Hydraulic system and injection molding machine

Abstract

The application discloses a hydraulic system applied to an injection molding machine, comprising a mold locking control loop and a melt injection control loop, wherein the mold locking control loop comprises a first directional valve, a second directional valve, a third directional valve, a fourth directional valve, a first cartridge valve, an overflow valve and a safety valve, and is configured to lock and maintain the pressure of a mold at a preset pressure; the melt injection control loop is connected with the mold locking control loop and comprises a hydraulic lock, a plurality of directional valves, a second cartridge valve and a proportional overflow valve, and is configured to control the melt density by using a proportional melt back pressure. The application solves the problem of low production efficiency of plastic products of the injection molding machine in the prior art.

Description

Technical Field

[0001] This application relates to the field of injection molding machine technology, and more specifically, to a hydraulic system and an injection molding machine. Background Technology

[0002] Injection molding machines play a vital role in national production, efficiently and in large quantities producing various plastic products to meet the needs of numerous sectors, including automobiles, electronics, and home appliances. They improve production efficiency, ensure product quality stability and consistency, reduce production costs, and promote the development of the plastic products industry, playing a significant role in driving economic growth in related industries.

[0003] In recent years, the production efficiency of injection molding machines for plastic products has been continuously improving, but the problems of long production time and low production efficiency still exist. Summary of the Invention

[0004] The main objective of this application is to provide a hydraulic system and an injection molding machine to solve the problem of low production efficiency of plastic products in existing injection molding machines.

[0005] According to one aspect of this application, a hydraulic system is provided for use in an injection molding machine, comprising: a mold clamping control circuit and an injection control circuit, wherein the mold clamping control circuit includes: a first directional valve, a second directional valve, a third directional valve, a fourth directional valve, a first cartridge valve, a relief valve, and a safety valve, configured to lock and maintain the mold at a preset pressure; wherein, the A port and B port of the second directional valve are respectively connected to the oil inlet and oil return port of the mold adjusting motor; the relief valve and the fourth directional valve are pilot valves of the first cartridge valve; the P port and A port of the safety valve are connected to the rodless chamber of the mold clamping cylinder, and the T port and B port of the safety valve are connected to the A port of the third directional valve; the B port of the third directional valve is connected to the rod chamber of the mold clamping cylinder; the injection control circuit, connected to the mold clamping control circuit, includes: a hydraulic lock, multiple directional valves, a second cartridge valve, and a proportional relief valve, configured to control the melt density by proportional melt back pressure.

[0006] Optionally, when the safety valve is not powered, its valve core is in the closed state; when the safety valve is powered, its P port is connected to its B port, its T port is connected to its A port, and its valve core is in the open state.

[0007] Optionally, when the electromagnet 2YA of the third directional valve and the electromagnet 4YA of the safety valve are powered, the valve core of the first cartridge valve is closed and the valve core of the safety valve is opened, forming a differential speed-increasing circuit. The oil enters the rodless chamber of the mold-closing cylinder through the third directional valve and the safety valve to perform a rapid mold-closing action. When approaching the set end position, the electromagnet 3YA of the fourth directional valve is powered, the valve core of the first cartridge valve is opened, and a slow mold-closing action is performed.

[0008] Optionally, when the electromagnet 1YA of the third directional valve and the electromagnet 5YA of the first directional valve are powered, the oil enters the rod chamber of the mold-locking cylinder through the third directional valve, and the oil in the rodless chamber of the mold-locking cylinder is quickly depressurized through the first directional valve to achieve a rapid mold opening action; when the electromagnet 3YA of the fourth directional valve is powered, the valve core of the first cartridge valve opens, generating back pressure for oil return, and performing a slow mold opening action.

[0009] Optionally, when the second directional valve controls the mold adjusting motor to rotate forward, the mold adjusting action is realized; when the second directional valve controls the mold adjusting motor to rotate in reverse, the mold adjusting action is realized.

[0010] Optionally, the injection control circuit includes multiple directional valves, including a fifth directional valve, a sixth directional valve, and a seventh directional valve. The fifth directional valve is connected to a hydraulic lock, and its port A is connected to the rod-side chamber of the injection cylinder, while its port B is connected to the rodless chamber of the injection cylinder. The sixth directional valve's port A is connected to the rodless chamber of the injection cylinder, and its port B is connected to the rod-side chamber of the injection cylinder. The port B of the sixth directional valve is also connected to the lower port of the second cartridge valve, and the side port of the second cartridge valve is connected to the oil tank. The seventh directional valve and the proportional relief valve are pilot valves of the second cartridge valve.

