Construction machine pump-controlled hydraulic system and control method thereof

Abstract

The application discloses an engineering machine pump-controlled hydraulic system, which comprises an oil tank, a variable pump assembly, an overflow valve, at least two sets of hydraulic executing devices, a hydraulic executing part, a proportional reversing valve, a one-way valve, a first pressure sensor, a first valve and a control device, wherein the oil inlet of the one-way valve is connected with the third oil port, the third oil port and the second oil port of the proportional reversing valve at the first valve position, the third valve position and the second valve position of the proportional reversing valve respectively; the oil inlet of the first pressure sensor detects the oil inlet of the one-way valve; the oil inlet and the oil outlet of the first valve are connected with the variable pump assembly and the oil tank respectively; the first valve comprises a first elastic control end and a first hydraulic control port, which make the valve body of the first valve tend to be closed, the first hydraulic control port is connected with the oil outlet of the one-way valve, the first valve further comprises a second hydraulic control port, which provides the hydraulic oil pressure for moving the valve body of the first valve to the direction of opening the communication channel between the oil inlet and the oil outlet, the second hydraulic control port of the first valve is communicated with the oil inlet of the first valve.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydraulic control of engineering machinery, and in particular to a pump-controlled hydraulic system of engineering machinery and a control method thereof. BACKGROUND

[0002] On engineering machinery products, such as cranes, truck-mounted cranes, pump trucks, fire trucks, etc., pump-controlled hydraulic systems with hydraulic cylinders or motors and other hydraulic actuators are used. In the field of hydraulic technology, the speed control mode of a hydraulic system is usually divided into throttle speed control and displacement speed control. The throttle speed control has the advantages of system stability and reliability and good control performance, but has the disadvantages of large throttling pressure loss and high energy consumption. The displacement speed control system mostly uses a proportional variable pump assembly to output different flow rates by changing the pump displacement, without a valve port throttling link, directly adjusting the speed of the actuator, and has the advantages of high efficiency and low energy consumption, but is less stable than the throttle speed control system in heavy load and low speed working conditions. SUMMARY

[0003] The purpose of the present application is to provide a pump-controlled hydraulic system of engineering machinery that can realize both displacement speed control and throttle speed control.

[0004] The present application discloses a pump-controlled hydraulic system of engineering machinery, comprising:

[0005] an oil tank;

[0006] a variable pump assembly;

[0007] an overflow valve connected between the variable pump assembly and the oil tank;

[0008] at least two sets of hydraulic actuators, the hydraulic actuators comprising:

[0009] a hydraulic actuator comprising a first working oil port and a second working oil port for controlling different actuation actions;

[0010] a proportional directional valve comprising a first oil port and a second oil port connected to the variable pump assembly and the oil tank, respectively, the proportional directional valve further comprising a third oil port and a fourth oil port connected to the first working oil port and the second working oil port of the hydraulic actuator, respectively, the proportional directional valve having a first valve position, a second valve position, and a third valve position; in the first valve position, the first oil port and the third oil port are in communication, and the second oil port and the fourth oil port are in communication; in the second valve position, the first oil port and the fourth oil port are in communication, and the second oil port and the third oil port are in communication; in the third valve position, the second oil port, the third oil port, and the fourth oil port are all in communication, and the first oil port is not in communication with the second oil port;

[0011] a one-way valve, an inlet of the one-way valve is connected with the third oil port of the proportional directional valve, at the second valve position of the proportional directional valve, the inlet of the one-way valve is connected with the second oil port of the proportional directional valve;

[0012] a first pressure sensor for detecting the pressure of the inlet of the one-way valve;

[0013] a first valve, an inlet and an outlet of the first valve are connected with the variable pump assembly and the oil tank respectively, the first valve comprises a first elastic control port for providing an elastic force for moving the valve body of the first valve to a direction of closing the communication passage between the inlet and the outlet of the first valve and a first hydraulic control port, the first hydraulic control port is connected with the outlet of the one-way valve, the first valve further comprises a second hydraulic control port for providing a hydraulic oil pressure for moving the valve body of the first valve to a direction of opening the communication passage between the inlet and the outlet of the first valve, the second hydraulic control port of the first valve is communicated with the inlet of the first valve;

[0014] a control device, the control device is connected with the proportional directional valve, the first pressure sensor and the variable pump assembly for controlling the actions of the proportional directional valve, the first pressure sensor and the variable pump assembly.

