Hydraulic injection system of a die casting machine and control method thereof

Abstract

The application discloses a hydraulic injection system of a die casting machine, which comprises a first valve module connected with a rodless cavity, a second valve module connected with a rod cavity, and a control module connected with the first valve module and the second valve module; when slow injection is performed, the control module is adapted to control the opening degree of the first valve module and the second valve module to be the same, so that the pressure of the rod cavity in the slow injection stage can be effectively reduced, and then the start-up impact can be avoided. The application further discloses a control method of the hydraulic injection system of the die casting machine, which comprises the following processes: a control module sends control signals to the first valve module and the second valve module according to the expected motion track of the injection cylinder; and the injection cylinder is corrected according to the deviation between the real-time motion state and the expected motion track of the injection cylinder, so that the accurate speed control of the injection cylinder can be realized, and the overshoot in the fast injection stage can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of die casting equipment, in particular to a die casting machine injection hydraulic system and a control method thereof. BACKGROUND

[0002] The die casting machine is a machine for pressure casting, which is commonly used in the production and processing of automobile parts and the like. The die casting machine can inject molten metal under the action of pressure into a mold to be cooled and formed into a solid metal casting.

[0003] The injection process of the existing cold chamber die casting machine can be divided into three stages: the first stage is slow injection, the second stage is fast injection, and the third stage is pressure injection. The existing cold chamber die casting machine can be divided into two mechanisms, namely a mold closing mechanism and an injection mechanism. Through the joint action of the mold closing mechanism and the injection mechanism, the molten alloy solution can be high-pressure cast and formed.

[0004] However, the injection mechanism of the existing cold chamber die casting machine has the following two shortcomings or problems when performing injection work:

[0005] (1) The slow injection process has a start-up impact;

[0006] (2) The piston rod movement speed curve of the high-speed injection process has overshoot and poor stability. SUMMARY

[0007] One of the purposes of the present application is to provide a die casting machine injection hydraulic system that can solve at least one of the defects in the background art.

[0008] Another purpose of the present application is to provide a control method for a die casting machine injection hydraulic system that can solve at least one of the defects in the background art.

[0009] To achieve the at least one purpose described above, the technical solution adopted by the present application is as follows: a die casting machine injection hydraulic system, comprising an injection cylinder, a first valve module, a second valve module, and a control module; a hydraulic oil source is connected to a rodless cavity of the injection cylinder through the first valve module, and a rod cavity of the injection cylinder is connected to the hydraulic oil source through the second valve module; the control module is connected to the first valve module and the second valve module for control; when slow injection is performed, the control module is adapted to control the first valve module and the second valve module to keep the same opening degree, so that the hydraulic oil enters the rodless cavity through the first valve module, and the hydraulic oil in the rod cavity is discharged along the second valve module.

[0010] Preferably, both the first valve module and the second valve module include a small-diameter valve unit and a large-diameter valve unit; when performing slow injection, the small-diameter valve unit is open and the large-diameter valve unit is closed; when performing rapid injection, both the small-diameter valve unit and the large-diameter valve unit are open, and the control module is adapted to suppress overshoot by controlling the opening degree of the small-diameter valve unit.

[0011] Preferably, the injection hydraulic system of the die-casting machine further includes an energy storage module, which is adapted to be connected to the rodless chamber through the first valve module, and the energy storage module is adapted to serve as the hydraulic oil source for the rodless chamber.

[0012] A control method for the injection hydraulic system of a die-casting machine, specifically including the following steps:

[0013] S100: The control module obtains the desired motion trajectory of the injection cylinder;

[0014] S200: The control module sends control signals to the first valve module and the second valve module according to the feedforward control;

[0015] S300: The injection cylinder works and sends its motion status as a feedback signal to the control module in real time;

[0016] S400: The control module corrects the operating status of the injection cylinder based on the deviation between the feedback signal and the desired motion trajectory.

[0017] Preferably, in step S200, the specific process of feedforward control is as follows:

[0018] S210: Obtain the desired velocity of the corresponding point of the injection cylinder based on the desired motion trajectory;

[0019] S220: Based on the desired speed obtained in step S210, the desired hydraulic oil flow rate corresponding to the injection cylinder is calculated using the formula.

[0020] S230: Based on the expected hydraulic oil flow rate obtained in step S220, the expected opening degree of the first valve module and the second valve module is calculated using the formula;

[0021] S240: Send corresponding control signals to the first valve module and the second valve module according to the desired opening degree obtained in step S230.

