Patent GB-499690-A (GB)
Title: Improvements relating to automatic control devices for variable-speed transmissions,particularly for automobile vehicles
Filed: 1938-01-22
Abstract: 499,690. Variable - speed gearing. FLEISCHEL, G. Jan. 22, 1938, No. 2197. [Class 80 (ii)] In a power transmission mechanism, particularly for automobiles, the variable-speed mechanism 4, Fig. 1, arranged between the driving engine 1 and the driven shaft 8 is automatically controlled by the speed of the engine and the suction in the induction pipe for " up " changes whilst for '' down " changes the suction effect can be over-ridden by volitional means under control of the driver. The gear lever 6 which has a number of positions corresponding to the various speed combinations is adapted to be actuated by a servomotor 40 under control of a valve 45 which is adapted to place either side of the piston 41 into communication with suction from the engine induction manifold through a pipe 79. The valve 45 is electrically controlled by solenoid windings 50d and 50m for moving the piston 41 to change " down " and " up " respectively and the circuits 39d and 39m of these windings are controlled by contacts 20d and 20m on a rocking bar 14 co-operating with fixed contacts 22d and 22m. The end 20m of the bar 14 is connected to a diaphragm 17 subjected to the induction pipe pressure through a conduit 36 whilst the other end 20d is connected -through spring 19d and a lost motion device 29, 30 with the engine accelerator pedal 3. The centre of the bar is connected by a link 13 for operation by a speed governor 10. When the engine has been started and is rotating at a slow speed the force from the governor 10 is unable to overcome the thrust of springs 19d or 19w and the contact 22d is kept closed and the contact 22m open which results in the valve 45 being operated to move piston 41 to the low speed position as shown. One general clutch 9 or separate clutch devices associated with the various gear trains may be provided and the operation may be automatic in the manner described in Specifications 376,730, 406,884, and 420,620 so that as the engine is accelerated the drive is taken up in this low or first speed. As the speed of the engine increases the governor acts on the bar 14 together with the suction on the diaphragm 17 to break the contact 22d and move bar 14 against springs 19d and 19m to close contact 22m which operates valve 45 to move piston 41 to the right for effecting a speed change to a higher gear. The movement of the piston 41 is controlled in steps by a spring detent 47 engaging with spaced notches 49 on piston rod 42. The slowing up of the engine resulting from the change of speed breaks the contact 22m to restore the valve 45 to neutral and prevent continued operation of the servomotor 41. On further increase in the speed of the engine the operation is repeated for changes to the next higher speeds or conversely on slowing down of the engine the action of the governor diminishes and the bar 14 is moved to close the contact 22d to bring in the next lower speed. This operation alone requires a rather considerable and un- . desirable reduction of speed before the speed change is effected and the lost-motion connection from the accelerator 3 is provided so that on complete depression of the accelerator pedal for the full load of the engine in the higher gear the stress of the spring 19d is increased to make the contact 22d for the change down to the lower gear without waiting for the speed of the engine to fall to a determined value. A valve 37 is provided in the conduit 36 under the control of the driver so that under certain conditions, for example on steep gradients, the action of the suction can be suppressed to prevent, to a certain extent, changes to a higher speed, the governor 10 only being in control. The interruption of the drive during the speedchanging operations may result in rapid changes of speed and of the suction operating on the automatic mechanism which may produce conditions for a further change of speed whilst one speed change is already in progress. To avoid this state of affairs and to ensure that the normal drive is resumed after each speed change a retarding device is provided which comprises an electrically actuated and dashpot-controlled switch 52d, 52m in the circuits of the windings 50d, 50m of the valve 45. When either of the contacts 22d, 22m is made a coil 54 is energized and breaks the contacts 52d, 52m with a fairly rapid action which is allowed by a dashpot 58 to return the valve 45 to its neutral position after it has been opened sufficiently long to move the piston 41 for the desired speed change. The contacts 52d 52m are then closed slowly by a spring 57 to allow time for the normal conditions of drive in the new speed to be resumed before the mechanism can operate for another speed change. A mechanical locking and retarding device may be provided as shown in Fig. 2, for the piston 41. In this device notches 63, 80 corresponding to the various speed positions are provided in a fixed guide 62 of the piston rod 42 which are adapted for engagement by balls 65 in a transverse groove 64 of the rod 42. Opposite the guide 62 is provided a sliding block 66, with corresponding notches 68, 81, which is connected to a rocking lever 71 co-operating with a spring-loaded dashpot piston 59<1>. When the piston 41 is moved to the right under the pressure of the actuating fluid the balls drop into the notch 68 of the lower block 66 which slides with the rod 42 and compresses the dashpot spring 571, the dashpot fluid escaping freely on this movement. When the balls have reached a position opposite the next notch 80 they forced by the pressure of the spring 57<1> into this notch to immobilize the rod 42 and piston 41 in this position, the block 66 sliding back to its original position under dashpot control so that an interval of time elapses before its next notch 81 is in a position to receive the balls 65 and free the rod 42 to allow another gear change. This action is repeated for further changes in either direction. This mechancal locking and retarding device may in addition be adapted by a lost-motion connection from the sliding block 66 to restore the valve 45 of Fig. 1, to its neutral position after each movement of the piston 41. In a modified arrangement in Fig. 5, the governor 10 and the induction pressure device 17 are arranged to operate the control valve 45 of the servomotor 40 directly through a link 20. The governor acts against a spring 19d, the effect of which can be modified by an extreme movement of the accelerator pedal through the lost-motion connection 29, 30 as before, and a spring 19m, which in the neutral position of valve 45 bears against a shoulder 89 and the stress of which is modified bv the suction on diaphragm 17. A locking and retarding device similar to that in Fig. 2, is provided comprising notches 801 along the side of the piston 41<1> itself which co-operate with a locking pin 65<1>, and a sliding rod 66<1> with corresponding notches 81<1> moved by the piston rod 42 through a spring connection 57<2> under control of a rotary vane-brake 100. The rod 66<1> therefore follows up the movement of the piston 41<1> with a certain amount of delay and by means of transverse passages 97d, 97m co-operating with multiple fluid-pressure conduits 98d, 99d and 98m, 99m ensures that the pressure communication to both sides of the piston 411 is open in each speed position of the piston. The locking pin 65<1> operates in a similar way to the balls 65 in Fig. 2. A pressure or hydraulic servomotor may be used instead of the suction servomotor 40 for operating the gear-change mechanism or mechanical or electrical power devices may be utilized.