TW202228884A - Tool head with balancing devices - Google Patents

Abstract

A tool head (300) for a gear cutting machine includes a first spindle unit (320) having a first spindle shaft (322) and a second spindle unit (330) having a second spindle shaft (332). A tool (340) is axially receivable between the first spindle shaft and the second spindle shaft. A balancing device (350, 360) is associated with each spindle unit. The balancing device radially surrounds the respective spindle shaft and is axially arranged between a tool-side spindle bearing (323, 333) of the corresponding spindle unit and the tool-side end of the corresponding spindle shaft. The tool is axially clamped between the two spindle shafts by a pull rod (370) and a clamping element (372).

Description

Tool head with balancing device

The present invention relates to tool heads. The invention further relates to a machine tool having such a tool head.

Many machine tools (Werkzeugmaschinen) use rotary tools. In order to achieve high-quality machining results, it is necessary to balance the tool, ie to eliminate the imbalance. This applies in particular to gear cutters, ie machines for machining gears.

Unbalance refers to a situation in which the axis of rotation of a rotating body does not correspond to one of its principal axes of inertia. There is a difference between static unbalance and dynamic unbalance. In most cases, both forms will occur at the same time. Static unbalance occurs when the axis of rotation does not pass through the center of gravity of the rotating body. When the main body rotates, the static imbalance will cause the circular motion of the main body's center of gravity. Dynamic unbalance occurs when the axis of rotation at the center of gravity is tilted relative to the main axis of inertia. Dynamic unbalance can cause a 180° shift in the circumferential vibration at the end of the axis. The center of gravity of the rotating body remains stationary, while the axis oscillates due to the opposite circular motion. If the axis is fixed by the bearing, a corresponding load will be generated on the bearing.

Tool imbalance can lead to reduced manufacturing accuracy during workpiece machining, poor surface quality, and increased tool wear. Also, bearing damage may occur. The purpose of balancing is to limit tool vibration and bearing forces to acceptable values.

Particular challenges arise when tools with small diameters are to be balanced. In particular, tools with small diameters are increasingly used in gear manufacturing. In order to achieve the desired cutting speed, such knives typically operate at relatively high rotational speeds. Since the unbalance force increases in proportion to the square of the rotational speed, extremely high unbalance forces can occur. At the same time, such tools are generally relatively long relative to their diameter. Therefore, the bending moment caused by dynamic unbalance has a particularly strong influence.

It is known from the prior art to minimise the imbalance on the rotating tool by suitable balancing means. The balancing device is usually arranged inside the tool, as shown in Figure 1 of EP3153277A1. However, such configurations have limitations when small diameter tools are to be used. Consequently, the space available inside the tool is often no longer sufficient to install a sufficiently efficient balancing device.

In order to solve this problem, EP3153277A1 proposes to accommodate the tool between the motor main shaft and the non-driven sub-spindle, and to integrate the balancing device in the shaft parts of the motor main shaft and the sub-spindle. The disadvantage of this solution is that the balancing device is relatively far from the tool, and from the bearing positions of the main and sub-spindles of the motor close to the tool. Also, there is often not enough free space available in the shafts of the motor main and sub-spindles to install an efficient balancing system.

It is an object of the present invention to provide a tool head that can be used with small diameter tools and that allows efficient balancing of such tools.

This object is solved by the tool head as in technical solution 1. Other embodiments are given in the accompanying technical solutions.

Accordingly, a tool head for a machine tool, especially a gear cutting machine, is disclosed. The tool head has: a first spindle unit having a first spindle shaft member mounted in the first spindle unit so as to be rotatable about a tool spindle axis; a first balancing device associated with the first spindle unit; a second spindle unit having a second spindle shaft member mounted in the second spindle unit so as to be rotatable about the tool spindle axis; A second balancing device is associated with the second spindle unit.

The first spindle unit and the second spindle unit are arranged coaxially with respect to each other, so that the tool can be axially accommodated between the first spindle shaft and the second spindle shaft. According to the invention, the first balancing device radially surrounds the first spindle shaft and is arranged axially between the tool-side spindle bearing of the first spindle unit and the tool-side end of the first spindle shaft, and/or the first spindle shaft The two balancing devices radially surround the second spindle shaft and are axially arranged between the tool-side spindle bearing of the second spindle unit and the tool-side end of the second spindle shaft.

Thus, when the tool is housed between the first and second spindle shafts, the first and/or second balancing device is arranged outside the respective spindle shaft and axially to the tool of the associated spindle unit between the side spindle bearing and the tool. The proposed configuration makes it possible also to balance knives with small diameters efficiently. By arranging at least one of the balancing devices, preferably both balancing devices, around the spindle shaft, much more space is available for the balancing element than if the two balancing devices were arranged inside the tool or inside the spindle shaft. Thus, even relatively large imbalances can be corrected. By arranging the corresponding balancing device axially between the tool side spindle bearing and the tool, the balancing device is used to balance the position close to the tool and the position of the corresponding bearing. This achieves a very precise balance.

A respective spindle unit will usually contain more than one spindle bearing. The term "tool-side spindle bearing" should then be understood in relation to the spindle bearing arranged along the axis of the tool spindle at the position closest to the tool in the respective spindle unit.

In detail, the configuration of the balance plane relative to the bearing planes of the two spindle units can be as follows: the tool-side first spindle bearing defines a first bearing plane perpendicular to the tool spindle axis, and the tool-side second spindle bearing defines a tool-side second spindle bearing that is perpendicular to the tool spindle. The second bearing plane of the axis. The first balance device defines a first balance plane perpendicular to the tool spindle axis, and the second balance device defines a second balance plane perpendicular to the tool spindle axis. Then preferably, the first balance plane is arranged between the first bearing plane and the second balance plane (especially closer to the first bearing plane than the second balance plane), and/or the second balance plane is arranged on the second balance plane Between the bearing plane and the first balance plane (especially closer to the second bearing plane than the first balance plane).

