A variable clamping force hydraulic control system for a double-action stretch forming equipment

Abstract

This invention belongs to the field of hydraulic circuit control technology, specifically disclosing a variable clamping force hydraulic circuit control system for a double-action stretch forming equipment. The system includes a first pump group, a first pump source control valve group, a second pump group, a second pump source control valve group, a locking control valve, a pressure cylinder filling valve, a main cylinder filling valve, and valve assembly components. The main cylinder is connected to the intermediate slider; the pressure cylinder is connected to the pressure slider, and a locking device locks the pressure slider to the intermediate slider. The valve assembly components include a two-pump confluence control valve group, a pressure cylinder lower chamber control valve group, a pressure cylinder upper chamber control valve group, a pressure cylinder upper chamber pressure control valve group, a main cylinder lower chamber control valve group, a main cylinder upper chamber control valve group, a main cylinder upper chamber pressure control valve group, a filling valve group, and a system pressure control valve group. While meeting the requirements of ordinary double-action forming processes, this invention adds a single-main-cylinder pressing process for small mold forming processes and a simultaneous pressing process of the main cylinder and pressure cylinder for large mold forming processes, achieving the effect of multiple uses for one press.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic circuit control technology, and particularly relates to a variable clamping force hydraulic circuit control system for a double-action stretching forming equipment. Background Technology

[0002] Reducing energy consumption, minimizing environmental pollution, and conserving limited resources are crucial and urgent issues facing my country. Broadly speaking, the number of equipment units directly determines the size of the required factory, thus influencing the amount of land used and the amount of water, electricity, gas, and other energy consumed. In detail, the clamping force, speed, energy consumption, control, and environmental impact of a single piece of equipment are central to the user's desired product.

[0003] Double-action stretch forming presses are generally hydraulic devices consisting of a main cylinder and multiple blank holder cylinders working together. In practical applications, they aim to produce products that meet objective needs with minimal resources. Diversity and energy efficiency have become essential for market development, which places higher demands on the press's clamping force, speed, and flexibility. Therefore, high-precision and flexible control of the clamping force, speed, and flow rate of the main cylinder and blank holder cylinders is crucial for this type of equipment. This also determines that such equipment typically uses multiple pump sets, resulting in high noise levels, large installed power in the hydraulic system, complex logic control, a large hydraulic station structure, and a large demand for hydraulic oil volume. Consequently, this leads to disadvantages such as high cost, numerous potential failure points, multiple oil leakage risks, and difficult and labor-intensive maintenance. Summary of the Invention

[0004] The purpose of this invention is to provide a variable clamping force hydraulic circuit control system for a double-action stretch forming equipment. This system can, while meeting the requirements of ordinary double-action forming processes, add a single master cylinder pressing process for small mold forming and a simultaneous pressing process using the master cylinder and pressure cylinder for large mold forming, achieving a multi-purpose effect with a single press and significantly reducing equipment costs. It also reduces energy consumption, press noise, space usage, and hydraulic system oil demand, simplifies the valve group and control unit, and to some extent reduces hydraulic system costs, minimizes potential failure points and oil leakage risks, and simplifies maintenance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a variable clamping force oil circuit control system for a double-action stretching forming equipment, comprising a first pump group, a first pump source control valve group, a second pump group, a second pump source control valve group, a locking control valve, a pressure cylinder filling valve, a middle main cylinder filling valve, and valve group components; the double-action stretching forming equipment includes a middle main cylinder and multiple groups of pressure cylinders, the middle main cylinder being connected to an intermediate slider; each group of pressure cylinders is connected to a pressure slider, each group of pressure sliders corresponds to a locking device, the locking device being used to lock the pressure slider to the intermediate slider; the locking control valve is connected to multiple locking devices and controls the locking devices; the bottom of each group of pressure cylinders is connected to the pressure cylinder filling valve, and the bottom of the middle main cylinder is connected to the middle main cylinder filling valve; the first pump source control valve group is used to control the first pump group, and the second pump source control valve group is used to control the second pump group;

