JP2002156018A - Ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a lubricant reservoir part between a spacer and a ball, heighten retention of a lubricant, and to prevent lowering of ball circulating performance and minimize reduction of load capacity. SOLUTION: In this ball screw, the spacer 6 is interposed between balls 3, 3, provided in grooves 4, 5 of a screw shaft 1 and a nut 2. The spacer 6 is like a ring having a penetrating hole, and a recessed surface 8 of the spacer facing to the ball 3 is formed by plural conical surfaces 8a, 8b. Among the conical surfaces 8a, 8b, the conical surface 8a near the outer edge part of the space has an angle of inclination smaller than the angle of inclination of the other conical surface 8b, and preferably it is in non-contact with the ball 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw for various uses, for example, a high load application such as an electric injection molding machine and an electric press machine, and other uses such as machine tools, industrial machines, and automobile parts. Related to ball screws.

[0002]

2. Description of the Related Art In a ball screw or the like used under a high load, the ball may be worn depending on the lubrication state due to friction caused by competition between adjacent balls. The ball screw is twisted because the rolling groove of the ball is a screw groove.
Alternatively, since there is a component such as an end cap for circulating balls, a retainer such as a bearing for eliminating friction between balls cannot be inserted.

For this reason, as shown in FIGS. 10 to 12, examples have been proposed in which a spacer 56 is inserted between the balls 53 so that the slip between the balls 53 is absorbed by the spacer 56. The shape of the spacer 56 is, as shown in FIG.
1 has a V-shaped cross section formed by only one conical surface (for example, Japanese Utility Model Publication No. Sho 63-178659), a single arc formed by an arc as shown in FIG. 11, or FIG.
As shown in FIG. 2, a gothic arch shape composed of two arcs different from each other with a center of curvature O (for example, see Japanese Unexamined Patent Application Publication No.
No. 00-120825).

In these V-shaped, single arc-shaped and Gothic arch shapes, the clearance between the ball 53 and the spacer 56 increases from the ball contact portion to the outer edge of the spacer. As the clearance increases, the spacer 56 moves along the ball 53 by the clearance. When this movement increases, the outer diameter portion of the spacer 56 may contact the thread groove of the screw shaft 51 or the thread groove of the nut 52 as shown in FIG. Further, in the V-shape of a single cone (FIG. 10), the gap between the ball 53 and the spacer 56 has a large ratio toward the outer edge side, which is disadvantageous in the stability of the behavior.

Next, considering the lubricant, the larger the gap capacity between the ball 53 and the spacer 56, the larger the capacity that the lubricant can enter. Regardless of whether the cross section of the concave surface 59 is V-shaped, arc-shaped, or Gothic arch-shaped, the clearance capacity is large and a large amount of lubricant can be filled. However, in retaining the lubricant, the V-shape,
Both arc shape and gothic arch shape, as described above,
Since the gap between the ball 53 and the spacer 56 increases from the ball contact portion to the spacer outer edge side, the holding performance is poor. That is, the spacer 56 is provided for that gap.
Moves along the ball 53, the lubricant accumulated in the gap is discharged, and as a result, the effect of retaining the lubricant is reduced. Since the lubricant is discharged over time in this manner, wear of the spacer is promoted when the ball screw is operated for a long period of time. As a result, the adjacent balls 53 cause point contact due to wear of the spacer 56, and the operation of the ball screw deteriorates.

The sectional shape of the concave surface 59 of the spacer 56 is V
The letter-shaped object (FIG. 10) has an arc-shaped cross section (FIG. 1).
Compared to 1), as shown in FIGS.
When the contact point P between the spacer 56 and the ball 53 is the same,
There are problems with strength and dimensions as follows. That is,
For the V-shaped one, the thickness t1 of the spacer outer diameter part (FIG. 14)
Is the outer diameter wall thickness t2 of the single circular arc spacer 56 (FIG. 1).
It becomes thinner as compared with 5), and the strength of that portion decreases. In order to compensate for the decrease in strength, the outer diameter φD of the spacer 56 is increased by ΔD as shown in FIG.
As shown in FIG. 7, it is necessary to reduce the thickness L of the spacer 56 in the width direction by ΔL and increase the outer diameter portion thickness t1 to t2.

