JP2005308081A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device capable of preventing the generation of damage in a ball when scooping up the ball, capable of improving load capacity without increasing the number of ball (the number of winding) per a circuit, and capable of reducing noise to be leaked outside from inside a nut. <P>SOLUTION: This ball screw device is provided with a circulation part 7, which leads the ball 6 rolling in a load area outside of the nut 5 from one circulation hole 10 of one pair of two circulation holes 10 provided in a side surface of the nut 5 and of which both ends are fitted in each of the circulation holes 10 to return the ball 6 from other circulation hole 10 to the load area. The circulation part 7 has leg parts 9 to be fitted in the circulation holes 10 of the nut 5 in both ends thereof, and a passage 10 for scooping up the ball and a passage for returning it are formed inside each of the leg parts 9, inclining against the peripheral surface of the leg parts 9, and the circulation part 7 is covered with a sound insulating member 30 through clay 50 (or gel). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ball screw device used in, for example, an industrial machine.

  In a conventional ball screw device, a nut having a thread groove corresponding to the thread groove of the screw shaft is fitted to an inner peripheral surface of a screw shaft having a thread groove on an outer peripheral surface and extending in the axial direction. The screw groove and the screw groove of the screw shaft face each other to form a helical load track between them. A large number of balls as rolling elements are slidably loaded on the load track, and the nut (or screw shaft) moves in the axial direction through the rolling of the ball by the rotation of the screw shaft (or nut). It is supposed to be.

By the way, when the nut (or screw shaft) moves in the axial direction, the ball moves while rolling on a spiral load track formed by both screw grooves, but the nut (or screw shaft) is continued. In order to move it, it is necessary to circulate the ball indefinitely.
As a method of circulating the balls infinitely, a circulation tube type, an end cap type, or the like is generally used. However, in the case of the circulation tube type, for example, a part of the outer peripheral surface of the nut is made flat and the both surfaces are placed on the flat surface. A set of two holes communicating with the screw groove is formed so as to straddle the screw shaft, and both ends of the substantially U-shaped circulation tube are fitted into this set of holes, so that the load trajectory between the two screw grooves is formed. A ball that revolves along the trajectory is picked up by a circulation tube from the middle of the load trajectory and returned to the original load trajectory, whereby the ball is infinitely circulated.

  Further, in the case of the end cap type, a ball circulation hole penetrating in the axial direction is formed in the nut, and the ball circulation hole is formed between the end cap fixed to both end surfaces in the axial direction of the nut and the end surface of the nut. A ball circulation R portion communicating between the two screw grooves is formed, and the ball revolving along the load trajectory between the two screw grooves is circulated infinitely by the ball circulation R portion and the ball circulation hole. ing.

  However, the circulation tube type ball screw device can be provided with a plurality of ball circulation circuits in one thread groove, but the direction of scooping up the ball is a direction perpendicular to the axial direction of the screw shaft. If the lead of the thread groove is large, the direction of travel of the ball changes abruptly at the circulating part of the ball. As a result, when the ball is picked up, the ball collides with the inner surface of the tube and damage or vibration occurs. There is.

  On the other hand, the above-mentioned end cap type ball screw device is a method of scooping up the balls by the end caps provided at both ends of the nut. However, since the number of ball circulation circuits is limited to the number of thread grooves, increasing the number of balls per circuit (increasing the number of windings) to increase the load capacity reduces the operability of the ball screw device. There are problems such as.

Therefore, in order to solve such problems, the present applicants have previously proposed a ball screw device described in Japanese Patent Application No. 2003-015129.
As shown in FIGS. 5 and 6, the ball screw device 1 includes a screw shaft 3 having a spiral thread groove 2 on the outer peripheral surface and extending in the axial direction, and a spiral corresponding to the screw groove 2 on the inner peripheral surface. A nut 5 having a thread groove 4 is fitted, and the screw groove 4 of the nut 5 and the screw groove 2 of the screw shaft 3 are opposed to each other to form a spiral load track between them. . A large number of balls 6 as rolling elements are loaded on the load track so as to be able to roll. The rotation of the screw shaft 3 (or nut 5) causes the nut 5 (or screw shaft 3) to roll the ball 6. It moves to the axial direction via.

  A flat surface is formed on the outer peripheral surface of the nut 5 to form a mounting surface 8, and a cap body 7 a of a side cap 7 as a circulating component is fixed to the mounting surface 8 by a fixing means such as a screw. . On the lower surface side of the cap body 7a, a pair of leg portions 9 such as columns or blocks extending in a direction perpendicular to the axial direction of the screw shaft 3 are separated from each other in the axial direction of the screw shaft 3, and the diameter of the screw shaft 3 is increased. They are spaced apart from each other in the direction. These leg portions 9 are fitted into a pair of circulation holes 10 which are communicated with the load track between the thread grooves 2 and 4 and are drilled in the mounting surface 8. 7a is fixed to the mounting surface 8 by fixing means such as screws.