When the tool is housed between the two spindle shaft members, the tool defines a center of gravity plane perpendicular to the axis of the tool spindle, the center of gravity plane including the center of gravity of the tool. The first balance plane is then preferably located between the first bearing plane and the center of gravity plane, and/or the second balance plane is preferably located between the second bearing plane and the center of gravity plane. Preferably, the respective balance plane is closer to the corresponding bearing plane than the center of gravity plane.

This balanced plane configuration enables efficient dual plane balancing.

In a preferred embodiment, the first balancing device and/or the second balancing device are configured as a ring balancing system. Ring balancing systems have long been known in the prior art (see eg DE4337001A1, US5757662A), and enable extremely precise automatic balancing without stopping the rotation of the main shaft. In various embodiments, it is commercially available. However, another type of balancing system may alternatively be used, such as a balancing system with a counterweight that can be moved by an electric motor or a hydraulic balancing system.

The balancing device can be configured to operate in a numerically controlled (NC) manner. For this purpose, the first and/or second balancing device may comprise at least one actuator for numerically adjusting the corrective imbalance of the relevant balancing device.

At least one vibration sensor may be provided on the tool head for detecting vibration caused by unbalance. This sensor can be integrated into one of the balancing devices or can be configured separately. The tool head may further have a control device associated with this sensor, the control device being configured to detect signals from the at least one vibration sensor, and to control one of the first balance device and/or the second balance device An actuator to adjust the corrective imbalance in the first balancing device and/or the second balancing device depending on the detected signal. This adjustment can be automatic, reducing imbalance. Preferably, the control device is configured to perform automatic dual plane balancing. Correspondence algorithms are well known from the prior art. The control device may be part of the machine control system, or may be a separate unit.

Preferably, the first balancing device and/or the second balancing device are arranged outside the casings of the respective spindle units. In detail, the first spindle unit may include a first housing, and the second spindle unit may include a second housing. The first balancing device and/or the second balancing device are then preferably arranged outside the first and second housings. Alternatively, the first spindle unit and the second spindle unit may comprise a common spindle housing, and the first balancing device and/or the second balancing device are then preferably arranged outside the common spindle housing.

In detail, when the tool is accommodated between the first spindle shaft and the second spindle shaft, the first balancing device is preferably axially arranged on the (first or common) spindle housing and the tool enclosing the first spindle unit. and the second balancing device is arranged axially between the (second or common) spindle housing enclosing the second spindle unit and the tool.

Preferably, the outer contour of the balancing device is optimized to minimize disturbing contours when machining the workpiece on the workpiece spindle of the machine. In particular, it is advantageous if the first balancing device and/or the second balancing device have an outer contour that tapers in the direction of the tool.

A significantly improved balancing result can be achieved if the two spindle shafts are axially clamped to the tool so that axial compressive forces act on both sides of the tool. For this purpose, the following design is particularly advantageous: the second spindle shaft has at least one axial bore. The tool head correspondingly comprises at least one pull rod (drag rod) extending through a corresponding axial hole of the second spindle shaft, the pull rod connectable to the first spindle shaft at a first end. The tie rod can be connected to the second spindle shaft at its second end so that an axial compressive force can be created on the tool between the first spindle shaft and the second spindle shaft. For this purpose, the tool also has correspondingly at least one axial hole, so that the respective tie rod can pass through the corresponding hole of the tool.

An axial support of this type results in a unit of two spindle shafts and tools, which is particularly resistant to torsion and bending. The combination of tie rod and clamping element enables high axial compressive forces between the tool and the two spindle shafts. Thus, the aforementioned unit acts as a single shaft. At the same time, this configuration can be extremely compact. This makes this configuration particularly suitable for knives with small diameters.

This configuration is also advantageous when no balancing device is present or when the balancing device is configured differently than described above. In this regard, the present invention also relates to a tool head for a machine tool, especially a gear cutting machine, comprising: a first spindle unit having a first spindle shaft member mounted in the first spindle unit so as to be rotatable about a tool spindle axis; and a second spindle unit having a second spindle shaft member mounted in the second spindle unit so as to be rotatable about the tool spindle axis, wherein the first spindle unit and the second spindle unit are configured such that the tool can be axially accommodated between the first spindle shaft member and the second spindle shaft member, so as to drive the tool to rotate around the tool spindle axis, Wherein the second main shaft shaft member has at least one axial hole, wherein the tool head includes at least one tie rod extending through the axial bore of the second spindle shaft, wherein the tie rod is connectable to the first spindle shaft at the first end, and Wherein the tie rod can be connected to the second spindle shaft at its other end so that an axial compressive force can be generated on the tool between the first spindle shaft and the second spindle shaft.

In this case, it is advantageous that the first spindle unit comprises at least one first spindle bearing, the first spindle shaft is mounted in the first spindle bearing so as to be rotatable about the tool spindle axis, and the first spindle bearing is configured to absorbs both radial and axial forces; and the second spindle unit correspondingly includes a second spindle bearing, wherein the second spindle shaft is mounted in the second spindle bearing so as to be rotatable about the tool spindle axis, and wherein the second spindle bearing Configured to absorb both radial and axial forces.

Preferably, exactly one tie rod extends through the central axial hole in the second spindle shaft member. Therefore, preferably, the tool also has a central axial hole through which the tie rod can pass.

In a particularly simple embodiment, the tie rod can be connected to the first spindle shaft by screwing the tie rod axially into the first spindle shaft. For this purpose, complementary threads (internal and external threads) can be formed on the corresponding ends of the tie rods and on the first spindle shaft. However, other types of connections are also conceivable, such as bayonet-type connections. The pull rod can also extend through the axial hole of the first spindle shaft and be provided at its end with, for example, a nut that pulls the first spindle shaft in the direction of the tool.

The tie rod may advantageously be provided with a clamping element at its free other end, forming an annular contact surface which bears on the second spindle shaft after the tie rod has been connected to the first spindle shaft, and is Axial compressive force is generated on the second main shaft shaft to push the second main shaft shaft in the direction of the first main shaft shaft. In the simplest case, the tie rod can be formed for this purpose as a screw with a screw head, for example. The screw can then be screwed into the first spindle shaft and the screw head can form a clamping element. The axial clamping force is then generated by tightening the screw.

