Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive – Plural elements selectively braked
Reexamination Certificate
2002-03-07
2003-03-18
Bonck, Rodney H. (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
Plural elements selectively braked
C475S216000
Reexamination Certificate
active
06533700
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to bicycle transmissions and, more particularly, to an internally mounted multi-speed hub transmission for a bicycle.
An internally-mounted multi-speed hub transmission sometimes is mounted to the rear wheel of a bicycle so that the rider can select different gear ratios to vary the pedaling effort. A typical hub transmission includes a hub axle that is mounted to the bicycle frame, a driver rotatably supported to the hub axle for receiving the pedaling force through a sprocket and chain, and a hub shell rotatably supported to the hub axle. A power transmitting mechanism is disposed between the driver and the hub shell for communicating rotational power from the driver to the hub shell through a plurality of power transmission paths, wherein each power transmission path typically produces a unique gear ratio. The power transmitting mechanism ordinarily comprises a planetary gear mechanism including one or more sun gears rotatably supported around the hub axle, a ring gear rotatably supported around the hub axle, a planet gear carrier rotatably supported around the hub axle, and a plurality of planet gears rotatably supported to the planet gear carrier and meshing with the sun gear and the ring gear. The plurality of power transmission paths and the corresponding gear ratios are selected by selectively nonrotatably coupling the various components to each other. For example, one gear ratio may be selected by nonrotatably coupling a sun gear to the hub axle, another gear ratio may be selected by nonrotatably coupling the driver relative to the planet gear carrier, and another gear ratio may be selected by nonrotatably coupling the driver relative to the ring gear. Many such coupling relationships often are possible in a typical hub transmission, thus resulting in a relatively large number of possible gear ratios.
When a gear ratio is selected by nonrotatably coupling the sun gear to the axle, the coupling may be accomplished by a ratchet and pawl mechanism disposed between an inner peripheral surface of the sun gear and the hub axle. More specifically, a plurality of pawls may be mounted to the inner peripheral surface of the sun gear such that an end of each pawl is biased radially inwardly by a spring. The outer peripheral surface of the hub axle typically forms a plurality of ratchet teeth or abutments which engage the ends of the pawls to nonrotatably couple the sun gear to the hub axle, and a control sleeve rotatably supported to the hub axle to selectively expose the abutments. As a result, the sun gear is free to rotate relative to the hub axle when the abutments are covered by the control sleeve, and the sun gear is nonrotatably coupled to the hub axle when the abutments are exposed.
The sun gears usually are supported to the hub axle through the plurality of pawls. As a result, often there is some looseness in the support of the sun gear on the hub axle which decreases the precision of the ratchet and pawl mechanism. Such looseness can be compensated for by increasing the number of pawls, but that increases the cost and complexity of the transmission, not to mention the risk of malfunction. Additionally, the circumferential distance between successive ratchet teeth or abutments on the hub axle ordinarily is relatively large. As a result, the sun gear ordinarily must rotate a substantial distance before the pawls engage the ratchet teeth or abutments. This causes undesirable delay in the gear switching operation.
Another type of hub transmission includes a sun gear rotatably mounted around the axle, wherein an inner peripheral surface of the sun gear defines a plurality of ratchet teeth. One or more pawls may be disposed in an aperture formed in a hollow axle to selectively engage the plurality of ratchet teeth. However, a hollow axle is not very strong and is not suitable for severe operating conditions. Yet another type of hub transmission also uses pawls mounted to the axle, but the pawls are operated by a control sleeve that directly supports the sun gears. Such a configuration causes excessive friction on the control sleeve.
Another disadvantage of conventional hub transmissions is that, when switching from one gear ratio to another gear ratio, the transmission sometimes must pass temporarily through another gear ratio that is not near the destination gear ratio as the various components change their coupling relationships. This phenomenon is discussed more fully in the detailed description below. For example, when shifting from a small gear ratio, wherein the hub shell rotates around the axle at a relatively slow rate relative to the driver, to a higher gear ratio, wherein the hub shell rotates around the axle at a larger rate relative to the driver (such as occurs when the bicycle is decelerating), the transmission may temporarily switch into a gear ratio that is lower than the original gear ratio. This causes the pedals to speed up temporarily, which is opposite the desired effect and can be very disconcerting to the rider.
Another disadvantage of conventional hub transmissions is that the sun gear ratchet and pawl mechanisms ordinarily are controlled by a relatively thin sleeve that is rotatably supported on the hub axle. As noted above, such a sleeve often is used to selectively expose the abutments on the hub axle for engaging the pawls on the sun gears. The sleeve typically is relatively long and is operated from outside the hub shell, thus creating significant torsional stresses on the sleeve. Such forces create a risk of bending or twisting the sleeve.
Another disadvantage of conventional hub transmissions is that the sleeve that controls the ratchet and pawl mechanisms (and any other desired coupling mechanisms) is sometimes coupled to an external actuating member such as an actuating ring through one or more return springs that bias the actuating ring to a start position. Such a biasing force is used not only to provide proper tensioning of the components during the switching operations but also to help control a shift assist function. Such a shift assist function uses the force of the rotating driver to help overcome resistance to the shift operation such as occurs when significant pedaling force is applied to the hub. More specifically, a coupling mechanism that is normally biased to an inoperative state is activated to couple the sleeve to the driver so that the force from the driver overcomes the excessive resistance. In any event, when such a biased actuating ring is operated by a battery-operated motor, the motor must overcome the biasing force of the return spring. This typically requires a relatively large motor that consumes a substantial amount of power, thus significantly reducing battery life.
SUMMARY OF THE INVENTION
The present invention is directed to a bicycle hub transmission wherein the sun gears are stably supported on the hub axle, wherein the gear switching operation is performed with precision and minimal delay and with minimal effect on the rider, wherein components such as the control sleeve used to control a ratchet and pawl mechanism is stably supported to minimize the risk of bending or other damage, and wherein the actuating member used for the gear switching operation does not cause excessive power consumption when driven by a battery-operated motor.
In one embodiment of the present invention directed to a basic sun gear apparatus, the sun gear apparatus includes an axle, a sun gear rotatably supported around the axle, and a sun gear guide ring disposed between an inner peripheral surface of the sun gear and the axle. The sun gear guide ring minimizes or eliminates looseness in the coupling between the sun gear and the axle. One or more such guide rings may be used to support a single sun gear, or one guide ring may be used to support multiple sun gears.
In a more specific embodiment of the present invention wherein a pawl is disposed between an inner peripheral surface of the sun gear and the axle for moving between an engaged position (wherein the sun gear is nonr
Bonck Rodney H.
Deland James A.
Pang Roger
Shimano Inc.
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