JP2004003595A - Rolling bearing for automobile power train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely suppress invasion of hydrogen into the inside of steel, and prevent hydrogen embrittlement like short life exfoliation even though the amount of hydrogen generated increases due to the change of use environment and lubricating environment. <P>SOLUTION: The rolling bearing is for peripheral auxiliary machinery such as a power train and an alternator, an idler pulley, an electromagnetic clutch for car air conditioners and a fuel injection pump. The coat with a thickness of 0.1 to 15 μm which makes nickel (Ni) and copper (Cu) main component is formed for at least one member among an inner race 1a, an outer race 1b and a ball 1d. <P>COPYRIGHT: (C)2004,JPO

Description

【００６４】
【表２】

【００６５】
【表３】

【００６６】
【表４】

【００６７】
【表５】

【００６８】
【表６】

【００６９】
表３，５より、短寿命でフレーキングを生じた場合、長寿命品に比べて水素侵入量が多いことがわかる。これにより、いびつな形態の白色組織を伴う短寿命剥離は侵入水素が起因となった水素脆性的な剥離形態であるといえる。つまり、侵入水素を抑制することで組織変化形態が水素脆性型からＤＥＣ型にシフトし、長寿命化することが考えられる。
【００７０】
表１，４，６に示すように、転動疲労寿命試験の結果、表面に水素遮断層として作用するＮｉまたはＣｕの皮膜を設けた本発明に係わる自動車パワートレイン用転がり軸受は、ＤＥＣ型の組織変化形態を呈しており、比較例の軸受に対して、大幅に転動疲労寿命が向上していることが実証された。
【００７１】
また、表２に示すように、めっきを施す基材表面の品質をＨＶ８５０以下、半価幅６．５以上、圧縮残留応力１０００ＭＰａ以下とすることで、さらに長寿命化が図れることが実証された。
【００７２】
上記した実施例では、本発明に係わる自動車パワートレイン用転がり軸受を図１に示す自動車パワートレイン周辺補機であるオルタネータ１０用の軸受とした場合，図３に示す同じく自動車パワートレイン周辺補機である燃料噴射ポンプ１５用のスラストころ軸受とした場合および図９に示す自動車パワートレインであるベルト式無段変速機用の軸受とした場合を示したが、これに限定されるものではなく、本発明に係わる自動車パワートレイン用転がり軸受を図５に示すアイドラプーリー４０用の軸受４としたり、図６に示すカーエアコン用電磁クラッチ５０の軸受５としたり、エンジンやトランスミッションやファイナルドライブなどの自動車パワートレインの動力伝達部品を支持する転がり軸受とすることができるのは言うまでもない。
【図面の簡単な説明】
【図１】本発明に係わる自動車パワートレイン用転がり軸受の一実施例を示すオルタネータ実機に組み付けた状態の断面説明図（ａ）および深溝玉軸受の拡大断面説明図（ｂ）である。
【図２】図１のオルタネータに組み付けた深溝玉軸受の急加減速試験を行うベンチの概略説明図である。
【図３】本発明に係わる自動車パワートレイン用転がり軸受の他の実施例を示す燃料噴射ポンプに組み付けた状態の断面説明図である。
【図４】図３の燃料噴射ポンプに組み付けたスラストころ軸受に対してスラスト試験機を用いて転動試験を行う際の概略断面説明図である。
【図５】本発明に係わる自動車パワートレイン用転がり軸受をアイドラプーリーに組み付けた状況を示す断面説明図である。
【図６】本発明に係わる自動車パワートレイン用転がり軸受をカーエアコン用電磁クラッチに組み付けた状況を示す断面説明図である。
【図７】本発明に係わる自動車パワートレイン用転がり軸受をベルト式無段変速機に組み付けた状況を示す断面説明図である。
【図８】急加減速試験後の深溝玉軸受の剥離部近傍における転がり方向断面組織（白色組織なし）を示す写真である。
【図９】急加減速試験後の深溝玉軸受の剥離部近傍における転がり方向断面組織（白色組織あり）を示す写真である。
【符号の説明】
１　深溝玉軸受（自動車パワートレイン用転がり軸受）
１ａ，２ａ　内レース
１ｂ，２ｂ　外レース
１ｄ　ボール（転動体）
２　スラストころ軸受（自動車パワートレイン用転がり軸受）
２ｄ　ころ（転動体）
１０　オルタネータ
１５　燃料噴射ポンプ
４０　アイドラプーリー
５０　カーエアコン用電磁クラッチ
６０　ベルト式無段変速機[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is used to support power transmission components such as gears, shafts, and pulleys in an automobile powertrain, for example, a transmission, and also supports power transmission components in a belt-type continuously variable transmission as an automobile powertrain. In addition, grease-filled bearings used in alternators, electromagnetic clutches, idler pulleys, and rolling bearings used in fuel injection pumps are also suitable for use as peripheral accessories in automotive powertrains. The present invention relates to a rolling bearing for a power train.
[0002]
[Prior art]
2. Description of the Related Art In recent years, power trains used in automobiles and the like have been required to be smaller and lighter in order to improve fuel efficiency and increase output. Along with this, rolling and sliding members such as rolling bearings and gears used in the power train are required to be operated in a severe environment such as high load and high rotation in addition to reduction in size and weight. .
[0003]
For example, grease-enclosed bearings used in alternators and electromagnetic clutches are required to be compact and lightweight, and are subject to vibration from the engine. Used below. As a result, NTN Technical Review No. 61, NSK Technical Technical Journal No. As described in 656, there is a report that peeling occurs in a short life with a unique form of tissue change inside the rolling surface.
[0004]
The cause of the short-life peeling is as described in NTN Technical Review No. As described in No. 61, use under severe environment such as high load, high speed rotation and high vibration causes mirror wear of the rolling surface, and the formation of a new metal surface thereby plays a catalytic role. It is considered that grease or mixed water is decomposed, and the hydrogen generated at this time penetrates into the steel, causing hydrogen-brittle separation.
[0005]
At this time, (1) the process of generating hydrogen atoms or ions due to the decomposition of hydrocarbons or mixed water → (2) the process of penetrating the generated hydrogen atoms or ions into the steel → (3) the brittleness of the material due to the penetrated hydrogen It is considered that hydrogen embrittlement separation within the rolling surface is caused through the formation process.
[0006]
