JP2011231785A - Rolling bearing for electric equipment and engine accessory of automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing for electric equipment and an engine accessory of an automobile with a long life not causing peeling following white texture change due to hydrogen embrittlement even when used at high temperature, at high speed, under a high load and in an environment susceptible to water intrusion from the outside.SOLUTION: The rolling bearing for electric equipment and an engine accessory of an automobile includes an inner ring 2 having a deep groove type inner ring track 3, an outer ring 5 having a deep groove type outer ring track 6 and arranged concentrically with the inner ring 2, a plurality of ceramic balls 8 provided so as to freely roll between the inner ring track 3 and the outer ring track 6, a retainer 9 rotatably retaining the balls 8 at substantially equal intervals, and a contact type conductive seal 10 attached to the outer ring 5 and slidably contacting the inner ring 2. The rolling bearing is lubricated by conductive grease G sealed in a space surrounded by the inner ring 2, the outer ring 5, and the seal 10.

Description

  The present invention relates to a rolling bearing used for automobile electrical components, alternators and intermediate pulleys as engine auxiliary machines, electromagnetic clutches for car air conditioners, and the like.

  Rolling bearings are generally used for automobile electrical components, alternators and intermediate pulleys as engine accessories, and electromagnetic clutches for car air conditioners, and grease is mainly used for lubrication.

  These electrical components and engine accessories are required to be smaller and have higher performance and higher output. However, output reduction due to miniaturization is unavoidable. For example, in the case of electromagnetic clutches for alternators and car air conditioners, the speed is increased. Compensates for the decrease in output.

  FIG. 2 shows the structure of the pulley portion of the alternator 20 intended for use at high speed rotation. The rolling bearing 21 that rotatably supports the pulley 22 has a bearing for maintaining lubricity at high speed rotation. Grease-filled bearings with grease inside are used.

  In the above structure, in order to prevent a reduction in transmission efficiency due to downsizing of the pulley 22, a method is adopted in which a large number of engagement grooves 23 of the transmission belt are formed in the pulley 22 and the belt tension is increased. For this reason, since the pulley 22 is similarly increased in speed and generates heat, the rolling bearing 21 is also required to have high temperature durability.

  Against this background, rolling bearings used in automobile electrical components, alternators and intermediate pulleys that are engine accessories, and electromagnetic clutches for car air conditioners, etc., use synthetic lubricating oil as the base oil and increase the amount of urea compounds. Rolling bearings in which urea-synthetic oil grease blended as an agent is enclosed have become the mainstream.

  Recently, however, the engine room has been sealed due to demands for quietness, and the engine room has been downsized to further increase the cabin space. The rise tends to be promoted more.

  The urea-synthetic oil-based grease can be sufficiently used up to an ambient temperature of about 170 to 180 ° C. However, under such use conditions that the ambient temperature becomes 200 ° C. or more due to such environmental changes, the urea-synthetic oil-based grease However, evaporation of the base oil, accompanying hardening of the grease, softening of the grease due to thermal decomposition of the thickener, etc. occur in a complex manner, causing seizure early and reducing the bearing life.

  Also, considering the phenomenon that occurs on the inner ring raceway surface and outer ring raceway surface in rolling bearings used under the conditions of high-speed rotation and high load, the vibration during rotation and the rolling elements that are in frictional contact with the surface constantly It is assumed that specular wear is caused. When such wear occurs, the formation of a new surface caused by the wear catalyzes and the grease is chemically decomposed, and a large amount of hydrogen is generated in the formation region of the new surface due to the decomposition of the grease. The generated hydrogen can easily penetrate into the steel, causing a crack on the back side of the metal surface to cause destruction.

  In order to suppress such a peeling phenomenon due to hydrogen embrittlement, for example, Patent Document 1 discloses a bearing in which a passivation oxidizing agent is added to grease. When a passivating oxidant such as sodium nitrite is added to the grease, the oxidant forms an oxide film on the new surface generated on the rolling surface, and makes the rolling surface inactive. Thereby, since the catalytic action of the new surface is prevented, the decomposition of the grease is suppressed, the generation of hydrogen can be prevented, and the occurrence of peeling due to hydrogen embrittlement can be prevented.

  By the way, the belt-driven auxiliary machine bearing outside the engine is liable to infiltrate muddy water and rainwater splashed from the road surface. These rolling bearings are usually configured to prevent water from entering from the outside with a contact rubber seal, but at present, they cannot be completely prevented. In addition, since the engine of an automobile is repeatedly operated and stopped, the temperature of the bearing decreases when the engine is stopped, the dew point is reached, moisture in the air around the bearing condenses into water droplets, and adheres to the bearing. Or may be mixed in grease. As a result, the hydrogen generated by the infiltrated moisture causes peeling with a white texture change.

