JPS6343608B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention supports axial movement and
This invention relates to a ball spline bearing that uses rotational motion for torque transmission alone or in combination with axial motion.

(Prior art) This type of conventional ball spline bearing is constructed by fitting an outer cylinder to a spline shaft through a number of steel balls so that it can move in the axial direction, and the outer circumference of the spline shaft and the inner circumference of the outer cylinder are formed with gossic arch-shaped load ball rolling grooves that face each other and extend in the longitudinal direction, and the opposing pairs of load ball rolling grooves on the spline shaft side and the outer cylindrical side are mutually in the same phase in the circumferential direction. That is, they were arranged at equal intervals in the circumferential direction, and all the steel balls were in four-point contact with the load ball rolling grooves in the shape of a gossock arch.

(Problem to be Solved by the Invention) However, in the conventional ball spline bearing described above, all the steel balls are in four-point contact with the load ball rolling groove, so the steel balls are subject to differential sliding during rolling. As a result, the relative movement between the spline shaft and the outer cylinder cannot be carried out easily and smoothly.
When a preload is applied to the steel ball, this tendency becomes stronger and the outer cylinder does not move smoothly with respect to the spline shaft, so there is a problem in that it is virtually impossible to apply a preload. In addition, due to manufacturing errors or the load applied to the steel ball when transmitting large torque, bumps may occur between the steel ball and the ball rolling groove, and loose movement may occur between the outer cylinder and the spline shaft, resulting in noise. Another problem was that the rigidity of the ball spline bearing as a whole was impaired, resulting in a shortened lifespan.

Therefore, the present invention has been made by focusing on the above-mentioned conventional problems, and its purpose is to allow the relative movement between the outer cylinder and the spline shaft to be carried out easily and smoothly, and even when preload is applied. The resistance to the rolling of the steel ball does not increase so much, and even if there is a manufacturing error or when large torque is transmitted, it prevents the occurrence of bumps and noise between the outer cylinder and the spline shaft. It is an object of the present invention to provide a ball spline bearing that can effectively prevent the above problems and increase the rigidity and life of the bearing.

(Means for solving the problems) In order to achieve the above object, the present invention includes the following:
At least one row of steel balls interposed between the spline shaft and the outer cylinder is brought into four-point contact with the load ball rolling groove that accommodates the steel balls, and the steel balls of the other rows are brought into contact with the load ball rolling groove that accommodates the steel balls. It was configured to make two points contact with the ball rolling groove.

(Example) Hereinafter, an example of a ball spline bearing according to the present invention will be described based on the drawings.

1 to 9 show an embodiment in which the present invention is applied to a ball spline bearing for infinite motion. In FIGS. 1 and 2, 1 is a spline shaft; A plurality of (three in the illustrated example) spline grooves, that is, load ball rolling grooves 1a, 1b, and 1c, extending in the axial direction parallel to each other at intervals in the circumferential direction are formed on the outer peripheral surface of the ball 1. , these loaded ball rolling grooves 1a, 1b, 1
As is clear from FIG. 4, c has a gothic arch-like cross-sectional shape consisting of two arcuate surfaces with different centers of curvature.

A cylindrical outer cylinder 2 is fitted onto the outer periphery of the spline shaft 1 so as to be movable in the axial direction, and a spline is formed on the inner peripheral surface of the outer cylinder 2, as clearly shown in FIGS. 4 to 6. Load ball rolling grooves 1a, 1b, 1 of shaft 1
A plurality of (three in the illustrated example) loaded ball rolling grooves 2a, 2b, and 2c are formed at intervals in the circumferential direction and extend in the axial direction, facing the ball rolling grooves. The cross-sectional shapes of the grooves 2a, 2b, and 2c also have a gothic arch shape.

