JP2020094635A - Ball screw device - Google Patents

Abstract

To provide a ball screw device capable of reducing the size in the radial direction.SOLUTION: The ball screw device includes a screw shaft having a first screw groove in the outer peripheral face, a nut provided with a second screw groove in the inner peripheral face corresponding to the first screw groove and a cutout part in the outer peripheral face, a plurality of balls for rolling between the first screw groove and the second screw groove, a circulation component having a body part and a pair of leg parts provided at both ends of the body part, and provided on the nut, a mounting component having a first portion and a second portion connected to the first portion for fixing the circulation component to the nut, and a fixing component for fixing the mounting component to the nut, the cutout part having a first bottom face and a second bottom face provided at a position nearer the rotation axis of the screw shaft than the first bottom face in the direction perpendicular to the first bottom face, the leg parts being inserted into through-holes provided in the first bottom face, the first portion being provided on the first bottom face overlapping with the leg parts, the second portion being fixed to the second bottom face with the fixing component.SELECTED DRAWING: Figure 10

Description

The present invention relates to a ball screw device.

A ball screw device is known as a device that converts a rotational motion into a linear motion. The ball screw device includes a screw shaft, a nut, and a plurality of balls. For example, the ball screw device described in Patent Document 1 has a return tube for circulating a ball and an attachment component for attaching the return tube to a nut. The return tube has a main body and a pair of legs formed at both ends of the main body. A flat surface is provided on the outer periphery of the nut, the main body portion is provided on the flat surface, and the leg portions are inserted into the through holes provided on the flat surface. The attachment component is a plate member made of metal. One end side of the mounting part holds the upper surface of the leg part and is a flat surface outside the leg part, and the other end side of the mounting part is fixed to the flat surface by a bolt.

JP, 2013-50148, A

In Patent Document 1, the mounting component is arranged on the same flat surface, and the bolt penetrates the through hole of the mounting component. Then, the attachment part is fixed to the nut by screwing the bolt into the female screw formed on the outer flat surface of the nut. Therefore, the maximum outer diameter of the ball screw device including the mounting parts and the bolts may be defined by the size and shape of the mounting parts and the bolts.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ball screw device that can be downsized in the radial direction.

In order to achieve the above object, a ball screw device according to an aspect of the present invention has a screw shaft having a first screw groove on an outer peripheral surface and a second screw groove corresponding to the first screw groove on an inner peripheral surface. A nut provided on the outer peripheral surface of which a notch is provided, a plurality of balls rolling between the first screw groove and the second screw groove, a main body portion, and both ends of the main body portion. An attachment having a pair of legs, a circulation part provided on the nut, a first part, and a second part connected to the first part, and fixing the circulation part to the nut. A part and a fixing part for fixing the mounting part to the nut, and the cutout portion has a first bottom surface and the screw shaft more than the first bottom surface in a direction perpendicular to the first bottom surface. A second bottom surface provided in a position close to the rotation axis of the leg, the leg portion is inserted into a through hole provided in the first bottom surface, and the first portion is the leg on the first bottom surface. The second portion is fixed to the second bottom surface by the fixing component.

According to this, compared with the case where the second bottom surface is formed in the same plane as the first bottom surface in the cutout portion, the space between the virtual curved surface obtained by extending the outer peripheral surface of the nut and the second bottom surface becomes large. .. Therefore, when viewed from the rotation axis direction of the screw shaft, it is possible to suppress the second portion of the fixed component and the mounting component from protruding outward in the radial direction from the outer peripheral surface of the nut. Therefore, the ball screw device can be downsized in the radial direction.

As a desirable mode of the ball screw device, the second bottom surface is disposed adjacent to the first bottom surface in a first direction parallel to the rotation axis of the screw shaft, intersects the first direction, and The width of the second bottom surface is larger than the width of the first bottom surface in a direction parallel to the bottom surface.

According to this, since the first bottom surface and the second bottom surface are arranged side by side in the first direction, the outer surface of the nut is larger than that in the case where the first bottom surface and the second bottom surface are arranged in a direction orthogonal to the first direction. The diameter can be reduced. Therefore, it is possible to reduce the size of the ball screw device in the radial direction. Moreover, since the width of the second bottom surface is larger than the width of the first bottom surface, the second part can be favorably fixed to the second bottom surface by the fixing component.

As a desirable mode of the ball screw device, the attachment part has a connecting portion that connects the first portion and the second portion, and the width of the second portion is larger than the width of the connecting portion.

According to this, when fixing the second portion to the second bottom surface, it is possible to increase the flexibility of the type of fixing component and the fixing method.

As a desirable mode of the ball screw device, the connecting portion is formed to be curved according to a step formed by the first bottom surface and the second bottom surface.

