1. Field of the Invention
The invention relates to a method for processing a toothed workpiece, wherein the workpiece is clamped on a rotating workpiece spindle and a first and a second tool set engage in the workpiece, wherein at least at a first side of the workpiece a chamfering is carried out at tooth front edges and a smoothing of tooth flanks is carried out close to the tooth front edges.
2. Background of the Invention
The basic principles for chamfering and smoothing hobbed workpieces are known, for example, from T. Bausch et al., Innovative Zahnradfertigung, 3rd edition (2006), expert verlag. Renningen (DE), P. 307-310.
During hobbing, toothed arrangements are cut into a workpiece using the teeth of a hob cutter, wherein the workpiece and the hob cutter are rotated with mutual engagement. Subsequently, a chamfering of the tooth front edges (tooth end edges) of the workpiece is generally carried out. The chamfering may in principle be carried out by means of machining or also shaping.
In shaping chamfering operations, a portion of a chamfering tool is pressed onto the tooth front edges of the workpiece so that the material of the workpiece is plastically deformed in a localized manner. In this instance, there are produced a secondary burr at the front face (end face) of a respective tooth of the workpiece (which is typically removed with a cutting tool) and a material protuberance on the tooth flank of the respective tooth. This material protuberance may be eliminated without a second cut by means of smoothing by a portion of a smoothing tool pressing on the tooth flank and thus rolling back the material protuberance.
A tool portion for the chamfering is constructed in a wedge-like manner and typically engages laterally in a tooth gap of the workpiece. Generally, a chamfering tool set comprises two toothed discs which roll on the workpiece and which engage in the workpiece from both front faces. The active tool portion is in this instance in abutment at both sides with a tooth of the workpiece. As a result of the acting mechanical forces and the geometric relationships, the inner angle of the wedge-like tool portion may not exceed approximately 50°. The sum of the chamfer angles of the produced opposing chamfers of the two adjacent teeth is thereby limited to approximately 50° (measured in each case relative to the inclination of the tooth arrangement or the extent direction of the tooth flanks), divided, for example, over a 20° chamfer and a 30° chamfer.
Small chamfer angles have the disadvantage that, in the event of further material removal (for instance, by means of a second cut on the workpiece or by means of a hard fine processing operation), a large part of the chamfer is lost again. The protection of the workpiece from excess hardening during the thermal processing operation is also impaired so that, when the workpieces are used, material breakages can occur more readily.
For smoothing, a tool portion is introduced into the tooth gaps of a workpiece, wherein the edges of the tool portion are in abutment at both sides at a shallow angle, in most cases approximately 2-4°, with the tooth flanks of the two surrounding teeth of the workpiece. A smoothing tool set may also be implemented by means of two toothed discs which roll on the workpiece.
The object of the invention is to provide a method for chamfering and smoothing toothed workpieces by means of which larger chamfer angles can readily be produced on the tooth front edges (tooth end edges) of the workpiece.
This object is achieved with a method of the type mentioned in the introduction, which is characterized in that the first tool set engages at the first side of the workpiece with a wedge-like tool portion laterally in the tooth gaps in the workpiece, wherein the tooth front edges are chamfered on front tooth flanks with respect to a running direction of the workpiece and a smoothing of the tooth flanks is carried out close to the tooth front edges on rear tooth flanks with respect to the running direction of the workpiece, and in that the second tool set engages at the first side of the workpiece with a wedge-like tool portion laterally in the tooth gaps in the workpiece, wherein a smoothing of the tooth flanks is carried out close to the tooth front edges on front tooth flanks with respect to a running direction of the workpiece and the tooth front edges are chamfered on rear tooth flanks with respect to the running direction of the workpiece.
