GB814999A - Improvements in or relating to automatic variable speed transmissions - Google Patents

Abstract

814,999. Change-speed gear. DUFFIELD, W. A. Aug. 30, 19.56 [Sept. 2, 1955], No. 26570/56. Class 80 (2). An automatic change-speed gear for a vehicle comprises an hydrodynamic torque-converter 10 of the overrun reactor type, which drives through countershaft gearing 57 &c. at one ratio and is automatically by-passed by a friction clutch 63 at a numerically lower mechanical ratio in response only to countershaft speed, together with a manual range selector 71, providing two or three ranges of operating ratios. In low range the synchromeshed clutch 71 is manually slid rearwards -to clutch an output shaft 69 to a freely mounted toothed wheel 68. First ratio drive passes from the engine crankshaft 13 through the torque converter 10, a release clutch 27, wheels 51, 57, one-way clutch 58, countershaft cluster 59, wheels 66, 68 and clutch 71 to the output shaft 69. At a predetermined adjustable speed of the countershaft 59, a centrifugal switch (Figs. 2 and 3, not shown), driven by a countershaft wheel 65, energizes a solenoid valve directing pressure from the engine lubrication system through a line 122 to act on a piston 128 engaging the disc clutch 63 in opposition to torque-converter pressure to provide a direct mechanical drive to an inner shaft 20 and thence, through meshing wheels 62, 61, to the countershaft, overrunning the one-way clutch 58, to drive through the wheels 66, 68, as before, but-now at higher speed. To shift to high range the synchromeshed clutch 71 is manually moved forwards to clutch the output shaft 69 direct to the inner shaft 20. The converter-driven low ratio is now through the wheel pairs 51, 57 and 61, 62, and the automatic upshift is to mechanical direct drive. For reverse, the synchromeshed clutch 71 is neutralized and a splined output wheel 81 is slid axially to mesh a countershaft-driven idler 82. Automatic upshift as above can still occur. An additional manual forward range may be provided by meshing the sliding wheel 81 with an additional countershaft wheel (Fig. 7, not shown). The release clutch 27 is released in neutral by mechanical, hydraulic or vacuum means not described. Torque converter pressure is regulated by a relief valve 137 spilling to a lubrication line 138 for a bearing 21. A one-way clutch 56 is arranged directly between the wheel 51 and the shaft 20 to prevent free-wheeling of the vehicle when the by-pass clutch 63 is disengaged.