Patent GB-1113709-A (GB)
Title: Variable-ratio power transmission mechanisms
IPC: F16H47/04
Filed: 1966-10-06
Abstract: 1,113,709. Motor vehicle driving gear; brake arrangements. GENERAL MOTORS CORPORATION. 6 Oct., 1966 [23 Oct., 1965], No. 44620/66. Heading B7H. [Also in Division F2] In an hydro-mechanical variable-speed gear for a heavy duty wheeled vehicle (single output) or, .as shown, track-laying vehicle (dual outputs), wherein aniinput:shaft 12 is .connected to one input element of a planetary gear 28 via a variable-ratio hydrostatic gear, such as 22, and to a further input element of the planetary gear via a friction clutch, such as 66, an element of the planetary set is .stationed by a friction brake, such as 56, for drive through the hydrostatic gear in a low ratio range, and the clutch 66, and brake 56, are respectively engaged and disengaged for split-torque drive simultaneously through the hydrostatic gear and the clutch for a higher ratio range, the driving and driven members of the clutch and the rotary and stationary members of the brake being arranged to be synchronized for upshift and downshift respectively at a maximum output speed of the hydrostatic gear. The hydrostatic gear permits optimum speed and torque operation of a prime mover such as a diesel engine, or constant speed of a prime mover, such as a gas-turbine engine. The track-laying vehicle drive shown .comprises, from a single prime mover 10, duplicate propulsion and steering drives to track-powering output shafts 14, 16. The input shaft 12 is, by bevel gears 30, 32 permanently. connected to drive pumps 38 of F-N-R hydrostatic .gears 22, 24 and is connectible by Forward and Reverse clutches 18, 20 to a common cross-shaft 64 carrying the driving members 82 of the clutches 66. The pumps 38 .are controlled ,for forward and reverse variable speed hydrostatic drive by controls 46. Each pump 38 drives a .fixed displacement motor 40 the.output shaft 44 of which carries suns 50, 51 of sunring trains 48, 49 respectively comprising also a carrier 54 brakable at 56 and a ring 58 fast with the output shaft 14, (16), and a carrier 60 also fast with said output shaft and a ring 62 connected by gears 70, 68 to the driven member 81 of the clutch 66. Parallel mechanical and conventional hydrodynamic brakes 74, 76 are provided to act on the output shafts, normal braking being hydrodynamic and by engine braking, and severe braking being mechanical. Operation.-In Low ratio range, with the Forward or Reverse clutch 18 or 20 engaged, and the clutches 66 disengaged, the brakes 56 are engaged and by control of the controls 46 drive is through the hydrostatic gears 22, 24 and the train 48, the rotation of the motor output shafts 44 being the " reverse " of that of the output shafts 14, 16. In the Low ratio range the train 49 rings 62 and gears 70, 68 are also rotated such that when said " reverse " motor rotation reaches its maximum speed the driving and the driven members 82, 81 of the clutches 66 are synchronized for upshift to High ratio range. This upshift at synchronism is effected by disengaging and engaging the brakes 56 and the clutches 66 respectively for split torque hydro-mechanical drive through the trains 49 output shaft speed in High ratio range is then continuously increased by bringing the motor speed from said maximum " reverse " through zero to maximum " forward." The drive is 100% mechanical with zero motor speed. In the Low ratio range change from Forward to Reverse can be effected without engagement or disengagement of clutches. Steering in both Low and High ratio ranges is accomplished by either independent (allowing true pivot steer) or simultaneous control of the hydrostatic gears 22, 24. In Fig. 2 (not shown), wherein shift to High ratio range is at lower speeds, the ring of one of the trains is brakable for Low ratio range and the carrier of the other train is connectible to the cross-shaft 64 by the High range clutch. In Fig: 3 (not shown), two split-torque ratio ranges, viz Intermediate and High are provided. The ring of one train is brakable for Low and connectible with the cross-shaft 64 by a High range clutch, and the carrier of the other train is connectible to the cross-shaft 64 by an Intermediate range clutch. Change between Low and Intermediate and Intermediate and High ratio ranges is carried out at synchronism respectively of the members of the Intermediate and High range clutches. Speed increase continuously and successively through the Intermediate and High ratio ranges is by bringing the motor speed from maximum in one direction through zero to maximum inthe other direction in Intermediate ratio range and then reversing the procedure in High ratio range. In Fig. 4 (not shown), propulsion is by a single hydro-mechanical drive, and steering is by a separate F-N-R variable-ratio hydrostatic gear (128). The output shaft of the propulsion drive is connected to the ring gears of two sun-ring trains (124), (126) the-carriers of which are connected to track-powering output shafts and the suns of which are connected by direction reversing gearing to the output of the steering hydrostatic gear (128). In the single hydro-mechanical propulsion drive, providing Low, Intermediate and High ratio ranges, the carrier of one train is brakable for Low and connectible with the input shaft by a High range clutch, and the ring of the other train is connectible with the input shaft by an Intermediate range clutch, the operation of this drive being. similar to that of Fig. 3 (not shown). Mechanical vehicle brakes are provided for the track-powering output shafts.