JPH10324884A - Solid lubricant and sealing member for ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid lubricant which hardly causes dust when used in bearings for electronic apparatuses and which does not pollute a clean atmosphere even in the absence of a magnetic fluid seal by heating a mixture of a high-vacuum lubricating oil and a high-mol.-wt. polyolefin powder to a temp. higher than the gel temp. of the powder. SOLUTION: A fluorine-based oil, a fluorosilicone oil, or an alkylcyclopentane oil can be used as the high-vacuum lubricating oil (A). Powders of high-mol.-wt. polyethylene, high-mol.-wt. polypropylene, high-mol.-wt. polybutene, ultrahigh- mol.-wt. polyethylene, etc., can be used as the high-mol.-wt. polyolefin powder (B). The compounding ratio by wt. of A/B is (5/95)-(99/1). This solid lubricant is prepd. by mixing the materials, pouring the mixture into a certain metal mold, heating the mixture to a temp. higher than the gel temp. of ingredient B, and solidifying the mixture by allowing it to cool to about normal temp. or quickly cooling it in a liq. cooling agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid lubricant comprising a high vacuum lubricating oil or a high vacuum lubricating grease and a high molecular weight polyolefin powder, and a self-lubricating bearing and ball screw seal using the same. Related to members and the like.

[0002]

2. Description of the Related Art In general, a bearing has a ball or a roller disposed between an inner ring and an outer ring, and serves to support a shaft that makes a rotary motion or a linear motion. This bearing uses a lubricant to smooth its movement.

A sealing device is provided to prevent the lubricating oil from being scattered as dust outside the bearing. The sealing device includes a non-contact type sealing device and a contact type sealing device. The former has a narrow gap between the shaft and the bearing, and is filled with grease. This is superior to the latter in terms of quietness during rotation and simplicity of the structure.

In the ball screw, a predetermined number of balls are arranged between a spiral groove provided on an outer peripheral surface of a screw shaft and a spiral groove provided on an inner peripheral surface of a ball nut. Rotational movement of the screw shaft or ball nut through the ball,
The motion is converted into the motion of the ball nut or the screw shaft.

[0005] The ball screw is filled with lubricating oil to smooth the movement of the ball screw. In order to prevent the leakage of the lubricant or the invasion of foreign matter from the outside, seal members are provided between the screw shafts at both ends of the ball screw and the ball nut. This seal member is generally manufactured by molding a rubber material such as resin rubber or fluorine rubber.

[0006] Recently, bearings and ball screws have been widely used in electronic equipment and semiconductor manufacturing equipment. When a bearing is used in an electronic device, further cleanliness is required. For example, a hard disk drive (hereinafter abbreviated as “HDD”),
In an apparatus such as a laser beam printer (hereinafter, abbreviated as “LBP”), if fine particles such as oil particles and dust (hereinafter, referred to as “dust”) are mixed in an atmosphere used, In the HDD, accidental contact between the magnetic head and the surface of the rotating data medium, so-called head crash, may occur, and in the LBP, the reflectance of the optical reflection surface may decrease.

In order to mechanically avoid such a situation, there has been known a method of mounting a magnetic fluid sealing device instead of or together with a non-contact type sealing device for a bearing. In this magnetic fluid seal, a magnet member is fixed to opposing end faces of a sandwiching portion of a bearing rolling element, and a magnetic fluid is gathered between the end faces to improve sealing performance.

On the other hand, grease sealed in such a sealing device or a bearing is not particularly improved for dust-proofing. A relatively low-viscosity mineral oil or synthetic oil is used as a base oil.
A general grease using a metallic soap containing lithium, calcium, and sodium as a thickener is used.

Further, when a ball screw is used in a semiconductor device or the like, it is often used in a vacuum atmosphere. Therefore, grease for vacuum is mainly used as a lubricant for the ball screw.

[0010]

However, there has been an increasing demand for the above-mentioned electronic equipment-related devices, and magnetic fluid seals have been used as lubricants for specific applications for further miniaturization and reduction of production costs. For bearings without bearings, there is a need to develop grease that satisfies lubricity.

When the above-described vacuum grease is used for a ball screw of a semiconductor device or the like, if the amount of the grease used is too large and a surplus occurs, the grease adheres to the screw shaft and scatters with the driving of the ball screw. Cheap. In particular, in a vacuum atmosphere, the sealing properties of the ball screw sealing member are generally not high, so that the vacuum grease is easily scattered to the outside.
At this time, the inside of the apparatus in a vacuum atmosphere undesirably generates dust and outgas.

