JP2010060100A - Ball screw mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of assembling a ball screw mechanism having a simple configuration, easily manufactured and preventing the possibility of looseness etc. of components due to vibration or the like, and a processing device. <P>SOLUTION: By caulking a plurality of rivets 5A, 5A inserted to a thin plate member 4 for holding a tube 3, the thin plate member 4 is fixed to nuts 2. Thus, a tap processing etc. for small screws of the nuts 2 can be eliminated, and looseness etc. due to vibration or the like can be prevented when the ball screw mechanism is used, to improve reliability. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ball screw mechanism that is assembled to a general industrial machine or used in an automobile.

  In recent years, labor saving of vehicles and the like has progressed, and for example, a system has been developed in which a transmission, a parking brake, and the like of an automobile are performed not by hand but by the power of an electric motor. An electric actuator used for such an application may use a ball screw mechanism in order to convert the rotational motion transmitted from the electric motor into the axial motion with high efficiency.

  However, a ball screw mechanism usually consists of a screw shaft, a nut, and a ball that rolls in a rolling path formed between them. A circulating member is attached to the nut to return the ball to the end. Here, in this type of ball screw mechanism, the ball is circulated by using an external circulation type in which a ball is guided to the outside of the nut using a tube and a ball provided on the screw shaft by a piece provided on the nut. There are internal circulation types that circulate along the outer surface. Therefore, the circulation member includes a tube and a top.

  By the way, when the tube or the piece is lifted from the nut, a step is generated in the rolling path, the ball is not smoothly circulated, and there is a possibility that abnormal noise is generated or the performance of the ball screw mechanism is lowered. In addition, if the tube or the piece is dropped from the nut, the function of the ball screw is lost. Therefore, it is important that the ball screw is securely fixed and attached.

On the other hand, in the case of a tube, it is often attached by fixing a tube pressing plate for holding the tube to a nut using a small screw (see Patent Document 1). On the other hand, in the case of a top, it is often attached by caulking a part of the top inserted into the through hole of the nut.
JP 2005-98356 A JP 2007-51655 A

  Here, when fixing the tube retainer plate to the nut using a small screw, it is necessary to perform tapping for screwing the nut, and it takes time and effort to break the tap. The parts must be disposed of and the yield is poor. Furthermore, vibrations generated during use of the ball screw mechanism may cause the small screw to loosen, and the tube to rise with the tube presser plate.

  On the other hand, Patent Document 2 discloses that a plate-like circulation member having a circulation groove formed on one surface is directly fixed to a nut with a rivet. However, depending on the type of rivet, the crimped inner end swells and may interfere with the screw shaft, so there is a problem that the rivets that can be selected are limited. Further, when an end cap is used as the circulating member, there is a problem of how to use a rivet.

  The present invention has been made in view of the problems of the prior art, and provides a ball screw mechanism that has a simple configuration, is easy to manufacture, and has no fear of loosening of parts due to vibration or the like. Objective.

A ball screw mechanism according to a first aspect of the present invention includes: a screw shaft having a male screw groove formed on an outer peripheral surface; a nut disposed so as to surround the screw shaft and having a female screw groove formed on an inner peripheral surface; A plurality of balls arranged so as to be able to roll along a rolling path formed between the grooves, and a circulation member inserted into the mounting hole of the nut to return the balls from one end to the other end of the rolling path; And a thin plate member for holding the circulation member,
The thin plate member is fixed to the nut by caulking a plurality of rivets inserted through the thin plate member.

A ball screw mechanism according to a second aspect of the present invention comprises: a screw shaft having a male screw groove formed on an outer peripheral surface; a nut disposed so as to surround the screw shaft and having a female screw groove formed on an inner peripheral surface; A plurality of balls arranged to roll along a rolling path formed between the grooves, and a pair of ends attached to both ends of the nut to return the balls from one end of the rolling path to the other end With a cap,
The pair of end caps are fixed to the nut by caulking a rivet penetrating the nut in the axial direction.

