Abstract:
A drive system for a lightweight electric vehicle comprises a drive train for mounting between an electric motor drive shaft and the vehicle&#39;s transaxle to provide a forward driving mode and coasting mode. Preferably, the system is shiftable to provide dynamic braking via the motor and differential and to provide a reverse mode. A motor drive shaft coupler couples with the motor drive shaft and a transaxle coupler couples with the transaxle. In the driving mode, the transaxle coupler rotates with the drive shaft coupler and in the coasting mode rotates relative to the drive shaft coupler in the same direction. A ratchet mechanism provides for the driving and coasting modes. A shifter is movable between an uncoupled position which allows the ratchet mechanism to operate in the coasting mode and a coupled position which overrides the coasting mode operation. The shifter provides for the dynamic braking and reverse mode.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates generally a vehicle drive system. More particularly, the invention relates to a drive system for a lightweight vehicle which is electrically powered. Specifically, the invention relates to a drive assembly in which the motor and transaxle may be disconnected to allow for coasting and also connectable to produce dynamic braking via the motor and transaxle while additionally providing a reverse mode for the vehicle. 
         [0003]    2. Background Information 
         [0004]    Various types of electrically powered lightweight vehicles are known in the art such as an electric tricycle. While these vehicles are light in comparison to full size automobiles and the like, they nonetheless usually weigh over 100 lbs. and are typically powered by two full sized car batteries. At speeds below 20 mph, these vehicles have very little air flow friction and likewise relatively minimal rolling friction due to the typical narrow bicycle tires and ball bearing wheels used thereon. Due to this minimal frictional drag, the kinetic energy of these lightweight vehicles when accelerated to a typical full speed of 15-18 mph would allow them to glide for several thousand feet depending on the road conditions. However, to take advantage of this kinetic energy, the electric motor must be operated to at least match the transaxle speed to prevent additional drag created by the highly geared down motor. 
         [0005]    U.S. Pat. No. 6,158,542 granted to Nolet utilizes two ratchet mechanisms respectively on each rear wheel of a motorized tricycle to allow it to coast. The ratchet mechanisms are engaged in the drive direction but at soon as the operator releases the throttle, the motor and transaxle drive system completely stop while the wheels continue to spin. One drawback of this invention is that it requires two ratchet mechanisms. In addition, when the operator stops the throttle, the axles and differential gears also stop, thus wasting rotational kinetic energy that might be used to help drive the wheels and coast even further. In addition, this system offers no dynamic braking effect from the motor and drive system because they are effectively disconnected in the coasting mode. These vehicles can obviously build up substantial speed on steep hills and so this becomes a significant safety issue. In addition, the Nolet tricycle is incapable of providing a reverse drive due to the ratchet mechanisms which would only spin without driving the wheels if the motor were reversed. The present invention addresses these and other problems in the art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention provides an apparatus comprising a drive train having a driving mode and a coasting mode; a motor drive shaft coupler on the drive train adapted to couple with a drive shaft of a motor; and a transaxle coupler on the drive train adapted to couple with a transaxle and rotationally engaging the drive shaft coupler so that the transaxle coupler is rotatable in a first direction with the drive shaft coupler in the driving mode and rotatable relative to the drive shaft coupler in the first direction in the coasting mode. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of the tricycle with which the drive assembly of the present invention is used. 
           [0008]      FIG. 2  is similar to  FIG. 1  and shows the box removed from the frame of the tricycle to show the drive assembly mounted on the electric motor and transaxle housing of the rear axle assembly. 
           [0009]      FIG. 3  is an enlarged perspective view of the axle assembly showing the drive mechanism mounted on the electric motor and the transaxle housing. 
           [0010]      FIG. 4  is an exploded perspective view of the components shown in  FIG. 3  and also showing the differential gears and pinion. 
           [0011]      FIG. 5  is an enlarged exploded perspective view of the components of the drive assembly. 
           [0012]      FIG. 6  is an enlarged exploded perspective view of the ratchet assembly and the pinion coupler. 
           [0013]      FIG. 7  is an enlarged sectional view of the drive assembly in the uncoupled position. 
           [0014]      FIG. 8  is a sectional view taken on line  8 - 8  of  FIG. 7 . 
