Linear Ball Bearings Research Articles

直動玉軸受の寿命に関する研究 (第2報)

In this paper, we present a general view on the basic dynamic load rating of a linear motion ball bearing, considering both the fluctuation of load distribution in the bearing during the time of the shaft movement and various positions of eccentric radial load. As an example, we offer calculations, under various working conditions, of the basic dynamic load rating of the bearing of six ball rows and examine the results. The followings are the summary of the results : (1) When the load is applied counter gravitationwise on the outer sleeve of the bearing, the ratios of the basic dynamic load rating of two cases -one is the case when the load is positioned on the mid-line of two ball rows and the other is the case of the load positioned on one ball row- are 1. 1 when the eccentricity factor of working load is zero, and 1. 16 when it is 1. 5. And, the differences affect obviously the traveling life of bearing. However, when the applied loads work gravitationwise, the difference is negligible. (2) It can be said that the basic dynamic load rating decreases remarkably in accordance with the increase of load eccentricity factor, and that it tends to increase in accordance with the increase of shaft stroke.

直動玉軸受の摩擦力発生の要因

From the basic study on the rolling friction the main causes for rolling friction of linear ball bearing can be assumed as follows. (1) The variation of rolling friction which is due primarily to waviness and roughness of the rolling surfaces, and to the angle of relief of the bearing raceway. (2) The inherent bearing friction by the sliding friction which is due to the spinning between the rolling elements and the retainer except the variation in the friction force. In this study, the friction forces of the linear ball bearings in a low speed range by the factor (2) except the variation by the factor (1) were obtained from the recorded waves of reciprocate measurement of forward and reverse rolling. Moreover to clarify quantitatively the characteristics of the individual friction forming the rolling friction of this bearing, some experiments on the rolling friction behavior using a ball were performed. From the results of the above experiments and analyses, the friction characteristics of linear ball bearing can be explained. The sliding friction due to the spinning accounts for 70 to 75% of the total friction, and the pure rolling friction accounts for about 10 to 15%.

直動玉軸受の寿命に関する研究 (第1報)

As the first report, this paper deals with a calculation method of the numbers of stress cycles at the raceway surfaces of the outer sleeve and the shaft, and the equation of the roll body loads. Some points are discussed concerning the calculated results for various shaft strokes. The principal results are as follows : (1) Applying to the new calculation method, which splits both raceway surfaces into small portions, the numbers of stress cycles of those raceways are counted accurately.(2) The roll body loads are considerably small in the case of short shaft stroke, but when the ratio between the shaft stroke and the raceway length of outer sleeve (ls/l) becomes greater than 1, the roll body load of outer sleeve (Qco) has a constant value while the one of shaft (Qcs) has comparatively high increasing ratio.(3) In the case of linear motion ball bearing, probability of flaking due to rolling contact fatigue on the shaft becomes higher than that of the outer sleeve, because of Qco/Qcs=1.25-1.17. Meanwhile, in the case of ball spline, Qco/Qcs≅1 for ls/l≤1 and Qco/Qcs=0.92 for ls/l=10, then the probability of flaking on the outer sleeve becomes higher than that of the shaft. And, if the conformity between ball and raceway groove is reduced, the roll body loads decrease extremely. Further, in the case of ball guide way, the roll body loads are nearly equal to those of the linear motion ball bearing.

直動玉軸受の負荷分布に関する研究(第5報)

直動玉軸受の負荷分布に関する研究(第5報)

A scanning Fabry-Perot interferometer

A scanning Fabry-Perot interferometer has been constructed for balloon-borne observations at 156 μm. The semi-reflecting surfaces are tightly stretched, electroformed, metallic mesh. Spectral scanning is accomplished by mechanically changing the reflector separation via a moveable carriage sliding on linear ball bearings. The instrument is designed to achieve a resolving power of 2000 using a reflective finesse >25. The construction and optical properties of the interferometer will be described.

