JP5527006B2 - Ball screw - Google Patents

Description

  The present invention relates to a ball screw.

  In ball screws, the ball that rolls in the ball rolling path formed by the space between the thread groove of the screw shaft and the screw groove of the nut is returned from the end point of the ball rolling path to the start point in the ball circulation path. Circulate in order to smoothly move the relative straight line between the screw shaft and the nut. The ball circulation system using the ball circulation path includes a tube type, a top type, an end deflector type, an end cap type, and the like.

  In the type of ball screw in which the relative linear movement between the screw shaft and the nut is performed at a high speed, an end deflector type or an end cap type ball circulation method that is generally advantageous for large leads is often employed. In these ball circulation systems, guide members are provided at both axial ends of the nut, and one guide member scoops up the ball from the end point of the ball rolling path in the tangential direction of the ball rolling path. The ball is guided to one end of a ball circulation path formed inside, and the other guide member guides the ball from the other end of the ball circulation path to the starting point of the ball rolling path.

On the other hand, when using a ball screw in the form of rotating the nut and moving the screw shaft linearly in the axial direction, a rolling bearing can be mounted directly on the outer peripheral surface of the nut or a timing belt drive for the purpose of reducing space There is a case where the pulley is attached directly to the end surface of the nut in the axial direction.
Also, in applications where a ball screw nut is used as a cylinder, the nut may be formed into a cylinder shape by increasing the axial length of the nut in order to ensure a sliding surface. In that case, the length of the threaded portion in which the thread groove is formed on the inner peripheral surface is left as it is, and the length of the non-threaded portion in which the thread groove is not formed on the inner peripheral surface is increased.

JP-A-10-141465

  However, the ball screw provided with the guide members at both axial end portions of the nut as described above has a thin wall thickness W at the axial end portion of the nut as shown in FIG. If a triangular screw is provided on the outer peripheral surface of the nut or a tapped hole for directly attaching a pulley is provided on the end surface of the nut in the axial direction, the strength of the end of the nut may be insufficient. . By increasing the nut outer dimension and increasing the wall thickness W at the axial end of the nut, the strength can be secured, so it is possible to provide triangular screws and tapped holes. There was a risk of not being able to.

  In addition, when a ball screw nut is used as a cylinder, no thread groove is formed on the inner peripheral surface of the extended portion, and therefore the ball rolling path starts or ends in the axial direction of the nut. Since the guide member is not disposed at the end, the guide member is provided not at both ends in the axial direction of the nut but at one end in the axial direction and in the vicinity of the central portion in the axial direction. In other words, in a ball screw in which guide members are provided at both ends in the axial direction of the nut, the axial length of the non-threaded portion of the nut cannot be extended.

Although it is possible to provide the guide member in the vicinity of the central portion in the axial direction (middle deflector type), since the outer dimension of the nut becomes large, the cylinder may not be made compact.
Accordingly, the present invention solves the problems of the prior art as described above, and allows the outer peripheral surface and end surface of the axial end portion of the nut to be processed without increasing the outer dimension of the nut. It is an issue to provide. Another object of the present invention is to provide a ball screw in which the non-threaded portion of the nut is long in the axial direction.

  In order to solve the above problems, the present invention has the following configuration. That is, the ball screw of the present invention is formed by a screw shaft having a helical thread groove on the outer peripheral surface, a nut having a screw groove facing the screw groove of the screw shaft on the inner peripheral surface, and the both screw grooves. A plurality of balls slidably loaded in a spiral ball rolling path, and a ball circulation path that is formed inside the nut and circulates the ball back from the end point of the ball rolling path to the starting point. A first guide member that scoops up the ball from the end point of the ball rolling path and guides the ball to one end of the ball circulation path; and a starting point of the ball rolling path from the other end of the ball circulation path. And a second guide member that guides to one of the two guide members in a recess provided in an end surface of one end of the nut in the axial direction, and the other to the axial direction of the nut. The outer peripheral surface of the end Characterized in that fitted into the through hole penetrating the inner circumferential surface.

