JP5168205B2 - Ball screw device - Google Patents

Description

  The present invention relates to a ball screw device, and more particularly to a ball screw device to which a ball spline is added.

  As a ball screw, a ball screw nut having a ball screw track formed on the inner peripheral surface is fitted on the outer side of a screw shaft having a ball screw track formed on the outer peripheral surface, and a plurality of balls are formed in a ball passage formed by both ball screw tracks. There are known ones in which the balls are arranged.

  In such a conventional ball screw, when the ball screw raceway is formed over the entire length of the screw shaft, the ball screw nut is removed when the ball screw is inspected and transported, or when the ball screw is assembled to the actuator. The ball may fall off from the end of the ball screw raceway of the screw shaft, and in this case, there is a problem that the work for restoration takes time.

  In order to solve such a problem, at the end of the ball screw raceway formed at the entire length of the screw shaft, the screw thread portion adjacent to the ball screw raceway is plastically deformed to reduce the width of the ball screw raceway. It has been proposed (see Patent Document 1).

JP 2005-121216 A

  In the ball screw disclosed in Patent Document 1, even when the ball screw raceway is formed over the entire length of the screw shaft, it is possible to prevent the ball from dropping off at a portion where the width of the end of the ball screw raceway is narrow.

  However, since it is plastic deformation, there is a problem that it becomes a process after passing the ball screw nut through the screw shaft, and once processed, it cannot be decomposed thereafter.

  An object of the present invention is to provide a ball screw device that prevents the ball screw nut from coming off during inspection and transportation of the ball screw, when assembling the ball screw to an actuator, etc., and has improved handling.

  A ball screw device according to the present invention includes a screw shaft provided with a ball screw raceway and a spline raceway, a ball screw nut screwed to the ball screw raceway of the screw shaft via a ball, and a ball on the spline raceway of the screw shaft. In a ball screw device having a ball spline outer cylinder fitted together, a ball screw nut is covered with a non-rotating cap having a through-hole inserted into the screw shaft so as not to be rotatable relative to the nut. An engaging convex portion that engages with a concave portion provided on the screw shaft is integrally provided on the peripheral portion of the through hole of the anti-rotation cap.

  A ball spline is added to the ball screw device, and a linear spline track is formed on the screw shaft in addition to the ball screw track. The engagement between the engaging convex portion of the locking cap and the concave portion of the screw shaft is for preventing relative rotation between them (rotating stop), and the concave portion for engagement provided on the screw shaft. For example, a spline track can be used. If the screw shaft has a recess other than the spline track, this may be used, or a recess for engaging the screw shaft may be additionally processed.

  The material of the anti-rotation cap is, for example, made of synthetic resin, but is not limited to this.

  The configuration that makes the ball screw nut and the non-rotating cap relatively non-rotatable is that the key groove is provided in the ball screw nut and the key that fits into the key is fitted in this key groove. What is necessary is just to form a groove (engagement part) in the inner periphery of a cap for rotation prevention, and when the coupling claw which protrudes in the direction of an axis is provided in the end of a ball screw nut in the peripheral direction, What is necessary is just to form the coupling nail | claw (engagement part) which fits between adjacent coupling claws in the outer periphery of the cap for rotation prevention. When the ball screw nut is provided with a bolt hole, a protrusion (engagement portion) that fits into the bolt hole may be formed on the anti-rotation cap. Furthermore, the inner diameter of the anti-rotation cap is made substantially equal to the outer diameter of the ball screw nut, and the ball screw nut and the anti-rotation cap are made to be elastically deformed only by friction between them or by a slight elastic deformation of the anti-rotation cap. The relative rotation may be disabled.

  The fact that the ball screw nut and the non-rotating cap cannot be rotated relative to each other means that they are trying to rotate together, and the engaging projection provided on the non-rotating cap is provided on the screw shaft. The rotation of the anti-rotation cap is prevented by engaging the recessed portion (for example, spline track), thereby preventing the rotation of the ball screw nut relative to the screw shaft, and the ball screw nut moving in the axial direction. The ball screw nut is prevented from coming off. The anti-rotation cap is put on when the ball screw device is assembled, and is removed when the ball screw device is attached to the device (for example, an actuator).

