Abstract: DB double row tapered roller bearing is widely used in truck gearbox, and the axial clearance standard of this type of bearing is strict (0.05mm). It is difficult to adjust the clearance, and many influencing factors need to be analyzed and solved to meet the requirements. This paper introduces the influencing factors found in the clearance adjustment sleeve and the analysis and solutions.

Key words: double row tapered roller bearing; Axial clearance; Error

DB double row tapered roller bearings are widely used in truck gearboxes. The axial clearance standard of this type of bearing is strict (0.05mm). It is difficult to adjust the clearance, and many influencing factors need to be analyzed and solved to meet the requirements. The following describes the influencing factors and analysis solutions found in the clearance adjustment sleeve.

1. Basic process of axial clearance adjustment

First, demagnetize, clean and check the two single sets, an outer spacer and a load block

Fig. 1 Schematic diagram of axial clearance measurement of DB double row tapered roller bearing

1 - load block 2 - inner ring 3 - roller 4 - first outer ring (upper row bearing outer ring) 5 - outer spacer ring 6 - inner spacer ring 7 - second outer ring (the following flanged outer ring)

They are combined as shown in Fig. 1 (without inner septum). Place it on the platform of the height measuring instrument, push the assembly gently by hand, and place the probe of the altimeter in the center of the load block (1). Rotate the bearing so that the roller of the bearing is in good contact with the inner and outer race raceways and the large flange of the inner race. Then turn the dial, align 0 with the dial indicator needle, install the inner spacer ring, rotate the bearing, and then contact the bearing rotation center with the height gauge probe. If the dial indicator pointer is within the specified axial clearance tolerance range, it indicates that the axial clearance standard requirements are met.

In order to determine whether the axial clearance is stable and qualified after sleeve closing, it is necessary to take out the inner spacer and repeat the previous sleeve closing measurement process. If the indicator position of the dial gauge overlaps or changes little with the previous one, the axial clearance of this set of bearings is qualified. Thus, the axial clearance selection process of a set of bearings is completed.

2. Question raising

During the actual selection and matching of the axial clearance GA of DB double row tapered roller bearings, it was found that some bearings were out of tolerance during repeated measurement. Taking 306 / 68.6/c9dbya1 product as an example (axial clearance GA = 0.102 ~ 0.152) mm, the four sets of finished bearings were measured for 10 times, and the measurement results are shown in Table 1.

Table 1 measured value of repeated measurement of axial clearance

3. Cause analysis

The data in Table 1 shows that the measurement error of axial clearance is large, which reflects that there is an indefinite value when the zero position is fixed. Through the analysis of the problem bearing, it is found that the following factors can cause this phenomenon.

(1) If the bearing is not cleaned cleanly and there is dirt in the outer raceway, part of the rollers shall be padded up so that the large end face of the remaining rollers may be out of contact or partially in contact with the large flange of the inner sleeve.

(2) The inner assembly is mixed with rollers, and part of the rollers are padded up to make the large end face of the remaining rollers out of contact with the large stop edge of the inner sleeve, and the watch needle swings greatly (more than 0.2mm);

(3) The roughness of the inner and outer race raceways and rollers exceeds the standard, which makes the "self-locking" clearance between the ball base surface of the inner assembly of the upper bearing roller and the large stop edge of the inner race an indefinite value, resulting in a large difference in the measured values of axial clearance;

(4) The convexity of the inner and outer ring raceways is large, and the rollers and raceways form an approximate point contact, so that the ball base surface of the inner assembly of the bearing roller and the large stop edge of the inner ring can not form a complete contact, resulting in unstable measurement and positioning of the axial clearance, affecting the stability of the measurement indication, and the needle swings more than 0.10mm. See Table 2 for the data of repeated measurement of the above factors on bit 0.

Table 2 measured value of repeated measurement of 0-bit of different factors unit: Um

4. Verification

(1) Re clean the bearings that are not cleaned and have dirt on the outer raceway;

(2) Replace the bearing sleeve of the mixed roller of the inner assembly with a group of qualified rollers and reassemble them;

(3) For the inner and outer ring raceways whose roughness exceeds the standard, the rollers (inner raceway RA 0.23; outer raceway RA 0.25; roller RA 0.22) shall be trimmed again, and the trimmed inner raceway RA 0.12; Outer raceway RA 0.10; Roller RA 0.10.

(4) The inner and outer raceways with large convexity (outer raceway convexity le8um, inner raceway convexity li7um) shall be re trimmed. After trimming, the outer raceway convexity is le3um and the inner raceway convexity li2um.

See Table 3 for the measured value of repeated measurement of axial clearance after re trimming, and see Table 4 for the measured value of repeated measurement of position 0 after trimming.

Table 3 measured value of repeated measurement of axial clearance after trimming unit: Um

Table 4 measured value of repeated measurement at position 0 after trimming

5. Conclusion

In the process of adjusting and matching the axial clearance of DB double row tapered roller bearings, under normal circumstances, when determining the zero position, as long as a specified small load block (2kg) is added to the upper row of bearings, and then the inner assembly is rotated by hand for more than one circle, the ball base surface of the inner assembly of the upper row of bearing rollers and the large flange of the inner ring can be fully contacted, so as to achieve a stable and accurate axial clearance value. However, in the process of adjusting and matching the axial clearance and matching the actual sleeve, due to the above listed factors, the ball base surface of the inner assembly of the upper bearing roller and the large stop edge of the inner ring can not form complete contact, and the measurement error of axial clearance is large and the zero position is not fixed during repeated measurement, which affects the sleeve quality and needs to be paid attention to and avoided. The above verification is our experience formed in the process of actual axial clearance adjustment and matching, which is only for reference.

More about ITS Tapered Roller Bearing:

ITS tapered roller bearing top quality brand has guaranteed production and highly active management. 

With a wide range of designs to choose from, ITS tapered roller bearings are also customizable to match your specific speed, load, contamination, temperature or vibration conditions.

ITS Tapered roller bearings feature a cup and cone assembly. The cup is comprised of the outer ring and the cone assembly consists of inner ring, rollers, and cage. This bearing construction accommodates combined loads and provides low friction during operation. By adjusting one single row tapered roller bearing against a second tapered roller bearing and applying a preload, a rigid bearing application can be achieved.

ITS tapered roller bearings are also made to Explorer class. ITS Explorer combines our expertise in bearing design, tribology, metallurgy, lubrication and manufacturing. ITS Explorer tapered roller bearings are typically used in bearing solutions where there is a need to increase performance, reduce friction or increase power density in applications.