Ball screw device

Abstract

To provide a ball screw device which is further suppressed in a deformation amount at attachment to a nut, or at a use of the ball screw device.SOLUTION: A ball screw device comprises a nut, a screw shaft, balls and a cooling liquid flow passage. The nut has a nut main body in which a recessed groove is formed at a first end face of an end part in an axial direction, a seal member fit into the recessed groove, and an annular cap for sealing the recessed groove. The cooling liquid flow passage includes a plurality of flow passages in the axial direction, and a flow passage in a circumferential direction extending along the circumferential direction, and the flow passage in the circumferential direction is formed by sealing the recessed groove of the nut main body by the cap. The seal member has an annular frame body and a reinforcing part for connecting long sides of the frame body when viewed from the axial direction. The seal member extends in a circular arc shape along the recessed groove.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The ball screw device, for example, includes a nut provided with an inner circumferential raceway groove, a screw shaft penetrating the nut and provided with an outer circumferential raceway groove, a plurality of balls arranged between the inner circumferential raceway groove and the outer circumferential raceway groove, and a coolant flow passage provided inside the nut through which a coolant flows (see Patent Document 1). The coolant flow passage includes an axial flow passage extending in the axial direction of the nut and a circumferential flow passage extending in the circumferential direction of the nut. The circumferential flow passage is formed by a circumferential groove formed at an axial end of the nut and opening to the axial outside, a seal member fitted into an end of an inner wall of the circumferential groove to seal the circumferential groove, and a seal member that seals the circumferential groove in a state of contact with the seal member. When viewed from the axial direction of the nut, the seal member has an annular shape extending in the circumferential direction of the nut. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Utility Model Registration No. 3217729 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, for example, when a sealing member is fastened to an axial end of a nut with a bolt, the sealing member is subjected to a circumferential or radial force when the bolt is fastened. Also, when thermal deformation occurs at an axial end of the nut during use of the ball screw device, the sealing member is subjected to a circumferential or radial force. In these cases, the sealing member may be deformed, reducing the airtightness of the circumferential groove.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a ball screw device having a sealing member that exhibits less deformation when attached to a nut or when the ball screw device is used. [Means for solving the problem]

[0006] In order to achieve the above object, a ball screw device according to one embodiment includes a nut having an inner circumferential raceway groove on its inner circumference and having a plurality of axial flow paths through which a coolant flows in an axial direction, a screw shaft penetrating the nut and having an outer circumferential raceway groove on its outer circumference, and a plurality of balls arranged between the inner circumferential raceway groove and the outer circumferential raceway groove, wherein the nut includes a nut body having a groove formed in a first end face arranged at at least one of one axial end and the other axial end of a central shaft, a seal member fitted into the groove, and a seal member attached to the axial end in a state covering the groove in the first end face, so that two of the plurality of axial flow paths are formed in the axial direction. and a cap that blocks the circumferential flow path, and coolant flows circumferentially through a groove that connects the ends of the flow paths, the groove being a recess that is recessed from the first end face toward the axial center, and which, as viewed in the axial direction of the nut, has an outer shape of the recess that extends along the circumferential direction of the nut and includes a first groove into which the sealing member is fitted, and a second groove that is provided inside the first groove as viewed in the axial direction of the nut and is recessed from a bottom of the first groove toward the axial center, with the ends of the two axial flow paths being exposed to the inside, and the sealing member has a frame body that extends along the first groove and a reinforcing portion that connects a pair of long sides of the frame body.

[0007] In the ball screw of the above-mentioned Patent Document 1, the seal member has an arc shape extending in the circumferential direction of the nut when viewed from the axial direction of the nut. Therefore, for example, when the sealing member is fastened to the axial end of the nut with a bolt, the seal member receives a circumferential or radial force when the bolt is fastened. Also, when the axial end of the nut is thermally deformed during use of the ball screw device, the seal member receives a circumferential or radial force. In these cases, the seal member may deform, reducing the airtightness of the circumferential groove.

[0008] In contrast, the seal member according to the present disclosure has a frame body and a reinforcing portion connecting a pair of long sides of the frame body. Therefore, the seal member has higher rigidity than a seal member without a reinforcing portion, and the amount of deformation is smaller when a force is applied in the circumferential or radial direction. This makes it possible to provide a ball screw device having a seal member that has a smaller amount of deformation when attached to a nut or when the ball screw device is used.

[0009] In a preferred embodiment, one reinforcing portion is provided, and the one reinforcing portion connects the circumferential centers of the pair of long sides to each other.

[0010] Therefore, the rigidity of the entire seal member is more uniform than when the portions of the pair of long sides other than the circumferential center of each of the pair of long sides are connected to each other with the reinforcing portion. Since a force may be input to the seal member from various directions, such as the circumferential direction or the radial direction, the amount of deformation of the seal member is smaller when the seal member is subjected to a force from various directions, such as the circumferential direction or the radial direction.

[0011] In a preferred embodiment, the reinforcing portion is provided in a plurality of parts, and the reinforcing portions are arranged at equal intervals along the circumferential direction. Therefore, the rigidity of the entire seal member is more uniform than when the reinforcing portions are arranged at unequal intervals along the circumferential direction. Since the force to the seal member may be input from various directions, such as the circumferential direction or the radial direction of the nut, the deformation of the seal member is smaller.

