JP2001099258A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device to prevent contact of an aligning member, incorporated in the indifinite circulation passage of a nut member, with a screw shaft, smoothly perform circulation of a ball and in turn, movement of the nut member and be manufactured simply and at a low cost. SOLUTION: Balls 1 are aligned at intervals of a given distance in an indefinite circulation passage and a ball aligning member 2 is provided to circulate through the indifinite circulation passage together with the ball 1. Guide pieces protruding to both sides in an aligning direction of the ball 1 by a distance longer than the diameter of the ball 1 are formed on the ball aligning member 2 and meanwhile, a linear holding member 40 having flexibility is wound around the inside diameter of the nut member 20 and an induction groove 21 fixed on both sides of a load rolling groove 35 and containing the guide piece of the ball aligning member 2 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction in which a screw shaft and a nut member are screwed together via a number of balls, and the rotational motion of a motor is converted into a linear motion in a sliding portion of a machine tool or an industrial robot. More particularly, the present invention relates to an improved ball screw device in which a ball alignment member for aligning a large number of balls at predetermined intervals is incorporated in a ball endless circulation path of the nut member.

[0002]

2. Description of the Related Art A ball screw device is frequently used in a linear slide portion of an industrial robot and the like, and is mainly used for giving a linear moving amount corresponding to a rotation amount of a motor to a movable body such as a table. Such a ball screw device generally includes a screw shaft having a spiral ball rolling groove formed on an outer peripheral surface thereof, an infinite circulation path which is screwed to the screw shaft via a large number of balls and circulates the balls. When the screw shaft is connected to a motor and rotated, a number of balls interposed between the screw shaft and the nut member have an infinite circulation path provided in the nut member. The nut member circulates lightly and linearly in the axial direction of the screw shaft.

On the other hand, in such a ball screw device, the individual balls circulating in the above-mentioned ball infinite circulation path come into contact with the balls located before and after the balls, thereby hindering smooth circulation of the balls. There is a drawback that the contact sound between the balls is harsh when the screw shaft rotates at a high speed.
A ball screw device disclosed in Japanese Patent No. 7408 has been proposed.

In the ball screw device disclosed in the publication,
A flexible band-shaped ball alignment member is provided so as to be capable of circulating in a ball endless circulation path of a nut member, and ball pockets for accommodating balls are arranged at predetermined intervals in the alignment member. Accordingly, the balls are accommodated in the ball endless circulation path of the nut member in a state where they are arranged at predetermined intervals in the band-shaped alignment member, thereby preventing the balls from circulating in the endless circulation path in the ball screw device. It is supposed to be.

However, in this ball screw device, in the region where the ball rolls between the screw shaft and the nut member, that is, in the load region, the outer peripheral surface of the screw shaft and the inner peripheral surface of the nut member are slightly formed. The alignment member is only inserted into the gap, and if the band-shaped alignment member fluctuates slightly with the circulation of the ball, the alignment member that moves relatively in the opposite direction and the outer peripheral surface of the screw shaft come into contact. This causes the alignment member to be worn out early and causes a large resistance to act on the circulation of the alignment member and thus the circulation of the ball, thereby hindering the smooth movement of the nut member with respect to the screw shaft. was there.

Accordingly, the applicant of the present application has proposed a ball screw device capable of guiding the circulation of the alignment member throughout the infinite ball circulation path including the load region, and preventing such an alignment member from coming into contact with the screw shaft. (Japanese Patent Application No. 10-077787). Specifically, a substantially cylindrical guide member provided with a spiral ball relief in order to avoid interference with the ball is fitted into the inner diameter of the nut member, and the guide member and the nut member cooperate with each other. A guide groove for accommodating both side edges of the alignment member is provided in the inner diameter of the nut member. According to such a ball screw device, when the alignment member circulates along with the ball in the load area between the nut member and the screw shaft, the alignment member is guided on both side edges thereof by the guide grooves. As a result, there was no contact with the screw shaft, and the circulation of the ball and, consequently, the movement of the nut member relative to the screw shaft could be facilitated.

