JP2015197184A - Ball screw device - Google Patents

Abstract

[PROBLEMS] To reduce heat generation due to friction of a lubricant-containing body that comes into contact with a screw shaft, and to provide a stable and long-term supply of lubricant that suppresses frictional heat, especially for high-speed and high-load applications, and the life of a lubricant-containing body An improved ball screw device is provided.
In a ball screw device (20) having a screw shaft (3) and a nut (1) screwed into the screw shaft (3) via a plurality of balls (6), lubrication for supplying a lubricant in contact with the outer peripheral surface of the screw shaft (3). An uneven portion 18 that reduces the area of the contact portion 8 c is formed on the contact portion 8 c of the lubricant-containing body 8 that has the agent-containing body 8 and contacts the outer peripheral surface of the screw shaft 3.
[Selection] Figure 1

Description

  The present invention relates to a ball screw device.

  Ball screw devices are well known as devices for converting rotational motion into linear motion. The ball screw device has a structure in which a large number of balls are interposed as rolling elements between the screw shaft and the nut, so the movement is light and the feed accuracy is excellent. It is often used in devices or precision positioning devices.

  In the ball screw device, a large number of balls are accommodated in spiral ball rolling grooves formed on the inner peripheral surface of the nut and the outer peripheral surface of the screw shaft inserted into the nut, so that the nut and the screw shaft can rotate relative to each other. Accordingly, the ball circulates between the ball return passage provided in the wall thickness of the nut or on the outer side of the nut and the spiral ball rolling groove. In order to reduce the rolling of the ball and reduce the wear of the ball rolling groove, there is a structure in which a lubricant is supplied to the outer peripheral surface of the screw shaft, in particular, the spiral ball rolling groove.

  As means for supplying a lubricant to a screw shaft of a ball screw device, devices described in Patent Documents 1 and 2 are known. This is because a cylindrical lubricant-containing body impregnated with a lubricant is attached to the end of the nut, and the inner periphery thereof is held so as to be in sliding contact with the screw shaft, while the nut and the screw shaft are rotating relative to each other. In addition, the lubricant is squeezed from the lubricant-containing body to the outer peripheral surface of the screw shaft, so that the lubricant can be supplied over a long period of time without maintenance.

  As another example, Patent Document 3 discloses a ball screw device provided with a lubricant-containing body provided with a seal portion. As shown in FIG. 6, a counterbore 23 is formed in the shape of a spigot on the inner diameter portion of one end of the nut 1 having the ball rolling groove 2 on the inner peripheral surface, and an annular lubrication is formed on the counterbore 23. The inner diameter portion of the inner end surface of the lubricant containing body 21 that press-fits the agent containing body 21 and makes the inner peripheral portion of the lubricant containing body 21 contact the outer peripheral surface of the screw shaft 3 and further contacts the bottom of the counterbore portion 23. In addition, a seal portion 22 that is in pressure contact with the ball rolling groove 5 along the ball rolling groove 5 of the screw shaft 3 is integrally formed. Due to the relative rotation between the nut 1 and the screw shaft 3, the ball 6 rolls between the nut 1 and the ball rolling grooves 2 and 5 of the screw shaft 3. With this structure, the lubricant of the lubricant-containing body 21 is applied to the outer peripheral surface of the screw shaft 3 and the ball rolling groove 5, and the dust prevention between the screw shaft 3 and the nut 1 is ensured by the seal portion 22.

JP 2000-81103 A JP-A-10-265794 Japanese Patent Laid-Open No. 08-277900

  In the conventional ball screw device that supplies the lubricant by bringing the inner peripheral surface of the lubricant-containing body into contact with the screw shaft, the entire inner peripheral surface of the lubricant-containing body is in direct contact with the screw shaft. Due to the relative rotation of the screw shaft, frictional heat is generated on the sliding contact surface between the lubricant-containing body and the screw shaft. The frictional heat becomes particularly high under high-speed and high-load use conditions, and the lubricant is dissolved and excessively discharged. Oil shortage occurs, and as a secondary factor, there is concern about material deterioration such as sag of the lubricant-containing body and dissolution.

  Also in the ball screw device of Patent Document 3, the inner peripheral surface of the lubricant-containing body 21 and the entire region of the seal 22 formed integrally with the lubricant-containing body 21 are the outer peripheral surface of the screw shaft 3 and the ball rolling. Since it is in sliding contact with the groove 5, a large amount of heat is generated due to friction, which may cause the same problem as described above.

