JPH09133195A - Ball screw and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a nut of this type from falling off without a stopper as well as to manufacture it efficiently by installing a shank at both ends, providing a rolled ball screw in the interval, and making up these ends into a raised form. SOLUTION: A ball screw 1 is provided with a shank 2 with a smooth surface at both ends, installing a thread part 3 in the space, and this thread part 3 is made up of a thread ridge 4 rolled by a roll die and a thread groove 5, and a thread bottom of this thread groove 5 is deeper than a surface of the shank 2, and an end of this thread groove 5 is provided with a raised part 6. One end of the roll die is pressed a rolling start end in the midway of a blank rod, and then rolling is carried out after relatively shifting the blank rod and the roll die in the axial direction as rotating them relatively. When the other end of the roll die is reached to a rolling finishing end in the midway of the blank rod, the rolling is over, forming the raised part 6 at both ends. Therefore an insert nut of this kind will in no case fall off from the thread, and thus the requirement of a stopper at the thread end falls into disuse. In addition, a span of manufacturing time is sharply reducible as compared with a method of turning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw having shafts at both ends and a method for manufacturing the ball screw.

[0002]

2. Description of the Related Art Conventionally, a thread rolling method and an in-feed thread rolling method are known as methods for manufacturing a screw by rolling. The through-rolling method is a method in which when a roll die is pressed against a rolling object to perform rolling, a slight angle difference is provided between the lead angle of the roll die and the lead angle of the rolling object. When the roll die or the rolled object is relatively rotated, the roll die and the rolled object are rolled while relatively moving due to the difference in the lead angle, which causes a so-called walking phenomenon, which causes the roll die and the rolled object to move. When relatively rotating, rolling is automatically performed without forcibly moving in the axial direction.

The roll die 31 used at this time is
As shown in FIG. 4, conical truncated cones having a diameter outwardly reduced are symmetrically formed at both ends of the cylindrical conical section, and one conical truncated cone passes through the cylindrical section to the other conical truncated cone. A spiral ridge 32 for rolling is provided which is connected to the roll. The angle θ ″ formed by the surface connecting the vertices of the spiral protrusions 32 of the cylindrical portion and the surface connecting the vertices of the spiral protrusions 32 of the truncated cone portion is generally 3 in order to reduce friction during rolling. In addition, the distance between both end surfaces 33 and 33 'of the truncated cone portion, that is, the width q of the roll die 31 and the helical protrusion 3 of the cylindrical portion.
The relation between the boundary between the surface connecting the two vertices and the surface connecting the vertices of the spiral protrusion 32 of the truncated cone part and the distance p between the end faces 33, 33 ′ on the side of the truncated cone part is In order to reduce, p / q has a value of 0.3-0.4.

In the in-feed rolling method, as shown in FIG. 5, a roll die 31 having a predetermined width and a spiral projection 32 on its side surface is used, and the lead angle of both is matched with the material rod 41. It is a method of pressing and rolling while pushing. According to this method, since the lead angle of the roll die 31 and that of the object to be rolled are made to coincide with each other, a walking phenomenon does not occur. By rolling a screw having the width of the roll die 31 used, the shaft portion 42 is provided at both ends.
It is possible to manufacture a screw having a rolled portion 43 between the two.

When the above-mentioned in-feed method is applied to the rolling of a ball screw, unlike a triangular screw or the like which normally uses this method, in the case of a ball screw, the difference between the crest diameter and the trough diameter of the thread groove is large. During the rolling, there is a difference in the lead angle between the two. Therefore, a walking phenomenon occurs, and it becomes difficult to roll a ball screw having a shaft portion at both ends and a screw having the width of the roll die used therebetween.

Further, in the above-mentioned thread rolling method, at least one end is cut through due to a walking phenomenon, and it is difficult to roll a ball screw having shaft portions at both ends.

Therefore, in order to manufacture a ball screw having shafts at both ends, the diameter of the rolled object is made larger than the portion where only the screw rolling portion is the shafts at both ends. A method is used in which only the above portion is rolled by a roll die and rolled. When this method is used, only the thick part is rolled using the walking phenomenon, and the shafts at both ends with a small diameter are not rolled by the ball dies because the roll dies do not contact each other. The ball screw which it has can be rolled. Also, although not rolling, by turning a screw only in a predetermined part with a thread cutting tool,
It is possible to manufacture a ball screw having shafts at both ends.

