Ball spline with detour track

Abstract

The present invention relates to a bearing including a rod-shaped spline shaft (110), a nut portion into which the spline shaft (110) is inserted and which is provided so as to be movable along the longitudinal direction thereof, and a plurality of balls (150) provided between the nut portion and the spline shaft (110) and which circulate. The nut portion includes a hollow nut (120) into which the spline shaft (110) is inserted, and hollow retainers (130) provided on both longitudinal sides of the nut (120) and into which the spline shaft (110) is inserted. The spline shaft (110) is formed with at least one raceway portion recessed and extending along the longitudinal direction, and the nut (120) is formed with at least one load bearing raceway groove (125) recessed along the longitudinal direction in an inner surface (121) of the hollow portion into which the spline shaft (110) is inserted. and at least one non-load circulation portion (127) formed along the longitudinal direction alongside the load bearing raceway groove (125), the retainer (130) is formed with at least one curved, recessed circulation groove (133) facing one end of the load bearing raceway groove (125) and the other end of the non-load circulation portion (127), the balls (150) are switched in direction in the circulation grooves (133) of the retainer (130) on both longitudinal sides, and circulate between the raceway portion and the load bearing raceway groove (125) and along the non-load circulation portion (127), the raceway portion including a raceway groove (111) formed along the longitudinal direction and a detour raceway portion (111-1) connected to the raceway groove (111) on both longitudinal sides.

Description

[Technical field]

[0001] The present invention relates to a ball spline, and more particularly to a ball spline having a detour track in a portion of the ball spline shaft along which a nut portion can rotate and move at a constant angle relative to the spline shaft. [Background technology]

[0002] The ball spline is a type of linear motion bearing that accurately transmits linear motion in the fields of automation and semiconductor industries.

[0003] As shown in Fig. 1, a conventional ball spline 10 has a loaded raceway groove 2 in which a ball 1 is housed and one side of the ball 1 is exposed, and the ball 1 circulating along the loaded raceway groove 2 enters a non-loaded circulation hole 5 along a circulation groove 4 of a retainer 3, forming an endless track through which the ball 1 circulates. In a nut 6, the loaded raceway groove 2 in which the ball 1 is housed may be formed in a cross section in the shape of a circular arc with a curvature radius larger than the radius of the ball, but it may also be machined to form two identical circular arcs on the left and right of a central axis of a central circle, and then the ball 1 is housed so that the ball 1 comes into contact with the loaded raceway groove 2 at two contact points formed on the left and right of the central axis of the central circle. When the ball 1 is housed in the loaded raceway groove 2, the angle between the two contact points where the ball 1 comes into close contact and the center of the ball 1 is increased to prevent the ball 1 from slipping out of the loaded raceway groove 2, and a curved surface is formed at the tip of the loaded raceway groove 2 to allow the ball 1 to circulate smoothly when it moves from the loaded raceway groove 2 along the circulation groove 4 of the retainer 3 to the non-loaded circulation hole 5. Since the ball 1 moves along the curved surface, no shock is generated and no noise or vibration is generated.

[0004] When the spline shaft 10 is inserted into the nut 6, the raceway groove 9 is formed in the spline shaft 10 so as to extend in the longitudinal direction and be recessed so that the balls 1 protruding from the spline shaft 10 can be inserted into the inner diameter of the nut 6. This allows the spline shaft 10 to accurately perform soft forward and backward motion in the nut 6 by the balls 1. The circulation of the balls 1 enables forward and backward motion regardless of the length of the spline shaft 8.

[0005] The raceway groove 9 formed on the spline shaft 8 may also have an arc-shaped cross section, but by machining it in the same manner as the load-bearing raceway groove 2, the ball 1 will roll by coming into contact at four contact points (four-point contact).

[0006] Reference numeral 7 in FIG. 1 denotes a seal provided between the nut 6 and the retainer 3, and reference numeral 4a denotes a circular protrusion provided on the retainer 3 and protruding inward.

[0007] In the ball spline as shown in FIG. 1, the nut 6 to which the retainer 3 is coupled can reciprocate along the spline shaft 10 in its longitudinal direction, but cannot rotate relative to the spline shaft 10.

[0008] Fig. 2 is a schematic cross-sectional view showing a part of a moving means coupled to a ball spline of the prior art, and is a diagram for explaining an application of the ball spline.

