JP2015031322A - Ball screw and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw and a manufacturing method for the ball screw which are capable of reducing manufacturing cost and preventing deterioration of lubrication in a load raceway caused by operation of the ball screw.SOLUTION: In a ball screw, a raceway constituted by a raceway groove 11 of a screw shaft 10 and a raceway groove 21 of a nut 20, includes a load raceway on which balls 30 are rollably disposed, and a not-loaded raceway on which the balls 30 are not disposed and grease is retained.

Description

  The present invention relates to a ball screw and a manufacturing method thereof, and more particularly, to a ball screw having a circulation member and a manufacturing method thereof.

Conventionally, an internal circulation type ball screw is known in which a plurality of balls interposed between a screw shaft and a nut are circulated. FIG. 7 shows a conventional internal circulation type ball screw.
In this type of ball screw, as shown in FIG. 7, a raceway groove 11 is formed on the outer peripheral surface of the screw shaft 10 with a predetermined lead. A raceway groove 21 is formed on the inner peripheral surface of the nut 20 corresponding to the raceway groove 11. These track grooves 11 and 21 form a track S when the ball (rolling element) 30 rolls, and a plurality of balls 30 are arranged on the track S.

The nut 20 is provided with a return passage that connects one end and the other end of the track S so that the ball 30 can circulate, and returns the ball 30 rolling on the track S from one end to the other end. A circulating top (also referred to as a deflector) 22 is used as the return passage.
In such a ball screw, a technique for holding grease in the ball screw for lubrication is disclosed (see Patent Documents 1 and 2).
Patent Document 1 discloses a technique in which a grinding relief groove is used as a stagnation ditch and grease is supplied periodically. Patent Document 2 discloses a technique in which a space portion is formed between circuits and grease is applied to the space portion.

Japanese Patent No. 5056973 JP 2008-19932 A

However, in the ball screw disclosed in Patent Document 1, the ball screw is scraped to the end of the nut by the operation of the ball screw (ball rolling), and the rolling range of the ball becomes longer when the operation time is long. In some cases, there was insufficient sliding.
In addition, since the ball screw disclosed in Patent Document 2 has a configuration in which “two pitches or more” circulation paths are provided and a space is provided between circuits, the manufacturing cost for forming this space is only excessive. However, there is a problem that the versatility is poor.
Accordingly, the present invention has been made paying attention to the above-mentioned problems, and its purpose is to suppress the manufacturing cost and prevent the decrease in lubrication in the load track accompanying the operation of the ball screw and the manufacturing thereof. It is to provide a method.

In one aspect of the ball screw for achieving the above object, a screw shaft having a spiral raceway groove on the outer peripheral surface, a nut having a spiral raceway groove on the inner peripheral surface, and a nut attached to the nut A load raceway in which a ball is rollably arranged in a raceway formed by the raceway groove of the screw shaft and the raceway groove of the nut, and the ball is returned to the front raceway, and a non-load raceway where the ball is not placed A circulation member divided into
Grease is held on the unloaded track.

According to such a ball screw, the grease applied to the groove of the nut where the ball between the circulating members (tops) does not roll is not scraped off by operation. Further, since the base oil of the grease is supplied to the screw shaft, nut, and ball gradually over a long period of time due to the temperature rise during operation of the ball screw and the environmental temperature, there is no possibility that the lubrication in the operating range will be exhausted. Further, since the grease is held on the existing unloaded track, the cost for manufacturing the region for holding the grease is not required.
Therefore, it is possible to provide a ball screw that can suppress the manufacturing cost and prevent a decrease in lubrication in the load track accompanying the operation of the ball screw.

In addition, a certain aspect of the ball screw manufacturing method for achieving the above object includes a screw shaft having a spiral raceway groove on the outer peripheral surface, and a nut having a spiral raceway groove on the inner peripheral surface. The ball is disposed on the track formed by the raceway groove of the screw shaft and the raceway groove of the nut and mounted on the nut so that the ball can roll and the ball is returned to the front track. A ball screw manufacturing method comprising a circulating member that is divided into a non-loading track that is not performed,
A grease application step of applying grease to a non-load raceway groove that constitutes a non-load raceway in which the balls are not arranged among the raceways;
An assembly step of assembling the screw shaft, the nut, the ball, and the circulation member.

