Ball screw device

Abstract

To achieve restriction of a stroke end of a nut, a linear motion element, with a small number of components to achieve downsizing of a ball screw device.SOLUTION: A projection-like non-rotation side engagement part 13 is provided at one axial end part of a nut 3 and a projection-like rotation side engagement part 18 is provided at a driving member 5 which is fixed in a manner that the driving member 5 does not rotate relative to a screw shaft 2 and rotationally drives the screw shaft 2. At a stroke end of the nut 3, the non-rotation side engagement part 13 and the rotation side engagement part 18 are engaged in a circumferential direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A ball screw device uses balls to roll between a screw shaft and a nut, and is therefore more efficient than a sliding screw device in which the screw shaft and the nut are in direct contact with each other. For this reason, ball screw devices are incorporated into various types of machinery, such as electric brake devices and automatic manual transmissions (AMTs) for automobiles, and positioning devices for machine tools, in order to convert the rotational motion of a drive source, such as an electric motor, into linear motion.

[0003] The ball screw device has a screw shaft having a helical shaft-side ball screw groove on its outer circumferential surface, a nut having a helical nut-side ball screw groove on its inner circumferential surface, and a plurality of balls arranged between the shaft-side ball screw groove and the nut-side ball screw groove. Depending on the application, the ball screw device is used with one of the screw shaft and the nut as a rotational motion element and the other of the screw shaft and the nut as a linear motion element.

[0004] In a ball screw device, the stroke end of a linear motion element is restricted to prevent the linear motion element from linearly moving beyond a predetermined range. Fig. 19 shows a ball screw device 100 of a conventional structure having a structure for restricting the stroke end of a linear motion element, which is described in JP 2016-70281 A (Patent Document 1).

[0005] The ball screw device 100 includes a screw shaft 101, a nut 102, a plurality of balls (not shown), and a stopper 103.

[0006] The screw shaft 101 has a threaded portion 104 and a fitting shaft portion 105 arranged adjacent to one axial side of the threaded portion 104. A spiral shaft-side ball screw groove 106 is formed on the outer peripheral surface of the threaded portion 104. The fitting shaft portion 105 has an outer diameter smaller than the threaded portion 104, and has male spline teeth formed on its outer peripheral surface. The screw shaft 101 is arranged coaxially with the nut 102 with the threaded portion 104 inserted into the inside of the nut 102.

[0007] The nut 102 has a cylindrical shape and has a helical nut-side ball screw groove and a generally S-shaped circulation groove (not shown) on its inner circumferential surface. The nut 102 has an engagement portion 107 at one end in the axial direction.

[0008] The shaft-side ball screw groove 106 and the nut-side ball screw groove are disposed so as to face each other in the radial direction, forming a spiral load path. The start point and end point of the load path are connected by a circulation groove formed on the inner peripheral surface of the nut 102. Therefore, the balls that reach the end point of the load path are returned to the start point of the load path through the circulation groove. The start point and end point of the load path are switched depending on the direction of relative displacement (relative rotation direction) between the screw shaft 101 and the nut 102 in the axial direction.

[0009] The stopper 103 has a boss portion 108 having an annular shape and a claw portion 109 having a protruding shape. The boss portion 108 is fitted onto the fitting shaft portion 105 of the screw shaft 101 so as not to rotate relative thereto. Specifically, the boss portion 108 is fitted onto the fitting shaft portion 105 so as not to rotate relative thereto by spline-engaging female spline teeth formed on the inner peripheral surface with male spline teeth formed on the outer peripheral surface of the fitting shaft portion 105. The claw portion 109 protrudes radially from a circumferential portion of the outer peripheral surface of the boss portion 108.

[0010] In the ball screw device 100 of the conventional structure, when either the linear motion element of the screw shaft 101 or the nut 102 moves linearly and reaches a stroke end, the engagement portion 107 provided on the nut 102 and the claw portion 109 provided on the stopper 103 engage in the circumferential direction. This prevents the rotation of either the rotational motion element of the screw shaft 101 or the nut 102, making it possible to regulate the stroke end of the linear motion element. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2016-70281 A Summary of the Invention [Problem to be solved by the invention]

[0012] In the ball screw device 100 of the conventional structure described in JP 2016-70281 A, a dedicated part, a stopper 103, is used to regulate the stroke end of the linear motion element. For this reason, for example, when the screw shaft 101 is used as the rotational motion element and the nut 102 is used as the linear motion element, a drive member for rotating the screw shaft 101 needs to be provided separately from the stopper 103. This increases the number of parts, and the ball screw device 100 tends to become large in size.