The invention makes provision for different functions to be carried out using the two edges of a wedge-like tool portion which engages at a (front/end) face of a workpiece between two teeth of the workpiece: one edge produces the chamfering on a first adjacent tooth of the workpiece, and the other edge produces the smoothing on a second adjacent tooth of the workpiece. Since for the smoothing of the second tooth only a shallow abutment angle of typically 5° or less is required, for the chamfering of the first tooth an angle of 40° or more, or even 45° or more, is readily available, even when the sum of the angles on the wedge-like workpiece portion (internal angle) is limited to approximately 50° as a result of the mechanical force relationships and the geometric relationships.
In order to both chamfer and smooth all the teeth on a (front/end) face of a workpiece, there are provided two tool sets which complement each other in the processing of the tooth flanks of the workpiece. The front tooth flanks with respect to a running direction of the workpiece during the chamfering and smoothing operation are chamfered by means of one of the tool sets and smoothed by means of the other of the tool sets, and the workpiece flanks at the rear in the running direction are smoothed by means of the other tool set and chamfered by means of the first mentioned tool set. It is possible using the two tool sets to carry out a corresponding operation for the opposing (front) face of the workpiece. Each tool set, more precisely each wedge-like tool portion of a tool set, thus carries out both a chamfering and a smoothing function in the context of the invention.
The wedge-like tool portions of a tool set are typically formed by the teeth of one or two tool toothed discs which are rolled on the workpiece. The toothed discs may in particular be constructed in the manner of a bevel gear. It should be noted that the wedge-like tool portions process the workpiece in a shaping manner, in particular during the chamfering operation. It should further be noted that the wedge-like tool portions do not need to terminate in a tip, simply as long as sufficiently long abutment edges (adjoining faces) which taper towards each other are constructed for the abutment against the teeth of the workpiece.
Generally, for the chamfering and smoothing processing operation, both tool sets engage in the workpiece at the same time. However, an intervention which alternates several times is also possible.
If an additional workpiece processing operation for material removal (for instance, a grinding or another hard fine processing operation) follows the chamfering and smoothing operations according to the invention, as a result of the steeper chamfers in the context of the invention, it is in principle possible to provide a greater residual chamfering region on the workpiece.
In an advantageous variant of the method according to the invention, the chamfering of the tooth front edges is carried out at an angle of at least 35°, preferably at least 40°, in a particularly preferred manner at least 45°, measured relative to an inclination of the tooth arrangement on the workpiece. The large chamfer angle enables a comparatively large chamfer length to be kept also in case of subsequent material removal; problems of excess hardening during a subsequent thermal processing operation are minimized. It should be noted that the inclination angle may also be 0°; the inclination then extends parallel with the rotation axis of the workpiece. It should further be noted that wedge-like tool portions according to the invention preferably have an internal angle of 55° or less, in a particularly preferred manner 50° or less, and more preferably 48° or less, but conversely also have an internal angle of preferably at least 40°, in a particularly preferred manner at least 45°.
A variant is also advantageous in which the smoothing is carried out at an angle of a maximum of 5°, preferably a maximum of 4°, measured relative to an inclination of the tooth arrangement on the workpiece. With a limited maximum internal angle of a wedge-like tool portion, there thereby remains a comparatively large chamfer angle for a tooth front edge which faces the smoothed tooth flank.
A method variant is preferred which also makes provision at a second side of the workpiece for a chamfering to be carried out on tooth front edges and a smoothing of tooth flanks to be carried out close to the tooth front edges, for the first tool set to engage at the second side of the workpiece with a wedge-like tool portion laterally in the tooth gaps in the workpiece, wherein a smoothing of the tooth flanks is carried out close to the tooth front edges on front tooth flanks with respect to a running direction of the workpiece and the tooth front edges are chamfered on rear tooth flanks with respect to the running direction of the workpiece, and for the second tool set to engage at the second side of the workpiece with a wedge-like tool portion laterally in the tooth gaps in the workpiece, wherein the tooth front edges are chamfered on front tooth flanks with respect to a running direction of the workpiece and a smoothing of the tooth flanks is carried out close to the tooth front edges on rear tooth flanks with respect to the running direction of the workpiece. This variant also provides the chamfering and smoothing processing operation according to the invention for the opposing front face of the workpiece. In the case of the angle division proposed in this instance, the same tool set for the same tooth flank carries out the chamfering operation at one side and the smoothing operation at the other side so that the introduction of force on the workpiece and on the tool sets is homogenized.
