JP2024035321A - Grease compositions and rolling bearings - Google Patents

Abstract

The present invention provides a grease composition that exhibits low dust generation, rust prevention, and high-temperature, high-speed durability, and a rolling bearing in which the grease composition is encapsulated. [Solution] Grease composition 7 includes a base oil, a thickener, and a rust preventive agent, and the base oil has a synthetic hydrocarbon oil as a main component, does not contain an ester oil, and has a kinematic viscosity at 40°C. is 40 mm2/s to 90 mm2/s, the thickener is a diurea compound obtained by reacting a diisocyanate component and a monoamine component, the monoamine component is an aliphatic monoamine and an alicyclic monoamine, and the base oil The rust preventive agent contains sorbitan fatty acid ester in an amount of less than 14% by mass based on the total amount of the thickener and the rust preventive agent, and has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220. [Selection diagram] Figure 1

Description

The present invention relates to a grease composition and a rolling bearing in which the grease composition is encapsulated, and in particular to a motor for industrial machinery used in home appliances and industrial equipment, an electric vehicle (EV), a hybrid vehicle (HEV), etc. The present invention relates to a grease composition used in rolling bearings used in high-temperature, high-speed rotations such as drive motors, and the rolling bearings.

Bearings used in rotating support parts of electric machines, such as electric motors, have lubricating grease sealed inside them. In such bearings, a method is generally adopted in which the grease is sealed using a sealing plate (sealing member) such as a rubber seal made by vulcanizing and bonding a rubber material to an iron plate or a core metal.

In recent years, high-temperature and high-speed bearings have become increasingly popular, and there is a demand for even greater high-temperature and high-speed durability (longer grease life). In addition, non-contact sealing members are used to reduce torque, but as the speed increases, oily particles generated from the grease inside the bearings adhere to electronic components such as encoders, causing trouble. There is a risk of

For example, drive motor bearings for EVs and HEVs are used in environments of about 120°C to 150°C. As a grease composition for such a drive motor bearing, a grease composition using a specific diurea compound and a specific ester oil has been proposed (see Patent Document 1).

International Publication No. 2013/015413

However, in Patent Document 1, low dust generation and rust prevention are not studied, and recent motor bearings, etc., which require low dust generation, rust prevention, and further high-temperature and high-speed durability, It is insufficient as a grease composition.

The present invention has been made in view of these circumstances, and provides a grease composition that achieves both low dust generation, rust prevention, and high-temperature and high-speed durability, and a rolling bearing containing the grease composition. The purpose is to

The grease composition of the present invention is a grease composition containing a base oil, a thickener, and a rust preventive agent, wherein the base oil contains a synthetic hydrocarbon oil as a main component and does not contain an ester oil. The thickener has a kinematic viscosity of 40 mm ² /s to 90 mm ² /s at 40°C, and the thickener is a diurea compound obtained by reacting a diisocyanate component and a monoamine component, and the monoamine component is an aliphatic monoamine and a monoamine component. The grease composition is an alicyclic monoamine and is contained in an amount of less than 14% by mass based on the total amount of the base oil and the thickener, the rust preventive agent contains a sorbitan fatty acid ester, and the grease composition conforms to JIS K 2220. It is characterized by having a worked penetration of 200 to 240 as measured in accordance with the standard.

The sorbitan fatty acid ester is characterized in that it is sorbitan trioleate.

The thickener is characterized in that the number of moles of the aliphatic monoamine is greater than the number of moles of the alicyclic monoamine.

The rolling bearing of the present invention includes an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, seal members provided in openings at both axial ends of the inner ring and the outer ring, and a bearing space. A rolling bearing having a grease composition enclosed therein, characterized in that the grease composition is the grease composition of the present invention.

The cage is characterized by being made of polyamide resin.

The sealing member is a non-contact type sealing member that is fixed to one of the inner ring and the outer ring and faces the other member with a gap.

The above rolling bearing is used under high temperature conditions of 100° C. to 150° C. and high speed conditions of dm·n value of 50×10 ⁴ to 180×10 ⁴ .

It is characterized by being a bearing for a motor.

The grease composition of the present invention has a synthetic hydrocarbon oil as a main component, does not contain ester oil, has a kinematic viscosity of 40 mm ² /s to 90 mm ² /s at 40°C, a base oil, a diisocyanate component, and a monoamine component. (Aliphatic monoamine and alicyclic monoamine), the grease composition contains a predetermined amount of a diurea thickener obtained by reacting with (an aliphatic monoamine and an alicyclic monoamine) and a sorbitan fatty acid ester as a rust preventive agent, and the grease composition complies with JIS K 2220. The worked penetration is 200 to 240, so it has low dust generation (prevents oil from flowing out of the bearing), rust prevention, and oil separation properties during high-temperature and high-speed rotation (prevents oil from flowing out through channeling). oil supply to contact parts). For example, by adding sorbitan fatty acid ester to a combination of a given base oil and a given thickener, synthetic hydrocarbon oil can be added without affecting the surface tension of the base oil while imparting rust prevention properties. It is thought that low dust generation can be maintained.

