Abstract:
The invention relates to a gear cutting machine for the grinding of external profiles and/or internal profiles of workpieces having at least one machining head which can be rotated about an axis and which has a grinding tool, and having a dressing unit. In accordance with the invention, the dressing unit is supported in the region of the pivot axis of the machining head such that it is pivotable about the common pivot axis together with the machining head and such that it can be moved along the pivot axis toward the grinding tool to be dressed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a gear cutting machine for the grinding of internal profiles or external profiles of workpieces having a machining head, which is arranged on a pivotable installation surface and which provides a grinding tool, and having a dressing unit, in particular a common dressing unit, for the dressing of the grinding tool of an installed external or internal grinding head. A worm grinding wheel or a grinding disc can be used as the grinding tool here, for example. 
         [0002]    To achieve or to maintain an exact true running and the correct geometrical shape of the grinding tool, the grinding tool has to be shaped and sharpened at different intervals by means of dressing. In addition, the dressing serves to true and/or calibrate a grinding tool. It also has the purpose of breaking out contaminants, and grain layers which have become blunt, out of the abrasive wheel and thus to expose sharp grains. It is desirable in this respect that this procedure of dressing by a suitable dressing tool can be carried out, where possible in the grinding machine, optionally during the grinding process. This so-called continuous dressing is a special form of dressing. 
         [0003]    DE 297 17 193 U1 describes a grinding head for the manufacture of internal profiles of gears.  FIG. 1  there shows a complete machine having an internal grinding head which can be pivoted to and fro between a working position and a dressing position by a pivoting device. In detail,  FIG. 2   a  shows the machining position in which an internal profile of a gear can be machined. In order now to dress the grinding disc, the arm is pivoted upwardly and rearwardly in the direction of the grinding head fastening and is dressed there by the dressing wheel. The disadvantage of this embodiment is the necessity of a pivot axle so that the position of the grinding disc at the time of dressing and at the time of grinding differ and the precision of the pivot bearing can thus enter into the grinding result. A further disadvantage of this invention is the circumstance that the length of the grinding arm and thus the maximum grindable width of the internal toothed arrangement is limited by the pivot mechanism. 
         [0004]    DE 103 29 724 B4 relates to a grinding head for the manufacture of internal profiles. In this respect, a special internal grinding head having the associated dressing device is described. The dressing device is in this respect movable relative to the grinding disc in the vertical direction and the grinding disc is movable relative to the dressing direction in a direction disposed transversely to the vertical direction of the grinding disc. It is a disadvantage of this invention that the dressing device is only usable for the internal grinding head and the grinding angle of the grinding disc has to be moved back into a basic position for the dressing during the grinding process. 
       SUMMARY OF THE INVENTION 
       [0005]    It is therefore the object of the present invention to provide a gear cutting machine for the grinding of internal and external profiles with straight and slanting toothed arrangements which is equipped with a dressing unit for the external dressing and internal dressing of profiles and which avoids the disadvantages of the above-described gear cutting machines. Furthermore, a pivoting of the grinding tool into a basic position for the dressing thereof should no longer be necessary. It is likewise the object of the present invention to provide the skilled person with an improved method for the dressing of a grinding tool for an internal profile or an external profile. 
         [0006]    This object is achieved by a gear cutting machine for the grinding of external profiles or internal profiles having the features herein. The gear cutting machine accordingly has a machining head, which is arranged on an installation surface and which provides a grinding tool, and in particular has a common dressing unit for the dressing of the grinding tool of an installed external or internal grinding head, with the gear cutting machine having a swivel bearing for the pivoting of the grinding tool and the dressing unit being supported at the rotation center of the pivot axis and being pivotable about the common pivot axis together with the grinding tool. 
