WO2006028141A1

WO2006028141A1 - Ball spline device

Info

Publication number: WO2006028141A1
Application number: PCT/JP2005/016435
Authority: WO
Inventors: Hidekazu Michioka; Hiroaki Mochizuki; Tomozumi Murata; Shigeo Tomita; Yuki Fujii
Original assignee: Thk Co., Ltd.
Priority date: 2004-09-08
Filing date: 2005-09-07
Publication date: 2006-03-16
Also published as: JPWO2006028141A1; JP2011017448A; JP5026575B2; JP4675326B2; JP2011017447A

Abstract

A ball spline device in which rigidity of a spline shaft can be increased without increasing the diameter of a spline nut, the spline shaft can be produced at low cost and high accuracy, and variation in movement resistance of the spline nut can be reduced as much as possible by smoothening circulation of balls in an endless circulation path. In the ball spline device, the spline nut (2) is composed of a metal hollow cylindrical nut body (4), synthetic resin inner plates (5) assembled to the inner peripheral surface of the nut body (4), and synthetic resin end caps (6) fitted to both ends in the axial direction of the nut body (4). A ball return hole (52) formed in an inner plate (5) is positioned closer to the outside, relative to the radial direction of the spline shaft (1), than a load path (31) for balls. The spline shaft (1) has an almost cross-section.

Description

Specification

Ball spline device

Technical field

[0001] In the present invention, a spline shaft and a spline nut are relatively linearly combined through a large number of balls, and are used as a linear guide part in a machine tool or various industrial machines, a torque transmission part in an industrial robot, or the like. The present invention relates to a ball spline device used.

Background art

Conventionally, as this type of ball spline device, those disclosed in Japanese Utility Model Laid-Open No. 61-179414 and Japanese Patent Application Laid-Open No. 58-137616 are known. These ball spline devices are provided with a spline shaft having a plurality of ball rolling grooves extending along the longitudinal direction, and assembled to the spline shaft via a large number of balls, and an infinite circulation path for the balls. The spline nut is configured such that the spline nut can freely move along the longitudinal direction of the spline shaft as the ball is infinitely circulated.

[0003] Further, the infinite circulation path of the ball provided in the spline nut is parallel to the load path in which the ball rolls while applying a load acting between the spline nut and the spline shaft. And a U-shaped direction change path connecting the load path and the ball return path. An infinite circulation path for the ball is configured by arranging the direction change paths at both ends of the load path and the ball return path.

[0004] If the ball return passage is formed through the spline nut itself, the spline nut tends to become thick and large in diameter, and when the ball diameter is small, the ball return hole diameter is also small. Therefore, it is difficult to form the ball return hole directly through the spline nut. For this reason, in the ball spline device disclosed in the above-mentioned document, a synthetic resin cage is interposed in the gap between the inner peripheral surface of the spline nut formed in a cylindrical shape and the spline shaft passing through the inner surface. The ball return passage and the direction change passage were formed by the cooperation of the cage and the spline nut. Patent Document 1: Japanese Utility Model Publication No. 61-179414

Patent Document 1: Japanese Patent Application Laid-Open No. 59-155617

Disclosure of the invention

Problems to be solved by the invention

[0005] However, in the conventional ball spline device disclosed in these documents, the axial force of the spline shaft is the distance force to the load passage of the ball. The axial force is substantially the same as the distance to the ball return passage. The cross-sectional shape perpendicular to the axial direction of the spline shaft has become complicated. That is, when the ball spline device is observed from the axial direction, the load passage and the ball return passage are aligned in the circumferential direction with respect to the axis of the spline shaft, so that the cage is connected to the spline shaft and the spline nut. In order to accommodate them, it is necessary to scrape the peripheral surface of the spline shaft to provide a storage space for the holding machine. Therefore, the conventional spline shaft has ridges along the longitudinal direction at three locations in the circumferential direction. Ball rolling grooves were formed on both sides of this ridge.