  The spline track of the ball spline is, for example, a pair that receives a clockwise rotation and a counterclockwise rotation, and a plurality of pairs (for example, three pairs) are provided. A plurality of (for example, three) ball receiving portions formed so as to protrude from the reference cylindrical surface are provided on the outer periphery of the screw shaft, and the clockwise and counterclockwise shoulder portions of the ball receiving portions are provided. , Respectively, a spline track is formed. Correspondingly, on the inner periphery of the ball spline outer cylinder, a spline track that faces the clockwise spline track of the ball receiving portion from the clockwise direction and a counterclockwise spline track of the ball receiving portion are counteracted. Spline tracks facing each other from the clockwise direction are formed. The balls circulate by rolling between a spline track formed on the screw shaft and a spline track formed on the outer cylinder.

  It is not necessary for the engaging convex portion that engages with the spline track provided on the detent cap to fit into all the spline tracks, but at least one of the plurality of spline tracks (for example, every other spline track). The spline track).

  The ball screw device according to the present invention may be used as an actuator (a configuration in which a hollow shaft and a ball screw nut are rotated by a motor, whereby the screw shaft moves linearly), and a shock absorber (the screw shaft is externally provided). In this case, the hollow shaft and the ball screw nut are rotated, and the electromagnetic force generated by the motor becomes a damping force.

  The ball screw nut is, for example, an end cap type (a pair of end caps are provided on both end surfaces of the ball screw nut in the axial direction, and a return passage penetrating the peripheral wall on the radially outer side of the ball screw raceway is formed in the ball screw nut. In addition, a groove-shaped direction changing path that connects the main passage and the return passage is formed on the end face of the end cap on the ball screw nut side). In addition to the end cap type, the ball screw nut may be a tube type in which the ball is circulated by a tube attached to the ball screw nut.

  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 screw nut may be made of bearing steel (SUJ2). The end cap is made of synthetic resin or steel.

  According to the ball screw device of the present invention, the ball screw nut and the anti-rotation cap cannot be rotated relative to each other, and the engaging projection provided on the anti-rotation cap is provided on the screw shaft. Engagement with the recess prevents rotation of the anti-rotation cap relative to the screw shaft, thereby preventing rotation of the ball screw nut relative to the screw shaft, and prevents the ball screw nut from moving linearly along the screw shaft. As a result, the ball screw nut is prevented from coming off from the end of the screw shaft.

FIG. 1 is a longitudinal sectional view showing a ball screw device according to a first embodiment of the present invention. FIG. 2A is a perspective view of a ball screw nut, and FIG. 2B is a perspective view of a detent cap. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a view showing a second embodiment of the ball screw device of the present invention, FIG. 4 (a) is a perspective view of a ball screw nut, and FIG. 4 (b) is a perspective view of a detent cap. is there.

  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 FIG.

  1 to 3 show a first embodiment of a ball screw device according to the present invention.

  The ball screw device (1) includes a ball screw raceway (2a) and a vertically extending steel screw shaft (2) provided with a spline raceway (2b), and a ball screw raceway (2) 2a), a rotatable steel ball screw nut (3) screwed together via a ball, and a screw shaft (2) fitted to the spline track (2b) via a ball on the lower end side of the screw shaft (2). ) With a ball spline outer cylinder (4) that guides the vertical (axial) linear motion, and a non-rotating cap (11) that is covered with the ball screw nut (3) in a relatively non-rotatable manner. ing.

  The ball screw nut (3) and the ball spline outer cylinder (4) are respectively provided with keys (5) and (6) for preventing rotation.

  The anti-rotation cap (11) has a cylindrical peripheral wall (12) and a top wall (13) formed with a through hole (14) inserted through the screw shaft (2). On the inner periphery of the peripheral wall (12), a key groove (engagement portion) (15) that fits into the key (5) of the ball screw nut (3) is provided at a predetermined position in the circumferential direction. ) And the key groove (15) are prevented from rotating relative to each other between the ball screw nut (3) and the locking cap (11). An engaging projection (16) that engages with the spline track (2b) of the screw shaft (2) is provided integrally with the periphery of the through-hole (14) of the top wall (13) of the locking cap (11). It has been. In the illustrated example, three engaging convex portions (16) are provided so as to be able to engage with every other spline track (2b) among the six spline tracks (2b) in total.

