WO2019039536A1 - Grease-sealed rolling bearing - Google Patents

Abstract

An object of the present invention is to provide a rolling bearing having both durability at high temperature and anti-cold noise characteristics. The rolling bearing 1 is used in an automotive electrical accessory, and includes an inner ring 2 having an inner ring raceway surface 2a on the outer periphery, an outer ring 3 having an outer ring raceway surface 3a on the inner periphery, an inner ring raceway surface 2a and an outer ring raceway surface 3a. The base oil of the grease 7 is mainly composed of ether oil; and (1) inner ring raceway surface 2a, (2) at least one surface selected from the outer ring raceway surface 3a and the rolling surface of the rolling element 4 is a bearing having a non-adhesive coating 8 of DLC, molybdenum disulfide, tungsten disulfide or fluorine resin ) The material of the rolling element is a ceramic and does not have a cage for holding the rolling element, or (3) the material of the rolling element is a ceramic, has a cage, and the rolling element Is the maximum number of units in the bearing size A bearing a number of 0 to 80%.

Description

Grease-filled rolling bearing

The present invention relates to a grease-sealed rolling bearing used in a wide temperature range from ultra low temperature to high temperature and used at high speed rotation. In particular, the present invention relates to a grease-sealed rolling bearing used in an automotive electrical accessory.

For example, a rolling bearing having a grease sealed therein is incorporated in an automotive electrical accessory, and the grease-sealed rolling bearing is used, for example, in a temperature range of −40 ° C. to 180 ° C. In a grease-sealed rolling bearing, when importance is placed on durability at high temperatures, grease having a highly heat resistant oil as a base oil is used. However, since oil with high heat resistance has high pour point and solidifies at low temperature, if grease filled rolling bearing is operated at such low temperature, abnormal noise (hereinafter referred to as cold abnormal noise) occurs at operation Have a problem.

Heretofore, various measures have been studied to reduce such cold abnormal noise. For example, Patent Document 1 discloses rolling in which grease containing a base oil mainly composed of oil having a low pour point is used. Bearings have been proposed.

Unexamined-Japanese-Patent No. 2006-249271

However, in general, an oil having a low pour point is suitable for reducing cold noise, but on the other hand, it has a property of being easily oxidized. Therefore, particularly in an environment of high-speed rotation such as an automotive electrical accessory, as a result of oxidation of oil having a low pour point, local heat generation becomes large, and there is a possibility that lubricating failure may occur early. Therefore, there is a need for a rolling bearing that is excellent in durability at high temperatures while reducing abnormal noise during cold weather.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a rolling bearing having both durability at high temperature and an anti-cold noise characteristic.

The grease-sealed rolling bearing according to the present invention is used in a vehicle electrical accessory, and includes an inner ring having an inner ring raceway surface on the outer periphery, an outer ring having an outer ring raceway surface on the inner periphery, the inner ring raceway surface and the outer ring raceway surface A grease-sealed rolling bearing comprising a plurality of rolling elements rolling between a plurality of rolling elements and a grease sealed around the rolling elements, wherein the base oil of the grease contains ether oil as a main component, (1) above Or at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, and the rolling surface of the rolling element, a bearing having a coating of DLC, molybdenum disulfide, tungsten disulfide, or fluorine resin (2 ) The material of the rolling element is a ceramic and does not have a cage for holding the rolling element, or (3) the material of the rolling element is a ceramic, and has the above-mentioned cage, Or , Wherein the number of the rolling elements are bearing a number of 40-80% of the maximum number of the bearing dimensions.

In general, the number of rolling elements of a rolling bearing is determined by the outer diameter dimension and the inner diameter dimension (hereinafter also referred to as a bearing dimension) of the bearing, and the maximum number of rolling elements accommodated in a given space from the bearing dimensions is In the present invention, it is referred to as "maximum number of bearings in size".

The grease-sealed rolling bearing is a bearing having the film on the surface, and does not have a cage for holding the rolling element.

In the grease-sealed rolling bearing, the material of the rolling element is a ceramic, and the ceramic is silicon nitride, alumina, or glass.

The ether oil is characterized in that it is an alkyl diphenyl ether oil. In addition, the above-mentioned ether oil is characterized by having a kinematic viscosity at 40 ° C. of 20 to 90 mm ² / s and a pour point of −30 ° C. or less.

The adhesion of the grease to the film or the adhesion to the ceramic at a temperature of −20 ° C. or less is 80% or less of the adhesion of the grease to the bearing steel at the same temperature.

The automotive electrical equipment accessory is a fan coupling device, an alternator, an idler pulley, a tension pulley, an electromagnetic clutch, or a compressor.

The grease-sealed rolling bearing of the present invention is excellent in durability at high temperatures because the grease uses a base oil containing ether oil as a main component. (1) Is the bearing having a coating of DLC, molybdenum disulfide, tungsten disulfide, or fluorine resin on at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, and the rolling surface of the rolling elements? (2) The material of the rolling element is a ceramic, and the bearing is a bearing that does not have a cage, or (3) the material of the rolling element is a ceramic, has a cage, and Since the number of moving bodies is a bearing that is 40 to 80% of the maximum number in the bearing size, cold noise can be reduced. For this reason, it is possible to obtain a rolling bearing having both durability at high temperature and noise resistance at cold.

Further, since the grease-sealed rolling bearing of the present invention is a bearing having a coating on the surface of the above (1) and does not have a cage, the contact portion inside the bearing is reduced to further suppress cold noise. It is effective.

