Patent GB-950985-A (GB)
Title: Epicyclic change-speed gearing
IPC: F16H3/66
Filed: 1961-05-16
Abstract: 950,985. Change-speed gear and control; friction clutches; ratchet clutches; cone brakes. FIAT S.p.A. May 16, 1961 [June 11, 1960], No. 17841/61. Headings F2C, F2D, F2E and F2F. Change-speed gearing for motor cars, &c., comprises an engine driven centrifugally engaged clutch 2, &e., Fig. 1, the output side of which is in splined engagement with an axially slidable shaft 9 carrying a toothed clutch wheel 12 selectively engageable in the hubs of two sun gears 17, 18, the sun gear 17 meshing planet pinions 21 mounted in a carrier 20 and in turn meshing a ring gear 23 fast with a driven shaft 24 and the sun gear 18 meshing stepped planet pinions 19 also mounted in the carrier and meshing the planet pinions 21. All three forward ratios of the gearing are obtained with the toothed clutch wheel 12 engaging the sun wheel 18. Two frusto-conical brake rings 32, 33 arc biased towards each other and to their disengaged position by springs 34, and are selectively moved to their engaged positions by supplying oil under pressure to ring-shaped servo cylinders containing pistons 35, 36. The brake ring 32 engages a coned brake ring 25 splined upon the carrier 20, and biased leftwards by a dished spring 26. The brake ring 31 engages a coned brake member 27 biased rightwards into clutching engagement with the brake ring 25 by a dished spring 29. First ratio is obtained by engaging the brake ring 33 with the coned brake ring 25, which slides rightwards against the bias of its spring 26 clear of the brake member 27, so that the planet carrier 20 is stationed and drive passes from the sun gear 18 to the ring gear 23. Second is obtained by disengaging the brake 32 and instead engaging the brake 33, which slides the coned brake member 27 leftwards against the bias of its spring 29, disengaging it from the coned brake member 25, and holds the sun gear 17 stationary. The third ratio, direct drive, is obtained by releasing both brakes 32, 33, so that the dished spring 29 clutches the brake member 27 with the coned brake ring 25. Reverse is established by manual actuation of a selector 11 to disengage the toothed clutch wheel 12 from the sun gear 18 and instead engage it with the sun wheel 17, simultaneously engaging the brake 32. In a modified form, giving four forward ratios and reverse, the sun gears 17, 18, Fig. 4, the planet carrier 20 and the planet pinions 19, 21 are provided as before, but the planet pinions 21 mesh a double ring gear 65 also meshed by planet pinions 68 carried by the driven shaft 24. The double ring gear 65 can be clutched to a brake member 71 by the bias of a spring 72, for rotation with the planet carrier 20, and can also be clutched to a brake member 73 by the bias of a spring 74. The planet pinions 68 mesh a sun gear 70 fast for rotation with the brake member 73. First ratio is obtained by engaging the brake 32 to station the sun gear 70, and simultaneously engaging the brake 33 to station the planet carrier 20. Drive then passes through the sun gear 18 to the ring gear 65, and thence with a further reduction in ratio through the planet pinions 68 to the driven shaft 24. Second is obtained by engaging the brake 33 to station the planet carrier 20, while releasing the brake 32 so that the dished spring 74 biases the brake member 73 into clutching engagement with the ring gear 65, the planetary train 68, &c., then being locked-up. Third is established by engaging the brake 32 to station the sun gear 70, thus disengaging the brake member 73 from clutching engagement with the ring gear 65, and releasing the brake 33, so that the dished spring 72 biases the brake member 71 into clutching engagement with the ring gear C5. The compound train 17, 18, 19, 21 is then locked-up, and a reduced ratio is obtained from the rear train 68, &c., only. For the fourth ratio, direct drive, both brakes 32, 33 are released, and the brake members 71, 73 are biased by their springs 72, 74 into clutching engagement with the ring gear 65. Control.-A slidable ratio selector valve 41, Fig. 8, actuated by the car driver, selectively connects a port 42 supplied with oil under pressure by an engine driven pump to pipes 45, 58 for engagement of the brakes 33, 32, respectively. The pipe 45, Fig. 10, leads through a valve 46 opened when a piston 50 is biased by a spring 52 to the position shown, and also through a by-pass port 48, to a pipe 53, Fig. 9, and a port 39 leading to the servo for engagement of the brake 33. When the ratio selector valve 41 is first moved to the position for engagement of the brake 33, oil flows freely from the pipe 45 through both the valve 46 and the by-pass port 48 to the pipe 53 and the brake servo. As pressure builds up in the pipe 53, &c., after the initial brake engaging movement, the piston 50 is forced leftwards against the bias of its spring 52, so that the valve 46 is closed. Further oil passes from the pipe 45 through the by-pass 48 at a reduced rate, so that further brake engagement is cushioned. As the pressure in the pipe 53 and the brake-engaging servo still further increases, the piston 50 moves still further leftwards, until a pipe 51 is uncovered, thus permitting oil to flow freely to the pipe 53, so that brake engagement is completed quickly. Cushioned engagement of the brake 32 is obtained through a somewhat similar valve and by-pass arrangement 63, 59, in this case a passage corresponding to the pipe 51 being omitted, so that initial brake engagement is obtained quickly, and final brake engagement is completed gently, without the ultimate application of unrestricted pressure. Friction clutches; ratchet clutches.-A flange 1, Figs. 1, 2, on an engine driven shaft, carries pins 2 upon which pivot shoes 3 moved radially outwards by centrifugal force with increasing engine speed against spring bias to engage a drum 4 fast with the gear input shaft 9. Friction ratchet pawls 5 also pivot upon the pins 2, and carry pins 7 engaging notches 8 in the friction shoes 3. The arrangement is such that, when the shoes 3 engage the drum 4, the pin-andnotch connection 7, 8 turns the ratchet pawls 5 to a position where they are clear of the driven clutch drum 4. However, when the engine and the flange 1 are stationary, the ratchet pawls 5 engage the drum 4 so that drive can be transmitted through the gearing to the engine.