JP4811784B2 - Ball screw mechanism and method of assembling the ball screw mechanism - Google Patents

Description

The present invention relates to a ball screw mechanism which is assembled to a general industrial machine or used in an automobile, and a method of assembling the ball screw mechanism .

  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 top is attached to the nut to return the ball to the end. Here, generally, the top is attached to the nut using an adhesive, but there is a problem that the adhesive having oil resistance, heat resistance, etc. is expensive. On the other hand, in Patent Document 1, after a piece is mounted in a dovetail groove formed on a nut, the back of the piece is widened by hitting it with a punch or the like, and it is prohibited to escape from the dovetail groove. A technique for attaching a top to a nut is disclosed.
Japanese Utility Model Publication No. 6-87762

  However, in the prior art described in Patent Document 1, there is a problem that it takes time and effort to accurately provide a groove having a width that becomes narrower in the radially outward direction, resulting in an increase in cost.

The present invention has been made in view of the problems of the prior art, and provides a ball screw mechanism and a method of assembling the ball screw mechanism that have a simple configuration, are easy to manufacture, and can prevent the circulation member from coming off. The purpose is to do.

The ball screw mechanism of the present invention is
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 an internal thread formed on an inner peripheral surface thereof;
A plurality of balls arranged to freely roll along a rolling path formed between opposing screw grooves;
A circulation member formed with a main body and a caulking portion,
The circulation member is attached to the attachment hole so as to sandwich the periphery of the attachment hole of the nut in the radial direction of the nut between the main body and the caulking portion ,
The caulking portion formed by caulking the outer periphery of the main body is located on the radially outer side of the nut with respect to the screw shaft side end portion of the main body .

According to the ball screw mechanism of the present invention, the circulation member is attached to the attachment hole so as to sandwich the periphery of the attachment hole of the nut in the radial direction of the nut between the main body and the caulking portion. since it is, the there is no need to provide a groove as in the prior art, it can be attached to the circulation member at least a portion of said end portion only is plastically deformed into the nut.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a top view of the ball screw mechanism according to the present embodiment, FIG. 2 is a view of the configuration of FIG. 1 taken along the line II-II and viewed in the direction of the arrow, and FIG. FIG. 4 is a partial perspective view of the ball screw mechanism according to the present embodiment. FIG.

  In the drawing, a male screw groove 1a is formed on the outer peripheral surface of a screw shaft 1 which is connected to a driven member and supported so as not to rotate and to move only in the axial direction. A land portion 1b that forms the outermost diameter of the screw shaft 1 is interposed between the male screw grooves 1a that are spirally wound and aligned in the axial direction.

  A cylindrical nut 2 supported so as to be rotatable only with respect to a housing (not shown) is disposed so as to surround the screw shaft 1 and has an internal thread groove 2a (in this case, an internal thread groove of slightly less than one turn is provided with 2 internal thread grooves). Book). A plurality of balls 3 are arranged so as to be able to roll in a spiral rolling path formed between the opposing screw grooves.

  On the outer periphery of the nut 2, as shown in FIG. 4, two flat portions 2c, 2c are formed side by side in the axial direction, and a cylindrical piece (attachment hole) 2b is formed at the center of each flat portion 2c. Is formed.

  As shown in FIG. 4, the circulation member 4 includes a rectangular plate-like main body 4a and a cylindrical piece 4b provided on the lower surface of the main body 4a. The main body 4a has a dimension projecting outward from the frame portion 4b. The outer diameter of the top part 4 b is substantially equal to the inner diameter of the top hole 2 b of the nut 2. An S-shaped circulation path 4c is formed on the lower surface of the top portion 4b (see FIG. 1).

  A method for assembling the ball screw mechanism will be described. FIG. 5 is a view showing a part of the manufacturing process of the ball screw mechanism, and FIG. 6 is an enlarged view showing an arrow VI part of FIG. In FIG. 4, the frame 4b is inserted and fitted into the frame hole 2b so that the main body 4a is attached so as to be in close contact with the flat surface 2c, and then the balls 3 are loaded appropriately.

In such a state, the insertion side end of the top part 4b protrudes from the inner diameter side end of the top hole 2b of the nut 2. Therefore, while holding the main body 4a of the circulation member 4 from the radially outer side of the nut 2, as shown in FIG. 5A, the tool T is positioned radially inward of the nut 2, and further, FIG. As shown in FIG. 4 , the projection Tp of the tool T crushes the vicinity of the outer periphery of the end portion of the top portion 4b to plastically deform it, thereby forming the crimped portion 4d. After the tool T is retracted, the crimped portion 4d protruding outward in the radial direction of the coma hole 2b at two locations (positions 180 degrees apart) on the entire inner diameter side of the nut 2 due to plastic deformation The shape will be maintained. Therefore, the circulation member 4 is attached to the nut 2 by the body 4a and the caulking portion 4d sandwiching the periphery of the top hole 2b of the nut 2 in the radial direction. Thereafter, the ball screw mechanism is completed by incorporating the screw shaft 1 (see FIG. 6). In addition, the protrusion amount of the insertion side end part of the top part 4b is slight, and does not interfere with the land part 1b of the screw shaft 1.

  The operation of the present embodiment will be described. When the nut 2 is rotationally driven by an electric motor (not shown), the rolling path rolls and one end of the rolling path is passed through the circulation path 4c of the top 4b of the circulation member 4. The rotating motion is efficiently converted into the axial motion of the screw shaft 1 by the balls 3 circulating from the other end to the other end, and a driven member (not shown) connected thereto can be moved in the axial direction.

  According to the ball screw mechanism of the present embodiment, after the circulation member 4 is inserted into the top hole 2 b of the nut 2, a part of the end on the insertion side is placed outside the top hole 2 b on the inner diameter side of the nut 2. Since it is plastically deformed so as to protrude in the direction, there is no need to provide a groove as in the prior art, and the circulating member 4 is attached to the nut 2 by a caulking portion 4d in which a part of the end portion is plastically deformed. Can do.

  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, it is needless to say that the circulation member main body is changed to various shapes such as a circular shape as well as a rectangular shape, and a tube may be used instead of the top portion.

It is a top view of the ball screw mechanism which is this Embodiment. It is the figure which cut | disconnected the structure of FIG. 1 by the II-II line | wire, and looked at the arrow direction. It is the figure which cut | disconnected the structure of FIG. 1 by the III-III line | wire, and looked at the arrow direction. It is a partial cross section perspective view of the ball screw mechanism of FIG. It is a figure which shows a part of manufacturing process of a ball screw mechanism. It is a figure which expands and shows the arrow VI part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw shaft 1a Male thread groove 1b Land part 2 Nut 2a Female thread groove 2b Top hole 2c Plane part 3 Ball 4 Circulating member 4a Main body 4b Top part 4c Circulation path 4d Caulking part

Claims (2)

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 an internal thread formed on an inner peripheral surface thereof;
A plurality of balls arranged to freely roll along a rolling path formed between opposing screw grooves;
A circulation member formed with a main body and a caulking portion,
The circulation member is attached to the attachment hole so as to sandwich the periphery of the attachment hole of the nut in the radial direction of the nut between the main body and the caulking portion ,
The ball screw mechanism , wherein the caulking portion formed by caulking the outer periphery of the main body is located on a radially outer side of the nut with respect to a screw shaft side end portion of the main body .   2. The method of assembling the ball screw mechanism according to claim 1, wherein a tool is positioned radially inward of the nut, and the tool pushes the vicinity of the outer periphery of the end of the circulation member inserted through the attachment hole. A method of assembling the ball screw mechanism, wherein the caulking portion is formed as described above.

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