Abstract:
The present invention discloses an electric vehicle chassis applicable to the field of the electric vehicle technology. The object is to provide an electric vehicle with light weight and good driving stability. The electric vehicle chassis according the present invention comprises a frame and a power real axle, wherein the left and right rear wheels connected to the rear axle are driven by left and right motors, respectively, and a pendulum shaft is provided between the real axle and the frame for the swinging of the rear axle. Meanwhile, the rear wheels on both sides of the rear axle can also be directly driven by the respective full gear reduction motors, and the rear axle can be provided with a limiting swinging device thereon. The present invention includes characteristics such as light weight, low center of gravity, impossibility of turning over sideward during full speed steering, flexibility and automatic restoration, and is suitable for sports and recreation.

Description:
TECHNICAL FIELD 
     The present invention relates to an electric vehicle, more especially, to a chassis for electric vehicles. 
     BACKGROUND ART 
     At present, motor vehicles have become necessary transportation means in daily life. Specifically, cars and motorcycles have almost been involved in every aspect of the life of the people nowadays. Today, with the increasing environment-friendly consciousness, as the fuel vehicles (consuming fuel), such as cars and motorcycles, bring about the problem of air pollution, electric vehicles with environment-friendly purpose have emerged. And various electric vehicles can be seen. 
     To reduce the vehicle self-weight and cost, the conventional chassis for electric vehicles, which has a differential and half-axle combination, can not meet current requirements. Consequently, an electric vehicle driven by double motors have been presented. 
     A double motor driving mechanism for electric vehicles disclosed in Chinese Patent No. CN200320127977.7 comprises two driving motors and two driving wheels, wherein said two driving motors are connected to the two driving wheels, respectively. Such driving means, i.e. in which double motors operate to drive individually, leaves out both the conventional rear axle combination having a differential and half-axle and the complicated mechanical driving gears, greatly decreasing the vehicle weight and cost as a whole and reducing the power loss. Also it can totally avoid the disadvantage with the conventional mechanical differential, i.e. the whole vehicle can not move forward as a result of that one wheel can not rotate while another one is wheelspining. However, when the ground is not absolutely flat, only three of the four wheels of a rigid vehicle frame are in contact with the ground. If the front wheel tilts, the steering stability will be affected. In case that a rear wheel is separated away from the ground, the driving force will be reduced. Additionally, both of the above situations seriously affect the safety and stability of vehicle driving. Accordingly, along with using the double motor for driving and reducing the total vehicle weight, it is also necessary to improve the stability and power output characteristics of electric vehicle chassis. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an electric vehicle chassis with light weight and good stability. 
     In order to achieve the above object, the electric vehicle chassis according to the present invention comprises a rigid frame and a rear axel, wherein that the left and right rear wheels on both sides of the rear axle are driven by left and right motors individually, the rear axle is connected with the frame through a pendulum shaft, and the pendulum shaft makes the rear axle swing relative to the frame. 
     Meanwhile, said frame is provided thereon with a contact surface, corresponding to which the rear axle is also provided with a contact surface, and the pendulum shaft is engaged with the pivot hole provided on the rear axle. 
     Meanwhile, the contact surface on said frame is a slant surface to which the pendulum shaft is provided perpendicular. 
     Meanwhile, said rear axle has a recess region in which the left and right motors are positioned, and a reduction device is disposed between the left motor and the left rear wheel and between the right motor and the right rear wheel. 
     Meanwhile, said rear axle includes left and right support parts supporting the left and right rear wheels and a connecting bracket connecting the left and right support parts, wherein the connecting bracket has             shape and is provided slantly downward.
     Meanwhile, a limiting device is provided between said rear axle and the frame, wherein the limiting device defines a swinging region of the rear axle relative to the frame. 
     Meanwhile, said limiting device includes left and right stop blocks, which are symmetrically provided at the connecting bracket and located on the both sides in respect to the longitudinal central plane of the frame. 
     Meanwhile, said limiting device comprises a movable pressing plate, a resistant member biasing against the pressing plate, and a guide post for the movable pressing plate, wherein the guide post is mounted on the frame. 
     Meanwhile, said electric vehicle chassis also includes an electric control system which in turn includes a power supply, left and right controllers electrically connected with the power supply and a control loop controlling the operation of the left and right controllers, wherein the left controller is electrically connected with the left motor while the right controller is electrically connected with the right motor. In addition, a Hall accelerator is arranged in the control loop and operates to output signal voltage. The left and right controllers receive the signal voltage and then output the corresponding driving voltages, respectively, to control the rotate speeds of the left and right motors. 
