The fastening screw replaces the pressing plate to improve the tightness and measurement accuracy of the tested bearing

Abstract:Aiming at the poor clamp tightness of fixing inner rings so as to affect the accuracy of measurement,the tightness and the accuracy of measurement for the bearing being measured have been improved by fixing the screw in lieu of the clamp and the clamping of the bearing being measured has become easier so as to make the structure simple and the measurement efficient.

Keywords:split inner ring angle contact ball bearing; radial clearance; measurement

1 Preface

With the different applications of bearings, there are more and more bearing shapes and types. The inner ring of some bearings is half. There is a double half inner ring angular contact ball bearing. When measuring its accuracy, the two inner rings of the bearing should be fixed first and regarded as a whole. In order to ensure the bearing quality, the bearing clearance is determined as the main inspection item. During the bearing manufacturing, appropriate clearance shall be reserved between the bearing ring and the rolling element to prevent the normal operation of the bearing from being affected by the expansion and contraction of the interference fit during the installation process and the thermal expansion of the bearing temperature rise during the operation.

2 Structural characteristics of double half inner ring angular contact ball bearing

The inner ring of the double half inner ring angular contact ball bearing is two half rings, and the outer ring is also provided with a flange. This type of bearing belongs to three-point angular contact ball bearing, and its structure is shown in Fig. 1.

1. Outer ring 2. Inner ring 3. Cage 4. Steel ball

Fig. 1 Structure of double half inner ring bearing

The three-point angular contact ball bearing refers to the three-point contact between the steel ball and the outer ring and the double inner half ring when it is not subjected to the axial force, and the two-point contact between the steel ball and the outer ring and the first inner half ring when it is subjected to the axial force. The radial clearance is the key to avoid failure due to multi-point contact during the operation of the bearing. Therefore, the minimum radial clearance value is specified. The three-point angular contact ball bearing is generally selected on the main shaft of the aero-engine, so as to reduce the displacement of the shafting under the action of external forces, maintain the stable and normal operation of the shafting, and the three-point angular contact ball bearing can bear the bidirectional axial load.

Clearance is an important technical parameter of rolling bearing matching, which is determined by the groove diameter of inner and outer rings and the selection of steel balls, and directly affects the technical performance of bearings such as vibration, noise, service life and mechanical operation accuracy. When the bearing works at a high temperature, the dimensions of its parts have changed, and the dimensions of the shaft and housing matched with the bearing have also changed. They interact with each other, which ultimately affects the radial clearance of the bearing. The clearance of the double half inner ring bearing is very high, and the clearance is too small. When the bearing rotates, the friction heats up and the temperature rises, resulting in hot shaft phenomenon, and even causing the bearing to bite during operation; If the clearance is too large, the bearing is prone to axial or radial movement during operation, and the noise is large, which shortens the bearing life. In the manufacturing process, the radial clearance of this type of bearing is a necessary inspection item.

3 Measurement method of radial clearance before instrument improvement

The radial clearance of the bearing refers to fixing the inner ring of the bearing and moving the outer ring from one radial limit position to the opposite radial limit position. The moving distance is the radial clearance value.

Since the inner ring of the double half inner ring angular contact ball bearing is two halves, the two inner rings of the bearing must be fixed together to form a whole and be regarded as a ferrule before measurement. The measurement method is shown in Fig. 2.

1. Instrument frame 2. Measuring spindle 3. Bushing 4. Measuring instrument 5. Bearing to be measured 6. Pressing plate 7. Handle 8. Handle seat

Figure 2 measurement method of radial clearance before improvement

Insert the measuring spindle 2 into the hole of the instrument frame, connect the handle base 8 with the spindle through the thread, select the bushing with the same inner diameter as the measured bearing, first place the measured bearing 5 on the bushing, then place the bushing and the measured bearing together on the measuring spindle, select the appropriate baffle 6 according to the inner and outer diameter of the measured bearing, insert the baffle into the clamping groove of the spindle, and pull the handle 7 to drive the handle base to rotate, Thus, the spindle moves to the left, and the spindle drives the baffle plate to fix the two inner rings of the tested bearing, so that the two inner rings form a whole. When the outer ring of the measured bearing moves from one limit position to the opposite limit position, the moving distance is the radial clearance value of the measured bearing, that is, the difference between the two values reflected by the measuring instrument 4 is the radial clearance value.

