Method for machining tooth edges and machining station designed for this purpose

Abstract

The invention concerns a method for the machining of the tooth edges between an axially facing surface and the tooth flanks of a gear with a machining tool that has a toothed contour. For the material-removing cutting operation, the machining tool, rotating about the axis of its toothed contour, is brought into rolling engagement with the toothed workpiece under a crossing angle different from zero between the rotary axes of the machining tool and the toothed workpiece.

Claims

1. Method for the machining of the tooth edges between an axially facing surface (3) and the tooth flanks of a toothed workpiece (2) to produce a chamfer wherein a tool (1) with a cutting edge removes material from the tooth edges of the toothed workpiece (2) through a cutting action as the toothed workpiece (2) rotates about its workpiece gear axis (Z), characterized in that the machining tool has a toothed contour comprising teeth and cutting edges arranged facing axially on said tool and that, for the material-removing cutting operation the machining tool, rotating about the axis (ZW) of its toothed contour, is brought into rolling engagement with the toothed workpiece (2) that is to be machined, with the rotary axes of the toothed workpiece and the machining tool (Z, ZW) in process being positioned relative to each other at an axis-crossing angle () different from zero.

2. Method according to claim 1, wherein as a result of the axis-crossing angle, the cutting direction(s) of the cutting movement has a directional component which along the tooth flank adjoining the machined tooth edge runs in the direction of the tooth width.

3. Method according to claim 1 wherein the tool and workpiece are positioned relative to one another at an angle of inclination () different from zero and which is the angle of the rotary axis of the tool relative to a plane extending orthogonal to the connecting line between the center of the workpiece gear profile and the center of the tool, the cutting direction(s) of the cutting movement has a directional component which runs orthogonal to the tooth flank.

4. Method according to claim 1 wherein the axis-crossing angle () is at least 4 and/or the axis-crossing angle is no larger than 45.

5. Method according to claim 3 wherein the angle of inclination () is at least 8 and/or the angle of inclination is no larger than 80.

6. Method according to claim 1 wherein the cutting velocity is at least 10 m/min and/or the cutting velocity is no larger than 450 m/min.

7. Method according to claim 1 wherein the tool (1) and the toothed workpiece (2) are subjected to a movement relative to each other which has a directional component parallel to the gear axis (Z) of the workpiece in process and serves to completely finish the tooth edges.

8. Method according to claim 1 wherein the tool is designed with a structure whereby a single rotation of the tool results in the complete finishing of the tooth edges.

9. Method according to claim 1 wherein during the machining of the tooth edges at an axially facing end surface the tool and the toothed workpiece are not subjected to a relative movement with a directional component parallel to the gear axis of the workpiece in process.

10. Machining station for the chamfering of the tooth edges between each of the axially facing end surfaces (3) and the tooth flanks of a toothed workpiece (2), comprising a driven, rotating workpiece spindle serving to hold a workpiece with the toothed contour to be machined, a driven, rotating tool spindle serving to hold a tool, characterized in that an axis-crossing angle () different from zero can be set between the tool spindle axis and the workpiece spindle axis (Z), and that a controller device is provided which controls the rotary movements of the spindles for a rolling engagement between the toothed workpiece (2) that is to be chamfered and a toothed contour of the tool (1) at an axis-crossing angle different from zero according to a method as defined in claim 1.

11. Machining station according to claim 10, with a linear movement axis comprising a first machine axis (X) with a directional component radial to the workpiece spindle axis extending in the radial direction of the workpiece spindle axis.

12. Machining station according to claim 10 wherein a machine axis effecting a relative movement with a directional component parallel to the workpiece spindle axis between the workpiece spindle and the tool spindle is provided.

13. Machining station according to claim 10 wherein an angle of inclination () different from zero can be set between the tool spindle axis and a plane that extends orthogonal to the connecting line between the center of the toothed contour and the center of the tool.

14. Machining station according to claim 10 wherein a further rotary machine axis is provided which comprises a directional component orthogonal to the rotary axis serving to set the axis-crossing angle () as well as to the workpiece spindle axis.

15. Machining station according to claim 10 wherein a second linear machine axis is provided which comprises a directional component lying in a plane that extends orthogonal to the workpiece spindle axis, wherein said directional component is linearly independent of a projection of the first machine axis onto said plane.

16. Machining station according to claim 10 wherein the tool is disk-shaped.

17. Machining station according to claim 10 wherein the tool has a step-ground contour.

18. Machining station according to claim 10 wherein the tool (10) is configured with a structure whereby a single rotation of the tool results in the complete finishing of the tooth edges at one axially facing end surface.

