阅读说明：本技术 圆锥滚子轴承用润滑脂组成物及圆锥滚子轴承 (Grease composition for tapered roller bearing and tapered roller bearing ) 是由 近藤凉太 川村隆之 于 2020-04-20 设计创作，主要内容包括：提供一种即使在高温、高负载条件下也具有优异的轴承寿命的圆锥滚子轴承用润滑脂组成物、以及填充有该圆锥滚子轴承用润滑脂组成物的圆锥滚子轴承。润滑脂(16)在圆锥滚子轴承(11)中填充于圆锥滚子(14)的周围,该圆锥滚子轴承具备具有滚道面(12a)的内圈(12)、具有滚道面(13a)的外圈(13)以及多个圆锥滚子(14),在内圈(12)的凸缘部与圆锥滚子(14)滑动接触,该润滑脂包含基础油、稠化剂以及添加剂,根据频率而变化的润滑脂(16)的储能模量达到极小的频率为7Hz以上。(Provided are a tapered roller bearing lubricating composition having excellent bearing life even under high-temperature and high-load conditions, and a tapered roller bearing filled with the tapered roller bearing lubricating composition. A grease (16) is filled around a tapered roller (14) in a tapered roller bearing (11) which is provided with an inner ring (12) having a raceway surface (12a), an outer ring (13) having a raceway surface (13a), and a plurality of tapered rollers (14), and which is in sliding contact with the tapered rollers (14) at a flange portion of the inner ring (12), wherein the grease contains a base oil, a thickener, and an additive, and the frequency at which the storage modulus of the grease (16) that changes according to the frequency becomes extremely low is 7Hz or higher.)

1. A lubricating composition for a tapered roller bearing, the composition being filled around tapered rollers in a tapered roller bearing comprising an inner ring having a tapered raceway surface on an outer circumferential surface thereof, an outer ring having a tapered raceway surface on an inner circumferential surface thereof, and a plurality of tapered rollers rolling between the raceway surface of the inner ring and the raceway surface of the outer ring, wherein either the inner ring or the outer ring has a flange portion in which the flange portion is in sliding contact with the tapered rollers,

the lubricating composition for a tapered roller bearing comprises a base oil, a thickener and an additive, and the frequency at which the storage modulus of the lubricating composition for a tapered roller bearing that changes according to the frequency is extremely low is 7Hz or higher.

2. The grease composition for a tapered roller bearing according to claim 1, wherein,

the additive contains an extreme pressure agent containing phosphorus in a molecular structure, and the extreme pressure agent is contained in an amount of 0.05 to 0.3 mass% in terms of phosphorus amount with respect to the entire tapered roller bearing lubricating composition.

3. The grease composition for a tapered roller bearing according to claim 2, wherein,

the additive also contains calcium additive or barium additive.

4. The grease composition for a tapered roller bearing according to claim 1, wherein,

the thickening agent is a complex lithium soap.

5. A tapered roller bearing comprising an inner ring having a tapered raceway surface on an outer circumferential surface thereof, an outer ring having a tapered raceway surface on an inner circumferential surface thereof, a plurality of tapered rollers rolling between the raceway surface of the inner ring and the raceway surface of the outer ring, and a lubricating composition filled around the tapered rollers, wherein either one of the inner ring and the outer ring has a flange portion in which the tapered rollers are in sliding contact with each other, characterized in that,

a lubricating composition for a tapered roller bearing as defined in claim 1.

6. The tapered roller bearing according to claim 5,

the tapered roller bearing is used under high temperature conditions and high load conditions,

the high temperature condition is 80 ℃ or higher, and the high load condition is a condition in which the maximum contact surface pressure of the inner ring and the outer ring is 0.5GPa or higher and the surface pressure of the flange portion is 0.07GPa or higher.

7. The tapered roller bearing according to claim 5,

the tapered roller bearing serves as a tapered hub unit that rotatably supports a wheel of a vehicle.

