JP6651892B2 - Ball screw, ball screw out-of-circuit ball detection method - Google Patents

Description

  The present invention relates to a ball screw and a ball screw out-of-circuit ball detection method.

  The ball screw is used as a mechanical element of, for example, a semiconductor manufacturing device, a compression molding machine, an injection molding machine, a general conveyance device, and the like. A ball screw has a screw shaft with a spiral screw groove formed on the outer peripheral surface, a nut with a spiral screw groove formed on the inner peripheral surface facing the screw groove of the screw shaft, and a screw groove of the screw shaft. This is a mechanism that includes a number of steel balls rotatably interposed in a ball rolling path formed by a thread groove of a nut and converts the rotational motion into a linear motion. A ball circulating member for returning the ball that has rolled on the ball rolling path to a predetermined position on the ball rolling path is attached to the nut. A circuit, which is a ball circulation path for infinitely circulating the ball by the ball circulation member and the ball rolling path, is formed. The ball screw has one or more such circuits.

  As the ball circulation member, there is a ball circulation tube. By providing the ball circulation tube, a large number of balls rolling on the ball rolling path are guided by the ball scooping portion of the ball circulation tube to the inside of the ball circulation tube, that is, the ball return path, and roll on the ball return path. The ball is returned to a predetermined position on the ball rolling path from the other ball scooping unit. Generally, in assembling a ball screw using a ball circulation tube, a ball circulation tube and a ball rolling path are each filled with a ball, and then the ball circulation tube filled with the ball is assembled to a nut.

  In a ball screw having a plurality of circuits, a ball non-circulation portion in which balls do not circulate exists between adjacent circuits. The ball non-circulation portion is formed by a portion of the screw groove of the nut between adjacent circuits, and a portion of the screw groove of the screw shaft facing the portion of the screw groove of the nut between the circuits. When assembling the ball circulation tube to the nut, the ball is likely to be erroneously filled in the ball non-circulation portion. If a ball screw is used while the ball is present in the ball non-circulation section, the ball in the ball non-circulation section collides with the ball scooping section of the ball circulation tube, and the ball scooping section is damaged, When the ball is clogged in the circulation portion, the ball screw may be locked.

  In the ball screw of Patent Document 1, when the ball circulation tube is fitted to the nut, the ball circulation tube is fitted to the nut, and then the ball circulation tube and the ball rolling path are fitted in a state where the ball circulation tube is fitted to the nut. It can be filled with balls. With this configuration, it is possible to prevent the ball from entering the ball non-circulation portion when assembling the ball circulation tube to the nut.

  The ball screw disclosed in Patent Document 2 has a configuration in which, among the screw grooves of the nut, the slant diameter of the screw groove portion forming the ball non-circulating portion is smaller than the slant diameter size of the screw groove portion forming the circuit. This prevents the ball from entering the ball non-circulation section.

JP 2001-99256 A JP-A-7-253146

  However, the ball entering the ball non-circulation portion is not limited only to assembling the ball circulation tube to the nut. Even after assembling the ball circulation tube to the nut, the ball may enter the ball non-circulation portion due to various factors. Therefore, even with the configuration of Patent Literature 1 or Patent Literature 2, it is impossible to completely prevent the ball from entering the ball non-circulation portion during the entire ball screw assembling process or after the ball screw is assembled. Have difficulty.

  The present invention has been made in view of such a situation, and is a ball screw provided with a ball circulation tube, and after a ball screw is assembled, reliably detects an out-of-circuit ball present in a ball non-circulation portion. It is an object to provide an out-of-circuit ball detection method for a ball screw which can be provided and a ball screw provided with a ball circulation tube.