[0006] The valve assembly includes a two-pump confluence control valve group, a lower chamber control valve group for the pressing cylinder, a higher chamber control valve group for the pressing cylinder, a higher chamber pressure control valve group for the pressing cylinder, a lower chamber control valve group for the middle main cylinder, a higher chamber control valve group for the middle main cylinder, a filling valve group, and a system pressure control valve group. The filling valve group and the system pressure control valve group are connected. The first pump source control valve group is connected to the two-pump confluence control valve group, and the second pump source control valve group is connected to the two-pump confluence control valve group, the lower chamber control valve group for the middle main cylinder, the upper chamber control valve group for the middle main cylinder, the filling valve group, and the system pressure control valve group. The two-pump confluence control valve group is also connected to the lower chamber control valve group for the pressing cylinder and the upper chamber control valve group for the pressing cylinder. The system comprises a cavity control valve group, a lower cavity control valve group for the middle main cylinder, an upper cavity control valve group for the middle main cylinder, a locking control valve, a filling valve group, and a system pressure control valve group. The upper cavity control valve group for the pressing cylinder is connected to the upper cavity pressure control valve group for the pressing cylinder, and the upper cavity control valve group for the middle main cylinder is connected to the upper cavity pressure control valve group for the middle main cylinder. The lower cavity control valve group for the pressing cylinder is connected to the lower cavity of multiple pressing cylinders, the upper cavity control valve group for the pressing cylinder is connected to the upper cavity of multiple pressing cylinders, the lower cavity control valve group for the middle main cylinder is connected to the lower cavity of the middle main cylinder, and the upper cavity control valve group for the middle main cylinder is connected to the upper cavity of the middle main cylinder. The filling valve for the middle main cylinder and the filling valve for the pressing cylinder are connected to the filling valve group.

[0007] Furthermore, the lower chamber control valve group of the pressing cylinder and the lower chamber control valve group of the middle main cylinder respectively control the oil inlet, oil outlet and support of the lower chamber of the pressing cylinder and the lower chamber of the middle main cylinder, and the upper chamber control valve group of the pressing cylinder and the upper chamber control valve group of the middle main cylinder respectively control the oil inlet and pressure holding of the upper chamber of the pressing cylinder and the upper chamber of the middle main cylinder.

[0008] Furthermore, the two-pump confluence control valve group includes a solenoid valve, a first cartridge valve, and a shuttle valve. The solenoid valve is connected to the control chamber of the first cartridge valve and is used to open and close the first cartridge valve. Port A of the first cartridge valve is connected to the first pump source control valve group, the upper chamber control valve group of the pressing cylinder, the lower chamber control valve group of the pressing cylinder, and the locking control valve, respectively. Port B of the first cartridge valve is connected to the second pump source control valve group, the lower chamber control valve group of the middle main cylinder, the upper chamber control valve group of the middle main cylinder, the filling valve group, and the system pressure control valve group, respectively. The oil outlet of the shuttle valve is connected to the solenoid valve, and the two oil inlets of the shuttle valve are connected to ports A and B of the first cartridge valve, respectively.

[0009] Furthermore, both the upper chamber pressure control valve group of the pressure cylinder and the upper chamber pressure control valve group of the middle main cylinder include a proportional relief valve, a relief valve, a second cartridge valve and a proportional valve filter. The control chambers of the proportional relief valve, the relief valve, the second cartridge valve and the proportional valve filter are connected together, and the proportional valve filter is connected to the oil port of the second cartridge valve.

[0010] Furthermore, the filtration accuracy of the proportional valve filter is no higher than 10μ.

[0011] Furthermore, the pressure limit conditions for the first pump source control valve group and the second pump source control valve group are not less than 26 MPa; the pressure of the external pressure oil of the pressure cylinder filling valve and the middle main cylinder filling valve is not higher than 5 MPa; the high pressure limit condition for the valve assembly is not less than 26 MPa, and the low pressure limit condition is not higher than 5 MPa.

[0012] Furthermore, a pressure cylinder displacement sensor is connected to the pressure block slider, and a central main cylinder displacement sensor is connected to the intermediate slider slider.

[0013] Furthermore, the first and second pump sets are high-pressure servo pump sets.

[0014] Furthermore, the lower chamber control valve group of the pressing cylinder and the lower chamber control valve group of the middle main cylinder both include an oil inlet valve, an oil outlet valve, a support valve, and a quick-down valve; the upper chamber control valve group of the pressing cylinder and the upper chamber control valve group of the middle main cylinder both include an oil inlet valve and a pressure holding valve.