In an alternative method variant, there is provision also at a second side of the workpiece for a chamfering to be carried out on tooth front edges and a smoothing of tooth flanks to be carried out close to the tooth front edges, for the first tool set at the second side of the workpiece to engage with a wedge-like tool portion laterally in the tooth gaps in the workpiece, wherein the tooth front edges are chamfered on front tooth flanks with respect to a running direction of the workpiece and a smoothing of the tooth flanks is carried out close to the tooth front edges on rear tooth flanks with respect to the running direction of the workpiece, and for the second tool set at the second side of the workpiece to engage with a wedge-like tool portion laterally in the tooth gaps in the workpiece, wherein the tooth flanks are smoothed close to the tooth front edges on front tooth flanks with respect to a running direction of the workpiece and the tooth front edges are chamfered on rear tooth flanks with respect to the running direction of the workpiece. This variant also provides the chamfering and smoothing processing operation according to the invention for the opposing front face of the workpiece. With the angle division used in this instance, the same tool set for the same tooth flank carries out the chamfering operation at both sides or the smoothing operation at both sides, whereby, in an individual case, torsion moments on the workpiece can be minimized.
A method variant is also preferred in which the first tool set and the second tool set engage in the workpiece at different locations on the periphery of the workpiece. The tool sets can then be configured and used independently of each other, which simplifies the method. Alternatively, both tool sets can also be constructed on a common universal tool (which typically comprises a toothed disc for each workpiece side which is intended to be processed), typically with one of the tool sets being produced over half of the periphery of the common universal tool; during the rolling of the universal tool on the workpiece, the first and the second tool set are then alternately active at the same fixed location of the periphery (with respect to the fixed workpiece spindle).
A further development of this variant is advantageous in which the first tool set and the second tool set engage at the same time in the workpiece facing each other. An introduction of force into the workpiece spindle on which the workpiece is retained can thereby be minimized.
The scope of the present invention also includes a processing station for chamfering and smoothing a toothed workpiece, having a workpiece spindle for the toothed workpiece, a first tool set and a second tool set, constructed to carry out the above method according to the invention. With the processing station according to the invention, workpieces with particularly large chamfer angles can be produced.
Other advantages of the invention will be appreciated from the description and the drawings. The features mentioned above and those set out below may also be used individually per se or together in any combination. The embodiments shown and described are not intended to be understood to be a conclusive listing but are instead of exemplary character for describing the invention.
The invention is illustrated in the drawings and is explained in greater detail with reference to embodiments. In the drawings:
After the hobbing of a tooth arrangement on a workpiece, the tooth edges are chamfered in order to prevent excess hardening of the tooth edges during a subsequent thermal processing operation which could lead to material notching during use and in order to reduce the risk of injury resulting from sharp edges or burrs when handling the toothed wheels.
The chamfers can be produced both in a machining and in a shaping manner. Depending on the production method, the results (chamfer angle with respect to inclination angle, chamfer size, chamfer path, etcetera) are different. Shaping methods of the chamfering are considered in greater detail below.
Customarily, the chamfering tool comprises two toothed discs which engage at both sides of the tooth arrangement of the workpiece in the tooth gaps of the workpiece. In this instance, the sum of the two chamfer angles is limited to approximately 50°. As a result of the relatively shallow chamfer angles, with a material removal in the event of a second cut and/or during the hard fine processing operation, a large portion of the chamfer is removed.
Since, during the chamfering operation, a material protuberance in the tooth flanks is produced close to the tooth front edges (for instance, in the region designated 5), the workpiece 1 in the prior art is also smoothed, cf.