     Meanwhile, said control loop further comprises a steering sensor connected in series in the control loop. The steering sensor senses and measures the steering of the front wheel and outputs the corresponding reduction signal voltage to reduce the speed of the motor connected to the rear wheel on the inner side of steering. 
     Meanwhile, said steering sensor basically includes a magnet block fixed to a steering swinging arm and the left and right Hall sensors provided symmetrically on both sides of the steering swinging arm, wherein the left and right Hall sensors sense and measure the steering of the steering swinging arm and output the corresponding reduction signal voltages. 
     Meanwhile, an electronic door lock and a brake powerdown switch are connected in series in said control loop. A reversing switch with the first position and second position is electrically connected between the left and right controllers and the left and right motors. With the reversing switch at the first position, the left and right motors are running forward. On the contrary, with the reversing switch at the second position, the left and right motors are running backward. 
     Meanwhile, said electric vehicle chassis further includes a brake device, which in turn includes a brake pedal, a brake tray provided on the left and right rear wheels, a dish brake clamp provided at the rear axle, and a driving steel rope connecting the brake pedal and the dish brake clamp, wherein the brake powerdown switch is disposed under the brake pedal. As the brake pedal is located at the brake position, the brake powerdown switch disconnects the control loop of controller. 
     Meanwhile, said electric vehicle chassis further includes a steering control device for the front axle and front wheel which are connected together with the rigid frame. The steering control device comprises a steering handlebar, a post transferring the torque of the steering handlebar, a steering swinging arm, a lateral draw rod, left and right steering knuckles connected with the left and right front wheels, and a long draw rod connecting the left and right steering knuckles, wherein the post is connected with the steering swinging arm to drive it rotating; the lateral draw rod at one end is connected with the end of the steering swinging arm far away from the post and at the other end is connected with one of the left and right steering knuckles; the left and right steering knuckles are connected pivotally to both ends of the front axle; the left and right front wheels are mounted on the left and right steering knuckles, respectively, and the left and right front wheels are driven to steer by the turning of the steering handlebar. 
     Meanwhile, said front axle is fixed with a steering knuckle bearing housing at both ends, wherein the left and right steering knuckles are pivotally connected together through a king bolt and the steering knuckle bearing housing, and the steering knuckles are slant backward while the king bolt is slant inwardly. 
     Meanwhile, alternatively, said frame has only one front wheel which is a steering wheel. 
     The electric vehicle chassis according to another aspect of the present invention includes a driven front axle, a rigid frame fixedly connected to the driven front axle, and a rear axle connected with the frame, wherein the left and right rear wheels supported at both sides of the rear axle are directly driven by the left and right full gear reduction motors, respectively, wherein the full gear reduction motor includes a motor and a gear reduction device forming a one-piece structure, and also, the rear axle is provided with a limiting swinging device of the real axle relative to the frame. 
     Meanwhile, said rear axle comprises left and right support parts supporting the left and right rear wheels and a connecting bracket fixedly connecting the left and right support parts. The left and right full gear reduction motors are positioned in the recess region defined by the connecting bracket. The limiting swinging device includes a pendulum shaft and limiting blocks. In addition, the pendulum shaft is slantly provided on the frame and located in the longitudinal central plane of the same. The limiting blocks are symmetrically provided on the connecting bracket with the pendulum shaft as the center, wherein the pendulum shaft connects the rigid frame and the connecting bracket of rear axle. 
     Meanwhile, said electric vehicle chassis further comprises a steering control device which in turn includes a steering handlebar, a post transferring the torque of the steering handlebar, a steering swinging arm, a lateral draw rod, left and right steering knuckles connected to the left and right front wheels, and a long draw rod connecting the left and right steering knuckles, wherein the post is fixedly connected to one end of the steering swinging arm to drive the steering swinging arm turning; the lateral draw rod at one end is pivotally connected to the end of the steering swinging arm far away from the post and at the other end is pivotally connected to one of the left and right steering knuckles; the left and right steering knuckles are pivotally connected to both ends of the front axle; the left and right front wheels are mounted on the left and right steering knuckles, respectively, and are driven to steer by the turning of the steering handlebar. 
     Meanwhile, a steering handlebar post is provided between said steering handlebar and the post, wherein the steering handlebar is mounted on the steering handlebar post with an adjustable position. The steering handlebar post is inserted into the steering post. The steering post has an upper post and a lower post which are pivotally connected together. 
