KR102523664B1 - Grease for rolling bearing in information recording and reproducing apparatus, rolling bearing, rolling bearing device, and information recording and reproducing apparatus - Google Patents

Abstract

It includes a base oil and a thickener, the base oil includes mineral oil and poly-α-olefin, the ratio of the mineral oil is 10 to 40% by mass with respect to 100% by mass of the base oil, and the kinematic viscosity ν1 of the mineral oil at 40 ° C is A grease having a kinematic viscosity higher than ν2 of the poly-α-olefin at 40° C., a rolling bearing, a rolling bearing device (6) and an information recording and reproducing device (1) provided with the grease.

Description

Grease, rolling bearing, rolling bearing device and information recording and reproducing device

The present invention relates to grease, rolling bearings, rolling bearing devices, and information recording and reproducing devices.

This application claims priority according to Patent Application No. 2015-009485 filed in Japan on January 21, 2015 and Patent Application No. 2015-236921 filed in Japan on December 3, 2015, the contents of which are incorporated herein by reference. do.

BACKGROUND OF THE INVENTION An information recording and reproducing apparatus such as a hard disk drive (HDD) is known as a device for magnetically or optically recording and reproducing various kinds of information on a disk. The information recording and reproducing apparatus generally includes a swing arm having a head gimbal assembly (magnetic head) for recording and reproducing signals on a disk, a rolling bearing device serving as a turning point of the swing arm, and an actuator for rotating the swing arm. By rotating the swing arm to move the magnetic head to a predetermined position on the disc, it is possible to record and reproduce signals.

A rolling bearing device generally includes two rolling bearings provided with a plurality of spherical rolling elements between an inner ring and an outer ring, and a shaft inserted inside the rolling bearing. The outer ring rotates around the axis of the shaft by the transmission of the plurality of rolling elements, and thus the swing arm connected to the outer ring rotates. Since the rolling bearing is required to operate stably over a long period of time, grease is used to smooth the movement of the rolling element between the inner ring and the outer ring.

The grease for rolling bearings of information recording and reproducing devices lowers the torque of rolling bearings, obtains excellent torque smoothness (property when torque is uniform in the rotational direction of rolling bearings), and also enhances the durability of rolling bearings. It is required. In addition, it is important that the amount of outgas in the grease for rolling bearings is small because outgas from the grease accumulates in the gap between the magnetic head and the disk, etc., causing problems in reading and writing of the information recording and reproducing apparatus.

As the grease for the rolling bearing of the information recording and reproducing apparatus, for example, mineral oil and a base oil containing poly-α-olefin (hereinafter referred to as "PAO"), a thickener (such as a urea compound), and an extreme pressure agent (such as an organophosphorus compound) It is known to contain (Patent Document 1). The grease has a relatively small amount of outgas, and can make rolling bearings low in torque, excellent in torque smoothness, and excellent in durability. However, recently, as the demand for high-density HDDs and server applications has increased, the distance between the disk and the magnetic head has become nano-order, so reduction in outgassing amount and improvement in durability are further demanded.

As a grease capable of reducing the amount of outgas, a rolling bearing grease using only PAO as a base oil without using mineral oil having a higher amount of outgas than PAO has been proposed (Patent Document 2). However, it is difficult to obtain a rolling bearing having sufficient durability even though the amount of outgas is small in the above grease.

(Patent Document 1) Japanese Unexamined Publication No. 2003-239954 (Patent Document 2) Japanese Unexamined Publication No. 2013-174334

An object of the present invention is to provide a grease capable of sufficiently reducing the amount of outgassing and ensuring durability of applied equipment, and a rolling bearing, rolling bearing device, and information recording/reproducing device using the grease.

The grease of the present invention includes a base oil and a thickener, the base oil includes mineral oil and PAO, the ratio of the mineral oil is 10 to 40% by mass with respect to 100% by mass of the base oil, and the kinematic viscosity ν1 of the mineral oil at 40 ° C is The kinetic viscosity at 40°C of the PAO is higher than ν2.

In the grease of the present invention, it is preferable that the ratio of the PAO is greater than the ratio of the mineral oil in the base oil.

In addition, it is preferable that the ratio of the kinematic viscosity ν1 to the kinematic viscosity ν2, ν1 / ν2, is 1.3 or more.

The kinematic viscosity ν1 is preferably 40 mm ² /s or more.

The kinematic viscosity ν2 is preferably 20 mm ² /s or more.

The kinematic viscosity ν of the base oil at 40° C. is preferably 25 to 45 mm ² /s.

In the grease of the present invention, the base oil includes refined mineral oil classified as Group III in the base oil category defined by the American Petroleum Institute, and the flash point of the refined mineral oil is preferably 240°C or higher, more preferably 250°C or higher. do.

It is preferable that the poly-α-olefin contains a mixture of tri- and pentamers of C8-C12 α-olefins.

It is preferable that the said thickener is a urea compound.

The rolling bearing of the present invention is provided with the grease of the present invention.

The rolling bearing device of the present invention has a shaft and the rolling bearing of the present invention.

The information recording and reproducing apparatus of the present invention includes the rolling bearing device of the present invention.

The amount of outgassing of the grease of the present invention is sufficiently reduced, and durability of equipment to which it is applied can be ensured.

Further, the rolling bearing, the rolling bearing device, and the information recording and reproducing device of the present invention can sufficiently reduce the outgassing amount of grease and are excellent in durability.

1 is a perspective view showing an example of an information recording and reproducing apparatus of the present invention.
Fig. 2 is a longitudinal sectional view showing the surroundings of the rolling bearing device of the information recording and reproducing apparatus of Fig. 1;
Figure 3 is a cross-sectional view showing the rolling bearing device of Figure 2;
Fig. 4 is a plan view showing a rolling bearing of the rolling bearing device of Fig. 3;
Fig. 5 is a AA cross-sectional view of the rolling bearing of Fig. 4;
6 is a perspective view showing the rolling bearing retainer of FIG. 5;
7 is a graph showing the relationship between the standing time and evaporation loss when the grease is left still at 85°C.
8 is a graph showing the relationship between the standing time and evaporation loss when the grease is left still at 100°C.
9 is a graph showing the relationship between the standing time and evaporation loss when the grease is left still at 130°C.

