JP2021070099A - Rotation support device, machine tool, and tool state monitoring method - Google Patents

Abstract

To obtain a rotation support device capable of acquiring current for rotating a workpiece holding part to a target position using servo control.SOLUTION: A rotation support device 10 includes: a servo motor 21; an input shaft 25 on which a cam surface is formed on an outer periphery, and which is rotationally driven by the servo motor 21; an output shaft 27 on which a plurality of cam followers engaged with the cam surface is provided aligned in a circumferential direction, and which rotates at a lower rotational frequency than the input shaft 25 when rotary power of the input shaft 25 is transmitted via the cam surface and the plurality of cam followers; a workpiece holding part 40 which is connected to the output shaft 27, and is capable of holding a workpiece W and rotating with the output shaft; a control part 50 which supplies current for rotating the workpiece holding part 40 to a target position in the rotational direction, to the servo motor 21, in a state that the workpiece holding part 40 receives external force in the rotational direction according to processing onto the workpiece; and an arithmetic part 51 which performs a prescribed calculation by acquiring a value related to the current at the time of processing the workpiece.SELECTED DRAWING: Figure 7

Description

This specification relates to a rotary support device, a machine tool, and a tool condition monitoring method.

The rotation support device is mounted on a machine tool such as a machining center and holds a workpiece which is an object to be machined. A general rotation support device includes a power source, a power transmission mechanism such as a worm gear, a table for holding a work (work holding portion), a brake for fixing the position of the table during work processing, and the like. When rotating the table, the table is rotated after releasing the brake to reduce the load. After positioning the work, the position of the table and the work is fixed by operating the brake. In this state, various processes such as cutting, grinding and drilling are performed on the work.

Japanese Unexamined Patent Publication No. 08-323584

When the worm gear and the brake mechanism as described at the beginning are adopted, the brake is turned on and off during a series of operations of positioning and processing the work, so that the processing time becomes long. In a state where the table (work holding portion) on which the work is placed is fixed by a brake, machining is performed while the tool moves with respect to the stopped work. In this case, since the table is fixed by the brake, it is not possible to perform cutting or the like on the work while rotating the work. It is also possible to perform cutting on the work while releasing the brake and rotating the work, but in the case of a worm gear, the effect of misalignment due to backlash is not small, so the work can be held or moved with high position accuracy. It is difficult to make it (especially, backlash is likely to occur when the rotation direction is reversed), and there is room for improvement in the worm gear in that the workpiece is machined with high precision.

Further, it is possible to monitor the load current during servo control, perform a predetermined calculation based on the load current (for example, estimate the progress of tool wear), and perform a predetermined process according to the calculation result (the above). (See Patent Document 1). However, when the worm gear and the brake mechanism as described at the beginning are adopted, the table (work holding portion) and the positioned state of the work can be held by the brake, but the table is fixed by the brake. On the other hand, it becomes impossible to carry out servo control, and it becomes impossible to acquire information on the load current at the time of servo control.

One of the purposes of the present specification is to disclose a rotation support device having a configuration in which a current for rotating a work holding portion to a target position by servo control can be obtained by not providing a brake. To do.

In the rotation support device based on the present specification, a servomotor, an input shaft having a cam surface formed on the outer periphery and rotationally driven by the servomotor, and a plurality of cam followers engaging with the cam surface are arranged in the circumferential direction. The output shaft is provided, and the rotational power of the input shaft is transmitted via the cam surface and the plurality of cam followers to rotate at a rotation speed lower than that of the input shaft, and is connected to the output shaft to hold the workpiece. With the work holding portion rotatable together with the output shaft and the work holding portion receiving an external force in the rotation direction due to machining into the work, the work holding portion is rotated to a target position in the rotation direction. A control unit for supplying a current for the purpose to the servomotor, and a calculation unit for acquiring a value related to the current at the time of machining the work and performing a predetermined calculation are provided.

In the rotation support device, the control unit is such that the work holding portion approaches a fixed position in the rotation direction while the work holding portion receives an external force in the rotation direction due to processing into the work. A current may be supplied to the servomotor.

In the rotation support device, the calculation unit compares the value stored in advance with the current at the time of machining the workpiece, and outputs the comparison result as information regarding the state of the tool machining the workpiece. You may.

A machine tool according to the present specification includes a tool for machining a work and the above-mentioned rotation support device based on the present specification.

