1. Overview

Axial clearance is an important technical index in the application of double and four-row tapered roller bearings, which has a direct impact on the service life of the bearing. JB/T8236—2010 "Rolling bearing double-row and four-row tapered roller bearing clearance and adjustment methods "The conversion and adjustment methods of the radial clearance and axial clearance of double and four-row tapered roller bearings are specified, that is, the split measurement method. The clearance of double and four-row tapered roller bearings is too small, which is likely to cause serious bearing failure accidents. The main engine users often need to recheck the axial clearance and measure the double and four-row tapered rollers according to the "split method" specified in the standard. When bearing axial clearance, a height gauge is used to determine the distance between the end face of the ring and the measurement platform. The requirements for the bearing test platform are high, and it is difficult for users to achieve it on site. Manufacturers and users of the main engine have explored various alternative measurement methods in practical applications. The "whole method" is currently an alternative measurement method widely used by users of the main engine. The measurement practice shows that when measuring the axial clearance of double and four-row tapered roller bearings , The measurement error of "Integral Method" and "Split Method" is about 0.01~0.10mm1. The difference in the measured values ​​obtained by different measurement methods forces bearing manufacturers to increase the axial clearance value to "match" the user's measurement method when configuring the clearance, causing the actual bearing clearance to be greater than the measured value, thereby reducing the rotation accuracy of the bearing and increasing the bearing Vibration and noise during operation will ultimately reduce the life of the bearing.

Some foreign companies have adopted the "projection method" when measuring the clearance of double and four-row tapered roller bearings without spacers, and have developed special measuring instruments, as shown in Figure 1. The calculation principle of this measurement method is the same as the "split method" stipulated by the standard. The end face of the ferrule is positioned in the measurement, without reciprocating leveling; 3 meter frames are read at the same time, and a total of 9 data in 3 groups can be obtained by measuring 3 times; The efficiency is greatly improved, and the accuracy requirements of the measurement platform are relatively low, which is convenient for measuring on the bearing application site. At present, this measurement method has been extended to the clearance measurement of double and four-row tapered roller bearings of various structural types.

To sum up, learn from the principle of the "protrusion method" measuring instrument of foreign companies, make simple tooling to carry out double and four-row tapered roller bearing axial clearance test experiments, and conduct a comparative analysis of the results obtained by different measurement methods.

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2. Measurement method

In order to verify the data difference between the "projection method" and the standard "split method" and "integral method", 32930 single row tapered roller bearings (face-to-face pairing) and SKFBT2-8131 double row with clearance to be fitted after manufacture were selected For tapered roller bearings, measure the gap between the outer rings of the two types of bearings and calculate the axial clearance 12. The number of test samples are: 100 sets of 32930 pairs are randomly selected to be 50 sets of 32930DF, 20 sets of SKFBT2-8131, the main reason for these two kinds of bearings as test objects is that the bearing gap is in the outer ring, which is convenient for overall measurement, and the weight and cone of the bearing The angle difference is also large, which is convenient for comparing data. The test data comes from the measured values when the clearance between the working procedures is combined.

3. Data analysis

The measured data of 3 measurement methods, 50 sets of 32930DF and 20 sets of SKFBT2-8131 are the average values ​​of axial clearance under different measurement methods.

(1) Same as previous research conclusions, the measured value of the "whole method" is significantly greater than the measured value of the "split method". This is due to the "integral method" measurement, due to the self-locking problem of the next row of rolling elements, the gap measurement value is greater than its actual value, resulting in the actual clearance of the bearing when the clearance configuration is greater than the true value.

(2) For 32930DF, the average measurement value of the "whole method" is 0.126mm larger than that of the "split method"; for SKFBT2-8131, the measurement mean value of the "whole method" is 0.201mm larger than that of the "split method". The measurement error exceeds 0.10mm, and the larger the bearing size and cone angle, the greater the measurement error.

(3) For the two types of bearings of 32930DF and SKFBT2-8131, the absolute value of the difference between the "projection method" and the "split method" measurement mean value is 0.010 and 0.009mm, respectively. The measurement results are very close. The "protrusion method" can be used as an alternative to the "split method".

(4) For the 32930DF, the "split method" measuring man-hours is 1.75 times that of the "whole method" and 1.4 times that of the "protrusion method". The efficiency advantage of the "protrusion method" is not significant, because the bearing weight is lower. Light, whether it is the "split method" or the "protrusion method", the proportion of the turning time in the bearing measurement process is relatively small; for the SKFBT2-8131, the "split method" measurement man-hour cost is the "whole method" 4 times, 2.18 times that of the "protrusion method". Compared with the "split method", the "protrusion method" has a significant efficiency advantage, and the main man-hour spent is the bearing turnover time. The actual measurement and reading time are longer. short. When measuring the axial clearance of heavy and large double-row tapered roller bearings, the "projection method" has a very outstanding advantage under the premise of ensuring the measurement accuracy. It can be used as a user to re-examine the axial direction of double-row tapered roller bearings on site. An important means of clearance.