Sealing member for ball screw, and ball screw

Abstract

A ball screw seal member is provided with: an annular seal body fixed to the inner peripheral surface of at least one axial end of a nut; and a seal mountain portion formed in the circumferential direction on the inner diameter side of the seal body portion so as to enter the screw groove of the screw shaft, the seal mountain portion forming a labyrinth gap between the seal mountain portion and the screw groove of the screw shaft, and the seal mountain portion being formed in the circumferential direction with a cavity portion cut from one side in the axial direction. As a result, it is possible to maintain more grease and achieve long-term stable lubrication.

Description

Technical Field

[0001] This invention relates to sealing components for ball screws and ball screws themselves. Background Technology

[0002] Traditionally, ball screws that convert rotary motion into linear motion typically have a screw shaft with a helical thread groove on its outer circumference and a nut with a helical thread groove on its inner circumference. Multiple balls that roll along with the rotational motion of the screw shaft or nut are filled between the two thread grooves of the screw shaft and the nut.

[0003] In addition, such as Figure 11 As shown in (a) and (b), a sealing member 140 is typically installed at the end of the nut 30 of the ball screw, which has two functions: inhibiting grease leakage from the nut 30 and preventing foreign matter from entering the nut 30. The general-purpose sealing member 140 is molded from resin and has a sealing body 141 installed at the end of the nut 30 and a sealing groove 142 that enters the threaded groove 21 of the screw shaft 20, forming a structure with a small gap between it and the threaded groove 21 of the screw shaft 20.

[0004] Lubrication of such ball screws is usually achieved by grease accumulating in the gaps inside the nut, without automatic grease supply at fixed intervals.

[0005] In the feed screw device described in Patent Document 1, the following is described: a sealing component is formed by a lubricant-containing polymer component, and a lubricant reservoir is formed at a location other than the portion of the lubricant-containing polymer component that contacts the sealed surface of the screw shaft. Lubricant sealed in the lubricant reservoir permeates into the lubricant-containing polymer component, thereby replenishing the lubricant. Furthermore, in the ball screw described in Patent Document 2, deformable grooves are formed on both the sealing body side and the sealing mountain side of the dustproof unit, facilitating the insertion of the nut and the threaded groove of the screw shaft.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 3648855

[0009] Patent Document 2: Chinese Utility Model No. 209430705 Specification Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] However, in ball screws, a larger space inside the nut to hold the grease is preferable, as it facilitates lubrication supply. On the other hand, if excessive space is provided inside the nut, the overall length of the nut increases, leading to issues such as damage and space-saving problems.

[0012] In reference 1, the lubricant reservoir is located on the side of the sealing body. However, the lubricant reservoir is relatively small, and it is also far from the inner circumferential surface of the sealing hill. Therefore, further improvements are required to retain and supply more grease. In reference 2, the deformation groove of the sealing hill is formed with insertion considerations, which makes it impossible to retain more grease.

[0013] The present invention was made in view of the above-mentioned problems, and its object is to provide a sealing component for ball screws and a ball screw that can retain more grease and achieve long-term stable lubrication.

[0014] means for solving problems

[0015] The above-mentioned objective of the present invention is achieved by the following structure.

[0016] [1] A sealing component for a ball screw, comprising: a screw shaft having a helical thread groove formed on its outer circumferential surface; a nut having a helical thread groove formed on its inner circumferential surface; and a plurality of balls rolling in a load raceway formed by the thread groove of the screw shaft and the thread groove of the nut, wherein the sealing component seals the gap between the screw shaft and the nut, wherein...

[0017] The ball screw sealing component comprises: an annular sealing body portion fixed to the inner circumferential surface of the axial end of the nut; and a sealing bevel portion formed circumferentially on the inner diameter side of the sealing body portion such that it enters the threaded groove of the screw shaft, and a labyrinthine gap is formed between the sealing bevel portion and the threaded groove of the screw shaft.

