Multi-speed gear hub shiftable under load

Details Multi-speed gear hub shiftable under load Multi-speed gear hub shiftable under load

2002-07-17

2004-02-17

Lewis, Tisha D (Department: 3681)

Planetary gear transmission systems or components

With means to vary drive ratio or disconnect drive

Plural drive ratios other than unity

C475S298000

Reexamination Certificate

active

06692400

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to multi-speed gear hub systems and more particular to an internal gear hub system shiftable under load for a bicycle.
Internal gear hub systems shiftable under load have devices which make it possible to disengage and engage gearing system elements that are currently in the power flow with little shifting force. This disengagement and engagement of gearing system elements, such as a ring gear, a planet carrier, driver, and clutch components, is preferably accomplished via controllable spring-loaded pawls.
Such a pawl control system is disclosed in DE 2937126 C2 for a two-speed gear hub. A preloaded pawl control member is displaced with relatively little shifting force against spring-loaded pawls by a selector element. The selector element is arranged in the axial direction and is displaceable by a selector rod between two end positions. The pawl control member hooks under the pawls and pivots them, even under load, out of a corresponding pawl tooth set, thereby interrupting the power flow.
Another pawl-controlled multi-speed hub shiftable under load is disclosed in DE 3443592 C2. The hub includes a planetary gear mechanism and a driver that carries a sprocket and is mounted on a hub shaft. The planetary gear mechanism includes a stationary sun gear, a planet carrier with a planet gears, and a ring gear. Four pawl freewheels are located in the power flow respectively between the driver and the ring gear, a selector element and the planet carrier, the ring gear and the hub shell, and the hub shell and a pawl carrier joined rotatably to the planet carrier. The pawls may be disengaged or engaged with corresponding pawl teeth, or overrun when the component having the pawl teeth is rotating faster than the component having the pawls.
To shift to a desired gear ratio, the selector element is slid into the desired ratio by a shift linkage via an axially displaceable actuation element, thus directing the power flow via the corresponding pawls. When the hub is in the high gear ratio, the power introduced into the driver from the sprocket is passed to the selector element and then to the selector element pawls to the planet carrier. The planet gears rotate the ring gear, and the ring gear pawls transfer the power to the hub shell connected to the driven wheel. In the high gear ratio, all the pawls are located opposite the corresponding pawl teeth, and the propulsion pawls and the pawls on the pawl carrier coupled nonrotatably to the planet carrier are overrun by their pawls teeth.
In order to engage the direct and low gear ratios, the actuation element is slid against the selector element. The rotation of the selector element is used to release the selector element pawls from engagement with the planet carrier, thereby greatly reducing the necessary shifting force. The power flow through the selector element is thus interrupted. In the direct gear ratio, the power flow travels from the driver via the driver pawl to the ring gear, and via the ring gear pawl to the hub shell. The pawls on the pawl carrier are overrun by their pawl teeth. In the low gear ratio, the ring gear pawl is additionally disengaged by a stop surface on the selector element, so that the power flow travels from the ring gear via the planet gears to the planet carrier and from there via the pawl carrier and the pawls to the hub shell.
The above mentioned multi-speed hub is shiftable under load but has several shortcomings. One problem is that in some shift positions, the spring-preloaded components with different rotation speeds rub against one another. Another problem is that shifting forces in the direction of the driver act, without a spring buffer, directly on the actuation element and the selector element, resulting in the gear ratio selection being more difficult under unfavorable shifting conditions and the gear ratio preselection is not possible. Another problem is the complex component configurations for the driver, the ring gear and the selector element, making production and assembly difficult.
SUMMARY OF INVENTION
An object of the present invention is to provide a multi-speed hub shiftable under load that eliminates the aforesaid shortcomings, ensures effective and ratio-independent braking performance, and moreover is easy to produce and assemble.
Specifically, there is to be no difference in rotational speed between the spring-loaded shifting components and the corresponding spring bracing. During unfavorable shifting situations it is desirable to have gear ratio preselection or temporary storage of the shifting force. The operation of switching over from propulsion mode to backpedal braking mode should occur with as little delay as possible, but with a desirable backlash. The braking operation should always occur in the low gear ratio. The configuration of the components are such that the sintered or molded plastic parts may be used, resulting in parts that are produced with as little reworking as possible and are easy to assemble.
The present invention provides these features by having a separate pawl carrier that receives a plurality of pawls directed outward and inward and arranged axially next to the driver, and also having a split ring gear for the receiving and supporting displaceable pawls. The pawl carrier sits on driving segments of the driver and the pawls are located on the periphery of the carrier. The pawls are engagable with the ring gear and are respectively oriented in a first rotational direction or a second rotational direction. The pawls are activated or deactivated by a cam element joined nonrotatably to the driver. The driving segments of the driver rotate the cam element about the hub shaft with zero-backlash. The pawl carrier is rotatable with respect to the driving segments, so that the corresponding spring-loaded pawls on the periphery of the pawl carrier are simultaneously engaged and disengaged by the cam element regardless of rotation direction. The cam element has several open spaces which form a cam profile which partially surrounds the pawls axially and, in the context of a relative rotation of the driver and the pawl carrier, bring about the radial motion of the spring-preloaded pawls.
The spring-preloaded pawls are also provided on the inside diameter of the pawl carrier. These pawls engage a coupler and are longer than a driving contour of the coupler. The pawls are engaged or disengaged via a control contour located on an axially displaceable shifting sleeve that is joined nonrotatably to the hub shaft.
During the shifting operation, the shifting motion of the selector element is transferred via a spacer bushing to the shifting sleeve that is axially preloaded by a spring. The spacer bushing is longer than the inside length of the spring-preloaded coupler. Such a configuration ensures that each shifting operation causes preloading of a spring, which does not execute a gear ratio change until a favorable shifting situation exists. As the selector element is displaced toward the planet gear, a displacement in the same direction of the preloaded shifting sleeve is thus already made possible, while the inwardly directed pawls on the pawl carrier are still engaged in the driving contour of the coupler. The preloaded shifting sleeve has a stop collar, a control contour, and a inclined collar that hold the pawls in the disengaged state. The stop collar diameter corresponds approximately to the root diameter of the driving contour of the coupler. The stop collar serves to pre-center the inwardly directed pawls on the pawl carrier. These pawls extend out beyond the driving teeth of the coupler, and which may result in the pawls being slightly tilted during nonuniform loading or an unfavorable tolerance situation. However, the tilting is compensated for by the pre-centering of the pawls which allows the control contour to hook under the pawls and disengage them from the driving contour on the coupler. The longer pawls allow for easier centering and hooking by the shifting sleeve. The unloaded coupler is then displaced by

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