Patent GB-1061379-A (GB)
Title: Improvements in or relating to gear ratio changing devices, particularly for vehicles
IPC: B60W30/18
Filed: 1964-08-04
Abstract: 1,061,379. Hydro-mechanical variable speed gear and control. SOC. ANON ANDRE CITROEN. Aug. 4, 1964 [July 31, 1963], No. 31424/64. Heading F2D. In a combination of an hydro-dynamic torque converter 1 and a change speed gear 3, particularly for automobile vehicles, arranged between driving and driven shafts 8, 9 and providing automatic hydro-mechanical to mechanical only ratio shift in at least one range, dog clutch sleeves 17a, 18a each having at least one gear engaging position are manually slidable respectively on coaxial relatively rotatable shafts 17, 18, respectively, connectable to the torque converter turbine 11 through a one-way clutch 16 and to the driving-shaft 8 of the converter through a converter by-pass friction plate clutch 5 automatically hydraulically engaged in response to driving-shaft speed and torque. Whilst the gear shown is for a front drive vehicle, the shaft 9 driving the road wheels through a bevel gearing, a leftwardly projecting output may be accommodated, as by using a small diameter multi-disc clutch at 5. The change-speed gear may comprise two loose gears constantly meshing gears fast on the driven shaft and providing one range with one automatic shift; or, as shown, gears 35, 36, 37 loose on the shafts 17, 18, constantly meshing gears 38, 39, 40 fast on the driven shaft, and providing an automatic shift in two manually selected ranges. Whilst, as shown, the automatic high ratio of the manual low range is the same as the automatic low ratio of the manual high range, the sleeves 17a, 18a both being engageable with the gear 38, the latter may be replaced by two gears providing different ratios. The torque converter comprises a reactor 13 reacting on a one-way detent 14. The dog clutches comprise known synchronizing means, and the sleeves 17a, 18a are moved together by forks 43, 44 on a rod 45 shiftable by a gear-shift lever 46. For Reverse an idler gear (not shown) is engaged, as by the lever 46, with gears 54, 55, respectively, on the shafts 17, 9. The by-pass clutch 5 is actuated, through a bearing 30 and levers 28, by pistons 31 in cylinders 7a pressurized through a valve (33) (Fig. 3, not shown) from a fluid pressure source (32) provided by the converter filling pump, separate pump, or external feed. The valve (33) is controlled by a device (34) responsive to driving shaft speed and torque. Operation.-In Low Range, with the sleeves 17a, 18a rightwardly shifted to clutch gears 35, 36, respectively, to the shafts 17, 18, drive is hydro-mechanical through the torque converter, one-way clutch 16, shaft 17, and gears 35, 38 until the by-pass clutch 5 is automatically engaged by the speed and torque responsive device (34) and the valve (33), for mechanical only drive through a shaft 25, clutch 5, shaft 18 and gears 36, 39, the one-way clutch 16 releasing. In High Range with the sleeves 17a, 18a leftwardly shifted to clutch gears 36, 37, respectively, to shafts 17, 18, drive is hydro-mechanical through the torque converter and the gears 36, 39 until the by-pass clutch is automatically engaged for mechanical only drive through the gears 37, 40, the one-way clutch 16 releasing. To facilitate manual shift with the vehicle stopped and the engine running slowly, an electric switch (52) is actuated by movement of the gear shift lever 46 to open a valve (51) to connect a fluid pressure source to cylinders of brake pistons which act on the periphery of the driving drum 15 of the one-way clutch 16 and thereby brake the torque converter turbine 11. The lever 46 may be flexible or articulated so that the switch (52) may be actuated before the rod 45 is moved. The control for braking the drum 15 may, alternatively, act to release elements for braking. To facilitate manual range-shift at high speeds the switch (52) is arranged to close the valve (33) and disengage the clutch 5. When range-shifting in hydro-mechanical drive, the driver releases the accelerator pedal so that the one-way clutch 16 automatically disconnects, thereby negating the necessity for braking the drum 15, the control of which may be suppressed (by means not described) when the driving shaft speed is sufficiently high.