The pilot ratio of the slewing balance valve in an XCMG truck-mounted crane is one of the core parameters affecting the system's response speed. It directly determines the hydraulic circuit's response efficiency to operating commands by adjusting the ratio between the pilot pressure and the main valve opening pressure. Essentially, the pilot ratio is the ratio of the balance valve spring setpoint to the pilot control pressure, reflecting the difference in valve core opening pressure with and without pilot oil pressure. In the slewing system of XCMG truck-mounted cranes, this parameter needs to be precisely matched according to load characteristics, operating frequency, and stability requirements to achieve a balance between rapid response and smooth control.
When the pilot ratio is small, it means that the pilot pressure needs to reach a higher value to overcome the spring setpoint pressure and push the main valve core open. At this time, the system has lower sensitivity to changes in pilot pressure, and the valve core movement is relatively slow, but its anti-interference ability is stronger. For example, when XCMG truck-mounted cranes perform heavy-load slewing, if the pilot ratio is set too small, although it can reduce valve spool malfunctions caused by pressure fluctuations, it will prolong the time difference between the operator's command and the actual start of the slewing mechanism, resulting in a "sluggish" system response. This may affect operational efficiency, especially in conditions requiring frequent starts, stops, or fine adjustments.
Conversely, a larger pilot ratio can reduce the pilot pressure required to open the main valve, making the valve spool more sensitive to pressure changes. In light-load or rapid slewing scenarios of XCMG truck-mounted cranes, a larger pilot ratio can shorten the command transmission time and improve the "agility" of the system response. For example, when the operator's handle is slightly pushed, a small change in pilot pressure can trigger the main valve spool to open quickly, driving the slewing motor to respond immediately and achieving smooth steering. However, if the pilot ratio is too large, the system may experience frequent valve spool vibration due to pressure fluctuations or external interference (such as hydraulic shock), causing slewing mechanism jitter and even affecting positioning accuracy. The slewing system of XCMG truck-mounted cranes typically faces dynamic load changes, such as boom length adjustments and increases or decreases in lifting weight. These factors alter the slewing resistance torque, thus affecting the pressure distribution in the hydraulic circuit. Therefore, the appropriate selection of the pilot ratio must consider load adaptability. For example, under long boom and heavy lifting conditions, the load variation is large. While a smaller pilot ratio can enhance system stability, it may sacrifice response speed. Conversely, a larger pilot ratio can improve response, but requires optimization of the pilot control circuit (such as adding damping or filtering) to suppress pressure fluctuations and prevent valve spool malfunctions. XCMG's technical team often uses a combination of simulation and actual measurement to determine the optimal pilot ratio range for different operating conditions.
From a control strategy perspective, the slewing system of XCMG truck-mounted cranes may integrate closed-loop control (such as PID regulation). In this case, the pilot ratio and control parameters need to be optimized collaboratively. For example, in applications requiring rapid positioning, a larger pilot ratio, combined with a high proportional gain, can shorten system settling time; while in applications requiring stable operation, a smaller pilot ratio can reduce the demand for differential action and decrease overshoot risk. This parameter matching requires extensive experimental verification to ensure compatibility between the pilot ratio and the control algorithm.
In practical applications, the pilot ratio of the slewing balance valve of XCMG truck-mounted cranes needs to be adjusted according to the specific model and operating scenario. For example, for urban construction sites with frequent start-stop operations, a medium pilot ratio (e.g., 4:1 to 6:1) may be preferred to balance response speed and stability; while for scenarios requiring high-precision positioning, such as container hoisting in ports, a smaller pilot ratio (e.g., 3:1 to 5:1) may be used, and pressure fluctuations may be suppressed by increasing the damping of the pilot hydraulic circuit. Through long-term data accumulation, the XCMG R&D team has developed recommended pilot ratio ranges for different models, providing users with optimization guidance.
The pilot ratio of the XCMG truck-mounted crane slewing balance valve, by influencing the relationship between valve core opening pressure and response speed, becomes a key parameter for regulating the dynamic performance of the system. Its selection requires comprehensive consideration of load characteristics, operating frequency, and stability requirements, achieving an optimal balance between response speed and control accuracy through a combination of theoretical calculations, simulation analysis, and field verification. The proper configuration of this parameter directly affects the operating efficiency and safety of XCMG truck-mounted cranes under complex working conditions.