Further, since the vacuum grease is deteriorated, it is necessary to replenish the grease periodically, that is, to increase the grease. In order to perform this grease-up, it is necessary to return the inside of the apparatus from a vacuum to the atmosphere, and it takes a considerable amount of time to return to a predetermined level of vacuum again, resulting in a decrease in the operation rate of the apparatus. Had a point.

Accordingly, an object of the present invention is to maintain a clean atmosphere in electronic equipment-related devices and semiconductor devices, and to suppress scattering of grease even in a vacuum atmosphere to achieve low dust and low outgas specifications. In addition, it is an object of the present invention to eliminate the need for grease for a long period of time and improve the operation rate of a device using a bearing or a ball screw.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention relating to a solid lubricant is based on a high vacuum lubricating oil of 5 to 9%.
9% by weight and 95-1% by weight of high molecular weight polyolefin powder
Is heated to a temperature equal to or higher than the gel point of the high molecular weight polyolefin powder and molded.

Further, 5 to 99% by weight of a grease based on a lubricating oil for high vacuum and 95 to 95% by weight of a high molecular weight polyolefin powder are used.
The mixture with 1% by weight is molded by heating to a temperature higher than the gel point of the high molecular weight polyolefin powder.

Further, the lubricating oil for high vacuum may be a lubricating oil selected from a fluoro oil, a fluoro silicone oil and an alkylcyclopentane oil.

Since a high vacuum lubricating oil such as fluorine oil, fluorine silicone oil or alkylcyclopentane oil is used as the lubricant, it has a very low volatility, and can be used not only in a vacuum atmosphere but also in an atmospheric pressure atmosphere. Even if it is used, there is almost no volatilization at the time of use, and it is possible to prevent the generation of dust such as dust and outgas.

Furthermore, the above-mentioned solid lubricant can constitute a seal member for a ball screw.

Since the above-mentioned solid lubricant is used as a seal member used for the ball screw, the seal member can be brought into direct contact with the screw shaft and the ball nut, thereby preventing the grease from scattering in the ball nut and preventing the vacuum. It is possible to prevent the generation of dust such as dust and outgas in the apparatus in the atmosphere, and maintain the vacuum atmosphere.

Further, since the above-mentioned solid lubricant is used as the seal member, the lubricating oil contained in the seal member gradually exudes, eliminating the need for grease up and improving the operation rate of the apparatus. .

[0021]

Embodiments of the present invention will be described below. The solid lubricant according to the present invention is a high-vacuum lubricating oil, or a mixture of a high-vacuum lubricating oil-based grease and a high-molecular-weight polyolefin powder at a temperature not lower than the gel point of the high-molecular-weight polyolefin powder. It is formed by heating.

The above-mentioned lubricating oil for high vacuum is a lubricating oil which has a small amount of evaporation even at high temperature and high vacuum and can be used for high vacuum. For example, silicate ester oil, fluorine oil, silicone oil, fluorine silicone oil, And synthetic hydrocarbon oils such as alkylcyclopentane oils. Among them, fluorine oil such as perfluoropolyether, fluorine silicone oil, alkylcyclopentane oil and the like are preferable. Examples of alkylated cyclopentane-based oils include Ny
e company: NYE SYNTHETIC OIL 200
1A.

The lubricating oil for high vacuum can be used as it is for the solid lubricant, but the lubricating oil for high vacuum is used as a base oil, which is kneaded with a thickener and used as grease. You may. The thickener includes a soap-based thickener and a non-soap-based thickener. Examples of the soap-based thickener include lithium soap, sodium soap, aluminum soap, and the like, and non-soap-based thickeners include bentonite, silica, polyurea, indanthrene, phthalocyanine such as copper phthalocyanine, and the like. Fluororesin and the like can be mentioned.

The high-molecular-weight polyolefin powder may be a powder composed of high-molecular-weight polyethylene, high-molecular-weight polypropylene, high-molecular-weight polybutene, ultra-high-molecular-weight polyethylene, ultra-high-molecular-weight polypropylene, ultra-high-molecular-weight polybutene, or a copolymer thereof, or a single powder thereof. May be mixed powder. Although the molecular weight of each of these powders is not particularly limited, a high molecular weight polyolefin powder having a viscosity average molecular weight of 1 × 10 ^{5 to} 5 × 10 ⁶ measured by a viscosity method is preferable, and 1 × 10 ^{6 to} 5 × 10 ⁶
Is more preferable. Polyolefins having such a molecular weight range are superior to low-molecular-weight polyolefins in rigidity and oil retention, and hardly flow even when heated to a high temperature.

