Piece type ball screw

Abstract

To provide a piece type ball screw capable of adjusting a position of a piece after checking the smoothness of actuation of a ball.SOLUTION: A piece type ball screw 10 includes a nut 20, a screw shaft 30, a plurality of balls 40, a piece 50, a sleeve 60, and a set screw 70. The nut 20 includes a first screw groove 25 provided on an inner peripheral surface, and a mounting hole 27 penetrating in a radial direction. The screw shaft 30 includes a second screw groove 35 provided on an outer peripheral surface and penetrates the nut 20. The plurality of balls 40 are disposed between the first screw groove 25 and the second screw groove 35. The piece 50 is disposed in the mounting hole 27 and circulates the balls 40. The sleeve 60 is a cylindrical member to be fitted with the outer peripheral surface of the nut 20, and includes a female screw 61 penetrating in a radial direction and overlapping with the piece 50. The set screw 70 is mounted to the female screw 61 and contacts with the piece 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a ball screw. [Background technology]

[0002] There is known a ball screw that includes a nut, a screw shaft that passes through the nut, and a number of balls that are arranged between the nut and the screw shaft. One type of ball screw known is a top-type ball screw that circulates balls using a top fitted in the nut. Patent Document 1 describes an example of a top-type ball screw. The top-type ball screw of Patent Document 1 can reduce vibrations that occur during operation by forming the joint between the screw groove of the nut and the groove of the top with an elastic member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-138179 A Summary of the Invention [Problem to be solved by the invention]

[0004] The top as described in Patent Document 1 is fixed to the nut with an adhesive. Therefore, if a malfunction in the operation of the ball is discovered after the top is fixed to the nut, it is necessary to remove the adhesive and then reattach the top to the nut. This can make the assembly work of the top-type ball screw complicated.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a top-type ball screw in which the position of the top can be adjusted after checking the smoothness of the ball operation. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the top-type ball screw disclosed herein comprises a nut having a first screw groove provided on its inner surface and a mounting hole penetrating radially, a screw shaft having a second screw groove provided on its outer surface and penetrating the nut, a plurality of balls arranged between the first screw groove and the second screw groove, a top arranged in the mounting hole and circulating the balls, a cylindrical member fitted to the outer circumferential surface of the nut, a sleeve having a female thread that penetrates radially and overlaps with the top, and a set screw that is attached to the female thread and contacts the top.

[0007] As a result, after the balls are loaded between the first and second screw grooves, the radial position of the top can be adjusted by changing the amount of insertion of the set screw into the female thread. Therefore, the top-type ball screw of the present disclosure allows the position of the top to be adjusted after checking the smoothness of the ball operation.

[0008] In a preferred embodiment of the above-mentioned set screw, the set screw has an adhesive applied to its outer circumferential surface.

[0009] As a result, if the adhesive hardens after it has been confirmed that the balls operate with the desired smoothness, the position of the top is maintained. Therefore, the top-type ball screw of the present disclosure can maintain the state in which the balls operate with the desired smoothness.

[0010] In a preferred embodiment of the above-mentioned set screw, the set screw has a resin coating on its outer circumferential surface, the resin coating including microcapsules filled with adhesive.

[0011] In this way, once it has been confirmed that the balls operate with the desired smoothness, the position of the top is maintained when the adhesive from the microcapsules hardens. Therefore, the top-type ball screw of the present disclosure can maintain the state in which the balls operate with the desired smoothness.

[0012] In a preferred embodiment of the above-mentioned top type ball screw, the set screw has a protrusion that narrows radially inward, and the top has a recess into which the protrusion fits.

[0013] As a result, the set screw restricts the circumferential movement of the top, and therefore the top-type ball screw of the present disclosure can suppress circumferential wobble of the top even if there is a gap between the inner wall of the mounting hole and the top. Effect of the Invention

[0014] According to the top-type ball screw of the present disclosure, the position of the top can be adjusted after checking the smoothness of the ball operation. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of the ball screw of this embodiment. [Diagram 2] FIG. 2 is a bottom view of the top of the present embodiment. [Diagram 3] FIG. 3 is a side view of the sleeve of the present embodiment. [Figure 4] FIG. 4 is a front view of the sleeve of the present embodiment. [Diagram 5] FIG. 5 is a schematic diagram for explaining a method for manufacturing the ball screw of this embodiment. [Figure 6] FIG. 6 is a schematic diagram for explaining a method for manufacturing the ball screw of this embodiment. [Figure 7] FIG. 7 is a schematic diagram for explaining the manufacturing method of the ball screw of this embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a modified top and set screw. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the following modes for carrying out the invention (hereinafter, referred to as embodiments). Furthermore, the components in the following embodiments include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be appropriately combined.

