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
2000-06-16
2002-01-15
Estremsky, Sherry (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...
C475S080000, C475S082000
Reexamination Certificate
active
06338689
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 hydraulic transmission and a planetary gear set. The hybrid transmission has multiple modes of operation and provides greater control of corner horsepower. The hybrid hydromechanical transmission of this invention is flexible in maximum output torque, maximum output speed, and maximum corner power without the need to alter the physical layout of the gears or change the size of hydrostatic transmission.
When similar vehicles are produced with different engine power levels, they frequently have requirements for a different “corner horsepower” value. The corner power is defined by the product of the maximum output torque and maximum output speed. See the dashed lines in FIG.
10
. The engine power and the required vehicle corner power normally vary somewhat in proportion, as limitations of tractive effort or vehicle speed also vary with engine power. When using gear transmissions, this may be accommodated without changing the transmission ratios as vehicle corner power is determined by the product of engine power and overall gear transmission ratio.
When using a hydraulic transmission, the vehicle corner power is defined by the product of maximum hydraulic unit torque and speed, and is usually not affected by engine power. Hydromechanical transmissions in general are discussed in U.S. Pat. No. 4,341,131 and 4,306,467. The complete disclosure of those patents is incorporated by reference herein.
There is a need for a hydromechanical transmission which provides greater flexibility and represents an improvement over the prior art. Thus, a primary objective of the present invention is the provision of an improved hydromechanical transmission.
A further objective of this invention is the provision of a hydromechanical transmission that uses the same hydraulic units and the same gear layout to achieve different hydromechanical corner horsepower outputs.
A further objective of this invention is the provision of a hydromechanical transmission that can provide at least two substantially different levels of overall corner horsepower while maintaining a constant package size for installation in a vehicle.
A further objective of this invention is the provision of a hydraulic unit and gear configuration that is flexible in maximum output torque, maximum output speed, and maximum corner power.
A further objective of this invention is the provision of a hydromechanical transmission that has a plurality of clutches that are used to establish a corresponding plurality of modes.
A further objective of this invention is the provision of a hydromechanical transmission with a compound gear set having a rotatable carrier plate assembly that has two powered output shafts extending therefrom for front and rear output.
A further objective of this invention is the provision of a hydromechanical transmission that has two centerlines and front and rear outputs.
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.
A further objective of this invention is the provision of a method of changing the overall corner horsepower of a hydromechanical transmission without changing the power rating of its hydrostatic transmission or the size of the planetary gear set housing.
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 THE INVENTION
An improved hydromechanical transmission includes a hydrostatic transmission driven by an engine and drivingly connected to a compound 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 so that at least some engage the ring gear, and sun gears meshed with the planet gears.
A first drive gear is drivingly attached to the input shaft of the variable unit and a second drive gear is drivingly attached to the output shaft of the fixed unit. A plurality of clutches are associated with elements of the planetary gear set to establish a plurality of operating modes in which additional overall transmission speed can be achieved while reducing the power consumed by the hydrostatic transmission.
Two-mode and three-mode configurations of the hydromechanical transmission of this invention are disclosed below, as well as their operation and the method of switching between them. 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. Thus, multiple overall corner horsepower capabilities can be provided with the same hydrostatic transmission and housing package size.
REFERENCES:
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patent: 5931758 (1999-08-01), Walter
patent: 5960671 (1999-10-01), Nguyen
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patent: 6090005 (2000-07-01), Schmidt et al.
patent: 6257086 (2001-07-01), Peterson
Estremsky Sherry
Sauer-Danfoss Inc.
Zarley, McKee, Thomte, Voorhees & Sease P.L.C.
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