Airlines launched machine bearing slide injury and avoid measures

Airlines launched machine bearing on the basis of using the principle of utility, general will use rolling bearing to stop work, because of the sliding friction coefficient is greater than the rolling friction coefficient, and some external factors make the roller and the inner and outer ring rolling on dry friction, provoked the slippery, roll forming roller and inner and outer ring road rub marks and appearance wear parts, etc. , the so-called 'ceng damage'. Bearing once appear smooth ceng damage, surface brightness is destroyed, the coefficient of friction increase, accelerate the wear process, make the roller diameter smaller, roll on present uneven slot mark, bearing damage, harm of rotor work, directly affect the launch machine to work properly. General machinery used in rolling bearing because of the low speed, and there has always been load act on it, rarely present skid phenomenon. But the aviation gas turbine main bearing is easy to slip, this is because: ( 1) High speed. Under the effect of high speed, the roller under the effect of large centrifugal force has a tendency to be out of the inner ring raceway contact; ( 2) The load is small. Airlines launched machine rotor are doing lighter, make effect on bearing radial load is small, and a maneuvering flight plane under certain conditions, when they make effect on the bearing load of smaller, and presents the zero load, as well as the rotor imbalance force under certain conditions would offset some effect on the bearing radial load, form the light load or no load bearing. The elements of these two aspects will make the drag power produced by friction is small, that is zero, so, will inevitably provoke bearing sliding, present smooth ceng damage. About the ball bearing, since it also receive axial load, so ordinary is not easy to skid. Bearing slide ceng damage and using time has no direct relation, sometimes working in a machine is presented in a short period of time, sometimes in a machine to work for a long time before rendering. In addition to bearing design, installation and working conditions on the bearing can be rendered slippery ceng is influential, launch machine assembly work sometimes play a major role. To launch machine such as turbine rotor assembly, in order to prevent the turbine before rolling rod bearing rolling bar block hoisting, commonly used vaseline coated between outer ring and the roll bar, to make the roll roll stick close to the outer ring road. Do so became a machine assembly, but as in the low temperature outdoor test for the first time, it may be because of vaseline sticky obstacle caused the rolling stick stick to frame the normal movement of the bearing slide ceng damage. Figure 1, the role in a campaign launched machine rotor axial load on the ball bearing with altitude, H) Ma change status of the rolling bearing with slide after ceng, abrade wear is the result of the most common appearance, appearance spalling, etc. Serious when, due to the friction between the roller and the inner ring produces too much heat can make the inner ring contraction, reduces the bearing internal clearance, bearing card to death. Therefore, in the aviation gas turbine on the main bearing, should pay special attention to avoid bearing slide ceng. At present, in most of the design, in order to reduce the sliding bearing, reduce barriers roller can be used both adhere to the movement resistance method, also can be used to increase drag power, or both. Using increase drag power steps to avoid bearing slide ceng decrease the bearing clearance, the roller under the action of centrifugal force can still insist on contact with the inner ring groove. For example CFM56 launched machine rolling bearing high pressure turbine rod bearing ( Intermediate bearing) With the small clearance that is negative clearance to reduce slippage; And as WJ6 launched machine roll bar before the compressor bearings in the long run appear serious slide after injury, the bearing clearance by 0. 070-0. 095 mm decrease to zero. 045-0. 065 mm, eliminate the phenomena of ceng. But, using the measures for decreasing the clearance will lead to other serious problems, and therefore should be treated with caution, especially on hot side bearings in a machine, should be more careful. Initiated in the early days of aviation gas turbine machine, to adhere to the frame of equilibrium solution, how will the persistence of the main bearing positioning from outer ring, but the design is easy to cause the bearing to present slip damage. This is because when stick to locate in the outer ring, exist in between outer ring and adhere to the frame of oil film under the action of viscous block rolling stick stick to frame for normal motion triggered skid. As will stick to locate in the inner ring, exists in the inner ring and adhere to the frame of the oil film between the roller insist on frame under the action of viscosity will assembly a drag power have made its normal movement. In this way, will be scheduled in the persistence of the outer ring into position on the inner ring, not only reduced the resistance, but also increase the power, will obviously reduce sliding ceng damage, of course this progress must also adhere to frame the machining precision of the equilibrium degree of progress.