[0015] The working principle of this technical solution is as follows:

[0016] Dual-action process: At the start of press operation, the pressing slide descends rapidly under its own weight, creating a negative pressure in the upper chamber of the pressing cylinder. This draws open the filling valve, filling the pressing cylinder with oil. Simultaneously, the support valve and fast-down valve of the lower chamber control valve group open, allowing for rapid oil discharge from the lower chamber. Control is achieved through displacement signals transmitted by the pressing cylinder displacement sensor, ensuring a perfect match between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid, smooth, and impact-free mold closing. The pressing process is implemented through the upper chamber control valve group and the upper chamber pressure control valve group. Pressure control can be achieved using the proportional overflow valve in the upper chamber pressure control valve group, allowing for pressing processes with varying pressing forces. Then, the middle slide of the press descends rapidly under its own weight, creating a negative pressure in the upper chamber of the main cylinder. This draws open the filling valve of the main cylinder, filling it with oil. The support valve and fast-down valve of the lower chamber control valve group of the main cylinder open, allowing for rapid oil discharge from the lower chamber. Displacement signals are transmitted via the main cylinder displacement sensor for control, achieving a perfect match between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid, stable mold closing without impact. The upper chamber control valve group and the upper chamber pressure control valve group of the main cylinder enable dual-action pressing. The proportional overflow valve in the upper chamber pressure control valve group can control the pressure, allowing for dual-action pressing with different clamping forces. Finally, the main cylinder and the pressure cylinder depressurize and return, completing the entire process. This process can also utilize the two-pump confluence control valve group to allow both pumps to work together to supply oil to the cylinders, meeting high-speed cycle requirements and saving various costs.

[0017] Single-action process for pressing with small molds and low clamping forces: At the start of press operation, the middle slide descends rapidly under its own weight, creating negative pressure in the upper chamber of the main cylinder. This draws open the main cylinder filling valve, filling it with oil. Simultaneously, the support valve and fast-down valve of the lower chamber control valve group open, allowing rapid oil discharge from the lower chamber. Displacement signals from the main cylinder displacement sensor are used for control, achieving a perfect match between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid, smooth, and impact-free mold closing. Dual-action pressing is achieved through the upper chamber control valve group and the upper chamber pressure control valve group of the main cylinder. The proportional overflow valve in the upper chamber pressure control valve group can control the pressure, enabling dual-action pressing with different clamping forces. Finally, the main cylinder depressurizes and returns, completing the entire process. If one pump group's speed meets the requirements, the other pump group can remain idle, significantly saving energy costs. In this process, the two pumps can be combined and the control valve group can be opened to allow the two pumps to work together to supply oil to the cylinder, meet the requirements of high speed cycle, and save various costs.

[0018] Single-action process for pressing with large molds and high clamping force: At the start of press operation, pressurized oil from either the first or second pump group is controlled by a locking control valve, locking the edge block and the middle block together via a locking device. The two-pump confluence control valve group is opened, maintaining the main oil circuit between the edge block cylinder and the middle main cylinder. Then, the connected edge block and middle block descend rapidly under their own weight, creating a negative pressure in the upper chambers of the edge block cylinder and the middle main cylinder. This draws open the filling valves of the edge block cylinder and the middle main cylinder, filling them with oil. The support valves and quick-descent valves of the lower chamber control valve group for the edge block cylinder and the middle main cylinder open simultaneously, allowing rapid oil discharge from the lower chambers of the edge block cylinder and the middle main cylinder. Displacement signals are transmitted via displacement sensors for the edge block cylinder and the middle main cylinder for control, achieving a perfect match between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid, smooth mold closing without impact. The pressing process is achieved through the upper chamber control valve group of the pressing cylinder, the upper chamber pressure control valve group of the pressing cylinder, the upper chamber control valve group of the middle main cylinder, and the upper chamber pressure control valve group of the middle main cylinder. The pressure can be controlled by the proportional relief valve in the upper chamber pressure control valve group of the pressing cylinder and the proportional relief valve in the upper chamber pressure control valve group of the middle main cylinder, so as to achieve single-action pressing process with different clamping forces. Finally, the middle main cylinder and the pressing cylinder are depressurized and return to their original positions, completing the entire process.

