Ball screw device

Abstract

A ball screw device includes a plurality of ball screw devices. The recirculation member in one ball screw device is larger than the recirculation member in another ball screw device in one of two installation dimensions and smaller than the recirculation member in the other ball screw device in the other of the two installation dimensions, wherein the two installation dimensions are selected from the circumferential length of a portion on the side of a pickup opening portion in each pickup portion, the circumferential length of a portion on the opposite side of each pickup portion from the pickup opening portion, and the circumferential length and axial length of a connecting channel portion, and wherein the other ball screw device differs from the one ball screw device in terms of the diameter of the screw shaft.

Description

Technical Field

[0001] The present invention relates to a ball screw device. Background Art

[0002] There are already existing automotive steering systems in which a motor generates axial thrust on a rack shaft to assist the operation of the rack shaft (for example, Japanese Patent Application Publication No. 2015-132308). In the steering system described in JP 2015-132308A, the rotational force of the motor is converted into axial thrust via a ball screw device and transmitted to the rack shaft.

[0003] The ball screw device described in JP 2015-132308A is a deflector-type ball screw device. It includes a screw shaft having a helical ball screw groove formed on its outer circumference, and a nut having a helical ball screw groove formed on its inner circumference. The ball screw grooves of the screw shaft and nut are arranged facing each other. This provides a rolling path for multiple balls. Summary of the Invention

[0004] In ball screw assemblies, the desired axial load can be achieved by varying the outer diameter of the screw shaft and the inner diameter of the nut. However, due to limitations in steering system design, for example, it is preferable not to significantly alter the outer diameter of the nut. Consequently, there are situations where multiple ball screw assemblies are manufactured, each with a similar appearance but varying load specifications. In many cases, these ball screw assemblies are manufactured on the same production line for cost-effective reasons.

[0005] In the case where ball screw devices having different specifications are manufactured on the same production line, there is a concern that when the deflector is assembled to the nut, a deflector of an incorrect specification may be mistakenly assembled to the nut.

[0006] The present invention provides a ball screw device that can easily prevent incorrect assembly when a plurality of ball screw devices are manufactured.

[0007] A ball screw device according to a first aspect of the present invention includes a plurality of ball screw devices. Each of the plurality of ball screw devices includes: a screw shaft including a spiral outer peripheral rolling groove provided in the outer peripheral surface of the screw shaft; a tubular nut including a spiral inner peripheral rolling groove provided in the inner peripheral surface of the nut such that the inner peripheral rolling groove faces the outer peripheral rolling groove; a plurality of balls rollably arranged in a rolling channel provided between the outer peripheral rolling groove and the inner peripheral rolling groove; and a recycling member providing a shortcut between two points in the rolling channel and forming a recycling channel, the recycling channel allowing the balls to circulate endlessly between the recycling channel and the rolling channel. The recycling member includes i) a pair of picking portions, each longitudinal direction of which is set to the circumferential direction of the nut, the picking portions are arranged point-symmetrically with each other and each includes a picking opening portion opened toward the inner peripheral surface of the nut at one end in the longitudinal direction and a connecting portion connected to the picking opening portion and opened toward the outer peripheral surface side of the nut, and ii) a connecting channel portion that connects between the picking portions and includes a through hole connecting the connecting portions. The recycling member in one of the multiple ball screw devices is larger than the recycling member in another ball screw device in the multiple ball screw devices in one of the two installation dimensions selected from the following, and smaller than the recycling member in the other ball screw device in the other installation dimension, wherein the two installation dimensions are selected from the circumferential length of the portion at the picking opening portion side of each picking portion in the picking portion, the circumferential length of the portion at the opposite side opposite to the picking opening portion of each picking portion in the picking portion, and the circumferential length of the connecting channel portion and the axial length of the connecting channel portion, and the other ball screw device is different from the one ball screw device in terms of the diameter of the screw shaft.