19. Machining station according to claim 10 wherein the tool (10) has areas with varying heights of its rake faces measured in the direction of the rotary axis (ZW) of the tool.

20. Machining station according to claim 19 wherein the rake faces of the tool (10) at least in part rise in the form of a spiral.

21. Gear-cutting machine for the machining of toothed workpieces, with a machining station according to claim 10, said gear cutting machine having a further machining station to generate the gear teeth on the workpiece by a soft-cutting process comprising hobbing, gear shaping, or power-skiving.

Description

(1) Further distinguishing features, details and advantages of the invention will become evident from the following description which refers to the attached drawings, wherein

(2) FIG. 1 schematically illustrates the geometry of the engagement between the tool and the gear profile to be machined, seen in a first viewing direction;

(3) FIG. 2 schematically illustrates the same machining engagement as shown in FIG. 1, seen in a second viewing direction;

(4) FIG. 3a illustrates a position of the axes used in the machining of the tooth edges;

(5) FIG. 3b for comparison to FIG. 3a, illustrates the positions of the axes used in power-skiving;

(6) FIG. 4 shows the profile of a tool for the machining of tooth edges in comparison to a profile of a tool that generates the underlying gear contour by means of power-skiving; and

(7) FIG. 5 shows a special form of a tool for the machining of tooth edges.

(8) FIG. 1 illustrates the underlying kinematics of the machine axes on which the inventive method is based. A workpiece with a toothed contour 2 is shown in FIG. 1 with its gear axis Z oriented vertically, but the individual teeth of the toothed contour 2 are not outlined in the schematic representation of FIG. 1. In its projected image in the drawing plane of FIG. 1 which extends orthogonal to the radial infeed direction X, the gear axis Z of the gear profile 2 encloses an axis-crossing angle with the rotary axis Z.sub.W of a tool 1. In the illustrated example, is 20. The axes X, Z and Y in this example form a rectangular coordinate system.

(9) FIG. 2 further illustrates the engagement between tool and workpiece as seen in the Y-direction Y, i.e. in a viewing direction that is turned by 90 in relation to the viewing direction of FIG. 1. As is evident from FIG. 2, the tool 1 is also inclined against a plane that extends orthogonal to the X-direction, specifically by an angle which is in this case 30. FIG. 2 illustrates the machining of the tooth edges that lie between the tooth flanks of the toothed contour 2 and the axially facing end surface 3 at the top. For the machining of the edges at the bottom side, the workpiece can be turned over, so that the bottom surface in FIG. 3 becomes the top surface, while the position of the tool remains the same as for the operating situation shown in FIG. 2. Alternatively, the same relative mutual positioning between the workpiece and the tool can also be accomplished by changing the position of the tool. This capability can in particular be realized through a design where the tool can be swiveled by 180 or more about the axis designated as X in FIG. 2.

(10) In principle, the cutting can be directed from the inside out (out of the gap) or the opposite way (into the gap). To change from one kind of cutting to the other, the sense of rotation needs to be reversed accordingly.

(11) As explained above, the machine does not require a second rotary axis to allow a desired position of the axis to be set. Instead, starting from the position shown in FIG. 3b which is used for power-skiving and where the location of the cutting engagement in the projected view of the drawing lies in the area of the projected crossing of the axes, the tool can be subjected to a shift movement (directed to the left in FIG. 3). In this shift movement, the orientation of the tool axis does not change, but the center of the tool is shifted. The plane that extends orthogonal to the connecting line between centers, which coincides with the drawing plane in FIG. 3b, is thus tilted out of the drawing planefiguratively speakingso as to be again perpendicular to the new connecting line in FIG. 3a. The rotary axis of the tool in FIG. 3a lies no longer in this plane, but is inclined at an angle from the latter in the direction towards the rotary axis of the workpiece.

(12) In FIG. 3a, the outlines of the individual teeth shown in FIG. 3b have been omitted. This is meant to indicate that the profile of the tool for the machining of the tooth edges does not match the tooth profile of the power-skiving tool shown in FIG. 3b. Rather, the tool profile of the tooth-edge-machining tool is modified for this purpose, since for the generation of the chamfer the edge has to be broken in the plane of the axially facing surface and, accordingly, the velocity vector has to be parallel to the chamfer of the surface. An example for this modification is shown in FIG. 4, wherein the solid line represents the tooth profile of the tool used for the power-skiving, while the broken line represents the corresponding profile of the chamfering tool.

