JP4655885B2 - Ball screw device assembling apparatus and its assembling method - Google Patents

Description

  The present invention relates to an assembling apparatus for a ball screw device used for a moving mechanism of a moving body of a machine device such as a machine tool or a precision machine, and an assembling method thereof.

A conventional ball screw device assembly device includes a spiral shaft raceway groove formed on the outer peripheral surface of the screw shaft, a nut raceway groove facing the shaft raceway groove formed on the inner peripheral surface of the cylindrical nut, A top piece is fixed in advance to a nut of a ball screw device that loads and circulates a plurality of balls in a plurality of circulation paths constituted by S-shaped connection paths that connect nut raceway grooves formed in the top part. In addition, a ball insertion jig with the same number of ball supply holes as the circulation path inside the nut installed in the vertical direction is aligned with the nut, and the nut track that forms the corresponding circulation path at the outlet of the ball supply hole It is installed at the highest position of the groove, a predetermined number of balls are aligned and continuously supplied to each ball supply hole, and the ball that does not fit after being loaded into the circulation path by its own weight is pushed in by the insertion rod. Loaded with nuts (for example, See Patent Document 1.).
Japanese Patent No. 2530401 (2nd page, paragraph 0006-paragraph 0014, FIG. 1)

However, in the above-described conventional technology, a predetermined number of balls are aligned and supplied at one time to the ball supply holes, and the balls that have not been fully inserted are pushed in by the insertion rod and loaded into the circulation path. There is a problem that clogging is more likely to occur as the track groove lead becomes smaller.
Further, since balls are simultaneously loaded into a plurality of circulation paths, smooth loading becomes difficult, and a ball that could not be loaded has to be pushed with an insertion rod, which may cause damage to the ball.

This is particularly noticeable when the ball has a light weight due to a small diameter of the ball loaded in the circulation path.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an assembly device for a ball screw device that prevents damage to even a lightweight ball and does not cause clogging. .

  In order to solve the above problems, the present invention provides a screw shaft in which a spiral shaft raceway groove is formed on the outer peripheral surface, and a cylindrical nut in which a nut raceway groove facing the shaft raceway groove is formed on the inner peripheral surface. A support block for a ball screw device assembly apparatus comprising: a connecting path for connecting the nut raceway grooves; and a plurality of balls circulating in a circulation path composed of the axial raceway grooves, the nut raceway grooves and the connecting paths. The nut is installed in a vertical direction, and a nut cradle that supports the nut so as to be movable up and down with respect to the support block, and is inserted into the inner diameter side of the nut installed on the nut cradle, A temporary shaft supported rotatably, an inclined surface formed at a tip portion of the temporary shaft, and a gap between a shoulder portion of the inclined surface and the outer peripheral surface of the temporary shaft and an inner peripheral surface of the nut. And a negative pressure chamber for supplying negative pressure That.

  Thereby, the present invention collects the ball on the shoulder portion of the temporary shaft by the inclined surface provided on the temporary shaft, and uses the frictional force with the shoulder portion accompanying the rotation of the temporary shaft to attract and hold the ball by the negative pressure. It can be smoothly fed into the nut raceway groove. Even when the lead of the nut raceway groove is small, it can prevent clogging even if the weight of the ball loaded in the circulation path is light, and The effect that damage can be prevented is obtained.

  Embodiments of an assembly apparatus for a ball screw device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing an assembly apparatus for a ball screw device according to an embodiment, FIG. 2 is a cross-sectional view showing the ball screw device according to the embodiment, and FIG.
FIG. 3 is a cross-sectional view of the nut top mounting portion cut in a direction perpendicular to the nut axis.
In FIG. 2, 1 is a ball screw device. In this embodiment, it is a top type ball screw device.

Reference numeral 2 denotes a screw shaft of the ball screw device 1, which is a rod-shaped member made of a steel material such as alloy steel. A substantially semicircular arc-shaped shaft raceway groove 3 is spirally formed with a predetermined lead on the outer peripheral surface thereof. Has been.
Reference numeral 4 denotes a nut of the ball screw device 1, which is a cylindrical member made of a steel material such as an alloy steel. A substantially semicircular arc-shaped nut raceway groove 5 facing the shaft raceway groove 3 is formed on the inner peripheral surface thereof. It is formed with the same lead as the shaft raceway groove 3.

Reference numeral 6 denotes a steel ball as a ball, which is a sphere made of a steel material such as an alloy steel. A plurality of balls are loaded between the shaft raceway groove 3 and the nut raceway groove 5, and the screw shaft 2 and the nut 4 are screwed together. Let
Reference numeral 7 denotes a top part, which is a plug-like member made of steel or the like and formed with a connecting path 8 that is a groove curved in an S shape with an arcuate cross section that connects two adjacent nut raceway grooves 5. Thus, the nut 4 is attached to a plurality of holes provided in the cylindrical wall at different circumferential angular positions.

