JPH0133883Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] This invention relates to a roller screw.

[Conventional technology and its problems]

A ball screw that moves an outer ring (nut) mounted on the outside in the axial direction by rotation of the shaft uses a threaded shaft as the shaft, and has a thread groove formed on the threaded shaft and an inner circumferential surface of the outer ring. A type in which a large number of balls are fitted between the threaded grooves and a return path for the balls is formed between both ends of the outer ring, and a type described in Nikkei Mechanical, No. 128, published March 25, 1985.
As shown on the page, an endless V-shaped raceway groove is provided on the inner peripheral surface of the outer ring mounted on the outside of the shaft, and a plurality of balls that go around the outer circumference of the shaft are installed between the raceway groove and the outer peripheral surface of the shaft. There is also a type in which the ball row is in contact with the outer periphery of the shaft within a range of 340° out of 360° around the shaft.

By the way, in a ball screw using a threaded shaft, the ball moves along the thread groove, so it has the advantage of being able to take any lead amount by appropriately determining the lead angle of the thread groove. The disadvantage is that it takes a lot of time to form.

On the other hand, ball screws with a V-shaped raceway groove on the outer ring have the advantage of being low cost because there is no need to cut a thread groove on the outer peripheral surface of the shaft. Since it is necessary to return to the start of contact with the shaft within a range of 20 degrees, there is a disadvantage that a large amount of lead cannot be taken.

[Problem for invention]

The technical problem of this invention is to solve the above-mentioned disadvantages, to use a round shaft that does not require machining as the shaft, and to enable a large lead amount.

[Structure of the idea]

In order to solve the above problems, this invention forms a raceway groove on the inner diameter surface of the outer ring fitted on the outside of the shaft, and in this raceway groove, multiple crown-shaped grooves are formed with the outer peripheral surface of the shaft as the rolling surface. Install rollers, make the radius of curvature of each roller larger than the radius of the shaft, arrange each roller at an angle to the shaft so that the roller is in line contact with the shaft, and install a ball between adjacent rollers. This is the structure.

[Effect]

In the roller screw with the above configuration, when the shaft is rotated, the crown-shaped roller that contacts the outer peripheral surface of the shaft rotates due to contact with the shaft and tries to roll in a direction perpendicular to the roller axis. The side surface of the raceway groove of the outer ring is pressed by the end face, and the outer ring moves in the axial direction of the shaft. The amount of axial movement of this outer ring is
It depends on the intersection angle between the roller and the shaft, and by increasing the intersection angle, the lead amount of the outer ring can be increased.

〔Example〕

Hereinafter, embodiments of this invention will be described based on the accompanying drawings.

As shown in the figure, an outer ring 2 is fitted on the outside of the shaft 1, and a raceway groove 3 is provided on the inner diameter surface of the outer ring 2. A plurality of crown-shaped rollers 4 are provided in an annular arrangement in this raceway groove 3, and a ball 5 disposed between the central small diameter portions of adjacent rollers 4 maintains the spacing between the rollers 4 and moves each roller 4 along the shaft 1. A preload is applied between the roller 4 and the shaft 1 by pressing against the outer peripheral surface.

Note that the outer diameter of the ball 5 is arbitrary, and in the case of the embodiment, it is made slightly smaller than the minimum diameter of the roller 4. The ball 5 may be brought into contact with the inner circumferential surface of the raceway groove 3 as shown in the figure, or may be brought into contact with the outer circumferential surface of the shaft 1.

The radius of curvature of the roller 4 is larger than the radius of the shaft 1. Further, the axis a of the roller 4 is inclined at a predetermined angle with respect to the axis A of the shaft 1 so that the outer periphery of the roller 4 is in line contact with the outer peripheral surface of the shaft 1. Intersection angle α of roller 4 with respect to axis 1
is determined by the radius of curvature of the roller 4, and by increasing this radius of curvature, the intersection angle α can be made smaller. The end surface 6 of this roller 4 has a conical shape, and the end surface 6 is guided by both side surfaces 3' of the raceway groove 3.

The roller screw shown in the embodiment has the above structure, and this roller screw moves the outer ring 2 in the axial direction by rotation of the shaft 1.

Now, when the shaft 1 is rotated in the direction of arrow A in Fig. 1, each roller 4 rotates in the direction of arrow B in the figure due to contact with the shaft 1, and rolls in the direction perpendicular to the roller axis (indicated by arrow C). try to. Therefore, both side surfaces 3' of the raceway groove 3 are pushed in the axial direction by the end surface 6 of the roller 4, and the outer ring 2 moves in the direction of the arrow in FIG.

The amount of movement per rotation of shaft 1 is the distance between roller 4 and shaft 1.
The amount of lead of the outer ring 2 increases as the intersection angle α increases. This intersection angle α is determined by the radius of curvature of the roller 4, so if the radius of curvature is made smaller,
The intersection angle α becomes larger, and the lead amount of the outer ring 2 can be increased.

Since the rollers 4 are crown-shaped, even if the intersection angle α changes, the rollers 4 are self-aligned and the outer circumference of the rollers 4 is always kept in line contact with the outer circumferential surface of the shaft 1, and the rotation of the shaft 1 is maintained. The outer ring 2 can be moved by a predetermined amount depending on the corner.

〔effect〕

As described above, according to this invention, the plurality of rollers incorporated in the raceway groove of the outer ring are crown-shaped,
The radius of curvature of the roller is made larger than the radius of the shaft,
The rollers are arranged at an angle with respect to the shaft so that the outer periphery of each roller is in line contact with the outer periphery of the shaft, so when the shaft is rotated, the rollers move in a direction perpendicular to the shaft center, and the end surface of the roller moves into the raceway groove. The outer ring can be moved along the axis by pushing the side of the outer ring.

Furthermore, since the roller is rotated by contact with the shaft, a round shaft that does not require threading can be used as the shaft, and a low-cost roller screw can be provided.

Furthermore, the intersection angle between the shaft and the roller that makes line contact with it varies depending on the radius of curvature of the roller.
Since the roller rolls in a direction perpendicular to the roller axis, changing the radius of curvature of the roller changes the amount of lead, and by decreasing the radius of curvature, the amount of lead of the outer ring can be increased. can.

In addition, the distance between the rollers is maintained by balls, and the rollers are always kept in line contact with the shaft due to self-aligning action, so the outer ring can be moved by a predetermined amount in response to the rotation angle of the shaft. In addition, it is possible to eliminate the need for parts for holding the roller in an inclined state. Therefore, the number of parts is extremely small and assembly is easy.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing one embodiment of a roller screw according to this invention, and FIG. 2 is a longitudinal sectional side view of the same. 1... shaft, 2... outer ring, 3... raceway groove, 4...
roller.

Claims (1)

[Scope of utility model registration request] An outer ring is fitted on the outside of the shaft, a raceway groove is formed on the inner diameter surface of the outer ring, and a plurality of crown-shaped rollers whose rolling surface is the outer peripheral surface of the shaft are incorporated into the raceway groove, and each roller has a radius of curvature. A roller screw with a radius larger than the shaft, each roller arranged at an angle to the shaft so that the outer periphery of the roller is in line contact with the shaft, and a ball incorporated between adjacent rollers.