  For such a problem, for example, Patent Document 2 discloses a bearing in which the hydrogen ion exponent pH of the grease is set to 7 to 13 in order to suppress the progress of the cathode reaction that causes hydrogen embrittlement. .

  Further, in the pulley driving by the belt, static electricity is generated between the belt and the pulley. Normally, while the bearing is rotating, the inner and outer rings are insulative due to the oil film of the lubricant. However, when a metal contact is caused by strong vibration or the like, the inner and outer rings are connected at once and a large potential difference is generated between the inner and outer rings. And the water mixed in the grease causes electrolysis and the generation of hydrogen ions is promoted, and the peeling accompanied by the white texture change as described above is more likely to occur.

Japanese Patent No. 2878749 Japanese Patent Laid-Open No. 11-072120

  As described above, in rolling bearings used for automotive electrical components, engine auxiliary machines such as alternators and intermediate pulleys, car air conditioner electromagnetic clutches, etc., white structure changes due to hydrogen embrittlement due to moisture entering from the outside. There is a problem that the accompanying peeling easily occurs and is further promoted by static electricity, and prevention thereof is a new important issue.

  However, the bearing of Patent Document 1 has a problem in that hydrogen cannot be prevented from entering until the oxide film is formed, and a sufficient effect cannot be obtained unless the oxide film is formed without a gap. .

  Moreover, in the bearing of patent document 2, there existed a problem that the pH adjusted initially may fluctuate with a time-dependent change, and it was difficult to acquire the stable effect.

  The present invention is a rolling bearing having a long service life without causing separation due to hydrogen embrittlement even when used in an environment with high temperature, high speed, high load, and easy to receive water from the outside. The purpose is to provide.

  In order to achieve the above object, the present invention comprises an inner ring having a deep groove type inner ring raceway at an axially intermediate portion of the outer peripheral surface, and a deep groove type outer ring raceway at an axially intermediate portion of the inner peripheral surface, An outer ring arranged concentrically with the inner ring, a plurality of rolling elements provided rotatably between the inner ring raceway and the outer ring raceway, and a holding for holding the plurality of rolling elements so as to be rotatable at substantially equal intervals. A rolling bearing for an automotive electrical component / engine accessory that is grease lubricated, and the rolling element is a ceramic ball. The contact-type seal is a conductive seal, and the grease is a conductive grease. A rolling bearing for automobile electrical parts and engine auxiliary machines is provided.

  According to the present invention, by using ceramic balls, the heat resistance is excellent, the load applied to the outer ring raceway can be reduced based on the centrifugal force during high-speed rotation, and the friction and wear inside the bearing are reduced. Therefore, the formation of a new surface caused by wear can be catalyzed and the grease can be chemically decomposed to prevent a large amount of hydrogen from being generated in the formation region of the new surface. Can do. Moreover, the occurrence of image sticking can be suppressed.

  In addition, the conductive seal and the conductive grease almost eliminate the potential difference between the inner and outer rings so that the water is not electrolyzed, and the occurrence and progress of peeling accompanied by the change in white structure can be suppressed.

It is a figure which shows the longitudinal drawing which shows the structure of the rolling bearing which is one Embodiment of this invention. It shows the structure of the pulley portion of the alternator intended for use at high speed rotation.

  Hereinafter, the rolling bearing of the present invention will be described in more detail. The configuration itself of the rolling bearing of the present invention is not limited. For example, FIG. 1 is a longitudinal sectional view showing the structure of a rolling bearing according to one embodiment.

  This rolling bearing 1 has an inner ring 2 having a deep groove type inner ring raceway 3 at an axially intermediate portion of the outer peripheral surface and a deep groove type outer ring raceway 6 at an axially intermediate portion of the inner peripheral surface, and is concentric with the inner ring 2. A plurality of ceramic balls 8 each of which is a rolling element provided between the outer ring 5 and the inner ring raceway 3 and the outer ring raceway 6, and the plurality of ceramic balls 8. The cage 9 is rotatably held at substantially equal intervals, and the contact-type conductive seals 10 and 10 are attached to the outer ring 5 and slidably contact the inner ring 2. The bearing space surrounded by the inner ring 2, the outer ring 5, and the conductive seals 10 and 10 is filled with a conductive grease G and sealed. The contact portion between the inner ring raceway 3, the outer ring raceway 6 and the balls 8 is lubricated by the conductive grease G.

