JP2501839B2 - Half type ball screw - Google Patents

Description

TECHNICAL FIELD The present invention relates to a half type ball screw (also referred to as a ball screw or a ball nut).

(Prior Art) Currently, bolts (screw shafts) are used during relative rotation.
The external thread formed on the outer peripheral surface of the nut and the screw formed on the inner peripheral surface of the nut slide in place of the classical screw mechanism that slides (hereinafter referred to as the sliding type screw mechanism). As shown in the drawing, spiral grooves 3 and 4 are formed in a state of facing the outer peripheral surface of the screw shaft 1 and the inner peripheral surface of the nut 2, and the spiral grooves 3 and 4 are formed around the screw shaft 1 by both the facing grooves. The passage 5 and the passage 6'in the nut that connects the start end and the end of the passage are configured to form an endless circulation path 7, and a plurality of balls (spheres) 8 are arranged in the circulation path. A so-called ball screw is used in which the nut and the screw shaft rotate relatively through the ball.

This ball screw has the following various advantages since the sliding type screw mechanism makes a sliding contact on the contact surface, while the contact surface makes a rolling contact with a ball.

(A). Low frictional resistance during rotation, (b). The difference between the dynamic friction resistance and the static friction resistance is small, and (c). It can be rotated with a small force, (d). Rotation at high speed is possible, (e). Smooth rotation is obtained, (f). It has the feature that the heat generated on the contact surface is extremely small.

Therefore, when these ball screws are used, the power consumption is low, the positioning accuracy is high, the thermal deformation (thermal strain) due to the heat generation of the contact surface is small, the high speed operation is possible, and the long time operation is possible. It is possible to provide a high-performance device that can maintain high accuracy even during use.

(Problems to be Solved by the Invention) However, in the ball screw, as described above, the passage through which the ball circulates is formed between the nut and the screw shaft and inside the nut. However, the overall external dimensions (especially the radial dimension) are larger than those of the conventional sliding type screws.

For this reason, it can be used in areas where space is limited, for example, in parts such as bed support / feed devices of machine tools where the height from the floor surface to the work bed (hereinafter simply referred to as the bed) upper surface is restricted. There was a problem that I could not do it.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a ball screw having a small overall outer dimension (in particular, a radial dimension).

(Means for Solving the Problem) The gist of the present invention is that a screw shaft having a spiral groove formed on the outer peripheral surface and a groove corresponding to the groove of the screw shaft formed on the inner peripheral surface. A ball configured such that a plurality of balls are circulated in a circulation path formed by both grooves of the nut facing each other, and the screw shaft and the nut are relatively rotated through the balls. In a screw, the nut is formed in a half-divided type (in the present specification, refers to a shape that is divided in the axial direction), and the passage divided by the half-divided nut is endless. In order to form a circular circulation path, a connection conduit for connecting the passages is provided on each end face on both sides of the half-divided nut with a central recess for disposing the screw shaft. It is characterized by that.

(Operation) However, the ball screw having the above-mentioned configuration, by making the nut a half-split type, and dividing the passage by dividing the nut into a half-split type, Since it is connected by a connection passage on each end surface on both sides of the central recess for disposing the screw shaft, one side in the radial direction of the screw shaft (for example, the upper side or the lower side) A passage or the like for circulating the nut and the ball does not project, and therefore, the entire external dimension becomes compact by the amount of the nut and the passage eliminated. Further, since the passage divided by the nut being divided in half is connected by the connecting pipe to form a circulation passage, it is interposed between the nut and the screw shaft during relative rotation, as in the conventional ball screw. It becomes possible for the playing ball to circulate in these circulation paths.

(Example) Hereinafter, an example of the present invention will be described. 1 is a side sectional view of a bed portion when the present invention is applied to a bed feed mechanism of a machine tool, FIG. 2 is a sectional view taken along the line I--I of FIG. 1, and FIG. 3 is shown in FIG. FIG. 4 is a plan view showing the structure of a ball screw used, FIG. 4 is a sectional view taken along the line II-II of FIG. 3, and FIG. 5 is a sectional view taken along the line III-III of FIG.

In the figure, 1 is a screw shaft, 2 is a half-divided nut, and spiral grooves 3 and 4 are formed on the outer peripheral surface of the screw shaft 1 and the inner peripheral surface of the nut 2 so as to face each other.
As shown in FIG. 4, the grooves 3 and 4 have a sectional shape of
It is formed in a U shape having a curvature substantially equal to the curvature r of the ball 8 (see FIG. 5). Then, screw shaft 1
The opposing grooves 3,4 of the nut 2 form a passageway 5 therebetween, as illustrated in FIGS.

Further, as shown in FIGS. 3, 4 and 5, the nut 2 has end faces 2a on both sides thereof apart from a central recess 2c (see FIG. 5) for positioning the screw shaft 1. , 2
At b (see FIGS. 3 and 5), a connection passage 6 is formed, the start end and the end of which are located and communicates with each other inside the nut.

Then, on each of the end faces 2a, 2b, as shown in FIGS. 3 to 5, the passage 5 formed in each of the end faces 2a, 2b and the start end or the end of the connection passage 6 are connected. U-shaped external connection for passage of balls inside
Is stuck. Therefore, in the case of this embodiment, as shown in FIGS. 3 and 5, a plurality of circulation paths 7 (see FIG. 5) which are independent in the axial direction are formed.