  According to the first aspect of the present invention, the thin plate member is fixed to the nut by, for example, penetrating a plurality of rivets inserted through the thin plate member holding the circulation member in the radial direction of the nut. Therefore, tapping of a small screw or the like on the nut can be omitted, and the reliability can be improved without being loosened due to vibration or the like when the ball screw mechanism is used.

  The mounting hole of the rivet in the nut is preferably opposed to the male thread groove of the screw shaft.

  The female screw groove is preferably rounded up inside the mounting hole. “Cutting up” means that the female thread groove gradually becomes shallower and disappears.

  It is preferable that the female thread groove is rounded up outward in the axial direction after passing through the attachment hole.

  The mounting hole of the rivet in the nut is preferably opposed to the land portion of the screw shaft, and the female screw groove is preferably rounded up inside the mounting hole.

  It is preferable that the rivet and a part of the land portion of the screw shaft can come into contact with each other.

  According to the second aspect of the present invention, a pair of end caps for returning the ball from one end of the rolling path to the other end is fixed to the nut by caulking a rivet penetrating the nut in the axial direction. Therefore, tapping of a small screw can be omitted from the nut, and the reliability can be improved without being loosened by vibration or the like when the ball screw mechanism is used. In addition, the cost can be reduced by significantly reducing the number of parts compared to the case where each end cap is fixed with a small screw.

  Next, embodiments of the present invention will be described with reference to the drawings. 1A is a cross-sectional view of the ball screw mechanism according to the present embodiment, and FIG. 1B is a cross-sectional view of the nut taken along line IB-IB in FIG. FIG. FIG. 2 is an enlarged view showing a part indicated by an arrow II in FIG. In FIG. 1, the ball screw mechanism is opposed to a screw shaft 1 having a male screw groove 1a formed on the outer peripheral surface and a nut 2 disposed so as to surround the screw shaft 1 and having a female screw groove 2a formed on the inner peripheral surface. Both ends 3a and 3a are inserted into a plurality of balls 6 arranged to roll along a rolling path formed between both screw grooves 1a and 2a, and a mounting hole 2c (FIG. 1B) of the nut 2. And a thin plate member 4 that holds the tube 3. The thin plate member 4 is formed by bending a metal plate, and has a central holding portion 4a that holds the outer periphery of the tube 3 and holes 4b and 4b in the vicinity of both ends.

  In the present embodiment, the rivet holes 2d and 2d communicating the inner and outer circumferences of the nut 2 are not formed on the extension line of the female thread groove 2a of the nut 2, and therefore, as shown in FIG. 2d and 2d are formed to face the land portion 1b of the screw shaft 1 (the spiral portion between the adjacent male screw portions 1a and 1a), and the female screw groove 2a is in front of the rivet hole 2d (inward in the nut axial direction). (Figure 1 (b)). This suppresses the ball from dropping out of the rolling path during assembly. Further, the hollow rivet 5A with a flat head penetrates the holes 4b and 4b and the rivet holes 2d and 2d of the thin plate member 4, and the end portion where the bag hole 5p is formed is caulked, whereby the nut 2 Is attached.

  The operation of the present embodiment will be described. When the nut 2 is rotationally driven by an electric motor (not shown), the ball 3 rolls on the rolling path and circulates from one end of the rolling path to the other end via the tube 3. Thus, the rotational motion is efficiently converted into the axial motion of the screw shaft 1, and a driven member (not shown) connected thereto can be moved in the axial direction.

  FIG. 3 is an enlarged cross-sectional view similar to FIG. 2 according to a modification. In this modification, a flat, semi-spherical thin round headed hollow rivet 5B passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2, and the bag hole 5p is formed. It is attached to the nut 2 by caulking the formed end.

  FIG. 4 is an enlarged cross-sectional view similar to FIG. 2 according to another modification. In this modification, a hollow rivet 5C with a hemispherical round head passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2 to form a bag hole 5p. It is attached to the nut 2 by crimping the end.

