FR2647041A1 - METHOD FOR FINISHING THE FLANGES OF CYLINDRICAL WHEELS BY DEVELOPING DECOLLETING, AND DEVICE FOR CARRYING OUT SUCH A METHOD - Google Patents

Abstract

The invention relates to a method for finishing the flanks of cylindrical wheels by involute cutting, in which the right and / or left flanks are generated in separate operations, and in which the device performs, depending on the movement of the axial carriage 2, a modification of the axial distance and / or of the auxiliary rotation of the part 10 relative to the tool 9, in order to produce modifications of the flank lines. The method is characterized in that one or more of the adjustment quantities, making it possible to describe the auxiliary rotation, are modified automatically, during the displacement of the axial carriage, so as to compensate for the warping of the flanks, produced by the modification of the lines. flanks, the tool, used for machining, having a cutting geometry adapted to the adjustment variables. The invention also relates to a device for carrying out this method, with a bench 1, on which are mounted a spindle 7 for a toothed tool and a workpiece headstock 6. The solution according to the invention makes it possible to avoid the veiling of the sides, or reduce it to a minimum.

Description

Finishing process for cylindrical wheel flanks by

  involute cutting, and device for

such a process.

  The present invention relates to a method for finishing

  cylindrical sidewalls with straight or helical

  dale, inside or outside, by bar turning

  in which the right and / or left flanks are generated in separate operations, and in which the device executes, as a function of the displacement of the axial carriage, a modification of the axial distance and / or a modification of the auxiliary rotation of the piece relative to the tool, to produce changes in sidewall lines, such as bending and / or flanking; the invention also relates to a device for carrying out such a method, with a bench, on which are

  mounted a pin for a toothed tool and a doll

piece.

  Involute turning is a continuous process of machining

  swimming cylindrical gears. The tool looks like an involute planing tool; but its axis of rotation

  is inclined relative to the axis of the part. During the

  swims, the tool and the part perform a basic rotation.

  Their respective speeds of rotation are then inversely related to their number of teeth. A helical movement of the tool relative to the workpiece is superimposed on the rotation

  basic. This helicoidal displacement consists of a displacement

  of the tool in the direction of the axis of the workpiece, and

  auxiliary rotation of the part, proportional to this movement

  cement. The auxiliary rotation is calculated so as to equal 2 r, in the case of machining of a part without modification of the side lines, when the axial carriage stroke is

  equal to the pitch of the helix of the teeth to be produced. As a result

accordingly:

13 Z

2ir H H and / or Z - * - A = p

27

  and = - AZ p With: L Z = Axial carriage displacement A = Auxiliary rotation H = Helical part pitch p = Reduced helical pitch

  It is often desired, in practice, not to achieve

  exactly the flanks of cylindrical toothings under

  developable helicoids, but to modify the

  profile and side ganes. The teeth must be curved and

  stripped, for example. The description of these modifications

  is usually done using line diagrams of

sidewalls and / or profiles.

  Involute turning allows the production of modifications

  flanks. As a first approximation:

  profile are obtained by a modification of the tool profile, and modifications of the flank lines are

  produced by a modification of the movement of the machine.

  However, a more detailed examination shows that changing the machine's motion also affects the profile of the part. This incidence leads, for example, to a curtain of

  flanks in the bar turning with involute teeth

  quiet because. This veiling means the presence of profiles, in different frontal sections, with different profile errors, and the presence of flank lines, on different

  cylinders, with different distortion errors.

  The formation of this curtain will be explained using the

figure 1.

  Figure 1 shows the right side of a cylindrical wheel

with helical teeth on the left.

  The notations correspond to: b = Width of the tooth z = coordinate in the direction of the axis of the part, with respect to the middle of the tooth width Fp = distortion error (and / or modification of the side line) I = Front face of the wheel II = Rear face of the wheel The concept of the front face is required to qualify the respective sidewall of the right or left sidewall. The distortion error is determined on the measuring cylinder, on the line F1 Fi of FIG. 1, the profile error in the frontal section being measured in the middle of the tooth width, that is to say on the line P1 Pi. It is necessary to imagine the flank deviations, with respect to the corresponding unmodified developable helicoide, perpendicular to the plane

drawing. -

  For a better understanding, it is first admitted that all the trajectories have the same pace on a sidewall, and that all the points of a trajectory have the same distance, compared to the developable helicoid.

  primitive, that is to say that they are also located

  above or below the drawing plane. In the description

  flank geometry, the simpli-

  These fications are naturally superfluous.