[0022] Preferably, when performing step S400, if the injection cylinder is in the slow injection stage, the control module corrects the motion state of the injection cylinder by simultaneously controlling the opening degree of the small-diameter valve unit corresponding to the first valve module and the second valve module based on the deviation between the feedback signal and the desired motion trajectory.

[0023] Preferably, when performing step S400, if the injection cylinder is in the rapid injection stage, the control module corrects the motion state of the injection cylinder by controlling the opening degree of the small-diameter valve unit corresponding to the first valve module and the second valve module respectively, based on the deviation between the feedback signal and the desired motion trajectory.

[0024] Preferably, the desired motion trajectory is the desired motion velocity trajectory or the desired motion displacement trajectory.

[0025] Preferably, if the desired motion trajectory adopts the desired motion speed trajectory, then in step S100, according to the process requirements, the corresponding speed values ​​of the injection cylinders at multiple displacement points in the process are determined, and then the speed values ​​of multiple displacement points are connected by a curve to obtain the desired motion speed trajectory.

[0026] Preferably, in step S300, the injection cylinder is adapted to send the movement speed of the piston rod as a feedback signal to the control module.

[0027] Compared with the prior art, the beneficial effects of this application are as follows:

[0028] (1) In the slow injection stage of the injection cylinder, compared with the traditional outlet speed regulation method, this application adopts the simultaneous control method of inlet and outlet, which can effectively reduce the pressure of the rod chamber during the operation of the injection cylinder, thereby ensuring that there will be no starting impact in the slow injection stage, and also improving the stability of the slow injection stage.

[0029] (2) During the rapid injection phase of the injection cylinder, by adding feedforward control to the speed control, the speed control cycle of the injection cylinder is shortened, which can effectively improve the response speed of the control module. Furthermore, by detecting the motion state of the injection cylinder in real time and comparing it with the desired motion trajectory, the motion state of the injection cylinder can be corrected based on the deviation between the two, so as to achieve precise speed control of the injection cylinder. This can prevent overshoot of the injection cylinder during the rapid injection phase and improve the stability of the injection cylinder during the rapid injection phase. Attached Figure Description

[0030] Figure 1 This is a partial structural schematic diagram of the hydraulic injection system of the present invention.

[0031] Figure 2 This is a schematic diagram illustrating the mathematical model of the control method in this invention.

[0032] Figure 3 This is a schematic diagram of the overall process of the control module controlling the injection cylinder in this invention.

[0033] Figure 4 This is a schematic diagram illustrating the specific process of the control module controlling the injection cylinder in this invention.

[0034] In the diagram: injection cylinder 100, rodless chamber 110, rod chamber 120, piston rod 130, first valve module 200, second valve module 300, and energy storage module 400. Detailed Implementation

[0035] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0036] In the description of this application, it should be noted that the directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this application.

[0037] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0038] One aspect of this application provides an injection hydraulic system for a die-casting machine, such as... Figure 1As shown, one preferred embodiment includes an injection cylinder 100, a first valve module 200, a second valve module 300, and a control module (not shown). The hydraulic oil source of the hydraulic system can be connected to the rodless chamber 110 of the injection cylinder 100 through the first valve module 200, while the rod chamber 120 of the injection cylinder 100 can be connected to the hydraulic oil source through the second valve module 300. The control module is electrically connected to the first valve module 200, the second valve module 300, and the injection cylinder 100. When the injection mechanism of the die-casting machine needs to perform slow injection, the control module can control the first valve module 200 and the second valve module 300 to open to the same degree, so that the hydraulic oil in the hydraulic oil source enters the rodless chamber 110 through the first valve module 200, while the hydraulic oil in the rod chamber 120 is discharged along the second valve module 300 and flows back into the hydraulic oil source. Thus, the piston rod 130 inside the injection cylinder 100 can slide along the cylinder body under the drive of hydraulic oil, thereby driving the die-casting machine to perform the slow injection stage. Since the first valve module 200 and the second valve module 300 are opened to the same degree, the injection cylinder 100 maintains constant pressure during the movement of the piston rod 130, thereby effectively avoiding the generation of starting shock.

