JP2009281534A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately and surely install a ball circulating member in a nut body, by improving strength in a chip guide part composed of a sidewall chip part inside (the central side) a ball circulating passage. <P>SOLUTION: The ball circulating member 15 is fixed to both ends of the nut body 13. The chip guide part 25a inside of the ball circulating passage 22 of the ball circulating member, projects to the inside from a plane A inside of a ball circulating part 21. A cutout part 30 is formed in a crest part 16<SB>3</SB>of a screw groove of the nut body 13, and the chip guide part 25a is suitable for the cutout part 30. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ball screw device that includes a screw shaft, a nut, and a large number of balls that are rollably interposed in the screw shaft and the screw groove of the nut. The present invention relates to a ball screw device in which a ball circulation member to be transferred between the ball circulation holes is mounted.

  Conventionally, there is a ball screw device in which a ball circulation member is fixed to both ends of a nut body with screws or snap rings (see, for example, Patent Document 1 and Patent Document 2). As shown in FIG. 5, the ball circulation member 1 includes a ball circulation portion 2 and a fixing portion 3, and is fixed to the nut body by fixing the fixing portion 3 with screws or the like so as to cover both ends of the nut body. Is done. The ball circulation part 2 has two projecting parts 5 and 5 corresponding to the double thread, and these projecting parts fit into the recesses of the nut body. A concave groove-shaped ball circulation path 6 is formed in the protruding portion 5 so as to cooperate with the screw groove of the nut. The ball circulation path 6 is formed by the left and right side walls 7, 8 and the bottom wall 9. The tip of the bottom wall 9 is a ball scooping piece 9a, and the other end is curved and communicates with a ball circulation hole formed in the nut body.

  In the ball circulation member 1, a ball that rolls due to the relative rotation of the nut and the screw shaft is scooped by the ball scooping piece 9a from the screw groove of the screw shaft, and the ball circulation member 6 cooperates with the screw groove of the nut body. Guide to the ball circulation hole in the nut body. In the ball circulation member 1 on the other end side, a ball continuously filled in the ball circulation hole is guided to the ball circulation path 6 and circulated from the tip to the thread groove of the nut body and the screw shaft.

  In the present specification, the outer side and the inner side are the outer sides on the both sides with respect to the axial direction of the nut, and the center side is the inner side. The inner diameter side and the outer diameter side mean the inner diameter side and the outer diameter side with respect to the axis of the nut. Further, the tip side means a thread groove side and an end side extending in one direction in the ball circulation member.

Japanese Examined Patent Publication No. 1-27303 JP 2003-240093 A

  The ball circulation member 1 is configured such that the inner end surface of the ball circulation portion (projecting portion 5) 2 is a plane perpendicular to the axial direction of the nut. In other words, the inner side surface 8a of the inner side wall 8 of the ball circulation path 6 is constituted by a flat surface (flat surface), and the side wall 8 does not interfere with the thread groove of the nut body so that the side wall 8 is the tip of the ball circulation path 6. It is configured to be inclined so as to be pointed toward the surface.

  For this reason, the side wall front end portion 8b serving as the guide portion of the ball circulation path 6 is formed thin (thin) and has a disadvantageous structure in terms of strength. When the protrusion 5 is fitted into the recess of the nut and the ball circulating member 1 is mounted on the nut, the side wall tip (tip guide) 8b may interfere with the thread groove of the nut body and bend. This may adversely affect the smooth circulation of the balls of the ball screw device and may cause a decrease in the performance and durability of the ball screw device.

  In particular, in the case of a multi-threaded screw or a precise screw with a small lead, there is a high possibility that the above problems will occur, and a ball screw device that can be reliably assembled with high accuracy and can always maintain ball circulation performance and durability is desired. It is rare.

  Therefore, the present invention improves the strength of the inner side (center side) side wall tip portion that becomes the tip guide portion, and accurately positions the ball circulation member on the nut body without interfering with the thread groove of the nut body. Therefore, an object of the present invention is to provide a ball screw device that can solve the above-described problems.

