JP2011133049A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device which can prevent an inner pressure within a nut from becoming large when a lubricant is applied within the nut, and prevent a foreign substance from being mixed from outside the nut. <P>SOLUTION: The outer diameter of a labyrinth seal 25 is made to be smaller a little than an inner diameter of recessed section 26 of the nut 112, and a radial clearance 34 is formed in the periphery of the seal 25 and inner circumferential section of the recessed section 26. This radial clearance 34 is sized from 0.125 to 0.5 mm. When the lubricant is filled in the nut 112 and fully filled in the nut 112, the lubricant passes through the radial clearance 34 and an axial clearance 35, and the excessive lubricant is ejected out of the nut 112. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a seal structure for a ball screw device.

  Most conventional ball screw devices are provided with a seal so that foreign matter does not enter the nut from the outside. Among the seals, there is a non-contact (slight gap) seal (hereinafter referred to as a labyrinth seal) on the screw shaft.

  However, in the labyrinth seal, while the lubricant is not in contact with the screw shaft, when the lubricant is supplied into the nut, the seal and the screw groove of the screw shaft come into contact with each other due to the movement of the seal, and the internal pressure of the nut increases.

  When the internal pressure rises, circulating parts and seals and other attached parts that are connected to the space between the nut and the screw shaft (the space to which the lubricant is supplied) (affected by the pressure) are removed, deformed, or damaged. If you want to. In particular, there is a problem that the circulation piece is lifted for a ball screw of a type in which a resin circulation piece is fitted to a nut as a circulation part with a small ball screw.

  As a prior art for preventing an increase in the internal pressure of a nut, there is a ball screw device shown in FIG. 10 (Patent Document 1: Japanese Patent Laid-Open No. 2003-343686).

  As shown in FIG. 10, the ball screw device 10 includes a screw shaft 11, a nut 12 that is screwed onto the outer periphery of the screw shaft 11, and a pair of seal units 13 that are assembled to both ends of the nut 12. A spiral rolling element rolling groove (hereinafter referred to as “ball screw groove”) 14 is formed on the outer peripheral surface of the screw shaft 11.

  The ball screw groove 14 is opposed to the ball screw groove 15 formed on the inner peripheral surface of the nut 12, and when one of the screw shaft 11 and the nut 12 rotates, a large number of balls 16 incorporated in the nut 12 are formed. It rolls between the ball screw grooves 14 and 15. The ball 16 that has rolled between the ball screw grooves 14 and 15 rolls within the return tube 17 assembled to the nut 12 and is returned to its original position. A lubricant such as grease is supplied to the groove surface of the ball screw groove 15 from a lubricant supply hole 18 provided in the nut 12.

  As shown in FIG. 11, the seal unit 13 includes a ring-shaped seal housing 131 and a plurality of fixing pins 132 for fixing the seal housing 131 to the nut 12. A seal body 133 is provided.

  The annular seal body 133 is made of a softer material (for example, resin) than the material constituting the screw shaft 11. The annular seal body 133 is formed to be thin with a thickness of about 0.5 mm, and has an inner peripheral edge portion that is in sliding contact with the groove surface of the ball screw groove 14 formed on the outer peripheral surface of the screw shaft 11. In addition to the annular seal body 133 described above, a C-shaped pressing member 134 that presses the annular seal body 133 against the inner surface of the seal housing 131 is provided in the seal housing 131.

  FIG. 12 is a front view of the annular seal body 133. As shown in FIG. 12, the annular seal body 133 has a vent hole 19 for releasing air in the nut 12 to which the annular seal body 133 is attached to the outside. It has been drilled. Thus, when the vent hole 19 is provided in the annular seal body 133, the inside of the nut 12 sealed by the annular seal body 133 communicates with the outside through the vent hole 19.

  Thus, even if a lubricant such as grease is supplied from the lubricant supply hole 18 to the inside of the nut 12, the flow of the lubricant is not hindered by the air enclosed in the nut 12, and the lubricant supply hole 18. Since the lubricant supplied to the inside of the nut 12 smoothly flows through the groove surface of the ball screw groove 15, it is formed on the inner peripheral surface of the nut 12 even if the inside of the nut 12 is sealed by the annular seal body 133. Further, a lubricant such as grease can be uniformly supplied to the entire groove surface of the ball screw groove 15.

  Further, when the lubricant is supplied from the lubricant supply hole 18 to the inside of the nut 12, the annular seal body 133 is elastically deformed by the air enclosed in the nut 12, and a pressure difference is generated between the inside of the nut 12 and the outside. Therefore, it is possible to prevent the lubricant from leaking out from the ball screw groove surface and sucking in foreign matters. Further, the pressure change that occurs during operation can be avoided by closing the lubricant supply hole 18.

