JP7398932B2 - thrust roller bearing - Google Patents
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- JP7398932B2 JP7398932B2 JP2019208661A JP2019208661A JP7398932B2 JP 7398932 B2 JP7398932 B2 JP 7398932B2 JP 2019208661 A JP2019208661 A JP 2019208661A JP 2019208661 A JP2019208661 A JP 2019208661A JP 7398932 B2 JP7398932 B2 JP 7398932B2
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
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- 239000000919 ceramic Substances 0.000 description 1
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- 229910052802 copper Inorganic materials 0.000 description 1
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- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
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Landscapes
- Rolling Contact Bearings (AREA)
Description
本発明は、スラストころ軸受に関する。 The present invention relates to thrust roller bearings.
スラストころ軸受は、針状ころ又は円筒ころが保持器に放射状に組込まれたスラスト保持器付きころと円板状の軌道輪とを組合わせた軸受である。すなわち、スラストころ軸受（スラスト針ころ軸受）は、図１７と図１８とに示すように、軸方向に互いに対向する一対の軌道輪１、２と、この軌道輪１、２の間に径方向に沿った状態で放射状に配設される複数個のころ３と、軌道輪１、２の間に介在されて複数個のころ３を保持する保持器４とを備える。 A thrust roller bearing is a bearing that combines a roller with a thrust cage, in which needle rollers or cylindrical rollers are radially incorporated into a cage, and a disc-shaped bearing ring. That is, as shown in FIGS. 17 and 18, thrust roller bearings (thrust needle roller bearings) include a pair of bearing rings 1 and 2 that face each other in the axial direction, and a radial space between these bearing rings 1 and 2. It is provided with a plurality of rollers 3 arranged radially along the radial direction, and a retainer 4 interposed between bearing rings 1 and 2 to hold the plurality of rollers 3.
環境保護の観点から、しゅう動部の摩擦低減と同時に潤滑油の使用量削減が重要な課題となっている。そのため、自動車や産業機器では潤滑油供給を必要最小量とした低摩擦運転が望まれている。また、潤滑油の消費が少ないグリース潤滑の適用拡大も検討されている。 From the perspective of environmental protection, reducing friction in sliding parts and reducing the amount of lubricant used are important issues. Therefore, in automobiles and industrial equipment, low-friction operation with the minimum amount of lubricant required is desired. Additionally, expansion of the application of grease lubrication, which consumes less lubricating oil, is also being considered.
各種機器のしゅう動部に数多く使用されているスラスト針状ころ軸受では、図１９に示すように内径側と外径側において、周速差が生じる。この周速差に起因する差動すべりが生じる。すなわち、図１９に示すように、ころ３が矢印Ａ方向に公転すると、内径側が矢印Ａ１のように進み、外径側が矢印Ａ２のうように遅れ、ころ３が矢印Ｂ方向に公転すると、内径側が矢印Ｂ１のように進み、外径側が矢印Ｂ２のうように遅れる。このように、差動すべりが生じた場合、潤滑油が不足すると比較的大きなトルクと摩耗とが発生するため、枯渇潤滑下での摩擦・摩耗特性の向上が求められている。 In thrust needle roller bearings that are widely used in sliding parts of various types of equipment, a difference in circumferential speed occurs between the inner diameter side and the outer diameter side, as shown in FIG. Differential slip occurs due to this circumferential speed difference. That is, as shown in FIG. 19, when the rollers 3 revolve in the direction of arrow A, the inner diameter side advances as shown by arrow A1, and the outer diameter side lags as shown by arrow A2. When the rollers 3 revolve in the direction of arrow B, the inner diameter The side advances as shown by arrow B1, and the outer diameter side lags as shown by arrow B2. As described above, when differential slip occurs, relatively large torque and wear occur if lubricating oil is insufficient, so there is a need to improve friction and wear characteristics under depleted lubrication.
そこで、従来では、特許文献１に記載のように、ころ３に、図２０に示すように、両端部のその外径寸法を軸方向端部側に向かって縮径するクラニング６、６を形成して、軌道輪１、２ところの接触面積を減少させて、差動すべりを低減させたものがある。 Therefore, conventionally, as described in Patent Document 1, the roller 3 is provided with crannings 6, 6 whose outer diameters at both ends are reduced toward the axial ends, as shown in FIG. There is one in which the contact area between the bearing rings 1 and 2 is reduced to reduce differential slip.
また、図２１に示すように、ころ３の外径面を円筒面として、軌道輪１、２のころ対応面を膨出させ、この膨出部７、８ところ３の外径面を摺接させるように構成したものがある（特許文献２）。この場合も、軌道輪１、２ところ３の接触面積を減少させて、差動すべりを低減させている。 Further, as shown in FIG. 21, the outer diameter surface of the roller 3 is made into a cylindrical surface, and the roller corresponding surfaces of the bearing rings 1 and 2 are bulged, and the outer diameter surface of the roller 3 is brought into sliding contact with the bulged portions 7 and 8. There is a device configured to do so (Patent Document 2). In this case as well, the contact area between the bearing rings 1, 2 and 3 is reduced to reduce differential slip.
しかしながら、ころ３にクラウニング６を形成したり、軌道輪側に膨出部７、８を形成して、差動すべりを低減させたとしても、差動すべりそのものの摩擦を低減できない。すなわち、枯渇潤滑下での摩擦・摩耗効果は乏しいものである。ところで、ころ３にクラウニング６，６を設ける場合、使用される全ころ３に対して設ける必要があり、また、軌道輪側に膨出部７、８を形成する場合、各膨出部の膨出量を精度よく構成する必要があり、これらにおいては生産性に劣り、コスト高となる。 However, even if the differential slip is reduced by forming the crowning 6 on the roller 3 or by forming the bulges 7 and 8 on the bearing ring side, the friction of the differential slip itself cannot be reduced. In other words, the friction and wear effects are poor under depleted lubrication. By the way, when providing crownings 6, 6 on rollers 3, it is necessary to provide them on all rollers 3 used, and when forming bulging portions 7, 8 on the raceway side, bulging portions of each bulging portion need to be provided. It is necessary to configure the output amount with high precision, which results in poor productivity and high costs.
本発明は、上記課題に鑑みて、枯渇潤滑下での焼き付きを有効に防止することができるスラストころ軸受を提供する。 In view of the above problems, the present invention provides a thrust roller bearing that can effectively prevent seizure under depleted lubrication.
本発明のスラストころ軸受は、軸方向に互いに対向する一対の軌道輪と、この軌道輪の間に径方向に沿った状態で放射状に配設される複数個のころとを備えたスラストころ軸受であって、少なくともいずれか一方の軌道輪におけるころの接触通過領域と、ころの外周面との少なくともいずれか一方に、複数の微細溝で構成されるグレーティング状凹凸の周期構造を設けたものである。 A thrust roller bearing according to the present invention includes a pair of bearing rings facing each other in the axial direction, and a plurality of rollers arranged radially between the bearing rings in a radial direction. A periodic structure of grating-like unevenness composed of a plurality of fine grooves is provided in at least one of the contact passage area of the roller in at least one of the bearing rings and the outer circumferential surface of the roller. be.
