Patent GB-898266-A (GB)
Title: Improvements in gear-change arrangements for change-speed gears
Inventor: ALTMANN WERNER
IPC: F16H63/30
Filed: 1960-06-17
Abstract: 898,266. Change-speed control. DAIMLERBENZ A.G. June 17, 1960, No. 21361/60. Class 80 (2). Change-speed control mechanism comprises an electric circuit including holding relays, energization of the circuit, e.g., by actuation of a ratio shift lever, producing a pulse of current which energizes the holding relays to maintain energization of ratio shift means until establishment of a selected ratio, cut-out switches then de-energizing the holding relays. In the form shown, a servomotor 11 energized by the inlet manifold depression of a motor car engine acts through a link 12 to disengage the main clutch 10 of the car, a link 13 connecting the clutch to a rod 14 slidden to act through pawls 18, 20 upon a ratchet wheel 15 turning the ratio selecting shaft 16 of the car change-speed gear 17. The servomotor 11 is controlled by a circuit containing holding relays 39, 37 energized when a ratio shift lever 21 is moved either up or down to close contacts 22, 23. Movement of the shift lever 21 downwards for a ratio downshift closes the contacts 23 and connects a positive line through a normally closed switch 41 to the coil of the relay 39, which is energized to close its normally open switch. Simultaneously, current is passed through the coil 37 of the relay 33 to close its switch, the current passing through a normally closed switch 35 and also passing to the control of the servomotor 11 to commence disengagement of the main clutch. Under the conditions described, for a downshift only the pawl 18 on the rod 14 can engage the ratchet wheel 15. Accordingly, as the link 12 is moved by the servomotor 11 and disengagement of the main clutch 10 takes place, the connecting link 13 slides the rod 14 and through the pawl and ratchet wheel 18, 15, turns the ratio selecting shaft 16 in the change-speed gear 17. The rod 14 is connected by linkwork 36 to the normally closed switches 35, 41, which are opened on completion of establishment of a ratio to de-energize the holding relays 33, 39. The clutch 10 is then re-engaged by its usual springs, and the apparatus returned to the position shown. If, however, an upshift is required, the ratio shift lever 21 is moved upwards to close the contacts 22, thereby energizing a relay 26 whose contacts 29 are closed to energize from a separate source of potential a holding relay 25 and close contacts 24, so that a solenoid 19 is energized to raise the ratio shift rod 14 to such a position that the pawl 18 lies clear of the ratchet wheel 15, but the pawl 20 instead lies in the path of the ratchet wheel. Closing the switch 29 simultaneously energizes the circuit leading through the switches 41, 35, so that a ratio upshift is now obtained in the same manner as described above for a downshift, completion of the ratio upshift acting through links 31 connected to the rod 14 to open a normally closed switch 30, thereby de-energizing the holding relay 25 to enable the switch 24 to open and allowing the ratio shift rod 14 to fall in preparation for a downshift. As a modification, the holding relay 39 can be omitted, the switches 22, 23 instead being connected directly by a line 38 to the relay 33. In this latter form, there is a risk that if the contacts 23 are maintained closed for a considerable period, the clutch 10 will not re-engage correctly, since the relay 37 will be maintained energized. As a modification, Fig. 2 (not shown), the servomotor 11 is connected to the link 12 by a spring, so that in the event of gear-wheels in the change-speed gear 17 not meshing during establishment of a ratio, the spring is compressed to cause closure of a switch energizing a relay in the line 32 leading to the servomotor, this switch then opening so that the servomotor no longer tries to force non- meshing teeth into engagement. As a further modification, the ratio shift lever 21 actuating the switches 22, 23 may be replaced by pushbuttons. These push-buttons may be connected mechanically in series so that a slight pressure actuates one button and a considerable pressure actuates the other. As a further modification, the switches 22, 23 may be disposed some distance from each other, for example by mounting the upshift switch 22 on the car dashboard and the downshift switch 23 near the floor for foot operation, in which case the latter switch may be combined with the accelerator and/or the brake pedal. In the form shown the servomotor 11 is vacuum operated, but alternatively the control circuit may be connected directly to electromagnetic ratio shift mechanism. The ratio selecting shaft 16 may be connected to a device for indicating the speed and operable manually by a knob containing the switches 22, 23 actuated by push-buttons.