JP2001259971A - Magnetic bearing device for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing device for a machine tool allowing automatic sensing of chattering vibrations and enhancement of the working effectiveness. SOLUTION: The magnetic bearing device for the machine tool is configured so that the spindle 1 is magnetically levitated from the stationary side by magnetic bearing means 2a, 2b and 5a and magnetic thrust bearing means 4a and 4b and rotated by a motor 7 and a work 9 is processed using a tool 8 attached to the spindle end, wherein the arrangement includes a vibration sensing means 5a to sense the vibrations of the spindle 1 and judging means 10a, 10b and 11 to extract the bending natural frequency component of the spindle 1 by processing the output signal from the vibration sensing means 5a and judge a chattering condition in processing if the level of the extracted vibration component has exceeded the specified level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic bearing device for a machine tool.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a conventional magnetic bearing device for a machine tool. FIG. 5 shows details of the radial control system of the spindle 1, and FIG. 6 shows details of the machining state.

In a magnetic bearing device for a machine tool, a main shaft 1 is magnetically levitated from a fixed side by a magnetic radial bearing means A and a magnetic thrust bearing means B, and the main shaft 1 is driven to rotate by a motor means 7 so that the main shaft 1 is rotated. The processing tool 8 attached to the end is moved in the radial direction as indicated by an arrow Y.
It is configured to perform processing by pressing against the surface.

The magnetic radial bearing means A includes radial magnet stators 2a and 2b arranged at predetermined intervals in the axial direction of the main shaft 1, radial sensors 5a, 5b, 5c and 5d for detecting the radial position of the main shaft 1, and a control unit. And part 14. The magnetic thrust bearing means B comprises thrust magnet stators 4a, 4b arranged on both sides of a center of a thrust plate 3 arranged on the base end side of the main shaft 1;
And a control unit (not shown).

When the main shaft 1 is magnetically levitated by the magnetic radial bearing means A and the magnetic thrust bearing means B, the position in the radial direction is detected by the radial sensors 5a, 5b, 5c and 5d, and the main shaft 1 is controlled by the PID control of the control unit 14. The currents of the radial magnet stators 2a and 2b are controlled so as to be at the center position determined by the reference signal. Similarly, in the thrust direction, the position control of the main shaft 1 is performed by the thrust sensor 6 and a control unit (not shown).

FIG. 6 is a more simplified illustration of FIG. 12 is a phase compensator and 13 is a current amplifier. The magnetically levitated main shaft 1 is driven to rotate by a motor means 7, and a machining tool 8 attached to an end of the main shaft 1.
Is brought into contact with the work 9 and pressed in the radial direction, whereby a predetermined processing is performed on the work 9.

[0007]

When performing the processing on the workpiece 9, the processing conditions such as the cutting amount (the amount of pressing in the radial direction) are set in advance based on the past experience. As described above, since the complicated processing is performed while pressing the processing tool 8 in the radial direction, the vibration of the main shaft 1 becomes larger than a normal state depending on the processing environment and processing conditions, and so-called chatter vibration is generated. This may cause significant deterioration in the processed surface properties of the work 9 in some cases.

The occurrence of chattering vibration cannot be detected automatically, and the operator determines the machined surface of the machined work 9 visually and takes countermeasures, thereby lowering work efficiency. SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic bearing device for a machine tool capable of solving the above-mentioned problems, automatically detecting chatter vibration, and improving workability.

[0009]

A magnetic bearing device for a machine tool according to the present invention is characterized in that it comprises a main shaft vibration detecting means and a judging means for judging chatter vibration based on a signal level output thereby. I do.

According to the present invention, chatter vibration during machining can be automatically detected, and workability can be improved.

[0011]

According to a first aspect of the present invention, there is provided a magnetic bearing device for a machine tool wherein a main shaft is magnetically levitated from a fixed side by a magnetic radial bearing means and a magnetic thrust bearing means, and the main spindle is motorized. In a magnetic bearing device for a machine tool used for machining a workpiece by a machining tool attached to an end of the spindle, a vibration detection unit that detects vibration of the spindle, And a determining means for processing an output signal to extract a bending natural vibration component of the spindle, and determining a state in which the level of the extracted vibration component exceeds a specified level as a machining chatter state. .

According to a second aspect of the present invention, there is provided a magnetic bearing device for a machine tool according to the first aspect, wherein the determining means comprises: a first vibration detecting section for detecting a bending natural vibration component of the spindle; A state in which the detection level of the second vibration detection unit for detecting the bending natural vibration component of the first vibration detection unit or the first vibration detection unit or the second vibration detection unit exceeds the specified level is a machining chatter state. And a judging unit for judging.

