JP2003120782A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of impact noise at the time of physical abutment, and reduce damage by collision to improve durability in a ball screw device in spite of such a form that a nut member or a screw shaft is forcedly stopped by the abutment at a prescribed position in a contraction direction. SOLUTION: To a nut member 2, integrated with a bracket 8 and the screw shaft 3, a stopper pin 18 and cut 19 for forcedly stopping the nut member 2 at the prescribed position in the contraction direction are provided to be distributed. The stopper pin 18 and the cut 19 are disposed in such a mode that they are applied in a circumferential direction. On an abutting part of at least either of the stopper pin 18 and the cut 19, elastic material 20 of a durometer hardness of 10-70 is installed. No collision noise is thus generated when the stopper pin 18 is abutted to a depth wall 19a of the cut 19. A collision load is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw device configured to convert torque between thrust force and torque between a nut member and a screw shaft.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed a ball screw device as
Japanese Patent Application Laid-Open No. 2001-116095 has been proposed.

In this structure, the screw shaft is immovably and non-rotatably supported in the axial direction, and the nut member is rotationally driven by the motor and the input gear to reciprocate in the axial direction. As a form in which the member is stopped at a predetermined position in the contraction direction, a part of the nut member is brought into contact with a part of the screw shaft in the axial direction to forcibly stop the member.

[0004]

In the above-mentioned conventional example, the nut member is stopped at a predetermined position in the contracting direction,
Since a part of the nut member is brought into contact with a part of the screw shaft in the axial direction to physically forcibly stop, the following problems occur.

That is, the nut member and the screw shaft are usually made of a metal material. However, a collision noise is generated when the nut member is forcibly stopped and a collision load is repeatedly applied to the nut member and the screw shaft. You will also be damaged.

In addition to the above, the applicant of the present application, as shown in FIG. 1 presented in the following embodiment, has an outer diameter of the screw shaft 3 with respect to the shaft body 12 inserted into the center hole of the cylindrical screw shaft 3. In the structure in which the nut member 2 disposed on the side is supported via the bracket 8, in order to forcibly stop the nut member 2 at a predetermined position in the shrinking direction with respect to the bracket 8 and the screw shaft 3 that are integral with the nut member 2. Stopper pin 18 and notch 1
9 and 9 are provided separately, and a structure in which the stopper pin 18 and the notch 19 are arranged so as to be in contact with each other in the circumferential direction is considered, but also in this case, the same problem as described above may occur.

In view of the above circumstances, the present invention provides a ball screw device in which the nut member or the screw shaft is forcibly stopped by physical contact at a predetermined position in the contracting direction, and The purpose is to prevent the generation of collision noise, reduce damage due to collision, and improve durability.

[0008]

According to a first aspect of the ball screw device of the present invention, between the thread groove provided on the inner peripheral surface of the nut member and the thread groove provided on the outer peripheral surface of the screw shaft. A plurality of balls are interposed in the nut member and the screw shaft to convert torque to thrust, or to convert thrust to torque, the nut member and the screw shaft in the contracting direction. When relatively moved, the nut member and the screw shaft are forced to stop at a predetermined position by abutting regions facing each other in the axial direction from the axial direction. Durometer hardness of at least one of the contact parts of the screw shaft is 1
An elastic body of 0 to 70 is attached.

In the ball screw device of the present invention, a plurality of balls are interposed between the thread groove provided on the inner peripheral surface of the nut member and the thread groove provided on the outer peripheral surface of the screw shaft. And a structure in which torque is converted into thrust between the nut member and the screw shaft, or thrust is converted into torque, and the screw shaft has a cylindrical shape, and the nut member is the screw. An inner cylinder that is supported via a bracket with respect to a shaft body that is inserted into the center hole of the shaft in a non-contact manner, and that the bracket is provided concentrically inside and outside in the radial direction and is connected to one end side in the axial direction. And an outer cylinder part, wherein the inner cylinder part is arranged in the center hole of the screw shaft in a non-contact state and supported by the shaft body, and the outer cylinder part is a shaft of the nut member. It is integrally fitted to the outer periphery of the region on the one end side in the axial direction, and The stopper and the notch for stopping at a predetermined position when the nut member and the screw shaft are relatively moved in the contraction direction with respect to the region where the nut and the screw shaft are opposed to each other in the axial direction. The elastic body having a durometer hardness of 10 to 70 is attached to the contact portion of at least one of the stopper and the notch.