[0009] As shown in FIG. 2, in the moving means V, a bracket IB having a hollow body with a circular cross section is installed on the outside of the nut 6, a rolling bearing B is installed on the outside of the bracket IB, and a wheel W is installed on the bracket IB so as to rotate integrally with the inner ring of the rolling bearing B. In this structure, the moving means V can move forward and backward in a direction perpendicular to the paper surface of FIG. 2 by the rolling bearing B rotatably supported by the wheel W. As shown in FIG. 2, a pinion P is installed on the outer end of the spline shaft 8, and the spline shaft 8 is pushed outward and meshes with a rack R installed in the vertical direction (see the dashed line part in FIG. 2), and when the spline shaft 8 is rotated, the moving means V moves in the vertical direction along the rack R. It is possible to move forward and backward as shown in FIG. 2, and the pinion P installed at the end of the spline shaft 8 meshes with the rack R to move in the vertical direction.

[0010] In the ball spline 10 required for such movement, when the spline shaft 8 is pushed outward and the pinion P moves forward toward the rack R, the gear of the pinion P does not position itself between the gears of the rack R, and the gear of the pinion P hits the gear of the rack R, causing the pinion P and the rack R to not mesh, which can cause damage to the pinion P and the rack R. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been proposed to solve the problems associated with the conventional technology described above, and has an object to provide a ball spline having a detour track portion, which allows the nut to rotate within a certain range relative to the spline shaft. [Means for solving the problem]

[0012] To achieve the above-mentioned object, the present invention provides a ball bearing assembly including a rod-shaped spline shaft, a nut portion into which the spline shaft is inserted and which is provided movably along the longitudinal direction of the nut, and a plurality of balls provided between the nut portion and the spline shaft and circulating therebetween, the nut portion including a hollow nut into which the spline shaft is inserted, and hollow retainers provided on both longitudinal sides of the nut into which the spline shaft is inserted, the spline shaft being formed with at least one raceway portion recessed and extending along the longitudinal direction, and the nut being formed with at least one raceway portion recessed into the inner surface of the hollow portion into which the spline shaft is inserted and formed along the longitudinal direction. the retainer is provided with at least one load-bearing raceway groove and at least one non-loaded circulating portion formed along a longitudinal direction parallel to the load-bearing raceway groove, the retainer is formed with at least one curved, recessed circulation groove one side of which faces an end of the load-bearing raceway groove and the other side of which faces an end of the non-loaded circulating portion, the balls are switched in direction in the circulation grooves of the retainer on both longitudinal sides, and circulate between the raceway portion and the load-bearing raceway groove and along the non-loaded circulating portion, the raceway portion including a raceway groove formed along the longitudinal direction and a detour raceway portion connected to the raceway groove on both longitudinal sides.

[0013] In the above, the detour track portion is characterized by comprising a detour track groove formed parallel to the track groove, and an inclined track groove extending obliquely from both sides in the longitudinal direction of the detour track groove and connected to the track groove.

[0014] In the above, the detour track portion is provided on both sides of the track groove.

[0015] In the above, the detour raceway is formed deeper than the load bearing raceway groove, and the balls have a clearance between the detour raceway and the load bearing raceway groove.

[0016] In the above, the retainer inner surface is formed in a cylindrical shape, and the circulation groove is open to the retainer inner surface.

[0017] In the above, the load bearing raceway groove is formed opposite the raceway groove, and the load bearing raceway groove is provided at both ends in the longitudinal direction with an expanded raceway extension portion.

[0018] In the above, the ball bushing portion further includes at least one bush loaded raceway groove recessed into an inner surface portion of the nut and formed along the longitudinal direction, at least one bush non-loaded circulation portion formed along the longitudinal direction at a position spaced from the bush loaded raceway groove, at least one bush circulation groove formed curvedly and recessed on an inner side of the retainer facing the nut, one side facing the bush loaded raceway groove and the other side facing the bush non-loaded circulation portion, and a plurality of rolling elements whose directions are switched in the bush circulation grooves on both sides and which circulate between the bush loaded raceway groove and an outer surface of the spline shaft and along the bush non-loaded circulation portion. Effect of the Invention

