Ball screw sealing member and ball screw

Abstract

This seal member for a ball screw comprises: an annular seal body section that is fixed to the inner circumferential surface of at least one axial-direction end portion of a nut; and a seal ridge section that is circumferentially formed on the inner-diameter side of the seal body section so as to be fitted into a screw groove of a screw shaft, and forms a labyrinth gap between the seal ridge section and the screw groove of the screw shaft, wherein the seal crest section has a hollow section circumferentially formed therein, the hollow section being formed by notching the seal crest section from one axial-direction side. As a result, more grease can be held, thereby achieving a long period of stable lubrication.

Description

Technical Field

[0001] The present invention relates to a seal member for a ball screw and a ball screw.

Background Art

[0002] Conventionally, a ball screw that converts rotational motion into linear motion generally includes a screw shaft having a spiral thread groove formed on its outer peripheral surface and a nut having a spiral thread groove formed on its inner peripheral surface. Between the thread grooves of both the screw shaft and the nut, a large number of balls that roll along with the rotational motion of the screw shaft or the nut are loaded.

[0003] Also, as shown in FIGS. 11(a) and (b), a seal member 140 is usually attached to the end of the nut 30 of the ball screw, which has two functions: suppressing grease leakage from the inside of the nut 30 and preventing foreign matter from entering the inside of the nut 30. A general-purpose seal member 140 is formed of resin and has a seal main body portion 141 attached to the end of the nut 30 and a seal thread portion 142 that enters the thread groove 21 of the screw shaft 20, and has a structure with a minute gap between it and the thread groove 21 of the screw shaft 20. Lubrication of such a ball screw is usually performed by grease accumulated in the gaps inside the nut when automatic grease supply at regular intervals is not carried out.

[0004] In the feed screw device described in Patent Document 1, the seal member is constituted by a lubricant-containing polymer member, and a lubricant reservoir portion is formed at a position other than the portion contacting the sealed surface of the screw shaft of this lubricant-containing polymer member, and it is described that lubricant replenishment is performed by the lubricant sealed in the lubricant reservoir portion permeating into the lubricant-containing polymer member. Also, in the ball screw described in Patent Document 2, deformation grooves are respectively formed on the seal main body portion side and the seal thread side of the dustproof unit to facilitate insertion into the thread grooves of the nut and the screw shaft.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent No. 3648855 [Patent Document 2] China Utility Model No. 209430705 Specification [Overview of the project] [Problems that the invention aims to solve]

[0006] By the way, in ball screws, the larger the space inside the nut where grease can be held, the easier it is for lubricant to be supplied, which is preferable. On the other hand, if you try to create extra space inside the nut, The increased overall length of the nut creates problems such as compromising space-saving design.

[0007] In Reference 1, the lubricant reservoir is provided on the seal body side, but the lubricant reservoir is relatively small and is far from the inner circumferential surface of the seal crest, so further improvements are needed to hold and supply more grease. Also, in Reference 2, the deformed groove of the seal crest is formed with insertability in mind and cannot hold more grease.

[0008] The present invention has been made in view of the aforementioned problems, and its objective is to provide a ball screw sealing member and a ball screw that can retain more grease and achieve stable lubrication over the long term. [Means for solving the problem]

[0009] The above objective of the present invention is achieved by the following configuration. [1] A ball screw seal member used in a ball screw comprising a screw shaft having a helical screw groove formed on its outer circumference, a nut having a helical screw groove formed on its inner circumference, and a plurality of balls that roll in a load track formed by the screw groove of the screw shaft and the screw groove of the nut, which seals the gap between the screw shaft and the nut, The nut comprises an annular seal body fixed to the inner circumferential surface of the axial end of the nut, and a seal crest formed along the circumferential direction on the inner diameter side of the seal body so as to fit into the screw groove of the screw shaft, forming a labyrinth gap between itself and the screw groove of the screw shaft. A ball screw sealing member, wherein the sealing ridge portion has a cavity formed along the circumferential direction, cut out from one side in the axial direction. [2] A screw shaft having a helical screw groove formed on its outer circumference, a nut having a helical screw groove formed on its inner circumference, a plurality of balls that roll along a load trajectory formed by the screw groove of the screw shaft and the screw groove of the nut, and a ball screw sealing member as described in [1] that seals the gap between the screw shaft and the nut, The aforementioned cavity is a ball screw that opens toward the space between the screw groove of the screw shaft and the screw groove of the nut. [Effects of the Invention]

