JP6524763B2 - Ball screw mechanism and actuator - Google Patents

Description

  The present invention relates to a ball screw mechanism and an actuator suitable for a linear actuator.

A ball screw type direct acting actuator has been widely used as a power conversion device that obtains a large axial output from a relatively small input torque by utilizing a ball screw that converts rotational motion into linear motion.
When a relatively small input torque from a drive source such as an electric motor is input to a screw shaft (or a nut) constituting a ball screw via a reduction mechanism, and the screw shaft (or a nut) is rotated in a desired direction. The rotational movement of the screw shaft (or nut) is converted to the linear movement of a nut (or screw shaft) screwed with the screw shaft (or nut) via a plurality of balls. Then, the linear motion of the nut (or screw shaft) is taken out from the output shaft connected with the nut (or directly from the screw shaft).

When the linear motion of the ball screw type linear motion actuator exceeds a predetermined level, the actuator may be damaged or the device driven by the actuator may be broken.
Therefore, in order to regulate linear motion of a ball screw type linear motion actuator beyond a predetermined level, one of a nut and a screw shaft that performs rotational motion, and the other of the nut and the screw shaft that are converted as linear motion, A stroke control unit is provided.

For example, the device of Patent Document 1 is provided with a pin attached to the end of a screw shaft performing rotational movement as a stroke restricting portion, and the axial end face of a nut performing linear movement engages with the pin to restrict the stroke. doing.
Further, the device of Patent Document 2 includes, as a stroke restricting portion, a stopper member mounted on the outer periphery of one end side of a screw shaft, and a locking portion formed on an end surface of one end side of a nut The stroke of the screw shaft or the nut is regulated by the engagement between the and the locking portion.

Japanese Patent Application Laid-Open No. 10-078100 JP, 2014-178023, A

However, in the device of Patent Document 1, since the pin is attached to the end portion of the screw shaft, there is a possibility that touch around may occur due to the deviation of the center of gravity of the screw shaft. In addition, a rail mechanism is required as the linear motion mechanism of the nut and the torque transmission mechanism, which may increase the size of the device configuration.
Further, in the device of Patent Document 2, since the stopper member mounted on the screw shaft and the locking portion provided on the end face on one end side of the nut must be offset in the axial direction, the axial length is short. It may be a long device. Further, the structure for mounting the stopper member on the outer periphery of the screw shaft is complicated, and there is a problem in terms of manufacturing cost.

  Therefore, the present invention has been made focusing on the unsolved problems of the above-described conventional example, and aims to reduce the manufacturing cost while achieving downsizing of the device, and convert rotational motion into linear motion with high accuracy. It is an object of the present invention to provide a ball screw mechanism and an actuator capable of restricting linear motion beyond a predetermined level.

In order to achieve the above object, a ball screw mechanism according to one aspect of the present invention corresponds to a screw shaft provided with a spiral screw shaft rolling path on the outer peripheral surface and a screw shaft rolling path on the inner peripheral surface. A nut provided with a helical nut rolling path, a plurality of rolling elements rollably interposed between the screw shaft rolling path and the nut rolling path, relative to one of the nut and the screw shaft A ball screw mechanism comprising: a torque transmission member for transmitting a rotational movement, and converting the rotational movement transmitted from the torque transmission member to the other of the nut and the screw shaft as a linear movement, on an outer peripheral side of an end face of one end side of the nut An axially projecting locking portion is formed;
A pin member press-fitted into a pin hole formed in a direction perpendicular to the screw axis of the screw shaft is mounted on one end side of the screw shaft, and the pin member is surrounded at least from the axially outer side. member and a driven member which concave grooves are formed engaging with slides, when regulating the linear movement, the locking portion and the pin member is abutting, the locking The groove of the part and the driven member is located in a state of being separated in the radial direction of the screw shaft and the nut.
An actuator according to an aspect of the present invention includes the above-mentioned ball screw mechanism.

  According to the ball screw mechanism and the actuator according to the present invention, the manufacturing cost can be reduced while achieving the downsizing of the device, and at least a predetermined linear movement can be performed while converting the rotational movement into the linear movement with high accuracy. It can be regulated.

It is the perspective view which showed the principal part which shows the ball screw mechanism of 1st Embodiment which concerns on this invention. It is principal part sectional drawing which looked at the ball screw mechanism of 1st Embodiment from the axial direction. It is the figure which showed typically the engagement state of the latching | locking part of the ball screw mechanism of 1st Embodiment, and a pin member. It is the figure which described typically operation | movement of the ball screw mechanism of 1st Embodiment. It is the perspective view which cut the principal part which shows the ball screw mechanism of 2nd Embodiment. It is sectional drawing along the axial direction which shows the ball screw mechanism of 2nd Embodiment. It is a VII-VII line arrow directional view of FIG. It is the perspective view which showed the principal part which shows the ball screw mechanism of 3rd Embodiment which concerns on this invention. It is a figure which shows the shape of the pin member used with the ball screw mechanism of 3rd Embodiment.

