JP2019113169A - Linear motion actuator - Google Patents

Abstract

To provide a linear motion actuator improved in an aligning property in spline-connecting a linear motion element and a cylindrical body having a projection, and surely restricting axial movement of the cylindrical body to the linear motion element.SOLUTION: A projection 36 of a ball screw mechanism 20 is formed on an outer peripheral face of a cylindrical portion 35 on which a spline hole portion 35a is formed. The cylindrical portion spline-connects the spline hole portion from one end toward the other end of a spline shaft portion 32. A tooth bottom 39 disposed between shaft portion-side spline teeth of the spline shaft portion, includes a first tooth bottom 39a formed at one end side of the spline shaft portion, a second tooth bottom 39b formed at the other end side of the spline shaft portion while increasing a radial dimension, and an inclined tooth bottom 39c between the first tooth bottom and the second tooth bottom. The first booth bottom is spline-connected with a clearance to a tooth tip of the hole portion-side spline tooth of the spline hole portion, and the second tooth bottom is spline-connected in a state of an interference to the tooth tip of the hole portion-side spline tooth.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a linear motion actuator provided with a ball screw mechanism that converts rotational motion transmitted to a rotational motion element into linear motion.

A linear actuator of this type has a hole screw mechanism having a ball screw shaft and a ball screw nut screwed to the ball screw shaft through a large number of balls, and rotates one of the ball screw shaft and the ball screw nut. It is a motion element, and the other is a linear motion element that moves linearly.
Some of the linear actuators described above are provided with a stroke limiting mechanism in order to limit axial movement of the linear motion element (e.g., Patent Document 1).

The linear actuator described in Patent Document 1 has a ball screw mechanism having a ball screw portion of a ball screw shaft which is a linear motion element, and a ball screw nut which is a rotational movement element which is screwed to this via a plurality of balls. A device having
In the stroke limiting mechanism of Patent Document 1, a projection projecting in the radial direction is provided on a shaft portion provided coaxially with the ball screw portion of the ball screw shaft, and the ball screw nut When the ball screw shaft is stroked in the shrinking direction by the rotation of the ball screw nut, the projection abuts the locking portion at a predetermined position, and the rotation of the ball screw nut is restricted, and the stroke of the ball screw shaft Limit.

Further, the projection is formed so as to protrude in the radial direction from the outer peripheral surface of the cylindrical portion in which the spline hole is formed on the inner peripheral surface.
A splined shaft portion is formed on the outer periphery of the shaft portion of the ball screw shaft, and the spline hole of the cylindrical portion is splined to the splined shaft portion of the shaft portion to restrict circumferential movement of the cylindrical portion with respect to the shaft portion. ing. Moreover, the axial direction movement of the cylindrical part with respect to an axial part is controlled by providing caulking parts in a plurality of places of a peripheral direction of a part of spline shaft part protruded from a cylindrical part.

Patent No. 5293887

By the way, if the stroke limiting mechanism of Patent Document 1 improves the centering property so that the axial center of the shaft portion of the ball screw shaft and the axial center of the cylindrical portion coincide with each other, the spline shaft portion and the spline hole are not spline-connected. It does not. In order to improve such alignment, it is necessary to process both spline teeth with high accuracy, which may increase the manufacturing cost.
Moreover, although patent document 1 provides a caulking part in a part of spline shaft part which has protruded from the cylindrical part, and restrict | limits axial movement of the cylindrical part with respect to a shaft part, restriction of axial movement of a cylindrical part is restrained. Manufacturing cost is further increased because of the increase in the number of processing steps.
Therefore, the present invention can improve the alignment when spline-coupling the shaft portion of the linear motion element and the cylindrical body provided with the projection, and ensure the axial movement of the cylindrical body with respect to the shaft portion. It is an object of the present invention to provide a linear actuator which can be restrained and can realize these while reducing the manufacturing cost.

