JP2024063416A - Groove grinding method, groove grinding device, and program - Google Patents

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

The present invention relates to a groove grinding method, a groove grinding device, and a program.

Patent Document 1 discloses a groove grinding machine that uses a grinding wheel that rotates at high speed to grind the grooves of a workpiece that is clamped between an index unit and a tailstock. With this groove grinding machine, once one groove has been ground, the index unit rotates the workpiece 120° to present the next groove to the grinding wheel.

JP-A-9-136254 (see, for example, FIG. 5, paragraph 0015)

When grinding the grooves on the shaft, the centered shaft will have runout. 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 edges of the groove, and there may be areas left unground.

The present invention was made in consideration of these problems, and aims to prevent the occurrence of unground areas after grinding.

A groove grinding method according to one aspect of the present invention is a groove grinding method for sequentially grinding a plurality of grooves provided at a predetermined angular interval on the outer peripheral surface of a shaft with a grindstone, the groove grinding method including a control step for identifying a position or region 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 grindstone and grinding the first grinding groove as the first grinding groove to be ground first among the plurality of grooves that exists at the position or region, and a control step for rotating the shaft by the predetermined angular interval to grind each of the remaining grooves among the plurality of grooves in sequence, the groove grinding method grinding all of the plurality of grooves by a processing step including the following steps.

According to another aspect of the present invention, a groove grinding device and a program corresponding to the above groove grinding method are provided.

According to these aspects, by setting the first grinding groove as described above, deviations in groove position caused by shaft runout when determining the positions of the remaining grooves are 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.

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

The following describes an embodiment of the present invention with reference to the attached drawings.

Figure 1 is a schematic diagram of the main parts of the groove grinding device 100 as viewed from above. Figure 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 grinds multiple grooves G provided at a predetermined angular interval on the outer peripheral surface of the workpiece W with the grinding wheel 23 in order. The workpiece W is a shaft, for example a fixed pulley of a continuously variable transmission. The number of grooves G in the multiple grooves G is three here, and in this case the predetermined angular interval is 120°. If the number of grooves G in the multiple grooves G is N, the predetermined angular interval is 360/N. Figure 2 shows a representative groove G facing the grinding wheel 23 among the multiple grooves G.

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 constitutes 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 in a state before each of the multiple grooves G is ground is set in the groove grinding device 100.

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 center the work W by pushing it in the axial direction and also rotates the work W. The first unit 10 comprises an index unit 11 and a center pushing unit 12.

The index unit 11 has a fixed center 111, a motor 112, and a gripper 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, which allows the rotational position of the workpiece W, such as the groove position, to be indexed. 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 gripper 113 clamps (holds) the workpiece W at one end. While the workpiece W is clamped by the gripper 113, it is rotated by the motor 112 via the gripper 113.

The tail push unit 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 central 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 10 (X direction in the figure). When the moving mechanism 122 moves along the axial direction of the first unit 10 toward the workpiece W, the tail center 121 center pushes the workpiece W in the axial direction of the first unit 10 and centers the workpiece W together with the fixed center 111.

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

The moving mechanism 22 has a motor 221, which rotates the rotating shaft 21. The moving 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 moving mechanism 22 moves, the rotating shaft 21 and the motor 221 provided in the moving mechanism 22 also move together.

The grindstone 23 is attached to 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.

The second unit 20 configured in this manner grinds the multiple grooves G in sequence together with the first unit 10 using the grindstone 23. In other words, the first unit 10 and the second unit 20 work together to grind the multiple grooves G in sequence.

The sensor unit 30 includes a sensor 31 and a moving mechanism 32. The sensor 31 is disposed on the outer periphery of the workpiece W. The sensor 31 is a proximity sensor that turns ON and OFF depending on whether it approaches or moves 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 disposed 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 capable of approaching and moving away from the workpiece W. Figure 2 shows the case where the sensor 31 is in the standby position.

Sensor 31 is used to detect groove G and to measure runout of workpiece W. Runout of workpiece W is the runout of the outer diameter of workpiece W, and is the runout in the radial direction of 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). Sensor 31 is positioned in these cases as described below.

