JP2006118683A - Roller type ball screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller type ball screw provided with a roller member with improved quietness by suppressing vibration when balls pass over the roller member. <P>SOLUTION: The roller type ball screw is provided with a screw shaft 1 formed with a helical thread groove 2 in an outer circumferential face, a nut 3 to be fit on the screw shaft 1 and formed with a helical thread groove in an inner circumferential face, a plurality of balls 5 held between both thread grooves, and the roller member 7 fit in a roller window 6 opened in the nut 3 and formed with a connecting groove 8 connecting the thread grooves 4. A generating line shape of a groove bottom 8b of the connecting groove 8 is formed into a convex surface protruding in an axial direction, and a rolling passage is composed of the connecting groove 8 and the thread groove 2 of the screw shaft 1. A radial moving amount C of the balls 5 and a diameter Dw of the balls 5 are set such that C=0.03-0.10 Dw. By this, the moving amount of the balls 5 are regulated to suppress vibration when passing the roller member 7, and the roller type ball screw with improved quietness can be provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ball screw used in various machine tools such as an electric discharge machine and a tapping center, or an electric power steering or actuator of an automobile, and more particularly, vibrations when a ball passes through a piece member that is a ball circulation part. It is related with the piece type ball screw which suppressed silence and improved silence.

  The ball screw is composed of a screw shaft having a helical thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft, and a spiral screw groove formed on the inner peripheral surface, and both opposing screw grooves. It is equipped with a large number of balls accommodated in the formed rolling path and a circulation mechanism having the rolling path as a circuit path, and is used as a motion conversion mechanism that linearly moves the screw shaft by rotating the nut, for example. ing.

  Generally, there are various types of ball screws having different ball circulation mechanisms, one of which is called a piece type. This piece-type ball screw has a threaded groove connection path, and a circulation piece member having a rolling path as a circular path is attached to the nut. This piece type ball screw has an advantage that the configuration is relatively simple and can be configured in a compact manner.

  A typical example of such a piece-type ball screw is shown in FIG. In this piece type ball screw, the nut 50 is provided with a piece member fitting opening 51 penetrating the inner and outer peripheral surfaces, and the piece member 52 is fitted into the piece member fitting opening 51 from the outer diameter side.

  The piece member 52 is provided with a connection groove 54 that connects adjacent one-circular portions of the screw groove 53 of the nut 50, and the screw groove 53 of the nut 50 is connected by this connection groove 54, thereby making one continuous rotation. It becomes the lap route. The piece member 52 has a pair of walls extending in the longitudinal direction of the main body portion 55 in order to form a main body portion 55 whose outer shape is substantially rectangular and a connecting groove 54 meandering in the longitudinal direction of the main body portion 55. Parts 56a and 56b, and a pair of flange parts 57a and 57b provided at both ends in the short direction of the main body part 55 so as to protrude outward from the wall parts 56a and 56b.

  One flange portion 57 a terminates on the same first surface 58 a as one wall portion 56 a at one longitudinal end of the main body portion 55, and the other flange portion 57 b It terminates on the same second surface 58b as the wall 56b. The first and second surfaces 58a and 58b are formed in a planar shape, and R chamfers 59a and 59b having an arcuate cross section are provided at the respective end portions.

The piece member 52 is formed by forging a billet having substantially the same shape (not shown) with the piece member 52 with a forging die, and is a surface portion continuous with the wall surface portion for forming the connecting groove of the forging die. The flange portions 57a and 57b are terminated on the end side in the longitudinal direction. Thereby, it is possible to sufficiently secure the height of the wall portions 56a and 56b of the piece member 52, and it is possible to effectively prevent the occurrence of cracks or the like in the piece member 52 by avoiding stress concentration.
JP-A-10-82458

