Patent Publication Number: US-2020287442-A1

Title: An integrated drive gear motor assembly for a vehicle

Description:
RELATED APPLICATION 
     This application claims priority to, and benefit of, Chinese Utility Model Application No. 201721130755.9 filed on Sep. 5, 2017 and hereby incorporated by reference in its entirety. 
     FIELD 
     An integrated drive gear motor assembly for a vehicle, such as for an electric vehicle, is described. 
     BACKGROUND 
     Motors, such as electric motors, are well-known devices. These motors typically comprise a stator and a rotor connected to shaft. These components typically reside in a housing. The rotor may have conductors that carry currents, which interact with the magnetic field of the stator to generate forces that turn the shaft. It is also known for some rotors to carry permanent magnets and the stator to hold the conductors. Typically, the stator is the stationary part of the motor&#39;s electromagnetic circuit and it usually consists of either windings or permanent magnets. Windings are wires that are typically wrapped around a magnetic core so as to form magnetic poles when energized with the circuit. 
     In most cases, the above-mentioned shaft is provided with a first set of splines. A drive gear may be mounted on the first set of splines with a second set of complementary splines. This spline to spline connection, however, has several disadvantages. The disadvantages include, but are not limited, requiring a large space to accommodate this type of connection. For example, for the connection between splines to be secure, the splines must be of a particular size. The splines thus increase the outer diameter of the shaft on which the drive gear resides. In addition, the internal splines on the drive gear require the drive gear outer diameter to increase. Even one of these increases can cause the motor to not fit in the available space. 
     As can be appreciated from the discussion above, the large internal and external splines also add weight to the motor. Here again, in environments where weight savings are critical, such unnecessary weight gains are undesirable. 
     When the spline sets are not adequately formed or mated with one another, the reliability of the prior art connection also becomes a liability of the system. It is also possible that the drive gear does not ride evenly or concentrically with the shaft if the splines, or other features of the shaft or gear, are not properly formed or mated. In machines requiring high precision, or where space is a premium, such an imprecise connection may cause the motor to require frequent maintenance or even fail. 
     In view of the disadvantages of the connection between the shaft and drive gear of the prior art devices, it would be advantageous to have a shaft and drive gear connection that is highly reliable, highly precise, compact, lightweight, quiet and which operates smoothly, but which also provides sufficient torque capacity. By way of example, such a device is highly desirable in an electric vehicle that uses one or more electric motors. 
     SUMMARY 
     An integrated active gear motor assembly may have a housing with a stator and a rotor located within the housing. The assembly may also have a motor output shaft located within the stator with a gear portion of the motor output shaft extending out of the housing. A drive gear may be connected to the gear portion of the shaft. The drive gear may be integrally formed, unitary and one-piece with the motor output shaft to rotate with the motor output shaft. 
     In another aspect, the motor output shaft may be hollow along its entire length. 
     In another aspect, the inner ball bearing may be located directly adjacent the housing on the motor output shaft and the outer ball bearing may be spaced from the inner ball bearing on the motor output shaft by the drive gear. 
     In another aspect, the outer ball bearing may be located directly adjacent an end of the shaft. 
     In another aspect, an outside side of the inner ball bearing may be directly adjacent an inside side of the drive gear and an outside side of the drive gear may be directly adjacent an inside side of the outer ball bearing. 
     In another aspect, the motor output shaft may be sized to accommodate the maximum torque experienced by the drive gear. 
     In another aspect, no auxiliary connection structures may be required to connect the motor output shaft to the drive gear. 
     In another aspect, the gear portion comprises only a fraction of the overall length of the motor output shaft. 
     In another aspect, there is no gearing located within the housing. 
     In another aspect, the motor output shaft is only mounted for rotation within the housing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic side view cross section of one embodiment of an integrated gear drive motor assembly. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the device described and depicted herein may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise. 
