ball screw

Abstract

The present invention relates to a ball screw, wherein an end deflector (16) includes a main portion (30) comprising a ball delivery path (36) for delivering balls (28) between a rolling path (20) and a ball circulation path (24), a tongue (38) for guiding balls from the rolling path to the ball delivery path, and a pair of protruding portions (42, 44) that cooperate with the inner circumferential surface of a deflector holding recess (26) formed in a nut body to define ball guide grooves (40) extending between the ball delivery path and the rolling path, extending from both sides of the tongue in the axial direction toward the circumferential direction of the nut body (14). The main portion has an outer circumferential surface (30A) with an inner circumferential surface (54B). A front portion (30Aa) of the outer circumferential surface relative to the insertion direction of the deflector holding recess is offset radially inward. At least the outer peripheral surface along the rear side (30Ab) of the deflector retaining recess relative to the insertion direction of the deflector retaining recess is engaged with the inner peripheral surface of the deflector retaining recess.

Description

[0001] This application is a divisional application of the original invention patent application with application number 201780092369.1 (international application number: PCT / JP2017 / 046403, application date: December 25, 2017, invention title: ball screw). Technical Field

[0002] The present invention relates to a ball screw, and more particularly to a ball screw including an end deflector attached to a nut body. Background Technology

[0003] As a ball screw used in linear motion mechanisms, a ball screw is known, comprising: a screw shaft having an outer peripheral surface on which a axial thread groove is formed; a nut body having an inner peripheral surface, a ball return path, and an end face, wherein a nut-side thread groove is formed on the inner peripheral surface, the nut-side thread groove being formed opposite to the axial thread groove to cooperatively define a rolling path, the ball return path extending along an axial direction, and the end face having a deflector retaining recess continuous with the nut-side thread groove, and the ball return... The axial end of the path opens in the deflector retaining recess; a plurality of balls are accommodated in a rolling manner in the rolling path and the ball return path; an end deflector is inserted into the deflector retaining recess and has a ball delivery path for delivering balls between the rolling path and the ball return hole and a tongue for guiding the balls from the rolling path to the ball delivery path; and mounting screws pass through the end deflector in the axial direction and engage with the nut body threadedly to secure the end deflector to the nut body (e.g., Patent Documents 1 to 4).

[0004] Reference List

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-24305

[0007] Patent Document 2: Japanese Patent Application Publication No. 2013-174316

[0008] Patent Document 3: Japanese Patent Application Publication No. 2014-16039

[0009] Patent Document 4: Japanese Patent Application Publication No. 2014-77459 Summary of the Invention

[0010] Technical issues

[0011] When the engagement gap between the deflector retaining recess and the end deflector is reduced to improve the accuracy of the end deflector's assembly position relative to the nut body, the workability of aligning and inserting the end deflector into the deflector retaining recess deteriorates.

[0012] As described in Patent Document 4, when the end deflector is provided with a pair of protruding portions (the pair of protruding portions extend from both sides of the tongue in the axial direction toward the circumference of the nut body, respectively, to define a ball guide groove extending between the ball delivery path and the rolling path in cooperation with the inner circumferential surface of the deflector retaining recess), when the end deflector is assembled to the nut body, the protruding portions may be damaged due to collision with the nut body, resulting in a decrease in yield.

[0013] The problem this invention aims to solve is to improve the workability of assembling the end deflector into the nut body in ball screws while ensuring the accuracy of the assembly and avoiding a decrease in yield.

[0014] Technical solution

[0015] A ball screw according to one embodiment of the present invention includes: a screw shaft having an outer peripheral surface on which a axial thread groove is formed; a nut body having an inner peripheral surface, a ball return path, and an end face, wherein a nut-side thread groove is formed on the inner peripheral surface, the nut-side thread groove being formed opposite to the axial thread groove to cooperatively define a rolling path, the ball return path extending along an axial direction, and the end face having a deflector retaining recess, the axial end of the ball return path opening in the deflector retaining recess; a plurality of balls being rotatably accommodated in the rolling path and the ball return path; and an end deflector inserted into the deflector retaining recess, wherein the end deflector... The deflector has a main portion comprising a ball delivery path for delivering balls between a rolling path and a ball return path, a tongue for guiding balls from the rolling path to the ball delivery path, and a pair of protruding portions extending circumferentially from the axial direction of the tongue toward the nut body, and cooperating with the inner circumferential surface of the deflector retaining recess to define a ball guide groove extending between the ball delivery path and the rolling path. A front portion of the outer circumferential surface of the main portion, which is radially opposite to the inner circumferential surface of the deflector retaining recess, is offset radially inward of the main portion relative to the insertion direction of the deflector retaining recess. A rear portion of the outer circumferential surface of the main portion, at least relative to the insertion direction of the deflector retaining recess, engages with the inner circumferential surface of the deflector retaining recess.

