JP4756645B2 - Koma type ball screw - Google Patents

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.

  This piece member is an important part for circulating the ball in the thread groove where the screw shaft and the nut face each other. If the piece member breaks or falls off the nut, it becomes a fatal defect in the function of the actuator. Sufficient measures are required.

  Patent Document 1 discloses a method for fixing a piece member with such a countermeasure to a nut. In this example, an arm that engages with a screw groove of the nut and positions the piece member in the axial direction with respect to the nut is provided on the piece member having a connecting groove that connects the screw grooves of the nut. The piece member is inserted into the piece window formed in the nut from the inner diameter side of the nut, and the arm provided on the piece member comes into contact with the screw groove surface of the nut that is not used for ball circulation, and against the nut screw groove. It is positioned and fixed to the nut by caulking a guide wall formed on the outer diameter side of the piece member.

According to this structure, the piece member is inserted into the nut from the inner diameter side, is positioned in the axial direction with respect to the nut by the arm, and the guide wall formed on the outer diameter side of the piece member is molded into the nut. Since the piece member is caulked and fixed to a pair of opposed inner diameter surfaces of the piece window, the piece member is firmly fixed to the nut. In the conventional guide wall, the outer surface has an R shape and the inner surface has a flat shape. Then, the entire flat inner surface is caulked so as to press outward.
JP 2001-289301 A

  When the piece member is fixed to the nut by caulking, that is, plastic deformation, the piece member needs to ensure ductility that can withstand plastic deformation. On the other hand, the piece member is an important part for circulating the ball, and is required to have sufficient mechanical strength against deformation and wear due to the ball circulation. Therefore, even when the piece member is caulked and fixed, it is necessary to increase the material strength at the expense of the ductility of the piece member to some extent.

  When the hardness of the piece member is increased in order to increase the material strength, it is unavoidable that a certain amount of spring back occurs after plastic deformation of the caulking portion of the piece member, and the piece member is formed on the nut. A rattling will be generated in the window. In particular, when the inner surface of the guide wall has a flat shape as in the prior art and the entire flat surface is caulked so as to press outward, the occurrence of this spring back is significant. The looseness of the piece member thus generated causes vibration and abnormal noise of the actuator, or promotes deformation and wear of the circulation groove of the piece member due to ball circulation, and eventually causes malfunction of the actuator. It can be a cause.

  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 fixing strength of the piece member to the nut and improves the reliability.

In order to achieve such an object, the present invention provides 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 thread 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 a body portion of the nut and having the rolling path as a circulation path A pair of guide walls rising on the outer diameter side are formed on both side edges of the nut in the circumferential direction, and the guide walls are caulked and fixed to the piece window. in bridge type ball screw, the inner surfaces of the guide wall has a R-shaped, the bridge member by caulking deformed so as to press the base point two places of the end portion is fixed to the nut, crimping adopted a configuration having a reduced amount of spring-back after plastic deformation by It was.

In this way, the inner surface of each guide wall has an R shape, and since it is caulked and deformed so as to be pressed using two points at the end, the cross-sectional area of the guide wall to be caulked is reduced. the entire guide wall for caulking as different, a smaller portion alone can be caulked to plastically deform, or spring back amount after the plastic deformation is that a smaller by tightening. As a result, the backlash after caulking of the piece member is reduced.

  Further, according to the present invention, the portion of the caulking punch that caulking and deforms the guide wall may be a flat shape, so that two portions on the inner side surface of each guide wall may be provided. Can be pressed.

  Further, in the present invention, the portion of the caulking punch that caulking and deforms the guide wall to be in contact with the guide wall can be configured to have an R shape larger than the R dimension of the inner surface of the guide wall. Two locations on the inner surface of the guide wall can be pressed.

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. A pair of guide walls that are formed on the both side edges of the nut in the circumferential direction, and that are caulked and fixed to the piece window. in formula ball screw, the inner surfaces of the guide wall has a R-shaped, the bridge member by caulking deformed so as to press the base point two places of the end portion is fixed to the nut, by caulking adopt a configuration having a reduced amount of spring-back after plastic deformation Since, it is possible to press the two places of the inner surface of the guide walls, increase the fixing strength of the nut piece member, it is possible to improve the reliability.

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 to a piece window formed in the trunk portion of the nut and having a connecting groove having the rolling path as a circulation path, In the piece member, a pair of guide walls rising on the outer diameter side are formed on both side edges of the nut in the circumferential direction, and a piece type ball screw for caulking and fixing the guide wall to the piece window, The inner surface has an R shape, and the piece member is fixed to the nut by caulking and deforming so as to press each of the two ends of the end, thereby reducing the amount of springback after plastic deformation by caulking. .

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 perspective view of the piece member according to the present invention. FIG. 3 shows a piece member according to the present invention, wherein (a) is a top view, (b) is a side view, and (c) is a bottom 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 screw groove 2a, 3a of the screw shaft 2 and the nut 3 may be a circular arc shape or a gothic arc shape, but here the contact angle with the ball 4 can be taken large and the axial clearance is It is formed in a gothic arc shape that can be set small. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  A cylindrical window 3 having a substantially circular cross section is formed in the body of the cylindrical nut 3 so as to penetrate the inner and outer peripheral surfaces and cut out a part of the screw groove 3a. A piece member 5 serving as a circulation member for the ball 4 is fitted in the piece window 6. Note that the piece window does not necessarily have a circular shape, and may be, for example, an oval shape.

  A connecting groove 5a that connects adjacent one rounds of the screw groove 3a is formed inward of the piece member 5. Thereby, the ball | bowl 4 can go around by the connection groove | channel 5a and the part of the substantially 1 round of the thread groove 3a. That is, the rolling path formed by the opposing screw grooves 2a and 3a becomes the circulation path. 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 grooves 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.

