At the end of the plunger in the pressure discharge, the plunger bottom chamber will still be some residual for the outlet pressure of the oil, in the plunger into the inhalation stroke, the first began to expand, the pressure drops to the inhalation pressure, so that the loss of a part of the inhalation volume. Therefore, the use of nylon filled plunger can effectively reduce the residual space in the plunger cavity, thus reducing the hydraulic elastic volume loss and improving the volumetric efficiency. The traditional design of the cylinder liner used in the material is basically bearing steel, from the economic point of view is more expensive than ordinary steel, and this material is very hard and very bad processing, so I chose 40Cr, that is, economic and easy to process. General pump life and oil distribution plate and plunger and the sliding part of the cylinder between the abrasion is related, so to increase the cylinder to the cylinder liner, if there is abrasion occurs, only need to replace a cylinder liner can be, so do not have to go to replace a new cylinder, this is both economical and convenient, but also extends the service life of the pump.When there is no load sensing signal in the control chamber (lower chamber) of the main control valve, all the flow of the pump is discharged back to the tank through Valve 1 and Valve 2; when a load sensing signal is applied to this control valve, the pump supplies liquid to the circuit; when the output pressure of the pump exceeds the predetermined value of the pressure of the load sensing valve, the pump supplies only the working flow to the circuit, and the excess flow is bypassed back to the tank through the throttling position of Valve 2. Gear oil pumps with load sensing elements have the advantages of low cost, high resistance to pollution and low maintenance requirements compared with piston pumps.