[0016] According to this construction, the insertion of the end deflector into the deflector retaining recess is performed by first inserting the front side of the outer peripheral surface of the main part into the rear side of the inner peripheral surface of the main part receiving part. Therefore, the insertion begins in a loosely engaged state with a radial gap. This improves the workability of aligning the main part of the end deflector and inserting it into the main part receiving part of the deflector retaining recess, and during assembly, the protruding piece, acting as a cantilever, is less likely to collide with the nut body, making it less likely for the protruding piece to be damaged during assembly.

[0017] The end deflector in this embodiment can be a resin-molded product or a metal product formed by casting or the like.

[0018] In the aforementioned ball screw, preferably, the outer peripheral surface of the main part is a surface parallel to the axial direction, and the front side of the main part in the insertion direction is offset radially inward from the main part by a shoulder, and the shoulder is located at the base of the front protrusion in the insertion direction, excluding one of the pair of protrusions.

[0019] According to this construction, the external force caused by fitting the end deflector into the deflector retaining recess is unlikely to act on the protruding piece on the front side relative to the insertion direction.

[0020] In the aforementioned ball screw, preferably, the inner circumferential surface of the deflector holding recess is a surface parallel to the axial direction, and the front side of the inner circumferential surface of the deflector holding recess in the insertion direction is offset radially inward towards the deflector holding recess via a shoulder formed at the same axial position as the shoulder of the main part.

[0021] According to this design, even when a large external force is applied to the end deflector, the protruding piece can be prevented from shifting.

[0022] In the aforementioned ball screw, preferably, the end deflector includes a flange portion disposed at the axial end of the main part and is fixed to the nut body by a mounting screw, the mounting screw passing through the flange portion along the axial direction and engaging with the nut body by threads.

[0023] According to this structure, the tightening force of the mounting screw is applied only to the flange portion, thus preventing deformation of the first and second recess portions and suppressing the deterioration of the accuracy of the ball delivery path and the position of the tongue relative to the nut body.

[0024] In the ball screw described above, preferably, the end deflector includes a rib that extends from the radial inner edge of the flange in a direction toward the depth side of the deflector retaining recess.

[0025] This construction improves the bending stiffness of the flange and prevents degradation of the ball delivery path and the positional accuracy of the tongue relative to the nut body.

[0026] In the aforementioned ball screw, preferably, the flange portion includes: a radial flange portion extending radially outward from the end of the main portion and including a portion integral with one of a pair of protruding portions located on the flange portion side; and a circumferential flange portion extending circumferentially from the end of the main portion in a direction opposite to the protrusion direction of the one protruding portion, and a rib provided on the circumferential flange portion.

[0027] According to this structure, the radial flange and the protruding plate act as reinforcing ribs to each other, thereby enhancing the bending stiffness of these parts, while the bending stiffness of the circumferential flange is enhanced by the ribs.

[0028] In the aforementioned ball screw, preferably, the rib includes a portion that overlaps radially with the inner circumferential surface of the nut body in a planar shape.

[0029] This construction further improves the bending stiffness of the flange and prevents degradation of the ball delivery path and the positional accuracy of the tongue relative to the nut body.

[0030] Beneficial effects of the present invention

[0031] The ball screw according to the present invention can improve the workability of assembling the end deflector into the nut body while ensuring the accuracy of assembling the end deflector into the nut body and avoiding a decrease in yield. Attached Figure Description

[0032] Figure 1 This is a schematic illustration of a longitudinal cross-sectional view of Embodiment 1 of the ball screw according to the present invention.

[0033] Figure 2 This is a perspective view of the ball screw according to embodiment 1.

[0034] Figure 3 This is a perspective view of a ball screw according to Embodiment 1, which involves removing the lead screw shaft.

[0035] Figure 4 This is an exploded perspective view of the ball screw in Embodiment 1, which involves removing the lead screw shaft.

[0036] Figure 5 This is an enlarged perspective view of the end deflector of the ball screw in Embodiment 1 (e.g., along...). Figure 4 (Magnified 3D view showing the direction of arrow A in the image).

[0037] Figure 6 This is an enlarged perspective view of the end deflector of the ball screw in Embodiment 1 (e.g., along...). Figure 5 (Magnified 3D view showing the direction of arrow B in the image).

[0038] Figure 7 This is a left-side view of the end deflector of the ball screw in Embodiment 1.

[0039] Figure 8 This is a right-side view of the end deflector of the ball screw in Embodiment 1.

[0040] Figure 9 This is a front view of the ball screw according to embodiment 2.

[0041] Figure 10 This is a rear view of the ball screw according to embodiment 2.

[0042] Figure 11 This is a left-side view of the ball screw in Embodiment 2.

[0043] Figure 12 This is a right-side view of the ball screw in embodiment 2.

[0044] Figure 13 This is a plan view of the ball screw in embodiment 2.

[0045] Figure 14 This is a bottom view of the ball screw in embodiment 2.

[0046] Figure 15 This is a perspective view of the ball screw in Embodiment 2 as observed from the previous view.

[0047] Figure 16 This is a perspective view of the ball screw in Embodiment 2 as viewed from the rear.

[0048] Figure 17 This is a perspective view of a ball screw according to Embodiment 3 of the present invention.

[0049] Figure 18 This is a perspective view of the ball screw in Embodiment 3, which involves removing the lead screw shaft.