[0013] The present invention has been made to solve the above-mentioned problems, and has an object to provide a ball screw device that can regulate the stroke end of the nut, which is a linear motion element, with a small number of parts, thereby enabling miniaturization. [Means for solving the problem]

[0014] A ball screw device according to one aspect of the present invention includes a screw shaft, a nut, a plurality of balls, and a drive member. The screw shaft has a helical ball screw groove on its outer circumferential surface, and rotates when in use. The nut has a helical nut-side ball screw groove on its inner peripheral surface, and a protruding non-rotating side engagement portion at one end in the axial direction, and moves linearly when in use. The plurality of balls are disposed between the shaft side ball screw groove and the nut side ball screw groove. The drive member is fixed to the screw shaft so as not to rotate relative to the screw shaft, and drives the screw shaft to rotate. In the ball screw device according to one aspect of the present invention, the drive member is provided with a protruding rotation side engagement portion that is capable of engaging with the non-rotation side engagement portion in a circumferential direction. a cylindrical tube portion having a torque input portion provided on an outer circumferential surface thereof; It shall have the following. A radially outer end of the rotation side engagement portion is connected to the inner circumferential surface of the cylindrical portion.

[0015] In the ball screw device according to an aspect of the present invention, the rotation side engaging portion may be provided in plurality. In this case, the rotation side engaging portions can be disposed at equal intervals in the circumferential direction of the drive member.

[0016] In the ball screw device according to one aspect of the present invention, the drive member has a connection portion that is fixed to the screw shaft so as not to rotate relative to the screw shaft, and the rotation side engagement portion can be configured integrally with the connection portion. 。

[0017] Books A ball screw device according to an aspect of the present invention In a ball screw device different from the above The rotation side engagement portion may be formed separately from the connection portion and fixed to the connection portion.

[0018] In the ball screw device according to one aspect of the present invention, the drive member may be any one of a gear, a pulley, and a sprocket.

[0019] A ball screw device according to an aspect of the present invention In a ball screw device different from the above The drive member may be a motor shaft. In this case, the drive member has a cylindrical connection portion that fixes it so that it cannot rotate relative to the screw shaft, and the rotating side engagement portion can be configured integrally with the connection portion, or can be configured separately from the connection portion and fixed to the connection portion. Effect of the Invention

[0020] According to the ball screw device of the present invention, the stroke end of the nut, which is a linear motion element, can be regulated with a small number of parts, making it possible to reduce the size. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a front view of a ball screw device according to a first embodiment of the present invention, as viewed from the other axial side. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, showing a state in which the stroke end of the nut is restricted in the ball screw device according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a partially enlarged view of FIG. [Figure 4] FIG. 4 is a perspective view of a ball screw device according to a first embodiment of the present invention. [Diagram 5] FIG. 5 is a perspective view showing a nut according to a first embodiment of the present invention. [Figure 6] FIG. 6 is a front view of the drive member according to the first embodiment, seen from the other axial side. [Figure 7] FIG. 7 is a perspective view showing a driving member according to a first embodiment of the present invention. [Figure 8] FIG. 8 is a schematic view taken along the line B in FIG. [Figure 9] FIG. 9 is a diagram showing a first example of an embodiment, and corresponds to FIG. [Figure 10] FIG. 10 is a diagram showing a first example of an embodiment, and corresponds to FIG. [Figure 11] FIG. 11 is a diagram showing a second reference example and corresponds to FIG. [Figure 12]FIG. 12 is a diagram showing a second reference example and corresponds to FIG. [Figure 13] FIG. 13 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 14] FIG. 14 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 15] FIG. 15 is a diagram showing a third reference example and corresponds to FIG. [Figure 16] FIG. 16 is a diagram showing a third reference example and corresponds to FIG. [Figure 17] FIG. 17 is a diagram showing a fourth reference example and corresponds to FIG. [Figure 18] FIG. 18 is a diagram showing a fourth reference example and corresponds to FIG. [Figure 19] FIG. 19 is a perspective view showing a ball screw device having a conventional structure.

[0022] [ Reference example First example of Reference example The first example will be described with reference to FIGS. 1 to 8. FIG.

[0023] [Overall configuration of ball screw device] This reference example The ball screw device 1 is incorporated in, for example, an electric brake booster device, and is used for applications such as converting the rotational motion of an electric motor, which is a drive source, into linear motion to operate a piston of a hydraulic cylinder.

[0024] The ball screw device 1 includes a screw shaft 2, a nut 3, a plurality of balls 4, and a drive member 5.

[0025] The screw shaft 2 is rotationally driven by a drive source (not shown) via a drive member 5, and is a rotational motion element that rotates when in use. The screw shaft 2 is inserted into the inside of the nut 3 and is arranged coaxially with the nut 3. The nut 3 is prevented from rotating together with the screw shaft 2 by a rotation prevention mechanism (not shown), and is a linear motion element that moves linearly when in use. For this reason, This reference exampleThe ball screw device 1 is used in such a manner that the screw shaft 2 is rotationally driven and the nut 3 is caused to move linearly.

