Superfinishing method and apparatus for gothic arc grooves

Abstract

To provide a method and device for superfinishing a specific area on the groove surface of a gothic arc groove. [Solution] A method for superfinishing a gothic arc groove involves tilting the oscillation axis Sa of the grinding wheel St with respect to the longitudinal direction of the gothic arc groove, and changing the distance between the oscillation axis and the gothic arc groove during the superfinishing process while also changing the degree of inclination of the oscillation axis with respect to the longitudinal direction of the gothic arc groove. Another method for superfinishing a gothic arc groove involves aligning the oscillation axis of the grinding wheel with the longitudinal direction of the gothic arc groove, and changing the degree of inclination of the grinding wheel with respect to the vertical at an intermediate position of its oscillation and the distance between the oscillation axis and the gothic arc groove during the superfinishing process.

Description

[Technical Field]

[0001] The present invention relates to a technique for superfinishing the thread grooves of ball screws and bearings having gothic arc grooves. [Background technology]

[0002] A ball screw is a mechanical element that converts rotational motion into linear motion, and is used in a wide range of fields, including industrial equipment such as semiconductor manufacturing equipment and machine tools, transportation equipment such as aerospace equipment and automobiles, as well as medical equipment and robots.

[0003] Ball screws are often used in combination with servo motors, and therefore require high operational accuracy. Ball screws are also required to make as little noise as possible, so it is preferable that the sliding surfaces of the screw shaft, nut, and balls that make up the ball screw are smooth.

[0004] Regarding the smoothing of the screw shaft, which is one of the components of a ball screw, a method has been proposed in which a grinding wheel that has been pre-formed by contact with the gothic arc groove of the screw shaft is oscillated around a specific oscillating axis relative to the cross-sectional shape of the gothic arc groove, thereby simultaneously superfinishing two curved surfaces (flanks) within the groove (Patent Document 1).

[0005] In superfinishing the Gothic arc groove of a screw shaft, a method has also been proposed in which each half of the grinding wheel in the spanning width direction is brought into contact with a different flank, and the inclination angle and position of the oscillating axis are set so that the grinding wheel oscillating within the groove and the Gothic arc groove form a continuous contact machining line (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-145410 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-159641 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, the screw grooves of the screw shaft and the nut of a ball screw are required to have smooth surfaces over the entirety. In particular, in a ball screw having a gothic arc groove, it is important that the screw groove surface that comes into point contact with the ball is smooth in order to ensure smooth operation of the ball screw and increase durability.

[0008] The superfinishing method for gothic arc grooves described in Patent Document 1, for example, in superfinishing the raceway groove of an inner ring for a ball bearing having a gothic arc groove, equalizes the machining accuracy of both flanks of the gothic arc groove by keeping the distance (center height) between the bottom of the gothic arc groove and the swing center of the grinding wheel within a specific range, thereby achieving low costs and high accuracy.

[0009] Furthermore, the superfinishing method for gothic arc grooves described in Patent Document 2 tilts the oscillation axis of the grinding wheel relative to the longitudinal direction of the gothic arc groove, and sets the inclination angle of the oscillation axis of the grinding wheel and the distance from the oscillation center of the grinding wheel to the bottom of the gothic arc groove so that the contact point between the gothic arc groove and the grinding wheel forms a continuous line from the groove shoulder to the groove bottom or near the groove bottom. As a result, the superfinishing method for gothic arc grooves described in Patent Document 2 aims to achieve high precision in the cross-sectional shape of the groove and low costs.

[0010] In a ball screw, for example, a gothic arc groove and a spherical ball make point contact, and the thread groove surface that makes point contact with the ball is specified by the angle of the line connecting the contact point between the ball and the thread groove and the center of the ball (hereinafter referred to as the "contact angle"). Generally, a contact angle of 45 degrees is considered appropriate. However, ball screw manufacturers may adopt contact angles smaller or larger than 45 degrees in order to optimize the axial clearance between the thread groove and the ball, for example.

[0011] Therefore, it is important for the inherent function of the ball screw that the entire groove surface of the gothic arc groove is smooth, and that the degree of superfinishing of the groove surface in a specific range, particularly in the vicinity of the contact angle, is improved.

[0012] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method and apparatus for superfinishing a specific area on the groove surface of a gothic arc groove. [Means for solving the problem]

[0013] The method for superfinishing gothic arc grooves according to the present invention changes the distance between the oscillation axis of the oscillating grinding wheel and the gothic arc grooves during the superfinishing process.

[0014] Another method for superfinishing a gothic arc groove according to the present invention involves tilting the oscillation axis of the grinding wheel relative to the longitudinal direction of the gothic arc groove, and during the superfinishing process, changing the distance between the oscillation axis and the gothic arc groove and also changing the degree of inclination of the oscillation axis relative to the longitudinal direction of the gothic arc groove.

