1. Design and selection of bearings
Like other mechanical products, high temperature
gear pump design should also consider its life principle. In order to use raw materials and spare parts economically and reasonably, improve the technical and economic indicators of products, in the design of products should strive to achieve the life of most parts and raw materials equal, should not result in the production of most parts have far not reached the service life, and a few parts have been scrapped. High temperature gear oil pump just exists such a problem, most of the scrap is due to bearing damage. At present, many high temperature gear oil pumps no longer use needle roller bearings, but instead of needle roller bearings with cage, although this can improve the life, but practice has proved that under the rated operating condition of less than 2000h due to bearing damage and scrap. For this reason, there are also plain bearings, mostly tin bronze, powder metallurgy, reinforced nylon 6 materials, but the effect is still not ideal, and the cost is high. SF type composite bearing material is ideal at present. The material is made of steel plate as the substrate, sintered copper net as the intermediate layer, and plastic (filled with tetrafluoroethylene and modified polyformaldehyde) as the lubricating material of friction surface. The material has high mechanical strength, low friction coefficient and low noise, and can be used in no oil or less oil lubrication conditions and a wide range of operating temperature. It has been proved that the service life of high temperature gear oil pump is greatly improved by using SF bearing.
2. End clearance problem
High temperature gear oil pump is often scrapped in use because of internal leakage increase, volume efficiency drop, pressure drop. Gear end leakage accounts for 75%-80% of the total leakage. Therefore, a reasonable end clearance is very important. For the high temperature gear oil pump with flow of 2.5L/min to 1OL/min, the end gap should be 0.02-0.04mm, while for the high temperature gear oil pump with flow of 16L/min to 32L/min, the gap should be 0.02-0.05mm, and the high temperature gear oil pump with flow of more than 40L/min, The clearance should be 0.02-0.06mm. If the clearance exceeds the upper flow, the volume efficiency is low and the pressure cannot reach the rated pressure. If the clearance is too small, the clearance will be sharply increased due to wear during operation, and the internal leakage will increase.
3. Technical reasons
In order to ensure the reasonable clearance between the front and back end of high temperature gear oil pump, the processing and assembly of gear ocean is very important. The verticality error between the two end faces of the gear and the shaft line of the hole should not exceed 0.01mm, and the axial direction of the gear should be in a floating state after it is mounted on the shaft. In order to ensure the mutual position of the two shafts after assembly, the center distance error of the two bearing holes before and after machining should not exceed 0. 03mm. In addition, the fracture of the input shaft end is also a common phenomenon. Therefore, it is necessary to master the heat treatment process of the shaft, so that it has a certain strength and hardness, and a high impact toughness, to prevent its fracture.
4. Reasonable selection of materials and components
In order to ensure reasonable clearance and fit in high-temperature gear oil pump operation, wear resistance of related materials is an important performance index. It is very important to choose reasonable materials and proper heat treatment process. Oil seal leakage is also a common reason for scrapping. Therefore, to choose good material oil seal, at the same time in processing and assembly pay attention to the oil seal and bushing with firm, oil seal inner hole and pump shaft should have enough tension, can not leak oil.
5. Installation and use
Correct installation and reasonable use of high temperature gear oil pump, for prolonging the service life of the pump is also very important. When the pump input journal is connected with the motor shaft, the coaxiality error cannot exceed 0.1mm. Do not use belt connection. In addition, appropriate hydraulic oil should be selected according to the pump instruction manual, and a filter should be added at the pump day, and the hydraulic oil should be filtered and replaced regularly according to the working environment of the hydraulic system.
