JPH0210856Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement of a hollow ball screw having a hollow hole for flowing a cooling medium.

(Prior art) A ball screw that rotates a screw shaft with a spiral groove formed thereon using an external drive source, and that makes a ball nut screwed onto the screw shaft and a movable base connected to the ball nut slide linearly in the axial direction of the screw shaft. A screw shaft having a hollow hole in the screw shaft is known.

The temperature of the entire screw shaft may rise due to high-speed rotation of the screw shaft and high-speed sliding of the moving table. To prevent this, a flow path is formed to send a cooling medium to the ball bearing and the hollow hole of the screw shaft. ing.

Seamless thick-walled pipes are often used as the material for such screw shafts. Seamless pipe is
A mandrel is applied to the center of a round bar that is fed between rolling rolls to create a thick hollow material, which is then subjected to processes such as rolling and punching to gradually change its wall thickness and diameter. It is manufactured by However, during this process, glass powder, scale, etc., which are used as a solid lubricant to prevent wear of the mandrel, adhere to the hollow part. If this is used as a screw shaft as it is, these deposits will be released into the coolant and wear out the pump that sends the coolant, or if the coolant also serves as lubricating oil for the bearings, it will wear out the bearings. Conventionally, the inner surface was slightly scraped off to remove these deposits before use as a screw shaft. However, since the screw shaft is generally longer than the diameter of the hollow hole, there is a drawback that a large number of man-hours are spent cutting the inner surface of the hollow hole.

Furthermore, when an electric resistance welded tube is used as a material for a screw shaft, there is a problem in that fatigue peeling is likely to occur in the ball groove of the sutured portion of the tube.

(Problems to be Solved by the Invention) The present invention aims to eliminate the above-mentioned drawbacks of the prior art, that is, to provide a hollow ball screw that can be manufactured with fewer man-hours, and to improve its mechanical properties. purpose.

(Structure of the invention) Instead of cutting the inner surface of the hollow hole of the screw shaft, the present invention has a structure in which a pipe having an inner diameter necessary as a flow path for the cooling medium is press-fitted into the hollow hole of the screw shaft after the screw shaft is formed. have

(Function) According to the present invention, the time-consuming process of cutting the inner surface of a long object is omitted, so the number of processing steps can be reduced. Furthermore, by appropriately selecting the material of the pipe to be press-fitted, the mechanical properties of the hollow ball screw can be improved.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a side view of a hollow ball screw, partially in section. A screw shaft 2 having a helical groove 1 on the outer surface of its central portion is supported at both ends by a pair of ball bearings 5, 6 and 7, 8 provided in brackets 3 and 4, respectively, fixed on a base 9. is supported on the shaft. Since the internal structures of brackets 3 and 4 are the same, only bracket 3 will be described below.

An annular inner ring spacer 10 is provided between the ball bearings 5 and 6.
is arranged to fit on the outer surface of the support portion of the screw shaft 2, and an annular outer ring spacer 11 is arranged to fit on the inner surface of the bracket 3. Inner ring spacer 10 and outer ring spacer 11
are arranged concentrically and spaced apart, so that an annular cavity 12 is formed between them. Ball bearings 5, 6
are provided with annular cavities 13, 14 communicating with the annular cavity 12 so that the cooling medium can reach the balls 5a, 6a. Lubricating oil is generally used as the cooling medium, but water-based cutting oil can also be used if the structure is such that only the screw shaft is cooled. Apertures 15 and 16 are formed in the inner ring spacer 10 and outer ring spacer 11 in the radial direction, respectively, and both the apertures 15 and 16 communicate with the annular cavity 12, and the aperture 16 is connected to the bracket. Through hole 17
The through hole 17 is connected to the through hole 1 of the base 9.
It is connected to 8.

Ball bearings 5, 6, inner ring spacer 10, outer ring spacer 11
is fitted between the inner surface of the bracket 3 and the outer surface of the screw shaft 2, is positioned in the axial direction by the spacer 19, and is sealed within the bracket 3 by the lid 20 and seals 21a to 21d. There is.

