GB1094002A - Variable speed transmission - Google Patents

Abstract

1,094,002. Change-speed gear; clutches. ROLLER GEAR Ltd. ZUG. May 10, 1965, No. 19699/65. Headings F2C and F2D. A motor vehicle transmission consists of a varable-speed gear unit 22 combined with an epicyclic gear 24 comprising units 44, 46, 48 with ratio shift clutches C 1 , C 2 , C 3 and brakes B R , B F hydraulically controlled by a valve 256 giving an automatic transmission with four forward and two reverse ratios. General arrangement (Fig. 4).-As shown the variable-speed unit 22 is the ball-type friction gear described in Specification 998,863 and the epicyclic unit 44 is of the three-element type, of which the sun gear 54 is connected to the output 30 from the unit 22. The intermediate epicyclic unit 46 has double planet pinions 82, 86, the former meshing with a sun-wheel 84 connected to the input shaft 26, while the latter meshes with an annulus 90 integral with the annulus 56 of the unit 44. The final epicyclic unit 48 has a sun-wheel 128 connected to an intermediate shaft 108 and double planet pinions 112 connected to the output shaft 28 and meshing with brake annuli 130, 126, the latter through idlers (124), Fig. 3 (not shown). Clutch and brake details (Fig. 2).-The clutches C 1 , C 2 , C 3 form a unit, the outer one Cl comprising discs 152 engaged by an annular piston 158, release springs 172 being provided in a balance chamber 176 filled with liquid not under pressure, but which counterbalances the centrifugal effect of liquid in the piston pressure chamber 162. The inner clutches C2, C3 comprise discs 184, 211 engaged by annular pistons 190, 220 respectively. Clutch C 1 couples the carrier 96 for planets 82, 86 to the intermediate shaft 108, while clutch C 2 couples the intermediate sun gear 88 with shaft 108 and clutch C 3 couples the ring gear 126 to shaft 108 and thus to the rear sun gear 128 for direct drive between the intermediate and driven shafts 108, 28. The brakes B R , B F are of the band type. hydraulically operated for selectively holding the annuli 126, 130. A modification, Fig. 20 (not shown), includes a further clutch (C 4 ) for coupling the ring gear member 64 with shaft 108 to provide an extra low or " creeper " ratio. Hydraulic control system (Fig. 11 ).-Regulator valve 256 is controlled by a servo valve 250 connected by a linkage 248 to an output-driven governor 244 and to the accelerator pedal 246, valve 250 controlling the supply of pressure liquid to a chamber 252 housing a piston 370 attached to the lower end of valve 256. The effect of the governor on valve 250 is more pronounced than that of the accelerator, so that a relatively small change in vehicle speed will cause a ratio shift. The brake pedal 506 is also connected to valve 250 and the brake linkage is so arranged that movement of the pedal first moves valve 250 to initiate engine braking before the wheel brakes are engaged. Outlet ports 168, 198, 228 communicate with the ratio clutches C 1 , C 2 , C3 respectively, and a further outlet 350 connects with a selector valve 352 controlling the brakes B R , B F . The upper end of valve 256 is connected by a linkage 242 to a lever 430 operating the control ring 254 of the variable-speed friction gear 22. Operation.-As the engine speed increases at starting a dashpot device 396 between the throttle valve 394 and regulator valve 256 causes opening movement of the latter at a rate depending on the rate of movement of the accelerator, to engage clutch C 1 and brake B F , and also set the control ring 254 of the friction gear unit for minimum ratio and thus provide first forward ratio. Second ratio is obtained by releasing clutch C 1 and engaging clutch C 2 , third ratio by engaging both clutches C 1 , C 3 and releasing brake B F , and setting ring 254 for maximum ratio of the friction gear 22, while fourth ratio is obtained by engaging both clutches C 2 , C 3 with both brakes released, and ring 254 returned to the minimum ratio setting. The governor and throttle control linkage arrangement 248 is such that the speeds at which ratio changes occur depend upon accelerator position, the speeds rising for heavy accelerator settings. The first ratio in reverse is obtained with clutch C 1 and brake B R engaged, and the second with clutch C 2 and the same brake engaged.