JP2003172426A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device which eliminates the possibility for entering of foreign matters therein from the outside, and prevents damage to separators due to the entry of the foreign matters. <P>SOLUTION: The ball screw device comprises: a screw stem 3 having a spiral ball screw groove 2 in the outer periphery face; a ball nut 5 having a ball screw groove 4 in the inner periphery face corresponding to the ball screw groove 2 of the screw stem 3 for linearly moving along the axis of the screw stem 3; a number of balls 6 for rolling between the ball screw groove 2 of the screw stem 3 and the ball screw groove 4 of the ball nut 5; and a circulation path 7 formed in the ball nut 5 for circulating the balls 6 from one end to the other end of the ball screw groove 4. The separators 8 having recessed surfaces at both ends are mounted between the balls and a lubricant contained polymer member 11 having slide contact with an outer periphery portion of the screw stem 3 and a sealing seal 12 are provided at, at least, the end of the ball nut 5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw device used in, for example, machine tools, industrial machines and the like.

[0002]

2. Description of the Related Art In a machining center as a machine tool, a robot as an industrial machine, etc., in order to smoothly convert a rotary motion into a straight motion and a straight motion of a work table, etc. Forming spiral ball screw grooves corresponding to each other on the inner peripheral surface of the ball nut,
A ball screw device in which a large number of balls are rotatably arranged in a spiral space formed by both ball screw grooves is widely used.

In the ball screw device, when the screw shaft and the ball nut are rotated relative to each other, the screw shaft and the ball nut make a relative spiral motion smoothly and accurately through the rolling of a large number of balls. The ball circulates in a circulation passage provided in the ball nut.

As a ball screw device used for machine tools, industrial machines, etc., for example, Japanese Patent Laid-Open No. 11-315835.
The publication is known. A disk-shaped separator is interposed between the balls of the ball screw groove, and the separator moves in the ball screw groove as the balls roll. This separator is made of a synthetic resin such as nylon, and has the advantage that the lubricating noise and elastic deformation of the separator are mixed together and drive noise is reduced.

Further, by forming both end surfaces of the separator into concave spherical surfaces having a radius of curvature larger than the radius of the ball, the contact area between the separator and the ball is reduced, and the ball nut as a ball screw body is moved between the two in a straight movement. The sliding contact resistance of is reduced.

[0006]

By the way, when the ball screw device is adopted in a machine tool such as a machining center,
It is used in an environment where it is exposed to cutting chips and a coolant containing cutting chips, and even when it is adopted in an industrial machine, it is often used in a severe environment where it is exposed to dust and the like.

[0007] Therefore, when used in the severe environment as described above, cutting chips and dust enter the inside of the ball screw groove from between the both end openings of the ball nut and the screw shaft, and the separator cuts the chips and dust. It is damaged by foreign matter such as and cannot function as a ball screw.

In Japanese Patent Laid-Open No. 11-315835, in order to solve the above-mentioned problem, dustproof plastic seals are attached to the openings at both ends of the ball nut. Since it has a structure that does not contact the ball screw groove of the shaft, it is not possible to completely prevent the intrusion of foreign matter such as cutting chips and dust. Therefore, there is a circumstance that the separator cannot be used in an environment where foreign matter enters from the outside due to damage to the separator.

The present invention has been made in view of the above circumstances, and its purpose is to completely prevent foreign matter from entering from the outside even in a severe environment where it is exposed to foreign matter such as cutting chips and dust. It is an object of the present invention to provide a maintenance-free ball screw device that can achieve low noise.

[0010]

In order to achieve the above object, the present invention corresponds to a screw shaft having a spiral ball screw groove on its outer peripheral surface and a ball screw groove of the screw shaft. A ball nut that has a ball screw groove on its inner peripheral surface and that moves straight along the axis of the screw shaft; and a large number that rolls between the ball screw groove of the screw shaft and the ball screw groove of the ball nut. A ball and a circulation passage formed in the ball nut for circulating the ball from one end side to the other end side of the ball screw groove,
Between each of the balls, a separator having concave surfaces at both ends is interposed, and a lubricant-containing polymer member and a hermetic seal that are in sliding contact with the outer periphery of the screw shaft are provided at the end of the ball nut. To do.

