Patent GB-1472055-A (GB)
Title: Control system for a transmission
IPC: B60W30/18
Filed: 1973-04-06
Abstract: 1472055 Hydrodynamic transmission control; Change-speed control SRM HYDROMEKANIK AB 8 April 1974 [6 April 1973] 16734/73 Headings F2W and F2D A vehicle transmission comprising an hydraulic torque converter and a forward/reverse gear, the torque converter consisting of pump and turbine members either of which can be released from its respective input or output shaft, and a reaction or guide member whose rotation is governed by brake means, is controlled by a pressure fluid system including valve means for controlling the releasable member and the brake means and subject to control by means sensing the ratio of output to input shaft speed (<SP>n</SP>2/ n 1) and manual remote control means. Torque converter and forward/reverse gear construction.-As shown, the pump member 11, Fig. 1, is movable axially to the right by pressure fluid admitted through a passage 24 and the hollow output shaft 15 so that it is driven by the shaft and rotating casing 10 by engagement of mating conical surfaces 25. It is also movable to the left by fluid admitted through a passage 23 and the annular space between the output shaft 15 and a tubular shaft 16 to effect direct drive by urging a disc 26 on the output shaft into engagement with the casing 10. Equal pressures applied in the passages 23, 24 result in the pump member taking up an intermediate, neutral position. The turbine member, which consists of two sets of blades 12, 13, is mounted on the output shaft 15 connected to the forward/reverse gear 21 which comprises bevel planetary gearing in which the forward/reverse selection is effected by axial movement by a servopiston (not shown) of a disc 28. The reaction member 14 is connected by the tubular shaft 16 to planetary gearing incorporating a brake 18 which, when applied, holds the planet carrier so that the member 14 is driven at a speed in proportion to that of the turbine member, and a brake 17 by which the member 14 may be held stationary. Control system.-Movement of the torque converter pump member to right or left is effected by pressure fluid in conduits 82, 83, Fig. 2, controlled by a valve 80, application of the brakes 17, 18 is effected by pressure fluid in conduits 94, 95 controlled by a valve 90, and the forward/reverse gear 21 is governed by pressure in a conduit 110 under remote control by a driver's valve having a spool 107 actuated by a rotary selector shaft 100 through a cam 105. Sensing of two different values of the ratio n 2 /n 1  is effected by a system of two pumps 45, 46 driven by the input side of the transmission and fed by a pump 40, and two pumps 50, 53 driven by the output side of the transmission and having respective series connections 47, 48 with the pumps 45, 46. The pumps are of different displacement so that a pressure exists in both connections 47, 48 when the ratio is below a predetermined value, the pressure in 48 falls to zero when that value is reached and the pressure in 47 falls to zero when a second, higher value of n 2 /n 1  is reached. The pressure in the connections 47, 48 acts on maximum pressure valves 51, 54 and servo valves 52, 55. For forward drive, the shaft 100 of the driver's valve is first turned to a forward-neutral position in which a valve 106 is depressed by a cam 104 to direct pressure fluid through a conduit 76 to a valve PN which is thereby displaced to the left so that fluid passing through the valve 55, both valves 52, 55 being depressed by the pressures in the connections 47, 48, from a pressurized conduit 42 to a conduit 67 can pass through the valve PN to a conduit 71 and thence through a valve BR1 to a conduit 97 to actuate the valve 90 in a direction to apply the brake 18. The shaft 100 is then turned further to the forward-drive position in which the valve 106 is depressed further to pressurize a conduit 108 and actuate a valve FN/RN which directs fluid from 42 to a conduit 85 resulting in deflection of the valve 80 to supply fluid to the conduit 82 and vent the conduit 83 so that the pump member 11 is clutched to the input shaft. When the output shaft attains a speed at which the first predetermined value of n 2 /n 1  is reached the valve 55 rises and vents the conduit 67 and directs pressure fluid through a conduit 66a, the valve 52 and conduit 66 to the valve PN through which it flows to the conduit 96. The valve 90 is thereby operated to release the brake 18 and apply the brake 17. At the second predetermined value of n 2 /n 1  the valve 52 rises to pass pressure fluid from 42 to a conduit 65 and thence through a centrifugally actuated valve 60 to a conduit 69, valve KD, conduit 70, valve FN/RN, and conduit 84 to actuate the valve 80 to cause leftward movement of the pump member 11 to establish direct drive. Shifting to and from direct drive is also subject to control by the throttle pedal which operates a valve 75 influencing the loading 63 of the centrifugal valve 60 and providing kick-down by affecting the valve KD. Indicators I, II, III situated at the driver's control sense hydraulic fluid temperature, oil level, and reverse selection. A modification (Fig. 3, not shown) employs solenoid operated valves controlling the valves 80, 90 and the forward/reverse gear 21, and electronic means controlling these solenoid valves. Electronic control means employing pulse generators for speed sensing and logic circuits for control purposes are described.