JP2021188687A - Ball screw device - Google Patents

Abstract

To obtain a ball screw device allowing the smooth circulation of a ball, and having a fixing structure of a circulation component.SOLUTION: A main body part 18 constituting a circulation component 5 is arranged inside an attachment hole 10 penetrating a nut 3 in a radial direction, and a pair of fixing parts 19 hanging out of an external peripheral face of the main body part 18 toward opposite sides are arranged inside a pair of attachment recessed grooves 13 which are formed at both sides with the attachment hole 10 sandwiched therebetween out of an external peripheral face of the nut 3. By making a pair of engagement protrusions 26 which are formed at the fixing parts 19 engaged with engagement recesses 16 which are formed at a pair of groove wall faces constituting the attachment recessed grooves 13, the circulation component 5 becomes non-displaceable to the outside of the radial direction with respect to the nut 3, and the attachment recessed grooves 13 becomes non-displaceable to a groove width direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a ball screw device.

Since the ball screw device rolls and moves the ball between the screw shaft and the nut, higher efficiency can be obtained as compared with the sliding screw device in which the screw shaft and the nut are in direct contact with each other. For this reason, the ball screw device is used for various mechanical devices such as an electric brake device for automobiles, an automatic manual transmission (AMT), and a positioning device for machine tools in order to convert the rotational motion of a drive source such as an electric motor into linear motion. It is built into.

The ball screw device includes a screw shaft having a spiral shaft-side ball screw groove on the outer peripheral surface, a nut having a spiral nut-side ball screw groove on the inner peripheral surface, a shaft-side ball screw groove, and a nut-side ball screw groove. It is provided with a plurality of balls that roll on a load path (load ball runway) and a circulation component that returns the balls from the end point of the load path to the start point. The circulation component has a circulation groove (circulation path, no-load ball rolling path) connecting the start point and the end point of the load path.

The ball screw device is roughly classified into an external circulation type ball screw device typified by a return tube (pipe) type and an internal circulation type ball screw device typified by a frame type. Of these, the internal circulation type ball screw device has a circulation component inside the nut, and is widely used because the ball screw device can be configured in a small size.

For example, Japanese Patent Application Laid-Open No. 2009-287702 (Patent Document 1) discloses a spinning top type ball screw device using a spinning top as a circulating component. 21 to 23 show a ball screw device 100 having a conventional structure described in Japanese Patent Application Laid-Open No. 2009-287702.

The ball screw device 100 includes a screw shaft 101, a nut 102, a plurality of balls 103, and a circulation component 104 up to this point. In the present specification and claims, the axial direction, the radial direction, and the circumferential direction mean the axial direction, the radial direction, and the circumferential direction with respect to the screw shaft, unless otherwise specified.

The screw shaft 101 has a spiral shaft-side ball screw groove 105 on the outer peripheral surface. The nut 102 has a spiral nut-side ball screw groove 106 on the inner peripheral surface. The screw shaft 101 is inserted inside the nut 102 and is arranged coaxially with the nut 102. The shaft-side ball screw groove 105 and the nut-side ball screw groove 106 are arranged so as to face each other in the radial direction, and form a spiral load path 107.

The start point and the end point of the load path 107 are connected by a substantially S-shaped circulation groove 108 formed on the radial inner surface of the circulation component 104. The ball 103 that has reached the end point of the load path 107 is returned to the start point of the load path 107 through the circulation groove 108. The start point and the end point of the load path 107 are interchanged according to the direction of relative displacement (relative rotation direction) with respect to the axial direction of the screw shaft 101 and the nut 102.

The nut 102 has a mounting hole 109 penetrating in the radial direction. Then, the circulation component 104 is attached to the attachment hole 109. The mounting hole 109 opens not only on the outer peripheral surface of the nut 102 but also on the inner peripheral surface of the nut 102, and a part of the nut-side ball screw groove 106 is cut out.

The circulation component 104 includes a substantially columnar main body 110, a pair of fixing portions 111 provided at the radial outer end of the main body 110, and a pair provided at the radial inner end of the main body 110. It has a retaining portion 112 of the above.

The main body 110 has a circulation groove 108 curved in a substantially S shape on the inner side surface in the radial direction facing the ball screw groove 105 on the shaft side. The main body 110 is fitted in a mounting hole 109 formed in the nut 102.

Each of the pair of fixing portions 111 is formed by forming a caulking portion 114 at the tip of each of the pair of protrusions 113 erected along the outer peripheral edge portion of the radial outer surface of the main body portion 110. .. The caulked portion 114 is pressed against the opening edge portion of the mounting hole 109. In the ball screw device 100 having a conventional structure, the caulking portion 114 is formed at the tip of the protrusion 113 to prevent the circulation component 104 from being displaced inward in the radial direction with respect to the nut 102, and the circulation component 104 is fixed to the nut 102. is doing.

Each of the pair of retaining portions 112 is formed in a substantially columnar shape, and extends in the circumferential direction from the radial inner portion of the main body portion 110. Each of the pair of retaining portions 112 is arranged inside the nut-side ball screw groove 106 and engages with the nut-side ball screw groove 106. This prevents the circulating component 104 from being displaced (outward) radially outward with respect to the nut 102.

Japanese Unexamined Patent Publication No. 2009-287702

In the ball screw device 100 having a conventional structure, a fixing portion 111 for fixing the circulation component 104 to the nut 102 is formed with a caulking portion 114 at the tip end portion of the protrusion 113 provided on the radial outer surface of the main body portion 110. It is composed of things. Therefore, a force applied when the tip of the protrusion 113 is plastically deformed may be applied to the main body 110 to cause deformation in the circulation groove 108 provided on the radial inner surface of the main body 110. .. As a result, the ball 103 may be clogged inside the circulation groove 108, which may hinder the smooth circulation of the ball 103.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a ball screw device having a fixing structure for circulating parts, which enables smooth circulation of balls.

