JP7342912B2 - ball screw mechanism - Google Patents

Description

The present invention relates to a ball screw mechanism equipped with a piece, and more particularly, to a ball screw mechanism that can be used for various purposes such as an electric actuator.

BACKGROUND ART In recent years, labor saving in vehicles and the like has progressed, and systems have been developed in which, for example, an automobile's transmission, parking brake, master cylinder, etc. are operated not manually but by the power of an electric motor. In electric actuators used for such applications, a ball screw mechanism may be used to convert rotational motion transmitted from an electric motor into axial motion with high efficiency.

Typically, a ball screw mechanism includes a screw shaft, a nut, and a ball, and when the nut rotates relative to the screw shaft, the ball rolls along a rolling path within the nut. Although this allows smooth operation, a circulation means is required to circulate the balls that have reached one end of the rolling path to the other end. Tubes, links, and the like are known as such circulation means, and since the links are used by being embedded in the holes of the nuts, they have the advantage that the structure of the nut can be easily made compact.

Conventionally, when attaching such a piece to a hole in a nut, it is fixed with an adhesive or the like. However, in the case of adhesive fixation, time is required for the adhesive to solidify, making it difficult to shorten the manufacturing time. On the other hand, it is also conceivable to attach the piece by fitting the piece into the hole of the nut and then plastically deforming the inner peripheral surface of the hole by caulking. However, when the entire nut is hardened to prevent wear, it is difficult to apply the nut, and there are problems in that it cannot be easily assembled. Furthermore, in the case of gluing or crimping nuts, if the ball screw mechanism is once assembled and then disassembled again for adjustment or maintenance, it becomes difficult to remove and reassemble the pieces.

On the other hand, Patent Document 1 discloses a ball screw mechanism including a cylindrical member that presses the top from the outside in the radial direction.

JP2006-97832A

The cylindrical member of Patent Document 1 has a simple cylindrical shape, and such a cylindrical member is usually formed by drawing (deep drawing). The molded product formed by the drawing process has a container shape having a flange portion extending radially outward on one end side and a bottom surface on the other end side opposite to the flange portion. Therefore, in order to form a cylindrical shape with openings at both ends, it is necessary to cut off the bottom and flange portions from the molded product. However, it is generally difficult to cut off the bottom surface and flange part to match the inner and outer diameters of the cylindrical member with a blade, and one end has a minute flange part (outward minute flange part) facing outward in the radial direction. remains, and a minute flange portion (inward minute flange portion) that goes radially inward remains on the other end side (bottom side). In particular, punching burrs may occur on the other end (bottom side) toward the outside in the axial direction of the cylindrical portion.

If you try to insert a cylindrical member into a nut from the inward facing minute flange side, the minute flange will interfere with the outer circumferential surface of the nut, causing the minute flange to fall off or the nut or piece to be damaged. Pieces may fall off. If a metal piece falls off between the cylindrical member and the nut, it is difficult to completely remove it by cleaning, and it may get into the circuit through the hole where the piece is installed during use. There is a risk that it will happen. Intrusion of metal particles can damage the ball transfer surface and cause various failures such as peeling, reduced efficiency, increased reverse actuation force, and reduced service life.

Therefore, when inserting the cylindrical member into the nut, it is necessary to insert the cylindrical member from the outward micro flange side to prevent the metal piece from falling off. However, the cylindrical member has a simple cylindrical shape, and the inward minute flange portion and the outward minute flange portion also have very fine structures, making it difficult to identify the direction of insertion.

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 mechanism that allows easy identification of the insertion direction of an annular member and that can suppress the occurrence of metal pieces falling off during insertion. do.

