Grinding machine

Abstract

To provide a grinder capable of more effectively suppressing occurrence of an eccentricity and an eccentric phase in a circular part.SOLUTION: A control device of a grinder has an eccentricity storage part, an interpolation eccentricity calculation part, and a traverse operation control part. The eccentricity storage part converts eccentricities e and eccentric phases d at a plurality of positions in an axial direction Z of a longest circular part 81A into target eccentricities Ea and target eccentric phases D, and stores the target eccentricities and the target eccentric phases. The interpolation eccentricity calculation part calculates target interpolation eccentricities Eb among the plurality of positions in the axial direction Z of the longest circular part 81A, on the basis of the target eccentricities Ea. The traverse operation control part subjects the longest circular part 81A to traverse grinding using the target eccentricities Ea, the target eccentric phases D and the target interpolation eccentricities Eb.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a grinding machine.

Background Art

[0002] A grinding machine includes a workpiece support device that supports and rotates a workpiece, a grinding wheel device that supports and rotates a grinding wheel, and grinds the outer peripheral surface of the workpiece supported by the workpiece support device with the grinding wheel. When precisely grinding a workpiece with a grinding machine, there are various error factors according to the required machining accuracy. Examples of error factors include deflection associated with both ends of the workpiece being supported by the workpiece support device, and differences in rigidity in the circumferential direction associated with a part of the shape of the workpiece being eccentric. These factors are known to cause roundness errors.

[0003] For example, in the cylindrical grinding method and apparatus of Patent Document 1, a device for correcting errors occurring in roundness is provided. Specifically, in this cylindrical grinding method, after performing a trial grinding of an unprocessed workpiece, the roundness error of this workpiece is measured, and roundness correction data is created based on this roundness error. Then, by performing normal grinding using the roundness correction data, the roundness of the cylindrical grinding surface is made highly accurate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a grinding machine, in addition to the occurrence of roundness errors in the workpiece, there may also occur eccentricity errors in which the position of the central axis of the workpiece is displaced in the radial direction in the axial direction of the workpiece. That is, in the workpiece to be ground on the grinding machine, for example, there are residual stresses (internal stresses) resulting from forging, heat treatment, etc. These residual stresses exist in various states depending on the shape, machining state, etc. of the workpiece. And when the workpiece is ground on the grinding machine, the residual stress of the workpiece may be released, causing the workpiece to bend (flex). Along with this, vibration may occur in the rotating workpiece, and there is a risk that the vibration accuracy of the ground workpiece deteriorates.

[0006] In a conventional grinding machine, in order to prevent the vibration accuracy of the workpiece from deteriorating, after rough grinding the workpiece, the residual stress of the workpiece is once released. Then, by reducing the amount of vibration generated by the rotation of the workpiece and performing finish grinding, it is made difficult for eccentricity errors to occur in the workpiece.

[0007] However, when the axial length of the grinding part where grinding is performed is longer than the width of the grinding wheel, after plunge grinding is performed in which the grinding wheel relatively moves in the intersecting direction of the workpiece with respect to a plurality of locations in the axial direction of this grinding part to grind the workpiece, traverse grinding is performed in which the grinding wheel relatively moves in the axial direction of the workpiece to grind the workpiece. In this case, through the inventor's research, it was found that there is room for improvement in a conventional grinding machine that once releases the residual stress of the workpiece in order to effectively suppress eccentricity errors.

[0008] The present invention has been made in view of such problems, and aims to provide a grinding machine that can more effectively suppress the occurrence of eccentricity amount and eccentricity phase in a circular-shaped part.

Means for Solving the Problems

[0009] One aspect of the present invention is a workpiece support device that holds a workpiece having a circular-shaped part by a chuck and rotates the workpiece about the central axis of the circular-shaped part, A grinding wheel device that supports and rotates a grinding wheel, An intersecting movement device that relatively moves the grinding wheel in an intersecting direction intersecting the central axis, A parallel movement device that relatively moves the grinding wheel in an axial direction parallel to the central axis, A control device that controls operations of the workpiece support device, the intersecting movement device, and the parallel movement device, and is provided with, The control device is, An eccentricity storage unit that converts and stores the eccentricity amounts and eccentricity phases at a plurality of positions in the axial direction of the circular portion, measured in a state where the gripping by the chuck is released after grinding of the circular portion, into a target eccentricity amount and a target eccentricity phase obtained by shifting the eccentricity phase by 180 degrees, An interpolation eccentricity calculation unit that calculates or calculates and stores a target interpolation eccentricity amount between a plurality of positions in the axial direction based on the target eccentricity amounts at the plurality of positions in the axial direction, The workpiece support device is given an angle command for the workpiece, the intersecting movement device is given, as a command, a calculated position calculated from the angle command for the workpiece, the target eccentricity amount, the target eccentricity phase, and the target interpolation eccentricity amount corresponding to the position in the axial direction, and the parallel movement device is given a position command in the axial direction of the grinding wheel with respect to the workpiece to perform traverse grinding on the circular portion, and has a traverse operation control unit in a grinding machine.

Effect of the Invention

[0010] In the grinding machine of the above aspect, when performing traverse grinding, measures are taken to make it difficult for eccentricity errors to occur. Specifically, the eccentricity storage unit of the control device stores the target eccentricity amounts and target eccentricity phases at a plurality of positions in the axial direction of the circular-shaped part. Further, the interpolation eccentricity calculation unit calculates or calculates and stores the target interpolation eccentricity amounts between a plurality of positions in the axial direction of the circular-shaped part. The target eccentricity amounts and target eccentricity phases are the eccentricity amounts and eccentricity phases at a plurality of positions in the axial direction that occur in the circular-shaped part of the workpiece in a state where traverse grinding is performed and the gripping by the chuck is released. After being obtained by actual measurement after trial grinding, these eccentricity amounts and eccentricity phases are stored as data for correcting the eccentricity amounts and eccentricity phases. The target interpolation eccentricity amounts are calculated based on the target eccentricity amounts at a plurality of positions in the axial direction of the circular-shaped part.

[0011] Then, the traverse motion control unit of the control device gives an angle command for the workpiece to the workpiece support device, gives an angle command for the workpiece, the calculated position calculated from the target eccentricity amount, target eccentricity phase, and target interpolation eccentricity amount corresponding to the axial position as a command to the cross movement device, and gives an axial position command for the grinding wheel carriage with respect to the workpiece to the parallel movement device to perform traverse grinding on the circular-shaped part.

[0012] With this configuration, according to the grinding machine of the above aspect, the generation of the eccentricity amount and eccentricity phase in the circular-shaped part can be more effectively suppressed.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 11

Mode for Carrying Out the Invention

[0014] Preferred embodiments of the above-described grinding machine will be described with reference to the drawings. <Embodiment 1> 1. Configuration of Grinding Machine 1 The configuration of the grinding machine 1 will be described with reference to FIGS. 1 and 2. The grinding machine 1 of this embodiment is a cylindrical grinding machine for grinding the outer peripheral surface of the workpiece 8. The grinding machine 1 rotates the workpiece 8 and rotates the grinding wheel 31, and relatively moves the grinding wheel 31 in a direction intersecting the central axis 801 of the workpiece 8 with respect to the workpiece 8, thereby grinding the outer peripheral surface of the workpiece 8. Further, the grinding machine 1 of this embodiment is for grinding a compressor shaft, a camshaft, etc.