[0012] In a preferred embodiment, the first groove faces an inner wall extending from the first end face toward the axial center and a bottom extending from an end of the inner wall toward the axial center along the first end face, and the sealing member includes a cylinder having a circular cross section, and an outer surface of the cylinder is in line contact with the inner wall of the first groove, the bottom, and the back surface of the cap. In this manner, the outer surface of the sealing member is in even contact with the inner wall, the first bottom surface, and the back surface of the cap, improving the assurance of airtightness by the sealing member.

[0013] In a preferred embodiment, the first groove faces an inner wall extending from the first end face toward the center in the axial direction and a bottom extending from an end of the inner wall toward the center in the axial direction along the first end face, and the seal member includes a prism having a polygonal cross-sectional shape. In this way, the polygon has at least one flat surface, and the flat surface can be brought into surface contact with any flat surface of the inner wall of the first groove, the first bottom surface, or the back surface of the cap. This allows the seal member to be stably attached to the nut.

[0014] In a preferred embodiment, the sealing member includes a prism having a rectangular cross section, and three side surfaces of the prism are in surface contact with the inner wall, the bottom, and the rear surface of the cap in the first groove, thereby allowing the sealing member to be stably disposed between the inner wall, the first bottom surface, and the rear surface of the cap.

[0015] In a preferred embodiment, the sealing member includes a prism having a regular hexagonal cross section, and one side surface of the prism is in surface contact with the inner wall of the first groove, thereby enabling the sealing member to be stably attached to the nut. Effect of the Invention

[0016] According to the present disclosure, it is possible to provide a ball screw device having a seal member that undergoes a smaller amount of deformation when attached to a nut or when the ball screw device is used. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is an exploded perspective view of a ball screw device according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the ball screw device according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5]FIG. 5 is a diagram showing a state in which the cap is removed from FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a cross-sectional view of the device shown in FIG. 7 with the seal member and cap removed. [Figure 9] FIG. 9 is a plan view of the seal member shown in FIGS. [Figure 10] FIG. 10 is a plan view of the seal member shown in FIG. [Figure 11] FIG. 11 is a schematic plan view showing another example of the sealing member. [Figure 12] FIG. 12 is a schematic diagram showing the flow of the coolant in the coolant flow passage in the nut. [Figure 13] FIG. 13 is a cross-sectional view of a portion of a ball screw device according to a first modified example, and corresponds to FIG. [Figure 14] FIG. 14 is a cross-sectional view of a portion of a ball screw device according to a first modified example, and corresponds to FIG. [Figure 15] FIG. 15 is a plan view of a seal member according to a first modified example. [Figure 16] FIG. 16 is a cross-sectional view of a portion of a ball screw device according to a second modified example, and corresponds to FIG. [Figure 17] FIG. 17 is a cross-sectional view of a portion of a ball screw device according to a second modified example, and corresponds to FIG. [Figure 18] FIG. 18 is a plan view of a seal member according to the second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A detailed description of the embodiment of the present invention will be given with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. The components described below can be appropriately combined. The same reference numerals are used for parts with the same structure, and the description is omitted. The X direction indicates the axial direction, and the Y and Z directions indicate the radial directions. The Y and Z directions are perpendicular (intersect) with the X direction. The Y direction is perpendicular (intersect) with the Z direction. The X1 side indicates one side in the axial direction, and the X2 side indicates the other side in the axial direction. The Y1 side is the opposite side to the Y2 side, and the Z1 side is the opposite side to the Z2 side.

[0019] [Embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below. Fig. 1 is an exploded perspective view of a ball screw device according to an embodiment. Fig. 2 is a cross-sectional view of the ball screw device according to an embodiment.

[0020] As shown in FIGS. 1 and 2, a ball screw device 100 according to an embodiment includes a screw shaft 1, a nut 2, a plurality of balls 12, and a coolant flow path 4.

[0021] The screw shaft 1 extends in the X direction (axial direction) of the central axis AX. An outer circumferential raceway groove 11 is provided on the outer periphery of the screw shaft 1. The outer circumferential raceway groove 11 extends spirally.

[0022] The nut 2 includes a nut body 20, a seal member 5, and caps 30 and 31. The nut body 20 has a cylindrical portion 21 and a flange portion 22.

[0023] The cylindrical portion 21 extends in the X direction (axial direction) of the central axis AX. An inner circumferential raceway groove 222 is provided on the inner circumference of the cylindrical portion 21. The screw shaft 1 penetrates the inner circumference of the cylindrical portion 21. The inner circumferential raceway groove 222 extends in a spiral shape. A plurality of balls 12 are arranged between the inner circumferential raceway groove 222 and the outer circumferential raceway groove 11. The cylindrical portion 21 has a cylindrical surface 211 on the outer circumference. The cylindrical portion 21 and the cylindrical surface 211 extend in the circumferential direction around the central axis AX. The flange portion 22 is provided at the end of the nut body 20 on the X2 side (the other side in the axial direction). That is, the flange portion 22 protrudes radially outward from the end of the nut body 20 on the X2 side. A plurality of mounting holes 221 are provided penetrating the flange portion 22 in the axial direction.