  In order to achieve the above object, a linear actuator according to an aspect of the present invention includes a rotary motion element and a linear motion element, and converts a ball screw mechanism that converts rotational motion transmitted to the rotary motion element into linear motion. The ball screw mechanism has a projection provided on the linear motion element. The projection is formed on the outer peripheral surface of a cylindrical portion having a spline hole formed on the inner peripheral surface, and the cylindrical portion is splined from one end of the spline shaft formed on the outer periphery of the linear motion element toward the other end The hole is fixed to the linear motion element by spline connection. And the tooth base provided between the shaft part side spline teeth of the spline shaft part is the first tooth base formed on one end side of the spline shaft part, and the first tooth base on the other end side of the spline shaft part And a second tooth base formed with a larger radial dimension. Then, at one end side of the spline shaft portion, the first tooth bottom is splined while providing a gap with the tooth tip of the hole side spline tooth of the spline hole portion, and at the other end side of the spline shaft portion, the second At least a part of the tooth bottom is splined in an interference state with the tips of the hole side spline teeth.

  ADVANTAGE OF THE INVENTION According to the linear motion actuator which concerns on this invention, the centering property at the time of carrying out spline connection of the axial part of a linear motion element, and the cylindrical body which provided protrusion can be improved. In addition, axial movement of the cylindrical body with respect to the shaft portion can be reliably restrained. And, the improvement of the alignment performance and the restraint of the axial movement of the cylindrical body with respect to the shaft portion can be realized while reducing the manufacturing cost.

It is a front view showing a direct-acting actuator of a 1st embodiment concerning the present invention. It is a side view of FIG. It is sectional drawing on the AA line of FIG. It is sectional drawing on the BB line of FIG. It is a figure showing a ball screw nut, and (a) is a perspective view, (b) is a front view, (c) is a side view, and (d) is a sectional view on the DD line of (c). It is a figure which shows the principal part of a ball screw axis, and (a) is a figure which expanded and showed an involute spline shaft part, (b) is a sectional view on the EE line of (a). It is a figure which shows a rotation prevention member, Comprising: (a) is a perspective view, (b) is a front view, (c) is a principal part enlarged view of a front view, (d) is sectional drawing. It is a front view of a ball screw mechanism.

  Next, a first embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimension, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that parts having different dimensional relationships and ratios among the drawings are included.

In addition, the first embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention includes materials, shapes, and structures of component parts. , Arrangement, etc. are not specified to the following. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.
In addition, the term which shows directions, such as "upper", "lower", "bottom", "front", "rear", etc. which are described by the following description is used with reference to the direction of an attached drawing.

[Configuration of Linear Actuation Actuator of First Embodiment]
1 is a front view showing the linear motion actuator according to the first embodiment, FIG. 2 is a side view, FIG. 3 is a sectional view taken along line AA of FIG. 1, and FIG. 4 is a sectional view taken along line BB of FIG. It is.
In the figure, reference numeral 10 denotes a linear actuator, and the linear actuator 10 has a main housing 11A and a sub housing 11B which are both die-casted of, for example, aluminum or an aluminum alloy.
As shown in FIG. 3, the main housing 11A has a motor mounting portion 13 for mounting the electric motor 12 on the front side, and a ball for mounting the ball screw mechanism 20 disposed parallel to the motor mounting portion 13 on the back side. And a screw mechanism mounting portion 14. The motor mounting portion 13 and the ball screw mechanism mounting portion 14 are formed such that central axes thereof are parallel to each other.

The motor mounting portion 13 is, as shown in FIG. 3, a flange mounting portion 13a for mounting a mounting flange 12a of the electric motor 12 formed on the front side and an electric motor 12 formed on the rear side of the flange mounting portion 13a. A large diameter hole portion 13b for inserting the large diameter portion 12b, a small diameter hole portion 13c for inserting the small diameter portion 12c of the electric motor 12 communicated with the back surface side of the large diameter hole portion 13b, and a back surface side of the small diameter hole portion 13c And a pinion housing 13d communicating with the motor.
The ball screw mechanism mounting portion 14 communicates with the ball screw mechanism storage portion 14a formed at a position corresponding to the small diameter hole portion 13c of the motor mounting portion 13 formed on the back side, and communicates with the ball screw mechanism storage portion 14a It has the cylindrical part 14b to extend, and the seal | sticker accommodating part 14c connected to the front end of this cylindrical part 14b.

  As shown in FIG. 3, the sub housing 11B is configured to cover the pinion housing 13d and the ball screw mechanism housing 14a formed on the back side of the main housing 11A. The sub-housing 11B forms the pinion housing 16 and the ball screw mechanism housing 17 corresponding to the pinion housing 13d and the ball screw mechanism housing 14a of the main housing 11A, and further forms the breather 18 on the lower side. . Here, the ball screw mechanism accommodating portion 17 is formed with an accommodating cylindrical portion 17 a on the back side. The thrust needle bearing 17b is disposed at a position where the thrust needle bearing 17b contacts the axial end face of the accommodation cylindrical portion 17a, which will be described later.