  The ball screw of the present invention is formed by a screw shaft having a helical screw groove on the outer peripheral surface, a nut having a screw groove facing the screw groove of the screw shaft on the inner peripheral surface, and the both screw grooves. A plurality of balls slidably loaded in a spiral ball rolling path, and a ball circulation path that is formed inside the nut and circulates the ball back from the end point of the ball rolling path to the starting point. A first guide member that scoops up the ball from the end point of the ball rolling path and guides the ball to one end of the ball circulation path; and a starting point of the ball rolling path from the other end of the ball circulation path. A ball guide comprising: a second guide member that guides to a nut; and the nut includes: a thread portion having the thread groove on an inner peripheral surface; and a non-thread portion not having the thread groove on an inner peripheral surface. The non-threaded portion of the threaded portion One of the guide members is fitted into a recess provided on the end surface of the other end in the axial direction of the screw portion, and the other is the outer periphery of the one end in the axial direction of the screw portion. It is characterized by being fitted into a through-hole penetrating the surface and the inner peripheral surface.

In these ball screws according to the present invention, at least one of the both guide members is provided with an engaging convex portion, and an engaging concave portion having a shape engageable with the engaging convex portion is provided in the concave portion and the penetrating nut. It is preferable that the guide member is fixed to the nut by being provided on at least one inner surface of the hole and engaging the engaging convex portion and the engaging concave portion.
Further, at least one of the both guide members may be fixed to the nut with an adhesive. Furthermore, the axial end portion of the nut may be inserted into a ring-shaped member, and the guide member fitted into the through hole may be pressed and fixed from the radially outer side by the ring-shaped member.
Furthermore, at least one of the both guide members may be a resin member formed by injection molding, or may be a member formed by pressure molding metal powder or ceramic powder.

  The ball screw of the present invention can process the outer peripheral surface and the end surface of the axial end portion of the nut without increasing the outer dimension of the nut. In the ball screw of the present invention, the non-threaded portion of the nut is long in the axial direction, and the nut can be used as a cylinder.

It is sectional drawing explaining the structure of one Embodiment of the ball screw which concerns on this invention. It is a figure explaining the end deflector engage | inserted by the recessed part provided in the end surface of the axial direction edge part of a nut. It is a perspective view of an end deflector. It is a figure explaining the end deflector inserted by the through-hole which penetrates the outer peripheral surface and inner peripheral surface of the axial direction edge part of a nut. It is a partial cross section figure of the ball screw with which the rolling bearing was mounted | worn. It is a perspective view of the end deflector which has an engagement convex part and an elastic part. It is a fragmentary perspective view of the nut which has a through-hole provided with the engagement recessed part. It is a perspective view of the end deflector which has an elastic part of a different type from the end deflector of FIG. It is a partial cross section figure of the nut of the structure where the non-screw part was extended from the axial direction one end part of the screw part. It is a perspective view of a cylindrical member. It is sectional drawing explaining the structure of the conventional ball screw.

DESCRIPTION OF EMBODIMENTS Embodiments of a ball screw according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view (a cross-sectional view cut along a plane along the axial direction) of a ball screw according to an embodiment of the present invention.
As shown in FIG. 1, the ball screw 1 has a screw shaft 3 having a helical screw groove 3a on the outer peripheral surface and a helical screw groove 5a facing the screw groove 3a of the screw shaft 3 on the inner peripheral surface. A plurality of balls 9 movably loaded in a spiral ball rolling path 7 formed by the nut 5 and both screw grooves 3a, 5a, and a ball 9 formed inside the nut 5 A ball circulation path 11 that circulates back from the end point of the ball rolling path 7 to the start point.

