Injection molding process for magnetic shaft core for magnetic shaft keyboard

Abstract

The application relates to the technical field of computer input devices, in particular to an injection molding process of a magnetic shaft core for a magnetic shaft keyboard, which mainly comprises the following steps: S1, providing injection materials and magnetic powder, and premixing the magnetic powder in the injection materials to form plastic composite materials; S2, heating the mixed materials to a molten state through an injection device; S3, injecting the plastic composite materials in the molten state into a molding mold through an injection mechanism, and obtaining a shaft core body through cooling and demolding, wherein the shaft core body has a matching part used for matching with a magnetic detection element of a keyboard; and S4, magnetizing the matching part through a magnetizing device to form a magnet component, so that the matching part of the shaft core body can be effectively detected when being close to the magnetic field detection element of the external keyboard. The process effectively omits the purchase and precise assembly links of independent magnets, improves the consistency and reliability of products, and reduces the comprehensive cost.

Description

Technical Field

[0001] This invention relates to the field of computer input device technology, and in particular discloses an injection molding process for a magnetic shaft core for a magnetic shaft keyboard. Background Technology

[0002] In existing technologies, magnetic key switches typically achieve magnetic sensing by embedding a permanent magnet within a plastic core. This separate structure not only increases the number of parts and production costs but also carries the risk of magnet loosening, shifting, or even detaching during long-term use, leading to inaccurate key presses and reduced keyboard reliability. Furthermore, current processes often neglect the stability of magnetic materials and the coordination of components within the core, resulting in unstable magnetization and making it difficult to guarantee the long-term performance of the magnetic key switch.

[0003] Therefore, existing technologies have failed to effectively solve the problems of structural integration, magnetic stability, and manufacturing process efficiency. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a novel injection molding process for magnetic shaft cores for magnetic shaft keyboards.

[0005] To achieve the above objectives, the present invention provides an injection molding process for a magnetic shaft core for a magnetic keyboard, comprising the following steps: S1 provides injection molding material and magnetic powder, and premixes magnetic powder into the injection molding material to form a plastic composite material; S2, providing an injection device with a molding die, a heating mechanism and a cooling demolding mechanism, wherein the molding die has a cavity with a shape structure for molding the required magnetic shaft core, and the plastic composite material is introduced into the heating mechanism of the injection device and heated to form a liquid plastic composite material; S3, the liquid plastic composite material obtained in step S2 is injected into the mold cavity using the injection mechanism of the injection equipment, and the liquid plastic composite material in the mold cavity is cooled and demolded using the cooling and demolding mechanism of the injection equipment to form the required shaft core body; the required shaft core body has a mating part for cooperating with the magnetic detection element of the external keyboard; S4, provide a magnetizing device, and use the magnetizing device to magnetize the mating part of the shaft body obtained in step S3, so that the mating part forms a magnetic component, so that the mating part of the shaft body can be detected by the magnetic field detection element of the external keyboard when it approaches the magnetic field detection element of the external keyboard during the pressing stroke.

[0006] Furthermore, the injection equipment provided in step S2 is a two-color injection equipment or a single-color injection equipment. The injection-molded shaft body is integrally molded by a two-color injection molding process using a two-color injection equipment, or integrally molded by a single-color injection molding process using a single-color injection equipment.

[0007] Furthermore, when using a two-color injection molding process, the two-color injection equipment includes a first upper mold and a first lower mold, which are closed to form a first mold cavity; the injection equipment includes two injection mechanisms, the first injection mechanism injects injection material without magnetic powder, which has been heated and liquefied by a heating mechanism, into the first upper mold to form a pressing section and a guiding section, and the second injection mechanism injects liquid plastic composite material containing magnetic powder into the first lower mold to form a mating part, and the mating part constitutes a magnetic structure that can be magnetized, and the mating part is individually magnetized.

[0008] Furthermore, when using a single-color injection molding process, the single-color injection equipment includes a second upper mold and a second lower mold, which are closed to form a second mold cavity; the single-color injection equipment includes an injection mechanism that injects liquid plastic composite material containing magnetic powder into the second mold cavity, so that the entire shaft core body is integrally formed from the liquid plastic composite material containing magnetic powder, and the entire shaft core body constitutes a magnetic structure that can be magnetized.

[0009] Furthermore, step S3 also includes forming a first annular groove on the shaft core body for accommodating one end of the external reset elastic member, and the lower housing of the external magnetic shaft button has a second annular groove for accommodating the other end of the external reset elastic member. The first annular groove and the second annular groove are used to maintain a gap between the external reset elastic member and the mating part; the core of the first upper mold is provided with an annular groove structure for forming the first annular groove.

