Patent ID: 8758093

Claim:
An internal gear grinding machine for use in grinding a to-be-machined internal gear by synchronously rotating the to-be-machined internal gear and a barrel-shaped threaded tool in mesh with each other, the to-be-machined internal gear being rotatable about a work rotation axis, the barrel-shaped threaded tool being rotatable about a tool rotation axis having a predetermined crossed axes angle with respect to the work rotation axis, the internal gear grinding machine comprising: dressing means for dressing the threaded tool with a disk-shaped dresser rotatable about a dresser rotation axis in accordance with a shape of the threaded tool, the dressing means including: dresser turning means for turning the dresser about a dresser pivot perpendicular to the dresser rotation axis; and braking and maintaining means for applying a braking force to the dresser turning means, and maintaining the dresser at a turned position thereof, the braking and maintaining means including: a rotary shaft disposed coaxially with the dresser pivot and rotatably supported in a casing; a disk-shaped rotary disk provided on the rotary shaft; a fixing member provided in the casing and opposing the rotary disk; an armature disposed between the rotary disk and the fixing member and supported to be slidable along the rotary shaft; a brake disk disposed at a side opposite to the armature with respect to the rotary disk; a spring member provided in the fixing member to bias the armature toward the rotary disk; and a coil member provided in the fixing member to generate a magnetic force when being supplied with power and thereby attract the armature against a biasing force of the spring member.