  In order to solve the above problems, a ball screw according to the present invention includes a screw shaft extending linearly and having a thread groove formed on an outer peripheral surface, and a thread groove facing the thread groove of the screw shaft on an inner peripheral surface. And a nut fitted on the screw shaft via a plurality of balls arranged to be rollable on a ball rolling path formed by the screw groove on the inner peripheral surface and the screw groove on the screw shaft. And a plurality of tube members fixed to the nut for returning the plurality of balls to a predetermined position of the ball rolling path, wherein the ball rolling path between each tube member and both ends of each tube member is provided. And a plurality of circuits for ball circulation are formed, and the plurality of balls are formed by a portion of the ball rolling path between the adjacent circuits in a ball screw arranged in the plurality of circuits. Ball non And further comprising a sensor for detecting the circuit outside the ball present in the ring portion.

  Preferably, in the ball screw according to the present invention, the nut has a through-hole that penetrates the nut in a radial direction and opens in a thread groove portion of the nut corresponding to the ball non-circulation portion. The sensor is attached to the through hole.

  Preferably, the ball screw according to the present invention is characterized in that the sensor detects the out-of-circuit ball when the out-of-circuit ball contacts the sensor.

  Preferably, the ball screw according to the present invention is characterized in that the sensor detects the out-of-circuit ball when the out-of-circuit ball approaches the sensor.

  Preferably, the ball screw out-of-circuit ball detecting method according to the present invention further comprises: a screw shaft having a thread groove extending linearly and having a thread groove formed on an outer peripheral surface; and a thread groove facing the thread groove of the screw shaft. On the inner peripheral surface, and is fitted to the screw shaft via a plurality of balls that are rollably disposed on a ball rolling path formed by the screw groove of the inner peripheral surface and the screw groove of the screw shaft. A mounted nut, comprising a plurality of tube members fixed to the nut, for returning the plurality of balls to a predetermined position of the ball rolling path, between the tube members and both ends of the tube members A plurality of circuits for ball circulation are formed by a portion of the ball rolling path, and the plurality of balls are a portion of the ball rolling path between adjacent circuits in a ball screw arranged in the plurality of circuits. By A ball detecting method of a ball screw for detecting an out-of-circuit ball present in a ball non-circulating portion to be formed, wherein the nut is radially penetrated through the nut and corresponds to the ball non-circulating portion. Forming a through hole that opens in the thread groove portion of the nut, and detecting the outer circuit ball by rotating the screw shaft and rolling the outer ball with a sensor attached to the through hole. Features.

  Preferably, in the ball screw out-of-circuit ball detection method according to the present invention, the sensor detects the out-of-circuit ball when the out-of-circuit ball contacts the sensor.

  Preferably, in the ball screw out-of-circuit ball detection method according to the present invention, the sensor detects the out-of-circuit ball when the out-of-circuit ball approaches the sensor.

  ADVANTAGE OF THE INVENTION According to this invention, it is a ball screw provided with a ball circulation tube, and after assembling the ball screw, a ball screw capable of reliably detecting an off-circuit ball present in a ball non-circulation portion, and a ball circulation tube A method for detecting an off-circuit ball in a ball screw provided with:

FIG. 1 is a perspective view of the ball screw according to the first embodiment, with a part of a nut cut away. FIG. 2 is a side view of a main part of the ball screw according to the first embodiment viewed from a radial direction, and a part of the ball screw is shown in cross section. FIG. 3 is a plan view schematically showing a main part of the ball screw according to the first embodiment. FIG. 4 is a sectional view taken along line AA ′ of FIG. FIG. 5 is a sectional view of a main part of the ball screw according to the second embodiment.

Hereinafter, a ball screw according to each embodiment of the present invention will be described with reference to the drawings.
First, the direction related to the ball screw in this specification is defined. In this specification, unless otherwise specified, the longitudinal direction in which the screw shaft extends is defined as the axial direction, and the direction orthogonal to the central axis of the screw shaft is defined as the radial direction. Also, in FIGS. 1 and 2, one side and the other side in the axial direction are indicated by arrows, the vertical direction of the ball screw is indicated by arrows, and the position and direction are indicated by the directions indicated by these arrows for convenience. The following embodiments will be described.