[0018] In the sealed mountain section, a cavity is formed along the circumferential direction by being cut out from one side of the axial direction.

[0019] [2] A ball screw,

[0020] The ball screw comprises: a screw shaft having a helical thread groove formed on its outer circumferential surface; a nut having a helical thread groove formed on its inner circumferential surface; a plurality of balls rolling in a load raceway formed by the thread groove of the screw shaft and the thread groove of the nut; and [1] a sealing member for the ball screw, the sealing member sealing the gap between the screw shaft and the nut.

[0021] The hollow portion faces the space between the threaded groove of the lead screw shaft and the threaded groove of the nut.

[0022] Invention Effects

[0023] According to the ball screw sealing component and ball screw of the present invention, the cavity retains more grease, and the oil of the grease accumulated in the cavity is gradually supplied to the space between the thread groove of the screw shaft and the thread groove of the nut, thereby achieving long-term stable lubrication. Attached Figure Description

[0024] Figure 1 This is a front view of the ball screw according to the first embodiment of the present invention.

[0025] Figure 2 It is shown Figure 1 The diagram shows a cross-sectional view of the sealing component installed with a nut.

[0026] Figure 3 (a) is a perspective view of the sealing component, and (b) is a side view of the sealing component.

[0027] Figure 4 It is along Figure 3 (b) Sectional view of line VI-VI.

[0028] Figure 5 (a) is a perspective view of the sealing component of the first modified example, and (b) is a side view of the sealing component of (a).

[0029] Figure 6 (a) is along Figure 5 (b) Sectional view of line VIa-VIa, Figure 6 (b) is along Figure 5 (b) is a cross-sectional view of line VIb-VIb. Figure 6 (c) is along Figure 5 (b) A sectional view of the VIc-VIc line. Figure 6 (d) is along Figure 5 (b) A cross-sectional view of the VId-VId line.

[0030] Figure 7 This is a perspective view of the sealing component in the second variation.

[0031] Figure 8 (a) is a perspective view of the sealing component of the third variation, and (b) is a side view of the sealing component of (a).

[0032] Figure 9 This is a side view of the sealing component of the fourth variation.

[0033] Figure 10This is a cross-sectional view of the sealing component in the fifth variation.

[0034] Figure 11 (a) shows the existing sealing component installed with the nut, and (b) is a perspective view of the existing sealing component. Detailed Implementation

[0035] Hereinafter, a ball screw according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0036] like Figure 1 As shown, the ball screw 10 of this embodiment includes: a screw shaft 20 having a helical threaded groove 21 on its outer peripheral surface and extending axially; a nut 30 having a helical threaded groove (not shown) on its inner peripheral surface corresponding to the threaded groove 21 of the screw shaft 20; a plurality of balls (not shown) rolling in a load raceway formed by the threaded groove 21 of the screw shaft 20 and the threaded groove of the nut 30; and a sealing member 40 sealing the gap between the screw shaft 20 and the nut 30.

[0037] Multiple circulation components (not shown) are provided on the outer circumferential surface of the nut 30. These circulation components penetrate the nut 30 at both ends, and each has a scooping portion for retrieving balls. Thus, balls scooped at one end of the load raceway return to the other end of the load raceway through the circulation components, thereby forming an infinite circulation path. Furthermore, in... Figure 1 In the figure, reference numeral 11 is a cover for the circulation component used to fix the circulation component to the nut.

[0038] exist Figure 1 In the nut 30, five circulation components are provided, thus forming five infinite circulation paths.

[0039] The nut 30 has a flange 32 formed at one axial end and circular recesses 33 with an inner diameter larger than the threaded groove formed concentrically at both axial ends. The flange 32 is fixed to a movable table or the like of a mechanical device (not shown) by mounting bolts or the like.

