JP2015137661A - ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a top-type ball screw which is low in manufacturing cost of a fixing part for fixing a top to a penetration hole of a nut.SOLUTION: As a fixing part 6 for fixing a top 4 to a penetration hole 22 of a nut 2, there is employed a part in which protrusions 62a, 62b, 63a and 63b do not exist at a center part 61c, and the center part 61c does not protrude to the top 4 side. A main body 61 of the fixing part 6 has a recess 61d at a contact face 61a in contact with the top 4. The nut 2 has recesses 23 in which first and second engagement parts 62, 63 of the fixing part 6 are arranged in positions being both sides with the penetration hole 22 sandwiched therebetween in a prescribed direction crossing an axial direction. The top 4 has a protrusion 41a fit into the recess 61d. When attaching the fixing part 6 to the nut 2 by moving the fixing part to a prescribed direction, the protrusion 41a of the top 4 and the recess 61d of the fixing part 6 are fit to each other, and the protrusions 62a, 62b, 63a and 63b are fit into groove 42a, 42b which are formed at the recesses 23 of the nut 2.

Description

  The present invention relates to a ball screw having a top as a part for forming a ball return path.

  The ball screw has a screw shaft, a nut, and a plurality of balls. The screw shaft is disposed in the nut. A ball rolling path is formed by the spiral groove of the screw shaft and the spiral groove of the nut. The nut includes a ball return path for returning the ball from the end point of the rolling path to the start point. The balls are arranged in a circulation path composed of a rolling path and a ball return path. A ball screw is a device in which a screw shaft and a nut move relative to each other through a ball that circulates in a circulation path and rolls (moves while rotating in a load state) in a rolling path. The ball return path is formed by attaching a return tube or a piece to the nut.

  In a top-type ball screw having a top as a part for forming a ball return path, the top is mounted in a through hole that penetrates a nut in a radial direction. Conventionally, in a top-type ball screw, in order to maintain the position of the top within the penetration, for example, a separate member is used or crimping or the like is performed to fix the top in the through hole. In addition, for the purpose of reducing working time and cost, proposals have been made regarding a structure for attaching a top to a through hole of a nut.

Japanese Patent Application Laid-Open No. 2004-228561 describes that in a top type ball screw, the top is prevented from coming off by using a come-off prevention member (a piece fixing part) whose mounting direction to the nut is different from that of the top.
Specifically, as shown in FIG. 18, the top 40 is inserted into the through hole 22 of the nut 2 from above the nut 2, and the removal preventing member 60 is laterally (direction perpendicular to the direction in which the through hole 22 extends). The nut 2 is moved along the recess 23 and the through hole 22 of the nut 2. This specific example will be described below.

  FIG. 19 is a diagram viewed from each direction of the frame 40. (A) shows the surface arrange | positioned at the inner peripheral surface side of the nut 2 of the top 40. FIG. (B) (c) is the figure which looked at the top 40 from the b direction c direction of (a), respectively. (D) is the figure which looked at the top 40 from the d direction of (c). (E) is the figure which looked at the top 40 from the e direction of (d). As shown in these drawings, the top 40 includes a disk-shaped main body 41 and a pair of protrusions 42 protruding from the outer periphery thereof, and an S-shaped recess (ball return path) 43 on the disk surface of the main body 41. Have

As shown in FIGS. 18 and 20, the drop prevention member 60 includes a body portion 601 and a flat plate portion 602. The planar shape of the body portion 601 and the flat plate portion 602 is a rectangle having a long side and a short side. The long sides of both rectangles are the same, and the short side of the body portion 601 is shorter than the flat plate portion 602. Thereby, a pair of convex part 602a protrudes to each side of the trunk | drum 601. FIG.
A surface of the body portion 601 opposite to the flat plate portion 602 is an arc surface 601b. A contact surface 602 b with the top 40 is formed on the surface of the flat plate portion 602 opposite to the body portion 601. A portion (center portion) 602c forming the contact surface 602b of the flat plate portion 602 protrudes from other portions. The circular arc surface 601b is a part of a concentric circle with the outer circumferential circle of the nut 2. That is, the convex portion 602a is formed along the entire long side of the rectangle that forms the removal preventing member 60, including the portion of the contact surface 602b.

