Seal member

Abstract

To achieve securing seal performance and reducing slide resistance in a seal member used in a screw device.SOLUTION: In a ball screw device 10 having a screw shaft 20 and a nut 30, a seal member 40 includes: an annular shaft seal 50 disposed in an approximately annular space A between the screw shaft 20 and the nut 30, and including an annular frame body 51 and a pile material 52 covering an inner peripheral surface 51a of the annular frame body 51; and an annular seal case 60 accommodating the shaft seal 50. The seal member has an annular recess 62 formed in an inner peripheral surface 61b, and accommodates the shaft seal 50 in the annular recess 62.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a sealing member technology. [Background technology]

[0002] A screw device is known as a mechanical element that converts the rotational motion of a motor or the like into linear motion. The screw device includes a screw shaft having a helical groove on its outer circumference, and a nut having a helical groove on its inner circumference. A ball screw device, which is an example of a screw device, further includes a plurality of balls that roll between the screw shaft and the nut. If foreign matter enters the inside of the screw device, the screw device may be deteriorated, such as by decreasing the feed accuracy of the screw device or increasing the torque required for rotation. For this reason, the screw device includes a seal member for suppressing the intrusion of foreign matter between the screw shaft and the nut. As seal members for such screw devices, non-contact type seal members using labyrinth seals (see Patent Document 1) and contact type seal members using elastomer materials such as rubber (see Patent Document 2) are known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-155702 A [Patent Document 2] Japanese Utility Model Application Publication No. 07-004952 Summary of the Invention [Problem to be solved by the invention]

[0004] With conventional non-contact type seal members, it is difficult to eliminate the gap between the seal member and the screw shaft, so it is difficult to sufficiently prevent the intrusion of foreign matter, i.e., to sufficiently ensure sealing performance. Also, conventional contact type seal members have the problem that the sliding resistance increases due to contact with the screw shaft.

[0005] An object of the present disclosure is to provide a sealing member used in a screw device that achieves both ensuring sealing performance and reducing sliding resistance. [Means for solving the problem]

[0006] The sealing member of the present disclosure is a sealing member that is arranged in an approximately annular space between a screw shaft and a nut in a screw device having the screw shaft and the nut, and includes a ring-shaped frame body, a ring-shaped shaft seal including a pile material covering the inner surface of the frame body, and a ring-shaped case that houses the shaft seal, wherein the case has an annular recess formed on its inner surface, and the shaft seal is housed in the annular recess. Effect of the Invention

[0007] According to the present disclosure, it is possible to ensure sealing performance and reduce sliding resistance in a sealing member used in a screw device. [Brief description of the drawings]

[0008] [Figure 1] FIG. 4 is an enlarged perspective view showing an arrangement of a seal member in the screw device. [Diagram 2] 4 is a cross-sectional view showing the arrangement of a seal member in a screw device. FIG. [Diagram 3] FIG. 2 is a perspective view showing a sealing member according to the first embodiment. [Figure 4] 3 is a cross-sectional view showing the positional relationship between the seal member and a screw shaft according to the first embodiment. FIG. [Diagram 5] FIG. [Figure 6] 5 is an explanatory diagram of a method for attaching a seal member to a screw shaft. FIG. [Figure 7] FIG. 11 is a perspective view showing a sealing member according to a second embodiment. [Figure 8] FIG. 11 is a cross-sectional view showing the positional relationship between a seal member and a screw shaft according to a second embodiment. [Figure 9] FIG. 11 is a perspective view of a seal case constituting a seal member according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Overview of the embodiment of the present disclosure> Below, an overview of the embodiments of the present disclosure will be listed and described. (1) The seal member of the present disclosure is a seal member disposed in a substantially annular space between a screw shaft and a nut in a screw device having the screw shaft and a nut. The seal member of the present disclosure includes an annular frame, an annular shaft seal including a pile material covering an inner peripheral surface of the frame, and an annular case that houses the shaft seal. The case has an annular recess formed on its inner peripheral surface, and houses the shaft seal in the annular recess.

[0010] The seal member of the above configuration uses the pile material to seal the gap between the seal member and the screw shaft, preventing foreign matter from entering through the gap, and also reduces the sliding resistance between the seal member and the screw shaft by bringing the tips of the cut piles that make up the pile material into point contact with the screw shaft. Therefore, the seal member of the above configuration can ensure both sealing performance and reduced sliding resistance for a seal member used in a screw device.