The above object of the present invention is achieved by the following configuration.
(1) A screw shaft having a male thread groove formed on the outer peripheral surface,
A nut arranged to surround the screw shaft, the nut having a female thread groove formed on an inner circumferential surface and a hole penetrating in the radial direction;
a plurality of balls arranged to be freely rollable along a rolling path formed between the opposing male thread groove and the female thread groove;
a piece disposed in the hole of the nut and having a circulation path for returning the ball from one end of the rolling path to the other end;
an annular member disposed on the outer peripheral surface of the nut;
A ball screw mechanism comprising:
The annular member has a cylindrical part that presses the top from the outside in the radial direction, and a flange part that projects radially outside from one end in the axial direction of the cylindrical part,
A corner connecting the inner circumferential surface of the cylindrical portion of the annular member and the one axial end surface of the flange portion is inclined radially outward from the other axial end toward the one axial end. It is a surface,
A ball screw mechanism characterized by:
(2) The ball screw mechanism according to (1), wherein the inclined surface includes an R shape.
(3) The ball screw mechanism according to (1) or (2), wherein the inclined surface includes a tapered shape.
(4) A circumferential groove is formed in the outer circumferential surface of the nut, with which the other axial end of the cylindrical portion of the annular member engages;
The circumferential groove includes a bottom, a first surface closer to one end in the axial direction than the bottom, and a second surface closer to the other end in the axial direction than the bottom,
The inclination angle of the first surface is smaller than the inclination angle of the second surface.
The ball screw mechanism according to any one of (1) to (3).
(5) The ball screw mechanism according to (4), wherein the other axial end of the cylindrical portion of the annular member is caulked to form a caulked portion that enters the circumferential groove.
(6) A convex portion protruding inward in the radial direction is formed at the other end in the axial direction of the cylindrical portion of the annular member,
the convex portion engages with the circumferential groove;
The ball screw mechanism described in (4).
(7) A protrusion portion that abuts the flange portion of the annular member in the axial direction is disposed on the outer peripheral surface of the nut,
The ball according to any one of (1) to (6), wherein the annular member is inserted into the outer circumferential surface of the nut, with the flange portion at the beginning, until the flange portion abuts the protrusion. Screw mechanism.
(8) The ball screw mechanism according to any one of (1) to (7), wherein the annular member is formed by drawing.
(9) The ball screw mechanism according to any one of (1) to (8), wherein the annular member is made of a galvanized steel plate.

According to the present invention, it is possible to provide a ball screw mechanism in which the insertion direction of the annular member can be easily identified and the occurrence of falling off of the metal piece during insertion can be suppressed.

FIG. 1 is an exploded perspective view of the ball screw mechanism according to the first embodiment. FIG. 2 is a sectional view of the ball screw mechanism. FIG. 3 is a perspective view of the annular member. FIG. 4 is a cross-sectional view of the annular member. FIG. 5 is a front view of the annular member. FIG. 6 is an enlarged view of the periphery of the other axial end of the annular member. FIG. 7 is an enlarged view of the vicinity of one axial end of the annular member. FIG. 8 is an enlarged view of the vicinity of one axial end of the annular member according to the modification. FIG. 9 is an enlarged view of the periphery of one axial end of the annular member according to the modification. FIG. 10 is an enlarged view of the periphery of the other axial end of the annular member in the second embodiment. FIG. 11 is a perspective view of the annular member in the second embodiment. FIG. 12 is a perspective view of an annular member 50 according to a modification.

(First embodiment)
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a ball screw mechanism 1 according to a first embodiment. FIG. 2 is a sectional view of the ball screw mechanism 1. FIG. 3 is a perspective view of the annular member 50. FIG. 4 is a cross-sectional view of the annular member 50. FIG. 5 is a front view of the annular member 50.

As shown in FIGS. 1 and 2, the ball screw mechanism 1 includes a screw shaft 10, a nut 20, a plurality of balls 30, a piece 40, and an annular member 50.

The screw shaft 10 has a male thread groove 11 formed on its outer peripheral surface, and is supported so as to be movable only in the axial direction. A substantially cylindrical nut 20 supported so as to be only rotatable is arranged so as to surround the outer periphery of the screw shaft 10 . The nut 20 has a female thread groove 21 formed on the inner circumferential surface and a hole 23 for a piece passing through in the radial direction. The plurality of balls 30 are arranged to freely roll along a spiral raceway formed between the male thread groove 11 of the screw shaft 10 and the female thread groove 21 of the nut 20 that face each other in the radial direction.

As shown in FIG. 2, a piece 40 is disposed within the hole 23 of the nut 20. The piece 40 has a head 41 that comes into contact with the stepped portion 23a of the hole 23, and a circulation path 43 provided on the inside in the radial direction. Through this circulation path 43, the balls 3 are returned and circulated from one end of the transfer path to the other end.

As shown in FIGS. 1 and 2, a flange portion 25 that protrudes outward in the radial direction is formed at one axial end portion of the nut 20 (the upper left end portion in FIG. 1; the right end portion in FIG. 2). A flange portion 53 of an annular member 50 abuts against the flange portion 25 in the axial direction, as will be described later. Therefore, the flange portion 25 is a protruding portion that is disposed on the outer circumferential surface of the nut 20 and comes into contact with the flange portion 53 of the annular member 50 in the axial direction. Note that the nut 20 is rotatable by being driven by a drive component (not shown).

