Groove grinding method, groove grinding device, and program

Abstract

To suppress the occurrence of an unground part after grinding.SOLUTION: A groove grinding method for grinding all a plurality of grooves provided at prescribed angle intervals in the outer circumferential surface of a shaft in order by a grindstone comprises: a control step of identifying a position or a region on an outer circumference in which a maximum or minimum point of oscillation of the centered shaft is present; a control step of grinding, with one of the grooves present in the position or the region as a first grinding groove to be ground first, the first grinding groove after aligning the center of the first grinding groove with that of the grindstone; and then a control step of rotating the shaft at prescribed angle intervals and sequentially grinding the remaining ones of the grooves.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a groove grinding method, a groove grinding device, and a program. [Background technology]

[0002] Patent Document 1 discloses a groove grinding machine that uses a grinding wheel that rotates at high speed to grind grooves in a workpiece clamped between an index unit and a tailstock. After grinding one groove, the index unit rotates the workpiece 120 degrees to expose the next groove to the grinding wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP-A-9-136254 (see, for example, FIG. 5, paragraph 0015) Summary of the Invention [Problem to be solved by the invention]

[0004] When grinding the grooves on a shaft, the centered shaft has runout, and as a result, the groove position determined by rotating the shaft may shift due to the runout of the shaft, resulting in no grinding allowance being available at the edge of the groove, leaving an unground portion.

[0005] The present invention has been made in view of the above problems, and has an object to suppress the occurrence of unground portions after grinding. [Means for solving the problem]

[0006] A groove grinding method according to one embodiment of the present invention is a groove grinding method for sequentially grinding a plurality of grooves provided at predetermined angular intervals on the outer peripheral surface of a shaft with a grinding wheel, the groove grinding method including the following processing steps: a control step for identifying a position or area on the outer peripheral surface where the maximum or minimum point of the runout of the centered shaft exists; a control step for aligning the center of the first grinding groove with the center of the grinding wheel and grinding the first grinding groove, among the plurality of grooves, that exists at the position or area as the first grinding groove to be ground first; and a control step for rotating the shaft by the predetermined angular intervals in sequence to grind each of the remaining grooves among the plurality of grooves, thereby grinding all of the plurality of grooves.

[0007] According to another aspect of the present invention, there are provided a groove grinding device and a program corresponding to the groove grinding method. [Effects of the Invention]

[0008] According to these aspects, by setting the first grinding groove as described above, deviation of the groove position caused by shaft runout when determining the positions of the remaining grooves is suppressed. As a result, it is possible to make it difficult for unground portions to occur across the multiple grooves, and the occurrence of unground portions remaining after grinding is suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the main parts of a groove grinding device as viewed from above. [Figure 2] FIG. 2 is a schematic diagram of the main part of the groove grinding device as seen from the side. [Figure 3] FIG. 3 is a diagram for explaining the groove detection position of the sensor. [Figure 4] FIG. 4 is a diagram illustrating the vibration measurement position of the sensor. [Figure 5] FIG. 5 is an explanatory diagram of the control process that constitutes the machining process. [Figure 6] FIG. 6 is a first diagram illustrating a method for identifying a shake in the shake identifying step. [Figure 7]FIG. 7 is a second explanatory diagram of the shake specifying method in the shake specifying step. [Figure 8] FIG. 8 is an explanatory diagram of the first grinding step and the second grinding step. [Figure 9] FIG. 9 is a flowchart illustrating an example of processing control. [Figure 10A] FIG. 10A is a first diagram illustrating the verification results. [Figure 10B] FIG. 10B is a second explanatory diagram of the verification results. [Figure 10C] FIG. 10C is a third diagram illustrating the verification results. [Figure 11] FIG. 11 shows three cases used in further verification. [Figure 12] FIG. 12 is a diagram showing the verification results of the first case. [Figure 13] FIG. 13 is a diagram showing the verification results of the second case. [Figure 14] FIG. 14 shows the verification results for the third case. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0011] FIG. 1 is a schematic diagram of the main parts of the groove grinding device 100 as viewed from above. FIG. 2 is a schematic diagram of the main parts of the groove grinding device 100 as viewed from the side. The Z direction in the figure corresponds to the vertical direction. The groove grinding device 100 has a grinding wheel 23, and uses the grinding wheel 23 to grind multiple grooves G provided at predetermined angular intervals on the outer peripheral surface of the workpiece W in sequence. The workpiece W is a shaft, for example, a fixed pulley of a continuously variable transmission. In this example, the number of grooves G is three, and in this case, the predetermined angular interval is 120°. If the number of grooves G is N, the predetermined angular interval is 360 / N. FIG. 2 representatively shows the grooves G facing the grinding wheel 23 among the multiple grooves G.

[0012] Each of the multiple grooves G extends along the axial direction of the workpiece W. Each of the multiple grooves G has an arc-shaped cross section and serves as a retaining groove for balls (rollers) that form a ball bearing structure in the fixed pulley. Each of the multiple grooves G is roughly machined, for example, in a forging process, heat-treated by carburizing, and then finished by grinding with the groove grinding device 100. Therefore, the workpiece W is set in the groove grinding device 100 in a state before each of the multiple grooves G is ground.

