JPH0341335A - Foreseeing method of failure of bearing - Google Patents

Abstract

PURPOSE:To perceive the breakdown of a lubricating film of molybdenum disulfide of a bearing and thereby to enable prevention of a failure of an apparatus by lowering the temperature of the bearing by cooling down a bearing element periodically, and by detecting a rise in a bearing friction torque. CONSTITUTION:A rolling bearing 2 lubricated by a solid-state lubricator containing molybdenum disulfide bears rotation of a shaft 1 and is fitted to a housing 3. When a periodic cycle of low and high temperatures is given to the bearing 2 in vacuum, each of friction torques in the low and high temperatures progresses first in a prescribed manner. However, the torque in the low temperature increases to be twice as large as that in the high temperature thereafter, and lastly an extraordinary increase in the friction torque is seen. This increase is caused by breakdown of a solid lubricating film. The friction torque in the low temperature starts to increase when the lubricating film starts to be broken down partially, and a solid contact occurs and results in burning when the lubricating film is broken down completely. By cooling down a bearing element periodically and monitoring the increase in the friction torque, accordingly, the breakdown of the lubricating film of molybdenum disulfide is perceived and a failure of an apparatus can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molybdenum disulfide solid lubricant film bearing used in a vacuum, and to a method for predicting failure thereof.

[Conventional technology]

Conventionally, to detect when the solid lubricant film of a bearing breaks, as described in Lubrication Vol. 23, No. 2 (1978), the electrical contact resistance between the inner and outer rings of the bearing was measured, and it was determined that the electrical contact resistance had decreased to 0Ω. It was determined that the bearing life was over.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, in order to measure electrical resistance, it is necessary to take out lead wires from both the rotating side and the stationary side, and it is necessary to attach a slip ring to the rotating side. moreover,
In a contact electrical resistance measuring circuit system formed by a lead wire, a bearing, a shaft, and a housing, all parts other than the bearing are required to be good electrical conductors.

An object of the present invention is to easily detect the timing of rupture of a molybdenum disulfide lubricating film to prevent equipment accidents, and it is also an object of the present invention to eliminate the need to set any restrictions on the materials that constitute the equipment.

[Means to solve the problem]

To be distantly related to the above purpose, in a molybdenum disulfide lubricated bearing for vacuum use, there is no change in bearing friction torque between high temperature and low temperature atmospheres until the lubricant film ruptures, but once the lubricant film ruptures, the friction torque at low temperatures The bearing is periodically cooled by taking advantage of the increase in

Furthermore, by utilizing liquid nitrogen used in a vacuum device to lower the temperature, it is possible to easily detect when the lubricant film breaks.

In addition, as another means for lowering the temperature, a Peltier element is used, and by periodically supplying electricity to the element, the bearing can be easily cooled.

[Effect]

Vacuum peripheral rolling bearings that are solid-lubricated with a molybdenum disulfide lubricant film experience an increase of one herk at low temperatures due to rupture of the molybdenum disulfide lubricant film. By periodically cooling the bearing and monitoring the friction torque, rupture of the molybdenum disulfide lubricant film can be detected from an increase in bearing friction 1-lux.

By using liquid nitrogen for cooling, the bearing is brought to a low temperature state, and changes in friction 1-lux can be detected.

Furthermore, by attaching a Peltier element near the bearing, the bearing is cooled when the Peltier element is energized, the bearing is brought to a low temperature state, and changes in friction torque can be detected.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

A bearing 2 supports the rotation of the shaft l. Bearing 2 is housing 3
is attached to the shaft to form a support system for the shaft. The housing 3 is provided with a liquid nitrogen (LN2) supply hole 4 and a discharge hole 5 for liquid nitrogen containing nitrogen gas connected to the supply hole. A liquid nitrogen reservoir 6 is formed in the groove.