The annular member 50 is a substantially cylindrical sleeve with a flange, and is made of, for example, a galvanized steel plate or stainless steel to prevent rust. Note that the annular member 50 may be made of an unplated steel plate. The annular member 50 is arranged on the outer peripheral surface of the nut 20. Referring also to FIGS. 3 to 5, the annular member 50 includes a cylindrical portion 51 that is disposed on the outer peripheral surface of the nut 20 and presses the piece 40 from the outside in the radial direction, and a cylindrical portion 51 that protrudes radially outside from one axial end of the cylindrical portion 51. A flange portion 53 is provided.

FIG. 6 is an enlarged view of the periphery of the other end of the annular member 50 in the axial direction. As shown in FIGS. 2 and 6, on the outer circumferential surface of the nut 20, on the other axial end side of the piece 40, there is a circumferential groove 28 with which the other axial end of the cylindrical portion 51 of the annular member 50 engages. is formed. At the other end in the axial direction of the cylindrical portion 51 of the annular member 50, a caulking portion 51a that enters the circumferential groove 28 is formed by caulking. In this manner, the caulking portion 51a is formed after the annular member 50 is inserted into the nut 20, thereby preventing the annular member 50 from coming off. The caulking portion 51a may be provided at least at one circumferential location on the other end of the cylindrical portion 51 in the axial direction, but it may be provided at multiple locations, in which case the caulking portions 51a may be provided at equal intervals in the circumferential direction, for example. It will be done.

Although the shape of the circumferential groove 28 is not particularly limited, the circumferential groove 28 in the illustrated example has a bottom portion 28a, a first surface 28b on one axial end side of the bottom portion 28a, and a first surface 28b on the other axial end side of the bottom portion 28a. and a second surface 28c. The inclination angle of the first surface 28b is set to be smaller than the inclination angle of the second surface 28c. In this example, the first surface 28b has a tapered cross section, and the second surface 28c has a semicircular cross section. In this way, by making the inclination angle of the first surface 28b relatively small, insertability of the annular member 50 into the nut 20 is improved. Further, by making the inclination angle of the second surface 28c relatively large, the annular member 50 becomes difficult to come off after the annular member 50 is inserted into the nut 20 and the caulked portion 51a is formed.

FIG. 7 is an enlarged view of the vicinity of one axial end of the annular member 50. As shown in FIG. 7, a relief portion 29 is recessed in a corner connecting the outer circumferential surface of the nut 20 and the other axial end surface of the flange portion 25 of the nut 20. As shown in FIG. The annular member 50 has an inclined surface 55 formed at a corner portion facing the relief portion 29 . More specifically, the corner portion connecting the inner circumferential surface of the cylindrical portion 51 of the annular member 50 and one axial end surface of the flange portion 53 is formed as the corner portion connects the inner circumferential surface of the cylindrical portion 51 of the annular member 50 and the axially one end surface of the flange portion 53 as it goes from the other axial end side to the axially one end side. An inclined surface 55 is formed radially outward.

As shown in FIG. 7, the entire inclined surface 55 may have an R shape (curved cross-sectional shape). When the thickness of the annular member 50 is 0.5 mm, the angle R of the inclined surface 55 is, for example, 0.2 mm or more. That is, the angle R of the inclined surface 55 is 0.4 times or more the thickness of the annular member.

Note that the shape of the inclined surface 55 is not particularly limited as long as it is a shape that goes radially outward from the other end in the axial direction toward the one end in the axial direction. For example, as shown in FIG. 8, the inclined surface 55 may have a tapered shape (straight line shape in cross section) at the axial middle portion, and an R shape (curved curve shape in cross section) at both axial end portions. Further, as shown in FIG. 9, the entire inclined surface 55 may have a tapered shape.

At the time of assembly, each piece 40 is first assembled into the hole 23. When the head 41 comes into contact with the stepped portion 23a, the piece 40 can be positioned in the radial direction. In this state, the annular member 50 is inserted into the nut 2 from the other end in the axial direction toward the one end in the axial direction, with the flange portion 53 leading, and is fitted onto the outer peripheral surface of the nut 2. Considering ease of separation, it is desirable that the annular member 50 has a loose fit with respect to the nut 2, but a tight fit may be adopted depending on the purpose and use. When the flange portion 53 of the annular member 50 is brought into contact with the flange portion 25 (projection portion) of the nut 20, the piece 40 disposed within the hole 23 is covered by the annular member 50.

