Ball screw actuator

Abstract

[Problem] To supply lubricating oil smoothly to return passages without increasing the lubricating oil supply pressure. [Solution] In a ball screw actuator (10), a slider (30) includes a slider main body (32) including a ball screw nut portion (100), and ball return members (36) attached to both ends, in an axial direction, of the slider main body (32), wherein: return passages (40) formed in each ball return member (36) include an outside end portion (40A) communicating with an external passage (74) for balls (72), and an inside end portion (40B) communicating with an internal passage (76) for the balls (72); and a lubricating oil supply passage (44) communicates with the return passages (40) on a side thereof closer to the outside end portions (40A) than the inside end portions (40B).

Description

Ball Screw Actuator

[0001] The present invention relates to a ball screw actuator, and more particularly to a lubricating oil supply structure for a linear ball bearing incorporated in a ball screw actuator.

[0002] A known linear motion actuator is a ball screw actuator that includes a linear guide rail having a concave cross-sectional shape with left and right side walls, a slider disposed between the left and right side walls of the guide rail, left and right linear ball bearings that guide axial movement of the slider relative to the guide rail, a ball screw nut portion provided on the slider, and a ball screw shaft that passes axially through a through hole provided in the slider and threadably engages with the ball screw nut portion provided on the slider via balls (see, for example, Patent Document 1). The slider provided in this ball screw actuator has a slider body that holds the ball screw nut portion, and ball return members attached to both axial ends of the slider body and provided with return passages for the left and right linear ball bearings.

[0003] The structure for supplying lubricating oil such as grease to the left and right linear ball bearings in the above-mentioned ball screw actuator includes a lubricating oil injection passage provided in the ball return member and a lubricating oil supply passage that supplies lubricating oil from the lubricating oil injection passage to the return passages of the left and right linear ball bearings.

[0004] JP-A-4-115842

[0005] When the pressure (internal pressure) of the lubricating oil in the return passage is high, it is difficult for the lubricating oil to enter the return passage, and the supply pressure of the lubricating oil must be increased, which makes the lubricating oil supply work less efficient.

[0006] The problem to be solved by the present invention is to smoothly supply lubricating oil to the return passage without increasing the supply pressure of the lubricating oil.

[0007] In order to solve the above-mentioned problems, one aspect of the present invention is a ball screw actuator comprising: a linear guide rail having left and right side walls and a concave cross-sectional shape; a slider arranged between the left and right side walls of the guide rail; left and right linear ball bearings having a plurality of balls circulating between the left and right side walls of the guide rail and the slider, and guiding axial movement of the slider relative to the guide rail; a ball screw nut portion provided on the slider; and a ball screw shaft that passes through a through hole provided in the slider in the axial direction and screws into the ball screw nut portion provided on the slider via balls, wherein the slider comprises a slider body including the ball screw nut portion and ball bearings attached to both ends of the slider body in the axial direction. and a ball return member attached to the slider body, and the left and right linear ball bearings each have an external passage formed by the corresponding side wall of the guide rail and the slider body, and an internal passage formed to extend axially inside the slider body, and at least one of the ball return members has left and right return passages through which balls of the left and right linear ball bearings move, a lubricant injection passage, and a lubricant supply passage for supplying lubricant from the lubricant injection passage to the left and right return passages, and the left and right return passages each have an outer end communicating with the corresponding external passage and an inner end communicating with the corresponding internal passage, and the lubricant supply passage communicates with the left and right return passages on the outer end side rather than the inner end side.

[0008] According to this aspect, the lubricating oil is smoothly supplied to the return passage without increasing the supply pressure of the lubricating oil.

[0009] In the above aspect, preferably, the lubricating oil supply passage communicates with the left and right return passages of the outer end portion.

[0010] According to this aspect, the lubricating oil is supplied to the return passage more smoothly without increasing the supply pressure of the lubricating oil.