[0010] According to the ball screw sealing member and ball screw of the present invention, the cavity holds more grease, and the oil content of the grease accumulated in the cavity is gradually supplied to the space between the screw groove of the screw shaft and the screw groove of the nut, thereby achieving stable lubrication over a long period of time. [Brief explanation of the drawing]

[0011] [Figure 1] This is a front view of a ball screw according to the first embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view showing the sealing member attached to the nut. [Figure 3] (a) is a perspective view of the sealing member, and (b) is a side view of the sealing member. [Figure 4] This is a cross-sectional view along the line VI-VI in Figure 3(b). [Figure 5] (a) is a perspective view of the sealing member according to the first modified example, and (b) is a side view of the sealing member in (a). [Figure 6](a) is a cross-sectional view taken along the line VIa-VIa of FIG. 5(b), (b) is a cross-sectional view taken along the line VIb-VIb of FIG. 5(b), (c) is a cross-sectional view taken along the line VIc-VIc of FIG. 5(b), and (d) is a cross-sectional view taken along the line VId-VId of FIG. 5(b). [Figure 7] It is a perspective view of the seal member according to the second modification. [Figure 8] (a) is a perspective view of the seal member according to the third modification, and (b) is a side view of the seal member of (a). [Figure 9] It is a side view of the seal member according to the fourth modification. [Figure 10] It is a cross-sectional view of the seal member according to the fifth modification. [Figure 11] (a) shows a state where a conventional seal member is attached to a nut, and (b) is a perspective view of the conventional seal member.

Mode for Carrying Out the Invention

[0012] Hereinafter, the ball screw according to an embodiment of the present invention will be described in detail based on the drawings.

[0013] As shown in FIG. 1, the ball screw 10 of the present embodiment includes a screw shaft 20 having a spiral screw groove 21 on its outer peripheral surface and extending in the axial direction, and a spiral screw groove corresponding to the screw groove 21 of the screw shaft 20 (not shown) on the inner peripheral surface, a plurality of balls (not shown) that roll on the load track formed by the screw groove 21 of the screw shaft 20 and the screw groove of the nut 30, and a seal member 40 that seals the gap between the screw shaft 20 and the nut 30.

[0014] On the outer peripheral surface of the nut 30, a plurality of circulation parts (not shown) are provided that penetrate the nut 30 so that both ends protrude into the load track and each have a scooping part for lifting the balls. Thereby, the balls lifted at one end of the load track pass through the circulation parts and By being returned to the other end of the load track, an infinite loop is formed. In Fig. 1, reference numeral 11 denotes a cover for a circulation component for fixing the circulation component to the nut. In Fig. 1, five circulation components are provided on the nut 30, and thus five infinite loops are formed.

[0015] The nut 30 has a flange portion 32 formed on one end side in the axial direction, and circular recesses 33 having an inner diameter larger than the thread groove are formed coaxially with the thread groove at both ends in the axial direction. The flange portion 32 is fixed to a moving table or the like of a mechanical device (not shown) with mounting bolts or the like.

[0016] A seal member 40 for sealing the gap between the screw shaft 20 and the nut 30 is provided on the inner peripheral surface of the circular recess 33. The seal member 40 is made of resin such as a polymer polyethylene resin, and as shown in Figs. 2 to 4, an annular seal main body portion 41 fixed to the inner peripheral surface of the circular recess 33 of the nut 30, and a seal thread portion (seal lip) 42 formed along the circumferential direction on the inner diameter side of the seal main body portion 41 so as to enter the thread groove 21 of the screw shaft 20, and forming a non-contact labyrinth gap between the seal thread portion 42 and the thread groove 21 of the screw shaft 20. The seal member 40 is formed by injection molding, and the seal thread portion 42 has a circumferential length that is less than one turn, that is, slightly shorter than the entire circumference of the inner peripheral surface of the seal main body portion 41.

[0017] In addition, a cavity portion 43 cut out from one side in the axial direction is formed along the circumferential direction in the seal thread portion 42 toward the space between the thread groove 21 of the screw shaft 20 and the thread groove of the nut 30. The cavity portion 43 is continuously formed over the entire circumference of the seal thread portion 42. As shown in Fig. 2, the cavity portion 43 opens toward the space between the thread groove 21 of the screw shaft 20 and the thread groove of the nut 30 in a state of being attached to the end portion of the nut 30.