[0015] In some embodiments, further comprising a first throttle valve arranged between the outlet of the one-way valve and the first hydraulic control port and further comprising a second throttle valve connected between the first throttle valve and the first hydraulic control port and the oil tank.

[0016] In some embodiments, further comprising a second pressure sensor connected with the control device for detecting the pressure of the first oil port of the proportional directional valve.

[0017] In some embodiments, the at least two sets of hydraulic actuators include a heavy load hydraulic actuator, a hydraulic actuating element of the heavy load hydraulic actuator includes a heavy load lifting actuating element for lifting a heavy load, a first working oil port of the heavy load lifting actuating element is used for connecting to hydraulic oil to lift the heavy load, a second working oil port of the heavy load lifting actuating element is used for connecting to hydraulic oil to lower the heavy load, the heavy load hydraulic actuator further includes a second valve connected between the heavy load lifting actuating element and a proportional directional valve of the heavy load hydraulic actuator, a first valve port of the second valve is connected with a third oil port of the proportional directional valve of the heavy load hydraulic actuator, a second valve port of the second valve is connected with the first working oil port of the heavy load lifting actuating element, the second valve has two valve positions, in a first valve position of the second valve, the second valve port and the first valve port of the second valve are connected through an internal one-way valve, the second valve port of the second valve is connected with an oil outlet of the internal one-way valve, the first valve port of the second valve is connected with an oil inlet of the internal one-way valve, in a second valve position of the second valve, the second valve port and the first valve port of the second valve are connected through an internal throttle valve, the second valve further includes a second elastic control end for moving a valve body of the second valve to a position where the second valve is switched to the first valve position and an oil control port for moving the valve body of the second valve to a position where the second valve is switched to the second valve position, the oil control port is connected with the second working oil port, during switching of the second valve to the second valve position, a flow area of the internal throttle valve gradually increases.

[0018] In some embodiments, further comprising a rotational speed sensor connected with the control device for detecting a rotational speed of the variable pump assembly and a swing angle sensor for detecting a displacement of the variable pump assembly.

[0019] The second aspect of the present application discloses a control method for the engineering machinery pump-controlled hydraulic system, comprising:

[0020] When only a hydraulic actuating element of one set of hydraulic actuators is in action and proportional directional valves of the remaining hydraulic actuators are all in the third valve position, an action speed of the hydraulic actuating element in action is calculated according to a detection result of the first pressure sensor of the remaining hydraulic actuators;

[0021] When only a hydraulic actuating element of one set of hydraulic actuators is in action, a proportional directional valve of the hydraulic actuator where the hydraulic actuating element is located is switched to the third valve position, and a pressure difference between an oil inlet and an oil outlet of the proportional directional valve is greater than an opening pressure difference of the first valve, the variable pump assembly is unloaded by using the opening of the first valve;

[0022] When hydraulic actuating elements of multiple sets of the hydraulic actuators are in action and the first valve is opened, a pressure difference between oil inlets and oil outlets of proportional directional valves of the multiple sets of the hydraulic actuators is maintained constant by using the first valve.

[0023] In some embodiments, the construction machinery pump-controlled hydraulic system further comprises a second pressure sensor connected to the control device for detecting the pressure of the first oil port of the proportional directional valve, and the control method further comprises calculating the action speed of the hydraulic actuator of each hydraulic actuator according to the detection results of the second pressure sensor and the first pressure sensor of each hydraulic actuator.

