Double-row and four-row cylindrical roller bearings mostly use single-jaw or double-jaw solid cages. Multi-row cylindrical roller bearings with double flanges on the outer ring or double flanges on the inner ring have roller assembly notches milled on one side of the flange. For this type of bearing, especially extra-large bearings, most bearing manufacturers currently use copper hammers or rubber hammers to strike the roller end faces when assembling cylindrical roller bearings. Some small and medium-sized bearings directly press the rollers by hand, first assembling the side without notches on the flange, and then pressing the side with notches on [1]. The hardness of the rollers is generally higher than that of the rings, and the raceway is easily scratched or the cage is deformed during the pressing process [2]. In severe cases, scaly scratches will appear, directly causing the bearing rings to be scrapped. A reasonable bearing assembly process can eliminate the hidden dangers to the normal operation of the bearing caused by the scratches on the raceway during roller assembly to the greatest extent.
1. Roller Assembly Press Rod
The cylindrical roller bearing assembly press rod designed in this example has the structure shown in Figure 1. The fixed support rod is a hollow steel tube, fastened to the base, providing stable support for the entire press rod structure; the movable support rod is fixed to the support rod with screws, and its height can be adjusted in the hole of the fixed support rod to adapt the press rod to the needs of bearing assembly at different heights; the crossbeam is a screw structure, fixed to the end of the movable support rod with a nut; one end of the assembly press rod has a hole machined and is hinged to the crossbeam; a spring retaining ring is installed in the annular groove in the middle of the crossbeam to prevent the press rod from moving; the press head is installed on the press rod by welding or threaded connection, and a bakelite block or rubber pad is installed on the press head to prevent scratching the roller end face during press-fitting; a rubber sleeve is fitted on the handle of the press rod. All parts of the assembly press rod are detachable for easy installation, replacement, and storage. For bearings produced in large batches, the assembly press rod can be designed as a fixed structure, that is, except for the press rod being hinged to the crossbeam, all other parts can be welded together to reduce the manufacturing cycle and cost of the press rod.
The working principle of the roller assembly pressure bar is shown in Figure 2. Place the bearing with the roller already installed on the unnotched side flat on the base. First, test-fit the roller on the notched side to adjust the relative position of the bearing and the pressure bar. Press the pressure bar head against the center of the roller's end face downwards. If the pressing force is appropriate, assembly can proceed directly. If the pressing force is slightly too high, apply grease to the chamfered area of the roller. This prevents excessive force from deforming the cage and causing the roller to jam, and also reduces the friction between the roller and the raceway contact surface. After the trial assembly, the relative position of the roller and the pressure bar head is determined. When pressing begins, the pressure bar head can quickly press against the center of the roller, achieving rapid assembly of the bearing roller.
2. Roller Assembly Stress Analysis
When assembling rollers by hammering, the stress point is often the chamfer of the roller. The radial component of the hammering force, FrZ, is large, resulting in a large impact force Z on the raceway of the bearing ring, and a high probability of raceway damage. However, the pressure applied by the bearing assembly press rod is along the roller axis, and the radial component F'r is relatively much smaller. The roller assembly stress analysis is shown in Figure 3. In Figure 3a, the angle β between the roller generatrix and the diagonal in the cross-sectional view is:
β = arctan(Dw/Lw), (1)
Where: Dw is the roller diameter, and Lw is the roller length.
The radial component of the hammering force is:
Fr = Fatan(α+β), (2)
Where: Fa is the axial component of the assembly force.
In Figure 3b, the radial component F'r of the press-fit is:
F'r = Fatanα. (3)
From equations (2) to (3), it can be concluded that under the same axial component force Fa, Fr > F'r, that is, the radial component force generated by the hammering assembly force is greater than the radial force generated by the pressure bar assembly force. During bearing assembly, the axial component force Fa of the assembly force is the actual assembly force that drives the rollers to be pressed into the cage pocket, while the radial component force, perpendicular to the raceway of the bearing ring, is a harmful force that damages the raceway. Therefore, the radial component force should be avoided or reduced as much as possible during the assembly process.
Suppose a cylindrical roller bearing of a certain model has Dw=40mm and Lw=40mm. At a certain moment during the bearing roller assembly process, the roller's inclination angle α=10°, and the required assembly force Fa=200N. Then, Fr≈286N and F'r≈35N. The example shows that assembling rollers by hammering causes far more damage to the bearing raceway than assembling with a pressure bar.
3. Conclusion
The cylindrical roller bearing assembly pressure bar utilizes the lever principle, replacing the traditional hammer-based assembly method with continuous pressure application via the pressure bar. Roller pressure bar assembly eliminates or reduces raceway indentations and/or cage pocket deformation during bearing assembly, improving assembly efficiency and reducing worker workload. This cylindrical roller bearing assembly fixture has a simple structure, is easy to manufacture, and can also be applied to the assembly of self-aligning roller bearings.
About LJHB:
LuoYang JinShuo Precision Bearing Co., Ltd. is mainly committed to the R&D and sales of high-precision bearings and other special products, and provides bearings and transmission parts with high performance for customers' equipment. With quick response, from pre-sales technical communication to on-time production delivery, as well as perfect after-sales service, we win the recognition and trust of customers.
Our main products include cylindrical roller bearings, tapered roller bearings, slew bearings, gear drives, spindle bearings, crossed roller bearings, turret bearings, thin-wall bearings, tandem roller bearings, spherical roller bearings, etc. The bearing dimensions rang from 100mm to 6000mm, the accuracy reaches P5, P4 and P2 levels. The bearing are widely used in mining and metallurgy, industrial equipment, industrial gearboxes, petroleum equipment, cranes, medical equipment, robotic equipment, etc. Among them, cylindrical roller bearings with better performance and high-precision deep groove ball bearings have been explored for high-speed tubular strander rotating cable equipment, which have completely replaced imports, saving customers costs and time, and improving work efficiency. It has been recognized and widely praised by customers.
Contact LJHB:
Address: Yiyang Bearing Industry Zone, Luoyang City, China 47100
Tel/Wechat: +86-18037970383
Whatsapp: +86-18037970383
Fax: 0086-379-65199160
E-mail: lyjh@lyjhbearing.com
Website: www.chinajhbearing.com
