JP2007147028A - Rolling element screw device and method of manufacturing its circulation member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling element screw device for preventing the opening of a return pipe at its split mating face. <P>SOLUTION: The rolling element screw device comprises a screw shaft 7 having a spiral rolling element rolling groove 7a formed on the outer peripheral face, a nut member 8 having a spiral load rolling element rolling groove 8a formed on the inner peripheral face in opposition to the rolling element rolling groove 7a, the circulation member 10 for linking one end of the load rolling element rolling groove 8a of the nut member 8 to the other end thereof, a load rolling element rolling passage 13 between the rolling element rolling groove 7a of the screw shaft 7 and the load rolling element rolling groove 8a of the nut member 8, and a plurality of rolling elements arranged in a rolling element circulation passage formed of a non-load rolling element passage in the circulation member 10 and adapted to be circulated accompanied by the rotation of the screw shaft 7 relative to the nut member 8. The circulation member 10 is a resin molded product, and split only with split mating faces 11a, 12a perpendicular or across the axis of the circulation member 10 instead of a split mating face along the axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rolling element screw device in which a rolling element is interposed between a screw shaft and a nut member so as to be capable of rolling, and the rolling element is circulated by a circulation member.

  A ball screw with a ball interposed between the screw shaft and the nut member so as to allow rolling motion can reduce the friction generated between the screw shaft and the nut member. It is incorporated in various machines such as a positioning mechanism, a feed mechanism, or a steering gear of an automobile.

  When the screw shaft is rotated relative to the nut member, the ball rolls on the loaded ball rolling path between the ball rolling groove of the screw shaft and the loaded ball rolling groove of the nut member. The ball that has rolled up to one end of the load ball rolling groove of the nut member is lifted up by a return pipe provided in the nut member and returned to the other end of the load ball rolling groove.

  The return pipe is formed by bending a metal pipe with a press or by injection molding a resin. FIG. 14 shows a return pipe 1 made of a resin molded product. Since the no-load ball passage 2 in which the ball moves is formed inside the return pipe 1, the inside of the return pipe 1 becomes hollow. The hollow return pipe 1 is formed by dividing the return pipe 1 into two at the dividing and joining surface 3 along the axis of the return pipe 1, and then forming the divided return pipe pieces 1a and 1b with adhesives, screws or the like. It was manufactured by joining with a joining means (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-232421

  However, when an overload is applied to the ball screw, the circulation of the ball in the return pipe 1 may be hindered. Then, the meandering ball pushes the inner wall of the return pipe 1, which may cause the return pipe 1 to open at the split mating surface 3.

  Specifically, for example, a ball screw used in an injection molding machine may be overloaded when filled with resin. When an overload is applied, the amount of elastic deformation of the ball on the loaded ball rolling path becomes larger than a specified value, and the loaded ball rolling path is also narrowed. When an excessive moment load is applied to the ball screw, the loaded ball rolling path is similarly narrowed. In this case, the deformation amount of the ball moving from the return pipe 1 to the loaded ball rolling path becomes larger than a specified value, so that the ball 4 is difficult to enter the loaded ball rolling path 5 as shown in FIG. Therefore, the circulation of the ball 4 in the return pipe 1 is inhibited.

  On the other hand, since the balls 4 enter one after another from the loaded ball rolling path 6 on the opposite side of the return pipe 1, the clogged balls in the return pipe 1 meander and push the inner wall of the return pipe 1. When the force of pushing the return pipe 1 of the ball 4 becomes stronger than the force of joining the return pipe 1 divided into two, the split mating surface 3 of the return pipe 1 becomes the escape path of the ball 4 and the return pipe 1 is divided. Open at mating surface 3.

  Certainly, if the coupling strength of the coupling means of the return pipe 1 is increased, the opening of the return pipe 1 can be suppressed, but it cannot be said to be a fundamental solution.

  Therefore, the present invention provides a rolling element screw device and a circulating member of the rolling element screw device that can prevent the return pipe from opening on the split mating surface by means different from that for increasing the coupling strength of the return pipe coupling means. An object is to provide a manufacturing method.

  The present invention will be described below. In addition, in order to make an understanding of this invention easy, the reference number of an accompanying drawing is attached in parenthesis writing, However, This invention is not limited to the form of illustration by it.

