JP5598131B2 - Ball screw device - Google Patents

Description

  The present invention relates to a ball screw device, and more particularly, to a ball screw device including a scraper that removes lubricant leaked from a nut.

A ball screw device used as a mechanical element that converts rotational motion into linear motion generally has a screw shaft and a cylindrical nut provided on the outer periphery of the screw shaft. A plurality of balls are incorporated between a spiral ball rolling groove formed on the outer peripheral surface of the screw shaft and a spiral ball rolling groove formed on the inner peripheral surface of the nut.
In such a ball screw device, a seal is often attached between the screw shaft and the nut in order to prevent foreign matter from entering the inside of the nut. An example of such a seal is a labyrinth seal that is non-contact with the screw shaft and wider than the lead.

  However, since the labyrinth seal is not in contact with the screw shaft, there is a possibility that foreign matter outside the nut may enter the nut as the screw shaft rotates. When foreign matter enters the nut, foreign matter enters between the ball, the ball rolling groove of the nut, and the ball rolling groove of the screw shaft. Become.

Therefore, in order to prevent such intrusion of foreign matter, a seal disclosed in Patent Document 1 has been proposed. According to Patent Document 1, a pair of lubricant scrapers are provided on one end surface of the nut so that the tip end faces the screw shaft outer circumferential surface along the axial direction of the screw shaft. The leakage lubricant is removed from the outer peripheral surface of the shaft. This seal is characterized in that the seal is brought into full contact with the outer peripheral surface of the screw shaft.
However, if the seal is brought into full contact with the outer peripheral surface of the screw shaft, the torque of the ball screw increases due to the seal. Further, it is necessary to manufacture a seal according to the specifications of the ball screw to be installed, which may increase the cost.

Therefore, a ball screw device that can remove foreign matters with a small contact area has been proposed (see Patent Document 2). According to the invention described in Patent Document 2, the lubricant (foreign matter) leaked from the ball groove can be removed without impairing the conventional sealing function.
Here, when the ball screw device is used under severe load conditions, lubrication with the lubricant is very important, so the system automatically lubricates the nut in small amounts at short time intervals inside the nut. Is used. In this case, the lubricant supply position is generally provided at several places such as the groove bottom of the thread groove formed on the inner peripheral surface of the nut or between the thread grooves of the screw shaft and the nut. Further, as a seal attached to both ends of the nut, a resin seal having a certain gap with a screw groove formed on the outer peripheral surface of the screw shaft is generally used.

JP-A-10-299854 JP 2008-291860 A

However, in the ball screw device described in Patent Document 2, the problem that it is necessary to produce a scraper for each specification of the ball screw device to be installed has not been solved as in Patent Document 1.
Accordingly, the present invention has been made paying attention to the above-mentioned problems, and its object is to provide a ball screw device that reduces the manufacturing cost and prevents the entry of foreign matter into the nut without increasing the torque. There is to do.

The invention according to claim 1 for achieving the above object includes a screw shaft, a nut provided on an outer periphery of the screw shaft, a spiral ball rolling groove formed on an outer peripheral surface of the screw shaft, and the The inner peripheral surface of the nut has a gap between a plurality of balls provided between the inner peripheral surface of the nut and a spiral ball rolling groove formed on the inner peripheral surface of the nut and the outer peripheral surface of the screw shaft. In a ball screw device provided with a provided seal,
The seal is formed with a slit that divides the seal in a direction perpendicular to the lead direction of the screw shaft,
A scraper that contacts the ball rolling groove of the screw shaft in a direction orthogonal to the lead direction of the screw shaft is provided by being fitted into the slit portion so as to be fitted in the radial direction of the seal. It is said.

