JP2013234294A - Lubricant composition and rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gelatinizer-based lubricant composition capable of preventing even a small-diameter rolling bearing from being put into a churning state, thereby achieving low torque.SOLUTION: A lubricant composition comprises a base oil and a gelatinizer. The gelatinizer is formed by mixing an amino acid-based gelatinizer with a benzylidene sorbitol derivative and has a yield stress of 1.1×10to 1.5 to 10Pa. The lubricant composition is enclosed in a rolling bearing.

Description

  The present invention relates to a lubricant composition and a rolling bearing formed by sealing the lubricant composition.

  Conventionally, in order to reduce the torque of a rolling bearing, a gelling agent is used instead of a thickener such as a metal soap or a urea compound. Gelling agent-based lubricant compositions that use a gelling agent instead of a thickener easily flow into oil when shearing force is applied, and quickly recover to a gel state when shearing force is no longer applied (Recoverability). Further, the gelling agent-based lubricant composition can reduce the amount of the gelling agent used and can reduce the rolling resistance and lower the torque as compared with the lubricant composition using the thickener.

  The present applicant has also proposed a gelling agent-based lubricant composition in which an amino acid-based gelling agent and a benzylidene sorbitol derivative are used in combination in Patent Document 1 in order to further reduce torque.

JP 2011-26432 A

  However, as a result of further investigation, in the gelling agent-based lubricant composition, the yielding stress of the gelling agent is small (high consistency), and especially in small diameter rolling bearings, a churning state in which the grease is totally agitated. Thus, it has been found that it is difficult to obtain low torque. Accordingly, an object of the present invention is to prevent a churn state even in a small-diameter rolling bearing in a gelling agent-based lubricant composition and to reduce torque.

In order to achieve the above object, the present invention provides the following lubricant composition and rolling bearing.
(1) A lubricant composition containing a base oil and a gelling agent,
A lubricant composition characterized in that the gelling agent is a mixture of an amino acid gelling agent and a benzylidene sorbitol derivative, and the yield stress is 1.1 × 10 ^{4 to} 1.5 × 10 ⁴ Pa. object.
(2) An inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be freely rollable, and encapsulating the lubricant composition according to (1) above. Rolling bearing.

  Although the lubricant composition of the present invention includes a gelling agent, since the yield stress is within a specific range, it is possible to prevent a churn state even in a small diameter rolling bearing and to obtain a low torque.

  In addition, the rolling bearing of the present invention in which the lubricant composition is enclosed also has a low torque and a stable rotational performance.

It is sectional drawing which shows an example of the rolling bearing which concerns on this invention. It is a graph which shows the relationship between the yield stress and relative torque which were obtained in the Example.

  Hereinafter, the present invention will be described in detail.

[Lubricant composition]
The lubricant composition of the present invention contains a base oil and a gelling agent, and various additives are added as necessary. Moreover, the yield stress is adjusted to 1.1 × 10 ^{4 to} 1.5 × 10 ⁴ Pa.

  As the gelling agent, an amino acid gelling agent and a benzylidene sorbitol derivative are used in combination. By using an amino acid-based gelling agent and a benzylidene sorbitol derivative in combination, the initial consistency can be lowered and the amount of gelling agent introduced to the transfer surface can be reduced compared to when each is used alone. And low torque can be obtained. Moreover, recoverability improves more by using together.

  The amino acid gelling agent and the benzylidene sorbitol derivative are not particularly limited as long as the base oil can be gelled, and various compounds can be used, but as the amino acid gelling agent, N-2-ethylhexanoyl-L -Glutamic acid dibutylamide, N-lauroyl-L-glutamic acid- [alpha], [gamma] -n-dibutylamide and the like are suitable, and each may be used alone or in combination of two or more. Further, as the benzylidene sorbitol derivative, dibenzylidene sorbitol, ditrilidene sorbitol, asymmetric dialkyl benzylidene sorbitol and the like are preferable, and each may be used alone or two or more of them may be used in combination.