The proportion of the high vacuum lubricating oil or the grease based on the high vacuum lubricating oil in the solid lubricant is 5 to 99% by weight, and the proportion of the high molecular weight polyolefin powder is 95 to 1% by weight. %. In such a predetermined range, the solid lubricant may be blended by increasing or decreasing according to the required degree of oil release, toughness and hardness of the solid lubricant. However, the greater the amount of the high molecular weight polyolefin, the greater the hardness of the gel after being dispersed and maintained at a predetermined temperature.

In order to disperse and hold the high molecular weight polyolefin powder in the high vacuum lubricating oil or the grease using the high vacuum lubricating oil as a base oil, the above-mentioned materials are mixed and then molded into a predetermined mold. And heated above the gel point of the high molecular weight polyolefin. Thereafter, the solid lubricant having a predetermined shape can be obtained by allowing it to cool to about room temperature, preferably by quenching it in a liquid coolant and solidifying it. As the liquid coolant, lubricating oil, grinding fluid, rust preventive oil or water can be used.

In the above-described molding method, a ball screw seal member can be manufactured by using a predetermined mold. Since the material of the seal member itself has lubricity, even if it is brought into direct contact with the rolling surface, the seal member exhibits lubricity and the lubricating oil for high vacuum contained in the seal member gradually exudes. Forms an oil slick. For this reason, the frictional resistance of the sliding contact portion is reduced. Therefore,
Even if the seal member is brought into close contact with the screw shaft and the ball nut, the torque loss is small and the heat generated by the friction of the sliding contact portion is small. Furthermore, the sealing performance of the ball screw can be improved. Therefore, it is possible to prevent the grease in the ball screw from scattering to the outside, and to prevent the generation of dust and outgas such as dust generation in the apparatus, particularly in the apparatus in a vacuum atmosphere, and contaminate the inside of the apparatus. Will be maintained without.

Next, a ball screw using a ball screw seal member made of the solid lubricant according to the present invention will be described.

As shown in FIG. 1, the ball screw 10 has a plurality of balls 3 between a spiral groove 1a provided on the outer peripheral surface 1b of the screw shaft 1 and a spiral groove 2a provided on the inner diameter surface of the ball nut 2. Are arranged, and the screw shaft 1 and the ball nut 2 are screwed through the ball 3. When the screw shaft 1 or the ball nut 2 rotates, the rotational force is transmitted to the ball nut 2 or the screw shaft 1 via the rolling circulation of the ball 3, and the ball nut 2 or the screw shaft 1 moves in the axial direction. The ring-shaped sealing member 5 is attached to both ends of the ball nut 2, and the sealing member 5 contacts the screw shaft 1 to seal the inside of the ball nut 2. A garter spring 6 is mounted on the outer periphery of the seal member 5.

As shown in FIGS. 2 (a) and 2 (b), the sealing member 5 is formed into a ring shape using a predetermined solid lubricant, and is formed into a ring shape so that each circumference is equally divided. It is divided at the points to form four divided portions 51, 51, 51, 52. Of the four divisions, three divisions 51 have protrusions 51a that protrude inward from the inner diameter surface 51b, and the inner diameter surface 52b of the remaining one division 52 is
Is provided slightly inside the inner diameter surface 51b. That is,
Although the outer diameter surfaces of the four divided portions are in a single circular shape as a whole, the inner diameter surfaces do not form one circular shape, and the inner diameter surface 52b of the divided portion 52 is the inner diameter of the other divided portion 51. Face 51
b and the inner surface of the protrusion 51a.

The divided portions 51 and 52 are pressed toward the inner diameter surface side by the garter spring 6 mounted on the outer diameter portion, and are brought into close contact with the screw shaft 1.

As shown in FIG. 1 (b), the fitting state of the divided portion 51 to the screw shaft 1 is such that the projection 51a of the divided portion 51 is fitted into and closely attached to the spiral groove 1a of the screw shaft 1. And the spiral groove 1
a to prevent foreign matter from entering and lubricant from leaking. Division unit 51
Is not in contact with the outer peripheral surface 1b of the screw shaft, and a slight clearance S is provided between the two. By providing the clearance S, the screw shaft 1 and the sealing member 5 can be formed.
Irrespective of the dimensional balance of the spiral groove 1
a.