As shown in FIG. 3, the electric motor 12 has a pinion gear 15 mounted on the tip of its output shaft 12d. Then, the electric motor 12 is mounted on the motor mounting portion 13. The electric motor 12 is mounted by inserting the electric motor 12 into the motor mounting portion 13 from the side of the pinion gear 15 and mounting the mounting flange 12a to the flange mounting portion 13a in a state where the pinion gear 15 is stored in the pinion storage portion 13d. Do.
On the other hand, as shown in FIG. 4, the ball screw mechanism 20 is a ball screw rotatably supported by rolling bearings 21a and 21b with seals in the ball screw mechanism accommodating portions 14a and 17 of the main housing 11A and the subhousing 11B. A nut 22 and a ball screw shaft 24 screwed to the ball screw nut 22 via a large number of balls 23 are provided.

  As shown in FIG. 5, the ball screw nut 22 is constituted by a nut cylindrical member 25 in which a ball screw groove 25a and a ball circulating groove 25b are formed on the inner peripheral surface. Here, as a ball circulation method of the ball screw nut 22, as shown in FIG. 5D, for example, an S-shaped circulation groove 25b in which one ball circulating portion exists in one turn is integrated with the ball screw nut 22. The form formed in is adopted. The circulation groove 25b is formed by cold forging, and the ball screw groove 25a is formed by cutting.

  The nut cylindrical member 25 is rotatably supported by the ball screw mechanism accommodating portion 14a via rolling bearings 21a and 21b at both axial end sides of the outer peripheral surface. A driven spline shaft 25c is formed between the inner rings of the rolling bearings 21a and 21b on the outer peripheral surface of the nut cylindrical member 25. Furthermore, when viewed from the front, a fan-shaped convex locking portion 25 d is integrally formed on the front end surface of the nut cylindrical member 25 so as to protrude. Here, the circumferential side surface of the convex locking portion 25d is a flat surface.

Further, as shown in FIG. 3, the nut cylindrical member 25 splines the driven gear 26 to the driven spline shaft 25c. The driven gear 26 meshes with a pinion gear 15 mounted on the output shaft 12 d of the electric motor 12. The driven gear 26 has an involute spline hole 26 a formed on the inner peripheral surface thereof for meshing with the driven spline shaft 25 c.
As shown in FIG. 4, the ball screw shaft 24 is mounted on a cylindrical portion 14b formed in the main housing 11A and a storage cylindrical portion 17a formed in the sub housing 11B.

The ball screw shaft 24 has a ball screw portion 31 formed on the rear end side (right side in FIG. 4) from the axial center portion, and a ball connected to the front end side (left side in FIG. 4) of the ball screw portion 31. The involute spline shaft portion 32 having a diameter smaller than that of the screw portion 31 and the connecting shaft portion 33 having a smaller diameter than the involute spline shaft portion 32 connected to the front end of the involute spline shaft portion 32 ing.
The involute spline shaft portion 32 of the ball screw shaft 24 has a bottom 39 formed between the plain teeth 38, as shown in FIG.

As shown in FIG. 6B, the first tooth bottom 39a is formed along the axial direction on the connecting shaft 33 side, and the diameter of the tooth bottom 39 is larger than the first tooth bottom 39a on the ball screw 31 side. The second tooth base 39b having a larger diameter is formed, and the diameter is gradually increased between the first tooth base 39a and the second tooth base 39b from the first tooth base 39a side to the second tooth base 39b side The tooth bottom 39c is formed.
And, a plurality of tooth bases 39 of the above-mentioned configuration are formed at a position of axial symmetry centering on the axis of the involute spline shaft 32.

As shown in FIG. 3, a detent member 34 is splined to the involute spline shaft portion 32 of the ball screw shaft 24.
The anti-rotation member 34 is, as shown in FIG. 7, a cylindrical portion 35 having an involute spline hole 35a formed on the inner peripheral surface, and a stopper 36 formed on the outer peripheral surface of the cylindrical portion 35 and projecting radially outward. And.
The stopper 36 is a portion that protrudes in a rectangular shape when viewed from the axial direction, and includes a first stopper side surface 36 a and a second stopper side surface 36 b that rise at circumferentially spaced apart positions on the outer peripheral surface of the cylindrical portion 35; The first and second stopper side surfaces 36a and 36b have stopper end surfaces 36c connected at the rising edges.

