JP2016223970A - Balance correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of sputter at the time of balance correction by laser beam irradiation.SOLUTION: While a turbine wheel (rotor) in an unbalanced state is rotated at a lower revolution speed than a resonant revolution speed, a wheel boss 211 is irradiated with a laser beam, whereby a laser beam irradiation position on an opposite phase side to a laser beam irradiation position on an unbalanced phase side drifts to the outside in a radius direction. Also, when the wheel boss 211 is heated by irradiating it with a laser beam, a laser beam irradiated portion of metal softens, and the softened metal floats to the outside in the radius direction of the rotor by a centrifugal force. The metal flow on the opposite phase side occurs more outside than does on the unbalanced phase side due to a drift of the laser beam irradiated position. This makes it possible to correct unbalance. By correcting unbalance by a metal flow occurring due to heating by laser beam irradiation this way, it is possible to suppress the occurrence of sputter at the time of balance correction.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a balance correction device that corrects an unbalance of a rotating body such as a compressor impeller or a turbine wheel of a turbocharger.

  As a technique for correcting the unbalance of the rotating body, the rotating body (for example, a compressor impeller) is rotated by irradiating the rotating body with laser light and cutting (removing) a part of the rotating body. There is one that corrects (adjusts) the unbalance of the body (for example, see Patent Document 1).

JP 2010-203803 A

  By the way, when correcting imbalance by cutting with laser light irradiation, the spatter (removed material) scattered by laser light irradiation adheres to the rotating body and the balance correcting device, and thus a step of removing the adhered material is required. .

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique capable of suppressing the occurrence of spatter in a balance correction apparatus that performs balance correction by irradiating a rotating body with laser light. And

  The present invention is a balance correction device for correcting an unbalance of a metal rotating body, the rotation control means for rotating the rotating body around its rotation axis and controlling the number of rotations of the rotating body, A laser irradiation unit that irradiates the rotating body with a laser beam from a rotation axis direction to a position inside the outer peripheral edge of the rotating body to heat the rotating body, and the rotation control unit causes the rotating body to By irradiating the rotating body with laser light from the laser irradiation means in a state where the rotating body is rotated at a rotational speed lower than the resonance rotational speed of the rotating body, a portion inside the outer peripheral edge of the rotating body is heated. It is characterized by being configured to soften.

  The operation of the present invention will be described.

  First, the vibration phase due to the unbalance of the rotating body changes at a constant phase (for example, 0 ° phase) from when the rotating body starts to rotate until it reaches the resonant rotational speed, and the rotational speed of the rotating body resonates. When the rotation speed is exceeded, the vibration phase is reversed (the phase becomes 180 °). Moreover, when the rotational speed of the rotating body is lower than the resonant rotational speed, the unbalanced position and the vibration phase (swinging phase) are the same phase. Therefore, by setting the unbalance correction rotation speed to a rotation speed lower than the resonance rotation speed, the rotation center of the rotating body can be shifted to the unbalance position side. When the rotating body is irradiated with the laser beam in such a state that the rotation center of the rotating body is shifted in this way, the laser beam irradiation position (heating) at the unbalanced position (0 ° phase) side and the opposite phase (180 ° phase) side. Position) shifts in the radial direction of the rotating body. That is, the heating position on the opposite phase side shifts outward in the radial direction of the rotating body with respect to the heating position on the unbalanced position (phase 0 °) side.

  On the other hand, when the rotating body is irradiated with laser light and heated, the metal in the laser light irradiated portion is softened, and the softened metal flows outward in the radial direction of the rotating body by centrifugal force. Here, as described above, when the rotating body is rotated at a rotational speed lower than the resonant rotational speed, the heating position on the opposite phase (180 ° phase) side becomes the heating position on the unbalanced position (phase 0 °) side. On the other hand, the metal flow on the opposite phase (180 ° phase) side is generated on the outer side in the radial direction than the metal flow on the unbalanced position (phase 0 °) side, and vice versa. The radius of the metal flow on the phase side increases. This can correct the imbalance.

  As described above, according to the present invention, since the rotating body is irradiated with the laser beam and the unbalance is corrected by the metal flow generated by the heating by the laser beam irradiation, the spatter is generated at the time of the balance correction. Can be suppressed.

