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Diesel generator accessories - valve train components

2014-04-03 16:53      Click:

Valve train components

Diesel generator accessories - valve train components by the camshaft, tappets, push rod and rocker arms zero components. Their role is to transmit motion to the cam diesel engine valve assembly to control opening and closing of the valve.

(1) Camshaft

Camshaft valve train is the key component, whose role is precisely to open and close the intake and exhaust valves on each cylinder through transmission parts by working cycle of the engine. In addition, the diesel engine, it is also driven fuel pump, fuel pump, etc. In order to ensure that diesel fuel injection and ignition gasoline engine punctual and reliable, camshaft and crankshaft timing must maintain a certain relationship between the engine running.

 ①The structure of the camshaft :     Most camshaft are made into integral, it consists of a number of inlet and exhaust CAM and supporting shaft neck, driven by the end of the timing gear. Because the type of engine is different, so the structure of the camshaft is not exactly the same. For four-stroke diesel engine camshaft, in addition to the intake and exhaust CAM CAM, and fuel injection pump CAM, such as 4105 and 4110 diesel engine CAM belong to this kind of structure. If using combined fuel injection pump of diesel engine, the fuel injection pump is driven by separate a transmission shaft, such as 4135 and 6135 diesel engine belongs to this kind of structure.

The camshaft is the most important part of the CAM, its contour shape, directly affect the work quality of valve-train. The CAM contour shape sort is more, but could be divided into two types: circular arc CAM CAM and function. The characteristics of the circular arc CAM can get larger when the face value (that is, the valve flow area and the corresponding opens the product of time), but the acceleration discontinuity, shock vibration is larger; Function CAM acceleration is the feature of continuous change, according to a single function without acceleration mutation phenomenon, make the distribution agencies from impact, to improve the dynamic performance.

The camshaft drive:    camshaft drive gear usually, rarely used chain drive. When using the gear, the gear is mounted on the front end of the camshaft, crankshaft gear engages directly or indirectly called the timing gears. For four-stroke engines, each completed a work cycle, the crankshaft rotates two weeks, each cylinder intake and exhaust valve opens once each camshaft revolution only, and thus the speed of the crankshaft and camshaft ratio of 2:1. Timing gear on the crankshaft gear for the active, the engine, drive gear through one or two intermediate gears, and then spread on the camshaft timing gear.

In order to make a smooth gear when driving, reduce noise and reduce wear and tear timing gear on the crankshaft, usually with different manufacturing materials, timing gear often used helical gears, which tilt about 100, timing gear on the crankshaft multi-alloy steel system, while on the camshaft timing gear with cast iron wood glue or clips. The gap between gears should be kept within a small range to reduce noise. If the gap is too large, not only between the teeth and the teeth while working impact, noise, impact on gas distribution, and the gear damaged.

In order to ensure the flywheel position with the valve opening and closing times of certain relationships with, care must be taken when assembling parts on the timing marks, in strict accordance with the provisions of the assembly.Crankshaft drive gear, camshaft drive gear around, fuel pump drive gear, transmission gear and intermediate gear pumps, etc. which are engraved above the fitting engagement marks.

(2) the transmission mechanism

Diesel generator accessories - gas distribution mechanism is used to drive the camshaft drive mechanism to the movement between the valves. OHV gas distribution agencies, including the valve tappet, push rod and rocker arm and other groups.

① valve tappet (pole) role valve tappet cam thrust is transmitted to the putter, and withstand lateral forces generated by the rotation of the camshaft.

When the camshaft rotates, the lateral force in order to avoid the direct action of the cam when the apex of the movable valve pin in the valve, causing the one-way valve stem wear, resulting in increase of the valve offset occurs, the impact of the seat correctly with the valve, the valve and the cam is provided between the cam shaft to pass tappet thrust. There tappet sliding, rolling and rolling three forms of arm structure, as shown in Figure 2.29.

Sliding tappet: it has bacteria and cylindrical shape of the points, the structure shown in Figure 2.29 (a), (b) shows, generally used in gasoline.

Roller tappet: fitted with a roller tappet below, so tappet cam contact surfaces by the sliding friction into rolling friction to reduce cam wear, and when the wheel bearings and other parts are easy to replace worn, its shortcomings is a multi-part manufacturing cost is higher. Roller tappet apply to large bore diesel engines, as 2.29 as shown in (c).

Roller tappet arm: To reduce the lateral pressure between the cam tappet lifters and putting in place of the roller rocker arm with a belt, the structure shown in Figure 2 29 (c) as shown. Roller arm set in a parallel with the camshaft axis, this axis is called roll axis. Copper sleeve between the arm and the shaft to reduce wear, with flat keys and roller shafts are connected. Copper sleeve top fuel pump wheel arm is eccentric to adjust the fuel injection time.

 putter overhead valve mechanism, since the camshaft and valves are set separately, the two distance, therefore, the use of the push rod to pass on the top cam thrust. Putting is a hollow elongated rod, usually made of cold drawn steel pushrod connected to the lower end of the first ball and put pressure on people tappet; upper head pressure spherical seat and arm people connected at both ends of the spherical surface treatment to be carried out to improve its approximate hardness.

③ rocker arm group    is set to change the direction of movement of the push rod to the valve, the valve opens and closes to control the transmission parts. It consists of rocker, rocker shaft, bearings and bearing housings and other parts of the composition, as shown in Figure 2.30 for the whole rocker group, all the cylinders are mounted on a rocker shaft, intake and exhaust valves per cylinder There are devices bearing arm and fastened with screws to the cylinder head. Rocker is a hole in the middle with the lever arms of unequal length, the short arm by adjusting the screw in contact with the putter, the long arm of contact with the valve, so you can make the putt to get a small amount of movement of the larger valve opening degree, the plunger moves up and down due to the small amount can be reduced inertial force transmission mechanism. There the rocker oil passages, oil via rocker arm shaft holder and supply, when the rocker work, then intermittently alternately at both ends of the friction surface lubrication, oil lubrication flow back into the sump after.

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