  FIG. 5 is an enlarged cross-sectional view similar to FIG. 2 according to another modification. In this modification, a hollow rivet 5D with a flat head having a top surface parallel to the surface of the thin plate member 4 passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2. And it is attached to the nut 2 by crimping the end portion where the bag hole 5p is formed. In this modification, the inner circumference of the holes 4b and 4b of the thin plate member 4 is preferably a tapered surface in accordance with the tapered surface shape of the lower part of the head of the hollow rivet 5D with a flat head.

  FIG. 6 is an enlarged cross-sectional view similar to FIG. 2 according to another modification. In this modification, a flat hemispherical solid round headed solid rivet 5E passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2, and has an inner end. It is attached to the nut 2 by caulking the part.

  FIG. 7 is a cross-sectional view of a ball screw mechanism according to another embodiment. In the ball screw mechanism of the present embodiment, as shown in FIG. 7, the rivet holes 2d and 2d of the nut 2 are formed so as to face the male screw portion 1a of the screw shaft 1, and the solid rivet with a flat head is formed. 5F passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d, and is attached to the nut 2 by caulking the inner end portion. According to the present embodiment, since the rivet holes 2d and 2d are formed on the extension line of the female screw groove 2a of the nut 2, the crimped end portion of the solid rivet 5F with a flat head is a male screw. It exists in the groove 1a. Therefore, as in the example shown in FIG. 6, it is not necessary to reduce the amount of protrusion from the inner periphery of the nut 2 in order to avoid interference with the screw shaft 1, and therefore, for example, a solid rivet other than the hollow rivet is used. be able to. The female thread groove 2a is rounded up before the rivet hole 2d in order to prevent the ball 6 from escaping out of the rolling path during assembly (see FIG. 1B). Other configurations are the same as those of the above-described embodiment.

  FIG. 8 is an enlarged cross-sectional view similar to FIG. 2 including rivets that can be used in the present embodiment. In this modification, a flat hemispherical solid round headed rivet 5G passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2, and has an inner end. It is attached to the nut 2 by caulking the part.

  FIG. 9 is an enlarged cross-sectional view similar to FIG. 2 including rivets that can be used in the present embodiment. In this modified example, a flat hemispherical thin round headed split rivet 5H passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2, and has an inner end. It is attached to the nut 2 by caulking the foot part 5f provided in the part so as to bend outward. The foot split rivet 5H requires a device for processing the crimped foot portion 5f, but if the rivet hole 2d faces the male screw groove 1a, the crimped foot portion as shown in FIG. The possibility that 5f interferes with the screw shaft 1 is reduced. Thereby, various rivets can be used, and the degree of freedom of rivet selection increases.

  FIG. 10 is a cross-sectional view of a ball screw mechanism according to another embodiment. Also in the ball screw mechanism of the present embodiment, the rivet holes 2d and 2d are formed on the extension line of the female screw groove 2a of the nut 2, but the female screw groove 2a is rounded up after passing through the rivet holes 2d and 2d. ing. As shown in FIG. 10, a solid rivet 5F with a flat head passes through the holes 4b, 4b and the rivet holes 2d, 2d of the thin plate member 4, and the inner end portion is swaged so that the nut 2 is attached. In the present embodiment, the female screw groove 2a is provided over the entire length of the nut 2 (or may be a part thereof), and further intersects the rivet holes 2d and 2d, that is, the rivet holes 2d and 2d are the female screw groove of the nut 2. Since it is formed in 2a, a larger space is created around the inner ends of the rivet holes 2d, 2d by facing the male thread groove 1a, and the crimped end of the solid rivet 5F with a flat head Even if the portion protrudes greatly, the possibility of interference with the screw shaft 1 is reduced.

