Cause Analysis and Improvement of Excessively High Oil Temperature in CPCD80A Forklift Hydraulic System
During the use of CPCD80A forklift, it was found that the temperature of the hydraulic oil rose to above 100°C in a short period of time, which caused the malfunction of the steering hydraulic cylinder and the jamming of the steering gear.
1 Analysis of excessive oil temperature in hydraulic system
The heat generated by the hydraulic system mainly comes from the heat generated by the pressure loss of the hydraulic component itself and the heat generated when the actuator works. The hydraulic system is now analyzed as follows:
(1) The output flow of the gear pump of the hydraulic system of CPCD80A forklift is 158Umin; the diameter of the pipeline from the outlet of the gear pump to the monostable diverter valve is too small, which causes excessive local resistance loss along the way when the oil flows through the pipeline.
(2) The design capacity of the hydraulic oil tank is too small, and the layout is unreasonable, and the ventilation is not good. About 1/3 of the surface area of the oil tank is covered by the battery box, and the distance between the inlet and outlet of the oil tank is too small, and the oil is not enough in the oil tank. To sufficient and effective circulation, the cooling effect is affected.
(3) The hydraulic oil cooling device is not installed in the hydraulic system, and the heat dissipation effect is very limited by the surface area of the oil pipeline and the oil tank, especially when working in a high temperature environment, the performance is particularly prominent.
(4) The structural design of the steering hydraulic cylinder in the actuator is unreasonable, the piston rod support ring and the piston support ring are made of nylon, and the contact area of the support ring with the cylinder body and the piston rod is too large. When the oil temperature is too high, the support ring is thermally expanded, and the thermal expansion coefficient of the nylon material is large, so that the matching gap between the moving parts becomes smaller, the oil film is damaged, and the support ring is stuck with the cylinder block and the piston rod, and an abnormality occurs. With a loud noise, the oil temperature rose sharply.
2 Improvement measures
(1) Increasing the diameter of the gear pump outlet to the monostable diverter valve pipeline, from φ18mm to φ25mm, the oil flow rate in the pipe is reduced from the original 10.3m/s to 5.3m/s, greatly reducing The pressure loss when the oil flows through the pipeline reduces vibration and noise.
(2) Move the battery box forward without changing the overall structure of the frame. The space saved is used to increase the volume of the fuel tank. The capacity of the fuel tank is increased from the original 100L to 150L: On the other hand, the inlet and outlet of the fuel tank are changed. The distance between the oil ports is increased from the original 300mm to 800mm, which ensures that the oil can be fully circulated in the oil tank, which not only increases the heat dissipation area of the oil tank, but also improves the heat dissipation effect of the oil tank.
(3) The torque converter oil radiator is changed to a hydraulic oil radiator, which is installed in the return oil circuit of the steering gear, and its installation position is unchanged, and the engine fan is forced to cool. The heat dissipation of the torque converter adopts the oil-water one-in-one radiator produced by Anhui Fengyang Water Tank Factory and the engine. It is installed behind the hydraulic oil radiator, and the position is the same as before the modification; its water tank heat dissipation area is 22.5m2, oil heat dissipation area 6m2, to ensure the heat dissipation effect of the engine and torque converter oil.
(4) Change the structure of the steering hydraulic cylinder, replace the nylon support ring in the original guide sleeve with QT40-10 ductile iron guide sleeve support, and add a Stir seal seal, and change the width of the piston support ring from 34mm to 28mm.
After the improvement, the system is tested. (1) First, unit test is performed on the improved steering hydraulic cylinder, and the improved steering hydraulic cylinder is installed on the steering axle body of the forklift, and the oil is gradually forced to be heated to above 120 ℃. At this time, the steering The hydraulic cylinder works normally and there is no abnormal noise; (2) Test the pressure loss of the hydraulic system of the whole machine. Under no-load conditions, the outlet pressure of the gear pump is reduced from the original 2.0MPa to 1.5MPa, reducing the resistance loss of the hydraulic system And heat generation; (3) The heat balance test of the whole machine is carried out according to the balance weight forklift test method JB/T3300-1992 standard. After the machine runs for 1h42min, the hydraulic oil tends to balance when it is close to 90Y, and the engine water temperature and change The torquer oil temperature is within the normal operating temperature range.
