JP2018123897A - Top type ball screw - Google Patents

Abstract

A top type ball screw having a structure in which a top protrudes from an outer diameter of a nut, and a top type ball screw that improves assembly while preventing the top from coming off in the outer diameter direction. A screw shaft 1, a nut 2, a plurality of balls 3, and a piece 4 formed with a ball return path 41 for returning the ball from the end point of the rolling path to the starting point, It has a protruding strip portion 50 protruding from the outer diameter of the nut 2, and the top 4 is provided with a gradient surface portion 50 c in the longitudinal direction of the screw shaft, and the maximum outer diameter portion at the end of the gradient surface portion 50 c. 50 b is smaller than the outer diameter of the nut 2, and the outer end surface of the top 4 is provided with notches 51 at both ends in the circumferential direction of the screw shaft 1. [Selection] Figure 3

Description

  The present invention relates to a piece-type ball screw having a piece 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.

  As a part for forming a ball return path, there is a top type ball screw having a top, and in this type of ball screw, the top is mounted in a through hole that penetrates a nut in a radial direction.

Conventionally, in a top-type ball screw, for example, the top is held by an annular sleeve (outer fitting member) so as not to come off in the outer diameter direction (Patent Document 1).
The outer diameter of the piece when the piece is inserted into the piece hole provided in the nut is approximately the same as the inner diameter of the sleeve and the outer diameter of the nut, and the piece is designed not to protrude from the outer diameter of the nut.

However, when there is a large clearance between the sleeve and the outer diameter of the nut, in order to reduce the play of the piece in the radial direction, it is necessary to design the piece to protrude from the outer diameter of the nut.
When the top has a structure projecting from the outer diameter of the nut, if the sleeve is inserted after the top is inserted into the top hole provided in the nut, the sleeve may be caught on the top and the assemblability may deteriorate.

JP2015-81636A

  The present invention has been made to solve such problems of the prior art, and the object of the present invention is to provide a piece-type ball screw having a structure in which the piece protrudes from the outer diameter of the nut. The aim is to improve the assemblability while preventing the detachment in the radial direction.

In order to achieve this object, the first present invention has 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,
The top protrudes from the outer diameter of the nut,
The top is provided with a gradient surface portion in the longitudinal direction of the screw shaft,
The top outer diameter portion of the end portion of the sloped surface portion is smaller than the outer diameter of the nut.

  According to a second aspect of the present invention, in the first aspect of the present invention, a notch portion is provided at both ends in the circumferential direction of the screw shaft on the outer end surface of the top in the radial direction of the screw shaft. This is a ball screw.

  According to the present invention, in a top-type ball screw having a structure in which a top projects from the outer diameter of the nut, it is possible to improve assembly while preventing the top from coming off in the outer diameter direction.

It is a schematic perspective view which shows one Embodiment of this invention type | formula ball screw. BRIEF DESCRIPTION OF THE DRAWINGS It is one Embodiment of the top integrated in this invention type | formula ball screw, Comprising: (a) is a schematic perspective view seen from the plane, (b) is a schematic perspective view seen from the back surface. It is a schematic sectional drawing which expands and shows the principal part of this invention piece type | formula ball screw. It is the schematic which shows the contact area | region of a top and a sleeve, (a) shows this embodiment, (b) shows a well-known form.

Hereinafter, an embodiment of the top ball screw of the present invention will be described with reference to the accompanying drawings.
The present embodiment is an embodiment of the present invention, and is not construed as being limited thereto. The design can be changed within the scope of the present invention.

FIG. 1 is a schematic perspective view of a top type ball screw according to the present embodiment, and the ball screw includes a screw shaft 1, a nut 2, a plurality of balls 3, and a top 4 (see FIGS. 1 to 3). . 3 is an annular sleeve (outer fitting member) into which a ball screw is inserted.
In the present embodiment, the sleeve is described as the mating member into which the ball screw is inserted. However, the mating member is not limited to the sleeve, and the design can be changed as appropriate within the scope of the present invention.

  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, and the screw shaft 1 passes through the nut 2.

The nut 2 includes a nut main body 2a formed in a cylindrical shape with both ends open, and a through hole (coma hole) 22 penetrating the nut main body 2a in the radial direction. The through-hole 22 has a substantially circular first hole 22a in a plan view and a substantially elongated rectangular shape in a plan view provided through and continuous with both sides of the first hole 22a in the circumferential direction of the nut body 2a. The second hole portions 22b and 22b.
The nut 2 is held in the sleeve 6 with a gap G. That is, the outer diameter of the nut 2 is smaller than the inner diameter of the sleeve 6 (see FIG. 3).

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 composed of a rolling path and a ball return path 41 of the top 4 described later.
The screw shaft 1 and the nut 2 move relative to each other via a ball 3 that rolls in the rolling path and circulates in the circulation path.

The top 4 is disposed in the through hole 22 of the nut 2 (see FIG. 1).
The top 4 is obtained by injection molding using a predetermined synthetic resin material such as polyphenylene sulfide resin (PPS) or polyacetal resin (POM). Moreover, you may manufacture the said top with the resin composition by which the reinforcing material which consists of glass fiber, potassium titanate fiber, etc. was mixed with these synthetic resins. Further, as an example of a metal piece, a piece formed by a metal powder injection molding method (MIM) can be used. Examples of the MIM alloy to be used include Fe—Ni—C (1 to 8% Ni, to 0.8% C).

