Patent Publication Number: US-2022216754-A1

Title: Electric machine with a fixation of multiple rotor laminations to a rotor shaft, said fixation allowing an axial tolerance compensation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2020/100234 filed Mar. 25, 2020, which claims priority to DE 102019113443.9 filed May 21, 2019, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to an electric machine for driving a motor vehicle, such as a purely electric or hybridized motor vehicle, e.g., a car, truck, bus or other utility vehicle, having a rotor, the rotor being a central rotor shaft and a laminated core which is made up of a plurality of rotor laminations and fixed to the rotor shaft. 
     BACKGROUND 
     Generic rotors of electric machines are well known in various implementations. For example, designs are known in which a press fit is provided directly between the individual rotor laminations of the laminated core and the rotor shaft. Fixings of the laminated core by means of a nut in connection with a groove are also known. Alternatively, welded connections are also implemented. 
     However, these known types of fixing have the disadvantage that they usually involve a relatively high manufacturing effort. With regard to the press fits implemented between the laminated core and the rotor shaft, the rotor laminations and the corresponding receptacles are laborious to adjust in diameter and to implement solidly. In most cases, each individual rotor lamination is reshaped in a critical region. Even with the alternative mounting of a nut, at least one thread must be provided on the rotor shaft, which likewise requires complex machining Such an increased manufacturing effort also exists in the case of a welded connection that must be made using a separate process. 
     SUMMARY 
     It is therefore the object of the present disclosure to eliminate the disadvantages known from the prior art and, in particular, to provide an electric machine the rotor of which is produced simply and with sufficient strength to transmit the highest possible torques. 
     This is achieved according to the disclosure by the fact that the laminated core is contacted on at least one axial side by an end lamination producing tolerance compensation, which end lamination is in turn supported by a securing ring pressed onto the rotor shaft. 
     This fixation of the laminated core via the end lamination and the securing ring results in a fixation between the laminated core and the rotor shaft that is simple to manufacture. This is because the securing ring can easily be individually adapted to the corresponding press connection without the shape of the rotor laminations of the laminated core having to be changed. As a result, a particularly robust rotor is implemented, the manufacturing effort of which is reduced. 
     Further advantageous embodiments are explained in more detail below. 
     Accordingly, it is also advantageous if the securing ring has an axially protruding cup region, which cup region is pressed onto a radial outer side of the rotor shaft. This cup region can easily be adjusted in its axial position during assembly. 
     If the securing ring has a disk region which is arranged radially outside the cup region and which disk region lies flat directly on the end lamination, the further structure of the securing ring is kept simple. 
     It is particularly advantageous if the disk region is connected to the cup region via an axially extending connection region. As a result, the securing ring can be skillfully mounted on the rotor shaft, axially offset from the laminated core. 
     Furthermore, it is convenient if the securing ring is pressed onto the rotor shaft in such a way that it effects/applies an axial pretensioning force to the end lamination. 
     When the securing ring is pushed onto a receiving surface of the rotor shaft, the receiving surface being formed by a radial step of the rotor shaft, the diameter onto which the securing ring is pressed can be easily adjusted. 
     The securing ring sits on a (second) outer diameter of the rotor shaft, which (second) outer diameter is smaller than a (first) outer diameter on which the laminated core and/or the at least one end lamination sit/sits. 
     It is also advantageous if a first end lamination rests on a first axial side of the lamination core and a second end lamination rests on a second axial side of the lamination core opposite the first axial side. Tolerance compensation can thus be easily implemented by means of the thickness of the end laminations. 
     In this context, it is also advantageous if the securing ring rests on the first end lamination and the second end lamination rests (directly) on a radial shoulder of the rotor shaft. As a result, the laminated core is supported directly on the rotor shaft towards one axial side, which further favors a simple structure. 
     Furthermore, it has proven to be advantageous if the electric machine is designed as a synchronous motor. 
     If the laminated core is additionally received in a rotationally fixed manner on the radial outside of the rotor shaft via a form-fitting connection, for example a form-fitting toothing, the rotationally fixed connection of the laminated core can also be easily manufactured. 
     In other words, according to the disclosure, a cost-efficient axial fixation and tolerance compensation of the rotor laminations on the rotor shaft are implemented. The rotor of the electric synchronous machine (electric machine) is shaped by using individual rotor laminations which together form a rotor core (laminated core). Tolerance compensation can be set using an end lamination, which tolerance compensation in turn depends on the installation space and on varying tolerances. A locking ring/securing ring is pressed onto the rotor shaft for axially fixing/supporting the laminated core. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the disclosure is now explained in more detail with reference to figures. 
       In the Figures: 
         FIG. 1  shows a longitudinal sectional view of an electric machine according to the disclosure according to a preferred exemplary embodiment, 
         FIG. 2  shows a detailed view of the electric machine from  FIG. 1  cut in the longitudinal direction, wherein a securing ring for axially supporting a rotor lamination relative to a rotor shaft can be seen in more detail, 
         FIG. 3  shows a perspective illustration of the rotor used in  FIG. 1  from a side having the securing ring, and 
         FIG. 4  shows a perspective representation of the securing ring used in  FIGS. 1 to 3 . 
     