[0015] Another method for superfinishing gothic arc grooves according to the present invention aligns the oscillation axis of the grinding stone with the longitudinal direction of the gothic arc groove, and changes the degree of inclination of the grinding stone from the vertical at intermediate positions of its oscillation during the superfinishing process.

[0016] Here, "intermediate position of the grinding wheel's oscillation" refers to the position of the grinding wheel at 0° when the grinding wheel rotates forward and backward around the oscillation axis, for example, by ±5°. "Inclination from the vertical direction" refers to the degree of inclination of the grinding wheel relative to the position of the grinding wheel when viewed from the direction of its oscillation axis (the longitudinal direction of the Gothic arc groove), with the grinding wheel standing upright (with the grinding surface of the grinding wheel facing downward). Also, "intermediate position of the grinding wheel's oscillation" refers to the position of the grinding wheel at 0°, which is the middle position, if the range of forward and backward oscillation of the grinding wheel is ±5°, for example.

[0017] Preferably, the distance between the oscillation axis and the gothic arc groove is changed simultaneously with the change in the degree of inclination of the grindstone with respect to the vertical direction at the middle of the oscillation range.

[0018] More preferably, the position of the oscillation shaft in the width direction of the Gothic arc groove is changed at the same time as the change in the distance between the oscillation shaft and the Gothic arc groove.

[0019] The grinding wheel holding device used for superfinishing Gothic arc grooves according to the present invention comprises a stone head for holding the grinding wheel, a swinging device for swinging the stone head around a swinging axis, a vertical movement device for moving the swinging device in the vertical direction, a front-to-back movement device for moving the stone head parallel to the swinging axis, a rotating device for rotating the stone head around a vertical rotation axis, a lateral movement device for moving the stone head in a direction perpendicular to both the vertical direction and the swinging axis, and a control device for controlling the operation of the swinging device, the up-to-down movement device, the front-to-back movement device, the swinging device, and the lateral movement device.

[0020] The rocking device can arbitrarily change the intermediate angle of rocking of the stone head around the rocking axis by means of a control device.

[0021] The stone head is configured so that the up-and-down moving device can move the swinging device upward without moving the grindstone upward.

[0022] The stone head in the grindstone holding device has a support part that moves upward together with the swinging device, and a movable part that can move up and down relative to the support part. The grindstone is held by the movable part.

[0023] The movable part of the stone head has a grinding stone holder with a holding hole that holds the grinding stone by passing it vertically through it, and a grinding stone holder that prevents the grinding stone from falling out of the holding hole. The control device cancels the grinding stone holder's function of preventing the grinding stone from falling out when the up-down moving device moves the swinging device upward. [Effects of the Invention]

[0024] According to the present invention, a method and apparatus for targeting and superfinishing a specific area on the groove surface of a gothic arc groove can be provided. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a plan view of the grindstone holding device. [Figure 2] FIG. 2 is a partial front cross-sectional view of the grindstone holding device. [Figure 3] FIG. 3 is a partial cross-sectional view of the right side of the grindstone holding device, focusing on the rotating unit and the forward / backward moving unit. [Figure 4] FIG. 4 is a partial cross-sectional view of the right side of the grindstone holding device, focusing on the vertical movement unit. [Figure 5] FIG. 5 is a partial cross-sectional view of the right side of the grindstone holding device, focusing on the swing unit. [Figure 6] FIG. 6 is a plan view of the stone head. [Figure 7] Figure 7 is a left side view of the stone head and its surroundings. [Figure 8] FIG. 8 is a left side cross-sectional view of the stone head. [Figure 9] FIG. 9 shows the movement of the grinding stone when superfinishing the inner ring of a ball bearing. [Figure 10] FIG. 10 shows the movement of the grinding stone when superfinishing the inner ring of a ball bearing. [Figure 11] FIG. 11 shows the movement of the grinding stone when superfinishing the inner ring of a ball bearing. [Figure 12] FIG. 12 shows the movement of the grinding stone when superfinishing the inner ring of a ball bearing. [Figure 13] FIG. 13 shows the movement of the grinding stone when superfinishing the inner ring of a ball bearing. [Figure 14] FIG. 14 shows the movement of the grinding stone when superfinishing the outer ring of a ball bearing. [Figure 15] FIG. 15 shows the movement of the grinding stone when superfinishing the outer ring of a ball bearing. DETAILED DESCRIPTION OF THE INVENTION

[0026] Figure 1 is a plan view of the grinding wheel holding device 1, Figure 2 is a partial cross-sectional front view of the grinding wheel holding device 1, Figure 3 is a partial cross-sectional right side view of the grinding wheel holding device 1 focusing on the rotating unit 3 and the forward / backward movement unit 4, Figure 4 is a partial cross-sectional right side view of the grinding wheel holding device 1 focusing on the up / down movement unit 5, and Figure 5 is a partial cross-sectional right side view of the grinding wheel holding device 1 focusing on the swinging unit 6.