     Turning now to  FIG. 1 , one embodiment of an integrated drive gear motor assembly  10  is depicted. The assembly  10  may include a housing  12 . The housing  12  may be comprised of several pieces that are secured together, or a single, integrally formed and unitary piece. The housing  12  may have an outer surface  14  and an inner surface  16 . The two surfaces  14 ,  16  may be connected by a constant thickness material or a variable thickness material. 
     Radially inward from the inner surface  16  at least one stator  18  is provided. The stator  18  may be one piece or comprised of a plurality of pieces that are connected together. The stator  18  may be secured to the housing  12  such that the two do not move with respect to one another. The stator  18  and housing  12  may be connected by fasteners, couplings, complementary fittings, adhesives, and/or friction fit and the like. The stator  18  is preferably located entirely within the housing  12 . 
     The stator  18  has an inner surface  20  and an outer surface  22 . The outer surface  22  is directly adjacent the inner surface  16  of the housing  12 . The stator outer surface  22  may in fact be in direct contact with the inner surface  16  of the housing  12 . One or more magnets or windings (not shown) may be located in or on the stator  18 . 
     At least partially radially inward from the at least one stator  18 , at least one rotor  24  is provided. The rotor  24  may be one piece or comprised of a plurality of pieces that are connected together. The rotor  24  is mounted within the housing  12  so that it can move, such as rotate along an axis A, with respect to the housing  12  and stator  18 . The rotor  24  is preferably located entirely within the housing  12 . 
     The rotor  24  has an inner surface  25  and an outer surface  26 . The outer surface  26  of the rotor  24  is directly adjacent the inner surface  20  of the stator  18 . Preferably, a gap separates the outer surface  26  of the rotor  24  and the inner surface  20  of the stator  18  so that the rotor  24  can rotate with respect to the stator  18 . 
     Radially inward from the inner surface  25  of the rotor  24  is a motor output shaft  28 . The rotor  24  may be connected to the motor output shaft  28 . The connection may be via fasteners, couplings, complementary fittings, adhesives and/or friction fit or the like. The connection is such that the rotor  24  and the motor output shaft  28  rotate together. The above relationship of the housing  12 , the stator  18 , the rotor  24  and the shaft  28  all lends itself to the compact nature of the design. 
     The motor output shaft  28  is partially located within the housing  12  and partially out of the housing  12 . The motor output shaft  28  may be mounted for rotation within the housing  12  on one or more bearings. In the depicted embodiment, the motor output shaft  28  is mounted on first and second bearings  30 ,  32 . In that embodiment, the bearings  30 ,  32  are located within the housing  12  at a first and second end portion  34 ,  36  of the motor output shaft  28 . The first and second end portions  34 ,  36  are located within the housing  12 . The bearings  30 ,  32  are separated by a central section  38  of the motor output shaft  28 . The bearings  30 ,  32  may be located within the housing  12  such as in housing bearing mounts  40 . 
     Each bearing described herein may include an inner race  42  and outer race  44  and a bearing  46 , such as one or more balls, located between the races  42 ,  44 . The inner races  42  may be in direct contact with the motor output shaft  28 . 
     The motor output shaft  28  may have an inner surface  48  and an outer surface  50 . The thickness of the motor output shaft  28  may vary between the inner surface  48  and the outer surface  50 . For example, the thickness of the motor output shaft  28  may be reduced adjacent the first and second bearings  30 ,  32 . For example, the thickness of the motor output shaft  28  may be reduced radially inward of the first and second bearings  30 ,  32  to accommodate the bearings  30 ,  32 , such as in bearing seats  52  formed in the motor output shaft  28 . Along the center section  38 , however, the motor output shaft  28  may have a relatively constant thickness. 
     The motor output shaft  28  may define a hollow cavity  54  from a first end  56  to a second end  58 . The hollow cavity may be continuous and uninterrupted. The cavity  54  may be defined by the inner surface  48 , which has a substantially constant diameter. The hollow cavity  54  lends itself to the lightweight nature of the assembly  10 . 
     Preferably, the thickness of the motor output shaft  28  is sized to accommodate the maximum torque experienced by a drive gear  60  (discussed below). The thickness depicted in the figure is simply for illustrative purposes: the thickness can increase or decrease as needed to accommodate more or less torque, respectively. 
