JP2019113167A - Linear motion actuator and assembling method of linear motion actuator - Google Patents

Abstract

To provide a linear motion actuator capable of securing strength of a projection to rotary torque received from a rotary motion element, and being miniaturized.SOLUTION: A ball screw mechanism 20 includes one projection 36 formed integrally with a cylindrical body 35 fixed to a shaft portion 32 of a linear motion element 24, and projecting radially outward from an outer peripheral face of the cylindrical body. The projection has a projection restriction face 36a for locking rotary motion of a rotary motion element by being kept into contact with a locking portion 25d formed on the rotary motion element 22 at a stroke end in a contraction direction, of the linear motion element. When observing the shaft portion from an axial direction, a thickness between the projection restriction face and a back face 36b in a circumferential direction to the projection restriction face is formed large at a basic end of a cylindrical body side with respect to a tip end in a radial direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a linear motion actuator including a mechanism for converting rotational motion transmitted to a rotary motion element into linear motion, and a method of assembling the linear motion actuator.

Some linear actuators of this type are provided with a stroke limiting mechanism to limit the axial movement of the linear motion element (e.g., Patent Documents 1 and 2).
The linear motion actuator described in Patent Document 1 has a stopper pin fixed by press fitting in a direction orthogonal to the axis of operation of a linear motion element, and a locking portion (see FIG. In patent document 1, it describes as a stopper). In the stroke limiting mechanism of Patent Document 1, the actuating shaft to which the rotational force is transmitted from the rotor moves in the axial direction, and the stopper pin abuts against the locking surface of the rotor, thereby restricting the rotation of the rotor. Limit the stroke.

  In addition, the linear actuator described in Patent Document 2 has a ball screw portion of a ball screw shaft which is a linear motion element, and a ball screw nut which is a rotational motion element which is screwed to this via a plurality of balls. It is a device having a screw mechanism. The stroke limiting mechanism of Patent Document 2 is provided with a projection that protrudes in the radial direction on the shaft portion of the ball screw shaft, and a locking portion (described as a stopper portion in Patent Document 1) is provided on the ball screw nut. Thus, when the ball screw shaft is made to stroke in the shrinking direction, the projection abuts on the locking portion at a predetermined position, the rotation of the ball screw nut is restricted, and the stroke of the ball screw shaft is limited.

JP, 2013-204697, A Patent No. 5293887

By the way, when receiving the rotational torque from the engaging part provided in the rotor, the stroke limiting mechanism of Patent Document 1 needs to secure the strength of the stopper pin pressed into the actuating shaft.
As a method of securing the strength of the stopper pin, it is conceivable to press in the stopper pin with the increased diameter on the actuating shaft, but in order to firmly press-hold the stopper pin with the increased diameter, the shaft diameter of the actuating shaft is also It must be increased. Thus, according to Patent Document 1, in order to secure strength against rotational torque from the rotary motion element, the shaft diameter of the stopper pin and the actuating shaft must be increased. There is a problem in terms of

In addition, the linear motion actuator provided with the stroke limiting mechanism of Patent Document 2 has a problem in adhesion and damage of contamination when transporting each part to the assembly plant.
That is, in the ball screw mechanism of Patent Document 2, since the axial length of the ball screw nut is short with respect to the ball screw shaft, the thread groove of the ball screw shaft is exposed to the outside when transporting the ball screw mechanism to the assembly plant. In many cases, contamination is attached, or some foreign matter is attached to the screw groove and a scratch is easily generated.

  Therefore, an object of the present invention is to provide a linear motion actuator capable of securing the strength of a protrusion against rotational torque received from a rotational motion element and achieving downsizing. Another object of the present invention is to provide a method of assembling a linear actuator capable of reliably preventing the entry of contamination into the interior of a ball screw mechanism and the occurrence of flaws in a screw groove when the linear actuator is assembled. And

  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. Have. The ball screw mechanism is integrally formed with a cylindrical body fixed to the shaft portion of the linear motion element, and has one protrusion radially projecting from the outer peripheral surface of the cylindrical body. The projection is formed with a projection restricting surface for restricting the rotational movement of the rotational movement element by the abutment of the locking portion formed on the rotational movement element at the stroke end of the linear movement element in the contraction direction. When viewed from the direction, the thickness between the protrusion restricting surface and the circumferential rear surface with respect to the protrusion restricting surface is such that the base end on the cylindrical body side is formed larger than the tip end in the radial direction.

  Further, in the method of assembling a linear motion actuator according to one aspect of the present invention, the ball screw mechanism is housed in a cylindrical ball screw nut as a rotational movement element and housed inside the ball screw nut via a large number of balls. And a ball screw shaft as the linear motion element coaxially provided with a screw-engaged ball screw portion and a shaft portion for spline-coupling a tubular body. The ball screw portion is positioned at the stroke end in the direction of contraction, and the entire axial length of the ball screw portion is unitized in a state housed in the ball screw nut, and the ball screw nut of this unitized ball screw mechanism The outer periphery of the housing is rotatably supported by the housing, and the rotational drive source is connected and assembled so that the rotational force is transmitted to the ball screw nut.

