GB1406305A - Fuel injection systems - Google Patents

Abstract

1406305 Spray carburetters ROBERT BOSCH GmbH 23 Nov 1972 [24 Nov 1971] 54232/72 Addition to 1336606 Heading F1B A fuel injection system for mixture compression, spark ignition I.C. engines with continuous injection into the inlet manifold, as claimed in Claim 1 of Specification 1336606 in which the pressure of the fluid is variable by means of at least one pressure control valve operable as a function of engine operating conditions, a first temperature responsive control element being arranged to control the tension of a closure spring of the pressure control valve, the effective force of the spring being additionally variable in dependence upon the inlet manifold pressure downstream of the throttle valve during heating up of the engine, a second temperature responsive element being arranged to oppose said spring for a brief period after starting the engine. Combustion air enters an inlet 1 and causes movement of a measuring element 2 attached to a lever 11, pivotally mounted at 12, the movement being linearly proportional to the air-flow. A boss 13 on the lever actuates the spool 14 of a fuel metering valve 10, the movement of the spool being opposed by the pressure of fuel in a chamber 38, into which the end-face of the spool projects. The fuel in this chamber is drawn from a pump-fed fuel line 21, through a fixed throttle 39. A line 40 leads to a pressure control valve 41, the effect of this valve being that when it operates to reduce the pressure in chamber 38 the engine receives a richer-than-normal mixture. The valve 41 consists of a diaphragm 44 which closes the end of a tube 43 and which is pressed against the tube by a spring 45. Fuel which is allowed to escape through the tube 43 drains to a tank 20 by a line 42. The spring is held between a cup 50 and a plate 53 having a projection which engages a recess in a member 54 attached to the diaphragm. The initial compression of the spring determines the pressure at which fuel begins to pass the valve 43, 44. The force exerted by the spring is modified by movement of the cup 50 which is mounted on the movable part of a temperature responsive element 52 which acts to move the cup to the right in Fig. 1 when the engine coolant liquid is cold, thus reducing the spring force. The spring force is opposed by a bi-metal spring 56, one end of which enters a slot 55 through the plate and which carries a stud 64 which presses on the plate. The other end of the spring is held in an electrically powered heater 57, which is energized when the ignition is switched on. The opposing force of the spring 56 decreases as the spring is heated and bends in a direction to move the stud 64 away from the plate 53. This occurs shortly after the engine has been started so that the amount of extra fuel injected is reduced to that necessary to keep the engine running during the warming-up period. The amount of air reaching the engine is increased by a duct 48, 49 which by-passes the throttle valve 7 and which is opened when the cup 50 is withdrawn clear of the ports 48, 49 in the body of the valve 41. The spring 56 is also used to modify the force of the spring 45 in dependence on the vacuum in the manifold downstream of the throttle valve. To achieve this the spring is connected by a rod 59 to a diaphragm 60 which closes one side of a box 61, the interior of which is connected by a pipe 62, including an adjustable restrictor 63, to the inlet manifold at a point which is downstream of the throttle by a distance which ensures that once the throttle valve 7 has moved through 10 degrees from its normally closed position, the end of the pipe 62 is no longer subject to vacuum. When the spring 56 has been fully heated, the stud 64 is no longer in contact with the plate 53, so that the effect of inlet manifold vacuum ceases.