According to a third aspect of the present invention, there is provided a ball screw device according to the second aspect, wherein the screw shaft is non-rotatable and axially immovable with respect to a fixed portion, and the nut member is the The bracket is rotatably attached to the shaft through rolling bearings, the shaft is arranged to be movable in the axial direction, and torque is applied to the bracket, whereby the bracket And the nut member and the shaft body are integrally moved along the screw shaft in the axial direction.

According to a fourth aspect of the ball screw device of the present invention, in the second or third aspect, the stopper faces the inner cylindrical portion of the bracket in the axial direction in the screw shaft. The notch is provided in a predetermined region on the circumference, and the notch is provided in a region of the inner tubular portion of the bracket that faces the screw shaft in the axial direction.

According to a fifth aspect of the present invention, there is provided the ball screw device according to any one of the second to fourth aspects, in which the nut member is forcibly stopped by the contact between the stopper and the notch. The bracket integral with the nut member and the screw shaft are arranged in a non-contact relationship in the axial direction.

According to a sixth aspect of the ball screw device of the present invention, in any one of the second to fifth aspects, the bracket is formed of a metal material, and the bracket is formed on the outer peripheral surface of the outer cylindrical portion. A resin gear is integrally molded.

According to a seventh aspect of the present invention, there is provided a ball screw device according to any one of the first to sixth aspects, wherein each of the balls is rotatable in an opposed annular space between the screw shaft and the nut member. A retainer ring for holding is interposed so as to be rotatable relative to each other.

In short, in the present invention, since the elastic body is interposed in the abutting portion when the nut member and the screw shaft are forcibly stopped at the predetermined position in the contraction direction, the collision noise is not generated. At the same time, the shock will be alleviated.

Particularly, in the ball screw device according to the second aspect, the nut member arranged on the outer diameter side of the screw shaft with respect to the shaft body inserted through the center hole of the cylindrical screw shaft has a double cylindrical shape. Assuming a structure that is made compact in the axial direction by supporting it through a bracket, the nut member and the screw shaft are contracted in the contracting direction by abutting the stopper provided on the nut member and the screw shaft with the notch in the circumferential direction. In addition to taking the form of forcibly stopping at a predetermined position, an elastic body is provided at the contact portion between the stopper and the notch.
As a result, it is possible to prevent the occurrence of a collision sound and reduce the impact. Moreover, with this structure, even in a situation where the driving torque is continuously applied for a predetermined time after the nut member is forcibly stopped, only the contact portion between the nut member and the bracket and the screw shaft is pressed in the circumferential direction. In this case, it is possible to avoid the bite phenomenon that occurs when the nut member and the screw shaft are brought into contact with each other in the axial direction. Therefore, the nut member and the screw shaft are quickly separated without any resistance when moving in the extension direction from the stop position, which is preferable.

In the invention of claim 3, the nut member and the bracket are moved forward and backward while rotating along the non-rotating and axially immovable screw shaft, that is, the positive efficiency for converting torque into thrust. It is specified in the usage form in. According to the invention of claim 4, the stopper and the notch are to be arranged.

According to the fifth aspect of the invention, the interference between the screw shaft and the bracket integral with the nut member is avoided while the nut member is forcibly stopped.

Further, in the invention of claim 6, since the gear is provided on the bracket, the torque can be transmitted between the nut member integrated with the bracket and the external device, and the gear is made of resin. Therefore, it can be easily manufactured by insert molding or the like.

Further, in the invention of claim 7, the cage ring is used to prevent the balls from interfering with each other, so that the behavior of the balls is stabilized.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described in detail with reference to the embodiments shown in the drawings.

