slot and with a tongue for torque transmission between a respective slot of a rotor laminate and the rotor shaft. According to the disclosure, the combination of a classic tongue and slot connection by means of a separate tongue and the use of differently arranged slots in the laminated core reduces the number of different rotor laminates, since the same rotor laminate can be used several times in the laminated rotor bundle. The slots are arranged in such a way that the correct rotational staggering angle is maintained for each slot. A different slot is used during assembly depending on the position of the laminated core. This ensures the correct rotational staggering angle of the laminated cores. The power is transmitted via one or more tongues, like a parallel key. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is explained below with the aid of drawings. In the figures: 
         FIG. 1  shows a perspective representation of a rotor according to the disclosure, 
         FIG. 2  shows a front view of the rotor, 
         FIG. 3  shows a front view of a rotor laminate of the rotor, 
         FIG. 4  shows a perspective sectional view of the rotor laminate, 
         FIG. 5  shows a view from above of a laminated rotor core composed of five laminated rotor laminates, 
         FIGS. 6 and 7  show perspective views of a rotor shaft of the rotor with a coupling element and without a coupling element, 
         FIG. 8  shows an enlarged section from  FIG. 2 , 
         FIG. 9  shows a sectional view of the rotor, sectioned along the line IX-IX on  FIG. 8 , and 
         FIG. 10  shows a sectional view of the rotor, cut along the line X-X from  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     The figures are only schematic in nature and serve only for understanding the disclosure. The same elements are provided with the same reference symbols. 
       FIG. 1  shows a rotor  1  according to the disclosure for an electric machine. The rotor  1  has a laminated rotor core  2  composed of a plurality of coated rotor laminates  3  layered in the axial direction. The laminated rotor core  2 , more precisely, poles of the rotor  1  which are arranged in the laminated rotor core  2 , has or have what is termed a staggering or rotation. This means that the rotor laminates  3  are arranged to be rotated by a predetermined rotation angle γ with respect to one another. In this way, a rotational staggering of the poles of the rotor  1  is achieved. In particular, the rotor laminates  3  are each arranged to be rotated by the rotation angle γ with respect to an axially adjacent rotor laminate  3 . In particular, the rotation angle γ between axially adjacent rotor laminates  3  is constant. 
     The rotor  1  has a rotor shaft  4 . The rotor laminates  3  are fitted onto the rotor shaft  4 , in particular onto an outer circumference of the rotor shaft  4 . The rotor shaft  4  is connected to the wheel  3  in a rotationally fixed manner. The rotor shaft  4  is connected to slots  6  formed in the rotor laminates  3  via a torque-transmitting connection  5 . The connection  5  is formed by a coupling element  7 , which is formed separately from the rotor laminates  3 , and the slots  6  of the rotor laminates  3 . In the embodiment shown, the coupling element  7  is formed separately from the rotor shaft  4 , but can alternatively also be formed integrally with the rotor shaft  4 , even if this is not shown. In the embodiment shown, the coupling element  7  is designed as a tongue  8 , in particular in the manner of a parallel key. The tongue  8  engages in a slot  9  in the rotor shaft  4  and in the slots  6  of the rotor laminates  3  to fix the rotor laminates  3  on the rotor shaft  4  in a rotationally fixed manner by means of a form fit. In the embodiment shown, the connection  5  is thus designed as a tongue and slot connection. In the embodiment shown, each rotor laminate  3  is connected to the rotor shaft  4 , in particular to the slots  9  of the rotor shaft  4 , via two tongues  8 . The rotor laminates  3  can, however, also be connected to the rotor shaft  4  via a tongue or via more than two tongues, even if this is not shown. 
     The slots  6  of the rotor laminates  3  are arranged on a radial inner circumference of the rotor laminates  3 . The slots  6  extend in the axial direction continuously through the respective rotor laminate  3 . The slots  6  have a substantially rectangular cross-section. The slots  6  each have the same cross-section, which corresponds to a partial cross-section of the coupling element  6  and/or a cross-section of the slot  9  in the rotor shaft  4 . 
       FIG. 2  shows a front view of the rotor  1 . In the rotor laminates  3 , a plurality of slots  6 , ten slots  6  in the embodiment shown, are arranged to be distributed over the inner circumference. The arrangement, the height and/or, in particular, the width of the slots  6  are matched to the rotation angle γ in such a way that the slots  6  form a duct  10  extending continuously through the rotor core  2  in the axial direction. The duct  10  can be used, for example, for coolant guidance for the rotor  1 . Of the slots  6 , at least one torque slot  11  is used to transmit torque and at least one other coolant slot  12  is used for coolant guidance. 
