2023 June the Third Week KYOCM Technical Knowledge: Measurement method for axial clearance of wide inner ring of double row angular contact ball bearings

Abstract: The inner ring of a wide inner ring double row angular contact ball bearing is wider than the outer ring, and the axial clearance cannot be measured on the bearing axial clearance measuring instrument X194. In response to this issue, a new measurement method is introduced, which designs and manufactures the required measurement accessories based on the external dimensions of each type of bearing. The cam components on the instrument are modified to increase the effective length of the cam, thereby increasing the width of the workpiece that the instrument can measure, and cleverly solving the problem of measuring axial clearance of such bearings. The production practice results show that this measurement method is accurate and reliable, easy to operate, and has high measurement efficiency.

Keywords: Double row angular contact ball bearing; Axial clearance; Axial clearance measuring instrument X194

0 Introduction

Double row angular contact ball bearings are widely used in fields such as aerospace, aviation, and high-speed rail, as they can withstand large radial and axial combined loads and torque loads, limiting the axial displacement of the shaft in both directions. The wide inner ring double row angular contact ball bearing not only has the above characteristics, but also has become more and more widely used in recent years due to the protruding inner ring, which makes installation more convenient in some places. The axial clearance size of double row angular contact ball bearings during operation has a significant impact on the rolling fatigue life, temperature rise, noise, vibration and other performance of the bearings, so it is necessary to control it, that is, 100% axial clearance measurement should be carried out during the production process of the bearings. The axial clearance of ordinary double row angular contact ball bearings can be measured using a special measuring instrument X194, but this instrument cannot measure wide inner ring double row angular contact ball bearings. Currently, there is no good measurement method in various literature. This article analyzes the external dimensions of wide inner ring double row angular contact ball bearings and the axial clearance measuring instrument X194, A solution for measuring the axial clearance of wide inner ring double row angular contact ball bearings has been proposed, which can achieve online 100% detection of the axial clearance of wide inner ring double row angular contact ball bearings, thereby ensuring the qualification rate of the axial clearance of this type of bearing.

1 Current situation

In the production process of bearings, generally double row angular contact ball bearings can be measured on the axial clearance measuring instrument X194, as the width of the inner and outer rings is basically the same, as shown in Figure 1. The measuring principle of this instrument is shown in Figure 2, where 4 is the tested bearing. Under the joint action of the upper outer cushion block 3 and the lower outer cushion block 8, the outer ring of the bearing can be fixed. The upper inner cushion block 9 and the lower inner cushion block 5 clamp the inner ring of the bearing and can move up and down under the action of load block 1 and load block 7. Firstly, rotate cam 2 to release load block 1, and under the action of load block, the entire bearing moves upwards, Then rotate cam 2 to apply load to load block 1 downwards through the top rod 10. At this time, under the action of load block 1, the overall movement is downward, and the amount of up and down movement is the axial clearance of the bearing. The clearance value can be read through the dial gauge 6.

Figure 1 Axial Clearance Measuring Instrument

1. Load block 2. Cam 3. Upper outer cushion block 4. Tested bearing 5. Lower inner cushion block 6. Dial gauge 7. Load block 8. Lower outer block 9. Upper inner cushion block 10. Ejector

Figure 2 Measurement Principle

However, for wide inner ring double row angular contact ball bearings such as KR5202A-2RS/ZH, as shown in Figure 3, due to the inner ring being 40mm wider than the outer ring, it cannot be measured on this instrument. There are two reasons: (1) the outer cushion block 3 on the instrument cannot fix the outer ring because the inner and outer rings are not of equal width. The instrument first presses on the inner ring, but the upper outer cushion block 3 is suspended and cannot contact the outer ring; (2) Due to the excessively long inner ring of the bearing, it exceeds the height at which the instrument can fit the product, so the bearing cannot be placed at all.

When measuring the axial clearance of a wide inner ring double row angular contact ball bearing, factories generally use the manual pushing method, as shown in Figure 4. First, fix the outer ring, and push the inner ring up and down by hand. The movement of the inner ring is the axial clearance, which can be read using a dial gauge. This method has low measurement accuracy and low measurement efficiency.

