Patent GB-799033-A (GB)
Title: Improved variable-speed power transmission mechanism for motor vehicles
IPC: F16H47/08
Filed: 1956-09-17
Abstract: 799,033. Torque converters. GENERAL MOTORS CORPORATION. Sept. 17, 1956 [Sept. 29, 1955]. No. 28331/56. Class 69 (2). [Also in Groups XXIV, XXXI and XXXIV] A variable-speed gear for a motor vehicle. comprises a hydrodynamic torque-converter which, in addition to an impeller 12 and oneway mounted reactor R, has three turbines T1, T2, T3, the first two T1, T2 connected to output 56 respectively through sun-ring-planet trains with output mounted planet carriers 42, 40, of which the former has the higher mechanical advantage and the reaction gears 58, 60 are prevented from reverse rotation, whilst the third turbine T3 is directly connected to output 56. The second train reaction sun 60 is held from reverse rotation by a releasable brake 72 acting through a one-way detent 68, and the first train reaction ring 58 is prevented from reverse rotation relative to the sun 60 by a one-way clutch 64 between the two reaction members 58, 60. The clutch 64 also transmits torque when a brake 38 is applied to the second train ring 37 and the forward brake 72 released for reverse. In forward drive an input sun 35 of the first train, input ring 37 of the second, and the common output carriers 42, 40 are each driven respectively by the three turbines T1, T2, T3 which deliver torque in succession with increase in speed as the torque of the preceding turbine vanishes and that turbine is overrun. The second turbine T2 and reactor R have controllable incidence blades. Blade incidence, various brakes and a clutch are all hydraulically controlled. Function summary.-A manual control-valve 460, Fig. 13, has four settings: Neutral, N; drive, D; brake, B; and reverse, R. D setting gives three degrees of performance under engine throttle and manifold-depression control as follows. First, a low performance in which the vehicle accelerates with both turbine and reactor blades at minimum incidence " low angle " (apart from a short initial period with the turbine blades at high angle). Second, a medium performance in which enginethrottle opening is sufficient for an enginesuction-modulated " TV " (throttle-variable) valve 510 to cause the turbine blades to shift to maximum incidence, " high angle," giving higher torque ratio and delaying converter coupling point to a higher speed. Third, a high performance in which, in addition, accelertor-overtravel at 484 mechanically opens a valve 482, setting the reactor blades also to high angle for further increase in torque-ratio and coupling-point speed. B setting of the manual valve 460 differs from D only in that it causes accelerator - release automatically to apply a friction disc-brake 19 to the final output shaft 16 during forward motion only. Torque-converter.-The three turbines T1, T2, T3 are carried respectively on concentric shafts 34, 36, 39 connected to the respective planet gear elements. The reactor blades 30, Fig. 2, are secured to pivot pins 84 having cranked ends engaging a grooved piston 252, axial movement of which changes the incidence of the blades. Pressure oil, supplied to the working circuit of the torque-converter through a restricted path 214, passes the reactor-detent 88 into a chamber 256 to urge the piston 252 leftwards to set the reactor blades 30 at high angle. A higher control pressure supplied, when required, to an opposing chamber 258 shifts the piston 252 right to set the blades 30 at low angle. A similar piston 284 controls the incidence of the blades 26 of the second turbine T2, a supporting cylinder 270 of which is connected to its shafthub 293 by tubular members 292 the outer ends of which communicate alternately with opposite pressure chambers 280, 282 of the blade-shift piston 284, and the respective inner ends with the torque-converter working space supply 214, giving high angle (chamber 280), and with a passage 310 having a higher control pressure supplied when required for low angle (chamber 282). The tubular members 292 are streamlined in the direction of oil now in the working circuit. A front closure plate 204 has internal vanes 232 to generate balancing centrifugal pressure, and liquid leaving the converter at 234 passes through a pressure-relief valve 238 into a central lubrication line 236. Blade incidence and discharge angles for all members are specified, the blades of the reactor and impeller having forward facing discharge angles. Gear phases and arrangement.