  Here, in the conventional piece type ball screw, as shown in an enlarged view in FIG. 5, the groove bottom generatrix shape of the connecting groove 54 is formed as a concave curved surface having a substantially arc shape along the thread groove 53 of the nut 50. ing. The depth of the ball 60 is such that the ball 60 can exceed the thread 62 a of the screw groove 62 of the screw shaft 61 in the connecting groove 54. That is, the inlet 54a of the connecting groove 54 is adjusted so as to be recessed from the screw groove 53 of the nut 50 so as not to hinder the rolling of the ball 60. In the rolling path constituted by the thread groove 62, the depth of the connecting groove 54 is set so that the radial movement amount C of the ball 60 is in the range of 10 to 20% with respect to the diameter Dw of the ball 60. (C = 0.1 to 0.2 Dw).

  However, in such a conventional piece type ball screw, the radial movement amount C of the ball 60 increases in the rolling path of the connecting groove 54, and when the ball 60 passes through the connecting groove 54, There is a risk that the center of the ball 60 rolls in a so-called zigzag state where it rolls out of a predetermined rolling trajectory along the connecting groove 54, and the silent circulation of the ball 60 is obstructed.

  The present invention has been made in view of such circumstances, and provides a piece-type ball screw provided with a piece member that suppresses vibration when the ball passes through the piece member and improves silence. It is aimed.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes a screw shaft having a spiral thread groove formed on the outer peripheral surface thereof, and is externally fitted to the screw shaft and spirally formed on the inner peripheral surface. And a plurality of balls accommodated in a rolling path formed by opposing screw grooves, and a piece window drilled in a body portion of the nut, and the rolling In a piece type ball screw provided with a piece member in which a connecting groove having a circulation path as a circulation path is formed, a groove bottom generatrix shape of the connecting groove is formed as a convex curved surface slightly protruding in the axial direction. Adopted the configuration.

  In this way, in the piece-type ball screw, the groove bottom generatrix shape of the connecting groove is formed as a convex curved surface that slightly protrudes in the axial direction, so it is composed of the connecting groove of the piece member and the screw groove of the screw shaft. It is possible to provide a piece-type ball screw that can restrict the amount of movement of the ball in the radial direction in the rolling path to be small, suppress vibration when the ball passes through the piece member, and improve quietness. it can.

  Preferably, as in the invention according to claim 2, in a rolling path constituted by the connection groove and the screw groove of the screw shaft, the radial movement amount C of the ball and the diameter Dw of the ball If the relationship is set so that C = 0.03 to 0.10 Dw, when the balls pass through the connecting grooves, the center of each ball rolls on a predetermined rolling track along the connecting grooves. It is possible to move and make a quiet circulation of the ball possible.

  In the invention according to claim 3, guide walls are integrally formed on both side edges of the piece member in the circumferential direction, the guide walls are plastically deformable, and have toughness that can secure the crimped portion strength, and heat treatment. Since at least the surface hardness of the connecting groove is set to 30 HRC or more, the toughness of the guide wall serving as the crimped portion is ensured, and cracking or the like is prevented when the piece member is fixed to the nut. In addition, it is possible to ensure the pressure resistance and wear resistance of the connecting groove where a large stress is generated.

  Further, as in the invention described in claim 4, if the arm that engages the screw groove of the nut is integrally formed on the piece member, positioning of the piece member and the piece member from the piece window of the nut It can be reliably prevented from coming out radially outward.

  Further, as in the invention described in claim 5, if the piece member is a sintered metal formed by MIM, even if it has a high workability and a complicated shape, the desired shape / Can be molded to dimensions.

  The piece ball screw according to the present invention includes a screw shaft having a helical thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft, and a spiral screw groove formed on the inner peripheral surface, A plurality of balls accommodated in a rolling path formed by opposing screw grooves, and a connecting groove that is fitted to a piece window drilled in a body portion of the nut and has the rolling path as a circulation path. In the piece type ball screw provided with the formed piece member, the groove bottom generatrix shape of the connecting groove is formed as a convex curved surface slightly projecting in the axial direction, so the connecting groove and screw shaft of the piece member It is possible to restrict the amount of movement in the radial direction of the ball in the rolling path constituted by the thread groove of the ball, and to suppress the vibration when the ball passes through the piece member, and to improve the quietness of the piece member The provided piece type ball screw can be provided.

