Precise closed oil circuit electro-hydraulic injection molding machine

Abstract

The present application relates to the technical field of fluid working system, specifically to a precise closed oil circuit oil-electricity composite injection molding machine, comprising a plurality of closed oil circuit driving systems, each of which comprises a plurality of hydraulic actuators, an oil pump, a motor and a control system, each of the hydraulic actuators comprises a hydraulic actuator component, a reversing device and a main sensor; the oil pump and each of the hydraulic actuators form a closed hydraulic oil circuit through an oil inlet pipeline and an oil outlet pipeline; the motor is in driving connection with the oil pump; the control system is in electrical connection with the motor and the main sensor, and is used to generate a control instruction according to load information to perform real-time closed-loop control on the motor. The precise closed oil circuit oil-electricity composite injection molding machine is more energy-saving and environmentally friendly, and can solve the problems of the prior art in control accuracy, service life and the like, improve control accuracy and prolong the service life of hydraulic components.

Description

Technical Field

[0001] This invention relates to the field of fluid working system technology, specifically to a precision closed-loop hydraulic-electric hybrid injection molding machine. Background Technology

[0002] Injection molding machines, also known as plastic injection molding machines, are the main molding equipment used to produce various shapes of plastic products from thermoplastic or thermosetting plastics using plastic molds. An injection molding machine typically consists of an injection system, a mold clamping system, a hydraulic system, an electrical control system, a lubrication system, a heating and cooling system, and a safety monitoring system. The hydraulic system provides power for the various actions of the injection molding machine according to the process requirements and meets the pressure, speed, and position control requirements of each part of the machine. The hydraulic system mainly consists of various hydraulic components and hydraulic auxiliary components.

[0003] As the domestic production of hydraulic components and servo motors has gradually matured, traditional hydraulic drive methods have evolved through several generations of technological development, from flow-throttling and remote pressure-regulating hydraulic systems to the latest servo-driven hydraulic systems. Compared to traditional hydraulic systems, energy-saving performance has been greatly improved. However, to date, hydraulic systems still have problems in the following aspects:

[0004] 1. Regarding control accuracy, (1) Some equipment's hydraulic drive system uses an open-loop oil circuit. The open-loop oil circuit requires a large-capacity open oil tank with a large volume and a large footprint. Therefore, the open oil tank is located far from the actuator. The oil pump is located at the open oil tank, so the pipeline connecting the oil pump to the oil cylinder is very long. The total length of the inlet and return oil pipelines can be 3-20 meters. In addition, some components are movable and need to be connected by hoses. Due to the compressibility of hydraulic oil, the elasticity of the hose connection, and the excessive length of the pipeline, overshoot is likely to occur, resulting in low control accuracy of the control system. (2) At the same time, the dynamic load changes greatly in actual applications, which will also lead to low control accuracy of the control system. (3) In the case of using an open-loop oil circuit, it is almost impossible to achieve closed-loop control when far from the load. Therefore, the existing oil circuit is usually open-loop control. However, since the internal leakage of the oil pump is related to the working speed, pressure, oil temperature, viscosity, etc., the oil pump will inevitably have internal leakage problems after long-term operation. Therefore, the accuracy of open-loop control is limited. (4) In the prior art, the driver of the hydraulic control system receives analog signals, performs analog-to-digital conversion, and outputs digital signals to control the servo motor. Analog signals are easily interfered with, easily distorted, and slow to respond, which also leads to low control accuracy of the hydraulic control system.

[0005] 2. In terms of energy conservation and environmental protection, open-loop oil circuits require large-capacity open-type oil tanks. Open-type oil tanks require a large amount of hydraulic oil. Taking a common 150-ton clamping injection molding machine as an example, the installed capacity is 200 liters of anti-wear hydraulic oil. Based on the operating environment of the injection molding machine and the fact that it has an open-type oil tank, the hydraulic oil needs to be changed every 4,000-6,000 hours. Under the condition of continuous operation for 80% of the time, 2,400 liters of hydraulic oil need to be replaced in a 12-year working cycle. Currently, there are more than 100,000 injection molding machines in China. The current unit price of anti-wear hydraulic oil is 10-15 yuan / liter. Changing the oil is a considerable cost for users. Waste oil disposal also incurs costs. The environmental impact of waste oil disposal is also a very serious social problem.

