Patent GB-559716-A (GB)
Title: Improvements in or relating to fuel control devices for internal-combustion engines
IPC: F02D9/00
Filed: 1942-08-25
Abstract: 559,716. Fluid-pressure servomotor-control systems. PUGH, C. A., BOOTH, D. G., JARVIS, P. J., and PLESSEY CO., Ltd. Aug. 25, 1942, No. 11976. [Class 135] A system for regulating the supplies of air and fuel to internal combustion engines particularly those used on aircraft has a throttle valve in the inlet to the supercharger actuated by a fluid pressure servomotor whose control valve is directly loaded by a spring and is coupled by a lever or other linkage to a pressure sensitive element subject to the pressure in the engine manifold (boost pressure). When the datum boost is varied the supply of fuel is correspondingly adjusted and when the supercharger is unable to maintain the datum boost the fuel supply is lowered in step with the reduced boost pressure. The law governing the relationship between the datum boost and the fuel supply is automatically changed at a predetermined point in the boost datum adjustment to give an enrichment effect. The fuel supply valve may also be adjusted by a servomotor controlled by the exhaust pressure and by a thermo-sensitive device responsive to the temperature in the intake to the engine. In the arrangement shown in the Figure a throttle valve 13 in the inlet to the supercharger 12 is connected by an arm 15 and link 16 to the mid-point 17 of a floating lever 18 connected at one end by a link 19 to an arm 20 on a manually adjustable shaft 21, and at the other end to the piston rod 23 of a servomotor piston 24 working in a cylinder 25 connected by pipes 48, 49 with a control valve 34. The control valve spindle 33 which is loaded by a spring 32 is connected by a lever 29 with an evacuated capsule 26 adjustably loaded by a spring 31. The adjustable abutment of the spring 32 is normally adjusted by a cam 22 on the shaft 21 acting through a lever 42. The pivot 43 is carried by a rod 44 on a spring loaded piston 45 subject to the pressures in the conduits 39, 40, so that a rise of pressure in the conduit 40 consequent on the piston 24 reaching the end of its stroke moves the piston against the return of the spring 47 to lower the tension of the spring 32, and so lower the datum boost. As the lever 42 is moved to vary the datum boost a rod 50 coupled through lever and linkage mechanism with the fuel valve 90 is moved to adjust the fuel supply to correspond with the boost nressure. The rod 50 is pivoted to a lever 51 at first turning on a fixed fulcrum at one end but at a certain point in the anti-clockwise movement engaging an alternative pivot 55 adjustable in two directions at right angles. The other end of this lever is connected by a link 155 with a lever 76 pivoted to a rod 72 carried by a piston 73 controlled by a valve 66 adjustably loaded by a spring 68 and actuated by an evacuated capsule subject to exhaust back pressure. The free end of the lever 76 engages an abutment on a rod 77 loaded by a spring 78 and pivoted to a slider 79 on a lever 80, having a fulcrum 81 mounted on a block 82 slidable in an inclined or contoured guide by a thermosensitive member 83 responsive to the temperature in the engine intake. A second slider 84 on the lever 80 is pivoted to a rod 85 carrying a plate 91 separated from a similar plate on the spindle 96 of the needle valve 90 by the crosspiece of a T-shaped lever turning on a fixed pivot 94. By a suitable choice of dimensions the area of opening of the needle valve can be made proportional to the linear movement of the rod 85.