Patent GB-434874-A (GB)
Title: Improvements in automatic variable speed gear transmission mechanism such as for automobiles driven by internal combustion engines
Filed: 1934-02-10
Abstract: 434,874. Controlling variable - speed gearing. FLURSCHEIM, C. H., Rushmoor, Fleet, Hampshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Feb. 10, 1934, Nos. 20155/35, 20156/35, and 20158/35. Divided out of 432,981. [Class 80 (ii)] Variable-speed gearing between an internal - combustion engine and a variable load comprises a governor responsive to the engine speed and adapted automatically to operate mechanism selecting the gear ratio employed, the governor acting to bring higher ratios into engagement as the engine speed increases, together with a connection between the throttle and the governor whereby with increase of throttle opening the effectiveness of the governor is reduced and a connection between the selector control and the governor whereby the effectiveness of the governor is increased as higher gear ratios are engaged, the throttle and the selector control acting simultaneously but independently. In a schematic arrangement shown in Fig. 1, an oil pump 1 driven from the engine of a vehicle pumps oil through a pipe 2 to a cylinder 3 so that pressure acts on the end of a piston 4 against the bias of a spring 10. The piston 4 is coupled to a cam 5 and both are rotated by a constantly-driven shaft 6 as described in Specification 432,981. The rotating cam 5 is moved axially by variations in pressure in the cylinder 3 and accordingly strikes arms 8 in succession when moving left in changing up, and arms 9 in succession when moving right in changing down, the arms 8, 9 being rigid upon a common shaft 7 which is rocked in steps to select or to effect speed changes, or to do both. The arms 8, 9 are relatively staggered to avoid governor hunting. The effectiveness of the governor is modified in accordance with engine torque by a leak valve 26 connected to the accelerator 24 which operates the throttle 25, and in accordance with the operative gear ratio by another leak valve 28 geared at 29 to the shaft 7. When the vehicle is accelerating, the engine and the pump 1 turn faster, the piston 4 is moved left, and the cam 5 strikes one of the changing-up arms 8. The shaft 7 is tilted, and, in one form, operates the selector cam shaft, not shown, of a Wilson gear box. Electric contacts 12, 14 and 15, 16 in series through a relay 18 bring in a servomotor 21 which then operates the executive control of the gear box automatically and by power. An executive control pedal 22 thus operated by power operates also the engine clutch, if fitted, and the gear ratio is changed up. The engine in consequence slows down and to prevent changing back, the effectiveness of the governor is increased by the leak valve 28 which is turned partially closed by the same rocking of the shaft 7 as effected the gear change. In Fig. 2 is shown a more practical form of the lay-out of Fig. 1 in which a profile member 34, described in the Specification referred to takes the place of the staggered arms 8, 9. The cam 5 is connected by a key and springs to the constantlyrotating shaft 6 so that it can move with snap action from one step to another of the member 34. The cam 5 is connected by a sleeve 33 to the piston 4 which is acted on by oil from the engine-driven pump 1. The cam 5 has a rim projection 69 by which it tilts the profile member 34 to make the actual selections and changes of speed both in changing up and changing down. The shaft 7 has a linkage connection with the multiple selector cam shaft 43 of the Wilson gear box, which connection can be broken by manually disengaging a clutch 46, after which the shaft 43 can be rocked manually from a lever 44. Contacts 11, 15, Fig. 2, put in motion automatically the executive control to effect the change selected by the shaft 43. The leak valves 26, 28 of Fig. 1 are combined in the arrangement of Figs. 2 and 2a in a single port 26 the size of which is subject both to movement of the accelerator pedal 24 and to movement of the selector shaft 7. Oil in the cylinder 3 passes freely to a chamber inside a sleeve 53 which has an arcuate opening 26 registering with an aperture 64 in an outer sleeve 70. As the throttle pedal 24 is depressed, through a linkage 48, 49, 50, 51, 52 it turns the sleeve 53 so that the effective size of the leak port 26 increases and the effectiveness of the governor decreases. The outer sleeve 70 is adapted to rise and fall and has an arm 71 bearing on a cam 72 on the shaft 7. Upon changing up, the shaft 7 is tilted in a direction to raise the sleeve 70, causing the lower edge of the aperture 54 to close the port 26 in part, and so, by allowing the oil pressure to build up, increases the effectiveness of the governor to compensate for the slowing of the engine and of the pump 1. An arrangement according to the invention is shown in Fig. 9 in which a centrifugal governor 138 mounted on an engine-driven shaft 6 replaces the oil pump governor. The leftward thrust of the governor 138 is exerted upon a sleeve 141 which is splined on the shaft 6 and which carries the cam 5 which engages the profile member 34. This governor thrust is resisted by a spring 148 which acts through a lever 147 pivoted at 149 against an arm 150 upon a rock shaft 151. The throttle lever, not shown, tilts the shaft 151 and so changes the pivot 149 of the lever 147, and thus modifies the action of the governor. This corresponds to the leak valve 26 of Fig. 1. The abutment end of the spring 148 is supported on a lever 152 pivoted at 153 and having a slot 154 engaging a helical cam 155 on the profile member 34. As the shaft 7 rocks to select or effect a speed change, the lever 152 rocks about its pivot, so altering the compression in the spring 148 and thus again modifying the action of the governor. This corresponds to the leak valve 28 of Fig. 1. The invention is applicable to variablespeed gearing of different types, variable stepwise or continuously.