CN107269695B

CN107269695B - Ball screw

Info

Publication number: CN107269695B
Application number: CN201710201614.XA
Authority: CN
Inventors: 坂井哲也; 武石正和
Original assignee: Co Ltd No 1; Nippon Thompson Co Ltd
Current assignee: Co Ltd No 1; Nippon Thompson Co Ltd
Priority date: 2016-03-30
Filing date: 2017-03-30
Publication date: 2020-08-07
Anticipated expiration: 2037-03-30
Also published as: CN107269695A; TWI705205B; JP6777416B2; JP2017180665A; KR20170113364A; KR102300419B1; TW201734333A

Abstract

The ball screw is small in size by disposing a return plate (4) on the outer peripheral surface of a nut body (3), and lubrication-free maintenance is realized by disposing an oil-containing member (5) in the return plate (4) to supply oil to balls (9) rolling in a circulation path. A nut (3) to which a screw shaft (1) is fitted is composed of a nut body (3) having a spiral groove (12) formed therein and a return plate (4) disposed on the outer peripheral surface (27) thereof, and an oil-containing member (5) having an oil supply section (6) is disposed in a recess (28) of the return plate (4). The balls (9) rolling in a return path (13) formed by the nut body (3) and the return plate (4) and a direction turning loop (14) of the nut body (3) are in contact with an exposed end surface (34) of the oil supply portion (6), and the lubricant is supplied to the balls (9).

Description

Ball screw

Technical Field

The present invention relates to a ball screw which can be incorporated into and used in various devices such as an mechatronic product such as a precision positioning table and a detection device, and which has a grease supply unit including a screw shaft and a nut that moves relative to the screw shaft.

Background

Conventionally, as a linear motion device that stably supplies lubricant by a self-lubricating method, for example, a device disclosed in japanese patent application laid-open No. 2013-174255 has been known. The linear motion device is a ball screw driving device of an end cover deflection type circulation mode, and comprises: a nut having a spiral groove formed on an inner circumferential surface thereof; a screw shaft having a spiral groove formed on an outer circumferential surface thereof to face the spiral groove of the nut; and a plurality of balls that are inserted between spiral raceway surfaces formed by the spiral groove of the nut and the spiral groove of the screw shaft. In the interior of the nut, a return passage is formed on the surface thereof by integral injection molding with an oil-containing resin in the axial direction.

Further, the present applicant has developed a rolling guide unit in which the degree of freedom of design is enhanced, the management of the lubricating oil is simple, and the sliding resistance against the rolling elements is small, and has already filed a patent (for example, refer to japanese patent application laid-open No. 2006-38195). The rolling guide assembly includes: a cylinder member through which the crossbar is slidably inserted; a track path formed by the barrel member and the crossbar in combination; a circulation path which communicates both ends of a track path formed in the cylindrical member through the concave portion of the direction change path; and a plurality of rolling bodies that roll in the circulation path and the raceway path. The rolling guide assembly circulates the rolling bodies in a circulating path and an orbital path in accordance with the relative movement of the cross bar and the barrel member. The rolling guide assembly includes: the oil supply member is provided along a contact surface of the rolling element in the raceway path or the circulation path, and is brought into contact with the oil-containing member.

Further, as the ball screw, for example, a return plate type circulation screw device is disclosed in japanese patent application laid-open No. 11-210858. The circulation type screw device has a circulation structure of a rolling roller which is easy to manufacture and inexpensive while securing the characteristics of a low friction mechanism equivalent to a ball screw, and has a roller circulation path communicating with both ends of a roller rolling portion in a spiral groove of a nut body, and a roller circulation portion communicating with roller lifting portions at both ends thereof.

