JP2002250351A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long service-life rolling bearing capable of preventing the occurrence of peeling accompanied with a white structural change due to hydrogen embrittlement even if it is used under a high temperature, high- speed, and high-load conditions and water intrudes from the outside. SOLUTION: This rolling bearing 1 is constituted such that a plurality of rolling elements 13 are turnably held at substantially equal intervals between an inner ring 10 and an outer ring 11 through a holder 12, and a grease composition prepared by blending an electrical conductive substance at a ratio of 0.1 to 10 mass % of the total amount of the grease composition with the grease composition having fluorine polymer oil as base oil and polytetrafluoroethylene as thickener is sealed therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing enclosing a grease composition, and more particularly, to an electrical component of an automobile,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing having an excellent durability life, which can be suitably used in an area where water is easily mixed under high-temperature, high-speed, and high-load conditions, such as an alternator, an intermediate pulley, and an electromagnetic clutch for a car air conditioner.

[0002]

2. Description of the Related Art Rolling bearings are generally used for electric components of automobiles, alternators and intermediate pulleys as engine accessories, electromagnetic clutches for car air conditioners, and the like, and grease is mainly used for lubrication thereof.

[0003] In these electrical components and engine accessories, miniaturization and high performance and high output are increasingly required.
The reduction in output due to miniaturization is inevitable. For example, in an alternator or an electromagnetic clutch for a car air conditioner, the reduction in output is compensated for by increasing the speed, and accordingly, the speed of the intermediate pulley is also increased. Further, the demand for improved quietness increases the sealing of the engine room and promotes a high temperature inside the engine room. Therefore, each of the above components must also withstand high temperatures.

On the other hand, the grease for rolling bearings used in each of the above components is generally a grease containing a synthetic oil as a base oil and a urea compound as a thickener. This urea-synthetic oil-based grease has a content of 170 to 180.
Up to a temperature of ° C, the bearing lubrication life is long and it can be used sufficiently. However, recently, as described above, the operating temperature tends to be high, and under the condition that the bearing temperature becomes 200 ° C. or more, the grease due to the evaporation of the base oil and the accompanying hardening of the grease, and the destruction of the thickener, Urea-synthetic oil-based grease may cause seizure at an early stage.

[0005] Further, since the rolling bearing for each component is used under high temperature, high speed and high load, Japanese Patent No. 2878 is used.
As described in Japanese Patent No. 749, grease may be decomposed to generate hydrogen. Then, the generated hydrogen infiltrates the bearing steel and causes peeling accompanied by a change in white structure due to hydrogen embrittlement, and prevention of the peeling is a new important issue.

Further, these rolling bearings are belt-driven auxiliary machine bearings provided outside the engine, and are susceptible to intrusion of muddy water and rainwater jumping up from a road surface. At present, it is impossible to completely prevent water intrusion even if the contact rubber seal can prevent water intrusion to some extent. In addition, since the engine of a car is a machine that repeats operation and suspension, the temperature in the housing of the rolling bearing decreases when the engine is suspended, reaching the dew point, and moisture in the air around the bearing condenses. Water droplets, which may adhere to the bearings or mix into the lubricant. And Japanese Patent Laid-Open No. 11-7212
As described in Japanese Patent Publication No. 0, these invading moistures generate hydrogen, and cause peeling accompanied by a change in white structure due to hydrogen embrittlement as described above.

Further, since the rolling bearing for each component is rotated by a pulley driven by a belt, static electricity is generated between the belt and the pulley. Normally, during rotation of the bearing, due to the oil film of the lubricant, the inner and outer rings are insulated and a large potential difference is generated.However, if metal contact is caused by strong vibration etc., the inner and outer rings are connected at once, The generated DC voltage causes electrolysis of water to promote the generation of hydrogen ions, and the peeling accompanied by the white structure change due to the hydrogen brittle peeling becomes more likely to occur.

[0008]

As described above, conventional urea-synthetic oil-based greases are difficult to use at 200 ° C. or higher, and therefore cannot meet the demand for further improvement in heat resistance. . In addition, effective measures for preventing exfoliation accompanied by white structure change due to hydrogen embrittlement have not been established.