[0011] In the above aspect, preferably, the left and right linear ball bearings are each configured in two upper and lower stages, the ball return member has return passages in two upper and lower stages, and the lubricating oil supply passage reaches between the upper and lower two stage return passages and is connected to the upper and lower two stage return passages.

[0012] According to this aspect, lubricating oil is smoothly supplied to each return passage of the two upper and lower stages of the left and right linear ball bearings without increasing the supply pressure of the lubricating oil.

[0013] In the above aspect, preferably, a passage defining member is included that is attached to the ball return member, extends across the upper and lower two stages of the return passages, and collectively defines the upper and lower two stages of the return passages including the outer end and the inner end, and a portion of the lubricating oil supply passage may be formed in the passage defining member.

[0014] According to this aspect, the structure of the lubricating oil supply passage does not become complicated.

[0015] In the above aspect, preferably, the portion of the lubricating oil supply passage is defined by a recessed groove formed in the passage defining member.

[0016] According to this aspect, the lubricating oil supply passage can be easily formed.

[0017] In the above aspect, the lubricating oil supply passage may preferably open outward from the passage defining member to the upper and lower two stages of the return passages.

[0018] According to this aspect, the lubricating oil is supplied accurately and evenly to the upper and lower external passages.

[0019] According to the ball screw actuator of the present invention, the lubricating oil is smoothly supplied to the return passage without increasing the supply pressure of the lubricating oil.

[0020] a perspective view showing a first embodiment of the ball screw actuator according to the present invention; an enlarged exploded perspective view of a main part of the ball screw actuator according to the first embodiment; an enlarged perspective view of a main part of a ball return member of the ball screw actuator according to the first embodiment; a perspective view of a main part of a partition member of the ball screw actuator according to the first embodiment; a front view of the ball return member of the ball screw actuator according to the first embodiment; a cross-sectional view taken along line VI-VI in FIG. 5; a skeleton view showing an outline of the linear ball bearing and lubricating oil passages of the ball screw actuator according to the first embodiment; a perspective view of a second embodiment of the ball screw actuator according to the present invention; a perspective view of the ball return member of the ball screw actuator according to the second embodiment;

[0021] A preferred embodiment of the present invention will be described with reference to the accompanying drawings.

[0022] (Embodiment 1)

[0023] A ball screw actuator 10 according to a first embodiment will be described with reference to Figures 1 to 7. Note that Figure 7 is a skeleton diagram showing an outline of the ball circulation path and lubricating oil passage of a linear ball bearing, and does not show a slider 30 and a side wall 22, which will be described later.

[0024] As shown in FIG. 1, the ball screw actuator 10 of embodiment 1 comprises a linear guide rail 20 having a concave cross-sectional shape with left and right side walls 22, a slider 30 disposed between the left and right side walls 22 of the guide rail 20, and left and right linear ball bearings 70 each having a plurality of balls 72 (see FIG. 7) that circulate between the left and right side walls 22 of the guide rail 20 and the slider 30, and which guide the axial movement of the slider 30 relative to the guide rail 20.

[0025] The ball screw actuator 10 further includes a ball screw nut portion 100 provided on the slider 30, and a ball screw shaft 102 that passes axially through a through hole 31 provided in the slider 30 and is screwed with the ball screw nut portion 100 provided on the slider 30 via balls 104 (see FIG. 6 ). The ball screw shaft 102 is driven to rotate by an electric motor (not shown) that is attached to the shaft end of the guide rail 20. The ball screw nut portion 100 may be integral with the slider 30.

[0026] The slider 30 has a slider body 32 having an approximately rectangular parallelepiped shape including a ball screw nut portion 100, and front and rear ball return members 36 having an approximately rectangular parallelepiped shape fixed to both axial ends (front and rear ends) of the slider body 32 by a plurality of bolts 34.

[0027] 2 and 5, each ball return member 36 has a through hole 38 that passes through a substantial center in the axial direction and forms part of the above-mentioned through hole 31. As shown in Fig. 6, the through hole 38 has an inner diameter that is substantially the same as or smaller than that of the through hole 31A of the through hole 31 that passes through the slider body 32, and is provided substantially coaxially (substantially concentrically) with the through hole 31A.

