Valve tappet: description and photo
In any internal combustion engine, there iscamshaft timing system. It includes a chain or belt drive, gears, intake and exhaust valves. The latter regulate the supply and output of the fuel-air mixture, which burns in the cylinder chamber. The engine valve pusher is also used here. What is this device and what are its features? About all this - later in our article.
Characteristic
The valve pusher (VAZ including) is aelement designed to transfer forces to the rod from the camshaft. Modern cars use barrel-shaped mechanisms. They are made of cast iron.
Other varieties
Some valve pushers are equipped with cams with a straight profile.
About a flat base
The valve pusher of this type is rotated ontheir guides. What does it give? This reduces the slippage between the pusher and the cam. Also reduces wear of the distributor. It is more even. As for the elements of the roller type, they should not rotate on their axes with rounded ends.
Hydraulic
The whole process of engine operation is accompanied bygreater heat release. And since most of the power unit's mechanisms are made of metal, it will tend to expand. Accordingly, the thermal gaps change, especially on the valves.
How are they arranged?
In the body of the hydraulic pusher there isplunger. In the latter there are two cameras. This is an injection and feed chamber, which receives lubricant from the engine during operation. Further, this oil passes through the ball valve to the discharge part. To compensate for gaps with high accuracy, the liquid volume is dosed in the plunger. It is pushed out of the body of the pusher spring. Thus, the thermal gap is restored to normal values. During the opening of the inlet or outlet valve, the oil is in the discharge chamber. The ball valve returns part of it back to the feed chamber. When the pusher body moves upward, a certain fluid pressure is created. The oil does not allow the plunger to move relative to the body. When the valve closes, the lubricant leaks from the plunger side. However, with a new discovery, this defect is compensated through the discharge chamber. When the engine starts, the elements of the gas-distributing mechanism gain operating temperature. The metal expands, and the volume of oil in the injection chamber decreases. Thanks to the harmonious operation of the mechanism, the gaps between the valves are compensated. Also in the work elements such as rocker arm and rod are used. Below we will consider what they are.
Rod and rocker
The first element is a metal tube with a diameter of 12 millimeters.
Which valve tappet to choose?
As we have already noted, there aremechanical, roller and hydraulic elements. When replacing these parts, the question arises of choosing the best type of pusher. So, let's start in order. Mechanical elements are the simplest and cheapest pushers. Their main drawback is the impossibility of compensating for the gap. As a result, when the engine sets operating temperature, they begin to emit a characteristic noise. All gaps have to be set manually, through the adjusting bolt. As for the hydraulic, they automatically expose all the gaps.
How to identify a malfunction?
The breakdown of this element can be identified bycharacteristic sounds. Since the part exposes the necessary clearance, if there is a breakdown, a metallic ring under the valve cover will be heard. As the speed increases, it increases. This means that the body of the element does not receive oil or one of the chambers does not work.
When is this normal?
It is worth noting that the noise from the valve cover when starting the engine is quite normal.
How to set the thermal gap?
If it is a mechanical pusher, it is necessary to doit's yourself. Adjustment is carried out on a cold engine. First, open the valve cover. Next, we expose the fourth cylinder at the top dead center. To do this, you should be aware of the central risk on the front cover of the ICE with the crankshaft pulley. The latter is rotated with a suitable lockscrew for the ratchet. Next, proceed to adjust the eighth and the sixth valve.
Conclusion
So, we found out what the data representelements. For any symptoms, do not hesitate to replace the pushers. This can reduce the life of the engine, in particular, the parts of the gas distribution mechanism.