GB670086A - Improvements in and relating to automatic control of vehicle infinitely-variable hydrostatic transmission gears - Google Patents

Abstract

670,086. Hydraulic power transmission devices ; fluid pressure servomotorcontrol systems. COOK, C. A. (Ges. der L. von Roll'schen Eisenwerke Akt.-Ges.). Nov. 25, 1948, No. 30633/48. Classes 69 (ii) and 135 [Also in Group XXXI] In an infinitely variable hydraulic vehicle drive comprising an oil pump driven directly from the engine and having a steplessly variable displacement and one or more oil motors having a fixed or regulable displacement serving for transmitting the arbitrarily variable engine output to the two or more driving wheels of a vehicle, a hydraulic governing means is provided in connection with the oil pump, biassed in accordance with the engine output on one hand and in accordance with the operating pressure of the hydraulic drive on the other hand and controlling the oil pump so that the torque available on the engine shaft is converted at any moment and in an infinitely variable fashion into the total torque required on the driving wheels. In Fig. 1 a vehicle engine 1, for example an internal combustion engine, drives an oil pump 2 which supplies oil under pressure to a pipe A and draws in oil through a pipe B. From the pipe A according to the position of a reversing valve 5 oil under pressure is supplied either to a pipe C or a pipe D, the latter pipes leading to liquid motors 3, each driving independently a vehicle driving wheel 17. The output of the pump 2 is variable by means of a regulator 4 shown in section in Fig. 2. A lever H is operated by movement of an engine throttle pedal. The lever H forces the parts S, K, T, U and M to the right together with the servomotor N. This causes the pump 2 to deliver oil and the pressure built up acts on the piston M and exerts a compressing force on the spring G. The pressures in the drive act on the pistons K L, and also influence the control. When the operator suddenly interrupts the supply of fuel to the engine the motors 3 act as pump and deliver power to the engine. The pressure produced by the motors, acts on the piston 4 and adjusts the pump displacement. When the pressure is reversed the piston L moves the pump to full displacement. This prevents an undesired braking of the vehicle. The higher the pressure in the pipe B, i.e. the steeper the gradient and the absorbed torque, the more the pump displacement is reduced and the smaller is the running speed. A safety valve 7, a braking valve 8, idling valve 9 and vent valve 10 are provided. Selector valves 6 enable any of the motors 3 to be disengaged. A pure front wheel or rear wheel drive may be established. Operating pressure actuated pistons may be provided to open the valves 6 when a certain limiting value of the operating pressure is attained, thus re-engaging all the motors. The reversing valve 5 includes a byepass passage through which the output of the pump is passed when the valve is in neutral position and thus serves to preheat the oil. The pump and motor may be built together as a unit and be coupled to the engine, the output of the unit being transmitted through a Cardan shaft mechanical differential gear and wheel shafts on to the driving wheels.