Patent GB-802956-A (GB)
Title: Improvements in or relating to variable-speed transmission
IPC: F16H47/08
Filed: 1955-05-10
Abstract: 802,956. Change-speed gear. BORGWARNER CORPORATION. May 10, 1955 [May 11, 1954], No. 13480/55. Class 80 (2).  Pumped fluid pressure 128, for engaging a power-train-completing clutch 15 or brake 17, 18 in a change-speed gear on a motor-vehicle, is modulated by a regulator-valve 174, the loading of which causes servo-pressure to decrease with increase in engine manifold depression 191 (reduction in torque) and also with increase in output speed, the latter effective through speedresponsive fluid pressure 203. Junction summary.-A shift valve 101 controlling the supply of fluid-pressure for shift between a fluid-driven reduction drive and an all-mechanical direct-drive, is operated automatically in response to two opposing fluidpressures, one increasing with increase in output speed, the other reducing with increase in engine-manifold depression (reduced torque). and also reducing with increase in output speed. A manual valve 100 provides, in addition to neutral and reverse, an enforced low by greatly reducing the first-mentioned shift pressure, and in one form a similar effect is also obtained mechanically or electrically by accelerator or service brake kick-down. The second-mentioned pressure is also servo-pressure applied to the clutch and brakes of the gear, and is not reduced below one-quarter maximum drive torque (corresponding to maximum overrun torque), nor below that speed at which the driving torque converter assumes one-to-one drive. Hydrodynamic braking in varying degrees is provided, the greatest effect, without engine-stall, being by selecting reverse and direct-drive together, all forms having a directdrive cut-in valve 167 for this purpose and one form interlocking this with the manual valve to cut in in reverse setting. Gear arrangement.-Intermeshed planets carried on a sleeve 12, fast with the turbine 20 of on an output shaft 11, and a sun 69 fast on an outer sleeve 13 which, through a sprag-type one-way clutch 36, supports the reactor 21 of the torque-converter, the impeller 19 of which is fast on the engine-shaft 10. Application of a band brake 18 to the sleeve 13 holds the sun 69 and also takes one-way reaction of the converter reactor 21, whereby the converterdriven planet-carrier sleeve 12 drives the output ring-gear 68 at reduced ratio. Application of fluid pressure to the left-face of a piston 54 engages a disc clutch 15, providing direct mechanical drive from input 10 to output 11. Application of a band-brake 17 alone holds the planet-carrier sleeve 12 and turbine 20 of the torque-converter, the reactor 21 of which is thereby driven reversely and, through the one way clutch 36 drives the sun 69 which passes a reduced drive, still in the reverse direction, to the output ring-gear 68. Hydrodynamic braking.-Application of the reduced drive brake 18 during running with the direct drive clutch 15 engaged, causes the output shaft 11 to drive the turbine 20 at an increased speed in relation to that of the impeller 19, providing hydrodynamic braking by the converter. Alternative application of the reverse brake 17 during forward running, stations the converter turbine 20, and causes the output shaft 11 to overdrive the reactor 21 forwards, which provides further augmented degrees of hydrodynamic braking, as follows. If the direct-drive clutch 15 is disengaged and output speed is above a predetermined value depending on blading characteristics of the torque-converter, the overdriving of the reactor 21 cause reversal of the direction of flow in the toroidal circuit of the converter and relatively gentle braking. Below this predetermined speed the reactor does not reverse the flow and the consequent impingement of the fluid on the more slowly rotating impeller vanes produces much more drastic braking. With the direct-drive clutch 15 engaged, the relative speed of impeller and output is fixed and the more drastic braking is obtained at all speeds. Servo system.-Both the brakes and the clutch are engaged by fluid-pressure supplied by input and output driven fixed displacement gear pumps 42, 82, the deliveries 228, 166 of which are connected by a check-valve 106, Fig. 2, which retains input-pump pressure when the output-pump is not working (e.g. when stationary or in reverse), and permits outputpump pressure to be used on the direct-drive clutch for a towed engine start.  Servo-pressure control.