The tool state monitoring method based on the present specification is a tool state monitoring method for monitoring the state of a tool for machining a work held by a work holding part, and the work holding part is rotatable together with an output shaft. In the output shaft, a plurality of cam followers engaging with a cam surface formed on the outer periphery of the input shaft rotationally driven by a servomotor are provided side by side in the circumferential direction, and the output shaft is the input shaft. The rotational power of the work is transmitted through the cam surface and the plurality of cam followers to rotate at a rotation speed lower than that of the input shaft, and the work holding portion receives an external force in the rotation direction by machining the work. In this state, a current for rotating the work holding portion to a target position in the rotation direction is supplied to the servomotor, and the tool state monitoring method uses a predetermined value and the current during machining of the work. It is provided with a step of comparing with the above and outputting the comparison result as information regarding the state of the tool.

According to the above means, it is possible to obtain a rotation support device having a configuration in which a current for rotating the work holding portion to a target position by servo control can be obtained by not providing a brake.

It is a figure which shows the structure of the machining center 1 (machine tool). It is a figure which shows the rotation support device 10, the spindle 4 and the tool 6. It is a figure which shows the internal structure of the index table 20. It is a figure which shows the functional block of the rotation support device 10. It is a figure which shows the state which the attachment part 41 of the work holding part 40 is arranged lower in the direction of gravity. It is a figure which shows the state which the work holding part 40 rotated 90 ° clockwise from the state shown in FIG. It is a graph which shows the time change of the torque around the A axis at the time of processing.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the following description, the same parts and equivalent parts may be given the same reference number, and duplicate explanations may not be repeated.

(Machining center 1)
FIG. 1 is a diagram showing a configuration of a machining center 1 (machine tool). The machining center 1 includes a main body 2, a display 3, a spindle 4, a magazine 5, a tool 6, and a rotation support device 10. The rotation support device 10 can also be called an indexer device, and supports the work W (workpiece). The spindle 4 can hold a tool 6 and a tool (not shown) held in the magazine 5. The tool 6 performs cutting or the like on the work W supported by the rotation support device 10.

(Rotation support device 10)
FIG. 2 is a diagram showing a rotation support device 10, a spindle 4, and a tool 6. The rotation support device 10 includes an index table 20, a support table 30, and a work holding unit 40. The index table 20 and the support table 30 are provided on the base 12. The work holding portion 40 is arranged between the index table 20 and the support table 30, and is rotatably supported around the A axis by these tables.

The work W is fixed to the work holding portion 40. The work holding portion 40 includes a mounting portion 41 and arms 42 and 43, and has a substantially cradle-like shape as a whole. The work W is fixed to the mounting portion 41. The arm 42 is provided on the side of the index table 20 when viewed from the mounting portion 41. The arm 43 is provided on the side of the support table 30 when viewed from the mounting portion 41. The rotation center axis A of the arm 42 rotated by the index table 20 and the rotation center axis A of the arm 43 held by the support table 30 are located on substantially the same straight line.

The work W is fixed to the mounting portion 41 by a plurality of clamp devices 44, 45 provided on the mounting portion 41. Flood control is supplied to the clamp devices 44 and 45 via rotary joints provided on each of the index table 20 and the support table 30, and the clamp devices 44 and 45 fix the work W to the mounting portion 41 by the hydraulic pressure. By rotating the work holding portion 40, the work W is rotatably supported around the A axis by the index table 20 and the support table 30 via the work holding portion 40.

(Index table 20)
FIG. 3 is a diagram showing the internal structure of the index table 20. FIG. 4 is a diagram showing a functional block of the rotation support device 10 including the index table 20. As shown in FIGS. 2 to 4, the index table 20 includes a servomotor 21, a position detector 22, gears 23, 24, an input shaft 25, an output shaft 27, a rotary joint 29, and the like.

The index table 20 rotatably supports the work holding portion 40 (arm 42) around the A axis by bearings. The support table 30 is also provided with a rotary joint and a bearing similar to these, and rotatably supports the work holding portion 40 (arm 43) around the A axis.

More specifically, the power from the servomotor 21 is transmitted to the input shaft 25 via the gears 23 and 24. The gear 24 rotates integrally with the input shaft 25 at a rotation speed lower than that of the gear 23. The input shaft 25 is indirectly rotationally driven by the servomotor 21 via the gears 23 and 24. A cam surface 26 extending spirally is formed on the outer surface of the input shaft 25.