           [0015]      FIG. 9  is a sectional view taken on line  9 - 9  of  FIG. 7  and shows the ratchet assembly in the driving mode. 
           [0016]      FIG. 10  is a sectional view taken on line  10 - 10  of  FIG. 7  and shows the ratchet assembly in the ratcheting mode. 
           [0017]      FIG. 11  is a sectional view similar to  FIG. 7  and shows the drive assembly in the coupled position. 
       
    
    
       [0018]    Similar numbers refer to similar parts throughout the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The drive assembly of the present invention is shown generally at  10  in  FIGS. 2-4  and is used with a lightweight motorized tricycle  8  shown in  FIGS. 1 and 2 . Tricycle  8  represents a typical lightweight vehicle and has a frame with a front wheel which is controlled by handlebars, a seat mounted on the frame and a pair of rear wheels mounted on the frame behind the seat. A box  12  is mounted intermediate and generally above the rear wheels as shown in  FIG. 1 . In  FIG. 2 , box  12  is removed to show the axle assembly mounted on the frame between the rear wheels. As shown in  FIGS. 2 and 3 , a transaxle housing  14  is mounted on the frame of tricycle  8  with first and second axles  16  and  18  extending outwardly therefrom in opposite directions and rotatably mounted thereon about a first axis A. The two rear wheels of tricycle  8  are mounted respectively on axles  16  and  18  and driven thereby. Housing  14  includes a differential enclosure  20  on which drive assembly  10  is mounted. An electric motor  22  is connected to drive assembly  10  with assembly  10  between motor  22  and enclosure  20 . Motor  22  includes a housing in which a drive shaft  24  ( FIG. 7 ) is rotatably mounted about a second axis B which is parallel to axis A. Motor  22  is powered by an onboard battery (not shown). 
         [0020]    Transaxle housing  14  includes first and second segments which are shown separated from one another in  FIG. 4  and attached to another in  FIG. 3  by a plurality of bolts. The first segment is an elongated portion  26  having a flange  28  which extends radially outwardly therefrom and forms part of differential enclosure  20 . A through bore  30  is formed in portion  26  and flange  28  for receiving therein first axle  16 . The second section of housing  14  includes a cup-shaped member  32  defining an interior chamber  34  in which is received a set of differential gears  36  and a pinion  38  which rotatably and drivingly engages gears  36 . Another through bore (not shown) similar to bore  30  is formed in the second section of housing  14  and communicates with interior chamber  34  for receiving therein second axle  18 . Differential gears  36  drive axles  16  and  18  and allow them to turn at different rates as is well known in the art. 
         [0021]    An annular mounting flange  40  is rigidly connected to radial flange  28  and has a central bore  42  formed therethrough which communicates with interior chamber  34  when housing  14  is assembled. A pair of mounting holes  44  is formed in flange  40  for receiving therein fasteners such as bolts (not shown) for mounting thereto drive assembly  10  and motor  22 . Flange  40  has a flat circular mounting surface  46  which mates with a flat circular mounting surface  48  of drive assembly  10 . Likewise, assembly  10  has a second mounting surface  50  which mates with mounting surface  52  of the housing of motor  22 . Drive pinion  38  has a coupling end  54  which is disposed in central bore  42  of flange  40  when assembled so that pinion  38  is rotatably mounted within flange  40  about axis B ( FIG. 3 ). 
         [0022]    In accordance with the invention and with reference to  FIGS. 4 and 5 , drive assembly  10  is described in further detail. 
         [0023]    Assembly  10  includes a housing  56  including three main components. More particularly, housing  56  includes a generally cylindrical main member  58 , an annular end cap  60  ( FIG. 5 ) which is generally circular, and a top cover  62  each of which is connected to the other when assembled. Main member  58  includes a generally cylindrical side wall  64  and an end wall  66  or flange which extends radially inwardly therefrom and includes mounting surface  50  at a first end of member  58 . Mounting holes  76  are formed through end wall  66 . Interior chamber  68  is formed within side wall  64  and end wall  66 . Side wall  64  and end wall  66  are truncated by a flat upper surface  70  so that a portion of interior chamber  68  opens upwardly to communicate with surface  70 . A slot  71  is formed in end wall  66  which extends downwardly from upper surface  70  and inwardly from mounting surface  50  and communicates with interior chamber  68 . Side wall  64  at an end opposite mounting surface  50  has a circular inner surface  72  and is stepped inwardly to form an annular stop  74  which extends radially inwardly from surface  72 . 
