JP2010142933A - Centering device and centering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centering device and a centering method capable of simplifying the entire device, and consistently centering a workpiece. <P>SOLUTION: The eccentricity of a workpiece W rotating via a rotary table 1 is detected. The centering action is executed, which corrects the eccentricity by imparting an impact to the workpiece W by a hammer means 25. The centering action is repeated until the eccentricity reaches a preset target convergence value. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a centering device and a centering method.

  When manufacturing a ring-shaped structure (annular workpiece) such as an inner ring or outer ring of a bearing, a lathe process or a grinding process is performed on the annular workpiece. In such a process, it is necessary to center the ring-shaped workpiece (work) by a centering device.

Conventionally, when grinding a ring-shaped workpiece such as a large bearing, a workpiece is temporarily placed on a grinding machine, and a skilled worker applies a gauge for measuring misalignment to the outer periphery of the workpiece. Measure the amount of deflection during one revolution while rotating. Then, a predetermined centering is performed by hitting the vicinity of the maximum shake position using a hammer. That is, in such manual centering work, a skilled worker measures the eccentric amount of the dial gauge, and if the measured result is out of the allowable range, the workpiece is removed using a hammer or the like. Strike, repeat measurement and tap until the work is within the allowable range. However, since this operation is completely a human operation, it is difficult to quantify the relationship between the hit position and the hitting force.

  Therefore, in recent years, a mechanical automatic centering device has been proposed (Patent Document 1 and Patent Document 2) regardless of the centering performed by a skilled worker.

  A centering device described in Patent Document 1 includes a rotation angle position detector that detects a rotation angle position of a rotary table, a radial deviation detector that detects a radial deviation of a workpiece, and detection by the detector. A calculation control circuit for calculating the rotation angle of the workpiece to be displaced based on the result and the detection result of the detector and a correction amount thereof, and a correction machine for pressing the workpiece toward the rotation center by the correction head; It is equipped with.

The centering device described in Patent Document 2 includes a first measuring unit, a first position adjusting unit, a second measuring unit, a second position adjusting unit, a position fixing unit, a control unit, and the like. It is.
JP 60-238258 A JP 2004-345029 A

  However, the one described in Patent Document 1 has a digital scale for measuring the amount of eccentricity in the mechanism of the correction head. For this reason, the structure of the entire apparatus is complicated and expensive. Moreover, when centering a large workpiece with such an apparatus, a large load is applied to the correction head. For this reason, the member which supports this head receives the reaction force of this load. Therefore, it has been difficult to accurately attach a cage for measuring the amount of eccentricity to such a member.

  Moreover, in the thing of patent document 2, a 1st measurement means, a 1st position adjustment means, a 2nd measurement means, a 2nd position adjustment means, a position fixing means, and a control means are provided. Therefore, the structure of the apparatus is equivalent to or more complicated than that described in Patent Document 1.

  In view of the above problems, the present invention provides a centering device and a centering method capable of simplifying the entire apparatus and capable of stably centering a workpiece.

  The centering device of the present invention is a rotation table for rotating a workpiece, a displacement detection means for detecting an eccentric amount of the workpiece rotating via the rotation table, and detected by the displacement detection means. Hammer means for correcting the amount of eccentricity by impact on the workpiece, and the hammer means is a rod capable of reciprocating in the axial direction, a weight attached to the tip of the rod, and a rod by elastic force. And an elastic member that approaches the work along the axial direction and causes the weight to collide with the work.

  According to the centering device of the present invention, the amount of eccentricity of the workpiece can be detected by the displacement detecting means. By applying an impact force to the workpiece with the hammer means, the detected eccentricity can be corrected. The hammer means causes the weight to collide with the work by the elastic force of the elastic member. At this time, the weight is an approach to the work along the axial direction of the rod. For this reason, the weight is guided by the rod to move (slide), and the application of impact force to the workpiece is stabilized.

  The displacement detection means includes a displacement sensor for detecting the eccentric size of the workpiece and a phase detection sensor for detecting the rotation angle phase of the table. The eccentricity detected by the displacement sensor and the phase detection sensor Based on the detected rotation angle phase, the optimum striking force is selected from preset conditions.

  Since the optimum batting force is selected from preset conditions based on the detected value, the optimum centering can be performed.

