JP2011236963A - Using method of ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a trouble caused by operation torque fluctuation through the reduction of operation torque fluctuation.SOLUTION: In a ball screw 110, both ends are freely rotatably and axially immovably supported by a support unit 50 in a state where a screw shaft 22 is arranged horizontally. A nut 24 is fixed to a moving table 51 of a mating member in a state where a plurality of circulation components 27 are arranged in a line on a top face of the nut 24. The screw shaft 22 has an end coupled to an output shaft of a motor 52, and is rotated by the motor 52. The moving table 51 fixed to the nut 24 by the rotation of the screw shaft 22 and guided by a linear motion guide device 53 is moved along a longitudinal direction of the screw shaft 22.

Description

  The present invention relates to an improvement in the operability of a ball screw.

  This has the problem of reducing operating torque fluctuations.

  As a prior art for improvement of this portion, there is a ball screw device disclosed in Japanese Patent Application Laid-Open No. 2003-314658, which indicates that the number N of balls 70 arranged in a circulation track as shown in FIG. The number of the separators 78 is one to three less than the maximum number that can be arranged on the pitch circle C projected in the axial direction, and the width of the separator 78 is a ball when N balls 70 are arranged at equal intervals on the pitch circle C. The size of the gap between 70 is set. In this way, a ball screw device that reduces torque fluctuation and operates smoothly is obtained.

JP 2003-314658 A

  However, this prior art may cause the following problems as a ball screw used in a machine tool that requires high-precision machining.

  In recent years, there has been a problem that a striped pattern is generated on a processed surface of a mold in the mold processing at a high-precision machining center, and the present inventor has conducted various experiments to find out the cause.

  In that experiment, an experiment was conducted using a separator-equipped ball screw as disclosed in Japanese Patent Application Laid-Open No. 2003-314658 (Patent Document 1). I understand. It has been found that the occurrence of the striped pattern on the processed surface is caused by fluctuations in the operating torque. Therefore, even if the ball screw described in Patent Document 1 is adopted, the effect of reducing the generation of the striped pattern is not expected to be so much. There was a problem. The present invention has been made to solve such problems, and it is an object of the present invention to provide a method of using a ball screw that can reduce operating torque fluctuations and reduce problems associated with operating torque fluctuations.

  In order to solve the above problems, the present invention has a screw shaft having a helical thread groove on the outer peripheral surface and a thread groove facing the screw groove of the screw shaft on the inner peripheral surface, and is screwed into the screw groove. An outer peripheral surface of the nut to form a ball circulation circuit for infinite circulation of a nut to be joined, a large number of balls slidably loaded between the screw grooves, and a ball rolling between the screw grooves A circulating part fixed to the ball, wherein the circulating part is a method of using a ball screw that crawls a ball in the ball circulation circuit in a tangential direction of the spiral track, and the ball screw has the screw shaft arranged in a horizontal direction The screw shaft is rotated, and the nut is used by being fixed to a mating member in a state where the circulating component is disposed on the upper surface of the nut.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that it can prevent the malfunction accompanying operating torque fluctuation | variation, for example, that a striped pattern generate | occur | produces on the surface of the workpiece by a high precision machining center.

The top view which shows the structure of a tangential scooping-up type ball screw is shown. The side view of the nut of a tangential scooping type ball screw is shown. The cross-sectional perspective view of a circulation component is shown. The usage method of the ball screw of this invention is shown. The measurement result of the operating torque fluctuation | variation by the usage method of the ball screw of this invention is shown. The measurement result of the operating torque fluctuation | variation by the usage method of the ball screw of a comparative example is shown. The state of the ball | bowl inside a circulation component in case the circulation component is arrange | positioned on the upper surface of a nut is shown. The state of the ball | bowl inside a circulation component in case the circulation component is arrange | positioned at the lower surface of a nut is shown. It is the figure which projected and looked at the circulation track | orbit of the ball screw mechanism described in patent document 1 to the axial direction.

  An embodiment of a method for using a ball screw according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view showing a structure of a tangential scooping type ball screw which is an object of the present invention. FIG. 2 is a side view of a nut of a tangential scooping ball screw. FIG. 3 is a cross-sectional perspective view of the circulating component.