(1st Embodiment)
The ball screw according to the first embodiment of the present invention will be described.
FIG. 1 is a perspective view of the ball screw according to the first embodiment, with a part of a nut cut away. FIG. 2 is a side view of a main part of the ball screw according to the first embodiment viewed from a radial direction, and a part of the ball screw is shown in cross section. FIG. 3 is a plan view schematically showing a main part of the ball screw according to the first embodiment, and FIG. 4 is a sectional view taken along line AA ′ of FIG.

  As shown in FIGS. 1 and 2, the ball screw 1 according to the present embodiment faces a linear screw shaft 7 having a spiral screw groove 4 formed on the outer peripheral surface, and the screw groove 4 of the screw shaft 7. The spiral screw groove 10 has a cylindrical nut 13 formed on the inner peripheral surface of the screw hole. A ball rolling path 16 is formed by the screw groove 4 of the screw shaft 7 and the screw groove 10 of the nut 13. The nut 13 is fitted on the outer peripheral side of the screw shaft 7 via a large number of steel balls 19 arranged to be able to roll on the ball rolling path 16. A flange 22 for attaching the nut 13 to a mechanical device such as an injection molding machine (not shown) is formed at one axial end of the nut 13. An annular seal member 23 for sealing the gap between the nut 13 and the screw shaft 7 is attached to both axial ends of the nut 13.

  The ball screw 1 according to the present embodiment includes two ball circulation tubes 25 as a circulation member for circulating the ball 19. A rectangular flat portion 28 is formed on the upper part of the nut 13, and one ball circulation tube 25 is disposed on one axial side portion of the flat portion 28, and the other ball circulation tube 25 is disposed on the other axial side of the flat portion 28. Is located in the part. As will be described later, the ball screw 1 according to the present embodiment has two ball circulation paths for circulating the ball 19 infinitely, and the ball circulation tube 25 on one axial side is connected to the ball circulation path on one axial side. The ball circulation tube 25 on the other side in the axial direction is for circulating the ball 19 arranged on the ball circulation path on the other side in the axial direction.

  The ball circulation tube 25 is a member formed by bending a steel pipe into a U-shape. As shown in FIG. 2, the ball circulation tube 25 includes a horizontal portion 31 disposed on the flat portion 28 of the nut 13 so as to extend in parallel with the flat portion 28. , And a pair of vertical portions 34, 34 that extend smoothly downward from both ends of the horizontal portion 31. The interior of the horizontal portion 31 and the pair of vertical portions 34 constitutes a ball return path. Ball scooping portions 37 are formed at both ends of the ball circulation tube 25, that is, at the lower ends of the pair of vertical portions 34, 34, respectively.

  The pair of vertical portions 34, 34 of the ball circulation tube 25 and the respective ball scooping portions 37 are attached to the nut 13 by being fitted into a pair of ball circulation holes 40, 40 formed on the upper portion of the nut 13, respectively. I have. Each of the ball circulation holes 40 extends vertically through the upper part of the nut 13 from the flat portion 28 and opens to the ball rolling path 16. When the pair of vertical portions 34, 34 are fitted into the pair of ball circulation holes 40, 40, the ball scooping portions 37 are respectively arranged at predetermined positions of the ball rolling path 16. The ball circulation tube 25 and the portion of the ball rolling path 16 between the ball scooping portions 37 at both ends of the ball circulation tube 25 form a circuit 43 (46) that is a ball circulation path for infinitely circulating the ball 19. Is done.

  Since the ball screw 1 according to the present embodiment includes two ball tubes 25, as shown in FIG. 2, the ball circulation tube 25 on one side in the axial direction and the ball circulation tube 25 on one side in the axial direction A portion of the ball rolling path 16 defined by the ball scooping portions 37, 37 forms a ball circulation path 43 on one side in the axial direction (hereinafter, referred to as a “first circuit 43”), and the other side in the axial direction. And the ball rolling path 16 defined by the ball scooping portions 37 at both ends of the ball circulation tube 25 on the other side in the axial direction. Hereinafter, referred to as “second circuit 46”). The plurality of balls 19 are arranged on the first circuit 43 and the second circuit 46.

