JP2012082902A - Ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent balls from bumping against each other when a nut moves down, to ensure smooth rolling of the balls when a ball screw is vertically used.SOLUTION: A cylindrical recess 13 is formed in a lower part of a straight path 11, to form a ball delivering member 5 having a ball passing hole 6. A protrusion 61 making an inner diameter of the ball passing hole 6 smaller than the diameter of a ball 3 is formed radially outside the ball passing hole 6 so as to be elastically deformable. The ball 3 falling from the straight path 11 temporarily stops on the protrusion 61 of the ball delivering member 5. The protrusion 61 elastically deforms by the weight of the ball 3. The return force of a movable piece 53 having opened outward delivers the ball 3 to the curved path 41. Each of the plurality of balls 3 is delivered to the curved path 41 at intervals. On a top surface 51 of the ball delivering member 5, a circular hole 8 is formed for housing a protrusion of a rotary jig to be used for removal.

Description

  The present invention relates to a ball screw characterized by a ball return path.

The ball screw is disposed between a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, and a raceway formed by the spiral groove of the nut and the spiral groove of the screw shaft. And a ball return path for returning the ball from the end point of the track to the start point, and the nut moves relative to the screw shaft as the ball rolls in the track.
The ball return path of the ball screw may be formed inside or outside the nut. When formed inside the nut, for example, as shown in FIGS. 10 and 11, the nut 1 is provided with a straight path 11 formed of a through hole extending in the axial direction, and recessed portions 12 are formed at both ends thereof. The end deflector 4 is disposed in the recess 12. The end deflector 4 is formed with a curved path 41 that connects the straight path 11 and the track. A circulation path of the ball 3 is formed by a ball return path constituted by the straight path 11 and the curved path 41 and a track formed by the spiral groove 1 a of the nut 1 and the spiral groove 2 a of the screw shaft 2. The ball 3 rolls in a loaded state in the track, and rolls in a no-load state in the ball return path.

After rolling in the track, the ball 3 enters the ball return path from the end point of the track and returns to the start point of the track, thereby circulating in the circulation path. The number of balls 3 arranged in the circulation path is set so that the total length of the diameters of the balls 3 is shorter than the length of the circulation path. That is, a gap is generated between the balls 3 in the circulation path.
In many cases, as shown in FIGS. 11 and 12, the ball screw is used with its axial direction oriented in the horizontal direction. However, as shown in FIG. 13, the axial direction may be used in the vertical direction. In this case, when the nut 1 descends, the balls 3 are likely to be concentrated in the circulation path (portion surrounded by A in FIG. 13) of the portion arranged on the lower side due to the action of gravity. Along with this, particularly during low-speed rotation or when lubrication is insufficient, the balls 3 compete with each other in the track (between the spiral grooves 1a and 2a), and the smooth rolling of the balls 3 is hindered. There is a possibility.

  Further, even when the axial direction is used in the horizontal direction, if the ball return path (the straight path 11 and the curved path 41) is arranged on the upper side of the screw shaft 2 as shown in FIG. As a result, the balls 3 are likely to be densely packed in the track (between the spiral grooves 1a and 2a). Accompanying this, there is a possibility that the balls 3 compete with each other in the track, particularly when rotating at a low speed or when lubrication is insufficient, and the smooth rolling of the balls 3 may be hindered.

As shown in FIG. 12, when the ball return path (the straight path 11 and the curved path 41) is arranged below the screw shaft 2, the balls 3 are densely packed in the ball return path due to the action of gravity. Since a gap is generated between the balls 3 in the space between the spiral grooves 1a and 2a, the above-described problem does not occur.
In the following Patent Document 1, the above-mentioned balls compete with each other by providing a restraining mechanism that restricts the movement of the ball (rolling element) at the connection portion between the ball return path (communication path) and the track (load path). Proposals have been made to prevent this. As a formation method of the restraining mechanism, a method of providing an elastic protrusion or a narrowed portion on the inner surface of the communication path, a method of providing a magnet on the outer side of the communication path, and the like are described.

