When the control oil outlet does not pass the pressure oil, the oil can only go from PA to PB. When the oil pressure is passed through the oil outlet, the positive and reverse oil can be freely passed. One-way valve cover: right angle check valve, one-way valve function, controllable one-way valve, low pressure one-way valve. When the oil reversely flows, the force balance expression of the spool is:

PKAK-pAAK-FKM=pBA-pAA=Fs Fs W (1)

PK - - control oil pressure, the unit is N;

PA - the reverse oil outlet pressure is N.

PB - the reverse oil inlet pressure is N.

FKM - control the piston friction resistance, the unit is N;

FM - the total friction resistance of the cone spool is N.

Fs - - spring force, the unit is N;

W - - the weight of the valve core, the unit is N;

AK - - control the area of the piston, the unit is m2;

A - the seat area of the seat is m2.

When the friction resistance of the piston and cone valve is omitted, the oil pressure is controlled as follows:

PK=[(pB-pA) A Fs W]/AK pA (2)

This value is the control oil pressure to ensure the reverse flow of oil. If the valve port is closed and the oil reverse flow stops, the pressure of the oil chamber is pA=0. According to the way of controlling the oil leakage on the upper cavity of the piston, it can be divided into internal leakage type and external leakage type. The internal vent is also a simple liquid controlled one-way valve. The leakage type hydraulic control one-way valve, this kind of leakage type hydraulic control one-way valve reverse oil outlet pressure pA only functions in the control of the upper end of the piston, the action area is much smaller, while the reverse oil cavity pressure oil and control pressure oil leak to the control piston between the upper and lower parts of the chamber, can be directly introduced into the valve through the outlet, in order to avoid by the valve. The accumulation of the leaking oil affects the upward movement of the piston, so it is called the drain hydraulic check valve. The compound structure hydraulic control one-way valve is equipped with a unloading small spool in a one-way spool. When the piston is controlled, the control pressure is only 4.5% of the working pressure, and the control pressure of the one way valve without the small valve core is 40% to 50% of the working pressure.