According to such a ball screw manufacturing method, the grease applied to the unloaded track groove is held on the unloaded track, and the grease is also supplied to the loaded track via the screw shaft. It is possible to prevent a decrease in lubrication along the load track, and it becomes difficult to insert a ball between the load track and the load track during assembly, and the operating torque increases even if it is inserted by mistake. The operator can easily recognize the wrong insertion.
Here, in the method for manufacturing the ball screw, the grease may be cooled to room temperature and applied to the unloaded track.
According to such a ball screw manufacturing method, the viscosity of the grease cooled from room temperature is increased and the operating torque is increased, so that the operator can more easily recognize the erroneous insertion.

  According to the present invention, it is possible to prevent a decrease in lubrication on the load track accompanying the operation of the ball screw.

It is a side view which shows the structure in embodiment with a ball screw. It is a fragmentary sectional view which follows the axial direction which shows the structure in embodiment with a ball screw. It is sectional drawing which follows the axial direction which shows the structure in embodiment with a ball screw. It is front sectional drawing which shows the structure of the ball screw assembly apparatus used in embodiment with the manufacturing method of a ball screw. It is side surface sectional drawing which shows the structure of the ball screw assembly apparatus used in embodiment with the manufacturing method of a ball screw. It is a figure explaining the filling state of the ball | bowl of a ball screw apparatus, (a) is the front view seen from the axial direction of the nut, (b) is 6b-6b sectional drawing of (a). It is a fragmentary sectional view which shows the structure of the conventional ball screw.

Embodiments of a ball screw and a manufacturing method thereof according to the present invention will be described below with reference to the drawings.
FIG. 1 is a side view showing the configuration of the ball screw of the present embodiment. FIG. 2 is a partial cross-sectional view along the axial direction showing the configuration of the ball screw of the present embodiment. FIG. 3 is a cross-sectional view along the axial direction showing the configuration of the ball screw of the present embodiment. In FIG. 2 and FIG. 3, for ease of explanation, only the non-load trajectory is hatched and not shown in the cross section. Further, a structure similar to that of the conventional ball screw will be described with reference to FIG. 7 as necessary.

(Ball screw configuration)
As shown in FIG. 1, the ball screw of this embodiment includes a screw shaft 10, a nut 20, a ball 30, and a circulation member 22. The nut 20 is fitted to the screw shaft 10 with a predetermined gap, and the inner diameter of the nut 20 is larger than the outer diameter of the screw shaft 10. The nut 20 has a substantially cylindrical shape, and is provided with a flange for coupling with a guide object at an end thereof.
On the outer peripheral surface of the screw shaft 10, a spiral raceway groove 11 having a substantially semicircular cross section is provided. Further, a spiral raceway groove 21 having a substantially semicircular cross section is provided on the inner peripheral surface of the nut 20 with the same lead as the raceway groove 11. All of these semicircular shapes have a radius of curvature larger than the radius of the ball. Then, the ball 30 is arranged to roll in a track S (see FIG. 7) having a substantially circular cross section formed by these track grooves 11 and 21.

  Here, a plurality of circulation members 22 are provided on the nut 20 as a mechanism for returning the ball 30 to the track S in front. The circulation member (hereinafter sometimes referred to as a “koma”) 22 is formed with a track groove 22 a that connects one end of the track S and the other end of the track S one turn before. Therefore, the ball 30 rolling on the track S toward the circulation member 22 is lifted up in the radial direction of the screw shaft 10 to get over the thread of the screw shaft 10 and returned to the track S before one winding (one lead before). The ball 30 can be circulated. Thus, a substantially circular infinite circulation path is formed outside the screw shaft 10 by the circulation path formed by the track S and the track groove 22a.

That is, the load raceway groove 11A communicating with the raceway groove 22a provided in the circulation member 22 and the raceway groove 21 are arranged so that the balls 30 can roll together with the two circulation members 22, and a load raceway that forms a closed circuit. Make. The track S has this load track and a non-load track between the two load tracks, that is, the non-load track groove 11B and the track groove 21 where no balls are arranged. In the present embodiment, grease is held on the unloaded track. Note that this grease only needs to be applied to at least the non-load raceway groove 21B constituting the non-load raceway.
With such a configuration, the ball 30 rolls in the track S as the screw shaft 10 rotates relative to the nut 20, and the nut 20 moves in the axial direction of the screw shaft 10 with respect to the screw shaft 10. It is possible to move linearly.

  In particular, in this embodiment, since the grease is held on the unloaded track, the grease is not scraped by the operation of the ball screw. Since oil is supplied to the screw shaft, nut, and ball little by little for a long time, there is an effect that the lubrication in the operating range is not exhausted.

