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问
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你得先了解下什么叫动压滑动轴承?
油槽通常位于轴承的非承载区,即不直接承受主要轴向载荷的地方。这是因为在非承载区,润滑油可以更容易地被引入到楔形空间中,并且随着轴的旋转而被带入到载荷区域。油槽应该具有一定的长度和宽度,以确保有足够的润滑油流量进入楔形空间。常见的油槽形状包括矩形、扇形或其他适合特定应用的形式。对于某些特殊情况下,如高转速或重载条件下,可能会采用多个较小的油槽来分散润滑点。
然而你谈的是止推轴承,静压止推滑动轴承见下图。
静压轴承通过油泵将润滑油以恒定压力输送到轴承的油腔中。这种压力油膜在轴承和轴之间形成,使得轴悬浮在油膜上,从而避免了直接接触和摩擦。
从楼主的描述中感觉楼主是不是把径向轴承给当成止推轴承了,又或者把静压动压搞混了。
因为动压润滑它必须有一个油在非承载区,在随着轴的旋转而被带入到承载区的动态过程,所以叫动压,而不同于静压轴承的油一开始就在承载区形成油膜。但是止推轴承不同于径向轴承的地方在于,轴的整个载荷都完全加载到轴承的环面或端面上,根本不像径向轴承那样会出现非承载区和承载区。
那么问题来了,如何让止推滑动轴承出现非承载区和承载区呢。所以在动压止推滑动轴承的设计中,通常会采用一种称为“倾斜板”或“推力衬垫”的结构。每个推力衬垫都有一个可调节的角度,允许它随着轴的转动而适应最佳的位置以形成有效的楔形空间。推力衬垫不是完全固定的,而是可以轻微倾斜调整以适应最佳的工作位置。当轴旋转时,润滑油最初接触的是衬垫的一个边缘(可以视为相对的“非承载区”),然后随着轴的转动,润滑油被引入到更靠近轴的位置,即实际承载区域,在那里建立起有效的油膜支撑。
Lubrication & Materials
The hydrodynamic film forms with shaft rotation, so an appropriate fluid must always be present during operation to keep the bearing and rotor surfaces separated. If the fluid flow is lost or interrupted during operation, the bearing surface will come in contact with the shaft and be damaged. The fluid used in most hydrodynamic bearing applications is a mineral oil or synthetic lubricant. The bearing components are typically steel with a layer of a soft tin alloy called Babbitt, bonded to the bearing surface, which helps protect the shaft from damage. In vertical applications, the bearings are submerged in a pot of lubricant with cooling coils to remove the heat generated by shear of the lubricant in the oil films. For low speed horizontal machines, the lubricant may be supplied by rings or discs that spin with the shaft, dip into a sump and distribute lubricant through passages to the bearings. A tremendous amount of heat is generated by the films in higher speed units and external lubrication systems are required to provide sufficient flow and cooling capacity. Pump applications allow two unique options compared to other rotating machines. The relatively low speed makes it possible to use a self-contained bearing system in some applications instead of a more expensive external lubrication system. One dual bearing thrust/journal system, for example, consists of flange mounted casings that contain pivoted shoe thrusts and cylindrical journal bearings, a sump, a heat exchanger and an oil circulator. This option is ideal for remote locations where electricity or cooling media are limited. Another option in some applications is to design the pump to use the process fluid as the bearing lubricating media using suitable hydrodynamic bearings.
The key considerations in the design and operation of hydrodynamic bearings are film thickness and bearing temperature. The film thickness in industrial hydrodynamic bearing applications is on the order of a thousandth of an inch and governs the manufacturing requirements of the shaft, collar and bearing surfaces. A high degree of precision is required of the components to ensure successful operation and life. The criteria for load capacity in low speed applications is the minimum oil film thickness, which decreases with increasing load. In practice, load capacity is set to achieve an operating film thickness that is larger than the filter size so that the small particles that pass through the filter do not score and damage the bearing surface. Hydrodynamic films become thicker at higher surface speeds, which would allow higher loads, but friction also increases and temperature becomes the limiting factor. The mechanical and thermal integrity of the bearing materials and the thermal limitations of the lubricant determine the load capacity in high speed applications. In critical applications, the bearings are instrumented with temperature detectors to monitor the health and integrity of the bearing. Vibration characteristics are another key consideration in design and application of the journal bearings. The stiffness and damping properties of the journal bearings influence the critical speeds and vibration levels of the rotor. The journal bearing type, geometry, clearances and additional factors are design parameters evaluated to ensure that the dynamic response of the rotor satisfies appropriate specifications.
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