Product Description
The hydraulic split-type multi-way directional valve used in excavators (referred to as the multi-way valve) is the "control center" and "nerve hub" of hydraulic excavators. It integrates multiple directional valves, pressure valves, flow valves, etc., required for controlling all working devices such as the boom, dipper stick, bucket, rotation, and movement, into a modular valve group. By centrally controlling the on-off, flow direction, and flow rate of each oil circuit, it achieves precise and coordinated control of the movements of multiple actuators (hydraulic cylinders, motors), and is the core component that determines the operation efficiency, control accuracy, and energy consumption level of the excavator.
Key Design Features and Advantages
1. Modular segmented structure, flexible customization:
Adopting advanced sectional design, it can be flexibly combined with the oil inlet section, working valve sections, and return oil tail sections according to the functional requirements of different tonnage excavators (usually 4-10 sections). It can be assembled like "building blocks". This design enables the valve group to precisely match various hydraulic circuits from micro to large excavators, simplifying the system piping, facilitating maintenance and functional expansion.
2. High pressure and large flow, powerful power:
Optimized for heavy-duty working conditions of construction machinery, the valve body is made of high-strength cast iron or alloy steel. The rated working pressure is generally up to 28-35 MPa, and some models have a peak pressure exceeding 39 MPa. The diameters cover series such as 12mm, 15mm, and 20mm, and the maximum flow rate of a single section can reach 100-200 L/min, providing abundant hydraulic power for heavy-load actions such as digging and crushing.
3. Load-sensitive and pressure compensation technology, precise and energy-saving control:
Integrating load-sensitive (LS) and pressure compensation (PC) systems. The system can real-time sense the load pressure of each actuator and maintain a constant pressure difference between the throttle port and the pressure compensation valve (either in front of or behind the valve). This ensures that the movement speed of the actuator only depends on the valve core opening (operating handle displacement), independent of the load size, completely solving the "flow competition" problem in compound actions and achieving precise and detailed control "aim where you point", while significantly reducing system energy consumption and heat generation.
4. Advanced anti-flow saturation (LUDV) system:
High-end models adopt LUDV technology independent of load pressure. When the pump output flow is insufficient to meet all action requirements (flow saturation), the system will automatically distribute the flow according to the proportion of each valve core opening to ensure all actions decelerate synchronously and coordinately, rather than the heavy-load action being stalled, greatly improving the operational coordination and efficiency in complex working conditions.
5. Integrated functions and high reliability:
The valve sections can integrate main safety valves, overload relief valves, supplementary oil valves, regeneration valves, and hold-up valves. The valve cores are surface hardened (hardness HRC ≥ 60), combined with precise clearance, have strong anti-pollution ability, and have a small internal leakage (≤ 15 mL/min at 10 MPa). The sturdy design ensures long-term, high-reliability operation in harsh environments with vibration and impact.
6. Diverse control methods:
Supports manual direct control, hydraulic pilot control, electro-hydraulic proportional control, and their combinations. Electro-hydraulic proportional control supports CAN bus interface, which can be deeply integrated with the intelligent control system of the excavator to achieve precise flow distribution, mode switching (such as economy mode, power mode), and remote control, laying the foundation for intelligent and automated upgrades.
Working Principle and Technical Analysis
The core of the multi-way valve lies in its pilot control and load pressure feedback mechanism.
Basic control: The operator turns the handle, generating pilot control pressure oil. This pressure oil drives the main valve core to move, opening the corresponding main oil path, allowing high-pressure oil to enter the actuator (oil cylinder or motor), and driving it to operate.
Load sensing and pressure compensation: The load pressure of each working valve plate is collected through a network of load-sensing spool valves, and the highest load pressure signal in the system is fed back to the variable mechanism of the pump and the pressure compensator inside the valve. The pressure compensator dynamically adjusts to ensure that the flow rate to each actuator is solely determined by the opening degree of this associated spool valve, decoupled from the load fluctuations of other connections, thereby achieving precise flow distribution and energy savings.
