From the patent:
The gears of modern bicycle allow the rider to exercise the muscle in the aerobic range to allow continuous long distance riding. The gears are utilized to keep the rider's pedal speed at a high rotating speed (usually between about 60 to 100 rpm). At higher pedaling speeds, the force output for muscle contraction is low so that the muscle is able to stay in the aerobic region.
The original bicycle used a single fixed gear ratio (similar to most electric bicycles) and was severely limited in its ability to negotiate steep terrain. The number of gears on a bicycle has evolved so that the present mountain bike has up to 27 gears to allow for riding on a variety of terrains.
Similar to the human muscle, the modern battery has an efficient and an inefficient region. The battery delivers current to the motor, which produces torque in the motor. The motor torque increases linearly with motor current. High currents are inefficient.
At high current discharge rates, the battery experiences problems similar to lactic acid buildup in the human muscle. More specifically, in the battery, hydrogen gas is formed on the charge plate. Hydrogen gas acts as a barrier to the transfer of electrons. As the high current discharge continues, the hydrogen continues to build on the plates until the battery is unable to deliver current.
Another important issue to consider at high current discharge rate is that the run time of the battery is reduced exponentially with linear increases in motor current. Further, motor thermal losses are experienced which increase with the square of the motor current. Hence, increased motor current wastes available energy two non-linear ways, i.e., battery losses and motor resistance losses.
As one example, a motor mounted directly to the rear wheel on the bicycle has only a fixed gear ratio. Hence, to obtain a four times increase in torque, the motor current must be increased by four times. However, the four times increase in the motor current increases motor resistive losses by 16 times and thus results in a significant loss in battery run time and reduction in motor efficiency.
The available power from the battery is an exponential function of the rate of current use. Hence, as current discharge increases, the available energy from the battery decreases exponentially. Hence, as more torque is required to move the bicycle (such as during hill climbing or acceleration), more current will be required, thereby exponentially decreasing the available power from the battery.
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In yet another aspect, the gear system comprises a set of planetary gears to rotate the output driver at a rate of rotation that is less than the motor. Preferably, the gears are configured so that the output speed of the motor is matched to the range of the human leg. For example, the planetary gears are preferably configured so that when the rate of rotation of the motor is in the rate from about 1,800 rpm to about 3,600 rpm, the rate of rotation of the output driver is in the range from about 60 rpm to about 120 rpm. In a specific aspect, the motor speed is approximately 2400 rpm and is employed to turn the crank arms at a rate of about 75 rpm. Such a gear reduction facilitates use of either the motor or pedal power to drive the bicycle. The motor is preferably operated at or near its maximum output level to maximize the efficiency of the motor and minimize current use, thereby prolonging the life of the battery. Operating the motor at or near its maximum output level is also advantageous in that the motor is able to generate more power at higher rates of rotation.
In still yet another aspect, the motor comprises a brushless DC motor. Such a motor is preferable because it provides superior cooling and a high power output.
The engineers on this project seem to have gotten everything right... very good job... but the prices are insane... many thousands of dollars for an ebike? :?
But I guess "quality" always has a premium price.
I'm sorry... a poorly chosen word to use.
