Patent Publication Number: US-8123645-B2

Title: Vehicle transmission

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application claims the benefit of priority as a continuation under 35 U.S.C. §120 of co-pending U.S. patent application Ser. No. 11/904,915, having a filing date of Sep. 28, 2007, and titled “VEHICLE TRANSMISSION,” the complete disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure relates generally to the field of vehicle transmissions. The disclosure more specifically relates to the control of the power path through a transmission to provide multiple speeds in the transmission. 
     It would be desirable to provide an improved multi-speed vehicle transmission which provides more than one speed using a planetary gear drive arrangement. However, the problems posed by this type of arrangement are particularly complicated because they exist within the complexity of an overall vehicle system. For example, the inputs and outputs of a vehicle transmission experience the torque, speed and power oscillations caused by vehicle dynamics, varying suspension systems, road conditions, loading conditions, engine and motor torque and speed characteristics, operator control, etc. Accordingly, the selection of a solution may result in unforeseen shifting control complications, shifting linkage complications, cost increases, manufacturing efficiency losses, expensive part configurations, performance and control losses, etc. Further complicating the use of this type of transmission is the need to use such transmissions in hybrid vehicles which utilize electric motors for all or portions of the vehicle drive power. 
     SUMMARY 
     One embodiment of the invention relates a two-speed power transmission for a hybrid drive vehicle. The transmission includes a bevel gear configured to provide power to a shaft of the vehicle and that is rotatably engaged with a collar assembly. The transmission also includes a planetary gear set selectively engageable with the collar assembly. The collar assembly includes a first collar and a second collar. The first collar and the second collar are axially coupled together and independently rotatable relative to one another. The collar assembly is slidable between a first position to engage the planetary gear set and rotate the shaft at a first speed, and a second position to disengage the planetary gear set and rotate the shaft at a second speed. Both the first collar and the second collar disengage the planetary gear set in the second position. 
     Another embodiment of the invention relates to a multi-speed power transmission for a hybrid drive vehicle. The transmission includes a power output source, a shaft coupled to one or more pairs of wheels of the vehicle, a planetary gear set concentrically disposed about the shaft and a collar assembly coupled to the power output source. The collar assembly is concentrically disposed about the shaft and includes a first collar and a second collar. The first collar and the second collar are axially coupled together and independently rotatable relative to one another. The collar assembly is slidable between a first position to engage the planetary gear set and rotate the shaft at a first speed, and a second position to disengage and bypass the planetary gear set and rotate the shaft at a second speed. Both the first collar and the second collar disengage the planetary gear set in the second position. 
     Another embodiment of the invention relates to a vehicle. The vehicle includes at least one drive wheel, at least one axle assembly having a shaft configured to rotate the at least one drive wheel, and a power transmission coupled to the shaft. The power transmission includes a collar assembly including a first collar and a second collar. The first collar and the second collar are axially coupled together and independently rotatable relative to one another. The transmission also includes a bevel gear configured to provide power to the shaft. The bevel gear is rotatably engaged with the collar assembly. The transmission further includes a planetary gear set that is selectively engageable with the collar assembly. The collar assembly is slidable between a first position to engage the planetary gear set and rotate the shaft at a first speed, and a second position to disengage the planetary gear set and rotate the shaft at a second speed. Both the first collar and the second collar disengage the planetary gear set in the second position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vehicle including an axle housing that packages a transmission according to one exemplary embodiment. 
         FIG. 2  is a sectional view of the transmission, motor, and wheel housing of the vehicle of  FIG. 1  according to an exemplary embodiment. 
         FIG. 3  is a perspective view of the transmission of  FIG. 1  according to an exemplary embodiment. 
         FIG. 4  is a perspective view of the transmission of  FIG. 2  from another angle according to an exemplary embodiment. 
         FIG. 5  is an exploded view of the transmission of  FIG. 1  according to an exemplary embodiment. 
         FIG. 6  is a perspective view of a collar assembly of the transmission of  FIG. 1  according to an exemplary embodiment. 
