JP4942321B2 - Hub bearing - Google Patents

Description

  The present invention relates to a grease for a hub bearing and a hub bearing for rotatably supporting a wheel of an automobile.

  Until the 1970s, automotive hub bearings were mainly designed by arranging two standard bearings conforming to ISO standards. In the 1980s, a double-row angular contact ball bearing or a double-row tapered roller bearing, called the first generation hub bearing (hereinafter referred to as GEN1), integrated with the outer ring of the back-to-back bearing, Used by automakers. By integrating the outer ring, the initial axial clearance is set to an appropriate value when the bearing is assembled, so preload adjustment is no longer necessary when assembling to the automobile. Next, a double row bearing called a second generation hub bearing (hereinafter referred to as GEN2) in which a flange portion is provided on the outer ring of GEN1 was developed. This is because there are limits to weight reduction and size reduction with standard bearings alone, and the result is a reduction in the number of parts and weight reduction by unitizing with the shaft (hub wheel) and housing (knuckle) that are peripheral parts of the bearing. It is. By changing the fixing to the knuckle from press-fitting to bolt fastening, assembly to the car body has become easier. Furthermore, in the third generation hub bearing (hereinafter referred to as GEN3), the shaft (hub ring) and the bearing inner ring are integrated to reduce the excess wall and further improve the assembly of the line. Recently, a fourth generation hub joint (hereinafter referred to as GEN4) in which a hub bearing and a constant velocity joint are integrated has been developed.

As mentioned above, the assembly workability is greatly improved, and since press-fitting is no longer necessary, it is possible to use a light alloy knuckle that is effective in improving running stability and reducing fuel consumption by reducing unsprung weight. Recently, the use of GEN2 and GEN3 is increasing.
Focusing on the bearing material, conventional bearing steel (eg, SUJ2) was used up to GEN1, but in GEN2 and GEN3 where the outer ring is provided with a flange, carbon steel for mechanical structure such as S53C, which has good forgeability and is inexpensive, is used. It came to be used. The carbon steel for machine structural use has high-frequency heat treatment applied to the raceway part to ensure the rolling fatigue strength of the bearing part, but the surface strength is weak because there are few alloy components, and it is more resistant to surface origin separation than the bearing steel. Inferior. Therefore, in the same lubrication specification as GEN1, durability may be inferior when use conditions are severe.

Wheel bearings are used in very bad conditions such as rainy weather, bad roads, and coastal driving as well as driving in fine weather. Intrusion of moisture and foreign matter into the bearing is suppressed by the seal, but it is not perfect. Therefore, it is inevitable that moisture and foreign matter enter the bearing. Further, from the viewpoint of energy saving, it is required to reduce the torque of the hub bearing. Therefore, the possibility of water intrusion increases, and the lubrication state in the bearing becomes worse. This problem is common to all generations. Furthermore, in GEN2, GEN3, and GEN4 hub bearings that use structural steel as the bearing material, there is a greater risk of surface-origin separation if the lubrication is poor. .
As for the improvement of the grease for the hub bearing, it is known to reduce rotational torque by using a low-viscosity base oil (see Patent Document 1) and impart conductivity for removing static electricity (see Patent Document 2). No consideration has been given to maintaining bearing performance when moisture enters the grease.
When moisture enters the bearing, the following problems arise. When water droplets enter the load area, the oil film is interrupted, which is disadvantageous in terms of lubricity, and there is a risk that metal contact will occur due to the oil film interrupting and surface-origin type peeling will occur. In addition, rust is generated inside the bearing depending on the state of water in the bearing.
JP 2003-239999 A JP 2004-169862 A

  The present invention has been made in view of such circumstances, and the surface resistance of a hub bearing using carbon steel for machine structure is used even under severe lubrication conditions in which water is mixed into grease during operation of the hub bearing. It is an object of the present invention to provide a grease for a hub bearing that improves the starting-type peelability, and a hub bearing that exhibits a long life using the grease.

The hub bearing grease of the present invention is a hub bearing grease sealed in a hub bearing that rotatably supports the wheel of an automobile, and the grease is used to add water to a base grease composed of a non-aqueous base oil and a thickener. It is obtained by blending an additive capable of being uniformly dispersed in the grease.
Further, the additive is a surfactant.

