Main control valve for construction machinery

Abstract

A main control valve for a construction machine includes: a valve housing; the main valve, the first load-sensitive overflow valve and the second load-sensitive overflow valve are integrated in the valve shell, and the main valve is at least provided with a first working oil port, a second working oil port and an oil return port; at a first working valve position of the main valve, the first working oil port is communicated with an oil inlet of the first load-sensitive overflow valve through a throttling channel in a valve element of the main valve, and an oil outlet of the first load-sensitive overflow valve is communicated with an oil return port through an overflow channel in a valve shell; at the second working valve position of the main valve, the second working oil port is communicated with the oil inlet of the second load-sensitive overflow valve through the throttling channel, and the oil outlet of the second load-sensitive overflow valve is communicated with the oil return port through the overflow channel; the first load-sensitive overflow valve, the second load-sensitive overflow valve, the first working oil port and the second working oil port are all arranged on the same side of the valve shell. The layout of the main control valve can be optimized.

Description

Technical Field

[0001] The present application relates to a main control valve for engineering machinery. Background Art

[0002] In construction machinery, such as aerial work vehicles and concrete tankers, the hydraulic system controls the main pump to supply hydraulic oil to the hydraulic actuator through the main control valve. The valve cores and corresponding channels of each valve in the main control valve are integrated into the valve housing. The main control valve is usually designed to include two working oil ports arranged in the valve housing and working oil port relief valves connected to the two working oil ports respectively. The working oil port relief valve is arranged on the upper side of the valve housing adjacent to the two working oil ports. The main control valve usually also includes an LS (load sensitive) relief valve, which is usually arranged at the lower side of the valve housing. This layout makes the main control valve complex to manufacture and difficult to install and maintain.

[0003] For some actuators, if the operating speed is not high or the hydraulic oil flow rate is not large, the hydraulic impact of the actuator side on the main control valve is not large. And considering that the hydraulic system usually needs to be equipped with a safety mechanism on the actuator side, such as a hydraulic lock or a balance valve, it is possible to consider canceling the working oil port overflow valve and redesigning the layout of the main control valve. Utility Model Content

[0004] The present application aims to provide a main control valve for engineering machinery, which eliminates the working oil port relief valve and thus can optimize the layout of the main control valve.

[0005] According to one aspect of the present application, a main control valve for an engineering machine is provided, comprising:

[0006] valve housing; and

[0007] A main valve, a first load-sensitive relief valve and a second load-sensitive relief valve integrated in the valve housing, wherein the main valve has at least a first working oil port, a second working oil port and an oil return port;

[0008] Wherein, in the first working valve position of the main valve, the first working oil port is communicated with the oil inlet of the first load-sensitive relief valve via a throttling channel in the valve core of the main valve, and the oil outlet of the first load-sensitive relief valve is communicated with the oil return port via an overflow channel in the valve housing; in the second working valve position of the main valve, the second working oil port is communicated with the oil inlet of the second load-sensitive relief valve via the throttling channel, and the oil outlet of the second load-sensitive relief valve is communicated with the oil return port via the overflow channel; the first load-sensitive relief valve, the second load-sensitive relief valve, the first working oil port, and the second working oil port are all arranged on the same side of the valve housing (preferably the upper side of the valve housing).

[0009] In one embodiment, the first load-sensing relief valve and the second load-sensing relief valve are respectively installed in the first load-sensing relief valve hole and the second load-sensing relief valve hole opened by the same side of the valve housing, and the first load-sensing relief valve hole and the second load-sensing relief valve hole and the first working oil port and the second working oil port are all open to the outside on the same side.

[0010] In one embodiment, the first load-sensing relief valve, the second load-sensing relief valve, the first working oil port, and the second working oil port are aligned with each other in the longitudinal direction of the valve housing.

[0011] In one embodiment, the distribution order of the first load-sensing relief valve and the second load-sensing relief valve in the longitudinal direction of the valve housing is the same as the distribution order of the first working oil port and the second working oil port in the longitudinal direction of the valve housing.

[0012] In one embodiment, the single relief passage connects the oil outlet of the first load-sensing relief valve and the oil outlet of the second load-sensing relief valve to the oil return port.

[0013] In one embodiment, the first load-sensing overflow valve and the second load-sensing overflow valve are arranged at different positions in the height direction of the valve housing, and the overflow channel is inclined relative to the longitudinal direction of the valve housing.

