Patent Abstract:
The invention relates to a device for use in production of bevel gears. The device comprises a turning machine ( 22 ), with a working spindle ( 22.1 ) and a counter-holder ( 23 ), arranged co-axially to a rotational axis (B 1 ) of the working spindle ( 22.1 ) for the coaxial tensioning of a workpiece blank (K 1 ). A multi-functional tool holder ( 24 ) is provided, which may be displaced relative to the workpiece blank (K 1 ) held in the turning machine ( 22 ) and comprises a tool base ( 25 ) mounted to rotate about an axis (B 2 ). The tool base ( 25 ) is provided for fixing one or more tools. A tool housing ( 26 ) with milling head ( 27 ) is provided, the tool housing ( 26 ) being displaceable relative to the workpiece blank (K 1 ) held in the turning machine ( 22 ) and the milling head ( 27 ) is mounted to rotate about a milling head axis (B 3 ). A controller is provided for control of the movement processes, to subject the workpiece blank (K 1 ) firstly to a turning process with a tool fixed to the tool base ( 25 ) and then a toothing machining with the milling head ( 27 ).

Full Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of PCT Application No. PCT/EP2005/053679, filed Jul. 28, 2005, the disclosure of which is herein incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to apparatuses for the soft machining of bevel gears, especially apparatuses designed for dry machining. The invention also relates to a respective method. 
     There are various machines which are used in the production of bevel gears and similar gearwheels. There has been a desire for some time to automate the production. One solution that has made only limited headway is a machining center which is designed in such a way that a large number of production steps can be performed on one and the same machine. Such machines are not only very complex and therefore expensive, but also require a relatively large amount of work in preparatory setup (setup time). On the other hand, such machines that were developed with a view to high flexibility are rather suited for individual productions or very small series. 
     The European patent EP 0 832 716 B1 shows and describes a compact machine which is designed for turning and gear hobbing a workpiece, with said workpiece not having to be re-chucked or transferred. In other words, the workpiece sits on a main spindle after chucking and is machined there with different tools. It is regarded as a disadvantage that as a result of the arrangement of the different elements it is not designed to carry out dry machining since the removal of the hot chips is especially relevant in dry machining. Moreover, the freedom of movement is limited with respect to the workpiece as a result of the lateral arrangement of the two carriages with the tools. The shown machine is not suitable for machining bevel gears or the like, but is designed for machining cylinder gears. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of simplifying the production of bevel gears. 
     It is a further object of the invention to provide a respective apparatus which is inexpensive. 
     These objects are achieved in accordance with the invention by an apparatus ( 20 ) comprising:
         a turning machine ( 22 ) having a working spindle ( 22 . 1 ) and a counter-holder ( 23 ) arranged coaxially to a rotational axis (B 1 ) of the working spindle ( 22 . 1 ) for coaxially clamping a workpiece blank (K 1 );   a tool base ( 24 ) which is displaceable relative to the workpiece blank (K 1 ) held in the turning machine ( 22 ) and comprises a multifunctional tool holder ( 25 ) mounted to rotate about an axis (B 2 ) extending substantially parallel to the rotational axis (B 1 ) of the working spindle ( 22 . 1 ), with the multifunctional tool holder ( 25 ) being configured for fastening at least one tool ( 25 . 1 - 25 . 4 );       

     a tool housing ( 26 ) displaceable relative to the workpiece blank (K 1 ) held in the turning machine ( 22 ); characterized in that:
         the tool housing holds a milling head ( 27 ) rotatable about a milling head axis (B 3 ) with a set of axially extending cutters chucked in the tool housing ( 26 );   the milling head ( 27 ) is mounted at an adjustable angle (W) respective to the rotational axis (B 1 ) of the working spindle ( 22 . 1 ); and   the milling head ( 27 ) is equipped with a set of cutters protruding from an axial end face thereof with respect to said milling head axis (B 3 ), the tool housing ( 26 ) also being arranged to advance the milling head ( 27 ) towards the workpiece blank (K 1 ) to machine the workpiece blank (K 1 ),   a CNC controller ( 28 ) for controlling different movement processes of the tool base ( 24 ) and the tool housing ( 26 ) in order to subject the workpiece blank (K 1 ) firstly to a turning process with a tool fixed to the tool base ( 24 ) and then to a tooth machining process with the milling head ( 27 ) to produce a bevel gear from the workpiece blank (K 1 ). These objectives are also achieved by a method for soft machining of bevel gears, comprising the following steps:       