JP 2008-175229 A

  In the method of forming the restraint mechanism described in Patent Document 1, there is room for improvement in terms of preventing the balls from competing when the nut descends when the axial direction of the ball screw is used in the vertical direction. There is. Further, there is room for improvement in terms of preventing the balls from competing in the track when the axial direction of the ball screw is directed to the left and right and the ball return path is disposed above the screw shaft.

  An object of the present invention is to prevent the balls from competing with each other when the nut descends when the axial direction is oriented vertically, and the axial direction is directed to the left and right, and the ball return path is located above the screw shaft. In the case of being used in an arrangement, it is to provide a ball screw that can ensure a smooth rolling of the ball by suppressing the competition between the balls in the track.

  In order to solve the above problems, a ball screw of the present invention includes a nut having a spiral groove formed on an inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, a spiral groove of the nut, and a spiral of the screw shaft. A ball disposed between tracks formed by grooves, and a ball return path for returning the ball from the end point of the track to the start point, and the nut rolls on the screw shaft by rolling the ball in the track. A ball screw that moves relative to each other, wherein the ball return path includes a straight path that is formed inside the nut and extends in the axial direction of the nut, and a curved path that is connected to both ends of the straight path. A cylindrical recess having a circular opening on the outer peripheral surface of the nut is formed in the road side portion, and a ball feeding member satisfying the following configurations (1) to (6) is disposed in the recess, and the configuration (4 ) Enters the recess provided on the inner peripheral surface of the recess. And wherein the are.

(1) A cylindrical body that fits into the recess.
(2) It has a ball passage hole penetrating in the radial direction of the cylindrical body and constituting the straight path.
(3) On the inner surface of the ball passage hole, a protrusion that makes the inner diameter of the ball passage hole smaller than the diameter of the ball is formed elastically deformable outward in the diameter direction of the ball passage hole.
(4) A claw portion protruding outward from the outer peripheral surface of the cylindrical body is formed so as to be elastically deformable in the radial direction of the cylindrical body.
(5) The engaging portion of the rotating jig is formed on the end surface in the axial direction arranged on the opening side of the nut of the cylindrical body.
(6) The ball is sent to the curved road side by the elastic deformation of the protrusion.

  According to the ball screw of the present invention, when the ball feeding member is disposed in the recess of the nut, the ball screw is disposed below the straight path when the axial direction is used in the vertical direction. The ball that has descended down the straight path enters the ball passage hole of the ball delivery member, temporarily stops on the projection, and then the projection is elastically deformed by the weight of the ball and the outer side. It is sent out to the curved road side by the force of returning to the original position after opening. Thereby, since the plurality of balls descending the straight path are sent out one by one in the curved path, the balls are arranged below the circulation path when the nut is descending. It is possible to prevent the balls from being concentrated in the portion (the portion following the curved path and the curved path of the track).

  When the ball return path is arranged on the upper side of the screw shaft with the axial direction turned to the left and right, the ball feeding member arranged on the opposite side of the nut traveling direction moves from the straight path. After the ball has entered the ball passage hole of the ball feeding member, comes into contact with the protruding portion and stops temporarily, the protruding portion is pushed by the ball and elastically deformed to open outward, and then return to the original position. It is sent out to the said curved road side by the force to do. As a result, the plurality of balls that have moved from the straight path are sent out one by one through the curved path, so that the balls are prevented from being concentrated in the track.

  Furthermore, in the ball screw of the present invention, the ball feeding member is attached to the concave portion of the nut by elastically deforming the claw portion inward in the diameter direction of the cylindrical body and inserting the claw portion into the recess of the nut. And since a ball delivery member has the said engaging part, a ball delivery member can be easily removed by engaging a rotation jig in the said engagement part and rotating a rotation jig.

  According to the ball screw of the present invention, when the axial direction is used in the vertical direction, the balls are prevented from competing when the nut is lowered, the axial direction is directed in the horizontal direction, and the ball return path is screwed. When arranged and used on the upper side of the shaft, the balls can be prevented from competing with each other in the track, thereby ensuring smooth rolling of the balls. Further, since the ball feeding member can be easily removed, the disassembling work can be easily performed.