The first stopper side surface 36a is a flat surface, and the side surface of the convex locking portion 25d of the ball screw nut 22 as a circumferential flat surface abuts in a surface contact state at a stroke end described later.
Note that both the first stopper side surface 36a and the side surface in the circumferential direction of the ridge engaging portion 25d are not limited to flat surfaces, and may be cylindrical surfaces or curved surfaces of spherical surfaces.
The second stopper side surface 36 b is formed as a slope surface in which the distance to the first stopper side surface 36 a gradually increases from the stopper end surface 36 c toward the outer peripheral surface of the cylindrical portion 35.

As shown in FIG. 7B, a position where the first stopper side surface 36a intersects with the outer peripheral surface of the cylindrical portion 35 is taken as a first intersection position 43a, and a position where the second stopper side surface 36b intersects with the outer peripheral surface of the cylindrical portion 35. As the second intersection position 43b.
Thus, the stopper 36 has a width dimension in the axis orthogonal direction of the stopper end face 36c as a, and a width dimension in the axis orthogonal direction of the base end side of the stopper 36 between the first intersection position 43a and the second intersection position 43b. Then, they are formed to have a relationship of a <b.

7C, the center of gravity of the stopper 36 is G, the height from the base end of the stopper 36 to the center of gravity G is e1, and the height from the center of gravity G to the end surface 36c of the stopper Assuming that the dimension is e2, they are formed to have a relationship of e1 <e2.
Further, as shown in FIG. 7D, when the axial dimension of the cylindrical portion 35 is L1 and the axial dimension of the stopper 36 is L2, the rotation preventing member 34 has a relationship of L1> L2 In addition, the stopper 36 is formed at a position close to the one end side opening of the cylindrical portion 36.

The involute spline hole portion 35 a of the cylindrical portion 35 is spline-connected to the involute spline shaft portion 32 of the ball screw shaft 24 in the rotation preventing member 34 configured as described above.
Then, as shown in FIG. 3 and FIG. 8, when the stopper 36 of the rotation preventing member 34 abuts against the ridge engaging portion 25d of the ball screw nut 22, the ball screw shaft 24 is in the stroke end position in the contraction direction. Become.
As shown in FIG. 4, the axial length of the ball screw nut 22 is set to substantially the same size as the axial length of the ball screw portion 31 of the ball screw shaft 24, and the ball screw shaft 24 is at the stroke end position in the contraction direction. When moved, the entire area of the ball screw portion 31 is accommodated in the ball screw nut 22.

Further, as shown in FIG. 4, a guide member 40 is attached to the inner peripheral surface of the cylindrical portion 14b of the main housing 11A.
The guide member 40 is a cylindrical body formed by cutting in the axial direction in a plane along a chord equal to or less than the diameter of the circle when the cylinder is viewed in cross section, and a guide groove 40c is formed along the axial direction .
The guide member 40 is held inside a support hole 41a formed in the cylindrical portion 14b of the main housing 11A. The stopper 36 of the rotation prevention member 34 of the ball screw shaft 24 is engaged with the guide groove 40c.
Further, on the outer peripheral surface on the front end side of the guide member 40, an engagement groove 40d is formed which engages with the protrusion 41c of the support hole 41a in the circumferential direction.
Further, in the main housing 11A, a seal 50 which is in sliding contact with the outer peripheral surface of the connecting shaft portion 33 of the ball screw shaft 24 is mounted on the seal accommodating portion 14c of the ball screw mechanism mounting portion 14. doing.

  Here, the rotary motion element described in the present invention corresponds to the ball screw nut 22, and the linear motion element described in the present invention corresponds to the ball screw shaft 24. Further, the cylindrical body described in the present invention corresponds to the cylindrical portion 35, and the fixing portion described in the present invention corresponds to the ball screw mechanism mounting portion 14. Further, the spline shaft portion described in the present invention corresponds to the involute spline shaft portion 32, and the spline hole portion described in the present invention corresponds to the involute spline hole portion 35a, and the shaft described in the present invention Part side spline teeth correspond to the spline teeth 38.