According to a second aspect of the present invention, a wiper seal is provided instead of the hermetically sealed seal of the first aspect.

According to the above construction, the contact between the balls can be prevented without reducing the number of balls by setting the thickness of the central portion of the separator to be small. By using a synthetic resin such as nylon as the material for the separator, the separator is lubricated and elastically deformed to reduce driving noise.

Further, by providing a lubricant-containing polymer member and a hermetically sealed seal which are in sliding contact with the outer peripheral portion of the screw shaft at the end of the ball nut, or by providing a wiper seal instead of the hermetically sealed seal, the screw shaft of the ball nut. The inside can be reliably sealed by sliding contact with the ball screw groove of
It is possible to prevent foreign matter such as dust from entering.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show a first embodiment, and FIG.
Is a side view in which a part of the ball screw device is cut away, and FIG.
3 is a sectional view taken along the line AA of FIG. 3, FIG. 3 is a sectional view taken along the ball screw groove, and FIG. 4 is a sectional view taken along the line BB of FIG.

As shown in FIG. 1, the ball screw 1 includes a screw shaft 3 having a spiral ball screw groove 2 formed on the outer peripheral surface thereof, and a spiral ball screw groove 4 corresponding to the screw shaft 3. The ball nut 5 formed on the peripheral surface and the ball screw groove 2 of the screw shaft 3 and the ball screw groove 4 of the ball nut 5 facing each other are provided with a large number of balls 6 and ball circulation provided in the ball nut 5. And the passage 7.

The ball 6 includes a screw shaft 3 and a ball nut 5.
It is inserted into the ball screw grooves 2 and 4 of FIG.
Further, as shown in FIGS. 2 and 3, disc-shaped separators 8 are interposed between the balls 6, respectively. These separators 8 move in the ball screw grooves 2 and 4 and the ball circulation passage 7 as the balls 6 roll.

The separator 8 is made of a synthetic resin such as nylon, and both ends thereof are formed into a concave curved surface 9 having a Gothic arch shape or a conical shape. Therefore, the separator 8 is in contact with the ball 6 with a relatively small area, and the thickness t of the central portion (that is, the interval between the balls 6) is smaller than the total length L thereof.

Further, a first annular recess 10a is provided on the inner peripheral surfaces of both ends of the ball nut 5, and a second annular recess 10b having a larger diameter than the first annular recess 10a is provided outside the first annular recess 10a. Is provided. Then, the lubricant-containing polymer member 11 is mounted in the first annular recess 10a,
A hermetic seal 12 as a highly dustproof seal is mounted in the second annular recess 10b.

A thin groove 13a is formed on the outer periphery of the lubricant-containing polymer member 11, and a garter spring 13 is fitted in the groove 13a. The lubricant-containing polymer member 11 is pressed by the garter spring 13 in the radial direction toward the outer circumference of the screw shaft 3 with a constant pressure, and therefore, the lubricant-containing polymer member 1 is not operated even for a long time.
Even if the inner peripheral surface of No. 1 is worn, proper contact with the screw shaft 3 is always maintained, and good lubrication is ensured.

As shown in FIG. 4, the lubricant-containing polymer member 11 has a substantially semi-cylindrical upper half 11a and a lower half 1 respectively.
1b, only the central portions of the upper half 11a and the lower half 11b contact the outer diameter surface of the screw shaft 3, and both ends in the circumferential direction form a gap g with respect to the outer diameter of the screw shaft 3. is doing.

The hermetically sealed seal 12 press-fitted to the outside of the lubricant-containing polymer member 11 is in continuous contact with the ball screw groove 2 of the screw shaft 3 over the outer diameter thereof.
By slidingly contacting the screw shaft 3 when moving, the inside is reliably sealed.