However, the linear motion device is formed integrally with the nut by injection molding the oleoresin material in the return passage of the nut. Since the oil-containing resin material is formed by mixing the resin material and the lubricating oil in advance and then injection molding the mixed material, the lubricating oil cannot be supplied when the capacity of the lubricating oil is small, and lubrication failure is likely to occur, and the oil-containing resin material needs to be injection molded integrally with the nut, which causes problems of high labor and high manufacturing cost. In the above-described rolling guide unit, the oil supply member is provided in the direction change path of the end cap of the ball spline, and the oil-containing member is provided in the outer cylinder, whereby the effect of lubrication-free maintenance is achieved. In addition, although the above-described circulating screw device is configured as a return plate type in which the rolling elements circulate, the rolling elements are rollers, and the lubricant cannot be supplied to the return plate.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide a ball screw in which a screw shaft having a row of spiral grooves formed therein is inserted into a nut having a row of spiral grooves formed on an inner peripheral surface thereof, and the nut is relatively moved on the screw shaft by balls serving as rolling bodies in a spiral raceway path formed between the two spiral grooves; a return plate having a return groove is disposed on a plane formed on a part of the outer peripheral surface of a nut corresponding to a return path formed on the nut, so that the device itself can be downsized in the longitudinal direction without changing the outer shape of a ball screw, an oil-containing member is disposed on the return plate, an oil supply portion provided in the oil-containing member is interposed between the return groove and a direction changing path, and balls rolling in the direction changing path and the return path are brought into contact with the oil supply portion to supply oil to the balls, thereby realizing lubrication-free maintenance.

The present invention relates to a ball screw, which comprises: a rotatable screw shaft having a row of first spiral grooves formed in an outer circumferential surface thereof in an axial direction, the first spiral grooves being formed by rolling balls as rolling bodies; and a cylindrical nut having a row of second spiral grooves formed on an inner circumferential surface thereof in an axial direction, the second spiral grooves being opposite to the first spiral grooves, and the cylindrical nut being inserted into the screw shaft by being screwed with the balls; it is constituted as follows: the nut moves on the screw shaft along the length direction along with the rotation of the screw shaft;

the nut includes: a cylindrical nut body having a second spiral formed on the inner circumferential surface, a first return groove formed on the outer circumferential surface and through which the balls roll, and a communication hole in which a direction change path that communicates the second spiral groove and the first return groove is formed; a return plate fixed to a mounting surface on an outer diameter side of the nut body and having a second return groove formed therein to face the first return groove; and an oil-containing member disposed in the recess inside the return plate and impregnated with a lubricant;

the oil-containing component, comprising: a main body portion disposed in the recess of the return plate and impregnated with a lubricant; and an oil supply portion that is disposed in a communication groove that communicates the recessed portion with the second return groove, and that protrudes from the main body portion toward the second return groove; the balls that roll between the direction change path and a return path formed by the first return groove and the second return groove contact an exposed end surface of the oil supply portion, so that the lubricant is supplied to the balls.

The ball screw has a flange portion formed with a mounting hole for mounting a fitting member.

In the ball screw, the mounting surface of the nut body on which the first return groove is formed as a quadrangular plane, an inner side surface of the return plate facing the mounting surface is formed as a quadrangular plane disposed on the quadrangular plane, an outer peripheral surface of the return plate is formed as a surface having an arc-shaped cross section, and the nut is formed as a substantially circular cylindrical body in a state where the return plate is disposed on the nut body.

In addition, the first return groove and the second return groove are formed on the quadrangular planes of the nut main body and the return plate, respectively, and are inclined in the axial direction, and the return paths formed by the first return groove and the second return groove communicate with the direction change path formed at each end of the second spiral groove extending in a spiral shape on the inner circumferential surface of the nut main body, respectively.

Further, the ball rolls in a circulation path including three of a spiral track path formed by the first spiral groove of the screw shaft and the second spiral groove of the nut body, a pair of direction change paths formed in the nut body and communicating with both ends of the track path, and the return path communicating with the direction change paths, as the screw shaft rotates, and the nut moves relative to the screw shaft by the ball.

In the oil-impregnated member disposed in the recess of the return plate, the outer peripheral surface on the return plate side is formed as a surface having an arc-shaped cross section, and the inner peripheral surface on the nut body side is formed as a flat surface.