When the outer diameter D of the spacer 56 is increased, the spacer 56 is only slightly inclined in the circulation path of the ball screw, so that the spacer 56 contacts the inner surface of the circulation path and the ball 53 smoothly moves. Inhibits circulation. When the thickness L in the width direction of the spacer 56 is reduced, the spacer 56 is damaged when a high load is applied due to insufficient strength in the width direction of the spacer 56, and the spacer 56 functions as a ball screw. Cannot be fulfilled.

In the case where the cross section of the concave surface 59 of the spacer 56 has a single arc shape (FIG. 11), the ball contact position P is
This is the spacer outer edge Q as shown in FIG. 8 or the opening edge X of the through hole 60 as shown in FIG. From the viewpoint of the holding performance of the ball 53, the spacer outer edge portion Q is preferable. However, the outer edge Q and the opening edge X of the through hole 60 are all angular. If a load from the ball 53 is received at such an angular portion, the corner may be damaged due to the concentration of the load. is there. In the case where the cross section of the concave surface 59 has a single arc shape, it is necessary to make the concave surface 59 and the ball 53 have the same diameter to make surface contact in order to avoid contact at corners. Then, the frictional resistance increases.

As shown in FIG. 12, the concave surface 59 of the spacer 56
Is a Gothic arch, the contact point P with the ball 53 can be arranged in the middle part of the concave surface 59, and the thickness of each part can be secured without increasing the outer diameter. However, since the Gothic arch shape is a combination of two arcs, it is difficult to manage the shape. In addition, since the arc surface of the concave surface 59 and the arc surface of the ball 53 come into contact with each other, if the shape management is incomplete, the variation of the contact points P increases. For this reason, if the shape is a gothic arch, it is difficult to secure the accuracy, and eventually, the edge of the concave surface 59 contacts and receives a concentrated load, which may cause a problem of damage. Therefore, it is difficult to secure a load capacity.

The problems and characteristics of the above-described shapes of the concave surface 59 are summarized as follows. . A single circular arc (FIG. 11) is in surface contact and increases frictional resistance. If this is avoided, cornering occurs, and it is difficult to secure a load capacity due to the risk of damage. . In the V-shape (FIG. 10), the frictional resistance is reduced, but the thickness of the spacer 56 is reduced and the strength is reduced, or the outer diameter is increased and the smooth operation of the ball 53 is hindered. Is done. . The Gothic arch shape is excellent in various performances if the shape management is sufficient, but the shape management is difficult, the contact points vary, and the corner hit occurs. . Each shape has a different degree, but the lubricating oil retainability is insufficient.

It is an object of the present invention to ensure the strength of the spacer and the smooth operation of the ball without being caught while having excellent lubricant retention, low friction, and minimizing the reduction in load capacity. It is to provide a ball screw which is excellent in productivity and cost. Another object of the present invention is to maintain ball holding performance. Still another object of the present invention is to be able to retain the lubricant even when the spacer behaves.

[0012]

