Contact sensor for ball screw, ball screw, and damage detection device

Abstract

To provide a contact type sensor for a ball screw, the ball screw and a damage detection device capable of detecting even minute damage such as minute peeling generated in an outer peripheral screw groove of a screw shaft in an early stage.SOLUTION: The ball screw 10 is provided with a contact type sensor 30 for a ball screw in which a probe 3 is brought into contact with left and right flanks 21a and 21b of an outer peripheral screw groove 21 outside a region of a ball circulation path 13 where balls 12 do not roll. In the damage detection device 40, the detection unit 34 detects a change in the physical quantity that occurs when the gauge head 33 comes into contact with the damage 22 in the outer circumferential thread groove 21, and damage occurrence information is output when the amount of change in the detected physical quantity exceeds a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a contact sensor for a ball screw, a ball screw, and a damage detection device. [Background technology]

[0002] Ball screws are used as mechanical elements in, for example, semiconductor manufacturing equipment, compression molding machines, injection molding machines, general conveying equipment, etc. A ball screw is a mechanism that converts rotational motion into linear motion, and includes a screw shaft with a helical thread groove formed on its outer periphery, a nut with a helical thread groove formed on its inner periphery that faces the thread groove of the screw shaft, and a large number of steel balls rollably mounted in a ball rolling path formed by the thread groove of the screw shaft and the thread groove of the nut. A ball circulation member is attached to the nut to return the balls that have rolled in the ball rolling path to their predetermined positions in the ball rolling path, and the ball circulation member and the ball rolling path form a ball circulation path that allows the balls to circulate endlessly.

[0003] When a ball screw is used for a long period of time, flaking can occur at the contact point with the ball due to rolling fatigue, and if the flaking progresses, it could cause the machine to stop. Therefore, early detection of flaking is important for improving productivity. Furthermore, when a load is applied to a ball screw, the contact pressure between the screw shaft and ball is greater than the contact pressure between the nut and ball, which means that flaking is more likely to occur on the screw shaft (peripheral thread groove).

[0004] Patent Document 1 discloses a screw device in which an eddy current displacement sensor is fixed to the nut and the displacement between the sensor and the screw shaft raceway surface is monitored to detect flaking. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-8112 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the eddy current displacement sensor provided in the screw device described in Patent Document 1 has a wide measurement range, which makes it difficult to detect minute peeling.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a contact sensor for a ball screw, a ball screw, and a damage detection device that can detect even minute damage that occurs in the outer peripheral screw groove of a screw shaft at an early stage. [Means for solving the problem]

[0008] Therefore, the above object of the present invention is achieved by the following configuration [1] relating to a contact sensor for a ball screw. [1] A screw shaft having a spiral outer thread groove formed on its outer surface; a nut having an inner peripheral surface formed with a spiral inner peripheral thread groove that faces the outer peripheral thread groove; a plurality of balls rollably interposed in a ball rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove; at least one ball circulation member disposed in the nut and cooperating with the ball rolling path to form a ball circulation path through which the plurality of balls circulate; A contact sensor for a ball screw used to detect damage to an outer peripheral screw groove of the screw shaft of a ball screw comprising: a probe that contacts the left and right flanks of the outer peripheral thread groove; a load measuring unit that supports the probe; a detection unit fixed to the load measurement unit and detecting a change in a physical quantity that occurs when the probe comes into contact with damage to the outer peripheral thread groove; and a contact sensor for a ball screw, the contact sensor being elastically supported by the nut at least in the radial direction of the screw shaft.

[0009] The above object of the present invention is also achieved by the following configuration [2] relating to a ball screw. [2] A screw shaft having a spiral outer thread groove formed on its outer surface; a nut having an inner peripheral surface formed with a spiral inner peripheral thread groove that faces the outer peripheral thread groove; a plurality of balls rollably interposed in a ball rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove; at least one ball circulation member disposed in the nut and cooperating with the ball rolling path to form a ball circulation path through which the plurality of balls circulate; [1] A contact sensor for a ball screw according to the present invention; Equipped with the ball screw contact sensor is fixed to the nut so as to face the outer peripheral screw groove of the screw shaft, the probe contacts left and right flanks of the outer peripheral thread groove outside a region of the ball circulation path in which the balls are not rolling.