It is sectional drawing which shows the ball screw (example which used the axial direction facing the up-down direction) equivalent to embodiment of this invention. It is sectional drawing which shows the attachment recessed part of the ball sending member in the nut of the ball screw of FIG. 1, Comprising: (a) is sectional drawing along the axial direction of the part arrange | positioned under a ball return path | route, (b) (A) is AA sectional drawing, (c) is a B arrow directional view of (b). It is a perspective view which shows the ball delivery member used with the ball screw of FIG. It is a figure which shows the ball delivery member used with the ball screw of FIG. 1, Comprising: (a) is a front view, (b) is a top view, (c) is a rear view, (d) is A arrow view of (a). (E) is a BB cross-sectional view of (a), and (f) is a CC cross-sectional view of (b). It is a figure which shows the state with which the ball delivery member was attached to the nut, Comprising: (a) is sectional drawing along the axial direction explaining the movement of the ball in a ball | bowl return path | route, (b) is A arrow view of (a) FIG. It is a figure explaining a motion of a ball sending member. It is the front view (a) and back view (b) which show the rotation jig of a ball sending member. It is the front view (a) which shows the attachment state of a ball delivery member, and the front view (b) which shows the state which rotated the ball delivery member from this state. It is sectional drawing which shows the ball screw (example which orient | assigned the axial direction to the left-right direction, and arrange | positioned and used the ball | bowl return path | route above the screw axis) equivalent to another embodiment of this invention. It is a perspective view which shows the nut of the conventional ball screw in which the ball | bowl return path | route is formed in the inside of a nut. It is sectional drawing which shows the state which orient | assigned the conventional ball screw in which the ball | bowl return path | route is formed inside the nut to the horizontal direction, and has arrange | positioned the ball | bowl return path above the screw shaft. It is sectional drawing which shows the state which orient | assigned the conventional ball screw in which the ball | bowl return path | route is formed inside the nut to the horizontal direction, and has arrange | positioned the ball | bowl return path below the screw axis. It is sectional drawing which shows the state which has arrange | positioned the conventional ball screw in which the ball | bowl return path | route is formed inside the nut toward the vertical direction.

Embodiments of the present invention will be described below.
FIG. 1 is a cross-sectional view showing the ball screw of this embodiment.
This ball screw includes a nut 1, a screw shaft 2, a ball 3, an end deflector 4, and a ball feeding member 5. A spiral groove 1 a is formed on the inner peripheral surface of the nut 1, and a spiral groove 2 a is formed on the outer peripheral surface of the screw shaft 2. By the spiral groove 1a of the nut 1 and the spiral groove 2a of the screw shaft 2, a track on which the ball 3 rolls in a loaded state is formed. The end deflector 4 is formed with a curved path 41 that connects the straight path 11 and the track.

The nut 1 is also formed with a straight path 11 formed of a through hole extending in the axial direction, and recessed portions 12 in which the end deflectors 4 are disposed are formed at both ends thereof. On the side disposed on the lower side of the nut 1 when the straight path 11 is used, as shown in FIG. 2A, a recess 13 for disposing the ball feeding member 5 is formed on the side close to the recess 12 of the straight path 11. Has been.
As shown in FIGS. 2 (b) and 2 (c), the recess 13 is formed in a columnar shape having the outer peripheral surface of the nut 1 as a circular opening. The recess 13 is formed with a recess 13 a for preventing the ball delivery member 5 from coming off.

  As shown in FIGS. 3 and 4, the ball delivery member 5 is formed of a cylindrical body that fits in the cylindrical recess 13. One end surface (upper surface) 51 in the axial direction of the cylindrical body forming the ball feeding member 5 is formed in an arc surface that is concentric with the outer peripheral circle of the nut 1 and has a slightly smaller diameter. The other axial end surface (lower surface) 52 is planar. The ball delivery member 5 is formed with a ball passage hole 6 penetrating in the radial direction of the cylindrical body.

A protrusion 61 is formed on the inner surface of the ball passage hole 6. The diameter d ₆ of the ball passage hole 6, except where the projecting portions 61 are formed is the same as the diameter d ₁₁ of the linear path 11. The diameter d ₆₁ of the portion where the protrusion 61 is formed is smaller than the diameter d _{3 of the} ball 3.
A movable piece 53 having a predetermined width (smaller than the diameter d ₆ ) is formed at the lower end of the cylindrical body forming the ball delivery member 5. The protrusion 61 is formed on the upper surface of the movable piece 53. By this movable piece 53, the protruding portion 61 can be elastically deformed outward in the diameter direction of the ball passage hole 6.