[0050] Figure 19 This is an exploded perspective view of the ball screw in Embodiment 3, which involves removing the lead screw shaft.

[0051] Figure 20 This is an enlarged perspective view of the end deflector of the ball screw in Embodiment 3 (as shown along...). Figure 19 (Magnified stereoscopic view showing the direction of arrow C in the image).

[0052] Figure 21 This is an enlarged perspective view of the end deflector of the ball screw in Embodiment 3 (as shown along...). Figure 20 (Magnified stereoscopic view showing the direction of arrow D in the image).

[0053] Figure 22 This is an enlarged perspective view of the end deflector of the ball screw in Embodiment 3 (as shown along...). Figure 21 (Magnified stereoscopic view showing the direction of arrow E in the image).

[0054] Figure 23 This is a front view of the ball screw according to embodiment 4.

[0055] Figure 24 This is a rear view of the ball screw according to embodiment 4.

[0056] Figure 25 This is a left-side view of the ball screw in embodiment 4.

[0057] Figure 26 This is a right-side view of the ball screw in embodiment 4.

[0058] Figure 27 This is a plan view of the ball screw in implementation method 4.

[0059] Figure 28 This is a bottom view of the ball screw in embodiment 4.

[0060] Figure 29 This is a perspective view of the ball screw in embodiment 4 as observed from the previous view.

[0061] Figure 30 This is a perspective view of the ball screw in embodiment 4, as viewed from the rear.

[0062] List of reference numerals

[0063] 10: Ball screw

[0064] 12: Lead screw shaft

[0065] 12A: Outer peripheral surface

[0066] 14: Nut body

[0067] 14A: Inner circumferential surface

[0068] 14B: End face

[0069] 16: End deflector

[0070] 18: Shaft-side thread groove

[0071] 20: Scroll path

[0072] 22: Nut side thread groove

[0073] 24: Ball return path

[0074] 24A: Axial end

[0075] 26: Deflector retaining recess

[0076] 28: Ball bearing

[0077] 30: Main part

[0078] 30A: Outer peripheral surface

[0079] 30Aa: Anterior side

[0080] 30Ab: Rear side

[0081] 30B: End face

[0082] 31: Shoulders

[0083] 32: Flange portion

[0084] 32A: Outer peripheral surface

[0085] 32B: End face

[0086] 34: Ball guide groove

[0087] 34A: Axial section

[0088] 34B: Circumferential part

[0089] 36: Ball delivery path

[0090] 38: Tongue

[0091] 40: Ball guide groove

[0092] 42: Highlight the part

[0093] 42A: Inner circumferential surface

[0094] 44: Highlight the part

[0095] 44A: Inner circumferential surface

[0096] 46: Radial flange portion

[0097] 48: Circumferential flange

[0098] 48A: Inner circumferential surface

[0099] 50: Screw through hole

[0100] 52: Ribs

[0101] 52A: Inner circumferential surface

[0102] 52B: Overlapping part

[0103] 52C: One end

[0104] 52D: The other end

[0105] 54: Main Receiving Department

[0106] 54A: Bottom surface

[0107] 54B: Inner circumferential surface

[0108] 54Ba: Front side

[0109] 54Bb: Rear side

[0110] 55: Shoulders

[0111] 56: Flange receiving part

[0112] 56A: Bottom surface

[0113] 56B: Inner circumferential surface

[0114] 58: Screw hole

[0115] 60: Mounting screws

[0116] 62: Rib receiving recess

[0117] X: Axis direction

[0118] Xi: Insertion direction Detailed Implementation

[0119] In the following text, reference will be made to Figures 1 to 8 Embodiment 1 of the ball screw according to the present invention is described.

[0120] like Figure 1 As shown, the ball screw 10 of Embodiment 1 includes a screw shaft 12, a nut body 14, and two end deflectors 16.

[0121] Here, the direction of the central axis of the ball screw 10 is defined as the axis direction X. For example, in... Figure 1 As seen in the image, the axial direction X is the left-right direction. The circumferential direction mentioned below refers to the direction around the central axis of the ball screw 10.

[0122] The lead screw shaft 12 is made of a round metal rod and has an outer peripheral surface 12A on which a axial thread groove 18 is formed.

[0123] The nut body 14 is made of a metal cylinder and has an inner circumferential surface 14A, a ball return path 24, and an end face 14B. A nut-side threaded groove 22 is formed on the inner circumferential surface 14A, which is formed opposite to the axial-side threaded groove 18 to define the rolling path 20 in cooperation with the axial-side threaded groove 18. The ball return path 24 extends through its cylindrical wall along the axial direction X. On either side of the end face 14B, a deflector holding recess 26 is formed inside, such that the end deflector 16 is inserted into the corresponding deflector holding recess 26.

[0124] Multiple metal balls 28 are housed in the rolling path 20 and the ball return path 24 for rolling within them.

[0125] Next, refer to Figures 2 to 8 Details are described regarding the end deflector 16, the deflector retaining recess 26, and the mounting structure of the end deflector 16.

