An extrusion hydraulic system and a control method thereof

Abstract

The application discloses an extrusion hydraulic system and a control method thereof. The system comprises an injection cylinder, a swing cylinder, an energy storage circuit, an injection circuit and a swing circuit. The injection cylinder and the swing cylinder are rotatably installed on a rack, and the driving end of the swing cylinder is hinged to the injection cylinder. The swing circuit is connected to the swing cylinder, so that the swing cylinder drives the injection cylinder to swing at a set angle under the driving of the swing circuit. The energy storage circuit and the injection circuit are connected in parallel to the rodless cavity of the injection cylinder, and the injection circuit is further connected to the rod cavity of the injection cylinder. The control method is applied to the system. The application has the advantages that, compared with the traditional mode, the injection process is jointly performed by the power source and the energy storage circuit, the stability of the injection can be effectively improved, and the die casting quality of the product is improved. The closed-loop V-P switching point position control method is adopted in the injection process, so that the safety and stability of the injection stage operation can be ensured.

Description

TECHNICAL FIELD

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

[0002] Extrusion casting (liquid die forging) technology is currently widely used in national defense, transportation, 3D forming and communication mobile phones, and has become one of the important technologies for realizing the formation of complex parts with little cutting in advanced manufacturing technology. The working principle is to inject a certain amount of molten metal liquid into a metal mold chamber, then close the mold to realize the filling and flow of the metal liquid, and under the action of mechanical static pressure, high-pressure solidification and a small amount of plastic deformation occur, thereby obtaining a blank or a part.

[0003] The vertical extrusion injection mainly includes the processes of energy storage, swing vertical, injection, back hammer and swing tilt. The control safety and stability of the hydraulic system of the traditional extrusion injection for the above injection processes are poor, and it is difficult to adapt to the high quality demand of the castings. SUMMARY

[0004] One of the purposes of the present application is to provide an extrusion injection hydraulic system capable of solving at least one defect in the background art.

[0005] Another purpose of the present application is to provide a control method of an extrusion injection hydraulic system capable of solving at least one defect in the background art.

[0006] In order to achieve at least one of the above purposes, the technical solution adopted by the present application is as follows: an extrusion injection hydraulic system, comprising an injection cylinder, a swing cylinder, an energy storage circuit, an injection circuit and a swing circuit; the injection cylinder and the swing cylinder are both rotationally installed on a rack, and the driving end of the swing cylinder is hingedly connected with the injection cylinder; the swing circuit is connected with the swing cylinder, so that the swing cylinder drives the injection cylinder to swing at a set angle under the drive of the swing circuit; the energy storage circuit and the injection circuit are connected in parallel to the rodless cavity of the injection cylinder, so that during injection, the energy storage circuit and the power source supply oil to the rodless cavity of the injection cylinder through the injection circuit; the injection circuit is also connected to the rod cavity of the injection cylinder, so that during injection, the rod cavity and the rodless cavity of the injection cylinder form a differential or are directly connected to the oil tank.

[0007] Preferably, the energy storage circuit comprises an accumulator V411, a cartridge valve V412 and a pilot directional valve V413; the power source is connected to the accumulator V411 through the cartridge valve V412; the control end of the cartridge valve V412 is connected to the accumulator V411 and the oil tank through the pilot directional valve V413; when the accumulator is charged before injection, the pilot directional valve V413 controls the cartridge valve V412 to open, so that the power source supplies oil to the accumulator V411; when injection is performed, the accumulator V411 supplies oil to the injection circuit through the branch of the oil inlet end of the cartridge valve V412.

[0008] Preferably, the injection circuit comprises a servo valve V441 and a cartridge valve V442; the oil inlet of the servo valve V441 is connected to the branch of the oil inlet end of the cartridge valve V412, and the oil outlet of the servo valve V441 is connected to the rodless chamber of the injection cylinder; the rodless chamber and the rod chamber of the injection cylinder are connected through the cartridge valve V442; when injection is performed, the servo valve V441 is controlled to be turned on based on the opening signal of the cartridge valve V412, and then the oil output by the accumulator V411 and the oil output by the power source both flow to the rodless chamber of the injection cylinder through the servo valve V441; at the same time, the oil in the rod chamber of the injection cylinder flows back to the rodless chamber through the cartridge valve V442 to form a differential circuit; wherein the opening degree of the servo valve V441 controls the injection speed.

[0009] Preferably, the injection circuit further comprises a cartridge valve V444 and a pilot directional valve V447; the cartridge valve V444 is connected between the rod chamber of the injection cylinder and the oil tank, and the control end of the cartridge valve V444 is connected to the oil tank and the power source through the pilot directional valve V447; when the injection cylinder is pressurized for injection, the pilot directional valve V447 controls the control end of the cartridge valve V444 to communicate with the oil tank, so that the oil in the rod chamber of the injection cylinder flows back to the oil tank through the cartridge valve V444; at this time, the accumulator V411 and the power source keep supplying oil to the rodless chamber of the injection cylinder.