The present invention includes a screw shaft having a screw groove on the outer periphery, a nut (12) having a screw groove (16. And a ball (11) interposed between
The nut (12) includes a nut body (13) having the thread grooves (16...) And a ball circulation hole (13c), and is fixed to both ends of the nut body. In a ball screw device comprising: a ball circulation member (15) having a ball circulation portion (21) communicating with the ball circulation hole (13c);
The nut body (13) has a recess (17) into which the ball circulation part (21) is fitted, and the ball circulation hole (13c) is opened at the bottom surface (H) of the recess, The inner diameter side is connected to the thread groove (16 ₁ ),
The ball circulation portion (21) includes a ball circulation path (22) formed by inner and outer side walls (25) (23) and a bottom wall (26), and the thread groove on the inner diameter side of the bottom wall. A ball scooping piece (27) protruding so as to enter, and an inner flat surface (A) thereof abuts against a bottom surface (H) of the concave portion (17), and a pair of side surfaces (D) (E ) Abuts the rising side surface (I) (G) of the recess (17),
An inner diameter side of the inner side wall (25) projects inward by a predetermined amount (d) with respect to the inner plane (A) to form a tip guide portion (25a),
In the peak portion (16 ₃ ) between the thread groove (16 ₁ ) connected to the ball circulation path (22) of the nut body (13) and the thread groove (16 ₂ ) adjacent to the thread groove, the tip A notch part (30) for fitting the guide part (25a) is formed,
It is in the ball screw device characterized by this.

Preferably, the tip guide portion (25a) has a crescent shape when viewed from the axial direction, and has an inner side surface (B) formed of a plane parallel to the bottom surface (H) of the concave portion (17), and the inner side surface (B). And a tapered surface (C) connecting between the inner planes (A),
The notch portion (30) of the nut body has a shape (J) (K) in which the inner surface and the tapered surface are just fitted.

  An outer tip guide portion (23a) formed on the inner diameter side of the outer side wall (23), and an inner tip guide portion (25a) formed on the inner diameter side of the inner side wall (25). However, it protrudes by a predetermined amount (m) in the circumferential direction from the tip (27a) of the ball scooping piece (27), and the tips of the two tip guide portions are aligned to have substantially the same length in the circumferential direction.

  The ball circulation member has an annular fixing portion (20), and the ball circulation portion (21) is formed by integral molding of a synthetic resin formed so as to protrude in the axial direction from the fixing portion.

The screw shaft and the screw groove of the nut are multi-threaded screws,
The ball circulation member (15) is formed by projecting the ball circulation portions (21, 21) having the same number of the multiple stripes from the fixed portion (20).

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on the structure of a claim by this.

  According to the first aspect of the present invention, the tip side guide portion is formed by projecting the inner diameter side of the inner side wall forming the ball circulation path inward by a predetermined amount with respect to the inner plane contacting the bottom surface of the recess of the nut body. Therefore, the tip guide portion is made thick to improve the strength, and the notch portion for fitting the tip guide portion is formed in the screw thread portion of the nut body, so that the ball circulation member is attached to the nut body. When mounting, the ball circulation part is accurately fitted into the recess of the nut body, and the tip guide part is not bent or damaged, and the tip guide part and the ball circulation path are connected to the thread groove of the nut body. In addition, positioning with high accuracy can improve ball circulation performance and durability.

  According to the second aspect of the present invention, the tip guide portion has an inner surface and a tapered surface formed of a crescent-shaped flat surface, and the notch portion of the nut main body has a shape that just fits the tip guide portion. Therefore, the front end guide portion can be accurately fitted to the notch portion and positioned reliably, and the front end guide portion can be easily formed by synthetic resin integral molding or the like, and the notch portion can be an end mill or the like. It can be easily formed with high accuracy by machining.

