Design of radial clearance measuring device for cylindrical roller bearings with special-shaped outer rings
PAN Xin 1
Wang Jiawei 2, Ma Yali 1, Wang Lianji 1
（1. School of Mechanical Engineering, Dalian University of Technology, Dalian, Liaoning 116023;2. AECC Harbin Bearing Co., Ltd., Harbin 150025)
DOI：10.19533/j.issn1000-3762.2024.04.014
Abstract In order to solve the problem of radial clearance measurement of special-shaped outer ring cylindrical roller bearings under high-precision and quantitative load conditions, the design of radial clearance measurement device for special-shaped outer ring cylindrical roller bearings was completed based on the measurement principle of static and dynamic combination. The structure and specific operation steps of the whole machine were introduced, and according to the special outer ring structure of the special-shaped outer ring cylindrical roller bearing and the problem of large friction caused by the weight, the design of loading, measuring position adjustable mechanism and guide rail instead of sliding friction was adopted. The deformation error, radial runout error and other errors were analyzed, and the errors of each part were relatively small.
Key words: rolling bearing; cylindrical roller bearings; flange bearings; radial clearance; error analysis; Structural design
1 Overview
Special-shaped bearings refer to bearings with different shapes and sizes from conventional bearings in the inner or outer rings, and are one of the key components in aero engines. As shown in Figure 1, the outer ring of the special-shaped outer ring cylindrical roller bearing is often designed as an integrated structure with flange mounting edges, which has the advantages of light weight and compact structure [1]. Bearing radial clearance has a great impact on its life, rotational accuracy, temperature rise, frictional resistance, noise and vibration, and reliability [2-3], so it is important to accurately measure the radial clearance of special-shaped bearings.
图1 异形外圈圆柱滚子轴承Fig.1 Cylindrical roller bearing with special-shaped outer ring
Domestic scholars have carried out a lot of research on the measurement principle and method of bearing radial clearance: the axial clearance of large radial spherical bearings was measured in Ref. [4], and the radial clearance was deduced by formula; In Ref. [5], a testing machine was designed to measure the clearance of spherical bearings in the wide core domain, and the measurement error of radial clearance was reduced by temperature compensation. In Ref. [6], the radial clearance of large three-row cylindrical roller bearings was measured by the rotational measurement method, and a multi-point measuring device was designed. In Ref. [7], a new radial clearance measurement principle was proposed for three-lobe corrugated raceway cylindrical roller bearings in the outer ring, and the feasibility was verified by experiments. In Ref. [8], the X294 cylindrical roller bearing radial clearance gauge was improved, which greatly improved the measurement range and saved costs. Ref. [9] improved the measurement method of radial clearance of three-row cylindrical roller slewing table bearings, and improved the assembly efficiency and installation accuracy of the bearings. In Ref. [10], a loaded, radial clearance measurement device for radial bearings was developed, which realized the measurement of the loaded radial clearance of medium and large radial bearings.
The above-mentioned research mainly focuses on the bearing clearance measurement of the ordinary outer ring, the outer ring of the cylindrical roller bearing of the special-shaped outer ring is an elastic support structure, and the direct loading will cause a large deformation during the measurement, and the radial clearance measurement of the bearing is difficult, and there are few radial clearance measurement devices that meet sufficient accuracy and apply quantitative load for this kind of bearing at present. In order to improve the measurement accuracy of radial clearance of cylindrical roller bearings with special-shaped outer rings, the measurement principle combining static and dynamic was proposed, the measuring device was designed, and the radial clearance measurement error was analyzed.
2. Measuring principle of bearing radial clearance
According to the motion state of the special-shaped outer ring cylindrical roller bearing during measurement, the radial clearance measurement principle is mainly divided into static and dynamic.
2.1 Static Measurement Principle
Static measurement refers to the measurement without circular motion of the inner and outer rings. At present, the static measurement of radial clearance of domestic bearings mainly adopts the simple measurement method, and its measurement principle is that the inner ring is positioned and fixed, and the radial clearance is measured by moving the outer ring by applying load, as shown in Figure 2. The radial clearance measurement is measured by applying an appropriate load in the A and B directions to move the outer ring to the limit position, and reading the maximum displacement A1 in the A direction and the minimum displacement B1 in the B direction
for
| | （1） |
图2 轴承径向游隙静态测量原理Fig.2 Principle of static measurement of bearing radial clearance
In order to compensate for the roundness error of the outer ring and the influence of other error factors, it can be measured multiple times at different angles, usually using a three-point measurement method, as shown in Figure 3. When measuring the radial clearance of the bearing, the steps of the simple measurement method are repeated in the three directions evenly distributed on the outer ring, and the arithmetic average of the three measurements is taken as the measured value of the radial clearance of the bearing.
