JP7495969B2 - Internal Circulation Ball Screw - Google Patents

Description

The present invention relates to a ball screw, and in particular to an internal circulation ball screw.

When adapting an internal circulation ball screw to a small lead, as shown in FIG. 1, it is common to adopt a design in which the return groove 2 of the return unit 1 is interrupted in order to prevent the return unit 1 from being damaged and losing its effectiveness due to the walls of the two adjacent return grooves 2 being too thin. Therefore, even if care is taken not to drop the balls 3 in any other area than the return groove 2 of the return unit 1 during the installation work of the balls 3, it is impossible to prevent some of the balls 3 from rolling into the invalid tooth area 4 between the two adjacent return grooves 2 during the installation work and becoming invalid balls 3'. The invalid balls 3' in the invalid tooth area 4 cannot be removed, which not only creates a large resistance to subsequent operation, but also wears out the accessories (screw shaft or nut). In other words, the work of installing the balls 3 in the conventional return unit 1 is very laborious.

In response to this, Patent Document 1 proposes arranging a recovery port for recovering lubricating oil on one arm of the bridge member, and a discharge port for discharging the recovered lubricating oil on another arm of the bridge member. However, because the recovery port and discharge port in this proposal are not used for rolling the balls, it does not solve the problem of the balls getting stuck in the ineffective tooth area.

Patent No. 6444760

The main objective of the present invention is to provide an internal circulation ball screw that can improve the efficiency of assembly work.

In order to solve the above-mentioned problems, the internal circulation ball screw comprises a screw shaft, a nut, a closing unit, a reflux unit, and a plurality of balls. The screw shaft has an outer screw groove. The nut is attached to the screw shaft so as to be movable along the axial direction of the screw shaft, and has an inner screw groove. The inner screw groove of the nut and the outer screw groove of the screw shaft correspond to each other to form a load path. The nut further has a placement groove that is connected to the inner screw groove along the radial direction, and a ball discharge hole that is connected to the placement groove along the radial direction. The reflux unit fits into the placement groove of the nut, and has a reflux groove on its inner surface. The reflux groove of the reflux unit is connected to the inner screw groove of the nut, thereby forming a non-load path between the outer screw groove of the screw shaft. The non-load path and the load path are connected to each other to form a circulation path. The plurality of balls are arranged to be rollable in the circulation path. The reflux unit further has a ball discharge passage that is in contact with the reflux groove. The ball discharge passage passes through the inner and outer surfaces of the reflux unit, with one end connecting to the dead tooth area of the nut's internal thread groove and the other end connecting to the ball discharge hole in the nut.

Due to the above-mentioned structural features, during the assembly work of the internal circulation type ball screw according to the present invention, ineffective balls that have rolled into areas other than the return groove can be made to roll from the ball discharge passage to the ball discharge hole, and discharged from the ball discharge hole to the outside of the nut. After the installation work of all the balls is completed, the ball discharge hole can be closed with the closing unit. In other words, the problem of ineffective balls getting stuck inside the nut and causing large resistance, which can lead to wear and tear on the accessories, can be eliminated.

In a more preferred embodiment, the reflux unit has two ball discharge passages. The two ball discharge passages extend in opposite directions away from each other. The above-mentioned structural features allow the ineffective balls to roll into one of the ball discharge passages and be discharged outside the nut.

In a more preferred embodiment, the ball discharge passage has an inlet and an outlet. The inlet is formed on the inner surface of the reflux unit. The outlet is formed on the outer surface of the reflux unit so as to connect to the ball discharge hole of the nut. The above-mentioned structural features allow the ineffective balls to roll from the inlet into the ball discharge passage and from the outlet to the ball discharge hole.

In a more preferred embodiment, the reflux unit further includes a convex guide portion adjacent to the inlet. The convex guide portion causes the invalid balls to roll into the ball discharge passage.

In a more preferred embodiment, the nut has a first groove on its inner circumferential surface. The reflux unit has a second groove on its inner surface. The first groove and the second groove are connected to each other to form an inlet of a ball discharge passage. The ball discharge passage has an outlet. The outlet is formed on the outer surface of the reflux unit so as to be connected to the ball discharge hole of the nut. The above-mentioned structural features allow the ineffective balls to roll from the inlet into the ball discharge passage and from the outlet to the ball discharge hole.

In a more preferred embodiment, the internal recirculating ball screw according to the present invention further comprises a closing unit. The closing unit is mounted in the ball discharge hole of the nut to close the ball discharge hole.

The detailed structure, features, assembly and usage of the internal recirculation ball screw according to the present invention will be made clear through the detailed description of the following embodiment. Furthermore, anyone with common sense in the field of the present invention should understand that the detailed description below and the embodiment presented by the present invention are merely examples for explaining the present invention and cannot limit the scope of the claims of the present invention.

