Repair device and repair method of ball screw

Abstract

To provide a repair device and repair method of a ball screw which, when peeling of a surface origin type occurs in a screw shaft of the ball screw, smoothly and easily grinds the screw shaft up to a peeling progress depth to remove an abnormality of a surface shape, and makes the ball screw normally operate with a rolling element smoothly rolling on the screw shaft.SOLUTION: Provided is a repair device of a ball screw including: a screw shaft having an outer peripheral surface formed with a spiral groove; a nut having an inner peripheral surface formed with a spiral groove; and a plurality of rolling elements. The repair device includes: a processing part provided with a grinding stone for grinding the spiral groove of the screw shaft; and an attachment part to be detachably attached to the nut or a fixing member to which the nut is fixed. Rotation of the screw shaft or the nut causes the grinding stone to move along an axial direction of the screw shaft.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ball screw repair device and repair method. [Background technology]

[0002] When a ball screw is used at high speed or under high load for a long period of time, damage occurs on the surface of the spiral groove of the screw shaft and the spiral groove of the nut, resulting in surface-originating flaking. In a ball screw with this flaking, the movement of the balls, which are the rolling elements that roll between the spiral groove of the screw shaft and the spiral groove of the nut, is hindered, and excessive torque may be required for the relative movement between the screw shaft and the nut.

[0003] To address this problem, Patent Document 1 discloses a method of improving the surface hardness by shot peening the raceway surfaces of the screw shaft and the nut in order to suppress the occurrence of surface-originated flaking resulting from machining marks on the raceway surfaces on which the rolling elements roll.

[0004] Patent Document 2 discloses a ball screw device that suppresses surface-originated spalling and improves the durability of the entire ball screw device by increasing the nitrogen concentration on the surface through carbonitriding or nitriding, and by keeping the area ratio of Si-Mn nitrides and the amount of retained austenite on the surface of the thread groove of the screw shaft within threshold values. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7176349 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-204069 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the contact pressure between the balls and the screw shaft tends to be greater on the screw shaft than on the nut, which makes the screw shaft surface more susceptible to damage, and there is a need for repair techniques that can restore the spiral grooves of the screw shaft after damage.Patent Document 1 and Patent Document 2 are both intended to prevent the occurrence of surface-originated flaking in ball screws, and are different from the above-mentioned techniques.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide a ball screw repair device and repair method that, when surface-originating flaking occurs on the screw shaft of a ball screw, removes abnormalities in the surface shape by smoothly and easily grinding the screw shaft to the depth to which the flaking has progressed, thereby allowing the rolling elements to roll smoothly on the screw shaft and enabling the ball screw to operate normally. [Means for solving the problem]

[0008] The above object of the present invention can be achieved by the following configurations [1] and [2].

[0009] [1] A repair device for a ball screw comprising a screw shaft having a spiral groove formed on its outer peripheral surface, a nut having a spiral groove formed on its inner peripheral surface, and a plurality of rolling elements, a processing unit provided with a grinding wheel for grinding the spiral groove of the screw shaft; a mounting portion that is detachably attached to the nut or a fixing member to which the nut is fixed, The grinding wheel moves along the axial direction of the screw shaft by rotation of the screw shaft or the nut. Ball screw repair device. [2] An attachment process of attaching the ball screw repair device described in [1] to the nut or the fixing member; an adjusting step of arranging the grinding wheel along the spiral groove of the screw shaft; A repair process in which the spiral groove is ground along the screw shaft by moving the processing portion along the screw shaft by rotational driving of the screw shaft. How to repair a ball screw. [Effects of the Invention]

[0010] According to the ball screw repair device and repair method of the present invention, even if surface-originating spalling occurs on the screw shaft of a ball screw, the spalling can be removed and the ball screw can be repaired to a state where it operates normally, thereby significantly extending the life of the ball screw.In addition, since the screw shaft of a ball screw can be repaired without disassembling the ball screw, the repair work can be carried out smoothly and easily. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a front view showing a ball screw to which a repair device is attached. [Figure 2] FIG. 2 is a front view showing the repair device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited to the embodiments described below.

[0013] The repair device 50 of this embodiment will be described below with reference to the drawings. Fig. 1 is a front view showing a ball screw to which the repair device is attached. Fig. 2 is a front view showing the repair device. The repair device 50 is a device for repairing the screw shaft 10 of a ball screw 100, and is detachably attached to the ball screw 100.

