Ball screw

Abstract

A circulation module (40) in a ball screw (10) comprises: a pair of circulation units (41, 41), in which a nut insertion part (42) to be fitted into a through hole (32) of a nut (30) and a direction-changing part (43) that converts the direction of motion of balls are provided continuously, and which constitute a partial path of a ball circulation path; and a connection securing unit (50) that is disposed between the pair of circulation units (41, 41) and constitutes a remaining partial path of the ball circulation path that communicates with the partial path of the circulation units (41). The circulation units (41) each have pressure-receiving portions respectively provided at the ends of the direction-changing part (43) on the side opposite from the nut insertion part (42). The connection securing unit (50) has a securing part secured to the nut (30) and pressure-applying parts which are provided at both open-end sides of the remaining partial path to respectively press against the pressure-receiving portions.

Description

ball screw

[0001] The present invention relates to an external circulation type ball screw.

[0002] Ball recirculation ball screws used in machine tools and the like require balls, which are arranged in a spiral ball rolling path (loaded track) consisting of a raceway groove in the screw shaft and a raceway groove in the nut, to be scooped up from the ball rolling path and returned from one end of the ball rolling path to the other. Known ball circulation methods include the tube type, the top type (also called the deflector type), the end cap type, and the end deflector type.

[0003] Of these, external circulation type ball screws, which circulate balls outside the nut, are equipped with a circulation component (circulation module) having a ball circulation path for scooping up and circulating balls rolling in the ball rolling path.

[0004] For example, the external circulation ball screw disclosed in Patent Document 1 includes a screw shaft, a nut, a circulation member (circulation module), and a fixed module. The nut is attached to the screw shaft and has a storage groove and two circulation holes. The circulation member has two circulation pipes whose second connecting portions are connected to each other, and whose first connecting portions at both ends are inserted separately into the circulation holes of the nut. The assembled screw shaft, nut, and circulation member form a circulation path that keeps the balls rolling.

[0005] The fixing module includes two fixing units and a connecting unit located between the two fixing units. Each of the two fixing units has a first fixing groove, and the connecting unit has a second fixing groove. The first fixing groove and the second fixing groove are fitted to the return member, and the first fixing groove corresponds to a curved portion connecting the first connecting portion and the second connecting portion of the return pipe.

[0006] The fixing module fits into the storage groove of the nut, covers the return member, and is screwed onto the nut to fix the return member to the nut. Thus, the fixing module can reliably fix the return member to the nut without causing misalignment between the mating surfaces of the second connecting portions of the two return pipes.

[0007] Japanese Utility Model Registration No. 3232612

[0008] However, in the external circulation ball screw of Patent Document 1, in order to fix the outer surface of the return pipe so that there is no misalignment at the mating surfaces of the two return pipes that make up the return member, a fixing module consisting of two fixing units and a connection unit is used to screw it onto the nut, which has the problem that the fixing module has a large number of parts and is prone to becoming large.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a compact external circulation type ball screw that can fix a circulation module to a nut with a small number of parts.

[0010] The above object of the present invention can be achieved by the following configuration. a ball screw comprising: a screw shaft having a spiral screw shaft-side raceway groove formed on its outer peripheral surface; a nut having a spiral nut-side raceway groove formed on its inner peripheral surface facing the screw shaft-side raceway groove and having at least a pair of through holes communicating the outer peripheral surface with the nut-side raceway groove; a plurality of balls that roll in a ball rolling path formed by the screw shaft-side raceway groove and the nut-side raceway groove; and a circulation module attached to the pair of through holes and forming a ball circulation path for circulating the balls rolling in the ball rolling path, wherein the circulation module has: a pair of circulation units each having a cylindrical nut insertion portion fitted into the through hole and a direction change portion that changes the moving direction of the balls, the pair of circulation units constituting a partial path of the ball circulation path; and a connection and fixing unit disposed between the pair of circulation units and constituting a remaining path of the ball circulation path that communicates with each partial path of the ball circulation path in the pair of circulation units, the pair of circulation units having pressure-receiving portions provided at ends of the direction change portions opposite to the nut insertion portion, The connection and fixing unit includes a fixing portion fixed to the nut, and pressure-reducing portions provided on both open end sides of the remaining portion path and configured to respectively press the pressure-receiving portions.