[0040] A sealing component 40 is provided on the inner circumferential surface of the circular recess 33 to seal the gap between the lead screw shaft 20 and the nut 30. The sealing component 40 is made of resin such as high molecular weight polyethylene resin. Figures 2 to 4As shown, the sealing component 40 comprises: an annular sealing body 41 fixed to the inner circumferential surface of the circular recess 33 of the nut 30; and a sealing lip 42 formed circumferentially on the inner diameter side of the sealing body 41 such that it enters the threaded groove 21 of the lead screw shaft 20, forming a non-contact labyrinthine gap between the sealing body 41 and the threaded groove 21 of the lead screw shaft 20. The sealing component 40 is formed by injection molding, and the sealing lip 42 has a circumferential length less than one circumference, that is, slightly shorter than the full circumference of the inner circumferential surface of the sealing body 41.

[0041] Additionally, a cavity 43 is formed along the circumferential direction in the sealing mountain 42. The cavity 43 is formed by cutting off the axial side of the space between the threaded groove 21 of the lead screw shaft 20 and the threaded groove of the nut 30 from the sealing mountain 42.

[0042] The cavity 43 is formed continuously around the sealed mountain 42. For example... Figure 2 As shown, the cavity 43, when installed at the end of the nut 30, opens toward the space between the threaded groove 21 of the lead screw shaft 20 and the threaded groove of the nut 30.

[0043] Therefore, as Figure 4 As shown, the sealing hill 42 is composed of a thin wall 44 with a substantially uniform wall thickness that protrudes from the inner circumferential surface of the sealing body 41 towards the inner diameter side and extends along the circumferential direction. Therefore, the thin wall 44 forms the inner circumferential surface (outer wall surface) 44a of the sealing hill 42 and the inner wall surface 44b of the cavity 43 together with the inner circumferential surface 41a of the sealing body 41.

[0044] It should be noted that, in this embodiment, the thin wall 44, in the circumferential phase formed as a cross-section arc or Gothic arch from the axial end of the sealing body portion 41 toward the inner diameter side, extends beyond the inner circumferential edge portion 44a1 closest to the inner diameter side. However, this thin wall 44 is also formed by injection molding, so the inner wall surface 44b of the thin wall 44 extending axially beyond the inner circumferential edge portion 44a1 is also formed.

[0045] Furthermore, at one end of the sealing mountain portion 42 in the circumferential direction, a rib 45 is formed along the axial direction to connect the inner circumferential surface 41a of the sealing body portion 41 with the inner wall surface 44b of the thin wall 44. From this end in the circumferential direction to a predetermined circumferential phase, a... Figure 4 The cross-sectional shape is as shown. On the other hand, when the sealing mountain 42 extends beyond a predetermined circumferential phase from one end in the circumferential direction, the axial width of the thin wall 44 gradually decreases, as shown. Figure 2As shown in the lower cross section, the thin wall 44 has a straight wall portion 44d extending radially toward the inner diameter side from the other end in the axial direction. Therefore, when the sealing mountain portion 42 exceeds a predetermined circumferential phase from one end in the circumferential direction, the axial width of the cavity portion 43 gradually decreases toward the other end in the circumferential direction.

[0046] In this type of sealing component 40, more grease can be retained in the cavity 43. The grease accumulated in the cavity 43 gradually flows out and is supplied to the space between the thread groove 21 of the lead screw shaft 20 and the thread groove of the nut 30, achieving long-term stable lubrication and forming a long-life ball screw 10. The sealing hill 42 is close to the thread groove 21 of the lead screw shaft 20 to which grease should be supplied, and can supply oil to the lead screw shaft 20. Therefore, by providing the cavity 43 for grease accumulation in the sealing hill 42, lubrication can be effectively aided.