[0008] The ball screw device according to the second aspect of the present invention includes a plurality of ball screw devices. Each of the plurality of ball screw devices includes: a screw shaft including a spiral outer peripheral rolling groove provided in the outer peripheral surface of the screw shaft; a tubular nut including: a spiral inner peripheral rolling groove provided in the inner peripheral surface of the nut so that the inner peripheral rolling groove faces the outer peripheral rolling groove, a pair of mounting holes radially extending through the outer periphery of the nut and the inner periphery of the nut, and an axially extending recirculation groove provided in the outer peripheral surface of the nut; a plurality of balls rollably arranged in a rolling channel provided between the outer peripheral rolling groove and the inner peripheral rolling groove; and a pair of recirculation members providing a shortcut between two points of the rolling channel and forming a recirculation channel, the recirculation channel allowing the balls to circulate infinitely between the recirculation channel and the rolling channel. Each longitudinal direction of the recirculation members is set to the circumferential direction of the nut. The recirculation members are inserted into corresponding mounting holes of the nut and are arranged point-symmetrically with respect to each other. Each of the recirculation members includes a pickup opening portion at one end in the longitudinal direction, which opens toward the inner circumference of the nut, and a connecting portion that communicates with the pickup opening portion and opens toward the outer circumference of the nut. The connecting portion is connected to the recirculation groove. Each of the recirculation members includes a protrusion provided on the outer circumference of the nut, which protrudes in the circumferential direction of the nut. Each recycling member of the recycling components in one of the multiple ball screw devices is larger than each recycling member of the recycling components in another of the multiple ball screw devices in terms of one of the following installation dimensions, and is smaller than each recycling member of the recycling components in the other ball screw device in terms of another of the following installation dimensions, wherein the installation dimensions are the circumferential length of the protrusion at the picking opening side of each recycling member in the recycling members, the circumferential length of the protrusion at the opposite side opposite to the picking opening of each recycling member in the recycling members, and wherein the other ball screw device is different from the one ball screw device in terms of the diameter of the screw shaft.

[0009] In the first aspect of the present invention, the recycling member includes: i) the pair of pickup portions, each longitudinal direction of the pair of pickup portions being set to the circumferential direction of the nut, the pickup portions being arranged point-symmetrically with respect to each other; and ii) a connecting channel portion connecting between the pickup portions. When two or more ball screw devices having different screw shaft diameters are compared with each other, the ball screw device according to the above aspect of the present invention is larger than the other ball screw device in at least one of the installation dimensions and smaller than the other ball screw device in at least another of the installation dimensions.

[0010] The recirculation member is assembled to the nut by being inserted into a mounting recess provided in the outer circumferential surface of the nut and conforming to the contour of the recirculation member. In ball screw devices A and B having different screw shaft diameters, the recirculation member of ball screw device A includes a portion having a smaller mounting dimension than the portion of the recirculation member of ball screw device B, and a portion having a larger mounting dimension than the portion of the recirculation member of ball screw device B. In other words, the recirculation member of ball screw device B also includes a portion having a smaller mounting dimension than the portion of the recirculation member of ball screw device A, and a portion having a larger mounting dimension than the portion of the recirculation member of ball screw device A. For example, in the event of an attempt to install the recirculation member of ball screw device A into the mounting recess provided in the nut of ball screw device B, the recirculation member cannot be installed because the portion having the larger mounting dimension interferes with the mounting recess. Similarly, when attempting to install the recycling member of ball screw device B into the mounting recess provided in the nut of ball screw device A, the recycling member cannot be installed because the portion with the larger mounting size interferes with the mounting recess. Therefore, incorrect assembly when manufacturing multiple ball screw devices can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Features, advantages, technical significance, and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein:

[0012] Figure 1 is a schematic diagram illustrating an electric power steering system including a ball screw device according to a first example;

[0013] Figure 2 yes Figure 1 An enlarged view of the steering assist mechanism and ball screw assembly;

[0014] Figure 3 is a perspective view illustrating a recycling member according to a first example;

[0015] Figure 4 is a diagram illustrating the appearance of a nut in which a recycling member according to a first example is mounted;

[0016] Figure 5 It is along Figure 4 A cross-sectional view of VV in FIG;

[0017] Figure 6 It is along Figure 4 The cross-sectional view taken along line VI-VI;

[0018] Figure 7 is a diagram illustrating the installation dimensions of a plurality of recycling components;

[0019] Figure 8is a perspective view illustrating a recycling member according to a second example;

