Grinding machine

Abstract

To provide a grinder capable of improving circularity generated at each position in an axial direction on a grinding outer peripheral surface of a circular part.SOLUTION: A control device of a grinder has a correction amount storage part, an interpolation correction amount calculation part and a traverse operation control part. The correction amount storage part converts a complete round error at each angle for a plurality of positions in an axial direction of a grinding outer peripheral surface of a circular part into correction amounts Da at each of the angles, and stores the complete round error. The interpolation correction amount calculation part calculates interpolation correction amounts Db at each of the angles among the plurality of positions in the axial direction of the grinding outer peripheral surface, on the basis of the correction amounts Da at each of the angles. The traverse operation control part subjects the circular part to traverse grinding using the correction amounts Da at each of the angles, and the interpolation correction amounts Db at each of the angles.SELECTED DRAWING: Figure 9

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. Workpieces to be ground by the grinding machine include, in addition to shaft members having only circular portions, eccentric shaft members such as crankshafts having circular portions and non-circular portions such as eccentric portions. In particular, when grinding an eccentric shaft member as a workpiece, an error may occur in the roundness of the ground outer peripheral surface.

[0003] For example, in the cylindrical grinding method and apparatus of Patent Document 1, a device for correcting an error occurring in roundness is provided. Specifically, in this cylindrical grinding method, after trial grinding of an unprocessed workpiece, the roundness error of this workpiece is measured, and roundness profile data is created based on this roundness error. Then, by performing normal grinding using the roundness profile 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] When grinding an eccentric shaft member as a workpiece having a circular shape portion and an eccentric shape portion, anisotropy of rigidity exists in the workpiece due to the shape. The anisotropy of rigidity indicates that when pressure is applied to the workpiece from the grinding wheel during grinding, the rigidity of the workpiece varies depending on the circumferential position of the workpiece where the pressure is applied. Further, when the axial length of the circular shape portion is longer than the width of the grinding wheel, plunge grinding is performed in which the grinding wheel relatively moves in the intersecting direction of the workpiece with respect to a plurality of positions in the axial direction of the circular shape portion to grind the workpiece, and then traverse grinding is performed in which the grinding wheel relatively moves in the axial direction of the workpiece to grind the workpiece.

[0006] In this case, according to the inventor's research, it has been found that due to the anisotropy of rigidity, a difference in roundness occurs in each part in the axial direction of the ground outer peripheral surface of the circular shape portion, and this roundness deteriorates. Therefore, further improvement is required to improve the roundness occurring in each part in the axial direction of the ground outer peripheral surface of the circular shape portion.

[0007] The present invention has been made in view of such problems, and aims to provide a grinding machine capable of improving the roundness occurring at each position in the axial direction of the ground outer peripheral surface of the circular shape portion.

Means for Solving the Problems

[0008] One aspect of the present invention is a workpiece support device that supports a workpiece having a circular shape portion and a non-circular shape portion and rotates the workpiece about the central axis of the circular shape 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 operations of the workpiece support device, the intersecting movement device, and the parallel movement device, and the control device A correction amount storage unit that stores, as positive and negative values with respect to a reference value for each angle centered on the central axis for a plurality of positions in the axial direction that occur on the ground outer peripheral surface of the circular shape portion, the roundness error measured as positive and negative values, and converts the positive and negative values into correction amounts for each angle at a plurality of positions in the axial direction and stores them. An interpolation correction amount calculation unit that calculates or calculates and stores an interpolation correction amount for each angle between a plurality of positions in the axial direction based on the correction amounts for each angle at a plurality of positions in the axial direction. The workpiece support device is given an angle command for the workpiece, the cross feed device is given, as commands, the correction amount and the interpolation correction amount corresponding to the position in the axial direction for each angle of the workpiece, and the parallel feed device is given a position command in the axial direction of the grinding wheel with respect to the workpiece, and a traverse operation control unit that performs traverse grinding on the circular shape portion is provided in the grinding machine.

Advantages of the Invention

[0009] In the grinding machine of the above aspect, a device for reducing the roundness error during traverse grinding is provided. Specifically, the correction amount storage unit of the control device stores the correction amount for each angle at a plurality of positions in the axial direction of the circular shape portion. Further, the interpolation correction amount calculation unit of the control device calculates or calculates and stores the interpolation correction amount for each angle between a plurality of positions in the axial direction of the circular shape portion. The correction amount is created as data for correcting the roundness error that occurs at a plurality of positions in the axial direction of the ground outer peripheral surface of the circular shape portion where traverse grinding has been performed, after the roundness error is obtained by actual measurement after rough grinding of the circular shape portion. The interpolation correction amount is calculated based on the correction amounts for each angle at a plurality of positions in the axial direction of the circular shape portion.

[0010] Then, the traverse operation control unit of the control device gives an angle command for the workpiece to the workpiece support device, gives, as commands, the correction amount and the interpolation correction amount corresponding to the position in the axial direction for each angle of the workpiece support device to the cross feed device, and gives a position command in the axial direction of the grinding wheel with respect to the workpiece to the parallel feed device, and performs traverse grinding on the circular shape portion.

[0011] With this configuration, according to the grinding machine of the above aspect, the roundness generated at each axial position of the grinding outer peripheral surface of the circular portion can be improved.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 11

Figure 12

Modes for Carrying Out the Invention

[0013] Preferred embodiments of the above-described grinding machine will be described with reference to the drawings. <Embodiment 1> 1. Configuration of the grinding machine 1 The configuration of the grinding machine 1 will be described with reference to FIGS. 1 and 2. The grinding machine 1 in 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 the grinding wheel spindle 31, and relatively moves the grinding wheel spindle 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 in this embodiment is for grinding a crankshaft, a camshaft, etc.

[0014] A workpiece traversing type grinding machine, a grinding wheel traversing type grinding machine, etc. can be applied to the grinding machine 1. The workpiece traversing type grinding machine is a grinding machine 1 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 spindle 31 in a direction intersecting the central axis 801 of the workpiece 8. The grinding wheel traversing type grinding machine is a grinding machine 1 that moves the grinding wheel spindle 31 in a direction parallel to the central axis 801 of the workpiece 8 with respect to the bed 11 and also moves it in a direction intersecting the central axis 801 of the workpiece 8.

[0015] Further, a radial grinding machine or an angular grinding machine can also be applied to the grinding machine 1 in this embodiment. The radial grinding machine is a grinding machine 1 in which the grinding wheel spindle 31 relatively moves in a direction orthogonal to the central axis 801 of the workpiece 8. The angular grinding machine is a grinding machine 1 in which the grinding wheel spindle 31 relatively moves in a direction obliquely intersecting the central axis 801 of the workpiece 8.