  A screw shaft having a spiral thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft and having a spiral thread groove formed on the inner peripheral surface, and a roller formed by both opposing screw grooves. A piece comprising a plurality of balls accommodated in a movement path, and a piece member that is fitted to a piece window formed in the trunk portion of the nut and has a connecting groove having the rolling path as a circulation path. In the type ball screw, the groove bottom generatrix shape of the connection groove is formed in a convex curved surface slightly protruding in the axial direction, and in the rolling path constituted by the connection groove and the screw groove of the screw shaft The relationship between the radial movement amount C of the ball and the diameter Dw of the ball is set to be C = 0.03 to 0.10 Dw.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1A and 1B show an embodiment of a piece-type ball screw according to the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a longitudinal sectional view. FIG. 2 is a plan view of a piece member serving as a circulation member, and FIG. 3 is a cross-sectional view.

  This piece-type ball screw has a screw shaft 1 having a helical thread groove 2 formed on the outer peripheral surface thereof, and a nut 3 fitted on the screw shaft 1 and having a helical screw groove 4 formed on the inner peripheral surface thereof. A plurality of balls 5 accommodated in a rolling path formed by the opposing screw grooves 2 and 4 and a piece member 7 fitted in a piece window 6 drilled in the trunk portion of the nut 3. I have.

  The cross-sectional shape of each of the thread grooves 2 and 4 may be a circular arc shape or a Gothic arc shape, but here a Gothic arc shape that allows a large contact angle with the ball 5 and a small axial clearance can be set. Is formed. Thereby, the rigidity with respect to an axial load becomes high, and vibration can be suppressed.

  An elliptical piece window 6 that penetrates the inner and outer peripheral surfaces and cuts out a part of the thread groove 4 is formed in the body portion of the cylindrical nut 3. Is fitted. A connecting groove 8 is formed on the inner side of the piece member 7 so as to connect adjacent ones of the screw grooves 4, and the ball 5 rolls between the connecting groove 8 and the substantially one part of the screw groove 4. Constitutes the road. A large number of balls 5 interposed between the inner and outer screw grooves 2 and 4 in the rolling path roll along the screw grooves 2 and 4, and are guided by the connecting grooves 8 of the piece members 7. After climbing over the crest 2a, it returns to the adjacent screw groove 4 and rolls along the screw grooves 2, 4 again.

  As shown in FIG. 2, the connecting groove 8 of the piece member 7 is formed to be curved in an S shape so as to smoothly connect the adjacent thread grooves 4 of the nut 3. Therefore, the connecting groove 8 is connected to the screw groove 4 so that the opening edge 8a at both ends thereof matches the window opening edge 6a of the adjacent screw groove 4 of the nut 3 (see FIG. 1B). Further, the depth of the connecting groove 8 to be described later is such a depth that the ball 5 can exceed the thread 2 a of the screw groove 2 in the screw shaft 1 in the connecting groove 8.

  A pair of arms 9, 9 project from the opposite ends of the piece member 7 in the axial direction and are opposite to each other in the circumferential direction. These arms 9, 9 have a substantially bowl-shaped cross section and are engaged with the thread groove 4 of the nut 3 via a predetermined radial clearance, positioning the piece member 7, and the piece member 7 having a diameter from the piece window 6. It is provided to prevent it from slipping out of the direction. Here, the portion of the thread groove 4 with which the arm 9 is engaged becomes a non-ball circulating portion.

  Further, as shown in FIG. 3, both side edges in the circumferential direction of the piece member 7 are formed as recessed portions 10 whose outer diameter surfaces are recessed from other portions, and a pair of guide walls 11 rising from these recessed portions 10 toward the outer diameter side. Is provided opposite to the circumferential direction of the piece member 7.