[0011] According to the present invention, it is possible to provide a compact external circulation type ball screw that can fix a circulation module with a nut using a small number of parts.

[0012] The present invention has been briefly described above. The details of the present invention will be further clarified by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings.

[0013] Fig. 1 is a perspective view showing a ball screw according to one embodiment of the present invention. Fig. 2 is a perspective view showing a nut of the ball screw shown in Fig. 1. Fig. 3 is a perspective view of the ball screw circulation module shown in Fig. 1, viewed obliquely from above. Fig. 4 is a perspective view of the ball screw circulation module shown in Fig. 1, viewed obliquely from below. Fig. 5 is a perspective view showing a pair of circulation units in the circulation module shown in Fig. 3. Fig. 6 is a perspective view showing a connection and fixing unit in the circulation module shown in Fig. 4. Fig. 7 is a perspective view showing a single item in a pair of molded parts that make up the connection and fixing unit shown in Fig. 6.

[0014] A ball screw according to an embodiment of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a perspective view showing a ball screw 10 according to an embodiment of the present invention. Fig. 2 is a perspective view showing a nut 30 of the ball screw 10 shown in Fig. 1.

[0015] As shown in FIG. 1 , the ball screw 10 according to this embodiment is an external circulation type ball screw including: a screw shaft 20 having a spiral screw shaft-side raceway groove 21 formed on its outer peripheral surface; a nut 30 having a spiral nut-side raceway groove 31 formed on its inner peripheral surface facing the screw shaft-side raceway groove 21 and having two pairs of through holes 32 communicating between the outer peripheral surface 33 and the nut-side raceway groove 31; a plurality of balls (not shown) that roll in a ball rolling path 25 formed by the screw shaft-side raceway groove 21 and the nut-side raceway groove 31; and a circulation module 40 attached to the pair of through holes 32 and forming a ball circulation path 60 for circulating the balls rolling in the ball rolling path 25.

[0016] As shown in Figure 2, the metal nut 30 is formed in a cylindrical shape with an annular flange 35 formed at one end. A plurality of mounting holes 35a are formed in the flange 35 and extend axially therethrough. A spiral nut-side raceway groove 31 is formed on the inner peripheral surface of the nut 30 with the same lead as the screw shaft-side raceway groove 21. In addition, a mounting surface 33a parallel to the axis O of the nut 30 is formed on the outer peripheral surface 33 of the nut 30.

[0017] Furthermore, two pairs (four) of through holes 32, each having a circular cross section, are formed at both axial ends of the mounting surface 33a, penetrating obliquely inward along the lead angle of the nut-side raceway groove 31 and communicating with the nut-side raceway groove 31. The through holes 32 communicate with the space within the ball rolling path 25 formed in the ball screw 10.

[0018] Two circulation modules 40 are attached adjacent to each other to the mounting surface 33a of the nut 30. The circulation modules 40 form a ball circulation path that circulates the plurality of balls rolling in the ball rolling path 25. The mounting surface 33a is provided with four screw holes 37 into which screws 71 are threaded. Each of the screw holes 37 has a circular recess 38 formed on the opening edge, giving it a stepped shape. The two circulation modules 40 are fixed to the nut 30 by the screws 71 that thread into the screw holes 37 of the nut 30.

[0019] The balls are spherical bodies made of steel such as alloy steel, and roll in a ball rolling path 25 consisting of opposing screw shaft side raceway grooves 21 and nut side raceway grooves 31 to thread the screw shaft 20 and nut 30 together and support the load applied to the ball screw 10.

[0020] 3 and 4 are perspective views of the circulation module 40 of the ball screw 10 shown in Fig. 1, viewed obliquely from above and below. Fig. 5 is a perspective view showing a pair of circulation units 41, 41 in the circulation module 40 shown in Fig. 3.

[0021] As shown in FIGS. 3 and 4, the circulation module 40 includes a pair of circulation units 41, 41, and a connection and fixing unit 50 disposed between the pair of circulation units 41, 41.