[0016] The grinding machine 1 in this embodiment is a workpiece traversing type grinding machine and a radial grinding machine, and this will be described 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 intersecting the axial direction Z. In particular, in this embodiment, the intersecting direction X is a direction orthogonal to the axial direction Z.

[0017] The grinding machine 1 includes a workpiece support device 2, a grinding wheel device 3, an orthogonal movement device 4, a parallel movement device 5, a radius measurement device 7, and a control device 6.

[0018] The workpiece support device 2 is configured to support both end portions of the workpiece 8 on the bed 11 and rotationally 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 portion of the workpiece 8, and a center rest 22 that rotatably supports the other end portion of the workpiece 8.

[0019] Further, the spindle headstock 21 may be provided with a center member that supports the center of the end portion of the workpiece 8, or may be provided with a chuck mechanism that grips the end portion 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. Also, the center rest 22 is provided with a center member that supports the center of the end portion of the workpiece 8.

[0020] 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 central 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, a 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.

[0021] 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 workpiece 8 is ground by the outer peripheral surface of the grinding wheel 31.

[0022] The cross-feed device 4 is configured to relatively move the grinding wheel carriage 31 in the cross direction X perpendicular to the central axis 801 of the workpiece 8. The cross-feed device 4 of this embodiment is configured to move the grinding device 3 and the grinding wheel carriage 31 in the cross direction X intersecting the central axis 801 of the workpiece 8. In this embodiment, the cross-feed device 4 is configured to bring the outer peripheral surface of the grinding wheel carriage 31 closer to the outer peripheral surface of the workpiece 8. In the cross-feed device 4, the feed rate of the grinding wheel carriage 31 to the outer peripheral surface of the workpiece 8 is determined. Further, in the cross-feed device 4, when the grinding wheel carriage 31 contacts the workpiece 8, the depth of cut k corresponding to the feed rate is determined. The rotational peripheral speeds of the workpiece 8 and the grinding wheel carriage 31 are faster than the feed rate of the grinding wheel carriage 31. Note that the rotational direction of the workpiece 8 and the rotational direction of the grinding wheel carriage 31 may be the same direction or the opposite direction.

[0023] The cross-feed device 4 includes a grinding wheel table 41 on which the grinding device 3 is mounted, 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 carriage 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 device 3 moves in the cross direction X. The cross-feed 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.

[0024] The moving position of the grinding wheel carriage 31 in the cross direction X by the cross-feed device 4 is detected by the encoder 45. Further, by time-differentiating the amount of movement of the grinding wheel carriage 31 per unit time by the encoder 45, the moving speed (feed rate) of the grinding wheel carriage 31 in the cross direction X is detected. The moving position of the grinding wheel carriage 31 in the cross direction X by the encoder 45 of the cross-feed 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.

[0025] The parallel movement device 5 is configured to relatively move the grinding wheel carriage 31 in the axial direction Z parallel to the central axis 801 of the workpiece 8. The parallel movement device 5 of this 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 carriage 31 of the grinding 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 carriage 31. Further, the movement speed of the grinding wheel carriage 31 in the axial direction Z of the workpiece 8 is determined by the parallel movement device 5.

[0026] The parallel movement device 5 is configured using a workpiece table 51 on which the spindle headstock 21 and the center 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 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 center 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.

[0027] 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 amount of movement of the workpiece 8 per unit time 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.

[0028] In the grinding machine 1, a radius measuring device 7 for measuring the radius and outer diameter of the workpiece 8 is used. The radius measuring device 7 is provided at a position facing the grinding wheel carriage 31 via the workpiece 8. The radius and outer diameter of the position of the workpiece 8 ground by the grinding wheel carriage 31 are measured by the radius measuring device 7.

[0029] The control device 6 controls the operations of the workpiece support device 2, the grinding wheel 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 can perform plunge grinding P in which the workpiece 8 is ground while relatively moving the grinding wheel carriage 31 in the cross direction X, and traverse grinding T in which the workpiece 8 is ground while relatively moving the grinding wheel carriage 31 in the axial direction Z.

[0030] 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. The plunge grinding P is performed such that the moving speed at which the cross movement device 4 approaches the workpiece 8 with the grinding wheel carriage 31 in the cross direction X becomes slower as the grinding wheel carriage 31 approaches the central axis 801 of the workpiece 8. The 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 grinding position of the workpiece 8.

[0031] 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 wheel 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 wheel device 3. The control device 6 feedback-controls the drive circuits 652, 654, and 655 of the respective motors 24, 44, and 54 of the workpiece support device 2, the cross movement device 4, and the parallel movement device 5 such that the detected values of the positions by the respective encoders 25, 45, and 55 of the workpiece support device 2, the cross movement device 4, and the parallel movement device 5 become the target values.

[0032] 2. Description of the workpiece 8 and the grinding wheel carriage 31 The shape of the workpiece 8 and the positional relationship between the workpiece 8 and the grinding wheel 31 during grinding will be described with reference to FIGS. 3 and 4. As shown in FIGS. 3 and 4, the workpiece 8 to be ground by the grinding machine 1 of this embodiment is, for example, a crankshaft. The crankshaft has a crank shape formed by a plurality of crank webs 821 and crank pins 822. The crankshaft has a shaft portion 811 provided at an end as a circular portion 81, and journal portions 812 provided at the ends and intermediate portions. Further, the crankshaft has a crank web 821, a crank pin 822, and a balance weight 823 as a non-circular portion 82. Note that the central axis 801 of the workpiece 8 and the central axis 801 of the circular portion 81 are the same. The non-circular portion 82 of this embodiment is formed as an eccentric shape portion.

[0033] In this embodiment, the circular portion 81 of the workpiece 8 is the object of grinding. Therefore, a plurality of plunge grindings P1, P2, P3 and one traverse grinding T are performed on the shaft portion 811 as the circular portion 81 of the workpiece 8. In FIG. 3, the case where plunge grinding is performed three times is indicated by arrows P1, P2, P3, and the case where traverse grinding is performed once is indicated by an arrow T. The directions of the arrows P1, P2, P3, T in FIG. 3 indicate the state in which the grinding wheel 31 moves relatively with respect to the workpiece 8.

[0034] The length of the shaft portion 811 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 are performed at different positions Z1, Z2, Z3 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 shaft portion 811.

[0035] 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 non-circular portion 82 of the workpiece 8 protrudes. That is, the rotation 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 the position of the workpiece 8 in the rotation position within the range of 0° to 360°.

[0036] 3. Roundness as an evaluation index In this embodiment, roundness is used as the evaluation index for the ground outer peripheral surface 83 of the circular portion 81 of the workpiece 8 ground by the grinding machine 1. The roundness will be described with reference to FIG. 5. The roundness is measured, for example, as the difference in radius r (the difference between the maximum value and the minimum value of the radius r) when the ground outer peripheral surface 83 of the workpiece 8 is sandwiched between two concentric inscribed virtual circles and circumscribed virtual circles.