  Further, a ball scooping passage 11 extending in a direction substantially coinciding with the lead angle of the thread grooves 2 and 4 is formed in each leg portion 9 so as to be inclined with respect to the outer peripheral surface of the leg portion 9, and the inside of the cap body 7 a. A ball passage 12 connecting the ball scooping passages 11 is formed in each of the ball scooping passages 11, and one of the ball scooping passages 11 and the ball passage 12 in the axial direction between the screw grooves 2 and 4 (or the other). The ball circulation path 20 that scoops up the ball 6 rolling on the load track in the direction substantially coincident with the lead angle of the screw grooves 2 and 4 and returns it to the other (or one) load track in the axial direction is formed in the side cap 7. Forming.

  Therefore, unlike the circulation tube type ball screw device, even if the lead of the thread groove is increased, the traveling direction of the ball does not change abruptly at the circulating portion of the ball. Balls per circuit can be prevented from being damaged due to collision with the inner surface of the tube and the number of ball circulation circuits is not limited to the number of thread grooves as in the case of an end cap type ball screw device. The load capacity can be increased without increasing the number (number of turns).

  However, in the side cap type ball screw device having the above configuration, the noise inside the nut is transmitted to the outside through the side cap, and in particular, the side cap in order to facilitate the formation of a ball circulation path in the side cap. Is divided along the ball circulation path and joined at the divided position, there is a problem that noise inside the nut leaks outside through the gap of the joint.

  The present invention has been made to eliminate such inconveniences, and can prevent damage to the ball when picking up the ball, and without increasing the number of balls per circuit (increasing the number of windings). It is an object of the present invention to provide a ball screw device capable of reducing the noise emitted from the inside of the nut to the outside as well as increasing the load capacity.

In order to achieve the above object, the invention according to claim 1 includes a screw shaft having a helical thread groove on an outer peripheral surface, and a thread groove corresponding to the screw groove of the screw shaft on the inner peripheral surface. A nut fitted to the screw shaft, a large number of balls loaded to be able to roll on a load track formed between the two screw grooves, and the ball rolling on the load region are provided on the side surface of the nut. A circulation part having both ends fitted to each circulation hole so as to be guided to the outside of the nut from one circulation hole of the set of two circulation holes and returned to the load region from the other circulation hole; In a ball screw device comprising:
The circulation component has legs that are fitted into the circulation holes of the nut at both ends, and a path for scooping up the ball and a return path in each leg are inclined with respect to the outer peripheral surface of the leg. And a sound insulation member is put on the circulating component through clay or gel.

  According to the above configuration, the ball that rolls on the load trajectory between both screw grooves can be picked up in a direction substantially coinciding with the lead angle of the both screw grooves by the circulating component and returned to the original load trajectory. Like ball-type ball screws, even if the lead of the ball screw groove increases, the direction of movement of the ball does not change abruptly at the circulating part of the ball, and when the ball is picked up, damage or vibration of the ball occurs. Unlike the end cap type ball screw device, the number of ball circulation circuits is not limited to the number of thread grooves, so the load capacity can be reduced without increasing the number of balls per circuit. Can be increased.

  In addition, since the sound insulation member is put on the circulating parts through clay or gel, the vibration and noise generated inside the nut and transmitted through the circulating parts are vibration compared to sound absorbing materials such as glass wool, steel wool, and sound absorbing rubber. Since the vibration and noise attenuated by clay or gel having excellent damping properties are blocked by the sound insulating member, the noise transmitted to the outside through the circulating parts can be greatly reduced.

  According to the present invention, it is possible to prevent the ball from being damaged when scooping up the ball, and to increase the load capacity without increasing the number of balls (number of turns) per circuit. Since the vibration and noise that permeate the sound are attenuated by clay or gel having excellent vibration damping properties and transmitted to the sound insulation member, the vibration and noise attenuated by the sound insulation member are cut off. The effect that the noise emitted to the outside can be greatly reduced is obtained.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing a nut of a ball screw device as an example of an embodiment of the present invention, and (a) is an exploded perspective view before a sound insulation member is attached to a side cap via clay (or gel). b) is a perspective view after the sound insulation member is attached to the side cap via the clay (or gel), and FIG. 2 is an axial view of the nut with the sound insulation member attached to the side cap via the clay (or gel). FIG. 3 is a graph seen from the end side, FIG. 3 is a graph showing the noise measurement results in Comparative Example 1 and Comparative Example 2, and FIG. 4 is a graph showing the noise measurement results in Comparative Example 2 and the inventive example. In this embodiment, since the basic structure of the ball screw device is substantially the same as that already described with reference to FIGS. 5 and 6, only the differences will be described using the reference numerals.