[0022] The circulation unit 41 is provided with a cylindrical nut insertion portion 42 that is fitted into the through hole 32 of the nut 30 and a direction change portion 43 that changes the moving direction of the balls, which are provided continuously. The nut insertion portion 42 is provided with a ball scooping portion 42a at its tip that protrudes into the ball rolling path 25 and scoops up the balls.

[0023] The circulation unit 41 forms a partial path 61 of the ball circulation path 60 for changing the direction of movement of the scooped balls so that they move from the direction of the ball scooping section 42a along the lead angle to the other circulation section along the axial direction.

[0024] 5, pressure-receiving portions 45 are provided at the end of the circulation unit 41 opposite the nut insertion portion 42 in the direction change portion 43. The pressure-receiving portions 45 in this embodiment have an upper pressure-receiving surface 45a and side pressure-receiving surfaces 45b, 45b, which are pressure-receiving surfaces formed on the top surface and both side surfaces of the direction change portion 43. The upper pressure-receiving surface 45a and the side pressure-receiving surfaces 45b, 45b are stepped surfaces that are lower than the outer peripheral surface of the direction change portion 43.

[0025] In this embodiment, the direction changer 43 has a polyhedral exterior surface. The bottom surface 47 facing the mounting surface 33a of the nut 30 can be in surface contact with the mounting surface 33a. The longitudinal end surface 48 on the nut insertion portion 42 side can be in surface contact with a side surface 58 of the connection and fixing unit 50 of the adjacent circulation module 40, as described below.

[0026] Furthermore, the circulation unit 41 of this embodiment is composed of a pair of molded parts 41a, 41b each having a semicircular cross-sectional rolling surface 61a, 61b that is divided into two along a partial path 61 of the ball circulation path 60. These molded parts 41a, 41b define the partial path 61 of the ball circulation path 60 for circulating the balls with the rolling surfaces 61a, 61b.

[0027] In addition, since these molded parts 41a, 41b constitute the partial path 61, which is a complex path made up of a combination of curves, it is preferable that they be formed by injection molding of synthetic resin, which allows a high degree of freedom in shape, or sintering molding using metal powder. These molded parts 41a, 41b are formed separately and then joined together with fixing screws or the like.

[0028] Fig. 6 is a perspective view showing the connection and fastening unit 50 in the circulation module 40 shown in Fig. 4. Fig. 7 is a perspective view showing a single item of a pair of molded parts 51, 51 that constitute the connection and fastening unit 50 shown in Fig. 6.

[0029] 6, the connecting and fixing unit 50 constitutes the remaining path 63 of the ball circulation path 60, which communicates with the partial paths 61 of the ball circulation path 60 in the pair of circulation units 41. The connecting and fixing unit 50 has a pair of fixing portions 52, 52 provided at both ends for fixing to the nut 30, and a pair of pressure-reducing portions 59, 59 provided on both open end sides of the remaining path 63 for respectively pressing down on the pressure-receiving portions 45 of the pair of circulation units 41, 41.

[0030] The pressure-reducing portion 59 of the connecting and fixing unit 50 according to this embodiment has an upper pressure-reducing surface 59a and a side pressure-reducing surface 59b, 59b (pressure-reducing surfaces) that respectively face the upper pressure-receiving surface 45a and the side pressure-receiving surfaces 45b, 45b (pressure-receiving surfaces) of the circulation unit 41, and can respectively press down the pressure-receiving portions 45 of the pair of circulation units 41, 41. Furthermore, the upper pressure-receiving surface 45a and the side pressure-receiving surfaces 45b, 45b, which are stepped surfaces, are less likely to become misaligned with the upper pressure-receiving surface 59a and the side pressure-receiving surfaces 59b, 59b.

[0031] Furthermore, in the fixing portion 52 of the connection fixing unit 50 according to this embodiment, a stepped hole 53 is formed toward the screw hole 71 so that the threaded portion 71 a of the screw 71 that screws into the screw hole 37 of the nut 30 can pass through. Therefore, by threading the threaded portion 71 a of the screw 71 inserted into the stepped hole 53 into the screw hole 37 of the nut 30, the connection fixing unit 50 can be fixed to the attachment surface 33 a of the nut 30.