[0018] Therefore, as shown in Figure 4, the seal ridge portion 42 is composed of a thin wall 44 with a generally uniform thickness that protrudes inward from the inner circumferential surface of the seal body portion 41 and extends along the circumferential direction. Thus, the thin wall 44 forms the inner wall surface 44b that, together with the inner circumferential surface (outer wall surface) 44a of the seal ridge portion 42 and the inner circumferential surface 41a of the seal body portion 41, forms the cavity portion 43.

[0019] In this embodiment, the thin wall 44 is formed in a circumferential phase from the other axial end of the seal body 41 toward the inner diameter side in an arc-shaped or Gothic arch-shaped cross-section, and in this phase, the inner circumferential surface 44a extends beyond the inner circumferential edge 44a1, which is the innermost part of the inner diameter. However, since this thin wall 44 is also formed by injection molding, the inner wall surface 44b of the thin wall 44 beyond the inner circumferential edge 44a1 extends along the axial direction.

[0020] Furthermore, a rib 45 is formed along the axial direction at one circumferential end of the seal crest 42, connecting the inner circumferential surface 41a of the seal body 41 and the inner wall surface 44b of the thin wall 44. From this circumferential end up to a predetermined circumferential phase, the cross-sectional shape shown in Figure 4 is obtained. On the other hand, when the seal crest 42 exceeds the predetermined circumferential phase from the circumferential end, the axial width of the thin wall 44 gradually decreases, and the thin wall 44 has a linear wall portion 44d at the other axial end, extending radially inward from the other axial end, as shown in the lower cross-section of Figure 2. Therefore, when the seal crest 42 exceeds the predetermined circumferential phase from the circumferential end, the axial width of the cavity 43 gradually decreases toward the other circumferential end.

[0021] In the sealing member 40 configured in this way, the cavity 43 can hold more grease, and the oil from the grease accumulated in the cavity 43 gradually flows out and is supplied to the space between the screw groove 21 of the screw shaft 20 and the screw groove of the nut 30, enabling stable lubrication over a long period of time and resulting in a long-life ball screw 10. The sealing peak 42 is close to the screw groove 21 of the screw shaft 20 to which grease should be supplied, and can supply oil to the screw shaft 20. Therefore, by providing a cavity 43 that serves as a grease reservoir in the sealing peak 42, lubrication can be effectively contributed to.

[0022] Furthermore, the larger the ball diameter, the larger the sealing ridge portion 42 becomes, and therefore the amount of grease that the cavity portion 43 can hold also increases. In particular, this embodiment is more effective when applied to ball screws with a ball diameter of 1 / 2 inch or larger, as the volume of the sealing ridge portion 42 increases. The larger the ball diameter, the greater the load-bearing capacity of the ball screw 10, and it is used under harsh conditions with heavy loads. Therefore, lubrication becomes more important, and the effects of the present invention are more easily obtained.

[0023] Figures 5(a) and (b) show a sealing member 40A of a first modified example of the present invention. In this case, a plurality of ribs 45 are provided extending axially within the cavity 43 of the sealing member 40A, connecting the inner circumferential surface 41a of the sealing body 41 and the inner wall surface 44b of the thin wall 44. Multiple ribs 45 are arranged at predetermined intervals in the circumferential direction, except for one end in the circumferential direction. In this embodiment, the multiple ribs 45 are connected to the inner circumferential surface 41a of the seal body portion 41 on one axial side rather than to the inner wall surface 44b of the thin wall 44. Also, the inner edge of the rib 45 is It may extend in one axial direction from the inner wall surface 44b of the thin wall 44.

[0024] The seal crest 42 is prone to deformation in the portion cut out by the cavity 43, which reduces its sealing performance. However, the multiple ribs 45 prevent this 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 and move along the screw groove 21 of the screw shaft 20, scraping off the grease adhering to the screw groove 21 and preventing the grease inside the nut 30 from flowing out along the screw shaft 20.

[0025] The cross-section of the seal crest 42 at the location of the rib 45 is the same as the cross-section of the seal crest 42 when there is no cavity. However, a part of the seal crest 42 may be cut out. The rib 45 is installed in a direction that extends radially from the axis center of the screw shaft 20, but for example, it may be angled in the circumferential direction from the inner diameter side to the outer diameter side.