  As shown in FIGS. 1 and 2, a ball screw device that is an example of an embodiment of the present invention has a plate-like shape on a cap body 7 a of a side cap (circulation component) 7 that is attached to an attachment surface 8 of a nut 5. The sound insulating member 30 is covered with clay 50 (or gel) having excellent vibration damping properties. The sound insulation member 30 has a cross-sectional shape substantially corresponding to the outer shape of the cap body 7a, and mounting flanges 31 are provided on both sides in the width direction. By attaching the mounting flange 31 to the mounting surface 8 by a fixing means such as a screw 32, the sound insulating member 30 is fixed to the mounting surface 8 with the cap body 7a covered with clay 50 (or gel).

The sound insulating member 30 is preferably made of a material having a higher density than the material of the side cap 7. For example, when the side cap 7 is made of a lightweight resin, the sound insulating member 30 is made of a metal such as iron or lead. It may be formed of rubber or the like whose density has been increased by mixing a metal powder inside the plate or inside.
As described above, in this embodiment, the plate-like sound insulation member 30 is placed on the cap body 7a of the side cap 7 attached to the attachment surface 8 of the nut 5 via the clay 50 (or gel) excellent in vibration damping. The vibration and noise generated inside the nut 5 and transmitted through the side cap 7 are transmitted to the sound insulation member 30 after being attenuated by the clay 50 (or gel), and are attenuated by the sound insulation member 30. Thus, noise emitted from the inside of the nut 5 to the outside can be greatly reduced.

  Although not shown in FIGS. 1 and 2, the side cap 7 is divided along the ball circulation path 20 and joined at the divided positions to facilitate the formation of the ball circulation path 20 in the side cap 7. Even in such a case, the sound insulation member 30 and the clay 50 (or gel) can be satisfactorily prevented from leaking the noise inside the nut 5 from the gap of the joint.

FIG. 3 shows a comparative example 1 in which the cap body 7a of the side cap 7 is simply covered with a sound insulation member 30, and the sound insulation member 30 is placed on the cap body 7a through a sound absorbing material such as glass wool (or steel wool, sound absorbing rubber). As a comparative example 2, the result of measuring each noise was compared. FIG. 4 compares the measurement results of noise with Comparative Example 2 with the cap body 7a covered with a sound insulation member 30 via clay 50 (or gel) as an example of the present invention. The ball screw device used for the measurement had a screw shaft diameter of φ25 mm, a lead of 25 mm, and a rotation speed of 4000 min ⁻¹ .
As is clear from each figure, Comparative Example 2 is superior in sound insulation compared to Comparative Example 1, but it can be seen that the inventive example is superior to Comparative Example 2 in sound insulation.
The configuration of the ball screw device of the present invention, particularly the configuration of the side cap and the sound insulation member, is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the nut of the ball screw apparatus which is an example of embodiment of this invention, (a) is a disassembled perspective view before attaching a sound insulation member to a side cap via clay (or gel), (b) is It is a perspective view after attaching a sound insulation member to a side cap via clay (or gel). It is the figure seen from the edge part side of the axial direction of a nut in the state which attached the sound-insulation member to the side cap via the clay (or gel). It is a graph which shows the measurement result of the noise in the comparative example 1 and the comparative example 2. It is a graph which shows the measurement result of the noise in the comparative example 2 and the example of this invention. It is a top view for demonstrating a side cap type ball screw apparatus. It is the figure seen from the right end part side of the axial direction of FIG.

Explanation of symbols

1 Ball screw device 2 Thread groove (screw shaft side)
3 Screw shaft 4 Thread groove (Nut side)
5 Nut 6 Ball 7 Side cap (Circulating part)
9 Leg 10 Circulation hole 11 Ball scooping passage 30 Sound insulation member 50 Clay (or gel)

Claims (1)

A screw shaft having a helical thread groove on the outer peripheral surface, a nut having a thread groove corresponding to the screw groove of the screw shaft on the inner peripheral surface and fitted to the screw shaft, and the two screw grooves A large number of balls loaded in a rollable manner on a formed load track, and one of the circulation holes in a set of two holes provided on the side surface of the nut. A ball screw device including a circulating part that is led to the outside of the nut from the other circulation hole and has both ends fitted to the circulation holes to return to the load region,
The circulation component has legs that are fitted into the circulation holes of the nut at both ends, and a path for scooping up the ball and a return path in each leg are inclined with respect to the outer peripheral surface of the leg. A ball screw device characterized in that the circulating component is covered with a sound insulation member via clay or gel.

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