According to the ball screw of the present invention, spiral screw grooves are provided on an outer diameter surface of a screw shaft and an inner diameter surface of a nut loosely fitted on an outer periphery of the screw shaft, respectively. In a ball screw in which a plurality of balls are rotatably housed in a spiral circulation path formed between the screw shaft and a screw groove of a nut, a ring-shaped spacer having a through hole is provided between the balls. It is characterized in that the concave surfaces facing the balls of the spacer are formed by a plurality of conical surfaces. The plurality of conical surfaces are concentric with each other.
According to this configuration, since the concave surface facing the ball of the spacer is formed by a plurality of conical surfaces, a large gap where lubricant is accumulated near the connecting portion between the conical surfaces is obtained. In the vicinity of the connecting portion of the conical surfaces, the ball does not contact, and even if there is a radial movement of the spacer, the lubricant is not discharged and the retention of the lubricant is excellent. As described above, both the holding capacity and the holding ability of the lubricant are excellent, and the lubrication performance is good. Therefore, wear of the spacer can be prevented. Since the lubricant can be retained as described above, it is possible to reduce the amount of lubrication of the lubricant and to eliminate the need for lubrication. Further, since a plurality of conical surfaces are used, the strength of the portion where the strength of the spacer is insufficient can be improved by arbitrarily adjusting the angles of the respective cones. For example, without increasing the outer diameter or substantial thickness of the spacer, the outer diameter portion and the thickness in the width direction can be ensured, and the contact of the ball with the edge of the concave surface can be avoided. For these reasons, even under a high load, the spacer can be prevented from being damaged, the load capacity can be minimized by using the spacer, and the ball can be smoothly circulated by preventing the spacer from being caught. . Because it is a conical surface, its cross section is a straight line, and the ball is in contact with the straight line and an arc. There is little variation. In addition, low friction due to point contact. In addition, since a conical surface is used, even when a plurality of surfaces are combined, shape management is easier than in a Gothic arch shape in which two arcs are combined. For this reason, the variation of the contact points is further reduced, and the problem of strength reduction due to the variation of the contact points is reduced. Moreover, it can be manufactured at low cost and with high accuracy. For example, even when the spacer is manufactured by injection molding, the shape of the mold can be easily controlled, and it can be manufactured at low cost.

[0013] In the present invention, among the above-mentioned conical surfaces, the inclination angle of the conical surface near the spacer outer edge may be smaller than the inclination angles of the other conical surfaces, and may not be in contact with the ball. In such a configuration, a conical surface close to the spacer outer edge portion can function as a ball holding portion. Therefore, the ball holding performance can be maintained. For example, even if the ball contact portion of the spacer is worn, the movement of the spacer can be restricted because the conical surface near the outer edge of the spacer serves as the ball holding portion or the ball restricting portion.

In the present invention, the contact angle between the spacer and the ball may be set in a range of 20 to 30 ° with respect to the axis of the spacer. If the contact angle is less than 20 °, it is difficult to provide a through-hole having sufficient strength, the through-hole cannot be used as a reservoir for the lubricant, and the lubrication performance deteriorates. Conversely, if the angle is larger than 30 °, it is difficult to form a cone for holding the ball, and it is necessary to increase the outer diameter of the spacer to have a ball holding function. 2
When the angle is in the range of 0 to 30 degrees, among the conical surfaces constituting the concave surface of the spacer, the conical surface that contacts the ball can be formed without increasing the outer diameter of the spacer, and a through hole having sufficient strength is provided. Can be provided in the spacer, and the through hole can function as a holding portion for the lubricant.

In the present invention, the intersection of the plurality of conical surfaces may be connected by a curved surface having a circular cross section. When the intersection of the conical surfaces is formed to have a shape in which the cross section is connected by a curved surface of an arc, the shape management is further facilitated when the spacer is a molded product such as a synthetic resin or a sintered alloy.

In the present invention, an annular recess for holding a lubricant may be provided at the intersection of the plurality of conical surfaces.
In such a configuration, the intersection of the conical surfaces can function more effectively as a lubricant retaining portion.

In the present invention, the diameter of the through hole of the spacer may be 32% or less of the ball diameter. However,
Through-holes are required and will therefore be greater than 0%. In order to minimize the reduction in the load capacity of the ball screw while maintaining the strength of the spacer, it is necessary to keep the width dimension of the spacer small, and the diameter of the through hole should be 32% or less of the ball diameter. It is desirable that When the hole diameter of the through hole exceeds 32% of the ball diameter, the outer diameter of the spacer and the thickness between the through holes (the thickness in the radial direction) are reduced, and when a high load is applied, the life of the ball screw is reduced. Even with a satisfactory load,
The spacer was broken and caught inside the ball screw,
The ball screw itself will be damaged. If the outer diameter of the spacer is increased to compensate for this, the circulation performance of the ball screw is impaired. Therefore, the range of 32% or less is preferable. The fact that the range of 32% or less is preferable is not limited to the cross-sectional shape of the concave surface of the spacer, and is not limited to the case where the concave surface has two conical shapes.

