Multifuntion spindle for a machine tool

Description

[0001] The invention relates to a multifunctional spindle for a machine tool for machining workpieces, comprising a spindle housing, a rotary drive and a tool holding unit, wherein the tool holding unit is arranged inside the spindle housing and is designed to be pivotable relative to the spindle housing about an axis lying transverse to the axis of rotation.

[0002] Machine tools for machining workpieces are known in numerous designs. In lathes, the workpiece is rotated while the stationary tool is moved both axially and radially relative to the workpiece to create round, rotationally symmetrical contours. In drilling machines, the tool rotates and is advanced relative to the stationary workpiece to create holes. In milling machines, a rotating tool is moved radially and axially relative to a stationary workpiece to create milling grooves, milled surfaces, or freeform surfaces. In the machine tool types described above, the tools are predominantly held in a tool spindle via a tool interface and clamped therein.A tool spindle essentially comprises a rotary drive, a rotating drive shaft, and an output shaft into which a tool holder is integrated. Such tool spindles are also used in machining centers, where they are automatically loaded with the appropriate tools. Furthermore, these tool spindles are suitable for machine tools used to produce non-circular contours. These machining operations are commonly referred to as non-circular or polygon turning. In this process, a rotating tool with a cutting head and a rotating workpiece are controlled with respect to their relative rotations.

[0003] The tool spindles initially had to be specifically modified for the different machining processes. However, a multifunctional tool spindle is now known from EP 3 216 557 A1, which is suitable for both conventional machining operations such as turning, drilling, and milling, as well as for novel machining operations such as polygon turning. This tool spindle has a housing, a rotary drive, and a tool holder unit in a manner known per se. However, the tool holder unit is now arranged within the spindle housing and is designed to be movable relative to the spindle housing about an axis transverse to the drive axis.

[0004] Such a basic principle of a tool spindle suitable for different machining processes on a machine tool is hereinafter referred to as a "multifunctional spindle" within the scope of the present invention description.

[0005] Although the basic principle of such a multifunctional spindle offers interesting possibilities for numerous applications, it has so far only achieved limited market acceptance. This is probably due to functional deficiencies that occur during polygon turning at higher speeds. At such operating points, the measuring technology, coolant supply, and unbalance compensation described in EP 3 216 557 A1 are insufficient to adequately compensate for the then considerable influence of imbalances.

[0006] A similar principle for such a multifunctional spindle is described in EP 0 922 528 B1, whereby presumably the use of only one measuring system can achieve either the necessary accuracy in positional positioning or the functional safety of the axis lying transverse to the drive axis. However, such a spindle could not be used commercially due to the lack of positioning accuracy or the non-functionally safe design.

[0007] The object of the invention is to create a multifunctional spindle that enables, in particular when turning polygon profiles, a fast and largely complete compensation of imbalances occurring, as well as an increase in the positioning accuracy of the axis lying transverse to the drive axis, while simultaneously ensuring functional safety.

[0008] This task is accomplished by connecting at least two independent measuring systems, arranged directly adjacent to each other, to the tool holder unit to independently acquire identical position angles. The measured position angle signals are then transmitted via a transmission unit to a controller of the machine tool equipped with the multi-function spindle, using at least two independent transmission paths. At least one transmission path is used for position control, and at least one transmission path is used to ensure the functional safety of the swivel axis, which is located transversely to the drive axis. The transmission unit supplies power to at least two connected measuring systems without physical contact. The transmission unit consists of at least two parts that rotate relative to each other at spindle speed.Furthermore, the transmission unit has a central bore through which media channels are guided centrally.

[0009] One embodiment provides that the spindle shaft has at least two axially adjacent annular grooves, in each of which a ring segment is arranged that can be actuated with hydraulics via channels in such a way that its relative position within the annular groove is adjustable for the purpose of compensating for imbalance.