         [0007]    By the pivoting of the dressing unit together with the grinding tool, it is no longer necessary to pivot the grinding tool back into a specific position, i.e. into a basic position, for the dressing. It is thus not necessary with the gear cutting machine in accordance with the invention to provide an additional pivot axle for the pivoting of the grinding tool in the direction of the dressing unit, whereby it is avoided that the positions of the grinding tool at the time of the dressing and at the time of the grinding differ and thus the precision of the pivot bearing could enter into the grinding result. 
         [0008]    In an embodiment variant, the swivel bearing for the pivoting of the grinding tool and the dressing unit are arranged at the machine body and the grinding tool is pivotable via the pivot axle over the pivotable installation surface and the machining head installed thereon. The advantage results in this respect that a common dressing unit can be used for the dressing of the grinding tool independently of the machining head installed on the installation surface. An internal grinding head installed on the installation surface can, for example, be dressed by the dressing unit of the gear cutting machine and the swapping of the internal grinding head for an outer grinding head does not require any further modification of the dressing unit. This considerably reduces the time effort in the conversion of the gear cutting machine in accordance with the invention in the production of gears. 
         [0009]    An alternative embodiment of the gear cutting machine in accordance with the invention is given in that the swivel bearing for the pivoting of the grinding tool is arranged at the end of the machining head at the grinding disc side and the dressing unit is likewise arranged at the end of the machining head at the grinding disc side, whereby the dressing unit and the grinding tool are pivotable about a common swivel axis. In this respect it is a special embodiment variant of a machining head for the preparation of internal profiles by means of the gear cutting machine in accordance with the invention. In particular with internal toothed arrangements with a larger internal workpiece diameter, the internal grinding head can be built so large that the swivel bearing for the pivoting of the grinding disc can be displaced downwardly from the suspension position of the grinding head into the tip of the internal grinding head. Furthermore, in this embodiment of the invention, the dressing device can be positioned within this pivot axle. A continuous dressing process can thereby also be carried out during the grinding of an internal toothed arrangement. 
         [0010]    The dressing unit is advantageously movable in a linear manner from the center of rotation of the pivot axis toward the respective grinding tool for the dressing. In this respect, the dressing unit is moved, starting from the center of rotation, that is, in the specific case from the swivel bearing, along the axis of rotation in the direction of the grinding tool. In this respect, only a movement of the dressing unit is required for the dressing of the grinding tool so that the grinding tool does not have to be moved out of its original machining position. Inexactness in the return movement of the grinding tool from a dressing position into the machining position can thereby be avoided. 
         [0011]    In a further advantageous manner, the dressing unit is movable in the axial direction of the grinding disc or worm grinding wheel. The dressing unit can thereby be moved laterally toward the corresponding grinding tool until the dressing unit contacts the surface of the grinding tool. 
         [0012]    It is also conceivable in this respect that the grinding tool is additionally movable along its axial direction in the direction of the dressing unit. However, this only represents an alternative to the moving of the dressing unit in the axial direction of the grinding tool, with an attempt preferably being made to hold the grinding tool constant at its processing position. Due to this preferred embodiment of the gear cutting machine in accordance with the invention, the grinding tool does not have to be moved out of its machining position for dressing, whereby inexactness in the machining of the workpiece is avoided which can result from the return movement of the grinding tool from the dressing position into the machining position. 
         [0013]    The dressing unit advantageously provides at least one individual dressing wheel. It is conceivable in this respect that two individual dressing wheels can be moved in a linear fashion along the pivot axis to the respective grinding tool and that the two dressing wheels are movable toward the surface of the grinding tool from the right and the left in the axial direction of the grinding tool. The grinding tool can thereby be dressed simultaneously from both sides or on its left flank and on its right flank by the dressing unit. 
         [0014]    The gear cutting machine can have a controller for the grinding of external profiles and internal profiles, said controller permitting an automatic control of the grinding process of external profiles and internal profiles as well as the dressing of the respective grinding tool used. In this respect, the control provides an automatic execution of the machining of a corresponding workpiece, with a dressing process being provided either parallel to the machining process of the workpiece by the grinding tool or the actual machining process being interrupted by the automatic carrying out of a dressing process. 