         FIG. 7  is a sectional view of the transmission of  FIG. 1  in a neutral position according to an exemplary embodiment. 
         FIG. 8  is a sectional view of the transmission of  FIG. 1  in a high speed position according to an exemplary embodiment. 
         FIG. 9  is a sectional view of the transmission of  FIG. 1  in a low speed position according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a hybrid vehicle  100 , such as a refuse vehicle, is configured to collect and manage refuse (or other cargo). Refuse vehicle  100  typically includes at least one axle assembly  107  including axle shafts  102  (see  FIG. 2 ) that may be configured for use with various suspension types (e.g., a walking beam suspension, independent suspension, an airbag suspension, etc.). It is noted that while the  FIGS. 1 and 2  illustrate an axle assembly embodied on refuse vehicle  100 , the axle assembly may be used on any conventional or hybrid drive vehicle (i.e., capable of electric and/or mechanical drive). 
     Referring to  FIG. 2 , a transmission  104  may be configured for use with axle assembly  107 . Transmission  104  receives power from a motor  105  (through a gear  116  shown attached to a shaft of motor  105 ) and transfers the power through a differential  108  to axle shafts  102 . Axle shafts  102  in turn rotates one or more wheels  103  on each side of vehicle  100 . While the figure illustrates two drive wheels coupled to an axle shaft  102  on each side of vehicle  100 , according to another exemplary embodiment a single drive wheel may be coupled to axle shaft  102  on each side. According to still another exemplary embodiment, more than two wheels may be coupled to the axle shaft  102  on each side of vehicle  100 . According to an alternative embodiment, the transmission may receive power from a drive shaft driven from an internal combustion engine or other suitable device. 
     Referring to  FIGS. 3 and 4 , transmission  104  includes a gear  110  (e.g. pinion gear, etc.) which engages a gear  106  (e.g. final drive gear, etc.) fastened to a differential  108 . Differential  108  is rotatably supported within the transmission  104  by appropriate bearings (not shown). Differential  108  is coupled to axle shafts  102  which are coupled to the wheels of vehicle  100 . Depending upon the application, wheel-end reduction units may be used to couple the axle shafts to the wheels. In addition to gear  110  which is fixed to a shaft  112 , transmission  104  includes bevel gears  114  and  116 , a planetary gear assembly  118 , a splined section  120  fixed to shaft  112 , and a collar assembly  122  (e.g., a coupling, etc.). Bevel gear  116  (shown as a power input gear) may be attached to an electric motor or engine directly or through a drive shaft. As explained in detail below, the power applied to gear  116  is transmitted through the transmission to differential  108  to move the vehicle. 
     By way of example, gears  106 ,  110  may have helical gear teeth configurations, and rotate about generally parallel axes. Gear  110  is fixed to shaft  112  at end  124  to transmit power from shaft  112  to gear  106 . Shaft  112  is supported within the housing of axle assembly  107  by roller bearings to rotate about an axis which is substantially parallel to the axis of rotation of differential  108 . Bevel gear  114  is supported upon shaft  112  which is supported relative to the housing by a pair of roller bearings so that the rotational axis of gear  114  is the same as that of gear  110 . Bevel gear  116  is engaged with gear  114 , and is rotationally supported relative to the housing by a drive shaft and bearings to rotate about an axis generally perpendicular with the axis of rotation of gear  114 . The drive shaft attached to gear  116  may be driven by an engine, electric motor in the case of a hybrid vehicle, or other suitable device. Gear  114  further supports a splined hub  144  (see  FIGS. 7-9 ), for example an input shaft, etc. In particular, hub  144  is bolted to gear  114  to rotate about shaft  112 . 
     Referring to  FIG. 5 , a splined section  120  is mated (e.g. pressed fit, etc.) to splines  142  of shaft  112 . In particular, section  120  includes external splines which are similar in size and shape to splines  145  on an outer portion of hub  144  (see  FIGS. 7-9 ) so that they may be axially aligned with one another. Section  120  includes internal splines which are configured to engage with splines  142  on shaft  112  with enough interference to prevent movement of section  120  relative to shaft  112 . 