軸方向運動球軸受の負荷分布に関する研究(第4報)

In this paper, the load distributions in the linear motion ball bearings, varying the radial clearances for the shaft from positive to negative value, were measured by means of strain gages bonded on the elastic beam type detecting units which were machine-worked on the outer sleeves of bearings. Then, the measured values weres compared with the theoretical analyzed and calculated results, reported already in 1st and 2nd reports, and after some discussion following results were obtained.(1) Fairly good agreement were obtained between measured and calculated values of the load distribution and the maximum distributed load in bearings.(2) When some radial clearance exists in the bearing and the eccentricity rate of external force for bearing becomes greater than unit, the maximum distributed load increases extremely and the stiffness of bearing decreases considerably owing to most of force is supported by two balls situated respectively at up and down ball tracks of bearing both ends.(3) Because the external force is supported by many balls in bearing provided the bearing is preloaded, then the maximum distributed load goes down considerably, moreover the stiffness of bearing is improved.

軸方向運動球軸受の負荷分布に関する研究(第3報)

軸方向運動球軸受の負荷分布に関する研究(第3報)

直動球軸受の球の挙動

The magnetized ball was included in the linear ball bearing and the measuring coil was set up also in the shaft so as to study three dimensional motion of the ball during operation, and an electric current of the coil circuit caused by the magnetic flux change owing to the motion of magnetized ball was recorded. Moreover, the theoretical analysis concerning such measuring method was performed and that was signified experimentally. The behaviours of ball about various bearing speeds, loads and lubrication conditions applying above mentioned method were measured. As this result, it was ascertained as follows.(1) The ball of linear ball bearing generates 6-19% rotational slip on the contact portion between ball and shaft.(2) The rotation axis of ball also changes about 10-30 degree on that contact portion.(3) The ball in the pocket portion of bearing retainer does hardly rotate and slides on that place pushing one another.

軸方向運動球軸受の負荷分布に関する研究(第2報)

In many cases of practical application of the linear motion ball bearing, some preload is given to the bearing for the purpose of removal of clearance between shaft and bearing. When the load is applied on the shaft under such condition, contact domains of each ball located between raceway of the bearing sleeve and the shaft are increased considerably as compared with the bearing which has some internal clearance. Consequently, the amount of load acting on ball in each ball row and also distributed situation are quite different from those which the bearing has some internal clearance. This paper deals with the theoretical analysis of the load distribution regarding to the case of symmetrical and asymmetrical arrangements of ball row in the linear motion bearing which supports both moment and radial load and has some preloading. As the result, in spite of any arrangement of ball row in the bearing and any load condition, it was found that the maximum distributed load acting on ball can be considerably reduced by means of giving preload such as a (the ratio between amount of radial preload and maximum radial displacement of the shaft at the center point in the bearing) is equal to 0.5-1.0.

予圧を与えた直動玉軸受の摩擦抵抗

This paper describes some experiments on the frictional resistances of preloading linear ball bearings called ball bushings. The experimental results obtained are as follows.(1) The frictional resistances increase with the increase in the preloading. In the case of radial preloading of 4-10 μm for a 25 mm diameter shaft, the value of the maximum frictional resistance is about twice of that in the case of no preloading. The rate of increase in the frictional resistance with the preloading decreases as the bearing load increases.(2) The maximum values of the frictional resistance increase approximately in proportion to the elastic contact deformation between the ball tracks and load-carrying balls.(3) The average values of the frictional resistance increase approximately in proportion to the total forces which are acting on the load-carrying balls.

直動玉軸受の摩擦抵抗について

Some experiments on the frictional resistances of linear ball bearings called ball bushings were performed.The experimental results obtained are as follows : (1) The maximum and average values of frictional resistance increase approximateiy in proportion to bearing load.(2) The maximum and average values in the case of rolling elements contacting with shaft in three-tracks are greater than the values in two-tracks.(3) The maximum frictional resistance is obtained when rolling elements pass from the load-side to the unload-side in tracks.