[0039] It should be understood that existing die-casting machines generally use an outlet speed control method for slow injection, that is, the movement speed of the piston rod 130 of the injection cylinder 100 is controlled by adjusting the opening of the second valve module 300, which is connected to the rod chamber 120 of the injection cylinder 100. Therefore, during the slow start-up phase of the injection cylinder 100, hydraulic oil enters the rodless chamber 110 of the injection cylinder 100 from the first valve module 200. Because the openings of the first valve module 200 and the second valve module 300 are different (generally, the opening of the first valve module 200 is greater than that of the second valve module 300), when the speed at which hydraulic oil is discharged from the rod chamber 120 is less than the speed at which hydraulic oil is introduced into the rodless chamber 110, the oil pressure in the rod chamber 120 will rapidly increase to approximately twice that of the rodless chamber within a short period of time. At this time, the hydraulic oil in the rod chamber 120 will generate a certain amount of compression under pressure, which will cause a sudden change in the moving speed of the piston rod 130. This will result in a "bulge" on the speed curve, which is the starting impact.

[0040] The embodiment employs a method of simultaneously controlling the inlet and outlet for slow movement. Specifically, during the slow start-up phase of the injection cylinder 100, the control module can maintain the same opening degree for both the first valve module 200 and the second valve module 300. This ensures that the hydraulic oil entering the rodless chamber 110 of the injection cylinder 100 travels at the same speed as the hydraulic oil exiting the rod chamber 120 of the injection cylinder 100. This guarantees that the hydraulic pressure in both the rodless chamber 110 and the rod chamber 120 of the injection cylinder 100 remains essentially constant, effectively reducing or avoiding start-up shock phenomena during the low-speed phase and improving the stability of the injection mechanism during the slow injection phase.

[0041] In this embodiment, as Figure 1 As shown, both the first valve module 200 and the second valve module 300 include a small-diameter valve unit and a large-diameter valve unit; the small-diameter valve units and large-diameter valve units included in each valve module are connected in parallel. When the injection cylinder 100 performs slow injection, the control module can control the small-diameter valve units of the first valve module 200 and the second valve module 300 to open to the same degree, while simultaneously closing the large-diameter valve units of both the first valve module 200 and the second valve module 300. When the injection cylinder 100 performs rapid injection, the control module can control both the small-diameter valve units and the large-diameter valve units of the first valve module 200 and the second valve module 300 to open; wherein, if the large-diameter valve units of the first valve module 200 and the second valve module 300 have the same opening degree, the control module can suppress overshoot by controlling the small-diameter valve units of the first valve module 200 and the second valve module 300 to have different opening degrees.

[0042] Understandably, during the slow injection phase when the injection mechanism starts, the hydraulic oil flow rate required by the injection cylinder 100 is relatively small, while during the rapid injection phase, the hydraulic oil flow rate required by the injection cylinder 100 is relatively large. Traditional injection mechanisms typically connect both the rod-side chamber 120 and the rodless chamber 110 of the injection cylinder 100 to the hydraulic oil source only through a large-diameter valve unit. Because the large-diameter valve unit has a large adjustment range, the control module's control accuracy for it is relatively poor, thus failing to effectively suppress overshoot during the rapid injection phase.

[0043] In this embodiment, by connecting a small-diameter valve unit and a large-diameter valve unit in parallel to both the rod-side chamber 120 and the rodless chamber 110 of the injection cylinder 100, during the slow injection phase of the injection mechanism, only the small-diameter valve unit needs to be opened to ensure normal hydraulic oil supply. During the rapid injection phase, both the small-diameter and large-diameter valve units of a single valve module can be opened. Overshoot occurring during rapid injection can be suppressed by controlling the opening degree of the small-diameter valve unit. Since the amount of hydraulic oil flowing through the small-diameter valve unit is small, adjusting its opening degree will not interfere with the hydraulic oil flow through the large-diameter valve unit. Furthermore, the small-diameter valve unit has a small adjustment range for hydraulic oil, allowing for rapid response to overshoot. Compared to traditional injection mechanisms, this embodiment achieves rapid response to overshoot, effectively shortening the control cycle and improving the overshoot suppression accuracy.

[0044] Specifically, such as Figure 1 As shown, for easy differentiation, the small-diameter valve unit corresponding to the first valve module 200 can be marked as V201, and the large-diameter valve unit can be marked as V202; the small-diameter valve unit corresponding to the second valve module 300 can be marked as V301, and the large-diameter valve unit can be marked as V302.

