The composition of a single pump: single pump by the plunger, plunger sleeve, return spring, spring seat, the valve out of the valve seat, the valve spring, the valve out of the valve nut and other components. 1. Outlet valve structure (1) out of the valve and the valve seat is a precision couple, made of high quality alloy steel, the guide hole, the upper and lower faces and seat hole after precision machining and grinding, after the match can not be exchanged. (2) The conical part of the oil outlet valve is the axial sealing conical surface of the valve, and the cone part of the valve slides in the guide hole to act as the guide. Tail processing groove, cross-shaped cross-section, so that the fuel through. The middle of the oil valve called the cylinder vacuum surface, with the sealing cone between the formation of a decompression volume. (3) The lower end of the valve seat and the upper end face of the plunger sleeve are precision machined closely fit, it is pressed by the tightening nut to the specified tightening torque. Compression between the nut and the seat has a thickness of copper high-pressure gaskets. There is also a low pressure gaskets between the outlet nut and the top of the housing. (4) In the oil pressure valve compression nut cavity with grooved reduction vessel, in order to reduce the volume of cavity space, to promote rapid spray stop, limit the maximum lift valve role. 2. Outlet valve role (1) to prevent drip oil before injection to improve the injection speed: fuel injection pump, until the oil pressure is higher than the preloading valve spring preload and residual pressure in the high-pressure tubing, the The valve rises and its sealing cone leaves the seat. Must wait until the vacuum valve on the valve with the valve seat completely out of the pilot hole, the pump oil chamber to enter the high-pressure fuel pipe. P pump <P spring + P residual - open; P pump spring + P residual - off. (2) to prevent drip after injection to increase the closing speed: stop feeding, the outlet valve vacuum belt into the catheter along the next, the high-pressure tubing and pump chamber access will be cut off. When the oil valve is fully landed after a drop h distance, so the high-pressure tubing volume has been increased, so that the rapid decline in oil pressure 1MPa ~ 2MPa, quickly and simply off the oil, to prevent the fluctuation of oil pressure and " "And after the spray drops. (3) to prevent the reverse flow of fuel, the high-pressure tubing to maintain a certain residual pressure.