Conventionally, as a countermeasure against the above-described hydrogen-brittle short-life peeling, a method in which triiron tetroxide is formed on the rolling surface by a blackening treatment (Japanese Patent Application Laid-Open No. 2-190615), a lubrication method containing an inactivator, The rolling surface is modified so that the reaction of the deactivator is promoted by using an agent (Japanese Patent Application Laid-Open No. 2001-20958), or the surface is increased by increasing the Cr content of the base material. There is one in which an inert oxide film such as FeCrO4 is formed (Japanese Patent Application Laid-Open No. 8-177864).
[0007]
These measures are to form an inert film on the rolling surface and suppress the catalytic action due to the formation of a new surface, thereby making it difficult for the decomposition reaction of hydrocarbons or mixed water to occur and reducing the amount of generated hydrogen, that is, This is an improvement of the above-mentioned (1) hydrogen generation process. However, the catalytic action on the decomposition reaction of hydrocarbons exists not only on the new surface but also on the mixed water and the acid generated by the decomposition of additives, etc. It cannot be suppressed and it is difficult to prevent these generated hydrogen from entering the steel.
[0008]
In addition, there is a conventional example (JP-A-5-255809) in which Al, Nb, N, and the like are added to steel to form a metal structure resistant to hydrogen embrittlement by refining austenite crystal grains.
[0009]
This is to improve the hydrogen embrittlement resistance of the material by refining the crystal grains, that is, to improve the embrittlement process of the above-mentioned material (3). However, miniaturization of crystal grains increases the area ratio of crystal grain boundaries, which are hydrogen entry paths, so that the amount of hydrogen that enters steel may increase.
[0010]
Therefore, by improving the hydrogen invasion process of the above item (2), which has not been improved in the above conventional example, even if the amount of generated hydrogen increases due to a change in the use environment or lubrication environment, the amount of hydrogen entering the inside of the steel increases. A rolling member or a sliding member capable of suppressing hydrogen-brittle short-life peeling by reliably suppressing the intrusion of hydrogen is required.
[0011]
[Problems to be solved by the invention]
Until now, it has been reported that such hydrogen-brittle short-life peeling phenomenon may occur in grease-enclosed bearings used in engine accessories such as alternators and idler pulleys as described above. However, rolling bearings for these other engine peripheral accessories, such as those used in electromagnetic clutches for car air conditioners and fuel injection pumps, and gears, shafts and pulleys in transmissions as automobile power trains Rolling bearings that support power transmission components such as power transmission components in belt-type continuously variable transmissions as automobile power trains are also used under high vibrations, similar to the above grease-sealed bearings. With the trend toward smaller and lighter parts and larger capacity, the aforementioned hydrogen embrittlement phenomenon will occur in the future. Has a problem that there is a potential, it has become a conventional problem to solve this problem.
[0012]
[Object of the invention]
The present invention has been made in view of the conventional problems described above, and even if the use environment or the lubrication environment changes and the amount of generated hydrogen increases, the intrusion of hydrogen into steel inside is surely suppressed. Accordingly, it is an object of the present invention to provide a rolling bearing for an automobile power train, which can prevent hydrogen-brittle short-life peeling.
[0013]
[Means for Solving the Problems]
The rolling bearing for an automobile power train according to the present invention is a rolling bearing used for an automobile power train and its peripheral accessories, wherein at least one of an inner race, an outer race and a rolling element is used. The present invention is characterized in that a coating having a thickness of 0.1 to 15 μm containing nickel (Ni) or copper (Cu) as a main component is formed on a member. This is a means for solving the conventional problem described above.
[0014]
Here, when the rolling bearing for an automobile power train according to the present invention is a thrust roller bearing, a race fixed to the shaft side is an inner race, and a race fixed to the housing side is an outer race.
[0015]