  The first to third embodiments 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 to third embodiments described below illustrate apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes materials of components, The shape, structure, arrangement, etc. are not specified in 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.
First Embodiment
FIGS. 1 to 4 show a ball screw mechanism 1 used as an actuator of a first embodiment according to the present invention.

  As shown in FIG. 1, the ball screw mechanism 1 according to the first embodiment has a screw shaft 2, a nut 3, and a screw groove 4 provided on the outer periphery of the screw shaft 2 and a screw groove provided on the inner periphery of the nut 3. (Not shown), a plurality of rolling elements installed in a freely rolling manner, a locking portion 5 axially formed on the outer peripheral side of the one end side end face 3a of the nut 3 and one end of the screw shaft 2 The cylindrical housing 7 is mounted on the side in a direction orthogonal to the screw axis 2P and is engaged with the pin member 6 that can abut the locking portion 5 and both axial end portions 6a and 6b of the pin member 6 And have. Here, a rolling element is code | symbol B of FIG. 6 which shows the ball screw mechanism 10 of 2nd Embodiment (Hereinafter, it calls the rolling element B.).

At one end side of the screw shaft 2, a projection 8 is formed to project from a position centered on the screw axis 2P of the flat end surface 2a.
A pin hole 9 is formed in the projection 8 in a direction orthogonal to the screw axis 2 P, and the pin member 6 is press-fit into the pin hole 9. The pin member 6 pressed into the pin hole 9 protrudes from the protrusion 8 to the both sides with the same dimension length.

The housing 7 is restrained by its fixing member (not shown) in its rotation and axial movement. On the inner peripheral surface of the housing 7, a pair of concave grooves 7a and 7b extending in the axial direction are formed at positions separated by 180 ° from each other, and both ends of the pin member 6 are formed in these grooves 7a and 7b. 6a and 6b are entering.
Here, the distance from one end side end face 3a of nut 3 to the center of pin hole 9 is S, the lead of screw shaft 2 is L, the diameter of pin member 6 is D, and one end of nut 3 of locking portion 5 The length protruding from the side end face 3a is H.

Further, as shown in FIG. 2, when the pin member 6 and the locking portion 5 are in contact with each other, the circumferential end of the first locking member 5 not in contact with the pin member 6 and the screw axis 2 P Assuming that a line connecting in a radial direction is an imaginary line G, and an angle formed by the imaginary line G and the pin axis 6P of the pin member 6 is α, the following equation (1) is satisfied.
S + D / 2 <((180-alpha) / 360) x L (1)
From this, the diameter D of the pin member 6 is reduced, or the angle α between the imaginary line G and the pin axis 6P of the pin member 6 is reduced, or the lead L of the screw shaft 2 is enlarged or all It is understood that the distance S from the one end side end face 3a of the nut 3 to the center of the pin hole 9 can be shortened if the condition

The operation of the ball screw mechanism 1 of the first embodiment will be described with reference to FIG.
In the initial state, the screw shaft 2 is located on the left side of FIG. 4, and the pin member 6 of the screw shaft 2 is not in contact with the locking portion 5 of the nut 3.
Then, the nut 3 to which the rotational force in the direction of arrow R is transmitted from the torque transmission mechanism rotates on the spot without moving, and the screw shaft 2 to which the rotational force is transmitted via the rolling element B does not rotate. Reciprocate in the C1 direction.

When the rotational movement of the nut 3 is transmitted as a linear movement to the screw shaft 2 via the rolling element B, the screw shaft 2 slides in the grooves 7a and 7b of the housing 7 at both ends 6a and 6b of the pin member 6. While moving linearly in the right direction of the arrow C 1, the pin member 6 abuts on the locking portion 5.
Here, even if the locking portion 5 of the nut 3 and the pin member 6 of the screw shaft 2 abut against each other with a relatively large collision force, the both end portions 6a and 6b of the pin member 6 contact the grooves 7a and 7b. Since the housing 7 intruding is received, the rolling elements B and the screw shaft 2 are less affected by the collision force.