  This is a prescribed "error" distortion curve, corresponding to

  in the right part of Figure 1. On the measuring cylinder, the high point of the flank is in the middle of the tooth width; it is located in SI in the zone of the feet of the toothing, in S in the zone of the heads. Between the cylinder at the top of the teeth and at the bottom of the teeth, each cylinder

  has almost the same distortion error curve.

  Only the high point is deported towards Z, in accordance with

  to the component z of the trajectory S1 S1. Since the length of the diagram F, 3 is always equal to the tooth width, a slightly different area of the prescribed curve will always be recorded on different measuring cylinders. To describe the pace Fp in the zone of the heads and feet of the toothing, it is therefore necessary to extend the curve, respectively, on the faces I and II, by

  relative to the curve on the prescribed measuring cylinder.

  The profile error in a given frontal section is the

  distance between the point considered and the spiral helicoid

  primitive wheat. According to the previous explanations, the profile error, obtained in the middle of the tooth width, at the points P1 (base circle) or P1 (head circle),

  for example, is represented by the distance of the trajec-

  through these points, and the unmodified developable helicoide. P1 therefore has the same distance as the point H6, with respect to the primitive developable helicoúde, namely

  the distance H% H6; the distance P is accordingly H H2.

  This study, carried out for other points between P1 and P, shows that the shape of the profile error F "in the middle of the tooth width is equal to the distortion error curve Fp, from H to The developments formulated above, applied to the tooth-bottomed cylinder and / or to the top of the teeth, for the distortion errors, and to the planes I and II, for the profile errors, lead to following results: Plan Size and / or Measure between Error Curve Measurement Cylinder of Measurement Points

I P2 -P1 g-H-

I- P2 3 H4 H5

  Fw Wheel center P1 P H '- HI' - H '

II P3 -P - H8 H7

  Cylinder with tooth base F -F3 H F13 Prescribed measuring cylinder F - Fi H '- H8 Cylinder tooth top F2 - F2 H' - H; Figure 2 is a graphical representation of these results. The difference, obtained at the point considered, is referenced by q. that is to say: ql H1 H = O q IL'Hil q2 H 2

q3 H3 'H ..

3 33

  Moreover: F pFf = Warped distortion errors on the cylinder with f3Ff teeth F Fa = Distortion errors on the cylinder on the top of the teeth With the exception of the points on the S1 SI trajectory, all the points of the modified sidewall are set backwards , with respect to a primitive developable helicoid; the magnitudes q2

at q9 therefore have a negative sign.

  References fH 1 f and f H / 3 "assigned to the error of

  distortion on the bottom of the cylinder and on the cylinder

  The offset of the flank lines is defined by: fHP = flpa fH f The profile errors in the plane I fH (I) = q5 - q3 and in plan II

fH, - II q7 - q9-

  allow to obtain the shift of the profile: tfH = fH II fHo I It should be noted that 4fH p and fH have a positive sign in the example considered. This result is easy to reconstruct, using the quantities represented on the

Figures 1 and 2.

  The above developments concern the right flanks

  helical teeth on the left. Studies are easy

  can be transposed to other cases, that is to say to the left flanks of the helicoidal toothing on the left, and to both

  flanks of helicoidal toothing on the right and / or

  right ture. The only data required is the look of the

  toolpath on the corresponding side of the workpiece.

  The trajectory is calculable in the context of calculating the tool and / or simulating the machining process. In the other cases also, that is to say for a straight toothing, in particular, it has an oblique aspect compared to

  side of the room. Figure 3 shows the trend of

  involves trajectories for the above cases.

  Only a helical gear can make it possible to machine a straight toothing by involute cutting. The sign of the "slope" of the trajectories then depends on the sign of the helix angle of the tool. The two rough shapes of the trajectories are therefore valid for parts with straight teeth, while the points of the trajectory, in the zone of the top of the toothing, are closer to plane II, for example.

  foot zone, on the right flank of the den-

  helicoidal left, these points of the left flank of the same toothing are closer to the plane I. The application of

  the method of calculation, previously described, makes it possible to

  ver that the offset of the flank lines and the offset of the profile of the left flank of the helical toothing on the left have a negative sign. As already mentioned, the corresponding magnitudes of the right flanks have a positive sign. The following remark also applies in other cases: the offset of the sidewall lines and profiles has, on the right flank, a sign opposite to the shift of these magnitudes on the

left flank.

