JP7319023B2 - ball spline - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ball spline used in linear guides or torque transmissions of various conveying devices, industrial robots, and the like.

As this type of ball spline, the one disclosed in Patent Document 1 is known. The ball spline disclosed in this document includes a spline shaft in which ball rolling grooves are formed along the longitudinal direction, a large number of balls rolling in the rolling grooves, and a through hole through which the spline shaft is inserted. and a spline nut assembled to the spline shaft via the ball.

The spline nut includes a spline nut having a load rolling groove facing the rolling groove of the spline shaft provided on the inner peripheral surface of the through hole, and the spline nut is fitted to the inner peripheral surface of the through hole of the spline nut. and a substantially cylindrical retainer that forms an endless circulation path for the balls. The retainer is present in a gap between the spline shaft and the spline nut, and the outer peripheral surface of the retainer facing the inner peripheral surface of the spline nut is provided with a circulation groove serving as an endless circulation path for the balls. It is The circulation groove includes a load path in which the balls roll while applying a load between the spline shaft and the spline nut, and a return path provided parallel to the load path in which the balls roll in an unloaded state. A passageway and a pair of U-shaped turnaround passages connecting the ends of the load passageway and the return passageway. In the load passage, an opening having a width narrower than the ball diameter is provided at the bottom of the circulation groove, and the ball contacts the rolling groove of the spline shaft through the opening. Further, the return path and the direction change path are configured as no-load paths in which the balls roll while being released from the load, and the width of these paths is formed larger than the diameter of the balls.

Therefore, when the spline nut moves along the spline shaft, the balls in the load passage move while rotating in the load passage. Instead, it advances through the litahane passage and the return passage while being pushed by subsequent balls continuously ejected from the load passage. In other words, the balls are arranged in the circulation direction without gaps in the no-load passage composed of the return passage and a pair of direction change passages positioned at both ends thereof.

Utility Model Registration No. 3108723

Since the discharge of balls from the load path to the unloaded path and the entry of balls from the unloaded path into the loaded path are not completely synchronized, the length of the ball train in the unloaded path is very small. Changes are repeated periodically. Therefore, in response to changes in the length of the ball row, the balls arranged in the no-load passage strongly rub against adjacent balls in the front and rear, causing a ball clogging phenomenon in the passage. There was a concern that the smooth circulation of the ball would be hindered.

The present invention has been made in view of such problems, and its object is to suppress the occurrence of the ball clogging phenomenon in the no-load passage and ensure the smooth circulation of the balls in the circulation groove. To provide a ball spline capable of achieving smooth movement of a spline nut with respect to a spline shaft.

That is, the present invention provides a spline shaft in which a plurality of ball rolling grooves are formed along the longitudinal direction, and a spline that is assembled to the spline shaft via a large number of balls and is movable along the spline shaft. A ball spline with a nut and The spline nut has a through hole through which the spline shaft is inserted, and a nut body in which a plurality of load rolling grooves are formed on the inner peripheral surface of the through hole so as to face the rolling grooves of the spline shaft. and a retainer mounted on the inner peripheral surface of the through hole of the nut body and provided with a plurality of circulation grooves on the outer peripheral surface thereof, the circulating grooves forming an endless circulation path for the balls. The circulation groove includes a load passage in which the balls roll while applying a load, a return passage provided in parallel with the load passage and a holding wall, and both ends of the load passage and the return passage. A load opening is provided at the bottom of the load passage so that balls rolling in the load passage come into contact with the rolling grooves of the spline shaft. is provided with a slit-shaped opening that enables elastic deformation of the holding wall.

According to the ball spline of the present invention, since the slit-shaped opening is formed in the bottom of the return passage that constitutes the circulation groove of the retainer, the holding wall that separates the return passage and the load passage elastically deforms against external force. Therefore, it is possible to suppress the occurrence of ball clogging in the circulation groove, ensure smooth circulation of the balls, and achieve smooth movement of the spline nut with respect to the spline shaft.