[0027] The grindstone holding device 1 is a device that holds a grindstone for superfinishing the groove surface of the screw shaft of a ball screw, moves it to an appropriate position, and oscillates it at high speed.

[0028] The grinding wheel holding device 1 includes a base 11, a lateral movement unit 2, a rotation unit 3, a front-to-back movement unit 4, a vertical movement unit 5, a swing unit 6, and a control device. The base 11 is shaped like a rectangular plate overall. The base 11 supports the swing unit 3, the front-to-back movement unit 4, the vertical movement unit 5, and the swing unit 6 on it via the lateral movement unit 2.

[0029] Here, the "... unit" in the lateral movement unit 2, rotation unit 3, forward / backward movement unit 4, up / down movement unit 5, and swing unit 6 is a collective term for, for example, the device for lateral movement (lateral movement device 13) and the part (lateral movement body 12) that moves laterally directly due to this device acting on it, in the case of the lateral movement unit 2.

[0030] It should be noted that the "lateral direction" refers to the left-right direction in FIG. 1, and the "front-rear direction" and "front-rear" refer to the up-down direction and up-down direction in FIG. 1, respectively.

[0031] The lateral movement unit 2 consists of a lateral movement body 12 and a lateral movement device 13. The lateral movement body 12 is a rectangular plate-shaped part that is approximately the same size as the base 11 in a plan view. A rotation unit 3, a front-back movement unit 4, a vertical movement unit 5, and a swing unit 6 are provided on the lateral movement body 12, and these move together with the lateral movement body 12.

[0032] Here, the "... body" in the lateral moving body 12 refers to the part excluding other "... units" (excluding the lateral moving unit 2) from the whole whose position or posture is changed by the lateral moving device 13. That is, in the grinding wheel holding device 1, the lateral moving device 13 moves the turning unit 3, the front-back moving unit 4, the up-down moving unit 5, and the swinging unit 6 in the lateral direction, and the lateral moving body 12 is the part excluding these "... units" from the whole part that is moved laterally by the lateral moving device 13.

[0033] This concept also applies to the "rotating body 28," "front-rear moving body 36," "up-down moving body 49," and "swinging body 62," which will be described later.

[0034] The lateral movement device 13 is composed of four linear guides 14, 14, 14, 14, a ball screw 15, and a lateral movement motor 16. The four rails 21, 21 of the linear guides 14, 14 are fixed to the base 11 in parallel and spaced apart in the lateral direction in FIG. 1. Each of the linear guides 14, 14, 14, 14 has two blocks 24, 24, and all of the blocks 24, 24 are integrated with the lateral movement body 12.

[0035] The ball screw 15 is disposed midway between the rails 21, . . . , 21 so that its screw shaft 22 is parallel to the rails 21, . . . , 21 and divides them into two halves. A bearing 25 of the screw shaft 22 is fixed to the base 11. A nut 23 of the ball screw 15 is integrated with the lateral mover 12.

[0036] The lateral movement motor 16 is fixed to the base 11, and its rotation shaft is connected to the screw shaft 22 of the ball screw 15. In the lateral movement device 13, the nut 23 moves laterally due to the rotation of the lateral movement motor 16 (rotation of the screw shaft). As a result, the lateral movement body 12 connected to the nut 23 also moves laterally together with the blocks 24, 24. The lateral movement motor 16 moves the lateral movement body 12 in the lateral direction. A servo motor is used as the lateral movement motor 16.

[0037] The rotation unit 3 includes a rotation table 27, a rotation body 28, an arc rack 29, a rotation motor 30, a reducer, and a pinion.

[0038] The rotating base 27 is fixed onto the horizontal moving body 12 and has a thick, fan-like shape overall, covering most of the base 11 and overlapping it. The rotating body 28 is rotatably connected to the rotating base 27 by a rotation shaft 32 provided on the rotating base 27 at a part corresponding to the pivot of the fan shape. The rotating body 28 holds the forward / backward moving unit 4, the vertical moving unit 5, and the swinging unit 6 thereon.

[0039] Arc rack 29 is fixed to the part of rotating table 27 that corresponds to the "top" of the fan-shaped part. Rotating motor 30 is fixed to rotating body 28, and its rotation is transmitted to arc rack 29 via a reducer and pinion, causing rotating body 28 to rotate relative to rotating table 27. Arc rack 29, rotating motor 30, reducer, and pinion form a rotating device that rotates rotating body 28 relative to rotating table 27. A servo motor is used as rotating motor 30.

