JP5621245B2 - Ball spline - Google Patents

Description

  The present invention relates to a ball spline.

  Ball splines are often used for electric actuators and shock absorbers in combination with ball screws. For example, in Patent Document 1, a ball screw nut rotates by connecting a motor to the ball screw nut. It is disclosed that a ball screw device with a ball spline in which a screw shaft extending vertically moves linearly in the axial direction is applied to a shock absorber.

  An example of a ball spline used in a conventional ball screw device with a ball spline is shown in FIG. In the figure, a ball spline (31) is fitted to a shaft (32) via a ball (34) and a shaft (32) provided with a ball screw raceway (32a) and a spline raceway (32b) extending in the axial direction. An assembled ball spline outer cylinder (33) and a housing (35) for holding the ball spline outer cylinder (33) are provided.

  The ball spline outer cylinder (33) is opposed to the spline raceway (32a) of the shaft (32), and has a substantially cylindrical outer cylinder body (36) formed with a spline raceway (36a) constituting the main passage. A substantially cylindrical cage (37) formed with a return passage and fitted to the inner periphery of the outer cylinder body (36), and for fixing the cage (37) to the outer cylinder body (36) A pair of C-shaped retaining rings (38).

JP 2008-143436 A

  According to the above ball spline (31), the use of the C-shaped retaining ring (38) requires a groove in the outer cylinder main body (36), and it takes time and effort to assemble the product. There was a problem of being up. Further, it is not preferable in that the axial length is increased by the amount of the retaining ring (38).

  An object of the present invention is to provide a ball spline that can reduce costs and shorten the axial length by eliminating the C-shaped retaining ring conventionally used in the ball spline outer cylinder.

A ball spline according to the present invention includes a shaft provided with a spline track, a ball spline outer cylinder fitted to the shaft via a ball, and a housing for holding the ball spline outer cylinder. A substantially cylindrical outer cylinder body in which a spline raceway constituting a main passage is formed by being opposed to the spline raceway, and a substantially cylindrical shape in which a return path is formed and fitted to the inner periphery of the outer cylinder body In the ball spline having the cage, the inner diameter of the end of the outer cylinder body is made smaller than the outer diameter of the end of the cage, and the cage is lightly press-fitted into the outer cylinder body. assembling are prevented falling off of the cage from the outer cylinder body before, the outer barrel body and the retainer are both inward one end of which is formed integrally with the housing The flange portion abuts, by its other end abuts against the annular member fixed to the housing and adapted to move in the axial direction is restricted, the inner peripheral surface and the axis of the inward flange portion of the housing splines The radial distance from the track bottom and the radial distance between the inner peripheral surface of the annular member and the spline track bottom of the shaft are smaller than the ball diameter.

  The ball rolls between the spline raceway formed on the shaft and the spline raceway formed on the outer cylinder body (main passage), and returns to the main passage again (circulates) through the return passage of the cage body. ).

  When the cage is assembled to the housing, one end abuts on an inward flange portion formed on the housing, and the other end abuts on an annular member that is restricted from moving outward in the axial direction. By restricting the movement in the axial direction, positioning in the axial direction and prevention of falling off from the outer cylinder main body can be achieved without a C-shaped retaining ring. In a state before being assembled to the housing, the cage may be movable in the axial direction relative to the outer cylinder main body, or may not be movable (positioned) in the axial direction. Further, the cage may be an integral product, or may be composed of a cage body and a cage lid. The cage is preferably made of synthetic resin.

  The inward flange part of the housing not only restricts the axial movement of the outer cylinder body, but also restricts the axial movement of the cage, and the radial distance between the inner peripheral surface and the spline track bottom of the shaft However, it is made smaller than the ball diameter. Similarly, the radial distance between the inner peripheral surface of the annular member and the spline track bottom of the shaft is also smaller than the ball diameter. If it does in this way, with respect to the force in which a ball | bowl presses a holder | retainer, an inward flange part and an annular member can receive this force, and it will become difficult for a holder | retainer to deform | transform.