[0026] A spiral load path 6 is provided between the outer peripheral surface of the screw shaft 2 and the inner peripheral surface of the nut 3. A plurality of balls 4 are arranged in the load path 6 so as to be able to roll. When the screw shaft 2 and the nut 3 are rotated relative to each other, the balls 4 that have reached the end point of the load path 6 are returned to the start point of the load path 6 through a circulation groove 7 formed on the inner peripheral surface of the nut 3. The structure of each component of the ball screw device 1 will be described below. In the following description, unless otherwise specified, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction with respect to the screw shaft 2. Furthermore, one axial side refers to the right side in Figs. 2 to 5 and 8, and the other axial side refers to the left side in Figs. 2 to 5 and 8.

[0027] <Screw shaft> The screw shaft 2 is made of metal and has a threaded portion 8 and a fitting shaft portion 9 arranged adjacent to one axial side of the threaded portion 8. The threaded portion 8 and the fitting shaft portion 9 are arranged coaxially and integrally formed with each other. The fitting shaft portion 9 has an outer diameter smaller than that of the threaded portion 8.

[0028] The threaded portion 8 has on its outer circumferential surface a helical shaft-side ball screw groove 10. The shaft-side ball screw groove 10 is formed on the outer circumferential surface of the threaded portion 8 by grinding (cutting) or rolling. This reference example In the example, the number of threads in the shaft-side ball screw groove 10 is 1. The cross-sectional groove shape (groove bottom shape) of the shaft-side ball screw groove 10 is a Gothic arch groove or a circular arc groove. This reference example In this case, the formation direction (winding direction) of the shaft side ball screw groove 10 is restricted to a direction that allows the nut 3 to move linearly to one side in the axial direction when the screw shaft 2 is rotated to one side in the circumferential direction.

[0029] The fitting shaft portion 9 has male spline teeth 11 on the outer circumferential surface over the entire circumference. Therefore, the fitting shaft portion 9 is a spline shaft portion. In the illustrated example, the male spline teeth 11 are involute spline teeth, but they may also be angular spline teeth.

[0030] The screw shaft 2 is arranged coaxially with the nut 3 with the threaded portion 8 inserted into the inside of the nut 3. This reference example In the embodiment, the screw shaft 2 is composed of a threaded portion 8 and an engaging shaft portion 9, but when implementing the present invention, the screw shaft may further be provided with a support shaft portion (second engaging shaft portion) for fixing a rolling bearing or the like for supporting the screw shaft rotatably relative to a housing or the like, and a spline portion or serration portion that functions as a torque transmission portion.

[0031] <nut> The nut 3 is made of metal and is configured to be cylindrical as a whole. The nut 3 has a helical nut-side ball screw groove 12 and a circulation groove 7 on its inner peripheral surface.

[0032] The nut side ball screw groove 12 has a helical shape, and is formed on the inner peripheral surface of the nut 3 by, for example, grinding (cutting) or rolling tapping (cutting tapping). The nut side ball screw groove 12 has the same lead as the shaft side ball screw groove 10. Therefore, in a state where the threaded portion 8 of the screw shaft 2 is inserted into the inside of the nut 3, the shaft side ball screw groove 10 and the nut side ball screw groove 12 are arranged so as to face each other in the radial direction, forming a helical load path 6. The number of threads of the nut side ball screw groove 12 is one, similar to the shaft side ball screw groove 10. The groove shape of the cross section of the nut side ball screw groove 12 is also a gothic arch groove or a circular arc groove, similar to the shaft side ball screw groove 10.

[0033] The circulation groove 7 has a substantially S-shape, and is formed on the inner peripheral surface of the nut 3 by, for example, forging (cold forging). The circulation groove 7 smoothly connects axially adjacent portions of the nut-side ball screw groove 12, and connects the start point and end point of the loaded path 6. Therefore, the ball 4 that has reached the end point of the loaded path 6 is returned to the start point of the loaded path 6 through the circulation groove 7. The start point and end point of the loaded path 6 are switched depending on the direction of relative displacement (relative rotation direction) between the screw shaft 2 and the nut 3 in the axial direction.

[0034] The circulation groove 7 has a substantially semicircular cross-sectional shape. The circulation groove 7 has a groove width slightly larger than the diameter of the ball 4, and a groove depth that allows the ball 4 moving in the circulation groove 7 to climb over the threads of the shaft-side ball screw groove 10.

[0035] The nut 3 has a protruding non-rotating side engagement portion 13 at one axial end. The non-rotating side engagement portion 13 is provided on a circumferential portion of a side surface on one axial end of the nut 3, and protrudes toward one axial end. The non-rotating side engagement portion 13 has a sector shape.