[0014] In one embodiment, the first load-sensing overflow valve and the second load-sensing overflow valve are arranged at the same position in the height direction of the valve housing, and the overflow channel is arranged parallel to the longitudinal direction of the valve housing.

[0015] In one embodiment, the main valve further has a load pressure sensing chamber formed in the valve housing, and the load pressure sensing chamber is communicated with the first working oil port and the second working oil port through the throttling channel.

[0016] In one embodiment, in the first working valve position of the main valve, the oil inlet of the first load-sensitive relief valve is connected to the load pressure sensing chamber; in the second working valve position of the main valve, the oil inlet of the second load-sensitive relief valve is connected to the load pressure sensing chamber.

[0017] In one embodiment, the main control valve also includes a compensating valve arranged in the valve housing, and the compensating valve is configured to adjust the amount of hydraulic oil delivered to the main valve through the compensating valve based on the output oil pressure of the main pump; the compensating valve has a spring chamber, and the spring chamber is connected to the load pressure sensing chamber through a compensation channel in the valve housing.

[0018] According to the main control valve for engineering machinery of the present application, the working oil port overflow valve associated with the working oil port is cancelled, and the load-sensitive overflow valve is arranged adjacent to the working oil port on the same side of the valve housing. The load-sensitive overflow valve combines the functions of the working oil port overflow valve in the prior art, and thus optimizes the layout of the main control valve, so that the main control valve has a more compact structure, reduces weight and cost, and is easy to manufacture and maintain. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The foregoing and other aspects of the present application will be more fully understood through the following detailed description made with reference to the accompanying drawings, in which:

[0020] Figure 1 It is a hydraulic circuit diagram of a feasible implementation of the main control valve of the engineering machinery according to the present application;

[0021] Figure 2 , Figure 3 They are the hydraulic symbol diagrams of the main valve and the compensating valve in the main control valve;

[0022] Figure 4 is a cross-sectional view showing the structure of the main control valve;

[0023] Figure 5 , Figure 6 It is a cross-sectional view showing the two working states of the main control valve. DETAILED DESCRIPTION

[0024] The present application generally relates to a main control valve (or main control valve assembly, main control valve module) in a hydraulic system suitable for construction machinery such as aerial work vehicles, concrete tankers, etc. The hydraulic system includes a main pump for supplying hydraulic oil to each hydraulic actuator of the construction machinery, and a plurality of main control valves for controlling the main pump to supply hydraulic oil to each hydraulic actuator. Each main control valve is usually integrated into a valve housing to form a module (valve block) type main control valve. The main control valves are assembled side by side to achieve the integration of the main control valves.

[0025] The main control valve of the present application is suitable for actuators with small hydraulic impact on the main control valve. For example, it can be limited to actuators with hydraulic oil flow less than 100L / min during operation. Of course, it can also be limited to actuators with operating speed (linear or rotational speed) less than a certain set speed value.

[0026] A hydraulic circuit diagram of an exemplary structure of the main control valve of the present application is shown in Figure 1 As shown in Figure 1 As shown, the main control valve includes a hydraulic passage formed in a common valve housing (not shown) and various hydraulic valves assembled in the valve housing.

[0027] The hydraulic channels in the main control valve include: an oil supply channel LP, used to receive hydraulic oil from a main pump (not shown); an oil return channel LT, used to return the hydraulic oil to the oil tank (not shown); a control pressure oil circuit LX, used to receive hydraulic oil from a control oil pump (not shown), and a control return oil circuit LY, which leads to the oil tank; an LS (load sensing) channel LLS, used to accept loads from each actuator and feed back the loads to the main control valve and the main pump to adjust the operation of the main control valve and the main pump.

[0028] The hydraulic valves in the main control valve include: main valve Vm, pressure compensation valve (hereinafter referred to as compensation valve) Vc, pilot valves Vma, Vmb, LS relief valves Va, Vb, and selection valve Vs.

[0029] The pilot valves Vma and Vmb are connected to the control ends on both sides of the main valve Vm, and are used to output pilot oil pressure to the main valve Vm to control the valve core of the main valve Vm to move to a desired position (valve position) in the valve housing, and the valve core of the main valve Vm preferably has an adjustable stroke end. The control oil pressure of the pilot valves Vma and Vmb is taken from the control pressure oil circuit LX.