Further, in the grease-sealed rolling bearing of the present invention, the material of the rolling elements is a ceramic (described in (2) or (3) above), and the ceramic is silicon nitride, alumina or glass, so it does not adhere to grease. And is more effective in reducing the excitation force.

Since the ether oil is an alkyl diphenyl ether oil, the durability at high temperatures is excellent. In addition, since this alkyl diphenyl ether oil has a dynamic viscosity of 20 to 90 mm ² / s at 40 ° C. and a pour point of -30 ° C. or less, it is possible to suppress cold noise while under an environment of high speed rotation. Good lubricity can be maintained.

The adhesion of the grease to the film at temperatures below -20 ° C or the adhesion to the ceramic is 80% or less of the adhesion of the grease to the bearing steel under the same temperature conditions, so it is possible to reduce cold noise. it can.

When applying grease filled bearings to fan coupling devices, alternators, idler pulleys, tension pulleys, electromagnetic clutches, or compressors that are automotive electrical equipment accessories, they can be used under high-speed rotation environments or a wide temperature environment Become. The grease-sealed rolling bearing according to the present invention has both durability at high temperatures and anti-cold noise characteristics, and therefore can be suitably used for these applications.

1 is a partial cross-sectional view showing an example of a grease-sealed rolling bearing of the present invention. It is a partial cross section figure which shows the other example of the grease-sealed rolling bearing of this invention. It is sectional drawing of the idler pulley using the rolling bearing of FIG. It is sectional drawing which shows the other example of the grease-sealed rolling bearing of this invention. It is sectional drawing which shows the other example of the grease-sealed rolling bearing of this invention. It is sectional drawing of the idler pulley using the rolling bearing of FIG. It is a figure which shows the measurement result of cold abnormal noise test 1. FIG. It is a figure which shows the measurement result of the adhesive force test 1. FIG. It is a figure which shows the measurement result of cold abnormal noise test 2. FIG. It is a figure which shows the measurement result of the adhesive force test 2. FIG.

The rolling bearing of the present invention is used in an automotive electrical accessory. Since rolling bearings used in automotive electrical equipment and accessories are used in a wide temperature range of -40 ° C. to 180 ° C., high temperature durability, low temperature performance, etc. are required. In addition, when the rolling bearing is used at low temperature, cold abnormal noise becomes a problem. The cold abnormal noise in the present invention is intended for all abnormal noises generated at a low temperature (jali noise and HOOT noise). In particular, the target is a javelin sound that is a sound that peels off an object that occurs in a short time at the start. This cold abnormal noise is more likely to occur as the operating temperature of the rolling bearing becomes lower.

The rolling bearing according to the present invention includes an inner ring, an outer ring, and rolling elements as bearing members, and DLC (diamond like carbon), molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS) are provided at predetermined positions of these bearing members. ₂ ) or having a film made of a fluorocarbon resin (hereinafter also referred to as "non-adhesive film") or that the material of the rolling element is a ceramic.

As an example of the rolling bearing of the present invention, a bearing having a non-adhesive coating will be described based on FIG. FIG. 1 is a partial sectional view of a rolling bearing (deep groove ball bearing) in which grease is sealed. 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 concentrically arranged. A plurality of inner rings 2 and the outer ring raceway surface 3a Each rolling element 4 is disposed. The plurality of rolling elements 4 are held by a cage 5. The seal member 6 is fixed to the outer ring 3, and grease 7 is enclosed at least around the rolling element 4. In the rolling bearing 1, the non-adhesive film 8 described above is formed on the outer peripheral surface (including the inner ring raceway surface 2 a) of the inner ring 2 and the inner peripheral surface (including the outer ring raceway surface 3 a) of the outer ring 3.

The occurrence of the cold abnormal noise is presumed to be due to the self-excited vibration of the system using the adhesive force of the grease at the contact portion inside the bearing as the excitation force. Under a low temperature, the grease having a high visco-elasticity at the contact portion is used as an adhesive to cause relative movement of objects between the contact portions. In this case, in a general grease-sealed rolling bearing, the grease receives a tensile load at the moment when the contact surfaces such as the rolling element and the bearing ring or the rolling element and the cage separate from each other, and the elastic energy is accumulated inside and fractures. It releases its stored energy. It becomes an exciting force to be applied to the rolling element, the bearing ring and the cage, which is considered to lead to the generation of vibration and sound.

Since the rolling bearing 1 in the form of FIG. 1 has the non-adhesive coating 8 on the inner ring raceway surface 2a and the outer ring raceway surface 3a, the interface between the grease and the raceway surface peels off with a weak force at low temperatures, causing strong excitation. Force does not occur. As a result, cold noise can be reduced. The non-adhesive film may be in various crystalline states as long as the film is highly non-adhesive to the grease. Moreover, a binder component can be mix | blended with a non-adhesive film other than DLC, a molybdenum disulfide, a tungsten disulfide, and a fluororesin. In addition, it is preferable that a non-adhesive film is a film which does not fall off easily by the adhesive force of grease.

Structurally, DLC used for a non-adhesive film has an intermediate structure of both diamond and graphite mixed. DLC is as hard as diamond and is excellent in wear resistance, solid lubricity, thermal conductivity, chemical stability and the like. A well-known method can be used for the method of forming a DLC film, For example, unbalanced magnetron sputtering, arc ion plating, plasma CVD etc. can be illustrated. When a DLC film is used as the non-adhesive film, chromium, tungsten, titanium, tungsten carbide, or silicon between the DLC film and the bearing member is used to enhance the adhesion between the DLC film and the bearing member. It is preferable to provide an intermediate layer containing at least one or more elements.