[0032] The connection and fastening unit 50 of this embodiment is configured as a polyhedron with a multifaceted exterior surface. The bottom surface 57 facing the mounting surface 33a of the nut 30 can be in surface contact with the mounting surface 33a. Furthermore, the side surface 58 can be in surface contact with the longitudinal end surface 48 of the adjacent circulation module 40 on the nut insertion portion 42 side, as described above (see FIG. 1). Therefore, the circulation module 40, which is made up of the pair of circulation units 41, 41 and the connection and fastening unit 50, and the nut 30 can be firmly fixed together by surface-to-surface contact with each other.

[0033] Furthermore, the connection and fixing unit 50 of this embodiment is composed of a pair of molded parts 51, 51 having a symmetrical shape divided into two along the central axis of a pair of stepped holes 53, 53, and a stepped hole 53 is formed between the mating surfaces 54, 54 of the pair of molded parts 51, 51.

[0034] Therefore, as shown in FIG. 7 , a molded part 51 has a pair of recesses 53 a, 53 a with semicircular inner circumferential surfaces in a mating surface 54, and a remaining portion path 63 with a circular cross section penetrates the mating surface 54 in the mating direction, and has an outer shape without an undercut that can be molded as a single unit using two molds that are released in the mating direction of the mating surface 54.

[0035] That is, the connection and fixation unit 50 is composed of a pair of molded parts 51, 51 that do not have an undercut shape. Therefore, the molded part 51 that constitutes the connection and fixation unit 50 does not require a complex molding die, and manufacturing costs can be reduced.

[0036] Furthermore, a cylindrical anti-splitting protrusion 55 is provided on the opening edge of the stepped hole 53 facing the screw hole 37, and fits into the recess 38 formed on the opening edge of the screw hole 37. The anti-splitting protrusion 55 is provided on each of the pair of molded parts 51, 51 in the shape of a split semicircular cross section.

[0037] When attaching the circulation module 40 to the nut 30, first, the nut insertion portions 42 are inserted into the corresponding through holes 32 of the nut 30, and the direction change portions 43 are placed on the attachment surface 33a, so that a pair of circulation units 41, 41 are positioned on the outer surface 33 of the nut 30.

[0038] In this case, since there is space between the pair of circulation units 41, 41 for arranging the connection and fixing unit 50, it is possible to check the step in the partial path 61 of the circulation unit 41 during assembly. As a result, the operability and durability of the ball screw 10 can be improved.

[0039] Next, the connecting and fixing unit 50 is interposed between the pair of circulation units 41, 41 so that the pair of pressure-reducing portions 59, 59 of the connecting and fixing unit 50 overlap the pressure-receiving portions 45, 45 of the pair of circulation units 41, 41, respectively.

[0040] Furthermore, when the upper pressure control surface 59a of the pressure control portion 59 of the connection fixing unit 50 is inserted until it abuts against the upper pressure receiving surface 45a of the pressure receiving portion 45 of the circulation unit 41, the half-shaped anti-splitting protrusions 55 protruding from each of the pair of molded parts 51, 51 fit into the recess 38.

[0041] Then, a screw 71 is inserted into the stepped hole 53 in the fixing portion 52 of the connection and fixation unit 50, and the screw portion 71 a is screwed into the threaded hole 37 of the nut 30 and tightened until the bottom surface 57 of the connection and fixation unit 50 abuts against the mounting surface 33 a. Then, the upper pressure-receiving surface 45 a of the pressure-receiving portion 45 is pressed by the upper pressure-controlling surface 59 a of the pressure-controlling portion 59, so that the pair of circulation units 41, 41 are fixed to the nut 30 by the connection and fixation unit 50.

[0042] At this time, the side pressure-receiving surfaces 45b, 45b of the pressure-receiving portion 45 are pressed by the side pressure-controlling surfaces 59b, 59b of the pressure-controlling portion 59, so that the pair of molded parts 41a, 41b in the circulation unit 41 are restricted from moving in the direction in which their mating surfaces move away from each other.