     Meanwhile, said electric vehicle chassis further comprises a control system for electric devices which in turn includes a power supply, left and right controllers electrically connected to the power supply, and a control loop controlling the operation of the left and right controllers; wherein a reversing switch is connected in series between the left controller and the left motor and between the right controller and the right motor. Moreover, a Hall accelerator, steering sensors, and a brake powerdown switch are electrically connected in the control loop, wherein the Hall accelerator and the steering sensors operate to output signal voltages to the left and right controllers which then output corresponding driving voltages to control the rotate speeds of the left and right motors, respectively. 
     In view of the above construction of the present invention, the rigid frame is provided so as to simplify the whole construction of vehicle and remove the traditional rear axle combination having a planet gear differential and a half-axle, thereby resulting in light weight as a whole and small power loss in vehicles. The swinging limiting device is provided for that the rear axle can adjust the running posture of the electric vehicle such that the rigid frame may secure the four wheels to keep in contact with the ground simultaneously in case of non-flat ground or random steering. Accordingly, during the traveling of the vehicle, it can avoid the problem of the running instability and power loss due to that the front or rear wheel tilts away from the ground. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the electric vehicle chassis according to the present invention; 
         FIG. 2  is a top construction view illustrating the electric vehicle chassis according to the present invention with the frame separated from the rear axle; 
         FIG. 3  is a front construction view illustrating the electric vehicle chassis according to the present invention with the frame engaging with the rear axle; 
         FIG. 4  illustrates the swinging limiting device of the electric vehicle chassis according to the present invention; 
         FIG. 5  illustrates another construction of the swinging limiting device of the electric vehicle chassis according to the present invention; 
         FIG. 6  illustrates the electric principle diagram of the electric control system for an electric vehicle chassis; 
         FIG. 7  is a view of a steering control device for an electric vehicle chassis; and 
         FIG. 8  is a schematic diagram of a steering sensor. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention are described in detail in conjunction with the accompanying figures. 
     Referring to  FIG. 1 ,  2  and  3 , a front axle  2  and a frame  1  are welded together as a rigid structure which is generally formed by welding square tubes with rectangle shape. The most front end of the rigid structure is a bumper  22 , which is connected backward to a lateral front axle  21  through double parallel tubes  231  and  232  and then is further connected backward to a rectangle structure  13  accommodating a storage battery  61  through a square tube  15 . On the rectangle structure  13 , the storage battery  61  is fixed at both sides with angle irons  121  and  122  on which plural mounting holes are arranged to fasten a driver seat (not shown) at different positions, i.e. front and rear positions. 
     A rear axle  3  comprises left and right support parts  351  and  352  supporting left and right real wheels and a connecting bracket  31  which connects said left and right support parts and has             shape, therefore the rear axle  3  has a recess region helping to receive a motor (described later). Additionally, as the connecting bracket  31  is provided slantly downward, in the case of the electric vehicle chassis, the height of center of gravity can be effectively lowered, such that the electric vehicle is relatively stable while running.
     In general, the left and right support parts  351  and  352  are provided with bears, respectively, wherein the axle of a rear wheel  331  is connected to the output shaft of a direct current (DC) full gear reduction motor  671  through the bear in the support part  351  and a shaft coupling, and the rear wheel  332  is connected to the output shaft of a direct current (DC) full gear reduction motor  672  through the bear in the support part  352  and a shaft coupling. The DC full gear reduction motors  671  and  672  described herein include motors and full gear reduction devices with the motor and the full gear reduction device integrated to one piece member. Such compact structure has low cost and long lifetime, and is adaptive for use and installation in small space without the maintaining and controlling. 
     It should be appreciated that the above gear reducer is an example of the reduction device which can be other types of reduction devices such as a harmonic gear reducer or a cycloid pin wheel reducer. It is apparent to those skilled in the art that the DC motor and gear reducer may also be separable structure and connected to the rear wheels through chain drive, belt drive or other driving means. Such double motor individual driving means eliminates the conventional rear axle combination having the planet gear differential and half axle while removing the corresponding mechanical driving mechanism. Accordingly, the weight and cost of whole vehicle and power loss are greatly reduced and at the same time, the problem with the conventional mechanical differential, i.e. the whole vehicle can not move due to the wheelspining occurring to one wheel, is completely prevented. 
