Injection nozzle based on a gradient temperature difference field

Abstract

The application discloses an injection nozzle based on a gradient temperature difference field, relates to the technical field of injection molding, and aims to solve the problems of uneven temperature distribution of a hot runner of an injection nozzle, temperature monitoring lag and insufficient temperature control precision in the prior art.The injection nozzle comprises a positioning ring, an injection nozzle, a driving mechanism and a hot nozzle, the injection nozzle is fastened to the positioning ring, and a liquid inlet channel is arranged in the injection nozzle; the hot nozzle is connected to the driving mechanism, a main flow channel is arranged in the hot nozzle, and the main flow channel is communicated with the liquid inlet channel; the heater comprises a spiral heating wire, and the spiral heating wire is arranged on the outer side of the hot nozzle; the diameter of the spiral heating wire gradually decreases along the conveying direction of the plastic melt, a gradient temperature difference is actively formed in the main flow channel, a flow driving force is formed through the temperature gradient, the melt is smoothly filled into a cavity, uneven flow rate is avoided, cooling rhythm is reasonably distributed, forming efficiency and product internal stress are balanced, the temperature difference between the melt and the mold and the temperature difference inside the melt are also reduced, and fusion quality is improved.

Description

Technical Field

[0001] This application relates to the field of injection molding technology, and in particular to an injection nozzle based on a gradient temperature field, wherein the injection nozzle controls the melt flow direction by constructing a gradient temperature field. Background Technology

[0002] In the field of injection molding, hot runner systems, by continuously heating the plastic melt within the runner to maintain a molten state, significantly reduce waste and improve production efficiency. They have become core process equipment in high-end manufacturing industries such as automotive, 3C electronics, and medical equipment. As the "heat source core" of this system, the heating uniformity and temperature control precision of the heating coil directly determine the flow stability of the melt, thus having a crucial impact on the quality of the final product. With downstream industries continuously increasing their requirements for the surface finish, dimensional accuracy, and mechanical properties of precision injection molded parts (such as automotive headlights, mobile phone casings, and medical consumables), the technical limitations of traditional heating coils in temperature uniformity control are becoming increasingly prominent. Furthermore, the difficulty in precisely controlling the melt flow direction within the runner also leads to unevenness or deviations during the filling process of complex cavities.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of this application and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Utility Model Content

[0004] The purpose of this application is to provide an injection nozzle based on a gradient temperature difference field for controlling melt temperature and flow direction.

[0005] To achieve the above objectives / to solve the above technical problems, the present invention adopts the following technical solution: the injection nozzle includes a positioning ring, an injection nozzle, a drive mechanism and a hot nozzle, the injection nozzle is fastened to the positioning ring, and the injection nozzle is provided with a liquid inlet channel; The hot nozzle is connected to the drive mechanism, and a main channel is provided inside the hot nozzle, which is connected to the liquid inlet channel. A valve needle is installed inside the main channel, and the valve needle is connected to the drive mechanism; a heater is installed on the outside of the hot nozzle. The outlet of the main channel is equipped with a nozzle; The heater includes a spiral heating wire, which is wound around the outside of the hot nozzle; The diameter of the spiral heating wire decreases sequentially along the conveying direction of the plastic melt.

[0006] The injection nozzle precisely engages with the mold's fixed platen via a positioning ring. The injection nozzle guides the molten plastic, while the drive mechanism actuates the valve needle within the hot runner. The heater maintains the temperature within the main runner. During injection, driven by the drive mechanism, the valve needle tip retracts from the nozzle, forming an annular channel between the valve needle and the nozzle. The molten plastic flows sequentially through the inlet channel and the main runner, entering the mold cavity. After injection, the drive mechanism propels the valve needle forward, its conical tip pressing tightly into the nozzle's gate to create a mechanical seal, cutting off the molten plastic flow. A spiral hot wire with progressively decreasing diameter along the molten plastic's transport direction actively creates a temperature gradient within the main runner. A thicker spiral hot wire has a higher power density and generates more heat, thus creating a temperature gradient within the main runner: high at the inlet, stable in the middle, and slightly lower at the outlet. This temperature gradient generates a "flow driving force," allowing the molten plastic to smoothly fill the cavity, preventing uneven flow rates, and rationally distributing the cooling rhythm. This balances molding efficiency and product internal stress, reduces the temperature difference between the molten plastic and the mold, and improves the fusion quality.