The ball screw device of the present invention includes a screw shaft, a nut, a plurality of balls, and a circulation component.
The screw shaft has a spiral shaft-side ball screw groove on the outer peripheral surface.
The nut has a spiral nut-side ball screw groove on the inner peripheral surface, and has a mounting hole penetrating in the radial direction so as to cut out a part of the nut-side ball screw groove.
The plurality of balls roll on a spiral load path including the shaft-side ball screw groove and the nut-side ball screw groove.
The circulation component is attached to the mounting hole and has a circulation groove on the inner side surface in the radial direction connecting the start point and the end point of the load path.
The nut has a pair of mounting recesses extending linearly and opening in the mounting hole on both side portions of the outer peripheral surface of the outer peripheral surface across the mounting hole.
Each of the pair of mounting concave grooves has a flat surface-shaped groove bottom surface and a pair of groove wall surfaces having engaging recesses formed in the radial intermediate portions thereof.
The circulation component projects from the main body portion arranged inside the mounting hole and the outer peripheral side surface of the main body portion in opposite directions, and a pair of fixings arranged inside the pair of mounting concave grooves. Has a part.
Each of the pair of fixing portions engages with the pair of engaging recesses provided in the mounting recess to laterally displace the circulating component with respect to the nut and mount. It has a pair of engaging protrusions that make it impossible to displace the concave groove in the groove width direction.

In the ball screw device according to one aspect of the present invention, each of the pair of fixing portions is arranged apart from each other in the groove width direction of the mounting concave groove, and each of the pair of fixing portions is provided with the engaging convex portion. It may have a side plate portion.
In this case, each of the pair of fixing portions is placed on the bottom surface of the groove, and the ends on both sides with respect to the groove width direction of the mounting concave groove are the inner ends in the radial direction of the pair of side plates. It is possible to further have a substrate portion connected to.

In the ball screw device according to one aspect of the present invention, the circulation component may be made of metal, and the engaging convex portion may be a caulked portion that is pressed against the inner surface of the engaging concave portion by plastic deformation.
When the circulating component is made of metal, the circulating component can be an injection-molded product made from metal powder. That is, the circulating component can be manufactured by a metal powder injection molding method.
Alternatively, the circulating component may be made of synthetic resin.
When the circulating component is made of synthetic resin, the engaging convex portion can be snap-fitted with the engaging concave portion.

The ball screw device according to one aspect of the present invention may have the engaging recess having a tapered cross-sectional shape.
In this case, the engaging recess may have a triangular cross-sectional shape.
Alternatively, the engaging recess may have, for example, a semi-circular (partially circular) cross-sectional shape.

In the ball screw device according to one aspect of the present invention, the main body portion can be loosely inserted inside the mounting hole.

In the ball screw device according to one aspect of the present invention, the pair of mounting recesses can be arranged on both sides of the mounting hole in the circumferential direction.
In this case, the center lines of the pair of mounting recesses can be present on a virtual plane orthogonal to the center axis of the mounting holes and orthogonal to the center axis of the screw shaft. ..

In the ball screw device according to one aspect of the present invention, the mounting hole may have an oval cross-sectional shape and have a pair of inner peripheral flat surface portions on the inner peripheral surface.
In this case, each of the pair of inner peripheral flat surface portions and each of the pair of groove wall surfaces can be arranged in parallel with each other.
Alternatively, the mounting hole may have a circular cross-sectional shape or a rectangular cross-sectional shape.

In the ball screw device according to one aspect of the present invention, the circulation component can have a rotationally symmetric shape centered on the central portion with respect to the arrangement direction of the pair of fixed portions.

According to the ball screw device of the present invention, it is possible to realize a fixing structure of a circulating component that enables smooth circulation of balls.

FIG. 1 is a perspective view of the ball screw device according to the first example of the embodiment. FIG. 2 is a plan view of the ball screw device according to the first example of the embodiment. FIG. 3 is a cross-sectional view taken along the line I-I of FIG. FIG. 4 is a perspective view showing a nut taken out from the ball screw device according to the first example of the embodiment. FIG. 5 is a partially enlarged view of FIG. FIG. 6 is a schematic cross-sectional view showing the first example of the embodiment for explaining the work of forming an engaging recess on a pair of groove wall surfaces constituting the mounting recess. FIG. 7 is a perspective view of the circulation component before forming the engaging convex portion taken out from the ball screw device according to the first example of the embodiment and viewed from the outside in the radial direction. FIG. 8 is a perspective view of the circulation component before forming the engaging convex portion taken out from the ball screw device according to the first example of the embodiment and viewed from the inside in the radial direction. FIG. 9 is a sectional view taken along line II-II of FIG. FIG. 10 is a partially enlarged view of FIG. FIG. 11 is a view taken along the line III of FIG. FIG. 12 is a schematic cross-sectional view taken along the line IV-IV of FIG. FIG. 13 is a partially enlarged view of FIG. 12. FIG. 14 is a schematic cross-sectional view corresponding to FIG. 12, which is shown for explaining a caulking step of forming an engaging convex portion on each of a pair of side plate portions with respect to the first example of the embodiment. FIG. 15 is a schematic view seen from the upper side of FIG. FIG. 16 is a diagram corresponding to FIG. 1, showing a second example of the embodiment. FIG. 17 is a diagram corresponding to FIG. 10, showing a second example of the embodiment. FIG. 18 is a diagram corresponding to FIG. 7, showing a second example of the embodiment. FIG. 19 is a diagram corresponding to FIG. 8 showing a second example of the embodiment. FIG. 20 is a diagram corresponding to FIG. 13, showing a third example of the embodiment. FIG. 21 is a plan view showing a ball screw device having a conventional structure. 22 is a sectional view taken along line VV of FIG. 21. FIG. 23 is a perspective view showing a circulating component before forming a caulked portion at the tip of the protrusion from a ball screw device having a conventional structure.