According to this, the rigidity of the 1st part which presses down the leg of a circulation component can be raised. Therefore, it is possible to suppress the damage of the mounting component and the detachment of the mounting component from the nut.

As a desirable mode of the ball screw device, a circulation component mounting groove communicating with the cutout portion is provided on the outer periphery of the nut, and the main body portion of the circulation component is provided inside the circulation component mounting groove. ..

According to this, since the leg portion of the circulating component is fixed to the nut by the mounting component, it is not necessary to provide a member for pressing the main body portion above the circulating component mounting groove and the main body portion. Therefore, it is possible to reduce the size of the ball screw device as compared with the configuration in which the mounting component is provided on the upper side of the main body to hold down the circulating component.

According to the present invention, it is possible to provide a ball screw device that can be downsized in the radial direction.

FIG. 1 is a perspective view of a ball screw device according to an embodiment. FIG. 2 is a plan view of the ball screw device. FIG. 3 is a partial cross-sectional view of the ball screw device. FIG. 4 is a perspective view of the circulating component. FIG. 5 is an exploded perspective view of the ball screw device. FIG. 6 is a plan view of the mounting component. FIG. 7 is an enlarged perspective view showing a part of the ball screw device. FIG. 8 is a side view showing a part of the ball screw device in an enlarged manner. FIG. 9 is a sectional view taken along line IX-IX′ shown in FIG. 7. FIG. 10 is a sectional view taken along line X-X′ shown in FIG. 8. FIG. 11 is a partial cross-sectional view of a ball screw device according to a comparative example.

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following modes for carrying out the invention (hereinafter referred to as embodiments). Further, the constituent elements in the following embodiments include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that are within the equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined appropriately.

(Embodiment)
FIG. 1 is a perspective view of a ball screw device according to an embodiment. As shown in FIG. 1, the ball screw device 1 includes a screw shaft 2, a nut 3, a plurality of balls 4 (see FIG. 3 ), a circulation component 5, a mounting component 6, and a fixing component 8. .

A first screw groove 21 is provided on the outer peripheral surface of the screw shaft 2. The screw shaft 2 penetrates the nut 3. A circulating component mounting groove 32 and a pair of notches 33 communicating with both ends of the circulating component mounting groove 32 are provided on a part of the outer peripheral surface of the nut 3.

The main body 51 of the circulating component 5 is provided in the circulating component mounting groove 32. The circulation component 5 is a component for circulating the balls 4, and is also called a return tube. A circulation passage 5m (see FIG. 3) is formed inside the circulation component 5, and the circulation passage 5m is formed on one end side of the rolling passage 41 (see FIG. 3) formed between the screw shaft 2 and the nut 3 and the other. Connect to the end.

The attachment part 6 and the fixed part 8 are provided in the notch 33. The attachment component 6 is a component that fixes the circulation component 5 to the nut 3. The mounting component 6 is a plate-shaped component formed of a metal material. The fixed component 8 is a component that fixes the mounting component 6 to the nut 3. The fixed component 8 is, for example, a bolt.

FIG. 2 is a plan view of the ball screw device. FIG. 3 is a partial cross-sectional view of the ball screw device. FIG. 3 shows a partial cross section of the ball screw device 1, and shows a cross section taken along the line III-III′ shown in FIG. 2. As shown in FIG. 2, the circulation component mounting groove 32 extends in a direction inclined with respect to the rotation axis AX of the screw shaft 2. The circulating component 5 has a main body portion 51 and a pair of leg portions 52 provided at both ends of the main body portion 51. The main body 51 is a tubular member extending along the circulation component mounting groove 32, and the side surface of the main body 51 faces the inner wall of the circulation component mounting groove 32 with a predetermined gap. The side surface of the main body 51 may be in contact with the inner wall of the circulation component mounting groove 32. The leg portion 52 is provided in a direction intersecting the extending direction of the main body portion 51 and along the first screw groove 21 (rolling path 41).

In addition, the leg portion 52, the cutout portion 33, the attachment component 6, and the fixed component 8 are provided two by two with the main body portion 51 interposed therebetween. The leg portion 52, the cutout portion 33, the attachment component 6 and the fixed component 8 on the one hand, and the leg portion 52, the cutout portion 33, the attachment component 6 and the fixed component 8 on the other end have the same configuration, and are the same as the rotation axis AX. They are arranged so as to be rotationally symmetric with respect to the intersecting direction (second direction Db). Therefore, the description of the one leg portion 52, the cutout portion 33, the attachment component 6, and the fixed component 8 can be applied to the other leg portion 52, the cutout portion 33, the attachment component 6, and the fixed component 8.

The cutout portion 33 has a first bottom surface 34 and a second bottom surface 35. The first bottom surface 34 is provided so as to be connected to the bottom surface of the circulation component mounting groove 32, and extends from the circulation component mounting groove 32 in a direction inclined with respect to the third direction Dc. The second bottom surface 35 is arranged adjacent to the first bottom surface 34 in the first direction Da.