According to a third aspect of the present invention, in the magnetic bearing device for a machine tool according to the first or second aspect, the radial magnet stator is excited in accordance with a detection signal of a radial sensor for detecting a radial position of the main shaft. The radial sensor in the controlled magnetic radial bearing means is the vibration detecting means.

FIG. 1 shows a specific embodiment of the present invention.
This will be described using FIGS. 5 and 6 showing the conventional example will be described with the same reference numerals.

(Embodiment) In this (embodiment),
This is different from the conventional example in that a vibration detecting means for detecting the vibration of the main shaft 1 and a determining means for determining the chatter state are provided so that the chatter state during machining can be automatically determined.

As shown in FIG. 1, in a magnetic bearing device for a machine tool constructed in the same manner as in FIGS. 5 and 6 showing the conventional example, a radial sensor 5a is used here as a vibration detecting means.

Further, as the determination means, the radial sensor 5
a first vibration detection unit 10a that processes an output signal from the main shaft 1 to detect a bending natural vibration component of the spindle 1, and a second vibration detection unit 10b that detects a bending natural vibration component of the machining tool 8
And the first vibration detecting unit 10a or the second vibration detecting unit 1
A determination unit 11 is provided for determining that the state where the detection level of 0b exceeds the respective specified level is the machining chatter state.

More specifically, the first and second vibration detectors 10
Reference numerals a and 10b denote band pass filters. The determination unit 11 is composed of first and second level comparators 11a and 11b.

In the magnetic bearing device for a machine tool configured as described above, the main shaft 1 is rotated at a constant speed and the machining tool 8 is pressed in the radial direction as shown by the arrow Y, so that a predetermined work is applied to the work 9. The normal operation for performing the processing is performed.

Hereinafter, the first and second vibration detecting units 10a, 1
The detection level of 0b and the configuration of the determination unit 11 will be described based on specific operations. For example, if the spindle 1 is 30,000 rpm
m, the main spindle 1
Is detected by the radial sensor 5a.

At this time, if processing is performed in a normal state, the relationship between time, frequency, and amplitude of the output signal detected by the radial sensor 5a is as shown by a waveform a1 shown in FIG.

FIG. 2 shows the frequency spectrum of the output signal of the radial sensor 5a. Radial sensor 5
The output signal a includes a noise component (not shown) in addition to the bending natural vibration component a2 of the main spindle 1 and the bending natural vibration component a3 of the machining tool 8 at the time of the constant speed rotation.

The first vibration detecting section 10a is composed of a band-pass filter whose center pass frequency is set so as to extract the bending natural vibration component a2 of the main shaft 1. Specifically, the center pass frequency was set to 1.1 KHz, which is the primary bending natural frequency of the main shaft 1.

The second vibration detecting section 10b is composed of a band-pass filter having a center pass frequency set so as to extract a bending natural vibration component a3 of the processing tool 8 attached to the main shaft 1. Specifically, the center pass frequency is set to 3.
It was set to 0 KHz.

FIG. 3 (a) shows an output signal of the radial sensor 5a in a normal machining state in which no machining chatter state has occurred. When this signal is supplied to the input of the first vibration detecting section 10a, the first signal is output. FIG. 3B shows the output of the vibration detection unit 10a.
As shown in (1), only the bending natural vibration component a2 of the main shaft 1 is extracted.

When the output signal of the radial sensor 5a shown in FIG. 3A is supplied to the input of the second vibration detecting unit 10b, the output of the second vibration detecting unit 10b is changed as shown in FIG. Then, only the bending natural vibration component a3 of the working tool 8 is extracted.

In the abnormal machining state in which the machining chatter state occurs, the radial sensor 5
A change in the signal waveform of the output signal a and an increase in the level are observed.

When the output signal of the radial sensor 5a at the time of machining abnormality shown in FIG. 4A is supplied to the input of the first vibration detecting unit 10a, the output of the first vibration detecting unit 10a is shown in FIG. As shown in FIG. 4B, a bending natural vibration component a2 having a higher level than the bending natural vibration component a2 of the main spindle 1 in the normal state shown in FIG. 4B is extracted.

When the output signal of the radial sensor 5a shown in FIG. 4A is supplied to the input of the second vibration detecting section 10b, the output of the second vibration detecting section 10b becomes as shown in FIG. 4C. In FIG. 3 (c), the bending natural vibration component a at a higher level than the bending natural vibration component a3 of the working tool 8 in the normal state.
3 is extracted.