[0015] The grinding machine 1 can be applied to a workpiece traversing type grinding machine, a grinding wheel traversing type grinding machine, etc. The workpiece traversing type grinding machine is a grinding machine that moves the workpiece 8 in a direction parallel to the central axis 801 of the workpiece 8 with respect to the bed 11 and moves the grinding wheel 31 in a direction intersecting the central axis 801 of the workpiece 8. The grinding wheel traversing type grinding machine is a grinding machine that moves the grinding wheel 31 in a direction parallel to the central axis 801 of the workpiece 8 and also moves it in a direction intersecting the central axis 801 of the workpiece 8 with respect to the bed 11.

[0016] In addition, a radial grinding machine or an angular grinding machine can also be applied to the grinding machine 1 of this embodiment. The radial grinding machine is a grinding machine in which the grinding wheel 31 moves relatively in a direction orthogonal to the central axis 801 of the workpiece 8. The angular grinding machine is a grinding machine in which the grinding wheel 31 moves relatively in a direction obliquely intersecting the central axis 801 of the workpiece 8.

[0017] The grinding machine 1 of this embodiment is a workpiece traversing type grinding machine and a radial grinding machine, and will be described by taking this as an example. In the grinding machine 1 of this embodiment, the axial direction Z is a direction parallel to the horizontal direction and along the central axis 801 of the circular portion 81 of the workpiece 8. The intersecting direction X is a direction parallel to the horizontal direction and intersects the axial direction Z. In particular, in this embodiment, the intersecting direction X is a direction orthogonal to the axial direction Z.

[0018] The grinding machine 1 includes a workpiece support device 2, a grinding wheel device 3, an intersecting movement device 4, a parallel movement device 5, an eccentricity measurement device 7, and a control device 6.

[0019] The workpiece support device 2 is configured to support both ends of the workpiece 8 on the bed 11 and rotate and drive the workpiece 8 at a predetermined rotational speed about the central axis 801 of the workpiece 8. The workpiece support device 2 has a spindle headstock 21 that transmits the rotational force from a motor 24 as a rotational drive source to one end of the workpiece 8, and a center rest 22 that rotatably supports the other end of the workpiece 8.

[0020] The spindle headstock 21 is provided with a center member that supports the center of the end of the workpiece 8 and a chuck 211 that grips the end of the workpiece 8. The rotational speed of the workpiece 8 can be appropriately changed by changing the rotational speed of the motor 24 of the spindle headstock 21. The tailstock 22 is provided with a center member that supports the center of the end of the workpiece 8.

[0021] An encoder 25 as a position detector is attached to the motor 24 of the spindle headstock 21, and the rotational position (rotation angle) of the center axis 801 of the workpiece 8 by the spindle headstock 21 is detected by the encoder 25. When the workpiece 8 is supported by the workpiece support device 2, the reference position C0 in the circumferential direction C of the workpiece 8 shown in FIGS. 4 and 5 is set as the rotational reference position in the circumferential direction C by the encoder 25.

[0022] The grinding wheel device 3 is configured to support and rotate a grinding wheel 31. The grinding wheel device 3 has a shaft portion 32 on which the grinding wheel 31 is supported and a drive portion 33 that rotationally drives the shaft portion 32 by a motor 34 as a rotational drive source. In this embodiment, the central axis of the grinding wheel 31 is parallel to the central axis 801 of the workpiece 8. The grinding wheel 31 is formed as a disk-shaped member, and the outer peripheral surface of the grinding wheel 31 grinds the outer peripheral surface of the workpiece 8.

[0023] The cross movement device 4 is configured to relatively move the grinding wheel 31 in a cross direction X perpendicular to the central axis 801 of the workpiece 8. The cross movement device 4 of this embodiment is configured to move the grinding wheel device 3 and the grinding wheel 31 in the cross direction X intersecting the central axis 801 of the workpiece 8. In this embodiment, the cross movement device 4 is configured to bring the outer peripheral surface of the grinding wheel 31 close to the outer peripheral surface of the workpiece 8. In the cross movement device 4, the feed speed of the grinding wheel 31 to the outer peripheral surface of the workpiece 8 is determined. Also, in the cross movement device 4, when the grinding wheel 31 contacts the workpiece 8, the cutting amount k corresponding to the feed speed is determined. The rotational peripheral speeds of the workpiece 8 and the grinding wheel 31 are faster than the feed speed of the grinding wheel 31. Note that the rotational direction of the workpiece 8 and the rotational direction of the grinding wheel 31 may be the same direction or the opposite direction.

[0024] The cross movement device 4 includes a grinding wheel table 41 on which the grinding wheel device 3 is placed, a ball screw 42 and a linear guide 43 for moving the grinding wheel table 41 in the cross direction X, a motor 44 for rotationally driving the ball screw 42, an encoder 45 as a position detector for detecting the position of the grinding wheel 31 in the cross direction X based on the rotation amount of the motor 44, and the like. When the motor 44 is driven and the grinding wheel table 41 moves in the cross direction X via the ball screw 42 and the linear guide 43, the grinding wheel device 3 moves in the cross direction X. The cross movement device 4 is configured on the bed 11 of the grinding machine 1. Note that a linear motor may be used instead of the ball screw 42.

[0025] The movement position of the grinding wheel 31 in the cross direction X by the cross movement device 4 is detected by the encoder 45. Further, by time-differentiating the movement amount per unit time of the grinding wheel 31 by the encoder 45, the movement speed (feed speed) of the grinding wheel 31 in the cross direction X is detected. The movement position of the grinding wheel 31 in the cross direction X by the encoder 45 of the cross movement device 4 is synchronized with the rotational position of the workpiece 8 in the circumferential direction C by the encoder 25 of the spindle headstock 21 of the workpiece support device 2.

[0026] The parallel movement device 5 is configured to relatively move the grinding wheel 31 in the axial direction Z parallel to the central axis 801 of the workpiece 8. The parallel movement device 5 of the present embodiment is configured to move the spindle headstock 21 and the center rest 22 in the workpiece support device 2 in the axial direction Z along the central axis 801 of the workpiece 8 with respect to the grinding wheel 31 of the grinding wheel device 3. The parallel movement device 5 is configured to change the position in the axial direction Z of the workpiece 8 that faces the outer peripheral surface of the grinding wheel 31. Further, the movement speed of the grinding wheel 31 in the axial direction Z of the workpiece 8 is determined by the parallel movement device 5.

[0027] The parallel movement device 5 is composed of a workpiece table 51 on which the spindle headstock 21 and the follower rest 22 are placed, a ball screw 52 and a linear guide 53 for moving the workpiece table 51 in the axial direction Z, a motor 54 for rotationally driving the ball screw 52, an encoder 55 serving as a position detector for detecting the position of the workpiece 8 in the axial direction Z based on the rotation amount of the motor 54, and the like. When the motor 54 is driven and the workpiece table 51 moves in the axial direction Z via the ball screw 52 and the linear guide 53, the workpiece 8 supported by the spindle headstock 21 and the follower rest 22 moves in the axial direction Z. The parallel movement device 5 is configured on the bed 11 of the grinding machine 1. Note that a linear motor may be used instead of the ball screw 52.

[0028] The movement position of the workpiece 8 in the axial direction Z by the parallel movement device 5 is detected by the encoder 55. Further, by time-differentiating the movement amount per unit time of the workpiece 8 by the encoder 55, the movement speed (feed speed) of the workpiece 8 in the axial direction Z is detected. The movement position of the workpiece 8 in the axial direction Z by the encoder 55 of the parallel movement device 5 is synchronized with the rotational position of the workpiece 8 in the circumferential direction C by the encoder 25 of the spindle headstock 21 of the workpiece support device 2.

