Analysis of Oil Sealing of Oil Seal of Gear Pump of Loader

"Gear pump oil", that is, hydraulic oil will break through the skeleton oil seal. This phenomenon is widespread, the host factory reflects strong, gear pump oil seriously affects the normal operation of the loader and the reliability of the gear pump and environmental pollution. In order to facilitate the solution of the problem, the causes and control methods of the gear pump oil seal oil failure are analyzed.

1. The impact of component manufacturing quality.


(1) Quality of oil seals.
If the geometry of the oil seal lip is unqualified, the tightening spring is too loose, etc., causing the airtightness test to leak, and the gear pump is loaded into the main machine and then smashed. At this point, the oil seal should be replaced and the material and geometry should be inspected (the domestic oil seal has a larger quality difference than the foreign advanced oil seal).


(2) Processing and assembly of gear pumps.
If the gear pump is processed or assembled with a problem, the center of rotation of the gear shaft is not concentric with the front cover stop, which will cause the oil seal to be eccentric. At this time, the symmetry and displacement of the front cover bearing hole to the pin hole and the coaxiality of the skeleton oil seal to the bearing hole should be checked.


(3) Sealing ring material and processing quality.
If this problem occurs, the seal ring will be cracked and scratched, resulting in a secondary seal that is not strict or even fails. The pressure oil enters the skeleton oil seal (low pressure passage), and the oil seals the oil. In this case, check the material and quality of the seal ring.


(4) Processing quality of variable speed pump.
The feedback information obtained from the main engine factory and the gear pump oil seal oil assembled with the variable speed pump are more serious. Therefore, the processing quality of the variable speed pump also has a great influence on the oil. The variable speed pump is mounted on the output shaft of the gearbox, and the gear pump is mounted on the output shaft of the transmission through the position of the shifting pump stop. If the end face of the variable speed pump is out of tolerance (verticality) of the center of rotation of the gear, The center of rotation of the gear shaft does not coincide with the center of the oil seal to affect the seal. During the processing and trial production of the variable speed pump, check the coaxiality of the center of rotation of the rotary center and the runout of the end face of the stop.
(5) The front cover oil return passage between the CBG gear pump oil seal and the seal ring is not smooth, causing the pressure to rise here, thereby breaking through the skeleton oil seal. By improving this, the pump's oil slick phenomenon has been significantly improved. Its structural form is shown in Figure 1.
2. The impact of gear pump and host installation quality.
(1) The installation requirement of the gear pump and the main machine is less than 0.05.
Usually the working pump is mounted on a variable speed pump, which in turn is mounted on the gearbox. If the end face of the gearbox or variable speed pump is out of tolerance to the center of rotation of the spline shaft, a cumulative error is formed, causing the gear pump to withstand radial forces at high speeds, causing the oil seal to simmer.
(2) Is the installation clearance between the components reasonable?
The outer stop of the gear pump and the inner stop of the variable speed pump and the external spline of the gear pump and the spline in the spline shaft of the gearbox, whether the clearance fit is reasonable, both have an influence on the oil of the gear pump. Because the inner and outer stops belong to the positioning part, the matching clearance should not be too large; the inner and outer splines belong to the transmission part, and the matching clearance should not be too small to eliminate interference.
(3) Gear pump oil is also related to its spline roller.
Because the gear pump shaft extension spline and the gearbox output shaft have a short effective contact length, while the gear pump transmits a large torque during operation, the spline is subjected to large torque and crush wear and even rolling keys generate heat. As a result, the rubber seal of the skeleton oil seal is burned and aged, resulting in oyster sauce. It is recommended that the main engine factory select the gear pump to check the strength of the external spline of the gear pump shaft to ensure sufficient effective contact length. 3. The effect of hydraulic oil.
(1) The cleanliness of hydraulic oil is extremely poor, and the pollution particles are large. The various hydraulic control valves and the sand and welding slag in the pipeline are also one of the causes of pollution.
Because the shaft diameter of the gear shaft and the clearance of the inner hole of the seal ring are small, large solid particles in the oil enter between them, causing wear, scratching or rotation with the shaft of the seal ring, so that the secondary seal pressure oil enters the low pressure zone ( At the skeleton oil seal), the oil seal is broken down. At this time, the new anti-wear hydraulic oil should be filtered or replaced.

(2) After the viscosity of the hydraulic oil drops and deteriorates, the oil becomes thinner. Under the high pressure state of the gear pump, the leakage through the secondary seal gap increases, and the pressure in the low pressure zone rises due to the lack of oil return, thereby breaking the oil seal. It is recommended to test the oil regularly and use anti-wear hydraulic oil.

(3) When the working time of the main load is too long and the oil level of the fuel tank is low, the oil temperature can be raised to 100 °C, causing the oil to become thinner and the skeleton oil seal to aging, thus causing the oil; the tank liquid should be checked regularly. The height of the surface is to avoid excessive oil temperature.