[0026] Figures 6(a) to 6(d) are cross-sectional views of Figure 5(b) at each circumferential phase. As explained in the above embodiment, the seal ridge portion 42 changes its axial position according to the circumferential phase, and the thin wall 44 has a portion composed of a wall portion formed in the shape of a circular arc or Gothic arch in cross-section, a portion composed of both a wall portion formed in the shape of a circular arc or Gothic arch in cross-section and a straight wall portion 44d, and a portion composed of a straight wall portion 44d, according to the circumferential phase.

[0027] Figure 7 shows a second modified example of the present invention, a sealing member 40B. In this sealing member 40B, in addition to the cavity 43 formed in the sealing ridge 42, a body-side cavity 46 is also formed in the sealing body 41, extending around its entire circumference in the circumferential direction. The body-side cavity 46 is cut out from one side in the axial direction, similar to the cavity 43. In such a sealing member 40B, the amount of grease that can be held can be increased by the two cavities 43 and 46.

[0028] Figures 8(a) and (b) show a third modified example of the sealing member 40C of the present invention. In this sealing member 40C, the inner wall surface of the main body side cavity 46 is located inside the main body side cavity 46, i.e., Multiple main body-side ribs 47 are provided, connecting the outer circumferential surface, side wall surface, and inner circumferential surface, and each extends along the axial direction. The multiple main body-side ribs 47 are arranged at predetermined intervals in the circumferential direction, except for one end in the circumferential direction. In this way, by providing multiple body-side ribs 47 inside the body-side cavity 46, the rigidity of the seal body 41 is ensured while retaining even more grease.

[0029] Furthermore, when multiple body-side ribs 47 are provided inside the body-side cavity 46, it is preferable to provide them circumferentially away from the multiple ribs 45 inside the cavity 43 of the seal peak 42, as shown in the fourth modified example seal member 40D in Figure 9. In the third modified example seal member 40C, the tension of each rib 45, 47 may cause the shape of the seal peak 42 in the area where the ribs 45 are located to become distorted due to the difference in shrinkage during molding between the seal body 41 and the seal peak 42. However, it is most preferable not to provide the main body side rib 47 inside the main body side cavity 46, as shown in the second modified example seal member 40B in Figure 7.

[0030] Figure 10 shows a fifth modified example of the present invention, a sealing member 40E. In this case, the thin wall 44 is formed in a circumferential phase from the other axial end of the seal body 41 toward the inner diameter, with a cross-sectional arc shape or Gothic arch shape, and the inner circumferential surface 44a extends to the inner circumferential edge portion 44a1, which is closest to the inner diameter. If the inner circumferential surface 44a of the thin wall 44 becomes shorter than the inner circumferential edge portion 44a1, the amount of grease that can be held decreases sharply. Therefore, it is preferable that the inner circumferential surface 44a of the thin wall 44 extends to the inner circumferential edge portion 44a1, or, as in the above embodiment, extends beyond the inner circumferential edge portion 44a1.

[0031] Furthermore, the present invention is not limited to the embodiments described above, and can be modified, improved, etc., as appropriate.

[0032] As described above, the following matters are disclosed in this specification: (1) A ball screw sealing member used in a ball screw comprising a screw shaft having a helical screw groove formed on its outer circumference, a nut having a helical screw groove formed on its inner circumference, and a plurality of balls that roll in a load track formed by the screw groove of the screw shaft and the screw groove of the nut, which seals the gap between the screw shaft and the nut, The nut comprises an annular seal body fixed to the inner circumferential surface of at least one axial end, and a seal crest formed along the circumferential direction on the inner diameter side of the seal body so as to fit into the screw groove of the screw shaft, forming a labyrinth gap between itself and the screw groove of the screw shaft. A ball screw sealing member, wherein the sealing ridge portion has a cavity formed along the circumferential direction, cut out from one side in the axial direction. With this configuration, the cavity holds more grease, and the oil from the grease accumulated in the cavity is gradually supplied to the space between the screw groove of the screw shaft and the screw groove of the nut, enabling stable lubrication over a long period of time.

[0033] (2) The seal ridge is formed by a thin wall that protrudes inward from the inner circumferential surface of the seal body and extends along the circumferential direction, The ball screw sealing member according to (1), wherein the thin wall forms an inner wall surface that forms the cavity together with the inner circumferential surface of the seal body. With this configuration, the seal crest can form a labyrinth gap between itself and the screw groove of the screw shaft, while retaining more grease in the cavity.