Here, the annular member 50 of this embodiment is formed by drawing (deep drawing). That is, the annular member 50 is formed by cutting off the bottom surface of a container-shaped intermediate molded product obtained by drawing a thin metal plate. Note that the intermediate molded product has a flange portion extending radially outward at one end in the axial direction, and a bottom surface at the other end in the axial direction. The flange portion of the intermediate molded product is left uncut to form the flange portion 53 of the annular member 50, and the bottom surface of the intermediate molded product is cut off. As mentioned above, it is generally difficult to cut off the bottom surface with a blade to match the inner diameter of the cylindrical portion 51 of the annular member 50 when mass production is intended, so the bottom surface is punched out by press processing. In some cases, a clearance is required between the inner surface of the cylindrical portion and the outer diameter of the punch. As a result, a minute flange portion (inward minute flange portion) that goes radially inward remains on the other end side in the axial direction of the cylindrical portion 51 of the annular member 50, and further, on the other end side in the axial direction of the cylindrical portion 51. Extraction burrs may occur toward the outside in the axial direction. Therefore, when inserting the annular member 50 into the nut 20, it is necessary to insert it from the side opposite to the inward minute flange portion (one end in the axial direction).

Therefore, since the annular member 50 of this embodiment is provided with a flange portion 53 at one end in the axial direction that becomes the leading end during insertion, the insertion direction can be easily and reliably identified. That is, it is possible to prevent mistakes such as inserting the other end in the axial direction opposite to the side where the flange portion 53 is provided first, and furthermore, it is possible to suppress the occurrence of falling off of the metal piece during insertion.

Furthermore, the corner portion connecting the inner circumferential surface of the cylindrical portion 51 of the annular member 50 and the one axial end surface of the flange portion 53 moves radially outward from the other axial end toward the one axial end. An inclined surface 55 is formed toward the opposite direction. Therefore, the insertability of the annular member 50 into the nut 20 is improved, and the occurrence of burrs and falling off of metal pieces can be further suppressed.

After the annular member 50 is inserted into the nut 20, as shown in FIG. 6, a caulking portion 51a is formed to prevent the annular member 50 from coming off.

In the ball screw mechanism 1 configured in this way, when power from an electric motor (not shown) is transmitted to the nut 20 via the drive component, the nut 20 rolls on the rolling path and passes through the circulation path 43 of the piece 40. The ball 30 that lubricates the screw shaft 10 efficiently converts the rotational motion into an axial motion of the screw shaft 10, and a driven member (not shown) can be moved in the axial direction. Note that the ball screw mechanism of the present invention is applicable not only to a method in which the nut 20 is rotated to drive the screw shaft 10, but also to a method in which the screw shaft 10 is rotated to drive the nut 20.

(Second embodiment)
Next, a ball screw mechanism 1 according to a second embodiment of the present invention will be described. FIG. 10 is an enlarged view of the periphery of the other axial end of the annular member 50 in the second embodiment. FIG. 11 is a perspective view of the annular member 50 in the second embodiment.

As shown in FIGS. 10 and 11, in the ball screw mechanism 1 of this embodiment, the crimped portion 51a (see FIG. 6) is not formed at the other end of the cylindrical portion 51 of the annular member 50 in the radial direction. A plurality of convex portions 51b that protrude inward and engage with the circumferential groove 28 are formed. The convex portions 51b are each formed by bending the other axial end of the cylindrical portion 51 inward in the radial direction.

During assembly, the annular member 50 is inserted into the outer circumferential surface of the nut 2 from the other axial end toward the one axial end, with the flange portion 53 leading. Here, the other end of the annular member 50 in the axial direction advances outward in the radial direction while being elastically deformed, and when the convex portion 51b engages with the circumferential groove 28, it contracts and returns to its original size.

Although six of the plurality of convex portions 51b in the illustrated example are provided at equal intervals in the circumferential direction, the arrangement and number are not limited to this. Further, it is not necessary to provide a plurality of convex portions 51b, and it is sufficient that at least one convex portion 51b is provided.

FIG. 12 is a perspective view of an annular member 50 according to a modification. In the annular member 50 of FIG. 12, an inward flange portion 51c that protrudes radially inward over the entire circumference is formed on the inner circumferential surface of the other axial end of the cylindrical portion 51. The annular member 50 of this example is formed by drawing (deep drawing). That is, the annular member 50 is formed from a container-shaped intermediate molded product obtained by drawing a thin metal plate by cutting off the center of the bottom surface so as to leave the inward flange portion 51c.