As shown in FIGS. 5, 21, and 7, the recesses 23 are on both sides of the through hole 22 in a direction K (a predetermined direction intersecting the axial direction of the nut 2) K perpendicular to the axial direction J of the nut 2. Formed in position. The depth direction of the recess 23 is the radial direction of the nut 2. The bottom surface of the recess 23 exists at a position slightly outside the outer end surface line L of the top 40 in the radial direction of the nut 2.
Grooves 24 are formed on both sides of the recess 23 of the nut 2 so that the projections 602a of the slip-off prevention member 60 are fitted. The concave portion 23 includes a portion (grooved portion) 23a in which the groove 24 is formed and a portion (wide) that is wider on the outer side (the opposite side to the through hole 22 in the direction K) than the grooved portion 23a. Part) 23b. The width of the opening of the recess 23 is slightly larger than the width of the body portion 601 at the grooved portion 23a, and slightly larger than the width of the flat plate portion 602 at the wide portion 23b.

Further, a pair of recesses 22 a (recesses into which the protrusions 42 are fitted) are formed at positions facing each other on the peripheral surface of the through hole 22. The recess 22 a is also opened at the bottom surface of the recess 23.
When attaching the top 40, first, the top 40 is inserted into the through hole 22 of the nut 2 from the upper side of the nut 2, and the protrusion 42 is fitted into the recess 22a. Next, as shown in FIG. 22A, for example, the removal prevention member 60 is directed from the left side of the nut 2 toward the recess 23, the projection 602a is fitted into the left groove 24b, and the removal prevention member 60 is moved to the right side. Moving. At that time, the central portion 602c protruding toward the top 40 moves in the recess 23 in a bent state.

By this movement, as shown in FIG. 22B, both end portions of the convex portion 602a are fitted into the grooves 24a and 24b. As a result, both end portions of the slip-off preventing member 60 are arranged in each recess 23, the central portion 602c enters to a position deeper than the bottom surface of the recess 23 of the through hole 22, and the contact surface 602b is in contact with the top 40, The top 40 is fixed to the through hole 22 by the removal preventing member 60.
Moreover, since the movement in the K direction of the removal preventing member 60 is restricted by having the convex center portion 602c, the removal preventing member 60 is prevented from coming off from the recessed portion 23 of the nut 2. Furthermore, rotation of the top 40 in the through hole 22 is prevented by the fitting of the protrusion 42 and the recess 22a.

JP 2005-9624 A

  As described above, in the specific example described in Patent Document 1, the protruding prevention member 60 is prevented from being detached from the nut 2 by the convex center portion 602 c of the removal prevention member 60. For this purpose, it is preferable to increase the projecting dimension of the central portion 602c to some extent. However, it is necessary to bend the central portion 602c when the convex portion 602a is fitted into the groove 24b to move the removal preventing member 60. To facilitate the movement of the removal preventing member 60, the protrusion of the central portion 602c is required. It is preferable to make the dimensions as small as possible.

Therefore, in the specific example of Patent Document 1, it is necessary to accurately process the central portion 602c after appropriately setting the protruding dimension of the central portion 602c of the removal preventing member 60. Manufacturing cost increases.
In the above-described top ball screw of the specific example of Patent Document 1, a concave portion is formed around a through hole in which a nut piece is arranged, and a fixing component (a removal preventing member) for the piece is formed. A groove is formed in which a convex portion formed on the side of the frame is fitted, and the frame is fixed to the through hole by a fixing component that is moved along the groove and arranged in the concave portion.
And the subject of this invention is the top type | formula which can reduce the manufacturing cost of the fixing component which fixes a top to the through-hole of a nut compared with the specific example of patent document 1 mentioned above in the top type | formula ball screw which has the said structure. It is to provide a ball screw.

In order to solve the above problems, a ball screw according to an aspect of the present invention has the following configurations (1) to (5).
(1) It has a screw shaft, a nut, and a plurality of balls, and the screw shaft passes through the nut. A rolling path on which the ball rolls is formed by the spiral groove of the screw shaft and the spiral groove of the nut. The nut has a top formed with a ball return path for returning the ball from the end point of the rolling path to the start point. The top is disposed in a through hole that penetrates the nut in a radial direction. The balls are arranged in the rolling path and the ball return path. It is a ball screw in which the screw shaft and the nut move relative to each other via the ball rolling in the rolling path.

(2) A fixed component having a main body having a contact surface with the top, and a first engagement portion and a second engagement portion independently formed at positions facing each other across the contact surface of the main body. I have. Each of the first engaging portion and the second engaging portion protrudes laterally of the main body (a direction perpendicular to a direction in which the first engaging portion and the second engaging portion face each other). Have The main body has a concave portion or a convex portion on the contact surface, and the top has a convex portion or a concave portion that fits into the concave portion or the convex portion.

