Jtekt Corporation

Shigeru Matsunaga

Toshiyuki Okita

Ryota Tanase

Reference phase variation values &#x3c3;kto &#x3c3;Kn, each of which is a variation among a plurality of phases that occur during non-machining and phase variation values &#x3c3;to &#x3c3;n, each of which is a variation among a plurality of phases that occur during machining are detected from measured vibration with the use of a chattering detector that is used to calculate phases of a desired number (n) of frequencies. If &#x3c3;Ki&#x2212;&#x3c3;i is smaller than a determination value TK, it is determined that chattering having a frequency i is occurring.

Chattering detection method for machine tool

Loads that act on all the bearings that support a main spindle are derived from a variation in the state of the main spindle and, in addition, raceway surface contact pressures of the respective bearings are analyzed, so it is possible to accurately keep track of the state of each bearing. Then, when the raceway surface contact pressure exceeds a corresponding threshold, a machining condition is changed to execute control such that the raceway surface contact pressure does not exceed the corresponding threshold, and, furthermore, when the raceway surface contact pressure exceeds the corresponding threshold even when the machining condition is changed, the main spindle is controlled to stop, so it is possible to prevent a seizure of each bearing. Thus, it is possible to improve machining accuracy by controlling the main spindle with high accuracy.

Main spindle device of machine tool

A spindle unit includes: a main spindle that holds a rotary tool, and that is rotated; bearings by which the main spindle is rotatably supported; and a damper bearing by which the main spindle is rotatably supported, and that has a damping coefficient larger than damping coefficients of the bearings. The damping coefficient of the damper bearing is set to a value within a range from 10,000 to 1,000,000 N&#xb7;s/m.

Spindle unit

A spindle device is provided with a temperature sensor for detecting the temperature of an antifriction bearing or the temperature of a part of either one of a housing and a spindle which part is influenced by a temperature change of the antifriction bearing, and an abnormality detection section for detecting the abnormality of the antifriction bearing based on the change speed of the temperature of the antifriction bearing detected by the temperature sensor, so that the abnormality of the antifriction bearing can be detected more precisely.

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Anjo, Japan

Shigeru Matsunaga