[0024] In some embodiments, the method further comprises: when the hydraulic actuator of the hydraulic actuator performs action on light load, using the construction machinery pump-controlled hydraulic system to volume-regulate the action of the hydraulic actuator, detecting the rotation speed and displacement of the variable pump assembly, and calculating the action speed of the hydraulic actuator according to the detection results of the detected rotation speed and displacement of the variable pump assembly.

[0025] Based on the construction machinery pump-controlled hydraulic system provided by the present application, by setting the first valve, when the hydraulic actuator of a single set of hydraulic actuators drives light load to act, the volume-regulation of the load can be realized by changing the output flow of the variable pump assembly, when the hydraulic actuators of multiple sets of hydraulic actuators simultaneously drive the load to act, the output flow of the variable pump assembly can be adjusted to make the oil inlet and oil outlet of the first valve communicate, so as to maintain the pressure difference between the oil inlet and oil outlet of the proportional directional valve of each hydraulic actuator constant, and the action speed of each hydraulic actuator is proportional to the opening area between the oil inlet and oil outlet of the proportional directional valve, so that proportional speed regulation can be realized by the proportional directional valve. At the same time, since the first pressure sensor is provided, when the hydraulic actuator of a single set of hydraulic actuators drives the load to act, the action speed of the acting hydraulic actuator can be calculated by combining the detection results of the first pressure sensor of other hydraulic actuators with the size data of the oil return pipeline, so that the control device can accurately control the action speed of the hydraulic actuator according to the calculation results.

[0026] Other features and advantages of the present application will become apparent from the following detailed description of illustrative embodiments thereof, which proceeds with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings described herein are intended to provide further understanding of the present application, and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0028] Figure 1 The hydraulic structure principle schematic diagram of the construction machinery pump-controlled hydraulic system of the embodiments of the present application;

[0029] Figure 2 is Figure 1A partial enlarged view of the hydraulic structure of the construction machine pump-controlled hydraulic system. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. The following description of at least one exemplary embodiment is merely illustrative in nature and not intended to limit the present application and its applications or uses in any way. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application.

[0031] Unless specifically stated otherwise, the relative arrangements of parts and steps, numerical expressions, and numerical values set forth in the various examples herein are not limiting but merely exemplary. Also, it is to be understood that the various embodiments can be utilized in different combinations, and that the illustrations are merely for purposes of clarity and that each component can be used or combined in other examples outside the scope of the claims. It will be apparent to those skilled in the art that the technology can be practiced without necessarily being limited to the details of the above-described embodiments, that the technology can be practiced with combinations of the embodiments, and that the technology is capable of many arrangements and embodiments. The above description is merely illustrative of the applications and not restrictive.

[0032] In the description of the present application, it needs to be understood that the use of the words "first", "second", and the like words of similar meaning to define parts are only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0033] In the description of the present application, it needs to be explained that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0034] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0035] like Figure 1 and Figure 2 As shown, the hydraulic pump control system for engineering machinery in this embodiment includes an oil tank, a variable pump assembly 4, an overflow valve 7.1, at least two sets of hydraulic actuators, a first valve 7.2, and a control device 6.

[0036] In the embodiment shown in the figure, the hydraulic oil pumping device includes a drive motor 1, a variable pump assembly 4, and a fixed displacement pump 5 that rotates coaxially with the variable pump assembly 4. The variable pump assembly 4 includes a variable pump body 4.1, a pump variable small plunger cylinder 4.5 for adjusting the displacement of the variable pump, a pump variable large plunger cylinder 4.6, a pump control electro-proportional control valve 4.4 for controlling the flow of hydraulic oil into the pump variable small plunger cylinder 4.5 and the pump variable large plunger cylinder 4.6, a shuttle valve 4.2 whose inlet is connected to the fixed displacement pump 5 and the variable pump body 4.1 respectively and whose outlet is connected to the pump control electro-proportional control valve 4.4, and an oil filter device 4.3 connected between the shuttle valve 4.2 and the pump control electro-proportional control valve 4.4. The function of shuttle valve 4.2 is to introduce pilot pressure oil to the variable displacement mechanism of the variable pump body. In this way, when the outlet pressure of the variable pump body 4.1 is ≤14 bar, the hydraulic oil output by the fixed displacement pump 5 can be delivered to the variable displacement mechanism of the variable pump body, so that the variable pump body 4.1 can perform variable displacement normally.