[0013] The groove grinding device 100 comprises a first unit 10, a second unit 20, a sensor unit 30, and a controller 50. The first unit 10 is a work-side unit that axially tailstocks the workpiece W to center it and also rotates the workpiece W. The first unit 10 comprises an index unit 11 and a tailstock unit 12.

[0014] The index unit 11 has a fixed center 111, a motor 112, and a gripping unit 113. The fixed center 111 is used to center the workpiece W. The fixed center 111 is inserted into a central hole provided at one end of the workpiece W. The motor 112 rotates the workpiece W. The motor 112 can rotate the workpiece W at regular angular intervals, thereby indexing the rotational position of the workpiece W, such as the groove position. When indexing the groove position, the workpiece W is positioned at 120°, that is, at regular angular intervals, and the groove G is ground each time. The gripping unit 113 clamps (holds) the workpiece W at one end. While clamped by the gripping unit 113, the workpiece W is rotated by the motor 112 via the gripping unit 113.

[0015] The tail stock section 12 has a tail center 121 and a moving mechanism 122. The tail center 121 centers the workpiece W together with the fixed center 111. The tail center 121 is inserted into a center hole provided at the other end of the workpiece W. The tail center 121 is provided on the moving mechanism 122. The moving mechanism 122 is configured to be movable along the axial direction of the first unit section 10 (the X direction in the figure). When the moving mechanism 122 moves along the axial direction of the first unit section 10 toward the workpiece W, the tail center 121 tail stocks the workpiece W in the axial direction of the first unit section 10 and centers the workpiece W together with the fixed center 111.

[0016] The second unit section 20 is a tool-side unit and includes a rotation shaft 21, a movement mechanism 22, and a grinding wheel 23. The rotation shaft 21 is disposed orthogonal to the axial direction of the first unit section 10. The axial direction of the rotation shaft 21 forms the axial direction of the second unit section 20 and corresponds to the Y direction in the figure. Therefore, the first unit section 10 and the second unit section 20 are disposed orthogonally, with their axes perpendicular to each other. The rotation shaft 21 is provided on the movement mechanism 22.

[0017] The movement mechanism 22 has a motor 221, and the motor 221 rotates the rotation shaft 21. The movement mechanism 22 is configured to be movable in the axial direction of the first unit part 10, the axial direction of the second unit part 20, and directions perpendicular to these axial directions, that is, the X direction, Y direction, and Z direction shown in the figure. When the movement mechanism 22 moves, the rotation shaft 21 and the motor 221 provided on the movement mechanism 22 also move together.

[0018] The grindstone 23 is provided on the rotating shaft 21. The grindstone 23 is fixed to the tip of the rotating shaft 21. The grindstone 23 has a disk-like shape and is arranged concentrically with the rotating shaft 21. The grindstone 23 rotates integrally with the rotating shaft 21 and grinds each of the multiple grooves G. The grindstone 23 has an outer periphery 231 with an arc-shaped cross section, and grinds each of the multiple grooves G with the outer periphery 231.

[0019] The second unit part 20 configured in this manner, together with the first unit part 10, grinds the plurality of grooves G in sequence with the grindstone 23. In other words, the first unit part 10 and the second unit part 20 cooperate to grind the plurality of grooves G in sequence.

[0020] The sensor unit 30 includes a sensor 31 and a moving mechanism 32. The sensor 31 is arranged on the outer periphery of the workpiece W. The sensor 31 is a proximity sensor that turns ON or OFF depending on whether the sensor is approaching or moving away from the workpiece W. The sensor 31 is provided on the moving mechanism 32 and moves together with the moving mechanism 32. The moving mechanism 32 is configured to be movable in the X and Z directions shown in the figure, and the sensor 31 is arranged to face the workpiece W from the Z direction. Therefore, the sensor 31 is movable directly above the workpiece W along the extension direction of the workpiece W, and is also capable of approaching and moving away from the workpiece W. Figure 2 shows the case where the sensor 31 is in the standby position.

[0021] The sensor 31 is used to detect the groove G and measure the runout of the workpiece W. The runout of the workpiece W is the runout of the outer diameter of the workpiece W, and is the runout in the radial direction of the workpiece W (a runout that is positive when measured in the direction of increasing radius and negative when measured in the direction of decreasing radius). The sensor 31 is arranged in these cases as described below.

[0022] Fig. 3 is a diagram illustrating the groove detection position of sensor 31. Fig. 4 is a diagram illustrating the runout measurement position of sensor 31. When detecting groove G, sensor 31 is moved, for example, from the standby position toward fixed center 111 along the axial direction of first unit part 10, to an axial position where it radially overlaps with multiple grooves G. This axial position is the groove detection position, and at the groove detection position, sensor 31 is further moved closer to workpiece W to a radial position where it can detect groove G. Groove G can be detected by detecting that sensor 31 has changed from ON to OFF based on a signal from sensor 31.