[0043] Furthermore, since the anti-splitting projections 55 of the pair of molded parts 51, 51 in the connecting and fixing unit 50 are fitted into the recesses 38 of the nut 30, movement of the mating surfaces 54, 54 in the direction away from each other is restricted.

[0044] Then, when a pair of circulation units 41, 41 and a connection and fixing unit 50, which are combined together, are fixed to a nut 30, two partial paths 61 in the pair of circulation units 41, 41 and one remaining path 63 in the connection and fixing unit 50 are connected, thereby forming a ball circulation path 60 of the circulation module 40.

[0045] Therefore, according to the ball screw 10 of this embodiment, the circulation module 40 can be configured with only the pair of circulation units 41 and 41 and the connection and fixing unit 50 , and the circulation module 40 can be fixed to the nut 30 .

[0046] Furthermore, in the ball screw 10 according to this embodiment, the connection and fixation unit 50 is configured from a pair of molded parts 51, 51 that do not have an undercut shape. Therefore, the molded parts 51 that configure the connection and fixation unit 50 do not require a complex molding die, and manufacturing costs can be reduced.

[0047] Furthermore, in the ball screw 10 according to this embodiment, the pair of circulation units 41, 41 are each composed of a pair of molded parts 41 a, 41 b that are split into two along a partial path 61 of the ball circulation path 60. Therefore, in order to configure the partial path 61, which is a complex path made up of a combination of curves, the molded parts 41 a, 41 b can be easily formed by injection molding of synthetic resin, which has a high degree of freedom in shape, or sinter molding using metal powder.

[0048] Furthermore, in the ball screw 10 according to this embodiment, the direction changer 43 of the circulation module 40 and the connection and fastening unit 50 are each configured as a polyhedron and are combined in a state of surface contact with each other. Furthermore, an attachment surface 33a parallel to the axis O of the nut 30 is formed on the outer peripheral surface 33 of the nut 30, and the direction changer 43 and the connection and fastening unit 50 are fixed in a state of surface contact with the attachment surface 33a. Thus, the circulation module 40, which is made up of a pair of circulation units 41, 41 and the connection and fastening unit 50, and the nut 30 can be firmly fixed together by surface-to-surface contact with each other.

[0049] Furthermore, in the ball screw 10 according to this embodiment, two circulation modules 40, 40 are attached to the nut 30 to form two rows of ball circulation paths 60, and the side surface 58 of the connection and fixing unit 50 can come into surface contact with the longitudinal end surface 48 on the nut insertion portion 42 side of the adjacent circulation module 40. Thus, these two circulation modules 40, 40 and the nut 30 can be firmly fixed together by their surface-to-surface contact with each other.

[0050] As described above, the ball screw 10 of this embodiment can provide a compact external circulation type ball screw that can fix the circulation module with a nut using a small number of parts.

[0051] The present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. Furthermore, the material, shape, size, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present invention.

[0052] The ball screw of the present invention is used, for example, in XY stages used for positioning devices that perform high-precision machining and measurement, and in semiconductor manufacturing, etc. The ball screw is also used, for example, in machine tools (machining centers, lathes, grinders, etc.), measuring machines (three-dimensional measuring devices), semiconductor manufacturing equipment (tables for exposure devices, inspection probes, etc.), etc.

[0053] Here, the features of the above-described embodiments of the ball screw according to the present invention will be briefly summarized and listed below in [1] to [7].

