JP7632161B2 - Ball screw device - Google Patents

Description

The present invention relates to a ball screw device.

Ball screw devices use balls to roll between a screw shaft and a nut, which allows for greater efficiency than sliding screw devices, which have a direct contact between the screw shaft and the nut. For this reason, ball screw devices are incorporated into a variety of machinery and equipment, such as electric brake devices and automatic manual transmissions (AMTs) for automobiles and positioning devices for machine tools, to convert the rotational motion of a drive source, such as an electric motor, into linear motion.

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 number 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 uses 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.

In ball screw devices, the stroke end of the linear motion element is restricted to prevent the linear motion element from moving linearly beyond a predetermined range. Figure 19 shows a ball screw device 100 of a conventional structure equipped with a structure for restricting the stroke end of the linear motion element, as described in JP 2016-70281 A (Patent Document 1).

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

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

The nut 102 has a cylindrical shape and has a helical nut-side ball screw groove and a substantially 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.

The shaft side ball screw groove 106 and the nut side ball screw groove are arranged to face each other in the radial direction, forming a spiral load path. The start and end points of the load path are connected by a circulation groove formed on the inner peripheral surface of the nut 102. Therefore, 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 and end points of the load path are switched depending on the direction of relative displacement in the axial direction between the screw shaft 101 and the nut 102 (relative rotation direction).

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 mating shaft portion 105 of the screw shaft 101 so as not to rotate relative to the mating shaft portion 105. Specifically, the boss portion 108 is fitted onto the mating shaft portion 105 so as not to rotate relative to the mating shaft portion 105 by spline-engaging the female spline teeth formed on the inner peripheral surface with the male spline teeth formed on the outer peripheral surface of the mating shaft portion 105. The claw portion 109 protrudes radially from a circumferential portion of the outer peripheral surface of the boss portion 108.

In a ball screw device 100 of a conventional structure, when either the screw shaft 101 or the nut 102, which is a linear motion element, 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 screw shaft 101 or the nut 102, which is a rotational motion element, and makes it possible to regulate the stroke end of the linear motion element.

JP 2016-70281 A

In the ball screw device 100 of the conventional structure described in JP 2016-70281 A, a dedicated part, the 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 must be provided separately from the stopper 103. This increases the number of parts, and makes it easy for the ball screw device 100 to become large.

The present invention has been made to solve the above problems, and aims 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.

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 has a protruding rotation side engagement portion capable of engaging with the non-rotation side engagement portion in the circumferential direction , and a cylindrical tubular 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 tubular portion.

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.

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

In a ball screw device according to another aspect of the present invention, the rotation-side engagement portion may be formed separately from the connection portion and fixed to the connection portion.

In a ball screw device according to one aspect of the present invention, the drive member can be any one of a gear, a pulley, or a sprocket.

In a ball screw device according to another aspect of the present invention, the driving 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.

The ball screw device of the present invention can regulate the stroke end of the nut, which is a linear motion element, with a small number of parts, making it possible to reduce the size.

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. 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 . FIG. 3 is a partially enlarged view of FIG. FIG. 4 is a perspective view of a ball screw device according to a first embodiment of the present invention . FIG. 5 is a perspective view showing a nut according to a first embodiment of the present invention . FIG. 6 is a front view of the drive member according to the first embodiment , as viewed from the other axial side. FIG. 7 is a perspective view showing a driving member according to a first embodiment of the present invention . FIG. 8 is a schematic view taken along the line B in FIG. FIG. 9 is a diagram showing a first example of the embodiment, and corresponds to FIG. FIG. 10 is a diagram showing a first example of the embodiment, and corresponds to FIG. FIG. 11 is a diagram showing a second reference example and corresponds to FIG. FIG. 12 is a diagram showing a second reference example and corresponds to FIG. FIG. 13 is a diagram showing a second example of the embodiment, and corresponds to FIG. FIG. 14 is a diagram showing a second example of the embodiment, and corresponds to FIG. FIG. 15 is a diagram showing a third reference example , which corresponds to FIG. FIG. 16 is a diagram showing a third reference example and corresponds to FIG. FIG. 17 is a diagram showing a fourth embodiment of the present invention , which corresponds to FIG. FIG. 18 is a diagram showing a fourth embodiment of the present invention , which corresponds to FIG. FIG. 19 is a perspective view showing a ball screw device having a conventional structure.

