Balanced valve, hydraulic cylinder expansion control loop and crane

Abstract

The invention provides balanced valve which comprises a main valve body (1) and a main valve core (4), wherein the main valve body (1) is provided with a positive oil outlet (A) and a reverse oil outlet (B); the main valve core (4) comprises a first acting surface (A1) and a second acting surface (A2) which are opposite to each other; the first acting surface is exposed in a first acting cavity (3) communicated with the reverse oil outlet; the second acting surface is exposed in a second acting cavity (17) communicated with the reverse oil outlet through a dumping groove (5); and the balanced valve further comprises a guiding control module which enables the second acting cavity to be selectively communicated with an oil draining port through a guiding control oil port (X). In addition, the invention also provides a hydraulic cylinder expansion control loop and a hydraulic crane. Due to the guiding control method, a large control ratio can be obtained through controlling the size of a guiding piston rod, the descending speed limitation control of the balanced valve is more sensitive, the influence of the load pressure on the openness of the main valve core is slight, frequent shaking can not be generated, the work stability is good, and the energy-saving effect is excellent.

Description

technical field [0001] The present invention relates to a balance valve, in particular to a balance valve. On this basis, the present invention also relates to a hydraulic cylinder expansion and contraction control circuit provided with the balance valve. Furthermore, the invention also relates to a crane. Background technique [0002] The balance valve is a valve widely used in construction machinery equipment, which plays an important role in improving the working performance of some hydraulic working mechanisms of construction machinery, such as the lifting mechanism, luffing mechanism and telescopic mechanism of hydraulic cranes. Typically, these working mechanisms use hydraulic cylinders as hydraulic actuators, and the hydraulic cylinders need to be telescopically controlled through the hydraulic cylinder telescopic control circuit, and the balance valve is generally set on the working oil circuit connected to the rodless chamber of the hydraulic cylinder. [0003] Wh...

AI Technical Summary

Problems solved by technology

Due to structural design reasons, this prior art balance valve has some insurmountable problems. For example, because D is determined by the flow capacity of the balance valve, this needs to be related to the working speed of the hydraulic working mechanism and the flow demand of the hydraulic actuator. and other factors, the hydraulic working mechanism selects a balance valve with matching flow capacity according to the application needs, so the size of D is relatively determined, and d belongs to the part of the control oil circuit, and it cannot be formed larger, otherwise it will lead to control oil flow. Insufficient quantity, difficult control and other defects, so the control ratio of the balance valve in the prior art is relatively large

In this case, although the balance valve can realize the function of descending speed limit in the process of descending speed limit, it is too sensitive to the change of load pressure. Once the load pressure changes slightly, the matching control oil pressure is required to change exponentially. Otherwise, the opening of the balance valve will change significantly, and during the working process of the hydraulic working mechanism, the load pressure often changes due to various reasons (especially in the hydraulic working mechanism using multi-stage telescopic cylinders), even if the load pressure Only slightly fluctuating, the opening of the balance valve will also change frequently, so that the balance valve in the prior art is easily affected by the load pressure, and is prone to frequent jitter and other unstable work; Relatively large, so the opening pressure of the balance valve is large when it realizes the function of descending speed limit, resulting in large power loss

Therefore, the opening of the balance valve of this prior art is easily affected by the load, and its controllability is poor. Even when the oil pressure of the pilot control oil port X is kept constant, it is still unable to maintain a stable opening of the balance valve.

[0010] It can be seen from the above description that the main disadvantages of the balance valve of the prior art are: first, due to the structural reasons of the balance valve, its control ratio is unreasonable, thus the controllability is poor, and the work is unstable, although it can realize the decline Speed ​​limit function, but the balance valve is too sensitive to the change of load pressure, prone to frequent vibration and other unstable work; second, the opening of the balance valve cannot be controlled relatively stably and reliably through the pilot control oil port X, even in light It is also difficult to achieve stable control when the load is high; thirdly, the control pressure is relatively high. In order to achieve a certain control ratio, the area of ​​the control oil action surface of the pilot piston 104 is often artificially formed to be larger, resulting in even less ideal control sensitivity. and high energy consumption

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