[0008]

However, among the above-mentioned objects to be rolled, only the portion for thread rolling is made larger in diameter than the portions for which the shaft portions at both ends are made, and only the portion having this large diameter is formed by the roll die. In the method of thread rolling, both ends of the ball screw are cut and threaded. For this reason, the nuts fitted into the ball screw are more likely to fall off than the ball screw portion. In order to prevent the nuts from falling off, it is necessary to provide a stopper such as a sleeve at the end of the screw.

Further, in the method of manufacturing a ball screw by turning, since both ends of the ball screw are cut up, it is possible to prevent the fitted nuts from falling off from the ball screw portion. However, this method requires cutting or grinding in at least two stages of rough finishing and finishing, and it takes time for turning and grinding, resulting in poor production efficiency.

Therefore, an object of the present invention is to provide a ball screw in which nuts fitted in the ball screw are prevented from falling off without a stopper such as a sleeve, and a method for manufacturing the ball screw with high production efficiency without cutting. To provide.

[0011]

In order to solve the above-mentioned problems, the invention of a ball screw has a shaft portion at both ends, and a rolled ball screw between the shaft portions. It adopted a configuration with a raised shape.

In the invention for manufacturing a ball screw by rolling a material rod with a roll die, one end of the roll die is pressed against the rolling start end of the ball screw located in the middle of the material rod, Rolling is performed by relatively moving the roll die relative to each other in the axial direction while relatively rotating, and the other end of the roll die reaches the rolling end end of the ball screw in the middle of the material rod. At that time, the rolling process is completed, so that the ball screw having the shaft portions at both ends and the both end portions being cut up between them is manufactured.

Further, in the invention of the roll die for ball screw rolling, a truncated cone portion having a diameter outwardly reduced is formed at both ends of the cylindrical portion, and one of the truncated cone portions passes through the cylindrical portion. In a ball screw rolling roll die in which a continuous rolling helix is provided over the other truncated cone portion, the distance a between the end faces of one truncated cone portion, the distance between the end faces of the other truncated cone portion Of the roll die and the width b of the roll die
And a / b is 0.1 or more and 0.4 or less,
The structure in which a '/ b is 0 or more and 0.3 or less is adopted.

According to the present invention, the roll die relatively moves from the ball screw rolling start end in the middle of the material rod in the axial direction of the roll die and the material rod as they relatively rotate. Since the rolling is performed and the rolling is finished at a predetermined end point of the ball screw rolling in the middle of the predetermined material rod, the ball screw having the shaft portions at both ends can be rolled. In addition, since the rolling is completed at the ball screw rolling end in the middle of the material rod, as in the conventional case,
It is not necessary to use a material rod with a thick diameter only for the screw rolling part, and even if a uniform material rod or a material rod with only a thin thread rolling part is used, a ball screw with shafts at both ends Can be rolled. As a result, the screw bottom of the ball screw can be made deeper than the surface of the shaft portion at both ends, so that both end portions can be shaped so as to be cut up from the screw bottom toward the shaft portion surface. Therefore, the nuts fitted into the ball screw stop at the cut-up portion, and the nuts can be prevented from falling off without a stopper such as a sleeve. Moreover, since the shaft portions at both ends can be designed thick, it is also effective for increasing the strength of the shaft.

Further, since smooth shafts can be formed at both ends, after rolling the ball screw, it is possible to provide various devices such as guides or the like on the shafts or perform arbitrary processing. Further, since the ball screw is manufactured by rolling without cutting, the screw can be manufactured by rolling once, and the manufacturing efficiency can be improved in a short time. Furthermore, since the distance between the end faces of one of the truncated cones of the roll die can be shortened, it is possible to shorten the incompletely incomplete screw portion of the screw rolled by this truncated cone portion. It is possible to form a complete full thread portion of the screw to be made longer.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, a ball screw 1 of the present invention is provided with a shaft portion 2 having smooth surfaces at both ends, and a screw portion 3 provided between them. The threaded portion 3 is formed of a thread 4 and a thread groove 5 which are rolled by a roll die, and the thread bottom of the thread groove 5 is formed deeper than the surface of the shaft portion 2, and the end of the thread groove 5 is formed. The part has a shape that is cut up from the bottom of the screw toward the surface of the shank, forming a cut-up part 6. The depth of the thread groove 5 is such that it can be used as a ball screw.