[0045] When the injection mechanism of the die-casting machine performs slow injection, such as Figure 1 As shown, the control module can control the simultaneous opening of small-diameter valve units V201 and V301, and the opening degrees of small-diameter valve units V201 and V301 remain equal at all times. Therefore, during the slow movement of the piston rod 130 of the injection cylinder 100 along the rod chamber 120, the amount of hydraulic oil Q1 flowing into the rodless chamber 110 of the injection cylinder 100 through the small-diameter valve unit V201 is approximately equal to the amount of hydraulic oil Q2 discharged from the rod chamber 120 of the injection cylinder 100 through the small-diameter valve unit V301. This ensures that during slow injection, the pressure in both the rod chamber 120 and the rodless chamber 110 of the injection cylinder 100 is relatively low, preventing severe compression of the hydraulic oil in the rod chamber 120, and effectively reducing or avoiding the start-up impact phenomenon of the die-casting machine. Meanwhile, during the above process, the control module can keep the large-diameter valve unit V202 and the large-diameter valve unit V302 closed.

[0046] When the injection mechanism of the die-casting machine performs rapid injection, such as Figure 1As shown, the control module can control the opening of both the small-diameter valve unit V201 and the large-diameter valve unit V202, as well as both the small-diameter valve unit V301 and the large-diameter valve unit V302. The opening degrees of the large-diameter valve units V202 and V302 can be kept consistent, and the specific values ​​of their opening degrees can be controlled according to the required movement speed of the piston rod 130. When overshoot occurs in the speed curve of the piston rod 130 of the injection cylinder 100, the control module can suppress the overshoot by controlling the opening degrees of the small-diameter valve units V201 and V301.

[0047] For ease of understanding, specific parameters will be used for explanation below. Let v1 be the moving speed of the piston rod 130 of the injection cylinder 100 corresponding to the slow injection stage, and v2 be the moving speed of the piston rod 130 of the injection cylinder 100 corresponding to the fast injection stage. Those skilled in the art should know that the ratio of v2 to v1 is generally greater than 10; for the sake of subsequent description, we can assume v2 / v1 = 10. Based on the ratio of v2 to v1, we can assume that the unit flow rate when the large-diameter valve unit is fully open corresponds exactly to the unit flow rate required by the injection cylinder 100 in the fast injection stage; and that the unit flow rate when the small-diameter valve unit is fully open corresponds exactly to the unit flow rate required by the injection cylinder 100 in the slow injection stage; that is, the unit flow rate when the large-diameter valve unit is fully open is 10 times the unit flow rate when the small-diameter valve unit is fully open.

[0048] When the injection mechanism performs slow injection, the control module only needs to control the small-diameter valve units V201 and V301 to be fully open and the large-diameter valve units V202 and V302 to be closed. This ensures that the movement of the piston rod 130 of the injection cylinder 100 meets the requirements of slow injection and can effectively reduce or avoid the starting impact phenomenon during slow injection.

[0049] When the injection mechanism performs rapid injection, the control module can control the large-diameter valve units V202 and V302 to maintain 90% of their maximum opening, and control the small-diameter valve units V201 and V301 to maintain 100% of their maximum opening. Thus, the piston rod 130 of the injection cylinder 100 can move to meet the requirements of rapid injection.

[0050] When the piston rod 130 of the injection cylinder 100 moves at an overshoot, meaning the actual moving speed of the piston rod 130 exceeds the theoretical moving speed, assuming the overshoot is 7%, the control module can control the opening of the small-diameter valve units V201 and V301 to be between 30% and 80% of their maximum opening (the maximum allowable overshoot is generally 5%).

[0051] Understandably, traditional die-casting machines only have large-diameter valve units V202 and V302 installed. Therefore, when overshoot occurs, the control module can reduce the opening of these valve units from 100% to between 93% and 98%. That is, the opening adjustment range of the large-diameter valve units V202 and V302 during overshoot suppression is 5% of their maximum opening. In this embodiment, however, by setting small-diameter valve units V201 and V301, the opening adjustment range during overshoot suppression is 50% of their maximum opening. Compared to traditional die-casting machines, this embodiment can significantly improve the overshoot suppression accuracy during the rapid injection stage and effectively shorten the overshoot suppression control cycle, thereby effectively improving the response speed of the control module.