[0006] 3. In terms of service life, due to the use of an open oil tank, with changes in liquid level, temperature and high-speed flow of oil, gases, dust and moisture in the air can easily enter the hydraulic oil, causing the hydraulic oil to easily emulsify and oxidize, and the hydraulic components to be prone to cavitation, thus reducing the service life of the hydraulic components. Summary of the Invention

[0007] The present invention aims to provide a precision closed-loop hydraulic-electric hybrid injection molding machine to solve the problems existing in the prior art in terms of control accuracy, energy saving and environmental protection, and service life.

[0008] This application provides the following technical solution:

[0009] A precision closed-loop hydraulic-electric hybrid injection molding machine includes a control system and several closed-loop hydraulic drive systems, wherein the closed-loop hydraulic drive system includes:

[0010] Several sets of hydraulic actuators, each set of hydraulic actuators includes a hydraulic actuator component, a reversing device, and a main sensor. The hydraulic actuator component includes a first oil port and a second oil port. The reversing device is connected to the first oil port of the corresponding hydraulic actuator component through a first oil circuit, and the reversing device is connected to the second oil port of the corresponding hydraulic actuator component through a second oil circuit. The main sensor is used to acquire load information that reflects the load movement driven by the hydraulic actuator component.

[0011] The oil pump has its suction port connected to each commutator via a return oil line, and its outlet port connected to each commutator via an inlet oil line. The oil pump, through its inlet and outlet oil lines, forms a closed hydraulic circuit with each hydraulic actuator.

[0012] An electric motor is connected to the oil pump via a drive mechanism, and the electric motor is used to drive the oil pump.

[0013] The control system is electrically connected to the motor and the main sensors. The control system is used to generate control commands based on load information to perform real-time closed-loop control of the motor.

[0014] Beneficial effects:

[0015] 1. In the technical solution of this application, each group of closed-loop hydraulic drive system includes multiple hydraulic actuators. By setting the corresponding reversing device, when the injection molding machine performs different actions, the closed-loop hydraulic drive system can control the actions of different hydraulic actuators in turn. When other reversing valves are closed, the various actions will not interfere with each other. That is, multiple groups of hydraulic actuators share the same set of oil pumps and pipelines, which is beneficial to reduce costs and facilitate unified control.

[0016] 2. When no action is required, the motor is in a stopped state, which can save power consumption. After the commutation device is closed, the oil circuit of the hydraulic actuator is closed, which can withstand the static load without energy consumption (the existing bidirectional pump closed circuit maintains the static position of the oil cylinder piston by adjusting the forward and reverse rotation of the oil pump, which requires the motor to work continuously and consumes a lot of energy). Moreover, the mechanical position is kept safer and will not cause mechanical displacement due to sudden power failure.

[0017] 3. This solution employs a closed-loop hydraulic circuit. Compared to existing open-loop hydraulic circuits, it eliminates the need for a large open oil tank, and the oil pump is no longer located far from the hydraulic actuators. This effectively shortens the pipeline and reduces the amount of oil in the pipeline, thus avoiding the drawbacks of overshoot caused by the compressibility of hydraulic fluid, the elasticity of hose connections, and large dynamic load variations due to excessively long pipelines. Simultaneously, load information reflecting the load status is acquired through a main sensor, and the control system performs real-time closed-loop control of the motor based on this load information. This effectively improves the control accuracy caused by oil overflow or leakage, thereby avoiding problems such as unstable motion due to impact and vibration, and inaccurate position control, ultimately improving control precision. Taking a hydraulic system with a clamping force of 110 tons for an injection molding machine as an example, when the cycle is 1.5 seconds, the opening and stopping repeatability of this invention is ±0.15mm, while that of the traditional method is ±2-5mm; the absolute stopping accuracy is ±0.3mm, while that of the traditional open hydraulic circuit is ±5-10mm; the operation is stable, without impact or vibration, and the accuracy does not change significantly when carrying a load of 150kg. Since injection molding is a linear motion, the screw repeatability control accuracy is 0.05mm and the absolute stopping accuracy is 0.08mm at an injection speed of 100mm / s.