[0010] Preferably, the swing circuit comprises a directional valve V421, a check valve V422 and a balance valve V423; the power source is connected to the oil inlet of the directional valve V421 through the check valve V422, the oil return port of the directional valve V421 is connected to the oil tank, one of the working oil ports of the directional valve V421 is connected to the rod chamber of the swing cylinder, and the other working oil port is connected to the rodless chamber of the swing cylinder through the balance valve V423.

[0011] Preferably, the extrusion hydraulic system further comprises a return stroke circuit for driving the injection cylinder to return stroke; the return stroke circuit comprises a pressure relief valve V451, a pilot directional valve V452, a cartridge valve V454, a pilot directional valve V455 and a cartridge valve V456; the pressure relief valve V451 and the cartridge valve V454 are connected in parallel between the rodless chamber of the injection cylinder and the oil tank, the control end of the cartridge valve V454 is connected between the rodless chamber of the injection cylinder and the oil tank through the pilot directional valve V452; the cartridge valve V456 is connected between the rod chamber of the injection cylinder and the power source, the control end of the cartridge valve V456 is connected between the power source and the oil tank through the pilot directional valve V455; when the injection is completed, the pressure relief valve V451 is adapted to open first for pressure relief; then the pilot directional valve V455 controls the cartridge valve V456 to open, so that the power source supplies oil to the rod chamber of the injection cylinder through the cartridge valve V456; at the same time, the pilot directional valve V452 controls the cartridge valve V454 to open, so that the oil in the rodless chamber of the injection cylinder flows back to the oil tank.

[0012] Preferably, the injection end of the injection cylinder is sealingly and slidingly mounted with an injection sleeve; the injection sleeve is connected with the injection cylinder through a lifting cylinder, the lifting cylinder is adapted to drive the injection sleeve to extend or retract relative to the injection cylinder under the control of a lifting circuit, so as to make the injection port of the injection sleeve sealingly connected with or separated from the mold cavity to be pressure cast.

[0013] Preferably, the lifting circuit comprises a directional valve V431, a balance valve V432 and a pressure valve V433; the oil inlet of the directional valve V431 is connected with the power source, and the oil return of the directional valve V431 is connected with the oil tank; the working oil port of the directional valve V431 is connected with the lifting cylinder through the balance valve V432; the pressure valve V433 is connected between the lifting cylinder and the oil tank; the oil provided by the power source is adapted to enter the lifting cylinder through the directional valve V431 and the balance valve V432 to drive the injection sleeve to extend relative to the injection cylinder; the oil in the lifting cylinder is adapted to flow back to the oil tank along the balance valve V432 and the directional valve V431 under the gravity of the injection sleeve, so as to make the injection sleeve retract relative to the injection cylinder; the pressure valve V433 is used to control the sealing pressure of the injection sleeve and the mold cavity.

[0014] A kind of injection control method, it is applied to the injection circuit described above, including the following steps: the piston speed expected value of injection cylinder is converted into the input signal value of servo valve V441;Actual input signal value of servo valve V441 It is converted into the actual displacement value of spool;Actual displacement value of spool is converted into actual injection cylinder piston speed value and is fed back;Injection cylinder piston speed actual value is compared with expected value, and according to the comparison result, the actual input signal value of servo valve V441 It is adjusted by PID controller.

[0015] Preferably, determine the injection speed value corresponding to multiple key points according to the injection process requirements;Based on the obtained injection speed value corresponding to different key points, the expected trajectory of injection cylinder piston movement speed is generated by curve generation algorithm.

[0016] Compared with the prior art, the beneficial effects of the present application are:

[0017] (1) Compared with the traditional way, the present application can effectively improve the stability of injection by power source and energy storage circuit together in the injection process, so as to improve the quality of product.

[0018] (2) The closed-loop V-P switching point position control method can ensure the safety and stability of injection stage operation, so as to improve production efficiency and improve the quality of castings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is the overall structure schematic diagram of the hydraulic system of the present application.

[0020] Figure 2 It is the structure schematic diagram of energy storage circuit in the present application.

[0021] Figure 3 It is the structure schematic diagram of swing circuit in the present application.

[0022] Figure 4 It is the structure schematic diagram of injection circuit in the present application.

[0023] Figure 5 It is the structure schematic diagram of back hammer circuit in the present application.

[0024] Figure 6 It is the structure schematic diagram of lifting circuit in the present application.

[0025] Figure 7 It is the control feedback process schematic diagram of injection cylinder in the present application.

[0026] In the figure: injection cylinder 100, injection sleeve 110, lifting oil cylinder 200, swing oil cylinder 300, energy storage circuit 41, swing circuit 42, lifting circuit 43, injection circuit 44, back hammer circuit 45. DETAILED DESCRIPTION

[0027] In the description of the present application, it should be noted that the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. in the description of the present application means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present application.