[Greece]

The grease of the present invention contains a base oil and a thickener.

(base oil)

Base oils include mineral oil and PAO.

As the mineral oil, known mineral oil used as a base oil may be used, and examples thereof include naphthenic mineral oil, paraffinic mineral oil, hydrogenated mineral oil, solvent-refined mineral oil, and highly refined mineral oil.

As a mineral oil, you may use individually by 1 type, and may use 2 or more types together. For example, you may use what was adjusted to the desired kinematic viscosity (average kinematic viscosity) by mixing various mineral oils of kinematic viscosity.

As for mineral oil, refined mineral oil classified as group III (GrIII) in the API (American Petroleum Institute) base oil category is preferable in that grease with a smaller outgassing amount, excellent heat resistance, and excellent low-temperature characteristics can be obtained. do. Examples of the refined mineral oil include paraffinic mineral oil obtained by further hydrorefining a lubricating oil fraction obtained by atmospheric distillation of crude oil. Refined mineral oil classified as Group III preferably has a flash point of 240°C or higher, more preferably 250°C or higher. This refined mineral oil has a high degree of refinement and can further reduce the outgassing amount. The reason for this is presumed to be that the low molecular weight components that cause outgas are reduced.

As the PAO, known PAO used as a base oil may be used without limitation, and for example, α-olefins (1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene) , 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-dococene, etc.). Among them, as PAO, from the viewpoint of reducing the amount of outgassing and evaporation loss, having excellent oxidation deterioration characteristics, and obtaining an appropriate viscosity, one type or two types of tri-pentomers of α-olefins having 8 to 12 carbon atoms are used. It is preferable to use in combination of the above.

As PAO, you may use individually by 1 type, and may use 2 or more types together. For example, a plurality of PAOs having different kinematic viscosities may be mixed and one adjusted to a desired kinematic viscosity (average kinematic viscosity) may be used. It is particularly preferable to use a tri- to pentameric mixture of ?-olefins having 8 to 12 carbon atoms in terms of low outgassing amount and long-term evaporation loss and excellent oxidative degradation properties.

The base oil may include, in addition to mineral oil and PAO, other oil components other than mineral oil and PAO.

Examples of other oil components include synthetic oils such as ester oil.

As the other milk components, one type may be used alone, or two or more types may be used together.

<Kinematic viscosity>

In the grease of the present invention, the kinematic viscosity ν1 of mineral oil at 40°C is higher than the kinematic viscosity ν2 of PAO at 40°C. When the kinetic viscosity ν1 of mineral oil is higher than the kinetic viscosity ν2 of PAO, the mineral oil has excellent heat resistance. As a result, the amount of outgassing in the mineral oil is reduced, and as a result, the amount of outgassing in the base oil is sufficiently reduced. In addition, PAO with a kinematic viscosity ν2 lower than the kinematic viscosity ν1 of mineral oil is combined, and the kinematic viscosity ν of the base oil is sufficiently lowered. Therefore, grease is sufficiently supplied to the parts requiring grease, such as the part where the rolling elements of the rolling bearing roll, and the lubrication effect of the grease can be sufficiently obtained.

In addition, in this invention, the kinematic viscosity of oil means the value measured at 40 degreeC based on JISK2283.

In addition, when a plurality of base oils of the same type having different kinetic viscosities are mixed, the kinetic viscosity of the mixture is considered as the kinetic viscosity of the base oil.

The ratio nu1/nu2 of the kinetic viscosity nu1 of mineral oil to the kinetic viscosity nu2 of PAO is preferably 1.3 or more, and more preferably 1.5 or more, from the viewpoint of facilitating reduction of the amount of outgas. Further, the ratio nu1/nu2 is preferably 4 or less, and more preferably 2 or less, from the viewpoint of lowering the torque of the rolling bearing.

The kinematic viscosity ν1 of mineral oil is preferably 40 mm ² /s or more, and more preferably 45 mm ² /s or more, from the viewpoint of facilitating reduction of the amount of outgas. In addition, the kinematic viscosity ν1 of mineral oil is preferably 80 mm ² /s or less, more preferably 60 mm ² /s or less, from the viewpoint that grease or base oil is easily supplied to surfaces requiring grease, such as rolling surfaces of rolling bearings.

The kinematic viscosity ν2 of PAO is preferably 20 mm ² /s or more, and more preferably 30 mm ² /s or more, from the viewpoint of facilitating reduction of the amount of outgas. Further, the kinematic viscosity ν2 of PAO is preferably 60 mm ² /s or less, and more preferably 40 mm ² /s or less, from the viewpoint of facilitating the supply of grease or base oil to a portion requiring grease, such as a rolling surface of a rolling bearing.

The kinematic viscosity ν of the base oil at 40°C is preferably 25 to 45 mm ² /s, and more preferably 30 to 40 mm ² /s. If the kinematic viscosity (nu) of base oil is more than the said lower limit, it is easy to reduce the amount of outgas. When the kinematic viscosity ν of the base oil is equal to or less than the above upper limit, grease or base oil is easily supplied to parts requiring grease, such as the raceway of rolling bearings. In addition, it can operate at low torque even in applications requiring stable operation at low temperatures (for example, automotive applications requiring stable operation even at low temperatures of -30 ° C). In particular, when the ratio of mineral oil to 100% by mass of the base oil is 30% by mass or less, the amount of outgas becomes smaller if the kinematic viscosity ν of the base oil at 40° C. is 25 mm ² /s or more.

(thickener)

The thickener serves to keep the grease in a semi-solid form.

As the thickener, known thickeners generally used for grease may be used without limitation. Specific examples of the thickener include, for example, a urea compound, lithium soap, and the like. Among them, the thickener is preferably a urea compound in terms of excellent heat resistance, and a diurea compound having two urea bonds in one molecule is more preferable.