A circulation path is formed by the shaft raceway groove 3 of the screw shaft 2, the nut raceway groove 5 of the nut 4 opposite to the shaft raceway groove 5, and the connecting path 8 of the top portion 7 that connects the nut raceway groove. And a predetermined amount of lubricant, such as grease, is enclosed.
As a result, the shaft raceway groove 3 and the nut raceway groove 5 are screwed together via the steel ball 6, and the nut 4 is moved in the axial direction while the steel ball 6 circulates in the circulation path by rotating the screw shaft 2. .

An assembling apparatus for loading the steel ball 6 into the nut 4 of the ball screw apparatus 1 will be described.
In FIG. 1, reference numeral 10 denotes an assembly device for the ball screw device 1.
The nut 4 of the ball screw device 1 to be assembled shown in the figure is a nut in which a plurality of pieces 7 are arranged in the circumferential direction, and the moving body of the mechanical device is provided by a flange portion provided on the outer peripheral portion of the nut 4. It is a nut of the type fixed to etc.

  Reference numeral 11 denotes a temporary shaft, which is a rod-like member that is inserted into the inner diameter side of the nut 4 instead of the screw shaft 2 when the steel ball 6 is loaded into the nut 4 made of a steel material such as alloy steel, and is an assembly target. The inner diameter of the inner diameter of the steel ball 6 is smaller than the diameter of the steel ball 6 than the BCD (Ball Center Diameter) of the nut 4, that is, the outer diameter obtained by subtracting a predetermined clearance from the diameter of the inscribed circle of the steel ball 6 circulating in the circulation path. Yes.

A conical conical protrusion 12 having a conical surface as an inclined surface is provided at the tip of the temporary shaft 11, and a fixed end 13 on the opposite side thereof is fitted in a fitting hole 15 at the end of the shaft 14. The notch provided in the fixed end 13 is fixed by pressing with a set screw.
In addition, the inclined surface provided in the front-end | tip part of the temporary shaft 11 is not restricted to the above, The inclined surface which formed the several inclined surface polygonally may be sufficient, and it may be a combination of a conical surface and a polygonal inclined surface. Good.

  Reference numeral 16 denotes a nut cradle, which is made of a steel material such as alloy steel, and is an annular member provided with an installation hole 16a for installing the nut 4 to be assembled in the vertical direction and fitting the outer peripheral surface thereof. In addition, a through hole 16b having a gap 17 formed between the outer diameter of the temporary shaft 11 is formed at the center, and the fitting portion 16c formed at the end opposite to the installation hole 16a is connected to the end of the slider 18. It is attached by loosely fitting in the mounting hole 18a.

Further, a gap 17 formed by the through hole 16 b and the outer diameter of the temporary shaft 11 is connected to a gap 19 formed by the outer peripheral surface of the temporary shaft 11 and the inner peripheral surface of the nut 4.
Further, on the outer peripheral surface of the fitting portion 16c of the nut receiving base 16, a plurality of indexing grooves 16d which are V-shaped grooves aligned with the angular positions of a plurality of connecting paths 8 formed in the nut 4 along the axial direction thereof. The tip of a ball plunger 20 as a positioning member protruding in the radial direction on the inner peripheral surface of the mounting hole 18a at the end of the slider 18 is fitted into the indexing groove 16d so that a plurality of circulations of the nut 4 is achieved. It functions as an angle indexing mechanism when the ball 6 is loaded on the road.

Further, the installation hole 16a of the nut cradle 16 is also provided with a ball plunger 20 projecting radially on the inner peripheral surface thereof, and its tip presses the outer peripheral surface of the nut 4, so that the nut 4 and the nut cradle 16 are provided. Synchronize with and rotate.
A suction port 21 is formed through the cylindrical side wall of the slider 18 and is connected to a vacuum generator (not shown) such as a vacuum pump by a tube or the like.

Reference numeral 22 denotes a support block, which is a cylindrical member made of a steel material such as alloy steel. The outer peripheral surface of the support member is loosely fitted with the inner peripheral surface of the slider 18 so that the slider 18 is axially connected to the shaft 14. Supports reciprocation.
The slider 18 is provided with an axial positioning mechanism (not shown) at the end opposite to the mounting portion of the nut cradle 16 and supports the nut cradle 16 with respect to the support block 22 so as to be movable up and down.