[0018] 4. This solution adopts a closed hydraulic circuit, which eliminates the need for a large open oil tank compared to the existing open hydraulic circuit. This significantly reduces the amount of hydraulic oil required. For example, with an injection molding machine having a clamping force of 110 tons, the hydraulic oil required for an open hydraulic circuit is 170 liters. With this solution, the required oil volume is only 16 liters, greatly saving costs. Furthermore, it eliminates the need to handle large amounts of waste oil, thus avoiding environmental impact and promoting energy conservation and environmental protection.

[0019] 5. This solution uses a closed-loop hydraulic circuit, which prevents gases, dust, and moisture in the air from easily entering the hydraulic circuit. The hydraulic oil is less likely to be emulsified and oxidized, and the hydraulic components are less prone to cavitation, thus extending the service life of the hydraulic components.

[0020] Furthermore, an overflow pipe is provided between the oil inlet pipe and the oil return pipe, and an overflow valve is provided on the overflow pipe.

[0021] The relief valve can eliminate the impact load of motion, provide upper limit pressure regulation for the oil circuit system, and thus protect the hydraulic system and prevent damage to hydraulic components caused by ultra-high pressure when the pressure sensor fails.

[0022] Furthermore, a negative pressure compensation pipeline is provided between the oil inlet pipeline and the oil return pipeline, and a one-way valve is installed on the negative pressure compensation pipeline.

[0023] The negative pressure compensation pipeline provides an installation location for the check valve, facilitating its installation. When a negative load suddenly occurs during the thrust-driven load movement, such as during mold opening and pressure relief in an injection molding machine, a negative pressure situation arises in the oil inlet pipeline. The check valve opens, and hydraulic oil from the return oil pipeline and the hydraulic accumulator enters the oil inlet pipeline to replenish the negative pressure, thereby preventing oil interruption, vibration, and damage to hydraulic components caused by negative loads.

[0024] Furthermore, it also includes a hydraulic accumulator and a cooler, both of which are installed on the return oil line.

[0025] The cooler is used to cool the hydraulic oil, ensuring that the oil temperature remains within the required process range. The hydraulic accumulator is used to store and release hydraulic oil. Taking the mold opening action of an injection molding machine as an example, since the oil return volume from the rodless chamber of the cylinder is greater than the oil inlet volume from the rod chamber, excess hydraulic oil not needed by the oil pump can flow into the hydraulic accumulator on the return oil line.

[0026] Furthermore, the reversing device is a reversing valve, which is used for opening, closing and reversing the closed hydraulic circuit. The reversing valve includes four ports, two of which are connected to the inlet oil line and the return oil line respectively, and the other two ports are connected to the first oil circuit and the second oil circuit respectively.

[0027] A directional control valve is used to reverse the direction of a closed hydraulic circuit. Taking a hydraulic cylinder as an example, assuming the first oil circuit connects to the rodless chamber of the cylinder and the second oil circuit connects to the rod chamber, when two ports of the directional control valve are connected to the inlet line and the first oil circuit, and the other two ports are connected to the return line and the second oil circuit, oil enters the rodless chamber and exits the rod chamber. Conversely, when two ports of the directional control valve are connected to the inlet line and the second oil circuit, and the other two ports are connected to the return line and the first oil circuit, oil exits the rodless chamber and enters the rod chamber, thus reversing the hydraulic circuit. It can control the hydraulic actuator to perform different actions, or control different hydraulic actuators to operate in turn, and achieve closed-loop control for pressure and speed regulation.

[0028] Furthermore, it also includes a mold clamping system and an injection system. The closed-loop hydraulic drive system consists of two sets, namely a first closed-loop hydraulic drive system and a second closed-loop hydraulic drive system. The first closed-loop hydraulic drive system is used to drive the mold clamping system, and the second closed-loop hydraulic drive system is used to drive the injection system.

[0029] The mold clamping system and injection system are equipped with independent closed-loop hydraulic drive systems, which do not interfere with each other and ensure the stable operation of the injection molding machine.