[0014] The ball screw 100 is used in devices that require precise positioning, such as machine tools and robots. The ball screw 100 is installed on a stand or the like (not shown). The ball screw 100 comprises a screw shaft 10 having a spiral groove 12 formed on its outer peripheral surface, a nut 20 having a spiral groove (not shown) formed on its inner peripheral surface, a rolling element consisting of a plurality of balls (not shown), and a circulating part (not shown).

[0015] The screw shaft 10 is connected to a power source such as a drive motor to rotate, and the nut 20, which is threaded onto the screw shaft 10 via multiple rolling elements, reciprocates along a straight line. In other words, the ball screw 100 converts rotational motion into linear motion. A device including a fixed member 30 such as a slider or table is connected to the nut 20. In this embodiment, a repair device 50 that repairs the ball screw 100 is attached to the fixed member 30. However, the repair device 50 may also be attached to the nut 20.

[0016] The repair device 50 is attached to the ball screw 100 and moves relative to the nut 20 along the screw shaft 10 as the screw shaft 10 rotates, thereby removing surface-originating spalling (hereinafter simply referred to as spalling) that has occurred in the spiral groove 12 of the screw shaft 10. The repair device 50 has a processing unit 60 that grinds the spiral groove 12 of the screw shaft 10, an attachment unit 70 for detachably attaching the device including the fixing member 30, and a grinding wheel adjustment unit 80 that adjusts the position of the processing unit 60.

[0017] The processing section 60 has a disk-shaped grinding wheel 61, a rotating shaft 62 attached and fixed to the center of the grinding wheel 61, a bearing unit 63 that supports the rotating shaft 62, a grinding motor 64 that drives the rotating shaft 62, and a support plate 65 made of an iron plate or the like that supports the grinding motor 64 and the bearing unit 63 (rotating shaft 62).

[0018] The outer edge of the grindstone 61 has a curved surface whose cross-sectional shape follows the shape of the spiral groove 12 of the screw shaft 10. The outer edge of the grindstone 61 rotated by the grinding motor 64 comes into contact with the spiral groove 12 of the screw shaft 10.

[0019] A timing belt 68 for synchronizing rotation is provided between a drive pulley 66 provided on the output shaft 64a of the grinding motor 64 and a transmission pulley 67 provided on the rotary shaft 62. The processing section 60 may be configured such that the bearing unit 63, the pulleys 66, 67, and the timing belt 68 are omitted, and the grindstone 61 is attached to the output shaft 64a of the grinding motor 64.

[0020] The attachment portion 70 is attached and fixed to the nut 20 or the fixing member 30 (fixing member 30 in the illustrated example) to which the nut 20 is connected. The attachment portion 70 may be configured to be firmly attached and detached to the nut 20 or fixing member 30, and may be configured to be fixed to the nut 20 or fixing member 30 with a bolt, may be a clamp that holds the nut 20 or fixing member 30, or may be configured to be attracted by a strong magnet or the like.

[0021] The grindstone adjustment unit 80 is disposed below the support plate 65 of the processing unit 60 , and the support plate 65 is attached and fixed to the grindstone adjustment unit 80 . This grinding wheel adjustment unit 80 adjusts the support position of the support plate 65 so that the inclination angle of the disk-shaped grinding wheel 61, which is perpendicular to the rotation axis 62, is parallel to the spiral groove 12, which is inclined with respect to a plane (YZ plane) perpendicular to the extension direction (X direction) of the screw shaft 10, thereby matching the lead angle of the spiral groove 12. In this embodiment, the grinding wheel adjustment unit 80 includes a first adjustment unit 81 that tilts the processing unit 60 (support plate 65) relative to a plane perpendicular to the extension direction of the screw shaft 10, and a second adjustment unit 82 that moves the processing unit 60 (support plate 65) radially of the screw shaft 10 (the forward / backward direction of moving it toward or away from the spiral groove 12).

[0022] The first adjustment unit 81 is a goniostage that rotates (tilts) the support plate 65 around a first axis that is perpendicular to the direction of travel of the nut 20 on a plane perpendicular to the direction of travel of the nut 20, and adjusts the yaw angle of the grindstone 61 with respect to the direction of travel (X direction) of the grindstone 61 that accompanies the rotation of the screw shaft 10. In the example shown in Fig. 1, the first axis is an axis parallel to the Z direction. The first adjustment unit 81 has a rotary table 81A that is attached and fixed to the support plate 65 and has an arc-shaped convex curved surface that rotates (tilts) the support plate 65, a support table 81B that has a concave curved surface that conforms to the rotary table 81A, and a screw-shaped angle adjustment device 81C that rotates (tilts) the rotary table 81A relative to the support table 81B to adjust the yaw angle of the grinding wheel 61.