(3) The nut has recesses in which the first engagement portion and the second engagement portion are respectively arranged at positions on both sides of the through hole in a predetermined direction intersecting the axial direction. The depth direction of the recess is the radial direction of the nut. The bottom surface of the recess is present at the same position as the outer end surface of the top in the radial direction of the nut.
(4) The nut includes first and second grooves in which the first engaging portion and the convex portion of the second engaging portion of the fixed component are movably fitted around at least the through hole of the concave portion. Have The width of the opening (the dimension in the direction perpendicular to the predetermined direction) of the part of the recess where the groove is formed is larger than the width of the part having the contact surface of the main body (the dimension in the same direction), and It is smaller than the maximum width of the first engaging portion and the second engaging portion.

(5) The concave portion or the convex portion of the main body and the convex portion or the concave portion of the piece are fitted, the convex portion of the first engaging portion is fitted into the first groove, and the second engaging portion is With the convex part fitted in the second groove, the fixing component is arranged radially outside the nut from the concave part of the nut and the top of the through hole, and the top is fixed to the through hole. Has been.
The fixing component constituting the ball screw of this aspect is formed at the position of the contact surface by forming the first engagement portion and the second engagement portion independently at positions facing each other across the contact surface with the top. Since there are no protrusions projecting on both sides of the main body, the fixed part can be put into the through hole of the nut and one of the recesses from above and placed on the bottom surface of the recess and the top. In this state, if the fixed component is moved in the predetermined direction, the first convex portion can be fitted into the first groove and the second convex portion can be fitted into the second groove.

In addition, since the main body of the fixed part has a concave portion or a convex portion on the contact surface with the top, and the top has a convex portion or a concave portion that fits the concave portion or the convex portion, the concave and convex fitting between the main body of the fixed component and the top is made. By fitting, the fixed part is fixed to the top. Therefore, compared with the case where there is no such uneven | corrugated fitting, a fixed component becomes difficult to remove | deviate from the recessed part of a nut.
Moreover, this fixed component has the same contact surface with the top of the main body as the surface disposed on the top side of the first engagement portion and the second engagement portion, so that the central portion (portion forming the contact surface) However, it does not protrude from the surface arranged on the frame side of the first engagement portion and the second engagement portion. That is, since it does not have a convex center part, the manufacturing cost of a fixed part can be reduced compared with what has a convex center part.
Note that the ball screw of this aspect is formed by forming the recess so as to satisfy the following configuration (6), for example, when the outer diameter of the nut is large in comparison with the size of the fixed part. The range and the formation range of the recess can be made narrower than the specific example of Patent Document 1.

(6) The groove is formed only around the through hole, and the concave portion is a wide portion in which the convex portion is located on a side opposite to the through hole in a portion where the groove is formed in the predetermined direction. Have The dimension of the wide part along the predetermined direction is longer than the dimension of the convex part along the same direction and shorter than the dimension of the fixed part along the same direction.

  According to the ball screw of the present invention, compared with the ball screw described in Patent Document 1, the manufacturing cost of the fixed component for fixing the top to the through hole of the nut can be reduced.

