JP2005076844A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device capable of improving durability and operability in high speed and high acceleration and deceleration by preventing exfoliation damage due to collision of a ball and a boundary portion between a guide groove and a ball screw groove of a ball nut. <P>SOLUTION: In the boundary portion 30 between the guide groove 18 and the ball screw groove 6 of the ball nut, chamfering is applied to the conventionally acutely shaped boundary portion (a portion indicated by the broken line) to provide a rounded shape. By this, a ball rolling from a ball rolling passage which is a ball load area passes the rounded boundary portion, and it rolls toward a direction change passage while smoothly rolling over the boundary portion 30 without collision. The ball B having rolled through the direction change passage rolls toward a ball return passage, and it is supplied to the ball rolling passage again. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ball circulation type ball screw device in which a guide groove for forming a direction changing path for communicating a ball rolling path and a ball return path is provided on an end face of a ball nut, and in particular, a high speed / high acceleration. The present invention relates to a ball screw device suitable for use in deceleration.

A ball screw device generally includes a screw shaft having a ball screw groove on an outer peripheral surface, a ball nut having a ball screw groove corresponding to the ball screw groove of the screw shaft on an inner peripheral surface, and balls of the screw shaft facing each other. The apparatus includes a plurality of balls that roll on a ball rolling path formed by a screw groove and a ball screw groove of the ball nut.
In this ball screw device, for example, as in the ball screw device described in Patent Document 1, a ball return path is formed in the ball nut, and a ball rolling path and a ball return path are formed on the end surface of the ball nut. 2. Description of the Related Art There is known a ball circulation type apparatus provided with a guide groove (referred to as a ball circulation R portion in Patent Document 1) for forming a direction change path for communication.

In this ball circulation system, the boundary between the load zone and the entrance of the direction change path, that is, the boundary between the ball screw groove of the ball nut forming the ball rolling path and the guide groove is formed at an acute angle. Has been.
Japanese Patent Laid-Open No. 2003-113922

By the way, when the guide groove is formed, the cutter rigidity escapes due to the load applied to the cutter during the machining, and a machining error is likely to occur. For this reason, when the guide groove is shallow due to machining errors, the ball collides with and passes through the boundary portion formed at an acute angle (the boundary portion between the ball screw groove of the ball nut and the guide groove). In addition, the ball may be peeled and damaged.
In particular, when the ball screw device is used at high speed and high acceleration / deceleration, the residual compressive stress in the boundary portion and inside the ball is increased at an early stage, so that the peeling progresses at an accelerated rate. When such peeling occurs, the peeling powder is caught between the screw shaft and the ball nut and the ball in the ball rolling path, and there is a possibility that the life of the apparatus is reduced and the operation is deteriorated.

Here, it is conceivable to form the guide groove deeply so that the ball does not collide with the boundary portion even if a processing error occurs, but in this case, the gap with the ball in the direction change path becomes large, There is a possibility that the operability during the swinging motion or low-speed driving is deteriorated, noise and vibration are increased.
Therefore, the present invention has been made in view of the above circumstances, preventing peeling damage due to collision between the ball screw groove and the guide groove of the ball nut and the collision with the ball, durability of high speed and high acceleration / deceleration, It is an object of the present invention to provide a ball screw device capable of improving operability and reducing noise and vibration.

Accordingly, the ball screw device of the present invention includes a screw shaft having a ball screw groove on the outer peripheral surface, a ball nut having a ball screw groove corresponding to the ball screw groove of the screw shaft on the inner peripheral surface, and the screws facing each other. A plurality of balls that roll on a ball rolling path formed by the ball screw groove of the shaft and the ball screw groove of the ball nut, the ball nut has a ball return passage, and the end surface of the ball nut In the ball screw device having a guide groove for forming a direction changing path for communicating the ball rolling path and the ball return path, a boundary portion between the ball screw groove and the guide groove of the ball nut, The shape is rounded by chamfering.
Further, it is preferable to treat the boundary portion so as to have a hardness lower than the hardness of the ball.