[0011] Optionally, when the seventh directional valve is not powered and the electromagnet 3YA of the sixth directional valve is powered, the valve core of the second cartridge valve is closed, and the oil enters the rod chamber of the injection cylinder, pushing the piston to perform the injection action.

[0012] Optionally, when the seventh directional valve is not powered and the electromagnet 4YA of the sixth directional valve is powered, the valve core of the second cartridge valve is closed, and the oil enters the rodless chamber of the injection cylinder, pushing the piston to perform the injection retraction action.

[0013] Optionally, when the fifth directional valve is not powered, no hydraulic fluid flows through the hydraulic lock, and the injection cylinder is locked; when the electromagnet 1YA of the fifth directional valve is powered, hydraulic fluid enters the rodless chamber of the injection cylinder, and the hydraulic fluid pushes the piston of the injection cylinder to move towards the rod chamber of the injection cylinder, thereby retracting the injection seat; when the electromagnet 2YA of the sixth directional valve is powered, hydraulic fluid enters the rod chamber of the injection cylinder, and the hydraulic fluid pushes the piston of the injection cylinder to move towards the rodless chamber of the injection cylinder, thereby advancing the injection seat.

[0014] Optionally, during the melting process, the screw retracts under the pressure of the material at the front end, the electromagnet 5YA of the seventh directional valve is powered, the valve core of the second cartridge valve opens, and the oil returns to the oil tank after passing through the second cartridge valve, the seventh directional valve and the proportional relief valve; the proportional relief valve is set to infinitely adjust the back pressure of the melt.

[0015] According to another aspect of this application, an injection molding machine is also provided, including the above-described hydraulic system.

[0016] This application provides a hydraulic system for injection molding machines. The hydraulic system focuses on optimizing the mold-locking hydraulic control circuit of a small mechanical hinge injection molding machine. While ensuring mold-locking accuracy, it improves the opening and closing speed of the mold, thereby shortening the production time and improving the production efficiency. In addition, the system has the characteristics of good versatility and fast response speed. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 This is a schematic diagram of a hydraulic system applied to an injection molding machine according to an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of a mold-locking control circuit of a hydraulic system according to an embodiment of this application;

[0020] Figure 3 This is a schematic diagram of a hydraulic system injection control circuit according to an embodiment of this application. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0024] To better understand the embodiments of this application, the technical terms involved in the embodiments of this application are explained below:

[0025] An injection molding machine, also known as an injection molding machine or injection molding machine, is a primary molding equipment used to mold thermoplastic or thermosetting plastics into various shapes of plastic products through plastic molds.

[0026] Figure 1 This is a schematic diagram of a hydraulic system for an injection molding machine according to an embodiment of this application. This hydraulic system is applied to an injection molding machine, such as... Figure 1 As shown, the hydraulic system includes: a mold clamping control circuit 1 and an injection control circuit 2.

[0027] Hydraulic systems are widely used in industrial and mechanical fields, utilizing the pressure of a fluid (usually oil) to transmit power and energy. They are widely used due to their ability to provide powerful force, precise control, and reliability in various environments. The working principle of a hydraulic system is based on Pascal's Law, which states that in a closed system, the pressure applied to a stationary fluid is equal in all directions. This means that in a hydraulic system, a force applied to a small area is proportionally amplified when transmitted through the fluid to a large area.

[0028] In the injection molding process, injection control is a crucial step, directly impacting the quality of the final product and production efficiency. The injection control loop is primarily responsible for injecting molten plastic into the mold cavity at a predetermined pressure and speed.

[0029] The clamping control circuit is a crucial component of an injection molding machine. It ensures that the mold remains closed during injection and holding pressure, and can withstand high pressure. The magnitude of the clamping force directly impacts product quality and production efficiency.

[0030] The hydraulic system in the embodiments of this application focuses on optimizing the mold clamping control circuit and injection control circuit of small machine-hinged injection molding machines. It is applicable to most high-speed small machine-hinged injection molding machines, has a high degree of system integration, a compact structure, and facilitates later maintenance. A detailed description follows.