As shown in FIG. 1C, the fitting state of the divided portion 52 to the screw shaft 1 is as follows.
b is in contact with the outer peripheral surface 1b of the screw shaft 1, and foreign matter intrusion and lubricating oil leakage from the outer peripheral surface 1b are prevented.

The sealing member 5 according to the present invention is a ball screw 11 as shown in FIG.
Can be used for

In the ball screw 11, a plurality of balls 3 are arranged between a spiral groove 1 a provided on the outer peripheral surface of the screw shaft 1 and a spiral groove 2 a provided on the inner diameter surface of the ball nut 2. When the screw shaft 1 or the ball nut 2 rotates, the rotational force is transmitted to the ball nut 2 or the screw shaft 1 via the ball 3,
The ball nut 2 or the screw shaft 1 moves in the axial direction. A concave portion is formed at both ends of the inner surface of the ball nut 2, and the seal member 5 and the auxiliary ring 7 are mounted in the concave portion.

As shown in FIGS. 4 (a) and 4 (b), the seal member 5 is formed into a ring shape using a predetermined solid lubricant, and is then formed into a ring shape so that each circumference is equally divided. Divided by location. The seal member 5 has a protrusion 5a projecting inward from an inner diameter surface 5b thereof.
Has a shape and dimensions corresponding to the spiral groove 1a.

The three divided members of the seal member 5 are shown in FIG.
(A) As shown in FIG.
The ball plunger 8 screwed into the screw hole 2b of
It is repressed in the inner diameter direction. Therefore, as shown in FIG. 3 (c), the fitting clearance between the projection 5a and the spiral groove 1a is zero or slightly negative, that is, a state in which the interference exists. It should be noted that there is a slight clearance between the divided portions of the seal member 5.

As described above, since the protrusion 5a is in close contact with the spiral groove 1a and is in sliding contact therewith, the lubricant in the ball nut 2 hardly leaks to the outside, and foreign matter hardly intrudes from the outside. Further, since each of the divided surfaces 5c of the seal member 5 scrapes off the foreign matter adhering to the surface of the spiral groove 1a, the sealing performance is extremely high as compared with the conventional one. The auxiliary ring 7 prevents the scraped foreign substance from trying to enter the ball nut 2 through the dividing surface 5b.

The seal member shown in FIGS.
Although a plurality of arc-shaped seal pieces are arranged in a ring shape at intervals along the outer periphery of the screw shaft, a ring-shaped seal continuous in the circumferential direction may be used. May be a partially continuous ring-shaped seal formed by cutting out a predetermined distance in the axial direction and continuing the other end in the circumferential direction.

[0040]

【Example】

[Examples 1 to 6] Ultra high molecular weight polyolefin (Miperon, manufactured by Mitsui Petrochemical Co., Ltd., gelling temperature: 136 ° C.) was used as the resin powder, and fluorine oil (Audimont), fluorine silicone oil ( Tolu Silicone Co., Ltd.), alkyl cyclopentane oil (Nye Co.), and as a lubricating grease, fluororesin / fluorine oil grease (Audimont), fluororesin / fluorosilicone oil grease (Toray Silicone), silica·
Using an alkylcyclopentane-based grease (manufactured by NTN), these are mixed as raw materials at the compounding ratio shown in Table 1, and this mixture is used as a ball bearing (manufactured by NTN: ball bearing 608).
Was sealed with a non-contact type rubber seal. The bearing was heated in a thermostat at 150 to 180 ° C. for 30 minutes and then cooled to solidify the mixture. The following ball bearings were subjected to the following dust generation test.
Table 1 shows the results.

Dust Generation Test Two sets of the ball bearings obtained above were mounted on a drive shaft as a set, and the ball bearings were subjected to a thrust load of 1 kgf and 200 rpm.
Driving for 4 hours. At this time, dust of 0.3 μm or more generated from the pair of bearings was measured.

Comparative Example 1 The ultrahigh molecular weight polyolefin and lithium soap / mineral oil-based grease were mixed at the compounding ratio shown in Table 1, and the mixture was filled into a bearing and solidified in exactly the same manner as in Example 1. The above dust generation test was performed on the obtained ball bearings. Table 1 shows the results.

[Comparative Examples 2 to 5] As commercial greases, lithium soap / diester oil-based grease, lithium soap / grease
0.2 g of polyol ester grease, urea / alkyl diphenyl ether grease, and fluororesin / fluorine oil grease were sealed in the ball bearing. The above dust generation test was performed on the obtained ball bearings. Table 1 shows the results.