(式中、Ｒ² は、炭素原子数 6〜15 の芳香族炭化水素基を、Ｒ¹ およびＲ³ は、脂環族炭化水素基および芳香族炭化水素基から選ばれた少なくとも一つの炭化水素基をそれぞれ示す。) The thickener is a urea compound represented by the following formula (1), and is characterized in that 1 to 40 parts by weight is blended with 100 parts by weight of the base grease.

Wherein R ² is an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R ¹ and R ³ are at least one hydrocarbon selected from an alicyclic hydrocarbon group and an aromatic hydrocarbon group. Each group is shown.)

The hub bearing of the present invention is a hub bearing having a sliding contact portion made of carbon steel for machine structure, wherein the hub bearing grease is sealed in the hub bearing.
Here, the slidable contact portion refers to, for example, an inner member having a hub ring and an inner ring in a hub bearing as shown in FIG. 1 described later, an outer member that is an outer ring, and a double row of rolling members interposed between both members. A rolling contact with a moving object. In addition, the grease is a hub bearing in an annular shape surrounded by an inner member, an outer member, and two seal members attached in a form that seals between both members and sandwiches double rows of rolling elements in the axial direction. Enclosed in space.

The hub bearing grease of the present invention is a hub bearing grease that is sealed in a hub bearing that rotatably supports an automobile wheel. The grease is a base grease composed of a base oil and a thickener, and water is added to the grease. Since the additive that can be uniformly dispersed therein is blended, the moisture that has entered the bearing can be dispersed as very small particles. For this reason, even if water is mixed in the grease, it is possible to suppress the action of moisture that inhibits oil film formation. For this reason, surface origin type peeling can be suppressed and a long life can be obtained even if lubrication conditions become severe.
Also for rust prevention, since the contact between the steel constituting the bearing and water can be reduced, the generation of rust can be suppressed.

The hub bearing of the present invention is a hub bearing made of carbon steel for machine structure and partially composed of a material subjected to induction heat treatment, and having the material at a sliding contact portion with a rolling element, the hub bearing Lubricate the rolling contact part of the bearing with grease.
As a result of examining the durability of such a hub bearing, it was found that a hub bearing filled with a grease containing an additive capable of uniformly dispersing water in the grease improves the lubrication performance of the rolling contact portion. It was. The present invention is based on such knowledge.

As an additive that can be used in the present invention and can uniformly disperse water in the grease, a surfactant is used. In the present invention, the surfactant is used to render the moisture in the grease harmless so that the oil film is not cut or rusted even if the moisture enters the grease of the hub bearing. Moisture that has entered the grease is dispersed into the grease as fine water particles by the surfactant. Since the water particles which are discontinuous phases are confined in the grease which is continuous phases, the formation of an oil film by the grease cannot be inhibited.
Similarly, water particles, which are discontinuous phases confined in grease, which is a continuous phase, have a very low probability of coming into contact with the structural steel constituting the hub bearing body. The structure steel cannot be rusted because it is immediately replaced with the continuous phase grease by the rotation of the rolling elements in conjunction with the rotation of the main body.
The surfactant that can be used in the present invention is a W / O (water phase dispersed in an oil phase (grease)) type interface that easily traps water particles as a discontinuous phase in a grease that is a continuous phase. The HLB (Hydrophilic-lipophilic Balance) value representing the degree of affinity of the surfactant for water and oil is preferably in the range of 3-7.

  Specific examples of the surfactant used in the present invention include glycol additives such as polyalkylene glycol, carboxylic acid alkylene glycol, and carboxylic acid polyalkylene glycol, carboxylic acid glycerin, and carboxylic acid polyoxyalkylglycerin. , Glyceryl additives such as glyceryl carboxylate, glyceryl additives such as polyglyceryl carboxylate and carboxylic acid polyoxyalkylene glyceryl, ethers such as polyoxyalkylene alkyl ether and carboxylic acid polyoxyalkylene alkyl ether Additives, carboxylic acid polyoxyalkylene alkyl ether diester, sorbitan ester and other ester additives, polyoxyalkylene hardened castor oil, carboxylic acid polyoxyalkylene hardened castor oil Castor oil-based additives, carboxylic acid polyoxyalkylene Rent trimethylolpropane-based additives, metal sulfonate based additive and the like. Of these, metal sulfonate additives and sorbitan ester additives are preferred.

  The blending ratio of the surfactant that can be used in the present invention is 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the base grease. If the amount is less than 0.1 parts by weight, it is difficult to obtain the desired effect sufficiently. If the amount exceeds 20 parts by weight, the effect reaches a peak and the grease characteristics deteriorate.