[First example of the embodiment]
The first example of the embodiment will be described with reference to FIGS. 1 to 15.

[Overall configuration of ball screw device]
The ball screw device 1 of this example is a frame-type ball screw device for automobiles. For example, it is incorporated in an electric brake booster device and converts the rotary motion of an electric motor, which is a drive source, into a linear motion of a hydraulic cylinder. It is used for applications such as operating a piston.

The ball screw device 1 includes a screw shaft 2, a nut 3, a plurality of balls 4, and a circulation component 5 up to this point.

The screw shaft 2 is inserted inside the nut 3 and is arranged coaxially with the nut 3. A spiral load path 8 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 rotatably arranged on the load path 8. When the screw shaft 2 and the nut 3 are relatively rotated, the ball 4 that has reached the end point of the load path 8 is returned to the start point of the load path 8 through the circulation groove 9 formed on the radial inner surface of the circulation component 5. Is done. The ball screw device 1 is used, for example, in a mode in which the screw shaft 2 is linearly moved with respect to the nut 3 by rotating the nut 3 relative to the screw shaft 2. Hereinafter, the structure of each component of the ball screw device 1 will be described.

<Screw shaft>
The screw shaft 2 is made of metal and has a spiral shaft-side ball screw groove 6 having a constant lead on the outer peripheral surface. The shaft-side ball screw groove 6 is formed by subjecting the outer peripheral surface of the screw shaft 2 to a grinding process (cutting process) or a rolling process. In this example, the number of threads of the ball screw groove 6 on the shaft side is one. The groove shape (groove bottom shape) of the cross section of the shaft-side ball screw groove 6 is a Gothic arch groove or a circular arc groove.

<nut>
The nut 3 is made of metal and has a substantially cylindrical shape as a whole. The nut 3 has a spiral nut-side ball screw groove 7 on the inner peripheral surface. The nut-side ball screw groove 7 is formed by subjecting the inner peripheral surface of the nut 3 to grinding (cutting) or rolling tapping (cutting tapping), and has the same lead as the shaft-side ball screw 6. Have. Therefore, with the screw shaft 2 inserted inside the nut 3, the shaft-side ball screw groove 6 and the nut-side ball screw groove 7 are arranged so as to face each other in the radial direction, and a spiral load path 8 is provided. Configure. The number of threads of the nut-side ball screw groove 7 is one as in the shaft-side ball screw groove 6. The groove shape of the cross section of the nut-side ball screw groove 7 is also a Gothic arch groove or a circular arc groove, similarly to the shaft-side ball screw groove 6.

The nut 3 has mounting holes 10 penetrating in the radial direction at a plurality of locations (three locations in the illustrated example) where the axial position and the circumferential position (phase) are deviated from each other. Each of the mounting holes 10 is open to each of the outer peripheral surface and the inner peripheral surface of the nut 3. Each of the mounting holes 10 is formed so as to cut out a part of the nut-side ball screw groove 7 formed on the inner peripheral surface of the nut 3. Each central axis of the mounting hole 10 is arranged toward the radial direction of the nut 3.

As shown in FIGS. 4 and 5, each of the mounting holes 10 has an oval (oval) cross-sectional shape, and the longitudinal direction is oriented in the circumferential direction and the lateral direction is directed in the axial direction. Is formed. That is, the mounting hole 10 has a larger circumferential width than the axial width. The inner peripheral surface of the mounting hole 10 is a pair of inner peripheral flat surface portions 11 that face each other in the axial direction and are arranged in parallel with each other, and a pair of concave portions that face each other in the circumferential direction and are curved in a concave arc shape. It is composed of a curved surface portion 12.

The nut 3 has a pair of mounting recesses 13 extending linearly in the circumferential direction and opening in the mounting hole 10 on both sides of the mounting hole 10 in the circumferential direction on the outer peripheral surface. Specifically, the center line of the mounting concave groove 13 exists on a virtual plane orthogonal to the central axis of the mounting hole 10 and orthogonal to the central axis of the screw shaft 2. Therefore, the groove width direction of the mounting concave groove 13 coincides with the axial direction.

Each of the mounting concave grooves 13 has an end portion on one side in the circumferential direction opened in the axial intermediate portion of the concave curved surface portion 12 constituting the inner peripheral surface of the mounting hole 10, and the end on the other side in the circumferential direction. The portion is open to the outer peripheral surface of the cylindrical surface of the nut 3. The radial depth of each of the mounting recesses 13 is deepest on one side in the circumferential direction near the mounting hole 10, and shallowest on the other side in the circumferential direction far from the mounting hole 10. The axial width, which is the groove width of the mounting concave groove 13, is smaller than the axial width (length in the lateral direction) of the mounting hole 10 and is constant over the entire length.