     The rotation of the laminated rotor core  2  can be clearly seen in the front view of  FIG. 2 . Pole recesses  13  for poles of the rotor  1  are provided in the rotor laminates  3 . The pole recesses  13  are arranged in the rotor laminates  3  to be evenly distributed over the circumference. This means that the pole recesses  13  of a rotor laminate  3  are arranged to be spaced apart at constant angular intervals with a pole angle β. The pole angle β thus corresponds to 360° divided by the number of poles of the rotor  1 , in the illustrated embodiment 36°. The pole recess  13  of a rotor laminate  3  is arranged to be rotated by the rotational staggering angle α to a pole recess  13  of an axially adjacent rotor laminate  3 . This rotational staggering angle α and the resulting offset of the rotor laminates  3  can be seen in  FIG. 2  on the pole recesses  13  (or on other recesses in the rotor laminates  3 ). 
     Each rotor laminate  3  of the rotor laminated core  2  has at least as many slots  6  as the rotor laminated core  2  has rotor laminates  3 . The slots  6  are arranged in such a way that the predetermined rotational staggering angle α of the rotor laminates  3  is maintained thereby. In this case, a different slot  6  is used for each rotor laminate  3  of the rotor laminated core  2 , depending on the position of the rotor laminate  3  in the rotor laminated core, via which the respective rotor laminate  3  is connected to the rotor shaft  4 . In the embodiment shown, the laminated rotor core  2  is formed from five laminated rotor laminates  3 . The laminated rotor core  2  can, however, also have fewer than five or more than five laminated rotor laminates  3 , even if this is not shown. Accordingly, each rotor laminate  3  has at least five slots  6 . 
     An arrangement of the slots  6  is described with reference to  FIGS. 3 and 4 , in which a single rotor laminate  3  is shown. The rotor laminate  3  has a first slot  14 , a second slot  15 , a third slot  16 , a fourth slot  17 , and a fifth slot  18  of the slots  6 . Depending on the position at which the rotor laminate  3  is arranged in the rotor laminated core  2 , the first slot  14 , the second slot  15 , the third slot  16 , the fourth slot  17 , or the fifth slot  18  serves as the torque slot  11  via which the rotor laminate  3  is connected to the rotor shaft  4  in a torque-transmitting manner. For example, the first slot  14  is used for a first rotor laminate  3 , which forms an axial end face of the rotor laminated core  2 , as the torque slot  11 , the second slot  15  for a second rotor laminate  3 , which is axially adjacent to the first rotor laminate  3 , as the torque slot  11 , the third slot  16  for a third rotor laminate  3 , which is axially adjacent to the second rotor laminate  3 , as the torque slot  11 , etc. 
     In this case, the first slot  14 , the second slot  15 , the third slot  16 , the fourth slot  17 , and the fifth slot  18  are formed in each rotor laminate  3 , so that the position is established and the position corresponding to the position in the rotor laminated core  2  is only determined during assembly as the torque slot  11  is connected to the tongue  7 . The remaining slots  6  are used as the coolant slots  12 . 
     To achieve the staggering of the poles of the rotor  1 , the arrangement of the slots  6  is matched to the rotational staggering angle α. In particular, an angular distance between the slots  6 , in particular between the first slot  14  and the second slot  15 , or between the second slot  15  and the third slot  16 , or between the third slot  16  and the fourth slot  17 , etc., corresponds to the rotation angle γ. The rotation angle γ corresponds to the sum of the rotational staggering angle α and the pole angle β or the sum of the rotational staggering angle α and a multiple of the pole angle β. In other words, the slots  6 , which are provided as torque slot  11  for axially adjacent rotor laminates  3 , for example the first slot  14  and the second slot  15 , are arranged such that two poles of axially adjacent rotor laminates  3  are offset by the rotational staggering angle α. Since the poles are arranged at regular angular intervals, namely at the distance of the pole angle β, the slots  6 , which are provided as a torque slot  11  for axially adjacent rotor laminates  3 , are offset from one another by the rotational staggering angle α and any multiple of the pole angle β. Accordingly, the third slot  16  is offset from the first slot  14  by twice the rotational staggering angle α and any multiple of the pole angle β. 
     In the embodiment shown, the distances, that is to say the rotation angle γ, between the slots  6 , which are provided as the torque slot  11  for axially adjacent rotor laminates  3 , are the same. In particular, the rotation angle γ corresponds to the sum of the rotational staggering angle α and the pole angle β. That is, the distance between the first slot  14  and the third slot  16  is 2γ. This also means that the distance between the first slot  14  and the fourth slot  17  is 3γ. That is, the distance between the first slot  14  and the fifth slot  18  is 4γ. 