  In the present invention, the taper surface in which the protrusion height in the rotation axis direction of the rotating body increases toward the outer peripheral portion of the rotating body (the portion irradiated with the laser beam) closer to the outer periphery of the rotating body in the radial direction of the rotating body. The laser beam may be focused on the outermost diameter of the tapered surface. In this way, the laser beam is more focused as it goes outward in the radial direction of the rotating body, so that the metal flow on the opposite phase (180 ° phase) side is shifted to the unbalanced position (phase 0 °) side. The metal flow can be promoted and the processing ability can be improved.

  According to the present invention, it is possible to suppress the occurrence of sputtering during balance correction by laser light irradiation.

It is a front view which shows schematic structure of an example of the balance correction apparatus of this invention. It is a side view of the balance correction apparatus of FIG. It is a side view of the turbine wheel of a turbocharger. It is the elements on larger scale of a turbine wheel. It is a partial expanded sectional view of a wheel boss. It is a flowchart which shows an example of the processing content of balance correction. It is a figure which shows together the graph which shows the relationship between the vibration of a turbine wheel, and turbine rotation speed, and the graph which shows the relationship between a vibration phase and turbine rotation speed. It is a figure which shows typically an example of the balance correction process of a turbine wheel. It is a figure which shows typically an example of the balance correction process of a turbine wheel. It is sectional drawing which shows the other example of the edge part shape of a wheel boss | hub. It is a figure which shows typically the other example of balance correction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Turbocharger-
First, an example of the turbocharger 200 that performs balance correction will be described with reference to FIGS.

  The turbocharger 200 of this example includes a turbine wheel (for example, made of Inconel (registered trademark)) 201, a compressor impeller (for example, made of aluminum alloy) 202, and the like, and a turbine integrally formed with the turbine wheel 201. A compressor impeller 202 is connected to an end of a shaft (not shown). The turbine wheel 201 is accommodated in the turbine housing 210, and the compressor impeller 202 is accommodated in the compressor housing 220. The turbine housing 210 is formed with a flow path (scroll) through which a fluid for rotationally driving the turbine wheel 201 flows.

  A bearing (not shown) for supporting the turbine shaft is accommodated in the center housing 230, and the turbine housing 210 and the compressor housing 220 are attached to both sides of the center housing 230.

  As shown in FIGS. 3 to 5, the turbine wheel 201 includes a wheel hub 212, a turbine blade 213, a wheel boss 211, and the like. The end surface (laser light irradiation surface) 211b of the wheel boss 211 in this example is a flat surface. The wheel boss 211 is integrally formed with an outer wall 211 a having a rectangular cross section that protrudes from the end surface 211 b along the entire circumference of the outer periphery of the wheel boss 211.

-Balance correction device-
As shown in FIGS. 1 and 2, the balance correction device 100 of the present embodiment includes a laser oscillator 1, a laser moving device 2, a driving air supply device 3, a rotation sensor 4, an acceleration sensor 5, a gantry 6, and arithmetic control. The apparatus 7 etc. are provided.

  The gantry 6 can detachably support the turbocharger 200. In a state where the turbocharger 200 is supported on the gantry 6, the rotation center of the turbocharger 200 (the rotation center of the turbine wheel 201) is along the horizontal direction (X direction).

  The laser oscillator 1 is a semiconductor laser capable of continuous oscillation, for example, and is arranged so that the optical axis is along the horizontal direction (the direction parallel to the rotation axis of the turbine wheel 201). The laser oscillator 1 can continuously irradiate the wheel boss 211 of the turbine wheel (rotary body) 201 of the turbocharger 200 attached to the gantry 6 from the rotation axis direction (X direction) of the turbine wheel 201. . A part of the turbine wheel 201 can be heated by this laser light irradiation. The driving of the laser oscillator 1 is controlled by the arithmetic and control unit 7. Laser light emitted from the laser oscillator 1 passes through the outlet 214 of the turbine housing 210 and is irradiated to the wheel boss 211 of the turbine wheel 201 in the housing. The laser oscillator 1 is an example of the “laser irradiation means” in the present invention.