1 is a perspective view showing an example of an embodiment of a ball spline to which the present invention is applied; FIG. FIG. 2 is a sectional view taken along the line II-II of FIG. 1; FIG. 4 is a perspective view showing a retainer of the ball spline according to the embodiment; FIG. 4 is a side view showing the retainer of the ball spline according to the embodiment; FIG. 5 is a cross-sectional view taken along line VV of FIG. 4; FIG. 4 is an exploded perspective view of the spline nut of the ball spline according to the embodiment; FIG. 4 is an exploded perspective view of a spline nut showing another example of a retainer;

FIG. 1 is a perspective view showing an example of an embodiment of a ball spline to which the present invention can be applied. This ball spline has a spline shaft 1 in which a plurality of ball rolling grooves 10 are formed along the longitudinal direction of the outer peripheral surface, and a through hole 20 through which the spline shaft is inserted. and a spline nut 2 assembled to 1. The spline nut 2 incorporates an endless circulation path in which the balls are arranged, and the balls roll in the rolling grooves 10 of the spline shaft 1 while circulating in the endless circulation path, thereby The nut 2 can freely move along the longitudinal direction of the spline shaft 1 . In addition, since the balls roll only in the longitudinal direction of the spline shaft 1 on the rolling grooves, the ball spline distributes the torque acting in the circumferential direction of the spline shaft 1 to the spline shaft 1 and the spline nut. It is possible to transmit between 2.

FIG. 2 is a cross-sectional view taken along line II--II of FIG. In this ball spline, six rolling grooves 10 are formed on the outer peripheral surface of the spline shaft 1 . Two sets of rolling grooves 10 constitute one set, and three sets of rolling grooves 10 are evenly arranged at an angle of 120 degrees with respect to the center of the spline shaft 1 . The number of threads of the rolling grooves 10 is not limited to this, and the design can be appropriately changed according to the load carrying capacity required for the spline nut 2 .

The spline nut 2 includes a substantially cylindrical nut body 2A having a load rolling groove 21 formed on the inner peripheral surface thereof facing the rolling groove 10 of the spline shaft 1, and an inner peripheral surface of the nut body 2A. A ball retainer 3 that is attached to the ball retainer 3 to construct an endless circulation path for the balls, and a large number of balls 4 arranged in the ball retainer 3 .

Loaded portions 22 and unloaded portions 23 are alternately formed on the inner peripheral surface of the nut body 2A along the circumferential direction. Two load rolling grooves 21 are formed in each of the load portions 22 , and the balls 4 are loaded between the load rolling grooves 21 and the rolling grooves 10 of the spline shaft 1 while applying a load. Roll. Therefore, the distance between the load portion 22 and the outer peripheral surface of the spline shaft 1 is set slightly narrower than the diameter of the ball 4 . Further, the no-load portion 23 is provided with two return passages in which the balls 4 roll in the no-load state. Therefore, the distance between the no-load portion 23 and the outer peripheral surface of the spline shaft 1 is set larger than the diameter of the balls 4 .

A plurality of lubricant supply holes 24 are provided in the nut body 2A. These supply holes 24 penetrate the nut body 2A in the radial direction and open to the non-loaded portion 23, so that lubricant can be supplied to the balls 4 rolling in the return passage. there is

Next, the retainer will be described. 3 is a perspective view showing the retainer 3, FIG. 4 is a side view showing the retainer, and FIG. 5 is a sectional view taken along line VV of FIG. The cage 3 has a through hole 30 through which the spline shaft 1 passes, and is formed in a substantially cylindrical shape. In the ball spline of this embodiment, six circuits of circulation grooves 31 are provided in the retainer 3 , and each circulation groove 31 corresponds to each of the rolling grooves 10 of the spline shaft 1 . In FIG. 3, in order to facilitate grasping of the circulation grooves 31, a state in which the balls 4 are arranged only in one circulation groove 31 is depicted.

Each circulation groove 31 includes a load passage 31a in which the balls 4 roll while applying a load between the spline shaft 1 and the nut body 2A, a return passage 31b provided parallel to the load passage 31a, It is composed of a pair of direction changing paths 31c connecting both ends of the load path 31a and the return path 31b. The arrangement of the six circulation grooves 31 in the retainer 3 is such that the load passages 31a are adjacent to each other and the return passages 31b are adjacent to each other. Two adjacent load passages 31a correspond to the load portion 22 of the nut body 2A, and two adjacent return passages 31b correspond to the non-load portion 23 of the nut body 2A.

