Deep groove ball bearings have the following advantages: can withstand radial load and bidirectional axial load, low friction torque, low noise, low cost, etc., so they are widely used as bearings for automobiles and industrial machinery. In recent years, countries around the world have promulgated and implemented fuel consumption regulations for automobiles, and will further tighten the fuel consumption regulations in the future. In addition, energy saving is also being promoted in the field of industrial machinery, and deep groove ball bearings used in these fields are required to further reduce the friction torque. The friction torque of rolling bearings is caused by the stirring resistance of the lubricant, the rolling viscous resistance, the sliding friction resistance caused by the ball spin and differential sliding, and the sliding friction resistance between the ball and the cage. In order to reduce the stirring resistance and rolling viscous resistance of the lubricant, the low viscosity of the lubricant is effective. In recent years, scholars have carried out a lot of research. However, although this type of method can achieve low friction torque, in many cases, other properties such as life are reduced. Deep groove ball bearings are often lubricated with grease. In the past, the improvement of grease has promoted the reduction of bearing friction torque, but there is a limit to reducing the friction torque only by improving grease. This article presents the visualization of grease behavior inside the bearing for reducing the friction torque of grease-lubricated deep groove ball bearings, obtaining guidelines for optimizing the shape of the cage used under grease-lubricated conditions. The low-friction torque technology was realized by developing a cage with a new structure that reduces grease shear resistance and stirring resistance without affecting other properties. 1 Basic test of new cage development 1.1 Test bearing In order to study the influence of cage on friction torque, ordinary deep groove ball bearings with non-contact seal used in automobiles and industrial machinery are used as test bearings, and their dimensions are shown in Table 1. The conventional deep groove ball bearing used as a test bearing has mainly used a crown resin cage in recent years, as shown in Figure 1. Table 1 Dimensions of deep groove ball bearing samples Test bearing inner diameter (mm) bearing outer diameter (mm) bearing width (mm) basic dynamic load rating (kN) basic static load rating (kN) number of balls cage material 6302ZZ15421514. 35.457 Nylon 66 Fig. 1 Cage (conventional) 1.2 Visualization test of grease distribution In order to understand the state of grease inside the deep groove ball bearing, and to study the related methods of reducing friction torque, the X-ray computer tomography (CT) system was used to make the rotation test The rear bearing is visualized inside. The appearance photo of the bearing for visualization is shown in Figure 2. Details of the structural parts and X-ray irradiation conditions are shown in Table 2 and Table 3, respectively. Fig. 2 Visualization test bearing Table 2 Visualization test bearing structural parts Grease inner ring outer ring ball cage dust cover Thickener Kinematic viscosity grease of base oil at 40℃ Acrylic Resin Acrylic Resin Quartz Glass Nylon 66ABS Resin Lithium Soap Base 250260.84 Table 3 X-ray Irradiation Conditions rays (tube voltage 100 kV) to discriminate the difference between grease and air. Here, the structural parts are made of materials with high X-ray transmittance so that the inside of the deep groove ball bearing can be visualized even with low-output X-rays. The inner and outer rings of the bearing are made of acrylic resin; the ball is made of quartz glass; the cage is made of nylon 66; the dust cover is made of acrylonitrile-butadiene-styrene synthetic resin (ABS resin). In the rotation test before the visualization test, the inner ring was rotated for 5 min at a speed of 1 800 r/min under an axial load of 20 N. Rotational tests were performed using the Frictional Torque Test Stand under Light Load as described in the next section. 1.3 Friction torque test The friction torque measurement of deep groove ball bearings is carried out according to 2 load conditions (light load/heavy load). The friction torque test bench under light load conditions is shown in Figure 3, and the test conditions are shown in Table 4; the friction torque test bench under heavy load conditions is shown in Figure 4, and the test conditions are shown in Table 5. Figure 3 Friction torque test bench under light load conditions Table 4 Test conditions under light load conditions Axial load (N) Radial load (N) Speed ​​(r/min) 1014000→12000→10000→8000→6000→4000→2000 Figure 4 Friction torque test bench under heavy load conditions Table 5 Test conditions under heavy load conditions Axial load (N) Radial load (N) Speed ​​(r/min) 100010010000→8000→6000→4000→2000 deep groove ball bearing The inner ring rotates, and the friction torque generated on the outer ring is measured with a load cell. Under light load conditions, the deep groove ball bearing only bears the axial load; under heavy load conditions, the deep groove ball bearing bears the combined axial and radial load. Since the axial load and radial load are applied through the air bearing, the friction torque of the deep groove ball bearing is measured with high precision. Under various load conditions, the maximum speed is 2000 r/min each time as a step, the final speed is reduced to 2000 r/min, and the interval of 1 min is maintained at each speed, and the average value of friction torque is read as the friction torque at each speed. value. The cross-section of the inner and outer ring grooves of deep groove ball bearings is arc-shaped. Under the condition of only axial load, theThe contact angles of all the balls and the inner and outer rings become equal, and the revolution radii also become equal, so the purpose of reducing the force between the ball and the cage can be achieved by assuming that the ball speed is constant.