[0007] Furthermore, the spiral heating wire is divided into several heating units, each corresponding to a temperature control zone. The diameter of the spiral heating wire in the inlet section heating unit is 1.2mm, the diameter of the spiral heating wire in the middle section heating unit is 1.0mm, and the diameter of the spiral heating wire in the outlet section heating unit is 0.8mm.

[0008] The spiral hot wire is protected by a protective sleeve for protection and heat preservation. Each heating unit is equipped with an independent drive chip, supporting stepless voltage adjustment from 0-220V. Combined with pulse width modulation technology, it achieves precise power output, with a unit power adjustment accuracy of 1W, meeting temperature difference control requirements of ±0.5℃. Heating units are connected via snap-fit ​​electrode interfaces. The protective sleeve uses a threaded sealing end cap design, allowing for individual removal and replacement in case of damage, without disassembling the entire flow channel. Spiral hot wires of different diameters actively create a gradient temperature difference. This gradient temperature difference generates flow driving force through viscosity difference, guiding the melt flow direction. The core principle is the "linked regulation of temperature, viscosity, and pressure." Temperature directly affects melt viscosity; higher temperatures result in lower melt viscosity and better fluidity, while lower temperatures result in higher viscosity and poorer fluidity. This gradient temperature difference forms a "viscosity gradient." A temperature gradient is constructed along the flow direction (from the inlet to the depth of the cavity), simultaneously forming a viscosity gradient from "high fluidity" to "low fluidity." Viscosity difference drives flow: High-viscosity regions exert "traction resistance" on low-viscosity melts, causing the low-viscosity melt to naturally move towards the direction of less resistance, ultimately guiding the melt to smoothly fill the cavity. Inlet high-temperature zone: The melt viscosity is lowest and its fluidity is strongest, forming a "propelling front" that quickly overcomes flow channel resistance; Mid-section constant-temperature zone: Maintains stable melt viscosity, preventing sudden viscosity changes due to rapid temperature drops, and ensuring uniform flow rate; Outlet / cavity end gentle descent zone: Viscosity moderately increases, flow rate slows, preventing excessive melt impact and overflow, while preparing for solidification.

[0009] Furthermore, three temperature measuring points are evenly arranged circumferentially on the main channel, and a K-type thermocouple is embedded every 50mm along the axial direction of the main channel; the distance between the K-type thermocouple and the spiral heating wire is ≤3mm.

[0010] A K-type thermocouple is embedded every 50mm along the axial direction of the main flow channel, and three temperature measuring points are evenly arranged around its circumference to form a three-dimensional sensing network, capturing real-time axial and cross-sectional temperature difference data of the main flow channel. The K-type thermocouples are embedded with a spacing of ≤3mm from the spiral heating wire, reducing the temperature response lag time from the traditional 2-3 seconds to less than 100ms. A miniature pressure sensor and a melt flow velocity sensor are integrated into the main flow channel to simultaneously collect pressure fluctuations and melt flow velocity data. Combined with temperature parameters, a multi-dimensional "heat-force-flow" database is constructed to improve control accuracy. The thermal field data is synchronized to the temperature controller in real time, achieving an overall channel temperature difference of ±0.5℃~±1℃ and a cross-sectional temperature difference of ≤2℃, which is 4-5 times more accurate than traditional temperature control. The temperature controller is existing technology and will not be described in detail here.