[0006] However, since the spline shaft having such a shape has a smaller cross-sectional area than a round shaft having the same maximum outer diameter, the rigidity to the radial load has to be small. In addition, if a spline shaft with such a shape is formed from a round shaft, the allowance increases. Therefore, the shape of the spline shaft is conventionally adjusted by drawing, followed by heat treatment such as carburizing and quenching. However, it is necessary to grind the rolling surface of the ball and correct the bending distortion of the spline shaft caused by the heat treatment. This increases the production process and increases the production cost. The management to maintain it has to be complicated.

[0007] In addition, the contact direction of the ball and the spline shaft in the load passage stands up greatly with respect to the circumferential direction of the spline shaft, and the ball rolling in the ball rolling groove of the spline shaft enters the direction change path. If the ball is smoothly raised and guided to the ball return hole, the positional relationship between the ball return hole and the load passage is preferably approximated to the contact direction. However, in the conventional ball spline device described above, since the load passage and the ball return hole are arranged in the circumferential direction of the spline shaft, the direction change path guides the ball along the circumferential direction of the spline shaft. , The rotation direction of the ball suddenly changes at the connection part of the load path and the direction change path The power that must be changed drastically. For this reason, the behavior of the ball in the direction change path is not stable. For example, when the spline shaft is used in a vertical position, the spline nut against the spline shaft is likely to be clogged in the turning direction change path. The movement resistance fluctuated easily, and there were two phenomena.

[0008] Further, in the conventional ball spline device, since the direction changing path and the ball return hole are formed by the cooperation of the synthetic resin cage and the metal spline nut, the ball in the unloaded state is directional. When rolling along the turning path and the ball return hole, the metal ball and the spline nut come into contact with each other to generate noise, especially under operating conditions where the spline nut moves back and forth at high speed. There was a sound. For this reason, there was a problem when it was not suitable for use in a sealed space such as a talin room or for use in medical equipment.

Means for solving the problem

[0009] The present invention has been made in view of such problems, and an object of the present invention is to increase the rigidity of the spline shaft without increasing the diameter of the spline nut, It is possible to produce such spline shafts at low cost and with high accuracy, and to minimize the fluctuation of the movement resistance of the spline nut by smoothing the circulation of the ball in the infinite circuit. It is an object of the present invention to provide a ball spline device capable of achieving the above.

[0010] Further, another object of the present invention is to suppress the generation of noise when the ball rolls in an infinite circulation path at high speed, to be used in a sealed space such as a clean room, or to a medical device. The object is to provide a ball spline device suitable for use.

In order to achieve the above object, a ball spline device according to the present invention includes a spline shaft in which a plurality of ball rolling grooves are formed along an axial direction, and the spline via a plurality of balls that circulate infinitely. The spline nut is assembled to a shaft and is reciprocally movable along the spline shaft. The spline nut is assembled to a metal cylindrical nut body and an inner peripheral surface of the nut body. And a plurality of inner blades constituting a part of the ball endless circulation path, and synthetic resin ends that are attached to both ends of the nut body in the axial direction and form an endless circulation path of the ball together with the inner plate. Cap and force are composed. The inner peripheral surface of the nut body is evenly divided in the circumferential direction. A load base portion is formed so as to be cut off, and a plate housing portion for housing the inner plate is formed between the load base portions. Further, a ball rolling of a spline shaft is formed on the load base portion. A ball rolling groove constituting a ball load passage is formed facing the groove, a ball return hole is formed through the inner plate in parallel with the ball rolling groove, and the end cap is connected with the load passage. A u-shaped direction change path is formed to connect the ball return hole of the inner plate to complete the infinite circulation path of the ball.