[0019] The beneficial effects of this technical solution are as follows:

[0020] Based on the characteristics of the double-action stretch forming process, two relatively independent high-pressure servo pump sets (first pump set and second pump set) are adopted. Under the control of the proportional relief valve, while meeting the requirements of the ordinary double-action forming process, a single master cylinder pressing process for small mold forming is added. A large mold forming process with high clamping force, where the master cylinder and the pressure plate cylinder simultaneously press when the pressure plate slider and the intermediate slider are locked together, is also added, achieving the effect of multiple uses for one press. This significantly reduces equipment costs, energy consumption, environmental pollution, and space usage. It also reduces the hydraulic system's oil demand, simplifies the valve group control unit, improves the flexibility and reliability of the entire machine's operation, and to some extent reduces the risk of failure and oil leakage. Maintenance is simple and convenient. It can better achieve the forming function requirements of a double-action forming press: fast, flexible, high-precision, and high-reliability forming.

[0021] The hydraulic system of the entire machine adopts two relatively independent high-pressure servo pump sets (first pump set and second pump set). When the two pumps' confluence control valve sets are not connected, they provide power to the main cylinder and the pressing cylinder respectively. When the two pumps' confluence control valve sets are connected, firstly, the speed of the main cylinder or the pressing cylinder can be increased, reducing the cycle time. Secondly, after the pressing slide and the intermediate slide are locked with a locking device, the high-pressure servo pump set simultaneously provides power to the main cylinder and the pressing cylinder to realize the pressing process action.

[0022] When using small molds and small tonnage, the pressing cylinder can be in a stationary state. If the second pump set can meet the speed requirements of the main cylinder, the high-pressure servo pump set of the first pump set connected to the pressing cylinder will also be in a stationary state, saving energy consumption.

[0023] The pressing cylinder and the middle main cylinder are pressed using a proportional relief valve for pressure control. The first pump group and the second pump group use open-loop speed control, which only controls the speed of the pressing cylinder and the middle main cylinder, simplifying the electrical logic. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the variable clamping force oil circuit control system of a double-action stretching forming equipment according to the present invention. Detailed Implementation

[0025] The following detailed description illustrates the specific implementation method:

[0026] The reference numerals in the accompanying drawings include: 1. First pump group; 2. Second pump group; 3. First pump source control valve group; 4. Second pump source control valve group; 5. Valve group assembly; 6. Two pumps confluence control valve group; 7. Lower chamber control valve group of the pressing cylinder; 8. Upper chamber control valve group of the pressing cylinder; 9. Lower chamber control valve group of the middle main cylinder; 10. Upper chamber control valve group of the middle main cylinder; 11. Filling valve group; 12. System pressure control valve group; 13. Upper chamber pressure control valve group of the pressing cylinder; 14. Upper chamber pressure control valve group of the middle main cylinder; 15. Locking control valve; 16. Middle main cylinder; 17. Pressing cylinder; 18. Intermediate slider; 19. Pressing slider; 20. Locking device; 21. Pressing cylinder filling valve; 22. Middle main cylinder filling valve; 23. Pressing cylinder displacement sensor; 24. Middle main cylinder displacement sensor; 25. Oil tank.

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The basic implementation examples are as follows: Figure 1The diagram shows a variable clamping force hydraulic circuit control system for a double-action stretch forming equipment, comprising a first pump group 1, a first pump source control valve group 3, a second pump group 2, a second pump source control valve group 4, a locking control valve 15, a pressure cylinder filling valve 21, a main cylinder filling valve 22, and a valve assembly 5. The double-action stretch forming equipment includes a main cylinder 16 and multiple symmetrical pressure cylinders 17. Typically, there is an even number of pressure cylinders 17; in this embodiment, there are two. The main cylinder 16 is connected to an intermediate slider 18. Each pressure cylinder 17 is connected to a pressure slider 19, and each pressure slider 19 corresponds to a locking device 20 (specifically, a locking cylinder). The locking device 20 is used to lock the pressure slider 19 to the intermediate slider 18. The locking control valve 15 is connected to multiple locking devices 20 and controls the locking devices 20. Each pressing cylinder 17 has a pressing cylinder filling valve 21 connected to its bottom, and the middle main cylinder 16 has a middle main cylinder filling valve 22 connected to its bottom. The first pump source control valve group 3 is used to control the first pump group 1, and the second pump source control valve group 4 is used to control the second pump group 2; the bottoms of the first pump group 1, the second pump group 2, the middle main cylinder 16, and the pressing cylinder 17 are respectively connected to the oil tank 25.

