Rotation mechanism, machine tool, and semiconductor manufacturing device

A rotation mechanism comprising:

• a housing including an inner wall and a top surface;
• a shaft inserted through a hole provided at the housing;
• a bearing attached to the inner wall of the housing installed at the housing and configured to rotatably support the shaft,
• wherein the bearing is a rolling bearing including an outer ring, an inner ring disposed on a radially inner side of the outer ring, and a rolling element disposed between the outer ring and the inner ring,
• wherein the outer ring is attached to the inner wall of the housing, and the inner ring is attached to an outer surface of the shaft, allowing to determine a position of the housing relative to the shaft in a rotational center axis direction,
• wherein the rotation mechanism further comprises a plate like rotary member provided at one end portion of the shaft, configured to be rotated together with the shaft, and having an outer rotary portion that projects to a radially outer side of the hole and faces the housing,
• wherein the rotation mechanism includes a gap that has a gap width in the rotational center axis direction and that is defined by a lower surface of the outer rotary portion and the top surface of the housing, a position of the top surface being allowed to be determined relative to the shaft in the rotational center axis direction,
• wherein the rotation mechanism further comprises a gas passage that is open to the top surface defining the gap, to connect the gap to an outside of the housing,
• wherein a groove extending in a circumferential direction of the hole is provided at a portion located in the rotary plate member and faces the housing,
• wherein the gas passage is provided in the housing and opened to a position located in the rotary plate member and faces the groove, and
• wherein the gap having the gap width is a sealing portion to seal a space between an inside and the outside of the housing and is connected to the gas passage, the gas passage allowing gas contained in a portion of the gap to pass to the outside of the housing through the groove located in the rotary plate member, the gap, and the gas passage that are connected,
• wherein a plurality of grooves is provided in the rotary plate member, the plurality of grooves including the groove, as a first groove, and a second groove, and a width of the first groove is different from a width of the second groove.