Patent GB-982311-A (GB)
Title: Improvements in or relating to overdrive mechanisms for automobile transmissions
IPC: F16H63/30
Filed: 1961-05-05
Abstract: 982,311. Change-speed and clutch control. REGIE NATIONALE DES USINES RENAULT. May 5, 1961 [May 23, 1960], No. 16407/61. Headings F2D, F2E and F2L. [Also in Division B7] The control of a planetary overdrive gear having input and output shafts 11, 23, a directdrive ratchet clutch 27 and an electromagnetic brake 18 engaged to station a reaction sun gear 15 for a step-up ratio, in a motor car transmission, is effected by release of the car accelerator pedal 3 to close switch contacts 47, 60 and thereby make a circuit through a resistor 64 giving cushioned engagement of the brake. With the car stationary and the engine idling, an engine speed proportional potential is applied from a wire 33 through a closed switch contact 36 to an automatic clutch 7, which does not engage, and a wire 41 fed from a source such as an accumulator is connected through a closed switch 45 to the switch contact 47 actuated through links 43 by the accelerator pedal 3. While the accelerator pedal 3 remains in its closed position, the switch contact 47 engages the contact 60 to feed accumulator current 41 through the resistor 64 to the electromagnetic brake 18 which is accordingly lightly engaged. When the accelerator pedal is depressed, the switch contact 47 is moved away from the contact 60 into engagement with a contact 59 leading through a wire 68 to a switch contact 52 at this moment in its open position. Accordingly accumulator current 41 is no longer fed to the electromagnetic brake 18, which disengages, so that the input and output shafts 11, 23 of the planetary gear are directly connected by the ratchet clutch 27. As the engine speeds up, the engine speed proportional potential applied through the wire 33 and the switch 36 to the clutch 7 increases, the clutch engages and the car moves off. When a sufficiently high engine speed has been achieved, an engine speedsensitive device 73 closes a switch 72, 71 to earth a line 69 connected to a switch-operating relay coil 51. The speed-sensitive device 73 may be a centrifugal governor, an electronic device, means responsive to the voltage developed by a separate speed-responsive generator, or means responsive to the pulse frequency of the ignition distributer, but in the form shown the speed-sensitive device comprises a servomotor having a diaphragm 76 subjected upon its opposite sides to the pressure developed across the pump 83 of the engine cooling system. When the high engine speed has been achieved, the diaphragm 76 moves rightwards of the Figure against the bias of a spring 90 to close the contacts 72, 71. While the driver keeps the accelerator pedal 3 depressed, the switch contact 47 does not engage the contact 60, and the switchoperating relay coil 51 remains de-energized. To obtain the step-up ratio in the overdrive, the driver first releases the accelerator pedal 3. The switch contact 47 then engages the contact 60, and accumulator current 41 is fed through a closed switch 45 and the switch 47, 60 to the resistor 64 and the electromagnetic brake 18, which is accordingly gently engaged. The reaction sun gear 15 is then stationed, and planet pinions 14 on a carrier integral with the driving shaft 11 drive a ring gear 22 fast on the output shaft 23 at a higher speed, the ratchet clutch 27 over-running. At the same time, accumulator current 41 is fed through the switch 47, 60 to the switch-operated relay coil 51 which is now earthed. The switch 52 and a switch 53 are thereby moved from their open to their closed positions. The switch 53 now connects accumulator current 41 directly to the switch-operating relay coil 51, so that depression of the accelerator pedal 3 will not prevent current flowing therethrough. On depression of the accelerator pedal 3, the switch 52 connects accumulator current 41 through the switch 60, 59 directly to the electromagnet brake 18, by-passing the resistor 64, as long as the accelerator pedal is maintained in its open position. To effect a ratio upshift in a main change-speed gear 28 (not further described) following the overdrive, the driver closes a gear-shift-lever mounted switch 31 to earth a switch-operating relay coil 42 connected to the accumulator current 41. The two associated switches 36, 45 are thereby moved to their open positions. Opening the switch 36 disconnects the speed-proportional current 33 from the automatic clutch 7, which is thereby disengaged. Opening the switch 45 disconnects accumulator current 41 from the acceleratorcontrolled switch 47, and thereby disengages the electromagnetic brake 18. On establishment of the selected ratio in the main change-speed gear 28, the driver releases the gear-shift-lever mounted switch 31, which is restored to its open condition. The switch-operating relay coil 42 is thereby de-energized, and the two switches 36, 45 are returned to their closed positions. Closing the switch 36 connects the speed-proportional current 33 to the automatic clutch 7, which re-engages. Closing the switch 45 connects accumulator current 41 to the accelerator pedal control switch 47. If the engine speed has now fallen to such a value that the engine speed-sensitive device 73 has opened the contacts 71, 72, the electromagnetic brake 18 will not be energized, and drive will be taken up with the planetary overdrive in its direct drive condition, through the ratchet clutch 27. If, however, the engine speed has not fallen sufficiently for the speed-sensitive device 73 to open the contacts 71, 72, then provided the driver has released the accelerator pedal 3, accumulator current 41 will be supplied through the contacts 47, 60 and the resistor 64 to engage the electromagnetic brake 18, and simultaneously through the switch-operating relay coil 51 to actuate the two switches 52, 53, thus bypassing the resistor 64. Accordingly the drive is taken up with the overdrive in its step-up condition. If, however, on completion of the shift, engine speed has not fallen to such a value that the speed sensitive device 73 has opened the contacts 71, 72, but the driver wishes drive to be taken up with the planetary gear in its direct drive instead of its step-up condition, then by maintaining the accelerator pedal 3 slightly depressed, the contacts 47, 60 are held open, and current is not fed to the electromagnetic brake 18. Further upshifts in the change-speed gear 28 are achieved in the same manner. Downshifts of the planetary gear from its step-up to its direct-drive condition are obtained in the form shown by decreasing engine speed acting upon the speed-sensitive device 73 to open the contacts 71, 72. In a modification, Fig. 2 (not shown), a kick-down accelerator pedal controlled switch is provided in the wire 46 feeding accumulator current 41 to the accelerator-pedal control switch 47. On kick-down of the accelerator pedal 3, this switch is opened, and supply of current to the electromagnetic brake 18 ceases. As a further modification, the kick-down switch may be provided in the wire 69 earthing the switch-controlling relay coil 51. When a ratio is established in the main change-speed gear 28, then on release of the accelerator pedal to energize the reaction brake 18, if the vehicle is on an up gradient, the ratchet clutch 27 and the reaction brake 18 lock-up the planetary overdrive, to prevent the car running backwards independently of engagement of the main clutch 7. Similarly, if reverse is established in the change-speed gear 28, the planetary gear will lock-up to prevent the car running forwards.