[0029] Valve assembly 5 includes a two-pump confluence control valve assembly 6, a lower chamber control valve assembly 7, an upper chamber control valve assembly 8, an upper chamber pressure control valve assembly 13, a lower chamber control valve assembly 9, an upper chamber control valve assembly 10, an upper chamber pressure control valve assembly 14, a filling valve assembly 11, and a system pressure control valve assembly 12; the filling valve assembly 11 and the system pressure control valve assembly 12 are connected. The first pump source control valve group 3 is connected to the two-pump confluence control valve group 6. The second pump source control valve group 4 is connected to the two-pump confluence control valve group 6, the lower chamber control valve group 9 of the middle main cylinder, the upper chamber control valve group 10 of the middle main cylinder, the filling valve group 11, and the system pressure control valve group 12, respectively. The two-pump confluence control valve group 6 is also connected to the lower chamber control valve group 7 of the pressing cylinder, the upper chamber control valve group 8 of the pressing cylinder, the lower chamber control valve group 9 of the middle main cylinder, the upper chamber control valve group 10 of the middle main cylinder, the locking control valve 15, the filling valve group 11, and the system pressure control valve group 12. The cavity control valve group 8 is connected to the upper cavity pressure control valve group 13 of the pressing cylinder, and the upper cavity control valve group 10 of the middle main cylinder is connected to the upper cavity pressure control valve group 14 of the middle main cylinder; the lower cavity control valve group 7 of the pressing cylinder is connected to the lower cavity of multiple pressing cylinders 17 respectively, the upper cavity control valve group 8 of the pressing cylinder is connected to the upper cavity of multiple pressing cylinders 17 respectively, the lower cavity control valve group 9 of the middle main cylinder is connected to the lower cavity of the middle main cylinder 16, and the upper cavity control valve group 10 of the middle main cylinder is connected to the upper cavity of the middle main cylinder 16; the middle main cylinder filling valve 22 and the pressing cylinder filling valve 21 are respectively connected to the filling valve group 11.

[0030] The lower chamber control valve group 7 of the pressing cylinder and the lower chamber control valve group 9 of the middle main cylinder control valve group respectively control the oil inlet, oil outlet, and support of the lower chamber of the pressing cylinder 17 and the lower chamber of the middle main cylinder 16. Both the lower chamber control valve group 7 and the lower chamber control valve group 9 of the middle main cylinder include an oil inlet valve, an oil outlet valve, a support valve, and a quick-release valve. The upper chamber control valve group 8 of the pressing cylinder and the upper chamber control valve group 10 of the middle main cylinder control valve group respectively control the oil inlet and pressure holding of the upper chamber of the pressing cylinder 17 and the upper chamber of the middle main cylinder 16. Both the upper chamber control valve group 8 of the pressing cylinder and the upper chamber control valve group 10 of the middle main cylinder include an oil inlet valve and a pressure holding valve.

[0031] Both the upper chamber pressure control valve group 13 of the pressing cylinder and the upper chamber pressure control valve group 14 of the middle main cylinder include proportional relief valves (BY1, BY2), relief valves (F1, F2), second cartridge valves (CZ2, CZ3), and proportional valve filters (NL1, NL2). The control chambers of the proportional relief valves, relief valves, and second cartridge valves, as well as the proportional valve filters, are connected together, and damping is provided between the connection point and the second cartridge valves, proportional relief valves, and proportional valve filters. The proportional valve filters and the upper chamber control valve group 8 of the pressing cylinder or the upper chamber control valve group 10 of the middle main cylinder are connected to the oil port of the second cartridge valve. The oil ports of the proportional relief valves, relief valves, and second cartridge valves are all connected to the oil tank. The filtration accuracy of the proportional valve filters is no higher than 10μ.

