GB879452A - Improvements relating to automobile transmission systems - Google Patents

Abstract

879,452. Variable-speed gearing. SAMPIETRO, A. C. Sept. 27, 1957 [Oct. 12, 1956], No. 31210/56. Class 80 (2). [Also in Group XXXI] A clutchless vehicle transmission comprises an assembly of an overdrive epicyclic train 90-94, an hydraulic torque converter 28, 35, 36 and an epicyclic changespeed and reversing train 69-72, 76, 77 driving directly the crown-wheel and pinion 44<SP>11</SP>, 441 of the rear wheel differential. The driving shaft 10 drives the impeller 28 of the torque converter direct when a clutch cone 97 forming sliding connection between the annulus 94 and the impeller casing 59 is engaged with a cone clutch member 93 on the sun gear 92. For overdrive the clutch 97, 93 is released and the sun 92 held from backward rotation by a one-way brake 951 so that the carrier 90 on the driving shaft 10 drives the annulus 94 at a higher speed. If engine braking is desired in this overdrive, the sun gear 92 must be held by a sliding brake cone 96 engaging the clutch member 93. This brake is adapted to slip at a torque equivalent to full engine torque. The torque converter is of the three element type, the reaction member 36 being held from reverse rotation by a oneway brake 38 but adapted to speed up to the runner 35. The epicyclic train 69-72, 76, 77 provides two forward speed and a reverse by means of a sun gear 69 on the intermediate shaft 34 from the converter meshing with intermeshing planets 70, 77 on a carrier 71. The planets 70 also mesh with an annulus 72 on the driven shaft 44 and the planets 77 with a second sun gear 76 adapted to be held by a brake 79 to give a reduced forward speed. The train is clutched solid for direct drive by a clutch cone 80 on shaft 34 engaging member 78 on sun 76 and reverse is obtained by holding the planet carrier 71 by a brake 74. The clutches and brakes are adapted to be actuated by oil pressure supplied from pumps 67 and 107 on the shafts 10 and 44 respectively. In a modified arrangement single and multiple-plate clutches and brakes are provided. An hydraulic control is shown in Fig. 4 for an arrangement having the overdrive train operated by a brake 101 and clutch 103 and a two speed and reversing train operated by brakes 74, 79 and clutch 104, 105. The front and rear pumps 67 and 107 supply low and high pressure oil respectively and are controlled by a dump and check valve device 136 which automatically relieves the load on the front pump 67 whenever the rear pump is providing sufficient pressure. A selector valve 108 is manually operated to neutral, high, low or reverse positions for the reversing train to control the pressure oil from valve 136 through pipe 109 to the brakes 74, 79 and clutch 104, 105. Pressure oil is also supplied from pipe 109 to a centrifugally actuated governor valve 110 which automatically controls the overdrive train in accordance with the engine speed and the position of the accelerator pedal 112. Thus at low engine speed direct drive is obtained while at higher speeds and low throttle openings the overdrive is engaged. Direct drive can always be obtained ,by over-riding the governor control by full depression of the accelerator pedal, a spring-loaded detent 150 providing an increased resistance to movement of the pedal under such conditions as an indication to the driver of the vehicle. Low, high or reverse drive of the reversing train is obtained by manual operation of selector valve 108 as desired. A reverse interlock valve 124 is provided operated from the rear oil pump so that operation of the reverse brake 74 is prevented if vehicle is in forward motion. A safety valve 120 is also provided to prevent actuation of the low speed brake 79 if the overdrive is in operation. This valve is controlled by pressure through a pipe 118 in accordance with the position of governor valve 110. The rear oil pump 107 wll also provide pressure for push start. Specification 879,456 is referred to.