[0007]

SUMMARY OF THE INVENTION However, Japanese Patent Application No.
In the ball screw device proposed in Japanese Patent No. 0777787, the guide member to be fitted to the inner diameter of the nut member must be manufactured according to the shaft diameter of the screw shaft and the lead length of the ball rolling groove.
It is troublesome to make guide members of different shapes for various ball screw devices with different load carrying capacity and size, and
There is a problem that the production cost is increased. Further, since the guide member exists in the gap between the nut member and the screw shaft, it must be formed to be extremely thin, and has a complicated shape such as a spiral ball escape portion being opened. When manufacturing by machining such as cutting, a large number of man-hours and labor are required, and even when manufacturing by injection molding of resin, the molding die becomes complicated. However, there is also a problem that the bulk increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent an alignment member incorporated in an infinite circulation path of a nut member from contacting a screw shaft. Therefore, it is possible to prevent such an alignment member from being caught during circulation in an infinite circulation path, thereby enabling the ball to be circulated and thus the nut member to be smoothly moved with respect to the screw shaft, and to be easily and inexpensively manufactured. It is to provide a possible ball screw device.

[0009]

In order to achieve the above-mentioned object, a ball screw device according to the present invention comprises a number of balls, a screw shaft having a spiral ball rolling groove formed on an outer peripheral surface, and an inner peripheral surface. A nut member screwed to the screw shaft via the ball, having a helical load rolling groove facing the ball rolling groove of the screw shaft, and both ends of the load rolling groove of the nut member; A ball screw device comprising a circulating path forming member that forms an infinite circulating path of the balls by communication and connection is premised. In the infinite circulating path, the balls are aligned at predetermined intervals and the infinite circulating path is formed. A ball alignment member that circulates with the ball in the path is provided, and a guide piece that protrudes from one side or both sides in the ball alignment direction with respect to the ball diameter in the ball alignment member is formed on the ball alignment member. The above ball alignment A guide groove for accommodating a guide piece of material is formed along the ball rolling direction, and a flexible linear holding member is wound around the inner diameter of the nut member, and one side of the load rolling groove or A guide groove fixed to both sides for accommodating the guide piece of the ball alignment member is formed, and the guide groove of the circulation path forming member and the guide groove formed in the nut member are communicatively connected. is there. Things.

According to such technical means, the ball alignment member circulating with the ball in the endless circulation path is provided between the ball rolling groove of the nut member and the ball rolling groove of the screw shaft, that is, in the load area. During rolling, the guide groove guides the nut member along the inner peripheral surface. Therefore, in such a load region, the ball alignment member that moves as the ball rolls does not fluctuate, and it is possible to prevent contact between the ball alignment member and the screw shaft. Further, since the guide groove is continuous with the guide groove formed on the inner diameter of the circulation path forming member, the tip of the ball alignment member that enters the circulation path formation member from the load area is caught at the entrance of the circulation path formation member. Does not occur, and it is possible to smoothly circulate the ball alignment member and thus the ball in the entire area of the infinite circulation path.

At this time, in the ball screw device of the present invention,
Fixing to one or both sides of the load rolling groove by winding a flexible linear holding member around the inner diameter of the nut member,
Thus, since the guide groove is formed on one or both sides of the load rolling groove, the guide groove can be easily formed. Moreover, the guide groove can be formed as long as the flexible linear holding member is fixed along the load rolling groove, so that a plurality of screw shafts having different shaft diameters and different ball rolling groove lead lengths are provided. One type of holding member can cope with the above ball screw device, and a ball screw device having such a guide groove can be manufactured at low cost.

Here, from the viewpoint that the guide groove guides the ball aligning member in the load area, the holding member forming the guide groove has a length corresponding to the length of the load area, that is, the length of the load rolling groove. If it is only wound around the inner diameter of the nut member, it does not matter. However, from the viewpoint that the guide groove of the circulation path forming member and the guide groove are accurately communicated and connected to facilitate the circulation of the ball holding member in the infinite circulation path, the holding member is not loaded with a load. It is preferable that the groove is formed longer than the groove, and both ends in the longitudinal direction are inserted into the circulation path forming member. According to this structure, the holding member functions as a positioning member when the circulation path forming member is mounted on the nut member, so that the guide groove formed by the holding member and the guide groove of the circulation path forming member can be precisely formed. The communication connection can be performed.

The guide groove is provided in the nut member by winding the holding member around the inner diameter of the nut member. The guide groove may be formed in advance along the longitudinal direction of the holding member itself. The guide groove may be formed by cooperation of the holding member and the inner peripheral surface of the nut member. In any case, the holding member needs to have a predetermined cross-sectional shape, but such a linear holding member can be easily formed into a long one by extrusion molding of a synthetic resin or the like. Can be manufactured.