In another, also very simple, embodiment, the draw rod is provided at its free end with an external thread onto which the nut can be screwed. In this case, the nut forms the clamping element and the axial compressive force is generated very easily by tightening the nut.

Preferably, however, the tool head comprises a clamping element which is releasably connected to the draw rod and produces a preferably only axially acting compressive force, while the tightening of the clamping element does not generate a clamping force about the tool spindle axis the torque component. For this purpose, the clamping element comprises a base element, which can be rigidly connected to the tie rod, eg via a screw connection, via a bayonet or via a clamping bush. The base element may have a central receiving opening to receive the tie rod, or (if sufficient space is available) a pin that can be secured in the axial hole of the tie rod. The clamping element further comprises an axial push element, which is axially movable in the direction of the second spindle shaft relative to the base element, in particular axially displaceable, so as to be axially movable in the direction of the first spindle shaft push the second spindle shaft. The axial push element can in particular be annular and surround a central receiving opening or pin of the base element, in which case the axial push element can also be referred to as a "push ring". The axial push element forms the already mentioned annular contact surface. The gripping element further comprises at least one actuating element movable relative to the base element to move the axial pushing element axially relative to the base element. The actuating element can be, for example, a pressure screw, which can be screwed into the base element in the longitudinal or transverse direction. Such clamping elements are known per se from the prior art, and many variants thereof are commercially available.

In some embodiments, the transfer of force from the actuating element to the axial pushing element is only mechanical. For example, the actuating element may be a plurality of capscrews that are held axially on the base element and that can be screwed into the axial pushing element to axially displace the axial pushing element relative to the base element. In other embodiments, one or more fixing screws act as the actuating element, which can be adjusted in the base element via a threaded connection in the direction of pushing the element axially. In still other embodiments, the actuating element acts, for example, on a gear that advances the axially urging element. Such clamping elements are available, for example, under the names ESB, ESG or ESD from the company Enemac, Klein Wallstadt, Germany.

In other embodiments, the transmission of force from the actuating element to the axial pushing element is hydraulic. For this purpose, the actuating element can be configured, for example, as a pressure screw, which, when screwed in, generates a pressure in the hydraulic system, which pressure acts on the axially pushing element. Such clamping elements are commercially available, for example, from the company Albert Schrem Werkzeugfabrik, Heilbrechtingen, Germany.

Instead of generating an axial compressive force between the tie rod and the second spindle shaft by means of a clamping element held on the tie rod during operation, it is also conceivable to first generate the compressive force by means of a clamping tool, fixing the connection by means of a simple nut in the gripping state, and then the gripping tool is removed again.

However, the tool can also be clamped between the first spindle shaft and the second spindle shaft in a manner that is not a continuous tie rod, as long as this results in a firmly clamped unit comprising the two spindle shafts and the tool. Thus, embodiments are conceivable in which the first tie rod can be connected to the tool at the first end, eg, can be screwed to the tool or can be connected via a hollow shank conical connection. The first tie rod can then extend through the axial bore of the first spindle shaft and can be connected to the first spindle shaft at its second end such that an axial direction can be created between the first spindle shaft and the tool compressive force. The second tie rod may be arranged on the opposite side of the tool. This second pull rod can in turn be connected to the tool at the first end, eg screwable to the tool or connectable via a hollow shank conical connection. The second tie rod can then extend through the axial bore of the second spindle shaft and can be connected to the second spindle shaft at its second end such that axial compression can be created between the second spindle shaft and the tool force.

In order to accommodate the tool between the spindle shafts and to be able to transmit torque to the tool, it is advantageous if the spindle nose is formed on the first and/or the second spindle shaft so that the tool can be acted upon by the tool. The axial compressive force with the spindle nose produces a non-positive connection and/or a positive connection (kraftschlüssige und/oder formsschlüssige Verbindung) to the tool at the respective spindle nose. Preferably, the connection to the tool is via a conical connection, more preferably via a conical connection with surface contact. For example, the connection can take place via one of the embodiments A, BF, BM, CF or CM mentioned in DIN ISO 666:2013-12.

It is advantageous if the two spindle noses are configured differently, so that the tool can only be received between the spindle noses in predetermined positions. For example, the diameters of the two spindle noses may be different.

To facilitate tool changing, it is advantageous that the second spindle unit is axially displaceable relative to the first spindle unit. If the two spindle units are accommodated in a common spindle housing, this can be achieved by making the spindle bearing for the second spindle shaft part axially displaceable relative to this spindle housing.

The first and/or second spindle units may include drive motors configured to drive corresponding spindle shafts to rotate about the tool spindle axis, thereby driving the tool. In some embodiments, only the first spindle unit includes a drive motor, and the second spindle unit forms a passive sub-spindle for the first spindle unit without its own drive motor. In other embodiments, the second spindle unit also includes its own drive motor. The respective drive motor may in particular be a direct drive.

The tool head may further comprise the aforementioned tool axially received between the first spindle shaft and the second spindle shaft and preferably axially clamped. The tool may be an abrasive tool, especially a tool for grinding teeth. In more detail, the tool can be a grinding worm or a profile grinding wheel, or comprise at least one grinding worm and/or at least one profile grinding wheel. The tool may be in one piece (eg, in the form of a non-dressable grinding worm with a hard-coated substrate that is received directly between the spindle shaft members), or it may be in two or more pieces (eg, in a dressable Grinding worm or in the form of a combined tool with more than one grinding body, in which one or more grinding bodies are held on separate tool holders that are housed between the spindle shafts).

