Patent GB-677185-A (GB)
Title: Improvements in or relating to variable-speed transmissions
IPC: F16H47/06
Filed: 1950-04-19
Abstract: 677,185. Change-speed gear. BORG-WARNER CORPORATION. April 19, 1950 [April 26, 1949], No. 9593/50. Class 80 (ii). [Also in Group XXIX] A two-speed and reverse planet gear 17 on a vehicle, wherein low and reverse each require engagement of one clutch 18 and one of two reaction brakes 20 or 21 respectively, whilst highspeed requires engagement of one second clutch 19 and the lowspeed brake 20, the last-named only for the purpose of taking the reaction of an associated torque-converter 16 in this case, is controlled by a nuid-pressure system including an acceleratorcontrolled valve 90, Fig. 3, for causing gradual engagement of either the low-speed and reverse clutch 18 (as shown) or of the low-speed and reverse brakes 20, 21, Fig. 7 (not shown), for gradual starting of the vehicle by initial depression of the accelerator-pedal (with or without automatic declutch on accelerator release). Two different systems are described, in the first of which, Figs. 2 and 3, there is an additional manual forward-neutral-reverse selector-valve 92 and a low-high shift-valve 91, electrically controlled automatically by a vehicle-driven governor switch 205 and by three further switches 202, 203, 204 controlled respectively by engine-manifold depression at 208; kickdown of the accelerator-pedal 131; and by a manual button 221, for automatic or manual downshift above governor upshift speed. The second system, Figs. 8-11 not shown, uses a solely manually controlled high, low, neutral and reverse rotary selector-valve together with the accelerator-controlled starting valve. The automatic system has a " retarder " valve 170, Fig. 3, producing gradual upshift. Gear arrangement. The torque-converter 16 is of the kind wherein the reactor 24 drives reversely when the turbine 23 is held by the brake 21 for reverse, the gear train 17 then providing a forward drive resulting in overall reverse. An input planet train 15 provides a split-torque drive at all times in high and low speeds, and is effective to provide an initial step-up drive of the impeller 22 at starting. A one-way clutch 30 is arranged reversely across two elements of the input train 15 for transmitting negative torque, by-passing, the converter for engine-braking in either forward ratio. The input shaft 10 is connected only to the ring-gear 25 of the input train 15, which has intermeshed planets 27, 28 carried by the impeller 22 of the torque-converter, the turbine 23 of which is fast to the sun 26 and to an intermediate shaft 12 through which all forward drive is transmitted hydromechanically to the planet carrier 36 of the output train 17. The latter comprises intermeshed planets 34, 35 engaging respectively a ring-gear 33, fast on the final output shaft 11, and a reaction sun 32. Low-speed is by frictionally clutching the reaction sun 32 at 18 to a brake drum which is then held by a band-brake 20, the same drum also taking the reaction of the torque-converter reactor 24 through a forward-overrun clutch 31. High-speed is by releasing the clutch 18 and engaging a clutch 19, connecting the reaction sun 32 and planet-carrier 36 for solid one-to-one drive in the output train only, the brake 20 remaining on to take the reaction of the torque-converter, which is still effective. Reverse is by engaging the lowspeed clutch 18 and reverse brake 21, to hold the planet-carrier 36 and with it the intermediate shaft 12 and converter-turbine 23, whereby the converter reactor 24 drives reversely through the one-way clutch 31 and clutch 18 to the sun 32, which drives the output shaft 11 slowly in the same direction (i.e. reverse of the input). Fluid system. Pressure oil for engaging the low and high speed disc clutches 18, 19 and the forward-reverse band brakes 20, 21, is supplied by an impeller-driven input pump 60 and an outputdriven pump 61 each feeding through non-return valves 162 a common pressure-main 128, 127, 130 in a triple valve chest 77, and provided with a common pressure relief-valve 154. The bottom valve 92 is a manual forward-neutral-reverse valve supplying fluid-pressure from the main 128 directly to either the forward or reverse brake 20, 21 on opposite sides of its neutral position shown. The top valve 90 is the accelerator operated valve for gradual starting, initial depression