[0047] Furthermore, the larger the ball diameter, the larger the sealing hill 42, and therefore the greater the amount of grease retained in the cavity 43. In particular, in this embodiment, it is more effective if the ball screw used in the sealing hill 42 has a ball diameter of 1 / 2 inch or more, which increases the volume of the ball. The larger the ball diameter, the greater the load-bearing capacity of the ball screw 10, enabling use under demanding load conditions. Therefore, lubrication becomes more important, and the effects of the present invention are easily achieved.

[0048] Figure 5 (a) and (b) represent the sealing member 40A of the first modified embodiment of the present invention. In this case, inside the cavity 43 of the sealing member 40A, a plurality of ribs 45 are provided extending axially to connect the inner peripheral surface 41a of the sealing body 41 to the inner wall surface 44b of the thin wall 44. The plurality of ribs 45 are arranged at predetermined intervals in the circumferential direction, except at one end in the circumferential direction.

[0049] Furthermore, in this embodiment, a plurality of ribs 45 are connected to the inner peripheral surface 41a of the sealing body portion 41 at a position closer to the axial side than the inner wall surface 44b of the thin wall 44. In addition, the inner edge of the ribs 45 may also extend from the inner wall surface 44b of the thin wall 44 to the axial side.

[0050] The portion of the sealing mountain 42 cut off by the cavity 43 is prone to deformation, resulting in reduced sealing performance. However, the multiple ribs 45 prevent deformation of the seal and suppress the reduction in sealing performance. When the ball screw 10 is driven, the multiple ribs 45 act as scrapers, scraping off the grease adhering to the thread groove 21 along the screw shaft 20 and preventing the grease inside the nut 30 from flowing out along the screw shaft 20.

[0051] The cross-section of the sealing hill 42 at the location of the rib 45 is the same as the cross-section of the sealing hill 42 without the cavity. However, a portion of the sealing hill 42 may also be removed. The rib 45 is provided in a direction extending radially from the axis center of the lead screw shaft 20, but it may also have an angle in the circumferential direction from the inner diameter side toward the outer diameter side, for example.

[0052] Additionally, Figures 6(a) to... Figure 6 (d) is Figure 5 (b) is a cross-sectional view of each circumferential direction phase. As also described in the above embodiment, the sealing mountain 42 changes its axial position according to the circumferential direction phase, and the thin wall 44 has a portion consisting of a wall portion formed in the shape of a circular arc or Gothic arch, a portion consisting of both a wall portion formed in the shape of a circular arc or Gothic arch and a straight wall portion 44d, and a portion consisting of a straight wall portion 44d, depending on the circumferential direction phase.

[0053] Figure 7 The sealing member 40B of the second variation of the present invention is shown. In this sealing member 40B, in addition to the cavity 43 formed in the sealing mountain portion 42, a body-side cavity 46 is also formed throughout the entire circumference of the sealing body portion 41. The body-side cavity 46, like the cavity 43, is cut off from one axial side.

[0054] In such a sealing component 40B, the amount of grease retained can be increased through the two cavities 43 and 46.

[0055] Figure 8 (a) and (b) show a sealing member 40C of a third variation of the present invention. In this sealing member 40C, a plurality of main body side ribs 47 are provided axially inside the main body side cavity 46, connecting the inner wall surface (i.e., the outer peripheral surface), the side wall surface, and the inner peripheral surface of the main body side cavity 46. The plurality of main body side ribs 47 are arranged at predetermined intervals in the circumferential direction, except for one end in the circumferential direction.

[0056] In this way, by providing multiple body side ribs 47 inside the body side cavity 46, more grease is retained and the rigidity of the sealed body part 41 is ensured.

[0057] Furthermore, if multiple main body side ribs 47 are provided inside the main body side cavity 46, such as Figure 9 As shown in the fourth modified example of the sealing member 40D, it is preferable that the plurality of ribs 45 inside the cavity 43 of the sealing mountain 42 are separated in the circumferential direction. In the sealing member 40C of the third modified example, due to the shrinkage difference between the sealing body 41 and the sealing mountain 42 during forming, there is a possibility that the shape of the sealing mountain 42 where the ribs 45 are located may be deformed.

