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1. Working Principle

The gear oil pump consists of a driving shaft, a driving gear, a driven shaft, a driven gear, a housing, etc. Two gears with the same number of teeth mesh with each other and are installed in the housing. The radial and end surface clearances between the gears and the housing are very small. There are oil inlets and oil outlets on the housing. The driving shaft is keyed to the driving gear, and the driven gear is loosely sleeved on the driven shaft. When the diesel engine is working, the helical gear on the crankshaft drives the transmission gear on the oil pump to rotate, and the driving gear in the oil pump housing drives the driven gear to rotate. The two gears rotate in opposite directions, and the oil moves between the teeth and flows from the oil inlet to the oil outlet. On one side of the oil inlet chamber, due to the disengagement of the gears and the continuous removal of the oil, a vacuum is generated to form a low pressure and generate suction, so that the oil in the oil pan enters the oil inlet chamber through the filter under the action of atmospheric pressure, and on the other side of the oil outlet chamber, due to the meshing of the gears and the continuous removal of the oil, the oil pressure increases, and the oil is pumped out at a certain pressure and pressed to the friction surfaces of each moving part.

In addition, at the meshing end of the two gears, due to the presence of high-pressure oil and the small gap between the gear end face and the housing, the oil is not easy to leak, which increases the pressure on the gear shaft, thereby aggravating the wear of the shaft and the hole. In order to eliminate this effect, a pressure relief is usually opened on the pump cover to make the oil flow to the oil outlet along the pressure relief to achieve the pressure relief effect. The oil pumping volume and oil pressure of the oil pump increase with the increase of the diesel engine speed. The oil pressure relief valve consists of a valve or a ball and a spiral spring. The oil is sucked through the filter and sent to the oil filter. When the oil supply pressure increases with the speed of the diesel engine, the pressure relief valve opens. At this time, the oil enters the inlet side from the outlet side through the bypass to maintain the specified pressure.

2. Structural characteristics

Simple structure, small size, light weight, and large oil delivery. The cycloid rotor pump adopts the structure of inner and outer rotor meshing, with a small number of teeth and compact structural dimensions. It can form a sealed cavity without the help of other isolation elements, and has a small number of parts.

3. Movement characteristics

Smooth operation and low noise. The number of teeth of the inner and outer rotors of the cycloid rotor pump differs by only one tooth. When they move relative to each other, the sliding speed of the tooth surface is low, and the meshing point is constantly moving along the tooth profile of the inner and outer rotors. Therefore, the mutual wear of the tooth surfaces of the two rotors is small. Since the envelope angle of the oil suction chamber and the oil discharge chamber is large, close to 145°, the oil suction and discharge time are relatively sufficient, so the oil flow is relatively stable, the movement is relatively stable, and the noise is significantly lower than that of the gear pump.

4. High-speed characteristics

For general involute gear pumps, if the speed is too high, the tooth valley will be insufficiently filled with oil due to the centrifugal force, forming a "cavity", which reduces the efficiency of the pump. Therefore, its speed rarely exceeds 3000rpm, and the circumferential speed is within 5-6m/s. For the cycloid rotor pump, the suction and discharge angle range is large. When rotating at high speed, the centrifugal force is conducive to the filling of oil in the tooth valley, and no harmful "cavity" phenomenon will occur. Therefore, the speed range of the cycloid rotor pump can be from several hundred to nearly ten thousand revolutions.