Patent GB-1370819-A (GB)
Title: Fuel injector
Inventor: PERR J
IPC: F02M57/02
Filed: 1971-12-21
Abstract: 1370819 Fuel injection pumps CUMMINS ENGINE CO Inc 21 Dec 1971 [30 Dec 1970] 59281/71 Heading F1B An injector for injecting fuel into the cylinder of an I.C. engine comprises an injector body having a variable volume fuel injection chamber having an opening communicating with the cylinder and controlled by a normally closed valve which is opened by fuel pressure, the body also having a fuel supply passage adapted to connect to a source of fuel under variable pressure and fluid displacement means movably mounted in the body and operable to vary the volume of the chamber to increase the fuel pressure and thereby cause the valve to open, spill port means being opened by movement of the fluid displacement means at the end of the injection stroke to vent a portion of the trapped fuel and the body having passage means connected to a low pressure fuel zone to permit fuel to flow from the zone to the chamber during retraction of the fluid displacement means. The injector comprises a body 102, nozzle member 103, needle valve 159 and two spacers 104, 105. A central bore in the body contains a plunger 118 and a ball 144. The plunger is reciprocated, by a rocker arm (not shown) and is biased upwardly by a spring 123. Fuel enters the body through a restrictor 134 and passes via a check-valve 140 to the receiving space 142 comprising the lower end of the bore 114 in which the plunger moves and a shallow cavity in the upper face of the spacer 104. When the plunger moves downwardly fuel is displaced from the space 142 along passages 146 and 151, past checkvalve 154, through passage 156 to chamber 143 where it acts on surface 163 to raise the needle against the force of a spring 172, allowing the fuel to be ejected from holes 157. To provide for variation in the volume of the receiving space 142, the space 183 above the ball is connected to a drain by means of a central bore 184 in the plunger and a cross bore 187, connecting via an annular space 189 formed by a reduced diameter section of the plunger, with a drain duct 193. As the plunger moves upwardly the free communication between space 183 and the drain prevents any vacuum developing in the space 183, which would cause the ball to adhere to the lower face of the plunger. Thus the upward movement of the plunger is determined only by the pressure of the fuel supplied to the space 142. Fuel injection is terminated as the plunger approaches the bottom of its stroke by a pressure relief passage comprising two bores 197, 198, Fig. 2, communicating with the space 142 and with transverse bores 201 and 202 the outer ends of which are plugged and the innner ends of which open through restrictors to the bore 114, so that as the lower edge 206 of the reduced diameter section of the plunger reaches the restricted openings, the space 142 is vented to the drain duct 193. The restricted openings control the drainage of fuel to prevent abrupt closing of the valve 159. The space 173 above the valve is connected to the drain duct 193 by passages 207, 208, 209 and 212. In a modification Fig.8 the supply passages are modified to include a transverse passage 318 which communicates with a groove 316 in the plunger and with a supply passage 313, so that fuel flows into the receiving space 321 during the upstroke of the plunger. On the downstroke of the plunger, the axial bore 327 is closed by the ball and the fuel pressure rapidly rises to injection pressure. In a further modification, Figs.13-15 (not shown) the lower face of the plunger bears on the upper end of the valve spring and increases its compression so that the valve shuts rapidly when the fuel injection chamber is vented. In a third modification, Figs. 16-19 (not shown) the high pressure fuel in the receiving space is vented to the supply passage rather than to the drain duct.