本発明のスラストころ軸受によれば、ころの外周面と、少なくともいずれか一方における軌道輪のころの接触通過領域との少なくともいずれか一方に、グレーティング状凹凸の周期構造を設けたことによって、周期構造の潤滑油保持や摩耗粉トラップ効果により差動すべりに起因する摩擦が抑制される。さらにグリース潤滑下においては、周期構造のグリース保持や摩耗粉トラップ効果に加えて、油分に対して高い濡れ性を示す周期構造が基油分離を促進することで増ちょう剤が高濃度化され、増ちょう剤由来の保護膜形成が促進されることで差動すべりに起因する摩耗が抑制される。 According to the thrust roller bearing of the present invention, the periodic structure of grating-like unevenness is provided on at least one of the outer circumferential surface of the roller and the contact passage area of the roller of the bearing ring on at least either one. Friction caused by differential slip is suppressed by the structure's lubricating oil retention and wear debris trapping effects. Furthermore, under grease lubrication, in addition to the periodic structure's ability to retain grease and trap wear debris, the periodic structure, which exhibits high wettability to oil, promotes base oil separation, increasing the concentration of the thickener. Wear caused by differential slip is suppressed by promoting the formation of a protective film derived from the thickener.
前記グレーティング状凹凸の周期構造が軌道輪におけるころの接触通過領域の外周側と内周側との少なくともいずれか一方に設けられているものであればよい。この場合であっても、グレーティング状凹凸の周期構造を設けたことに起因する作用効果を発揮することができる。 It is sufficient that the periodic structure of the grating-like unevenness is provided on at least one of the outer circumferential side and the inner circumferential side of the contact passage area of the roller in the bearing ring. Even in this case, the effects resulting from the provision of the periodic structure of grating-like unevenness can be exhibited.
外周側に設けられたグレーティング状凹凸の周期構造は、接触通過領域の外周縁よりも外径側にはみ出していても、内周側に設けられたグレーティング状凹凸の周期構造は、接触通過領域の内周縁よりも内径側にはみ出していてもよい。このように、接触通過領域外まで周期構造を設けることによって、周期構造の油分に対する高い濡れ性によって、ころの接触通過領域外に排出された潤滑油やグリースの基油成分が、ころの接触通過領域内に再流入することで枯渇潤滑下での摩擦・摩耗を抑制することができる。 Even if the periodic structure of grating-like unevenness provided on the outer circumferential side protrudes beyond the outer circumferential edge of the contact passage area, the periodic structure of grating-like unevenness provided on the inner circumference side extends beyond the outer circumferential edge of the contact passage area. It may protrude radially inward from the inner peripheral edge. In this way, by providing the periodic structure outside the contact passage area, the base oil components of lubricating oil and grease discharged outside the roller contact passage area are absorbed by the roller contact passage due to the high wettability of the periodic structure to oil. Friction and wear under depleted lubrication can be suppressed by re-flowing into the region.
接触通過領域の中心線上は差動すべりが生じない。そこで、接触通過領域の中心線上に周期構造を形成しないことで、弾性流体潤滑油膜の形成を阻害せず、良好な油膜形成と差動すべりに起因する摩擦抑制を両立することができる。 No differential slip occurs on the center line of the contact passing area. Therefore, by not forming a periodic structure on the center line of the contact passage area, the formation of an elastohydrodynamic lubricating oil film is not inhibited, and it is possible to achieve both good oil film formation and friction suppression due to differential slip.
前記グレーティング状凹凸の周期構造が、前記軌道輪の円周方向に沿って配向しているのが好ましい。このように構成することによって、ころの接触通過領域外に潤滑油やグリースが排出されにくく、周期構造に沿って保持されるため、潤滑油やグリースの担持性が向上し、さらには、摩耗粉のトラップ効果も向上する。 It is preferable that the periodic structure of the grating-like unevenness is oriented along the circumferential direction of the bearing ring. With this configuration, lubricating oil and grease are not easily discharged outside the contact passage area of the rollers, and are retained along the periodic structure, which improves lubricating oil and grease retention, and further improves the ability to carry wear particles. The trap effect will also be improved.
前記グレーティング状凹凸の周期構造の凹凸が５０ｎｍ以上１０μｍ以下かつ周期ピッチが１０μｍ以下であるのが好ましい。このように構成することによって、油分の保持性、移動性を向上することができる。すなわち、周期構造の凹凸が５０ｎｍ未満では十分な量の油分やグリースを担持できず、凹凸および周期ピッチが１０μｍを超えると油分やグリースが周期構造の凹凸から流出するおそれがある。 It is preferable that the periodic structure of the grating-like unevenness has an unevenness of 50 nm or more and 10 μm or less, and a periodic pitch of 10 μm or less. With this configuration, oil retention and mobility can be improved. That is, if the irregularities of the periodic structure are less than 50 nm, a sufficient amount of oil or grease cannot be supported, and if the irregularities and the periodic pitch exceed 10 μm, oil or grease may flow out from the irregularities of the periodic structure.
前記グレーティング状凹凸の周期構造は、凸部頂点が非平坦面となって連続的に高さが変化するのが好ましい。このように構成することによって、開口部が広くなり、潤滑油やグリースを効率的に取り込むことができる。 It is preferable that the periodic structure of the grating-like unevenness has a height that changes continuously with the apexes of the protrusions being non-flat surfaces. With this configuration, the opening becomes wide and lubricating oil and grease can be taken in efficiently.
本発明では、差動すべりに起因する摩擦・摩耗の低減を図ることができ、しかも、良好な油膜形成を図ることができる。このため、摺動部の摩擦低減と同時に潤滑油の使用量削減が可能なスラストころ軸受を提供できる。 According to the present invention, it is possible to reduce friction and wear caused by differential slip, and also to form a good oil film. Therefore, it is possible to provide a thrust roller bearing that can reduce the amount of lubricating oil used at the same time as reducing the friction of the sliding portion.
以下本発明の実施の形態を図１～図１６に基づいて説明する。 Embodiments of the present invention will be described below based on FIGS. 1 to 16.
図１は本発明に係るスラストころ軸受５０を示す。スラストころ軸受５０は、針状ころ又は円筒ころが保持器に放射状に組込まれたスラスト保持器付きころと円板状の軌道輪とを組合わせた軸受である。この場合の軸受５０は、軸方向に互いに対向する一対の軌道輪１１、１２と、この軌道輪１１、１２の間に径方向に沿った状態で放射状に配設される複数個のころ１３と、軌道輪１１、１２の間に介在されて複数個のころ１３を保持する保持器１４とを備える。 FIG. 1 shows a thrust roller bearing 50 according to the present invention. The thrust roller bearing 50 is a bearing that combines a roller with a thrust cage, in which needle rollers or cylindrical rollers are radially incorporated into the cage, and a disc-shaped bearing ring. The bearing 50 in this case includes a pair of bearing rings 11 and 12 facing each other in the axial direction, and a plurality of rollers 13 arranged radially between the bearing rings 11 and 12 along the radial direction. , and a retainer 14 that is interposed between the bearing rings 11 and 12 and holds a plurality of rollers 13.
軌道輪１１、１２は、図２に示すよう、中心孔１１ａ、１２ａが設けられたリング状平板体からなる。そして、一方の軌道輪１１の他の軌道輪１２に対向する面（内面）１１ｂにころ転動面（摺動面）１５が形成され、他方の軌道輪１２の一方の軌道輪１１に対向する面（内面）１２ｂがころ転動面（摺動面）１６とされる。この場合、軌道輪１１、１２は、炭素鋼、銅、アルミニウム、白金、超硬合金等であっても、炭化ケイ素や窒化ケイ素等のシリコン系セラミックスであっても、エンジニアプラスチック等であってもよい。 As shown in FIG. 2, the bearing rings 11 and 12 are ring-shaped flat plates provided with center holes 11a and 12a. A roller rolling surface (sliding surface) 15 is formed on a surface (inner surface) 11b of one bearing ring 11 facing the other bearing ring 12, and a roller rolling surface (sliding surface) 15 is formed on the surface (inner surface) 11b of one bearing ring 11 facing the other bearing ring 12. The surface (inner surface) 12b is the roller rolling surface (sliding surface) 16. In this case, the bearing rings 11 and 12 may be made of carbon steel, copper, aluminum, platinum, cemented carbide, etc., silicon-based ceramics such as silicon carbide or silicon nitride, or engineered plastic. good.
