According to the working condition of the sliding bearing, the screw bushing is generally matched with the shaft by the clearance of the bushing hole. The deviation between the shaft diameter of the part and the diameter of the bushing is generally reasonable when the average working temperature is 20 °C. The gap is determined by the change. There are many factors affecting the overheating failure of the sliding bearing. In the case of reasonable bearing structure design and correct material selection, the overheating of the sliding bearing is mainly caused by improper assembly of the radial clearance of the bearing and improper use.
The radial clearance of the sliding bearing of the screw pump affects the overheating fault of the bearing. The radial clearance Δ of the sliding bearing is the difference between the diameter of the bearing bore and the diameter of the journal. The sliding bearing should have a certain radial clearance. The function is as follows: The minimum condition for coupling with the bearing activity; it is the guarantee for controlling the running accuracy of the shaft; it is an important condition for forming liquid lubrication. Therefore, the radial clearance of the plain bearing is very important, and it is extremely harmful if it is too large or too small. If the gap is too small, it is difficult to form a lubricating oil film, and the friction heat is not easily taken away, so that the bearing is overheated. When it is serious, the shaft will be hung. If the gap is too large, the oil film is difficult to form, which will reduce the running accuracy of the machine and cause severe vibration and noise. Even causing burnt tile accidents
The radial clearance of the sliding bearing of the screw pump is determined by the technical performance of the screw pump: the journal speed n=2950r/min, the journal diameter d=30mm; the motor is a synchronous motor, the lubricating oil is the residual oil, and the bearing material is tin-based copper sliding bearing. Theoretical value of radial clearance sliding bearing radial clearance Δ=K?d
In the formula: K———High-precision bearing coefficient, found in the “Mechanical Design Manual†K=0.0008
d———the diameter of the journal, d=30mm
Substituting: Δ=0.02mm
Found by the Mechanical Design Manual, the maximum clearance Δmax=0.10mm
Measurement of the original bushing, data and position. Measuring the shaft diameter, corresponding position and size data. Shaft diameter 1: 29.99mm29.94mm29.90mm Shaft diameter 2: 29.92mm29.90mm29.90mm
Bushing 1: 30.01mm29.97mm29.92mm bushing 2: 29.94mm29.92mm29.915mm
The actual value of the radial clearance of the sliding bearing is the maximum clearance: active rod: 0.03mm follower rod: 0.02mm
In the actual use of the bearing, because the clearance is too small, the friction heat is not easily taken away, and the lubricating oil is the medium residual oil, which has more impurities and easy to enter the gap, so that the bearing is overheated, and when it is serious, the shaft will be hung and burned. Tile phenomenon
Screw pump prevention and improvement measures In order to prevent the bearing from overheating fault, if the radial clearance is increased, Δ=0.03mm
At this time, the bearing pair of the bearing can work normally, but its service life is greatly shortened. Therefore, when determining the radial clearance of the bearing, it should be ensured that the bearing is kept as small as possible under the premise of normal operation. After the bearing is assembled, the first run-in and trial run should be carried out according to the running-in test run specification, and then the acceleration is gradually applied to smooth the joint surface of the shaft and the bearing, and finally put into normal operation. Otherwise, even if the gap is not adjusted, it is put into normal operation because it is not subjected to the running-in test after assembly, resulting in overheating or even burning of the bearing. In this regard, the radial clearance of the sliding bearing should be controlled between 0.10mm and 0.15mm.
The radial clearance of the sliding bearing has a great influence on the bearing overheating and life. Therefore, the radial clearance must be strictly controlled within a reasonable range. When determining the radial clearance of the bearing, the factors affecting the radial clearance should be fully considered. In addition to considering the diameter, speed, load and accuracy of the shaft, the following bearing materials should be considered. Different bearing materials, different expansion coefficients, different clearances, shaft and bearing surface roughness, journal and bearing geometry and mutual position error (ie roundness, cylindricity, coaxiality, etc.)
Operating temperature of the bearing Sudden changes in starting conditions Different media and different speeds have different requirements for the screw bushing clearance. Through the above calculation and analysis, the optimal gap data of the bushing is obtained.