[0037] 4. Circularity error e In the workpiece 8 having the non-circular portion 82, when the circular portion 81 of the workpiece 8 is ground, a circularity error e occurs on the ground outer peripheral surface 83 of the circular portion 81. The circularity error e will be described with reference to FIGS. 5 and 6.

[0038] When the grinding wheel 31 contacts the workpiece 8 for grinding, a grinding resistance occurs on the grinding wheel 31, and the workpiece 8 is deflected by elastic deformation in the direction of trying to escape from the grinding wheel 31. At this time, in the workpiece 8 having the non-circular portion 82, a difference in rigidity occurs in the workpiece 8 depending on the position in the circumferential direction C where the grinding wheel 31 contacts.

[0039] This difference in rigidity forms anisotropy of rigidity in the circumferential direction C of the ground outer peripheral surface 83 where grinding has been performed, and an error occurs in the radius r at each position in the circumferential direction C of the ground outer peripheral surface 83 of the workpiece 8. Then, this error in the radius r causes an error in roundness. The ground outer peripheral surface 83 of the circular portion 81 of the crankshaft as the workpiece 8 in this embodiment is ground in a state close to an elliptical shape.

[0040] Further, when the grinding wheel 31 contacts the workpiece 8 and grinding is performed, the deflection due to the elastic deformation generated in the workpiece 8 by the grinding wheel 31 generally increases as the position approaches the center in the axial direction Z of the workpiece 8 because both ends of the workpiece 8 are supported by the workpiece support device 2. And at each position in the axial direction Z of the shaft portion 811 as the circular portion 81, the amount of deflection increases as the position approaches the center in the axial direction Z, and accordingly, the roundness error also increases. That is, the roundness error e at a plurality of positions in the axial direction Z of the ground outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 after the plunge grinding P1, P2, P3 and the traverse grinding T is performed is larger as the position approaches the center in the axial direction Z.

[0041] In the crankshaft as the workpiece 8 of the present embodiment, as shown in FIG. 5, the roundness error e (error in radius r) at a plurality of positions in the circumferential direction C of the ground outer peripheral surface 83 is generated so as to form a shape close to an ellipse with respect to the design radius reference circle r0. Further, FIG. 6 shows the roundness error e at each position from 0 to 360° in the circumferential direction C of the ground outer peripheral surface 83 as values at the outer position Z1, the intermediate position Z2, and the center side position Z3 in the axial direction Z of the ground outer peripheral surface 83 in FIG. 3. The position of 0° in the circumferential direction C is set as any one of two positions that are 180° different from each other in which the crankpin 822 is provided with respect to the central axis 801 of the workpiece 8.

[0042] As shown in FIG. 6, the roundness error e becomes maximum on the plus side in the vicinity of 45° and 225° in the circumferential direction C at any of the outer position Z1, the intermediate position Z2, and the center side position Z3 in the axial direction Z, while becoming maximum on the minus side in the vicinity of 135° and 315° in the circumferential direction C. Further, the roundness error e increases as it approaches the center in the axial direction Z.

[0043] 5. Detailed Configuration of the Control Device 6 The detailed configuration of the control device 6 will be described with reference to FIGS. 1 to 10. As shown in FIG. 7, the control device 6 includes a basic grinding program acquisition unit 61, a plunge operation control unit 62A, a traverse operation control unit 62B, a correction amount storage unit 63, and an interpolation correction amount calculation unit 64.

[0044] The basic grinding program acquisition unit 61 acquires a basic grinding program that does not include the correction process for the true circularity error e. The basic grinding program is a program for performing a plurality of plunge grindings P1, P2, P3 and one traverse grinding T on the shaft portion 811 as the circular portion 81.

[0045] The plunge operation control unit 62A sequentially performs plunge grindings P1, P2, P3 at a plurality of positions in the axial direction Z of the grinding outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 before the traverse grinding T. The traverse operation control unit 62B performs a traverse grinding T on the grinding outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 after the plunge grindings P1, P2, P3 are performed.

[0046] As shown in FIGS. 1 and 2, the plunge 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 cross direction X by the encoder 45 of the cross 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. Further, 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 shaft portion 811 as the circular portion 81 is facing the grinding wheel 31.

[0047] When performing plunge grinding P1 and P2, the plunge motion control unit 62A gives an angle command for the workpiece 8 to the workpiece support device 2. When performing plunge grinding P3, the plunge motion control unit 62A gives an angle command for the workpiece 8 to the workpiece support device 2, and gives a correction amount Da at the center side position Z3 in the axial direction Z of the circular portion 81 for each angle of the workpiece 8 to the cross movement device 4 as a command. When performing plunge grinding P3, the plunge motion control unit 62A uses profile data for plunge grinding. The plunge motion control unit 62A gives a predetermined cutting amount k for plunge grinding in the cross direction X of the grinding wheel 31 with respect to the workpiece 8 to the cross movement device 4 as a command.

[0048] Also, when performing plunge grinding P1, P2, and P3, the plunge motion control unit 62A controls the drive circuit 654 of the cross 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 cross direction X. Thereby, when plunge grinding P1, P2, and P3 are performed, the rotational position of the workpiece 8 in the circumferential direction C and the movement position of the grinding wheel 31 in the cross direction X are synchronized.

[0049] 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, gives a correction amount Da and an interpolation correction amount Db corresponding to the position in the axial direction Z of the circular portion 81 for each angle of the workpiece 8 to the cross movement device 4 as commands, and gives a position command in the axial direction Z of the grinding wheel 31 with respect to the workpiece 8 to the parallel movement device 5. When performing traverse grinding T, the traverse motion control unit 62B uses profile data for traverse grinding. The traverse motion control unit 62B gives a predetermined cutting amount k for traverse grinding in the cross direction X of the grinding wheel 31 with respect to the workpiece 8 to the cross movement device 4 as a command.

[0050] Further, when performing traverse grinding T, the traverse motion control unit 62B controls the drive circuit 654 of the cross-feed device 4 according to the rotational position of the workpiece 8 in the circumferential direction C detected by the encoder 25 of the workpiece support device 2 and the moving position of the workpiece 8 in the axial direction Z detected by the encoder 55 of the parallel movement device 5, so as to change the moving position of the grinding wheel 31 in the cross-feed direction X. Thereby, when the traverse grinding T is performed, 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 are synchronized with the moving position of the grinding wheel 31 in the cross-feed direction X.

[0051] The predetermined depth of cut k is given from the plunge operation control unit 62A to the cross-feed device 4 as the predetermined depth of cut k for plunge grinding used for plunge grinding, and is given from the traverse operation control unit 62B to the cross-feed device 4 as the predetermined depth of cut k for traverse grinding used for traverse grinding.