[Assembling method of linear actuator according to the first embodiment]
Next, a method of assembling the linear motion actuator 10 of the first embodiment will be described.
The ball screw mechanism 20 used in the linear motion actuator 10 is transported in advance to the assembly plant in a unitized state at the manufacturing plant.
In the united ball screw mechanism 20, the involute spline hole 35a of the cylindrical portion 35 of the rotation preventing member 34 is splined to the involute spline shaft 32 of the ball screw shaft 24.
Further, grease is applied to the ball screw portion 31 of the ball screw shaft 24 and screwed into the ball screw nut 22 via the ball 23.

Then, the ball screw shaft 24 is moved to and held at the stroke end position in the contraction direction so that the entire area of the ball screw portion 31 of the ball screw shaft 24 is accommodated in the ball screw nut 22.
Here, the method for fixing the rotation prevention member 34 to the ball screw shaft 24 is to insert the connecting shaft portion 33 into the cylindrical portion 35 of the rotation prevention member 34, and then to move the involute spline hole portion 35a of the cylindrical portion 35 to the involute spline shaft. The connecting shaft portion 33 of the portion 32 is fitted.
At this time, the cylindrical portion 35 is a ball while providing a gap between the tooth tips of the hole side spline teeth (not shown) of the involute spline hole portion 35a and the first tooth bottom 39a of the tooth bottom 39 of the involute spline shaft portion 32. It moves to the screw part 31 side.

When the cylindrical portion 35 further moves toward the ball screw portion 31, the tips of the spline teeth on the hole portion side of the involute spline hole portion 35a are fitted to the inclined tooth bottom 39c in a state of being press-fitted.
Then, when the cylindrical portion 35 moves to the end on the ball screw 31 side of the involute spline shaft 32, the tip of the hole side spline tooth of the involute spline hole 35a is crimped to the second bottom 39b. It will be fitted.
Therefore, the rotation preventing member 34 is made non-rotatable with respect to the ball screw shaft 24 by the spline connection, and the spline of the involute spline hole 35a is crimped to the second tooth bottom 39b of the involute spline shaft 32. Thus, the axial movement of the ball screw shaft 24 is restrained and fixed to the ball screw shaft 24.
Then, in the assembling method of the linear motion actuator 10, first, the guide member 40 is mounted and held in the support hole 41a of the main housing 11A.

Next, with the engagement groove 40d of the guide member 40 facing the projection 41c of the support hole 41a, the guide member 40 is inserted into the support hole 41a to engage the projection 41c in the engagement groove 40d. And the guide member 40 which has blocked the axial movement inside the support hole 41a.
Next, the driven gear 26 is splined to the outer peripheral surface of the nut cylindrical member 25 of the ball screw nut 22 of the unitized ball screw mechanism 20, and the rolling bearings 21a and 21b are mounted on both sides thereof. And 21b fix the driven gear 26 by the inner ring.

Next, the ball screw mechanism 20 is inserted into the ball screw mechanism accommodating portion 14a of the main housing 11A from the connecting shaft portion 33 side, and the stopper 36 is engaged with the guide groove 40c of the guide member 40 attached to the main housing 11A.
Next, the outer ring of the rolling bearing 21a is fitted into the inner peripheral surface of the ball screw mechanism housing 14a, and is stored in the driven gear 26 ball screw mechanism housing 14a, completing the mounting of the ball screw mechanism 20 on the main housing 11A. Do.

Next, the electric motor 12 is inserted into the motor mounting portion 13 of the main housing 11A from the side of the pinion gear 15, and the pinion gear 15 is meshed with the driven gear 26 of the ball screw mechanism 20. Then, the mounting flange 12a of the electric motor 12 is bolted to the flange mounting portion 13a.
The attachment of the electric motor 12 to the main housing 11A may be performed before the attachment of the ball screw mechanism 20 to the main housing 11A.
Thus, when the mounting of the electric motor 12 and the ball screw mechanism 20 to the main housing 11A is completed, the sub-housing 11B is mounted on the back side of the main housing 11A via a packing (not shown) and fixed by fixing means such as bolting. Then, the seal 50 is inserted into the seal storage portion 14c of the main housing 11A and the snap ring 51 prevents the seal 50 from being removed, thereby completing the assembly of the linear actuator 10.