  According to the first aspect of the present invention, since the scraper fitted into the seal contacts only the ball rolling groove of the screw shaft and the contact area is small, the foreign matter in the nut is not increased without increasing the torque. Can prevent intrusion. In particular, since the contact of the screw shaft with the ball rolling groove of the scraper is defined in a direction perpendicular to the lead direction of the screw shaft, the contact pressure increases, and foreign matter can be more reliably infiltrated into the nut. Can be prevented. In addition, since the scraper is formed and installed based on the lead and ball diameter of the ball screw device, it can be used in common for ball screw devices having the same lead and ball diameter regardless of the shaft diameter of the screw shaft. Cost can be reduced. In addition, since the scraper is in contact only with the ball rolling groove of the screw shaft, the seal installed on the inner peripheral surface of the nut is maintained on the outer periphery of the screw shaft while maintaining low torque. Since the predetermined gap is provided with respect to the surface and the ball rolling groove, the lubricant can be easily supplied. Therefore, it is possible to provide a ball screw device that reduces the manufacturing cost and prevents foreign matter from entering the nut without increasing the torque.

According to a second aspect of the invention for achieving the above object, there is provided a screw shaft, a nut provided on an outer periphery of the screw shaft, and a spiral ball rolling groove formed on an outer peripheral surface of the screw shaft. And an inner peripheral surface of the nut so as to have a gap between a plurality of balls provided between the inner peripheral surface of the nut and a spiral ball rolling groove formed on the inner peripheral surface of the nut and the outer peripheral surface of the screw shaft. In a ball screw device provided with a seal provided on the surface,
The seal is formed with a groove portion that communicates the inner peripheral surface and the outer peripheral surface of the seal in a direction orthogonal to the lead direction of the screw shaft,
A scraper that contacts the ball rolling groove of the screw shaft in a direction perpendicular to the lead direction of the screw shaft is provided by being fitted into the groove portion so as to be fitted in the radial direction of the seal . .

  According to the present invention, it is possible to provide a ball screw device that reduces the manufacturing cost and prevents the entry of foreign matter into the nut without increasing the torque.

It is sectional drawing which shows the structure in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is a top view which shows the positional relationship of the screw axis | shaft and seal | sticker in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is a figure which shows the structure of the scraper in 1st Embodiment of the ball screw apparatus which concerns on this invention, (a) is a front view, (b) is a side view. It is sectional drawing which shows the positional relationship of the screw axis | shaft and seal | sticker in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is a schematic sectional drawing which shows the flow of the lubricant in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is sectional drawing which shows the fixing aspect of the scraper in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is sectional drawing which shows the fixing aspect of the scraper in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is a fragmentary sectional view which shows the structure in 2nd Embodiment of the ball screw apparatus which concerns on this invention. It is a fragmentary sectional view which shows the structure in 2nd Embodiment of the ball screw apparatus which concerns on this invention. It is sectional drawing of the labyrinth seal and scraper which show the structure in 3rd Embodiment of the ball screw apparatus which concerns on this invention.

Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a cross-sectional view showing a configuration of a ball screw device according to a first embodiment of the present invention. FIG. 2 is a plan view showing the positional relationship between the screw shaft and the seal in the first embodiment of the ball screw device according to the present invention. 3A and 3B are diagrams showing the configuration of the scraper in the first embodiment of the ball screw device according to the present invention, wherein FIG. 3A is a front view and FIG. 3B is a side view. FIG. 4 is a sectional view showing the positional relationship between the screw shaft and the seal in the first embodiment of the ball screw device according to the present invention. FIG. 5 is a schematic sectional view showing the flow of the lubricant in the first embodiment of the ball screw device according to the present invention. FIG. 6 is a cross-sectional view showing how the scraper is fixed in the first embodiment of the ball screw device according to the present invention. FIG. 7 is a cross-sectional view showing how the scraper is fixed in the first embodiment of the ball screw device according to the present invention.

