JP2007255488A - Roller type ball screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller type ball screw capable of increasing strength of a roller member and improving reliability inexpensively. <P>SOLUTION: Since the roller member 5 is molded from a steel plate 7 by cold forging, a protruding bar 15 is formed in an end part of an outer peripheral face 14, is positioned in a piece window 6, and is fixed by projection welding in this roller type ball screw provided with the roller member 5 fitted into the piece window 6 provided in a barrel part of a nut 3 and forming a connection groove 5a using a rolling passage as a circumferential path, the roller member 5 having high strength and excellent wear resistance can be formed by hardening to improve reliability inexpensively and fix the piece member 5 to the nut 3 firmly, and electric current for welding is concentrated in the protruding bar 15 to keep satisfactory heat balance and suppress heat input to the minimum extent so that thermal warp of the roller member 5 is prevented and airtightness is increased. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 more particularly to a piece type ball screw using a piece member that is a ball circulation part. .

  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 with a rolling path as a circulation path is attached to the nut. The structure is relatively simple and compact. There are advantages you can do.

  A typical example of such a piece-type ball screw is shown in FIG. This piece type ball screw is mainly composed of a screw shaft 50, a nut 51, and a ball 52. The screw shaft 50 has a spiral thread groove 53 having a predetermined lead on the outer peripheral surface thereof. The thread groove 53 is a Gothic arch groove that contacts the ball 52 at two points.

  The nut 51 has a cylindrical shape and is externally attached to the screw shaft 50, and has a flange 54 on the outer periphery of the end. A spiral thread groove 55 having a lead equal to the lead of the screw shaft 50 is formed on the inner peripheral surface thereof. The screw groove 55 is a Gothic arch groove that contacts the ball 52 at two points.

  A track 56 having a substantially circular cross section is formed between the opposing screw grooves 53 and 55. A plurality of balls 52 are filled in the track 56. Further, as shown in an enlarged view in FIG. 6, the nut 51 is formed with an insertion port 57 formed of a long hole penetrating from the outer periphery toward the inner periphery, and a circulation piece member 58 is attached to the insertion port 57. ing. The piece member 58 is formed with a connecting groove 58 a that connects adjacent one-round portions of the thread groove 55.

  As shown in FIG. 7, the piece member 58 is formed by pressing a steel plate made of a stainless steel strip or the like, and has a piece main body 59 and a locking portion 60. This piece main body 59 has end portions 59a formed in a semicircular shape in alignment with the insertion port 57 of the nut 51 at both ends in the longitudinal direction. Further, in order to return the ball 52, a connecting groove 58a continuous in the longitudinal direction of the piece body is formed in a substantially S shape.

The locking portion 60 is bent outward with respect to the piece main body 59 to form a locking end portion 60a. The planar shape of the locking end portion 60a is fitted to the insertion port 57 of the nut 51. It has a rectangular shape that matches 57 locked portions 61. And the piece main body 59 is positioned by the latching | locking part 60, and is elastically supported. Thereby, the piece member 58 can be easily positioned with respect to the nut 51, and the time and cost required for assembly can be reduced.
JP 2004-251296 A

  In such a conventional piece type ball screw, a thin metal plate is used for the circulation piece member 58, and it is formed into a complicated shape by repeating deep drawing and bending, so that material breakage occurs during press working. In addition, there is a problem that, depending on the processing part, there is a problem that stress is left due to press processing exceeding the limit processing degree, the material strength is insufficient, and durability as the piece member 58 is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a piece-type ball screw that increases the strength of the piece member and is improved in reliability at low cost.

  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, the piece member is formed from a steel plate by cold forging.

  Thus, in the piece type ball screw provided with the piece member that is fitted to the piece window formed in the trunk portion of the nut and is formed with the connecting groove having the rolling path as the circulation path, the piece member is made of a steel plate. Since it is formed by cold forging, a piece member with high strength and excellent wear resistance can be formed by work hardening, and a piece type ball screw with improved reliability at low cost can be provided. .