Three rows of steel balls 3a, 3b, 3c are accommodated between the load ball rolling grooves 1a to 1c, 2a to 2c facing each other on the spline shaft 1 and the outer cylinder 2. As shown in FIG. 4, one row 3a is in four-point contact with the loaded ball rolling grooves 1a, 2a that accommodate the steel balls 3a, and the other two rows of steel balls 3b, 3c are in contact with the loaded ball rolling grooves 1a, 2a that accommodate the steel balls 3a. Two points of contact are made with load ball rolling grooves 1b, 1c, 2b, and 2c that accommodate steel balls. For this reason, spline shaft 1
A pair of opposing load ball rolling grooves 1a and 2a of the outer cylinder 2 are arranged in the same phase in the circumferential direction and contact the steel balls 3a at four points, so that the spline shaft 1 and the outer cylinder 2
While the other two pairs of load ball rolling grooves 1b, 1
c, 2b, 2c are opposite to each other, while 1b, 1c
are arranged so as to be out of phase with respect to the other steel balls 3b, 2c in the circumferential direction, whereby the loaded ball rolling grooves 1b, 1c, 2b, 2c
It is designed to make two-point contact with c. To explain in more detail, the load ball rolling grooves 2a, 2b,
2c, the distance in the circumferential direction between the load ball rolling groove 2a for positioning and the other load ball rolling grooves 2b, 2c, that is, the angular position, is the same as that of the spline shaft 1.
This is different from the circumferential interval, that is, the angular position, of the other load ball rolling grooves 1b and 1c with respect to the side positioning load ball rolling groove 1a. In this case, the line of action C of the load applied to the steel balls 3b of the second row and the line of action D of the load applied to the steel balls 3c of the third row are the center 3o of the steel balls 3a of the first row. It is preferable to make it symmetrical with respect to a plane P passing through the center axis 1o of the spline shaft 1. In the illustrated example, other load ball rolling grooves 1b, 1c, 2 are used for positioning load ball rolling grooves 1a, 2a.
b and 2c are placed approximately 120 degrees apart,
Load ball rolling grooves 1b and 1c on the spline shaft 1 side
The angle α with respect to the positioning groove 1a is the positioning groove 2a of the load ball rolling grooves 2b and 2c on the outer cylinder 2 side.
Although the angle β is slightly larger than the angle β, this relationship may be reversed.

A steel ball 3a is provided between the spline shaft 1 and the outer cylinder 2.
A cylindrical retainer 4 is provided to guide the rolling of ~3c and to prevent the retainer 4 from falling off.
As shown in FIG. 7 to FIG. 9, has three protrusions 4a extending in the longitudinal direction and protruding in the radial direction from the outer peripheral surface at approximately equal intervals in the circumferential direction,
The outer peripheral shape is approximately equal to the inner peripheral shape of the outer cylinder 2, and the inner peripheral shape is approximately equal to the outer peripheral shape of the spline shaft 1. The retainer 4 has three slits 5 for guiding and holding load balls extending in the longitudinal direction, which are bored at approximately equal intervals in the circumferential direction between the protrusions 4a.
a to 5c, and three unloaded ball rolling grooves 6a to 6a, which are formed on the protrusion 4a in proximity to the slits 5a to 5c, respectively, and extend in the longitudinal direction and are open to the outside.
6c are formed alternately in the circumferential direction, and each of the slits 5a to 5c and the corresponding no-load ball rolling grooves 6a to 6c are formed in an arc shape at both ends, as shown in FIG. Extending communication groove 7a
is contacted by. No-load ball rolling groove 6
a to 6c form unloaded ball rolling paths in cooperation with the inner peripheral surface of the outer cylinder 2; It is connected to the load ball rolling path formed by the grooves 1a to 1c, 2a to 2a and the slits 5a to 5c of the retainer 4 via the communication groove 7a, and provides an endless track for circulating the steel balls 3a to 3c. is forming. In addition, the slits 5a to 5c of the cage 4
At both ends, tongue pieces 4b for scooping up the steel balls 3a-3c from the loaded ball rolling grooves 1a-1c, 2a-2c are integrally formed.

