JP2005233331A - Ball screw for actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw for an actuator, fitting a screw shaft in a simple fitting structure in a compact space even when the position of a rotating shaft of a driven member is fixed. <P>SOLUTION: A nut 2 engaged with a screw shaft 1 of the ball screw to make linear motion is provided with a pair of connecting parts 3 having a U-shaped groove 3a opened to the outside diameter side and opposite to the screw shaft 1 at right angles. A connecting pin 4 to which a link 5 as a driven member is connected is stretched over the U-shaped groove 3a, and both end parts provided with parallel slide surface 4a formed by double corner rounding are slidably fitted in each U-shaped groove 3a, whereby even if the rotating shaft of the driven member is fixed, the ball screw for an actuator can be fitted in a simple fitting structure in a compact space without rocking the screw shaft 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ball screw for an actuator that rotates a driven member by connecting a driven member to a nut that is screwed into a screw shaft of a rotationally driven ball screw and linearly moves.

  A ball screw for an actuator used in an electric actuator of an automobile device or the like includes a coupling portion that couples a driven member with a coupling pin to a nut screwed through a plurality of balls to a screw shaft that is driven to rotate by a motor or the like. And the driven member connected to the connecting pin is rotated by the linear motion of the nut (see, for example, Patent Documents 1, 2, and 3). In Patent Documents 1 and 2, a connecting pin for connecting a driven member is fitted in a pin hole provided in a nut. Moreover, what was described in patent document 3 fits the connection pin in the groove bottom provided in the nut, and is preventing slippage with the retaining ring.

Japanese Patent Laid-Open No. 2002-155716 (page 5, FIG. 1-2) Japanese Unexamined Patent Publication No. 2003-150075 (page 3-5, FIG. 1-2) JP 2002-332498 A (page 3-6, Fig. 1-4)

  In each of the conventional actuator ball screws described above, the connecting pin for connecting the driven member is fixed to the pin hole or the groove bottom of the nut. For example, the actuator ball screw described in Patent Document 1 is employed. As in a variable valve device for an internal combustion engine, the position of the pivot shaft on the arm base end side which is a driven member coupled to the coupling pin is fixed between the pivot shaft and the screw shaft of the ball screw. Since the vertical distance changes with the rotation of the arm, the screw shaft needs to be swingable. For this reason, the mounting structure of the screw shaft of the ball screw that is rotationally driven becomes complicated, and there is a problem that a large space is required for swinging the screw shaft.

  Accordingly, an object of the present invention is to provide a ball screw for an actuator that can mount a screw shaft in a compact space with a simple mounting structure even if the position of the rotation shaft of the driven member is fixed. It is.

  In order to solve the above-described problems, the present invention provides a connecting portion for connecting a driven member with a connecting pin to a nut that is linearly moved by being screwed to a screw shaft of a rotationally driven ball screw. In a ball screw for an actuator that rotates a driven member to be connected by linear movement of the nut, a pair of U-shaped grooves that open to the outer diameter side of the connecting portion of the nut are opposed to the screw shaft in a direction perpendicular to the screw shaft. The connecting pin was passed through the opposing U-shaped grooves and both ends thereof were slidably fitted into the U-shaped grooves.

  That is, the connecting portion of the nut is provided with a pair of U-shaped grooves that open to the outer diameter side so as to be opposed to the screw shaft in a direction perpendicular to the screw shaft, and the connecting pins are passed to the opposing U-shaped grooves, Is slidably fitted in each U-shaped groove, so that the position of the rotation shaft of the driven member is fixed, and the vertical distance between the rotation shaft and the screw shaft of the ball screw changes with the rotation. Even so, the change in the vertical distance is absorbed by the slide displacement within the U-shaped groove of the connecting pin, so that it can be mounted in a compact space with a simple mounting structure without swinging the screw shaft. .

  By providing slide surfaces formed in parallel planes at both ends of the connecting pin and sliding the inner surfaces of the U-shaped grooves with the slide surface, both ends of the connecting pin are brought into surface contact with the U-shaped grooves. The contact pressure during sliding can be lowered to prevent creep deformation and wear. If play occurs in the connecting part due to creep deformation or wear, not only the smooth movement of the driven member connected to the connecting pin is disturbed, but also the noise increases, especially those used for electric actuators for automobiles It becomes a big problem.

  By forming the central part between the slide surfaces at both ends of the connecting pin to have a diameter larger than the width of each U-shaped groove, the connecting pin can be removed from the connecting part in the axial direction without using a retaining ring or the like. Can be stopped and the number of parts can be reduced.

  The driven member connected to the connecting pin may be a link member that rotationally drives the automobile device.