[0030] Furthermore, the hydraulic actuators of the first closed-loop hydraulic drive system include a mold adjustment actuator, a mold opening and closing actuator, an ejector pin action actuator, and an auxiliary core-pulling action actuator. The mold adjustment actuator includes a mold adjustment directional valve and a mold adjustment hydraulic motor; the mold opening and closing actuator includes a mold opening and closing directional valve and a mold opening and closing hydraulic cylinder; the ejector pin action actuator includes an ejector pin action directional valve and an ejector pin hydraulic cylinder; and the auxiliary core-pulling action actuator includes an auxiliary core-pulling action directional valve.

[0031] The mold adjustment mechanism, mold opening and closing mechanism, ejector pin action mechanism, and auxiliary core pulling action mechanism drive the various processes and actions of the mold closing system during operation.

[0032] Furthermore, the hydraulic actuator of the second closed-loop hydraulic drive system includes an injection nozzle moving actuator and an injection actuator. The injection nozzle moving actuator includes an injection nozzle moving directional valve and an injection nozzle moving hydraulic cylinder. The injection actuator includes an injection directional valve and an injection hydraulic cylinder.

[0033] The injection system's various process steps are driven by the injection nozzle movement actuator and the injection actuator.

[0034] Furthermore, it also includes a slave sensor, which is installed on the oil inlet line and the oil return line. The slave sensor is used to detect the hydraulic pressure information at its location, and the control system is also used to adjust the control command according to the pressure information.

[0035] By acquiring pressure information from sensors in pipelines and actuators, such as the pressure information of the rod-side and rodless sides of the hydraulic cylinder, the control system can adjust the control commands based on the pressure information, thereby further improving the control accuracy of hydraulic drive control.

[0036] Furthermore, the control system employs a fully digital PID motion control algorithm for real-time closed-loop control.

[0037] Employing a fully digital PID motion control algorithm, it boasts strong anti-interference capabilities, fast response speed, and improved control accuracy. The PID motion control algorithm enables real-time closed-loop correction, further enhancing the control precision of the drive. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the closed-loop hydraulic drive system in the embodiment of the precision closed-loop hydraulic-electric hybrid injection molding machine of this application;

[0039] Figure 2 This is a three-dimensional structural schematic diagram of the closed-loop hydraulic drive system in the embodiment of the precision closed-loop hydraulic-electric hybrid injection molding machine of this application;

[0040] Figure 3 This is a schematic diagram of the structure of the first closed-loop hydraulic drive system in the embodiment of the precision closed-loop hydraulic-electric hybrid injection molding machine of this application;

[0041] Figure 4 This is a schematic diagram of the structure of the second closed-loop hydraulic drive system in the embodiment of the precision closed-loop hydraulic-electric hybrid injection molding machine of this application;

[0042] Figure 5 This is a three-dimensional structural diagram of the precision closed-loop hydraulic-electric hybrid injection molding machine embodiment of this application. Detailed Implementation

[0043] The following detailed description illustrates the specific implementation method:

[0044] The markings in the accompanying drawings include: oil pump 1, motor 2, hydraulic accumulator 3, hydraulic actuator 4, main sensor 5, reversing device 6, slave sensor 7, cooler 8, return oil line 9, inlet oil line 10, overflow line 11, negative pressure compensation line 12, overflow valve 13, check valve 14, second oil line 15, first oil line 16, suction port 17, outlet port 18, controller 19, servo driver 20, mold adjustment reversing valve 21, mold adjustment hydraulic motor 22, mold opening and closing hydraulic cylinder 23, mold opening and closing reversing valve 24, ejector pin action reversing valve 25, ejector pin hydraulic cylinder 26, auxiliary core pulling action reversing valve 27, injection nozzle movement reversing valve 28, injection nozzle movement hydraulic cylinder 29, injection reversing valve 30, and injection hydraulic cylinder 31.

[0045] The precision closed-loop hydraulic-electric hybrid injection molding machine of this embodiment includes an injection system, a mold clamping system, a lubrication system, a heating and cooling system, a safety monitoring system, etc., as well as a control system and several sets of closed-loop hydraulic drive systems. The closed-loop hydraulic drive systems are used to drive the injection system and the mold clamping system to work.