That is, the ball 9 moves in the ball rolling path 7 and rotates around the screw shaft 3 a plurality of times to reach the end point of the ball rolling path 7, where it is scooped up from the ball rolling path 7 and is moved to the ball circulation path. 11 enters one end (the right end in FIG. 1). The ball 9 entering the ball circulation path 11 passes through the ball circulation path 11 and reaches the other end (the left end in FIG. 1) of the ball circulation path 11, and from there to the starting point of the ball rolling path 7. It is supposed to be returned.
In addition, the raw material of the screw shaft 3, the nut 5, and the ball 9 is not particularly limited, and general materials can be used, and examples thereof include metals such as steel and ceramics. Further, the cross-sectional shape of the thread grooves 3a, 5a may be an arc shape or a gothic arc shape.

  When such a ball screw 1 is rotated relative to a nut 5 and a screw shaft 3 that are screwed to the screw shaft 3 via a ball 9, the screw shaft 3 and the nut 5 are moved via the rolling of the ball 9. And move relative to each other in the axial direction. An endless ball path is formed by the ball rolling path 7 and the ball circulation path 11 so that the ball 9 rolling in the ball rolling path 7 circulates infinitely in the endless ball path. Therefore, the screw shaft 3 and the nut 5 can continuously move relative to each other.

  Here, the circulation system of the balls 9 in the ball screw 1 of the present embodiment will be described in detail with reference to FIGS. In this embodiment, a deflector system in which a hole provided in the nut 5 is a ball circulation path 11 is adopted as a circulation system of the balls 9. In other words, the ball guide member 12A called a deflector for scooping up the ball 9 from the end point of the ball rolling path 7 and guiding it to one end of the ball circulation path 11 (the right end in FIG. 1) And a ball guide member 12B called a deflector that guides the ball 9 from the other end (the left end in FIG. 1) of the ball circulation path 11 to the starting point of the ball rolling path 7. (Corresponding to a second guide member which is a constituent element of the present invention) is provided at both axial ends of the nut 5. Hereinafter, these deflectors are referred to as end deflectors.

  The nut 5 is formed with a ball circulation path 11 formed of a hole extending substantially in the axial direction, and both ends of the ball circulation path 11 are arranged in the vicinity of the start point and end point of the ball rolling path 7, respectively. The ball 9 moves from the ball rolling path 7 to the ball circulation path 11 at the end point of the ball rolling path 7, and the ball 9 moves from the ball circulation path 11 to the ball rolling path 7 at the start point of the ball rolling path 7. However, in order to smoothly move the ball 9, end deflectors 12 </ b> A and 12 </ b> B for guiding the movement of the ball 9 are arranged at the end point and the start point of the ball rolling path 7, respectively.

  Of the two end deflectors 12A and 12B, the end deflector 12A arranged at the right axial end in FIG. 1 scoops up the ball 9 from the end of the ball rolling path 7 and ends one end of the ball circulation path 11. However, the nut 5 is fitted in a recess 14 provided on the end surface of one end portion in the axial direction of the nut 5 (the right end portion in FIG. 1) (see FIG. 2). On the other hand, the end deflector 12B disposed at the left axial end in FIG. 1 guides the ball 9 from the other end of the ball circulation path 11 to the starting point of the ball rolling path 7, but the axial direction of the nut 5 The other end (left end in FIG. 1) is fitted into a through hole 15 that penetrates the outer peripheral surface and the inner peripheral surface (see FIGS. 3 and 4).

  Both end deflectors 12A and 12B include a fitting portion 17 that fits into the recess 14 of the nut 5 and the opening of the through hole 15, and a tongue 18 that protrudes from the fitting portion 17, and the end deflector 12A. , 12B are attached to the nut 5, the tongue 18 is arranged along the screw groove 3 a of the screw shaft 3. Therefore, the ball 9 rolling to the end point of the ball rolling path 7 is scooped up from the ball rolling path 7 by the tongue portion 18 of the end deflector 12A, and reaches the end of the ball circulation path 11 along the tongue portion 18. Guided. The scooped up ball 9 passes through the ball circulation path 11 to reach the other end of the ball circulation path 11 and is guided by the tongue 18 of the end deflector 12B to be returned to the starting point of the ball rolling path 7.