[First Reference Example]
A first embodiment of the present invention will be described with reference to FIGS.

[Overall configuration of ball screw device]
The ball screw device 1 of this embodiment 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.

The ball screw device 1 comprises a screw shaft 2, a nut 3, a number of balls 4, and a drive member 5.

The screw shaft 2 is rotationally driven by a driving source (not shown) via a driving 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 co-rotating 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, the ball screw device 1 of this reference example is used in a mode in which the screw shaft 2 is rotationally driven and the nut 3 is moved linearly.

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 a rollable manner in the load path 6. 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. In addition, one axial side refers to the right side in Figures 2 to 5 and 8, and the other axial side refers to the left side in Figures 2 to 5 and 8.

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

The threaded portion 8 has a helical shaft-side ball screw groove 10 on its outer circumferential surface. The shaft-side ball screw groove 10 is formed by grinding (cutting) or rolling on the outer circumferential surface of the threaded portion 8. In this reference example , the number of threads in the shaft-side ball screw groove 10 is one. 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. In this reference example , the formation direction (winding direction) of the shaft-side ball screw groove 10 is restricted to a direction in which the nut 3 can be linearly moved to one axial side when the screw shaft 2 is rotated toward one circumferential side.

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

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

<nut>
The nut 3 is made of metal and has a cylindrical shape as a whole. The nut 3 has a helical nut-side ball screw groove 12 and a circulation groove 7 on its inner circumferential surface.

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, when 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, just like 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, just like the shaft side ball screw groove 10.

The circulation groove 7 has a roughly S-shape and is formed on the inner peripheral surface of the nut 3, for example, by forging (cold forging). The circulation groove 7 smoothly connects the axially adjacent portions of the nut side ball screw groove 12, and connects the start point and end point of the load path 6. Therefore, the ball 4 that has reached the end point of the load path 6 is returned to the start point of the load path 6 through the circulation groove 7. The start point and end point of the load 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.

The circulation groove 7 has a roughly semicircular cross-sectional shape. The circulation groove 7 has a groove width slightly larger than the diameter of the ball 4, and has a groove depth that allows the ball 4 moving through the circulation groove 7 to overcome the threads of the shaft-side ball screw groove 10.

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

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

In the illustrated example, the nut 3 is constructed as a single unit, including the non-rotating side engagement portion 13, 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 circumferential surface to the non-rotating side engagement portion.

The ball screw device 1 of this embodiment uses a nut 3 as a linear motion element. For this reason, in this embodiment , a rotation prevention mechanism (not shown) is used to prevent the nut 3 from rotating. As the rotation prevention mechanism, various conventionally known structures can be used. For example, a structure 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 can be used.

<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.

<Driving member>
The driving member 5 transmits torque input from a driving source such as an electric motor to the screw shaft 2, thereby rotating the screw shaft 2. The driving member 5 of this reference example 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.

In the ball screw device 1 of this reference example , when the drive 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 drive 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.

The driving member 5 has a base plate portion 15, a cylindrical portion 16, a torque input portion 17, and a protruding rotating-side engaging portion 18. The driving member 5 of this embodiment is constructed as a single unit, including the rotating-side engaging portion 18. The driving member 5 is made of a metal such as carbon steel or stainless steel, or a synthetic resin. For example, a gear, a pulley, a sprocket, or the like can be used as the driving member 5.

The base plate portion 15 corresponds to the connection 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 fixed to the mating shaft portion 9 so that it cannot rotate relative to the mating 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 mating shaft portion 9. The radially inner portion of the side surface 15a on the other axial side of the base plate portion 15 abuts or faces closely against the end face on one axial side of the threaded portion 8 constituting the screw shaft 2.