[0011] (2) In the seal member according to the embodiment (1), it is preferable that the case further has a labyrinth seal portion protruding radially inward from the inner circumferential surface at at least one end portion of the annular recess on one axial side and the other axial side. The seal member having the above configuration can improve sealing performance while preventing an increase in sliding resistance by including a labyrinth seal portion that does not contact the screw shaft.

[0012] (3) In the seal member according to the embodiment (2), it is preferable that the case has the labyrinth seal portion at one and the other axial end portions of the annular recess. The seal member having the above configuration can further improve the sealing performance by providing labyrinth seal portions that do not come into contact with the screw shaft at both axial end portions.

[0013] (4) In the seal member according to any one of the embodiments (1) to (3), it is preferable that the inner diameter of the inner peripheral part of the pile material is smaller than the outer diameter of the screw shaft. A seal member having such a configuration can reliably bring the inner peripheral surface of the pile material (the tips of the cut piles) into contact with the outer peripheral surface of the screw shaft. This allows the pile material to reliably seal the gap between the screw shaft and the pile material, ensuring the sealing performance of the seal member.

[0014] (5) In the seal member according to any one of the embodiments (1) to (4), it is preferable that the frame has a slit portion that is discontinuous in the circumferential direction. In the seal member having such a configuration, the shaft seal can ensure elasticity in the radial direction by having the slit portion. Therefore, the shaft seal can make the outer circumferential surface tightly contact the inner circumferential surface of the annular recess by utilizing this elasticity. This makes it possible to suppress the gap between the shaft seal and the case, and reliably ensure the sealing performance of the seal member.

[0015] (6) In the seal member according to any one of the embodiments (1) to (5), it is preferable that the shaft seal is configured to be detachable from the case. The seal member configured in this way allows the shaft seal to be replaced in a cartridge-like manner. This improves the efficiency of the work of replacing the seal member.

[0016] <Details of the embodiment of the present disclosure> Hereinafter, the details of the embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any combination.

[0017] [Overall configuration of the screw device] FIG. 1 is an enlarged perspective view showing the arrangement of the sealing member in the screw device. FIG. 2 is a cross-sectional view showing the arrangement of the sealing member in the screw device. In addition, an xyz Cartesian coordinate system is attached to FIG. 1 and FIG. 2 for the purpose of explaining the screw device. In the following explanation, the x-axis direction is referred to as the "axial direction", the positive side of the x-axis direction is referred to as the "one axial side", and the negative side of the x-axis direction is referred to as the "other axial side". In addition, the yz plane is a plane perpendicular to the axial direction.

[0018] 1 and 2 show a ball screw device 10, which is one embodiment of a screw device. The ball screw device 10 is an example of a screw device to which the seal member of the present disclosure is applied. As shown in Fig. 1 and 2, the ball screw device 10 includes a screw shaft 20, a nut 30, and a seal member 40.

[0019] The ball screw device 10 is a device that converts the rotation of one of the screw shaft 20 and the nut 30 into the axial displacement of the other of the screw shaft 20 and the nut 30. One of the screw shaft 20 and the nut 30 is connected to a rotating mechanism (not shown) such as a motor and a pulley, and is rotated around a center line C by the rotating mechanism. As a result, the other of the screw shaft 20 and the nut 30 moves linearly in the axial direction. That is, the screw shaft 20 and the nut 30 rotate relatively around the center line C. Note that, in the present embodiment, the ball screw device 10 in which the nut 30 includes a ball 32a (see FIG. 3) is illustrated for explanation, but the screw device to which the seal member of the present disclosure is applied does not have to be a ball screw device, and may be a screw device that does not include a ball.

[0020] As shown in Figs. 1 and 2, the screw shaft 20 is an axial member whose axis is a center line C, and is provided so as to be rotatable around the center line C. A screw thread 21 is formed helically on an outer peripheral surface 20a of the screw shaft 20. A screw groove 22 is formed helically between two screw threads 21 adjacent to each other in the axial direction. The center line C is parallel to the x-axis direction (axial direction). In the following description, the direction perpendicular to the center line C is referred to as the "radial direction", and the direction around the center line C is referred to as the "circumferential direction".

[0021] 2, the nut 30 supports the screw shaft 20 so as to be rotatable in the circumferential direction and displaceable in the axial direction. The nut 30 includes a housing 31 and a nut portion 32.