[0037] The overflow valve 7.1 is connected between the variable pump assembly 4 and the oil tank.

[0038] Hydraulic actuators are used to perform actions such as moving loads and lifting loads. A hydraulic actuator includes a hydraulic actuator, a proportional directional valve, a check valve, and a first pressure sensor 8.1.

[0039] The hydraulic actuator includes a first working oil port b1 and a second working oil port b2 for controlling different actuation actions. The hydraulic actuator includes hydraulic cylinder, hydraulic motor and other hydraulic actuating devices. The proportional directional valve includes a first oil port and a second oil port connected with the variable pump assembly 4 and the tank respectively, and the proportional directional valve further includes a third oil port and a fourth oil port connected with the first working oil port b1 and the second working oil port b2 of the hydraulic actuator respectively. The proportional directional valve has a first valve position, a second valve position and a third valve position; in the first valve position of the proportional valve, the first oil port and the third oil port are communicated, and the second oil port and the fourth oil port are communicated; in the second valve position of the proportional valve, the first oil port and the fourth oil port are communicated, and the second oil port and the third oil port are communicated; in the third valve position of the proportional valve, the second oil port, the third oil port and the fourth oil port are all communicated, and the first oil port is not communicated with the second oil port. The check valve, in the first valve position and the third valve position of the proportional directional valve, the inlet of the check valve is connected with the third oil port of the proportional directional valve, and in the second valve position of the proportional directional valve, the inlet of the check valve is connected with the second oil port of the proportional directional valve; the first pressure sensor 8.1 is used for detecting the pressure of the inlet of the check valve. In the embodiment as shown in the figure, two sets of hydraulic actuating devices are included, the hydraulic actuators of the two sets of hydraulic actuating devices are respectively the telescopic cylinder 11 and the bidirectional motor 9, the proportional directional valves of the two sets of hydraulic actuating devices are respectively the first electromagnetic proportional directional valve 7.5 and the second electromagnetic proportional directional valve 7.7, and the check valves of the two sets of hydraulic actuating devices are respectively the first check valve 7.4 and the second check valve 7.6.

[0040] The inlet and the outlet of the first valve 7.2 are connected with the variable pump assembly 4 and the tank respectively, the first valve 7.2 includes a first elastic control end and a first hydraulic control port a1. The first elastic control end provides an elastic force for moving the valve body of the first valve 7.2 to a direction of closing the communication passage between the inlet and the outlet of the first valve 7.2, and the first hydraulic control port a1 provides a hydraulic oil pressure for moving the valve body of the first valve 7.2 to a direction of closing the communication passage between the inlet and the outlet of the first valve 7.2. The first hydraulic control port a1 is connected with the outlet of the check valve of the hydraulic actuating device, and the first valve 7.2 further includes a second hydraulic control port a2. The second hydraulic control port a2 provides a hydraulic oil pressure for moving the valve body of the first valve 7.2 to a direction of opening the communication passage between the inlet and the outlet of the first valve 7.2, and the second hydraulic control port a2 of the first valve 7.2 is communicated with the inlet of the first valve 7.2.

[0041] The control device 6 is signal connected with the proportional directional valve, the first pressure sensor 8.1 and the variable pump assembly 4, and the control device 6 is used for controlling the actions of the proportional directional valve, the first pressure sensor 8.1 and the variable pump assembly 4.