[0040] The front-rear movement unit 4 is made up of a front-rear movement device 35 and a front-rear movement body 36. The front-rear movement device 35 has a front-rear movement motor 37, a ball screw 38, and two linear guides 39, 39. The front-rear movement motor 37 has a body (frame) fixed to the rotating body 28, and a shaft connected to a screw shaft 40 of the ball screw 38. A nut 41 of the ball screw 38 is fixed to the front-rear movement body 36. The front-rear movement motor 37 is a servo motor.

[0041] The linear guides 39 have rails 42 fixed to the rotating body 28, and blocks 43 fixed to the front-rear moving body 36. In the front-rear moving unit 4, the nut 41 moves back and forth in response to forward and reverse rotation of the front-rear moving motor 37, causing the front-rear moving body 36 fixed to the nut 41 to move back and forth. The front-rear moving body 36 holds the up-down moving unit 5 and the swinging unit 6.

[0042] The vertical movement unit 5 is made up of a vertical movement device 48 and a vertical moving body 49. The vertical movement device 48 has a vertical movement motor 50, a ball screw 51, and two linear guides 52, 52. The vertical movement motor 50 has a main body (frame) fixed to the front-rear moving body 36, and its shaft is connected to a screw shaft 53 of the ball screw 51. A nut 54 of the ball screw 51 is fixed to the vertical moving body 49. A servo motor is used for the vertical movement motor 50.

[0043] The linear guides 52 have rails 55 fixed to the front-rear moving body 36, and blocks 56 fixed to the vertical moving body 49. In the vertical movement unit 5, the nut 54 moves up and down reciprocally as the vertical movement motor 50 rotates forward and backward, causing the vertical moving body 49 fixed to the nut 54 to move reciprocally. The vertical moving body 49 holds the swing unit 6.

[0044] The oscillating unit 6 is composed of an oscillating device 61 and an oscillating body 62. The oscillating device 61 is a servo motor, and its main body (frame) is fixed to the vertical moving body 49. The oscillating body 62 is composed of a connecting shaft 63 and a stone head 7. The connecting shaft 63 is a substantially round bar, and one end of the connecting shaft 63 is connected to the shaft of the servo motor. The connecting shaft 63 connects the stone head 7 and the servo motor so that the stone head 7 can oscillate.

[0045] The oscillating device 61 rotates (oscillates) the stone head 7 equipped with the grinding stone St in forward and reverse directions at high speed around the oscillation axis Sa. The range of rotation is ± several degrees. Note that the "oscillating body 62" refers to the part that is oscillated by the oscillating device 61, and non-oscillating parts such as the bearings of the connecting shaft 63 are considered to be part of the "vertical moving body 49."

[0046] 6 is a plan view of the stone head 7, FIG. 7 is a left side view of the stone head 7 and its surroundings, and FIG. 8 is a left side cross-sectional view of the stone head 7. As shown in FIG.

[0047] The stone head 7 is composed of a support part 66 and a movable part 67. The support part 66 is equipped with a double-acting air cylinder 68. A rod 69 of the air cylinder 68 protrudes from the lower rod cover and is connected at its tip to the movable part 67. The support part 66 is integrated with the connecting shaft 63 of the swing unit 6.

[0048] The movable part 67 is made up of a base 70, a biasing member 71, a clamp 72, and a grindstone holder 73. The base 70 is connected to the support part 66 by two cross roller guides 74, 74 so as to be movable in the same direction as the movement direction of the rod 69. The base 70 is connected below it to the tip of the rod 69, and moves up and down as the rod 69 moves up and down.

[0049] A compression coil spring is used as the biasing member 71. The biasing member 71 is disposed on the base 70 so as to bias the rod 69 in a direction perpendicular to the moving direction of the rod 69 (=approximately horizontal).

[0050] Clamp 72 is formed into a rectangular shape from a plate material. Clamp 72 is attached to base 70 at approximately the middle between the top and bottom of its longitudinal direction by a clamp shaft 75 that is perpendicular to both the moving direction of rod 69 and the biasing direction of biasing member 71. The width direction of clamp 72 is perpendicular to clamp shaft 75.

[0051] The lower portion of the clamp 72 contacts one end of the biasing member 71 in the biasing direction. The clamp 72 has a pressing portion 76 that can press the grindstone holding portion 73 on the substantially opposite side in the width direction from the portion that contacts the biasing member 71. The biasing member 71, clamp shaft 75, and pressing portion 76 are arranged in this order in the front-to-rear direction (the horizontal direction in FIG. 8).

