Patent Publication Number: US-2021194304-A1

Title: Rotor shaft arrangement for an electric machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to PCT Application PCT/EP2019/073227, filed Aug. 30, 2019, which claims priority to German Patent Application No. DE 10 2018 216 120.8, filed Sep. 21, 2018. The disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a rotor shaft arrangement for an electric machine having a fluid passage within a rotor shaft of the rotor shaft arrangement. 
     BACKGROUND OF THE INVENTION 
     Many electric motors, electric machines and/or electrodynamic machines have a rotor shaft arrangement with a rotor shaft and a fluid passage within the rotor shaft, e.g. as an oil feed or as a passage for cooling liquid. In this case, the fluid gets into the fluid passage of the rotor shaft via holes. In this design, however, the fluid feed may be disrupted, especially at relatively high speeds of the rotor shaft, e.g. because of centrifugal forces, which force the fluid against the wall of the fluid passage and/or to the holes and hence impair introduction and/or transfer of the fluid through the fluid passage. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide an improved rotor shaft arrangement for an electric machine and/or an electric motor. 
     The object is achieved by the subject matter described herein. Advantageous embodiments are indicated in the following description and in the Figures. 
     One aspect of the invention relates to a rotor shaft arrangement for an electric machine and/or an electric motor. In this case, the rotor shaft arrangement has a rotor shaft and a fluid passage, which is arranged at least partially within the rotor shaft and is designed to carry a cooling fluid along a longitudinal extent direction of the fluid passage, wherein the longitudinal extent direction of the fluid passage is parallel to an axial direction and/or a longitudinal extent direction of the rotor shaft. The rotor shaft arrangement furthermore has at least one feed channel, which is arranged at least partially within the rotor shaft and is connected to the fluid passage at one end of the fluid passage, wherein the at least one feed channel is configured and/or designed to produce fluid communication between the fluid passage and a fluid feed that stores the cooling fluid, and wherein the feed channel is arranged with respect to the longitudinal extent direction of the fluid passage so as to form a bend at the end of the fluid passage. 
     In this case, the rotor shaft arrangement has the rotor shaft. In an embodiment, the rotor shaft is part of an electric motor and/or of an electric machine. It is also possible for the rotor shaft to be part of some other machine connected directly or indirectly to the electric motor. 
     The rotor shaft arrangement furthermore has a fluid passage, which is arranged at least partially within the rotor shaft. Here, the fluid passage is formed in the rotor shaft. In other words, the rotor shaft and the fluid passage may be of integral design. In an embodiment, the fluid is a cooling fluid, for example, in an embodiment, a dielectric cooling fluid, but it may also be some other fluid, e.g. an oil, such as a lubricating oil and/or a hydraulic oil. In an embodiment, the fluid passage is arranged coaxially with a rotor axis of the rotor shaft. In this case, the axial direction of the rotor shaft is parallel to the rotor axis. 
     The rotor shaft arrangement furthermore has at least one feed channel, which is arranged at least partially within the rotor shaft and is connected to the fluid passage at one end of the fluid passage and/or is in fluid communication therewith. The at least one feed channel is configured and/or designed to produce fluid communication between the fluid passage and a fluid feed that stores the cooling fluid. By virtue of this arrangement, the cooling fluid is conveyed from the fluid feed into the fluid passage via the at least one feed channel. In this case, the feed channel is arranged with respect to the longitudinal extent direction of the fluid passage so as to form a bend at the end of the fluid passage. In other words, the fluid passage, together with the at least one feed channel, is of bent configuration. The at least one feed channel may thus be arranged so as to form an inflection and/or a curve between the longitudinal extent direction of the feed channel and the longitudinal extent direction of the fluid passage at the end of the fluid passage. The bend, the curve and/or the inflection may as it were be formed at the end of the fluid passage and/or in one region of this end. In an embodiment, the longitudinal extent direction of the feed channel is transverse to the longitudinal extent direction of the fluid passage. Alternatively or in addition, a longitudinal axis of the feed channel is oblique and/or skewed with respect to a longitudinal axis of the fluid passage. 
     As a result of the rotor shaft arrangement, the effect of the centrifugal force on the cooling fluid during rotation of the rotor shaft arrangement is, at least partially, counteracted because, owing to the bend, only part of the centrifugal force acts on the cooling fluid, and therefore the introduction and/or transfer of the cooling fluid through the fluid passage is ensured even at relatively high speeds of the rotor shaft. The result is therefore a significantly more reliable supply of cooling fluid because a reduction in pressure due to the centrifugal force is counteracted. The production of this rotor shaft arrangement may furthermore be accomplished quite easily and cheaply. 