       FIG. 4  illustrates a swinging limiting device or a swinging limit mechanism for an electric vehicle. The swinging limit mechanism comprises a pendulum shaft  111  and limiting blocks  371  and  372 . The pendulum shaft  111  is fastened on a beam  11  on the back side of a rectangle structure  13 , wherein the beam II and the rectangle structure  13  are welding together to form a structure having a contact surface  113  thereon to which the pendulum shaft  111  is perpendicular. 
     The connecting bracket  31  of the rear axle  3  is provided with a opening  311  to receive the pendulum shaft  111  and with a contact surface  313 . When the pendulum shaft  111  is cooperating with the opening  311  and is fastened by a holding member such as a nut  312 , the rear wheel  3  can swing relative to the frame  1 . Herein, the contact surface  313  is also cooperating with the contact surface  113  in order to prevent the rear axle from shaking relative to the frame and affecting the driving stability during driving. In general, the pendulum shaft  111  and the opening  311  are positioned in the longitudinal central plane of the frame  1 . Obviously, if necessary, it is possible to properly adjust the position of the pendulum shaft such that the lateral driving stability is not impacted during driving even if the pendulum shaft  111  is offset from the longitudinal central plane of the frame  1 . 
     Preferably, the contact surface  113  of the beam  11  is slantly provided with an angle A with the vertical plane and the pendulum shaft  111  is perpendicular to the contact surface  113 , therefore there is also an angle A between the pendulum shaft and the horizontal plane. It is understood that the angle A is provided to help the contact between the contact surface  113  of the frame and the contact surface  313  of the rear axle, so when the frame is driven by the rear axle during driving, the power can be smoothly transferred to the frame. In the figures of the present invention, although it is shown that the contact surface  113  and the contact surface  313  cooperating with the former slant forward such that in the case that the vehicle encounters an obstacle, only small part of the swinging of rear wheels is transferred to the frame, thus the driving is stable without the feeling of encountering the obstacle, the contact surface  113  and the contact surface  313  cooperating with the former can be provided slantly backward such that the contact surface  113  of the frame is located above the contact surface  313  of the connecting bracket, causing that it is difficult for the rear axle to twist during the driving of the vehicle. Herein, the value of the angle A can be selected according to a design requirement, such as within the range from 10 degrees to 30 degrees, for example, 12 degrees, 18 degrees etc. 
     Certainly, the swinging region of the rear axle relative to the frame is preferably limited through a limiting device, so the problem that the vehicle is turned over due to the excess swinging of the rear axle during making a turn at a high speed can be avoided while all of the four wheels are secured in contact with the ground. Referring to  FIG. 4 , in the present invention, it is achieved through a swinging limiting device that, on the connecting bracket  31  of the rear axle, the opening  311  is provided at both sides with stop blocks  371  and  372  which contact with the upper end face of the beam  11 , respectively, when the rear axle swings through a certain angle, so as to prevent the rear axle from further rotating, i.e., when the rear axle  3  is swinging around the central axis of the opening  311  relative to frame  1 , the stop blocks  371  and  372  limit the swinging region of the rear axle, for example, the two stop blocks  371  and  372  limit the swinging of the rear axle between −6° and +6°. 
       FIG. 5  illustrates another swinging limiting mechanism (or swinging limiting device) limiting the steering of the rear axle  3  engaging with the frame  1 , which is similar to  FIG. 4  except that a resistant limiting device is provided to replace the stop blocks. The resistant limiting device comprises a movable pressing plate  361 , a resistant member  363  biasing against the pressing plate  361 , and a guide post  362  for the movable pressing plate  361 . When the rear axle  3  is rotating, the movable pressing plate  361  comes to contact with the beam  11  and then the rear axle keeps on rotating. When the movable pressing plate moves to the top dead center along the guide post, the rotating of the rear axle is stopped. During the rotating of the rear axle, the vibration is absorbed by a spring, resulting in the more comfortable driving of the electric vehicle. 
     According to the principle of the relative motion, it is apparent to those skilled in the art that the pendulum shaft can also be provided on the rear axle and a hole is provided on the beam  11  corresponding to the pendulum shaft. The stop block or resistant limiting mechanism can be provided either on the rear axle or on the beam or the frame as long as it can limit the swinging region or angle of the rear axle. The contact surface can also be provided perpendicularly. Additionally, other members can be used to implement the function of said contact surface. Moreover, it may be sliding friction or rolling friction between the hole and pendulum shaft, for example, rollers may be provided between the pendulum shaft and the hole. Of course, said hole may be the inner hole of the bear. Also, all of the above arrangements may be applicable for the frame and rear axle of a three-wheel electric vehicle. 