The invention further provides a machine tool comprising a tool head of the type mentioned above, and at least one workpiece spindle for driving the workpiece in rotation about the workpiece axis. The machine tool can be configured as a gear cutter, in particular as a gear grinder. For this purpose, the machine tool may comprise a machine control system configured, in particular suitably programmed, to cause the machine to machine the gear teeth of the workpiece accommodated on the at least one workpiece spindle with the tool. In particular, the machine control system may be configured such that the machine machined the gear teeth of the workpiece by profile grinding or generation grinding. For this purpose, the machine control system can be configured to establish a suitable rolling coupling between the workpiece spindle and the tool spindle.

definition

Gear Cutter : A machine configured to create or machine gear teeth on a workpiece, especially the internal or external gear teeth of a gear. For example, a gear cutter may be a machine for fine machining that machined pre-toothed workpieces, especially a hard machine that machined pre-toothed workpieces after hardening. Gear cutters include a machine control system programmed to control the automatic machining of gear teeth.

Generating Gear Machining : A type of gear machining in which a tool rolls over a workpiece, creating a cutting motion. Various gear-generating machining procedures are known, whereby a distinction is made between those with geometrically undefined edges, such as grinding or hobbing, and those with geometrically defined edges, such as hobbing, stripping, skiving or shaved teeth.

Generation Grinding : The Generation Grinding procedure is a continuous chip removal procedure with a geometrically undefined cutting edge for producing an axially symmetrical periodic structure in which a grinding wheel with a worm-shaped outer profile ("grinding worm" ) are used as knives. The tool and workpiece are mounted on the rotating spindle. The rolling motion typical of the program is achieved by coupling the rotational movement of the tool and workpiece around the axis of rotation. This rolling motion and the axial feed motion of the tool or workpiece along the workpiece axis produces the cutting motion.

Spindle unit : In machine tool construction, the rotatable shaft that holds the tool or workpiece is often referred to as the "spindle". However, in addition to the rotatable shaft, an assembly that also includes an associated spindle bearing for rotatably supporting the shaft and associated housing is also often referred to as a "spindle". In this document, the term "spindle" is used in this sense. The individual shafts are called "spindle shafts". In addition to the spindle shaft, the assembly containing at least the associated spindle bearings is called the "spindle unit". A "spindle unit" may comprise its own housing, but it may also be housed in a common housing together with another spindle unit.

Tool Head : In this document, the term "tool head" refers to an assembly configured to receive and drive a machining tool in rotation. In particular, the tool head may be mounted on the body of revolution and/or on one or more slides to align and position the tool relative to the workpiece.

Ring Balance System : A ring balance system has two adjacently arranged balance rings that surround and are driven by a shaft. Each gimbal has a predetermined additional unbalance of the same size. The orientation of the balance around the axis of rotation of the shaft is adjustable. If the additional imbalances of the two gimbals are completely opposite, their effects cancel each other out. If both additional imbalances have the same angular position, the maximum balance capability is achieved. By setting other angles, the resulting corrective imbalance can be freely adjusted by magnitude and direction within these constraints. Configuration of an exemplary machine tool

Figure 1 shows an example of a machine tool for hard finishing of gears by generation grinding. The machine comprises a machine bed 100 on which a tool holder 200 is arranged so as to be displaceable in the horizontal feed direction X. FIG. The Z slider 210 is disposed on the tool holder 200 so as to be Z-displaceable along the vertical direction. The Z-slide 210 carries a revolving body 220 which is pivotable relative to the Z-slide 210 about a horizontal axis of rotation A. The axis of rotation A is parallel to the feed direction X. The cutter head 300, shown only symbolically, is disposed on the body of revolution 220 and will be described in more detail below.

Furthermore, a pivotable workpiece carrier in the form of a rotary table 400 is arranged on the machine bed 100 . The rotary table 400 is pivotable between several rotational positions about the vertical axis of rotation C3. It carries two workpiece spindles 500 on which a workpiece 510 can be clamped. Each of the workpiece spindles 500 can be driven to rotate about the workpiece axis. In FIG. 1, it can be seen that the workpiece axis of the workpiece spindle 500 is designated C2. The workpiece axis of the workpiece spindle, which is not visible in Figure 1, is designated as the C1 axis. The two workpiece spindles are located in diametrically opposed positions on the rotary table 400 (ie offset by 180° with respect to the axis of rotation C3). In this way, one of the two workpiece spindles can be loaded and unloaded while a workpiece is machined on the other workpiece spindle. This largely avoids undesirable non-productive time. Such machine concepts are known, for example, from WO 00/035621 A1.

The machine has a machine control system 700 , shown only symbolically, that includes a plurality of control modules 710 and a control panel 720 . Each of the control modules 710 controls the machine axis and/or receives signals from the sensors. Tool head according to the first embodiment

2 to 4 illustrate a tool head according to a first embodiment. The tool head includes a base 310 rigidly connected to the body of revolution 220 . The linear guide 311 is formed on the base 310 . The first spindle unit 320 and the second spindle unit 330 are guided displaceably along the displacement direction Y on the linear guide 311 . For this purpose, the spindle units each have corresponding guide blocks 326 , 336 . The displacement direction Y is perpendicular to the X axis and forms an angle with the Z axis that can be adjusted around the A axis. The tool 340 is held between the spindle units 320 and 330 .

The second spindle unit 320 and the first spindle unit 330 may be coupled to each other after the tool 340 is accommodated therebetween. When coupled, it can be moved together along the displacement direction Y by the displacement drive and ball screw drive 312, not shown, to change the area of the tool that engages the workpiece 510 on the C1 axis along the tool axis. Configuration of Spindle Unit

3 and 4 illustrate the configuration of the spindle units 320, 330 in more detail.

In this example, the spindle unit 320 is a motorized spindle with a drive motor 324 that directly drives the first spindle shaft 322 to rotate about the tool spindle axis B. As shown in FIG. The tool spindle axis B is parallel to the displacement direction Y.