     In one embodiment, in a longitudinal section plane through the rotor shaft, the bend has a first bend angle between a longitudinal extent direction of the feed channel and the longitudinal extent direction of the fluid passage. In this case, the longitudinal extent direction of the fluid passage is given and/or defined by a projection of the longitudinal central axis of the fluid passage into the longitudinal section plane, and the longitudinal extent direction of the feed channel is given and/or defined by a projection of the longitudinal central axis of the feed channel into the longitudinal section plane. The first bend angle is between 95° and 175°, in one embodiment, is between 100° and 150°, e.g. between 110° and 140°. This bend in the longitudinal extent direction of the feed channel relative to the longitudinal extent direction of the fluid passage may allow a significantly lower loss of fluid from the fluid passage because the deflection of the fluid takes place at an obtuse angle. At an angle of 90° between the longitudinal extent direction of the feed channel and the longitudinal extent direction of the fluid passage, a centrifugal force on the cooling fluid would be significantly higher, which would result in a higher loss of cooling fluid, especially at high speeds. 
     In one embodiment, in a cross section plane through the rotor shaft, the bend has a second bend angle between a projection of the longitudinal extent direction of the feed channel into the cross section plane and a radial direction of the fluid passage. The feed channel may as it were be arranged and/or designed in such a way that an offset is formed between the projection of the longitudinal extent direction and/or a longitudinal axis of the feed channel with respect to a longitudinal central axis of the fluid passage. The second bend angle is between 10° and 80°, in one embodiment, is between 30° and 60°, e.g. between 30° and 40°. The second bend angle not only makes an additional contribution to keeping the loss of fluid from the fluid passage as low as possible but also has the additional effect as it were of “scooping” the fluid out of a fluid supply, e.g. a reservoir, into the feed channel, i.e. of improving the feeding of the fluid into the feed channel. 
     In one embodiment, the fluid passage has at the end a widening in the longitudinal extent direction of the fluid passage, wherein the widening has an acute angle in relation to the longitudinal extent direction of the fluid passage. In this case, the angle of the widening is measured between a tangent to a wall or inner surface of the fluid passage and the longitudinal extent direction of the fluid passage. This widening makes a further contribution to keeping the loss of fluid from the fluid passage as low as possible. Moreover, the widening contributes to the fluid undergoing an additional pressure in the direction of the widening and/or in the longitudinal extent direction of the fluid passage owing to the centrifugal force, especially at relatively high speeds. 
     In one embodiment, the acute angle of the widening is in a range of from 1° to 30°, and in an embodiment, is from 1° to 15°, e.g. from 1° to 10°. These angles have proven to be suitable in practice for the stated advantageous effects. 
     In one embodiment, the rotor shaft arrangement has a plurality of feed channels, which are spaced apart from one another in the circumferential direction of the fluid passage and/or in the circumferential direction of the rotor shaft. This contributes in an advantageous manner to increasing a flow of fluid through the fluid passage. 
     In one embodiment, the rotor shaft is connected to the fluid passage and to the at least one feed channel for conjoint rotation therewith. This contributes to stable conditions for the fluid dynamics in the fluid passage and in the feed channel. Alternatively or in addition, the rotor shaft, the fluid passage and the feed channel are of integral design. 
     In one embodiment, the rotor shaft has a first portion, in which the at least one feed channel is arranged, and a second portion, in which the fluid passage is arranged. In this case, an outside diameter of the first portion is smaller than an outside diameter of the second portion of the rotor shaft, with the result that an annular channel is formed in the first portion along an outer circumference of the rotor shaft. The annular channel may promote an improvement in the feeding of the fluid into the feed channel. In an embodiment, the annular channel is similar in design to channeling in the rotor shaft. 
     In one embodiment, the rotor shaft arrangement furthermore has a trough-shaped fluid feed, which has a semicircular trough portion and which is configured for feeding the cooling fluid to the at least one feed channel of the rotor shaft arrangement. In this case, the first portion of the rotor shaft, in which the annular channel is arranged, is accommodated at least partially in the semicircular trough portion, with the result that, when the rotor shaft rotates, cooling fluid is conveyed out of the fluid feed into the fluid passage via the at least one feed channel. 
     In one embodiment, the first portion of the rotor shaft is arranged in such a way in the semicircular trough portion that a center of curvature of the semicircular trough portion is arranged eccentrically with respect to a rotor axis of the rotor shaft. As a result, a tapering gap is formed between the semicircular trough portion and the rotor shaft, thereby furthermore improving the feeding of fluid into the feed channel. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For further clarification, the invention will now be described on the basis of exemplary embodiments shown in the Figures. 
