JP6894773B2 - Linear actuator - Google Patents

Description

The present invention includes a motor unit having a hollow rotating shaft, an output screw shaft inserted on the axis of the hollow rotating shaft, and the output screw shaft and a screw arranged in the hollow rotating shaft. The present invention relates to a linear actuator that includes a matching screw nut and converts the rotary motion of the hollow rotary shaft into a linear motion of the output screw shaft via the screw nut.

Conventionally, as a linear actuator of this type, for example, there is one as shown in Patent Document 1.
In Patent Document 1, a stopper is provided to prevent the screw shaft from moving more than a predetermined amount. Since the limit position of the screw shaft in the forward direction is defined by the stopper, the screw shaft is forcibly stopped when the limit position is reached.

Japanese Unexamined Patent Publication No. 2009-156354

However, in such a conventional linear actuator, when the screw shaft reaches the limit position and the screw shaft is forcibly stopped, the stopper abuts on the screw shaft output portion (flange) of the actuator case and stops. Even if the stopper and the screw shaft are fixed by press fitting, screwing, adhesion, etc., when the stopper comes into contact with the screw shaft, the stopper and the screw shaft may be misaligned due to the impact on the stopper. , There was a problem that it came off.
In Patent Document 1, a braking means is provided to prevent an indentation from being generated in the raceway portion of the ball screw due to the rotational inertial force of the screw nut due to the collision between the stopper and the flange, and when the stopper comes into contact with the flange, Although the speed is reduced to some extent, there is still an impact on the stopper when the stopper comes into contact with the screw shaft.

The present invention has been made by paying attention to such a conventional problem.
A two-sided milling cutter having a length of several millimeters in the axial direction is formed by leaving a small cylindrical portion at the tip of the output screw shaft.
A U-shaped inner circumference that fits into the two-sided milling cutter formed on the output screw shaft and an axial width are formed, and the outer circumference is also provided with cut portions on the two sides parallel to the inner circumference of the milling cutter. The above problem is solved by fixing the U-shaped set collar (stopper) to the two-sided milling portion of the output screw shaft.
Even if the set collar (stopper) is impacted when the set collar (stopper) comes into contact with the flange, the milling part on the two sides of the U-shaped inner circumference of the set collar and the output screw shaft will be firm. Since the set collar (stopper) does not shift because it is fitted, the purpose is that the place where the set collar (stopper) comes into contact with the flange can be the origin of the linear actuator.

In order to solve the above problems, the present invention is provided with a motor unit having a hollow rotating shaft, an output screw shaft inserted on the axis of the hollow rotating shaft, and the hollow rotating shaft. The screw nut is provided so as to include a screw nut to be screwed with the output screw shaft, and the rotary motion of the hollow rotary shaft is converted into a linear motion of the output screw shaft, and the screw nut is provided for the output. The ultimate position of the tip of the screw shaft in the forward direction is defined by a stopper, a cylindrical portion is formed at the tip of the output screw shaft, and two surfaces parallel to each other in the radial direction are formed between the cylindrical portion and the screw portion. The flat surface portion is formed to have substantially the same dimensions as the axial thickness of the stopper, the stopper has a substantially U-shape, and the inner surface is a flat surface that fits into the two flat surface portions formed on the output screw shaft. It is formed in a shape.
Further, the present invention is to set the limit position defined by the stopper to the origin position.
Further, in the present invention, two flat surfaces parallel to each other in the radial direction are formed on the outer periphery of the substantially U-shaped stopper.
Furthermore, the present invention is provided with a threaded cover made stretchable multi cylinder axially for covering the output screw shaft, the stopper covers the output screw shaft further into the interior of the screw cover The convex part to be incorporated is formed.
Further, in the present invention, the output screw shaft is a ball screw shaft, and the screw nut is a ball screw nut.
Further, in the present invention, the output screw shaft is a slip screw shaft, and the screw nut is a slip screw nut.

According to the present invention, the stopper can be used not only to prevent the output screw shaft from coming off, but also to set the origin, so that it is not necessary to separately prepare an origin position sensor.