[0023] The groove G is detected by the sensor 31 as a reference groove that serves as a reference for the circumferential position on the workpiece W, for example. The groove G detected as the reference groove is used to measure the runout of the workpiece W as a reference for the circumferential position on the workpiece W. The reason for detecting any one of the multiple grooves G as the reference groove is that by detecting any one of the multiple grooves G that can be detected by the sensor 31 and using it as a reference, it becomes easy to align the runout measurement position (measurement point) with the groove position of each of the multiple grooves G in the circumferential direction of the workpiece W.

[0024] On the other hand, in order to grasp the relationship between the rotational position of the workpiece W and the circumferential position on the workpiece W, for example, when the sensor 31 faces an arbitrary circumferential position on the workpiece W, that circumferential position may be detected and set as a reference. Even in this case, if one of the multiple grooves G is detected after the reference is set, the positional relationship between the detected groove G and the reference can be grasped, so it is possible to align the measurement point with the groove position of the multiple grooves G. However, in this case, it takes time because the groove G must be detected separately from the reference setting.

[0025] During runout measurement, the sensor 31 is moved from the groove detection position to an axial position where it does not overlap with the grooves G in the radial direction and where the workpiece W has a circular cross section. This axial position is the runout measurement position, and at the runout measurement position, the sensor 31 is gradually moved closer to the workpiece W from a distant position where the sensor 31 is OFF, and the Z-axis position when the sensor 31 is turned ON is stored. As a result, the outer diameter position of the workpiece W at the circumferential position corresponding to the reference groove is measured. Then, starting from the circumferential position corresponding to the reference groove, the first unit 10 rotates the workpiece W at 60° intervals and measures the outer diameter position each time, thereby measuring the outer diameter position of the workpiece W at six locations. Since the outer diameter position of the workpiece W indicates the runout of the workpiece W, the runout of the workpiece W is measured at a total of six locations.

[0026] Rotating at 60° intervals corresponds to rotating at 180 / N degree intervals, where N is the number of grooves in the plurality of grooves G. Furthermore, measuring at six locations corresponds to measuring at 2N locations, where N is the number of grooves in the plurality of grooves G. By setting the measurement start point, which is the first measurement among the plurality of measurement points, at a circumferential position corresponding to the reference groove, it is possible to correspond the measurement points to the groove positions of each of the plurality of grooves G. The measurement start point may also be set at another circumferential position.

[0027] 1 and 2, the controller 50 is composed of one or more computers (microcomputers) equipped with a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and an input / output interface (I / O interface). The controller 50 performs control by having the CPU execute a program stored in the ROM or RAM. The program may be stored in a non-transitory storage medium such as a CD-ROM.

[0028] The controller 50 controls the first unit section 10, the second unit section 20, and the sensor section 30. In the first unit section 10, the motor 112, the gripping section 113, and the moving mechanism 122 are controlled by the controller 50. In the second unit section 20, the moving mechanism 22 and the motor 221 are controlled by the controller 50, and in the sensor section 30, the moving mechanism 32 is controlled by the controller 50. For example, a signal from the sensor 31 is input to the controller 50. Other signals necessary for processing control may also be input to the controller 50 as appropriate.

[0029] Based on the stored program, the controller 50 executes machining control that forms a machining process consisting of a plurality of control steps, thereby grinding all of the plurality of grooves G in the workpiece W. The machining control is executed based on the machining program. Therefore, in other words, the program stored in the controller 50 causes the controller 50 to perform control to grind all of the plurality of grooves G in the workpiece W using the machining program. The machining process is composed of a plurality of control steps that will be explained next.

[0030] Figure 5 is an explanatory diagram of the control processes that make up the machining process. As shown in Figure 5, the machining process is broadly divided into four control processes: a centering process PC1, a runout identification process PC2, a first grinding process PC3, and a second grinding process PC4. The centering process PC1 is a process in which the first unit section 10 performs a tail push on the workpiece W in the axial direction to center it. The centering process PC1 is followed by a runout identification process PC2.

[0031] The runout identification process PC2 is a process of identifying the position or region R on the outer periphery where the maximum or minimum point of runout of the centered workpiece W exists. In other words, the runout identification process PC2 is a process of identifying the maximum or minimum point of runout of the centered workpiece W by the position or region R on the outer periphery, and identification by region R identifies that the maximum or minimum point of runout exists in that region R. In addition to detecting the reference groove and measuring the runout of the workpiece W described above, the runout identification process PC2 further includes runout identification, which will be explained next.

[0032] 6 and 7 are explanatory diagrams of the runout identification method in the runout identification process PC2. Fig. 6 shows the case where a groove G exists in the first region Rmax, and Fig. 7 shows the case where a groove G exists in the second region Rmin. The first region Rmax is the region R on the outer periphery where the maximum point of runout exists, and the second region Rmin is the region R on the outer periphery where the minimum point of runout exists. The workpiece center P1 indicates the center of the workpiece W.