  The elastic member is formed of a spring member, and the weight collides with the workpiece by an impact force obtained by the elastic force proportional to the compression length of the spring member and the mass of the weight. At this time, it is preferable to be able to adjust the impact force by changing the elastic force of the elastic member and / or the mass of the weight.

  The workpiece may be a workpiece in a vertical lathe and a horizontal lathe, or a workpiece in a vertical grinder and a horizontal grinder. Further, the eccentricity can be corrected even when the workpiece rotation is stopped after the eccentricity of the workpiece is detected.

  The centering method of the present invention detects the amount of eccentricity of a workpiece rotating via a centering rotary table, and applies an impact force to the workpiece with a hammer means to correct the amount of eccentricity. The centering method repeats the centering operation until the eccentric amount reaches a preset convergence target value, wherein the workpiece eccentric amount when the workpiece makes one rotation and the phase of the rotary table The relationship is obtained, and the centering operation is repeated until the amount of eccentricity falls within the convergence target value.

  In the present invention, an impact force may be applied to the workpiece by the hammer means according to the detected amount of eccentricity, and centering can be easily performed. Since the weight moves while being guided by the rod, the application of impact force to the workpiece is stable, and the correction accuracy can be improved.

  Since the optimum striking force is selected from preset conditions based on the detected value, optimum centering can be performed and relatively high-precision centering can be performed.

  If the impact force can be adjusted by changing the elastic force of the elastic member and / or the mass of the weight, the impact force according to the correction amount can be applied, and the centering operation time can be shortened.

  The centering device can be used for a vertical lathe and a horizontal lathe, and can be used for a vertical grinder and a horizontal grinder, so that the processing accuracy by the lathe and the grinder can be improved.

  According to the method of the present invention, centering can be performed until the convergence target value is reached, and high-precision centering can be performed.

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

  1 to 3 show a centering device according to the present invention. The centering device includes a rotary table 1 on which a workpiece W is placed, and a drive mechanism 2 that rotates the rotary table 1 about its axis. And an impact force imparting structure 3 that imparts an impact force to the workpiece W (ring-shaped workpiece such as an inner ring and an outer ring of a bearing) on the rotary table 1.

  The drive mechanism 2 includes a bearing structure 6 that supports the center shaft 5 of the turntable 1 so as to be rotatable about its axis, a drive motor 7, an output shaft 8 of the drive motor 7, and the center shaft 5. And an interlocking member 9 that interlocks and couples. The interlocking member 9 includes a sprocket 11 attached to the center shaft 5 of the rotary table 1, a sprocket 12 attached to the output shaft 8 of the drive motor 7, and a chain (not shown) that is hung around these sprockets 11, 12. ). The bearing structure 6 and the drive motor 7 are supported by the base 10. The base 10 includes a substrate 14 and legs 15 that support the substrate 14. An adjuster 19 is attached to the lower end of the corner portion of the leg 15.

  For this reason, when the drive motor 7 is driven, the rotation of the output shaft 8 is transmitted to the central shaft 5 through the interlocking member 9, and the rotary table 1 rotates about its axis. A tension applying mechanism 23 that applies tension to the chain is provided between the sprockets 11 and 12. That is, the tension applying mechanism 23 has a rotating disk 24, and the rotating disk 24 presses the chain from the outside. This applies tension to the chain.

  A plurality of workpiece receivers 13 are arranged on the turntable 1 at a predetermined pitch along the circumferential direction. The workpiece receiver 13 includes a horizontal portion 16 fixed to the rotary table 1 and a vertical portion 17 erected from the outer diameter side of the horizontal portion 16, and a workpiece W is formed on an upper end surface 17 a of the vertical portion 17. Will receive.

  A plurality of rough guides 18 are provided at a predetermined pitch along the circumferential direction on the outer peripheral side of the work receiver 13. It has a guide surface 20 for guiding a corner portion between the lower end surface of the work W and the outer diameter surface. That is, the rough guide 18 includes a horizontal portion 21 fixed to the rotary table 1 and a vertical portion 22 erected from the inner diameter side of the horizontal portion 21, and a tapered surface is formed on the upper inner diameter side of the vertical portion 22. This tapered surface forms the guide surface 20. When the work W is placed on the turntable 1, the center of the work W (eccentricity) should be several millimeters smaller than the outer diameter surface of the work W so as not to be excessive. The guide surface 20 of the rough guide 18 is arranged on a large arc.

