Patent ID: 6485387
Filing Date: 2002-11-26
Classification: F16H

Abstract:
A hydro-mechanical transmission adapted to be driven by an engine comprising:a variable speed hydrostatic unit having a pump and a motor with a hydrostatic unit output shaft whereby the hydrostatic unit output shaft speed is variable; a planetary system having first and second planetary gear sets, the first planetary gearset having a sun gear (S1) adapted to be driven by the engine, planet gears (P1) and a planet carrier while the second planetary gearset includes a ring gear (R2) driven by the hydrostatic unit output shaft, a sun gear (S2) and planet gears (P2) integral with the planet gears (P1) and carried by the planet carrier, whereby the carrier speed is a function of the speed of the sun gear (S1) and the speed of the ring gear (R2); the transmission further having a reversing planetary gearset having a sun gear (S3) driving a transmission output shaft and planet gears (P3) carried by the planet carrier and a pair of clutches including a low range clutch (CL) and a high range clutch (CH), the clutches (CL), (CH) being selectively engagable to connect the carrier or the sun gear (S2), respectively, to the output shaft; an electronic transmission controller that commands a desired hydrostatic unit output shaft speed; and a pair of transmission speed sensors providing feedback to the controller of the hydrostatic unit output shaft speed, the first sensor of the pair directly measuring the speed of the hydrostatic unit output shaft and the second sensor indirectly measuring the speed of the hydrostatic unit output shaft by measuring the speed of a transmission element driven by the first planetary gear set from which the speed of the hydrostatic unit output shaft can be determined based on the speed of sun gear (S1) and gear ratios of the gears.