In the ball screw, the second return groove is formed in the concave portion formed in the return plate, and the oil-containing member disposed in the concave portion is formed as a single piece and is communicated with the second return groove through the communication groove formed in each of both end portions of the wall portion of the second return groove. The concave portion formed in the return plate is divided into two parts along the longitudinal direction with a wall portion forming the second return groove as a boundary, the oil-containing member is formed as two oil-containing members respectively disposed in the concave portion divided into two parts, and the oil supply portion is formed in each of the two oil-containing members.

The screw shaft is a ball screw shaft of a round shaft type having both ends rotatably supported. In addition, annular fitting portions into which seal rings for sealing a gap between the screw shaft and the nut are fitted are formed at both end portions of the nut body.

The oil-containing member and the oil-supplying member are formed of a porous molded body formed by compacting and then thermoforming fine synthetic resin particles of polyethylene or polypropylene and having porous portions that maintain communication between the fine synthetic resin particles, and the porous portions are impregnated with the lubricant.

In the ball screw according to the present invention, the return plate forming the return path is disposed on the outer peripheral surface of the nut main body, the outer shape of the ball screw is not required to be changed in the ball screw formed in a small diameter size, the oil-containing member is disposed in the recess of the return plate, the nut main body and the return plate form the direction change path communicating the spiral groove and the return path, the oil supply portion provided in the oil-containing member is positioned at the boundary between the nut main body and the return plate, and the balls as the rolling bodies rolling between the direction change path and the return path are brought into contact with the oil supply portion to supply the lubricant to the balls, thereby achieving lubrication-free maintenance. Further, in the ball screw, since the oil-impregnated member is disposed by providing the recess in the return plate and the direction change path is provided in the nut body, the length direction can be shortened, and since the holding metal fitting for accommodating the lubricating member in the related art is not required, the stroke amount of the nut can be increased accordingly, the number of components can be reduced, and a contribution can be made to cost reduction, and since the space for holding the lubricating plate in the related art is not required, the components other than the lubricating member can be mounted in this portion. Further, since the return plate provided in the nut main body is not inserted into the threaded shaft, even after the oil-containing member is assembled, the oil-containing member can be attached and detached only by detaching the return plate from the nut main body, and therefore, for example, the oil-containing member can be easily replaced with a new oil-containing member.

Drawings

Fig. 1 is a perspective view showing one embodiment of a ball screw of the present invention.

Fig. 2 is a perspective view showing the ball screw of fig. 1 with a part broken away.

Fig. 3 is a perspective view showing an embodiment of an oil-containing member and a nut body in a perspective view for explaining a screw shaft and a return plate of the ball screw of fig. 1.

Fig. 4 is a sectional view showing a state in which an oil-containing member having an oil supply part is disposed in a boundary region between a return path and a direction change path in a circulation path formed in a nut constituting the ball screw of fig. 1, and balls are lubricated.

Fig. 5 is a perspective view showing a state in which an oil-containing member is disposed on an inner peripheral surface side of an embodiment of a return plate attached to a nut main body constituting the ball screw of fig. 1.

Fig. 6 is a perspective view showing the outer peripheral surface side of the oil-impregnated member disposed in the recess of the return plate of fig. 5.

Fig. 7 is a perspective view showing the inner circumferential surface side after the oil-containing member is detached from the return plate of fig. 5.

Fig. 8 is a perspective view showing another embodiment of the oil-impregnated member and the nut main body in a perspective view for explaining the screw shaft and the return plate of the ball screw of fig. 1.

Fig. 9 is a perspective view showing another embodiment in which an oil-containing member is disposed in a recess of a return plate attached to a nut main body constituting the ball screw of fig. 1.

Fig. 10 is a perspective view showing the outer peripheral surface side of one of the two oil-impregnated members disposed in the recess of the return plate of fig. 9.

Fig. 11 is a perspective view showing the outer peripheral surface side of the other oil-impregnated member of the two sheets disposed in the concave portion of the return plate of fig. 9.

Fig. 12 is a perspective view showing the inner circumferential surface side after the oil-containing member is detached from the return plate of fig. 9.

