GB518581A - Improvements in and relating to internal combustion engines - Google Patents

Abstract

518,581. Fluid-pressure servomotor-control systems. PORSCHE, F. Aug. 26, 1938, No. 25085. Convention date, Sept. 18, 1937. [Class 135] [Also in group XXIV] The valve timing of an internal combustion engine is varied by altering the relative positions of two parts of the valve control shaft by means of a hydraulic or pneumatic motor controlled directly or indirectly in accordance with the speed of the engine and the position of the engine throttle valve. In the arrangement shown in Fig. 2 a double-acting annular piston 45 is connected by a ball-bearing 44 with a coupling member 13 having a steep pitched screw-threaded engagement with a shaft connected by bevel wheels 8, 9 with the crank shaft 7 and connected by vertical splines with a bevel wheel 11 meshing with a bevel wheel 12 on the valve timing shaft 6. A control valve 59 is influenced by the vacuum in the intake manifold 74, the latter raising a spring-loaded piston 71 connected to the control valve by levers 64, 61 of which the former 64 has an adjustable fulcrum 67 whilst the pivotal connection 63 between the levers moves between adjustable stops 65, 66. The control valve has follow-up mechanism comprising the lever 61 and a rod 62 connected to the coupling at 70. The feed pump has a bye-pass relief valve 22. In a modification the coupling is actuated by a single-acting spring loaded piston acting through a lever and under the control of a governor pump, the suction and delivery sides of the pump being connected through a bye-pass passage controlled by a throttle valve linked to the accelerator pedal. The Specification as open to inspection under Sect. 91 comprises also a modification in which the engine lubricating pump is connected with a power cylinder, the piston of which actuates the coupling. A bye-pass conduit connecting the suction and delivery sides of the pump is fitted with a slide valve controlled by an enginedriven centrifugal governor acting through a lever. The arrangement is such that the timing is advanced as the engine speed increases and the characteristic of the governor may be such as to produce first a rapid advance followed by a more gradual advance as the speed increases. The centrifugal governor may be replaced by a governor pump or by an electric generator. This subject-matter does not appear in the Specification as accepted.