[0052] The profile data of this embodiment is prepared as profile data for plunge grinding corresponding to the predetermined depth of cut k for plunge grinding and profile data for traverse grinding corresponding to the predetermined depth of cut k for traverse grinding. In the plunge operation control unit 62A, the larger the depth of cut k, the profile data with a larger correction amount Da is used. In the traverse operation control unit 62B, the larger the depth of cut k, the profile data with larger correction amounts Da and interpolation correction amount Db is used.

[0053] In the trial grinding of the workpiece 8 and the finish grinding of the workpiece 8 as a product, the depth of cut k is set to the same value. On the other hand, in the trial grinding and the finish grinding, as the depth of cut k increases, the grinding resistance generated on the grinding wheel 31 also increases. Therefore, when grinding a plurality of types of workpieces 8, in the case where there are a plurality of patterns with different grinding methods of the workpiece 8, as the depth of cut k of each increases, the roundness error e generated according to the grinding resistance also increases, and in order to correct the roundness error e, profile data with large correction amounts Da and interpolation correction amount Db is required.

[0054] As shown in FIG. 8, the correction amount storage unit 63 stores a correction amount Da based on the true circularity error e obtained by actual measurement as shown in FIGS. 5 and 6. The correction amount Da is the true circularity error e measured as positive and negative values with respect to a reference value for each position (angle) in the circumferential direction C centered on the central axis for a plurality of positions in the axial direction Z that occur on the ground outer peripheral surface 83 of the circular portion 81. The true circularity error e is inverted in positive and negative values and converted into a correction amount Da for each position (angle) in the circumferential direction C at a plurality of positions in the axial direction Z and stored. In the present embodiment, the angle of the circular portion 81 or the workpiece 8 is referred to as the position or rotational position in the circumferential direction C of the circular portion 81.

[0055] As shown in FIG. 9, the interpolation correction amount calculation unit 64 calculates and stores an interpolation correction amount Db for each position (angle) in the circumferential direction C between a plurality of positions in the axial direction Z of the circular portion 81 based on the correction amount Da for each position (angle) in the circumferential direction C at a plurality of positions in the axial direction Z. The interpolation correction amount Db is stored in the same format as the correction amount Da.

[0056] The correction amount Da for each position (angle) in the circumferential direction C of the circular portion 81 in the correction amount storage unit 63 and the interpolation correction amount Db for each position (angle) in the circumferential direction C of the circular portion 81 in the interpolation correction amount calculation unit 64 are configured by the profile data of the circular portion 81 of the workpiece 8.

[0057] The profile data is stored as data for correcting the true circularity error e indicating the error from the radius reference value r0 at a plurality of positions in the circumferential direction C centered on the central axis 801 of the circular portion 81 for a plurality of positions in the axial direction Z that occur on the ground outer peripheral surface 83 of the circular portion 81. Here, the "ground outer peripheral surface 83" not only indicates the outer peripheral surface after being ground by the grinding wheel 31 but may also indicate the outer peripheral surface set to be ground by the grinding wheel 31. When storing the correction amount Da in the correction amount storage unit 63 of the present embodiment, trial grinding by plunge grinding P1, P2, P3 and traverse grinding T is performed on workpieces 8 of various shapes by the grinding machine 1, and the radii r at a plurality of positions in the axial direction Z and the circumferential direction C of the ground outer peripheral surface 83 of the workpiece 8 after grinding are actually measured.

[0058] The radius r of the grinding outer peripheral surface 83 can be measured using an external measuring device (not shown) after the workpiece 8 is removed from the grinding machine 1. Further, the radius r of the grinding outer peripheral surface 83 may be measured as the radius r at a plurality of positions in the axial direction Z and the circumferential direction C with respect to the grinding outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 of the workpiece 8 using the radius measuring device 7. The radius measuring device 7 of the present embodiment is configured to measure the radius r of the grinding outer peripheral surface 83 of the workpiece 8 supported by the workpiece support device 2 of the grinding machine 1 after the traverse grinding T.

[0059] As shown in FIG. 5, the roundness error e occurs as an error in the radius r at a plurality of positions in the axial direction Z and the circumferential direction C of the grinding outer peripheral surface 83, and the correction amount Da in the correction amount storage unit 63 is stored as a position offset by the amount of the roundness error e in the inner and outer circumferential direction C opposite to the inner and outer circumferential direction C of the radius at which the roundness error e has occurred with respect to the radius reference value r0. The roundness error e in FIG. 5 is exaggeratedly shown, and the actually occurring roundness error e is about several μm.

[0060] Note that the external measuring device or the radius measuring device 7 includes a contact type measuring instrument in which a measuring probe contacts the grinding outer peripheral surface 83 of the circular portion 81 of the workpiece 8 for measurement, and a non-contact type measuring instrument in which light rays, electromagnetic waves, etc. are scanned on the grinding outer peripheral surface 83 of the circular portion 81 of the workpiece 8 for measurement. In the present embodiment, for example, a dimension measuring device provided on the grinding machine 1 may be used as the radius measuring device 7, and the radius r at a plurality of positions in the circumferential direction C of the grinding outer peripheral surface 83 may be measured when the workpiece 8 is rotated about its central axis 801 by the workpiece support device 2.

[0061] As shown in FIGS. 3, 5, and 8, in the correction amount storage unit 63 of this embodiment, correction amounts Da based on the roundness errors e at a plurality of positions in the axial direction Z of the ground outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 are stored after the plunge grinding P1, P2, P3 and traverse grinding T are performed. In the grinding machine 1 of this embodiment, after the plunge grinding P1, P2 is performed at a plurality of positions in the axial direction Z on the shaft portion 811 as the circular portion 81, while the roundness error e is corrected, the plunge grinding P3 and traverse grinding T at the final position are performed. When the roundness error e is actually measured after the plunge grinding P1, P2, P3 and traverse grinding T as trial grinding are performed, the radii r at a plurality of positions in the circumferential direction C are actually measured for a plurality of positions in the axial direction Z of the shaft portion 811 as the circular portion 81. Note that the plurality of positions in the circumferential direction C may be, for example, a plurality of positions arranged at equal intervals at an angle of 1 to 5° etc. in the circumferential direction C.

[0062] In the correction amount storage unit 63, the correction amount Da at each position in the circumferential direction C may be stored as data indicating whether to correct to the plus side where the radius r increases or the minus side where the radius r decreases from the design radius reference value r0 of the shaft portion 811 as the circular portion 81, in the direction opposite to the roundness error e. In FIG. 5, the case where the roundness error e results in the radius r being on the plus side from the radius reference value r0 is indicated by the sign (+), and the case where the radius r is on the minus side from the radius reference value r0 is indicated by the sign (-). The actually measured roundness error e may be subjected to regression analysis etc. to obtain data with continuous values in the circumferential direction C and the axial direction Z, and then converted into the correction amount Da and stored.