  The ball 5 is assembled by attaching the piece member 7 to the piece window 6 of the nut 3 from the inner diameter side of the nut 3, and then applying the nut 3 from the shaft end of the screw shaft 1. The nut 3 is rotated while being sequentially inserted into the screw shaft 1, and the nut 3 is moved to the screw shaft 1. Besides this, after the piece member 7 is mounted on the piece window 6 of the nut 3, the ball 5 may be similarly inserted using a temporary shaft.

  The piece member 7 is made of a sintered alloy prepared by adjusting a metal powder into a plastic shape and molded by an injection molding machine. In this injection molding, first, metal powder and a binder made of plastic and wax are kneaded with a kneader, and the kneaded product is granulated into pellets. The granulated pellets are molded by so-called MIM (Metal Injection Molding), which is supplied to a hopper of an injection molding machine and pushed into a mold in a heated and melted state. A sintered alloy formed by such an MIM can be easily and accurately formed into a desired shape / dimension even if it has a high workability and a complicated shape.

  In this embodiment, as the metal powder, a material that can be subsequently carburized and quenched, for example, C (carbon) is 0.13 wt%, Ni (nickel) is 0.21 wt%, and Cr (chromium) is 1.1 wt%. Cu (copper) is 0.04 wt%, Mn (manganese) is 0.76 wt%, Mo (molybdenum) is 0.19 wt%, Si (silicon) is 0.20 wt%, and the remainder is Fe (iron). The SCM 415 can be exemplified. In addition to this, it may be a precipitation hardening stainless steel SUS630 in which C is 0.07 wt%, Cr is 17 wt%, Ni is 4 wt%, Cu is 4 wt%, and the remainder is Fe or the like. This SUS630 can appropriately increase the surface hardness by solution heat treatment, and can ensure toughness and high hardness.

  When the piece member 7 is formed of a carburizing material such as SCM415, the piece member 7 is hardened by carburizing and quenching so that the surface hardness is in the range of 30 to 40 HRC, and using a high-frequency temper device, FIG. And the guide wall 11 is annealed, and the surface hardness is set in the range of 15 to 23 HRC.

  Here, if the surface hardness of the hardened layer by carburizing and quenching is less than 30 HRC, the pressure resistance and wear resistance of the connecting groove 8 are insufficient, and if it exceeds 40 HRC, the heat treatment deformation of the piece member 7 becomes undesirably large. . Further, if the surface hardness of the guide wall 11 by annealing is less than 15 HRC, the strength of the caulking portion is insufficient, and if it exceeds 23 HRC, cracks or the like may occur during caulking, which is not preferable.

  On the other hand, when the piece member 7 is formed of precipitation hardening stainless steel such as SUS630, the surface hardness is set to be 30 HRC or more by the solution heat treatment. This SUS630 has a feature that the alloy element is easily solid-solutioned by heating to a predetermined temperature and then rapidly cooling.

  Since the piece member 7 is made of a sintered alloy formed by molding these carburized materials or precipitation hardened stainless steel by MIM, at least the connecting groove 8 where a large stress is generated has sufficient pressure resistance and wear resistance. Moreover, the toughness of the guide wall 11 serving as the crimping portion is high, and the occurrence of cracks and the like can be prevented when the piece member 7 is fixed to the nut 3.

  As a material of the piece member 7, medium carbon steel such as S45C may be used other than the above-described sintered alloy formed by MIM. In this case, the surface hardness can be set in a range of 15 to 23 HRC by tempering in advance, and a hardened layer having a surface hardness of 30 HRC or more can be formed on at least the surface of the connecting groove 8 by induction hardening.