[0046] like Figure 1 and Figure 2 As shown, the closed-loop hydraulic drive system of this embodiment includes several sets of hydraulic actuators, an oil pump 1, a motor 2, a hydraulic accumulator 3, and a cooler 8.

[0047] Each hydraulic actuator includes a hydraulic actuator 4, a reversing device 6, and a main sensor 5. The hydraulic actuator 4 includes a first oil port and a second oil port. The reversing device 6 is connected to the first oil port of the corresponding hydraulic actuator 4 through a first oil passage 16, and the reversing device 6 is connected to the second oil port of the corresponding hydraulic actuator 4 through a second oil passage 15. The main sensor 5 is used to acquire load information that reflects the load movement driven by the hydraulic actuator 4.

[0048] In this embodiment, the hydraulic actuator 4 is a hydraulic cylinder (oil cylinder) or a hydraulic motor (oil motor), and the reversing device 6 is a reversing valve. The reversing valve is used for opening, closing and reversing the closed hydraulic oil circuit. The reversing valve includes four ports, two of which are connected to the oil inlet pipe 10 and the oil return pipe 9 respectively, and the other two ports are connected to the first oil circuit 16 and the second oil circuit 15 respectively. The directional control valve is used to reverse the direction of a closed hydraulic circuit. Taking the hydraulic actuator 4 as an example, assuming the first oil circuit 16 connects to the rodless chamber of the cylinder and the second oil circuit 15 connects to the rod chamber, when the two ports of the directional control valve are connected to the inlet pipe 10 and the first oil circuit 16, and the other two ports are connected to the return pipe 9 and the second oil circuit 15, oil enters the rodless chamber and exits the rod chamber. Conversely, when the two ports of the directional control valve are connected to the inlet pipe 10 and the second oil circuit 15, and the other two ports are connected to the return pipe 9 and the first oil circuit 16, oil exits the rodless chamber and enters the rod chamber, thus reversing the hydraulic circuit. It can control the hydraulic actuator 4 to perform different actions, or control different hydraulic actuators 4 to operate in turn, achieving closed-loop control of pressure and speed regulation.

[0049] The main sensor 5 is mounted on the hydraulic actuator 4. Specifically, it can be a built-in displacement sensor, an external displacement sensor, or a rotary sensor. In this embodiment, the main sensor 5 is an external magnetostrictive linear displacement sensor. The main sensor 5 includes an electronic chamber, a waveguide scale, and a movable magnetic ring. The electronic chamber is connected to the waveguide scale, and the movable magnetic ring is fitted onto the waveguide scale. Taking its installation on a hydraulic cylinder as an example, during installation, the displacement sensor is mounted on the injection molding machine's mold-locking tail plate and fixed relative to the hydraulic cylinder. The magnetic ring can move on the waveguide scale and moves synchronously with the piston rod via a connecting rod. In other embodiments, the main sensor 5 is a built-in magnetostrictive linear displacement sensor. The electronic chamber is fixedly connected to the outside of the hydraulic cylinder body, the waveguide is parallel to the outside of the hydraulic cylinder body, and the movable magnetic ring is connected to the piston rod. That is, when the piston rod moves, the movable magnetic ring moves along the waveguide with the piston rod. In another embodiment, the piston rod is connected to a rack and pinion. When moving, it drives the gear to drive a rotary encoder, converting linear motion into rotational motion, obtaining angular information, and obtaining the linear movement position and speed through the rotational information. The real-time position signal is fed back to the control system to obtain position and speed signals.

[0050] The oil pump 1's suction port 17 is connected to each reversing device 6 through the return oil line 9, and the oil pump 1's outlet port 18 is connected to each reversing device 6 through the inlet oil line 10. The oil pump 1 forms a closed hydraulic circuit with each hydraulic actuator through the inlet oil line 10 and the outlet oil line.

[0051] Motor 2 is connected to oil pump 1 for transmission, and motor 2 is used to drive oil pump 1; specifically, the output shaft of motor 2 is keyed to the input shaft of oil pump 1. In this embodiment, motor 2 is a synchronous servo motor 2, and oil pump 1 is a fixed displacement pump. Oil pump 1 is one of gear pump, screw pump, plunger pump, vane pump, etc. In this embodiment, a gear pump is selected.