The movable piece 53 is separated from the cylindrical body in a range from one end in the length direction of the ball passage hole 6 to the center position by a notch 52a reaching the ball passage hole 6 from the lower surface 52 in the axial direction of the cylindrical body. Further, the lower surface 53a of the movable piece 53 is higher than the lower surface 52 of the cylindrical body by the cut 52b on the lower surface 52 side of the cylindrical body.
The ball delivery member 5 further includes a pair of claw portions 7 projecting outward from the outer peripheral surface of the columnar body at a position slightly below the upper surface 51 of the columnar body in an arrangement perpendicular to the length direction of the ball passage hole 6. Is formed. Each claw portion 7 and the outer peripheral portion 71 of the cylindrical body continuous with the claw portions 7 are formed in the cylindrical body to a position slightly below the center of the ball passage hole 6 by a notch 51a that enters along the axial direction from the upper surface 51 side of the cylindrical body. Separated from the central portion 72.

A gap W1 between the central portion 72 and the claw portion 7 due to the cut 51a is slightly larger than a protruding dimension W2 of the claw portion 7 from the cylindrical body. Therefore, the outer diameter by both the nail | claw part 7 can be made smaller than the outer diameter of a cylindrical body by elastically deforming both the nail | claw parts 7 to the center part 72 side. A recess 13 a provided in the recess 13 of the nut 1 has a shape in which the claw portion 7 is fitted.
This ball delivery member 5 further includes two circular holes (of the rotating jig) at a position above the ball passage hole 6 on the upper surface (axial end surface arranged on the opening side of the nut) 51 of the cylindrical body. The engaging portion) 8 is formed with a depth that does not reach the ball passage hole 6. Each circular hole 8 is disposed to face along the length direction of the ball passage hole 6, and the center of the cross-sectional circle of both the circular holes 8 is disposed on the concentric circle D of the cylindrical body.

The ball delivery member 5 can be produced by, for example, injection molding using polyacetal, polyethylene, or polypropylene.
As shown in FIG. 2, the ball delivery member 5 is formed such that the side where the projection 61 in the length direction of the ball passage hole 6 is formed is directed to the end deflector 4 side, and both the claw portions 7 are directed to the central portion 72 side. It is inserted into the recess 13 from the outer peripheral side of the nut 1 while being elastically deformed. As a result, as shown in FIG. 5, the outer peripheral portion of the claw portion 7 enters the recess 13 a of the concave portion 13, and the ball passage hole 6 communicates with the straight path 11. That is, the ball passage hole 6 constitutes a straight path of the ball return path together with the straight path 11 formed in the nut 1.

Thus, the portion of the ball return path of the ball screw that is disposed on the lower side when used is the ball of the ball feeding member 5 disposed in the straight path 11 formed in the nut 1 and the recess 13 of the nut 1. The passage hole 6 and the curved path 41 of the end deflector 4 disposed in the recess 12 of the nut 1 are formed. A line L in FIG. 5 indicates the position of the outer peripheral surface of the screw shaft 2.
When this ball screw is used with the screw shaft 2 oriented in the vertical direction, the ball 3 descending from the straight path 11 is first a ball of the ball delivery member 5 as shown in FIG. It stops once on the protrusion 61 of the passage hole 6. Next, as shown in FIG. 6B, the protrusion 61 is elastically deformed by the weight of the ball 3, and the movable piece 53 opens outward.

Along with this, when the ball 3 passes through the position of the protruding portion 61 of the ball passage hole 6, the movable piece 53 tries to return to the original position. As shown in FIG. 6C, the ball 3 is sent out from the ball passage hole 6 toward the curved path 41 by the force that the movable piece 53 returns to the original position. Further, the next ball 3 temporarily stops on the protruding portion 61.
Thus, since the plurality of balls 3 descending from the straight path 11 are sent out one by one through the curved path 41, the curved line disposed on the lower side when the nut 1 is descending. It is possible to prevent the balls 3 from being densely gathered in the portion following the curved path 41 of the path 41 and the track (spiral groove 2a). A two-dot chain line in FIG. 5 is a predicted contact line between the ball 3 and the spiral groove of the nut 1.