[0028] In the description of the present application, it should be noted that for orientation words such as the terms "center", "transverse", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation and positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the specific protection scope of the present application.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0030] In the present application, unless otherwise specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be connected, or detachable, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0033] One aspect of this application provides a hydraulic extrusion injection system, such as... Figure 1 As shown, one preferred embodiment includes an injection cylinder 100, a swing cylinder 300, an energy storage circuit 41, an injection circuit 44, and a swing circuit 42. The injection cylinder 100 needs to be in a horizontal position to ensure the injection of raw materials. After the injection of raw materials, the injection cylinder 100 needs to rotate to a vertical position for bottom-up extrusion casting. Therefore, the injection cylinder 100 is rotatably mounted on a frame (not shown). Simultaneously, the swing cylinder 300 is also rotatably mounted on the frame, and the drive end of the swing cylinder 300 is hinged to the injection cylinder 100. The swing circuit 42 is connected to the swing cylinder 300, so that when the injection cylinder 100 needs to change position, the swing cylinder 300 can drive the injection cylinder 100 to swing at a set angle under the drive of the swing circuit 42, that is, the injection cylinder 100 swings between the horizontal and vertical directions. The energy storage circuit 41 and the injection circuit 44 are connected in parallel to the rodless chamber A1 of the injection cylinder 100. During injection, the energy storage circuit 41 and the power source jointly supply oil to the rodless chamber A1 of the injection cylinder 100 through the injection circuit 44. This effectively improves the continuous pressure output during the die-casting process, enhances the stability of the injection, and thus improves the die-casting quality of the product. Simultaneously, the injection circuit 44 is also connected to the rod chamber A2 of the injection cylinder 100, allowing the rod chamber A2 and the rodless chamber A1 to form a differential connection or direct connection to the oil tank during injection. Based on the differential connection between the rod chamber A2 and the rodless chamber A1 of the injection cylinder 100, sudden changes in injection speed can be suppressed, further improving the stability of the injection process.

[0034] It should be known that the injection cylinder 100 is part of the injection module, the injection module is provided with an injection cavity, and the raw material for die casting can be injected into the injection cavity through the injection machine, and the function of the injection cylinder 100 is to inject the raw material injected into the injection cavity into the mold cavity through the hammer head driven by the piston. The swing cylinder 300 is actually a common drive of the injection module and the injection cylinder 100; that is, the swing cylinder 300 drives the injection module to be in a horizontal state to inject the raw material in the injection cavity, and after the injection of the raw material is completed, the swing cylinder 300 drives the injection module to be in a vertical state, at this time the opening of the injection cavity is upward and connected with the mold cavity, and then under the drive of the injection cylinder 100, the raw material in the injection cavity is injected into the mold cavity from bottom to top through the hammer head.

[0035] It can be understood that the drive of the swing cylinder 300 to the injection module can be directly connected with the injection module, or the swing cylinder 300 can be connected with the injection cylinder 100; the embodiment will be described in detail with the swing cylinder 300 connected with the injection cylinder 100. The specific way of the swing cylinder 300 driving the position of the injection cylinder 100 is known to those skilled in the art, so it will not be described in detail here.

[0036] Those skilled in the art should know that the specific working process of the vertical extrusion injection hydraulic system of the present application mainly includes an energy storage stage, a swing vertical stage, an injection stage and a hammer return stage. In order to facilitate understanding, the specific process will be described below.

[0037] In the embodiment, the specific structure of the energy storage circuit 41 capable of realizing the above functions has many kinds, in order to facilitate understanding, one of the structures will be described in detail below. As shown in Figure 2 and Figure 4 The energy storage circuit 41 includes an accumulator V411, a cartridge valve V412 and a pilot reversing valve V413. The power source P is connected with the accumulator V411 through the cartridge valve V412; the control end of the cartridge valve V412 is connected with the accumulator V411 and the oil tank T through the pilot reversing valve V413. The cartridge valve V412 and the power source P are also connected with the injection circuit 44 through the branch X.

[0038] When the energy storage circuit 41 is not working, the pilot reversing valve V413 can deliver part of the oil in the accumulator V411 to the control end of the cartridge valve V412, so that the control cartridge valve V412 is in the closed state, and the oil output by the power source P cannot enter the accumulator V411, and the oil in the accumulator V411 cannot be output. When the pre-injection energy storage is performed, the pilot reversing valve V413 can communicate the control end of the cartridge valve V412 with the oil tank T, so that the oil in the control end flows back to the oil tank T to open the cartridge valve V412; so that the oil output by the power source P can flow into the accumulator V411 through the cartridge valve V412 to store energy. When the injection is performed, the cartridge valve V412 is in the open state, at this time the oil in the accumulator V411 can flow to the injection circuit 44 through the branch X of the oil inlet end of the cartridge valve V412; at the same time, the oil output by the power source P can also flow to the injection circuit 44 through the branch X, so that the injection circuit 44 can supply oil to the rodless cavity A1 of the injection cylinder 100 through double power input to realize stable injection.