When the chatter vibration is generated in this manner, the waveform a2 of the bending natural vibration component of the main shaft 1 and the processing tool 8 is generated.
a3 has a larger amplitude than in the normal case. Therefore, the first level comparator 11a that evaluates the output of the first vibration detecting unit 10a determines whether the reference level REF1 is equal to that of FIG.
The level is set to a level higher than the peak level of the vibration component a2 in the normal state shown in FIG. 4B, and to a level lower than the peak level of the vibration component a2 in which the machining chatter state is occurring as shown in FIG. The output level of the first level comparator 11a changes from a high level to a low level upon detecting that the output of the first vibration detection unit 10a has exceeded the reference level REF1.

The second level comparator 11b which evaluates the output of the second vibration detecting section 10b has a reference level REF2 of:
As shown in FIG. 4C, the level is lower than the peak level of the vibration component a3 during the occurrence of the machining chatter state.
The level is set to be higher than the peak level of the vibration component a3 in the normal state shown in FIG.
The output level of the second level comparator 11b changes from a high level to a low level upon detecting a state in which the output of 0b exceeds the reference level REF2.

The determination unit 11 includes a first level comparator 11a
Is detected or the output level of the second level comparator 11b becomes low level, and it is automatically determined that the machining chatter state has occurred.

More specifically, the determination unit 11 is configured to detect any of the following states and determine that the machining chatter state has occurred. (Case 1) A case where the output level of the first level comparator 11a has been in a low level state for a prescribed time and the output level of the second level comparator 11b has been detected as a high level (Case 2) (2) Case in which the output level of the second level comparator 11b has been in the low level state for a specified time and the output level of the first level comparator 11a has been detected in the high level state (case 3) The level of the output of the level comparator 11a is in a low level state for a prescribed time, and the output level of the second level comparator 11b detects the low level state for a prescribed time. The specified time in the cases (3) to (Case 3) is configured to be determined using a single specified time in any case, or the length of the specified time is determined for each case. As I said varied, and allowed to set to a time of appropriate length for each case configured to implement the automatic determination of machining chatter condition.

By structuring the judging section 11 in this way, chatter vibration can be detected very accurately and automatically.
, The operator can be immediately notified of the occurrence of the machining chatter state.

In the above description, an example in which chatter vibration is detected using only the radial sensor 5a disposed at the end of the main shaft 1 has been described. However, the present invention is not limited to this. By making a comprehensive determination using the plurality of radial sensors 5a to 5d, chatter vibration can be determined more accurately.

[0036]

As described above, according to the magnetic bearing device for a machine tool of the present invention, the vibration detecting means for detecting the vibration of the main shaft, and the level of each vibration component of the output signal of the vibration detecting means are at a specified level. By providing the determination means for determining that the state is greater than the machining chatter state, the chatter state can be automatically determined, and the productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic bearing device for a machine tool according to an embodiment of the present invention.

FIG. 2 is a frequency spectrum diagram of a signal during normal processing measured by the radial sensor 5a of the embodiment.

FIG. 3 is a signal waveform diagram of a main part when processing is normal in the embodiment.

FIG. 4 is a signal waveform diagram of a main part at the time of processing abnormality according to the embodiment.

FIG. 5 is a configuration diagram of a conventional magnetic bearing.

FIG. 6 is a configuration diagram of a control system in a radial direction of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft 2a, 2b Radial magnet stator 4a, 4b Thrust magnet stator 5a, 5b Radial sensor 7 Motor means 8 Processing tool 10a First vibration detection unit 10b Second vibration detection unit 11 Judgment unit 15 Alarm device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Isao Tashiro 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F-term (reference) 3C029 DD15 3C045 FD16 FD23 3J102 AA01 BA03 BA19 CA12 DA02 DA03 DA09 DB05 DB10 DB11 DB37 GA07

Claims (3)

[Claims] A magnetic head is magnetically levitated from a fixed side by a magnetic radial bearing means and a magnetic thrust bearing means, and the main shaft is rotationally driven by a motor means. In a magnetic bearing device for a machine tool used for machining, a vibration detection unit that detects vibration of the main shaft, and an output signal of the vibration detection unit is processed to extract and extract a bending natural vibration component of the main shaft. A magnetic bearing device for a machine tool, comprising: determination means for determining a state in which the level of a vibration component exceeds a prescribed level as a machining chatter state. 2. A first vibration detecting unit for detecting a bending natural vibration component of the main shaft, a second vibration detecting unit for detecting a bending natural vibration component of the machining tool, 2. The magnetic bearing device for a machine tool according to claim 1, further comprising: a determination unit that determines that a state in which a detection level of the vibration detection unit or the second vibration detection unit exceeds a specified level is a machining chatter state. . 3. The vibration detecting means according to claim 1, wherein said radial sensor in said magnetic radial bearing means for controlling excitation of a radial magnet stator in accordance with a detection signal of a radial sensor for detecting a radial position of a spindle. A magnetic bearing device for a machine tool according to claim 2.