Patent ID: 6338689
Filing Date: 2002-01-15
Classification: F16H

Abstract:
A variable ratio hydromechanical transmission for propelling a vehicle, comprising:a hydrostatic transmission having a given corner horsepower and including a variable displacement hydraulic unit with a shaft connected to a source of rotational power and drivingly connected to a first drive gear, a fixed displacement hydraulic unit fluidly connected to the variable displacement hydraulic unit in a closed loop circuit and having a shaft drivingly connected to a second drive gear; a compound planetary gear set including a rotatable ring gear mounted in a housing of a given size, a carrier plate assembly rotatably mounted in the ring gear, and four gear elements rotatably and removably mounted on the carrier plate, the four gear elements including a first sun gear having given number of teeth thereon and being driven by the second drive gear, a first planetary gear having a given number of teeth thereon for mating with the first sun gear, a second sun gear connectable to the first drive gear and having a given number of teeth thereon, and a second planetary gear having a given number of teeth thereon for simultaneously mating with the first planetary gear, the ring gear and the second sun gear; the carrier plate assembly including oppositely directed centrally located power output shafts rigidly mounted thereto and extending to define an axis of rotation; the planetary gear set defining gear ratios K1 and K2; K1 having a numerator equal to the number of teeth on the ring gear and a denominator equal to the number of teeth on the first sun gear; K2 having a numerator equal to the number of teeth on the ring gear and a denominator equal to the number of teeth on the second sun gear; a first clutch for selectively fixing the ring gear to the housing so as to prevent rotation of the ring gear relative to the housing and thereby act as a brake; a second clutch selectively connecting the first drive gear to the second sun gear; at least one of the ratios K1 and K2 of the planetary gear set being changeable by removing one of the four gear elements and replacing the removed element with another element having a number of teeth thereon that is different from the number of the removed element without changing the size of the housing and the corner horsepower of the hydrostatic transmission.