[0011] Furthermore, the drive mechanism includes a cylinder, a piston, and a base. The cylinder and the base are fastened together, the piston is slidably connected to the cylinder, and the output end of the piston is drivenly connected to the valve needle.

[0012] Furthermore, the drive mechanism moves the valve needle via a piston, thereby opening and closing the injection molding channel. The base and cylinder are fixed together to provide space for the piston to move.

[0013] The nozzle includes a nozzle head and a nozzle core. The nozzle head is securely connected to the hot nozzle, and the nozzle core is securely connected to the inner wall of the nozzle head. The nozzle core has a constriction channel that is connected to the main channel.

[0014] Furthermore, the diameter of the main flow channel gradually changes from 12mm to 8mm for the contraction flow channel, with a compression ratio of 1.5:1, to ensure smooth melt flow.

[0015] Furthermore, a sealing ring is provided on the contact surface between the nozzle and the hot nozzle.

[0016] An annealed copper sealing ring is placed between the nozzle and the hot nozzle to prevent the molten material from leaking out from the joint.

[0017] Furthermore, an insulating layer is installed inside the main channel.

[0018] The insulation layer is made of mica, which is used for heat insulation to optimize temperature control.

[0019] Furthermore, a heating coil is provided on the outside of the injection nozzle, and a thermocouple is provided on the heating coil.

[0020] The heating coil is used to maintain the temperature of the injection nozzle and prevent the melt from condensing and clogging. The thermocouple transmits the temperature signal to the temperature controller to realize closed-loop regulation of the heating power.

[0021] Compared with the prior art, the beneficial effects achieved by this application are as follows: 1. By sequentially arranging spiral hot wires with gradually decreasing wire diameters on the outer side of the main channel, a gradient temperature difference is actively constructed within the main channel. This creates a temperature gradient within the main channel that is "high at the inlet, stable in the middle, and slightly lower at the outlet." This temperature gradient forms a "flow driving force," allowing the melt to smoothly fill the cavity, avoiding uneven flow rate, and rationally distributing the cooling rhythm to balance molding efficiency and product internal stress. It also reduces the temperature difference between the melt and the mold, as well as within the melt itself, thereby improving the fusion quality.

[0022] 2. A K-type thermocouple is embedded every 50mm along the axial direction of the main channel, and three temperature measuring points are evenly arranged around it to form a three-dimensional sensing network. This network captures the axial and cross-sectional temperature difference data of the main channel in real time. A miniature pressure sensor and a melt flow velocity sensor are integrated into the main channel to simultaneously collect pressure fluctuation and melt flow velocity data within the channel. Combined with temperature parameters, a multi-dimensional "thermal-mechanical-fluid" database is constructed. This overcomes the limitations of traditional single-point temperature measurement and provides a real and comprehensive data foundation for precise temperature control, thereby improving the accuracy of temperature regulation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of this application; Figure 2 for Figure 1 Enlarged view of a portion at point A; Figure 3 This is a schematic diagram of the nozzle in this application; Figure 4 This is a schematic diagram of the heater in this application.

[0025] In the diagram: 1. Positioning ring; 2. Injection nozzle; 21. Liquid inlet channel; 3. Drive mechanism; 31. Cylinder; 32. Piston; 33. Base; 4. Hot nozzle; 41. Main channel; 5. Valve needle; 6. Heater; 61. Spiral heating wire; 7. Nozzle; 71. Nozzle tip; 72. Nozzle core; 721. Contraction channel; 73. Sealing ring; 8. Heating ring; 9. Insulation layer. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. Example 1

[0027] like Figure 1 As shown, this embodiment provides an injection nozzle based on a gradient temperature difference field, including: a positioning ring 1, an injection nozzle 2, a drive mechanism 3 and a hot nozzle 4. The injection nozzle 2 is fastened to the positioning ring 1, and the injection nozzle 2 is provided with a liquid inlet channel 21. The hot nozzle 4 is connected to the drive mechanism 3. The hot nozzle 4 has a main channel 41 inside, which is connected to the liquid inlet channel 21. A valve needle 5 is provided inside the main channel 41, and the valve needle 5 is connected to the drive mechanism 3; a heater 6 is provided on the outside of the hot nozzle 4. The outlet of the main channel 41 is equipped with a nozzle 7; The heater 6 includes a spiral heating wire 61, which is wound around the outside of the hot nozzle 4; The diameter of the spiral hot wire 61 decreases sequentially along the conveying direction of the plastic melt.