[0033] As shown in Figures 6 and 7, in the runout identification process PC2, the outer periphery of the workpiece W is divided into multiple regions R. The multiple regions R are set to be uniformly spaced from one another, and if there are a total of six measurement points, a total of six regions R are set at 60° intervals. In other words, the same number of regions R as the measurement points are set. Therefore, there is always one measurement point in each of the multiple regions R. Each of the multiple regions R can be set so that the groove G is located in the circumferential center in one of the multiple regions R, allowing the region R to be set in a balanced manner for each of the multiple grooves G. If the number of grooves G is N, then the first region Rmax or the second region Rmin is set as a predetermined region for the workpiece W, and multiple regions R are set at 180 / N degree intervals including the predetermined region.

[0034] The first region Rmax shown in Figure 6 is identified based on the measurement point with the largest runout. In other words, the region R containing the measurement point with the largest runout among multiple measurement points is identified as the first region Rmax. The measurement point with the largest runout can be identified by comparing the runouts measured at a total of six locations. Therefore, the first region Rmax is identified based on a comparison of the runouts measured at a total of six locations.

[0035] The second region Rmin shown in Figure 7 is located on the opposite side of the first region Rmax with respect to the workpiece center P1, and is point-symmetric with the first region Rmax. Therefore, the second region Rmin is indirectly identified by identifying the first region Rmax. In other words, identifying either the first region Rmax or the second region Rmin also identifies the other. In this sense, the runout identification process PC2 can be said to be a process for identifying the region R on the outer periphery where the maximum or minimum runout point exists.

[0036] The first region Rmax is specified to determine the first grinding groove to be ground first among the multiple grooves G. As shown in Fig. 6, if a groove G exists in the first region Rmax, the groove G existing in the first region Rmax is determined as the first grinding groove. On the other hand, if a groove G does not exist in the first region Rmax, the groove G existing in the second region Rmin is determined as the first grinding groove, as shown in Fig. 7.

[0037] The setting of the first grinding groove as described above can be considered as part of the control for grinding the first grinding groove. Therefore, the setting of the first grinding groove can be understood as part of the control of the first grinding step PC3, which will be described next. As shown in Figure 5, the runout identification step PC2 is followed by the first grinding step PC3, which is then followed by the second grinding step PC4. The first grinding step PC3 and the second grinding step PC4 will be described as follows.

[0038] 8 is an explanatory diagram of the first grinding step PC3 and the second grinding step PC4. The first grinding step PC3 is a step in which a groove G that exists in the first region Rmax or the second region Rmin among the multiple grooves G is set as a first grinding groove, and the center Y1 of the first grinding groove is aligned with the center Y2 of the grinding wheel 23, and the first grinding groove is then ground.

[0039] For this reason, in the first grinding process PC3, first, the first grinding groove is detected (control A). To detect the first grinding groove, the sensor 31 is moved from the runout detection position described above to the groove detection position and brought close to the workpiece W. Then, while the workpiece W is rotated in this state, the first grinding groove is detected based on a signal from the sensor 31. At this time, the workpiece W can be rotated so that the sensor 31 detects the first grinding groove within the range of the first region Rmax (or the second region Rmin).

[0040] When the first grinding groove is detected, the center Y1 of the first detection groove is detected (control B). The center Y1 of the first detection groove is the center in the Y direction and is detected as follows: The center Y1 is detected by moving the sensor 31 in the Y direction to detect both circumferential edge portions of the first grinding groove with the sensor 31, and then calculating the Y-direction center coordinate between these based on the Y-direction coordinates of the two detected edge portions.

[0041] In control B, the center Y1 of the first grinding groove is further aligned with the center Y2 of the grinding wheel 23. The center Y2 of the grinding wheel 23 is also the center in the Y direction, and the alignment of the first grinding groove with the grinding wheel 23 is performed by moving the grinding wheel 23 in the Y direction and aligning the center Y2 of the grinding wheel 23 with the center Y1 of the first grinding groove.

[0042] When the center Y1 of the first detection groove and the center Y2 of the grinding wheel 23 are aligned, the grinding wheel 23 grinds the first grinding groove (control C). The grinding of the first grinding groove is performed by moving the grinding wheel 23 from the position of the grinding wheel 23 shown by the two-dot dashed line in Figure 2 toward the fixed center 111 along the X direction while rotating it.

[0043] The second grinding process PC4 is a process in which the workpiece W is rotated sequentially at predetermined angular intervals, i.e., 120° intervals, to grind each of the remaining grooves G among the plurality of grooves G. In other words, after the first grinding process PC3, the remaining grooves G are ground in the second grinding process PC4 (control D).

[0044] The remaining grooves G are the second grinding groove that is ground second and the third grinding groove that is ground third, and when grinding of the first grinding groove is completed, the workpiece W is rotated 120° and the second grinding groove is ground. Also, when grinding of the second grinding groove is completed, the workpiece W is rotated again 120° and the third grinding groove is ground.