Technical Field

The present invention relates to a lubricating composition for a tapered roller bearing. The present invention also relates to a tapered roller bearing filled with the lubricating composition for a tapered roller bearing, and more particularly to a tapered roller bearing for a tapered hub unit for rotatably supporting a wheel of a vehicle.

Background

Tapered roller bearings are widely used as bearings for power transmission systems and the like for automobiles and industries. For example, in a wheel support device for rotatably supporting a wheel of an automobile or the like, a tapered roller bearing having a large load capacity and high rigidity is used as a rolling bearing for rotatably supporting a boss. The tapered roller bearing is lubricated by a lubricating composition filled between the axle and the boss.

Tapered roller bearings used for wheel supporting apparatuses are used under such severe conditions as high speed and high load. In particular, since the large end surface of the roller and the flange portion of the raceway wheel perform sliding motion, the lubricating oil film of the grease is likely to break. If the lubricating oil film breaks, metal contact occurs, which causes heat generation and increases frictional wear. Therefore, extreme pressure agent-containing greases are used to improve lubricity and load resistance at high speeds and under high loads and to prevent metal contact due to the fracture of the lubricating oil film.

As such an extreme pressure agent-containing grease, for example, a grease for a wheel bearing of an automobile containing a base oil, a diurea thickener, and an organic molybdenum compound is known (see patent document 1). In patent document 1, the use of the grease prolongs the flaking life and the lubrication life, and reduces fretting wear.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2006-77056

Disclosure of Invention

Problems to be solved by the invention

In recent years, the use environment of a bearing has become more severe with the increase in performance, the increase in rotational speed, the increase in load, and the like of a device using a tapered roller bearing. As the conditions for use of the tapered roller bearing become severe, it is concerned that the conventional lubricating composition is difficult to use for a long period of time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a lubricant composition for a tapered roller bearing having an excellent bearing life even under high-temperature and high-load conditions, and a tapered roller bearing filled with the lubricant composition for a tapered roller bearing.

Means for solving the problems

The present invention provides a lubricating composition for a tapered roller bearing, which is filled around tapered rollers in a tapered roller bearing comprising an inner ring having a tapered raceway surface on an outer circumferential surface thereof, an outer ring having a tapered raceway surface on an inner circumferential surface thereof, and a plurality of tapered rollers rolling between the raceway surface of the inner ring and the raceway surface of the outer ring, wherein either the inner ring or the outer ring has a flange portion, and the tapered rollers are in sliding contact with the flange portion, wherein the lubricating composition for a tapered roller bearing comprises a base oil, a thickener, and an additive, and wherein the lubricating composition for a tapered roller bearing has a frequency at which the storage modulus (japanese: diesel property ratio) of the lubricating composition for a tapered roller bearing that changes depending on the frequency becomes extremely low, and is 7Hz or more.

The additive contains an extreme pressure agent containing phosphorus in the molecular structure (hereinafter also referred to as a phosphorus-based extreme pressure agent), and the extreme pressure agent is contained in an amount of 0.05 to 0.3 mass% in terms of phosphorus content with respect to the entire tapered roller bearing lubricating composition.

Characterized in that the additive also contains calcium additives or barium additives. Further, the thickener is a complex lithium soap.

The tapered roller bearing of the present invention is a tapered roller bearing comprising an inner ring having a tapered raceway surface on an outer circumferential surface thereof, an outer ring having a tapered raceway surface on an inner circumferential surface thereof, a plurality of tapered rollers rolling between the raceway surface of the inner ring and the raceway surface of the outer ring, and a lubricating composition filling the periphery of the tapered rollers, wherein either one of the inner ring and the outer ring has a flange portion, and the lubricating composition is in sliding contact with the tapered rollers at the flange portion, and is characterized in that the lubricating composition is the tapered roller bearing lubricating composition of the present invention.

The tapered roller bearing is used under high temperature conditions of 80 ℃ or higher and under high load conditions of 0.5GPa or higher at the maximum contact surface pressure between the inner ring and the outer ring and 0.07GPa or higher at the surface pressure of the flange portion.

The tapered roller bearing is used as a tapered hub unit for rotatably supporting a wheel of a vehicle.