  FIG. 1 is a plan view showing an example of a tangential scooping-up type ball screw that is an object of the method of using the ball screw of the present invention, FIG. 2 is a side view of FIG. 1, and FIG. It is.

  As shown in FIGS. 1 and 2, the ball screw 20 that is the object of the method of using the ball screw according to the present invention has a screw shaft 22 having a helical thread groove 21 on the outer peripheral surface and a screw groove 21 on the inner peripheral surface. A nut 24 having a helical screw groove 23 corresponding to the screw groove 23 is fitted, and the screw groove 23 of the nut 24 and the screw groove 21 of the screw shaft 22 face each other and form a spiral track that receives a load therebetween. Forming. A large number of balls 25 as rolling elements are slidably loaded in the spiral track, and the nut 24 (or screw shaft 22) rolls the balls 25 by the rotation of the screw shaft 22 (or nut 24). It moves in the axial direction.

  A flat surface 24 a is formed on a part of the side surface in the circumferential direction of the nut 24, and a circulating component 27 is fixed to the flat surface 24 a through a presser 28 by, for example, a set screw 29. The circulation component 27 includes a pair of leg portions 30 and a main body 31 that connects the pair of leg portions 30. The inside of the circulation component 27 is a ball circulation path 32, and is point-symmetric along the path direction of the ball circulation path 32. The divided body 27a (see FIG. 3) divided into two parts is joined to each other at the dividing surface, and a circulation groove 33 constituting a ball circulation path 32 is formed on the divided surface of the divided body 27a.

As a result, the circulating component 27 can be easily assembled by joining the two divided bodies 27a having the same shape, and the cost can be reduced because only one type of mold is required for the divided body 27a. In this embodiment, two circulation parts 27 are arranged to form two circulation circuits.
The pair of leg portions 30 are spaced apart from each other in the axial direction of the screw shaft 22 and spaced apart from each other in the radial direction of the screw shaft 22. There is provided a tongue portion 30a for scooping up the ball 25 rolling on the spiral trajectory in a direction substantially coincident with the tangential direction of the spiral trajectory.

These leg portions 30 communicate with a spiral track between the screw grooves 21 and 23 and are formed in a pair of circulation holes 34 drilled in a flat surface 24a of the nut 24 in a direction substantially perpendicular to the axis of the nut 24. It is mated. The pair of circulation holes 34 are arranged with their axial centers spaced apart from the axis of the screw shaft 22 by the same dimension in opposite directions. In addition, the escape part 35 (refer FIG. 3) is formed so that the front-end | tip of the leg part 30 by which the tongue part 30a of the division | segmentation body 27a of the circulation component 27 is not provided may not contact the screw shaft 22. FIG.
Then, by this circulating component 27, the ball 25 rolling on the spiral path between the screw grooves 21 and 23 is scooped up from one leg 30 and guided into the main body 31 outside the nut 24, and the other leg 30 An infinite circulation trajectory of the ball returning to the spiral trajectory is formed.

  As shown in FIG. 4, the ball screw 20 is supported at both ends by the support unit 50 so that the screw shaft 22 is arranged in the horizontal direction so as to be rotatable and not movable in the axial direction. On the other hand, the nut 24 includes a plurality of circulating parts 27 (in this embodiment, two circulating parts are provided for each of the two nuts in a double nut system) on the upper surface of the nut 24 along the axial direction of the nut 24. It is being fixed to the movement table 51 which is an other party member in the state arrange | positioned in a line.

  One end of the screw shaft 22 is connected to the output shaft of the motor 52 and is rotated by the motor 52.

  The moving table 51 fixed to the nut 24 by the rotation of the screw shaft 22 and guided by the linear motion guide device 53 moves along the longitudinal direction of the screw shaft 22.

  According to the method of using the ball screw of the present invention, since a gap is always generated in the ball circulation path 32 of the circulation component 27, the balls are not clogged. Accordingly, fluctuations in the operating torque can be reduced, and problems associated with fluctuations in the operating torque, such as the occurrence of striped patterns generated on the workpiece surface of the machine tool, can be solved.

  FIG. 5 shows a measurement result of the operating torque fluctuation in a state where the circulating parts 27 according to the method of using the ball screw of the present invention are arranged in a row on the upper surface of the nut 24, and FIG. The measurement result of the operating torque fluctuation in the state arrange | positioned in a line on the lower surface of 24 is shown.

