JPH11335657A - Oil-containing seal device for ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil-containing seal device for a ball screw, capable of normally sliding for a sliding distance of at least >=60 km, preferably >=1,100 km, under use conditions at room temperature. SOLUTION: This oil-containing seal device has a seal 6 which is placed between a screw shaft 1 for ball screws and a ball nut 3 and which slides on the screw shaft 1. The oil-containing seal device comprises an oil-containing resin molded product having an oil-oozing amount A of 2-10 wt.%, when left at room temperature for 7 days. The oil-oozing amount A is expressed by the following equality: the oil-oozing amount A (wt.%)= [(the weight of the seal device before left) - (the weight after left)]/(the weight of the seal device before left)} × 100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oil-impregnated sealing device for a ball screw.

[0002]

2. Description of the Related Art Referring to FIG. 1, a general ball screw includes a screw groove 2 formed on an outer peripheral surface of a screw shaft 1,
A plurality of balls 5 are interposed between thread grooves 4 formed on the inner peripheral surface of the ball nut 3, and the rotational power of the screw shaft 1 or the ball nut 3 is transmitted through the ball 5 to the ball nut 3 (or the screw 3). This is transmitted to the shaft 1) to move the ball nut 3 in the axial direction.

[0003] A lubricant such as lubricating grease is applied to the inside of the ball nut 3 to reduce the coefficient of friction with the screw shaft 1. However, a lubricant such as lubricating grease does not contaminate the periphery of the ball screw. A labyrinth-type seal corresponding to the shape of the thread surface of the screw shaft 1 is additionally provided.

The seal seals both ends of the ball nut 3 and the thread groove 2 of the screw shaft 1, and a plurality of arc-shaped seal pieces are arranged at intervals in the circumferential direction so as to surround the screw shaft 1. There are also embodiments. Then, the arc-shaped seal piece is screwed into the screw hole 8 formed on the outer periphery of the ball nut 3 and pressed against the screw surface by the elastic force of the spring 7a, or attached to the inner periphery of the ball nut 3. It is elastically pressed against the outer periphery of the screw shaft 1 by a garter spring (not shown) or the like.

A ball screw sealing device disclosed in Japanese Utility Model Laid-Open No. 4-83704 or Japanese Utility Model Laid-Open No. 6-47762 is similar to the above-described labyrinth type sealing device, except that 1 to 95% by weight of polyethylene powder and grease are used. 99 ~
By heating the mixture with 5% by weight to a predetermined temperature,
An oil-impregnated sealing device comprising an oil-impregnated resin molded product solidified in a state in which lubricating oil or lubricating grease is dispersed in a synthetic resin.

In such an oil-impregnated sealing device for a ball screw, when torque is transmitted from the ball screw, the lubricating oil retained in the plastic structure gradually exudes to form an oil film on the friction surface, and the sliding contact portion of the screw shaft is formed. To reduce frictional resistance.

[0007]

However, the conventional oil-impregnated sealing device for a ball screw as described above is not yet sufficiently satisfactory in terms of durability. When evaluated, an abnormality may occur at a sliding distance of less than 360 km at room temperature.

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems and provide an oil-impregnated sealing device for a ball screw capable of lubricating at least a sliding surface of at least 360 km or more under normal use conditions at room temperature. More preferably, an object of the present invention is to provide an oil-impregnated sealing device for a ball screw which can lubricate a sliding distance of 1100 km or more at room temperature without any abnormality.

[0009]

According to the present invention, there is provided an oil-impregnated sealing device having a seal surface interposed between a screw shaft of a ball screw and a ball nut and slidably contacting the screw shaft. When this oil-impregnated sealing device is allowed to stand still at room temperature (normal room temperature, usually 10 to 35 ° C.), the amount of oil seepage A represented by the following formula
Is an oil-impregnated sealing device for a ball screw made of an oil-impregnated resin molded product of 2 to 10% by weight. The oil bleeding amount A can be evaluated by an oil bleeding amount when the oil-containing resin molded body is allowed to stand at room temperature for 7 days (168 hours).

The amount of oil seeping out A (% by weight) = {(weight before standing−weight after standing) / weight before standing} × 100 In the above oil-impregnated sealing device for a ball screw, the oil-impregnated resin molded body is Alternatively, an oil-impregnated resin molded product solidified in a state in which a lubricating oil or lubricating grease is dispersed in a synthetic resin can be employed.