[Operation of Linear Motion Actuator of First Embodiment]
In this state, consider a case where the electric motor 12 is rotationally driven to transmit rotational driving force from the pinion gear 15 to the driven gear 26, and the ball screw nut 22 is rotated clockwise as viewed in FIG. 8, for example. In this case, the rotational force of the ball screw nut 22 is transmitted to the ball screw shaft 24 through the ball 23 so that the ball screw shaft 24 tends to rotate clockwise in the same direction as the ball screw nut 22.
At this time, the stopper 36 of the anti-rotation member 34 fixed to the ball screw shaft 24 also tries to rotate clockwise, but since the stopper 36 is engaged in the guide groove 40c of the guide member 40 Rotation of the direction is restricted. For this reason, the rotation prevention member 34 exerts a rotation prevention function of the ball screw shaft 24 by regulating the rotation of the stopper 36.

Then, by continuing to turn the ball screw nut 22 clockwise as seen in FIG. 8, the ball screw shaft 24 moves without turning leftward as seen in FIGS. 3 and 4. At this time, the stopper 36 moves while sliding in the guide groove 40 c of the guide member 40.
Thereafter, when the ball screw nut 22 continues to rotate clockwise as viewed in FIG. 8 and the ball screw shaft 24 reaches a desired forward position, the electric motor 12 is stopped to move the ball screw shaft 24 forward. Stop.
On the other hand, when the ball screw nut 22 is rotated counterclockwise in FIG. 8 by reversely driving the electric motor 12 from the state where the ball screw shaft 24 has reached the desired forward position, the ball screw shaft 24 Since the stopper 36 is engaged with the guide groove 40c of the guide member 40, it is retracted without being rotated in the axial direction while being detented. At this time, the stopper 36 moves while sliding in the guide groove 40 c of the guide member 40.

Then, when the stopper 36 fixed to the ball screw shaft 24 receding in the axial direction and the convex locking portion 25 d of the ball screw nut 22 rotating in the counterclockwise direction face in the circumferential direction, As shown in FIG. 8, the first stopper side surface 36 a of the stopper 36 abuts on the convex locking portion 25 d.
As described above, when the first stopper side surface 36a of the stopper 36 and the convex locking portion 25d of the ball screw nut 22 abut each other in a surface contact state, further reverse rotation of the ball screw nut 22 is restricted. The axis 24 reaches the stroke end position in the direction of contraction.
At the stroke end position in the contraction direction, the entire area of the ball screw portion 31 is accommodated in the ball screw nut 22.

[Operation and effect of linear actuator according to the first embodiment]
Next, the operation and effect of the linear motion actuator 10 of the first embodiment will be described.
When securing the detent member 34 to the ball screw shaft 24, after inserting the connecting shaft portion 33 into the cylindrical portion 35 of the detent member 34, the involute spline hole portion 35 a of the cylindrical portion 35 is connected to the involute spline shaft portion 32. The shaft portion 33 is fitted.
At this time, the tips of the spline teeth on the hole side of the involute spline hole 35a are the first tooth bottoms of the plurality of tooth bases 39 formed in a plurality of axially symmetrical positions about the axis of the involute spline shaft 32. It moves to the ball screw 31 side while providing a gap between it and 39a. As a result, the cylindrical portion 35 moves toward the inclined tooth bottom 39 c while being corrected so that the axis of the cylindrical portion 35 matches the axis of the involute spline shaft portion 32.

As a result, it is possible to improve the alignment performance when the cylindrical portion 35 is splined to the involute spline shaft portion 32.
In addition, when the cylindrical portion 35 is moved to the ball screw portion 31 side, the tip of the hole-side spline tooth of the involute spline hole 35a slides on the inclined tooth bottom 39c and is gradually press-fitted. The tooth root 39 b is crimped, and the axial movement of the ball screw shaft 24 is restrained and fixed to the ball screw shaft 24.
Thus, axial movement of the cylindrical portion 35 can be reliably restrained with respect to the involute spline shaft portion 32.
And, even if the spline teeth 38 of the involute spline shaft 32 and the hole side spline teeth of the involute spline hole 35a are not formed with high accuracy, the alignment of the cylindrical portion 35 and the involute spline shaft 32 is enhanced. As a result, manufacturing costs can be reduced.