[0028] Each ball return member 36 further has left and right return passages 40 that are provided symmetrically with respect to the through hole 38 and through which the balls 72 of the left and right linear ball bearings 70 rollably move, a lubricant oil injection passage 42 that extends in the axial direction and is provided offset to one of the left and right sides with respect to the through hole 38, and a lubricant oil supply passage 44 that supplies lubricant oil such as grease from the lubricant oil injection passage 42 to the left and right return passages 40. A lubricant oil nipple 46 (see FIGS. 1 and 7) that communicates with the corresponding lubricant oil injection passage 42 is attached to the outer wall of each ball return member 36.

[0029] As shown in FIG. 7 , which will be described in detail later, each of the left and right linear ball bearings 70 has an external passage 74 formed to extend in the axial direction between the corresponding side wall 22 (see FIG. 1 ) of the guide rail 20 and the slider body 32 (see FIG. 1 ), and an internal passage 76 formed to extend in the axial direction inside (through) the slider body 32 (see FIG. 1 ). Each external passage 74 is formed by a groove 24 (see FIG. 1 ) with a substantially semicircular cross section formed in the inner surface of the side wall 22 and a groove (not shown) with a substantially semicircular cross section formed in the outer surface of the slider body 32. The inner surface of the side wall 22 and the outer surface of the slider body 32 are not in contact with each other, and an air gap G (see FIG. 5 ) is formed between the inner surface of the side wall 22 and the outer surface of the slider body 32, extending in the axial direction with a gap width in the left-right direction.

[0030] 2 and 5, each of the left and right return passages 40 is a passage having a substantially semicircular (U-shaped) planar shape in which the balls 72 can roll, and which is defined by a recessed groove 41 having a substantially semicircular planar shape formed in the ball return member 36 and a passage defining member 43 having a substantially semicircular planar shape attached to the ball return member 36. Each return passage 40 has an outer end 40A that communicates with the corresponding external passage 74 and an inner end 40B that communicates with the corresponding internal passage 76.

[0031] Each ball return member 36 has a ball fall prevention portion 39 having an approximately semicircular cross-sectional shape that protrudes outward from the left and right outer walls to prevent the balls 72 of the linear ball bearings 70 from falling outward from the outer ends 40A of the left and right return passages 40.

[0032] The left and right linear ball bearings 70 each have an external passage 74, an internal passage 76, and front and rear return passages 40 that communicate with each other, forming a closed loop circulation path through which the plurality of balls 72 circulate.

[0033] The lubricating oil supply passage 44 includes a first passage 48 that extends to the right from the lubricating oil injection passage 42 as viewed in Figures 5 and 7, passes through the center of the through hole 38, and reaches a branch position B on a left-right symmetrical line A that extends in the vertical direction, and a left-side second passage 50 and a right-side second passage 52 that branch off to the left and right from the branch position B and reach the left and right return passages 40, which are left-side and right-side symmetrical.

[0034] The left-side second passage 50 has a left-side extending portion 50A extending leftward from the branching position B, and an inclined extending portion 50B bending obliquely downward from the left end of the left-side extending portion 50A to reach the left-side return passage 40. The inclined extending portion 50B includes a communicating end 50C that communicates with a portion of the return passage 40 near the left-side outer end portion 40A.

[0035] The communication end 50C may be open at a position on the outer end 40A side of the position that divides the left return passage 40 equally between the inner end 40B and the outer end 40A. The communication end 50C preferably communicates with the return passage 40 at the left outer end 40A that is closest to the air gap G of the left external passage 74, as shown by the imaginary line in FIG. 5 .

[0036] The right-side second passage 52 has a right-side extending portion 52A extending rightward from the branching position B, and an inclined extending portion 52B bending obliquely downward from the right end of the right-side extending portion 52A to reach the right-side return passage 40. The inclined extending portion 52B includes a communicating end 52C that communicates with the return passage 40 near the right-side outer end portion 40A.

