Patent GB-717111-A (GB)
Title: Improvements in or relating to change-speed power transmission
IPC: F16H47/08
Filed: 1948-05-12
Abstract: 717,111. Change - speed control; friction clutches. ROCHE, C. R. May 12, 1948 [May 16, 1947], No. 13006/48. Class 80 (2) [Also in Groups XXIX and XXXIV] A change-speed gear comprises a pair of planetary trains 8, 11, Fig. 1, each having three elements, an input member 6 adapted to drive one element 7 of the train 8, and an output member 13 connected to one element 12 of the other train 11, a second element 9 of the train 8 being connected with a second element 10 of the train 11 and to one member of a brake 17, and there being a clutch 20 acting between two elements, e.g. 9, 18, of the train 8 to lock it .solid, whilst means, such as a brake 27 and one-way roller clutches 28, 25, are provided for preventing backward rotation of the third elements 18, 23 of the trains, part 27, 28 of the said means being adapted to function jointly with the clutch 20 to provide one gear ratio. As shown, applied to a motor vehicle transmission, a hydraulic torque converter 1, 2 is mounted ahead of the gearing, and both the gearing and the converter may be by-passed by a direct-drive friction clutch 14. Fast with the engine crankshaft 6 is a housing 1 forming the casing and pump of the converter and also the driving member of the clutch. The converter, which is of the kind having a reactor 3 allowed by a one-way roller detent to rotate forwardly under suitable working conditions, powers the gearing via a turbine 2. The gearing comprises two sunplanet-annulus trains 8, 11 in series, the first having its annulus 7 rigid with the turbine 2, its carrier 9 rigid with the annulus 10 of the second train, and its sun 18 connected to the sun 23 of the second train via the one-way roller clutch 25 allowing the sun 18 to overrun the sun 23 in the forward direction of rotation. The carrier 12 of the second train is fast on the load shaft 13, to which the single driven disc 36 of the clutch 14 is also slidably splined. For reverse drive, the brake 17 is applied to station the carrier 9 and annulus 10. The brake 17 is supplemented by a positive detent 17B as described below. To condition the. gearing for forward 'drive, the brake 27 is applied to prevent, through the one-way roller clutch 28, backward rotation of the suns 18 and 23. Both trains are then operative to give a double reduction through the gearing which, in conjunction with the converter, provides a range of low ratios. Change to an intermediate ratio range is effected by additionally engaging a multiplate clutch 20 between the sun 18 and carrier 9 to lock up the first train, the second train alone then being operative with the sun 18 overrunning the sun 23. Finally, for direct drive, the clutch 14 is engaged. An emergency twoway low speed as for engine braking is provided by applying the brake 27 and simultaneously stationing the sun gear 18 by a brake 21. To give neutral, all the clutches and brakes are released, when torque reaction tends to lock up the clutch 25 and prevents excessive rotation of the planets of the train 8. The clutch 25 also locks up if the vehicle overruns the engine in the intermediate ratio range, and both trains 8, 11 then drive solid to give, apart from the converter 1, 2, a direct drive. In the intermediate ratio range the gearing acts as a sprag to prevent rearward vehicle movement. Friction clutches and brakes. Both the clutches 14, 20 are fluid-operated. The clutch 14 is engaged by pressure fluid supplied through shaft passages 150C. to a combined piston and presser plate 35, and is disengaged, when the fluid pressure is released, solely by the pressure of the converter working fluid which is allowed free access to the piston 35 via holes 36c in the clutchdriven disc 36. The clutch 20 has a combined piston and presser plate 32 acted on by fluid supplied through passages 149B, 149E. The brakes 17, 21, 27 are also fluid-operated. The brakes 21, 27 have piston-and-cylinder assemblies 99 and 102, Fig. 4, operating directly on brake bands. The brake 17 has a band acted on, at one end through a torque-multiplying lever 115, Fig. 2, by a piston-and-cylinder assembly 96 and connected at the other end to a lever 118A co-acting with a detent pawl 17B to move it, when the torque reaction on the band exceeds a predetermined value, into engagement with ratchet teeth 16A on the carrier 9. Release springs 119, 17E are provided. Two detent pawls spaced at 120 degrees from the band ends and from each other may be used. Main change-speed control. Gear-changing between the normal forward drive ratios is effected automatically under the joint control of a speed-responsive governor and of the vehicle accelerator pedal, as described below, whilst selection of reverse drive, neutral, low speed two-way drive or normal forward drive is manual by movement of a steering-column mounted or other hand lever 90 into position R. N, LU or F respectively to move a valve 83 to direct oil