In the first embodiment, the tooth base 39 (the first tooth base 39a, the second tooth base 39b and the inclined tooth base 39c) formed between the plain teeth 38 of the involute spline shaft 32 is an involute spline shaft in the first embodiment. Although a plurality is formed at the position of axial symmetry centering on the axis line of the part 32, if formed between the plain teeth 38 of the entire circumference of the involute spline shaft 32, the alignment can be further improved.
Further, in the first embodiment, the case where the ball screw nut 22 is rotationally driven by the electric motor and the ball screw shaft 24 is a linear motion element has been described, but the present invention is not limited thereto. The present invention can be applied to the case where the screw shaft 24 is a rotational movement element rotated by a rotational drive source, and the ball screw nut 22 is a linear movement element.

10 linear actuator 11A main housing 11B sub housing 12 electric motor 12a mounting flange 12b large diameter portion 12c small diameter portion 12d output shaft 13 motor mounting portion 13a flange mounting portion 13b large diameter hole portion 13c small diameter hole portion 13d pinion housing portion 14 ball screw Mechanism mounting portion 14a Ball screw mechanism storage portion 14b Cylindrical portion 14c Seal storage portion 15 Pinion gear 16 Pinion storage portion 17 Ball screw mechanism storage portion 17a Storage cylindrical portion 17b Thrust needle bearing 18 Breather 20 Ball screw mechanism 21a, 21b Rolling bearing 22 Ball screw Nut 23 Ball 24 Ball screw shaft 25 Nut cylindrical member 25a Ball screw groove 25b Ball circulation groove 25c Driven spline shaft 25d Convex locking portion 26 Driven gear 26a Involute spline hole 31 Roll screw 32 Involute spline shaft 33a Two-sided width 33 Connecting shaft 34 Rotation stop member 35 Cylindrical portion 35a Involute spline hole 36 Stopper 36a First stopper side 36b Second stopper side 36c Stopper end face 38 Involute spline shaft Spline teeth 39 Tooth bottom 39a First tooth bottom 39b Second tooth bottom 39c Angled tooth bottom 43a First intersection position 43b Second intersection position 40c Guide groove 40d Engagement groove 41a Support hole 41c Projection 50 Seal 51 Retaining ring a Stopper end face Width in the direction perpendicular to the axis b Width in the direction perpendicular to the axis on the proximal side of the stopper G Center of gravity position of the stopper e1 Height from the base of the stopper to the center of gravity e2 Height from the center of gravity to the end of the stopper L1 Axial dimension of cylindrical part L2 Axial dimension of stopper

Claims (4)

A ball screw mechanism having a rotational movement element and a linear movement element, and converting the rotational movement transmitted to the rotational movement element into a linear movement;
The ball screw mechanism has a projection provided on the linear motion element,
The projection is formed on an outer peripheral surface of a cylindrical portion in which a spline hole is formed on an inner peripheral surface,
The cylindrical portion is fixed to the linear motion element by spline-connecting the spline hole portion from one end of the spline shaft portion formed on the outer periphery of the linear motion element to the other end,
The tooth base provided between the shaft side spline teeth of the spline shaft is:
A first tooth bottom formed on the one end side of the spline shaft portion, and a second tooth bottom formed on the other end side of the spline shaft portion so as to have a radial dimension larger than that of the first tooth bottom; Equipped with
At one end side of the spline shaft portion, the first tooth bottom is splined while providing a gap between the first tooth bottom and the tip end of the hole side spline tooth of the spline hole portion,
A linear motion actuator characterized in that at the other end side of the spline shaft portion, at least a part of the second tooth bottom is splined in an interference state with the tip of the hole side spline tooth.   Between the first tooth base and the second tooth base, there is provided an inclined tooth base formed by gradually increasing the radial dimension from the first tooth base to the second tooth base. The linear motion actuator according to claim 1, characterized in that:   The shaft-side spline teeth provided with the first tooth bottom, the inclined tooth bottom, and the second tooth bottom are between the shaft-side spline teeth at positions axially symmetrical with respect to the axial center of the spline shaft. The linear motion actuator according to claim 1 or 2, wherein the linear motion actuator is formed.   The shaft side spline tooth provided with the first tooth bottom, the inclined tooth bottom and the second tooth bottom is formed between the shaft side spline teeth of the entire circumference of the spline shaft. The linear motion actuator according to claim 1 or 2.

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