[0031] Figure 2 This is a schematic diagram of a mold-locking control circuit of a hydraulic system according to an embodiment of this application, such as... Figure 2 As shown, the mold locking control circuit 1 includes: a first directional valve 101, a second directional valve 102, a third directional valve 104, a fourth directional valve 105, a first cartridge valve 103, an overflow valve 106, and a safety valve 107, which are configured to lock and maintain the mold at a preset pressure.

[0032] Directional valves (also known as directional control valves) are very important control components in hydraulic and pneumatic systems, used to change the direction of fluid flow, thereby controlling the action of actuators (such as cylinders or motors).

[0033] Cartridge valves are compact hydraulic control valves typically integrated into multi-way blocks or valve blocks within hydraulic systems. They can perform various functions, including directional control, pressure control, and flow control. Common functions include reversing, relief, pressure reduction, and sequential action.

[0034] A relief valve is a pressure control valve in a hydraulic system. Its main function is to limit the maximum working pressure of the system and protect the system from overpressure damage.

[0035] A safety valve is an important protective device used to prevent pressure in hydraulic or pneumatic systems from exceeding a set safety limit. When the system pressure exceeds the preset value, the safety valve will automatically open, releasing excess fluid (oil or gas), thereby reducing the system pressure and preventing equipment damage or safety accidents.

[0036] like Figure 2 As shown, ports A and B of the second directional valve 102 are connected to the oil inlet and return port of the mold adjusting motor, respectively; the overflow valve 106 and the fourth directional valve 105 are the pilot valves of the first cartridge valve 103; ports P and A of the safety valve 107 are connected to the rodless chamber of the mold clamping cylinder, and ports T and B of the safety valve 107 are connected to port A of the third directional valve 104; port B of the third directional valve 104 is connected to the rod chamber of the mold clamping cylinder.

[0037] The clamping cylinder is one of the key components in an injection molding machine. Its main function is to provide sufficient clamping force during injection molding to ensure that the mold remains closed under high pressure. The design and operation of the clamping cylinder are crucial for ensuring product quality, mold life, and production efficiency.

[0038] According to an optional embodiment of this application, when the safety valve 107 is not powered, its valve core is in a closed state; when the safety valve 107 is powered, its P port is connected to its B port, its T port is connected to its A port, and its valve core is in an open state.

[0039] When safety valve 107 is not powered, its internal valve core is in the closed state. At this time, if the pressure in the system exceeds the predetermined value, the oil cannot release the pressure through this valve because the valve core is closed.

[0040] When safety valve 107 is powered, port P will connect to port B, and port T will connect to port A. This allows high-pressure oil from port P to flow to port B, while oil from port A can return to the tank via port T. This process allows the oil to flow under specific conditions, such as when pressure needs to be released or the direction of the oil circuit needs to be changed.

[0041] The hydraulic system provided in this application employs a self-locking safety valve in its mold-locking control circuit, enabling it to cut off the oil circuit during both the mold opening and closing stages, thus protecting the operator's safety.

[0042] According to another optional embodiment of this application, when the electromagnet 2YA of the third-party directional valve 104 and the electromagnet 4YA of the safety valve 107 are powered, the valve core of the first cartridge valve 103 is closed and the valve core of the safety valve 107 is opened, forming a differential speed-increasing circuit. The oil enters the rodless chamber of the mold-closing cylinder through the third-party directional valve 104 and the safety valve 107 to perform a rapid mold-closing action. When approaching the set end position, the electromagnet 3YA of the fourth directional valve 105 is powered, and the valve core of the first cartridge valve 103 is opened to perform a slow mold-closing action.

[0043] High-pressure hydraulic fluid enters the rodless chamber of the mold-locking cylinder through the third-party directional valve 104 and the already opened safety valve 107. The increased pressure in the rodless chamber pushes the piston to move rapidly. The hydraulic fluid in the rod chamber of the mold-locking cylinder flows back to the rodless chamber through a one-way valve, forming a differential circuit and further accelerating the piston's movement. This configuration utilizes the area difference between the two chambers, allowing the piston to advance at a faster speed.