  The impact force imparting structure 3 is installed on a support column 56 erected from the substrate 14 of the base 10. As shown in FIGS. 4 to 8, the impact force applying structure 3 includes hammer means 25 that applies an impact force to the workpiece W. The hammer means 25 includes a rod 26 that can reciprocate in the axial direction, a weight 27 attached to the tip of the rod 26, and a resilient force that causes the rod 26 to approach the workpiece W along the axial direction. And an elastic member 28 for causing the weight 27 to collide with the workpiece W. The support column 56 includes a support column 56a and a receiving plate 56b connected to the upper end of the support 56a, and the substrate 30 is placed and fixed on the receiving plate 56b.

  A support base 31 is erected on the substrate 30, and a rod support 32 is attached on the support base 31. That is, the rod support 32 has a bearing structure 34 that accommodates the bearings 33, 33, and the rod 26 can slide along the axial center direction through the bearings 33, 33 of the bearing structure 34. Is inserted. Note that a recess 36 (see FIG. 8) for fitting an elastic member is provided on the end surface of the bearing structure 34 on the weight side. The support base 31 includes a pair of legs 31a and 31a and an upper wall 31b connecting the upper ends of the legs 31a and 31a. The rod support 32 is disposed on the upper wall 31b.

  The weight 27 is formed of a disc body in which a circumferential groove 35 having a V-shaped cross section is formed on the proximal end side of the outer diameter surface 27 a, and the proximal end surface 27 b is connected to the distal end of the rod 26. For example, a screw portion may be provided at the tip of the rod 26 and this screw portion may be screwed into a screw hole provided in the base end surface 27 b of the weight 27. As a result, the weight 27 is detachable from the rod 26. A spring member made of a coil spring constituting the elastic member 28 is interposed between the weight 27 and the rod support 32. Moreover, the front end surface 27c of the weight 27 is a convex curved surface.

A stopper member 37 is attached to the end of the rod 26 on the side opposite to the weight. That is, a threaded portion 38 is provided at the end of the rod 26 on the side opposite to the weight, and nut members 39, 39 constituting the stopper member 37 are screwed onto the threaded portion 38. Therefore, in the free state, the elastic member 28 between the weight 27 and the rod support 32 presses the weight 27 in the direction of arrow A in FIG. 7 so that the stopper member 37 contacts the rod support 32. It touches. From this state, if the weight 27 is pressed in the direction of arrow B, the weight 27 and the rod 26 slide in the direction of arrow B against the resilient force of the resilient member 28.

  The operation mechanism 40 slides the weight 27 in the direction of arrow B against the elastic force of the elastic member 28. The operation mechanism 40 includes a chuck mechanism 41 that engages with the weight 27, and a moving mechanism 42 that moves the chuck mechanism 41 parallel to the axial direction of the rod 26.

The moving mechanism 42 is configured by a linear guide mechanism that is a single-axis actuator. The linear guide mechanism includes a mechanism main body 43 fixed on the substrate 30 and a movable table 45 that reciprocates along the longitudinal direction of the main body 43. The chuck mechanism 41 includes a pair of claw members 46 and 46 that engage with the circumferential groove 35 of the weight 27, and a drive unit 47 that opens and closes the pair of claw members 46 and 46.

The claw members 46 and 46 have a triangular shape so that the cross-sectional shape thereof fits in the circumferential groove 35, is disposed along the vertical direction, and is disposed at a 180 ° symmetrical position with respect to the axis of the weight 27. . The drive unit 47 includes a casing 48 disposed on the table 45 and a drive mechanism (not shown) such as a ball screw mechanism built in the casing 48. Then, the claw members 46 and 46 are connected to the drive mechanism via the attachment pieces 49 and 49.

  For this reason, the claw members 46 and 46 approach and separate by driving of the drive mechanism. That is, as shown in FIG. 6, the claw members 46, 46 are simultaneously moved in the direction of arrow C so that the claw members 46, 46 approach and engage with the circumferential groove 35 of the weight 27. . Further, the claw members 46 and 46 are simultaneously moved in the direction of the arrow D, the claw members 46 and 46 are separated, and the engaged state is released.

  A position detector 50 including a proximity sensor that detects the position of the weight 27 is disposed in the vicinity of the weight 27. That is, the support arm 51 is erected from the table 45, and the position detector 50 is attached to the tip of the support arm 51. A flange 52 is provided on the outer diameter surface 27 a of the weight 27, and the position detector 50 faces the outer diameter surface of the flange 52. When the position detector 50 is not a proximity sensor, a contact sensor such as a non-contact photo sensor or a differential transformer may be used.