[0037] The communication end 52C may be open at a position closer to the outer end 40A than the position that divides the right return passage 40 equally between the inner end 40B and the outer end 40A. The communication end 52C preferably communicates with the return passage 40 at the right outer end 40A, which is closest to the air gap G of the right external passage 74, as shown by the imaginary line in FIG. 5 .

[0038] The left second passage 50 and the right second passage 52 are symmetrical with respect to a line of symmetry A, and the passage lengths are equal to each other.

[0039] The lubricating oil supply passage 44 further includes a left-side third passage 54 and a right-side third passage 56 that extend vertically and symmetrically from the left-side second passage 50 and the right-side second passage 52 radially outward from the through hole 38, and a fourth passage 58 that extends horizontally and connects the lower ends of the left-side third passage 54 and the right-side third passage 56 to each other. The fourth passage 58 includes an opening end 58A that opens toward the lower part of the through hole 38 and leads to the through hole 38.

[0040] The first passage 48, the left second passage 50, the right second passage 52, the left third passage 54, the right third passage 56, and the fourth passage 58 each include a portion formed by a groove that opens into the surface of the ball return member 36 that joins to the end face of the slider body 32. The opening of the groove is closed by the end face of the slider body 32, thereby defining a lubricating oil supply passage having a closed cross-sectional shape. This facilitates the configuration of a lubricating oil supply passage with a high degree of freedom.

[0041] The first passage 48 and the left extension 50A of the left second passage 50 include portions that overlap each other in the axial front and rear. This overlapping portion of the first passage 48 and the left extension 50A of the left second passage 50 is isolated as much as possible to form separate passages by a partition member 60 (see FIG. 4) that is fitted into a recess 62 (see FIG. 3) formed in the ball return member 36.

[0042] The isolation structure will now be described in detail. As shown in FIG. 3 , the recess 62 of the ball return member 36 has a deep bottom surface 62A, to which the lubricant injection passage 42 opens, and a shallow bottom surface 62B formed on a portion of the outer periphery of the deep bottom surface 62A. The partition member 60 abuts against the shallow bottom surface 62B, defining the first passage 48 between the rear surface of the partition member 60 and the deep bottom surface 62A. The recess 62 defined by the deep bottom surface 62A includes a portion extending to the right beyond the branching position B (see FIG. 5 ), and the first passage 48 also extends in the same direction. The partition member 60 has a lateral dimension such that its right end does not extend beyond the branching position B, so that the first passage 48 opens toward its base end into the left-side second passage 50 and the right-side second passage 52 at the branching position B.

[0043] 4, the portion where the leftward extending portion 50A of the left-side second passage 50 overlaps with the first passage 48 is defined by a groove 50D formed in the surface of the partition wall member 60. A groove 54A is formed in the surface of the partition wall member 60, and forms the branch end of a left-side third passage 54 that branches off from the left-side second passage 50.

[0044] With this configuration, there is no interference between the first passage 48 and the left extending portion 50A of the left second passage 50 at the portion where they overlap in the axial direction. Moreover, the portion where the first passage 48 and the left extending portion 50A of the left second passage 50 overlap in the axial direction can be easily formed without using a special construction method.

[0045] The second left passage 50, the second right passage 52, the third left passage 54, the third right passage 56, and the fourth passage 58 cooperate to include a portion that surrounds the radially outward side of the through hole 38. As shown in Figures 2, 5, and 6, a seal plate 64 is attached to the surface of the ball return member 36 that joins with the end face of the slider body 32. The seal plate 64 covers openings of the recessed grooves in the portion where the second left passage 50, the second right passage 52, the third left passage 54, the third right passage 56, and the fourth passage 58 surround the through hole 38, which open to the surface of the slider body 32. The seal plate 64 has an opening 68 that is substantially concentric with the through hole 31 (31A, 38) and has an inner diameter smaller than that of the through hole 31.

