Method for solving low-speed crawling of hydraulic cylinder

Solution:

1. The hydraulic cylinder has a low-speed creep caused by the presence of gas in the rod chamber and the rodless chamber. The cylinder can be exhausted by repeatedly operating the hydraulic cylinder. If necessary, an exhaust device can be installed in the two chambers of the pipeline or the hydraulic cylinder. Vent the system while it is working.

2. The low-speed crawling caused by the improper design gap of the hydraulic cylinder can correctly design the sliding fit clearance between the piston and the cylinder, the piston rod and the guide sleeve in the hydraulic cylinder. The theoretical clearance is H9/N or H9/f8. H8/f8; According to the author's experience, the cylinder bore and rod diameter from small to large, such as according to this design fit clearance, for larger bore (≥  200mm) and rod diameter (≥  140mm) With the clearance gap appears too large, the actual process should be such a low-speed crawling cylinder of this type of hydraulic cylinder bore more than the emergence of such foreign hydraulic cylinder sliding surface clearance is generally designed to 0.05mm ∽ 0.15mm, From the actual comparison results, the low-speed crawling problem of the hydraulic cylinder is obviously improved. Therefore, it is recommended to use this method for large cylinder hydraulic cylinders.

3. Low-speed crawling caused by non-uniform frictional force of the guide elements in the hydraulic cylinder. It is recommended to use metal as the guide support preferentially, such as QT500-7, ZQAL9-4, etc. If non-metallic support rings are used, it is recommended to use dimensional stability in the fluid. A good non-metallic support ring, in particular, a small coefficient of thermal expansion, and in addition to the thickness of the support ring, the dimensional tolerances and thickness uniformity must be strictly controlled.

4, for the sealing material caused by the problem of hydraulic cylinder crawling at low speed, it is recommended under the conditions allowable conditions, priority to use PTFE as a sealed combination of seals, such as the commonly used Gelei ring, Stein seal, etc.; If the lip seal is selected, it is recommended that the material is preferably a seal of NBR or a similar material, which has good followability.

5, the impact of parts processing accuracy, in the manufacturing process of the hydraulic cylinder should strictly control the cylinder surface and the piston rod surface machining accuracy, especially geometric accuracy, especially the straightness is the key, in the domestic processing technology, the piston rod surface The processing is basically grinding after the car, which ensures that the straightness is not a big problem. However, for the processing of the inner wall of the cylinder, there are many processing methods, such as boring-rolling, boring-boring, direct honing, etc., but due to domestic materials The basic level of the foundation is different from that of foreign countries. The straightness of the tube blank, the uneven wall thickness, and the uneven hardness often directly affect the straightness after machining of the inner wall of the cylinder. Therefore, it is recommended to use boring-rolling, boring-boring Processes, such as direct honing, must first increase the straightness of the tube billet.

In addition to the above methods, the wall thickness of the cylinder of the hydraulic cylinder is allowed as much as possible, and the safety factor is selected as large as possible to increase the thick wall of the cylinder, especially the cylinder used under high pressure conditions to reduce the cylinder under oil pressure. Body deformation, the deformed cylinder will also cause the cylinder to crawl at low speed.