[0029] In the grinding machine 1, an eccentricity measuring device 7 for measuring the outer diameter of the workpiece 8 is used. The eccentricity measuring device 7 is provided at a position facing the grinding wheel spindle 31 via the workpiece 8. The outer diameter of the portion of the workpiece 8 ground by the grinding wheel spindle 31 is measured by the eccentricity measuring device 7.

[0030] The control device 6 controls the operations of the workpiece support device 2, the grinding device 3, the cross movement device 4, and the parallel movement device 5. The control device 6 synchronously controls the operations of the workpiece support device 2, the cross movement device 4, and the parallel movement device 5, and enables plunge grinding P in which the workpiece 8 is ground while the grinding wheel spindle 31 is relatively moved in the cross direction X, and traverse grinding T in which the workpiece 8 is ground while the grinding wheel spindle 31 is relatively moved in the axial direction Z.

[0031] For example, when the control device 6 performs plunge grinding P on the workpiece 8, it mainly performs plunge grinding control for controlling the cross movement device 4. Further, when the control device 6 performs traverse grinding T on the workpiece 8, it mainly performs traverse grinding control for controlling the parallel movement device 5.

[0032] In plunge grinding P, the moving speed at which the grinding wheel 31 approaches the workpiece 8 in the cross direction X by the cross movement device 4 is made slower as the grinding wheel 31 approaches the central axis 801 of the workpiece 8. With this configuration, as the grinding by plunge grinding P becomes deeper, the cutting amount k by the grinding wheel 31 becomes smaller, and the machining accuracy after grinding can be maintained well.

[0033] The plunge grinding P of the longest circular shape portion 81A of this embodiment is performed by a single cut. In other words, the plunge grinding P of the longest circular shape portion 81A is not performed stepwise as rough grinding and finish grinding, but is performed as grinding by a single continuous cut. Traverse grinding T is performed such that the moving speed of the workpiece 8 in the axial direction Z by the parallel movement device 5 is constant over the entire length in the axial direction Z of the longest circular shape portion 81A.

[0034] The control device 6 is configured to control the rotation of the motor 24 of the workpiece support device 2, the rotation of the motor 34 of the grinding device 3, the rotation of the motor 44 of the cross movement device 4, the rotation of the motor 54 of the parallel movement device 5, and the like. The control device 6 drives the drive circuit 653 to control the rotation of the motor 34 of the grinding device 3. The control device 6 feedback-controls the motors 24, 44, 54 of the workpiece support device 2, the cross movement device 4, and the parallel movement device 5 by the drive circuits 652, 654, 655 so that the position detection values by the encoders 25, 45, 55 of the workpiece support device 2, the cross movement device 4, and the parallel movement device 5 become target values.

[0035] 2. Description of the workpiece 8 and the grinding wheel 31 Regarding the shape of the workpiece 8 and the positional relationship between the workpiece 8 and the grinding wheel 31 during grinding, reference will be made to FIGS. 3 and 4 for description. As shown in FIGS. 3 and 4, the workpiece 8 to be ground by the grinding machine 1 of the present embodiment is, for example, a compressor shaft. The compressor shaft has a circular portion 81 having a circular cross-section centered on the central axis 801, and an eccentric-shaped portion 82 having a cross-section shaped eccentric in any radial direction from the central axis 801. The eccentric-shaped portion 82 may be a non-circular portion having a non-circular cross-section that is not circular. In the circular portion 81, there are journal portions 812 formed at both ends of the compressor shaft, and a longest circular portion 81A as a grinding portion 811 formed at a portion on one side in the axial direction Z. The eccentric-shaped portion 82 is formed at a portion on the other side in the axial direction Z. It should be noted that the central axis 801 of the workpiece 8 and the central axis 801 of the circular portion 81 are the same.

[0036] In the present embodiment, the longest circular portion 81A of the workpiece 8 is the object of grinding. Therefore, a plurality of plunge grindings P1, P2, P3, P4 and one traverse grinding T are performed on the longest circular portion 81A of the workpiece 8. In FIG. 3, the case of performing plunge grinding four times is indicated by arrows P1, P2, P3, P4, and the case of performing traverse grinding once is indicated by arrow T. The directions of the arrows P1, P2, P3, P4, T in FIG. 3 indicate the state in which the grinding wheel 31 moves relative to the workpiece 8.

[0037] The length of the longest circular portion 81A in the axial direction Z, which is the object of grinding, is longer than the width of the grinding wheel 31. Therefore, as shown in FIG. 3, the plurality of plunge grindings P1, P2, P3, P4 are performed at different positions in the axial direction Z of the workpiece 8. One traverse grinding T is performed from one side to the other side in the axial direction Z of the longest circular portion 81A.

[0038] As shown in Fig. 4, the reference position C0 in the circumferential direction C of the workpiece 8 is set, for example, as the 0° position in the circumferential direction C where any eccentric-shaped portion 82 of the workpiece 8 protrudes. That is, the rotational reference position in the circumferential direction C by the encoder 25 of the spindle headstock 21 shown in Figs. 1 and 2 is set as the position where the reference position C0 in the circumferential direction C of the workpiece 8 faces the grinding wheel 31. When the workpiece 8 rotates by the spindle headstock 21, the encoder 25 detects at which position in the range of 0° to 360° the rotational position of the workpiece 8 is located.

[0039] 3. Eccentric error When grinding the longest circular-shaped portion 81A of the workpiece 8, an eccentric error occurs in this longest circular-shaped portion 81A. The eccentric error will be described with reference to Figs. 5 and 6.

[0040] In the workpiece 8 to be ground on the grinding machine 1, there are residual stresses (internal stresses) resulting from, for example, forging, heat treatment, etc. These residual stresses are balanced as positive and negative (tensile and compressive) residual stresses so as to maintain the force equilibrium condition throughout the workpiece 8. Also, the residual stresses exist in various states depending on the shape, processing state, etc. of the workpiece 8. When the workpiece 8 is ground on the grinding machine 1, deflection (bending) may occur due to the release of the residual stresses of the workpiece 8. The deflection occurring in this workpiece 8 causes an eccentric error in the workpiece 8, which is shown as an eccentric phase (eccentric direction or orientation of eccentricity) d and an eccentric amount e centered on the central axis 801 of the workpiece 8.

[0041] The deflection in the workpiece 8 is considered to occur during and after grinding. Also, this deflection in the workpiece 8 is considered to occur when the support of the workpiece 8 by the workpiece support device 2 is released. Further, when grinding is performed on the first grinding site 811 and the second grinding site 811 spaced apart in the axial direction Z in the workpiece 8, it is also considered that deflection occurs in the already ground first grinding site 811 due to the grinding of the second grinding site 811. The direction of the eccentricity phase d that occurs in the workpiece 8 is determined according to the shape, processing state, etc. of the workpiece 8. In FIGS. 5 and 6, for convenience, the eccentricity phase d is shown as the direction of 270° from the reference position C0 (0°).

[0042] 4. Detailed Configuration of the Control Device 6 The detailed configuration of the control device 6 will be described with reference to FIGS. 1 to 9. As shown in FIG. 7, the control device 6 includes a basic grinding program acquisition unit 61, a plunge motion control unit 62A, a traverse motion control unit 62B, an eccentricity storage unit 63, and an interpolation eccentricity calculation unit 64.

