Patent GB-826373-A (GB)
Title: Improvements in or relating to engine speed governors
IPC: F02D9/00
Filed: 1956-02-21
Abstract: 826,373. Fluid-pressure servomotor-control systems. THORNER, R. H. Feb. 21, 1956, No. 5342/56. Class 135. An engine speed governor comprises a first pressure-responsive member, such as the diaphragm 9, connected to engine speed control means such as the throttle valve 4, a second pressure-responsive member such as the disc 51 subject to the pressure in a region 35 of the air intake passage of the engine wherein the pressure varies as a function of engine speed, an open fluid circuit one end of which, when the engine is working, is exposed to a pressure higher than that at the other end of the circuit, and a movable valve element 37 in the open circuit connected for operation by the second pressure-responsive member and adapted to direct pressure fluid to the first pressureresponsive member for the operation of the engine speed control means. The open fluid circuit comprises a conduit 21 connected to the carburetter entrance 17, a chamber 15a bounded at one side by the diaphragm 9, the chamber 25, of the valve element 37, a chamber 31 of which the disc 51 forms a wall portion, a passage 33 leading to the engine intake passage 35. Fig. 1 shows a speed governor for internal-combustion engines having a throttle valve 4 on the engine side of the usual accelerator-operated throttle 5. The throttle 4 is operated by the diaphragm 9 under the control of a pilot valve 37 actuated by a pressure-sensing disc 51 moving with restricted clearance in a short cylinder 50 extending from a plate 53. The plate 53 divides the governor housing 1 into two chambers 15a, 15b connected through an orifice 53b. The chamber 15a is open to one side of the diaphragm 9 and is connected to the carburetter entrance 17 by a conduit 21. The other chamber 15b is connected via the clearance between the disc 51 and the cylinder 50 with the chamber 31. The vacuum in the passage 35 is a measure of engine speed for a given position of the throttle 5. The pilot valve 27 is of the shuttle lift type and controls orifices 23, 29 opening into the chambers 15a, 31 respectively. The valve chamber 25 between the orifices is connected by a conduit 27 having a restriction 27a with a diaphragm chamber 13, the pressure in which may thus vary between that in the carburetter inlet 17 and that in the intake passage 35. The pilot valve 37 is mounted in a housing section 49 and is supported frictionlessly by two leaf-springs 45, 47, secured to the section by screws 152, the valve with the disc 51 being rigidly and non- rotatably connected to the leaf-spring 47. The other end of the valve 37 abuts the other leafspring 45 and has a sliding fit with the stem of a spring abutment 63. Elongated slots 153 in the leaf-springs and anti-torque washers 155 engaging undercut surfaces 150 are provided to facilitate alignment of the pilot valve 37 with its seats. The plate 53 is secured to the housing section 49 by screws 55 passing through holes in the plate with appreciable clearance to facilitate the alignment of the cylinder 50 with the disc 51. The throttle 4 is biased towards the open position by a spring 43 connected to a point on the housing 1 and to a plate 79 rigid with a block 75 clamped to the throttle shaft 4a. The pilot valve 37 is biased against the prevailing vacuum in the chamber 31 by a spring 61 arranged between abutments 63, 65. The abutment 65 is adjustable on the shank of a yoke 71 pivotally connected to an arm 67 swinging about a pin 69. The arm 67 or a cam follower 67a on the pivotpin 73 engages a cam 81 adjustably mounted on the block 75 so that the movements of the throttle 4 adjust or reset the spring 61 and therefore pilot valve also. The cam is designed to compensate for the change in vacuum which results from the change in position of the throttle. The governed speed may be adjusted over a limited range by adjustment of the abutment 65 but for larger speed ranges it is necessary to provide interchangeable cams or a threedimensional cam which can be adjusted axially as well as rotationally. The rotational adjustability of the cam facilitates the adjustment of speed droop and enables tolerances in manufacture to be catered for. The cam 81 may be provided with a nose to produce an increase of speed above the governed speed at full load. In an emergency requiring maximum speed, the conduit 27 may be vented to atmosphere to cause the throttle to open fully. Such venting is effected by rupturing a frangible plug 36 sealing a chamber 34 connected to the conduit 27. The chamber 34 may be located near the instrument panel of the vehicle for operation by a release ring 36a or may be at a remote point for operation by a flexible cable. To facilitate cleaning of the air passages in the governor, the conduit 21 is provided with a Venturi 132 the throat of which is connected by a pipe 134 with the float bowl 136 of the carburetter. The pipe 134 has air holes 140 opening into a cup 142 extending below the normal level in the bowl 136 so that a quantity of petrol and air is sucked into the pipe 21 to clean the air conduits. In a modification, the diaphragm 9 is double-acting, its opposite sides being under the control twin axially aligned and rigidly connected pilot valves. Specification 826,374 is referred to.