It is a perspective view of the linear actuator according to the embodiment of this invention. A linear actuator according to an embodiment of the present invention is shown, (a) is a left side view of FIG. 1, and (b) is a sectional view taken along line BB of (a). It is a perspective view of the set collar attached to a ball screw shaft. (A) is a perspective view showing the ball screw shaft and the set collar, and (b) is a perspective view in which the set collar is fitted to the ball screw shaft. It is a side view of the state where the ball screw shaft of FIG. 2A is in the origin position. It is a perspective view of the state where the milling part of a set collar is fixed with a spanner when a load is attached to a ball screw shaft. It is a perspective view which shows the linear actuator of this application provided with a ball screw cover. A second embodiment of the present invention is shown, (a) is a front view, and (b) is a sectional view taken along line CC of (a) showing an origin position. It is a perspective view which shows the set color of the 2nd Embodiment. It is an enlarged view of the X part of FIG. 8 (b). It is a perspective view which shows the modification of the set color of 2nd Embodiment. (A) is a side view of a modified example of the set collar of the second embodiment fitted to the ball screw shaft, and (b) is a sectional view taken along line DD of (a).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 (a) and 2 (b) show a linear actuator 1 according to the present invention.
In the linear actuator 1, the motor unit 10 is composed of a stator 11, a rotor 12, and a hollow shaft 13 which are concentrically arranged on the same axis.

The hollow shaft 13 is provided with a small diameter portion 13a whose outer peripheral surface is supported by a counter-output side bearing 15 and a large diameter portion 13b whose outer peripheral surface is supported by a thrust / radial bearing 14 so as to be displaced in the axial direction. .. The rotor 12 is integrally provided on the outer peripheral surface of the small diameter portion 13a of the hollow shaft 13, and the stator 11 is arranged concentrically with a gap around the rotor 12.

One end of the outer ring 14a of the thrust / radial bearing 14 is locked by a step portion 19a provided on the inner peripheral surface of the case 19, and the other end is fixed by a bearing fixing ring 16. One end of the inner ring 14b of the thrust / radial bearing 14 is locked by a step portion 13c provided on the outer peripheral surface of the large diameter portion 13b of the hollow shaft 13, and the other end is locked by a lock nut 17. .. The locknut 17 is screwed and fixed to a threaded portion 13d provided on the outer peripheral surface of the large diameter portion 13b. The thrust / radial bearing 14 is built in a case 19 having a cylindrical inner circumference, and the case 19 includes an actuator housing 22 together with a bracket 20 and a flange 21.

The ball screw shaft 23 is an output screw shaft inserted on the axis of the hollow portion 13e of the hollow shaft 13, and is inserted into the screw portion 23a of the ball screw shaft 23 into the large diameter portion 13b of the hollow shaft 13. An annular ball screw nut 24 is concentrically screwed and attached.
The ball screw nut 24 is provided with a flange portion 24a on the outer peripheral surface of the large diameter portion 13b of the hollow shaft 13 on the opening end side, and an opening hole formed in the coaxial direction with the ball screw shaft 23 of the flange portion 24a. The ball screw nut fastening screw 18 is inserted through 24b and screwed onto the lock nut 17.

At the tip of the ball screw shaft 23, a cylindrical portion 23b having the same outer diameter as the ball screw shaft 23 is left several millimeters in the axial direction (1.5 mm in this embodiment), and several millimeters in the axial direction from the cylindrical portion 23b. Two parallel milling cut portions 23c (5 mm in the embodiment) are formed in the screw portion 23a.

A substantially U-shaped set collar 28 as a stopper that defines the limit position of the screw shaft in the forward direction, prevents the ball screw shaft 23 from coming off, and defines the origin is formed on the screw portion 23a of the ball screw shaft. It is fastened to the two-sided milling cut portion 23c.

As shown in FIG. 3, the substantially U-shaped set collar 28 has an inner circumference 28a formed in a U shape so as to fit into the two-sided milling cut portion 23c formed on the ball screw shaft 23. .. The outer circumference 28b of the set collar 28 is formed with cut portions 28b1 on two surfaces parallel to the fitting portion 28a1 on the inner circumference.

As shown in FIG. 4A, the axial width L1 of the fitting portion 28a1 on the inner circumference of the substantially U-shaped set collar 28 is determined by the two-sided milling cut portion 23c formed on the ball screw shaft 23. It is the same as the formed axial width L2. As shown in FIG. 4B, the set collar 28 is fitted to the two-sided milling cut portion 23c formed on the ball screw shaft 23. Further, a screw hole 28b2 is formed in the outer peripheral two-sided cut portion 28b1 of the substantially U-shaped set collar, and is fastened to the milling portion 23c of the ball screw shaft by a set screw (not shown). Alternatively, it may be fastened by press fitting or adhesion without using a set screw.

