JP2003113919A - Ball screw apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operational responsiveness in the ball screw apparatus while maintaining a situation where a nut member or a screw shaft are forced to stop by means of physical abutment in a predetermined position in a retracting direction, the nut member and the screw shaft may be rapidly separated without resistance when moving from the stop position to the expanding direction. SOLUTION: In a structure wherein the nut member 2 disposed on the outer circumference side of the screw shaft 3 is supported, via a bracket 8, on a shaft body 12 inserted into a center hole of the cylindrical screw shaft 3, for the bracket 8 and the screw shaft 3 internal with the nut member 2, a stopper pin 18 for forcibly stopping the nut member 2 in the predetermined position in the retracting direction and a notch 19 are independently provided and the stopper pin 18 and the notch 19 are disposed in contact with each other in the peripheral direction, to thereby prevent the stopper pin 18 and the notch 19 in a stop state from engaging with each other as in a conventional example so as to easily separate.

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. When the nut member is moved in the direction that shortens the total length of the member and the screw shaft, a part of the nut member is brought into contact with a part of the screw shaft from the axial direction to stop forcibly. I am trying to let you.

[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, normally, when the nut member is forcibly stopped in the contraction direction, the motor is controlled to stop after a predetermined time lag. With this, since the driving torque of the motor is continuously applied to the nut member for a predetermined time even when the nut member is forcibly stopped,
The abutting portion between the nut member and the screw shaft bites strongly in the form of biting, resulting in an increased frictional resistance.

Therefore, it is necessary to excessively increase the driving torque of the motor in the initial stage of moving the nut member in the extending direction from the above state, and the time until the nut member is separated from the screw shaft and started to move is lost. As a result, the responsiveness of the operation decreases.

However, if the nut member is stopped by interrupting the input of the driving torque of the motor to the nut member by controlling the phase of the motor, for example, the above problem can be avoided, but the nut deteriorates due to aging, for example. Considering that power transmission loss occurs due to a ball sliding between the member and the screw shaft, there is a concern that the stop position of the nut member may vary with time.

In view of such circumstances, the present invention relates to a ball screw device, in which a nut member or a screw shaft is forcibly stopped by physical contact at a predetermined position in the contraction direction, while extending from the stop position. The purpose is to enhance the responsiveness of operation by allowing the nut member and the screw shaft to be quickly separated without resistance when moving in the direction.

[0009]

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 the thrust to torque, the screw shaft is a cylindrical shape, The nut member is supported via a bracket with respect to a shaft body that is inserted into the central hole of the screw shaft in a non-contact manner, and the bracket is provided concentrically inside and outside in the radial direction and has one end side in the axial center direction. And an outer tubular portion connected to each other by the inner tubular portion, the inner tubular portion being disposed in the center hole of the screw shaft in a non-contact state and supported by the shaft body, and the outer tubular portion. Is integrally fitted to the outer circumference of the area on the one end side in the axial direction of the nut member. And a stopper and a 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 bracket and the screw shaft face each other in the axial direction. Are provided so as to be in contact with and separated from each other in the circumferential direction.

According to a second aspect of the present invention, there is provided a ball screw device according to the first 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 third aspect of the ball screw device of the present invention, in the first or second 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 fourth aspect of the present invention, there is provided a ball screw device according to any one of the first to third aspects, wherein 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 fifth aspect of the ball screw device of the present invention, in any one of the first to fourth aspects, the bracket is made 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 sixth aspect of the present invention, there is provided a ball screw device according to any one of the first to fifth 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, according to the present invention, the nut member arranged on the outer diameter side of the screw shaft with respect to the shaft body inserted through the central hole of the cylindrical screw shaft is supported via the double-cylindrical bracket. As a result, the nut member and the screw shaft are forcibly stopped by physically abutting them at a predetermined position in the contraction direction on the premise of a compact structure in the axial direction. Even in the situation where the driving torque is continuously applied with respect to time, the contact portion between the bracket integral with the nut member and the screw shaft is merely pressed in the circumferential direction, and does not act like biting as in the conventional example. This allows the nut member and the screw shaft to be quickly separated without resistance when moving from the stop position in the extension direction.

In particular, according to the second aspect of the present invention, the nut member and the bracket are used in such a manner that the nut member and the bracket are moved back and forth while being rotated 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. Further, in the invention of claim 3, the stopper and the notch are to be arranged.

Further, in the invention of claim 4, the interference between the screw shaft and the bracket integral with the nut member is avoided in the state where the nut member is forcibly stopped.

Further, in the invention of claim 5, since the bracket is provided with the gear, 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 6, the cage ring is used to prevent the balls from interfering with each other, so that the behavior of the balls is stabilized.

[0020]

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 an 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 illustrated ball screw device 1, a nut member 2, a screw shaft 3, a plurality of balls 4, and a 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 one 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 separated from each other by the maximum distance, 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 two thread grooves 31a, 31b adjacent to each other in the axial direction of the screw shaft 3, 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 of the ball. 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 matching between the bracket 8 and the nut member 2 in the joining process,
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 in the axial direction changes greatly. 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.

