Bearing Temperature Rise Research Articles

潤滑油の粘性変化を考慮した静圧スラスト軸受の解析

The lubricant temperature rise in hydrostatic bearings becomes large under the condition of high load and high speed operation. Therefore the effects of lubricant viscosity change on bearing performance are not negligible. In this study, the performance characteristics of capillary compensated multi recess hydrostatic thrust bearings are analysed theoretically and experimentally considering the lubricant viscosity change. The relations between the lubricant viscosity change and the load carrying capacity or the bearing clearance variation are shown quantitatively. The close agreement was obtained between theoretical results and experimental ones. Consequently, it was pointed out that the hydrostatic bearings should be analysed considering the lubricant viscosity change.

Wear Rates of Boundary-Lubricated Cast Bronze Bearings

An experimental study, supplemented by a thermal analysis, has been made to determine the frictional behavior, wear rates, and temperature rise of grease-lubricated sand-cast CDA 932 bronze bearings running against mild steel shafts under boundary lubricated conditions. The results showed that when the bearings were operating effectively, the wear factors,“K”, were essentially constant over a wide range of loads and speeds. Good correlation was obtained between the experimental bearing temperature measurements and the analytical predictions of the bearing temperature rise as a result of frictional heating. If the bearing temperatures exceeded 150 C (300 F), extremely high wear rates were obtained. At low speeds and high loads, there was often a transition region above which the wear rates and frictional characteristics of the bearing decreased to very low values. This transition appeared to be the result of the formation of some type of protective film. Presented at the 31st Annual Meeting in Philadelphia...

An Experimental Investigation of Cylindrical Roller Bearings Having Annular Rollers

This study deals with an experimental investigation of a cylindrical roller bearing having annular rollers. Comparisons are made with a solid roller bearing having the same configuration and dimensions. Radial deformations and load distribution between rollers are measured under static load and compared with numerical solutions. Bearing temperature rise and roller wear are investigated in a specially designed tester. A radioactive tracing technique is utilized for the measurement of roller wear and proved to be reliable for wear detection. The results show several advantages of annular rollers over the solid rollers.

Fog Lubrication of High Speed Ball Bearing (2nd Report)

Succeeding to the research of 1st report(1), the cooling effect of air and the influence of viscosity of oil and rotating speed upon the performances or preloaded ball bearing operated at a high speed under fog lubrication have been investigated. The experimental results obtained are as follows : The tendency of bearing temperature rise under fog lubrication may be explained by the ordinary formula of heat conduction with cooling velocity index. According to the increase of rotating speed of ball bearing, the bearing temperature rises rapidly, while the coefficient of friction increases rather gradually, and the increasing rates of temperature rise and coefficient of friction decrease as the rotating speed increases. The coefficient of friction and bearing temperature change are directly proportional to the oil viscosity at the running temperature of bearing. After all, it is concluded that the fog lubrication contains the oil film lubrication very much in spite of very few amount of oil and the effect of viscosity is predominant.

Fog Lubrication of High Speed Ball Bearings (1st Report)

In pursuit of information concerning the performances of the preloaded ball bearing operating under fog lubrication at high speed, the coefficient of friction and the temperature rises of ball bearing and fog have been measured for angular contact type ball bearing of 40 mm bore with bakelite cage under the supply of spindle oil. The conclusions obtained from the experimental results are as follows. The fog lubrication widely reduces the hydrodynamic friction losses of the ball bearing as it may be lubricated with oil of minimum requirement securely and continuously. Though the higher rotational speed requires the more quantity of oil, about 3 cc/h of oil supply is sufficine at a dn-value of 800 000 in this case. The cooling effect of air is somewhat remarkable, but the effect of air for the temperature rise of bearing is less than the influence of oil under definite ratio of oil to air. Though the temperature rise and friction moment increase proportionally to the amount of preload under fog lubrication, when oil is supplied sufficiently, the increase of preload does not so much influence upon the temperature and friction. In the comparison with ordinary lubrications, the bearing temperature rise and coefficient of friction under fog lubrication are much smaller than that under oil lubrication, and the differences between fog and oil lubrications become larger according to the increase of rotating speed.