Each of the mounting concave grooves 13 has a substantially rectangular cross-sectional shape, and has a flat surface-shaped groove bottom surface 14 and a flat surface-shaped pair of groove wall surfaces 15. The pair of groove bottom surfaces 14 arranged on both sides of the mounting hole 10 in the circumferential direction are arranged on the same plane, and are arranged on a virtual plane orthogonal to the central axis of the mounting hole 10. The pair of groove wall surfaces 15 face each other in the axial direction and are arranged substantially at right angles to the groove bottom surface 14. Therefore, the pair of groove wall surfaces 15 are arranged in parallel with each other. In this example, each of the groove wall surfaces 15 is arranged parallel to the inner peripheral flat surface portion 11 constituting the inner peripheral surface of the mounting hole 10. Each of the groove wall surfaces 15 has a quarter-circular shape (a fan shape having a right-angled central angle) when viewed from the axial direction.

In this example, a pair of mounting concave grooves 13 arranged on both sides of the mounting hole 10 in the circumferential direction are formed by cutting using a cutting tool such as an end mill. Further, when performing cutting, the inner peripheral flat surface portion 11 constituting the inner peripheral surface of the mounting hole 10 is used as a reference surface for positioning the cutting tool. As described above, each of the mounting concave grooves 13 has a substantially rectangular cross-sectional shape and extends linearly in the circumferential direction, and since the shape is not complicated, it can be easily machined with high accuracy by cutting. Can be done.

Each of the groove wall surfaces 15 has an engaging recess 16 extending in the circumferential direction in the radial intermediate portion. Therefore, a pair of engaging recesses 16 are provided in the mounting recesses 13. As shown in FIGS. 12 to 13, the engaging recess 16 has a tapered cross-sectional shape, and in the illustrated example, it has a triangular cross-sectional shape. The end on one side of the engagement recess 16 in the circumferential direction is not opened in the mounting hole 10, but the end on the other side in the circumference of the engagement recess 16 is on the outer peripheral surface of the cylindrical surface of the nut 3. It is open. The end or middle portion of the engaging recess 16 on one side in the circumferential direction is not open to the outer peripheral surface of the nut 3. Further, as shown in FIG. 5, one side portion (inner portion) in the circumferential direction of the engaging recess 16 has a triangular cone shape, and the closer to the mounting hole 10 (toward one side in the circumferential direction), the more. Each of the axial depth and the radial width becomes smaller. Therefore, the axial width between the groove bottoms (vertices having a triangular cross section) of the pair of engaging recesses 16 facing in the axial direction approaches the mounting hole 10 on one side in the circumferential direction of the engaging recesses 16. It gets narrower. In the illustrated example, the end portion of the engaging recess 16 on one side in the circumferential direction is not opened in the mounting hole 10, but in the case of carrying out the present invention, it can be opened in the mounting hole 10.

As shown in FIG. 6, the pair of engaging recesses 16 provided in the mounting recess 13 is a cutting tool 17 having, for example, a diamond-shaped cross-sectional shape (cross-sectional shape like an abacus bead). By moving from the opening on the other side in the circumferential direction toward one side in the circumferential direction, the pair of groove wall surfaces 15 can be formed at the same time.

<ball>
The ball 4 is a steel ball having a predetermined diameter, and is rotatably arranged in the load path 8 and the circulation groove 9. The ball 4 arranged in the load path 8 rolls while receiving a compressive load, whereas the ball 4 arranged in the circulation groove 9 is pushed by a subsequent ball 4 and rolls without receiving a compressive load. Move.

<Circulation parts>
The circulation component 5 includes an injection-molded product made from metal powder, which is manufactured by a metal powder injection molding method (MIM), and is attached to each of the mounting holes 10 of the nut 3. Examples of the metal powder (alloy for MIM) constituting the circulation component 5 include Fe-Ni-C (1 to 8% Ni, to 0.8% C) and Fe-Cr-C (0.5 to 2%). Cr, ~ 0.8% C), SCM415, SUS630 and the like can be used.

As shown in FIGS. 7 and 8, the circulation component 5 includes a main body portion 18 and a pair of fixing portions 19. The circulation component 5 has a rotationally symmetric shape centered on the central portion with respect to the arrangement direction of the pair of fixed portions 19 (longitudinal direction of the circulation component 5).

The main body portion 18 has a substantially long cylindrical shape, and is loosely inserted inside the mounting hole 10 in a state where its central axis is aligned with the central axis of the mounting hole 10. That is, the main body portion 18 is arranged inside the mounting hole 10 with a gap (small gap) so as not to apply a load to the main body portion 18.

The outer peripheral side surface of the main body 18 is composed of a pair of outer peripheral flat surface portions 20 arranged in parallel with each other and a pair of convex curved surface portions 21 each curved in a convex arc shape. In a state where the main body portion 18 is arranged inside the mounting hole 10, each of the pair of outer peripheral flat surface portions 20 faces each of the pair of inner peripheral flat surface portions 11 via a minute gap in the axial direction, and a pair. Each of the convex curved surface portions 21 faces each of the pair of concave curved surface portions 12 via a minute gap in the circumferential direction. Therefore, the main body portion 18 has an axial width dimension and a circumferential width dimension that are slightly smaller than the axial width dimension and the circumferential width dimension of the mounting hole 10. Of the convex curved surface portion 21, the portion located on the radial outer side of the fixed portion 19 is cut out in a flat surface shape.
When carrying out the present invention, the main body may have a cylindrical shape, a polygonal column shape (including a rectangular columnar shape), or the like. Further, by arranging (fitting, press-fitting) the main body portion inside the mounting hole without rattling, it is possible to position the circulating component with respect to the nut.