  FIG. 11 is an enlarged sectional view similar to FIG. 2 including rivets that can be used in the present embodiment. In this modification, a flat, semi-spherical thin round headed hollow rivet 5B passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2, and the bag hole 5p is formed. It is attached to the nut 2 by caulking the formed end. Also in the present embodiment, the female screw groove 2a intersects the rivet holes 2d and 2d, that is, the rivet holes 2d and 2d are formed in the female screw groove 2a of the nut 2, so that the thin round head In the case of the attached hollow rivet 5B, the crimped inner end portion is accommodated in the female screw groove 2a and does not protrude inward from the inner diameter of the nut 2, so that the possibility of interference with the screw shaft 1 is further reduced. .

  FIG. 12 is an enlarged cross-sectional view similar to FIG. 2 including rivets that can be used in the present embodiment. In this modification, a flat hemispherical thin round headed blind rivet 5I passes through the holes 4b and 4b of the thin plate member 4 and the rivet holes 2d and 2d of the nut 2, and has an inner end portion. Is attached to the nut 2 by caulking. Also in this embodiment, the female thread groove 2a intersects the rivet holes 2d and 2d, and the rivet holes 2d and 2d are formed on the extension line of the female thread groove 2a of the nut 2, so that the blind rivet In this way, even with a rivet in which the crimped inner end tends to protrude greatly, the risk of interference with the screw shaft 1 is low. Thereby, a wide range of rivets can be used.

  FIG. 13 is a side view of a screw shaft 1 ′ that can be used in the present embodiment, and FIG. 14 is an enlarged sectional view similar to FIG. 2 of a ball screw mechanism using the screw shaft 1 ′. In the screw shaft 1 'of the present embodiment, a projecting portion 1c is formed by plastic deformation between the land portion 1b and the male screw groove 1a at the end of the male screw groove 1a, thereby reducing the groove cross section. . When the nut 2 and the screw shaft 1 are displaced relative to each other, the crimped end portion of the solid rivet 5F with a flat head is brought into contact with the protruding portion 1c, so that the nut 2 and the screw shaft 1 are further increased. The relative displacement with is suppressed.

  15 is a top view of a ball screw mechanism according to another embodiment, FIG. 16 is a view of the configuration of FIG. 15 cut along the XVI-XVI line and viewed in the direction of the arrow, and FIG. It is the figure which cut | disconnected the structure of FIG. 15 by the XVII-XVII line, and looked at the arrow direction. Also in this embodiment, a female thread groove and a mounting hole for a rivet may be formed in the nut in the relationship as shown in FIGS.

  In the figure, a male screw groove 21a is formed on the outer peripheral surface of a screw shaft 21 that is connected to a driven member and is supported so as not to rotate but to move only in the axial direction. A land portion 21b that forms the outermost diameter of the screw shaft 21 is interposed between the male screw grooves 21a that are spirally wound and aligned in the axial direction.

  A cylindrical nut 22 supported so as to be able to rotate only with respect to a housing (not shown) is arranged so as to surround the screw shaft 21 and has an internal thread groove 22a (in this case, an internal thread groove of a little less than 1 turn is provided with 2 internal thread grooves). Book). A plurality of balls 23 are arranged so as to be able to roll in a spiral rolling path formed between the opposing screw grooves.

  A shallow groove portion 22 c extending in the axial direction is formed on the outer periphery of the nut 22, and two cylindrical piece holes (attachment holes) 22 b are further separated from the bottom surface of the shallow groove portion 22 c in the axial direction of the nut 22. Is formed. In the bottom surface of the shallow groove portion 22c, through holes 22d and 22d are formed in the vicinity of both ends of the nut 22. When one through hole 22d is in the male screw groove 21a of the screw shaft 21, the other through hole is formed. The holes 22d are also arranged in the male screw groove 21a.