According to the ball screw device of the present invention, since the ball rolling from the ball rolling path does not collide with the boundary portion, it is possible to prevent the boundary portion and the ball from being peeled and damaged. In addition, the state where the ball does not collide with the boundary portion as described above is maintained even when the ball screw device is used at high speed / high acceleration / deceleration, so that no foreign matter such as peeling powder is generated, and high speed / high acceleration / deceleration occurs. It is possible to improve the durability and operability and reduce noise and vibration.
Further, since the boundary portion and the ball can be prevented from being peeled and damaged regardless of the processing error of the guide groove, the manufacturing cost can be reduced.

Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.
1 is a view partially showing an end face of the ball screw device, and FIG. 2 is a view taken along the line II-II in FIG.
The ball screw device of this embodiment includes a screw shaft 4 having a ball screw groove 2 on the outer peripheral surface, a ball nut 8 having a ball screw groove 6 corresponding to the ball screw groove 2 of the screw shaft 4 on the inner peripheral surface, A ball rolling path 10 formed of ball screw grooves 2 and 6 facing each other and having a predetermined ball pitch circular diameter BCD, and a number of balls B rolling in the ball rolling path 10 are provided.

The ball nut 8 includes a ball return passage 11 extending in the axial direction, and one opening 12 of the ball return passage is opened on the nut end surface 8a.
A first counterbore 14 into which a later-described direction changing member 24 fits in the nut end surface 8a, and a second counterbore hole adjacent to the first counterbore 14 and into which a scooping member 26 described later fits. 16 is formed.

  A curved guide groove 18 that is continuous between the opening 12 and the ball rolling path 10 on the bottom surface of the first counterbore 14 and that provides a direction changing path with the direction changing member 24 described above. Is formed. Further, the second counterbore 16 is formed as a shallow hole with respect to the first counterbore 14. In addition, the code | symbol 20 of FIG. 1 is the flange provided in the outer periphery of the ball nut 8, The bolt insertion hole 22 which a connection bolt penetrates is formed in this flange 20. As shown in FIG.

Next, FIG. 3 is a diagram in which the above-described direction changing member 24 and scooping member 26 are mounted in the first counterbore 14 and the second counterbore 16 of the nut end surface 8a, and FIG. FIG. 5 is a view showing the direction changing member 24, and FIG. 6 is a view showing the scooping member.
As shown in FIG. 5, the direction changing member 24 has a curved guide surface 24 a on a curved side surface. As shown in FIG. 4, the direction changing member 24 is arranged so that the guide surface 24 a faces the guide groove 18 formed in the bottom surface of the first counterbore 14.

A space between the guide groove 18 and the guide surface 24 a is a direction change path 28 that communicates the ball rolling path 10 and the ball return path 11.
As shown in FIG. 6, the scooping member 26 is formed with a scooping part 26 a that scoops up the ball, and as shown in FIG. 4, the scooping part 26 a is located in the middle of the direction change path 28. Has been placed.
Here, FIG. 7 is an enlarged view of the first counterbore 14 and the second counterbore 16 formed in the nut end surface 8a. The position indicated by the symbol P1 and the symbol P2 in this figure. A solid line portion between the positions is a boundary portion 30 between the guide groove 18 formed on the bottom surface of the first counterbore 14 and the ball screw groove 6 of the ball nut 8.
In this embodiment, as shown in FIG. 8 (a view taken along the line VIII-VIII in FIG. 7), the chamfering of the boundary portion (portion shown by the broken line in FIG. 8) formed at an acute angle in the conventional apparatus is performed. It is set as the boundary part 30 of the shape which gave and rounded.