[0020] Figure 9 is a diagram illustrating the appearance of a nut in which a recycling member according to a second example is mounted; and

[0021] Figure 10 It is along Figure 9 Cross-sectional view of XX in . DETAILED DESCRIPTION

[0022] First example

[0023] Will refer to Figure 1 and Figure 2 A ball screw device 40 according to a first example is described. Figure 1 FIG2 is an overall diagram of an electric power steering system, illustrating an example in which a ball screw device 40 is applied to an electric power steering system of a vehicle. Note that the ball screw device 40 can be applied to any of various systems to which a ball screw device can be applied, such as a four-wheel steering system, a rear-wheel steering system, and a steer-by-wire system, in addition to the electric power steering system.

[0024] Configuration of power steering system

[0025] The electric power steering system 100 (hereinafter also simply referred to as “the steering system 100 ”) is a steering system that assists steering force using a steering assist force.

[0026] The electric power steering system 100 is configured by rotating a rotation shaft 20 coupled to a steering wheel in an axial direction ( Figure 1 A system that changes the direction of the steering wheels of a vehicle by reciprocating in the same direction A as in the right-left direction).

[0027] like Figure 1 As shown, the steering system 100 includes a housing 11 , a steering wheel 12 , a steering shaft 13 , a torque detection device 14 , a motor M, a rotation shaft 20 , a steering assist mechanism 30 , and a ball screw device 40 .

[0028] The housing 11 is a fixed member fixed to the vehicle. The housing 11 has a tubular shape and allows the rotation shaft 20 to be inserted therein so that the rotation shaft 20 can move relative to the housing 11 in the direction A. The housing 11 includes a first housing 11a and one end side ( Figure 1 The second shell 11b on the left side of the figure.

[0029] The steering wheel 12 is fixed to an end portion of a steering shaft 13 and is rotatably supported in a vehicle cabin. The steering shaft 13 transmits torque applied to the steering wheel 12 by a driver's operation to a rotary shaft 20 .

[0030] A pinion 13a included in the rack-and-pinion mechanism is provided at the rotation axis 20 side end portion of the steering shaft 13. The torque detecting device 14 detects torque applied to the steering shaft 13 based on its twisting amount (ie, torsion amount).

[0031] The rotating shaft 20 extends in direction A. A rack 22 is provided on the rotating shaft 20. The rack 22 meshes with the pinion 13a of the steering shaft 13 and, together with the pinion 13a, forms a rack-and-pinion mechanism. The maximum axial force that can be transmitted between the steering shaft 13 and the rotating shaft 20 is set for the rack-and-pinion mechanism based on, for example, the application of the steering system 100.

[0032] Furthermore, a ball screw portion 23 is provided in the rotating shaft 20 at a position different from that of the rack 22. The ball screw portion 23, together with the nut 21 (described later), forms a ball screw device 40 and receives the steering assist force transmitted by the steering assist mechanism 30. The opposite ends of the rotating shaft 20 are respectively coupled to left and right steering wheels (not shown) via, for example, tie rods and knuckle arms (not shown), and the steering wheels are steered left and right by the axial movement of the rotating shaft 20 in the direction A.

[0033] The steering assist mechanism 30 utilizes a motor M as a drive source to provide steering assist force to the rotary shaft 20. The steering assist mechanism 30 includes the motor M, a control unit ECU that drives the motor M, and a drive force transmission mechanism 32. The motor M and the control unit ECU for driving the motor M are housed in a housing 31 fixed to the first housing 11a of the casing 11. The control unit ECU determines the steering assist torque based on the output signal of the torque detection device 14 to control the output of the motor M.

[0034] like Figure 2 As shown in FIG, the driving force transmission mechanism 32 includes a driving pulley 36, a driven pulley 34, and a toothed belt 35. The driving pulley 36 is mounted on the output shaft 37 of the motor M. The output shaft 37 is arranged parallel to the axis of the rotating shaft 20. The driven pulley 34 is arranged on the outer peripheral side of the nut 21 so as to be rotatable together with the nut 21. One end side of the nut 21 in the direction A ( Figure 2 The left side of the second housing 11b is rotatably supported by the inner circumferential surface 11b1 of the second housing 11b via a ball bearing 33. A toothed belt 35 is wound around the driving pulley 36 and the driven pulley 34. The driving force transmission mechanism 32 transmits the rotational driving force generated by the motor M between the driving pulley 36 and the driven pulley 34 via the toothed belt 35.