[0063] As shown in FIG. 5, in the correction amount storage unit 63, the correction amount Da at each position in the circumferential direction C is 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 non-circular portion 82 protrudes from the central axis 801 of the workpiece 8. Also, 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.

[0064] The correction amount Da is stored as data for moving the grinding wheel head 31 further away from the workpiece 8 in the intersecting direction X as the position in the circumferential direction C where the radius of the ground outer peripheral surface 83 decreases due to the roundness error e. By the traverse motion control unit 62B using the correction amount Da and the interpolation correction amount Db, the roundness error e generated on the ground outer peripheral surface 83 can be appropriately reduced.

[0065] The correction amount Da stored in the correction amount storage unit 63 and the interpolation correction amount Db stored in the interpolation correction amount calculation unit 64 are data in which the moving positions of the grinding wheel head 31 in the intersecting direction X for correcting the roundness error e at a plurality of positions in the axial direction Z of the ground outer peripheral surface 83 during the traverse grinding T change continuously in the axial direction Z of the ground outer peripheral surface 83. In other words, the correction amount Da and the interpolation correction amount Db are stored as data that undergoes regression analysis or the like and changes continuously and smoothly in the circumferential direction C and the axial direction Z of the ground outer peripheral surface 83. With this configuration, the traverse motion control unit 62B can smoothly correct the roundness error e during the traverse grinding T.

[0066] As shown in FIG. 8, the correction amount Da in this embodiment is such that the correction amount Da of the moving position of the grinding wheel head 31 in the intersecting direction X for correcting the roundness error e at a plurality of positions in the axial direction Z of the ground outer peripheral surface 83 during the traverse grinding T increases as the position approaches the center in the axial direction Z of the workpiece 8. In other words, it increases as the position approaches the center in the axial direction Z of the shaft portion 811 as the circular portion 81. In FIG. 8, for the outer position Z1, the intermediate position Z2, and the center side position Z3 in the axial direction Z of the workpiece 8, it shows that the correction amount Da has the relationship of Z3>Z2>Z1. With this configuration, the roundness error e generated according to the difference in the position in the axial direction Z can be appropriately corrected.

[0067] The correction amount Da is stored for the case where the radius r is larger than the reference radius value r0 or the case where the radius r is smaller than the reference radius value r0 at an appropriate position in the circumferential direction C and the axial direction Z. Note that the correction amount Da may be stored as a value that changes stepwise in the circumferential direction C or the axial direction Z.

[0068] As shown in FIGS. 8 and 9, the profile data is composed of a combination of a correction amount Da for correcting the roundness error e at a plurality of positions in the circumferential direction C for a plurality of positions in the axial direction Z obtained by actual measurement, and an interpolation correction amount Db for correcting the roundness error e at a plurality of positions in the circumferential direction C between a plurality of positions in the axial direction Z. In this embodiment, for example, the roundness error e is actually measured at three positions, i.e., an outer position Z1, an intermediate position Z2, and a center-side position Z3 in the axial direction Z of the ground outer peripheral surface 83, and the correction amount Da is created based on the roundness error e at these positions Z1, Z2, and Z3.

[0069] Also, for the position Z12 between the outer position Z1 and the intermediate position Z2, the roundness error e of the outer position Z1 and the roundness error e of the intermediate position Z2 are interpolated to create an interpolation correction amount Db. Also, for the position Z23 between the intermediate position Z2 and the center-side position Z3, the roundness error e of the intermediate position Z2 and the roundness error e of the center-side position Z3 are interpolated to create an interpolation correction amount Db. The interpolation correction amount Db may be created by linear interpolation or by various interpolation methods other than linear interpolation.

[0070] The correction amount Da and the interpolation correction amount Db may be stored in the correction amount storage unit 63 as data of the radius r at each position in the axial direction Z and the circumferential direction C of the ground outer peripheral surface 83. Also, the interpolation correction amount Db may be obtained by calculation during the operation of the grinding machine 1. Even if the interpolation correction amount Db is not stored in the interpolation correction amount calculation unit 64, it is still called profile data together with the correction amount Da.

[0071] Also, instead of performing trial grinding, the roundness error e for creating the profile data may be estimated as the roundness error e at a plurality of positions in the circumferential direction C for a plurality of positions in the axial direction Z that occurs on the ground outer peripheral surface 83 of the shaft portion 811 as the circular shape portion 81 by performing a simulation of grinding.

[0072] As shown in FIGS. 4 and 7, the plunge motion control unit 62A is configured to control the movement position of the grinding wheel head 31 in the cross direction X in synchronization with the rotational position (rotation angle) in the circumferential direction C of the workpiece 8 based on profile data so as to correct the roundness error e at the center side position Z3 in the axial direction Z of the outer peripheral grinding surface 83, and perform plunge grinding P3. Further, the traverse motion control unit 62B is configured to control the movement position of the grinding wheel head 31 in the cross direction X in synchronization with the rotational position in the circumferential direction C of the workpiece 8 and the movement position in the axial direction Z of the workpiece 8 based on profile data so as to correct the roundness error e at a plurality of positions in the axial direction Z of the outer peripheral grinding surface 83, and perform traverse grinding T.

[0073] The plunge motion control unit 62A receives, from the correction amount storage unit 63, profile data for plunge grinding as the correction amount Da of the roundness error e. The traverse motion control unit 62B receives, from the correction amount storage unit 63 and the interpolation correction amount calculation unit 64, profile data for traverse grinding as the correction amount Da and the interpolation correction amount Db of the roundness error e. Then, when executing the basic grinding program by the basic grinding program acquisition unit 61, the plunge motion control unit 62A and the traverse motion control unit 62B control the respective motors 24, 34, 44, 54 using the profile data.

[0074] When plunge grinding P3 is performed, the rotational position in the circumferential direction C of the workpiece 8 and the movement position in the cross direction X of the grinding wheel head 31 are synchronized in a state where the roundness error e is corrected by the plunge motion control unit 62A. When traverse grinding T is performed, the rotational position in the circumferential direction C of the workpiece 8 and the movement position in the axial direction Z of the workpiece 8 and the movement position in the cross direction X of the grinding wheel head 31 are synchronized in a state where the roundness error e is corrected by the traverse motion control unit 62B.

[0075] In the grinding machine 1 of this embodiment, in order to correct the roundness error at each position in the axial direction Z of the grinding outer peripheral surface 83 of the circular portion 81 at each position in the axial direction Z of the grinding outer peripheral surface 83 of the circular portion 81, the plunge grinding P3 at the center side position Z3 of the grinding outer peripheral surface 83 is performed by the plunge motion control unit 62A, and the traverse grinding T at the outer side position Z1 and the intermediate position Z2 of the grinding outer peripheral surface 83 is performed by the traverse motion control unit 62B. When the plunge grinding P3 is performed with 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 synchronized, the plunge motion control unit 62A adjusts the moving position in the intersecting direction X of the grinding wheel 31. When the traverse grinding T is performed 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 and the moving position in the intersecting direction X of the grinding wheel 31 synchronized, the traverse motion control unit 62B adjusts the moving position in the intersecting direction X of the grinding wheel 31.