[0052] It should be understood that the specific structure and working principle of large-diameter valve units and small-diameter valve units are well known to those skilled in the art; common large-diameter valve units and small-diameter valve units can both use servo valves, etc.

[0053] One embodiment of this application, such as Figure 1 As shown, the injection hydraulic system of the die-casting machine also includes an energy storage module 400. The energy storage module 400 can be connected to the rodless chamber 110 through the first valve module 200, so that the energy storage module 400 can serve as a hydraulic oil source to supply hydraulic oil to the rodless chamber 110 during the injection process.

[0054] It should be understood that traditional hydraulic oil sources often use oil tanks. However, during the rapid injection and pressurized injection phases of the injection mechanism, the hydraulic oil pressure generated by the pump in the oil tank cannot meet the operating requirements of the injection mechanism. Therefore, an energy storage module 400 is used as the hydraulic oil source for the injection mechanism; specifically, the rodless chamber 110 of the injection cylinder 100 is connected to the energy storage module 400 via a first valve module 200, and the rod chamber 120 of the injection cylinder 100 is connected to the oil tank via a second valve module 300. Thus, during the injection process, the high-pressure hydraulic oil in the energy storage module 400 can enter the rodless chamber 110 through the first valve module 200; simultaneously, the hydraulic oil in the rod chamber 120 is discharged to the oil tank through the second valve module 300, and then the hydraulic oil in the oil tank can be pumped to the energy storage module 400 for pressurized energy storage.

[0055] Another aspect of this application provides a control method for the injection hydraulic system of a die-casting machine, such as... Figures 2 to 4 As shown, one preferred embodiment specifically includes the following steps:

[0056] S100: The control module obtains the desired motion trajectory of the injection cylinder 100.

[0057] S200: The control module sends control signals to the first valve module 200 and the second valve module 300 according to the feedforward control.

[0058] S300: The injection cylinder 100 operates and sends its motion status as a feedback signal to the control module in real time.

[0059] S400: The control module corrects the operating status of the injection cylinder 100 based on the deviation between the feedback signal and the desired motion trajectory.

[0060] In layman's terms, such as Figure 3 As shown, the control module can obtain the desired flow rate of the rodless chamber 110 and the rod chamber 120 of the injection cylinder 100 in the corresponding injection stage according to the set desired motion trajectory. Then, the control module controls the opening degree of the first valve module 200 and the second valve module 300 respectively according to the desired flow rate of the corresponding rod chamber 110 and the rod chamber 120. After the first valve module 200 and the second valve module 300 are opened, the injection cylinder 100 can move under the pressure of the incoming hydraulic oil. The control module can detect the motion state of the injection cylinder 100, thereby obtaining the actual motion trajectory of the injection cylinder 100, and compare the actual motion trajectory with the desired motion trajectory. Based on the comparison result, the deviation between the actual motion trajectory and the desired motion trajectory is corrected.

[0061] In this embodiment, the motion state of the injection cylinder 100 includes the motion speed of the piston rod 130 and the motion displacement of the piston rod 130. Therefore, the desired motion trajectory in step S100 can correspond to the desired motion speed trajectory or the desired motion displacement trajectory.

[0062] In this embodiment, if the desired motion trajectory adopts the desired motion speed trajectory, then in step S100, those skilled in the art can first determine several important displacement points in the process according to the process requirements, and then determine the speed values ​​of the piston rod 130 of the injection cylinder 100 at the multiple displacement points by formula calculation or industry experience, and finally connect the speed values ​​of multiple displacement points by fitting curves to obtain the desired motion speed trajectory.

[0063] If the desired motion trajectory adopts the desired motion displacement trajectory, in step S100, those skilled in the art can first determine several important time nodes in the process according to the process requirements, and then determine the displacement of the piston rod 130 of the injection cylinder 100 at multiple time nodes by formula calculation or industry experience, and finally connect the displacement of multiple time nodes by fitting curves to obtain the desired motion displacement trajectory.

[0064] In this embodiment, in step S300, the injection cylinder 100 can send the movement speed of the piston rod 130 as a feedback signal to the control module.

[0065] It is understandable that when the desired motion trajectory adopts the desired motion speed trajectory, the actual motion speed trajectory of the injection cylinder 100 can be directly obtained from the motion speed of the piston rod 130. When the desired motion trajectory adopts the desired motion displacement trajectory, the actual motion displacement trajectory of the injection cylinder 100 can be obtained from the motion speed of the piston rod 130 according to the displacement calculation formula.