Next, the operation of the present invention will be explained. At least the steel balls of the bearing 2 are lubricated by a solid lubricant film containing molybdenum disulfide, and exhibit low friction characteristics in a vacuum. By the way, when a rolling bearing lubricated with a solid lubricant containing molybdenum disulfide is subjected to the temperature cycle shown in Fig. 3 in a vacuum,
As shown in Figure 4, the friction torque at low temperatures and the friction torque at high temperatures remain almost constant until a certain time, but after that, the torque at low temperatures becomes about twice the torque at high temperatures. Eventually, the abnormal increase in bearing friction torque leads to seizure and other damage. This increase in bearing torque is due to the breakage of the solid lubricant film made of molybdenum disulfide on the steel balls, and when the solid lubricant film begins to partially break, the friction torque in the low-temperature section begins to increase and is completely removed. When the solid lubricant film breaks, solid metal-to-metal contact occurs between the steel ball and the inner and outer rings, resulting in seizure. Therefore, if a rolling bearing lubricated with a solid lubricant film containing molybdenum disulfide is exposed to low and high temperatures and the friction torque is monitored, the state of rupture of the molybdenum disulfide film can be determined from the difference in friction torque at low and high temperatures. . If the operation is stopped when the friction torque between the high-temperature and low-temperature sections suddenly starts to differ, the molybdenum disulfide film will have partially broken, but the bearing will not be damaged, so there will be no damage to the shaft system. There isn't. The high temperature needs to be higher than room temperature, and this is achieved by the frictional heat of the bearings. On the other hand, low temperatures are achieved by liquid nitrogen used in the oil trap of vacuum equipment and vacuum pumps, and by periodically supplying liquid nitrogen from the supply port, it is possible to monitor changes in friction torque at low temperatures. Become.

According to this example, by cooling a rolling bearing lubricated with a solid lubricant containing molybdenum disulfide in liquid nitrogen, which is often used in vacuum equipment, in a vacuum, the life of the solid lubricated bearing can be reduced by reducing changes in frictional torque at low temperatures. Detection and prevention of equipment failure accidents.

Another embodiment of the invention is shown in FIG. Near the bearing 2,
A Peltier element 7 is provided in the housing 3, and a current is turned off to the Peltier element 7 via a switch 8.

With this configuration, each time the switch 8 is turned on, the Peltier element cools the bearing section and brings the bearing into a low temperature state.

According to this embodiment, rupture of the solid lubricant film of a rolling bearing can be easily detected without making any major changes to the shaft support system including the bearing, and there is an effect of preventing equipment failure accidents.

〔Effect of the invention〕

The present invention is configured as described above, and produces the effects described below.

By periodically cooling the bearing part, the bearing temperature is lowered, and by detecting an increase in the bearing friction torque, it is possible to detect a break in the molybdenum disulfide lubricating film of the bearing, thereby preventing equipment failure.

Furthermore, according to an example in which liquid nitrogen is used to cool the bearing,
Breakage of a lubricating film can be detected easily and inexpensively.

Furthermore, according to the embodiment in which a Peltier element is used to cool the bearing, breakage of the lubricant film can be easily detected.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a bearing according to one embodiment of the present invention, Fig. 2 is a longitudinal sectional view of a bearing according to another embodiment, Fig. 4 is a diagram illustrating changes in friction torque, and Fig. 3 is a longitudinal sectional view of a bearing according to an embodiment of the present invention. It is a diagram explaining a temperature cycle. l・shaft, 2...bearing, 3...housing, 7...
Peltier element.

Claims (1)

[Claims] 1. A rolling bearing consisting of an inner ring, an outer ring, steel balls, and a cage for holding the steel balls, in which at least one of the steel balls, the inner ring, and the outer ring is coated with a molybdenum disulfide film. In vacuum rolling equipment, the bearing part is periodically exposed to a low temperature atmosphere.
A bearing failure prediction method that determines when to replace a bearing based on changes in the frictional force generated in the bearing. 2. A bearing failure prediction method as claimed in claim 1, characterized in that the low-temperature atmosphere is formed with liquid nitrogen, liquid helium, or a Pertsch element. 3. In the bearing failure prediction method described in claim 1, when the frictional force of the bearing exceeds 1.5 times the arithmetic mean value of the previous frictional force in a low-temperature atmosphere, it is determined that it is time to replace the bearing. A bearing failure prediction method characterized by determining that.