In the present invention, the outer diameter of the spacer may be set in a range of 50 to 80% of the ball diameter. In this case, as described above, it is more desirable to set the contact angle between the spacer and the ball in a range of 20 to 30 ° with respect to the axis of the spacer, and the width of the spacer is preferably It is desirable that the diameter be 25 to 35% of the ball diameter used. When the concave surface of the spacer is formed by a plurality of conical surfaces, for example, when it is formed by two conical surfaces, if the outer diameter of the spacer is 80% or more, the circulation performance is adversely affected. For example, when the circulation path is a return tube, the spacer is caught at the joint between the ball screw groove and the lubricating portion. When the outer diameter is 50% or less, it is difficult to stabilize the behavior of the ball. As described above, the outer diameter of the spacer is 50 to 8 of the ball diameter.
When it is in the range of 0%, smooth circulation and stable behavior of the ball can be obtained.

In the present invention, the minimum thickness of the spacer is preferably set in a range of 4 to 10% of the ball diameter. The minimum thickness in this case refers to a thickness in the axial direction at a position corresponding to a through portion of the through hole in the spacer. When the minimum thickness is set in this manner, the number of balls inserted into the ball screw is reduced little, the load capacity can be reduced, and the strength of the spacer can be secured. For example, when the thickness of the through hole exceeds 10% in the spacer having an outer diameter dimension that does not hinder the circulation of the ball screw, the number of balls inserted into the ball screw decreases, and the load capacity decreases significantly. Too much. On the other hand, when the thickness is less than 4%, the thickness of the spacer through-hole becomes too thin, and the strength becomes too weak.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The ball screw has helical thread grooves 4 and 5 on the outer diameter surface of the screw shaft 1 and the inner diameter surface of the nut 2.
Are provided, and a plurality of balls 3 are provided between the screw grooves 4 and 5.
In the ball screw with the interposition, the spacer 6 is interposed between the balls 3. The nut 2 is provided with a circulation path 7 for circulating the ball 3 interposed between the screw shaft 1 and the screw grooves 4 and 5 of the nut 2 from the screw grooves 4 and 5. Screw shaft 1, nut 2, and ball 3
Is made of a tempering material such as bearing steel or case hardened steel.

As the circulation path 7, various types can be adopted as will be described later in another example. In this example, an end cap type ball screw is used. That is, the nut 2 is composed of a nut body 2a and a pair of end caps 2 connected to both ends of the nut 2 with connecting members (not shown) such as bolts.
b, 2c. The circulation path 7 includes the nut body 2a
And a guide groove 7b, 7c provided in each end cap 2b, 2c and extending from the screw groove 4 of the screw shaft 1 to the circulation through hole 7a.
Each of the balls 3 of the screw groove 4 of the screw shaft 1 is provided with one of the guide grooves 7b and 7c in accordance with the rotation direction of the screw shaft 1 in accordance with the rotation direction.
And is returned to the screw groove 4 of the screw shaft 1 from the other guide grooves 7b and 7c after passing through the circulation through hole 7a.

The spacer 6 will be described with reference to FIG. The spacer 6 has two concave surfaces 8, 8 serving as contact surfaces with the ball 3, and has a ring shape in which the concave surfaces 8 are communicated with each other through a through hole 9. The concave surface 8 of the spacer 6 is formed by a plurality (here, two) of conical surfaces 8a and 8b. That is, the concave surface 8 comprises a conical surface 8a formed on the outer edge of the spacer 6 and a conical surface 8b formed on the inner edge. The inclination angle of the conical surface 8a on the outer edge side with respect to the spacer axis O1 is smaller than the inclination angle of the conical surface 8b on the inner edge side. The contact position A with the ball 3 on the conical surface 8b on the inner edge side
Is set, and the conical surface 8a on the outer edge side is the ball 3
And non-contact.

