Patent GB-665463-A (GB)
Title: Improvements relating to power transmission systems for vehicles
IPC: F16H3/089
Filed: 1948-08-25
Abstract: 665,463. Change speed control. SULZER FRERES SOC. ANON. Aug. 25, 1948 [March 16, 1948], No. 22451/48. Class 80 (ii). [Also in Groups XXVII and XXXI] In a motor vehicle transmission including a change-speed gear 4, a governor 21 driven by the vehicle engine controls both the supply to the engine fuel pumps 34 and the gear-changing means in such a way that when due to running conditions the engine torque is reduced by the governor to a pre-determined value an upward speed change is initiated and when due to running conditions the engine speed falls to a predetermined value at which the governor lies outside the limit of the fuel regulating range a downward speed change is initiated. The governor spring 25 may be adjustably loaded by a hand control lever 27 which also determines the maximum fuel supply for any particular governing speed and itself influences the gear changing means. As described, the vehicle transmission between the engine 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 constantmesh gear pairs brought into engagement by synchromesh double dog clutches 7, 8 actuated by servomotors 9, 12, 15, 18 and centralised in neutral by springs 11 when the associated servomotors are de-energized. The servomotors are powered from a compressed air or other fluid pressure source by the operation of the appropriate ones of a series of solenoid valves 76, 78, 80, 82, a further like valve 84 monitoring the supply of compressed air to the right-hand side of a servomotor 87 controlling the clutch 3. The solenoid valves are controlled by a contact plate 89 movable by a compressed air servomotor 62 controlled by valves 58, 59 operated by the governor 21 and lever 27 through a linkwork 69, 68, 66, 65, 52. The rod 33 controlling the supply of fuel to the engine, which is of internal or other combustion type, is actuated by the governor 21 through a spring 171, subject to a maximum setting determined by the position of the lever 27 acting via the abutment of the rod 33 against an auxiliary lever 28 connected to the lever 27 by a spring 29 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 left-hand position, the engine is set for idling running by the abutment of a stop 30 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 the right-hand side of the servomotor 87 be simultaneously energized. To increase engine output, the lever 27 is moved to the right. The plate 89 has four positions corresponding to first, second, third and fourth gears, a lower stepped contact area 73 being constantly supplied with potential and, according to the position of the plate 89, energizing a corresponding one of the solenoid valves 76, 78, 80 or 82 when this is also connected to earth on the other side thereof either bv the connection of contacts 107-110 to a contact 111 by a bridging contact 85 operated on disengagement of the clutch 3, or by the bridging of appropriate contacts by interlock levers 9', 15<SP>1</SP> actuated with the clutches 7, 8. The solenoid valve 84 is also energized from the area 73 when appropriate ones of further sets of contacts are bridged by the levers 9', 15<SP>1</SP>, the arrangement being such that, upon the plate 89 moving from one to another of its gear positions, the previously operative one of the servomotors 9, 12, 15, 18 is de-energized simultaneously with disengagement of the clutch 3, which latter causes bridging of the contacts 107-111 and effects energization of the servomotor corresponding to the new gear ratio. The resultant gear-establing movement acts through the associated interlock finger both to bridge contacts energizing the valve 84 to re-engage the clutch 3 and to bridge contacts maintaining the circuit to the operative one of the valves 76, 78, 80, 82 despite this action. 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 fuel supply control rod 33. With continued decrease in running resistance, however, the governor moves outwardly sufficiently to operate, through the linkage 69, 68, 66, 65, 52, a valve control 53 so as to open the valve 58 to initiate an upward gear change at a predetermined minimum engine torque. Conversely, on continued increase in running resistance, the valve 59 is opened to initiate a downward gear change, but this is arranged not to occur until the maximum setting of the rod 33 has been exceeded and the engine speed has further decreased by a predetermined amount. Upward or downward gear changes are made one at a time under the control of an interlock mechanism comprising a quarter-turn pawl device 155, 156 and elliptic cams 158, 159 alternately depressing plungers 160, 161 co-acting with a locking bar 164 fast with the piston of the servomotor 62. The pawl device 155, 156, which is centralized by a spring-loaded star wheel 157, is stepped round by a servomotor 152 which is actuated through a two-way valve 150 whenever pressure is built up in either of the conduits 60, 61 from the valves 58, 59 to the servomotor 62. To prevent operation of the interlock mechanism by air discharging from the servomotor 62, there may be a clearance between the members 155, 156 or the air may pass through throttling devices on leaving the servomotor. On re-engagement of the clutch 3 after gear-changing the reaction on the governor 21 is normally such as to close whichever valve 58 or 59 had been opened to initiate the gear change so that the servomotor 62 is de-energized ready for a further change when required. To ensure that the servomotor 152 is de-energized at each gear-change, a solenoid valve 151 is placed in the supply line to the servomotor and allows compressed air to pass thereto only when energized. Such energization is normally effected by the contact 85 bridging contacts 122, 123 when the clutch 3 is engaged, so that the disengagement of the clutch 3 on gear-changing closes the valve 151. In order to effect gear-changing when the lever 27 is in the idling position and the clutch 3 is held disengaged, the solenoid 151 is then energized from an upper contact area 74 to which potential is at such times supplied by the closing of contacts on the valve 88 to energize a lead 75, the area 74 being appropriately gapped as shown to cause consecutive energization and de-energization of the solenoid 151 as required. An auxiliary linkage 45, 48, 50 is acted upon by the lever 27 when placed in its idling position so as to move the fulcrum of the lever 52 and ensure the engagement of first gear at such times. The manner of operation of the control mechanism at starting and during vehicle acceleration, in response to actuation of the lever 27, is also described. During initial acceleration in first gear, the linkwork 69, 68, 66 tends to be displaced in parallelogram fashion without moving the rod 65 appreciably. A dashpot 90 is employed in conjunction with a spring 99 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. To achieve a non-linear stiffness characteristic, the springs- 25, 99, 171 may each be replaced by multiple springs, or each spring may have a non- linear stiffness characteristic which is inherent therein or provided by a suitable lever linkage. An indicator 71 showing which gear is engaged may be provided. The clutch 3 and also the clutch 5 may be dispensed with. In a hydraulically operated version of the transmission, Fig. 2 (not shown), the control valves 76, 78, 80, 82 and 84 monitor pressure liquid and are operated by a sliding bar cam mechanism similar to that of Fig. 1 of Specification 664,252 and actuated by an oil or other liquid pressure servomotor.