Created on:2021-07-08 14:14

Tractor hydraulic failure of farm tools can not be lifted

Tractor hydraulic failure of farm tools can not be lifted

Hydraulic system is an important part of tractor, which is mainly used for hanging farm tools. Tractor running environment is poor, hydraulic failure rate is often relatively high, this paper introduces the tractor hydraulic fault diagnosis and troubleshooting method through an example.

When the engine is working, pull the control handle to the lifting position, the suspension rod does not lift, so it should be checked from the outside.

① External inspection A. whether the transmission mechanism of hydraulic pump is engaged; b. Whether the oil level of the hydraulic oil tank is correct; c. Whether a large amount of hydraulic oil leakage is caused by tubing rupture and joint loosening; d. Whether the clearance of 10-15mm between the positioning valve of hydraulic cylinder and the positioning baffle is guaranteed; e. Whether the weight of the hanging farm tools exceeds the rated carrying capacity; f. Whether the compression nut of the self sealing joint is loose, if it is loose, the closing valve will be closed, and the hydraulic oil will not enter the hydraulic cylinder from the distributor. In general, external causes can be eliminated immediately.

② The analysis and judgment of internal faults are checked externally, and the internal faults can be checked after they are confirmed to be normal. The hydraulic components of the hydraulic system (hydraulic pump, distributor, hydraulic cylinder, etc.) work in the sealed state, and the fault parts cannot be observed directly. It can take the distributor as the center, through changing the different positions of the distribution handle, observe the different phenomena reflected by the distributor and its surrounding, analyze, judge, check by sections, and eliminate the fault.

After the engine is running, the following phenomena will appear when the distributor handle is placed in different positions.

① When the distributor handle is placed in the "lifting" position, the handle will immediately "click" and jump back to the "neutral" position, and the farm tools can not be lifted. If the handle is forced to stay in the "lifting" position, and the distributor makes a sharp "quack" sound (safety valve opening sound), the engine running sound becomes heavy, the load increases significantly, and the oil pipe leading to the lower chamber of the hydraulic cylinder vibrates. This fault indicates that the hydraulic pump and distributor are working normally, and the oil path to the hydraulic cylinder is blocked. In most cases, the positioning valve is stuck in the closed position or the buffer valve is blocked by dirt.

② After the distributor handle is placed in the "lifting" position, the farm tools will not be lifted, the handle will not jump, and the engine load will not change. This indicates that there is leakage inside the hydraulic system, so that the oil can not establish high pressure. The reason may occur in the hydraulic pump, distributor and hydraulic cylinder, which needs further inspection.

First press the positioning valve on the hydraulic cylinder to block the return oil circuit of pressure drop. Then put the distributor handle in the "pressure drop" position for fixing. There are two situations. The first case: the distributor makes a sharp "quack" noise, the engine makes a heavy noise, and the load increases, which indicates that the hydraulic pump and distributor are working normally, and the fault occurs in the hydraulic cylinder. The second case: the distributor has no noise, and the engine load has no change, which indicates that the fault occurs in the distributor and the hydraulic pump, so the distributor should be checked first and then the hydraulic pump.

Most of the distributor faults occur at the return valve. When the oil return valve is in the open position, it is stuck in the guide sleeve or the sealing between the conical surface and the valve seat of the oil return valve is not tight, so that the oil pumped by the hydraulic pump can not lead to the hydraulic cylinder, but leaks from the oil return valve and flows directly back to the oil tank. In case of this kind of failure, a small wooden hammer can be used to knock the return valve at the place where the distributor is installed to make the return valve fall back to the valve seat due to vibration; Or remove the oil return valve, make the valve move flexibly in the guide sleeve hole, clean and install it with diesel oil. Under special circumstances, the guide sleeve and oil return valve must be removed, cleaned in clean diesel oil, and whether the tail of valve body moves flexibly in the guide sleeve shall be checked. If it is stuck, the engine oil shall be used for matching research until the valve can move flexibly in the guide sleeve hole, and then the valve shall be cleaned and installed back to its original position.

In the case of normal operation of the return valve, if it still cannot be lifted, check the hydraulic pump. The fault of hydraulic pump usually occurs in the Triangle rubber ring and the self tightening oil seal of driving shaft. When the partial pressure rubber ring is damaged, the high and low pressure oil cavities are connected, resulting in a sudden drop in the working capacity of the hydraulic pump. If you touch the pump shell with your hand, you will feel that the temperature is very high, so you need to replace it with a new rubber ring. When the self tightening oil seal is damaged, the working capacity of the hydraulic pump will drop suddenly, and the engine oil will increase. When replacing the self tightening oil seal, check the seal ring on the shaft sleeve to prevent the seal ring from aging and failure, which may cause early damage to the self tightening oil seal.

In addition to the above analysis and judgment, the weakening or breaking of the automatic spring and the early opening of the oil return valve caused by the breaking of the spring of the safety valve will make the farm tools unable to be lifted.

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