As shown in FIG. 2B, a retaining locking member 26 is screwed to the base end of the ball screw shaft 23 by a screw 27.
A manual feed knob 29 is attached to the end of the small diameter portion 13a of the hollow shaft 13, and a motor lead wire bush 30 for pulling out the motor lead wire is attached to the upper portion of the bracket 20 (FIG. 2 (FIG. 2). a) See) is built-in.

Next, the operation of the linear actuator according to the above embodiment will be described.
As shown in FIGS. 1 and 2, in the linear actuator 1, the rotor 12 of the motor portion 10 is fastened to the small diameter portion 13a of the hollow shaft 13, and the inner ring of the thrust and radial bearing 14 is attached to the large diameter portion 13b of the hollow shaft 13. Is fixed with a lock nut 17.
A ball screw nut 24 is arranged in the large diameter portion 13b of the hollow shaft 13, and the flange portion 24a of the ball screw nut 24 is fastened to the lock nut 17 by the ball screw nut fastening screw 18. Therefore, the rotor 12 rotates by switching the excitation of the winding of the stator 11 (not shown), and the ball screw nut 24 also rotates in synchronization with the rotor 12. The ball screw shaft 23 is screwed into the ball screw nut 24, and by fixing the tip of the ball screw shaft 23 to a load (not shown) that moves linearly so as to prevent rotation, the ball screw shaft 23 becomes a ball screw. The nut 24 moves linearly as it rotates.

When performing positioning drive by linear motion, it is necessary to determine the origin position. As shown in FIG. 5, it is convenient to set the ball screw shaft 23 to the left side and set the set collar 28 to the position where it comes into contact with the flange 21, that is, the extreme position.

The set collar 28 is press-fitted into the two-sided milling cut portion 23c formed on the ball screw shaft 23, and is firmly fastened to the milling portion 23c of the ball screw shaft 23 by the set screw 40 of the screw hole 28b2 of the set collar 28. ing. Therefore, as shown in FIG. 5, when the set collar 28 is driven to the left side and comes into contact with the flange 21, the set collar 28 does not shift. As a result, the set collar 28 defines the limit position in the forward direction of the screw shaft and functions as a stopper for preventing the ball screw shaft 23 from coming off, and also detects the position O in contact with the flange 21 to obtain the origin. It has a function to put out. Therefore, it is not necessary to prepare a separate origin position sensor.

Next, on the outer circumference 28b of the set collar 28, cut portions 28b1 are provided on two surfaces parallel to the milling portion 28a1 on the inner circumference. This will be described. When attaching the load driven by the ball screw shaft 23, the load is attached using the screw hole 23d at the tip of the ball screw shaft 23. When attaching the load, it is necessary to fix and attach the ball screw shaft 23 so as not to rotate. Specifically, as shown in FIG. 6, the cut portions 28b1 provided on the two outer peripheral surfaces of the set collar 28 are fixed by the spanner 41 so as not to rotate, and the screw hole 23d at the tip of the ball screw shaft 23 is used. A load (not shown) is attached via the screw 42.

7 to 10 show another embodiment of the present invention in which the same parts as those in FIGS. 1 to 3 are designated by the same reference numerals and the description of the same parts is omitted.
FIG. 7 shows an example in which a dustproof ball screw cover 31 is attached to the ball screw shaft 23. The ball screw cover 31 is composed of a multi-cylinder body that can expand and contract in the axial direction in response to the linear movement of the ball screw shaft 23. , Expands and contracts while covering the ball screw shaft 23. In this case, in FIG. 7, when the ball screw shaft 23 is driven in a linear motion, the left limit position needs to be larger than the position where the ball screw cover 31 contracts to the minimum.

FIG. 9 is a perspective view of the set collar 128, forming a cylindrical convex portion 128A having a partial opening of the set collar 128. The inner circumference of the convex portion 128A covers the ball screw shaft 23, and the outer circumference is covered by the ball screw cover 31. Further, the axial length of the convex portion 128A is made longer than the axial length when the ball screw cover 31 is contracted.