It is a figure explaining the ball screw of an embodiment, Comprising: It is a schematic structure figure which made a nut a section. It is the figure which looked at the top which constitutes the ball screw of a first embodiment from each direction, (a) is a figure showing the field arranged at the inner skin side of a nut, (b) is b of (a) (C) is a view from the c direction of (a), (d) is a view from the d direction of (c), (e) is a view from the e direction of (d). It is a figure. It is the figure which looked at the fixed component which comprises the ball screw of 1st embodiment from each direction, Comprising: (a) is a figure which shows the surface arrange | positioned at the frame | top | piece side, (b) is b direction c direction of (a). (C) is a diagram viewed from the c direction of (a), (d) is a diagram viewed from the d direction of (c), (e) is a diagram viewed from the e direction of (d), (F) is a perspective view. It is a perspective view explaining the attachment method of the top of the ball screw of a first embodiment. It is a top view which shows the through-hole and recessed part of a nut which comprise the ball screw of embodiment and a prior art example. It is sectional drawing of the nut which comprises the ball screw of embodiment, Comprising: It corresponds to AA sectional drawing of FIG. It is BB sectional drawing of FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a ball screw piece mounting method (first method) according to a first embodiment (a nut is a cross-sectional view shown in FIG. 6), and (a) is a view showing a state where a piece is inserted into a through hole. (B) is a figure which shows the state which attached the fixing component to the nut. It is a figure which shows the state of FIG.8 (b), Comprising: A nut is sectional drawing shown in FIG. It is a figure explaining the attachment method (2nd method) of the ball screw piece of 1st embodiment, (a) And (b) is a figure which shows the state in the middle of attaching the fixing component to a nut, (c) ) Is a diagram showing a state in which the fixing component is attached to the nut. It is the figure which looked at the coma which constitutes the ball screw of a second embodiment from each direction, (a) is a figure showing the field arranged at the inner skin side of a nut, (b) is b of (a) (C) is a view from the c direction of (a), (d) is a view from the d direction of (c), (e) is a view from the e direction of (d). It is a figure. It is the figure which looked at the fixing component which comprises the ball screw of 2nd embodiment from each direction, Comprising: (a) is a figure which shows the surface arrange | positioned at the frame | top | piece side, (b) is b direction c direction of (a). (C) is a diagram viewed from the c direction of (a), (d) is a diagram viewed from the d direction of (c), (e) is a diagram viewed from the e direction of (d), (F) is a perspective view. It is a perspective view explaining the attachment method of the top of the ball screw of a second embodiment. FIG. 8 is a view for explaining a method of attaching a ball screw piece according to the second embodiment (a nut is a cross-sectional view shown in FIG. 6), where (a) is a view for explaining a first method, and (b) is a second method. (C) is a figure which shows the state after attaching a fixing component to a nut by each method. It is a figure which shows the state of FIG.14 (c), Comprising: A nut is sectional drawing shown in FIG. It is the figure which looked at the fixed component which comprises the ball screw of a comparative example from each direction, Comprising: (a) is a figure which shows the surface arrange | positioned at the frame | top | piece side, (b) is seen from b direction c direction of (a). (C) is a diagram viewed from the c direction of (a), (d) is a diagram viewed from the d direction of (c), (e) is a diagram viewed from the e direction of (d), (f ) Is a perspective view. It is a figure explaining the attachment method of the ball screw piece of a comparative example, (a) is a figure which shows the state which inserted the piece in the through-hole, (b) is a figure which shows the state which attached the fixing component to the nut. . It is a perspective view explaining the attachment method of the top of the ball screw of a prior art example. It is the figure which looked at the top which constitutes the ball screw of a conventional example and a comparative example from each direction, (a) is a figure showing the field arranged at the inner skin side of a nut, (b) is a figure of (a) b view from the c direction, (c) is a view from the c direction of (a), (d) is a view from the d direction of (c), (e) is from the e direction of (d). FIG. It is the figure which looked at the drop prevention member which comprises the ball screw of a prior art example from each direction, (a) is a figure showing the field arranged at the frame side, and (b) is from b direction c direction of (a). (C) is a diagram viewed from the c direction of (a), (d) is a diagram viewed from the d direction of (c), (e) is a diagram viewed from the e direction of (d), ( f) is a perspective view. It is sectional drawing of the nut which comprises the ball screw of a prior art example, Comprising: It corresponds to AA sectional drawing of FIG. It is a figure explaining the attachment method of the ball screw piece of a prior art example, Comprising: (a) is a figure which shows the state which inserted the piece in the through-hole, (b) is a figure which shows the state which attached the removal prevention member to the nut. is there.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.
[First embodiment]
As shown in FIG. 1, the ball screw of this embodiment includes a screw shaft 1, a nut 2, a plurality of balls 3, a plurality of pieces (a part in which a ball return path 43 is formed) 4, a pair of seals 5, a plurality of Fixed parts (parts for fixing the frame) 6. Helical grooves 11 and 21 are formed on the outer peripheral surface of the screw shaft 1 and the inner peripheral surface of the nut 2. The screw shaft 1 passes through the nut 2.

As shown in FIG. 1, the nut 2 has a flange portion 2B at one axial end of the cylindrical portion 2A. The cylindrical portion 2A of the nut 2 has a through hole 22 penetrating in the radial direction.
The spiral groove 11 of the screw shaft 1 and the spiral groove 21 of the nut 2 form a rolling path on which the ball 3 rolls. The ball 3 is disposed in a circulation path (indicated by a one-dot chain line in FIG. 1) including a rolling path and a ball return path 41 of the top 4. The top 4 is disposed on the radially inner side of the nut 2 in the through hole 22 of the nut 2 and is fixed by a fixing component 6 disposed on the radially outer side. The ball 3 rolls in the rolling path and circulates in the circulation path. The screw shaft 1 and the nut 2 move relative to each other via the ball 3.

