Patent Publication Number: US-8540041-B2

Title: Driving system for electric vehicle

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to vehicle driving systems and more particularly, to a driving system for electric vehicle, which uses a clutch switching unit to control a motor rotor-driven bushing in rotating a wheel hub via a direct-drive active clutch or via a set of planet gears and a reducing clutch. At the initial state after startup of the motor, the direct-drive active clutch runs idle, enabling the wheel hub to provide a low-speed high-torque output, saving power consumption. When the vehicle speed reaches a predetermined level, a control circuit drives a clutch motor to move the clutch switching unit in releasing the reducing clutch to idle the planet gears, enabling the direct-drive active clutch to be switched on so that the rotor of the motor can rotate the wheel hub directly to accelerate the vehicle speed. 
     2. Description of the Related Art 
       FIG. 11  illustrates a conventional driving system used in an electric vehicle. According to this design, the driving system comprises a motor  9  and a transmission mechanism  91 . The transmission mechanism  91  comprises a driving wheel set  911  rotatable by the motor  9 , a transmission wheel set  912 , a transmission belt  913  coupled between the driving wheel set  911  and the transmission wheel set  912  for enabling the transmission wheel set  912  to be rotated by the driving wheel set  911 , an output shaft  914  that is rotatable by the driven wheel set  911  to rotate a reducing mechanism  915  and a wheel hub  916 , and a clutch  92 . 
     The transmission wheel set  912  comprises a main transmission wheel  9121  and a sliding transmission wheel  9122 . The clutch  92  controls displacement of the sliding transmission wheel  9122  subject to a centrifugal force to change the transmission radius of the transmission belt  913 , achieving transmission and speed reducing. 
     According to the aforesaid design, the motor  9  drives the driving wheel set  911  to rotate the transmission wheel set  912  by means of the transmission belt  913 , enabling the output torque to be transferred to the reducing mechanism  915  and then the wheel hub  916 . By means of friction, the transmission belt  913  transfers the rotary driving force from the driving wheel set  911  to the transmission wheel set  912 . This friction transmission consumes much electric power. Further, after transmission of the rotary driving power from the driving wheel set  911  to the transmission wheel set  912  through any transmission measure, the reducing mechanism  915  reduces the output speed. Thus, the motor  9  cannot perform efficiently and consumes much electric power during operation. Thus, an electric vehicle using this design of driving system is not practical for long distance application. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a driving system for electric vehicle, which enables the vehicle motor to rotate the wheel hub directly at the initial stage when it is started up, and to rotate the wheel hub through a set of planet gears and a reducing clutch after the vehicle speed reaches a predetermined level, thereby enhancing the performance and saving power consumption. 
     To achieve this and other objects of the invention, a driving system uses a speed sensor for sensing the vehicle speed for controlling switching between two clutches. A clutch switching unit is used to control a vehicle motor rotor-driven bushing to rotate the wheel hub via a direct-drive active clutch or via a set of planet gears and a reducing clutch. At the initial state after startup of the motor, the direct-drive active clutch runs idle, enabling the wheel but to provide a low-speed high-torque output, saving power consumption. When the vehicle speed reaches a predetermined level, the speed sensor gives a signal to a control circuit to drive a clutch motor, causing the clutch motor to drive the clutch switching unit in releasing the reducing clutch to idle the planet gears, enabling the direct-drive active clutch to be switched on so that the rotor of the motor can rotate the wheel hub directly to accelerate the vehicle speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a driving system for electric vehicle in accordance with the present invention. 
         FIG. 2  is another exploded view of the present invention, illustrating the component parts of the driving system partially assembled. 
         FIG. 3  is an elevational assembly view of the driving system for electric vehicle in accordance with the present invention. 
         FIG. 4  is a sectional assembly view of the driving system for electric vehicle in accordance with the present invention. 
         FIG. 5  is a schematic sectional view of the driving system for electric vehicle in accordance with the present invention, illustrating the reducing clutch and the planet gears rotated with the rotor of the vehicle motor and the wheel hub. 
         FIG. 6  is a schematic sectional view of the driving system for electric vehicle in accordance with the present invention, illustrating the first clutch presser plate compressed by the associating spring members and the direct-drive active clutch engaged with the wheel hub for direct rotation with the rotor of the vehicle motor. 
         FIG. 7  is a schematic sectional view of the driving system for electric vehicle in accordance with the present invention, illustrating the axial drive gear rotated by the clutch motor. 
         FIG. 8  is an applied view of the present invention, illustrating the driving system installed in an electric motorcycle. 
         FIG. 9  corresponds to  FIG. 8  when viewed from another angle. 
         FIG. 10  is a sectional elevational view of the driving system for electric vehicle in accordance with the present invention. 