[0023] In addition, the first adjustment unit 81 in this embodiment is a so-called goniostage that tilts the support position of the grinding wheel 61, but it is not limited to the above-mentioned configuration as long as it is capable of adjusting the posture of the grinding wheel 61 along the spiral groove 12.

[0024] The second adjustment unit 82 is a device that supports the first adjustment unit 81 so that it can move radially (Z direction) of the screw shaft 10, thereby moving the grinding wheel 61 in an advancing / retreating direction to move it closer to or away from the spiral groove 12 of the screw shaft 10. The second adjustment unit 82 has a second adjustment table 82A whose one end is attached and fixed to the fixed member 30 via the attachment portion 70 and whose other end supports the first adjustment unit 81 (support table 81B) so that it can move in the forward and backward directions, and an advance / retract adjustment tool 82B that adjusts the position of the first adjustment unit 81 (processing unit 60) in the forward and backward directions.

[0025] Next, a method for repairing the ball screw 100 using the repair device 50 will be described. The method for repairing the ball screw 100 using the repair device 50 includes an installation step, an adjustment step, a repair step, and a removal step.

[0026] In the mounting step, the mounting portion 70 is attached to the nut 20, the nut housing, or the fixing member 30, thereby detachably mounting the repair device 50 to the ball screw 100. As a result, by rotating the screw shaft 10 of the ball screw 100, the repair device 50 moves along the screw shaft 10 together with the nut 20.

[0027] In the adjustment step, the attitude of the grindstone 61 is adjusted so that the grindstone 61 is aligned with the portion of the spiral groove 12 of the screw shaft 10 to be repaired. Specifically, first, the yaw angle of the disk-shaped grindstone 61 is adjusted using the first adjustment unit 81 of the grindstone adjustment unit 80, thereby making the disk-shaped grindstone 61 parallel to the spiral groove 12 of the screw shaft 10. This causes the outer edge of the disk-shaped grindstone 61 to coincide with the lead angle of the spiral groove 12 of the screw shaft 10.

[0028] The repairing process involves carrying out a repairing operation in which the spiral groove 12 of the screw shaft 10 is continuously ground. Specifically, first, the second adjustment part 82 of the grindstone adjustment part 80 adjusts the position of the grindstone 61 in the forward / backward direction, thereby bringing the grindstone 61 into contact with the spiral groove 12 of the screw shaft 10. Next, the grinding motor 64 that rotates the grindstone 61 is rotated, and the drive motor that rotates the screw shaft 10 is also rotated. This allows repair work to be performed simultaneously by grinding the surface of the spiral groove 12 of the screw shaft 10 using the grinding wheel 61 and by moving the processed part 60 (grinding wheel 61) along the screw shaft 10 (spiral groove 12).

[0029] The peripheral speed of the grinding wheel 61 is set to approximately 10 to 80 m / s, and is changed as appropriate depending on the type and size of the grinding wheel 61. The rotation speed of the grinding wheel 61 is calculated from the peripheral speed of the grinding wheel 61 and the diameter of the grinding wheel 61, and is set so that the peripheral speed of the grinding wheel 61 is smaller than the maximum setting value. The rotation speed of the screw shaft 10 is preferably about 1 / 100 of the rotation speed of the grinding wheel 61. However, if the rotation speed of the screw shaft 10 is set to, for example, about 1 rpm or less, it becomes difficult to form an oil film between the rolling elements and the thread grooves of the screw shaft 10 and the nut 20, and new wear is likely to occur during grinding. For this reason, it is desirable to increase the rotation speed of the screw shaft 10 at least until an oil film is formed between the rolling elements and the thread grooves of the screw shaft 10 and the nut 20. By adjusting the position of the grindstone 61 in the forward and backward directions using the second adjustment section 82, the amount of grinding of the screw shaft 10 by the grindstone 61 can be adjusted.

[0030] At this time, chips are generated when the screw shaft 10 is ground by the grindstone 61, so the repair device 50 may be provided with a cleaning device (not shown) for supplying a cleaning liquid to wash away the chips. This makes it possible to prevent foreign matter such as chips from entering the inside of the nut 20 of the ball screw 100 when the screw shaft is ground.