[0012] According to such technical means, the load base portion protrudes from the inner peripheral surface of the nut body, while the inner-blade accommodating portion is formed between the load base portions adjacent to each other. In addition, a ball rolling groove in which the ball rolls is formed in the load base portion, while a ball return hole is formed through the inner plate. For this reason, the ball return hole is located outside the ball load passage in the radial direction of the spline shaft, and the formation position of the forceful ball return hole does not interfere with the outer diameter of the spline shaft. Accordingly, the spline shaft can be formed so that its cross section is close to a circular shape, and the cross sectional area of the shaft can be made larger than before, so that the rigidity of the spline shaft can be increased.

[0013] Further, since the cross-sectional shape of the spline shaft can be made closer to a circular shape, it is sufficient to grind only the ball rolling groove and its periphery with respect to the round shaft when manufacturing such a spline shaft. It is possible to manufacture spline shafts that are machined with high precision while using inexpensive round shafts that have been heat-treated and produced by centerless grinding.

[0014] In addition, since the ball return hole is located radially outside of the ball load passage, the positional relationship between the ball return passage and the load passage approximates the contact direction of the ball with respect to the spline shaft. Thus, it is possible to smoothly circulate the ball between the load passage and the ball return hole.

[0015] Furthermore, of the load path, the direction changing path, and the ball return hole that constitute the infinite circulation path of the ball, the ball return hole is formed through the inner blade, and the direction changing path is also formed by the end cap. If these inner plates and end caps are made of synthetic resin, the endless circulation path of the ball is formed of synthetic resin except for the load passage. For this reason, coupled with the smooth circulation of the ball, Noise generated with the circulation of the ball can be reduced. If a synthetic resin spacer is interposed between the balls that run ahead and behind, further noise reduction can be achieved.

Brief Description of Drawings

FIG. 1 is a perspective view showing an embodiment of a ball spline device to which the present invention is applied.

2 is a front sectional view of the ball spline device shown in FIG.

FIG. 3 is an exploded perspective view of a spline nut.

FIG. 4 is a front sectional view of a spline shaft.

FIG. 5 is a front view showing a nut body constituting a spline nut.

[Fig. 6] Diagram showing the inner plate that constitutes the spline nut, with a partial view (a) showing a plan view, a partial view (b) showing a partial view (a) as viewed from the arrow b, and a partial view (c) showing a partial view. A cross-sectional view taken along the line cc of FIG. (A), an enlarged view (d) is an enlarged view showing details of the positioning flange, and a cut-away view (e) is a cross-sectional view taken along the line ee of the divided view (d).

FIG. 7 is a view showing an end cap that constitutes a spline nut, wherein a partial view (a) is a rear view showing an inner surface, and a partial view (b) is a side view.

[FIG. 8] An exploded view showing a fitting state of the direction change path of the end cap and the return piece of the inner blade.

Explanation of symbols

[0017] 1 ... Spline shaft, 2 ... Spline nut, 3 ... Ball, 4 ... Nut body, 5 ... Inner plate, 6 ... End cap, 10a, 10b ... Ball rolling groove (spline shaft), 30 ... Infinite circulation , 31 · · · Load passage, 41 · · · Load base, 42a, 42b… Ball rolling groove (nut body), 44… Plate receiving portion, 52 ·· Ball return hole, 54 ·· Return piece , 61 · · · turnaround route BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the ball spline device of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 and FIG. 2 show an embodiment of a ball spline device to which the present invention is applied. The ball spline is formed in a substantially cylindrical shape having a spline shaft 1 in which a plurality of ball rolling surfaces 10 are formed along a longitudinal direction and a hollow hole through which the spline shaft 1 passes. The spline nut 2 is assembled to the spline shaft 1 through a large number of balls 3. The spline nut 2 is connected to the endless circulation path 30 of the ball 3. A plurality of balls 3 rolling on the ball rolling surface 10 of the spline shaft 1 circulate in an infinite circulation path 30 provided in the spline nut 2, so that the spline nut 2 is applied along the spline shaft 1. It is possible to freely reciprocate linearly.