[0039] It should be known that the specific structure type of the pilot reversing valve V413 is various, for example Figure 2 As shown in the embodiment, a two-position four-way electromagnetic reversing valve is preferably used. When the energy storage circuit 41 does not work, the coil S401 at the right end of the pilot reversing valve V413 is not powered, at this time the accumulator V411 can communicate with the control end of the cartridge valve V412 through the pilot reversing valve V413 to realize the closing of the cartridge valve V412. When the energy storage circuit 41 needs to store energy or assist injection, the coil S401 at the right end of the pilot reversing valve V413 is powered, at this time the control end of the cartridge valve V412 can communicate with the oil tank T through the pilot reversing valve V413, so as to depressurize the control end to open the cartridge valve V412. It should be noted that the opening of the cartridge valve V412 means that the cartridge valve V412 can normally open under the oil pressure of the working oil port.

[0040] In the embodiment, as shown in the Figure 2 The energy storage circuit 41 also includes a shuttle valve V414 connected between the accumulator V411 and the oil tank T, which is mainly used to prevent pressure rebound and pressure loss caused by oil backflow when the accumulator V411 discharges energy. The specific structure of the shuttle valve V414 is known to those skilled in the art, and will not be described in detail here.

[0041] In the embodiment, the specific structure of the swing circuit 42 capable of realizing the above functions is various, in order to facilitate understanding, one of the structures will be described in detail below. As shown in the Figure 3As shown, the swing circuit 42 comprises a reversing valve V421, a check valve V422 and a balance valve V423. The power source P is connected to the oil inlet of the reversing valve V421 through the check valve V422, the oil outlet of the reversing valve V421 is connected to the oil tank T, one of the working oil ports of the reversing valve V421 is connected to the rod cavity C2 of the swing cylinder 300, and the other working oil port is connected to the rodless cavity C1 of the swing cylinder 300 through the balance valve V423.

[0042] It should be understood that the swing cylinder 300 can drive the injection cylinder 100 to move from horizontal to vertical by extending the piston rod, or can drive the injection cylinder 100 to move from horizontal to vertical by retracting the piston rod. In this embodiment, the swing cylinder 300 drives the injection cylinder 100 to move from horizontal to vertical by retracting the piston rod. Then the specific working process of the swing circuit 42 is as follows: when the injection cylinder 100 needs to swing from horizontal to vertical, the oil output by the power source P flows into the rod cavity C2 of the swing cylinder 300 through the reversing valve V421 after passing through the check valve V422, and the oil in the rodless cavity C1 of the swing cylinder 300 can flow back to the oil tank T in turn through the balance valve V423 and the reversing valve V421, thereby realizing the retraction of the swing cylinder 300. When the injection cylinder 100 needs to swing from vertical to horizontal to realize soup making, the oil output by the power source P flows into the rodless cavity C1 of the swing cylinder 300 through the balance valve V423 after passing through the reversing valve V421, and the oil in the rod cavity C2 of the swing cylinder 300 can flow back to the oil tank T after passing through the reversing valve V421, thereby realizing the extension of the swing cylinder 300.

[0043] It can be understood that the balance valve V423 provides a certain pressure during the swing of the injection cylinder 100, ensures that the swing of the injection cylinder 100 is more stable, and also prevents the injection cylinder 100 from spontaneously rotating vertically to cause impact due to its own weight in the inclined state. The check valve V422 mainly prevents the oil from flowing back when the power source P stops supplying oil, which causes the swing to not reach the vertical position.

[0044] It should be understood that there are many specific structure types of the reversing valve V421, for example Figure 3 As shown, the reversing valve V421 preferably adopts a three-position four-way reversing valve. When the swing circuit 42 is not working, the reversing valve V421 is in the middle cut-off position. When the injection cylinder 100 needs to swing from horizontal to vertical, the right coil S403 of the reversing valve V421 is powered, so that the valve core of the reversing valve V421 moves to the left. When the injection cylinder 100 needs to swing from vertical to horizontal to realize soup making, the left coil S402 of the reversing valve V421 is powered, so that the valve core of the reversing valve V421 moves to the right.

[0045] In this embodiment, the specific structure of the injection circuit 44 capable of realizing the above functions is various, in order to facilitate understanding, one of the structures will be described in detail below. As shown in Figure 4 The injection circuit 44 includes a servo valve V441, a cartridge valve V442, a cartridge valve V444, and a pilot reversing valve V447. The oil inlet of the servo valve V441 is connected to the branch of the oil inlet end of the cartridge valve V412, and the oil outlet of the servo valve V441 is connected to the rodless cavity A1 of the injection cylinder 100; the rodless cavity A1 and the rod cavity A2 of the injection cylinder 100 are connected through the cartridge valve V442. The cartridge valve V444 is connected between the rod cavity A2 of the injection cylinder 100 and the oil tank, and the control end of the cartridge valve V444 is connected to the oil tank and the power source through the pilot reversing valve V447.

