Measurement of worm gears
A method of determining the minimum radius and the mounting distance of a worm gear member ( 6 ) of a worm drive ( 2 ). The root portion ( 26 ) of a tooth slot ( 24 ) is probed at a plurality of points along the length of the root and the locations of the points are utilized as the basis for determining the minimum radius and the mounting distance.
1. A method of determining a minimum root radius of a worm gear member of a worm drive, said worm gear member having an axis of rotation extending in a direction Z, a periphery comprising a plurality of teeth, and a face width with said plurality of teeth being located along said face width and extending between an upper face and a lower face of said worm gear member with a tooth space having a root located between adjacent teeth, a root radius being defined between said axis and said root, said method comprising:
probing a root of a tooth space between adjacent teeth, said probing comprising establishing a center location in said tooth space between said adjacent teeth and probing along said root at a plurality of points, each of said points being defined by a root radius position and a Z-direction position, said plurality of points forming a shape,
best fitting a defined curve to the shape formed by said plurality of points, and determining a minimum root radius and a corresponding location in said Z-direction from said defined curve.
2. The method of claim 1 further comprising:
establishing an actual mounting distance defined by said determined minimum root radius and said corresponding location in said Z-direction.
3. The method of claim 1 wherein said probing is carried out by a contacting probe.
4. The method of claim 1 wherein said probing is carried out by a non-contacting probe.
5. The method of claim 2 further comprising communicating said actual mounting distance to a gear manufacturing machine and adjusting gear manufacturing process parameters on said machine in accordance with said actual mounting distance.
6. The method of claim 5 wherein said gear manufacturing machine comprises a hobbing machine.
7. The method of claim 6 wherein the adjusted process parameters comprise an adjustment to the position of a hob and a workpiece relative to one another so as to modify the mounting distance for subsequent gears produced on said hobbing machine.
8. The method of claim 1 wherein said probing along said root commences at a center point along the length of said root.
9. The method of claim 8 wherein said probing occurs in a first direction along the root with respect to said center point and in a second and opposite direction along the root with respect to said center point.
10. The method of claim 9 wherein each of said first direction and said second and opposite comprises 40 percent of the face width of said worm gear member.
11. The method of claim 1 wherein said plurality of points comprises at least five points.
12. The method of claim 11 wherein said plurality of points comprises seven points.
13. The method of claim 1 wherein the best fitted defined curve comprises a second order polynomial curve, a cubical spline or higher degree mathematical curve.
14. The method of claim 1 further comprising identifying a theoretical minimum root radius with respect to said axis, said theoretical minimum root radius being axially located at a theoretical mounting distance measured in said Z-direction.
15. The method of claim 14 wherein the theoretical mounting distance and the actual mounting distance are established in the Z-direction with respect to a reference surface located on said upper face or said lower face of said worm gear member.