  The laser moving device 2 moves the laser oscillator 1 in the horizontal direction (X direction) and the radial direction of the turbine wheel 201 (direction perpendicular to the rotation axis of the turbine wheel 201: Y direction). By moving the laser oscillator 1 by the laser moving device 2, focusing on the laser processing portion of the turbine wheel 201 can be performed. Moreover, the laser beam irradiation position in the radial direction (Y direction) of the turbine wheel 201 can be set.

  The driving air supply device 3 includes an air supply source 31, an air duct 32, and the like. The air duct 32 is connected to a scroll inlet of the turbine housing 210, and driving air from the air supply source 31 can be supplied to the scroll of the turbine housing 210. By supplying the driving air to the scroll, the driving air flows through the turbine wheel 201 and the turbine wheel 201 rotates. The rotational speed (the number of rotations) of the turbine wheel 201 can be variably set by adjusting the flow rate of the drive air output from the air supply source 31 (the flow rate of the drive air flowing through the turbine wheel 201). The flow rate of the driving air output from the air supply source 31 is controlled by the arithmetic and control unit 7. The driving air supply device 3 and the arithmetic control device 7 are examples of the “rotation control means” in the present invention.

  The rotation sensor 4 is disposed in the vicinity of the compressor impeller 202 of the turbocharger 200 attached to the gantry 6 and detects the phase (rotation angle) from the reference position of the compressor impeller 202. From the output signal of the rotation sensor 4, the rotation angle and rotation speed (turbine rotation speed) of the turbine wheel 201 connected to the compressor impeller 202 so as to be integrally rotatable can be measured. The output signal of the rotation sensor 4 is input to the arithmetic control device 7. Various sensors such as a magnetic sensor and an optical sensor can be applied as the rotation sensor 4.

  The reference position is set by, for example, paint application, seal sticking, notch processing, or the like on the compressor impeller 202. Further, the rotation angle detected by the rotation sensor 4 changes from 0 degrees to 360 degrees when the compressor impeller 202 (turbine wheel 201) rotates once from the reference position (= 0 degrees).

  The acceleration sensor 5 is attached to the gantry 6 that supports the turbocharger 200. The acceleration sensor 5 detects vibration of the gantry 6 (vibration of the turbocharger 200) when the turbocharger 200 (turbine wheel 201) is rotating. The output signal of the acceleration sensor 5 is input to the arithmetic control device 7.

  The arithmetic and control unit 7 is, for example, a personal computer, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a backup RAM, an input / output interface, and the like.

  The CPU executes arithmetic processing based on various control programs and maps stored in the ROM. The ROM stores various control programs and maps that are referred to when the various control programs are executed. The RAM is a memory that temporarily stores calculation results by the CPU. The backup RAM is a non-volatile memory that stores data to be saved when the arithmetic control device 7 is turned off.

  A laser oscillator 1, a laser moving device 2, a driving air supply device 3, a rotation sensor 4, an acceleration sensor 5, and the like are connected to the input / output interface of the arithmetic control device 7.

-Balance correction-
Next, an example of performing balance correction using the balance correction apparatus 100 described above will be described with reference to the flowchart of FIG. The control routine of FIG. 6 is executed in the arithmetic and control unit 7.

  First, as a process before performing balance correction, as shown in FIG. 1, a turbocharger 200 that is a balance correction target is attached to the gantry 6 of the balance correction apparatus 100. Further, the laser moving device 2 is operated to focus the laser oscillator 1 on the end surface 211b of the wheel boss 211, and the laser beam irradiation position to the end surface 211b is a predetermined position inside the outer wall 211a (FIG. 8A). The position of the laser oscillator 1 is adjusted so that the laser beam irradiation position shown in FIG.

  After completing the above settings, balance correction is started. When the balance correction is started, in step ST101, the driving air supply device 3 is controlled, the turbine wheel 201 is rotated by the air drive, and the rotation speed (turbine rotation speed) of the turbine wheel 201 is used by the turbocharger. Raise to rotation area. While the turbine rotational speed is increasing, the output signal of the rotation sensor 4 and the output signal of the acceleration sensor 5 are sampled (tracking measurement of rotation primary vibration).

  The relationship between the acceleration data (vibration data) measured by such tracking measurement and the turbine rotational speed is as shown in FIG. Further, the relationship between the rotation data (phase data) and the turbine rotation speed is as shown in FIG.