  Preferably, if the piece window is formed in a substantially circular cross section and the piece member is formed in a circular shape corresponding to the piece window as in the invention described in claim 2, the man-hours for processing the piece window Thus, the cost can be reduced, and the piece member can be accurately and easily positioned in the axial direction with respect to the nut, and the reliability can be improved.

  In addition, if a protrusion is formed on the outer periphery of the end portion of the piece window as in the invention described in claim 3, the piece member becomes a positioning portion when being mounted on the piece window, and the piece member is accurately attached. Can be positioned and fixed.

  Further, as in the invention according to claim 4, if the piece member is fixed to the piece window by projection welding, the piece member can be firmly fixed to the nut, and the protrusion of the piece member can be fixed. The welding current can be concentrated, the heat balance of the piece members can be maintained, and the heat input can be minimized. Therefore, the heat distortion of the piece member can be prevented and the airtightness can be improved.

  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 coupling groove fitted into a piece window drilled in the nut body and having the rolling path as a circulation path In the piece type ball screw provided with the formed piece member, since the piece member is formed by cold forging from a steel plate, it is possible to form a piece member having high strength and excellent wear resistance by work hardening. It is possible to provide a piece type ball screw with improved reliability at a low cost.

  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 plurality of balls accommodated in the movement path, and a piece member fitted with a piece window having a substantially circular cross section formed in the trunk portion of the nut and having a connecting groove having the rolling path as a circulation path; The piece member is formed from a steel plate by cold forging, a protrusion is formed on the outer periphery of the end portion, positioned at the piece window, and fixed by projection welding.

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. 2A to 2D are explanatory views showing the manufacturing process of the piece member according to the present invention, FIG. 3A is a plan view of the piece member in the process of FIG. ) Is a sectional view, FIG. 4A is a plan view of a piece member in the step of FIG. 2D, and FIG. 4B is a sectional view.

  This piece-type ball screw 1 includes a screw shaft 2 having a helical thread groove 2a formed on the outer peripheral surface, and a nut externally fitted to the screw shaft 2 and having a helical screw groove 3a formed on the inner peripheral surface. 3, a large number of balls 4 accommodated in a rolling path formed by both opposing screw grooves 2 a and 3 a, and a piece member 5 serving as a circulation member for these balls 4.

  The cross-sectional shape of each thread groove 2a, 3a may be a circular arc shape or a Gothic arc shape, but here, it has a Gothic arc shape that allows a large contact angle with the ball 4 and a small axial clearance. Is formed. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  The cylindrical nut 3 has a generally circular piece window 6 having a substantially circular cross section that penetrates the inner and outer peripheral surfaces and cuts out a part of the screw groove 3a. A circular piece member 5 is fitted. A connecting groove 5a is formed on the inner side of the piece member 5 so as to connect adjacent ones of the screw grooves 3a, and the ball 4 rolls between the connecting groove 5a and the substantially one part of the screw groove 3a. Constitutes the road. A large number of balls 4 interposed between the inner and outer screw grooves 2a and 3a in the rolling path roll along the screw grooves 2a and 3a, and are guided by the connecting groove 5a of the piece member 5 to be screw shafts. 2 over the thread 2 and return to the adjacent thread groove 3a, and roll along the thread grooves 2a and 3a again. In this embodiment, the piece window 6 is formed in a substantially circular cross section, and the piece member 5 is formed in a circular shape corresponding to the piece window 6, so that the number of processing steps of the piece window 6 can be reduced and the cost can be reduced. In addition, the piece member 5 can be easily and accurately positioned in the axial direction with respect to the nut 3, and the reliability can be improved. Note that the piece window does not necessarily have a circular shape, and may be, for example, an oval shape.

  The connecting groove 5a of the piece member 5 is formed to be curved in an S shape so as to smoothly connect the adjacent screw grooves 3a and 3a of the nut 3, and is smoothly connected to the screw groove 3a. The depth of the connecting groove 5a is set to a depth at which the ball 4 can exceed the thread of the screw groove 2a in the screw shaft 2 within the connecting groove 5a.

