JP2010112513A - Ball spline - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball spline improving the service life by preventing edge stress when the moment is applied. <P>SOLUTION: A ball spline outer cylinder 4 is formed in a barrel shape, and is fitted in a cylindrical surface 16 formed in an inner periphery of a housing 6 through a cylindrical elastic supporting body 13 having a cylindrical outer peripheral surface 22 and a barrel shaped inner peripheral surface 21. Key grooves 17 and 18 are respectively formed on an outer peripheral surface 15 of the ball spline outer cylinder 4 and the inner peripheral surface 16 of the housing 6, and an inward protruding part 23 and an outward protruding part 24 fitted in the key grooves 17 and 18 are provided on the outer peripheral surface and the inner peripheral surface of the elastic supporting body 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ball spline, and more particularly to a ball spline used under a condition that is susceptible to a moment.

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 having a configuration in which a screw shaft extending vertically moves linearly in an axial direction is applied to a shock absorber.
JP 2005-264992 A

  In actuators and shock absorbers that use ball screws with ball splines, lateral force (force in the direction perpendicular to the axial direction) may act on the end of the screw shaft. In this case, edge stress is generated by the moment. As a result, the end of the ball spline outer cylinder, the raceway and the like may be damaged, and the protection thereof is an issue.

  An object of the present invention is to provide a ball spline having an improved life by preventing edge stress when a moment is applied.

  A ball spline according to the present invention is a ball spline comprising a shaft provided with a spline track and a ball spline outer tube fitted to the shaft via a ball. The ball spline outer tube is formed in a barrel shape. The cylindrical inner surface formed on the inner periphery of the housing is fitted through a cylindrical elastic support body having an outer peripheral surface of a cylindrical surface and an inner peripheral surface of a barrel shape.

  In the ball spline outer cylinder, a return passage is formed at both ends, so the spline track is provided in a portion excluding both ends. Conventionally, the outer peripheral surface of the ball spline outer cylinder is a cylindrical surface having the same diameter as a whole. However, in the ball spline according to the present invention, the outer diameter of both end portions is a barrel shape smaller than the outer diameter of the central portion. .

  The barrel-shaped outer peripheral surface and inner peripheral surface can be obtained, for example, by making the both side portions of the spherical surface cut by parallel surfaces, but the shape is not limited to the spherical surface, and the cross section is circular. Any diameter may be used as long as the diameter continuously increases toward the outer side in the axial direction at the maximum in the axial central portion. In addition, the barrel-shaped outer peripheral surface and the inner peripheral surface are usually formed symmetrically with respect to a plane passing through the center in the axial direction so that the same performance can be obtained even if the top and bottom (or front and back) are reversed. It is not necessary to be symmetric, and the one side in the axial direction may be longer than the other side based on the position of the maximum diameter.

  The ball spline outer cylinder is supported so as not to rotate with respect to the housing in a normal state (when an excessive lateral force does not act). For this, for example, a frictional force between the elastic support and the ball spline outer cylinder and a frictional force between the elastic support and the housing may be used. , One side of the key penetrating the elastic support member in the radial direction may be fitted into the ball spline outer cylinder, and the other side may be fitted into the housing.

  According to the ball spline of the present invention, because the ball spline outer cylinder is barrel-shaped, the load position on the outer peripheral side of the ball spline outer cylinder is closer to the center than the conventional one, Edge stress when subjected to a moment is prevented and the life of the ball spline is improved. In addition, since the ball spline outer cylinder is barrel-shaped and supported by the housing via the elastic support, the ball spline outer cylinder is concentric with the shaft when the lateral force acting on the ball spline outer cylinder is small. This state is maintained to prevent the rotation of the shaft and guide the linear movement of the shaft. When a large lateral force acts on the ball spline outer cylinder, the ball spline outer cylinder can freely tilt with respect to the axial direction by elastically deforming the elastic support. Thereby, the load which acts from a housing is relieve | moderated and the impression of a spline track | orbit is prevented. In addition, since an excessive moment is prevented from being generated, damage such as separation at the end of the spline track is also prevented, and the life of the ball spline is further improved.