Therefore, according to the ball screw mechanism 1 of the first embodiment, since the screw shaft 2 is not rotating, the pin member 6 provided on one end side of the screw shaft 2 does not move around and the grooves 7a and 7b of the housing 7 are Because it is guided, it can be transmitted as linear motion of the screw shaft 2 with high accuracy.
Further, even if the locking portion 5 of the nut 3 and the pin member 6 of the screw shaft 2 abut on each other with a relatively large collision force, the influence of the rolling element B and the screw shaft 2 on the collision force can be suppressed. Even if the ball screw mechanism 1 is formed, it is possible to provide an actuator that can be used stably with high accuracy over a long period of time.

Further, in the first embodiment, the pin member 6 is mounted on one end side of the screw shaft 2 in the direction orthogonal to the screw axis 2P, and the pin member 6 and the locking portion 5 are arranged in a state of being offset in the radial direction. As a result, the length of the axial direction (the direction of the screw axis 2P) is short, and further downsizing can be achieved.
Further, the pin member 6 is mounted in a state of being press-fitted into a pin hole 9 formed in a direction orthogonal to the screw axis 2P of the projection 8 provided on one end side of the screw shaft 2 The structure of mounting 6 is simple, and the manufacturing cost can be reduced.
Furthermore, even if the pin member 6 moves in the axial direction of the pin hole 9, the bottom surfaces of the pair of concave grooves 10a and 10b formed in the inner peripheral surface of the housing 7 abut on both ends 6a and 6b. It is possible to prevent the pin member 6 from disengaging from the projection 8 of the screw shaft 2.

Furthermore, in the first embodiment, since the relationship of the above-mentioned equation (1) is satisfied, the diameter D of the pin member 6 is reduced, or the imaginary line G and the pin axis 6P of the pin member 6 are formed. If the angle α is reduced, or if the lead L of the screw shaft 2 is increased, or all conditions are satisfied, the distance S from the end face 3 a of the nut 3 to the center of the pin hole 9 can be shortened. Furthermore, it is possible to provide a ball screw mechanism 1 and an actuator in which axial shortening can be achieved.
Here, the driven member according to the present invention corresponds to the housing 7, and with the offset according to the present invention, the locking portion 5 and the grooves 7a and 7b of the housing 7 are separated in the axial direction of the pin member 6. It corresponds to the

Second Embodiment
Next, FIGS. 5 to 7 show a ball screw mechanism 10 according to a second embodiment of the present invention. The same components as those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof will be omitted.
The ball screw mechanism 10 of the second embodiment includes a cap member 13 engaged with the pin member 6.
The cap member 13 is restricted in its rotation and axial movement by a fixing member (not shown), and as shown in FIG. 7, coaxial with the inside of the cap cylindrical body 13a having a lid and the cap body 13a. And the formed cap inner cylindrical portion 13b.

A pair of slits 14a and 14b extending in the radial direction is formed in the inner cylindrical portion 13b, and a portion inside the both end portions 6a and 6b of the pin member 6 is inserted into the slits 14a and 14b.
Further, as shown in FIG. 6, a spherical convex portion 15 is formed at an axial end of the projection 8 projecting from one end of the screw shaft 2, and abuts on the inner surface of the cap main body 13a. ing.

Next, the operation of the ball screw mechanism 1 of the second embodiment will be described with reference to FIG.
In the initial state, the screw shaft 2 is located on the left side of FIG. 5, and the pin member 6 of the screw shaft 2 is not in contact with the locking portion 5 of the nut 3.
Then, the nut 3 to which the rotational force in the arrow R1 direction is transmitted from the torque transmission mechanism rotates on the spot without moving, and the screw shaft 2 to which the rotational force is transmitted through the rolling element B does not rotate. Reciprocate in the C2 direction.

When the rotational movement of the nut 3 is transmitted as a linear movement to the screw shaft 2 through the rolling element B, the screw shaft 2 slides on the slits 14 a and 14 b of the cap member 13 at both ends 6 a and 6 b of the pin member 6. While moving linearly in the right direction of the arrow C 2, the pin member 6 abuts on the locking portion 5.
Also in the ball screw mechanism 10 of the second embodiment, since the screw shaft 2 is not rotating, the pin member 6 provided on one end side of the screw shaft 2 is guided by the slits 14a and 14b of the cap member 13 without swinging. Therefore, it can transmit as linear motion of screw axis 2 with high accuracy.