As shown in FIG. 1, the ball screw device 1 according to the first embodiment includes a screw shaft 10, a nut 20, a plurality of balls 30, and a seal 40.
A ball rolling groove 11 having a spiral shape in the axial direction of the screw shaft 10 is formed on the outer peripheral surface 10 a of the screw shaft 10. A ball rolling groove 21 spiraling in the axial direction of the nut 20 is formed on the inner circumferential surface 20a of the nut 20 provided on the outer periphery of the screw shaft 10 with the same lead as the ball rolling groove 11. The ball rolling grooves 11 and 21 are opposed to each other, and the plurality of balls 30 provided between the ball rolling grooves 11 and 21 are rotated by the relative rotation of the screw shaft 10 with respect to the nut 20. It rolls between the moving grooves 11 and 21. The ball 30 that has rolled between the ball rolling grooves 11 and 21 passes through the ball return tube 22 assembled to the nut 20 and is returned to its original position.

The nut 20 has end surface portions 20b and 20c, and annular recesses 23 and 23 are formed on the inner peripheral surface of the nut 20 in the vicinity of the end surface portions 20b and 20c. In the recesses 23, 23, annular labyrinth seals 40, 40 are fitted and provided. That is, the concave portions 23 and 23 function as a labyrinth seal fitting portion that fits and accommodates the labyrinth seals 40 and 40.
The labyrinth seals 40, 40 are formed in the recesses 23, 23 so that the inner peripheral surface thereof and the outer peripheral surface 10a of the screw shaft 10 and the ball rolling groove 11 are separated from each other with a predetermined distance D (see FIG. 4). Is provided. By providing the labyrinth seals 40, 40 in the recesses 23, 23, foreign matter is prevented from entering between the screw shaft 10 and the nut 20.

  A flange portion 24 extending in the radial direction of the nut 20 is formed on one end surface portion 20 c of the nut 20. The flange portion 24 is formed with a lubricant supply hole 25 that penetrates the outer peripheral surface 24 a of the flange portion 24 and the inner peripheral surface 20 a of the nut 20. The lubricant is supplied from the lubricant supply hole 25 to the inside of the nut 20 (ball rolling grooves 11 and 21).

Next, as shown in FIG. 2, the labyrinth seal 40 positioned so as to surround the screw shaft 10 is formed with a slit 41 that divides the labyrinth seal 40 in a direction d2 orthogonal to the lead direction d1 of the screw shaft 10. ing. A scraper 50 that contacts the ball rolling groove 11 of the screw shaft 10 is fitted between the slit surfaces 41 a and 41 a forming the slit 41.
As shown in FIG. 3, the scraper 50 has a predetermined thickness, a rectangular main body 51, and extends from one end of the main body 51, and the shaft of the ball rolling groove 11 of the screw shaft 10. And a distal end portion 52 having a distal end formed in a circular shape along the sectional shape in the direction.
As a material constituting the scraper 50, a softer material than the labyrinth seal 40 is preferable. Specifically, rubber materials such as nitrile rubber and elastomer are preferable.

As shown in FIG. 4, the scraper 50 is fitted between the slit surfaces 41 a and 41 a so that the tip 52 that protrudes in a circular shape contacts the ball rolling groove 11 of the screw shaft 10. Note that the scraper 50 is fitted into the slot 41 so that there is no gap in the axial direction of the screw shaft 10 and the tightening direction. By inserting the scraper 50 into the slit surfaces 41 a and 41 a, the scraper 50 comes into contact with the ball rolling groove 11 of the screw shaft 10 in a direction orthogonal to the lead direction of the screw shaft 10.
When the screw shaft 10 rotates with respect to the nut 20 by the scraper 50 provided in this way, the foreign matter attached to the ball rolling groove 11 of the screw shaft 10 is removed. In addition, foreign matter adhering to the outer diameter surface 10a of the screw shaft 10 (those whose maximum dimension exceeds approximately the dimension D (see FIG. 3)) is removed by a labyrinth seal 40 that does not contact the screw shaft 10.

