Ceramic Ball Bearings Research Articles

510 総セラミック玉軸受の振動と音 : 第2報,総セラミック玉軸受の音の特性,および音と振動の関係(O.S.5-2 衝突・接触問題)(オーガナイズドセッション5 : 機械の動的問題)

The sound of all-ceramic ball bearing having silicon nitride rings and balls was investigated and compared with those of hybrid ceramic ball bearings and conventional steel ball bearings. From the experimental results and discussion, the following results were obtained. (1) The overall sound pressure level of the all-ceramic ball bearing is influenced by the rotational velocities, and does not change with axial load. (2) In the radial direction, the overall sound pressure level of the all-ceramic ball bearing is lower than that of the hybrid ceramic ball bearing and the conventional steel ball bearing. On the other hand, in the axial direction, the overall sound pressure level is about the same with the all-ceramic ball bearing, the hybrid ceramic ball bearing and the steel ball bearing. (3) The peaks of radial and axial sound of the all-ceramic ball bearing appear in higher frequencies compared with the corresponding peaks of the hybrid ceramic ball bearing and the conventional steel ball bearing. The peaks are caused by the natural vibrations of the outer ring. (4) The sound pressure of the all-ceramic ball bearing is almost in proportion to the acceleration of the vibration.

303 マシニングセンタ用超高速転がり軸受主軸の開発

This paper describes the development of a ultra-high speed spindle using ceramic ball bearing. Recently, rotational speed of ball bearing spindle for machining center must be increased to satisfy the requirement of high-productivity. In this paper, we present two types high speed spindles which are a 50000 (min)^<-1> spindle with a diameter of 50mm, and a 20000 (min)^<-1> spindle with a diameter of 90mm.

Vibration and Sound of All-Ceramic Ball Bearings. 1st Report, Vibration Charecteristics of All-Ceramic Ball Baring.

The vibrations of all-ceramic ball bearings having silicon nitride rings and balls were investigated and compared with those of hybrid ceramic ball bearings and conventional steel ball bearings. From the experimental results and discussion, the following results were obtained. (1)The overall vibratory velocity level of the all-ceramic ball bearing is influenced by the rotational velocities, and do not change with axial load. (2)The overall vibratory velocity level of the all-ceramic ball bearing is lower than that of the hybrid ceramic ball bearing and the conventional steel ball bearing. (3)The peaks of radial and axial vibration of the all-ceramic ball bearing appear in higher frequencies compared with the corresponding peaks of the hybrid ceramic ball bearing and the conventional steel ball bearing. The peaks are caused by the natural vibrations of the outer ring. (4)The vibration spectra of the all-ceramic ball bearing are mainly determined by the amplitude of the waviness of the raceways and ball suface, the Hertzian spring constant associated with the elastic contact between the raceways and balls, the normal elastic contact deflection between the raceway and ball, the number of balls, the contact angle, and the mobility.

NMR probe for heterogeneous catalysis with isolated reagent flow and magic-angle spinning

We have developed an isolated flow MAS NMR probe to enable simultaneous observation of events occurring on a catalytic surface with characterization of the effluent gas using an external analytical instrument. The probe design is unique in that it uses ceramic ball bearings to support the rotor. The spinning and spectroscopic capabilities of the probe were proven by obtaining a 13C CP/MAS NMR spectrum of hexamethylbenzene at MAS rates of 2 kHz. The flow capabilities of the probe were demonstrated by observing methanol adsorption onto zeolite HZSM-5 and by studying conformational changes of a vapochromic sensor material when it was exposed to volatile organic compounds. The variable-temperature capabilities were shown by monitoring the change in the 207Pb chemical shift of Pb(NO 3) 2 as a function of temperature. Temperatures >300°C were achieved for the probe. The reaction of methanol to dimethyl ether on zeolite HZSM-5 was used to demonstrate the ability of the probe to study heterogeneous catalysis reactions in situ. The observed products varied depending on whether flow vs. batch conditions were used. Under flow conditions only dimethyl ether was observed. In previous studies under sealed (i.e. batch) conditions, an equilibrium was observed between methanol and dimethyl ether.