[0036] The non-rotation side engagement portion 13 has a flat non-rotation side stopper surface 14 on the other circumferential side (the front side surface in Figs. 4 and 5, and the lower side surface in Fig. 8). The non-rotation side stopper surface 14 is disposed approximately parallel to the central axis of the nut 3.

[0037] In the illustrated example, the nut 3, including the non-rotating side engagement portion 13, is constructed as a single unit, but when implementing the present invention, the nut can also be constructed by connecting and fixing a tubular member having a nut side ball screw groove and a circulation groove on its inner surface to the non-rotating side engagement portion.

[0038] This reference example The ball screw device 1 uses the nut 3 as a linear motion element. This reference example In the present embodiment, the nut 3 is prevented from rotating by a rotation-prevention mechanism (not shown). As the rotation-prevention mechanism, various conventionally known structures can be used. For example, a structure can be used in which a protrusion (key) provided on the inner peripheral surface of a fixed member such as a housing is engaged with a recessed groove formed in the axial direction on the outer peripheral surface of the nut 3.

[0039] <ball> The balls 4 are steel balls having a predetermined diameter, and are arranged so as to be able to roll in the load path 6 and the circulation groove 7. The balls 4 arranged in the load path 6 roll while being subjected to a compressive load, whereas the balls 4 arranged in the circulation groove 7 roll by being pushed by the succeeding balls 4 without being subjected to a compressive load.

[0040] <Driving member> The driving member 5 transmits torque input from a driving source such as an electric motor to the screw shaft 2, thereby driving the screw shaft 2 to rotate. This reference example The driving member 5 not only has the function of rotating the screw shaft 2 but also has the function of regulating the stroke end of the nut 3 which is a linear motion element.

[0041] This reference example In the ball screw device 1, when the driving member 5 is rotationally driven toward one side in the circumferential direction, the nut 3 moves relatively to one side in the axial direction with respect to the screw shaft 2. In contrast, when the driving member 5 is rotationally driven toward the other side in the circumferential direction, the nut 3 moves relatively to the other side in the axial direction with respect to the screw shaft 2.

[0042] The driving member 5 has a base plate portion 15, a cylindrical portion 16, a torque input portion 17, and a rotation side engagement portion 18 in the form of a protrusion. This reference example The driving member 5 is integrally configured as a whole, including the rotating side engaging portion 18. The driving member 5 is made of metal such as carbon steel or stainless steel, or made of synthetic resin. The driving member 5 may be, for example, a gear, a pulley, or a sprocket.

[0043] The base plate portion 15 corresponds to the connecting portion described in the claims and has a circular flat plate shape. The base plate portion 15 has an attachment hole 19 penetrating in the axial direction in the radial center. Female spline teeth 20 are formed on the inner peripheral surface of the attachment hole 19. The base plate portion 15 is externally fitted and fixed to the fitting shaft portion 9 so as not to rotate relative to the fitting shaft portion 9 by spline-engaging the female spline teeth 20 formed on the inner peripheral surface of the attachment hole 19 with the male spline teeth 11 formed on the outer peripheral surface of the fitting shaft portion 9. A radially inner portion of a side surface 15a on the other axial side of the base plate portion 15 abuts against or closely faces an end face on one axial side of the threaded portion 8 constituting the screw shaft 2.

[0044] The tubular portion 16 has a cylindrical shape and is provided at the radially outer end of the driving member 5. One axial end of the tubular portion 16 is connected to the radially outer end of the base plate portion 15. The tubular portion 16 has an inner diameter larger than the outer diameter of the nut 3. The tubular portion 16 covers the periphery of one axial end of the threaded portion 8.

[0045] The torque input portion 17 is provided on the outer circumferential surface of the driving member 5 . This reference example In the illustrated example, the torque input portion 17 is provided on the outer circumferential surface of the cylindrical portion 16. Therefore, the torque input portion 17 is disposed at a position overlapping with the threaded portion 8 in the radial direction. In the illustrated example, the outer diameter of the portion of the cylindrical portion 16 where the torque input portion 17 is provided is larger than the outer diameter of the portion deviated from the torque input portion 17 in the axial direction. In other words, the torque input portion 17 is provided on the large diameter portion of the cylindrical portion 16.

[0046] The torque input unit 17 serves as a gear section when a gear is used as the driving member 5, serves as a belt receiving surface (tooth section) around which a belt is passed when a pulley is used as the driving member 5, and serves as a tooth section around which a chain is passed when a sprocket is used as the driving member 5. In any case, torque is input to the torque input unit 17 from a driving source.

[0047] The rotation side engagement portion 18 is capable of engaging with the non-rotation side engagement portion 13 in the circumferential direction. The rotation side engagement portion 18 is provided in a circumferential part of a radially intermediate portion of the side surface 15a on the other axial side of the base portion 15, and protrudes toward the other axial side. The rotation side engagement portion 18 has a sector shape.