As a diurea compound, the aliphatic diurea compound whose terminal is an aliphatic group, the alicyclic diurea compound whose terminal is an alicyclic group, the aromatic diurea compound whose terminal is an aromatic group, etc. are mentioned, for example.

Specific examples of diurea compounds include diisocyanates (phenylene diisocyanate, tolylene diisocyanate, etc.) and monoamines (octylamine, dodecylamine, stearylamine, aniline, p-toluidine, etc.) compounds can be mentioned.

Examples of the lithium soap include lithium stearate and lithium 12-hydroxystearate.

As a thickener, you may use individually by 1 type, and may use 2 or more types together.

(other ingredients)

The grease of the present invention may contain other components other than the base oil and thickener, as needed, in addition to the base oil and thickener.

As other components, known components commonly used in grease may be used, and examples thereof include additives such as extreme pressure agents, antioxidants, rust inhibitors, oiliness improvers, and metal deactivators.

Examples of the extreme pressure agent include organic molybdenum compounds (molybdenum dithiocarbamate, molybdenum dithiophosphate, etc.), organic fatty acid compounds (oleic acid, naphthenic acid, succinic acid, etc.), organic phosphorus compounds (trioctyl phosphate, triphenyl phosphate, etc.) triethyl phosphate, etc.), phosphoric acid ester, and the like. Further, as the extreme pressure agent, zinc dithiocarbamate, antimony dithiocarbamate, or the like may be used.

As the extreme pressure agent, one type may be used alone, or two or more types may be used in combination.

Examples of the antioxidant include phenolic antioxidants (such as 2,6-di-t-butyl-4-methyl phenol), amine antioxidants (such as p,p'-dioctyldiphenylamine), and the like. there is. As antioxidant, you may use individually by 1 type, and may use 2 or more types together. When the grease of the present invention contains an antioxidant, it is preferable to use a phenolic antioxidant and an amine antioxidant together. In addition, in this case, it is more preferable that the content of the amine-based antioxidant in the grease is greater than the content of the phenol-based antioxidant.

Examples of the rust inhibitor include alkali metal salts or alkaline earth metal salts of organic sulfonic acids (such as calcium sulfonate, magnesium sulfonate, and barium sulfonate), partial esters of polyhydric alcohols (such as sorbitan monooleate), and the like.

As a rust inhibitor, you may use individually by 1 type, and may use 2 or more types together.

(Ratio of each ingredient)

The ratio of the base oil to 100 mass% of the grease of the present invention is preferably 75 to 93 mass%, more preferably 80 to 90 mass%. When the ratio of the base oil is equal to or greater than the lower limit, grease or base oil is likely to be supplied to surfaces requiring grease, such as rolling bearing raceways. When the proportion of the base oil is below the upper limit, the grease is in a semi-solid state and is difficult to leak and scatter.

The ratio of mineral oil to 100% by mass of the base oil is 10 to 40% by mass, preferably 20 to 30% by mass. When the proportion of mineral oil is equal to or greater than the lower limit, a grease with excellent durability and torque smoothness can be obtained. If the proportion of mineral oil is below the above upper limit, grease with significantly reduced outgassing amount is obtained.

The ratio of PAO to 100 mass% of the base oil is preferably 50 to 90 mass%, more preferably 60 to 80 mass%. When the ratio of PAO is equal to or greater than the above lower limit, grease with a significantly reduced amount of outgas can be obtained. If the ratio of PAO is less than the above upper limit, grease with excellent durability and torque smoothness in balance can be obtained.

The ratio of the total of mineral oil and PAO to 100 mass% of the base oil is preferably 70 mass% or more, more preferably 80 mass% or more, and still more preferably 90 mass% or more. A low-torque grease can be obtained if the ratio of the total of mineral oil and PAO is equal to or greater than the lower limit. The upper limit of the total ratio of mineral oil and PAO is 100% by mass.

In the grease of the present invention, it is preferable that the ratio of PAO is greater than that of mineral oil in the base oil from the viewpoint of reducing the outgassing amount and achieving both excellent durability.

The mass ratio of PAO to mineral oil in the base oil (PAO/mineral oil) is preferably from 1.25 to 9, and more preferably from 1.5 to 4. It is easy to sufficiently reduce the amount of outgas as the said mass ratio is more than the said lower limit. When the weight ratio is equal to or less than the upper limit, excellent durability and torque smoothness can be obtained.

The ratio of the thickener to 100 mass% of the grease of the present invention is preferably 7 to 20 mass%, more preferably 10 to 15 mass%. When the ratio of the thickener is equal to or greater than the lower limit, the grease is in a semi-solid state and is difficult to leak and scatter. When the ratio of the thickener is equal to or less than the above upper limit, grease or base oil is easily supplied to surfaces requiring grease, such as rolling surfaces of rolling bearings.

The ratio of the extreme pressure agent to 100% by mass of the grease of the present invention is preferably 0.2 to 4% by mass, more preferably 0.5 to 2% by mass.

The ratio of antioxidant to 100 mass% of the grease of the present invention is preferably 0.05 to 4 mass%, more preferably 0.2 to 2 mass%.

The ratio of rust inhibitor to 100 mass% of the grease of the present invention is preferably 0.2 to 4 mass%, more preferably 0.5 to 2 mass%.

(Usage)

The grease of the present invention is particularly useful as a grease used in rolling bearings of information recording and reproducing apparatuses and electronic equipment manufacturing apparatuses. As an electronic product manufacturing apparatus, a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, PCB manufacturing equipment, etc. are mentioned, for example. In addition, the grease of the present invention can also be used as grease sealed in linear guides and ball screws.

(action mechanism)

The grease of the present invention described above contains, in addition to PAO, mineral oil having a kinematic viscosity ν1 higher than the kinetic viscosity ν2 of PAO in a specific ratio, so that the amount of outgas can be sufficiently reduced, and excellent durability in equipment requiring grease such as rolling bearings can be secured Factors that can obtain the above effect are considered as follows.