         [0024]    As shown in  FIG. 5 , end cap  60  includes mounting surface  48  and has an opposed flat and substantially circular surface  78 . End cap  60  further includes a cylindrical outer surface  80  and cylindrical inner surface  82  each of which extends between surfaces  48  and  78 . A pair of mounting holes  84  extends through end cap  60  from surface  48  to surface  78  and align with holes  76 . When assembled, end cap  60  slides into a portion of interior chamber  68  of main member  58  so that outer surface  80  is flush against inner surface  72  and an outer portion of surface  78  abuts stop  74 . End cap  60  has a flat upper surface  86  which is coplanar with upper surface  70  when housing  56  is assembled. 
         [0025]    Top cover  62  has an arched upper surface and a flat lower surface  88  which abuts upper surfaces  70  and  86  of member  58  and cap  60  when assembled. Top cover  62  is typically connected to member  58  and end cap  60  by screws or bolts extending into holes formed in top surfaces  70  and  86 . Top cover  62  defines an interior chamber (not shown) and includes a cable receiving hole  90  which communicates with side interior chamber for receiving therethrough an actuating cable  92 . The lower end of cable  92  is connected to a mounting clevis  94  which has a pair of spaced arms with holes formed therein for receiving a cylindrical pivot  96 . 
         [0026]    A shifter arm  98  includes first and second legs  100  and  102  which are connected and extend generally perpendicularly to one another. A hole  104  is formed in first leg  100  for receiving therethrough pivot  96  when first leg  100  is disposed between the arms of mounting clevis  94  so that leg  100  is pivotally connected to mounting clevis  94 . Another hole  106  is formed in shifter arm  98  adjacent the intersection of first and second legs  100  and  102  for receiving therethrough another pivot  108  which is mountable internally on top cover  62  so that shifter arm  98  is pivotally mounted on top cover  62  via pivot  108 . Second leg  102  includes first and second spaced fingers  110  and  112  defining there between a recess or space  114 . 
         [0027]    In accordance with the invention, drive assembly  10  includes a drive train  116  indicated generally by the bracket in  FIG. 5 . Drive train  116  has four major components, namely a motor drive shaft coupler  118 , a shifter  120 , a ratchet mechanism  122  and a differential or pinion coupler  124 . Drive train  116  is rotatable about axis B and is thus coaxial with drive shaft  24  ( FIG. 7 ) and pinion  38  ( FIG. 4 ). Drive train  116  has a driving mode ( FIG. 9 ) and a coasting mode ( FIG. 10 ) which are discussed further below. Drive train  116  is disposed within housing  56  but is not in contact therewith when mounted on tricycle  8 . In part, housing  58  serves as a spacer or extender which is rigidly mounted on motor  22  and flange  40  in order to provide sufficient space for drive train  116  to extend between motor  22  and pinion  38 . Top cover  62  of housing  56  also provides a support for the movable attachment of shifter arm  98  and cable  92 . 
         [0028]    Motor coupler  118  serves as an input of the drive train which is coupled with or rotationally engaged with drive shaft  24  ( FIG. 7 ) of motor  22 . Pinion coupler  124  serves as an output of drive train  116  which couples with and rotationally engages coupling end  54  of pinion  38  ( FIG. 4 ). Thus, drive shaft  24  of motor  22  rotationally engages motor coupler  118  to provide rotational engagement with pinion coupler  124  via shifter  120  and/or ratchet mechanism  122  (in the driving mode) to provide rotational output at coupler  124 . It is noted, however, that pinion coupler  124  may serve as an input and motor coupler  118  may serve as an output when axles  16  and  18  are rotating faster than a rotational input of drive shaft  24  so that the driving force is applied in a reverse direction, as will be discussed further below. 
         [0029]    Motor coupler  118  includes an elongated cylindrical shaft  126  with splines or keys  128  extending outwardly therefrom. A hole  130  is formed in shaft  126  for receiving therein a spring-biased detent  132 . An enlarged coupling head  134  is connected to shaft  126  and defines a cavity  136  for receiving therein an end of drive shaft  124  of motor  22 . A threaded hole  138  is formed in head  134  for receiving therein a screw or threaded pin  140  for mounting drive shaft  24  to coupler  118 . 