ADVANTAGEOUS EFFECTS OF INVENTION

The grease composition for a tapered roller bearing according to the present invention contains a base oil, a thickener and an additive, and the storage modulus of the grease composition that changes according to the frequency is extremely low, and therefore, the grease state can be maintained up to high frequencies under low strain conditions that simulate the micro-vibration of a vehicle, and therefore, grease can be present in the flange portion, and the oil film fracture of the flange portion can be suppressed. As a result, the bearing has excellent bearing life even when used under high temperature conditions and high load conditions.

The additive contains a phosphorus-based extreme pressure agent, and the extreme pressure agent is contained in a predetermined amount with respect to the entire lubricant composition, so that extreme pressure properties can be obtained. Further, it is considered that the inclusion of the calcium-based additive or the barium-based additive suppresses the change in consistency and improves shear stability. The thickener is a composite lithium soap, so that the fibers of the thickener are not easy to break and the shear stability is excellent.

The tapered roller bearing of the present invention is filled with the lubricating composition for a tapered roller bearing of the present invention, and therefore has an excellent bearing life even when used under high temperature conditions and high load conditions.

Drawings

Fig. 1 is a sectional view showing an example of a tapered roller bearing according to the present invention.

Fig. 2 is a graph showing an example of the relationship between storage modulus and frequency.

Fig. 3 is a cross-sectional view showing an example in which the tapered roller bearing of the present invention is used as a tapered hub unit.

Fig. 4 is a graph showing dynamic viscoelasticity measurement using a rheometer.

Detailed Description

The present inventors have conducted extensive studies to extend the life of a tapered roller bearing, and as a result, found that in a correlation graph of storage modulus and frequency of a lubricating composition, the frequency at which the storage modulus becomes extremely small is related to the life of the tapered roller bearing. Specifically, it was found that a grease composition having a viscosity transition frequency of 7Hz or higher can maintain a grease-like state up to a high frequency under low strain conditions simulating micro-vibration of a vehicle, and therefore grease can be present in the flange portion, and oil film breakage in the flange portion is suppressed. The present invention is based on such findings.

An example of the tapered roller bearing of the present invention will be described with reference to fig. 1. As shown in fig. 1, the tapered roller bearing 11 includes an inner ring 12 having tapered raceway surfaces 12a on an outer peripheral surface thereof, an outer ring 13 having tapered raceway surfaces 13a on an inner peripheral surface thereof, a plurality of tapered rollers 14 rolling between the raceway surfaces 12a of the inner ring 12 and the raceway surfaces 13a of the outer ring 13, and a cage 15 holding each of the tapered rollers 14 so as to be rollably in a pocket portion. The cage 15 connects the large-diameter ring portion and the small-diameter ring portion by a plurality of pillar portions, and the tapered rollers 14 are housed in pocket portions between the pillar portions. In the inner race 12, a large flange 12b is integrally formed at the large-diameter side end portion, and a small flange 12c is integrally formed at the small-diameter side end portion. In the tapered roller bearing, the inner ring has a tapered raceway surface, and thus has a small diameter side and a large diameter side as viewed in the axial direction, the "small flange" is a flange provided at the end on the small diameter side, and the "large flange" is a flange provided at the end on the large diameter side. When a load is applied, the tapered roller 14 is pressed against the large diameter side, and the load is received by the large flange 12 b. The small flange 12c prevents the tapered rollers 14 from falling off on the small diameter side until the bearing is incorporated into various devices.

In fig. 1, the tapered rollers 14 receive rolling friction with the raceway surface 12a of the inner ring 12 and the raceway surface 13a of the outer ring 13, and receive sliding friction with the large flange 12b of the inner ring 12. In order to reduce these frictions, grease 16 is filled at least around the tapered rollers 14. The grease 16 corresponds to the grease composition for a tapered roller bearing of the present invention. When the tapered roller bearing 11 is used, the load on the portion where the large flange 12b and the tapered rollers 14 are in sliding contact is particularly large, and therefore, this portion is easily broken and affects the bearing life.