1 to 9 show one embodiment of the present invention. 1 is a vertical cross-sectional view of a ball screw device, and FIG. 2 is
1 is a longitudinal sectional view showing a state where the nut member is moved to one side in the axial direction from the state of FIG. 1, FIG. 3 is an exploded perspective view of the ball screw device, and FIG. 4 is a plan view of a part of the ball screw device. FIG. 5, FIG. 5 is a cross-sectional view taken along the line (5)-(5) of FIG. 4, FIG. 6 is a side view schematically showing the ball circulation path, and FIG. 7 is a front view of the ball circulation path of FIG. FIG. 8 is a perspective view showing a forced stop structure in the contraction direction of the nut member, FIG.
[FIG. 6] is a plan development view showing how the notch engages with the stopper pin.

In the ball screw device 1 of the illustrated example, the nut member 2, the screw shaft 3, the plurality of balls 4, and the cage ring 5 are provided.
And the balls 4 are circulated between the opposing surfaces of the nut member 2 and the screw shaft 3.

The nut member 2 is formed with a single thread groove 21 which is continuous from one shaft end to the other shaft end,
In addition, the screw shaft 3 is formed with discontinuous screw grooves 31a and 31b in the middle of its axial direction. The thread groove 21 of the nut member 2 and the thread groove 31 of the screw shaft 3
a and 31b are set to have the same lead angle. The cross-sectional shape of these two thread grooves 21, 31a, 31b is a Gothic arc shape, but it may be a semicircular shape.

By the way, in this embodiment, the nut member 2 and the screw shaft 3 are maximally separated from each other, and the overlapped region of a predetermined length in the axial direction is secured in the maximum extension state. Two winding screw grooves 31a and 31b are set to be arranged, and these two winding screw grooves 31a and 31b are set as independent closed loops, respectively, and balls arranged in the closed winding two winding screw grooves 31a and 31b. The four groups are made to circulate independently.

Specifically, in the screw thread (land portion) 32 existing between the two thread grooves 31a, 31b adjacent to each other in the axial direction of the screw shaft 3, the two thread grooves 31a, 31b are wound.
Ball circulation grooves 33 and 34 are individually provided as closed loops. The two ball circulation grooves 33 and 34 respectively connect and connect the upstream side and the downstream side of the two winding screw grooves 31a and 31b, respectively, and the balls located downstream of the respective winding screw grooves 31a and 31b. It has a meandering shape such that the fourth group is sunk toward the inner diameter side, and the thread (land portion) 22 of the nut member 2 is passed over and returned to the upstream side.

The retainer ring 5 rotatably retains each of the plurality of balls 4 at equal intervals around the circumference. The cage ring 5 is made of a thin cylindrical member, and a plurality of ball pockets 51 having an elongated hole along the axial direction are provided at several places on its circumference. Two ball pockets 51 are provided for each ball pocket 51. The balls 4 are stored one by one.

The retainer ring 5 is attached to the outer diameter side of the screw shaft 3 in a state of being substantially immovably positioned in the axial direction and in a relatively rotatable state.
Therefore, a reduced diameter portion 35 is provided on the free end side of the thread groove 3, and a radially inwardly facing flange 5 is provided at one end of the cage ring 5.
2 are respectively provided, the flange 52 of the cage ring 5 is fitted into the reduced diameter portion 35 of the screw shaft 3, and the screw shaft 3
The retaining ring 7 is engaged with the circumferential groove provided in the reduced diameter portion 35. However, the retaining ring 7 has a reduced diameter portion 35 of the screw shaft 3.
And the flange 52 of the retainer ring 5 between the retaining ring 7 and the step wall surface 36.
Are arranged with some play in the axial direction.
As a result, the cage ring 5 is substantially immovable with respect to the screw shaft 3 in the axial direction and is allowed to rotate relatively.