[0044] When the piston approaches the set endpoint, the electromagnet 3YA of the fourth directional valve 105 is energized. The valve core of the first cartridge valve 103 opens under pilot action. At this time, the high-pressure oil no longer flows directly into the rodless chamber through the safety valve 107, but enters after being regulated by the first cartridge valve 103, thereby reducing the pressure or flow rate supplied to the rodless chamber. As a result, the piston changes from rapid movement to a slower speed for final positioning or pressurization, i.e., slow mold closing action.

[0045] The hydraulic system provided in this application achieves zero back pressure control in the mold-locking control circuit and performs full-process differential control during the mold-closing stage, thereby increasing the mold-closing speed. Typical small mechanical injection molding machines have three or more stages of mold-closing control, mostly involving slow mold-closing first, then fast mold-closing, and finally a final slow control at the end of the mold-closing stage. The mold-locking control circuit in this application can achieve zero back pressure control at the beginning of the mold-closing stage via a pilot valve, combined with a check valve for rapid differential control. At the end of the mold-closing stage, back pressure is added via the pilot valve to reduce the differential speed, achieving the required slow control at the end of the mold-closing stage. During the mold-opening stage, the first stage is depressurized by a directional valve, and the remaining oil in the second stage can flow back to the main oil circuit through a safety valve.

[0046] The mold-locking control circuit in the hydraulic system provided in this application has the advantage of fast mold closing speed, which can realize rapid differential operation throughout the mold closing process, reduce machine cycle time, and improve production efficiency.

[0047] In some optional embodiments of this application, when the electromagnet 1YA of the third directional valve 104 and the electromagnet 5YA of the first directional valve 101 are powered, the oil enters the rod chamber of the mold-locking cylinder through the third directional valve 104, and the oil in the rodless chamber of the mold-locking cylinder is quickly depressurized through the first directional valve 101 to achieve a rapid mold opening action; when the electromagnet 3YA of the fourth directional valve 105 is powered, the valve core of the first cartridge valve 103 opens, generating back pressure for oil return, and performing a slow mold opening action.

[0048] When the electromagnet 1YA of the third directional valve 104 is energized and the electromagnet 5YA of the first directional valve 101 is energized, high-pressure oil enters the rod chamber of the mold-locking cylinder through the third directional valve 104, pushing the piston backward (i.e., in the mold-opening direction). The oil in the rodless chamber of the mold-locking cylinder returns directly to the oil tank through the switched first directional valve 101, achieving rapid pressure relief. With this configuration, because the oil in the rodless chamber of the mold-locking cylinder can be quickly discharged without encountering significant resistance, rapid mold-opening action can be achieved.

[0049] When it is necessary to slow down the mold opening speed, the electromagnet 3YA of the fourth directional valve 105 is energized. The valve core of the first cartridge valve 103 opens, but at this time a certain back pressure is introduced. This back pressure is generated by the adjustment of the oil return path by the first cartridge valve 103, so that the oil in the rodless chamber of the mold locking cylinder encounters resistance when it is discharged, thereby slowing down the piston's movement speed and realizing a slow mold opening action.

[0050] To further adjust the required back pressure level, the pressure setting of the relief valve 106 can be adjusted. The relief valve 106 here serves to limit the maximum back pressure, ensuring a safe operating pressure range is maintained even during slow mold opening, thus achieving zero back pressure during mold opening.

[0051] The above design allows the system to initially execute most of the mold opening stroke at a higher speed, then automatically switch to a slower speed near the end point to facilitate precise control of the final position and reduce impact. This achieves the technical benefits of protecting the mold and improving machining accuracy.

[0052] The mold-locking control circuit in the hydraulic system provided in this application has the advantage of stable mold opening. It releases pressure before opening the mold, reducing hydraulic shock. This control method can ensure the stability of the machine during the mold opening process, reduce return oil impact, and make the mold opening smoother.

[0053] In some other optional embodiments of this application, when the second directional valve 102 controls the mold adjusting motor to rotate forward, the mold adjusting forward action is realized; when the second directional valve 102 controls the mold adjusting motor to rotate in reverse, the mold adjusting backward action is realized.

[0054] The mold adjustment motor is a crucial component in injection molding machines used to adjust mold thickness. During injection molding, the mold thickness may need to be adjusted according to different product and process requirements. The mold adjustment motor achieves precise adjustment of the mold thickness by driving a mold movement mechanism (usually a screw or rack and pinion mechanism).

