GB607120A - Improvements in or relating to variable-speed power transmission mechanisms - Google Patents

Abstract

607,120. Variable-speed gearing. EVERNDEN, H. I. F. Nov. 3, 1944, No. 21608. [Class 80 (ii)] [Also in Group XXIX] A sun and ring-gear epicyclic reversing-gear 44 is driven by a hydraulic torque-converter of the kind in which, to produce unit ratio, either the reaction-wheel 35, Fig. 1, can be clutched to the converter driven member 33 by a clutch 41 to change from fluid-converter to fluidcoupling or the final driven member 25, Fig. 3, can be clutched at 27 to the driving member 12 to change from fluid-converter to mechanical solid drive, the change from converter to unit-ratio drive being under the joint automatic control of output-shaft speed (i.e. road speed on a vehicle) and the position of the engine throttle - pedal, acting through pneumatic, hydraulic or electric means. In Fig. 1, the converter reactionmember 35 is connected through a forward-overrun one-way clutch 95 with a brake-drum 37, which, for torque conversion, is held by a brake-band 38 and, for unit-ratio fluid-coupling drive, is clutched to the converter-driven shaft 34, to which is secured the converter-driven member 33 and also the driving sun 42 of the reversing-gear, the driven ring-gear 45 of which is secured to the final output shaft 46. The converter driving member 32 is connected to the driving shaft 30 through a flexible coupling 31. For forward drive, the reversing-gear is locked solid by engaging a clutch 47 between the ring-gear and planet-carrier, whilst, for reverse, the clutch is released and the carrier held by a brake-band 48. In Fig. 3, the reversing-gear, similarly controlled by a clutch 26 and brake 23, has its driving sun 19 connected through a one-way clutch 17 with the driven member 16 of the converter, and the driving shaft 12 carries one half of the solid-drive clutch 27, the other half of which forms one half of the forward-drive clutch 26 between the planet-carrier and the final output shaft 25. The converter reaction member 14 is permanently fixed. Speed- and throttle-responsive hydraulic control for the Fig. 1 form comprises pumps 51, 52, Fig. 2, the former driven by the driven member 33 of the converter, the latter, 52, by the output shaft, so that oil-pressure is always available, the suction of the converter-driven pump 51 being cut off at 93 by the attainment of a suitable working pressure by the outputdriven pump 52. Each pump has its own relief-valve 53, 58 and feeds a forward-neutralreverse manual selector-valve 55 and a centrifugally-controlled valve 64 driven by the output shaft so as to supply speed-responsive oil-pressure to a line 65 leading to the piston of a shift-valve 69. In its forward position shown, the manual selector-valve 55 directs pressure-fluid through lines 77, 75 to engage the forward-drive clutch 47 and disengage the reverse-brake 48, and, through a line 70, shiftvalve 69 and a line 71, to engage the converter reaction-brake 38. Speed-responsive oil-pressure in the line 65 from the centrifugal valve 64 acts on the shift-valve 69 in opposition to a spring 78 adjustably loaded in accordance with the position of the engine-throttle pedal 81, so that at predetermined values of vehicle speed and throttle opening, the shift-valve 69 is moved to the right to supply pressure through a line 72 to disengage the converter reaction-brake 38 and engage the clutch 41 to change from converter to fluid-coupling drive, the shift-speed being higher at larger throttle-openings. In the neutral position of the manual valve 55 all the members may be freed'or, as shown, pressure is directed through lines 74, 75 to engage the converter-coupling clutch 41 and disengage both brakes, so that the converter idles as a coupling, or alternatively to engage only the converter reaction-brake 38 so that it idles as a converter. In the reverse position the epicyclic reverse-brake 48 and converter-coupling clutch 41 are engaged. The control of the Fig. 3 form (Fig. 4, not shown), functions in an equivalent manner.