     Referring again to  FIG. 5 , planetary gear set  118  includes a sun gear  128 , a carrier  130 , three planetary gears  136  rotatably attached to carrier  130  by appropriate pins and bearings, and ring gear  132 . Sun gear  128  is located within carrier  130  so that gear teeth  129  of sun gear  128  are engaged with the gear teeth of all three planetary gears  136 . Ring gear  132  is fixed to the housing of axle assembly  107  and includes gear teeth which are engaged with the gear teeth of all three planetary gears  136 . 
     The structure with which power is transmitted from splined hub  144  either directly to shaft  112  or indirectly to shaft  112  through planetary gear set  118  will now be described in reference to  FIGS. 5 and 6 . In particular, the structure includes a two-piece collar assembly  122  (e.g., a coupling, etc.). Assembly  122  includes a first collar  134  and a second collar  140 . Collars  134  and  140  both include internal teeth  135  and  141 , respectively, which are similar in size and shape to and configured to mate with the splines  145  on the outer section of hub  144  and splined section  120 . Collar  134  includes external teeth  137  which are configured to engage with internal teeth  127  of sun gear  128 , and collar  140  includes external teeth  139  which are configured to engage with internal teeth  131  of carrier  130 . Collar  134  further includes a circumferential groove  148  which is engaged by flanges  146  (e.g., hooks, etc.) of collar  140 . Flanges  146  are slid into groove  148  before the collars are slid onto the splines of hub  144  and splined section  120 . Flanges  146  and groove  148  allow second collar  140  rotate independently around collar  134 . While the figure illustrates the use of two flanges  146 , according to other exemplary embodiments, more or fewer flanges could be used as long as second collar  140  is both coupled to and rotatable relative to collar  134 . 
     Referring to  FIG. 7 , which illustrates a “neutral” position of the transmission, assembly  122  is positioned relative to shaft  112  so that the splines of collar  134  are engaged solely with the splines  145  of hub  144  and external teeth  137  are not engaged with internal teeth  127  of sun gear  128 . In this position, teeth  141  of collar  140  are engaged solely with the splines of section  120 , and teeth  139  are not engaged with internal teeth  131  of carrier  130 . In this position, collar  134  rotates while collar  140  is idle, and no power is transmitted from gear  114  through planetary set  118  to shaft  112 , or directly from gear  114  to shaft  112 . 
     Referring to  FIG. 8 , which illustrates a “high speed” position of the transmission, assembly  122  is positioned so that there is a direct drive (i.e. no speed difference between) from hub  144  to shaft  112 . In particular, assembly  122  is slid to a position where the internal teeth  135  of collar  134  engage both the outer splines  145  of hub  144  and section  120  to fix gear  114  relative to shaft  112 . Furthermore, the external teeth of collars  134  and  140  are disengaged from the internal teeth of sun gear  128  and carrier  130 , respectively, thus removing the planetary gear set from the flow of power. 
     Referring to  FIG. 9 , which illustrates a “low speed” position of the transmission, assembly  122  is positioned relative to shaft  112  so that the teeth  135  of collar  134  are engaged solely with the outer splines  145  of hub  144  and external teeth  137  are engaged with internal teeth  127  of sun gear  128 . In this position, teeth  141  of collar  140  are engaged solely with the splines of section  120 , and external teeth  139  of collar  140  are engaged with internal teeth  131  of carrier  130 . In this position, collars  134  and  140  rotate relative to each other, and transmit power from gear  114  through planetary set  118  to shaft  112 . This provides a torque multiplication of approximately 2.74 between gear  114  and shaft  112 , and a speed reduction ratio of approximately 2.74:1. 