[0031] Next, after grinding of the screw shaft 10 by the grinding wheel 61 is completed, the grinding wheel 61 is moved away from the spiral groove 12 of the screw shaft 10 by adjusting the position of the grinding wheel 61 in the forward / backward direction using the second adjustment section 82 of the grinding wheel adjustment section 80. In the repair process, the grinding range may be adjusted so that grinding is limited to the area of the spiral groove 12 of the screw shaft 10 where peeling or damage has occurred.

[0032] In the removal step, after all repair work on the screw shaft 10 is completed, the attachment portion 70 is removed from the nut 20 or the fixing member 30.

[0033] According to the repair method for the ball screw 100 using the repair device 50 described above, it is possible to smoothly remove shape abnormalities caused by flaking, scratches, etc. that have occurred in the spiral groove 12 of the screw shaft 10. As a result, a ball screw 100 in which flaking has occurred in the screw shaft 10 and excessive torque is required can be repaired so that the rolling elements can roll smoothly in the spiral groove 12 of the screw shaft 10. Furthermore, repair work on the screw shaft 10 can be carried out without removing the ball screw 100 from the device including the fixing member 30, which improves convenience.

[0034] Furthermore, when the repair device 50 performs repair work on the ball screw 100 and grinds the screw shaft 10 to change the effective diameter of the screw shaft 10, the radial or axial clearance of the ball screw 100 increases, which changes the contact state between the rolling elements and the spiral groove 12 when an axial load is applied. For this reason, in preparation for changes in the characteristics of the ball screw 100, such as the dynamic friction torque and rigidity, the shape of the grinding wheel 61 may be appropriately changed from the groove shape of the spiral groove 12 of the screw shaft 10 before grinding. This makes it possible to adjust for changes in dynamic friction torque characteristics and rigidity caused by an increase in the radial or axial clearance of the ball screw 100 that occurs during repair work.

[0035] Furthermore, when the repair work on the ball screw 100 using the repair device 50 grinds the screw shaft 10 and reduces the effective diameter of the screw shaft 10, the radial gap calculated as the sum of the distances between the screw shaft 10, the rolling elements, and the nut 20 increases. For this reason, in an offset preload method in which a preload is not applied unless the radial gap is equal to or less than a certain value relative to the nut lead offset, the radial gap or axial gap in the assembled state after grinding the screw shaft 10 becomes large, and the effective diameter of the screw shaft 10 relative to the nut lead offset becomes abnormally small, and there are cases in which a preload is not applied. Therefore, the ball screw 100 that is repaired by the above-mentioned repair device 50 does not include the offset preload type, in which the preload load is adjusted by changing the ball diameter of the internal rolling elements after grinding the screw shaft 10.

[0036] Furthermore, if the flaking that occurs on the surface of the screw shaft 10 reaches a certain depth or more, it becomes necessary to grind the screw shaft 10 that much deeper, which results in an excessively large radial or axial clearance of the ball screw 100. This can cause the rolling elements of the ball screw 100 to ride up onto the land portions of the spiral groove 12 when an axial load is applied to the ball screw 100, or can cause the contact state between the rolling elements and the spiral groove 12 of the screw shaft 10 to become unstable when an axial load is applied to the ball screw 100 and it is driven, resulting in a deterioration in operability. As a preventative measure, the repair device 50 may be configured to be equipped with a torque detection device in advance, which includes a detection sensor that constantly detects the torque acting on the screw shaft 10 of the ball screw 100, and an output means such as a monitor that can monitor the detected torque. According to this configuration, when an error equal to or greater than a predetermined threshold is detected in the torque detected by the torque detection device, repair work on the screw shaft 10 can be performed using the repair device 50. This makes it possible to perform repair of the screw shaft 10 at an appropriate timing.

[0037] Furthermore, in the case where the ball screw 100 is configured such that the nut 20 rotates around the screw shaft 10 by a drive motor, the repair device 50 may be configured to be attached and fixed to the outer diameter portion of the nut 20 . In this case, the grindstone 61 moves along the screw shaft 10 while rotating along the spiral groove 12 of the screw shaft 10 together with the nut 20, so that the spiral groove 12 can be continuously ground as in the above-described embodiment.

[0038] The present invention is not limited to the above-described embodiment, and modifications and improvements can be made as appropriate.