[0126] Each end deflector 16 is a single molded product made of resin such as polyacetal (POM), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polyamide (PA), and includes a main portion 30 and a flange portion 32 disposed on one end of the main portion 30 relative to the axial direction X (this one end may be referred to as the "outer end").

[0127] The main portion 30 includes a ball guide groove 34, which is curved to include an axial portion 34A and a circumferential portion 34B, to cooperate with the inner circumferential surface 54B of the deflector retaining recess 26, which will be described later, to define a ball delivery path 36 having a closed cross-section (see [link to relevant documentation]). Figure 3 The tongue 38 extends circumferentially from the distal end of the circumferential portion 34B and bulges radially inward to enter the corresponding portion of the axial thread groove 18; and a pair of protruding portions 42 and 44 extend approximately parallel to each other from both sides of the tongue 38 in the axial direction X towards the circumferential direction of the nut body 14.

[0128] The protruding portions 42 and 44 are independent cantilever arms, which are formed having base ends on the tongue 38 side and spaced apart from each other along the axial direction X. The protruding portions 42 and 44 cooperate with the inner peripheral surface 54B of the deflector retaining recess 26 (described later) to define a ball guide groove 40 that continues to the ball guide groove 34 (see Figure 3 The ball guide groove 40 extends between the ball delivery path 36 and the rolling path 20, and delivers the ball 28 between the ball delivery path 36 and the rolling path 20, so as to cooperate with the shaft-side threaded groove 18 to form an extension of the rolling path 20. The tongue 38 guides the ball 28 from the ball guide groove 40 to the ball delivery path 36 in such a way that it scoops up the ball 28 from the ball guide groove 40.

[0129] The ball guide groove 40 cooperates with a portion of the axial thread groove 18 of the lead screw shaft 12 located at the corresponding position to form a rolling path for the ball 28 (connecting the rolling path 20 and the ball delivery path 36). The protruding portions 42 and 44 include inner circumferential surfaces 42A and 44A formed by circumferential arcuate surfaces, respectively, and are shaped to avoid interference with the lead screw shaft 12.

[0130] The main portion 30 has an outer peripheral surface 30A that radially opposes the inner peripheral surface 54B of the deflector holding recess 26. The outer peripheral surface 30A is a surface parallel to the axial direction and includes a shoulder (stepped portion) 31 at its midpoint relative to the axial direction. The shoulder 31 is formed to extend circumferentially over the entire outer peripheral surface 30A at a position in the axial direction, excluding the insertion direction Xi of the main portion 30 relative to the deflector holding recess 26 (see [reference]). Figures 4 to 8 The base (proximal end) of the protruding piece 44 on the front side of the shoulder 31, in other words, the shoulder 31 is formed to extend at a position on the flange 32 side that does not overlap with the protruding piece 44 as seen along the axial direction. In the outer peripheral surface 30A, the front side portion 30Aa located on the front side (distal side) of the shoulder 31 relative to the insertion direction Xi is offset radially inward towards the main portion 30 compared to the rear side portion 30Ab located on the rear side (flange 32 side) of the shoulder 31 relative to the insertion direction Xi.

[0131] The flange portion 32 is a mounting part of the end deflector 16 relative to the nut body 14, and is composed of a cap-shaped portion that extends radially and circumferentially outward from the axial end of the main portion 30 on the side corresponding to the opening edge of the deflector retaining recess 26 in the end face 14B.

[0132] More specifically, the flange portion 32 includes: a radial flange portion 46 extending radially outward from the outer end of the main portion 30 and including a portion integral with substantially the entire protruding piece portion 42; and a circumferential flange portion 48 extending from the outer end of the main portion 30 in a circumferential direction opposite to the protrusion direction of the protruding piece portion 42. Both the radial flange portion 46 and the circumferential flange portion 48 are provided with a screw through hole (through hole) 50 extending through it in the axial direction X. The circumferential flange portion 48 includes an inner circumferential surface 48A made of a circumferential arcuate surface, which is continuous with the inner circumferential surface 42A of the protruding piece portion 42, and the circumferential flange portion 48 is shaped to avoid interference with the lead screw shaft 12.

[0133] The radial flange 46 serves as the aforementioned mounting element and as a reinforcing rib to enhance the bending stiffness of the protruding piece 42 extending in the circumferential direction. In other words, the protruding piece 42 is located on the radial inner edge of the radial flange 46 and acts as a reinforcing rib to enhance the bending stiffness of the radial flange 46. Thus, the radial flange 46 and the protruding piece 42 mutually reinforce each other.

[0134] The end deflector 16 includes a rib 52 that extends inwardly from the radial inner edge of the circumferential flange 48 along the axial direction X and along the inner circumferential surface 48A. Note that the inwardly extending side in the axial direction X refers to the side opposite to the outer end in the axial direction X, that is, the depth side of the deflector holding recess 26 on the corresponding side in the axial direction X.