According to the linear motion actuator of the present invention, the strength of the projection can be secured against the rotational torque received from the rotary motion element, and the linear motion actuator can be miniaturized. According to the method of assembling the actuator, it is possible to assemble the linear actuator by reliably preventing contamination from entering the inside of the ball screw mechanism and the occurrence of flaws in the screw groove.

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, as shown in FIG. 6, tooth bases 39 of the same shape formed between the spline teeth 38.
As shown in FIG. 6 (b), the first tooth base 39 a is formed along the axial direction on the connecting shaft 33 side, and the diameter of the tooth base 39 is larger than that of the first tooth base 39 a on the ball screw 31 side. A large second tooth base 39b is formed, and between the first tooth base 39a and the second tooth base 39b, the inclined teeth gradually increase in diameter from the first tooth base 39a side to the second tooth base 39b side. A bottom 39c is formed.
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.
At this time, the splines of the involute spline hole portion 35 a of the cylindrical portion 35 are crimped to the second tooth bottom 39 b of the tooth bottom 39 of the involute spline shaft portion 32. 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 ball screw shaft 24 can not be moved in the axial direction and is fixed to the ball screw shaft 24.

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 shaft portion described in the present invention corresponds to the involute spline shaft portion 32, the cylindrical body described in the present invention corresponds to the cylindrical portion 35, and the fixing portion described in the present invention is a ball. It corresponds to the screw mechanism mounting portion 14. Further, the locking portion described in the present invention corresponds to the convex locking portion 25d, the protrusion described in the present invention corresponds to the stopper 36, and the protrusion regulating surface described in the present invention is the first. 1 corresponds to the stopper side surface 36a. Furthermore, the back surface in the circumferential direction with respect to the protrusion restricting surface described in the present invention corresponds to the second stopper side surface 36b, and the housing described in the present invention corresponds to the storage cylindrical portion 17a of the sub housing 11B. The rotational drive source described in corresponds to the electric motor 12.

[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. As a specific method of this holding, there is a method of temporarily joining the first stopper side surface 36a of the stopper 36 shown in FIG. 8 and the convex locking portion 25d of the ball screw nut 22 by joining means, etc. is there.
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.

[Linear actuator of the first embodiment and effects in assembling]
Next, the operation and effect of the linear motion actuator 10 of the first embodiment will be described.
According to the linear actuator 10 of the first embodiment, when the electric motor 12 is reversely driven, the ball screw shaft 24 is prevented from rotating since the stopper 36 is engaged with the guide groove 40c of the guide member 40. It retreats in the axial direction while being done. Then, when the ball screw shaft 24 reaches the stroke end position in the shrinking direction, the stopper 36 of the anti-rotation member 34 fixed to the ball screw shaft 24 is convexly engaged with the ball screw nut 22 which rotates counterclockwise. The large rotational torque is received from the portion 25 d to stop the rotation of the ball screw nut 22.

Here, the cylindrical portion 35 in which the stopper 36 is integrally formed is fixed to the involute spline shaft portion 32 of the ball screw shaft 24 by spline connection, and a hole or the like for allowing the stopper member to pass through the shaft as in the conventional device. There is no need to increase the shaft diameter to increase the strength of the ball screw shaft 24. Therefore, the linear actuator 10 can be downsized by suppressing the increase in size of the ball screw shaft 24.
Further, since the stopper 36 has a shape in which the width dimension b at the proximal end side is larger than the width dimension a at the distal end side (see FIG. 7B), a large rotational torque is generated from the convex locking portion 25d. Even in this case, it becomes a highly rigid member that can receive rotational torque reliably.

  Further, the stopper 36 has a shape in which the width dimension b on the proximal end side is larger than the width dimension a on the distal end side, and the position of the center of gravity G of the stopper 36 is half the height dimension e2 of the stopper 36 Further, the cross section coefficient can be set large because it is positioned closer to the cylindrical portion 35 (see FIG. 7C). Thus, the stopper 36 having a large cross section coefficient can be formed as a small part, and the arrangement space of the stopper 36 can be reduced, so that the linear actuator 10 can be miniaturized.

Further, in the detent member 34, the axial dimension L1 of the cylindrical portion 35 is set larger than the axial dimension L2 of the stopper 36 (see FIG. 7D), and the rotational torque received by the stopper 36 is dispersed by the cylindrical portion 35. As a result, it is possible to provide a highly rigid member capable of receiving an even larger rotational torque.
Furthermore, since the first stopper side surface 36a of the stopper 36 and the convex locking portion 25d contact in a surface contact state, it is possible to disperse the collision energy at the time of the contact over the entire contact surface.