  When the screw shaft 7 is rotated, the ball 19 moves by rolling on each ball rolling path 16 of the first circuit 43 and the second circuit 46. When the ball 19 that has rolled on each ball rolling path 16 reaches one ball scooping section 37 of the corresponding ball circulation tube 25, the ball scooping section 37 moves the ball 19 to the inside of the ball circulation tube 25, that is, to the ball return path. The ball is guided, rolls on the ball return path, and is returned from the other ball scooping section 37 to a predetermined position on the ball rolling path 16. When the screw shaft 7 is rotated, the ball 14 circulates in the first circuit 43 and the second circuit 46 in this way, whereby the nut 13 moves in the axial direction of the screw shaft 7.

  As shown in FIG. 2, the ball screw 1 has a ball non-circulation portion 49 between the first circuit 43 and the second circuit 46 where the ball 19 does not circulate. The ball non-circulation portion 49 is a portion of the thread groove 10 of the nut 13 between the first circuit 43 and the second circuit 46 (hereinafter, the portion of the thread groove 10 of the nut 13 is referred to as a “circuit outside thread groove 52”). ) And a portion of the screw groove 4 of the screw shaft 7 which faces the outer circuit screw groove 52 of the nut 13. The ball 19 is not disposed in the ball non-circulation portion 49.

  As shown in FIGS. 1 and 3, a tube pressing member 55 extending in the axial direction is disposed outside of the two ball circulation tubes 25 in contact with the two ball circulation tubes 25. In FIG. 2, the illustration of the tube pressing member 55 is omitted. The tube pressing member 55 is fixed to the flat portion 28 of the nut 13. The tube holding member 55 prevents the two ball circulation tubes 25 from coming out of the nut 13 in the radial direction.

  As shown in FIG. 3, a through hole 58 in the vertical direction, that is, in the radial direction, is formed in the tube pressing member 55 at the center and near both ends. In the upper part of the nut 13, a radial screw hole 61 (see FIG. 4) having an internal thread formed on the inner peripheral surface is formed at a position corresponding to each through hole 58 of the tube holding member. Each screw hole 61 of the nut 13 is formed by penetrating the nut in the radial direction from the outer peripheral surface to the inner peripheral surface of the nut 13. Specifically, each screw hole 61 of the nut 13 penetrates the upper part of the nut 13 in the vertical direction, that is, in the radial direction from the flat surface portion 28, and opens to the screw groove 10 of the nut 13.

  Each of the screw holes 61 of the nut 13 is open to the screw groove 10 at a position different from that of the first circuit 43 and the second circuit 46. Specifically, the screw hole 61 of the nut 13 corresponding to the through hole 58 at one axial end of the tube pressing member 55 is opened to the screw groove 10 at a position on one axial side of the first circuit 43. I have. A screw hole 61 of the nut 13 corresponding to the through hole 58 on the other axial side of the tube pressing member 55 is open to the screw groove 10 at a position on the other axial side of the second circuit 46. The screw hole 61 of the nut 13 corresponding to the through hole 58 at the center of the tube holding member 55 is opened to the screw groove 10 at a position between the first circuit 43 and the second circuit 46, that is, at the ball non-circulation portion 49. ing.

  In the ball screw 1 according to the present embodiment, as shown in FIG. 3, bolts 64 are inserted into the through holes 58 on both ends of the tube pressing member 55, and the bolts 64 are tightened in the screw holes 61 of the nut 13. The tube holding member 55 is fixed to the nut 13. As shown in FIGS. 3 and 4, a contact-type sensing sensor 67 is attached to the through hole 58 at the center of the tube pressing member 55. As the contact-type sensing sensor 67, for example, a micro switch is attached. The sensing sensor 67 or the holder of the sensing sensor 67 has an external thread formed on the outer peripheral side, and is fixed to the nut 13 by being tightened into an internal thread of the screw hole 61 of the nut 13. The contact-type sensing sensor 67 is a sensor for detecting the ball 19a existing in the ball non-circulation portion 49, as described later.