[0010] The above object of the present invention is also achieved by the following configuration [3] relating to the damage detection device. [3] [2] A ball screw according to the present invention; a control unit that outputs damage occurrence information when the change amount of the physical quantity detected by the detection unit exceeds a predetermined value; A damage detection device comprising: [Effects of the Invention]

[0011] The ball screw contact sensor, ball screw, and damage detection device of the present invention can detect even minute damage, such as minute flaking, that occurs in the outer peripheral thread groove of the screw shaft at an early stage. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram of a ball screw according to a first embodiment of the present invention. [Figure 2] FIG. 2(a) is a diagram showing the configuration of the contact sensor for a ball screw shown in FIG. 1 as seen from the radial direction, and FIG. 2(b) is a diagram showing the configuration of the contact sensor for a ball screw as seen from the axial direction. [Figure 3]FIG. 3(a) is a side view showing how a probe with a relatively small contact area detects minute peeling, and FIG. 3(b) is a side view showing how a probe with a relatively large contact area detects advanced peeling. [Figure 4] FIG. 4 is a configuration diagram of the damage detection device. [Figure 5] FIG. 5(a) is a diagram showing the configuration of a contact sensor for a ball screw according to a second embodiment of the present invention as viewed from the radial direction, and FIG. 5(b) is a diagram showing the configuration of the contact sensor for a ball screw as viewed from the axial direction. [Figure 6] FIG. 6 is a diagram showing the configuration of a contact sensor for a ball screw according to a third embodiment of the present invention, as viewed from the radial direction. [Figure 7] FIG. 7 is a configuration diagram of a contact sensor for a ball screw according to a fourth embodiment of the present invention, as viewed from the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a contact sensor for a ball screw, a ball screw, and a damage detection device according to the present invention will be described in detail with reference to the accompanying drawings.

[0014] (First embodiment) FIG. 1 is a diagram of a ball screw according to a first embodiment of the present invention, and FIG. 2 is a front view and a side view of a contact sensor for a ball screw.

[0015] As shown in FIG. 1, the ball screw 10 of this embodiment is a tube-type ball screw that includes a screw shaft 20 having a spiral outer peripheral screw groove 21 formed on its outer peripheral surface, a nut 25 having a spiral inner peripheral screw groove 26 formed on its inner peripheral surface that faces the outer peripheral screw groove 21 of the screw shaft 20 and that is provided around the screw shaft 20, a large number of balls (steel balls) 12 rollably interposed in ball rolling paths 11 formed by the outer peripheral screw groove 21 of the screw shaft 20 and the inner peripheral screw groove 26 of the nut 25, and a ball circulation member (return tube) 28 that circulates the balls 12 rolling in the ball rolling paths 11, and converts rotational motion into linear motion.

[0016] The ball circulation member 28 is fixed to the notched flat surface 27 of the nut 25 by a presser plate 29. The ball circulation member 28 cooperates with a circulation path (not shown) formed inside and the ball rolling path 11 to form a ball circulation path 13 that returns the plurality of balls 12 rolling in the ball rolling path 11 to predetermined positions and circulates them endlessly.

[0017] The ball rolling path 11 formed by the outer peripheral screw groove 21 and the inner peripheral screw groove 26 is divided into a ball passing portion 11a through which the balls 12 pass and a non-ball passing portion 11b through which the balls 12 do not pass, in order to form a ball circulation path 13 via the ball circulation member 28.

[0018] 1, four ball circulation members 28 are provided, thereby forming four ball circulation paths 13. The non-ball passing portions 11b are formed between the three ball passing portions 11a that form each ball circulation path 13, and at five locations axially outside the ball passing portions 11a formed on both axial sides.

[0019] The ball screw contact sensor 30 can be disposed in a portion of the nut 25 facing the outer peripheral thread groove 21 located in these five non-ball passing portions 11b. Furthermore, the ball screw contact sensor 30 can be disposed so as to face the outer peripheral thread groove 21 even in a portion of the nut 25 that is axially outer than the position of the nut 25 where the inner peripheral thread groove 26 that forms the ball rolling path 11 is formed (for example, a portion axially outer than the seal mounting portion). In other words, the ball screw contact sensor 30 can be disposed in the nut 25 facing the outer peripheral thread groove 21, outside the region of the ball circulation path 13 where the balls 12 are not rolling.

[0020] Specifically, seven small dashed circles X shown in Fig. 1 indicate possible positions for placing the ball screw contact sensor 30. It is not necessary to place the ball screw contact sensor 30 in all seven locations, and it is sufficient to place it in at least one location.

[0021] As shown in FIG. 2, the ball screw contact sensor 30 is mainly composed of a holding cover 31, a load measuring section 32, a probe 33, a detecting section 34, and a plurality of springs 37.