[0052] The grindstone holding portion 73 has a holding hole 80, a first clamping member 81, and a second clamping member 82. The holding hole 80 is located on the opposite side of the clamp 72 from the biasing member 71, and has a rectangular opening that penetrates vertically in side view (FIGS. 7 and 8). A portion of the holding hole 80 on the clamp 72 side is open to the outside. The pressing portion 76 of the clamp 72 can enter this portion of the holding hole 80 that is open to the outside.

[0053] The first clamping member 81 and the second clamping member 82 are "L" shaped in plan view (FIG. 6), and when combined together form a rectangular hole, they are fitted into the holding hole 80. The grinding stone St is inserted parallel to the rod 69 with its grinding surface facing downward and passes through this rectangular hole.

[0054] In the stone head 7, the movable part 67 moves back and forth relative to the support part 66 as the air cylinder 68 extends and contracts (see the two-dot chain line in Figure 8). In the stone head 7, the clamp 72 biased by the biasing member 71 swings around the clamp shaft 75, and the pressing part 76 presses the first clamping member, thereby preventing the grinding wheel St from falling from the grinding wheel holding part 73. The stone head 7 swings at high speed by the forward and reverse rotation of the swinging device 81 (servo motor).

[0055] The grindstone holding device 1 also includes a grindstone clamp releasing device 85 and a grindstone holding device 86 .

[0056] The grinding wheel clamp release device 85 has an air cylinder that releases the clamping of the grinding wheel St in the grinding wheel holding part 73. When the rod of the air cylinder is extended, an unclamping part 87 fixed to the tip of the rod presses one end of the clamp 72 toward the grinding wheel St. "One end of the clamp 72" refers to the end opposite the pressing part 76 across the clamp shaft 75. This releases the pressing part 76 of the clamp 72 from pressing against the first clamping member 81, allowing the grinding wheel St to move relative to the grinding wheel holding part 73.

[0057] The grinding wheel holding device 86 is a device that prevents the grinding wheel St from rising together with the movable part 67 when the movable part 67 rises in a state where the clamp has been released by the grinding wheel clamp release device 85. When the grinding wheel holding device 1 is operating (super finishing), the grinding wheel holding device 86 moves upward and away from the upper end of the grinding wheel St.

[0058] The control device has a microcomputer, a memory device, an interface for input and output, etc., and controls the operation of the lateral movement unit 2, the rotation unit 3, the front-back movement unit 4, the up-down movement unit 5, and the swinging unit 6 in the grinding wheel holding device 1 when, for example, superfinishing the groove surface of the screw shaft of a ball screw.

[0059] Next, we will explain how to superfinish a gothic arc groove using the grinding wheel holding device 1. For ease of explanation, we will use the inner and outer rings of a ball bearing as an example of the workpiece to be superfinished. There is no difference in the operation of the grinding wheel St when superfinishing the thread grooves of the screw shaft and nut of a ball screw compared to when superfinishing the grooves of the inner and outer rings of a ball bearing.

[0060] 9 to 13 are diagrams showing the movement of the grinding wheel St when the inner ring BIR of a ball bearing is superfinished by the grinding wheel holding device 1. Figures 9 to 11 explain superfinishing in which the oscillation axis of the grinding wheel St is aligned with the direction in which the grooves of the inner ring BIR extend (hereinafter referred to as the "longitudinal direction of the grooves").

[0061] Figure 9 shows the superfinishing of the area near the bottom of the groove surface Bg of the inner ring BIR (hereinafter referred to as the "groove bottom"), with the grinding wheel St oscillating at a high speed of, for example, ±5°. Once the superfinishing of the groove bottom (Figures 9(b)-(c)) is complete, the control device operates the up-and-down movement unit 5 to move the oscillating unit 6 upward. As the oscillating unit 6 moves upward, the oscillating axis Sa also moves upward (H2-H1). At this time, the support part 66 of the stone head 7 also moves upward. However, the air cylinder 68 (by extending the piston) prevents the grinding wheel holder 73 from moving upward, so the grinding surface of the grinding wheel St remains in contact with the groove surface Bg of the inner ring BIR.

[0062] As the oscillating unit 6 moves upward, i.e., upward on the oscillating axis Sa, the control device changes the intermediate position of the oscillating device 61 during oscillation—for example, the position when the grinding wheel is oscillated at 0°, which is the middle of a ±5° range—from 0° to 20° relative to the vertical. Fig. 10 shows the state immediately after this change in oscillating position. When the position of the grinding wheel St at the intermediate position of oscillation is tilted by 20°, only the end Sp in its width direction (the horizontal direction in Fig. 9) comes into contact with the groove surface Bg, and until the grinding surface of the grinding wheel St settles into this position, the end Sp will superfinish a specific area of ​​the groove surface Bg that is higher than the groove bottom.