[0135] Rib 52 is a reinforcing rib used to enhance the bending stiffness of the circumferential flange 48. It is connected to the main portion 30 at its circumferential end and includes an inner circumferential surface 52A formed by a circumferential arcuate surface that is continuous with the inner circumferential surface 48A of the circumferential flange 48 (see...). Figure 6 ), and is shaped to avoid interference with the lead screw shaft 12. For example Figure 3 As shown, the rib 52 includes an overlapping portion 52B, which overlaps radially with the inner circumferential surface 14A of the nut body 14 to form a planar shape.

[0136] Each deflector retaining recess 26 includes a main receiving portion 54 and a flange receiving portion 56. The main receiving portion 54 is formed to have a shape that is substantially the same as the outline shape of the main portion 30 so as to receive the main portion 30. The flange receiving portion 56 is located more on the outer end side along the axial direction X than the main receiving portion 54, and is formed to have a shape that is substantially the same as the outline shape of the flange portion 32 so as to receive the flange portion 32.

[0137] like Figure 4 As shown, the main receiving portion 54 has a bottom surface 54A on its inward side (depth side of the deflector holding recess 26) relative to the axial direction X (i.e., the front side relative to the insertion direction Xi), formed by a flat surface orthogonal to the axial direction X. The axial end 24A of the ball return path 24 (see...) Figure 4 The main receiving portion 54 has an opening in the bottom surface 54A. Between the opening edge adjacent to the flange receiving portion 56 and the bottom surface 54A, the main receiving portion 54 includes an inner peripheral surface 54B having a shape substantially the same as the outer peripheral surface 30A of the main portion 30. The nut-side threaded groove 22 reaches the inner peripheral surface 54B, and the end of the nut-side threaded groove 22 is located within the inner peripheral surface 54B.

[0138] The inner circumferential surface 54B of the main receiving portion 54 is a surface parallel to the axial direction, and includes a shoulder (step portion) 55 at its middle portion relative to the axial direction. The shoulder 55 is formed to extend circumferentially over the entire inner circumferential surface 54B at a position in the axial direction, excluding the base (proximal end) of the protruding piece 44 provided on the front side of the main portion 30 of the end deflector 16 fixed relative to the insertion direction Xi of the deflector holding recess 26 to the nut body 14. In other words, the shoulder 55 is formed to extend at a position on the flange portion 32 side that does not overlap with the protruding piece 44 as seen along the axial direction (i.e., at the same axial direction as the shoulder 31 of the end deflector 16 fixed to the nut body 14). In the inner peripheral surface 54B, the front side portion 54Ba, located on the front side (far end side) of the shoulder 55 relative to the insertion direction Xi or on the bottom surface 54A side of the shoulder 55, is offset radially inward towards the main receiving portion 54 compared to the rear side of the shoulder 55 relative to the insertion direction Xi or on the flange receiving portion 56 side of the shoulder 55. The shoulder 55 can be equivalent to a finishing allowance, which is generated by cutting the rear side portion 54Bb of the inner peripheral surface 54B during the finishing process of the main receiving portion 54 by a milling cutter or the like, and the rear side portion (entry side) 54Bb of the inner peripheral surface 54B is formed as a finishing surface with higher precision than the front side portion (depth side) 54Ba.

[0139] Because only the rear side portion 54Bb needs to be finished with high precision, the machining time for the deflector holding recess 26 is shortened and the tool life is extended compared to the case where the entire inner circumferential surface 54B is finished with high precision. Furthermore, the area to be finished, namely the rear side portion 54Bb, is located on the tool entry side of the main receiving portion 54 relative to its axial direction. This shortens the tool's protrusion length in the axial direction during finishing and reduces the bending deformation of the tool shank, thereby improving the finishing accuracy of the rear side portion 54Bb.

[0140] Once each end deflector 16 is inserted into the corresponding deflector holding recess 26 along the insertion direction Xi, the rear side 30Ab of the outer peripheral surface 30A of the main part 30 fits tightly into (contacts) the rear side 54Bb of the inner peripheral surface 54B of the main receiving part 54 of the nut body 14, and by means of this fit, the circumferential and radial mounting position relative to the nut body 14 is determined.

[0141] In this engaged state, the front side 30Aa of the outer peripheral surface 30A of the main part 30 faces the front side 54Ba of the inner peripheral surface 54B of the main part receiving part 54. The relative dimensions between the front side 30Aa of the outer peripheral surface 30A and the front side 54Ba of the inner peripheral surface 54B are set to include a certain degree of gap, which can absorb the error in the flatness of the front side 54Ba of the inner peripheral surface 54B due to the bending deformation of the shank of the milling cutter or the like caused by cutting resistance (the error in the inward inclination of the front side 54Ba of the inner peripheral surface 54B toward the bottom surface 54A in the radial direction of the main part receiving part 54).

[0142] Therefore, even if there is a flatness error in the front portion 54Ba, the main portion 30 is not strongly compressed radially by the interlocking of the front portion 30Aa of the outer peripheral surface 30A and the front portion 54Ba of the inner peripheral surface 54B, and positional errors of the protruding piece 44 caused by deformation of the main portion 30 are prevented. Thus, the delivery of the ball 28 between the rolling path 20 and the ball guide groove 40 can be performed smoothly.