[0048] The rotation-side engagement portion 18 has a flat rotation-side stopper surface 21 on one side surface in the circumferential direction (the left side surface in FIG. 6, the upper side surface in FIG. 8). The rotation-side stopper surface 21 is disposed approximately parallel to the central axis of the drive member 5. The rotation-side stopper surface 21 exists on an imaginary plane including the central axis of the drive member 5.

[0049] The rotation side engaging portion 18 has a radially outer side surface (outer peripheral surface) in the form of a partial convex cylindrical surface centered on the central axis of the drive member 5, and has a radially inner side surface (inner peripheral surface) in the form of a partial concave cylindrical surface centered on the central axis of the drive member 5. In addition, the tip surface (the end surface on the other axial side) of the rotation side engaging portion 18 is a flat surface existing on an imaginary plane perpendicular to the central axis of the drive member 5.

[0050] This reference example In the embodiment, the rotation side engagement portion 18 is integrally formed with the base plate portion 15. However, ,times The rotation side engagement portion may be configured integrally with the tubular portion rather than the base portion, and the rotation side engagement portion may be configured separately from the base portion and the tubular portion and fixed to the base portion or the tubular portion.

[0051] This reference example In the above, the diameter of a circumscribing circle passing through the radial outer surface of the rotation side engagement portion 18 is smaller than the inner diameter of the cylindrical portion 16. For this reason, an arc-shaped gap 22 is provided between the radial outer surface of the rotation side engagement portion 18 and the inner peripheral surface of the cylindrical portion 16.

[0052] The radial width dimension of the rotating side engagement portion 18 is slightly larger than the radial width dimension of the non-rotating side engagement portion 13. The circumscribing circle diameter passing through the radial outer surface of the rotating side engagement portion 18 is approximately the same as the circumscribing circle diameter passing through the radial outer surface of the non-rotating side engagement portion 13, and the inscribing circle diameter passing through the radial inner surface of the rotating side engagement portion 18 is slightly smaller than the inscribing circle diameter passing through the radial inner surface of the non-rotating side engagement portion 13.

[0053] The rotation side stopper surface 21 comes into surface contact with the non-rotation side stopper surface 14 when the nut 3 moves relatively to one side in the axial direction with respect to the screw shaft 2 and reaches the stroke end. For this reason, the rotation side stopper surface 21 is disposed substantially parallel to the central axis of the drive member 5. The axial dimension of the rotation side stopper surface 21 is set to a size that ensures an engagement margin (axial width of the abutment portion with the non-rotation side stopper surface 14) δ sufficient to prevent rotation of the screw shaft 2 between the rotation side stopper surface 21 and the non-rotation side stopper surface 14 of the non-rotation side engagement portion 13 provided on the nut 3. In the illustrated example, the axial dimension of the rotation side stopper surface 21 is slightly larger than the axial dimension of the non-rotation side engagement portion 13 (non-rotation side stopper surface 14).

[0054] <Explanation of the operation of the ball screw device> This reference example The ball screw device 1 rotates the screw shaft 2 via a driving member 5 by a driving source (not shown), thereby causing the nut 3 to move linearly. This reference example In the ball screw device 1, when the driving member 5 (screw shaft 2) is rotationally driven toward one circumferential side via the torque input unit 17 provided on the driving member 5, the nut 3 moves relatively to one axial side with respect to the screw shaft 2. In contrast, when the driving member 5 (screw shaft 2) is rotationally driven toward the other circumferential side via the torque input unit 17, the nut 3 moves relatively to the other axial side with respect to the screw shaft 2.

[0055] When the nut 3 moves relative to the screw shaft 2 toward one side in the axial direction and reaches the stroke end, the non-rotation side engagement portion 13 circumferentially engages with the rotation side engagement portion 18. Specifically, the non-rotation side stopper surface 14 provided on the side surface on the other circumferential side of the non-rotation side engagement portion 13 and the rotation side stopper surface 21 provided on the side surface on one circumferential side of the rotation side engagement portion 18 engage in the circumferential direction. This reference example Here, the non-rotation side stopper surface 14 and the rotation side stopper surface 21 are in surface contact with each other, thereby preventing the screw shaft 2 from rotating.

[0056] As mentioned above, This reference exampleAccording to the ball screw device 1, the stroke end related to the relative movement of the nut 3 to one side in the axial direction with respect to the screw shaft 2 can be regulated by utilizing the driving member 5. Note that the stroke end related to the relative movement of the nut 3 to the other side in the axial direction with respect to the screw shaft 2 can be regulated by utilizing various conventionally known stroke limiting mechanisms.

[0057] As mentioned above This reference example According to the ball screw device 1, the stroke end of the nut 3, which is a linear motion element, can be restricted with a small number of parts, and the ball screw device 1 can be made smaller in size.