[0066] Of course, the injection cylinder 100 can also send the movement displacement of the piston rod 130 as feedback to the control module. The specific choice can be made according to the actual needs of those skilled in the art. In this embodiment, the movement speed of the piston rod 130 is preferably used as the feedback signal.

[0067] To facilitate understanding, the above control methods can be explained using mathematical models.

[0068] like Figure 2 As shown, firstly, the desired motion trajectory is input into the control module, and the input quantity R(S) of the mathematical model corresponding to the entire control method can be obtained. R(S) represents the desired piston rod velocity value after function transformation.

[0069] Then, the control module can input the input quantity R(S) into the transfer function G4(S) of the feedforward channel for calculation, and send the calculation result to the transfer function G1(S) of the forward channel. After calculation by the transfer function G1(S), the control signals for the opening degree of the first valve module 200 and the second valve module 300 can be obtained. Here, G4(S) represents the function that converts the desired speed value into the valve's input control signal value, and G1(S) represents the function expression of the valve itself. That is, after the input signal value of the valve module is passed into the valve module, the valve core of the control valve module is actuated, generating a certain valve core displacement, thereby controlling the opening degree of the valve module.

[0070] Then, the control module can control the first valve module 200 and the second valve module 300 to open according to the control signal, so that the injection cylinder 100 moves under the drive of hydraulic oil.

[0071] Then, the control module can input the motion parameters of the injection cylinder 100 into the transfer function G2(S) corresponding to the injection cylinder 100; thereby obtaining the output C(S) of the entire control method, that is, the actual motion trajectory of the injection cylinder 100. Here, G2(S) represents the functional expression that converts the valve core displacement into the output speed of the hydraulic piston.

[0072] Finally, the control module can send the output quantity C(S) as a feedback signal to the input of the mathematical model through the transfer function H(S) of the feedback channel, thereby comparing the actual motion trajectory of the injection cylinder 100 with the desired motion trajectory. If there is a deviation between the actual motion trajectory and the desired motion trajectory, the control module can use a control algorithm to control the value of the transfer function G1(S) of the forward channel according to the corresponding deviation value, that is, to control the control signal controlling the opening of the first valve module 200 and the second valve module 300 to correct the deviation value.

[0073] In simpler terms, the actual control process involves inputting the desired piston speed change into the control system. First, the piston speed is converted into an input signal value for the valve module via the G4(S) function expression. Then, the actual input signal value of the valve module is converted into the actual displacement value of the valve core via G1(S), and the actual displacement value of the valve core is converted into the actual hydraulic piston speed value via G2(S). The actual piston speed value is then fed back through H(S), where the actual speed value is subtracted from the desired speed value. The PID controller then adjusts the actual input signal value of the valve module to ultimately eliminate starting shock and suppress overshoot.

[0074] It should be understood that, for starting shock, the above-described control strategy can be applied to the small-diameter valve unit connected to the rod chamber 120 of the injection cylinder 100 to eliminate the starting shock. For high-speed overshoot, the above-described control strategy can be applied to both the large-diameter valve unit and the small-diameter valve unit connected to the rod chamber 120 and the rodless chamber 110 of the injection cylinder 100 to suppress high-speed overshoot.

[0075] In this embodiment, the specific process of feedforward control in step S200 is as follows:

[0076] S210: Obtain the desired velocity of the corresponding point of the injection cylinder 100 according to the desired motion trajectory.

[0077] S220: Based on the desired speed obtained in step S210, the desired hydraulic oil flow rate corresponding to the injection cylinder 100 is calculated using the formula.

[0078] S230: Based on the expected hydraulic oil flow rate obtained in step S220, the expected opening degree of the first valve module 200 and the second valve module 300 is calculated using the formula.

[0079] S240: Send corresponding control signals to the first valve module 200 and the second valve module 300 according to the desired opening degree obtained in step S230.

[0080] It is understood that the calculation formulas for speed and flow rate in steps S220 and S230 are well-known to those skilled in the art, so the detailed conversion process will not be elaborated here.

[0081] In this embodiment, when the injection cylinder 100 is in the slow injection stage, if the feedback signal in step S400 deviates from the expected motion trajectory, the control module can correct the motion state of the injection cylinder 100 by simultaneously controlling the opening degree of the small-diameter valve unit corresponding to the first valve module 200 and the second valve module 300.