The first spindle shaft member 322 is supported in the spindle housing 321 of the first spindle unit 320 at three bearing positions of the spindle bearings 323 , 323 ′, 323 ″. The bearing locations are located at different axial locations along the first spindle shaft 322 . Two of these bearing positions are located between the drive motor 324 of the first spindle unit 320 and the tool-side end. Corresponding spindle bearings 323, 323' form locating-non-locating bearings or support bearings, ie at at least one of these bearing positions, the spindle bearings can absorb both radial and axial forces. Another bearing location is on the side of the drive motor 324 facing away from the tool. The spindle bearing 323 ″ arranged at this bearing location is configured as a non-locating bearing, ie it absorbs radial forces but allows axial movement.

Each of the three bearing locations defines a radial bearing plane. The bearing planes are each orthogonal to the tool spindle axis B. In FIG. 4, the bearing plane closest to the bearing location of the tool tip of the first spindle shaft 322 is drawn as the first bearing plane L1. The corresponding spindle bearing closest to the end of the tool is spindle bearing 323 .

In this example, the second spindle unit 330 is a non-driven sub-spindle. The second spindle unit 330 has a second spindle shaft 332 supported in the spindle housing 331 of the second spindle unit 330 at two bearing positions along the spindle shaft in the spindle bearings 333, 333'. Depending on the embodiment, these spindle bearings may be locating bearings or non-locating bearings. Each of the two bearing locations in turn defines a radial bearing plane. In FIG. 4 , the bearing plane disposed closest to that bearing position of the tool-side end of the second spindle shaft 332 is drawn as the second bearing plane L2. The corresponding spindle bearing near the end of the tool is the spindle bearing 333 . Axial clamping of tools

In this example, the tool 340 has a tool holder 341 that carries a worm-shaped dressable abrasive body 342 . In the present example, the tool holder 341 is formed as a retaining flange for the grinding body according to DIN ISO 666:2013-12. For connection to the spindle shafts 322, 332, the tool holder 341 has a tapered receptacle (also called a tapered socket or a tapered seat) with face contact at each end, eg according to DIN ISO 702-1:2010- 04 short conical receptacle 1:4.

Opposite spindle nose ends 325 , 335 are formed at tool-side ends of the spindle shaft members 322 , 332 . The shape of the spindle noses 324 , 325 is complementary to the shape of the tapered receptacles of the tool holder 341 . They each have a conical shape directed towards the cutter 340 and have flat contact surfaces on their respective end faces. For example, according to DIN ISO 702-1:2010-04, each spindle nose can be formed as a tapered shank 1:4.

Thus, there is a conical connection with face contact between the tool 340 and each of the spindle shafts 322, 332. The conical connection can have different diameters at the two ends of the tool to ensure that the tool 340 can only be received between the spindle shafts 322, 332 in the correct orientation.

The tool 340 is axially clamped between the spindle shaft members 332 and 332 by the tie rod 370 and the clamping nut 372 . To this end, the tool 340 and the second spindle shaft 332 each have a central axial hole extending therethrough. At its tool end, the first spindle shaft 322 also has a central axial hole. In this example, the hole is not continuous. It is open on the tool side and an internal thread is formed in the hole. The pull rod 370 is inserted through the central hole of the spindle shaft 332 and the tool 340 . At its end facing the first spindle unit 320 , the pull rod 370 has an external thread that is screwed into the internal thread of the first spindle shaft 322 . At the other end of the tie rod, there is also an external thread. The clamp nut 372 is screwed onto the outer thread. By tightening the clamping nut 372 , the clamping nut 372 applies axial pressure to the second spindle shaft 332 in the direction of the tool 340 . This causes the tool 340 to be axially clamped between the spindle shafts 332 , 332 . The result is a single continuous shaft with high rigidity. balance equipment

The first balance unit 350 is disposed on the first spindle shaft 322 in the axial region between the housing 321 of the first spindle unit 320 and the tool 340 . The second balance unit 360 is axially disposed on the second spindle shaft 332 between the housing 331 of the second spindle unit 330 and the tool 340 . The balancing units 350 , 360 surround the respective spindle shaft members 322 , 332 outside the housing of the respective spindle units 320 , 330 . Each includes a housing that tapers toward the tool 340 from the associated spindle unit. The tapered outer contours of the balancing units 350 , 360 reduce the risk of collisions between the balancing units and the workpiece 510 .

Each of the balance units 350, 360 is configured as a ring balance system. For this purpose, each of the balancing units 350, 360 has a rotor with two balancing rings surrounding and driven by the respective main shaft shaft. Each of the balancing units 350, 360 also has a stator. The stators are connected to the respective main shaft housings 321 , 331 . In one aspect, the stator includes sensors for detecting vibrations of the respective spindle housings, rotational speeds of the respective spindle shafts, and angular position of each gimbal. On the other hand, the stator includes an actuator having a coil arrangement for contactlessly changing the angular position of the gimbal on the respective spindle shaft.

The first balance unit 350 defines a first balance plane E1 on which the balance ring of the balance unit is configured. The first balance plane E1 is orthogonal to the axis B of the tool spindle. It runs parallel to the first bearing plane L1 and the radial center of gravity plane of the tool 340 . With respect to the tool spindle axis B, the first balance plane E1 is located between the center of gravity plane M and the first bearing plane L1 outside the first spindle housing 321 .

Correspondingly, the second balance unit 360 defines a second balance plane E2 on which the balance ring of the balance unit is configured. This balance plane is located outside the second main shaft housing 331 between the center of gravity plane M and the second bearing plane L2. Automatic balance in two planes

Figure 5 illustrates in a highly schematic way a system for automatic balancing in two planes E1, E2. The vibration sensors 351 , 361 and the actuators 352 , 362 of the two balance units 350 , 360 interact with the control device 730 . Control device 730 may be integrated into machine control system 700 or may be configured separately. By means of the control device 730, the angular positions of the balance rings of the two balance units 350, 360 are automatically calculated and adjusted so that the resulting corrected unbalance 353, 363 compensates for the tool 340 and the spindle shafts 322, 332 clamped thereon The static and dynamic unbalance of the system, and therefore, the vibration of the spindle housings 321, 331 is minimized. In this way, the system is balanced in two equilibrium planes E1, E2.

