JP5037323B2 - Ball screw device - Google Patents

Description

  The present invention relates to a ball screw device used in, for example, an industrial machine.

  As shown in FIG. 8, the ball screw device includes a helical shaft screw groove 3 and a nut screw groove 4 which are opposed to each other on the outer peripheral surface of the screw shaft 1 and the inner peripheral surface of the ball nut 2 positioned outside the screw shaft 1. In the spiral ball load rolling path 5 formed by the two screw grooves 3 and 4, a large number of balls 6 are arranged to roll freely. When the screw shaft 1 and the ball nut 2 are rotated relative to each other, the screw shaft 1 and the ball nut 2 are smoothly and relatively spirally moved through the rolling of the ball 6. .

  The ball nut 2 of such a ball screw device is provided with a ball circulation path 7 for circulating the ball 6 by scooping the ball 6 at one end of the ball load rolling path 5 and sending it to the other end. That is, the ball 6 moves in the ball load rolling path 5 and passes around the screw shaft 1 a plurality of times, and then, one end of the ball load rolling path 5, that is, the end of the ball circulation path 7 and the ball load rolling path. It is scooped up into the ball circulation path 7 through the circulation piece 8a at the junction with the movement path 5. The scooped up ball 6 passes through the ball circulation path 7 and is returned from the other end of the ball circulation path 7 to the other end of the ball load rolling path 5 through the circulation piece 8b.

  FIG. 9 shows a cross-sectional view of the joint portion of the conventional example. Since the ball guide passages of the circulation pieces 8a and 8b and the ball circulation passage 7 are non-load regions, the inner diameters thereof are both the screw shaft 1 and the ball nut 2. It is made larger than the ball load rolling path 5 composed of the grooves 3 and 4. Therefore, as shown in FIG. 9A, a step 11 is formed at the joint 10 between the circulation piece 8 and the ball load rolling path 5, and the ball 6 moves from the circulation piece 8 to the ball load rolling path 5. This causes noise and vibration when the ball screw device is driven by colliding with the step 11.

  When the screw shaft 1 and the ball nut 2 are rotated in the reverse direction, the ball 6 moves from the ball load rolling path 5 to the ball circulation path 7 through the circulation piece 8 at the joint 10 as shown in FIG. At this time, when the ball screw device is driven at a low speed, the ball 6 is scooped up by the inner wall surface 12 of the circulation piece 8 and moved into the ball circulation path 7 in the ball nut 2.

  When the ball screw device is driven at a high speed, the ball 6 jumps out from the joint 10 in the tangential direction T of the ball load rolling path 5, that is, in the same direction as the axis of the inner wall surface 12 of the circulation piece 8. Further, the inner wall 12 does not collide with the inner wall 12 of the circulation piece 8, and the inner wall 12 is not worn.

  However, due to the movement of the ball 6 as shown in FIG. 9A, the step 11 is worn by the collision of the ball 6 during use, and the inclined portion 13 as shown in FIG. 10 is naturally formed. The abrasion powder generated at that time also causes a decrease in the durability of the ball screw device. In order to solve these problems, Patent Documents 1 and 2 have been proposed.

  In Patent Document 1, the nut screw groove just before entering the return tube ball circulation path from the ball load rolling path 5 and the nut thread groove entering the load rolling path 5 from the return tube are gradually grooved toward the return tube side. A step is eliminated by cutting into a taper shape so that the shape spreads.

  In Patent Document 2, a crowned portion is formed with a processing amount of about 0.1 to 1% of the ball diameter in the thread groove on the ball nut side of the joint portion between the ball load rolling path 5 and the ball circulation path 7. Has been.

JP 2001-254800 A JP 2005-180655 A

  As in Patent Documents 1 and 2, according to the method of providing the inclined portion by taper portion or crowning, the step 11 shown in FIG. 9 when the ball 6 of the ball circulation path 7 moves to the ball load rolling path 5 is obtained. The problem can be solved.

  Further, as shown in FIG. 11, when the inclined portion 14 is provided by the taper portion or the crowning process, when the ball 6 enters the ball circulation path 7 from the ball load rolling path 5 through the circulation piece 8, There arises a new problem that it moves along the inclined portion 14 and collides with the inner wall surface 12 of the ball circulation path 7 to cause wear of the inner wall surface 12.

  Further, Patent Literature 3 has been proposed as a method for eliminating wear on the inner wall surface 12 of the circulation piece 8. That is, a cushioning material that is softer than the material of the screw shaft 1 is disposed on the restraining surface of the ball 6 on the ball nut 2 side from the inner wall surface 12 to the load region between the screw grooves 3 and 4.

  In Patent Document 4, the inner wall surface 12 is formed of a high-strength material that is stronger than the strength of the material of the circulation piece 8, or a plate for preventing peeling is attached to the inner surface in the radial direction so that the plate surface is a ball running surface. It prevents peeling wear.

  That is, according to Patent Documents 1 and 2, the step 11 of the joint 10 between the circulation piece 8 and the ball load rolling path 5 can be eliminated, but in order to eliminate wear on the inner wall surface 12 of the ball circulation path 7. Patent Documents 3 and 4 must be employed together, and there are problems such as an increase in cost due to the addition of new parts and restrictions on the material of the circulation piece 8.

