The radial force of the hydraulic gear pump is unbalanced, and the gear shaft is deformed and deviates to the low pressure area of the pump body, which may lead to scraping and boring. At the same time, the floating property of the shaft sleeve will become worse, and the service life of the bearing will be reduced. In the design of the side plate, the method of adding high-pressure drainage groove is adopted to increase the high-pressure oil area of the gear pump. Only two to three teeth in front of the pump inlet play a sealing role, so the radial force on the gear is partially balanced, thus reducing the radial imbalance force.

The structure of the external gear pump leads to the phenomenon of oil entrapment. It is a conventional way to reduce the phenomenon of oil entrapment to set an unloading groove on the side plate. On the premise of ensuring that the import and export are not connected with each other, when the trapped oil area is reduced, it is connected with the pump outlet through the outlet unloading groove, and when the trapped oil area increases, it is connected with the spring inlet through the inlet unloading groove. Reasonable design of trapped oil area and unloading groove can greatly improve the working performance of gear pump. There are many specific design methods, which are not carried out here.