The tubular portion 16 has a cylindrical shape and is provided at the radially outer end of the drive 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.

The torque input portion 17 is provided on the outer peripheral surface of the drive member 5. In this reference example , the torque input portion 17 is provided on the outer peripheral surface of the tubular 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 tubular 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 tubular portion 16.

When a gear is used as the driving member 5, the torque input unit 17 becomes a gear portion. When a pulley is used as the driving member 5, the torque input unit 17 becomes a belt receiving surface (tooth portion) around which a belt is passed. When a sprocket is used as the driving member 5, the torque input unit 17 becomes a tooth portion around which a chain is passed. In either case, torque from a driving source is input to the torque input unit 17.

The rotation side engagement portion 18 can engage with the non-rotation side engagement portion 13 in the circumferential direction. The rotation side engagement portion 18 is provided in a circumferential portion of the radially middle portion of the side surface 15a on the other axial side of the base plate portion 15, and protrudes toward the other axial side. The rotation side engagement portion 18 has a sector shape.

The rotating side engagement portion 18 has a flat rotating side stopper surface 21 on one side in the circumferential direction (the left side surface in FIG. 6, the upper side surface in FIG. 8). The rotating side stopper surface 21 is disposed approximately parallel to the central axis of the driving member 5. The rotating side stopper surface 21 exists on an imaginary plane that includes the central axis of the driving member 5.

The rotating side engaging portion 18 has a radially outer surface (outer peripheral surface) in the shape of a partially convex cylindrical surface centered on the central axis of the driving member 5, and a radially inner surface (inner peripheral surface) in the shape of a partially concave cylindrical surface centered on the central axis of the driving member 5. In addition, the tip surface (the end surface on the other axial side) of the rotating side engaging portion 18 is a flat surface that exists on an imaginary plane perpendicular to the central axis of the driving member 5.

In this reference example , the rotation side engagement portion 18 is configured integrally with the substrate portion 15. However , the rotation side engagement portion may be configured integrally with the tube portion instead of the substrate portion, or the rotation side engagement portion may be configured separately from the substrate portion and the tube portion and fixed to the substrate portion or the tube portion.

In this reference example , the diameter of a circumscribing circle passing through the radially outer surface of the rotation side engagement portion 18 is smaller than the inner diameter of the tubular portion 16. Therefore, an arc-shaped gap 22 is provided between the radially outer surface of the rotation side engagement portion 18 and the inner peripheral surface of the tubular portion 16.

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

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

<Explanation of the operation of the ball screw device>
In the ball screw device 1 of this reference example , the screw shaft 2 is rotationally driven by a driving source (not shown) via a driving member 5, thereby linearly moving the nut 3. In particular, in the ball screw device 1 of this reference example , when the driving member 5 (screw shaft 2) is rotationally driven toward one circumferential side via a 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.

When the nut 3 moves relative to the screw shaft 2 toward one side in the axial direction and reaches a stroke end, the non-rotation side engagement portion 13 engages with the rotation side engagement portion 18 in the circumferential direction. 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. In this reference example , the non-rotation side stopper surface 14 and the rotation side stopper surface 21 are in surface contact with each other. This prevents the screw shaft 2 from rotating.

As described above, according to the ball screw device 1 of this reference example , 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 restricted by utilizing the drive 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 restricted by utilizing various conventionally known stroke limiting mechanisms.

According to the ball screw device 1 of this embodiment as described above, 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.

That is, in this reference example , the driving member 5 can not only rotate the screw shaft 2, but also regulate the stroke end of the nut 3 moving relative to the screw shaft 2 in one axial direction. Therefore, unlike the conventional structure described in JP 2016-70281 A, there is no need to use a dedicated part (stopper) for regulating the stroke end of the nut. Therefore, according to the ball screw device 1 of this reference example , the number of parts can be reduced. In addition, by omitting the 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. Therefore, the ball screw device 1 can be made smaller in size.

In addition, this is more advantageous in terms of ensuring the strength of the base plate portion 15 than when an engagement groove that can engage with the non-rotating side engagement portion 13 in the circumferential direction is formed on the base plate portion 15 that constitutes the driving member 5. This allows the driving member 5 to transmit a large torque.