[0063] Figure 9(e) shows the movement of the grinding wheel St when the oscillation axis Sa is moved upward by "H3-H1" from Figure 9(b)-(c). Comparing Figure 9(e) with Figure 10(b), it is clear that tilting the attitude of the grinding wheel St at the midpoint of the oscillation of the oscillating device 61 relative to the vertical is more effective for superfinishing a specific range of the groove surface Bg higher than the groove bottom, rather than moving the oscillation axis Sa (grinding wheel St) upward.

[0064] 9 and H2 in FIG. 10 respectively indicate the distance from the outer periphery of the inner ring BIR to the oscillation axis Sa, and the oscillation axis Sa in FIG. 10 is higher than the oscillation axis Sa in FIG. 9 by "H2-H1".

[0065] Figure 11 shows the state immediately after the position of the oscillation axis Sa shown in Figure 9 has been changed to the height shown in Figure 10 and the grinding wheel St has simultaneously been moved a distance W1 in one direction in the width direction. The movement of the grinding wheel St in one direction in the width direction is performed by the control device controlling the operation of the lateral movement device 13. In Figure 11, the oscillation of the grinding wheel St has also been changed to a range of ±5°, with an inclination of 20° as the intermediate position of the oscillation. By moving the oscillation axis Sa of the grinding wheel St upward and further offsetting it to one side in the width direction from the center Mc of the groove of the inner ring BIR, it is possible to superfinish a specific range of the groove surface Bg, which is higher from the groove bottom, by using its end Sp until the grinding surface adjusts to this position.

[0066] 12 and 13 show superfinishing performed with the oscillation axis Sa of the grinding wheel St inclined at 5° and 10°, respectively, relative to the longitudinal direction of the groove of the inner ring BIR. In addition, in Fig. 13, the processing is performed with the oscillation axis Sa of the grinding wheel St at a higher position (farther away from the groove bottom) than in Fig. 12. The inclination of the oscillation axis Sa relative to the direction perpendicular to the axis of the inner ring BIR is performed by the control device controlling the operation of the rotary motor 30.

[0067] 12 and 13, both widthwise flanks of the groove surface Bg of the inner ring BIR can be superfinished simultaneously. In the case of Figure 12, where the inclination of the oscillation axis Sa is small, superfinishing is performed near the groove bottom, while in the case of Figure 13, where the inclination of the oscillation axis Sa is large and its position is high, superfinishing is performed on the groove surface Bg further away from the groove bottom.

[0068] The grinding stone St used in superfinishing is one that wears easily and conforms to the shape of the surface to be polished. Therefore, the polishing surface of the grinding stone St retreats during the superfinishing process, but the air cylinder 68 of the stone head 7 extends its piston, moving the grinding stone St downward by the amount of retreat, allowing the superfinishing to continue.

[0069] 9 to 13 show the groove surface Bg of the inner ring BIR of a ball bearing as an example, but the groove surface of the threaded shaft of a ball screw can also be superfinished in a similar manner. That is, the range of the groove surface desired to be superfinished can be selected by changing the height of the oscillation axis Sa of the grinding wheel St from the groove bottom and the distance between the groove center and the oscillation axis Sa in the groove width direction, as well as by changing the degree of inclination of the oscillation axis Sa with respect to the longitudinal direction of the thread groove and the height of the inclined oscillation axis Sa from the groove bottom.

[0070] 10, 11 and 13, the symbol Bc indicates the center of the ball.

[0071] However, once the grinding wheel St has finished superfinishing the groove surfaces Bg of the inner rings BIR of multiple ball bearings or the groove surfaces of the threaded shafts of ball screws, its grinding surface recedes, making superfinishing difficult. Therefore, after superfinishing a certain number of inner rings BIR or threaded shafts has been completed, or before the next superfinishing is started, the control device moves only the grinding wheel St downward relative to the movable part 67 by the amount by which its grinding surface has receded.

[0072] To move only the grinding wheel St downward relative to the movable part 67, for example, the grinding wheel St is brought into contact with the inner ring BIR or the groove surface of the screw shaft, and the grinding wheel clamp release device 85 is operated to allow the grinding wheel St to move relative to the grinding wheel holding part 73. Then, the double-acting air cylinder 68 is contracted to lift the movable part 67. At this time, the end of the grinding wheel St opposite to the grinding surface comes into contact with the grinding wheel presser device 86, preventing it from moving upward.

[0073] When the upward movement of the movable part 67 stops, the operating pressure of the air cylinder of the grindstone holder 73 is reduced, and the grindstone St is again clamped to the grindstone holder 73. Finally, the air cylinder 68 is extended to bring the grinding surface of the grindstone St into contact with the groove surface of the inner ring BIR or the screw shaft, thereby making the next superfinishing possible.

