JP2582917Y2 - Ball screw - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw used for machine tools, industrial robots, semiconductor manufacturing equipment and the like.

[0002]

2. Description of the Related Art In a ball screw, a plurality of balls are passed through a spiral circulation path formed between an inner spiral groove provided on an outer peripheral surface of a screw shaft and an outer spiral groove provided on an inner peripheral surface of a ball nut. The power is transmitted between the screw shaft and the ball nut through the rolling circulation of the ball, but the ball rolls with sliding due to the combined force in the rotation direction and the axial direction. Therefore, at the contact portion between the ball and the two spiral grooves, rolling friction and sliding friction occur simultaneously. Further, when the balls come into contact with each other, the rotation directions of the adjacent balls are reversed, so that the relative sliding speed between the balls is twice that of a single ball, and a large frictional force is generated. For these reasons, lubrication is a particularly important factor in a ball screw. Normally, grease is often used for lubricating the ball screw, but oil lubrication may be used in some cases.

[0003]

[Problems to be Solved by the Invention] With the recent tendency to increase the speed, when the ball screw is rotated at a high speed, the grease in the ball nut is pushed out of the ball circulation path, so-called grease pushing phenomenon may occur. is there. If the amount of grease pushed out is large, lubrication may be insufficient and adverse effects such as accelerated wear of the screw shaft and ball nut may be caused. Also,
With the diversification of use environments, use in the presence of foreign substances such as dust, cutting chips, and dust is increasing, and these foreign substances may adhere to the screw shaft and enter the ball nut. If a foreign matter enters the ball nut, the ball may enter into a gap between the ball and the spiral groove, which may shorten the life of the ball nut.

[0004] As a means for preventing the above-mentioned adverse effects, a sealing device is conceivable. However, it is difficult to completely prevent adverse effects such as extrusion of grease and intrusion of foreign matter by the sealing device. This is true not only when a sealing device having a general configuration is used, but also when a sealing device is manufactured with high precision. That is, the sealing device seals the inside of the ball nut by fitting the sealing member into the inner spiral groove of the screw shaft. However, as shown in FIG. 2, in the case of a ground ball screw,
A grinding relief groove 1a1 is provided at the bottom of the inner spiral groove 1a of the screw shaft 1.
(Usually provided to prevent bending during grinding), and even if the seal member is manufactured with high precision and is closely attached to the inner spiral groove 1a, the grinding escape groove 1a1
This inevitably creates a gap.

On the other hand, in the case of oil lubrication, the problem of grease extrusion does not occur, but if the lubrication interval is long, lubrication may still be insufficient. For example, according to oil drop lubrication or the like, an oil film is formed when oil is dropped, but if the interval between drops is long, the oil film breaks, and if the operation is continued as it is, the above-described adverse effects may occur. There is. A similar problem also occurs when the machine is stopped for a long time for some reason and then restarted without refueling.

[0006] The present invention is intended to improve the lubricating and sealing properties of a ball screw with a relatively simple structure, thereby ensuring optimum operation particularly under high-speed rotation or in a severe environment.

[0007]

According to a first aspect of the present invention, there is provided a ball screw comprising: a screw shaft having an inner spiral groove on an outer peripheral surface; a ball nut having an outer spiral groove on an inner peripheral surface; And a plurality of balls arranged in a helical circulation path formed in (1), wherein a solid lubricant containing polyolefin is fixed to at least one of the inner and outer spiral grooves.

[0008] The ball screw according to claim 2 is a screw shaft having an inner spiral groove formed on an outer peripheral surface, a ball nut having an outer spiral groove formed on an inner peripheral surface, and a spiral formed between the inner and outer spiral grooves. A plurality of balls arranged in the circulation path, and a seal member provided at the end of the ball nut and having a fitting portion fitted to the inner spiral groove, wherein at least one of the inner and outer spiral grooves A solid lubricant containing polyolefin is fixed to the inner spiral groove.

The ball screw according to claim 3 is the ball screw according to claim 2, having a grinding relief groove at the bottom of the inner spiral groove, wherein the grinding relief groove of the inner spiral groove includes a polyolefin-containing solid lubricant. Is filled and fixed.
Here, the “grinding relief groove” refers to a groove provided to prevent the screw shaft from being bent by grinding heat when the inner spiral groove of the screw shaft is ground by a grinding wheel.

[0010] The ball screw according to the fourth aspect is a screw shaft formed with an inner spiral groove on an outer peripheral surface, a ball nut provided with an outer spiral groove on an inner peripheral surface, and a spiral formed between the inner and outer spiral grooves. A plurality of balls arranged in the circulation path, and a seal member provided at the end of the ball nut and having a fitting portion fitted to the inner spiral groove, wherein at least one of the inner and outer spiral grooves A solid lubricant containing polyolefin is fixed to the outer spiral groove.