[0058] However, as Figure 7 As with the sealing member 40B of the second modified example shown, it is most preferable that the main body side rib 47 is not provided inside the main body side cavity 46.

[0059] Figure 10 The sealing member 40E of the fifth variation of the present invention is shown. In this case, the thin wall 44 extends to the inner peripheral edge 44a1, which is formed in a circumferential direction phase in the cross-section arc or Gothic arch shape from the axial end of the sealing body portion 41 toward the inner diameter side, and becomes the innermost diameter side. Furthermore, if the inner peripheral surface 44a of the thin wall 44 is shorter than the inner peripheral edge 44a1, the amount of grease retained is drastically reduced. Therefore, the inner peripheral surface 44a of the thin wall 44 is preferably formed to the inner peripheral edge 44a1, or, as in the above embodiment, is formed beyond the inner peripheral edge 44a1.

[0060] Furthermore, the present invention is not limited to the embodiments described above, and can be appropriately modified or improved.

[0061] As stated above, the following matters are disclosed in this specification.

[0062] (1) A sealing component for a ball screw, used in a ball screw comprising: a screw shaft having a helical thread groove formed on its outer circumferential surface; a nut having a helical thread groove formed on its inner circumferential surface; and a plurality of balls rolling in a load raceway formed by the thread groove of the screw shaft and the thread groove of the nut, the sealing component for the ball screw sealing the gap between the screw shaft and the nut, wherein,

[0063] The ball screw sealing component includes: an annular sealing body portion fixed to the inner circumferential surface of the axial end of the nut; and a sealing bevel portion formed circumferentially on the inner diameter side of the sealing body portion such that it enters a threaded groove of the screw shaft, forming a labyrinthine gap between the sealing bevel portion and the threaded groove of the screw shaft.

[0064] In the sealed mountain section, a cavity is formed along the circumferential direction by being cut out from one side of the axial direction.

[0065] According to this structure, the cavity retains more grease, and the oil in the grease accumulated in the cavity is gradually supplied to the space between the thread groove of the lead screw shaft and the thread groove of the nut, which can achieve long-term stable lubrication.

[0066] (2) The sealing component for the ball screw according to (1), wherein,

[0067] The sealing mountain is composed of a thin wall that protrudes from the inner circumference of the sealing body towards the inner diameter side and extends along the circumferential direction.

[0068] The thin wall, together with the inner circumferential surface of the sealing body, forms the inner wall surface constituting the cavity.

[0069] According to this structure, the sealing mountain can form a labyrinthine gap between itself and the threaded groove of the lead screw shaft, and the cavity can retain more grease.

[0070] (3) The sealing component for ball screws according to (2), wherein a plurality of ribs are provided extending axially inside the cavity to connect the inner peripheral surface of the sealing body to the inner wall surface of the thin wall.

[0071] According to this structure, multiple ribs act as scrapers, which can scrape out foreign objects from the outside of the nut and prevent the grease inside the nut from flowing out along the screw axis.

[0072] (4) The sealing component for the ball screw according to (2) or (3), wherein,

[0073] The thin wall extends at least to the innermost inner circumferential edge in a circumferential phase that is formed in the cross-section of an arc or Gothic arch from the other end of the sealing body toward the inner diameter side.

[0074] According to this structure, more grease can be retained by the cavity, and foreign objects from the outside of the nut can be scraped out and the grease inside the nut can be prevented from flowing out.

[0075] (5) A sealing member for a ball screw according to any one of (1) to (4), wherein,

[0076] The cavity is formed continuously or intermittently over the entire circumference of the sealed mountain.

[0077] This structure allows for the retention of more grease within the cavities.

[0078] (6) A sealing member for a ball screw according to any one of (1) to (5), wherein,

[0079] The sealing body has a body-side cavity formed along the circumferential direction by being cut off from one side of the axial direction.