The contact angle θ between the spacer 6 and the ball 3, that is, the angle of the line segment connecting the ball center O and the contact position A with respect to the spacer axis O is set in the range of 20 to 30 °.
The intersection of the two conical surfaces 8a and 8b is connected by an arcuate curved surface R in cross section. Diameter φd of through hole 9 of spacer 6
Is 32% or less of the diameter φDw of the ball 3. Further, the outer diameter φDa of the spacer 6 is 5 times the diameter φDw of the ball 3.
It is set in the range of 0 to 80%. The minimum thickness of the spacer 6, that is, the thickness h of the portion corresponding to the length of the through hole 9 is set in a range of 4 to 10% of the diameter φDw of the ball 3. The width of the spacer 6 is set in a range of 31 to 40% of the diameter φDw of the ball 3.

Various materials can be selected as the material of the spacer 6 according to the requirements of the properties of the ball screw. For example,
The spacer 6 may be made of a sintered alloy. In this case, a sintered alloy obtained by sintering a metal powder injection-molded product may be used, and the sintered alloy may be mainly composed of stainless steel. In addition, the spacer 6 may be formed of a synthetic resin having self-lubricating properties. As this synthetic resin, for example, polyimide (PI) containing a reinforcing material
Or polyamide (PA) or the like.

According to the ball screw having this configuration, the ball 3 does not come into contact with the vicinity of the joint between the two conical surfaces 8a and 8b constituting the concave surface 8 of the spacer 6, so that the lubricant is held near the joint. And the retention performance of the lubricant can be improved. In addition, since the ball 3 is brought into line contact with the conical surface 8b of the concave surface 8, the frictional resistance is reduced as compared to a shape in which the spacer has a single arc shape or a Gothic arch shape, which tends to make surface contact. it can. The shape management of the concave surface 8 is also easier than that of the Gothic arch shape, and even when the spacer 6 is manufactured by injection molding, the shape management of the mold is easy and the manufacturing can be performed at low cost.

The angle of inclination of the conical surface 8a near the spacer outer edge is smaller than the angle of inclination of the conical surface 8b of the spacer inner edge.
The following actions can be obtained because of non-contact. That is, the conical surface 8a close to the outer periphery of the spacer can function as a ball holding portion, so that the holding performance of the ball 3 can be maintained, and the outer diameter of the spacer 6 can be increased or the thickness in the width direction can be increased. The thickness of the outer diameter portion at the end face of the spacer can be sufficiently secured without reducing the thickness of the spacer, the strength of the spacer 6 can be secured, and the reduction in the load capacity of the ball screw can be reduced.

Further, by arbitrarily adjusting the inclination angle of each of the conical surfaces 8a and 8b, the strength of the portion where the strength of the spacer 6 becomes insufficient can be increased. Damage can be prevented. As a result, the ball 3 can be smoothly circulated without lowering the function of the ball screw.

Since the contact angle θ between the spacer 6 and the ball 3 is set in the range of 20 to 30 degrees with respect to the spacer axis O1, the conical surfaces 8a, 8b, the conical surface 8b contacting the ball 3 can be formed without increasing the outer diameter of the spacer 6, and the through hole 9 having sufficient strength can be provided in the spacer 6, and the through hole 9 can be formed.
Can function as a lubricant holding portion. That is, when the contact angle θ is smaller than 20 °, it is difficult to provide the through-hole 9 having sufficient strength, and the through-hole 9 cannot be used as a holding portion for the lubricant, thereby deteriorating the lubrication performance. Conversely, if the contact angle θ is larger than 30 °, it is difficult to form a conical surface for holding the ball 3,
The outer diameter of the spacer 6 must be increased in order to provide the ball holding function.

