JP2006088793A - Ball screw device of steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device provided with a damper for supporting a ball screw to improve vehicle performance by eliminating noise and vibration generated at the time of an operation of the ball screw device. <P>SOLUTION: This device has a structure in which the damper is installed to eliminate vibration and noise generated due to rolling motions of a plurality of balls between a ball nut and the ball screw at the time of the operation of the ball screw device, and the damper is installed to perform damping by supporting the ball screw on the ball nut to reduce noise and vibration between inner peripheral surfaces of the ball nut screw-connected to the ball screw by interposing an outer peripheral surface of the ball screw and the plurality of balls. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ball screw device of a steering system in which a damper is installed in a ball nut in order to reduce vibration and noise generated by a plurality of balls for mediating the ball nut and the ball screw during operation of the ball screw device, In the following, a conventional ball screw device in an electric power steering system will be closely observed.

  The electric power steering system is provided with a return structure in the ball nut that allows the ball that rolls to circulate. However, a deflector type in which a return piece is formed inside the ball nut (Defector Type, internal circulation) Type) and return tube type (return tube type, external circulation type) in which a return tube is formed outside the ball nut, and end gap type (end cap type) in which circulation is performed through an end gap installed at one end. Can be done.

  The ball screw device of FIG. 1 is a cross-sectional view showing a conventional deflector type ball screw device having a return piece for circulating an internal ball 10. As shown in the figure, a spiral outer peripheral groove 12 is formed on the outer peripheral surface of a long ball screw.

  A ball nut 13 having a spiral inner circumferential groove 14 is provided outside the ball screw 11 so as to be prepared as a hollow cylindrical tube and to face the outer circumferential groove 12 of the ball screw on the inner circumferential surface. A plurality of balls 10 made of steel are inserted between the outer circumferential groove 12 and the inner circumferential groove 14 having a semicircular cross section arranged so as to face each other in this way, A return piece 18 is formed on one inner side of 13 so that the ball 10 circulates.

  Thus, in the ball screw device, when an external rotational force is transmitted to the ball nut 13 and the ball nut 13 is rotated, the ball 10 inside the ball nut rolls along the outer peripheral groove 12 and the inner peripheral groove 14 to have a ball screw. The shaft 1 is pushed in the axial direction and circulates again through the return piece 18.

  However, such a conventional ball screw device does not have a device for reducing vibration and noise generated by rolling motion of a plurality of balls 10 for mediating the ball nut 13 and the ball screw 11 of the shaft. This is transmitted to the driver as it is, so that the vehicle performance is deteriorated and there is a problem that durability is lowered by such vibration.

  In order to solve such a conventional problem, the present invention provides a damper that supports a ball screw so that vehicle performance can be improved by reducing noise and vibration generated during operation of the ball screw device. An object is to provide a ball screw device provided.

  In order to achieve such an object, the present invention includes a ball screw that can move in the axial direction and has an outer peripheral surface formed with a spiral outer peripheral groove, and an inner peripheral groove that faces the outer peripheral groove of the ball screw. A ball nut, a plurality of balls inserted between the outer peripheral groove and the inner peripheral groove so that the ball screw and the ball nut can be screwed together, an inner peripheral surface of the ball nut, and an outer peripheral surface of the ball screw There is provided a ball screw device of a steering system having a damper that can reduce noise and vibration in the meantime, and thus, the damper according to the present invention is installed on a ball nut to form a ball screw trough. It has a structure that supports the part or the mountain part.

  As described in detail above, the ball screw device in the steering system according to the present invention includes a damper made of a synthetic resin material that supports the valley or peak of the ball screw at both side ends or one side end of the ball nut. Install and reduce the vibration and noise generated during the rolling motion of the ball to improve the reliability of the product.

  Further, such a vibration reducing effect has an advantage of increasing durability as compared with a ball screw device in which no damper is installed.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same reference numerals as those of the above-mentioned drawings indicate the same members.

  FIG. 2 is a cross-sectional view showing a coaxial type rack drive electric power steering system (R-EPS) that can be applied so that the ball screw device according to the present invention is useful. FIG.

  As shown in FIG. 2, the rack-driven electric power steering apparatus includes a shaft 1 that can be reciprocated linearly in an outer casing, a pinion that is installed in the lower stage of the handle shaft 5 behind the shaft, and a pinion A rack (Rack: not shown) that meshes and allows the shaft 1 to move in the axial direction is provided, and the rotation of the steering wheel can be converted into the axial linear motion of the shaft 1 by this rack and pinion gear 2. The shaft 1 also has a ball screw 11 on its outer peripheral surface on the side far from the rack.

