Patent GB-506739-A (GB)
Title: Device for automatic ascertainment of the transmission ratio of a gear coupled to aninternal combustion engine
IPC: F02D29/02
Filed: 1937-11-30
Abstract: 506,739. Comparative-speed indicators; gearing. HEFEL, K. Nov. 30, 1937, Nos. 33103 and 33104. Convention dates, Dec. 1, 1936 and Nov. 23, 1937. [Class 106 (iii)] [Also in Group XXIV] Comprises a device for the automatic adjustment and /or indication of the transmission ratio of a gear coupled to an engine which gives optimum efficiency at any time, characterized in that the adjusting and /or indicating means are brought into dependence on the speed of the driven shaft and also on the regulating member for the engine control such that they adjust the transmission ratio to a value or indication that corresponds to the most economic speed for the driven shaft having regard to the particular characteristic of the engine as described with respect to Fig. 1. In Fig. 1, 0A, 0B, &c. represent curves of output against speed corresponding to, the full charge half charge &c. If points of equal effective output (brake power) always with the most favourable angle of ignition advance, are connected, the curves a-a, b-b &c. result. The lowest points on these curves give the most favourable working conditions and the dotted line curve 1-2-3- 4-A give the characteristic for the particular engine along which the charge and speed of the engine must be adjusted for maximum efficiency at different effective outputs. This may be achieved by proper selection of the transmission ratio. A governor 11 driven from the driven shaft n<2> moves a contact 12 across a band of conducting strips 14-19 insulated from each other carried by a plate 15. The band, as a whole is moved bodily at right-angles to the path of the contact 12 by the accelerator pedal 27 and the strips are shaped so that the lines 22-22, 23-23, &c. correspond with the points 1, 2, &c. of Fig. 1. The result is that the correct relay 26 is energized to release the corresponding gears or to operate indicating mechanism for the gear to be changed by hand. By fitting 'a device which allows arbitrary disconnection and reconnection between the pedal 27 and valve 29, the engine may be used as a brake. In a mechanical form a cam drum operated from the pedal 27 has pressed against it a roller on an arm carried by the rod moved by the governor. A pointer moved over a scale. carried by the rod indicates the most economical transmission ratio. Fig. 7 shows an automatic arrangement in which the accelerator pedal 51 is extended at 53 and provided with a pin 54 engaging a slot in a pivoted plate 56 which slot is shaped according to the optimum efficiency characteristic of the engine, the plate having a second slot 60 engaging a pin 59 to impart movement to a contact plate 441. The lengths of the contact areas on the rod are proportional to the logarithm of the speed of the engine. A pump 68 driven from the shaft 61 by eccentric and rod 62, 64 pumps liquid from a sump 67 through non-return valves 66, 66<1> to a spring piston 73. Graded holes 75 fitted with adjustable needle valves (not shown) are provided, the arrangement being that the piston 73 and rod 48 are moved horizontally proportionally to the logarithm of the speed of the driven shaft n<2>. An electric transmission gear 82 of the type described in Specification 461,306, [Group XXXV], is connected to contact bars 90, 94, 90<1>, 941 as shown. A battery 96 is connected through a resistance 92 to the contact 90<1>. As relative movement takes place between contact 12 carried by the rod 48 and the contact bar 44<1> moved by plate 56, resistances 85 are cut in or out of the field of the variable speed drive so that the optimum ratio between n<1>, n<2> is kept. A byepass 77 with a regulating'valve 7 affords an adjustment by which movement of a pointer operated from the piston 73 can be kept aligned with-the pointer of a speedometer.