Worm polishing method and device thereof

1. A worm polishing method for polishing tooth faces of a gear tooth of the worm with a polishing tape, comprising the steps of:

rotatably retaining a worm and rotating the worm about a rotational axis of the worm;

continuously or intermittently transferring the polishing tape from a source to pass proximate to the worm;

inserting and retracting the polishing tape into and from a tooth space between opposing tooth faces of the worm by a pressure contact roll, wherein a rotational axis of the pressure contact roll is tilted corresponding to a tooth lead angle of the tooth space of the worm, and the polishing tape is transferred and guided along a perimeter of the pressure contact roll, wherein the pressure contact roll has a tapered peripheral edge defined by a top edge and a pair of slant edge faces on a periphery of the pressure contact roll, and the polishing tape is bent into a substantially V-shape in cross section by the tapered peripheral edge of the pressure contact roll forming a bent portion of the polishing tape along each of the slant edges;

swinging the pressure contact roll transversely across the tooth space of the worm;

alternately advancing and retreating the pressure contact roll along the rotational axis direction, and alternately pressure contacting each of the bent portions of the polishing tape against the tooth faces on opposing sides of the tooth space of the worm;

moving the polishing tape along an axial direction of the worm;

synchronizing a rotating speed of the worm with a moving speed of the polishing tape such that the polishing tape tracks a lead of the tooth space of the worm;

whereby the tooth faces of the worm are polished by a combined operation of the rotation of the worm, the transfer of the polishing tape, the swing motion of the pressure contact roll and the movement of the polishing tape synchronized with the rotating speed of the worm.

2. A worm polishing device for polishing tooth faces of a gear tooth of the worm with a polishing tape, comprising:

a retention mechanism which rotationally retains a worm;

a rotation mechanism which rotates the worm about a rotational axis of the worm;

a tape transfer mechanism which continuously or intermittently transfers a polishing tape from a source;

a tape insertion and retraction mechanism which advances and retreats the tape transfer mechanism, and inserts and retracts the polishing tape into and from a tooth space between opposing tooth faces of the worm with a pressure contact roll;

a tilting mechanism which tilts a rotational axis of the pressure contact roll corresponding to a tooth lead angle of the tooth space of the worm;

loopback rolls which can transfer and guide the polishing tape in a tangential direction of the pressure contact roll;

a swing mechanism which linearly swings the pressure contact roll transversely across the tooth space of the worm;

a switchable pressure contact mechanism having a pressure contact roll which has a tapered peripheral edge having a top edge face and a pair of slant edge faces formed on a periphery of the pressure contact roll, by both of which the polishing tape can be bent into a substantially V-shape in cross section, wherein the switchable pressure contact mechanism alternately advances and retreats the pressure contact roll along the rotational axis direction to alternately pressure contact each of the bent portions of the polishing tape against the tooth faces on opposing sides of the tooth space of the worm;

a tape moving mechanism which moves the polishing tape along an axial direction of the worm; and

a speed synchronization means which synchronizes a rotating speed of the worm with a moving speed of the polishing tape such that the polishing tape tracks a lead of the tooth space of the worm.

3. The worm polishing device according to claim 2 , wherein an elastic pressure contact ring member is provided on the tapered peripheral edge of the pressure contact roll, and has the top edge face and the pair of slant edge faces.

4. The worm polishing device according to claim 2 , wherein the switchable pressure contact mechanism comprises a switchable moving stand, and a pair of opposing cylinder mechanisms, and wherein the pressure contact roll is provided on the switchable moving stand, the switchable moving stand is arranged to advance and retreat along the rotational axis direction of the pressure contact roll, and the pair of opposing cylinder mechanisms advance and retreat the switchable moving stand.

5. The worm polishing device according to claim 2 , wherein the swing mechanism comprises an eccentric mechanism which linearly swings the pressure contact roll transversely across the tooth space of the worm.

6. The worm polishing device according to claim 2 , wherein the speed synchronization means comprises a rotation control motor rotating the worm, a movement control motor moving the polishing tape, and a synchronization control portion which synchronously controls a rotating speed of the rotation control motor and a rotating speed of the movement control motor.