Spindle device and machine tool utilizing the same

A spindle device with at least one combined externally pressurized gas-magnetic bearing assembly for rotatably supporting a main shaft, having a machining tool fitted to a tip thereof, and having a spindle drive source for rotating the main shaft, said at least one combined externally pressurized gas-magnetic bearing assembly comprising an externally pressurized gas bearing and a magnetic bearing combined together, said spindle device comprising:

• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• and
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the spindle drive source;
• displacement detecting means for detecting a displacement of the main shaft;
• and
• a machining status determining means for determining a machining status performed by the machining tool in reference to the displacement value detected by the displacement detecting means.

A spindle device comprising a main shaft;

• at least one combined externally pressurized gas-magnetic radial bearing assembly in which an externally pressurized gas bearing and a magnetic bearing are combined together, said at least one combined bearing assembly supporting the main shaft rotatably;
• a housing accommodating the at least one combined bearing assembly and the main shaft therein;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• and
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device;
• slide members disposed within the housing and positioned adjacent the main shaft with a radial gap, radial being defined with respect to an axis of rotation of the main shaft, defined between them and the main shaft, said radial gap having a size smaller than a radial bearing gap defined by the externally pressurized gas bearing and the magnetic bearing both forming respective part of the at least one combined bearing assembly, each of said slide members being made of carbon or graphite.

A spindle device which comprises:

• a main shaft;
• at least one combined externally pressurized gas-magnetic bearing assembly comprising an externally pressurized gas bearing and a magnetic bearing combined together, for supporting the main shaft rotatably;
• a housing accommodating the main shaft and the at least one combined bearing assembly therein;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• and
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device;
• a temperature measuring means for measuring a temperature of the housing;
• and
• a temperature measurement associated output means for determining a predetermined output in reference to a temperature value detected by the temperature measuring means, wherein said predetermined output is represented by at least one of (i) an output from the temperature measuring means, (ii) a converted value obtained by converting the temperature value measured by the temperature measuring means into an axial position of a tip of the main shaft or an axial position of a member fitted to the tip of the main shaft, according to a predetermined thermal displacement calculation, and (iii) an abnormality signal determined by comparing the temperature value measured by the temperature measuring means or the converted value with a predetermined value, wherein the axial positions are axial with respect to an axis of rotation of the main shaft;
• and
• an external output means for outputting the predetermined output from the temperature measurement associated output means to an outside of the spindle device.

A spindle device which comprises:

• a main shaft;
• at least one combined externally pressurized gas-magnetic bearing assembly comprising and externally pressurized gas bearing and a magnetic bearing combined together, for supporting the main shaft rotatably;
• a housing accommodating the main shaft and the at least one combined bearing assembly therein;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device;
• a temperature measuring means for measuring a temperature of the housing;
• a temperature measurement associated output means for determining a predetermined output in reference to a temperature value detected by the temperature measuring means, wherein said predetermined output is represented by at least one of (i) an output from the temperature measuring means, (ii) a converted value obtained by converting the temperature value measured by the temperature measuring means into an axial position of a tip of the main shaft or an axial position of a member fitted to the tip of the main shaft, according to a predetermined thermal displacement calculation, and (iii) an abnormality signal determined by comparing the temperature value measured by the temperature measuring means or the converted value with a predetermined value, wherein the axial positions are axial with respect to an axis of rotation of the main shaft;
• and
• an external output means for transmitting the predetermined output from the temperature measurement associated output means to an outside of the spindle device through a communication line.

A mold machining apparatus which comprises:

• a spindle device for driving a machining tool, said spindle device comprising a main shaft and at least one combined externally pressurized gas-magnetic bearing assembly for rotatably supporting the main shaft, said at least one combined bearing assembly comprising an externally pressurized gas bearing and a magnetic bearing combined together;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• and
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device;
• an electric current detecting means for detecting an excitation current for the magnetic bearing;
• and
• a machining status determining means for determining a machining status performed by the machining tool in reference to a current value detected by the current detecting means,
• wherein said machining status determining means includes a current smoothing unit for smoothing the current value detected by the current detecting means, and a machining status determining unit for converting a smoothed output from the current smoothing unit into a static load acting on the main shaft and for determining the machining status in reference to a result of the calculation of the static load.

A mold machining apparatus which comprises:

• a spindle device for driving a machining tool, said spindle device comprising a main shaft and at least one combined externally pressurized gas-magnetic bearing assembly for rotatably supporting the main shaft, said at least one combined bearing assembly comprising an externally pressurized gas bearing and a magnetic bearing combined together;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device;
• a displacement detecting means for detecting a displacement of the main shaft, and
• a machining status determining means for determining a machining status performed by the machining tool in reference to a displacement value detected by the displacement detecting means.

A mold machining apparatus which comprises:

• a spindle device for driving a machining tool, said spindle device comprising a main shaft and at least one combined externally pressurized gas-magnetic bearing assembly for rotatably supporting the main shaft, said at least one combined bearing assembly comprising an externally pressurized gas bearing and a magnetic bearing combined together;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• and
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device.

A mold machining apparatus which comprises:

• a spindle device for rotating a machining tool and comprising a main shaft, at least one combined externally pressurized gas-magnetic bearing assembly comprising an externally pressurized gas bearing and a magnetic bearing combined together, said at least one combined bearing assembly supporting the main shaft rotatably;
• a housing accommodating the main shaft and the at least one combined bearing assembly therein;
• a spindle controller for controlling the at least one externally pressurized gas-magnetic bearing assembly;
• and
• an external command responsive ON-OFF means for turning energization of the magnetic bearing on and off in response to a command supplied from an outside of the spindle controller without starting or stopping the rotation of the spindle device;
• a temperature measuring means for measuring a temperature of the housing;
• a temperature measurement associated output means for determining a predetermined output in reference to a temperature value detected by the temperature measuring means;
• and
• a temperature associated processing means for performing a predetermined process in reference to the output from the temperature measurement associated output means;
• wherein said predetermined output from the temperature measurement associated output means is represented by at least one of (i) an output from the temperature measuring means, (ii) a converted value obtained by converting the temperature value measured by the temperature measuring means into an axial position of a tip of the main shaft or an axial position of a member fitted to the tip of the main shaft, according to a predetermined thermal displacement calculation, and (iii) an abnormality signal determined by comparing the temperature value measured by the temperature measuring means or the converted value with a predetermined value, wherein the axial positions are axial with respect to an axis of rotation of the main shaft;
• and
• a communication means for transmitting the output from the temperature measurement associated output means to a remote place through a communication line.