         [0015]    The controller advantageously has corresponding software for the control of the gear cutting machine, with only one program or program part being necessary for the dressing of a grinding tool for the grinding of an external profile and/or internal profile. It is thereby likewise achieved that, on the replacement of the machining head of the gear cutting machine in accordance with the invention for the grinding of external profiles or internal profiles, no further measures have to be taken for the adaptation of the dressing unit to the replaced machining head. 
         [0016]    The present invention furthermore shows a method which is suitable for the operation of a previously described gear cutting machine for the grinding of external profiles or internal profiles. In this respect, such a method has the following operating phases for the dressing of a grinding tool:
   1. Moving the dressing unit in a linear direction along the pivot axis toward the grinding tool;   2. Moving the dressing wheel or the at least two dressing wheels in the axial direction of the grinding tool;   3. Engaging the dressing wheel or dressing wheels in each case from the right or from the left to the surface of the grinding tool;   4. The movements of 1. and 2. are controlled along the flank line of the grinding tool during the dressing procedure.   Practically any desired contours are possible by a suitable control of the movement of the dressing unit along the two axes. Complicated flank line modifications such as are partly required with profile grinding can thus also be realized.   
 
         [0022]    It is furthermore possible that the grinding tool is additionally moved along an axial direction in the direction of at least one dressing wheel, whereby a time saving results during the dressing process. 
         [0023]    The described method for the dressing of a grinding tool in a gear cutting machine in accordance with the invention is advantageously controlled by an NC controller. The movements which the dresser has to carry out are identical on the dressing of the external disc wheels or internal disc wheels. This provides some advantages in the software since only one program is required for the dressing process. Practically any desired contour can furthermore be realized by the NC control of the two axes of movement of the dressing wheels. 
         [0024]    The grinding tool can be dressed continuously by the dressing unit during the grinding process of an external profile due to the method in accordance with the invention for the operation of the gear cutting machine in accordance with the invention. The advantage is exploited in this respect that the grinding tool does not have to be moved into a dressing position. It is rather the case that the dressing unit is moved toward the grinding tool for the dressing, whereby the grinding tool can be dressed by the dressing unit during a grinding process. This substantial advantage results from the feature of the gear cutting machine in accordance with the invention that the latter has a swivel bearing for the pivoting of the grinding tool and the dressing device is supported at the center of rotation of the pivot axis of the grinding tool and is pivoted about a common axis of rotation together with the grinding tool. The dressing unit is thereby pivoted together with the grinding tool during the machining process of a workpiece, whereby a parallel extent of the two wheels, that is, of the grinding tool and of the dressing wheel, results at all times. 
         [0025]    A few special features have to be observed in the dressing of a grinding tool for the grinding of an internal profile. The grinding tool is advantageously moved upwardly or downwardly out of the toothed arrangement for the further cycling into the next gap during the grinding of the internal profile and the dressing process is controlled such that the grinding disc or worm grinding wheel is always dressed by the dressing unit in the upper part position thereof. An additional pivot movement is also not necessary in this respect since the total internal grinding head and the dressing device are pivoted together. This constructional shape is preferably selected with smaller internal diameters of the toothed arrangement. 