[0039] As described above, the present specification discloses the following: (1) A repair device for a ball screw including a screw shaft having a spiral groove formed on its outer peripheral surface, a nut having a spiral groove formed on its inner peripheral surface, and a plurality of rolling elements, a processing unit provided with a grinding wheel for grinding the spiral groove of the screw shaft; a mounting portion that is detachably attached to the nut or a fixing member to which the nut is fixed, By rotation of the screw shaft or the nut, the grinding wheel moves along the spiral groove of the screw shaft. Ball screw repair device. According to this configuration, even if surface-originating flaking occurs on the screw shaft of the ball screw, the flaking can be removed and the ball screw can be repaired to a state where it operates normally, thereby significantly extending the life of the ball screw.In addition, since the screw shaft of the ball screw can be repaired without disassembling the ball screw, the repair work can be carried out smoothly and easily.

[0040] (2) The grinding wheel has a cross-sectional shape that conforms to the groove shape of the spiral groove of the screw shaft. A repair device for a ball screw according to (1). According to this configuration, by grinding the screw shaft so as to transfer the shape of the grindstone, the spiral groove of the screw shaft can be ground along the shape of the spiral groove. Therefore, the screw shaft can be repaired without grinding the spiral groove with the grindstone more than necessary.

[0041] (3) The processing unit includes the grindstone, a rotation shaft on which the grindstone is supported, and a motor that drives the rotation shaft. A repair device for a ball screw according to (1) or (2). According to this configuration, the grinding process can be performed simply by bringing the grinding stone into contact with the portion of the screw shaft to be repaired, so that the repair work can be carried out efficiently.

[0042] (4) A grinding wheel adjusting unit that tilts the grinding wheel along the spiral groove of the screw shaft. A ball screw repair device according to any one of (1) to (3). According to this configuration, the grinding stone can be arranged along the spiral groove of the screw shaft, and the angle of the grinding stone can be made to match the lead angle of the spiral groove.

[0043] (5) An attachment step of attaching the ball screw repair device according to any one of (1) to (4) to the nut or the fixing member; an adjusting step of arranging the grinding wheel along the spiral groove of the screw shaft; A repair process in which the spiral groove is ground along the screw shaft by moving the processing portion along the screw shaft by rotational driving of the screw shaft. How to repair a ball screw. According to this configuration, even if surface-originating flaking occurs on the screw shaft of the ball screw, the flaking can be removed and the ball screw can be repaired to a state where it operates normally, thereby significantly extending the life of the ball screw.In addition, since the screw shaft of the ball screw can be repaired without disassembling the ball screw, the repair work can be carried out smoothly and easily. [Explanation of symbols]

[0044] 10 axes 12 Spiral groove 20 nuts 30 Fixing member 50 Repair Equipment 60 Processing Department 61 Whetstone 62 Rotation axis 63 Bearing unit 64 Grinding motor 64a Output shaft 65 Support plate 66 Drive pulley 67 Transmission pulley 68 Timing belt 70 Mounting part 80 Grindstone adjustment section 81 1st adjustment section 81A Rotary Table 81B Support table 81C Angle adjuster 82 2nd adjustment section 82A Second Adjustment Table 82B Forward / backward adjustment tool

Claims

1. A repair device for a ball screw including a screw shaft having a spiral groove formed on its outer peripheral surface, a nut having a spiral groove formed on its inner peripheral surface, and a plurality of rolling elements, a processing unit provided with a grinding wheel for grinding the spiral groove of the screw shaft; a mounting portion that is detachably attached to the nut or a fixing member to which the nut is fixed, The grinding wheel moves along the axial direction of the screw shaft by rotation of the screw shaft or the nut. Ball screw repair device.

2. The grinding wheel has a cross-sectional shape that follows the groove shape of the spiral groove of the screw shaft. The ball screw repair device according to claim 1.

3. The processing unit includes the grindstone, a rotation shaft on which the grindstone is supported, and a motor that drives the rotation shaft. The ball screw repair device according to claim 1.

4. a grindstone adjustment unit that tilts the grindstone along the spiral groove of the screw shaft; The ball screw repair device according to claim 3.

5. an attachment step of attaching the ball screw repair device according to any one of claims 1 to 4 to the nut or the fixing member; an adjusting step of arranging the grinding wheel along the spiral groove of the screw shaft; A repair process in which the spiral groove is ground along the screw shaft by moving the processing portion along the screw shaft by rotational driving of the screw shaft. How to repair a ball screw.

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