[0052] The hydraulic accumulator 3 is installed on the return oil line 9 and is used to store and release hydraulic oil. The cooler 8 is installed on the return oil line 9 and is used to cool the hydraulic oil, so that the oil temperature is always kept within the process requirements range.

[0053] In this embodiment, there are two closed-loop hydraulic drive systems: a first closed-loop hydraulic drive system and a second closed-loop hydraulic drive system. The first closed-loop hydraulic drive system drives the mold clamping system, and the second closed-loop hydraulic drive system drives the injection system. The mold clamping system and the injection system each have independent closed-loop hydraulic drive systems, ensuring they do not interfere with each other and guaranteeing stable operation of the injection molding machine.

[0054] like Figure 3 and Figure 5As shown, the hydraulic actuators of the first closed-loop hydraulic drive system include a mold adjustment actuator, a mold opening and closing actuator, an ejector pin actuator, and an auxiliary core-pulling actuator. The mold adjustment actuator includes a mold adjustment directional valve 21 and a mold adjustment hydraulic motor 22; the mold opening and closing actuator includes a mold opening and closing directional valve 24 and a mold opening and closing hydraulic cylinder 23; the ejector pin actuator includes an ejector pin directional valve 25 and an ejector pin hydraulic cylinder 26; and the auxiliary core-pulling actuator includes an auxiliary core-pulling directional valve 27. The mold adjustment actuator, mold opening and closing actuator, ejector pin actuator, and auxiliary core-pulling actuator respectively drive the various process flows and actions of the mold closing system during operation.

[0055] like Figure 4 and Figure 5 As shown, the hydraulic actuators of the second closed-loop hydraulic drive system include an injection nozzle moving actuator and an injection actuator. The injection nozzle moving actuator includes an injection nozzle moving directional valve 28 and an injection nozzle moving hydraulic cylinder 29; the injection actuator includes an injection directional valve 30 and an injection hydraulic cylinder 31. The injection nozzle moving actuator and the injection actuator, etc., drive each process step of the injection system.

[0056] An overflow line 11 is provided between the inlet line 10 and the return line 9, and an overflow valve 13 is installed on the overflow line 11. A negative pressure compensation line 12 is also provided between the inlet line 10 and the return line 9, and a one-way valve 14 is installed on the negative pressure compensation line 12. The overflow valve 13 is set to a pressure slightly higher than the rated maximum working pressure. When a high-pressure impact load occurs in the system oil circuit or when the system pressure sensor fails and causes pressure runaway, the hydraulic oil can return to the return line 9 through the overflow valve 13. This can resist impact loads, protect the oil pump 1, and prevent damage to components caused by excessive high pressure in the event of a pressure sensor failure, thus providing upper limit pressure regulation safety protection for the oil circuit system.

[0057] The negative pressure compensation pipeline 12 provides an installation position for the check valve 14, facilitating its installation. During normal operation, hydraulic oil does not flow through the check valve 14 to the return pipeline 9. However, when a sudden negative load occurs during the thrust-driven load movement, such as when a momentary high-pressure load pushes the piston of the cylinder during mold opening and pressure relief in an injection molding machine, causing negative pressure stall, the return oil from the hydraulic accumulator 3 and the cylinder can be replenished to the inlet pipeline 10 through the automatically opening check valve 14, and then replenished to the cylinder's inlet chamber through the reversing valve and the first oil circuit 16. This allows the cylinder to operate continuously without impact, pauses, or vibrations, and the control system will not experience erroneous overshoot due to brief negative pressure, thus improving the control accuracy and service life of the servo system.

[0058] It also includes a sensor 7, which is installed on the inlet oil line 10 and the return oil line 9. The sensor 7 is used to detect the hydraulic pressure information at its location. The number and installation position of the sensor 7 can be selected according to requirements. In this embodiment, the sensor 7 is a pressure sensor, which is installed between the inlet oil line 10 and the directional valve. Specifically, there is one sensor 7, which includes a sensing end installed between the inlet oil line 10 and the directional valve, and is used to detect the pressure at the directional valve interface. In other embodiments, there are two sensors 7, which are respectively installed on the inlet oil line 10 and the return oil line 9, and are used to detect the pressure at both ends of the first and second oil ports of the hydraulic actuator 4.