[0044]

[Table 1]

Results As is clear from the test results in Table 1,
Fluorine oil, fluorosilicone oil, alkylcyclopentane oil, or a mixture of grease and ultrahigh molecular weight polyolefin powder based on the above oils is heated to a temperature higher than the gel point of the ultrahigh molecular weight polyolefin powder and cooled. As a result, the lubricant became solid, and the amount of dust generation was extremely lower than that of a solid lubricating oil mixed with a mineral oil-based grease and an ultrahigh molecular weight polyolefin powder, heated and cooled, and commercially available grease.

[0046]

According to the present invention, since the above-mentioned solid lubricant is used, the amount of dust generated from bearings used in electronic devices such as HDDs and LBPs is extremely small, and cleanliness can be obtained without a magnetic fluid seal. Does not pollute the atmosphere. Therefore, it is possible to reduce the number of components of the device including the rotating part by using such a bearing, and it is possible to reduce the size of the device and to reduce the manufacturing cost.

Further, since the above-mentioned solid lubricant is used as a seal member for a ball screw used in a semiconductor manufacturing apparatus or the like, even if this seal member is brought into direct contact with the screw shaft and the rolling surface of the ball nut, lubrication is not required. The lubricating oil for high vacuum contained in the seal member gradually exudes to form an oil film. For this reason, the frictional resistance of the sliding contact portion is reduced. Therefore, even if this seal member is brought into close contact with the screw shaft and the ball nut, torque loss is small, and
Low heat generation due to friction of the sliding part. Furthermore, the sealing performance of the ball screw can be improved. Therefore, it is possible to prevent the grease in the ball screw from scattering to the outside, prevent generation of dust and outgas in the device in a vacuum atmosphere, and maintain the vacuum atmosphere without contamination.

Further, since the above-mentioned solid lubricant is used as the seal member, the lubricating oil for high vacuum contained in the seal member gradually exudes. Therefore, by adjusting the degree of oil release, the required minimum amount of high vacuum lubricating oil
It can be provided in the ball screw, eliminating the need for grease. Therefore, maintenance-free operation can be performed for a long period of time, and the operation rate of an apparatus such as a semiconductor manufacturing apparatus can be improved.

When the seal member is brought into direct contact with the rolling surface of the screw shaft and the ball nut to drive the ball screw, lubricating oil for high vacuum oozing from the sealing member is applied to the rolling surface. Thus, the ball screw can be driven in a vacuum atmosphere without using another lubricant for the ball screw. For this reason, the amount of contamination of the atmosphere with the lubricant can be minimized, and a maintenance-free ball screw can be provided for a long period of time.

[Brief description of the drawings]

FIG. 1A is a sectional view showing an example of a ball screw using a seal member according to the present invention. FIG. 1B is a partially enlarged sectional view of FIG.

FIG. 2A is a front view showing an example of a seal member according to the present invention; FIG. 2B is a side sectional view showing a state where the seal member shown in FIG.

3A is a cross-sectional view showing another example of a ball screw using the seal member according to the present invention. FIG. 3B is a cross-sectional view showing an example of a ball plunger used in FIG. 3A. Partially enlarged sectional view of

4A is a front view showing another example of the seal member according to the present invention. FIG. 4B is a side view of the seal member shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 screw shaft 1a spiral groove 1b outer peripheral surface 2 ball nut 2a spiral groove 2b screw hole 3 ball 5 sealing member 5a protrusion 5b inner diameter surface 5c division surface 6 garter spring 7 auxiliary ring 8 ball plunger 10 ball screw 11 ball screw 51 division portion 51a Projecting portion 51b Inner surface 52 Dividing portion 52b Inner surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 107: 02 105: 50 107: 50 105: 04) C10N 40:34 50:08 80:00

Claims (4)

[Claims] 1. A solid formed by heating a mixture of 5-99% by weight of a lubricating oil for high vacuum and 95-1% by weight of a high molecular weight polyolefin powder to a temperature not lower than the gel point of the high molecular weight polyolefin powder. lubricant. 2. A grease 5 using a high vacuum lubricating oil as a base oil.
A solid lubricant obtained by heating a mixture of 99 to 99% by weight of a high molecular weight polyolefin powder and 95 to 1% by weight of the high molecular weight polyolefin powder at a temperature not lower than the gel point of the high molecular weight polyolefin powder. 3. The solid lubricant according to claim 1, wherein the high vacuum lubricating oil is a lubricating oil selected from fluorine oil, fluorine silicone oil, and alkylcyclopentane oil. 4. A ball screw seal member comprising the solid lubricant according to claim 1.