For example, rolling bearings of information recording and reproducing devices have complex and wide operating conditions, such as the swing speed and rotation range of a swing arm. Grease using only PAO with a narrow molecular weight distribution as the base oil of Patent Document 2 is difficult to cope with various operating conditions of rolling bearings. Therefore, it is difficult to secure excellent durability because the movement of the swing arm cannot be sufficiently smooth.

On the other hand, in the grease of the present invention, mineral oil with a wider molecular weight distribution than PAO is used together with PAO, so it is possible to respond to various operating conditions of rolling bearings. For example, even when the motion of the swing arm is slow, an oil film having a sufficient thickness is formed due to the influence of a component having a high molecular weight and a high viscosity in mineral oil, and a sufficient lubricating effect is exhibited. In addition, even when the swing arm moves quickly or in a minute range, grease is sufficiently supplied to the rolling part due to the low molecular weight and low viscosity components in mineral oil. Therefore, since it can respond to a wide range of operating conditions for rolling bearings, it is possible to secure excellent durability.

In addition, since the kinetic viscosity ν1 of the mineral oil of the grease of the present invention is higher than the kinetic viscosity ν2 of PAO, it has excellent heat resistance and is less likely to generate outgas than mineral oil having a low kinematic viscosity. In the grease of the present invention, the proportion of the mineral oil in the base oil is controlled within a specific range. Therefore, the amount of outgas is sufficiently reduced. In addition, since the kinematic viscosity ν as a whole of the base oil can be sufficiently lowered by PAO having a kinematic viscosity ν2 lower than that of mineral oil, the torque of rolling bearings, etc. is suppressed, and the grease is sufficiently applied to surfaces requiring grease, such as the rolling surfaces of rolling elements of rolling bearings. are supplied Therefore, it is possible to achieve both the effect of reducing outgas and the effect of improving durability.

In addition, since PAO has no polarity, it is difficult to uniformly disperse the thickener and additives, and it is difficult to sufficiently obtain the effect when only PAO is used as a base oil having low affinity for the thickener and additives having polarity. However, in the grease of the present invention, mineral oil having polarity is used together with PAO, so that the affinity between the base oil and the thickener and additives is good. As a result, the difference in size of the thickener synthesized in the base oil is suppressed, and the size can be miniaturized, and torque smoothness is excellent because the dispersibility of the thickener is excellent. And the effects of the additives are fully exhibited.

[Information Recording and Reproducing Device]

For the rolling bearing, rolling bearing device, and information recording/reproducing device of the present invention, known forms can be adopted except for using the grease of the present invention. Hereinafter, examples of the rolling bearing, the rolling bearing device, and the information recording/reproducing device of the present invention are shown and described.

The information recording and reproducing apparatus 1 of the present embodiment is a device for recording in a vertical recording method on a disk (magnetic recording medium) D, and as shown in FIG. 1, the disk D, the swing arm 2, An optical waveguide 3, a laser light source 4, a head gimbal assembly (HGA) 5, a rolling bearing device 6, an actuator 7, a spindle motor (rotation driving unit) 8, A control unit 9 and a housing 10 are provided.

The housing 10 accommodates each component of the information recording and reproducing apparatus 1.

The housing 10 includes a rectangular bottom portion 10a in plan view, a main wall portion (not shown) standing around the bottom portion 10a, and a cover body (shown) that is detachably fixed to the upper portion of the main wall portion and closes the opening. not included). In the housing 10, each component is accommodated inside the circumferential wall on the bottom portion 10a. In FIG. 1, the circumferential wall portion and the cover body are omitted for convenience.

The material of the housing 10 is not particularly limited, and examples thereof include metal materials such as aluminum.

A spindle motor 8 is installed approximately at the center of the bottom 10a of the housing 10 . In addition, the central hole formed in the center of the disk D is inserted into the spindle motor 8, and the three disks D are attached so as to be detachable. The spindle motor 8 is configured to rotate the disk D in a certain direction around the rotational axis L1.

An actuator 7 is installed so as to be located outside the disk D of one right corner of the bottom 10a of the housing 10. The actuator 7 is connected to a swing arm 2 extending toward the disk D. A rolling bearing device 6 is installed on the proximal end of the swing arm 2 . Driven by an actuator 7, the swing arm 2 rotates in a horizontal plane about the rotational axis L2 of the rolling bearing device 6 as an axis.

The swing arm 2 has a base 2a connected to the actuator 7 and an arm 2b extending from the base 2a toward the disc D. The swing arm 2 is obtained by, for example, cutting the base 2a and the arm 2b and integrally forming them by processing or the like.

The base 2a has a substantially rectangular parallelepiped shape, surrounds the rolling bearing device 6, and is supported by the rolling bearing device 6 so that rotation is possible.

The arm portion 2b is flat and has a tapered shape tapered from the proximal end toward the distal end. The arm portion 2b is in the plane direction (horizontal plane direction) of the surface of the base portion 2a from the front surface (surface opposite to the right angle portion) 2d on the opposite side to the rear surface 2c where the actuator 7 of the base portion 2a is installed. It is installed to produce.

In the swing arm 2 of this embodiment, three arm portions 2b are provided in the height direction (vertical direction) of the base portion 2a so that the disk D is sandwiched between the respective arm portions 2b. That is, the arm portion 2b and the disk D are alternately arranged in the height direction, and the arm portion 2b is parallel to the disk surface (the surface of the disk D) D1 by driving the actuator 7. It is meant to move in one direction.

A head gimbal assembly 5 is installed at the tip of the arm portion 2b of the swing arm 2. A laser light source 4 is installed on the side surface of the base 2a of the swing arm 2 . Optical waveguides 3 connecting the laser light source 4 and the head gimbal assembly 5 are installed on the base 2a and the arm 2b of the swing arm 2 . Therefore, light can be supplied from the laser light source 4 to the head gimbal assembly 5 through the optical waveguide 3.

