Patent GB-633388-A (GB)
Title: Power transmission mechanism for motor vehicles
IPC: F16D67/00
Filed: 1947-07-18
Abstract: 633,388. Hydro-mechanical variable-speed gear. GENERAL MOTORS CORPORATION. July 18, 1947, No. 19252. Convention date, Dec. 15, 1941. [Class 80 (ii)] A four-speed and reverse gear, for a motor-vehicle, comprises a fluid-coupling, the impeller 20 of which is driven from the inputshaft 1 through a clutch-braked planetary input train 52, providing direct and reduced ratios, whilst the coupling-runner 21 is permanently and directly connected through a central shaft 13 with two integral suns 51, 51a of a compound planetary output train, comprising a first ring-gear 64 adapted to be held by a band-brake 70 or drivingly connected by a disc-clutch 67 and concentric outer shaft 8 with the input impeller 20 of the fluidcoupling ; a second ring-gear 64a integral with the first planet-carrier 71 ; and a second planet-carrier 71a integral with the output shaft 50. In second and high ratios the drive is branched through the fluid-coupling and a mechanical path, whilst in low and third, the whole of the drive torque passes through the fluid-coupling. The planetary input train comprises a ring-gear 54 always fast with the input shaft 1 through a drum 3 ; a planet-carrier 52 always fast, through the sleeve 8 with the coupling input impeller 20 ; and a reaction sun 55 which can be held by a band brake 60 to drive the fluid-coupling at reduced speed, or clutched solid to the planet-carrier to drive the fluid-coupling at engine-speed. Gear operation. With the output train brake 70 engaged to provide reduced drive in the output train, low and third ratios are provided by driving the fluid coupling at reduced- or engine-speed by engaging either the input-train brake 60 or clutch 61 respectively, all the drive-torque passing through the fluid-coupling 20 and inner shaft 13 to the output-train suns 51, 51a. With the output-train brake 70 released and clutch 67 engaged, the ring-gear 64 and suns 51, 51a of the output train are driven at the same speed by the output planet-carrier 52 of the input train, the ring-gear 64 being driven mechanically through the sleeve 8 and clutch 67 ; the suns 51, 51a having a fluid drive through the fluid-coupling and inner shaft 13, the drives being combined in the output train and passed to the output shaft 50 at one-to-one engine-speed for high or at the reduction ratio of the input train alone for second ratio according as to whether the input-train clutch 61 or brake 60 respectively is engaged. Reverse. Reverse is provided by engaging the input-train brake 60, releasing both the output-train brake 70 and clutch 67, and applying a radiallysliding detent 80 to hold the freely-mounted ring-gear 77 of an additional train, the planet-carrier of which is fast on the output shaft 50, whilst its freely-mounted sun 75 is fast to the first output-train ring-gear 64. The additional train is thus compounded with the two output trains for reverse. The detent 80 is applied through a spring 81 by turning a crankshaft 22. Clutch-brake operation. The brakes 60, 70 are operated by fluid-pressure through pistons in single laterally-mounted cylinders acting on one end of each band, whilst the disc-clutches 61, 67 are engaged by groups of pistons 86, 91. The brakes may be applied by spring-pressure assisted by fluid-pressure if required, and released by the same fluid-pressure as that supplied to engage the clutch of the same train. The reversed arrangement, viz., spring and pressure disengagement, and pressure engagement, may alternatively be used. Fluid controls. The clutch and brake of each train are controlled by a common pressure-balanced piston-valve, one for each train, to which oil-pressure is supplied by single engine-driven gear-pump 30 having a relief-valve, the spill from which is led to a space between the concentric shafts from which radial ports 130, 132 &c., lead oil to the gears for lubrication. The pump also supplies oil through a passage 15 to the fluid-coupling drum 3, excess pressure in the coupling being relieved at 17 either to the lubrication line or to the sump. The clutch-brake valve of the output train has three positions giving engagement of either the clutch or brake or release of both, the latter for neutral and reverse, whilst the valve of the input train may have only two positions or a similar additional neutral position so that all the clutches and brakes are disengaged for neutral. The reversedetent control-shaft 22 is operated mechanically by the common control (not described), for the two shift-valves. Valve-control may be manual or automatic, operating through mechanical, electrical or fluid-pressure means. Specifications 492,084 and 630,938 are referred to.