  In the detection sensor 67, the detection unit 70 at the tip projects radially inward from the bottom surface of the screw groove 10 of the nut 13, that is, toward the screw shaft 7, and the bottom surface of the screw groove 10 of the nut 13 and the screw groove 4 of the screw shaft 7. The nut 13 is attached to the screw hole 61 of the nut 13 so as to be disposed at an intermediate position with respect to the bottom surface of the nut 13 or at a position closer to the bottom surface of the screw groove 4 of the screw shaft 7. The upper end of the sensing sensor 67 is formed in a size to close the through hole 58 of the tube holding member 55 as shown in FIG. 4 in a state where the sensing sensor 67 is attached to the screw hole 61 of the nut 13. .

  The three through-holes 58 of the tube pressing member 55 and the screw holes 61 of the nut 13 corresponding to these through-holes 58 are originally formed to tighten bolts 64 for fixing the tube pressing member 55 to the nut 13. It is a thing. In the present embodiment, the ball 19a existing in the ball non-circulating portion 49 is detected by using the central screw hole 61 opened to the ball non-circulating portion 49 among the screw holes 61 of the nut 13. Sensor 67 for the purpose.

Next, an assembly process of the ball screw 1 according to the present embodiment will be described.
First, the screw shaft 7 is inserted through the nut 13 to which the ball circulation tube 25 is not attached. Next, with the screw shaft 7 being inserted through the nut 13, a plurality of balls 19 are filled in the ball rolling path 16 constituting the first circuit 43. The ball rolling path 16 is filled with the ball 19 through the ball circulation hole 40 (see FIGS. 1 and 2). Further, the inside of the ball circulation tube 25 constituting the first circuit 43 is also filled with the plurality of balls 19. Thereafter, the pair of vertical portions 34, 34 of the ball circulation tube 25 filled with the balls 19 are fitted into the pair of ball circulation holes 40, 40, respectively, and the ball circulation tube 25 is attached to the nut 13. At this time, the end of each vertical portion 34 is pressed with grease or the like so that the ball 19 does not drop from the ball circulation tube 25.

  The ball rolling path 16 and the ball circulation tube 25 constituting the second circuit 46 are also filled with a plurality of balls 19 similarly to the first circuit 43, and a pair of vertical portions of the ball circulation tube 25 filled with the balls 19 are provided. The ball circulation tube 25 is attached to the nut 13 by inserting the ball circulation tubes 25 into the pair of ball circulation holes 40, 40, respectively.

  After that, the tube pressing member 55 is fixed to the nut 13. Bolts 64 are inserted into the through holes 58 at both ends of the tube pressing member 55, and each bolt 64 is tightened into the screw hole 61 of the nut 13. Finally, the contact sensor 67 is inserted into the through hole 58 at the center of the tube pressing member 55, and the sensor 67 is fastened to the screw hole 61 of the nut 13, and the sensor 67 is fixed to the nut 13. Thus, the ball screw 1 according to the present embodiment is assembled.

  Next, a method of detecting the ball 19a existing in the ball non-circulation portion 49 of the ball screw 1 will be described. The ball 19a existing in the ball non-circulation portion 49 is referred to as an "out-of-circuit ball 19a". The detection of the out-of-circuit ball 19a can be performed as a product inspection after the assembling in the above-described assembling process, or can be performed during normal use of the ball screw 1.

  In the process of assembling the ball screw 1, if the ball 19 enters the ball non-circulation portion 49 for some reason and the ball screw 1 is assembled as it is, as shown in FIG. The ball 19a will be present. In the detection inspection of the ball 19a outside the circuit after the assembling process of the ball screw 1, the contact type sensor 67 is connected to a receiving device (not shown) of the signal transmitted from the sensor 67, and the screw shaft 7 is rotated. This is done by causing When the screw shaft 7 of the ball screw 1 is rotated, the ball 19a outside the circuit rolls on the ball non-circulation portion 49 and comes into contact with the detection portion 70 of the detection sensor 67. Then, a predetermined signal is transmitted from the sensing sensor 67, and the presence of the off-circuit ball 19a in the ball non-circulation portion 49 is easily and reliably detected. If the non-circuit ball 19a does not exist in the ball non-circulation portion 49, the sensor 67 does not transmit a signal no matter how much the screw shaft 7 is rotated.