[0076] Further, based on the profile data, the plunge motion control unit 62A and the traverse motion control unit 62B correct such that the grinding wheel 31 approaches the workpiece 8 at the position in the circumferential direction C of the grinding outer peripheral surface 83 having a positive roundness error e where the radius r increases. On the other hand, based on the profile data, the plunge motion control unit 62A and the traverse motion control unit 62B correct such that the grinding wheel 31 moves away from the workpiece 8 at the position in the circumferential direction C of the grinding outer peripheral surface 83 having a negative roundness error e where the radius r decreases.

[0077] As shown in FIG. 10, the plunger operation control unit 62A performs plunge grinding P1 and P2 at the outer position Z1 and the intermediate position Z2 in the axial direction Z of the shaft portion 811 as the circular portion 81. Next, the plunger operation control unit 62A adjusts the moving position of the grinding wheel 31 in the intersecting direction X synchronized with the rotational position in the circumferential direction C of the shaft portion 811, and performs plunge grinding P3 at the center side position Z3 in the axial direction Z of the shaft portion 811 so as to correct the roundness error e. Thereafter, the traverse operation control unit 62B adjusts the moving position of the grinding wheel 31 in the intersecting direction X to the grinding outer peripheral surface 83 synchronized with the rotational position in the circumferential direction C of the shaft portion 811 and the moving position in the axial direction Z of the shaft portion 811, and performs traverse grinding T at the intermediate position Z2 and the outer position Z1 in the axial direction Z of the shaft portion 811 so as to correct the roundness error e.

[0078] In FIG. 10, the grinding amounts Kp by the plunge grindings P1, P2, and P3 and the grinding amount Kt by the traverse grinding T are schematically shown. At the center side position Z3 in the axial direction Z of the shaft portion 811, it is ground to the finish position by the plunge grinding P3.

[0079] The profile data of this embodiment is stored in the correction amount storage unit 63 and the interpolation correction amount calculation unit 64 as profile data for plunge grinding for correcting the roundness error e after the plunge grinding P3 is performed and profile data for traverse grinding for correcting the roundness error e after the traverse grinding T is performed. The profile data for plunge grinding has a correction amount Da at each position (for each angle) in the circumferential direction C of the circular portion 81. The profile data for traverse grinding has a correction amount Da and an interpolation correction amount Db at each position (for each angle) in the circumferential direction C for a plurality of positions in the axial direction Z of the circular portion 81. Then, the plunge grinding P3 by the plunger operation control unit 62A is performed using the profile data for plunge grinding, and the traverse grinding T by the traverse operation control unit 62B is performed using the profile data for traverse grinding.

[0080] In FIGS. 8 and 9, the correction amount Da and the interpolation correction amount Db for each position (for each angle) in the circumferential direction C of the workpiece 8 of the movement position in the crossing direction X of the grinding wheel 31 at each position from 0 to 360° in the circumferential direction C of the ground outer circumferential surface 83 are shown as values at the outer position Z1, the intermediate position Z2, the center side position Z3, the position Z12 between the outer position Z1 and the intermediate position Z2, and the position Z23 between the intermediate position Z2 and the center side position Z3 in the axial direction Z of the ground outer circumferential surface 83 in FIG. 10. The correction amount Da and the interpolation correction amount Db of the movement position in the crossing direction X of the grinding wheel 31 become maximum on the minus side in the vicinity of 45° and 225° in the circumferential direction C and maximum on the plus side in the vicinity of 135° and 315° in the circumferential direction C so as to cancel the roundness error e at any of the outer position Z1, the intermediate position Z2, the center side position Z3, the position Z12, and the position Z23 in the axial direction Z. Further, the correction amount Da and the interpolation correction amount Db of the movement position in the crossing direction X of the grinding wheel 31 become larger as it gets closer to the center in the axial direction Z.

[0081] The traverse motion 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 shaft portion 811 as the circular shape portion 81 while correcting the roundness error e. In addition to this, the traverse motion 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 shaft portion 811 as the circular shape portion 81. In this case, the traverse motion control unit 62B may correct the roundness error e when performing the last traverse grinding T, and may correct the roundness error e when performing the plurality of traverse grindings T.

[0082] 6. Grinding method of the grinding machine 1 The grinding method of the grinding machine 1 will be described with reference to FIGS. 10 and 11. Before the shaft portion 811 as the circular shape portion 81 is ground by the grinding machine 1, plunge grindings P1, P2, P3 and traverse grinding T of the shaft portion 811 are performed as trial grindings, and the error of the radius r generated in the circumferential direction C and the axial direction Z of the shaft portion 811 is measured as the roundness error e together with the rotation angle of the workpiece W, and the profile data created based on the rotation angle and the roundness error e is stored in the correction amount storage unit 63 and the interpolation correction amount calculation unit 64.

[0083] When the shaft portion 811 of the workpiece 8 as a product is ground, as shown in FIGS. 10 and 11, the plunger operation control unit 62A of the control device 6 performs, as the first plunger grinding P1, plunge grinding of the outer position Z1 in the axial direction Z of the shaft portion 811 by the grinding wheel carriage 31 (step S101). At this time, the outer position Z1 in the axial direction Z of the shaft portion 811 is ground to a predetermined outer diameter, leaving a predetermined grinding allowance for performing traverse grinding T.

[0084] Next, as shown in FIGS. 10 and 11, the plunger operation control unit 62A of the control device 6 performs, as the second plunger grinding P2, plunge grinding of the intermediate position Z2 offset toward the center side from the outer position Z1 in the axial direction Z of the shaft portion 811 by the grinding wheel carriage 31 (step S102). At this time, the intermediate position Z2 in the axial direction Z of the shaft portion 811 is ground to a predetermined outer diameter, leaving a predetermined grinding allowance for performing traverse grinding T.

[0085] Next, as shown in FIGS. 10 and 11, the plunger operation control unit 62A of the control device 6 performs, as the third plunger grinding P3, plunge grinding of the center side position Z3 in the axial direction Z of the shaft portion 811 by the grinding wheel carriage 31 (step S103). As shown in FIG. 10, the center side position Z3 is the position where the traverse grinding T is started, and the plunge grinding P3 at the center side position Z3 is performed until the outer diameter forming the final shape of the grinding outer peripheral surface 83 is reached.