1 is a partial cross-sectional view showing a known reflux unit attached to a nut; 1 is a perspective view showing an internal circulation type ball screw according to a first embodiment of the present invention; FIG. 1 is an exploded perspective view showing an internal circulation type ball screw according to a first embodiment of the present invention. 1 is a cross-sectional view showing an internal circulation type ball screw according to a first embodiment of the present invention. FIG. FIG. 2 is a top perspective view of a circulation unit of the internal circulation type ball screw according to the first embodiment of the present invention. FIG. 2 is a bottom perspective view of a circulation unit of the internal circulation type ball screw according to the first embodiment of the present invention. 1 is a cross-sectional side view of an internal circulation type ball screw according to a first embodiment of the present invention, with the screw shaft omitted. FIG. 1 is a cross-sectional view of an internal circulation type ball screw according to a first embodiment of the present invention, viewed from the tip, with a screw shaft and a closing unit omitted. FIG. 3 is a cross-sectional view of the internal circulation type ball screw according to the first embodiment of the present invention, showing a state in which one end of a hollow tube is inserted into a ball discharge passage, as viewed from the tip. FIG. FIG. 11 is a partial cross-sectional view showing a state in which a screw shaft is omitted in an internal circulation type ball screw according to a second embodiment of the present invention.

The internal recirculation ball screw according to the present invention will be described below with reference to the drawings. Note that in the specification and drawings, directional terms are expressed based on the directions in the drawings. The same reference numerals indicate structural features of the same or similar parts.

First Embodiment
As shown in FIGS. 2 and 3 , the internal circulation ball screw 10 according to the first embodiment of the present invention includes a screw shaft 20 , a nut 30 , a closing unit 38 , a reflux unit 40 and a number of balls 50 .

The screw shaft 20 has an outer screw groove 22 on its outer circumferential surface. The outer screw groove 22 is formed to extend along the axial direction of the screw shaft 20.

The nut 30 is attached to the screw shaft 20 so as to be movable along the axial direction of the screw shaft 20, and has an inner screw groove 32 on its inner circumferential surface and a placement groove 34 that is radially connected to the inner screw groove 32. The inner screw groove 32 of the nut 30 and the outer screw groove 22 of the screw shaft 20 correspond to each other to form a load path 52 (see FIG. 4). The nut 30 further has a ball discharge hole 36 that penetrates the inner and outer circumferential surfaces. The ball discharge hole 36 is radially connected to the placement groove 34.

The closure unit 38 is fitted into the ball discharge hole 36 of the nut 30 by a fitting method, an adhesive method or another method to close the ball discharge hole 36.

The reflux unit 40 fits into the arrangement groove 34 of the nut 30. As shown in FIG. 5 and FIG. 6, the reflux unit 40 has three reflux grooves 43 arranged at intervals on the inner surface 41. As shown in FIG. 4, the three reflux grooves 43 of the reflux unit 40 are connected to the inner screw groove 32 of the nut 30, forming a non-load path 54 between the outer screw groove 22 of the screw shaft 20. The non-load path 54 and the load path 52 are combined to form a circulation path 56. A plurality of balls 50 are arranged to be able to roll in the circulation path 56. As shown in FIG. 5 and FIG. 6, the reflux unit 40 has two ball discharge passages 44 between two adjacent reflux grooves 43, but is not limited thereto. There may be one or more ball discharge passages 44. One end of each of the two ball discharge passages 44 is connected to the invalid tooth area 58 (see FIG. 7) of the inner screw groove 32 of the nut 30, and the other end is connected to the ball discharge hole 36 of the nut 30. The two ball discharge passages 44 are arranged in front and behind each other, extending in opposite directions and offset from each other. Each ball discharge passage 44 penetrates the inner surface 41 and the outer surface 42 of the reflux unit 40 and has an inlet 45 and an outlet 46. In this embodiment, the inlet 45 is formed on the inner surface 41 of the reflux unit 40. The outlet 46 is formed on the outer surface 42 of the reflux unit 40. As shown in FIG. 5, the reflux unit 40 has four convex guide portions 47 on the inner surface 41. The four convex guide portions 47 are arranged so that each one contacts the inlet 45. As shown in FIG. 7, the ineffective tooth area 58 is an area where the balls 50 circulating between the nut 30 and the screw shaft 20 do not pass. The effective tooth area 59 is an area where the balls 50 circulating between the nut 30 and the screw shaft 20 pass.

