Patent GB-600963-A (GB)
Title: Control mechanism for supercharged internal combustion engines
IPC: F02D9/00
Filed: 1945-10-06
Abstract: 600,963. Fluid-pressure servomotors. GENERAL MOTORS CORPORATION. Oct. 6, 1945, No. 26062. Convention date, Oct. 20, 1944. [Class 135] [Also in Groups XXVII and XXXIII] Means for controlling a supercharged internal combustion engine comprises a manually operable air intake throttle valve automatically controlled to maintain a elected intake pressure a manually controlled intake liquid injection apparatus and an intake pressure selection device under conjoint control of the manual controls. Fig. 1 shows an air intake pipe 12 of an aircraft engine having a throttle valve 40 controlling the inlet to a two-speed supercharger 14 driven from the engine from a two-speed gear 28. The two-speed gear is operated by a manual lever 31. The throttle valve 40 is operated by a differential control comprising a manual lever 62 and a fluid pressure servomotor 50 which is arranged to keep the intake pressure at a selected value. The lever 62 is arranged to rotate a shaft 55 carrying a lever 54 on which is pivoted at 53 a lever 52 one end of which is connected by links &c. with the throttle valve 40 while the other end is guided by a pin 67a connected to a link 66 pivoted on the servomotor operating shaft 65 and carried by a lever 69 pivoted freely on the shaft 55. The shaft 55 also carries a lever 156 which is connected by link 154 and lever 152 which operates a cam (not shown) in the servomotor. The position of the cam selects the value of the intake pressure which the servomotor will operate to keep constant. The cam is also under the control of the change speed mechanism 28 for the supercharger and a water or water-alcohol injection system described later. When the servomotor shaft 65 is stationary the manual lever controls the throttle valve 40 the lever 52 pivoting about the pin 67a. At the same time the cam in the servomotor is operated by link 154 and so varies the value at which the servomotor will keep the intake pressure. When the lever 62 is stationary the servomotor shaft 65 can operate the throttle valve 40 by pivoting the lever 52 about its pivot 53 on the lever 54. The lever 31 operates the change speed gear by a link 144 and levers 137, 138 operate the cam in the servomotor by means of an eccentric bushing to vary the intake pressure. The air intake pressure is taken by a pipe 123 to the servomotor which keeps this pressure constant by varying the opening of the throttle 40 as the intake pressure changes. The water injection means includes means for operating a stop to prevent the cam being moved past a certain position until the water injection is operating, thus the intake pressure is prevented from exceeding a certain limit until water injection is in operation. As shown a supercharging blower 18 directly driven by the engine is fed by the two-speed supercharger 14 fuel metered by a carburetter 11 being injected through a nozzle 23 in the pipe between the blowers. Fig. 2 shows a section of the servomotor. The operating rod 65 carries a piston 71 and is spring pressed by a spring 75. The piston is controlled by fluid entering at 76 the rate of flow being governed by a valve 79. When the valve moves to the right it supplies fluid to the right hand side of the piston and when it moves to the left it supplies fluid to the left hand side of the piston. The valve is carried by a lever pivoted at 104 to a bridge piece between two bellows 108, 109. Induction pipe pressure is supplied to the interior of bellows 109 and bellows 108 is evacuated so that induction pipe pressure varies the position of the pivot 104 and operates the valve 79. The end of the lever opposite to that of the valve is held by a spring 131 against a cam 130. Movement of the cam also operates the valve 79. Fig. 3 shows the method of operating the cam. The cam shaft 130 is connected to the lever 152 by a spring 160 and the lever is fixed to a bush 133 carrying a flange 150 and a pin 151. The shaft 132 and bush 133 are mounted eccentrically in a second bush 134. As the lever 152 is rotated anticlockwise, Fig. 1, the cam follows it by the action of the spring until a pin 163 on the-cam engages a stop 164, Figs. 2 and 3. Continued rotation of the lever stretches the spring but the cam does not move. The stop 164 is moved out of the path of the cam when water injection is in action by the pressure of water which is supplied to a bellows 214. When the stop is removed the spring can shift the cam to the position of high pressure operation. Lever 137, Figs. 1 and 3, is spring tensioned and as lever 138 is moved clockwise, Fig. 1, the lever 137 follows it. This moves the cam shaft 132 by reason of the eccentric bush, and varies the induction pipe pressure setting in accordance with the position of the supercharger two-speed gear which is interconnected with and operates the lever 138. The lever 137 may be moved into the low speed position independently of the lever 31 by a cam surface 152a, Fig. 1, on the hub of lever 152 engaging a roller 152b mounted on the servomotor housing. If the servomotor ceases to fuction the throttle valve may be opened. sufficiently by the manual control to effect a safe landing.