[0024] A coolant flow passage 4 is formed inside the nut 2. The coolant 40 flows inside the coolant flow passage 4. As shown in FIG. 2, the coolant flow passage 4 includes, for example, an inlet 401 provided in the flange portion 22, a first axial flow passage (axial flow passage) 43 and a second axial flow passage (axial flow passage) 45 provided in the nut body 20. In addition, the nut body 20 is provided with a first end face 23 at one end (axial end) 24 in the axial direction and the other end (axial end) 25 in the axial direction. The first end face 23 extends in a radial direction perpendicular to (intersecting) the axial direction. FIG. 1 shows the first end face 23 provided at one end (axial end) 24 in the axial direction. A recessed groove 26 and a tapped hole 232 are formed in the first end face 23. A seal member 5 is fitted in the recessed groove 26. In addition, the cap 30 is provided with a central hole 301 in the radial center, and a plurality of bolt holes 302 along the circumferential direction. The cap 30 has an annular shape. The bolt BL passes through the bolt hole 302 of the cap 30 and is fastened to the tapped hole 232. As a result, the cap 30 is attached to one axial end portion (axial end portion) 24 in a state in which the cap 30 covers the first end face 23, and the recessed groove 26 is sealed.

[0025] Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 2. Fig. 5 is a view showing a state in which the cap is removed from Fig. 4.

[0026] 3 and 5, an inlet 401 is provided on the Z1 side of the flange portion 22, and an outlet 402 is provided midway between the Z1 side and the Y1 side. The coolant 40 flows into the coolant flow path 4 from the inlet 401, and then flows out from the outlet 402.

[0027] As shown in FIG. 3, two first seal members (seal members) 51 are provided at one axial end (axial end) 24 of the nut body 20. Specifically, one of the first seal members 51 extends along the circumferential direction from the Z1 side to the Y2 side of the first end face 23. The one of the first seal members 51 overlaps with a first circumferential flow passage (circumferential flow passage) 42 when viewed from the axial direction. The first circumferential flow passage 42 extends along the circumferential direction of the nut body 20. The first circumferential flow passage 42 extends along the circumferential direction of the nut body 20 from a flow passage end 421 to a flow passage end 422.

[0028] The other first seal member 51 extends circumferentially from the Y1 side to the Z2 side of the first end face 23. The other first seal member 51 overlaps with the third circumferential flow passage (circumferential flow passage) 46 when viewed from the axial direction. The third circumferential flow passage 46 extends circumferentially of the nut body 20 from a flow passage end 461 to a flow passage end 462.

[0029] As shown in FIG. 5, a first seal member (seal member) 51 and a second seal member (seal member) 52 are provided at the other end (axial end) 25 in the axial direction of the nut body 20. Specifically, the first seal member 51 extends along the circumferential direction from the Y2 side to the Z2 side of the first end face 23. The first seal member 51 overlaps with the second circumferential flow passage (circumferential flow passage) 44 when viewed from the axial direction. The second circumferential flow passage 44 extends along the circumferential direction of the nut body 20 from a flow passage end 441 to a flow passage end 442. The second seal member 52 extends along the circumferential direction from the middle between the Z1 side and the Y1 side of the first end face 23 to the Y1 side. The second seal member 52 overlaps with the fourth circumferential flow passage (circumferential flow passage) 48 when viewed from the axial direction. The fourth circumferential flow passage 48 extends along the circumferential direction of the nut body 20 from a flow passage end 481 to a flow passage end 482.

[0030] Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 3. Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 3. Fig. 8 is a cross-sectional view taken from Fig. 7 with the seal member and cap removed.

[0031] 8, a recessed groove 26 is provided in each of one axial end portion (axial end portion) 24 and the other axial end portion (axial end portion) 25 of the nut body 20. The recessed groove 26 provided in the one axial end portion 24 will be described below, but the recessed groove 26 provided in the other end portion 25 has the same configuration.

[0032] As shown in FIG. 8, the recessed groove 26 includes a first groove 261 and a second groove 262. As shown in FIG. 8, the first groove 261 is recessed from the first end face 23 toward the X2 side (the center side in the axial direction). The first groove 261 faces inner walls 261a, 261b and first bottom faces 261c, 261d. The inner walls 261a, 261b extend toward the X2 side perpendicularly (intersecting) the first end face 23. The inner walls 261a and 261b face each other in the radial direction. The first bottom faces 261c, 261d extend along the first end face 23. Specifically, the first bottom face 261c extends toward the Z2 side from the end of the inner wall 261a on the X2 side. The first bottom face 261d extends toward the Z1 side from the end of the inner wall 261b on the X2 side. The width of the first groove 261 in the radial direction is width W10.

[0033] As shown in FIG. 8, the second groove 262 is recessed from the first bottom surfaces 261c, 261d toward the X2 side (the center side in the axial direction). The second groove 262 communicates with the first groove 261. The second groove 262 faces the inner walls 262a, 262b and the second bottom surface 262c. The inner walls 262a, 262b are perpendicular (intersect) with the first end surface 23 and extend toward the X2 side. The inner walls 262a and 262b face each other in the radial direction. The second bottom surface 262c extends along the first end surface 23. The second bottom surface 262c connects the end of the inner wall 262a on the X2 side and the end of the inner wall 262b on the X2 side. The first groove 261 and the second groove 262 each have a rectangular cross section as shown by the two-dot chain line. The width of the second groove 262 in the radial direction is width W20. Width W10 is greater than width W20. Therefore, when the recessed groove 26 is viewed from the axial direction, the first bottom surfaces 261c and 261d are exposed.