In the above-described oil-impregnated sealing device for a ball screw, the oil-impregnated resin molded product has an average molecular weight (Mn).
An oil-impregnated resin molded product in which lubricating oil or lubricating grease is dispersed in 1 × 10 ^{6 to} 5 × 10 ⁶ ultrahigh molecular weight polyolefin and solidified can be employed.

In the above-described oil-impregnated sealing device for a ball screw, an oil-impregnated resin molded article in which a porous synthetic resin molded article is impregnated with lubricating oil or lubricating grease can be employed.

The oil-impregnated sealing device for a ball screw according to the present invention, which is constructed as described above, is formed of an oil-impregnated resin molded body that limits the amount of oil seeping out, so that the lubrication is stable and the durability of the seal is remarkably improved. Specifically, an oil-impregnated sealing device for a ball screw exhibiting a durability of a sliding distance of at least 360 km or 1100 km or more under a use condition at room temperature.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An oil-impregnated resin molded article used in the invention according to each of the claims of the present application is obtained by solidifying a lubricant or lubricating grease in a state of being dispersed in a synthetic resin, or a porous body of lubricating oil or lubricating grease. Impregnated into a high quality synthetic resin molded article.

As the synthetic resin, a thermoplastic resin or a thermosetting resin can be used. As the thermoplastic resin, polyolefin, polyamide, polyacetal, polycarbonate, polybutylene terephthalate,
Examples thereof include polyphenylene sulfide, polyether sulfone, polyether ketone, polyamide imide, and polystyrene. Examples of the thermosetting resin include a phenol resin, a urea resin, a melamine resin, an alkyd resin, an unsaturated polyester resin, an epoxy resin, a diallyl phthalate resin, a polyurethane resin, and a silicone resin.

Among the thermoplastic resins, examples of the polyolefin resin include polyethylene resin, polypropylene resin, and polybutene resin. In particular, powder made of polyethylene, polypropylene, polybutene or a copolymer thereof, or a single polymer thereof is used. It is preferable to use an ultra-high molecular weight polyolefin powder composed of the mixed powder because the degree of oil separation and the amount A of oil ooze can be easily adjusted.

Such an ultrahigh molecular weight polyolefin powder has an average molecular weight (Mn) of 1 as measured by a viscosity method.
× 10 ^{6 to} 5 × 10 ⁶ , preferably with an average particle size of 10
３０30 μm powder. Such ultra-high molecular weight polyolefin powder, when mixed with lubricating oil or lubricating grease and heated above the gelling temperature of the resin, forms a gel composition that hardly flows while maintaining a stable dispersed state, and is formed. After that, the ball screw seal exhibits the required rigidity and oil retention (oil separation).

When the lubricant to be mixed with the resin powder is a grease which is semi-solid at room temperature, the heating temperature of the mixture is adjusted to a temperature higher than the gel point of the resin powder and lower than the drop point of the grease. This is preferable for the homogeneity of the oil-containing resin molded article, that is, for the uniform dispersion of the lubricant.

The compounding ratio of the ultrahigh molecular weight polyolefin in the oil-containing resin molded product is 94 to 1% by weight, and the mechanical strength such as the degree of oil separation, toughness and hardness of the molded product composition is adjusted by the compounding amount. it can. That is, as the blending amount of the ultra-high molecular weight polyolefin increases, the molded body in which the lubricating oil or lubricating grease is dispersed and held at a predetermined temperature becomes harder, and the oil bleeding amount A (% by weight) represented by the above formula decreases. Commercially available ultra-high molecular weight polyolefin powders include Miperon manufactured by Mitsui Chemicals, Inc.

When a porous synthetic resin molded body is employed as the oil-containing resin molded body, a hardly meltable synthetic resin powder such as a polyimide resin is temporarily molded and then sintered, or the fusible synthetic resin is foamed. A well-known method such as forming and forming a continuous ventilation hole can be adopted.

The lubricating oil used in the invention according to each claim of the present application is not particularly limited in its kind, and may be, for example, a mineral oil, a synthetic hydrocarbon oil, a polyalkylene glycol oil, a diester oil, a polyol ester oil, Well-known lubricating oils such as phosphate ester oil, polyphenyl ether oil, silicone oil, and fluorine oil can be used.