[0022] The holding lid 31 has an accommodation groove 35 which is a rectangular hole with a bottom capable of accommodating the load measuring part 32, and is fitted and fixed in a through hole 36 formed in the nut 25 so as to penetrate therethrough in the radial direction.

[0023] The load measuring unit 32 includes a rectangular parallelepiped base portion 32a and a thin plate-like measuring portion 32b with low rigidity in the rotational direction (left-right direction in FIG. 2(b)) of the screw shaft 20, and the base portion 32a and measuring portion 32b are integrally formed. The measuring portion 32b has a shape that makes it easy for distortion to occur in the rotational direction.

[0024] The depth d of the accommodating groove 35 is deeper than the height of the base portion 32a of the load measuring portion 32, the axial width W1 of the accommodating groove 35 is larger than the axial width of the base portion 32a (see Figure 2(a)), and further the circumferential width W2 of the accommodating groove 35 is formed to be approximately the same width as the circumferential width of the base portion 32a (see Figure 2(b)).

[0025] That is, the base portion 32a of the load measuring portion 32 is accommodated in the accommodation groove 35 so as to be movable in the radial and axial directions, and is elastically supported on the holding cover 31 by a plurality of springs 37, which are elastic members. On the other hand, the load measuring portion 32 is fitted into the accommodation groove 35 with its circumferential movement restricted.

[0026] As shown in FIG. 2(a), the contact sensor 30 for a ball screw of this embodiment has two probes 33, which are fixed integrally to the measuring section 32b and protrude in a V-shape.

[0027] The probes 33 include a generally rod-shaped base 33a and a spherical contact portion 33b formed integrally with the tip of the base 33a. One end (root portion) of the base 33a is fixed to the measuring portion 32b of the load measuring portion 32, and the contact portions 33b of the two probes 33 are in contact with the left and right flanks 21a, 21b of the outer peripheral thread groove 21. From the viewpoint of accurately detecting peeling, it is desirable that the material of the contact portions 33b has low friction with the outer peripheral thread groove 21.

[0028] The load measuring portion 32 is elastically supported by a plurality of springs 37 so as to be movable radially and axially within the accommodation groove 35, so that the contact portions 33b of both probes 33 always follow the outer peripheral thread groove 21 and are in contact with the left and right flanks 21a, 21b.

[0029] The contact positions between the two contact portions 33b of the probe 33 and the left and right flanks 21a, 21b are preferably located at areas where the contact surface pressure with the ball 12 is large and separation is likely to occur. Specifically, the contact positions are generally in the range of θ=40° to 70° when the phase of the line connecting the center of the outer peripheral thread groove 21 and the bottom of the outer peripheral thread groove 21 is set to 0°, and the angle also becomes larger when the load acting on the ball screw 10 is large.

[0030] Therefore, when the magnitude of the load acting on the ball screw 10 is estimated in advance, it is preferable to set the contact position of the contact portion 33b in accordance with the load.

[0031] A detection unit 34, which is, for example, a strain gauge, is fixed to the side surface of the thin plate-like measurement unit 32b of the load measurement unit 32. When strain occurs in the load measurement unit 32 (measurement unit 32b), the detection unit 34 detects the strain and sends out a detection signal.

[0032] Note that the load measuring unit 32 cannot move in the circumferential direction of the accommodating groove 35, and therefore there is a risk that the detection of peeling may be affected if the load measuring unit 32 comes into strong contact with the accommodating groove 35. For this reason, it is desirable to keep the pressing force of the spring 37 and the range of movement of the load measuring unit 32 relative to the accommodating groove 35 to the minimum necessary.

[0033] In this way, the ball screw contact sensor 30 is compactly provided on the holding cover 31 disposed on the nut 25 .

[0034] Next, the operation of the contact sensor 30 for a ball screw according to this embodiment will be described. 3(a) and 3(b), when the screw shaft 20 of the ball screw 10 is rotationally driven and the probe 33 passes through the damaged flakes 22, the probe 33 (contact portion 33b) enters the flakes 22, and when it exits the flakes 22, a load is generated in the probe 33 in the circumferential direction of the outer peripheral thread groove 21. Because the probe 33 and the load measuring unit 32 are integrated, a distortion is also generated in the load measuring unit 32, and the detector 34 detects this distortion and sends out a detection signal.