图3 轴承径向游隙三点测量原理Fig.3 Three-point measurement principle of bearing radial clearance
2.2 Dynamic Measurement Principle
Dynamic measurement refers to the measurement of the inner or outer ring in a circular motion. The dynamic measurement principle of the radial clearance of the bearing is that the inner ring is positioned and fixed, and the spindle drives the inner ring to rotate and then applies a load to move the outer ring to measure the radial clearance, as shown in Figure 4. The load is applied in the A direction to move the outer ring to the limit position, and the corresponding displacements A1, A2, A3,...,An of the instrument are read out in the evenly distributed n measuring points; The load is applied in the B direction to move the outer ring to the limit position, and the corresponding displacement B1, B2, B3,...,Bn in the instrument is read. According to the static measurement principle, the radial clearance measurement of dynamic measurement is the arithmetic mean of the difference between the two displacements in the same direction n times, i.e.,
| | （2） |
图4 轴承径向游隙动态测量原理Fig.4 Principle of dynamic measurement of bearing radial clearance
Dynamic measurement can reduce the roundness error of the raceway of the inner and outer rings, and the eccentricity error of the geometric center and the rotation center of the inner ring [11], and because the number of measurement points n is larger, the random error of the measured value is smaller, and the results are more accurate.
3. Design of clearance measuring device
Due to the characteristics of the cylindrical roller bearing with a special-shaped outer ring with a thin outer ring wall that is not easy to load, a special-shaped structure and a large mass, a measurement method combining static and dynamic measurement principles is proposed, and the radial clearance measurement device of the cylindrical roller bearing with the special-shaped outer ring is designed considering the elastic support and loading problems of the special-shaped bearing.
3.1 Structure and measurement of the whole machine
The overall structure of the radial clearance measuring device of the cylindrical roller bearing of the special-shaped outer ring is shown in Figure 5, which is mainly composed of the equipment frame, the driving system, the rotating spindle and the measuring and loading mechanism, among which the driving system is mainly composed of the motor, gear, etc., to realize the rotation function of the spindle; The rotary spindle and the tooling guide rail mechanism adopt an integrated design, which makes the structure more compact. During the measurement, the inner ring is first fixed on the spindle through the pressure plate, and then the drive system drives the spindle to rotate, and the loading is carried out with the measurement loading mechanism, so as to complete the measurement of the radial clearance. The specific measurement steps are as follows: 1) replace tooling, pressure plate, mandrel and other components according to different special-shaped outer ring cylindrical roller bearings; 2) Use the pressure plate to fix the bearing; 3) Adjust the handwheel, nut, etc. to move the measuring loading mechanism to the designated position; 4) Measurement through the human-computer interaction page, including static single-point measurement, static three-point measurement and dynamic measurement 3 modes, including inner ring clamping, measurement, stop, emergency stop and other operations, can be one-button measurement. The device can measure bearings with an inner diameter of as small as 50 mm and an outer diameter of up to 350 mm, with a maximum permissible bearing width of 120 mm.
图5 异形外圈圆柱滚子轴承径向游隙测量装置整体结构Fig.5 Overall structure of radial clearance measurement device for cylindrical roller bearing with special-shaped outer ring
3.2 Design of measurement and loading mechanism
In order to carry out loading measurement in the area where the bearing rigidity is relatively strong, a mechanism that can make the position of the loading head and the sensor measuring point up and down is designed in order to carry out the loading measurement in the area of the bearing with relatively strong rigidity, as shown in Figure 6, the mechanism is connected by a hand wheel, a nut and a lead screw, a pin shaft and a mechanism base. The handwheel is used to adjust the loading head and the height of the sensor measuring point at the same time; The nut can adjust the height and angle of the loading head individually, and the structure of the loading head can be adjusted according to the shape of the outer ring, so as to realize the loading and measurement of different structural special-shaped bearings; A pressure sensor is installed inside the base of the mechanism, and it is connected to the PLC control system, which can monitor the output loading force in real time; The control system can adjust the cylinder air pressure according to the data of the pressure sensor to achieve the output of a fixed load.