In the following description, the direction parallel to the rotation axis AX of the screw shaft 2 is represented as the first direction Da. The directions orthogonal to the first direction Da are referred to as the second direction Db and the third direction Dc. The second direction Db is a normal line direction of the first bottom surface 34. The third direction Dc is a direction parallel to the first bottom surface 34 and a direction orthogonal to the first direction Da and the second direction Db.

The attachment component 6 has a first portion 61, a second portion 62, and a connecting portion 63. The first portion 61 is arranged on the first bottom surface 34. A part of the first portion 61 is provided so as to overlap the upper surface 52t of the leg portion 52 and presses the leg portion 52. Further, the second portion 62 is arranged on the second bottom surface 35. The fixed component 8 is fastened to the screw hole 35a (see FIG. 5) provided in the second bottom surface 35 via the through hole 62c of the second portion 62. The detailed fixing structure of the attachment component 6, the fixing component 8, the leg portion 52 and the nut 3 will be described later.

As shown in FIG. 3, a second thread groove 31 corresponding to the first thread groove 21 is provided on the inner peripheral surface of the nut 3. The first thread groove 21 and the second thread groove 31 form a spiral rolling path 41. The plurality of balls 4 roll on the rolling path 41. As a result, the screw shaft 2 and the nut 3 can smoothly move relative to each other. When the screw shaft 2 rotates, the nut 3 moves in the rotation axis AX direction. As a result, the ball screw device 1 converts the rotational movement into the linear movement. The present invention is not limited to the case where the nut 3 moves in the rotation axis AX direction, but can be applied to a configuration in which the nut 3 rotates and the screw shaft 2 moves in the rotation axis AX direction.

The first bottom surface 34 of the nut 3 is provided with a through hole 34a. The through hole 34 a penetrates the first bottom surface 34 and the rolling path 41. The leg portion 52 of the circulation component 5 is inserted into the through hole 34a. Further, the lower surface 51s of the main body portion 51 contacts the bottom surface of the circulation component mounting groove 32. Inside the circulation component 5, a circulation path 5m continuous with the main body 51 and the pair of legs 52 is formed. The leg portion 52 is configured such that the end of the circulation path 5m is smoothly connected to the rolling path 41. As a result, the ball 4 is returned from the end point of the rolling path 41 to the starting point of the rolling path 41 through the circulation path 5m, thereby infinitely circulating in the rolling path 41.

FIG. 4 is a perspective view of the circulating component. As shown in FIG. 4, the circulating component 5 has two divided bodies 5a and 5b divided along a line L indicating the moving direction of the ball 4. The divided body 5a has a divided main body portion 51a and leg portions 52. The divided body 5b has a divided main body portion 51b and a leg portion 52. By combining the divided bodies 5a and 5b, the circulating component 5 is formed. The divided main body 51a and the divided main body 51b are connected to form a tubular main body 51, and legs 52 are provided at both ends of the main body 51, respectively. Since the divided main body portion 51a and the divided main body portion 51b are provided inside the circulation component mounting groove 32, even when the force F1 from the ball 4 is applied, the divided body 5a and the divided body 5b are separated from each other. Can be suppressed.

The divided bodies 5a and 5b are each formed by injection molding of synthetic resin. The divided bodies 5a and 5b have the same shape. However, the shape is not limited to this, and the divided bodies 5a and 5b may have different shapes. Moreover, the circulation component 5 may be integrally formed.

Next, a fixing structure of the attachment component 6, the fixing component 8, the leg portion 52 and the nut 3 will be described. FIG. 5 is an exploded perspective view of the ball screw device. FIG. 6 is a plan view of the mounting component. FIG. 7 is an enlarged perspective view showing a part of the ball screw device. FIG. 8 is a side view showing a part of the ball screw device in an enlarged manner. FIG. 9 is a sectional view taken along line IX-IX′ shown in FIG. 7. Note that, in FIG. 5, the mounting component 6 and the fixed component 8 are omitted. FIG. 10 is a sectional view taken along line X-X′ shown in FIG. 8. FIG. 11 is a partial cross-sectional view of a ball screw device according to a comparative example.

As shown in FIG. 5, the cutout portion 33 has a first wall portion 36, a second wall portion 37, and a third wall portion 38. The first wall portion 36, the second wall portion 37, and the third wall portion 38 are provided around the first bottom surface 34 and the second bottom surface 35. Specifically, the first wall surface 36s of the first wall portion 36 is a surface that intersects the first direction Da, is connected orthogonally to the first bottom surface 34, and is located in one of the circulation component mounting grooves 32. Connected to the wall.