JP 2005-83522 A JP 2004-340220 A

The object of the present invention is to eliminate the above-mentioned problems, circulate the ball more smoothly, suppress vibrations and noises, prevent wear and the like from occurring in the passage, and have high durability. To provide an apparatus.

In order to achieve the above object, a ball screw device according to the present invention includes a screw shaft having a shaft screw groove formed on an outer peripheral surface thereof, and a ball having a nut screw groove positioned outside the screw shaft and facing the shaft screw groove. and a nut, said along with the relative rotation of the screw shaft and the ball nut of the ball is rolled move the ball load rolling path between the two screw grooves, inner diameter larger than an inner diameter of the ball load rolling path A ball screw device provided with a ball circulation path for circulating the ball, and provided with a circulation member having a ball guide path therein and communicating between the ball load rolling path and the ball circulation path at two locations. , at the junction of the circulation member and the ball nut, said ball nut, an inclined portion expanding the diameter inclined from said nut screw groove on the outside, the ball of the circulation member is connected to the inclined portion A buffer portion comprising a flat portion smoothly connected to the inner passage is provided, and the flat portion is inclined toward the axial center direction side with respect to the tangential direction T of the screw groove at the load release point P which is the starting point of the inclined portion. It is characterized by that.

According to the ball screw device of the present invention, by forming the buffer portion that softens the impact of the ball on the ball nut side of the joint portion between the ball nut and the circulation member, wear or the like does not occur in the joint portion.

  Moreover, since the collision point by a ball | bowl can be transfered from the conventional circulation member to the buffer part formed in the ball nut, durability improvement and noise reduction can be achieved.

  The present invention will be described in detail based on the embodiment shown in FIGS.

  1 is an exploded perspective view of a ball nut and a circulation piece according to the first embodiment, FIG. 2 is a cross-sectional view of a joint between the ball nut and the circulation piece, and FIG. 3 is a perspective view thereof. The structure of the main part including the screw shaft 1, the ball nut 2, and the ball 6 of the ball screw device is the same as in FIG. 8, and the same members as those in FIG.

  Cutout portions 21 are provided at two locations on both ends of the ball nut 2, and circulation pieces 22, which are circulation members, are incorporated in the cutout portions 21 and fixed by attachment screws 23. In addition, the circulation piece 22 of the both ends of the ball nut 2 is made into the same shape, and has an equivalent function. One circulation piece 22 communicates with the ball load rolling path 5, scoops up the ball 6 from the ball load rolling path 5, and passes through a ball circulation path 7 formed through the ball nut 2 in the axial direction. The other circulating piece 22 rolls.

  For this reason, the circulation piece 22 has a ball guide passage in the inside thereof. The ball guide passage has a bowl upper portion 24 for scooping up the ball 6 from the ball load rolling path 5, and the ball 6 from the bowl upper section 24 to the ball circulation path. And a ball turning portion 25 for guiding to 7. Reference numeral 26 denotes a flange for fixing the ball nut 2.

  As described above, the inner diameters of the ball circulation path 7 and the ball guide path are larger than the diameter of the ball load rolling path 5. Moreover, since the shape of the circulation piece 22 is complicated, it is made of metal made of lost wax or synthetic resin made of a mold.

  FIG. 4 shows a cross-sectional view of the joint 27 of the screw shaft 1, the ball nut 2, and the circulation piece 22. In the joint portion 27, the diameter of the nut screw groove 4 of the ball nut 2 is expanded outward to match the end portion of the upper portion 24 of the circulation piece 22. That is, in the nut screw groove 4, the portion between the load release point P that starts to change its diameter for expansion and the vicinity of the end surface of the nut screw groove 4 is an inclined portion 28, and the end point of the inclined portion 28 and the end of the ball nut 2 are A flat portion 29 is formed between the end portion and the end portion of the flat portion 29 and the upper portion 24 of the circulation piece 22 are aligned and smoothly connected in a straight line. That is, the cross-sectional shape seen from the axial direction of the nut screw groove 4 of the flat portion 29 formed on the ball nut 2 partially matches the inlet shape of the collar upper portion 24 of the circulation piece 22.

  At the load release point P, the load of the ball load rolling path 5 with respect to the ball 6 is released, the ball 6 jumps out from the ball load rolling path 5 in the tangential direction T, and the inclined portion 28 is in the tangential direction in which the ball 6 jumps out. The flat part 29 inclined in the same or outer diameter direction with respect to T and connected to the inclined part 28 is inclined relative to the tangential direction T in the axial center direction. The circle of the ball load rolling path 5 through which the load release point P passes is actually a single arc or a combination of two arcs.

  During operation, the ball 6 jumps out from the load release point P in the tangential direction T of the ball load rolling path 5 and passes through the inclined portion 28. At this time, if the inclination of the inclined portion 28 is the same as the tangential direction T, the ball 6 comes into contact with the inclined portion 28. However, since the inclination of the inclined portion 28 is inclined in the axial outer diameter direction, the ball 6 is inclined. There is no contact with the inclined portion 28 by jumping over the portion 28.