[0043] The basic grinding program acquisition unit 61 acquires a program for basic grinding that does not include correction processing for eccentricity error. As shown in FIG. 3, the basic grinding program is a program for executing a plurality of plunge grindings P1, P2, P3, P4 and one traverse grinding T on the longest circular shape portion 81A.

[0044] The plunge motion control unit 62A sequentially performs plunge grindings P1, P2, P3, P4 at a plurality of locations in the axial direction Z of the longest circular shape portion 81A before the traverse grinding T. The traverse motion control unit 62B performs traverse grinding T on the longest circular shape portion 81A after the plunge grindings P1, P2, P3, P4 are performed.

[0045] As shown in FIGS. 1, 2, and 4, the plunger operation control unit 62A and the traverse operation control unit 62B of the control device 6 are configured to synchronize the movement position of the grinding wheel 31 in the crossing direction X by the encoder 45 of the crossing movement device 4, the movement position of the workpiece 8 in the axial direction Z by the encoder 55 of the parallel movement device 5, and the rotational position of the workpiece 8 in the circumferential direction C by the encoder 25 of the workpiece support device 2. More specifically, when the workpiece 8 makes one rotation by the workpiece support device 2, the encoder 25 of the workpiece support device 2 detects how many rotational positions from the rotation reference position C0 of the workpiece 8 in the circumferential direction C are facing the grinding wheel 31. Also, when the workpiece 8 moves in the axial direction Z by the parallel movement device 5, the encoder 55 of the parallel movement device 5 detects which position in the axial direction Z of the longest circular shape portion 81A is facing the grinding wheel 31.

[0046] When performing the plunge grinding P1, P2, P3, P4, the plunge operation control unit 62A gives an angle command of the workpiece 8 to the workpiece support device 2. When performing the plunge grinding P4, the plunge operation control unit 62A gives an angle command of the workpiece 8 to the workpiece support device 2, and gives, as a command, the calculated position calculated from the angle command of the workpiece 8, the target eccentricity amount Ea, and the target eccentric phase D at the outer position Z4 in the axial direction Z of the longest circular shape portion 81A to the crossing movement device 4. The plunge operation control unit 62A gives, as a command, a predetermined cutting amount k for plunge grinding in the crossing direction X of the grinding wheel 31 with respect to the workpiece 8 to the crossing movement device 4.

[0047] Also, when performing the plunge grinding P1, P2, P3, P4, the plunge operation control unit 62A controls the drive circuit 654 of the crossing movement device 4 according to the rotational position of the workpiece 8 in the circumferential direction C by the encoder 25 of the workpiece support device 2 to change the movement position of the grinding wheel 31 in the crossing direction X. Thereby, when the plunge grinding P1, P2, P3, P4 is performed, the rotational position of the workpiece 8 in the circumferential direction C and the movement position of the grinding wheel 31 in the crossing direction X are synchronized.

[0048] When performing traverse grinding T, the traverse motion control unit 62B gives an angle command for the workpiece 8 to the workpiece support device 2, and gives a command to the cross movement device 4 with the angle command for the workpiece 8, the target eccentricity Ea according to the position in the axial direction Z of the longest circular shape portion 81A, the target eccentricity phase D, and the calculated position calculated from the target interpolation eccentricity Eb, and gives an axial direction Z position command of the grinding wheel 31 with respect to the workpiece 8 to the parallel movement device 5. The traverse motion control unit 62B gives a predetermined cutting amount k for traverse grinding to the cross movement device 4 as a command in the cross direction X of the grinding wheel 31 with respect to the workpiece 8.

[0049] Also, when performing traverse grinding T, the traverse motion control unit 62B controls the drive circuit 654 of the cross movement device 4 according to the rotational position in the circumferential direction C of the workpiece 8 by the encoder 25 of the workpiece support device 2 and the moving position in the axial direction Z of the workpiece 8 by the encoder 55 of the parallel movement device 5, to change the moving position in the cross direction X of the grinding wheel 31. Thereby, when the traverse grinding T is performed, the rotational position in the circumferential direction C of the workpiece 8, the moving position in the axial direction Z of the workpiece 8, and the moving position in the cross direction X of the grinding wheel 31 are synchronized.

[0050] The predetermined cutting amount k is given to the cross movement device 4 from the plunge motion control unit 62A as the predetermined cutting amount k for plunge grinding used for plunge grinding, and is given to the cross movement device 4 from the traverse motion control unit 62B as the predetermined cutting amount k for traverse grinding used for traverse grinding.

[0051] The eccentricity storage unit 63 stores the target eccentricity phase D and the target eccentricity amount Ea based on the eccentricity phase d and the eccentricity amount e obtained by actual measurement as shown in FIGS. 5 and 6. The target eccentricity amount Ea is made the same as the eccentricity amounts e at a plurality of positions in the axial direction Z of the longest circular shape portion 81A obtained by actual measurement. The target eccentricity phase D is obtained by shifting the eccentricity phase d of the longest circular shape portion 81A obtained by actual measurement by 180 degrees.

[0052] When storing the target eccentricity phase D and the target eccentricity amount Ea in the eccentric memory unit 63 of this embodiment, trial grinding is performed on workpieces 8 of various shapes by plunge grinding P1, P2, P3, P4 and traverse grinding T using the grinding machine 1. Then, the eccentricity phase d and the eccentricity amount e of the longest circular portion 81A of the workpiece 8 after grinding are measured, and the target eccentricity phase D and the target eccentricity amount Ea obtained based on the eccentricity phase d and the eccentricity amount e are stored in the eccentric memory unit 63.

[0053] The interpolation eccentricity calculation unit 64 calculates and stores the target interpolation eccentricity amount Eb between a plurality of positions in the axial direction Z of the longest circular portion 81A based on the target eccentricity amounts Ea at the plurality of positions in the axial direction Z. The target interpolation eccentricity amount Eb is calculated as a value between two adjacent target eccentricity amounts Ea in the axial direction Z. The target interpolation eccentricity amount Eb is stored in the same format as the target eccentricity amount Ea.

[0054] The eccentricity phase d and the eccentricity amount e of the longest circular portion 81A are measured in a state where the chuck 211 of the spindle headstock 21 releases the gripping of the workpiece 8 after grinding the longest circular portion 81A. The eccentricity phase d and the eccentricity amount e are obtained by various methods. The eccentricity phase d and the eccentricity amount e can be measured using an external measuring device (not shown) after removing the workpiece 8 from the grinding machine 1. Also, the eccentricity phase d and the eccentricity amount e may be measured using the encoder 25 and the eccentricity measuring device 7 of the workpiece support device 2 in the grinding machine 1.

[0055] In the external measuring device or the eccentricity measuring device 7, for a plurality of locations in the axial direction Z of the longest circular portion 81A after the traverse grinding T, the center points of the diameters at a plurality of locations corresponding to 180° in the circumferential direction C are actually measured as a group of center points, and how much and in which radial direction the center of gravity of this group of center points deviates from the central axis 801 of the workpiece 8 is obtained as the eccentricity phase d and the eccentricity amount e. Note that the plurality of locations corresponding to 180° in the circumferential direction C may be, for example, a plurality of locations arranged at equal intervals at an angle of 1 to 5° etc. in the circumferential direction C.