  In addition, the rack is received in a hollow rack housing 3 formed long on the left and right sides of the shaft 1, and a motor for doubling the steering force is installed so that the rack can be operated more smoothly. However, at this time, the motor housing 4 that forms the outer shape of the motor is connected to the rack housing 3.

  A stator 7 is fixed and installed in close contact with the inner surface of the motor housing 4, and a rotor 8 arranged rotatably is installed inside the stator 7. The motor shaft 9 is installed through

  On the other hand, a ball screw device is installed inside the motor shaft 9, and this ball screw device is a ball nut 23 installed inside one end of the motor shaft 9, and a ball that is inserted into the nut and moves in the axial direction. A screw 11 and a ball 10 inserted between a ball nut and a ball screw are provided.

  Therefore, by providing the ball screw device according to the present invention to such a rack drive type electric power steering system, the ball screw generated while the shaft moves in the axial direction according to the manual steering force applied from the steering wheel. The vibration and noise from the device are transmitted to the outside of the ball screw device, and the problem of reducing the steering feeling can be solved.

  The damper according to the present invention can be applied not only to the coaxial R-EPS but also to a non-coaxial R-EPS in which the shaft of the motor is smoothly coupled to the shaft 1 shaft.

  In the following, the configuration of the ball screw device according to the present invention will be seen in more detail through preferred embodiments.

  FIG. 3 is a detailed view of the ball screw device of FIG. 2, and shows a ball screw device having a damper 20 installed so as to support the valley 16 of the ball screw at both ends of the ball nut 23. It is sectional drawing shown. As shown in FIGS. 2 and 3, the ball screw 11 is prepared integrally with the shaft on one side of the shaft 1 far from the rack, and a helical outer peripheral groove 12 is formed on the outer peripheral surface thereof. Have.

  The ball nut 23 installed outside the ball screw 11 is prepared in a hollow shape and is rotatably installed to assist the axial movement of the shaft 1, and has an inner peripheral surface on the outer periphery of the ball screw. The outer circumferential groove 12 and the inner circumference of the semicircular cross section having the inner circumferential groove 14 extending spirally so as to correspond to the groove 12 and arranged so as to face each other in this manner A plurality of balls 10 made of steel are inserted between the grooves 14.

  In such a ball screw device, when an external rotational force is transmitted to the ball nut 23 and the ball nut 23 is rotated, the internal ball 10 rolls to move the shaft 1 in the axial direction.

  At this time, a damper 20 using a fluoropolymer (PTFE) is installed on the ball nut 23 to support the ball screw 11 in the direction perpendicular to the axis of the shaft 1, and is generated by the rotation of the ball 10. To reduce the roar and vibration.

  In other words, by installing dampers 20 having a beak shape on both ends of the ball nut 23, it is possible to support the valley 16 that is a bent portion corresponding to the center of the outer peripheral groove 12 of the ball screw. The noise generated during the rolling motion of the ball 10 and the vibration in the axial direction of the shaft or in the vertical direction of the shaft are reduced.

  Further, the damper according to the present invention has a structure installed on the ball nut 23, and in order to perform the damping while supporting the trough portion 16 of the ball screw, the protruding portion 22 corresponding to the upper end portion of the uneven damper 20 is provided. It is desirable that the tip is round-processed.

  As shown in FIG. 4, the damper 30 according to the present invention can be configured to support the valley 16 of the ball screw by being installed at one end of the ball nut 33, and its operation is the case according to FIG. 3. Is the same.

  FIG. 5 shows another embodiment according to the present invention, in which the damper 40 is supported so as to support the ball screw crest 15 which is a portion corresponding to the screw crest at both side ends of the ball nut 43. By installing, it is possible to reduce the noise generated during the rolling motion of the ball 10 and the vibration in the vertical direction of one shaft. Also in this case, although the damper is not shown in the drawing, it can be installed on one end side of the ball nut 43 so as to support and dump the mountain portion 15 of the ball screw.

  However, the protruding portion 42 of the damper that supports the peak portion 11 of the ball screw can be rounded at the tip as in the case of supporting the valley portion 16, but it can be processed into a flat surface. desirable.

  In the following, the structure of a ball nut on which a damper according to the present invention is installed will be closely observed.

  FIG. 6 is a cross-sectional view showing the inside of a ball nut by cutting a part of the ball nut provided with a damper for supporting the valley portion 16 of the ball screw according to the present invention. As shown in the figure, a groove in which a damper can be installed is formed at the end of the inner circumferential groove 14 of the ball nut in which the damper 20 that supports the valley 16 of the ball screw is installed. Unlike the round semicircular inner circumferential groove 14, the groove formed to be extended is prepared as a square with a square or the like so that the damper 20 cannot be separated from the ball nut 23.