[0042] The construction machinery pump-controlled hydraulic system of the embodiment can realize the advantages of high efficiency and low energy consumption when only one hydraulic actuator of at least two sets of hydraulic actuators is in action, for example, driving a light load. At this time, the first valve 7.2 is not opened, that is, the oil inlet and outlet of the first valve 7.2 are not communicated, and the volumetric speed of the load can be adjusted by changing the output flow of the variable pump assembly 4. When the hydraulic actuators of multiple sets of hydraulic actuators are in action at the same time, the output flow of the variable pump assembly 4 can be adjusted to make the oil inlet and outlet of the first valve 7.2 communicated, so as to maintain the constant pressure difference between the oil inlet and outlet of the proportional directional valve of each hydraulic actuator. The action speed of each hydraulic actuator is proportional to the opening area between the oil inlet and outlet of the proportional directional valve, so that proportional speed regulation can be realized by the proportional directional valve, and the system is stable and reliable, and has good control performance. At the same time, since the first pressure sensor 8.1 is arranged, when the hydraulic actuator of a single set of hydraulic actuators is in action, the action speed of the hydraulic actuator can be calculated by combining the detection result of the first pressure sensor 8.1 of the other hydraulic actuators with the size data of the oil return pipeline. For example, a back pressure valve is arranged on the oil return pipeline leading to the oil tank. Since the proportional directional valve of the non-acting hydraulic actuator is in the third valve position, the detection result of the first pressure sensor of the non-acting hydraulic actuator is the return oil pressure of the hydraulic actuator of the acting hydraulic actuator, which is also the pressure difference on both sides of the throttle of the back pressure valve. According to the size of the throttle flow area of the back pressure valve, the return flow can be calculated according to the structure size of the back pressure valve combined with the throttle flow formula, so that the action speed of the acting hydraulic actuator can be obtained according to the structure size data of the acting hydraulic actuator (such as the piston area of the hydraulic cylinder). Therefore, the control device 6 can accurately control the action speed of the hydraulic actuator according to the calculation result.

[0043] In some embodiments, as shown in Figure 1 and Figure 2 The construction machinery pump-controlled hydraulic system further comprises a first throttle valve 7.8 arranged between the oil outlet of the check valve and the first hydraulic control port a1, and a second throttle valve 7.3 connected between the first throttle valve and the oil tank. Through the arrangement, the oil circuit where the check valve is arranged can be unloaded when the construction machinery pump-controlled hydraulic system is not working.

[0044] In some embodiments, the working machine pump-controlled hydraulic system further comprises a second pressure sensor 8.2 connected to the control device 6 for detecting the pressure of the first oil port of the proportional directional valve. The second pressure sensor is arranged to detect the pressure of the first oil port of the proportional directional valve of each hydraulic actuator, and in combination with the detection result of the first pressure sensor 8.1, the pressure difference between the inlet and outlet of each proportional directional valve can be obtained, and in combination with the structural size data of each proportional directional valve, the flow rate of the hydraulic oil to each hydraulic actuator of each proportional directional valve can be calculated according to the orifice flow formula, and thus the action speed of the hydraulic actuator of each hydraulic actuator can be calculated.

[0045] In some embodiments, the proportional directional valve, the second valve, and the overflow valve of each hydraulic actuator are integrated into a multi-way valve 7, the multi-way valve 7 is provided with a Ls1 port, a Ls2 port, and the like connected to the first pressure sensor, the multi-way valve 7 is provided with an Mp port connected to the second pressure sensor 8.2, the multi-way valve 7 is provided with a P port connected to the variable pump assembly, and the multi-way valve 7 is provided with a T port connected to the oil tank.