[0045] 9 is a flowchart showing an example of processing control performed by the controller 50. In step S1, the workpiece W is centered. That is, step S1 corresponds to a centering step PC1. Steps S2 to S4 correspond to a runout identification step PC2. In step S2, the reference groove is detected, in step S3, the runout of the workpiece W is measured, and in step S4, the first region Rmax is identified.

[0046] Steps S5 to S9 correspond to the first grinding process PC3. In step S5, it is determined whether or not there is a groove G in the first region Rmax. If the determination in step S5 is affirmative, the groove G present in the first region Rmax is set as the first grinding groove in step S6. If the determination in step S5 is negative, the groove G present in the second region Rmin is set as the first grinding groove in step S7. After step S6 or step S7, the process proceeds to step S8, where the first grinding groove and the grinding wheel 23 are centered. Furthermore, in step S9, the first grinding groove is ground.

[0047] Steps S10 to S13 correspond to the second grinding process PC4. In step S10, the workpiece W is rotated 120° to determine the groove position of the second grinding groove, and in step S11, the second grinding groove is ground. In step S12, the workpiece W is rotated again 120° to determine the groove position of the third grinding groove, and in step S13, the third grinding groove is ground. As a result, all of the multiple grooves G are ground.

[0048] The second grinding groove and the third grinding groove, whose groove positions are determined by the rotation of the workpiece W, are not centered with the grinding wheel 23. On the other hand, the centered workpiece W has runout. For this reason, the determined groove positions of the second grinding groove and the third grinding groove are shifted due to the runout of the workpiece W, which may result in no grinding allowance being available at the edge portions, leaving unground portions (residual scale).

[0049] In this embodiment, in consideration of the above circumstances, the first region Rmax or the second region Rmin is identified in the runout identification process PC2, and the grooves G present in the first region Rmax or the second region Rmin among the plurality of grooves G are ground as the first grinding grooves in the first grinding process PC3. This is based on the verification results described next.

[0050] 10A to 10C are explanatory diagrams of the verification results. In FIGS. 10A to 10C, groove G1, groove G2, and groove G3, which are multiple grooves G, are schematically indicated by circles, and the case where groove G1 is located at the maximum point of runout, i.e., groove G1 is located in the first region Rmax, is shown. In FIGS. 10A to 10C, the horizontal direction of the diagram corresponds to the Y direction, and the vertical direction of the diagram corresponds to the Z direction. This also applies to FIGS. 11 to 14, which will be described later.

[0051] Fig. 10A shows the case where grinding is started from groove G1. Fig. 10B shows the case where grinding is started from groove G2, and Fig. 10C shows the case where grinding is started from groove G3. Therefore, as can be seen from Fig. 6, Figs. 10B and 10C show the case where grinding is started with groove G, which does not exist in the first region Rmax or the second region Rmin, as the first grinding groove.

[0052] The first groove arrangement indicates the groove arrangement of the multiple grooves G when grinding the multiple grooves G for the first time. The second groove arrangement indicates the groove arrangement of the multiple grooves G when grinding is performed secondly, and the third groove arrangement indicates the groove arrangement of the multiple grooves G when grinding is performed thirdly. In the first groove arrangement, the workpiece center P1 corresponds to the center Y1 of the first grinding groove. The workpiece center P1 also corresponds to the centers of the second grinding groove and the third grinding groove. The machining center P2 indicates the rotation center of the centered workpiece W.

[0053] 10A, when groove G1 is the machining start groove, i.e., the first grinding groove, groove G1 is located at the maximum runout point, so workpiece center P1 is shifted directly above machining center P2. As a result, in the first workpiece arrangement, the angles about machining center P2 are reduced by an amount α from 120° between grooves G1 and G2, and between grooves G1 and G3, and are increased by an amount 2α from 120° between grooves G2 and G3.

[0054] In the first groove arrangement, the groove G1, which is the first grinding groove, is centered with the grinding wheel 23. In centering, the center Y2 of the grinding wheel 23 is aligned with the center Y1 in the Y direction. As a result, the center Y2 of the grinding wheel 23 is located at the same Y direction position as the processing center P2. The relative positional relationship in the Y direction between the center Y2 of the grinding wheel 23 and the processing center P2 does not change even if the workpiece W rotates. For this reason, in the case shown in FIG. 10A, the center Y2 of the grinding wheel 23 is located at the same Y direction position as the processing center P2 in all of the first to third groove arrangements.

[0055] In the second groove arrangement, the workpiece center P1 is eccentric from the machining center P2 due to runout, and is rotated 120° from the first groove arrangement around the machining center P2 as the center of rotation. In this case, the groove G2 to be machined is in a state where an angle of "+α" has been added on the right side of the drawing (hence, "-α" on the left side of the drawing) in relation to the center Y2 of the grinding wheel 23. As a result, the edge portion of the left side of the drawing of the groove G2 is shifted downward and to the left compared to the ideal state, and the grinding allowance at that edge portion is reduced.