Figure 3 KR5202A-2RS/ZH Bearing

Figure 4 Measurement by Hand Pushing Method

2 Measurement methods

2.1 Improving Instrument X194

Due to the high height of this type of wide inner ring double row angular contact bearing, which exceeds the height that instrument X194 can fit into the product, improvements were made to the instrument. Specifically, the cam shown in Figure 5 is improved to extend the overall length of the cam, as shown in Figure 6. This can increase the distance the instrument moves up and down, thereby increasing the height of the product. As shown in the figure, increasing the cam L from 35mm to 65mm can increase the height of the measured workpiece by about 30mm.

Figure 5 Original Instrument  Figure 6 Improved Instrument  Figure 7 Cam Parts

2.2 Design and manufacturing attachments

(1) Design attachments

Find the parameters of the bearing to be measured: the height of the outer ring of the bearing is H1, the outer diameter of the outer ring is D1, the inner diameter of the outer ring is d1, and the height of the inner ring is H2. After calculation, it can be concluded that the height of the attachment H=H2 H1; The outer diameter of the attachment D=D1; The inner diameter of the attachment is d=d1.

The designed attachment is shown in Figure 8

Figure 8 Attachment             Figure 9 Attachment inserted into bearing

(2) Manufacturing accessories

Process the attachment as shown in Figure 8, and the parallelism of the attachment is a key parameter that cannot exceed 0.002mm.

2.3 Measurement

Insert the processed accessory into the bearing, as shown in Figure 9, so that the inner and outer rings of the bearing with the accessory are of equal height and can be measured on the X194 instrument like normal bearings.

3. Verification of measurement methods

For the axial clearance of double row angular contact ball bearings, the calculation formula is:

Ga=Ai+2 (Re+Ri Dw) Sin α－ Ae

In the formula, Ga is the axial clearance; Ae is the distance between the outer groove centers; Ai is the distance between the inner groove centers; Re is the radius of curvature of the external groove; Ri is the radius of curvature of the inner groove; Dw is the diameter of the steel ball; α Is the contact angle.

Verification method: Extract the inner and outer rings of the bearing and measure Ae, Ai, Re, and Ri on a specialized instrument. After measurement, use a steel ball with appropriate gauge values for fitting. After fitting, measure the contact angle on the bearing contact angle measuring instrument α， Then use the formula to calculate the theoretical axial clearance Ga (theoretical clearance), and measure the actual axial clearance Ga (measured clearance) of the assembled bearing on the improved X194. Compare and determine whether the measurement method is correct. At the production site, 10 inner and outer rings of KR5202A-2RS/ZH (bearing appearance as shown in Figure 3) were selected, and the Ae, Ai, Re, Ri of each ring were tested on a dedicated instrument and recorded. At the same time, all 10 sets of bearings were assembled using steel balls with a gauge value of 0 (ball diameter of 5.556mm), and the bearing contact angle was measured after assembly α， Finally, the axial clearance Ga was measured on the improved X194 measuring instrument, and the specific data is shown in Table 1. From the table, it can be seen that the error between the theoretical clearance and the measured clearance is all within 0.002mm, which meets the technical requirements of the drawing. This indicates that this measurement method is reliable and can be used for mass production.

Table 1 Comparison between Theoretical Clearance and Measured Clearance

4 Conclusion

There is no good measurement method for the axial clearance of wide inner ring double row angular contact bearings in the industry, and some units even use the original manual pushing method for measurement, resulting in low accuracy. In response to this issue, this article proposes a new measurement method based on the analysis of the wide inner ring double row angular contact bearing and axial clearance measuring instrument X194. The measurement principle is clear, the measurement results are accurate, and the measurement accuracy is high. The indication error can be accurate to ± 0.002mm, and the measurement efficiency is also higher than the original manual pushing method, This measurement method is a good solution for measuring the axial clearance of wide inner ring double row angular contact bearings. After more than 3 years of on-site verification, the quality of the products produced is stable and has been recognized by customers. Therefore, this measurement method can meet the needs of mass production measurement and has great promotion value in the bearing industry.

More about KYOCM Spherical Plain Bearing：

A spherical plain bearing is a bearing that permits angular rotation about a central point in two orthogonal directions (usually within a specified angular limit based on the bearing geometry). Typically these bearings support a rotating shaft in the bore of the inner ring that must move not only rotationally, but also at an angle.

KYOCM The Spherical Bearing is a heavy-duty self-aligning sliding bearing. Highly resistant to impact loads, this product is most fitted to the oscillating section under slow, heavy loads.

https://www.kyocm.com/products/Spherical-Plain-Bearing/742.html