Control Method for Rib Contact Points of Tapered Roller Bearings

Abstract: Based on pure rolling design theory for tapered roller bearings，the accurate and approximate calculation formulas for position dimension of contact points between back face rib of inner ring and roller sphere base surface are derived according to geometrical relationship between inner ring and roller． The position control for contact points in the production process is analyzed by combining bearing manufacturing process． Finally，the actual examples are introduced．

Key words: tapered roller bearing; back face rib; roller sphere base surface; contact point; control method

Symbol Description

Di -- Maximum diameter of inner ring raceway with straight edge, Dw -- Diameter of roller head, SR -- Curvature radius of roller ball base surface, β -- Angle between inner ring raceway centerline and axis, λ -- Angle between inner ring large edge cone surface and end face, ρρ -- Curvature radius of inner ring curved edge, phi -- Half cone angle of roller, Ω -- Angle between inner ring large edge cone surface and raceway surface

In tapered roller bearings, the position of the contact point between the base surface of the roller ball and the large edge of the inner ring is very important. If the contact point is too close to the overtravel groove of the large edge of the inner ring, the edge of the overtravel groove will be in the contact elliptical area during operation, causing stress concentration and fatigue peeling; The contact point is too close to the highest point of the large retaining edge, which can easily cause deformation or even fracture of the inner ring large retaining edge during operation. Therefore, it is necessary to reasonably control the contact point between the base surface of the roller ball and the large edge of the inner ring. Reference [1] provides a calculation formula for the distance bi from the contact point between the roller ball base surface and the inner ring large retaining edge of the tapered roller bearing to the edge of the overtravel groove from a design perspective. However, there is no relevant literature on what size range the contact point position should be within and how to effectively control it during the processing and production process. Therefore, this article introduces the reasonable size range of the contact point position and its control and adjustment during the production process.

1. Exploration of the range of contact points

As shown in Figure 1, starting from the intersection point of the large edge of the inner ring of the tapered roller bearing and the inner ring raceway, it is divided into three sections outward, labeled as 0, 1/3, 1/2, and 1. Based on years of bearing design and practical experience in foreign host supporting projects, when the contact point is between 0-1/3 and close to the root, it is conducive to forming a lubricating wedge between the roller and the retaining edge, and can reduce the pressure on the bearing retaining edge. However, the oil in the oil groove is not conducive to lubrication, and the contact point is prone to falling into the oil groove or the edge of the oil groove. When the roller works, it forms an edge effect, which increases the wear of the roller ball base surface and reduces the bearing life; When the contact point is at 1/3, although it is conducive to the formation of a lubricating wedge between the roller and the edge, and the pressure strength of the large edge is also lower, it is easy to cause the roller to get stuck; When the contact point is 1/2 in the middle of the large gear edge, the lubrication wedge formed is more conducive to bearing lubrication; When the contact point is at the highest point 1 of the large edge, deformation is prone to occur due to the high pressure intensity of the large edge. Therefore, in design, the contact points should be controlled as much as possible within the range of 1/2 in the middle of the large edge.

Figure 1 Schematic diagram of the contact point between the base surface of the roller ball and the large edge of the inner ring

2. Accurate calculation of contact point position

According to the pure rolling design theory of tapered roller bearings, the centerline of the inner and outer raceways and the centerline of the rollers intersect at the same point. The geometric relationship between the rollers and the inner ring is shown in Figure 2. According to the geometric relationship in Figure 2:

Figure 2 Schematic diagram of geometric relationship between roller and inner ring

From equation (8), it can be seen that in the actual production process, it is only necessary to accurately measure the values of SR, Dw, phi, É, β, and di, and substitute them into equation (8) to accurately obtain the position of the contact point of the tested bearing. Due to the large number of rollers in the same set of tapered roller bearings, it is difficult to accurately locate the roller ball base surface during the precision grinding process, and the SR value is difficult to precisely control. The SR dimensional accuracy generally varies within a tolerance range of 0-15 mm. Therefore, for the SR value, it is usually necessary to accurately measure multiple (normally 5) rollers, and take the average value as the input for precise calculation of the contact point.

3. Approximate calculation of contact point position

From equation (13), it can be seen that by accurately measuring SR, Dw, phi, and the average value of 5 roller SRs, the position of the contact point can be approximately calculated, without the need for precise measurements of β and di.

As shown in Figure 2, due to CO ≈ BO, if CO1 ≈ BO1=SR=0.95 ρ=0.95BO, then CD ≈ BD, ∠ O1CD ≈ ∠ O1BD, thus having

4. Control of contact point position during production process

Whether it is the trial production of new products or mass production, synchronous engineering is used to organize production, and the production cycle is generally controlled within 45 days. The rollers are produced by professional manufacturers according to the drawing requirements and relevant technical agreements, and it takes about 35 days to complete processing, testing, and packaging; The machining process of bearing rings is relatively complex, usually carried out by professional forging and turning cooperation, and then transferred to internal inspection, heat treatment, grinding, and assembly within the company, thus requiring a relatively long time. Under normal circumstances, when the rollers and cages are inspected and qualified for storage, the inner ring of the bearing basically enters the precision grinding process of the raceway and retaining edge. Therefore, it is almost impossible to precisely control the position of the contact point by adjusting the geometric parameters of the rollers, and only the inner ring parameters can be selected for appropriate adjustment.

