JP2007024174A - Ball screw mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw mechanism reducible in cost and capable of positively fixing a piece to a nut. <P>SOLUTION: The piece 4 is formed from a thin metal plate by pressing. The cost can thereby be reduced. Further, since the piece 4 is positively fixed to the nut 2 with a screw 5, even if the piece 4 receives large force radially outward from rolling balls 3, the piece 4 is restrained from falling inadvertently. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ball screw mechanism that is assembled to a general industrial machine or used in an automobile.

  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, normally, the ball screw mechanism is composed of a screw shaft, a nut, and a ball that rolls in a rolling path formed between the two. In the so-called top-type ball screw mechanism, the ball screw mechanism starts from one end of the rolling path. In order to return the ball to the other end, a member called a top is attached to the nut. Generally, since the top is formed by cutting, sintering, forging, or the like, there is a problem that the cost is high. On the other hand, Patent Document 1 discloses a frame formed by pressing a thin metal plate.
JP 2004-251296 A

  Here, in the top described in Patent Document 1, the locking end portion of the locking portion bites into the V-shaped groove formed in the nut by a wedge action, so that the radial force of the nut is increased. To receive. However, there is a problem that it is difficult to process and form the V-shaped groove portion that receives the locking end portion of the frame on the side surface of the through hole of the nut. In addition, when assembling the frames, a dedicated jig is required, and there is a problem that the assembling cost increases.

  The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a ball screw mechanism that can suppress the cost and can securely fix the top to the nut.

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;
Having a piece inserted into the mounting hole of the nut,
The top is formed from a thin plate by pressing, and is attached to the nut by a screw.

  According to the ball screw mechanism of the present invention, since the piece is formed from a thin plate by pressing, the cost can be kept low, and the piece is attached to the nut by a screw. The top can be securely attached to the nut using a tool.

  It is preferable that the top has a flange portion extending along an outer peripheral surface of the nut, and the flange portion is attached to the nut using the screw.

  The screw is preferably attached to a step formed on 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 first embodiment, and 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. FIG. 4 is a top view of the frame, and FIG. 4 is a view of the frame of FIG. 3 as viewed in the direction of arrow IV.

  In FIG. 1, a male screw groove 1a is formed on the outer peripheral surface of a screw shaft 1 connected to a driven member and supported so as not to rotate but to move only 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 a female screw groove 2a formed on an inner peripheral surface thereof. 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.

  A frame hole (attachment hole) 2b penetrating in the radial direction is formed on the outer periphery of the nut 2, and the frame 4 is attached in a manner described later. A pair of screw holes 2c are formed on both sides (on both sides in the axial direction and on both sides in the circumferential direction) across the mounting hole 2b.

  The top 4 is formed by pressing a thin metal plate, and as shown in FIGS. 3 and 4, a semi-tubular body 4a, which is an S-shaped circulation groove on which the ball 3 rolls, The connecting portions 4b and 4b rise in parallel from both edges of the main body 4a, and the flange portions 4c and 4c extend sideways so as to be separated from the upper ends of the connecting portions 4b and 4b. The lengths of the connecting portions 4b and 4b are substantially equal to the thickness of the nut 2. A hole 4d is provided in the center of each flange portion 4c (FIG. 3).

  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 circulates from one end of the rolling path to the other end via the circulation path of the top 4. The rotating motion is efficiently converted into the axial motion of the screw shaft 1, and the driven member (not shown) connected thereto can be moved in the axial direction. The nut 2 may be moved in the axial direction by rotating the screw shaft 1.

  The assembly of the top 4 of the ball screw mechanism according to the present embodiment will be described. In FIG. 2, the main body 4 a of the top 4 having the shape shown in FIGS. 3 and 4 is inserted into the mounting hole 2 b of the nut 2 from the outer peripheral side of the nut 2, and the flange portions 4 c and 4 c are abutted against the outer peripheral surface of the nut 2. At this time, the connecting portions 4 b and 4 b extend along the side surface of the mounting hole 2 b, and the flange portions 4 c and 4 c extend along the outer peripheral surface of the nut 2. It is preferable that the flange portions 4 c and 4 c are curved according to the outer peripheral surface of the nut 2.