[0020] As shown in FIG. 4, the spline shaft 1 has a substantially circular cross section perpendicular to the axial direction, and six ball rolling grooves 10 along the longitudinal direction are formed on the outer peripheral surface thereof. Is formed. These ball rolling grooves 10 are formed as two sets of two ball rolling grooves 10a and 10b, and three sets are formed, and the three sets of ball rolling grooves divide the peripheral surface of the spline shaft 1 into three equal parts. It is provided as follows. The ball rolling groove 1 Oa and the ball rolling groove 1 Ob have different formation directions with respect to the circumferential surface of the spline shaft 1, and the ball rolling groove 10a is formed by tilting clockwise with respect to the circumferential surface of the shaft. On the other hand, the ball rolling groove 10b is formed to be inclined in the counterclockwise direction. Further, on the outside of the two ball rolling grooves 10a and 10b that form one set, flat ball relief surfaces 11a and ib are formed adjacent to these ball rolling grooves. The ball flank surfaces 11a and 1 lb are formed to prevent the spline shaft 1 from interfering with the ball infinite circulation path 30 provided in the spline nut 2.

[0021] As a result of the formation of the ball rolling grooves 10a and 10b and the ball flank 11a and ib in this way, the spline shaft 1 has a force applied to its outer peripheral surface as if three protrusions 12 were formed. The force having a cross-sectional shape The outer diameter of the reference outer diameter portion 13 and the protrusion 12 sandwiched between the ball flank surfaces 11a and l ib adjacent to each other is the same, and the protrusion 12 is greater than the reference outer diameter portion 13. Is not projected outwards. Therefore, this spline shaft 1 has an extremely circular cross section, and the machining allowance for forming the ball rolling grooves 10a, 10b and the ball flank 11a, 1 lb is small. The ball rolling grooves 10a and 10b and the ball flank 11a and l ib can be formed by direct grinding. A grinding wheel is used for grinding the ball rolling grooves 10a and 10b and the ball flank 11a and l ib. As the round shaft of the material, heat treated and centerless ground can be used, and the ball rolling grooves 10a, 10b are formed directly on the round shaft by grinding, so it is extremely straight. It is possible to manufacture a spline shaft 1 with excellent accuracy.

On the other hand, as shown in FIG. 3, the spline nut 2 includes a metal nut body 4 having a hollow hole 40 and formed into a cylindrical shape, and a hollow hole 40 in the nut body 4. Mounted on the circumference And three synthetic resin inner blades 5 and a pair of synthetic resin end caps 6 fitted to both ends of the hollow hole 40 of the nut body 4. To assemble the spline nut 2, first, three inner plates 5 are fitted into predetermined positions of the hollow holes 40 of the nut body 4, and then the end cap 6 is fitted into the hollow holes 40 from both sides of the nut body 4. However, when the end cap 6 is fitted, the nut body 4, inner blade 5 and end cap 6 are positioned among the three members, and the inner plate 5 is fixed to the nut body 4. Assembling of the spline nut 2 is now complete.

FIG. 5 is a front view of the nut body 4 observed from the axial direction. Three load base portions 41 project from the inner peripheral surface of the inner cavity 40 of the nut body 4, and these load base portions 41 are provided at positions that divide the inner peripheral surface of the nut body 4 into three equal parts. It has been. The tip surface 42 of each load base portion 41 protruding toward the center of the hollow hole 40 has a gentle arc shape, and the tip surface 42 has a set of ball rolling grooves 10a formed on the spline shaft 1. , 10b, ball rolling grooves 42a, 42b are formed. When the spline nut 2 is assembled to the spline shaft 1, the ball rolling groove 10a of the spline shaft 1 and the ball rolling groove 42a of the load base 41 and the force rolling ball 10b of the spline shaft 1 The ball rolling groove 42b of the load base 41 faces each other, and two load passages 31 are formed in which the ball 3 rolls while applying a load. As can be seen from FIG. 3, a pair of large inner diameter portions 43 for fitting the end cap 6 are formed at both ends of the hollow hole 40 in the axial direction, and the load base portion 41 is Only between these large inner diameter portions 43 is formed on the inner peripheral surface of the hollow hole 40.