[0055] In the embodiments of this application, the second directional valve 102 is used in the injection molding machine to control the forward and reverse rotation of the mold adjusting motor, thereby realizing the adjustment of the mold thickness (i.e., mold adjusting forward and backward movements). This allows the injection molding machine to flexibly adjust the mold closing thickness, ensuring that the optimal state is achieved each time the mold is closed, thereby improving production efficiency and product quality.

[0056] Figure 3 This is a schematic diagram of a hydraulic system injection control circuit according to an embodiment of this application, such as... Figure 3 As shown, the injection control circuit 2 is connected to the mold clamping control circuit 1 and includes: a hydraulic lock 201, multiple directional valves, a second cartridge valve 204, and a proportional overflow valve 206, which is configured to control the melt density by proportional melt back pressure.

[0057] A hydraulic lock is a device used to keep the position of actuators (such as cylinders or motors) in a hydraulic system fixed. It prevents movement of the actuator by blocking the flow of hydraulic fluid within it, thus ensuring the system remains stable when no action is required.

[0058] A proportional relief valve is a pressure control valve used in hydraulic systems. It regulates system pressure based on an input electrical signal (usually current or voltage). Unlike traditional relief valves, proportional relief valves offer stepless pressure regulation, providing more precise and flexible pressure control.

[0059] like Figure 3As shown, the injection control circuit 2 includes multiple directional valves, including a fifth directional valve 202, a sixth directional valve 203, and a seventh directional valve 205. The fifth directional valve 202 is connected to the hydraulic lock 201, and its port A is connected to the rod chamber of the injection cylinder, while its port B is connected to the rodless chamber of the injection cylinder. The sixth directional valve 203 has its port A connected to the rodless chamber of the injection cylinder, its port B connected to the rod chamber of the injection cylinder, and its port B is connected to the lower port of the second cartridge valve 204. The side port of the second cartridge valve 204 is connected to the oil tank. The seventh directional valve 205 and the proportional relief valve 206 are pilot valves of the second cartridge valve 204.

[0060] The injection transfer cylinder (also known as the injection seat transfer cylinder or injection unit transfer cylinder) is an important component of an injection molding machine. Its main function is to move the injection unit (including the screw, barrel, and nozzle) during the injection process to achieve precise injection position control.

[0061] According to an optional embodiment of this application, when the seventh directional valve 205 is not powered and the electromagnet 3YA of the sixth directional valve 203 is powered, the valve core of the second cartridge valve 204 is closed, and the oil enters the rod chamber of the injection cylinder, pushing the piston to perform the injection action.

[0062] The injection cylinder (also known as the injection cylinder or injection tank) mainly functions to push the screw forward during the injection molding process, injecting molten plastic into the mold.

[0063] After the sixth directional valve 203 switches, high-pressure oil enters the rod chamber of the injection cylinder through the sixth directional valve 203. Because the valve core of the second cartridge valve 204 is closed, the oil in the rodless chamber of the injection cylinder cannot flow out through the second cartridge valve 204. The oil in the rodless chamber of the injection cylinder is forced to be discharged through the sixth directional valve 203 and return to the oil tank. The high-pressure oil pushes the piston of the injection cylinder towards the rodless chamber, thereby performing the injection action.

[0064] This configuration ensures that the hydraulic fluid can only drive the piston for injection in one direction, while allowing fluid to flow freely back to the tank in the other direction. This design helps improve efficiency and control precision during the injection process.

[0065] According to another optional embodiment of this application, when the seventh directional valve 205 is not powered and the electromagnet 4YA of the sixth directional valve 203 is powered, the valve core of the second cartridge valve 204 is closed, and the oil enters the rodless chamber of the injection cylinder, pushing the piston to perform the injection retraction action.

[0066] After the sixth directional valve 203 switches, high-pressure oil enters the rodless chamber of the injection cylinder through the sixth directional valve 203. Because the valve core of the second cartridge valve 204 is closed, the oil in the rod chamber of the injection cylinder cannot flow out through the second cartridge valve 204. The oil in the rod chamber of the injection cylinder is forced to be discharged through the sixth directional valve 203 and return to the oil tank. The high-pressure oil pushes the piston of the injection cylinder towards the rod chamber, thereby performing the ejection action.