  A shallow groove portion 22 c extending in the axial direction is formed on the outer periphery of the nut 22, and two cylindrical piece holes (attachment holes) 22 b are further formed on the bottom surface of the shallow groove portion 22 c, separated in the axial direction of the nut 22. Is formed. In the bottom surface of the shallow groove portion 22c, through holes 22d and 22d are formed in the vicinity of both ends of the nut 22. When one through hole 22d is in the male screw groove 21a of the screw shaft 21, the other through hole is formed. The holes 22d are also arranged in the male screw groove 21a.

  The circulation member 24 also serving as a thin plate member is composed of a rectangular plate-shaped main body 24a and two cylindrical piece portions 24b and 24b provided on the lower surface of the main body 24a. An S-shaped circulation path 24c is formed on the lower surface of each piece portion 24b (see FIG. 15). Note that through holes 24d and 24d are formed near both ends of the main body 24a.

  A method for assembling the ball screw mechanism will be described. First, after the frame portions 24b and 24b are inserted into the frame holes 22b and 22b and the main body 24a is attached so as to be in close contact with the bottom surface of the shallow groove portion 22c, the balls 23 are appropriately loaded. In this state, since the through holes 24d and 24d of the main body 24a are superposed on the through holes 22d and 22d of the nut 22, the headed rivets 25 and 25 are projected from the inside in the radial direction through the through holes 24d and 24d. . In this state, similarly to the above-described embodiment, the protruding tips 25b and 25b of the headed rivets 25 and 25 are caulked and plastically deformed to be deformed into a shape that cannot pass through the through holes 24d and 24d. As a result, the circulation member 24 is fixed to the nut 22. In addition, as an aspect of plastic deformation, the end part is crushed in the axial direction to expand the diameter, thinned flat in the radial direction, bent, and the like. Further, the headed rivets 25 and 25 to which all the rivets described above can be applied may be inserted from the outer side in the radial direction of the nut 22 through the through holes 24d and 24d, and the inner diameter side end portions may be crimped. Thereafter, the ball screw mechanism is completed by incorporating the screw shaft 21.

  The operation of the present embodiment will be described. When the nut 22 is rotationally driven by an electric motor (not shown), the rolling path rolls and the circulation portions 24b and 24b of the circulation member 24 are connected via the circulation paths 24c and 24c. By the balls 23 circulating from one end of the rolling path to the other end, the rotational motion is efficiently converted into the axial motion of the screw shaft 21, and a driven member (not shown) connected thereto can be moved in the axial direction. it can.

  FIG. 18 is a cross-sectional view of an end cap type ball screw mechanism. In the end cap type ball screw mechanism, a cylindrical nut 32 having a female screw groove 32a opposed to the male screw groove 31a on the inner peripheral surface of the screw shaft 31 having a male screw groove 31a on the outer peripheral surface is opposed to both screws. The grooves 31a and 32a are screwed via balls 36 that roll. End caps 34 and 34, which are circulation members and thin plate members, are disposed on both end faces of the nut 32, an attachment hole 32d that penetrates the nut 32 in the axial direction, and an attachment hole that penetrates the end caps 34, 34 in the axial direction. The end caps 34, 34 are attached to the nuts 32 by caulking the penetrating end portions of the four rivets 35 inserted so as to pass through 34 d, 34 d.

  A ball return passage 32 e that is an axial through hole is provided in the peripheral wall portion of the nut 32. Each end cap 34 is provided with a curved path 34a on the end face of the nut 32 so as to allow the opposing screw grooves 31a and 32a and the ball return path 32e to communicate with each other. Here, when the screw shaft 31 and the nut 32 rotate relative to each other, the steel ball 36 advances while rolling in both screw grooves 31a and 32a between the screw shaft 31 and the nut 32, and ends the end cap. The circulation is repeated through the curved path 34a provided in 34 and the ball return path 32e provided in the nut 32 to return to the original position.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, a plurality of rivets may be temporarily fixed in a hole in the thin plate member in a manner that restricts separation in advance, and then assembled to a nut. The number of rivets is not limited to two, and may be three or more. The material of the rivet may be steel, aluminum, brass or the like.