     Referring to the FIGURES as a whole, when power is provided by a power output source, such as electric motor  105  to rotate bevel gear  116 , bevel gear  114  rotates about (and independently of) shaft  112 . As bevel gear  114  rotates, planetary gear set  118  is engaged (for low speed operation) or disengaged (for high speed operation) by movement of the collar assembly  122  between a first position and a second position. If collar assembly  122  is in the first position (shown also in  FIG. 9 ) to define a first speed of axle shafts  102  (e.g., a low speed or rate of rotation of axle shafts  102  for each rotation of bevel gear  116 ), bevel gear  114  and hub  144  couple to and engage planetary gear set  118  and splined section  120  via collar assembly  122  to rotate shaft  112  and in turn gear  110 , gear  106 , and axle shafts  102 . If collar assembly  122  is in a second position (shown also in  FIG. 8 ) to define a second speed of axle shafts  102  (e.g., a higher speed or rate of rotation of axle shafts  102  for each rotation of bevel gear  116 ), bevel gear  114  couples to and engages splined section  120  via hub  144  and collar assembly  122  without engaging (i.e. bypassing) planetary gear set  118  to rotate shaft  112  and in turn gear  110 , gear  106 , and axle shafts  102 , while planetary gear set  118  remains idle. 
     Referring again to  FIGS. 5-9 , operation of transmission  104  is discussed more particularly. According to the illustrated embodiments, planetary gear set  118  includes a sun gear  128 , planetary gears  136 , a rotatable carrier  130 , and a ring gear  132  arranged to define an annulus. When collar assembly  122  is shifted (e.g. slid, etc.) into the first position (shown as a “low speed” position in  FIG. 9 ), collar  134  is rotated as internal teeth  135  engage the outer splines  145  of hub  144  (see  FIGS. 6-8 ). External teeth  137  of collar  134  engage and rotate sun gear  128 , the sun gear  128  having a set of external gear teeth  129 . Gear teeth  129  of sun gear  128  turns planetary gears  136 , which travel around ring gear  132  and turn carrier  130  at a rate of speed slower than the rotation rate of bevel gear  116 . Teeth  131  on an internal surface of carrier  130  engage external teeth  139  on second collar  140  to rotate the second collar  140 , which is configured to independently rotate about collar  134  while engaging and rotating splined section  120  via teeth  141 . Splined section  120  engages splines  142  of shaft  112  thus rotating shaft  112 , gear  110 , gear  106  and differential  108  and axle shafts  102 . 
     According to one exemplary embodiment, the total reduction ratio between the electric motor that drives bevel gear  116  and differential  108  when transmission  104  is in a first or “low speed” position may be within a range of approximately 50:1 and 75:1, and more particularly, approximately 61:1. 
     When collar assembly  122  is slid into the second position (shown as a “high speed” position in  FIG. 8 ), the external teeth  137  of collar  134  are shifted out of engagement with sun gear  128  (i.e. sun gear  128  is idle), but the internal teeth  135  of collar  134  remains engaged with the outer splines  145  of hub  144  and also now engage and rotate splined section  120 . Splined section  120  engages splines  142  of shaft  112  thus rotating shaft  112 , gear  110 , gear  106  and differential  108  and axle shafts  102  at a rate of speed greater than when collar assembly  122  is in the first position, while bypassing the planetary gear set  118 . 
     According to one exemplary embodiment, the total reduction ratio between the electric motor that drives bevel gear  116  and differential  108  when transmission  104  is in a second or “high speed” position may be within a range of approximately 15:1 and 30:1, and more particularly, approximately 22:1. 
     Referring further to  FIGS. 7-9 , transmission  104  is shown in neutral, high, and low positions, respectively. Bevel gear  114  is coupled (shown for example by bolts, etc.) to hub  144  having a splined outer surface  145 , which transfers power from the bevel gear  116  to collar  134 . As bevel gear  114  rotates about shaft  112 , splined hub  144  also rotates about and independently from shaft  112 , thus engaging internal teeth  135  of internal collar  134  and rotating collar  134 . Collar assembly  122  is shifted or slid into one of a neutral, first (or low speed), or second (or high speed) position by a shift mechanism  150 . Collar assembly  122  may be moved between any of the positions by a single shift operation. According to various exemplary embodiments, shift mechanism  150  may be operated manually by a vehicle operator or automatically according to predetermined conditions (e.g. a software routine, etc.). Differential  108  may be locked to remove torque biasing and lateral movement by a differential lock  152 . 
