JP2016196927A - Ball screw mechanism and actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw mechanism capable of reducing manufacturing costs while miniaturizing a device.SOLUTION: A ball screw mechanism includes a screw shaft 2 provided with a spiral screw shaft rolling path on its outer peripheral face, a nut 3 provided with a spiral nut rolling path corresponding to the screw shaft rolling path, on its inner peripheral face, a plurality of rolling elements B rollably disposed between the screw shaft rolling path and the nut rolling path, and a torque transmission member for transmitting relative rotary motion to one of the nut and the screw shaft, and the rotary motion transmitted from the torque transmission member is converted into linear motion to the other of the nut and the screw shaft. A locking portion 5 projecting to an axial direction is formed on an outer peripheral side of one end-side end face of the nut, and a pin member 6 press-fitted to a pin hole 9 formed in a direction orthogonal to a screw axis 2P of the screw shaft is mounted on one end side of the screw shaft. When the linear motion is restricted, the locking portion and the pin member are kept into contact with each other.SELECTED DRAWING: Figure 1

Description

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

2. Description of the Related Art Conventionally, 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 using 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 nut) constituting a ball screw via a speed reduction mechanism, the screw shaft (or nut) is rotated in a desired direction. The rotational motion of the screw shaft (or nut) is converted into linear motion of the 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 to the nut (or directly from the screw shaft).

If this ball screw type linear motion actuator exceeds a predetermined linear motion, the actuator may be damaged or a device driven by the actuator may be damaged.
Therefore, in order to restrict the linear motion of the ball screw type linear actuator more than a predetermined amount, one of the nut and the screw shaft that performs the rotational motion and the other of the nut and the screw shaft that is converted as the linear motion, A stroke restricting portion is provided.

For example, the device of Patent Document 1 provides a pin attached to the end of a screw shaft that performs a rotational motion as a stroke restricting portion, and the stroke is regulated by the axial end surface of a nut that performs a linear motion engaging the pin. doing.
The device of Patent Document 2 includes a stopper member mounted on the outer periphery on one end side of the screw shaft as a stroke restricting portion, and a stopper provided on the end surface on one end side of the nut, and provided on the stopper member. And the locking portion are engaged to restrict the stroke of the screw shaft or the nut.

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

However, the device of Patent Document 1 has a possibility that a touching may occur due to a shift in the center of gravity of the screw shaft by attaching a pin to the end of the screw shaft. In addition, a rail mechanism is required as a linear motion mechanism and a torque transmission mechanism of the nut, which may increase the size of the apparatus.
Moreover, since the apparatus of patent document 2 must arrange | position the stopper member attached to the screw shaft, and the latching | locking part provided in the end surface of the one end side of a nut in the axial direction, axial direction length is There is a risk of becoming a long device. In addition, the structure of 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 paying attention to the above-mentioned unsolved problems of the conventional example, reducing the manufacturing cost while reducing the size of the apparatus, and converting rotational motion into linear motion with high accuracy. It is another object of the present invention to provide a ball screw mechanism and an actuator that can regulate a linear motion that exceeds a predetermined value.

In order to achieve the above object, a ball screw mechanism according to an aspect of the present invention corresponds to a screw shaft in which a spiral screw shaft rolling path is provided on an outer peripheral surface, and a screw shaft rolling path on an inner peripheral surface. Relative to one of the nut provided with a spiral nut rolling path, a plurality of rolling elements rotatably mounted between the screw shaft rolling path and the nut rolling path, and one of the nut and the screw shaft In a ball screw mechanism that includes a torque transmission member that transmits rotational motion, and converts the rotational motion transmitted from the torque transmission member to the other of the nut and the screw shaft as a linear motion, on the outer peripheral side of one end surface of the nut, A locking portion protruding in the axial direction is formed, and 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 linear motion is performed. When restricting, the locking part and the pin member are in contact with each other. It was.
An actuator according to one embodiment of the present invention includes the above-described ball screw mechanism.

  According to the ball screw mechanism and the actuator according to the present invention, it is possible to reduce the manufacturing cost while reducing the size of the apparatus, and to perform a linear motion more than a predetermined value while converting the rotational motion into the linear motion with high accuracy. Can be regulated.

It is the perspective view which cut 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 the VII-VII line arrow directional view of FIG. It is the perspective view which cut down the principal part which shows the ball screw mechanism of 3rd Embodiment concerning this invention. It is a figure which shows the shape of the pin member currently used with the ball screw mechanism of 3rd Embodiment.

  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 dimensions, 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 portions having different dimensional relationships and ratios are included between the drawings.