A roll die 11 used for rolling the ball screw 1 has a cylindrical portion 1 as shown in FIG.
Frustum portions 13 and 1 that have a diameter that decreases outward at both ends
3'is also formed, and a rolling spiral ridge 18 continuous from the truncated cone portion 13 to the truncated cone portion 13 'via the column portion 12 is provided. The surface connecting the vertices of the spiral protrusions 18 of the cylindrical portion 12 forms a cylindrical side surface 16 along the outer peripheral surface of the cylinder portion, and connects the vertices of the spiral protrusions 18 on the truncated cone portions 13 and 13 'side. The faces form frustoconical side faces 17, 17 'along the frustoconical angle. The cylindrical part side face 16 and the truncated cone part side face 17 have a clearance angle of a predetermined angle θ with respect to the cylindrical part side face 16, and the cylindrical part side face 16 and the truncated cone part side face 17 ′ are conical. The base side surface 17 ′ has a clearance angle of a predetermined angle θ ′ with respect to the cylindrical side surface 16.

Next, a method of rolling a ball screw using the roll die 11 will be described. As shown in FIG. 3 (a), a rolling start end 24 in the middle of the material rod 21 has a θ ′ side end face 14 which is an end face on the side of a truncated cone 13 ′ having a clearance angle θ ′ of the roll die 11. The frustoconical side end 19 ′, which is the boundary with the frustoconical side surface 17 ′, is pressed. At this time, the truncated cone portion 13 having the clearance angle θ of the roll die 11
The θ-side end surface 15, which is the side end surface, faces the direction of the rolling end 25 of the roll die 11. When the roll die 11 is pressed against the material rod 21, the lead angle of the roll die 11 and the lead angle of the material rod 21 are not the same, but are shifted by a predetermined angle. As a result, the roll die 11 and the material rod 2
When a relative rotation of 1 occurs, a walking phenomenon occurs, and the roll die 11 and the material rod 21 are automatically moved relative to each other in the axial direction of them to perform rolling.

Since rolling is performed by a walking phenomenon, if rolling is continued as it is, rolling is performed up to the end of the material rod 21. In order to finish the rolling in the middle of the material rod 21 and form the threadless shaft portion at the end, the walking phenomenon is stopped in the middle of the material rod 21. In this case, as shown in FIG. 3B, the position at which the rolling is finished, that is, the material rod 2
The fact that the truncated cone side end 19 of the boundary between the truncated cone side surface 17 of the roll die 11 and the θ side end surface 15 has reached the rolling end end 25 of No. 1 is detected by a sensor or the like, and the roll die 11 is made of the material. Escape from stick 21. As a result, the walking phenomenon can be stopped at the correct position and the rolling can be completed.

Roll die 11 used for this rolling
As shown in FIG. 2, the clearance angle θ ′ and the clearance angle θ do not have to be the same. By pressing the roll die 11, the material rod 21 relatively advances as shown in FIG. 3A, and the screw is rolled. Therefore, the clearance angle θ is important from the point that the rolling of the screw is started, and θ is 3 to 15 °, preferably 5 to 15 °. The clearance angle θ ′ may be large because it does not relate to the direct rolling of the screw, and is 5 to 90 °, preferably 5 to 1
5 °.

Further, the distance a between the end faces of one of the truncated cone portions 13 of the roll die 11, that is, the distance a between the boundary between the side face 16 of the cylindrical portion and the side face of the truncated cone portion 17 and the .theta. Side end face 15 described above. , And the distance a between the end faces of the other truncated cone portion 13 ′ of the roll die 11, that is, the distance a between the boundary between the side face 16 of the cylindrical portion and the side face 17 ′ of the truncated cone portion and the θ ′ side end face 14 described above. 'Need not be the same. further,
The θ ′ side end surface 14 which is both end surfaces of the roll die 11
The distance between the end surface 15 and the end face 15 on the θ side, that is, the width b of the roll die 11 and the relation a is that the side of the clearance angle θ is the side on which the screw is directly rolled, and therefore has a direct influence on the occurrence of friction. Exert. Therefore, a / b is 0.1 or more and 0.4 or less, preferably 0.2 or more and 0.4 or less. a / b to 0.
When it is less than 1, friction is large and it is not preferable. On the other hand, if it is larger than 0.4, the incomplete thread portion of the thread to be rolled becomes long, which is not preferable.

The relationship between the width b and the a'is such that the clearance angle θ'is not related to the direct rolling of the screw, and a '/ b is 0 or more and 0.3 or less, 0.2 or more
The following is preferred. When it is larger than 0.3, the incomplete thread portion becomes long, which is not preferable. Further, since it does not relate to the direct rolling of the screw, there may be a state in which there is no escape, that is, θ ′ = 90 ° and a ′ / b = 0. Further, the roll die 11 has the truncated cone portion 1 at both ends thereof.
3, 13 'may be asymmetric, in which case a' /
b can be 0 or more and less than 0.2.