Accordingly, the present invention is used under high temperature, high speed and high load conditions, and does not cause exfoliation accompanied by a change in white structure due to hydrogen embrittlement even if it receives water from the outside, and has a long life. An object of the present invention is to provide a rolling bearing.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a plurality of rolling elements rotatably held at substantially equal intervals between an inner ring and an outer ring via a retainer, and A grease composition containing a fluorinated polymer oil as a base oil and polytetrafluoroethylene (PTFE) as a thickener is added with a conductive substance in an amount of 0.1 to 10% by mass based on the total amount of the grease composition.
The present invention provides a rolling bearing characterized by enclosing a grease composition blended at a ratio of:

In the rolling bearing of the present invention, since the grease composition contains a fluorinated polymer oil and PTFE, it has high heat resistance and excellent seizure resistance even at a high temperature of about 200 ° C. In addition, the electrolysis of water that promotes the generation of hydrogen ions is prevented by applying a current between the inner and outer rings by using a conductive substance, and the occurrence of peeling accompanied by a change in white structure due to hydrogen embrittlement is suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The rolling bearing of the present invention will be described below in more detail.

The configuration of the rolling bearing of the present invention is not limited. For example, a ball bearing 1 shown in a sectional view in FIG. 1 can be exemplified. In the ball bearing 1, a plurality of balls 13 as rolling elements are rotatably held at substantially equal intervals between an inner ring 10 and an outer ring 11 via a retainer 12, and furthermore, the inner ring 10, the outer ring 11, and A bearing space S formed by the balls 13 is filled with a grease composition (not shown) described later in a predetermined amount, and is sealed with a seal 14.

[Base oil] Fluorine is used as the base oil of the grease composition.
Although generalized polymer oils can be used,
The degree is 20-200mm^Two/ Sec, especially 30 to 180 mm^Two/
It is preferable to use a fluorinated polymer oil
New 200mm viscosity at 40 ° C ^TwoOver / sec
In such cases, agitation resistance increases and heat generation increases.
Each element of the rolling bearing (inner ring, outer ring, rolling element) expands
Internal clearance decreases, causing abnormal wear and seizure.
There is. The viscosity at 40 ° C. is 20 mm^Two/ Se
If less than c, a sufficient oil film cannot be formed,
May cause seizure at an early stage.

Further, the fluorinated polymer oil has, for example, the following (1):
Those having a side chain structure as shown in the formula (2) are desirable. In the formula, m and n are positive integers.

[0016]

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Fluorinated polymer oils having a linear structure generally have a high viscosity index and stable torque characteristics over a wide temperature range, but tend to have poor seizure resistance due to heat generation. On the other hand, a fluorinated polymer oil having a side chain structure has low heat build-up and thus has excellent seizure resistance and can be said to be preferable as a grease for a rolling bearing used in each of the above components.

[Thickener] As long as it is made of PTFE, it may be spherical, polyhedral (cubic or rectangular) or extremely needle-like. These PTFEs can be used alone or as a mixture. The amount of PTFE is set so that the penetration of the grease composition is No. 1 to No. 1 in the grade specified by NLGI in order to have fluidity suitable for the present invention.
An amount such as to be 3 is preferred.

[Conductive Material] A conductive material is an essential additive in the grease composition sealed in the rolling bearing of the present invention. This conductive substance is not particularly limited as long as it has good conductivity, and may be a liquid or a solid. Among them, it is particularly preferable to use carbon black from the viewpoints of easy handling and availability, and not deteriorating lubricity. In addition, this carbon black, considering the dispersibility in the grease composition, etc.,
It is preferable to select one having an average particle size of about 10 to 300 nm.

The preferable amount of the conductive substance is 0.1 to 10% by mass based on the total amount of the grease composition. If the amount is less than this, sufficient conductivity cannot be imparted to the grease composition. If the amount is more than this, the grease composition is hardened, and the seizure life may be reduced. If the conductivity is ensured and the reduction in the seizure life is taken into account, the amount is preferably 0.5 to 10% by mass based on the total amount of the grease composition. Further, it is more desirable that the amount of the grease composition after the addition of the conductive substance is such that the mixing consistency becomes NLGI Nos. 1 to 3 described above.

[Additives] In the present invention, in addition to the above-mentioned fluorinated polymer oil, PTFE and a conductive substance, the grease composition is not impaired in its preferable properties.
Known additives such as an antioxidant, a rust preventive, and an extreme pressure additive may be contained. It is preferable that these additives make up less than 10% by mass of the total amount of the grease composition.

[Production Method] There is no particular limitation on the method for preparing the above grease composition. It is preferable to mix a predetermined amount of the conductive substance with a base grease obtained from a fluorinated polymer oil and PTFE. However, after the addition of the conductive substance, it is necessary to sufficiently disperse the mixture by sufficiently stirring with a kneader or a roll mill. When performing this treatment, heating is also effective. In the above-mentioned production method, other additives such as an antioxidant and a rust preventive are preferably added at the same time as the conductive substance in the process.