As shown in FIG. 4 , a load opening 32 is provided at the bottom of the load passage 31 a of the circulation groove 31 , and the balls 4 rolling in the load passage 31 a pass through the load opening 32 to the spline shaft 1 . contacts the rolling groove 10 of As a result, the ball rolling in the load passage can apply a load between the nut body 2A and the spline shaft. The opening width of the load opening 32 is set smaller than the diameter of the balls 4, so that even if the spline shaft 1 is removed from the spline nut 2, the balls 4 are held in the circulation grooves 31. It's like

The load passage 31 a and the return passage 31 b are separated by a retaining wall 33 , and the balls 4 arranged in the circulation groove 31 circulate around the retaining wall 33 . As shown in FIGS. 4 and 5, a partition wall 34 is provided between a pair of adjacent return passages 31b to separate a pair of adjacent circulation grooves 31. As shown in FIGS.

A slit-shaped opening 35 is formed at the bottom of each return passage 31b to facilitate smooth rolling of the ball 4 in the return passage 31b. The opening width of the slit-shaped opening 35 is set smaller than the opening width of the load opening 32, so that the ball 4 in the return passage 31b rolls in the return passage 31b without contacting the spline shaft 1. move. As shown in FIG. 5, the return passage 31b is adjacent to the load passage 31a with the holding wall 33 interposed therebetween, and is adjacent to the other return passage 31b with the partition wall 34 interposed therebetween. The load opening 32 is formed at the bottom of the return passage 31a, and a slit-shaped opening 35 is formed at the bottom of the return passage 31b. Therefore, the holding wall 33 and the partitioning wall 34 are likely to be elastically deformed by an external force, and when the balls 4 are arranged, the retainer 3 is easily deformed in the radial direction.

FIG. 6 is an exploded perspective view showing assembly of the spline nut 2. As shown in FIG. As shown in the figure, the retainer 3 comprises a retainer main body 3A and a pair of ring-shaped sub-caps 3B attached to both longitudinal ends of the retainer main body 3A. The sub-caps 3B are fitted so as to cover the outer peripheral surfaces of the longitudinal ends of the retainer main body 3A. A substantially U-shaped guide groove 36 corresponding to the circulation groove 31 of the retainer main body 3A is formed in the sub-cap 3B. An inner peripheral wall of 36 serves as a guide wall on the outer peripheral side of the turn path 31c. As a result, the depth of the direction change path 31c is set to be slightly deeper than the diameter of the balls 4 over the entire area of the direction change path 31c. It is possible to improve circulation.

As shown in FIG. 6, since the load portion 22 formed with the load rolling groove 21 protrudes from the inner peripheral surface of the nut body 2A, the sub-caps 3B are attached to both ends of the retainer body 3A. The retainer 3 cannot be assembled to the nut body 2A in the mounted state. Therefore, when assembling the spline nut 2, first, the retainer body 3A is inserted into the nut body 2A. At this time, positioning of the retainer main body 3A with respect to the circumferential direction of the nut main body 2A is performed by the load portion 22. As shown in FIG.

After that, the sub-caps 3B are inserted through the through-holes at both ends of the nut body 2A, respectively, and the sub-caps 3B are fitted to both ends of the retainer body 3A. This completes the positioning of the retainer 3 in the longitudinal direction of the nut body 2A. Finally, the seal ring 5 and the C-shaped retaining ring 6 are attached to the mouth of the through hole of the nut body 2A, and the assembly of the spline nut 2 is completed.

When the spline nut 2 moves along the spline shaft 1, the balls 4 in the load passage 31a are in contact with the rolling grooves 10 of the spline shaft 1 and the load rolling grooves 21 of the nut body 2A. , move in the load passage 3a while rotating. However, when the ball 4 exits the load passage 3a and enters the direction change passage 3c and becomes unloaded in the direction change passage 3c, it does not rotate by itself and continues from the load passage 3a. While being pushed by the subsequent ball 4 that is discharged, it advances through the direction change path 3c and the return path 3b. That is, the balls 4 are pushed by the following balls, and are arranged without gaps as they travel through the direction change path 3c, the return path 3b, and the direction change path 3c beyond.

On the other hand, the ejection of the balls 4 from the load passage 3a to the direction change passage 3c and the entry of the balls 4 from the direction change passage 3c to the load passage 3a are not completely synchronized. The lengths of the rows of balls arranged in the direction change path 3c and the return path 3b change periodically according to the movement of the balls 4 into and out of the load path 3a. Therefore, when the balls 4 are arranged in the circulation groove 31 of the retainer 3 without gaps, the balls 4 arranged one behind the other in the return passage 3b rub strongly against each other periodically, causing the return passage to move. There is a concern of disturbing the arrangement in a staggered manner within 3b.