[0056] In the third groove arrangement, the workpiece W is rotated an additional 120 degrees from the second groove arrangement, with the machining center P2 as the rotation center. In this case, groove G3 is in a state where, in relation to the center Y2 of the grinding wheel 23, the angle on the right side of the drawing is increased by "-α" compared to the ideal state (hence, the angle on the left side of the drawing is increased by "+α"). As a result, the edge portion on the right side of groove G3 in the drawing is shifted downward and to the right compared to the ideal state, and the grinding allowance at that edge portion is reduced.

[0057] As shown in Fig. 10B, when groove G2 is the first grinding groove, the first groove arrangement is the same as the second groove arrangement shown in Fig. 10A. On the other hand, in the first groove arrangement, the first grinding groove and the grinding wheel 23 are centered. Therefore, in this case, the center Y2 of the grinding wheel 23 is aligned with the center Y1 of the first grinding groove, and as a result, there is no deviation in the groove position in the Y direction due to the magnitude α as shown in the second groove arrangement in Fig. 10A. On the other hand, in this case, as a result of centering, the center Y2 of the grinding wheel 23 is shifted in the Y direction toward groove G1 with respect to the processing center P2.

[0058] In the second groove arrangement, the workpiece W is rotated 120° from the first groove arrangement. Meanwhile, the relative positional relationship in the Y direction between the center Y2 of the grinding wheel 23 and the processing center P2 remains unchanged. Therefore, in this case, groove G2 is in a state where an angle of "-2α" has been added to the right side of the drawing (hence, "+2α" on the left side of the drawing) in relation to the center Y2 of the grinding wheel 23. As a result, in this case, the edge portion of groove G3 on the right side of the drawing is significantly shifted to the right from the grinding wheel 23, and the grinding allowance is also reduced.

[0059] Even in the third groove arrangement, the relative positional relationship in the Y direction between the center Y2 of the grinding wheel 23 and the processing center P2 does not change. Therefore, in this case too, the groove G1 is in a state where the angle "-α" is added on the right side of the drawing (hence, "+α" on the left side of the drawing) in relation to the center Y2 of the grinding wheel 23.

[0060] As shown in FIG. 10C , even when groove G3 is the first grinding groove, in the first groove arrangement, the center Y2 of the grinding wheel 23 is aligned with the center Y1 of the first grinding groove, and as a result, the center Y2 of the grinding wheel 23 is shifted toward groove G1 in the Y direction relative to the processing center P2. In this case, too, in the second and third groove arrangements, the relative positional relationship in the Y direction between the center Y2 of the grinding wheel 23 and the processing center P2 remains unchanged. As a result, in the second groove arrangement, groove G1 appears to have an angle "+α" added to it on the right side of the drawing (hence, "-α" on the left side of the drawing) in relation to the center Y2 of the grinding wheel 23. Furthermore, in the third groove arrangement, groove G2 appears to have an angle "+2α" added to it on the right side of the drawing (hence, "-2α" on the left side of the drawing) in relation to the center Y2 of the grinding wheel 23.

[0061] From the above, it can be seen that in the case shown in Figure 10A, where the groove G1 located at the maximum point of runout is the first grinding groove, positional deviation of the second grinding groove and the third grinding groove relative to the grinding wheel 23 is suppressed compared to the cases shown in Figures 10B and 10C. Based on the above, further verification and the verification results will be explained below.

[0062] FIG. 11 shows three cases used in further verification. In the further verification, the following three cases in which black scale residue is likely to occur were examined. The first case is when groove G1 is located on the opposite side of the maximum point of runout (i.e., the minimum point). The second case is when groove G1 is located at the maximum point of runout. The third case is when the maximum point of runout is located directly to the side of groove G1 on the groove G2 side, and groove G1 is not located in either the first region Rmax or the second region Rmin.

[0063] Figures 12 to 14 show the verification results for three cases. Figure 12 corresponds to the first case, Figure 13 corresponds to the second case, and Figure 14 corresponds to the third case. Figures 12 to 14 show the grinding allowances for grooves G1, G2, and G3, respectively, when the first grinding grooves are grooves G1, G2, and G3.

[0064] The first grinding groove is centered with the grinding wheel 23. Therefore, the machining allowance of the first grinding groove is equal on both sides in each case shown in Figures 12 to 14, as indicated by the bold frame, and the grinding result is good (circle).

[0065] In the first case shown in Figure 12, when groove G1, which is located at the position where runout is minimum, is used as the first grinding groove, there is a bias in the machining allowance between the left and right edges of grooves G2 and G3, but the machining allowance is secured (triangle mark). On the other hand, when grooves G2 and G3 are used as the first grinding grooves, there are cases where the machining allowance becomes a negative value, that is, there is no machining allowance at all (cross mark). As a result, when groove G2 is used as the first grinding groove, black scale remains on the left edge of groove G3, and when groove G3 is used as the first grinding groove, black scale remains on the right edge of groove G2.

[0066] In the second case shown in Fig. 13, when groove G1, which is located at the position where runout is maximum, is used as the first grinding groove, the machining allowance is secured, as in the first case shown in Fig. 12. On the other hand, when groove G2 is used as the first grinding groove, black scale remains on the right edge of groove G3, and when groove G3 is used as the first grinding groove, black scale remains on the left edge of groove G2.