[0032] The two-pump confluence control valve group 6 includes a solenoid valve (YV1), a first cartridge valve (CZ1), and a shuttle valve (C). The solenoid valve is connected to the control chamber of the first cartridge valve and is used to open and close the first cartridge valve. Port A of the first cartridge valve is connected to the first pump source control valve group 3, the upper chamber control valve group 8 of the pressing cylinder, the lower chamber control valve group 7 of the pressing cylinder, and the locking control valve 15, respectively. Port B of the first cartridge valve is connected to the second pump source control valve group 4, the lower chamber control valve group 9 of the middle main cylinder, the upper chamber control valve group 10 of the middle main cylinder, the filling valve group 11, and the system pressure control valve group 12, respectively. The oil outlet of the shuttle valve is connected to the solenoid valve, and the two oil inlets of the shuttle valve are connected to the A and B ports of the first cartridge valve, respectively.

[0033] The first pump group 1 and the second pump group 2 are high-pressure servo pump groups. The pressure limit conditions for the first pump source control valve group 3 and the second pump source control valve group 4 are not less than 26 MPa. The pressure of the external pressure oil connected to the pressure cylinder filling valve 21 and the middle main cylinder filling valve 22 is not higher than 5 MPa. The high pressure limit conditions for the valve assembly are not less than 26 MPa and the low pressure limit conditions are not higher than 5 MPa.

[0034] A pressure cylinder displacement sensor 23 is connected to the pressure slider 19, and a central main cylinder displacement sensor 24 is connected to the middle slider 18.

[0035] The specific implementation process is as follows:

[0036] Dual-action process: Upon press start-up, the pressing slide 19 descends rapidly under its own weight, creating a negative pressure in the upper chamber of the pressing cylinder 17. This pressure draws open the pressing cylinder filling valve 21, filling the pressing cylinder 17 with oil. Simultaneously, the support valve and fast-down valve of the lower chamber control valve group 7 open, allowing rapid oil discharge from the lower chamber of the pressing cylinder 17. Displacement signals are transmitted via the pressing cylinder displacement sensor 23 for control, achieving a perfect connection between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid and stable mold closure without impact. The pressing process is achieved through the upper chamber control valve group 8 and the upper chamber pressure control valve group 13. Pressure control can be achieved using the proportional overflow valve (BY1) in the upper chamber pressure control valve group 13, enabling pressing processes with different pressing forces. Then, the middle slide block 18 of the press descends rapidly under its own weight, creating a negative pressure in the upper chamber of the main cylinder 16. This draws open the filling valve 22 of the main cylinder, filling it with oil. The support valve and fast-down valve of the lower chamber control valve group 9 of the main cylinder open, allowing the lower chamber of the main cylinder 16 to drain oil quickly. Displacement signals are transmitted via the displacement sensor 24 of the main cylinder for control, achieving a perfect connection between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid and stable mold closing without impact. The upper chamber control valve group 10 and the upper chamber pressure control valve group 14 of the main cylinder achieve a dual-action pressing process. The proportional overflow valve (BY2) in the upper chamber pressure control valve group 14 can control the pressure, enabling dual-action pressing with different clamping forces. Finally, the main cylinder 16 and the pressure cylinder 17 depressurize and return, completing the entire process. During this process, the two-pump confluence control valve group 6 can be opened to allow both pumps to work together to supply oil to the cylinders, meeting high-speed cycle requirements and saving various costs.

[0037] Single-action process for pressing with small molds and low clamping force: At the start of press operation, the intermediate slide 18 descends rapidly under its own weight, creating negative pressure in the upper chamber of the main cylinder 16. This draws open the main cylinder filling valve 22, filling the main cylinder 16 with oil. The support valve and fast-down valve of the lower chamber control valve group 9 open, allowing rapid oil discharge from the lower chamber of the main cylinder 16. Displacement signals are transmitted via the main cylinder displacement sensor 24 for control, achieving a perfect connection between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid and stable mold closing without impact. Dual-action pressing process is achieved through the upper chamber control valve group 10 and the upper chamber pressure control valve group 14 of the main cylinder. The proportional overflow valve (BY2) in the upper chamber pressure control valve group 14 can control the pressure, enabling dual-action pressing processes with different clamping forces. Finally, the main cylinder 16 depressurizes and returns, completing the entire process. If one pump group's speed meets the requirements, the other pump group can remain idle, significantly saving energy costs. In this process, the two pumps can be opened to allow the two pumps to work together to supply oil to the cylinder, meeting the requirements of high-speed cycle and saving various costs.

