a. The clearance between valve core and valve body hole is too small;

b. Dirt particles wedge into the gap;

C. The valve body hole and core are deformed and bent;

d. The temperature change causes the valve hole deformation;

e. All kinds of mounting fastening screws are pressed too tightly, resulting in the deformation of the valve body;

f. Stuck valve caused by trapped oil.

① Methods and methods of reducing hydraulic clamping

a. Improve the machining accuracy of valve core and valve body hole. The accuracy of shape and position is improved. At present, the shape accuracy of valve core and valve body hole, such as roundness and cylindricity, can be controlled within 0.003mm by the manufacturers of hydraulic parts. Generally, there is no hydraulic clamping phenomenon when the accuracy is reached.

b. Several pressure equalizing grooves are opened on the surface of the valve core, and the pressure equalizing groove is concentric with the outer circle of the valve core.

c. The gear pump adopts a conical shoulder, with the small end of the shoulder facing the high pressure area, which is conducive to the centering of the valve core in the inner diameter of the valve hole.

d. If possible, make the valve core or valve body hole vibrate with high frequency and small amplitude in axial or circumferential direction.

e. Carefully remove the burr on the convex shoulder of the valve core and the sharp edge of the undercut groove of the valve hole to prevent damage to the outer circle of the valve core and the inner hole of the valve body due to collision. Improve the cleanliness of the oil.

② Methods and measures to eliminate other causes of stuck valve.

a. Ensure reasonable assembly clearance between valve core and valve body hole. For example, for the valve core and valve body hole of ping16, the assembly clearance is 0.008 ~ 0.012mm.

b. Improve the casting quality of valve body and reduce the bending deformation of valve core during heat treatment.

C. Control the oil temperature and try to avoid excessive temperature rise.

1. Tighten the fastening screws evenly and diagonally to prevent the deformation of the valve body hole during assembly.