  The invention described in this prior art vents the air in the nut, and can prevent an increase in internal pressure due to the air in the nut that occurs as the lubricant is sealed when the lubricant is supplied.

  However, when the nut is fully filled with the lubricant, the vent hole 19 is not large enough to discharge the lubricant, and the annular seal body 133 may be deformed or damaged by the pressure increase of the enclosed lubricant. Conceivable.

  Further, in the invention described in Patent Document 1, there is a problem that foreign matter may enter from the outside of the nut by providing the annular seal body with a vent hole that directly communicates with the nut.

JP 2003-343686 A

  Therefore, the present invention solves the above-described problems of the prior art, prevents the internal pressure in the nut from increasing when supplying the lubricant into the nut, and mixes foreign matter from the outside of the nut. It is an object of the present invention to provide a ball screw device that can prevent the above.

  In order to solve the above-described problems, the present invention has the following configuration. That is, the ball screw device according to the present invention includes a nut in which a spiral rolling element rolling groove is formed on an inner peripheral surface, a screw shaft in which a spiral rolling element rolling groove is formed on an outer peripheral surface, and the nut. A ball disposed between the rolling element rolling groove of the rolling element and a rolling element raceway groove formed by the rolling element rolling groove of the screw shaft, a circulating component for circulating the ball, and an axial end of the nut. A nut screw having a lubricant supply port for supplying a lubricant into the nut, and the seal is provided at both ends of the nut. A radial gap is formed between the outer periphery of the seal and the inner periphery of the recess, and the gap supplies lubricant from a lubricant supply port provided in the nut. The size and size of the lubricant that leaks through the gap. It is characterized in that.

  In the ball screw device according to the present invention, the gap is 0.125 mm to 0.5 mm.

  Furthermore, the ball screw device according to the present invention is a circulation piece type ball screw device.

  According to the present invention, when the lubricant is supplied into the nut, it is possible to prevent the internal pressure in the nut from increasing, and there is no possibility that the attached parts such as the circulating parts are detached or damaged. There is an effect that foreign matter can be prevented from entering from the outside.

It is a perspective view which shows the structure of a circulation piece type | formula ball screw. It is a fragmentary sectional view of the nut of a circulation piece type ball screw. It is a perspective view of a circulation piece. The partial top view of a circulation piece type ball screw is shown. It is a partial expanded sectional view of the seal part of FIG. It is a figure which shows the state which the seal | sticker moved to the axial direction in FIG. It is a front view of the seal | sticker of FIG. It is a figure which shows the modification of a seal | sticker. It is a figure which shows the other modification of a seal | sticker. It is a fragmentary sectional view of the conventional ball screw device. It is sectional drawing of the seal unit shown in FIG. It is a front view of the annular seal body shown in FIG.

An embodiment of a ball screw device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing the structure of a circulating top ball screw to which the present invention can be suitably applied. FIG. 2 is a partial cross-sectional view of the nut of the circulating top ball screw. FIG. 3 is a perspective view of the circulation piece.

  As shown in FIGS. 1 and 2, the circulation piece type ball screw device 110 has a circulation piece 30 that is a circulation part on the inner peripheral surface of a nut 112. The bypass path 32 provided in the circulation piece 30 connects both ends of the spiral rolling element raceway groove 22 formed by the rolling element rolling groove 116 of the screw shaft 114 and the rolling element rolling groove 20 of the nut 112 facing each other. The infinite circulation circuit 24 is configured. A large number of rolling elements B are filled in the endless circulation circuit 24, and the rolling elements B endlessly circulate in the endless circulation circuit 24.

  Next, the configuration of the circulation piece 30 will be described with reference to FIGS. The upper surface 31 of the circulation piece 30 is an elongated oval surface, is curved with a curvature corresponding to the curved surface forming the inner peripheral surface of the nut 112, and is the same height as the screw thread 21 on the inner peripheral surface of the nut 112. In position. The height of the circulation piece 30 is larger than the diameter of the rolling element B. A groove that forms a bypass path 32 is formed on the upper surface 31, and continues from the entrance / exit 34 at one end of the circulation piece 30 to the entrance / exit 34 b at the other end. The cross-section of the bypass path 32 is U-shaped, and the bottom of the bypass path 32 is a curved surface corresponding to the spherical surface of the rolling element B.

  The bypass path 32 includes an entrance / exit passage 36a on the entrance / exit 34a side, an entrance / exit passage 36b on the entrance / exit 34b side, and an intermediate passage 38 connecting the entrance / exit passages 36a and 36b.