[0038] Single-action process for pressing with large molds and high clamping force: At the start of press operation, pressurized oil from either the first pump group 1 or the second pump group 2 is controlled by the locking control valve 15, and the locking device 20 locks the pressing slide 19 and the intermediate slide 18 together. The two-pump confluence control valve group 6 is opened, maintaining the main oil circuit between the pressing cylinder 17 and the central main cylinder 16. Then, the connected pressing slide 19 and intermediate slide 18 descend rapidly under their own weight, creating a negative pressure in the upper chambers of the pressing cylinder 17 and the central main cylinder 16. This negative pressure draws open the pressing cylinder filling valve 21 and the central main cylinder filling valve 22, filling the pressing cylinder 17 and the central main cylinder 16 with oil. The support valve and quick-descent valve of the lower chamber control valve group 7 for the pressing cylinder, and the support valve and quick-descent valve of the lower chamber control valve group 9 for the central main cylinder, open together, allowing rapid oil discharge from the lower chambers of the pressing cylinder 17 and the central main cylinder 16. Displacement signals are transmitted through the pressure cylinder displacement sensor 23 and the main cylinder displacement sensor 24 for control, achieving a perfect connection between the fast-to-slow flexible speed curve and the pressing speed, resulting in rapid and stable mold closing without impact. The pressing process is achieved through the pressure cylinder upper chamber control valve group 8, the pressure cylinder upper chamber pressure control valve group 13, the main cylinder upper chamber control valve group 10, and the main cylinder upper chamber pressure control valve group 14. Pressure control can be achieved through the proportional relief valve (BY1) in the pressure cylinder upper chamber pressure control valve group 13 and the proportional relief valve (BY2) in the main cylinder upper chamber pressure control valve group 14, enabling single-action pressing processes with different mold closing forces. Finally, the main cylinder 16 and the pressure cylinder 17 release pressure and return to their original positions, completing the entire process.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0040] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A variable clamping force hydraulic circuit control system for a double-action stretch forming equipment, characterized in that: The equipment includes a first pump group (1), a first pump source control valve group (3), a second pump group (2), a second pump source control valve group (4), a locking control valve (15), a pressure cylinder filling valve (21), a middle main cylinder filling valve (22), and a valve group assembly (5); the double-action stretch forming equipment includes a middle main cylinder (16) and multiple pressure cylinders (17), wherein the middle main cylinder (16) is connected to an intermediate slider (18); each pressure cylinder (17) is connected to a pressure slider (19), and each pressure slider (19) corresponds to a locking device (20). The locking device (20) is used to lock the edge pressing slider (19) and the middle slider (18); the locking control valve (15) is connected to multiple sets of locking devices (20) and controls the locking devices (20); the bottom of each set of edge pressing cylinders (17) is connected to the edge pressing cylinder filling valve (21), and the bottom of the middle main cylinder (16) is connected to the middle main cylinder filling valve (22); the first pump source control valve group (3) is used to control the first pump group (1), and the second pump source control valve group (4) is used to control the second pump group (2); The valve assembly (5) includes a two-pump confluence control valve assembly (6), a lower chamber control valve assembly for the pressing cylinder (7), an upper chamber control valve assembly for the pressing cylinder (8), an upper chamber pressure control valve assembly for the pressing cylinder (13), a lower chamber control valve assembly for the middle main cylinder (9), an upper chamber control valve assembly for the middle main cylinder (10), an upper chamber pressure control valve assembly for the middle main cylinder (14), a filling valve assembly (11), and a system pressure control valve assembly (12); the filling valve assembly (11) and the system pressure control valve assembly (12) are also included. The valve group (12) is connected; the first pump source control valve group (3) is connected to the two pumps confluence control valve group (6), and the second pump source control valve group (4) is connected to the two pumps confluence control valve group (6), the middle main cylinder lower chamber control valve group (9), the middle main cylinder upper chamber control valve group (10), the filling valve group (11), and the system pressure control valve group (12), respectively; the two pumps confluence control valve group (6) is also connected to the edge pressing cylinder lower chamber control valve group (7) and the edge pressing cylinder upper chamber control valve group (7). The control valve group (8), the lower chamber control valve group (9) of the middle main cylinder, the upper chamber control valve group (10) of the middle main cylinder, the locking control valve (15), the filling valve group (11) and the system pressure control valve group (12) are connected; the upper chamber control valve group (8) of the pressing cylinder is connected to the upper chamber pressure control valve group (13) of the pressing cylinder, and the upper chamber control valve group (10) of the middle main cylinder is connected to the upper chamber pressure control valve group (14) of the middle main cylinder; the lower chamber control valve group (7) of the pressing cylinder is connected to the upper chamber control valve group (9) of the middle main cylinder, the upper chamber control valve group (10) of the middle main cylinder, the upper chamber control valve group (15) of the middle main cylinder, and the lower chamber control valve group (9) of the middle main cylinder are connected to the upper chamber control valve group (14) of the middle main cylinder. The upper chamber control valve group (8) of the pressing cylinder is connected to the lower chamber of the pressing cylinder (17) respectively. The lower chamber control valve group (9) of the middle main cylinder is connected to the lower chamber of the middle main cylinder (16). The upper chamber control valve group (10) of the middle main cylinder is connected to the upper chamber of the middle main cylinder (16). The filling valve (22) of the middle main cylinder and the filling valve (21) of the pressing cylinder are connected to the filling valve group (11) respectively.