  When the ball screw 1 is rotated in the reverse direction, the functions of both end deflectors 12A and 12B are reversed. That is, in the case of reverse rotation, the end deflector 12A has a function of guiding the ball 9 from the end of the ball circulation path 11 to the starting point of the ball rolling path 7, and the end deflector 12B It has a function of scooping up from the end point of the rolling path 7 and guiding it to the end of the ball circulation path 11.

  Such a ball screw 1 is not of a type in which one of the end deflectors 12A and 12B at both ends in the axial direction is fitted into a recess provided in the end surface of the end in the axial direction of the nut 5; Since this is a type that is fitted from the radially outer side into the through hole 15 that penetrates the inner peripheral surface, the outer dimension of the nut 5 is increased at the axial end of the nut 5 to which the end deflector 12B is attached. A large wall thickness is ensured.

  Therefore, when the ball screw 1 is used in such a manner that the nut 5 is rotated and the screw shaft 3 is linearly moved in the axial direction, a rolling bearing is directly mounted on the outer peripheral surface of the nut 5 for the purpose of reducing the space. There is a case where the pulley for driving the timing belt is directly attached to the end face of the axial end of the nut 5 (the left end in FIG. 1), but since the wall thickness W of the axial end of the nut 5 is thick, A triangular screw for directly mounting the rolling bearing can be provided on the outer peripheral surface of the nut 5, or a tapped hole for directly attaching the pulley can be provided on the end surface of the axial end portion of the nut 5 (FIG. 5). See). Since it is not necessary to increase the outer dimension of the nut 5, it is possible to reduce the space and reduce the inertia of the ball screw 1 to which a rolling bearing and a pulley are attached.

  The end deflectors 12 </ b> A and 12 </ b> B are preferably firmly fixed to the nut 5. The fixing method is not particularly limited, and examples thereof include fixing with an adhesive. The type of the adhesive is not particularly limited, and a general-purpose adhesive can be used without any problem. For example, an epoxy resin-based adhesive can be used.

  Moreover, you may fix using a ring-shaped member and a cylindrical member (refer FIG. 10). If the end of the nut 5 in the axial direction is inserted into a ring-shaped member or a cylindrical member, and the end deflector 12B fitted in the through hole 15 is pressed from the radially outer side with the ring-shaped member or the cylindrical member, the end deflector 12B Can be firmly fixed to the nut 5. The ring-shaped member or the cylindrical member is preferably a member having an inner diameter that fits into the outer peripheral surface of the nut 5 without a gap, but a member having a substantially C-shaped cross section having a slot may be used. The material of the ring-shaped member, cylindrical member, and member having a substantially C-shaped cross section is not particularly limited, and examples thereof include resin, metal, and ceramics.

  Furthermore, by providing the engagement convex portion 20 on the end deflectors 12A and 12B, and providing the nut 5 (the inner surface of the concave portion 14 or the through-hole 15) with an engagement concave portion that can be engaged with the engagement convex portion 20, The end deflectors 12A and 12B and the nut 5 may be fixed. For example, as shown in FIG. 6, the engaging convex portion 20 is projected from the fitting portion 17 of the end deflector 12B, and the engaging convex portion 20 is formed on the inner surface of the through hole 15 of the nut 5 as shown in FIG. If an engagement recess 21 having a shape that can be engaged is provided, and the engagement protrusion 20 and the engagement recess 21 are engaged when the end deflector 12B is fitted into the through-hole 15, the engagement Since the self-locking mechanism is formed, the end deflector 12B can be firmly fixed to the nut 5.