The screw shaft 2 has a through hole 22 bored at the center of the shaft and a pipe 23 press-fitted into the through hole 22. Furthermore, the screw shaft 2 is provided with an inner ring spacer 10.
An opening 25 is formed in the radial direction to connect and communicate the opening 15 of the pipe 23 with a hollow hole 24 formed inside the pipe 23.

As can be seen from the above configuration, the through holes 18 and 17 of the base 9 and the bracket 3, the openings 16 and 15 of the outer ring spacer 11 and the inner ring spacer 10, the annular cavity 12, and the opening 25. constitutes a channel means for sending the cooling medium, and this channel means and the hollow hole 2
4 and similar passage means formed inside the bracket 4 form a cooling medium passage. Therefore, the cooling medium sent from an external pump (not shown) flows in accordance with the arrows in the figure. The cooling medium is also adapted to simultaneously perform lubricant cooling of the ball bearings via the annular cavities 13, 14.

An external drive source (not shown) is attached to one end of the screw shaft 2.
A gear 26 connected to the screw shaft 2 is fixed by a bearing nut 27, and the hollow hole 24 of the screw shaft 2 is formed by a plug 28 attached to the shaft end of the screw shaft 2 and a plug 29 attached to the other end of the screw shaft 2. It is sealed at both ends.

A ball nut 30 that is screwed into the helical groove 1 on the outer surface of the screw shaft 2 via balls is connected to the moving table 31, and the ball nut 30 has a closed helical groove (not shown) that faces the helical groove 1 of the screw shaft 2 ) is formed, and a large number of balls (not shown) are arranged in a rotatable manner in the passage formed by both spiral grooves, and as the gear 26 rotates, the ball nut 30 and therefore the movable table 31 move as shown in FIG. It is designed to be able to slide to the left or right.

(Effects of the invention) Unlike conventional methods, in the present invention, the hollow hole in the screw shaft is formed by a pipe press-fitted into the screw shaft. Therefore, the labor-intensive work of cutting the inner surface of the screw shaft, which has been conventionally performed, can be omitted, and the number of machining steps can be significantly reduced.

Furthermore, various materials can be selected for the pipe to be press-fitted. It can be manufactured at low cost by using a general electric resistance welded tube. Furthermore, by using an aluminum tube with a well-finished surface, it is possible to obtain a ball screw that has advantages such as good heat conduction and resistance to corrosion. Furthermore, if a pipe material having a coefficient of thermal expansion smaller than that of the material of the screw shaft is used, the thermal expansion as a whole can be suppressed. Furthermore, by creating internal stress between the screw shaft and the press-fit tube, the rigidity against bending can be increased, and if the materials of the screw shaft and the press-fit tube are different, a vibration damping effect can be expected. Enables weight reduction of equipment.

As described above, the present invention has the excellent effect of increasing manufacturing efficiency by omitting the process of cutting the hollow hole, which was a key process in manufacturing hollow ball screws, and improving the mechanical properties of the screw shaft. It is something to do.

[Brief explanation of drawings]

FIG. 1 shows a partially sectional side view of a hollow ball screw according to the present invention. Explanation of the symbols of the main parts, spiral groove...1, screw shaft...2, {bracket...3,4, ball bearing...5,
6, 7, 8} Support means, ball nut...30,
Through holes...22, pipes...23, coolant channels...15-18, 12, 24.

Claims (1)

[Claims for Utility Model Registration] A screw shaft having a spiral groove formed on its outer surface; a support means for rotatably supporting the screw shaft; In a hollow ball screw having a ball nut capable of relative helical movement, and a cooling medium flow path for cooling the screw shaft, the cooling medium flow path is press-fitted into a through hole formed in the screw shaft. A hollow ball screw characterized by being equipped with a pipe.