[0035] The overall structure of the ball screw device

[0036] like Figure 2As shown in FIG, the ball screw device 40 is primarily housed within the second housing 11b. The ball screw device 40 includes a ball screw portion 23 of the rotating shaft 20 (equivalent to the screw shaft), a nut 21, a plurality of rolling balls 24, and a recycling member 50. An outer peripheral rolling groove 201 is helically formed on the outer peripheral surface of the ball screw portion 23 of the rotating shaft 20. The outer peripheral rolling groove 201 has multiple turns.

[0037] The nut 21 is tubular in shape and is arranged coaxially with the ball screw portion 23 (rotating shaft 20) on the outer peripheral side of the ball screw portion 23. The inner peripheral surface of the nut 21 includes an inner peripheral rolling groove 211 formed in a spiral shape. The inner peripheral rolling groove 211 has multiple turns. The outer peripheral rolling groove 201 of the ball screw portion 23 and the inner peripheral rolling groove 211 of the nut 21 are arranged facing each other, and a rolling channel R1 in which the multiple rolling balls 24 roll is formed by the outer peripheral rolling groove 201 and the inner peripheral rolling groove 211. The multiple rolling balls 24 are arranged in a manner that allows them to roll inside the rolling channel R1. Therefore, the outer peripheral rolling groove 201 of the ball screw portion 23 (rotating shaft 20) and the inner peripheral rolling groove 211 of the nut 21 are threadedly connected via the multiple rolling balls 24.

[0038] In addition, if Figure 4 and Figure 5 As shown, the nut 21 includes a mounting recess 213 on its outer circumferential surface 212 for accommodating a recycling member. The mounting recess 213 includes a pair of mounting holes 41, 42 extending between the outer circumferential surface 212 and the inner circumferential surface of the nut 21, and a connecting groove 43 connecting the mounting holes 41, 42. The mounting holes 41, 42 are arranged spaced apart and point-symmetrically with respect to each other in direction A, such that the multiple turns of the inner circumferential rolling groove 211 of the nut 21 are disposed between the mounting holes 41, 42.

[0039] The recycling member 50 as a deflector is accommodated in the mounting recess 213 of the nut 21 and forms a recycling passage R2 that provides a shortcut between two points in the rolling passage R1 and allows the balls 24 to circulate infinitely between the recycling member 50 and the rolling passage R1.

[0040] Structure of recycled components

[0041] Will refer to Figures 3 to 6The structure of the recycling member 50 will be described. The recycling member 50 includes a pair of pickup portions 51, 52, each of which has its longitudinal direction aligned with the circumferential direction of the nut 21 and is received in the respective mounting holes 41, 42 of the nut 21. The pickup portions 51, 52 have the same configuration, so only the pickup portion 51 will be described. The pickup portion 51 includes a through-hole, which includes a pickup opening 54 at one end in the longitudinal direction, which opens toward the inner circumference of the nut 21. A connecting portion 55 is provided at the other end of the through-hole, communicating with the pickup opening 54 of the pickup portion 52 through the through-hole.

[0042] The pickup portions 51 and 52 are arranged separately from each other in the axial direction of the nut 21 so that the respective connecting portions 55 face each other. Regardless of the specifications of the ball screw device 40, the distance between the pickup portions 51 and 52 can be kept constant (i.e., kept consistent). In other words, even in a plurality of ball screw devices with different screw shaft diameters, the length of the recycling member 50 in the axial direction relative to the nut 21 and the lead of the ball screw can be made constant. If the length of the recycling member 50 in the axial direction of the nut 21 is constant, the number of turns of the inner peripheral rolling groove 211 of the nut 21 spanned by the recycling member 50 is constant. Therefore, the axial length of the portion where the nut 21 and the ball screw portion 23 are threadedly connected remains constant. In addition, the lead of the ball screw can be made constant, and the respective cross-sectional shapes and sizes of the rolling grooves 201 and 211 of the screw shaft and the nut and the diameter of each ball 24 can be made constant. In this case, in the plurality of ball screw devices having different screw shaft diameters, if the axial load of the ball screw applied by each ball is the same (i.e., the axial load is constant), the stress distribution on the ball and on the rolling groove is substantially the same (i.e., the stress distribution is substantially constant). The performance and durability results of a ball screw designed and evaluated using one screw shaft diameter (i.e., one pitch circle diameter) can be used to design another ball screw including a screw shaft having a different diameter and to estimate the evaluation results of the other ball screw. Therefore, for a plurality of ball screw devices having different screw shaft diameters, it becomes easy to design the performance and durability (including the axial load) of each ball screw.