As shown in FIG. 2, the top 4 includes a disk-shaped main body 41 and a pair of protrusions 42 protruding from the outer periphery thereof, and an S-shaped recess (ball return path) 43 is formed on the disk surface of the main body 41. Have. A semi-columnar convex portion 41 a is formed on the surface of the main body 41 opposite to the concave portion 43. The axial direction of the semi-cylinder that forms the convex portion 41 a extends in a direction orthogonal to the opposing direction of the pair of protrusions 42.
As shown in FIG. 3, the fixed component 6 includes a main body 61, a first engagement portion 62, and a second engagement portion 63. The main body 61 has a contact surface 61a with the top 4 and an arc surface 61b. The contact surface 61a and the circular arc surface 61b are surfaces opposite to each other.

  The arc that forms the arc surface 61b is a part of a circle that is concentric with the outer circumference of the nut 2 and has a slightly smaller diameter. The planar shape of the main body 61 is a shape in which a rectangular short side composed of a long side and a short side protrudes in an arc shape. The first engagement portion 62 and the second engagement portion 63 have the same shape, and the contact surface 61a in the thickness direction at both ends in the long side direction of the main body 61 (the direction of the perpendicular line dropped from the top of the arc surface 61b to the contact surface 61a). Formed on the side. That is, the first engaging portion 62 and the second engaging portion 63 are independently formed at positions facing each other across the contact surface 61 a of the main body 61.

  The central portion 61c in the long side direction of the main body 61 is the same as the surface disposed on the top 4 side of the first engaging portion 62 and the second engaging portion 63, and is disposed on the top 4 side of the central portion 61c. The surface to be contacted is a contact surface 61 a with the top 4. A semi-cylindrical concave portion 61d into which the convex portion 41a of the frame 4 is fitted is formed on the contact surface 61a. The axial direction of the semi-cylinder that forms the recess 61 d extends in the short side direction of the main body 61.

As shown in FIG. 3A, the planar shapes of the first engaging portion 62 and the second engaging portion 63 form an arc 64 at both ends in the long side direction of the main body 61, its extension line 65, and the top 4. The arc 66 is a part of a circle, and the perpendicular 67 extends from the intersection of the arc 66 and the rectangle to both sides of the long side.
That is, the first engaging portion 62 has a pair of convex portions 62a and 62b that protrude to the side of the main body 61 (the direction perpendicular to the direction in which the first engaging portion 62 and the second engaging portion 63 face each other). The second engaging portion 63 has a pair of convex portions 63 a and 63 b that project to the side of the main body 61. The protrusions 62a, 62b, 63a, 63b do not exist at the position of the contact surface 61a of the fixed component 6.

In addition, the fixed component 6 has a protruding portion 602a that is missing at the position of the contact surface 602b in the removal preventing member 60 shown in FIG. 20, does not have the protruding central portion 602c, and is the length of the body portion 601 and the flat plate portion 602. Both sides in the side direction have a circular arc shape.
In this embodiment, the top 4 and the fixed component 6 are made of synthetic resin. Examples of the synthetic resin forming the top 4 and the fixed part 6 include PPS (polyphenylene sulfide), POM (polyacetal), PEEK (polyether ether ketone), 6 nylon, 4, 6 nylon, 6, 6 nylon, and the like. Further, the top 4 and the fixed component 6 may be formed of a resin composition in which a reinforcing material made of glass fiber, potassium titanate fiber, or the like is mixed with these synthetic resins.

The top 4 may be made of metal, for example, may be formed by a metal powder injection molding method (MIM). Examples of the MIM alloy to be used include Fe—Ni—C (1 to 8% Ni, to 0.8% C).
As shown in FIGS. 4 to 7, the cylindrical portion 2 </ b> A of the nut 2 is formed with a through hole 22, a pair of recesses 22 a, a pair of recesses 23, and two pairs of grooves 24. As shown in FIG. 4, one of the two pairs of grooves 24 is a first groove 24a, and the other is a second groove 24b. The two pairs of grooves 24a and 24b are formed to have dimensions that allow the first engaging portion 62 and the second engaging portion 63 of the fixed component 6 to be movably fitted. Further, the nut 2 is formed with a pair of recesses 22 a (recesses into which the protrusions 42 of the top 4 are fitted) at positions facing each other on the peripheral surface of the through hole 22. The recess 22 a is also opened at the bottom surface of the recess 23.

