| 摘要 |
1426979 Variable-speed gear GENERAL MOTORS CORP 16 May 1974 [20 July 1973] 21774/74 Heading F2D A variable-speed hydromechanical drive system for a vehicle powered by a gas turbine engine of the kind having a free turbine constituting the output means, which delivers maximum torque when stalled, comprises a hydrostatic transmission of which at least the pump 26 is of variable displacement, first continuous drive means 28, 20 between the turbine 14 and the pump, a planetary gear set comprising a sun gear 46 connected by second continuous drive means 34 with the motor 30, a ring gear 48 connected to the output shaft 54, and planets 50 meshing with the sun and ring gears and mounted on a carrier 42 which is connectible by selectively engageable clutches 22, 36 with the first and second continuous drive means. The arrangement allows use of hydrostatic units with relatively low torque handling capacity by enabling power to be transmitted solely mechanically at low speeds, when torque is highest. As shown, both pump and motor are of variable capacity, having servo adjusting means 28, 32, and the carrier 42 may be held by a brake 40 for reversing. When starting, both pump and motor are set to the same displacement, the brake 40 is released, and clutches 22, 36 are engaged, so that drive is transmitted from the turbine, which may start from a stalled condition, direct to the output shaft 54, the planetary train being locked by the clutch 36, and the pump and motor rotating idly in unison. When the turbine reaches its maximum speed the clutch 36 may be disengaged whereupon the planets will attempt to drive the sun and motor at increased speed so that the pump acts as reaction means. The pump displacement may now be reduced to slow down the motor and sun so that output speed is increased. Further increase of output speed is obtained by adjusting the pump displacement through zero to maximum displacement in the opposite sense, followed by reduction of the motor displacement. For reverse drive the pump is set initially at zero displacement, clutches 32, 36 are disengaged, and the brake 40 is applied. The motor and sun will then drive the ring gear through the non- orbiting planets as the pump displacement is increased. As operation in this mode is limited by the torque handling capacity of the pump and motor means may be provided for limiting the hydraulic system pressure. Various alternative modes of operating the drive system are described. To enable full torque to be transmitted in reverse a modification is described having a reversing gear between the turbine and the clutch 22. |