  As a configuration for supporting the ball spline outer cylinder so as not to rotate with respect to the housing, preferably, a key groove is provided on each of the outer peripheral surface of the ball spline outer cylinder and the inner peripheral surface of the housing, and the outer peripheral surface of the elastic support body. Further, an inner projecting portion and an outer projecting portion that are fitted in these key grooves are provided on the inner peripheral surface. In this way, when an impact load is input, the key portion is elastically deformed, whereby the rotational torque generated in the ball spline outer cylinder is absorbed, and a damper effect can be obtained.

  The elastic support is made of rubber, synthetic resin, or the like, and has a structure that can be divided into two at the center. The elastic support is fitted into a barrel-shaped ball spline outer cylinder from both ends and abutted at the center. The elastic support and the ball spline are previously integrated and inserted into the housing. The housing is formed with a flange portion for receiving one end surface of the integrated product, and the other end surface of the integrated product is fixed so as not to move in the axial direction by a retaining ring or the like.

  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 the 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.

  In a ball screw with a ball spline, the ball spline outer cylinder is prevented from rotating against the housing by a key or other non-rotating part, preventing the rotation of the screw shaft and the reaction force of torque generated by the ball screw nut. Receive. When the screw shaft is bent due to a lateral force, the screw shaft is supported at two points, that is, a ball spline and a ball screw, and a radial load is applied to the ball spline. At this time, in the conventional one, an offset occurs in the load load position between the outer peripheral side and the inner peripheral side of the ball spline outer cylinder, and a large moment is generated, so that separation at the end of the spline track tends to occur. In addition, the key used in the conventional ball spline is made of metal (substantially rigid body), and the rotatable amount of the ball spline outer cylinder with respect to the housing is almost zero. When excessive torque is applied to the shaft, the screw shaft is twisted while being regulated by the ball spline outer cylinder, so that indentations are likely to occur on the spline track.

  On the other hand, according to the ball spline of the present invention, the offset of the load position on the outer peripheral side and the inner peripheral side of the barrel-shaped ball spline outer cylinder is reduced, and a moment is hardly generated. Further, since the rotation preventing portion (fitting between the key groove and the protruding portion of the elastic support) can be elastically deformed, the amount of rotation of the ball spline outer cylinder relative to the housing increases, resulting in excessive torque. In this case, the excessive torque can be absorbed by moving the ball spline outer cylinder by a predetermined amount in the rotation direction with respect to the housing. Thus, according to the ball spline of the present invention, it is advantageous for the separation at the end of the spline track and the indentation of the spline track, and the life of the ball spline is greatly improved.

  The screw shaft, the ball screw nut, and the ball spline outer cylinder 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.

  When used in an actuator or shock absorber, for example, a ball screw with a ball spline, a hollow shaft integrated with a ball screw nut, a hollow shaft rotatably supported via a bearing and a ball spline outer cylinder And a motor composed of a motor rotor fixed to the hollow shaft and a motor stator fixed to the inner diameter of the housing.

  The screw shaft reciprocates linearly and is usually provided with a stopper for preventing movement beyond a predetermined amount. The stopper can be formed, for example, by providing the screw shaft with a flange portion that contacts the housing when the screw shaft moves by a predetermined amount or more, and the stopper is formed on a member that moves linearly integrally with the screw shaft. Alternatively, it may be provided on a member that does not move linearly (a housing or a hollow shaft).

  According to the ball spline of the present invention, since the ball spline outer cylinder is formed in a barrel shape and is fitted into the housing via the elastic support, the load load position on the outer peripheral side of the ball spline outer cylinder is at the center. As a result, the edge stress when subjected to a moment is prevented, and damage such as peeling at the end of the spline track is prevented. Further, when a large lateral force is applied to the ball spline outer cylinder, the ball spline outer cylinder can be freely tilted with respect to the axial direction by elastically deforming the elastic support, thereby acting from the housing. The load is relaxed and the indentation of the spline track is prevented. As a result, the life of the ball spline is greatly improved.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the top and bottom refer to the top and bottom of FIGS. 1 and 3.

  FIG. 1 shows a ball screw device with a motor as an example to which a ball spline according to the present invention is applied.

