JPS63163060A - Noiseproof device for ball screw - Google Patents

Abstract

PURPOSE:To reduce noise and vibration, by covering a ball return tube to be enclosed by a tube retaining member made by a buffer material. CONSTITUTION:A ball screw nut 1 flatly cuts one part of its outside part, and on this cut surface 5, a ball return tube 2, formed in a squared shape opening its one end, is arranged in almost a diagonal direction providing balls 7 to pass through in said tube. The ball return tube 2 inserts its both ends into a tube insertion hole provided in the cut surface 5. A semicircular tube retaining member 8, which forms its whole structure by a buffer material and a noise absorbing material of flexible synthetic resin or the like, is provided to be arranged so that the retaining member 8 is closely attached to the tube 2 further covering its whole unit exposed from the cut surface 5. This retaining member 8 is provided so that it can be mounted to and removed from the cut surface 5 by screw threads 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a soundproofing device for a ball screw for protecting a ball return tube of a ball screw and reducing noise and vibration caused by ball rolling.

[Prior Art] As is well known, a ball screw has a spiral groove formed on the inner periphery of a nut and the outer periphery of a shaft inserted into the nut, and a large number of balls are interposed between the spiral grooves. Both ends of the rolling portion are communicated through separate ball return passages to circulate the balls and cause the nut and shaft to move relative to each other in a helical manner. Various types of ball return circulation means have been proposed in the past, and in the example shown in FIG.
A ball return tube 2 formed in a U-shape from the outer periphery of
The ball return tube 2 is attached to a machined iron block 3 fixed to the outside of the nut 1 with a set screw 4.
(or a pressed tube holding member). There is also one in which the tube itself is exposed and fixed directly to a nut by caulking without using a tube holding member. The example shown in FIG. 6 shows two ball return tubes and two ball circulation paths. Still another example is one in which a part of the outer part of the nut is cut out and a steel or cast iron guide plate with a guide groove for returning the ball is attached to this part (for example,
7-25419), or the entire outer periphery of the nut, including the ball return tube, is completely fixed by embedding a molded layer of synthetic resin, cast iron, etc., thereby reducing the number of components of the ball circulation path, increasing rigidity, and improving productivity. There are some that have improved elasticity and have a molded layer that allows the overall external shape to be formed into an arbitrary shape (for example, Japanese Patent Publication No. 57-3883C).

[Problems to be Solved by the Invention] The conventional ball screw described above either partially covers and fixes the ball return tube with a metal tube insertion member, or
The ball return tube is exposed and fixed with screws, etc., so there is no noise when the balls collide inside the spiral groove or inside the tube, or when the ball is scooped up from the spiral groove into the metal tube. The sound, vibration, etc. when the ball collides with the unit is transmitted to the outside. Such sounds and vibrations are likely to occur due to moment loads due to mounting errors, and especially as the speed of the ball screw increases, loud noises are generated. In recent years, the use of ball screws has expanded, and in the case of equipment used in quiet environments, such as office electronic equipment, medical equipment, or automatic drafting machines, they can become a source of unpleasant noise, noise, and vibration. Even if the ball return path is formed with a guide plate that closes the notch on the side of the nut instead of a tube, noise and vibration may be generated due to metal contact between the ball and the guide plate.
Also, since the plate is made of metal (iron), it has no soundproofing or vibration absorption properties.
Propagates directly to the outside from the guide plate. Said Special Publication No. 57-3883 in which the entire circumference of the nut is hardened with a molded layer of synthetic resin, cast iron, etc.
Even in the case of No. 0, vibrations cannot be absorbed and sound insulation cannot be achieved depending on the material of the molded layer. In addition, since the outer periphery of the nut is completely fixed together with the ball return tube by the molding layer, the tube part and ball rolling part cannot be disassembled and repaired, and the material and thickness of the molding layer must be changed depending on the usage conditions of the ball screw. There are various problems such as not being able to do so. If the ball return tube is exposed, there is a risk of hitting or damaging the tube itself.

[Means for Solving the Problems] Therefore, the present invention provides a tube inserting member made of a cushioning material and having a groove that comes into close contact with the ball return tube exposed on the outside of the ball screw nut. The above-mentioned problem was solved by attaching it and wrapping the entire ball return tube. That is, in the soundproofing device for a ball screw of the present invention, a flat cutout surface is formed on the outer side of the ball screw nut, and a ball return tube communicating with both ends of the helical groove of the ball screw nut is arranged on the cutout surface. A groove portion that comes into close contact with the ball return tube is provided on the back surface of a tube insertion member made of a material such as hard rubber, and the cutout surface is closed with the tube insertion member made of a cushioning material so as to enclose the entire ball return tube. This is what I did.

[Function] By doing this, the vibrations generated in the ball return tube due to the rolling of the balls can be absorbed by the elasticity of the tube insertion member, and since the ball return tube is isolated from the outside air, the vibrations of the ball return tube can absorb the outside air. This prevents vibrations from being transmitted.

[Example] Next, the present invention will be explained by way of example with reference to the drawings.

FIG. 1 is a partial perspective view of a ball screw according to an embodiment of the present invention with the shaft removed.