[0082] When the injection cylinder 100 is in the rapid injection stage, if the feedback signal in step S400 deviates from the expected motion trajectory, the control module can correct the motion state of the injection cylinder 100 by controlling the opening degree of the small-diameter valve units corresponding to the first valve module 200 and the second valve module 300 respectively.

[0083] In this embodiment, as Figure 4 As shown, the control module includes a controller, an I / O module, pressure sensors, and displacement sensors; the energy storage module 400 includes a rapid energy storage unit and a booster energy storage unit. Multiple pressure sensors are used to detect the pressure in the rapid energy storage unit, the booster energy storage unit, and the injection cylinder 100. Simultaneously, displacement sensors detect the displacement of the piston rod 130 of the injection cylinder 100. The pressure and displacement sensors send the detection results to the controller. The controller can control the first valve module 200, the second valve module 300, and the corresponding replenishing valves for the rapid and booster energy storage units via the I / O module.

[0084] Specifically, in combination Figure 4 The specific working process of the injection cylinder 100 can be described.

[0085] When the injection cylinder 100 performs slow injection, the controller can obtain the control signals of the inlet and outlet servo valves of the injection cylinder 100 based on the trajectory segment corresponding to the desired motion trajectory. The controller can then send these control signals to the first valve module 200 and the second valve module 300 via the I / O module, ensuring that the small-diameter valve units V201 and V301 of the first and second valve modules 200 and 300 maintain the same opening degree. During this process, the pressure sensor and displacement sensor corresponding to the injection cylinder 100 can send the real-time pressure of the injection cylinder 100 and the real-time displacement of the piston rod 130 to the controller, respectively. If the pressure sensor data is abnormal, the controller can promptly stop the injection cylinder 100 to prevent malfunction. The real-time displacement of the piston rod 130 of the injection cylinder 100 allows the determination of the actual motion trajectory of the injection cylinder 100 during the slow injection phase. Due to the small flow rate and slow speed during the slow injection phase, overshoot is generally not observed.

[0086] When the injection cylinder 100 performs rapid injection, the controller can obtain control signals from the inlet and outlet servo valves and the rapid accumulator of the injection cylinder 100 based on the trajectory segment corresponding to the desired motion trajectory. The controller then sends these control signals via the I / O module to the first valve module 200, the second valve module 300, and the replenishing valve of the rapid accumulator, ensuring that the first valve module 200 and the second valve module 300 maintain the same opening degree, and that the rapid accumulator is activated. During this process, when the oil pressure of the rapid accumulator reaches the set value, the corresponding pressure sensor sends a pressure signal to the controller, which can then control the replenishing valve of the rapid accumulator to stop operating via the I / O module. Simultaneously, the pressure sensor and displacement sensor corresponding to the injection cylinder 100 send the real-time pressure of the injection cylinder 100 and the real-time displacement of the piston rod 130 to the controller, respectively. If the pressure sensor data is abnormal, the controller can promptly stop the injection cylinder 100 to prevent malfunction. The actual motion trajectory of the injection cylinder 100 during the rapid injection phase can be obtained by measuring the real-time displacement of the piston rod 130 of the injection cylinder 100. Since the flow rate and speed are relatively high during the rapid injection phase, overshoot is likely to occur, meaning that the actual motion trajectory of the injection cylinder 100 exceeds the corresponding expected motion trajectory. The controller can then synchronously adjust the opening of the small-diameter valve units V201 and V301 based on the deviation between the actual and expected motion trajectories to correct the overshoot.

[0087] When the injection cylinder 100 performs pressurized injection, the controller can obtain control signals from the inlet and outlet servo valves and the booster accumulator of the injection cylinder 100 based on the trajectory segment corresponding to the desired motion trajectory. The controller then sends these control signals via the I / O module to the first valve module 200, the second valve module 300, and the replenishing valve of the booster accumulator, ensuring that the first valve module 200 and the second valve module 300 maintain the same opening degree, and that the booster accumulator is activated. During this process, when the oil pressure of the booster accumulator reaches the set value, the corresponding pressure sensor sends a pressure signal to the controller. The controller can then use the I / O module to stop the replenishing valve of the booster accumulator. Simultaneously, the pressure sensor and displacement sensor corresponding to the injection cylinder 100 send the real-time pressure of the injection cylinder 100 and the real-time displacement of the piston rod 130 to the controller, respectively. If the pressure sensor data is abnormal, the controller can promptly stop the injection cylinder 100 to prevent malfunction. The actual movement trajectory of the injection cylinder 100 during the rapid injection phase can be obtained by the real-time displacement of the piston rod 130 of the injection cylinder 100. Since the pressure only needs to meet the actual requirements during the pressurization injection phase, the movement speed is low and overshoot generally does not occur.