     When collar assembly  122  and transmission  104  are in the neutral position of  FIG. 7  (shown as a “mid” or “neutral” position), the external teeth  137  of collar  134  do not engage sun gear  128  and the internal teeth  135  of collar  134  do not engage splined section  120 . Therefore, planetary gear set  118  remains stationary. Further, because collar  134  engages only the outer splined portion  145  of hub  144  (via teeth  135 ) and the because the second collar  140  engages only the splined section  120  (via teeth  139 ) and because first collar  134  and second collar  140  are rotatable independently of one another, there is no engagement point with the shaft  112 . Thus, none of splined section  120 , shaft  112 , gear  110 , gear  106 , differential  108 , or axle shafts  102  are driven by the bevel gear  116 . 
     When collar assembly  122  and transmission  104  are shifted to (or are in) the second or high speed position of  FIG. 8  (shown as shifted toward end  126  of shaft  112 ), external teeth  137  of collar  134  do not engage the internal teeth  127  of sun gear  128 , but internal teeth  135  remain in engagement with the outer splines  145  of hub  144  and now also engage splined section  120 . Splined section  120  engages splines  142  of shaft  112  and thus power is provided in a high speed arrangement from bevel gear  116 , to bevel gear  114 , to splined hub  144 , to collar  134 , to splined section  120 , to shaft  112 , to gear  110 , to gear  106 , to differential  108  and to axle shafts  102  at a higher speed than when in the first (or low speed) position, while the planetary gear set  118  is bypassed and stationary (to avoid “parasitic” power losses, etc.). 
     When collar assembly  122  and transmission  104  are shifted to (or are in) the first (or low speed) position of  FIG. 9  (shown as shifted away from end  126  of shaft  112 ), the planetary gear set  118  is engaged. Collar  134  does not directly engage splined section  120 , but internal teeth  135  engaged the outer splines  145  of hub  144  and external teeth  137  engage internal teeth  127  of sun gear  128  to rotate the sun gear. As described above, external gear teeth  129  of sun gear  128  engages planetary gears  134  to rotate carrier  130  relative to ring gear  132 . Internal teeth  131  on carrier  130  engages the external teeth  139  on second collar  140  to rotate second collar  140  about (and independently from) collar  134 , whereby teeth  141  on second collar  140  engage and rotate splined section  120 . Splined section  120  engages splines  142  of shaft  112  and thus power is provided to shaft  112 , gear  110 , gear  106 , and differential  108  at a lower speed than when in the second or high position. Accordingly, in the first (or low speed) position, power is provided in a low speed arrangement from bevel gear  116 , to bevel gear  114 , to splined hub  144 , to collar  134 , to sun gear  128 , to planetary gears  136 , to carrier  130 , to second collar  140 , to splined section  120 , to shaft  112 , to gear  110 , to gear  106 , to differential  108  and to axle shafts  102  at a lower speed than when in the second (or high speed) position, due to engagement with the planetary gear set  118 . 
     According to any exemplary embodiment, the components of the vehicle transmission as shown and described are arranged in a compact and efficient manner so that the number of rotating components is minimized, and the components “fit” within the space or volume provided by traditional axle housings and may be used with various types of vehicle suspensions. The vehicle transmission as shown and described is intended to provide flexibility in adapting the transmission to various vehicles, and is adaptable for use in retrofit applications with vehicles having conventional drive systems. 
     Although the present invention has been described with reference to example embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. Because the technology of the present invention is relatively complex, not all changes in the technology are foreseeable. The present invention described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements.