JP2012255524A - Ball screw device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device in which the centering of a screw shaft and a seal member and the phase adjustment of the seal member and the screw shaft can be easily performed regardless of the dimension of the seal member in an axial direction.SOLUTION: An end of a nut 3 of the ball screw device 100 and a fixing part 11 of the seal member 7 compose a spigot part 13. Long holes 12 for fixing are formed in the seal member 7. The long holes 12 penetrate in the axial direction of the screw shaft, have an arc-like shape formed along the rotation axis of the screw shaft as a center, and fix the seal member 7 to an end part of the nut 3 by means of a fixing screw 8 inserted through the long holes 12.

Description

  The present invention relates to a ball screw device used as a mechanical element for converting rotational motion into linear motion, for example, a steering device, a device for moving heavy objects, a processing device, a precision positioning device, and the like, and a method for manufacturing the ball screw device.

  2. Description of the Related Art Conventionally, there is a ball screw device provided with a seal member for protecting and sealing a lubricating oil supplied to the inside of a ball screw nut while protecting a screw groove portion where the ball rolls from entry of dust and the like. In such a ball screw device, in order to obtain good dust resistance and sealing performance, it is necessary to align the cores of the screw shaft and the seal member and adjust the phase of the seal member and the screw shaft. It is difficult to do at the same time, which takes a lot of work and time.

  Therefore, in the conventional ball screw, a radial fitting hole is provided in the seal ring, the seal ring is set at a desired position on the screw shaft, and has a protrusion that fits into a screw groove on the screw shaft. There is one in which a seal ring is fixed to a nut after the seal member is mounted in the fitting hole (see, for example, Patent Document 1).

Japanese Utility Model Publication No.59-19156

  However, since the sealing device described above needs to be provided with a fitting hole for mounting a sealing member having a protrusion, the seal ring must be considerably thick in the axial direction. The above-mentioned technical means cannot be applied when using a thin seal ring in the axial direction in order to reduce the size and weight of the nut. In the above sealing device, the seal ring is set at a predetermined position in accordance with the phase of the screw shaft, and then the nut is rotated to fit the seal ring and the nut. Deviation is considered to occur, and it takes time and effort to resolve this. In view of such a problem, the present invention easily adjusts the phase of the seal member and the screw shaft by aligning the cores of the screw shaft and the seal member regardless of the axial thickness of the seal member. It is an object of the present invention to provide a ball screw device that can perform the above-mentioned.

In order to solve the above problems, in the present invention, a screw shaft having a spiral ball rolling groove formed on the outer peripheral surface;
A nut provided on the outer periphery of the screw shaft and having a spiral ball rolling groove formed on the inner peripheral surface;
A substantially donut-shaped sealing member that seals a gap between the screw shaft and the nut;
In the ball screw device comprising the screw shaft and a plurality of balls provided between the ball rolling grooves of the nut,
The nut has a convex portion extending outward in the axial direction from an axial end so as to surround the screw shaft,
The seal member and the convex portion constitute an inlay portion composed of a cylindrical contact surface having a rotation axis of the screw shaft as a central axis.
The seal member has a long hole portion,
The ball screw device is characterized in that the seal member is fixed to the nut by a fixing member through the elongated hole portion.

  Preferably, the long hole portion penetrates in the screw shaft direction and has an arc shape centering on the rotation axis of the screw shaft.

  More preferably, the inlay portion includes a convex portion having a cylindrical inner peripheral surface having a rotation axis of the screw shaft as a central axis, and a cylindrical outer periphery having a rotation axis of the screw shaft as a central axis. And a sealing member having a surface.

  In order to solve the above problems, in the present invention, in the method of manufacturing a ball screw device according to any one of claims 1 to 3, after the fixing angle of the seal member is adjusted, the elongated hole portion is passed. There is provided a method of manufacturing a ball screw device, wherein the sealing portion is fixed to the nut by the fixing member.

  According to the present invention, a ball screw device that can easily adjust the phase of a seal member and a screw shaft by aligning the cores of the screw shaft and the seal member regardless of the axial thickness of the seal member. Can be provided.

It is a figure which shows the ball screw apparatus of embodiment of this application. An axial section of the nut and a side surface of the screw shaft are shown. It is a figure which shows the nut which has not attached the sealing member. (A) is a figure which shows the cross section of the axial direction of a nut in the assembly state of a nut and a screw shaft, and the side surface of a screw shaft. (B) is an elevation view showing a nut end face. It is an elevation view which shows a nut and a sealing member. (A) has shown the nut end surface of the state which fitted the seal member in the nut. (B) has shown the state which screw-fixed the sealing member to the nut. It is a figure which shows the ball screw apparatus which concerns on the modification of embodiment of this application. (A) has shown the cross section of the axial direction of a nut, and the side surface of a screw shaft. (B) is the elevation which looked at the state where the seal member was screwed to the nut from the axial direction.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In the ball screw device 100 according to the present embodiment, as shown in FIG. 1, a spiral ball rolling groove 2 is formed on the outer peripheral surface of the screw shaft 1 and provided on the outer periphery of the screw shaft 1. A spiral ball rolling groove 4 facing the ball rolling groove 2 is also formed on the inner peripheral surface of the nut 3.

  The cross-sectional shape of the ball rolling groove 2 of the screw shaft 1 may be one in which a relief groove is formed at the bottom of a generally used Gothic arc shape. However, in order to further improve the sealing performance, the relief groove as shown in FIG. It is preferable that the shape is abolished.

  A plurality of balls 5 are interposed between the ball rolling grooves 2 and 4, and the balls 5 roll between the ball rolling grooves 2 and 4 by the relative rotation of the screw shaft 1 and the nut 3. To do. When the rolled ball 5 reaches the end point of the ball rolling groove 4, it passes through the inside of a circulation member (not shown), returns to the starting point of the ball rolling groove 4, and again between the ball rolling grooves 2, 4. The cycle of rolling is repeated. As the circulation member, an end deflector type, a tube type, a top type, an end cap type, or the like can be used. A preload may be applied between the screw shaft 1, the nut 3, and the ball 5. By applying the preload, the axial clearance can be reduced to prevent backlash. As the preloading method, overball preloading, integral preloading, double nut preloading, or the like can be used.

  A lubricant supply mechanism (not shown) is provided inside the nut 3 in order to improve dust resistance and durability. As the lubricant supply mechanism, for example, a lubrication unit “NSK K1 (registered trademark)” in which resin is impregnated with oil or grease can be used.

  In the present embodiment, a cylindrical convex portion 6 having a rotation axis of the screw shaft 1 as a central axis is formed at the end of the nut 3 in the axial direction.

  In the present invention, the convex portion 6 does not necessarily have a cylindrical shape, and the inner peripheral surface of the convex portion 6 may have a cylindrical inner peripheral surface with the rotation axis of the screw shaft 1 as the central axis. It ’s fine. That is, the outer peripheral surface of the convex part 6 does not need to be a cylindrical surface, and can be variously modified as necessary. For example, the outer peripheral surface may be a quadrangular prism surface, and the size may be different at each position in the axial direction.

  In the present embodiment, the end surface of the nut 3 on the inner diameter side of the convex portion 6 is a surface perpendicular to the axial direction, and a screw hole 9 used for fixing the seal member 7 is formed. The end face of the nut 3 to which the seal member 7 is not attached is shown in FIG. Three screw holes 9 are formed at equal intervals in the circumferential direction.

  In the present invention, the fixing member that fixes the seal member 7 is not limited to a screw. Therefore, when a member other than a screw is used, an end face corresponding to the nut 3 can be provided. For example, in the case of fixing by a fixing pin described later, a hole for a fixing pin can be used instead of the screw hole 9. Moreover, although the number of screw holes 9 etc. is not restricted to three places, it is preferable that there are two or more. Although it is desirable that the circumferential intervals of the screw holes 9 and the like be equal, it is not limited to this.

  A seal member 7 is attached to the end surface of the nut 3 on the inner peripheral side of the convex portion 6. The seal member 7 is made of a donut-shaped elastomer, and integrally includes a lip portion 10 and a fixing portion 11. FIG. 3A shows a state in which the seal member 7 is fitted into the convex portion 6.

  In the present invention, the seal member 7 may be an elastic body other than an elastomer. Further, in order to maintain the shape of the seal member 7 and increase the strength, the fixing portion 11 may include a cored bar.

  The lip portion 10 of the seal member 7 has an in-groove sliding contact portion 10a and an outer peripheral sliding contact portion 10b formed continuously therewith. The in-groove sliding contact portion 10a is a portion that protrudes inward in the radial direction from the inner diameter portion of the fixed portion 11 over a predetermined angle range, and is in sliding contact with the ball rolling groove 2 of the screw shaft 1, and the outer peripheral sliding contact portion 10b is The portion that protrudes inward in the radial direction from the inner diameter portion of the fixing portion 11 over the remaining angle range and is in sliding contact with the outer peripheral surface of the screw shaft 1 where the ball rolling groove 2 is not formed. In the present embodiment, the sliding contact portion of the in-groove sliding contact portion 10a with the screw shaft 1 is linear in a plan view, and the sliding contact portion of the outer peripheral sliding contact portion 10b with the screw shaft 1 is a circle in the plan view. It has an arc shape. As a result, the inner periphery of the lip portion 10 is formed without causing a large deformation at a certain angle in the circumferential direction when the seal member 7 is attached to the nut 3 together with the core of the screw shaft 1. It touches around the cross section of no gap. Accordingly, the lip portion 10 can be slidably contacted with the entire circumference of the cross section of the screw shaft 1 with a uniform force, and sufficient sealing performance can be obtained without generating excessive torque.