Further, the labyrinth seal used in the present embodiment has a high rigidity with respect to the width of the ball rolling groove 11 of the screw shaft 10 (having a thickness larger than the width of the ball rolling groove 11). As a result, as shown by the arrows in FIG. 5, when the lubricant is supplied into the nut 20 by the lubricant injection hole 24 provided in the flange portion 23, the lubricant spreads throughout the nut. The old (unnecessary) lubricant in the nut 20 is discharged out of the nut 20 through the gap between the labyrinth seal 40 and the screw shaft 10 by the newly lubricated lubricant. Thus, since the scraper 50 is in contact only with the ball rolling groove 11 of the screw shaft 10, the labyrinth seal 40 installed on the inner peripheral surface of the nut 20 is screwed while maintaining low torque. Since there is a predetermined gap with respect to the outer peripheral surface 10a of the shaft 10 and the ball rolling groove 11, it is possible to easily supply the lubricant.
Here, as shown in FIG. 5, the labyrinth seal 40 including the scraper 50 may be provided in the vicinity of both end faces of the nut 20. With such a configuration, entry of foreign matter into the nut 20 can be prevented more reliably.

Next, as shown in FIG. 6, the scraper 50 is fixed by, for example, a labyrinth seal by a seal fixing tool (for example, a screw) 70 screwed into a seal fixing hole 26 provided through the nut 20. It is energized by a force (indicated by an arrow) generated through the slit surfaces 41a and 41a when 40 is fixed.
As another method of fixing the scraper 50, a scraper fixing hole 42 penetrating the slit surfaces 41 a and 41 a and the outer peripheral surface of the labyrinth seal 40 is formed, and a scraper fixing tool (for example, a screw) 80 is used as a scraper. Examples include a method of directly fixing 50 (see FIG. 7) and fixing with an adhesive.

  As described above, according to the present embodiment, the scraper 50 fitted and provided in the labyrinth seal 40 contacts only the ball rolling groove 11 of the screw shaft 10 and the contact area is small, so that the torque is increased. Without intrusion of foreign matter into the nut 20 can be prevented. In particular, since the contact of the scraper 50 with the ball rolling groove 11 of the screw shaft 10 is defined in a direction orthogonal to the lead direction of the screw shaft 10, the contact pressure increases, and foreign matter enters the nut 20 more. It can be surely prevented. Further, since the scraper 50 is formed and installed based on the lead and the ball diameter of the ball screw device 1, regardless of the shaft diameter of the screw shaft 10, it can be used in common for the ball screw device having the same lead and ball diameter, Manufacturing cost can be reduced. Further, since the scraper is in contact only with the ball rolling groove of the screw shaft, the labyrinth seal installed on the inner circumferential surface of the nut is maintained at the low torque while the outer circumferential surface of the screw shaft and the ball rolling are maintained. Since the predetermined gap is provided with respect to the moving groove, the lubricant can be easily supplied. Therefore, it is possible to provide a ball screw device that reduces the manufacturing cost and prevents foreign matter from entering the nut without increasing the torque.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. Since the ball screw device according to the present embodiment is different from the first embodiment only in the configuration of the labyrinth seal, the description of the same configuration given the same reference numerals as in the first embodiment is omitted. 8 and 9 are sectional views showing the positional relationship between the screw shaft and the seal in the second embodiment of the ball screw device according to the present invention. First, as shown in FIG. 8, in the present embodiment, a groove 43 is formed on the slit surface 41 a so that the inner peripheral surface and the outer peripheral surface of the labyrinth seal 40 communicate with each other. A predetermined gap is formed between the outer peripheral surface of the labyrinth seal 40 and the inner peripheral surface of the nut 20, and this gap communicates with the outside.