         [0030]    Shifter  120  includes a tubular structure having a cylindrical side wall  142  with splines or keys  144  extending radially outwardly therefrom. Four engaging projections  146  extend axially outwardly from an end of side wall  142  and define there between respective cutouts or recesses  148 . A cup-shaped collar  150  extends radially outwardly from side wall  142  at an end opposite projections  146  and defines therein a cavity  151 . An annular flange  152  extends radially outwardly from collar  150  and is received in space  114  between fingers  110  and  112  of shifter arm  98 , as shown in  FIG. 7 . Internal splines are formed on the surface of side wall  142  or key ways  154  are formed therein for slidably receiving therein keys  128 . Shaft  126  is thus slidably received in the axial direction within the interior chamber defined by side wall  142 . A portion of coupling head  134  is receivable within cavity  151  as shown in  FIG. 7 . As also shown in  FIG. 7 , first and second axially spaced detent notches  156  and  158  are formed in side wall  142  extending outwardly from the inner surface thereof. The tip of detent  132  is received in first notch  156  when shifter  120  is in the uncoupled position shown in  FIG. 7  and received in second notch  158  when the shifter is in the coupled position shown in  FIG. 11 . 
         [0031]    In accordance with the invention and with reference to  FIGS. 5-7 , ratchet mechanism  122  is described in further detail. Ratchet mechanism  122  includes a pair of ratchet members in the form of a hub  160  and an outer sleeve  162  which received therein hub  160 . A bearing  164  is mounted on each of hub  160  and sleeve  162  whereby hub  160  and sleeve  162  are rotatable about axis B relative to one another. Ratchet mechanism  122  further includes a pair of pawls  166 . Hub  160  includes several generally cylindrical sections including a bearing support  168  having an outer surface on which the inner surface of bearing  164  is mounted. Hub  160  steps outwardly from support  168  to a pawl-mounting ring  170 . A pair of pawl-receiving recesses  176  are formed in ring  170  extending inwardly from the outer surface thereof for receiving pawls  166  therein. A concave arcuate surface  178  bounds each recess  176 . Hub  160  steps outwardly from ring  170  to a bearing support  172  on which a bearing  174  is mounted. Hub  160  has an internal splined section comprising splines or keys  180  alternating with key ways  182  which receive therein splines or keys  144  of shifter  120  whereby shifter  120  rotationally engages and is axially slidable relative to ratchet mechanism  122 . 
         [0032]    Outer sleeve  162  includes a generally cylindrical side wall having a smaller diameter section  190  which steps outwardly to a larger diameter section  192 . Section  190  includes an externally threaded portion  194  on a cylindrical bearing support  196  within which bearing  164  is received. An annular flange  198  extends radially inwardly from support  196  and abuts bearing  164 . The sidewall steps inwardly from flange  196  to a ratchet wall  200  having a series of internal one-way ratchet teeth  202  extending radially inwardly therefrom. Each tooth  202  has an engaging or drive surface  204  which is drivingly engagable with drive surfaces  188  of pawls  166  when hub  160  and outer sleeve  162  are rotated in a driving direction. Sliding surface  186  of pawls  166  are slidable along the outer surfaces of teeth  202  when hub  160  and sleeve  162  are rotated in an opposite ratcheting direction. Sidewall section  192  steps outwardly to form a bearing recess  206  in which bearing  174  is received to rotatably support sleeve  162  on hub  160  along with bearing  164 . 
         [0033]    Coupler  124  is a generally tubular member having a stepped sidewall including a first sidewall section  208 , a second sidewall section  210  stepped outwardly from section  208  and a third sidewall section  212  stepped outwardly from section  210 . A coupling cavity  214  ( FIG. 7 ) is formed in first section  208  for receiving therein coupling end  54  of pinion  38  ( FIG. 4 ). A hole  216  is formed in section  214  for receiving the pin on coupling end  54  to connect pinion  38  to coupler  124 . Second section  210  defines a larger bore cavity  218  for receiving engaging projections  146  therein. A hole  220  is formed in second section  210  and communicates with cavity  218  for receiving therethrough a drive pin  222  which is received in a pair of opposed recesses  148  between respective pairs of adjacent projections  146  when shifter  120  is in the coupled position shown in  FIG. 11 . Third sidewall section  212  has an internally threaded portion  224  which threadably engages threaded portion  194  of outer sleeve  162  to join coupler  124  and sleeve  162 . 
