Patent GB-715746-A (GB)
Title: Improvements in or relating to power transmission systems including friction clutches
Inventor: BRADBURY FREDERICK JAMES
IPC: B60K23/02
Filed: 1951-02-20
Abstract: 715,746. Controlling clutches; change-speed gearing. AUTOMOTIVE PRODUCTS CO., Ltd. Feb. 11, 1952 [Feb, 20, 1951], No. 4144/51. Class 80 (2) An engine-suction servomotor 36 for disengaging the centrifugally-engaged friction clutch 10 of a motor vehicle has electric control means such that the servo is energized to disengage the clutch and the throttle opening is reduced when the change-speed gears are disengaged, while upon engagement of any gear electric contacts which are opened or closed by friction means, depending on whether or not the driving clutch member is rotating faster than the driven member, ensure that the servo remains energized and the throttle opening is increased until the driving clutch member overtakes the driven member. The clutch comprises centrifugal weights 47, Fig. 3, acting between the presser plate 44 and a reaction plate 45 loaded by springs which provide the engaging pressure, the two plates being urged towards each other by other springs. A control lever 52 acts through, a collar 13 on disengaging levers 12 acting on the plate 45 through links 59, and carries a pulley 55 round which passes a cable 56, one end 58 of which is fixed while the other end is secured to the rod 57 of the servo 36. Two resilient contact fingers 65, 66, Fig. 5, carried by the clutch cover 40 secured to the driving flywheel 42 extend into a cam groove 82 in the side face of a ring 74 which is in frictional connection with the driven clutch disc 43 but limited in its rotation relative to the cover 40 by pins 83, 84 co-acting with a projection on the cover 40, the finger 65 being earthed on the cover while finger 66 is connected to a slip ring 68, the arrangement being such that when the cover 40 over-runs disc 43 the fingers are free in the slot 82, but when disc 43 over-runs cover 40 the fingers engage the outer edge of the slot so as to be electrically connected together and so to earth the finger 66. The throttle spindle 104 is normally operated from an accelerator-controlled rod 112 through a normally-rigid telescopic link 109 connected to a plate 105 fixed on the spindle 104, but a pin 106 carried by the plate co-operates with movable stops 107, 108 controlled respectively by single-acting and double-acting engine-suction servomotors 37, 38 which when operative serve respectively to close and open the throttle, the link 109, during this over-riding action, being expanded or contracted against spring action. The rod 57 of the servo 36 has limited axial movement against spring action relative to the diaphragm 86 and carries a valve 95 controlling communication between the working chamber 88 and a conduit 97 connected to a bore in the rod 57. A restricted bypass 98 between chamber 88 and conduit 97 is controlled by a needle valve 101 connected to the accelerator so that the restriction is reduced as the accelerator is depressed. A control valve unit 39 has two solenoids 147, 148 with spring- pressed armatures carrying valve heads 149, 150 which normally close the ends of a central bore 129 connected through a conduit 139 with a non- return valve to the engine inlet manifold 141 and connected to a vacuum reservoir 144 through a conduit 143. Chambers 138, 132 adjacent the solenoid 148 are connected respectively to atmosphere and, through a conduit 146, to servo 37 and to the left-hand chamber 125 of servo 38, while chambers 137, 131 adjacent the solenoid 147 are connected respectively to chamber 132 and to the right-hand chamber 126 of servo 37 through a conduit 145. Chamber 131 is also connected to conduit 97. A two-way switch 41 is operated by cam strips 155, 156 on a shaft 18 adjacent the steering column 15, shaft 18 being slidable to select a gear-shift bar and turnable to displace the selected shift bar by a manual control lever. When shaft 18 is turned to engage any gear, switch 41 connects the battery 159, provided a main control switch 170 and the ignition switch 169 are closed, through a conductor 160 to one end of solenoid 147, while when the gears are disengaged switch 41 is reversed to connect the battery to one end of solenoid 148, the other end of which is earthed. The other end of solenoid 147 is connected to earth via a switch 163, normally open but closed by lever 52 when the clutch is disengaged, and a normally-open switch 164 which is adapted to be closed by a relay 165 connected between slip ring 67 and conductor 160. Alternatively, switch 164 may be omitted and switch 163 connected directly to the slip ring. In operation, when the gears are disengaged so that solenoid 148 is energized, valve head 150 moves to open bore 129 to chamber 132 and to shut off the latter from chamber 138. Suction is thus communicated to chamber 132 and thence to chambers 137, 131 and is effective in servo 37 to move stop 107 to the left to reduce the throttle opening, in servo 36 to disengage the clutch, and in both chambers 125, 126 of servo 38 which is thus inoperative. As a gear is engaged, switch 41 is reversed so that solenoid 148 is de-energized and valve head 150 moves to shut off chamber 132 from bore 129 and open it to atmosphere through chamber 138. Air is thus admitted to servo 37, causing stop 107 to be retracted, and to chamber 125 of servo 38. If at this time the driving clutch member is over-running the driven member so that finger 66 is not earthed and consequently switch 164 is open, the circuit through solenoid 147 is not completed and air passes from chamber 138 to chambers 137, 131 and conduits 97, 145 to servo 36 and chamber 125 of servo 38, causing the clutch to re-engage and the servo 38 to remain inoperative. Should, however, the driven clutch part be over-running the driving part so that finger 66 is earthed and switch 164 is consequently closed, solenoid 147 is energized, moving valve head 149 to open chamber 131 to the bore 129 and to shut it off from chamber 137. Suction is thus communicated to conduits 97, 145 so that the clutch remains disengaged and servo 38 is operated to move stop 108 to the right to open the throttle, until the driving clutch part overtakes the driven part, whereupon the solenoid 147 is de-energized, clutch re-engages and stop 108 is retracted. Clutch engagement is at first rapid, since valve 95 is kept open by the pull on the rod 57, but, on initial contact of the clutch plates, the pull on the rod is reduced, valve 95 closes, and the speed of the final engagement is determined by the restricted bypass 98. A third contact finger may be so arranged that clutch re-engagement is prevented also when the driving clutch member over-runs the driven member and the throttle opening is reduced, this third finger being connected to a separate slip ring and controlling a relay switch in an additional lead to the solenoid 148. The gear control may be automatic. Specification 715,747 is referred to.