Description of reference numerals

1: screw shaft

2: nut

3: nut body

4: return plate

5: oil-impregnated member (Single piece)

6: oil supply (for single sheet)

7(7A, 7B): oil-impregnated member (two pieces)

8: oil supply part (for two sheets)

9: rolling ball (Rolling element)

10: outer peripheral surface (screw shaft)

11: spiral groove (first spiral groove, screw shaft)

12: spiral groove (second spiral groove, nut main body)

13: return path (nut body)

14: direction change path (end cap)

15: spiral track path

16: circulation path

17: inner peripheral surface (nut main body)

18: end (nut main body)

19: sealing ring (set at two ends of nut main body)

20: flange part (nut main body)

21: mounting surface (nut main body)

22: inner side (Return board)

23: peripheral surface (Return board)

24: communicating groove (Return plate)

25: mounting hole (flange)

26: end (screw shaft)

27: outer peripheral surface (nut main body)

28: recessed portion (Single piece, return plate)

28T: concave part (two pieces, return plate)

29: first return groove (nut main body)

30: second return groove (return plate)

31: fixing screw (fixing nut main body and return plate)

32: wall parts (Return board)

33: inserting hole (nut body)

34: exposed end face (oil supply part)

35: concave part (oil-containing component, convex part embedded into return plate)

36: long hole (oil-containing part, wall part embedded into return groove)

37: end (second spiral groove)

38: end (spiral track path)

39: inner surface (oil-containing component)

40: ring-shaped fitting part (for fitting the end of the nut body and the seal ring)

41: intercommunicating pore (nut main body)

42: main body part (oil-containing component)

43: outer peripheral surface (oil-containing component)

44: hole for mounting (Return board)

45: bulge (Return plate)

46: end partition (return plate, two pieces)

47: groove (sealing ring)

Detailed Description

The ball screw according to the present invention is preferably applied to various apparatuses such as an mechatronic product such as a precision positioning table and a detection device.

Hereinafter, an embodiment of a ball screw according to the present invention will be described with reference to the drawings. First, an embodiment of a ball screw according to the present invention will be described with reference to fig. 1 to 7. The ball screw has: a rotatable screw shaft 1 having a single row of spiral grooves 11 (first spiral grooves) formed in an outer circumferential surface 10 in an axial direction, the spiral grooves rolling a plurality of balls 9 as rolling elements; and a cylindrical nut 2 having a spiral groove 12 (second spiral groove) formed in a row on an inner circumferential surface 17 (fig. 2) thereof in an axial direction so as to face the spiral groove 11, and having a ball 9 as a rolling element inserted and inserted into the screw shaft 1; the ball screw is configured as a return plate type in which the nut 2 moves in the longitudinal direction on the screw shaft 1 as the screw shaft 1 rotates. Nut 2, comprising: a cylindrical nut body 3 having a row of helical grooves 12 formed in an inner peripheral surface 17, return grooves 29 (first return grooves) formed in an outer peripheral surface 27, through which the balls 9 roll, and communication holes 41 in which direction change paths 14 are formed to communicate the helical grooves 12 and the return grooves 29, respectively; a return plate 4 fixed to a mounting surface 21 formed on an outer peripheral surface 27 on the outer diameter side of the nut body 3 and having a return groove 30 (second return groove) formed to face the return groove 29; and an oil-containing member 5 disposed in the recess 28 inside the return plate 4, having an outer surface 43 covered with the return plate 4, and impregnated with a lubricant. The spiral track path 15 is formed by the spiral groove 11 of the threaded shaft 1 and the spiral groove 12 of the nut body 3. The return path 13 is formed by the return groove 29 of the nut body 3 and the return groove 30 of the return plate 4. The spiral raceway path 15 and the return path 13 are communicated with each other by a direction change path 14 formed by a communication hole 41 formed in the nut body 3.