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

[ First Example of the Embodiment]
The first embodiment will be described with reference to FIGS.

In this example, the outer diameter of the rotation side engaging portion 18a constituting the driving member 5a is made larger than that of the structure of the first reference example . The radially outer end of the rotation side engaging portion 18a is connected to the inner peripheral surface of the tubular portion 16. Therefore, in this example, unlike the structure of the first reference example , there is no gap between the radially outer surface of the rotation side engaging portion 18a and the inner peripheral surface of the tubular portion 16.

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

[ Second Reference Example]
The second reference example will be described with reference to FIGS.

The drive member 5b of this reference example has a plurality (two in the illustrated example) of rotation side engaging portions 18, which are different from the structures of the first embodiment and the first reference example . The rotation side engaging portions 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 engaging portions 18, the two rotation side engaging portions 18 are disposed on opposite sides in the diametric direction of the drive member 5b.

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

In the case of this reference example , the driving member 5b as described above is used in combination with a nut 3 (see Figure 5, etc.) having only one non-rotating side engagement portion 13, similar to the structures of the first example of the embodiment and the first example of the reference example .

In the present embodiment , the drive member 5b is provided with a plurality of rotation side engaging portions 18, and therefore 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, making the assembly easier than with a structure having only one rotation side engaging portion. In addition, the plurality of rotation side engaging portions 18 are disposed at equal intervals in the circumferential direction of the drive member 5b, which makes it possible to achieve good rotational balance of the drive member 5b.
The other configurations and effects are the same as those of the first reference example .

[Modification of the second embodiment of the reference example ]
In a modification of the second reference example , a drive member 5b having a plurality of rotation side engaging portions 18 is used in combination with a nut having the same number of non-rotation side engaging portions as the rotation side engaging portions 18. In a modification employing such a configuration, the stroke end of the nut can be restricted by simultaneously engaging the plurality of rotation side engaging portions 18 with the plurality of non-rotation side engaging portions in the circumferential direction. This reduces the force acting on each of the rotation side engaging portions 18, effectively preventing damage to the drive member 5b.

[ Second Example of the Embodiment]
A second embodiment will be described with reference to FIGS.

The driving member 5c of this example has a configuration in which the driving member 5a of the first embodiment and the driving member 5b of the second reference example are combined. That is, 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.

In the case of the above-described example, the rigidity of the rotation side engagement portion 18a can be increased. Furthermore, compared to a structure with only one rotation side engagement 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.

The driving member 5c of this example can be used in combination with a nut 3 (see Figure 5, etc.) having only one non-rotating side engagement portion 13, as in the second reference example, or can be used in combination with a nut having the same number of non-rotating side engagement portions as the rotating side engagement portions 18, as in the modified example of the second reference example .
The other configurations and functions and effects are the same as those of the first embodiment and the first and second reference examples .

[ Third Reference Example]
The third reference example will be described with reference to FIGS.

Unlike the first reference example, the driving member 5d of this reference example does not have the rotation side engaging portion 18b integral with the base plate portion 15. In this reference example , the rotation side engaging 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.

In this reference example , the base end (one end on one axial side) of the rotation side engaging portion 18b is press-fitted or screwed into a fixing hole 23 formed at one location in the circumferential direction of the substrate portion 15, thereby fixing the rotation side engaging portion 18b to the substrate portion 15. The fixing hole 23 may be a bottomed hole that does not penetrate the substrate portion 15 in the axial direction, or may be a through hole that penetrates the substrate portion 15 in the axial direction . There is no particular limit to the fixing structure of the rotation side engaging portion 18b to the substrate portion 15. For example, the rotation side engaging portion may be fixed to the substrate portion by a fixing means such as welding, adhesive, or screwing.

In this 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 circumferential side of the driving member 5d as the rotation side stopper surface 21a. The non-rotation side stopper surface may be a flat surface as in the structure of the first embodiment , or may be a concave curved surface capable of surface contact with the rotation side stopper surface 21a.