         [0026]    A method in which the grinding tool is dressed continuously by the dressing unit during the grinding process of an internal profile can advantageously be carried out on a gear cutting machine for the grinding of external profiles or internal profiles having a swivel bearing arranged at an end of the machining head at the grinding disc side for the pivoting of the grinding tool. In this respect, the dressing unit integrated in the machining head for the internal gear cutting is moved along into the inner space of the tool to be processed, whereby the continuous dressing process is made possible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Further features, details and advantages of the invention result from the embodiments shown with reference to the drawing. There are shown: 
           [0028]      FIG. 1 : the gear cutting machine in accordance with the invention without an installed machining head; 
           [0029]      FIG. 2 : the gear cutting machine in accordance with the invention with an installed machining head for the grinding of external profiles; 
           [0030]      FIG. 3 : the gear cutting machine in accordance with the invention with an installed machining head for the grinding of an internal profile; 
           [0031]      FIG. 4 : the gear cutting machine in accordance with the invention of  FIG. 2  during a dressing process; 
           [0032]      FIG. 5 : the gear cutting machine in accordance with the invention of  FIG. 3  during a dressing process; and 
           [0033]      FIG. 6 ; a modified embodiment of the gear cutting machine in accordance with the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    The general design of the gear cutting machine will be explained in more detail with reference to  FIG. 1 . It has a machine table  5  for the installation of a tool receiver and a workpiece can be clamped onto said machine table. The machine table  5  is in this respect rotatable about an axis C which is advantageously aligned in a perpendicular manner. Alternatively, however, horizontally aligned workpiece receivers can also be used. The gear cutting machine  1  furthermore has one or more installation surfaces  9  for the installation of a machining head  2 ,  7  (see  FIG. 2  and  FIG. 3  respectively). Either an external grinding head  2  for the machining of the external profile of a workpiece can be installed on the gear cutting machine  1  or an internal grinding head  7  for the machining of the internal profile of a further workpiece (see  FIG. 2  and  FIG. 3  respectively). One or more grinding tools  6 ,  8  can be clamped on the respective machining heads  2 ,  7 . The grinding tools  6 ,  8  are in this respect set into rotation about an axis of rotation B by a motor  11 , with the axis of rotation B of the grinding tools being pivotable in a plane which extends parallel to the axis of rotation C of the machine table  5 . For this purpose, the installation surface  9  and thus the respective machining head  2 ,  7  can be pivoted about a pivot axis A (cf.  FIG. 1 ) which stands perpendicular on the plane in which the axis of rotation B of the grinding tool  6 ,  8  extends and which additionally extends perpendicular to the axis of rotation C of the machine table  5 . The installation surface  9  can furthermore be displaced in a linear manner in the direction of its axis of rotation B, that is, along the arrow V. In addition, the installation surface  9  can be moved in a linear manner in a direction parallel to the axis of rotation C of the machine table  5 , that is, along the arrow Z. The installation surface can furthermore be moved in a linear fashion in a direction perpendicular to the axis of rotation C of the machine table  5 , that is, along the arrow X to move the grinding tools  6 ,  8  toward a workpiece clamped in the workpiece receiver installed on the machine table  5  or away therefrom or to achieve direct corrections. 
         [0035]    The gear cutting machine  1  in accordance with the invention furthermore has a dressing unit  3  which can dress the grinding tool  6 ,  8  of the machining head  2 ,  7  independently of the installed machining head  2 ,  7 . In this respect, the dressing unit  3  can be pivoted together with the installation surfaces  9  or the installed machining head  2 ,  7  about the pivot axis A which stands perpendicular on the plane in which the axis of rotation B of the grinding tool  6 ,  8  extends and which extends perpendicular to the axis of rotation C of the machine table  5 . Furthermore, the dressing unit  3  arranged on the pivot axis A can be moved along the pivot axis A in the direction of the arrow X 2  in a linear manner to the respective grinding tool  6 ,  8  for dressing. It is arranged on an axial carriage  14  for this purpose. In this respect, the installation surface  9  has an opening  13  through which the dressing unit  3  can be moved starting from the machine stand  12  along the pivot axis A in the direction of the installed grinding tool  6 ,  8 . 
         [0036]    The dressing unit  3  furthermore provides two individual dressing wheels  4  which are set into rotation by a further motor about an axis of rotation parallel to the axis of rotation B of the grinding tool  6 ,  8  used. It is ensured by the gear cutting machine  1  in accordance with the invention that the axis of rotation of the grinding tool  6 ,  8  and of the dressing wheels  4  extend parallel to one another at all times independently of the degrees of freedom of the machine movement. An undesired pivot movement on the moving between the machining position and the dressing position is thereby avoided. In addition, the two dressing wheels  4  can be displaced along the axis V 2  ( FIG. 2 ), with the two dressing wheels  4  being able to be moved in the direction V 2  together or separately. 