  When the end deflectors 12A and 12B are inserted into the recesses 14 or the through holes 15, the engaging projections 20 may interfere with the inner surfaces of the recesses 14 or the through holes 15 and smooth insertion may not be possible. It is preferable to provide an elastic portion that can be elastically deformed along the protruding direction of the engaging convex portion 20 in a portion where the engaging convex portion 20 is provided in the fitting portion 17 of 12A and 12B. That is, if the engagement convex part 20 is provided in the fitting part 17 through the elastic part, when the engagement convex part 20 interferes with the inner surface of the concave part 14 or the through hole 15, the elastic deformation of the elastic part. As a result, the engaging convex portion 20 moves to the fitting portion 17 side, so that the interference is alleviated and the end deflectors 12A and 12B can be smoothly inserted.

  The configuration of the elastic portion is not particularly limited, but a thinning structure as shown in FIGS. 6A is an enlarged perspective view showing the vicinity of the fitting portion 17 of the end deflectors 12A and 12B, and FIG. 6B is an overall perspective view of the end deflectors 12A and 12B. In the lightening structure of FIG. 6, the portion where the engaging convex portion 20 is formed and the fitting portion 17 are connected by two connecting portions, and the portion where the engaging convex portion 20 is formed and the fitting portion. This is a structure in which a cylindrical cavity 23 is formed between the two. Since the engagement convex portion 20 is movable toward the cavity 23, the interference is mitigated.

  8A is an enlarged perspective view showing the vicinity of the fitting portion 17 of the end deflectors 12A and 12B, and FIG. 8B is an overall perspective view of the end deflectors 12A and 12B. is there. 8 includes a portion where the engaging convex portion 20 is formed and the fitting portion 17 are connected by a single linear connecting portion, and a portion where the engaging convex portion 20 is formed. In this structure, a cavity 23 having a substantially U-shaped cross section is formed between the fitting portion 17 and the fitting portion 17. As in the case of the thinning structure shown in FIG. 6, the engagement convex portion 20 is movable toward the cavity 23, so that the interference is mitigated.

  The material of the end deflectors 12A and 12B is not particularly limited, and examples thereof include a resin (or a resin composition in which a reinforcing material or an additive is mixed with a resin), metal, ceramics, and the like. Also, the manufacturing method of the end deflectors 12A and 12B is not particularly limited, and an injection molding method can be used for a resin material, and a conventional processing method such as cutting can be used for a metal material or a ceramic material. . Moreover, if resin powder, metal powder, and ceramic powder are used as materials, pressure molding can be employed.

  In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, the ball screw 1 may include a nut having a structure as shown in FIG. That is, it comprises a threaded portion having a thread groove on the inner peripheral surface and a non-threaded portion not having a thread groove on the inner peripheral surface, and the non-threaded portion is one end in the axial direction of the threaded portion (the left side in FIG. 9) The nut may be extended from the end).

In the case of a ball screw having such a nut, one end deflector (not shown in FIG. 9) is placed in a recess provided on the end surface of the other end in the axial direction of the screw portion (the right end in FIG. 9). 9 and the other end deflector shown in FIG. 9 is connected to the outer periphery of one end of the screw portion in the axial direction (in FIG. 9, the end on the left side of the screw portion is the substantially central portion of the nut in the axial direction). It is good to fit in the through-hole which penetrates a surface and an inner peripheral surface.
The ball screw including the nut having such a structure has the same axial length of the threaded portion as that of the conventional ball screw, and the axial length of the non-threaded portion is long. Therefore, the nut can be used as a cylinder. That is, the outer peripheral surface of the non-threaded portion of the nut can be used as the sliding surface of the cylinder.