Reference numeral 24 denotes a rolling bearing such as a ball bearing. The inner ring is fitted to the shaft 14 and the outer ring is fitted and fixed to the inner peripheral surface of the support block 22 so that the shaft 14 is rotatable with respect to the support block 22. I support it.
Reference numeral 25 denotes a sealing body, which is an annular member made of an elastic material such as natural rubber or synthetic rubber, and its outer peripheral surface is fitted and fixed to the support block 22 and is provided on its inner peripheral surface. The lip portion slidably contacts the outer peripheral surface of the shaft 14 and functions as a contact seal.

  Reference numeral 26 denotes a negative pressure chamber, which is a space partitioned by the inner peripheral surface of the slider 18 and the nut holder 16, the temporary shaft 11, the shaft 14, the support block 22, and the seal body 25, and is assembled when the ball screw device 1 is assembled. The air in the negative pressure chamber 26 is sucked from the suction port 21, and the negative pressure is supplied to the gap 19 formed by the outer peripheral surface of the temporary shaft 11 and the inner peripheral surface of the nut 4 via the gap 17. Have.

  Reference numeral 27 denotes a ball insertion jig, in which an insertion portion 28 having an outer diameter obtained by subtracting a predetermined clearance margin from the diameter of the inner peripheral surface of the nut 4 is formed, and a conical shape of the temporary shaft 11 is formed on the end surface of the insertion portion 28. A conical recess 28a facing the protrusion 12 and having the same conical surface as the conical protrusion 12 is formed, and the ball is introduced from the upper surface 27a to the conical recess 28a through the ball insertion jig 27 in the axial direction. A hole 29 is formed.

  When the above components are assembled into the assembly device 10 of the ball screw device 1, the rolling bearing 24 and the seal body 25 are fitted to the inner peripheral surface of the support block 22 and assembled, and the shaft 14 is sealed. 25, the shaft 14 is fitted and assembled to the inner ring of the rolling bearing 24, the inner circumferential surface of the slider 18 is loosely fitted to the outer circumferential surface of the support block 22, and is supported by a positioning mechanism (not shown).

Then, the fixed end 13 of the temporary shaft 11 is inserted into the shaft 14 and fastened and fixed with a set screw, the temporary shaft 11 is inserted into the through hole 16b of the nut receiving base 16, and the fitting portion 16c of the nut receiving base 16 is inserted. The assembly device 10 is assembled by inserting it into the mounting hole 18a of the slider 18 and fitting the tip of the ball plunger of the mounting hole 18a into the indexing groove 16d.
The nut 4 is inserted vertically into the installation hole 16a of the nut receiving base 16 of the assembly device 10 of the ball screw device 1 assembled in this way while the inner diameter side of the nut 4 to be assembled is inserted into the temporary shaft 11. Then, it is pressed and installed at the tip of the ball plunger 20 in the installation hole 16a, and the slider 18 is moved up and down by a positioning mechanism (not shown) so that the conical surface of the conical protrusion 12 of the temporary shaft 11 and the outer peripheral surface of the temporary shaft 11 are located. A corner portion (referred to as a shoulder portion 30) is positioned near the lower portion of the upper opening to the nut raceway groove 5 of the connection path 8 of the lowest frame portion 7 of the nut 4.

  And the insertion part 28 of the ball | bowl insertion jig 27 is inserted in the nut 4, and the space | interval of the conical surface of the conical recessed part 28a and the conical surface of the conical protrusion 12 of the temporary shaft 11 is integrated in the nut 4 used as an assembly object. The distance between the steel balls 6 is larger than the diameter of the steel balls 6, and the outlets of the ball introduction holes 29 are assembled toward the angle direction of the upper opening to the nut raceway groove 5 of the connection path 8 of the lowermost frame portion 7 of the nut 4. A predetermined number of steel balls 6 to be loaded in one circulation path are inserted into the ball introduction hole 29 of the ball insertion jig 27 using a counting pan or the like, and a vacuum generator (not shown) is operated to negatively pressurize the negative pressure chamber 26. Maintain state.

  The steel ball 6 thrown into the ball introduction hole 29 is thrown onto the conical protrusion 12 from the opening of the ball introduction hole 29 of the conical recess 28a, and rolls on the conical surface of the conical protrusion 12 as shown in FIG. When the temporary shaft 11 gathers around the shoulder portion 30 of the temporary shaft 11 and is rotated by the shaft 14 supported by the rolling bearing 24, the steel ball 6 moves between the outer peripheral surface of the temporary shaft 11 and the nut raceway groove 5 of the nut 4. Sent in between.