  The motorized ball screw device (1) consists of a ball screw raceway (2a) and a vertically extending steel screw shaft (2) provided with a spline raceway (2b), and a ball screw of the screw shaft (2). A rotatable steel ball screw nut (3) screwed to the raceway (2a) via a ball, and a screw shaft fitted to the spline raceway (2b) via a ball on the lower end side of the screw shaft (2). The ball spline outer cylinder (4) that guides the vertical movement (axial direction) of (2), the hollow shaft (5) that is integrated with the ball screw nut (3), and the bearing (7) Through which the hollow shaft (5) is rotatably supported and the ball spline outer cylinder (4) is supported, a cylindrical motor rotor (9) fixed to the hollow shaft (5), and the housing (6 And a motor (8) comprising a cylindrical motor stator (10) fixed to the inner diameter.

  The motor (8) is a permanent magnet type three-phase synchronous motor, the motor rotor (9) is a permanent magnet, and a U-phase, V-phase and W-phase three-phase coil (10a) is provided on the motor stator (10). ) Is wound.

  The screw shaft (2) and the hollow shaft (5) are arranged concentrically, and the ball screw device with motor (1) includes a ball screw nut (3), a hollow shaft (5), and a motor rotor (9). The screw shaft (2) is used in such a form that it is rotated and moved linearly.

  The hollow shaft (5) has a small-diameter portion (11) for guiding the screw shaft (2), and a large diameter whose inner peripheral surface is fixed to the outer peripheral surface of the ball screw nut (3) and that holds the bearing (7) on the outer peripheral surface. It consists of a diameter part (12).

  The ball spline outer cylinder (4) prevents the rotation of the screw shaft (2) and guides its vertical movement, has a barrel shape, and is held in the elastic support (13) in the housing ( Supported by 6). The assembly of the ball spline outer cylinder (4) and the elastic support (13) is supported at its lower end surface by a flange portion (6a) provided on the inner periphery of the housing (6). It is regulated by 14).

  2 and 3, the ball spline outer cylinder (4) has a barrel-shaped outer peripheral surface (15) corresponding to the elastic support (13). The shape of the inner peripheral surface (21) is a barrel shape. The inner peripheral surface (16) of the housing (6) is a cylindrical surface, and correspondingly, the outer peripheral surface (22) of the elastic support (13) is a cylindrical surface.

  The elastic support (13) is divided into two parts separated at the center, and is formed by an upper half elastic support (13a) and a lower half elastic support (13b).

  A key groove (17) is formed at a predetermined circumferential position on the outer peripheral surface (15) of the ball spline outer cylinder (4), and a key groove is also formed at a predetermined circumferential position on the inner peripheral surface (16) of the housing (6). (18) is formed. To correspond to these key grooves (17) and (18), the key groove (17) of the ball spline outer cylinder (4) is provided at a predetermined position in the circumferential direction of the inner peripheral surface (21) of the elastic support (13). The inner projecting portion (23) fitted to the outer circumferential surface (22) of the elastic support (13) is fitted to the key groove (18) of the housing (6). Each outward projection (24) is formed.

  The motor-equipped ball screw device (1) is suitable for use as, for example, an automobile electromagnetic shock absorber. In the electromagnetic shock absorber, the screw shaft (2) linearly moves in the axial direction due to the external force transmitted from the tire, and the ball screw nut (3) and the hollow shaft (5) rotate accordingly. 8), the electromagnetic force generated by the motor (8) is used as the damping force.

  In the ball screw device with motor (1) used in such an electromagnetic shock absorber, not only the force in the vertical direction (axial direction of the screw shaft (2)) but also the force in the front / rear / right / left direction (lateral force) is applied from the tire. In this case, the lower end of the ball spline outer cylinder (4) and the spline track (4a) are easily damaged, and the protection thereof is a problem.

  When a lateral force acts on the lower end of the screw shaft (2), this is loaded on the screw shaft (2) as a moment. This load is largely supported at two points: the ball screw nut (3) and the ball spline outer cylinder (4). One side of the ball screw nut (3) perpendicular to the axial direction and the ball spline outer cylinder ( The load is applied to the other side in the direction orthogonal to the axial direction of 4). In conventional ball splines, a large moment tends to occur at the lower end of the ball spline outer cylinder, and edge stress is generated when the ball passes through the lower end (axial end) of the spline track by receiving this moment. In addition, peeling off of the end portion and damage to the ball may occur.

