1.Overview

Angular contact (thrust) spherical plain bearings have large load capacity and impact resistance due to large spherical sliding contact area and large inclination angle, and have corrosion resistance, wear resistance, self-aligning, good lubrication or self-lubricating type without lubrication Therefore, it is widely used in low-speed swing motion, tilt motion and rotary motion, such as engineering hydraulic cylinders, forging machine tools, engineering machinery, automation equipment, automobile shock absorbers, water conservancy machinery, etc.

Angular contact spherical plain bearings and thrust spherical plain bearings are the leading products of two of the six series of our company, with a wide range of product models and mass production every month. The assembly height of the product (the H value in Figure 3) is an important technical parameter, especially the self-lubricating type, which is a full inspection item during the final inspection of the finished product. Therefore, how to improve the measurement accuracy and measurement efficiency and reduce the labor intensity of the inspection personnel has become an urgent problem for enterprises to ensure the quality of mass-produced products and meet market demand.

2. Original measurement methods and existing problems

Since the working sliding surfaces of the inner and outer rings of the angular contact (thrust) spherical plain bearing are less hemispherical, the outer ring and the inner ring can swing each other, and the commonly used height measuring instrument cannot measure this parameter. There are mainly two kinds of original detection methods: the first is to use the mandrel method to measure, as shown in Figure 1. This inspection method has four defects: (1) Each model needs to be equipped with a mandrel with the same size as the inner diameter of the shaft ring; (2) The mandrel and the shaft ring are clearance fit, the gap is too large, and the measurement value error is large; If it is too small, it is not easy to install and unload the mandrel, and it is difficult to measure; (3) When testing large-scale and large-scale products, the physical requirements of the inspectors are high during the process of loading and unloading the mandrel, and the labor intensity is high. A little carelessness may crush your fingers; (4) The mandrel must be repeatedly loaded and unloaded for each set of measurements, and the detection efficiency is low. The second is measured with a micrometer, as shown in (Figure 2). Use two micrometers to measure at the symmetrical positions of the product. During the measurement, the measured value of the micrometer should be adjusted repeatedly until the measured value of the two micrometers is consistent, and the measured value at this time is the assembly height. The defects of this inspection method are: (1) The two micrometers have to be adjusted many times to obtain the measurement value, which is cumbersome and inefficient, and is not suitable for batch measurement; (2) It requires certain measurement skills to obtain accurate measurement values. The defects of the above two measurement methods are mainly caused by overcoming the mutual swing of the outer ring and the inner ring during the measurement. Therefore, how to quickly ensure that the two measurement datum planes are parallel to each other during the measurement has become the focus and core of the design. To this end, I designed this angular contact (thrust) spherical plain bearing assembly height measuring instrument to solve this problem.

3. Measuring principle of the measuring instrument

Since the angular contact (thrust) spherical plain bearing has the characteristics of concentric inner and outer ring ball diameters and self-aligning, and the surface roughness of the spherical surface is less than Ra0.8, so after applying a small pressure F to the shaft ring, as shown in Figure 3, The datum plane of the shaft washer can be made parallel to the datum plane of the seat ring, and the H value measured at this time is the assembly height of the bearing.

4. The main structure of the measuring instrument

In order to realize the measurement principle shown in Figure 3, it can be realized by the measurement mechanism shown in Figure 4. The instrument is mainly composed of the following parts: basic device (table, column, cantilever, V-shaped positioning fork, anti-wear gasket, etc.); lifting transmission system (threaded knob, trapezoidal threaded shaft, pressure plate); measuring system (indicating instrument frame, precision 0.01 indicating instrument); anti-overload system (anti-overload bushing, handle, etc.); V-shaped positioning fork (adjustable position, positioning the bearing under test). In order to meet the detection of bearings of different types and specifications in the production process, the measuring instrument is designed to cover as many types as possible, ranging from GAC25 to GAC150, GX10 to GX120 (nominal outer diameter of bearing seat ring Φ30 to Φ230mm) can be measured.