A ball screw according to a fifth aspect of the present invention is the ball screw according to the fourth aspect, wherein a grinding relief groove is provided at a bottom portion of the outer spiral groove, wherein a solid lubricant containing polyolefin is filled in the grinding relief groove of the outer spiral groove. Filled and fixed. Here, the “grinding relief groove” refers to a groove provided to prevent the influence of grinding heat when grinding the outer spiral groove of the ball nut with a grinding wheel.

[0012]

The solid lubricant containing a polyolefin is, for example, a mixture of a polyolefin, a lubricating grease comprising a base oil and a thickener, as described in JP-B-63-23239. So-called plastic grease which has been solidified by heating into a predetermined shape. In some cases, various additives may be added to suppress bleeding of oil. When the ball rolls and circulates along the inner and outer spiral grooves, by contacting the solid lubricant fixed to at least one of the raceway grooves, the lubricant supplied from the solid lubricant is applied to the surface of the ball. Transforms to form an oil film.

In the ball screw provided with the seal member, the clearance between the fitting portion of the seal member and the inner spiral groove can be reduced by fixing a solid lubricant at least to the inner spiral groove. Therefore, in addition to lubricity, sealability can be improved.

In particular, the solid lubricant is filled and fixed in the grinding relief groove of the inner raceway groove, so that the clearance formed by the grinding relief groove is closed by the solid lubricant, so that the sealing performance is further improved. Improvement can be achieved.

When the outer spiral groove has a grinding relief groove, a solid lubricant is filled and fixed in the grinding relief groove, so that the clearance formed by the grinding relief groove is solid lubricant. As a result, the sealing performance can be further improved.

[0016]

Embodiments of the present invention will be described below.

As shown in FIG. 1, a plurality of balls 3 are arranged between an inner spiral groove 1a provided on the outer peripheral surface of the screw shaft 1 and an outer spiral groove 2a provided on the inner peripheral surface of the ball nut 2. ing. Further, seal members 5 are mounted on both ends of the ball nut 2, and a fitting portion 5a provided on the inner diameter portion of the seal member 5 is fitted into the inner spiral groove 1a to seal the inside of the ball nut 2. I have. When the screw shaft 1 (or the ball nut 2) rotates, the rotational power is transmitted to the ball nut 2 (or the screw shaft 1) via the ball 3, and the ball nut 2 (or the screw shaft 1) moves in the axial direction. .

As shown in FIG. 2 in an enlarged manner, a grinding relief groove 1 a 1 remains at the bottom of the inner spiral groove 1 a of the screw shaft 1. The grinding relief groove 1a1 is provided to prevent the screw shaft 1 from being bent when grinding the inner spiral groove 1a, and is in an unground state. Therefore, its surface is rougher than the inner spiral groove 1a that has been ground. In this embodiment, a solid lubricant containing a polyolefin, for example, plastic grease 6 is filled and fixed in the grinding relief groove 1a1. The plastic grease 6 is, for example, ultrahigh molecular weight polyolefin 1 to 95.
The mixture is obtained by heating and solidifying a mixture of at least 30% by weight, preferably at least 30% by weight, and 99 to 5% by weight of soap or non-soap thickened lubricating grease. Alternatively, an additive for suppressing bleeding of oil may be added to the above components in an amount of 1 to 50% by weight (for details, see JP-B-63-23239).
Reference). The plastic grease 6 is fixed over the entire length of the screw shaft 1.

When the ball 3 rolls and circulates in the inner spiral groove 1a, the ball 3 comes into contact with the plastic grease 6 fixed to the grinding relief groove 1a1, whereby a lubricating oil film of the plastic grease 6 is formed on the surface of the ball 3. This ball screw can be used in combination with ordinary grease lubrication or oil lubrication, or only with plastic grease 6. The plastic grease 6 acts as a lubricant supply source for compensating for insufficient lubrication due to grease extrusion when used in combination, and as a lubricant supply source when used alone. Further, by filling and fixing the plastic grease 6 in the grinding relief groove 1a1, the clearance between the grinding relief groove 1a1 and the sealing member 5 formed by the grinding relief groove 1a1 is closed, so that the sealing performance is improved. In addition, the grinding relief groove 1a is in an unground state, and its surface is appropriately rough, so that the plastic grease 6 has a high fixing property and does not easily fall off. Therefore, by filling and fixing the plastic grease 6 into the grinding relief 1a1, the lubricating property and the sealing property can be improved, and at the same time, due to the high fixing property of the plastic grease 6, these effects are long-term. Has the advantage of being maintained over time. This is the same even when the plastic grease 6 is fixed to the entire surface of the inner spiral groove 1a including the grinding relief groove 1a1.

This ball screw has a structure in which the fitting portion 5a of the seal member 5 is brought into close contact with the inner spiral groove 1a (the fitting clearance between the two is zero, and the clearance is now minus).
By doing so, it is possible to further improve the sealing performance, but in this case, the tip of the fitting portion 5a comes into contact with the plastic grease 6 to reduce friction, so that the sealing member 5 The adverse effects such as accelerated wear and increased torque hardly occur. As a means for bringing the fitting portion 5a into close contact with the inner spiral groove 1a, in addition to manufacturing the sealing member 5 with high precision, for example, the sealing member 5 is divided into a plurality of portions in the axial direction, and each divided portion is formed in the inner diameter direction. (See Japanese Utility Model Application No. 4-45435 and Japanese Utility Model Application No. 4-45436 filed by the present applicant).