[0056] The eccentric phase d is usually measured in the same radial direction of the workpiece 8, and the eccentricity e is usually measured as a larger value the closer it is to the central position in the axial direction Z of the workpiece 8. The measured eccentricity e may be made into the target eccentricity Ea and the target interpolation eccentricity Eb whose values are continuous in the axial direction Z by performing regression analysis or the like. The target eccentricity Ea and the target interpolation eccentricity Eb may be stored as values that change stepwise in the axial direction Z.

[0057] Note that the external measuring device or the eccentricity measuring device 7 includes a contact type measuring instrument in which a measuring element contacts the longest circular portion 81A of the workpiece 8 for measurement, and a non-contact type measuring instrument in which a laser or the like is scanned on the longest circular portion 81A of the workpiece 8 for measurement. In the present embodiment, for example, a dimension setting device or the like provided on the grinding machine 1 is used as the eccentricity measuring device 7, and when the workpiece 8 is rotated about its central axis 801 by the workpiece support device 2, the eccentric phase d and the eccentricity e at each location in the axial direction Z of the longest circular portion 81A may be measured.

[0058] In the eccentricity storage unit 63 of the present embodiment, the target eccentric phase D and the target eccentricity Ea for a plurality of locations in the axial direction Z of the longest circular portion 81A after the plunge grinding P1, P2, P3, P4 and the traverse grinding T are performed are stored. In the grinding machine 1 of the present embodiment, after the plunge grinding P1, P2, P3 are performed at a plurality of locations in the axial direction Z with respect to the longest circular portion 81A, the plunge grinding P4 at the final position is performed while correcting the eccentric phase d and the eccentricity e, and the traverse grinding T is performed while correcting the eccentric phase d and the eccentricity e. After the plunge grinding P4 and the traverse grinding T at the final position as trial grinding are performed, the eccentric phase d and the eccentricity e are actually measured for a plurality of locations in the axial direction Z of the longest circular portion 81A.

[0059] As shown in FIG. 4, in the eccentric memory unit 63, the target eccentric phase D and the target eccentric amount Ea of each part in the axial direction Z of the longest circular shape part 81A are stored with reference to the reference position C0 in the circumferential direction C of the workpiece 8. The reference position C0 in the circumferential direction C of the workpiece 8 may be, for example, the direction in which any one of the eccentric shape parts 82 protrudes from the central axis 801 of the workpiece 8. Further, the rotational reference position in the circumferential direction C of the workpiece 8 supported by the workpiece support device 2 may be the reference position C0 in the circumferential direction C of the workpiece 8.

[0060] The eccentric phase d and the eccentric amount e are caused by the release of the stress remaining inside the workpiece 8 before grinding when the plunge grinding P1, P2, P3, P4 and the traverse grinding T are performed. More specifically, the eccentric phase d and the eccentric amount e of the present embodiment are stored as the deflection in the longest circular shape part 81A of the workpiece 8 after the traverse grinding T is performed and after the ground workpiece 8 is removed from the workpiece support device 2. Note that the eccentric phase d and the eccentric amount e may be actually measured in the state where the ground workpiece 8 is supported by the workpiece support device 2 after the traverse grinding T is performed.

[0061] This deflection in the longest circular shape part 81A generally becomes larger at a position closer to the center in the axial direction Z of the workpiece 8. And after the plunge grinding P1, P2, P3, P4 and the traverse grinding T are performed, at each part in the axial direction Z of the longest circular shape part 81A, the deflection amount becomes larger at a position closer to the center in the axial direction Z, and accordingly, the eccentric amount e also becomes larger.

[0062] As shown in FIGS. 5 and 6, in the compressor shaft as the workpiece 8 of the present embodiment, the eccentric phase d of the longest circular shape part 81A as the grinding part 811 is directed to one side in the radial direction with respect to the central axis 801 of the workpiece 8 in design. Further, the eccentric amount e of the longest circular shape part 81A becomes larger as it approaches the center in the axial direction Z of the workpiece 8. The target eccentric amount Ea stored in the eccentric memory unit 63 and the target interpolation eccentric amount Eb stored in the interpolation eccentric calculation unit 64 are stored as values that change continuously and smoothly in the axial direction Z through regression analysis or the like.

[0063] As shown in FIG. 9, in the plunger operation control unit 62A and the traverse operation control unit 62B, a target eccentricity Ea for correcting the eccentricity e at a plurality of positions in the axial direction Z obtained by actual measurement and a target interpolation eccentricity Eb for correcting the eccentricity e between a plurality of positions in the axial direction Z are used. In this embodiment, for example, the eccentricity e and the eccentric phase d are actually measured at four positions, i.e., the center side position Z1, the intermediate positions Z2 and Z3, and the outer side position Z4 in the axial direction Z of the outer peripheral surface 83 to be ground, and the target eccentricity Ea and the target eccentric phase D are created based on the eccentricity e and the eccentric phase d at these positions Z1, Z2, Z3, and Z4.

[0064] Also, for the position Z12 between the center side position Z1 and the first intermediate position Z2, the target interpolation eccentricity Eb is created by interpolating the target eccentricity Ea of the center side position Z1 and the target eccentricity Ea of the first intermediate position Z2. Also, for the position Z23 between the first intermediate position Z2 and the second intermediate position Z3, the target interpolation eccentricity Eb is created by interpolating the target eccentricity Ea of the first intermediate position Z2 and the target eccentricity Ea of the second intermediate position Z3. Also, for the position Z34 between the second intermediate position Z3 and the outer side position Z4, the target interpolation eccentricity Eb is created by interpolating the target eccentricity Ea of the second intermediate position Z3 and the target eccentricity Ea of the outer side position Z4. The target interpolation eccentricity Eb may be created by linear interpolation or by various interpolation methods other than linear interpolation.

[0065] The target eccentricity Ea and the target interpolation eccentricity Eb may be stored in the eccentricity storage unit 63 and the interpolation eccentricity calculation unit 64 as data of the offset amount of the position of the central axis at each position in the axial direction Z of the longest circular shape portion 81A. Also, the target interpolation eccentricity Eb may be obtained by calculation during the operation of the grinding machine 1.

[0066] Also, when storing the target eccentricity Ea and the target eccentric phase D in the eccentricity storage unit 63, instead of performing trial grinding, grinding simulation may be performed to estimate the eccentricity e and the eccentric phase d at a plurality of locations in the axial direction Z generated in the longest circular shape portion 81A.

[0067] As shown in FIGS. 5, 6, 8, and 9, the plunger operation control unit 62A adjusts the moving position of the grinding wheel 31 in the intersecting direction X with respect to the longest circular portion 81A of the workpiece 8 in synchronization with the rotational position in the circumferential direction C of the workpiece 8 so as to correct the eccentricity e and the eccentric phase d at the outer position Z4 in the axial direction Z of the longest circular portion 81A. Further, the traverse operation control unit 62B adjusts the moving position of the grinding wheel 31 in the intersecting direction X with respect to the longest circular portion 81A of the workpiece 8 in synchronization with the rotational position in the circumferential direction C of the workpiece 8 and the moving position in the axial direction Z of the workpiece 8 so as to correct the eccentricity e and the eccentric phase d at the intermediate positions Z2, 3 and the central side position Z1 in the axial direction Z of the longest circular portion 81A.