  Therefore, the present invention can reduce the heat generation due to friction of the lubricant-containing body that comes into contact with the screw shaft, and can suppress the heat of friction even in high-speed, high-load applications and can stably supply a lubricant for a long time. An object is to provide an apparatus.

The present invention
In a ball screw device having a screw shaft and a nut screwed with the screw shaft via a plurality of balls,
A lubricant-containing body that supplies a lubricant in contact with the outer peripheral surface of the screw shaft;
Provided is a ball screw device, wherein a concavo-convex portion for reducing an area of the contact portion is formed in a contact portion of the lubricant-containing body that contacts the outer peripheral surface of the screw shaft.

  According to the present invention, by forming the uneven portion on the inner peripheral surface that contacts the screw shaft of the lubricant-containing body, the surface pressure of the contact surface is reduced, heat generation due to friction on the contact surface is reduced, high speed, A ball screw device capable of supplying a stable lubricant for a long period of time can be obtained even for a ball screw device for heavy loads.

FIG. 1 is a partial longitudinal sectional view of a ball screw device according to an embodiment of the present invention. FIG. 2 is an exploded longitudinal sectional view of the lubricant supply unit. 3A is a perspective view showing the lubricant-containing body, FIG. 3B is a view showing the outer end surface of the lubricant-containing body, and FIG. 3C is a view showing the garter spring. It is. FIG. 4 is an exploded perspective view of a first modification of the lubricant-containing body. FIG. 5 is an exploded perspective view of a third modification of the lubricant-containing body. FIG. 6 is a partial longitudinal sectional view showing a ball screw device having a conventional lubricant-containing body.

  Next, embodiments of the present invention shown in the drawings will be described in detail.

  Referring to FIGS. 1 and 2, in the ball screw device 20 according to the present embodiment, a ball rolling groove 2 is spirally formed on the inner peripheral surface of a cylindrical nut 1 and inserted into the nut 1. A spiral ball rolling groove 5 is formed on the outer peripheral surface of the screw shaft 3 in a form corresponding to the rolling groove 2 of the nut 1, and a large number of balls 6 are interposed between these ball rolling grooves 2, 5. It is disguised. A ball return tube 7 is provided on the outer side of the nut 1, and both ends of the ball return tube 7 communicate with both ends of the ball rolling groove 2 on the nut side. As the nut 1 and the screw shaft 3 move relative to each other, each ball 6 moves in the nut 1 in a direction opposite to the direction in which the nut 1 moves relative to the screw shaft 3 while spirally moving in the nut 1. Then, it is scooped up from the groove end of the ball rolling groove 2 of the nut 1 to the ball return tube 7 and moves in the ball return tube 7 in the relative movement direction of the nut 1, and again from the other end of the nut side ball rolling groove 2. The ball 1 enters the ball rolling grooves 2 and 5 between the nut 1 and the screw shaft 3 and rolls in the nut 1 in the direction opposite to the relative movement direction of the nut 1 to repeat this circulation.

  An end portion of the nut 1 is provided with a lubricant supply portion 15 for supplying a lubricant to the screw shaft 3 in order to lighten rolling of the ball 6 and reduce wear of the ball rolling grooves 2 and 5. ing. The lubricant supply unit 15 includes a lubricant containing body 8, a seal member 11, and a cylindrical housing 9 that accommodates them, which will be described later. An annular body portion 10 having a slightly smaller diameter than the outer peripheral portion of the housing 9 is integrally formed at an end portion of the housing 9 on the nut 1 side, and the annular body portion 10 is inserted into a counterbore portion of the nut 1 end portion in an inlay shape. The housing 9 is fixed to the nut 1 by a set screw (not shown) that is screwed in from the radially outer side of the nut 1. In addition, attachment of the housing 9 to the nut 1 is not limited to the above-mentioned form, Other well-known means may be sufficient.

  An annular seal member 11 made of, for example, an elastomer is fitted into the housing 9 so as to be in contact with the bottom of the housing 9, and is fixed by a set screw 12 that is screwed from the outside in the radial direction of the housing 9. In this state, the inner diameter portion of the seal member 11 is brought into pressure contact with the outer diameter portion of the screw shaft 3 and the ball rolling groove 5 to provide a dustproof and sealing action. Of course, the seal member 11 may be formed of an elastic body other than the elastomer.

  The lubricant supply unit 15 according to the present invention will be described in more detail with reference to FIGS. 1 and 2 and FIG. 3. The housing 9 is in contact with the outer end surface of the seal member 11, that is, the end surface opposite to the nut 1. The lubricant containing body 8 is accommodated therein. The outer end surface of the lubricant-containing body 8, that is, the end surface 8 a opposite to the nut 1, is restrained by a locking pin 16 inserted from the radially outer side into the outer peripheral portion of the housing 9.