图6 游隙测量加载及调整机构Fig.6 Loading and adjusting mechanism for measuring of clearance
3.3 Tooling guide rail mechanism design
If the measured bearing is loaded directly on the tooling plane, its friction is large, which affects the loading accuracy. In order to reduce the friction force and make the overall structure more compact, a tooling guide rail mechanism is designed, and the sliding friction of the guide rail is used to replace the rolling friction, and the perspective view of the guide rail device is shown in Figure 7. The guide rail is installed under the outer ring tooling in the same direction as the loading direction, and a needle cylinder is also installed at the outer end of the guide rail to facilitate the center position of the guide rail.
图7 导轨装置透视图Fig.7 Perspective view of guide rail device
Knowing the mass of the bearing and the tooling m1=5.0 kg, the mass of the guide rail mounting plate m2=4.5 kg, the dynamic friction coefficient between the tooling μ1=0.02, the static friction coefficient μ2=0.40, the dynamic friction coefficient of the guide rail μ3=0.001 0, and the static friction coefficient μ4=0.002 5, then the forward dynamic friction of the installation guide rail
1 N, Static friction force
20 N, post-friction force after installing the guide rail
=0.095 N，静摩擦力
0.238 N。 Since the coefficient of friction after installing the guide rail is an order of magnitude smaller than before installation, the friction is significantly reduced and the loading force output on the outer ring is more precise.
4. Analysis of bearing radial clearance measurement error
The clearance measurement device will inevitably produce errors when measuring the clearance, mainly including the deformation error and radial runout error caused by the loading force. In order to ensure the measurement accuracy of the radial clearance of the bearing, the deformation of the loading force was simulated and studied, and the possible errors of the device were analyzed.
4.1 Deformation error analysis
When a load is applied to the outer ring, the outer ring and the rollers are slightly deformed, resulting in a certain measurement error. ANSYS finite element analysis software was used to calculate the deformation of the bearing, and the simulation model was created in Solidworks and imported into workbench. The outer ring material is GCr15, and the material properties are shown in Table 1.
表1 GCr15材料属性Tab.1 Material properties of GCr15
Components were meshed using Hypermesh and imported into ANSYS workbench. The number of nodes is 1 160 204 and the number of grid elements is 226 384. According to the force analysis, the cylindrical surface of the inner ring is fixed, the displacement of the lower surface of the inner ring and the outer ring is limited, and a radial force with a maximum load of 300 N is applied to the contact surface of the outer ring, and the maximum deformation of the outer ring due to the load is 0.1 μm. Therefore, the influence of the deformation error due to the loading force on the radial clearance measurement is negligible.
4.2 Analysis of spindle radial runout error
The radial runout error is mainly based on the radial runout error, and the radial runout error of the spindle is analyzed in order to improve the dynamic measurement accuracy because the radial runout of the spindle inevitably occurs during the rotation process. As shown in Figure 8, when radial runout occurs, a gap is created between the inner ring raceway and the rollers, which affects the radial clearance measurement of profiled bearings [12].
图8 主轴径向跳动对径向游隙的影响Fig.8 Effect of radial runout of spindle on radial clearance
There are many reasons for radial runout, such as roundness, temperature rise, surface characteristics, vibration, etc., among which the influence of roundness error is the main one [13], and the radial runout of the spindle increases with the increase of the roundness error of the bearing groove and decreases with the increase of preload [14]. Therefore, an appropriate preload can be applied to the angular contact ball bearings on the measuring spindle to ensure that the spindle runout is not more than 1 μm during the spindle design and installation of the device to reduce the impact on the clearance measurement.
4.3 Other Error Analysis
There are many reasons for errors in radial clearance measurement, such as the perpendicularity between the sensor and the spindle axis, the inclination of the inner and outer rings in dynamic measurement, and the different axes of the stopover and raceway, but these errors are relatively small and negligible in this device.
The sensor selected in the device is a contact displacement sensor, and the measurement error of the sensor itself is ±1 μm, accounting for about 0.5% ~ 1.0% of the radial clearance measurement, and the impact is relatively small.
4.4 Summary
According to the above error analysis results and take corresponding measures to avoid errors, especially when ensuring that the spindle runout is not more than 1 μm, it is expected that the final measurement results can be compared with the manufacturer's bearing clearance data, and the relative error can be controlled within 10%, which can meet the measurement accuracy of radial clearance.
5 Concluding remarks
The radial clearance measuring device is designed for the special-shaped outer ring cylindrical roller bearing, which adopts the measurement principle of combining dynamic and static, and the measuring loading mechanism and the tooling guide rail mechanism are designed according to the bearing outer ring structure and the outer ring friction factor, and the device can measure the bearing of different outer ring structures, and the error of each part is relatively small.