The head gimbal assembly 5 includes a suspension 5a and a slider 5b attached to the front end of the suspension 5a.

The slider 5b has a near-field light generating element. When light from the laser light source 4 is guided to the slider 5b, near-field light is generated in the near-field light generating element. Various kinds of information can be recorded or reproduced on the disk D by using the near-field light.

The near-field light generating element is composed of, for example, optical fine holes or nanometer-sized protrusions.

The head gimbal assembly 5 moves in a direction parallel to the disk surface D1 together with the arm portion 2b of the swing arm 2 by driving the actuator 7. In addition, the swing arm 2 and the head gimbal assembly 5 are retracted from the disk D by driving the actuator 7 when the disk D stops rotating.

The control unit 9 is connected to the laser light source 4. In the controller 9, the luminous flux of light supplied to the slider 5b of the head gimbal assembly 5 can be controlled by the current modulated according to the information.

(rolling bearing device)

As shown in FIGS. 2 and 3, the rolling bearing device 6 includes a shaft 20, a sleeve 21 installed coaxially with the shaft 20 outside the shaft 20, and a shaft 20. Two rolling bearings 22 installed between the sleeves 21 are provided.

The shaft 20 is a rod-shaped member having a cylindrical shape, and is placed upright on the bottom portion 10a of the housing 10 . The central axis of the shaft 20 becomes the axis of rotation L2 when the swing arm 2 rotates.

In the portion of the shaft 20 on the side of the bottom 10a of the housing 10, a flange portion 20b having a diameter larger than that of the body portion 20a and a diameter reducing portion 20c having a diameter smaller than that of the body portion 20a are provided at the base end of the shaft 20. are installed in order. A male screw 20d is formed on the outer circumferential surface of the diameter reduced portion 20c.

Insert the diameter reduced portion 20c of the shaft 20 into the hole 10b provided in the bottom portion 10a of the housing 10, and the female screw 10c0 formed on the inner circumferential surface of the hole 10b and the male thread of the reduced diameter portion 20c ( 20d), the shaft 20 is placed on the bottom 10a of the housing 10. At this time, the lower surface of the flange 20b0 is in contact with the bottom 10a of the housing 10, and the shaft 20 Positioning in the height direction of is made.

The sleeve 21 is a member formed in a cylindrical shape. The inner diameter of the sleeve 21 is substantially the same as the outer diameter of the flange portion 20b.

The sleeve 21 surrounds the shaft 20 from the outside in the radial direction, and is installed so that its inner circumferential surface is spaced apart from the outer circumferential surface of the shaft 20 at predetermined intervals. The central axis of the shaft 20 and the central axis of the sleeve 21 coincide.

In addition, the sleeve 21 is press-fitted directly into the mounting hole 2e formed in the base 2a of the swing arm 2, press-fitted through an elastic body such as a corrugated metal ring, or adhesively fitted to the swing arm. (2) is integrally combined with

At the center of the inner circumferential surface of the sleeve 21 in the height direction, a spacer portion 21a protrudes inward over the entire circumferential direction is formed. Between the shaft 20 and the sleeve 21, two rolling bearings 22 are installed above and below the spacer 21a, and the distance between the two rolling bearings 22 is maintained at a predetermined distance. .

<rolling bearing>

The two rolling bearings 22 provided in the rolling bearing device 6 are identical.

As shown in FIGS. 3 to 6, the rolling bearing 22 includes an inner ring 30, an outer ring 31, a retainer 32, a plurality of rolling elements 33, and two shield plates 34 do.

The inner ring 30 is a cylindrical member.

The inner diameter of the inner ring 30 is dimensioned to enable insertion of the shaft 20. In this embodiment, the inner diameter of the inner ring 30 is slightly larger than the outer diameter of the shaft 20. The shaft 20 is fitted inside the inner ring 30 and the inner ring 30 is fixed to the shaft 20 with an adhesive or the like.

In addition, the inner diameter of the inner ring 30 may be the same as or slightly smaller than the outer diameter of the shaft 20, as long as it can be installed on the shaft 20. In this case, the shaft 20 is press-fitted to the inner ring 30.

In the rolling bearing 22, a so-called inner ring preload can be employed in which the inner ring 30 is fixed to the shaft 20 in a state where the inner ring 30 is relatively preloaded to the shaft 20 in the axial direction. Accordingly, the rigidity of the rolling bearing 22 can be increased, and the resonance frequency (resonance) of the rolling bearing device 6 can be increased. Therefore, the rolling bearing device 6 capable of responding to high-speed rotation is obtained.

In addition, in the rolling bearing 22, a so-called outer ring preload is employed in which the outer ring 31 is fixed to the sleeve 21 in a state where the outer ring 31 is relatively preloaded to the sleeve 21 in the axial direction.

At an intermediate portion of the outer peripheral surface of the inner ring 30 in the axial direction, a concave inner rolling surface 30a for guiding the rolling of the rolling elements 33 is formed over the entire circumference of the inner ring 30 . The inner rolling surface 30a has an arcuate cross-sectional shape when cut with a plane passing through the central axis of the inner ring 30.

As the material of the inner ring 30, metal materials such as stainless steel can be used, for example. The inner ring 30 can be manufactured by, for example, forging and machining.

The outer ring 31 is a cylindrical member similar to the inner ring 30 having a larger diameter than the inner ring 30 .

The outer ring 31 is fixed to the inside of the sleeve 21, and is installed on the outside of the inner ring 30 while being spaced apart from the inner ring 30. The inner ring 30 and the outer ring 31 are installed coaxially so that their central axes coincide with the central axis of the shaft 20 together.

At the middle part of the inner circumferential surface of the outer ring 31 in the axial direction, a concave outer rolling surface 31a, which guides the rolling of the rolling element 33 so as to face the inner rolling surface 30a of the inner ring 30, is formed on the outer ring 31. formed throughout The outer rolling surface 31a has an arcuate cross-sectional shape when cut with a plane passing through the central axis of the outer ring 31.