The nut member 2 is attached to the bracket 8
Are integrally connected to. This bracket 8
Is a reduction gear 10 whose rotational power source such as a motor (not shown) is
Is supported via a rolling bearing 12 with respect to a cylindrical shaft 11 inserted through a central hole of the cylindrical screw shaft 3 so as to be movable in the axial direction. Further, the screw shaft 3 is supported via a rolling bearing 14 with respect to a rotating shaft 13 that is spline-fitted to the inner diameter side of the cylindrical shaft 11. Although not shown, the rotary shaft 13 is rotatably supported by a fixed portion such as a case so as not to move in the axial direction. It should be noted that a pair of flanges 15 and 16 having opposed tapered surfaces are provided separately on one end side of the cylindrical shaft 11 and the rotating shaft 13 in the axial center direction. The gap is adjusted in size as the nut member 2 reciprocates in the axial direction, so that the winding diameter of the belt 17 wound between the facing surfaces of the flanges 15 and 16 is changed.

The bracket 8 is made of a metal material whose upper half has a substantially U-shaped cross section. In other words, the bracket 8 has a shape in which one end side in the axial center direction of the inner tubular portion 81 and the outer tubular portion 82 that are concentrically provided inside and outside the radial direction are connected. The inner cylindrical portion 81 is arranged in the center hole of the screw shaft 3 in a non-contact state, and the inner cylindrical portion 81 rolls with respect to the cylindrical shaft 11.
Is supported through. Further, the outer tubular portion 82 is integrally fitted to the outer periphery of the region of the nut member 2 on the one axial end side, and is provided on the inner peripheral surface of the outer tubular portion 82 at the base side as shown in FIG. The bracket 8 and the nut member 2 are integrally coupled in the circumferential direction by fitting the serrations 83 and the serrations 23 provided on the outer peripheral surface on the inner side of the nut member 2 in the fitting direction. A resin gear 9 is integrally formed on the outer peripheral surface of the outer cylinder portion 82.

By the way, when the gear 9 is molded on the bracket 8, the region of the outer cylindrical portion 82 of the bracket 8 excluding the serration portion, that is, the surface on which the nut member 2 is fitted is used as a reference surface for the mold. To do. With this configuration, the roundness and the surface roughness of the fitting surface are finished with high precision, so that the tooth profile of the gear can be formed with high precision, which is preferable.

Further, in order to facilitate the phase alignment of the bracket 8 and the nut member 2 in the connecting step,
By eliminating one tooth of both serrations 83 and 23, the bracket 8 and the nut member 2 can be coupled only at a predetermined phase.

Now, a procedure for assembling the ball screw device 1 described above will be described. First, after attaching the cage ring 5 to the screw shaft 3, grease is applied to the ball pocket 51 of the cage ring 5 so as to fill the ball pocket 51, and the ball pocket 51 is attached to the ball pocket 51. Insert the required number of balls 4. The grease here is urea-based grease having a viscosity that prevents the balls 4 from falling by its own weight, and the grease holds the balls 4 in the ball pockets 51. After this, the retainer ring 5 is assembled in the nut member 2 in a state where the retainer ring 5 is not rotated with respect to the screw shaft 3.

Next, the operation of the ball screw device 1 described above will be described. First, when the bracket 8 and the nut member 2 are rotated by driving a motor (not shown), the nut member 2 itself can be linearly moved in one axial direction along the screw shaft 3 while rotating. Thus, for example, the state shown in FIG. 1 is changed to the state shown in FIG.
On the other hand, when the motor is driven in the reverse rotation direction to the above, the nut member 2 is moved in the other axial direction while rotating in the opposite direction to that described above, so that the state shown in FIG. It becomes a state.

As described above, by reciprocating the nut member 2 in the axial direction, the range in which the nut member 2 and the screw shaft 3 overlap with each other in the axial direction changes greatly, but in the screw shaft 3, the ball circulation groove is formed. The ball group 4 rolls and circulates while being guided by the cage ring 5 in the two thread grooves 31a and 31b of the screw shaft 3 which are individually closed loop by 33 and 34. In addition to being smoothly guided, it is possible to reliably prevent the phenomenon in which the ball 4 comes off during the process in which the nut member 2 reciprocates within a predetermined movement stroke range.

In the above description of the operation, in order to forcibly stop the nut member 2 at a predetermined position in the contracting direction,
A stopper pin 18 and a notch 19 are provided separately for the bracket 8 and the screw shaft 3.

