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 friction plates and the corresponding press plate, hydraulic cylinder, etc.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 maintenance opportunity, shortening 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 transmission is engaged, the pressure of the hydraulic oil overcomes the spring force to compress the friction plate.With the increase of hydraulic oil pressure, friction plate and metal plate contact and gradually compressed, 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.