  In the present invention, the planar shape of the lip portion 10 is not limited to that shown in FIG. 3, and various changes can be made according to the cross section of the screw shaft 1. For example, the number of in-groove sliding contact portions 10a varies depending on how many ball rolling grooves 2 appear in the cross section perpendicular to the axial direction of the screw shaft 1. That is, in the lip portion 10 of the present embodiment, the in-groove sliding contact portion 10a is provided at one location. However, when the lead of the screw shaft 1 is made shorter or a multi-thread screw is used, two or more locations are provided. It may become. Further, depending on the cross-sectional shape of the ball rolling groove 2, the sliding contact portion with the thread groove of the in-groove sliding contact portion 10a may not be linear in a plan view, and may be, for example, an elliptical arc shape.

  In the present embodiment, the in-groove sliding contact portion 10a extends from the fixed portion 11 in an inclined direction outward in the axial direction of the nut 3, and comes into contact with the ball rolling groove 2 as shown in FIG. Yes. By setting it as such a structure, the penetration | invasion of the dust from the outside can be prevented more effectively.

  In the present invention, the angle at which the in-groove slidable contact portion 10a extends is not limited to this, and conversely, the in-groove slidable contact portion 10a is moved from the fixed portion 11 toward the inside of the nut 3 in the axial direction. It may be inclined to contact the ball rolling groove 2. In this case, it is possible to more effectively prevent leakage of the lubricating oil / fat supplied to the inside of the nut 3. Further, the in-groove sliding contact portion 10a may be perpendicular to the axial direction.

  The outer peripheral surface of the fixing portion 11 is a cylindrical surface having a slightly smaller diameter than the inner peripheral surface of the convex portion 6, and the surface on the nut 3 side in the axial direction of the fixing portion 11 is a surface perpendicular to the axial direction. Yes. Thereby, the inlay part 13 is comprised by the convex part 6 and the sealing member 7. FIG. With such a configuration, when the ball screw device 100 is assembled, it is not necessary to perform the centering operation of the screw shaft 1 and the seal member 7. In addition, entry of foreign matter from the contact surface between the nut 3 and the seal member 7 can be effectively prevented.

  Note that, as in the modification shown in FIG. 4A, the inlay portion 13 formed by the convex portion 6 and the seal member 7 can be configured such that the convex portion 6 is fitted inside the seal member 7. is there. That is, the cylindrical part 11a which protruded to the nut 3 side by the axial direction can be provided in the fixing | fixed part 11 of the sealing member 7 so that the outer peripheral surface of the convex part 6 may be made into a cylindrical surface shape and the sealing member 7 fits externally. . In this case, as in the modification shown in FIG. 4A, the outer peripheral surface of the convex portion 6 is formed into a cylindrical surface shape having a diameter smaller than the outer diameter of the other portion of the nut 3, so that the cylinder of the seal member 7 is formed. The end of the portion 11a on the nut 3 side can be brought into contact with the end of the nut 3, and the sealing performance of the contact surface between the nut 3 and the seal member 7 can be enhanced.

  Further, in the present embodiment shown in FIG. 1, the edge on the inner diameter side of the convex portion 6 can be an inclined surface or a curved surface, so that it is possible to prevent catching when the seal member 7 is fitted. Similarly, in the embodiment of FIG. 4, the edge on the inner diameter side of the cylindrical portion 11 a protruding to the nut 3 side can be an inclined surface or a curved surface.

  In the present embodiment shown in FIG. 1, three long hole portions 12 are formed at equal intervals in the circumferential direction in the fixing portion 11 of the seal member 7. The long hole portion 12 has an arc shape with the rotation axis of the screw shaft 1 as a central axis, and penetrates in the axial direction. As shown in FIG. 3B, the seal member 7 is fixed to the nut 3 by screwing the fixing screw 8 into the screw hole 9 through the long hole portion 12.

  In the present invention, the number of the long hole portions 12 is not limited to three and may be different from the number of the screw holes 9. The long hole portions 12 are preferably formed at equal intervals in the circumferential direction, but are not limited thereto. The long hole portion 12 preferably has an arc shape with the rotation axis of the screw shaft 1 as the central axis, but the fixing screw 8 can be passed through the screw hole 9 after adjusting the fixing angle of the seal member 7. If it is a shape, it will not be restricted to this, For example, a linear play hole may be sufficient. Further, as described above, the fixing member for fixing the seal member 7 to the nut 3 is not limited to the screw, and may be a fixing pin or other fixing member.