Ceramic Materials in Hybrid Ball Bearings

A computational study was conducted to make comparisons regarding heat generation, frictional torque, and ball wear between conventional all steel bearings using M50 steel balls and hybrid bearings using silicon nitride (Si3N4) ceramic balls. Both were modeled using M50 steel races and the study was accomplished for radially loaded bearings only. Although most realistic applications also include axial loads on angular contact ball bearings, this study helps to recognize and quantify the performance increases of hybrid bearings due to slip and tractive rolling losses. Performance benefits for the hybrid bearings due to reduced centrifugal loads and the higher elastic modulus of silicon nitride balls are primarily demonstrated. Lubrication is assumed and reflected in the wear and friction coefficients, although hydrodynamic losses were nor accounted for. This configuration could occur with air/oil or grease lubrication or with dry lubricating films where environmental conditions might preclude the use of wet lubrication. Including hydrodynamic losses could be a future extension of this work. The predicted losses are calculated based mainly on the micro-slippage mechanism Poritsky (1) and elastic deformation mechanisms Johnson (2) in Hertzian contact regions. As part of the study, software was developed to predict micro-slippage, tractive forces, and traction coefficients between bearing races and balls. Energy losses (heat generation and torque) and wear rate are predicted for varying race curvature ratios and angular velocities. Predictions are for bearings with an outer race of 152.4 mm and ten 25.4 mm diameter rolling elements. Example calculations predict Si3N4, ceramic ball bearings reduce frictional losses over M50 steel ball bearings by approximately 20 percent and wear rates are reduced by about 50 percent. Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

Tribo-Characteristics of Cryogenic Hybrid Ceramic Ball Bearings for Rocket Turbopumps: Bearing Wear and Transfer Film©

The self-lubricating performance of the two types of modified, angular-contact 25-mm-bore ball bearings, i.e., a hybrid ceramic bearing with Si3N4 ceramic balls and an all-steel bearing, was evaluated based on wear inspection as well as X-ray photoelectron spectroscopic (XPS) analysis of transfer films. These bearings had been tested in liquid hydrogen (LH2), liquid oxygen (LO2), or liquid nitrogen (LN2) at speeds to 50,000 rpm and thrust loads to 2840 N. In LH2, both the hybrid ceramic and all-steel bearings demonstrated excellent wear performance made possible by the thick transfer film consisting of PTFE (polytetrafluoroethylene)/CaF2 or CaF2/FeF2, in which CaF2 and FeF2 were tribocatalytically formed by the reducing ability of LHτ This film was generated from a glass cloth-reinforced PTFE retainer. In LO2, the all-steel bearing exhibited excellent wear performance as the result of the intense formation of a Cr2O3 layer beneath an extremely thin PTFE transfer film. By contrast, the hybrid ceramic bearing showed marked wear of the ceramic balls because of an extremely thin, weakly adhering PTFE transfer film. In LN2, the hybrid ceramic bearing exhibited better wear performance provided by the thick transfer film consisting of FeF2/iron oxide, as compared with seizure of the all-steel bearing under identical operating conditions. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998

Tribo-Characteristics of Cryogenic Hybrid Ceramic Ball Bearings for Rocket Turbopumps: Self-Lubricating Performance©

Experiments were conducted to investigate and compare the self-lubricating performance of two types of modified, 25 mm-bore ball bearings: a hybrid bearing with Si3N4 ceramic balls, and an all-steel bearing. The modified bearings had a single outer land-guided retainer with elliptical pockets and a narrow axial pocket clearance to reduce wobbling of the retainer. The bearings were tested under high thrust loads to 2840 N and at speeds up to 50,000 rpm in liquid hydrogen (LH2), liquid oxygen (LO2), or liquid nitrogen (LN2). Testing showed that the bearing torque of the modified all-steel bearing was drastically decreased to about one-half that of the conventional double outer land-guided bearing at a speed of 50,000 rpm in LH2 Furthermore, the hybrid bearing had relatively stable variation of bearing torque and better load capacity than those of the all-steel bearing in both LH2 and NH2. However, in LO2, the all-steel bearing exhibited excellent performance with high load capacity at high speeds, contrasted with poor self-lubrication by the hybrid bearing. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