[0088] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A hydraulic injection system for a die-casting machine, characterized in that, include: The system comprises an injection cylinder, a first valve module, a second valve module, and a control module; a hydraulic oil source is adapted to be connected to the rodless chamber of the injection cylinder through the first valve module, and the rod chamber of the injection cylinder is adapted to be connected to the hydraulic oil source through the second valve module; the control module is connected to both the first valve module and the second valve module for control purposes. When performing slow injection, the control module is adapted to control the first valve module and the second valve module to maintain the same opening degree; Both the first valve module and the second valve module include a small-diameter valve unit and a large-diameter valve unit; When slow injection is performed, the small-diameter valve unit is opened and the large-diameter valve unit is closed; During rapid injection, both the small-diameter valve unit and the large-diameter valve unit are open, and the control module is adapted to suppress overshoot by controlling the opening degree of the small-diameter valve unit. The unit flow rate of the large-diameter valve unit when fully open is 10 times that of the small-diameter valve unit when fully open.

2. The injection hydraulic system of the die-casting machine as described in claim 1, characterized in that: The injection hydraulic system of the die-casting machine also includes an energy storage module, which is adapted to be connected to the rodless chamber through the first valve module, and the energy storage module is adapted to serve as the hydraulic oil source for the rodless chamber.

3. A control method for the injection hydraulic system of a die-casting machine as described in claim 1 or 2, characterized in that, Specifically, the steps include the following: S100: The control module obtains the desired motion trajectory of the injection cylinder; S200: The control module sends control signals to the first valve module and the second valve module according to the feedforward control; S300: The injection cylinder works and sends its motion status as a feedback signal to the control module in real time; S400: The control module corrects the operating status of the injection cylinder based on the deviation between the feedback signal and the desired motion trajectory.

4. The control method for the injection hydraulic system of the die-casting machine as described in claim 3, characterized in that: In step S200, the specific process of feedforward control is as follows: S210: Obtain the desired velocity of the corresponding point of the injection cylinder based on the desired motion trajectory; S220: Based on the desired speed obtained in step S210, the desired hydraulic oil flow rate corresponding to the injection cylinder is calculated using the formula. S230: Based on the expected hydraulic oil flow rate obtained in step S220, the expected opening degree of the first valve module and the second valve module is calculated using the formula; S240: Send corresponding control signals to the first valve module and the second valve module according to the desired opening degree obtained in step S230.

5. The control method for the injection hydraulic system of the die-casting machine as described in claim 3, characterized in that: When performing step S400, if the injection cylinder is in the slow injection stage, the control module corrects the motion state of the injection cylinder by simultaneously controlling the opening degree of the small-diameter valve unit corresponding to the first valve module and the second valve module based on the deviation between the feedback signal and the desired motion trajectory.

6. The control method for the injection hydraulic system of the die-casting machine as described in claim 3, characterized in that: During step S400, if the injection cylinder is in the rapid injection stage, the control module corrects the motion state of the injection cylinder by controlling the opening degree of the small-diameter valve units corresponding to the first valve module and the second valve module respectively, based on the deviation between the feedback signal and the desired motion trajectory.

7. The control method for the injection hydraulic system of the die-casting machine as described in any one of claims 3-6, characterized in that: The desired motion trajectory is either the desired velocity trajectory or the desired displacement trajectory.

8. The control method for the injection hydraulic system of the die-casting machine as described in claim 7, characterized in that: If the desired motion trajectory adopts the desired motion speed trajectory, then in step S100, according to the process requirements, the corresponding speed values ​​of the injection cylinders at multiple displacement points in the process are determined, and then the speed values ​​of multiple displacement points are connected by a curve to obtain the desired motion speed trajectory.

9. The control method for the injection hydraulic system of the die-casting machine as described in claim 3, characterized in that: In step S300, the injection cylinder is adapted to send the movement speed of the piston rod as a feedback signal to the control module.

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