[0074] The movement of the grindstone St relative to these grindstone holders 73 is controlled by the control device.

[0075] 14 and 15 are diagrams showing the movement of the grindstone St when the outer ring BOR of the ball bearing is superfinished by the grindstone holding device 1.

[0076] Figure 14 shows the case where superfinishing is performed with the oscillation axis Sa of the grinding wheel St aligned with the longitudinal direction of the groove in the outer ring BOR. In Figure 14, (a) to (c) show the state when superfinishing the groove surface Bg near the groove bottom at the start of superfinishing, (d) to (f) show the state of superfinishing after the oscillation axis Sa is subsequently moved upward, (g) to (i) show the state of superfinishing after the oscillation axis Sa is further moved a distance W2 to one side in the width direction of the grinding wheel St, and (j) to (l) show the state of superfinishing after superfinishing with the grinding wheel St in the vertical position during oscillation midway ((a) to (c)) at the start of superfinishing, and then tilting the position of the grinding wheel St midway through its oscillation by 25° and oscillating it by ±5°.

[0077] Comparing (a)-(c) with (d)-(f), when the oscillation axis Sa is moved upward by "H2b-H1b" and away from the groove surface Bg, the oscillation radius of the grinding surface of the grinding wheel St increases, and the groove surface Bg away from the groove bottom (at a higher position) is superfinished.

[0078] Furthermore, by moving the oscillating axis Sa by a distance W2 in one direction in the width direction of the grinding wheel St as shown in (g) to (i), the groove surface Bg further away from the groove bottom (at a higher position) can be superfinished (for example, compare (d) and (g)).

[0079] In addition to these, by changing the intermediate tilt angle (relative to the vertical) during oscillation of the grinding wheel St from 0° to 25° ((j) to (l)), it is possible to superfinish a specific range of the groove surface Bg that is farther from the groove bottom (at a higher position) (for example, compare (a) and (j)).

[0080] Furthermore, if the intermediate tilt angle during oscillation of the grinding wheel St is inclined relative to the vertical and the oscillation axis Sa is moved to one side of the width direction of the grinding wheel St, the synergistic effect of (g) to (i) and (j) to (l) makes it possible to super-finish the groove surface Bg that is further away from the groove bottom (at a higher position) than with only (j) to (l).

[0081] Figure 15 shows the case where superfinishing is performed with the oscillation axis Sa of the grinding wheel St inclined relative to the longitudinal direction of the groove in the outer ring BOR. In Figure 15, (a) to (c) show the state when the groove surface Bg near the groove bottom is superfinished with the inclination of the oscillation axis Sa at 5° at the start of superfinishing, (d) to (f) show the state when the inclination of the oscillation axis Sa is subsequently maintained at 5° and the oscillation axis Sa is moved upward by "H2c-H1c" to perform superfinishing, and (g) to (i) show the state when superfinishing is performed with the inclination of the oscillation axis Sa further changed to 10° relative to the longitudinal direction of the groove.

[0082] Even when the oscillation axis Sa of the grinding wheel St is inclined relative to the longitudinal direction of the groove, moving the oscillation axis Sa upward increases the oscillation radius of the grinding surface of the grinding wheel St, changing the superfinishing range on the groove surface Bg. Furthermore, if the inclination of the oscillation axis Sa relative to the longitudinal direction of the groove is further increased, the superfinishing range on the groove surface Bg changes to a range farther away from the groove bottom.

[0083] When superfinishing the groove surfaces of the outer ring BOR of the ball bearing and the nut of the ball screw, the stone head 7 of the grindstone holding device 1 is replaced with a stone head suitable for a short grindstone St, rather than the one shown in Figures 6 to 8. The stone head that holds this short grindstone St has a support part and a movable part that are basically the same in structure and operation as the support part 66 and movable part 67 of the stone head 7.

[0084] The superfinishing of the groove surfaces of the inner ring BIR and outer ring BOR of the ball bearing, which is explained in Figures 14 and 15, is basically the same as the superfinishing of the groove surfaces of the screw shaft and nut of a ball screw.

[0085] When the inner ring BIR and outer ring BOR of the ball bearing, the screw shaft of the ball screw, and the nut are superfinished using the grinding wheel holding device 1, the vertical and horizontal movement of the oscillating axis Sa, the degree (angle) at which the intermediate position of the oscillating range of the grinding wheel St is tilted from the vertical, and the oscillating range (±5° is exemplified above) are determined by the control device based on artificial prior settings.