The screw shaft 1 is a round-shaft type ball screw shaft 1 having both end portions 26 rotatably supported. In addition, annular fitting portions 40 are formed at both end portions 18 of the nut body 3, and a seal ring 19 having a groove 47 formed on an inner peripheral surface is fitted to the annular fitting portions 40 so as to seal a gap between the threaded shaft 1 and the nut 2, and the groove 47 is fitted to the spiral groove 11 of the threaded shaft 1. The return plate 4 has a boss 45 formed with an attachment hole 44, and the return plate 4 is fixed to the nut body 3 by inserting the fixing screw 31 into the attachment hole 44 and screwing it into the attachment surface 21 of the nut body 3. The return groove 30 formed in the return plate 4 is formed at the periphery thereof with a partition wall 32 projecting from the recess 28, in other words, the return groove 30 is formed in the recess 28 of the return plate 4. The oil-containing member 5 disposed in the recess 28 is formed in a single piece. A communication groove 24 into which the oil supply portion 6 is fitted is formed in the wall portion 32 of the return plate 4 toward the return groove 30. The nut body 3 is formed with an insertion hole 33 into which the inner peripheral surface 17 of the screw shaft 1 is inserted, and the screw shaft 1 is inserted into and inserted through the nut body 3 by the balls 9 in the spiral track path 15 formed by the spiral groove 12 formed in the insertion hole 33 and the spiral groove 11 of the screw shaft 1.

The oil-containing member 5 includes a main body 42 impregnated with a lubricant and a pair of oil supply portions 6 protruding from the main body 42. The main body portion 42 of the oil-containing member 5 is disposed in the concave portion 28 of the return plate 4, and the oil supply portion 6 is disposed in the communication groove 24 that communicates the concave portion 28 of the return plate 4 with the return groove 30. The oil supply portion 6 disposed in the communication groove 24 is disposed such that the exposed end surface 34 protrudes into the return groove 30 to contact the balls 9 rolling in the return path 13. The main body 42 of the oil-impregnated member 5 is configured such that the return groove 30 is formed in an elongated hole 36, and the wall 32 of the return groove 30 of the return plate 4 is fitted into the elongated hole 36. The oil-impregnated member 5 is formed with a recess 35 into which the boss 45 of the return plate 4 is fitted. When the oil-containing member 5 is disposed in the recess 28 of the return plate 4, the elongated hole 36 of the oil-containing member 5 is fitted around the wall 32 constituting the return groove 30 of the return plate 4. The main body portion 42 of the oil-containing member 5 is disposed in the recess 28 of the return plate 4 in a state where the boss 45 of the return plate 4 is fitted into the recess 35 of the oil-containing member 5. In other words, the oil supply portion 6 disposed in the recess 28 of the return plate 4 is located between the attachment surface 21 of the nut body 3 and the inner surface 22 of the return plate 4 in the state of being attached to the nut body 3. The exposed end surface 34 of the oil supply portion 6 is exposed to the return path 13 in a state of being disposed and attached to the communication groove 24, so that the balls 9 rolling between the return path 13 and the direction change path 14 formed by the return groove 29 and the return groove 30 are in contact with the exposed end surface 34, and the lubricant is supplied to the balls 9.

The nut body 3 is provided with a flange portion 20 having a mounting hole 25 for mounting a mating member such as a workpiece or equipment. The mounting surface 21 formed on the outer peripheral surface 27 of the nut body 3 is a rectangular plane, and a row of return grooves 29 is formed. The inner surface 22 of the return plate 4 is formed as a quadrangular plane disposed on the quadrangular planar attachment surface 21, and the oil-impregnated member 5 is formed flush with the plane. The outer peripheral surface 23 of the return plate 4 is formed into a surface having an arc-shaped cross section, and the nut 2 is actually formed into a circular cylindrical body in a state where the return plate 4 is disposed on the nut body 3.

In this ball screw, the return groove 29 formed in the nut body 3 and the return groove 30 formed in the return plate 4 are formed on the quadrangular planes of the nut body 3 and the return plate 4 so as to be inclined in the longitudinal direction, which is the axial direction, respectively, and the return path 13 formed by the return groove 29 and the return groove 30 communicates with a pair of direction changing paths 14 serving as communication holes 41 formed at both end portions of the spiral groove 12 extending spirally on the inner peripheral surface 17 of the nut body 3, respectively.

