Abstract: Aiming at the problem that the axial clearance is commonly used to control the radial clearance in the production of deep groove ball bearings, and the radial clearance is out of tolerance after fitting, the accuracy of the inner and outer raceways and steel balls is strictly controlled, and the shaft is compressed and calculated. For the radial clearance range in the direction of clearance, the lower limit remains unchanged, and the upper limit is compressed by 15%. The axial clearance obtained by this method is used as the benchmark to control the actual radial clearance after the sleeve is fitted, and the example verification shows that this method can meet the technological requirements.
The radial clearance of deep groove ball bearings is an inspection item specified in the standard, and it is also one of the basis for users to select bearings. Radial clearance is generally measured with a radial clearance meter, and the measured value is relatively accurate, but the adjustment time of the instrument is long and the efficiency is low, which is not suitable for mass production. Relatively speaking, the measurement of axial clearance is convenient and efficient; therefore, most manufacturers use empirical formulas to convert radial clearance into axial clearance in actual production, and measure and control the axial clearance for fitting. . However, in actual production, it is found that after controlling the axial clearance and fitting the sleeve, the measured radial clearance of some bearings is out of tolerance. Aiming at this problem, an in-depth analysis is carried out, and a set of improvement methods for deep groove ball bearing clearance control are given.
1. existing problems
In actual production, the experience of conversion between radial clearance and axial clearance of deep groove ball bearings Ga is the axial clearance; Gr is the radial clearance; R is the radius of curvature of the groove; Dw is the diameter of the steel ball. It can be seen from formula (1) that the diameter and axial clearance of deep groove ball bearings are related to R and Dw. When calculating the axial clearance, when the radius of curvature R of the inner and outer ring grooves is different, it shall be calculated according to its geometric arithmetic mean value. Taking 6030EM bearing as an example, the inner groove curvature radius Ri=12.26+0.10mm, the outer groove curvature radius Re=12.5+0.10mm, the steel ball diameter Dw=23.8125mm, and the basic group radial clearance Gr=0.018～0.053mm. The corresponding axial clearance Ga=0.26～0.41mm calculated by formula (1). Ga is controlled to fit the sleeve, and the actual radial clearance Grs of the bearing after the sleeve is detected, as shown in Table 1.
It can be seen from Table 1 that the actual radial clearance of bearings 9 and 10 is out of tolerance by using the axial clearance to control the radial clearance, which cannot meet the technical requirements.
2. Improvement of control method
2.1 Control of inner and outer groove curvature radius R and steel ball size
The shape of the channel is precisely controlled by using CNC grinding equipment and profilometer measurement. Strictly control the steel ball production process to make its precision meet the application requirements. By strictly controlling the machining process of the inner and outer race channels and steel balls, the influence of the channel and steel ball errors on the axial clearance error is minimized.
2.2 Improvement methods
When the radial clearance of the deep groove ball bearing is converted into the axial clearance, the Gr is adjusted and its upper limit value is compressed by 15% (ie G’r=0.018～0.045mm) for calculation. The axial clearance is G’a=0.26～0.38mm. The bearing is fitted on the basis of G’a, and the actual radial clearance Grs after fitting is shown in Table 2. It can be seen from Table 2 that the radial clearance is controlled by the axial clearance obtained after adjustment, which meets the requirements.
3. Instance Verification
With the adjusted method, choose any type of bearing (6232E) to verify the method. It is known that the inner groove curvature radius Ri=18.8+0.150mm, the outer groove curvature radius Re=19.17+0.15mm, the steel ball diameter Dw=36.5125mm, and the basic group radial clearance Gr=0.018～0.053mm. Adjust the radial clearance Gr and compress its upper limit by 15%, that is, G’r=0.018～0.045mm, and the axial clearance obtained at this time is G’a=0.41～0.51mm. Taking G’a as the benchmark for fitting, the actual radial clearance Grs measured after fitting is shown in Table 3.
Then, 10 types of bearings were continuously tracked and tested, and the corresponding adjustments were made. Finally, the radial clearance after the fitting met the technological requirements.
It has been proved by production practice: keep the lower limit of radial clearance unchanged, compress its upper limit by 15%, calculate the axial clearance according to the geometric arithmetic mean of the curvature radius of the inner and outer ring grooves, and use the axial clearance as The datum is fitted, and the radial clearance after fitting meets the technological requirements.