[0067] 14, groove G2 is the groove G at the position where runout is minimum among the multiple grooves G, and groove G3 is the groove G at the position where runout is maximum among the multiple grooves G. In other words, groove G2 is a groove G that is not located at the minimum runout point but is located in the second region Rmin, and groove G3 is a groove G that is not located at the maximum runout point but is located in the first region Rmax. In this case, if groove G1 is the first grinding groove, the machining allowance on the left edge of groove G3 is -0.02 mm.

[0068] On the other hand, when groove G2 is used as the first grinding groove, the removal allowance on the right edge of groove G1 is -0.0006 mm, and when groove G3 is used as the first grinding groove, the removal allowance on the right edge of groove G1 is very small at -0.0001 mm. As a result, when groove G2 or groove G3 is used as the first grinding groove, the remaining black scale is negligible or falls within a range that can be removed by adjusting the grinding process.

[0069] From the above, it can be seen that by using the groove G present in the first region Rmax or the second region Rmin as the first grinding groove, the occurrence of residual black scale can be suppressed compared to when the groove G present in neither the first region Rmax nor the second region Rmin is used as the first grinding groove.

[0070] Next, the main effects of this embodiment will be described.

[0071] (1) The groove grinding method of this embodiment is a groove grinding method in which a plurality of grooves G provided at 120° intervals on the outer peripheral surface of the workpiece W are ground sequentially with a grinding wheel 23, and is a groove grinding method in which all of the plurality of grooves G are ground through processing steps including: a runout identification process PC2 in which an area R on the outer periphery where the maximum or minimum point of runout of the centered workpiece W exists, i.e., a first area Rmax or a second area Rmin; a first grinding process PC3 in which a groove G existing in the first area Rmax or the second area Rmin among the plurality of grooves G is first ground by aligning a center Y1 of the first grinding process groove with a center Y2 of the grinding wheel 23 and grinding the first grinding process groove; and a second grinding process PC4 in which the workpiece W is then rotated by 120° intervals to grind each of the remaining grooves G among the plurality of grooves G.

[0072] According to this method, by setting the first grinding groove as described above, it is possible to suppress deviation of the groove position caused by runout of the workpiece W when determining the positions of the remaining grooves G. As a result, it is possible to make it difficult for residual black scale to occur across the multiple grooves G, and the occurrence of residual black scale is suppressed.

[0073] (2) Each of the multiple grooves G is formed at 360 / N degree intervals on the outer circumference of the shaft, where N is the number of grooves. The runout identification process PC2 involves rotating the workpiece W at 180 / N degree intervals and measuring the runout of the workpiece W each time using the sensor 31, thereby measuring the runout of the workpiece W at 2N locations, and comparing the runouts measured at the 2N locations to identify the maximum or minimum point of the runout of the workpiece W between the 2N locations. When N=3, the multiple grooves G are formed at 120° intervals. Furthermore, the workpiece W is rotated at 60° intervals, and runout is measured at a total of six locations.

[0074] According to this method, it is possible to determine whether the maximum or minimum point of runout of the workpiece W over the entire circumference is within a certain angular range based on the maximum or minimum point of runout of the workpiece W among 2N locations, even without measuring the runout of the workpiece W over the entire circumference. Therefore, even if an existing facility does not have a sensor capable of measuring the runout of the workpiece W over the entire circumference, this method is highly applicable in that it can be applied as long as it has a proximity sensor capable of detecting the presence or absence of a groove G. Furthermore, it is advantageous in terms of cost in that a proximity sensor, which is less expensive than a sensor capable of measuring the runout of the workpiece W over the entire circumference, can be used as the sensor 31.

[0075] (3) The runout identification process PC2 is a process for identifying the first region Rmax or the second region Rmin, in which the first region Rmax or the second region Rmin is set as a predetermined region, and multiple regions R including the predetermined region are set at 180 / N degree intervals for the workpiece W, and the first region Rmax or the second region Rmin is identified based on the maximum or minimum point of runout of the workpiece W among 2N locations. When N=3, the multiple regions R are set at 60° intervals.

[0076] According to this method, one measurement point is included in each of the multiple regions R. Therefore, the region R in which the maximum point of runout of the workpiece W among the 2N points exists can be identified as the first region Rmax, and the region R in which the minimum point of runout of the workpiece W among the 2N points exists can be identified as the second region Rmin.

[0077] (4) The first grinding process PC3 includes, if any of the multiple grooves G exists in the first region Rmax, designating the groove G existing in the first region Rmax as the first grinding groove, and, if none of the multiple grooves G is included in the first region Rmax, designating the region R among the multiple regions R located on the opposite side of the first region Rmax from the workpiece center P1 as the second region Rmin, and designating the groove G included in the second region Rmin as the first grinding groove.

[0078] According to this method, the first grinding groove can be set by specifying either the first region Rmax or the second region Rmin, which simplifies the processing control.