[0028] The injection nozzle is precisely fitted to the mold's fixed platen via the positioning ring 1. The injection nozzle 2 guides the molten plastic. The drive mechanism 3 drives the valve needle 5 inside the hot runner 4. The heater 6 maintains the temperature inside the main runner 41. During injection, driven by the drive mechanism 3, the tip of the valve needle 5 exits from the nozzle 7, forming an annular channel between the valve needle 5 and the nozzle 7. The molten plastic flows sequentially through the inlet channel 21 and the main runner 41, injecting into the mold cavity. After injection, the drive mechanism 3 drives the valve needle 5 forward, and the conical tip of the valve needle 5 is tightly pressed into the gate of the nozzle 7, forming a mechanical seal. The flow of the melt is cut off by a spiral hot wire 61 with a decreasing diameter along the conveying direction of the plastic melt. This spiral hot wire 61 is used to actively create a temperature gradient in the main channel 41. The thicker the spiral hot wire 61, the greater the power density and the greater the heat generated. This creates a temperature gradient in the main channel 41 with a "high inlet, stable middle section, and slightly lower outlet". The temperature gradient forms a "flow driving force", which allows the melt to fill the cavity smoothly, avoids uneven flow rate, and reasonably distributes the cooling rhythm to balance molding efficiency and product internal stress. It can also reduce the temperature difference between the melt and the mold, and between the melt and the interior of the melt, thus improving the fusion quality.

[0029] The spiral heating wire 61 is divided into several heating units, each corresponding to a temperature control zone. The diameter of the spiral heating wire 61 in the inlet section heating unit is 1.2mm, the diameter of the spiral heating wire 61 in the middle section heating unit is 1.0mm, and the diameter of the spiral heating wire 61 in the outlet section heating unit is 0.8mm.

[0030] The spiral hot wire 61 is equipped with a protective sleeve for protection and heat preservation. Each heating unit is equipped with an independent drive chip, supporting stepless voltage adjustment from 0-220V. Combined with pulse width modulation technology, it achieves precise power output with a unit power adjustment accuracy of 1W, meeting the temperature difference control requirements of ±0.5℃. The heating units are connected through snap-on electrode interfaces. The protective sleeve adopts a threaded sealing end cap design, which can be disassembled and replaced individually if damaged, without disassembling the entire flow channel. Spiral hot wires 61 with different wire diameters actively form a gradient temperature difference. The gradient temperature difference generates a flow driving force through viscosity difference to guide the melt flow direction. The core principle is the "linked regulation of temperature, viscosity, and pressure". Temperature directly affects the melt viscosity. The higher the temperature, the lower the melt viscosity and the better the fluidity; the lower the temperature, the higher the viscosity and the worse the fluidity. The gradient temperature difference forms a "viscosity gradient". A temperature gradient is built along the flow direction (from the inlet to the depth of the cavity), and a viscosity gradient of "high fluidity → low fluidity" is formed simultaneously. Viscosity difference drives flow: High-viscosity regions exert "traction resistance" on low-viscosity melts, causing the low-viscosity melt to naturally move towards the direction of less resistance, ultimately guiding the melt to smoothly fill the cavity. 1. High-temperature inlet zone: The melt viscosity is lowest and the fluidity is strongest, forming a "propelling front" that quickly overcomes flow channel resistance; 2. Constant-temperature mid-section zone: Maintains stable melt viscosity, avoiding sudden viscosity changes due to rapid temperature drops, and ensuring uniform flow rate; 3. Slow-descent outlet / cavity end zone: Viscosity increases moderately, and the flow rate slows down, preventing excessive melt impact and overflow, while also preparing for solidification.