  According to the ball screw device having the above configuration, the ball B rolling from the ball rolling path 10 that is the ball load zone is scooped up by the scooping portion 26 and then the guide groove 18 and the guide surface of the direction changing member 24. It rolls toward the direction change path 28 provided by 24a. At this time, the rolling ball B passes through the boundary portion 30, but since the boundary portion 30 has a rounded shape, the ball B does not collide with the boundary portion 30 and smoothly rolls on the boundary portion 30. It moves to the direction change path 28 while moving. Then, the ball B rolling on the direction changing path 28 rolls from the opening 12 to the ball return path 11 and is supplied again toward the ball rolling path 10.

Therefore, in the apparatus of the present embodiment, the boundary portion 30 between the guide groove 18 and the ball screw groove 6 of the ball nut 8 is rounded, so that the ball B rolling from the ball rolling path 10 is formed. Since it rolls smoothly on the boundary portion 30 without colliding with the boundary portion 30, it is possible to prevent the boundary portion 30 and the ball B from being peeled and damaged.
In this way, the state where the ball B does not collide with the boundary portion 30 is maintained even when the ball screw device is used at high speed and high acceleration / deceleration, so that no foreign matter such as peeling powder is generated and high speed / high acceleration / deceleration is achieved. It is possible to improve the durability and operability and reduce noise and vibration.

Further, since the boundary portion 30 and the ball B can be prevented from being peeled regardless of the processing error of the guide groove 18, the manufacturing cost can be reduced.
Next, what is shown in FIG. 9 shows a second embodiment according to the present invention.
In this embodiment, the boundary portion 32 between the guide groove 18 and the ball screw groove 6 of the ball nut 8 is formed at an acute angle, and the region from the surface to the inside of the boundary portion 32 (indicated by the hatching in FIG. 9) The portion shown) is preliminarily subjected to a carburizing treatment, and then a carburizing heat treatment is performed. Thus, the carbon concentration of the surface of the portion requiring high hardness other than the boundary portion 32 is increased by carburizing treatment without increasing the carbon concentration of the boundary portion 32. Further, the ball B has the same degree of hardness as a portion other than the boundary portion 32 that requires high hardness.

By performing such processing, the hardness of the boundary portion 32 can be set lower than the hardness of the ball B.
According to the ball screw device of the present embodiment, the ball B rolling from the ball rolling path 10 that is the ball load zone is scooped up by the scooping portion 26 and then guided by the guide groove 18 and the direction changing member 24. It rolls toward the direction change path 28 provided with the surface 24a. At this time, even if the rolling ball B collides with the boundary portion 32, the boundary portion 32 having a lower hardness than the ball B absorbs the collision energy. Then, the ball B rolling on the direction changing path 28 rolls from the opening 12 to the ball return path 11 and is supplied again toward the ball rolling path 10.

Therefore, in the apparatus of the present embodiment, the hardness of the boundary portion 32 between the guide groove 18 and the ball screw groove 6 of the ball nut 8 is set lower than that of the ball B, so that the ball rolling from the ball rolling path 10 Even if B collides with the boundary portion 32, the boundary portion 32 absorbs the collision energy, and therefore, the separation damage of the boundary portion 32 and the ball B can be prevented.
In this way, the state where the ball B does not collide with the boundary portion 32 is maintained even when the ball screw device is used at high speed and high acceleration / deceleration, so that no foreign matter such as peeling powder is generated, and high speed / high acceleration / deceleration is achieved. It is possible to improve the durability and operability and reduce noise and vibration.

Further, since the separation damage of the boundary portion 32 and the ball B can be prevented regardless of the processing error of the guide groove 18, the manufacturing cost can be reduced.
Furthermore, what is shown in FIG. 10 shows a third embodiment according to the present invention.
In the present embodiment, the boundary portion 34 between the guide groove 18 and the ball screw groove 6 of the ball nut 8 is rounded, and the region from the surface to the inside of the boundary portion 34 (the broken line in FIG. 10). A portion indicated by hatching) is preliminarily subjected to a carburizing treatment, and thereafter a carburizing heat treatment is performed.