[0022] The housing 31 is a substantially cylindrical member, and has a through hole 31a penetrating in the axial direction, and a seal case portion 31b in which the through hole 31a is enlarged at one end in the axial direction. The seal case portion 31b is an annular recess formed coaxially with the through hole 31a, and accommodates the seal member 40. The seal case portion 31b has a step portion 31d at the other end in the axial direction. The seal member 40 accommodated in the seal case portion 31b has an outer peripheral surface (an outer peripheral surface 61a of a case main body 61 described later) in contact with the inner peripheral surface 31f, and an end face on the other axial direction in contact with the step portion 31d.

[0023] The nut portion 32 is a portion that functions as a nut that screws onto the screw shaft 20 (the thread 21 and the thread groove 22), and is formed on the other axial side of the housing 31. The case portion 32b is a substantially cylindrical portion that protrudes radially inward from the inner peripheral surface of the through hole 31a. The nut portion 32 includes a plurality of balls 32a and a case portion 32b that houses the plurality of balls 32a. A screw groove 32c that holds the balls 32a between the screw groove 22 and the inner peripheral surface of the case portion 32b is formed in a spiral shape. A passage 32d that communicates between one end of the screw groove 32c in the axial direction and the other end of the screw groove 32c in the axial direction is formed inside the case portion 32b. The balls 32a circulate in a series of closed paths formed by the screw groove 32c and the passage 32d.

[0024] The housing 31 further has a flange portion 33. The flange portion 33 is a portion extending radially outward from one axial end of the housing 31. The flange portion 33 is used as a portion for fixing the nut 30 to a device (not shown). The seal case portion 31b is located radially inward of the flange portion 33.

[0025] The housing 31 further has a through hole 34. The through hole 34 is a hole for passing a set screw 35, and penetrates radially from the radial outside of the flange portion 33 to the seal case portion 31b. The through hole 34 has a female thread (not shown) for screwing in the set screw 35. The set screw 35 is a member for fixing the seal member 40 housed in the seal case portion 31b to the nut 30 (housing 31).

[0026] As shown in FIGS. 1 and 2, in the ball screw device 10, a space A having a substantially annular shape is formed between the screw shaft 20 and an inner circumferential surface 31f of the seal case portion 31b.

[0027] The seal member 40 is a sealing material that seals the space A, and has an annular shape. The seal member 40 prevents foreign matter from entering the inside of the nut 30 through the space A.

[0028] 1 and 2, the seal member 40 is accommodated in the seal case portion 31b (space A) and is fixed to the housing 31 by the set screws 35. The set screws 35 restrict displacement of the seal member 40 in the axial, radial, and circumferential directions.

[0029] [About sealing materials] FIG. 3 is a perspective view showing a seal member according to the first embodiment. FIG. 4 is a cross-sectional view showing the positional relationship between the seal member according to the first embodiment and a screw shaft. FIGS. 3 and 4 show a first embodiment of a seal member 40 of the present disclosure. In the following description, the seal member 40 according to the first embodiment is also referred to as a first seal member 40X. In the following description, when simply referring to the seal member 40, a common configuration between the first seal member 40X and a seal member according to another embodiment described later (a second seal member 40Y described later) will be described.

[0030] 3 and 4, the seal member 40 of the present disclosure has an annular shape and includes a through hole 40a that penetrates in the axial direction. The seal member 40 includes a shaft seal 50 and a seal case (case) 60. The through hole 40a is defined by an inner periphery 52a of the shaft seal 50, which will be described later.

[0031] [About shaft seals] Fig. 5 is an explanatory diagram of a shaft seal. Fig. 4 and Fig. 5 show a shaft seal 50, which is one embodiment of the shaft seal constituting the seal member 40 of the present disclosure. As shown in Fig. 4 and Fig. 5, the shaft seal 50 is a seal body having an annular shape, and is configured to include a frame body 51 and a pile material 52.

[0032] The frame 51 is a member made by bending a metallic ribbon-shaped plate material into a substantially circular ring shape. The frame 51 is made by bending the ribbon-shaped plate material so that one end and the other end in the length direction are opposed to each other. The substantially circular frame 51 has an inner peripheral surface 51a and an outer peripheral surface 51b. The frame 51 has a slit portion 53 by providing a gap between the one end and the other end when bending the ribbon-shaped plate material. In other words, the frame 51 has the slit portion 53 with a part of the circumferential direction being discontinuous. The slit portion 53 has a gap of a predetermined distance when no radial stress is applied to the frame 51 (also called a steady state).