  In order to solve the above-mentioned problems, the invention described in claim 1 includes a screw shaft (7) having a spiral rolling element rolling groove (7a) formed on an outer peripheral surface, and the rolling element rolling on an inner peripheral surface. A nut member (8) formed with a spiral loaded rolling element rolling groove (8a) facing the running groove (7a), and one end of the loaded rolling element rolling groove (8a) of the nut member (8) And the other rolling member rolling groove (8a) of the nut member (8) and the circulating member (10, 31, 35) connecting the other end, the rolling member rolling groove (7a) of the screw shaft (7). The rolling shaft (7) is arranged in a rolling element circulation path constituted by a loaded rolling element rolling path (13) between the rolling member and an unloaded rolling element passage in the circulation member (10, 31, 35). A rolling element screw device comprising: a plurality of rolling elements (9) that circulate with relative rotation of the nut member (8) relative to the nut member (8); The circulation member (10, 31, 35) is a resin molded product, and is not a divisional alignment surface along the axis of the circulation member (10, 31, 35), but a division perpendicular to or intersecting with the axis. It is characterized by being divided only by the mating surfaces (11a, 12a, 33a, 37a).

  According to a second aspect of the present invention, in the rolling element screw device according to the first aspect, the circulating member (10) includes a central portion (11) attached to a side surface of the nut member (8), and the central portion. And a pair of legs (12) bent with respect to (11), and at the dividing and mating surfaces (11a, 12a), the center (11) and the pair of legs (12) are divided into three. Each of the pair of leg portions (12) is divided into a linear passage (12c) that extends linearly and an arc passage (12b) that bends in an arc shape, and the arc of each of the pair of leg portions (12). The passage (12b) and the straight passage (12c) are formed by rotating an arc passage core (19) inserted into the arc passage (12b) along the arc passage (12b). And the straight passage (12c) Inserted is straight passage core (20) is slid along said straight path (12c), characterized in that it is formed by pulling from said straight path (12c) with.

  According to a third aspect of the present invention, in the rolling element screw device according to the first aspect, the circulating member (31, 35) includes a central portion (32, 36) attached to a side surface of the nut member (8). And a pair of legs bent with respect to the central portion (32, 36), and the whole is divided into two at the dividing / mating surfaces (33a, 37a), and the dividing / mating surfaces (33a, 37a) ) Is provided in the central portion (32, 36) having a linear passage extending linearly.

  According to a fourth aspect of the present invention, there is provided the rolling element screw device according to any one of the first to third aspects, wherein the plurality of divided circulation member pieces (11, 12, 33, 37) are coupled to each other. For this purpose, a bonding resin is filled by two-color molding.

  The invention according to claim 5 is the spiral rolling element rolling groove (7a) on the outer peripheral surface of the screw shaft (7) and the helical load rolling element rolling groove on the inner peripheral surface of the nut member (8). (8a) is provided in a rolling element screw device with a rolling element (9) interposed between them and the nut rolling member rolling groove (9) of the nut member (8) so that the rolling element (9) can circulate ( 8a) is a method of manufacturing a circulating member (10) of a rolling element screw device that connects one end and the other end of the rolling element, wherein the circulating member (10) is not a split mating surface along its axis but is orthogonal to or intersects the axis. The circulating member piece (12) divided only by the dividing and mating surfaces (11a, 12a) is inserted into the mold by inserting the linear path core (20) and the arc path core (19). A step of forming cavities for the legs, and the divided circulation member piece by pushing resin into the cavities 12), and the linear passage core (20) inserted into the linear passage (12c) of the divided circulation member piece (12) is slid along the linear passage (12c). ) And the arc passage core (19) inserted into the arc passage (12b) of the divided circulation member piece (12) is rotated along the arc passage (12b) to rotate the arc passage (12b). It is characterized by being manufactured by a process of removing from.

  According to the first aspect of the invention, since the division along the axis of the circulation member can be avoided, the circulation member can be prevented from opening on the division mating surface.

  According to invention of Claim 2, the leg part which consists of a combination of a straight line and a circular arc can be shape | molded with resin.

  According to the third aspect of the present invention, since the split mating surface is disposed at the central portion having the straight passage, the phenomenon that the circulation member opens can be further alleviated. Further, not only when the circulation of the rolling element is inhibited, but also in the normal circulation of the rolling element, the rolling element pushes the outside of the arc passage by the centrifugal force. By arranging the divisional mating surfaces in the center, it is possible to prevent the rolling elements from being pressed by the rolling mating surfaces even in the normal circulation of the rolling elements.

  According to invention of Claim 4, a circulation member can be joined by a division | segmentation mating surface.

  According to invention of Claim 5, the leg part of the circulation member comprised by the combination of a straight line and a circular arc can be shape | molded with resin.