The total amount of the amino acid-based gelling agent and the benzylidene sorbitol derivative (total gelling agent amount) and the mixing ratio of the amino acid-based gelling agent and the benzylidene sorbitol derivative have a yield stress of 1.1 × 10 ^{4 to} 1.5. is not limited as long as the × ¹⁰ 4 Pa, mixing ratio, by weight, amino acid-based gelling agent: benzylidene sorbitol derivatives = 20-80: 80-20 is preferred. When the mixing ratio is outside the above range, the synergistic effect due to the combined use of the amino acid-based gelling agent and the benzylidene sorbitol derivative is lowered, and the degree of improvement in recoverability is lowered. In particular, it is preferable to mix the amino acid gelling agent and the benzylidene sorbitol derivative in equal amounts.

  In a lubricant composition using a general thickener such as a metal soap or a urea compound, the amount of the thickener needs to be 10 to 30% by mass, but an amino acid gelling agent and a benzylidene sorbitol derivative are added. By using in combination, the total amount of gelling agent can be reduced to about 10% by mass or less, and torque can be stabilized with low torque.

If the yield stress is small, the lubricant composition is in a churning state and low torque cannot be obtained. However, by increasing the yield stress to 1.1 × 10 ⁴ Pa or more, the lubricant composition once bounced from the transfer surface As a result, the lubricant composition is not introduced into the transfer surface more than necessary, and a channeling state in which the rolling resistance is reduced is obtained, and a low torque can be obtained. However, when the yield stress exceeds 1.5 × 10 ⁴ Pa, the torque reduction effect becomes insufficient. In addition, when the yield stress is set to 1.1 × 10 ^{4 to} 1.5 × 10 ⁴ Pa using a general thickening agent, the amount of the thickening agent introduced into the transfer surface decreases and the fluidity decreases. Low torque cannot be obtained.

  The base oil is not particularly limited as long as it is gelled by the gelling agent, and is usually used as a base oil of a lubricant composition (a mineral oil, a synthetic oil or a natural oil) ) Can be used. Specifically, as mineral oil-based lubricating oil, mineral oil is refined by appropriately combining vacuum distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, etc. Synthetic oil base oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, etc., and natural oil base oils include beef tallow, lard, soybean oil, rapeseed oil, rice bran Oils and oils such as coconut oil, palm oil, and palm kernel oil, or hydrides thereof can be used.

In consideration of the low torque, it is advantageous that the base oil viscosity is low, and the kinematic viscosity at 40 ° C. is preferably 10 to 400 mm ² / s in consideration of lubrication performance and the like.

  In order to further improve various performances, various additives may be mixed in the lubricant composition as desired. Additives include antioxidants such as amines, phenols, sulfurs, zinc dithiophosphates and zinc dithiocarbamates, rust preventions such as metal sulfonates, esters, amines, metal naphthenates, and succinic acid derivatives. 1 or 2 types of additives used in lubrication, such as agents, phosphorus-based, extreme pressure agents such as zinc dithiophosphate, organic molybdenum, oiliness improvers such as fatty acids and animal and vegetable oils, metal deactivators such as benzotriazole A mixture of the above can be used. In addition, the addition amount of these additives will not be specifically limited if it is a grade which does not impair the objective of this invention.

  There is no limitation on the method for producing the lubricant composition. For example, a predetermined amount of an amino acid gelling agent and a benzylidene sorbitol derivative is blended in the base oil, and the mixture is heated and stirred until the gelling agent is dissolved. After dissolution, pour into a pre-cooled aluminum pad and cool with running water. Then, the lubricant composition solidified in a gel state is applied to three rolls to obtain a lubricant composition. The additive may be previously dissolved in the base oil, or may be blended with the gelling agent.

[Rolling bearings]
The rolling bearing of the present invention is not limited in the type and structure of the bearing as long as the above-described lubricant composition is enclosed, but includes a non-contact type seal in order to promote torque reduction by the lubricant composition. Those are preferred. FIG. 1 is a cross-sectional view showing an example thereof. The illustrated ball bearing includes an inner ring 2 having an inner ring raceway surface 1 on an outer peripheral surface and an outer ring 4 having an outer ring raceway surface 3 on an inner peripheral surface. The balls 5 are arranged as rolling elements and are held by the cage 7. The bearing space formed by the inner ring 2, the outer ring 4 and the balls 5 is filled with the lubricant composition (not shown) and sealed with a non-contact seal 6.

  Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto.

(Examples 1-3, Comparative Examples 1-5)
As shown in Table 1, a lubricant composition was prepared by blending a base agent with a gelling agent or a thickener. In addition, each numerical value of a base oil, a gelatinizer, and a thickener is a ratio (mass%) with respect to the total amount of a base oil and a gelling agent, or the total amount of a base oil and a thickener. Each lubricant composition was subjected to the following (1) yield pressure measurement, (2) bearing torque test, and (3) bearing leakage test.

(1) Yield Stress Measurement Using a rheometer used for viscoelasticity measurement of a viscoelastic body, the yield stress was defined as G ″ (loss elastic modulus)> G ′ (storage elastic modulus) under the following conditions. Is shown in Table 1.
Test condition gap: 0.1 mm
Temperature: 30 ° C
Oscillation mode: Stress sweep frequency: 10 Hz

(2) Bearing torque test Relative torque value where the dynamic torque 60 minutes after the start of rotation under the following conditions is the torque value, and the torque value of Comparative Example 1 using lithium soap as a general thickener is 1. Asked. The test bearing is assumed to be a small-diameter rolling bearing. The results are shown in Table 1, and a relative torque value of less than 0.7 was accepted. Moreover, the relationship between this relative torque value and the yield stress measured above is shown in a graph in FIG.
Test condition test bearing: NSK Ltd. rolling bearing “608 (inner diameter Φ8 mm, outer diameter Φ22 mm,
Width 7mm) "
Seal type: Steel shield on both sides (non-contact type)
Rotation speed: 1800min ^-1
Axial load: 29.4N
Temperature: Room temperature

(3) Bearing leakage test The bearing was continuously rotated for 100 hours under the following conditions, and the leakage rate of the lubricant composition was calculated from the weight difference before and after the rotation. The test bearing is assumed to be a small-diameter rolling bearing. And the relative leak rate which made the leak rate of the comparative example 1 1 was calculated | required. The results are shown in Table 1. A relative leakage rate of 1.0 or less was accepted.
Test condition test bearing: NSK Ltd. rolling bearing “608 (inner diameter Φ8 mm, outer diameter Φ22 mm,
Width 7mm) "
Seal type: Steel shield on both sides (non-contact type)
Rotational speed: 15000min ^-1
Axial load: 29.4N
Temperature: 120 ° C

As shown in Table 1, Examples 1 to 3 use an amino acid gelling agent and a benzylidene sorbitol derivative in combination, and the yield stress is 1.1 × 10 ^{4 to} 1.5 × 10 ⁴ Pa. Higher torque, lower torque than Comparative Example 1, and less leakage of grease.

  On the other hand, in Comparative Examples 2 and 3, the amino acid gelling agent and the benzylidene sorbitol derivative are used in combination, but the yield stress is lower than those in Examples 1 to 3, and the torque is twice as high. In Comparative Example 4, although the amino acid gelling agent and the benzylidene sorbitol derivative are used in combination, the yield stress is higher than in Examples 1 to 3, and the torque is also high. Comparative Example 5 is a single use of a benzylidene sorbitol derivative, and the yield stress is low and the torque is high even though the content is higher than in Examples 1 to 3. Furthermore, the leak rate is also higher than in Examples 1 to 3 except for Comparative Example 4.

2 Inner ring 4 Outer ring 5 Ball 6 Seal 7 Cage

Claims (2)

A lubricant composition containing a base oil and a gelling agent,
A lubricant composition characterized in that the gelling agent is a mixture of an amino acid gelling agent and a benzylidene sorbitol derivative, and the yield stress is 1.1 × 10 ^{4 to} 1.5 × 10 ⁴ Pa. object.   A rolling bearing comprising: an inner ring; an outer ring; and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be freely rollable, wherein the lubricant composition according to claim 1 is enclosed. .

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