[0017] (Embodiment) FIG. 1 is a cross-sectional view of the top type ball screw of this embodiment. FIG. 2 is a bottom view of the top of this embodiment. FIG. 3 is a side view of the sleeve of this embodiment. FIG. 4 is a front view of the sleeve of this embodiment. The top type ball screw 10 is a device that converts rotational motion into linear motion. As shown in FIG. 1, the top type ball screw 10 of this embodiment includes a nut 20, a screw shaft 30, a plurality of balls 40, a top 50, a sleeve 60, and a set screw 70.

[0018] In the top type ball screw 10, the screw shaft 30 rotates around the rotation axis Z. For example, the screw shaft 30 is supported by a support structure so that it can rotate around the rotation axis Z but does not move in a direction along the rotation axis Z. The nut 20 is supported by a support structure so that it does not rotate around the rotation axis Z but moves in a direction along the rotation axis Z. When the screw shaft 30 rotates, the nut 20 moves in a direction along the rotation axis Z. For example, the top type ball screw 10 is applied to a conveying device. Note that the application of the top type ball screw 10 is not particularly limited. Note that in the top type ball screw 10, the nut 20 may rotate and the screw shaft 30 may move in a direction along the rotation axis Z.

[0019] In the following description, the direction along the rotation axis Z of the screw shaft 30 is simply referred to as the axial direction. The direction perpendicular to the axial direction is simply referred to as the radial direction. The radial direction is also called the radial direction. The direction along the cylinder centered on the rotation axis Z is simply referred to as the circumferential direction.

[0020] As shown in FIG. 1, the nut 20 includes a main body 21, a flange 23, a first screw groove 25, and a mounting hole 27. The main body 21 is a cylindrical member. The flange 23 is disposed at one end of the main body 21 in the axial direction. The flange 23 extends from the main body 21 toward the outside in the radial direction. The flange 23 is an annular member. The first screw groove 25 is disposed on the inner circumferential surface of the main body 21. The first screw groove 25 is a spiral groove. The first screw groove 25 is continuously provided from one end to the other end in the axial direction of the main body 21. For example, the cross-sectional shape of the first screw groove 25 is a Gothic arch including two arcs. The mounting hole 27 is a hole that penetrates the main body 21 in the radial direction. The mounting hole 27 is circular when viewed from the radial direction. The nut 20 includes three female threads 61. The three mounting holes 27 are disposed offset from each other in the axial direction. The three mounting holes 27 are disposed at equal intervals in the circumferential direction.

[0021] As shown in FIG. 1, the screw shaft 30 penetrates the nut 20. The screw shaft 30 has a second screw groove 35 on its outer circumferential surface. The second screw groove 35 is a spiral groove. For example, the cross-sectional shape of the second screw groove 35 is a Gothic arch including two circular arcs. The pitch of the second screw groove 35 is equal to the pitch of the first screw groove 25.

[0022] 1, a plurality of balls 40 are disposed between the first screw groove 25 and the second screw groove 35. The balls 40 move along a rolling path formed by the first screw groove 25 and the second screw groove 35.

[0023] 1, top 50 is placed in mounting hole 27 of nut 20. Top 50 is mounted in mounting hole 27 so as to be movable radially inside mounting hole 27. For example, top 50 is clearance-fitted into mounting hole 27. Top 50 is pushed radially outward by balls 40, and therefore does not fall out radially inward from mounting hole 27.

[0024] The top 50 is a member for circulating the balls 40. As shown in Fig. 2, the top 50 has a circulation groove 51 facing the screw shaft 30. The circulation groove 51 connects one end and the other end of a portion of the first screw groove 25 that makes approximately one revolution in the circumferential direction. The circulation groove 51 has a depth sufficient to allow the balls 40 that reach the circulation groove 51 to climb over the land portion of the screw shaft 30. The circulation groove 51 allows the balls 40 to circulate endlessly in the rolling path.

