What is the correct way to disassemble the bearing? Don't use a hammer again!
After the bearing has been running for a period of time, it is inevitable that there will be maintenance or damage replacement requirements. In the early days of the development of the machinery industry, the popularity of professional knowledge was insufficient, and the awareness of safe operating procedures was insufficient. Today we will only talk about the disassembly of the bearing and see how the cattle dismantle the bearing.
Classification of bearing disassembly
In the case where the support dimensions are properly designed, the direction-aligned bearings can be removed as long as they are not excessively used to cause deformation or rust and are caught on the mating parts. Reasonable disassembly of the bearing in the case of interference fit is the core of the bearing disassembly technology. The bearing interference fit is divided into inner ring interference and outer ring interference. The following two cases will be introduced separately.
1. The inner ring of the bearing is over-filled and the outer ring is matched.
1, cylindrical shaft
Proper bearing disassembly is inseparable from the use of tools. For small size bearings, the conventional tool is a puller. The puller is divided into two types of two claws and three claws, which are divided into threads and hydraulics.
The thread puller is a relatively traditional tool. The operation is to align the center screw with the center hole of the shaft, apply a small amount of grease lubrication to the center hole of the shaft, hook the hook to the end surface of the inner ring of the bearing, and twist the center rod with a wrench. The bearing can be pulled out. The hydraulic puller uses a hydraulic device instead of a thread. When the middle piston is continuously extended during pressurization, the bearing is continuously pulled out, which is faster than the conventional thread puller and the hydraulic device can be quickly retracted.
In some designs, the distance between the end face of the bearing inner ring and other components is small, and there is no operation space of the traditional puller claw. In this case, a two-piece splint (as shown below) can be used to select a suitable size splint for disassembly and disassembly. pressure. The splint can be made thinner and deeper into the narrow space.
▲ Puller operation
When there is a large batch of small-sized bearings that need to be disassembled, a quick-disassembling hydraulic device (as shown below) can also be used.
▲ quick release hydraulic device
For the disassembly of railway vehicle axle integral bearings, there is also a dedicated mobile disassembly device.
▲Mobile disassembly device
When the bearing size is increased, the force required to disassemble the bearing is also increased, the universal puller is not applicable, and special tooling is required for disassembly. The minimum force required for disassembly can be estimated based on the bearing's mounting force required to overcome the interference fit. The formula is as follows:
F=0.5 *π *u*W*δ* E*(1-(d/d0)2)
F = force (N)
μ = friction coefficient between inner ring and shaft, generally about 0.2
W = inner ring width (m)
δ = interference fit (m)
E = Young's modulus 2.07x1011 (Pa)
d = bearing inner diameter (mm)
D0=inner ring outer raceway intermediate diameter (mm)
▲ heating disassembly method
When the force of disassembly is too large to be removed by ordinary methods, and the disassembly force generated by the conventional method is likely to damage the bearing, an oil hole is generally designed at the end of the shaft, and the oil hole extends to the bearing position and then radially penetrates to the shaft surface. An annular groove is added, and a hydraulic pump is used to pressurize the inner ring from the shaft end during disassembly to reduce the disassembly force.
When the bearing size is too large and the simple hard pull type cannot be disassembled, the heat disassembly method is required. Complete tools such as jacks, height gauges, spreaders, etc., are required before operation. The method of heating and disassembling is to directly wind the coil onto the raceway of the inner ring to heat and expand it, so that the bearing can be easily disassembled. Roller detachable cylindrical bearings are also suitable for the same heating method. This method allows the bearing to be removed without damage.
2, the cone axis
Since the area of the two end faces of the inner ring of the tapered bearing is significantly different, the large end face of the inner ring of the bearing is usually disassembled for heating. A flexible coil intermediate frequency induction heater is used to disassemble the inner ring of the bearing by rapidly heating the inner ring of the bearing to create a sufficient temperature difference with the shaft. Since the tapered bearings are used in pairs, after the inner ring is removed, the other inner ring must be exposed to heat. If the inner ring of the bearing is placed in an unheatable position on the large end face, the cage must be broken, the roller removed, the inner ring body exposed, and the coil placed directly on the raceway for heating.
The heater heating temperature must be set no more than 120 degrees Celsius, because bearing disassembly requires a rapid temperature difference and operating process, not temperature. If the ambient temperature is very high or the interference is very large, if the temperature difference is insufficient, dry ice (solid carbon dioxide) can be used as an auxiliary means to place the dry ice on the inner wall of the hollow shaft to quickly reduce the temperature of the shaft (such a large-sized workpiece is generally) , thereby increasing the temperature difference.
For the removal of the tapered inner bore bearing, do not completely remove the clamping nut or mechanism at the end of the shaft before disassembly, and only loosen it to avoid the bearing drop accident.
The removal of the large-sized tapered shaft requires the removal of the oil hole. Taking the four-row tapered bearing TQIT of the tapered inner bore of the rolling mill as an example, the inner ring of the bearing is divided into three parts, two single inner rings and one double inner ring in the middle, and three oil holes at the end of the roll, corresponding to the mark 1, respectively. 2,3, where 1 corresponds to the outermost inner ring, 2 is the double inner ring corresponding to the middle position, and 3 corresponds to the inner ring with the largest inner diameter. When disassembling, disassemble in the order of the serial numbers, and pressurize the holes of 1, 2, and 3 separately. When all the vehicles are completed, the bearing can be lifted, and then the hinge ring at the end of the shaft is removed, and the bearing is removed.
If the bearing needs to be used again after disassembly, the force applied during disassembly must never be transmitted through the rolling elements. For split bearings, the bearing ring with the rolling element cage assembly can be removed separately from the other bearing ring. When disassembling non-separable bearings, the bearing rings with clearance fit should be removed first, and the bearings with interference fit should be disassembled. Different tools need to be used according to their type, size and fit.
Second, bearing outer ring interference fit
The premise of removing the bearing in the case of an interference fit on the outer ring of the bearing is that the diameter of the outer ring shoulder cannot be smaller than the required support diameter of the bearing. The outer ring can be removed by using the drawing tool diagram as shown in the following figure.
If the shoulder diameter of some application outer rings is required to be completely covered, then the following two design options should be considered during the design phase:
• Two or three notches can be reserved at the steps of the housing to make the puller claws forceful for easy removal.
• Four threaded holes are designed on the back of the bearing housing to reach the bearing end face. Usually, the screw can be sealed with a screw. When disassembling, change to a long screw and tighten the long screw to gradually push out the outer ring.
Flexible coil induction heating can also be used when the bearing is large or the amount of interference is large. Disassemble by heating the outer diameter of the case. The outer surface of the cabinet should be regularly flat to prevent local overheating. The center line of the cabinet should be perpendicular to the ground and assisted by a jack if necessary.
The above is a general introduction to the disassembly method of the bearing for various situations. Due to the wide variety of bearings and the wide range of applications, the disassembly process and precautions are also different.