In the ball spline of this embodiment, when focusing on the specific return passage 31b provided in the retainer 3, since the slit-shaped opening 35 is formed in the bottom of the return passage 31b, as described above, The holding wall 33 and the partitioning wall 34 located on both sides of the return passage 31b are characterized by being easily elastically deformed by external force. Therefore, even if the balls 4 are arranged in a staggered manner in the return passage 31b, the holding walls 33 and the partition walls 34 are pressed by the balls 4 and deformed in the radial direction of the retainer 3. , it is possible to suppress an increase in the frictional force acting between the balls 4 .

That is, in the ball spline of the present embodiment, even if the balls 4 strongly rub against each other periodically in the circulation groove 31 of the retainer 3, it is possible to prevent clogging of the inside of the circulation groove 31. It is possible to smoothen the circulation of the balls 4 in the endless circulation path, and thus smoothen the movement of the spline nut 2 with respect to the spline shaft 1 .

Further, in the ball spline of this embodiment, the retainer 3 is divided into the retainer body 3A and the pair of sub-caps 3B, and the sub-caps 3B fill the gap between the nut body 2A and the retainer body 3A. Since the guide wall on the outer peripheral side of the direction change path 31c is formed by burying the balls 4, the alignment of the balls 4 in the direction change path 31c is improved. It is being facilitated. In particular, when the spline shaft 1 is arranged along the vertical direction, clogging of balls in the direction change path 31c is eliminated, and the effect is remarkable.

The embodiment of the retainer 3 in the ball spline of the present invention is not limited to the examples shown in FIGS. 1 to 6. For example, as shown in FIG. It may be divided into 3C. The return piece 3C is inserted into the gap between the nut body 2A and the retainer body 3A from openings at both ends of the nut body 2A. A part of the guide wall on the outer peripheral side of the direction change path 31c is formed. The return pieces 3C assembled to the retainer main body 3A are positioned at both longitudinal ends of the load portion 22 of the nut main body 2A and fill the gap between the retainer main body 3A and the inner peripheral surface of the nut main body 2A. , the trajectory of the balls 4 in the direction changing path 31c is arranged, and smooth rolling of the balls 4 in the endless circulation path is achieved in the same manner as the sub-cap 3B.

Reference Signs List 1 spline shaft 2 spline nut 2A nut body 3 retainer 3A retainer body 3B sub-cap 4 balls 31 circulation groove 31a load passage 31b return passage 31c... turning path, 32... load opening, 33... retaining wall, 34... partition wall, 35... slit opening

Claims (3)

a spline shaft in which a plurality of ball rolling grooves are formed along the longitudinal direction;
a spline nut assembled to the spline shaft via a large number of balls and movable along the spline shaft;
The spline nut is
a nut body having a through hole through which the spline shaft is inserted, and a plurality of load rolling grooves formed on the inner peripheral surface of the through hole so as to face the rolling grooves of the spline shaft;
a retainer that is mounted on the inner peripheral surface of the through hole of the nut body and has a plurality of circulation grooves on the outer peripheral surface that serve as an endless circulation path for the balls;
The circulation grooves include a load passage through which the balls roll while applying a load, a return passage separated from the load passage by a holding wall, and a pair of connecting ends of the load passage and the return passage. and a turning road of
The bottom of the load passage is provided with a load opening in which the balls rolling in the load passage come into contact with the rolling grooves of the spline shaft. A slit-shaped opening having a small opening width is provided, the load passage and the return passage are opened to the inner peripheral surface and the outer peripheral surface of the cage, respectively, and the holding wall separating the load passage and the return passage is the holding wall. A ball spline characterized by being elastically deformable in the radial direction of the vessel. A plurality of circulation grooves are arranged with respect to the retainer such that the load passages and the return passages of the circulation grooves adjacent to each other are adjacent to each other, and a dividing wall is provided between a pair of return passages adjacent to each other. 2. The ball spline according to claim 1, wherein said slit openings are located on both sides of said ball spline. The retainer includes a retainer body in which the circulation grooves are formed, and a pair of sub-caps attached to both ends of the retainer body in the longitudinal direction to fill a gap between the nut body and the retainer body,
2. The ball spline according to claim 1, wherein the sub-cap is formed with a guide groove serving as a guide wall on the outer peripheral side of the direction changing path.

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