In FIGS. 8A and 8B to 10, the origin can be set by detecting the position where the base end 128A1 of the convex portion 128A of the set collar 128 abuts on the flange 21 by driving to the left side. .. In addition, the ball screw cover 31 can be protected.

Further, unlike the set collar 128, the convex portion 128A is not integrated, but as shown in FIG. 11, a substantially U-shaped main body portion 128B of the set collar and a ring-shaped tubular portion 128C as the convex portion are combined. It may be a new one. As shown in FIG. 12, the set collar 128B is fixed to the two-sided milling cut portion 23c formed on the ball screw shaft 23 through the slit-shaped opening of the substantially U-shaped main body portion 128B of the set collar, and has a ring shape. The set collar convex portion 128C is inserted into the ball screw shaft 23, and the concave portion 128B1 formed in the main body portion of the set collar 128B and the flange portion 128C1 formed in the set collar convex portion 128C are fitted and fixed.

As described above, according to the present invention, the effects listed below can be obtained.
Since the set collars 28 and 128 can be used not only for preventing the ball screw from coming off (defining the limit position) but also for setting the origin, it is not necessary to prepare a separate origin position sensor.
On the outer circumferences 28b and 128b of the set collars 28 and 128, cut portions 28b1 and 128b1 are formed on two surfaces parallel to the fitting portions 28a1 and 128a1 on the inner circumference, and there are two milling portions. Since it can be used to prevent the rotation of the ball screw shaft 23, the load can be easily attached.
By using it together with the ball screw cover 31, a dustproof structure of the ball screw portion can be made.

The present invention is not limited to the above embodiment, and for example, although the ball screw shaft 23 and the ball screw nut 24 have been described in the above embodiment, the present invention can also be applied to a sliding screw shaft, a sliding screw nut, and the like. It goes without saying that the present invention can be appropriately modified and implemented without changing the technical scope of the present invention.

1 Linear actuator 10 Motor part 11 Stator 12 Rotor 13 Hollow shaft 13a Small diameter part 13b Large diameter part 13c Step part 13d Thread part 13e Hollow part 14 Thrust and radial bearing 14a Outer ring 14b Inner ring 15 Non-output side bearing 16 Bearing fixing ring 17 Lock nut 18 Ball screw nut fastening screw 19 Case 19a Step part 20 Bracket 21 Flange 22 Actuator housing 23 Ball screw shaft 23a Thread part 23b Columnar part 23c Milling cut part 24 Ball screw nut 24a Flange part 24b Opening hole 26 Locking member for retaining Screw 28,128 set collar (stopper)
28a Inner circumference 28a1,128a1 Inner circumference fitting part 28b, 128b Outer circumference 28b1,128b1 Cut part 28b2,128b2 Screw hole 128A Convex part 128A1 Base end 128B Approximately U-shaped body part of set collar 128C Cylinder part 128C1 Collar 29 Feeding knob 31 Ball screw cover

Claims (6)

A motor unit having a hollow rotating shaft, an output screw shaft inserted on the axis of the hollow rotating shaft, and a screw nut disposed in the hollow rotating shaft and screwed with the output screw shaft. The screw nut is provided so that the rotary motion of the hollow rotary shaft is converted into the linear motion of the output screw shaft, and the extreme position of the tip portion of the output screw shaft in the forward direction. Is specified by the stopper,
A cylindrical portion is formed at the tip of the output screw shaft, and two flat surfaces parallel to the radial direction are formed between the cylindrical portion and the screw portion with substantially the same dimensions as the axial thickness of the stopper. The linear actuator is characterized in that the stopper has a substantially U-shape, and the inner surface is formed in a planar shape that fits into two planar portions formed on the output screw shaft. The linear actuator according to claim 1, wherein the limit position defined by the stopper is set to the origin position. The linear actuator according to claim 1 or 2, wherein two flat surfaces parallel to each other in the radial direction are formed on the outer periphery of the substantially U-shaped stopper. With a screw cover made stretchable multi cylinder axially for covering the output screw shaft, the stopper covers the output screw shaft, and further protrusions incorporated into the interior of the screw cover form claims 1, characterized in that that to the linear actuator according to any one of claims 3. The linear actuator according to any one of claims 1 to 4, wherein the output screw shaft is a ball screw shaft, and the screw nut is a ball screw nut. The linear actuator according to any one of claims 1 to 4, wherein the output screw shaft is a sliding screw shaft, and the screw nut is a sliding screw nut.

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