[0019] According to the ball spline 100 having a detour raceway of the present invention, it is provided with a detour raceway portion 111-1, the nut 120 is rotatable within a certain range relative to the spline shaft 110, there is a rotational clearance, damage to the raceway inclined portion 111b-1 of the detour raceway portion 111-1 due to contact between the balls 150 and the raceway inclined portion 111b-1 is prevented, damage to the retainer 130 due to interference between the spline shaft 110 and the retainer 130 due to the rotation of the nut 120 is prevented, and there are advantages in that it has a large bending resistance. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an exploded perspective view showing a ball spline according to a conventional art; [Diagram 2] FIG. 1 is a schematic partial front sectional view of an application example of a ball spline. [Diagram 3] 1 is a perspective view showing a ball spline having a detour raceway according to the present invention with some parts omitted; [Figure 4]1A and 1B are partial perspective and sectional views of a spline shaft included in a ball spline having a detour raceway according to the present invention; [Diagram 5] FIG. 2 is a perspective view showing a nut included in a ball spline having a bypass raceway according to the present invention; [Figure 6] 1 is a partial longitudinal sectional view and a partial enlarged view of a ball spline having a detour raceway according to the present invention; [Figure 7] FIG. 2 is a perspective view of a retainer included in a ball spline having a bypass raceway according to the present invention; [Figure 8] FIG. 11 is a partially cutaway perspective view showing a modified example of a ball spline having a detour raceway according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a ball spline having a detour raceway according to the present invention will be described in detail with reference to the accompanying drawings.

[0022] FIG. 3 is a perspective view showing a ball spline having a bypass track according to the present invention with some parts omitted, FIG. 4 is a partial perspective view and a cross-sectional view of a spline shaft included in a ball spline having a bypass track according to the present invention, FIG. 5 is a perspective view showing a nut included in a ball spline having a bypass track according to the present invention, FIG. 6 is a partial cross-sectional view and a partially enlarged view in the longitudinal direction of a ball spline having a bypass track according to the present invention, FIG. 7 is a perspective view of a retainer included in a ball spline having a bypass track according to the present invention, and FIG. 8 is a partially cut-away perspective view showing a modified example of a ball spline having a bypass track according to the present invention.

[0023] As shown in Figures 3 and 5, a ball spline 100 having a detouring track according to the present invention includes a rod-shaped spline shaft 110, a nut portion into which the spline shaft 110 is inserted and which is movable along the longitudinal direction of the spline shaft 110, and a plurality of balls 150 which are provided between the nut portion and the spline shaft 110 and circulate.

[0024] The nut portion includes a cylindrical hollow nut 120 into which the spline shaft 110 is inserted, and a hollow retainer 130 provided on both sides of the nut 120 in the longitudinal direction and into which the spline shaft 110 is inserted. The nut 120 is made of high carbon steel such as bearing steel. The retainer 130 has a donut shape with the inner diameter portion removed from a disk. The retainer 130 may be made of engineering plastic (nylon 6, nylon 66, or one of these with glass fiber added), but may also be made of a metal such as bearing steel, similar to the nut 120. A seal, which is not shown and is also a hollow body, may be included between the nut 120 and the retainer 130. The retainer 130 may be connected to the nut 120 by a bolt, as shown in FIG. 1.

[0025] The spline shaft 110 has at least one raceway portion recessed and extending along the longitudinal direction. The spline shaft 110 may be manufactured by machining a raceway portion recessed into a rod-shaped outer surface having a circular cross section. Two raceways may be provided at positions facing each other, or four raceways may be provided at 90° intervals. The spline shaft 110 may have a shaft mounting portion 113 having a reduced diameter at an end. A key groove (not shown) is formed in the shaft mounting portion 113, and a pinion or the like is installed therein.

[0026] The nut 120 has at least one load bearing raceway groove 125 formed along the longitudinal direction and recessed into an inner surface 121 of a hollow portion into which the spline shaft 110 is inserted, and at least one non-loaded circulation portion 127 formed along the longitudinal direction parallel to the load bearing raceway groove 125. The load bearing raceway groove 125 and the non-loaded circulation portion 127 are provided in the same number as the raceway portions provided on the spline shaft 110. The non-loaded circulation portion 127 may be formed as a through hole formed in the nut 120 along the longitudinal direction. The load bearing raceway groove 125 is formed at a position facing the raceway portion.

[0027] A curved and recessed circulation groove 133 is formed on an inner surface of the retainer 130 facing the nut 120. At least one circulation groove 133 is formed. The number of circulation grooves 133 is the same as the number of raceways. One side of the circulation groove 133 faces an end of the loaded raceway groove 125, and the other side faces an end of the non-loaded circulation portion 127.

[0028] The balls 150 have their direction switched in the circulation grooves 133 of the retainers 130 on both sides in the longitudinal direction, roll between the raceway and the loaded raceway groove 125, and circulate along the non-loaded circulation portion 127. The circulation of the balls 150 is a known technique, so a description thereof will be omitted.