[0035] The contact portions 33b of the two probes 33 are in contact with the left and right flanks 21a, 21b of the outer peripheral thread groove 21, so even if the peeling 22 occurs on only one of the left and right flanks 21a, 21b, the peeling 22 can be detected. In other words, the single ball screw contact sensor 30 can simultaneously monitor the left and right flanks 21a, 21b.

[0036] As described above, the ball screw contact sensor 30 of this embodiment is a system that detects the flakes 22 by bringing the contact portion 33b of the probe 33 into contact with the raceway surface of the outer peripheral thread groove 21, and therefore it is possible to easily adjust the size of the flakes 22 to be detected by changing the size of the contact portion 33b to correspond to the size of the flakes 22 to be detected. The smaller the size (radius of curvature) of the contact portion 33b relative to the size of the flakes 22, the easier it is to detect the flakes 22, so it is desirable to set the size of the contact portion 33b to, for example, 50% or less of the depth of the flakes 22 to be detected.

[0037] Therefore, not only can the peeling 22 that has progressed and grown larger be detected, but even a minute peeling 22 in the initial stage of peeling can be detected early on, which is a function unique to the contact sensor.

[0038] 4 is a configuration diagram of a damage detection device using the ball screw contact sensor 30 of this embodiment. As shown in FIG. 4, the damage detection device 40 includes the ball screw contact sensor 30, a control unit 41, a monitor 42, and an alarm 43.

[0039] As described above, when the screw shaft 20 of the ball screw 10 is rotated and the probe 33 passes through the peel 22, the detector 34 detects the distortion of the load measuring part 32 caused by the contact part 33b moving in and out of the peel 22 and sends out a detection signal.

[0040] The detection signal is processed by the control unit 41 and compared with a threshold value stored in advance in the control unit 41. If the detection signal is below the threshold value, it is determined that there is no abnormality (there is no peeling 22, or it is to an extent that does not interfere with operation), and if the detection signal is above the threshold value, it is determined that there is an abnormality, and information about the occurrence of damage is displayed on the monitor 42, and an alarm is issued from the alarm 43 to notify the operator of the abnormality.

[0041] (Second embodiment) 5A and 5B are a front view and a side view of a contact sensor for a ball screw according to a second embodiment of the present invention. In the contact sensor for a ball screw 30 of this embodiment, the bases 33a of the two probes 33 shown in the first embodiment are integrally formed at the base. That is, the two probes 33 protrude in a V-shape from one base 33a.

[0042] The integrally formed base portion 33a is swingably supported on a support pin 38 which has its center in a direction perpendicular to the axial center of the screw shaft 20 and is fixed to the load measuring portion 32. The depth d of the accommodating groove 35 is formed deeper than the height of the base portion 32a of the load measuring portion 32, but the axial width W1 and circumferential width W2 of the accommodating groove 35 are formed to be approximately the same as the axial width and circumferential width of the base portion 32a. In other words, the load measuring portion 32 is fitted into the accommodating groove 35 so as to be movable in the radial direction while being elastically supported by the spring 37, but not in the axial or circumferential directions.

[0043] In the contact sensor 30 for a ball screw of this embodiment, due to the radial elastic support against the accommodating groove 35 and the swinging action of the load measuring part 32 by the support pin 38, the two contact parts 33b always follow the outer peripheral screw groove 21 and contact the left and right flanks 21a, 21b, thereby enabling the peeling 22 to be reliably detected.

[0044] That is, in the second embodiment, the function of elastically supporting the load measuring part 32 so that it can move axially in the housing groove 35 (see FIG. 2(a)), which was described in the first embodiment, is realized by supporting the measuring element 33 so that it can swing freely around the support pin 38. The other configurations and operations are the same as those of the contact sensor 30 for a ball screw of the first embodiment, and therefore the explanation will be omitted.

[0045] (Third embodiment) FIG. 6 is a front view of a contact sensor for a ball screw according to a third embodiment of the present invention. In the ball screw contact sensor 30 of this embodiment, like the ball screw contact sensor 30 of the second embodiment, the bases 33a of the two probes 33 are integrally formed at their bases. The bases 33a of the probes 33 are formed in a semicircular shape and are supported by a support pin 38 so as to be able to swing freely on the load measuring part 32. The two contact parts 33b are located at the tips of the straight parts of the semicircular bases 33a.

[0046] In the contact sensor 30 for a ball screw of this embodiment, as in the contact sensor 30 for a ball screw of the second embodiment, the base 33a is supported so that it can swing freely around the support pin 38, so that the two contact portions 33b are always in contact with the left and right flanks 21a, 21b, and the peeling 22 can be reliably detected.