[0024] In addition, on the inner peripheral surface of the hollow hole 40, a plate accommodating portion 44 for accommodating the inner blade 5 is formed between the load base portions 41 adjacent to each other. The depth d of the plate accommodating portion 44 formed so as to be sandwiched between the pair of load base portions 41 is set to be deeper than the diameter of the ball 3, and the inner plate 5 formed thicker than the ball diameter d. Can be prevented from interfering with the inner blade 5 and the spline shaft 1 even if they are fitted in the plate receiving groove 44. Each plate accommodating portion 44 is provided with a lubricating oil supply hole 45 so as to penetrate the nut body 4. Furthermore, plate reference holes 46 for positioning the end cap 6 and the inner plate 5 are formed on each end face of the load base portion 41 in the axial direction. These plate reference holes 46 are formed in the vicinity of the respective ball rolling grooves 42a and 42b of the load base 41, and the inner plate 5 and the end cap 6 are connected to the respective ball rolling grooves 42a and 42b. Consideration is given to positioning with high accuracy.

On the other hand, FIG. 6 shows the inner plate 5. The inner plate 5 includes a plate body 50 that fits into the plate housing groove 44 of the nut body 4 and positioning flanges 51 provided at both ends of the plate body 50 in the axial direction. As shown in the cross-sectional view of FIG. 6 (c), the plate body 50 is formed to have substantially the same cross-sectional shape as the plate housing portion 44 of the nut body 4, and the plate body 50 has one endless circulation path 30. A ball return hole 52 constituting the portion is formed penetrating along the longitudinal direction. The ball return hole 52 corresponds to the ball rolling grooves 42a and 42b of the load base portion 41 adjacent to the left and right of the plate housing groove 44, and two ridges are formed therethrough. As described above, the depth d of the plate accommodating portion 44 is formed to be larger than the diameter of the ball 3, so that even the plate main body 50 formed through the ball return hole 52 in this way has a nut main body 4. It can be accommodated in the plate receiving groove 44 that is strong enough not to protrude from the plate receiving groove 44.

In addition, the positioning flange 51 protrudes from the left and right sides of the plate body 50 along the circumferential direction of the nut body 4, and when the inner blade 5 is fitted into the plate receiving groove 44 of the nut body 4. In addition, the locating flange 51 is configured to overlap both end surfaces of the load base portion 41 of the nut body 4 in the axial direction. Each positioning flange 51 has a positioning hole 53 that overlaps the plate reference hole 46 of the load base 41. By fitting an end cap 6 side force pin into these holes 46, 53, The inner plate 5 is positioned in the plate receiving groove 44 with reference to the positioning hole 53 of the nut body 4.

[0028] A semicircular cutout 55 corresponding to the entrance and exit of the load passage 31 of the ball 3 is formed at the end of the positioning flange 51. Further, the cutout 55 and the ball return hole 52 are formed. A semicircular return piece 54 protrudes from the surface of the positioning flange 51 between the two. The return piece 54 moves between the load passage 31 and the ball return hole 52. A ball guide groove 56 having a semicircular cross section is formed on the peripheral surface thereof.

Furthermore, a lubricating oil supply groove 57 is formed in the plate body 50 of the inner plate 5 so as to face the inner peripheral surface of the nut body 4. The supply groove 57 extends in four directions from the position where it overlaps with the supply hole 45 formed through the nut body 4, and finally communicates with the ball return hole 52 formed in the plate body 50. Yes. Accordingly, when lubricating oil is injected into the supply hole 45 from the outside of the nut body 4, the lubricating oil reaches the ball return hole 52 via the supply groove 57 of the inner blade 5 and rolls through the ball return hole 52. Lubricating oil will be supplied to Ball 3.

In this embodiment, the inner 5 is made of a synthetic resin, but may be formed using an aluminum alloy. In the case of the inner resin made of synthetic resin 5, the ball return hole 52 is formed by a drill cage, and in the case of the inner alloy made of aluminum alloy 5, the ball return hole 52 is formed by drilling or wire cutting. .

