The present invention relates to a car transmission system, and more particularly to a car transmission system which has enhanced transmission efficiency and reduced volume.
Conventional car transmission systems can be generally divided into manually operated transmission system, automatically operated transmission system and continuously variable transmission system.
The manually operated transmission system employs gear sets with different gear ratios for transmitting power and has better transmission efficiency. However, when driving a car with manually operated transmission system, a driver must frequently step and release the clutch pedal and shift the gear lever according to the running speed and road condition for changing the transmission ratios and transmission torque. Such procedures consume the driver's physical and mental energy. Especially, when the traffic condition is complex or to a driver not skilled in the driving, the shifting movement may disable the driver from concentrating on the driving and thus cause accident.
The automatically operated transmission can eliminate the troublesome procedures of stepping and releasing the clutch pedal and shifting the gear lever. However, because the automatically operated transmission employs a fluid as the medium for transmitting the power of the engine and a power transmission delay phenomenon occurs at two ends of the fluid torque changing device, the efficiency is not desirable. This results in that the automatic transmission car is more fuel-consuming than the manual transmission car and the acceleration/deceleration of the automatic transmission car is more obtuse than the manual transmission car. In addition, the braking frequency of the automatic transmission car is higher and the wear of the brake thereof is greater.
The continuously variable transmission is composed of a belt and a pair of pulleys connected therewith. A very great transmission torque is created between the belt and the pulleys. The axial force exerted on the belt incurs a very great compression force on the triangular belt, so that the thickness of the belt must be considerably large for avoiding axial break or damage thereof. When the thickness of the belt is increased, the centrifugal force thereof is correspondingly increased. This results in greater tension load of the belt. In addition, when the thickness of the belt is increased, an even greater stress is exerted on the pulleys so that the dimension thereof must be enlarged. Moreover, the triangular belt must be continuously pulled out of the compression grooves of the two pulleys, so that the wear loss and dullness of the belt will be apparently caused. This negatively affect the efficiency and using life of the continuously variable transmission system.