Further, as the screw shaft 1 rotates, the balls 9 roll in the circulation path 16 formed of three of the spiral raceway path 15 formed by the spiral groove 11 of the screw shaft 1 and the spiral groove 12 of the nut main body 3, the pair of direction change paths 14 serving as the communication holes 41 formed in the nut main body 3 and communicating with both ends of the raceway path 15, and the return path 13 communicating with the direction change paths 14, whereby the nut 2 can smoothly move relatively to the screw shaft 1 via the balls 9.

In the oil-impregnated member 5 disposed in the recess 28 of the return plate 4, the outer surface 43 on the return plate 4 side is formed as a surface having an arc-shaped cross section, and the inner surface 39 on the nut body 3 side is formed as a flat surface. In the present embodiment, the single oil-impregnated member 5 is disposed in the recess 28 formed in the return plate 4. The return groove 30 formed in the return plate 4 is disposed to face the return groove 29 formed in the nut body 3, thereby forming the return path 13. In the ball screw, the oil-containing member 5 and the oil supply portion 6 are formed of a porous molded body formed by compacting and then heat-molding synthetic resin fine particles of polyethylene or polypropylene and having porous portions in which the synthetic resin fine particles are kept in communication with each other, and the lubricant is impregnated in the porous portions. Therefore, in the ball screw, since the return path 13 is formed by the return plate 4 and the outer peripheral surface 27 of the nut body 3, the balls 9 rolling in the return path 13 are in contact with the end surface 34 exposed to the return path 13 from the communication groove 24 of the concave portion 28 of the return plate 4, and the lubricant impregnated in the oil-containing member 5 and the oil supply portion 6 is supplied to the balls 9, and lubrication-free maintenance can be achieved. In the ball screw, for example, the shaft diameter of the screw shaft 1 may be Φ 6, the spiral grooves 11 formed in the outer peripheral surface 10 of the screw shaft 1 may be formed in a single row, and the lead may be 1 mm.

Next, another embodiment of the ball screw according to the present invention will be described with reference to fig. 8 to 12. In the second embodiment, the same components are given the same reference numerals and the description thereof is omitted, except that the oil-impregnated member 7 is formed as two pieces of the oil-impregnated

members

7A and 7B, as compared with the embodiment in which the oil-impregnated member 5 of the first embodiment is formed as a single piece. The ball screw according to the second embodiment is formed in a two-piece shape so that a large amount of lubricant is impregnated into the oil-impregnated

members

7A and 7B disposed in the recess 28T of the return plate 4. That is, the oil-containing

members

7A and 7B disposed in the recess 28T of the return plate 4 are divided into two parts in the longitudinal direction in the case where the lubricant is impregnated more than in the case of the first embodiment. In other words, the amount of lubricant that can be impregnated in the oil-containing

members

7A, 7B disclosed in the second embodiment is changed to a larger impregnation amount than the oil-containing member 7 disclosed in the first embodiment. Accordingly, the recess 28T formed in the return plate 4 is divided into two parts in the longitudinal direction with the wall 32 forming the return groove 30 as a boundary, and the oil-containing member 7 is formed as two oil-containing

members

7A and 7B. Further, the return plate 4 has an end partition wall 46 formed at an end opposite to the flange portion 20 to prevent the oil-impregnated member 7A disposed in the recess portion 28T from protruding from the end. The pair of oil-containing

members

7A and 7B are each formed with an oil supply portion 8. In the ball screw, as in the first embodiment, the oil-containing

members

7A and 7B and the oil supply portion 8 are formed of a porous molded body formed by compacting and then thermoforming fine synthetic resin particles of polyethylene or polypropylene and having porous portions in which the fine synthetic resin particles are kept in communication with each other, and the porous portions are impregnated with the lubricant. Therefore, in the ball screw, the return path 13 is formed by the return plate 4 and the outer peripheral surface 27 of the nut body 3, and the balls 9 rolling in the return path 13 are in contact with the end surface 34 exposed to the return path 13 from the communication groove 24 of the concave portion 28T of the return plate 4, so that the lubricant impregnated in the oil-containing

members

7A and 7B and the oil supply portion 8 is supplied to the balls 9, and lubrication-free maintenance can be achieved. In the ball screw, for example, the shaft diameter of the screw shaft 1 may be formed to be Φ 8, the spiral grooves 11 formed in the outer peripheral surface 10 of the screw shaft 1 may be formed in a row, and the lead may be formed to be 2 mm.

