JP2006038099A - Piece type ball screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piece type ball screw, in which assemblage work is easy, and in which need of position adjustment or fixing work for a piece member is eliminated. <P>SOLUTION: This piece type ball screw is provided with a screw shaft 1 in which a spiral screw groove 2 is formed on an outer circumferential surface, a nut 3 engaged around the screw shaft 1, having a spiral screw groove 4 in an inner circumferential surface, a plurality of balls 5 contained in a rolling passage formed of both screw grooves 2 and 4 facing each other, and a piece member 7 engaged in a piece window 6 bored in a drum part of the nut 3 to make the rolling passage into a circumferential route. An arm 8 is provided on the piece member 7 to be engaged with the screw groove 4 in the nut 3, in such a way that the piece member 7 is engaged with the piece window 6 with clearance, and that outer diameter 7a is guided by outer diameter 1a of the screw groove 1 in a floating state to form a radial clearance e of 0.5-5% of the ball diameter to the screw shaft 1 in a floating state. The piece member 7 need not be fixed to the nut 3, thereby position deflection of the piece member 7 due to fixture is eliminated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ball screw used for various machine tools such as an electric discharge machine and a tapping center, or an electric power steering or an actuator of an automobile, and in particular, it is not necessary to adjust and fix the position of a piece member that is a ball circulation part. It becomes a piece type ball screw.

  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 circulation path is mounted on a nut. This piece type ball screw has an advantage that the configuration is relatively simple and can be configured in a compact manner.

  In such a piece-type ball screw, in general, the ball is inserted between the screw shaft and the nut by removing one of the piece members provided on the nut from the nut and from the fitting hole of the piece member. Done. However, there are some pieces in which the piece member cannot be removed outside the nut. That is, there is an element in which an arm for positioning in the axial direction is provided on the piece member and is fitted into the thread groove of the nut. Such a piece member with an arm is widely and generally adopted because the piece member prevents the piece member from being detached and is positioned, and a high-precision and high-strength performance is obtained. However, because it is an internal fitting type, it is possible to reliably prevent the piece member from falling off, but the piece member cannot be removed to the outside of the nut, and the workability when assembling the ball is poor, resulting in increased man-hours and increased costs. Was.

  As a solution to these problems, the present applicant has already proposed a piece-type ball screw as shown in FIG. The piece ball screw 51 includes a screw shaft 52, a nut 53, a plurality of balls 54, and a piece member 55. The screw shaft 52 is formed with a helical thread groove 56 on the outer peripheral surface, the nut 53 is externally fitted to the screw shaft 52 in a loosely fitted state, and the helical screw groove 57 is formed on the inner peripheral surface. The ball 54 is accommodated in a rolling path formed by both screw grooves 56 and 57 of the screw shaft 52 and the nut 53 facing each other. A plurality of piece members 55 are attached to the nut 53, and a connection groove 58 is formed to connect to a screw groove 57 formed in the nut 53. The piece member 55 is attached by fitting in a fitting hole 59 provided in the nut 53.

  At least one of the plurality of piece members 55, for example, one piece member 55 at one end (the right end in FIG. 6A) has a through hole 60 that communicates the rolling path and the outer peripheral surface of the nut 53. have. The through hole 60 is a circular hole larger than the ball diameter. And this through-hole 60 is obstruct | occluded by the sealing means 61 which consists of a plug. The sealing means 61 is made of a metal material such as brass, and is formed in a shaft shape that is press-fitted into the through hole 60.

When the piece type ball screw 51 is assembled, the piece member 55 is mounted on the nut 53 in advance, and the screw shaft 52 is inserted into the nut 53, and then the ball 54 enters the rolling path from the through hole 60 of the piece member 55. Inserted. Thereafter, the sealing means 61 is press-fitted into the through hole 60 to close the through hole 60. According to this piece type ball screw 51, the piece member 55 is provided with a through hole 60 for inserting a ball, and the ball 54 can be directly inserted into the rolling path from the through hole 60 for assembly. After the ball 54 is inserted, the ball 54 can be prevented from falling off by closing the through hole 60 with the sealing means 61. For this reason, even if the piece member 55 is an inner fitting type, the work of assembling the ball 54 is simple, and the piece type ball screw 51 can be easily assembled.
JP 2003-202063 A