  As the lubricant-containing body 8, a lubricant-containing polymer as described in Patent Document 1 or Patent Document 2 described above is effectively employed. Examples of the lubricant-containing polymer applied to the present invention include a synthetic resin selected from a group of polyolefin resins having basically the same chemical structure such as polyethylene, polypropylene, polybutylene, polymethylpentene, etc. Paraffinic hydrocarbon oil such as poly-α-olefin oil, naphthenic hydrocarbon oil, mineral oil, ether oil such as dialkyldiphenyl ether oil, ester oil such as phthalate ester, etc. The material prepared by mixing is heated to a temperature above the melting point of the resin, plasticized, and then cooled to solid form. In some cases, the lubricant is pre-oxidized, rust inhibitor, anti-wear. Various additives such as an agent, a foam remover, and an extreme pressure agent can also be added.

  As clearly shown in FIGS. 3 (a) and 3 (b), the lubricant-containing body 8 is composed of two semicylindrical bodies facing each other, and a circumferential concave portion is formed at a substantially central portion of the outer circumferential surface of each semicylindrical body. A groove 8b is formed. A cylindrical lubricant-containing body 8 is obtained by fitting the garter springs 17 (FIG. 2, FIG. 3C) into the outer circumferential concave groove 8 b by abutting the semicylindrical bodies. This garter spring 17 pressurizes the lubricant-containing body 8 radially inward in addition to combining the two semi-cylindrical bodies of the lubricant-containing body 8, thereby causing more effective lubricant oozing. It has a function.

  When such a lubricant-containing body 8 is accommodated in the housing 9, the inner peripheral surface of the lubricant-containing body 8 comes into contact with the outer peripheral surface of the screw shaft 3, and the relative rotation between the nut 1 and the screw shaft 3 occurs. Then, the lubricant exudes from the lubricant-containing body 8, and the lubricant is supplied to the screw shaft 3.

  Here, the lubricant-containing body 8 has an uneven portion formed on the inner peripheral surface 8c thereof. In the present embodiment, the concavo-convex portion is composed of a knurled surface 18 formed by subjecting the inner peripheral surface 8c of the lubricant-containing body 8 to twill (lattice) knurling. Since the convex portion of the knurled surface 18 contacts the outer peripheral surface of the screw shaft 3 and the concave portion of the knurled surface 18 does not contact the screw shaft 3, the contact area of the lubricant containing body 8 that contacts the outer peripheral surface of the screw shaft 3. Can be reduced as compared with the case where the concave and convex portions are not formed on the inner peripheral surface 8c of the lubricant-containing body 8. Thereby, the frictional force between the lubricant containing body 8 and the screw shaft 3 is reduced, and heat generation due to frictional contact is reduced. For this reason, even in a ball screw device that normally generates a large amount of frictional heat such as high speed and high load, oil runs out due to excessive exudation of the contained lubricant due to temperature rise, deterioration of the material containing the lubricant-containing body 8, dissolution, etc. Is prevented, and a stable supply of lubricant over a long period of time becomes possible. The knurled surface 18 is not limited to the twill, but may be flat (striped) or the like.

(First modification)
The uneven portion formed on the inner peripheral surface 8c of the lubricant-containing body 8 is not limited to the knurled surface as described above, and does not impair the leaching and leaching of the lubricant of the lubricant-containing body 8 with respect to the screw shaft 3. Thus, any material can be used as long as the substantial contact area with the screw shaft 3 is reduced to suppress frictional heat generation. For example, as a first modification of the lubricant-containing body 8, the uneven portion of the inner peripheral surface 8c may be configured with a dimple processed surface (not shown). In this example, a plurality of dimple-shaped recesses, for example, a plurality of small hemispherical recesses formed on the surface of a golf ball are formed on the inner peripheral surface 8c of the lubricant-containing body 8 (not shown). By forming the lubricant-containing body 8 into two semi-cylindrical bodies, it is easy to form such a dimple processed surface.

(Second modification)
FIG. 4 is an exploded perspective view of a second modified example of the lubricant-containing body 8. In this case, at least one concave groove 8d extending in the circumferential direction as an uneven portion on the inner peripheral surface 8c of the lubricant-containing body 8, In this modification, two concave grooves 8d are formed. The concave groove 8d is not in direct contact with the screw shaft 3, thereby reducing the contact area of the lubricant-containing body 8 in contact with the outer peripheral surface of the screw shaft 3 and suppressing the generation of large frictional heat.