[0143] The flange receiving portion 56 has a bottom surface 56A on its inward (depth side) side relative to the axial direction X, consisting of a flat surface orthogonal to the axial direction X. A screw hole 58 for mounting a screw 60 opens in the bottom surface 56A at a position corresponding to the corresponding screw through hole 50. The flange receiving portion 56 has an inner circumferential surface 56B on its radially outer side between its open end corresponding to the end face 14B of the nut body 14 and the bottom surface 56A. This inner circumferential surface 56B has a shape substantially the same as the outer circumferential surface 32A of the flange portion 32. The outer circumferential surface 32A of the flange portion 32 and the inner circumferential surface 56B of the flange receiving portion 56 can loosely fit together so as not to obstruct the aforementioned positioning due to the fit between the main portion 30 and the main receiving portion 54.

[0144] Because the shoulder 31 is positioned in the axial direction excluding the base of the protruding piece 44 located on the front side of the insertion direction Xi relative to the pair of protruding pieces 42 and 44, the external force caused by the end deflector 16 engaging in the deflector holding recess 26 is unlikely to act on the protruding piece 44, thus suppressing positional changes in the protruding piece 44. This also allows the ball 28 to be smoothly delivered between the rolling path 20 and the ball guide groove 40.

[0145] Because the front side 54Ba of the inner circumferential surface 54B of the deflector retaining recess 26 is offset radially inward towards the deflector retaining recess 26, the offset of the protruding piece 44 is limited, and the protruding piece 44 is prevented from offset even when a large external force is applied to the end deflector 16. This also helps to enable the ball 28 to be smoothly delivered between the rolling path 20 and the ball guide groove 40.

[0146] Once the main part 30 is inserted into the main part receiving part 54 and the flange part 32 is inserted into the flange receiving part 56, the mounting screw 60, which is made of countersunk screw, is inserted from the outer end side in the axial direction X into the corresponding screw through hole 50, and engages with the corresponding screw hole 58 at the corresponding position (tightened in), thereby fixing each end deflector 16 to the nut body 14 by tightening the mounting screw 60.

[0147] The insertion of the end deflector 16 into the deflector retaining recess 26 is performed as follows: First, the front side 30Aa of the outer peripheral surface 30A of the main part 30 passes through the flange receiving part 56 along the axial direction and is inserted into the rear side 54Bb of the inner peripheral surface 54B of the main part receiving part 54. Thus, the insertion begins in a loose engagement state with a gap equal to the size of the step in the shoulder 31. This improves the workability of aligning the main part 30 of the end deflector 16 and inserting it into the main receiving part 54 of the deflector retaining recess 26. In addition, during this insertion operation, the protruding piece 44, which acts as a cantilever, is unlikely to collide with the nut body 14, and the protruding piece 44 is unlikely to be damaged during assembly.

[0148] As described above, by fixing the end deflector 16 to the nut body 14, the end of the nut-side threaded groove 22 is connected to the ball guide groove 40, and the ball delivery path 36 is connected to the ball return path 24.

[0149] In this fixed state, the inner end face 32B of the flange portion 32 in the axial direction X is strongly pressed against the bottom surface 56A of the flange receiving portion 56, while the inner end face 30B of the main portion 30 in the axial direction X can be weakly pressed against the bottom surface 54A of the main portion receiving portion 54, or can be in slight contact with the bottom surface 54A.

[0150] Because the mounting screw 60 passes through the flange portion 32 of the end deflector 16 along the axial direction and is screwed into the nut body 14, the axial force generated by the tightening of the mounting screw 60 acts on the end face 32B of the flange portion 32 and the bottom face 56A of the flange receiving portion 56 that abut against each other along the axial direction, and does not act on the main portion 30.

[0151] In this way, the tightening force of the mounting screw 60 acts only on the flange portion 32, and the deformation of the end deflector 16 due to the tightening of the mounting screw 60 is limited to the flange portion 32, thereby suppressing the deformation of the main portion 30 due to the tightening force of the mounting screw 60. Therefore, the deterioration of the positioning accuracy of the ball guide grooves 34 and 40, the tongue 38, and the protruding portions 42 and 44 relative to the nut body 14 caused by the tightening of the mounting screw 60 is prevented, and the smooth circulation of the balls 28 is ensured. This improves the operating performance of the ball screw 10 and the durability of the end deflector 16.

[0152] As described above, when the end deflector 16 is fixed to the nut body 14, the mounting position of the end deflector 16 relative to the nut body 14 in the circumferential and radial directions is determined by tightly fitting the rear side portion 30Ab of the outer peripheral surface 30A of the main portion 30 to the rear side portion 54Bb of the inner peripheral surface 54B of the main receiving portion 54 of the nut body 14. The position of the end deflector 16 relative to the nut body 14 in the axial direction is determined by the abutment between the end face 30B of the main portion 30 and the bottom surface 54A of the main receiving portion 54, the abutment between the shoulder portion 31 and the shoulder portion 55, or the abutment between the end face 32B of the flange portion 32 and the bottom surface 56A of the flange receiving portion 56.