  Since the holes 4d are respectively aligned with the screw holes 2c of the nut 2 in a state where the flange portion 4c is in close contact with the outer peripheral surface of the nut 2, the screw 5 is inserted into the hole 4d from the radially outer side of the nut 2 and the screw hole 2c. The frame 4 can be attached to the nut 3 by being screwed onto the nut 3.

  According to the present embodiment, since the top 4 is formed by pressing from a thin metal plate, the cost can be kept low. Further, since the top 4 is securely fixed to the nut 2 by the screw 5, even if the top 4 receives a large force outward in the radial direction from the rolling ball 3, it is suppressed from being inadvertently dropped. The

  5 is a top view of the ball screw mechanism according to the second embodiment, and FIG. 6 is a view of the configuration of FIG. 6 cut along the arrow VI-VI line and viewed in the direction of the arrow. These are the figures which looked at the top from the same direction as FIG.

  The second embodiment differs from the above-described embodiment in the shapes of the nut 2 'and the piece 4'. More specifically, a step portion 2e is formed on the outer peripheral surface of the nut 2 'so as to extend on both sides with the attachment hole 2b interposed therebetween, and is lowered by one step from the outermost peripheral surface toward the radially inner side. A screw hole 2c is formed in the bottom surface of the stepped portion 2e. On the other hand, as shown in FIG. 7, in the frame 4 ', the lengths of the connecting portions 4b and 4b are shortened. The lengths of the connecting portions 4b and 4b are substantially equal to the thickness of the nut 2 obtained by subtracting the depth of the step portion 2e. The shapes of the flange portions 4c and 4c correspond to the shape of the step portion 2e. If the bottom surface of the step portion 2e is a flat surface, the flange portions 4c and 4c may be flat. Since other configurations are the same as those of the above-described embodiment, the same reference numerals are given and description thereof is omitted.

  In FIG. 6, the main body 4a of the top 4 'having the shape shown in FIG. 7 is inserted into the mounting hole 2b of the nut 2' from the outer peripheral side of the nut 2 ', and the flange portions 4c and 4c are inserted into the step 2e of the nut 2'. Hit the bottom. In this state, the holes 4d are respectively aligned with the screw holes 2c of the nut 2 '. From the outside of the nut 2' in the radial direction, the screws 5 are inserted into the holes 4d and screwed into the screw holes 2c. 'Can be attached to the nut 3.

  According to the present embodiment, it is possible to avoid the flange portions 4c and 4c of the top 4 'and the head portion of the screw 5 from projecting radially outward from the outer peripheral surface of the nut 2'. It can be set as a compact structure.

  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.

It is a top view of the ball screw mechanism which is 1st Embodiment. It is the figure which cut | disconnected the structure of FIG. 1 by the arrow II-II line | wire, and looked at the arrow direction. It is a top view of the top concerning this embodiment. It is the figure which looked at the top of Drawing 3 in the direction of arrow IV. It is a top view of the ball screw mechanism which is 2nd Embodiment. It is the figure which cut | disconnected the structure of FIG. 6 by the arrow VI-VI line and looked at the arrow direction. It is the figure which looked at the top from the same direction as FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw shaft 1a Male screw groove 2, 2 'Nut 2a Female screw groove 2b Mounting hole 2c Screw hole 2e Step part 3 Ball 4, 4' Frame 4a Main body 4b Connection part 4c Flange part 4d Hole

Claims (3)

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;
Having a piece inserted into the mounting hole of the nut,
The ball screw mechanism is characterized in that the top is formed from a thin plate by a press and is attached to the nut by a screw.   The ball screw mechanism according to claim 1, wherein the top has a flange portion extending along an outer peripheral surface of the nut, and the flange portion is attached to the nut using the screw. The ball screw mechanism according to claim 1, wherein the screw is attached to a step portion formed on the nut.

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