1 Ball Screw 3 Screw Shaft 3a Screw Groove 5 Nut 5a Screw Groove 7 Ball Rolling Path 9 Ball 11 Ball Circulation Path 12A, 12B End Deflector (Ball Guide Member)
14 recessed portion 15 through hole 17 fitting portion 18 tongue portion 20 engaging convex portion 21 engaging concave portion

Claims (8)

A screw shaft having a helical thread groove on the outer peripheral surface, a nut having a thread groove facing the screw groove of the screw shaft on the inner peripheral surface, and a spiral ball rolling path formed by the both screw grooves. A plurality of balls loaded so as to be freely rollable, a ball circulation path formed inside the nut and circulating the ball from the end point of the ball rolling path to the starting point, and the ball rolling path A first guide member that scoops up from the end point of the ball and guides it to one end of the ball circulation path, a second guide member that guides the ball from the other end of the ball circulation path to the start point of the ball rolling path, In a ball screw comprising:
One of the guide members is fitted into a recess provided in an end surface of one end of the nut in the axial direction, and the other is a through-hole penetrating the outer peripheral surface and the inner peripheral surface of the other end in the axial direction of the nut. only write fit in,
An engagement protrusion is provided on at least one of the guide members, and an engagement recess having a shape engageable with the engagement protrusion is provided on an inner surface of at least one of the recess and the through hole. The guide member is fixed to the nut by the engagement of the engagement convex portion and the engagement concave portion ,
An elastic portion that is elastically deformable along a protruding direction of the engagement convex portion is provided at a portion of the guide member where the engagement convex portion is provided, and the engagement portion is formed by elastic deformation of the elastic portion. A ball screw characterized in that the joint convex portion is movable toward the elastic portion . A screw shaft having a helical thread groove on the outer peripheral surface, a nut having a thread groove facing the screw groove of the screw shaft on the inner peripheral surface, and a spiral ball rolling path formed by the both screw grooves. A plurality of balls loaded so as to be freely rollable, a ball circulation path formed inside the nut and circulating the ball from the end point of the ball rolling path to the starting point, and the ball rolling path A first guide member that scoops up from the end point of the ball and guides it to one end of the ball circulation path, a second guide member that guides the ball from the other end of the ball circulation path to the start point of the ball rolling path, In a ball screw comprising:
The nut includes a threaded portion having the thread groove on an inner peripheral surface and a non-threaded portion not having the thread groove on an inner peripheral surface, and the non-threaded portion is one axial end portion of the threaded portion. Has been extended from
One of the guide members is fitted into a recess provided on the end surface of the other end portion in the axial direction of the screw portion, and the other is passed through the outer peripheral surface and the inner peripheral surface of the one end portion in the axial direction of the screw portion. only write fitted into the through-hole,
An engagement protrusion is provided on at least one of the guide members, and an engagement recess having a shape engageable with the engagement protrusion is provided on an inner surface of at least one of the recess and the through hole. The guide member is fixed to the nut by the engagement of the engagement convex portion and the engagement concave portion ,
An elastic portion that is elastically deformable along a protruding direction of the engagement convex portion is provided at a portion of the guide member where the engagement convex portion is provided, and the engagement portion is formed by elastic deformation of the elastic portion. A ball screw characterized in that the joint convex portion is movable toward the elastic portion . The ball screw according to claim 1, wherein the elastic portion has a hollow structure. The lightening structure is a structure in which the engaging convex portion and the guide member are connected by two connecting portions, and a cylindrical cavity is formed between the engaging convex portion and the guide member. The ball screw according to claim 3, wherein the ball screw is provided. In the lightening structure, the engagement convex portion and the guide member are connected by a single linear connecting portion, and a cavity having a substantially U-shaped cross section is formed between the engagement convex portion and the guide member. The ball screw according to claim 3, wherein the ball screw has a formed structure. The axial end of the nut is inserted into a ring-shaped member, and the guide member fitted in the through hole is fixed by pressing from the radially outer side with the ring-shaped member . The ball screw according to any one of 5 . The ball screw according to any one of claims 1 to 6 , wherein at least one of the two guide members is a resin member formed by injection molding. The ball screw according to any one of claims 1 to 6 , wherein at least one of the guide members is a member formed by pressure molding metal powder or ceramic powder.

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