Patent GB-871585-A (GB)
Title: Improvements in power transmission mechanisms
IPC: F16H61/56
Filed: 1959-07-21
Abstract: 871,585. Hydro-mechanical variable-speed gear; change-speed control. FORD MOTOR CO. Ltd. July 21, 1959 [July 21, 1958], No. 25013/59. Class 80 (2). [Also in Groups XXIX and XXXIV] A variable-speed gear for a vehicle comprises a hydrokinetic torque converter comprising a pump 34, a one-way mounted reactor 56, and primary and secondary turbines 40, 46; the primary turbine is connected to a ring gear 140 by a shaft 88, and the secondary turbine is connected to the ring gear through an over-running clutch 84, and to a sun gear 144 through a friction clutch 170, shaft 82 and a sleeve 54. A planet carrier 148 of the epicyclic gear is fast with an output shaft 150. The exit sections of the pump and the secondary turbine have adjustable blades 106, 126, the pump blades 106 being adjustable to vary the torque and the turbine blades 126 being adjustable to provide reverse. Function summary.-A manual control valve 238 has five settings: reverse R, neutral N, first drive range D, second drive range Ds, and hill brake HB. The first drive range D setting gives two speed ranges under engine throttle and vehicle speed control; first a low-speed ratio range in which the vehicle accelerates with both the sun 144 and the secondly turbine 46 held stationary and the primary turbine driving the output shaft through the epicyclic reduction gear; and secondary a high-speed range in which the primary turbine drives the ring gear and the secondly turbine drives the sun gear. The second drive range Ds gives in addition to the two ranges obtained in the D setting an intermediate speed range in which both turbines drive the ring gear and the sun gear is held stationary. In both drive ranges, for high throttle openings the pump blades are set in a position giving increased torque conversion unless the vehicle speed is unduly high. In the HB position three stages of braking are obtained: firstly, at high speeds during coasting, the sun gear is stationed to cause overspeeding of the ring gear and the primary turbine 40; secondly, at lower speeds, the sun gear and the secondary turbine 46 are stationed; and thirdly, at still lower speeds, a brake 188 acting on the output shaft is also applied. In reverse setting a reverse brake 138 stations the primary turbine and the ring gear, the blades of the secondary turbine are set in their alternative position and the secondary turbine drives the sun gear. Torque converter.-The pump 34 is driven by the engine crankshaft 10 and has radial blades and also adjustable blades 106 at its exit portion mounted on pivot pins 108 having cranked portions operatively connected to a piston 94 in a servo cylinder formed in the inner shroud of the pump. The blades 106 are spring biased to a position giving maximum toroidal flow for high-torque ratio operation, and are moved to their other position by pressure in the servo cylinder. The primary turbine 40 is fast with the inner race of the one-way clutch 84 which is splined to the shaft 88, and the inner shroud of the turbine 40 is splined to a disc 78 which is splined to a sleeve 80 fast with the reverse brake drum 136. The outer shroud 48 of the secondary turbine 46 is fast with the outer race of the oneway clutch 84 and is splined to the sleeve 54. The outer shroud is also formed with a cylinder which houses a piston 118 connected to cranked parts of pivot pins 124 of the blades 126 in the exit part of the secondary turbine. The blades are moved to a reverse drive position by pressure in the cylinder and are biased to a forward drive position by pressure in the torus. The reactor 56 is mounted on a one-way brake 60. Control arrangement and operation.-Fluid pressure is supplied by input and output driven gear pumps 74, 178 which both deliver through check valves to a passage 222 the pressure in which (control pressure) is controlled by a main regulator valve 212 which also by-passes surplus liquid from the input pump 74 to exhaust. The valve 212 is subject to the control pressure acting on a piston 230 against the pressure of a spring 228. A valve 290 provides throttled communication between a passage 302 communicating with passage 222 and a passage 304, this throttle (TV) pressure in passage 304 acting on the right-hand end of the valve 290 to counterbalance a spring 300 compressed in accordance with the opening of the engine throttle. The pump 178 is formed with two working regions, one of which supplies to the control pressure passage 222 and the other of which supplies to a passage 322 the pressure in which (governor pressure) is determined by a restricted exhaust passage 324 and by the vehicle's speed. A compensator valve 330 supplies, through a line 342, biasing pressure to the main regulator valve 212 which pressure is a function of both engine throttle setting and the vehicle speed, and is such that if the vehicle speed increases for any