Lubrication - Junkatsu
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When two solid objects slide against each other while in contact, such as bearings, the friction and wear between the two surfaces must be minimized. If the friction parts of a machine do not have special measures to slide smoothly, they will burn out and stop working. Or, even if they do work, they will wear out quickly, which will affect the machine. If the friction is high, the loss of power to operate the machine will also be large. To prevent this, it is important to select the appropriate material for the friction parts of the machine, but it is also necessary to supply an appropriate lubricant to the friction surface. This is a technology that must be paid special attention to, especially in modern production factories with advanced automation. For this reason, many modern factories also place importance on lubrication management. Lubrication is not only used in parts where flat surfaces come into contact with each other, such as bearings, but is also recognized as having an important effect on tool life, improved finishing surface accuracy, and increased work efficiency in machining processes such as cutting, wire drawing, rolling, and pressing. [Hidetaro Nakayama] Lubrication conditionLubricants (usually oil) are used to reduce friction on the friction surfaces, and there are two main types of lubrication. (1) Fluid lubrication Fluid lubrication is when there is a certain thickness of lubricant between two surfaces (usually about 0.1 to 0.001 millimeters) and the frictional surfaces do not come into contact with each other. In this state, since the two surfaces are not in contact, there is no wear and no friction. Therefore, this is an ideal lubrication state. (2) Boundary lubrication When the viscosity of the oil is low and the relative sliding speed of the two surfaces is low, or when a large load is applied, the thickness of the lubricating film becomes small, and the oil film becomes several times thicker than the molecular film. This state is called boundary lubrication. In this state, the friction surfaces are partially in contact, and friction and wear become large, sometimes causing seizure. This state occurs on the meshing surfaces of gears or on friction surfaces that are subjected to a high load, so it is necessary to use an appropriate lubricant (extreme pressure additive) to prevent accidents. [Hidetaro Nakayama] Lubrication MethodGenerally, liquid lubricating oil and semi-solid grease are used as lubricants. It is necessary to consider the appropriate lubrication method by utilizing the characteristics of both. No matter how good the lubricant is, if the lubrication method is incorrect, its effectiveness will be lost. Oil lubrication has good fluidity, so when dust or dirt gets mixed in, it is easy to filter out, and it helps to release heat generated on the friction surface. Therefore, it is suitable for high-speed rotation and high-load bearings. In particular, forced lubrication, in which oil is pressurized from a nozzle and sprayed onto the required part, cannot be used with anything other than oil lubricants. For precision high-speed bearings such as machine tools, there is also a spray lubrication method in which oil is mixed with air and sprayed in a mist. The oil is useful for lubrication, and the air is useful for cooling. In forced lubrication, the oil is usually circulated and continuously supplied. Forced lubrication is used in most large machines. Grease lubrication does not flow out from the friction surfaces, so there is less dirt in the vicinity and it also helps to maintain airtightness, which is effective in preventing dust and other particles from entering. If the bearing housing is packed with grease, it can be used for long periods of time, which is convenient. The lubricant between the friction surfaces is not limited to oil. It can be a gas such as air or gas, or a solid such as graphite powder. [Hidetaro Nakayama] [Reference item] |Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend |
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軸受などのように、二つの固体が接触しながら互いに滑るとき、2面間の摩擦や摩耗をできるだけ少なくすること。機械の摩擦部分は、滑らかに滑るように特別の手段を施さないと、焼け付いて動かなくなる。あるいは動いても摩耗が激しく、機械に影響を与える。摩擦が大きいと、機械を動かす動力の損失も大きくなる。これを防ぐのには、機械の摩擦部分の材料を適切に選ぶことも重要であるが、摩擦面に適当な潤滑剤を供給することも必要である。とくに自動化の進んだ近代的生産工場では、注目しなければならない技術である。そのため近代的工場では、潤滑管理も重視しているところが多い。また潤滑は、軸受などの平面が接触する部分だけでなく、工作機械の切削作業、線引き、圧延、プレスなど機械加工などにおいても、工具の寿命、仕上げ面の精度の向上、作業能率増進などにとって重要な影響を及ぼすものとして、その意義が認められるようになった。 ［中山秀太郎］ 潤滑状態摩擦面の摩擦を少なくするために潤滑剤（通常は油）が使用されるが、この潤滑状態は大きく分けて二つある。 (1)流体潤滑 二つの面の間に潤滑剤がある程度厚く（普通0.1～0.001ミリメートル程度）存在し、摩擦面が互いに接触しない状態を流体潤滑という。この状態では、2面は接触していないので摩耗はおこらず、摩擦もない。したがって潤滑状態としては理想的である。 (2)境界潤滑 油の粘度が低く、また2面の相対的滑り速度が小さいとき、あるいは大きな荷重が加わったときなどでは、潤滑膜の厚さは小さくなり、油膜は分子膜の数倍程度となる。この状態を境界潤滑という。この状態では、摩擦面が部分的に接触し、摩擦、摩耗も大きくなり、ときには焼付きをおこすこともある。歯車のかみ合っている面、あるいは高荷重の加わる摩擦面などで、このような状態になるので、適切な潤滑剤（極圧添加剤）を使用し、事故が起こらないようにすることが必要である。 ［中山秀太郎］ 潤滑法潤滑剤としては一般には液状の潤滑油と半固体のグリースが使用される。この両者の特性を利用して適切な潤滑法を考える必要がある。潤滑剤の性質がいかによくても、潤滑法を誤れば、その効果は失われるからである。油による潤滑法では流動性がよいので、ちりやほこりが混入したときには、濾過(ろか)が容易であるし、摩擦面で発生する熱を逃がすのに役だつ。したがって高速回転、高荷重軸受などに適している。とくにノズルから圧力を加えた油を必要部分に噴出して供給するような強制潤滑法は、油の潤滑剤以外は使用できない。工作機械などの精密高速軸受には、油と空気とを混ぜ、霧状にしてかける噴霧潤滑法もある。油は潤滑に役だち、空気は冷却に役だつ。強制潤滑法では油は循環し、連続的に給油するのが普通である。大型機械ではほとんど強制潤滑法が採用されている。 グリース潤滑は、摩擦面から流れ出ないので、付近の汚れが少なく、また気密を保つのにも役だつので、ほこりなどが侵入するのを防止する効果もある。軸受箱にグリースを詰めておけば、長時間そのまま使用することができて便利である。摩擦面間に介在する潤滑剤は、油とは限らない。空気、ガスのような気体のときもあるし、黒鉛粉末のように固体のときもある。 ［中山秀太郎］ [参照項目] |出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例 |
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