     a) clamping of a workpiece blank (K 1 ) on a first workpiece spindle ( 22 . 1 ) of a turning machine ( 22 ) which comprises a counter-holder ( 23 ) for coaxially clamping the workpiece blank (K 1 ), which counter-holder is arranged coaxially to a rotational axis (B 1 ) of the workpiece spindle ( 22 . 1 ); 
     b) performing a turning machining with a tool fastened to the tool base ( 24 ), with the turning machine ( 22 ) comprising the tool base ( 24 ) which is movable relative to the workpiece blank (K 1 ) clamped in the turning machine ( 22 ) and comprising a multifunctional tool holder ( 25 ) being rotatably held about an axis (B 2 ) which extends substantially parallel to the rotational axis of the first workpiece spindle (B 1 ), with the multifunctional tool holder ( 25 ) being configured for fastening the tool; 
     c) performing gear-tooth forming with a milling head ( 27 ), with the turning machine ( 22 ) comprising a tool housing ( 26 ) for the milling head ( 27 ) and the tool housing ( 26 ) is movable relative to the workpiece blank (K 1 ) clamped in the turning machine ( 22 ) and the milling head ( 27 ) is rotatably held about a machining head axis (B 3 ) at an adjustable angle (W) respective to the rotational axis (B 1 ) of the working spindle ( 22 . 1 ). 
     The apparatus in accordance with the invention is relatively inexpensive and can therefore be used in situations where complex and therefore often expensive machine tools are not economical. The method in accordance with the invention is especially designed for machining tooth flanks prior to a hardening process, i.e. in the soft state. The tools which are used must be chosen accordingly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are described in closer detail by reference to the drawings, wherein: 
         FIG. 1  shows a schematic view of the various machining steps in producing bevel gears; 
         FIG. 2  shows a schematic view of a first apparatus for use in soft machining of bevel gears in accordance with the invention; 
         FIG. 3  shows a schematic view of a second apparatus for use in soft machining of bevel gears in accordance with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Terms will be used in connection with the present description, which are also used in relevant publications and patents. Notice shall be taken however that the use of such terms shall merely serve better understanding. The inventive idea and the scope of protection of the claims shall not be limited in their interpretation in any way by the specific choice of the terms. The invention can easily be transferred to other terminological systems and/or specialist fields. The terms shall apply analogously in other specialist fields. 
     In accordance with the invention, the machining of bevel gears is concerned. This term shall also include crown wheels and bevel pinions, according to definition. It also includes bevel gears without axial offset and bevel gears with axial offset, so-called hypoid bevel gears. 
       FIG. 1  shows a schematic view of an exemplary process run  10 . The invention can be used advantageously in the shown context. As was already mentioned, it concerns an example for machining a bevel gear. Based on a workpiece blank (box  101 ), the following soft machining steps are performed in the illustrated example. Based on a workpiece blank (box  101 ), the following soft machining steps are performed in the illustrated example. A (central) bore can be produced by drilling for example (box  102 ). The workpiece blank can then be machined by turning (box  103 ) with a lathe tool. These steps are referred to in this context as preform production or pre-machining. Other steps or alternative steps can be carried out within the scope of preform production. The workpiece is referred to as a gear blank at the end of preform production. 
     This is followed by the so-called gear-tooth forming. In accordance with the invention, preferably (dry) bevel gear milling (box  104 ) is used in order to produce teeth in the gear blank. This is followed by trimming as an optional step (box  105 ). The steps  102 ,  103  and  104  or the steps  102  to  105  can be carried out in accordance with the invention in an apparatus  20  in accordance with the invention. 