  As shown in FIG. 5, the recesses 23 are formed at positions on both sides of the through hole 22 in a direction K (a predetermined direction intersecting the axial direction of the nut 2) K perpendicular to the axial direction J of the nut 2. . As shown in FIGS. 6 and 7, the depth direction of the recess 23 is the radial direction of the nut 2. As shown in FIG. 6, the bottom surface of the recess 23 exists at the same position as the outer end surface line L of the top 4 in the radial direction of the nut 2.

  As shown in FIG. 5, the concave portion 23 includes a grooved portion 23 a that is formed on a portion (grooved portion) 23 a in which the groove 24 is formed and on the outer side (the side opposite to the through hole 22 in the direction K). It consists of a wider part (wide part) 23b. The width of the opening of the recess 23 is slightly larger than the width of the main body 61 at the grooved portion 23a, and slightly larger than the width of the first engaging portion 62 and the second engaging portion 63 at the wide portion 23b.

When attaching the top 4, first, the top 4 is inserted into the through hole 22 of the nut 2 from above the nut 2, and the protrusion 42 is fitted into the recess 22 a.
Next, as shown in FIG. 8A, for example, the fixing component 6 is directed from the left side of the nut 2 toward the concave portion 23, and the convex portions 62a and 62b of the first engaging portion 62 are formed in the groove ( The fixed component 6 is moved to the right along the groove 24b by fitting in the second groove) 24b. At that time, the fixed component 6 gets over the convex portion 41a of the top 4 in a bent state.

By this movement, as shown in FIGS. 8B and 9, the concave portion 61 d of the central portion 61 c of the fixed component 6 fits into the convex portion 41 a of the top 4, and the convex portions 62 a, 62 a of the first engaging portion 62 are fitted. 62b is fitted into the groove (first groove) 24a of the right concave portion 23, and the convex portions 63a and 63b of the second engaging portion 63 are fitted into the groove (second groove) 24b of the left concave portion 23. And
As a result, as shown in FIG. 8 (b), both ends in the long side direction of the main body 61, the first engaging portion 62 and the second engaging portion 63 are disposed in the recess 23, and the contact surface 61a of the central portion 61c is The piece 4 comes into contact with the piece 4 and the piece 4 is fixed to the through hole 22 by the fixing component 6. In addition, the fixing component 6 is fixed to the top 4 by fitting the concave portion 61 d of the main body 61 and the convex portion 41 a of the top 4, so that the fixing component 6 is not easily detached from the concave portion 23. Further, the fitting of the protrusion 42 and the recess 22a prevents the top 4 from rotating in the through hole 22.

As a method for attaching the top 4 using the fixed component 6, in addition to the method shown in FIG. 8 (first method), the attachment method shown in FIG. 10 (second method) can also be employed.
In this method, after the top 4 is inserted into the through hole 22 from the upper side, first, as shown in FIG. 10A, the fixing component 6 is inserted into the through hole 22 and the right concave portion 23 from the upper side. Place on the bottom and top 4. As shown in FIG. 10B, in this state, the second engagement portion 63 is disposed in the through hole 22, and the first engagement portion 62 protrudes to the right side of the recess 23. The reason why the first engaging portion 62 and the second engaging portion 63 (the convex portions 62a, 62b, 63a, 63b) are not present at the position of the contact surface 61a of the fixed component 6 is that the arrangement can be made in this way.

  Next, the fixed component 6 is moved to the left, and the concave portion 61d of the central portion 61c of the fixed component 6 fits into the convex portion 41a of the top piece 4 as shown in FIGS. The convex portions 62a and 62b of the engaging portion 62 are fitted in the groove (first groove) 24a of the right concave portion 23, and the convex portions 63a and 63b of the second engaging portion 63 are grooves of the left concave portion 23 (second groove). No. of grooves) 24b. During this movement, the fixed component 6 gets over the convex portion 41a of the top 4 in a bent state.

  As a result, as shown in FIG. 10 (c), both ends in the long side direction of the main body 61, the first engaging portion 62 and the second engaging portion 63 are disposed in the recess 23, and the contact surface 61a of the central portion 61c is The piece 4 comes into contact with the piece 4 and the piece 4 is fixed to the through hole 22 by the fixing component 6. In addition, the fixing component 6 is fixed to the top 4 by fitting the concave portion 61 d of the main body 61 and the convex portion 41 a of the top 4, so that the fixing component 6 is not easily detached from the concave portion 23. Further, the fitting of the protrusion 42 and the recess 22a prevents the top 4 from rotating in the through hole 22.