Further, when the above-mentioned holding member is wound around the inner diameter of the nut member and fixed, any fixing method such as adhesion or welding can be adopted, but from the viewpoint of fixing the holding member more easily. For example, it is preferable that the holding member is provided with elasticity, and the holding member is expanded at the inner diameter of the nut member by such elastic force and is pressed against the inner peripheral surface of the nut member. With this configuration, simply holding the holding member around the inner diameter of the nut member allows the holding member to be naturally fixed to the inner peripheral surface of the nut member, that is, one or both sides of the load rolling groove. No special fixing work is required, and the formation of the guide groove can be easily performed.

When the holding member is fixed to the inner peripheral surface of the nut member by utilizing the elastic force of the holding member, for example, the holding member is formed in a coil shape having a diameter larger than the inner diameter of the nut member. Then, it may be inserted into the inner diameter of the nut member so as to shrink the diameter,
The holding member formed in a straight line may be successively rolled into the inner diameter of the nut member so as to slide from one end of the load rolling groove.

Further, from the viewpoint of more accurately fixing the holding member to one side of the load rolling groove, a fixing groove into which the holding member is fitted is provided on one or both sides of the load rolling groove. And the shape of the fixing groove is devised so that the holding member is positioned in the fixing groove by its elastic force. The specific shape of the fixing groove will be described later with reference to the drawings.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a ball screw device according to the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 and 2 show an embodiment of a ball screw device to which the present invention is applied. In the figure, reference numeral 10 denotes a screw shaft on which a spiral ball rolling groove 11 is formed by a predetermined lead, and reference numeral 20 denotes an infinite circulation path through which the ball 1 circulates, and the screw shaft 10 through the ball 1. Reference numeral 30 denotes a ball return pipe (circulation path forming member) which is inserted from the outer peripheral surface of the nut member 20 to the inner peripheral surface to form an infinite circulation path of the ball 1. , These screw shafts 1
The nut member 20 is configured to move in the axial direction of the screw shaft 10 by the relative rotation between the nut member 20 and the nut member 20.

As shown in FIG. 3, the nut member 20 is formed in a cylindrical shape having a through hole 31 of the screw shaft 10 at the center, and the nut member 20 is provided with a movable member such as a table on its outer peripheral surface. A flange portion 32 for fixing the projection is provided. The screw shaft 1 is provided on the inner peripheral surface of the through hole 31.
A spiral load rolling groove 35 opposing to the ball rolling groove 11 is formed. When the screw shaft 10 and the nut member 20 rotate relative to each other, the ball 1 is moved to the ball rolling groove 11. It rolls while applying a load between it and the load rolling groove 35. In the vicinity of both ends of the load rolling groove 35, communication holes 36 penetrating the nut member 20 in the tangential direction are opened, and both ends of the ball return pipe 50 are connected to the nut member 20 through these communication holes 36. It is designed to be inserted from outside to inside. And the nut member 20
The ball 1 that has rolled in the load rolling groove 35 while applying a load between the ball 1 and the screw shaft 10 is released from the load when the ball 1 reaches the opening position of one of the communication holes 36 and enters the ball return pipe 50. Rolling, ball return pipe 5
After rolling inside 0, it is returned again between the nut member 20 and the screw shaft 10 through the other communication hole 36.

The load rolling groove 3 of the nut member 20
5 are formed at both ends corresponding to the communication holes 36, respectively. The distal end surface of the ball return pipe 50 inserted into the nut member 20 from the communication holes 36 is It is designed to abut against the part 38 and be locked. Further, a mounting surface 33 for fixing the ball return pipe 50 is formed on an outer peripheral surface of the nut member 20, and the ball return pipe 50 is fixed to the nut member 20 using a fastener 51. (See FIG. 1). As shown in FIG. 3, a tap hole 34 is formed in the mounting surface 33 of the nut member 20, and a fixing bolt 52 inserted into the fastener 51 is screwed thereto.

Here, the balls 1 are not individually incorporated in the infinite circulation path of the nut member 20, but are arranged in a line in a ball alignment member 2 made of a synthetic resin having flexibility. Built into the infinite circuit. FIG. 4 shows the balls 1 and the ball aligning member 2 arranged in the infinite circulation path of the nut member 20, and the screw shaft 10 and the nut member 20 are drawn through. The ball aligning member 2 forms the receiving holes 4 for the balls 1 at predetermined intervals with respect to the flat belt-shaped connecting body belt 3, arranges the balls 1 in the receiving holes 4, and forms the receiving holes 4 adjacent to each other. A spacer portion 5 for enclosing the spherical surface of the ball 1 is formed therebetween, and the ball 1 is confined in the accommodation hole 4. Each ball 1 is rotatably held by a ball alignment member 2. ing. Such a ball alignment member 2 can be manufactured by, for example, injection molding of a synthetic resin using the ball 1 as a core.

