Answer: The function of the diesel generator oil pump is to increase the pressure of the oil and send it to the friction surfaces of the lubricating parts to ensure the continuous circulation of the oil in the lubrication system. The oil pressure and flow in the oil circuit are supplied by the oil pump. Therefore, the technical condition of the oil pump directly affects the normal operation of the lubrication system. There are two types of oil pumps commonly used in internal combustion engines: gear type and rotor type.
1. Gear oil pump
The gear oil pump is divided into two types: external gear type and internal gear type. Here, the external gear oil pump used in common domestic diesel engines is used as an example to introduce its structure and working principle.
The gear type oil pump is mainly composed of a casing, a driving gear, a driven gear, a driving shaft, a driven shaft, a front cover and a driving gear, as shown in Figure 6-1.
The driving gear is fixed on the driving shaft with a semi-circular key, and the driving shaft is supported in the copper bushing of the pump body and the front cover.
Figure 6-1 Structure of gear oil pump
The driven gear is sleeved on the driven shaft, and the driven shaft is press-fitted in the pump body. The pump body and the front cover are positioned by two positioning pins, and oil-resistant paper gaskets are installed between them to prevent oil leakage, and the end face clearance of the gear can be adjusted by changing the thickness of the gasket. The front end of the drive shaft is equipped with an oil pump driving gear, and the ring groove at the rear end is equipped with a retaining ring to prevent the drive shaft from coming out. A thrust bearing is installed between the drive gear and the front cover to bear the axial thrust generated by the driving shaft.
When the internal combustion engine is working, the crankshaft gear drives the oil pump drive gear to rotate through the intermediate gear, so the driving gear rotates with the driving shaft, and drives the driven gear to rotate in the opposite direction, as shown in Figure 6-2. At this time, the volume of the oil inlet cavity increases due to the disengagement of the gears, forming vacuum suction, and the oil is sucked into the pump body from the oil pan through the filter; the oil filled between the teeth is brought from the oil inlet to the oil outlet, As the gears mesh, the volume becomes smaller, the oil pressure rises, and the oil is sent to each friction surface with a certain pressure.
The gear type oil pump has simple structure, convenient machining, reliable operation and long service life, so it is widely used.
2. Rotary oil pump
The rotor type oil pump is widely used due to its compact structure, small shape, uniform oil supply and low noise due to the use of rotors with few internal meshes. The rotor type oil pump is composed of pump body, inner rotor, outer rotor, pump shaft, front cover, driving gear, etc. The number of teeth of the inner rotor is one less than that of the outer rotor, and the inner rotor and the pump body are eccentrically installed.
Figure 6-2 Working principle of gear oil pump
When the internal combustion engine is working, the inner rotor drives the outer rotor to rotate in the same direction, as shown in Figure 6-3. Since the number of teeth of the inner and outer rotors is different and they are not concentric, when they rotate, the volume of the cavity formed between the teeth will change. When turning to the oil inlet hole, the volume of the cavity increases from small to large, and vacuum suction is generated. At this time, the oil is sucked into the cavity through the oil inlet hole. With the rotation of the rotor, the oil is brought to the side of the oil outlet. At this time, the volume of the cavity changes from large to small, and the oil is sent out by the oil outlet. In this way, the rotor is constantly rotating, and the oil is continuously sucked in and pressed out.
Figure 6-3 Working principle of the rotor oil pump
The oil pump of the 135 series diesel engine has two types: single-section and double-section, the latter is used for the variant products that require large diesel engine trim. The oil pump of the base wood diesel engine is a single-section gear type, which is installed on the first beam on the bottom surface of the front end of the body and positioned with pins, and is driven by the crankshaft driving gear through the idler gear. Because the oil flow required by the 12-cylinder V-type diesel engine is quite different from that of the 4.6-cylinder in-line diesel engine, there are two types of oil pumps, as shown in Figure 6-4. The 4.6-cylinder diesel engine has a common oil pump.
Figure 6-4 Oil pump of 12-cylinder V-type diesel engine
1 one oil pump body 2 one driving gear 3 one driving shaft 4 one oil pump cover 5 one bushing 6 one thrust
Bearing 7 – Transmission gear 8 – Gear bushing 9 – Driven gear 10 – Driven shaft 11 – Cylindrical pin 12 – Adjusting washer
The driving gear of the oil pump is fixed on the driving shaft with a semi-circular key, the driven shaft is pressed into the pump body, and the matching clearance between the driven gear hole and the driven shaft is 0.03-00 082mm. The fitting clearance should be measured during overhaul. Excessive clearance will affect the transmission accuracy, increase noise, and even cause unilateral wear or seizure. Too little clearance can also cause shaft seizure.
When replacing parts or reinstalling, the gap between the end face of the oil pump gear and the cover plate should be measured, as shown in Figures 6-5, the gap is specified as 0.05-0.115mm, if necessary, it can be adjusted with a gasket made of oil-resistant paper . Rotate the drive shaft by hand after assembly, and there must be no jamming phenomenon, otherwise the positioning pin on the oil pump cover should be reconfigured with a hinge.