Specifically, as shown in FIG. 8, the stopper pin 18 projects in a posture along the axial direction with respect to the inner end surface of the thick portion 37 which bulges radially inward on the screw shaft 3. The notch 19 is embedded in the state, and the notch 19 is provided in the inner cylindrical portion 82 of the bracket 8 and is directed inward in the radial direction.
It is provided at the inner diameter side edge of 5 for a predetermined angular range on the circumference. The notch 19 has a width that gradually increases in the axial direction from the upstream side to the downstream side in the rotation direction toward the contraction side of the bracket 8 and has a substantially triangular shape when seen in a plan view.

The stopper pin 18 and the notch 19 are also provided.
In the state where the nut member 2 is forcibly stopped at a predetermined position in the contraction direction by contact with, the bracket 8 integrated with the nut member 2 and the screw shaft 3 are arranged in a non-contact relationship in the axial direction. .

Moreover, the back wall 1 on the wide side of the notch 19 is formed.
9a absorbs the impact at the time of collision with the stopper pin 18,
An elastic body 20 for relaxing is provided. The elastic body 20 preferably has a durometer hardness within the range of 10 to 70. For example, rubber or the thermoplastic elastomer resin described below is selected. The thermoplastic elastomer resin having a durometer hardness within the range of 10 to 70 is, for example, Hytrel manufactured by Toray DuPont Co., Ltd., Santoprene manufactured by AES Japan Co., Ltd., or Dainippon Ink Co., Ltd. The trade name Pandex is preferred. When the hardness of the elastic body 20 is smaller than the lower limit value of 10, the strength is insufficient and the upper limit value of 70 is obtained.
If it is larger than this, the shock absorbing effect becomes thin. Further, the elastic body 20 can be provided in the embedded state as well as the attached state as illustrated. Further, the elastic body 20 may be attached to the protruding portion of the stopper pin 18 instead of being provided on the back wall 19a of the notch 19.

According to this structure, in the above description of the operation, when the nut member 2 is moved in the contracting direction and the nut member 2 approaches the predetermined stop position, as shown in FIG. Bracket 8 that rotates together with 2
The notch 19 starts to overlap with the stopper pin 18 of the screw shaft 3 in the radial direction from the end on the narrow side, and finally the wide wall 19a on the wide side of the notch 19 is the peripheral surface of the stopper pin 18. With this, the nut member 2 and the bracket 8 are physically forcibly stopped. Here, the impact sound and impact when the notch 19 comes into contact with the stopper pin 18 are absorbed and attenuated by the elastic body 20 arranged in the notch 19, so that damage to the stopper pin 18 and the bracket. It is possible to contribute to improving the durability of the resin gear 9 integrally molded with the resin gear 8 by reducing damage.

When the nut member 2 is forcibly stopped as described above, the drive current of the motor (not shown) generally rises above the specified value accordingly.
A control device or the like detects this phenomenon and stops the motor. In this way, when there is a time lag from the time when the nut member 2 and the bracket 8 are forcibly stopped until the motor is stopped, after the nut member 2 and the bracket 8 are forcibly stopped, the motor is driven for a predetermined time. Since the torque is continuously applied to the bracket 8 and the nut member 2, the notch 19 of the bracket 8 is pressed against the stopper pin 18 from the circumferential direction. It is possible to avoid the biting phenomenon that occurs when the contact is made. Therefore, when the motor is driven in the reverse rotation direction from the stopped state, the notch 1 of the bracket 8 is cut off from the stopper pin 18.
9 separates immediately without resistance, and the bracket 8 and the nut member 2 move in the extension direction. Therefore,
The operation response of the ball screw device 1 is greatly improved, which can contribute to the improvement of reliability.