[0010] Another advantageous embodiment provides that the spindle housing is equipped with at least two independent rotary unions. At least one of these rotary unions is designed to accommodate hydraulic supply channels for a hydrodynamic bearing arrangement of the spindle shaft. Such a hydrodynamic bearing arrangement is created by a precisely calibrated leakage oil flow from the control channels of the rotary union, superimposed on the machine spindle speed. The other rotary union supplies coolant and pneumatic fluid centrally and without leakage losses. This separation between the hydraulic rotary union and the coolant rotary union enables a contamination-free design of the hydrodynamic bearing arrangement.

[0011] Further advantageous embodiments are described below as exemplary embodiments with reference to the drawing. The drawing shows: Fig. 1 shows a sectional view of the structure of a multifunctional spindle according to the invention. Fig. 2 shows the arrangement of a first ring segment for compensating for imbalances. Fig. 3 shows the arrangement of a second ring segment for compensating for imbalances.

[0012] The in Fig. 1 The multifunctional spindle shown is designed for a machine tool for machining workpieces. A spindle shaft 1 is arranged in a spindle housing 2. The spindle shaft 1 is supported in the spindle housing 2 by a front bearing 3 and a rear bearing 4. The front bearing 3 is formed by two separate bearing segments 3' and 3". The spindle shaft 1 rotates about an axis 24. The rotary drive required for this rotation comprises a stator unit 5 and a rotor unit 6.

[0013] The multi-function spindle has at least two rotary feedthroughs or channels 11 for hydraulics and pneumatics, and 12 and 23 for coolant and pneumatics respectively.

[0014] The spindle shaft 1 has a recess at the end section facing the workpiece (not shown), in which a tool holder 9 is arranged. This tool holder 9 is pivotable relative to the spindle housing 2 about an axis 10 that lies transversely to the axis of rotation 24. The pivoting movement is stylized with an arc-shaped arrow.

[0015] In the tool holder unit 9, a tool 8 is clamped at the end face facing the workpiece. A dimensioning body 13 is arranged at the opposite end face. Two measuring heads 14 are arranged immediately adjacent to the dimensioning body 13. Further along, behind the measuring heads 14, a telemetry transmitter 15 and a telemetry receiver 16 are arranged.

[0016] Between the bearing segments 3' and 3" a first ring segment 22 and a second ring segment 7 are arranged at a small distance from each other. Both ring segments 22 and 7 have an annular contour and are guided in an annular groove that runs circumferentially on the spindle shaft 1. The ring segments 7 and 22 compensate for imbalances during operation of the multifunction spindle, as will be explained in more detail later. At least two such ring segments 22 and 7 are required for this purpose. However, additional ring segments can also be provided.

[0017] The data to be acquired during the operation of the multifunction spindle and any parameter changes to be initiated are generated wirelessly or via measuring lines. In the drawing, such measuring lines are stylized as examples: line 25 to a measuring head 14, line 26 to a telemetry receiver 16, and line 27 to hydraulic or pneumatic components.

[0018] If, during the operation of the multi-function spindle during machining of workpieces, a positional deviation of the tool holder unit 9 from its optimal position occurs, thus creating a risk of imbalance, this irregularity is detected by the dimensional standard 13 in conjunction with the measuring heads 14. The corresponding signals are transmitted to the machine control, which triggers a change in the hydraulic flow rates supplied to the annular grooves of the ring segments 7 and 22.

[0019] This is done according to Fig. 2 Hydraulic fluid is supplied via bores 17 and 18 into the annular groove in which the ring segment 7 is located. Bores 17 and 18 are each positioned at the end sections of the annular groove, which is interrupted by a pressure chamber partition 19. This allows the relative position of the ring segment 7 within this annular groove to be changed.

[0020] At the same time, according to Fig. 3 Hydraulic fluid is supplied via bores 20 and 21 into the annular groove in which the ring segment 22 is arranged. Bores 20 and 21 are each located at the end sections of the annular groove, which is interrupted by a pressure chamber partition 19. This allows the relative position of the ring segment 22 within this annular groove to be changed.