  The entrance / exit passage 36a and the entrance / exit passage 36b are greatly curved on the upper surface 31 and have a shape in which the letter S is reversed. Further, the entrance / exit 34 a is connected to one end of the rolling element rolling groove 22, and the entrance / exit 34 b is connected to the other end of the rolling element rolling groove 22. From one end of the rolling element rolling groove 22 to the other end, it almost swivels along the outer periphery of the screw shaft 114. Between the entrance 34a and the entrance 34b, the thread 118 of the screw shaft 114 and the screw of the nut There is one mountain 21 each. The intermediate passage 38 is gently curved toward the outer periphery of the nut 112 so as to get over the thread 118 between the entrance 34a and the entrance 34b.

  Then, the rolling element B moves to one end of the rolling element rolling groove 22, enters the entrance / exit passage 36 a through the entrance / exit 34 a, bends the traveling direction along the entrance / exit passage 36 a, and enters the intermediate passage 38. The rolling element B that has entered the intermediate passage 38 gets over the thread 118 along the intermediate passage 38 and enters the entrance / exit passage 36b. Return to the other end of the groove 22. The circulation piece type ball screw 110 has a plurality of infinite circulation circuits 24 including the rolling element rolling groove 22 and the bypass path 32 in the circulation piece 30.

  Since the circulation piece 30 exists on the inner peripheral surface of the nut 112, the outer diameter of the nut 112 is reduced, and the circulation piece type ball screw device 110 having a compact structure can be obtained.

  In the circulating top ball screw device described above, seals are usually attached to both ends of the nut 112. In the example shown in FIG. 4, the inner diameter portion of the seal as the seal has the same shape as the cross-sectional shape perpendicular to the axis of the screw shaft (see FIG. 7), and the inner diameter portion is the outer diameter portion of the screw shaft 114 and the rolling element rolling groove. A labyrinth seal 25 having a slight gap (approximately 0.1 mm) from 116 is attached.

  As shown in FIG. 7, the outer diameter portion of the labyrinth seal 25 has a circular shape.

  Concave portions 26 are formed at both ends of the nut 112, and screw holes 28 penetrate from the outer peripheral portion of the nut 112 to the concave portion 26. A set screw 29 having a tip formed in a pin shape with a thin tip is inserted into the screw hole 28.

  A recess 27 is formed in the outer peripheral portion of the labyrinth seal 25, the labyrinth seal 25 is disposed in the recess 26, and the tip of the set screw 29 is inserted into the recess 27 to fix the labyrinth seal 25 to the nut 112. . The inner diameter of the recess 27 is larger than the outer diameter of the distal end portion of the set screw 29 (approximately 0.4 mm in diameter), and the labyrinth seal 25 can move slightly in the axial direction of the screw shaft 114.

  The outer diameter of the labyrinth seal 25 is slightly smaller than the inner diameter of the recess 26, and a radial gap 34 is formed between the outer periphery of the labyrinth seal 25 and the inner periphery of the recess 26. The size of the radial gap 34 is 0.125 mm to 0.5 mm. 5 and 6, this radial gap 34 is exaggerated.

  When a lubricant such as grease is supplied from the lubricant supply port 18 into the nut 112 using a lubricant supply device such as a grease gun, the nut 112 is gradually filled with the lubricant. Gradually passes through the gap between the inner peripheral surface of the labyrinth seal 25 and the rolling element rolling groove 116 or the axial gap 35 generated when the labyrinth seal 25 is slightly moved outward in the axial direction of the nut 112 by air pressure. Go outside.

  Further, when the lubricant is filled in the nut 112 and fully filled in the nut 112, the lubricant that does not fully enter the nut 112 is discharged out of the nut 112 through the axial gap 35 and the radial gap 34.

  In the ball screw device using the conventional labyrinth seal 25, the radial clearance 34 is set to 0.05 mm to 0.1 mm and 0.1 mm or less. In order to prevent foreign matter from entering the inside of the nut 112, the gap between the inner peripheral portion of the labyrinth seal 25 and the rolling element rolling groove 116 is set as small as about 0.1 mm. Therefore, if the radial gap 34 is large, the labyrinth seal This is because the inner peripheral portion of 25 and the rolling element rolling groove 116 come into contact with each other.

  The circulation piece type ball screw device using the conventional labyrinth seal 25 has a problem that the circulation piece rises, and the inventors obtained the following knowledge as a result of the experiment.

  When the lubricant is further supplied after the lubricant is fully filled in the nut 112, the labyrinth seal 25 is pressed against the rolling element rolling groove 116 along the axial direction by the pressure of the lubricant.

