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What Should I Do if the Intake Valve and Valve Seat Are Worn?

The intake valve consists of a valve body, a rotary check valve, a butterfly valve and a control cylinder. The rotary check valve has its own counterweight and fluororubber sealing ring. When the compressor is turned on, the main body of the compressor inhales. Due to the pressure difference, the check valve opens quickly. The valve can be tightly closed in time and quickly to ensure that there is no oil discharge phenomenon. The opening and closing of the butterfly valve is controlled by the control cylinder. According to the length of the piston of the control cylinder, the butterfly valve opens or closes, thereby adjusting the air intake of the compressor.

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intake valve

1. Intake Valve and Valve Seat Wear Characteristics

In a supercharged four-stroke diesel engine, with the increase of the supercharging degree, the average effective pressure is also higher and higher, and the wear of the intake valve and valve seat is also increasingly serious. Therefore, the wear of the intake valve and valve seat has gradually been paid attention to at home and abroad, and this problem has also been encountered in the 12V180ZL diesel engine produced by a certain factory. After hundreds of hours of operation, not only the valve seat is severely worn and eccentrically worn, but also the valve cone surface is also severely grooved; in the worst case, after 530 hours of operation, the wear amount is as high as 2.38mm.

2. Causes of Intake Valve and Valve Seat Wear

It is tentatively believed that the main cause of wear is friction-related slippage between the valve and the valve seat. This slippage is caused by deflection of the valve and cylinder head. Under the action of the burst pressure, the pressure of the air valve on the valve seat is very high. It is conceivable that under very high pressure, even a small sliding, dry friction will cause wear. Similarly, the cylinder head and valve are deformed. Why is the wear of the exhaust valve and valve seat much lighter than that of the intake valve? This is because a thin non-metallic layer exists on the working surfaces of the exhaust valve and valve seat. These things are made up of engine oil, ash, and soot left in the exhaust. It prevents metal contact between the air valve and the working surface of the valve seat, so that the frictional movement will not cause damage. On the one hand, the residual oil and ash on the intake valve surface and the seat surface are blown clean to cause dry friction and damage.

3. Improvement Measures

(1) Increase the Valve Rotation Mechanism

(2) Reduce the Deformation of Each Part

1 There must be a gasket between the cylinder head and the body, and there must be a certain amount of compression to reduce the assembly deformation of the bottom surface of the cylinder head.

2 Reduce the deformation of the intake valve disc.

3 Strengthen the rigidity of the valve seat.

4 Improve the casting quality of the cylinder head, ensure that the water cavity is unobstructed and the size is correct, so that the wall thickness and temperature of the cylinder head are evenly distributed, the cooling water is sufficient (especially the valve area), and local boiling is avoided.

4. Aspects for Further Research

1. Carry out temperature measurement of cylinder head, air valve and valve seat with accurate price comparison, so as to provide a basis for improving the design of cylinder head.

2. Carry out high-temperature hardness and high temperature metallographic inspection of cylinder head alloy cast iron and various valve surfacing alloys to determine whether the materials used are suitable under the working temperature of cylinder, valve and valve seat.

3. Seek better valve seat materials and valve surfacing alloys to meet the requirements of further strengthening in the future.

4. Test to determine the reasonable rotation speed of the valve rotating mechanism.

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