Examples of base oils that can be used in the grease for hub bearings of the present invention include mineral oil, poly-α-olefin (hereinafter referred to as PAO) oil, ester oil, phenyl ether oil, fluorine oil, and a Fischer-Tropsch reaction. Synthetic hydrocarbon oil (GTL base oil) and the like. Moreover, these mixtures can be used.
As the mineral oil, for example, any of those usually used in the field of lubricating oils and greases such as naphthenic mineral oil, paraffinic mineral oil, liquid paraffin, and hydrodewaxed oil can be used.
Examples of the PAO oil include α-olefin polymers, α-olefin and olefin copolymers, and polybutene. These are oligomers which are low polymers of α-olefin, and have a structure in which hydrogen is added to the terminal double bond. Polybutene, which is a kind of α-olefin, can also be used, which can be produced by polymerizing a starting material mainly composed of isobutylene using a catalyst such as aluminum chloride. Polybutene may be used as it is or after hydrogenation.
Other specific examples of the α-olefin include 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-docosene, 1-tetracocene and the like, and usually a mixture thereof is used.
In consideration of lubrication performance and price, among these base oils, it is preferable to use mineral oil or a mixed oil of mineral oil and synthetic hydrocarbon oil.

The base oil that can be used in the present invention is liquid at room temperature and has a kinematic viscosity at 40 ° C. of 30 to ²⁰⁰ mm ² / sec. Preferably, it is 40-120 mm < ² > / sec. If it is less than 30 mm ² / sec, the base oil deteriorates in a short time, and the resulting deteriorated product promotes the deterioration of the entire base oil, so the durability of the bearing is reduced and the life is shortened. On the other hand, if it exceeds 200 mm ² / sec, the temperature rise of the bearing due to the increase in rotational torque becomes large, which is not preferable.

The blending ratio of the base oil used in the present invention is preferably 60 to 99 parts by weight, more preferably 70 to 95 parts by weight with respect to 100 parts by weight of the base grease.
If the blending ratio of the base oil is less than 65 parts by weight, the grease is hard and the lubricity at low temperatures is poor. If it exceeds 98 parts by weight, it will be soft and leaky.

  Thickeners that can be used in the grease for hub bearings of the present invention include metal soaps such as aluminum, lithium, sodium, barium, calcium, composite aluminum, composite lithium, composite sodium, composite barium, composite calcium, and diurea compounds, Examples include urea compounds such as polyurea compounds. In consideration of durability, fretting resistance, and the like, urea compounds are preferable.

（Ｒ² は、炭素原子数 6〜15 の芳香族炭化水素基を、Ｒ¹ およびＲ³ は、脂環族炭化水素基および芳香族炭化水素基から選ばれた少なくとも一つの炭化水素基をそれぞれ示す。）
ウレア系化合物は、イソシアネート化合物とアミン化合物を反応させることにより得られる。反応性のある遊離基を残さないため、イソシアネート化合物のイソシアネート基とアミン化合物のアミノ基とは略当量となるように配合することが好ましい。
反応は、例えばモノアミン酸とジイソシアネート類を、70〜120℃程度の基油中で十分に反応させた後、温度を上昇させ 120〜180℃で 1〜2 時間程度保持し、その後冷却し、ホモジナイザー、3 本ロールミル等を使用して均一化処理することによりなされ、各種配合剤を配合するためのベースグリースが得られる。 The urea compound is represented, for example, by the following formula (1).

(R ² represents an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R ¹ and R ³ represent at least one hydrocarbon group selected from an alicyclic hydrocarbon group and an aromatic hydrocarbon group, respectively. Show.)
The urea compound is obtained by reacting an isocyanate compound with an amine compound. In order not to leave a reactive free radical, the isocyanate group of the isocyanate compound and the amino group of the amine compound are preferably blended so as to be approximately equivalent.
For example, the reaction is carried out by sufficiently reacting monoamine acid and diisocyanate in a base oil of about 70 to 120 ° C., then raising the temperature and holding at 120 to 180 ° C. for about 1 to 2 hours, and then cooling and homogenizer The base grease for blending various compounding agents can be obtained by homogenizing using a three-roll mill or the like.

