1. Introduction of eccentric shaft of the jaw crusher
The eccentric shaft is the main shaft of the jaw crusher. It is subjected to huge bending and torsion forces and is made of high carbon steel. The eccentric part shall be finished, heat treated, and the bearing bush shall be cast with Babbitt alloy. One end of the eccentric shaft is equipped with a belt wheel, and the other end is equipped with a flywheel.
For jaw crushers, the number of swings of the movable jaw is determined by the rotation speed of the eccentric shaft. Within a certain range, the eccentric shaft rotation speed increases, and the crusher's production capacity increases accordingly. However, when the movable jaw swings beyond a certain limit, and the rotation speed is increased, the production capacity increases very slowly, sometimes even decreases, but its power consumption Rising rapidly, due to the excessively high eccentric shaft speed, the crushed materials cannot be discharged from the discharge port, which affects the increase in production capacity. In order to ensure that the crusher has the best working capacity, it is necessary to reasonably determine the number of rotations of the eccentric shaft of the jaw crusher.
In order to obtain the rotational speed of the eccentric shaft, the following two hypotheses can be made: Since the jaw body is longer and the swing amplitude is not large, it is assumed that the movable jaw moves in translation and the clamp angle a remains unchanged; when the movable jaw leaves the fixed jaw, the broken The prismatic body with trapezoidal cross-section of materials falls freely by its own weight. In order not to hinder the discharge of materials, the conditions that must be met when the material prism body falls are: the height of the crushed material that must fall within the time t of the movable jaw plate should be h; when the eccentric shaft rotates once, the movable jaw swings twice .
2. Calculation the eccentric shaft of the jaw crusher
The formula for calculating the number of swing times of the movable jaw. When the theoretical production capacity of the upper jaw crusher is the highest, the swing times of the movable jaw are n, a is the clamp angle, g is the acceleration of gravity (m/s2), and s is the stroke of the lower end of the movable jaw (m ). Since the above formula does not consider the influence of factors such as the nature of the material and the type of the crusher, it can only be used to roughly determine the speed of the crusher. Generally, when crushing hard materials, the speed should be lower; when crushing brittle materials, the speed should be higher; for larger size crushers, the speed should be appropriately reduced to reduce vibration and save power consumption.
Actually, since the material is still in the compressed state at the beginning of the idling stroke of the movable jaw and cannot fall down immediately, the eccentric shaft speed should be about 30% lower than the value calculated by the above formula. The speed of the eccentric shaft can also be calculated according to the following empirical formula:
For the feed port width B≤1.2m, so: n=310-145B; for the feed port width B1.2m, so: n=160-42B.
3. Repair method for wear eccentric shaft of the jaw crusher
Jaw crushers using sliding bearings are prone to eccentric shaft wear. The journals and eccentric section journals are severely worn, and the axis bending and fatigue fracture will cause the eccentric shaft to wear. Because the straightening and correction and broken shaft replanting processes are more complicated, and the repair quality is difficult to guarantee, Red Star Heavy Industry recommends the following three specific repair measures:
Surfacing journal surface
Manual arc welding is used to build up the surface of the journal, and then perform cutting processing to achieve the original design journal size. When surfacing welding, the surfacing welding process should be selected correctly to prevent the bending and deformation of the distracting shaft. The electrode should be selected reasonably during surfacing, the diameter of the electrode should be small, and the current intensity should not be too high. A reasonable centering reference should be selected during the post-surfacing process to maintain the operation accuracy after assembly.
Journal insert
Turn the worn journal to light, and make another steel sleeve. The inner hole of the steel sleeve and journal should be an interference fit (S7/h6), and the outer diameter is processed according to the original design size and tolerance. The steel sleeve should be hot-fitted to the journal. The thickness dimension of the steel sleeve must satisfy D-d>b, D is the outer diameter of the steel sleeve, d is the journal diameter, and b is the thickness of the bearing where the journal fits (the thickness of copper or babbitt alloy).
Turn worn axle journals
Under the premise of ensuring the design surface roughness, the smallest processing amount is used for processing. Then, based on the machined journal size and its deviation, the bearing is prepared according to the original design matching performance.