[Second Embodiment]
The ball screw of this embodiment has a top 4A shown in FIG. 11 instead of the top 4 of FIG. 2 constituting the ball screw of the first embodiment, and instead of the fixed component 6 of FIG. It has a fixed part 6A shown. Other points are the same as the ball screw of the first embodiment.
As shown in FIG. 11, the main body 41 of the top 4A has a semicircular convex portion 41b instead of the semi-cylindrical convex portion 41a of the top 4 shown in FIG. The convex portion 41 b is formed at the center of the disc surface that forms the main body 41. The frame 4A is the same as the frame 4 of the first embodiment except for this point.
As shown in FIG. 12, the main body 61 of the fixed component 6A has a semispherical recess 61e on the contact surface 61a instead of the semi-cylindrical recess 61d of the fixed component 6 shown in FIG. The recess 61e is formed at the center of the main body 61 in the long side direction and the short side direction. The fixing component 6A is the same as the fixing component 6 of the first embodiment except for this point.

When attaching the top 4A, first, the top 4A is inserted into the through hole 22 of the nut 2 from the upper side of the nut 2, and the protrusion 42 is fitted into the recess 22a.
Next, in the first method, as shown in FIG. 14A, for example, the fixing component 6A is directed from the left side of the nut 2 toward the concave portion 23, and the convex portions 62a and 62b of the first engaging portion 62 are left side. The fixed part 6A is moved to the right along the groove 24b. At that time, the fixed component 6A gets over the convex portion 41b of the top 4A in a bent state.

In the second method, after the top 4A is inserted into the through hole 22 from the upper side, first, as shown in FIG. 14B, the fixing component 6A is inserted into the through hole 22 and the right side concave portion 23 from the upper side. It is arranged on the bottom surface of 23 and the top 4A. Next, the fixed component 6A is moved to the left. At that time, the fixed component 6A gets over the convex portion 41b of the top 4A in a bent state.
As a result, as shown in FIGS. 14C and 15, the concave portion 61e of the central portion 61c of the fixed component 6A is fitted into the convex portion 41b of the top 4A, and the convex portions 62a and 62b of the first engaging portion 62 are fitted. Is fitted into the groove (first groove) 24a of the right concave portion 23, and the convex portions 63a, 63b of the second engaging portion 63 are fitted into the groove (second groove) 24b of the left concave portion 23; To do.

  As a result, as shown in FIGS. 14C and 15, both ends in the long side direction of the main body 61, the first engaging portion 62, and the second engaging portion 63 are disposed in the recess 23, and the center portion 61 c is in contact. The surface 61a comes into contact with the top 4A, and the top 4A is fixed to the through hole 22 by the fixing component 6A. Further, the fixing component 6A is fixed to the top 4A by fitting the concave portion 61e of the main body 61 and the convex portion 41b of the top 4A, so that the fixing component 6A is not easily detached from the concave portion 23. Further, the fitting of the protrusion 42 and the recess 22a prevents the top 4A from rotating in the through hole 22.

[Ball screw of comparative example]
As a ball screw of a comparative example, a ball screw having a fixed part 6D shown in FIG. 16 and a conventional piece 40 shown in FIG. In the fixed component 6D, the central portion 61c in the long side direction of the main body 61 protrudes downward from the lower surfaces of the first engagement portion 62 and the second engagement portion 63 when the arcuate surface 61b side is the upper side. . The lower surface of the central portion 61 c is a contact surface 61 a with the top 4. The fixing component 6D is the same as the fixing component 6 shown in FIG.

Further, since the conventional piece 40 shown in FIG. 19 is provided, the bottom surface of the recess 23 exists slightly outside the outer end line L of the piece 4 in the radial direction of the nut 2 as shown in FIG.
Therefore, when the piece 40 is attached to the nut 2 by the first method using the fixed part 6D, first, the piece 40 is first attached to the through hole 22 of the nut 2 from the upper side of the nut 2 as shown in FIG. And the protrusion 42 is fitted into the recess 22a.

Next, as shown in FIG. 17A, for example, the fixing component 6 </ b> D is directed from the left side of the nut 2 toward the concave portion 23, and the convex portions 62 a and 62 b of the first engagement portion 62 are formed in the groove ( The fixed component 6D is moved to the right along the groove 24b by fitting in the second groove) 24b. At that time, the central portion 61c protruding toward the top 40 moves in the recess 23 in a bent state.
By this movement, as shown in FIG. 17B, the convex portions 62 a and 62 b of the first engaging portion 62 fit into the groove (first groove) 24 a of the right concave portion 23, and the second engaging portion 63. The convex portions 63a and 63b are fitted in the groove (second groove) 24b of the left concave portion 23.