  The ball screw for an actuator according to the present invention has a connecting portion of a nut for connecting a driven member that rotates with a pair of U-shaped grooves that open to the outer diameter side facing the screw shaft in a direction perpendicular to the screw shaft. Since the pins are passed through the opposing U-shaped grooves and both ends thereof are slidably fitted into the respective U-shaped grooves, the position of the rotation shaft of the driven member is fixed, and the rotation is accompanied by the rotation. Even if the vertical distance between the dynamic axis and the screw axis of the ball screw changes, the change in the vertical distance is absorbed by the slide displacement in the U-shaped groove of the connecting pin, and the screw axis is not swung. Can be installed in a compact space with a simple mounting structure.

  By providing slide surfaces formed in parallel planes at both ends of the connecting pin, and sliding the inner surface of each U-shaped groove with this slide surface, both ends of the connecting pin are brought into surface contact with each U-shaped groove, The contact pressure at the time of sliding can be lowered to prevent creep deformation and wear, and the backlash can be prevented from occurring at the connecting portion, so that the smooth movement of the driven member can be ensured and the generation of noise can be prevented.

  By forming the central part between the slide surfaces at both ends of the connecting pin larger in diameter than the width of each U-shaped groove, the connecting pin is prevented from coming off the connecting part in the axial direction without using a retaining ring or the like. The number of parts can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This actuator ball screw is used in a variable valve mechanism of an automobile engine, and is screwed onto a screw shaft 1 via a plurality of balls (not shown) as shown in FIGS. 1 (a) and 1 (b). The nut 2 is provided with a pair of connecting portions 3 that are opposed to the screw shaft 1 in a direction perpendicular to each other, and each connecting portion 3 is formed with a U-shaped groove 3a that opens to the outer diameter side. The connecting pin 4 is passed through the groove 3a, and parallel slide surfaces 4a formed by double-sided are formed at both ends of the groove 3a so as to contact the inner surface of each U-shaped groove 3a and slidably fit. A link 5 as a driven member of the pin 4 is connected. Although illustration is omitted, the screw shaft 1 is rotationally driven by a motor, and the nut 2 linearly moves left and right on the screw shaft 1 along with the rotational drive.

  The connecting pin 4 fitted in each U-shaped groove 3a has a central portion 4b between the slide surfaces 4a at both ends formed in a circular cross section having a larger diameter than the width of each U-shaped groove 3a. It has been prevented from coming off. The link 5 has a distal end side rotatably connected to the central portion 4b of the connecting pin 4 and a proximal end side attached to a rotating shaft 6 whose position is fixed.

  As shown by a two-dot chain line in FIG. 2, when the nut 2 linearly moves left and right by the rotational drive of the screw shaft 1, the connecting pin 4 connecting the link 5 slides up and down in each U-shaped groove 3 a of the connecting portion 3. Then, the link 5 is rotated together with the rotation shaft 6. A cam for operating the piston of the variable valve mechanism is attached to the rotating shaft 6.

  In the embodiment described above, the link is connected as the driven member of the connecting pin, but a cam, an arm member, or the like can also be connected.

a is a partially omitted front view showing an embodiment of a ball screw for an actuator, and b is a cross-sectional view taken along line Ib-Ib of a. The front view explaining the movement of the connecting pin when rotating the link of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Nut 3 Connection part 3a U-shaped groove 4 Connection pin 4a Slide surface 4b Center part 5 Link 6 Rotating shaft

Claims (4)

  A nut that is linearly moved by being screwed to a screw shaft of a ball screw that is driven to rotate is provided with a connecting portion that connects a driven member with a connecting pin, and the driven member connected to the connecting pin is moved by a linear motion of the nut. In the ball screw for the actuator to be rotated, the connecting portion of the nut is provided with a pair of U-shaped grooves that open to the outer diameter side facing the screw shaft in a direction perpendicular to the screw shaft, and the connecting pin faces this. A ball screw for an actuator, wherein the ball screw for actuator is inserted into a U-shaped groove, and both ends thereof are slidably fitted into the U-shaped grooves.   2. The ball screw for an actuator according to claim 1, wherein a slide surface formed in a parallel plane is provided at both ends of the connecting pin, and the slide surface is slid with an inner surface of each of the U-shaped grooves.   The ball screw for an actuator according to claim 2, wherein a central portion between the slide surfaces at both ends of the connection pin is formed to have a larger diameter than the width of each U-shaped groove.   The ball screw for an actuator according to any one of claims 1 to 3, wherein the driven member connected to the connection pin is a link member that transmits a rotational motion to an automobile device.

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