     This is typically followed by heat treatment (box  106 ) in order to harden the gear blank and by aftertreatment or finishing (box  107 ). The bevel gear is then finished. 
     Further details of the invention are described below by reference to a more detailed description of the individual method steps and by means of an embodiment. 
     The method in accordance with the invention for soft machining of bevel gears comprises the following steps. The reference numerals relate to  FIG. 2 . A workpiece blank K 1  is clamped in a first working spindle  22 . 1  of a turning machine  22  which is part of the apparatus  20  in accordance with the invention. A first soft machining of the workpiece blank K 1  is performed with one or several tools  25 . 1 ,  25 . 2 ,  25 . 3 . The tool or tools  25 . 1 ,  25 . 2 ,  25 . 3  are clamped in a first multifunctional tool holder  25  of apparatus  20 . This first soft machining can concern one or several of the following machining steps: drilling, turning, milling. The goal of this first soft machining is to produce a gear blank from the workpiece blank K 1 . 
     The gear-tooth forming is now also carried out in the same apparatus  20 . This occurs as follows. A second soft machining of the gear blank is performed with a milling head  27  which is chucked on a tool housing  26 . The goal of said second soft machining is to produce a gearing on the gear blank. Preferably, the second soft machining comprises the (dry) bevel gear milling of the gear blank by means of a milling head  27 . 
     In order to perform said steps in the mentioned manner, the multifunctional tool holder  25  is located on the tool base  24  and the milling head  27  on the tool housing  26  in a horizontal plane relative to the main axis B 1  of the turning machine  22 . The tool base  24  is preferably located on the one side and the tool housing  26  on the other side next to axis B 1 . 
     Preferably, all machining steps can be carried out in a dry manner. In this case, however, it is necessary to configure and arrange the apparatus  20  accordingly, especially in order to enable the removal of the hot chips. 
     The apparatus  20  in accordance with the invention is shown in  FIG. 2 . The apparatus  20  is specially designed for use in soft machining of bevel gears and comprises a CNC-controlled turning machine  22  with a working spindle  22 . 1  for receiving the workpiece blank K 1 . The apparatus  20  comprises a tool base  24  with different tools  25 . 1  to  25 . 3  and a tool housing  26  for receiving the gearing tool (a milling head  27  for example) for gear-tooth forming the gear blank. A counter-holder  23  can also be provided. 
     In accordance with the invention, the apparatus  20  concerns a horizontally operating machining station on the basis of a turning machine in which the tool housing  26  with the milling head  27  is arranged to the side of the working spindle  22 . 1  with the gear blank during the gear-tooth forming. (It is also possible to provide a vertical configuration with a similar overall arrangement.) 
     In accordance with the invention, the turning machine  22  forms a functional unit in combination with the tool housing  26 , in which the workpiece blank K 1  is subjected to a first soft machining in order to be subjected to gear forming after the first soft machining as a gear blank by the milling head  27 . The apparatus  20  has a CNC controller  28  which is indicated in  FIG. 2 . The CNC controller  28  is linked by control at least with the following parts of the system  22 ,  24 ,  25 ,  26 , which is indicated in  FIG. 2  by the arrows  28 . 1 . This linkage can also be made via a bus or via a cable connection. It is also possible to use another kind of the interface, e.g. a wireless connection, in order to link the CNC controller  28  with the individual system parts  22 ,  24 ,  25 ,  26 . 