However, the invention makes provision, using the two abutment edges (adjoining faces) of a wedge-like tool portion, for chamfering in the direction towards a tooth flank and for smoothing in the direction towards the other tooth flank, as will be explained in greater detail below with reference to
There are used on a workpiece 11 a first tool set WS1 (illustrated with dashed lines) and a second tool set WS2 (illustrated with continuous lines) which are used at a first location of the workpiece 11 (illustrated with dashed lines) and at a second location of the workpiece 11 (illustrated with continuous lines). The first and second location are located over the periphery of the workpiece 11 so far apart that the tool sets WS1, WS2 do not mutually impede each other.
The processing operation at a first side S1 of the workpiece 11 on the left in
The first tool set WS1 comprises at the first side S1 a large number of wedge-like tool portions 17 on a bevel gear. For simplification, only one of these wedge-like tool portions 17 which engages currently in a tooth gap 12 in the workpiece 11 is illustrated. The workpiece 11 rotates in accordance with the running direction LR marked with an arrow. The tooth gap 12 is delimited by a front tooth flank 13 of a tooth 14 on the workpiece 11 in the running direction LR and is further delimited by a rear tooth flank 15 of a tooth 16 on the workpiece 11.
The wedge-like tool portion 17 has two abutment edges 18, 19 which enclose an internal angle α of approximately 50°. The abutment edge 18 produces in the region of the tooth front edge (tooth end edge) 20 on the front tooth flank 13 a chamfer. The abutment edge 19 smooths the rear tooth flank 15 in a region close to the tooth front edge (tooth end edge) 21, wherein the abutment edge 19 is in abutment with the rear tooth flank 15 at a shallow angle.
The second tool set WS2 has wedge-like tool portions 22 on another bevel gear. For simplification, only one of these wedge-like tool portions 22 which engages currently in a tooth gap 23 in the workpiece 11 is again illustrated. It should be noted that the tooth gaps 12 and 23 are illustrated here for better understanding directly one above the other, but in practice in most cases are located spaced apart from each other over a considerable portion of the periphery of the workpiece 11, for instance over half of the periphery. The tooth gap 23 is again delimited by means of a front tooth flank 13 and a rear tooth flank 15 with respect to the running direction LR.
The wedge-like tool portion 22 also has two abutment edges 24, 25 which enclose an internal angle α of approximately 50°. The abutment edge 25 produces a chamfer in the region of the tooth front edge 21 on the rear tooth flank 15. The abutment edge 24 smooths the front tooth flank 13 in a region close to the tooth front edge 20, wherein the abutment edge 24 is in abutment with the front tooth flank 13 at a shallow angle.
As a result of the two wedge-like tool portions 17, 22, all the tooth front edges 20, 21 of the workpiece 11 are chamfered at the first side S1 at an angle β of approximately 45°, and all the tooth flanks 13, 15 are smoothed close to the tooth front edges 20, 21 of the first side S1 at an angle γ of approximately 4°, as can also be seen from
The processing operation at the second side S2 of the workpiece 11 on the right in
The first tool set WS1 has at the second side S2 a large number of wedge-like tool portions 26 on a bevel gear. For simplification, only one of these wedge-like tool portions 26 which engages currently in the tooth gap 12 in the workpiece 11, is again illustrated.
The wedge-like tool portion 26 has two abutment edges 27, 28 which enclose an internal angle α of approximately 50°. In the variant set out, the abutment edge 28 produces a chamfer in the region of the tooth front edge (tooth end edge) 30 at the rear tooth flank 15. The abutment edge 27 smooths the front tooth flank 13 in a region close to the tooth front edge (tooth end edge) 29, wherein the abutment edge 27 is in abutment with the front tooth flank 13 at a shallow angle.
The second tool set WS2 has at the second side S2 a large number of wedge-like tool portions 31 on a bevel gear. For simplification, only one of these wedge-like tool portions 31 which engages currently in a tooth gap 23 in the workpiece 11, is again illustrated.