[0021] Thus, it is possible to displace the ring segments 7 and 22 into a position preferably offset by 180° relative to each other, so that the imbalances that occur can be very effectively compensated. Since imbalances occur particularly during the machining of polygon profiles, the multifunctional spindle according to the invention is especially advantageously suited for polygon turning. Reference symbol list

[0022] 1 Spindle shaft 2 Spindle housing 3 Front bearing of the spindle shaft 3 Separate bearing segment 3 Separate bearing segment 4 Rear bearing of the spindle shaft 5 Stator unit 6 Rotor unit 7 Ring segment 8 Tool 9 Tool holder unit 10 Swivel axis transverse to the spindle rotation axis 11 Rotary union for hydraulics and pneumatics 12 Rotary union for coolant and pneumatics 13 Scale 14 Measuring heads 15 Telemetric transmitter 16 Telemetric receiver 17 Bore to annular groove for ring segment 7 18 Bore to annular groove for ring segment 7 19 Pressure chamber separation 20 Bore to annular groove for ring segment 22 21 Bore to annular groove for ring segment 22 22 Ring segment 23 Rotary union for coolant and pneumatics 24 Rotation axis of the spindle shaft 25 Line to measuring head 26 Cable to telemetry receiver 27 Cable to hydraulic / pneumatic components

Claims

1. Multifunctional spindle for a machine tool for machining workpieces, comprising a spindle housing (2), a rotary drive and a tool holder unit (9), wherein the tool holder unit (9) is arranged inside the spindle housing (2) and is designed to pivot relative to the spindle housing (2) about an axis (10) lying transversely to the axis of rotation (24), characterised in that at least two measuring systems (14) arranged directly next to one another and functioning independently of one another are connected to the tool holder unit (9) for detecting identical position angles of the tool holder unit (9), wherein there is a transmission unit connected to the measuring systems (14) that provides two transmission paths functioning independently of one another, wherein the measuring systems (14) are configured to transmit measured position angle signals via the transmission paths to a control system of a machine tool equipped with the multifunctional spindle, wherein one of the transmission paths can be used to control the position of the swivel axis lying (10) transversely to the drive axis and the other transmission path can be used to establish the functional safety of the swivel axis lying transversely to the drive axis, and wherein the transmission unit is configured to contactlessly supply the two measuring systems (14) with power, wherein the transmission unit consists of at least two parts configured to rotate relative to each other at spindle speed, and wherein the transmission unit has a central bore through which media channels are centrically guided.

2. Multifunctional spindle according to Claim 1, characterised in that the spindle shaft (1) has at least two axially adjacent annular grooves with a ring segment (7, 22) arranged inside each one that can be hydraulically pressurised via channels in such a way that its relative position within the annular groove is adjustable.

3. Multifunctional spindle according to Claim 2, characterised in that a front bearing of the spindle shaft (1) features two separate bearing segments (3', 3") with a first ring segment (7) and a second ring segment (22) arranged between the bearing segments (3', 3") at a close distance from each other, each of which has a circular ring-shaped contour and is guided in its own annular groove running circumferentially around the spindle shaft (1).

4. Multifunctional spindle according to Claim 2, characterised in that each annular groove has feed bores (17, 18, 20, 21) for hydraulics, wherein the bores (17, 18, 20, 21) are arranged, spaced apart from one another, at the two end sections of the annular grooves that are interrupted by a pressure chamber partition (19).

5. Multifunctional spindle according to Claim 1, characterised in that the spindle housing (2) is equipped with at least two rotary feedthroughs (11, 12, 23) functioning independently of one another, wherein at least one of these rotary feedthroughs (11) is configured to accommodate hydraulic feed channels for hydrodynamic bearing of the spindle shaft (1), the hydrodynamic bearing being generated as a result of a defined, coordinated leak oil flow from the control channels of the rotary feedthrough (11) in interaction with the machine spindle speed, and wherein at least one other rotary feedthrough (12, 23) is configured for the central passage of cooling lubricant and pneumatic media.