  Note that the curve L1 shown in FIG. 7A is obtained from the vibration data measured in the first tracking measurement (step ST101). In the example shown in FIG. 7A, the peak (maximum amplitude) of the vibration G measured in the first tracking measurement is based on the vibration G reference (allowable amount of unbalance amount (vibration amplitude)). Is also big.

  Next, in step ST102, an unbalance correction rotation speed Nt_B is set. Specific processing will be described below.

  First, in the graph shown in FIG. 7A, the peak of the vibration G is the primary rotation vibration (primary resonance), and the turbine speed Nt at which the peak, that is, the amplitude G is maximum, is the resonance speed Nt_R.

  On the other hand, as shown in FIG. 7B, the vibration phase (swinging phase) of the turbine wheel 201 is a constant phase (this phase) until the resonance rotational speed Nt_R is reached after the turbine wheel 201 starts rotating. In the example, the phase shifts at 0 ° phase. When the turbine rotation speed Nt further increases, the vibration phase attenuates as the vibration amplitude increases, and when the turbine rotation speed Nt exceeds the resonance rotation speed Nt_R, the vibration phase is reversed to a phase of 180 °. Become.

The turbine rotation speed Nt is lower than the resonance rotation speed Nt_R, and the vibration phase (swinging phase) is “0 °” (less than the maximum rotation speed Nt ₀ _max of phase 0 °). The position and the vibration phase (swinging phase) are the same phase. Therefore, the rotational center of the turbine wheel 201 can be shifted to the unbalanced position side by setting the unbalance correction rotational speed Nt_B to a rotational speed lower than the resonant rotational speed Nt_R (see FIGS. 8 and 9). .

In view of this point and the minimum rotation speed Nt _{0 —} min that can sufficiently obtain the vibration G gain, in this embodiment, the unbalance correction rotation speed Nt_B is in the range of [Nt _{0 —} min ≦ Nt_B ≦ Nt _{0 —} max]. Set to. Here, in this example, the maximum rotation speed Nt _{0 —} max (see FIG. 7) at the phase “0 °” is set as the unbalance correction rotation speed Nt_B.

  In step ST103, the driving air supply device 3 and the laser oscillator 1 are controlled to set the turbine rotational speed Nt and the laser output of the laser oscillator 1. Specifically, the drive air supply device 3 is controlled so that the turbine rotation speed Nt becomes the unbalance correction rotation speed Nt_B. Further, the laser output (energy) of the laser oscillator 1 can be heated to a temperature range where the wheel boss 211 is not melted but softened by irradiating the wheel boss 211 (metal) of the turbocharger 200 with laser light. This is a possible laser output value and is set by experiment or simulation.

  Then, with the turbine wheel 201 rotated at the unbalance correction rotation speed Nt_B, the laser beam is continuously irradiated to the end surface 211b of the wheel boss 211 for a certain period of time under the above-described conditions. By the heating by the laser light irradiation, the metal in the laser light irradiation portion is softened, and the softened metal flows outward in the radial direction by the centrifugal force (FIG. 8C).

  Here, when the turbine wheel 201 in the unbalanced state (1) is rotated at the unbalance correction rotational speed Nt_B, as shown in FIGS. 8B and 8C, the rotation center of the turbine wheel 201 is obtained. Since it shifts to the unbalanced position (unbalanced phase (0 ° phase)) side with respect to the swing center, the laser beam irradiation position (heating position) on the unbalanced phase (0 ° phase) side and 180 ° opposite phase side Shifts in the radial direction. That is, the heating position on the 180 ° reverse phase side is shifted by the amount of swinging outward in the radial direction with respect to the unbalanced phase (phase 0 °) side. As a result, as shown in FIG. 8C, the 180 ° opposite phase side is closer to the outer side in the radial direction of the wheel boss 211 (the outer periphery of the wheel boss 211 is closer to the unbalanced phase (0 ° phase) side. Metal flow rate will be generated. That is, as shown in FIG. 9A, the metal flow radius r180 on the 180 ° opposite phase side is larger than the metal flow radius r0 on the unbalanced phase (0 ° phase) side. As a result, the same effect as that obtained by adding a weight to the 180 ° antiphase side can be obtained, so that the unbalance is automatically adjusted (correction processing in the unbalanced state (1)).