It is sectional drawing of the ball screw mechanism and nut of this Embodiment. It is a figure which expands and shows the site | part shown by the arrow II of FIG. It is an expanded sectional view similar to FIG. 2 concerning a modification. It is an expanded sectional view similar to FIG. 2 concerning another modification. It is an expanded sectional view similar to FIG. 2 concerning another modification. It is an expanded sectional view similar to FIG. 2 concerning another modification. It is sectional drawing of another ball screw mechanism. It is an expanded sectional view similar to FIG. 2 containing the rivet which can be used for this Embodiment. It is an expanded sectional view similar to FIG. 2 containing the rivet which can be used for this Embodiment. It is sectional drawing of another ball screw mechanism. It is an expanded sectional view similar to FIG. 2 containing the rivet which can be used for this Embodiment. It is an expanded sectional view similar to FIG. 2 containing the rivet which can be used for this Embodiment. It is a side view of screw axis 1 'which can be used for this embodiment. FIG. 3 is an enlarged cross-sectional view similar to FIG. 2 of a ball screw mechanism using a screw shaft 1 ′. It is a top view of the ball screw mechanism which is another embodiment. It is the figure which cut | disconnected the structure of FIG. 15 by the XVI-XVI line, and looked at the arrow direction. It is the figure which cut | disconnected the structure of FIG. 15 by the XVII-XVII line, and looked at the arrow direction. It is sectional drawing of an end cap type ball screw mechanism.

Explanation of symbols

1, 1 'screw shaft 1a male screw groove 1b land portion 1c projecting portion 2 nut 2a female screw groove 2b flat portion 2c tube hole 2d rivet hole 3 tube 4 thin plate member 4a holding portion 4b hole 5A to 5I rivet 21 screw shaft 21a male screw groove 21b Land portion 22 Nut 22a Female screw groove 22b Top hole 22c Shallow groove portion 22d Shallow hole 23 Ball 24 Circulating member 24a Main body 24b Top portion 24c Circulation path 24d Through hole 25 Rivet 25b Tip 31 Screw shaft 31a Male screw groove 32 Nut 32a Female screw groove 32 32e passage 34 end cap 34a curved path 34d mounting hole 36 ball 35 rivet

Claims (7)

Along a rolling shaft formed between a screw shaft having a male screw groove formed on the outer peripheral surface, a nut disposed so as to surround the screw shaft and having a female screw groove formed on the inner peripheral surface, and both screw grooves facing each other. A plurality of balls arranged to be freely rollable, a circulation member that is inserted into the mounting hole of the nut and returns the ball from one end of the rolling path to the other end, and a thin plate member that holds the circulation member Have
A ball screw mechanism, wherein the thin plate member is fixed to the nut by caulking a plurality of rivets inserted through the thin plate member.   The ball screw mechanism according to claim 1, wherein the mounting hole of the rivet in the nut is opposed to a male screw groove of the screw shaft.   The ball screw mechanism according to claim 2, wherein the female screw groove is rounded up inside the mounting hole.   The ball screw mechanism according to claim 2, wherein the female screw groove is rounded up after passing through the attachment hole.   2. The ball screw according to claim 1, wherein a mounting hole of the rivet in the nut faces a land portion of the screw shaft, and the female screw groove is rounded up inside the mounting hole. mechanism.   The ball screw mechanism according to any one of claims 1 to 5, wherein the rivet and a part of a land portion of the screw shaft can come into contact with each other. Along a rolling shaft formed between a screw shaft having a male screw groove formed on the outer peripheral surface, a nut disposed so as to surround the screw shaft and having a female screw groove formed on the inner peripheral surface, and both screw grooves facing each other. A plurality of balls arranged so as to be freely rollable, and a pair of end caps attached to both ends of the nut for returning the balls from one end of the rolling path to the other end;
The pair of end caps are fixed to the nut by caulking a rivet penetrating the nut in the axial direction.

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