A part of the outer side of the ball screw nut 1 is cut flat, and on this cutout surface 5, a ball return is formed in a U-shape approximately diagonally to allow the ball to pass through the tube. A tube 2 is arranged. Both ends of the ball return tube 2 are inserted into tube insertion holes provided in the cutout surface 5, and the inner hole of the ball return tube is communicated with the spiral groove 6 in the ball screw nut 1. Although not shown, a helical groove corresponding to the helical groove 6 of the nut 1 is also formed on the outer periphery of the shaft inserted into the nut 1. Before installing the tube 2 with the shaft inserted into the nut 1, a large number of balls 7 are stuffed into these spiral grooves and into the ball return tube 2 through the tube insertion hole in the cutout surface 5 of the nut 1. Next, cover and attach the ball return tube filled with the required number of balls. Due to the relative rotational movement between the shaft and the nut 1, the ball 7 is sandwiched between the spiral groove of the shaft and the spiral groove 6 of the nut 1 and rolls along the spiral groove 6, and from one end of the ball rolling portion of the groove. The ball is scooped up into the return tube 2, and the tube 2
through which it returns to the other end of the ball rolling portion of the spiral groove 6 and is recirculated. During this ball circulation, the hole 7 intermittently collides with the ball return tube 2 and generates sound. especially,
Noise and vibration are generated at the ball scooping part 2a at the end of the tube 2. Since this type of tube 2 is usually formed of a thin metal tube, the sound of vibration is transmitted to the surroundings as resonance sound and echo sound. In the present invention, in order to elastically support the ball return tube and damp it, and to reduce the sound generated by the vibration of the ball return tube from leaking to the outside, a damping material such as flexible synthetic resin or hard rubber is used. A half-moon-shaped tube inserting member 8 made entirely of a sound-absorbing material is removably attached to the notch surface 5 with a set screw 4 so as to be in close contact with the tube 2 and to cover the entire tube exposed from the notch surface 5. has been done.

As shown in FIGS. 2 to 4, the tube insertion member 8 has a bottom surface 8a having a size that exactly matches the cutout surface 5 on the outer side of the nut 1, and an outer surface 8b that is the same as the outer side of the nut 1. A counterbore hole 9 is formed into a curved surface with a circular curvature and is used to attach the member 8 to the cutout surface 5 of the nut 1.

On the bottom surface 8a of the tube inserting member 8, there is a groove 1o having a U-shaped cross section that is sufficient to tightly contact and wrap the ball return tube 2 exposed on the nut notch surface 5, and corresponds to the direction of extension of the tube. It is formed almost diagonally. In this case, the depth of the groove 10 of the tube inserting member is formed to be slightly smaller than the amount of protrusion of the cutout surface 5 of the tube 2. When the notch surface 5 of the nut 1 is closed with such a half-moon-shaped tube insertion member 8 and the setscrew 4 is tightened, the ball return tube 2 is brought into close contact with the bottom of the groove 10 of the bottom surface 8a, and the tube 2 is elasticized. By pressing and sealing the tube 2, the sound and vibration transmitted from the tube 2 to the outside are absorbed by the vibration absorption principle due to the elasticity of the member 8.
Low noise and vibration.

Figure 5(a) shows the amplitude waveform of the sound of a conventional ball screw in which the ball return tube is held down by an iron guide plate.
Figure (b) is a diagram showing the amplitude waveform of sound generated by a ball screw using the hard rubber tube inserting member of the present invention, and Figure 5 (a) is the one with the loudest sound by hearing, and Figure 5 ( b) is an example of an experimental example showing no acoustic problem. Both were detected by a microphone at a position 40 marks away from the ball screw. It can be seen that the amplitude of the sound frequency is reduced to about 1/2 in the case of 5KH or less and in the case of 50KH or more in the present invention. According to various experiments, the soundproofing effect differs depending on the operating conditions of the ball screw (rotation speed, axial load, etc.) even when the material of the cushioning material of the tube insertion member is the same.

Therefore, it is necessary to select and use a material that provides the best effect under various operating conditions, but in the present invention,
Since the tube insertion member is fixed to a nut with a screw, it can be easily changed to a different cushioning material depending on the conditions at that time.

[Effects of the Invention] As explained above, the present invention reduces the noise generated during the operation of the ball screw by covering the ball return tube exposed from the nut with a tube inserting member made entirely of an elastic soundproofing material. This has the effect of reducing vibration and preventing damage caused by accidental collision of the ball return tube with other members. Since the tube insertion member is removable from the nut, there are no problems with disassembly and repair of the ball screw, and members made of the appropriate material can be selected and used each time depending on the operating conditions. effect is brought about.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a ball screw according to an embodiment of the present invention with the shaft removed, FIG. 2 is an enlarged bottom view of a tube insertion member applied to the present invention, and FIG. 3 is a sectional view taken along the line ■-■ in Fig. 2, and Fig. 4 is a cross-sectional view taken along the line ■-■ in Fig. 2.
5(a) and 5(b) are diagrams comparing the generated sound amplitude of the ball screw with that of the conventional structure and the present invention, and FIG. 6 is a cross-sectional view taken along the line IV. FIG. 2 is a partially cutaway perspective view of an example of a screw structure. 1...Nut, 2...Ball return tube, 3.8
... Tube holding member, 5 ... Notch surface, 6 ... Spiral groove, 7 ... Ball, 9 ... Counterbore hole, 10 ...
Groove. Patent Applicant NSK Ltd. Agent Patent Attorney Rikichi Somekawa (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 9 Counterbore

Claims (2)

[Claims] (1) A flat cutout surface is formed on the outer side of the ball screw nut, a ball return tube is arranged on the cutout surface and communicates with both ends of the ball rolling portion of the spiral groove of the ball screw nut, and the ball return tube is made of a cushioning material. Soundproofing of a ball screw, characterized in that a groove portion that comes into close contact with the ball return tube is provided on the back surface of the tube holding member, and the cutout surface is covered with the tube holding member made of a cushioning material to completely enclose the ball return tube. Device. (2) The buffer material tube holding member is made of a hard rubber material such as nitrile rubber, and is removably attached to the notch surface of the ball screw nut. Soundproofing device for ball screws.