What is Valve and Valve Rotation, defects of valve





What is Valve

A path control device is called a valve whether it is a water valve or a stove valve. But when we are talking about automobile engineering, then obviously we will talk about the valves installed in the engine.

What is valve rotation

The power of an engine depends on the operation of its combustion and the combustion depends on the mixture of air and fuel entering the engine cylinder. The larger the valve or the more open it is, the more air will enter the engine cylinder. The valve is mounted above the Cylinder Head. 

Valve working   - 

Valve has the following functions 

1. Inserting maximum air and fuel mixture into the engine cylinder during the Suction Stroke.
2. Sealing the combustion chamber during compression and power stroke.
3. Exhaling the maximum burnt gases during exhaust stroke. 

Type of Valve:-

 Valves are of the following types

     1.    Rotary Valve .

     2.    Sleeve Valve .

            (a)    Single Sleeve.

            (b)    Double Sleeve.

     3.    Poppet Valve.

            (a)    Flat Head type.

            (b)    Slotted Head Type.

            (c)    Mushroom Head Type.

            (d)    Convex Head Type. 

Heat effect on the valves:- 

The temperature of exhaust gases inside the combustion chamber increases greatly and gases have to pass through the exhaust valve, so let us know what effect the heat has on the valve.

1.     Exhaust Valve   - 

The burnt gases pass through the exhaust valve so that the temperature of the valve rises to around 1200 to 1400 degree Fahrenheit.

The head of the valve is very hot but the face is less hot, its temperature is around 1050 to 1200 degree Fahrenheit, due to such a high temperature, there are some effects which are as follows -

(A) Carbon particles get deposited between the Valve face and the Valve seat due to which sealing does not occur properly.

(B) Valve Face and Valve Head can be burnt.

(C) Valve Head crack may occur.

2.     Inlet Valve   - 

The heat effect on the inlet valve is not so much because whenever cold air comes in, it cools back to some extent. 

Due to this heat, the following effects occur -

(a)     Warping Effect - 

This effect is above the valve head, due to continuous working at high temperatures and the engine oscillation can worsen sealing. To overcome this, a layer of CHROMIUM ELECTROPLATE  is mounted on the valve head and valve face  .

(b)     Carbon Deposit   - 

There is carbon deposit on the valve head and valve face which weakens sealing. Carbon freezing on the Valve Stem causes the valve sticking, which is removed by Valve Rotation.

Precaution from carbon deposit  -

(a)     Interference Angle   - 

This angle is formed between the valve face and the valve seat. This angle is achieved by grinding the valve, it is from 42 degrees to 46 degrees.

Due to this angle, when the valve sits in its seating, it cuts the carbon particle and they go out of the way of exhaust.

(b)     Valve Cooling   - 

The valve is placed in the cylinder head and the water around the cylinder head keeps circulating due to which the heat of the valve goes into the head and the head heat goes into the water, thus cooling the valve. If the exhaust valve is overheated then the exhaust valve is made hollow from inside.

And it is filled with metallic sodium which takes the heat of the valve inside itself.  





3. Valve Rotation   : - 

Frequent air and fuel are ignited inside the engine cylinder due to which carbon deposits accumulate on the face and valve head of the valve, which can cause the valve to deteriorate and the valve seat to move. She goes. Due to which the mixture starts leaking and the pulsing power of the engine is also weakened. To overcome this problem, the valve was rotated, ie the valve was rotated, due to which the carbon deposited on the valve fell down. 

This valve rotation is of 4 types -

 1. Free Valve Rotation   : - To operate the valve, the valve is pressed by Rocker Arms, when the pressure of the arms is removed from the valve  , the valve is free for some time. Vibration of the engine causes the valve to rotate and the carbon deposited on it falls below, this is called free valve rotation. 

 2.  Positive Valve Rotation : - In this, grooves are made above the stem of the valve, due to these grooves, the valve gets rotated, this is called positive valve rotation. 

 3.   Roto Cap Valve Rotation   : - In this rotation a roto cap is placed in the path that guides the valve, this roto cap has a spring ball, when the rocker arms press the valve.  So the roto cap gets rounded due to which the spring in the roto cap is pressurized but when the rocker arms pressure is removed then the spring of the roto cap fails and the valve also rotates in the rounding, this is called roto rotation. 

4.  Off set Valve Rotation   : - In this the thimble end of the rocker arms is fitted at the edge of the valve stem by not fitting it in the middle of the valve stem, so that whenever the rocker arms press and release the valve. The valve receives rotation, this is called off set valve rotation.