As a fluorine resin used for the non-adhesive film, PTFE (polytetrafluoroethylene) resin, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether) copolymer resin, ETFE (tetrafluoroethylene-ethylene) copolymer resin, Examples thereof include FEP (perfluoroethylene-propene) copolymer resin, PVDFF (polyvinylidene fluoride) resin, ECTFE (chlorotrifluoroethylene-ethylene) copolymer resin and the like.

When using molybdenum disulfide, tungsten disulfide, or fluorocarbon resin as the non-adhesive film, the film may be a film made of a single material, or if resin, sodium silicate, etc. are used if the non-adhesiveness is not impaired. It may be a film made of a composite material containing as a binder. A well-known method can be used for the method of forming a molybdenum disulfide film, a tungsten disulfide film, or a fluorine resin film, for example, a shot process (process which sprays raw material powder to the target surface at high speed with air) , Sputtering, coating with a dispersion, etc. can be exemplified.

The film thickness of the non-adhesive film (film thickness including the intermediate layer in the case of the DLC film) is preferably 0.1 μm or more and 1.0 μm or less. If it is less than 0.1 μm, measurement and control of the film thickness are difficult, and if it exceeds 1.0 μm, the non-uniformity of the film thickness tends to lead to the roundness defect of the raceway surface and the rolling surface.

The grease sealed in the rolling bearing of the present invention is composed of a base oil containing ether oil and a thickener. Examples of the ether oil include polyphenyl ether oil, alkyl diphenyl ether oil, alkyl triphenyl ether oil, alkyl tetraphenyl ether oil and the like. Among these, alkyl diphenyl ether oils are preferable in terms of durability at high temperatures. As the alkyl diphenyl ether oil, mono alkyl diphenyl ether oil, dialkyl diphenyl ether oil, polyalkyl diphenyl ether and the like can be mentioned.

In particular, among the ether oils, an ether oil having a kinematic viscosity of 20 to 150 mm ² / s at 40 ° C. and a pour point of −20 ° C. or less is preferable, and a kinematic viscosity at 40 ° C. of 20 to 90 mm ² / s, Ether oil having a pour point of −30 ° C. or less is more preferable.

The above-mentioned base oil consists only of ether oil, or is a mixture of ether oil and other base oils. As an oil to be mixed with ether oil, for example, highly refined oil, mineral oil, ester oil, synthetic hydrocarbon oil (PAO oil), silicone oil, fluorine oil, and a mixture oil of these, etc. can be used. In addition, it is preferable that the dynamic viscosity range and pour point exist in the said range also in the oil mixed with ether oil. Since the base oil of the present invention contains an ether oil as a main component, the content of the ether oil is 50% by mass or more, preferably 80% by mass or more, based on the whole base oil (mixed oil). In particular, it is preferable to use a base oil consisting only of ether oil (ether oil 100%).

Taking these into consideration, as the base oil used for the grease, for example, only alkyl diphenyl ether oil is used, the kinetic viscosity at 40 ° C. of the alkyl diphenyl ether oil is 20 to 90 mm ² / s, and the pour point is −30 ° C. It is particularly preferred that

The base oil is preferably contained in an amount of 60 to 90% by mass with respect to the entire grease. If the content of the base oil is less than 60% by mass, the life may be reduced, and if it exceeds 90% by mass, the amount of the thickening agent may be relatively reduced to make it difficult to form a grease.

The thickener to be used for the grease is not particularly limited, and any conventional thickeners can be used. For example, soap-based thickeners such as metal soaps and complex metal soaps, and non-soap-based thickeners such as bentones, silica gels, urea compounds and urea-urethane compounds can be used. Examples of metal soaps include sodium soap, calcium soap, aluminum soap, lithium soap and the like, and urea compounds, and examples of the urea-urethane compound include diurea compounds, triurea compounds, tetraurea compounds, other polyurea compounds, diurethane compounds and the like.

The above-mentioned thickener is preferably contained in an amount of 10 to 40% by mass with respect to the whole grease. More preferably, it is 10 to 20% by mass with respect to the whole grease. If the content of the thickening agent is less than 10% by weight, the thickening effect is reduced, and if it exceeds 40% by weight, the amount of the base oil is relatively reduced and there is a possibility that the life may be reduced.

The combined penetration (JIS K 2220) of the grease is preferably in the range of 200 to 350. If the consistency is less than 200, oil separation may be small, resulting in poor lubrication. On the other hand, when the consistency is more than 350, the grease is soft and tends to flow out of the bearing, which is not preferable.

Further, known additives can be added to the grease as required. Additives include, for example, extreme pressure agents such as organic zinc compounds and organic molybdenum compounds, antioxidants such as amines, phenols and sulfur compounds, antiwear agents such as sulfur and phosphorus compounds, polyhydric alcohols Antirust agents such as esters, friction reducing agents such as molybdenum disulfide and graphite, and oil agents such as esters and alcohols.