[0029] The raceway includes a raceway groove 111 formed along the longitudinal direction of the spline shaft 110, and a detour raceway 111-1 whose longitudinal opposite sides are connected to the raceway groove 111. When an external force in a rotational direction acts on the nut 120 or on the spline shaft 110, the balls 150 move between the detour raceway 111-1 and the load bearing raceway groove 125, and the nut 120 can rotate by a certain angle relative to the spline shaft 110.

[0030] The detour track portion 111-1 is composed of a detour track groove 111b that is spaced apart from and formed alongside the track groove 111, and inclined track grooves 111b-1 that extend at an angle from both longitudinal sides of the detour track groove 111b and are connected to the track groove 111. When the ball 150 rolls between the track groove 111 and the load-bearing track groove 125 and then moves between the load-bearing track groove 125 and the detour track portion 111-1, it moves along the inclined track groove 111b-1, the detour track groove 111b, and further along the inclined track groove 111b-1 on the other side, and then along the track groove 111.

[0031] The ball 150 can roll with two points of contact with the raceway groove 111 and two points of contact with the load bearing raceway groove 125, resulting in four-point contact. The raceway groove 111 and the load bearing raceway groove 125 may be formed in an arc shape having a curvature radius larger than the radius of the ball 150, allowing the ball 150 to roll with two-point contact. This is a conventionally known technique, so a detailed description of it will be omitted.

[0032] As shown in Fig. 4, the detour raceway 111-1 may be provided on both sides in the circumferential direction with the raceway groove 111 in between. The detour raceway 111-1 may be formed deeper than the raceway groove 111, and the balls 150 may have a clearance between the detour raceway 111-1 and the load bearing raceway groove 125. Since the balls 150 have a clearance between the detour raceway 111-1 and the load bearing raceway groove 125, the nut 120 may also have a clearance in the rotational direction with respect to the spline shaft 110, and smooth meshing may be performed in the meshing process of the rack and pinion as shown in Fig. 2.

[0033] Reference numeral 111a in Figs. 2 and 3 denotes a portion of the track groove 111 aligned with the detour track groove 111b.

[0034] 5 and 6, the load-bearing track groove 125 faces the track groove 111, and is provided with expanded track extension portions 125a at both longitudinal ends of the load-bearing track groove 125. When the ball 150 moves to the track extension portion 125a, the amount of play of the ball 150 between the track extension portion 125a and the detour track portion 111-1 increases, and therefore damage to the inclined track groove 111b-1 by the ball 150 can be suppressed or prevented.

[0035] 7, the retainer inner surface portion 131 is formed in a cylindrical shape, the circulation groove 133 opens into the retainer inner surface portion 131, and the circulation groove 133 has, on its inner diameter side, an inner surface opening portion 135 that opens into the retainer inner surface portion 131. Therefore, the radially inner side of the retainer 130 is not provided with a configuration that protrudes inward from the retainer inner surface portion 131, and when the retainer 130 is moved, no interference with the inclined track groove 111b-1 occurs, and therefore no damage to the retainer 130 occurs due to interference with the inclined track groove 111b-1.

[0036] As shown in Fig. 8, the ball spline 100 having a bypass raceway according to the present invention further includes a ball bushing portion. Raceway portions are formed in opposing positions on the spline shaft 110, and a ball bushing portion is provided between the raceway portions. The provision of the ball bushing portion improves the rigidity of the nut 120 against a radial load acting on the nut 120. Two raceway portions are formed at an angle of 180° apart, and a ball bushing portion is provided between the raceway portions on both sides.

[0037] The ball bushing portion includes at least one bushing loaded raceway groove 125-1 formed along the longitudinal direction in a recessed manner on the inner surface of the nut 120, at least one bushing non-loaded circulation portion 127-1 formed along the longitudinal direction at a position spaced apart from the bushing loaded raceway groove 125-1, at least one bushing circulation groove 133-1 formed on the inner side of the retainer 110 facing the nut 120, one side facing the bushing loaded raceway groove 125-1 and the other side facing the bushing non-loaded circulation portion 127-1, and a plurality of balls 150-1 whose directions are switched at the bushing circulation grooves 133-1 on both sides and which circulate between the bushing loaded raceway groove 125-1 and the outer surface of the spline shaft 110 and along the bushing non-loaded circulation portion 127-1. The bushing non-loaded circulation portion 127-1 may be formed as a through hole penetrating along the longitudinal direction. The bushing loaded raceway groove 125-1 faces the outer surface of the spline shaft 110, the cross section of which is arc-shaped. The balls 150-1 roll between the bushing loaded raceway groove 125-1 and the outer surface of the spline shaft 110 (the outer surface having an arc-shaped cross section), have their direction changed in the bushing circulation groove 133-1, are guided to the bushing non-loaded circulation portion 127-1, and move along the bushing non-loaded circulation portion 127-1 to be infinitely circulated. [Industrial Applicability]

[0038] The ball spline 100 having a detour raceway according to the present invention may be used in a variety of applications.