[0068] Then, when the plunger operation control unit 62A and the traverse operation control unit 62B execute the basic grinding program by the basic grinding program acquisition unit 61, they control the respective motors 24, 34, 44, 54 in consideration of the correction amounts of the eccentricity e and the eccentric phase d. When the plunge grinding P4 is performed, the rotational position in the circumferential direction C of the workpiece 8 and the moving position in the intersecting direction X of the grinding wheel 31 are synchronized in a state where the eccentricity e and the eccentric phase d are corrected by the plunger operation control unit 62A. When the traverse grinding T is performed, the rotational position in the circumferential direction C of the workpiece 8, the moving position in the axial direction Z of the workpiece 8, and the moving position in the intersecting direction X of the grinding wheel 31 are synchronized in a state where the eccentricity e and the eccentric phase d are corrected by the traverse operation control unit 62B.

[0069] The plunger operation control unit 62A and the traverse operation control unit 62B are configured to correct the grinding wheel 31 to approach the workpiece 8 at positions in the circumferential direction C closer to the eccentric direction as the eccentric phase d in the longest circular portion 81A, and to correct the grinding wheel 31 to approach the workpiece 8 at positions in the axial direction Z where the eccentricity e is larger in the longest circular portion 81A. With this configuration, the eccentricity e generated in the longest circular portion 81A can be appropriately reduced.

[0070] Also, with this configuration, when the longest circular portion 81A is deflected after the traverse grinding T, the central axis of this longest circular portion 81A is likely to coincide with the central axis 801 of the workpiece 8. The plunger operation control unit 62A and the traverse operation control unit 62B intentionally change the grinding positions in the axial direction Z and the circumferential direction C by the grinding wheel 31 in anticipation of the deflection occurring in the longest circular portion 81A after the plunge grinding P4 and the traverse grinding T.

[0071] As shown in FIG. 9, the plunger operation control unit 62A performs plunge grindings P1, P2, and P3 on the central side position Z1 and the intermediate positions Z2 and Z3 in the axial direction Z of the longest circular portion 81A. Next, when the plunge grinding P4 is performed at the outer position Z4 in the axial direction Z of the longest circular portion 81A, a cutting feed for plunge grinding is given by the plunger operation control unit 62A, and a cutting feed for traverse grinding is given by the traverse operation control unit 62B. That is, the plunge grinding P4 at the outer position Z4 in the axial direction Z of the longest circular portion 81A is performed by the plunger operation control unit 62A giving a cutting feed for plunge grinding, and then, when the traverse operation control unit 62B gives a cutting feed for traverse grinding, the moving position in the cross direction X of the grinding wheel 31 synchronized with the rotational position in the circumferential direction C of the longest circular portion 81A is adjusted to correct the eccentricity e and the eccentric phase d. Thereafter, the traverse operation control unit 62B synchronizes with the rotational position in the circumferential direction C of the longest circular portion 81A and the moving position in the axial direction Z of the longest circular portion 81A, and performs traverse grinding T on the intermediate positions Z2 and Z3 and the central side position Z1 in the axial direction Z of the longest circular portion 81A so as to correct the eccentricity e and the eccentric phase d by adjusting the moving position in the cross direction X of the grinding wheel 31 to the grinding outer peripheral surface 83.

[0072] In FIG. 9, the grinding amounts Kp by the plunge grindings P1, P2, P3, and P4 and the grinding amount Kt by the traverse grinding T are schematically shown. At the outer position Z4 in the axial direction Z of the longest circular portion 81A, it is ground to the finish position by the plunge grinding P4.

[0073] Also, as shown in FIG. 8, the target eccentricity Ea and the target interpolated eccentricity Eb are set to be larger at positions closer to the center in the axial direction Z of the workpiece 8, in other words, at positions closer to the center in the axial direction Z of the longest circular portion 81A. With this configuration, it is possible to make the correction amount in the cross direction X of the grinding wheel 31 by the plunge motion control unit 62A and the traverse motion control unit 62B larger at positions closer to the center in the axial direction Z where the eccentricity amount e in the eccentricity direction becomes larger.

[0074] FIGS. 5 and 6 schematically show, with exaggeration of the target eccentricity Ea and the target interpolated eccentricity Eb, the states in which plunge grinding P1, P2, P3, P4 and traverse grinding T are performed on the longest circular portion 81A of the workpiece 8. The eccentricity amount e generated in the longest circular portion 81A of the actual workpiece 8 is about several micrometers.

[0075] In FIGS. 5 and 6, for the longest circular portion 81A, the shape before grinding is indicated by reference symbol X0. Also, the eccentric shape with the eccentric phase d and the eccentricity amount e generated in the state where the workpiece 8 is released from the chuck 211 is indicated by reference symbol X1. Further, the corrected shape based on the target eccentric phase D and the target eccentricity Ea stored in the eccentricity storage unit 63 in the state where the workpiece 8 is gripped by the chuck 211 is indicated by reference symbol X2. Furthermore, the shape in which the residual stress of the workpiece 8 is released is indicated by reference symbol X3.

[0076] When in the state of X3 after grinding, if the workpiece 8 is released from the chuck 211 from the state of X3, the residual stress of the workpiece 8 is released by the chuck 211 and becomes the state of X1. On the other hand, if the workpiece 8 is released from the chuck 211 from the state of X2, the residual stress is released by the chuck 211 and becomes the state of X3.

[0077] That is, when the residual stress of the workpiece 8 is released, the workpiece 8 eccentrically moves downward in FIGS. 5 and 6, but part of the residual stress is stored in the chuck 211. Since the residual stress is stored by the chuck 211, it is necessary to grind aiming at the state of X2 instead of grinding aiming at the state of X3. By the plunging operation control unit 62A and the traversing operation control unit 62B, the plunge grinding P4 and the traverse grinding T are performed by intentionally eccentrically moving in the direction opposite to the eccentric direction d and the eccentric amount e in which the longest circular shape portion 81A tends to eccentrically move in response to the release of the residual stress, so that almost no eccentricity occurs in the central axis of the longest circular shape portion 81A after grinding.

[0078] FIG. 8 shows the relationship between the eccentric amount e in the eccentric direction and the target eccentric amount Ea (correction amount) in the target eccentric direction in the eccentric memory unit 63 at each position in the axial direction Z of the longest circular shape portion 81A. The eccentric amount e of the longest circular shape portion 81A increases as it goes toward the center side Za in the axial direction Z. And the target eccentric amount Ea increases as it goes toward the center side Za in the axial direction Z in the direction opposite to the eccentric direction in order to cancel the eccentric amount e.

[0079] The traverse operation control unit 62B of this embodiment performs the traverse grinding T only once from one side to the other side in the axial direction Z of the longest circular shape portion 81A while correcting the eccentric phase d and the eccentric amount e. In addition to this, the traverse operation control unit 62B may perform the traverse grinding T a plurality of times toward one side and the other side in the axial direction Z of the longest circular shape portion 81A. In this case, the traverse operation control unit 62B may correct the eccentric phase d and the eccentric amount e when performing the last traverse grinding T, or may correct the eccentric phase d and the eccentric amount e when performing the plurality of traverse grindings T.

[0080] In the eccentric memory unit 63, not only the target eccentric phase D and the target eccentric amount Ea based on the eccentric phase d and the eccentric amount e generated after grinding the longest circular portion 81A, but also the target eccentric phase D and the target eccentric amount Ea based on the eccentric phase d and the eccentric amount e generated in the longest circular portion 81A after grinding the grinding site 811 other than the longest circular portion 81A in the workpiece 8 may be included. In this case, the plunge motion control unit 62A and the traverse motion control unit 62B can also correct the eccentric phase d and the eccentric amount e generated in the longest circular portion 81A after grinding the grinding site 811 other than the longest circular portion 81A in the workpiece 8.