[0046] Furthermore, a shelf portion 36A (see Figure 2) having the same depth as the thickness of the seal plate 64 is formed in the portion of the ball return member 36 where the seal plate 64 can be attached, and the outer peripheral edge of the seal plate 64 fits into the shelf portion 36A, so that the surface where the slider body 32 joins to the end face of the slider body 32 is flush, including the portion of the seal plate 64.

[0047] According to the above-described configuration, the lubricating oil injected into the lubricating oil injection passage 42 flows through the first passage 48 to reach the branching position B on the left-right symmetrical line A of the through hole 38, and from the branching position B flows through the left-right symmetrical second passage 50 and right-side second passage 52, and is supplied to the return passages 40 of the left and right linear ball bearings 70 from the communicating ends 50C, 52C.

[0048] The lubricating oil injected into the lubricating oil injection passage 42 first flows to the branching position B via the first passage 48, and most of it flows through the symmetrical left-side second passage 50 and right-side second passage 52 to be supplied to the return passages 40 of the left and right linear ball bearings 70. Therefore, even if the lubricating oil injection passage 42 is biased to one side in the left-right direction with respect to the branching position B, the lubricating oil from the lubricating oil injection passage 42 is supplied evenly to the return passages 40 of the left and right linear ball bearings 70.

[0049] In other words, the left-side second passage 50 and the right-side second passage 52 are symmetrical with respect to the line of symmetry A, and the lengths of the passages are equal to each other. Therefore, even if the lubricating oil injection passage 42 is biased to one side in the left-right direction with respect to the branch position B, the left and right linear ball bearings 70 are lubricated equally with the lubricating oil on both sides.

[0050] Since the lubricating oil injection passage 42 is biased to one side in the left-right direction with respect to the branch position B, the distance between the upper edge of the through hole 31 (31A, 38) of the slider 30 including the ball return member 36 and the upper edge (top surface) of the slider 30 can be made smaller than when the lubricating oil injection passage 42 is at the branch position B. This makes it possible to reduce the height dimension H (see FIG. 5) of the slider 30, thereby enabling the ball screw actuator 10 to be downsized in the vertical direction.

[0051] Between the outer end 40A and the inner end 40B of the return passage 40, the outer end 40A is closest to the air gap G of the external passage 74 and is on the side that is open to the atmosphere, so the lubricating oil pressure at the outer end 40A is lower than the lubricating oil pressure at the inner end 40B. In other words, the lubricating oil pressure in the return passage 40 is lower on the outer end 40A side than on the inner end 40B side.

[0052] The communication ends 50C, 52C of the left second passage 50 and the right second passage 52, which correspond to the return passage 40, communicate with a portion of the return passage 40 closer to the outer end 40A than the position that bisects the return passage 40 between the inner end 40B and the outer end 40A. Due to the structure of the left second passage 50 and the right second passage 52, the lubricating oil is supplied to the low-pressure return passage 40, which has a lower lubricating oil pressure (internal pressure) than the inner end 40B.

[0053] This allows the lubricating oil to be supplied smoothly to the return passage 40 without increasing the lubricating oil injection pressure compared to when the lubricating oil is supplied to the return passage 40 on the inner end 40B side, improving the ease of supplying the lubricating oil.

[0054] The internal pressure of the lubricating oil in the return passage 40 is lowest at the outer end 40A, which is closest to the air gap G of the external passage 74. Therefore, it is preferable for the communication ends 50C, 52C to communicate with the outer end 40A, as shown by the phantom lines in FIG. 5, in order to smoothly supply the lubricating oil to the return passage 40.

[0055] Since the communication ends 50C, 52C of the left-side second passage 50 and the right-side second passage 52 to the corresponding return passages 40 are connected to a portion of the return passage 40 closer to the outer end 40A than the position that divides the return passage 40 in half between the inner end 40B and the outer end 40A, lubricating oil is supplied to the return passage 40 in a portion where the lubricating oil pressure (internal pressure) is lower than that of the inner end 40B.

