Method for producing an internal toothing and component having internal toothing

A method of producing internal gear teeth with deflecting surfaces such that the internal gear teeth are arranged in a component having an end and a longitudinal axis, as well as an end face that is offset relative to the end of the component in the direction of the longitudinal axis. The method comprises the steps of machining the end face of the internal teeth using a conical tool that rotates about a tool axis arranged parallel to the longitudinal axis, the rotating tool first being introduced axially and then moved along a circular path coaxial to the longitudinal axis, and finally being withdrawn parallel to the axis.

This application is a National Stage completion of PCT/EP2010/062804 filed Sep. 1, 2010, which claims priority from German patent application serial no. 10 2009 045 137.4 filed Sep. 30, 2009.

FIELD OF THE INVENTION

The invention concerns a method for producing internal toothing with deflecting surfaces and a component with internal toothing.

BACKGROUND OF THE INVENTION

Components with internal gear teeth, for example drive teeth or spline-shaft teeth, are brought together in the axial direction with other components such as shafts or spindles that have corresponding external teeth in order to produce an interlock between the two components. While bringing the two components together a so-termed tooth-on-tooth position can occur, so that brining them together in the axial direction is blocked. The two components then have to be rotated relative to one another far enough for the teeth to align with the corresponding tooth gaps, so that the blocking is eliminated. Such rotation of the components makes efficient assembly more difficult and slower. Moreover, there are cases when rotation of the components is not readily possible.

For example, this problem is known in the case of synchronization devices in gearwheel transmissions, where a shifting sleeve with internal gear teeth is pushed over a clutch element with external teeth. To facilitate sliding of the shifting sleeve and clutch element one over the other, at their front ends the teeth are provided with oblique or deflecting surfaces. The production of such deflecting surfaces on internal or external teeth is not problematic when the ends of the teeth are flush with the end faces of the components.

From DE 37 21 949 A1 components with internal and external gear teeth are known, which are chamfered at their front ends. In this case the ends of the teeth have a roof-like edge shape with roof-like guide surfaces extending from a cutting-edge-like ridge. The roof-like edge shape is produced by machining the ends with a profile cutter guided in a straight line or on a curved path, which engages in and cuts out the tooth gaps. This production method does not work when the internal gear teeth are offset inward relative to the end face of the component concerned, i.e. not accessible to a milling cutter of that type.

From EP 1 116 901 A2 a planetary transmission with gearwheels is known, whose ends are chamfered to facilitate assembly. The inclined or deflecting surfaces on the teeth are produced by cold forging, i.e. by means of a forging die that has to be produced for the purpose. The dimensional accuracy and surface quality of gear teeth produced in this way do not satisfy stricter requirements.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a method of the type mentioned above, i.e. for the production of “inward-offset” internal gear teeth, with which facilitates assembly when components with internal and external gear teeth are brought together. A further purpose of the invention is to provide a component of the type mentioned earlier, which has deflecting surfaces that allow components with internal and external teeth to be brought together easily.

According to the invention, in a method for producing internal gear teeth in a component it is provided that the end faces of the internal teeth are machined using a conical milling cutter whose rotational axis is orientated parallel to the longitudinal axis of the teeth, the conical milling cutter being guided on a circular path over a defined circumferential angle until a first circumferential position has been reached. Then, the tool is drawn back in the axial direction leaving behind it a machined end face that corresponds to the profile of the conical milling head. In a subsequent process step, after axial re-introduction the conical milling tool is applied along a circular path in the opposite direction to the first circumferential position, so that a cutting edge is formed between the first machined surface and the second machined surface. This cutting edge is located centrally on the end side of a tooth of the internal teeth, and forms a deflecting edge. This produces a roof-like form of the end face of a tooth, with deflecting surfaces falling away from the deflecting edge. The process can be repeated many times in order to provide several teeth at the circumference of the internal gear teeth with such deflecting surfaces and a deflecting edge. Preferably, the method according to the invention is used to produce three teeth, uniformly distributed around the circumference, with deflecting surfaces at the end. With the method according to the invention, internal gear teeth whose ends are offset inwardly in the component can be provided with deflecting surfaces in order to facilitate and speed up assembly when they are brought together.

In a preferred process variant the gear teeth can be made either before or after the machining operation with the conical milling cutter. In this case the teeth can preferably be made by hollowing out or slotting.