[0031] Three temperature measuring points are evenly arranged around the circumference of the main channel 41, and a K-type thermocouple is embedded every 50mm along the axial direction of the main channel 41; the distance between the K-type thermocouple and the spiral heating wire 61 is ≤3mm.

[0032] A K-type thermocouple is embedded every 50mm along the axial direction of the main channel 41, and three temperature measuring points are evenly arranged around its circumference to form a three-dimensional sensing network, capturing the axial and cross-sectional temperature difference data of the main channel 41 in real time. The K-type thermocouples are embedded and the distance between them and the spiral heating wire 61 is ≤3mm, reducing the temperature response lag time from the traditional 2-3 seconds to less than 100ms. A miniature pressure sensor and a melt flow rate sensor are integrated into the main channel 41 to simultaneously collect pressure fluctuations and melt flow rate data within the channel. Combined with temperature parameters, a multi-dimensional "thermal-mechanical-fluid" database is constructed to improve the accuracy of control. The thermal field data is synchronized to the temperature controller in real time, achieving an overall channel temperature difference of ±0.5℃~±1℃ and a cross-sectional temperature difference of ≤2℃, which is 4-5 times more accurate than traditional temperature control. The temperature controller is existing technology and will not be described in detail here.

[0033] The drive mechanism 3 includes a cylinder 31, a piston 32 and a base 33. The cylinder 31 and the base 33 are fastened together, the piston 32 is slidably connected to the cylinder 31, and the output end of the piston 32 is connected to the valve needle 5.

[0034] The drive mechanism 3 drives the valve needle 5 to move through the piston 32, thereby opening and closing the injection molding channel. The base 33 and the cylinder 31 are fixed together to provide space for the piston 32 to move.

[0035] The nozzle 7 includes a nozzle head 71 and a nozzle core 72. The nozzle head 71 is fastened to the hot nozzle 4, and the nozzle core 72 is fastened to the inner wall of the nozzle head 71. The nozzle core 72 is provided with a constriction channel 721, which is connected to the main channel 41.

[0036] The diameter of the main flow channel 41 gradually changes from 12mm to 8mm in the contraction flow channel 721, with a compression ratio of 1.5:1, to ensure smooth melt flow.

[0037] A sealing ring 73 is provided on the contact surface between the nozzle 71 and the hot nozzle 4.

[0038] An annealed copper sealing ring 73 is installed between the nozzle 71 and the hot nozzle 4 to prevent the molten material from leaking from the joint.

[0039] The main channel 41 is equipped with an insulation layer 9.

[0040] The insulation layer 9 is made of mica and is used for thermal insulation, thereby optimizing temperature control. Example 2

[0041] In order to maintain the temperature of the liquid inlet channel 21 inside the injection nozzle 2, a heating coil 8 is provided on the outside of the injection nozzle 2, and a thermocouple is provided on the heating coil 8.

[0042] Heating coil 8 is used to maintain the temperature of injection nozzle 2 and prevent melt from condensing and clogging. The thermocouple transmits the temperature signal to the temperature controller to realize closed-loop regulation of heating power.

