This application claims priority under 35 U.S. C. §§119(a)-(d) to German patent application no. 10 2016 006 070.0 filed May. 19, 2016 which is hereby expressly incorporated by reference as part of the present disclosure.
The present invention relates to grinding machines fitted with a pivotable tool spindle. At least some grinding machines are concerned whose tool spindle is fitted with a grinding screw for grinding gearwheel workpieces.
The workpiece to be ground is not shown in
In order to intercept unequal torques which act on the tool spindle 120 in this known configuration, the pivot plate, or the pivot axis A, can be mechanically clamped during the grinding of the workpiece. In this case, the pivot axis A can be used only as a setting axis. This means that the pivot axis A cannot be used dynamically, but only statically.
If one wishes to use the pivot axis A as a moving axis during grinding, mechanical clamping is not useful. In this case, a drive motor is required which keeps the pivot axis A in position and can also move it dynamically. The size of the drive motor depends on the torque to be applied. This temporary retaining can be effected, for example, in such a way that the drive motor, which serves to pivot the pivot plate, predetermines a correspondingly large holding current. However, the predetermination of a holding current increases the power consumption of the grinding machine.
It is the object of some of the embodiments of the invention to provide a technical approach for operating a grinding machine which allows the pivot axis to be operated dynamically. In addition, the grinding machine should be economical to purchase and operate.
The object is achieved according to some of the embodiments of the invention by a grinding machine with a pivotable tool spindle according to claim 1.
Some embodiments of the invention are based on the approach of changing the overall constellation of the grinding machine in such a way that the pivot axis, which is used for pivoting the tool spindle, is arranged laterally offset with respect to the workpiece spindle axis.
In addition, a constellation might be selected in which the pivot axis for pivoting the tool spindle lies in the region of the mass center point of the combination of tool spindle and tool.
These two aspects are combined with one another in at least some embodiments in such a way that the pivot axis is arranged laterally offset with respect to the workpiece spindle axis, and that the pivot axis lies in the region of the center of mass of the combination of the tool spindle and the tool.
At least some embodiments in which the pivot axis directly or indirectly carries a shift axis have an asymmetric shift path of the shift axis.
The grinding machine of some of the embodiments comprises a pivotable tool spindle and is provided with a workpiece spindle adapted to receive a gearwheel workpiece and to rotationally drive the gearwheel workpiece about a workpiece spindle axis. The tool spindle is designed/configured for accommodating a grinding tool and for rotationally driving the grinding tool about a tool spindle axis and is supported by a pivot axis such that the tool spindle together with the grinding tool can be pivoted about the pivot axis. In at least some embodiments, the pivot axis can carry a shift axis directly or indirectly. However, embodiments are also possible which operate without an actual shift axis. In such embodiments, the shift movement parallel to the tool rotation axis is typically generated by the superimposed movement of other linear axes. In this case, the pivot axis is supported directly or indirectly by one or more linear axes.
The grinding machine of some of the embodiments is wherein the pivot axis is offset laterally relative to the workpiece spindle axis and therefore the pivot axis and the workpiece spindle axis do not intersect.
The fact that the pivot axis and the workpiece spindle axis do not intersect can also be expressed as follows. The pivot axis and the workpiece spindle axis cross each other in the three-dimensional space and they only intersect when the pivot axis is projected into the plane of the workpiece-spindle axis planes.
The tool spindle, including the grinding tool in some of the embodiments, has a center of mass which lies directly in the region of the pivot axis. If the pivot apparatus of the pivot axis does not support a shift axis, then the center of mass is a static point that is fixed with respect to the tool spindle, including the grinding tool. If the pivot apparatus of the pivot axis carries a shift axis, then the center of mass is a point which can shift depending on the shift position of the tool spindle and the grinding tool.
If the center of mass is directly in the region of the pivot axis, a balanced constellation of the tool spindle and the tool is obtained. A balanced constellation is designated as an arrangement in which the pivot axis lies exactly in the central center of mass of the pivot apparatus, including the tool spindle and the grinding tool, or the pivot axis lies directly in the region of the center of mass.
It is a significant advantage of some of the embodiments that the drive of the pivot axis can be dimensioned smaller than before, since it is only necessary to compensate for smaller torques. The drive of the pivot axis can be designed smaller, which leads to an improved energy efficiency of the machine.