       FIG. 7  illustrates a steering control device (or called as steering operating mechanism) of the present invention. Referring to  FIG. 7 , a steering control device or steering operating mechanism  5  basically comprises a post  55 , a steering swinging arm  56 , a lateral draw rod  57 , a long draw rod  58 , a left steering knuckle  581 , and a right steering knuckle  582 . The post  55  is connected at one end with a steering handlebar post  52  and at the other end with a steering swinging arm  56 . When the steering handlebar  51  is steering, the steering swinging arm  56  is rotating with it simultaneously. The lateral draw rod  57  is pivotally connected at one end with the steering swinging arm  56  and at the other end with the left steering knuckle  581 . Alternatively, the other end of the lateral draw rod  57  may be pivotally connected with the right steering knuckle  582 . The long draw rod  58  is provided at one end with a draw rod ball bearing  572  and at the other end with a draw rod ball bearing  573 , wherein the long draw rod  58  is movably connected with the left steering knuckle  581  through the draw rod ball bearing  572  and with the right steering knuckle  582  through the draw rod ball bearing  573 . In this way, the left and right steering knuckles  581  and  582  are formed in coupling relationship. The front axle  21  is welded at both ends with steering knuckle supporting bases  211  and  212  symmetrically. The left and right steering knuckles  581  and  582  are pivotally connected to their respective steering knuckle supporting bases  211  and  212  through a king bolt. The steering knuckle supporting bases  211  and  212  are welded to both ends of the lateral front axle  21 . 
     The steering handlebar  51  drives the steering swinging arm  56  to swing to right and left through the steering handlebar post  52  and the steering post  55  and drives the left front wheel  262  to steer through the lateral draw rod  57 . And then the right font wheel  261  is driven to steer simultaneously through the long draw rod  58 . Thereby the steering action of the whole vehicle is completed. Those skilled in the art can calculate the length of the steering arm and the base angle of the trapezoid according to the trapezoid construction principle for vehicle steering. Thereby, during the steering of the vehicle, the temporal turning center of the two front wheels is located on the extension of the axis of rear wheels. In addition, properly, the steering knuckles are provided slantly backward while the king bolt is provided slantly inward, which can secure flexible steering, facilitated returning, and minimized side friction of the tires of the front wheels when steering. 
     Since the left and right steering knuckles of the front axle  2  have a backward inclination angle and an inward inclination angle, the movement loci of the lowermost ends of the front wheels  261  and  262  are not in a plane parallel with the ground, and the lowermost ends of the front wheels on the inner and outer sides with respect to steering are shifted downward and upward respectively. In the rigid frame, although all of the four wheels are in contact with the ground simultaneously during direct movement, only the front wheel on the inner side with respect to the steering and the both rear wheels are in contact with ground when steering and contrarily the front wheel on the outer side with respect to the steering is warped away from the ground. The swinging limiting mechanism is provided such that it can be secured that when the ground is not flat or the steering is arbitrarily implemented, the rigid frame  1  still can assure that all of the four wheels are in contact with the ground simultaneously, thereby the problem that the vehicle is turned over sideward due to the excess swinging of the rear axle can be avoided during driving. 
     As shown in  FIGS. 1 and 3 , the steering handlebar  51  is mounted in a slipknot  54  at the upper end of the steering handlebar post  52  inserted in the steering post  55  and clamped by a speedy chuck  53 , wherein the angle of the steering handlebar  51  may be adjusted by the slipknot  54  and the vertical position of the steering handlebar post  52  is determined by the length thereof inserted in the steering post  55 . The lower end of the steering post is configured to have two sections, thus the steering post  55  may be folded downward after the releasing of a set screw, causing the minimized volume during the packing, transporting and storing. In addition, there are other ways to reduce the volume during the packing, transporting and storing, for example, the seat (not shown in figures, which is mounted on an angle iron  121  with holes and above the battery) may be made as a foldable structure so as to reduce the occupied space for the whole vehicle. 
     As shown in  FIG. 1 , the electric vehicle chassis or the electric vehicle according to the present invention also comprises a brake device. The brake device includes a brake pedal  691 , brake trays  692  provided on the left and right rear wheels, a dish brake gripper mounted on the rear axle, and a driving steel wire connecting the brake pedal and the dish brake gripper. The brake device is known for those skilled in the art and not described in detail herein. The description of the electric control system  6  for the electric vehicle chassis according to the present invention is given in the following. As shown in  FIG. 6 , the electric control system according to the present invention basically includes a power supply device  61  (which is battery  61  in the embodiment) and controllers  66  electrically connected with the power supply device, wherein the controllers  66  includes left and right controllers  661  and  662  