Since the intersections of the conical surfaces 8a and 8b are connected by a curved surface R having an arcuate cross section, when the spacer 6 is made of a synthetic resin or a sintered alloy, it is easier to control the shape. Becomes However, it is desirable that the diameter of the curved surface R at the intersection is smaller than the diameter φDw of the ball 3. If the diameter of the curved surface R is larger than the ball diameter φDw, the ball 3 rolls over that portion, and a problem occurs in which the retained lubricant is discharged by the ball 3, and the two conical surfaces 8a,
8b reduces the effect of holding the lubricant.

It is desirable that the spacer 6 be connected not only at the intersection of the conical surfaces 8a and 8b but also at the intersection of the concave surface 8 and the other portion of the spacer 6 with a curved surface having an arc-shaped cross section. By doing so, the load applied to such intersections is dispersed, and the strength of the corners of the spacer 6 can be increased. In particular, when the intersection between the outer diameter portion of the spacer 6 and the concave surface 8 is connected by a curved surface having an arc-shaped cross section, the spacer 6 becomes difficult to be caught by the circulation path 7 inside the ball screw. Therefore, conventionally,
When a general ball screw is used as a ball screw having a spacer, various shapes of the circulation path 7 need to be changed. However, as described above, the intersection between the outer diameter portion of the spacer 6 and the concave surface 8 is required. When the connection is made by a curved surface having an arc-shaped cross section, a conventional ball screw part without a spacer can be used as it is without changing the shape of the circulation path 7.

Further, since the diameter φd of the through hole 9 of the spacer 6 is 32% or less of the ball diameter φDw, the radial thickness of the spacer 6 is maintained at a certain value or more for securing the strength of the spacer 6. As a result, the reduction in the load capacity of the ball screw can be kept small. That is, if the diameter φd of the through hole 9 exceeds 32%, the thickness (radial thickness) between the outer diameter surface of the spacer 6 and the through hole 9 becomes thin, and a high load (the life of the ball screw) When the load applied is satisfied), the spacer 6 is damaged, and the damaged spacer 6 is caught inside the ball screw,
The ball screw itself will be damaged. In order to compensate for such insufficient strength, the outer diameter φ of the spacer 6
When Da is increased, the circulation performance of the ball screw is impaired. This dimensional limitation is applicable not only to the shape of the concave surface 8 of the spacer 6 in this embodiment, but also to other shapes including the case of the conventional example.

Since the outer diameter φDa of the spacer 6 is set in the range of 50 to 80% of the ball diameter φDw, it is possible to prevent the spacer 6 from obstructing the circulation of the ball screw and to reduce the behavior of the ball. Can be stabilized. That is, when the outer diameter φDa of the spacer 6 is 80% or more, the spacer 6 is caught at the joint between the thread grooves 4 and 5 and the circulation path 7. Here, an end cap type ball screw is illustrated, but for example, in the case of a return tube circulation type ball screw, the spacer 6 is likely to be caught. When the outer diameter φDa of the spacer 6 is 50% or less, it is difficult to stabilize the behavior of the ball 3. The width L of the spacer 6 is the ball diameter φ.
It is preferable to set it to 25 to 35% of Da. When the width L exceeds 35%, the circulation performance of the ball screw is adversely affected as in the case where the outer diameter is large. Width L is 25
%, It is difficult to provide the spacer 6 with sufficient strength, and in some cases, the spacer 6 may be damaged.

Since the minimum thickness h of the spacer 6 is set in the range of 4 to 10% of the ball diameter φDw, the number of balls inserted into the ball screw is small and the load capacity is small. In addition to being small, the strength of the spacer 6 can be secured. That is, when the outer diameter φDw of the spacer 6 is a size that does not hinder the circulation of the ball screw, the minimum thickness h is 10%.
Is exceeded, the number of balls 3 inserted into the ball screw is reduced, so that the load capacity is significantly reduced. If the minimum thickness h is less than 4%, the spacing 6
Is weakened and is damaged.