[0046] In some embodiments, the at least two sets of hydraulic actuators include a heavy load hydraulic actuator, the hydraulic actuating element of the heavy load hydraulic actuator includes a heavy load lifting actuating element for lifting a heavy load, the first working oil port b1 of the heavy load lifting actuating element is used for inputting hydraulic oil to lift the heavy load, the second working oil port b2 of the heavy load lifting actuating element is used for inputting hydraulic oil to lower the heavy load, the heavy load hydraulic actuator further includes a second valve 10 connected between the heavy load lifting actuating element and the proportional directional valve of the heavy load hydraulic actuator, the first valve port of the second valve 10 is connected with the third oil port of the proportional directional valve of the heavy load hydraulic actuator, the second valve port of the second valve 10 is connected with the first working oil port b1 of the heavy load lifting actuating element, the second valve 10 has two valve positions, in the first valve position of the second valve 10, the second valve port and the first valve port of the second valve 10 are connected through an internal one-way valve 10.1, the second valve port of the second valve 10 is connected with the oil outlet of the internal one-way valve 10.1, the first valve port of the second valve 10 is connected with the oil inlet of the internal one-way valve 10.1, in the second valve position of the second valve 10, the second valve port and the first valve port of the second valve 10 are connected through an internal throttle valve 10.2, the second valve 10 further includes a second elastic control end for moving the valve body of the second valve 10 to the first valve position and an oil control port for moving the valve body of the second valve 10 to the second valve position, the oil control port is connected with the second working oil port b2, and the flow area of the internal throttle valve 10.2 gradually increases during the switching of the second valve 10 to the second valve position. The internal one-way valve 10.1 and the internal throttle valve 10.2 can be separate valve assemblies in the second valve 10 or integrated structures capable of achieving the same function. In the embodiment, when the heavy load lifting actuating element is used to lift the heavy load, the hydraulic oil output by the proportional directional valve of the heavy load hydraulic actuator enters the second valve 10 through the first valve port of the second valve 10, at this time the second valve is in the first valve position, the hydraulic oil enters the internal one-way valve 10.1, and then flows out of the internal one-way valve 10.1, and then flows out of the second valve port of the second valve and enters the heavy load lifting actuating element through the first working oil port b1, in the embodiment shown in the figure, the heavy load lifting actuating element is a hydraulic oil cylinder, at this time the lifting speed of the heavy load can be smoothly controlled by adjusting the flow of the hydraulic oil entering the second valve 10 through the first valve port of the second valve 10. When the heavy load is lowered, the hydraulic oil output by the proportional directional valve of the heavy load hydraulic actuator directly enters the heavy load lifting actuating element through the second working oil port b2, and at the same time the hydraulic oil acts on the oil control port of the second valve, when the hydraulic oil pressure is small, the flow area of the internal throttle valve 10.2 is small, the second valve is closer to the first valve position, the hydraulic oil flowing out of the first working oil port b1 of the heavy load lifting actuating element enters the second valve through the second valve port of the second valve, and the hydraulic oil does not pass through or passes through a small amount of the second valve, at this time the lowering speed of the heavy load is slow.When the hydraulic oil pressure increases, the flow area of the internal throttle valve 10.2 increases at this time, the second valve is closer to the second valve position state, the hydraulic oil flowing out of the first working oil port b1 of the heavy load lifting actuator enters the second valve from the second valve port of the second valve, and then flows out from the first valve port of the second valve through the internal throttle valve 10.2 more quickly, that is, the heavy load descending speed is faster at this time, that is, the pressure of the hydraulic oil directly entering the heavy load lifting actuator through the second working oil port b2 from the proportional directional valve output of the heavy load hydraulic actuator can directly control the heavy load descending speed, and accurate and smooth control of the heavy load descending speed is realized.

[0047] In some embodiments, the construction machinery pump-controlled hydraulic system further comprises a rotating speed sensor 2 connected to the control device 6 for detecting the rotating speed of the variable pump assembly 4 and a swing angle sensor 3 for detecting the displacement of the variable pump assembly 4, and the swing angle sensor 3 can detect the displacement of the variable pump assembly 4 by detecting the swash plate swing angle of the variable pump body 4.1.

[0048] In some embodiments, the control device described above can be a general-purpose processor, a programmable logic controller (PLC), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component or any appropriate combination thereof for performing the functions described in the present application.