また、潤滑剤としては、ＰＡＯ６（ポリアルファオレフィン）やＵ－３Ｐ（脂肪族ウレアグリース）等を使用できる。ＰＡＯ６は、合成炭化水素は鉱油に近い組成ながら、高粘度指数で低流動点を有し、低温から高温まで使用温度領域が広いという特長を持っている。また、粘度指数が高く、高温においても厚い油膜の保持が可能である点、ワックス分を含まないので、流動点が非常に低く、低温粘度特性が良好なため、内燃機関などの低温始動性や暖気運転時間の短縮が可能である点、および、添加剤の添加効果が高く、熱酸化安定性が良好で、高温での使用、および長寿命化が可能である点等の利点がある。 Further, as the lubricant, PAO6 (polyalphaolefin), U-3P (aliphatic urea grease), etc. can be used. Although PAO6 is a synthetic hydrocarbon with a composition similar to that of mineral oil, it has a high viscosity index, a low pour point, and has a wide operating temperature range from low to high temperatures. In addition, it has a high viscosity index and can maintain a thick oil film even at high temperatures, and since it does not contain wax, it has a very low pour point and good low-temperature viscosity characteristics, so it is suitable for low-temperature startability of internal combustion engines, etc. It has advantages such as being able to shorten the warm-up operation time, being highly effective in adding additives, having good thermal oxidation stability, being able to be used at high temperatures, and having a long life.
また、ウレアグリースとは、ウレア基（－ＮＨ－ＣＯ－ＮＨ－）を２個以上有する有機化合物を増ちょう剤としたグリースである。また、ウレアグリースには、脂肪族ウレアと、脂環式ウレアと、芳香族ウレアとがある。脂肪族ウレアは、長鎖アルキル基を両末端に用いると耐熱性がリチウム石けんグリース並となる点、短鎖アルキル基を用いると耐熱性が向上する点、脂環式および芳香族ウレアに比べ寿命が短い点の特徴を有する。脂環式ウレアは、増ちょう効果が優れている点、比較的耐熱性に優れている点、せん断安定性に優れている点、寿命が長い点の特徴を有する。芳香族ウレアは、増ちょう効果が脂肪族ウレアや脂環式ウレアよりも劣る点、耐熱性に優れている点、寿命が長い点の特徴を有する。 Further, urea grease is a grease that uses an organic compound having two or more urea groups (-NH-CO-NH-) as a thickener. Further, urea grease includes aliphatic urea, alicyclic urea, and aromatic urea. Aliphatic ureas have heat resistance comparable to that of lithium soap grease when long chain alkyl groups are used at both ends, heat resistance is improved when short chain alkyl groups are used, and they have a longer lifespan than alicyclic and aromatic ureas. It is characterized by a short point. Alicyclic urea has the characteristics of excellent thickening effect, relatively excellent heat resistance, excellent shear stability, and long life. Aromatic ureas are characterized by having a thickening effect inferior to that of aliphatic ureas and alicyclic ureas, superior heat resistance, and long life.
各軌道輪１１、１２の内面には、図２に示すように、それぞれ、外周側及び内周側に複数の微細溝で構成さされるグレーティング状凹凸の周期構造２０（２０Ａ、２０Ｂ）が設けられている。この場合、図４に示すように、外周側の周期構造２０Ａは、ころ１３の接触通過領域Ｒの外周縁よりも外径側にはみ出し、内周側の周期構造２０Ｂは、ころ１３の接触通過領域Ｒの内周縁よりも内径側にはみ出している。 As shown in FIG. 2, the inner surface of each bearing ring 11, 12 is provided with a periodic structure 20 (20A, 20B) of grating-like irregularities, which is composed of a plurality of micro grooves on the outer and inner circumferential sides, respectively. ing. In this case, as shown in FIG. 4, the periodic structure 20A on the outer circumferential side protrudes outward from the outer circumferential edge of the contact passage area R of the roller 13, and the periodic structure 20B on the inner circumference side protrudes beyond the outer circumferential edge of the contact passage area R of the roller 13. It protrudes radially inward from the inner peripheral edge of region R.
また、外周側の周期構造２０Ａと、内周側の周期構造２０Ｂとの間には、周期構造２０を有さない未加工部２１が形成されている。すなわち、この未加工部２１は接触通過領域Ｒの中心線（ピッチ円）Ｐ上に配設され、未加工部２１の範囲としては、その軸方向長さＨ２として、ころの軸方向全長Ｈ１の１／３程度とされる。このため、各周期構造２０Ａ、２０Ｂの幅寸法は、（１－１／３）／２となる。また、外周側の周期構造２０Ａの接触通過領域Ｒのはみ出し量Ｔ1としては、例えば、０．５ｍｍ～５．０ｍｍ程度とし、内周側の周期構造２０Ｂの接触通過領域Ｒのはみ出し量Ｔ２としては、例えば、０．５ｍｍ～５．０ｍｍ程度としている。 Furthermore, an unprocessed portion 21 that does not have the periodic structure 20 is formed between the periodic structure 20A on the outer circumferential side and the periodic structure 20B on the inner circumferential side. That is, this unprocessed portion 21 is arranged on the center line (pitch circle) P of the contact passage area R, and the range of the unprocessed portion 21 is defined as its axial length H2, which is equal to the total axial length H1 of the roller. It is said to be about 1/3. Therefore, the width dimension of each periodic structure 20A, 20B is (1-1/3)/2. Further, the protrusion amount T1 of the contact passing region R of the periodic structure 20A on the outer circumference side is, for example, approximately 0.5 mm to 5.0 mm, and the protrusion amount T2 of the contact passage region R of the periodic structure 20B on the inner circumference side is, for example, approximately 0.5 mm to 5.0 mm. , for example, about 0.5 mm to 5.0 mm.
周期構造２０は、配向方向が周方向であり、図３に示すように、微小の凹部２２と微小の凸部２３とが交互に所定ピッチで配設されてなるものである。周期構造２０の凹凸の高低差（凹部２２の底部から凸部２３の頂点までの高さ）が５０ｎｍ以上１０μｍ以下とするのが好ましい。また、周期構造２０の周期ピッチを１０μｍ以下とするのが好ましい。図３（ａ）は周期構造２０の拡大図を示し、図３（ｂ）は断面プロファイルを示している。このように、周期構造２０は、凸部頂点が非平坦面となって連続的に高さが変化するグレーティング状凹凸の周期構造２０である。 The periodic structure 20 is oriented in the circumferential direction, and as shown in FIG. 3, minute recesses 22 and minute protrusions 23 are arranged alternately at a predetermined pitch. It is preferable that the height difference between the irregularities of the periodic structure 20 (the height from the bottom of the recess 22 to the top of the convex part 23) is 50 nm or more and 10 μm or less. Further, it is preferable that the periodic pitch of the periodic structure 20 is 10 μm or less. FIG. 3(a) shows an enlarged view of the periodic structure 20, and FIG. 3(b) shows a cross-sectional profile. In this way, the periodic structure 20 is a grating-like uneven periodic structure 20 in which the apex of the convex portion becomes a non-flat surface and the height changes continuously.