[0054] [1] A ball screw (10) comprising: a screw shaft (20) having a spiral screw shaft-side raceway groove (21) formed on its outer peripheral surface; a nut (30) having a spiral nut-side raceway groove (31) formed on its inner peripheral surface facing the screw shaft-side raceway groove (21) and provided with at least a pair of through holes (32, 32) communicating the outer peripheral surface (33) with the nut-side raceway groove (31); a plurality of balls rolling in a ball rolling path (25) formed by the screw shaft-side raceway groove (21) and the nut-side raceway groove (31); and a circulation module (40) attached to the pair of through holes (32, 32) and forming a ball circulation path (60) for circulating the balls rolling in the ball rolling path (25), wherein the circulation module (40) a pair of circulation units (41, 41) that have a cylindrical nut insertion portion (42) that is fitted into the through hole (32) and a direction change portion (43) that changes the moving direction of the balls, and that form a partial path (61) of the ball circulation path (60); and a connection and fixing unit (50) that is disposed between the pair of circulation units (41, 41) and forms a remaining path (63) of the ball circulation path (60) that communicates with the partial path (61) of the ball circulation path (60) in the pair of circulation units (41, 41), respectively; the pair of circulation units (41, 41) have pressure-receiving portions (45) that are respectively provided at the end of the direction change portion (43) opposite to the nut insertion portion (42), The connection and fixation unit (50) has a fixing portion (52) fixed to the nut (30), and pressure-reducing portions (59) provided on both open end sides of the remaining portion path (63) and pressing down on the pressure-receiving portions (45), respectively.

[0055] According to the ball screw (10) having the configuration [1] above, a circulation module (40) can be constructed using only a pair of circulation units (41, 41) and a connection and fixing unit (50), and the circulation module (40) can be fixed to the nut 30.

[0056] [2] The ball screw (10) according to the above [1], wherein the connection and fixing unit (50) is composed of a pair of molded parts (51, 51) that do not have an undercut shape.

[0057] According to the ball screw (10) having the configuration [2] above, the molded part (51) constituting the connection and fixing unit (50) does not require a complex molding die, and manufacturing costs can be reduced.

[0058] [3] A ball screw (10) according to the above item [2], wherein a stepped hole (53) provided in the fixing part (52) toward the screw hole (37) of the nut (30) to allow a threaded portion (71 a) of a screw (71) to thread into the screw hole (37) is defined and formed in the mating surfaces (54) of the pair of molded parts (51, 51), and an opening edge of the stepped hole (53) facing the screw hole (37) is provided with a split prevention protrusion (55) that fits into a recess (38) formed in the opening edge of the screw hole (37).

[0059] According to the ball screw (10) having the configuration [3] above, the pair of molded parts (51, 51) in the connection and fixing unit (50) have their half-split anti-splitting protrusions (55) fitted into the recesses (38) of the nut (30), so that the movement of their mating surfaces (54, 54) in the direction away from each other is restricted.

[0060] [4] The ball screw (10) according to the above [1], wherein the pair of circulation units are each composed of a pair of molded parts (41a, 41b) split into two along the path of the ball circulation path.

[0061] According to the ball screw (10) having the configuration [4] above, the partial path (61) is configured as a complex path made up of a combination of curves, and therefore the molded parts (41 a, 41 b) can be easily formed by injection molding of synthetic resin, which has a high degree of freedom in shape, or sinter molding using metal powder.

[0062] [5] The ball screw (10) according to the above [4], wherein a pressure receiving surface of the pressure receiving portion is a stepped surface that is lower than an outer peripheral surface of the direction changing portion, and a pressure suppressing surface of the pressure suppressing portion presses against the pressure receiving surface.

[0063] According to the ball screw (10) having the configuration [5] above, the pressure control portion (59) of the connection and fixing unit (50) has pressure control surfaces (upper pressure control surface 59a and side pressure control surfaces 59b, 59b) that face the pressure receiving surfaces (upper pressure receiving surface 45a and side pressure receiving surfaces 45b, 45b) of the circulation unit (41), respectively, and can hold down the pressure receiving portions (45) of the pair of circulation units (41, 41). Furthermore, misalignment is less likely to occur between the pressure receiving surfaces (upper pressure receiving surface 45a and side pressure receiving surfaces 45b, 45b) that are stepped surfaces and the pressure control surfaces (upper pressure control surface 59a and side pressure control surfaces 59b, 59b).

[0064] [6] The ball screw (10) according to any one of the above [1] to [5], wherein the circulation module (40) is configured such that the direction changer (43) and the connection and fixing unit (50) are each configured as a polyhedron and are combined in a state of surface contact with each other.