As described above, in this embodiment, the plastic grease 6 is fixed to the inner spiral groove 1a, which is also fixed to the grinding relief groove 1a1, but in addition to this, the outer spiral groove 2a of the ball nut 2 is also fixed. The plastic grease 6 may be fixed. Lubricity can be further improved. Alternatively, the plastic grease 6 may be fixed only to the outer spiral groove 2a of the ball nut 2. The configuration in which the plastic grease 6 is fixed only to the outer spiral groove 2a improves lubrication, but has little relevance to improvement in sealing. However, a grinding relief groove 1 is formed in the outer spiral groove 2a.
In the case where the same relief groove as that of a1 is formed and the plastic grease 6 is fixed thereto, the sealing performance is improved. Further, when the sealing property is not particularly required, a configuration in which the sealing member 5 is not attached may be adopted. Further, the present invention can be applied to a rolled ball screw or the like, regardless of the type of the ball screw.

[0022]

According to the present invention, a solid lubricant containing polyolefin is fixed to at least one of the inner spiral groove of the screw shaft and the outer spiral groove of the ball nut. By acting as a lubricant replenishment source or a lubricant supply source by contact with the lubrication, shortage of lubrication does not occur even under high-speed rotation, and a good operating state can be maintained for a long time. In the ball screw provided with the seal member, the clearance between the fitting portion of the seal member and the inner spiral groove can be reduced by fixing the solid lubricant to at least the inner spiral groove. Therefore, in addition to lubricity, sealability can be improved. In particular, by adopting a configuration in which the solid lubricant is filled and fixed in the grinding relief groove of the inner raceway groove, the clearance formed by the grinding relief groove is closed by the solid lubricant, so that the sealing performance is further improved. be able to. Also, the grinding relief groove is not ground,
Since the surface roughness is appropriately rough, the solid lubricant has high fixability, and good lubricity and sealability are maintained for a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional view (FIG. A) showing an embodiment of the present invention, and an enlarged sectional view (FIG. B) around the inner and outer spiral grooves in FIG.

FIG. 2 is an enlarged cross-sectional view around an inner / outer spiral groove according to a conventional configuration.

[Explanation of symbols]

 Reference Signs List 1 screw shaft 1a spiral groove 1a1 grinding relief groove 2 ball nut 2a spiral groove 3 ball 6 plastic grease

Continuation of front page (56) References JP-A-52-40267 (JP, A) JP-A-62-283252 (JP, A) JP-A-4-302709 (JP, A) JP-A-3-194246 (JP) JP-A-4-236845 (JP, A) JP-A-3-149448 (JP, A) JP-A-6-6794 (JP, U) JP-A-6-6795 (JP, U) JP-A 62-134957 (JP, U) JP-A-59-164861 (JP, U) JP-A-58-60048 (JP, U) JP-A-61-64523 (JP, U) JP-B 63-23239 (JP, U) B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) F16H 25/22 F16H 25/24

Claims (5)

(57) [Scope of request for utility model registration] A screw shaft provided with an inner spiral groove on an outer peripheral surface;
A ball nut having an outer spiral groove on the inner peripheral surface;
In those having a plurality of balls disposed in a spiral-shaped circulation path formed between the outer helical groove, on at least one of said inner and outer helical groove, <br/> solid lubricant containing Po Li olefin A ball screw having a material fixed thereto. 2. A screw shaft provided with an inner spiral groove on an outer peripheral surface,
A ball nut having an outer spiral groove on the inner peripheral surface;
A plurality of balls arranged in a spiral circulation path formed between the outer spiral grooves, and a seal member mounted on an end of the ball nut and provided with a fitting portion that fits into the inner spiral groove. in those having, at least on the inner helical groove of said inner and outer helical groove, a solid containing Po Li olefin lubricating
A ball screw having a material fixed thereto. 3. A ball screw of claim 2 having a grinding relief grooves at the bottom of the inner helical groove, said grinding relief grooves of the inner spiral groove, filling the solid lubricant containing Po Li olefin A ball screw characterized by being fixed. 4. A screw shaft provided with an inner spiral groove on an outer peripheral surface,
A ball nut having an outer spiral groove on the inner peripheral surface;
A plurality of balls arranged in a spiral circulation path formed between the outer spiral grooves, and a seal member mounted on an end of the ball nut and provided with a fitting portion that fits into the inner spiral groove. in those having, at least on the outer helical groove of said inner and outer helical groove, a solid containing Po Li olefin lubricating
A ball screw having a material fixed thereto. 5. A ball screw of claim 4 having a grinding relief grooves at the bottom of said outer helical groove, said grinding relief grooves of said outer helical groove, filling the solid lubricant containing Po Li olefin A ball screw characterized by being fixed.