During the installation of the balls 50, if the balls 50 roll into the invalid tooth area 58 between two adjacent return grooves 43, they become invalid balls 50'. Due to the above-mentioned structural features, as shown in Figures 7 and 8, the invalid balls 50' can roll from the entrance 45 into the ball discharge passage 44 by the convex guide portion 47 and roll from the exit 46 to the ball discharge hole 36. The invalid balls 50' can then be discharged from the ball discharge hole 36 to the outside of the nut 30. In other words, the problem of the invalid balls 50' getting stuck in the invalid tooth area 58 can be eliminated. After the installation of all the balls 50 is completed, the closing unit 38 can close the ball discharge hole 36 to prevent foreign matter from entering the nut 30.

As shown in FIG. 9, in order to smoothly discharge the ineffective balls 50', a hollow tube 60 is inserted into the ball discharge passage 44 from the outlet 46. Then, air is blown or sucked into the ball discharge passage 44 through the hollow tube 60, which quickly discharges the ineffective balls 50' to the outside of the nut 30, improving the efficiency of the assembly work.

Second Embodiment
In the first embodiment, the inlet 45 of the ball discharge passage 44 is formed on the inner surface 41 of the reflux unit 40, but is not limited thereto. As shown in Fig. 10, in the second embodiment, the inlet 45 of the ball discharge passage 44 is formed between the nut 70 and the reflux unit 80. More specifically, the nut 70 has a first groove 72 on its inner peripheral surface. The reflux unit 80 has a second groove 82 on its inner peripheral surface. The first groove 72 and the second groove 82 are connected to each other to form the inlet 45 of the ball discharge passage 44. Due to the above-mentioned structural features, the ineffective balls 50' can be rolled from the inlet 45 into the ball discharge passage 44 and discharged to the outside.

Due to the above-mentioned structural features, during the assembly work of the internal circulation type ball screw 10 according to the present invention, the ineffective balls 50' that have rolled into the ineffective tooth area 58 can be made to roll from the ball discharge passage 44 to the ball discharge hole 36, and can be discharged from the ball discharge hole 36 to the outside of the nut 30. In other words, the problem of the ineffective balls 50' getting stuck in the ineffective tooth area 58 and causing large resistance, which leads to wear and tear on the accessories, is eliminated, and the assembly work can be improved.

1: Circulation unit 2: Circulation groove 3: Ball 3': Ineffective ball 4: Ineffective tooth area 10: Internal circulation type ball screw 20: Screw shaft 22: External screw groove 30: Nut 32: Internal screw groove 34: Arrangement groove 36: Ball discharge hole 38: Closure unit 40: Circulation unit 41: Internal surface 42: External surface 43: Circulation groove 44: Ball discharge passage 45: Inlet 46: Outlet 47: Convex guide portion 50: Ball 50': Ineffective ball 52: Load path 54: Non-load path 56: Circulation path 58: Ineffective tooth area 59: Effective tooth area 60: Hollow tube 70: Nut 72: First concave groove 80: Circulation unit 82: Second concave groove

Claims (5)

The screw shaft includes a nut, a closing unit, a reflux unit, and a plurality of balls.
The screw shaft has an external screw groove,
The nut is attached to the screw shaft so as to be movable along the axial direction of the screw shaft, and has an inner screw groove, a radially extending arrangement groove connected to the inner screw groove, and a ball discharge hole connected to the radially extending arrangement groove;
The inner screw groove of the nut and the outer screw groove of the screw shaft correspond to each other to form a load path,
The circulation unit is fitted into the arrangement groove of the nut and has a circulation groove on its inner surface, and the circulation groove of the circulation unit is connected to the inner screw groove of the nut to form a non-load path between the circulation groove and the outer screw groove of the screw shaft, and the non-load path and the load path are mutually connected to form a circulation path,
the reflux unit further comprises a ball discharge passage adjacent to one or more of the reflux grooves, the one or more ball discharge passages extending through the inner surface and the outer surface of the reflux unit, one end of the ball discharge passages connecting to a dead tooth area of the internal thread groove of the nut and another end of the ball discharge passages connecting to the ball discharge holes of the nut;
The plurality of balls are rollably disposed in the circulation path.
Internal circulation ball screw. The internal circulation ball screw according to claim 1, characterized in that the circulation unit has two of the ball discharge passages, and the two ball discharge passages extend in opposite directions and are offset from each other. The internal circulation ball screw according to claim 1 or 2, characterized in that the ball discharge passage has an inlet and an outlet, the inlet being formed on the inner surface of the reflux unit, and the outlet being formed on the outer surface of the reflux unit so as to connect to the ball discharge hole of the nut. The internal circulation ball screw according to claim 3, characterized in that the reflux unit further has a convex guide portion that contacts the inlet. The nut has a first groove on an inner circumferential surface,
The reflux unit has a second groove on the inner surface;
3. The internal circulation ball screw according to claim 1, wherein the first groove and the second groove are connected to each other to form the inlet of the ball discharge passage, the ball discharge passage has an outlet, and the outlet is formed on the outer surface of the circulation unit so as to be connected to the ball discharge hole of the nut.

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