  According to the above-described ball screw device (1), the ball screw nut (3) and the non-rotating cap (11) cannot be rotated relative to each other, and the engagement provided on the non-rotating cap (11). Since the mating projection (16) is engaged with the spline track (concave) (2b) provided on the screw shaft (2), rotation of the non-rotating cap (11) with respect to the screw shaft (2) is prevented. This also prevents the ball screw nut (3) from rotating relative to the screw shaft (2) and prevents the ball screw nut (3) from moving linearly along the screw shaft (2). The ball screw nut (3) is prevented from coming off from the end of (2).

  FIG. 4 shows a second embodiment of the ball screw device (1) according to the present invention. The second embodiment is different from the first embodiment in the shapes of the ball screw nut (20) and the non-rotating cap (21), and the ball screw nut corresponding to FIG. Only the view of the anti-rotation cap (21) (FIG. 4 (b)) corresponding to the view of FIG. 20 (FIG. 4 (a)) and FIG. 2 (b) is shown.

  As shown in the figure, the anti-rotation cap (21) has a plate shape, and a through hole (24) inserted through the screw shaft (2) is formed at the center thereof.

  The ball screw nut (20) has a plurality of (three) coupling claws (22) extending in the axial direction and provided at predetermined intervals in the circumferential direction as a configuration for coupling instead of the keys (5) and (15). ), And can be coupled to a cylindrical member having a plurality of similar coupling claws.

  Corresponding to the shape of this ball screw nut (20), the coupling claw that fits between the coupling claw (22) of the ball screw nut (20) on the outer peripheral edge of the detent cap (21) (Engagement part) (23) is provided, and the relative rotation between the ball screw nut (20) and the non-rotating cap (21) is prevented by the engagement of these coupling claws (22) and (23). Has been.

  On the periphery of the through hole (24) of the locking cap (21), as in the first embodiment, the engaging projection (26) that engages with the spline track (2b) of the screw shaft (2). Are provided integrally.

  According to the ball screw device (1) having the ball screw nut (20) and the anti-rotation cap (21) shown in FIG. 4, the ball screw nut (20) and the anti-rotation cap (21) cannot be rotated relative to each other. And the engaging projection (26) provided on the anti-rotation cap (21) engages with the spline track (concave) (2b) provided on the screw shaft (2). The rotation of the locking cap (21) with respect to the screw shaft (2) is prevented, thereby preventing the rotation of the ball screw nut (20) with respect to the screw shaft (2). As a result, the ball screw nut (20) is prevented from coming off from the end of the screw shaft (2).

  In the above configuration, the ball screw nuts (3) (20) and the non-rotating caps (11) (21) are configured to be relatively non-rotatable, and the keys (5) (15) and the coupling claws (22) ( 23), but the ball screw nut (3) (20) may be provided with a bolt hole, and the columnar protrusion that fits into the bolt hole is provided with the key groove (15) or The caps (11) and (21) may be provided as engaging portions in place of the coupling claws (23), and various configurations may be employed according to the shape of the ball screw nut. In addition, as a configuration for engaging the non-rotating cap (11) (21) with the screw shaft (2), it is not necessary to use the spline track (2b) of the screw shaft (2). If there is a place other than) that can be prevented from rotating, an engaging convex portion that engages with that portion can be formed on the locking cap.

  The ball screw device (1) can be used as an electric actuator, and can also be used for an electromagnetic shock absorber.

(1) Ball screw device
(2) Screw shaft
(2a) Ball screw raceway
(2b) Spline track (concave)
(3) Ball screw nut
(4) Ball spline outer cylinder
(11) Non-rotating cap
(14) Through hole
(16) Engaging projection
(20) Ball screw nut
(21) Non-rotating cap
(24) Through hole
(26) Engaging projection

Claims (1)

A screw shaft provided with a ball screw raceway and a spline raceway, a ball screw nut screwed to the ball screw raceway of the screw shaft via a ball, and a ball spline outer tube fitted to the spline raceway of the screw shaft via a ball In a ball screw device comprising:
The ball screw nut is covered with a non-rotating cap having a through-hole inserted into the screw shaft so as not to be relatively rotatable and detachable, and is provided on the screw shaft at the periphery of the through-hole of the non-rotating cap. A ball screw device characterized in that an engaging convex portion that engages with the concave portion is provided integrally.

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