The type of the lubricating grease used in each invention is not particularly limited, and the base oil used as the lubricating oil is soap or non-soap (for example, Benton, silica airgel, sodium terephthalamate). , Urea, polytetrafluoroethylene, etc.)
The lubricating grease thickened in the above was used.

Specific examples of the grease in the material system of the thickener-base oil are as follows. That is, lithium soap-diester grease, lithium soap-mineral oil grease, sodium soap-mineral oil grease, aluminum soap-mineral oil grease, lithium soap-diester mineral grease, non-soap-diester grease, non-soap-mineral oil Greases such as grease, non-soap-polyol ester-based grease, lithium soap-polyol ester-based grease, lithium soap-silicone oil-based grease, and PTFE-fluoro oil-based grease are exemplified.

The ball screw in the invention according to each claim of the present application is a ball screw in which the ball nut, the rolling friction surface, the sliding friction surface of the screw shaft, and the ball constituting the component are formed of a well-known material. (Eg SU
S440C), metal materials such as tungsten-based high-speed tool steel (eg, SKH4), ceramics (eg, silicon nitride-based, silicon carbide-based, etc.) are constituent materials.

A sealing device according to an embodiment will be described below with reference to the accompanying drawings. As shown in FIG. 1, the ball screw is
A plurality of balls 5 are rotatably interposed between a screw groove 2 formed on an outer peripheral surface of a screw shaft 1 and a screw groove 4 formed on an inner peripheral surface of a ball nut 3. The rotational power of the ball nut 3 is transmitted to the ball nut 3 (or the screw shaft 1) via the plurality of balls 5 and is moved in the axial direction.

The sealing device of the first embodiment mounted on such a ball screw is a device for sealing between the screw shaft 1 and the ball nut 3 at both ends of the ball screw, and is divided into four parts in the circumferential direction. The arc-shaped seals 6 are arranged at intervals along the outer periphery of the screw shaft 1.

The thread-shaped convex portion 6a projecting from the inner periphery of the seal 6 is fitted into the thread groove 2 of the screw shaft 1, and foreign matter enters the inside of the ball screw from the thread groove 2 and lubrication of the lubricant to the outside. Prevents leaks. This ball screw sealing device employs a ball plunger 7 as a means for elastically pressing the seal 6 against the outer peripheral surface of the screw shaft 1, and the compression gap of the spring 7 a reduces the fitting gap between the convex portion 6 a and the screw groove 2. , Zero (nothing at all) or slightly minus (state with interference).

Although the illustrated seal 6 has four arc-shaped seal pieces arranged at intervals in the outer circumferential direction of the screw shaft 1, it may be a ring-shaped seal continuous in the circumferential direction. Alternatively, a partially continuous ring-shaped seal may be used in which one end of the ring-shaped seal is cut off by a predetermined distance in the axial direction and the other end is continuous in the circumferential direction.

[0029]

EXAMPLES The raw materials of the solid lubricant used in Examples and Comparative Examples are collectively shown as follows. (1) Ultra-high molecular weight polyolefin (Mitsui Chemicals: Miperone, average particle size 10 to 30 μm, Mn = 2 × 10 ⁶ ) (2) Low molecular weight polyolefin-containing solid wax (Mitsui Chemicals: Sunwax) (3) Lithium soap-mineral oil-based grease (manufactured by Showa Shell) (4) Polyol ester oil (manufactured by Ciba Geigy: Leo Lube) (5) Synthetic hydrocarbon oil (manufactured by Mitsui Chemicals: Lucant) (6) Mineral oil (manufactured by Mobile Oil: DTE oil) [Examples 1 to 4] The raw materials shown in Table 1 were mixed in the mixing ratio (% by weight) shown in the same table, and this mixture was placed in a mold to obtain 1%.
After heating at 50 ° C. for 30 minutes, the mixture was cooled to room temperature to be solidified, thereby producing a seal device including the seal shown in FIG.