As described above, the occurrence of cold abnormal noise is presumed to be due to the self-excited vibration of the system using the adhesive force of the grease at the contact portion inside the bearing as the excitation force, so the grease at the low temperature and the contact portion It is preferable that the cohesion of By reducing the adhesion, the energy stored in the grease can be reduced. For example, it is preferable to use a grease having a lower tackiness when having a non-tacky coating at a temperature of −20 ° C. or lower than when not having a non-tacky coating. As a specific numerical value, the grease of the present invention preferably has an adhesion to a non-adhesive coating of 25 N or less, more preferably 20 N or less, at a temperature of −20 ° C. or less. As a result, since the grease and the non-adhesive film peel off with a weak force at a low temperature, a strong vibration force is not generated, which contributes to the reduction of abnormal noise during cold. In other words, the grease and the non-adhesive film may be selected such that the adhesion of the grease to the non-adhesive film at a temperature of -20 ° C or less is 25 N or less.

In FIG. 1, the rolling bearing 1 has a non-adhesive coating 8 on the raceway surface of the rolling bearing 1, that is, on the inner ring raceway surface 2a of the inner ring 2 and the outer ring raceway surface 3a of the outer ring 3. The rolling bearing 1 may be configured to have the non-adhesive film 8 on the surface of the rolling element 4, that is, the rolling surface. Also in this configuration, the adhesive force of the contact portion between the bearing members can be reduced. That is, at the time of low temperature, the interface between the grease and the rolling surface peels off with a weak force, and a strong vibration force is not generated, so it is possible to suppress the occurrence of cold abnormal noise. The non-adhesive film 8 may be formed on at least one surface selected from the inner ring raceway surface 2 a of the inner ring 2, the outer ring raceway surface 3 a of the outer ring 3, and the rolling surface of the rolling element 4. Therefore, as a specific configuration other than that described above, for example, the non-adhesive film may be formed on any of the raceway surface of the rolling bearing 1 and the rolling surface of the rolling element 4.

Moreover, although it was set as the structure which has the holder 5 in FIG. 1, the rolling bearing 1 is good also as a structure which does not have a holder. FIG. 2 is a partial cross-sectional view of a rolling bearing (deep groove ball bearing) having a configuration without a cage. The bearing configuration other than the cage in the rolling bearing 11 of FIG. 2 is the same as that of the rolling bearing of FIG. 1. Since cold noise is generated at the contact portion inside the bearing, as shown in FIG. 2, the structure without the cage causes vibration due to the adhesive force generated at the contact surface of the rolling element and the cage. You can lose your strength. In addition, it is possible to eliminate the increase in the adhesive force of the contact surface and the enhancement of the persistent force caused by the highly visco-elastic grease adhering to the back surface of the pocket surface of the cage scattering to the raceway surface. Therefore, by employing a configuration without the retainer, the excitation force is further reduced, which is more effective in reducing cold abnormal noise.

Further, in the rolling bearing, the number of rolling elements is not particularly limited, but the number of rolling elements can be reduced as compared with the usual number of rolling bearings of the same diameter size. For example, in a bearing having an outer diameter size of 30 mm to 50 mm, normally 6 to 8 rolling elements are used, but the number of rolling elements can be 3 to 5. In this case, since the area of the rolling surface of the rolling element is reduced, the adhesive force of the contact surface between the bearing members can be reduced. When the number of rolling elements is reduced than usual, it is preferable to apply the present invention to a small-sized rolling bearing with a small load, in consideration of the bearing life. For example, the outer diameter size of a rolling bearing is 40 mm, and it can apply to the rolling bearing of 200 N of radial loads.

Here, according to the relational expression based on Lundberg-Palmgren theory for calculating the basic dynamic load rating Cr of the ball bearing, the index of the number of balls Z is 2/3. For example, when the number of balls is 4 in a ball bearing having 7 balls, the basic dynamic load rating Cr is theoretically 4 ^(2/3) / 7 ^(2/3) times as large as the number of balls 7 (About 0.69 times). For example, in the embodiment to be described later, the basic dynamic load rating Cr of the rolling bearing 6203 with seven balls is 9600 N. On the other hand, when the number of balls is four, the basic dynamic load rating Cr is 6610 N. However, since it is sufficiently large relative to the radial load 200 N which is the working load, there is almost no influence on the bearing life. Similarly, according to the formula for calculating the basic static load rating (Reference: Junmoto Okamoto, "Introduction to Ball Bearing Design Calculation", Nikkan Kogyo Shimbun, September 2011, see p. 142) Is one. For example, in the embodiment to be described later, the basic static load rating Cor of the 7-ball rolling bearing 6203 is 4600 N. On the other hand, when the number of balls is four, the basic static load rating Cor is theoretically 4/7 times (about 0.57 times) the case of seven balls, so it is sufficiently lower than the working load You can confirm that.

An example of the automotive electrical equipment auxiliary machine to which the rolling bearing of FIG. 1 is applied is shown in FIG. FIG. 3 is a cross-sectional view of the structure of an idler pulley used as a drive belt tensioner. This pulley is composed of a pulley main body 51 made of steel plate press and a single row of rolling bearings 1 fitted in the inner diameter of the pulley main body 51. The pulley main body 51 includes an inner diameter cylindrical portion 51a, a flange portion 51b extending to the outer diameter side from one end of the inner diameter cylindrical portion 51a, an outer diameter cylindrical portion 51c axially extending from the flange portion 51b, and an inner diameter cylindrical portion 51a. It is an annulus including a flange 51d extending from the other end to the inner diameter side. The outer ring 3 of the rolling bearing 1 shown in FIG. 1 is fitted to the inner diameter of the inner diameter cylindrical portion 51a, and the outer diameter of the outer diameter cylindrical portion 51c is provided with a pulley circumferential surface 51e in contact with a belt driven by the engine. ing. By bringing the pulley circumferential surface 51e into contact with the belt, the pulley serves as an idler.