  When the convex portion 6 is fitted into the seal member 7 as in the modification shown in FIG. 4 described above, the screw hole 9 and the fixing pin hole are formed in the convex portion 6. For example, as shown in FIG. 4A, the fixing screw 8 or the like passes through the long hole portion 12 formed in the fixing portion 11 of the seal member 7 and from the axial end portion of the convex portion 6 to the nut 3 side in the axial direction. It can be configured to be inserted toward. Further, the fixing screw 8 or the like is inserted from the outer diameter side of the convex portion 6 toward the inner diameter side through the long hole portion 12 formed so as to penetrate the cylindrical portion 11a of the seal member 7 in the radial direction. May be. Therefore, in the above-described modification, the screw holes 9 and the like are provided at positions corresponding to these fixing methods.

  Since the cross-sectional shape and phase of the ball rolling grooves 2 and 4 differ depending on the type of the ball screw device 100, the fixing angle in the circumferential direction of the seal member 7 varies depending on the type, but the cross-sectional shape and From a design condition such as a phase, it is possible to calculate a theoretical fixed angle (an angle in the rotation direction) at which the lip portion 10 of the seal member 7 is in sliding contact with the screw shaft 1 without a gap over the entire circumference. However, since there is an error in manufacturing the screw shaft 1 and the nut 3, it is necessary to adjust the angle when each ball screw device 100 is assembled in order to fix the seal member 7 at an appropriate fixing angle.

  Therefore, in the present invention, first, when the seal member 7 is manufactured, the long hole portion 12 is formed so that the central portion of the long hole portion 12 is disposed at a position corresponding to a theoretical fixed angle calculated in advance. Then, when the seal member 7 is attached to the nut 3, the fixing screw 8 is screwed into the screw hole 9 through the long hole portion 12 after adjusting to an appropriate fixing angle while looking at the gap with the screw shaft 1. Thereby, it is possible to adjust and fix the fixing angle of the seal member 7 very easily. Moreover, since it is not necessary to provide a fitting hole like patent document 1, this invention can be used irrespective of the thickness of an axial direction.

  The angle can be adjusted by the length of the long hole portion 12 in the circumferential direction. Therefore, when the seal member 7 is used for a specific ball screw, the circumferential length of the long hole portion 12 may be ensured according to an error in manufacturing the screw shaft 1 and the nut 3. . That is, if the error in manufacturing or the like is small, the error is short and if the error is large, the error is long.

  In addition, since the adjustable range is expanded by increasing the circumferential length of the long hole portion 12, the seal member 7 having a specific shape can be used for a plurality of ball screws. Moreover, since the arrangement of the fixing member can be changed by arranging many screw holes 9 of the nut 3, it is possible to use the sealing member 7 having a different shape in a specific shape of the ball screw.

  As described above, according to the present invention, it is possible to easily adjust the phases of the seal member and the screw shaft by aligning the cores of the screw shaft and the seal member regardless of the axial dimension of the seal member. A ball screw device can be provided.

1 Screw shaft 2 Ball rolling groove (screw shaft side)
3 Nut 4 Ball rolling groove (Nut side)
5 Ball 6 Protruding part 7 Seal member 8 Fixing screw 9 Screw hole 10 Lip part 10a Sliding contact part in groove 10b Outer sliding part 11 Fixing part 11a Cylindrical part 12 Long hole part 13 Inlay part 100 Ball screw device

Claims (4)

A screw shaft having a spiral ball rolling groove formed on the outer peripheral surface;
A nut provided on the outer periphery of the screw shaft and having a spiral ball rolling groove formed on the inner peripheral surface;
A substantially donut-shaped sealing member that seals a gap between the screw shaft and the nut;
In the ball screw device comprising the screw shaft and a plurality of balls provided between the ball rolling grooves of the nut,
The nut has a convex portion extending outward in the axial direction from an axial end so as to surround the screw shaft,
The seal member and the convex portion constitute an inlay portion composed of a cylindrical contact surface having a rotation axis of the screw shaft as a central axis.
The seal member has a long hole portion,
The ball screw device, wherein the seal member is fixed to the nut by a fixing member through the elongated hole portion.   2. The ball screw device according to claim 1, wherein the elongated hole portion penetrates in the screw shaft direction and has an arc shape centering on a rotation axis of the screw shaft.   The inlay portion includes the convex portion having a cylindrical inner peripheral surface with a rotation axis of the screw shaft as a central axis, and the cylindrical outer peripheral surface with a rotation axis of the screw shaft as a central axis. The ball screw device according to claim 1, wherein the ball screw device is constituted by a seal member. In the manufacturing method of the ball screw device according to any one of claims 1 to 3,
A method of manufacturing a ball screw device, comprising: adjusting a fixing angle of the seal member; and fixing the seal portion to the nut by the fixing member through the elongated hole portion.

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