Composition of The Valve Train Parts

All types of valve train parts can be divided into two major parts: valve group and valve transmission group. The valve group includes the valve and its associated parts, its composition and the form of gas distribution mechanism is basically irrelevant.

Valve transmission group is from the timing gear to push the valve action of all parts, its composition depends on the form of gas distribution mechanism and different, its function is to drive the valve to open and close at regular intervals.

Valve Set

Valve set includes valve, valve guide, valve seat and valve spring and other parts. Some intake valves are also equipped with valve rotation mechanism, valve set should ensure that the valve to the cylinder seal, valve set has the following requirements.

Valve head and valve seat fit tightly.

Valve in the valve guide up and down movement is good.

The two end faces of the valve spring are perpendicular to the center line of the valve stem to ensure that the valve head is not deflected on the valve seat.

The valve spring force is enough to overcome the inertia force of the valve movement, so that the valve can open and close smoothly.

Valve

Valve is composed of valve head and rod. Valve head temperature is very high (intake valve 570 ~ 670, exhaust valve 1050 ~ 1200), and also under the pressure of the gas, valve spring force and transmission components inertia force, its lubrication, cooling conditions are poor, requiring the valve must have a certain strength, stiffness, heat and wear resistance. Intake valves are generally alloy steel (chrome steel, nickel-chromium steel), exhaust valves using heat-resistant alloy (silicon chrome steel). Sometimes in order to save heat-resistant alloy, the exhaust valve head with heat-resistant alloy, and the rod with chrome steel, and then the two welded together.

The shape of the valve head is flat top, spherical top and flared top, etc. Flat tops are generally used. Flat top valve head structure is simple, easy to manufacture, small heat absorption area, small mass, intake and exhaust valves can be used. Spherical top valve is suitable for exhaust valve, its strength is high, exhaust resistance is small, exhaust gas elimination effect is good, but its heat area is large, mass and inertia is large, processing is complicated. The flared type has a certain streamline shape and can reduce the intake resistance, but its head has a large heat area and is only suitable for intake valves.

Valve taper angle is the angle of the valve sealing surface is generally 45 °, some are 30 ° (CA1091 sex car 6102 type engine).30 of the valve is considered the same lift, valve taper is small, the valve through the end surface is large, the intake resistance is small, but due to the taper of the valve head edge is thin, stiffness is small, poor sealing and thermal conductivity, generally used for the intake valve. The thickness of the valve edge is generally 1 ~ 3mm to prevent damage or burned by high temperature during work and valve seat impact. In order to reduce the intake resistance, improve the efficiency of the cylinder intake, most engines intake valve than the exhaust door. Used intake valve and exhaust door color is also different. Valve rod is cylindrical, in the valve guide constantly reciprocating movement, its surface must be heat-treated and polished. The shape of the valve stem end depends on the form of valve spring fixing, the common structure is two halves of the locking plate to fix the spring seat, the end of the valve stem has a ring groove to install the locking plate, some are fixed with a locking pin, the end of which has a hole for the installation of the locking pin.

Valve Guides

The role of the valve guide is to play a guiding role, to ensure that the valve to do straight movement. So that the valve and valve seat can be correctly fit. In addition, the valve guide also in the valve stem and the cylinder block between the role of heat conduction.

Valve guide tube working temperature is high, about 500K, valve rod in which the movement, only by the air distribution mechanism splash out of the oil for lubrication, easy to wear, so most of the valve guide tube applicable gray cast iron, ductile iron and other manufacturing.

The outer cylindrical surface of the valve guide is pressed into the cylinder head after machining, in order to prevent the valve guide from loosening in use, some engines are positioned with a snap ring. There is 0.05~0.12mm clearance between the valve stem and valve guide, so that the valve stem can move freely in the guide.

Valve Seat

Valve seats can be made directly on the cylinder head (valve top-mounted) or cylinder body (valve side-mounted) and the valve seats are made separately from the crossover material and then set into the cylinder head or cylinder body. Together with the head of the valve, they act as a seal to the cylinder and receive the heat coming out of the valve.

The temperature of the intake valve is low, can be directly bored out but the temperature of the exhaust valve is high, poor lubrication conditions, and easy to wear, more inlay type. The disadvantage of inlay type is poor thermal conductivity, high processing accuracy, easy to fall off, generally good for direct boring out. With aluminum alloy cylinder head, due to the soft aluminum alloy material, inlay intake and exhaust valves are inlaid.

Valve springs

The function of the valve spring is to overcome the inertia force of the valve and transmission parts in the valve closing process, to prevent the action of inertia between the transmission parts to produce a gap. To ensure that the valve is located in a timely manner and close contact, to prevent the valve from jumping when the engine vibrates, destroying its seal.

Valve springs are mostly cylindrical spiral springs, the material for high-carbon manganese steel cold-drawn steel wire, heat treatment after processing, steel wire surface to polish, polishing or with shot peening treatment. In order to prevent rusting, the surface is galvanized.

One end of the valve spring is supported on the cylinder head or cylinder body, while the other end is pressed against the spring seat at the end of the valve stem, the spring seat is fixed with a locking piece at the end of the valve stem. In order to prevent resonance of the spring, variable pitch cylindrical spring (such as the 8V100 engine valve spring of the red flag car). Most high-speed engines are a valve with concentric installation of the inner and outer two valve springs. This can improve the valve spring work reliability, that is, not only to prevent resonance, and when a spring breaks, the other one can also maintain the work. In addition, the height of the valve spring can be reduced. When two valve springs are used, the direction of the spring coil spiral should be reversed. This can prevent the broken spring ring stuck in another spring ring. 680Q engine, 492Q engine and CA6102 engine are used double valve springs.