The main body portion 18 is arranged inside the mounting hole 10 and has a circulation groove 9 curved in a substantially S shape on the radial inner surface (lower surface) facing the axial side ball screw groove 6 of the screw shaft 2 in the radial direction. have. The circulation groove 9 smoothly connects the screw grooves adjacent to each other in the axial direction of the ball screw groove 7 on the nut side. The circulation groove 9 has a semi-elliptical cross-sectional shape. The circulation groove 9 has a groove width slightly larger than the diameter of the ball 4, and has a groove depth that allows the ball 4 moving in the circulation groove 9 to get over the thread of the shaft-side ball screw groove 6. ing.

The radial outer surface (upper surface) of the main body 18 has a flat surface 22 at the center in the circumferential direction so as not to project radially outward from the outer peripheral surface of the nut 3, and the flat surface 22 has a circumferential direction. Both sides have a pair of inclined surfaces 23 that are inclined inward in the radial direction as the distance from the flat surface 22 increases. However, the radial outer surface of the main body 18 may be formed in a partially cylindrical surface shape having a radius of curvature substantially the same as the radius of curvature of the outer peripheral surface of the nut 3.

Each of the pair of fixing portions 19 has a substantially U-shaped (U-shaped) cross-sectional shape, and projects from the radial intermediate portion of the outer peripheral side surface of the main body portion 18 in the opposite direction with respect to the circumferential direction. .. Therefore, as shown in FIGS. 7 and 8, a pair of fixing portions 19 are provided at both ends of the circulation component 5 in the circumferential direction, which are separated from the main body portion 18 in the circumferential direction. Each of the fixing portions 19 is composed of a flat plate-shaped substrate portion 24 and a pair of side plate portions 25.

The substrate portion 24 is arranged in parallel with a virtual plane orthogonal to the central axis of the main body portion 18, and is placed without a gap on the bottom surface 14 of the groove. This prevents the circulation component 5 from being displaced inward in the radial direction with respect to the nut 3.

The pair of side plate portions 25 are separated in the axial direction corresponding to the groove width direction of the mounting concave groove 13, and are arranged so as to face (overlap) each of the pair of groove wall surfaces 15. The ends on both sides of the substrate portion 24 in the axial direction are connected to the inner ends of each of the pair of side plate portions 25 in the radial direction. Therefore, each of the pair of side plate portions 25 is bent at a substantially right angle toward the outer side in the radial direction with respect to the substrate portion 24. In the state before the fixing portion 19 is arranged inside the mounting concave groove 13 and the engaging convex portion 26 described later is formed, the side plate portion 25 and the groove wall surface 15 face each other through a minute gap, or It abuts without gaps like an intermediate fit. Each of the pair of side plate portions 25 is provided with a chamfered portion 27 at the radial outer end portion of the end portion (tip portion) on the other side in the circumferential direction. This prevents the side plate portion 25 from protruding outward in the radial direction from the outer peripheral surface of the nut 3.

As shown in FIGS. 7 and 8, the pair of side plate portions 25 are configured as thin flat plates as a whole in the state before forming the engaging convex portion 26 described later, but the circulation component 5 is provided. In the state of being fixed to the nut 3, as shown in FIGS. 12 and 13, an engaging convex portion 26, which is a caulked portion pressed against the inner surface of the engaging concave portion 16 by plastic deformation, is provided. In this example, the thickness of each of the side plate portions 25 is made smaller than the plate thickness of the substrate portion 24 so that the processing load when forming the engaging convex portion 26 which is the caulking portion is suppressed to a small size.

In the engaging convex portion 26, the main body portion 18 is arranged inside the mounting hole 10, and each of the pair of fixing portions 19 is arranged inside each of the pair of mounting concave grooves 13. As shown in FIG. 15, the punches 28 arranged on the radial outer side of each fixing portion 19 are simultaneously moved toward the radial inner side, and each radial outer portion of the pair of side plate portions 25 is axially (s). It is formed by plastically deforming (pushing and bending) in the plate thickness direction). That is, a pair of shoulder portions 29 provided at the tip portion of the punch 28 simultaneously expands (caulks and deforms) each radial outer portion of the pair of side plate portions 25 in the axial direction. The engaging protrusions 26 of the above are formed at the same time. In this example, a pair of engaging convex portions 26 are simultaneously formed on a pair of fixed portions 19 provided on both sides of the main body portion 18 in the circumferential direction. Preferably, the four engaging protrusions 26 of the circulation component 5 are formed at the same time. When forming the engaging convex portion 26 on the radial outer portion of the side plate portion 25, the portion of the side plate portion 25 that is radially inwardly separated from the engaging convex portion 26 is formed on the groove wall surface 15 of the mounting concave groove 13. Press.

The engaging convex portion 26 formed by pushing and bending the radial outer portion of the side plate portion 25 sufficiently penetrates into the inside of the engaging concave portion 16 provided on the groove wall surface 15, and is pressed against the inner surface of the engaging concave portion 16 to be in close contact with the inner surface. .. More specifically, as shown in FIG. 13, the axial end portion of the engaging convex portion 26 is pushed into the inner portion of the engaging concave portion 16, so that the radial outer surface of the engaging convex portion 26 is formed. The engagement recess 16 is pressed against the radial outer inner surface, and the radial inner surface of the engagement protrusion 26 is pressed against the radial inner inner surface of the engagement recess 16. As a result, the engaging convex portion 26 is unable to engage with the engaging concave portion 16 in the radial outward displacement, and is unable to engage in the axial displacement.