Accordingly, when the ball 1 circulates in the infinite circulation path provided in the nut member 20 with the relative rotation of the screw shaft 10 and the nut member 20, the ball aligning member 2 and the ball alignment member 2 are also moved in the infinite circulation path. Circulates inside. At this time, as shown in FIG.
Since a pair of guide grooves 53 are formed in the inner diameter of the ball 0 along the rolling direction of the ball 1, the ball alignment member 2
When the ball circulates in the ball return pipe 50, both edges of the connecting member belt 3 projecting to both sides of the ball 1 in the direction of alignment of the ball 1 are accommodated in the guide groove 53, and the ball alignment member 2 moves in the ball return pipe 50 so as to be guided by the guide groove 53. That is, in this embodiment, both edge portions of the connecting body belt 3 function as guide pieces of the present invention. This prevents the ball alignment member 2 from fluttering in the ball return pipe 50, thereby facilitating the circulation of the ball 1 rotatably held by the ball alignment member 2.

On the other hand, a pair of members spirally shown along both side edges of the ball alignment member 2 in FIG. 4 is a holding member 40 of the present invention. As shown in FIG. 5, these holding members 40 are fixed along both sides of the load rolling groove 35 of the nut member 20, and are spirally wound around the inner peripheral surface of the nut member 20. Each holding member 40 is formed of a flexible synthetic resin, is formed in a linear shape slightly longer than the length of the load rolling groove 35, and guides the ball alignment member 2 along its longitudinal direction. Guide groove 21
Are formed. A pair of holding members 40, 40 that face each other with the load rolling groove 35 interposed therebetween face the guide grooves 21, and the ball alignment member 2 has both side edges of the connecting member belt 3 inserted into these guide grooves 40. In the state, it moves in the load area, that is, between the nut member 20 and the screw shaft 10.

The nut member 20 is provided with a concave fixing groove 37 along both sides of the load rolling groove 35, and the holding member 40 is fitted in the fixing groove 37. The holding member 40 before being wound around the inner diameter of the nut member 20 is formed in a substantially linear shape by extrusion molding of a synthetic resin or the like, and is wound around the inner diameter of the nut member 20 in a state where it is forcibly bent. ing. Therefore, the holding member 40 itself has elasticity to restore the original linear shape, and the holding member 40 expands at the inner diameter of the nut member 20 by such elastic force and is pressed against the fixing groove 37. Using this elastic force, the holding member 4
0 is positioned in the fixing groove 37,
Has a wedge-shaped cross section. The holding member 40 is positioned in the fixing groove 37 by being moved to one side in the fixing groove 37 in cooperation with its own elastic force and the shape of the fixing groove 37.

As shown in FIG. 6, the holding member 40 is inserted into the inner diameter of the nut member 20 through a communication hole 36 formed in the nut member 20. That is, the holding member 40
Is flexible, and is fixed to the fixing groove 37 of the nut member 20 only by its own elastic force. Therefore, the holding member 40 is connected to the end of the fixing groove 37 facing the communication hole 36. When the holding member 40 is successively pulled into the inner diameter of the nut member 20 in such a manner as to slide, the holding member 40 spirally advances the inner diameter of the nut member 20, and finally, as shown in FIG. It is fixed at a position corresponding to the communication hole 36.

The holding member 40 is provided with a load rolling groove 35.
Are formed in a linear shape slightly longer than the length of the load rolling groove 3.
5 slightly protrudes from the locking step 38 of the nut member 20 toward the communication hole 36. Therefore, when the tip of the ball return pipe 50 is inserted into the communication hole 36, the tip of the holding member 40 is inserted into the ball return pipe 50, as shown in FIG. And the guiding groove 21 is surely connected.