         FIG. 1 a   : shows a perspective view of a rotor shaft arrangement according to one exemplary embodiment of the present invention; 
         FIG. 1 b   : shows a longitudinal section of the rotor shaft arrangement in  FIG. 1   a;    
         FIG. 2 : shows a longitudinal section through a rotor shaft arrangement according to one exemplary embodiment; 
         FIG. 3 : shows a cross section through the rotor shaft arrangement in  FIG. 2 ; 
         FIG. 4 : shows a longitudinal section through a rotor shaft arrangement according to one exemplary embodiment; 
         FIG. 5 : shows a cross section through the rotor shaft arrangement in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
       FIG. 1 a    shows a schematic diagram of a rotor shaft arrangement  19 , having a rotor shaft  10  and a fluid passage  20  (depicted in dashed lines) in a perspective view. In the exemplary embodiment shown, a central axis  25  or longitudinal central axis  25  of the fluid passage  20  is identical with a central axis  25 , a longitudinal central axis  25  and/or a rotor axis  25  of the rotor shaft  10 . In other words, the fluid passage  20  is coaxial with the rotor shaft. Accordingly, a longitudinal extent direction  50  of the fluid passage  20  is parallel to a longitudinal extent direction  50  and/or axial direction  50  of the rotor shaft  10 , which, in turn, is parallel to the x axis in a coordinate system depicted at the bottom right in  FIG. 1   a.    
     A cross section plane and/or the cross sections through the rotor shaft  10  which are shown in  FIGS. 3 and 5  may extend in a plane parallel to the y-z plane. 
     The rotor shaft  10  has a first end  11  and a second end  12 . Formed at a distance from the first end  11  of the rotor shaft  10  is an annular channel  38 , which is arranged at least along part of the outer circumference of the rotor shaft  10 . At least one feed channel  30  is arranged in the rotor shaft  10  in the region of the annular channel  38 . In this arrangement, the at least one feed channel  30  is arranged at one end  21  of the fluid passage  20 . More specifically, the rotor shaft arrangement  19  has a plurality of feed channels  30 , which are spaced apart from one another in the circumferential direction of the rotor shaft  10 . 
       FIG. 1 b    shows a longitudinal section in the x-z plane of the rotor shaft arrangement  10  in  FIG. 1   a.    
     The rotor shaft  10  has a first portion  17 , in which the feed channels  30  are arranged and/or the annular channel  38  is formed. The rotor shaft  10  has a second portion  18 , in which the fluid passage  20  is arranged. An outside diameter of the first portion  17  is smaller than an outside diameter of the second portion  18  of the rotor shaft  10 , with the result that the annular channel  38  is formed in the first portion  17  along an outer circumference of the rotor shaft  10 . 
     As shown in  FIG. 1 b   , the rotor shaft  10  has, in the region of the end  21  of the fluid passage  20 , a widening  23 , which extends in the longitudinal extent direction  50  of the fluid passage  20  as far as an inflection  24  of the fluid passage  20 . 
     In the region of the end  21  and/or at the end  21  of the fluid passage  20 , a plurality of feed channels  30  is arranged adjoining and in fluid communication with the fluid passage  20 . The feed channels  30  each have an opening  31  in the region of the annular channel  38  and open into the fluid passage  20  in the region of the end  21  of the fluid passage  20 . 
     As shown in  FIGS. 1 a  and 1 b   , the feed channels  30  are arranged on the fluid passage  20  so as to form a bend  52 , as will be explained in greater detail below. 
       FIG. 2  shows a longitudinal section through a rotor shaft arrangement  19  according to one exemplary embodiment. Unless otherwise described, the rotor shaft arrangement in  FIG. 2  has the same elements and features as the rotor shaft arrangement  19  in  FIGS. 1 a    and  1   b.    
     The openings  31  of the feed channels  30  are arranged in the region of the annular channel  38 . The arrows  32  show the direction in which, via the openings  31 , the fluid enters the region of the end  21  of the fluid passage  20  and flows onward through the widening  23  into the fluid passage  20 . The widening  23  extends from the end  21  of the fluid passage  20  as far as the inflection  24 . An angle w 1  indicates the angle of the widening  23 . In this context, the angle w 1  denotes an angle which is enclosed by a tangent to a wall and/or a lateral surface, facing the longitudinal central axis  25 , of the fluid passage  20  and the longitudinal central axis  25 . 
     As mentioned above, the fluid passage  20  and each of the feed channels  30  form a bend  52 . In an embodiment, the longitudinal extent direction  54  of each feed channel  30  is transverse to the longitudinal extent direction  50  of the fluid passage, as shown in  FIG. 2 . In a longitudinal section plane through the rotor shaft  10 , as shown in  FIG. 2 , the bend  52  has a first bend angle w 2  between the longitudinal extent direction  54  of the feed channel and the longitudinal extent direction  50  of the fluid passage  20 , wherein the first bend angle w 2  is between 95° and 175°, in an embodiment is between 100° and 150°, e.g. between 110° and 140°. 
