Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid pump and motor in one of plural paths to or from...
Reexamination Certificate
2001-10-29
2003-03-18
Parekh, Ankur (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid pump and motor in one of plural paths to or from...
C475S074000
Reexamination Certificate
active
06533695
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of propulsion systems for vehicles. More particularly, this invention relates to a hybrid hydromechanical vehicle transmission that includes both a hydrostatic transmission and a planetary gear set.
Hydromechanical transmissions in general are discussed in U.S. Pat. Nos. 4,341,131 and 4,306,467. The complete disclosure of those patents is incorporated by reference herein. Low power transmissions are needed for various vehicles including but not limited to two-wheel and four-wheel all terrain vehicles (ATVs), farm tractors, lawn and garden vehicles, and utility vehicles. Conventional low power transmissions for such uses utilize variable belts. Unfortunately, variable belts often have very limited lives when exposed to the elements and can slip when wet. Thus, there is a need for a compact, low cost, continuously variable transmission that overcomes the limitations of the current, competitive variable belt technology.
Therefore, a primary objective of the present invention is the provision of an improved hydromechanical transmission.
Another objective of this invention is the provision of a hydromechanical transmission that is an improvement over variable belt driven transmissions.
Another objective of this invention is the provision of a hydromechanical transmission that does not require service access to a belt and therefore can be sealed in an oil tight compartment to protect it from external water immersion.
Another objective of this invention is a hydromechanical transmission design that can be easily tailored to different variable ratio range requirements for different vehicles.
A further objective of this invention is the provision of a hydromechanical transmission that has a space efficient layout and a simple, cost-effective gear design.
These and other objectives will be apparent to one skilled in the art from the drawings, as well as from the description and claims that follow.
SUMMARY OF INVENTION
This invention relates to a hybrid hydromechanical vehicle transmission that includes both a hydrostatic transmission and a planetary gear set. This transmission is designed to be a very compact integrated continuously variable transmission package. The hydromechanical transmission of this invention can be used as a complete transmission, or more probably, as a portion of a complete transmission package. In the latter case, a range gearbox could be added after this variable transmission to cover a wider range of torques and speeds.
The hydromechanical transmission includes a hydrostatic transmission connected to a planetary gear set. The hydrostatic transmission includes a variable displacement unit connected in a closed loop circuit to a fixed displacement unit. The planetary gear set includes a ring gear rotatably mounted in a housing, a carrier plate assembly with output shafts protruding therefrom, a plurality of planet gears rotatably mounted on the carrier plate assembly engaging the ring gear and a sun gear.
The gears of the planetary gear set can be removed and replaced with gears having a different number of teeth so as to change the overall ratio of the hydromechanical transmission without changing the power rating of the hydrostatic transmission or the size of the housing.
This set of components is capable of providing a continuously variable ratio between the input and output speeds and torques. As the variable hydrostatic unit strokes from maximum negative displacement to maximum positive displacement the transmission ratio will vary continuously from a deep reduction to nearly no reduction (1:1 ratio).
All the components are arranged along a common shaft centerline, i.e.—coaxially. The relative connections to the planetary elements (ring, sun, carrier) shown here are optimized to achieve a compact package and a single centerline. This coaxial design minimizes the relative speeds between components. At the maximum output speed all components are rotating at the same speed.
It is possible to use many different planetary ratios to tailor the transmission ratio spread and speeds. Also, the absolute and relative displacements of the hydrostatic kits can be changed to optimize the transmission to the application.
REFERENCES:
patent: 2296929 (1942-09-01), Ifield
patent: 4373408 (1983-02-01), Mills
patent: 4976666 (1990-12-01), Meyerle
patent: 5807199 (1998-09-01), Keller
patent: 5967927 (1999-10-01), Imamura et al.
patent: 11-2307 (1999-01-01), None
patent: 2000-179648 (2000-06-01), None
Bretz Lyle R.
Gluck Steven H.
Moline John D.
Pierce Thomas D.
Pollman Frederic W.
Parekh Ankur
Sauer-Danfoss Inc.
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