[0033] The frame 51 is configured such that the outer diameter dimension when the circumferential gap formed in the slit portion 53 is the predetermined distance (i.e., in a steady state) is slightly larger than the inner diameter dimension of the annular recess 62, and the outer diameter dimension when the frame 51 is deformed so that the gap in the slit portion 53 is substantially "0" is smaller than the inner diameter dimension of the annular recess 62. The shaft seal 50 can be easily fitted into the annular recess 62 in a state in which the gap in the slit portion 53 is reduced. In addition, the shaft seal 50 can make the outer peripheral surface 51b of the frame 51 adhere closely to the inner peripheral surface of the annular recess 62 by restoring the frame 51 to the steady state after fitting into the annular recess 62. With such a configuration, the shaft seal 50 can suppress the gap between the annular recess 62.

[0034] The pile material 52 is a fiber material mainly made of polyester. The pile material 52 is a sheet-like pile knitted fabric including cut pile protruding from the surface. The pile material 52 may be a fiber material made of PFA (perfluoroalkoxyalkane) or PTFE (polytetrafluoroethylene).

[0035] In the shaft seal 50, the inner peripheral surface 51a of the frame body 51 is covered with the pile material 52. Therefore, each fiber of the cut pile constituting the pile material 52 is arranged so as to extend radially toward the center of the frame body 51 in the radial direction. In the shaft seal 50, the tip of the cut pile is arranged on the inner peripheral portion 52a of the pile material 52.

[0036] The pile material 52 is fixed to the inner peripheral surface 51a of the frame body 51 using an adhesive. The adhesive used to fix the pile material 52 to the frame body 51 is, for example, a hot melt adhesive, more specifically, a rubber-based or polyester-based hot melt adhesive. By using a hot melt adhesive, for example, swelling when a liquid such as a coolant liquid penetrates into the seal member 40 during use of the ball screw device 10 can be suppressed, and peeling of the pile material due to swelling of the adhesive can be suppressed. Note that, if there is a low possibility of swelling during use of the ball screw device 10, a solvent-based adhesive that exerts its adhesive function by drying an organic solvent may be used as the adhesive, or a water-based adhesive containing vinyl acetate resin as a component may be used, or a double-sided tape may be used.

[0037] Conventional sealing members such as nonwoven fabric seals, wiper-type resin seals, and brush seals have surface or line contact between the sealing member and the screw shaft. On the other hand, the sealing member 40 of this embodiment uses pile material 52, so that the contact between the pile material 52 (the tip of the cut pile) and the outer circumferential surface 20a of the screw shaft 20, the thread 21, and the thread groove 22 becomes point contact, and the resistance that the sealing member 40 gives to the screw shaft 20 can be reduced. In addition, the sealing member 40 of this embodiment uses pile material 52, so that the sealing performance against foreign matter, dust, etc. can be ensured, and the retention of grease used in the nut 30 can be improved.

[0038] [About the seal case] 3 and 4 show a seal case 60 according to the first embodiment. In the following description, the seal case 60 according to the first embodiment is also referred to as a first seal case 60X. The first seal member 40X is configured to include the first seal case 60X. Note that in the following description, when simply referring to the seal case 60, a common configuration between the first seal case 60X and a seal case according to another embodiment described later (a second seal case 60Y described later) will be described.

[0039] 3 and 4, the seal case 60 includes an annular case body 61. The case body 61 includes an outer peripheral surface 61a and an inner peripheral surface 61b. The inner peripheral surface 61b is an annular recess 62 for accommodating the shaft seal 50.

[0040] [Regarding the first embodiment of the sealing member] The first seal member 40X shown in Figs. 3 and 4 includes a shaft seal 50 and a first seal case 60X. The first seal member 40X is formed by fitting the shaft seal 50 into an annular recess 62 in the first seal case 60X and integrating the first seal case 60X and the shaft seal 50. The shaft seal 50 is fitted into a position where an end face in the axial direction contacts a step portion 63 of the first seal case 60X. The shaft seal 50 is detachable from the first seal case 60X. The first seal member 40X requires only replacement of the shaft seal 50, and the first seal case 60X can be repeatedly reused.