[0030] The hydraulic symbol of an exemplary configuration of the main valve Vm is shown in Figure 2 As shown in the figure, the main valve Vm is a three-position seven-way valve, having an intermediate valve position, a first working valve position, and a second working valve position, and seven oil ports: P port, T port, A port, B port, C port, D port, and E port. Port A and port B are two working oil ports of the main control valve, port P is the oil inlet port, and port T is the oil return port. In the intermediate valve position of the main valve Vm, port A, port B, and port P are cut off, and port E is connected with port C, port D, and port T. In the first working valve position, port P is connected with port A, port B is connected with port T, port D is connected with port T, port C is connected with port E, and both are connected with port P through a throttling channel. In the second working valve position, port P is connected with port B, port A is connected with port T, port C is cut off, port D is connected with port E, and both are connected with port P through a throttling channel. Port E constitutes a load pressure sensing chamber.

[0031] The hydraulic symbol of an exemplary construction of the compensating valve Vc is shown in Figure 3 As shown in the figure, the compensation valve Vc is a three-position three-way valve, having a first working valve position, a second working valve position and a third working valve position, and three oil ports: Pc port, Ac port and Bc port. In the first working valve position, the Bc port is connected to the Pc port, and the Ac port is connected to the Pc port through a throttling channel. In the second working valve position, the Ac port is connected to the Bc port, and both are connected to the Pc port through a throttling channel. In the third working valve position, the Ac port is connected to the Bc port, and the Pc port is cut off.

[0032] The selector valve Vs is in the form of a shuttle valve, having two oil inlets and one oil outlet, wherein the first oil inlet is connected to the pressure collection section of the LS channel LLS, the second oil inlet is connected to the first control end of the compensation valve Vc, and the oil outlet is connected to the variable mechanism of the main pump or to the pressure collection section of the LS channel LLS in the downstream main control valve. The selector valve Vs is capable of transmitting the highest load pressure among multiple load pressures to the variable mechanism of the main pump so as to adjust the displacement of the main pump according to the highest load pressure.

[0033] The second control terminal of the compensating valve Vc is connected to its Bc port. The Pc port of the compensating valve Vc is connected to the oil supply passage LP, and the Ac port is connected to the P port of the main valve Vm.

[0034] The T port of the main valve Vm is connected to the oil return channel LT, the A port and the B port are respectively connected to the two oil ports of the actuator, the C port and the D port are respectively connected to the oil inlet ports of the LS relief valves Va and Vb, and the E port is connected to the second oil inlet port of the selection valve Vs, that is, to the first control end of the compensation valve Vc.

[0035] The oil outlets of the LS relief valves Va and Vb are connected to the oil return passage LT. The first and second oil ports of the pilot valve Vma are connected to the control pressure oil circuit LX and the control return oil circuit LY, respectively, and the third oil port is connected to the first control end of the main valve Vm. The first and second oil ports of the pilot valve Vmb are connected to the control pressure oil circuit LX and the control return oil circuit LY, respectively, and the third oil port is connected to the second control end of the main valve Vm. The valve positions of the pilot valves Vma and Vmb are controlled by a control device not shown to selectively transmit the oil pressure of the control pressure oil circuit LX to the two control ends of the main valve Vm through the first and third oil ports of the pilot valves Vma and Vmb, respectively, or to release the pressure of the two control ends of the main valve Vm to the control return oil circuit LY through the third and second oil ports of the pilot valves Vma and Vmb.

[0036] The pressure detection port M is connected to the E port of the main valve Vm, that is, connected to the second oil inlet port of the selector valve Vs.

[0037] The main control valve does not have a working oil port relief valve (or shock absorbing valve, secondary relief valve) associated with the two working oil ports, namely port A and port B. The present application modifies the main control valve, cancels the working oil port relief valve, and configures the load-sensitive relief valve to have the function of the working oil port relief valve, and thus the layout of the main control valve can be adjusted. An exemplary structure of the modified main control valve of the present application is as follows Figure 4 shown.

[0038] See also Figure 4 The valve housing of the main control valve includes: a valve housing body, referred to herein as a valve body 1; and a first valve cover 2 assembled at a first axial end (i.e. longitudinal direction, or length direction) of the valve body 1 and a second valve cover 3 assembled at a second axial end of the valve body 1.

[0039] Each valve of the main control valve is assembled in the valve housing. Specifically, a valve cavity of each valve is formed in the valve housing, and a valve core of each valve is installed in the corresponding valve cavity. The connecting channel between each valve can be formed by a channel formed in the valve cavity. The structure of each valve (especially the valve core and the corresponding valve cavity) in the present application can adopt a structure known in the art, which will not be described in detail here.

