JPH0154571B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a small ball spline bearing in which a hollow cylindrical outer cylinder is fitted into a sliding groove of a spline shaft via rolling elements. In particular, the present invention relates to a small ball spline bearing that has self-aligning properties that can accommodate minute changes in shaft diameter.

[Prior Art] Conventional small ball spline bearings use a ball spline shaft in which three or more rows of sliding grooves are formed in the axial direction, and the outer cylinder also has a plurality of rolling elements in one row. They were arranged side by side and had a structure that could receive bearing loads.

[Problem that the invention seeks to solve]

Bearings with a conventional structure have a large number of load balls in one row, so they have a large load capacity as a bearing and can carry loads in all directions, but in reality, small bearings are used for loads. Most of the conditions do not require a particularly large load capacity, and if the manufacturing accuracy of the shaft is low and there is a slight change in the shaft diameter, there is a disadvantage that the linear motion accuracy will be significantly reduced. There is a problem in that the feature of large load capacity of bearings is not always fully utilized, resulting in unnecessary costs.

Furthermore, in the case of rolling bearings, in the case of a type in which the rolling elements circulate infinitely, the thickness of the outer cylinder becomes thick and the outer diameter of the bearing becomes large, making it impossible to manufacture small bearings, and in the case of a limited circulation type, the stroke length increases. It had the disadvantage of being limited.

[Purpose of the invention]

The present invention solves the shortcomings of conventional small ball spline bearings, and provides a self-aligning small ball spline bearing that is smaller, cheaper, has alignment properties that can accommodate minute changes in shaft diameter, and has improved linear motion accuracy. is intended to provide.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a spline shaft having sliding grooves for balls formed at two positions diametrically symmetrical with respect to the axis of the spline shaft. , a ball is disposed in the center of a portion corresponding to one of the sliding grooves on the inner surface of the outer cylinder, which is a hollow cylinder fitted onto the outside of the spline shaft. One ball is disposed at each of two locations near both ends of the outer cylinder in a portion that is fitted into the moving groove and corresponds to the other sliding groove, and is fitted into the other sliding groove. The balls are arranged so that the center of the remaining ball is located at the apex of a triangle whose base is an imaginary line connecting the centers of the two balls near both ends of the outer cylinder. are being taken.

[Effect]

In the present invention, two sliding grooves are formed at diametrically symmetrical positions on the spline shaft, and on the inner surface of the outer cylinder,
A set of two balls having a ball center at both ends of the base of the triangle and a set of one ball having a ball center at the apex position of the triangle are fitted into the two sliding grooves. , even if there is a slight change in the shaft diameter of the spline shaft due to processing errors, at least two balls, the ball at the apex position and the ball at either end of the base, It is possible to occupy a regular shaft diameter position, the spline shaft and the outer cylinder can be maintained at a generally constant axial center position, and the linear motion accuracy as a ball spline bearing can be maintained at a high level.

Furthermore, in terms of structure, it is sufficient to provide two sliding grooves and three balls that fit into these grooves, which allows the device to be constructed relatively compact and to reduce costs.

〔Example〕

The drawings show embodiments of the present invention; FIG. 1 is a front view showing the first embodiment of the present invention, FIG. 2 is a sectional view taken along A-B-CD in FIG. 1, and FIG. is a front view showing the second embodiment of the present invention, and FIG. 4 is a front view showing the second embodiment of the present invention.
-B-C-D sectional view, FIG. 5 shows a projected view of a presser bolt capable of holding a ball, and FIG. 6 is a sectional view of the presser bolt shown in FIG. 5 assembled into an outer cylinder.

As shown in FIG. 1, the present invention provides a ball spline shaft 2 in which sliding grooves 2a for balls 3 are formed in one row in the axial direction at the top and bottom of the shaft, that is, at diametrically symmetrical positions.
This is a small ball spline bearing consisting of a hollow cylindrical outer cylinder 1 with balls 3 attached to the inner wall corresponding to the sliding groove 2a.

The hollow cylindrical outer cylinder 1 has two sliding grooves 2a.
At the positions corresponding to the balls, there is a ball at one location in the center of the outer cylinder 1 in the axial direction for one sliding groove 2a, and one location at each end in the axial direction for the other sliding groove 2a. A mounting hole 1a for fitting 3 is formed.

A protruding portion 1b having a diameter slightly smaller than the ball diameter is formed near the inner circumferential wall surface of the outer cylinder of this mounting hole 1a to hold the ball 3. When the spline shaft 2 and the outer cylinder 1 are removed, The ball 3 is designed not to fall off from the outer cylinder 1.

To assemble the outer cylinder 1 and the ball 3, the ball 3 is inserted into the mounting hole 1a of the outer cylinder 1, and the presser bolt 4 is screwed onto the ball 3.

The spline shaft 2 and the balls 3 may be in rolling contact (the balls rotate) or in sliding contact (the balls do not rotate), which may be selected depending on the usage conditions of the bearing.

FIG. 2 shows a sectional view taken along A-B-C-D in FIG. 1. In order to provide alignment to the bearing, the present invention has a spline shaft 2 in which a single row of upper and lower sliding grooves 2a is formed, and a set of balls that contacts one of the sliding grooves of the spline shaft 2. The set of two balls that come into contact with the other sliding groove are formed such that each ball center is located at the intersection of each side of a triangle in the axial cross section.

That is, each ball is arranged so that the center of one ball set is located at the vertex of a triangle whose base is an imaginary line connecting the centers of the two sets of balls.

An isosceles triangle provides better centering balance, and in the first embodiment, an equilateral triangle is used.