[0041] As shown in FIG. 4, the first seal member 40X is used in a state where the screw shaft 20 is inserted into the through hole 40a. The first seal member 40X is configured so that the inner diameter φD2 of the through hole 40a (the inner peripheral portion 52a of the shaft seal 50) is smaller than the outer diameter φD1 of the screw shaft 20 (φD1>φD2). Therefore, in the first seal member 40X, the inner peripheral portion 52a (the tip of the cut pile) of the pile material 52 is reliably in contact with the outer peripheral surface 20a of the screw shaft 20, the thread 21, and the thread groove 22. Therefore, the first seal member 40X can reliably seal the gap between the screw shaft 20 and the pile material 52. As a result, the first seal member 40X can ensure high sealing performance.

[0042] In the first seal member 40X, the shaft seal 50 has tips of cut piles constituting the pile material 52 that make point contact with the outer circumferential surface 20a of the screw shaft 20, the threads 21, and the screw grooves 22. Therefore, the first seal member 40X can suppress the sliding resistance between the screw shaft 20 and the shaft seal 50, compared to conventional seal members that make surface and line contact with the screw shaft. Therefore, the first seal member 40X used in screw devices including the ball screw device 10 can ensure both sealing performance and reduction of sliding resistance.

[0043] [How to install the seal] FIG. 6 is an explanatory diagram of a method of attaching a seal member to a screw shaft. As shown in FIG. 6, the seal member 40 is attached from the axial end of the screw shaft 20. When attaching the seal member 40 to the screw shaft 20, the shaft seal 50 and the seal case 60 are first separated, and the seal case 60 is attached to the screw shaft 20 first, and then the shaft seal 50 is attached to the screw shaft 20. Next, the shaft seal 50 is fitted into the annular recess 62 of the seal case 60 to form the seal member 40. Then, the seal member 40 is displaced toward the nut 30 along the screw shaft 20 and is housed in the seal case portion 31b. The seal member 40 of the present disclosure is disposed in the seal case portion 31b (space A) by the above procedure.

[0044] [Second embodiment of the sealing member] FIG. 7 is a perspective view showing a seal member according to a second embodiment. FIG. 8 is a cross-sectional view showing the positional relationship between the seal member according to the second embodiment and the screw shaft. FIG. 9 is a perspective view of a seal case constituting the seal member according to the second embodiment. FIGS. 7 and 8 show a seal member 40 according to a second embodiment of the present disclosure. In the following description, the seal member 40 according to the second embodiment is also referred to as a second seal member 40Y. The second seal member 40Y differs from the first seal member 40X (see FIG. 3) in that it includes a seal case 60 according to a second embodiment shown in FIGS. 7 to 9. In the following description, the seal case 60 according to the second embodiment is also referred to as a second seal case 60Y. In the following description, the configuration of the second seal member 40Y that is different from that of the first seal member 40X will be described, and a description of common features will be omitted.

[0045] The second seal member 40Y shown in Figures 7 and 8 includes a shaft seal 50 and a second seal case 60Y. The second seal member 40Y is configured by fitting the shaft seal 50 into the annular recess 62 of the second seal case 60Y to integrate the second seal case 60Y and the shaft seal 50. The shaft seal 50 is detachable from the second seal case 60Y. The second seal member 40Y requires only the shaft seal 50 to be replaced, and the second seal case 60Y can be repeatedly reused.

[0046] As shown in FIG. 8, the second seal member 40Y is used in a state where the screw shaft 20 is inserted into the through hole 40a. The second seal member 40Y is configured so that the inner diameter φD2 of the through hole 40a (the inner peripheral portion 52a of the shaft seal 50) is smaller than the outer diameter φD1 of the screw shaft 20 (φD1>φD2). Therefore, the inner peripheral portion 52a (the tip of the cut pile) of the pile material 52 of the second seal member 40Y is reliably in contact with the outer peripheral surface 20a of the screw shaft 20, the thread 21, and the thread groove 22. Therefore, the second seal member 40Y can reliably seal the gap between the screw shaft 20 and the pile material 52. As a result, the second seal member 40Y can ensure high sealing performance.