of the accelerator pedal 131 moving the valve 90 to the left through an arcuate pin-andslot connection 143 which allows the further accelerator travel to be without effect on the valve 90. A lost-motion spring link is used in Fig. 8, not shown, in place of this slotted connection. This initial movement of the accelerator-valve 90 supplies pressure gradually from the main 128 to an inlet 129 of a high-low shiftvalve 91, which, in its initial left position shown, feeds pressure from the accelerator-controlled inlet 129 through a duct 168 to the low-speed clutch 18, which is thereby gradually engaged under accelerator-control for starting, whilst the brake 20 is fully and directly engaged. In its right position the shift-valve 91 directs unmodulated pressure from the main 128 through a duct 169 and " retarder " valve 170 to the high-speed clutch 19, the idle clutch 18 or 19 in each position being exhausted through outlets 124, 123 respectively. The retarder 170 permits rapid initial flow to the high-speed clutch 19 through a port 183 which is gradually closed by the build-up of clutch-engaging pressure acting on the larger right face of a spring-loaded differential piston 176 forcing it to the left, to close the port 183, further pressure-supply being through a restricted central passage 177. This produces a gradual engagement of the highspeed clutch 19. In Figs. 4-7, not shown, the retarder is combined with the high-low shift valve 91, which is then actuated by a spring- loaded lost motion connection and has clutch engaging pressure applied to the left face of a reduced extension of its left end. In this form the low-speed clutch 18 is also gradually released as the high-speed clutch 19 is gradually engaged due to the arrangement of the shift-valve porting. In Fig. 7, not shown, the low and high speed clutches 18, 19 are fed with main pressure, not accelerator modulated, and the accelerator modulated starting control is operative on the low and reverse brakes 20, 21. This form is further modified by the provision of a pressureconnection from the output pump 61 only, to act on the left face of an enlarged head at the right end of the accelerator-valve 90, which pressure holds the valve in its right position, preventing its return to the idle position with the accelerator pedal until the vehicle stops, lost-motion being provided in the accelerator linkage to permit full release of the pedal. The drive does not then automatically disengage on release of the accelerator pedal so that freewheeling is prevented. Electric control. The high-low shift valve 91 is moved rightwards from its low position shown, to the high position, in opposition to a spring 146 by a solenoid 144, energized through a relay 186, Fig. 2, controlled by the four series switches 202-205 and in circuit with a fuse 193, ignition switch 192 and battery 191. With the vehicle running below cut-in speed, the governor switch 205 is open, and although engine manifold depression at 208 may close the switch 202, the relay circuit is incomplete and the shiftvalve 91 selects low. Above cut-in speed the governor switch 205 closes, but this is without effect, since during acceleration through the cut-in speed manifold depression would not be sufficient to close the manifold switch 202. Release of the accelerator-pedal above cut-in speed causes increased manifold depression, which closes the switch 202 completing the circuit to energise the relay 186 which closes contacts 194 energising the solenoid 144 to move the shiftvalve 91 to the high position, in which it breaks contacts 147 feeding its main coil but is held in this position by a hold-on coil 201. Energization of the relay 186 also closes contacts 195 shorting the manifold-switch 202 so that subsequent downshift can be effected only by either the opening of the governor-switch 205 by reduced vehicle-speed; by opening a manual switch 204 for enforced downshift at any time; or by kickdown of the accelerator 131 to open the switch 203. Modification. In Figs. 8-11, not shown, a low, high, neutral, reverse rotary distributorvalve, manually controlled by a steering- column-mounted lever, operates in conjunction with an accelerator controlled valve similar to that 90, Fig. 3, which latter valve also can be manually operated through a direct cable control to prevent automatic drive-disengagement on accelerator-release, thus inhibiting freewheeling.