         [0037]      FIG. 2  shows the gear cutting machine  1  with an external grinding head  2  installed on the installation surface  9 . In this respect, the outer grinding head  2  has a grinding tool  6  which serves the grinding of the external profile or of the external toothed arrangement of a corresponding workpiece clamped in a workpiece receiver installed on the machine table  5 . In this respect, the grinding tool  6  used is set into a rotating movement around the axis of rotation B by the motor  11 . It can furthermore be seen from  FIG. 2  that the gear cutting machine  1  is in a grinding machining process. The dressing unit  3  in accordance with the invention is in this respect in a moved in state in which the dressing unit  3  is positioned in direct proximity to the machine body behind the installation surface  9  and behind the opening  13 . 
         [0038]    In  FIG. 3 , the gear cutting machine  1  in accordance with the invention is shown with an internal grinding head  7  installed on the installation surface  9 . In this respect, the installation surface  9  and the installed internal grinding head  7  are pivoted counter clockwise about the pivot axis A. The dressing unit  3  is likewise in the moved in state behind the installation surface  9 , with it being able to be seen that the dressing unit  3  is likewise pivoted counter clockwise about the pivot axis A synchronously with the internal grinding head  7 . The circular surfaces of the dressing wheels  4  and of the grinding disc  8  are thereby located on parallel planes. 
         [0039]    The method in accordance with the invention for the dressing of the grinding tool  6 ,  8  of an internal grinding head or external grinding head will be explained with reference to  FIGS. 4 ,  5 . In this respect,  FIG. 4  shows the dressing unit  3  moved in the direction X 2  along the pivot axis A toward the grinding tool  6 . Furthermore, the two dressing wheels  4  were moved along the axis V 2  in each case from the right and/or left toward the surface of the grinding tool  6 . The dressing process of the grinding tool  6  now takes place by the rotational movement about the axes of rotation B of the dressing wheels  4  and of the grinding tool  6  extending in parallel. Practically any desired contours are produced by means of an implemented NC control by specific movements of the dressing wheels along the directions V 2 , X 2 . Complicated profile modifications such as are required in part in profile grinding are thus also possible. 
         [0040]    The corresponding dressing process of the gear cutting machine  1  is shown in  FIG. 5  for an installed internal grinding head  7 . 
         [0041]    If the two axes of rotation B of the individual grinding tools  6  and  8  respectively of the two machining heads  2 ,  7  are identical, that is, if they have the identical location in space, the movements which the dressing unit has to perform are identical in the dressing of the external grinding discs or internal grinding discs. This provides some advantages for the preparation of the control software since only one program is required for the dressing process. 
         [0042]    In the embodiment variant of the gear cutting machine  1  in accordance with the invention having an installed external grinding head  2  shown in  FIG. 4 , a continuous dressing process is possible during the grinding process. 
         [0043]    In the gear cutting machine  1  in accordance with the invention having an installed internal grinding head  7 , some special features must be observed in the dressing of the internal grinding disc  8 , as can be seen in  FIG. 5 . In this respect, on internal profile grinding in the individual part process, the grinding tool  8  is moved upwardly or downwardly for the further cycling into the next gap, that is, along the arrow direction Z, out of the toothed arrangement so that the grinding tool  8  does not collide with the tooth flank. If the dressing process is controlled so that dressing also always takes place in the upper part position, only slight additional paths upwardly are required to provide sufficient free space for the dressing unit  3  above the workpiece. An additional pivot movement is not necessary since the total internal grinding head  7  and the dressing unit  3  are pivoted together. 
         [0044]      FIG. 6  shows an alternative embodiment variant of the gear cutting machine  1  in accordance with the invention having a large internal grinding head  7  with a grinding tool  8  clamped on. The same components as in the previously described embodiments have the same reference numerals in  FIG. 6 .