  In the case of the rolling bearing of the present invention configured as described above, by using ceramic balls 8 as a plurality of rolling elements, compared with a rolling bearing using balls made of bearing steel which has been generally used conventionally. In addition to being excellent in heat resistance and being able to withstand higher temperatures, it is possible to reduce rolling friction that acts on the contact portion between the ball and the outer ring raceway and the inner ring raceway. That is, since the ceramic balls 8 and the inner ring raceway 3 of the inner ring 2 made of hard metal such as bearing steel are brought into contact with each other, the outer ring raceway 6 of the outer ring 5 is brought into contact with each other, so that different materials are brought into contact with each other. In comparison, the frictional resistance at the contact portion is reduced. Further, since the specific gravity is smaller than that of the steel rolling element, it is possible to reduce the load applied to the outer ring raceway 6 based on the centrifugal force during high-speed rotation, and the friction and wear inside the bearing are reduced. For this reason, it is possible to suppress the wear of the rolling elements and, consequently, the occurrence of seizure.

Here, as ceramics used as the rolling element, silicon nitride (Si ₃ N ₄ ), zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), silicon carbide (SiC), and the like, which may be combined in some cases. It is also possible to use it. As a sintering method, any of HIP (hot isostatic press) method, gas pressure sintering method, HP (hot press) method, normal pressure sintering method, reaction sintering method and the like may be applied. As the additive component, alumina (Al ₂ O ₃ ) -yttria (Y ₂ O ₃ ), magnesia (MgO), ceria (CeO ₂ ) -magnesia (MgO), etc. are known as silicon nitride, but there are no particular limitations. Absent.

  The conductive seal 10 is formed in an annular shape by covering a core metal 12 as a reinforcing member with a conductive rubber 11. Seal fixing grooves 7 and 7 are formed at both end portions on the inner and outer sides of the outer ring 5, and the outer peripheral portion of the conductive seal 10 is fitted into the seal fixing groove 7 using the elasticity of the conductive rubber 11. Thus, the conductive seal 10 is fixed to the outer ring 5. Further, seal grooves 4 and 4 are formed at both outer peripheral outer end surface portions of the inner ring 2, and a seal lip 13 provided on the inner peripheral portion of the conductive seal 10 is in sliding contact with the seal groove 4. Thereby, the inner ring 2 and the outer ring 5 are always electrically energized.

  The conductive rubber 11 is formed by mixing a desired amount of carbon black and conductive fibers as conductive particles in an arbitrary rubber material. As the rubber material, nitrile rubber, acrylic rubber, fluorine rubber, silicon rubber or the like generally used as a sealing material can be appropriately selected.

  As the conductive particles, conductive metal oxides such as graphite, indium / tin oxide, and antimony / tin oxide can be used instead of the carbon black, and these materials can be appropriately selected. As the conductive fiber, stainless fiber, carbon fiber (carbon fiber, carbon tube), or conductive fiber plated on potassium titanate (for example, manufactured by Otsuka Chemical Co., Ltd.) can be used. Further, any thickness and length of the conductive fiber can be selected.

  The total amount of conductive particles and conductive fibers mixed in the rubber material is preferably 20 to 120% by mass with respect to the rubber material. When the total amount of the conductive particles and the conductive fibers is less than 20% by mass, sufficient conductivity cannot be obtained, and when 120% by mass or more is contained, sufficient elasticity cannot be obtained.

  As described above, since the conductive seal 11 is formed by coating an arbitrary rubber material with the conductive rubber 11 in which carbon black as conductive particles and conductive fibers are mixed in a desired amount, the carbon black is connected to each other. Reinforced with conductive fibers, as a result, the volume resistivity representing the magnitude of electrical insulation resistance can be reduced to about 0.1 to 1 Ω · cm.

  The conductive grease G is filled in the bearing space surrounded by the inner ring 2, the outer ring 5, and the conductive seals 10, 10 in order to make the inner ring 2 and the outer ring 5 have the same potential as the conductive seal 10. Is sealed.

The base oil used for the conductive grease G is not particularly limited, and any oil that is normally used as a base oil for lubricating oil can be used. However, no abnormal noise is generated at low temperature startup due to insufficient low temperature fluidity, and in particular, considering the durability to high temperatures exceeding 200 ° C., the kinematic viscosity at 40 ° C. is preferably 30 to 250 mm ² / sec, more preferably Is preferably a synthetic lubricating oil of 50 to ²⁰⁰ mm ² / sec. When the kinematic viscosity at 40 ° C. is less than 30 mm ² / sec, it is difficult to form a sufficient oil film at a high temperature exceeding 200 ° C., and metal contact is likely to occur and early seizure is likely to occur. On the other hand, when the kinematic viscosity at 40 ° C. exceeds 250 mm ² / sec, the agitation resistance of the grease increases and the amount of heat generation increases, so that each element (inner ring, outer ring, rolling element) of the rolling bearing expands and becomes internal The gap is reduced and abnormal wear and seizure are likely to occur. Moreover, it is inferior in the fluidity | liquidity at the time of low temperature, and it becomes difficult to fully satisfy | fill the low temperature starting property as a rolling bearing for motor vehicle electrical components or an engine auxiliary machine.