  However, in this conventional piece type ball screw 51, the ball 54 is inserted into the rolling path from the through hole 60 of the piece member 55 with the piece member 55 fitted in the fitting hole 59 of the nut 53, and then the ball 54 The piece member 55 is fixed to the nut 53 by adhesive, screwing, caulking, etc., and the position adjustment and fixing work of this piece member 55 and further the fixing work are performed. The reassembly for the position correction by the method is complicated and takes a lot of assembly time.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a piece-type ball screw that is easy to assemble and that does not require position adjustment or fixing work of the piece member.

  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 having a moving path as a revolving route, an arm that engages with a screw groove of the nut is protruded from the piece member, and the piece member is loosely fitted to the piece window. In addition, a configuration is adopted in which the inner diameter is guided by the outer diameter of the screw shaft and is supported so as to have a predetermined radial clearance with respect to the screw shaft in a floating state.

  In this way, in the piece type ball screw, an arm that engages with the screw groove of the nut is projected from the piece member, the piece member is loosely fitted into the piece window, and the inner diameter thereof is guided by the outer diameter of the screw shaft. Since it is supported to have a predetermined radial clearance with respect to the screw shaft in the floating state, there is no need to fix the piece member to the nut by adhesive, screwing, caulking, etc. The position of the piece member does not go wrong. In addition, machining errors in each part can be absorbed by the clearance in the radial direction, adjustment during assembly due to machining errors is not required, assembly work can be simplified, and low-cost piece balls with improved operability. Screws can be provided.

  The invention according to claim 2 is characterized in that in the state where the inner diameter of the piece member is in contact with the outer diameter of the screw shaft, a predetermined radial clearance is provided between the arm and the thread groove of the nut. Since the arm is formed, the guide clearance of the piece member can be set easily.

  Preferably, if the radial clearance is set in the range of 0.5 to 5% with respect to the diameter of the ball as in the invention described in claim 3, the machining error of each part is reduced to this diameter. It can be absorbed effectively by the directional clearance, and adjustment during assembly due to processing errors is not necessary.

  According to a fourth aspect of the present invention, in the state where the inner diameter of the piece member is in contact with the outer diameter of the screw shaft, a step outward in the radial direction is generated in the connecting groove with respect to the screw groove of the nut. Since the piece members are connected, the ball can smoothly roll between the connecting groove and the thread groove of the nut adjacent to the connecting groove.

  Preferably, as in the invention described in claim 5, if the step is restricted to 15% or less with respect to the diameter of the ball, the operability is improved and vibration and noise are suppressed. And stable quality can be maintained.

  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 housed in a rolling path formed by opposing screw grooves, and a piece member fitted into a piece window drilled in a body portion of the nut and having the rolling path as a revolving path; The piece member is provided with an arm that engages with the thread groove of the nut, the piece member is loosely fitted to the piece window, and the inner diameter thereof is guided by the outer diameter of the screw shaft, and is floated. In the state, it is supported so as to have a predetermined radial clearance with respect to the screw shaft, so that it is not necessary to fix the piece member to the nut by an adhesive, screwing, caulking, etc. as in the prior art. The position of the member does not go wrong. In addition, machining errors in each part can be absorbed by the clearance in the radial direction, adjustment during assembly due to machining errors is not required, assembly work can be simplified, and low-cost piece balls with improved operability. Screws 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. In the piece type ball screw provided with a plurality of balls accommodated in the movement path, and a piece member fitted into a piece window drilled in the trunk portion of the nut and having the rolling path as a circulation path, An arm that engages with the screw groove of the nut protrudes from the piece member, and the piece member is loosely fitted into the piece window, and an inner diameter thereof is guided by an outer diameter of the screw shaft, and the screw is in a floating state. The shaft is supported so as to have a radial clearance of 0.5 to 5% with respect to the diameter of the ball.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an embodiment of a piece type ball screw according to the present invention, FIG. 2 is a transverse sectional view taken along line II-II in FIG. 1, and FIG. 3 shows a nut alone according to the present invention. FIG. 4 is a longitudinal sectional view showing a nut according to the present invention, FIG. 5 shows a piece member according to the present invention, (a) is a plan view, and (b) is a longitudinal sectional view.