(Ball screw manufacturing method)
Next, a ball screw manufacturing method according to the present embodiment will be described with reference to the drawings. The manufacturing method of the ball screw of this embodiment includes a grease application process and an assembly process.
FIG. 4 is a front sectional view showing a configuration of a ball screw assembling apparatus used in the ball screw manufacturing method according to the present embodiment. FIG. 5 is a side sectional view showing the configuration of the ball screw assembling apparatus used in the ball screw manufacturing method according to this embodiment. 6A and 6B are views for explaining a state of filling the ball of the ball screw device according to the present embodiment, wherein FIG. 6A is a front view seen from the axial direction of the nut, and FIG. 6B is 6b-6b of FIG. It is sectional drawing. As shown in FIGS. 4 to 6, the nut 20 as an assembly target installed in the ball screw assembly apparatus 40 has a circulating member (top) 22 attached to four locations with a 180 ° shift in the circumferential direction. It is a nut for screws.

  The temporary shaft 41 is a rod-like member that is inserted into the inner diameter side of the nut 20 instead of the screw shaft 10 when the ball 30 is loaded into the nut 20 made of a steel material such as alloy steel. The temporary shaft 41 has an inner circumference smaller than the diameter of the ball 30 than the BCD (Ball Center Diameter) of the nut 20 to be assembled, that is, an outer diameter smaller than the inner circumference of the ball 30 circulating in the circulation path. .

The tip of the temporary shaft 41 is provided with a conical conical protrusion 42 having a conical surface as an inclined surface, and a fixed end 43 on the opposite side is fitted to a shaft 45 fixed to the base 44 with a screw. Then, the notch provided in the fixed end 43 is pressed and fixed by the set screw 46. Thereby, the temporary shaft 41 is fixed to the base 44 via the shaft 45.
In addition, the inclined surface provided in the front-end | tip part of the temporary shaft 41 is not restricted 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.

The nut pedestal 47 is an annular member which is made of a steel material such as alloy steel, and is provided with an installation hole 47a for fitting the outer peripheral surface of the nut 20 to be assembled in the vertical direction. A through hole 47b in which the temporary shaft 41 is loosely fitted is formed at the center.
The positioning block 48 is formed in accordance with the nut 20 to be assembled, and is made of a steel material such as alloy steel. The positioning block 48 is an arcuate member that is mounted on the base 44 by two pilot pins 49 provided on the base 44, and has an inclined portion 48a on which the roller follower 50 slides on the outer periphery thereof. The portions 48b are provided alternately.

  The step portion 48b provided in the positioning block 48 has the same number of steps as the number of circulation members 22 of the nut 20 to be assembled, that is, the number of circulation paths formed in the ball screw, and the step is the nut to be assembled. It is formed so as to coincide with the pitch between the circulating members 22 in the axial direction of the nut 20 of the 20 circulating members 22. The inclined portion 48a is formed so as to smoothly connect the step portions 48b.

Since the nut 20 assembled using the ball screw assembly apparatus 40 of the present embodiment is provided with the circulation member 22 at four locations, the number of steps 48a is four.
The roller follower 50 is formed by using a rolling bearing such as a ball bearing, and the inner diameter portion thereof is press-fitted into a handle 52 screwed to a large diameter portion of a slider 51 formed in a stepped cylindrical shape so as to be freely rotatable. The outer diameter portion is supported, and slides while rotating the inclined portion 48 a and the stepped portion 48 b of the positioning block 48.
The slide bearing 54 is loosely fitted on the outer peripheral surface of the shaft 45 and is disposed by being press-fitted or fixed by screwing inside the cylindrical portion of the slider 51, so that the slider 51 can be moved up and down and rotated with respect to the shaft 45. I support it.

The height adjustment nut 55 is a cylindrical member made of a steel material such as alloy steel, and a screw portion that is screwed into a screw portion provided in a small diameter portion of the slider 51 is provided on the inner peripheral surface of the lower end portion thereof. It has been.
The clamp knob 56 is screwed into a screw portion provided on the cylindrical wall of the height adjustment nut 55 and has a function of fixing the rotation of the height adjustment nut 55 by tightening a small diameter portion of the slider 51 at the tip. Yes.
A thrust bearing 58 such as a thrust needle bearing sandwiched between thrust rings 57 is installed between the upper end surface of the height adjustment nut 55 and the lower end surface of the nut receiving base 47, and the nut receiving base 47 is attached to the base 44. On the other hand, it is supported rotatably.

  When the above-described components are assembled into the ball screw assembling apparatus 40, the shaft 45 and the pilot pin 49 are attached to the base 44 and the positioning block 48 is fitted to the pilot pin 49 and attached to the base 44. Thereafter, the handle 52 attached with the roller follower 50 is screwed and fixed to the slider 51, and the inner peripheral surface of the slide bearing 54 provided on the slider 51 is loosely fitted to the shaft 45, and the slider 51 is assembled to the shaft 45.