The width of the spacer 6 is 31 of the ball diameter φDw.
Since it is set in the range of ％ 40%, the behavior of the ball 3 is stabilized, and the ball screw can be operated smoothly. That is, the width of the spacer 6 is set to 31 of the ball diameter φDw.
%, It becomes difficult to stabilize the behavior of the ball 3, and the thickness of the spacer 6 itself becomes thin, so that the spacer 6 may be damaged depending on the material. Conversely, when the width of the spacer 6 is larger than 40% of the ball diameter φDw, the groove bottom of the thread groove 4 of the screw shaft 1 and the spacer 6 are formed inside the ball screw.
Interfere with each other to hinder the smooth operation of the ball screw.

FIG. 3 is a longitudinal sectional view showing a modification of the spacer 6. In the spacer 6, an annular recess 10 for retaining lubricant is positively provided at the intersection of the two conical surfaces 8a and 8b constituting the concave surface 8. Other configurations are the same as those of the previous spacer 6.

In the case of this modification, the lubricant retaining function at the intersection of the two conical surfaces 8a and 8b constituting the concave surface 8 of the spacer 6 is further improved by the annular recess 10 provided in this portion. .

In the example of FIG. 3, the annular recess 10
Is a U-shaped groove, but may be a groove-shaped recess 10A having an L-shaped cross section as shown in FIG.

5 and 6 show still another modification of the spacer 6. FIG. Also in this case, the concave surface 8 of the spacer 6 is constituted by the conical surface 8a on the outer edge of the spacer and the conical surface 8b on the inner edge of the spacer. It is set on the conical surface 8a on the seat outer edge side. The other configuration is the same as the example of the spacer 6 shown in FIG.

7 to 9 show a ball screw according to another embodiment of the present invention. In the example of FIG. 7, a top ball screw is used.
A is composed of a circulating component 12 called a piece. The circulating component 12 is a component for communicating approximately one round of the thread groove 5 of the nut 2, and a plurality of circulating components 12 are provided for one nut 2. FIG.
Is a return tube type ball screw, and the circulation path 7B is constituted by the return tube 13. The return tube 13 is provided between both ends of the thread groove 5 of the nut 2. In the example of FIG. 9, a ball screw of a guide plate type is used, and a circulation path 7 </ b> C is formed by a guide groove of a guide plate 14 provided in the nut 2. At the entrance of the circulation path 7C composed of guide grooves,
Deflector 15 for scooping ball 3 between screw grooves 4 and 5
Is provided. In each of the examples of FIGS.
Any of the spacers 6 described in the above embodiments is
It is used between each ball 3. In each of the examples of FIGS. 7 to 9, the other configuration of the above items is the same as that of FIG. 1.

[0040]

According to the ball screw of the present invention, a ring-shaped spacer having a through hole is interposed between the balls, and the concave surfaces facing the balls of the spacer are formed by a plurality of conical surfaces. The ball does not come into contact with the vicinity of the connecting portion of the plurality of conical surfaces constituting the concave surface, and the lubricant can be held in the vicinity of the connecting portion, so that the lubricant holding performance is excellent. Therefore, the friction becomes low, and the wear of the spacer can be prevented, and the lubrication amount of the lubricant can be reduced or the necessity of the lubrication can be eliminated. Further, since a plurality of conical surfaces are used, the strength of the portion where the strength of the spacer is insufficient can be improved by arbitrarily adjusting the angles of the respective cones. Therefore, the strength can be secured without increasing the spacer, the ball circulation performance is not impaired by the spacer, and the reduction in load capacity due to the use of the spacer can be minimized. Furthermore, since a plurality of conical surfaces are used, shape management is easier, quality variation is less, manufacturing is easier, and cost can be reduced as compared with a Gothic arch shape in which arc surfaces are combined. If the inclination angle of the conical surface near the spacer outer edge of the conical surface is smaller than the inclination angles of the other conical surfaces and is not in contact with the ball, the contact portion between the ball and the spacer is Even if worn, the conical surface of the outer edge portion becomes the ball restraining portion, so that the behavior of the spacer can be suppressed, and more stable circulation performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a ball screw according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a relationship between a spacer and a ball in the ball screw.

