Patent GB-638151-A (GB)
Title: Intake pressure control apparatus for supercharged internal combustion engines
IPC: F02D9/00
Filed: 1947-01-02
Abstract: 638,151. Fluid-pressure servomotor-control systems. GENERAL MOTORS CORPORATION. Jan. 2, 1947, No. 145. Convention date, Feb. 5, 1946. [Class 135] Intake pressure control apparatus for an internal-combustion engine, e.g. an aircraft engine, having a variable speed supercharger, comprises a throttle valve regulator controllable by engine intake pressure for so positioning the throttle valve as to maintain a selected intake pressure, and means operative coincidentally with movement of the throttle valve from nearly to fully wide open position for causing an infinitesimally progressive increase of supercharger speed. In the embodiment described, the supercharger whose speed is controlled is an auxiliary supercharger which idles during the greater part of the range of movement of the throttle valve. The throttle valve 11 is mounted on a shaft 12 carrying an arm 13 and is actuated directly by a pilot's lever 72 fixed to a shaft 71 carrying a lever 73 which is connected by a pin-and-slot mechanism 78, 18 to a floating lever 17 connected to the arm 13 by a link 15, and by a spring-loaded servo-piston 23 connected at 19 to the floating lever and controlled by a piston valve 43 connected by a flexible rod 44 and a further floating lever 47 to a pair of bellows 50, 51. The bellows 50 is evacuated, whilst the bellows 51 is subject internally to the intake pressure. The selected pressure is varied by a cam 70 fixed to the shaft 71 and coacting with a follower 69 carried by the centre arm of a three-armed lever 63 pivoted at 64, the lower arm of which is connected to a spring 67 to maintain the follower against the cam, and the upper arm being connected by a link to the floating lever 47. Pressure fluid is supplied to the valve 43 from a pump 39 and through conduits 37, 36, the righthand end of the cylinder 24 housing the servopiston 23 being connected by a conduit 31 to the right-hand end of the valve 43 and the left-hand end of the cylinder connecting with the left-hand end of the valve. Thus, during operation, a change in the intake pressure causes either contraction or extension of the bellows 51, which actuates the piston valve 43 and causes movement of the servo-piston to readjust the throttle valve to maintain the selected pressure. Due to the direct manual control of the throttle valve, the latter may become fully opened without the servo-piston reaching the end of its travel, and to prevent further movement of the servo-piston in this event a spring-loaded arm 85 is provided, loosely mounted on the shaft 12 and adapted for engagement by a pin 90 on the arm 13 as the throttle valve approaches the fully open position, whereby an abutment 89 engages the end of the piston valve 43 to prevent further movement thereof in the direction to open the throttle valve. The auxiliary supercharger 95 is driven through gearing 97, 98 and a hydraulic coupling 100, from an engine-driven shaft 103. The coupling is supplied with oil from the pump 39 and its speed ratio is determined by the level of oil in its casing 104 which, in turn, is dependent upon the position of a scoop or hollow dipstick 108 actuated by a servopiston 122. A control valve 136 for the servopiston, also supplied by the pump 39 is connected by a flexible rod 137 to a lever 138 pivoted at 139 and biassed by a spring 145 towards a stop 146, whereby the valve is normally in the position shown with the scoop 108 in its lowest position. A rod 147 connected to the lever 138 carries a pin 149 which is engaged by the arm 85 when the throttle valve reaches a position slightly less than fully open, causing movement of the control valve 136 to the right and consequent movement to the left of the servo-piston 122 thus increasing the level of oil in the coupling and, therefore, the speed ratio of the coupling. The resulting increase in induction pressure causes movement of the servo-piston 23 in a direction to close the throttle valve whereupon the rod 147, lever 138 and control valve 136 are returned towards their original positions, causing a fall in induction pressure occasioned by slowing down of the supercharger 95 which again gives rise to opening of the throttle valve. Thus, the supercharger is again accelerated, and this cycle is repeated so long as it is necessary to increase the speed of the auxiliary supercharger to meet the pressure demand. A degree of stability in operation is attained by a connection from the servo-piston 122 back to its control valve in the form of a link 142 and lever 141 which, on deflection of the servopiston 122, causes rotation of the pivot 139 about eccentric trunnions 140 with consequent movement of the control valve towards its normal position. To provide for stability in the event of a sudden increase in pressure selection, the piston 122 is connected through its rod 124 and springs 151, 152 to a dashpot piston 154 having notches 155 and whose cylinder is interconnected by an orifice 171 and a check-valve controlled orifice 172, with a further cylinder containing a spring-loaded piston 158 connected by a bell-crank 162 and link 164 with an eye 165 which rotates the pivot 64 about eccentric trunnions 65. Thus, a rapid increase in selected pressure, causing a rapid movement of the piston 122 causes a rotation of the pivot 64 about its trunnions 65 decreasing momentarily the selected pressure. A modification is described in which the lever 141, instead of acting on the pivot 139, actuates a rotarv valve which controls the flow of oil from the pump 39 to the hydraulic coupling. Specifications 597,930 and 601,814 are referred to.