[0067] The above configuration ensures that the hydraulic fluid can drive the piston from the rodless side of the injection cylinder to perform the injection retraction action, while allowing the hydraulic fluid from the rod side to freely flow back to the oil tank. This design facilitates fast and controllable injection retraction, which is crucial for equipment such as injection molding machines, as it helps reduce cycle time and improve production efficiency.

[0068] In some optional embodiments of this application, when the fifth directional valve 202 is not powered, no oil flows through the hydraulic lock 201, and the injection cylinder is locked; when the electromagnet 1YA of the fifth directional valve 202 is powered, oil enters the rodless chamber of the injection cylinder, and the oil pushes the piston of the injection cylinder to move towards the rod chamber of the injection cylinder, thereby retracting the injection seat; when the electromagnet 2YA of the sixth directional valve 203 is powered, oil enters the rod chamber of the injection cylinder, and the oil pushes the piston of the injection cylinder to move towards the rodless chamber of the injection cylinder, thereby advancing the injection seat.

[0069] When the fifth directional valve 202 is de-energized, no oil can enter or leave the injection cylinder through the fifth directional valve 202. Since there is no oil flow, the hydraulic lock 201 will maintain its current state to prevent the oil in the injection cylinder from moving, thereby locking the injection cylinder in the current position.

[0070] When the electromagnet 1YA of the fifth directional valve 202 is energized, high-pressure oil enters the rodless chamber of the injection cylinder through the fifth directional valve 202. The oil pushes the piston of the injection cylinder towards the rod chamber, realizing the retraction of the injection seat. The oil in the rod chamber of the injection cylinder is discharged through the fifth directional valve 202 and returns to the oil tank.

[0071] When the electromagnet 2YA of the sixth directional valve 203 is energized, high-pressure oil enters the rod chamber of the injection cylinder through the sixth directional valve 203. The oil pushes the piston of the injection cylinder towards the rodless chamber, realizing the forward movement of the injection seat. The oil in the rodless chamber of the injection cylinder is discharged through the sixth directional valve 203 and returns to the oil tank.

[0072] The above configuration enables the system to lock the position of the injection cylinder when needed, and to quickly and accurately control the forward and backward movement of the injection seat, ensuring precise positioning and efficient operation during the injection process.

[0073] In some other optional embodiments of this application, during the melting process, the screw retracts under the action of the front material pressure, the electromagnet 5YA of the seventh directional valve 205 is powered, the valve core of the second cartridge valve 204 opens, and the oil returns to the oil tank after passing through the second cartridge valve 204, the seventh directional valve 205 and the proportional relief valve 206; the proportional relief valve 206 is configured to infinitely adjust the melt back pressure.

[0074] When the electromagnet 5YA of the seventh directional valve 205 is energized, the spool of the second cartridge valve 204 opens, allowing oil to pass through. This provides a return path for the injection cylinder or related actuators.

[0075] When the seventh directional valve 205 is energized, oil can flow from the actuator (such as a hydraulic cylinder) and through the valve. The proportional relief valve 206 can adjust the pressure on the return path as needed, thereby achieving adjustable back pressure. The proportional relief valve is usually controlled by an electrical signal, and its opening pressure can be adjusted very precisely, thereby achieving continuous stepless regulation of the back pressure.

[0076] Back pressure helps maintain the uniformity and consistency of molten plastic, prevents bubble formation, and in some cases can even help improve plasticizing quality. The opening pressure of the proportional relief valve 206 can be continuously adjusted by changing the electrical signal applied to it, and the desired back pressure value can be set via a control system.

[0077] The injection circuit in the hydraulic system provided in this application controls the melt density by using proportional melt back pressure.

[0078] This application also provides an injection molding machine that includes the aforementioned hydraulic system. Therefore, this injection molding machine possesses all the technical effects of the aforementioned hydraulic system. Since the technical effects of the hydraulic system have already been described in detail above, they will not be repeated here.