Figure 3 is a diagram explaining the groove detection position of the sensor 31. Figure 4 is a diagram explaining the runout measurement position of the sensor 31. When detecting groove G, the sensor 31 is moved, for example, from the standby position toward the fixed center 111 along the axial direction of the 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, the sensor 31 is further moved closer to the workpiece W to a radial position where it can detect the groove G. The groove G can be detected by detecting that the sensor 31 has changed from ON to OFF based on a signal from the sensor 31.

Groove G is detected by 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. One of the multiple grooves G is detected as the reference groove because by detecting one of the multiple grooves G that can be detected by sensor 31 and using it as a reference, it becomes easier 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.

In contrast, 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 any 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 since the groove G must be detected separately from setting the reference.

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 the separated position where it is OFF, and the Z-direction position when the sensor 31 is 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, the circumferential position corresponding to the reference groove is used as the measurement starting point, and 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 points. The outer diameter position of the workpiece W indicates the runout of the workpiece W, so that the runout of the workpiece W is measured at a total of six points.

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

Returning to Figures 1 and 2, the controller 50 is composed of one or more computers (microcomputers) equipped with a central processing unit (CPU), a read-only memory (ROM), a 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.

The controller 50 controls the first unit 10, the second unit 20, and the sensor 30. In the first unit 10, the motor 112, the gripper 113, and the moving mechanism 122 are controlled by the controller 50. In the second unit 20, the moving mechanism 22 and the motor 221 are controlled by the controller 50, and in the sensor 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 be input to the controller 50 as appropriate.

Based on the stored program, the controller 50 executes processing control that forms a processing process consisting of multiple control steps, thereby grinding all of the multiple grooves G in the workpiece W. The processing control is executed based on the processing program. In other words, the program stored in the controller 50 causes the controller 50 to perform control to grind all of the multiple grooves G in the workpiece W using the processing program. The processing process is composed of multiple control steps, which are explained below.

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 10 presses the workpiece W in the axial direction to center it. The centering process PC1 is followed by a runout identification process PC2.

The runout identification process PC2 is a process for identifying the position on the outer periphery or the region R 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 for identifying the maximum or minimum point of runout of the centered workpiece W by the position on the outer periphery or the region R, 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 as described above, the runout identification process PC2 further includes runout identification, which will be described next.

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

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 as equal regions, and if there are a total of six measurement points, a total of six regions R spaced 60° apart are set. In other words, the same number of regions R as the measurement points are set. Therefore, each of the multiple regions R always has one measurement point. Each of the multiple regions R can be set so that the groove G is 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 multiple regions R spaced 180/N degrees apart are set for the workpiece W, including the first region Rmax or the second region Rmin as a specified region.

The first region Rmax shown in FIG. 6 is identified based on the measurement point with the maximum runout. In other words, the region R in which the measurement point with the maximum runout exists among the multiple measurement points is identified as the first region Rmax. The measurement point with the maximum runout can be identified by comparing the runouts measured at a total of six points. Therefore, the first region Rmax is identified based on a comparison of the runouts measured at a total of six points.

The second region Rmin shown in FIG. 7 is located on the opposite side of the first region Rmax with respect to the workpiece center P1, and is point-symmetrical 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 point of runout exists.

The first region Rmax is identified 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 no groove G exists 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.

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 process PC3, which will be described next. As shown in FIG. 5, the runout identification process PC2 is followed by the first grinding process PC3, which is then followed by the second grinding process PC4. The first grinding process PC3 and the second grinding process PC4 will be described as follows.

Figure 8 is an explanatory diagram of the first grinding process PC3 and the second grinding process PC4. The first grinding process PC3 is a process 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 the first grinding groove, and the center Y1 of the first grinding groove is aligned with the center Y2 of the grinding wheel 23, and then the first grinding groove is ground.

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 rotating the workpiece W 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).

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. That is, the center Y1 is detected by detecting the edge portions on both sides of the circumference of the first grinding groove with the sensor 31 by moving the sensor 31 in the Y direction, and calculating the Y direction center coordinate between them based on the Y direction coordinates of the two detected edge portions.