Since the above-mentioned sorbitan fatty acid ester is sorbitan trioleate, the grease composition has excellent rust prevention properties and low dust generation.

Since the number of moles of the aliphatic monoamine in the thickener is greater than the number of moles of the alicyclic monoamine, the thickener has better low dust generation properties as shown in Examples below.

The rolling bearing of the present invention, in which the grease composition of the present invention is sealed in the bearing space, is suitable for, for example, bearings used in electric machines such as motors, and is useful for increasing high temperatures and speeds and improving reliability of the electric machines. I can contribute.

1 is a cross-sectional view of a deep groove ball bearing, which is an example of a rolling bearing of the present invention. It is a sectional view of a deep groove ball bearing which is another example of a rolling bearing of the present invention. 1 is a sectional view of a motor using a rolling bearing of the present invention.

The grease composition of the present invention is characterized by containing a predetermined base oil, a predetermined thickener, and a predetermined rust inhibitor.

The base oil used in the grease composition of the present invention has a synthetic hydrocarbon oil as a main component, does not contain ester oil, and has a kinematic viscosity at 40°C (in the case of a mixed oil, the kinematic viscosity of the mixed oil) of 40 mm ² /s to 90mm ² /s. The kinematic viscosity is preferably 40 mm ² /s to 70 mm ² /s, more preferably 40 mm ² /s to 55 mm ² /s at 40°C.

As the synthetic hydrocarbon oil, poly-α-olefin oil (PAO oil) is more preferred. PAO oils are mixtures of α-olefins or isomerized α-olefin oligomers or polymers. Specific examples of α-olefins 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-tetradocosene, etc., and mixtures thereof are usually used.

The base oil has a synthetic hydrocarbon oil as its main component, and its content is 50% by mass or more, preferably 80% by mass or more, based on the entire base oil. As the base oil, only synthetic hydrocarbon oil (for example, 100% PAO oil) may be used.

The base oil used in the present invention may contain other base oils. For example, mineral oils such as paraffinic mineral oils and naphthenic mineral oils, ether oils such as alkyldiphenyl ether oils, silicone oils, fluorine oils, and mixed oils thereof can be used. However, the base oil used in the present invention does not contain ester oil. Ester oils include diester oils obtained from the reaction of dibasic acids and branched alcohols, aromatic ester oils obtained from the reaction of aromatic tribasic acids and branched alcohols, and aromatic ester oils obtained from the reaction of polyhydric alcohols and monobasic acids. Examples include polyol ester oil. As shown in the examples, when the base oil was mainly composed of PAO oil and contained ester oil, the amount of dust generated increased. Note that the ester oil herein does not include sorbitan fatty acid ester.

The thickener used in the grease composition of the present invention is a diurea compound obtained by reacting a diisocyanate component and a monoamine component. In the present invention, aliphatic monoamines and alicyclic monoamines are used as monoamine components. Examples of the diisocyanate component include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Examples of aliphatic monoamines include hexylamine, octylamine, dodecylamine, hexadecylamine, stearylamine, and oleylamine. Examples of the alicyclic monoamine include cyclohexylamine.

In the thickener, the relationship in mole number between the aliphatic monoamine and the alicyclic monoamine, which are raw materials for the diurea compound, is not particularly limited. From the viewpoint of low dust generation, the number of moles of the aliphatic monoamine is preferably larger than the number of moles of the alicyclic monoamine. Specifically, the molar ratio (number of moles of aliphatic monoamine/number of moles of alicyclic monoamine) is preferably greater than 1.0 and 4.0 or less, and preferably 1.5 to 3.0. More preferred.

Base grease is obtained by blending a diurea compound as a thickener with base oil. Base grease using a diurea compound as a thickener is produced by reacting a diisocyanate component and a monoamine component in a base oil. The content of the thickener is less than 14% by mass based on the total amount (100% by mass) of the base oil and the thickener, preferably 5% by mass or more and 13% by mass or less, and 8% by mass or more and 13% by mass or less. More preferably, it is 10% by mass or more and 13% by mass or less.