A plurality of cam followers 28 that engage with the cam surface 26 are provided on the output shaft 27 side by side in the circumferential direction. The rotational power of the input shaft 25 is transmitted to the output shaft 27 via the cam surface 26 and the plurality of cam followers 28, and the output shaft 27 is integrated with the work holding portion 40 (arm 42) at a rotation speed lower than that of the input shaft 25. Rotate to. The gears 23 and 24 form one deceleration mechanism, and the input shaft 25 and the output shaft 27 form another deceleration mechanism. The torque from the servomotor 21 is increased by these reduction mechanisms and transmitted to the output shaft 27 and the work holding portion 40, and the work holding portion 40 rotates together with the output shaft 27.

When the power of the servomotor 21 is transmitted to the output shaft 27, some of the cam followers 28 are in contact with the cam surface 26. For example, among these several cam followers 28, the cam follower 28 located on one end side in the circumferential direction and the cam follower 28 located on the other end side in the circumferential direction are as shown by arrows AR1 and AR2 (FIG. 3). Press the cam surface 26. The cam surface 26 receives preload from a plurality of (two in this case) cam followers 28, and this prevents backlash and backlash from occurring between the input shaft 25 and the output shaft 27. ..

The index table 20 is not provided with a braking means such as a friction brake for stopping the rotation of the arm 42. By using a roller gear type index table that can rotate and support the work holding portion 40 only by the servomotor 21 without using the friction brake as the index table 20, the braking time can be reduced and the productivity can be improved. Can contribute.

Each of the plurality of cam followers 28 is rotatably provided, and transmits power from the input shaft 25 to the output shaft 27 while rotating. As a result, the friction between the cam surface 26 and the plurality of cam followers 28 is reduced. The roller cam mechanism including the cam surface 26 and the plurality of cam followers 28 can transmit the power from the input shaft 25 to the output shaft 27 with high accuracy, and can position the work holding portion 40 with high accuracy.

As shown in FIG. 4, the rotation support device 10 includes a control unit 50, a calculation unit 51, and an amplifier 52 as functional blocks. The amplifier 52 is connected to the control unit 50, and the amplifier 52 is connected to the servomotor 21 and the position detector 22 via a power cable and a signal cable, respectively. The control unit 50 can collect the current value of the servomotor 21 and the position information from the position detector 22 through the amplifier 52. The control unit 50 and the calculation unit 51 calculate the motor torque value, external load data, position and speed information from the current value collected by the servomotor 21. The calculation unit 51 calculates or compares information such as a motor torque value output and received from the control unit 50, and performs a predetermined process.

For example, the control unit 50 applies a current for rotating the work holding unit 40 to a target position in the rotation direction while the work holding unit 40 receives an external force in the rotation direction due to machining into the work W. Supply to. For example, servo control is performed so that the work holding portion 40 approaches (stops) a certain position in the rotation direction, whereby the required current is supplied to the servo motor 21. More specifically, for example, the control unit 50 and the servomotor 21 perform position control or attitude control on the work holding unit 40 so as not to deviate from a predetermined stop position. When the signal from the position detector 22 or the like is compared with the target value possessed by the control unit 50 and it is determined that there is a deviation between them, an attempt is made to return to the stop position (target position). A command for this is supplied from the control unit 50 (servo driver or the like) to the servomotor 21 as a current value, and torque is generated. Torque as a load will be generated only when the position deviates from the stopped position. The same processing is appropriately performed in the amplifier 53 connected to the control unit 50, the servomotor 54 for the spindle 4 (feed shaft), and the position detector 55.

When machining the work W while the work holding portion 40 is servo-controlled so as to approach a fixed position in the rotation direction (in other words, hold a substantially stopped state at a fixed position). Since almost no play occurs between the cam follower 28 and the cam surface 26, it is possible to suppress the occurrence of unnecessary minute displacement in the work holding portion 40, and the position of the work holding portion 40 in the rotation direction is the target. It is possible to suppress deviation from the position. Even when the work W is machined while the work holding portion 40 is continuously rotated around the A axis (while feeding the work W), there is almost no backlash between the cam follower 28 and the cam surface 26, so that the work is held. It is possible to prevent the movement of the unit 40 in the rotation direction from deviating from the target movement path.