[0079] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0080] For example, a sensor capable of measuring the runout of the workpiece W over the entire circumference may be used as the sensor 31. In this case, in the runout identification process PC2, for example, the maximum or minimum point of the runout of the centered workpiece W can be identified by its position on the outer circumference. Furthermore, in this case, if a groove G exists at the maximum or minimum point of the runout of the workpiece W, grinding can be performed with the groove G existing at the identified position as the first grinding groove.

[0081] The maximum or minimum point of runout of the workpiece W among the 2N locations may be used to regard it as the maximum or minimum point of runout on the entire circumference of the workpiece W. In this case, the measurement point of the maximum or minimum point of runout of the workpiece W among the 2N locations can be regarded as the position on the outer periphery where the maximum or minimum point of runout on the entire circumference of the workpiece W exists. In this case as well, if the measurement point of runout of the workpiece W corresponds to each groove position of the multiple grooves G, grinding can be performed with the groove G present at the specified position as the first grinding groove. [Explanation of symbols]

[0082] 10 Unit 1 20 Second Unit 21 Rotation axis 23 Whetstone 31 Sensors 50 Controllers G groove PC1 Centering process PC2 Runout identification process PC3 1st grinding process PC4 2nd grinding process R Region (multiple regions) Rmax 1st region (predetermined region, region where the maximum point of shaft runout exists) Rmin Second region (predetermined region, region where the minimum point of shaft runout exists) Y1 Center of the first grinding groove Y2 Center of the grinding wheel W Work (shaft) 100 groove grinding equipment

Claims

1. A groove grinding method for grinding a plurality of grooves provided at predetermined angular intervals on an outer peripheral surface of a shaft in order with a grindstone, comprising: a control step of identifying a position or area on the circumference where a maximum or minimum point of runout of the centered shaft exists; a control process of grinding a groove present at the position or in the region among the plurality of grooves as a first grinding groove to be ground first, after aligning a center of the first grinding groove with a center of the grindstone; a control step of rotating the shaft by the predetermined angular intervals to perform grinding on each of the remaining grooves among the plurality of grooves; grinding all of the plurality of grooves by a processing step including Groove grinding method.

2. The groove grinding method according to claim 1, The plurality of grooves are formed at intervals of 360 / N degrees on the outer periphery of the shaft, where N is the number of grooves; The control step of identifying the position or the region includes measuring the runout of the shaft at 2N points by rotating the shaft at intervals of 180 / N degrees and measuring the runout of the shaft each time using a sensor arranged on the outer periphery of the shaft, and comparing the runouts measured at the 2N points to identify the maximum point or the minimum point of the runout of the shaft among the 2N points. Groove grinding method.

3. 3. The groove grinding method according to claim 2, The control step of identifying the position or the region is a step of identifying the region, setting a plurality of regions at intervals of 180 / N degrees including the predetermined region on the shaft, with the region being a predetermined region, and identifying the predetermined region based on the maximum point or minimum point of the deflection of the shaft among the 2N positions. Groove grinding method.

4. The groove grinding method according to claim 3, The control step of grinding the first grinding groove includes: When any of the plurality of grooves exists in a first region, which is the predetermined region and is a region where a maximum point of runout of the shaft exists, the groove existing in the first region is set as the first grinding groove; If none of the plurality of grooves exists in the first region, a region of the plurality of regions that is located on the opposite side of the first region with respect to the center point of the shaft is designated as a second region in which a minimum point of runout of the shaft exists, and the grooves that exist in the second region are designated as the first grinding grooves; A groove grinding method comprising:

5. a first unit portion that axially centers the shaft and rotates the shaft; a second unit having a rotating shaft on which a grinding wheel is provided, and which, together with the first unit, sequentially grinds a plurality of grooves provided at predetermined angular intervals on the outer peripheral surface of the shaft with the grinding wheel; a sensor disposed on the outer periphery of the shaft; a controller that controls the first unit and the second unit; A groove grinding device comprising: The controller a control for identifying a position or an area on the outer periphery where a maximum point or a minimum point of runout of the shaft centered by the first unit portion exists based on an output of the sensor; a control for grinding a groove present at the position or in the region among the plurality of grooves as a first grinding groove to be ground first, after aligning a center of the first grinding groove with a center of the grindstone by the second unit; Thereafter, the first unit rotates the shaft by the predetermined angular intervals, and the second unit performs grinding on each of the remaining grooves of the plurality of grooves in sequence; grinding all of the plurality of grooves by processing control including Groove grinding equipment.

6. A computer-executable program for a groove grinding device that uses a grinding wheel to grind a plurality of grooves provided at predetermined angular intervals on the outer peripheral surface of a shaft, the program comprising: Identifying a location or area on the circumference where a maximum or minimum point of runout of the centered shaft exists; a groove present at the position or in the region among the plurality of grooves is ground first as a first grinding groove, and the center of the first grinding groove is aligned with the center of the grindstone, and then the first grinding groove is ground; Thereafter, the shaft is rotated by the predetermined angular intervals to perform grinding on each of the remaining grooves among the plurality of grooves. and performing control to grind all of the plurality of grooves by a machining program including the following: program.

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