周期構造２０は、加工閾値近傍の照射強度で直線偏光のレーザを照射し、その照射部分をオーバラップさせながら走査して、自己組織的に形成している。具体的には、図６に示すフェムト秒レーザ表面加工装置を使用する。レーザ発生器３１（フェムト秒レーザ発生器）で発生したレーザ（例えば、パルス幅：９００ｆｓ、中心波長１０３０ｎｍ、繰り返し周波数：１～１０００ｋＨｚ、パルスエネルギー：０．２５～４００μＪ／ｐｕｌｓｅ）は、ミラー３２により加工材料Ｗに向けて折り返され、メカニカルシャッタ３３に導かれる。レーザ照射時はメカニカルシャッタ３３を開放し、レーザ照射強度は１／２波長板３４と偏光ビームスプリッタ３６によって調整可能とし、１／２波長版３５によって偏光方向を調整し、集光レンズ（焦点距離：１５０ｍｍ）３７によって、ＸＹθステージ３９上の加工材料Ｗ表面に集光照射する。なお、フェムト秒レーザはフェムト秒（１０００兆分の１秒）オーダーという極端に短い時間単位の中にエネルギーを圧縮した光源である。 The periodic structure 20 is formed in a self-organized manner by irradiating linearly polarized laser with an irradiation intensity near the processing threshold and scanning the irradiated portions while overlapping each other. Specifically, a femtosecond laser surface processing apparatus shown in FIG. 6 is used. A laser (for example, pulse width: 900 fs, center wavelength 1030 nm, repetition frequency: 1 to 1000 kHz, pulse energy: 0.25 to 400 μJ/pulse) generated by the laser generator 31 (femtosecond laser generator) is transmitted by the mirror 32. It is folded back toward the workpiece W and guided to the mechanical shutter 33. During laser irradiation, the mechanical shutter 33 is opened, the laser irradiation intensity can be adjusted by the 1/2 wavelength plate 34 and the polarizing beam splitter 36, the polarization direction is adjusted by the 1/2 wavelength plate 35, and the focusing lens (focal length :150mm) 37, the surface of the workpiece W on the XYθ stage 39 is irradiated with condensed light. Note that a femtosecond laser is a light source that compresses energy into an extremely short time unit on the order of a femtosecond (1/1000 trillionth of a second).
ところで、固体表面に液滴が接触すると、接触角が形成される。そして、液体Ｓの濡れ性は、以下のWenzelの式（数１）で表される。ここで、θｗは粗い面での接触角を示し、θｅは同じ材質で平坦面（平滑面）での接触角を示す。ｒは表面積倍率（平面に対する粗面の面積比）を示す。
平坦面（平滑面）において、θｅ＜９０°であれば、粗い面ではθw＜θｅとなる。すなわち、表面積倍率ｒが大きいほど油の接触角が低減する。このため、表面粗さの導入により潤滑油の濡れ性向上が可能となる。 If θe<90° on a flat surface (smooth surface), θw<θe on a rough surface. That is, the contact angle of oil decreases as the surface area magnification r increases. Therefore, the wettability of lubricating oil can be improved by introducing surface roughness.
本発明のスラストころ軸受によれば、グレーティング状凹凸の周期構造２０を設けたことによって、周期構造２０の潤滑油保持や摩耗粉トラップ効果により差動すべりに起因する摩擦が抑制される。さらにグリース潤滑下においては、周期構造２０のグリース保持や摩耗粉トラップ効果に加えて、油分に対して高い濡れ性を示す周期構造２０が基油分離を促進することで増ちょう剤が高濃度化され、増ちょう剤由来の保護膜形成が促進されることで差動すべりに起因する摩耗が抑制される。 According to the thrust roller bearing of the present invention, by providing the periodic structure 20 having grating-like irregularities, friction caused by differential sliding is suppressed by the lubricating oil retention and wear powder trapping effects of the periodic structure 20. Furthermore, under grease lubrication, in addition to the grease retention and wear debris trapping effects of the periodic structure 20, the periodic structure 20, which exhibits high wettability to oil, promotes base oil separation, resulting in a high concentration of thickener. This promotes the formation of a protective film derived from the thickener, thereby suppressing wear caused by differential slip.
このため、本発明では、差動すべりに起因する摩擦・摩耗の低減を図ることができ、しかも、良好な油膜形成を図ることができ、摺動部の摩擦低減と同時に潤滑油の使用量削減が可能なスラストころ軸受を提供できる。しかも、本発明に係るスラストころ軸受として、従来のように、ころ１３にクラウニング６を設けたり、軌道輪１１，１２に膨出部７，８を設ける必要がなくなる。これらを形成するための加工を行う必要がなく、生産性に劣ったり、コスト高となったりすることがない。 Therefore, in the present invention, it is possible to reduce the friction and wear caused by differential sliding, and also to form a good oil film, thereby reducing the amount of lubricating oil used at the same time as reducing the friction of the sliding parts. We can provide thrust roller bearings that are capable of Furthermore, the thrust roller bearing according to the present invention eliminates the need to provide the crowning 6 on the roller 13 or the bulges 7 and 8 on the bearing rings 11 and 12 as in the conventional case. There is no need to perform processing to form these, and there is no problem of poor productivity or high cost.
また、前記実施形態では、両軌道輪１１、１２の内面の外周側と内周側とに周期構造２０を設けているが、いずれか一方の軌道輪１１（１２）のみに設けても、外周側と内周側とのいずれか一方のみであってもよい。すなわち、いずれか一方の軌道輪１１（１２）のみに設ける場合、外周側と内周側と両方に周期構造２０を設けても、外周側にのみ設けたり、内周側にのみに設けたりでき、両軌道輪１１、１２も設ける場合、実施形態のように、外周側と内周側と両方に周期構造２０を設けても、外周側にのみ設けたり、内周側にのみに設けたりできる。 Further, in the above embodiment, the periodic structure 20 is provided on the outer circumferential side and the inner circumferential side of the inner surfaces of both the bearing rings 11 and 12, but even if it is provided only on one of the bearing rings 11 (12), It may be only one of the side and the inner peripheral side. That is, when provided only on one of the bearing rings 11 (12), even if the periodic structure 20 is provided on both the outer and inner circumferential sides, it cannot be provided only on the outer circumferential side or only on the inner circumferential side. , when both bearing rings 11 and 12 are also provided, even if the periodic structure 20 is provided on both the outer circumferential side and the inner circumferential side as in the embodiment, it can be provided only on the outer circumferential side or only on the inner circumferential side. .
未加工部２１を設けないもの、すなわち、外周側の周期構造２０Ａと内周側周期構造２０Ｂとの間にも周期構造２０を設けるものであってもよい。 The unprocessed portion 21 may not be provided, that is, the periodic structure 20 may also be provided between the outer periodic structure 20A and the inner periodic structure 20B.
これらのように、いずれか一方の軌道輪１１（１２）のみに設けても、外周側と内周側とのいずれか一方のみに設けた構成であっても、未加工部２１を設けないもの等であっても、周期構造２０を設けたことに起因する作用効果を発揮することができる。 Like these, even if it is provided only on one of the bearing rings 11 (12) or only on either the outer circumferential side or the inner circumferential side, the unprocessed part 21 is not provided. etc., the effects resulting from the provision of the periodic structure 20 can be exhibited.
また、周期構造２０を、接触通過領域Ｒ外まで周期構造を設けることによって、周期構造の油分に対する高い濡れ性によって、ころ１３の接触通過領域Ｒ外に排出された潤滑油やグリースの基油成分が、ころ１３の接触通過領域内に再流入することで枯渇潤滑下での摩擦・摩耗を抑制することができる。 In addition, by providing the periodic structure 20 to the outside of the contact passage area R, the base oil components of lubricating oil and grease discharged outside the contact passage area R of the rollers 13 due to the high wettability of the periodic structure to oil. However, by re-flowing into the contact passage area of the rollers 13, friction and wear under depleted lubrication can be suppressed.