         FIG. 11  is a sectional view of a driving system for electric vehicle according to the prior art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1˜4  and  FIG. 10 , a driving system in accordance with the present invention is shown for use in an electric vehicle for rotating the wheels of the electric vehicle, comprising a wheel hub  1 , a hubcap  11 , a vehicle motor  2 , a direct-drive active clutch  3  mounted in the wheel hub  1 , a first clutch presser plate  33 , a reducing clutch  4  mounted on the outer side of the hubcap  11 , a switching push-pull plate  43  set between the reducing clutch  4  and the hubcap  11 , a set of planet gears  46 , a bushing  23  mounted on an axle  221  of a stator  22  of the vehicle motor  2  to support the aforesaid components and a clutch switching unit. The vehicle motor  2  further comprises a housing  25 , a rotor  21  accommodated in the housing  25  and adapted for rotating the wheel hub  1 . At the initial stage after the vehicle motor  2  is started up, the direct-drive active clutch  3  is not forced by associating spring members  34  and runs idle, and the reducing clutch  4  is forced by respective spring members  751  to transfer the rotary driving force to the planet gear set  46  so that the wheel hub  1  is in a low-speed high-torque driving status. When the revolving speed of the wheel hub  1  reaches a predetermined value, a speed sensor  56  senses the speed and gives a signal to a control circuit  55 , causing the control circuit  55  to turn on a clutch motor  8  in driving the clutch switching unit to pull apart the reducing clutch  4 , and at the same time, the direct-drive active clutch  3  in the wheel hub  1  is forced by the associating spring members  34  to let the wheel hub  1  be directly rotated by the rotor  21  of the vehicle motor  2  at a high speed. 
     The wheel hub  1  defines therein an accommodation space. The vehicle motor  2  is accommodated in the wheel hub  1 . The bushing  23  is fixedly connected with the rotor  21  of the vehicle motor  2 , having a pair of axle bearings mounted therein. The axle  221  of the stator  22  of the vehicle motor  2  is inserted through the axle bearings in the bushing  23 . Thus, the rotor  21  of the vehicle motor  2  and the bushing  23  are pivotally supported on the axle  221  of the stator  22 . The wheel hub  1  and the hubcap  11  are respectively mounted on the bushing  23  by a respective axle bearing  16 , and rotatable relative to each other. Further, a driving wheel  24  is fixedly mounted on the bushing  23  for synchronous rotation, having a plurality of transverse grooves  241  spaced around the periphery. The direct-drive active clutch  3  comprises a clutch drive plate  31 , a clutch driven plate  32 , the aforesaid first clutch presser plate  33  and associating spring members  34 . The clutch drive plate  31  has a plurality of radially extending peripheral teeth  311  meshed with an internal toothed engagement portion  14  of the wheel hub  1 . The clutch driven plate  32  is set between the clutch drive plate  31  and the first clutch presser plate  33 , having a plurality of inner teeth  321  respectively engaged into the transverse grooves  241  of the driving wheel  24 . The first clutch presser plate  33  has a plurality of radially extending peripheral teeth  331  meshed with the internal toothed engagement portion  14  of the wheel hub  1 . The spring members  34  are equiangularly mounted in the wheel hub  1  to impart a pressure to the first clutch presser plate  33  toward the clutch driven plate  32  and the clutch drive plate  31 . The hubcap  11  is covered on the wheel hub  1  to keep the direct-drive active clutch  3  inside the wheel hub  1 , having an annular flange  13  protruded from one side thereof opposite to the wheel hub  1 . The annular flange  13  has a plurality of transverse grooves  131  equiangularly spaced around the periphery for the mounting of the aforesaid reducing clutch  4  and a push-pull plate  75 . The reducing clutch  4  comprises a clutch drive plate  41 , a clutch driven plate  42 , the foresaid switching push-pull plate  43 , a second clutch presser plate  44 , a planet gear holder  45  and the aforesaid planet gears  46 . The switching push-pull plate  43  has a plurality of inner teeth  431  respectively engaged into the transverse grooves  131  of the annular flange  13  of the wheel hub  1 . The clutch driven plate  42  has a plurality of inner teeth  421  respectively engaged into the transverse grooves  131  of the annular flange  13  of the wheel hub  1 . Thus, the switching push-pull plate  43  and the clutch driven plate  42  can transfer a torque to the hubcap  11  and the wheel hub  1 . The clutch drive plate  41  and the second clutch presser plate  44  each have a plurality of radially extending peripheral teeth  411 ; 441  meshed with a toothed engagement portion  451  of the planet gear holder  45  for synchronous rotation. The planet gears  46  are equiangularly and pivotally mounted on the outside wall of the planet gear holder  45  by a respective axle bearing  462  and a respective pivot pin  461 . The pivot pin  461  