The second wall portion 37 is adjacent to the first wall portion 36 in the first direction Da with the first bottom surface 34 interposed therebetween. The second wall surface 37s1 of the second wall portion 37 is a surface that intersects the third direction Dc, and is connected orthogonally to the second bottom surface 35. The end surface 37s2 of the second wall portion 37 is a surface between the second wall surface 37s1 and the other inner wall surface of the circulation component mounting groove 32, and faces the first wall surface 36s. The second wall portion 37 is provided between the circulation component mounting groove 32 and the cutout portion 33 in the third direction Dc, and the circulation component mounting groove 32 and the cutout portion between the first wall surface 36s and the end surface 37s2. The part 33 is connected.

The third wall surface 38s of the third wall portion 38 is a surface that intersects the first direction Da. The third wall surface 38s is connected to the second wall surface 37s1 and the second bottom surface 35. The third wall surface 38s faces the first wall surface 36s with the first bottom surface 34 and the second bottom surface 35 interposed therebetween in the first direction Da.

The first wall portion 36 is provided with a first mounting groove 36a. The first mounting groove 36a extends along the third direction Dc. One end of the first mounting groove 36a opens to the outer periphery of the nut 3, that is, the outer periphery of the portion where the cutout portion 33 of the nut 3 and the circulation component mounting groove 32 are not provided. The other end of the first mounting groove 36a is provided at a position adjacent to the through hole 34a.

The second wall portion 37 is provided with a second mounting groove 37a. A through hole 34a is provided between the first mounting groove 36a and the second mounting groove 37a. That is, when the circulation component 5 is attached to the nut 3, the leg portion 52 is located between the first attachment groove 36a and the second attachment groove 37a.

Further, a step is formed between the first bottom surface 34 and the second bottom surface 35, and the position of the first bottom surface 34 in the second direction Db is different from the position of the second bottom surface 35 in the second direction Db. The second bottom surface 35 is arranged at a position closer to the rotation axis AX than the first bottom surface 34 in the second direction Db.

As shown in FIG. 6, the first portion 61 and the second portion 62 of the mounting component 6 are plate members each having a substantially quadrangular shape. The connecting portion 63 connects the first portion 61 and the second portion 62 in the first direction Da. As shown in FIG. 8, the connecting portion 63 is curved. Thereby, the attachment part 6 can make the position of the 1st part 61 and the 2nd part 62 different in the 2nd direction Db. Note that the connection portion 63 is not limited to the example shown in FIG. 8, and the connection portion 63 is formed in a linear shape when viewed from the side surface, and the first portion 61 and the second portion 62 and the connection portion 63 have a bent portion. It may be connected.

As shown in FIG. 6, the first portion 61 has a first end portion 61a and a second end portion 61b that face each other in the first direction Da. The first portion 61 also has a third end portion 61c and a fourth end portion 61d that face each other in the third direction Dc. In a plan view when viewed from the second direction Db, the second end portion 61b projects from the one end portion 63a of the connecting portion 63 in the third direction Dc. The fourth end portion 61d is arranged in line with the other end portion 63b of the connecting portion 63.

Further, one end 62 a of the second portion 62 is provided in line with the one end 63 a of the connecting portion 63 in a plan view. The other end 62b of the second portion 62 is provided so as to project from the other end 63b of the connecting portion 63 in the third direction Dc. That is, the second end portion 61 b projects more than the one end portion 62 a of the second portion 62. The other end 62b of the second portion 62 projects more than the fourth end 61d.

That is, the width W1 of the first portion 61 in the third direction Dc is larger than the width W3 of the connecting portion 63 in the third direction Dc. The width W2 of the second portion 62 in the third direction Dc is larger than the width W3 of the connecting portion 63 in the third direction Dc.

The configuration of the attachment component 6 is merely an example, and can be changed as appropriate. For example, the corners of the first portion 61 may be chamfered. Further, the third end portion 61c and the fourth end portion 61d of the first portion 61 are provided in parallel, but may be non-parallel. That is, the width W1 of the first portion 61 on the first end 61a side may be smaller than the width W1a of the second end 61b side. Alternatively, the width W1 may be larger than the width W1a. Further, the first end portion 61a and the second end portion 61b may be provided so as to be inclined with respect to the direction orthogonal to the third end portion 61c.

As shown in FIGS. 7 to 9, the first portion 61 is provided on the first bottom surface 34, and the first end portion 61a is arranged in the first mounting groove 36a. The second end portion 61b is arranged in the second mounting groove 37a. As shown in FIG. 9, the portion of the first portion 61 between the first end portion 61 a and the second end portion 61 b overlaps with the upper surface 52 t of the leg portion 52. Note that, in FIG. 6, the first attachment region Ra, the second attachment region Rb, and the overlapping portion Rc in the first portion 61 are shown by hatching. The first attachment area Ra is a portion of the first portion 61 that is arranged in the first attachment groove 36a. The second attachment region Rb is a portion of the first portion 61 that is arranged in the second attachment groove 37a. The overlapping portion Rc is a portion of the first portion 61 that overlaps the leg portion 52. The upper surface 52t of the leg portion 52 and at least a part of the through hole 34a overlap the first portion 61.