In the tapered roller bearing of the present invention, the bearing members of the inner ring, the outer ring, and the tapered rollers are made of an iron-based metal material. As the iron-based metal material, bearing steel, carburized steel, carbon steel for machine structural use, cold rolled steel, or hot rolled steel can be used. Among them, case hardening steel having high heat resistance is preferably used. Examples of the case hardening steel include SCM415 and the like. Further, the iron-based metal materials used for the respective bearing members may be different materials from each other.

The lubricating composition for tapered roller bearings of the present invention is defined by the frequency at which the storage modulus G' of the lubricating composition, which varies with frequency, is extremely low. The storage modulus G' was measured by a dynamic viscoelasticity measurement method according to JIS K7244 using a rheometer. The storage modulus G' represents the elastic component of the dynamic viscoelasticity. Specifically, the ratio of the elastic stress in phase with the strain generated when the external force is applied to the grease means a portion corresponding to energy that can be elastically stored in the external force to which the grease is subjected.

Fig. 2 shows an example of the results of dynamic viscoelasticity measurement in which the frequency is varied by using a rheometer. Fig. 2 shows the variation of the storage modulus G 'in frequency with the storage modulus G' on the vertical axis and the frequency on the horizontal axis. In the dynamic viscoelasticity measurement shown in fig. 2, when the frequency is changed from a low frequency to a high frequency, the state of the grease is changed, and the storage modulus is extremely low at a specific frequency. This variation is considered to be because the grease exhibits solid properties in a low frequency region, but the structure that remains solid at a frequency at which the storage modulus reaches a minimum is destroyed. Further, in a high frequency region higher than a frequency at which the storage modulus is extremely small, the grease exhibits liquid properties. That is, the grease can be judged to be viscous within the range of a frequency at which the storage modulus is extremely low. In the present invention, the frequency at which the storage modulus becomes extremely small is defined as "viscosity transition frequency", and is characterized in that the viscosity transition frequency of the lubricating composition is 7Hz or more.

When the viscosity transition frequency of the lubricating composition is 7Hz or higher, the grease remains in the flange portion and the lubricating property is improved. As a result, the life time can be extended. If the viscosity transition frequency is less than 7Hz, grease is less likely to remain in the flange portion, and the life is likely to be shortened. In the present invention, the viscosity transition frequency of the lubricating composition is preferably 10Hz or more, more preferably 20Hz or more. The upper limit of the viscosity transition frequency is 100Hz or less, preferably 50Hz or less.

As the conditions for measuring the viscosity transition frequency, it is preferable that the measurement temperature is 25 ℃ and the strain amount is 100%. In addition, as the rheometer, a rheometer having elements of a parallel plate type is preferably used.

The lubricating composition for tapered roller bearings of the present invention comprises a base oil, a thickener and an additive. The base oil is not particularly limited, and a common base oil generally used in the field of grease can be used. For example, synthetic oils such as highly refined oils, ether oils, ester oils, synthetic hydrocarbon oils, silicone oils, fluorine oils, etc., mineral oils such as spindle oils, refrigerator oils, turbine oils, engine oils, motor oils, etc., and the like can be used. Further, a mixed oil thereof may be used. In the present invention, as the base oil, a synthetic oil is preferably used, and more preferably, 50% by mass or more of the base oil is an ester oil.

As the kinematic viscosity of the base oil (in the case of a mixed oil, the kinematic viscosity of the mixed oil), 100mm at 40 ℃ is preferable²/s～200mm²And s. More preferably 150mm²/s～200mm²(ii) s, more preferably 150mm²/s～180mm²/s。

The base oil is preferably contained in an amount of 60 to 95% by mass based on the total amount of the base oil and the thickener (base grease). If the content of the base oil is less than 60 mass%, the life may be reduced, and if it exceeds 95 mass%, the amount of the thickener may be relatively reduced, making it difficult to grease the composition. More preferably, the base oil is contained in an amount of 80 to 90 mass% based on the total amount of the base oil and the thickener.