In the rolling bearing for an automobile power train according to the present invention, the thickness of the film formed on the inner race, the outer race, and the rolling element is determined by the following equation. (Thickness of film + thickness of rolling element film) ≦ 15 μm. In a third aspect, the film is formed by electroplating or electroless plating. In a fourth aspect, after plating is performed, In this step, the baking process is performed at a temperature of 200 ° C. or less. According to a fifth aspect of the present invention, the average microhardness (HV (0.025)) of the substrate surface of the rolling contact portion to be plated is HV850 or less. The half-width of the α-Fe [211] peak on the material surface is 6.5 or more, and the compressive residual stress on the base material surface of the rolling contact portion to be plated is 1000 MPa or less. I have.
[0016]
The rolling bearing for an automobile power train according to the present invention is configured as claim 8 in which peripheral accessories of the automobile power train are any one of an alternator, an idler pulley, and an electromagnetic clutch for a car air conditioner. Peripheral accessories of the vehicle power train are fuel injection pumps, and as claim 10 a structure used to support power transmission components of the vehicle power train such as a transmission, and as claim 11 as a vehicle power train Used to support power transmission components in the belt-type continuously variable transmission.
[0017]
Effect of the Invention
In the rolling bearing for an automobile power train according to the first aspect of the present invention, a coating having a thickness of 0.1 to 15 μm mainly composed of nickel (Ni) or copper (Cu) having a low hydrogen diffusion coefficient constitutes the bearing. Since it is formed on at least one member of the inner race, outer race, and rolling elements such as balls and rollers, exposure of the newly formed iron surface due to micro metal contact is suppressed, and decomposition of hydrocarbons or mixed water, etc. Thereby, the intrusion of hydrogen generated during rolling into the steel is suppressed. In other words, elements such as nickel and copper have an extremely low diffusion coefficient of hydrogen compared to iron, so if these films are formed on the surface, the diffusion of hydrogen will be greatly delayed at the surface, and the hydrogen will be retained on the surface. As a result, the penetration of hydrogen into a portion having a high internal stress is delayed, and the amount of hydrogen per unit time is reduced.
[0018]
Here, when narrowing the film formation site in consideration of cost, etc., a portion where hydrogen embrittlement is likely to occur, such as an inner race or an outer race (at least a fixed race in a radial ball bearing) or a ball in a ball bearing. In a roller bearing, it is preferable to form a film on the rollers.
[0019]
Also, the reason that the thickness of the coating containing nickel (Ni) or copper (Cu) as a main component is preferably 0.1 to 15 μm is that if the coating thickness is less than 0.1 μm, the coating is worn during use. This is because it is difficult to obtain the function of the film for blocking hydrogen intrusion and the function of suppressing the exposure of the newly formed iron surface for a long period of time, so that sufficient hydrogen embrittlement resistance cannot be obtained.
[0020]
On the other hand, even if the thickness of the coating mainly composed of nickel (Ni) or copper (Cu) exceeds 15 μm, the hydrogen embrittlement resistance is not particularly deteriorated, but as the thickness of the coating increases. It is not preferable because the stress in the film becomes excessive, and the film peels relatively early and does not contribute much to the improvement of the rolling fatigue life. In particular, in the case of a radial bearing, rotation accuracy is deteriorated due to an increase in a radial gap of the bearing due to abrasion of a film during use, and vibration is increased or noise is caused, thereby shortening a bearing peeling life. . Since the processing time is prolonged at the same time as the film thickness is increased, and the cost is also increased, it is not preferable that the film thickness exceeds 15 μm.
[0021]
Further, in the rolling bearing for an automobile power train according to claim 2 of the present invention, the sum of the film thicknesses formed on the inner race, the outer race, and the rolling elements is equal to the film thickness of the fixed-side race + 2 × (drive side (Thickness of the coating of the race + thickness of the rolling element)) ≦ 15 μm.
[0022]
For example, in a radial bearing in which a radial load is applied from one direction, if a coating of 5 μm is formed only on the fixed-side race and it is assumed that all of the coating will be worn out during use, the wear will occur only in the load zone. Only on the side, the bearing gap increases by 5 μm. On the other hand, if a 5 μm film is formed only on the drive side race or ball and all of them are worn out during use, the radial gap increases by 5 μm × 2 = 10 μm because both are rotating. .