throttle setting the regulator valve is adjusted to reduce the control (222) pressure correspondingly; and if the throttle setting is increased for any given speed up to a limiting speed, the control pressure is increased. In the D position (shown), the manual control valve 238 supplies control pressure through passages 256, 254 and via a shuttle valve 252 and a hill hold valve 248 to a clutch servo 210 to engage the clutch 170 throughout the shift sequence so that the secondary turbine is permanently connected to the sun gear. At low speeds control pressure is also supplied through passage 254, a low servo shift valve 262 and a passage 278 to a servo 204 to apply a brake 160 to station the sun gear 144. Valve 262 is biased to the left by a spring and is subject to governor (322) pressure at its left-hand end, and when this pressure rises sufficiently as the vehicle speed increases, valve 262 is moved to the right and the servo line 278 opened to exhaust to release the brake 160. In the Ds position of the valve 238, on starting the servo 210 and the apply side of brake servo 204 are energized to engage the clutch 170 and apply the brake 160. After the vehicle begins to accelerate, governor pressure urges the hill hold valve 248 to the right and the clutch servo 210 is then exhausted through passage 246, valve 248, passages 372, 378 and an exhaust port of a shift valve 306. The brake 160 continues to be applied to station the sun gear and the transmission is thus conditioned for the intermediate speed range, both turbines driving the ring gear. With continued acceleration the governor pressure is sufficient to move the shift valve 306 to the right, and control (222) pressure is supplied through the manual valve 238, passages 352, 354 and the shift valve to the line 372 and thence to the servo 210 to engage the clutch 170 and to the release side of servo 204, the apply side of which continues to be pressurized, so that the brake 160 is released by a spring to give high-speed operation. For " kickdown " to the intermediate range from the high-speed range, fully depressing the accelerator moves a valve element 292 to the right to apply TV pressure (which now equals the control pressure) to the shift valve 306 to move it to the left to open the clutch servo 210 and the release side of the brake servo 204 to exhaust. The apply side of the brake servo continues to be pressurized so that the brake 160 is applied to give intermediate speed range operation. An "hydraulic detent" associated with the valve element 292 reduces risk of unintentional down shift. In the HB position, at high vehicle speeds, the brake 160 is applied and the clutch servo 210 is exhausted through the shift valve 306. Also the leftward fluid bias on the compensator valve 330 is increased to decrease the pressure in passage 342 which acts on the main regulator valve 212 and thus increases the control pressure so that the pressure in the brake servo 204 is sufficient to prevent slip during torque reversal. The sun gear is thus stationed and the primary turbine overspins. As the vehicle speed falls the regulator (322) pressure drops and is insufficient to hold the hill hold valve 248 in its right-hand position; valve 248 therefore shifts and supplies control pressure to the clutch servo 210 so that the secondary turbine is stationed. With the throttle closed the TV (304) pressure is zero and a valve 392 is spring urged to the right so that a valve 396 is biased to the right by governor pressure against spring action. As the governor pressure falls valve 396 is moved to the left, and control pressure, modulated by a valve 408, is applied to the servo of the output brake 188 to brake the output shaft. Pump blade adjustment.-The servo for the adjustable blades 106 of the pump exit section is pressurized when the blades are in the normal cruising position, and fluid supplied to the servo is controlled by a valve 424 biased in the direction for supplying fluid by a spring and biased in the exhaust direction by TV pressure. At high vehicle speeds the spring bias on valve 424 is supplemented by control pressure to prevent downshift at undesirably high speeds. The admission of control pressure is determined by a valve 426 subject to opposed converter (torus) pressure and governor pressure. Reverse drive.-At all times control pressure is supplied through the regulator valve 212 to a passage 432 whence a lubrication pressure valve 434 subject to opposed lubricating pressure and spring bias controls the degree of communication to a passage 436. In the R position of the manual valve 238 control pressure is supplied to a line 442 and acts on a piston 440 to increase the spring bias on the valve 434 and thus increase the pressure in the lubricating passage 436 sufficiently to move the secondary turbine blades 126 to their reverse position. Control pressure is also supplied to a servo 196 applying the reverse brake 138 stationing the primary turbine and the ring gear.