  Here, the piece member 5 is formed by pressing a steel plate such as a stainless steel plate (JIS standard SUS430 series or the like) or a cold rolled steel plate (JIS standard SPCC type) into FIGS. 2 (a) to 2 (d). It is molded through the steps shown. That is, the material steel plate 7 having a predetermined thickness shown in (a) is punched into a button-shaped piece material 8 as shown in (b) by a transfer type automatic press. Next, a coining process (printing pressure process) is performed on the piece material 8 to form a rough connection groove 9 as shown in FIG. And this rough connection groove | channel 9 is finish-molded by the last process shown to (d), and the piece member 5 is formed.

  In the coining process shown in FIG. 2 (c), as shown in FIG. 3, the punch 11 is pressed from the other end surface while the outer edge of the one end surface of the piece material 8 is supported by the die 10, and the section is substantially semicircular and S-shaped. A rough connection groove 9 extending in a shape is formed. Further, as shown in FIG. 4, the outer peripheral surface 14 and the connecting groove 5 a are simultaneously finished by the punch 13 from the other end surface with one end surface of the piece material 8 of the previous process supported by the die 12. As a result, the connecting groove 5a can be finished to a desired shape and size with extremely high precision. Here, the molding of the outer peripheral surface 14 is stopped in the vicinity of the one end surface, and the protrusion 15 is formed at the end of the outer peripheral surface 14. This protrusion 15 becomes a positioning part when the piece member 5 is attached to the piece window 6 in the nut 3 described above.

  The piece member 5 is press-fitted into the piece window 6 of the nut 3 via a predetermined scissors, but the piece member 5 is welded to the piece window 6 by concentrating the welding current on the protrusion 15 of the piece member 5, so-called projection welding. can do. Thereby, since the heat balance of the piece member 5 can be maintained and heat input can be suppressed to the minimum, the piece member 5 can be firmly fixed to the nut 3 and the thermal distortion of the piece member 5 can be prevented. Airtightness can be increased.

  In this embodiment, since the piece member 5 is formed by cold forging from a steel plate, the piece member 5 having high strength and excellent wear resistance can be formed by work hardening, and the reliability is improved at low cost. A piece-shaped ball screw 1 can be provided. Here, the piece member 5 is described as being formed by the transfer type automatic press. However, the present invention is not limited to this, and for example, a robot type automatic press or a single function type power press may be used.

  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 a piece type ball screw used for an electric actuator of an automobile or the like.

(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 explanatory drawing which shows the manufacturing process of the piece member which concerns on this invention, (a) shows a raw material steel plate, (b) shows the punching of a piece material. Moreover, (c) shows the coining process which shape | molds a rough connection groove | channel, (d) has shown finishing process. (A) is a top view which shows the piece member in the process of FIG.2 (c). (B) is a cross-sectional view of the above. (A) is a top view which shows the piece member in the process of FIG.2 (d). (B) is a cross-sectional view of the above. It is a longitudinal section showing a conventional piece type ball screw. It is a principal part enlarged view of FIG. It is a perspective view which shows the piece member of FIG.

Explanation of symbols

1 ······ Poma type ball screw 2 ············· Screw shafts 2a, 3a Nut 4 ... Ball 5 ... Piece member 5a ... Connection groove 6 ... Piece Window 7 ··· Material steel plate 8 ··· Frame material 9 ··· Coarse connecting grooves 10 and 12 ··· Dies 11, 13 ... Punch 14 ... Outer peripheral surface 15 ... Projection 50 ... Screw shaft 51 ... ········································ Balls 53 and 55 ············································ · Track 57 ·············· Insertion port 58 ··········· Piece member 58a ··· ... Linking groove 59 ......... Frame body 59a ... End 60 ......... Locking portion 60a ... Locking end part 61 ..... Locked part

Claims (4)

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 that is fitted to a piece window drilled in the trunk portion of the nut and has a connection groove having the rolling path as a circulation path,
The piece type ball screw, wherein the piece member is formed from a steel plate by cold forging.   The piece-type ball screw according to claim 1, wherein the piece window is formed in a substantially circular cross section, and the piece member is formed in a circular shape corresponding to the piece window.   The piece type ball screw according to claim 1, wherein a protrusion is formed on an outer periphery of an end of the piece window.   The piece-type ball screw according to claim 3, wherein the piece member is fixed to the piece window by projection welding.

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