How to Improve the Performance of Gear Pump?

A Feasible Circuit to Improve the Performance of Gear Oil Pump

Gear oil pump belongs to hydraulic parts, because of the structure of the fixed displacement, it is usually considered that the gear pump can only be used as a constant flow hydraulic source.

The direct installation of the control valve on the pump can eliminate the pipeline between the pump and the direction valve, thus controlling the cost. Fewer fittings and connectors reduce leakage and improve reliability. And the pump itself installed valve can reduce the circulation pressure of the loop, improve its performance. The following are some circuits that can improve the basic function of the gear pump. Some of them are proven basic circuits, while some are innovative research.

Unloading Loop

The unloading element will be combined in the high flow pump with the low power single pump. The fluid from the two gear oil pumps is limited by the structure of the fixed displacement. It is usually considered that the gear pump can only be used as a constant flow hydraulic source. Gear oil pump can only be used as constant flow hydraulic source because of the structure limitation of constant displacement. However, the accessory and threaded combination valve solution is effective in improving its function, reducing system cost and improving system reliability, so that the performance of the gear pump can approach that of the expensive and complex plunger pump. At this point, the high-flow pump circulates the flow from its outlet to the inlet, thereby reducing the output flow of the pump to the system, that is, the pump power is reduced to slightly higher than the value required for the high-pressure part of the operation. The percentage of flow reduction depends on the proportion of ununloaded displacement to total displacement at this time. Combination or threaded unload valves reduce or eliminate piping, orifices, fittings, and other possible leaks.

The simplest offloading element is manually operated. The spring enables the unloading valve to be switched on or off. When a control signal is given to the valve, the on-off state of the valve is switched. A lever or other mechanical mechanism is the easiest way to operate such a valve.

Pilot-controlled (pneumatic or hydraulic) discharge valves are an improvement on handling because they can be controlled remotely. Its greatest advance is the use of electrical or electronic switch controlled solenoid valve, which can be controlled not only remotely but also automatically by microcomputer, this simple unloading technique is generally considered to be the best case for application.

Manually operated unloading components are often used in circuits that require large flow rates for fast action and large flow rates for fast action and reduced flow rates for precise control, such as fast telescopic boom circuits. When the unloading valve of the loop has no operation signal, the loop always outputs large flow. For normally open valves, the loop will output a small flow under normal conditions.

Pressure sensing unloading valve

Pressure sensing offloading valves are the most common solution. The spring action puts the unloading valve in its high flow position. When the loop pressure reaches the pre-set value of the relief valve, the relief valve opens and the unloading valve switches to its low flow position under the action of hydraulic pressure. The pressure sensing unloading circuit is mainly used for the hydraulic cylinder which needs fast speed in the stroke and high pressure and low speed at the end of the stroke. The pressure sensing offloading valve base is basically an automatic offloading component that achieves system pressure - off. It is commonly used in log splitters and hydraulic vises.

The unloading valve in the flow sensing unloading loop is also pressed to the high flow position by a spring. The fixed orifice size in the valve is determined by the flow required for the engine optimum speed of the equipment. If the engine speed is outside this optimal range, the throttle hole pressure drop will increase, thereby shifting the unloading valve to a low-flow position. Therefore, the adjacent components of the large flow pump can be made to the maximum flow throttling size, so the loop has less energy consumption, stable work and low cost. Typical applications of such loops are to limit the loop flow to an optimal range to improve overall system performance, or to limit the loop pressure during high speeds. Often used in garbage trucks, etc.

The unloading valve of the pressure-flow sensing unloading loop is also pressed to the position of large flow by the spring, and will be unloaded no matter it reaches the predetermined pressure or flow. The equipment can complete high pressure work at idling or normal working speed. This feature reduces unnecessary flow and therefore reduces the required power. Because this circuit has a wide range of load and speed variation, it is often used in mining equipment.

The pressure sensing unloading circuit with power synthesis consists of two sets of slightly changed pressure sensing unloading pumps, which are driven by the same prime mover. Each pump receives the pilot and control unloading signal of the other unloading pump. This type of sensing, called interactive sensing, allows one set of pumps to operate under high pressure and another set of pumps to operate under high flow. Two relief valves can be adjusted to the particular pressure of each loop to allow one or two pumps to be unloaded. This scheme reduces the power demand, so small capacity and cheap prime movers can be used.

Load sensing unloading loop. When there is no load sensing signal in the control chamber (lower chamber) of the main control valve, all the flow of the pump is discharged back to the tank through valve 1 and valve 2; When the load sensing signal is applied to the control valve, the pump supplies liquid to the circuit; When the output pressure of the pump exceeds the predetermined pressure value of the load sensing valve, the pump only provides working flow to the circuit, and the excess flow is bypassed back to the tank through the throttle position of valve 2.

Compared with the piston pump, the gear pump with load sensing element has the advantages of low cost, strong anti-pollution ability and low maintenance requirement.