    
    
     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. 
     In  FIG. 1  an electric machine  1  according to the disclosure can be clearly seen in its basic structure. The electric machine  1  is implemented as a synchronous machine/synchronous motor. The electric machine  1  has a rotor  2  which is arranged centrally so as to be rotatable about an axis of rotation  17 . A stator  18  of the electric machine  1  is mounted radially outside the rotor  2 . The stator  18  is fixedly received in a housing  19 . The rotor  2  is rotatably mounted in this housing  19 . 
     In this context, it should be pointed out that the electric machine  1  is usually dimensioned as a drive machine of a motor vehicle. The electric machine  1  is therefore preferably used in a drive train of a motor vehicle, winch is not shown here for the sake of clarity. In the present exemplary embodiment in  FIG. 1 , the electric machine  1  is integrated in an electric axle drive unit (E-axle). When implementing this electric axle drive unit, the motor vehicle is preferably implemented as a purely electrically driven vehicle. According to further embodiments, the electric machine  1  is also used in a hybrid module, which hybrid module is inserted in a known manner between an internal combustion engine and a transmission of the drive train and is thus prepared for implementing a hybridized drive of the motor vehicle. In further embodiments, the electric machine  1  is also used as a wheel hub machine/wheel hub motor. 
     In connection with  FIGS. 2 and 3  the further structure of the rotor  2  designed according to the disclosure is shown, which can also be used separately from the illustrated electric machine  1  in other electric machines as an independent unit. The rotor  2  has a central rotor shaft  3 . The rotor shaft  3  is arranged concentrically to the axis of rotation  17 . The rotor shaft  3  is provided with an essentially cylindrically extending receiving region  20 . A laminated core  5  of the rotor  2  is fixed to this receiving region  20  (radially from the outside). The laminated core  5  typically has a plurality of rotor laminations  4  which rest on one another in the axial direction. The rotor laminations  4  are typically implemented as identical parts. The rotor laminations  4  are already pre-assembled to form the laminated core  5 . The laminated core  5  is held on the receiving region  20  in a rotationally fixed manner via a form-fitting connection  16 , here in the form of a form-fitting toothing. 
     According to the disclosure, for axial tolerance compensation of the rotor  2 , the laminated core  5  is supported on a first axial side  6   a  (viewed along the axis of rotation  17 ) by a first end lamination  7   a , which first end lamination  7   a  is in turn directly supported by a securing ring  8  pressed onto the rotor shaft  3 . This axial securing of the laminated core  5  by means of the securing ring  8  is shown in detail in  FIG. 2 . In connection with  FIG. 3  it is also clear that the first end lamination  7   a  from the first axial side  6   a  of the laminated core  5  rests flat directly against the laminated core  5 . The first end lamination  7   a  is also supported on the receiving region  20  and received in a rotationally fixed manner. The receiving region  20  has a constant first outer diameter over its entire length. 