[0034] 6, in a cross section of a portion overlapping with the third axial flow passage (axial flow passage) 47 as viewed in the axial direction, the first groove 261 and the second groove 262 communicate with the third axial flow passage 47. That is, as shown in Fig. 6 and Fig. 7, the first groove 261 and the second groove 262 form the third circumferential flow passage (circumferential flow passage) 46. Note that the other circumferential flow passages, that is, the first circumferential flow passage 42, the second circumferential flow passage 44, and the fourth circumferential flow passage 48, are also formed by the first groove 261 and the second groove 262.

[0035] Here, the first seal member (seal member) 51 is fitted into the first groove 261. Specifically, the first seal member (seal member) 51 is accommodated in the first groove 261 in a state in which the first seal member (seal member) 51 abuts against the inner walls 261a, 261b, the first bottom surfaces 261c, 261d, and the back surface 30a of the cap 30. As a result, the recessed groove 26 is sealed by the cap 30.

[0036] Next, the sealing member will be described. Fig. 9 is a plan view of the sealing member shown in Fig. 3 and Fig. 5. Fig. 10 is a plan view of the sealing member shown in Fig. 5. Fig. 11 is a schematic plan view showing another example of the sealing member.

[0037] As shown in FIG. 9, the first seal member (seal member) 51 has a frame body 511 and a reinforcing portion 512 when viewed from the axial direction. The frame body 511 extends in an arc shape along the circumferential direction of the nut body 20. In other words, the longitudinal direction of the frame body 511 is the circumferential direction of the nut body 20. The frame body 511 has an outer circumferential portion 513, an inner circumferential portion 514, side end portions 515, 516, and a reinforcing portion 512. The outer circumferential portion 513 and the inner circumferential portion 514 extend in an arc shape. The outer circumferential portion 513 is located radially outward of the nut body 20 with respect to the inner circumferential portion 514. The circumferential end portion of the outer circumferential portion 513 and the circumferential end portion of the inner circumferential portion 514 are connected via the side end portions 515, 516. The first portion 513a of the outer circumferential portion 513 and the second portion 514a of the inner circumferential portion 514 are connected via the reinforcing portion 512. The reinforcing portion 512 extends in the radial direction of the nut body 20. The reinforcing portion 512 is located between the two side ends 515, 516. In this embodiment, the reinforcing portion 512 is provided at the circumferential center of the two side ends 515, 516. That is, the first portion 513a is located at the circumferential center of the outer circumferential portion 513, and the second portion 514a is located at the circumferential center of the inner circumferential portion 514. The reinforcing portion 512 crosses one opening formed by the frame body 511. Therefore, two openings 517, 518 are provided in the first seal member 51. In addition, the widths of the outer circumferential portion 513, the inner circumferential portion 514, and the side ends 515, 516 are all the same width W1. The width of the reinforcing portion 512 is width W2. The width W2 is the same as or larger than the width W1. That is, the width W2 is equal to or larger than the width W1.

[0038] The first seal member 51 is a prism having a square cross section. Specifically, the frame 511 and the reinforcing portion 512 are all prisms having a square cross section. Therefore, for example, as shown in FIG. 6, three side surfaces of the outer peripheral portion 513 of the first seal member 51 are in surface contact with the inner wall 261b, the first bottom surface 261d, and the rear surface 30a of the cap 30 in the first groove 261. Furthermore, three side surfaces of the inner peripheral portion 514 of the first seal member 51 are in surface contact with the inner wall 261a, the first bottom surface 261c, and the rear surface 30a of the cap 30 in the first groove 261. Note that, as shown in FIG. 6, the inner peripheral surface of the outer peripheral portion 513 of the first seal member 51 is flush with the inner wall 262b of the second groove 262, and the inner peripheral surface of the inner peripheral portion 514 of the first seal member 51 is flush with the inner wall 262a of the second groove 262.

[0039] As shown in FIG. 10, the second seal member (seal member) 52 has a frame body 521 and a reinforcing portion 522 when viewed from the axial direction. The circumferential length of the second seal member 52 is shorter than the circumferential length of the first seal member 51. The frame body 521 extends in an arc shape along the circumferential direction of the nut body 20. The frame body 521 has an outer circumferential portion 523, an inner circumferential portion 524, side ends 525, 526, and a reinforcing portion 522. The first portion 523a of the outer circumferential portion 523 and the second portion 524a of the inner circumferential portion 524 are connected via the reinforcing portion 522. In this embodiment, the reinforcing portion 522 is provided at the center of the two side ends 525, 526 in the circumferential direction. The second seal member 52 has two openings 527, 528. Additionally, the width of outer circumferential portion 523, inner circumferential portion 524, and side ends 525, 526 is width W3. The width of reinforcing portion 522 is width W4. Width W4 is the same as or larger than width W3. In other words, width W4 is equal to or larger than width W3.