The lubricant-containing polymer member 11 is made of a synthetic resin selected from the group of polyolefin resins having basically the same chemical structure such as polyethylene, polypropylene, polybutylene, and polymethylpentene, and poly-α-olefin as a lubricant. Paraffin hydrocarbon oil such as oil, naphthene hydrocarbon oil, mineral oil, ether oil such as dialkyldiphenyl ether oil, ester oil such as phthalate ester, etc., either alone or mixed in the form of a mixed oil. The raw material is heated above the melting point of the resin to plasticize it,
It is then solidified by cooling, and various additives such as an antioxidant, an antirust agent, an antiwear agent, a defoaming agent and an extreme pressure agent may be added to the lubricant in advance.

According to the ball screw 1 constructed as described above, the ball nut 5 is non-rotatably and axially movably supported, and is axially immovably supported.
When is rotated, a large number of balls 6 fitted in the ball screw groove 2 of the screw shaft 3 and the ball screw groove 4 of the ball nut 5 are rotated.
Rolls along with the separator 8 between the ball screw grooves 2 and 4 and the ball circulation passage 7, and the ball nut 5 is connected to the screw shaft 3
Moves in the axial direction by a stroke proportional to the rotation amount of.

At this time, the screw shaft 3 slides with respect to the lubricant-containing polymer member 11 and the hermetically sealed seal 12. The lubricant-containing polymer member 11 is pressed in the radial direction toward the outer circumference of the screw shaft 3 with a constant pressure.
Since a gap g is formed between the screw shaft 3 and both circumferential ends of the a and the lower half 11b, no matter which direction the screw shaft 3 is rotated, the upper half 11a and the lower half 11b are rotated. Both ends of the portion 11b do not scrape off the lubricant adhering to the outer periphery of the screw shaft 3, and the lubricant enters the gap g. Therefore, the lubricant adhering to the screw shaft 3 is retained, whereby the lubrication of the balls 6 and the ball screw grooves 2, 4 can be ensured.

Further, the hermetically sealed seal 12 press-fitted to the outside of the lubricant-containing polymer member 11 makes continuous contact with the ball screw groove 2 of the screw shaft 3 over the outer diameter, and the ball nut 5
Since it is in sliding contact with the screw shaft 3 when moving, the inside of the ball nut 5 is sealed.

Therefore, the ball screw device of the present invention is used in a machine tool such as a machining center to be exposed to cutting chips and a coolant containing cutting chips, or to an industrial machine to be exposed to dust or the like in a severe environment. Even when used in, the foreign matter does not enter from the outside, the separator 8 is not damaged by the entry of the foreign matter, the noise is low, and the maintenance-free ball screw device can be provided.

FIG. 5 shows a second embodiment and is a partially cut-away side view of the ball screw device. The same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

A first annular recess 21a is provided on the inner peripheral surfaces of both ends of the ball nut 5, and a second annular recess 21b is provided outside the first annular recess 21a. The lubricant-containing polymer member 11 is attached to the first annular recess 21a, and the wiper seal 22 as a highly dustproof seal is attached to the second annular recess 21b.

The wiper seal 22 has a cylindrical shape made of synthetic resin, and a plurality of slits 23 are formed in the axial direction in the outer peripheral portion of the wiper seal 22 except the base end portion thereof, and the slits 23 have elasticity in the radial direction. A plurality of sealing pieces 24 are provided. The ball screw groove 2 of the screw shaft 3 is provided on the inner surface of the seal piece 24.
Is provided with the protrusion 25, and the seal piece 24 is uniformly pressed against the screw shaft 3 by a plurality of garter springs 26 fitted to the outside thereof.

Also in this embodiment, since the wiper seal 22 mounted on the outer side of the lubricant-containing polymer member 11 has the convex portion 25 which fits into the ball screw groove 2 of the screw shaft 3, the ball nut. Since it is in sliding contact with the ball screw groove 2 when moving 5, the inside of the ball nut 5 is sealed.