As shown in FIG. 5, when the mounting portion 41 of the work holding portion 40 is arranged downward in the gravity direction, the position of the rotation center axis A in the horizontal direction and the position of the center of gravity of the work holding portion 40 in the horizontal direction Are almost the same. It can be said that the work holding portion 40 forms a stable posture.

On the other hand, if necessary, as shown in FIG. 6, the work holding portion 40 is rotated by 90 ° in the clockwise direction from the state shown in FIG. In this state, the position of the rotation center axis A and the position of the center of gravity of the work holding portion 40 are deviated from each other in the horizontal direction, and a moment for rotating the work holding portion 40 is formed around the rotation center axis A. It's working.

According to the rotation support device 10 provided with the roller gear mechanism described above, even if the friction brake mechanism for holding the rotational position of the work holding portion 40 is not provided, the servo control alone sufficiently counteracts this moment. For example, the work W can be easily machined in a state where the work holding portion 40 is servo-controlled so as to approach a fixed position or a predetermined machining path in the rotation direction.

(Calculation unit 51)
With reference to FIG. 4 again, in the present embodiment, the calculation unit 51 acquires a value related to the current when the work W is machined and performs a predetermined calculation. For example, when the tool 6 processes the work W, the work holding portion 40 receives an external force in the rotational direction around the A axis. The control unit 50 applies a necessary current to the servomotor so that the work holding unit 40 approaches a fixed position or a predetermined machining path in the rotation direction around the A axis while the work holding unit 40 is receiving the external force. Supply to 21. The calculation unit 51 acquires a value related to the current supplied to the servomotor 21.

As shown in FIG. 7, assuming that the value related to the current supplied to the servomotor 21 is converted into the torque around the A axis and the relationship with the time axis is measured, the result is as shown in the graph shown in FIG. expressed. It can be seen that the torque generated around the A-axis is momentarily increased each time the cutting process is performed by the tool 6. In FIG. 7, the temporal change in torque when the worn tool 6 (weared tool) is used is shown by a dotted line (broken line), and the wearless tool 6 (non-weared tool) is shown. The temporal change of torque when used is shown by a solid line (continuous line).

As can be read from FIG. 7, the torque generated around the A-axis is larger when the tool 6 with wear is used than when the tool 6 without wear is used. For example, when machining a work W, by monitoring the current supplied to the servomotor 21 for attitude control of the work holding unit 40, for example, when the current value deviates from a predetermined range, the degree of wear progress. Can be estimated to have exceeded the threshold.

At the time of machining, the current supplied to the servomotor 21 so that the work holding portion 40 approaches a constant position (maintains the same position) in the rotation direction around the A axis is defined as the first current. At the time of machining, the current supplied to the servomotor 21 is set so that the movement of the work holding portion 40 in the rotation direction around the A axis becomes the target movement path (so that the work W is sent along a predetermined path). Let the current be 2. In this case, the first current required to hold the work W in place is sufficiently smaller than the second current required to feed the work W.

Since the second current required for the feed operation of the work W during machining also increases due to the influence of wear, the wear state of the tool 6 is estimated based on the amount of increase (degree of change from the normal value). May be good. On the other hand, during machining, the work holding portion 40 is worn by monitoring the first current supplied to the servomotor 21 so as to approach a certain position (maintain the same position) in the rotation direction around the A axis. It is possible to estimate the progress of the above with high accuracy, and for example, it is possible to prompt the user to replace the wear when the progress of wear exceeds the threshold value with high accuracy. The calculation unit 51 is not limited to such a monitoring operation, compares the value stored in advance with the above-mentioned current at the time of machining the work W, and obtains the comparison result as an arbitrary state regarding the state of the tool machining the work W. (For example, information for judging, determining, and devising economical cutting conditions) may be output.

Although the above-described embodiment has been described by focusing on the so-called roller gear mechanism, the description of the above-described embodiment means that the use of the worm gear is positively excluded from the scope of disclosure of the invention according to the present specification. Not intended. For example, if a mechanism that does not cause (or hardly occurs) backlash or backlash even if a friction brake is not provided can be realized by means other than roller gears, the above idea can be applied to such a configuration. Is. It may be necessary to increase the size of the device, but the idea of monitoring the current value required for servo control with the above brakeless configuration is familiar to the structure of worm gears and so-called DD (direct drive) motors. It's easy.