Mid-position unloading and flow regeneration: When all the valve cores are in the middle position, the main pump's incoming oil is unloaded at a low pressure through the valve's mid-position oil passage, reducing energy consumption during no-load operation. Some valve plates are designed with flow regeneration functionality. Under the gravitational or inertial force of the actuator (such as the lowering of the boom or the retraction of the bucket arm), the return oil from the no-piston chamber is directly introduced into the piston chamber, increasing the flow rate and thereby enhancing the operation speed (tested to increase by 25%-30%) and reducing energy consumption.
Control Method and Valve Core Functionality
Control method:
Hydraulic pilot control: The most common method, with low operating force, excellent micro-motion performance, and a comfortable feel.
Electro-hydraulic Proportional Control (EH):
By receiving electrical signals through proportional electromagnets, the valve core displacement is controlled, enabling continuous speed regulation and remote control. This is the foundation of intelligent control.
Manual control:
This is mainly used for small-sized equipment or in emergency situations.
Valve core function:
The common valve core functions in a three-position four-way valve include:
O-type: All oil ports are sealed, and the actuating element can be locked in any position. It is used in scenarios where the machine needs to stop under load.
Y-type: The oil inlet is closed, the working oil outlet is connected to the return oil outlet, and the actuating element is in a floating state.
Type A: Suitable for single-acting hydraulic cylinders.
P type: The oil inlet is connected to both working oil outlets, enabling differential rapid movement.
Application and Selection Guide
Application Matching:
Small excavators (< 6 tons): Typically, a multi-way valve with a bore size of 12-15mm is selected. It integrates basic functions such as the boom, dipper stick, bucket, rotation, and travel (two-way linkage), and often uses a constant-flow pump or a single-variable pump system.
Medium-sized excavators (6-20 tons): Mainstream market. Typically, multi-way valves with a bore size of 15-20mm are used. Load-sensing variable pumps and LUDV systems must be equipped to achieve efficient compound actions and energy conservation.
Large excavators (over 20 tons): Select multi-way valves with a bore diameter of 20-25mm or larger. These valves have high working pressure, large flow capacity, and extremely high requirements for response speed, reliability, and the integration of electronic control systems.
Key points for selection:
1. Determine the number of valves: Based on the number of the excavator's working devices (such as the boom, bucket arm, bucket, rotation, left and right movement, bulldozer blade, hydraulic breaker hammer, etc.), determine the required number of valve pieces.
2. Confirm pressure and flow: Match the rated pressure and flow of the main engine's hydraulic pump, and consider peak demand.
3. Select the control system: According to the overall control and intelligent requirements of the machine, choose pilot control or electro-hydraulic proportional control.
4. Clarify additional functions: Confirm whether special function valve pieces such as regenerative valves, hold valves, and merge valves need to be integrated.
Key Points for Installation, Maintenance and Troubleshooting
• Installation:
Ensure the installation surface is flat and clean; tighten the bolts in a diagonal sequence evenly to the specified torque; when connecting the pilot oil pipe and the main oil pipe, be careful to keep it clean to prevent contaminants from entering.
• Maintenance:
Regularly check the cleanliness of the oil; monitor whether the system pressure is normal; pay attention to listening for any abnormal noises during the operation of the valve group (which may indicate cavitation or wear).
• Common Faults:
The movement is slow or weak: This may be caused by insufficient pump pressure, the main safety valve set at too low a level, excessive internal leakage due to worn valve core, or a malfunction of the pressure compensator.
Incoordination or stalling of movements: This is usually caused by blockage in the load-sensitive feedback oil circuit, jamming of the shuttle valve, or failure of the pressure compensator.
The valve core fails to reset or the operation is heavy: This may be caused by a broken reset spring, valve core jamming (due to oil contamination), or insufficient pilot control pressure.
Technological Development Trends
In the future, multi-way valves for excavators will continue to evolve towards higher pressure, greater flow capacity, greater energy efficiency, and greater intelligence. The integration of electro-hydraulic technology is a definite trend, where digital control of the valves is achieved through CAN bus and sensors, deeply integrated with the vehicle controller to realize advanced functions such as predictive maintenance, adaptive control, and remote diagnosis. At the same time, advanced hydraulic control concepts such as anti-flow saturation (LUDV) technology and load port independent control (LSIC) will further enhance the operational efficiency and user experience of excavators.
