Patent GB-664252-A (GB)
Title: Improvements relating to power transmission systems for vehicles
IPC: F02D29/00
Filed: 1948-10-04
Abstract: 664,252. Change-speed control. SULZER FR’RES SOC. ANON. Oct. 4, 1948 [Feb. 17, 1948], No. 25823/48. Class 80 (ii) [Also in Groups XXVII and XXXI] In a motor vehicle transmission including a change-speed gear 4, Fig. 2, a governor 21 responsive to the speed of the vehicle combustion engine 1, and which to govern the engine speed controls the engine torque by acting on the means 33 for controlling the supply to the engine fuel pumps 34, initiates an upward speed change when the engine torque has dropped to a predetermined value, while a governor 39 responsive to engine or primary gear shaft speed initiates a downward speed change when this speed has fallen to a predetermined value, and an adjusting member 27 is provided which acts (a) on the governor 21 as through its spring 25 to adjust the governed speed of the engine, (b) on the governor 39 as through a linkage 35, 37 to adjust the speed at which downward changes are initiated, (c) on the means 33 to adjust the maximum quantity of fuel supplied thereby, and (d) on means 66 to adjust the value of engine torque at which initiation of an upward change occurs. The adjusting member may also control a main clutch 3. As described, the vehicle transmission between the engine 1 and road wheels comprises in series a fluid coupling 2, a friction clutch 3, the gear 4, an overrunning clutch 5 and a reversing-gear (not shown). The gear 4 has four constant-mesh gear pairs brought into engagement by syncro-mesh double dog clutches 7, 8 actuated by servomotors 9, 12, 15, 18 and centralized in neutral by springs 11 when the associated servomotors are de-energized. The servomotors are powered from a fluid pressure source by the operation of the appropriate ones of a series of valves 76, 78, 80, 82, a further valve 84 monitoring the supply of compressed air to the right hand side of a servomotor 87 controlling the clutch 3. The valves are controlled by a sliding cam bar 73 movable by a fluid pressure servomotor 62 controlled through a valve mechanism 50, 51 actuated by the governors 21, 39 through linkwork 66, 68, 69 and a lever 44 respectively. A rod 33 controlling through a spring link 33a the supply of fuel to the engine, which may be of compression-ignition internal combustion type, is operated by the governor 21, subject to a maximum setting determined by the position of a hand lever 27 acting via the abutment of the rod 33 against an auxiliary lever 28 connected to the lever 27 by a spring 39 which is strong enough to prevent relative movement between the levers under the action of the governor spring 25. With the lever 27 in its extreme lefthand position, the engine is set for idle running by the abutment of a stop 31 with the lever 28, and the left-hand side of the servomotor 87 is supplied with compressed air, to cause disengagement of the clutch 3, via a valve 88 acted on by the lever 27 in this position. A spring 87a ensures clutch disengagement should both sides of the servomotor 87 be simultaneously energized or de-energized. To increase engine output, the lever 27 is moved to the right. The cam bar 73 has four positions corresponding to first, second, third and fourth gears, an appropriate projection on the bar opening the corresponding one of the valves 76, 78, 80 or 82 to a supply source in each position. Further projections on the bar 73 co-act with the valve 84 to cause engagement of the clutch 3 in each gear position, with momentary disengagement during each gear change. The valve mechanism 50, 51 comprises a valve member 50 acted on through springs by rods 94, 95 connected to levers 44, 66, and a movable valve sleeve 51 pressed to the right by a spring. The valve sleeve 51 can be moved to the left by the pressure of fluid admitted behind a shoulder 56 via a conduit 54 and ports 52, 53, and co-acts with the member 50 in a manner described in the Specification, to ensure correct gear changing at all times. A stop 47 limits the movement of the valve member 50 to the left. For a given setting of the lever 27 in a given gear ratio, the engine tends to run at a definite speed through the action of the governor 21 on the rod 33. With continued decrease in running resistance, however, the governor 21 moves the valve member 50, through the linkage 69, 68, 66, sufficiently far to the left to connect the left-hand side of the servomotor 62 to a supply source and so initiate an upward gear change at a predetermined minimum engine torque. With continued increase in running resistance, after the governor 21 has moved the rod 33 to the maximum fuel setting allowed by the' position of the lever 28, the corresponding movement of the linkage 69, 68, 66 being insufficient to move the valve member 50 to the right far enough to open the right-hand side of the servomotor 62 to supply, the governor 39 collapses until the arm 44, at a predetermined engine speed, effects such opening so as to initiate a downward gear change. The action of the lever 27 on the setting of the governors 21, 39 is such as to effect upward changes at higher engine torques, and downward changes at higher engine speeds, as the lever is moved to the right. To correlate the action of the two governors, the simple control linkages shown may be replaced by mechanism such as disc gearing or a cam. As shown, also, the spring 42 of the governor 39 has a fixed abutment, but the action of the lever 27 on the governor may be effected by allowing the lever to act directly on the spring 42 so as to compress the spring as the lever is moved to the right. The lever 27 may be moved in steps, when it may be positioned by a notched quadrant, or may be continuously displaced as by a threaded rod turned by a handwheel. A gear ratio indicator 71 is provided. Upward and downward gear changes are made one at a time under the control of an interlock mechanism 98, 105, 106 shown in detail in Fig. 5. When operative pressure fluid is supplied to either side of the servomotor 62 a corresponding piston 110 or 112 is forced inwards and acts on a valve 108 or 109 to pressurize a cylinder 115 and lift a locking plunger 105 from one of a series of notches in the cam bar 73 to allow it to move. A second plunger 106 is allowed bv an interlock lever 118 to be immediately afterwards spring pressed into another notch on the bar 73 so that the latter is prevented from moving by more than the distance between two notches. On release of the pressure in the servomotor 62, a spring 117 returns the device 105, 106 to its starting position. To allow a succession of downward changes when the lever 27 is moved quickly into its lefthand position, the valve 88 supplies compressed air via a conduit 107 to lift the plunger 106. As the plunger 105 is also lifted due to the collapse of the governor 39 having pressurized the righthand side of the servomotor 62, the locking device is immobilized. To compensate for undercharging by an exhaust driven supercharger 121, as on sudden acceleration or due to partial or complete failure thereof, the quantity of fuel supplied is limited to a value suited to the changing air pressure by an overriding lost-motion connection 125 actuated by a bellows 124 subjected to this pressure. The overrunning clutch 5 may be in front of the change-speed gear 4, when the governor 39 is arranged between them and the stop 47 may be of resilient construction. The connection between the levers 27, 66 may be resilient and a dashpot may be employed to prevent the upper end of the lever 66 moving too rapidly to the left on quick actuation of the lever 27 to the right. The manner of operation of the control mechanism at starting and during vehicle acceleration and deceleration, in response to actuation of. the lever 27, is also described. During initial acceleration in first gear, the linkwork 66, 68, 69 tends to be displaced in parallelogram fashion without moving the valve member 50 appreciably. In a modified version of the transmission, Fig. 1 (not shown), the supercharger and the interlock mechanism are oinitted. The governor 21 acts directly on the rod 33 without spring interposition, and the levers 44, 66 are operatively connected to a floating lever pivotally connected directly to the valve member 50.