  According to the third aspect of the present invention, the tip guide portion made of the inner side wall and the tip guide portion made of the outer side wall protrude in the circumferential direction by a predetermined amount from the tip of the ball scooping piece, and both the tips are aligned. Therefore, it is possible to smoothly raise the ball from the thread groove to the ball circulation path and to improve the performance and durability of the ball screw device.

  According to the fourth aspect of the present invention, the ball circulation member can be easily formed by integral molding by projecting the ball circulation portion to the annular fixed portion.

  According to the present invention according to claim 5, it is possible to provide a ball screw device with high accuracy easily by applying a multi-threaded thread integrally with the fixed threaded part by forming a plurality of ball circulating parts in the same shape. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The ball screw device includes a screw shaft having a screw groove on the outer periphery, a nut 12 having a screw groove in a through hole, and a large number of balls 11 interposed in both screw grooves of the screw shaft and the nut.

  As shown in FIG. 1, the nut 12 includes a nut body 13 made of metal and ball circulation members 15, 15 made of synthetic resin. The nut body 13 is made of a cylindrical member having a through hole 13b penetrating in the center part, a flange 13a for connection is formed in the outer peripheral part, and two screw grooves 16, a through hole (center hole) 13b, 16 is formed. Furthermore, ball circulation holes 13c, 13c are formed so as to penetrate in the axial direction symmetrically about the center hole 13b.

  As shown in FIG. 2, the nut body 13 has recesses 17 and 17 formed at 180 degrees apart from each other so as to extend in the tangential direction of the center hole 13b. A ball circulation hole 13c is opened. A plurality (four) of screw holes 19 for fixing the ball circulation member 15 are formed.

  The ball circulation member 15 is attached to both ends of the nut body 13. As shown in FIG. 3, the ball circulation member 15 includes an annular fixing portion 20 and a ball circulation portion 21 that protrudes in the axial direction at a position 180 degrees apart from the fixing portion. The fixing portion 20 has four concave portions 24 formed on the surface opposite to the ball circulation portion 21, and fixing holes 24 a are formed in these concave portions 24. The ball circulation member 15 is fixed to both end portions of the nut body 13 by screwing the holes 24 a and the screw holes 19 of the nut body 13.

  Two ball circulation portions 21 of the same shape are formed corresponding to the double thread, and are fitted into the recesses 17 of the nut body. A ball circulation path 22 is formed in the ball circulation portion 21 continuously to the thread groove 16 of the nut body 13. The ball circulation path 22 is formed of a semicircular or U-shaped groove surrounded by left and right side walls 23, 25 and a bottom wall 26, and an inner diameter side end of the bottom wall 26 enters a screw groove of the nut body. In this way, a ball scooping piece 27 formed of a semicircular cross-sectional protrusion projecting in the inner diameter direction (in the direction of the center hole 28) is formed. The groove of the ball circulation path 22 extends in the tangential direction of the thread groove 16 of the nut body 13 and is curved in an L-turn shape at the outer diameter portion and is connected to the ball circulation hole 13c of the nut body. In FIG. 3A, the ball scooping piece 27 shows a portion protruding in the direction of the center hole 28 (inner diameter), and the ball circulation path 22 made of a groove is on the opposite surface and is not shown (the ball in FIG. 5). (Refer to the circulation path 6 and the ball scooping piece 9a).

  The inner side wall 25 of the ball circulation path 22 protrudes from the groove constituting the ball circulation path 22 (ie, the ball scooping piece 27) to the front end side to form a front end guide portion 25a. The tip guide portion 23a is configured to extend in the circumferential direction of the same length with respect to the groove for the ball circulation path 22. The tips of both the inner and outer tip guide portions protrude a predetermined amount m in the circumferential direction from the tip 27a of the ball scooping piece 27, and both the tips are aligned to the same length. The inner tip guide portion 25a protrudes inward by a predetermined amount d with respect to a flat surface (plane) A formed by the tip of the protruding portion constituting the ball circulation portion 21, and the protruding tip guide portion 25a is shown in FIG. As shown to (b), it is comprised by the flat surface (plane) B of the crescent moon shape of the front view seen from the axial direction, and this flat surface B and the said flat surface A are orthogonal to the nut axis OO. The flat surfaces B and A are connected by a tapered surface C. The flat surfaces B and A are parallel to each other.