  At this time, negative pressure is applied from the negative pressure chamber 26 to the gap 19 between the outer peripheral surface of the temporary shaft 11 and the inner peripheral surface of the nut 4 via the gap 17 between the outer peripheral surface of the temporary shaft 11 and the through hole 16b of the nut cradle 16. The steel balls 6 gathered around the shoulder 30 of the temporary shaft 11 due to the negative pressure of the clearance 19 are sucked downward and the clearance between the shoulder 30 of the temporary shaft 11 and the inner peripheral surface of the nut 4 The steel ball 6 is held in a stable state, and the steel ball 6 is pressed against the shoulder 30 of the temporary shaft 11, and the frictional force therebetween increases to rotate a predetermined number of times by rotation of the temporary shaft 11. The steel ball 6 is fed into the circulation path of the nut 4 without difficulty, and starts from the lower opening of the nut raceway groove 5 of the connection path 8 so that the gap between the nut raceway groove 5 and the outer peripheral surface of the provisional shaft 11 is sequentially spaced from the bottom. To align.

The holding of the steel ball 6 by this negative pressure is particularly effective when the weight of the steel ball 6 is light.
That is, when the own weight is light, the steel ball 6 may be pushed into the connection path 8 of the top part 7 in the feeding to the circulation path only by its own weight, and the feeding to the circulation path becomes unstable. However, if the steel balls 6 are held around the shoulder 30 of the temporary shaft 11 by negative pressure as in this embodiment, the steel balls 6 gathered on the shoulder 30 can be smoothly fed into the circulation path. Because.

  In this way, when the steel ball 6 is loaded in the lowest circulation path of the nut 4, the slider 18 is lowered by a positioning device (not shown), and the shoulder 30 of the temporary shaft 11 is moved to the top of the nut 4. The nut 7 is positioned near the lower part of the upper opening of the connecting path 8 of the portion 7, and the tip of the ball plunger of the mounting hole 18 a is fitted into the next indexing groove 16 d of the nut table 16, The angle direction of the upper opening portion of the connection path 8 of the top portion 7 of the nut 4 that rotates in synchronization with the nut receiving base 16 is set toward the outlet direction of the ball introduction hole 29 of the ball insertion jig 27, and the same as described above. The steel ball 6 is loaded into the circulation path while sucking the steel ball 6, and this is repeated sequentially to load the steel ball 6 from the lower circulation path toward the upper circulation path. A steel ball 6 is loaded into the circulation path.

Thereafter, the ball insertion jig 27 is removed, a sleeve (not shown) is fitted to the conical protrusion 12 of the temporary shaft 11, the nut 4 is pulled up while pushing the sleeve, and the nut 4 is transferred to the sleeve. 2 is screwed together to assemble the ball screw device 1.
Thus, in this embodiment, the steel balls 6 gathered on the shoulder 30 of the temporary shaft 11 are held by the negative pressure between the shoulder 30 and the inner peripheral surface of the nut 4, and the temporary shaft 11 is rotated. Since the steel ball 6 is fed into the circulation path of the nut 4, the steel ball 6 gathered around the shoulder portion 30 of the temporary shaft 11 is sucked downward and the steel ball 6 is stabilized on the shoulder portion 30 of the temporary shaft 11. The frictional force between the steel ball 6 held by the shoulder 30 of the temporary shaft 11 and the shoulder 30 increases and the temporary shaft 11 rotates, so that the steel ball 6 is easily placed in the circulation path of the nut 4. Can be sent to.

This is particularly effective in preventing clogging when the weight of the steel ball 6 is light or when the lead of the nut raceway groove 5 is small.
Further, since the steel ball 6 is sucked and smoothly fed into the circulation path of the nut 4, it becomes unnecessary to push the steel ball 6 with an insertion rod or the like, and the steel ball 6 is not damaged. .
Further, the nut raceway groove of the connecting path 8 of the top portion 7 of the nut 4 by an angle indexing mechanism in which the ball plunger 20 provided in the mounting hole 18a of the slider 18 is fitted to the indexing groove 16d provided in the nut receiving base 16 is provided. 5 is matched with the direction of the exit of the ball introduction hole 29 of the ball insertion jig 27, the index position of the ball insertion jig 27 and the nut 4 can be easily indexed.

