Motor vehicles – Special wheel base – Rider propulsion with additional source of power – e.g.,...
Reexamination Certificate
1998-09-22
2001-03-06
Vanaman, Frank (Department: 3611)
Motor vehicles
Special wheel base
Rider propulsion with additional source of power, e.g.,...
C180S220000
Reexamination Certificate
active
06196347
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric bicycle, and more particularly to a power transmission and pedal force sensing system for an electric bicycle.
2. Description of the Related Art
A conventional electric bicycle generally comprises a high speed electric motor used as an auxiliary power source, a gear reduction mechanism for reducing speed of the motor and increasing the output torque, and a power combining mechanism for combining the power from the motor after speed reduction and the pedaling power from the cyclist for subsequent transmission to a chain wheel for driving the electric bicycle at a labor-saving mode. A pedal force sensor is provided on a pedal force transmission path to detect the magnitude of the pedal force to thereby control auxiliary output power from the electric motor.
A transmission mechanism for the above conventional electric bicycle includes a frame mounted adjacent to a crankshaft of a bicycle and including a main casing and an auxiliary casing arranged in a direction perpendicular to the main casing. The power combining mechanism and the pedal force sensing mechanism are mounted in the main casing, while the electric motor and the gear reduction mechanism are mounted in the auxiliary casing. Bevel gears are used for transmission. Such a transmission mechanism has a low transmission efficiency as there are too many stages for gear reduction and the transmission path is too long. In addition, the electric motor is not mounted inside the main casing such that additional supporting casing and transmission elements are required, and this results in a bulky structure. Further, the sensing system adopts a bolt and nut or plane cam to convert relative angular displacement into axial displacement, which, in turn, is detected by a proximity sensor for outputting a signal corresponding to a magnitude of the pedal force. Yet, the elements of the pedal sensing system are located on the pedal force transmission path and are thus liable to wear.
The present invention is intended to provide a power transmission and pedal force sensing system that mitigates and/or obviates the drawbacks of the above conventional electric bicycle.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a power transmission and pedal force sensing system for an electric bicycle, in which the power transmission path is shortened and the transmission efficiency is improved.
It is a further object of the present invention to provide a power transmission and pedal force sensing system for an electric bicycle that has a smaller volume and a lower weight.
It is another object of the present invention to provide a power transmission and pedal force sensing system for an electric bicycle to reduce friction between elements.
In order to effectively solve the drawbacks of the conventional transmission design and to achieve the above-mentioned objects, the present invention provides a power transmission system and a pedal sensing system. In accordance with the present invention, a casing is mounted to the crankshaft for housing an electric motor, a gear reduction train, a pedal force sensing system, and a power combination mechanism. These four mechanisms are concentrically, closely mounted in the single casing.
The power transmission system for an electric motor of the present invention comprises a casing, a crankshaft for pedals extended through the casing, a hollow axle mounted around the crankshaft, and a motor hollow shaft mounted around the hollow axle. A left part of the motor hollow axle is connected to an electric motor, and a right part of the motor hollow axle is connected to an input gear of a gear reduction train. The gear reduction train is preferably a Ferguson's mechanical paradox gear that has a high gear reduction ratio. An output gear of the gear reduction ratio is connected to an outer periphery of an enlarged hollow end of the hollow axle via a first single direction clutch of the power combination mechanism. An inner periphery of the enlarged end of the hollow axle and the crankshaft together define a space therebetween for receiving a pedal force sensing system. The pedal force sensing system includes a pedal force transmitting sleeve that has an inner ring securely mounted around the crankshaft to rotate therewith and an outer ring connected to the inner periphery of the enlarged end of the hollow axle via a second single direction clutch of the power combination mechanism. The first single direction clutch and the second single direction clutch are mounted to the outer periphery and inner periphery of the enlarged end of the hollow axle along a radial direction. The other end of the hollow axle is securely connected to a chain wheel to rotate therewith. Thus, the pedal force is transmitted to the hollow axle via the crankshaft, the pedal force transmitting force of the pedal force sensing system, and the second single direction clutch to thereby drive the chain wheel and the bicycle frame. The power from the electric motor is transmitted to the hollow axle via the motor hollow shaft, the gear reduction train, and the first single direction clutch to thereby drive the chain wheel and the bicycle frame. By such an arrangement, the power transmission path is shortened and thus has a higher transmission efficiency. In addition, the electric motor is housed in the casing such that the overall volume and the overall weight are both reduced.
In the pedal force sensing system, an elastic means is provided between the inner ring and the outer ring of the pedal force transmitting sleeve. A pedal force sensing sleeve is mounted adjacent to the pedal force transmitting sleeve and includes a square key groove so as to be securely mounted on the crankshaft. In addition, at leas tone plane cam is provided on one side of the pedal force sensing sleeve that faces the pedal force transmitting sleeve. When pedaling, the crankshaft drives the inner ring of the pedal force transmitting sleeve and thus exerts a force on the outer ring of the pedal force transmitting sleeve such that the elastic means between the inner ring and the outer ring deforms. As a result, a relative angular displacement occurs between the inner ring and the outer ring. Namely, the pedal force sensing sleeve and the outer ring of the pedal force transmitting sleeve have a relative angular displacement therebetween. This relative angular displacement causes axial displacement of the pedal force sensing sleeve, and a proximity sensor is used to detect the axial displacement and outputs a voltage signal representing the magnitude of the pedal force. Friction between the elements is eliminated, as the elements of the pedal force sensing system are not located on the pedal force transmission path.
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Chao Chin-Yu
Hwang Yuh-Wen
Luo Yin-Jao
Wang Chih-Jin
Industrial Technology Research Institute
Vanaman Frank
LandOfFree
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