Tool head, machine tool and boring method of bore of cylinder block using the machine tool

A machine tool comprises:

• a tool head having a boring cutter and a grinding tool;
• rotating means for rotating said tool head;
• a hollow main shaft rotatable about its axis by a rotating means to said tool head and transmitting rotational power from said rotating means to said tool head;
• a support, said main shaft being rotatably supported in said support and is roatatably supported in said support;
• moving means for moving said support in an axial direction of said main shaft;
• and
• a shaft housed in the main shaft and axially movably splined to the main shaft,
• wherein said tool head comprises expanding means for radially expanding said boring cutter and said grinding tool under predetermined expanding forces and at a predetermined position in response to axial movement of said shaft, said expanding means including a driving source fixedly mounted on said support,
• wherein said main shaft remains unchanged in diameter while being rotated by said rotating means during both a boring process, in which said tool head is rotated and moved towards a workpiece while said boring cutter bores said workpiece, and a grinding process, in which said tool head is rotated and reciprocally moved while said grinding tool grinds said workpiece,
• wherein the machine tool performs boring process and grinding process by radially expanding said boring cutter and said grinding tool, and
• wherein said expanding means comprises:
• a pinion gear rotatable or securable in phase by said driving source;
• a tubular ring gear having outer circumferential gear teeth meshed with said pinion gear and an internally threaded inner surface, said ring gear being rotatably supported on said support;
• a tubular ball screw having outer circumferential gear teeth meshed with said internally threaded inner surface of said ring gear, said ball screw being movable in an axial direction of said shaft in response to rotation thereof;
• and
• a bearing having an inner race fitted over said shaft and an outer race fitted in said ball screw, thereby allowing said shaft to move axially in unison with said ball screw.

A machine tool comprising:

• a hollow main shaft rotatable about its axis by a rotating means;
• a support, being rotatably supported in said support;
• a shaft housed in said main shaft and axially movably splined to said main shaft;
• and
• a tool head coupled to a distal end of said main shaft and accommodating a boring cutter and a grinding tool therein, said boring cutter and said grinding tool being radially expandable and contractible;
• said tool head having expanding means for radially expanding said boring cutter and said grinding tool under predetermined expanding forces and at a predetermined position, in response to axial movement of said shaft, for boring and grinding a workpiece;
• said expanding means comprising:
• a servomotor fixedly mounted on said support;
• a pinion gear rotatable or securable in phase by said servomotor;
• a tubular ring gear having outer circumferential gear teeth meshed with said pinion gear, and an internally threaded inner surface, said ring gear being rotatably supported on said support;
• a tubular ball screw having outer circumferential gear teeth meshed with said internally threaded inner surface of said ring gear, said ball screw being movable in an axial direction of said shaft in response to rotation thereof;
• and
• a bearing having an inner race fitted over said shaft and an outer race fitted in said ball screw, thereby allowing said shaft to move axially in unison with said ball screw.

A machine tool comprising a tool head comprising:

• a plurality of said grinding tools;
• a main body supporting said grinding tools;
• and
• expanding and contracting means disposed in said main body, for expanding or contracting said first and second grinding tools radially in directions across an axis of said main body,
• said expanding and contracting means comprising:
• a first tool base, said first grinding tool being mounted on an outer surface of said first tool base;
• a first cone shaft held against an inner side surface of said first tool base for pressing said first tool base;
• a second tool base radially expandable or contractible simultaneously with or independently of said first tool base, said second grinding tool being mounted on an outer surface of said second tool base;
• a second cone shaft held against an inner side surface of said second tool base for pressing said second tool base, said second cone shaft being inserted in said first cone shaft and slidable against said first cone shaft;
• and
• a moving member for simultaneously or individually axially moving said first cone shaft and said second cone shaft;
• said first cone shaft defining therein an oblong hole having a bottomed end;
• said second cone shaft having a portion held against the inner side surface of said second tool base through said oblong hole.