The diurea compound represented by the formula (1) can be obtained, for example, by reaction of diisocyanate and monoamine. Diisocyanates include phenylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 2,4-tolylene diisocyanate, 3,3-dimethyl-4,4-biphenylene diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate. Examples of the monoamine include octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, aniline, p-toluidine, cyclohexylamine and the like.
In the present invention, an alicyclic-aromatic urea compound or an aromatic urea compound obtained by a reaction of an aromatic diisocyanate with an alicyclic monoamine and an aromatic monoamine, or an aromatic monoamine alone is preferable.

  The blending ratio of the thickener used in the present invention is preferably 1 to 40 parts by weight, more preferably 3 to 25 parts by weight with respect to 100 parts by weight of the base grease. If the blending amount of the thickener is less than 1 part by weight, the thickening effect is reduced, making it difficult to make a grease. If it exceeds 40 parts by weight, the grease becomes too hard and the desired effect is difficult to obtain.

  A known additive can be added to the hub bearing grease of the present invention as needed within a range not impairing the function. Examples of additives include antioxidants such as amine-based, phenol-based and sulfur-based compounds, anti-wear agents such as sulfur-based and phosphorus-based compounds, rust preventives such as metal sulfonates and polyhydric alcohol esters, metal sulfonates, metal Examples thereof include detergents and dispersants such as phosphates. These can be added alone or in combination of two or more.

An example of the hub bearing of the present invention (third generation hub bearing for a driven wheel) is shown in FIG. FIG. 1 is a cross-sectional view of a hub bearing. The hub bearing 6 includes an inner member 5 having a hub wheel 1 and an inner ring 2, an outer member 3 that is an outer ring, and double-row rolling elements 4 and 4. The hub wheel 1 integrally has a wheel mounting flange 1d for mounting a wheel (not shown) at one end thereof, an inner rolling surface 1a on the outer periphery, and a small diameter step portion extending in the axial direction from the inner transfer surface 1a. 1b is formed.
In the present specification, “outside” in the axial direction means the outside in the width direction when assembled to the vehicle, and “inside” means the center in the width direction.
An inner ring 2 having an inner rolling surface 2a formed on the outer periphery is press-fitted into the small-diameter step portion 1b of the hub wheel 1. The inner ring 2 is prevented from coming off in the axial direction with respect to the hub wheel 1 by a crimped portion 1c formed by plastically deforming the end of the small-diameter stepped portion 1b of the hub wheel 1 radially outward. .
The outer member 3 integrally has a vehicle body mounting flange 3b on the outer periphery, an outer rolling surface 3a, 3a on the inner periphery, and an inner rolling surface 1a facing the double row outer rolling surfaces 3a, 3a, Two rows of rolling elements 4 and 4 are accommodated between 2a so as to roll freely.
The hub bearing grease of the present invention is sealed in a space surrounded by the seal member 7, the outer member 3, the seal member 8, the inner member 5, and the hub wheel 1, and the outer member 3, Covering the periphery of the double row rolling elements 4, 4 sandwiched between the side members 5, and the rolling surfaces of the rolling elements 4, 4 and the inner rolling surfaces 1a, 2a and the outer rolling surfaces 3a, 3a. It is used for lubrication of rolling contact parts.

  The grease for hub bearings of the present invention can be used for bearings that are subjected to high loads other than hub bearings.

  Examples of the material that can be used for the hub bearing of the present invention include bearing steel, carburized steel, and carbon steel for machine structure. Among these, it is preferable to use carbon steel for mechanical structure such as S53C which has good forgeability and is inexpensive. The carbon steel is generally used after high-frequency heat treatment to ensure the rolling fatigue strength of the bearing portion. However, even if the carbon steel for mechanical structure is subjected to high-frequency heat treatment, the surface strength is weak because there are few alloy components, and the resistance to surface-origin separation at the sliding contact portion is inferior to the bearing steel. In response to this surface-origin type peeling, the hub bearing grease of the present invention can prevent surface-origin type peeling of carbon steel for machine structures used in hub bearings by improving the lubrication performance at the sliding contact portion. it can.

The present invention will be specifically described with reference to examples and comparative examples, but is not limited to these examples.
Example 1 and Reference Example 1
A mineral oil / urea base grease (JIS consistency No. 2 grade, consistency: 265 to 295) in which a urea compound was uniformly dispersed as a thickener in a mineral oil as a base oil was prepared.
In 2000 g of mineral oil (Nippon Oil Co., Ltd. turbine 100, kinematic viscosity at 40 ° C .: 100 mm ² / sec), 21.7 g of diphenylmethane-4,4′-diisocyanate, 86.2 g of aniline and 91.7 g of cyclohexylamine And the resulting urea compound was uniformly dispersed to obtain a base grease. The base grease was blended with additives as shown in Table 1 to obtain a hub bearing grease.
The obtained grease for hub bearings was subjected to an oil film formation rate test and a water dispersion confirmation test described below, and the oil film formation rate, how to mix with water, and the water particle diameter were measured. The results are also shown in Table 1.