  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.

  A pair of arms 5b and 5b protrude from opposite ends of the piece member 5 in the axial direction at opposite ends in the circumferential direction. These arms 5b and 5b are formed in a substantially circular cross section, and are engaged with the thread groove 3a of the nut 3 via a predetermined radial clearance to position the piece member 5 and to move the piece member 5 radially from the piece window 6. It is provided to prevent it from slipping out. Here, the portion of the thread groove 3a where the arms 5b and 5b are engaged becomes a non-ball circulating portion.

  As shown in FIGS. 2, 3A, and 3B, the piece member 5 includes a barrel portion 5c in which arms 5b and 5b project, and an outer diameter side (nut) from the barrel portion 5c. 3 of the head 5d extending radially outward). The trunk portion 5 c has a substantially circular cross section so as to correspond to the shape (circular hole) of the piece window 6 of the nut 3 and is fitted to the piece window 6.

  The head portion 5d is formed with a recessed portion 5e whose outer diameter surface is recessed from the other portions on both sides (both sides in the circumferential direction of the nut 3), rising from the recessed portion 5e to the outer diameter side, and having a pair of arcuate circumferential surfaces. The guide walls 5f and 5f are arranged to face each other. The outer surfaces of the guide walls 5f and 5f have an R shape so as to correspond to the shape (circular hole) of the piece window 6. In the present embodiment, the inner surfaces of the guide walls 5f and 5f have an R shape that spreads in an R shape around the axis of the piece member. The R-shaped portion on the inner side surface has a smaller R shape than the outer side surface, and the thickness of the guide walls 5f and 5f is substantially the same. The shape of the guide wall 5f is not limited to this, and the R dimension of the R shape is not limited to this, and can be variously designed.

Next, a method for fixing the piece member 5 will be described.
4A and 4B are views showing a method of fixing a piece member according to the present invention, wherein FIG. 4A is a side view and FIG. 4B is a top view. FIG. 5 is a partially enlarged view showing details when the piece member is fixed.

  When fixing the piece member 5, first, the piece member 5 is fitted into the piece window 6 of the nut 3 from the inner diameter side of the nut 3. Next, the arms 5 b and 5 b are engaged with the thread groove 3 a of the nut 3. In this state, a core (not shown) is put in the nut 3 and the caulking punch 10 is pushed in from the outer diameter side. The caulking punch 10 has a tapered pressure surface 10 a at the tip thereof, and the pair of guide walls 5 f and 5 f of the piece member 5 are crimped so that the tip is bent obliquely outward, and is fastened to the nut 3. It will be in an engaged state.

  Here, the machining surface 10a of the caulking punch 10 first makes point contact with the end portions 5g and 5g on the inner side surfaces of the guide walls 5f and 5f, as shown in FIG. When the caulking punch 10 is pushed downward in this state, the guide walls 5f and 5f are plastically deformed in all directions as indicated by arrows in FIG. . As described above, since the inner side surfaces of the guide walls 5f and 5f are formed in the R shape, the cross-sectional area of the guide walls 5f and 5f to be caulked is reduced, and the caulking and fixing can be performed only by plastically deforming a smaller portion. As a result, the amount of springback after plastic deformation due to caulking is reduced, and the backlash after caulking of the piece member 5 is reduced.

  In addition, although the processing surface 10a of the caulking punch of this example is tapered, the processing surface can be flat so as to face the guide walls 5f and 5f. Further, the machining surface 10a of the caulking punch may have an R dimension larger than the R dimension of the inner surface of the guide walls 5f and 5f. In any case, if the machining surface 10a of the caulking punch is initially in point contact with the end portions 5g and 5g of the inner surface of the guide walls 5f and 5f, when the caulking punch 10 is pushed downward, The guide walls 5f and 5f are plastically deformed in all directions as shown by the arrows in FIG. 4B with the end portions 5g and 5g as base points. By doing so, the piece member 5 is stably fixed to the nut 3.

  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.

BRIEF DESCRIPTION OF THE DRAWINGS One Embodiment of the piece type ball screw which concerns on this invention is shown, (a) is a top view, (b) is a longitudinal cross-sectional view. It is a perspective view of the piece member concerning the present invention. The top member which concerns on this invention is shown, (a) is a top view, (b) is a side view, (c) is a bottom view. It is a figure which shows the fixing method of the piece member which concerns on this invention, (a) is a side view, (b) is a top view. It is the elements on larger scale which show the detail at the time of fixation of a piece member.

Explanation of symbols

1 ······ Poma type ball screw 2 ·············· Screw shafts 2a, 3a Nut 4 ... Ball 5 ... Piece member 5a ... Connection groove 5b ... Arm 5c ·········· 5d ························································ 5 ····· End 6 ····························································································

Claims (3)

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;
A piece member fitted with a piece window drilled in the trunk portion of the nut and formed with a connecting groove having the rolling path as a circulation path;
In the piece member, a pair of guide walls rising on the outer diameter side are formed on both side edges in the circumferential direction of the nut, and a piece type ball screw for caulking and fixing the guide wall to the piece window,
The inner surface of each of the guide walls has an R shape, and the piece member is caulked and deformed so as to be pressed at two positions of the end portions to fix the piece member to the nut, and the spring after plastic deformation by caulking A piece-type ball screw with a small back amount .   The piece type ball screw according to claim 1, wherein a portion of the caulking punch that caulking and deforms the guide wall is in a flat shape. The piece type ball screw according to claim 1, wherein a portion of the caulking punch that caulking and deforms the guide wall is in an R shape larger than an R dimension of an inner side surface of the guide wall.

Images