As shown in FIG. 2, the top 4 is formed in a substantially short cylindrical shape, and has a main body 40 in which a ball return path 41 is formed on one bottom surface 40 a and a convex strip 50 is formed on the other bottom surface 40 b. And a pair of arm portions 42 and 42 for preventing rotation as well as a guide formed on the peripheral surface 40c of the main body 40.
The main body 40 is inserted into the through hole 22 through the first hole portion 22a of the nut 2. The ball return path 41 is formed in a groove having a predetermined depth in a substantially S shape in plan view.

The arm portions 42, 42 protrude from the peripheral surface 40 c of the main body 40 on the same axis in the horizontal direction. The arm portion 42 includes a rectangular portion 42a having a predetermined thickness that is continuous from the peripheral surface 40c, and a downwardly inclined portion 42b that is continuous from the rectangular portion 42a (see FIG. 2). The arm portions 42 and 42 are inserted into the through hole 22 through the second hole portions 22 b and 22 b of the nut 2.
In this embodiment, the arm part 42 is provided in a direction orthogonal to the ridge part 50 (see FIG. 2).

  The protrusion 50 provided on the other bottom surface 40b of the main body 40 is formed in an elongated rectangular shape at the center of the bottom surface (a region extending in the diameter direction of the bottom surface). The left and right sides of the ridge 50 are provided as flat notches 51 and 51 that are recessed from the ridge 50.

The ridges 50 leave the central region 50a in the radial direction of the bottom surface 40b (the direction indicated by the arrow R in the figure), and the maximum length of the longitudinal direction of the screw shaft 1 (the same direction as the radial direction R) from the central region 50a. Gradient surface portions 50c and 50c are provided in a downwardly inclined manner toward the diameter portions 50b and 50b. The maximum outer diameter portion 50b at the end of the sloped surface portion 50c is formed smaller than the outer diameter of the nut 2.
For example, the ridge 50 may be divided into a plurality of ridges extending in the length direction of the ridge as long as the strength surface can be cleared. The design can be changed within the range.

  When the top 4 is disposed in the nut 2 through the through hole 22, the protruding portion 50 and a part of the sloped surface portions 50c and 50c protrude outward from the outer diameter of the nut 2, and Only the protrusions 50 are formed so as to be in contact with the inner diameter of the sleeve 6 (see FIG. 3). Thereby, the top 4 does not come off in the outer diameter direction. In the present embodiment, the main body 40 and the arm portions 42 and 42 are configured to fit into the first hole portion 22a and the second hole portions 22b and 22b of the nut 2.

According to the present embodiment, since there is a gap G between the outer diameter of the nut 2 and the inner diameter of the sleeve 6, the top 4 is positioned outside the nut 2 while the ball 3 is disposed in the circulation path. The structure protrudes from the diameter (see FIG. 3). When the top 4 protrudes from the outer diameter of the nut 2 as described above, when the sleeve 6 is inserted after the top 4 is inserted into the through hole (top hole) 22 provided in the nut 2, There is a possibility that a problem occurs that 6 is caught and the assemblability deteriorates.
However, in the case of this embodiment, the top 4 is provided with a sloped surface portion 50c in the longitudinal direction of the screw shaft 1 (the direction indicated by the symbol R in the drawing), and the ball 3 is disposed in the circulation path. In this state, the maximum outer diameter portion 50b at the end of the sloped surface portion 50c is formed to be smaller than the outer diameter of the nut 2, so that the sleeve 6 is not caught by the top 4 during assembly and can be assembled smoothly.

Further, by providing the notches 51 and 51 on the bottom surface 40b of the top 4 as in the present embodiment, the processing accuracy of the bottom surface 40b (outer diameter surface) is further lowered as compared with the case where the notch portions are not provided. be able to.
That is, for example, when the outer diameter surface 101 of the top 100 is formed in a predetermined curved surface without providing a notch as shown in FIG. 4B, the processing accuracy of the outer diameter surface 101 is poor. In this case, there is a possibility that the periphery of the one end portion 101a and the periphery of the other end portion 101b of the outer diameter surface 101 may locally contact an opposing member such as the sleeve 6. As shown in FIG. 4A, high-precision machining is achieved by providing notches 51 and 51 on the bottom surface 40b of the top 4 and reducing the contact area between the bottom surface 40b (outer diameter surface) and the sleeve 6 or the like. Is no longer needed.

  The present invention can be used for all types of top ball screws.

1 Screw shaft 11 Groove 2 Nut 22 Through hole (top hole)
3 Ball 4 Top 40 Main body 41 Return path 42 Arm part 50 Projection line part 50b Maximum outer diameter part 50c Gradient surface part 51 Notch part 6 Sleeve

Claims (2)

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,
The top protrudes from the outer diameter of the nut,
The top is provided with a gradient surface portion in the longitudinal direction of the screw shaft,
A top type ball screw, wherein a maximum outer diameter portion of an end portion of the inclined surface portion is smaller than an outer diameter of the nut.   2. The top ball screw according to claim 1, wherein notches are provided at outer end surfaces of the top in the radial direction of the screw shaft and at both ends in the circumferential direction of the screw shaft.

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