JP4671113B2 - Ball screw mechanism - Google Patents

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 them. 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 locked portion formed on the nut by a wedge action, thereby receiving a force in the deformation direction of the nut. It is like that. However, since such a prior art piece is formed by pressing a thin plate, the locking portion is also a thin plate shape that is easy to bend. For example, when receiving a large radial force from a rolling ball In addition, the frame is likely to be displaced, which may cause noise and vibration of the nut.

  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 by pressing from a thin plate, and an outward force support portion that supports a force toward the radially outer side of the nut, and an inward force support portion that supports a force toward the radially inner side of the nut. I have a,
The outward force support portion abuts against a radially inward surface of the nut in a groove formed in the nut mounting hole, and the inward force support portion is radially outward of the nut in the groove portion. It is characterized by abutting on the surface facing the surface .

  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 further, the piece supports an outer force that supports a force directed radially outward of the nut. Since it has a direction force support portion and an inward force support portion that supports a force directed radially inward of the nut, even when the top receives a large force in both radial directions, the nut is reliably Can be fixed.

  The outward force support portion abuts against a radially inward surface of the nut in the groove portion formed in the nut mounting hole, and the inward force support portion is radially outward of the nut in the groove portion. It is preferable that the top is in contact with the surface facing to the nut, since the top can be reliably fixed to the nut in the radial direction by the outward force support portion and the inward force support portion.

  It is preferable that at least one tip of the outward force support portion and the inward force support portion is bent because an elastic force is applied by the bending.

  In such a case, the top is preferably assembled from the outside of 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 top, FIG. 4 is a view of the top of FIG. 3 viewed in the direction of arrow IV, and FIG. 5 is a cross-sectional view of the nut showing a state where the top is assembled.

  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. The attachment hole 2b has a pair of step portions 2c that are narrowed by one step on the inner peripheral side thereof. 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 claw portion (inward force support portion) formed between the four claw portions (external force support portions) 4b extending oppositely on the plane from the edge of the main body 4a and the claw portion 4b on the same side. 4c. The claw part 4c intersects the claw part 4b at an angle of about 90 degrees.

  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 assembly of the top 4 of the ball screw mechanism according to the present embodiment will be described. In FIG. 5, 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 inner peripheral side of the nut 2, and the claw portion 4 b is abutted against the inner peripheral surface of the nut 2. In this state, the claw portion 4c is located in the vicinity of the step portion 2c of the attachment hole 2b. Here, as shown by an arrow C in FIG. 5, when the tip of the claw portion 4 c is crimped, the tip is bent and closely adheres to the surface of the stepped portion 2 c, so that a force directed radially inward can be supported. .

  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, the top 4 has a claw portion 4b that supports a force toward the radially outer side of the nut 2 and a claw portion 4c that supports a force toward the radially inner side of the nut 2, so that the top 4 is large in both radial directions. Even when a force is applied, the nut 2 can be securely fixed.

  By the way, in the above-mentioned embodiment, although the top 4 is assembled | attached from the inner peripheral side of the nut 2, in the case of an automatic assembly etc., there exists a case where it is desired to assemble | attach a top from the outer peripheral side of the nut 2, for example. . The following embodiment is effective in such a case.

  6 is a top view of the ball screw mechanism according to the second embodiment, and FIG. 7 is a view of the configuration of FIG. 6 taken along the line VII-VII and viewed in the direction of the arrow. FIG. 9 is a view of the frame viewed from the same direction as in FIG. 4, and FIG.

  The second embodiment differs from the above-described embodiment in the shapes of the nut 12 and the top 14. More specifically, a pair of groove-shaped step portions (groove portions) 12c are formed on both side walls in the axial direction of the attachment hole 12b in the nut 12. On the other hand, as shown in FIG. 8, the top 14 is formed between four L-shaped claw portions (inward force support portions) 14b extending upward from the lower edge of the main body 14a and the claw portions 14b on the same side. And a claw portion (external force support portion) 14c extending obliquely and straightly. Note that the maximum width of the paired claw portions 14b and claw portions 14c (left and right in FIG. 8) is larger than the width of the attachment hole 12b in the short direction. Other configurations are the same as those in the above-described embodiment, and thus description thereof is omitted.

  The assembly of the top 14 of the ball screw mechanism according to the present embodiment will be described. Referring to FIG. 7, the top 14 of the shape shown in FIG. 8 is elastically deformed so that the pair of claw portions 14 b and claw portions 14 c are close to each other in the mounting hole 12 b of the nut 12. When inserted from the outer peripheral side, the claw portion 14b first returns from the elastic deformation and falls into the stepped portion 12c. When the insertion is further continued, the claw portion 14c also returns from the elastic deformation and falls into the stepped portion 12c.

  According to the present embodiment, as shown in FIG. 9, the claw portion 14 c of the top 14 abuts on the outer peripheral side (that is, radially inward) surface 12 e of the step portion 12 c, thereby causing the nut 12 to move in the radial direction. The outward force can be supported, and the claw portion 14b abuts the inner peripheral side (ie, radially outward) surface 12d of the step portion 12c, thereby supporting the radially inward force of the nut 12. Accordingly, the top 14 can be securely fixed to the nut 12.

  FIG. 10 is a view of a frame according to a modification of the present embodiment as seen from the same direction as FIG. In this modification, the tip of the claw portion 14c 'of the frame 14 is bent with a curvature, thereby enhancing the engagement with the stepped portion 12c. Other configurations are the same as those of the above-described embodiment, and thus the same reference numerals are given and description thereof is omitted.

  FIG. 11 is a view of a frame according to a modification of the present embodiment viewed from the same direction as FIG. In the present modification, the tip of the claw portion 14c ″ of the frame 14 is bent at a right angle to form an L shape, thereby enhancing the engagement with the stepped portion 12c. Since it is the same as that of embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  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 sectional drawing of the nut which shows the state which assembles | attaches a top. 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 VII-VII line, and looked at the arrow direction. It is the figure which looked at the top from the same direction as FIG. It is a figure which expands and shows the arrow IX part of FIG. It is the figure which looked at the top concerning the modification of this Embodiment from the same direction as FIG. It is the figure which looked at the top concerning the modification of this Embodiment from the same direction as FIG.

Explanation of symbols

1 Screw shaft 1a Male thread groove 2, 12 Nut 2a, 12a Female thread groove 2b, 12b Mounting hole 2c, 12c Step 3 Ball 4, 14 Top 4a, 14a Body 4c, 14c, 14c ', 14c "Claw 4b, 14b Claw Part

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 top is formed by pressing from a thin plate, and an outward force support portion that supports a force toward the radially outer side of the nut, and an inward force support portion that supports a force toward the radially inner side of the nut. I have a,
The outward force support portion abuts against a radially inward surface of the nut in a groove formed in the nut mounting hole, and the inward force support portion is radially outward of the nut in the groove portion. A ball screw mechanism that abuts on a surface facing the surface . The ball screw mechanism according to claim 1 , wherein at least one end of the outward force support portion and the inward force support portion is bent. The piece is a ball screw mechanism according to claim 2 or 3, characterized in that it is assembled from the outside of the nut.

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