By the way, as in the above-described embodiment, by providing the two ball circulation grooves 33, 34 on the thread 32 of the screw shaft 3, two thread grooves 31 adjacent to each other in the axial direction are provided.
If each of a and 31b is an independent closed loop, and the ball group 4 is circulated in the closed loop,
It is possible to eliminate the high-precision part known as a circulating top,
For example, it is possible to save the labor of forming a through hole for mounting the circulating top in the nut member 2 and the labor of assembling the circulating top.
In addition to contributing to the reduction of manufacturing cost, it is possible to avoid the quality deterioration due to the misalignment such as the necessity of aligning the ball circulation groove of the circulation top with the screw groove. Moreover, as shown in FIG. 6, if the two ball circulation grooves 33 and 34 are provided in substantially the same phase and adjacent to each other in the axial direction, the screw grooves 31a and 31b of the screw shaft 3 are formed.
Can be arranged closer to each other in the axial direction, which is advantageous in reducing the occupied area in the axial direction. However, in this case, the balls 4 located in the ball circulation grooves 33 and 34 are
Since the radial load and the axial load cannot be received, if the two ball circulation grooves 33, 34 are provided close to each other in the circumferential direction and the axial center direction, a load non-bearing region can be formed in a predetermined angular range on the circumference. . However, as in the above-described embodiment, if the axial dimension of the nut member 2 and the screw shaft 3 is shortened and the outer diameter dimension is set large, as shown in FIG. 7, the ball circulates on the circumference. The angle θ range of the region where the grooves 33, 34 are present is small, and the balls 4 located in the ball circulation grooves 33, 34
Since it is possible to reduce the number of load bearings, it is possible to suppress a decrease in load bearing capacity, which is not a problem in practical use.

The present invention is not limited to the above-described embodiments, and various applications and modifications can be considered.

First, in the above-described embodiment, in order to independently circulate and circulate the group of balls 3 by individually winding the two thread grooves 31a and 31b provided in the screw shaft 3 as a closed loop, the ball shaft is circulated in the screw shaft 3. Although an example in which the grooves 33 and 34 are provided is given, the present invention can be applied to a configuration in which a conventional general circulating top is attached to the nut member 2.

Further, in the above embodiment, the notch 19 provided on the bracket 8 and the stopper pin 18 provided on the screw shaft 3 are provided.
And the nut member 2 are forcibly stopped by abutting from the circumferential direction, but unlike such a form, although not shown, a part of the nut member 2 or the bracket 8 and a part of the screw shaft 3 are not shown. The present invention can be applied to a configuration in which the nut member 2 is forcibly stopped by abutting from the axial direction. In this case, the elastic body 20 may be provided on at least one of the contact portions.

In the above embodiment, the screw shaft 3 is used to forcefully stop the nut member 2 at a predetermined position in the contracting direction.
Although the stopper pin 18 is provided on the bracket 8 and the notch 19 is provided on the bracket 8, the arrangement may be reversed.
As shown in 0, a convex portion 18A is provided on the outer periphery of the base of the inner tubular portion 82 of the bracket 8 in place of the stopper pin 18, while a notch 19A is provided at one shaft end of the screw shaft 3 so as to contact with each other. It is possible to forcibly stop the nut member 2 at a predetermined position in the contracting direction. In this case, the elastic body 20 may be provided on either the convex portion 18A or the notch 19A.

Further, in the above embodiment, the bracket 8 is coupled to the nut member 2 by the serrations 83 and 23. However, as shown in FIG. Protrusions 84 are provided at several places on the circumference, and recesses 24 are provided at several places on the inner side in the fitting direction of the nut member 2, and the bracket 8 and the nut member 2 are fitted by fitting these in the axial direction. You may make it couple | bond so that relative rotation is impossible. In this case, in order to facilitate the phase matching between the bracket 8 and the nut member 2 in the joining process, one of the plurality of protrusions 84 provided on the bracket 8 and the plurality of recesses 24 provided on the nut member 2 are provided. It is preferable that the circumferential width of one of them is set to be larger than that of the other convex portion 84 and the concave portion 24 so that the bracket 8 and the nut member 2 can be coupled only at a predetermined phase.

In addition to the above, the ball screw device 1 is configured such that one of the nut member 2 and the screw shaft 3 is rotated to move the other in the axial direction, or one of the nut member 2 and the screw shaft 3 is moved. By moving in the axial direction, the other can be rotated to be used. The former usage pattern is called positive efficiency for converting torque to thrust, and the latter usage pattern is called reverse efficiency for converting thrust to torque. Hereinafter, four patterns (A-1 to A-4) related to the usage pattern in the normal efficiency and four patterns (B-1 to B-4) related to the usage pattern in the reverse efficiency will be described.