In addition, the reference numeral 8 is an annular washer that comes into contact with both end surfaces of the retainer 4, and the reference numeral 9 is an annular washer that is engaged with the inner peripheral surface of the outer cylinder 2.
This is a circlip to prevent the washer 8 from falling off.

By the way, in order to apply preload to the steel balls 3a to 3c to eliminate backlash between the steel balls and the load ball rolling grooves 1a to 1c, 2a to 2c, or to form a negative gap between them, it is necessary to apply a preload to the steel balls 3a to 3c. Ball 3a
The diameter of ~3c is set as
It is only necessary to make the width larger than the minimum gap width between c.

In the above configuration, the spline shaft 1 and the outer cylinder 2
When transmitting torque between the spline shaft 1 and the spline shaft 1 rotates clockwise in FIG.
Torque is transmitted from the spline shaft 1 to the outer cylinder 2 along the line of force A of the load through the steel balls 3a of the third row, and at the same time, the line of force of the load is transmitted through the steel balls 3c of the third row. Torque is transmitted along line D. On the other hand, when the spline shaft 1 rotates counterclockwise in FIG. At the same time as the second
Torque is transmitted along the line of action C of the load via the steel balls 3b in the row, and when the outer cylinder 2 side is further rotated, torque is transmitted from the outer cylinder 2 to the spline shaft 1, contrary to the above. Ru.

Furthermore, when the outer cylinder 2 moves in the axial direction with respect to the spline shaft 1 during torque transmission, the steel balls 3a to 3c interposed between the load ball rolling grooves 1a to 1c and 2a to 2c facing each other move around the shaft. rolling in the direction,
When the loaded ball reaches the end of the rolling groove, it is scooped up by the tongue piece 4b of the retainer 4 and the retainer 4
is guided to the no-load ball rolling grooves 6a to 6c through one of the communication grooves 7a, and from there to the communication groove 7 on the opposite side.
a to load ball rolling grooves 1a to 1c, 2 again.
Return to a to 2c. At this time, the first row of steel balls 3a,
When the steel balls 3a... roll in the loaded ball rolling grooves 1a, 2a, the steel balls 3a, 3a... roll in the loaded ball rolling grooves 1.
a, 2a, there is strong contact in the vicinity of the line of action of the load on the side that transmits torque (A or B), but in the vicinity of the line of action of the load on the side that does not transmit torque (B or A). Since the contact force at is very weak, the steel balls 3a, 3a, . Further, the steel balls 3b, 3c in the second and third rows are connected to the load ball rolling grooves 1b, 1c;
When passing through the ball rolling grooves 1b, 2c, the steel balls 3b, 3c only contact the wall surfaces of the loaded ball rolling grooves 1b, 1c; 2b, 2c at two points. Therefore, steel balls 3a-3
c rolls easily within the load ball rolling grooves 1a to 1c and 2a to 2c without being subjected to much frictional resistance. Furthermore, even when preload is applied to the steel balls 3a to 3c, the steel balls 3b and 3 in the second and third rows
c maintains two-point contact with the wall surfaces of the loaded ball rolling grooves 1b, 1c; 2b, 2c, so the steel balls 3b, 3
The frictional resistance against the steel balls 3b and 3c does not increase so much, and smooth rolling of the steel balls 3b and 3c can be ensured. As is clear from the above, the outer cylinder 2 can move easily and smoothly relative to the spline shaft 1 in the axial direction. Also, steel ball 3a
By applying preload to ~3c, the steel balls 3a~3
If the clearance between c and the load ball rolling grooves 1a to 1c, 2a to 2c is set to a negative clearance, even if there is a manufacturing error or an excessive load is applied to the entire ball spline bearing, the problem can be avoided. Steel balls 3a-3c
There is no occurrence of bumps between the ball rolling grooves 1a to 1c and 2a to 2c, and
Therefore, it is possible to effectively prevent free movement between the outer cylinder 2 and the spline shaft 1 and generation of noise caused by this.

