When the inner diameter of the Koyo bearing is greater than 70mm or the fit interference is large, the heating method is used to expand the Koyo bearing hole, so as to save labor and time in installation and avoid damage caused by excessive force.
At this time, the heating temperature needs to be controlled. Generally, it is enough to heat the Koyo bearing to 80 ℃ and 100 ℃ higher. Exceeding 120 ℃ will lead to tempering of Koyo bearing, resulting in lower hardness and accuracy of ferrule.
1. Electric heating plate heating method:
Place the Koyo bearing on an electric heating plate with a temperature of 100 ℃ for a few minutes. This method is simple. If it is turned over several times, the Koyo bearing can be heated evenly and has high efficiency. This method can be used for all sizes of Koyo bearings.
2. Electric furnace heating method:
The Koyo bearing is heated in a closed automatic temperature control electric furnace. It has the advantages of uniform heating, accurate temperature control and fast heating. It is suitable for heating many Koyo bearings in a batch.
3. Induction heating method:
The induction heater can quickly, reliably and cleanly heat the Koyo bearing to the required temperature, which is especially suitable for the tight fit of the inner ring. Because only the inner ring is heated and the outer ring is rarely heated, it can be easily installed on the shaft and in the seat hole.
4. Electric bulb heating method:
Using 50W electric bulb to heat Koyo bearing can ensure that the heating temperature is about 100 ℃. The smaller Koyo bearing can be directly placed on the bulb, and the larger Koyo bearing can be placed in the conical cover of the bulb. The conical cover can prevent the heat loss of the bulb and make the heating uniform.
The conical cover can be adjusted up and down, which can adapt to heating Koyo bearings of different sizes within a certain range. If a far-infrared bulb is used, note that the direction of the bulb should be downward to avoid infrared rays being harmful to people’s eyes. This kind of bulb can save energy. The bulb heating method is suitable for less quantity and less frequent use; When heating the Koyo bearing, the bulb can also be used for lighting at ordinary times. In addition, no other equipment is required.
5. Oil tank heating method:
This is a widely used traditional heating method. A metal mesh is set at the place 50 ~ 70mm from the bottom of the oil tank, the Koyo bearing is placed on the mesh, and the large Koyo bearing should be lifted with a hook. The Koyo bearing should not be placed directly at the groove bottom to prevent the local heating of the Koyo bearing contacting the groove bottom from being too high, or the dirt precipitated at the groove bottom from entering the Koyo bearing.
The key points of oil tank heating method are as follows. Mineral oil with non corrosivity and good thermal stability shall be used, especially transformer oil. The oil and container shall be kept clean. The capacity of the oil tank shall be determined by the size and oil quantity of the heated Koyo bearing. If the container is too small, the oil temperature will drop quickly as soon as the Koyo bearing is put into continuous operation, and the effect is not good.
① The heating temperature should be controlled properly. If the temperature is too high, the Koyo bearing will be damaged. If the temperature is too low, the expansion of the ferrule is insufficient, and the effect is not significant. The thermal expansion of the inner diameter of the inner ring obtained at the heating temperature of 80 ~ 1000 ℃ is sufficient for Koyo bearings with general interference.
② Once the required heating temperature is reached, the installation shall be carried out as soon as possible to avoid installation difficulties due to cooling.
③ Koyo bearing also shrinks in the width direction during cooling, so a certain pressure shall be applied during installation to compress the inner ring to the shoulder, and a very thin feeler gauge shall be used to test whether there is a gap between the end face of the inner ring and the shaft shoulder after cooling. In short, butterfly work requires proficiency, speed and accuracy.