  By the way, in this device, the striking position and the striking force are automatically set, and the centering operation is performed. For this reason, a control unit 81 is provided as shown in FIG. That is, the rotary table 1 and the like are housed in a casing 80, and a control unit 81 is attached to the casing 80.

  As shown in FIG. 9, the control unit 81 includes a setting unit 75 that sets a convergence value of the eccentric amount of the workpiece W, a displacement detection unit 70 that detects the eccentric amount of the workpiece W, and a data table storage unit 76. And a control means 77.

  The convergence value set by the setting means 75 is an acceptable convergence value of the misalignment of the workpiece W. In the present invention, the centering operation is performed until the convergence value is within the convergence value. As shown in FIG. 4, the displacement detection means 70 includes a displacement sensor 71 that detects the eccentric size of the workpiece W and a phase detection sensor 72 that detects the rotation angle phase of the table 1. In addition, the displacement sensor 71 is installed in the support pillar 79 standingly arranged from the board | substrate 14 of the base 10, as shown in FIG. The support column 79 includes a support column 79a and a receiving plate 79b connected to the upper end of the support column 79a.

The displacement sensor 71 is disposed close to the impact force applying structure 3. Since the displacement sensor 71 only needs to be able to detect the eccentric size of the workpiece, it may be a non-contact type or a contact type, and various types of sensors can be used.

  In this case, the phase detection sensor 72 uses the proximity sensor 73. A proximity sensor is a sensor that detects that a detection object has approached without contact, instead of a mechanical switch such as a limit switch or a micro switch. The main proximity sensors are roughly classified into the following three types according to the difference in operating principle. There are three types: a high-frequency oscillation type that uses electromagnetic induction, a magnetic type that uses magnets, and a capacitance type that uses changes in capacitance. Although not shown, the proximity sensor 73 is also installed on a support column that is erected from the substrate 14 of the base 10.

  In this embodiment, a plurality of recesses (dogs) 74 are provided on the outer peripheral surface 1 a of the turntable 1 at a predetermined pitch (constant pitch) along the circumferential direction, and the recesses (dogs) 74 are detected by the proximity sensor 73. I have to. That is, the number of pulses when the table 1 makes one round is counted by detecting the concave portion (dog) 74 with the proximity sensor 73.

  The control unit 77 calculates the maximum eccentricity position (rotation angle phase) from the eccentricity obtained by the displacement sensor 71 and information from the proximity sensor 73 that detects the rotation angle phase of the table 1. Further, it is determined which position should be hit with the condition (hitting force) of which data table (data table stored in the data table storage means), and a command is issued to the hammer means 25. Further, a centering command is issued until the eccentricity amount falls within a preset convergence value. Control of the displacement detection means 70 and the control means 77 is performed using PLC (Programmable Logic controller).

  The data table for selecting the striking angle (striking force or impact force) is divided into two types: a position (distance) at which the weight 27 is retracted and a time from each retracted position until the weight 27 collides with the workpiece W (arrival time). Create For example, this data table is prepared in about five stages. In addition, a dial gauge is applied to the vicinity of the hammer means 25 on the outer periphery of the workpiece W, and the hammering operation is performed about 10 times by manual operation, and sampling of the movement amount (center misalignment correction amount) of the workpiece W at that time Measurement) to obtain an average value of the movement amount. These operations are performed in five stages.

  Next, a centering method using the centering apparatus configured as described above will be described with reference to FIG. First, as shown in step S1, a centering convergence value for the workpiece W is set. Next, as shown in step S <b> 2, a work (workpiece) W is mounted on the turntable 1. That is, it is placed on the workpiece receiver 13. At this time, as shown in step S3, rough alignment is performed with the rough guide 18 (implementation). The above is the preparation process.

  Next, as shown in step S4, an automatic start is instructed. Thereby, as shown in step S5, the phase detection sensor 72 (displacement measurement sensor) is brought into contact with the workpiece (workpiece) W. In this state, as shown in step S6, rotation driving of the turntable 1 is started. Along with this rotation, as shown in step S <b> 7, the eccentric amount of the workpiece (workpiece) W is measured by the displacement sensor 71.