[0058] That is, This reference example In this embodiment, the driving member 5 not only rotates the screw shaft 2, but also regulates the stroke end of the nut 3 moving relative to the screw shaft 2 in one axial direction. This eliminates the need to use a dedicated part (stopper) for regulating the stroke end of the nut, as in the conventional structure described in JP 2016-70281 A. This reference example According to the ball screw device 1, the number of parts can be reduced. Also, by omitting a dedicated part for regulating the stroke end, the axial dimension of the screw shaft 2 can be shortened, and therefore the axial dimension of the ball screw device 1 can be shortened. As a result, the ball screw device 1 can be made more compact.

[0059] In addition, this is more advantageous in terms of ensuring the strength of the base plate portion 15 than when an engagement groove capable of engaging with the non-rotation side engagement portion 13 in the circumferential direction is formed in the base plate portion 15 constituting the driving member 5. Therefore, a large torque can be transmitted by the driving member 5.

[0060] Furthermore, the torque input portion 17 provided on the outer peripheral surface of the tubular portion 16 that constitutes the driving member 5 is positioned so as to overlap with the screw portion 8 in the radial direction, which is advantageous in terms of shortening the axial dimension of the ball screw device 1.

[0061] [Embodiment 1 1 example] The first embodiment 1 An example will be described with reference to FIGS.

[0062] In this example, the outer diameter of the rotation side engagement portion 18a constituting the driving member 5a is set as follows: Reference example The structure of the first example is larger than that of the first example. The radially outer end of the rotation side engagement portion 18a is connected to the inner circumferential surface of the cylindrical portion 16. Reference example Unlike the structure of the first example, there is no gap between the radially outer surface of the rotation side engagement portion 18 a and the inner circumferential surface of the cylindrical portion 16 .

[0063] In the above-described embodiment, the radially outer end of the rotation side engagement portion 18a is connected to the inner peripheral surface of the cylindrical portion 16, so that the rigidity of the rotation side engagement portion 18a can be increased. This reduces the amount of elastic deformation of the rotation side engagement portion 18a that occurs when the non-rotation side engagement portion 13 (see FIG. 5, etc.) and the rotation side engagement portion 18a engage in the circumferential direction. This also increases the rigidity of the cylindrical portion 16 in the radial direction. For other configurations and effects, Reference example This is the same as the first example.

[0064] [ Reference example The first 2 example] Reference example The first 2 An example will be described with reference to FIGS.

[0065] This reference example The driving member 5b is the same as that in the first embodiment and Reference example The first 1 Unlike the structure in the example, the drive member 5b has a plurality of (two in the illustrated example) rotation side engagement parts 18. The plurality of rotation side engagement parts 18 are disposed at equal intervals in the circumferential direction of the drive member 5b. In the illustrated example, since the drive member 5b has two rotation side engagement parts 18, the two rotation side engagement parts 18 are disposed on opposite sides in the diametric direction of the drive member 5b.

[0066] Each of the multiple rotation-side engagement portions 18 has a rotation-side stopper surface 21 on one circumferential side surface. In the illustrated example, the two rotation-side stopper surfaces 21 exist on the same imaginary plane that includes the central axis of the drive member 5b.

[0067] This reference example In this case, the driving member 5b as described above is Reference example No. 1 As in the structure of the example, it is used in combination with a nut 3 having only one non-rotating side engagement portion 13 (see FIG. 5, etc.).

[0068] As mentioned above This reference example In the present embodiment, since the driving member 5b is provided with a plurality of rotation side engaging portions 18, when assembling the ball screw device 1, it is only necessary to align the phase of any one of the rotation side engaging portions 18 with the non-rotation side engaging portion 13, which makes the assembly easier than with a structure having only one rotation side engaging portion. Also, since the plurality of rotation side engaging portions 18 are disposed at equal intervals in the circumferential direction of the driving member 5b, the rotation balance of the driving member 5b can be improved. For other configurations and effects, Reference example This is the same as the first example.

[0069] [ Reference example The first 2 Example Variations] Reference example The first 2 In the modified example, a drive member 5b having a plurality of rotation side engagement portions 18 is used in combination with a nut having the same number of non-rotation side engagement portions as the rotation side engagement portions 18. In the modified example employing such a configuration, the stroke end of the nut can be regulated by simultaneously engaging the plurality of rotation side engagement portions 18 with the plurality of non-rotation side engagement portions in the circumferential direction. This reduces the force acting on each of the rotation side engagement portions 18, effectively preventing damage to the drive member 5b.

[0070] [Embodiment 1 2 example] The first embodiment 2 An example will be described with reference to FIGS.