or other pressure fluid supplied by a conduit 70 to the appropriate ones of the assemblies 96, 99, 102 and to exhaust those not operative, either through a vent 104 or the righthand valve body opening. When the valve is in the position for forward drive, fluid is additionally supplied to a conduit 106, at other times exhausted via the vent 104 or the left-hand valve body opening, via ports 113, 114 interconnected through a bore in the valve interior. The conduit 106 supplies fluid to a valve 124, which is moved by a speed-responsive governor 131 driven from the load shaft 13 and having its right-hand end connected to the valve through a rigid link 126 so as to draw the valve to the left as the vehicle speed increases. At low forward speeds, with the valve 124 in the position shown, conduits 149A, 150 supplying the clutches 20, 14 respectively are exhausted through a port 151. As the speed increases, first the conduit 149A, and later the conduit 150, are cut off from the port 151 and placed in communication with the conduit 106 so as approximately to engage the clutches 20, 14. The valve 124 is assisted to,locate in definite gear ratio positions by ball detents 153 co-acting with suitably shaped sections 156, 157 of the valve, and hunting is further minimized by a dashpot comprising a liquid reservoir 159 communicating with the right-hand end of the valve 124 through a restricted orifice 161. The datum setting of the governor 131 is varied by the accelerator pedal (not shown) or other engine throttle control acting, through a rod 80, bell crank 79, telescopic link 143 and bellcrank 145, on the left-hand end of the governor 131 to move the latter to the right on accelerator depression and tend to force a down change. The link 143 allows throttle release independently of governor setting. To provide a twoway drive over the normal low ratio range of forward speeds, the brake 21 may be additionally operable by a piston-and-cylinder assembly 210 venting through a conduit 215 when the valve 124 is other than in the position shown and supplied through a 'conduit 214 when the valve is in this position. Brake, clutch and converter fluid supply and pressure-regulating systems. The engaging pressures of the friction brakes and clutches are a function of accelerator depression, with successive additional increases as engagement of the clutches 20, 14 is successively initiated. Fluid from a reservoir or sump 39 is forced by pumps 41, 42, respectively engine and vehicle driven, into a main supply conduit 43 at a pressure determined by a relief valve 44, a check valve 45 nullifying reversal of the pump 42 on vehicle backing. A valve 48 determines the pressure at which fluid from the conduit 43 passes to the conduit 70 supplying the clutches 14, 20 via the valves 88, 124. Accelerator depression acting through a linkage 78, 77, 74 incorporating springs 81, 75 tends to open the valve 48 against balancing pressure from the conduit 70 via a port 71 and against a spring 82, which, to ensure smooth clutch take-up during high-idling engine conditions incident on carburetter choking, is at such times additionally compressed by a piston 83 operated from the choke control. Leakage past the valve 48 accumulates in a dashpot chamber 85 having a bleed vent. In the position of the lever 90 corresponding to low-speed two-way drive, a connection 120, 121 ensures a desired minimum opening of the valve 48 irrespective of accelerator positioning. When the clutch 20 is to be engaged, a conduit 172 previously vented via bores 174, 123, 175 in the valve 124 is sealed off by the operative movement of the valve and fluid passing from the conduit 43 via a restricted bore 170 raises a piston 163 until it uncovers an alternative vent line 177, 179, consequent stressing of a spring 86 acting via a rocker 167 to increase the opening of the valve 48. When the clutch 14 is to be engaged, the operative pressurizing of the conduit 150 acts through a conduit 65 to move a valve 61 to the left to interrupt the line 177, 179 and cause the piston 163 to rise higher to uncover a vent port 180, thereby further increasing the opening of the valve 48. A valve 47 controls the pressure of fluid delivered from the conduit 43 to the converter casing 1 via a conduit 54, and, when the clutch 14 is disengaged, is balanced, by counter-action of a spring 66 and fluid pressure supplied to a chamber 57 from the conduit 54 via a conduit 56, to give a high operative pressure in the converter. The movement of the valve 61 to the left on initiation of engagement of the clutch 14 stops previous venting of a chamber 59 via a metered duct 55 and a port 62 and supplies the chamber with fluid from the conduit 43 via ducts 63, 55 when the balance position of the valve 47 is correspondingly altered to reduce the converter pressure considerably so as not appreciably to resist engagement of the clutch 14. Both valves 47, 48 vent via a duct 53 when appropriately positioned. Rapid filling of the converter casing 1 on engine startin