which are electrically connected with the left and right motors  671  and  672  through the reversing switch  65 , and the left controller  661  controls the rotating speed of the left motor  671  and the right controller  662  controls the rotating speed of the right motor  672 . The reversing switch operates to change the polarity of the motor electrode. It should be understood that the reversing switch is operated causing that the polarity of the motor electrode is changed and then the motor runs forward or backward. As the result, with the vehicle, the function of advancing and backing is achieved. In the present embodiment, the reversing switch has a handle  64  with first, second and middle positions. With the reversing switch at the first position, the left and right motors run forward. With the reversing switch at the second position, the left and right motors run backward. With the same at the middle position, the reversing switch electrically disconnects the battery from the controllers, and then the left and right motors stop. 
     Hereinbefore, the reversing switch is provided such that the function of backing is achieved in vehicles. Hereinafter, it will be given that, in vehicles, a Hall accelerator  62  is provided so as to obtain the function of adjusting speed, steering sensors  68  are provided so as to obtain the function of electronic differential speed, and a brake powerdown switch is provided as so to obtain the function of brake powerdown momentum. 
     As shown in  FIG. 6 , the left and right controllers  661  and  662  are also electrically connected with a control loop controlling the actions of the controllers. The control loop includes the Hall accelerator  62  connected in series, an electronic door lock  63 , the brake powerdown switch  691 , and the steering sensors  68  having two Hall sensors, i.e. a left Hall sensor  681  electrically connected to the left controller  661  and a right Hall sensor  682  electrically connected to the right controller  662 . The operating voltage Vc of the Hall accelerator, which is generally +5V, is supplied by the left and right controllers. The Hall accelerator  62  is operated to generally output a signal voltage of 1-4.2V which is fed back to the left controller  661  through the electronic door lock  63 , the brake powerdown switch  691 , and the left Hall sensor  681 . At the same time, the signal voltage is fed back to the right controller  662  through the electronic door lock  63 , the brake powerdown switch  691 , and the right Hall sensor  682 . Thereby, the control loop is disconnected if only one of the electronic door lock  63  and the brake powerdown switch  691  is turned off. 
     It is apparent to those skilled in the art that if the left and right sensors can change the signal voltage controlling the controllers, the left and right controllers can output different control voltages depending on the signal voltages of the control loop and control the motors to run at different speeds. In this way, during steering, as long as the left and right Hall sensors sense the steering of the front wheels and output the corresponding voltages, the value of the signal voltage is changed. For example, during steering, the Hall sensor sensing the inner side of the steering outputs a reduction signal voltage causing the signal voltage output from the Hall accelerator is decreased while the Hall sensor sensing the outer side of the steering does not output the reduction signal voltage, thereby the motor connected to the rear wheel on the inner side of steering is reduced on the speed and the motor connected to the rear wheel on the outer side of steering is not changed on the speed. As the result, the function of the electric differential is fulfilled. 
     Meanwhile, as shown in  FIG. 8 , the steering sensor  68  comprises a magnet  683  provided on the one side of the steering swinging arm far away from the post and the Hall sensors  681  and  682  provided on both sides of the steering swinging arm. During the direct movement of the vehicle, the steering swinging arm is located at the middle position between the two Hall sensors. Because of the weak magnetic flux received by the two Hall sensors, as connected with the control loop in series, the two Hall sensors do not impact on the signal voltage controlling the left and right controllers, and operate the Hall accelerator, thus the vehicle obtains different driving speeds. As the steering swinging arm is offset from the middle position due to the steering of the steering handlebar, the two sensors sensing different flux are connected in series in the control loop, causing the signal voltages of the left and right controllers are different, e.g., the motor driving the rear wheel on the inner side of steering is made to be reduced on the speed and the motor driving the rear wheel on the outer side of steering is made to be unchanged on the speed. Accordingly, the effect of differential speed that is equivalent to the conventional differential half-axle is obtained. 
     Meanwhile, the brake powerdown switch  691  is provided below the brake pedal. During the braking, the brake powerdown switch  691  is actuated to disconnect the return path of signal voltages. An accelerating pedal  621  controls the above Hall accelerator  62  through a steel wire. It is obvious to those skilled in the art that the Hall accelerator can also be controlled by a handle and the left and right controllers may be a chopping speed regulator (PWM). The associated operating principle and configuration are known for those skilled in the art, so not described again herein. 
     While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention that come within the scope of the appended claims and their equivalents. 
     