[0040] As shown in FIG. 11, the third seal member (seal member) 53 has a frame body 531 and reinforcing parts 532 and 533 when viewed from the axial direction. The circumferential length of the third seal member 53 is longer than the circumferential length of the first seal member 51. The frame body 531 extends in an arc shape along the circumferential direction of the nut body 20. The frame body 531 has an outer circumferential part 534 and an inner circumferential part 535, side ends 536 and 537, and reinforcing parts 532 and 533. The first part 534a of the outer circumferential part 534 and the second part 535a of the inner circumferential part 535 are connected via the reinforcing part 532. The first part 534b of the outer circumferential part 534 and the second part 535b of the inner circumferential part 535 are connected via the reinforcing part 533. In this embodiment, the reinforcing portion 532 and the reinforcing portion 533 are disposed at equal intervals in the circumferential direction between the side end portion 536 and the side end portion 537. Therefore, the circumferential lengths of the opening portion 538, the opening portion 539, and the opening portion 540 are the same. In the present invention, the circumferential positions of the reinforcing portions 532 and 533 are not limited, and they do not have to be disposed at equal intervals between the side end portion 536 and the side end portion 537. In addition, the width of the outer circumferential portion 534, the inner circumferential portion 535, and the side end portions 536 and 537 is width W5. The width of the reinforcing portions 532 and 533 is width W6. Width W6 is the same as or larger than width W5. That is, width W6 is equal to or larger than width W5.

[0041] Next, the flow of the coolant will be described with reference to Fig. 12, which is a schematic diagram showing the flow of the coolant in the coolant flow passage in the nut.

[0042] The axial flow passage 410 includes a first axial flow passage 43, a second axial flow passage 45, a third axial flow passage 47, and a fourth axial flow passage 49. The circumferential flow passage 420 includes a first circumferential flow passage 42, a second circumferential flow passage 44, a third circumferential flow passage 46, and a fourth circumferential flow passage 48.

[0043] First, the coolant 40 flows from the inlet 401 into the first axial flow passage 43 through the flow passage end 431. The first axial flow passage 43 has flow passage ends 431 and 432. That is, the coolant 40 flows from the flow passage end 431 to the flow passage end 432. Thereafter, the coolant 40 flows along the first circumferential flow passage 42 from the flow passage end 421 to the flow passage end 422, and flows along the second axial flow passage 45 from the flow passage end 451 to the flow passage end 452. Thereafter, the coolant 40 flows along the second circumferential flow passage 44 from the flow passage end 441 to the flow passage end 442, flows along the third axial flow passage 47 from the flow passage end 471 to the flow passage end 472, and flows along the third circumferential flow passage 46 from the flow passage end 461 to the flow passage end 462. Then, the cooling liquid 40 flows along the fourth axial flow passage 49 from the flow passage end 491 to the flow passage end 492, flows along the fourth circumferential flow passage 48 from the flow passage end 481 to the flow passage end 482, and then flows out of the nut 2 from the outlet 402. In this way, the cooling liquid 40 flows alternately through the axial flow passages 410 and the circumferential flow passages 420, thereby uniformly cooling the entire nut 2.

[0044] As described above, the ball screw device 100 includes the nut 2 having the inner circumferential raceway groove 222 on its inner circumference, the screw shaft 1 penetrating the nut 2 and having the outer circumferential raceway groove 11 on its outer circumference, a plurality of balls 12 arranged between the inner circumferential raceway groove 222 and the outer circumferential raceway groove 11, and the coolant flow path 4 provided inside the nut 2 and through which the coolant 40 flows. The nut 2 includes a nut body 20 having the inner circumferential raceway groove 222 and a groove 26 provided on a first end face 23 extending radially at one axial end (axial end) 24 and the other axial end (axial end) 25, a first seal member (seal member) 51 fitted into a part of the groove 26, and an annular cap 31 attached to the axial end in a state of covering the first end face 23 and sealing the groove 26. The recessed groove 26 is a recess recessed from the first end face 23 toward the axial center, and includes a first groove 261 facing inner walls 261a, 261b and first bottom surfaces (bottoms) 261c, 261d extending from the axial center ends of the inner walls 261a, 261b along the first end face 23, and a second groove 262 recessed from the first bottom surfaces (bottoms) 261c, 261d toward the axial center. When viewed from the axial direction, the first groove 261 and the second groove 262 extend along the circumferential direction of the nut body 20, the width W10 of the first groove 261 is larger than the width W20 of the second groove 262, and the first seal member (seal member) 51 fits into the first groove 261. The coolant flow passage 4 includes a plurality of axial flow passages 410 provided in the nut body 20 and extending in the axial direction, and a circumferential flow passage 420 that connects the axial ends of two of the plurality of axial flow passages 410 and extends along the circumferential direction of the nut body 20, and the circumferential flow passage 420 is formed by sealing the groove 26 of the nut body 20 with a cap 31. When viewed in the axial direction, the first sealing member (sealing member) 51 has a ring-shaped frame body 511 and a reinforcing portion 512 that crosses the inner opening of the frame body 511. The frame body 511 has an outer circumferential portion (long side) 513 and an inner circumferential portion (long side) 514 that extend in an arc along the inner walls 261a, 261b of the first groove 261, and two side ends 515, 516 that connect the circumferential end of the outer circumferential portion 513 and the circumferential end of the inner circumferential portion 514. The reinforcing portion 512 is located between the two side ends 515, 516 and connects the outer circumferential portion 513 and the inner circumferential portion 514.