  As is apparent from the measurement results shown in FIG. 5, it can be seen that according to the method of using the ball screw according to the present invention, the operating torque fluctuation is significantly reduced as compared with the method of use of the comparative example. It can also be seen that the operating torque is reduced overall.

The specifications and measurement conditions of the ball screw used for the measurement are as follows.
Ball screw specifications:
Shaft diameter 70mm, lead 12mm, double nut preload system, number of circuits 2.5 turns × 2 rows (× 2), preload load 4500N
Measurement condition:
Rotation speed 10min-1, stroke 12mm (1rev.), ISO VG # 68 lubrication, after 50 reciprocations

Next, it will be described below that the method of using the ball screw of the present invention is more effective in reducing the operating torque fluctuation than the method of using the comparative example.
1. When the circulating component 27 is disposed on the lower surface of the nut 24 (1) In <1> of FIG. 8, the screw shaft rotates and the ball in the load range rolls.
(2) In <2> of FIG. 8, the first ball enters the circulating component. The ball moves to the bottom of the circulating component under its own weight.
(3) In <3> of FIG. 8, the second ball enters the circulating component.
(4) In <4> of FIG. 8, the third ball enters the circulating component.
(5) Up to seven balls enter <5> in FIG.
(6) When the ninth ball enters the circulating component in <6> of FIG. 8, the ball in the circulating component is moved to the circulating component outlet side by being pushed by the ball entering the circulating component.
(7) In <7> of FIG. 8, the ball in the circulating part is pushed even if the next ball enters the circulating part, but it cannot be put because there is a ball on the outlet side of the circulating part. As a result, ball clogging occurs, and the operating torque of the ball screw increases instantaneously. However, the increase in operating torque is eliminated by the movement of the ball on the exit side to the load zone. By repeating the increase and decrease of the operating torque, the operating torque fluctuation in the ball passing period is generated.

2. When the circulating component 27 is disposed on the upper surface of the nut 24 (1) In <1> of FIG. 7, the screw shaft rotates and the ball in the load range rolls.
(2) In <2> of FIG. 7, when the first ball enters the circulating component, the ball stays at the circulating component entrance by its own weight.
(3) In <3> of FIG. 7, the second and third balls enter the circulating component.
(4) In <4> of FIG. 7, the fourth and fifth balls enter the circulating component.
(5) When the next ball enters in <5> of FIG. 7, the leading ball is pushed and moves to the load zone entrance by its own weight, so that a clearance always occurs in the circulating component. Therefore, the ball clogging phenomenon does not occur, and the operating torque fluctuation in the ball passing period does not occur.

  Although the example in which the circulating component 27 of the ball screw of the above embodiment is provided with two circulating components in one nut 24 is shown, one or three or more circulating components 27 may be provided in one nut 24. . Further, although the double nut in which two nuts are connected is used for measuring the operating torque fluctuation, the effect of the present invention can be obtained even when a single nut is used.

  The present invention can be widely applied to various mechanical devices as a method of using a ball screw provided with a circulating component.

21 Thread groove (Thread shaft side thread groove)
22 Screw shaft 23 Thread groove (Nut side thread groove)
24 Nut 25 Ball 27 Circulating component 30 Circulating component leg 31 Circulating component main body 32 Ball circulating path 33 Circulating groove 50 Support unit 51 Moving table 52 Motor 53 Linear motion guide device

Claims (1)

  A screw shaft having a helical thread groove on the outer peripheral surface, a nut having a thread groove facing the screw groove of the screw shaft on the inner peripheral surface and screwed into the screw groove, and between the two screw grooves A circulating part fixed to the outer peripheral surface of the nut so as to form a ball circulation circuit for infinite circulation of a large number of balls loaded in a rollable manner and a ball rolling between the two screw grooves; Is a method of using a ball screw that crawls a ball in the ball circulation circuit in a tangential direction of a spiral track, wherein the ball screw rotates the screw shaft in a state where the screw shaft is disposed in a horizontal direction, and the nut A method of using a ball screw, wherein the circulating part is used by being fixed to a mating member in a state where the circulating part is arranged on the upper surface of the nut.

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