[0023]
Therefore, when the coating thickness of the fixed-side race + 2 × (the coating thickness of the driving-side race + the coating thickness of the rolling elements) exceeds 15 μm, the rotational accuracy is increased due to an increase in the radial gap of the bearing, as described above. It is not preferable because it deteriorates, and increases the vibration and causes noise to shorten the peeling life of the bearing.
[0024]
For example, as shown in FIG. 1, in the case of the bearing 1 for the alternator 10, the fixed side is the outer race 1 b, and as shown in FIG. 4, in the case of the bearing 4 used for the idler pulley 40, the fixed side Becomes the inner race 4a.
[0025]
Further, in the rolling bearing for an automobile power train according to claim 3 of the present invention, since the film is formed by electroplating or electroless plating, the film for blocking invasive hydrogen is formed by a relatively simple treatment. Thus, it becomes a preferable product excellent in versatility and mass productivity.
[0026]
Furthermore, in a rolling bearing for an automobile power train according to claim 4 of the present invention as a more preferred embodiment, a baking treatment at a temperature of 200 ° C. or less is performed in a stage after the plating treatment. Therefore, hydrogen that has intruded into the substrate or film during electroplating or electroless plating, and hydrogen that has invaded into the substrate during heat treatment of a rough material (for example, carburizing and quenching) are released. Here, if the temperature at the time of the baking treatment is higher than 200 ° C., the amount of dehydrogenation due to the baking increases, but the base material may be softened by holding at a high temperature. Therefore, by setting the temperature during the baking treatment to 200 ° C. or lower, the softening of the base material is prevented while the dehydrogenating effect is maintained. The baking treatment is more preferably performed in a vacuum furnace, which further enhances the dehydrogenation effect.
[0027]
Furthermore, in the rolling bearing for an automobile power train according to claims 5 to 7 of the present invention as a more preferred embodiment, the average micro hardness (HV (0.025)) of the base material surface of the rolling contact portion to be plated is provided. HV850 or less, half-width of α-Fe [211] peak is 6.5 or more, and compressive residual stress on the substrate surface of the rolling contact portion to be plated is 1000 MPa or less, so that adhesion between the film and the substrate is obtained. Is improved, and the effect of suppressing hydrogen intrusion is enhanced, and as a result, hydrogen-brittle separation is suppressed, which is preferable.
[0028]
【The invention's effect】
According to the rolling bearing for an automobile power train according to claims 1 and 2 of the present invention, since the above-described configuration is used, even if the use environment or the lubrication environment changes and the amount of generated hydrogen increases, the micro metal contact can be prevented. By suppressing the exposure of the newly formed iron surface, it is possible to reliably prevent hydrogen from entering the interior of the steel, and as a result, it is possible to prevent hydrogen-brittle short-life delamination, which is a very excellent feature. The effect is brought.
[0029]
According to the rolling bearing for an automobile power train according to the third aspect of the present invention, since the above-described configuration is employed, a film that blocks invading hydrogen can be formed by performing relatively simple processing, and versatility can be achieved. A very excellent effect that it is also possible to realize improvement in mass productivity.
[0030]
According to the rolling bearing for an automobile power train according to the fourth aspect of the present invention, since the above-described configuration is employed, hydrogen that has invaded into a substrate or a film during electroplating or electroless plating, and heat treatment of a coarse material (for example, In the rolling bearing for an automobile power train according to claims 5 to 7 of the present invention, it is possible to release the hydrogen that has penetrated into the substrate during carburizing and quenching. With this configuration, the adhesion between the film and the substrate is improved, and the effect of suppressing hydrogen intrusion can be enhanced. As a result, it is possible to effectively suppress hydrogen embrittlement peeling. Excellent effect is obtained.
[0031]