Ring balancing systems with controls for automatic biplane balancing are known per se and are available from various suppliers. An example is the AB 9000 electromagnetic ring balancing system from Hofmann Mess- und Auswuchttechnik GmbH & Co. KG, Pfungstadt, Germany. Common Spindle Housing

In Fig. 6, a tool head 300' according to a second embodiment is illustrated. Components that are the same or function in the same way as in the first and second embodiments have the same reference numerals as in FIGS. 2 to 5 .

The tool head 300 ′ of the second embodiment differs from the tool head 300 of the first embodiment in that the two spindle units 320 , 330 are accommodated in a common spindle housing 380 . The housing is guided along the displacement direction Y on the linear guide 311 by the guide block 386 .

To change the tool, the second spindle unit 330 is retracted axially relative to the spindle housing 380 . For this purpose, the spindle bearing 333 of the second spindle unit is accommodated in the bearing receptacle 391 . In this example, the bearing receptacle 391 is a bearing bush, which may be, for example, a plain bearing bush or a ball bearing bush. A bearing receptacle 391 is guided in the spindle housing 380 so that it can be displaced axially.

The rotor 361 of the second balancing unit 360 is axially displaceable relative to the stator 362 of this balancing unit. The outer diameter of the rotor 361 is smaller than the inner diameter of the other part of the guide bearing receptacle 391 of the main shaft housing 380 . When the second main shaft unit 330 is axially retracted from the main shaft housing 380, it moves in the axial direction together with the rotor 361 of the second balance unit 360, so that the rotor is retracted together with the second main shaft unit 330 to the main shaft housing 380 in. In contrast, the stator 362 of the second balance unit 360 is fixed to the spindle housing 380 and remains stationary during the retraction of the second spindle unit 330 .

Alternatively, it is also conceivable to configure the second balancing unit 360 such that the entire second balancing unit 360, ie both the rotor 361 and the stator 362, can be retracted together with the second spindle unit 330 for tool changing. Double side drive

7 and 8 illustrate a tool head 300 ″ according to a third embodiment. Components that are the same or have the same effect as in the first and second embodiments have the same reference numerals as in FIGS. 2 to 6 .

The tool head 300 ″ of the third embodiment differs from the tool head 300 of the first embodiment in that the second spindle unit 330 is also configured as a motor spindle with a second drive motor 334 . Preferably, the second drive motor 334 is sized smaller than the first drive motor 324 such that it produces less than half of the total torque on the tool 340, eg, between 35% and 45% of the total torque. This asymmetric torque-generating distribution between the two drive motors 324, 334 avoids stray resonances. Clamping Nut

9 and 10 illustrate an exemplary clamp nut 372, such as may be used in the embodiments described above.

Clamping nut 372 includes a base member 373 defining a central hole with internal threads for screwing base member 373 onto a tie rod with corresponding external threads. At one end, the base element 373 is formed externally in the manner of a hex nut. The support ring 374 is mounted on the base member 373 . The support ring rests on the collar of the base element 373 so that the support ring is prevented from moving axially in one direction (to the left in Figure 9). Furthermore, the annular axial push element 375 is guided on the base element 373 in an axially displaceable manner. Actuating elements 376 in the form of pressure screws are screwed into the axial push element 375 and are supported axially on the support ring 374 so as to prevent the actuating elements from going in one direction (to the left in FIG. 9 ) move axially. By unscrewing the pressure screw from the axial pushing element 375 , the axial pushing element 375 is advanced relative to the base element 373 in the opposite direction to the supporting direction (rightward in FIG. 9 ).

In order to clamp the tool 340 between the two spindle shafts 322, 332, first the axial push element 375 is fully rearward relative to the base element 373 by screwing the pressure screw as far as possible into the axial push element 375 move. Now, the clamping nut 372 is screwed onto the pull rod 370 and is adjusted against the second spindle shaft 332 by means of the hexagon formed on the outside of the base element 373 . This is done at relatively low torque. Subsequently, by means of the pressure screw, the annular axial pushing element 375 is advanced in a controlled manner in the direction of the second spindle shaft 332 until the desired clamping force acts on the tool 340 . Thereby, the axial pushing element 375 rests on the second spindle shaft 332 by means of the annular contact surface.

Of course, other configurations of clamping nuts can also be used, as known per se from the prior art. For example, force transmission may be accomplished in a manner other than that illustrated. In particular, hydraulic clamping nuts can be used.

Instead of a clamping nut with an internal thread, it is also possible to use clamping elements which can be connected to the tie rod in a way that is not threaded, for example via a bayonet or via a clamping bush. other variants

The interface between the spindle shafts 322, 332 and the tool 340 may also be formed in a manner different from the embodiments described above. In particular, different types of conical connections can be used. Any known conical connection can be used, for example the embodiments A, BF, BM, CF or CM mentioned in DIN ISO 666:2013-12. For details, refer to DIN ISO 666:2013-12 and other standards mentioned therein DIN EN ISO 1119:2012-04, DIN ISO 702-1:2010-04, ISO 12164-1:2001-12 and ISO 12164-2 : 2001-12.

In any embodiment, the tie rod 370 may extend through the first spindle shaft 322 rather than through the second spindle shaft 332 and may be connected to the second spindle shaft 332 at its ends. Thus, the clamping element then exerts an axial force on the first spindle shaft in the direction of the second spindle shaft.

To axially clamp the tool 340 between the first spindle shaft 322 and the second spindle shaft 332, instead of or in addition to the central tie rod, two or more tie rods may be used, which are parallel to each other and Extends radially spaced from the tool spindle axis B and is disposed at different angular positions relative to the tool spindle axis B.

The tool can also be fixed between the first spindle shaft and the second spindle shaft in another way other than by means of a continuous tie rod, for example by a clamping system arranged inside the respective spindle shaft. For this purpose, the connection between the tool and the spindle shaft can be realized, for example, by means of a hollow shank conical connection according to ISO 12164-1:2001-12 and ISO 12164-2:2001-12.