The Performance of a Hybrid Ceramic Ball Bearing Under High Speed Conditions with the Under-Race Lubrication Method

Large bore (150 mm) hybrid ceramic ball bearings and all-M50 steel bearings were tested with under-race lubrication to compare the heat generation and the temperature rise at speeds up to 2.25 million DN. Furthermore, oil shut-off tests were carried out with both bearings over 2.25 million DN. The experimental results of the heat generation for both bearings were nearly the same at an axial load of 19.6 kN. at 34.3 kN, the heat generation of the hybrid bearing was lower than that of the M50 steel bearing at low speed. The heat generation of both bearings gradually approached each other with increasing speed and became nearly equal at a speed of 15,000 rpm. The survivability of the hybrid bearing in the oil shut-off test was superior to that of the M50 bearing. These experimental results were explained by the calculation results using a computer analysis software which simulates the kinematics and the performance of ball bearings. Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

VIBRATIONS OF HYBRID CERAMIC BALL BEARINGS

Hybrid ceramic ball bearings with silicone nitride balls and steel rings were tested, and the vibration characteristics were compared with those of conventional steel ball bearings. In this study, two types of hybrid ceramic ball bearings and two types of conventional steel ball bearings were used as test bearings. The test bearings were operated under several rotational speeds and axial loads. The radial and the axial vibrations on the outer ring of each test bearing were detected by an accelerometer. The vibrations were examined by using an FFT analyzer. From the experimental results, analysis and discussion, the vibration characteristics of hybrid ceramic ball bearings, compared with those of conventional steel ball bearings, are explained.

Vibrations of Hybrid Ceramic Ball Bearings. 1st Report. Vibration Characteristics of Bearings under Axial Load.

The vibrations of hybrid ceramic ball bearings having steel rings and silicon nitride balls were investigated and compared with those of conventional steel ball bearings. The test ball bearings were operated at several speeds under axial loads. The radial and axial vibrations on the outer ring were monitored by an accelerometer. The vibrations were examined using a fast Fourier transform analyzer. From the experimental results and discussion, the following conclusions were obtained. ( 1 ) The overall values of vibratory velocity for hybrid ceramic ball bearings are higher than those of conventional steel ball bearings. ( 2 ) The peaks of radial and axial vibration of hybrid ceramic ball bearings appear in higher frequencies compared with the corresponding peaks of conventional steel ball bearings. ( 3 ) The peaks are caused by the radial natural vibrations of arbor, the in-plane natural vibrations and the out-of-plane natural vibrations of the outer ring.

ステアケース法によるセラミックス玉軸受の寿命試験

ステアケース法によるセラミックス玉軸受の寿命試験

The Material Removal Mechanism in Magnetic Fluid Grinding of Ceramic Ball Bearings

Recently a new process known as magnetic fluid grinding has been developed in Japan which can remove material in the finishing of ceramic balls some fifty times more rapidly than can the lapping processes that are conventionally used. Balls are driven round a cell by a rotating shaft in an arrangement similar to a thrust race but submerged in a magnetic fluid placed above permanent magnets. The magnets and fluid create buoyancy forces that levitate grinding grits in the fluid and also provide the loads for the process, but it is not clear why the process is more effective than lapping. This paper reports on experimental studies of the grinding rates of silicon nitride balls in magnetic fluids loaded with diamond grits and of the motion of the balls through the fluids. The high removal rates occur when skidding occurs between the balls and drive shaft. A kinematic theory is developed to calculate sliding speeds and is used to deduce an abrasive wear coefficient for the process of 0.07 ± 0.02, indicative of two-body abrasion. The high removal rates are a consequence of the large sliding speeds that can be developed, of several metres per second.