(13) Using the tool 10 shown in FIG. 5 eliminates the need for moving the tool in its axial direction during the machining of the tooth edges on an axially facing surface. The toothed contour 12 of the tool 10 winds about the rotary axis Z.sub.W in the form of a continuously rising spiral and therefore has a discontinuity 16 at a location 14. A single complete rotation of the tool 10 about its rotary axis causes the profile-forming contact lines to be pushed fully over both tooth edges of a tooth gap of the gear profile to be machined, whereby a particularly time-saving way of machining the tooth edges is achieved. The continuous spiral shape is preferred but not required. Configurations with a plurality of segments interrupted by steps are also possible.

(14) In principle, unlike the chamfering of gear tooth edges through plastic deformation, the generation of a chamfer on the tooth edges through a cutting operation does not require a second step to follow. This shortens the machining time for the workpieces.

(15) To further clarify the invention, the primary purpose of the following discussion is to allow the reader to visualize the cutting process on which the inventive method is based.

(16) To start, in a simplified view a line element dl of a cutting edge of the tool is considered which lies on a tooth edge of the gear-toothed contour of the machining tool, i.e. in a plane that extends orthogonal to the rotary axis Z.sub.W of the tool. In a snapshot, the directional vector of the cutting edge element dl can be described for example as (cos , sin , 0), wherein stands for the angle at which the cutting edge element is inclined relative to a radial axis, in the snapshot for example relative to the axis X.sub.W of the reference system of rest (X.sub.W, Y.sub.W, Z.sub.W) of the machining tool.

(17) A movement along the orientation vector of the cutting edge itself in relation to a non-moving workpiece does not cause any cutting action, and the cutting edge element dl always moves in the plane that extends orthogonal to the rotary axis Z.sub.W. For the purposes of the following explanation, a cutting direction (in an absolute reference system) is therefore assumed which lies in this plane and is directed orthogonal to the cutting edge element dl. Accordingly, this cutting direction can be defined by a directional vector s.sub.W=( sin , cos , 0) in relation to the reference frame of rest of the machining tool.

(18) Considering at first only the crossing angle that has been set between the rotary axes, this represents the equivalent of tilting the tool about the infeed axis X, so that the cutting direction, excluding the inclination but including the axis-crossing angle , can be represented in the spatially fixed coordinate system (X, Y, Z) as s.sub.=( sin , cos cos , cos sin ).

(19) The third of the vector components of this cutting direction also illustrates how the component parallel to the gear axis depends on the axis-crossing angle.

(20) The configuration of the axis-crossing angle without the additional angle of inclination represents the basic constellation for the machine axes that is used in power-skiving, wherein in view of the shape of the tooth flank surfaces already completed by power-skiving with maximum radial infeed, the cutting direction in the relative movement against the likewise rotating gear in process cannot have a component orthogonal to the tooth flank. If this requirement is applied to a snapshot in the sense that in a coordinate system rotated about the gear axis Z, the first component of the cutting direction represents the (vanishing) component orthogonal to the (in this case spatially fixed) component and the second component along the tooth flank represents the direction of the tooth height, a rotation by an angle is required so that the first component of s.sub. vanishes, i.e. a rotation for which the condition tan.sub.=tan /cos is met.

(21) However, in the preferred embodiment of the invention, the rotary axis Z.sub.W is additionally tilted in the spatially fixed system about the axis Y, specifically by the tilt angle . In the spatially fixed system (X, Y, Z), the vector of the (absolute) cutting direction thus takes on the form
s.sub.,=(cos sin sin sin cos ,cos cos ,cos sin cos +sin sin ).

(22) Changing to a coordinate system that is rotated by the angle where the cutting direction takes on the form s.sub.,,=(s.sub., s.sub.|, s.sub.Z), one arrives at the following expression for the component perpendicular to the tooth flank
s.sub.=(sin sin cos cos sin )cos.sub.+cos cos sin.sub.

(23) Thus, the cutting direction has a non-vanishing component s.sub., which has the consequence that in the cutting action the profile lines are pushed over the tooth edge. Inserting the value =0 for the sake of transparency, the result for s.sub. is reduced to
s.sub.195|.sub.=0=sin sin

(24) Interpreting this result graphically, the non-vanishing axis-crossing angle makes it possible to realize a cutting direction with a vector component perpendicular to the tooth flank which in the preferred embodiment also includes the sine of the additional angle of inclination. Consequently, in this preferred embodiment, the vector component of the cutting direction that is directed perpendicular to the tooth flank of the gear tooth profile in process is predominantly dependent on the factor sin sin.sub..

(25) Furthermore, the invention is not limited to the examples of embodiments presented in the description of the drawings. Rather, the features of the following claims and of the foregoing description can be essential, individually or in combination, for the realization of the invention in its different embodiments.