The knives can be formed in a different way than the embodiments explained above. In particular, the tool can be formed in one piece. For example, the tool may be a non-dressable CBN grinding worm with a CBN coating applied directly to the tool substrate. The interface to the spindle noses 325, 335 is then formed directly on the tool base rather than on a separate tool holder. The tool is not necessarily a ground worm. The tool can also be, for example, a profile grinding wheel, a combination of two or more profile grinding wheels, or a combination of one or more grinding worms and one or more profile grinding wheels.

In the above-described embodiment, the main shaft bearing 323 is a rolling bearing. Alternatively, other types of spindle bearings may be used, such as hydrostatic, hydrodynamic or aerodynamic bearings, as known per se in the prior art.

In the embodiments described above, a direct drive is used as the drive motor. Alternatively, it is also conceivable to use a gear motor.

Although ring balancing systems are preferably used as balancing devices, other types of balancing devices are also conceivable, such as hydraulic balancing systems as known per se from the prior art. In such balancing systems, balancing is performed by injecting fluid into balancing chambers distributed in the circumferential direction.

100: Machine bed 200: Tool holder 210: Z Slider 220: Rotary body 300,300',300'': Tool head 310: Base 311: Linear guide 312: Ball screw drive 320: The first spindle unit 321: The first spindle housing 322: The first spindle shaft 323, 323', 323'': The first main shaft bearing 324: First drive motor 325: First spindle nose 326: Guide block 330: Second Spindle Unit 331: Second Spindle Housing 332: Second spindle shaft 333,333': Second Spindle Bearing 334: Second drive motor 335: Second spindle nose 336: Guide block 340: Knives 341: Tool holder 342: Abrasive body 350: The first balance device 351: Vibration sensor 352: Actuator 360: Second Balance Device 361: Vibration Sensor 362: Actuator 370: Pull rod (tow rod) 372: Clamping Nut 373: Base element 374: Support Ring 375: Axial push element 376: Actuating element 380: Common Spindle Housing 386: Guide block 387: Bearing receptacle 400: Rotary table 500: Workpiece spindle 510: Artifact 700: Machine Control System 710: Control Module 720: Control Panel 730: Controls X,Y,Z: Linear axes A: Rotation axis B: Tool axis C1, C2: Workpiece axis C3: Tower rotation axis E1, E2: balance plane L1, L2: Bearing plane

Preferred embodiments of the present invention are described below with reference to the drawings, which are for illustrative purposes only and are not to be interpreted in a limiting manner. In the schema, [Fig. 1] Shows in a schematic perspective view an example of a machine tool for hard finishing of gears by generation grinding, the machine tool having a tool head according to the first embodiment; [Fig. 2] A schematic perspective view showing the cutter head of the first embodiment; [FIG. 3] The cutter head of the first embodiment is shown in a perspective cross-sectional view; [FIG. 4] The cutter head of the first embodiment is shown in a cross-sectional view from the front against the X direction; [Fig. 5] shows a schematic block diagram illustrating the control of the balance device in the cutter head of the first embodiment; [FIG. 6] A cutter head according to the second embodiment is shown in a perspective cross-sectional view; [FIG. 7] Shows in a perspective cross-sectional view the tool head according to the third embodiment together with the workpiece spindle; [Fig. 8] Shows an enlarged view of the area D in Fig. 7; [Figure 9] shows the clamping nut in the center longitudinal section; and [Fig. 10] The clamping nut of Fig. 9 is shown in a perspective view.

300: Tool head

310: Base

311: Linear guide

312: Ball screw drive

320: The first spindle unit

321: The first spindle housing

322: The first spindle shaft

323: The first spindle bearing

324: First drive motor

325: First spindle nose

330: Second Spindle Unit

331: Second Spindle Housing

332: Second spindle shaft

333: Second spindle bearing

335: Second spindle nose

340: Knives

341: Tool holder

342: Abrasive body

350: The first balance device

360: Second Balance Device

370: Pull rod (tow rod)

372: Clamping Nut

Y: Linear axis

B: Tool axis

E1, E2: balance plane

L1, L2: Bearing plane

Claims (18)