(A-1) As described in the above embodiment, the nut member 2 is moved in the axial direction while being rotated. In this case, the screw shaft 3 may be non-rotating and immobile in the axial direction, and the nut member 2 may be rotationally driven.

(A-2) The nut member 2 is moved in the axial direction without being rotated. In this case, while making the screw shaft 3 immobile in the axial direction, the nut member 2 is not rotated,
The screw shaft 3 may be driven to rotate.

(A-3) The screw shaft 3 can be moved in the axial direction while rotating. In this case, the nut member 2 may be non-rotated and immobile in the axial direction, and the screw shaft 3 may be rotationally driven.

(A-4) The screw shaft 3 is moved in the axial direction without being rotated. In this case, while the screw shaft 3 is not rotated, the nut member 2 may be immobile in the axial direction and the nut member 2 may be rotationally driven.

(B-1) The nut member 2 is rotated immovably in the axial direction. In this case, while making the nut member 2 immobile in the axial direction, the screw shaft 3 is kept non-rotating,
Should be moved in the axial direction.

(B-2) The nut member 2 is rotated while being moved in the axial direction. In this case, the screw shaft 3 may be immobile and non-rotatable in the axial direction, and the nut member 2 may be moved in the axial direction.

(B-3) The screw shaft 3 is rotated immovably in the axial direction. In this case, while the screw shaft 3 is immovable in the axial direction, the nut member 2 is not rotated and the nut member 2 is not rotated.
Should be moved in the axial direction.

(B-4) The screw shaft 3 is rotated while being moved in the axial direction. In this case, the nut member 2 may be immobile in the axial direction and not rotated, and the screw shaft 3 may be moved in the axial direction.

[0057]

In the ball screw device according to the invention of claims 1 to 7, an elastic body is interposed at the abutting portion when the nut member and the screw shaft are forcibly stopped at a predetermined position in the contracting direction. Therefore, the collision noise is not generated and the impact is alleviated, which contributes to the improvement of durability.

In particular, according to the second aspect of the invention, when the nut member is forcibly stopped at a predetermined position in the shrinking direction, the nut member and the screw shaft are not brought into contact with each other in the axial direction unlike the conventional example. Since the nut members are brought into contact with each other in the circumferential direction, even if the driving torque is continuously applied for a predetermined time after the nut member is forcibly stopped, the contact portion between the nut member and the bracket and the screw shaft is in contact with each other. It is possible to avoid the biting phenomenon that occurs when the blades are pressed in the circumferential direction and brought into contact with each other in the axial direction. Therefore, when the nut member is moved in the extension direction from the stop position, the nut member can be moved quickly without resistance, and the operation response and reliability can be improved.

Further, in the invention of the fifth aspect, since the interference between the nut member and the bracket integral with the nut member and the screw shaft is avoided while the nut member is forcibly stopped, the nut member is stopped in the contracting direction. This is advantageous in stabilizing the position.

Further, according to the invention of claim 6, since the bracket is provided with the gear, the torque can be transmitted between the nut member integrated with the bracket and the external device.
Moreover, since this gear is made of resin, it can be easily manufactured by insert molding or the like, and the cost can be reduced.

Further, in the invention of claim 7, since the plurality of balls are prevented from interfering with each other by using the retainer ring, the behavior of the balls is stabilized and the relative rotation between the nut member and the screw shaft is prevented. This is advantageous in improving the operational stability such as being kept smooth.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a ball screw device according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a state in which the nut member is moved to one side in the axial direction from the state of FIG.

FIG. 3 is an exploded perspective view of a ball screw device.

FIG. 4 is a plan view of a part of the ball screw device in section.

5 is an arrow view of a cross section taken along line (5)-(5) of FIG.

FIG. 6 is a side view schematically showing a ball circulation path.

FIG. 7 is a front view of the ball circulation path of FIG.

FIG. 8 is a perspective view showing a forcible stop structure in a contracting direction of a nut member.

FIG. 9 is a plan development view showing how the notch engages with the stopper pin.

FIG. 10 is a perspective view showing another example of the forced stop structure in the contraction direction of the nut member.