[0034] (3) The ball screw seal member according to (2), wherein a plurality of ribs extending axially from the inside of the cavity connect the inner circumferential surface of the seal body and the inner wall surface of the thin wall. In this configuration, the multiple ribs act as scrapers, scraping away foreign matter from the outside of the nut and preventing grease from flowing out along the screw axis.

[0035] (4) The ball screw seal member according to (2) or (3), wherein the thin wall extends at least to the innermost circumferential edge in the circumferential phase, where the cross section is formed in an arc shape or Gothic arch shape toward the inner diameter from the other axial end of the seal body toward the inner diameter side. This configuration allows for the retention of more grease in the cavity, and also helps to scrape out foreign matter from the outside of the nut while preventing grease from leaking out of the inside of the nut.

[0036] (5) The ball screw sealing member according to any one of (1) to (4), wherein the cavity is formed continuously or intermittently around the entire circumference of the sealing ridge. This configuration allows for more grease to be retained in the cavity.

[0037] (6) The seal body portion is a ball screw seal member according to any one of (1) to (5), wherein a body-side cavity portion cut out from one side in the axial direction is formed along the circumferential direction. This configuration allows for greater grease to be retained in the cavity on the main body side.

[0038] (7) A screw shaft having a helical screw groove formed on its outer circumference, a nut having a helical screw groove formed on its inner circumference, a plurality of balls that roll along a load track formed by the screw groove of the screw shaft and the screw groove of the nut, and a ball screw sealing member according to any one of (1) to (6) that seals the gap between the screw shaft and the nut, The aforementioned cavity is a ball screw that opens toward the space between the screw groove of the screw shaft and the screw groove of the nut. With this configuration, the cavity holds more grease, and the oil from the grease accumulated in the cavity is gradually supplied to the space between the screw groove of the screw shaft and the screw groove of the nut, enabling stable lubrication over a long period of time.

[0039] This application is based on the Japanese Patent Application No. 2023-066365 filed on April 14, 2023, the contents of which are incorporated by reference within this application. [Explanation of Symbols]

[0040] 10 Ball screws 20 Screw shaft 21 Screw groove 30 nuts 40, 40A, 40B, 40C, 40D, 40E sealing members 41 Seal body 42 Seal Mountain 43 Cavity 44 Thin wall 45 Ribs 46 Hollow section on the main body side 47 Ribs on the main body

Claims

1. A ball screw sealing member is used in a ball screw comprising a screw shaft with a helical screw groove formed on its outer circumference, a nut with a helical screw groove formed on its inner circumference, and a plurality of balls that roll along a load track formed by the screw groove of the screw shaft and the screw groove of the nut, and seals the gap between the screw shaft and the nut, The nut comprises an annular seal body fixed to the inner circumferential surface of the axial end of the nut, and a seal crest formed along the circumferential direction on the inner diameter side of the seal body so as to fit into the screw groove of the screw shaft, forming a labyrinth gap between itself and the screw groove of the screw shaft. The seal ridge has a cavity formed along the circumferential direction, cut out from one side in the axial direction. The seal ridge is formed by a thin wall that protrudes inward from the inner circumferential surface of the seal body and extends along the circumferential direction. The thin wall, together with the inner circumferential surface of the seal body, forms an inner wall surface that forms the cavity, and is a sealing member for a ball screw.

2. The ball screw seal member according to claim 1, wherein a plurality of ribs extending axially within the cavity portion connect the inner circumferential surface of the seal body portion and the inner wall surface of the thin wall portion.

3. The ball screw seal member according to claim 1, wherein the thin wall extends at least to the innermost circumferential edge in a circumferential phase formed in a cross-sectional arc shape or Gothic arch shape toward the inner diameter side from the other axial end of the seal body portion toward the inner diameter side.

4. The ball screw sealing member according to claim 1, wherein the cavity is formed continuously or intermittently around the entire circumference of the sealing ridge.

5. The seal body portion is a ball screw seal member according to claim 1, wherein a body-side cavity portion cut out from one side in the axial direction is formed along the circumferential direction.

6. The ball screw comprises a screw shaft having a helical screw groove formed on its outer circumference, a nut having a helical screw groove formed on its inner circumference, a plurality of balls that roll along a load trajectory formed by the screw groove of the screw shaft and the screw groove of the nut, and a ball screw sealing member according to any one of claims 1 to 5 that seals the gap between the screw shaft and the nut. The aforementioned cavity is a ball screw that opens toward the space between the screw groove of the screw shaft and the screw groove of the nut.

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