What is difference between variable vane pump and fix vane pump?

In the hydraulic transmission system, vane pumps are widely used due to their compact structure, smooth operation, and low noise. According to whether the displacement is adjustable, vane pumps can be classified as constant-displacement vane pumps and variable-displacement vane pumps. These two types of pumps have significant differences in structure, working principle, performance characteristics, and application scenarios. This article will systematically analyze their differences and discuss how to make reasonable selections.

Characteristics of the quantitative vane pump

Structure and working principle

The core structure of the quantitative vane pump includes the rotor, stator, vanes and the flow distributor. The inner surface of the stator is circular, and there is an eccentricity between the rotor and the stator. Under the action of centrifugal force and liquid pressure, the vanes closely adhere to the inner wall of the stator. As the rotor rotates, the sealed volume between the vanes changes periodically, achieving oil suction and oil pressure generation. Due to the fixed shape of the stator, the amount of oil discharged per revolution is constant, so it is called a quantitative pump.

Performance features

Fixed displacement: The output flow is solely determined by the rotational speed and cannot be adjusted.
Simple structure: Fewer components, lower manufacturing and maintenance costs.
High efficiency: The volumetric efficiency can reach over 90% under rated conditions.
Suitable for constant flow systems: Suitable for scenarios with stable flow requirements, such as machine tools, injection molding machines, etc.

Advantages:

• Low cost
• High reliability
• Low noise

Disadvantages:

• Unable to adapt to variable flow requirements. Excess flow needs to be discharged as overflow, which may lead to energy waste.

Characteristics of variable vane pumps

Structure and working principle

The stator of a variable vane pump is movable. By adjusting mechanisms (such as springs, hydraulic cylinders), the eccentricity between the rotor and the stator can be changed, thereby adjusting the pump’s displacement. When the eccentricity is zero, the pump outputs zero flow; as the eccentricity increases, the flow increases. Common variable methods include pressure compensation, load sensitivity, and manual adjustment, etc.

Performance Features

Variable Displacement:

The flow rate can be automatically or manually adjusted according to system requirements.
Energy-saving and High Efficiency: Reduces overflow losses and is suitable for variable flow systems.

Complex Control:

Requires the installation of variable mechanisms, such as pressure compensation valves, servo control, etc.
Fast Dynamic Response: Suitable for applications where the flow rate needs to be adjusted frequently.

Advantages and Disadvantages

Advantages: Energy-saving, adaptable, can reduce system heat generation.
Disadvantages: Complex structure, high cost, difficult maintenance.

Conclusion

Both the constant-flow vane pump and the variable-flow vane pump have their own advantages and disadvantages. When choosing, one needs to consider the system requirements, cost, and energy efficiency comprehensively. The constant-flow pump is suitable for simple systems with stable flow, while the variable-flow pump is more suitable for dynamic loads and high-energy-saving requirements. With the development of hydraulic technology, variable pumps are increasingly widely used in industrial automation, construction machinery, and other fields. In the future, intelligent variable control will become a trend.