In addition, the first to third embodiments shown below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material of a component, The shape, structure, arrangement, etc. are not specified below. 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]
1 to 4 show a ball screw mechanism 1 used as an actuator according to a first embodiment of the present invention.

  As shown in FIG. 1, the ball screw mechanism 1 of the first embodiment includes a screw shaft 2, a nut 3, 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 so as to be freely rollable, a locking portion 5 formed to protrude in the axial direction on the outer peripheral side of one end surface 3a of the nut 3, and one end of the screw shaft 2. A pin member 6 mounted on the side in a direction orthogonal to the screw axis 2P and capable of contacting the locking portion 5 and a cylindrical housing 7 engaged with both end portions 6a and 6b in the axial direction of the pin member 6 And. Here, a rolling element is the code | symbol B of FIG. 6 which shows the ball screw mechanism 10 of 2nd Embodiment (henceforth the rolling element B).

On one end side of the screw shaft 2, a protruding portion 8 is formed so as to protrude from a position centering on the screw axis 2P of the flat end surface 2a.
A pin hole 9 is formed in the protrusion 8 in a direction orthogonal to the screw axis 2P, and the pin member 6 is press-fitted into the pin hole 9. The pin member 6 press-fitted into the pin hole 9 protrudes from the protrusion 8 to both sides with the same length.

The rotation and axial movement of the housing 7 are restricted by a fixing member (not shown). 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 180 ° apart from each other, and both end portions of the pin member 6 are formed in the grooves 7a and 7b. 6a and 6b have entered.
Here, the distance from the end surface 3a on one end side of the nut 3 to the center of the pin hole 9 is S, the lead of the screw shaft 2 is L, the diameter of the pin member 6 is D, and one end of the nut 3 of the locking portion 5 is used. The length protruding from the side end face 3a is defined as 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 portion of the first locking member 5 that is not in contact with the pin member 6 and the screw axis 2P A line connecting the two in the radial direction is an imaginary line G, and α is an angle formed by the imaginary line G and the pin axis 6P of the pin member 6, the following relationship (1) is established.
S + D / 2 <((180-α) / 360) × L (1)
From this, the diameter D of the pin member 6 is reduced, the angle α formed by 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 increased, or all It can be seen that the distance S from the end surface 3a on one end side of the nut 3 to the center of the pin hole 9 can be shortened if the condition is satisfied.

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.
The nut 3 to which the rotational force in the direction of the arrow R is transmitted from the torque transmission mechanism does not move and rotates on the spot, and the screw shaft 2 to which the rotational force is transmitted via the rolling element B does not rotate. Go back and forth in the C1 direction.

When the rotational motion of the nut 3 is transmitted as a linear motion to the screw shaft 2 via the rolling elements B, the screw shaft 2 has both end portions 6a and 6b of the pin member 6 sliding in the grooves 7a and 7b of the housing 7. While moving linearly in the right direction of the arrow C 1, the pin member 6 comes into contact with 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 collision force causes the both end portions 6a and 6b of the pin member 6 to be in the grooves 7a and 7b. Since the housing 7 is received, the impact of the collision force on the rolling element B and the screw shaft 2 is suppressed.

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 swing around, and the grooves 7a and 7b of the housing 7 are not swung. Since it is guided, it can be transmitted as a 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 against 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 when 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.

In the first embodiment, the pin member 6 is mounted on one end side of the screw shaft 2 in a 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. Therefore, the apparatus has a short length in the axial direction (direction of the screw axis 2P), and can be further downsized.
The pin member 6 is mounted in a state where it is press-fitted into a pin hole 9 formed in a direction perpendicular to the screw axis 2P of the protrusion 8 provided on one end side of the screw shaft 2. The structure for 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 on the inner peripheral surface of the housing 7 come into contact with both end portions 6a and 6b. The pin member 6 can be prevented from escaping from the protrusion 8 of the screw shaft 2.

Furthermore, in the first embodiment, since the relationship of the above-described formula (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, the lead L of the screw shaft 2 is increased, or all the conditions are satisfied, the distance S from the end surface 3a of the nut 3 to the center of the pin hole 9 can be shortened. Further, it is possible to provide the ball screw mechanism 1 and the actuator that are shortened in the axial direction.
Here, the driven member according to the present invention corresponds to the housing 7, and the offset according to the present invention is that the locking portion 5 and the grooves 7 a and 7 b of the housing 7 are separated from each other in the axial direction of the pin member 6. It corresponds to being.

[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 description thereof is omitted.
The ball screw mechanism 10 of the second embodiment includes a cap member 13 that is engaged with the pin member 6.
The cap member 13 is restrained from rotating and axially moving by a fixing member (not shown). As shown in FIG. 7, the cap body 13a having a lid shape is coaxial with the inside of the cap body 13a. The cap inner cylinder part 13b formed is provided.

