Abstract: Aiming at such issues as low assembly efficiency，damaged raceway affecting service life and the potential risks existed during assembly of extra large size spherical roller bearings，the hydraulic assembly machine is designed， and its structure and operating principle are introduced． The practice proves that the assembly accuracy and production efficiency are effectively improved for large size spherical roller bearings．

Key words: spherical roller bearing; large size bearing; assembly machine; process improvement

Extra large self-aligning roller bearings can withstand heavy loads and impact loads, and are widely used in heavy machinery equipment such as mining, metallurgy, petroleum, cement, etc. Among them, The CA type extra large self-aligning roller bearing has 2 rows of symmetrical spherical rollers, with double raceways on the inner ring and a small guard edge at each of the 2 end faces. The outer raceway is spherical, and the inner components of the bearing can rotate in the axial and circumferential directions of the outer ring, with self-aligning performance; Multi use vehicle made solid metal cages.

The assembly method of the extra large self-aligning roller bearing is to lift the inner ring and cage into the outer ring, place the supporting rollers at the bottom, then fit the ball gap of the inner ring into the corresponding cage pocket hole, and then press the rollers into the two raceways of the inner ring one by one.

1. Traditional assembly methods and existing problems

The roller diameter of the oversized self-aligning roller bearing is greater than 120 mm, and the roller mass is greater than 15 kg. Due to the lack of suitable assembly tools, the traditional assembly method is manually operated, which has many shortcomings.

1) Low efficiency, high labor intensity, and potential safety hazards. Manual assembly requires 5 people to work together. Use a pry bar to pry up the cage, manually rotate the inner ring to match the ball loading port with the cage pocket hole, and use an iron rod to hit the end face of the roller to load it into the raceway from the ball loading port, resulting in low assembly efficiency; High intensity of manual labor; Manual operation can easily lead to safety hazards such as pinching hands and smashing feet during installation.

2) Highly destructive, affecting bearing accuracy. The roller is placed at the gap of the inner ring ball, and the roller is installed into the cage by tapping the end face of the roller. Due to the certain angle between the roller and the raceway during assembly, defects such as raceway bumps and scratches are prone to occur during the assembly process, which seriously affects the accuracy and lifespan of the bearing.

2. Design concept and assembly method of assembly machine

To replace manual rotation of the inner ring and avoid hitting the roller end face, a simple turning wrench can be designed using the lever principle to achieve inner ring rotation, saving manpower and improving the accuracy of rotation; Design a robotic arm to replace manual pushing of rollers into the raceway, with simple operation, accurate movements, and appropriate force. The designed large self-aligning roller bearing assembly machine is shown in Figure 1, mainly composed of a hydraulic propulsion assembly mechanism and a connecting pressure plate.

1- Outer ring; 2- Inner ring; 3, 22- Connect the pressure plate; 4, 13- Screw; 5, 14- Oil cylinder; 6, 15- Cylinder assembly hole; 7, 16- cylinder block seat; 8, 19- piston rod through-hole; 9, 18- Pin shaft; 10, 17- pull rod; 11, 20- Pressure plate; 12, 21- Install roller lever

Figure 1 Schematic diagram of assembly machine structure

The hydraulic propulsion assembly mechanism has one set on the left and one set on the right, including screws, oil cylinders, and roller levers; The connecting pressure plate is set parallel to the width of the inner ring and fixed by screws. The oil cylinder is arranged in parallel between the connecting pressure plates, and the front end of the piston rod of the oil cylinder is fixed with a connecting rod. The connecting rod passes through the through-hole of the piston rod and is connected to the roller lever through a pin shaft; The cylinder block seat passes through the cylinder assembly hole and is connected to the connecting pressure plate. During assembly, the connecting pressure plate is set on both ends of the bearing inner ring and fixed by screws. Activate the control cylinder switch, hydraulic oil enters and pushes the piston rod inside the cylinder to extend. The piston rod drives the roller lever to move through the connecting piece, and the roller end face is pressed to fully fit the roller that needs to be installed into the raceway. The control cylinder switch can be activated separately or simultaneously to complete the assembly of the self-aligning roller on one or both sides simultaneously.

3. Conclusion

Practice has proven that the designed oversized self-aligning roller assembly machine simplifies the assembly process and reduces manual labor intensity; The assembly machine has a simple structure, convenient manufacturing, and low cost; The assembly efficiency is high and has good universality. By replacing the connecting plate, one assembly machine can complete the assembly of bearings with an inner diameter of 500-1000 mm, covering dozens of product models, greatly reducing production costs. At the same time, it solves the problem of using a pry bar to pry the ball mouth during the assembly of rollers, which damages the raceway and the ball mouth (such as scratches and scratches), and improves the service life of the bearings.

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