The wedge-like tool portion 31 has two abutment edges 32, 33 which enclose an internal angle α of approximately 50°. The abutment edge 32 produces a chamfer in the region of the tooth front edge 29 on the front tooth flank 13. The abutment edge 33 smooths the rear tooth flank 15 in a region close to the tooth front edge 30, wherein the abutment edge 33 is in abutment with the rear tooth flank 15 at a shallow angle.
As a result of the two wedge-like tool portions 26, 31, all the tooth front edges 29, 30 of the workpiece 11 are chamfered at the second side S2 at an angle β of approximately 45°, and all the tooth flanks 13, 15 are smoothed close to the tooth front edges 29, 30 of the second side S2 at an angle γ of approximately 4°, as can also be seen in
In
The first tool set WS1 has at the second side S2 a large number of wedge-like tool portions 34 on a bevel gear. For simplification, only one of these wedge-like tool portions 34 which engages currently in the tooth gap 12 in the workpiece 11 is again illustrated.
The wedge-like tool portion 34 has two abutment edges 35, 36 which enclose an internal angle α of approximately 50°. The abutment edge 35 in this variant produces a chamfer in the region of the tooth front edge 29 on the front tooth flank 13. The abutment edge 36 smooths the rear tooth flank 15 in a region close to the tooth front edge 30, wherein the abutment edge 36 is in abutment with the rear tooth flank 15 at a shallow angle.
The second tool set WS2 has at the second side S2 a large number of wedge-like tool portions 37 on a bevel gear. For simplification, only one of these wedge-like tool portions 37 which engages currently in the tooth gap 23 in the workpiece 11 is again illustrated.
The wedge-like tool portion 37 has two abutment edges 38, 39 which enclose an internal angle α of approximately 50°. In this variant, the abutment edge 39 produces a chamfer in the region of the tooth front edge 30 on the rear tooth flank 15. The abutment edge 38 smooths the front tooth flank 13 in a region close to the tooth front edge 29, wherein the abutment edge 38 is in abutment with the front tooth flank 13 at a shallow angle.
In this variant, as a result of the two wedge-like tool portions 34, 37, all the tooth front edges 29, 30 of the workpiece 11 at the second side 2 are also chamfered at an angle β of approximately 45° and all the tooth flanks 13, 15 are smoothed close to the tooth front edges 29, 30 of the second side S2 at an angle γ of approximately 4°, in accordance with
In the variant of
The toothed workpiece 11, which is arranged on a workpiece spindle 41 and which for the method is rotated in a motorized manner by means of the workpiece spindle 41 in the running direction LR, is in the embodiment shown in engagement with a first tool set WS1 and a second tool set WS2 which in this instance comprise toothed bevel gears (cf.
The tool sets WS1, WS2 engage in the workpiece 11 at different locations on the periphery of the workpiece 11, that is to say, at locations which are offset through 180° so that the workpiece 11 is arranged between them.
The tool sets WS1, WS2 are toothed in such a manner that the teeth of the bevel gears of the tool sets WS1, WS2 can each be used as wedge-like tool portions, by means of which a chamfering operation is carried out in the direction towards a first adjacent tooth of the workpiece 11 and a smoothing operation is carried out in the direction towards a second adjacent tooth (cf. in this regard, for example,
The bevel gears 51, 52 of the first tool set WS1 of
In a similar manner, the bevel gears of the second tool set WS2 of
Number | Date | Country | Kind |
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10 2013 218 542.1 | Sep 2013 | DE | national |
This continuation application claims priority to PCT/EP2014/069120 filed on Sep. 9, 2014 which has published as WO 2015/036373 A2 and also the German Patent Application No. 10 2013 218 542.1, filed Sep. 16, 2013, the entire contents of which are fully incorporated herein with these references.
Number | Date | Country | |
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Parent | PCT/EP2014/069120 | Sep 2014 | US |
Child | 15069858 | US |