[0081] 5. Grinding method of the grinding machine 1 The grinding method of the grinding machine 1 will be described with reference to FIGS. 9 and 10. Before the longest circular portion 81A is ground by the grinding machine 1, as trial grinding, plunge grinding P1, P2, P3, P4 and traverse grinding T of the longest circular portion 81A are performed, and the eccentric phase d and the eccentric amount e generated in the longest circular portion 81A are converted into the target eccentric phase D and the target eccentric amount Ea and stored in the eccentric memory unit 63.

[0082] Then, when grinding the longest circular portion 81A of the workpiece 8 as a product, as shown in FIGS. 9 and 10, the control device 6 performs plunge grinding of the center side position Z1 in the axial direction Z of the longest circular portion 81A by the grinding wheel carriage 31 as the first plunge grinding P1 (step S101). At this time, the center side position Z1 of the longest circular portion 81A is ground to a predetermined outer diameter, leaving a predetermined grinding allowance for performing traverse grinding T.

[0083] Next, as shown in FIGS. 9 and 10, the control device 6 performs plunge grinding at a first intermediate position Z2 offset outward Zb from the center side position Z1 in the axial direction Z of the longest circular portion 81A as the second plunge grinding P2 (step S102). Next, the control device 6 performs plunge grinding at a second intermediate position Z3 offset outward Zb from the first intermediate position Z2 in the axial direction Z of the longest circular portion 81A as the third plunge grinding P3 (step S103). At this time, the intermediate positions Z2 and Z3 of the longest circular portion 81A are ground to a predetermined outer diameter that leaves a predetermined grinding allowance for performing traverse grinding T.

[0084] Next, as shown in FIGS. 9 and 10, the control device 6 performs plunge grinding at an outer position Z4 in the axial direction Z of the longest circular portion 81A as the fourth plunge grinding P4 (step S104). As shown in FIG. 9, the outer position Z4 is the position where the traverse grinding T is started, and the plunge grinding P4 at the outer position Z4 is performed until the outer diameter forming the final shape of the longest circular portion 81A is reached.

[0085] When the fourth plunge grinding P4 is given a plunge grinding cut and then a traverse grinding cut, the position in the cross direction X at each position in the circumferential direction C of the grinding wheel 31 at the outer position Z4 is appropriately changed, and correction is performed with the target eccentricity Ea, the target eccentric phase D, and the target interpolation eccentricity Eb. In other words, at the outer position Z4 of the longest circular portion 81A, the eccentricity error as the eccentric phase d and the eccentricity amount e is corrected when the plunge grinding P4 is performed.

[0086] In this way, the plunger operation control unit 62A performs the plunge grinding P1, P2, and P3 based on the basic grinding program obtained by the basic grinding program acquisition unit 61, and performs the plunge grinding P4 based on the basic grinding program and the correction program by the eccentricity storage unit 63 and the interpolation eccentricity calculation unit 64. Then, for the four positions in the axial direction Z of the longest circular shape portion 81A, the plunge grindings P1, P2, P3, and P4 are sequentially performed. Note that the number of times the plunge grindings P1, P2, P3, and P4 are performed is the number corresponding to the relationship between the length of the longest circular shape portion 81A in the axial direction Z and the width of the grinding wheel carriage 31.

[0087] Next, as shown in FIGS. 9 and 10, the control device 6 performs traverse grinding T on the longest circular shape portion 81A while relatively moving the grinding wheel carriage 31 in the axial direction Z of the longest circular shape portion 81A (step S105). At this time, the traverse operation control unit 62B of the control device 6 corrects according to the target eccentricity Ea, the target eccentricity phase D, and the target interpolation eccentricity Eb, and relatively moves the grinding wheel carriage 31 at the position where the fourth plunge grinding P4 is performed from the outer side Zb to the center side Za in the axial direction Z of the longest circular shape portion 81A.

[0088] Then, according to the target eccentricity Ea, the target eccentricity phase D, and the target interpolation eccentricity Eb, the moving position of the grinding wheel carriage 31 in the intersection direction X to each position in the circumferential direction C of the longest circular shape portion 81A changes. Also, as it goes to the center side Za in the axial direction Z of the longest circular shape portion 81A, the target eccentricity Ea of the position of the grinding wheel carriage 31 in the intersection direction X according to the eccentricity e gradually increases. The traverse operation control unit 62B performs traverse grinding T based on the basic grinding program and the correction program by the eccentricity storage unit 63 and the interpolation eccentricity calculation unit 64. In this way, the plunge grindings P1, P2, P3, and P4 and the traverse grinding T are performed on the longest circular shape portion 81A, and the longest circular shape portion 81A with improved eccentricity error as the eccentricity phase d and the eccentricity amount e is formed.

[0089] 6. Function and Effect In the grinding machine 1 of this embodiment, when performing traverse grinding T, a measure is taken to make it difficult for eccentricity errors to occur. Specifically, the eccentricity storage unit 63 of the control device 6 stores the target eccentricity amount Ea and the target eccentricity phase D at a plurality of positions in the axial direction Z of the longest circular shape portion 81A. Further, the interpolation eccentricity calculation unit 64 calculates and stores the target interpolation eccentricity amount Eb between a plurality of positions in the axial direction Z of the longest circular shape portion 81A. The target eccentricity amount Ea and the target eccentricity phase D are data for correcting the eccentricity amount e and the eccentricity phase d at a plurality of positions in the axial direction Z, which occur in the longest circular shape portion 81A of the workpiece 8 in a state where traverse grinding is performed and the gripping by the chuck 211 is released, after being obtained by actual measurement after trial grinding, and are stored as such. The target interpolation eccentricity amount Eb is calculated based on the target eccentricity amount Ea at a plurality of positions in the axial direction Z of the longest circular shape portion 81A.

[0090] Then, the traverse motion control unit 62B of the control device 6 gives an angle command for the workpiece 8 to the workpiece support device 2, gives an angle command for the workpiece 8, a calculated position calculated from the target eccentricity amount Ea, the target eccentricity phase D, and the target interpolation eccentricity amount Eb corresponding to the position in the axial direction Z as a command to the cross movement device 4, and gives a position command in the axial direction Z of the grinding wheel carriage 31 with respect to the workpiece 8 to the parallel movement device 5, and performs traverse grinding on the longest circular shape portion 81A.

[0091] According to the grinding machine 1 of this embodiment, considering the difference in the eccentricity amount e occurring at each part in the axial direction Z of the longest circular shape portion 81A, the movement position in the cross direction X of the grinding wheel carriage 31 is corrected, and plunge grinding P4 and traverse grinding T can be performed. Therefore, according to the grinding machine 1 of this embodiment, the occurrence of eccentricity errors as the eccentricity amount e and the eccentricity phase d in the longest circular shape portion 81A can be more effectively suppressed, and the accuracy of the runout of the workpiece 8 as a product can be improved.

[0092] In addition, in the grinding machine 1 of the present embodiment, traverse grinding T is performed by the eccentricity storage unit 63, the interpolation eccentricity calculation unit 64, the plunge operation control unit 62A, and the traverse operation control unit 62B, so that plunge grinding P1, P2, P3, and P4 is only performed in one step, and the eccentricity error caused by the release of the residual stress of the workpiece 8 after plunge grinding P1, P2, P3, and P4 can be absorbed when traverse grinding T is performed.

