Injection Machine Electrohydraulic Servo System Technology and Application (1)

Electro-hydraulic servo drive system is one of the most concerned drive technologies in recent years. This paper takes the injection-molded electro-hydraulic servo system independently developed by Shanghai Royal Energy Technology Co., Ltd. as an example to analyze and introduce the basic technology and application effect of electro-hydraulic servo system.
In the automatic control system, the system whose output changes with a certain degree of accuracy in accordance with changes in the input volume is called a servo system. The stability, high accuracy, and quick response are the basic requirements for it. Specifically to the injection molding machine, the electro-hydraulic servo system realizes that the output flow and pressure of the controlled oil pump follow the change of the given signal of the upper computer quickly and accurately, and adapt to the pressure, speed, and time requirements of the injection molding process.
According to the drive motor used, the servo system can be divided into DC and AC servo systems, which can be divided into induction motor servo system and permanent magnet synchronous motor AC servo system. The excitation circuit and the armature circuit of the DC motor are independent from each other, and one of the two magnetic fields is independently adjusted for speed control. The control performance is excellent, but it adopts a mechanical commutation device, the carbon brush is easy to wear, and the spark easily occurs during operation. Synchronous servo motors with permanent magnets in rotors are more widely used than non-synchronous AC servo motors. The main reason is that the performance of permanent magnet materials is continuously increasing and the price is decreasing. Compared with non-synchronous motors, the control is simple and the high performance is easily achieved. Control requirements, therefore, in recent years, the development of permanent magnet servo motor AC servo system is very rapid, the emergence and development of injection molding electromechanical servo system is in line with this trend.
The composition of the electro-hydraulic servo system The following uses the Eugene injection electro-hydraulic servo system as an example to briefly introduce the structure of the electro-hydraulic servo system. As shown in Fig. 1, Yueneng injection electromechanical hydraulic servo system is mainly composed of permanent magnet synchronous servo motor, motor rotor position/speed sensor, servo drive controller, and oil pump coaxially connected to the servo motor, and the pressure of the detection system hydraulic pressure. Sensors and other key components.
AC permanent magnet synchronous motor

Permanent magnet synchronous motor is characterized by: simple structure, small size, light weight, low loss and high efficiency. Compared to induction asynchronous motors, rotor losses are small because there is no rotor current; it does not require reactive excitation current, high power factor, stator current and stator losses are reduced, so the overall efficiency of permanent magnet motors is higher than that of induction motors. 5%-10%. In addition, the ratio between the maximum output torque and the rotor inertia of the permanent magnet motor can be much larger than that of the induction motor, so the permanent magnet motor has superior dynamic performance and is suitable for use as a servo motor with high precision and high dynamic performance. (To be continued)