-The delivery 166 of the output-driven pump 82 is rendered speedresponsive independently of temperatureviscosity changes by turbulent discharge through a sharp-edged orifice 155, restricted by a taper plug 156 loaded by a blade spring 160. Delivery 128 of the input-driven pump 42, which is also servo-pressure actuating the brakes and clutch, is rendered both enginetorque and output-speed responsive by the regulator-valve 174 relieving to pump-suction 184 and loaded towards closed position by three spring groups, one 196 acting constantly; a second, 200, acting against a shoulder 199 on a free loading stem 194, in opposition to speedresponsive pressure 166, 203 acting rightwards on an abutment piston 197; and a third, 192, thrusting a diaphragm 186 against the stem 194, in opposition to engine-manifold depression 191 acting rightwards on the diaphragm. Delivery pressure 128 is thus reduced with increasing output speed and increased with increasing engine-torque (reducing depression), subject to the following limitations. Above that predetermined speed at which the torqueconverter reactor 21 overruns its one-way detent 36, whereby the torque-converter is incapable of torque multiplication, the speedresponsive piston 197 leaves contact with the loading-stem shoulder 199, so that further speed increase merely compresses the springs 200 without causing any further reduction in servo-pressure. For values of engine-suction exceeding that corresponding to one-quarter of the maximum engine drive torque, the diaphragm 186 leaves contact with the loading- stem 194 and thereafter merely compresses the spring 192 without further reducing the servopressure. This quarter-maximum drive torque corresponds to maximum engine brake torque, so that servo-pressure is always adequate to prevent brake or clutch-slip during closed throttle overrun. The pressure supply 213 to the torque converter 19 is taken from the input pump 42 and is subject to the same torque and speed-responsive control, but is in addition regulated to a fractionally lower value by a regulator valve 105. Shift control.-Co-operating are a manual LDNR valve 100, an automatic shift valve 101, responsive to opposing speed- and torqueresponsive fluid pressures, and a manual direct-drive clutch lock-in valve 167. In reverse position R, the manual valve 100 supplies servo-pressure 128 directly to the reverse brake 17 only. In neutral, N, the pressure supply line 128 is blocked and all clutch and brake lines exhausted. In drive, D, position shown, servo-pressure 128 is fed at 129 to the automatic shift-valve 101, which, in its initial left position (not shown), supplies pressure to the low brake 18 from feed passage 129 through 141, 151, whilst exhausting the direct-drive clutch 15 through passages 173, 170, 140, 142. Output pump pressure 166, which increases with speed, acts rightwards on an end land 133 of the automatic shift-valve 101, in opposition to servo-feed pressure 128, 129 acting leftwards on the same land and also on the right-end of the valve, and regulated to increase with enginetorque-increase and decrease with output-speedincrease. When the former pressure 166 overcomes the latter 128 and a spring 150, the shift valve 101 is moved to its rightward position shown, to supply servo-pressure 128, 129 through passages 170, 173 to engage the directdrive clutch 15 whilst exhausting the low brake 18 at 142, causing upshift. The sequence is reversed for automatic downshift, which occurs at a lower corresponding speed since leftward pressure from 129, 141 is cut-off from the right end of the valve. In low position L of the manual valve 100, the fluid feed is as for D, but now a stem 119 on the manual valve 100 releases pressure of the blade-spring 160 on the orifice restrctor 156 whereby speed-responsive pressure 166 acting rightwards on the automatic shift-valve 101 is greatly reduced, causing downshift, but still retaining a sufficiently high maximum speed-responsive pressure to prevent downshift at speeds which would result in excessive engine speeds. In the direct-drive clutch supply passage 170 is the cut-in valve 167 which, when manually turned clockwise from the normal position shown, supplies output pump pressure 166 directly to the direct-drive clutch 15, as for a towed enginestart, or for use in conjunction with the L or R settings of the manual valve 100 for obtaining the various degrees of hydrodynamic braking above referred to. Fig. 3 (not shown), differs from Fig. 2 in the following respects. Accelerator kick-down shift is provided by a cam rocked by accelerator overtravel to thrust a slidable pin through the valve-block and relieve pressure on the blade-spring 160 loading the orifice restrictor 156, which has the same effect on greatly reducing output-pump speed-responsive pressure 166 as has the end 119 of the manual valve 100 in Fig. 2 when moved to L position. In this case the end 119 is omitted and a levercontrol for the manual valve has a cam coaxial with the kick-down cam and acting in identical manner in L position of the manual valve, the sequence of which latter is changed to NDLR. A cable-controlled piston valve replaces the direct-drive clutch lock-in valve 167. Fig. 4 (not shown), differs from Fig. 2, as follows. The pressure-reducing valve 105, through which pressure is fed to the torque-converter, is provided with an elongated exhaust port to relieve the upsurge of pressure created in the torqueconverter by the rightward engaging movement of the direct-drive clutch-p