Further, in the above-described embodiment, a plurality of cam followers 28 that engage with the cam surface 26 are provided side by side in the circumferential direction on the outer periphery of the output shaft 27. The range in the circumferential direction in which the plurality of cam followers 28 are provided extends 360 ° (entire circumference) in the drawing, but the range in the circumferential direction in which the plurality of cam followers 28 are provided is 90 °, 180 °, etc. It may be a part of the outer circumference of the output shaft 27.

Further, in the above-described embodiment, the plurality of cam followers 28 are provided so as to extend radially along the radius of gyration direction of the output shaft 27. The rotation center axes of the plurality of cam followers 28 extend in a direction orthogonal to the rotation center axes of the output shaft 27. Not limited to such a configuration, the plurality of cam followers 28 may be provided at other positions on the output shaft 27. For example, a plurality of cam followers 28 may be provided on the output shaft 27 so as to form a barrel cam type as disclosed in (Japanese Patent Laid-Open No. 2008-045662). In this case, the rotation center axes of the plurality of cam followers 28 extend parallel to the rotation center axes of the output shaft 27. Further, a plurality of cam followers 28 may be provided on the output shaft 27 so as to form a form between the roller gear type and the barrel cam type as disclosed in the same publication. In this case, the rotation center axes of the plurality of cam followers 28 extend so as to intersect the rotation center axes of the output shaft 27 at an angle of, for example, about 45 °. It is not limited to 45 ° and can take any inclination angle other than 45 °.

Although the embodiments have been described above, the above disclosure contents are examples in all respects and are not restrictive. The technical scope of the present invention is indicated by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

1 Machining center, 2 Main body, 3 Display, 4 Spindle, 5 Magazine, 6 Tools, 10 Rotational support, 12 Base, 20 Index table, 21,54 Servo motor, 22,55 Position detector, 23,24 Gears, 25 Input shaft, 26 Cam surface, 27 Output shaft, 28 Cam follower, 29 Rotary joint, 30 Support table, 40 Work holding part, 41 Mounting part, 42,43 Arm, 44,45 Clamping device, 50 Control part, 51 Calculation part , 52, 53 amplifier, A rotation center axis, AR1, AR2 arrow, W work.

Claims (5)

Servo motor and
An input shaft having a cam surface formed on the outer circumference and rotationally driven by the servomotor,
A plurality of cam followers engaging with the cam surface are provided side by side in the circumferential direction, and the rotational power of the input shaft is transmitted through the cam surface and the plurality of cam followers to rotate at a rotation speed lower than that of the input shaft. Output axis and
A work holding unit that is connected to the output shaft, holds the work, and can rotate with the output shaft.
A control unit that supplies a current for rotating the work holding portion to a target position in the rotation direction while the work holding portion receives an external force in the rotation direction due to machining into the work. ,
A calculation unit that acquires a value related to the current at the time of processing the work and performs a predetermined calculation is provided.
Rotational support device. The control unit supplies the current to the servomotor so that the work holding portion approaches a certain position in the rotational direction while the work holding portion receives an external force in the rotational direction due to machining into the work. To do,
The rotation support device according to claim 1. The calculation unit compares the value stored in advance with the current at the time of machining the work, and outputs the comparison result as information regarding the state of the tool that is machining the work.
The rotation support device according to claim 1 or 2. Tools for machining workpieces and
The rotation support device according to any one of claims 1 to 3 is provided.
Machine Tools. It is a tool condition monitoring method that monitors the condition of the tool that processes the workpiece held in the workpiece holder.
The work holding portion can rotate together with the output shaft, and in the output shaft, a plurality of cam followers engaging with a cam surface formed on the outer periphery of the input shaft rotationally driven by the servomotor are arranged in the circumferential direction. The output shaft is provided so that the rotational power of the input shaft is transmitted via the cam surface and the plurality of cam followers to rotate at a rotation speed lower than that of the input shaft.
With the work holding portion receiving an external force in the rotation direction due to machining into the work, a current for rotating the work holding portion to a target position in the rotation direction is supplied to the servomotor.
The tool condition monitoring method includes a step of comparing a predetermined value with the current at the time of machining the workpiece and outputting the comparison result as information regarding the condition of the tool.
Tool condition monitoring method.

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