In this example, as described above, a pair of engaging protrusions 26 are engaged with a pair of engaging recesses 16 for each fixing portion 19 provided at both ends in the circumferential direction of the circulation component 5. By doing so, the radial (outer and inner) and axial displacements of the circulation component 5 with respect to the nut 3 are made impossible, and the circulation component 5 is fixed to the nut 3. Therefore, the radial and axial positioning of the circulation component 5 with respect to the nut 3 is achieved. Further, since the four engaging convex portions 26 are engaged with the engaging concave portions 16 for each circulating component 5, the circulating component 5 is prevented from rotating around the central axis of the main body portion 18.

In this example, as shown in FIG. 15, only the circumferential middle portion of the radial outer portion of the side plate portion 25 is plastically deformed in the axial direction to form an engaging convex portion 26 in the portion. There is. As a result, when the engaging convex portion 26 is formed, the deformation occurs at the end portion (base end portion) on one side in the circumferential direction of the side plate portion 25, thereby suppressing the deformation of the main body portion 18. There is.

With the circulation component 5 attached to the nut 3, the pair of openings of the circulation groove 9 are opened on the opposite sides in the circumferential direction, and are adjacent to the screw grooves in the axial direction of the ball screw groove 7 on the nut side, respectively. Be connected. As a result, the circulation groove 9 is connected to the start point and the end point of the load path 8, respectively. Then, one circuit is formed by the circulation groove 9 and the load path 8 formed between the shaft side ball screw groove 6 and the nut side ball screw groove 7 (a range of about one winding). In other words, the start point and the end point of the load path 8 are connection points between the load path 8 and the circulation groove 9. The start point and the end point of the load path 8 are interchanged as the direction of relative displacement (relative rotation direction) with respect to the axial direction of the screw shaft 2 and the nut 3 changes and the moving direction of the ball 4 changes.

According to the ball screw device 1 of this example as described above, it is possible to realize a fixed structure of the circulation component 5 that enables smooth circulation of the ball 4.
That is, in this example, the circulation component 5 is not a main body portion 18 having a circulation groove 9 on the inner side surface in the radial direction, but a pair of fixing portions 19 provided at positions separated from the main body portion 18 on both sides in the circumferential direction. The circulating component 5 is fixed to the nut 3 by engaging the engaging convex portion 26 formed by plastic deformation with the engaging concave portion 16 of the mounting concave groove 13 provided on the outer peripheral surface of the nut 3. ing. Therefore, it is possible to suppress the force applied from the punch 28 to the side plate portion 25 from being transmitted to the main body portion 18 when the engaging convex portion 26 is formed. Therefore, when the engaging convex portion 26 is formed on the side plate portion 25, it is possible to prevent the circulation groove 9 formed on the inner side surface in the radial direction of the main body portion 18 from being deformed. As a result, it is possible to prevent the ball 4 from being clogged inside the circulation groove 9, and it is possible to realize smooth circulation of the ball 4.

In addition, in this example, only the circumferential middle portion of the radial outer portion of the side plate portion 25 is plastically deformed in the axial direction to form the engaging convex portion 26 in the portion, so that the main body is formed. It is possible to effectively suppress the deformation of the portion 18.

Further, according to the fixed structure of the circulation component 5 of this example, the circulation component 5 is provided with a retaining portion 112 (see FIG. 23) for preventing displacement in the radial direction as in the conventional structure described above. There is no need. That is, in this example, by engaging the pair of engaging protrusions 26 provided for each fixing portion 19 with the pair of engaging recesses 16, the radial outside of the circulation component 5 with respect to the nut 3. Displacement to can be disabled. Therefore, it is not necessary to provide the circulation component 5 with the retaining portion 112, and the circulation component 5 can be downsized. Further, since the circulation component 5 can be attached to the nut 3 from the outside in the radial direction, the man-hours for assembling work can be reduced.

Further, since the engaging convex portion 26 is formed by pushing and bending the radial outer portion of the thin plate-shaped side plate portion 25, the amount of protrusion (projection amount) of the engaging convex portion 26 in the axial direction is large. It can be secured, and a sufficient engagement margin between the engaging convex portion 26 and the engaging concave portion 16 can be secured. Further, when the engaging convex portion 26 is formed on the side plate portion 25, the punch 28 is moved inward in the radial direction while the substrate portion 24 is placed on the groove bottom surface 14, so that the groove bottom surface 14 is received. Can be used as. Therefore, the force can be efficiently transmitted from the punch 28 to the side plate portion 25, and the side plate portion 25 can be sufficiently plastically deformed. Therefore, the engaging convex portion 26 can be firmly pushed toward the engaging concave portion 16 to be engaged. Therefore, according to the fixing structure of this example, a sufficient fixing force of the circulation component 5 to the nut 3 can be sufficiently secured, and the circulation component 5 can be effectively prevented from rattling to the nut 3. Further, since the portion of the side plate portion 25 that is radially inwardly displaced from the engaging convex portion 26 can be pressed against the groove wall surface 15, it is effective that the circulation component 5 is displaced in the axial direction with respect to the nut 3. Can be suppressed.

Further, the axial width between the groove bottoms of the pair of engaging recesses 16 facing in the axial direction provided in the mounting recess 13 is the circumference of the engaging recess 16 which is a side portion close to the mounting hole 10. On one side in the direction, the closer to the mounting hole 10, the narrower it is. Therefore, it is possible to prevent the pair of engaging protrusions 26 engaged with the pair of engaging recesses 16 from being displaced to one side in the circumferential direction. Therefore, it is possible to prevent the circulation component 5 from being displaced in the circumferential direction with respect to the nut 3.