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 centering of the first grinding groove and the grinding wheel 23 is performed by moving the grinding wheel 23 in the Y direction to align the center Y2 of the grinding wheel 23 with the center Y1 of the first grinding groove.

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.

The second grinding process PC4 is a process in which the remaining grooves G are then ground by rotating the workpiece W at predetermined angular intervals, i.e., 120° intervals. In other words, after the first grinding process PC3, the remaining grooves G are ground in the second grinding process PC4 (control D).

The remaining grooves G are the second grinding groove, which is ground second, and the third grinding groove, which is ground third. When the grinding of the first grinding groove is completed, the workpiece W is rotated 120° and the second grinding groove is ground. When the grinding of the second grinding groove is completed, the workpiece W is rotated again 120° and the third grinding groove is ground.

Figure 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 process PC1. Steps S2 to S4 correspond to a runout identification process 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.

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 positive, the groove G existing 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 existing 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 is centered with the grinding wheel 23. In addition, grinding of the first grinding groove is performed in step S9.

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, grinding is performed on all of the multiple grooves G.

For the second and third grinding grooves, whose groove positions are determined by the rotation of the workpiece W, centering with the grindstone 23 is not performed. On the other hand, the centered workpiece W has runout. For this reason, in the second and third grinding grooves, the determined groove positions are shifted due to the runout of the workpiece W, and as a result, there is a concern that there will be no grinding allowance at the edge portions, leaving unground portions (the occurrence of so-called black scale residue).

In view of these circumstances, in this embodiment, the first region Rmax or the second region Rmin is identified in the runout identification process PC2, and in the first grinding process PC3, the grooves G that exist in the first region Rmax or the second region Rmin among the multiple grooves G are ground as the first grinding groove. This is based on the verification results described next.

Figures 10A to 10C are explanatory diagrams of the verification results. In Figures 10A to 10C, groove G1, groove G2, and groove G3, which are multiple grooves G, are shown as schematic circles, and the case where groove G1 is located at the maximum point of runout, and therefore groove G1 is located in the first region Rmax, is shown. In Figures 10A to 10C, the horizontal direction of the figures corresponds to the Y direction, and the vertical direction of the figures corresponds to the Z direction. This also applies to Figures 11 to 14 described later.

Figure 10A shows the case where grinding starts from groove G1. Figure 10B shows the case where grinding starts from groove G2, and Figure 10C shows the case where grinding starts from groove G3. Therefore, as can be seen from Figure 6, Figures 10B and 10C show the case where grinding starts with a groove G that does not exist in the first region Rmax or the second region Rmin as the first grinding groove.

The first groove arrangement indicates the groove arrangement of the multiple grooves G when grinding is performed for 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 for the second time, and the third groove arrangement indicates the groove arrangement of the multiple grooves G when grinding is performed for the third time. 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.

As shown in FIG. 10A, when groove G1 is the machining start groove, i.e., the first grinding groove, groove G1 is located at the maximum point of runout, so work center P1 is shifted directly above machining center P2. As a result, in the first work arrangement, the angle centered on machining center P2 is reduced by a magnitude α from 120° between groove G1 and groove G2, and between groove G1 and groove G3, and is increased by a magnitude 2α from 120° between groove G2 and groove G3.

In the first groove arrangement, the center of the grinding wheel 23 is aligned with the groove G1, which is the first grinding groove. 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.

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 in relation to the center Y2 of the grinding wheel 23 as if an angle of "+α" had been added on the right side of the figure (hence, "-α" on the left side of the figure). As a result, the edge portion of the groove G2 on the left side of the figure is shifted to the lower left compared to the ideal state, and the grinding allowance at that edge portion is reduced.

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 center of rotation. In this case, in relation to the center Y2 of the grinding wheel 23, groove G3 is in a state as if an angle of "-α" had been added to the right side of the figure compared to the ideal state (hence, an angle of "+α" had been added to the left side of the figure). As a result, the edge portion of groove G3 on the right side of the figure is shifted to the lower right compared to the ideal state, and the grinding allowance at that edge portion is reduced.

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, centering is performed, and the center Y2 of the grinding wheel 23 is shifted in the Y direction toward the groove G1 with respect to the processing center P2.