[0080] This structure allows more grease to be retained in the cavity on the main body side.

[0081] (7) A ball screw comprising: a screw shaft having a helical thread groove formed on its outer circumferential surface; a nut having a helical thread groove formed on its inner circumferential surface; a plurality of balls rolling in a load raceway formed by the thread groove of the screw shaft and the thread groove of the nut; and a sealing member for the ball screw as described in any one of (1) to (6), the sealing member sealing the gap between the screw shaft and the nut.

[0082] The hollow portion faces the space between the threaded groove of the lead screw shaft and the threaded groove of the nut.

[0083] According to this structure, the cavity retains more grease, and the oil in the grease accumulated in the cavity is gradually supplied to the space between the thread groove of the lead screw shaft and the thread groove of the nut, which can achieve long-term stable lubrication.

[0084] Furthermore, this application is based on Japanese Patent Application No. 2023-066365, filed on April 14, 2023, the contents of which are incorporated herein by reference.

[0085] Explanation of reference numerals in the attached figures

[0086] 10 Ball Screws

[0087] 20 lead screw shaft

[0088] 21 Threaded groove

[0089] 30 nuts

[0090] Sealing components 40, 40A, 40B, 40C, 40D, 40E

[0091] 41 Sealing Body

[0092] 42 Seal Mountain

[0093] 43. Hollow Section

[0094] 44 Thin-walled

[0095] 45 ribs

[0096] 46. ​​Main body side cavity

[0097] 47 Main body side ribs

Claims

1. A sealing component for a ball screw, characterized in that, A ball screw comprising: a screw shaft having a helical threaded groove formed on its outer circumferential surface; a nut having a helical threaded groove formed on its inner circumferential surface; and a plurality of balls rolling in a load raceway formed by the threaded grooves of the screw shaft and the nut, the ball screw sealing the gap between the screw shaft and the nut using a sealing member. The ball screw sealing component comprises: an annular sealing body portion fixed to the inner circumferential surface of the axial end of the nut; and a sealing bevel portion formed circumferentially on the inner diameter side of the sealing body portion such that it enters the threaded groove of the screw shaft, and a labyrinthine gap is formed between the sealing bevel portion and the threaded groove of the screw shaft. In the sealed mountain section, a cavity is formed along the circumferential direction by being cut out from one side of the axial direction.

2. The sealing component for ball screws according to claim 1, characterized in that, The sealing mountain is composed of a thin wall that protrudes from the inner circumference of the sealing body towards the inner diameter side and extends along the circumferential direction. The thin wall, together with the inner circumferential surface of the sealing body, forms the inner wall surface constituting the cavity.

3. The sealing component for ball screws according to claim 2, characterized in that, Multiple ribs are provided along the axial direction inside the cavity to connect the inner circumferential surface of the sealing body to the inner wall surface of the thin wall.

4. The sealing component for ball screws according to claim 2, characterized in that, The thin wall extends at least to the innermost inner circumferential edge in a circumferential phase that is formed in the cross-section of an arc or Gothic arch from the other end of the sealing body toward the inner diameter side.

5. The sealing component for ball screws according to claim 1, characterized in that, The cavity is formed continuously or intermittently over the entire circumference of the sealed mountain.

6. The sealing component for ball screws according to claim 1, characterized in that, The sealing body has a body-side cavity formed along the circumferential direction by being cut off from one side of the axial direction.

7. A ball screw, characterized in that, The ball screw comprises: a screw shaft having a helical thread groove formed on its outer circumferential surface; a nut having a helical thread groove formed on its inner circumferential surface; a plurality of balls rolling in a load raceway formed by the thread grooves of the screw shaft and the nut; and a sealing member for the ball screw according to any one of claims 1 to 6, the sealing member sealing the gap between the screw shaft and the nut. The hollow portion faces the space between the threaded groove of the lead screw shaft and the threaded groove of the nut.

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