Further, by engaging the pair of engaging protrusions 26 provided for each fixing portion 19 with the pair of engaging recesses 16, the radial and axial positioning of the circulation component 5 with respect to the nut 3 is performed. Therefore, it is not necessary to position the circulation component 5 with respect to the nut 3 by inserting the main body 18 into the mounting hole 10. Therefore, the shape accuracy and the dimensional accuracy of the mounting hole 10 can be relaxed, and the processing cost of the mounting hole 10 can be reduced.

Further, since the cross-sectional shape of the fixed portion 19 is substantially U-shaped and the opening width of the fixed portion 19 (distance between the pair of side plate portions 25) can be widely secured, a punch is punched between the pair of side plate portions 25. The 28 can be easily inserted from the outside in the radial direction. Therefore, the shape accuracy of the punch 28 can be relaxed, which is advantageous in reducing the processing cost.

In this example, a pair of mounting recesses 13 are formed on both sides of the outer peripheral surface of the nut 3 in the circumferential direction so that the arrangement direction of the pair of fixing portions 19 faces the circumferential direction. There is. Therefore, it is possible to prevent the axial dimension of the nut 3 from increasing as compared with the case where the pair of mounting concave grooves are arranged on both sides of the mounting hole 10 in the axial direction. In particular, in this example, since the center line of the mounting concave groove 13 is arranged on a virtual plane orthogonal to the central axis of the mounting hole 10 and orthogonal to the central axis of the screw shaft 2, the axis of the nut 3 is arranged. The increase in directional dimensions can be effectively suppressed. Further, since the center line of the mounting concave groove 13 is arranged on a virtual plane orthogonal to the central axis of the screw shaft 2, the processing cost of the mounting concave groove 13 can be reduced, and the mounting work of the circulation component 5 can be performed. Workability can also be improved.

Further, since the mounting hole 10 has an oval cross-sectional shape having a pair of inner peripheral flat surface portions 11 on the inner peripheral surface, when the pair of mounting concave grooves 13 is machined using a cutting tool such as an end mill, The inner peripheral flat surface portion 11 can be used as a reference surface for positioning the cutting tool. Therefore, the processing man-hours can be reduced and the processing cost can be reduced.

In the ball screw device 1 of this example, the mounting hole 10 and the pair of mounting recesses 13 are provided so that the circulation component 5 does not project radially outward from each of the mounting holes 10 and the pair of mounting recesses 13. Since it is arranged inside, it is possible to prevent the ball screw device 1 from becoming large. Further, it is possible to prevent the circulation component 5 from becoming an obstacle when attaching another member to the nut 3.

In this example, since the circulation component 5 has a rotationally symmetric shape centered on the central portion with respect to the arrangement direction of the pair of fixed portions 19, it is possible to relax the restriction on the assembly direction of the circulation component 5. Therefore, the assembly man-hours can be reduced, which is advantageous in reducing the assembly cost.

[Second example of the embodiment]
A second example will be described with reference to FIGS. 16 to 19.

In the ball screw device 1a of this example, the configuration of the pair of fixing portions 19a included in the circulation component 5a is changed from the structure of the first example of the embodiment. Specifically, each of the pair of fixing portions 19a is arranged apart from each other in the axial direction corresponding to the groove width direction of the mounting concave groove 13, with respect to each of the pair of groove wall surfaces 15 of the mounting concave groove 13. It is composed of only a pair of side plate portions 25 that are arranged so as to face each other (overlap). Therefore, each of the pair of fixing portions 19a does not have a substrate portion to be mounted on the groove bottom surface 14 of the mounting concave groove 13.

According to the ball screw device 1a of this example as described above, since each of the side plate portions 25 can be strongly pressed against the groove wall surface 15, the circulation component 5a is radially and axially with respect to the nut 3. It is possible to effectively suppress the displacement to each of the above. Further, since the two substrate portions can be omitted as compared with the structure of the first example of the embodiment, the weight of the circulating component 5a can be reduced.
Other configurations and actions and effects are the same as those of the first embodiment.

[Third example of the embodiment]
A third example of the embodiment will be described with reference to FIG.

In the ball screw device 1b of this example, the shape of the engaging recess 16a formed on the groove wall surface 15a of the mounting recessed groove 13a provided in the nut 3a is changed from the structures of the first and second examples of the embodiment. .. Specifically, the engaging recess 16a has a semicircular cross-sectional shape among the tapered cross-sectional shapes.

Then, the engaging convex portion 26 formed by pushing and bending the radial outer portion of the side plate portion 25 is pressed against the inner surface of the engaging concave portion 16a. Specifically, as shown by a solid line in FIG. 20, the axial tip portion of the engaging convex portion 26 is pressed against the inner surface of the engaging concave portion 16a, or as shown by a broken line in FIG. 20, the engaging concave portion is formed. The entire radial inner surface of the engaging protrusion 26 bent so as to be curved along the inner surface of 16a is pressed against the inner surface of the engaging recess 16a.

Also in the case of the ball screw device 1b of this example as described above, the axial tip portion of the engaging convex portion 26 or the entire radial inner surface surface can be pressed against the inner surface of the engaging concave portion 16a, and the engaging convex portion can be pressed. The 26 can be engaged with the engaging recess 16a so that the displacement in the radial direction cannot be engaged and the displacement in the axial direction cannot be engaged with the engaging recess 16a. In the structure of this example, the contact area between the engaging convex portion 26 and the engaging concave portion 16a is smaller than that of the structure of the first example of the embodiment, so that the engaging force (fixing force) is smaller. , It is sufficient to fix the circulation component 5 to the nut 3a.
Other configurations and actions and effects are the same as those of the first embodiment.