[0071] The driving member 5c of this example is the first embodiment. 1 Example driving member 5a and Reference example The first 2 In other words, the driving member 5c has a plurality of (two in the illustrated example) rotation side engaging portions 18a, and the radially outer end of each of the rotation side engaging portions 18a is connected to the inner circumferential surface of the cylindrical portion 16.

[0072] In the case of this example as described above, the rigidity of the rotation side engaging portion 18a can be increased. Also, compared to a structure having only one rotation side engaging portion, the assembly work of the ball screw device 1 can be simplified and the rotation balance of the drive member 5c can be improved.

[0073] The driving member 5c in this example is Reference example The first 2 As in the previous example, it can be used in combination with a nut 3 having only one non-rotating side engagement portion 13 (see FIG. 5, etc.). Reference example The first 2 As in the modified example, the nut 18 may be used in combination with a nut having the same number of non-rotating side engaging portions as the rotating side engaging portions 18. For other configurations and effects, see the first embodiment. , Reference Example 1 and Reference Example 2 is the same as:

[0074] [ Reference example The first 3 example] Reference example The first 3 An example will be described with reference to FIGS.

[0075] This reference example The driving member 5d is Reference example Unlike the first example, the rotation side engaging portion 18b and the base plate portion 15 are not integrally formed. This reference example In this embodiment, the rotation side engagement portion 18b is formed separately from the base plate portion 15 and is fixed to one location in the circumferential direction on the side surface 15a on the other axial side of the base plate portion 15.

[0076] This reference exampleIn the embodiment, the base end (one end in the axial direction) of the rotation side engaging portion 18b is press-fitted or screwed into a fixing hole 23 formed in one circumferential position of the base plate portion 15, thereby fixing the rotation side engaging portion 18b to the base plate portion 15. The fixing hole 23 may be a bottomed hole that does not pass through the base plate portion 15 in the axial direction, or may be a through hole that passes through the base plate portion 15 in the axial direction. . basis There is no particular limitation on the structure for fixing the rotation side engagement portion 18b to the plate portion 15. For example, the rotation side engagement portion can be fixed to the base plate portion by a fixing means such as welding, adhesion, or screw fastening.

[0077] This reference example In the present embodiment, the rotation side engaging portion 18b is cylindrical (pin-shaped). The outer peripheral surface of the rotation side engaging portion 18b has a convex curved surface facing one side in the circumferential direction of the driving member 5d, which serves as the rotation side stopper surface 21a. Reference example It may be a flat surface like the structure of the first example, or it may be a concave curved surface that can come into surface contact with the rotation side stopper surface 21a.

[0078] The material of the rotation side engagement portion 18b is not particularly limited, and may be the same material as that of the base plate portion 15, or may be a different material from that of the base plate portion 15.

[0079] As mentioned above This reference example In this case, the rotation side engaging portion 18b is configured separately from the base plate portion 15 and fixed to the base plate portion 15, so that the degree of freedom regarding the shape and material of the rotation side engaging portion 18b can be improved compared to the case where the rotation side engaging portion is configured integrally with the base plate portion. Also, by changing the axial dimension of the rotation side engaging portion 18b, the size of the engagement margin with the non-rotation side engaging portion 13 can be appropriately changed. Also, by changing the diameter and shape of the rotation side engaging portion 18b, the position of the stroke end of the nut 3 (see FIG. 5, etc.) can be easily changed. For other configurations and effects, Reference example This is the same as the first example.

[0080] [ Reference example The first 4 example] Reference example The first 4 An example will be described with reference to FIGS.

[0081] This reference example teeth, Reference example The first 3 This is a variation of the example. This reference example The driving member 5e does not have the rotation side engagement portion 18c and the base plate portion 15 integrally formed therewith, but rather the rotation side engagement portion 18c is formed separately from the base plate portion 15 and is fixed to one location in the circumferential direction on the side surface 15a on the other axial side of the base plate portion 15.

[0082] The rotation side engaging portion 18c has a rectangular column shape (rectangular parallelepiped shape). Among the outer peripheral side surfaces of the rotation side engaging portion 18c, the side surface facing one circumferential direction side of the driving member 5e is the rotation side stopper surface 21b. The rotation side stopper surface 21b is flat and exists on a virtual plane including the central axis of the driving member 5e.

[0083] This reference example In this case, the base end (one end on one axial side) of the rotation side engaging portion 18c is press-fitted into a rectangular fixing hole 23a formed at one location in the circumferential direction of the base plate portion 15, thereby fixing the rotation side engaging portion 18c to the base plate portion 15. The fixing hole 23a may be a bottomed hole (concave groove) that does not pass through the base plate portion 15 in the axial direction, or may be a through hole that passes through the base plate portion 15 in the axial direction. ,times The fixing structure of the rotating side engaging portion 18c can be changed as appropriate.