4 Measurement method of radial clearance after instrument improvement

Since the inner ring of the double half inner ring angular contact ball bearing is two halves, during the measurement, the two inner rings of the bearing must be fixed together to form a whole, which can be regarded as a ferrule, and then it is measured. The measurement method is as shown in Fig. 3. Insert the measuring mandrel 2 into the hole of the instrument frame body 1, fasten the measuring mandrel on the instrument frame body with the fastening screw 8, and then place the measured bearing 5 on the bushing 3, Place the bushing together with the measured bearing on the measuring mandrel. The inner hole of the measuring mandrel is threaded. Screw the fastening screw 7 into the threaded hole of the measuring mandrel. Select the appropriate pressing plate 6 according to the inner and outer diameter of the measured bearing, insert the pressing plate into the stepped shaft of the fastening screw, and then tighten the fastening screw. Fix the inner ring of the measured bearing through the pressing plate to form a whole. When the outer ring of the measured bearing moves from one limit position to the opposite limit position, the moving distance is the radial clearance value of the measured bearing, that is, the difference between the two values reflected by the measuring instrument 4 is the radial clearance value.

Before the improvement, because the measuring mandrel is long, it is troublesome to install the measured bearing, and the structure is complex, and the measuring efficiency is low. It is very convenient to install the tested bearing after the improvement, with simple structure and high measurement efficiency.

1. Instrument frame 2. Measuring spindle 3. Bushing 4. Measuring instrument 5. Measured bearing 6. Pressing plate 7. Fastening screw 8. Locating pin

Figure 3 improved radial clearance measurement method

Due to the existence of the shape error of the raceway of the bearing ring, the shape error of the rolling element and the size difference of the rolling element, the radial clearance in different angular directions of the bearing circumference may be different. In order to ensure the accuracy of the measured radial clearance value, it is generally necessary to measure it at three different positions with an interval of 120 ° in the radial direction of the outer ring. The average value of the three measurement results is the radial clearance value of the bearing.

When measuring the radial clearance of bearing, the following technical requirements shall be met:

(1) When measuring the ball bearing, the steel ball shall be free in the groove of the inner and outer rings.

(2) The inner and outer rings of the tested bearing shall not be inclined.

(3) The inner ring shall not move radially due to the measured load.

(4) The inner ring rotates with the rotating shaft for a full circle as far as possible.

When measuring the radial clearance of different types of bearings, it is necessary to replace the measuring mandrel and pressing plate that are consistent with the inner diameter of the bearing, readjust the instrument, place the measured bearing on the mandrel, press the pressing plate on the inner ring of the measured bearing with the fastening screw, fix the bearing, and re measure the gauge.

5 Concluding remarks

The double half inner ring angular contact ball bearing is mainly used in the main shaft of aero-engine. The quality of the bearing directly affects the performance and reliability of the engine. It is characterized by being able to bear a large two-way thrust load and a certain radial load. Since the bearing clearance is an important technical index, the clearance qualification directly affects the accuracy and service life of the bearing. With high-precision bearings, the machine can be guaranteed to develop in the direction of higher speed, higher accuracy, stronger function and higher cost performance.

More about KYOCM Angular Contact Ball Bearing:

Angular contact ball bearings have inner and outer ring raceways that are displaced relative to each other in the direction of the bearing axis. This means that these bearings are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads.

The axial load carrying capacity of angular contact ball bearings increases as the contact angle increases. The contact angle is defined as the angle between the line joining the points of contact of the ball and the raceways in the radial plane, along which the combined load is transmitted from one raceway to another, and a line perpendicular to the bearing axis.

In KYOCM, angular contact ball bearings include Single-row Angular Contact Ball Bearings, Double-row Angular Contact Ball Bearings and Three Point And Four Point Angular Contact Ball Bearings.