  FIG. 1 shows a ball screw as a rolling element screw device according to an embodiment of the present invention. This ball screw includes a screw shaft 7 having a spiral ball rolling groove 7a formed on the outer peripheral surface and a nut member 8 having a load ball rolling groove 8a opposed to the ball rolling groove 7a formed on the inner peripheral surface. Between the two, a plurality of balls 9 are interposed so as to allow rolling motion. Between the plurality of balls 9, spacers 22 for preventing contact between the balls 9 are interposed as necessary. When the screw shaft 7 is rotated relative to the nut member 8, the ball 9 rolls between the ball rolling groove 7 a of the screw shaft 7 and the loaded ball rolling groove 8 a of the nut member 8. The ball 9 rolled to one end of the loaded ball rolling groove 8a of the nut member 8 is returned to the original position of the ball rolling groove several turns before by a return pipe 10 as a circulation member.

  A spiral ball rolling groove 7 a having a predetermined lead is formed on the outer periphery of the screw shaft 7. The cross-sectional shape of the ball rolling groove 7a is formed as a circular arc groove composed of a single arc or a Gothic arch groove formed by combining two arcs. Various types of screws such as a single thread, a double thread, and a triple thread can be used.

  A spiral load ball rolling groove 8a facing the ball rolling groove 7a of the screw shaft 7 is formed on the inner peripheral surface of the nut member 8 through which the screw shaft 7 passes. The cross section of the load ball rolling groove 8a is also formed as a circular arc groove formed of a single arc or a Gothic arch groove combining two arcs. A flat surface portion 8b is formed on the side surface of the nut member 8, and a fitting hole 8c into which the leg portion 12 of the return pipe 10 is inserted is formed in the flat surface portion 8b. The fitting hole 8 c penetrates to the inner peripheral surface of the nut member 8 and is connected to the load ball rolling groove 8 a on the inner peripheral surface of the nut member 8.

  The return pipe 10 has a central portion 11 attached to the side surface of the nut member 8 and leg portions 12 bent with respect to the central portion 11 and is formed in a gate shape as a whole. As shown in FIG. 3, the central portion 11 is integrally formed with an extending portion 11a, and a mounting hole 11b through which a screw as a coupling means passes is formed in the extending portion 11a. The pair of leg portions 12 of the return pipe 10 are inserted into the fitting holes 8 c on the side surface of the nut member 8, and the center portion 11 is fixed to the side surface of the nut member 8 with a coupling means, so that the return pipe 10 is attached to the nut member 8. It is attached. That is, the return pipe 10 is attached from the side surface side of the nut member 8.

  Inside the return pipe 10, a ball return passage is formed as a no-load rolling element passage having a circular cross section. The inner diameter of the ball return passage is slightly larger than the diameter of the ball 9. In this ball return path, the front ball 9 moves while being pushed by the subsequent ball 9. An infinite circulation path is constituted by the load ball rolling path between the ball rolling groove 7a of the screw shaft 7 and the load ball rolling groove 8a of the nut member 8 and the ball return path.

  As shown in FIG. 2A, the pair of leg portions 12 of the return pipe 10 are disposed in the tangential direction 14 of the center line of the load ball rolling path 13 when viewed from the axial direction of the screw shaft. Then, as shown in FIG. 2B, when viewed from the side surface direction of the screw shaft 7, the angle α is inclined to coincide with the lead angle of the load ball rolling path 13. The opposite leg 12 is also inclined at an angle α in the opposite direction in accordance with the lead angle. That is, the pair of leg portions 12 of the return pipe 10 are arranged in the tangential direction of the spiral load ball rolling path 13. Since the ball 9 is picked up and returned in the tangential direction of the spiral loaded ball rolling path 13, no excessive force is applied to the ball 9.

  As shown in FIGS. 4 and 5, the return pipe 10 is divided into three parts, that is, a center part 11 and a pair of leg parts 12 at split mating surfaces 11 a and 12 a orthogonal to the axis of the return pipe 10. The cylindrical central portion 11 is formed with a linear passage 11b extending linearly inside. Each of the pair of legs 12 includes a linear passage 12c that extends linearly and an arc passage 12b that bends in an arc. The center line of the leg 12 is composed of a combination of a straight line 18 and an arc 17 (see FIG. 6). The center line of the circular arc passage 12b is composed of a single circular arc 17 having a constant curvature radius. The center line of the straight passage 12c extends in the tangential direction of the center line of the arc passage 12b. When the pair of leg portions 12 of the return pipe 10 are arranged in the tangential direction of the load ball rolling path 13 as in this embodiment, the central angle of the arc 17 is set slightly larger than 90 degrees. On the other hand, when the leg portion 12 is not arranged in the tangential direction of the load ball rolling path 13, the center angle of the arc 17 may be set to 90 degrees or less.