The thickener used for the grease of the present invention is not particularly limited, and a commonly used thickener generally used in the field of greases can be used. For example, soap-based thickeners such as metal soaps and complex metal soaps, and non-soap-based thickeners such as bentonite, silica gel, diurea compounds, triurea compounds, tetraurea compounds, and urea/urethane compounds can be used. Examples of the metal soap include sodium soap, calcium soap, and lithium soap, and examples of the complex metal soap include complex lithium soap. Among them, as the thickener, a complex lithium soap or a diurea compound is preferably used.

The complex lithium soap is synthesized from lithium hydroxide, aliphatic monocarboxylic acid, and dibasic acid such as aliphatic dicarboxylic acid. Examples of the aliphatic monocarboxylic acid include stearic acid, 12-hydroxystearic acid, 12-hydroxylauric acid, and 16-hydroxypalmitic acid. Examples of the aliphatic dicarboxylic acid include azelaic acid, sebacic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, undecanedioic acid, and dodecanedioic acid.

Among the complex lithium soaps, an aliphatic monocarboxylic acid having 10 or more carbon atoms and an aliphatic dicarboxylic acid having less than 10 carbon atoms are preferably used in combination. In particular, stearic acid is more preferable as the aliphatic monocarboxylic acid having 10 or more carbon atoms, and azelaic acid is more preferable as the aliphatic dicarboxylic acid having less than 10 carbon atoms.

The diurea compound is obtained by reacting a diisocyanate component with a monoamine component. Examples of the diisocyanate component include p-phenylene diisocyanate, diphenylmethane diisocyanate (MDI), and the like. The diurea compound may be an aliphatic diurea compound, an alicyclic diurea compound, or an aromatic diurea compound, and these compounds are classified according to the type of the substituent of the monoamine component used. In the case of the aliphatic diurea compound, an aliphatic monoamine (octylamine or the like) is used as the monoamine component. In the case of the alicyclic diurea compound, an alicyclic monoamine (e.g., cyclohexylamine) is used as the monoamine component. In the case of an aromatic diurea compound, an aromatic monoamine (e.g., p-toluidine) is used as the monoamine component.

The base grease containing the complex lithium soap as a thickener is produced by reacting an aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid, and lithium hydroxide in a base oil. Further, a base grease containing a diurea compound as a thickener is produced by reacting a diisocyanate component and a monoamine component in a base oil. The blending ratio of the thickener in the base grease is preferably 5 to 30 mass%, more preferably 10 to 20 mass%.

The additive used in the lubricating composition of the present invention preferably contains a phosphorus-based extreme pressure agent. The phosphorus-based extreme pressure agent is a compound containing phosphorus in the molecular structure, and a known extreme pressure agent can be used. Examples thereof include phosphates such as tricresyl phosphate and triphenyl phosphate, phosphites such as acidic phosphate, tricresyl phosphite and triphenyl phosphite, acidic phosphites, thiophosphates, thiophosphites, zinc alkyldithiophosphate (ZnDTP), molybdenum alkyldithiophosphate (MoDTP) and the like. They can be used alone or in combination of plural ones. As the phosphorus-based extreme pressure agent, an extreme pressure agent other than zinc alkyldithiophosphate is preferably used, and alkylated triphenyl phosphate excellent in oxidation stability and thermal stability is more preferably used.

The phosphorus-based extreme pressure agent is preferably contained in an amount of 0.05 to 0.3% by mass in terms of phosphorus content relative to the entire lubricant composition. By setting the numerical range, good extreme pressure properties can be obtained while maintaining shear stability. The phosphorus-based extreme pressure agent is more preferably contained in an amount of 0.1 to 0.2% by mass in terms of phosphorus amount.

The additive preferably further contains a calcium-based additive or a barium-based additive. Examples of the calcium-based additive include overbased calcium sulfonates. Examples of the barium-based additive include overbased barium sulfonate. The Total Base Number (TBN) of the calcium sulfonate and the barium sulfonate is not particularly limited, but is preferably 10 to 500mgKOH/g, more preferably 50 to 400mgKOH/g, and still more preferably 100 to 400 mgKOH/g. TBN is measured in accordance with JIS K2501.