Next, as another example of the rolling bearing of the present invention, a bearing having ceramic rolling elements will be described based on FIG. FIG. 4 is a cross-sectional view of a rolling bearing (deep groove ball bearing) in which grease is sealed. In the rolling bearing 21, an inner ring 22 having an inner ring rolling surface 22a on the outer peripheral surface and an outer ring 23 having an outer ring rolling surface 23a on the inner peripheral surface are concentrically arranged. The inner ring rolling surface 22a and the outer ring rolling surface 23a A plurality of rolling elements 24 are disposed between the two. The seal member 26 is fixed to the outer ring 23, and grease 27 is enclosed at least around the rolling element 24. Further, the rolling bearing 21 does not have a cage for holding the plurality of rolling elements 24. That is, the general grease-sealed rolling bearing is configured by removing the cage.

Since the rolling bearing of the form of FIG. 4 does not have a retainer, the contact part inside a bearing can be reduced. That is, it is possible to eliminate the excitation force accompanying the adhesive force generated at the contact surface of the rolling element and the cage. In addition, it is possible to eliminate the increase in the adhesive force of the contact surface and the enhancement of the persistent force caused by the highly visco-elastic grease adhering to the back surface of the pocket surface of the cage scattering to the raceway surface. As described above, the structure without the retainer can reduce the excitation force and thus reduce the cold abnormal noise.

Furthermore, the rolling bearing 21 is characterized in that the rolling element 24 is made of ceramic. Examples of the material of the ceramic include silicon nitride, silicon carbide, aluminum oxide (alumina), zirconium oxide (zirconia), sialon, glass and the like. The ceramic rolling element can be manufactured by polishing raw balls obtained by a forming method such as HIP (hot isostatic compression) or gas pressure sintering. In the embodiment of FIG. 4, since the material of the rolling element is ceramic, as described later, the non-adhesiveness of the rolling element against grease can be increased. Among the ceramics, silicon nitride, alumina and glass are more preferable in terms of non-adhesiveness to the grease.

The grease sealed in the rolling bearing of FIG. 4 is composed of a base oil containing ether oil and a thickener. As the base oil and the thickening agent, those similar to the rolling bearing shown in FIG. 1 can be used, and the preferred form of the grease is also the same.

As described above, the energy stored in the grease can be reduced by reducing the adhesion between the grease and the contact portion under low temperature. For example, it is preferable to use a grease whose adhesive strength is lower when the rolling element material is a ceramic than that of a bearing steel at a temperature of −20 ° C. or less. As a specific numerical value, the grease of the present invention preferably has an adhesion to rolling elements (ceramics) of 25 N or less, more preferably 20 N or less, at a temperature of −20 ° C. or less. As a result, since the grease and the rolling elements are separated by a weak force at low temperature, a strong vibration force is not generated, which contributes to the reduction of abnormal noise during cold. In other words, the grease and the ceramic may be selected such that the adhesion of the grease to the rolling element at a temperature of -20 ° C or less is 25 N or less.

Another example of a rolling bearing having ceramic rolling elements will be described based on FIG. The rolling bearing in FIG. 4 is configured not to have a cage, but the rolling bearing in FIG. 5 is configured to have a cage. In the rolling bearing 31, the inner ring 32 and the outer ring 33 are disposed concentrically, and a plurality of ceramic rolling elements 34 are arranged between the inner ring rolling surface 32a and the outer ring rolling surface 33a. The plurality of rolling elements 34 are held by a cage 35. The embodiment of FIG. 5 is characterized in that the number of rolling elements is 40 to 80% of the maximum number in the bearing dimension. That is, in the rolling bearing 31, the number of rolling elements 34 is smaller than the usual number of rolling elements of the rolling bearing of the same dimension.

The number of rolling elements included in the rolling bearing is determined by the inner diameter size and the outer diameter size, and the raceway surface curvature, the distance between rolling elements, and the like can also be taken into consideration. Due to the stringent requirements for bearing life, it is common practice to design the space between the inner and outer rings as much as possible to maximize the rated load in a given space. Therefore, the number of rolling elements in a normal rolling bearing is the maximum number in the bearing dimensions. For example, in the case of a bearing having an outer diameter of 40 mm and an inner diameter of 17 mm, the maximum number is seven, and in the bearing having an outer diameter of 62 mm and an inner diameter of 30 mm, the maximum number is nine. In the embodiment of FIG. 5 in the present invention, in the case of the former, the number of rolling elements is set to three (43%) to five (71%). In the latter case, the number of rolling elements is four (44%) to seven (78%).

In the rolling bearing shown in FIG. 5, the number of rolling elements is 40 to 80% of the maximum number in the bearing dimensions, so the area of the rolling surface of the rolling elements is reduced, and the contact surface between the bearing members Adhesiveness can be reduced. Preferably, the number of rolling elements is 50 to 70% of the maximum number. When the number of rolling elements is reduced below the maximum number, it is preferable to apply the present invention to a small-sized rolling bearing with a small load, in consideration of the bearing life. For example, the rolling bearing can be applied to a rolling bearing having a radial load of 200 N with an outer diameter of 40 mm. The relationship between the basic dynamic load rating Cr and the basic static load rating Cor and the number of balls is as described above.