[0025] As shown in FIG. 1, the sleeve 60 is a cylindrical member fitted onto the outer circumferential surface of the main body 21 of the nut 20. The sleeve 60 is fixed to the main body 21. For example, the sleeve 60 is press-fitted onto the outer circumferential surface of the main body 21. The sleeve 60 has an internal thread 61 penetrating in the radial direction. When viewed from the radial direction, the internal thread 61 overlaps with the top 50 of the nut 20. As shown in FIGS. 3 and 4, the sleeve 60 has three internal threads 61. The three internal threads 61 are arranged corresponding to the three mounting holes 27. The three internal threads 61 are arranged offset from one another in the axial direction. The three internal threads 61 are arranged at equal intervals in the circumferential direction.

[0026] The set screw 70 is a member for stopping the movement of the top 50. As shown in FIG. 1, the set screw 70 is attached to the female thread 61. The set screw 70 protrudes radially inward from the sleeve 60. The radially inner tip of the set screw 70 contacts the outer peripheral surface of the top 50. For example, the tip of the set screw 70 is a flat surface. By contacting the outer peripheral surface of the top 50, the set screw 70 restricts the movement of the top 50 radially outward.

[0027] 5 to 7 are schematic diagrams for explaining the manufacturing method of the top type ball screw of this embodiment. In the manufacturing method of the top type ball screw 10 of this embodiment, first, the top 50 is attached to the mounting hole 27 of the nut 20 as shown in Fig. 5. For example, the top 50 is loosely fitted into the inside of the mounting hole 27. The top 50 is temporarily fixed in the mounting hole 27 by a jig or the like.

[0028] After the top 50 is attached to the mounting hole 27, the sleeve 60 is attached to the body 21 of the nut 20 as shown in Fig. 6. The sleeve 60 is attached so that the three female threads 61 overlap the top 50 when viewed from the radial direction. For example, the sleeve 60 is press-fitted onto the outer circumferential surface of the body 21. The sleeve 60 is positioned in the axial and circumferential directions by friction generated between the sleeve 60 and the body 21.

[0029] After the sleeve 60 is attached to the nut 20, as shown in FIG. 7, the set screw 70 is attached to the female thread 61. For example, the set screw 70 is inserted into the female thread 61 with an adhesive applied thereto. The adhesive applied to the set screw 70 is an adhesive that takes a predetermined time or more to harden. Therefore, when the set screw 70 is inserted into the female thread 61, the set screw 70 can move relative to the female thread 61.

[0030] After the set screw 70 is attached to the female thread 61, the balls 40 are inserted into the first screw groove 25. A temporary shaft is used to insert the balls 40 into the first screw groove 25. The temporary shaft is a cylindrical member having an outer diameter smaller than that of the screw shaft 30. More specifically, the outer diameter of the temporary shaft is smaller than the diameter of a circle passing through the radially inner ends of the plurality of balls 40 arranged between the first screw groove 25 and the second screw groove 35 when the ball screw 10 is viewed from the axial direction. With the temporary shaft inserted into the nut 20, the balls 40 are inserted into the gap between the temporary shaft and the nut 20. Then, after a predetermined number of balls 40 are filled between the temporary shaft and the nut 20, the screw shaft 30 connected to the temporary shaft is slid in the axial direction, so that the temporary shaft is replaced with the screw shaft 30. As a result, a state is created in which a plurality of balls are filled between the first screw groove 25 of the nut 20 and the second screw groove 35 of the screw shaft 30.

[0031] After all the balls are filled between the nut 20 and the screw shaft 30, the nut 20 or the screw shaft 30 is rotated to check the operation of the balls 40. If vibrations or the like occur in the balls 40 when the nut 20 or the screw shaft 30 is rotated, the setscrews 70 are operated to adjust the positions of the tops 50. The positions of all the tops 50 are adjusted so that all the balls 40 operate smoothly. After it is confirmed that the balls 40 operate with the desired smoothness, the adhesive applied to the setscrews 70 hardens, and the positions of the tops 50 are maintained.

[0032] The top 50 may be press-fitted into the mounting hole 27. In this case, the friction generated between the top 50 and the mounting hole 27 by the press-fitting is adjusted to a level that allows the top 50 to move radially when pressed by the set screw 70.

[0033] The adhesive does not necessarily have to be applied directly to the outer peripheral surface of the set screw 70. For example, a resin coating containing microcapsules filled with adhesive may be provided on the outer peripheral surface of the set screw 70. In this case, when the set screw 70 is attached to the female thread 61, the microcapsules of the resin coating are broken, and the adhesive seeps out from the microcapsules and then hardens.