However, in the geometric parameters of the inner ring, β and di cannot be changed, otherwise it does not comply with the pure rolling theory of bearings, which can easily lead to increased sliding friction during bearing operation and affect the height of the bearing after assembly. Therefore, the only thing that can be adjusted is É. According to the current design method for tapered roller bearings [2], ω=90 ° - λ+β. Since β cannot be changed, changing ω is essentially fine-tuning λ, which achieves precise control of the contact point position through fine-tuning λ.

In order to express the position of the contact point more intuitively and conveniently, and to assist production and process personnel in accurately judging whether the control of the contact point is reasonable, 1-2 inner rings are randomly taken before the inner ring precision grinding of the edge guard. The bearing inspection instrument and contour instrument are used to accurately measure the inner ring parameters β, di, B, N, F, and ω as shown in Figure 3, as well as the roller parameters SR, Dw, and phi. The relevant calculation formulas of the contact point are included in an Excel spreadsheet. With the help of the functions of the Excel spreadsheet, the range of the ω angle is determined to guide the installation of the grinding wheel and the adjustment and control of the angle in the edge guard precision grinding process, achieving the purpose of effectively controlling the contact point.

Figure 3 Geometric parameters to be measured for inner ring and roller

5. Examples of touchpoint control

Taking the actual control of the contact point between the large retaining edge of the inner ring of 524467 tapered roller bearing and the base surface of the roller ball as an example, this paper introduces the calculation steps for the contact point position after producing 5.1. The calculation steps for the contact point position are as follows:

(1) Use a special bearing inspection instrument and a contour gauge to accurately measure the geometric dimensions of the rollers and inner rings, as shown in Table 1;

(2) Enter and design two Excel spreadsheets for accurate and approximate calculation formulas of contact point positions separately;

(3) According to the data input requirements of the precise and approximate calculation formula for the contact point position, input the measurement parameter values in Table 1 to obtain the precise and approximate calculation position dimensions of the contact point, which are 2.90 mm and 2.89 mm, respectively. The calculation results of these two methods only differ by 0.01, which is very close, and both calculation results show that the contact point is located 1/2 above the large edge of the inner ring.

Table 1 Precision measurement results of roller and inner ring parameters

5.2 Adjustment and control of contact point position

The adjustment and control method for controlling the contact point between 1/3 and 1/2 of the inner ring large edge: Enter different values of the angle in an Excel spreadsheet. When the calculation result is equal to or close to the values of the two control points (the contact point position size at 1/3 is 1.881 mm, and the contact point position size at 1/2 is 2.821 mm), the corresponding angle range is the angle range required for the installation of the grinding wheel in the production process of the inner ring large edge precision grinding process. For precise calculation of the size of the contact point position, when the input value is 89 ° 35'47 ", the calculated result of the contact point position is 1.88 mm; When the input value is 89 ° 17'31 ″, the calculation result shows 2.82 mm. Therefore, if comparing the accurate and approximate calculation results of the contact point position, it is necessary to control the contact point position of the 524467 tapered roller bearing between 1/3 and 1/2 of the inner ring large retaining edge. The actual controlled angle range is very close, which further proves that the difference between the accurate calculation and approximate calculation of the contact point position size is extremely small. Therefore, approximate calculation can be used instead of accurate calculation in the production process to determine the control range required for the angle.

Finally, use the calculation results to guide the installation and adjustment of the grinding wheel angle in the inner ring edge grinding process. For different edge grinding machines, after the installation and adjustment of the grinding wheel, first try grinding 1-2 large inner ring edges, and use a profilometer to accurately measure the angle. If the value of the angle is within the calculated range, maintain the installation angle of the grinding wheel for precision grinding of the inner ring edges; If the measured angle value is not within the calculated angle range, the installation angle of the grinding wheel must be adjusted until the angle value enters the calculated angle range to ensure that the contact points of the batch bearings are in a reasonable position.

6. Conclusion

Based on the pure rolling design theory of tapered roller bearings, using the geometric relationship between rollers and inner rings, accurate and approximate calculations were carried out for the contact point positions of the roller ball base surface and the inner ring large retaining edge. Through examples, it was proven that the accurate calculation results are very close to the approximate calculation results. Therefore, approximate calculation methods can be used to precisely measure the bearing parameters SR, Dw, phi, É, B, N, and F, and by fine-tuning the É angle, the contact point between the roller ball base surface and the inner ring large retaining edge can be ensured to be in the ideal position range during the bearing production process.

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