  As described above, according to the present embodiment, it is possible to reliably detect the presence of the out-of-circuit ball 19a during product inspection. As a result, it is possible to prevent the ball screw 1 in which the ball 19a outside the circuit exists in the ball non-circulation portion 49 from being shipped as a finished product. According to the present embodiment, it is also possible to automatically detect the out-of-circuit ball 19a. As a result, the inspection efficiency can be improved.

  Even in the case of the ball screw 1 for which the presence of the ball 19a outside the circuit has not been confirmed at the time of the product inspection, the ball screw 1 may be subjected to some impact or the ball scooping portion 37 of the ball circulation tube 25 during normal use after being assembled to a mechanical device or the like. There is a possibility that the ball 19 enters the ball non-circulation portion 49 due to damage or the like. The ball screw 1 according to the present embodiment can immediately detect that the ball 19 has entered the ball non-circulation portion 49 by operating the detection sensor 67 even during normal use. When operating the sensor 67 during normal use, it is preferable to provide a control device (not shown) or an alarm device (not shown) that outputs an alarm when a signal transmitted from the sensor 67 is received.

  When the ball 19 enters the ball non-circulating portion 49 during normal use of the ball screw 1 and the screw shaft 7 rotates in this state, the ball 19a outside the circuit rolls on the ball non-circulating portion 49 and contacts the sensing sensor 67. I do. Then, a signal is transmitted from the sensing sensor 67, and a warning is transmitted from a control device or a warning device (not shown). Thus, the user of the ball screw 1 can immediately know that the ball 19 has entered the ball non-circulation portion 49.

  As described above, according to the present embodiment, it is possible to immediately detect that the ball 19 has entered the ball non-circulation portion 49 during normal use of the ball screw 1. As a result, it is possible to minimize the spread of trouble to the mechanical device or the like to which the ball screw 1 is attached due to the locking of the ball screw 1 or the like.

(2nd Embodiment)
Next, a second embodiment of the present invention will be described.
The ball screw 101 according to the second embodiment will be described mainly with respect to a configuration different from the first embodiment, and the same configuration as the first embodiment will be described with reference to FIGS. 1 to 4 used in the description of the first embodiment. The same reference numerals as those in the first embodiment are used, and duplicate description is omitted.

FIG. 5 is a cross-sectional view of a main part of the ball screw 101 according to the second embodiment, and is a cross-sectional view similar to FIG. 4 of the first embodiment.
The ball screw 101 according to the present embodiment is different from the first embodiment in a sensor for detecting the presence of the ball 19a outside the circuit. That is, in the present embodiment, a non-contact type sensor 167 is attached to the nut 13 as a sensor for detecting the presence of the out-of-circuit ball 19a. As the non-contact type sensor 167, for example, an inductive proximity sensor is attached. The non-contact type sensor 167 is attached to the bolt hole 61 of the nut 13 such that the detection unit 170 at the tip is located above the bottom surface of the thread groove 10 of the nut 13. That is, the detection portion 170 of the detection sensor 167 does not protrude from the bottom surface of the thread groove of the nut 13 toward the screw shaft 7. Other configurations are the same as those of the ball screw 1 according to the first embodiment.

  In the present embodiment, when the screw shaft 7 is driven at the time of product inspection after the ball screw 101 assembling process, the ball 19a outside the circuit rolls on the ball non-circulating portion 19 and passes under the detecting portion 170 of the sensing sensor 167. pass. Then, a predetermined signal is transmitted from the sensing sensor 167, and the presence of the off-circuit ball 19a in the ball non-circulation portion 49 is easily and reliably detected. If there is no ball 19a outside the circuit in the ball non-circulation portion 49, the sensor 167 does not transmit a signal no matter how much the screw shaft 7 is rotated. In addition, even during normal use, when the ball 19 enters the ball non-circulation portion 49 and then the screw shaft 7 rotates, the ball 19a outside the circuit passes below the detection portion 170 of the detection sensor 167. Thus, the user of the ball screw 101 can immediately know that the ball 19 has entered the ball non-circulation portion 49. Thus, also in the present embodiment, the presence of the off-circuit ball 19a can be reliably detected as in the first embodiment.