[0045] In the ball screw of the above-mentioned Patent Document 1, the seal member has an arc shape extending in the circumferential direction of the nut when viewed from the axial direction of the nut. Therefore, for example, when the sealing member is fastened to the axial end of the nut with a bolt, the seal member receives a circumferential or radial force when the bolt is fastened. Also, when thermal deformation occurs at the axial end of the nut during use of the ball screw device, the seal member receives a circumferential or radial force. In these cases, the seal member may be deformed, decreasing the sealing ability of the seal member.

[0046] In contrast, the first seal member (seal member) 51 according to this embodiment has an annular frame 511 and a reinforcing portion 512 that connects two long sides (an outer circumferential portion 513 and an inner circumferential portion 514) of the frame 511. Therefore, the first seal member 51 has higher rigidity than a seal member that does not have the reinforcing portion 512, and the amount of deformation is smaller when a force is applied in the circumferential or radial direction of the nut 2. This makes it possible to provide a ball screw device 100 having a first seal member 51 that has a smaller amount of deformation when attached to the nut 2 or when the ball screw device 100 is used.

[0047] Further, the second seal member (seal member) 52 has an annular frame body 521 and a reinforcing portion 522 connecting the long sides of the frame body 521 (an outer circumferential portion 523 and an inner circumferential portion 524) when viewed in the axial direction.

[0048] The second seal member 52 has a shorter circumferential length at the first end face 23 than the first seal member 51. Specifically, the first seal member 51 has a quarter length of the entire circumferential circumference at the first end face 23, whereas the second seal member 52 has a one-eighth length of the entire circumferential circumference at the first end face 23. Thus, even in the second seal member 52 having a shorter circumferential length than the first seal member 51, the reinforcing portion 522 is provided between the outer circumferential portion 523 and the inner circumferential portion 524, so that the second seal member 52 has a higher rigidity than a seal member without the reinforcing portion 522 and has a smaller deformation amount when a force is applied in the circumferential or radial direction.

[0049] When viewed from the axial direction, the third seal member (seal member) 53 has an annular frame 531 and reinforcing portions 532, 533 connecting the long sides (an outer circumferential portion 534 and an inner circumferential portion 535) of the frame 531. A plurality of reinforcing portions 532, 533 are provided, and the plurality of reinforcing portions 532, 533 are disposed at equal intervals along the circumferential direction between the two side ends.

[0050] Therefore, the third seal member 53 has a more uniform overall rigidity than a seal member in which multiple reinforcing portions 532, 533 are arranged at unequal intervals along the circumferential direction. Since force may be input to the third seal member 53 from various circumferential or radial directions, the amount of deformation of the third seal member 53 is smaller when the third seal member 53 is subjected to a circumferential or radial force.

[0051] The reinforcing portions 512, 522 are provided on the first seal member 51 and the second seal member 52, one each, and connect the circumferential center of the outer circumferential portions 513, 523 to the circumferential center of the inner circumferential portions 514, 524. Therefore, the rigidity of the entire first seal member 51 and the entire second seal member 52 is more uniform than when the reinforcing portions 512, 522 connect the parts of the outer circumferential portions 513, 523 other than the circumferential center and the parts of the inner circumferential portions 514, 524 other than the circumferential center. Since a force may be input to the first seal member 51 and the second seal member 52 from various circumferential or radial directions, the amount of deformation of the first seal member 51 and the second seal member 52 when the first seal member 51 and the second seal member 52 are subjected to a force in the circumferential or radial direction is smaller.

[0052] Furthermore, the frame 511 and the reinforcing portion 512 of the first seal member 51 are prism bodies having a rectangular cross section, and three side surfaces of the prism body are in surface contact with the inner walls 261a, 261b, the first bottom surfaces 261c, 261d of the first groove 261, and the rear surface 30a of the cap 30. This allows the first seal member 51 to be stably disposed between the inner walls 261a, 261b, the first bottom surfaces 261c, 261d, and the rear surface 30a of the cap 30.

[0053] [First Modification] The first modified example will be described below. Fig. 13 is a cross-sectional view of a portion of a ball screw device according to the first modified example, and corresponds to Fig. 6. Fig. 14 is a cross-sectional view of a portion of a ball screw device according to the first modified example, and corresponds to Fig. 7. Fig. 15 is a plan view of a seal member according to the first modified example.

[0054] In the first modified example, as shown in Figures 13 and 14, a fourth seal member (seal member) 54 having a circular cross-sectional shape is used. This will be described in detail below.