A pair of slits 14 a, 14 b extending in the radial direction is formed in the inner cylinder portion 13 b, and portions inside the both end portions 6 a, 6 b of the pin member 6 enter the slits 14 a, 14 b.
Further, as shown in FIG. 6, a spherical convex portion 15 is formed at the axial end portion of the protruding portion 8 protruding from one end side of the screw shaft 2, and abuts against the inner surface of the cap 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.
The nut 3 to which the rotational force in the direction of the arrow R1 is transmitted from the torque transmission mechanism does not move and rotates on the spot, and the screw shaft 2 to which the rotational force is transmitted via the rolling element B does not rotate. Go back and forth in the C2 direction.

When the rotational motion of the nut 3 is transmitted as a linear motion to the screw shaft 2 via the rolling element B, both ends 6a and 6b of the pin member 6 slide on the slits 14a and 14b of the cap member 13 in the screw shaft 2. The pin member 6 comes into contact with the locking portion 5 while moving linearly in the right direction of the arrow C2.
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 to the slits 14a and 14b of the cap member 13 without swinging. Therefore, it can be transmitted as a linear motion of the screw shaft 2 with high accuracy.

Further, the pin member 6 is attached to one end side of the screw shaft 2 in a direction orthogonal to the screw axis 2P, and the pin member 6 and the locking portion 5 are disposed in a state of being offset in the radial direction. It becomes an apparatus with a short length in the direction (direction of the screw axis 2P), and can be downsized.
Furthermore, even if the pin member 6 moves in the axial direction of the pin hole 9, both end portions 6 a and 6 b of the pin member 6 abut on the inner peripheral surface of the cap body 13 a of the cap member 13, so that the pin member 6 is It is possible to prevent the screw shaft 2 from escaping from the protruding portion 8.
Here, the driven member according to the present invention corresponds to the cap member 13, and the offset according to the present invention is that the locking portion 5 and the slits 14 a and 14 b of the cap member 13 are in the axial direction of the pin member 6. It corresponds to being away.
ing.

[Third Embodiment]
Next, FIG.8 and FIG.9 shows the ball screw mechanism 17 of 3rd Embodiment from which the shape of the pin member 16 differs.
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 a collision force when the first locking portion 11 and the second locking portion 12 are in contact with the pin member 16, and durability is improved. Thus, it is possible to provide the ball screw mechanism 17 with improved.

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

  That is, 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. However, the present invention is not limited to this, and the screw shaft 2 may be rotated 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 face 4 of nut 1 ... Screw groove 5 ... Locking part 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 ... Spherical convex part 16 ... Pin members 16a, 16b ... Flat contact surface 17 ... Ball screw mechanism B ... Rolling element

Claims (6)

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 the inner peripheral surface;
A plurality of rolling elements interposed between the screw shaft rolling path and the nut rolling path so as to freely roll;
A torque transmission member that transmits a relative rotational motion to one of the nut and the screw shaft, and the rotational motion transmitted from the torque transmission member is converted to the other of the nut and the screw shaft as a linear motion. In the ball screw mechanism,
A locking portion protruding in the axial direction is formed on the outer peripheral side of the end surface on one end side of the nut,
A pin member press-fitted into a pin hole formed in a direction perpendicular to the screw axis of the screw shaft is attached to one end side of the screw shaft,
The ball screw mechanism, wherein the locking portion and the pin member are in contact with each other when the linear motion is restricted.   The ball screw mechanism according to claim 1, wherein the locking portion and the pin member are positioned in a state offset in a radial direction of the screw shaft and the nut.   The ball screw mechanism according to claim 1, wherein the locking portion and the pin member are in contact with each other in a surface contact state. A protrusion protrudes from a position around the screw axis of the one end surface of the screw shaft,
Form the pin hole in this protrusion,
The distance from the end face on one end side to the center of the pin hole is S,
L is the lead of the screw shaft,
When the pin member press-fitted into the pin hole and the locking portion abut, the circumferential end of the locking member that is not in contact with the pin member and the screw axis are connected in the radial direction. The angle between the imaginary line and the pin axis of the pin member is α,
The diameter of the pin member having a circular cross section is D,
When the length that the locking part protrudes from the end surface on the one end side of the nut is H,
S + D / 2 <((180-α) / 360) × L
The ball screw mechanism according to claim 1, wherein the ball screw mechanism has a relationship of   5. The driven member according to claim 1, further comprising a driven member that surrounds the pin member from at least an axially outer side and engages with the pin member while sliding. 6. Ball screw mechanism.   An actuator comprising the ball screw mechanism according to any one of claims 1 to 5.

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