[0031] On the other hand, when the inner plate 5 is elongated along the axial direction of the spline shaft 1, machining errors due to drill tip deflection, wire stagnation, and the like cannot be ignored. Therefore, depending on the size of the inner plate 5, it is preferable to manufacture the inner plate 5 by dividing it into a pair of halves at the position indicated by the broken line p in FIG. 6 (a). If the inner plate 5 is manufactured by combining a pair of halves thus divided, even if the inner plate 5 is elongated, it can be formed with high accuracy. Further, since the center of the supply groove 57 for the lubricating oil 57 extending in all directions and the dividing surface p are aligned, the strong supply groove 57 functions as a mark indicating the joint between the pair of halves constituting the inner blade 5. This makes it possible to prevent assembly errors of the inner plate 5.

Next, FIG. 7 shows the end cap 6 fitted to the large inner diameter portions 43 formed at both axial ends of the nut body 4. The end cap 6 is formed in a ring shape with a hollow hole 60 through which the spline shaft 1 passes through a slight gap, and the inner surface of the nut body 4 facing the hollow hole 40 is provided with the load passage. A direction changing path 61 that connects 31 and the ball return hole 52 of the inner blade 5 is formed. As shown in FIG. 8, the direction changing path 61 has a substantially U-shaped cross section. The return piece 54 protruding from the lunge 51 is configured to fit! RU

[0033] Then, when the end cap 6 is fitted to the large inner diameter portion 43 of the nut body 4, the return piece 54 is fitted to the direction change path 61, and the inner diameter slightly larger than the diameter of the ball 3 is passed. A path, that is, a U-shaped direction change path 61 is completed, and the load change path 31 of the ball 3 and the ball return hole 52 are connected to each other by the direction change path 61. That is, by attaching the inner plate 5 and the end cap 6 to the nut body 4, the infinite circulation path 30 through which the ball 3 circulates is completed.

In addition, a stud 62 that fits into a plate reference hole 46 formed in the load base portion 41 of the nut body 4 is erected on the end cap 6. The stud 62 is configured to pass through a positioning hole 53 formed in the positioning flange 51 of the inner plate 5 and fit into the plate reference hole 46. That is, by fitting the stud 62 of the end cap 6 into the plate reference hole 46 of the nut body 4, the direction change path 61 of the end cap 6, the ball return hole 52 of the inner plate 5, and the ball of the nut body 4 Positioning between the three rolling grooves 42a and 42b is performed at the same time, so that there is no continuity between the load path → direction change path → ball return hole → direction change path → load path. Is ensured, and smooth circulation of the ball 3 in the infinite circulation path 30 is achieved.

Further, as is clear from the cross-sectional view of the ball spline device shown in FIG. 2, the direction switching path 61 connects the load path 31 of the ball 3 and the ball return hole 52 with the shortest distance. In this case, the direction change path 61 is positioned in a specific plane including the load path 31 and the ball return hole 52. For example, the ball 3 introduced into the direction change path 61 from the load path 31 changes the rolling direction. The ball is returned to the ball return passage 52 without any change. For this reason, the resistance acting on the circulation of the ball 3 in the infinite circulation path 30 can be kept small, and in this respect, the circulation of the ball 3 can be facilitated! /.

[0036] The balls are arranged inside the endless circulation path 30 configured as described above. The force is unlimited between the balls 3 rolling back and forth inside the endless circulation path 30. 32 is installed. Each spacer is formed in a substantially disk shape whose diameter is smaller than the diameter of the ball 3, and concave and spherical surfaces that substantially match the spherical surface of the ball 3 are formed on both front and back surfaces. Each ball 3 rolls in the ball rolling groove while making sliding contact with the concave spherical surface of this spacer. Since the spacers are interposed between the adjacent balls 3 in this manner, the balls are prevented from coming into contact with each other and a lubricating oil film is easily formed on the surface of the balls. The circulation of 3 is smoothed, and the fluctuation of the resistance acting on the movement of the spline nut with respect to the spline shaft can be minimized.