[0034] As described above, the top-type ball screw 10 includes the nut 20, the screw shaft 30, the balls 40, the top 50, the sleeve 60, and the set screw 70. The nut 20 includes the first screw groove 25 on the inner peripheral surface and the mounting hole 27 penetrating in the radial direction. The screw shaft 30 includes the second screw groove 35 on the outer peripheral surface and penetrates the nut 20. The balls 40 are disposed between the first screw groove 25 and the second screw groove 35. The top 50 is disposed in the mounting hole 27 and circulates the balls 40. The sleeve 60 is a cylindrical member fitted to the outer peripheral surface of the nut 20, and includes a female thread 61 penetrating in the radial direction and overlapping the top 50. The set screw 70 is attached to the female thread 61 and contacts the top 50.

[0035] As a result, after the balls 40 are loaded between the first screw groove 25 and the second screw groove 35, the radial position of the top 50 can be adjusted by changing the amount of insertion of the set screw 70 into the female thread 61. Therefore, with the top-type ball screw 10 of this embodiment, the position of the top 50 can be adjusted after checking the smoothness of the operation of the balls 40.

[0036] In the set screw 10, the set screw 70 has an adhesive applied to its outer circumferential surface.

[0037] As a result, if the adhesive hardens after it has been confirmed that the balls 40 move with the desired smoothness, the position of the top 50 is maintained. Therefore, the top-type ball screw 10 of this embodiment can maintain the state in which the balls 40 move with the desired smoothness.

[0038] In the set screw 10, the set screw 70 may have a resin coating on its outer circumferential surface, the resin coating including microcapsules filled with adhesive.

[0039] As a result, once it has been confirmed that the balls 40 operate with the desired smoothness, the adhesive from the microcapsules hardens, and the position of the top 50 is maintained. Therefore, the top-type ball screw 10 of this embodiment can maintain the state in which the balls 40 operate with the desired smoothness.

[0040] (Modification) Fig. 8 is a cross-sectional view of a top and a set screw of a modified example. The same components as those described in the above embodiment are given the same reference numerals, and duplicated explanations are omitted. As shown in Fig. 8, the top-type ball screw 10 of the modified example includes a top 50A and a set screw 70A.

[0041] The top 50A has a recess 53 on its radially outer surface. The recess 53 is, for example, a conical depression. The set screw 70A has a main body 71 and a protrusion 73. The main body 71 has a thread on its outer circumferential surface that meshes with the female thread 61. The outer diameter of the main body 71 is approximately constant. The protrusion 73 is disposed on the radially inner side of the main body 71. The protrusion 73 becomes thinner toward the radially inner side. The protrusion 73 is, for example, a conical protrusion. The outer diameter of the protrusion 73 becomes smaller toward the radially inner side. The protrusion 73 fits into the recess 53.

[0042] As described above, in the modified top type ball screw 10, the setscrew 70A has the projection 73 that tapers radially inward. The top 50A has the recess 53 into which the projection 73 fits.

[0043] As a result, the set screw 70A restricts the circumferential movement of the top 50A. Therefore, the modified top-type ball screw 10 can suppress the circumferential wobble of the top 50A even if there is a gap between the inner wall of the mounting hole 27 and the top 50A. [Explanation of symbols]

[0044] 10. Ball screw 20 Nut 21 Main body 23 Flange 25 First Thread Groove 27 Mounting hole 30 Screw shaft 35 Second screw groove 40 Ball 50, 50A top 51 Circulation groove 53 Recess 60 Sleeve 61 Female thread 70, 70A Set screw 71 Main body 73 Convex Z Rotation Axis

Claims

1. A nut having a first thread groove provided on an inner circumferential surface and a mounting hole passing through in a radial direction; A screw shaft having a second screw groove provided on an outer peripheral surface and penetrating the nut; A plurality of balls disposed between the first screw groove and the second screw groove; a top disposed in the mounting hole for circulating the balls; A sleeve is a cylindrical member fitted to the outer peripheral surface of the nut, the sleeve having a female thread that penetrates radially and overlaps with the top; a set screw attached to the female thread and contacting the top; A top-type ball screw equipped with a ball screw.

2. The set screw has an adhesive on its outer periphery.

2. The ball screw according to claim 1.

3. The set screw has a resin coating on its outer periphery, the resin coating including microcapsules filled with adhesive.

2. The ball screw according to claim 1.

4. The set screw has a protrusion that narrows radially inward, The top has a recess into which the protrusion fits.

4. The ball screw according to claim 1 ,

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