[0086] When the third plunger grinding P3 is performed, both a plunge cut and a traverse cut are applied. The third plunger grinding P3 is performed based on a basic grinding program during the plunge cut, and during the traverse cut, based on profile data, the position in the intersection direction X at each position in the circumferential direction C of the grinding wheel carriage 31 at the center side position Z3 is appropriately changed, and the circularity error e is corrected while being performed. In other words, at the center side position Z3 in the axial direction Z of the shaft portion 811, the circularity error e is corrected when the plunge grinding P3 is performed.

[0087] In this way, the plunger operation control unit 62A performs the plunge grinding P1 and P2 based on the basic grinding program by the basic grinding program acquisition unit 61, and performs the plunge grinding P3 based on the basic grinding program and the profile data. Then, for the three positions in the axial direction Z of the shaft portion 811, the plunge grindings P1, P2, and P3 are sequentially performed. Note that the number of times the plunge grindings P1, P2, and P3 are performed is the number corresponding to the relationship between the width of the grinding wheel 31 and the length of the shaft portion 811 in the axial direction Z.

[0088] Next, as shown in FIGS. 10 and 11, the traverse operation control unit 62B of the control device 6 performs traverse grinding T on the shaft portion 811 while relatively moving the grinding wheel 31 in the axial direction Z of the shaft portion 811 (step S104). At this time, the traverse operation control unit 62B of the control device 6 relatively moves the grinding wheel 31 at the center side position Z3 where the third plunge grinding P3 is performed in the axial direction Z from the center side to the outside of the shaft portion 811 based on the profile data.

[0089] The traverse grinding T is performed based on the profile data. As the relative position of the grinding wheel 31 in the axial direction Z with respect to the shaft portion 811 changes, the position of the grinding wheel 31 in the intersection direction X at each position in the circumferential direction C of the shaft portion 811 is appropriately changed, and the roundness error e is corrected. Further, as going to the outside in the axial direction Z of the shaft portion 811, the correction amount Da of the position of the grinding wheel 31 in the intersection direction X corresponding to the roundness error e gradually decreases.

[0090] In this way, the traverse operation control unit 62B performs traverse grinding T based on the basic grinding program by the basic grinding program acquisition unit 61 and the profile data. Then, at the intermediate position Z2 and the outer position Z1 in the axial direction Z of the shaft portion 811, the roundness error e is corrected when the traverse grinding T is performed. In this manner, the plunge grindings P1, P2, and P3 and the traverse grinding T are performed on the ground outer peripheral surface 83 of the shaft portion 811, and the shaft portion 811 with improved roundness is formed.

[0091] 7. Operational Effects In the grinding machine 1 of this embodiment, when performing plunge grinding P3 and traverse grinding T, measures are taken to make it difficult for circularity errors e to occur. Specifically, the correction amount storage unit 63 of the control device 6 stores the correction amount Da for each angle at a plurality of positions in the axial direction Z of the shaft portion 811. Further, the interpolation correction amount calculation unit 64 of the control device 6 calculates and stores the interpolation correction amount Db for each position (angle) in the circumferential direction C between a plurality of positions in the axial direction Z of the shaft portion 811. The correction amount Da is created as data for correcting the circularity error e after the circularity error e generated at the center side position Z3 in the axial direction Z of the shaft portion 811 where plunge grinding P3 is performed and the circularity errors e generated at the outer side position Z1 and the intermediate position Z2 in the axial direction Z of the shaft portion 811 where traverse grinding is performed are obtained by actual measurement after rough grinding of the shaft portion 811. The interpolation correction amount Db is calculated based on the correction amount Da for each position (angle) in the circumferential direction C at a plurality of positions in the axial direction Z of the shaft portion 811.

[0092] Then, the plunge motion control unit 62A gives an angle command for the workpiece 8 to the workpiece support device 2, gives the correction amount Da as a command for each angle of the workpiece support device 2 to the cross movement device 4, and performs plunge grinding P3 at the center side position Z3 in the axial direction Z of the shaft portion 811. Further, the traverse motion control unit 62B gives an angle command for the workpiece 8 to the workpiece support device 2, gives the correction amount Da and the interpolation correction amount Db corresponding to the position in the axial direction Z for each angle of the workpiece support device 2 as commands to the cross movement device 4, 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 T at the outer side position Z1 and the intermediate position Z2 in the axial direction Z of the shaft portion 811.

[0093] According to the grinding machine 1 of this embodiment, considering the difference in the circularity error e generated at each position in the axial direction Z of the shaft portion 811 as the circular shape portion 81, the movement position of the grinding wheel carriage 31 in the cross direction X can be corrected to perform plunge grinding P3 and traverse grinding T. Therefore, according to the grinding machine 1 of this embodiment, the roundness generated at each position in the axial direction Z of the ground outer peripheral surface 83 of the shaft portion 811 can be more effectively improved.

[0094] 8. Confirmation of roundness As shown in Fig. 3, as an example of grinding the shaft portion 811, when the roundness correction of the roundness error e is not performed, the roundness at the outer position Z1 is 1.3 μm, at the intermediate position Z2 is 1.8 μm, and at the center position X3 is 2.1 μm. On the other hand, when corrections of 0 μm at the outer position Z1, 0.5 μm at the intermediate position Z2, and 1.0 μm at the center position X3 are performed using the profile data, the roundness at the outer position Z1 is 1.3 μm, at the intermediate position Z2 is 1.3 μm, and at the center position X3 is 1.1 μm. From this result, the effect of improving the roundness by the control of the plunge motion control unit 62A and the traverse motion control unit 62B using the profile data was confirmed.

[0095] <Embodiment 2> As shown in the flowchart of Fig. 12, this embodiment shows the case where the control device 6 of the grinding machine 1 performs control using the correction amount storage unit 63, the interpolation correction amount calculation unit 64, the plunge motion control unit 62A, and the traverse motion control unit 62B both when performing plunge grinding P1, P2, P3 and when performing traverse grinding T. In Fig. 12, the grinding method of the grinding machine 1 is shown by steps S201 to S204. In any of steps S201 to S204, the plunge motion control unit 62A and the traverse motion control unit 62B execute the basic grinding program obtained by the basic grinding program acquisition unit 61 using the profile data as the correction amount Da and the interpolation correction amount Db stored in the correction amount storage unit 63 and the interpolation correction amount calculation unit 64.

[0096] The profile data of this embodiment is profile data for plunge grinding indicating the correction amount Da in the correction amount storage unit 63 for correcting the roundness error e at a plurality of positions in the axial direction Z of the ground outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 after the plunge grinding P1, P2, P3 is performed, and the correction amount Da in the correction amount storage unit 63 and the interpolation correction amount Db in the interpolation correction amount calculation unit 64 for correcting the roundness error e at a plurality of positions in the axial direction Z of the ground outer peripheral surface 83 of the shaft portion 811 as the circular portion 81 after the traverse grinding T is performed, and is stored as profile data for traverse grinding.