It is a further advantage of some of the embodiments that, due to the balanced constellation of the tool spindle and tool, no holding forces or smaller holding forces are required for holding the pivot axis. The balanced constellation of some of the embodiments provides an additional degree of freedom which makes it possible to carry out pivoting movements at any time, wherein the corresponding drive can be smaller-dimensioned than in previous solutions. At least some embodiments of the invention thus make possible the transition from a machining approach that has hitherto been static in nature to a dynamic machining approach.
Some of the embodiments can be used for example in gear grinding machines.
Some of the embodiments can be used above all in gear grinding machines which are designed for the grinding machining of straight and helical teeth. In particular, this concerns grinding machines which are designed for continuous rolling or profile grinding.
Some of the embodiments can be used above all in gear grinding machines which are designed for the grinding machining of workpieces which are arranged in the gear grinding machine on a workpiece spindle with a vertical axis of rotation and which comprise a tool spindle with a grinding tool (in at least some embodiments with a grinding worm) which can be pivoted about a pivot axis standing perpendicularly to the workpiece spindle axis.
It is a further advantage of some of the embodiments that the machine width can be provided with a smaller dimension if the tool spindle with a grinding tool is arranged offset to the left for example. This is because the relatively long end of the grinding spindle, or the housing of the grinding spindle, protrudes less far above the carriage of the shift axis.
The shift axis is arranged symmetrically to the workpiece spindle axis in at least some embodiments.
The carriage width of the shift axis can be reduced in at least some embodiments.
The carriage width, or the shift path of the shift axis, can be asymmetric in at least some embodiments.
Within the scope of the present description, terms are used which are also used in relevant publications and patents. It should be noted, however, that the use of these terms is intended only for better understanding. The inventive concepts are not to be limited by the specific choice of the terms. At least some embodiments of the invention can be transferred without further ado to other conceptual systems and/or subject areas. In other areas, the terms can be applied mutatis mutandis.
On the basis of the initially described
The concept of the center of mass MP as used herein refers to the point in which the weight of those parts of the tool spindle 120, together with the tool 20, which are to the right of the center of mass MP are the same as the weight of those parts of the tool spindle 120, together with tool 20, which are to the left of the center of mass MP. The center of mass MP is thus the mean value weighted by the mass of the positions of all mass points of the tool spindle 120 together with the tool 20.
In other words, the tool spindle 120 together with the tool 20 is in an exactly balanced state when an axis perpendicular to the drawing plane of
If a pivoting table 122 is used as a pivoting device which carries a shift axis and a tool spindle 120 together with a tool 20, the center of mass MP is the mean value weighted with the mass of the positions of all mass points of the pivoting table 122, the shift axis, the tool spindle 120 and the tool 20.
A first example of an embodiment will now be described with reference to
The two steps which led to the constellation according to at least some embodiments of the invention are explained with reference to
A=MP.
More generally, the passage of the pivot axis A can lie directly in the region of the central center of mass in at least some embodiments. Therefore the more general statement applies:
A˜MP.
It can be recognized with respect to
Furthermore, if possible, the tool 20 should be arranged centrally with respect to the workpiece 10 to be ground, so that all regions of the workpiece 10 can be easily reached and machined with all regions of the tool 20. Therefore, an axis offset ΔA2 is provided as described below.
The offset between the conventional position of the tool spindle 120 in
Instead of selecting an overall constellation, in which the pivot axis A and the workpiece spindle axis C continue to intersect (as shown in
According to at least some embodiments of the invention, an overall constellation is provided for at least some embodiments in which the pivot axis A has a lateral offset ΔA2 relative to the workpiece spindle axis C, as can be clearly seen in
However, the pivot axis A and the workpiece spindle axis C always intersect in a common plane projection. The plane projection mentioned here stands perpendicularly to the drawing plane. The corresponding plane can be the plane, for example, in which the workpiece spindle axis C lies.
In at least some embodiments, the pivot axis A extends perpendicularly to the workpiece spindle axis C in the mentioned plane projection, as can be seen in
In at least some embodiments, in order to enable a grinding machining of a gearwheel workpiece 10 (a straight spur gear 10 is shown by way of example in
Therefore, a shift axis Sh is used in at least some embodiments, which is designed for the transverse displacement of the tool spindle 120 together with the grinding tool 20 in a vertical plane which stands perpendicularly to the pivot axis A. The transverse displacement is performed along a shift path Shw. In the representations of
In
In at least some embodiments, the shift axis Sh is designed as a linear carriage 124, which can comprise two linear guides 123 for example, as indicated in
In addition to the transverse displacement along the shift path Shw, which is made possible here by means of the shift axis Sh, further controlled movements in the three-dimensional space are typically required. In principle, this involves relative movements of the grinding tool 20 with respect to the gearwheel workpiece 10. It is irrelevant for at least some embodiments of the invention whether, for example, the grinding tool 20 is moved and the gearwheel workpiece 10 is rotationally driven only about the workpiece spindle axis C, or whether the also gearwheel workpiece 10 can carry out (linear) movements for example.