  In order to prevent the cage from falling off the outer cylinder main body before the housing is assembled, the inner diameter of the outer cylinder main body is made smaller than the outer diameter of the end of the cage, and the cage is lightly press-fitted into the outer cylinder main body. May have. Here, “light press-fitting” is press-fitting in which the inner diameter of the outer cylinder body is made smaller than the outer diameter of the cage and both are forcibly fitted, but due to a relatively weak force that does not deform the cage. Refers to press-fitting. Since the housing can be prevented from falling off from the outer cylinder main body after the housing is assembled, the cage does not come out of the outer cylinder main body even if it is transported before assembling. It is sufficient if the press-fitting is of a degree.

  The inner diameter of the outer cylinder body and the outer diameter of the cage end need not be a smooth cylindrical surface. The outer diameter of the outer cylinder body and the outer diameter of the cage end are the smallest. It is only necessary that the portion with the largest diameter is prevented from coming off by a required pressure input.

  Instead of light press-fitting, the outer diameter of the end of the outer cylinder body is made larger than the outer diameter of the end of the cage, and a convex portion is formed on either the outer circumferential surface of the cage end or the inner circumferential surface of the outer cylinder body. May be provided with a concave portion fitted to the convex portion on the other side.

  If neither light press-fitting nor concave / convex fitting is used, a stopper with an outer diameter smaller than the inner diameter of the housing is attached to the shaft, and the spline is assembled to the housing, and then the stopper is removed. It is possible to prevent the retainer from separating during the attaching operation.

  The ball spline is preferably combined with a ball screw, a screw shaft provided with a ball screw raceway and an axially extending spline raceway, and a rotatable ball screwed to the ball screw raceway of the screw shaft via a ball. A screw nut and a ball spline outer tube that is fitted to the spline track via a ball and guides the axial linear motion of the screw shaft are included.

  The shaft and the ball spline outer cylinder main body are made of carbon steel such as S45C and S55C or SAE4150 steel, and the ball is made of bearing steel (SUJ2), for example.

  The ball spline according to the present invention may be used in combination with a ball screw as an actuator (a configuration in which a ball screw nut is rotated by a motor, whereby the screw shaft moves linearly), and a shock absorber (screw shaft). Is moved linearly by an external force, whereby the ball screw nut is rotated and the electromagnetic force generated by the motor is used as a damping force.

  According to the ball spline of the present invention, the cage of the ball spline outer cylinder is restricted in the axial movement by the inward flange portion and the annular member of the housing in a state where it is assembled to the housing. Prevents falling off from the outer cylinder main body. Further, the radial distance between the inner peripheral surface of the inward flange portion and the shaft spline track bottom and the radial distance between the inner peripheral surface of the annular member and the spline track bottom of the shaft are smaller than the ball diameter. The inward flange portion and the annular member can receive this force against the force with which the ball presses the cage, and the cage is not easily deformed. Therefore, the C-type retaining ring used for stopping the cage can be eliminated, and the cost and the axial length can be shortened.

FIG. 1 is a longitudinal sectional view showing a ball spline according to a first embodiment of the present invention. FIG. 2 is an enlarged longitudinal sectional view of a main part showing a second embodiment of the ball spline according to the present invention. FIG. 3 is a perspective view showing a third embodiment of the ball spline according to the present invention. FIG. 4 is a longitudinal sectional view showing a third embodiment of the ball spline according to the present invention. FIG. 5 is a longitudinal sectional view of a conventional ball spline.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a first embodiment of a ball spline according to the present invention.

  The ball spline (1) is used in a ball screw device with a ball spline.A ball screw raceway (2a) and a shaft (2) provided with a spline raceway (2b) extending in the axial direction and a ball (4) A ball spline outer cylinder (3) fitted to the shaft (2) via a pin, and a housing (5) for holding the ball spline outer cylinder (3).

  The ball spline outer cylinder (3) is a substantially cylindrical metal outer cylinder formed with a spline track (6a) constituting the main passage (8) by being opposed to the spline track (2b) of the shaft (2). It has a main body (6) and a substantially cylindrical synthetic resin cage (7) in which a return passage (9) is formed and fitted to the inner periphery of the outer cylinder main body (6).