As the material of the outer ring 31, metal materials such as stainless steel can be used, for example. The outer ring 31 can be manufactured by, for example, forging and machining.

As shown in FIG. 6, the retainer 32 includes a circular annular body portion 32a and seven pairs of claws rising in an arc shape so that the distance between them approaches the tip formed at the upper end of the body portion 32a. It has parts 32b and 32c. Seven pairs of claws 32b and 32c are provided at regular intervals in the circumferential direction of the retainer 32 . A ball bag B having a substantially circular shape when viewed from the front is formed on the inner side of each facing nail portion 32b and nail portion 32c to hold the rolling element 33 rotatably.

Also, the number of pairs of claws, that is, the number of ball bags B is not limited to 7, but may be 6 or less, or may be 8 or more.

The inner diameter of the retainer 32 is larger than the outer diameter of the inner ring 30, and the outer diameter of the retainer 32 is smaller than the inner diameter of the outer ring 31. In the state where the retainer 32 is installed between the inner ring 30 and the outer ring 31, the rolling elements 33 are each rotatably held in each ball bag B. In this way, in a state where the inner ring 30, the outer ring 31 and the retainer 32 do not interfere with each other, the inner ring 30a of the inner ring 30 and the outer ring 31a of the outer ring 31 transfer The fuselage 33 is disposed.

The retainer 32 is capable of rotating around the central axis L2 while holding the rolling elements 33 rollably on each ball bag B.

The material of the retainer 32 is not particularly limited, and examples thereof include resins such as polyamide resin.

Between the pair of claws 32b and 32c at the upper end of the retainer 32 and the pair of claws 32b and 32c next to it, a grease bag G is formed that is shallower than the ball bag B. has been That is, in the retainer 32, ball bags B and grease bags G are alternately formed in the circumferential direction by pairs of claws 32b and 32c.

When the rolling element 33 rotates along with the retainer 32 in the state where the grease of the present invention is located in the grease bag G and the rolling element 33 is arranged in the cheek bag B, the grease bag G Grease comes out between the inner ring 30 and the outer ring 31 and the rolling element 33, and a lubrication effect by the grease can be obtained.

By applying grease to the rolling bearing 22 using the grease bag G, the amount of grease used can be reduced. This can suppress an increase in the torque of the rolling bearing 22 due to an excessive amount of grease, and it is possible to obtain sufficient cleanliness required for reading and writing to the disk D.

The rolling element 33 in this embodiment is spherical. The rolling element 33 is disposed in the ball bag B of the retainer 32 between the inner rolling surface 30a of the inner ring 30 and the outer rolling surface 31a of the outer ring 31, and the inner rolling surface 30a ) and roll along the outer rolling surface 31a. Each rolling element 33 is uniformly arranged in the circumferential direction by a retainer 32.

The number of rolling elements 33 is 7 in this embodiment, but it may be determined according to the number of ball bags B of the retainer 32, and may be 6 or less or 8 or more.

The material of the rolling elements 33 may be, for example, metal materials such as rolling bearing steel.

The shield plate 34 is an annular plate member that blocks up and down a circular annular space formed between the inner race 30 and the outer race 31. The shield plate 34 is installed above and below the retainer 32 and the plurality of rolling elements 33 between the inner ring 30 and the outer ring 31. Each shield plate 34 is fixed to the outer ring 31 in a state where its outer periphery enters an annular groove 40 for engagement formed in the outer ring 31 .

(action mechanism)

In the information recording and reproducing apparatus 1, the grease of the present invention is placed in the grease bag G of the retainer 32 of the rolling bearing 22. When the swing arm 2 is rotated by the drive of the actuator 7, the grease disposed in the grease bag G passes through the inner ring 30, the outer ring 31, and the sides of the retainer 32, and the inner ring 30 ) and supplied between the outer ring 31 and the rolling element 33, and the lubrication effect of the grease is exerted.

In the information recording and reproducing apparatus 1, since the grease of the present invention is used, the amount of outgas can be sufficiently reduced. Therefore, it is difficult for outgas to collect in the gaps between the head gimbal assembly and the disk D, and stable reading and writing is possible. In addition, since excellent durability can be secured, a state of excellent torque smoothness at low torque can be maintained for a long period of time.

(another embodiment)

The rolling bearing, rolling bearing device, and information recording/reproducing device of the present invention may be those using the grease of the present invention, and are not limited to the above.

For example, the information recording and reproducing apparatus 1 provided with the rolling bearing 22 and the rolling bearing device 6 uses a near field light, but includes a rolling bearing using the grease of the present invention and a rolling bearing device. A general HDD or optical disk (D) equipment may be used.

Also, the rolling bearing device may be without a sleeve. Specifically, for example, a rolling bearing without a sleeve having an annular spacer ring between two rolling bearings arranged axially spaced apart from the outside of the shaft to keep the distance between the rolling bearings from each other at a predetermined distance. It is also good as a bearing device. In this case, the outer ring of the rolling bearing may be directly press-fitted or adhesively fitted into the mounting hole formed at the base of the swing arm.

Also, the rolling element of the rolling bearing may be a cylindrical roller.

[Example]

Hereinafter, the present invention will be described in detail by examples, but the present invention is not limited by the following description.

[Kinematic viscosity]

Kinematic viscosities of mineral oil, PAO, and base oil were measured at 40°C using a Cannon-Fenske viscometer in accordance with JIS K2283.

[Measurement of Outgas Amount]

Sample grease (4.5 to 5.5 mg) was evenly applied to each 15 mm aluminum foil with a glass rod to obtain a measurement sample. The measurement sample was heated in an oven at 85° C. for 3 hours together with 5 μL (100 ng) of a standard reagent (Hexa), and the generated gas was adsorbed to the collection tube. Subsequently, the collection tube was installed in a heating and desorption device (TD-100), heated to 320 ° C, and the gas generated in the collection tube was sent to a gas chromatograph mass spectrometer (GC-MS). GC-MS is maintained at 40 ° C. for 2 minutes, heated to 280 ° C. over 20 minutes at 12 ° C./min, chromatogram data is obtained by a temperature profile maintained at 280 ° C. for 20 minutes, and in the GC-MS internal library Component identification was performed. The amount of outgassing was calculated at the standard reagent exchange rate based on the chromatographic peak (equivalent to 100 ng) of the standard reagent (hexa).

