Nsk Corporation

Hisakazu Tadokoro

Hiroyuki Matsuzaki

In a bearing rigidity evaluation apparatus, a vibration portion,excites a bearing,to vibrate. Vibrations of the bearing,thus excited are detected by vibration detecting sensors,and,Output signals of the vibration detecting sensors,and,for an outer race,are added up in time sequence by an adder,and then supplied to a transfer function computing unit,An output signal of the vibration detecting sensor,is supplied to the transfer function computing unit,The transfer function computing unit,calculates a transfer function H between inner and outer races (between a hub shaft,and the outer race,) by FFT. On the basis of this transfer function H, there is obtained a vibration mode in which a resonance frequency (natural frequency) fa appears in a position of &minus;&pgr;/2 phase difference from local-mode vibration components (in-phase components) contained in the aforementioned input signals after erasing of the local-mode vibration components.

Bearing rigidity evaluation apparatus

In a duplex bearing 10 in which a preload is applied to balls 14a and 14b interposed between an outer race 11 and first and second inner races 12 and 13 by tightening a nut 16, a preload jig 19 fitted to the lower end of the second inner race 13 is turned by a motor 21 and applied with an axial load by a rod 31. The rod 31 has a load detector 31 at the middle. Position sensors 24 and 25, each of which is adapted to detect an amount of displacement in the direction of axis, are provided at the ends of the outer race 11 and the second inner race 13, respectively. A rotation detecting sensor 33 adapted to detect a rotational position is provided below the lower surface of the preload jig 9. Under the condition that the axial load is applied to the extent that measuring loads are FH and FL, the amounts of average displacement XAH and XAL of the outer race 11, and the amounts of average displacement XBH and XBL are detected, and the amounts of displacement .DELTA.XH and .DELTA.XL which are the differences between those amounts are calculated, so that the aimed rigidity KA is calculated by utilizing the amounts of displacement .DELTA.XH and .DELTA.XL thus calculated.

Bearing preload measuring method and apparatus

A vibration measurement system 1 comprises a shrink-type chuck 5, a spindle 14, and a servo motor 16 as mechanical elements, and has a vibration pickup 41 attached to the outer peripheral surface of a jaw 5a holding an outer ring 4 of a roller bearing 2. A ring groove 5b is formed on the inner face of the jaw 5a holding the bearing 2, and a shell 18 with oil pressure as back pressure is fitted into the ring groove 5b. When vibration is measured, the oil pressure of the shell 18 is raised to bring bearing clearance to zero, thereby preventing so-called roller drop from causing impulsive vibration.

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Kanagawa, Japan

Hisakazu Tadokoro