The speed regulation of the hydraulic cylinder is an important part of the hydraulic system, which is mainly achieved through the following methods.
1. Throttling speed regulation
Throttling speed regulation is one of the most common methods. It is based on installing a throttle valve in the hydraulic circuit to control the flow, thereby regulating the speed of the hydraulic cylinder. In the quantitative pump oil supply system, before the pressure oil enters the hydraulic cylinder, the throttling effect of the throttle valve changes the flow into the hydraulic cylinder. The throttle valve controls the flow rate by changing the flow cross-sectional area of the valve port. For example, when the valve port opening of the throttle valve becomes smaller, the resistance of the oil passing through increases, the amount of oil entering the hydraulic cylinder per unit time decreases, and the piston movement speed of the hydraulic cylinder will decrease; conversely, when the valve port opening increases, the piston movement speed increases.
Throttling speed regulation can be divided into oil inlet throttling speed regulation, oil return throttling speed regulation and bypass throttling speed regulation. Inlet throttling speed control is to install the throttle valve on the oil inlet line of the hydraulic cylinder, while return throttling speed control is to install the throttle valve on the oil return line. These two methods have their own characteristics in terms of speed stability, load capacity and power loss. Bypass throttling speed control is to install the throttle valve on the bypass oil line in parallel with the hydraulic cylinder, and indirectly control the flow entering the hydraulic cylinder by adjusting the flow of the bypass oil line. However, this method is relatively poor in speed-load characteristics, but the power loss is low.
2. Volumetric speed control
Volume speed control mainly adjusts the speed of the hydraulic cylinder by changing the displacement of the hydraulic pump or hydraulic motor. In the volumetric speed control system of variable pump-fixed motor (or hydraulic cylinder), the flow output to the hydraulic cylinder can be changed by changing the displacement of the variable pump. For example, in some large-scale engineering machinery, when the hydraulic cylinder needs to be extended or retracted quickly, the displacement of the pump is increased by adjusting the angle of the swash plate of the variable pump, thereby providing more flow for the hydraulic cylinder and accelerating the piston movement speed.
The advantages of volumetric speed regulation are high efficiency and low heat generation, and it is suitable for high-power hydraulic systems. It can also be divided into multiple forms such as variable pump-fixed hydraulic cylinder, fixed pump-variable motor and variable pump-variable motor, each of which has its applicable working scene and performance characteristics.
3. Combined speed regulation
Combined speed regulation is a speed regulation method that combines throttling speed regulation and volumetric speed regulation. This method combines the simplicity of throttling speed regulation and the high efficiency of volumetric speed regulation. For example, in some equipment that requires both speed regulation accuracy and efficiency, the speed of the hydraulic cylinder is first roughly adjusted by volumetric speed regulation, and then fine-tuned by throttling speed regulation, so as to reduce the power loss of the system while meeting the speed regulation accuracy and improve the performance of the entire hydraulic system.