[0046] It should be understood that the entire injection process can be divided into slow injection, fast injection and pressure boosting injection; among them, the slow injection and the fast injection have smaller requirements for injection force, and the injection process can be realized by the same circuit. The injection processes with different injection force requirements will be described in detail below.

[0047] When the injection cylinder 100 performs slow injection and fast injection, the servo valve V441 can be controlled to be turned on based on the opening signal of the cartridge valve V412, and then the oil output by the accumulator V411 and the oil output by the power source P can flow to the rodless cavity A1 of the injection cylinder 100 through the servo valve V441. At the same time, the oil in the rod cavity A2 of the injection cylinder 100 flows back to the rodless cavity A1 through the cartridge valve V442 to form a differential circuit. Among them, the slow injection and fast injection speed control can be realized by controlling the opening degree of the servo valve V441.

[0048] It can be understood that the specific type of the servo valve V441 is various, for example Figure 4 As shown, a two-position two-way servo valve is preferred in this embodiment. When the injection circuit 44 is not working, the servo valve V441 is closed through the right stop; and when the injection works, the coil S406 on the left side of the servo valve V441 is powered, and then the spool of the servo valve V441 moves left to realize the connection of the branch X. It should be understood that in order to ensure the safety of the injection process, an overflow valve V443 can be connected between the rod cavity A2 of the injection cylinder 100 and the oil tank T; when the pressure in the rod cavity A2 is too large, part of the oil can flow back to the oil tank T through the overflow valve V443.

[0049] When the injection cylinder 100 is in the process of pressure injection, the pilot reversing valve V447 controls the control end of the cartridge valve V444 to communicate with the tank T, and then the oil in the rodless chamber A2 of the injection cylinder 100 flows back to the tank T through the cartridge valve V444. At this time, the servo valve V441 keeps the left coil S406 powered to make the accumulator V411 and the power source P keep supplying oil to the rodless chamber A1 of the injection cylinder 100.

[0050] It can be understood that the specific type of the pilot reversing valve V447 is various, for example Figure 4 As shown in the figure, the K-type three-position four-way reversing valve is preferred in the embodiment. The pilot reversing valve V447 is also connected with the tank T through the pressure valve V445; when the injection cylinder 100 is in the process of slow injection or fast injection, the pilot reversing valve V447 is in the middle position, at this time, the control end of the cartridge valve V444 forms a large back pressure through the overflow valve V443 and the pressure valve V445, thereby realizing the cut-off of the cartridge valve V444. When the injection cylinder 100 needs to be pressure injected, the right coil S408 of the pilot reversing valve V447 is powered, so that the spool moves to the left, at this time, the pressure valve V445 is opened, and then the oil in the control end of the cartridge valve V444 flows back to the tank T through the opened pressure valve V445. In order to avoid the oil backflow when the cartridge valve V444 is opened, a one-way valve V446 can be connected between the control end of the cartridge valve V444 and the pilot reversing valve V447.

[0051] In the embodiment, the extrusion injection hydraulic system also includes a rebound circuit 45 for driving the injection cylinder 100 to rebound; the specific structure of the rebound circuit 4 for realizing the above functions is various, in order to facilitate understanding, one of the structures will be described in detail below. As shown in the figure Figure 5 The rebound circuit 45 includes a pressure relief valve V451, a pilot reversing valve V452, a cartridge valve V454, a pilot reversing valve V455 and a cartridge valve V456. The pressure relief valve V451 and the cartridge valve V454 are connected in parallel between the rodless chamber A1 of the injection cylinder 100 and the tank T, and the control end of the cartridge valve V454 is connected between the rodless chamber A1 of the injection cylinder 100 and the tank T through the pilot reversing valve V452. The cartridge valve V456 is connected between the rod chamber A2 of the injection cylinder 100 and the power source P, and the control end of the cartridge valve V456 is connected between the power source P and the tank T through the pilot reversing valve V455.

[0052] When the injection is completed, the pressure relief valve V451 can be opened first to release pressure, so as to avoid the high-pressure oil in the rodless chamber A1 of the injection cylinder 100 causing impact due to too fast rebound speed. The specific structure type of the pressure relief valve V451 is various; for example Figure 5As shown, the pressure relief valve V451 is a two-position two-way pressure relief valve; when the injection circuit 44 is working normally, the pressure relief valve V451 is in the left closed position; when the back hammering is needed, the coil S409 on the right side of the pressure relief valve V451 is powered, and then the spool moves left to connect the rodless chamber A1 with the oil tank T, so as to realize the pressure relief of the high-pressure oil.

