GB721353A - Variable speed transmission - Google Patents

Abstract

721,353. Change-speed gear. COSTA, G., and BRERO, E. Aug. 1, 1950, No. 19190/50. Class 80 (2). An automatic direct overdrive planet unit, for installation between a main clutch and a manual direct-reduced gear (not shown) on a motorvehicle, comprises planets 11 carried by a clutchdriven input shaft 5, a ring-gear 12 carried by an aligned intermediate shaft 8, a one-way clutch 7 directly connecting the shafts for one-to-one forward drive, and a reaction sun 13, which is prevented by a one-way detent 15 from reverse rotation, and is also capable of being held for bi-directional overdrive by a fluid brake. The latter comprises a gear pump 50 driven by the reaction sun 13 and rendered effective by throttling under control of a centrifugal governor 20, which is driven through reducing gear by the intermediate shaft 8, and acts on a valve 57, which in the idle position shown, connects both input and delivery 52, 53 of the pump to an air space of a hydraulic fluid tank 56, and in the operative position (left) connects the input 52 to the fluid space and blanks the delivery 53 to brake the sun 13 for overdrive. Connected with lost-motion 33 to the governor-valve linkage is the usual clutch-pedal 31, depression of which, necessarily made during a shift in the manual unit, overcomes the governor and permits the valve 57 to return to the brake-release position, shown. An additional manual control may also be provided for the valve 57, and brake engagement is cushioned by a spring-loaded piston 61 in the brake-pump delivery line 53. Governor spring loading may be manually adjustable, Fig. 3 (not shown). The manual change-speed gear provides two ratios; 3 to 1 and 1 to 1, whilst the planetary gear provides 1 to 1 and 1 to 1.5. Shift sequence is as follows-On accelerating from start in first speed, overall direct-reduced 3 to 1, the governor 20 operates at an engine speed of 4,000 r.p.m. to upshift the planetary unit automatically, giving second speed, overall overdrive-reduced (2 to 1). Upshift to third is commenced in the manual unit, and the accompanying depression of the clutch-pedal 31 operates the valve 57 to downshift the planet unit, giving third speed overall direct-direct (1 to 1), which persists after release of the clutch-pedal 31 since the combined shifts have reduced the speed of the intermediate shaft 8 below governor cut-in speed. On further acceleration to governor cut-in speed, the planetgear again upshifts; giving fourth speed, overall overdrive-direct (1 to 1.5). Downshift occurs similarly, and to avoid loss of engine speed on an upgrade may also be induced in the planet unit by momentarily depressing the clutch-pedal.