     Since two tongues  8  are provided in the illustrated embodiment of the rotor  1  to form the torque-transmitting connection  5 , the rotor laminates have two first slots  14 , two second slots  15 , two third slots  16 , two fourth slots  17 , and two fifth slots  18 , wherein the first slots  14 , the second slots  15 , the third slots  16 , the fourth slots  17 , and/or the fifth slots  18  are each opposite in the circumferential direction. Because the slots  6  are offset by the rotational staggering angle α in addition to the pole angle β, the spacing of an angle δ between the fifth slot  18  and the first slot  14  is different from the spacing of the rotation angle γ between the other circumferentially adjacent slots  6 . 
     Thus, all of the slots  6  of the axially adjacent rotor laminates  3  can be arranged to be completely congruent. The slots  6 , in particular the width of the slots  6 , is matched to the rotation angle γ (and thus to the rotational staggering angle α and the pole angle β) and thus to the arrangement of the slots  6 , so that the duct  10 , which is formed through the coolant slots  12  is formed, is axially continuous. This means that the cross-sections of the coolant slots  12  at least partially overlap. 
       FIG. 5  shows a view of the laminated rotor core  2  from above, in which it can be seen that the individual laminated rotor laminates  3  are arranged to be rotated relative to one another. The rotor laminates  3  are rotated with respect to one another by the same rotation angle γ, which appears different due to the curvature of the rotor laminates  3  in the view from above. 
       FIGS. 6 and 7  show perspective representations of the rotor shaft  4  with the tongue  8  (see  FIG. 6 ) and without the inserted tongue  8  (see  FIG. 8 ). The rotor shaft  4  is designed as a hollow shaft  19 . The slot  9 , which has a constant depth, is made on the outer circumference of the rotor shaft  4 . In the embodiment shown, the rotor shaft  4  has two slots  9  which are arranged to be opposite one another. The slot  9  extends longer in the axial direction than the tongue  8 . The slot  9  is open to an axial end face of the rotor shaft  4 . As a result, the tongue  8  can be pushed in in the axial direction. The tongue  8  has a greater axial extent than the laminated rotor core  2 . 
     The rotor shaft  4  has at least one duct  20  which extends in the radial direction and connects an inner circumference of the rotor shaft  4  to the outer circumference of the rotor shaft  4 . The duct  19  is used to guide coolant. In the embodiment shown, several ducts  20  are formed. The ducts  20  are arranged in such a way that they open into the slots  6 , in particular into the coolant slots  12 , when the rotor laminates  3  are mounted on the rotor shaft  4 . As a result, coolant can be guided from an interior of the rotor shaft  4  through the ducts  20  into the coolant slots  12  to the rotor laminates  3 . 
       FIGS. 9 and 10  show perspective sectional views of the rotor  1  which were cut along the line IX-IX from  FIG. 8  and along the line X-X from  FIG. 8 , respectively. A dotted line in  FIGS. 9 and 10  indicates a coolant flow  21  from the interior of the rotor shaft  4  through the duct  10 . In  FIG. 9  it can be seen that the second slot  15 , the third slot  16 , the fourth slot  17 , and the fifth slot  18  completely overlap, and an offset is formed between the fifth slot  18  and the first slot  14 . As a result, the first slot  14  and the fifth slot  18  only partially overlap. The continuous axial duct  10  is formed by the partial overlap between all the slots  6 . In  FIG. 10  it can be seen that the fourth slot  17  and the fifth slot  18  completely overlap, an offset is formed between the fifth slot  18  and the first slot  14 , and the first slot  14 , the second slot  15 , and the third slot  16  completely overlap. As a result, the first slot  14  and the fifth slot  18  only partially overlap. The continuous axial duct  10  is formed by the partial overlap between all the slots  6 . Depending on which one of the coolant slots  12  is cut through, the offset is located at a different point in the rotor core  2 . In the torque slot  11 , all the slots  6  completely overlap in the axial direction. 
     LIST OF REFERENCE SYMBOLS 
     
         
         
           
               1  Rotor 
               2  Rotor laminated core 
               3  Rotor laminate 
               4  Rotor shaft 
               5  Connection 
               6  Slot 
               7  Coupling element 
               8  Tongue 
               9  Slot 
               10  Duct 
               11  Torque slot 
               12  Coolant slot 
               13  Pole recess 
               14  First slot 
               15  Second slot 
               16  Third slot 
               17  Fourth slot 
               18  Fifth slot 
               19  Hollow shaft 
               20  Duct 
               21  Coolant flow 
             α Rotational staggering angle 
             β Polar angle 
             γ Rotation angle 
             δ Angle