  As shown in FIG. 1, the screw shaft 1 has a spiral thread groove 2 formed on the outer periphery thereof, and a spiral screw corresponding to the screw groove 2 is formed on the inner periphery of a nut 3 that is externally fitted to the screw shaft 1. A groove 4 is formed. A large number of balls 5 are accommodated between the screw grooves 2 and 4. 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 penetrating the inner and outer peripheral surfaces and notching a part of the thread groove 4 is formed in the barrel portion of the cylindrical nut 3, and an elliptical piece member 7 is formed in the piece window 6. Is loosely fitted (see FIGS. 3 and 4). Here, the fitting clearance between the piece window 6 and the piece member 7 is set to 0.05 to 0.3 mm. As shown in FIG. 5, the piece member 7 is provided with an arm 8 having a substantially hook-shaped cross section on both sides. The arm 8 is provided in order to prevent the piece member 7 from being positioned in the axial direction with respect to the nut 3 and to prevent the piece member 7 from coming out of the piece window 6 radially outward.

  In addition, a connecting groove 9 is formed on the inner side of the piece member 7 so as to connect adjacent one rounds of the screw groove 4, and the ball 5 is formed by the connecting groove 9 and a substantially one round part of the screw groove 4. It constitutes a rolling path. A large number of balls 5 interposed between the inner and outer screw grooves 2, 4 in the rolling path roll along the screw grooves 2, 4, and are guided by the connecting grooves 9 of the piece members 7. After overcoming the thread, it returns to the adjacent thread groove 4 and rolls along the thread grooves 2 and 4 again.

  The connecting groove 9 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 9 of the piece member 7 is connected to the screw groove 4 so that the opening edge 9 a at both ends matches the window opening edge 6 a of the adjacent screw groove 4 of the nut 3. Further, the depth of the connecting groove 9 is set to such a depth that the ball 5 can exceed the thread of the screw groove 2 in the screw shaft 1 in the connecting groove 9.

  The piece member 7 is made of a sintered alloy prepared by adjusting a metal powder into a plastic shape and molding it with 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 pellet is supplied to a hopper of an injection molding machine and molded by being pushed into a mold in a heated and melted state. The metal powder is preferably a material that can be subsequently carburized and quenched. For example, C (carbon) is 0.3 wt%, Ni (nickel) is 1 to 2 wt%, and the remainder is Fe (iron). . The material of the piece member 7 is not limited to this, and may be formed of, for example, an injection-moldable thermoplastic resin such as PA (polyamide) 66.

  The ball 5 is assembled by attaching the piece member 7 to the piece window 6 of the nut 3, then applying the nut 3 from the shaft end of the screw shaft 1, and inserting the ball 5 between both the screw grooves 2 and 4 sequentially. 3 is rotated 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.

  In the present embodiment, as shown in FIG. 2, the inner diameter 7a of the piece member 7 is guided by the outer diameter 1a of the screw shaft 1, and is supported via a predetermined radial clearance e with respect to the screw shaft 1 in a floating state. Yes. The radial clearance e is formed by forming a predetermined radial clearance between the arm 8 and the thread groove 4 of the nut 3 in a state where the inner diameter 7a of the piece member 7 is in contact with the outer diameter 1a of the screw shaft 1. It can be set easily.

  When the inner diameter 7a of the piece member 7 is guided by the outer diameter 1a of the screw shaft 1, that is, at the lowest floating point (contact state), the step δ between the connecting groove 9 and the screw groove 4 of the nut 3 Is set in a range of 0 to 10% (δ = 0 to 0.1d) with respect to the diameter d of the ball 5. Thus, if the piece member 7 is connected to the thread groove 4 of the nut 3 so that a step δ in the radial direction is formed in the connection groove 9, the ball 5 is connected to the connection groove 9 and the connection groove 9. It is possible to smoothly roll between the screw grooves 4 of the nut 3 adjacent to the groove 9.