  Various sensors can be used as the contact-type sensor 67 of the first embodiment and the non-contact-type sensor 167 of the second embodiment as long as the contact or approach of the ball 19a outside the circuit can be detected. The present invention is also applicable to a ball screw having three or more circuits. In this case, a contact type or non-contact type detection sensor may be attached to each ball non-circulation portion 49.

1, 101 ball screw device 4 (screw shaft side) screw groove 7 screw shaft 10 (nut side) screw groove 13 nut 16 ball rolling path 19 ball 19a outer circuit ball 22 flange 23 sealing member 25 ball circulation tube 28 plane portion 31 Horizontal part 34 Vertical part 37 Ball scooping part 40 Ball circulation hole 43 First circuit 46 Second circuit 49 Ball non-circulation part 52 Circuit outside screw groove 55 Tube holding member 58 Through hole 61 Screw hole 64 Bolt 67, 167 Sensing sensor 70 , 170 detector

Claims (7)

A screw shaft extending linearly and having a thread groove formed on an outer peripheral surface thereof;
A screw groove facing the screw groove of the screw shaft is provided on the inner peripheral surface, and is arranged so as to be rollable on a ball rolling path formed by the screw groove of the inner peripheral surface and the screw groove of the screw shaft. A nut fitted on the screw shaft via a plurality of balls,
A plurality of tube members fixed to the nut, for returning the plurality of balls to a predetermined position of the ball rolling path,
A plurality of circuits for ball circulation are formed by each of the tube members and a portion of the ball rolling path between both end portions of each of the tube members,
The plurality of balls are ball screws arranged on the plurality of circuits,
A ball screw further comprising a sensor for detecting an off-circuit ball existing in a ball non-circulation portion formed by a portion of the ball rolling path between the adjacent circuits.   The nut has a through-hole that penetrates the nut in the radial direction and opens in a thread groove portion of the nut corresponding to the ball non-circulation portion, and the sensor is attached to the through-hole. The ball screw according to claim 1, wherein:   The ball screw according to claim 1, wherein the sensor detects the out-of-circuit ball when the out-of-circuit ball contacts the sensor.   The ball screw according to claim 1, wherein the sensor detects the out-of-circuit ball when the out-of-circuit ball approaches the sensor. A screw shaft extending linearly and having a thread groove formed on an outer peripheral surface thereof;
A screw groove facing the screw groove of the screw shaft is provided on the inner peripheral surface, and is arranged so as to be rollable on a ball rolling path formed by the screw groove of the inner peripheral surface and the screw groove of the screw shaft. A nut fitted on the screw shaft via a plurality of balls,
A plurality of tube members fixed to the nut, for returning the plurality of balls to a predetermined position of the ball rolling path,
A plurality of circuits for ball circulation are formed by the tube members and a portion of the ball rolling path between both end portions of the tube members,
The plurality of balls are ball screws arranged on the plurality of circuits,
A ball screw detection method of a ball screw for detecting an out-of-circuit ball present in a ball non-circulation portion formed by a portion of the ball rolling path between adjacent circuits,
In the nut, the nut is radially penetrated, and a through hole is formed in a thread groove portion of the nut corresponding to the ball non-circulation portion, and a through hole is formed. A method for detecting an out-of-circuit ball of a ball screw, comprising detecting the out-of-circuit ball by rotating and rolling the out-of-circuit ball.   The method of claim 5, wherein the sensor detects the out-of-circuit ball by contacting the out-of-circuit ball with the sensor.   The method according to claim 5, wherein the sensor detects the out-of-circuit ball when the out-of-circuit ball approaches the sensor.

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