On the other hand, as shown in FIG. 4 (a), the concave portion 17 into which the ball circulation portion 21 of the nut body 13 is fitted is a flat surface G, I composed of a pair of rising side surfaces extending parallel to the tangential direction of the center hole 28. Further, the bottom surface H is orthogonal to the ball circulation hole 13c and the both side surfaces G and I formed of the plane are in contact with a pair of rising side surfaces D and E of the ball circulation portion 21. At the same time, the bottom surface H comes into contact with the inner flat surface A. Therefore, the screw groove 16 ₁ outermost of the nut body 13 are continuous in the ball circulation passage (groove) 22. Then, _(in the present embodiment, the screw groove of the other strip of double threaded screw) screw groove 16 2 adjacent thereto and the screw groove 16 ₁ thread 16 ₃ between is cut away. Cutout portion 30, together with the inner side of the front guide portion 25a of the ball circulation portion 21 is formed exactly to fit, as shown in FIG. 4 (b), the screw groove 16 ₂ to the adjacent It is formed as deep as possible without causing interference. Specifically, the crescent-shaped flat surface B of the tip guide portion 25a abuts on the bottom surface J of the notch 30, and the tapered surface C abuts on the taper surface K of the notch.

  Since the present embodiment is configured as described above, the ball circulation portions 21 and 21 are fitted into the recesses 17 and 17 of the nut body 13 and the ball circulation members 15 are attached to both ends of the nut body. Then, both ball circulating members 15 are fixed to the nut body 13 by screwing screws into the screw holes 19 through the holes 24a.

At this time, the inner front guide portion 25a of the ball circulation member 15 is fitted to the cutout portion 30 of the nut body 13, the tip guide portion 25a is continuous with the threaded portion 16 ₃ of the nut body, and a ball the scoop piece 27 screw groove 16 ₁ is positioned so as to be continuous, ball circulation unit 21 is fitted into the recess 17 of the high precision and accurate to the nut body. That is, the flat surfaces A and H, G and E, I and D, and B and J, C and K are fitted so as to be in close contact with each other. Further, when the nut main body 13 of the ball circulation portion 21 is fitted, the inner tip guide portion 25a has a crescent-shaped wall structure protruding from the tip flat surface A and has a sufficient strength and is bent. Or deformed.

  The nut 12 with the ball circulation member 15 fixed to both ends of the nut body 13 moves in the axial direction by relative rotation with a screw shaft (not shown). Along with the relative rotation, the ball 11 interposed between the screw shaft and the screw groove of the nut 12 moves relative to the screw groove while rolling. The ball circulating member 15 at one end of the nut 12 guides the ball 11 with the left and right tip guide portions 25a and 23a, while the ball scooping piece 27 scoops up from the screw shaft and the screw groove of the nut, and the ball circulation path (groove). 22 is guided to the ball circulation hole 13c through the ball circulation path 22 whose upper surface is closed by the flat surface G of the nut body 13.

  The ball 11 continuously filled in the ball circulation hole 13c and the like is simultaneously returned from the ball circulation path 22 of the ball circulation member at the other end to the screw groove of the screw shaft and the nut. When the ball 11 is circulated, in particular, when it is rolled up into the ball circulation path 22, the inner tip guide portion 25 a is accurately positioned and fitted into the notch portion 30 of the nut body 13, and the tip guide portion 25 a itself. Has a crescent-shaped structure with high wall thickness, and accurately guides the ball 11 with high accuracy and passes it between the thread groove and the ball circulation path 22. Thereby, the ball screw device can always move smoothly and maintain its performance over a long period of time.

