The power shift transmission of the loader adopts the shift mechanism of the hydraulically pressed multi-disc wet clutch to change the speed. Each shift is composed of 2-5 pieces of friction plates and the corresponding press plate and hydraulic cylinder.When the control gear lever is placed in a gear position, the pressure oil flows into the corresponding hydraulic cylinder through the control valve to push the piston to compress the driving piece and the driven piece, so as to achieve the purpose of power transmission.In actual use, often wait until the machine can not work normally before maintenance, resulting in the loss of the best time for maintenance, shorten the service life of the transmission.This paper analyzes the cause of clutch damage of power shift transmission, introduces a method to detect the tightness of clutch piston and measures to prevent transmission failure, so as to improve the service life of power shift transmission.
1. Causes of clutch damage
When the clutch of the power shift gearbox is engaged, the pressure of the hydraulic oil overcomes the spring force to compress the friction plate.With the increase of hydraulic oil pressure, the friction plate and the metal plate contact and gradually compress, so that the clutch will fly wheel power smoothly transfer to the transmission shaft.Each shift, the friction plate and the steel plate friction, the heat generated by the coolant out.When the friction plate and thinning of the steel, in order to make them fully joint requires more hydraulic oil, engine further acceleration, friction slices on the sheet steel skid time is to lengthen, the resulting friction heat more, pushing the hydraulic oil temperature increase, when reaching enough to change the transmission seal in the performance of the temperature, the transmission can produce inside leaking.The internal leakage continues to cause the increase of heat from two aspects: the high pressure oil leakage through the damaged seal, so that the oil temperature continues to rise;Due to oil leakage, the hydraulic pump is bound to transport more oil to ensure the pressure required to engage the clutch, so that the clutch is fully engaged, which also requires the engine to continue to accelerate, so that the hydraulic pump produces greater flow.Such a vicious cycle will eventually lead to overheating or burning of the clutch, until complete failure.
2. Clutch piston sealing test
When the loader is unable to walk or the oil temperature is too high, it is necessary to determine whether the clutch piston seal is lax or the oil pressure is insufficient, but the conventional detection means are sometimes difficult to determine which reason causes the failure, especially in the case of no power, it is more difficult to check the sealing rings of the assembled transmission assembly.At this time, the air pressure valve can be used for testing.
First of all, the transmission control valve down (to the assembled transmission should be before loading control valve), and in turn to the transmission oil hole of 0.6 a 0.8 MPa gas of our factory, if a hole gas of our factory, hearing 1 of “bang” and there is no air or sound is very small, explain and the matching between piston and cylinder of the clutch of good seal;If the sound of the piston pressing the friction plate is not heard and the air leakage sound is large, it indicates that the seal between the clutch piston and the cylinder is invalid, and the seal should be replaced.
3. Transmission failure prevention
The bearings and gear pairs of the power shift transmission are vulnerable parts, so the transmission should be checked and maintained regularly.The maintenance time interval of typical transmission abroad is 5000 to 10000h.According to China’s national conditions, it is recommended to check the clutch wear every 2500 to 5000h, and catch abnormal signals at any time.Because power shift transmissions are not likely to fail quickly, they can usually continue to be used for 750-1000h after the first signs of wear on the friction plates.If regular inspection and maintenance are carried out during this period, and the friction plates, seals and individual bearings are replaced in time, the damage of undamaged parts (such as steel plates, gears, shafts, hydraulic cylinders and most bearings, etc.) can be avoided.