  In contrast, in the ball spline according to the present invention, the ball spline outer cylinder (4) has a barrel shape and is supported by the housing (6) via the elastic support (13). The load load position that the outer peripheral surface of 4) receives from the housing (6) is higher than the conventional one, so that the inner peripheral surface of the ball spline outer cylinder (4) is arranged on the spline track (4a). The offset with respect to the load applied position received via the ball is almost zero, so that a large moment is not generated. Therefore, according to the ball spline of the present invention, damage due to edge stress when a moment is applied can be prevented, and the life of the motorized ball screw device (1) using this spline can be improved.

  In the electromagnetic shock absorber, the motor (8) was rotating at a high speed by the bump stopper that moves up and down integrally with the screw shaft (2) colliding with the housing (6), etc. May suddenly stop and an excessive torque may be applied to the spline raceways (2b) and (4a) of the ball spline due to the inertia torque of the motor (8), and the protection thereof is an issue.

  The conventional ball spline outer cylinder has high torsional rigidity, and the load applied to the ball increases as the torsion of the screw shaft (2) increases because the torsion of the screw shaft (2) does not twist itself. On the other hand, in the ball spline according to the present invention, the rotation preventing portion that restricts the rotation of the ball spline outer cylinder (4) includes the protruding portions (23) and (24) of the elastic support (13) and the key groove (17) ( This is due to fitting with 18) and is elastically deformable. Therefore, if excessive torque is applied to the conventional ball spline and the screw shaft (2) is twisted, if a metal key is used, the torsional rigidity is high, which corresponds to the twist amount of the screw shaft (2). However, in the ball spline according to the present invention, when a force causing twisting is applied to the screw shaft (2), the screw shaft ( Corresponding to the twist of 2), the ball spline outer cylinder (4) is deformed integrally with the screw shaft (2) by deforming the elastic support (13), whereby the spline track (2b) (4a) Indentation is prevented from occurring.

  Although the above-described ball screw device (1) with a motor has been described for an electromagnetic shock absorber, the present invention is not limited to this and can also be used as an electric actuator. In this case, the rotational driving force of the motor (8) is converted to the axial thrust of the screw shaft (2) via the ball screw nut (3), and the axial reaction force of the thrust is supported by the bearing (7) and screwed. The shaft (2) is moved linearly, the axial load acting on the screw shaft (2) is applied by the ball screw nut (3), and the torque is supported by the ball spline outer cylinder (4). .

FIG. 1 is a longitudinal sectional view showing a ball screw device with a ball spline in which the ball spline of the present invention is used. FIG. 2 is an exploded perspective view showing a ball spline outer cylinder and an elastic support, which are characteristic parts of the ball spline of the present invention. FIG. 3 is an enlarged longitudinal sectional view of a main part of FIG.

Explanation of symbols

(2) Screw shaft (shaft)
(2b) Spline track
(4) Ball spline outer cylinder
(4a) Spline track
(6) Housing
(13) Elastic support
(15) Barrel type outer peripheral surface
(16) Cylindrical inner peripheral surface
(17) Keyway
(18) Keyway
(21) Barrel inner peripheral surface
(22) Cylindrical outer peripheral surface
(23) Inward protrusion
(24) Outward protrusion

Claims (2)

In a ball spline comprising a shaft provided with a spline track and a ball spline outer cylinder fitted to the shaft via a ball,
The ball spline outer cylinder is formed in a barrel shape, and is fitted into a cylindrical surface formed on the inner periphery of the housing via a cylindrical elastic support body having an outer peripheral surface of a cylindrical surface and an inner peripheral surface of a barrel shape. Ball spline characterized by being.   Key grooves are provided on the outer peripheral surface of the ball spline outer cylinder and the inner peripheral surface of the housing, respectively, and the inner protrusion and the outer portion are fitted to the outer peripheral surface and the inner peripheral surface of the elastic support member. 2. The ball spline according to claim 1, wherein a protrusion is provided.

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