  FIG. 6 shows a manufacturing process of a leg portion using a mold. The arc passage 12b and the straight passage 12c of the leg portion 12 are removed from the arc passage 12b by rotating the arc passage core 19 inserted into the arc passage 12b along the arc passage 12b and inserted into the straight passage 12c. The straight passage core 20 is slid along the straight passage 12c and pulled out from the straight passage 12c.

  The leg manufacturing process will be described in detail below. First, the straight passage core 20 and the arc passage core 19 are inserted into the mold 21 to form a leg cavity. Next, resin is pushed into the cavity by injection molding to mold the leg portion 12 as a divided circulation member piece. Next, the straight path core 20 inserted in the straight path 12c is slid along the straight path 12c to be removed from the straight path, and the arc path core 19 inserted in the arc path 12b is removed from the arc path 12b. And is extracted from the circular arc passage 12b. Thus, the leg portion 12 is formed.

  The central portion 11 and the pair of leg portions 12 as a return pipe piece are joined by a two-color molding method. FIG. 7 shows a process diagram of the two-color molding method. When the central portion 11 and the leg portion 12 are combined and placed in the molds 23 and 24, a bonding resin filling cavity 25 is formed between the central portion 11 and the leg portion 12. Gates 26 connected to the cavity for filling the bonding resin are formed on the dies 23 and 24. When the bonding resin 27 is filled from the gate 26 into the bonding resin filling cavity 25, the bonding resin 27, the central portion 11, and the pair of leg portions 12 are mutually resinous, so that the central portion 11 and the pair of leg portions 12 are bonded. The resin 27 is joined.

  The central portion 11 and the pair of leg portions 12 are firmly joined by the two-color molding method. As a means for preventing the split mating surfaces 11a and 12a from further shifting, the split mating surfaces 11a and 12a may be provided with uneven steps, or after the return pipe 10 is attached to the nut member 8, the split mating surfaces are separated. The boundary between the surfaces 11a and 12a may be pressed with a pipe presser or the like.

  8 and 9 show another example of the return pipe. The return pipe 31 is divided into two at a central portion 32 having a linear passage extending linearly. A split mating surface 33 a of the return pipe piece 33 that is split into two is disposed at the center of the return pipe 31 and is orthogonal to the axis of the return pipe 31. By arranging the divisional mating surface 33a at the center of the return pipe 31, it is possible to further alleviate the phenomenon that the return pipe 31 opens at the divisional mating surface when the circulation of the balls 9 is inhibited. Further, not only when the circulation of the ball 9 is obstructed, but also in the normal circulation of the ball 9, there is a clearance between the ball 9 and the no-load ball passage, so that the ball 9 is placed in the arc passage by centrifugal force. Touch the outside. By arranging the divisional mating surface 33a at the center, it is possible to suppress the force of the balls from contacting the divisional mating surface 33a even during normal circulation of the balls 9.

  10 and 11 show still another example of the return pipe. The return pipe 35 is also divided into two at the central portion 36, but the divided joining surface 37 a of the divided return pipe piece 37 intersects the axis of the return pipe 35. As described above, the pair of leg portions 38 of the return pipe 35 is inclined according to the lead angle. By intersecting the dividing mating surface 37a with the axis of the return pipe 35, when the two return pipe pieces 37 are joined, they can be joined while maintaining a constant inclination angle.

  FIG. 12 is a process diagram of the return pipe 31 shown in FIGS. The return pipe piece 33 divided into two parts is injection-molded by the core method in the same way as the return pipe piece divided into three parts shown in FIG. However, in the shape of the return pipe piece 33 in this example, since the return pipe piece 33 is configured by a combination of a straight line, an arc, and a straight line, it is difficult to remove the core 41 from the return pipe piece 33. Therefore, a meltable resin is used for the core 41. Then, after the return pipe piece 33 is injection molded, the core 41 is melted. The two divided return pipe pieces 33 are joined by a two-color molding method.

  FIG. 13 shows a return pipe 42 of a resin molded product having no split mating surface. If a molding method in which the core 43 is melted is adopted, it is possible to manufacture the return pipe 42 having no divisional mating surface. Of course, since there is no divisional mating surface, it is out of the scope of the present invention. However, since there is no division at all, there is no need to worry about the splitting surface opening.

  In addition, this invention is not restricted to the said embodiment, In the range which does not change the summary of this invention, it can change variously. For example, the present invention is not limited to a return pipe of a return pipe type ball screw, but can also be applied to a so-called end cap type ball screw in which a circulation member is attached from an end face side of a nut member. Also, a roller can be used as a rolling element instead of a ball.