Further, the nut 4 installed on the nut cradle 16 is installed by indexing the angular position between the ball insertion jig 27 and the nut 4 by an angle indexing mechanism, and a predetermined number of steels are formed on the conical protrusion 12 of the temporary shaft 11. By simply inserting the ball 6 and rotating the temporary shaft 11 while supplying a negative pressure, the steel ball 6 can be easily loaded into the nut 4 and the work time for loading the steel ball can be shortened. .
As described above, in this embodiment, the nut is installed in the vertical direction on the nut support supported by the support block of the assembly device of the ball screw device so as to be movable up and down, and the support block can be rotated on the inner diameter side of the nut. The temporary shaft supported on the temporary shaft is inserted, and negative pressure is supplied from the negative pressure chamber to the gap between the shoulder of the conical protrusion of the temporary shaft and the inner peripheral surface of the nut. The steel balls are collected on the shoulder of the temporary shaft by the conical protrusions, and the steel ball sucked and held by the negative pressure is smoothly fed into the nut raceway groove using the frictional force with the shoulder due to the rotation of the temporary shaft. Even when the lead of the nut raceway groove is small, clogging can be prevented and damage to the steel ball can be prevented even if the steel ball loaded in the circulation path has a small diameter and its own weight is light. The effect that it can prevent is acquired.

In the above embodiment, the ball is described as a steel ball, but the ball is not limited to the above, and may be a lightweight ball formed of a ceramic material or a resin material. If the present invention is applied to a ball formed of such a material, the same effect as described above can be obtained.
In addition, the negative pressure chamber is described as being a space that is opened by a suction port on the side wall of the slider, and is partitioned by the inner peripheral surface of the slider and a nut holder, a temporary shaft, a shaft, a support block, and a seal body. The negative pressure chamber is not limited to the above, and any configuration may be used as long as the negative pressure chamber supplies a negative pressure to the gap between the shoulder of the conical protrusion and the inner peripheral surface of the nut.

Furthermore, although the cross-sectional shape of the index groove has been described as a V-shape, the cross-sectional shape of the index groove is not limited to the above, and may be a rectangular shape, a trapezoidal shape, an arc shape, or the like.
Further, in each of the above embodiments, when the screw shaft is screwed to the nut via the steel ball, the nut is once transferred to the sleeve, and then the nut is screwed to the screw shaft. A conical protrusion or C chamfer of the temporary shaft may be formed in accordance with the shape of the shaft end, and may be directly screwed onto the screw shaft while rotating the nut. Thereby, the assembly efficiency of the ball screw device can be improved.

  Further, in each of the above embodiments, the screw shaft of the ball screw device is rotated and the nut is moved in the axial direction. However, in the ball screw device of the type in which the nut is rotated and the screw shaft is moved in the axial direction. The same effect can be obtained even when the present invention is applied.

Sectional drawing which shows the assembly apparatus of the ball screw apparatus of an Example Sectional drawing which shows the ball screw apparatus of an Example Explanatory drawing which shows the ball loading state of the assembly apparatus of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Screw shaft 3 Axis raceway groove 4 Nut 5 Nut raceway groove 6 Ball 7 Top part 8 Connection way 10 Assembly apparatus 11 Temporary shaft 12 Conical protrusion 13 Fixed end 14 Shaft 15 Fitting hole 16 Nut stand 16a Installation Hole 16b Through-hole 16c Fitting portion 16d Indexing groove 17, 19 Clearance 18 Slider 18a Mounting hole 20 Ball plunger 21 Suction port 22 Support block 24 Rolling bearing 25 Seal body 26 Negative pressure chamber 27 Ball insertion jig 21a Top surface 28 Insertion portion 28a Conical recess 29 Ball introduction hole 30 Shoulder

Claims (3)

A screw shaft having a spiral shaft raceway groove formed on the outer peripheral surface, a cylindrical nut having a nut raceway groove opposed to the shaft raceway groove on the inner peripheral surface, and a connecting path for connecting the nut raceway groove; In an assembly device of a ball screw device comprising a plurality of balls circulating in a circulation path composed of the shaft raceway groove, the nut raceway groove and a connection path,
A support block; a nut holder that vertically installs the nut, and supports the nut so as to be movable up and down relative to the support block; and the support inserted into an inner diameter side of the nut installed on the nut holder. A temporary shaft that is rotatably supported by the block, an inclined surface formed at the tip of the temporary shaft, a shoulder between the inclined surface and the outer peripheral surface of the temporary shaft, and an inner peripheral surface of the nut. An assembly apparatus for a ball screw device, comprising: a negative pressure chamber for supplying a negative pressure to the gap. In claim 1,
An assembly apparatus for a ball screw device, wherein the inclined surface of the temporary shaft is a conical protrusion. Using the ball screw device assembling apparatus according to claim 1 or 2,
A gap between the shoulder portion and the inner peripheral surface of the nut due to the negative pressure supplied from the negative pressure chamber with a predetermined number of balls loaded in the circulation path thrown into the inclined surface of the temporary shaft. The ball screw device is assembled by rotating the temporary shaft and feeding the ball into the circulation path.

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