[0059] The control system is electrically connected to motor 2, main sensor 5, and commutator 6. The control system generates control commands based on load information to perform real-time closed-loop control of motor 2. It also switches the conduction state of commutator 6. Furthermore, the control system adjusts the control commands based on pressure information. In this embodiment, the control system employs a fully digital PID motion control algorithm for real-time closed-loop control. In this embodiment, the control system includes a host controller 19 and a servo driver 20. The host controller 19 is connected to the servo driver 20, and the servo driver 20 is electrically connected to motor 2. The fully digital PID motion control algorithm provides strong anti-interference capabilities, fast response speed, and improved control accuracy. The use of the PID motion control algorithm enables real-time closed-loop correction, thereby improving the control accuracy of the drive control.

[0060] The control system automatically generates a smooth continuous speed curve based on pre-set endpoint positions and speeds for the starting, running, and tail phases, as well as load information. The control system then generates control commands based on this continuous speed curve to control motor 2. Furthermore, the control system employs a position closed-loop algorithm in the tail phase. Using real-time load information detected by the main sensor 5 and speed changes based on the continuous speed curve, it generates a deceleration curve and adjusts the control commands in a closed-loop manner based on real-time detected pressure information.

[0061] Taking the operation of the first closed-loop hydraulic system as an example, the main sensor 5 is used to acquire the movement information of the hydraulic cylinder and transmit it to the controller 19, i.e., to the control subsystem. The slave sensor 7 is used to acquire the pressure information of the hydraulic cylinder and transmit it to the controller 19, i.e., to the control subsystem. The control subsystem is used to generate control commands based on the movement information and adjust the control commands based on the pressure information. The control commands include speed and torque. The control subsystem is also used to send the control commands to the driver, i.e., the controller 19 transmits the control commands to the driver, and the driver controls the operation of the motor 2 according to the control commands.

[0062] The load movement process is divided into a starting phase, a running phase, and a tail phase. The initial state is manually set, including the endpoint position and speed in the starting phase, the speed at the midpoint of the running phase, and the final stop position in the tail phase. The control subsystem generates control commands based on these parameters, including the endpoint position and speed in the starting, running, and tail phases, as well as the movement information. Specifically, it automatically generates a completely smooth, continuous speed curve command. The slope of the curve cannot exceed the maximum acceleration of the power system. Control commands are then generated based on the speed curve, and these commands are used to control motor 2 to ensure smooth, continuous, and shock-free speed control. The control subsystem is also used to adjust control commands based on pressure information. Specifically, a position closed-loop algorithm is used in the tail stage to detect position and speed changes in real time, generate deceleration curves, and adjust control commands in a high-speed closed loop based on the actual detected pressure information. This ensures accurate and shock-free stopping position. Unlike mold clamping motion control requirements, injection molding requires the execution speed to completely follow the set requirements. Smooth and rapid speed switching transitions are only provided during segmented injection molding changes to reduce speed abrupt changes and shearing during the filling process. Typically, injection molding requires pressure and speed dual-loop control. With this system, users can select either the conventional speed-priority dual-loop or pressure-priority dual-loop working mode according to their actual production needs. This effectively reduces filling defects caused by abrupt impacts in traditional injection molding machine control methods. The upper computer controller 19 and servo driver 20 of the injection molding machine work together to identify the state during different motion control actions and operate in different algorithm modes to obtain the optimal operating state.