On the other hand, the effect at the time of assembling the direct acting actuator 10 of 1st Embodiment is demonstrated.
The ball screw mechanism 20 of the linear actuator 10 uses a unitized device.
In the unitized ball screw mechanism 20, grease is applied to the ball screw portion 31 of the ball screw shaft 24, and the entire area of the ball screw portion 31 screwed into the ball screw nut 22 via the ball 23. Are housed in the ball screw nut 22.

  When the unitized ball screw mechanism 20 is transported to the assembly plant of the linear actuator 10, the ball screw portion 31 is not exposed to the outside. For this reason, contamination (contamination) such as dust and iron powder does not enter the ball screw portion 31. Further, no damage occurs to the ball screw nut 22 or the screw groove of the ball screw portion 31. Moreover, the amount of grease applied to the ball screw portion 31 leaking to the outside can be significantly reduced while the ball screw mechanism 20 is being transported.

Therefore, when assembling the linear motion actuator 10, the unitized ball screw mechanism 20 is prevented from invading contamination during transport and generation of flaws in the screw groove, etc. Since the quality is guaranteed, the high precision linear actuator 10 can be assembled.
Further, since the operation of sealing the grease in the ball screw shaft 24 is not necessary at the time of the assembly of the linear actuator 10, the assembly efficiency of the linear actuator 10 can be improved.
In the first embodiment, the ball screw nut 22 is driven to rotate by the electric motor and the ball screw shaft 24 is used as a linear motion element. However, the present invention is not limited to this. 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 Driven spline hole 31 Threaded portion 32 Involute spline shaft portion 33a Two-sided width 33 Connecting shaft portion 34 Detent member 35 Cylindrical portion 35a Involute spline hole portion 36 Stopper 36a First stopper side surface 36b Second stopper side surface 36c Stopper end surface 38 Involute spline shaft portion 32 spline 39 tooth bottom 39a first tooth bottom 39b second tooth bottom 39c inclined tooth bottom 40c guide groove 40d engagement groove 41a support hole 41c protrusion 43a first intersection position 43b second intersection position 50 seal 51 snap ring a shaft of stopper end face Width dimension in the orthogonal direction b Width dimension in the axis orthogonal direction of the proximal end side of the stopper G Center of gravity position of the stopper e1 Height dimension from the base end of the stopper to the center of gravity e2 Height dimension from the center of gravity to the end face of the stopper L1 Axial dimension of part L2 Axial dimension of stopper

Claims (8)

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 is integrally formed with a cylindrical body fixed to the shaft portion of the linear motion element, and has one protrusion radially projecting from the outer peripheral surface of the cylindrical body, the linear motion It is configured to stop the rotation of elements,
The projection is formed with a projection restricting surface for restricting the rotational movement of the rotational movement element by the abutment of the locking portion formed on the rotational movement element at the stroke end of the linear movement element in the contraction direction. When the shaft portion is viewed in the axial direction, the thickness between the protrusion restricting surface and the back surface in the circumferential direction with respect to the protrusion restricting surface is larger at the base end on the cylindrical body side than the distal end in the radial direction. A linear motion actuator characterized in that When the projection is viewed in the axial direction, the thickness between the projection restricting surface and the circumferential back surface with respect to the projection restricting surface is from the distal end in the radial direction to the proximal end on the tubular body side. It is formed to increase gradually as it
The center of gravity of the projection is set to a position closer to the cylindrical body side from a position of 1/2 of the height from the outer periphery of the cylindrical body to the tip in the radial direction. Direct acting actuator described.   The linear motion actuator according to claim 1 or 2, wherein an axial length of the cylindrical body is formed to be larger than an axial length of the protrusion.   The linear motion actuator according to any one of claims 1 to 3, wherein the projection control surface is formed to abut on the locking portion in a surface contact state. The ball screw mechanism fixes a cylindrical ball screw nut as the rotational movement element, a ball screw portion housed in the ball screw nut and screwed together via a large number of balls, and the cylindrical body. A ball screw shaft as the linear motion element in which the shaft portion is coaxially provided;
When the ball screw portion moves to the stroke end position in the shrinking direction, the locking portion abuts on the protrusion integrally formed on the cylindrical body of the ball screw shaft, thereby the ball screw nut The linear motion actuator according to any one of claims 1 to 4, wherein the rotation of the linear motor is restricted.   The linear motion actuator according to claim 5, wherein when the ball screw portion is moved to the stroke end in the contraction direction, the entire axial length is accommodated in the ball screw nut. A method of assembling a linear actuator according to claim 6, comprising
The ball screw mechanism is unitized in a state where the ball screw portion is located at the stroke end in the contraction direction, and the entire axial length of the ball screw portion is accommodated in the ball screw nut.
The outer periphery of the ball screw nut of the unitized ball screw mechanism is rotatably supported by a housing, and a rotational driving source is connected and assembled so that a rotational force is transmitted to the ball screw nut. A method of assembling a linear motion actuator characterized by   8. The method of assembling a linear motion actuator according to claim 7, wherein the ball screw portion housed in the ball screw nut is coated with grease.

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