As shown in FIG. 3 (b), the rolling portion 23 has a complete thread portion 27 in which a screw is completely rolled and an incomplete thread portion 26, 26 'in which a screw is not completely rolled. It is formed. If the clearance angles θ and θ ′ are small or a and a ′ are long, incomplete thread portions 26 and 26 ′ of the rolled ball screw are formed at the end of rolling, so that the effective thread portion 27 becomes short. In the present invention, since rolling can be performed by sufficiently taking the clearance angle θ and the above a, the lengths of the above a ′ and the above b can be shortened and the incomplete threaded portion 26 ′ can be shortened, It is possible to reduce the resistance during rolling.

The material bar 21 used in the method for manufacturing a ball screw according to the present invention has a uniform diameter, a thick part or a thin part for rolling the ball screw. The same applies. If the diameter of the rolled part of the ball screw is thicker, depending on the diameter, if both ends of the screw do not have a raised shape but a cut through shape, the conventional method can be sufficiently used. Even if the diameter of the rolled portion of the screw is made thicker, if both ends of the screw are rounded up, the method for manufacturing a ball screw according to the present invention can be applied,
The same effect as this invention can be obtained. Also, if the diameter of the material rod is uniform or if the diameter of the part where the ball screw is rolled is thin, both ends of the screw are rounded up,
The same effect as this invention can be obtained.

[0025]

As described above, the ball screw according to the present invention has smooth shaft portions at both ends thereof, and both ends thereof have a cut-up shape, so that the nuts fitted therein fall off from the screw. No need to provide a stopper such as a sleeve at the end of the screw.

Further, since both ends have smooth shaft portions, the shaft portions can be freely processed according to the purpose.
Moreover, since the shaft portions at both ends can be designed thick, it is also effective for increasing the strength of the shaft.

Further, according to the present invention, the method of manufacturing a ball screw having smooth shaft portions at both ends by stopping the rolling during the thread rolling, compared with the conventional manufacturing method by cutting, the manufacturing time is longer. Can be greatly shortened, which can greatly contribute to the improvement of production efficiency. Furthermore, by using the roll die of the present invention, the incompletely threaded portion in the rolling portion can be shortened and the completely threaded portion can be formed longer.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of a ball screw according to the present invention.

FIG. 2 is a sectional view of an embodiment of a roll die according to the present invention.

FIG. 3 is a schematic view showing an embodiment of a ball screw manufacturing method according to the present invention.

FIG. 4 is a schematic view showing a conventional roll die.

FIG. 5 is a schematic view showing a conventional ball screw manufacturing method.

[Explanation of symbols]

 1 Ball Screw 2 Shaft Part 3 Screw Part 4 Screw Thread 5 Screw Groove 6 Screw Groove Upward Part 11 Roll Die 12 Cylindrical Part 13, 13 'Frustum Part 14 θ'side End Surface 15 θ Side End Surface 16 Cylindrical Part Side Surface 17, 17 'Frustum part side surface 18 Rotating ridge 19, 19' Frustum part side end part 21 Material rod 22 Shaft part 23 Rolling part 24 Rolling start end 25 Rolling end end 26, 26 'Incomplete thread part 27 Complete Screw part 31 Roll die 32 Rotating ridge 33, 33 'End face of truncated cone part 41 Material rod 42 Shaft part 43 Rolling part

Claims (3)

[Claims] 1. A ball screw having shaft portions at both ends, and a ball screw rolled between the shaft portions, and both end portions of the ball screw having a cut-up shape. 2. A method for manufacturing a ball screw by rolling a material rod with a roll die, wherein one end of the roll die is pressed against a rolling start end of a ball screw in the middle of the material rod, Rolling is performed by relatively moving the roll die relative to each other in the axial direction while relatively rotating, and the other end of the roll die reaches the rolling end end of the ball screw in the middle of the material rod. A method for producing a ball screw, characterized in that the rolling is finished at that time to produce a ball screw having shaft portions at both ends and having both ends cut up between them. 3. A circular truncated cone portion is formed at both ends of the cylindrical portion, the diameter of which is reduced outward, and continuous rolling from one circular truncated cone portion to the other circular truncated cone portion via the cylindrical portion. In a ball screw rolling roll die provided with a spiral protrusion, a distance a between end faces of one truncated cone part, a distance a ′ between end faces of the other truncated cone part, and a width of the roll die. The ball screw used in the method of manufacturing a ball screw according to claim 2, wherein a / b is 0.1 or more and 0.4 or less and a '/ b is 0 or more and 0.3 or less, when b is set. Roll die for rolling.