[0047] (Fourth embodiment) FIG. 7 is a side view of a contact sensor for a ball screw according to a fourth embodiment of the present invention. In the contact sensor 30 for a ball screw of this embodiment, the detection section 34 is composed of a piezoelectric element.

[0048] A fixing plate 39 with its flat surface facing the circumferential direction is fixed to the housing groove 35 of the presser lid 31. The load measuring unit 32, to which the two probes 33 are fixed, is overlapped with the fixing plate 39 with the detecting unit 34, which is a piezoelectric element, sandwiched between them, and is elastically supported in the housing groove 35 in the radial and axial directions by springs 37.

[0049] When the screw shaft 20 of the ball screw 10 rotates and the measuring element 33 passes through the peel 22, the load measuring unit 32 integrated with the measuring element 33 is pressed against the fixed plate 39, and the detecting unit 34 (piezoelectric element) detects the pressing force and sends out a detection signal.

[0050] As described above, the contact sensor 30 for a ball screw, the ball screw 10, and the damage detection device 40 of this embodiment can detect even minute spalling (damage) 22 occurring in the outer peripheral screw groove 21 of the screw shaft 20 at an early stage, and when damage is detected, the occurrence of the damage can be confirmed by the damage detection device 40 using the monitor 42 and the alarm 43.

[0051] The present invention is not limited to the above-described embodiment, and modifications and improvements are possible as appropriate. For example, in the above embodiment, a tube-type ball screw has been described as an example, but in the case of a bridge-type or middle deflector-type ball screw, the ball screw contact sensor 30 can be similarly installed outside the area of ​​the ball circulation path 13 where the balls 12 are not rolling. In the case of an end deflector-type ball screw, the ball screw contact sensor 30 is installed axially outside the end deflectors attached to both ends of the nut 25.

[0052] Furthermore, the contact sensor for a ball screw is not limited to being fixed to the nut, but may also be attached to a part that works in conjunction with the nut, as long as the probe is configured to contact the left and right flanks of the outer thread groove outside the area of ​​the ball circulation path where the balls are not rolling.

[0053] As described above, the present specification discloses the following: (1) a screw shaft having a spiral outer peripheral thread groove formed on its outer peripheral surface; a nut having an inner peripheral surface formed with a spiral inner peripheral thread groove that faces the outer peripheral thread groove; a plurality of balls rollably interposed in a ball rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove; at least one ball circulation member disposed in the nut and cooperating with the ball rolling path to form a ball circulation path through which the plurality of balls circulate; A contact sensor for a ball screw used to detect damage to an outer peripheral screw groove of the screw shaft of a ball screw comprising: a probe that contacts the left and right flanks of the outer peripheral thread groove; a load measuring unit that supports the probe; a detection unit fixed to the load measurement unit and detecting a change in a physical quantity that occurs when the probe comes into contact with damage to the outer peripheral thread groove; and a contact sensor for a ball screw, the contact sensor being elastically supported by the nut at least in the radial direction of the screw shaft. According to this configuration, even minute damage such as minute flaking occurring in the outer peripheral thread groove of the screw shaft can be detected early.

[0054] (2) The tip of the probe that comes into contact with the outer peripheral thread groove has a spherical shape whose size corresponds to the size of the damage to be detected. The contact sensor for a ball screw according to claim 1. According to this configuration, the size of the damage to be detected can be adjusted by changing the shape of the tip of the probe.

[0055] (3) The probe is supported so as to be swingable in the axial direction of the screw shaft relative to the load measuring unit. Or the contact sensor for a ball screw according to (2). According to this configuration, by swinging the probe relative to the load measuring section, the probe can be kept in contact with the outer peripheral thread groove of the screw shaft.

[0056] (4) The detection unit is a strain gauge. The contact sensor for a ball screw according to any one of (1) to (3). According to this configuration, damage occurring in the outer peripheral thread groove can be detected with high accuracy using a strain gauge.

[0057] (5) The detection unit is a piezoelectric element. The contact sensor for a ball screw according to any one of (1) to (3). According to this configuration, damage occurring in the outer peripheral thread groove can be detected with high accuracy by the piezoelectric element.

[0058] (6) a presser lid that is fixed to a through hole formed in the nut and that penetrates the nut in the radial direction, and has an accommodation groove that accommodates the load measuring unit on a surface facing the outer peripheral screw groove; an elastic member that connects the accommodation groove of the pressing lid and the load measuring unit; Further provided with The contact sensor for a ball screw according to any one of (1) to (5). According to this configuration, by elastically supporting the measuring element on the holding cover, the ball screw contact sensor can be arranged compactly on the nut.