接触通過領域Ｒの中心線Ｐ上は差動すべりが生じない。そこで、接触通過領域Ｒの中心線Ｐ上に周期構造２０を形成しないことで、弾性流体潤滑油膜の形成を阻害せず、良好な油膜形成と差動すべりに起因する摩擦抑制を両立することができる。 No differential slip occurs on the center line P of the contact passing region R. Therefore, by not forming the periodic structure 20 on the center line P of the contact passing region R, it is possible to achieve both good oil film formation and friction suppression due to differential slip without inhibiting the formation of the elastohydrodynamic lubricating oil film. can.
周期構造２０が、軌道輪１１（１２）の円周方向に沿って配向しているのが好ましい。このように構成することによって、ころ１３の接触通過領域Ｒ外に潤滑油やグリースが排出されにくく、周期構造２０に沿って保持されるため、潤滑油やグリースの担持性が向上し、さらには、摩耗粉のトラップ効果も向上する。 It is preferable that the periodic structure 20 is oriented along the circumferential direction of the bearing ring 11 (12). With this configuration, the lubricating oil and grease are not easily discharged outside the contact passage area R of the rollers 13 and are retained along the periodic structure 20, so that the lubricating oil and grease can be carried better. , the effect of trapping wear particles is also improved.
周期構造２０の凹凸が５０ｎｍ以上１０μｍ以下かつ周期ピッチが１０μｍ以下であるのが好ましい。このように構成することによって、油分の保持性、移動性を向上することができる。すなわち、周期構造２０の凹凸が５０ｎｍ未満では十分な量の油分やグリースを担持できず、凹凸および周期ピッチが１０μｍを超えると油分やグリースが周期構造の凹凸から流出するおそれがある。 It is preferable that the periodic structure 20 has irregularities of 50 nm or more and 10 μm or less and a periodic pitch of 10 μm or less. With this configuration, oil retention and mobility can be improved. That is, if the irregularities of the periodic structure 20 are less than 50 nm, a sufficient amount of oil or grease cannot be supported, and if the irregularities and the periodic pitch exceed 10 μm, oil or grease may flow out from the irregularities of the periodic structure.
周期構造２０は、凸部頂点が非平坦面となって連続的に高さが変化するのが好ましい。このように構成することによって、開口部が広くなり、潤滑油やグリースを効率的に取り込むことができる。 It is preferable that the periodic structure 20 has a convex apex that is a non-flat surface so that the height changes continuously. With this configuration, the opening becomes wide and lubricating oil and grease can be taken in efficiently.
ところで、前記実施形態では、軌道輪１１（１２）に周期構造を設けたものであったが、図５（ａ）（ｂ）に示すように、ころ１３側に周期構造２０を設けてもよい。この場合の周期構造２０は、ころ１３の円周方向に沿って配向している。 By the way, in the embodiment described above, the periodic structure was provided on the bearing ring 11 (12), but as shown in FIGS. 5(a) and 5(b), the periodic structure 20 may be provided on the roller 13 side. . The periodic structure 20 in this case is oriented along the circumferential direction of the roller 13.
図５（ａ）では、軸方向両端部側に周期構造２０（２０Ｃ）（２０Ｄ）を設けている。すなわち、ころは、径方向に沿った状態で放射状に配設されるものであるので、一方の周期構造２０Ｃ（２０Ｄ）が外径側に配設され、他方の周期構造２０Ｄ（２０Ｃ）が内径側に配設される。この場合、周期構造２０Ｃ、２０Ｄ間の周期構造が設けられていない未加工部２１Ａの範囲（軸方向長さＬ１）としては、ころ１３の軸方向全長の１／３程度としている。また、各周期構造２０Ｃ、２０Ｄの軸方向長さＬ２、Ｌ３としては、Ｌ２＝Ｌ３としている。なお、Ｌ２＞Ｌ３であっても、Ｌ２＜Ｌ３であってもよい。また、図５（ｂ）では、ころ１３の軸方向全長に周期構造２０を設けている。 In FIG. 5A, periodic structures 20 (20C) (20D) are provided at both ends in the axial direction. That is, since the rollers are arranged radially along the radial direction, one periodic structure 20C (20D) is arranged on the outer diameter side, and the other periodic structure 20D (20C) is arranged on the inner diameter side. placed on the side. In this case, the range (axial length L1) of the unprocessed portion 21A in which the periodic structure is not provided between the periodic structures 20C and 20D is approximately ⅓ of the total axial length of the roller 13. Further, the axial lengths L2 and L3 of the periodic structures 20C and 20D are set to L2=L3. Note that L2>L3 or L2<L3 may be satisfied. Further, in FIG. 5(b), a periodic structure 20 is provided along the entire length of the roller 13 in the axial direction.
このようにころ１３側に周期構造２０を設けても、グレーティング状凹凸の周期構造２０を設けたことに起因する作用効果を発揮することができる。 Even if the periodic structure 20 is provided on the roller 13 side in this manner, the effects resulting from the provision of the periodic structure 20 having grating-like irregularities can be exhibited.
本発明は前記実施形態に限定されることなく種々の変形が可能であって、例えば、ころ１３側に周期構造２０を設ける場合、ころ１３側のみに設けても、ころ１３側および軌道輪１１（１２）側の両方に設けてもよい。また、ころ１３側に設ける場合、いずれか一方の周期構造２０Ｃ（２０Ｄ）のみであってもよい。また、ころ１３として、実施形態では、クラウニングを設けないものあったが、クラウニングを設けたものであってもよい。クラウニングを設けた場合であっても、ころ１３の外周面と、軌道輪１１（１２）におけるころの接触通過領域Ｒとの少なくともいずれか一方に周期構造２０を設けることになる。 The present invention is not limited to the above embodiments and can be modified in various ways. For example, when the periodic structure 20 is provided on the roller 13 side, even if it is provided only on the roller 13 side, the periodic structure 20 may be provided on the roller 13 side and the bearing ring 11. (12) may be provided on both sides. Further, when provided on the roller 13 side, only one of the periodic structures 20C (20D) may be provided. Further, although the roller 13 in the embodiment is not provided with a crowning, it may be provided with a crowning. Even when crowning is provided, the periodic structure 20 is provided on at least one of the outer circumferential surface of the roller 13 and the contact passage area R of the roller in the bearing ring 11 (12).
図２に示すグレーティング状凹凸の周期構造では、軌道輪１１（１２）の円周方向に沿って配向しているが、これに限るものではなく、軌道輪１１（１２）の径方向に沿って配向していてもよく、さらには、径方向に沿って所定角度（任意の角度）で配向していてもよい。また、外周側の周期構造２０Ａと内周側の周期構造２０Ｂを設ける場合、周期構造２０Ａと周期構造２０Ｂとの配向方向が同じであっても相違させてもよい。 In the periodic structure of grating-like unevenness shown in FIG. 2, the orientation is along the circumferential direction of the bearing ring 11 (12), but the orientation is not limited to this, and the orientation is along the radial direction of the bearing ring 11 (12). It may be oriented, and furthermore, it may be oriented at a predetermined angle (any angle) along the radial direction. Further, when providing the periodic structure 20A on the outer circumferential side and the periodic structure 20B on the inner circumferential side, the orientation directions of the periodic structure 20A and the periodic structure 20B may be the same or different.