  That is, the connecting portion 21 of the damper corresponding to the lower step portion of the concave and convex portions is seated in a groove extending from the inner peripheral groove 14 of the ball nut and does not come off from the ball nut 23 and corresponds to the upper end portion of the concave and convex shape. The protruding portion 22 that supports the valley portion 16 of the ball screw reduces vibrations generated from the ball screw device.

  FIG. 7 is a cross-sectional view showing the inside of a ball nut by cutting a part of a ball nut 43 provided with a damper 40 that supports the mountain portion 15 of the ball screw according to the present invention. Unlike the portion illustrated in FIG. 6 which is an internal cross-sectional view of the ball nut 23 that supports the valley portion 16, a damper 40 that supports the mountain portion of the ball screw is provided at the end portion of the inner circumferential groove 14 of the ball nut. A groove with a corner such as a square for installation is provided between the inner circumferential groove 14 and the inner circumferential groove 14 of the ball nut 43.

  FIG. 8 is a perspective view of the dampers 20 and 30 that support the valleys of the ball screw. The damper in the form of a beak is formed from one end of the ball nut to have a circumference of one pitch (Pitch). Installed. At this time, both ends of the damper are shifted from each other by a distance of one pitch corresponding to the structure of the ball nut on which the damper is installed.

  The present invention relates to a ball screw device of a steering system, and by installing a damper made of a synthetic resin material to support a valley portion or a mountain portion of a ball screw at both side ends or one side end of a ball nut, Vibration and noise generated during exercise can be reduced. Therefore, the present invention can be used for a vehicle steering apparatus.

Sectional drawing which showed the conventional ball screw apparatus of the deflector system provided with the return piece. Sectional drawing which showed the general rack drive type electric power steering system. Sectional drawing which showed the ball screw apparatus provided with the damper installed so that the trough part of a ball screw might be supported by the both ends of a ball nut. Sectional drawing which showed the ball screw apparatus provided with the damper installed so that the trough part of a ball screw might be supported by the one side end of a ball nut by this invention. Sectional drawing which showed the ball screw apparatus provided with the damper installed so that the peak part of a ball screw might be supported by the both ends of a ball nut by this invention. Sectional drawing which cut | disconnected some ball nuts in which the damper which supports the trough part of a ball screw by this invention was installed, and showed the inside of a ball nut. Sectional drawing which cut | disconnected some ball nuts in which the damper which supports the peak part of a ball screw by this invention was installed, and showed the inside of a ball nut. The perspective view of the damper which separated and showed the damper installed in the ball nut by this invention from the ball nut.

Explanation of symbols

1: Shaft 2: Rack & pinion gear 3: Rack housing 4: Motor housing 6: Tie rod 7: Stator 8: Rotor 9: Motor shaft 10: Ball 11: Ball screw 12: Peripheral groove 13, 23, 33, 43: Ball nut 14: Inner peripheral groove 15: Mountain portion 16: Valley portion 20, 30, 40: Damper 21, 31, 41: Coupling portion 22, 32, 42: Protruding portion

Claims (7)

In the ball screw device,
A ball screw that can move in the axial direction and has an outer peripheral surface formed with a spiral outer peripheral groove, a ball nut that has an inner peripheral groove facing the outer peripheral groove of the ball screw, and the ball screw and the ball nut are screwed Noise and vibration can be reduced between a plurality of balls inserted between the outer peripheral groove and the inner peripheral groove so as to be coupled, and between the inner peripheral surface of the ball nut and the outer peripheral surface of the ball screw. A ball screw device for a steering system, characterized by comprising a damper.   The ball screw device for a steering system according to claim 1, wherein the damper supports the ball screw at one end side of the ball nut.   The ball screw device for a steering system according to claim 1, wherein the damper supports the ball screw at both ends of the ball nut.   The ball screw device of the steering system according to claim 1, wherein the damper supports a valley portion of the ball screw.   The ball screw device for a steering system according to claim 1, wherein the damper supports a mountain portion of the ball screw.   The ball screw device for a steering system according to claim 1, wherein the damper is made of a synthetic resin material.   7. The ball nut according to claim 1, wherein the ball nut has a groove with a corner formed on a predetermined portion of an inner peripheral surface thereof so that the damper is not detached when the damper is installed. 8. Ball screw device for steering system.

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