5 Design points

(1) This measuring instrument is designed using the characteristics that the inner and outer rings of the bearing can swing each other and the ball diameters are concentric and can be automatically adjusted. Whether the pressure plate and the worktable are parallel is an important factor affecting the measurement accuracy. In order to ensure the measurement accuracy, in addition to the rigidity and shape and position tolerances of the relevant components of the basic device, the matching clearance between the outer diameter of the trapezoidal threaded shaft and the cantilever aperture must be precisely guided under the premise that the trapezoidal threaded shaft can move up and down flexibly ( The clearance fit is controlled at 0.02-0.04mm) to eliminate the influence of the clearance on the measurement accuracy.

(2) In the lifting transmission system, the trapezoidal thread (lead 20, pitch 5) with good craftsmanship, high thread strength and good neutrality is used for load transmission and stroke transmission. The lifting mechanism can realize rapid lifting movement, improve work efficiency and reduce labor intensity; at the same time, in order to prevent excessive load on the measuring bearing and cause deformation of the measuring instrument and product, a set of anti-overload system is specially designed for overload protection, such as shown in Figure 5. The handle drives the anti-overload bushing and the steel ball to rotate, and the threaded knob rotates under the pressure of the steel ball. When the load is too large, the steel ball is lifted up, and the anti-overload bushing slips and rotates, thus playing an overload protection role.

(3) Since the non-reference plane of the shaft washer of the finished angular contact bearing and the reference plane of the seat ring are in the same plane, as shown in Figure 6, before the shaft washer is flattened, point A will be lower than the reference plane, so it is necessary to use a support during measurement. The assembly height can only be measured by the block height of the bearing race. To this end, we designed two movable support blocks on the workbench to support the tested bearings. For thrust spherical plain bearings, since the small end face of the shaft washer is higher than the datum plane of the seat ring, before the shaft ring is flattened, point A will not be lower than the datum plane, so the support block can be removed and the bearing can be measured directly on the workbench.

The above are some innovations and design ideas of the instrument. The biggest innovation in the design of the instrument is to convert the measurement difficulties (the outer ring and the inner ring can swing each other) that need to be overcome in the original two measurement methods into design ideas. And through the measuring instrument to achieve fast and accurate measurement.

6. Measurement error analysis

(1) Analysis from the measurement principle: the rigidity and manufacturing accuracy of the instrument are guaranteed (the manufacturing accuracy of the instrument mainly refers to two aspects: the matching accuracy of the outer diameter of the trapezoidal threaded shaft and the cantilever aperture, and the parallelism of the pressure plate relative to the worktable). In addition, with the features of anti-overload system protection and the automatic centering of the tested bearing, the measurement accuracy of the instrument can be guaranteed, and the measurement and positioning are fast.

(2) Verification from actual use: After the instrument is manufactured, we actually verify the measurement error from the following two aspects:

First, repeat the measurement verification with different standard height blocks. Table 1 shows the verification data.

Second, use the mandrel measurement method and the measuring instrument to measure the assembly height of the same set of GAC110S/K bearings multiple times to verify the repeatability of the measurement results. The measurement data is shown in Table 2.

From the data in Table 1, it can be seen that the measurement accuracy and repeatability of the measurement results are within 0.01mm; from the data in Table 2, it can be seen that the repeatability of the mandrel method is worse than the repeatability of the measuring instrument, which is inconsistent with the core axis method. The measurement defects of the axial method are closely related. In conclusion, the device can fully meet the product measurement requirements (the assembly height tolerance value is above 0.1mm).

7. Comparison of detection efficiency

After the practical application of on-site production, this measuring instrument can reduce the labor intensity of inspectors, and improve the detection efficiency by nearly 10 times compared with the mandrel method (taking GAC110S/K as an example, the mandrel method is 30-40 seconds per piece, this measurement instrument for 3 to 5 seconds/piece).

8. Conclusion

The measuring instrument solves the problems of poor detection accuracy and high labor intensity of inspectors when using the original detection method.

The detection efficiency of this measuring instrument is nearly 10 times higher than that of the original detection method, and it can detect bearings of the same series of different specifications to meet the requirements of mass production.

Therefore, the design of the measuring instrument is a success.