[0153] Furthermore, each end deflector 16 includes a rib 52 on the circumferential flange 48, which improves the bending stiffness of the circumferential flange 48. Additionally, since the protruding piece 42 acts as a reinforcing rib for the radial flange 46, the bending stiffness of the radial flange 46 is also improved. Therefore, deformation of the flange 32 caused by tightening the mounting screw 60 is suppressed. This also helps prevent deterioration of the positional accuracy of the ball guide grooves 34 and 40, the tongue 38, and the protruding pieces 42 and 44 relative to the nut body 14 due to tightening of the mounting screw 60, thereby ensuring smooth circulation of the balls 28 and improving the operating performance of the ball screw 10 and the durability of the end deflectors 16.

[0154] Furthermore, because the rib 52 includes an overlapping portion 52B that overlaps radially with the inner circumferential surface 14A of the nut body 14, the rib 52 effectively improves the bending rigidity of the circumferential flange 48 and more reliably suppresses deformation of the circumferential flange 48. This also helps prevent deterioration of the positional accuracy of the ball guide grooves 34 and 40, the tongue 38, and the protruding portions 42 and 44 relative to the nut body 14 due to the tightening of the mounting screw 60, thereby ensuring smooth circulation of the balls 28 and improving the operating performance of the ball screw 10 and the durability of the end deflector 16.

[0155] Because the rib 52 extends from the radial inner edge of the circumferential flange 48 toward the inward side relative to the axial direction X, the rib 52 does not cause an increase in the axial length of the nut, nor does it cause an increase in the outer diameter of the nut.

[0156] Next, refer to Figures 9 to 16 Embodiment 2 of the ball screw according to the present invention is described. Note that in Figures 9 to 16 In, with Figures 1 to 8 The parts in the middle correspond to the parts with Figures 1 to 8 The same reference numerals are used to indicate the figures in the accompanying drawings, and their descriptions will be omitted.

[0157] The ball screw 10 of Embodiment 2 has a structure that is substantially the same as that of the ball screw 10 of Embodiment 1. Therefore, the ball screw 10 of Embodiment 2 operates in the same manner as the ball screw 10 of Embodiment 1 and performs a function similar to that of the ball screw 10 of Embodiment 1.

[0158] Next, refer to Figures 17 to 22 Embodiment 3 of the ball screw according to the present invention is described. Note that in Figures 17 to 22 In, with Figures 1 to 8 The parts in the middle correspond to the parts with Figures 1 to 8 The same reference numerals are used to indicate the figures in the accompanying drawings, and their descriptions will be omitted.

[0159] Similarly, in Embodiment 3, the outer peripheral surface 30A of the main portion 30 of the end deflector 16 and the inner peripheral surface 54B of the main portion receiving portion 54 of the deflector holding recess 26 of the nut body 14 are similar to the shape of Embodiment 1. Therefore, an effect similar to that of the ball screw 10 in Embodiment 1 can be obtained.

[0160] In embodiment 3, the flange portion 32 of each end deflector 16 has an annular shape concentric with the center of the nut body 14 as seen along the axial direction X, and has an end face 32B that abuts against the end face 14B on the corresponding side of the nut body 14 in the axial direction X. Screw holes 58 are formed at multiple locations along the circumference of the nut body 14 to open in each end face 14B. Screw through holes 50 are formed at multiple locations along the circumference of the flange portion 32 to extend through the flange portion 32 along the axial direction.

[0161] The end deflector 16 is secured to the end face 14B of the nut body 14 by a plurality of mounting screws 60 corresponding to the corresponding screw through holes 50 and corresponding screw holes 58.

[0162] Therefore, also in Embodiment 3, the tightening force of the mounting screw 60 acts only on the flange portion 32, and the deformation of the end deflector 16 due to the tightening of the mounting screw 60 is limited to the flange portion 32, thereby suppressing the deformation of the end deflector 16 due to the tightening force of the mounting screw 60. Thus, the deterioration of the positioning accuracy of the ball guide grooves 34 and 40, the tongue 38, and the protruding portions 42 and 44 relative to the nut body 14 caused by the tightening of the mounting screw 60 is prevented, and the smooth circulation of the balls 28 is ensured. This improves the operating performance of the ball screw 10 and the durability of the end deflector 16.

[0163] Rib 52 extends from approximately the entire circumference of the radial inner edge of flange 32 toward the inward side relative to the axial direction X. That is, deflector retaining recess 26 has one end 52C, which engages with the distal end of protruding piece 42C and the other end 52D, which engages with the tongue 38D side of main part 30, on the depth side of the corresponding side relative to axial direction X, and forms a closed loop along the circumference of flange 32 in cooperation with main part 30.

[0164] In this way, the rib 52, together with the main portion 30, acts as a reinforcing rib to enhance the bending stiffness of the flange portion 32. Because the two ends of the rib 52 are joined to the main portion 30 to form a closed loop together with the main portion 30, the bending stiffness of the rib 52 itself is also enhanced, and the rib 52 has a significant effect on improving the bending stiffness of the flange portion 32.