[0097] In this embodiment, when performing trial grinding for measuring the roundness error e generated in the shaft portion 811, after performing plunge grinding P1, P2, P3 at a plurality of positions in the axial direction Z of the shaft portion 811, the radius r at a plurality of positions in the circumferential direction C of the ground outer peripheral surface 83 of the shaft portion 811 is measured. Then, the difference in how much the radius r at the plurality of positions in the circumferential direction C where this measurement is performed differs from the radius reference value r0 becomes the roundness error e after the plunge grinding P1, P2, P3, and the profile data for plunge grinding as the correction amount Da for correcting the roundness error e is stored.

[0098] Also, when performing trial grinding, after performing traverse grinding T on the shaft portion 811, the radius r at a plurality of positions (rotation angles) in the circumferential direction C of the ground outer peripheral surface 83 of the shaft portion 811 is measured. Then, the difference in how much the radius r at the plurality of positions (rotation angles) in the circumferential direction C where this measurement is performed differs from the radius reference value r0 becomes the roundness error e after the traverse grinding T, and the profile data for traverse grinding in relation to the rotation angle, the correction amount Da, and the interpolation correction amount Db for correcting the roundness error e is stored.

[0099] The plunge motion control unit 62A of this embodiment controls the moving position of the grinding wheel 31 in the crossing direction X synchronized with the rotational position (rotation angle) in the circumferential direction C of the workpiece 8 based on the profile data for plunge grinding, and performs plunge grinding P1, P2, P3. The traverse motion control unit 62B controls the moving position of the grinding wheel 31 in the crossing direction X synchronized with the rotational position (rotation angle) in the circumferential direction C of the workpiece 8 and the moving position in the axial direction Z of the workpiece 8 based on the profile data for traverse grinding, and performs traverse grinding T.

[0100] The profile data for plunge grinding for correcting the circularity error e of the grinding outer peripheral surface 83 when performing plunge grinding P1, P2, P3 in the correction amount storage unit 63 and the interpolation correction amount calculation unit 64 is set to continuously change in the circumferential direction C of the grinding outer peripheral surface 83. With this configuration, the plunge motion control unit 62A can smoothly correct the circularity error e when performing plunge grinding P1, P2, P3. The correction of the circularity error e in the circumferential direction C during plunge grinding by the plunge motion control unit 62A is performed in the same manner as the correction of the circularity error e in the circumferential direction C during plunge grinding and traverse grinding shown in Embodiment 1.

[0101] In this embodiment, the configuration of the traverse motion control unit 62B and the like is the same as the configuration of Embodiment 1. In this embodiment, at the outer position Z1 and the intermediate position Z2 in the axial direction Z of the shaft portion 811, the circularity error e of the grinding outer peripheral surface 83 can be corrected separately during plunge grinding and traverse grinding. Thereby, the correction of the circularity error e can be performed more appropriately.

[0102] 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 denoted by the same reference numerals as those shown in Embodiment 1 are the same as the components of Embodiment 1.

[0103] <Other Embodiments> The control device 6 is configured to perform plunge grinding and traverse grinding on the ground outer peripheral surfaces 83 of the circular portions 81 formed separately at a plurality of locations in the axial direction Z of the workpiece 8, and profile data indicating the relationship between the rotation angle, the correction amount Da, and the interpolation correction amount Db may be stored for the plurality of circular portions 81. In this case, the traverse grinding T in which the roundness error e is corrected by the traverse motion control unit 62B is performed for the plurality of circular portions 81. Also, in this case as well, plunge grinding in which the roundness error e is corrected by the plunge motion control unit 62A may be performed for the plurality of circular portions 81. In this case, the roundness after grinding can be improved for the plurality of circular portions 81.

[0104] Further, the grinding machine 1 of each of the above-described embodiments suppresses the roundness error generated on the ground outer peripheral surface 83 of the circular portion 81 without using a rest device. The rest device mainly supports the vicinity of the central portion in the axial direction Z of the workpiece 8 by a contactor, and suppresses the workpiece 8 from deflecting due to elastic deformation in the radial direction when pressure acts on the workpiece 8 from the grinding wheel 31. The correction amount Da for correcting the roundness error e in the correction amount storage unit 63 is actually measured as a value obtained by performing trial grinding without using a rest device.

[0105] The present invention is not limited to only the above-described embodiments, 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.

Description of Reference Numerals

[0106] 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 Correction amount memory unit 64 Interpolation correction amount calculation unit 7 Radius measuring device 8 Workpiece 801 Central axis 81 Circular shape part 811 Shaft part 82 Non-circular shape part 83 Grinding outer peripheral surface e True circularity error Da Correction amount Db Interpolation correction amount Z-axis direction X-intersection direction C Circumferential direction

Claims

1. A workpiece support device that supports a workpiece having a circular shape portion and a non-circular shape portion and rotates the workpiece about the central axis of the circular shape 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, The control device, A correction amount storage unit that stores, as positive and negative values with respect to a reference value for each angle centered on the central axis at a plurality of positions in the axial direction, the true circularity error measured as positive and negative values for each angle centered on the central axis at a plurality of positions in the axial direction on the grinding outer peripheral surface of the circular shape portion, and converts the positive and negative values into correction amounts for each angle at a plurality of positions in the axial direction by reversing the positive and negative values, An interpolation correction amount calculation unit that calculates or calculates and stores an interpolation correction amount for each angle between a plurality of positions in the axial direction based on the correction amounts for each angle at a plurality of positions in the axial direction, A traverse operation control unit that gives an angle command of the workpiece to the workpiece support device, gives the correction amount and the interpolation correction amount corresponding to the position in the axial direction for each angle of the workpiece as commands to the intersecting movement device, and gives a position command in the axial direction of the grinding wheel with respect to the workpiece to the parallel movement device to perform traverse grinding on the circular shape portion.

2. The correction amount for each angle and the interpolation correction amount for each angle are profile data of the circular shape portion of the workpiece, and a predetermined cutting amount is given as a command to the intersecting movement device. The grinding machine according to claim 1.

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

4. 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. The grinding machine according to claim 3.

5. When the circular shape portion of the workpiece is subjected to traverse grinding after plunge grinding, during the plunge grinding, a predetermined cutting amount for plunge grinding is given and the profile data is used, During the traverse grinding, a predetermined cutting amount for traverse grinding is given and the profile data is used. The grinding machine according to claim 4.

6. When the circular portion of the workpiece is plunge ground and then traverse ground, during the plunge grinding, only a predetermined depth of cut for plunge grinding is given. During the traverse grinding, a predetermined depth of cut for traverse grinding is given and the profile data is used. The grinding machine according to claim 4. **Claim 7** The profile data prepares profile data for plunge grinding according to a predetermined depth of cut for plunge grinding and profile data for traverse grinding according to a predetermined depth of cut for traverse grinding, and uses profile data with a larger correction amount as the depth of cut increases. The grinding machine according to claim 5.

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