-Initially, drive is from the first turbine T only, to the sun 35 of the first train, the ring 58 of which is held from reverse rotation through the. one-way detents 64, 68 by the forward brake 72, so that the first train acts alone in reduction, the overall initial ratio being the product of that, 1.5, due to the converter and that, 2.55, of the gear. At this time the inner one-way clutch 64 prevents forward rotation of the sun 60 of the second train 46, so that the common output carrier now overdrives the ring 37 and second turbine T2 in the forward direction. With speed increase, the second turbine T2 begins to contribute torque, increasing to a maximum of 0.55 times engine torque, and multiplied by 1.6 in the second gear train, the second turbine taking over as the torque of the turbine T1, after continuously decreasing from an initial maximum, finally reaches zero, that turbine being then overrun. The output-connected turbine T3 initially contributes negative torque, which, with increase in speed, increases positively until, at the coupling point, the torque of the preceding turbine T2 vanishes and T3 takes over entirely, both turbines T1, T2 then free-wheeling. In low performance the coupling point is reached at 1,300 r.p.m. In medium performance, T2 turbine blades at high angle, torque of the turbine T2 is increased and extended to a higher speed, and coupling occurs at 2,200 r.p.m. In high performance, reactor blades also at high angle, the torque of the turbine Tl is also increased and the coupling point further extended to 2,340 r.p.m. Reverse is by releasing the forward reaction brake 72 and applying a brake 38 to the second train ring 37, the second turbine T2 also being held thereby to form a reaction member in the converter. The inner one-way clutch 64 now prevents forward rotation of the second train sun 60 relative to the first train ring 58 and the trains act in compound. Torque ratio-speed curves of all the elements and of the complete assembly are given for all conditions forward and reverse. In a constructional form, Figs. 2a, 2b, not shown, the brakes 38, 72 are hollow conical shells gripped between internal and external cones, and the output shaft brake 19 is a multi-disc one. A friction clutch 18, released in neutral, is arranged between the gear output shaft 56 and final output shaft 16, which latter has also a notched flange for engagement by a positive park-lock, not shown. Fluid pressure supply.-Fluid pressure for servos 400, 391, 328, 432, Figs. 13, 13a, of the clutch 18, forward brake 72, reverse brake 38 and output shaft brake 19, and for blade-angle control servos 284, 252, is supplied by input and output driven pumps 208, 408. The former is of the constant-pressure variable-delivery vanetype having its delivery 452 varied, as described in Specification 716,134, [Group XXIV], in accordance with engine suction acting at 538 on a regulator valve 510 which meters TV (throttle-variable) pressure into line 512 which reacts on the delivery control of the pump. Both pumps deliver to a common chamber 453, the output pump 408 through a non-return valve 459 which opens only when output pump pressure exceeds that of the input pump. The pressure chamber 453 supplies the system main 458 through a cooler 455, with by-pass relief 457, and the main 458 supplies the torqueconverter 12 through a restrictor 454 formed by the annular passage 214 (see also Fig. 2) itself. Due to the restrictor 454 and the constant relief exit 238 to the lubrication line 236, pressure in the torque-converter and its supply passage 214 is always less than line pressure 458. This reduced pressure 214 is supplied directly to both high-angle chambers 280, 256 of the turbine and reactor blade-shift pistons 284, 252. Fluid system components.-In addition to the pumps 208, 408, cooler 455, manual valve 460 and TV valve 510, the system includes a turbine blade-angle control valve 500, operated by TV pressure 512; reactor blade-angle control valve 482, operated mechanically at 484 by accelerator overtravel; and integral with the valve 482 a valve 556 controlling the output shaft brake 19 through a relay valve 554, brake apply valve 552, and brake-pressure regulator valve 550. Control operation.-Initially with the engine running and output stationary, pressure is supplied by the input pump 208 only. Reduced torque-converter pressure 214 reaches the highangle chambers 280, 256. In neutral, N, the manual valve 460 blanks a line 480 leading to the low angle chamber 258 of the reactor blades 30, and all brakes and the clutch 18 are exhausted. In D setting, shown, the manual valve 460 supplies main pressure 458 to the clutch 18, forward brake 72, and through the line 480 and reactor blade valve 482, to the low-angle chamber 258 where it overcomes the lower pressure 214 in the high-angle chamber 256, to shift the reactor blades 30 to low angle. Accelerating the engine starts the vehicle in medium performance (turbine blades high angle, reactor blades low angle) but the subsequently developed output pump pressure 504 then acts in the low-angle chamber 282 to shift the blades 26 of the turbine T2 to low angle, and further acceleration is in low performance (turbine blades low angle, reactor blades low angle). Gear phase-shift occurs automatically as above described. If the engine-throttle opening is sufficient to produce, at the suctioncontrolled TV valve 510, a high enough TV pressure 512 to shift the turbine blade valve 500 to the right, the low-angle chamber 282 is exhausted, and the turbi