  As a result, as shown in FIG. 17 (b), both ends of the main body 61 in the long side direction, the first engaging portion 62 and the second engaging portion 63 are disposed in the recess 23, and the central portion 61c of the main body 61 penetrates. The hole 22 enters a position deeper than the bottom surface of the recess 23 and the contact surface 61a comes into contact with the top 40, and the top 40 is fixed to the through hole 22 by the fixing component 6D. Further, the fixing part 6D is prevented from coming off from the recess 23 by the central part 61c. Further, the fitting of the projection 42 and the recess 22a prevents the top 40 from rotating in the through hole 22.

As described above, the fixing part 6D of the comparative example has the central part 61c formed in a convex shape, but the fixing parts 6 and 6A of the first and second embodiments have the central part 61c formed in a convex shape. Absent. Therefore, the fixing parts 6 and 6A of the first and second embodiments can reduce the manufacturing cost as compared with the fixing part 6D of the comparative example.
Moreover, since the center part 602c is also formed in a convex shape as described above, the fixing member 6 and 6A of the first and second embodiments are also provided in the conventional example. The manufacturing cost can be reduced compared to the above.

DESCRIPTION OF SYMBOLS 1 Screw shaft 11 Screw shaft spiral groove 2 Nut 2A Nut cylindrical part 2B Nut flange part 21 Nut spiral groove 22 Nut through hole 23 Nut recessed part 23a Recessed groove part 23b Recessed wide part 24 Nut groove 24a First groove 24b Second groove 3 Ball 4 Top 41 Main body 41a Top protrusion 41b Top protrusion 42 Projection 43 Ball return path 5 Seal 6 Fixing part 6A Fixing part 6D Fixing part 61 Main body 61a Contact with top Surface 61b Arc surface of main body (surface opposite to contact surface)
61c Center part of main body (part which makes contact surface)
61d Contact surface recess 61e Contact surface recess 62 First engagement portion 63 Second engagement portion 62a, 62b First engagement portion protrusion 63a, 63b Second engagement portion protrusion 60 Disengagement prevention member 601 Part 601b Arc surface of trunk 602 Flat plate part 602a Convex part 602b Contact surface with frame 602c Center part of flat plate part (part forming contact surface)

Claims (1)

A screw shaft, a nut, and a plurality of balls;
The screw shaft passes through the nut;
A rolling path on which the ball rolls is formed by the spiral groove of the screw shaft and the spiral groove of the nut.
The nut has a top formed with a ball return path for returning the ball from the end point of the rolling path to the start point,
The top is disposed in a through hole that penetrates the nut in a radial direction,
The balls are disposed in the rolling path and the ball return path,
In the ball screw in which the screw shaft and the nut move relative to each other through the ball rolling in the rolling path,
A fixing part having a main body having a contact surface with the top, and a first engagement portion and a second engagement portion independently formed at positions facing each other across the contact surface of the main body,
Each of the first engaging portion and the second engaging portion has a convex portion protruding to the side of the main body,
The main body has a concave portion or a convex portion on the contact surface, and the top has a convex portion or a concave portion that fits the concave portion or the convex portion,
The contact surface of the main body with the top is the same as the surface disposed on the top side of the first engaging portion and the second engaging portion,
The nut has a recess in which the first engagement portion and the second engagement portion are respectively disposed at positions on both sides of the through hole in a predetermined direction intersecting the axial direction.
The depth direction of the recess is the radial direction of the nut, and the bottom surface of the recess exists in the same position as the outer end surface of the top in the radial direction of the nut,
The nut has first and second grooves in which the convex portions of the first engaging portion and the second engaging portion of the fixed part are movably fitted around at least the through hole of the concave portion. The width of the opening of the concave portion where the groove is formed is larger than the width of the portion having the contact surface of the main body and smaller than the maximum width of the first engaging portion and the second engaging portion. ,
The concave portion or convex portion of the main body and the convex portion or concave portion of the top are fitted together, the convex portion of the first engaging portion is fitted into the first groove, and the convex portion of the second engaging portion is In the state where it is fitted in the second groove, the fixing component is disposed on the radially outer side of the nut with respect to the concave portion of the nut and the top of the through hole, and the top is fixed to the through hole. A ball screw characterized by that.

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