Claims

1. A ball screw is characterized in that,

it has the following components: a rotatable screw shaft having a row of first spiral grooves formed in an outer circumferential surface thereof in an axial direction, the first spiral grooves being formed by rolling balls as rolling bodies; and a cylindrical nut having a row of second spiral grooves formed on an inner circumferential surface thereof in an axial direction, the second spiral grooves being opposite to the first spiral grooves, and the cylindrical nut being inserted into the screw shaft by being screwed with the balls;

it is constituted as follows: the nut moves on the screw shaft along the length direction along with the rotation of the screw shaft;

the nut includes: a cylindrical nut body including a second spiral formed on the inner peripheral surface, a first return groove formed on an outer peripheral surface and through which the balls roll, and a communication hole in which a direction change path that communicates the second spiral groove and the first return groove is formed; a return plate fixed to a mounting surface on an outer diameter side of the nut body and having a second return groove formed therein to face the first return groove; and an oil-containing member disposed in the recess inside the return plate and impregnated with a lubricant;

the oil-containing component, comprising: a main body portion disposed in the recess of the return plate and impregnated with a lubricant; and an oil supply portion that is disposed in a communication groove that communicates the recessed portion with the second return groove, and that protrudes from the main body portion toward the second return groove; the balls that roll between the direction change path and a return path formed by the first return groove and the second return groove contact an exposed end surface of the oil supply portion, whereby the lubricant is supplied to the balls,

the nut body is formed such that the mounting surface on which the first return groove is formed is a quadrangular plane, the inner surface of the return plate facing the mounting surface is a quadrangular plane arranged on the quadrangular plane, the outer peripheral surface of the return plate is a surface having an arc-shaped cross section, and the nut is formed into a substantially circular cylindrical body in a state where the return plate is arranged on the nut body,

the oil-containing member disposed in the recess of the return plate has a return plate-side outer peripheral surface formed as a surface having an arc-shaped cross section, and a nut body-side inner peripheral surface formed as a flat surface.

2. The ball screw of claim 1,

the nut body has a flange portion formed with an attachment hole for attaching an engaging member.

3. The ball screw of claim 1,

the first return groove and the second return groove are formed on the quadrangular planes of the nut main body and the return plate, respectively, and are inclined in the axial direction, and the return paths formed by the first return groove and the second return groove communicate with the direction change path formed at each end of the second spiral groove extending in a spiral shape on the inner circumferential surface of the nut main body, respectively.

4. The ball screw of claim 3,

as the screw shaft rotates, the balls roll in a circulation path including three of a spiral track path formed by the first spiral groove of the screw shaft and the second spiral groove of the nut body, a pair of direction change paths formed in the nut body and communicating with both ends of the track path, and the return path communicating with the direction change paths, and the nut is relatively moved on the screw shaft by the balls.

5. The ball screw of claim 1,

the second return groove is formed in the concave portion formed on the return plate,

the oil-containing member disposed in the concave portion is formed as a single piece, and communicates with the second return groove via the communication groove, wherein the communication groove is formed at each of both end portions of a wall portion of the second return groove.

6. The ball screw of claim 1,

the concave portion formed on the return plate and divided into two parts along the longitudinal direction with a wall portion forming the second return groove as a boundary,

the oil-containing member is formed as two oil-containing members respectively disposed in the recesses divided into two parts, and the oil supply portions are formed on the two oil-containing members respectively.

7. The ball screw of claim 1,

the screw shaft is a ball screw shaft of a round shaft type having both ends rotatably supported.

8. The ball screw of claim 1,

annular fitting portions are formed at both end portions of the nut body, and seal rings for sealing a gap between the screw shaft and the nut are fitted to the annular fitting portions.

9. The ball screw of claim 1,