A tool head (300) for a machine tool, especially a gear machine, comprising: a first spindle unit (320) having a first spindle shaft (322) mounted in the first spindle unit (320) so as to be rotatable about a tool spindle axis (B); a first balancing device (350) associated with the first spindle unit (320); a second spindle unit (330) having a second spindle shaft (332) mounted in the second spindle unit (330) so as to be rotatable about the tool spindle axis (B); and a second balancing device (360) associated with the second spindle unit (330), Wherein the first spindle unit (320) and the second spindle unit (330) are coaxially arranged relative to each other so that a tool (340) can be axially received in the first spindle shaft (322) and the second spindle Between the main shaft parts (332), It is characterized in that, The first balancing device (350) radially surrounds the first spindle shaft (322), and is axially arranged between a tool-side spindle bearing (323) of the first spindle unit (320) and the first spindle between one of the tool-side ends of the shaft (322), and/or The second balancing device (350) radially surrounds the second spindle shaft (332), and is axially arranged between a tool-side spindle bearing (333) of the second spindle unit (330) and the second spindle between one of the tool-side ends of the shaft (332). The tool head (300) of claim 1, wherein the tool (340) can be clamped between the first spindle shaft (322) and the second spindle shaft (332) so that an axial compressive force acts on the tool (340) between the first spindle shaft (322) and the second spindle shaft (332). If the tool head (300) of request item 2, Wherein the second main shaft shaft member (332) has at least one axial hole, wherein the tool head (300) includes at least one pull rod (370) extending through the axial bore of the second spindle shaft (332), the pull rod (370) connectable to the first end at a first end Spindle Shaft (322), and Wherein the tie rod (370) can be connected to the second main shaft shaft (332) at a second end such that the connection between the first main shaft shaft (322) and the second main shaft shaft (332) is possible An axial compressive force is created on the tool (340). The tool head of claim 3, wherein the tool head (300) includes a gripping element (372) connectable to the tie rod (370) at its second end and configured to face the The first main shaft shaft (322) pushes the second main shaft shaft (332) axially. The tool head of claim 4, wherein the clamping element comprises: a base element (373) rigidly connectable to the pull rod (370); An axial push element (375) which is axially movable relative to the base element (373) in the direction of the second spindle shaft (332) to be axially towards the first spindle shaft (322) push the second spindle shaft (332); and At least one actuating element (376) movable relative to the base element (373) to move the axial pressure member (375) axially relative to the base element (373). If the tool head (300) of any one of claims 1 to 5, One of the first spindle noses (325) is formed at the tool-side end of the first spindle shaft (322) so that an axial compressive force can be generated at the first spindle nose (325) to the a non-positive connection and/or positive connection of the tool (340), in particular a conical connection, preferably a conical connection with surface contact, and One of the second spindle noses (335) is formed at the tool-side end of the second spindle shaft (332) so that an axial compressive force can be generated at the second spindle nose (335) to the A non-positive and/or positive connection of the tool (340), in particular a conical connection, preferably a conical connection with surface contact. If the tool head (300) of claim 6, Wherein the first spindle nose (325) and the second spindle nose (335) are formed differently, so that the tool (340) can only be stored in a predetermined position between the spindle noses (325, 335) middle. If the tool head (300) of any one of claims 1 to 7, wherein the tool-side first spindle bearing (323) defines a first bearing plane (L1) perpendicular to the tool spindle axis (B), wherein the tool-side second spindle bearing (333) defines a second bearing plane (L2) perpendicular to the tool spindle axis (B), wherein the first balancing device (350) defines a first balancing plane (E1) perpendicular to the tool spindle axis (B), The second balancing device (360) defines a second balancing plane (E2) perpendicular to the tool spindle axis (B), and Wherein the first balance plane (E1) is arranged between the first bearing plane (L1) and the second balance plane (E2), and/or the second balance plane (E2) is arranged on the second bearing plane ( L2) and the first equilibrium plane (E1). The tool head (300) of any one of claims 1 to 8, wherein the first balancing device (350) and/or the second balancing device (360) are configured as a one-ring balancing system. The tool head (300) of any one of claims 1 to 9, wherein the first balancing device (350) and/or the second balancing device (360) comprise at least one actuator (352, 362), which For numerical control adjustment of one of the respective balancing devices (350, 360) to correct unbalance (353, 363). If the tool head (300) of any one of claims 1 to 10, comprising at least one vibration sensor (351, 361) for detecting vibration caused by an imbalance in one of the tool heads (300), wherein the tool head (300) has a control device (730) associated with the vibration sensor, the control device being configured to detect signals from the at least one vibration sensor (351, 361) and control Actuators (352, 362) in the first balancing device (350) and the second balancing device (360) to adjust the first balancing device (350) and the second balancing device depending on the detected signal means (360) such that the imbalance is reduced, Wherein the control device (730) is preferably configured to perform automatic dual plane balancing. If the tool head (300) of any one of claims 1 to 11, wherein the first spindle unit (320) includes a first housing (321) and the second spindle unit (330) includes a second housing (331), and wherein the first balancing device (350) and/or the first Two balancing devices (360) are disposed outside the first casing (321) and the second casing (331), or Wherein the first spindle unit (320) and the second spindle unit (330) comprise a common spindle housing (380), and wherein the first balancing device (350) and/or the second balancing device (360) are arranged in The common spindle housing (380) is external. The tool head (300) of claim 12, wherein the first balancing device (350) and/or the second balancing device (360) have an outer profile that tapers toward the tool (340). If the tool head (300) of any one of claims 1 to 13, wherein the first spindle unit (320) includes a first drive motor (324) configured to drive the first spindle shaft (322) to rotate about the tool spindle axis (B), and/or Wherein the second spindle unit (330) includes a second drive motor (334) configured to drive the second spindle shaft (332) to rotate about the tool spindle axis (B). The tool head ( 300 ) of any one of claims 1 to 14, further comprising a tool ( 340 ), in particular a grinding tool, preferably a grinding tool for grinding teeth, which axially holds Between the first main shaft shaft member (322) and the second main shaft shaft member (332), an axial compression force acts on the first main shaft shaft member (322) and the second main shaft shaft member (332) on the cutter (340) in between. A tool head (300) for a machine tool, especially a gear machine, comprising: a first spindle unit (320) having a first spindle shaft (322) mounted in the first spindle unit (320) so as to be rotatable about a tool spindle axis (B); and a second spindle unit (330) having a second spindle shaft (332) mounted in the second spindle unit (330) so as to be rotatable about the tool spindle axis (B), Wherein the first spindle unit (320) and the second spindle unit (330) are configured such that a tool (340) can be axially received in the first spindle shaft (322) and the second spindle shaft (332) )between, It is characterized in that, The second spindle shaft (332) has at least one axial hole, The tool head (300) includes at least one pull rod (370) extending through the axial bore of the second spindle shaft (332), the pull rod (370) connectable to the first spindle at a first end shaft (322), and The pull rod (370) can be connected to the second spindle shaft (332) at a second end such that the connection between the first spindle shaft (322) and the second spindle shaft (332) can be An axial compressive force is created on the tool (340). The tool head of claim 16, wherein the tool head (300) includes a gripping element (372) connectable to the tie rod (370) at its second end and configured to face the The first spindle shaft (322) pushes the second spindle shaft (332) axially, and wherein the clamping element comprises: a base element (373) rigidly connectable to the pull rod (370); An axial push element (375) which is axially movable relative to the base element (373) in the direction of the second spindle shaft (332) to be axially towards the first spindle shaft (322) push the second spindle shaft (332); and At least one actuating element (376) movable relative to the base element (373) to move the axial pushing element (375) axially relative to the base element (373). A machine tool comprising: A tool head (300) as claimed in any one of claims 1 to 17; and at least one workpiece spindle (500) for driving a workpiece (510) to rotate about a workpiece axis (C1), The machine tool is preferably all gear machines, especially a gear grinding machine.

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