An example of the automotive electrical equipment auxiliary machine to which the rolling bearing of FIG. 4 is applied is shown in FIG. FIG. 6 is a sectional view of the structure of an idler pulley used as a drive belt tensioner. The basic configuration of this pulley is the same as that shown in FIG. The rolling bearing of FIG. 5 may be applied to the idler pulley.

The rolling bearing according to the present invention is also used for an automotive electrical accessory such as a fan coupling device, an alternator, a tension pulley, an electromagnetic clutch or a compressor other than an idler pulley. Further, although a ball bearing is illustrated as a rolling bearing in FIGS. 1 to 6, the rolling bearing of the present invention can be any type of bearing.

(1) Cold abnormal noise test 1
In the cold abnormal noise test 1, assuming a tensioner for a drive belt of an automotive electrical accessory, as a rolling bearing, a NTN 6203 bearing with a bearing gap of 0 to -0.010 mm (zero to negative gap) Used (see Figure 1). Among these, in Examples 1 to 7, bearings having a non-adhesive coating were used as the bearing members, and in Comparative Examples 1 to 4, bearings having no non-adhesive coating were used. In Examples 1 to 7 and Comparative Examples 1, 3 and 4, as the grease, the base oil is alkyl diphenyl ether oil (kinetic viscosity at 40 ° C. is 65 mm ² / s, pour point is −42.5 ° C.) A thickener was used which contained an alicyclic diurea compound and contained 15% by mass of the thickener based on the entire grease (base oil + thickener). In Comparative Example 2, as the grease, the base oil is PAO oil (Kinematic viscosity is 30 mm ² / s at 40 ° C., the pour point is −55 ° C.), and the thickening agent is an alicyclic diurea compound. An agent was used that contained 20% by mass with respect to the entire grease (base oil + thickener). Further, the consistency of the greases of Examples 1 to 7 and Comparative Examples 1, 3 and 4 is 280, and the consistency of the grease of Comparative Example 2 is 235. The amount of grease sealed in the bearing is 0.5 g. It shows below about each non-adhesive film of an Example and a comparative example.

A cross-sectional view of the pulley in a state where the bearing of Example 1 is attached is as shown in FIG. For measurement of abnormal noise, a bearing equipped pulley cooled in a low temperature tank at -50 ° C for a certain period of time is taken out of the low temperature tank and attached to a tester at normal temperature, and when the bearing temperature reaches -40 ° C, radial The operation was started under a constant load of 200 N, and the sound pressure was measured for 10 seconds from the start. The rotational speed was accelerated from the stop state to 7500 min ^-1 in 30 seconds. The sound pressure effective value (sound pressure effective value) after A characteristic filter processing was used for evaluation of cold abnormal noise. The results are shown in FIG.

(2) Adhesiveness test 1
In order to confirm the adhesion between the grease and each material (including the non-adhesive film), using the plate material and the shim (thin film of metal) made of each material of Examples 1 to 4 and Comparative Examples 1 and 2. The adhesion was measured. To measure the adhesion, attach a shim to a plate coated with grease, cool it in a low temperature tank at -50 ° C for a certain period of time, and then attach it to a tester at room temperature. When the plate reaches -40 ° C, the shim The plate was peeled off from the plate, and the method was used to measure the maximum load when peeling off. The results are shown in FIG.
Plate material: Dimensions Φ 50 mm × 7 mm, material SUJ2 (bearing steel, same below)
Shim: Dimensions 10mm x 100mm x 0.01mm, material SUS 304
Grease-applied area dimensions: 10 mm (shimmer width) x 20 mm
Measurement speed: 1 m / s (speed when peeling the shim)

Example 1
A DLC film containing chromium and tungsten carbide as an intermediate layer was formed on the raceway of the bearing and the surface of the plate by unbalanced magnetron sputtering. The film thickness of the DLC film and the intermediate layer was 1.0 μm. The cold abnormal noise test was performed using the film-formed bearing, and the adhesion test was performed using the film-formed plate. As the bearings, except for Example 7 and Comparative Example 4, seven rolling elements (balls) were used.

Example 2
A molybdenum disulfide film was formed by shot treatment on the raceway of the bearing and the surface of the plate material. The film thickness was 0.5 μm. The cold abnormal noise test was performed using the film-formed bearing, and the adhesion test was performed using the film-formed plate.

Example 3
A tungsten disulfide film was formed by shot treatment on the surface of the rolling elements (balls) of the bearing and the above plate material. The film thickness was 0.3 μm. The cold abnormal noise test was performed using the film-formed bearing, and the adhesion test was performed using the film-formed plate.

Example 4
A PTFE resin film was formed by magnetron sputtering on the raceway of the bearing and the surface of the plate material. The film thickness was 0.8 μm. The cold abnormal noise test was performed using the film-formed bearing, and the adhesion test was performed using the film-formed plate.

Example 5
A DLC film containing chromium and tungsten carbide as an intermediate layer was formed on the raceway of the bearing by unbalanced magnetron sputtering. The film thickness of the DLC film and the intermediate layer was 1.0 μm. A cold abnormal noise test was conducted using a bearing (see FIG. 2) having a DLC film and no holder.

Example 6
A tungsten disulfide film was formed by shot treatment on the raceway surface of the bearing and the rolling elements (balls) of the bearing. The film thickness was 0.3 μm. A cold noise test was conducted using the film-formed bearing.