[0084] As mentioned above This reference example Even in this case, the rotation side engagement portion 18c is constructed separately from the substrate portion 15 and fixed to the substrate portion 15, thereby improving the freedom regarding the shape and material of the rotation side engagement portion 18c compared to the case where the rotation side engagement portion is constructed integrally with the substrate portion. For other configurations and effects, Reference example The first example and 3 Same as the example.

[0085] The above is an embodiment of the present invention. And reference examplesHowever, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. And reference examples The structures of the above examples can be appropriately combined as long as no contradiction occurs.

[0086] Embodiment And reference examples In each of the examples, a sector-shaped non-rotation side engagement part is shown as an example of a protruding non-rotation side engagement part, but when implementing the present invention, the shape of the non-rotation side engagement part is not limited to a sector shape, and other shapes such as a cylindrical shape or a rectangular column shape can be used. And reference examples The shape is not limited to the sectorial, cylindrical, and rectangular columnar shapes shown in the examples, and other shapes may be used.

[0087] First Example of the Embodiment and No. 2 example And the first and second reference examples Although the above description has been given of the case where the protruding rotation side engagement portion is integrally formed with the base plate portion constituting the drive member, when implementing the present invention, the protruding rotation side engagement portion may be integrally formed with a portion other than the base plate portion. Reference example The first 3 Examples and 4 In the example, a case has been described in which the protruding rotating side engagement portion is configured separately from the base portion that constitutes the drive member and fixed to the base portion, but when implementing the present invention, a configuration can also be adopted in which the protruding rotating side engagement portion is fixed to other parts, such as the tubular portion that constitutes the drive member.

[0088] Embodiment And reference examplesIn each of the above examples, the fitting shaft portion of the screw shaft has male spline teeth on its outer circumferential surface, the drive member has a mounting hole with female spline teeth on its inner circumferential surface, and the drive member is spline-fitted to the fitting shaft portion. However, when implementing the present invention, the fixing structure of the drive member to the fitting shaft portion is not particularly limited. For example, it is also possible to adopt a structure in which the fitting shaft portion has an elliptical (oval) cross section and a two-sided shape with a pair of parallel flat outer surfaces on the outer circumferential surface, the mounting hole of the drive member is an elliptical hole (oval hole) and a two-sided shape with a pair of parallel flat inner surfaces on the inner circumferential surface, and the drive member is non-circularly fitted to the fitting shaft portion.

[0089] Embodiment And reference examples In each example, a structure in which a circulation groove is formed directly on the inner surface of the nut has been described, but when implementing the present invention, the circulation groove can also be formed in a circulation part (for example, a top) separate from the nut, and the circulation part can be fixed to the nut. [Explanation of symbols]

[0090] 1. Ball screw device 2 Screw shaft 3 Nut 4. Ball 5, 5a to 5e Driving members 6 Load path 7 Circulation groove 8 Threaded Part 9. Mating shaft 10 Ball screw groove on shaft side 11 Male spline teeth 12 Nut side ball screw groove 13 Non-rotating side engagement part 14 Non-rotating side stopper surface 15 Circuit Board 15a side 16 Cylinder 17 Torque input section 18, 18a, 18b, 18c Rotation side engagement portion 19 Mounting hole 20 female spline teeth 21, 21a, 21b Rotation side stopper surface 22 Gap 23, 23a fixing hole 100 Ball screw device 101 Screw shaft 102 Nut 103 Stopper 104 Threaded part 105 Fitting shaft 106 Ball screw groove on shaft side 107 Engagement part 108 Boss 109 Claw

Claims

1. A screw shaft having a helical shaft-side ball screw groove on an outer circumferential surface thereof and rotating during use; a nut having a helical nut-side ball screw groove on an inner peripheral surface and a protruding non-rotating side engagement portion at one end in an axial direction, the nut moving linearly when in use; A plurality of balls arranged between the shaft side ball screw groove and the nut side ball screw groove; A drive member that is fixed to the screw shaft so as not to rotate relative to the screw shaft and drives the screw shaft to rotate; the drive member has a protruding rotation side engagement portion that is circumferentially engageable with the non-rotation side engagement portion, and a cylindrical tube portion having a torque input portion provided on an outer circumferential surface thereof, A radially outer end of the rotation side engagement portion is connected to an inner circumferential surface of the cylindrical portion. Ball screw device.

2. 2. The ball screw device according to claim 1, wherein a plurality of the rotation side engaging portions are provided.

3. 3. The ball screw device according to claim 2, wherein the plurality of rotation side engagement portions are disposed at equal intervals in a circumferential direction of the drive member.

4. The drive member has a connection portion fixed to the screw shaft so as not to rotate relative to the screw shaft, The rotation side engagement portion is integrally formed with the connection portion. A ball screw device according to any one of claims 1 to 3.

5. 5. The ball screw device according to claim 1, wherein the driving member is any one of a gear, a pulley, and a sprocket.

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