Note that the irradiation time for continuously irradiating laser light is set with reference to, for example, an unbalance amount (maximum amplitude of vibration measured by tracking measurement) and a metal flow amount due to laser light irradiation described later. Further, the unbalance correction rotation speed Nt_B at the time of balance correction is not limited to the maximum rotation speed Nt ₀ _max of the phase “0 °”, but is an arbitrary rotation within a range of [Nt ₀ _min ≦ Nt_B ≦ Nt ₀ _max]. A number may be employed.

  In step ST104, as in step ST101 described above, tracking measurement of the primary rotation vibration is performed, and the maximum value (measurement vibration G) of the amplitude of acceleration data (vibration data) measured by this tracking measurement is collected. .

  In step ST105, it is determined whether or not the measurement vibration G collected in step ST104 is equal to or less than the vibration G reference. When the determination result is an affirmative determination (YES) (when measurement vibration G ≦ vibration G reference), after the turbine wheel 201 stops rotating (after the determination result of step ST106 becomes an affirmative determination (YES)) ) Ends the balance correction process.

On the other hand, the vibration data measured in the second tracking measurement is vibration data such as a curve L2 shown in FIG. 7A, for example, and the maximum amplitude of vibration (measured vibration G) is higher than the vibration G reference. If so, the judgment result of the step ST105 is a negative determination (NO), and the process returns to step ST 102, sets the maximum rotational speed Nt ₀ _max phase "0 °" (see FIG. 7) as the unbalance correction rotation speed Nt_B .

  Next, in step ST103, the turbine wheel 201 is rotated at the unbalance correction rotation speed Nt_B. Here, since the turbine wheel 201 is subjected to unbalance correction (first time), when the turbine wheel 201 is rotated at the unbalance correction rotation speed Nt_B, as shown in FIG. The deviation (swing amount) between the center of rotation 201 and the center of swing is small.

  Then, with the turbine wheel 201 in such an unbalanced state (2) rotated at the unbalance correction rotation speed Nt_B, the laser beam is continuously irradiated to the end surface 211b of the wheel boss 211 for a certain period of time under the above-described conditions. By the heating by the laser light irradiation, the metal in the laser light irradiation part is softened, and the softened metal further flows outward in the radial direction by centrifugal force (FIG. 9B), and the metal to the outside The flow amount becomes larger than that in FIG. As a result, the unbalance is further adjusted (correction processing in the unbalanced state (2)).

  After the correction processing in the unbalanced state (2) is completed, in step ST104, tracking measurement of the primary rotation vibration is performed in the same manner as in step ST101 described above, and the acceleration measured by the tracking measurement is measured. The maximum amplitude (measurement vibration G) of the data (vibration data) is collected.

  In step ST105, it is determined whether or not the measured vibration G collected in step ST104 is equal to or less than the vibration G reference. Here, the vibration data measured in the third tracking measurement is, for example, vibration data such as a curve L3 shown in FIG. 7A, and the maximum amplitude of vibration (measured vibration G) is below the vibration G reference. (When measurement vibration ≦ vibration G reference), the determination result in step ST105 is affirmative (YES), and after the turbine wheel 201 stops rotating (the determination result in step ST106 is affirmative determination (YES)). The balance correction process is finished.

  If the measurement vibration G does not fall below the vibration G reference even after the correction processing in the unbalanced state (2), the processes in steps ST102 to ST104 are repeated until the measurement vibration G falls below the vibration G reference. Run repeatedly.

<Effect>
As described above, according to the present embodiment, the laser beam is continuously irradiated onto the end surface 211b of the wheel boss 211, and the unbalance is corrected by the metal flow generated by the heating by the laser beam irradiation. It is possible to suppress the occurrence of sputtering in This eliminates the need for a sputter removal step, thereby reducing the balance correction cycle time.

<Modification 1>
In the above embodiment, the shape of the end portion of the wheel boss 211 is a shape in which the outer wall 211a protruding from the end surface 211b is integrally formed along the entire circumference of the peripheral edge of the wheel boss 211, but is not limited thereto. Instead, the shape of the end portion of the wheel boss 211 may be, for example, a shape as shown in FIG.