The grease composition of the present invention contains sorbitan fatty acid ester as a rust preventive agent. By adding sorbitan fatty acid ester, rust prevention can be imparted to the grease composition while maintaining low dust generation. Examples of sorbitan fatty acid esters include sorbitan fatty acid monoesters such as sorbitan monolaurate, sorbitan monostearate, and sorbitan monooleate, and sorbitan trioleate. Among these, sorbitan trioleate is preferred.

The blending amount of sorbitan fatty acid ester is preferably 0.5 to 3 parts by mass, more preferably 0.5 to 2 parts by mass, based on 100 parts by mass of the total amount of base oil and thickener. , more preferably from 0.5 parts by mass to 1.5 parts by mass. By setting the content within these ranges, it becomes easier to achieve both low dust generation and rust prevention.

As shown in the examples, when an amine-based rust preventive agent or a succinate-based rust preventive agent was added as a rust preventive agent, there was a tendency for the amount of dust generation to increase. Therefore, the grease composition preferably does not contain any other rust preventives (such as amine rust preventives, succinate ester rust preventives, sulfonate rust preventives, etc.) other than sorbitan fatty acid esters.

Furthermore, known additives can be added to the grease composition of the present invention, if necessary. Examples of additives include antioxidants such as amine, phenol, and sulfur compounds; phosphate esters such as tricresyl phosphate, phosphite esters such as tricresyl phosphite, thiophosphate, and thiophosphate. Examples include extreme pressure agents such as phthalate, zinc alkyl dithiophosphate (ZnDTP), molybdenum alkyl dithiophosphate (MoDTP), and zinc dithiocarbamate (ZnDTC).

The worked penetration (JIS K 2220) of the grease composition of the present invention is in the range of 200 to 240. From the viewpoint of high-speed rotation performance, it is preferable that oil is easily separated, and from the viewpoint of low dust generation, it is preferable that oil is difficult to separate. In the present invention, by combining a predetermined base oil, a predetermined thickener, and a predetermined rust preventive agent and setting the consistency within the above range, low dust generation, rust prevention, and high-speed durability are achieved. The result is a grease composition that has a well-balanced combination of Furthermore, from the viewpoint of low dust generation, the worked penetration is preferably in the range of 200 to 220.

A rolling bearing containing the grease composition of the present invention will be explained based on FIG. 1. FIG. 1 is a sectional view of a deep groove ball bearing. In the rolling bearing 1, an inner ring 2 having an inner ring raceway surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring raceway surface 3a on the inner peripheral surface are arranged concentrically, and a plurality of rings are arranged between the inner ring raceway surface 2a and the outer ring raceway surface 3a. rolling elements 4 are arranged. This rolling element 4 is held by a cage 5. Furthermore, openings 8a and 8b at both axial ends of the inner and outer rings are sealed by sealing members 6, and the above-described grease composition 7 is sealed at least around the rolling elements 4. The seal member 6 shown in FIG. 1 is a contact-type seal member in which an inner diameter lip contacts inside the seal groove of the inner ring 2. The seal member 6 shown in FIG. The inner ring 2, the outer ring 3, and the rolling elements 4 are made of iron-based metal materials, and a grease composition 7 is interposed on the raceway surfaces of the rolling elements 4 to lubricate them.

In the rolling bearing 1, the ferrous metal material constituting the bearing members of the inner ring 2, outer ring 3, and rolling elements 4 is any material commonly used as a bearing material, such as high carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; JIS G 4805), carburized steel (SCr420, SCM420, etc.; JIS G 4053), stainless steel (SUS440C, etc.; JIS G 4303), high speed steel (M50, etc.), cold rolled steel Examples include.

The cage 5 is made of iron-based material or resin material. As the iron-based material, any material commonly used for retainers can be used, such as cold rolled steel plate for retainers (SPCC; JIS G 3141), stainless steel (SUS440C, etc.; JIS G 4303), retainers. Examples include carbon steel (JIS G 4051), high-strength brass casting for cages (JIS H 5102), and the like. Examples of resin materials include polyamide resins such as phenol resin, polyetheretherketone (PEEK) resin, polyphenylene sulfide (PPS) resin, thermoplastic polyimide resin, polyamideimide resin, polyamide 66 resin, and polyamide 46 resin. As a base material, a resin material containing reinforcing fibers such as carbon fiber or glass fiber and other additives is used.