[0053] After the pressure of the rodless chamber A1 of the injection cylinder 100 is reduced to the set value, the plug valve V456 can be controlled to open by the pilot directional valve V455, so that the power source P supplies oil to the rod chamber A2 of the injection cylinder 100 through the plug valve V456; at the same time, the plug valve V454 is controlled to open by the pilot directional valve V452, so that the oil in the rodless chamber A1 of the injection cylinder 100 flows back to the oil tank T.

[0054] It can be understood that the specific structure type of the pilot directional valve V452 and the pilot directional valve V455 is various, for example Figure 5 As shown, the pilot directional valve V452 and the pilot directional valve V455 are both two-position four-way directional valves. When the injection circuit 44 is working normally, the pilot directional valve V452 and the pilot directional valve V455 are both in the parallel position, at this time the rodless chamber A1 of the injection cylinder 100 is connected with the control end of the plug valve V454 through the pilot directional valve V452, and at the same time the power source P is connected with the control end of the plug valve V456 through the pilot directional valve V455. When the back hammering is needed, the coil S410 on the right side of the pilot directional valve V452 is powered, so that the spool moves left, and then the oil in the control end of the plug valve V454 flows back to the oil tank T through the cross position circuit; at the same time, the coil S411 on the left side of the pilot directional valve V455 is powered, so that the spool moves right, and then the oil in the control end of the plug valve V456 flows back to the oil tank T through the cross position circuit.

[0055] It should be known by those skilled in the art that in order to ensure the stability of the die casting process, it is necessary to ensure that the port of the injection chamber is in a completely sealed state with the mold cavity when the injection cylinder 100 is injecting. Therefore, when the injection cylinder 100 is rotated again from the vertical position to the horizontal position after the die casting of the product is completed, the close contact between the port of the injection chamber and the mold cavity will interfere with the swinging of the injection cylinder 100, so the injection cylinder 100 needs to be separated from the mold cavity before the swinging of the injection cylinder 100. There are various specific ways for the injection cylinder 100 to be separated from the mold cavity, one of which will be described in detail below.

[0056] In this embodiment, as shown in Figure 1As shown, the injection mold set includes an injection sleeve 110 for connecting the mold cavity; the injection sleeve 110 is in sealing sliding connection with the injection end of the injection cylinder 100. The injection sleeve 110 and the injection cylinder 100 are connected through the lifting cylinder 200, which can drive the injection sleeve 110 to extend or retract relative to the injection cylinder 100 under the control of the lifting circuit 43, so as to make the injection port of the injection sleeve 110 sealingly connected or disconnected with the mold cavity to be pressure cast.

[0057] In this embodiment, the specific structure of the lifting circuit 43 capable of realizing the above functions can be various, in order to facilitate understanding, one of the structures will be described in detail below. As shown in Figure 6 As shown, the lifting circuit 43 includes a reversing valve V431, a balance valve V432 and a pressure valve V433. The oil inlet of the reversing valve V431 is connected to the power source P, and the oil return of the reversing valve V431 is connected to the oil tank T; the working oil port of the reversing valve V431 is connected to the chamber interface B of the lifting cylinder 200 through the balance valve V432; the pressure valve V433 is connected between the lifting cylinder 200 and the oil tank T.

[0058] The oil provided by the power source P can enter the chamber of the lifting cylinder 200 through the reversing valve V431 and the balance valve V432 to drive the injection sleeve 110 to extend relative to the injection cylinder 100. The oil in the lifting cylinder 200 can flow back to the oil tank T along the balance valve V432 and the reversing valve V431 under the action of the gravity of the injection sleeve 110, so as to make the injection sleeve 110 retract relative to the injection cylinder 100. The pressure valve V433 is used to control the sealing pressure of the injection sleeve 110 and the mold cavity.

[0059] It can be understood that the specific number of the lifting cylinder 200 can be one or multiple, and multiple lifting cylinders 200 are connected to the balance valve V432 and the pressure valve V433. The connection mode of the lifting cylinder 200 can be various, for example, the lifting cylinder 200 is connected to the injection sleeve 110 through the cylinder body, and the piston rod of the lifting cylinder 200 is connected to the injection cylinder 100; of course, it can also be installed reversely, and the specific mode can be selected by the person skilled in the art according to the actual needs.

[0060] It should be understood that the specific structure type of the reversing valve V431 can be various, for example Figure 6As shown, the directional control valve V431 is an O-type three-position four-way directional control valve. When the lifting cylinder 200 is not working, the directional control valve V431 is in the middle cut-off position. When the lifting cylinder 200 raises the injection sleeve 110, the coil S404 on the left side of the directional control valve V431 is energized, causing the valve core to move to the right, so that the directional control valve V431 connects the power source P to the balance valve V432 through the cross position. When the lifting cylinder 200 retracts the injection sleeve 110, the coil S405 on the right side of the directional control valve V431 is energized, causing the valve core to move to the left, so that the directional control valve V431 connects the oil tank T to the balance valve V432 through the parallel position.