<Modification 2>
As another modified example, as shown in FIG. 11A, a tapered surface 211c may be provided on the outer peripheral portion (laser light irradiation portion) of the end surface 211b of the wheel boss 211. The taper surface 211c is a conical taper surface in which the protrusion height in the rotation axis direction of the turbine wheel 201 increases as the distance from the outer periphery (outer wall 211a) of the wheel boss 211 increases. In this example, as shown in FIG. 11A, the laser beam focus of the laser oscillator 1 is adjusted to the outermost diameter Dmax of the tapered surface 211c.

  As described above, the laser light irradiation portion of the end surface 211b of the wheel boss 211 is a tapered surface 211c, and the laser light focus (focus position) of the laser oscillator 1 is adjusted to the outermost diameter Dmax of the tapered surface 211c. The metal flow (metal flow on the 180 ° reverse phase side) generated by the above can be promoted. This will be described below.

  First, as described above, when the turbine wheel 201 in the unbalanced state is rotated at the unbalance correction rotational speed Nt_B, the laser light irradiation position on the 180 ° opposite phase side is irradiated with the laser light on the unbalanced phase (0 ° phase) side. It shifts to the outside in the radial direction (outer peripheral side). Further, when the laser beam focus of the laser oscillator 1 is adjusted to the outermost diameter Dmax of the tapered surface 211c, the laser beam irradiation position becomes closer to the outer periphery of the wheel boss 211 so that the laser beam is focused.

  For this reason, the condensing diameter of the laser light irradiation position on the 180 ° opposite phase side is larger than the condensing diameter of the laser light irradiation position on the unbalance position side (unbalance phase (0 ° phase) side). . As a result, as shown in FIG. 11B, the energy density is increased and the metal flow is promoted on the 180 ° opposite phase side with respect to the unbalanced phase (0 ° phase) side. The balance correction amount becomes large. Here, assuming that the metal flow mass on the 180 ° reverse phase side is m180 and the metal flow mass on the unbalanced phase (0 ° phase) side is m0, the mass difference between m180 and m0 is larger than that in the above embodiment. Increases unbalance efficiency.

  Also in the example shown in FIG. 11, the balance is corrected by the process shown in FIG.

-Other embodiments-
In addition, embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, the technical scope of the present invention includes all modifications within the scope and meaning equivalent to the scope of the claims.

  For example, in the above embodiment, the example in which the balance correcting device of the present invention is used for the balance correction of the turbine wheel 201 has been described. However, the present invention is not limited to this, and is applied to the balance correction of the compressor impeller 202. Also good. In addition, the balance correction device has a structure including a laser oscillator that individually irradiates laser light to each of the turbine wheel 201 and the compressor impeller 202, and the balance correction is performed on both the turbine wheel 201 and the compressor impeller 202. Also good.

  In the above embodiment, the example in which the balance correction device of the present invention is applied to the balance correction of the turbine wheel 201 and the compressor impeller 202 of the turbocharger 200 has been described. However, the present invention is not limited to this, and any other arbitrary It can be applied to balance adjustment of a rotating body.

  INDUSTRIAL APPLICABILITY The present invention can be used for a rotating body balance correcting device that corrects unbalance of rotating bodies such as a compressor impeller of a turbocharger and a turbine wheel.

DESCRIPTION OF SYMBOLS 100 Balance correction apparatus 1 Laser oscillator 2 Laser moving apparatus 3 Drive air supply apparatus 4 Rotation sensor 5 Acceleration sensor 6 Base 7 Arithmetic control apparatus 200 Turbocharger 201 Turbine wheel (rotating body)
211 Wheel boss 211b End surface 211c Tapered surface 202 Compressor impeller

Claims (1)

A balance correction device for correcting an unbalance of a metal rotating body,
A rotation control means for rotating the rotating body around its rotation axis and controlling the number of rotations of the rotating body;
A laser irradiation means for irradiating the rotary body with a laser beam from a rotation axis direction to a position inside the outer peripheral edge of the rotary body to heat the rotary body;
By irradiating the rotating body with laser light from the laser irradiation means in a state where the rotating body is rotated at a rotation speed lower than the resonance rotation speed of the rotating body by the rotation control means, the rotating body A balance correction device configured to heat and soften a portion inside the outer peripheral edge of the balance.

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