Another form of the rolling bearing of the present invention will be explained based on FIG. 2. Note that the same configurations as those in the form of FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. The deep groove ball bearing shown in FIG. 1 uses a contact type seal member, whereas the deep groove ball bearing shown in FIG. 2 uses a non-contact type seal member. In the deep groove ball bearing 9, openings at both axial ends of the inner and outer rings are sealed by seal members 10, and the above-described grease composition 7 is sealed at least around the rolling elements 4. This seal member 10 forms a labyrinth gap between the inner diameter lip and the inside of the seal groove of the inner ring 2, so that they are not in contact with each other. Since the grease composition of the present invention has excellent low dust generation properties, it can also be applied to rolling bearings having non-contact type seal members. Further, by making the sealing member non-contact, it is possible to further reduce the torque.

Although ball bearings are illustrated as bearings in FIGS. 1 and 2, the rolling bearings of the present invention include cylindrical roller bearings, tapered roller bearings, spherical roller bearings, needle roller bearings, thrust cylindrical roller bearings, and thrust tapered roller bearings. It can also be used as thrust needle roller bearings, thrust spherical roller bearings, etc.

The rolling bearing of the present invention can be used, for example, to support the rotor of a motor for industrial machinery, electrical equipment, or electric vehicle driving. FIG. 3 shows an example in which the rolling bearing of the present invention is applied to, for example, a motor. FIG. 3 is a sectional view of the structure of the motor. The motor includes a stator 12 made of a motor magnet arranged on the inner circumferential wall of a jacket 11, a rotor 15 wound with a winding 14 fixed to a rotating shaft 13, and a commutator fixed to the rotating shaft 13. 16, a brush holder 17 disposed on an end frame 19 supported by the jacket 11, and a brush 18 housed within the brush holder 17. The rotating shaft 13 is rotatably supported by the jacket 11 by a deep groove ball bearing 1 and a support structure for the bearing 1. The bearing 1 is a rolling bearing of the present invention.

Motors to which the rolling bearing of the present invention can be applied include industrial machine motors such as ventilation fan motors, fuel cell blower motors, cleaner motors, fan motors, servo motors, and stepping motors, automobile starter motors, electric power steering motors, and steering motors. Examples include adjustment tilt motors, blower motors, wiper motors, motors for electrical equipment such as power window motors, and drive motors for electric vehicles and hybrid vehicles. In particular, it is suitable for bearings that require low dust generation and rust resistance and are used in high-temperature, high-speed rotation, and are not limited to bearings for motors.

As mentioned above, the rolling bearing of the present invention is suitable for use under high temperature and high speed conditions. Specifically, the high temperature condition is such that the temperature of the outer diameter portion of the bearing outer ring is 80°C or higher, preferably 100°C or higher. The upper limit of the temperature of the outer diameter portion of the bearing outer ring is not particularly limited, but is, for example, 180°C, preferably 150°C. Specifically, the high speed condition is such that the dm·n value is 50×10 ⁴ or more, preferably 70×10 ⁴ or more. The upper limit of the dm·n value is not particularly limited, but is, for example, 200×10 ⁴ or 180×10 ⁴ . For example, grease-lubricated bearings for drive motors of EVs and HEVs are used under high-temperature conditions of 100° C. to 150° C. and high-speed conditions of dm·n values of 70×10 ⁴ to 180×10 ⁴ . The rolling bearing of the present invention has excellent low dust generation properties, rust prevention properties, and long grease life under such usage environments.

Grease compositions having the compositions shown in Tables 1 and 2 were prepared. In Tables 1 and 2, the contents of the base oil, thickener, and rust preventive agent indicate the content (% by mass) relative to the base grease (base oil + thickener). Note that in Tables 1 and 2, PAO oil is used as the synthetic hydrocarbon oil, and the grease composition consists only of a base oil, a thickener, and a rust inhibitor. Further, 1) to 9) below in Table 1 are the same in Table 2.

<Dust generation test>
Each grease composition was encapsulated in a ball bearing 608 (inner diameter 8 mm, outer diameter 22 mm, width 7 mm) equipped with a non-contact sealing member to produce test bearings. As the cage, a resin cage (polyamide 66 resin + 25% by mass of glass fiber) was used in Example 5, and an iron cage was used in the other cases. The inner ring of the obtained test bearing was rotated at an axial load of 9.8 N and a speed of 5000 min ^-1 for 8 hours. Dust with a particle size of 0.1 μm or more generated during the 30 minutes before the end of the 8-hour test (9 liters of suction volume) was measured using a particle counter with a suction volume of 0.3 liters/min. Regarding the evaluation of the amount of dust generated, less than 30,000 pieces is ``A'', 30,000 to 45,000 pieces is ``B'', more than 45,000 pieces and 60,000 pieces or less is ``C'', and more than 60,000 pieces. is also listed in Tables 1 and 2 as "D".