     Further details of the apparatus  20  shown in  FIG. 2  will be explained below. The turning machine  22  has a main rotational axis B 1 . The working spindle  22 . 1  can be rotated about said axis B 1 , as is indicated by the double arrow  29 . 1 . Furthermore, the counter-holder  23  sits coaxially to the working spindle  22 . 1  on a carriage  23 . 1  and can be displaced in the longitudinal direction to the main rotational axis B 1 , as indicated by arrow x 1 . In addition, the tool base  24  has a rotational axis B 2 . The tool holder  25  can be rotated about said axis B 2 , as is indicated by the double arrow  29 . 2 . In the illustrated embodiment, the tool base  24  sits on a carriage  24 . 1 ,  24 . 2  and can thus be displaced together with the tool  25 . 1 ,  25 . 2 ,  25 . 3  in the axes x 2 , y 2 . A drive  24 . 3  is connected with the carriages  24 . 1 ,  24 . 2  and the tool holder  25  to enable advancing various tools ( 25 . 1 ,  25 . 2 ,  25 . 3 ) with respect to the workpiece blank (K 1 ) by rotation of the tool holder ( 25 ) about its axis (B 2 ) extending substantially parallel to the rotational axis (B 1 ) of the working spindle ( 22 . 1 ) and by translatory movements of the tool base ( 24 ). 
     The milling head  27  can rotate about axis B 3 , as indicated by the double arrow  29 . 3 . Furthermore, the tool housing  26  sits on a carriage  26 . 1 ,  26 . 2  and can be displaced in different directions, as is indicated by arrows x 3 , y 3 . 
     In the illustrated embodiment, the working spindle  22 . 1  plus workpiece blank K 1  and/or gear blank cannot be displaced in a translatory manner. The displacing capability parallel to the to the axis x 1  is not necessary in a mandatory fashion because the tool  25 . 1 ,  25 . 2 ,  25 . 3  and the milling head  27  can be advanced in that the tool base  24  or the tool housing  26  are displaced parallel to the axis x 1 . A displacement of the turning machine  22  in the plane of projection perpendicular to the axis x 1  is also not necessary in a mandatory manner because the tool base  24  and the tool housing  26  can be displaced in the y-direction y 2 , y 3 . The working spindle  22 . 1  can still be arranged on a carriage in order to gain further degrees of freedom. 
     The different axes concern numerically controlled axes. As a result, the individual movements can be controlled numerically by the CNC controller  28 . Preferably, the controller  28  is arranged in such a way that all axes can be controlled numerically. Important is, that every single one of the movement sequences occurs in a coordinated manner. Said coordination is carried out by the CNC controller  28 . 
     The apparatus  20  in accordance with the invention is thus special and thus stands out from other known approaches in that the individual machining stations  24 ,  26  are arranged horizontally. Moreover, the position of the different numerically controlled axes was chosen in such a way that there is the highest possible range for movement for machining the workpiece/blank. The following arrangement of the individual axes is especially preferred. 
     Tool base  24 : Axis x 2  extends parallel to the axis x 1 , with the two axis being offset against one another in that a relative movement parallel to the y 2  direction is performed. In this way it is possible for example to machine a central bore in the workpiece blank K 1  with a drill  25 . 3 . The tool base  24  plus carriage  24 . 1 ,  24 . 2  is arranged adjacent to the working spindle  22 . 1  and it is possible to change the relative distance to one another in that relative displacements are made parallel to x 2  and/or y 2 . Preferably, the two axes x 1 , x 2  can also be offset against one another in the depth (perpendicular to the plane of projection). For this purpose, the carriage  24 . 1 ,  24 . 2  can be displaced parallel to an optional z 2  axis. 
     Tool housing  26  with milling head  27 : Axis x 3  preferably extends parallel to the axis x 1 . The tool housing  26  plus carriage  26 . 1 ,  26 . 2  is also arranged horizontally to the working spindle  22 . 1  and the relative distance towards one another can be changed in that a relative displacement is performed parallel to the x 3 , y 3  axes. The two axes x 1 , x 3  can preferably be offset against another laterally (in the plane of projection). Carriage  26 . 1  can be displaced parallel to the y 3  axis for this purpose. Preferably, the two axes x 1 , x 3  can also be offset against each other in the depth (perpendicular to the plane of projection). Carriage  26 . 1 ,  26 . 2  can be displaced parallel to an optional z 3  axis for this purpose. 
     It is also possible to associate the tool housing  26  with milling head  27  to another system of coordinates and to arrange the axes of such system of coordinates differently. In this case, the CNC controller  28  needs to take a coordinate transformation into account in order to enable the coordination of sequences of movements between the different coordinate systems. 