  In addition, the front-end | tip side guide part which consists of thickness is easily formed by the synthetic | combination molding of the synthetic resin to the ball | bowl circulation member 15 without accompanying a big cost increase. Further, the notch 30 of the nut main body 13 can be easily processed by an end mill or the like when the fitting recess 17 is machined, and can be formed with high accuracy without a large cost increase.

  The embodiment described above is applied to a double thread, but not limited to this, it may be a multiple thread such as three or four threads, or a single thread with a small lead, and between adjacent thread grooves. The ball screw device according to the present invention is suitable for a small and highly accurate screw device, but can be applied to any ball screw device.

The longitudinal cross-sectional view which shows the nut of the ball screw apparatus which concerns on this invention. The front view seen from the axial direction of the nut main part. It is a figure which shows a ball | bowl circulation member, (a) is PP sectional drawing of (b), (b) is the front view seen from the inner side. It is a figure which shows the part of a nut main body, (a) is QQ arrow sectional drawing of FIG. 2, (b) is the RR line | wire end view of (a). The side view which shows the ball | bowl circulation member by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ball 12 Nut 13 Nut main body 13b Through hole 13c Ball circulation hole 15 Ball circulation member 16, 16 ₁ , 16 ₂ thread groove 16 ₃ mountain part 17 Recess 20 Fixing part 21 Ball circulation part 22 Ball circulation path (groove)
DESCRIPTION OF SYMBOLS 23 Outer side wall 23a Tip guide part 25 Inner side wall 25a Tip guide part 26 Bottom wall 27 Ball scooping piece 27a Tip 30 Notch part A Inner flat surface B Inner side surface (plane)
C taper surface D, E side surface G, I rising side surface H bottom surface of recess J bottom surface K taper surface d predetermined amount m predetermined amount

Claims (5)

A screw shaft having a thread groove on the outer periphery, a nut having a thread groove in a through-hole, and a ball that rolls between the thread shaft and the both thread grooves of the nut, and
The nut includes a nut body having the screw groove and a ball circulation hole, and a ball circulation having a ball circulation portion fixed to both ends of the nut body and communicating between the screw groove and the ball circulation hole. A ball screw device comprising:
The nut body has a concave portion into which the ball circulation portion is inserted, the ball circulation hole is opened at the bottom surface of the concave portion, and the inner diameter side of the concave portion is connected to the screw groove,
The ball circulation part has a ball circulation path formed by inner and outer side walls and a bottom wall, and a ball scooping piece protruding so as to enter the screw groove on the inner diameter side of the bottom wall, The inner plane is in contact with the bottom surface of the recess, the pair of side surfaces is in contact with the rising side surface of the recess,
An inner diameter side of the inner side wall protrudes inward by a predetermined amount with respect to the inner side plane to form a tip guide part,
A notch for fitting the tip guide portion is formed at a crest between a screw groove connected to the ball circulation path of the nut body and a screw groove adjacent to the screw groove.
A ball screw device characterized by that. The tip guide portion has a crescent shape when viewed from the axial direction, and includes an inner surface formed of a plane parallel to the bottom surface of the concave portion, and a tapered surface connecting the inner surface and the inner plane.
The notch of the nut body has a shape in which the inner surface and the tapered surface are just fitted.
The ball screw device according to claim 1. An outer tip guide portion formed on the inner diameter side of the outer side wall and an inner tip guide portion formed on the inner diameter side of the inner side wall in the circumferential direction from the tip of the ball scooping piece. It protrudes by a predetermined amount, and the tips of the two tip guide portions are aligned to have substantially the same length in the circumferential direction.
The ball screw device according to claim 1 or 2. The ball circulation member has an annular fixing portion, and the ball circulation portion is formed by integral molding of a synthetic resin formed to protrude in the axial direction from the fixing portion.
The ball screw device according to any one of claims 1 to 3. The screw shaft and the screw groove of the nut are multi-threaded screws,
The ball circulation member is formed by projecting the ball circulation portion formed of the same number of the multiple stripes on the fixed portion.
The ball screw device according to claim 4.

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