Continuously variable reversible transmission

Details Continuously variable reversible transmission Continuously variable reversible transmission

2002-06-14

2004-05-04

Hannon, Thomas R. (Department: 3682)

Endless belt power transmission systems or components

Pulley with belt-receiving groove formed by drive faces on...

Including actuator interconnecting plural pulleys on spaced...

C474S008000

Reexamination Certificate

active

06729985

ABSTRACT:

This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/AU00/01568 which has an International filing date of Dec. 18, 2000, which designated the United States of America.
The present invention is directed to the area of mechanical continuously variable power transmissions, in particular continuously variable transmission (CVT) systems for vehicles.
There is presently a trend towards the use of CVT systems in automobiles, beginning in the super-mini class and progressing through to mid-size luxury vehicles. There are many advantages to using a CVT system over a conventional manual or automatic transmission, for example, improvements in economy, performance and versatility. Electronic control easily allows the CVT to be switched between automatic operation and a “manual” mode where it can emulate a clutch-less manual transmission on demand. However most of the CVT systems proposed to date have been limited in that they need additional arrangements of gears to provide reverse and neutral functions.
A small number of prior art CVT systems which can continuously vary the output from a range of forward speeds, though zero to reverse ratios have been proposed. These can have additional application in mopeds and motorcycles as they include an integral reverse. They all use twin, parallel power transmission paths, one path including a CVT, to achieve the desired result of a CVT which can continuously vary the output ratio between two opposite directions, passing cleanly through zero. This prior art can be grouped into two basic arrangements. The first arrangement, proposed by Cowan in U.S. Pat. No. 5,121,936 and by Wilkes et al. in WO 98/54489, uses a planetary gear set to combine the output of the parallel transmission paths of the CVT and another direct or geared drive, such that the final output may vary continuously through a range of forward speeds, zero, and reverse. The second arrangement, proposed by Suzuki in JP 10-274293 and Kanetani JP 8-61459 utilises a differential to combine the CVT path and the linear power transmission path to achieve the same result of a CVT which can continuously vary the output ratio between two opposite directions, passing cleanly through zero. All of these arrangements can be quite bulky and involve more complexity and parts as they use planetary gear-sets or differentials in addition to a CVT.
It is therefore the object of the present invention to provide a continuously variable reversible transmission (CVRT) which overcomes some or all of the disadvantages of the prior art, namely complexity and package size.
With this object in view, there is provided by the present invention a continuously variable reversible transmission system including an input shaft, a housing, an input arm, first and second CVT shafts, a fixed input wheel, a ratio selector mechanism, an overall output wheel and an output shaft. The input shaft has a major axis and the input arm may be fixed to the input shaft, the input arm may include at least first and second portions, each input arm portion extending substantially perpendicular to the input shaft. At each end of the input arm first and second portions, a respective first and second CVT shaft may be rotatably mounted, each of the first and second CVT shafts having a respective major axis extending substantially parallel to the input shaft, the major axis of each of the respective first and second CVT shafts being the axis of rotation of the respective shaft with respect to the input arm.
The fixed input wheel may be aligned with the major axis of the input shaft, the first CVT shaft may be coupled with the fixed input wheel, the second CVT shaft may be coupled with the first CVT shaft, the overall output wheel may be coupled with the second CVT shaft, and the overall output wheel may be fixed to the output shaft. In this arrangement, the first and second CVT shafts may orbit around the major axis of the input shaft due to rotation of the input shaft, such that changing a ratio of at least one of the couplings produces a variation of the speed of the output shaft from forwards, through zero to reverse.
The continuously variable reversible transmission may include a CVT sub-assembly which rotates about the major axis of the input shaft, the CVT sub-assembly including the input arm, the first and second CVT shafts, a CVT input wheel and a CVT output wheel. The CVT input wheel may be mounted on the first CVT shaft such that relative rotation of the CVT input wheel and the first CVT shaft is prevented. The CVT output wheel being mounted on the second CVT shaft such that relative rotation of the CVT output wheel and the second CVT shaft is prevented. The coupling of the first CVT shaft with the fixed input wheel may include the CVT input wheel, and the coupling of the second CVT shaft with the overall output wheel including the CVT output wheel. The rotation of the CVT sub-assembly may thereby cause rotation of the CVT input wheel relative to the fixed input wheel, resulting in a rotation of the first CVT shaft about its major axis in addition to its orbit about the major axis of the input shaft. The coupling between the first CVT shaft and the second CVT shaft in the CVT sub-assembly may be arranged to permit a variable rotation of the second CVT shaft relative to the first CVT shaft, producing a variable CVT ratio. The variable rotation of the second CVT shaft and the CVT output wheel about the major axis of the second shaft in addition to the orbit of the second shaft about the major axis of the input shaft may thereby cause a rotation of the overall output wheel due to the coupling between the CVT output wheel and the overall output wheel, the overall output wheel being fixed to the output shaft. The rotation of the output shaft may then be zero when the CVT ratio is of a set magnitude. As the CVT ratio is increased above the set magnitude, the output shaft turns in a forward direction and as the CVT ratio is decreased below the set magnitude, the output shaft turns in a reverse direction.
The set magnitude of the CVT ratio required to produce zero rotation of the output shaft may be calculated from the effective pitch circle diameters of at least the CVT input wheel, the CVT output wheel and the overall output wheel. As the transmission system is a planetary arrangement, the sizes of the components are all interrelated. Other dimensions can therefore be substituted to enable the same calculation using different combinations of dimensions.
The fixed input wheel and the CVT input wheel may both be toothed gear wheels. The fixed input wheel may be an external tooth gear wheel, like a sun gear in a conventional planetary gear system. Alternatively, the fixed input wheel may be an internally toothed gear wheel meshing with the CVT input wheel like a ring gear in a planetary gear system.
Alternatively the coupling between the fixed input wheel and the CVT input wheel may be achieved by using a looped link, such as a belt, chain or other form of segmented strap. If the fixed input wheel and the CVT input wheel are pulley wheels, then the looped link may be a belt. If these pulley wheels are of variable width, the pulley wheels and belt may thereby provide a variable ratio of the coupling between the fixed input wheel and the CVT input wheel. However, in yet another possible alternative, the looped link may be a chain.
Similarly, on the output side, the overall output wheel and the CVT input wheel may both be toothed gear wheels. The overall output wheel may be an external tooth gear wheel like a sun gear in a conventional planetary gear system. Alternatively, the overall output wheel may be an internally toothed gear wheel meshing with the CVT output wheel like a ring gear in a planetary gear system.
The coupling between the overall output wheel and the CVT output wheel may be by a looped link which can be any belt or chain type device, for example it may be a segmented strap. If the overall output wheel and the CVT output wheel are pulley wheels then the looped link may be a belt,

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