One hundred years goes on since rolling bearings have been manufactured within in the country. Thus the performance of rolling bearings is progressive in a considerable way by the advanced technologies for materials, lubrication and analysis. At the same time, evaluation technology is absolutely necessary to improve the performance of rolling bearings. As a matter of course, measurement technology for processing accuracy of bearing parts is important. Moreover, it is thought that if the evaluation technologies for torque, life and rotating condition are not erected, technological development of rolling bearings, whose use conditions get strict more and more, cannot correspond. This report have an overview of evaluation technology for rolling bearings such as measuring method and observation method.
If the amount of lubricating oil in the rolling bearings can be reduced, the agitating resistance of the rolling bearing can be reduced, contributing to energy savings. However, reducing the amount of lubricating oil in rolling bearings reduces the EHL oil film thickness. As a result, the lubricating film may break, resulting in a short life due to heat generation. Therefore, it is important to measure the oil film thickness distribution under the starved condition. This paper introduces three methods that can measure the oil film thickness distribution using optical interferometry. The first is a single-wavelength measurement method, in which the brightness of the interference fringes is visually counted and the oil film distribution is measured. The second is a measurement method using hue, which measures the oil film distribution using the fact that the hue changes periodically as the oil film thickness increases. The third is a measurement method using three wavelengths, which is measured by using the difference in luminance value of the interference light of red, green, and blue. In addition, an example of measuring oil film thickness distribution of texturing surfaces by using three wavelength method will be shown.
Lubricating grease shows typical rheological properties such as yield stress and shear thinning, and these properties cause complex flow behavior in rolling bearings. Grease behavior is investigated by using various evaluation technologies to reveal a mechanism of grease lubrication. Macroscopic behavior of grease such as flow process and channeling state in a rolling bearing can be evaluated by using a tracer grease method and X-ray CT. Microscopic behavior at a contact region such as the replenishment is conventionally investigated by using a ball-on-disk test apparatus with the optical interferometry method, and this method has applied to a rolling bearing recently. This article describes these technologies for the evaluation of grease behavior.
High durability has been required for electrical components of automobiles, especially rolling bearings used in alternators. It is due to the reduction in size and weight of automotive parts, which are exposed to a higher surface pressure and higher temperature load on electrical components than ever before. Rolling bearings in such an environment often have a markedly shortened life with flaking. It is considered that the cause of flaking is the structural change of steel (hydrogen embrittlement) induced by the penetration of hydrogen into the steel material of the rolling bearing. However, this theory is based on confirming the short life of rolling bearings that have absorbed hydrogen by various methods, and there have been few examples of directly observation that hydrogen penetrates into rolling bearings during lubrication. Therefore, in order to describe the features of time-of-flight secondary ion mass spectrometry (ToF-SIMS) with extremely high performance of surface analyses, and introduce in detail of a case that ToF-SIMS measurements succeeded in directly observing hydrogen that has penetrated into the bearing steel.
In the field of tribology, a measuring technique that continuously monitors the state of the frictional parts of major machine elements and enables highly sensitive and accurate diagnosis and evaluation becomes one of the key technologies for realizing IoT and smart machine systems. In order to perform accurate maintenance at the optimal timing, a measuring technique that can not only detect the abnormal state of the frictional part early but also identify the cause and location of the abnormality is required. Furthermore, it is necessary to accurately diagnose and evaluate the steady progress of wear and the state of surface damage before abnormalities occur. In this commentary article, in order to utilize an acoustic emission (AE) technique for the damage evaluation of rolling bearings, trends in the AE research, features and evaluation methods in the AE technique are widely reviewed. In addition, the advantages and future prospects in the AE technique application are summarized with introducing some research cases on rolling bearings.
Friction and wear tests play important roles in order to shorten terms of life evaluation in development of rolling bearings, such as screening of lubricants. In recent space development, life prediction methods for rolling bearings using simple tribological tests have been studied because spacecraft mechanisms are required a long life of up to 20 years and development in several years. This paper introduces the role of friction and wear tests in the evaluation of the lubrication life of rolling bearings, focusing on studies for oil or grease lubricated rolling bearings in spacecraft mechanisms.
Rolling bearing stiffness is an important factor to predict vibration and running accuracy of rotating machineries. It is highly effective and useful for designing rotating machineries to obtain bearing stiffness by using numerical analyses, instead of doing wasteful experimental measurements. Consequently, in this paper, numerical analyses for rolling bearing stiffness are summarized as an examination technique of rolling bearing stiffness. The followings are the main topics: Analyses considering Hertzian contact deformation between rolling elements and races and their static behaviors, analyses considering whole elastic deformation of races and their peripherals in addition to the previous, and an analysis considering dynamic phenomena between rolling elements and races.
We have developed the new bearing in order to reduce NV and improve a Dry-performance for third generation electrical water pump. Thermosetting resin and over-molding of a rotor has been adopted in order to achieve the requirements. Additionally, in order to improve reliability, we found a prediction method to calculate wear volume of a bearing. The method contributes to reduce duration of a durability test, to downsize a bearing, and to reduce the cost.