     The securing ring  8  is fixed directly to the rotor shaft  3 , that is to say pressed on, by means of a cup region  9  arranged radially on the inside. The axially protruding cup region  9  is pressed onto a receiving surface  13  which is formed by a radial step  14 . The radial step  14  is offset inwardly in the radial direction with respect to the receiving region  20 . The receiving surface  13  consequently has a second outer diameter which is smaller than the first outer diameter. The length/axial extension of the receiving surface  13  is selected to be greater than the length of the cup region  9  and is matched to the further shape of the securing ring  8  so that the position of the securing ring  8  can be varied along the receiving surface  13  during assembly. With a disk region  11  arranged radially outside of the cup region  9 , the securing ring  8  rests flat directly on the first end lamination  7   a . A connection region  12  connecting the disk region  11  to the cup region  9  extends in such a way that the disk region  11  is arranged offset in the axial direction with respect to the cup region  9 . Due to the design of the disk region  11 , the securing ring  8  is also referred to as a securing disk. The securing ring  8  can also be seen particularly clearly in  FIG. 4  where it is illustrated separately. It will be clear here that the connection region  12  is essentially implemented as an axial bulge. The securing ring  8 , like the first end lamination  7   a , is made from a metal sheet (steel). 
     A second end lamination  7   b  is arranged on a second axial side  6   b  of the laminated core  5  facing away from the first axial side  6   a . The second end lamination  7   b  also rests flat against the laminated core  5  on the second axial side  6   b . On a side of the second end lamination  7   b  again facing axially away from the laminated core  5 , the second end lamination  7   b  is supported directly on a shoulder  15  of the rotor shaft  3  projecting radially outward ( FIG. 1 ). The shoulder  15  is integrally formed with the rotor shaft  3 . This results in an axial reception of the laminated core  5  together with the end laminations  7   a ,  7   b  between the shoulder  15  and the securing ring  8 . 
     It should also be pointed out that the securing ring  8  is preferably pressed onto the rotor shaft  3  with an axial pretensioning force, so that the first end lamination  7   a  presses on the laminated core  5  with an axial pretensioning force and the laminated core  5  in turn presses the second end lamination  7   b  against the shoulder  15  with an axial pretensioning force. 
     In other words, the embodiment according to the disclosure provides a cost-efficient and compact solution in terms of installation space for fixing the rotor laminations  4  to the rotor shaft  3 . This solution offers a simple and inexpensive fixation option. In addition, this solution offers a high degree of flexibility and can be installed in many different electric machines  1 , which differ either in terms of the active length (power) and/or the transmission interface. The inventive solution therefore also consists of an inexpensive, simple and modular-compatible technical solution. The tolerance compensation is effected by the end lamination (first end lamination  7   a ), which can be adapted dependent on the installation space and for the tolerance compensation. The axial fixation is effected with the axial securing ring  8 , which is pressed onto the rotor shaft  3 . Thus, the rotor laminations  4  and the end laminations  7   a ,  7   b  are held in position. A preferred installation variant takes place in an e-axle. 
     LIST OF REFERENCE NUMBERS 
     
         
         
           
               1  Electric machine 
               2  Rotor 
               3  Rotor shaft 
               4  Rotor lamination 
               5  Laminated core 
               6   a  First axial side 
               6   b  Second axial side 
               7   a  First end lamination 
               7   b  Second end lamination 
               8  Securing ring 
               9  Cup region 
               10  Outer side 
               11  Disk region 
               12  Connection region 
               13  Receiving surface 
               14  Step 
               15  Shoulder 
               16  Form-fitting connection 
               17  Axis of rotation 
               18  Stator 
               19  Housing 
               20  Receiving region