[0043] The pickup portion 51 is received in the mounting hole 41 of the nut 21 and secured to the nut 21. The bottom of the pickup portion 51 is configured to conform to the arc shape of the inner circumferential surface of the nut 21. The through-hole in the pickup portion 51 extends from the inner circumferential surface of the nut 21 toward the outer circumferential surface of the nut 21, generally in a direction tangential to the rolling passage R1. The through-hole then tilts along the circumferential direction of the nut to pick up the balls 24 rolling in the rolling passage R1 from the pickup opening toward the outer circumferential surface of the nut 21.

[0044] Between the pair of pickup portions 51, 52 arranged in a manner facing each other, a connection passage portion 53 is provided in a manner integrally joined to the pickup portions 51, 52. The connection passage portion 53 includes a connection passage 56 that is a through-hole connecting the connection portions 55 of the pickup portions 51, 52, thereby providing a continuous path from one pickup opening portion 54, through one connection portion 55, the connection passage 56, and the other connection portion 55 to the other pickup opening portion 54, and this path serves as a recycling passage R2.

[0045] The connecting channel portion 53 is received in the mounting recess of the nut 21 and includes a main body portion 531 and a protruding portion 532. The main body portion 531 is provided with a connecting channel 56. The protruding portion 532 is provided on the outer circumference of the nut 21 and protrudes to opposite sides along the circumferential direction of the nut 21. The connecting channel portion 53 is as follows: Figure 6 The illustrated substantially T-shaped shape, in which the portion of the connecting passage portion 53 at the outer peripheral side of the nut 21 protrudes in a cross section orthogonal to the axial direction of the nut 21. The protruding amount (length) of the protruding portion 532 can be arbitrarily set regardless of the form of the recirculation passage R2. Figure 4 As shown in FIG, the recycling member 50 is divided into two parts by a dividing plane 50S, which is a curved plane formed by displacing a line extending substantially along the centerline of the recycling passage R2 in parallel in the radial direction of the nut. This facilitates the formation of the recycling passage R2. Depending on the manufacturing method and shape of the recycling member 50, the entire recycling member 50 can be provided as an integral component (i.e., a one-piece component).

[0046] Assembly of the ball screw unit

[0047] The recycling member 50 is assembled to the nut 21 by being inserted into a mounting recess 213 provided in the outer peripheral surface 212 of the nut 21. The mounting recess 213 has a shape corresponding to the outline of the recycling member 50, and the shape is determined according to the mounting dimensions of the recycling member 50. The mounting dimensions of the recycling member 50 are selected from the circumferential length of the portion 514 on the pickup opening portion 54 side of the pickup portion 51 (i.e., the portion 514 on one side of the pickup opening portion 54 in the pickup portion 51), the circumferential length of the opposite side portion 515 on the side opposite to the pickup opening portion 54 in the pickup portion 51, the circumferential length of the connecting passage portion 53, and the axial length of the connecting passage portion 53.