[0049] In some embodiments, a control method for the construction machinery pump-controlled hydraulic system described above is also disclosed, comprising:

[0050] When only the hydraulic actuator of one set of hydraulic actuator moves, and the proportional directional valves of the remaining hydraulic actuators are all in the third valve position, the moving speed of the moving hydraulic actuator is calculated according to the detection result of the first pressure sensor 8.1 of the remaining hydraulic actuators;

[0051] When only the hydraulic actuator of one set of hydraulic actuator moves, and the proportional directional valve of the hydraulic actuator moves to the third valve position and the pressure difference between the oil inlet and the oil outlet is greater than the opening pressure difference of the first valve 7.2, the variable pump assembly 4 is unloaded by the opening of the first valve 7.2;

[0052] When the hydraulic actuators of the multiple hydraulic actuators are operated and the first valve 7.2 is opened, the pressure difference between the inlet and outlet of the proportional directional valve of the multiple hydraulic actuators is maintained constant by the first valve 7.2.

[0053] In some embodiments, the construction machine pump-controlled hydraulic system further comprises a second pressure sensor 8.2 connected to the control device 6 for detecting the pressure of the first oil port of the proportional directional valve, and the control method further comprises calculating the operating speed of the hydraulic actuator of each hydraulic actuator according to the detection results of the second pressure sensor 8.2 and the first pressure sensor 8.1 of each hydraulic actuator.

[0054] In some embodiments, further comprising: when the hydraulic actuator of the hydraulic actuator operates on a light load, the operating volume of the hydraulic actuator is regulated by the construction machine pump-controlled hydraulic system, and the rotating speed and displacement of the variable pump assembly 4 are detected, and the operating speed of the hydraulic actuator is calculated according to the detection results of the detected rotating speed and displacement of the variable pump assembly 4.

[0055] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application claimed.

Claims

1. A pump controlled hydraulic system for a construction machine, characterized in that, The hydraulic system comprises: a tank; a variable pump assembly; an overflow valve connected between the variable pump assembly and the tank; at least two sets of hydraulic actuators, each of which comprises: a hydraulic actuator comprising a first working oil port and a second working oil port for controlling different actuation actions; a proportional directional valve comprising a first oil port and a second oil port connected to the variable pump assembly and the tank respectively, the proportional directional valve further comprising a third oil port and a fourth oil port connected to the first working oil port and the second working oil port of the hydraulic actuator respectively, the proportional directional valve having a first valve position, a second valve position and a third valve position; in the first valve position, the first oil port and the third oil port are in communication, and the second oil port and the fourth oil port are in communication; in the second valve position, the first oil port and the fourth oil port are in communication, and the second oil port and the third oil port are in communication; in the third valve position, the second oil port, the third oil port and the fourth oil port are all in communication, and the first oil port is not in communication with the second oil port; a check valve, in the first valve position and the third valve position of the proportional directional valve, the inlet of the check valve is connected to the third oil port of the proportional directional valve, and in the second valve position of the proportional directional valve, the inlet of the check valve is connected to the fourth oil port of the proportional directional valve; a first pressure sensor for detecting the pressure of the inlet of the check valve; a first valve, the inlet and the outlet of which are connected to the variable pump assembly and the tank respectively, the first valve comprising a first elastic control port providing elastic force for moving the valve body of the first valve in a direction tending to close the communication passage between the inlet and the outlet of the first valve, and a first hydraulic control port for hydraulic oil pressure, the first hydraulic control port being connected to the outlet of the check valve, the first valve further comprising a second hydraulic control port for hydraulic oil pressure, which provides hydraulic oil pressure for moving the valve body of the first valve in a direction tending to open the communication passage between the inlet and the outlet of the first valve, the second hydraulic control port of the first valve being in communication with the inlet of the first valve; a control device, which is signal connected to the proportional directional valve, the first pressure sensor and the variable pump assembly, and is used for controlling the actions of the proportional directional valve, the first pressure sensor and the variable pump assembly.

2. The work machine pump hydraulic system of claim 1, wherein, Further comprising a first throttle valve arranged between the outlet of the check valve and the first hydraulic control port, and a second throttle valve connected between the pipeline between the first throttle valve and the first hydraulic control port and the tank.