[0055] As shown in FIG. 15, the fourth seal member (seal member) 54 has a frame body 541 and a reinforcing portion 542 when viewed from the axial direction. The frame body 541 extends in an arc shape along the circumferential direction of the nut body 20 when viewed from the axial direction of the nut 2. The frame body 541 has an outer circumferential portion 543, an inner circumferential portion 544, side ends 545, 546, and a reinforcing portion 542. The outer circumferential portion 543 and the inner circumferential portion 544 extend in an arc shape. The outer circumferential portion 543 is located radially outward of the nut body 20 with respect to the inner circumferential portion 544. The circumferential end of the outer circumferential portion 543 and the circumferential end of the inner circumferential portion 544 are connected via the side ends 545, 546. The first portion 543a of the outer circumferential portion 543 and the second portion 544a of the inner circumferential portion 544 are connected via the reinforcing portion 542. The reinforcing portion 542 extends in the radial direction of the nut body 20. The reinforcing portion 542 is located between the two side ends 545, 546. In the first modified example, the reinforcing portion 542 is provided in the circumferential center of the two side ends 545, 546. The reinforcing portion 542 crosses one opening formed in the frame body 541. Therefore, two openings 547, 548 are provided in the fourth seal member 54. In addition, the widths of the outer peripheral portion 543, the inner peripheral portion 544, and the side ends 545, 546 are all the same width W7. The width of the reinforcing portion 542 is width W8. The width W7 is the same as or larger than the width W8. That is, the width W7 is equal to or larger than the width W8.

[0056] 13 and 14, the fourth seal member 54 has a frame 541 and a reinforcing portion 542 that are all cylindrical bodies with a circular cross section, and the outer surface of the cylindrical body is in line contact with the inner walls 261a, 261b, the first bottom surfaces 261c, 261d of the first groove 261, and the rear surface 30a of the cap 30. That is, as shown in FIG. 13, the outer periphery 543 of the fourth seal member 54 is in line contact with the inner wall 264a and the fourth bottom surface 264c of the fourth groove 264, and the rear surface 30a of the cap 30. The inner periphery 544 of the fourth seal member 54 is in line contact with the inner wall 264b and the fourth bottom surface 264d of the fourth groove 264, and the rear surface 30a of the cap 30.

[0057] As described above, in the first modified example, the fourth seal member 54 has the frame 541 and the reinforcing portion 542 all formed as cylindrical bodies with a circular cross section. This allows the outer surface of the fourth seal member 54 to be in even contact with the inner walls 261a, 261b, the first bottom surfaces 261c, 261d, and the rear surface 30a of the cap 31, improving the assurance of airtightness by the fourth seal member 54. Note that a portion of the fourth seal member 54 may be a cylindrical body with a circular cross section.

[0058] [Second modified example] The second modified example will be described below. Fig. 16 is a cross-sectional view of a portion of a ball screw device according to the second modified example, and corresponds to Fig. 6. Fig. 17 is a cross-sectional view of a portion of a ball screw device according to the second modified example, and corresponds to Fig. 7. Fig. 18 is a plan view of a seal member according to the second modified example.

[0059] In the second modified example, a fifth seal member (seal member) 55 having a regular hexagonal cross-sectional shape is used as shown in Figures 16 and 17. This will be described in detail below.

[0060] As shown in FIG. 18, the fifth seal member (seal member) 55 has a frame body 551 and a reinforcing portion 552 when viewed from the axial direction. The frame body 551 extends in an arc shape along the circumferential direction of the nut body 20. The frame body 551 has an outer circumferential portion 553, an inner circumferential portion 554, side ends 555, 556, and a reinforcing portion 552. The outer circumferential portion 553 and the inner circumferential portion 554 extend in an arc shape. The outer circumferential portion 553 is located radially outward of the nut body 20 with respect to the inner circumferential portion 554. The circumferential end of the outer circumferential portion 553 and the circumferential end of the inner circumferential portion 554 are connected via the side ends 555, 556. The first portion 553a of the outer circumferential portion 553 and the second portion 554a of the inner circumferential portion 554 are connected via the reinforcing portion 552. The reinforcing portion 552 extends in the radial direction of the nut body 20. The reinforcing portion 552 is located between the two side ends 555, 556. In the second modified example, the reinforcing portion 552 is provided at the circumferential center of the two side ends 555, 556. The reinforcing portion 552 crosses one opening formed in the frame body 551. Therefore, two openings 557, 558 are provided in the fifth seal member 55. In addition, the widths of the outer peripheral portion 553, the inner peripheral portion 554, and the side ends 555, 556 are all the same width W9. The width of the reinforcing portion 552 is width W10. Width W9 is the same as or larger than width W10. That is, width W9 is equal to or larger than width W10.

[0061] 16 and 17, the fifth seal member 55 is a prism having a regular hexagonal cross section. Specifically, the frame 551 and the reinforcing portion 552 are prisms having a regular hexagonal cross section.