[0048] The design is performed such that, when comparing two or more ball screw devices 40a, 40b having different screw shaft diameters, at least one of the installation dimensions of one ball screw device is larger than the at least one installation dimension of the other ball screw device, and at least one of the installation dimensions of the one ball screw device is smaller than the at least one installation dimension of the other ball screw device. For example, Figure 7 As shown, when the circumferential length of the opposite side portion 515 of the recycling member 50a, which is opposite to the pickup opening 54, is greater than the circumferential length of the opposite side portion 515 of the recycling member 50b, the circumferential length of the protrusion 532 of the connecting channel portion 53 of the recycling member 50a is smaller than the circumferential length of the protrusion 532 of the connecting channel portion 53 of the recycling member 50b. For example, the circumferential length is the distance from the center plane CP, which is located at the circumferential center of the recycling member 50 and extends through the central axis of the nut, to the end of each portion. With this configuration, in the two ball screw devices 40a and 40b having different screw shaft diameters, the recycling member 50a of the ball screw device 40a interferes with the mounting recess 213b of the nut 21b of the ball screw device 40b and cannot be installed in the mounting recess 213b. On the other hand, the recycling member 50 b also interferes with the mounting recess 213 a of the nut 21 a and thus cannot be mounted in the mounting recess 213 a .

[0049] The circumferential length of the portion of the pickup portion 51 circumferentially opposite the pickup opening 54 and the circumferential length of the connecting channel 53 can be adjusted as installation dimensions. The circumferential length of the portion of the pickup portion 51 circumferentially opposite the pickup opening 54 and the circumferential length of the connecting channel 53 are less likely to affect the shape of the recirculation channel R2 for the balls 24. By adjusting the installation dimensions based on these lengths, the center path of the balls 24 rolling in the recirculation channel R2 can be easily adjusted regardless of the adjusted installation dimensions. More specifically, it is desirable to maximize the three-dimensional curvature radius of the center path of the balls 24 in the recirculation member 50 based on the screw shaft diameter. Furthermore, when providing the mounting recess 213 in the nut 21, it is preferable to leave an allowance in the axial length of the recess corresponding to the connecting channel 53, for example, to improve operational efficiency. Therefore, by adjusting these two dimensions as installation dimensions, manufacturability can be improved. In addition, in a plurality of ball screw devices having different screw shaft diameters, the center orbits of the balls 24 in the recycling member 50 may be the same in a plan view viewed in the radial direction of the nut 21. In this case, the design man-hours for the center orbits of the balls 24 can be reduced.

[0050] In a plurality of ball screw devices 40 having different screw shaft diameters, two dimensions in each installation dimension are changed. The installation dimension of the recycling member 50 is selected from the circumferential length of the side portion 514 of the pickup opening portion 54 of the pickup portion 51 (i.e., the portion 514 on one side of the pickup opening portion 54 in the pickup portion 51), the circumferential length of the opposite side portion 515 on the side opposite to the pickup opening portion 54 in the pickup portion 51, the circumferential length of the connecting channel portion 53, and the axial length of the connecting channel portion 53. When the installation dimension is changed, the installation dimension of the recycling member 50 can be adjusted using the circumferential length of the protrusion 532 (i.e., by adjusting the circumferential length of the protrusion 532). The protrusion of the recycling member 50 is a portion protruding from the main body portion provided with the recycling channel R2, and has nothing to do with the shape of the recycling channel R2. Therefore, the installation dimension can be adjusted while maintaining the shape of the recycling channel R2.

[0051] In order to prevent the recycling member from being installed in the mounting recess of a nut of the wrong specification, it is necessary to increase any of the mounting dimensions. However, if only one of the mounting dimensions of the recycling member of one ball screw device in the ball screw devices 40a, 40b with different screw shaft diameters is increased, the recycling member of the other ball screw device can still be accommodated in the mounting recess 213 of the nut 21 of the one ball screw device, although there is a gap. Therefore, in the ball screw devices 40a, 40b with different screw shaft diameters, the increase in one length and the decrease in the other length of at least two mounting dimensions cause the recycling member 50 of one ball screw device to interfere with the mounting recess 213 of the nut 21 of the other ball screw device with different specifications at one portion having the one mounting dimension and the other mounting dimension, thereby preventing the recycling member 50 from being installed in the mounting recess 213. Therefore, even if multiple ball screw devices with different screw shaft diameters are produced on the same production line, assembly errors can be prevented.

[0052] Second example

[0053] The first example indicates an example of an integral type recycling member 50 in which the pair of pickup portions 51, 52 and the connecting passage portion 53 are integrally provided. Figures 8 to 10 As shown, in the ball screw device 140 of the second example, only the pickup portions 151 and 152 are provided as the recycling member 150 .

