Why doesn t the hydraulic support need to adjust the valve clearance?

In order to ensure that the valve closes tightly, there is an appropriate clearance between the valve stem end and the valve actuator (rocker, tappet, or cam), called valve clearance. The valve clearance is smaller in hot cars and larger in cold cars, because when the engine is running, the valve stem expands and elongates due to the increase in temperature, resulting in a narrowing of the clearance. If the valve clearance is not properly adjusted, the engine will run abnormally, which will affect the opening amount of the valve, and the valve lift will be reduced to cause insufficient air intake and incomplete exhaust; Too small will cause the valve to be closed loosely, causing air leakage, resulting in a decrease in power.

In order to avoid the trouble caused by improper valve clearance adjustment, hydraulic tappets that can adjust the valve clearance by themselves are generally used in high-speed engines.

One end of the tappet is in contact with the cam and the other end is in contact with the valve, and its role is to transfer the thrust of the cam to the valve. Whereas the tappets on older engines had an adjustment screw and lock nut at one end to adjust the valve clearance, the hydraulic tappet omitted the adjustment screw and lock nut and replaced the role of these rigid parts with hydraulic adjustment.

The hydraulic tappet is in contact with the camshaft at all times and runs without backlash. Inside the tappet, hydraulic force is used to achieve the effect of gap adjustment. The hydraulic tappet is mainly composed of a plunger, a check valve and a check valve spring, etc., using the role of the check valve to store or release the oil, and the working length of the hydraulic tappet can be changed by changing the oil pressure in the tappet body cavity, so as to play the role of automatically adjusting the valve clearance.

When the engine is working, when the valve is closed, the oil enters the plunger cavity (A) through the hole of the tappet body (1) and the plunger (2), pushes open the check valve (3) and goes straight into the tappet body cavity (B), and the plunger rises under the action of the oil pressure of the tappet body cavity and the spring (4), and compresses the valve push rod (5). At this point, the lifting force of the plunger is not enough to overcome the tension of the valve spring, and the valve is not opened, but only the gap in the entire valve train is eliminated. At this moment, the tappet body cavity has been filled with oil, and the check valve is closed under the effect of oil pressure and spring (6), and the oil circuit is cut off.

When the cam (7) turns to the working face, the tappet rises, and the valve spring tension acts on the plunger through the valve pusher, but at this moment, the check valve is closed so that the oil can not escape, and the incompressibility of the oil makes the tappet push the valve open like a whole. In this process, due to the high oil pressure in the body cavity of the tappet, a little oil leaks out through the gap between the tappet body and the plunger and "shortens" the working length of the tappet. When the cam turns over the working face, the tappet descends, the valve closes, and the oil pressure in the tappet body cavity also drops, so the oil of the main oil passage is pushed open again and injected into the tappet body cavity, the oil is replenished, and the above actions are repeated.

Through the oil leakage and replenishment in the body cavity of the tappet, the working length of the tappet is constantly and automatically adjusted, so as to keep the valve working normally and there is no gap in the whole mechanism, which reduces the impact and noise between the parts and eliminates the disadvantages of the valve clearance of the old engine. At the same time, the use of hydraulic tappets makes the camshaft profile a little more promising, allowing the valves to open and close faster, which is more in line with the requirements of modern high-speed engines.

Because the hydraulic support is self-adjusting by oil pressure.

Not hydraulic, but hydraulic tappet, which automatically adjusts the valve clearance by oil pressure.

Reasons for doing engine valve clearance adjustment:

1. When the valve is closed in the cold state of the engine, the gap between the valve and the transmission part is called the valve clearance.

2. The gap is too large: after the intake and exhaust valves are opened late, the intake and exhaust time is shortened, the opening height of the valve is reduced, and the normal valve phase is changed, so that the engine power decreases due to insufficient air intake and unclean exhaust, in addition, the impact of the valve mechanism parts is increased and the wear is accelerated.

3. The clearance is too small: after the engine works, the parts are heated and expanded, and the valve is pushed open, so that the valve is not closed tightly, resulting in air leakage, power decline, and serious carbon accumulation or burnout on the sealing surface of the valve, and even the valve hits the piston. The valve train with hydraulic tappets does not require valve clearance.

Hydraulic tappets and valve-related parts and components are: valve guides, valve seats, valve springs and transmission groups (cam day, timing gears, rocker arms, rocker shafts, tappets, push rods, etc.), the above parts and components are relatively simple in structure and relatively simple in working principle.

The hydraulic tappet has complex structure, high processing accuracy requirements, and cannot be adjusted after wear, and can only be replaced. So I'm here to briefly describe how it works. The purpose is just to let everyone know how the engine can be damaged by mixing various grades of oil and additives on hydraulic tappets.

Finally make the engine not work in condition.

There are two kinds of hydraulic tappets on the market now, one is a hydraulic tappet with a check valve inside (like an 8V100 engine), which is higher. General cars such as Audi, some Santana, Jetta, etc. use ball valve hydraulic tappets, which have a simple structure.

The hydraulic design principle is to close the inner oil channel to establish oil pressure when the valve is opened, and when the valve is closed, the oil channel is opened so that it can hold up against the camshaft to make up for the gap for oil filling, which reduces the noise in this link, and the tappet has always been attached to the camshaft in the whole cycle. So this is not a gap.

The hydraulic tappet relies on the oil of the engine to generate oil pressure, and as long as there is no clearance between the valve and the camshaft, the gap is automatically adjusted by oil pressure.

So there is no need to reserve a gap to reduce noise and work reliably.

Prevents the valve from being pushed open during thermal expansion and contraction, making it difficult to start the car or wasting power.

Thermal expansion and cold contraction. If there is no clearance, the rocker arm and the valve of the engine will not close the valve because the clearance is too small at high temperature, but the clearance should be appropriate, and the valve can not leak or have too much noise when the engine is working at normal temperature. ,

Prevent the engine from expanding at high temperatures, leaving no valve clearance, the rocker arm and valve will be too small to close the valves!

The gap is too large: the intake and exhaust valves are opened late, the intake and exhaust time is shortened, the opening height of the valve is reduced, the normal valve phase is changed, and the power of the tank bucket engine decreases due to insufficient air intake and unclean exhaust, in addition, the impact of the valve mechanism parts increases, and the wear accelerates.

The clearance is too small: after the engine works, the parts are heated and expanded, pushing the valve open, making the valve not closed tightly, causing air leakage, power dropping, and causing serious carbon accumulation on the sealing surface of the valve or burning out of the blind grind, and even the valve hitting the piston.

The valve mechanism with Shenda hydraulic tappet does not need to leave valve clearance.

Thermal expansion and cold contraction. If there is no clearance, the rocker arm and valve of the engine at high temperature will not close the valve because the gap is too small, but the clearance should be appropriate. ,