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 1 
                 frame 
                 11 
                 beam 
               
               
                 111 
                 pendulum shaft 
                 121/122 
                 left/right angle iron 
               
               
                 13 
                 rectangle structure 
                 15 
                 square tube 
               
               
                 2 
                 front axle 
                 21 
                 lateral front axle 
               
               
                 211/212 
                 left/right supporting base 
                 22 
                 bumper 
               
               
                 231/232 
                 square tube 
                 261/262 
                 left/right front wheel 
               
               
                 3 
                 rear axle 
                 31 
                 connecting bracket 
               
               
                 311 
                 opening 
                 312 
                 nut 
               
               
                 351/352 
                 left/right support part/s 
                 361 
                 movable pressing plate 
               
               
                 362 
                 resistant member 
                 363 
                 guide post 
               
               
                 671/672 
                 left/right full gear 
                 331/332 
                 left and right rear 
               
               
                   
                 reduction motor 
                   
                 wheel 
               
               
                 371/372 
                 limiting block 
                 5 
                 steering control device 
               
               
                 51 
                 steering handlebar 
                 52 
                 steering handlebar post 
               
               
                 53 
                 speedy chuck 
                 54 
                 slipknot 
               
               
                 55 
                 steering post 
                 56 
                 steering swinging arm 
               
               
                 57 
                 lateral draw rod 
                 571/572/573 
                 draw rod ball bearing 
               
               
                 56 
                 long draw 
                 581/582 
                 left/right steering 
               
               
                   
                 rod 
                   
                 knuckle 
               
               
                 6 
                 electric control system 
                 61 
                 battery 
               
               
                 62 
                 Hall accelerator 
                 63 
                 electronic door lock 
               
               
                 64 
                 handle 
                 65 
                 reversing switch 
               
               
                 66 
                 controller 
                 661/662 
                 left/right controller 
               
               
                 671/672 
                 left/right rear wheel 
                 691 
                 brake pedal 
               
               
                 68 
                 steering sensors 
                 681/682 
                 left/right Hall sensor