  Then, the fixed end 43 of the temporary shaft 41 is inserted into the shaft 45 and is fastened and fixed by the set screw 46, and the thread portion of the height adjusting nut 55 in which the thrust bearing 58 and the clamp knob 56 sandwiched by the thrust ring 57 are assembled. Is screwed into the threaded portion of the slider 51. Then, the slider 51 is fastened and assembled by the clamp knob 56, and the assembly table 40 is assembled by assembling the nut receiving base 47 loosely fitted to the temporary shaft 41 to the upper thrust ring 57.

The adjustment of the ball screw assembling apparatus 40 assembled in this way is performed by installing the nut 20 to be assembled vertically in the installation hole 47a of the nut receiving base 47 arranged at the upper part of the assembling apparatus 40, and then operating the handle 52. Thus, the slider 51 is rotated to guide the roller follower 50 to the lowermost inclined surface 48a of the positioning block 48 and to be positioned at the lowermost step 48b.
At this time, a corner portion (hereinafter referred to as a shoulder portion 60) between the conical surface of the conical protrusion 42 of the temporary shaft 41 and the outer peripheral surface of the temporary shaft 41 is connected to the raceway groove 22 a of the uppermost circulation member 22 of the nut 20. It is located in the vicinity of the upper opening 22b (see FIG. 6).

<Grease application process>
Here, in the present embodiment, as the “grease application step”, grease is applied to the non-load raceway groove 21B of the nut 20. This makes it difficult for the ball to be erroneously inserted into the non-load track during assembly, and the operating torque increases even if it is accidentally inserted, making it easy for the operator to recognize.
In addition, it is preferable that the grease applied to the unloaded raceway groove 21B is cooled. This makes it more difficult for the ball to be erroneously inserted into the unloaded track, and even if it is accidentally inserted, the operating torque is further increased compared to when the normal temperature grease is applied, so that the operator is also aware. Cheap. In addition to using the cooled grease, the nut with grease applied to the unloaded raceway groove 21B may be cooled.

<Assembly process>
Then, as the “assembly process”, when a predetermined number of balls 30 to be loaded into one circulation path are introduced from above the nut 20 to the inner diameter side thereof using a counting pan or the like, the introduced balls 30 are provided with a conical protrusion 42. Rolls around the conical surface and gathers around the shoulder 60 of the temporary shaft 41.
Thereafter, when the nut 20 is rotated in the counterclockwise direction in FIG. 6 through the thrust bearing 58 together with the nut cradle 47, the ball 30 rolls downward along its inclination by the lead of the raceway groove 21 of the nut 20 by its own weight. drop down. When the ball 30 rolls down, the groove of the circulation member 22 is deep and the ball 30 escapes to the outside, so that the frictional force between the shoulder portion 60 of the temporary shaft 41 and the raceway groove 21 of the rotating nut 20 becomes difficult to act. Therefore, it stays in the vicinity of the lower opening 22c of the raceway groove 21 of the nut 20 of the circulation member 22, and is sequentially aligned between the raceway groove 21 of the nut 20 and the outer peripheral surface of the temporary shaft 41 without any gap from the bottom. To go.

  When the nut 20 is continuously rotated in this state, the interval between the balls 30 is opened at the highest position of the raceway groove 21 of the nut 20 near the upper opening 22b of the raceway groove 22a. Then, the ball 30 that cannot fully enter the raceway groove 21 of the nut 20 and remains in the vicinity of the shoulder portion 60 is already aligned with the raceway groove 21 of the nut 20 by the frictional force of the shoulder portion 60 accompanying the rotation of the nut 20. It is possible to load all the balls 30 that have been inserted between the balls 30 into one circulation path.

At this time, in FIG. 6B, if the ball 30 remains on the left shoulder 60 of the circulation member 22, the clamp knob 56 is loosened and the height adjusting nut 55 is rotated to remove the nut 20 from the temporary shaft 41. Raise a little against. On the other hand, if the ball 30 remains on the shoulder 60 on the right side of the circulation member 22, the adjustment nut 55 is rotated to slightly lower the nut 20 with respect to the temporary shaft 41 so that the shoulder 60 and the upper opening 22b The clamp knob is adjusted by adjusting the relative position to a position where the ball 30 can smoothly move into the raceway groove 21 of the nut 20, that is, a position where the shoulder portion 60 of the temporary shaft 41 is located near the lower portion of the upper opening 22b. The height adjusting nut 55 is fixed by 56.
After the height of the shoulder portion 60 is adjusted in this way, the stepped portion 48b of the positioning block 48 is formed in accordance with the pitch of the nut 20 to be assembled. It becomes unnecessary.

