Engine lubrication system

Lubricating device

For the engine to operate normally, engine oil is necessary. Some of the main roles of the engine oil includes the following.

Lubricating action: Creates a film of oil lubrication by providing lubricating oil to each moving-friction part, and decreases friction between metals.

Cooling action:

Cools the engine by circulating through each engine part.

Cleaning action:

Washes away the metal powder generated by the friction with the oil.

Prevents rust:

Prevents rust and corrosion on the engine.

The mechanism of lubricating the engine oil that has such functions is called the lubricating device.

(1) Splashing method

The splashing method is also called the Scattering formula. It uses the spoon-like oil spoon installed at the large end of the con-rod to spoon up the oil inside the crankcase (oil pan), and splash it onto the cylinder wall and each bearing. This is mainly used for a small air-cooling engine.

(2) Pressure feed method

The pressure feed method uses the oil pump driven by the engine. It is a method of sending the oil to each moving-friction part by applying pressure on it. Using this method makes sure that lubrication is applied to every small part of the engine without fail, and also makes it possible to supply the oil amount befitting to the number of rotation frequency of the engine. Therefore, most engines, except for small aircooling gasoline engines, employ the Pressure Feed method.

For example, in the vertical water-cooled diesel engine, forced lubrication is carried out onto the crankshaft, the Camshaft, the Rockerarm, the idle gear and so on by the pressure feed, and the Pushrod, the Tappet, the Piston, and the Piston pin and others are lubricated with the oil that is leaked from the forced lubrication portion

■ Flow of oil

The oil that has been stored in the oil pan is absorbed into the oil pump after going through the oil strainer. The oil that is discharged from the pump goes through the oil filter and fine foreign matter is removed (in the filtering process).

The filtered oil goes through the oil passage (oil gallery), the crank shaft, idle gear shaft, the governor shaft, the cam shaft, and furthermore, it goes through the cylinder head and finally sent to the Rocker Arm shaft.

The lubrication on the crank shaft is sent from the oil passage to each journal portion, and
furthermore lubricates the crank pin portion after going through the oil passage within the crank shaft.

The oil that leaked from the crank pin area is sprayed into each part including the inside of the piston, the cylinder wall, etc. The oil passage is equipped with oil switches and when the lubrication pressure is low, they are lit and issue a warning. It is also equipped with a relief valve which lets out extra oil to the oil pan and keeps the pressure inside the circuit constant.

１) Oil pump

The oil pump is driven by the Camshaft, Crank shaft, etc., and the oil that has been input via the oil strainer has the function of putting pressure on it and sending it to each moving-friction part. Trochoid pumps and gear pumps are generally in use.

Trochoid pump: The trochoid pump has two rotors installed in its pump body. The rotor on the inside (inner rotor) has 4 to 10 gears and the rotor on the outside (outer rotor) has 5 to 11 gears eccentrically engaged with one another.

Gear pump: The gear pump has two spur gears of the same shape engaged with each other in the pump chamber without hardly any gap. When one gear shaft rotates the other gear shaft also rotates, and the oil that has entered the pump chamber from the suction opening comes between the gear teeth and the wall surface of the pump chamber, and after spinning half the circumference, it is carried to the ejection opening on the opposite side and is pushed out.

２） Oil strainer

The oil strainer consists of fine netting turned into a strainer. A permanent magnet that is installed onto it lets the fine metal powder in the oil that passes through adhere to it. The horizontal diesel engine, air-cooled gasoline engine and some others use this oil strainer only as the oil filter

3） Cartridge oil filter

The oil that has been pressure-fed from the oil pump is all filtered through the oil filter, and then sent to each lubrication area.

Special filter paper is used on the element.

The oil that has entered the oil filter pushes the check bulb open and comes into the periphery of the element. After it is filtered by the element, it is discharged from the central portion of the element.

Also, in preparation for the time when the element gets dirty and clogged, a bypass valve is equipped so that the oil flows without going through the element, thus preventing the lack of lubrication when the element gets clogged.

4) Oil switch and oil signal

If the lubricating oil pressure is low when the engine is in operation, lubrication becomes deficient and could possibly cause burning or damage. That is where the oil switch and the oil signal come in: they are equipped for the purpose of determining whether the lubricating oil pressure is normal or not.

Oil switch: Lights up the alarm lamp using a switch which is actuated when the hydraulic oil is below the standard value. It is used with vertical diesel engines, etc.

Oil signal: When the oil pressure is normal, displays a blue signal, and when the oil pressure is below the standard value, retracts the signal tube and displays red. This is mainly used on horizontal diesel engines.