[0043] The working principle of this application is as follows: The plastic melt is injected into the mold cavity through the inlet channel 21 and the main channel 41 in sequence for injection molding. By winding a spiral hot wire 61 with a decreasing wire diameter on the main channel 41, a gradient temperature difference is actively constructed. The temperature gradient forms a "flow driving force", which allows the melt to fill the cavity smoothly, avoids uneven flow rate, and reasonably distributes the cooling rhythm to balance molding efficiency and product internal stress. It can also reduce the temperature difference between the melt and the mold and the interior of the melt, and improve the fusion quality. During injection molding, several K-type thermocouples arranged on the main channel 41 capture the axial and cross-sectional temperature difference data of the main channel 41 in real time. Together with the miniature pressure sensor and melt flow rate sensor integrated in the main channel 41, they synchronously collect the pressure fluctuation and melt flow rate data in the channel. Combined with the temperature parameters, a multi-dimensional "thermal-mechanical-fluid" database is constructed to improve the control accuracy. After injection molding is completed, the drive mechanism 3 drives the valve needle 5 forward. The pointed conical surface of the valve needle 5 is tightly pressed into the gate of the nozzle 7 to form a mechanical seal and cut off the melt flow.

[0044] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to explain the relative positional relationship and movement between components in a specific orientation. If the specific orientation changes, the directional indication will also change accordingly. These terms are used only for the convenience of describing this application and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0045] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0046] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0047] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An injection nozzle based on a gradient temperature difference field, characterized in that, include: Positioning ring (1), injection nozzle (2), drive mechanism (3) and hot nozzle (4), wherein the injection nozzle (2) is fastened to the positioning ring (1), and the injection nozzle (2) is provided with a liquid inlet channel (21). The hot nozzle (4) is connected to the drive mechanism (3), and the hot nozzle (4) is provided with a main channel (41), which is connected to the liquid inlet channel (21); The main channel (41) is provided with a valve needle (5), which is connected to the drive mechanism (3) for transmission. A heater (6) is provided on the outside of the hot nozzle (4); The outlet of the main channel (41) is provided with a nozzle (7). The heater (6) includes a spiral heating wire (61) which is wound around the outside of the hot nozzle (4); The diameter of the spiral hot wire (61) decreases sequentially along the conveying direction of the plastic melt.

2. The injection nozzle based on a gradient temperature difference field according to claim 1, characterized in that: The spiral heating wire (61) is divided into several heating units, each of which corresponds to a temperature control zone. The diameter of the spiral heating wire (61) of the heating unit in the inlet section is 1.2 mm, the diameter of the spiral heating wire (61) of the heating unit in the middle section is 1.0 mm, and the diameter of the spiral heating wire (61) of the heating unit in the outlet section is 0.8 mm.

3. The injection nozzle based on a gradient temperature difference field according to claim 1, characterized in that: The main channel (41) has three temperature measuring points evenly arranged in the circumference, and a K-type thermocouple is embedded in the main channel (41) every 50mm in the axial direction. The distance between the K-type thermocouple and the spiral heating wire (61) is ≤3mm.

4. The injection nozzle based on a gradient temperature difference field according to claim 1, characterized in that: The drive mechanism (3) includes a cylinder (31), a piston (32) and a base (33). The cylinder (31) and the base (33) are fastened together. The piston (32) is slidably connected to the cylinder (31). The output end of the piston (32) is connected to the valve needle (5) in a transmission connection.

5. The injection nozzle based on a gradient temperature difference field according to claim 1, characterized in that: The nozzle (7) includes a nozzle head (71) and a nozzle core (72). The nozzle head (71) is fastened to the hot nozzle (4). The nozzle core (72) is fastened to the inner wall of the nozzle head (71). The nozzle core (72) is provided with a shrinkage channel (721) and the shrinkage channel (721) is connected to the main channel (41).

6. The injection nozzle based on a gradient temperature difference field according to claim 5, characterized in that: A sealing ring (73) is provided on the contact surface of the nozzle (71) and the hot nozzle (4).

7. The injection nozzle based on a gradient temperature difference field according to claim 1, characterized in that: The main channel (41) is provided with an insulating layer (9).

8. The injection nozzle based on a gradient temperature difference field according to claim 1, characterized in that: The injection nozzle (2) is provided with a heating coil (8) on its outer side, and a thermocouple is provided on the heating coil (8).

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