1. Field of the Invention
This invention generally relates to a freewheel for a bicycle. More specifically, the present invention relates to a freewheel for a bicycle that is compact to receive a small gear, such as an eleven teeth gear, at one end.
2. Background Information
Bicycling is becoming an increasingly popular form of recreation as well as a means of transportation. Moreover, bicycling has a become a very popular competitive sport. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving their components. One particular component of the bicycle which has been extensively redesigned over the past years are the freewheel of the rear bicycle hub.
Specifically, most bicycles have several speeds. One popular form of drive train for a bicycle includes utilizing a plurality of sprockets that are mounted on the hub of the rear bicycle wheel. During pedaling, the bicycle chain engages one of the rear sprockets to rotate the rear wheel. When bicycle rider stops pedaling, the rear wheel should be able to continue to rotate while the sprockets remain stationary. Accordingly, the rear hub is provided with a freewheel that has a one-way clutch.
With an increased number of speeds provided by a derailleur of a bicycle today, a multi-step sprocket wheel unit for the rear wheel includes an increased number of sprockets which is now five to seven.
Freewheels used to transmit a driving force to the rear bicycle wheel in one rotation direction only are usually mounted on the rear hub of a bicycle. Freewheels are used so that the bicycle can advance freely without any rotation of the pedals. Freewheels include boss type freewheels which are mounted on the boss of the rear hub by being screwed onto the rear hub, and freehub type freewheels which are fastened to the rear hub as integral parts of the rear hub. Both types of freewheels are equipped with an outer tubular part, an inner tubular part which is installed radially inwardly of the outer tubular part so that the inner tubular part is free to rotate relative to the outer cylinder part, and a one-way clutch which is installed between the outer tubular part and inner tubular part for transmitting the driving force from the outer tubular part to the inner tubular part in one rotational direction only. The outer tubular part has a plurality of gears mounted thereon, while the inner tubular part is usually mounted on the rear hub of the bicycle.
Splines are formed between the sprocket wheels and boss to prohibit relative rotation therebetween positively. Since this unit is used for the rear wheel of a bicycle, drive must be transmitted between the rear wheel axle and boss through a one-way mechanism. For this purpose, the boss is formed as an outer race of a one-way clutch, and the one-way clutch and inner race are disposed on an inner periphery of the boss.
As the number of rear gears or sprockets have increased over the years, the freewheel has become larger and heavier. Moreover, with the increased number of gears or sprockets, a wider range of torque is being applied from the sprockets to the freewheel.
In view of the above, there exists a need for a freewheel for a bicycle which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.