The calcium-based additive is preferably contained in an amount of 0.05 to 0.3% by mass, more preferably 0.1 to 0.2% by mass, in terms of calcium content, based on the entire lubricant composition. In relation to the content of the phosphorus-based extreme pressure agent, it is more preferable that the amount of the phosphorus element derived from the phosphorus-based extreme pressure agent is larger than the amount of the calcium element derived from the calcium-based additive in the lubricating composition. The barium-based additive is preferably contained in an amount of 0.05 to 0.3% by mass, more preferably 0.1 to 0.2% by mass, in terms of barium amount, based on the entire lubricant composition.

The above-mentioned lubricating composition may contain known additives as needed. Examples of the additive include antioxidants such as amine compounds and phenol compounds, solid lubricants such as graphite, and oily agents such as esters and alcohols.

The mixed consistency (Japanese: ちょう degrees blend) (JIS K2220) of the lubricating composition used in the present invention is preferably in the range of 200 to 350. If the consistency is less than 200, the oil separation may be small and the lubrication may be poor. On the other hand, if the consistency exceeds 350, the lubricating composition is not preferable because it is soft and easily flows out of the bearing. The consistency after mixing is more preferably in the range of 250 to 300.

The tapered roller bearing of the present invention is preferably used under high temperature conditions and high load conditions. As the high load condition, the maximum contact surface pressure on the raceway wheel is 0.5GPa or more and the surface pressure of the flange portion (large flange in the case of the tapered roller bearing) is 0.07GPa or more, preferably 0.1GPa or more in specific numerical values. The high temperature condition is, for example, 80 ℃ or higher, preferably 100 ℃ or higher, and more preferably 120 ℃ or higher.

The tapered roller bearing of the present invention can be used as a tapered hub unit that rotatably supports a wheel of a vehicle. FIG. 3 is a cross-sectional view of the cone hub unit. As shown in fig. 3, the tapered hub unit 21 includes: an inner ring 22 that rotates together with the wheel constituent member; an outer ring 23 disposed opposite to the inner ring 22, fixed to a vehicle body constituent member, and maintained in a non-rotating state; and a plurality of tapered rollers (rolling elements) 24a, 24b rollably housed between mutually facing rows of raceway surfaces 28a, 23a and between raceway surfaces 29a, 23b formed on the inner ring 22 and the outer ring 23, respectively. The tapered rollers 24a and 24b are rotatably held in pockets formed in the cage 25 one by one. Here, with respect to the axial direction, "outer" means toward the widthwise outer side in the vehicle-mounted state, and "inner" means the widthwise central side.

The inner ring 22 includes a hub wheel 27 that rotates together with a wheel (not shown) and the like, and 2 inner ring members 28, 29 that are externally fitted to the outer peripheral surface of the hub wheel 27 and are disposed in a state in which the ends on the small-diameter side are in contact with each other. The hub wheel 27 integrally has a wheel mounting flange 27c for mounting a wheel at one end portion thereof, and is formed with a stepped portion 27a extending in the axial direction.

The inner ring members 28, 29 are press-fitted to the step portion 27a of the hub wheel 27. The inner ring members 28 and 29 are prevented from coming off the hub wheel 27 in the axial direction by the tightening portion 27b formed by plastically deforming the axially inner end portion of the hub wheel 27 radially outward. The inner ring member 28 is disposed on the axially inner side of the hub wheel 27, and has a raceway surface 28a formed on the outer peripheral surface thereof so as to face the raceway surface 23a of the outer ring 23. The inner ring member 29 is disposed axially outward of the hub wheel 27, and has a raceway surface 29a formed on the outer circumferential surface thereof so as to face the raceway surface 23b of the outer ring 23.

