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A、Classes and structures of electric bikes
1．Classes
Electric bikes are divided into full electric dynamic type and intelligent electric assistant type.
（1） Full electric bike： It may be pedaled resorting to no human power or be driven fully by electricity realizing stepless speed changing of 0～20km/h controled by the handle.
（2） Intelligent electric assistant bike： It has similar operation method to oridnary bikes. Driven mainly by human power and assisted by electricity, it has no pure electromotive mode. Electric current is supplied according to magnitude of human power and when a designed velocity is achieved, the current is shut off.
2．Basic structures
The electric bike is composed of body, motor, rechargable battery, charger and control system. Various sorts of electric bikes have different locations of batteries and controller forms.
（1） Body：As the state restricts the highest speed to 20km/h, no special requirement is made to the electric bike other than those to the ordinary bike.
（2） Motor：There are mainly three types of electromotive modes：
① Friction transmission：The contact wheel on the motor axle loads force directly on the tire and drives it by friction. Its advantage is simple structure and low cost, but the tire suffers big wearing and slides in rainy season.
② Middle axle driving mode：The middle axle is driven by the motor via a reducer, then it drives the back wheel via the chain. The advantage is proper barcenter of the motor and gear shifting by the reducer, but mechanical loss is great.
③ Electromotive hub：The motor is installed inside the hub of the front wheel or the back wheel and drives in sequence the hub, the spokes and the wheel. The advantage is small bulk, light weight, low energy cost and high efficiency, but heat dissemination and lubrication are difficult. Now most domestic electric bikes adopt this mode.
The motors include brushless motors and brush motors. The former is used as low velocity great moment motors that need no gear transmission and thus avoid mechanical loss and noises in operation. But they need greater initiating current, and more complicated controlling system, while the latter adopt advanced technique to raise brush life and motor efficiency and have relatively simple controlling circuits.
（3）Chargable battery：including small type sealed maintenance free lead-acid accumulator, nickle-cadmium battery and nickle-hydrogen battery. The first type is widely adopted by domestic producers for its low cost and high capacity.
（4）Charger：The charger adopts auto-shifting mode among the three phases constant current, constant voltage and floating charging, thus protecting the battery and prolonging its life.
（5）Control system： The control system has some functions to protect the motor and battery including electricity amount display, stepless speed adjustment, soft start, protection against inadequate voltage and excessive current, and shutting off electricity on braking. At the same time it control the orderly ouput of current to generate enough driving force. At present, most domestic electric bikes adopt handle speed adjustment to choose the current supplying mode. |
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