(Third Modification)
FIG. 5 is an exploded perspective view of a third modification of the lubricant containing body 8. In this case, at least one protrusion 8e extending in the circumferential direction as an uneven part is formed on the inner peripheral surface 8c of the lubricant-containing body 8, and in this modification, one protrusion 8e is formed. This protrusion 8e is in contact with the outer peripheral surface of the screw shaft 3, and is not slidably in contact with the outer peripheral surface of the screw shaft 3 at portions other than the protrusion 8e. Reduction and suppression of temperature rise are achieved. Of course, a plurality of ridges 8e may be provided, and the inner peripheral surface of the ridges 8e is formed to have a smooth wide width in order to bring about effective leaching of the lubricant.

  Also in the case of the first to third modifications described above, the cylindrical lubricant-containing body 8 is composed of two semi-cylindrical bodies, and an annular groove 8b for mounting the ring-shaped garter spring 17 is formed on the outer periphery thereof. ing. The spring 17 tightens the lubricant-containing body 8 inward in the radial direction, and more effective lubricant exudation is performed. Such two semi-cylindrical bodies facilitate the uneven processing on the inner peripheral surface of the lubricant-containing body 8, but in some cases, particularly in the case of the second and third modifications, the two semi-cylindrical bodies. It is possible to adopt a form that does not. Moreover, although the example which gives a knurl process, a dimple process, a ditch | groove formation, and a protrusion formation to the internal peripheral surface 8c as an uneven | corrugated | grooved part of the lubricant containing body 8 was shown, the form which combined these may be sufficient. The material, shape, arrangement on the screw shaft 3, arrangement and number of the uneven portions of the lubricant-containing body 8 are not particularly limited as long as the object is achieved. The uneven portion of the inner peripheral surface 8c of the lubricant-containing body 8 is for lowering the contact pressure with the screw shaft 3 of the lubricant-containing body 8 and suppressing the increase in frictional heat. A plurality of concave grooves or ridges extending in the axial direction may be used. Moreover, you may comprise the uneven | corrugated | grooved part of the internal peripheral surface 8c of the lubricant containing body 8 with the embossing surface which provided many protrusion uniformly on the internal peripheral surface 8c.

  The ball screw device 20 shown in FIG. 1 uses the ball return tube 7 as a circulation form of the ball 6, but other ball circulation methods such as an end deflector type, a top type, an end cap type, etc. In addition, the present invention can be similarly applied.

DESCRIPTION OF SYMBOLS 1 Nut 2, 5 Ball rolling groove 3 Screw shaft 6 Ball 7 Ball return tube 8 Lubricant containing body 9 Housing 11 Seal member 15 Lubricant supply part 17 Garter spring 18 Knurled surface 20 Ball screw device

Claims (8)

In a ball screw device having a screw shaft and a nut screwed with the screw shaft via a plurality of balls,
A lubricant-containing body that supplies a lubricant in contact with the outer peripheral surface of the screw shaft;
A ball screw device, wherein an uneven portion for reducing an area of the contact portion is formed in a contact portion of the lubricant-containing body that contacts the outer peripheral surface of the screw shaft. The lubricant-containing body has a cylindrical shape,
The screw shaft is slidably inserted into the lubricant-containing body,
The ball screw device according to claim 1, wherein the uneven portion is formed on an inner peripheral surface of the lubricant-containing body.   The ball screw device according to claim 2, wherein the uneven portion of the lubricant-containing body is formed by knurling the inner peripheral surface.   4. The ball screw device according to claim 2, wherein the uneven portion of the lubricant-containing body is formed by performing dimple processing on the inner peripheral surface.   The ball screw device according to any one of claims 2 to 4, wherein the uneven portion of the lubricant-containing body is formed with a groove portion extending in a circumferential direction on the inner peripheral surface. .   The ball screw according to any one of claims 2 to 5, wherein the uneven portion of the lubricant-containing body is formed with a protrusion extending in a circumferential direction on the inner peripheral surface. apparatus.   The lubricant-containing body is composed of two semi-cylindrical bodies, and the two half-cylindrical bodies are combined into a cylindrical shape by mounting an annular garter spring on the outer periphery of the lubricant-containing body. The ball screw device according to any one of claims 2 to 6.   The ball screw device according to any one of claims 2 to 7, wherein an annular seal member that seals an outer periphery of the screw shaft is provided adjacent to the lubricant-containing body.

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