[0040] Continue to view Figure 4 The main body of the valve core of the main valve Vm is arranged in the valve body 1 along the axial direction, and the end spring is arranged in the spring cavity formed in the first valve cover 2. The two working oil ports of the main valve Vm, namely port A and port B, are opened on the upper surface of the valve body 1 along the vertical direction perpendicular to the axial direction.

[0041] The valve core of the compensation valve Vc is axially arranged in the valve body 1 in parallel with the valve core of the main valve Vm and is located below the valve core of the main valve Vm. The valve cores of the pilot valves Vma and Vmb are axially arranged in the first valve cover 2.

[0042] LS relief valves Va and Vb are arranged in corresponding LS relief valve holes opened in valve body 1. The LS relief valve hole is open to both port A and port B in the vertical upward direction. Such a configuration facilitates wiring (wires, hydraulic lines) for operators. The LS relief valve hole is located on the first axial side of port A and port B (i.e., the side close to the first valve cover 2). And optionally, the arrangement order of LS relief valves Va and Vb is the same as that of port A and port B, so as to facilitate identification and avoid wiring errors. Further optionally, LS relief valves Va, Vb, port A and port B are roughly aligned in the axial direction to further facilitate wiring of the main control valve.

[0043] The selector valve Vs is not shown in the figure, but it can be understood that it can be arranged in the valve body 1 or the first valve cover 2, close to the spring chamber of the compensation valve Vc.

[0044] It should be pointed out here that, depending on the actual installation direction of the main control valve, ports A and B may not be strictly opened in the vertical upward direction in actual applications. Therefore, in this application, it can be broadly defined as the two working oil ports of the main valve Vm, namely ports A and B, being opened on the first surface of the valve body 1 along the height direction of the valve shell, that is, ports A and B are opened outward along the height direction; ports A and B, LS relief valves Va and Vb are all arranged on the first side of the height direction of the main valve Vm, and the compensation valve Vc is arranged in the valve body 1 on the second side of the height direction of the main valve Vm. The height direction of the valve shell is perpendicular to the longitudinal direction (length direction) and thickness direction of the valve shell.

[0045] Continue to view Figure 4, a throttling channel L1 is formed in the valve core of the main valve Vm. The throttling channel L1 includes an axial inner hole, and a first radial through hole, a second radial through hole, and a radial throttling flow hole that are axially separated from each other and respectively connected to the axial inner hole and radially extend to the surface of the valve core. The throttling channel L1 formed by these through holes and the axial inner hole is used to achieve the connection between the corresponding oil ports of the main valve Vm in various valve positions (see the previous explanation). The first radial through hole and the second radial through hole are used to selectively disconnect and connect with the A port and the B port, respectively, and the radial throttling flow hole is connected with the E port. The specific structure of the valve core of the main valve Vm, especially the various oil grooves (undercut grooves) on the valve core and in the valve cavity, and the throttling channel L1 inside the valve core, are well known in the art in design and will not be repeated here.

[0046] In the valve body 1, the oil inlets of the LS relief valves Va and Vb are opened at the C port and the D port, respectively. The C port and the D port are formed on both sides of the axial direction of the E port. In the middle valve position of the main valve Vm, the oil inlets of the LS relief valves Va and Vb remain disconnected from the E port, and in the first and second valve positions of the main valve Vm, the oil inlets of the LS relief valves Va and Vb are connected to the E port, respectively.

[0047] Furthermore, in the valve body 1, a compensation passage L3 is provided for connecting the E port with the spring chamber of the compensation valve Vc.

[0048] In addition, in the valve body 1, a common and single overflow channel L2 is formed, which connects the oil outlets of the LS overflow valves Va and Vb to the T port. The overflow channel L2 can be formed by drilling a hole on the axial first side end face of the valve body 1 toward the T port (T chamber) in the valve body 1. As shown in the figure, the LS overflow valves Va and Vb can be set at different height positions (in the illustrated example, the position of the LS overflow valve Va is higher than that of the LS overflow valve Vb), so that their oil outlets are located at different height positions from each other. In this case, the overflow channel L2 is in the form of an inclined hole inclined relative to the axial direction so as to facilitate communication with the oil outlets of the LS overflow valves Va and Vb. However, the LS overflow valves Va and Vb can also be set at the same height position so that their oil outlets are located at the same height position from each other. In this case, the overflow channel L2 is in the form of a hole extending parallel to the axial direction.