       FIG. 3  shows a cross section through the rotor shaft arrangement  19  in  FIG. 2 . 
     The central axis  25  and/or longitudinal central axis  25  of the fluid passage  20  is shown in the center of the fluid passage  20 . 
     As is clearly visible in  FIG. 3 , in a cross section plane through the rotor shaft  10 , the plane of the drawing in  FIG. 3  for instance, the bend  52  of each feed channel  30  has a second bend angle w 3  between a projection  56  of the longitudinal extent direction  54  of the feed channel  30  into the cross section plane and a radial direction  58  of the fluid passage  20 . In this embodiment, the radial direction  58  of the fluid passage may be parallel to a radial direction of the rotor shaft  10  and/or parallel to a transverse axis of the rotor shaft  10 . The second bend angle w 3  is between 10° and 80°, in an embodiment is between 30° and 60°, e.g. from 30° to 40°. 
     The feed channels  30  are thus arranged in such a way at the end  21  of the fluid passage  20  that the bend  52  is formed with the first bend angle w 2  and the second bend angle w 3 . As is seen in  FIG. 3 , this leads as it were to a longitudinal central axis that is parallel to the longitudinal extent direction  54  of each feed channel  30  being skewed relative to the longitudinal central axis  25  of the fluid passage  20 . As a result, effects of the centrifugal force on the fluid are reduced, and better conveyance of fluid via the feed channels  30  into the fluid passage  20  is achieved. Overall, it is thus possible to improve cooling with the fluid. 
       FIG. 4  shows a longitudinal section through a rotor shaft arrangement  19  according to one exemplary embodiment. 
     In the region of the annular channel  38  and/or with the first portion  17 , the rotor shaft  10  is arranged in a reservoir  41  and/or a fluid feed  40  having a reservoir  41 , wherein the fluid feed  40  may store the fluid. In this case, the openings  31  of the feed channels  30  are arranged in the reservoir  41  and/or the fluid feed  40 , and therefore fluid is conveyed out of the fluid feed  40  into the fluid passage  20  via the feed channels  30  when the rotor shaft  10  rotates. The fluid is then transferred onwards through the fluid passage  20  via the widening  23 . 
       FIG. 5  shows a cross section through the rotor shaft arrangement  19  in  FIG. 4 . 
     In a lower region  43 , the reservoir  41  and/or the fluid feed  40  has a semicircular trough portion  44  having a center of curvature  45  of the trough portion  44 . As is clearly apparent in  FIG. 5 , the central axis  25 , the longitudinal central axis  25  and/or the rotor axis  25  are/is arranged eccentrically and/or with an eccentricity  35  and/or a spacing  35  with respect to the center of curvature  45 . As a result, there is a gap  47  (see arrow  60 ) between the semicircular trough portion  44  of the reservoir  41  and the rotor shaft  10  or annular channel  38 , the gap tapering in the circumferential direction of the rotor shaft  10  and/or of the annular channel  38 . When the reservoir  41  is filled with a fluid and the rotor shaft  10  rotates in the direction of the taper of the tapering gap  47 , the fluid is forced into the feed channels  30  of the rotor shaft  10  by the rotary motion of the rotary shaft  10 , thereby further improving the fluid feed into the feed channel  30 . This is further assisted by the annular channel  38  (see  FIG. 4 ). 
     In addition, it is to be noted that “comprising” and “have” do not exclude any other elements or steps, and “a” or “an” do not exclude a plurality. Furthermore, it is to be noted that features or steps which have been described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference designations are not to be considered to be limiting. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 
     LIST OF REFERENCE SIGNS 
     
         
           10  rotor shaft 
           11  first end of the rotor shaft 
           12  second end of the rotor shaft 
           17  first portion of the rotor shaft 
           18  second portion of the rotor shaft 
           19  rotor shaft arrangement 
           20  fluid passage 
           21  end of the fluid passage 
           23  widening 
           24  inflection 
           25  central axis of the fluid passage and of the rotor shaft 
           30  feed channels 
           31  opening 
           32  fluid path 
           35  eccentricity/spacing 
           38  annular channel 
           40  fluid feed 
           41  reservoir 
           43  lower region of the reservoir 
           44  semicircular trough portion 
           45  center of curvature 
           47  tapering gap 
           50  longitudinal extent direction of the fluid passage/rotor shaft 
           52  bend 
           54  longitudinal extent direction of the feed channels 
           56  projection of the longitudinal extent direction  54   
           58  radial direction of the fluid passage/rotor shaft 
         w 1  angle of the widening 
         w 2  first bend angle 
         w 3  second bend angle