A plurality of balls 8 (see FIG. 5) are arranged in the circulation path 7 so that there is no gap substantially in the longitudinal direction of the circulation path 7.

In use, the ball screw thus configured functions basically in the same manner as a conventional ball screw. That is, when the bed B shown in FIG. 1 is moved in the longitudinal direction, when the motor M attached to the side portion of the bed B is rotated, the screw shaft 1 connected to the drive part of the motor M is rotated. Rotate. The rotation of the screw shaft 1 causes the balls 8 to come into contact with the screw shaft 1 and support the screw shaft 1 from below as shown in FIGS.
Are rotated with the nut 2 by the friction between the contact surfaces, and the balls 8 circulate while rolling in the circulation path 7. Therefore, depending on the pitch angle of the screw shaft 1, the screw shaft 1 and the nut 2 relatively rotate via the ball 8, and the screw shaft 1 moves back and forth in the axial direction. For this reason,
Similar to the conventional ball screw, the screw shaft 1 and the nut 2 make rolling contact with the balls 8 and therefore rotate smoothly with extremely small force.

As shown in FIG. 4 or FIG. 5, the ball screw having the above-described configuration has no passage, such as a nut, for circulating balls, above the screw shaft 1. As shown in FIG.
The upper surface b of the bed B can be provided at a position lower than the floor surface F. That is, the height from the floor surface to the upper surface of the bed can be suppressed to about the same level as that of the conventional sliding type screw mechanism.

Further, in the above embodiment, the screw shaft is configured to have substantially the same length as the bed length (full stroke of the bed), and the nut is configured to be shorter than the length of the screw shaft, but the opposite configuration, that is, the first As shown in FIGS. 6 and 7, the nut 2 may be configured to have substantially the same length as the entire stroke of the bed B, and the screw shaft 1 may be configured to be short.

Further, in the embodiment shown in FIGS. 1 to 5, the ball circulation path is provided independently for each groove of the screw shaft 1 as shown in FIG. As shown in FIG. 9, one circulation path 7 may be formed by a plurality of grooves.

In the above embodiment, the nut 2 is composed of a plurality of (three) blocks and these are screwed together with the bolts 10. However, this is solely due to the working reason. Above all, it is not necessary to be composed of a plurality of blocks as described above.

Further, in the above-mentioned embodiment, the connection passage is provided inside the half-divided nut, but the connection passage may be formed outside the nut by another pipe passage.

Further, in the above-described embodiment, the nut is contact-supported within a range of about 180 ° below the axial center of the screw shaft, but it may be contact-supported within a larger angle range or may be contact-supported within a smaller angle range. Even so, the effect of the present invention can be obtained. Further, in the above embodiment, the main ball screw is horizontally arranged as the feeding mechanism of the bed of the machine tool, but it goes without saying that it can be vertically arranged and used as the elevating mechanism. When used as such a lifting mechanism,
When the contact angle of the nut with the screw shaft is 180 ° or less, restraint means for keeping the screw shaft in contact with the nut side (for example, contact the screw shaft with the nut from two facing directions). Let's keep it)
Will be required separately.

(Effect) The ball screw according to the present invention, as described above,
In the past, it was not possible to use it in terms of space, because it has the advantages of a ball screw and the size in the radial direction can be made extremely compact (similar to a sliding type screw mechanism) when it is externally shaped. Ball screws can also be used in places.

Therefore, it is possible to drive a device that was conventionally forced to use a prime mover of large horsepower with a small prime mover, or dig a pit on the floor because the height from the floor is limited. The present invention has a great spillover effect, such as eliminating the need for what was necessary.

[Brief description of drawings]

FIG. 1 is a side sectional view of a bed portion when the present invention is applied to a bed feed mechanism of a machine tool, and FIG. 2 is I- of FIG.
Sectional view taken in the direction of arrow I, FIG. 3 is a plan view showing the structure of the ball screw used in FIG. 1, FIG. 4 is a view taken along the line II-II of FIG. 3, and FIG. III arrow sectional view, FIG. 6 is a side sectional view showing another embodiment, FIG. 7 is a IV-IV arrow view of FIG. 6, and FIG. 8 is a plan view showing the structure of a ball screw having another configuration. FIG. 9 is a conceptual diagram showing the three-dimensional circulation path of the ball screw of FIG. 8, and FIG. 10 is a side sectional view showing the structure of a conventional ball screw. 1 ... screw shaft, 2 ... nut, 3,4 ... groove, 5 ...
... (composed of grooves), 6 ... connecting passage, 7 ... circulating passage, 8 ... ball, 9 ... connecting conduit.

Claims (1)

(57) [Claims] 1. A screw shaft having a spiral groove formed on the outer peripheral surface thereof and a nut having a groove corresponding to the groove of the screw shaft formed on the inner peripheral surface of the screw shaft, which are formed by both facing grooves of the screw shaft. By arranging multiple balls so that they can circulate,
In a ball screw configured such that a screw shaft and a nut rotate relative to each other through the ball, a passage formed by dividing the nut into a half mold shape and dividing the nut by the half mold. So that it becomes an endless circulation path, on the respective end faces on both sides of the half-divided nut, apart from the central concave portion for disposing the screw shaft, a connection conduit for connecting the respective passages. Is provided.