In the second groove arrangement, the workpiece W is rotated 120° from the first groove arrangement. However, 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, groove G2 is in a state in which an angle of "-2α" has been added to the right side of the figure (hence, "+2α" on the left side of the figure) 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 figure is significantly shifted to the right from the grinding wheel 23, and the grinding allowance is also reduced.

Even with 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 in which the angle "-α" is added to the right side of the figure (hence, "+α" on the left side of the figure) in relation to the center Y2 of the grinding wheel 23.

As shown in FIG. 10C, when groove G3 is the first grinding groove, in the first groove arrangement, the center Y2 of the grindstone 23 is aligned with the center Y1 of the first grinding groove, so that the center Y2 of the grindstone 23 is shifted toward the 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 grindstone 23 and the processing center P2 does not change. As a result, in the second groove arrangement, groove G1 is in a state as if an angle "+α" (hence, "-α" on the left side of the figure) has been added to it in relation to the center Y2 of the grindstone 23 on the right side of the figure (hence, "-2α" on the left side of the figure). In addition, in the third groove arrangement, groove G2 is in a state as if an angle "+2α" (hence, "-2α" on the left side of the figure) has been added to it in relation to the center Y2 of the grindstone 23 on the right side of the figure.

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, the 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 next.

Figure 11 shows three cases used in further verification. In 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 (hence 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 directly to the side of groove G1 on the groove G2 side, and groove G1 is not present in either the first region Rmax or the second region Rmin.

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 groove is groove G1, groove G2, or groove G3.

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 shown by the bold frame, and the grinding results are good (circle).

In the first case shown in FIG. 12, when groove G1, which is the position where the runout is smallest, is used as the first grinding groove, the machining allowance is biased between the left and right edge portions 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, the machining allowance may become negative, that is, there may be no machining allowance (X mark). As a result, when groove G2 is used as the first grinding groove, black scale remains on the left edge portion of groove G3, and when groove G3 is used as the first grinding groove, black scale remains on the right edge portion of groove G2.

In the second case shown in FIG. 13, if the groove G1 at the position where the 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, if the groove G2 is used as the first grinding groove, black scale will remain on the right edge of the groove G3, and if the groove G3 is used as the first grinding groove, black scale will remain on the left edge of the groove G2.

In the third case shown in FIG. 14, groove G2 is the groove G at the position where the runout is the smallest among the multiple grooves G, and groove G3 is the groove G at the position where the runout is the largest among the multiple grooves G. In other words, groove G2 is a groove G that does not exist at the minimum runout point but exists in the second region Rmin, and groove G3 is a groove G that does not exist at the maximum runout point but exists in the first region Rmax. In this case, if groove G1 is the first grinding groove, the machining allowance of the left edge portion of groove G3 is -0.02 mm.

On the other hand, when groove G2 is the first grinding groove, the removal allowance of the right edge portion of groove G1 is -0.0006 mm, and when groove G3 is the first grinding groove, the removal allowance of the right edge portion of groove G1 is -0.0001 mm, which is very small. As a result, when groove G2 or groove G3 is the first grinding groove, the remaining black scale can be ignored or falls within a range that can be removed by adjusting the grinding process.

From the above, it can be seen that by using a groove G that exists 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 the case where a groove G that does not exist in either the first region Rmax or the second region Rmin is used as the first grinding groove.

Next, we will explain the main effects of this embodiment.

(1) The groove grinding method according to this embodiment is a groove grinding method in which multiple grooves G provided at 120° intervals on the outer peripheral surface of the workpiece W are sequentially ground with a grinding wheel 23, and includes a runout identification process PC2 for identifying the region R on the outer periphery where the maximum or minimum runout point of the centered workpiece W exists, i.e., the first region Rmax or the second region Rmin, a first grinding process PC3 for grinding the first grinding groove by aligning the center Y1 of the first grinding groove with the center Y2 of the grinding wheel 23, and then a second grinding process PC4 for rotating the workpiece W by 120° intervals to grind each of the remaining grooves G.