アンダレース潤滑スピンドルの高速回転特性の解析と評価

This paper deals with the temperature and thermal deformation performance of the machine tool spindle with high speed and under-race lubrication. As a result of measurement on rotating test, under-race jet lubrication has succeeded in rotating at a 20000 min-1 (dmn=2.5×106) and achieved a high precision on a small thermal deformation by oil cooling of the spindle inside, and also achieved a smaller power loss than usual oil-jet lubrication, because the amount of lubricant used was much less than that of usual oil-jet lubrication system to get the same speed. In the same way under-race oil-air lubrication achieved a higher rotational speed than usual oil-air lubrication, and also achieved a further high rotational speed by using ceramic ball bearings. Analysis of preload increment showed that oil cooling of the spindle inside is better than the use of ceramic ball bearings in terms of preload restraining effect.

Contour mapping of precision ball defects with laser Doppler vibrometry

Laser Doppler vibrometry is presented as an effective inspection technique for contour mapping of defects on precision roller bearing balls. Localized defects are characterized by measuring the Doppler shift of a laser beam incident on a rotating ball. Contour maps are obtained by scanning the ball at equally spaced azimuths with the laser beam as the ball rotates about a vertical axis. A technique for characterizing the repeatable runout of a ferrofluid spindle is discussed. Tests were performed on two different grades of ceramic ball bearings. With the experimental setup, a height resolution of 5.5 nm could be attained. Defects of 22 μm in width could be detected. Use of the contour mapping technique greatly enhances visualization of defects on ball bearing surfaces.

Magnetic Fluid Grinding Cell Design

Magnetic fluid grinding is a process for the rapid grinding and polishing of ceramic ball bearings. Grinding grits are levitated in a ferrofluid contained above a bed of permanent magnets; and balls to be finished are driven through this medium by a shaft against which they are loaded, also by magnetic forces. This paper describes a theoretical and experimental study of the magnetic forces which exist in the process and discusses design of the magnetic hid grinding cell in terms of these. Shaft contact loads of the order of Newtons per ball are achievable and grits may be levitated tens of mm above the magnet bed.

工作機械の温度制御に関する研究 Ｖ 主軸頭内の熱流分布

This paper deals with heat flow in the spindle head of machine tools and with the methods which decrease thermal displacements of the spindle, especially in Z axis direction. Simple analytical method of heat.flow and temperature rise has been developed for the estimation of the heat load on the spindle. This method was applied to the spindle heads of the model and the actual machining center. The results show that the calculated temperature rises fairly agreed with those measured, and the adaptations of ceramic ball bearings and fins at spindle noze decreased thermal displacements of the spindle.

Development of the minimum-friction adiabatic engine

The Minimum-Friction Adiabatic Engine Program was initiated by Cummins Engine Company and the U.S. Army Tank-Automotive Command to research the feasibility of a significant reduction in an engine's mechanical friction. Basically, three areas are unique to this engine: gas-supported piston assembly; solidlubricated ceramic ball and roller bearings for the crankshaft, crankpin, wrist pin, and turbocharger; and solid-lubricated timing gears, camshaft, and valveand injector-train bearings. Oil lubrication and water cooling of the entire engine, including the turbocharger, are eliminated. Based on computer calculations, a reduction in the engine mechanical friction of approximately 75% is estimated. Rig tests of each component have been completed and a single-cylinder engine has been successfully operated for a limited time.

Glass ceramic ball bearings

Glass ceramic ball bearings

Mechanical features of the r.f. system for the Berkeley 88-inch cyclotron

Four features are described: the movable-panel drive system, ceramic ball bearings, r.f. hinges, and dee construction. The r.f. tuning is accomplished by varying the volume between the dee stem and six movable panels. Power to move the panels is supplied by four hydraulic cylinders. The hydraulic drive mechanism and control system are described. A special ceramic ball bearing, with alumina balls and stainless steel races, was developed. It operates in the presence of high vacuum, r.f. field, and radiation—and without organic lubrication. Bearing construction and test results are described. The r.f. current-carrying hinges between the movable panels were designed to optimize the hinge thickness and length so that bending stresses and temperature rise were minimized. Graphs showing the relationships between hinge thickness, length bending stress, and temperature rise are presented, together with hinge configuration. The dee-stem and dee structure is approx 14 ft long and weighs 2800 lb. Support for the entire assembly is provided by cantilevering it from the rear of the resonator tank. Materials and fabrication procedure for the dee panel structure are described.