[0056] This allows the lubricating oil to be supplied smoothly to the return passage 40 without increasing the injection pressure compared to when the lubricating oil is supplied to the return passage 40 on the inner end 40B side, improving the ease of supplying the lubricating oil.

[0057] As shown by the imaginary lines in FIG. 5, it is preferable that the communicating ends 50C, 52C communicate with the outer end 40A of the corresponding external passage 74 that is closest to the air gap G, in order to ensure smooth supply of the lubricating oil in relation to the internal pressure described above.

[0058] A portion of the lubricating oil injected into the lubricating oil injection passage 42 first flows to the branch position B via the first passage 48, then flows through the left-side second passage 50, the right-side second passage 52, the left-side third passage 54, the right-side third passage 56 and the fourth passage 58, and flows out from the opening end 58A into the through hole 38.

[0059] As a result, lubricating oil is applied to the outer peripheral surface of the portion where the ball screw shaft 102 passes through the through hole 38, thereby lubricating the ball screw shaft 102.

[0060] 6, the inner diameter of the opening 68 of the seal plate 64 is smaller than the inner diameter of the through hole 31A of the slider 30, so that the seal plate 64 acts as a barrier separating the through hole 31A from the through hole 38, making it difficult for the lubricating oil that has flowed out from the opening end 58A of the fourth passage 58 into the through hole 38 to flow into the through hole 31A. In other words, the lubricating oil supplied to the through hole 38 of the ball return member 36 is prevented from flowing excessively toward the slider body 32. This makes it difficult for the lubricating oil to flow more than necessary toward the ball screw nut portion 100 inside the slider body 32, reducing unnecessary consumption of lubricating oil.

[0061] (Embodiment 2) A ball screw actuator 10 according to embodiment 2 will be described with reference to Figures 8 to 10. In Figures 8 to 10, parts corresponding to those in Figures 1 to 9 are designated by the same reference numerals as those in Figures 1 to 9, and descriptions thereof will be omitted.

[0062] In the ball screw actuator 10 of the second embodiment, the left and right linear ball bearings 70 are each configured in two upper and lower stages. Each ball return member 36 has two upper and lower return passages 40. The inclined extension portion 50B of the left second passage 50 and the inclined extension portion 52B of the right second passage 52 are formed symmetrically, including a portion defined by the recessed groove 43A formed in the corresponding passage defining member 43, and reach between the upper and lower two stages of return passages 40. They communicate with the upper and lower return passages 40 by upper and lower symmetrical communicating ends 50C, 52C that open outward.

[0063] The passage defining member 43 extends across the upper and lower two stages of the return passages 40, and collectively defines the upper and lower two stages of the return passages 40 including the outer end 40A and the inner end 40B.

[0064] The communicating ends 50C, 52C of the inclined extension portion 50B of the left-side second passage 50 and the inclined extension portion 52B of the right-side second passage 52 each open outward toward the upper and lower two-stage return passages 40 from the portion where the passage defining member 43 is located midway between the upper and lower two-stage return passages 40.

[0065] In the second embodiment, too, the lubricating oil injected into the lubricating oil injection passage 42 flows through the first passage 48 to reach the branching position B on the left-right symmetrical line A of the through hole 38, and from the branching position B flows through the left-side second passage 50 and the right-side second passage 52, which are left-side symmetrical, and is supplied to each return passage 40 of the two upper and lower linear ball bearings 70 on the left and right from the upper and lower symmetrical communicating ends 50C, 52C for the two upper and lower return passages 40.

[0066] As a result, even if the lubricating oil injection passage 42 is biased to one side in the left-right direction with respect to the branch position B, the lubricating oil is supplied equally up and down and left and right to the two upper and lower tiers of linear ball bearings 70 on the left and right.

[0067] A portion of the inclined extension portion 50B of the left-side second passage 50 and the inclined extension portion 52B of the right-side second passage 52, more specifically, the portions where the inclined extension portion 50B and the inclined extension portion 52B each cross the upper return passage 40 from top to bottom, are formed by a groove 43A formed in the passage defining member 43, so that the configuration of the inclined extension portion 50B and the inclined extension portion 52B is not complicated and the formation of these portions is easy.