According to the rolling bearing for an automobile power train according to claim 8 of the present invention, the peripheral components of the engine, that is, the alternator, the idler pulley, and the electromagnetic clutch for a car air conditioner can be smoothly and smoothly operated in a severe environment without any trouble. According to the rolling bearing for an automobile power train according to the ninth aspect of the present invention, it is possible to smoothly operate the peripheral components of the engine, that is, the fuel injection pump in a severe environment. According to the rolling bearing for an automobile power train according to the tenth aspect of the present invention, it is possible to reduce the size and the capacity of the power transmission component, and according to the rolling bearing for an automobile power train according to the eleventh aspect of the present invention. Very excellent effect that the unit of the belt type continuously variable transmission can be reduced in size and increased in capacity. It brought about.
[0032]
【Example】
Hereinafter, embodiments of the rolling bearing for an automobile power train according to the present invention will be described, and its usefulness will be shown in comparison with a comparative example. The measured values of the rolling bearing for a vehicle power train according to the present invention were measured values obtained by the following methods.
[0033]
[Coating thickness measurement method]
The film thickness of the prepared sample is quantified by observing the cross section of the film forming portion using a scanning electron microscope (SEM).
[0034]
[Method for measuring phosphorus content of film]
The phosphorus content of the film of the prepared sample is determined using a commercially available X-ray fluorescence analyzer. A plurality of samples having different and different phosphorus contents are measured, and an intensity-content calibration curve is prepared from the respective intensities. Under the same conditions, the rolling bearing for an automobile power train according to the present invention is cut out to an appropriate size and measured, and the measured strength is converted into the phosphorus content based on the above-mentioned calibration curve.
[0035]
[Micro hardness of substrate surface]
The microhardness of the base material surface of the rolling contact portion to be plated was measured from a cross section of a rolling portion plated after plating. The measurement was performed using a micro Vickers hardness measuring device under a pressing load of 25 g (= HV (0.025)). The measurement position was measured at several points at a depth of 5 to 10 μm from the substrate surface (= plating interface), and the average value was defined as the average microhardness of the substrate surface.
[0036]
[Α-Fe [211] peak half width at substrate surface and compressive residual stress at substrate surface]
The measurement of the half-value width and the compressive residual stress of the α-Fe [211] peak on the surface of the base material of the rolling contact portion to be plated was performed by using a micropart X-ray stress measuring device. In the measurement, the substrate was polished by electropolishing to a position at a depth of 10 μm from the substrate surface (= plating interface), and the measured value on that surface was defined as α-Fe [211] peak half width and compressive residual stress. The circumferential residual stress was used as the compressive residual stress.
[0037]
Next, a method of manufacturing the rolling bearing for an automobile power train according to the present invention will be described.
[0038]
Various coatings were formed under the following conditions using a commercially available deep groove ball bearing (see FIGS. 1 and 9) and a thrust roller bearing (see FIG. 3) made of SUJ2.
[0039]
[Conditions for forming a coating mainly composed of nickel (Ni)]
1) Base material to be coated: race surface, ball and roller of rolling bearing
2) Composition of plating bath:
A. Strike plating bath (Ni-based)
Nickel chloride @ 200g / L
Hydrochloric acid 80g / L
Boric acid @ 30g / L
pH 1 or less
Plating bath temperature 50-55 ° C
Current density 0.1-10A / dm²
B. Electroplating bath (Ni-based)
60% sulfamic acid
Nickel ¥ 800g / L
Nickel chloride @ 15g / L
Boric acid 45g / L
Saccharin soda @ 5g / L
50% hypophosphorous acid 0 or 1 g / L
pH 4 ~ 5
Plating bath temperature @ 55-60 ° C
Current density 1-10A / dm²
C. Electroless plating bath (Ni-based)
Nickel chloride @ 16g / L
Sodium hypophosphite 24g / L
Sodium succinate @ 16g / L
Malic acid 18g / L
Diethylamine @ 10g / L
pH 5-6
Plating bath temperature 90-95 ° C
[0040]
[Preparation conditions for coating containing copper (Cu) as a main component]
D. Electroplating bath (Cu-based)
Cuprous cyanide @ 60g / L
Sodium cyanide @ 75g / L
Sodium carbonate @ 30g / L