[0047] As shown in FIG. 8, the second seal case 60Y constituting the second seal member 40Y includes a labyrinth seal portion 64. The labyrinth seal portion 64 has a shape that can be screwed with the screw groove 22 with a gap. The radial inner end of the labyrinth seal portion 64 is inserted into the screw groove 22. The labyrinth seal portion 64 can scrape off foreign matter attached to the outer circumferential surface 20a (thread 21 and screw groove 22) of the screw shaft 20, thereby preventing the foreign matter from entering the axial inner side of the second seal member 40Y. The labyrinth seal portion 64 can prevent foreign matter having an outer shape larger than the gap between the labyrinth seal portion 64 and the screw shaft 20 from entering the axial inner side. In addition, the labyrinth seal portion 64 can also prevent the foreign matter from flowing out again to the outside of the second seal member 40Y (pile material 52) when the foreign matter enters the axial inner side of the second seal member 40Y.

[0048] In the second seal case 60Y, the labyrinth seal portion 64 is provided at both ends in the axial direction. Therefore, the second seal member 40Y can suppress foreign matter that attempts to enter the nut 30 from one side in the axial direction of the second seal member 40Y by the two labyrinth seal portions 64 provided on both axial sides. By providing the labyrinth seal portion 64 twice, the second seal member 40Y is more effective in suppressing foreign matter from passing over the second seal member 40Y and entering the nut 30. Note that, although the second seal member 40Y shown in this embodiment is provided with the labyrinth seal portion 64 at both ends in the axial direction, the seal member 40 of the present disclosure may be configured such that the labyrinth seal portion 64 is provided at either one end on the one axial side or the other axial side. In addition, in the second seal case 60Y, the labyrinth seal portion 64 fulfills the function of the step portion 63 (see FIG. 3) in the first seal case 60X, so that the step portion 63 is omitted.

[0049] The seal member 40 having the labyrinth seal portion 64 can ensure a certain degree of sealing performance in the screw groove 22 only with the labyrinth seal portion 64, for example, when the depth of the screw groove 22 is sufficiently large. On the other hand, when the depth of the screw groove 22 is relatively small, it is difficult to provide the seal member 40 with a labyrinth seal portion 64 with a small height, and therefore it is difficult to ensure a sealing performance in the screw groove 22 only with the labyrinth seal portion 64. On the other hand, the seal member 40 having the shaft seal 50 including the pile material 52 can accommodate to a certain degree the height of the screw thread 21 and the depth of the screw groove 22 within the range of the fiber length of the cut pile of the pile material 52. Therefore, the seal member 40 having the shaft seal 50 can be used as a general-purpose seal material regardless of the size of the screw groove 22.

[0050] The second seal member 40Y, which has both the shaft seal 50 and the labyrinth seal portion 64, can ensure stable sealing performance regardless of the form of the foreign matter that is expected to intrude, by suppressing the intrusion of foreign matter with a relatively small particle size with the shaft seal 50 and suppressing the intrusion of foreign matter with a relatively large particle size with the labyrinth seal portion 64. The second seal member 40Y of the present disclosure can ensure sealing performance for both foreign matter with a relatively small particle size and foreign matter with a relatively large particle size by combining the pile material 52 made of cut pile with the labyrinth seal portion 64.

[0051] In the second seal member 40Y, the pile material 52 has a tip that is in point contact with the outer peripheral surface 20a, the thread 21, and the thread groove 22 of the screw shaft 20. Therefore, the second seal member 40Y can suppress the sliding resistance between the screw shaft 20 and the shaft seal 50, compared to a conventional seal member that makes surface contact and line contact with the screw shaft. In addition, in the second seal member 40Y, the labyrinth seal portion 64 is not in contact with the outer peripheral surface 20a, the thread 21, and the thread groove 22 of the screw shaft 20, and does not become a factor that increases the sliding resistance between the screw shaft 20 and the shaft seal 50. Therefore, the second seal member 40Y can suppress the sliding resistance generated between the screw shaft 20 and the shaft seal 50, compared to a conventional seal member that makes surface contact and line contact with the screw shaft 20. Therefore, the second seal member 40Y used in a screw device including a ball screw device 10 can ensure both sealing performance and reduction of sliding resistance.

[0052] [Actions and Effects of the Present Embodiment] (1) The seal member 40 of this embodiment is a seal member disposed in a substantially annular space A between a screw shaft 20 and a nut 30 in a ball screw device 10 having the screw shaft 20 and the nut 30. The seal member 40 includes an annular frame 51, an annular shaft seal 50 including a pile material 52 covering an inner circumferential surface 51a of the frame 51, and an annular seal case 60 that houses the shaft seal 50. The seal case 60 has an annular recess 62 formed on an inner circumferential surface 61b, and houses the shaft seal 50 in the annular recess 62.