外周側に設けられた周期構造２０（２０Ａ）は、外周側の接触通過領域Ｒよりも外径側にはみ出し、内周側に設けられた周期構造２０（２０Ｂ）は、内周側の接触通過領域Ｒよりも内径側にはみ出していたが、はみ出さないようにしてもよい。はみ出すようにする場合、外周側のみはみ出すようにしたり、内周側のみはみ出したりするようにしてもよい。なお、はみ出さないようにする場合、接触通過領域Ｒの境界線（外周縁又は内周縁）上であっても、境界線より接触通過領域Ｒ内になっていてもよい。 The periodic structure 20 (20A) provided on the outer circumference side protrudes to the outer diameter side beyond the contact passage area R on the outer circumference side, and the periodic structure 20 (20B) provided on the inner circumference side protrudes beyond the contact passage area R on the inner circumference side. Although it protruded to the inner diameter side from the region R, it may be arranged not to protrude. When it protrudes, it may protrude only on the outer periphery side or may protrude only on the inner periphery side. In addition, in order to prevent it from protruding, it may be on the boundary line (outer periphery or inner periphery) of the contact passage area R, or it may be within the contact passage area R from the boundary line.
周期構造２０を形成する際に、前記実施形態では、パルスレーザであるフェムト秒レーザを用いたが、フェムト秒レーザ以外のピコ秒レーザやナノ秒レーザといったパルスレーザを使用することもできる。 When forming the periodic structure 20, in the embodiment, a femtosecond laser, which is a pulsed laser, is used, but a pulsed laser other than a femtosecond laser, such as a picosecond laser or a nanosecond laser, can also be used.
環境保護の観点から、摺動部の摩擦低減と同時に潤滑油の使用量削減が重要な課題となっている。そのため、自動車や産業機器では潤滑油供給を必要最小量とした低摩擦運転が望まれている。また、潤滑油の消費が少ないグリース潤滑の適用拡大も検討されている。各種機器の摺動部に数多く使用されているスラスト針状ころ軸受では、周速差に起因する差動すべりが生じ、潤滑油が不足すると比較的大きなトルクと摩耗が発生するため、枯渇潤滑下での摩擦・摩耗特性の向上が求められている。一方、超短パルスレーザにより形成されるグレーティング状の周期構造２０は、油分に対し高い濡れ性を示し、潤滑油の保持性を向上することができる。また、グリース潤滑下では、基油分離が促進され、高濃度化した増ちょう剤による保護膜が形成されることから、スラストころ軸受やスラスト針状ころ軸受の枯渇潤滑下での摩擦・摩耗特性の向上が期待できる。そこで、スラスト針状ころ軸受のレース面（軌道輪の軌道面：摺動面）にグレーティング状の周期構造を形成し、摩擦・摩耗に及ぼす影響を油膜切れが生じやすい低速条件下において検証した。 From the perspective of environmental protection, reducing friction in sliding parts and reducing the amount of lubricant used are important issues. Therefore, in automobiles and industrial equipment, low-friction operation with the minimum amount of lubricant required is desired. Additionally, expansion of the application of grease lubrication, which consumes less lubricating oil, is also being considered. In thrust needle roller bearings, which are used in many sliding parts of various devices, differential slip occurs due to differences in circumferential speed, and a lack of lubricating oil generates relatively large torque and wear. Improvements in friction and wear characteristics are required. On the other hand, the grating-like periodic structure 20 formed by an ultrashort pulse laser exhibits high wettability to oil and can improve lubricant retention. In addition, under grease lubrication, base oil separation is promoted and a protective film formed by highly concentrated thickener is formed, which improves the friction and wear characteristics of thrust roller bearings and thrust needle roller bearings under depleted lubrication. can be expected to improve. Therefore, a grating-like periodic structure was formed on the race surface (sliding surface of the bearing ring) of a thrust needle roller bearing, and its effect on friction and wear was examined under low-speed conditions where oil film is likely to run out.
スラストころ軸受５０として、スラスト針状ころ軸受(ＢＡ２０３５)を用い、図２に示すように、両軌道輪１１，１２の内面１１ｂ、１２ｂに外周側と内周側とのグレーティング状の周期構造(ピッチ約９００ｎｍ、深さ約２５０ｎｍ)２０（２０Ａ，２０Ｂ）を形成し、回転トルク測定を行った。周期構造２０の配向方向は円周方向とした。ニードル（ころ１３）のピッチ径を含む領域(幅２．９ｍｍ)は未加工とし、大きな差動すべりが生じるニードル（ころ１３）の外端面側１ｍｍと内端面側０.５ｍｍは周期構造上を通過する配置とした。比較のため、周期構造２０を形成しない未加工レース（未加工軌道輪）でも回転トルク測定を実施した。 A thrust needle roller bearing (BA2035) is used as the thrust roller bearing 50, and as shown in FIG. 20 (20A, 20B) with a pitch of about 900 nm and a depth of about 250 nm), and the rotational torque was measured. The periodic structure 20 was oriented in the circumferential direction. The region (width 2.9 mm) including the pitch diameter of the needle (roller 13) is left unprocessed, and 1 mm on the outer end surface side and 0.5 mm on the inner end surface side of the needle (roller 13), where large differential slip occurs, are processed on the periodic structure. It was arranged so that it would pass through. For comparison, rotational torque was also measured on an unprocessed race (unprocessed bearing ring) in which the periodic structure 20 was not formed.
試験条件は荷重を４０Ｎとし、潤滑剤はＰＡＯ６(ポリアルファオレフィン)、Ｕ３－Ｐ（脂肪族ウレアグリース）(増ちょう剤量：１３％、基油：ＰＡＯ６、ちょう度：２８２)の２種類とした。この場合、図８に示すような試験機５１を用いた。この試験機５１は、軸受５０を受ける下型５２と、軸受５０を押圧する上型５３と、上型５３から突出される軸部５４とを備える。この場合、軸部５４に矢印Ｘ方向の荷重を付加して、その状態で図示省略の回転駆動機構にて、その軸部５４を中心に矢印Ｙ方向に回転させる。 The test conditions were a load of 40N, and two types of lubricants: PAO6 (polyalphaolefin) and U3-P (aliphatic urea grease) (thickener amount: 13%, base oil: PAO6, consistency: 282). did. In this case, a testing machine 51 as shown in FIG. 8 was used. This testing machine 51 includes a lower mold 52 that receives the bearing 50, an upper mold 53 that presses the bearing 50, and a shaft portion 54 that projects from the upper mold 53. In this case, a load is applied to the shaft portion 54 in the direction of the arrow X, and in this state, the shaft portion 54 is rotated in the direction of the arrow Y using a rotation drive mechanism (not shown).
試験前に潤滑剤を上下レース（軌道輪１１、１２の軌道面）にそれぞれ約１５ｍｇずつ付着させ、無負荷にて軸受を回転させて潤滑剤を均等化した。次に、余剰な潤滑剤を除去するため、保持器付さニードルを取り出しエタノールにて超音波洗浄を行った後、なじみを実施した。なじみとして、１０ｍｉｎ毎に各５段階の増速・減速運転(ピッチ径位置での回転速度: ３４.１ｍｍ／ｓ→１８２．６ｍｍ／ｓ→３４．１ｍｍ／ｓ)に続いて、一定速度(５０．５ｍｍ／ｓ)で５時間の運転を行った。 Before the test, approximately 15 mg of lubricant was applied to each of the upper and lower races (the raceway surfaces of raceways 11 and 12), and the bearing was rotated under no load to equalize the lubricant. Next, in order to remove excess lubricant, the needle with the retainer was taken out and subjected to ultrasonic cleaning with ethanol, followed by running-in. For acclimatization, the speed is increased and decelerated in 5 steps every 10 min (rotational speed at pitch diameter position: 34.1 mm/s → 182.6 mm/s → 34.1 mm/s), followed by constant speed (50 mm/s). .5 mm/s) for 5 hours.