  The ball (4) is disposed in the main passage (8) and the return passage (9), and the ball (4) rolling on the main passage (8) is connected to the shaft (2) and the ball spline outer cylinder (4). It is designed to guide relative linear motion.

  One end (left end in the figure) of the cage (7) abuts an inward flange portion (11) formed in the housing (5), and the other end (right end in the figure) is attached to the housing (5) with a retaining ring ( The axial movement is restricted by contacting the annular member (12) fixed via 13).

  A radial distance R1 between the inner peripheral surface of the inward flange portion (11) and the bottom of the spline track (2b) of the shaft (2) is smaller than the diameter of the ball (4). Similarly, the radial distance R2 between the inner peripheral surface of the annular member (12) and the bottom of the spline track (2b) of the shaft (2) is smaller than the diameter of the ball (4). For this reason, the inward flange portion (11) and the annular member (12) can receive this force against the force with which the ball (4) pushes the cage (7) outward in the axial direction, and the cage ( 7) is difficult to deform.

  The inner diameter of the end of the outer cylinder main body (6) is slightly smaller than the outer diameter of the end of the retainer (7), and the retainer (7) is lightly press-fitted into the outer cylinder main body (6). This light press-fitting is performed with a relatively weak force that does not deform the synthetic resin cage (7), so that the cage (7) can be removed from the outer cylinder body (6) even if it is transported. It is designed not to come out.

  FIG. 2 shows a second embodiment of the ball spline according to the present invention.

  In this embodiment, instead of the light press-fitting in the first embodiment, the inner diameter of the end of the outer cylinder body (6) is made larger than the outer diameter of the end of the cage (7), and the cage (7) An annular convex portion (21) is formed on the outer peripheral surface of the end, and an annular concave portion (22) fitted to the convex portion (21) is provided on the inner peripheral surface of the end portion of the outer cylinder main body (6). Yes. The fitting between the convex portion (21) and the concave portion (22) is not press-fitting but a clearance fit. The other configuration is the same as that of the first embodiment.

  3 and 4 show a third embodiment of the ball spline according to the present invention.

  In this embodiment, when the outer cylinder body (6) and the cage (7) are neither light press-fitting nor uneven fitting, they can be prevented from being removed during transportation, and the screw shaft (2) The passed stopper (31) is applied to both ends of the ball spline (3) from the outside in the axial direction. The stopper (31) is made of soft synthetic resin or the like, has an inner diameter substantially equal to the outer diameter of the screw shaft (2), and the inner diameter of the flange portion (11) of the housing (7) and the annular member (12). The outer diameter is smaller than the inner diameter. The stopper (31) is prevented from coming off the shaft (2) by frictional force and elastic force, and the ball spline (3) is removed after the ball spline (3) is assembled to the housing (7). It is possible to prevent the cage (7) from being loosened during the assembling work of (3).

(1) Ball spline
(2) Axis
(2b) Spline track
(3) Ball spline outer cylinder
(4) Ball
(5) Housing
(6) Outer cylinder body
(6a) Spline track
(7) Cage
(8) Main passage
(9) Return passage
(11) Inward flange
(12) Ring member

Claims (1)

A shaft provided with a spline track, a ball spline outer tube fitted to the shaft via a ball, and a housing for holding the ball spline outer tube, the ball spline outer tube being made to face the spline track of the shaft A substantially cylindrical outer cylinder body in which a spline track constituting the main passage is formed, and a substantially cylindrical retainer in which a return path is formed and fitted to the inner periphery of the outer cylinder body. In the ball spline
The inner diameter of the end of the outer cylinder body is made smaller than the outer diameter of the end of the cage, and the cage is lightly press-fitted into the outer cylinder body. Omission is prevented,
The outer cylinder main body and the cage are both moved in the axial direction by abutting one end with an inward flange portion formed integrally with the housing and the other end with an annular member fixed to the housing. The radial distance between the inner peripheral surface of the inward flange portion of the housing and the spline track bottom of the shaft and the radial distance between the inner peripheral surface of the annular member and the spline track bottom of the shaft are as follows: A ball spline characterized by being smaller than the ball diameter.

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