[Durability test]

The rolling bearing device 6 illustrated in FIGS. 3 to 6 is manufactured, grease of each example is placed in the grease bag G of the retainer 32, continuous operation is performed under the following operating conditions, and the initial torque before the continuous operation The torque fluctuation range (hash) was measured as a ratio of torque after continuous operation for .

<Operating conditions>

Operating frequency: 30Hz

Action angle: 10deg

Operating time: 100 hours

Operating temperature: 80℃

[Grease bump test]

The rolling bearing device 6 illustrated in FIGS. 3 to 6 was manufactured, each grease was placed in the grease bag G of the retainer 32, continuous operation was performed under the following operating conditions, and the torque immediately after the continuous operation was measured and evaluated according to the following criteria.

<Operating conditions>

Operating frequency: 15Hz

Action angle: 5deg

Operating time: 50 hours

Operating temperature: room temperature

<Evaluation Criteria>

○: Compared with the initial torque before continuous operation, the torque immediately after continuous operation hardly changes.

x: Compared with the initial torque before continuous operation, the torque immediately after the continuous operation changes greatly.

[Low Temperature Torque Test]

In accordance with JIS K 2220 (Low Temparature Torque Test Rolling Bearing: 6204), low-temperature torque tests were conducted at 0°C and -30°C, and the rotational torque was measured after the starting torque (initial torque) and the torque after starting were stable.

[Long-term evaporation loss test]

Put 5g of grease in a Petri dish with an outer diameter of 41mm, an inner diameter of 37mm, and a height of 8mm (receiving height: 5mm), place it in a thermostat set to 85℃, 100℃, or 130℃ on a smooth and flat surface, and take out the grease at regular intervals. measured the mass of The evaporation loss (% by mass) of the grease was calculated from the change in mass at each time relative to the mass of the grease before leaving it in the thermostat.

[Example 1]

Refined mineral oil (categorized in Group III in the API base oil category. Kinematic viscosity ν1 = 47mm ² /s (40℃) Flash point 250℃ or higher) and PAO (a mixture of tri- and pentamers of C8-C12 α-olefins, kinematic viscosity ν2 = 30 mm ² /s (40°C)) was mixed at a weight ratio of 3:7 (kinematic viscosity ν = 34 mm ² /s (40°C)).

Subsequently, grease was performed using the base oil and an alicyclic diurea compound as a thickener, and an antioxidant and a rust preventive were added and mixed. The ratio of each component was 86.0 mass % of the base oil, 12.5 mass % of the thickener, 0.5 mass % of the antioxidant, and 1.0 mass % of the rust inhibitor with respect to 100 mass % of the grease.

[Example 2]

It was carried out in the same manner as in Example 1 except that the base oil and an alicyclic diurea compound were used as a thickener, grease was added, an antioxidant and a rust inhibitor were added, and an extreme pressure agent was added and mixed. The ratio of each component was 85.0 mass% of base oil, 12.5 mass% of thickener, 0.5 mass% of antioxidant, 1.0 mass% of rust inhibitor, and 1.0 mass% of extreme pressure agent with respect to 100 mass% of grease.

[Comparative Example 1]

Mineral oil (kinematic viscosity ν1 = 52 mm ² /s (40°C) flash point 220°C or higher), PAO (mixture of tri-pentomers of C8-12 α-olefins, kinematic viscosity ν2 = 52 mm ² /s (40°C)) They were mixed at a mass ratio of 1:1 to obtain a base oil (kinematic viscosity ν = 52 mm ² /s (40°C)). Subsequently, grease was performed using the base oil and an alicyclic diurea compound as a thickener, and an antioxidant and a rust preventive were added and mixed.

[Comparative Example 2]

A grease was obtained in the same manner as in Example 1 except that PAO (a mixture of tri- and pentamers of C8-C12 α-olefins, kinematic viscosity ν = 30 mm ² /s (40° C.)) was used as the base oil.

[Comparative Example 3]

Grease was obtained in the same manner as in Example 2, except that PAO (a mixture of tri- and pentamers of C8-C12 α-olefins, kinematic viscosity ν = 30 mm ² /s (40° C.)) was used as the base oil.

[Reference Example 1]

As the grease, a commercially available grease α for rolling bearings of an information recording and reproducing apparatus was prepared. Grease α also contains a urea compound as a thickener.

Table 1 shows the outgassing amount measurement, durability test, and grease impact test results of each Example and Comparative Example. In addition, Table 2 shows the low-temperature torque test results of the greases of Examples 2 and 1, and the long-term evaporation loss test results are shown in FIGS. 7 to 9.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3
base oil

Kinematic viscosity of mineral oil v1 [mm ² /s] 47 47 52 - - Kinematic viscosity of PAOv2 [mm ² /s] 30 30 52 30 30 v1/v2 1.57 1.57 One - - Kinematic viscosity of base oil v [mm ² /s] 34 34 52 30 30 Outgas volume [ng]










whole amount 866 917 7622 812 1444 aliphatic hydrocarbons 284 272 3817 288 363 Aromatic Hydrocarbon 40 39 187 13 42 Amine type 5 4 1213 9 17 phenolic 309 404 128 266 341 alcoholic 32 20 120 10 29 aldehyde type 14 29 0 22 27 etheric 0 0 0 0 0 ketone system 10 22 374 21 25 ester type 46 34 508 55 50 Benzotriazole 79 50 0 82 496 unknown ingredient 49 43 1275 46 54 Endurance test (torque fluctuation range) [times] 1.8 1.6 5 2 1.7 grease bump test ○ ○ X (x6) △ (2.4 times) △ (1.5 times)

Example 2 Reference example 1 Measurement temperature -30℃
Starting torque [mN m] 220 470 Rotational torque [mN m] 35 74 Measurement temperature 0℃
Starting torque [mN m] 55 99 Rotational torque [mN m] 17 27

As shown in Tables 1 and 2, the greases of Examples 1 and 2 containing the base oil using mineral oil having a kinematic viscosity ν1 higher than the kinematic viscosity ν2 of PAO at the ratio of the present invention had a small amount of outgas. In addition, in Examples 1 and 2, torque fluctuation was small and excellent durability was shown even in the durability test and the grease bump test. In addition, the grease of Example 2 had superior low-temperature characteristics and less evaporation loss than the commercially available grease α of Reference Example 1.