[0037] Further, the infinite circulation path of the ball is other than a load path where the ball rolls while applying a load, that is, the ball return hole and the direction change path are formed by an inner blade made of synthetic resin and an end cap. As described above, since the synthetic resin spacer is interposed between the balls, metal contact does not occur when the ball rolls under no load. In addition to reducing noise generated, it is possible to reduce dust generation due to metal wear. As a result, the ball spline device of the present invention is suitable for use in measuring instruments and various automatic assembly devices in a sealed environment such as a clean room, and for medical equipment.

[0038] According to the ball spline device of the present invention configured as described above, the ball return hole 52 is located outside the load passage 31 of the ball 3 in the radial direction of the spline shaft 1, The formation position of the ball return hole 52 is not at a position where it interferes with the outer diameter of the spline shaft 1. As a result, the spline shaft 1 can be formed so that its cross section is close to a circular shape, so that the cross-sectional area of the shaft can be made larger than before and the rigidity of the spline shaft 1 can be increased. Become.

[0039] Further, as described above, since the cross-sectional shape of the spline shaft 1 can be made closer to a circular shape, the ball rolling grooves 10a, 1 Ob and It is sufficient to grind only the periphery of the spline shaft, which uses an inexpensive round shaft produced by centerless grinding and has excellent straightness and ball rolling grooves 10a and 10b with high precision. Obtainable.

[0040] Furthermore, since the ball return hole 52 is located radially outside the load passage 31 of the ball 3, the positional relationship between the ball return hole 52 and the load passage is such that the ball 3 with respect to the spline shaft 1 It becomes closer to the contact direction, and it becomes possible to smoothly circulate the ball 3 between the load passage 31 and the ball return hole 52.

Claims

The scope of the claims

[1] A spline shaft in which a plurality of ball rolling grooves are formed along the axial direction and a plurality of balls that circulate infinitely. The spline shaft is assembled to the spline shaft, and can reciprocate along the spline shaft. A spline nut, and

The spline nut includes a metal cylindrical nut body, a plurality of inner blades that are assembled to an inner peripheral surface of the nut body, and constitute a part of the ball infinite circulation path, and both ends of the nut body in the axial direction. And a ball spline device configured with an end cap that forms an infinite circulation path of the ball together with the inner blade.

On the inner peripheral surface of the nut body, a load base portion is formed so as to divide the inner peripheral surface evenly in the circumferential direction, and the inner blade is accommodated between the load base portions. A plate housing portion is formed, and further, a ball rolling groove constituting a ball load passage is formed in the load base portion so as to face the ball rolling groove of the spline shaft, and the inner plate has a ball rolling groove. A ball return hole is formed in parallel with the running groove, and the end cap is formed with a u-shaped direction change path that connects the load passage and the ball return hole of the inner blade to complete the infinite circulation path of the ball. A ball spline device characterized by

[2] Plate reference holes are formed on both end surfaces of the load base portion of the nut body, while positioning flanges are formed on both end portions of the inner base in the axial direction so as to overlap the front and rear end surfaces of the load base portion. 2. The ball spline device according to claim 1, wherein the end cap is formed with a stud that penetrates a positioning flange of the inner plate and fits into a plate reference hole of the load base portion.

3. The ball spline device according to claim 1, wherein a return piece that forms an inner peripheral side guide surface of the direction changing path protrudes from the positioning flange of the inner blade.

4. The ball spline apparatus according to claim 1, wherein the direction changing path of the end cap is located in a specific plane including the ball return hole and the load path.

[5] The inner braid and the end cap are made of synthetic resin. The ball spline device described.

6. The ball spline device according to claim 1, wherein a spacer made of a synthetic resin is interposed between balls that roll back and forth in the endless circulation path.