[0068] The present invention has been described above in terms of its preferred embodiments, but as can be easily understood by those skilled in the art, the present invention is not limited to such embodiments and can be modified as appropriate within the scope of the invention.

[0069] For example, the partition wall separating the first passage 48 and the left extending portion 50A of the left second passage 50 from each other at the front and rear axial overlapping portions may be integrally formed with the ball return member 36 by molding or the like, without using the partition wall member 60. The lubricant supply passage 44 does not necessarily have to be configured symmetrically. The lubricant supply structure for the linear ball bearing 70 including the lubricant supply passage 44 does not necessarily have to be configured in each of the ball return members 36 at both axial ends of the slider body 32, but may be configured in only one of the ball return members 36 at both ends.

[0070] The lubricating oil supply structure including the first passage 48, the left second passage 50, the right second passage 52, etc. of the linear ball bearing 70 is not limited to application to the linear ball bearing 70 of the slider 30 of the ball screw actuator 10, but can also be applied to the lubricating oil supply structure of a pair of left and right linear ball bearings 70 of a linear guide device in which the slider 30 is driven by a linear motor or the like other than the one driven by the ball screw actuator 10.

[0071] Furthermore, not all of the components shown in the above embodiment are necessarily essential, and they can be selected as appropriate without departing from the spirit of the present invention.

[0072] DESCRIPTION OF SYMBOLS 10: Ball screw actuator 20: Guide rail 22: Side wall 24: Groove 30: Slider 31: Through hole 31A: Through hole 32: Slider body 34: Bolt 36: Ball return member 36A: Ledge portion 38: Through hole 39: Ball fall prevention portion 40: Return passage 40A: Outer end portion 40B: Inner end portion 41: Groove 42: Lubricating oil injection passage 43: Passage defining member 43A: Groove 44: Lubricating oil supply passage 46: Lubricating oil nipple 48: First passage 50: Left-side second passage 50A: Left-side extension portion 50B: Inclined extension portion 50C: Communication end 50D: Groove 52: Right-side second passage 52A : Rightward extension portion 52B : Inclined extension portion 52C : Communication end 54 : Left-side third passage 54A : Groove 56 : Right-side third passage 58 : Fourth passage 58A : Opening end 60 : Partition member 62 : Recess 62A : Deep bottom surface 62B : Shallow bottom surface 64 : Seal plate 68 : Opening 70 : Linear ball bearing 72 : Ball 74 : External passage 76 : Internal passage 100 : Ball screw nut portion 102 : Ball screw shaft 104 : Ball A : Line of left-right symmetry B : Branch position G : Air gap

Claims

1. a linear guide rail having a concave cross-sectional shape with left and right side walls; a slider disposed between the left and right side walls of the guide rail; left and right linear ball bearings each including a plurality of balls that circulate between the left and right side walls of the guide rail and the slider, and that guide the axial movement of the slider relative to the guide rail; a ball screw nut portion provided on the slider; a ball screw shaft that passes through a through hole provided in the slider in an axial direction and is screwed into the ball screw nut portion provided in the slider via a ball, the slider has a slider body including the ball screw nut portion, and ball return members attached to both ends of the slider body in the axial direction, each of the left and right linear ball bearings has an external passage formed by a corresponding one of the left and right side walls of the guide rail and the slider body, and an internal passage formed to extend axially inside the slider body; At least one of the ball return members has left and right return passages through which the balls of the left and right linear ball bearings move, a lubricant oil injection passage, and a lubricant oil supply passage that supplies lubricant oil from the lubricant oil injection passage to the left and right return passages, the left and right return passages each have an outer end communicating with the corresponding external passage and an inner end communicating with the corresponding internal passage, The lubricating oil supply passage communicates with the left and right return passages located closer to the outer end than the inner end.

2. 2. The ball screw actuator according to claim 1, wherein the lubricating oil supply passage communicates with the left and right return passages at the outer end portion.