  When removing the ball delivery member 5, for example, a rotating jig 9 shown in FIG. 7 is used. Two columnar projections 91 are formed at the tip of the rotating jig 9 in an arrangement corresponding to the two circular holes 8 of the ball feeding member 5. As shown in FIG. 8, from the state (a) attached to the nut 1, the projection 91 of the rotating jig 9 is fitted in the circular hole 8 of the ball delivery member 5 and rotated, whereby the claw portion 7 is moved. It will be elastically deformed and will be removed from the recess 13a and will be in the state of (b). Thereby, since the ball delivery member 5 can be easily removed, the work of disassembling the ball screw can be easily performed.

In the ball screw of this embodiment, the curved path is connected to both ends of the straight path 11 formed in the nut 1 by arranging the end deflector 4 having the curved path 41 in the recess 14 of the nut 1. However, instead of this, an end cap having a curved path 41 may be attached to both ends of the nut 1 in the axial direction.
In addition, as shown in FIG. 10, when the ball screw of the present invention is used with the axial direction oriented in the left-right direction and the ball return path disposed on the upper side of the screw shaft, On the near side, a recess 13 in which the ball delivery member 5 is arranged is formed, and the ball delivery member 5 is arranged in the two recesses 13. As a result, a plurality of balls 3 that have moved from the straight path 11 are sent out to the curved path 41 one by one by the action of the ball delivery member 5 arranged on the opposite side of the nut traveling direction. Therefore, it is possible to suppress the balls 3 from being crowded in the track.

DESCRIPTION OF SYMBOLS 1 Nut 1a Spiral groove of nut 11 Straight path 12 Recessed part which arrange | positions an end deflector 13 Recessed part which arrange | positions a ball feeding member 2 Screw shaft 2a Spiral groove of a screw shaft 3 Ball 4 End deflector 41 Curved path 5 Ball feeding member 51 Ball feeding member Upper surface 51a cut 52 lower surface of ball feeding member 52a cut 52b cut 53 movable piece 53a lower surface of movable piece 6 ball passage hole 61 projecting portion 7 claw portion 71 outer peripheral portion of cylindrical body 72 central portion of cylindrical body 8 circular hole (engagement) Part)
9 Rotating jig 91 Projection d ₁₁ Diameter of cross-sectional circle of straight path d ₃ Diameter of ball d ₆ Diameter of ball passage hole d ₆₁ Diameter of protrusion

Claims (1)

A nut having a spiral groove formed on the inner peripheral surface; a screw shaft having a spiral groove formed on the outer peripheral surface; and a ball disposed between a spiral groove of the nut and a spiral groove of the screw shaft; A ball return path for returning the ball from the end point of the track to the start point, and a ball screw that moves relative to the screw shaft by rolling the ball in the track,
The ball return path is formed inside the nut, and includes a straight path extending in the axial direction of the nut and curved paths connected to both ends thereof.
A cylindrical recess having a circular opening on the outer peripheral surface of the nut is formed in a portion of the straight path on the curved path side,
In the recess,
It consists of a cylindrical body that fits into the recess,
Penetrating in the radial direction of the cylindrical body, having a ball passage hole constituting the straight path,
On the inner surface of the ball passage hole, a protrusion that makes the inner diameter of the ball passage hole smaller than the diameter of the ball is formed elastically deformable outward in the diameter direction of the ball passage hole,
The claw portion that protrudes outward from the outer peripheral surface of the cylindrical body is formed to be elastically deformable in the radial direction of the cylindrical body,
On the axial end surface disposed on the opening side of the nut of the cylindrical body, an engaging portion of the rotating jig is formed,
A ball delivery member for delivering the ball to the curved road side by elastic deformation of the protruding portion is disposed;
The ball screw characterized in that the claw portion is in a recess provided on the inner peripheral surface of the recess.

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