Hiroyuki Ohta

This paper deals with rolling traction in isoviscous-rigid (IVR), piezoviscous-rigid (PVR), and elastohydrodynamic lubrication (EHL) regimes at line contact. First, a measuring method of rolling traction using the two-disk machine supported by ball bearings was explained. Then, the rolling traction in the IVR, PVR, and EHL regimes at line contact was measured. The measured results showed that as load P increases, the time average rolling traction F_{R AVG} in the IVR and PVR regimes increases, while that in the EHL regime does not significantly increase. The measured F_{R AVG} was lower than the rolling traction F_{R TED/CPA} under the isothermal condition calculated by using the commercial software TED/CPA. To establish the rolling traction expression, a rolling traction expression under the isothermal condition F_{R iso} was first derived by means of curve fitting the calculated F_{R TED/CPA}. Then, a rolling traction expression (which takes into account the thermal effects of the inlet shear heating) F_{R thermal} was derived by multiplying the thermal correction factor C_t to the expression F_{R iso}. Finally, it was shown that the proposed expression F_{R thermal} is effective for estimating the rolling traction in the IVR, PVR, and EHL regimes at line contact.

This article deals with the expressions of friction force of a four-point contact linear ball bearing with two rows under low-speed operation. First, the slip velocity on a contact area and the equilibrium of moments acting on a ball were theoretically examined. Then, an expression for the location of the pure rolling point (where the slip velocity is zero) was derived. Using the location of the pure rolling point, expressions of the friction force were developed. Next, to confirm the validity of the developed expressions, the friction force of four-point contact linear ball bearings with two rows was measured. The results showed that the developed expressions for the friction force in this study are effective. The developed expression would be applicable for estimating the friction force as a basic performance in the design procedure and for checking the product quality in bearing manufacturing.

This paper deals with friction forces in a linear-guideway type recirculating ball bearing (linear bearing) under grease lubrication. During the experiments, the friction force, temperature and electric contact voltage of a grease lubricated linear bearing (test bearing) without seals were measured. Experimental results showed that the measured friction forces of the test bearing were fluctuated with the ball passage period. The measured time-average friction force F_AVG (measured F_AVG) was nearly constant when the grease filling rate x (= grease filling volume / internal space of the bearing) ≥ 0.13, while the measured F_AVG decreased as x decreased when x0, the measured F_AVG was greater than the calculated F_D+F_E+F_RT. This means that when x>0, an agitating resistance (F_A) from the grease might cause the measured F_AVG to be greater than the calculated F_D+F_E+F_RT. Finally, an expression for the friction force of a linear bearing, F_AVG=F_D+F_E+F_RT+F_A (which can estimate the measured ones) is proposed.

This paper deals with the reduction of sticking in a linear-guideway type recirculating ball bearing (linear bearing), which is the significant increase in the required driving force for a linear bearing in a back-and-forth short stroke operation. First, the driving force of a linear bearing with five carriage-body types (A–E, having different dimensions and shapes) under rolling moment load was measured. Simultaneously, the ball's position in the load zone was observed. The experimental results showed that regardless of the carriage-body types, the increasing rate of the driving force and the interspace (space between balls around the center of the load zone on the raised side) decreases and sticking tends to hardly occur as the maximum linear velocity and the stroke length increase. Also, the occurrence of sticking was affected by the carriage-body types. Finally, to examine the relationship of carriage-body types, carriage-body deformation, and the occurrence of sticking, the carriage-body deformation (caused by preloading and tightening torque of bolts) was calculated by finite element method (FEM). The FEM results showed that carriage-body type, which is more deformable, had a tendency to reduce sticking.

総合学術電子ジャーナルサイト「J-STAGE」－国内で発行された学術論文全文を読むことのできる、日本最大級の総合電子ジャーナルプラットフォームです。

総合学術電子ジャーナルサイト「J-STAGE」－国内で発行された学術論文全文を読むことのできる、日本最大級の総合電子ジャーナルプラットフォームです。

In this paper, the driving force of a linear-guideway type recirculating ball bearing (linear bearing) is measured and explained as the first step toward an understanding of sticking, which is the significant increase in driving force required to move a linear bearing under back-and-forth operation with a short stroke length. First, the driving force required for operation of a test bearing (which is a linear-guideway type recirculating ball bearing with load balls) and acceleration of a moving body (which consists of a carriage of the test bearing, an arm, and weight) were measured. The measurements showed that the sticking occurred when the test bearing, under a relatively higher rolling moment load, was driven in an offset position for a certain period. Next, the driving force of a test bearing with alternating load balls and spacer balls was measured, and it was clear that the cause of the sticking was the sliding friction between rolling balls. Finally, the ball locations in the load zone of the test bearing with load balls were observed in operation, and the occurrence process of the sticking is explained.

総合学術電子ジャーナルサイト「J-STAGE」－国内で発行された学術論文全文を読むことのできる、日本最大級の総合電子ジャーナルプラットフォームです。

This paper deals with the load–displacement relationship of a ball bearing with axial, radial, and angular displacements for both the inner and outer rings. First, the expressions for the load–displacement relationship of ball bearings with any number of balls under the combined axial, radial, and moment loads were presented by using a system in which both the inner and outer rings are allowed to move in the axial, radial, and angular directions. Second, the presented expressions were compared with Jones' expressions (which are typical conventional expressions for the load–displacement relationship), then the range of application of Jones's expressions were elucidated. Third, the relative axial displacement, the relative radial displacement, and the relative angular displacement of a miniature ball bearing type 692 under the combined axial, radial, and moment loads were calculated. Finally, it was shown that the relative angular displacement in the case with no inner ring angular displacement is R_i/R_o times the relative angular displacement in the case with no outer ring angular displacement, in which R_i and R_o are the radii of the inner and outer race curvature center loci.

総合学術電子ジャーナルサイト「J-STAGE」－国内で発行された学術論文全文を読むことのできる、日本最大級の総合電子ジャーナルプラットフォームです。