A preferred constellation of a grinding machine 100 of an embodiment is shown in
In addition, in at least some embodiments, the grinding machine 100 can have three further axes X, Y, Z which are designed as linear axes.
A first of these further axes, referred to here as a Y-axis, extends in the example shown parallel to the workpiece spindle axis C, as shown in
The Y-axis is used to perform a stroke (grinding stroke parallel to the C-axis). The Y-axis can be integrated in at least some embodiments into the machine stand 101, which also carries the tool spindle 120, as shown in
A second one of these further axes, referred to here as the Z-axis, extends, for example, parallel to the pivot axis A. In the representation of
The X-axis of such a grinding machine 100 can extend parallel to the drawing plane. In the illustrated snapshot, the tool spindle axis B lies parallel to the X-axis. If the shift axis Sh is located on the pivot plate 122, as shown in
The three further axes X, Y, Z form a Cartesian coordinate system in at least some embodiments, as shown in
Depending on the embodiment, the pivot axis A, or the pivot plate 122, can carry a plurality of components. In the embodiments according to
In the comparison of
If, on the other hand, the axis Sh (in this case, the axis Sh is not a shift axis in the actual sense but a linear axis) carries the pivot plate 122 together with the tool spindle 120 and the tool 20, the components of the axis Sh do not need to be considered in the determination of the center of mass MP. In this case, the corresponding center of mass MP is also referred to as a static center of mass MP.
In embodiments with a static center of mass MP, it can be advantageous to combine the passage of the pivot axis A in the design of the machine 100 with the center of mass MP, as already described. In embodiments with a moving center of mass MP, it can be advantageous to lay the passage of the pivot axis A into the displacement range of the center of mass MP when designing the machine 100, as shown in
Since the pivot axis A according to at least some embodiments of the invention does not intersect with the workpiece spindle axis C (except possibly in the mentioned temporary special case), a certain asymmetry of the tool spindle 120, or of the tool 20, relative to the workpiece spindle axis C is obtained. This asymmetry can be compensated for in at least some embodiments in such a way that the shift axis Sh is designed for the asymmetrical transverse displacement of the tool spindle 120 together with the grinding tool 20 with respect to the pivot axis A. If the shift axis Sh enables movements of ±150 mm for example in one embodiment of the prior art, the shift axis Sh can allow a movement of +150 mm to the left and a movement of −120 mm to the right in some embodiments. These are merely examples of numbers.
Due to the balanced arrangement, the means for holding can be smaller in size because smaller torques are to be compensated.
In order to illustrate the effect of at least some embodiments of the invention graphically, the numerical examples of a conventional machine constellation were compared with the numerical examples of a machine constellation according to embodiments of the invention in
In
In an ideally balanced constellation, the values of the positive and the negative torque DM are the same. In order to remain at similar numerical values as in
The quality of the balancing can thus be defined for example via the torque values. The smaller the amount-related difference ΔDM of the torque values is, the better the constellation is balanced. At ΔDM=0, the constellation is ideally balanced.
According to at least some embodiments of the invention, the center of mass MP is then directly in the region of the pivot axis A if at least one of the following conditions is fulfilled (the figures in brackets refer to the numerical example in
In at least some embodiments, the conditions B1 and/or B2 are applied to constellations in which the pivot axis A does not carry a shift axis Sh (see
In at least some embodiments, the conditions B2 and/or B3 and/or B4 are applied to constellations in which the pivot axis A carries a shift axis Sh (see
With respect to
As may be recognized by those of ordinary skill in the pertinent art based on the teachings herein, numerous changes and modifications may be made to the above described and other embodiments of the present invention without departing from the spirit of the invention as defined in the claims. Accordingly, this detailed description of embodiments is to be taken in an illustrative, as opposed to a limiting sense.
Number | Date | Country | Kind |
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102016006070.0 | May 2016 | DE | national |