[0053] The seal member 40 of this embodiment uses the pile material 52 to seal the gap between the seal member 40 and the screw shaft 20, preventing foreign matter from entering through the gap, and also reduces sliding resistance between the seal member 40 and the screw shaft 20 by bringing the tips of the cut piles constituting the pile material 52 into point contact with the screw shaft 20. Therefore, with the seal member 40 configured in this way, it is possible to ensure both sealing performance and reduction in sliding resistance for the seal member 40 used in screw devices including the ball screw device 10.

[0054] (2) In the seal member 40 of this embodiment, the seal case 60 further has a labyrinth seal portion 64 protruding radially inward from the inner circumferential surface 61b at least one end portion on one axial side and the other axial side of the annular recess 62. The seal member 40 having such a configuration is provided with the labyrinth seal portion 64 that does not come into contact with the screw shaft 20, thereby preventing an increase in sliding resistance and further improving the sealing performance.

[0055] (3) In the seal member 40 of this embodiment, the seal case 60 has labyrinth seal portions 64 at one and the other axial ends of the annular recess 62. The seal member 40 configured in this manner can further improve the sealing performance by providing the labyrinth seal portions 64, which do not come into contact with the screw shaft 20, at both axial ends.

[0056] (4) In the seal member 40 of this embodiment, the inner diameter φD2 of the inner peripheral portion 52a of the pile material 52 of the shaft seal 50 is smaller than the outer diameter φD1 of the screw shaft 20 (φD1>φD2). The seal member 40 having such a configuration can reliably bring the pile material 52 (tips of the cut piles) into contact with the outer peripheral surface 20a of the screw shaft 20. This allows the pile material 52 to reliably seal the gap between the pile material 52 and the screw shaft 20, ensuring the sealing performance of the seal member 40.

[0057] (5) In the seal member 40 of this embodiment, the frame 51 has a slit portion 53 that is discontinuous midway in the circumferential direction. In the seal member 40 configured in this manner, the shaft seal 50 can ensure elasticity in the radial direction by having the slit portion 53. Therefore, the shaft seal 50 can make the outer circumferential surface 51b tightly contact the inner circumferential surface of the annular recess 62 by utilizing this elasticity. This makes it possible to reduce the gap between the shaft seal 50 and the seal case 60, and ensure the sealing performance of the seal member 40.

[0058] (6) In the seal member 40 of the present embodiment, the shaft seal 50 is configured to be detachable from the seal case 60. The seal member 40 configured in this manner allows the shaft seal 50 to be replaced in a cartridge-like manner. This improves the efficiency of the work of replacing the seal member 40. [Explanation of symbols]

[0059] 10 Ball screw device (screw device) 20 Screw shaft 30 Nut 40 Sealing material 40X First seal member 40Y Second seal member 50 Shaft seal 51 Frame 51a Inner surface 52 Pile material 53 Slit section 60 Seal Case (Case) 61a Inner surface 62 Annular recess 64 Labyrinth seal part A Space φD1 Outer diameter of screw shaft φD2 Inner diameter of the inner circumference

Claims

1. A seal member disposed in a substantially annular space between a screw shaft and a nut in a screw device having a screw shaft and a nut, An annular shaft seal including a ring-shaped frame and a pile material covering an inner peripheral surface of the frame; a ring-shaped case that houses the shaft seal; The case has an annular recess formed on an inner circumferential surface thereof, and the shaft seal is housed in the annular recess.

2. 2. The sealing member according to claim 1, wherein the case further has a labyrinth seal portion protruding radially inward from the inner circumferential surface at at least one end portion on one axial side and the other axial side of the annular recess.

3. The seal member according to claim 2 , wherein the case has the labyrinth seal portion at one end and the other end in the axial direction of the annular recess.

4. 3. The sealing member according to claim 1, wherein the inner diameter of the inner peripheral portion of the pile material is smaller than the outer diameter of the screw shaft.

5. The seal member according to claim 1 or 2, wherein the frame has a slit portion that is discontinuous midway in the circumferential direction.

6. The seal member according to claim 1 or 2, wherein the shaft seal is configured to be detachable from the case.

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