When carrying out the present invention, the structures of the examples of the embodiments can be appropriately combined and carried out as long as there is no contradiction.

When carrying out the present invention, the pair of mounting recesses arranged so as to sandwich the mounting hole has a structure arranged on both sides of the mounting hole in the circumferential direction as described in each example of the embodiment. Not limited to this, it can be arranged on both sides of the mounting hole in the axial direction. Also, when a pair of mounting concave grooves are arranged on both sides in the circumferential direction of the mounting hole, the center line of the pair of mounting concave grooves is set at the center of the screw shaft by the same amount as the lead angle of the ball screw groove on the nut side. It can also be tilted with respect to a virtual plane orthogonal to the axis. Further, when carrying out the present invention, the pair of fixing portions is not limited to the structure provided in the radial intermediate portion of the outer peripheral side surface of the main body portion, but may be provided in the radial outer end portion.

When carrying out the present invention, the circulating parts may be made of synthetic resin. In this case, as the synthetic resin, for example, a fiber-reinforced polyamide resin material obtained by appropriately adding glass fiber to a polyamide 66 resin can be used. Further, if necessary, an amorphous aromatic polyamide resin (modified polyamide 6T / 6I) and a low water absorption aliphatic polyamide resin (polyamide 11 resin, polyamide 12 resin, polyamide 610 resin, polyamide 612 resin) are added to the polyamide resin. By adding it as appropriate, the water resistance can be further improved. When the circulating component is made of synthetic resin, the engaging convex portion provided in the fixing portion can be snap-fitted with the engaging concave portion provided in the accommodating concave groove of the nut.

1, 1a, 1b ball screw device 2 screw shaft 3, 3a nut 4 ball 5, 5a circulation parts 6 shaft side ball screw groove 7 nut side ball screw groove 8 load path 9 circulation groove 10 mounting hole 11 inner peripheral flat surface 12 concave Curved surface 13, 13a Mounting concave groove 14 Groove bottom surface 15, 15a Groove wall surface 16, 16a Engagement recess 17 Cutting tool 18 Main body 19, 19a Fixed part 20 Outer peripheral flat surface part 21 Convex curved surface part 22 Flat surface 23 Inclined surface 24 Board part 25 Side plate part 26 Engagement convex part 27 Chamfered part 28 Punch 29 Shoulder part 100 Ball screw device 101 Thread shaft 102 Nut 103 Ball 104 Circulation parts 105 Shaft side ball screw groove 106 Nut side ball screw groove 107 Load path 108 Circulation groove 109 Mounting Hole 110 Main body 111 Fixed part 112 Retaining part 113 Protruding part 114 Caulking part

Claims (12)

A screw shaft having a spiral shaft-side ball screw groove on the outer peripheral surface,
A nut having a spiral nut-side ball screw groove on the inner peripheral surface and a mounting hole penetrating in the radial direction so as to cut out a part of the nut-side ball screw groove.
A plurality of balls rolling on a spiral load path including the shaft-side ball screw groove and the nut-side ball screw groove, and
A circulation component, which is mounted inside the mounting hole and has a circulation groove on the inner side surface in the radial direction connecting the start point and the end point of the load path, is provided.
The nut has a pair of mounting recesses extending linearly and opening in the mounting hole on both side portions of the outer peripheral surface sandwiching the mounting hole.
Each of the pair of mounting concave grooves has a flat surface-shaped groove bottom surface and a pair of groove wall surfaces having engaging recesses formed in the radial intermediate portions thereof.
The circulation component projects from the main body portion arranged inside the mounting hole and the outer peripheral side surface of the main body portion in opposite directions, and a pair of fixings arranged inside the pair of mounting concave grooves. Has a part and
Each of the pair of fixing portions engages with the pair of engaging recesses provided in the mounting recess to laterally displace the circulating component with respect to the nut and mount. It has a pair of engaging protrusions that make it impossible to displace the concave groove in the groove width direction.
Ball screw device. The ball according to claim 1, wherein each of the pair of fixing portions is arranged apart from each other in the groove width direction of the mounting concave groove, and each has a pair of side plate portions having the engaging convex portion. Screw device. Each of the pair of fixing portions is placed on the bottom surface of the groove, and the ends on both sides in the groove width direction of the mounting concave groove are connected to the radial inner ends of the pair of side plate portions. The ball screw device according to claim 2, further comprising a portion. The circulating component is made of metal and is made of metal.
The engaging convex portion is a caulking portion that is pressed against the inner surface of the engaging concave portion by plastic deformation.
The 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 each of the engaging recesses has a tapered cross-sectional shape. The ball screw device according to claim 5, wherein each of the engaging recesses has a triangular cross-sectional shape. The ball screw device according to any one of claims 1 to 6, wherein the main body portion is loosely inserted inside the mounting hole. The ball screw device according to any one of claims 1 to 7, wherein the pair of mounting concave grooves are arranged on both sides in the circumferential direction of the mounting holes. The eighth aspect of the present invention, wherein each center line of the pair of mounting recesses exists on a virtual plane orthogonal to the central axis of the mounting hole and orthogonal to the central axis of the screw axis. Ball screw device. The ball screw device according to any one of claims 1 to 9, wherein the mounting hole has an oval cross-sectional shape and has a pair of inner peripheral flat surface portions on the inner peripheral surface. The ball screw device according to claim 10, wherein each of the pair of inner peripheral flat surface portions and each of the pair of groove wall surfaces are arranged in parallel with each other. The ball screw device according to any one of claims 1 to 11, wherein the circulation component has a rotationally symmetric shape centered on a central portion with respect to the arrangement direction of the pair of fixed portions.

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