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

(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 using the sensor 31 each time, 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 among the 2N locations. When N=3, the multiple grooves G are formed at 120° intervals. In addition, the workpiece W is rotated at 60° intervals, and the runout is measured at a total of six locations.

According to this method, it is possible to determine that the maximum or minimum point of the runout of the workpiece W over the entire circumference is within a certain angle range based on the maximum or minimum point of the 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 that can measure the runout of the workpiece W over the entire circumference, it is highly applicable in that it can be applied as long as there is a proximity sensor that can detect the presence or absence of a groove G. In addition, it is advantageous in terms of cost in that a less expensive proximity sensor can be used for the sensor 31 compared to a sensor that can measure the runout of the workpiece W over the entire circumference.

(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 for the workpiece W, and multiple regions R including the predetermined region are set at intervals of 180/N degrees, and the first region Rmax or the second region Rmin is identified based on the maximum or minimum point of the runout of the workpiece W among the 2N locations. When N=3, the multiple regions R are set at intervals of 60 degrees.

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

(4) The first grinding process PC3 includes determining the groove G present in the first region Rmax as the first grinding groove when any of the multiple grooves G exists in the first region Rmax, and determining the region R located on the opposite side of the first region Rmax from the workpiece center P1 as the second region Rmin and determining the groove G included in the second region Rmin as the first grinding groove when none of the multiple grooves G is included in the first region Rmax.

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 processing control.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

For example, the sensor 31 may be a sensor capable of measuring the runout of the workpiece W over the entire circumference. 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.

The maximum or minimum point of runout of the workpiece W among the 2N locations may be used to consider 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 considered as the position on the outer circumference where the maximum or minimum point of runout on the entire circumference of the workpiece W exists. In this case, too, if the measurement point of the runout of the workpiece W corresponds to each of the groove positions of the multiple grooves G, grinding can be performed with the groove G existing at the specified position as the first grinding groove.

10 First unit section 20 Second unit section 21 Rotating shaft 23 Grindstone 31 Sensor 50 Controller G Groove PC1 Centering process PC2 Runout identification process PC3 First grinding process PC4 Second grinding process R Region (plural regions)
Rmax First region (predetermined region, region where the maximum point of the shaft deflection exists)
Rmin Second region (predetermined region, region where the minimum point of the shaft deflection exists)
Y1 Center of the first grinding groove Y2 Center of the grindstone W Work (shaft)
100 Groove grinding device

Claims (6)

A groove grinding method for grinding a plurality of grooves provided at predetermined angular intervals on an outer peripheral surface of a shaft in sequence with a grindstone, comprising:
a control step of identifying a location 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 region among the plurality of grooves as a first grinding groove to be first ground, 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 the steps of:
Groove grinding method. 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 process for 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. 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, in which the region is set as a predetermined region, a plurality of regions including the predetermined region are set at intervals of 180/N degrees on the shaft, and the predetermined region is identified based on a maximum point or a 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 in which a maximum point of runout of the shaft exists, the groove existing in the first region is determined as the first grinding groove;
When 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 defined as a second region in which a minimum point of the runout of the shaft exists, and the groove existing in the second region is defined as the first grinding groove;
A groove grinding method comprising: a first unit portion that axially centers the shaft and rotates the shaft;
a second unit having a rotating shaft provided with a grindstone, and configured to grind a plurality of grooves provided at predetermined angular intervals on an outer circumferential surface of the shaft in sequence with the grindstone together with the first unit;
A sensor disposed on an 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 an outer circumference where a maximum point or a minimum point of the 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 region among the plurality of grooves as a first grinding groove to be ground first by aligning a center of the first grinding groove with a center of the grindstone by the second unit; and
Thereafter, the first unit rotates the shaft by the predetermined angular intervals to perform grinding on each of the remaining grooves among the plurality of grooves by the second unit;
grinding all of the plurality of grooves by processing control including
Groove grinding device. A program executable by a computer for a groove grinding device that uses a grindstone to grind a plurality of grooves provided at predetermined angular intervals on an outer circumferential 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 region among the plurality of grooves is ground as a first grinding groove to be ground first, 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 a grinding process 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 steps of:
program.

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