FIG. 3 is a sectional view of a modified example of the spacer in the ball screw.

FIG. 4 is a sectional view of another modification of the spacer.

FIG. 5 is a sectional view of still another modification of the spacer.

FIG. 6 is an explanatory view showing a relationship between the same spacer and a ball.

FIG. 7 is a perspective view of a ball screw according to another embodiment of the present invention.

FIG. 8 is a perspective view of a ball screw according to still another embodiment of the present invention.

FIG. 9 is a perspective view of a ball screw according to still another embodiment of the present invention.

FIG. 10 is a cross-sectional view of a conventional example in which the concave surface of the spacer has a V-shaped cross section.

FIG. 11 is a sectional view of a conventional example in which the concave surface of the spacer has a single arc shape.

FIG. 12 is a cross-sectional view of a conventional example in which the concave surface of the spacer has a Gothic arch shape.

FIG. 13 is an operation explanatory diagram of the conventional example.

FIG. 14 is an operation explanatory view of a conventional example in which the concave surface of the spacer has a V-shaped cross section.

FIG. 15 is an operation explanatory view of a conventional example in which the concave surface of the spacer has a single arc shape.

FIG. 16 is an explanatory view showing an example in which the outer diameter of the spacer is increased to strengthen the outer edge portion in the conventional example in which the concave surface of the spacer has a V-shaped cross section.

FIG. 17 is an explanatory diagram showing an example in which the width of the spacer is reduced to reinforce the outer edge strength in a conventional example in which the concave surface of the spacer has a V-shaped cross section.

FIG. 18 is an explanatory view showing a problem in a conventional example in which the concave surface of the spacer has a Gothic arch shape in cross section.

FIG. 19 is an explanatory view showing a problem in the conventional example in which the concave surface of the spacer has a single arc shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Screw shaft 2 ... Nut 3 ... Ball 4, 5 ... Thread groove 6 ... Spacer 7 ... Circulation path 8 ... Concave surface 8a, 8b ... Conical surface 9 ... Through hole 10, 10A ... Concave θ ... Contact angle h ... Minimum Thickness

Claims (8)

[Claims] A spiral screw groove is provided on each of an outer diameter surface of a screw shaft and an inner diameter surface of a nut loosely fitted on an outer periphery of the screw shaft, and is formed between the screw shaft and the screw groove of the nut. In a ball screw in which a plurality of balls are rotatably accommodated in a spiral circulating path, a ring-shaped spacer having a through hole is interposed between the balls and faces the balls of the spacer. A ball screw, wherein the concave surface is formed by a plurality of conical surfaces. 2. The method according to claim 1, wherein the inclination angle of the conical surface of the conical surface close to the outer periphery of the spacer is smaller than the inclination angles of the other conical surfaces and is not in contact with the ball. Ball screw. 3. The ball screw according to claim 1, wherein a contact angle between the spacer and the ball is set in a range of 20 to 30 ° with respect to an axis of the spacer. 4. The ball screw according to claim 1, wherein the intersections of the plurality of conical surfaces are connected by a curved surface having a circular cross section. 5. The ball screw according to claim 1, wherein an annular recess for retaining a lubricant is provided at an intersection of the plurality of conical surfaces. 6. The ball screw according to claim 1, wherein the diameter of the through hole of the spacer is 32% or less of the ball diameter. 7. An outer diameter of the spacer is set to a value equal to 50% of the ball diameter.
The ball screw according to any one of claims 1 to 6, wherein the ball screw is set in a range of up to 80%. 8. The ball screw according to claim 1, wherein a minimum thickness of the spacer is set in a range of 4 to 10% of the ball diameter.