Oil film formation rate test Bearing used: Angular contact ball bearing 7006ADLLB was used as a hub bearing.
Test conditions: 1.0 g of the obtained grease for hub bearing is sealed in an angular ball bearing 7006ADLLB, and the amount of water injection is 0.35 ml / hour while rotating at a radial load of 650 N, an axial load of 200 N, and a bearing speed of 1000 rpm. The oil film formation rate of grease when water was poured for 10 hours was measured.

Water dispersion confirmation test In order to confirm the degree of dispersion of water in the grease, it was carried out as follows.
Mix and stir the mixture of water and grease so that the water content is 20 parts by weight with respect to 100 parts by weight of the total amount of water and grease, and collect a 0.025 mm thick shim on the glass plate. The glass plate was sandwiched between different glass plates, a load was uniformly applied to the entire glass plate, the grease was spread, and the particle size of water droplets existing in the grease was measured with a microscope.

Example 2 and Comparative Examples 1 to 2
A mineral oil / urea base grease (JIS consistency No. 2 grade, consistency: 265 to 295) in which a urea compound was uniformly dispersed as a thickener in a mineral oil as a base oil was prepared.
In 2000 g of mineral oil (Super Oil C manufactured by Nippon Oil Corporation, kinematic viscosity at 40 ° C .: 100 mm ² / sec), 234.8 g of diphenylmethane-4,4′-diisocyanate and 174.8 g of aniline were reacted. The formed urea compound was uniformly dispersed to obtain a base grease. The base grease was blended with additives as shown in Table 1 to obtain a hub bearing grease.
The obtained hub bearing grease was evaluated in the same manner as in Example 1. The results are also shown in Table 1.

In Table 1, the water particle diameter in the grease that could uniformly disperse water in the grease was very small. In addition, the formation of an oil film was maintained with the grease having a uniform water dispersion in the oil film formation rate, but the oil film was not formed with the grease having a non-uniform water dispersion.
From the above, when water is mixed in the grease, grease that cannot uniformly disperse water cannot form an oil film and may cause surface-origin peeling, but water can be evenly dispersed. Since grease can form an oil film, the occurrence of surface damage can be prevented.

  The hub bearing grease of the present invention is obtained by blending a base grease composed of a base oil and a thickener with an additive capable of uniformly dispersing water in the grease. Even if water is mixed in, the action of moisture that inhibits the formation of an oil film of grease can be suppressed, so that surface-origin separation at the hub bearing for automobiles can be suppressed, and structural steel is used for the bearing rings. Even in conventional bearings, a long life can be obtained even if the lubrication conditions become severe. Therefore, it can be suitably used for railway vehicles, construction machines, automobile electrical accessories and the like that are required to have long-term durability in addition to wear resistance.

It is sectional drawing of a hub bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hub wheel 1a Inner rolling surface 1b Small diameter step part 1c Clamping part 1d Wheel mounting flange 2 Inner ring 2a Inner rolling surface 3 Outer member 3a Outer rolling surface 3b Car body mounting flange 4 Rolling element 5 Inner member 6 Hub bearing 7 Seal member 8 Seal member

Claims (2)

A hub bearing that rotatably supports the wheel of an automobile and has a sliding contact portion made of carbon steel for machine structure,
Grease that lubricates the sliding contact portion is enclosed, and the grease includes a base grease composed of a non-aqueous base oil and a thickener, and an additive that can uniformly disperse water in the grease. Blended ,
The non-aqueous base oil is a mineral oil, and the additive is a Ca sulfonate, which is a surfactant,
The Ca sulfonate is blended in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the base grease.
A hub bearing , wherein the thickener is a urea compound obtained by a reaction of an aromatic diisocyanate with an alicyclic monoamine and an aromatic monoamine, or an aromatic monoamine alone . The hub bearing according to claim 1, wherein the thickener is blended in an amount of 1 to 40 parts by weight with respect to 100 parts by weight of the base grease.

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