[0049] Figure 4 The middle valve position of the main valve Vm is shown, at which the A port and the B port of the main valve Vm are both cut off relative to the P port, and no hydraulic oil from the main pump is output through the main control valve.

[0050] Figure 5The first working valve position of the main valve Vm is shown. At this time, the P port of the main valve Vm is connected to the A port, and the B port is connected to the T port, so that the hydraulic oil from the main pump is delivered to the actuator through the P port and the A port, and the hydraulic oil at the actuator returns to the oil tank through the B port and the T port. In addition, the E port is connected to the C port, so that the A port is connected to the oil inlet of the LS relief valve Va through the throttling channel L1, the E port, and the C port, and a part of the hydraulic oil in the A port enters the oil inlet of the LS relief valve Va. In addition, a part of the hydraulic oil in the A port enters the spring chamber (first control end) of the compensation valve Vc through the compensation channel L3. When the load pressure in the E port does not reach the opening pressure of the LS relief valve Va, the LS relief valve Va is closed. When the load pressure in the E port is higher than the opening pressure of the LS relief valve Va, the LS relief valve Va opens, so that the hydraulic oil in the C port flows through the LS relief valve Va into the overflow channel L2, and then enters the T port from the overflow channel L2 and returns to the oil tank. The flow of hydraulic oil in the main control valve is as follows Figure 4 As indicated by the arrow in .

[0051] Figure 5 The second working valve position of the main valve Vm is shown. At this time, the P port of the main valve Vm is connected to the B port, and the A port is connected to the T port, so that the hydraulic oil from the main pump is delivered to the actuator through the P port and the B port, and the hydraulic oil at the actuator returns to the oil tank through the A port and the T port. In addition, the E port is connected to the D port, so that the B port is connected to the oil inlet of the LS overflow valve Vb through the throttling channel L1, the E port, and the C port, and a part of the hydraulic oil in the B port enters the oil inlet of the LS overflow valve Vb. In addition, a part of the hydraulic oil in the B port enters the spring chamber (first control end) of the compensation valve Vc through the compensation channel L3. When the load pressure in the E port does not reach the opening pressure of the LS overflow valve Vb, the LS overflow valve Vb is closed. When the load pressure in the E port is higher than the opening pressure of the LS overflow valve Vb, the LS overflow valve Vb is opened, so that the hydraulic oil in the D port flows through the LS overflow valve Vb into the overflow channel L2, and then enters the T port from the overflow channel L2 and returns to the oil tank. The flow of hydraulic oil in the main control valve is as follows Figure 5 As indicated by the arrow in .

[0052] It can be seen that since the LS relief valves Va and Vb provide a relief function for the two working oil ports (port A and port B), the working oil port relief valves specially provided for the two working oil ports in the prior art can be eliminated.

[0053] Those skilled in the art can make various adaptive modifications to the structure of the main control valve described above according to specific applications. It should be noted that the specific structural design of various valves in the integrated valve module is well known and easy to implement by those skilled in the art, and will not be described in detail in this application.

[0054] For example, the oil port settings of the main valve Vm and the compensation valve Vc may be different from the forms described above, as long as the same or similar control functions can be achieved.

[0055] According to the main control valve for engineering machinery of the present application, the working oil port overflow valve associated with the working oil port is cancelled, and two load-sensitive overflow valves are arranged adjacent to the two working oil ports on the same side of the valve housing. The load-sensitive overflow valve is configured to have the functions of the working oil port overflow valve (or shock absorber valve, secondary overflow valve) in the prior art, so that the main control valve has a more compact structure, reduces the number of parts, weight and cost, and facilitates the assembly and maintenance operations of the main control valve.

[0056] Furthermore, in an optional embodiment, the two load-sensing relief valves and the two working oil ports are both arranged on the upper side of the valve housing and open upward, which is more conducive to the assembly and maintenance operations of the main control valve.

[0057] In addition, in an optional embodiment, the two load-sensitive relief valves can be distributed in the same order as the two working oil ports, that is, LS relief valve Va, LS relief valve Vb, port A, and port B in the axial direction, which is convenient for operators to identify and reduces the possibility of assembly errors.

[0058] In addition, in an optional embodiment, the oil outlets of the LS relief valves Va, Vb are connected to the main valve T port (ie, connected to the oil return channel LT) through the first relief channel L2, which simplifies the structure of the main control valve.

