What is the oil trapping phenomenon in gear pumps?

[KiaraFitz]

The oil trapping phenomenon in gear pumps refers to the pressure impact and cavitation caused by changes in the size of the enclosed volume. Here is a detailed introduction to the oil trapping phenomenon in gear pumps: 1. Principle: To ensure smooth gear transmission, strict isolation between the suction and discharge chambers, and continuous oil supply of the gear pump, the gear overlap coefficient ε must be greater than 1 (typically ε=1.05-1.3) according to gear meshing principles. This means that before one pair of gears disengages, the next pair has already engaged. During the simultaneous meshing of two pairs of gears, a portion of oil becomes trapped in the enclosed oil cavity formed by the two pairs, neither connected to the suction chamber nor the discharge chamber. The volume of this enclosed cavity initially decreases as the gears rotate and then gradually increases. When the enclosed cavity volume decreases, the trapped oil is compressed, generating high pressure as it is forced through gaps, leading to oil heating and increased bearing load. Conversely, when the enclosed cavity volume increases, a partial vacuum is created, resulting in cavitation. These phenomena cause strong vibrations and noise in the gear pump, leading to the oil trapping phenomenon. 2. Unloading measures: The root cause of the oil trapping phenomenon is the overlap coefficient ε > 1. Theoretically, setting ε=1 would eliminate the oil trapping phenomenon. However, due to manufacturing and installation errors, ε < 1 may occur, causing discontinuous gear transmission and instantaneous communication between high and low-pressure chambers, leading to backflow from the high-pressure chamber to the low-pressure chamber. Therefore, reducing ε should be limited, and ε is typically designed to be no less than 1.05. A common method to eliminate the oil trapping phenomenon is to create unloading grooves on components such as the front and rear cover plates or floating bushings of the pump. Although there are various structural forms of unloading grooves, their principle is the same: ensuring no communication between high and low-pressure chambers while allowing the trapped oil volume to connect with either the high-pressure or low-pressure chamber.

[VonJune]

I often discuss gear pumps with my friends, and the phenomenon of oil trapping is like when oil gets stuck between the teeth as the two gears rotate. The oil has nowhere to go, causing pressure to surge, which makes the pump whine and also leads to increased wear on the components. The main cause is imperfect gear meshing design, where oil gets trapped in the closed area. Over time, this can reduce the pump's efficiency and even damage the entire hydraulic system, such as a car's power steering pump. The solution is to add pressure relief grooves to the pump, allowing excess oil to flow out and balance the pressure. This issue is quite common, and if not addressed, it can lead to vibrations and loud noises, affecting the driving experience. Regularly checking the hydraulic oil level can also help prevent it. I always pay attention to these details when driving.

[McMarcus]

In my daily auto repair work, I've dealt with the phenomenon of oil trapping, which refers to the situation where oil gets trapped in the gear teeth grooves of a gear pump during operation, forming a sealed space and causing a sudden spike in pressure. This leads to sharp noises and severe vibrations. If not addressed promptly, it can accelerate gear wear and shorten the pump's lifespan. The causes are often improper assembly clearance or aging components. I recommend starting with cleaning the pressure relief grooves to ensure smooth oil flow; oil quality is also crucial, and regular replacement can alleviate the issue. The impact is significant, especially when the hydraulic power steering system fails, making the steering wheel feel heavier. Simple maintenance goes a long way—don't overlook minor issues, or you'll face major repairs later.

[DeLogan]

The phenomenon of trapped oil in a gear pump occurs when oil gets clamped between the gears and cannot move, akin to oil being compressed between two tightly closed doors, resulting in abnormal noises and vibrations. This happens when oil gets stuck in the gaps at the meshing point, causing pressure to rise and making the pump shake with a harsh noise. In daily vehicle use, if left unaddressed, it can lead to instability in the hydraulic system, such as sluggish brake assistance or steering response. I’ve tried checking it myself, focusing on whether the pressure relief valve is clogged. Simply put, prevention is key—using higher-quality oil can help, and avoid overloading the pump.