Further, the pin member 6 is mounted on one end side of the screw shaft 2 in the direction orthogonal to the screw axis 2P, and the pin member 6 and the locking portion 5 are arranged in a state of being offset in the radial direction. It becomes an apparatus with a short length in the direction (screw axis 2P direction), and miniaturization can be achieved.
Furthermore, even if the pin member 6 moves in the axial direction of the pin hole 9, the pin member 6 is moved by the both end portions 6a and 6b of the pin member 6 being in contact with the inner peripheral surface of the cap body 13a of the cap member 13. It is possible to prevent detachment from the projection 8 of the screw shaft 2.
Here, the driven member according to the present invention corresponds to the cap member 13, and the offset according to the present invention includes the locking portion 5 and the slits 14a and 14b of the cap member 13 in the axial direction of the pin member 6. It corresponds to being separated.
ing.

Third Embodiment
Next, FIGS. 8 and 9 show a ball screw mechanism 17 according to a third embodiment in which the shape of the pin member 16 is different.
As shown in FIG. 9, flat contact surfaces 16 a and 16 b that are in surface contact with the locking portion 5 are formed on the outer periphery of the pin member 16 of the fourth embodiment.
By forming such flat contact surfaces 16a and 16b, it is possible to reduce the collision force when the first locking portion 11 and the second locking portion 12 and the pin member 16 are in contact, and the durability The ball screw mechanism 17 can be provided.

Here, the contact between the locking portion and the pin member according to the present invention in the surface contact state corresponds to the contact between the locking portion 5 and the flat contact surfaces 16a and 16b.
As mentioned above, the scope of the present invention is not limited to the above-mentioned embodiment, and it is needless to say that various embodiments etc. are included. Therefore, the technical scope of the present invention is defined only by the invention-specifying matters described in the scope of claims appropriate from the above description.

  That is, although the ball screw mechanism 10 of the first embodiment, the ball screw mechanism 14 of the second embodiment, and the ball screw mechanism 17 of the third embodiment rotate the nut 3 by the torque transmission member, the gist of the present invention The present invention is not limited to this, and the screw shaft 2 may be rotationally moved by a torque transmission mechanism, and the rotational motion of the screw shaft 2 may be converted into the linear motion of the nut 3.

DESCRIPTION OF SYMBOLS 1 Ball screw mechanism 2 Screw shaft 2P Screw axis 3 Nut 3a End surface of one end of nut 4 Thread groove 5 Locking portion 6 Pin member 7 Housing 7a, 7b Concave groove 8 Projection Part 9 ... Pin hole 10 ... Ball screw mechanism 11 ... First locking part 12 ... Second locking part 13 ... Cap member 13a ... Cap body 13b ... Cap inner cylinder part 14a, 14b ... Slit 15 ... Convex part of spherical shape 16: Pin member 16a, 16b: Flat contact surface 17: Ball screw mechanism B: Rolling element

Claims (4)

A screw shaft provided with a spiral screw shaft rolling path on the outer peripheral surface,
A nut provided with a spiral nut rolling path corresponding to the screw shaft rolling path on an inner circumferential surface;
A plurality of rolling elements rollably interposed between the screw shaft rolling path and the nut rolling path;
And a torque transmitting member for transmitting a relative rotational movement to one of the nut and the screw shaft, and converting the rotational movement transmitted from the torque transmitting member to the other of the nut and the screw shaft as a linear movement. In the ball screw mechanism,
A locking portion protruding in the axial direction is formed on the outer peripheral side of the end face on one end side of the nut,
A pin member press-fit into a pin hole formed in a direction orthogonal to the screw axis of the screw shaft is attached to one end side of the screw shaft,
The driven member includes a concave-shaped groove formed to surround the pin member from at least the axially outer side and slidably engaged with the pin member.
When restricting the linear movement, the locking portion and the pin member is abutting, the grooves of the locking portion and the driven member is positioned in a state apart in the radial direction of the screw shaft and the nut the ball screw mechanism, characterized in that it has been. The ball screw mechanism according to claim 1 , wherein the locking portion and the pin member abut in a surface contact state . A projection is formed to project from a position centered on the screw axis of the end face on the one end side of the screw shaft,
Forming the pin holes in the protrusions;
Let S be the distance from the one end side end face to the center of the pin hole,
Let the lead of the screw shaft be L,
When the pin member press-fit into the pin hole and the locking portion abut, a circumferential end portion of the locking portion not in contact with the pin member and the screw axis are radially connected. Let an imaginary line be an imaginary line, and let α be an angle between the imaginary line and the pin axis of the pin member,
Let D be the diameter of the pin member of circular cross section,
Assuming that the length of the locking portion protruding from the end face of the one end side of the nut is H,
S + D / 2 <((180-α) / 360) × L
The ball screw mechanism according to claim 1 or 2, which has the following relationship . An actuator comprising the ball screw mechanism according to any one of claims 1 to 3 .

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