On the other hand, the grease of Comparative Example 1 with a large proportion of mineral oil had a large amount of outgas. Further, in Comparative Example 1, the torque fluctuation range in the endurance test was large, and the durability was poor compared to Examples 1 and 2. Also, in the grease crash test, the torque after continuous operation increased up to 6 times compared to the torque before continuous operation. This is considered to be due to the formation of bumps due to accumulation of oxidation-degraded grease at the edge of the operating range of continuous operation, or to increased wear at the edge of the operating range of continuous operation.

Further, in the greases of Comparative Examples 2 and 3 not using mineral oil, the outgas amount was small, but the durability was inferior.

[Experimental Example 1]

The outgassing amount was measured for the following four components A to D.

Component A: A mixture of 3 to 5 monomers of α-olefins having 10 carbon atoms (Kinematic viscosity ν2 = 30 mm ² /s (40 ° C) or less, referred to as PAO (decene)).

Component B: A mixture of 3 to 5 monomers of α-olefins having 8 to 12 carbon atoms (Kinematic viscosity ν2 = 30 mm ² /s (40 ° C) or less, referred to as PAO (MIX)).

Component C: A component obtained by adding an antioxidant to PAO (decene) so that the content of the antioxidant is 0.2% by mass based on the total mass of PAO (decene) and antioxidants.

Component D: A component obtained by adding an antioxidant to PAO (MIX) so that the content of antioxidant is 0.2% by weight based on the total mass of PAO (MIX) and antioxidants.

The results are shown in Table 3.

Component A (decene) Component B (PAO (MIX)) Ingredient C (decene + antioxidant) Ingredient D (PAO (MIX) + antioxidant) Outgassing amount [ng]










whole amount 1544 351 1430 257 aliphatic hydrocarbons 975 43 894 31 aromatic hydrocarbons 8 9 5 9 Amine type 0 0 4 0 phenolic 89 84 96 64 alcoholic 0 0 2 11 aldehyde type 5 18 35 12 etheric 0 0 0 0 ketone system One 0 5 4 ester type 7 4 74 16 Benzotriazole 0 0 0 0 unknown ingredient 454 191 311 110

As shown in Table 3, compared to components A and C in which PAO is a single component, components B and D in which PAO is a mixture of tri- to pentamers of α-olefins having 8 to 12 carbon atoms have a small amount of outgas.

[Experimental Example 2]

An oxidative degradation test was conducted on the above components A to D. Specifically, 5 g of each component was collected in a beaker (outer diameter X height: 30 mm X 40 mm) and left in a thermostat at 100°C.

After 240 hours, the components of each beaker were measured by FT-IR every 24 hours, and the presence or absence of oxidative deterioration was confirmed. The time at which oxidative degradation was first confirmed is shown in Table 4.

oxidation deterioration time Component A (decene) 288 hours Component B (PAO (MIX)) 1848 hours Ingredient C (decene + antioxidant) 1560 hours Ingredient D (PAO (MIX) + antioxidant) 2064 hours

As shown in Table 4, components B and D, in which the PAO is a mixture of tri- to pentamers of α-olefins having 8 to 12 carbon atoms, were superior in oxidation resistance volatility to components A and C in which the PAO was a single component.

In the above, preferred embodiments of the present invention have been described, but the present invention is not limited to these embodiments. Addition, omission, substitution, and other changes to the configuration are possible without departing from the spirit of the present invention. The present invention is not limited by the foregoing description, but only by the appended claims.

Claims (13)

Contains a base oil and a thickener,
The base oil includes mineral oil and poly-α-olefin,
The ratio of the mineral oil to 100 mass% of the base oil is 10 to 40 mass%,
The kinematic viscosity ν1 of the mineral oil at 40 ° C is higher than the kinematic viscosity ν2 of the poly-α-olefin at 40 ° C,
The poly-α-olefin includes a mixture of 3 to 5 monomers of α-olefins having 8 to 12 carbon atoms. According to claim 1,
A grease in which the ratio of the poly-α-olefin is greater than the ratio of the mineral oil in the base oil. According to claim 1,
A grease having a ratio ν1 / ν2 of the kinematic viscosity ν1 to the kinematic viscosity ν2 of 1.3 or more. According to claim 1,
A grease having a kinematic viscosity ν1 of 40 mm ² /s or more. According to claim 1,
A grease having a kinematic viscosity ν2 of 20 mm ² /s or more. According to claim 1,
A grease having a kinematic viscosity ν of the base oil at 40° C. of 25 to 45 mm ² /s. According to claim 1,
The base oil includes refined mineral oil classified as Group III in the base oil category defined by the American Petroleum Institute, and the flash point of the refined mineral oil is 240 ° C. or higher. According to claim 1,
The base oil includes refined mineral oil classified as Group III in the base oil category set by the American Petroleum Institute, and the flash point of the refined mineral oil is 250 ° C. or higher. delete According to claim 1,
A grease wherein the thickener is a urea compound. A rolling bearing comprising the grease according to any one of claims 1 to 8 and 10. A rolling bearing device comprising a shaft and the rolling bearing according to claim 11. An information recording/reproducing device comprising the rolling bearing device according to claim 12.

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