As shown in FIG. 9, the first end 61a side of the first portion 61 fits in the first mounting groove 36a. The upper surface and the lower surface of the first portion 61 on the first end 61a side are in contact with the first inner wall surface 36as and the second inner wall surface 36at of the first mounting groove 36a, respectively. The first end 61a of the first portion 61 is separated from the third inner wall surface 36au. However, a part of the first end portion 61a may be in contact with the third inner wall surface 36au. The first inner wall surface 36as and the second inner wall surface 36at are provided facing the second direction Db among the inner wall surfaces of the first mounting groove 36a. The third inner wall surface 36au is provided between the first inner wall surface 36as and the second inner wall surface 36at.

Similarly, the second end 61b side of the first portion 61 fits in the second mounting groove 37a. The upper surface and the lower surface of the first portion 61 on the second end 61b side are in contact with the fourth inner wall surface 37as and the fifth inner wall surface 37at of the second mounting groove 37a, respectively. The second end portion 61b of the first portion 61 is separated from the sixth inner wall surface 37au. However, a part of the second end portion 61b may be in contact with the sixth inner wall surface 37au. The fourth inner wall surface 37as and the fifth inner wall surface 37at are provided facing the second direction Db among the inner wall surfaces of the second mounting groove 37a. The sixth inner wall surface 37au is provided between the fourth inner wall surface 37as and the fifth inner wall surface 37at.

As a result, as shown in FIG. 9, when a force F1 is applied from the ball 4 to the circulation component 5 in the second direction Db, the circulation component 5 is moved in the second direction Db by the force F1. The upper surface 52t of the portion 52 contacts the lower surface of the first portion 61. At this time, the reaction force F2 in the opposite direction to the force F1 acts on the first end portion 61a and the second end portion 61b of the first portion 61, respectively. As a result, the first portion 61 can suppress the upper surface 52t of the leg portion 52 and prevent the circulating component 5 from coming off the nut 3 by the force F1. Further, the first end portion 61a and the second end portion 61b are provided so as to sandwich the leg portion 52 in the first direction Da. Therefore, the force F1 can be received by both the first end portion 61a and the second end portion 61b. As a result, compared to a configuration in which the force F1 is received by either the first end portion 61a or the second end portion 61b, the circulation component 5 can be prevented from coming off even with a large force F1. Further, even when the force F1 is repeatedly applied for a long period of time, it is possible to suppress damage to the mounting component 6. Therefore, the ball screw device 1 can improve durability.

Further, as shown in FIG. 6, the width W1 of the first portion 61 of the mounting component 6 is larger than the width W3 of the connecting portion 63. As a result, the length of the first end portion 61a arranged in the first mounting groove 36a and the length of the second end portion 61b arranged in the second mounting groove 37a can be increased. Therefore, the reaction force F2 with respect to the force F1 applied from the ball 4 to the circulation component 5 can be increased, so that the attachment component 6 is damaged or the attachment component 6 moves from the first attachment groove 36a and the second attachment groove 37a. It is possible to suppress the separation.

In the present embodiment, the end portion of the first mounting groove 36 a opens on the outer circumference of the nut 3. As a result, when the attachment component 6 is attached to the cutout portion 33, the first end portion 61a is in a state in which the first portion 61 and the second portion 62 are substantially parallel to the first bottom surface 34 and the second bottom surface 35, respectively. The mounting component 6 is slid in a direction parallel to the third direction Dc along the first mounting groove 36a. As a result, the first end portion 61a and the second end portion 61b are respectively arranged in the first mounting groove 36a and the second mounting groove 37a. In this way, in the ball screw device 1, the mounting component 6 can be slid to be mounted on the nut 3, and the circulating component 5 can be easily fixed by the mounting component 6.

As shown in FIGS. 8 and 9, in the direction perpendicular to the first bottom surface 34 (second direction Db), the first mounting groove 36 a is arranged at a position apart from the first bottom surface 34. That is, a step is formed between the first bottom surface 34 and the second inner wall surface 36at. Thereby, the first mounting groove 36a can be easily formed by cutting or the like. Further, in the second direction Db, the lower surface of the first portion 61 is separated from the first bottom surface 34 by a predetermined distance.