  As shown in step S8, the maximum value of misalignment and the rotation angle phase of the turntable 1 are calculated, and the optimum hitting force is selected from the data table as shown in step S9. Then, as shown in step S10, the hammer means 25 is instructed to center.

  The emphasis operation of the displacement sensor 71 that detects the amount of eccentricity and the hammer means 25 that performs the centering operation will be described. At this time, the number of pulses when the table 1 makes one round is counted by the recess (dog) 74 provided on the outer periphery of the rotary table 1 at a predetermined interval (a predetermined angle) and the proximity sensor 73 provided in the vicinity of the rotary table 1. It can be so. Further, since the concave portion (dog) 74 provided mechanically cannot provide a fine interval, it is divided as necessary electrically to increase the accuracy of angle detection. The rotary table 1 is provided with an origin sensor that outputs once during one round.

  The angular velocity obtained by the set table rotation speed is obtained. Based on the angular velocity obtained under the above conditions and the data obtained from the proximity sensor for phase detection and the origin sensor, the number of positions where the maximum shake is seen from the origin position of the table 1 is specified. Using this specified information, the timing (advancing angle) at which the hammer strikes the maximum eccentric position is calculated. With these controls, it is possible to know how far the table should be advanced from the eccentric maximum position obtained by the displacement sensor 71 even if the set speed of the rotary table 1 is changed. Naturally, when the weight 27 and the rod 26 are pulled further rearward, the collision speed increases, so that the hitting position is calculated in consideration of the conditions obtained from the data table.

  The horizontal positioning of the single-axis actuator (linear guide mechanism 43) obtained from the parameters of the data table is performed. That is, with the claw members 46, 46 of the moving mechanism 42 closed, the linear guide mechanism 43 is driven with the claw members 46, 46 engaged with the circumferential grooves 35 of the weight 27, and the weight 27 is stopped at a position to be appropriately positioned. Thereafter, the claw members 46 are separated from each other to be opened. As a result, the restriction state of the weight 27 by the moving mechanism 42 is released, and the weight 27 collides with the workpiece W by the elastic force of the elastic member 28. That is, the outer peripheral surface of the workpiece W can be hit with the weight 27, and a centering operation can be performed.

  Thereafter, the process proceeds to step S11 to determine whether the misalignment is within the convergence value. That is, if the misalignment is within the convergence value, the centering operation is finished (completed), and if the misalignment is not within the convergence value, the process returns to step S7. That is, at the time of automatic operation, a target centering amount (target convergence value) is set in advance, and the work is rotated once by the combination of the displacement sensor 71 and the proximity sensor 73 for detecting the rotary table phase. The relationship between the amount of eccentricity and the phase is obtained, and the centering operation is repeated until the amount of eccentricity is within the convergence.

  In the present invention, it is only necessary to apply an impact force to the workpiece W by the hammer means 25 according to the detected amount of eccentricity, and centering can be performed easily. Since the weight moves while being guided by the rod, the application of impact force to the workpiece is stable, and the correction accuracy can be improved.

  Since the optimum striking force is selected from preset conditions based on the detected value, optimum centering can be performed and relatively high-precision centering can be performed.

  In the embodiment, the weight 27 can be attached to and detached from the rod 26, so that the weight 27 can be replaced, and the mass of the weight 27 can be changed. Further, the elastic force of the elastic member can be changed by changing the retracted position of the weight 27. For this reason, it is possible to adjust the impact force by changing the elastic force of the elastic member 28 and / or the mass of the weight 27. That is, the impact force can be adjusted by changing only the elastic force of the elastic member 28, changing only the mass of the weight 27, or changing the elastic force of the elastic member 28 and the mass of the weight 27. . Thus, if the impact force can be adjusted by changing the elastic force of the elastic member 28 and / or the mass of the weight 27, the impact force according to the correction amount can be applied, and the centering operation time can be shortened. Can be achieved.

  In addition, since the optimum striking force is selected from preset conditions based on the detected value, optimum centering can be performed, and relatively highly accurate centering can be performed.

  According to the method of the present invention, centering can be performed until the convergence target value is reached, and high-precision centering can be performed.