[0093] <Embodiment 2> As shown in the flowchart of FIG. 11, in the present embodiment, the control device 6 of the grinding machine 1 performs control by the eccentricity storage unit 63, the interpolation eccentricity calculation unit 64, the plunge operation control unit 62A, and the traverse operation control unit 62B both when performing plunge grinding P1, P2, P3, and P4 and when performing traverse grinding T. In FIG. 11, the grinding method of the grinding machine 1 is shown by steps S201 to S205. In any of steps S201 to S205, the plunge operation control unit 62A and the traverse operation control unit 62B correct and execute the basic grinding program obtained by the basic grinding program acquisition unit 61 with a correction program based on the target eccentricity amount Ea, the target eccentricity phase D, and the target interpolation eccentricity amount Eb stored in the eccentricity storage unit 63 and the interpolation eccentricity calculation unit 64.

[0094] The eccentricity storage unit 63 of the present embodiment stores the target eccentricity amount Ea and the target eccentricity phase D for a plurality of locations in the axial direction Z of the longest circular portion 81A after plunge grinding P1, P2, P3, and P4 and traverse grinding T are performed. The interpolation eccentricity calculation unit 64 of the present embodiment stores the target interpolation eccentricity amount Eb for a plurality of locations in the axial direction Z of the longest circular portion 81A after traverse grinding T is performed.

[0095] In this embodiment, when performing trial grinding of the workpiece 8, plunge grinding P1, P2, P3, P4 is performed at multiple positions in the axial direction Z of the longest circular portion 81A. After performing traverse grinding T on the longest circular portion 81A, in a state where the chuck 211 of the spindle headstock 21 releases the gripping of the workpiece 8, the eccentricity phase d and the eccentricity amount e at multiple positions in the axial direction Z of the longest circular portion 81A are measured. The measured eccentricity phase d and eccentricity amount e are converted, and the target eccentricity amount Ea, the target eccentricity phase D, and the target interpolated eccentricity amount Eb, which are correction data when performing traverse grinding T, are stored.

[0096] The encoder 25 and the eccentricity measuring device 7 of the workpiece support device 2 of this embodiment measure the eccentricity phase d and the eccentricity amount e of the longest circular portion 81A of the workpiece 8 in a state where the workpiece 8 is center-supported and in a state where the chuck 211 of the spindle headstock 21 releases the gripping of the workpiece 8 after the trial grinding of the plunge grinding P1, P2, P3, P4 and the traverse grinding T.

[0097] The plunge motion control unit 62A of this embodiment performs plunge grinding P1, P2, P3, P4 by adjusting the moving position of the grinding wheel head 31 in the intersecting direction X in synchronization with the rotational position of the workpiece 8 in the circumferential direction C so as to correct the eccentricity error as the eccentricity phase d and the eccentricity amount e. Further, the traverse motion control unit 62B performs traverse grinding T by adjusting the moving position of the grinding wheel head 31 in the intersecting direction X in synchronization with the rotational position of the workpiece 8 in the circumferential direction C and the moving position of the workpiece 8 in the axial direction Z so as to correct the eccentricity error.

[0098] In this embodiment, the configuration such as the traverse motion control unit 62B is the same as the configuration of Embodiment 1. In this embodiment, the eccentricity error of the longest circular portion 81A can be corrected separately during plunge grinding and traverse grinding. Thereby, the correction of the eccentricity error can be performed more appropriately.

[0099] Regarding other configurations, functions, and effects of the grinding machine 1 of this embodiment, they are the same as those of Embodiment 1. Also, in this embodiment, the components indicated by the same reference numerals as those shown in Embodiment 1 are the same as the components of Embodiment 1.

[0100] The present invention is not limited to only each embodiment, and it is possible to configure further different embodiments without departing from the gist thereof. Further, the present invention includes various modifications, modifications within an equivalent range, and the like.

Explanation of Signs

[0101] 1 Grinding machine 2 Workpiece support device 21 Headstock 22 Center rest 3 Grinding wheel device 31 Grinding wheel 4 Cross movement device 41 Grinding wheel table 5 Parallel movement device 51 Workpiece table 6 Control device 61 Basic grinding program acquisition unit 62A Plunger operation control unit 62B Traverse operation control unit 63 Eccentric memory unit 64 Interpolation eccentricity calculation unit 7 Eccentric measurement device 8 Workpiece 801 Central axis 81 Circular part 81A Longest circular part 811 Grinding part 82 Eccentric shaped part d Eccentric phase e Eccentricity Da Target eccentric phase Ea Target eccentricity Eb Target interpolation eccentricity k Depth of cut Z-axis direction X Cross direction C Circumferential direction

Claims

1. A workpiece support device that grips a workpiece having a circular portion by a chuck and rotates the workpiece about the central axis of the circular portion, A grinding wheel device that supports and rotates a grinding wheel, An intersecting movement device that relatively moves the grinding wheel in an intersecting direction intersecting the central axis, A parallel movement device that relatively moves the grinding wheel in an axial direction parallel to the central axis, A control device that controls the operations of the workpiece support device, the intersecting movement device, and the parallel movement device, and The control device, An eccentricity storage unit that converts and stores the eccentricity amounts and eccentricity phases at a plurality of positions in the axial direction of the circular portion, which are measured in a state where the gripping by the chuck is released after grinding of the circular portion, into a target eccentricity amount and a target eccentricity phase obtained by shifting the eccentricity phase by 180 degrees, An interpolation eccentricity calculation unit that calculates or calculates and stores a target interpolation eccentricity amount between a plurality of positions in the axial direction based on the target eccentricity amounts at the plurality of positions in the axial direction, A traverse operation control unit that gives an angle command for the workpiece to the workpiece support device, gives a calculated position calculated from the angle command for the workpiece, the target eccentricity amount, the target eccentricity phase, and the target interpolation eccentricity amount corresponding to the position in the axial direction as a command to the intersecting movement device, and gives a position command in the axial direction of the grinding wheel with respect to the workpiece as a command to the parallel movement device to perform traverse grinding on the circular portion.

2. The grinding machine according to claim 1, wherein, in addition to giving the calculated position as a command to the intersecting movement device, a predetermined cutting amount is given as a command.

3. The grinding machine according to claim 2, wherein the control device further has a plunge operation control unit that performs plunge grinding on the circular portion before the traverse grinding.

4. The grinding machine according to claim 3, wherein the predetermined cutting amount includes a predetermined cutting amount for plunge grinding used for the plunge grinding and a predetermined cutting amount for traverse grinding used for the traverse grinding.

5. In the case where the circular portion of the workpiece is subjected to traverse grinding after plunge grinding, during the plunge grinding, the predetermined cutting amount for plunge grinding is given, and an angle command for the workpiece and a calculated position calculated from the target eccentricity amount and the target eccentricity phase corresponding to the position in the axial direction are given as commands to the intersecting movement device.

6. In the case where the circular portion of the workpiece is plunge ground and then traverse ground, during the plunge grinding, only a predetermined depth of cut for the plunge grinding is applied, and the cross feed device is not given, as a command, a position calculated from the angle command of the workpiece, the target eccentricity amount, and the target eccentric phase corresponding to the position in the axial direction, the grinding machine according to claim 4.

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