FIG. 9 shows a state in which the force F1 is not applied, and a predetermined clearance CL is provided between the lower surface of the first portion 61 and the upper surface 52t of the leg portion 52. As a result, it is possible to suppress contact between the first portion 61 and the leg portion 52 when the attachment component 6 is attached to the nut 3. It should be noted that a preload may be applied between the first portion 61 and the leg portion 52 while the force F1 is not applied.

Further, the first end portion 61a and the second end portion 61b are fitted in the first mounting groove 36a and the second mounting groove 37a, respectively, but not limited to this. That is, the width of the first mounting groove 36a (the distance between the first inner wall surface 36as and the second inner wall surface 36at) may be larger than the thickness of the first end portion 61a. The width of the second mounting groove 37a (the distance between the fourth inner wall surface 37as and the fifth inner wall surface 37at) may be larger than the thickness of the second end portion 61b. Even in this case, when the force F1 is applied, the upper surface on the first end portion 61a side contacts the first inner wall surface 36as, and the upper surface on the second end portion 61b side contacts the fourth inner wall surface 37as, The reaction force F2 acts on each.

As shown in FIGS. 7 and 8, the second portion 62 and the connecting portion 63 are arranged outside the second wall portion 37 in the third direction Dc. The second portion 62 is fixed to the second bottom surface 35 by the fixing component 8. The fixed component 8 is, for example, a bolt, and is fastened to the screw hole 35 a (see FIG. 5) provided in the second bottom surface 35. Note that, as shown in FIG. 2, the second portion 62 is provided separately from the second wall portion 37 and the third wall portion 38. However, the second portion 62 may be in contact with at least one of the second wall portion 37 and the third wall portion 38.

As shown in FIGS. 7 and 8, in the portion outside the second wall portion 37 in the third direction Dc, one end side (first end portion 61a) of the attachment component 6 is located in the first attachment groove 36a. It is arranged and supported, and the other end side (second portion 62) is supported by the fixed component 8. That is, the first end portion 61a and the fixed component 8 are arranged so as to sandwich the overlapping portion Rc (see FIG. 6) in the first direction Da. As a result, the circulation component 5 can be prevented from coming off the nut 3 by the force F1.

Further, the first portion 61 and the second portion 62 are arranged on the first bottom surface 34 and the second bottom surface 35, which are adjacent to each other in the first direction Da. That is, the first portion 61 that directly receives the force F1 and the second portion 62 that is fixed by the fixing component 8 are arranged in different regions in the first direction Da. Further, the second end portion 61 b is provided between the portion (superimposed portion Rc) of the first portion 61 that receives the force F1 and the second portion 62. Further, a curved connecting portion 63 is provided between the first portion 61 and the second portion 62. With such a configuration, when the force F1 is applied to the first portion 61, the force F1 is received by the first end portion 61a and the second end portion 61b, and the force acting on the second portion 62 side can be reduced. .. As a result, it is possible to prevent the force F1 from directly acting on the fixed component 8. Therefore, even when the repeated force F1 is applied for a long period of time, it is possible to prevent the fixed component 8 from loosening and the fixed component 8 from separating from the nut 3.

As shown in FIG. 10, the second bottom surface 35 is arranged at a position closer to the rotation axis AX than the first bottom surface 34 in the second direction Db. Specifically, the distance H2 from the virtual line L1 to the second bottom surface 35 in the second direction Db is shorter than the distance H1 from the virtual line L1 to the first bottom surface 34. In other words, the distance from the second bottom surface 35 to the upper end of the second wall surface 37s1 is longer than the distance from the first bottom surface 34 to the upper end of the second wall surface 37s1. Here, the virtual line L1 is a virtual line that is orthogonal to the rotation axis AX and is parallel to the second bottom surface 35.

On the other hand, in the ball screw device 100 of the comparative example shown in FIG. 11, the second bottom surface 35 is provided in the same plane as the first bottom surface 34. As shown in FIG. 11, the distance H1 from the virtual line L1 to the second bottom surface 35 in the second direction Db is equal to the distance H1 from the virtual line L1 to the first bottom surface 34. In this case, when viewed from the first direction Da, the second portion 62 of the attachment component 6 and the head of the fixed component 8 protrude outside the outer peripheral surface 3s of the nut 3. As a result, the diameter of the maximum circumscribing circle MD of the ball screw device 100 including the mounting component 6 and the fixing component 8 is larger than the outer diameter of the nut 3. The maximum circumscribing circle MD is a circumscribing circle of the ball screw devices 1 and 100 centering on the rotation axis AX, and is a portion farthest from the rotation axis AX among members constituting the ball screw devices 1 and 100. Contact.