[0023]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto.

(Preparation of Test Grease) Test greases of Examples and Comparative Examples were prepared with the compositions shown in Table 1. The base oil A in the table is a fluorinated polymer oil represented by the general formula (1), and the base oil B is a fluorinated polymer oil represented by the following general formula (3). Carbon black having an average particle size of 30 nm was used. In Examples A and B, fluorinated polymer oils having different kinematic viscosities were used, and in Example C, test greases were prepared by changing the amount of carbon black added. Further, the test grease was adjusted so that the penetration consistency became NLGI Nos. 1 to 3.

[Table 1]

[0025]

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(Test-1: High-temperature seizure life test)
Using a deep groove ball bearing with a contact rubber seal having a diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm, each test grease shown in Examples A and B and Comparative Example A for comparison was sealed so as to occupy 30% of the bearing space volume. The bearing was continuously rotated under the conditions of an inner ring rotation speed of 20000 min ^-1 , a bearing outer ring temperature of 200 ° C., and a radial load of 686 N. The test was terminated when seizure occurred and the temperature of the bearing outer ring rose to 220 ° C. or higher.
The number of tests was 4 in each case, and the relative comparison was performed with the lifetime of Comparative Example A set to 1. The results are shown in FIG.

(Test-2: Sudden Acceleration / Deceleration Test and High-Temperature Seizure Life Test) The peeling life was evaluated by rapidly accelerating and decelerating a bearing incorporated in an alternator using an engine. That is, the test grease of Example C and the test grease of Comparative Example A for comparison were used for a single row deep groove ball bearing (inner diameter φ17).
mm, outer diameter φ47mm, width 14mm) 30% of bearing space volume
And bearing rotation speeds of 1200 to 9600
repetition of min ^-1, the bearing outer ring temperature 120 ° C., was continuously rotated under conditions of the pulley load 980 N, were tested with the goal of 300 hours. Then, the test was terminated at the time when the bearing outer ring rolling surface was separated and vibration occurred. After the test was completed, the presence or absence of a structural change inside the bearing was visually observed. The number of tests was 10 in each case, and the probability of occurrence of peeling and the probability of occurrence of structural change were calculated by the following equations. Probability of peeling = (number of peeling / number of tests) × 100 Probability of structure change = (number of occurrences of structure change / number of tests) × 10
0

Further, the above-mentioned high temperature seizure life test was performed in the same manner. As a result, the value of Comparative Example A was set to 1, and a relative comparison was performed. The results are shown in FIG.

From the results of both tests, it was found that a fluorinated polymer oil, particularly a fluorinated polymer having a viscosity at 40 ° C. of 20 to 200 mm ² / sec, was used as a base oil, PTFE was used as a thickening agent, and carbon black was used in an amount of 0.1 to 10 mm. It can be seen that by enclosing the grease composition blended at a ratio of mass%, a rolling bearing having an excellent seizure life and a low probability of occurrence of peeling and structural change can be obtained. On the other hand, if the added amount of carbon black is less than 0.1% by mass, conductivity is insufficiently imparted, and peeling and structural change are apt to occur, and if the added amount exceeds 10% by mass, seizure tends to occur. Become.

[0030]

As described above, according to the present invention,
Rolling bearings with excellent heat resistance and anti-peeling effect can be obtained, especially for high-temperature, high-speed, high-load conditions such as automotive electrical components, alternators and intermediate pulleys as engine accessories, electromagnetic clutches for car air conditioners, etc. It is suitable for a part where water is easily mixed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a rolling bearing of the present invention.

FIG. 2 is a graph showing the results of Test-1 in Examples.

FIG. 3 is a graph showing the results of Test-2 in Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball bearing 10 Inner ring 11 Outer ring 12 Cage 13 Ball 14 Seal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 19/52 F16C 19/52 // C10N 20:00 C10N 20:00 Z 30:00 30:00 Z 30 : 08 30:08 40:02 40:02 50:10 50:10 F term (reference) 3J101 AA02 AA32 AA42 AA52 AA62 EA53 EA64 EA72 FA06 FA53 FA60 GA01 GA16 GA24 4H104 AA04C CD02B CD04A EA14C LA04 LA20 QA18

Claims (1)

[Claims] 1. A plurality of rolling elements are rotatably held at substantially equal intervals between an inner ring and an outer ring via a retainer, and fluorinated polymer oil is used as a base oil, and polytetrafluoroethylene is added. A rolling bearing, wherein a grease composition obtained by mixing a conductive substance with a grease composition as an agent in a ratio of 0.1 to 10% by mass of the total amount of the grease composition is sealed.