GB642791A - Speed change system - Google Patents

Abstract

642,791. Change-speed control; positive clutches. TAYLOR, R. S. Feb. 24, 1948. No. 5462. Convention date, Aug. 25, 1942. [Class 80(ii)] A change-speed gear having planetary gearing which may be locked for direct drive includes a rotor, means for selectively connecting or disconnecting the rotor to the gearing, and a bar positively engageable with the rotor to hold a part of the gearing coaxial with the rotor against rotation when the rotor is connected to the gearing, said bar being movable transversely to, and along an axis spaced from, the axis of the rotor. As shown, applied to a motor vehicle auxiliary two - speed overdriving unit 2, Fig. 1, following the main change-speed gear 7 and having a housing 8 forming an enlarged section of the torque tube 6, the gear comprises a driving carrier 16, Fig. 5, the planet of which meshes a driven annulus 17 and a reaction sun 22. In normal operation, the sun 22 is connected to a rotor 32 by a clutch sleeve 34 engaging teeth on clutch members 23, 33 integral with the sun and rotor respectively. The rotor 33 has teeth 48; Fig. 6, engaged by a sliding bar 43 to lock the rotor and sun 22 bidirection ally' for overdrive. The bar 43 is retained in engagement by a plunger 51, Figs. 3 and 6 entering between rollers 53. Direct drive through the gear is established by withdrawing the plunger 51 when the reaction torque (clockwise in Fig. 6) on the rotor drives back the bar 43 and frees the rotor and sun 22, and a previously overrun one-way roller clutch 106 between the sun and the annulus 17 picks up to lock the gearing solid. Withdrawal of the plunger 51 is effected against spring loading by a Bowden cable 59, Figs. 1 and 3, having fast on the remote end thereof abutments 64, 68 operatively moved by elements of the engine throttle and main clutch linkages 67, 69 whenever the accelerator pedal 58 is fully depressed or the clutch pedal 71 is actuated for clutch release. In the latter case, the plunger is withdrawn far enough for a spring-urged sliding latch 74, Fig. 3, to engage behind a shoulder on the plunger and retain it despite subsequent main clutch engagement until the bar 43 is retracted when the latch is carried back to release the plunger by a rotary catch 74 actuated by the bar movement. The plunger 51 then rests idly upon the rollers 53. Overdrive is re-established by torque reversal on the rotor 32, as by accelerator release. A ring 81 fast with the rotor then turns, through ratchets 78, Fig. 7, a ring 77 and moves the bar 43 into engagement through a drag link 84 connecting it to the ring. Snap-over means are provided to ensure that bar travel in either direction, once initiated by torque reversal, is fully completed. Such means comprise a tangent spring 91 acting between the ring 77 and an anchor ring 92, Fig. 5, so as to bias the ring 77 in the bardisengaging direction of rotation. ' The knee 99 of an overcentre toggle 97, 98 between the housing 2 and the ring 77 is acted upon by a spring plunger 96, Fig. 5, so that the toggle acts to oppose and finally overcome the bias of the spring 91 when broken as shown in Fig. 7, but assists the latter when the bar is disengaged and the link 97 is swung overcentre slightly past a radial position. The ring 92 reacts against stepped tangent screws (not shown) in the housing 2 which are adjustable to turn the ring 92 and vary the loading of the spring 91. The clutch sleeve 34 is operated from a rock shaft 115 and may be moved against the loading of a spring 116, Fig. 11, to disengage the rotor 32 and clutch the sun 22 bi-directionally to the annulus 17. The teeth 39 of the sleeve 34 co-act with complimentarily chamfered teeth 138 on a ring 134 having also axial teeth 136, Figs. 5 and 13. constantly engaging with rotary play teeth 137 on an extension 108 of the annulus. The teeth 138 have bevelled leading edges 139 to facilitate clutch engagement, but if the teeth 138, 39 abut end on despite this, bevels 141 are provided on the member 108 to cam the ring 34 into a position of free engagement. The clutch 34, 134 is engaged automatically when the main transmission 7 is put into reverse, a lever 117, Fig. 1, actuating the shaft 115 being connected by a linkage 126, 127 to the main reverse selector rod 128. Movement of the lever 117 to engage the clutch 34, 134 throws a spring-loaded linkage 122, 118 over-centre about a pivot 119 until an abutment 123 on the link 122 rests on the lever 118. Subsequent disengagement of the clutch 34, 134 can be effected only by depressing a manual dash-button 132 connected to the lever 118 via a Bowden cable 129. The button 132 forms an overriding manual control whereby bi-directional direct drive may be instituted at any time. The shape of teeth 48 and bar 43 is such that the bar locks the rotor bi-directionally and acts to prevent the vehicle running backwards down a gradient when in overdrive. The gearing is lubricated by a screw impeller 142, Fig. 5, which pumps oil from the bottom of the housing 2 to the gearing through an opening 144, the oil returning to the housing through a further opening 146. A scoop ring 149 on the carrier 16 feeds oil via the hollow planet bearing shaft 14 and a conduit 152 to the planet pinion bearing.