なじみを終了した軸受から保持器付きニードルを取り出してエタノールにて超音波洗浄し、一定速度(５０．５ｍｍ／ｓ)で１回目の回転トルク測定を１時間行った。同じ手順で超音波洗浄と回転トルク測定を４回繰り返した。トルク測定回数が増えるほど保持器付きニードルに付著した潤滑剤が除去されるため、厳しい枯渇状態での評価となる。測定で得られた回転トルクをニードルのピッチ半径と荷重で除して摩擦係数を算出した. The needle with retainer was taken out from the bearing that had finished breaking in, and it was ultrasonically cleaned with ethanol, and the first rotational torque measurement was performed at a constant speed (50.5 mm/s) for 1 hour. Ultrasonic cleaning and rotational torque measurement were repeated four times using the same procedure. As the number of torque measurements increases, the lubricant attached to the retainer-equipped needle is removed, resulting in evaluation under severe depletion conditions. The coefficient of friction was calculated by dividing the rotational torque obtained in the measurement by the pitch radius of the needle and the load.
潤滑剤としてＰＡＯ６(ポリアルファオレフィン)を用いた場合
一定速度(５０．５ｍｍ／ｓ)で５時間のなじみ運転中の摩擦係数を図９に示す。周期構造の有無にかかわらず、なじみ開始９０分後に摩擦係数が最大となり、その後５時間まで摩擦係数の低下が継続した。周期構造形成品のなじみ運転中の最大摩擦係数は未加工品より大きくなったが、５時間後の摩擦係数は未加工品に対し半減した。なじみ終了後に測定した１回目～４回目までの摩擦係数を図１０に示す。測定回数の増加にともない潤滑剤が枯渇するが、周期構造形成品の摩擦係数は全潤滑状態で未加工品より低下した。未加工品は４回目の測定で急激な摩擦係数の上昇が発生したが、周期構造形成品では安定した摩擦係数が維持された。低速条件下での主要な摩擦要因として、ころ１３とレース（軌道輪１１，１２）とのすべり摩擦、保持器１４とレース（軌道輪１１，１２）のすべり摩擦などがあるが、周期構造２０の潤滑油保持や摩擦粉トラップ効果により摩擦の増加が抑制されたと考えられる。一方、未加工品では潤滑油の枯渇により摩擦が増大し、逃げ場のない摩耗粉が大きく成長、移着することで急激な摩擦係数の上昇が発生したと考えられる。
When PAO6 (polyalphaolefin) is used as a lubricant, the friction coefficient during a 5-hour break-in operation at a constant speed (50.5 mm/s) is shown in FIG. Regardless of the presence or absence of a periodic structure, the friction coefficient reached its maximum 90 minutes after the start of break-in, and the friction coefficient continued to decrease for up to 5 hours thereafter. The maximum friction coefficient of the periodic structure formed product during running-in was greater than that of the unprocessed product, but the friction coefficient after 5 hours was half that of the unprocessed product. Figure 10 shows the friction coefficients measured from the first to fourth times after the break-in. As the number of measurements increases, the lubricant becomes depleted, but the friction coefficient of the periodic structure-formed product was lower than that of the unprocessed product under full lubrication. For the unprocessed product, a sudden increase in the friction coefficient occurred at the fourth measurement, but for the periodic structure formed product, a stable friction coefficient was maintained. The main friction factors under low speed conditions include sliding friction between the rollers 13 and races (bearing rings 11, 12), sliding friction between the retainer 14 and races (bearing rings 11, 12), etc. It is thought that the increase in friction was suppressed by the retention of lubricating oil and the effect of trapping friction particles. On the other hand, in the unprocessed product, the friction increases due to the depletion of lubricating oil, and it is thought that the wear particles that have no place to escape grow and transfer, causing a sudden increase in the coefficient of friction.
大きな差動すべりが生じる外端面から１１５０μｍのニードル表面（ころ表面）の試験後の様子を図１１に示す。未加工レース（周期構造未加工品）を用いたニードル表面（ころ表面）は転がり方向に明瞭な傷が認められたが、周期構造が形成された加工品を用いたニードル表面（ころ表面）では、ほとんど傷の発生が認められなかった。 FIG. 11 shows the state of the needle surface (roller surface) 1150 μm from the outer end surface, where a large differential slip occurs, after the test. Clear scratches were observed in the rolling direction on the needle surface (roller surface) made of unprocessed race (product without periodic structure), but on the needle surface (roller surface) made with processed product with periodic structure formed. , almost no scratches were observed.
また、差動すべりが生じない 中央部付近のニードル表面の試験後の様子を図１２に示す。中央部付近では差動すべりが生じないため，未加工レース（周期構造未加工品）を用いたニードル表面（ころ表面），周期構造が形成された加工品を用いたニードル表面（ころ表面）ともにほとんど傷の発生が認められなかった。 Figure 12 shows the state of the needle surface near the center, where differential slip does not occur, after the test. Since differential slip does not occur near the center, both the needle surface (roller surface) using an unprocessed race (periodically structured product) and the needle surface (roller surface) using a processed product with a periodic structure are Almost no scratches were observed.
潤滑剤としてＵ３－Ｐ（脂肪族ウレアグリース）を用いた場合
一定速度（５０．５ｍｍ／ｓ)で５時間のなじみ運転中の摩擦係数を図１３に示す。周期構造の有無にかかわらず、ＰＡＯ６潤滑時より摩擦係数が低下した。１００ｍｍ／ｓ以下の低速域では、増ちょう剤由来の付着物により潤滑膜厚が増加し、これが摩擦係数低減の要因と考えられる。未加工品は５時間のなじみ期間中に９％の摩擦増加が見られた。一方、周期構造形成品は、ほぼー定の摩擦係数を維持し、５時間の平均摩擦係数は未加工品に対して１６％低減した。周期構造の基油分離作用で増ちょう剤が高濃度化され、増ちょう剤由来の保護膜形成が促進されたことで摩擦が低減したと考えられる。未加工品では保護膜の剥離速度が形成速度を上回るため、摩擦が増加したと考えられる。なじみ終了後に測定した１回目から４回目までの摩擦係数を図１４に示す。
When U3-P (aliphatic urea grease) was used as the lubricant, the friction coefficient during 5 hours of break-in operation at a constant speed (50.5 mm/s) is shown in FIG. Regardless of the presence or absence of a periodic structure, the coefficient of friction was lower than when using PAO6 lubrication. In a low speed range of 100 mm/s or less, the lubricant film thickness increases due to deposits derived from the thickener, and this is considered to be a factor in reducing the friction coefficient. The raw product showed a 9% increase in friction during the 5 hour break-in period. On the other hand, the periodic structure formed product maintained a nearly constant friction coefficient, and the average friction coefficient for 5 hours was reduced by 16% compared to the unprocessed product. It is thought that friction was reduced by increasing the concentration of the thickener due to the base oil separation effect of the periodic structure and promoting the formation of a protective film derived from the thickener. In the unprocessed product, the rate of peeling of the protective film exceeded the rate of formation, which is thought to be the reason for the increase in friction. FIG. 14 shows the friction coefficients measured from the first to fourth times after the break-in was completed.