     In one embodiment, an axial outboard portion  62  of the motor output shaft  28  that is axially outboard of the first bearing  30  may further reduce in thickness. As shown in  FIG. 1 , the axial outboard portion  62  may taper, or step down, in thickness from the first bearing  30  outward. 
     The motor output shaft  28  extends axially outward from the housing  12  through an opening  64  in the housing  12  adjacent the second bearing  32 . The portion of the motor output shaft  28  extending outside of the housing  12  may be designated the gear portion  66  via these bearings  68 ,  70 . 
     The gear portion  66  may be supported for rotation on a third and fourth bearing  68 ,  70 . The gear portion  66  may be located within another structure which is not shown in  FIG. 1  in which the gear portion  66  requires rotational support. 
     The gear portion  66  may comprise a fraction of the overall length of the motor output shaft  28 . By way of one example, the gear portion  66  may be such as ¼ to ⅙ of the overall length of the motor output shaft  28 . 
     The third bearing  68  may be located directly axially adjacent the housing  12 . In one embodiment, there is no gap between the third bearing  68  and the housing  12 , thus the third bearing  68  and housing  12  are in direct contact with one another. In another embodiment, there may be a gap between the third bearing  68  and the housing  12 . 
     The fourth bearing  70  may be located adjacent the second end  58  of the motor output shaft  28 . In the depicted embodiment, an outer surface  72  of the fourth bearing  70  is located axially aligned with an end surface  74  of the motor output shaft  28 . 
     The gear portion  66  may have a reduced thickness at the third and fourth bearings  68 ,  70 , similar to the reduced thickness of the motor output shaft  28  and the first and second bearings  30 ,  32 . Alternatively, the thickness of the gear portion  66  may remain constant with the center shaft section  38 . 
     The drive gear  60  is located on the gear portion  66 . Preferably, the drive gear  60  is integrally formed, unitary and one-piece with the gear portion  66  of the motor output shaft  28  so that the two rotate together at all times. More particularly, there are no auxiliary connection structures required to connect the drive gear  60  to the gear portion  66 . 
     The drive gear  60  may be comprised of a plurality of circumferentially extending teeth  75  on an outer surface  77  of the drive gear  60 . The teeth  77  are designed to be engaged with, such as in mesh with, complementary teeth on another gear (not shown) or shaft (not shown) to provide rotational drive thereto. 
     Forming the drive gear  60  with the gear portion  66  results in a compact package where the drive gear  60  and gear portion  66  are securely and precisely attached to one another. The direct connection ensures that the drive gear  60  and gear portion  66  provide a fixed, concentric connection between the two. The compact nature of the connection also reduces the linear velocity of the drive gear  60 , which desirably reduces noise. 
     It is also preferred that the drive gear  60  be located between the third and fourth bearings  68 ,  70 . More particularly, an inner surface  76  of the drive gear  60  may be located in direct axial contact with an outer surface  78  of the third bearing  68  and an outer surface  80  of the drive gear  60  may be located in direct axial contact with an inner surface  82  of the fourth bearing  70 . It is also permissible for gaps to be located between the bearings  68 ,  70  and the drive gear  60 . 
     The motor output shaft  28  is only mounted for rotation within the housing  12 . The motor output shaft  28  is not adapted for axial, or other, movement within the housing  12 . 
     Preferably, there is no gearing or related structures within the housing  12 . The housing  12  contains the above-mentioned structures in a relatively self-contained and self-sufficient structure. This lends itself to the compact nature of the assembly  10 . Of course, electrical power and/or controls may be added to the housing  12 , or connected to the stator  18 /rotor  24 . 
     The above-described integrated drive gear motor assembly  10  is a smoothly operating, compact, lightweight design that provides a precise but robust driveshaft and gear connection. In accordance with the provisions of the patent statutes, the present device has been described in what is considered to represent its preferred embodiments. However, it should be noted that the device can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.