is inserted through the associating axle bearing  462  and connected between the planet gear holder  45  and the push-pull plate  75 . The planet gear holder  45  and the push-pull plate  75  are fixedly fastened together. Further, the planet gears  46  are meshed with a pinion  231  that is fixedly connected with the bushing  23  and disposed near the distal (outer) end of the axle  221  of the stator  22  of the vehicle motor  2 . Further, an outer cover  5  is covered on the wheel hub  1  over the hubcap  11  to protect the reducing clutch  4 . The outer cover  5  comprises an external mounting portion  51  affixed to the vehicle frame  54  of an electric vehicle (not shown), and a tooth ring  52  mounted therein. The tooth ring  52  has an internal gear  53  meshed with the planet gears  46 . Subject to the functioning of the planet gears  46 , the output speed of the vehicle motor  2  is reduced, and the output torque of the vehicle motor  2  is increased. Further, the aforesaid clutch switching unit is mounted inside the outer cover  5 , comprising the aforesaid clutch motor  8 , a worm gear set  81 , a constraint member  62 , a sliding guide sleeve  7 , a cylindrical sliding member  72  and a push-pull plate  75 . The sliding guide sleeve  7  is fixedly mounted on the axle  221  of the stator  22  of the vehicle motor  2  and engaged with a toothed end thereof into a grooved positioning portion  57  in the outer cover  5 , having longitudinal grooves  71  equiangularly spaced around the periphery. The cylindrical sliding member  72  is axially slidably mounted on the sliding guide sleeve  7 , having a plurality of longitudinal ribs  73  respectively slidably coupled to the longitudinal grooves  71  of the sliding guide sleeve  7  and an outer thread  74  spirally extending around the periphery thereof and meshed with an inner thread  61  of an axial drive gear  6  that is mounted in the constraint member  62  inside the outer cover  5  to revolve on its own axis. The push-pull plate  75  is mounted on the cylindrical sliding member  72  by an axle bearing  741  and a retainer (not shown). Further, spring members  751  are inserted through equiangularly spaced through holes  452  of the planet gear holder  45  and stopped between the push-pull plate  75  and the second clutch presser plate  44 . When the electric vehicle is started, the cylindrical sliding member  72  is moved toward the hubcap  11  to the extent subject to a predetermined setting, causing the push-pull plate  75  to move the planet gears  46 , the planet gear holder  45  and the spring members  751  in forcing the reducing clutch  4  into engagement with the hubcap  11 . Thus, the wheel hub  1  is in a deceleration driving status. When the rotor  21  of the vehicle motor  2  rotates the bushing  23  as the wheel hub  1  is in the deceleration driving status, the pinion  231  is meshed with the planet gears  46  that are also meshed with the internal gear  53  of the tooth ring  52 . Thus, the planet gears  46  are rotated in one same direction between the tooth ring  52  and the pinion  231 , enabling the wheel hub  1  to provide the desired low-speed high-torque output (see  FIG. 5 ), and therefore the electric vehicle is efficiently started with less power consumption. Under this deceleration driving status, the thrust pins  121  are inserted through the hubcap  11  are forced by the switching push-pull plate  43  to move the first clutch presser plate  33  and the associating spring members  34 , thereby releasing the direct-drive active clutch  3  for idle running. When the revolving speed of the wheel hub  1  (the speed of the electric vehicle) reaches a predetermined level, the speed sensor  56  senses the speed and gives a signal to the control circuit  55 , causing the control circuit  55  to turn on the clutch motor  8  in driving the axial drive gear  6 . When the axial drive gear  6  is rotated, the cylindrical sliding member  72  is forced to move the push-pull plate  75  toward the outer cover  5 , and therefore the reducing clutch  4  is released from the pressure of the associating spring members  751 . At this time, the first clutch presser plate  33  of the direct-drive active clutch  3  is compressed by the associating spring members  34 , allowing the wheel hub  1  to be rotated by the vehicle motor  2  directly, thereby accelerating the speed of the electric vehicle (see  FIGS. 6 and 7 ). 
     When the electric vehicle is started, stopped or shifted to a low-speed mode, the speed sensor  56  senses the speed and gives a signal to the control circuit  55 , causing the control circuit  55  to drive the clutch switching unit in switching on the reducing clutch  4  and the planet gear holder  45  (see  FIGS. 8 and 9 ), and therefore the wheel hub  1  provides a low-speed high-torque output (see  FIG. 5 ). Thus, the electric vehicle can be started efficiently, run over a steep slope, or carry a heavy load. When a cruising or high speed is needed, switch the vehicle motor  2  to drive the wheel hub  1  directly, lowering the torque and increasing the speed with less power consumption. 
     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.