[0059] (7) a screw shaft having a spiral outer peripheral thread groove formed on its outer peripheral surface; a nut having an inner peripheral surface formed with a spiral inner peripheral thread groove that faces the outer peripheral thread groove; a plurality of balls rollably interposed in a ball rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove; at least one ball circulation member disposed in the nut and cooperating with the ball rolling path to form a ball circulation path through which the plurality of balls circulate; A contact sensor for a ball screw according to any one of (1) to (6), Equipped with the ball screw contact sensor is fixed to the nut so as to face the outer peripheral screw groove of the screw shaft, the probe contacts left and right flanks of the outer peripheral thread groove outside a region of the ball circulation path in which the balls are not rolling. According to this configuration, even in a ball screw having a ball circulation path, minute damage occurring in the outer peripheral screw groove can be detected.

[0060] (8) The ball screw according to (7), a control unit that outputs damage occurrence information when the change amount of the physical quantity detected by the detection unit exceeds a predetermined value; having Damage detection equipment. According to this configuration, minute damage occurring in the outer peripheral thread groove can be detected and damage occurrence information can be output. [Explanation of symbols]

[0061] 10 Ball screw 11 Ball rolling path 12 balls 13 Ball circulation path 20 Screw shaft 21 Peripheral thread groove 21a, 21b Frank 22 Peeling (damage) 25 Nut 26 Internal thread groove 28 Ball circulation member 30 Contact sensor for ball screw 31 Presser cover 32 Load measurement section 33 Probe 34 Detection unit (strain gauge, piezoelectric element) 35 Storage groove 36 Through hole 37 Spring (elastic member) 38 Support pin 40 Damage detection device 41 Control Unit

Claims

1. a screw shaft having a spiral outer peripheral thread groove formed on its outer peripheral surface; a nut having an inner peripheral surface formed with a spiral inner peripheral thread groove that faces the outer peripheral thread groove; a plurality of balls rollably interposed in a ball rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove; at least one ball circulation member disposed in the nut and cooperating with the ball rolling path to form a ball circulation path through which the plurality of balls circulate; A contact sensor for a ball screw used to detect damage to an outer peripheral screw groove of the screw shaft of a ball screw comprising: a probe that contacts the left and right flanks of the outer peripheral thread groove; a load measuring unit that supports the probe; a detection unit fixed to the load measurement unit and detecting a change in a physical quantity that occurs when the probe comes into contact with damage to the outer peripheral thread groove; and a contact sensor for a ball screw, the contact sensor being elastically supported by the nut at least in the radial direction of the screw shaft.

2. the tip of the probe that comes into contact with the outer peripheral thread groove has a spherical shape of a size corresponding to the size of the damage to be detected; 2. The contact sensor for a ball screw according to claim 1.

3. The probe is supported so as to be swingable in the axial direction of the screw shaft relative to the load measuring unit.

2. The contact sensor for a ball screw according to claim 1.

4. The detection unit is a strain gauge.

2. The contact sensor for a ball screw according to claim 1.

5. The detection unit is a piezoelectric element.

2. The contact sensor for a ball screw according to claim 1.

6. a presser lid that is fixed to a through hole formed in the nut and that penetrates in a radial direction, and has an accommodation groove that accommodates the load measuring unit on a surface facing the outer peripheral screw groove; an elastic member that connects the accommodation groove of the pressing lid and the load measuring unit; Further provided with 2. The contact sensor for a ball screw according to claim 1.

7. a screw shaft having a spiral outer peripheral thread groove formed on its outer peripheral surface; a nut having an inner peripheral surface formed with a spiral inner peripheral thread groove that faces the outer peripheral thread groove; a plurality of balls rollably interposed in a ball rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove; at least one ball circulation member disposed in the nut and cooperating with the ball rolling path to form a ball circulation path through which the plurality of balls circulate; A contact sensor for a ball screw according to any one of claims 1 to 6, Equipped with the ball screw contact sensor is fixed to the nut so as to face the outer peripheral screw groove of the screw shaft, the probe contacts left and right flanks of the outer peripheral thread groove outside a region of the ball circulation path in which the balls are not rolling.

8. The ball screw according to claim 7, a control unit that outputs damage occurrence information when the change amount of the physical quantity detected by the detection unit exceeds a predetermined value; having Damage detection equipment.

Images