<Grease life test>
1.8 g (equivalent to 38% of the total space) of each grease composition was sealed in a ball bearing 6204 (inner diameter 20 mm, outer diameter 47 mm, width 14 mm) equipped with a non-contact type sealing member, and a test bearing was prepared. Created. The obtained test bearing was rotated at a rotational speed of 15,000 min ^-1 under the conditions of the outer diameter of the bearing outer ring temperature of 150°C, axial load of 67 N, and radial load of 67 N, and the time until seizure occurred was measured. did. The dm·n value under this condition is 50×10 ⁴ . Regarding the evaluation of grease life time, over 2,500 hours is marked as "A", 1,500 to 2,500 hours as "B", 1,000 to less than 1,500 hours as "C", and less than 1,000 hours as "D" and listed in Tables 1 and 2. .

As shown in Table 1, a base oil made of PAO oil and having a predetermined kinematic viscosity, a thickener made of a diurea compound using an aliphatic monoamine and an alicyclic monoamine as the monoamine component, and a sorbitan fatty acid ester are used. The combined Examples 1 to 7 showed good results in all tests. When a resin cage was used as the cage (Example 5), the grease life was extended compared to the case where an iron cage was used. Further, regarding the thickener, when the monoamine component used as a raw material contained a larger number of moles of aliphatic monoamine than alicyclic monoamine, excellent results were obtained in low dust generation.

As shown in Table 2, when ester oil was added to the base oil (Comparative Example 1), although the base oil viscosity and consistency were similar to those of Examples 1 to 7, the amount of dust generated was small. It increased. In Comparative Example 2, in which the base oil had a low viscosity, the grease life was significantly reduced. When an amine type (amine salt of alkyl aromatic sulfonic acid) or succinate type is used as a rust preventive agent (Comparative Examples 3 and 4), the amount of dust generated is lower than that of sorbitan fatty acid ester (for example, Example 1). has increased. The increase or decrease in the amount of dust generated is affected by the surface tension of the base oil, and by adding amine-based or succinate-based rust inhibitors, the surface tension of the base oil decreases, resulting in an increase in the amount of dust generated. It is presumed that he did. When the penetration was less than 200 (Comparative Example 6), the grease composition became hard and the grease life decreased. Furthermore, when the penetration was over 240 (Comparative Example 7), the grease composition became soft, leading to an increase in the amount of dust generated.

From the above, the grease composition of the present invention optimizes oil separation from grease by combining a predetermined base oil, a predetermined thickener, and a predetermined rust preventive agent, and further optimizes the consistency. Achieved both dust-generating properties, rust prevention properties, and long life under high-speed, high-temperature rotation.

The grease composition of the present invention can achieve both low dust generation, rust prevention, and high-temperature, high-speed durability. It can be suitably used for bearings for drive motors of cars and HEVs.

1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease 8a, 8b Opening 9 Rolling bearing 10 Seal member 11 Jacket 12 Stator 13 Rotating shaft 14 Winding 15 Rotor 16 Commutator 17 Brush holder 18 Brush 19 End frame

Claims (8)

A grease composition comprising a base oil, a thickener, and a rust inhibitor,
The base oil is mainly composed of synthetic hydrocarbon oil, does not contain ester oil, and has a kinematic viscosity at 40° C. of 40 mm ² /s to 90 mm ² /s,
The thickener is a diurea compound obtained by reacting a diisocyanate component and a monoamine component, and the monoamine component is an aliphatic monoamine and an alicyclic monoamine, and the total of the base oil and the thickener is Contains less than 14% by mass based on the amount,
The rust inhibitor contains sorbitan fatty acid ester,
The grease composition has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220. The grease composition according to claim 1, wherein the sorbitan fatty acid ester is sorbitan trioleate. 3. The grease composition according to claim 1, wherein the number of moles of the aliphatic monoamine in the thickener is larger than the number of moles of the alicyclic monoamine. an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, a seal member provided at openings at both axial ends of the inner ring and the outer ring, and a grease composition sealed in a bearing space. A rolling bearing having
A rolling bearing characterized in that the grease composition is the grease composition according to claim 1 or 2. 5. The rolling bearing according to claim 4, wherein the cage is a polyamide resin cage. 5. The rolling bearing according to claim 4, wherein the sealing member is a non-contact type sealing member fixed to one of the inner ring and the outer ring and facing the other member with a gap. The rolling bearing according to claim 4, wherein the rolling bearing is used under high-temperature conditions of 100° C. to 150° C. and high-speed conditions of dm·n value of 50×10 ⁴ to 180×10 ⁴ . The rolling bearing according to claim 4, which is a bearing for a motor.

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