1 is a perspective view (including a partial cross-sectional view) illustrating a ball screw according to an embodiment of the present invention. Sectional view showing the ball screw (FIG. (A) shows a sectional view orthogonal to the axis of the screw shaft, and FIG. (B) shows a sectional view along the axis of the screw shaft) Return pipe perspective view Plan view showing the return pipe divided in three Side view showing the return pipe divided in three The figure which shows the manufacturing process of the leg by a metal mold Process diagram of two-color molding method Plan view of the return pipe divided into two (orthogonal type) Side view of bifurcated return pipe (orthogonal type) Plan view of the return pipe divided into two (intersection type) Side view of the return pipe divided into two (intersection type) Manufacturing process diagram of the return pipe divided into two Diagram showing return pipe without split mating surface A perspective view showing a return pipe made of a conventional resin molded product Conventional view showing an example where the ball circulation is hindered (cross-sectional view perpendicular to the screw shaft)

Explanation of symbols

7a ... Ball rolling groove (rolling element rolling groove)
7 ... Screw shaft 8 ... Nut member 8a ... Loaded ball rolling groove (Loaded rolling element rolling groove)
9 ... Ball (rolling element)
10 ... Return pipe (circulation member)
DESCRIPTION OF SYMBOLS 11 ... Center part 11b ... Linear channel | path 11a, 12a ... Dividing surface 12b ... Arc path 12 ... Leg part 12c ... Linear channel 13 ... Load ball rolling path (load rolling element rolling path)
DESCRIPTION OF SYMBOLS 19 ... Arc path core 20 ... Linear path core 21 ... Mold 23, 24 ... Mold 25 ... Bonding resin filling cavity 27 ... Bonding resin 31 ... Return pipe 32 ... Center part 33 ... Return pipe piece 33a ... division mating surface 35 ... return pipe 36 ... central portion 37 ... return pipe piece 37a ... division mating surface

Claims (5)

A screw shaft in which a spiral rolling element rolling groove is formed on the outer peripheral surface, a nut member in which a spiral load rolling element rolling groove facing the rolling element rolling groove is formed on the inner peripheral surface, and A circulating member that connects one end and the other end of the load rolling element rolling groove of the nut member, and a load rolling element between the rolling element rolling groove of the screw shaft and the load rolling element rolling groove of the nut member A plurality of rolling elements that are arranged in a rolling path and a rolling element circulation path constituted by a no-load rolling element passage in the circulation member and circulate with relative rotation of the screw shaft with respect to the nut member; In a rolling element screw device comprising:
The circulation member is a molded product of resin, and is divided not by a division and alignment surface along the axis of the circulation member but only by a division and alignment surface orthogonal to or intersecting the axis. Moving body screw device. The circulation member has a central portion attached to a side surface of the nut member and a pair of legs bent with respect to the central portion, and the central portion and the pair of legs at the division mating surface And divided into three
Each of the pair of leg portions has a linear passage extending linearly and an arc passage bending in an arc shape,
The arc passage and the linear passage of each of the pair of leg portions are extracted from the arc passage by rotating the arc passage core inserted in the arc passage along the arc passage and inserted into the linear passage. 2. The rolling element screw device according to claim 1, wherein the rolling element screw device is formed by sliding the straight path core along the straight path and withdrawing the straight path core from the straight path. The circulation member has a central portion attached to the side surface of the nut member and a pair of legs bent with respect to the central portion, and the whole is divided into two at the division mating surface,
2. The rolling element screw device according to claim 1, wherein the split mating surface is provided in the central portion having a linear passage extending linearly. 4. The rolling element screw device according to claim 1, wherein a joining resin is filled between the plurality of divided circulation member pieces by two-color molding in order to join them. 5. Provided in a rolling element screw device in which a rolling element is interposed between a spiral rolling element rolling groove on the outer peripheral surface of the screw shaft and a helical load rolling element rolling groove on the inner peripheral surface of the nut member; A rolling member manufacturing method for a rolling element screw device that connects one end and the other end of the load rolling element rolling groove of the nut member so that the rolling element can circulate,
The circulating member is not divided along the axis, but is divided only at the division / intersection orthogonal to or intersecting the axis,
The divided circulation member piece includes a step of inserting a linear passage core and an arc passage core into a mold to form a leg cavity, and a resin is pushed into the cavity to insert the divided circulation member piece into the mold. Forming the linear passage core inserted in the linear passage of the divided circulation member piece and sliding the linear passage core along the linear passage, and inserting it into the arc passage of the divided circulation member piece. A method of manufacturing a circulating member for a rolling element screw device, wherein the circular path core is rotated along the arc path and is extracted from the arc path.

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