The material of the rotating side engagement portion 18b is not particularly limited, and may be the same material as the base plate portion 15 or a different material than the base plate portion 15.

In the case of the present reference example as described above, 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 in terms of 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.
The other configurations and effects are the same as those of the first reference example .

[ Fourth Reference Example]
The fourth reference example will be described with reference to FIGS.

This reference example is a modification of the reference example 3. In the driving member 5e of this reference example , the rotation side engagement portion 18c and the base plate portion 15 are not integrally formed, but 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.

The rotation side engagement portion 18c has a rectangular columnar shape (cuboid shape). The outer peripheral side surface of the rotation side engagement portion 18c that faces one circumferential side of the drive member 5e serves as the rotation side stopper surface 21b. The rotation side stopper surface 21b is flat and exists on an imaginary plane that includes the central axis of the drive member 5e.

In this reference example , 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 axially penetrate the base plate portion 15, or may be a through hole that axially penetrates the base plate portion 15. The fixing structure of the rotation side engaging portion 18c may be modified as appropriate.

In the case of the present reference example as described above, 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.
The other configurations and effects are the same as those of the first and third reference examples .

Although the embodiment and the reference examples of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical concept of the invention. Furthermore, the structures of the embodiments and the reference examples can be combined as appropriate as long as no contradiction occurs.

In each of the embodiments and reference examples , a sector-shaped non-rotation side engagement portion is shown as an example of a protruding non-rotation side engagement portion, but when implementing the present invention, the shape of the non-rotation side engagement portion is not limited to a sector shape, and other shapes such as a cylindrical shape, a rectangular column shape, etc. Furthermore, the protruding rotation side engagement portion is also not limited to the sector shape, cylindrical shape, and rectangular column shape shown in each of the embodiments and reference examples , and other shapes can be used.

In the first and second embodiments and the first and second reference examples , the protruding rotation side engaging portion is integral with the base plate portion constituting the drive member, but in carrying out the present invention, the protruding rotation side engaging portion may be integral with other portions other than the base plate portion. In the third and fourth reference examples , the protruding rotation side engaging portion is separate from the base plate portion constituting the drive member and fixed to the base plate portion, but in carrying out the present invention, the protruding rotation side engaging portion may be fixed to other portions such as the tube portion constituting the drive member.

In each of the embodiments and reference examples , a structure has been shown in which 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, a structure can be adopted in which the fitting shaft portion has an elliptical (oval) cross section and a two-sided shape with a pair of flat outer surfaces parallel to each other 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 flat inner surfaces parallel to each other on the inner circumferential surface, and the drive member is non-circularly fitted to the fitting shaft portion.

In each of the embodiments and reference examples , 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 (e.g., a top) separate from the nut, and the circulation part can be fixed to the nut.

REFERENCE SIGNS LIST 1 ball screw device 2 screw shaft 3 nut 4 balls 5, 5a to 5e drive member 6 load path 7 circulation groove 8 screw portion 9 fitting shaft portion 10 shaft side ball screw groove 11 male spline teeth 12 nut side ball screw groove 13 non-rotating side engagement portion 14 non-rotating side stopper surface 15 base plate portion 15a side surface 16 cylindrical portion 17 torque input portion 18, 18a, 18b, 18c rotating side engagement portion 19 mounting hole 20 female spline teeth 21, 21a, 21b rotating side stopper surface 22 gap 23, 23a fixing hole 100 ball screw device 101 screw shaft 102 nut 103 stopper 104 screw portion 105 fitting shaft portion 106 shaft side ball screw groove 107 engagement portion 108 Boss part 109 Claw part

Claims (5)

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. The ball screw device according to claim 1, which is provided with a plurality of rotation side engagement parts. The ball screw device according to claim 2, wherein the rotation side engagement portions are arranged at equal intervals in the circumferential direction of the drive member. 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. The ball screw device according to any one of claims 1 to 4 , wherein the driving member is any one of a gear, a pulley, and a sprocket.

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