[0054] The pickup portions 151, 152 are inserted into and fixed in respective mounting holes provided in the nut 121. The mounting holes are mounting recesses. In the outer peripheral surface of the nut 121, a recycling groove 123 is provided in a manner of connecting portions of the mounted pickup portions 151, 152. The balls 24 picked up by one pickup portion pass through the recycling groove 123 and circulate from the other pickup portion to the rolling channel R1. In other words, a path from the pickup opening portion 54 of one pickup portion through the connecting portion 55 of the one pickup portion, the recycling groove 123, and the connecting portion 55 of the other pickup portion to the pickup opening portion 54 of the other pickup portion serves as the recycling channel R2.

[0055] In this case, each recycling member 150 includes a main body portion 511, which is accommodated in the mounting hole of the nut 121 and in which a portion of the recycling passage R2 is provided, and a protrusion portion, which is provided on the outer peripheral side of the nut 121 relative to the main body portion 511 (that is, the protrusion portion is provided closer to the outer periphery of the nut 121 than the main body portion 511), and protrudes in the circumferential direction of the nut 121. The recycling member 150 includes a protrusion 512 protruding on one side of the pickup opening portion 54 in the longitudinal direction of the pickup portion 151, and a protrusion 513 protruding on the side of the pickup opening portion 54 opposite to the pickup opening portion 54 in the pickup portion 151. As shown in Figure 10 As shown in FIG, the pickup portion 151 has a generally T-shaped configuration, with the outer circumferential side of the nut 121 protruding in a cross section perpendicular to the axial direction of the nut 121. For the recycling member 150, the circumferential length of the protrusion 512 on one side of the pickup opening 54 in the pickup portion 151 and the circumferential length of the protrusion 513 on the side opposite to the pickup opening 54 in the pickup portion 151 are adjusted to the mounting dimensions. More specifically, while the length L1 of the portion of the circumferential length of the protrusion 513 on the side opposite to the pickup opening 54 in the pickup portion 151 that circumferentially protrudes from the side of the main body 511 is made larger than that of another ball screw device, the length L2 of the portion of the circumferential length of the protrusion 512 on the side of the pickup opening 54 in the pickup portion 151 that circumferentially protrudes from the side of the main body 511 is made smaller than that of another ball screw device. By adopting this structure, it is possible to form a portion that interferes with the mounting recess 213 while maintaining the length of the main body 511 constant. Furthermore, one of the mounting dimensions to be changed may be the axial dimension of the recycling member 150, for example, the axial length of the protrusion 512 or 513. The recycling member 150 prevents incorrect assembly by varying the amount of protrusion on the left and right sides of the T-shaped portion when viewed in a cross-section perpendicular to the axial direction of the nut 121.

[0056] In the ball screw of each of the first and second examples of the present invention, a deflector-type recycling member including a recycling channel having a closed cross-section is inserted into a hole that passes through from the outer periphery of the nut to the inner periphery of the nut, thereby forming a ball circulation channel. However, the present invention is not limited to these examples. The present invention can be applied to an internal deflector-type ball screw or an end deflector-type ball screw, in which an internal deflector-type ball screw is installed in a recess in the inner periphery of the nut, in which a recirculation member that picks up balls from the rolling channel of the screw shaft and circulates the balls is installed in corresponding recess portions at two opposite ends in the axial direction of the nut.