The inner ring member 28 and the inner ring member 29 are formed in a substantially truncated cone shape having a small-diameter side end portion and a large-diameter side end portion. Large flanges 28b and 29b protruding outward in the radial direction are formed on the outer peripheral surfaces of the large-diameter-side end portions of the inner ring members 28 and 29, respectively, and small flanges 28c and 29c protruding outward in the radial direction are formed on the outer peripheral surfaces of the small-diameter-side end portions of the inner ring members 28 and 29, respectively. A raceway surface 28a is formed between the small flange 28c and the large flange 28b, and a raceway surface 29a is formed between the small flange 29c and the large flange 29 b. The tapered rollers 24a and 24b receive rolling friction between the raceway surfaces 28a and 29a of the inner ring 22 and the raceway surfaces 23a and 23b of the outer ring 23, and receive sliding friction between the large flanges 28b and 29b of the inner ring 22.

The outer ring 23 has a vehicle body attachment flange integrally formed on the outer periphery thereof, and raceway surfaces 23a and 23b formed on the inner peripheral surface thereof. Seal members 30, 31 are provided at both axial ends of the outer ring 23. The seal member 30 seals between the outer race 23 and the inner race member 28, and the seal member 31 seals between the outer race 23 and the inner race member 29. Grease 26 is filled in an internal space surrounded by the seal member 30, the outer ring 23, the seal member 31, and the inner ring 22, and is used for lubrication of rolling contact and sliding contact between the rolling surfaces of the tapered rollers 24a and 24b, the raceway surfaces 28a and 29a of the inner ring, and the raceway surfaces 23a and 23b of the outer ring. The grease 26 is the above-mentioned grease composition.

The tapered roller bearing of the present invention has an excellent bearing life even under high-temperature conditions and high-load conditions, and is therefore suitable for a tapered hub unit that rotatably supports a wheel of a vehicle (particularly, a large vehicle). Here, the "large vehicle" is not particularly limited, and examples thereof include special vehicles such as a truck of about 2t or more, a passenger car (a minibus, a bus), a tractor car (a trailer, a tank car), and a crane.

The tapered roller bearing of the present invention is not limited to the embodiment shown in fig. 1 and 3. For example, although the flange portion is provided on the inner ring in fig. 1 and 3, the flange portion may be provided on the outer ring. In fig. 3, the outer ring and the hub wheel may be integrated.

Examples

The present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples.

Each test grease of the components shown in table 1 was adjusted. The complex lithium soap shown in table 1 was prepared by reacting azelaic acid with stearic acid. In table 1, the element amount of the additive means the content (mass%) of each element (phosphorus, calcium, etc.) derived from the additive with respect to the entire grease.

The base oils of table 1 are shown below.

Synthetic oil 1 (ester oil): h2372 (kinematic viscosity at 40 ℃ C. of 120mm, manufactured by HATCO Co., Ltd.)²/s)

Mineral oil 1: daphne Turbine Oil 100 (kinematic viscosity at 40 ℃ C. of 98.6 mm), manufactured by Daphne Ltd²/s)

Mineral oil 2: daphne Itanity Oil D Grade220 (Japanese: ダフニーイタニティーオイル D グレード 220) (kinematic viscosity at 40 ℃ C. of 227.3mm, manufactured by Daphne Ltd.)²/s)

Synthetic oil 2: mobil SHC627 (kinematic viscosity at 40 ℃ C. of 100 mm) manufactured by EMG Lubricant Co²/s)

Synthetic oil 3: mobil SHC630 (kinematic viscosity at 40 ℃ C. of 220 mm), manufactured by EMG Lubricant Co., Ltd²/s)

The respective test greases were used, and the measurement of consistency after mixing, the measurement of dynamic viscoelasticity, and the high-temperature grease life test were carried out, and the results are shown in table 1.

(1) Measurement of the after-mixing consistency

The consistency after mixing was measured according to JIS K2220.

(2) Dynamic viscoelasticity measurement

The dynamic viscoelasticity of the grease was measured by using a parallel plate type rheometer 41 shown in fig. 4. As shown in FIG. 4, the grease 44 for test was placed in the test chamberLower plate 43 ofThe upper plate 42 is sandwiched from above and below. The gap between the plates was set to 0.1 mm. The upper plate 42 was rotated to apply a periodic strain due to vibration to the test grease 44, and the storage modulus was measured from the waveform of the shear stress in response and the phase difference between the waveforms. The measurement was carried out by changing the frequency from 0.1Hz to 30Hz under the conditions of a temperature of 25 ℃ and a strain amount of 100% (oscillation angle 4.6 ℃). From the measurement results, a graph of the storage modulus versus frequency as shown in fig. 2 was obtained, and the frequency at which the storage modulus became extremely small was obtained as the viscosity transition frequency.