pH 12 ~ 13
Plating bath temperature 50-60 ℃
Current density 2-5A / dm²
E. FIG. Electroless plating bath (Cu-based)
Copper sulfate 10g / L
Lossell salt 50g / L
Sodium hydroxide @ 10g / L
Formalin (37%) 10g / L
Stabilizer-trace amount
pH 11-13
Plating bath temperature room temperature
[0041]
<Deep groove ball bearings (radial bearings)>
(Examples 1 to 6, 8 and Comparative Example 2)
After the strike plating (using the bath of A) containing nickel (Ni) as a main component is applied to the bearing groove 1c of the outer race 1b on the fixed side of the rolling bearing 1 or the inner race 1a on the drive side, and then electroplating is performed. (Using the bath B) to form a film mainly composed of Ni.
[0042]
In Example 8 and Comparative Example 2, 1 g / L of 50% hypophosphorous acid was added as a plating bath (bath B) when forming a film mainly containing Ni by electroplating. A bath was used. In Examples 1 to 6, a plating bath to which 50% hypophosphorous acid was not added was used. In Example 6, after plating, baking treatment was performed at 130 ° C. for 20 hours in a vacuum furnace.
[0043]
(Examples 2.1, 2.2, and 2.3)
At this time, in order to confirm the influence of the quality of the base material surface (micro hardness, half width and compressive residual stress), the outer race was subjected to fine particle shot peening and then Ni-plated on the outer race which was polished again. (Examples 2.2 and 2.3) were prepared, and the same plating treatment as in Example 2 was applied to the samples (Examples 2 and 2.1) not subjected to fine particle shot peening. Table 2 shows the substrate surface quality of each sample in each example.
[0044]
(Example 7)
The outer race 1b on the fixed side of the rolling bearing 1 and the bearing groove 1c of the inner race 1a on the driving side are subjected to strike plating (using the above bath A) containing nickel (Ni) as a main component, and then to electroless plating. A film containing Ni as a main component was formed by a method (using the bath C).
[0045]
(Examples 9 to 11, Comparative Example 3)
A plating film mainly composed of copper (Cu) was formed on the bearing groove 1c of the outer race 1b on the fixed side of the rolling bearing 1 or the inner race 1a on the driving side. In forming the Cu plating, the electroplating method (using the bath of D) was used in Examples 9 and 10 and Comparative Example 3, and the electroless plating method (using the bath of E above) was used in Example 11. It was adopted. In Example 10, after plating, baking treatment was performed at 130 ° C. for 20 hours in a vacuum furnace. In this embodiment, the film is formed on the race. However, when the rolling elements (balls) peel off, a film may be formed on the rolling elements.
[0046]
(Comparative Example 1)
A sample not subjected to a plating process was prepared.
[0047]
<Thrust roller bearing>
(Examples 1 ', 2', 4 ', Comparative Example 2')
Roller 2d of thrust roller bearing 2 is subjected to strike plating (using bath A) using nickel (Ni) as a main component, and then Ni is used as a main component by electroplating (using bath B). Was formed.
[0048]
In Example 4 'and Comparative Example 2', 1 g / L of 50% hypophosphorous acid was used as a plating bath (bath B) for forming a film mainly containing Ni by electroplating. The added bath was used. In Examples 1 'and 2', a plating bath to which 50% hypophosphorous acid was not added was used. In Example 1 ', after plating, baking treatment was performed in a vacuum furnace at 130C for 20 hours.
[0049]
(Example 3 ')
The roller 2d of the thrust roller bearing 2 is subjected to strike plating (using the bath A) containing nickel (Ni) as a main component, and then Ni is mainly electrolessly plated (using the bath C). A film as a component was formed.
[0050]
(Examples 5 ', 6', 7 ', Comparative Example 3')
On the roller 2d of the thrust roller bearing 2, a plating film containing copper (Cu) as a main component was formed. In forming the Cu plating, the electroplating method (using the bath D) was employed in Examples 5 ′ and 6 ′ and Comparative Example 3 ′, and the electroless plating method (using the bath E described above) was used in Example 7 ′. Bath). In Example 5 ', after plating, baking treatment was performed at 130C for 20 hours in a vacuum furnace. In this embodiment, the film is formed on the rollers. However, when the lace is peeled off, the film may be formed on the lace.
[0051]
(Comparative Example 1 ')
A sample not subjected to a plating process was prepared.
[0052]
<Belt type continuously variable transmission>
(Example 1 '')