Example 7
A DLC film containing chromium and tungsten carbide as an intermediate layer was formed on the raceway of the bearing by unbalanced magnetron sputtering. The film thickness of the DLC film and the intermediate layer was 1.0 μm. A cold noise test was conducted using a bearing having a DLC film and having four rolling elements (balls).

Comparative Example 1
A cold noise test was performed using a bearing having no non-stick coating, and an adhesion test was performed using a plate having no non-stick coating.

Comparative example 2
Each test was carried out in the same manner as Comparative Example 1 except that a PAO oil having good low temperature fluidity was used as the base oil of the grease.

Comparative example 3
A cold noise test was conducted using a bearing having no non-stick coating and no cage.

Comparative example 4
A cold noise test was conducted using a bearing having no non-stick coating and having four rolling elements (balls).

From FIG. 7, in the case of the bearing having the non-adhesive film on at least one of the raceway surface and the rolling surface (Examples 1 to 7), in the case of the bearing having no non-adhesive film (Comparative Example 1) In comparison, cold abnormal noise could be suppressed. Moreover, from Example 1 and Example 5, the cold abnormal noise was further suppressed by eliminating the retainer of the rolling bearing. From this, it was found that the adhesion of the grease at the contact portion between the rolling element and the cage also affects the abnormal noise. That is, combining the non-adhesive coating and the configuration without the retainer is more effective in suppressing cold abnormal noise. In addition, it was found that by reducing the number of balls themselves in contact with the raceway surface and the cage, cold noise is reduced to a small width (Comparative Example 1, Comparative Example 4). However, since the effect of reducing the number of balls is limited, a better effect of reducing abnormal noise during cold was obtained by combining the non-adhesive film on the raceway surface (Example 7).

Further, from the results of FIG. 7 and FIG. 8, it was found that when the adhesive force of the grease at low temperature is reduced, the cold abnormal noise is also reduced. According to FIG. 7, in the case of the plate material having the non-adhesive film on the surface (Examples 1 to 4), the plate material without the non-adhesive film, that is, the plate material having the surface of SUJ 2 (comparative example 1) is compared. The adhesive strength of the grease was 80% or less. Here, Comparative Example 2 uses a grease based on PAO oil having good low-temperature fluidity, so that the adhesion is small and cold noise is reduced. However, since this PAO oil has a low pour point and is easily oxidized, there is a concern about durability at high temperatures. On the other hand, ether oil which is a base oil of the greases of Examples 1 to 7 is excellent in durability at high temperature.

Moreover, in the molybdenum disulfide (Example 2) and the tungsten disulfide (Example 3), although the adhesive force became remarkably low by the drop-off phenomenon of the surface layer, the cold abnormal noise did not reduce so much. It is considered that this is because the highly viscoelastic grease scrapes off the non-tacky coating during operation and partially exposes the substrate. As described above, since the rolling bearing having the non-adhesive film has both durability at high temperatures and anti-cold noise characteristics, it is suitable for use in a wide temperature range from low temperatures to high temperatures. .

(3) Cold abnormal noise test 2
In the cold abnormal noise test 2, assuming a tensioner for a drive belt of an automotive electrical accessory, as a rolling bearing, NTN 6203 (outer dimension: 40 mm, inner diameter: 17 mm), bearing clearance is 0 to 0 A .010 mm (zero to negative clearance) bearing was used. In Examples 8 to 12, bearings having rolling elements made of ceramics are used. Among them, in Examples 8 to 10, bearings having no cage are used, and in Examples 11 to 12, a cage (resin cage) is used. It was used as a bearing. Further, in Comparative Examples 5 to 8, bearings having a cage (resin cage) were used. The number of balls of the rolling elements (balls) was seven as usual (maximum number), except for Examples 11 to 12 and Comparative Example 8.

In Examples 8 to 12 and Comparative Examples 5 to 6 and 8, as the grease, the base oil is an alkyl diphenyl ether oil (kinetic viscosity at 40 ° C. is 65 mm ² / s, pour point is −42.5 ° C.) A thickener was used which contained an alicyclic diurea compound and contained 15% by mass of the thickener based on the entire grease (base oil + thickener). In Comparative Example 7, as the grease, the base oil is PAO oil (Kinematic viscosity of 30 mm ² / s at 40 ° C., pour point of −55 ° C.), and the thickening agent is an alicyclic diurea compound. An agent was used that contained 20% by mass with respect to the entire grease (base oil + thickener). Further, the consistency of the greases of Examples 8 to 12 and Comparative Examples 5 to 6 and 8 is 280, and the consistency of the grease of Comparative Example 7 is 235. The amount of grease sealed in the bearings is 0.5 g in each case. The material of each rolling element of an Example and a comparative example is shown below.

The bearings of each example and each comparative example were attached to a pulley, and the sound pressure was measured by the same method and condition as the cold abnormal noise test 1. The results are shown in FIG.

(4) Adhesion test 2
In order to confirm the adhesion between the grease and each material, the adhesion was measured using a plate made of each material of Examples 8 to 10 and Comparative Examples 5 and 7 and a shim (thin metal film). The measurement of adhesive force was performed by the same method and conditions as the adhesive force test 1 except using ceramics for the board | plate material of the Example. The results are shown in FIG.

