Abstract: A method for diagnosing an abnormality of rolling bearing includes: measuring a vibration of a rotator; performing a frequency analysis on the vibration to calculate a magnitude of a vibration at each frequency; calculating a characteristic frequency as a frequency of a vibration from a specification of the rolling bearing and a rotation speed of the rotator at a vibration measurement in the measuring; calculating a vibration value from which an effect of the rotation speed is removed by dividing a magnitude of a vibration at the characteristic frequency by a value including a base and an exponent, the base being a predetermined physical quantity in a proportional relation with an angular velocity of the rotator at the vibration measurement in the measuring, the exponent being a positive number; calculating an evaluation index based on the vibration value; and determining an existence of an abnormality based on the evaluation index.

Abstract: A main spindle device for a machine tool includes a main spindle, a cushioning member, and an arithmetic unit. The cushioning member is disposed on a position where a vibration displacement of a rotator exists. The arithmetic unit uses data of a tool to be used to analyze a vibration mode in a free vibration of the rotator based on a support rigidity of a bearing, masses of respective parts of the rotator including the tool, an attenuation coefficient, and an equation of motion derived from rigidity and inertia by a rotation. An outer diameter of a sleeve positioned outside the bearing is changed such that a position of an antinode of the vibration or a position on which a vibration displacement exists in the vibration mode matches a position of the cushioning member inside the main spindle to change a preload on the bearing.

Abstract: A bearing diagnostic device senses a failure in a bearing of a machine tool including a rotation shaft device. The bearing diagnostic device includes a rotation counting unit, a temperature measuring unit, a frictional torque calculating unit, a rolling speed calculating unit, a bearing characteristic calculating unit, a storage unit, and a determination unit. The frictional torque calculating unit is configured to calculate a frictional torque of the rotation shaft device. The rolling speed calculating unit is configured to calculate a rolling speed of the bearing from the count of rotations. The bearing characteristic calculating unit is configured to calculate a bearing characteristic from the frictional torque and the rolling speed. The determination unit is configured to compare the bearing characteristic calculated by the bearing characteristic calculating unit with a reference bearing characteristic stored in the storage unit to determine a presence of a failure.

Abstract: A main spindle device for a machine tool includes a main spindle, a cushioning member, and an arithmetic unit. The cushioning member is disposed on a position where a vibration displacement of a rotator exists. The arithmetic unit uses data of a tool to be used to analyze a vibration mode in a free vibration of the rotator based on a support rigidity of a bearing, masses of respective parts of the rotator including the tool, an attenuation coefficient, and an equation of motion derived from rigidity and inertia by a rotation. An outer diameter of a sleeve positioned outside the bearing is changed such that a position of an antinode of the vibration or a position on which a vibration displacement exists in the vibration mode matches a position of the cushioning member inside the main spindle to change a preload on the bearing.

Abstract: A bearing diagnostic device senses a failure in a bearing of a machine tool including a rotation shaft device. The bearing diagnostic device includes a rotation counting unit, a temperature measuring unit, a frictional torque calculating unit, a rolling speed calculating unit, a bearing characteristic calculating unit, a storage unit, and a determination unit. The frictional torque calculating unit is configured to calculate a frictional torque of the rotation shaft device. The rolling speed calculating unit is configured to calculate a rolling speed of the bearing from the count of rotations. The bearing characteristic calculating unit is configured to calculate a bearing characteristic from the frictional torque and the rolling speed. The determination unit is configured to compare the bearing characteristic calculated by the bearing characteristic calculating unit with a reference bearing characteristic stored in the storage unit to determine a presence of a failure.

Abstract: A main spindle device of a machine tool includes a plurality of bearings that rotatably support a main spindle of the machine tool, and that are placed inside a housing with a pressure receiving member interposed between the bearings and the housing. The pressure receiving member is capable of moving in a direction perpendicular to an axial direction of the main spindle. A pressure chamber, which a pressure medium pressing the pressure receiving member toward the bearings in the perpendicular direction is supplied to, is formed in the housing. A plurality of the pressure chambers are independently formed in the housing so as to correspond to the bearings, respectively. The main spindle device further includes a plurality of adjustment units provided independently so as to correspond the pressure chambers, respectively, and each capable of independently adjusting a pressure of the pressure medium for a corresponding one of the pressure chambers.

Abstract: A main spindle device of a machine tool includes a plurality of bearings that rotatably support a main spindle of the machine tool, and that are placed inside a housing with a pressure receiving member interposed between the bearings and the housing. The pressure receiving member is capable of moving in a direction perpendicular to an axial direction of the main spindle. A pressure chamber, which a pressure medium pressing the pressure receiving member toward the bearings in the perpendicular direction is supplied to, is formed in the housing. A plurality of the pressure chambers are independently formed in the housing so as to correspond to the bearings, respectively. The main spindle device further includes a plurality of adjustment units provided independently so as to correspond the pressure chambers, respectively, and each capable of independently adjusting a pressure of the pressure medium for a corresponding one of the pressure chambers.