(3) High temperature grease life test

Each test grease was sealed in a tapered roller bearing of 4T-30204 to prepare a test bearing. Each of the obtained bearings for test was subjected to conditions (load conditions A) of 120 ℃ temperature, 640N axial load and 67N radial load for 5000min^－1The rotational speed of (2) was measured, and the time until thermal adhesion was achieved was measured. The maximum contact surface pressure of the raceway wheel under this load condition a was 0.5GPa, and the surface pressure at the large flange of the inner ring was 0.07 GPa. The grease life time is set to 800 hours or more as a pass. Table 1 shows the test results.

Each of the above-described test bearings was used in the same manner, and was subjected to a temperature of 120 ℃ and a radial load of 2940N and 5880N (load conditions B) for 5000min^－1The rotational speed of (2) was measured, and the time until thermal adhesion was achieved was measured. The maximum contact surface pressure of the raceway wheel under this load condition B was 2.0GPa, and the surface pressure at the large flange of the inner ring was 0.18 GPa. Under the load condition B, the lifetime of 100 hours or more was defined as acceptable. Table 1 shows the test results.

[ Table 1]

1) Octylamine + MDI

2) Cyclohexylamine + MDI

3) P-toluidine + MDI

According to Table 1, the greases of examples 1 to 3 had a viscosity transition frequency of 7Hz or higher, and were acceptable under both the load condition A and the load condition B. On the other hand, the greases of comparative examples 1 to 4 had viscosity transition frequencies of less than 7Hz, short life times, and failed the high temperature grease life test. Further, the grease of example 3 and the grease of comparative example 4 have the same thickener, base oil viscosity, and consistency, but have different viscosity transition frequencies, and as a result, example 3 shows about 10 times as long life time as that of comparative example 4 under the load condition a and about 16 times as long life time as that of comparative example 4 under the load condition B. Further, it is considered that the additive (particularly, phosphorus-based extreme pressure agent) contributes to an increase in the viscosity transition frequency.

The greases of examples 1 to 3 of the present invention clearly showed a viscosity transition frequency of 7Hz or higher, and were able to prolong the bearing life. From such findings, the bearing life of the grease composition for a tapered roller bearing can be estimated in advance by comparing the viscosity transition frequency of the grease with a predetermined threshold value of frequency (for example, 7 Hz). Specifically, the viscosity transition frequency of the lubricating composition measured by the dynamic viscoelasticity measurement is compared with a threshold value (7Hz), and when the viscosity transition frequency is 7Hz or more, it can be determined that the life time is excellent. Further, according to table 1, the lifetime tends to be longer as the viscosity transition frequency is higher, and therefore, the viscosity transition frequency can be used as an index for determining the quality of the bearing lifetime. For example, the viscosity transition frequency of a plurality of lubricant composition compositions can be measured, and the lubricant composition having the highest viscosity transition frequency is determined to have the most excellent bearing life. Thus, the present invention can also be applied to the prediction of the bearing life of the lubricating composition.

Industrial applicability

The grease composition for tapered roller bearings of the present invention has excellent bearing life even under high temperature and high load conditions, and therefore, is widely used as grease for tapered roller bearings used under such conditions. The tapered roller bearing of the present invention is preferably used as a tapered roller bearing of a tapered hub unit that rotatably supports a wheel of a vehicle.

Description of the reference numerals

11 tapered roller bearing

12 inner ring

13 outer ring

14 tapered roller

15 holding rack

16 grease

21 conical hub unit

22 inner ring

23 outer ring

24 tapered roller

25 holding rack

26 lubricating grease

27 wheel hub

28 inner race component

29 inner race member

30 sealing member

31 sealing the member.