Although the present invention has been described above with reference to each embodiment, the present invention should not be interpreted as being limited to the above-mentioned embodiments. , number, arrangement location, etc. are arbitrary as long as the present invention can be achieved, and are not limited.

In the above embodiment, the flange portion 25 of the nut 20 is exemplified as the protruding portion that comes into contact with the flange portion 53 of the annular member 50 in the axial direction. The flange portion 25 is not limited to the flange portion 25 as long as it has a configuration that abuts the portion 53 in the axial direction. For example, the protrusion may be a bearing fixed to the outer circumferential surface of the nut 20, or a retaining ring that restricts axial movement of the bearing.

1 Ball screw mechanism 10 Screw shaft 11 Male thread groove 20 Nut 21 Female thread groove 23 Hole 23a Step portion 25 Flange portion (protruding portion)
28 Circumferential groove 29 Relief portion 30 Ball 40 Top 41 Head 43 Circulation path 50 Annular member 51 Cylindrical portion 51a Caulked portion 51b Convex portion 51c Inward flange portion 53 Flange portion 55 Inclined surface

Claims (9)

a screw shaft having a male thread groove formed on the outer peripheral surface;
A nut arranged to surround the screw shaft, the nut having a female thread groove formed on an inner circumferential surface and a hole penetrating in the radial direction;
a plurality of balls arranged to be freely rollable along a rolling path formed between the opposing male thread groove and the female thread groove;
a piece disposed in the hole of the nut and having a circulation path for returning the ball from one end of the rolling path to the other end;
an annular member disposed on the outer peripheral surface of the nut;
A ball screw mechanism comprising:
The annular member has a cylindrical part that presses the top from the outside in the radial direction, and a flange part that projects radially outside from one end in the axial direction of the cylindrical part,
A corner connecting the inner circumferential surface of the cylindrical portion of the annular member and the one axial end surface of the flange portion is inclined radially outward from the other axial end toward the one axial end. surface ,
The one axial end surface of the flange portion is one axial end surface of the annular member.
A ball screw mechanism characterized by: a screw shaft having a male thread groove formed on the outer peripheral surface;
A nut arranged to surround the screw shaft, the nut having a female thread groove formed on an inner circumferential surface and a hole penetrating in the radial direction;
a plurality of balls arranged to be freely rollable along a rolling path formed between the opposing male thread groove and the female thread groove;
a piece disposed in the hole of the nut and having a circulation path for returning the ball from one end of the rolling path to the other end;
an annular member disposed on the outer peripheral surface of the nut;
A ball screw mechanism comprising:
The annular member has a cylindrical part that presses the top from the outside in the radial direction, and a flange part that projects radially outside from one end in the axial direction of the cylindrical part,
A corner connecting the inner circumferential surface of the cylindrical portion of the annular member and the one axial end surface of the flange portion is inclined radially outward from the other axial end toward the one axial end. surface,
A protrusion portion that abuts the flange portion of the annular member in the axial direction is disposed on the outer circumferential surface of the nut,
The annular member is inserted into the outer circumferential surface of the nut, with the flange portion at the beginning, until the flange portion contacts the protruding portion.
Ball screw mechanism. The inclined surface includes an R shape.
The ball screw mechanism according to claim 1 or 2 . The inclined surface includes a tapered shape.
The ball screw mechanism according to any one of claims 1 to 3 . A circumferential groove is formed in the outer circumferential surface of the nut, and the other axial end of the cylindrical portion of the annular member engages with the circumferential groove;
The circumferential groove includes a bottom, a first surface closer to one end in the axial direction than the bottom, and a second surface closer to the other end in the axial direction than the bottom,
The inclination angle of the first surface is smaller than the inclination angle of the second surface.
The ball screw mechanism according to any one of claims 1 to 4 . At the other axial end of the cylindrical portion of the annular member, a caulking process is performed to form a caulking portion that enters the circumferential groove.
The ball screw mechanism according to claim 5 . A convex portion projecting inward in the radial direction is formed at the other end in the axial direction of the cylindrical portion of the annular member,
the convex portion engages with the circumferential groove;
The ball screw mechanism according to claim 5 . The ball screw mechanism according to claim 1, wherein the annular member is formed by drawing. The ball screw mechanism according to any one of claims 1 to 8, wherein the annular member is made of a galvanized steel plate.

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