The characteristic part of the present invention will now be described. That is, the stopper pin 18 and the notch 19 for forcibly stopping the nut member 2 at a predetermined position in the contraction direction are provided separately for the bracket 8 and the screw shaft 3.

Specifically, as shown in FIG. 8, the stopper pin 18 projects in the posture along the axial direction with respect to the inner end surface of the thick portion 37 that 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. .

According to this structure, in the above description of the operation, when the nut member 2 is moved in the contracting direction, the nut member 2 approaches the predetermined stop position, and 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.

Along with this, the drive current of a motor (not shown) generally rises above a specified value, and the control device or the like detects this phenomenon and stops the motor. In this way, the nut member 2 and the bracket 8
When a time lag occurs from the time when the motor is forcibly stopped until the motor is stopped, after the nut member 2 and the bracket 8 are forcibly stopped, the driving torque from the motor is applied to the bracket 8 and the nut member 2 for a predetermined time. The notch 19 of the bracket 8 is pressed against the stopper pin 18 from the circumferential direction in order to continue to be applied. However, since the notch 19 is pressed against the stopper pin 18, it does not need to bite like the conventional example. Therefore, when the motor is driven in the reverse rotation direction from the stopped state, the notch 19 of the bracket 8 is immediately separated from the stopper pin 18 without resistance,
The bracket 8 and the nut member 2 move in the extension direction.

As described above, in this embodiment,
By supporting the nut member 2 arranged on the outer diameter side of the screw shaft 3 with respect to the cylinder shaft 11 inserted through the center hole of the cylindrical screw shaft 3 via the double cylinder-shaped bracket 8, the shaft center In the ball screw device 1 having a compact structure in the direction, in order to stop the nut member 2 at a predetermined position in the contracting direction, the stopper pin 18 provided on the screw shaft 3 is provided on the bracket 8 integrated with the nut member 2. The movement of the nut member 2 is physically forcibly stopped so that the inner wall 19a of the notch 19 is brought into contact with the notch 19 from the circumferential direction. As a result, similarly to the conventional example, while the nut member 2 and the screw shaft 3 are physically abutted at a predetermined position in the contraction direction and forcedly stopped, the bracket 8 and the nut member 2 are stopped for a predetermined time after the stop. Even if the drive torque is continuously applied from the motor, the stopper pin 18
Since the frictional resistance of the contact portion between the notch 19 and the notch 19 does not increase, the nut member 2 and the screw shaft 3 are quickly separated without resistance when the nut member 2 is moved in the extension direction from the stop position. become. 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 and 34 on the screw thread 32 of the screw shaft 3, two screw 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-mentioned embodiments, and various applications and modifications can be considered.

First, in the above embodiment, in order to forcibly stop the nut member 2 at a predetermined position in the contraction direction, the screw shaft 3
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.

Further, in the above embodiment, the bracket 8 is connected 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, in the ball screw device 1, 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 rotated. 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.

[0054]

In the ball screw device according to the inventions of claims 1 to 6, when the nut member is forcibly stopped at a predetermined position in the contracting direction, the bracket and the screw shaft integral with the nut member are screwed as in the conventional example. Since the contact is made in the circumferential direction instead of the contact in the axial direction, even when the driving torque is continuously applied for a predetermined time after the nut member is forcibly stopped, Since the abutting part of the integral bracket and the screw shaft is only pressed in the circumferential direction, it does not have to act like biting as in the conventional example, and as a result, when the nut member is moved in the extension direction from the stop position. In addition, it becomes possible to move quickly without resistance and improve the operation response and reliability.

Particularly, in the invention of claim 4, the nut member is forcibly stopped so that the bracket integral with the nut member and the screw shaft are prevented from interfering with each other. Therefore, the nut member is stopped in the contracting direction. This is advantageous in stabilizing the position.

Further, according to the invention of claim 5, 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 6, since the plurality of balls are prevented from interfering with each other by using the cage ring, the behavior of the balls is stabilized and the relative rotation between the nut member and the screw shaft is made. 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

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isao Usuki             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. F term (reference) 3J030 BC01 BD06 CA10                 3J050 AA02 BA03 BB05                 3J062 AB22 AC07 BA16 BA31 CD05                       CD08 CD13 CD22 CD23 CD63

Claims (6)

[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 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. The ball screw device, wherein the stopper and the notch are separately provided so as to come into contact with and separate from each other in the circumferential direction. 2. The ball screw device according to claim 1, wherein the screw shaft is non-rotating with respect to a 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. 3. The ball screw device according to claim 1 or 2, 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. 4. The ball screw device according to claim 1, wherein the nut member is forcibly stopped by the contact between the stopper and the notch, and the bracket and the screw shaft are integral with the nut member. A ball screw device in which and are arranged in a non-contact relationship in the axial direction. 5. The ball screw device according to claim 1, wherein the bracket is made of a metal material, and a resin gear is integrally formed on an outer peripheral surface of an outer cylinder portion of the bracket. A ball screw device characterized in that 6. The ball screw device according to claim 1, wherein a cage ring that rotatably holds the balls 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.