In the above description of the embodiment, the spline shaft 1 and the outer cylinder 2 have load ball rolling grooves 1a to 1c, 2a to 2.
We have described the case where 2c is formed in three strips at a time,
The number of load ball rolling grooves may be four or more, and in this case, at least a pair of opposing load ball rolling grooves are brought into contact with the steel ball at four points to position the outer cylinder 2 and the spline shaft 1. groove and the other loaded ball rolling groove are configured to contact the steel ball at two points. At this time, it is preferable to apply the preload so that the reaction force due to the preload applied to the steel balls in contact at two points is balanced as a whole.

In addition, load ball rolling grooves 1a and 2 for positioning are also provided.
Load ball rolling grooves 1b, 1c other than a; 2b, 2
The cross-sectional shape of c may be a circular arc.

(Effects of the Invention) The present invention has the structure and operation described above, and has at least one row of steel balls interposed between the spline shaft and the outer cylinder at four points relative to the load ball rolling groove that accommodates the steel balls. By simply making contact, steel balls in other rows are brought into two-point contact with the load ball rolling groove that accommodates them, so all conventional steel balls are placed in four-point contact with the load ball rolling groove. Compared to point contact, the frictional resistance against rolling of the steel ball is extremely small, allowing for easy and smooth relative movement between the outer cylinder and the spline shaft. In addition, even if preload is applied to the steel balls, all steel balls maintain approximately two-point contact with the loaded ball rolling groove during torque transmission, so even if preload is applied, the resistance to the loaded steel balls is hardly increases, and therefore, easy axial movement between the outer cylinder and the spline bearing can be guaranteed. Furthermore, by applying preload, the gap between the steel ball and the load ball rolling groove is made negative, which prevents the occurrence of backlash and keeps the ball quiet even when there are manufacturing errors or when transmitting large torque. In addition to ensuring proper operation at all times, the rigidity of the ball spline bearing as a whole is increased, resulting in a longer service life.

[Brief explanation of drawings]

The drawings show an embodiment of the ball spline bearing according to the present invention, in which FIG. 1 is a partially cutaway overall side view, FIG. 2 is a partially cutaway front view, and FIG.
Fig. 3 is a front view of the spline shaft, Fig. 4 is a sectional view taken along the - line in Fig. 1 with the retainer removed, Fig. 5 is a longitudinal sectional side view of the outer cylinder, and Fig. 6 is a - line sectional view in Fig. 5. 7 is a partially cutaway side view of the cage, FIG. 8 is a sectional view taken along the line -- in FIG. 7, and FIG. 9 is a plan view of the cage. Explanation of symbols, 1... Spline shaft, 1a to 1c
... Load ball rolling groove, 2 ... Outer cylinder, 2a to 2c
...Load ball rolling groove, 3a-3b...Steel ball.

Claims (1)

[Scope of Claims] 1. A spline shaft and an outer cylinder fitted therewith are each formed with a plurality of load ball rolling grooves extending in the longitudinal direction and facing each other, and the plurality of load ball rolling grooves facing each other are formed. In a ball spline bearing in which multiple rows of steel balls are accommodated between ball rolling grooves, at least one row of steel balls is brought into four-point contact with the load ball rolling groove that accommodates them, and the steel balls in other rows are , a ball spline bearing configured to make two-point contact with a load ball rolling groove that accommodates the ball spline bearing. 2. At least one pair of load ball rolling grooves formed opposite to the ball spline shaft and the outer cylinder and in contact with the steel ball at four points have the same phase in the circumferential direction and also in contact with the steel ball at two points. The ball spline bearing according to claim 1, wherein the other opposing pairs of loaded ball rolling grooves have different phases in the circumferential direction. 3. The ball spline bearing according to claim 1 or 2, wherein the ball rolling grooves that contact the steel balls at four points are formed to have a gossic arch shape in cross section.