Examples of the synthetic lubricating oil include hydrocarbon oils, aromatic oils, ester oils, ether oils, and the like. Examples of the hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of the ester oil include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl cinnolate, or trioctyl trimellitate. , Aromatic ester oils such as tridecyl trimellitate, tetraoctyl pyromellitate, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol belargonate, etc. Examples thereof include polyol ester oils, and complex ester oils that are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids. Examples of the ether oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, and monoalkyl. Examples thereof include phenyl ether oils such as tetraphenyl ether and dialkyl tetraphenyl ether.
Other synthetic lubricating base oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether and the like. These synthetic lubricating oils can be used alone or as a mixture, and are adjusted to the above-mentioned preferable kinematic viscosity.

  In addition, mineral oil and natural oil-based lubricating oil can be used in combination as long as high temperature durability is not impaired. In addition, as mineral oil-based lubricating oil, use one obtained by appropriately combining mineral oil with vacuum distillation, degreasing, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, etc. Can do. Examples of natural oil-based lubricating oils include beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other oils and hydrides thereof.

Then, in order to remove the potential difference between the inner and outer rings of the bearing and prevent the peeling phenomenon, conductive powder is added. The conductive powder is not particularly limited, but carbon powder such as carbon black or carbon nanotube can be suitably used in consideration of maintaining conductivity up to a high temperature and not deteriorating the lubricity of grease.
Carbon black preferably has an average particle size of 5 μm or less, and more preferably 2 μm or less. Most preferably, an average particle diameter of 10 to 300 nm is used. Such carbon black is also available from the market, and examples thereof include Ketjen Black EC and Ketjen Black EC600JD manufactured by Lion Akzo. Carbon nanotubes having a diameter of 15 nm or less and a length of 5 μm or less, including C60 and C70 fullerenes, can be suitably used. Preferably, those having a diameter of 10 nm or less and a length of 2 μm or less are used.
Such carbon nanotubes can also be obtained from the market, and examples thereof include carbon nanofiber VGCF manufactured by Showa Denko KK.

  The amount of the conductive powder added is preferably 0.5 to 5% by mass of the total amount of the grease composition. If the addition amount is 0.5% by mass or less, the effect of addition cannot be obtained, and if it exceeds 5% by mass, the fluidity of the grease deteriorates and the seizure life may be reduced, which is not preferable. Further, if the average particle diameter or length exceeds 2 μm, the acoustic performance of the bearing may be affected.

  In addition, in order to further improve the lubrication performance, an antiwear agent, an antioxidant, a rust inhibitor, an extreme pressure agent, an oiliness agent, a metal deactivator, a viscosity index improver, a cleaning dispersant, etc. are used alone as necessary. In addition, or by appropriately adding to the grease in combination, bearing damage can be suppressed, a stable conductive life can be imparted to the grease, and the peeling life can be extended. And in order to suppress the fall over time of conductivity over a longer period, it is preferable to use an antiwear agent and an oily agent in combination. In particular, when a phosphite ester is used as an antiwear agent and a carboxylic acid anhydride is used as an oiliness agent, the effect of suppressing a decrease in conductivity over time is particularly excellent.

  As described above, according to the present invention, it is possible to obtain a long-life rolling bearing that is extremely excellent in high-temperature seizure resistance and anti-separation effect, and in particular, an automotive electrical component, an alternator that is an engine accessory, It can be suitably used as a rolling bearing used in pulleys, electromagnetic clutches for car air conditioners, and the like.

1 Rolling bearing
2 Inner ring
3 Inner ring raceway
4 Seal groove
5 Outer ring
6 Outer ring raceway
7 Seal fixing groove
8 Ceramic balls
9 Cage
10 Conductive seal
11 Conductive rubber
12 Core
13 Seal Lip G Conductive Grease
20 Alternator
21 Rolling bearing
22 pulley
23 Engaging groove of transmission belt

Claims (1)

An inner ring having a deep groove type inner ring raceway at an axially intermediate portion of the outer peripheral surface, an outer ring having a deep groove type outer ring raceway at an axially intermediate portion of the inner peripheral surface, and being arranged concentrically with the inner ring, and the inner ring raceway; A plurality of rolling elements provided between the outer ring raceways and the outer ring raceways, a retainer for rotatably holding the plurality of rolling elements at substantially equal intervals, and attached to the outer ring and in sliding contact with the inner ring. In a rolling bearing for an electrical component of an automobile and an engine auxiliary machine that is lubricated with grease enclosed in a space surrounded by the inner ring, the outer ring, and the seal, the rolling element includes: A rolling bearing for automobile electrical parts and engine accessories, wherein the ball is a ceramic ball, the contact seal is a conductive seal, and the grease is a conductive grease.

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