Secondary relief valve, hydraulic system for crane fall and crane

Abstract

The invention provides a secondary overflow valve, a crane hydraulic system and a crane. The secondary overflow valve includes a valve body, a valve core and a pressure regulating device. Pressure spring and pressure regulating plug, one end of the primary pressure regulating spring presses against the end of the valve core, and the other end presses against the pressure regulating plug, the pressure regulating device also includes a secondary pressure regulating spring, the secondary pressure regulating spring The diameter and length of the spring are smaller than the primary pressure regulating spring, and the stiffness coefficient is greater than that of the primary pressure regulating spring. The pressure and flow relationship of the two-stage relief valve of the present invention has two states. When it is applied to the hydraulic system of crane hydraulic system, it can make the crane hydraulic system have two kinds of control of self-weight and power. When the falling speed is low, the self-weight falling method can be used to achieve good falling control performance. If the falling speed needs to be accelerated, the flow rate can be increased through the gas pedal to realize the power falling and increase the falling speed.

Description

technical field [0001] The invention relates to the field of hydraulic pressure, in particular to a secondary relief valve, a crane hydraulic system and a crane. Background technique [0002] There are two main types of existing crane hydraulic systems. One is the power drop system, that is, the rod cavity of the luffing cylinder enters the pressure oil, and the luffing cylinder is driven by hydraulic pressure to retract to realize the drop action. This method can control the falling speed, but because the volume of the rod cavity is small, and the flow of pressure oil connected is relatively large, so the fretting performance of this method is not good. jitter. The other is the self-weight drop system, and the rod chamber of the luffing cylinder is connected to the oil circuit, and the oil in the rodless chamber of the luffing cylinder returns to the oil under the self-weight of the boom and the load to realize the drop action. The falling speed of this method is stable,...

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Problems solved by technology

The falling speed of this method is stable, but its falling speed is greatly affected by factors such as the hanging load, the extension angle of the boom, and the lubrication of the hinge point. The above-mentioned factors are different, and the falling speed will also be different, so it is not easy to control

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