2. The variable clamping force oil circuit control system for a double-action stretch forming equipment according to claim 1, characterized in that: The lower chamber control valve group (7) of the pressing cylinder and the lower chamber control valve group (9) of the middle main cylinder control the oil inlet, oil outlet and support of the lower chamber of the pressing cylinder (17) and the lower chamber of the middle main cylinder (16) respectively. The upper chamber control valve group (8) of the pressing cylinder and the upper chamber control valve group (10) of the middle main cylinder control the oil inlet and pressure holding of the upper chamber of the pressing cylinder (17) and the upper chamber of the middle main cylinder (16) respectively.

3. The variable clamping force oil circuit control system for a double-action stretch forming equipment according to claim 1, characterized in that: The two-pump confluence control valve group (6) includes a solenoid valve, a first cartridge valve, and a shuttle valve. The solenoid valve is connected to the control chamber of the first cartridge valve and is used to open and close the first cartridge valve. Port A of the first cartridge valve is connected to the first pump source control valve group (3), the upper chamber control valve group (8) of the pressing cylinder, the lower chamber control valve group (7) of the pressing cylinder, and the locking control valve (15), respectively. Port B of the first cartridge valve is connected to the second pump source control valve group (4), the lower chamber control valve group (9) of the middle main cylinder, the upper chamber control valve group (10) of the middle main cylinder, the filling valve group (11), and the system pressure control valve group (12), respectively. The oil outlet of the shuttle valve is connected to the solenoid valve, and the two oil inlets of the shuttle valve are connected to the A and B ports of the first cartridge valve, respectively.

4. The variable clamping force oil circuit control system for a double-action stretch forming equipment according to claim 1, characterized in that: The pressure limit conditions for the first pump source control valve group (3) and the second pump source control valve group (4) are not less than 26 MPa; the pressure of the external pressure oil of the pressure cylinder filling valve (21) and the middle main cylinder filling valve (22) is not higher than 5 MPa; the high pressure limit condition for the valve group assembly (5) is not less than 26 MPa, and the low pressure limit condition is not higher than 5 MPa.

5. The variable clamping force oil circuit control system for a double-action stretch forming equipment according to claim 1, characterized in that: The pressing block (19) is connected to the pressing cylinder displacement sensor (23), and the intermediate block (18) is connected to the middle main cylinder displacement sensor (24).

6. The variable clamping force oil circuit control system for a double-action stretch forming equipment according to claim 1, characterized in that: The first pump group (1) and the second pump group (2) are high-pressure servo pump groups.

7. The variable clamping force oil circuit control system for a double-action stretch forming equipment according to claim 1, characterized in that: The lower chamber control valve group (7) of the pressing cylinder and the lower chamber control valve group (9) of the middle main cylinder both include an oil inlet valve, an oil outlet valve, a support valve and a quick-down valve; the upper chamber control valve group (8) of the pressing cylinder and the upper chamber control valve group (10) of the middle main cylinder both include an oil inlet valve and a pressure holding valve.

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