FIG. 11 is a front view showing another example of the connecting portion between the nut member and the bracket.

[Explanation of symbols]

1 Ball screw device 2 Nut member 21 Thread of nut member 3 screw shaft 31a, 31b Thread groove of screw shaft 33, 34 Ball circulation groove of screw shaft Four balls 5 cage ring 8 brackets 81 Inner tube of bracket 82 Bracket outer cylinder 9 Bracket gear 11 cylinder axis 12 Rolling bearing 18 Stopper pin 19 Notch in the inner cylinder of the bracket 20 elastic body

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isao Usuki             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. (72) Inventor Masahiro Inoue             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. F-term (reference) 3J062 AB22 AC07 BA26 CD04 CD23                       CD54

Claims (7)

[Claims] 1. A plurality of balls are interposed between a thread groove provided on an inner peripheral surface of a nut member and a thread groove provided on an outer peripheral surface of a screw shaft, and torque is provided between the nut member and the screw shaft. Is a ball screw device for converting a thrust force into a thrust force or a thrust force into a torque, and when the nut member and the screw shaft are relatively moved in the contraction direction, the nut member and the screw shaft are in a predetermined position. In the structure described above, the regions that face each other in the axial direction are forcibly stopped by abutting from the axial direction, and at least one of the contact portion of the nut member and the screw shaft has a durometer hardness of 10. A ball screw device characterized in that elastic bodies 70 to 70 are attached. 2. A plurality of balls are interposed between a screw groove provided on the inner peripheral surface of the nut member and a screw groove provided on the outer peripheral surface of the screw shaft, and torque is provided between the nut member and the screw shaft. Is a ball screw device for converting a thrust force into a thrust force, or a thrust force into a torque force, wherein the screw shaft has a cylindrical shape, and the nut member is inserted into the central hole of the screw shaft in a non-contact manner. The body is supported via a bracket, and the bracket has an inner cylinder portion and an outer cylinder portion that are concentrically provided inside and outside in the radial direction and are connected to each other at one end side in the axial direction,
The inner tubular portion is disposed in the center hole of the screw shaft in a non-contact state and is supported by the shaft body, and the outer tubular portion is integrally formed on the outer periphery of the one end side in the axial direction of the nut member. Are fitted together in order to stop at a predetermined position when the nut member and the screw shaft are relatively moved in the contraction direction with respect to the region where the bracket and the screw shaft face each other in the axial direction. Stoppers and notches are provided so as to be brought into contact with and separated from each other in the circumferential direction, and at least one of the stoppers and the notches has an elastic body having a durometer hardness of 10 to 70. A ball screw device characterized by being attached. 3. The ball screw device according to claim 2, wherein the screw shaft is non-rotating with respect to the fixed portion and is immobile in the axial direction, and the nut member is rotating with respect to the shaft body via a rolling bearing. The shaft member is freely attached to each other, and the shaft member is arranged so as to be movable in the axial direction. When torque is applied to the bracket, the bracket member, the nut member, and the shaft member are three members. A ball screw device, wherein the ball screw device is integrally moved in the axial direction along the screw shaft. 4. The ball screw device according to claim 2 or 3, wherein the stopper is provided in a predetermined region on a circumference of the screw shaft that faces the inner cylindrical portion of the bracket in the axial direction. The ball screw device, wherein the notch is provided in a region of the inner cylindrical portion of the bracket that faces the screw shaft in the axial direction. 5. The ball screw device according to claim 2, wherein the nut member is forcibly stopped by the contact between the stopper and the notch, and the bracket and the screw shaft are integrated with the nut member. A ball screw device in which and are arranged in a non-contact relationship in the axial direction. 6. The ball screw device according to any one of claims 2 to 5, wherein the bracket is made of a metal material, and a resin gear is integrally formed on an outer peripheral surface of an outer cylindrical portion of the bracket. A ball screw device characterized in that 7. The ball screw device according to claim 1, wherein a retainer ring that rotatably holds each ball is relatively rotatably interposed in an opposed annular space between the screw shaft and the nut member. A ball screw device characterized by being mounted.