High speed bearing structure and performance
First, the improvement of high-speed bearing structure design
Rolling bearings under high speed conditions
Due to the centrifugal force, the rolling body pressure generates a large contact stress to the bearing outer ring raceway; the slip between the rolling element and the inner ring occurs.
, resulting in bearing wear and heat, resulting in early bearing damage, in order to reduce the centrifugal force of the rolling elements and effective
To prevent slippage, Hanau et al. proposed preloading on the circumferential equidistant spacing of the ferrules, using hollow rollers.
The method is to reduce the impact of high-speed cylindrical roller bearings (hereinafter referred to as He B). Harris et al. improved the Han a u method
The radial preload is applied by the elliptical ring, and the roller still adopts the hollow structure. In the early 1970s, Coe, Scibbe, Parke: and Anderson et al. analyzed and estimated the electron beam welding hollow ball and the through hole ball bearing, and at 1.8 ~ Many experimental studies have been carried out within the range of 3 x 10"
Bowen et al. also performed hollow roller tests. These analyses and experimental results prove that the hollow rolling element and the elliptical outer ring structure are effective.
. In order to reduce the skewness of the roller during HCB operation, a roller structure with a convexity is generally used. Vertical block
Changing the edge to the inclined rib is another improvement in the design of the HcB structure, which not only reduces the contact and friction between the rib and the end face of the cylindrical roller, but also facilitates the formation of a lubricating oil film between the end face of the roller and the rib. Bearing (hereinafter referred to as HBB), the outer ring channel is replaced by an arched groove.
The circular groove can make the contact between the rolling element and the outer ring change from one point to two points, so that the contact stress is dispersed.
Second, the update of high-speed bearing materials
Gas turbine engines HcB and HBB often require high speed (above 10000:/min) and high temperature (200 to 250 °C).
. In order to adapt to such working conditions, the inner and outer rings of the aero-engine main shaft bearings and the rolling element materials are generally made of high-speed steel with good thermosetting properties.
. The United States and Japan mainly use aluminum M50 steel, while the United Kingdom uses tungsten.
T-l steel. In the past, most of the ball bearings in the United States were made of lAsI52100 steel, which has a maximum temperature of about 163 °C during continuous operation.
This is not enough for the working conditions of modern aircraft gas turbine main shaft bearings. The M 50 steel is hardened by heat treatment and has a hardness of up to 62HRc.
The continuous operating temperature of the bearing can reach at least 3 ° 6 °C.
Third, the improvement of high-speed bearing lubrication methods
In the 1950s and 1960s, high-speed bearings were always sprayed with nozzles, but when the bearing speed was high, it was difficult to enter the bearing due to the large centrifugal force.
, resulting in poor lubrication and cooling effects, as the 1nI value continues to increase, jet lubrication can no longer meet the requirements
. In 1970, Brown proposed a ring-down lubrication method, which uses a number of radial holes in the inner ring to directly spray oil onto the channel table.
In addition, this method not only improves the lubrication cooling effect, but also allows the lubricating oil entering the bearing channel to easily flush out the powder ground from the holder. In addition, the amount of oil used for lubrication under the ring is also less than that of jet lubrication, so that the loss of the oil and the heat of the bearing can be reduced. The high-speed bearing lubricated by the ring lubrication method can have a lower inner ring temperature than the outer ring temperature. Effectively prevent the inner ring of high speed bearings
Bruises that often occur on the channel. Most of today's aero-engine spindle bearings use this lubrication method.
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