Therefore, the ball screw device of the present invention is applied to a machine tool such as a machining center to be exposed to cutting chips or a coolant containing cutting chips, or to an industrial machine to be exposed to dust or the like under a severe environment. Even when used in, the foreign matter does not enter from the outside, the separator 8 is not damaged by the entry of the foreign matter, the noise is low, and the maintenance-free ball screw device can be provided.

In the above-described embodiment, the lubricant-containing polymer member 11 is formed in the substantially half-cylindrical upper half portion 1.
Although it is formed from 1a and the lower half portion 11b, it may be C-shaped with a cut in a part of the circumference, and is not limited to the shape of the lubricant-containing polymer member.

Also, an example has been shown in which the inner peripheral surface of the lubricant-containing polymer member contacts only the outer diameter surface of the screw shaft 3, but a spiral protrusion is provided on the inner peripheral surface of the lubricant-containing polymer member. The protrusion may be brought into sliding contact with the ball screw groove 2 of the screw shaft 3.

[0035]

As described above, according to the present invention, a lubricant-containing polymer member and a highly dust-proof seal are provided at both ends of a ball nut, so that the ball nut can be used as a machine tool for cooling including cutting chips and cutting chips. Even if it is used in a severe environment where it is exposed to liquid or is used in industrial machinery and exposed to dust, etc.
It is possible to provide a maintenance-free ball screw device in which foreign matter does not enter from the outside, the separator is not damaged by the entry of foreign matter, and noise is low.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of the present invention, in which a part of a ball screw device is cut away.

FIG. 2 is a cross-sectional view showing the same embodiment and taken along line AA of FIG.

FIG. 3 is a cross-sectional view showing the same embodiment and taken along a ball screw groove.

FIG. 4 is a cross-sectional view showing the same embodiment and taken along line BB in FIG. 1.

FIG. 5 is a side view showing a second embodiment of the present invention, in which a part of the ball screw device is cut away.

[Explanation of symbols]

1 ... Ball screw 2, 4 ... Ball screw groove 3 ... Screw shaft 5 ... Ball nut 6 ... ball 7. Ball circulation passage 8 ... Separator 11 ... Polymer member containing lubricant 12 ... hermetic seal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16H 25/22 F16H 25/22 LF term (reference) 3J062 AA22 AA23 AA38 AB22 AC07 BA17 BA24 BA26 CD06 CD33 CD67 CD75

Claims (2)

[Claims] 1. A screw shaft having a spiral ball screw groove on the outer peripheral surface, and a ball screw groove corresponding to the ball screw groove of the screw shaft on the inner peripheral surface, and straightly moving along the shaft of the screw shaft. A moving ball nut; a number of balls rolling between the ball screw groove of the screw shaft and the ball screw groove of the ball nut; and a ball nut formed on the ball nut, from one end of the ball screw groove to the other end. In a ball screw device having a circulation passage for circulating balls on the side, a separator having concave surfaces at both ends is interposed between the balls, and an end portion of the ball nut is slidably contacted with an outer peripheral portion of the screw shaft. A ball screw device comprising a lubricant-containing polymer member and a hermetic seal. 2. A screw shaft having a spiral ball screw groove on the outer peripheral surface, and a ball screw groove corresponding to the ball screw groove of the screw shaft on the inner peripheral surface, and linearly moving along the shaft of the screw shaft. A moving ball nut; a number of balls rolling between the ball screw groove of the screw shaft and the ball screw groove of the ball nut; and a ball nut formed on the ball nut, from one end of the ball screw groove to the other end. In a ball screw device having a circulation passage for circulating balls on the side, a separator having concave surfaces at both ends is interposed between the balls, and an end portion of the ball nut is slidably contacted with an outer peripheral portion of the screw shaft. A ball screw device comprising a lubricant-containing polymer member and a wiper seal.