[0062] 16, for example, one side surface of an outer circumferential portion 553 of the fifth seal member 55 comes into surface contact with the inner wall 261b of the first groove 261. Also, one side surface of an inner circumferential portion 554 of the fifth seal member 55 comes into surface contact with the inner wall 261a of the first groove 261. This improves the airtightness provided by the fifth seal member 55. [Explanation of symbols]

[0063] 1 Screw shaft 11 Outer raceway groove 12 Ball 100 Ball screw device 2 Nuts 20 Nut body 21 Cylindrical part 211 Cylindrical Surface 22 Flange 221 Mounting hole 222 Inner raceway groove 23 First end surface 232 Tapped hole 24 One end in the axial direction (axial end) 25 Other end in the axial direction (axial end) 26 Groove 261 First groove 261a Interior wall 261b Interior wall 261c 1st bottom surface (bottom) 261d 1st bottom surface (bottom) 262 2nd groove 262a Interior wall 262b Interior wall 262c 2nd bottom 30 Cap 30a back 301 Central hole 302 Bolt hole 31 Cap 4 Coolant flow path 40 Coolant 401 Inlet 402 Outlet 410 Axial flow passage 420 Circumferential flow path 42 First circumferential flow passage (circumferential flow passage) 421 Channel End 422 Channel End 43 First axial passage (axial passage) 431 Channel End 432 Channel End 44 Second circumferential flow passage (circumferential flow passage) 441 Channel End 442 Channel End 45 Second axial flow passage (axial flow passage) 451 Channel End 452 Channel End 46 3rd circumferential flow passage (circumferential flow passage) 461 Channel End 462 Channel End 47 Third axial flow passage (axial flow passage) 471 Channel End 472 Channel End 48 4th circumferential flow passage (circumferential flow passage) 481 Channel End 482 Channel End 49 4th axial flow passage (axial flow passage) 491 Channel End 492 Channel End 5. Sealing material 51 First seal member (seal member) 511 Frame 512 Reinforcement 513 Outer periphery (long side) 513a Part 1 514 Inner circumference (long side) 514a 2nd part 515 Side edge 516 Side edge 517 Opening 518 Opening 52 second seal member (seal member) 521 Frame 522 Reinforcement 523 Outer periphery (long side) 523a Part 1 524 Inner circumference (long side) 524a 2nd part 525 Side edge 526 Side edge 527 Opening 528 Opening 53 Third seal member (seal member) 531 Frame 532 Reinforcement 533 Reinforcement 534 Outer periphery (long side) 534a Part 1 534b Part 1 535 Inner circumference (long side) 535a 2nd part 535b Part 2 536 Side edge 537 Side edge 538 Opening 539 Opening 540 Opening 54 Fourth seal member (seal member) 541 Frame 542 Reinforcement 543 Outer periphery (long side) 543a Part 1 544 Inner circumference (long side) 544a Part 2 545 Side edge 546 Side edge 547 Opening 548 Opening 55 Fifth seal member (seal member) 551 Frame 552 Reinforcement 553 Outer periphery (long side) 553a Part 1 554 Inner circumference (long side) 554a 2nd part 555 Side edge 556 Side edge 557 Opening 558 Opening AX center axis BL Bolt

Claims

1. a nut having an inner circumferential raceway groove on an inner periphery and having a plurality of axial flow paths through which a coolant flows in an axial direction; a screw shaft that penetrates the nut and has an outer periphery formed with an outer periphery raceway groove; a plurality of balls disposed between the inner circumferential raceway groove and the outer circumferential raceway groove, The nut is A nut body having a first end surface disposed at at least one of an axial end portion and an axial end portion of a central shaft, the first end surface being provided with a recessed groove; A seal member that fits into the groove; a cap that covers the groove in the first end surface and is attached to the axial end portion in a state where the groove is covered, and a cooling liquid flows in a circumferential direction through a groove that communicates between ends of two of the axial flow paths among the plurality of axial flow paths, and closes a circumferential flow path; The groove is A recess that is recessed from the first end face toward a center in the axial direction, and an outer shape of the recess extends along a circumferential direction of the nut when viewed from the axial direction of the nut, and a first groove into which the seal member is fitted; A second groove is provided inside the first groove when viewed in the axial direction of the nut, and is recessed from a bottom of the first groove toward the axial center, with ends of the two axial flow paths exposed to the inside. The sealing member is A frame extending along the first groove; A reinforcing portion connecting a pair of long sides of the frame body, Ball screw device.

2. The reinforcing portion is provided in one piece, One of the reinforcing portions connects the circumferential centers of the pair of long sides to each other. The ball screw device according to claim 1 .

3. The reinforcing portion is provided in plurality, The reinforcing portions are arranged at equal intervals along the circumferential direction. The ball screw device according to claim 1 .

4. The first groove faces an inner wall extending from the first end face toward a center in the axial direction and a bottom portion extending from an end portion of the inner wall toward the center in the axial direction along the first end face, The sealing member includes a cylindrical body having a circular cross section, and an outer surface of the cylindrical body is in line contact with the inner wall of the first groove, the bottom, and the back surface of the cap. The ball screw device according to any one of claims 1 to 3.

5. The first groove faces an inner wall extending from the first end face toward a center in the axial direction and a bottom portion extending from an end portion of the inner wall toward the center in the axial direction along the first end face, The sealing member includes a prism having a polygonal cross-sectional shape. The ball screw device according to any one of claims 1 to 3.

6. The sealing member includes a prism having a rectangular cross section, Three side surfaces of the prism body are in surface contact with the inner wall of the first groove, the bottom, and the back surface of the cap. The ball screw device according to claim 5.

7. The sealing member includes a prism having a regular hexagonal cross section, One side surface of the prismatic body is in surface contact with the inner wall of the first groove. The ball screw device according to claim 5.

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