  When the ball 30 is loaded into the nut 20 using the ball screw assembly apparatus 40 adjusted as described above, the nut 20 to be assembled is vertically installed in the installation hole 47a of the nut receiving base 47 of the ball screw assembly apparatus 40. The roller follower 50 is positioned on the uppermost step 48b of the positioning block 48 by the handle 52 in the same manner as in the above adjustment. At this time, the shoulder portion 60 of the temporary shaft 41 is positioned near the lower portion of the upper opening portion 22b of the raceway groove 22a of the lowest circulating member 22 of the nut 20.

Then, in the same manner as in the case of the above adjustment, when a predetermined number of balls 30 to be loaded into one circulation path from above the nut 20 are thrown in and the thrown-in balls 30 gather around the shoulder portion 60 of the temporary shaft 41, The nut 20 is rotated together with the nut cradle 47 several times in the counterclockwise direction in FIG. 6, and all the balls 30 thrown in are loaded into the lowest-order circulation path in the same manner as in the above adjustment.
Next, the roller follower 50 is positioned by the handle 52 on the stepped portion 48b of the positioning block 48, and the shoulder portion 60 of the temporary shaft 41 is moved upwardly of the connecting path 22a of the circulating member 22 above the nut 20. In the same manner as described above, the ball 30 is loaded into the circulation path, and this is repeated sequentially to load the ball 30 from the lower circulation path toward the upper circulation path. The ball 30 is loaded into the circulation path.
Thereafter, the sleeve 61 is fitted to the conical protrusion 42 of the temporary shaft 41, the nut 20 is pulled up while the sleeve 61 is pushed in, the nut 20 is moved to the sleeve 61, and a predetermined screw shaft 10 is screwed in place of the sleeve 61. Assemble the ball screw.

  As described above, in the present embodiment, the ball screw assembly device 40 is provided with a temporary shaft having a conical protrusion fixed to the base and a nut in the vertical direction, and this is rotatable with respect to the base. And a positioning block for positioning the shoulder portion of the temporary shaft at the lower portion of the upper opening to the nut raceway groove of the connection path by raising and lowering the nut support by the stepped portion. The ball is collected on the shoulder of the temporary shaft by the conical protrusions on the shaft, and the ball is loaded into the nut raceway groove using the ball's own weight and the frictional force associated with the relative rotation of the nut raceway groove and the temporary shaft. Even with a small lead, clogging of the ball can be prevented and damage to the ball can be prevented.

As described above, according to the present embodiment, it is possible to provide a ball screw and a method for manufacturing the ball screw that can suppress the manufacturing cost and prevent a decrease in lubrication in the load track accompanying the operation of the ball screw.
The ball screw and the manufacturing method thereof according to the present embodiment are suitable for a ball screw used for an actuator or the like, for example.
The ball screw and the manufacturing method thereof according to the present invention have been described above. However, the ball screw and the manufacturing method thereof according to the present invention are not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. Deformation is possible.

10 Screw shaft 11 Raceway groove 20 Nut 21 Raceway groove 21A Load raceway groove 21B Non-load raceway groove 22 Circulating member (top)
22a Load raceway groove 30 ball (rolling element)
S orbit

Claims (3)

A screw shaft provided with a spiral raceway groove on the outer peripheral surface, a nut provided with a spiral raceway groove on the inner peripheral surface, a raceway groove of the screw shaft and a raceway groove of the nut attached to the nut A circulating member that divides the track formed by a load track that returns the ball to a previous track and a non-load track in which the ball is not disposed.
A ball screw characterized in that grease is held on the unloaded track. A screw shaft provided with a spiral raceway groove on the outer peripheral surface, a nut provided with a spiral raceway groove on the inner peripheral surface, a raceway groove of the screw shaft and a raceway groove of the nut attached to the nut The ball screw is provided with a circulating member that divides the track formed by the load track into which the ball is rollable and returns the ball to the previous track and the non-load track without the ball. And
A grease application step of applying grease to an unloaded track groove constituting the unloaded track;
A method for manufacturing a ball screw, comprising: an assembling step for assembling the screw shaft, the nut, the ball, and the circulation member.   The ball screw manufacturing method according to claim 2, wherein the grease is cooled from room temperature and applied to the unloaded raceway groove.

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