The Oil Bath Lubrication of Ball and Roller Bearings at High Speed

In pursuit of information concerning the performances of the high speed rolling bearings operating under oil bath 1ubrication and light load, measurements of bearing temperature rise and friction coefficient have been made using radial ball and roller bearings of 40mm bore with pressed cages. As the lubricant, spindle oil or turbine oil is applied and the level of oil bath is always kept in somewhat lower than the centre of rolling element which is placed at the lowest position in the bearing. The experimental results of bearings, operated at a rotating speed up to 24, 000 rpm for the ball bearing and 16, 000 rpm for the roller bearing, indicate that the bearing temperature rise and friction coefficient increase proportionally to the rotating speed of bearing. From the fact that bearings had been operated securely under such high speed, it may be convinced that, under light load, the oil bath lubrication can be applied for a speed far higher than the speed which is adopted customarily under the limitation of dn-value of 250, 000. Furthermore, at such a high speed, the friction coefficients of bearings under oil bath lubrication take the values nearly twice as the values lubricated with minimum oil, and such differences depend on the hydrodynamic friction losses owing to churning oil.

NEW DRY BEARINGS HAVE UNIQUE ANTI‐FRICTIONAL PROPERTIES

TheSE NEW BEARINGS owe their properties and certain advantages over other bearing materials to Polytetrafluorethylene, known as PTFE. PTFE is a long straight chain plastic consisting of carbon and fluorine with an unusually low dry surface coefficient of friction in the region of 0.05. This value is comparable with that between ice and ice and is lower than boundary friction usually associated with a well lubricated bearing. This property is due to the unique surface of this material and does not depend upon the formation of a low shear strength film, as is the case with graphite. Therefore, under ideal conditions, no appreciable wear takes place and any wear that occurs is due to the roughness of the mating surface “ploughing” through the PTFE. This material is stable up to 327°C. which means that it can be used as a bearing material in an ambient temperature of 280°C. since this will give permissible margin for bearing temperature rise. Higher temperatures can be tolerated if cooling is provided. The chemical properties of this plastic are such that it is not attacked or affected in any way by known organic liquids, solvents, acids, gases, etc. except for molten potassium, molten sodium and florine gas.

Studies on Lubrication of Ball Bearing with Oil Jet : (1st and 2nd Report)

Excess oil supply to ball bearing causes an increase in friction. At high speed, however, temperature rise of bearing becomes considerable amount. Therefore ; forced lubrication with a large quantity of oil is used for the purpose of cooling of bearing rather than lubrication in spite of the disadvantage with regard to friction. We investigated the cooling effect of oil jet and determined appropriate method of oil supply.

Explosions in Enclosed Crankcases of Reciprocating Engines: Their Cause, Effect, and Possible Remedy

In this paper is treated the important problem of crankcase explosion prevention in practice. After dealing with the cause of such explosions the author concludes that, whilst much can be done to minimize explosions, to prevent them altogether is not practicable. The merits of ventilation of crankcases are discussed and ways are suggested to prevent bearings running hot, while means to detect a temperature rise in inaccessible bearings and pistons are described. Tests carried out with the object of preventing injury to personnel and damage to property in the event of an explosion are described. A relief valve which opens and closes instantly is described and illustrated. The danger of burning gases issuing from relief valves is discussed, and the experiments are described which resulted in the evolution of a simple but effective flame trap. Relevant particulars are given of a Diesel engine in which two crankcase explosions took place, one before and one after a relief valve was fitted. The gas pressure in the crankcase when damage resulted is estimated and views are expressed regarding the relation of crankcase cubic contents to the area of relief devices.

A short account of the theory of lubrication. IV. Temperature rise and temperature distribution in bearings

The modern understanding of lubrication is based on the equations of the hydrodynamic theory. These equations, as has been seen, describe the performance of a bearing in terms of the actual film viscosity but, of course, this depends on the temperature of the film, which in general is unknown. We have next to consider whether there is any way of calculating or predicting the steady running temperature of a bearing.It is not commonly realized that there is a rational solution for this problem.The solution depends both on the rate of generating heat by friction, and on the rate of heat transfer from the bearing to its surroundings.