[0061] Another aspect of this application provides a pressure injection control method applied to the aforementioned pressure injection circuit 44, such as... Figure 7 As shown, one preferred embodiment includes the following steps: converting the desired piston speed of the injection cylinder 100 into an input signal value for the servo valve V441; converting the actual input signal value of the servo valve V441 into an actual displacement value of the valve core; converting the actual displacement value of the valve core into an actual piston speed value of the injection cylinder 100 and providing feedback; comparing the actual piston speed value of the injection cylinder 100 with the desired value, and adjusting the actual input signal value of the servo valve V441 using a PID controller based on the comparison result.

[0062] Specifically, such as Figure 7 As shown, the desired piston speed of the injection cylinder 100 can be represented by the function R(S), the transfer function of the servo valve V441 is represented by G1(S), the injection cylinder 100 is represented by the transfer function G2(S), the transfer function of the feedback channel is H(S), the transfer function of the feedforward channel is G4(S), and the actual piston speed of the injection cylinder 100 is represented by the function C(S). The specific control process of the injection circuit 44 is as follows: The change in the desired piston speed value R(S) of the injection cylinder 100 is input to the control system. First, the piston speed value is converted into the input signal value of the servo valve V441 through the transfer function G4(S). Then, the servo valve V441 converts the actual input signal value into the actual displacement value of the valve core through the function G1(S), thereby controlling the valve core to move accordingly. Finally, the actual displacement value of the valve core is converted into the actual piston speed value of the injection cylinder 100 through the function G2(S). Finally, the actual piston speed value of the injection cylinder 100 is fed back through the function H(S), causing the actual speed value to be subtracted from the desired speed value. The PID controller then adjusts the actual input signal value of the servo valve V441, ultimately achieving precise control. Compared to traditional methods, this embodiment employs a closed-loop VP switching point position control method, which ensures the safety and stability of the injection stage, thereby improving production efficiency and casting quality.

[0063] It can be understood that the movement control of the injection cylinder 100 is realized by setting the expected trajectory of the piston movement speed of the injection cylinder 100 and converting it into a control signal of the servo valve V441 to control the servo valve V441. The movement speed of the injection cylinder 100 is measured as a feedback signal of the control system, and the deviation value of the signal from the expected signal is corrected by using a PID control algorithm, so as to realize the accurate speed control of the injection cylinder 100. The feedforward control is mainly used to overcome or reduce the fluctuation of the system speed caused by the external disturbance, and the control signal output by the feedforward control channel directly acts on the servo valve V441 at the inlet of the injection cylinder 100, so as to improve the rapid response speed of the system.

[0064] It should be known that, for setting the expected trajectory of the piston movement speed of the injection cylinder 100, a plurality of key point corresponding injection speed values can be determined according to the injection process requirements; based on the obtained injection speed values corresponding to different key points, the expected trajectory of the piston movement speed of the injection cylinder 100 is generated by using a curve generation algorithm.

[0065] The above describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. An extrusion press hydraulic system characterized by, The injection molding machine comprises: a plunger cylinder and a swing cylinder, both of which are rotatably installed on a frame, and a driving end of the swing cylinder is hingedly connected to the plunger cylinder; a swing circuit, which is connected to the swing cylinder so that the swing cylinder drives the plunger cylinder to swing at a set angle under the drive of the swing circuit; and an energy storage circuit and a plunger circuit, which are connected in parallel to a rodless chamber of the plunger cylinder so that, during plunger injection, the energy storage circuit and a power source supply oil to the rodless chamber of the plunger cylinder through the plunger circuit; the plunger circuit is also connected to a rod chamber of the plunger cylinder so that, during plunger injection, the rod chamber and the rodless chamber of the plunger cylinder form a differential circuit or are directly connected to an oil tank; the energy storage circuit comprises an accumulator (V411), a cartridge valve (V412), and a pilot directional valve (V413); the power source is connected to the accumulator (V411) through the cartridge valve (V412), and a control end of the cartridge valve (V412) is connected to the accumulator (V411) and an oil tank through the pilot directional valve (V413); when energy storage is performed before plunger injection, the pilot directional valve (V413) controls the cartridge valve (V412) to open, so that the power source supplies oil to the accumulator (V411); when plunger injection is performed, the accumulator (V411) supplies oil to the plunger circuit through a branch of an oil inlet end of the cartridge valve (V412); the plunger circuit comprises a servo valve (V441) and a cartridge valve (V442); an oil inlet of the servo valve (V441) is connected to the branch of the oil inlet end of the cartridge valve (V412), an oil outlet of the servo valve (V441) is connected to the rodless chamber of the plunger cylinder, and the rodless chamber and the rod chamber of the plunger cylinder are connected through the cartridge valve (V442); when plunger injection is performed, the servo valve (V441) is controlled to be turned on based on an opening signal of the cartridge valve (V412), so that oil output by the accumulator (V411) and oil output by the power source both flow to the rodless chamber of the plunger cylinder through the servo valve (V441); oil in the rod chamber of the plunger cylinder flows back to the rodless chamber through the cartridge valve (V442) to form a differential circuit; wherein the opening degree of the servo valve (V441) controls the plunger injection speed.