According to the above configuration, as mentioned above, even if the shaft diameter of the spline shaft repeatedly changes in thickness in the axial direction within the range of machining tolerance,
Since the balls in the set of one ball and the balls in the set of two balls are in contact with the sliding groove with an interval in the axial direction, the pitch of change in thickness is shorter than the interval. In this case, at least one ball in the set of balls and one of the balls in the set of two balls will come into contact with the sliding groove at approximately the correct position, thereby developing alignment and improving linear motion performance. Generally holds well.

Furthermore, even if there is a slight misalignment of the shaft, the positional relationship between the ball 3 and the sliding groove 2a changes slightly to respond, and alignment is achieved.

3 and 4 show a second embodiment of the present invention.

In the second embodiment, the structure of two rows and three points of contact is further utilized to ensure alignment even with large changes in shaft diameter and misalignment.

Among the upper and lower ball rows, the balls 3 that contact the upper row are fixed in the radial direction, but the two balls 3 that contact the lower row are moved in the radial direction. It is supported by pin 6. Further, the presser pin 6 is in contact with an endless coil spring 5 that is fitted into a circumferential groove 1c provided around the outer cylinder 1 at the position of the presser pin 6.

Therefore, when the presser pin 6 protrudes from the circumferential groove 1c, a force is exerted by the coil spring 5 to return it to its original position, and the ball 3 of the outer cylinder 1 self-aligns in response to the change in the spline shaft 2. .

The amount of alignment can be determined by changing the spring characteristics of the coil spring 5, and it is also possible to apply a preload by fitting the coil spring 5 into the circumferential groove 1c with some compression.

Moreover, even if a disc spring is fitted into the hole for the presser pin 6 formed in the outer cylinder 1 instead of the coil spring 5, the bearing can be provided with alignment properties.

In other words, it is sufficient to fix the balls in contact with one of the two upper and lower rows within the outer cylinder 1, and to support the balls in contact with the other sliding groove with an elastic member that is movable in the radial direction. The known technology is
There are other possibilities as well.

FIG. 5 shows a modification of the holding bolt 4. Since the presser bolt 4 shown in the second embodiment cannot hold the ball 3, the ball 3 will fall off when the spline shaft 2 is removed from the outer cylinder 1. A presser bolt 4 shown in FIG. 5 solves this drawback.

Projections 4b are formed at two locations to the extent that they do not contact the sliding groove 2a of the spline shaft 2.
The ball 3 is held by making the minimum width between the balls slightly smaller than the ball diameter. An oil hole 4d is formed at the bottom of the sliding surface 4a that contacts the ball 3 of the holding bolt 4. It is easy to apply this technique to the presser pin 6.

Figure 6 shows the ball 3 attached to the presser bolt 4 shown in Figure 5.
FIG. 2 is a cross-sectional view of the fitting and screwing it into the mounting hole 1a of the outer cylinder 1. An oil groove is formed in the mounting hole 1a of the outer cylinder 1 to lubricate the bearing.

〔effect〕

The present invention has the above-described configuration and operation, and has one sliding groove formed at each of two diametrically symmetrical positions on the spline shaft, and a ball on the inner surface of the outer cylinder that is externally fitted on the spline shaft. , one ball is fitted into one sliding groove, two balls are fitted into the other sliding groove, and each ball has its base connected to an imaginary line connecting the spherical centers of the two sets of balls. Since the ball is assembled so that the spherical center of the other ball is located at the apex position of the triangle, even if there is a slight change in the diameter of the spline shaft or a slight misalignment of the spline shaft. However, at least one of the balls that fit into the two sliding grooves generally occupies the normal bearing position and performs an alignment function, so that the linear motion performance as a ball spline bearing is improved. It has the effect of maintaining the

In addition, it has a relatively simple structure in which two sliding grooves are provided on the spline shaft and three balls placed on the inner surface of the outer cylinder are fitted into the sliding grooves, so the bearing structure is simple and compact. It also has the advantage that it can be provided at a relatively low cost.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a front view showing the first embodiment of the present invention, FIG. 2 is a sectional view taken along A-B-CD in FIG. 1, and FIG. is a front view showing the second embodiment of the present invention, and FIG. 4 is a front view showing the second embodiment of the present invention.
-B-C-D sectional view, FIG. 5 is a perspective view of a presser bolt capable of holding a ball, and FIG. 6 is a sectional view of the presser bolt shown in FIG. 5 assembled into an outer cylinder. 1: Outer cylinder, 1a: Mounting hole, 1b: Projection, 1
c: circumferential groove, 2: spline shaft, 2a: sliding groove,
3: Ball, 4: Presser bolt, 4a: Sliding surface, 4
b: protruding part, 4c: threaded part, 4d: oil hole, 5: coil spring, 6: presser pin.

Claims (1)

[Claims] 1. A spline shaft is provided with sliding grooves for balls at two positions diametrically symmetrical with respect to the axis of the spline shaft, and a hollow cylindrical body externally fitted on the spline shaft. On the inner surface of the cylinder, one ball is disposed at the center of a portion corresponding to one of the sliding grooves, and is fitted into the one sliding groove, and a ball is disposed at the center of a portion corresponding to one of the sliding grooves, and a ball is disposed at the center of a portion corresponding to one of the sliding grooves. One ball is disposed at each of the two locations near both ends of the outer cylinder, and is fitted into the sliding groove of the other.
This self-aligning small ball spline bearing is arranged so that the center of the remaining ball is located at the apex of a triangle whose base is an imaginary line connecting the centers of the balls. 2 In the radial direction toward the axis of the spline shaft, either one of the sets of one ball fitted into one sliding groove and the set of two balls fitted into the other sliding groove The self-aligning small ball spline bearing according to claim 1, wherein the self-aligning small ball spline bearing is elastically supported by an elastic member so as to be movable.