  In this state, the floating amount until the arm 8 contacts the screw groove 4 of the nut 3, that is, the radial guide clearance e between the inner diameter 7 a of the piece member 7 and the outer diameter 1 a of the screw shaft 1 is Is set in a range of 0.5 to 5% (e = 0.05 to 0.05d) with respect to the diameter d of the above. Thereby, the processing error of each part can be effectively absorbed by the radial guide clearance e, and adjustment during assembly due to the processing error becomes unnecessary. Further, the maximum step δmax between the connecting groove 9 of the piece member 7 and the thread groove 4 of the nut 3 can be restricted to 15% or less with respect to the diameter d of the ball 5. The maximum step δmax is preferably regulated to 15% or less with respect to the diameter d of the ball 5 in terms of quality stability such as operability and vibration.

  In the piece type ball screw according to the present invention, a piece member 7 is loosely fitted to a piece window 6 formed in the nut 3, and an inner diameter 7 a of the piece member 7 is guided by an outer diameter 1 a of the screw shaft 1. Since it is supported so as to have a predetermined radial clearance e with respect to the screw shaft 1 in the state, there is no need to fix the piece member 7 to the nut 3 by an adhesive, screwing, caulking, etc. The position of the piece member 7 is not changed by the fixing. In addition, machining errors in each part can be absorbed by the radial clearance e, so that adjustment during assembly due to machining errors is unnecessary, and assembling can be simplified, and a low-cost piece type with improved operability. A ball screw can be provided.

  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.

It is a longitudinal section showing one embodiment of a piece type ball screw concerning the present invention. It is a cross-sectional view along the II-II line of FIG. It is a longitudinal section showing a nut simple substance concerning the present invention. It is a longitudinal section showing a nut concerning the present invention. The top member which concerns on this invention is shown, (a) is a top view, (b) is a longitudinal cross-sectional view. The conventional piece type ball screw is shown, (a) is a front view, (b) is a longitudinal sectional view, and (c) is a perspective view of the piece member.

Explanation of symbols

1 ... Screw shaft 1a ... Outer diameter 2, 4 ... Screw groove 3 ... Nuts 5 ... Ball 6 ... Frame window 6a ... Window opening edge 7 ... Piece member 7a ········ Inner diameter 8 ········· Arm 9 ········ Connection groove 9a ······· Open edge 51 ····························································································· Ball 55 ············· Frame members 56, 57 ··· Screw groove 58 ·········· Connection groove 59 ············ Fitting hole 60 ··· .... Through hole 61 ... Sealing means d ... Ball diameter e ...・ ・ ・ ・ ・ ・ ・ Diameter clearance δ between the outer diameter of the screw shaft and the piece member ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Step δmax between the connecting groove and the screw groove of the nut Maximum step between groove and screw groove of nut

Claims (5)

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. In a piece type ball screw provided with a plurality of balls accommodated in a movement path, and a piece member fitted into a piece window drilled in the trunk portion of the nut and having the rolling path as a circulation path,
The piece member is provided with an arm that engages with the screw groove of the nut, and the piece member is loosely fitted to the piece window, and the inner diameter thereof is guided by the outer diameter of the screw shaft, and in the floating state, A piece-type ball screw that is supported so as to have a predetermined radial clearance with respect to a screw shaft.   The arm is formed so as to have a predetermined radial clearance between the arm and a thread groove of the nut in a state where the inner diameter of the piece member is in contact with the outer diameter of the screw shaft. Piece ball screw.   The piece type ball screw according to claim 2, wherein the radial clearance is set in a range of 0.5 to 5% with respect to the diameter of the ball.   2. The piece member is connected so that a step outward in the radial direction is formed in the coupling groove with respect to the screw groove of the nut in a state where the inner diameter of the piece member is in contact with the outer diameter of the screw shaft. 4. The piece type ball screw according to any one of 3 to 3.   The piece type ball screw according to claim 4, wherein the step is regulated to 15% or less with respect to the diameter of the ball.

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