2. The extrusion press hydraulic system of claim 1, wherein, the plunger circuit further comprises a cartridge valve (V444) and a pilot directional valve (V447); the cartridge valve (V444) is connected between the rod chamber of the plunger cylinder and the oil tank, and a control end of the cartridge valve (V444) is connected to the oil tank and the power source through the pilot directional valve (V447); when the plunger cylinder performs pressure boosting plunger injection, the pilot directional valve (V447) controls the control end of the cartridge valve (V444) to communicate with the oil tank, so that oil in the rod chamber of the plunger cylinder flows back to the oil tank through the cartridge valve (V444). At this time, the accumulator (V411) and the power source keep supplying oil to the rodless chamber of the injection cylinder.

3. The extrusion press hydraulic system of claim 1, wherein, The swing circuit comprises a reversing valve (V421), a check valve (V422) and a balance valve (V423); The power source is connected to the oil inlet of the reversing valve (V421) through the check valve (V422), the oil return of the reversing valve (V421) is connected to the oil tank, one of the working oil ports of the reversing valve (V421) is connected to the rod chamber of the swing cylinder, and the other working oil port is connected to the rodless chamber of the swing cylinder through the balance valve (V423).

4. The extrusion press hydraulic system of claim 1, wherein, The extrusion injection hydraulic system further comprises a back hammer circuit for driving the injection cylinder to perform back hammering; the back hammer circuit comprises a pressure relief valve (V451), a pilot reversing valve (V452), a cartridge valve (V454), a pilot reversing valve (V455) and a cartridge valve (V456); The pressure relief valve (V451) and the cartridge valve (V454) are connected in parallel between the rodless chamber of the injection cylinder and the oil tank; The control end of the cartridge valve (V454) is connected between the rodless chamber of the injection cylinder and the oil tank through the pilot reversing valve (V452); The cartridge valve (V456) is connected between the rod chamber of the injection cylinder and the power source, and the control end of the cartridge valve (V456) is connected between the power source and the oil tank through the pilot reversing valve (V455); When the injection is completed, the pressure relief valve (V451) is adapted to be opened first for pressure relief; Subsequently, the pilot reversing valve (V455) controls the cartridge valve (V456) to be opened, so that the power source supplies oil to the rod chamber of the injection cylinder through the cartridge valve (V456); at the same time, the pilot reversing valve (V452) controls the cartridge valve (V454) to be opened, so that the oil in the rodless chamber of the injection cylinder flows back to the oil tank.

5. An extrusion press hydraulic system as claimed in any one of claims 1 to 4, wherein, The injection end of the injection cylinder is sealingly and slidingly mounted with an injection sleeve; The injection sleeve is connected with the injection cylinder through a lifting cylinder, and the lifting cylinder is adapted to drive the injection sleeve to extend or retract relative to the injection cylinder under the control of a lifting circuit, so as to sealingly connect or disconnect the injection port of the injection sleeve with a mold cavity to be pressure cast.

6. The extrusion press hydraulic system of claim 5, wherein, The lifting circuit comprises a reversing valve (V431), a balance valve (V432) and a pressure valve (V433); The oil inlet of the reversing valve (V431) is connected to the power source, and the oil return of the reversing valve (V431) is connected to the oil tank; the working oil port of the reversing valve (V431) is connected to the lifting cylinder through the balance valve (V432); and the pressure valve (V433) is connected between the lifting cylinder and the oil tank; The oil supplied by the power source is adapted to enter the lifting cylinder through the reversing valve (V431) and the balance valve (V432) to drive the injection sleeve to extend relative to the injection cylinder; The oil in the lifting cylinder is adapted to flow back to the oil tank along the balance valve (V432) and the reversing valve (V431) under the gravity of the injection sleeve, so as to make the injection sleeve retract relative to the injection cylinder. The pressure valve (V433) is used to control the sealing pressure of the injection sleeve and the mold cavity.

7. A method of controlling the injection, applied to the extrusion injection hydraulic system according to claim 1, characterized in that, The method comprises the following steps: The piston speed expectation value of the injection cylinder is converted into the input signal value of the servo valve (V441); The actual input signal value of the servo valve (V441) is converted into the actual displacement value of the valve core; The actual displacement value of the valve core is converted into the actual piston speed value of the injection cylinder and fed back; The actual piston speed value of the injection cylinder is compared with the expectation value, and the actual input signal value of the servo valve (V441) is adjusted by the PID controller according to the comparison result.

8. The injection control method according to claim 7, characterized by, According to the injection process requirements, the injection speed values corresponding to a plurality of key points are determined; based on the obtained injection speed values corresponding to different key points, the injection cylinder piston motion speed expectation trajectory is generated through a curve generation algorithm.

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