[0063] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A precision closed-loop hydraulic-electric hybrid injection molding machine, characterized in that, include: The system includes an injection system, a mold clamping system, a lubrication system, a heating and cooling system, a safety monitoring system, a control system, and several closed-loop hydraulic drive systems. The closed-loop hydraulic drive systems are used to drive the injection system and the mold clamping system. The closed-loop hydraulic drive system includes several sets of hydraulic actuators, an oil pump (1), a motor (2), a hydraulic accumulator (3), and a cooler (8); Each hydraulic actuator includes a hydraulic actuator (4), a reversing device (6), and a main sensor (5). The hydraulic actuator (4) includes a first oil port and a second oil port. The reversing device (6) is connected to the first oil port of the corresponding hydraulic actuator (4) through a first oil passage (16), and the reversing device (6) is connected to the second oil port of the corresponding hydraulic actuator (4) through a second oil passage (15). The main sensor (5) is used to acquire load information that reflects the load movement driven by the hydraulic actuator (4). The hydraulic actuator (4) is a hydraulic cylinder or a hydraulic motor, and the reversing device (6) is a reversing valve. The reversing valve is used for opening, closing and reversing the closed hydraulic circuit. The reversing valve has four ports, two of which are connected to the inlet oil line (10) and the return oil line (9) respectively, and the other two ports are connected to the first oil line (16) and the second oil line (15) respectively. The main sensor (5) is installed on the hydraulic actuator (4). The main sensor (5) is an external magnetostrictive linear displacement sensor. The main sensor (5) includes an electronic chamber, a waveguide ruler and a movable magnetic ring. The electronic chamber is connected to the waveguide ruler and the movable magnetic ring is sleeved on the waveguide ruler. The oil pump (1)’s suction port (17) is connected to each reversing device (6) through the return oil line (9), and the oil pump (1)’s outlet port (18) is connected to each reversing device (6) through the inlet oil line (10). The oil pump (1) forms a closed hydraulic circuit with each hydraulic actuator through the inlet oil line (10) and the outlet oil line. The motor (2) is connected to the oil pump (1) for transmission, and the motor (2) is used to drive the oil pump (1). The hydraulic accumulator (3) is installed on the return oil line (9) to store and release hydraulic oil; the cooler (8) is installed on the return oil line (9) to cool the hydraulic oil so that the oil temperature of the hydraulic oil is always kept within the range required by the process. The closed-loop hydraulic drive system consists of two sets: a first closed-loop hydraulic drive system and a second closed-loop hydraulic drive system. The first closed-loop hydraulic drive system drives the mold clamping system, and the second closed-loop hydraulic drive system drives the injection system. The mold clamping system and the injection system are equipped with independent closed-loop hydraulic drive systems, which do not interfere with each other and ensure the stable operation of the injection molding machine. The hydraulic actuators of the first closed-circuit hydraulic drive system include a mold adjustment actuator, a mold opening and closing actuator, an ejector pin action actuator, and an auxiliary core-pulling action actuator. The mold adjustment actuator includes a mold adjustment directional valve (21) and a mold adjustment hydraulic motor (22); the mold opening and closing actuator includes a mold opening and closing directional valve (24) and a mold opening and closing hydraulic cylinder (23); the ejector pin action actuator includes an ejector pin action directional valve (25) and an ejector pin hydraulic cylinder (26); and the auxiliary core-pulling action actuator includes an auxiliary core-pulling action directional valve (27). The hydraulic actuators of the second closed-circuit drive system include an injection nozzle moving actuator and an injection actuator. The injection nozzle moving actuator includes an injection nozzle moving directional valve (28) and an injection nozzle moving hydraulic cylinder (29). The injection actuator includes an injection directional valve (30) and an injection hydraulic cylinder (31). An overflow pipeline (11) is provided between the oil inlet pipeline (10) and the oil return pipeline (9), and an overflow valve (13) is provided on the overflow pipeline (11); a negative pressure compensation pipeline (12) is also provided between the oil inlet pipeline (10) and the oil return pipeline (9), and a one-way valve (14) is provided on the negative pressure compensation pipeline (12). It also includes a sensor (7), which is installed on the oil inlet line (10) and the oil return line (9). The sensor (7) is used to detect the hydraulic pressure information at its location. The control system is electrically connected to the motor (2), the main sensor (5) and the commutator (6). The control system is used to generate control commands based on load information to perform real-time closed-loop control of the motor (2). The control system is also used to switch the conduction state of the commutator (6). The control system is also used to adjust the control commands based on pressure information. The control system uses a fully digital PID motion control algorithm for real-time closed-loop control. The control system includes a host controller (19) and a servo driver (20). The host controller (19) is connected to the servo driver (20), and the servo driver (20) is electrically connected to the motor (2).

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