Patent GB-1258953-A (GB)
IPC: F16H61/08
Filed: 1969-07-29
Abstract: 1,258,953. Change-speed control. AUTOMOTIVE PRODUCTS CO. Ltd. 16 July, 1970 [29 July, 1969], No. 37945/69. Heading F2D. To permit a high I.C. engine idling speed, to avoid undesirable exhaust emission producing atmospheric pollution, and prevent resultant idle drag or creep in the drive position of an automatic transmission manual selector 27, an automatic multi-speed vehicle transmission comprising a planetary bevel gear assembly controlled by hydraulic servo clutches 18, 19 and brakes 15, 23, 24, includes the usual torque converter 26 the turbine of which is initially braked by the engagement of brakes 15, 23 prior to engagement of the forward clutch 18 during manual selection of 1st (low) ratio, i.e. when the vehicle is at rest with its engine idling and the manual selector valve 27 is moved from neutral to its drive position, to eliminate the idle drag of the torque converter at the high engine idling speed, the brakes 15, 23 being released during the final stages of full engagement of clutch 18 to facilitate a smooth shift into 1st ratio. Transmission details.-As shown (Fig. 1) the planetary bevel gear provides four forward ratios and one reverse and is of known type in which the turbine of the torque converter (not shown in Fig. 1) drives through gearing 13 to an input bevel 12 which drives through bevel pinion clusters 10, on a carrier 11, to bevel gears 16, 17 selectively coupled through the clutches 18, 19 to an output shaft 21 for forward and reverse drive respectively, the brakes 23, 15 and 24 serving to station the carrier 11, a reaction bevel gear 14 and the bevel gear 17 respectively, and a one-way brake 22 serving to hold the carrier 11 in one-way only. Engagement of the forward clutch 18 selects 1st ratio and the clutch 18 remains engaged for all the high ratios which are obtained by applying first the brake 24 for 2nd and then the brake 15 with the brake 24 released for 3rd, direct drive (4th) being effected by additionally engaging the clutch 19 all brakes being released. Reverse ratio is effected by engagement of both the clutch 19 and brake 23.  Operation.-As shown (Fig. 2) an engine driven pump 25 supplies pressure liquid to the torque converter 26 and to the manual selector valve 27 which may individually select the forward gear ratios or when the valve 27 is in the position to produce engagement of the forward clutch 18 for 1st ratio, the higher ratios may be selected automatically by a centrifugal governor controlled valve 36. The manual selector valve 27 is connected to the forward clutch 18 by a pressure line 41 in which is arranged a spring- loaded isolating valve 42 normally exhausting the clutch 18 at 45. The line 41 is additionally connected via lines 55 and spring-loaded shuttle valves 48, 49 to the brakes 15, 23, the spring- loaded sides of the valves 48, 49 also normally being exhausted via lines 56, 57 and the valve 42 at 45. When the selector valve 27 is moved to engage the forward clutch 18 for 1st (low) ratio, a pressure build up in the line 41 initially downwardly moves the shuttle valves 48, 49 to engage the brakes 15, 23 to hold the gear train including the input bevel gear 12 and hence the T.C. turbine against rotation to eliminate the idle drag of the torque converter at the high engine idling speed. Further increase in pressure moves the plunger 43 of valve 42 to initiate engagement of the forward clutch 18 and to supply a counter-balancing fluid pressure at the spring- loaded side of the shuttle valves 48, 49 which are thus spring urged back to their initial position to release the brakes 15, 23 the pressure further increasing to fully engage the clutch 18 whereby 1st ratio is engaged smoothly without jerking. In an alternative arrangement, a separate brake acting directly on the input member to hold the gear train against the idle drag of the T.C., may be controlled by a single shuttle valve arranged and operated in a similar manner to the shuttle valves 48, 49.