  By the way, the workpiece W may be a workpiece in a vertical lathe and a horizontal lathe, or a workpiece in a vertical grinder and a horizontal grinder. As described above, the centering device according to the present invention can be used for a vertical lathe and a horizontal lathe, and can be used for a vertical grinder and a horizontal grinder, thereby improving processing accuracy by the lathe and the grinder. be able to. Further, the eccentricity can be corrected even when the workpiece rotation is stopped after the eccentricity of the workpiece is detected.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the data table prepared in advance is not limited to five stages. The increase or decrease is arbitrary. Further, the number of hits by manual operation when sampling the movement amount (center misalignment correction amount) of the workpiece is not limited to ten. In addition, the increase / decrease in the number of the concave portions 74 for the proximity sensor is arbitrary, but if it is too small, the measurement accuracy is lowered, and if it is too large, the workability is poor. For this reason, the number of the recessed parts 74 can be variously set according to the size of the workpiece W, the rotation speed of the turntable 1, and the like. Further, the size of the recess 74 can be variously changed within a range that can be detected by the sensor to be used. The size and weight of the weight 27 can be variously changed within a range where an optimum hitting force is obtained. The workpiece W is not limited to the inner ring and the outer ring of the bearing, and may be a disk-shaped workpiece that is not a ring-shaped workpiece. Further, the workpiece posture may be vertical or horizontal.

  As the material of the weight 27 to be used, various materials can be selected as long as the strength that does not cause deformation or damage when the workpiece W is struck and the mass that can give a desired striking force can be secured. . In addition, the work striking surface (in this case, the front end surface 27c) of the weight 27 is a convex arc surface in the embodiment, but can be variously changed within a range in which a desired striking force can be applied to the work W. . For this reason, the shape of the entire weight 27 is not limited to the disk body as in the embodiment.

It is a front view of the centering apparatus of this invention. It is a rear view of the centering device. It is a top view of the said centering apparatus. It is a principal part enlarged plan view of the said centering apparatus. It is an enlarged view which shows the hammer means of the said centering apparatus. It is a side view of the hammer means of the centering device. It is an enlarged front view of the hammer means of the centering device. It is an enlarged plan view of the hammer means of the centering device. It is a simplified block diagram of the control part of the said centering apparatus. It is a flowchart figure of the centering method of this invention.

Explanation of symbols

1 Rotary table 25 Hammer means 26 Rod 27 Weight 28 Elastic member 70 Displacement detecting means 71 Displacement sensor 72 Phase detection sensor W Workpiece

Claims (10)

  A rotary table for rotating the work, a displacement detecting means for detecting the eccentric amount of the work rotating through the rotary table, and the eccentric quantity detected by the displacement detecting means for impacting the work The hammer means comprises a rod capable of reciprocating in the axial direction, a weight attached to the tip of the rod, and a resilient force that moves the rod along the axial direction. A centering device comprising: an elastic member that causes the weight to collide with the workpiece.   The displacement detection means includes a displacement sensor for detecting the eccentric size of the workpiece and a phase detection sensor for detecting the rotation angle phase of the table. The eccentricity detected by the displacement sensor and the phase detection sensor 2. The centering device according to claim 1, wherein an optimum hitting force is selected from preset conditions based on the detected rotation angle phase.   2. The elastic member comprises a spring member, and the weight collides with the workpiece by an impact force obtained by an elastic force proportional to a compression length of the spring member and a mass of the weight. Or the centering apparatus of Claim 2.   4. The centering device according to claim 3, wherein the impact force can be adjusted by changing the elastic force of the elastic member and / or the mass of the weight.   The centering device according to any one of claims 1 to 4, wherein the workpiece is a workpiece in a vertical lathe.   The centering apparatus according to claim 1, wherein the workpiece is a workpiece in a horizontal lathe.   The centering device according to any one of claims 1 to 4, wherein the workpiece is a workpiece in a vertical grinding machine.   The centering apparatus according to claim 1, wherein the workpiece is a workpiece in a horizontal grinding machine.   The centering device according to any one of claims 1 to 8, wherein the eccentric amount can be corrected even after the workpiece rotation is stopped after the workpiece eccentric amount is detected.   The amount of eccentricity of the rotating workpiece is detected via the rotary table, and the centering operation is performed to correct the amount of eccentricity by applying an impact force to the workpiece with the hammer means, and the amount of eccentricity is preset. A centering method that repeats the centering operation up to a convergence target value, and obtains the relationship between the amount of eccentricity of the workpiece and the phase of the rotary table when the workpiece rotates once, and the amount of eccentricity is the convergence target value. The centering method is characterized in that the centering operation is repeated until within the range.

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