In the ball screw device 1 of the present embodiment shown in FIG. 10, the width WB1 of the second bottom surface 35 in the third direction Dc is longer than the width WB2 shown in FIG. The widths WB1 and WB2 are the lengths from the portion where the second wall surface 37s1 and the second bottom surface 35 are connected to the portion where the outer peripheral surface 3s and the second bottom surface 35 are connected. Further, the distance from the second bottom surface 35 to the upper end of the second wall surface 37s1 is also longer than that of the ball screw device 100 of the comparative example shown in FIG. As a result, the ball screw device 1 is configured such that the second bottom surface 35, the second wall surface 37s1, and the virtual outer peripheral surface obtained by extending the outer peripheral surface 3s are compared to the case where the second bottom surface 35 is formed on the same surface as the first bottom surface 34. The space surrounded by and becomes large.

Therefore, it is possible to prevent the second portion 62 of the mounting component 6 and the head of the fixed component 8 from protruding outside the outer peripheral surface 3s of the nut 3. As a result, the maximum circumscribing circle MD of the ball screw device 1 becomes equal to the outer peripheral surface 3s of the nut 3. Therefore, the ball screw device 1 can be downsized in the radial direction. Further, when attaching other components or the like to the outer periphery of the nut 3, contact between the other components and the attachment component 6 and the fixed component 8 is suppressed. Therefore, restrictions on the mounting positions of other components are reduced, and the degree of freedom can be increased. Therefore, when mounting other parts or the like on the outer periphery of the nut 3, or when incorporating the ball screw device 1 into various devices such as a manufacturing device and a machine tool, it is easy to reduce the size of the entire device.

Further, since the width WB1 becomes long, a sufficient fastening force can be obtained when the fixing component 8 fastens the mounting component 6 to the second bottom surface 35, and the mounting component 6 can be favorably fixed. Furthermore, since the width WB1 is increased, the degree of freedom of the type of the fixing component 8 and the fixing method can be increased. The fixed component 8 is not limited to a bolt. The fixing component 8 may be a rivet, for example, and the second portion 62 may be fixed to the second bottom surface 35 by caulking the rivet. Since the ball screw device 1 can reduce the force acting on the second portion 62 side, even if a device different from the fastening device such as a bolt is used as the fixed component 8, the fixed component 8 is loosened or fixed. It is possible to prevent the component 8 from separating from the nut 3.

The configurations of the first bottom surface 34 and the second bottom surface 35 are not limited to the example shown in FIG. For example, the width WB1 of the second bottom surface 35 and the size of the step formed between the first bottom surface 34 and the second bottom surface 35 (difference between the distance H1 and the distance H2) depend on the type of the fixing component 8 and the fixing method. It can be changed accordingly.

As described above, the ball screw device 1 has the screw shaft 2, the nut 3, the plurality of balls 4, the circulation component 5, the mounting component 6, and the fixing component 8. The screw shaft 2 has a first screw groove 21 on the outer peripheral surface. The nut 3 is provided with a second screw groove 31 corresponding to the first screw groove 21 on the inner peripheral surface and a notch 33 on the outer peripheral surface 3s. The plurality of balls 4 roll between the first screw groove 21 and the second screw groove 31. The circulating component 5 has a main body portion 51 and a pair of leg portions 52 provided at both ends of the main body portion 51, and is provided on the nut 3. The attachment part 6 has a first part 61 and a second part 62 connected to the first part 61, and fixes the circulation part 5 to the nut 3. The cutout portion 33 has a first bottom surface 34 and a second bottom surface 35 provided at a position closer to the rotation axis AX than the first bottom surface 34 in the direction perpendicular to the first bottom surface 34 (second direction Db). Have. The leg portion 52 is inserted into the through hole 34 a provided in the first bottom surface 34. The first portion 61 is provided on the first bottom surface 34 so as to overlap the leg portion 52, and the second portion 62 is fixed to the second bottom surface 35 by the fixing component 8.

According to this, as compared with the case where the second bottom surface 35 is formed in the same plane as the first bottom surface 34 in the cutout portion 33, the virtual curved surface obtained by extending the outer peripheral surface 3s of the nut 3 and the second bottom surface 35 are formed. The space between them becomes large. Therefore, when viewed from the rotation axis AX direction of the screw shaft 2, the second portion 62 of the fixed component 8 and the attachment component 6 can be suppressed from protruding outward in the radial direction from the outer peripheral surface 3s of the nut 3. Therefore, the ball screw device 1 can be downsized in the radial direction.

Further, in the ball screw device 1, the second bottom surface 35 is arranged adjacent to the first bottom surface 34 in the first direction Da parallel to the rotation axis AX of the screw shaft 2. In a direction (third direction Dc) that intersects the first direction Da and is parallel to the first bottom surface 34, the width WB1 of the second bottom surface 35 is larger than the width of the first bottom surface 34. The width of the first bottom surface 34 is the length from the portion where the second wall surface 37s1 and the first bottom surface 34 are connected to the portion where the outer peripheral surface 3s and the first bottom surface 34 are connected.