  The ball 6 that has passed over the inclined portion 28 moves to the flat portion 29. However, since the flat portion 29 is inclined in the axial center direction with respect to the tangential direction T, the ball 6 collides with the flat portion 29. . That is, conventionally, as shown in FIG. 9B, the ball 6 jumping out in the tangential direction T directly collided with the upper part 24 of the circulation piece 22, but in this embodiment, as shown in FIG. The collision point is shifted to a flat portion 29 formed on the ball nut 2.

  Therefore, even if a material having a lower strength than the ball nut 2 such as a material excellent in castability used for lost wax or a synthetic resin having a low mechanical strength is used for the circulation piece 22, the circulation piece 22 is made of a material. Thus, it is possible to prevent wear without being restricted and without adding new parts.

  FIG. 5 is an explanatory view of a modified example. The inclined portion 28 may have a large diameter on the side connected to the flat portion 29, a small diameter on the load release point P side, and a tapered axis parallel section. As shown in (a) and (b), any one of the connecting portions of the flat portion 29, the inclined portion 28, and the load release point P can be connected by a curved surface. Alternatively, as shown in (c), these connecting portions may be connected by curved surfaces, and the axial parallel cross section may be formed in an S shape.

  Further, only the surface of the flat portion 29 may be increased in hardness by a nitriding process or the like, whereby the wear resistance can be improved, and the entire nut screw groove 4 is not subjected to a nitriding process. Because it is good, the cost can be reduced.

  6 shows a so-called tube type longitudinal sectional view of the second embodiment, and FIG. 7 shows a transverse sectional view. Circulating members are integrally provided at both ends of a return tube 32 having a ball circulation path 31.

  The ball 6 is scooped up from the ball load rolling path 5 by the bowl upper part 33 which is a circulation member formed at the end of the return tube 32, and rolls and moves in the ball circulation path 31 in the return tube 32. Is returned to the ball load rolling path 5 again from the top of the bowl.

  Further, as in the first embodiment, the ball nut 2 has a load release point P at which the ball 6 jumps in the tangential direction T of the ball load rolling path 5 and the same or outer shaft diameter with respect to the tangential direction T from which the ball 6 jumps out. An inclined portion 34 that is inclined in the direction and a flat portion 35 that is connected to the inclined portion 34 and partially coincides with the flange upper portion 33 are formed.

  The ball 6 protrudes from the load release point P of the ball nut 2 in the tangential direction T and passes through the inclined portion 34. The ball 6 that has passed through the inclined portion 34 moves to the flat portion 35, and the ball 6 collides with the flat portion 35 and does not collide with the upper portion 33 of the return tube 32.

  Therefore, even if a material having a lower strength than the ball nut 2 is used for the return tube 32, wear of the return tube 32 can be prevented without being restricted by materials and without adding new parts. .

It is a disassembled perspective view of a ball nut and a circulation piece. It is a cross-sectional view of a joined part. It is a perspective view of a junction part. It is a cross-sectional view of a joined part. It is explanatory drawing of the junction part of a modification. 6 is a longitudinal sectional view of Example 2. FIG. It is a cross-sectional view. It is a longitudinal cross-sectional view of a ball screw apparatus. It is sectional drawing of the junction part of a prior art example. It is sectional drawing of the junction part of a prior art example. It is sectional drawing of the junction part of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Ball nut 3 Shaft screw groove 4 Nut screw groove 5 Ball load rolling path 6 Ball 7, 31 Ball circulation path 21 Notch part 22 Circulation piece 24, 33 Ball bowl upper part 25 Ball turning path 27 Joint part 28, 34 Inclined part 29, 35 Flat part 32 Return tube P Load release point

Claims (4)

A screw shaft having a shaft screw groove formed on an outer peripheral surface thereof, and a ball nut having a nut screw groove positioned outside the screw shaft and facing the shaft screw groove, the relative rotation of the screw shaft and the ball nut Accordingly, a ball circulation path is provided for rolling the ball in the ball load rolling path between the both screw grooves and circulating the ball having an inner diameter larger than the inner diameter of the ball load rolling path , A ball screw device provided with a circulation member having a ball guide passage therein and communicating between a load rolling path and the ball circulation path at two locations, wherein the ball nut is connected at the joint between the ball nut and the circulation member. the, an inclined portion, a buffer portion made of a flat portion smoothly connected to the ball guide path of the circulation member is connected to the inclined portion provided to expand the diameter inclined from said nut screw groove on the outside, Serial plateau ball screw device which is characterized in that is inclined in the axial center direction with respect to the tangential direction T of the thread groove at the starting point at which the load release point P of the inclined portion.   The ball screw device according to claim 1, wherein the ball circulation path is formed in the ball nut.   The ball screw device according to claim 2, wherein notches are provided at both ends of the ball nut, and the circulation member is incorporated into these notches.   The ball screw device according to claim 1, wherein the circulation member is integrally provided at both ends of a return tube having the ball circulation path.

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