According to the invention, in the case of a component with internal gear teeth and an inset end face it is provided that at least one tooth of the internal teeth has deflection surfaces that start from a deflection edge and fall away in the circumferential direction. Preferably, three teeth distributed uniformly around the circumference are provided with deflecting surfaces. This has the advantage that assembly during combination with a component having corresponding external teeth is facilitated and sped up. It is no longer necessary to rotate the two components relative to one another in the event of a tooth-on-tooth position. Thanks to the deflecting surfaces, the component to be combined slides in the circumferential direction and finds its way into the tooth gaps, so enabling axial combination.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a view in the axial direction, of a component1with internal gear teeth2having a larger inside diameter and internal gear teeth3having a smaller inside diameter. The arrows P1, P2, P3point to three circled circumferential positions, of which one is shown as a detail Y inFIG. 4.

FIG. 2shows a section along the plane2-2inFIG. 1, i.e. an axial section through the component1. The component1, in the form of a hollow cylinder, has a longitudinal axis1aand a front end1b. The internal toothing has a conically shaped end face2awhich is offset inward in the axial direction relative to the front end1bof the component1. Not shown in the figure is that the component1is to be assembled to a further component which has external gear teeth that correspond to the internal gear teeth2,3so as to form an interlock between the two components. For example, the components to be combined can be used in an automatic transmission of a motor vehicle. To facilitate fitting of the two components, i.e. their axial combination, deflecting elements are provided at the front face2aof the internal teeth2, which are shown as a detail X inFIG. 3.

FIG. 3shows an enlarged section of the internal teeth2, their front face2a, and a tooth4extending in the axial direction which has a tooth crown4aand tooth flanks4b,4carranged laterally. The front surface of the tooth4is formed by two deflecting surfaces5,6that meet one another along a linear deflecting edge7, the “roof ridge”. The production of the deflecting surfaces5,6will be explained with reference toFIG. 2.

Into the component1from its front end1bis introduced a tool8with a rotational axis that extends parallel to the longitudinal axis1aof the component1. The tool8is in the form of a conical milling cutter, i.e. it has a conically shaped milling head8b. According to the invention, the deflecting surfaces5,6with the deflecting edge7according to the invention are produced by the conical milling tool8as described below:

The conical milling tool8rotating about its axis8ais first brought in eccentrically in the axial direction, i.e. offset by a radius e, and is then guided along a circular path of radius e over a defined circumferential angle. Along the path, the conical milling cutter8, with its rotating, conical milling head8b, produces a conical end surface2awhose conic angle α is indicated in the drawing (FIG. 2). When it reaches a first circumferential position, which is circled inFIG. 2as the detail X, the conical milling tool8is stopped along its circular path and withdrawn axially, i.e. moved out of the component1(toward the right in the drawing). Then the conical tool8is moved to the first circumferential position from the other side, and this, far enough for the two machined surfaces to produce a line of intersection7, which is shown inFIG. 3. By stopping the conical tool8as it approaches the first circumferential position from its two respective opposite directions the deflecting surfaces5,6are obtained, which are part-surfaces of the cone mantle of the milling head8b. Thus, the deflecting edge7is the intersection line of two cones arranged parallel to one another. During the process described, the tool8is moved in such manner that the intersection line or deflecting edge7is positioned centrally to a tooth, indexed tooth4inFIG. 3.

The three circumferential positions indicated by the arrows P1, P2, P3inFIG. 1correspond in each case to the representation inFIG. 3. Thus, in total the end face2aof the internal teeth2has three teeth, separated by circumferential angles of approximately 120 degrees, which have deflecting surfaces5,6and deflecting edges7. This enables simpler assembly when the counter-component (not shown) with corresponding external teeth is brought in axially. The ends of the external teeth to be fitted—this is not shown—are chamfered, i.e. they are provided with roof-shaped deflecting surfaces. The deflecting surfaces on the external teeth can be produced by methods known from the prior art, for example in accordance with DE 37 21 949 A1 mentioned at the beginning.

The circumferential position Y indicated by the arrow P1inFIG. 1is represented in detail inFIG. 4. Thus,FIG. 4shows a view in the axial direction toward the end face2aof the internal gear teeth2with deflecting surfaces5,6on either side. As already mentioned, the deflecting surfaces5,6are part-surfaces of the cone mantle of the milling head8b, and are therefore concave.

FIG. 5shows a 3D representation of the internal teeth with deflecting surfaces5,6according to the invention for the tooth4; the indexes used are the same as inFIG. 3andFIG. 4. Relative to the conical end face2a, the concavely shaped deflecting surfaces5,6are delimited by edges5a,6a. Thus the edges5a,6a, also show the position of the conical milling tool8(FIG. 2) in which the movement along the circular path of radius e is stopped and the movement in the axial direction out of the component begins.

INDEXES