Ring gear for an epicyclic reduction gear
A method for aligning toothing in an assembly of two half-ring gears is provided: an angular positioning pin is provided which is to be received in respective holes of the half-ring gears; the holes are drilled on the first half-ring gear such that the first hole has a first cross-section that is smaller than the final cross-section thereof; the angles between the teeth are compared between the two half-ring gears, and an angular difference between said angles of the half-ring gears is deduced therefrom; the first hole is redrilled to the final cross-section, while the centre of the hole is angularly shifted by the value of the angular difference; the pin is engaged in the holes, and the half-ring gears are then assembled using an interference fit.
1. A method for assembling first and second half-ring gears according to a common axis, the method comprising:
providing an angular positioning pin for the first and second half-ring gears in relation to each other, the angular positioning pin to be received in first and second respective holes of the said first and second half-ring gears, wherein the first and second respective holes each have a final cross-section adapted to the angular positioning pin;
with reference to a pre-established manufacturing drawing, drilling the first and second holes such that the first hole has a first cross-section that is smaller than the final cross-section on the first half-ring gear and that the second hole has a second cross-section equal to the said final cross-section on the second half-ring gear,
for each of the first and the second half-ring gears:
indexing or defining a plurality of teeth equidistant from each other, with a first tooth that is closer to the respective hole of its respective half-ring gear than the other teeth, to define a common index mark to the first and second half-ring gears;
determining on each tooth indexed, multidimensional coordinates with respect to a center of the respective half-ring gear, of a reference point;
comparing the determined multidimensional coordinates with theoretical coordinates of these same points from the pre-established manufacturing drawing;
noting a difference between the determined multidimensional coordinates and the theoretical coordinates for defining a positional deviation of said reference points;
redrilling the first hole to said final cross-section, positioning the first hole based on the positional deviations of the reference points of each half-ring gear such that, during assembly, each tooth indexed to the first half-ring gear faces a tooth indexed from the second half-ring gear, parallel to said axis, according to a common frame,
and assembling the first and second half-ring gears by tightly engaging said angular positioning pin in the first and second holes, and by an interference fit of the first and second half-ring gears together.
2. The method according to claim 1 , wherein each reference point is located on both an active flank and on a pitch circle of the respective half-ring gear.
3. The method according to claim 1 , wherein the multidimensional coordinates of each reference point are three-dimensional, said reference point being on a middle extension plane of the respective tooth.
4. The method according to claim 1 , wherein the assembly step of the first and second half-rings comprises an interference fit assembly.
5. The method according to claim 1 , wherein before drilling the first and second holes, the toothing on each half-ring gear is separately rectified.
6. The method according to claim 1 , wherein for each half-ring gear, at least three teeth equidistant from each other are defined.
7. The method according to claim 1 , wherein for each half-ring gear, four teeth equidistant from each other are defined and distributed at 90 degrees in pairs.