According to this, since the first bottom surface 34 and the second bottom surface 35 are arranged side by side in the first direction Da, compared to the case where the first bottom surface 34 and the second bottom surface 35 are arranged in the third direction Dc, the nut. The outer diameter of 3 can be reduced. Therefore, it is possible to reduce the size of the ball screw device 1 in the radial direction. Moreover, since the width WB1 of the second bottom surface 35 is larger than the width of the first bottom surface 34, the second part 62 can be favorably fixed to the second bottom surface 35 by the fixing component 8.

Further, in the ball screw device 1, the attachment part 6 has a connecting portion 63 that connects the first portion 61 and the second portion 62, and the width W2 of the second portion 62 is larger than the width W3 of the connecting portion 63. large.

According to this, when fixing the second portion 62 to the second bottom surface 35, it is possible to increase the degree of freedom in the type of the fixing component 8 and the fixing method.

Further, in the ball screw device 1, the connecting portion 63 is formed to be curved according to the step formed by the first bottom surface 34 and the second bottom surface 35.

According to this, the rigidity of the 1st part 61 which presses the leg part 52 of the circulation component 5 can be improved. Therefore, it is possible to suppress the damage of the mounting component 6 and the detachment of the mounting component 6 from the nut 3.

Further, in the ball screw device 1, a circulation component mounting groove 32 communicating with the cutout portion 33 is provided on the outer periphery of the nut 3, and the main body portion 51 of the circulation component 5 is provided inside the circulation component mounting groove 32. Be done.

According to this, since the leg portion 52 of the circulation component 5 is fixed to the nut 3 by the attachment component 6, it is not necessary to provide a member for pressing the main body portion 51 on the circulation component attachment groove 32 and the main body portion 51. .. Therefore, the size of the ball screw device 1 can be reduced as compared with the configuration in which the mounting component 6 is provided on the upper side of the main body portion 51 to press the circulating component 5. Since the main body 51 is provided inside the circulation component mounting groove 32, the area of the outer circumference of the nut 3 can be secured as compared with the configuration in which the main body 51 is provided on the flat surface of the nut 3. As a result, when attaching other components or the like to the outer periphery of the nut 3, restrictions on the attachment positions of the other components or the like are reduced, and the degree of freedom can be increased. Further, since the main body 51 is provided inside the circulation component mounting groove 32, when other components are mounted on the outer periphery of the nut 3, the ball screw device 1 is used in various devices such as a manufacturing device and a machine tool. When assembled, contact between the main body 51 and external parts can be suppressed.

1 Ball Screw Device 2 Screw Shaft 3 Nut 4 Ball 5 Circulation Component 6 Mounting Component 8 Fixed Component 21 First Screw Groove 31 Second Screw Groove 32 Circulation Component Mounting Groove 33 Notch 34 34 First Bottom 35 Second Second Bottom 36 1st Wall part 36a First mounting groove 37 Second wall part 37a Second mounting groove 38 Third wall part 41 Rolling path 51 Main body part 52 Leg part 61 First part 61a First end part 61b Second end part 62 Second part 63 connection

Claims (5)

A screw shaft having a first screw groove on the outer peripheral surface,
A nut having a second thread groove corresponding to the first thread groove on the inner peripheral surface and a cutout portion on the outer peripheral surface;
A plurality of balls rolling between the first screw groove and the second screw groove;
A body part and a pair of leg parts provided at both ends of the body part, and a circulation component provided on the nut,
An attachment part having a first part and a second part connected to the first part, for fixing the circulation part to the nut;
A fixing component for fixing the attachment component to the nut,
The cutout portion has a first bottom surface and a second bottom surface provided in a position closer to the rotation axis of the screw shaft than the first bottom surface in a direction perpendicular to the first bottom surface,
The leg portion is inserted into a through hole provided on the first bottom surface,
The ball screw device in which the first portion is provided so as to overlap the leg portion on the first bottom surface, and the second portion is fixed to the second bottom surface by the fixing component. The second bottom surface is disposed adjacent to the first bottom surface in a first direction parallel to the rotation axis of the screw shaft,
The ball screw device according to claim 1, wherein a width of the second bottom surface is larger than a width of the first bottom surface in a direction that intersects the first direction and is parallel to the first bottom surface. The attachment part has a connecting portion that connects the first part and the second part,
The ball screw device according to claim 1 or 2, wherein a width of the second portion is larger than a width of the connecting portion. The ball screw device according to claim 3, wherein the connecting portion is curved according to a step formed by the first bottom surface and the second bottom surface. A circulation component mounting groove that communicates with the cutout portion is provided on the outer periphery of the nut,
The ball screw device according to claim 1, wherein the main body portion of the circulating component is provided inside the circulating component mounting groove.

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