3. The construction machine pump control hydraulic system according to claim 1 or 2, characterized by, Further comprising a second pressure sensor signal connected to the control device, which is used for detecting the pressure of the first oil port of the proportional directional valve.

4. The work machine pump hydraulic system of claim 1, wherein, The at least two sets of hydraulic actuators include a heavy load hydraulic actuator, a hydraulic actuating element of the heavy load hydraulic actuator includes a heavy load lifting actuating element for lifting a heavy load, a first working oil port of the heavy load lifting actuating element is used for passing hydraulic oil to lift the heavy load, a second working oil port of the heavy load lifting actuating element is used for passing hydraulic oil to lower the heavy load, the heavy load hydraulic actuator further includes a second valve connected between the heavy load lifting actuating element and a proportional directional valve of the heavy load hydraulic actuator, a first valve port of the second valve is connected with a third oil port of the proportional directional valve of the heavy load hydraulic actuator, a second valve port of the second valve is connected with the first working oil port of the heavy load lifting actuating element, the second valve has two valve positions, in a first valve position of the second valve, the second valve port and the first valve port of the second valve are connected through an internal one-way valve, the second valve port of the second valve is connected with an oil outlet of the internal one-way valve, the first valve port of the second valve is connected with an oil inlet of the internal one-way valve, in a second valve position of the second valve, the second valve port and the first valve port of the second valve are connected through an internal throttle valve, the second valve further includes a second elastic control end for moving a valve body of the second valve to a position where the second valve is switched to the first valve position and an oil control port for moving the valve body of the second valve to a position where the second valve is switched to the second valve position, the oil control port is connected with the second working oil port, in the process of switching the second valve to the second valve position, a flow area of the internal throttle valve gradually increases.

5. The work machine pump control hydraulic system of claim 1, wherein, Further comprising a rotating speed sensor for detecting a rotating speed of the variable pump assembly and a swing angle sensor for detecting a displacement of the variable pump assembly, which are signal connected with the control device.

6. A control method for a pump-controlled hydraulic system of a working machine according to any one of claims 1 to 5, characterized in that, Further comprising: When only one hydraulic actuating element of one set of hydraulic actuators is in action and proportional directional valves of the remaining hydraulic actuators are all in the third valve position, an action speed of the hydraulic actuating element in action is calculated according to a detection result of the first pressure sensor of the remaining hydraulic actuators; When only one hydraulic actuating element of one set of hydraulic actuators is in action and a proportional directional valve of the hydraulic actuator where the hydraulic actuating element is located is switched to the third valve position and a pressure difference between an oil inlet and an oil outlet of the proportional directional valve is greater than an opening pressure difference of the first valve, the variable pump assembly is unloaded by using the opening of the first valve; When hydraulic actuating elements of multiple sets of hydraulic actuators are in action and the first valve is opened, a pressure difference between the oil inlets and the oil outlets of the proportional directional valves of the multiple sets of hydraulic actuators is maintained constant by using the first valve.

7. The control method of a construction machine pump hydraulic system according to Claim 6, characterized by, The construction machinery pump-controlled hydraulic system further comprises a second pressure sensor for detecting a pressure of the first oil port of the proportional directional valve, which is signal connected with the control device, and the control method further comprises calculating an action speed of a hydraulic actuating element of each hydraulic actuator according to detection results of the second pressure sensor and the first pressure sensor of each hydraulic actuator.

8. The control method of a construction machine pump hydraulic system according to claim 7, characterized by, Further comprising: When the hydraulic actuator of the hydraulic actuating device acts on a light load, the action of the hydraulic actuator is volume-regulated by the working machine pump-controlled hydraulic system, the rotational speed and displacement of the variable pump assembly are detected, and the action speed of the hydraulic actuator is calculated according to the detection results of the detected rotational speed and displacement of the variable pump assembly.

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