[0086] In superfinishing the groove surfaces of the inner ring BIR of a ball bearing and the screw shaft of a ball screw, and in superfinishing the groove surfaces of the outer ring BOR of a ball bearing and the nut of a ball screw, the order of changing the position of the oscillation axis Sa of the grinding wheel St and the attitude at the intermediate position when the grinding wheel St is oscillating (the inclination angle of the intermediate position relative to the vertical direction) is not limited to the above-mentioned embodiment and can be changed taking into account the size of the groove surface Bg and the size of the grinding wheel St to be used.

[0087] Even when the oscillation axis Sa of the grinding wheel St is inclined relative to the longitudinal direction of the groove (Figures 12, 13, and 15), the degree of inclination of the oscillation axis Sa and its change (for example, from 5° to 10°) as well as the order of its vertical movement can be different from those in the above-described embodiments.

[0088] As described above, in superfinishing a Gothic arc groove, the desired range of the groove surface Bg can be superfinished by appropriately combining the vertical position of the oscillating axis Sa of the grinding wheel St, the degree of inclination of the posture of the oscillating grinding wheel St at the intermediate position, the distances W1 and W2 between the center Mc in the groove width direction and the oscillating axis Sa, and the degree of inclination and the vertical position of the oscillating axis Sa when the oscillating axis Sa is inclined relative to the longitudinal direction of the groove.

[0089] Additionally, the grindstone holding device 1 and each component or the overall structure, shape, dimensions, number, material, etc. of the grindstone holding device 1 can be modified as appropriate in accordance with the spirit of the present invention. [Industrial Applicability]

[0090] The present invention can be utilized for superfinishing the thread grooves of ball screws and bearings having gothic arc grooves. [Explanation of symbols]

[0091] 1 Grindstone holding device 7 Stonehead 13 Lateral movement device 30 Rotation motor (rotation device) 35 Back and forth movement device 48 Vertical movement device 61 Oscillating device 66 Support part 67 Moving parts 73 Grindstone holder 80 Retention hole 86 Grindstone holder Sa Oscillation axis St grinding stone

Claims

1. In super-finishing Gothic arc grooves, During the superfinishing process, the distance between the swing axis of the swinging grindstone and the gothic arc groove is changed. A method for superfinishing Gothic arc grooves.

2. In super-finishing Gothic arc grooves, The oscillation axis of the grinding wheel is inclined with respect to the longitudinal direction of the gothic arc groove; During the superfinishing process, the distance between the oscillation shaft and the gothic arc groove is changed, and at the same time, the degree of inclination of the oscillation shaft with respect to the longitudinal direction of the gothic arc groove is changed. A method for superfinishing Gothic arc grooves.

3. In super-finishing Gothic arc grooves, The oscillation axis of the grinding wheel is aligned with the longitudinal direction of the gothic arc groove, During the superfinishing process, the degree of inclination of the grindstone with respect to the vertical direction in the intermediate position of the swing is changed. A method for superfinishing Gothic arc grooves.

4. The distance between the swing shaft and the gothic arc groove is changed simultaneously with the change in the degree of inclination of the grinding wheel with respect to the vertical direction at the middle of the swing range.

4. The method for superfinishing gothic arc grooves according to claim 3.

5. The distance between the oscillation shaft and the gothic arc groove is changed, and at the same time, the position of the oscillation shaft in the width direction of the gothic arc groove is changed.

4. The method for superfinishing gothic arc grooves according to claim 3.

6. A grindstone holding device used for superfinishing gothic arc grooves, comprising: A stone head that holds the grindstone; a swinging device that swings the stone head around a swing axis; a vertical movement device that moves the rocking device in a vertical direction; a forward / backward moving device that moves the stone head parallel to the swing axis; a rotating device that rotates the stone head around a vertical rotation axis; a lateral movement device that moves the stone head in a direction perpendicular to both the vertical direction and the swing axis; a control device that controls the operations of the swinging device, the vertical movement device, the front-rear movement device, the rotation device, and the horizontal movement device; and The stone head is configured so that the vertical movement device can move the swing device upward without moving the grinding stone upward. A grindstone holding device characterized by:

7. The rocking device is The control device is configured to be able to arbitrarily change an intermediate angle of the rocking of the stone head around the rocking axis.

7. The grindstone holding device according to claim 6.

8. The stone head is a support part that moves upward together with the rocking device; a movable part that is movable up and down relative to the support part; and The grindstone is held by the movable part.

7. The grindstone holding device according to claim 6.

9. The movable part is a grindstone holder having a holding hole that passes through the grindstone in the vertical direction and holds the grindstone; a grindstone holder that prevents the grindstone from falling out of the holding hole; and The control device When the vertical movement device moves the swing device upward, the grindstone pressing device The function to prevent the grindstone from falling off is released.

9. The grindstone holding device according to claim 8.

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