Patent GB-634155-A (GB)
Title: Improved means for controlling internal-combustion engines
IPC: F02D29/00
Filed: 1946-03-05
Abstract: 634,155. Fluid-pressure servomotor-control systems. BENDIX AVIATION CORPORATION. March 5, 1946, No. 6762. Convention date, March 9, 1945. [Class 135] Control mechanism for internal-combustion engines of the kind in which a fluid-pressure servomotor adjusts the throttle valve of the engine in accordance with the induction pipe pressure and a manual setting, has a cam for adjusting the datum of the servomotor over the whole range of engine power in accordance with a first predetermined programme, a second cam for adjusting the datum of the servomotor in accordance with a second predetermined programme operative within a limited range of engine power, a first manually-adjustable means for setting simultaneously the two cams' and a second manually-adjustable means for rendering the second cam effective and the first cam ineffective over the said limited range of engine power. As shown, a main control lever 1 actuates the throttle valve 19 of an aircraft engine through mechanism comprising a link 3, an arm 5 fixed to a shaft 6, a crank 11 also fixed to the shaft and to which is pivoted a rocking lever 12 connected by links 13 to a further lever 14 which is fixed to a shaft 16 carrying an arm 17 connected to the throttle valve. At the end of the lever 12 remote from the links 13 are further links 93 connecting the lever to a spring-loaded servo-piston, the supply of pressure-fluid to either end of which is controlled by a valve 60 having supply and exhaust connections 80, 81, respectively, and which is connected through a link 59, a floating lever 55, and a link 57 to a partition 111 between a pair of bellows 97, 98. The bellows 97 is subject internally to the induction pipe or boost pressure through a conduit 110, whilst the bellows 98 is partially evacuated. Also fixed to the shaft 6 is a lever 8 connected by a link 30 to a lever 34 fixed to a shaft 35 which carries a lever 130 for adjusting an airscrew governor, and a pair of cams 36, 37 for varying the datum of the servomotor. The cam 36 coacts with a follower 41 carried by a lever 200 pivoted at 205 and consisting of a straight portion with integral offset ends 201, 202, the ends having pivoted thereto links 220, 210 which are pivoted to a member 212. A torsion spring 225 biasses the member 212 into contact with an adjustable screw 229 in the lever 200. The member 212 is connected by links 50 to a spring-loaded lever 43 pivoted at 44 and carrying an adjustable screw 56 for engagement with one end of a spring-loaded push-rod 52 whose other end carries a pivot for the lever 55. The cam 37, which permits of higher boost pressures in relation to the engine speed over the cruising power range of the engine is rendered effective by a lever 230 connected through a link 235 and a lever 236, to a shaft 238 having an eccentric end 243 engaging a slot 240 in a lever 245. This lever carries a follower 40 for the cam 37 and is pivotally connected to the lever 200 by a shaft 250. Thus, upon movement of the lever 230, the eccentric 243 rocks the lever 245 about the axis of the shaft 250 until the follower 40 engages the cam 37 when continued movement of the lever 230 rocks the lever 245 about the follower 40, causing the lever 200 to withdraw the cam-follower 41 from the cam 36, thereby increasing the datum of the servomotor, which is then varied by the cam 37 over the limited power range. Movement of the main control lever 1 beyond this range causes the cam 36 to over-ride the cam 37. Manual control only of the throttle valve 19 below a predetermined induction pipe pressure is permitted by the provision of an adjustable stop 114 within the bellows 97, which is engaged by the partition 111 at the predetermined pressure, thus preventing movement of the control valve 60 to the left, i.e., in the direction to cause opening of the throttle valve, under the influence of the bellows 97, 98. Means is also provided for preventing the automatic opening of the throttle valve beyond a predetermined maximum pomtion, the means comprising a lever 118 mounted on an adjustable pivot 120 and carrying a roller 124 for engagement by an extension 117 of the lever 14. The lever 118 coacts with a plunger 126 which, at the predetermined throttle opening, engages the left-hand end of the control valve 60 and prevents movement thereof to the left, to open the throttle valve. Any further opening of the throttle valve is then effected manually by the lever 1. The lever 130 is connected through links 133, an adjustment device 135, and links 156, to an arm 157 connected to the governor loading spring of the airscrew. The device 135 comprises a plate 136 fixed to a shaft 140 and having a lug 155 to which the links 156 are connected, and a plate 137 having a slot 141 through which passes the shaft 140 and a lug 150 to which the links 133 are connected. The plates 136, 137 are interconnected by links 138, 139 and are maintained in fixed adjusted relation by a sleeve 143 mounted on the shaft 140 and tightened against the plate 137 by a nut 148. Specification 603,157 is referred to.