Analysis of the function and technology of the hot

Analysis of the function and technology of gear pump replacing plunger pump (Part 2)

the pressure sensing unloading circuit with power integration is composed of two groups of slightly changed pressure sensing unloading pumps, which are driven by the same prime mover, and each other magnet receives the pilot unloading signal of another unloading pump. This sensing method is called interactive sensing, which enables one group of pumps to work under high pressure and the other pump to work under large flow. Two overflow valves can be adjusted according to the special pressure of each circuit to unload one or two pumps. This scheme reduces the power demand, so a low-cost prime mover with small capacity can be used

priority flow control

regardless of the pump speed, working pressure or the flow required by the branch, the fixed primary flow control valve can always ensure the flow required for the operation of the equipment. The fixed primary flow valve (proportional valve) combines the primary control with the hydraulic pump, eliminating the pipeline and eliminating external leakage, so the cost is reduced. The typical application of this gear pump circuit is the steering mechanism often seen on truck cranes, which saves a pump. The function of the load sensing flow control valve is very similar to that of the fixed primary flow control: that is, the primary flow is provided regardless of the pump speed, working pressure or the amount of branch pumping flow. However, in the scheme shown, the required flow is only provided to the primary oil circuit through the primary oil port until its maximum adjustment value. This circuit can replace the standard primary flow control circuit to obtain the maximum output flow. Because the pressure of the no-load circuit is lower than the fixed value of the primary flow control scheme, the circuit temperature rise is low, and the no-load e hydraulic system has oil leakage and low power consumption. Like the primary flow control valve, the load sensing proportional flow control valve is typically used in power steering

bypass flow control

for bypass flow control, regardless of the pump speed or working pressure, the pump always supplies liquid to the system according to the predetermined maximum value, and the excess part is discharged back to the oil tank or the inlet of the pump. This scheme limits the flow of the system and makes it have the best performance. Its advantage is that the maximum adjustment flow is controlled by the loop scale, and the cost is reduced; The pump and valve are combined into one, and the bypass control of the pump is used to minimize the circuit pressure and reduce the pipeline and its leakage

the bypass flow control valve can be designed together with the medium ball load sensing control valve that limits the range of working flow (working speed). This type of gear pump circuit is often used in garbage truck or power steering pump circuit that restricts hydraulic control to make the engine reach the best speed, and it can also be used in fixed mechanical equipment

dry oil suction valve

dry and made a breakthrough. The oil suction valve is a kind of pneumatic hydraulic valve, which is used to throttle the oil inlet of the pump. When the hydraulic pressure of the equipment is empty, only a very small flow passes through the pump; When there is load, the full flow suction pump. This circuit can eliminate the clutch between the pump and the prime mover, thus reducing the cost, and also tightening the processing of both ends of the sample to be as smooth as possible, reducing no-load power consumption, because the very small flow through the circuit maintains the prime mover power of the equipment. In addition, the noise of the pump at no-load is reduced. The dry suction valve circuit can be used in the on-off hydraulic system in any vehicle driven by internal combustion engine, such as garbage loading truck and industrial equipment

selection of hydraulic pump scheme

at present, the working pressure of the gear pump is close to that of the plunger pump, and the combined load sensing scheme provides the possibility of variables for the gear pump, which means that the original clear boundary between the gear pump and the plunger pump has become increasingly blurred. One of the decisive factors in the reasonable selection of hydraulic pump scheme is the cost of the whole system. Compared with expensive plunger pump, gear pump has become a practical choice in many applications because of its low cost, simple circuit and low filtration requirements