ＰＡ０６潤滑時と同様、周期構造形成品の摩擦係数は全潤滑状態で、未加工品より低下した。また、未加工品は4回目の測定で急激な摩擦係数の上昇が発生したが、周期構造形成品では安定した摩擦係数が維持された。グリース潤滑時では、周期構造のグリース保持や摩耗粉トラップ効果に加えて、油分に対して高い濡れ性を示す周期構造が、増ちょう剤由来の保護膜形成を促進することや転走面外に排出されたグリースが基油分離され、転走面（摺動面）周縁部から基油が再流入することで、枯渇潤滑下での摩擦係数上昇が抑制されたと考えられる。 As with the case of PA06 lubrication, the friction coefficient of the periodic structure-formed product was lower than that of the unprocessed product in the fully lubricated state. In addition, although the friction coefficient of the unprocessed product suddenly increased at the fourth measurement, the friction coefficient of the periodic structure-formed product remained stable. During grease lubrication, in addition to the effect of the periodic structure in retaining grease and trapping wear particles, the periodic structure, which exhibits high wettability to oil, promotes the formation of a protective film derived from the thickener and prevents the formation of particles outside the rolling contact surface. It is thought that the base oil was separated from the discharged grease and the base oil re-inflowed from the peripheral edge of the raceway surface (sliding surface), thereby suppressing the increase in the coefficient of friction under depleted lubrication.
大きな差動すべりが生じる外端面から１１５０μｍのニードル表面（ころ表面）の試験後の様子を図１５に示す。未加工レース（周期構造未加工品）を用いたニードル表面（ころ表面）は転がり方向に明瞭な傷が認められたが、周期構造が形成された加工品を用いたニードル表面（ころ表面）では、ほとんど傷の発生が認められなかった。 FIG. 15 shows the state of the needle surface (roller surface) 1150 μm from the outer end face after the test, where a large differential slip occurs. Clear scratches were observed in the rolling direction on the needle surface (roller surface) made of unprocessed race (product without periodic structure), but on the needle surface (roller surface) made with processed product with periodic structure formed. , almost no scratches were observed.
また、差動すべりが生じない 中央部付近のニードル表面の試験後の様子を図１６に示す。中央部付近では差動すべりが生じないため、未加工レース（周期構造未加工品）を用いたニードル表面（ころ表面）、周期構造が形成された加工品を用いたニードル表面（ころ表面）ともにほとんど傷の発生が認められなかった。 Figure 16 shows the state of the needle surface near the center, where differential slip does not occur, after the test. Since differential slip does not occur near the center, both the needle surface (roller surface) using an unprocessed race (periodic structure unprocessed product) and the needle surface (roller surface) using a processed product with a periodic structure are formed. Almost no scratches were observed.
このため、スラストころ軸受（スラスト針状ころ軸受）の摩擦・摩耗に及ぼす周期構造の影響について検証した結果、以下の結論を得た。
（１）周期構造が形成された軌道輪は、潤沢潤滑下での摩擦低減効果が認められる。
（２）周期構造が形成された軌道輪は、枯渇潤滑下での焼き付き防止に有効である。
（３）周期構造が形成された軌道輪は、ニードル（ころ）の摩耗低下に有効である。
Therefore, as a result of examining the influence of the periodic structure on the friction and wear of thrust roller bearings (thrust needle roller bearings), we came to the following conclusions.
(1) A bearing ring with a periodic structure is recognized to have a friction reducing effect under abundant lubrication.
(2) A bearing ring with a periodic structure is effective in preventing seizure under depleted lubrication.
(3) A bearing ring with a periodic structure is effective in reducing wear on needles (rollers).
１１、１２ 軌道輪
１３ ころ
２０、２０Ａ、２０Ｂ、２０Ｃ、２０Ｄ 周期構造
２１ 未加工部
５０ 軸受
Ｒ 接触通過領域
11, 12 Bearing ring 13 Roller 20, 20A, 20B, 20C, 20D Periodic structure 21 Unprocessed part 50 Bearing R Contact passage area
Claims (4)
少なくともいずれか一方の軌道輪におけるころの接触通過領域と、ころの外周面との少なくともいずれか一方に、複数の微細溝で構成されるグレーティング状凹凸の周期構造を設けたものであり、前記グレーティング状凹凸の周期構造が軌道輪におけるころの接触通過領域の内周側および外周側に設けられ、外周側に設けられた周期構造は、接触通過領域の外周縁よりも外径側にはみ出し、内周側に設けられた周期構造は、接触通過領域の内周縁よりも内径側にはみ出し、接触通過領域の中心線上の差動すべりが生じない範囲は、前記グレーティング状凹凸の周期構造を有さない面としたことを特徴とするスラストころ軸受。 A pair of bearing rings facing each other in the axial direction, and a plurality of rollers arranged radially between the bearing rings in a radial direction , each of the pair of bearing rings having a center hole. A thrust roller bearing consisting of a ring-shaped flat plate body provided with rollers, the rollers being needle rollers or cylindrical rollers,
A periodic structure of grating-like unevenness composed of a plurality of fine grooves is provided on at least one of the contact passage area of the roller in at least one of the bearing rings and the outer circumferential surface of the roller. A periodic structure with irregularities in the shape of a groove is provided on the inner and outer circumferential sides of the contact passage area of the roller in the bearing ring, and the periodic structure provided on the outer circumference protrudes to the outer diameter side from the outer circumference of the contact passage area, and The periodic structure provided on the circumferential side protrudes radially inward from the inner peripheral edge of the contact passage area, and the range where differential slip does not occur on the center line of the contact passage area does not have the periodic structure of the grating-like unevenness. A thrust roller bearing characterized by a flat surface.
少なくともいずれか一方の軌道輪におけるころの接触通過領域と、ころの外周面との少なくともいずれか一方に、複数の微細溝で構成されるグレーティング状凹凸の周期構造を設けたものであり、前記グレーティング状凹凸の周期構造が軌道輪におけるころの接触通過領域の内周側および外周側に設けられ、外周側に設けられた周期構造は、接触通過領域の外周縁よりも外径側にはみ出し、内周側に設けられた周期構造は、接触通過領域の内周縁よりも内径側にはみ出し、接触通過領域の中心線上の差動すべりが生じない範囲は、前記グレーティング状凹凸の周期構造を有さない面とし、前記グレーティング状凹凸の周期構造が、前記軌道輪の円周方向に沿って配向していることを特徴とするスラストころ軸受。 A thrust roller bearing comprising a pair of bearing rings facing each other in the axial direction and a plurality of rollers arranged radially along the radial direction between the bearing rings,
A periodic structure of grating-like unevenness composed of a plurality of fine grooves is provided on at least one of the contact passage area of the roller in at least one of the bearing rings and the outer circumferential surface of the roller. A periodic structure with irregularities in the shape of a groove is provided on the inner and outer circumferential sides of the contact passage area of the roller in the bearing ring, and the periodic structure provided on the outer circumference protrudes to the outer diameter side from the outer circumference of the contact passage area, and The periodic structure provided on the circumferential side protrudes radially inward from the inner peripheral edge of the contact passage area, and the range where differential slip does not occur on the center line of the contact passage area does not have the periodic structure of the grating-like unevenness. A thrust roller bearing characterized in that the periodic structure of the grating-like unevenness is oriented along the circumferential direction of the bearing ring.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2009108901A (en) | 2007-10-29 | 2009-05-21 | Canon Machinery Inc | Rolling slide face structure |
| JP2018194149A (en) | 2017-05-22 | 2018-12-06 | キヤノンマシナリー株式会社 | Slide surface structure |
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| JP2008128398A (en) * | 2006-11-22 | 2008-06-05 | Ntn Corp | Manufacturing method of bearing ring for thrust bearing, manufacturing device of thrust bearing, bearing ring for thrust bearing and thrust bearing |
| JP2009108963A (en) * | 2007-10-31 | 2009-05-21 | Ntn Corp | Rolling member |
| JP2015175497A (en) * | 2014-03-18 | 2015-10-05 | Ntn株式会社 | thrust needle bearing |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2009108901A (en) | 2007-10-29 | 2009-05-21 | Canon Machinery Inc | Rolling slide face structure |
| JP2018194149A (en) | 2017-05-22 | 2018-12-06 | キヤノンマシナリー株式会社 | Slide surface structure |
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