[0079] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0080] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0081] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hydraulic system, characterized in that, This hydraulic system is used in injection molding machines and includes: a mold clamping control circuit and an injection control circuit, wherein, The mold locking control circuit includes: a first directional valve, a second directional valve, a third directional valve, a fourth directional valve, a first cartridge valve, an overflow valve, and a safety valve, configured to lock and maintain the mold at a preset pressure. Wherein, the A port and B port of the second directional valve are connected to the oil inlet and oil return port of the mold adjusting motor, respectively; the overflow valve and the fourth directional valve are the pilot valves of the first cartridge valve; the P port and A port of the safety valve are connected to the rodless chamber of the mold locking cylinder, and the T port and B port of the safety valve are connected to the A port of the third directional valve; the B port of the third directional valve is connected to the rod chamber of the mold locking cylinder; The injection control circuit, connected to the mold clamping control circuit, includes: a hydraulic lock, multiple directional valves, a second cartridge valve, and a proportional overflow valve, configured to control the melt density by proportional melt back pressure; The seventh directional valve and the proportional relief valve among the multiple directional valves included in the injection control circuit are the pilot valves of the second cartridge valve. During the melting process, the screw retracts under the pressure of the material at the front end, the electromagnet 5YA of the seventh directional valve is powered, the valve core of the second cartridge valve opens, and the oil returns to the oil tank after passing through the second cartridge valve, the seventh directional valve and the proportional relief valve. The proportional overflow valve is configured to infinitely adjust the melt back pressure. When the safety valve is not powered, its valve core is in the closed state; When the safety valve is powered, its P port is connected to its B port, its T port is connected to its A port, and its valve core is in the open state. When the electromagnet 2YA of the third directional valve and the electromagnet 4YA of the safety valve are powered, the valve core of the first cartridge valve is closed and the valve core of the safety valve is opened, forming a differential speed-increasing circuit. The oil enters the rodless chamber of the mold-closing cylinder through the third directional valve and the safety valve to perform a rapid mold-closing action. When the target position is approached, the electromagnet 3YA of the fourth directional valve is powered, and the valve core of the first cartridge valve opens to perform a slow mold closing action. When the electromagnet 1YA of the third directional valve and the electromagnet 5YA of the first directional valve are powered, the oil enters the rod chamber of the mold-locking cylinder through the third directional valve, and the oil in the rodless chamber of the mold-locking cylinder is quickly depressurized through the first directional valve to achieve a rapid mold opening action. When the electromagnet 3YA of the fourth directional valve is powered, the valve core of the first cartridge valve opens, generating back pressure for oil return and performing a slow mold opening action.

2. The hydraulic system according to claim 1, characterized in that, When the mold adjusting motor is controlled to rotate forward by the second directional valve, the mold adjusting advance action is realized; When the mold adjustment motor is reversed under the control of the second directional valve, the mold adjustment retraction action is realized.

3. The hydraulic system according to claim 1, characterized in that, The injection control circuit includes multiple directional valves, including a fifth directional valve, a sixth directional valve, and a seventh directional valve, wherein... The fifth directional valve is connected to the hydraulic lock, and port A of the fifth directional valve is connected to the rod chamber of the injection cylinder, and port B is connected to the rodless chamber of the injection cylinder. The A port of the sixth directional valve is connected to the rodless chamber of the injection cylinder, and the B port is connected to the rod chamber of the injection cylinder. The B port of the sixth directional valve is connected to the lower oil port of the second cartridge valve, and the side oil port of the second cartridge valve is connected to the oil tank.

4. The hydraulic system according to claim 3, characterized in that, When the seventh directional valve is not powered and the electromagnet 3YA of the sixth directional valve is powered, the valve core of the second cartridge valve is closed, and the oil enters the rod chamber of the injection cylinder, pushing the piston to perform the injection action.

5. The hydraulic system according to claim 3, characterized in that, When the seventh directional valve is not powered and the electromagnet 4YA of the sixth directional valve is powered, the valve core of the second cartridge valve is closed, and the oil enters the rodless chamber of the injection cylinder, pushing the piston to perform the injection retraction action.

6. The hydraulic system according to claim 3, characterized in that, When the fifth directional valve is not powered, no oil flows through the hydraulic lock, and the injection cylinder locks up. When the electromagnet 1YA of the fifth directional valve is powered, the oil enters the rodless chamber of the injection cylinder, and the oil pushes the piston of the injection cylinder to move towards the rod chamber of the injection cylinder, thereby realizing the retraction of the injection seat; When the electromagnet 2YA of the fifth directional valve is powered, the oil enters the rod chamber of the injection cylinder, and the oil pushes the piston of the injection cylinder to move towards the rodless chamber of the injection cylinder, thereby advancing the injection seat.

7. An injection molding machine, characterized in that, The hydraulic system includes any one of claims 1 to 6.

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