Claims

1. A ball screw device, characterized in that: include A plurality of ball screw assemblies, each of the plurality of ball screw assemblies comprising: a screw shaft including a spiral outer peripheral rolling groove provided in an outer peripheral surface of the screw shaft; a tubular nut including a helical inner circumferential rolling groove provided in an inner circumferential surface of the nut such that the inner circumferential rolling groove faces the outer circumferential rolling groove; a plurality of balls rollably arranged in a rolling channel provided between the outer peripheral rolling groove and the inner peripheral rolling groove; and a recirculation member providing a shortcut between two points in the rolling channel and forming a recirculation channel, the recirculation channel allowing the balls to circulate endlessly between the recirculation channel and the rolling channel, wherein: The recycling component includes a pair of pickup portions, each longitudinal direction of which is set to the circumferential direction of the nut, the pickup portions being arranged point-symmetrically with each other and each including a pickup opening portion opened toward the inner peripheral surface of the nut at one end in the longitudinal direction and a connecting portion communicating with the pickup opening portion and open toward the outer peripheral surface side of the nut, and a connecting channel portion connected between the pickup portions and comprising a through hole connecting the connecting portions; and In the plurality of ball screw devices, the lengths of the recycling members in the axial direction of the nut are uniform, The recycling member in one of the multiple ball screw devices is larger than the recycling member in another ball screw device in the multiple ball screw devices in one of the two installation dimensions, and smaller than the recycling member in the other ball screw device in the other installation dimension, wherein the two installation dimensions are selected from the circumferential length of the portion at the side of the picking opening portion in each of the picking portions, the circumferential length of the portion at the opposite side opposite to the picking opening portion in each of the picking portions, the circumferential length of the connecting channel portion and the axial length of the connecting channel portion, and wherein the other ball screw device is different from the one ball screw device in terms of the diameter of the screw shaft.

2. The ball screw device according to claim 1, wherein: The recycling member in the one ball screw device is larger than the recycling member in the other ball screw device that is different from the one ball screw device in the diameter of the screw shaft in one of the following installation dimensions, and is smaller than the recycling member in the other ball screw device in another installation dimension of the following installation dimensions, wherein the installation dimensions are the circumferential length of the portion on the opposite side of each of the picking portions opposite to the picking opening portion and the circumferential length of the connecting channel portion.

3. The ball screw device according to claim 1 or 2, characterized in that: Each center track of the balls rolling in the recirculation channel in the plurality of ball screw devices is identical in a plan view of the center track viewed in a radial direction of the nut.

4. The ball screw device according to any one of claims 1 or 2, characterized in that: The recycling member includes a protrusion provided on an outer peripheral side of the nut, the protrusion protruding in a circumferential direction of the nut; and The length of one of the installation dimensions of the recycling member is changed by changing the length of the protrusion.

5. A ball screw device, characterized in that: include A plurality of ball screw assemblies, each of the plurality of ball screw assemblies comprising: a screw shaft including a spiral outer peripheral rolling groove provided in an outer peripheral surface of the screw shaft; A tubular nut comprising: a helical inner circumferential rolling groove provided in an inner circumferential surface of the nut such that the inner circumferential rolling groove faces the outer circumferential rolling groove; a pair of mounting holes radially extending through the outer circumference of the nut and the inner circumference of the nut; and an axially extending recirculation groove provided in the outer circumferential surface of the nut; a plurality of balls rollably arranged in a rolling channel provided between the outer peripheral rolling groove and the inner peripheral rolling groove; and a pair of recirculation members providing a shortcut between two points in the rolling channel and forming a recirculation channel that allows the balls to circulate endlessly between the recirculation channel and the rolling channel, wherein: Each longitudinal direction of the recycling members is set to the circumferential direction of the nut, the recycling members are inserted into the corresponding mounting holes of the nut and are arranged point-symmetrically with each other, and each of the recycling members includes a pickup opening portion opened toward the inner peripheral surface of the nut at one end in the longitudinal direction and a connecting portion communicating with the pickup opening portion and open toward the outer peripheral surface of the nut; The connecting portion is connected to the recirculation tank; each of the recycling members includes a protrusion provided at an outer peripheral side of the nut, the protrusion protruding in a circumferential direction of the nut; and In the plurality of ball screw devices, the lengths of the recycling members in the axial direction of the nut are uniform, Each recycling member of the recycling components in one of the multiple ball screw devices is larger than each recycling member of the recycling components in another of the multiple ball screw devices in terms of one of the following installation dimensions, and is smaller than each recycling member of the recycling components in the other ball screw device in terms of another of the following installation dimensions, wherein the installation dimensions are the circumferential length of the protrusion at the picking opening side of each of the recycling members and the circumferential length of the protrusion at the opposite side of each of the recycling members opposite to the picking opening, and wherein the other ball screw device is different from the one ball screw device in terms of the diameter of the screw shaft.

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