  On cylindrical wheels, finished by free-cutting

  the veiling of the flanks, described by the decapa-

  lage of flanks and profiles, is often inappropriate. The invention therefore aims to develop the method and the device, as defined above, so as to avoid

  curtaining the flanks, or reducing it to a negligible value

  geable. The method according to the invention is characterized in that, during the displacement of the axial carriage, one or more of the adjustment variables, axial distance, eccentricity of

  the tool, pivoting angle and reduced helical pitch,

  describing the auxiliary rotation, are modified automatically, so as to compensate for the curvature of the sidewall, produced by the modification of the sidewall lines, the tool, used for machining, having a cutting geometry, on the right and / or left flanks,

  adapted to the actual adjustment values during the removal

  chips by the corresponding cutting edge. The provision

  of the invention, is characterized in that

  the axis of rotation of the tool can be modified in relation to -

  the axis of the part being machined.

  In another judicious form of construction, it is possible to modify the eccentricity of the tool in progress

machining.

  A solution according to the invention lies in the removal of the eccentricity of the tool (e = 0), and in a modification of the pivot angle during the

  displacement of the axial carriage, that is to say in a modification

  dynamic cation. As a result, in the middle of the tooth width, a profile deviation on the two sides of the piece,

  which should be taken into account when calculating the tool.

  Dynamic modification of the pivot angle ú pro-

  at the same time, minimal bending. If this phenomenon were to cause the tolerances on the part to be exceeded, this should be taken into account when defining the movement of the machine, in order to produce the bending

required (by a (z) and / or p (z)).

  The proposed solution provides the additional benefit of being able to use, in many cases, a purely

  cylindrical, that is to say without draft angle.

  It is also possible to compensate a curtain of flanks

  by modifying the eccentricity of the tool during the

  axial carriage, that is to say by a dynamic modification of the eccentricity e. This solution requires relatively large changes in eccentricity. This results in different basic circles on the piece, in

  different frontal sections. This effect must be

  square by an adaptation of the axial distance during the

displacement of the axial carriage.

  The dynamic modification of eccentricity produces simul-

  a significant distortion error, which must be compensated for by a dynamic adaptation of the reduced helical pitch p. The tool should be calculated in such a way as to avoid any

  profile error in the middle of the tooth width.

  The simulation of the machining process, previously formulated, must be reproduced by iteration, in order to adapt

  adjustment data, until the tolerances

  rances of the room are repre-

  The involute cutting machine, provided for carrying out the method described, is reproduced in FIGS. 4 and 5. It has a bench 1, on which an axial carriage 2 can move in the Z direction. The carriage 2 supports a radial carriage 3, movable in the X direction relative to the axial carriage 2. A free cutting head 4, mounted on the radial carriage 3 with a possibility of rotation about the axis 5, can move in the X direction with the carriage 3. A workhead doll 6 is fixed on the bench 1. The free cutting head 4 and the holding headstock 6 respectively have a spindle 7 and 8, for mounting

of a tool 9 and / or a part 10.

  During the machining of the workpiece 10, the tool 9 and the workpiece 10 perform a basic rotation, in a known manner, by rotating in a ratio inverse to their respective number of teeth. A narrow band of the definitive toothing is formed during a rotation of the workpiece. The realization of the toothing, over the entire width of the part 10, requires a helical displacement. The latter is produced by a displacement of the axial carriage 2 in the Z direction, and by a simultaneous auxiliary rotation of the workpiece 10. During machining, the axes of the tool 9 and the workpiece 10 are oriented one relative to each other under an angle,

known way.

i1

Claims (3)

Claims.   1. Method for finishing the cylindrical wheel flanks, with straight or helical gears, inside or outside, by involute cutting, in which the right and / or left flanks are generated in separate operations,   and in which the device executes, depending on the displacement   cementing of the axial carriage, a modification of the axial distance and / or a modification of the auxiliary rotation of the workpiece relative to the tool, in order to produce modifications of the sidewall lines, such as bending and / or flanking , characterized in that, during the   displacement of the axial carriage, one or more of the   Adjustment tools, axial distance (a), eccentricity (e) of the tool (9), pivot angle (ú) and reduced helical pitch (p), for describing the auxiliary rotation, are automatically changed, so as to compensating for the curvature of the sidewall produced by the modification of the sidewall lines, a tool (9) used for machining, having a cutting geometry, on the right and / or left flanks, adapted to the adjustment variables effective   during chip removal by the corresponding cutting edge   ing. 2. Device for carrying out the method according to claim 1, with a bench, on which are mounted a   spindle for a toothed tool and a workhead doll,   in that the axis of rotation of the tool (9) can be   modified relative to the axis of the part, during machining.   Device according to Claim 2, characterized in that the eccentricity (e) of the tool (9) can be modified in machining course.