As shown in FIG. 7, in the belt-type continuously variable transmission 60, nickel (Ni) is a main component in the bearing grooves 1c of the fixed outer race 1b and the driving inner race 1a of the rolling bearing 1 supporting the pulley. Was applied (using the bath A), and a film containing Ni as a main component was formed by electroplating (using the bath B). In the present embodiment, the film is formed on the race. However, when the rolling elements (balls) peel off, a film may be formed on the rolling elements.
[0053]
Next, a method for evaluating the rolling bearing for an automobile power train according to the present invention will be described.
[0054]
In this example, the following two types of evaluation were performed using three types of bearings.
[0055]
(1) Deep groove ball bearing (simulates an alternator bearing as an engine accessory)
An alternator 10 provided with the deep groove ball bearing (6303 type) 1 shown in FIG. 1 is fixed to a horizontally movable table 21 of a bench 20, as shown in FIG. A rapid acceleration / deceleration test was conducted by transmitting the power to the pulley 11 of the alternator actual machine 10 via the belts 24 and 25. The evaluation was performed while abrupt acceleration / deceleration in which the rotation speed of the pulley 11 was changed from 2000 rpm to 14000 rpm to 2000 rpm in several seconds with a shaft load of about 1.8 kN in the direction of the arrow being applied was repeated. The rolling fatigue life was detected by a vibration sensor, and the life was defined as the test time until the fixed groove of the front bearing or the bearing groove of the drive wheel reached flaking.
[0056]
(2) Thrust roller bearing (assuming a roller bearing for a fuel injection pump as an engine accessory) As shown in FIG. 4, in a lubricating oil O containing about 1000 ppm of water, which was created by adding water to engine oil, A roller bearing (FNTA-2542C manufactured by NSK) 2 is set on the bottom surface of the lubricating oil container C filled with the lubricating oil O, and the pressing plate 32 of the rotating shaft 31 of the thrust tester 30 is mounted on the inner race 2a located on the upper side in the figure. The rolling test of the roller bearing 2 was performed by rotating the rotating shaft 31 at 1000 rpm while applying a load (5880 Nm) in the direction indicated by the arrow in the drawing. The rolling fatigue life was detected by a vibration sensor, and the test time until the rollers reached flaking was defined as the life.
[0057]
(3) Belt-type continuously variable transmission (rolling bearing that supports power transmission components)
As shown in FIG. 7, the CVT section of the belt-type continuously variable transmission 60 includes a primary pulley 61, a secondary pulley 62, and a steel belt 63. The speed is changed by continuously changing the radius. A box durability test was performed using a box tester incorporating the CVT section. The test conditions are as follows.
[0058]
Input rotation speed: 4000 rpm
Input torque: 30kgfm
Gear ratio: 1.0
Oil: Nissan CVT Fluid NS-1
In order to evaluate the life of the rolling bearing, other parts were periodically replaced to evaluate the life of the rolling bearing peeling off.
[0059]
Tables 1, 4 and 6 show a list of the rolling fatigue life test results of the bearings of the present example and comparative examples evaluated under the above test conditions. Tables 1, 4, and 6 also show the film characteristic values of the bearings according to the present example and the comparative example which were examined before the test. Peeling evaluated under the above test conditions occurred in the outer race in Tables 1 and 6, and all occurred in Table 4 in Table 4.
[0060]
8 and 9 show micrographs of the cross section in the rolling direction in the vicinity of the peeled portion of the deep groove ball bearing.
[0061]
The photograph in FIG. 8 is observed for a long-lived sample, and a slightly corroded structure is observed inside, but no white structure is present. On the other hand, the photograph of FIG. 9 was observed in a sample having a short life, and a distorted white structure was confirmed. These two types of structural changes were confirmed in a similar tendency in the vicinity of the peeled portion of the thrust roller bearing. Tables 1, 4 and 6 show the structural changes together with the results of the rolling fatigue test. The above-mentioned black-corroded structure is described as DEC, and the white structure is described as hydrogen-brittle type.
[0062]
Tables 3 and 5 show the results obtained by cutting out the rolling parts from the samples after the rolling fatigue test having different structural changes and measuring the amount of diffusible hydrogen in the steel. The measurement was performed using a thermal desorption gas analyzer (UPM-ST-200R, Japan Vacuum Technology Co., Ltd.), and the amount of hydrogen released at a heating temperature of 400 ° C. or lower was defined as the amount of diffusible hydrogen.
[0063]
[Table 1]

