Motor driven resistance spot welding gun

A motor-driven welding gun comprising:

• a welding gun assembly including a pair of electrode tips, a servomotor, and a feed screw mechanism coupled to said servomotor and rotatable thereby for moving one of said electrode tips toward and away from the other electrode tip;
• said servomotor comprising:
• a motor housing mounted on said welding gun assembly;
• a stator fixedly mounted in said motor housing;
• a hollow rotor rotatably housed in said motor j housing, and
• a plurality of magnets fixed to said hollow rotor;
• each of said magnets having a constant radial dimension and a constant thickness;
• said magnets being arranged along an axis of said hollow rotor depending on the output poorer of said servomotor, so that the whole of said magnets has an axial dimension, which is substantially proportional to the magnitude of the output power of said servomotor;
• said stator including a coil having an axial dimension which is commensurate with the axial dimension of said magnet which is disposed in confronting relation to said coil.

A motor-driven welding gun comprising:

• a welding gun assembly including a pair of electrode tips, a servomotor, and a feed screw mechanism coupled to said servomotor and rotatable thereby for moving one of said electrode tips toward and away from the other electrode tip;
• said servomotor comprising:
• a motor housing mounted on said welding gun assembly;
• a stator fixedly mounted in said motor housing;
• and
• a hollow rotor rotatably housed in said motor I housing;
• said feed screw mechanism comprising:
• a feed screw coupled to and rotatable with said hollow rotor;
• and
• a nut threaded over said feed screw for moving said one of said electrode tips toward and away from the other electrode tip in response to rotation of said feed screw;
• said hollow rotor and said feed screw being joined to each other by an interfitting fastening structure or by a press-fitting structure, said interfitting fastening structure comprising splined members.

A motor-driven welding gun comprising:

• a welding gun assembly including a pair of electrode tips, a servomotor, and a feed screw mechanism coupled to said servomotor and rotatable thereby for moving one of said electrode tips toward and away from the other electrode tip;
• said servomotor comprising:
• a motor housing mounted on said welding gun assembly;
• a stator fixedly mounted in said motor housing;
• and
• a hollow rotor rotatably housed in said motor housing;
• and
• a seal member interposed between said motor housing and said hollow rotor and disposed on an open end that faces said electrode tips.

A motor-driven welding gun comprising:

• a welding gun assembly including a pair of electrode tips, a servomotor, and a feed screw mechanism coupled to said servomotor and rotatable thereby for moving one of said electrode tips toward and away from the other electrode tip;
• said servomotor comprising:
• a motor housing mounted on said welding gun assembly;
• a stator fixedly mounted in said motor housing;
• and
• a hollow rotor rotatably housed in said motor housing;
• said feed screw mechanism comprising:
• a feed screw coupled to and rotatable with said hollow rotor ;
• and
• a nut threaded over said feed screw for moving said one of said electrode tips toward and away from the other electrode tip in response to rotation of said feed screw ;
• and
• a damping member disposed in a region of contact between said hollow rotor and said nut , for absorbing shocks produced between said nut and said hollow rotor when said one of said electrode tips is moved away from the other electrode tip .