Example 8
Cold abnormal noise test: silicon nitride rolling elements (balls), without cage Adhesion test: silicon nitride plate material

Example 9
Cold abnormal noise test: rolling element (ball) is alumina, no cage Adhesion test: plate material is alumina

Example 10
Cold abnormal noise test: rolling element (ball) is glass, no cage Adhesion test: plate material is glass

Example 11
Cold abnormal noise test: silicon nitride, 3 balls, with cage, rolling element (ball) Adhesiveness test: not conducted

Example 12
Cold abnormal noise test: rolling element (ball) is silicon nitride, 5 balls, with cage Adhesive test: not conducted

Comparative example 5
Cold abnormal noise test: rolling element (ball) is SUJ2 (bearing steel, same as the following), with cage Adhesive strength test: Material of plate material is SUJ2

Comparative example 6
Cold abnormal noise test: rolling element (ball) is silicon nitride, with cage Adhesive test: not conducted

Comparative example 7
Cold abnormal noise test: Rolling elements (balls) used are SUJ2 and base oil with low temperature fluidity is used, cage is available Adhesive strength test: Material of plate material is SUJ2

Comparative Example 8
Cold abnormal noise test: rolling element (ball) SUJ2, 3 balls, with cage Adhesive test: not conducted

From FIG. 9, in the case of the ceramic rolling element and the bearing having no cage (Examples 8 to 10), compared to the case of the rolling element other than ceramic and having the cage (comparative example 5), It was possible to suppress cold abnormal noise remarkably. Further, even in the case of bearings having ceramic rolling elements and having a cage (Examples 11 to 12), in the case of bearings having the maximum number of rolling elements other than ceramics, by reducing the number of rolling elements to less than the maximum number. Compared to (Comparative Example 5), cold abnormal noise could be suppressed significantly. When Comparative Example 5 and Comparative Example 6 are compared, it has been found that, even in the bearing having the cage, the use of the ceramic rolling element has the effect of reducing abnormal noise upon cooling. As described above, in the rolling bearings of Examples 8 to 12, excellent suppression of abnormal cold noise is achieved by combining the ceramic rolling element and the configuration without the cage or the configuration in which the number of rolling elements is reduced. Exert an effect.

Further, from the results of FIG. 9 and FIG. 10, it was found that when the adhesion of the grease to the rolling element at a low temperature is reduced, the cold abnormal noise is also reduced. From FIG. 10, in the case of the ceramic plate (Examples 8 to 10), the adhesive force of the grease was 80% or less as compared with the case of the plate made of SUJ 2 (Comparative Example 5). Here, Comparative Example 7 uses a grease based on PAO oil having good low-temperature fluidity, so that the adhesive strength is small, and cold noise is reduced. However, since this PAO oil has a low pour point and is easily oxidized, there is a concern about durability at high temperatures. On the other hand, ether oil, which is a base oil of the greases of Examples 8 to 12, is excellent in durability at high temperatures. As described above, since the rolling bearing having the ceramic rolling element has both durability at high temperature and anti-cold noise characteristics, it is suitable for use in a wide temperature range from low temperature to high temperature.

The rolling bearing according to the present invention has both durability at high temperatures and anti-cold noise characteristics, and thus is widely used as a bearing used in a wide temperature range from low temperature to high temperature. In particular, it is suitable as a grease-sealed rolling bearing applied to a fan coupling device, an alternator, an idler pulley, a tension pulley, an electromagnetic clutch, or a compressor, which is an automotive electrical accessory.

1, 11, 21, 31 rolling bearing 2, 12, 22, 32 inner ring 3, 13, 33 outer ring 4, 14, 24, 34 rolling element 5, 35 cage 6, 16, 26, 36 seal member 7, 17, 27, 37 Grease 8, 18 Non-adhesive film 51, 61 Pulley body

Claims (7)

A plurality of rolling elements that are used in an automotive electrical accessory and have an inner ring raceway surface on the outer periphery, an outer ring having an outer ring raceway surface on the inner periphery, and the inner ring raceway surface and the outer ring raceway surface A grease-sealed rolling bearing comprising: and a grease sealed around the rolling element,
The grease base oil is mainly composed of ether oil,
(1) A bearing having a coating of DLC, molybdenum disulfide, tungsten disulfide, or fluorine resin on at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, and the rolling surface of the rolling element. (2) The material of the rolling element is a ceramic and is a bearing which does not have a cage for holding the rolling element, or (3) the material of the rolling element is a ceramic and the cage A grease-sealed rolling bearing according to claim 1, wherein the number of rolling elements is 40 to 80% of the maximum number in the bearing size. The grease-sealed rolling bearing according to claim 1, wherein the grease-sealed rolling bearing is a bearing having the coating on the surface and does not have a cage for holding the rolling element. The grease-sealed rolling bearing according to claim 1, wherein the material of the rolling element in the grease-sealed rolling bearing is a ceramic, and the ceramic is silicon nitride, alumina, or glass. The grease-sealed rolling bearing according to claim 1, wherein the ether oil is an alkyl diphenyl ether oil. 5. The grease-sealed rolling bearing according to claim 4, wherein the ether oil has a kinematic viscosity at 40 ° C. of 20 to 90 mm ² / s and a pour point of −30 ° C. or less. The adhesion of the grease to the film or the adhesion to the ceramic at a temperature of -20 ° C. or less is 80% or less of the adhesion of the grease to the bearing steel at the same temperature. The grease-sealed rolling bearing according to 1). The grease-sealed rolling bearing according to claim 1, wherein the automotive electrical equipment accessory is a fan coupling device, an alternator, an idler pulley, a tension pulley, an electromagnetic clutch, or a compressor.

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