According to the ball screw device of the present embodiment, the ball B rolling from the ball rolling path 10 that is the ball load zone is scooped up by the scooping portion 26 and then guided by the guide groove 18 and the direction changing member 24. It rolls toward the direction change path 28 provided with the surface 24a. At this time, the rolling ball B rolls on the direction change path 28 while smoothly rolling on the boundary portion 34. Here, even if an external force is applied to the boundary portion 34 from the rolling ball B, the boundary portion 34 having a lower hardness than the ball B absorbs the energy of the external force. Then, the ball B rolling on the direction changing path 28 rolls from the opening 12 to the ball return path 11 and is supplied again toward the ball rolling path 10.
Therefore, in the apparatus according to the present embodiment, the boundary portion 34 is rounded and the hardness of the boundary portion 34 is set lower than that of the ball B, so that peeling damage of the boundary portion 34 and the ball B is surely prevented. It is possible to improve the durability and operability of high speed / high acceleration / deceleration, and to reduce noise and vibration.

It is a figure which shows the nut end surface of the ball screw apparatus which concerns on this invention. It is the II-II arrow directional view in FIG. It is a figure which shows the state which has arrange | positioned the direction change member and the scooping member to the nut end surface shown in FIG. It is the IV-IV arrow directional view in FIG. It is a figure which shows the direction change member used by this invention. It is a figure which shows the scooping member used by this invention. It is the figure which expanded the structure of the nut end surface concerning this invention. It is a figure which shows the boundary part of 1st Embodiment which concerns on this invention. It is a figure which shows the boundary part of 2nd Embodiment which concerns on this invention. It is a figure which shows the boundary part of 3rd Embodiment which concerns on this invention.

Explanation of symbols

2 Ball Screw Groove of Screw Shaft 4 Screw Shaft 6 Ball Screw Groove of Ball Nut 8a Nut End Face 8 Ball Nut 10 Ball Rolling Path 11 Ball Return Path 12 Ball Return Path Opening 18 Guide Groove 24 Direction Change Member 26 Scooping Member 28 Direction change path 30, 32, 34 Ball screw B and boundary part of guide groove Ball B

Claims (3)

A screw shaft having a ball screw groove on the outer peripheral surface, a ball nut having a ball screw groove corresponding to the ball screw groove of the screw shaft on the inner peripheral surface, a ball screw groove of the screw shaft and the ball nut facing each other. A plurality of balls that roll on a ball rolling path formed by a ball screw groove, and the ball nut has a ball return path, and the ball rolling path and the ball return path are formed on an end surface of the ball nut. In a ball screw device provided with a guide groove for forming a direction change path for communicating
A ball screw device, wherein a boundary portion between the ball screw groove and the guide groove of the ball nut is rounded by chamfering. A screw shaft having a ball screw groove on the outer peripheral surface, a ball nut having a ball screw groove corresponding to the ball screw groove of the screw shaft on the inner peripheral surface, a ball screw groove of the screw shaft and the ball nut facing each other. A plurality of balls that roll on a ball rolling path formed by a ball screw groove, and the ball nut has a ball return path, and the ball rolling path and the ball return path are provided on an end surface of the ball nut. In a ball screw device provided with a guide groove for forming a direction change path for communicating
A ball screw device, wherein a boundary portion between the ball screw groove and the guide groove of the ball nut is processed to have a hardness lower than the hardness of the ball. A screw shaft having a ball screw groove on the outer peripheral surface, a ball nut having a ball screw groove corresponding to the ball screw groove of the screw shaft on the inner peripheral surface, a ball screw groove of the screw shaft and the ball nut facing each other. A plurality of balls that roll on a ball rolling path formed by a ball screw groove, and the ball nut has a ball return path, and the ball rolling path and the ball return path are provided on an end surface of the ball nut. In a ball screw device provided with a guide groove for forming a direction change path for communicating
A boundary portion between the ball screw groove and the guide groove of the ball nut is rounded by chamfering, and the boundary portion is processed to have a hardness lower than the hardness of the ball. A ball screw device characterized by that.

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