[0065] According to the ball screw (10) having the configuration [6] above, the direction change section (43) of the circulation module (40) and the connecting and fixing unit (50) are each configured as a polyhedron and are combined in a state of surface contact with each other. Therefore, the circulation module (40) consisting of a pair of circulation units (41, 41) and the connecting and fixing unit (50) can be firmly fixed by surface contact with each other.

[0066] [7] The ball screw (10) described in [6] above, wherein an attachment surface parallel to the axis of the nut is formed on the outer peripheral surface of the nut, and the direction change section and the connection and fixing unit are fixed in a state of surface contact with the attachment surface.

[0067] According to the ball screw (10) having the configuration [7] above, the circulation module (40) consisting of a pair of circulation units (41, 41) and a connection and fixing unit (50) and the nut (30) can be firmly fixed to each other by their surfaces coming into contact with each other.

[0068] This application is based on a Japanese patent application (Patent Application No. 2024-083287) filed on May 22, 2024, the contents of which are incorporated herein by reference.

[0069] According to the ball screw of the present invention, it is possible to provide a compact external circulation type ball screw that can fix a circulation module with a nut using a small number of parts.

[0070] REFERENCE SIGNS LIST 10 ball screw 20 screw shaft 21 screw shaft side raceway groove 25 ball rolling path 30 nut 31 nut side raceway groove 32 through hole 33 outer peripheral surface 40 circulation module 41 circulation unit 42 nut insertion portion 43 direction change portion 45 pressure receiving portion 50 connection fixing unit 52 fixing portion 59 pressure control portion 60 ball circulation path 61 partial path 63 remaining path

Claims

1. A ball screw comprising: a screw shaft having a spiral screw shaft-side raceway groove formed on its outer peripheral surface; a nut having a spiral nut-side raceway groove formed on its inner peripheral surface facing the screw shaft-side raceway groove and having at least a pair of through holes communicating the outer peripheral surface with the nut-side raceway groove; a plurality of balls that roll in a ball rolling path formed by the screw shaft-side raceway groove and the nut-side raceway groove; and a circulation module attached to the pair of through holes and forming a ball circulation path for circulating the balls rolling in the ball rolling path, wherein the circulation module has: a pair of circulation units each having a cylindrical nut insertion portion fitted into the through hole and a direction change portion that changes the moving direction of the balls, the pair of circulation units constituting a partial path of the ball circulation path; and a connection and fixing unit disposed between the pair of circulation units and constituting the remaining path of the ball circulation path that communicates with each of the partial paths of the ball circulation path in the pair of circulation units, the pair of circulation units having pressure-receiving portions provided at the ends of the direction change portions opposite the nut insertion portion, The connection and fixing unit includes a fixing portion fixed to the nut, and pressure-reducing portions provided on both open end sides of the remaining portion path and configured to respectively press the pressure-receiving portions.

2. The ball screw according to claim 1, wherein the connection and fixing unit is composed of a pair of molded parts that do not have an undercut shape.

3. A ball screw as set forth in claim 2, wherein a stepped hole provided in the fixed part facing the screw hole to allow the threaded portion of a screw to thread into the screw hole of the nut to pass through is defined and formed on the mating surfaces of the pair of molded parts, and an anti-splitting protrusion that fits into a recess formed on the opening edge of the screw hole is provided on the opening edge of the stepped hole facing the screw hole.

4. The ball screw according to claim 1, wherein the pair of circulation units are each composed of a pair of molded parts split into two along the path of the ball circulation path.

5. A ball screw as set forth in claim 4, wherein the pressure receiving surface of the pressure receiving portion is a stepped surface that is lower than the outer peripheral surface of the direction changing portion, and the pressure suppressing surface of the pressure suppressing portion presses against the pressure receiving surface.

6. A ball screw according to any one of claims 1 to 5, wherein the circulation module is configured such that the direction change section and the connection and fixing unit are each configured as a polyhedron and are combined in a state of surface contact with each other.

7. The ball screw according to claim 6, wherein an attachment surface parallel to the axis of the nut is formed on the outer peripheral surface of the nut, and the direction change section and the connection and fixing unit are fixed in a state of surface contact with the attachment surface.

Images