Claims

1. the spline shaft (110) is inserted into a rod-shaped spline shaft; a nut portion into which the spline shaft (110) is inserted and which is provided so as to be movable along the longitudinal direction of the spline shaft; and a plurality of balls (150) which are provided between the nut portion and the spline shaft (110) and circulate therebetween, the nut portion including a hollow nut (120) into which the spline shaft (110) is inserted, and hollow retainers (130) which are provided on both longitudinal sides of the nut (120) and into which the spline shaft (110) is inserted; The spline shaft (110) is formed with at least one raceway portion recessed and extending along the longitudinal direction, and the nut (120) is provided with at least one load-bearing raceway groove (125) recessed along the longitudinal direction on an inner surface (121) of a hollow portion into which the spline shaft (110) is inserted, and at least one non-load-bearing circulating portion (127) formed along the longitudinal direction parallel to the load-bearing raceway groove (125), At least one curved, concave circulation groove (133) is formed in the retainer (130), one side of which faces an end of the loaded raceway groove (125) and the other side of which faces an end of the non-loaded circulation portion (127). The balls (150) are switched in direction in the circulation grooves (133) of the retainer (130) on both sides in the longitudinal direction, and circulate between the raceway portion and the loaded raceway groove (125) and along the non-loaded circulation portion (127). The ball spline (100) having a detour track is characterized in that the track portion includes a track groove (111) formed along a longitudinal direction, and a detour track portion (111-1) connected to the track groove (111) on both longitudinal sides thereof, The detour track portion (111-1) is characterized by comprising a detour track groove (111b) formed in parallel with the track groove (111), and inclined track grooves (111b-1) extending obliquely from both sides in the longitudinal direction of the detour track groove (111b) and connected to the track groove (111), The ball spline (100) has a detour raceway, the detour raceway portion (111-1) being formed deeper than the raceway groove (111), and the ball (150) has a clearance between the detour raceway portion (111-1) and the load-bearing raceway groove (125).

2. 2. The ball spline (100) having a detour raceway according to claim 1, wherein the detour raceway portions (111-1) are provided on both sides of the raceway groove (111).

3. the spline shaft (110) is inserted into a rod-shaped spline shaft; a nut portion into which the spline shaft (110) is inserted and which is provided so as to be movable along the longitudinal direction of the spline shaft; and a plurality of balls (150) which are provided between the nut portion and the spline shaft (110) and circulate therebetween, the nut portion including a hollow nut (120) into which the spline shaft (110) is inserted, and hollow retainers (130) which are provided on both longitudinal sides of the nut (120) and into which the spline shaft (110) is inserted; The spline shaft (110) is formed with at least one raceway portion recessed and extending along the longitudinal direction, and the nut (120) is provided with at least one load-bearing raceway groove (125) recessed along the longitudinal direction on an inner surface (121) of a hollow portion into which the spline shaft (110) is inserted, and at least one non-load-bearing circulating portion (127) formed along the longitudinal direction parallel to the load-bearing raceway groove (125), At least one curved, concave circulation groove (133) is formed in the retainer (130), one side of which faces an end of the loaded raceway groove (125) and the other side of which faces an end of the non-loaded circulation portion (127). The balls (150) are switched in direction in the circulation grooves (133) of the retainer (130) on both sides in the longitudinal direction, and circulate between the raceway portion and the loaded raceway groove (125) and along the non-loaded circulation portion (127). The ball spline (100) having a detour track is characterized in that the track portion includes a track groove (111) formed along a longitudinal direction, and a detour track portion (111-1) connected to the track groove (111) on both longitudinal sides thereof, When an external force in a rotational direction acts on the nut (120) or when an external force in a rotational direction acts on the spline shaft (110), the balls (150) move along between the detour raceway portion (111-1) and the load bearing raceway groove (125), and the nut (120) can rotate by a fixed angle relative to the spline shaft (110).

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