[0064]
[Table 2]

[0065]
[Table 3]

[0066]
[Table 4]

[0067]
[Table 5]

[0068]
[Table 6]

[0069]
From Tables 3 and 5, it can be seen that when flaking occurs with a short life, the amount of hydrogen penetration is larger than that of a long life product. Thus, it can be said that short-life exfoliation with a distorted white structure is a hydrogen embrittlement exfoliation form caused by invading hydrogen. In other words, it is conceivable that suppressing the intrusion hydrogen shifts the structure change form from the hydrogen embrittlement type to the DEC type, thereby extending the life.
[0070]
As shown in Tables 1, 4 and 6, as a result of the rolling fatigue life test, the rolling bearing for an automobile power train according to the present invention having a Ni or Cu film acting as a hydrogen barrier layer on the surface is a DEC type. It exhibited a structural change, and it was demonstrated that the rolling fatigue life was significantly improved over the bearing of the comparative example.
[0071]
In addition, as shown in Table 2, it was demonstrated that by setting the quality of the surface of the base material to be plated to HV850 or less, a half-value width of 6.5 or more, and a compressive residual stress of 1000 MPa or less, the life can be further extended. .
[0072]
In the embodiment described above, when the rolling bearing for an automobile power train according to the present invention is a bearing for the alternator 10 which is an auxiliary machine for the automobile power train shown in FIG. The case where the thrust roller bearing is used for a certain fuel injection pump 15 and the case where the bearing is used for a belt-type continuously variable transmission which is an automobile power train shown in FIG. 9 are shown, but the present invention is not limited to this. The rolling bearing for an automobile power train according to the invention is used as the bearing 4 for the idler pulley 40 shown in FIG. 5, the bearing 5 for the electromagnetic clutch 50 for a car air conditioner shown in FIG. Needless to say, it can be a rolling bearing that supports the power transmission components of the train
[Brief description of the drawings]
1A and 1B are a cross-sectional explanatory view showing an embodiment of a rolling bearing for an automobile power train according to the present invention, which is assembled to an actual alternator, and an enlarged cross-sectional explanatory view of a deep groove ball bearing.
FIG. 2 is a schematic explanatory view of a bench for performing a rapid acceleration / deceleration test of a deep groove ball bearing assembled to the alternator of FIG. 1;
FIG. 3 is an explanatory sectional view of a state in which the rolling bearing for an automobile power train according to another embodiment of the present invention is assembled to a fuel injection pump.
4 is a schematic sectional explanatory view when a rolling test is performed on a thrust roller bearing assembled to the fuel injection pump of FIG. 3 using a thrust tester.
FIG. 5 is an explanatory cross-sectional view showing a state where the rolling bearing for an automobile power train according to the present invention is assembled to an idler pulley.
FIG. 6 is an explanatory sectional view showing a state in which the rolling bearing for an automobile power train according to the present invention is assembled to an electromagnetic clutch for a car air conditioner.
FIG. 7 is an explanatory cross-sectional view showing a state where the rolling bearing for an automobile power train according to the present invention is assembled to a belt-type continuously variable transmission.
FIG. 8 is a photograph showing a cross-sectional structure in the rolling direction (no white structure) in the vicinity of a peeled portion of a deep groove ball bearing after a rapid acceleration / deceleration test.
FIG. 9 is a photograph showing a cross-sectional structure in the rolling direction (with a white structure) near a peeled portion of a deep groove ball bearing after a rapid acceleration / deceleration test.
[Explanation of symbols]
1 Deep groove ball bearings (rolling bearings for automobile power trains)
1a, 2a inner race
1b, 2b outside race
1d ball (rolling element)
2 thrust roller bearings (rolling bearings for automotive powertrains)
2d roller (rolling element)
10 alternator
15 fuel injection pump
40 idler pulley
Electromagnetic clutch for 50cm car air conditioner
60 ° belt type continuously variable transmission

Claims (11)

A rolling bearing used for an automobile power train and its peripheral accessories, wherein at least one member of an inner race, an outer race, and a rolling element contains nickel (Ni) or copper (Cu) as a main component. A rolling bearing for an automobile power train, wherein a coating having a thickness of 0.1 to 15 μm is formed. The thickness of the coating formed on the inner race, the outer race, and the rolling elements is set as follows: the coating thickness of the fixed-side race + 2 × (the coating thickness of the driving-side race + the coating thickness of the rolling elements) ≦ 15 μm. The rolling bearing for an automobile power train according to claim 1. 3. The rolling bearing according to claim 1, wherein the coating is formed by electroplating or electroless plating. 4. The rolling bearing for an automobile power train according to claim 3, wherein a baking treatment is performed at a temperature of 200 [deg.] C. or less in a stage after the plating treatment. The rolling bearing for an automobile power train according to claim 3 or 4, wherein an average microhardness (HV (0.025)) of a base material surface of a rolling contact portion to be plated is HV850 or less. The rolling bearing for an automobile power train according to claim 3 or 4, wherein the half-value width of the α-Fe [211] peak on the base material surface of the rolling contact portion to be plated is 6.5 or more. The rolling bearing for an automobile power train according to claim 3 or 4, wherein the compressive residual stress on the surface of the base material of the rolling contact portion to be plated is 1000 MPa or less. 8. The rolling bearing for an automobile power train according to claim 1, wherein the peripheral accessories of the automobile power train are any one of an alternator, an idler pulley, and an electromagnetic clutch for a car air conditioner. 8. The rolling bearing for an automobile power train according to claim 1, wherein peripheral accessories of the automobile power train are fuel injection pumps. The rolling bearing for an automobile power train according to any one of claims 1 to 7, which is used to support a power transmission component of the automobile power train such as a transmission. 8. The rolling bearing for an automobile power train according to claim 1, which is used to support a power transmission component in a belt-type continuously variable transmission as an automobile power train.

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