Thus, together with the ball 1 and the nut member 2
When the ball 1 is rolling between the ball rolling groove 11 of the screw shaft 10 and the load rolling groove 35 of the nut member 20, that is, when the ball 1 is circulating in the infinite circulation path of zero. Is guided along the inner peripheral surface of the nut member 20 by the guide groove 21, and when the ball 1 rolls from the load region into the ball return pipe 50, that is, into the no-load region, the ball 1 is continuously guided by the guide groove 53 of the ball return pipe 50. Is done.

As described above, in the ball screw device of this embodiment, the guide groove 21 is formed along both sides of the load rolling groove 35 by winding the linear holding member around the inner diameter of the nut member. Since the guide groove 21 guides both side edges of the ball alignment member 2 along the inner peripheral surface of the nut member 20, the ball alignment member 2 moving in the load area together with the ball 1 comes into contact with the screw shaft 10. Therefore, the resistance acting on the rolling of the ball 1 can be reduced, and the wear of the ball alignment member 2 can be prevented.

At this time, the holding member 40 is pressed against the inner diameter of the nut member 20 by its own elastic force, so that no special fixing work is required. Therefore, the guide groove 53 is provided on the nut member 20 very easily. Can be done. In addition, the holding member formed in a linear shape can be easily and inexpensively manufactured with an arbitrary cross-sectional shape including the above-mentioned guide groove by extrusion molding of synthetic resin or the like. It is also possible to produce a ball screw device capable of smoothly guiding the ball alignment member at extremely low cost.

[0029]

As described above, according to the ball screw device of the present invention, by winding the holding member around the inner diameter of the nut member, the ball alignment member can be moved along both sides of the load rolling groove. Since a pair of guide grooves for guiding is formed, the ball alignment member incorporated in the infinite circulation path of the nut member is prevented from coming into contact with the screw shaft, and the alignment member is circulated in the infinite circulation path. It is possible to prevent the ball from being caught and thereby to smoothly circulate the ball, and thus to smoothly move the nut member with respect to the screw shaft, and to manufacture such a ball screw device easily and at low cost. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a ball screw device to which the present invention is applied.

FIG. 2 is a cross-sectional view of the ball screw device according to the embodiment.

FIG. 3 is a perspective view of a nut member according to the embodiment.

FIG. 4 is a perspective perspective view showing a state in which a ball circulates in an infinite circulation path provided in the nut member according to the embodiment.

FIG. 5 is an enlarged sectional view showing a state in which the holding member according to the embodiment is fixed to the nut member.

FIG. 6 is a perspective view illustrating an operation of assembling the holding member to the nut member according to the embodiment.

FIG. 7 is a perspective perspective view showing a connection state between a ball return pipe and a holding member according to the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ball, 2 ... Ball alignment member, 10 ... Screw shaft, 11
... ball rolling groove, 20 ... nut member, 21 ... guide groove, 3
5 ... load rolling groove, 37 ... fixed groove, 40 ... holding member, 50
... ball return pipe (circulation path forming member), 53 ... guide groove

Claims (4)

[Claims] 1. A number of balls, a screw shaft having a spiral ball rolling groove formed on the outer peripheral surface, and a spiral load rolling groove opposed to the ball rolling groove of the screw shaft on the inner peripheral surface. A nut member screwed to a screw shaft via the ball, and a circulation path forming member communicating with and connecting to both ends of the load rolling groove of the nut member to form an infinite circulation path of the ball. In the ball screw device, a ball alignment member for arranging the balls at predetermined intervals and circulating with the balls in the infinite circulation path is provided in the infinite circulation path. A guide piece projecting to one side or both sides in the ball alignment direction, and a guide groove for accommodating the guide piece of the ball alignment member is formed along the ball rolling direction in the inner diameter of the circulation path forming member. Forming and also possible Forming a guide groove for accommodating a guide piece of the ball alignment member by winding a linear holding member having a characteristic around the inner diameter of the nut member and fixing the linear holding member to one or both sides of the load rolling groove; A ball screw device wherein a guide groove of a forming member and a guide groove formed in a nut member are communicatively connected. 2. The ball screw device according to claim 1, wherein both ends in the longitudinal direction of the holding member are inserted into a circulation path forming member. 3. The ball screw device according to claim 1, wherein the holding member has elasticity, and the holding member expands at the inner diameter of the nut member by the elastic force, and is pressed against the inner peripheral surface of the nut member. A ball screw device. 4. The ball screw device according to claim 3, wherein one or both sides of the load rolling groove of the nut member is formed with a fixing groove in which the holding member is fitted. A ball screw device wherein a member has a cross-sectional shape positioned by its elastic force.