     During the gear-tooth forming, an angle W can be set and changed between the two axes B 1  and B 3 , as shown in  FIG. 2  where the angle is approximately 40°. An angular adjustability in the range from W 1  to W 2  is preferably possible. W is usually not set to a fixed value, but is changed during the milling. 
     According to an embodiment of the invention, the working spindle  22 . 1  for receiving the workpiece blank K 1  comprises a clamping or grasping means in order to enable clamping of the workpiece blank/gear blank. An embodiment is especially preferable where the clamping or grasping means is designed for automatic mounting. 
     The tool base  24  of apparatus  20  is preferably equipped with a tool turret  25 . 2  which can receive several tools. An embodiment is especially preferable in which at least one of the tools which is located in the multifunctional tool head  25  or in the tool turret  25 . 2  can be driven individually. The tool turret  25 . 2  itself can be rotated about an axis B 4 , as indicated by the double arrow  25 . 4 . 
     The tool base  24  can be used for turning, fluting, drilling, etc. 
     The multifunctional tool holder  25  shows in the illustrated embodiment several tool holders. Three tools  25 . 1  to  25 . 3  are present in the illustrated embodiment. The multifunctional tool holder  25  is preferably arranged in such a way that at least one of the tool holders is arranged as a spindle head in order to enable driving the respective tool individually. The tool  25 . 3  can concern a drill or a milling head which can be made to rotate about its longitudinal axis. The tools  25 . 1  and  25 . 2  can be tool turrets, lathe tools or deburring heads which are each fixedly clamped in a tool holder of the multifunctional tool holder  25 . 
     The apparatus  20  can be modified and adjusted to the parameters accordingly. 
     An apparatus  20  is especially preferable which is characterized in such a way that the apparatus  20  comprises a CNC controller  28  which is designed in such a way that the turning machine  22 , the tool base  24  and the tool holder  25  can be operated as a functional unit together with the tool housing  26 . The advantage of the fact that there is only one CNC controller which is located in the turning lathe  21  or is designed for operation with the lathe  21  is that the apparatus  20  can thus be realized in a more cost-effective way. These savings in cost are mainly realized in such a way that bevel gear milling with the milling head  27  does not require a separate CNC controller  28 . Moreover, the linkage of the axes is less complex and the coordination of the individual sequences of movements on apparatus  20  will become simpler. 
     A further embodiment is shown in  FIG. 3 . This embodiment is based on the principle of the invention as described above. Insofar as useful, the same reference numerals will be used in  FIG. 3 . 
       FIG. 3  shows an apparatus  30  in which the multifunctional tool holder  34  also acts as a tool housing  36  for a milling head  27 . The carriage  24 . 2  can be rotated about a perpendicular axis B 5 , as indicated by the double arrow  29 . 3 . The milling head  27  can thus be turned to position  27 ′ as shown schematically in  FIG. 3 . Bar cutters on the milling head  27  can then perform the milling of the gear blank K 1 . During this milling, both the milling head  27  is turned about its axis B 3  as well as the gear blank about the axis B 2 . During machining by turning, which precedes milling for example, one of the other tools  25 . 1  or  25 . 3  can be used. Control is carried out by a CNC controller  38  which is provided with a different configuration than the controller  28  in  FIG. 2  due to the slightly different arrangement of the axes and the integration of the milling head  27  in the tool holder  34 . 
     An embodiment is especially preferable in which the tool housing  26 ,  36  or  46  is configured for dry milling of bevel gears or milling with minimal quantities of lubricant (MQL). 
     Tools made of high-duty steel, hard metal, ceramics or cermet (combination of metal and ceramics) with a respectively suitable hard solid coating are used according to the invention for gear-tooth machining by bevel gear mills depending on the hardness of the tool. 
     It is regarded as an advantage of the present invention that a workpiece, without having to be re-chucked, can be machined from the blank to the finished bevel gear. It thus concerns a virtually very compact production line which through special measures can be realized in the smallest possible space and made available at affordable prices.

Technology Classification (CPC): 8