[0059] In addition, in an optional embodiment, the LS overflow valves Va and Vb can be set at different heights, and the overflow channel L2 is formed by the oblique hole in the valve body 1. This structure can reduce the material usage of the valve body 1. Of course, the LS overflow valves Va and Vb can also be set at the same height to achieve the same function.

[0060] Although the present application is described herein with reference to specific embodiments, the scope of the present application is not limited to the details shown. Various modifications may be made to these details without departing from the basic principles of the present application.

Claims

1. A main control valve for engineering machinery, comprising: Valve housing; as well as A main valve (Vm), a first load-sensitive relief valve (Va) and a second load-sensitive relief valve (Vb) integrated in the valve housing, wherein the main valve (Vm) has at least a first working oil port (A), a second working oil port (B) and an oil return port (T); It is characterized in that, in the first working valve position of the main valve (Vm), the first working oil port (A) is connected to the oil inlet of the first load-sensitive relief valve (Va) via a throttling channel (L1) in the valve core of the main valve (Vm), and the oil outlet of the first load-sensitive relief valve (Va) is connected to the oil return port (T) via an overflow channel (L2) in the valve housing; in the second working valve position of the main valve (Vm), the second working oil port (B) is connected to the oil inlet of the second load-sensitive relief valve (Vb) via the throttling channel (L1), and the oil outlet of the second load-sensitive relief valve (Vb) is connected to the oil return port (T) via the overflow channel (L2); the first load-sensitive relief valve (Va), the second load-sensitive relief valve (Vb), the first working oil port (A), and the second working oil port (B) are all arranged on the same side of the valve housing.

2. The main control valve for engineering machinery according to claim 1, characterized in that: The first load-sensitive relief valve (Va) and the second load-sensitive relief valve (Vb) are respectively installed in a first load-sensitive relief valve hole and a second load-sensitive relief valve hole opened on the same side of the valve housing, and the first load-sensitive relief valve hole and the second load-sensitive relief valve hole and the first working oil port (A) and the second working oil port (B) are all open to the outside on the same side.

3. The main control valve for engineering machinery according to claim 1, characterized in that: The first load-sensing relief valve (Va), the second load-sensing relief valve (Vb), the first working oil port (A) and the second working oil port (B) are aligned with each other in the longitudinal direction of the valve housing.

4. The main control valve for engineering machinery according to claim 3, characterized in that: The distribution order of the first load-sensing relief valve (Va) and the second load-sensing relief valve (Vb) in the longitudinal direction of the valve housing is the same as the distribution order of the first working oil port (A) and the second working oil port (B) in the longitudinal direction of the valve housing.

5. The main control valve for engineering machinery according to claim 1, characterized in that: The single relief passage (L2) connects the oil outlet of the first load sensing relief valve (Va) and the oil outlet of the second load sensing relief valve (Vb) to the oil return port (T).

6. The main control valve for engineering machinery according to claim 5, characterized in that: The first load-sensing overflow valve (Va) and the second load-sensing overflow valve (Vb) are arranged at different positions in the height direction of the valve housing, and the overflow channel (L2) is arranged to be inclined relative to the longitudinal direction of the valve housing.

7. The main control valve for engineering machinery according to claim 5, characterized in that: The first load-sensing overflow valve (Va) and the second load-sensing overflow valve (Vb) are arranged at the same position in the height direction of the valve housing, and the overflow channel (L2) is arranged parallel to the longitudinal direction of the valve housing.

8. The main control valve for engineering machinery according to any one of claims 1 to 7, characterized in that: The main valve (Vm) also has a load pressure sensing chamber (E) formed in the valve housing, and the load pressure sensing chamber (E) is connected to the first working oil port (A) and the second working oil port (B) through the throttle passage (L1).

9. The main control valve for engineering machinery according to claim 8, characterized in that: In the first working valve position of the main valve (Vm), the oil inlet of the first load-sensitive relief valve (Va) is connected to the load pressure sensing chamber (E); in the second working valve position of the main valve (Vm), the oil inlet of the second load-sensitive relief valve (Vb) is connected to the load pressure sensing chamber (E).

10. The main control valve for engineering machinery according to claim 8, characterized in that: The main control valve also includes a compensation valve (Vc) arranged in the valve housing, and the compensation valve (Vc) is configured to adjust the amount of hydraulic oil delivered to the main valve (Vm) through the compensation valve (Vc) based on the output oil pressure of the main pump; the compensation valve (Vc) has a spring chamber, and the spring chamber is connected to the load pressure sensing chamber (E) through a compensation channel (L3) in the valve housing.

Images