[0165] This suppresses deformation of the flange 32 and also prevents deterioration of the positional accuracy of the ball guide grooves 34 and 40, the tongue 38, and the protruding plates 42 and 44 relative to the nut body 14. This ensures smooth circulation of the balls 28 and improves the operating performance of the ball screw 10 and the durability of the end deflector 16.

[0166] Because the rib 52 extends from the radial inner edge of the circumferential flange 48 toward the inward side relative to the axial direction X, the rib 52 does not cause an increase in the axial length of the nut, nor does it cause an increase in the outer diameter of the nut.

[0167] Furthermore, a generally annular rib receiving recess 62 is formed at the open end corresponding to the end face 14B of the nut body 14, such that the diameter of the rib receiving recess 62 is enlarged to receive the rib 52. The rib 52 fits into the rib receiving recess 62, which also helps to prevent the outer diameter of the nut from increasing.

[0168] Next, refer to Figures 23 to 30 Embodiment 4 of the ball screw according to the present invention is described. Note that in Figures 23 to 30 In, with Figures 17 to 22 The parts in the middle correspond to the parts with Figures 17 to 22 The same reference numerals are used to indicate the figures in the accompanying drawings, and their descriptions will be omitted.

[0169] The ball screw 10 of Embodiment 4 has a structure that is substantially the same as that of the ball screw 10 of Embodiment 3. Therefore, the ball screw 10 of Embodiment 4 operates in the same manner as the ball screw 10 of Embodiment 3 and performs a function similar to that of the ball screw 10 of Embodiment 3.

[0170] Although the invention has been described with reference to preferred embodiments, modifications may be made to the invention without departing from its spirit and scope.

[0171] For example, the number of steps formed in the outer peripheral surface 30A of the main portion 30 and the inner peripheral surface 54B of the main receiving portion 54 is not limited to one in the above embodiment, but can be multiple, such as two or three, and the outer peripheral surface 30A of the main portion 30 and the inner peripheral surface 54B of the main receiving portion 54 can be tapered. The inner peripheral surface 54B of the main receiving portion 54 may not include the shoulder 55, and the entire inner peripheral surface 54B may have a rear side portion 54Bb sized. In this case, a radial gap is generated between the front side portion 30Aa of the outer peripheral surface 30A of the main portion 30 of the end deflector 16 and the front side portion 54Ba of the inner peripheral surface 54B of the main receiving portion 54, but this gap is useful in preventing unnecessary external forces in the radial direction from the nut body 14 from being applied to the protruding piece 44.

[0172] The end deflector 16 does not always have to be made of resin, but can be made of metal by casting or the like. The ball screw 10 can be of the type in which the end deflector 16 is provided only on one side of the nut body 14. The structure of the nut body 14 including the rib receiving recess 62 for receiving the rib 52 of the end deflector 16 can also be similarly applied to embodiment 1.

[0173] All components shown in the above embodiments are not necessarily necessary, but can be appropriately selected without departing from the spirit and scope of the invention.

Claims

1. A ball screw, the ball screw comprising: A lead screw shaft having an outer peripheral surface on which a axial thread groove is formed; The nut body has an inner circumferential surface, a ball return path, and an end face. A nut-side thread groove is formed on the inner circumferential surface. The nut-side thread groove is formed opposite to the axial-side thread groove to cooperate with the axial-side thread groove in defining the rolling path. The ball return path extends along the axial direction. The end face is provided with a deflector holding recess. The axial end of the ball return path opens in the deflector holding recess. Multiple balls, the multiple balls being accommodated in the rolling path and the ball return path in a rollable manner; as well as An end deflector is inserted into a deflector retaining recess, wherein... The end deflector has a main portion, the main portion including a ball delivery path for delivering the ball between the rolling path and the ball return path, a tongue for guiding the ball from the rolling path to the ball delivery path, and a pair of protruding portions extending from both sides of the tongue in the axial direction toward the circumference of the nut body, and cooperating with the inner circumferential surface of the deflector retaining recess to define a ball guide groove extending between the ball delivery path and the rolling path, and The front portion of the outer peripheral surface of the main part, which is radially opposite to the inner peripheral surface of the deflector holding recess, is offset radially inward from the main part in the insertion direction relative to the deflector holding recess. Furthermore, the rear portion of the outer peripheral surface of the main part, at least in the insertion direction relative to the deflector holding recess, engages with the inner peripheral surface of the deflector holding recess. The end deflector includes a flange portion located at the axial end of the main portion and secured to the nut body by a mounting screw. The mounting screw passes through the flange portion along the axial direction and engages with the nut body by threads. The end deflector also includes a rib portion extending from the radially inner edge of the flange portion in a direction toward the depth side of the deflector retaining recess. The flange portion includes: a radial flange portion extending radially outward from the end of the main portion and including a portion integral with one of the pair of protruding pieces located on the flange portion side; and a circumferential flange portion extending circumferentially from the end of the main portion in a direction opposite to the protrusion direction of the one protruding piece, and the rib portion being disposed on the circumferential flange portion.

2. The ball screw according to claim 1, wherein, The rib includes a portion that overlaps with the inner circumferential surface of the nut body in a planar shape along the radial direction.

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