  In the present embodiment, the bus bar shape of the groove bottom 8b of the connecting groove 8 is formed as a convex curved surface that slightly protrudes in the axial direction unlike the conventional case. Thereby, in the rolling path constituted by the connecting groove 8 and the screw groove 2 of the screw shaft 1, the radial movement amount C of the ball 5 can be restricted to be small. Here, the relationship between the radial movement amount C of the ball 5 and the diameter Dw of the ball 5 is set to be C = 0.03 to 0.10 Dw. Thus, by restricting the radial movement amount C of the ball 5 in the rolling path of the connecting groove 8 to be small, when the ball 5 passes through the connecting groove 8, the center of each ball 5, 5 is the connecting groove 8. It is possible to roll on a predetermined rolling trajectory along the ball 5, thereby enabling a quiet circulation of the ball 5.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  The piece type ball screw according to the present invention can be applied to various type machine tools such as an electric discharge machine and a tapping center, or a piece type ball screw used for an electric power steering or an actuator of an automobile.

(A) is a top view which shows one Embodiment of the piece-type ball screw which concerns on this invention. (B) is a longitudinal cross-sectional view same as the above. It is a top view which shows the piece member which concerns on this invention. It is sectional drawing of the piece member which concerns on this invention. It is principal part sectional drawing of the piece type ball screw which concerns on this invention. It is principal part sectional drawing of the conventional piece type ball screw. (A) is principal part sectional drawing of the conventional piece type | formula ball screw. (B) is a perspective view which shows the piece member of the conventional piece type ball screw.

Explanation of symbols

1 ... Screw shaft 2, 4 ... Screw groove 3 ... Nut 5 ... Ball 6 ... Frame window 6a ... Window opening edge 7 ... Frame member 8 ...・ Connection groove 8a ・ ・ ・ ・ ・ ・ ・ ・ ・ Open edge 8b ・ ・ ・ ・ ・ ・ ・ ・ Groove bottom 9 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Arm 10 ・ ・ ・ ・ ・ ・ ・ ・ ・ Dent 11 ······················································································· Member 53, 62 ... Screw groove 54 ... Connection groove 54a ... Inlet 55 ... Main body 56a, 56b ..... wall part 57a, 57b ... flange part 58a ... first surface 58b・ ・ ・ ・ Second surface 59a, 59b ・ ・ ・ ・ Chamfer 60 ・ ・ ・ ・ ・ ・ ・ ・ ・ Ball 61 ・ ・ ・ ・ ・ ・ ・ ・ ・ Screw shaft C ・ ・ ・ ・ ・ ・・ Diameter movement amount Dw ・ ・ ・ ・ ・ ・ ・ ・ ・ Ball diameter

Claims (5)

A screw shaft having a helical thread groove formed on the outer peripheral surface;
A nut externally fitted to the screw shaft and having a spiral thread groove formed on the inner peripheral surface;
A plurality of balls housed in a rolling path formed by opposing screw grooves;
In a piece-type ball screw provided with a piece member fitted to a piece window drilled in the trunk portion of the nut and having a connection groove having the rolling path as a circulation path,
A piece type ball screw characterized in that a groove bottom generatrix shape of the connecting groove is formed as a convex curved surface slightly projecting in the axial direction.   In the rolling path constituted by the connecting groove and the screw groove of the screw shaft, the relationship between the radial movement amount C of the ball and the diameter Dw of the ball is C = 0.03 to 0.10 Dw. The piece type ball screw according to claim 1 set up as follows.   Guide walls are integrally formed on both side edges of the piece member in the circumferential direction, the guide walls are plastically deformable and have toughness that can secure the crimped portion strength, and at least the surface hardness of the connecting groove is 30 HRC by heat treatment. The piece type ball screw according to claim 1 or 2 set up above.   The piece type ball screw according to any one of claims 1 to 3, wherein an arm that engages with a screw groove of the nut is formed integrally with the piece member.   The piece type ball screw according to any one of claims 1 to 4, wherein the piece member is made of a sintered metal formed by MIM.

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