         [0034]    The operation of drive assembly  10  is now described with reference to FIGS.  7  and  9 - 11 . In the uncoupled position shown in  FIG. 7 , motor  22  is operated to rotate drive shaft  24  which in turn rotates motor coupler  118 , shifter  120  and hub  160  via the various spline engagements there between. This rotational motion is shown by arrow C in  FIG. 9 , which illustrates the driving mode. This driving torque is translated from hub  160  to outer sleeve  162  via the engagement of pawls  166  with ratchet teeth  202  so that outer sleeve  162  rotates as shown at arrow D in  FIG. 9 . This rotational torque is translated to pinion coupler  124  and thereby pinion  38  to drive differential gears  36  in a standard manner to drive axles  16  and  18  and the corresponding rear wheels of tricycle  8 . 
         [0035]    The coasting mode, on the other hand, is illustrated in  FIG. 10 . This occurs when the wheel speed of tricycle  8  and rotation of its rear wheels is sufficiently high to cause pinion  38 , coupler  124  and outer sleeve  162  to rotate faster than the rotational speed of drive shaft  24  of motor  22 . This causes ratchet mechanism  122  to enter a ratcheting or skipping mode in which outer sleeve  162  continues to rotate in the same direction as indicated at arrow E but at a speed which is faster than any rotation of hub  160 . Thus, pawls  166  slide along the inner surfaces of teeth  202  to allow for the coasting of tricycle  8  without the drag which would otherwise be created by the force necessary to rotate drive shaft  24  of motor  22 . This allows for the efficient coasting of tricycle  8  while motor  22  may be stopped altogether to preserve the charge on the battery which powers motor  22 . 
         [0036]    When desired, the operator of tricycle  8  may shift drive assembly  10  to the coupled position shown in  FIG. 11 . Typically, a manually operable shift lever or the like is attached to cable  92  which the operator can manipulate in order to apply a force to move it as indicated at arrow F in  FIG. 11 , causing shifter arm  98  to pivot about pivots  104  and  108  as shown respectively at arrows G and H so that first leg  110  slides shifter  120  axially as indicated at arrow J relative to the other members of drive train  116  so that drive pin  222  is received in a pair of recesses  148  between adjacent pairs of engaging projections  146 . During this movement, detent notch  156  moves out of engagement with detent  132  and detent notch  158  moves into engagement with detent  132 . 
         [0037]    In the coupled position, engaging projections  146  drivingly engage drive pin  222  to directly drive pinion coupler  124  and to eliminate the ability of outer sleeve  122  to rotate relative to hub  160  so that the ratcheting or skipping mode discusses with reference to  FIG. 10  is no longer available. This allows the transaxle and motor to provide dynamic braking to help slow tricycle  8  due to the force applied by motor  22  to the highly geared transaxle, which is commonly geared at a ratio of about 20:1. More particularly and as previously noted, pinion coupler  124  serves as the input of drive train  116  so that rotational force from the rear wheels and axles of tricycle  8  rotates coupler  124  to drivingly rotate shifter  120  via engagement of pin  222  and projection  146 . In turn, shifter  120  drivingly rotates motor coupler  118  and drive shaft  24  against any force applied by motor  22  via shaft  24 . In addition, the coupled mode allows for the reversal of the polarity of the DC motor  22  so that it may be run in reverse in order to drive tricycle  8  rearwardly, which is not possible in the uncoupled position due to the ratcheting mode of ratchet mechanism  122 . In this reverse mode, drive shaft  24  rotates in the reverse direction to respectively drive motor coupler  118 , shifter  120  and pinion coupler  124  via pin  222  in the direction opposite that shown by arrows C and D in  FIG. 9 . 
         [0038]    Drive train  116  thus provides for a forward driving mode and coasting mode, the latter of which may be overridden by the coupled position of shifter  120  to provide for dynamic braking as well as a reverse mode. 
         [0039]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
         [0040]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.