  As a result, the gap between the inner surface of the labyrinth seal 25 and the rolling element rolling groove 116 is closed, and the lubricant tends to flow into the axial gap 35. However, in the conventional case, since the radial gap 34 is as small as 0.05 mm to 0.1 mm, the lubricant hardly flows out from the radial gap 34, and the pressure of the lubricant is a circulation piece 30 that is a circulation component. It was found that the circulation piece 30 floated.

  As a result of the experiment, when the size of the radial gap 34 is 0.1 mm, which is the current maximum, the circulating piece is lifted. However, if it is set to 0.125 mm or more, which is 0.025 mm larger than this gap, the circulating piece is raised. It was confirmed that it was possible to prevent the lifting of

  However, if the radial gap 34 is too large, it is difficult to adjust the inner peripheral portion of the labyrinth seal 25 and the rolling element rolling groove 116 so that they do not come into contact with each other, and in order to make it difficult for foreign matter to enter the nut. The gap 34 is desirably 0.5 mm or less.

  In contrast to the conventional ball screw device, according to the ball screw device of the present invention, the labyrinth seal 25 is axially pressed against the rolling element rolling groove 114 of the screw shaft 114 by the pressure of the lubricant, and the inner surface of the labyrinth seal 25 is Even if the gap between the rolling element and the rolling element rolling groove 114 is closed, a radial gap 34 necessary for the lubricant to flow out is secured. Therefore, there is no possibility that the circulating piece 30 floats, and as a result, the circulating piece is detached or damaged.

  Further, the outlet of the lubricant is between the outer peripheral portion of the labyrinth seal 25 and the inner peripheral portion of the concave portion 26 of the nut 112, and is not a gap that directly communicates with the inside of the nut 112, and the gap is also 0.125 mm to 0 mm. Since it is as small as 5 mm, there is little possibility of foreign matter entering the nut 112 from the outside.

  Further, when the lubricant leaks and the internal pressure of the nut 112 decreases, the seal 25 is pressed against the rolling element rolling groove 116 as shown in FIG. As shown, since the state returns to a state where the axial gap 35 is not generated or is reduced, the foreign matter mixing path from the outside is blocked.

  As described above, an example in which the shape of the labyrinth seal 25 has a circular outer peripheral portion has been shown as an embodiment of the present invention. It is good also as a shape different from the inner peripheral shape of the recessed part 26, such as providing or making it elliptical like the labyrinth seal 25b shown in FIG. A radial gap 34 is formed between the inner periphery of the recess 26 also by these recesses and oval shapes, and the lubricant overflowing from the supply of the lubricant can be discharged out of the nut 112.

The same effect can be obtained even if one or more concave portions are provided on the inner peripheral portion of the concave portion 26.
Furthermore, in the above embodiment, an example in which the ball circulation system is a top type is described as a ball screw apparatus to which the present invention is applied. However, the present invention is not limited to a top type, but is a tube type, end cap type, or end deflector type ball screw apparatus. Even if it is applied to the above, it is possible to obtain an effect that it is possible to prevent the parts affected by the pressure increase inside the nut from being adversely affected.

  The seal structure of the present invention can be applied to various ball screws.

18 Lubricant supply port 20 Rolling element rolling groove (nut side)
22 Rolling body rail groove 25 Seal (labyrinth seal)
26 Concave 30 Circulating parts (Circular top)
31 Radial clearance 110 Ball screw device 112 Nut 114 Screw shaft 116 Rolling element rolling groove (screw shaft side)
B ball

Claims (3)

A nut in which a spiral rolling element rolling groove is formed on the inner peripheral surface, a screw shaft in which a spiral rolling element rolling groove is formed in the outer peripheral surface, and the rolling element rolling groove and the screw shaft of the nut. Ball screw device comprising: balls arranged between rolling element raceway grooves formed by rolling element rolling grooves; circulating parts for circulating the balls; and seals arranged at both axial ends of the nut. Because
The nut has a lubricant supply port for supplying a lubricant into the nut, and the seal is disposed in a recess provided at both ends of the nut, and the outer peripheral portion of the seal and the recess A gap in the radial direction is formed between the inner periphery of the nut and the gap so that the lubricant leaks from the gap when the lubricant is supplied from the lubricant supply port provided in the nut. A ball screw device characterized by having a size.   The ball screw device according to claim 1, wherein the gap is 0.125 mm to 0.5 mm.   3. The ball screw device according to claim 1, wherein the ball screw device is a circulation piece type ball screw device, and the circulation piece is made of resin.

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