The physical properties of the obtained seal (test piece) were evaluated in terms of seal hardness, oil bleeding amount, and durability test, and the results are shown in Table 1. Seal hardness: Hs (spring hardness) was measured according to JIS K6301 5.2. Oil bleeding amount: A mold was filled with the raw material mixture shown in Table 1, heated at 150 ° C. for 30 minutes, then cooled and solidified to form a cylindrical seal test having a diameter (φ) of 10 mm and a length of 8 mm. Pieces were formed. The test piece was placed at room temperature (10-35
C.) in a laboratory for 7 days (168 hours), and after the elapse of the period, the oil oozing out on the seal surface was wiped off, and the oil oozing amount A was calculated by the following formula.

Oil bleeding amount A (% by weight) = {(weight before standing-weight after standing) / weight before standing} × 100 Seal durability test: The durability of the seal (solid lubricant) is determined by the shaft diameter. (Φ) A ball screw having a lead of 32 mm and a lead of 10 mm was mounted as the seal shown in FIG. 1, and the ball screw was placed in a room (room temperature) and a load of 15 g was supplied without supplying grease.
The screw shaft was rotated at 0 kg at a rotation speed of 2000 rpm, and a sliding distance at which the seal surface could be lubricated without any abnormality was calculated.

[0032]

[Table 1]

Comparative Example 1 In the same manner as in Examples 1 to 4, the raw materials were mixed at the compounding ratios shown in Table 1, and a sealing device comprising the seal shown in FIG. 1 was manufactured.

The physical properties of the obtained seal (test piece) were evaluated with respect to the above-mentioned seal hardness, oil bleeding amount and durability test, and the results are shown in Table 1.

As is clear from the results shown in Table 1, in Comparative Example 1 in which the oil bleeding amount A when left at room temperature for 7 days (168 hours) was less than a predetermined range, the sliding distance in which lubrication was possible was 355.
km, which was not enough for use.

On the other hand, in Examples 1 to 4 in which the oil bleeding amount A is within a predetermined range, the oil-impregnated sealing device for a ball screw can lubricate a sliding distance of 1100 km or more at room temperature without any abnormality. Was something.

For reference, a durability test was performed on a ball screw without a seal (blank test), and the sliding distance between the ball screw and the ball nut was 0.3.
When it reached km, rotation was poor.

[0038]

As described above, the present invention provides an oil-impregnated sealing device for a ball screw made of an oil-impregnated resin molded body having a predetermined amount of oil bleeding A when left at room temperature for a predetermined time. There is an advantage that it is an oil-impregnated sealing device for a ball screw which can lubricate at least a sliding surface of at least 360 km under the conditions of use, and more preferably lubricate a sliding distance of at least 1100 km at room temperature. .

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw shaft 2, 4 Screw groove 3 Ball nut 5 Ball 6 Seal 6a Convex part 7 Ball plunger 7a Spring 8 Screw hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16H 25/24 F16H 25/24 J // C10N 40:34

Claims (5)

[Claims] 1. An oil-impregnated sealing device having a seal surface interposed between a screw shaft of a ball screw and a ball nut and slidably contacting the screw shaft, the oil-impregnated sealing device is represented by the following equation when left at room temperature. An oil-impregnated sealing device for a ball screw, comprising an oil-impregnated resin molded body having an oil exudation amount A of 2 to 10% by weight. Oil bleeding amount A (% by weight) = {(weight before standing−weight after standing) / weight before standing} × 100 2. The oil-impregnated sealing device for a ball screw according to claim 1, wherein the oil oozing amount A is an oil oozing amount when the oil-containing resin molded body is allowed to stand at room temperature for 7 days. 3. The oil-impregnated sealing device for a ball screw according to claim 1, wherein the oil-impregnated resin molded article is an oil-impregnated resin molded article solidified in a state where lubricating oil or lubricating grease is dispersed in a synthetic resin. 4. The oil-containing resin molded article has an average molecular weight (Mn).
2. The oil-impregnated sealing device for a ball screw according to claim 1, wherein the oil-impregnated resin molded article is a solidified oily resin or lubricating grease dispersed in 1 × 10 ^{6 to} 5 × 10 ⁶ ultrahigh molecular weight polyolefin. 5. The oil-impregnated sealing device for a ball screw according to claim 1, wherein the oil-impregnated resin molded article is an oil-impregnated resin molded article obtained by impregnating a porous synthetic resin molded article with lubricating oil or lubricating grease.