As shown in FIG. 9, a groove 43 is formed in the slit surface 41 a to communicate the inner peripheral surface of the labyrinth seal 40 and the outside on the end surface portion 20 b side of the nut 20.
As in these configurations, the scraper 50 scrapes off the inner peripheral surface of the labyrinth seal 40 and the outer peripheral surface of the labyrinth seal 40 or the groove portion 43 that communicates with the outside on the end surface portion 20b side of the nut 20. Foreign matter can be discharged to the outside.
Instead of forming the groove 43 in the slit surface 41a, a through hole (not shown) that penetrates the inner peripheral surface of the labyrinth seal 40 and the outer peripheral surface of the labyrinth seal 40 or the outside on the end surface portion 20b side of the nut 20 However, the formation of the groove 43 is preferable in that the cost can be reduced.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. The ball screw device according to the present embodiment is different from the first embodiment described above only in the manner in which the scraper is installed with respect to the labyrinth seal. Omitted. FIG. 10 is a partial cross-sectional view showing the configuration of the ball screw device according to the third embodiment of the present invention. As shown in FIG. 10, in this embodiment, instead of forming the slit 41 in the labyrinth seal 40 (see FIG. 2), a groove portion 44 for fitting the scraper 50 is formed on the inner peripheral surface of the labyrinth seal 40. The groove 44 is formed in a direction orthogonal to the lead direction of the screw shaft 10, similarly to the slit 41 in the first embodiment. By inserting the scraper 50 into the groove 44, the scraper 50 comes into contact with the ball rolling groove 11 of the screw shaft 10 in a direction orthogonal to the lead direction of the screw shaft 10.

Thus, the strength of the labyrinth seal 40 can be maintained high by forming the groove portion 44 into which the scraper 50 is fitted on the inner peripheral surface of the labyrinth seal 40 in a direction orthogonal to the lead direction of the screw shaft 10. Intrusion of foreign matter into the nut can be further improved.
As mentioned above, although embodiment of the ball screw apparatus which concerns on this invention was described, this invention is not limited to the said embodiment, A various deformation | transformation is possible unless it deviates from the meaning of this invention. For example, in the above embodiment, a ball is used as the rolling element, but a roller may be used.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 10 Screw shaft 11 Ball rolling groove 20 Nut 21 Ball rolling groove 22 Ball return tube 23 Flange part 24 Lubricant injection hole 26 Seal fixing hole 30 Ball (rolling element)
40 Seal 41 Slot 41a Slot 42 Scraper fixing hole 43 Groove 50 Scraper 70 Seal fixture 80 Scraper fixture

Claims (2)

A screw shaft, a nut provided on the outer periphery of the screw shaft, a spiral ball rolling groove formed on the outer peripheral surface of the screw shaft, and a spiral ball rolling formed on the inner peripheral surface of the nut A ball screw device including a plurality of balls provided between the groove and a seal provided on an inner peripheral surface of the nut so as to have a gap between the outer peripheral surface of the screw shaft;
The seal is formed with a slit that divides the seal in a direction perpendicular to the lead direction of the screw shaft,
A scraper that contacts the ball rolling groove of the screw shaft in a direction orthogonal to the lead direction of the screw shaft is provided by being fitted into the slit portion so as to be fitted in the radial direction of the seal. And ball screw device. A screw shaft, a nut provided on the outer periphery of the screw shaft, a spiral ball rolling groove formed on the outer peripheral surface of the screw shaft, and a spiral ball rolling formed on the inner peripheral surface of the nut A ball screw device including a plurality of balls provided between the groove and a seal provided on an inner peripheral surface of the nut so as to have a gap between the outer peripheral surface of the screw shaft;
The seal is formed with a groove portion that communicates the inner peripheral surface and the outer peripheral surface of the seal in a direction orthogonal to the lead direction of the screw shaft,
A scraper that contacts the ball rolling groove of the screw shaft in a direction orthogonal to the lead direction of the screw shaft is provided by being fitted into the groove portion so as to be fitted in the radial direction of the seal. Rubo Lumpur screw device.

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