Patent GB-643652-A (GB)
Title: Control mechanism for supercharged, internal combustion engines
IPC: F02D9/00
Filed: 1946-08-21
Abstract: 643,652. Spray carburetters; regulating. BENDIX AVIATION CORPORATION. Aug. 21, 1946, No. 24966. Convention date, Sept. 26, 1945. [Classes 7(iii) and 7(vi)] [Also in Group XXIX] A fluid-pressure servomotor boost control for a supercharged internal combustion aero-engine for automatically regulating the pressure in the intake manifold at a predetermined value dependent upon the setting of the pilot's hand-lever is provided with a switch for setting the boost control to operate over a higher pressure range which switch at the same time operates a water &c. injection system to prevent predetonation of the 'fuel at high booster pressures. The boost control is housed in a casing 7, Figs. 1 and 3, and is shown applied to the control of a throttle valve 19 connected directly to the pilot's hand-lever 1, Fig. 4, through linkage 3, 5, a shaft 6 carrying a crankpin 11, a floating lever 12, links 13, a bell crank 15, a shaft 16 and linkage 17, 18. Movement of the shaft 6 is limited by a stop 9 which engages an arm 10 and an adjustable screw 9a. The floating lever.12 is also connected through links 75 with a spring- loaded servo-piston 68 under the control of a piston valve 56 itself actuated by pressure responsive mechanism 53 through links 52, 54 and a floating lever 50. The mechanism 53 comprises two opposed bellows 76, 77 having a common movable head 82 connected to the link 52 and fixed outer ends 79, 84. The bellows 77 is partly evacuated and houses a spring 78 whilst, the bellows 76 is open to manifold pressure through a .port 80 and a pipe 81; Fig. 3. An adjustable rod 135 limits the contraction of the bellows 76 and the further automatic opening of the throttle below a minimum critical manifold pressure whilst a rod 137 prevents excessive expansion of the bellows 76 and contraction of the bellows 77. The datum of the mechanism 53 is adjustable over both the predetermined pressure ranges. To set a datum over the lower range a cam 33 is adjusted by the lever 1 through the linkage 3, 5, shaft 6, links 8, 30, 31 and a shaft 32, and co-acts with a lever 36 connected to the floating-lever 50 and supported on a pivot 37 carried by an arm 38 fulcrumed on a fixed but adjustable pivot 39 arranged to pass through a hole in the lever 36. A torsion spring 42 urges the lever 36 into engagement with the cam 33, and opposes the setting of the datum to the higher pressure range. Anticlockwise movement of the lever 1 rotates the cam clockwise to reduce its " rise and permit anticlockwise rotation of the lever 36 due to the spring 42 being stronger than a spring 57 carried by the valve 56. The link 52 then moves to the right to adjust the datum of the mechanism 53 to a position to increase the operating manifold pressure. Conversely, clockwise movement of the lever 1 rotates the cam to increase its " rise " and reduce the operating manifold pressure. To set a datum over the higher range and at the same time operate the water &c. injection system a switch 110 is closed to open a solenoid-actuated valve 108 and so permit the supply from a pump 107 of liquid, e.g. water-alcohol, through a nozzle 102 into the manifold 22. At the same time some of this liquid is supplied through a line 113 to the back of a diaphragm 118 which is thereby moved against a spring 122 to move a rod 47 to the left. The rod 47 co-acts with the upper end of the arm 38 and through the pivot 37 rotates the lever 36 anticlockwise about the cam 33, whence the floating-lever 50 also rotated anticlockwise about its centre pivot moves the link 52 further to the right and thus adjusts the datum of the mechanism 53 to a still higher pressure setting. In operation, on a decrease in manifold pressure below the value set, the bellows 76 will contract to move the link 52, and, through the lever 50, the piston valve 56 to the left of its neutral position to connect the fluid supply port 60 via a port 59 with the left hand side of the piston 68. The piston is thereby moved to the right and through the link 75 connected to the floating-lever 12 opens the throttle 19 wider. Conversely an increase in manifold pressure above the value set will effect the movement of the throttle towards closure. To prevent further automatic opening of the throttle on the manifold pressure reaching a predetermined minimum value the bell-crank 15 is arranged through the link 75, floating- lever 12 and the link 13 to engage a lever 139 which through a stop-pin 145 prevents the movement of the valve 56 to the left. Further like movement of the bell-crank 15 moves the valve 56 to the right of its neutral position to open communication hetween ports 60, 61 to urge the piston 68 to its extreme left position and thence any further opening of the throttle may only be effected by anticlockwise movement of the lever 1 by the pilot. At low altitudes with 'the datum set on the lower pressure range the bellows 76 will never contract sufficiently for the rod 135 to become effective. Specifications 603,157, [Group XXIX], and 611,909 are referred to.