[0010] Furthermore, the mass percentage of magnetic powder in the plastic composite material is 60%-95%.

[0011] Furthermore, the magnetic powder is ferrite magnetic powder, rare earth permanent magnet powder, iron-based magnetic powder, or alloy magnetic powder.

[0012] Furthermore, the shaft core body formed in step S3 also has a pressing section and a guiding section. The first upper mold is provided with a first concave mold core for forming the pressing section and a second concave mold core for forming the guiding section and the mating part. The first concave mold core, the second concave mold core and the punch core of the first lower mold surround to form the first mold cavity. The pressing section and the guiding section are integrally formed by the first upper mold, and the mating part is formed on the guiding section and is formed together with the guiding section by the second concave mold core of the first upper mold.

[0013] Furthermore, the pressing section is also formed with a connecting rib that is installed in conjunction with the keycap of the external button. The connecting rib is provided with a first protruding rib, which extends along the length direction of the connecting rib and extends in the thickness direction of the connecting rib. The free end of the connecting rib is provided with a first inclined guide surface. The first concave mold core and the second concave mold core are provided with a preset structure for forming the connecting rib.

[0014] Furthermore, the guide section includes two limiting walls, which are symmetrically arranged and extend along the pressing direction of the shaft core body to form a semi-enclosed structure, so that the guide section forms an area with an opening in the circumferential direction.

[0015] Furthermore, each of the limiting walls is provided with a guide rib on its outer side. The guide rib extends along the pressing direction of the shaft core body and is used to slide and cooperate with the guide groove preset in the outer button housing to limit the rotation of the shaft core body and guide the shaft core body to move along the preset pressing direction.

[0016] Furthermore, the insert rib of the pressing section is provided with two limiting frames on its periphery, forming a semi-enclosed structure with an opening at the top and openings on both sides, so that the preset structure of the external keycap is inserted between the insert rib and the limiting frame to form an installation fit.

[0017] Furthermore, after the magnetization process in step S4, the process also includes step S5: heat treatment or annealing of the shaft core body, wherein the heat treatment or annealing process includes heating the shaft core body to a preset temperature and maintaining it at the preset temperature for a preset time; the preset temperature range is 80°C to 110°C and the preset time range is 60 minutes to 180 minutes.

[0018] Furthermore, in the cooling and demolding process in step S3, directional cooling technology is used to achieve rapid cooling of the shaft core body by setting cooling channels and cooling nozzles. The cooling channels are set with different cooling rates in different areas of the shaft core body to optimize the cooling process and reduce the stress that may be generated during the cooling process.

[0019] Furthermore, after step S5 is completed, step S6 is also included: performing surface treatment on the shaft core body, wherein the surface treatment is spraying, coating treatment or laser surface hardening.

[0020] Furthermore, when magnetizing the mating part, the non-matting part of the shaft core body is placed within a magnetic shielding structure preset by the magnetizing device. The magnetic shielding structure is used to block the external magnetic field, so that the external magnetic field mainly acts on the mating part, thereby selectively magnetizing the mating part.

[0021] Furthermore, when magnetizing the mating part, the shaft core body is installed into the magnetizing fixture of the magnetizing equipment. The magnetizing fixture is provided with a positioning structure that matches the guide section of the shaft core body to maintain the spatial posture of the shaft core body during the magnetization process, so that the mating part forms a magnetized state in a preset direction.

[0022] Furthermore, the magnetization process of the mating part includes at least two magnetization stages, in which an external magnetic field of different intensity or direction is applied to the mating part in different magnetization stages, so that the mating part forms a preset magnetization distribution state.

[0023] Furthermore, the magnetization direction of the mating part is set parallel to the pressing direction of the shaft core body, so that the shaft core body generates a magnetic field gradient that varies along the pressing direction during the pressing stroke.

[0024] The process of this invention involves mixing magnetic powder with thermoplastic materials to form a plastic composite, and then molding it into an integrated shaft core body using injection molding technology. The shaft core body includes a pressing section, a guiding section, and a mating part. The mating part is magnetized using a magnetizing device to ensure that the shaft core body can generate a stable magnetic field change during the pressing stroke, which can then be detected by an external magnetic field detection element. Through this integrated injection molding and magnetization process, this invention effectively solves the problems of magnet loosening and magnetic instability in traditional technologies, while improving production efficiency and product reliability.

[0025] The beneficial effects of this invention are: (1) The injection molding process is used to integrate the components of the magnetic shaft core, which not only reduces the production cost, but also improves the molding accuracy and structural stability.

[0026] (2) By rationally designing the magnetization process, especially through the innovation of magnetization fixtures and magnetic shielding structures, the magnetization of mating parts is made more precise, avoiding the influence of magnetic fields on non-matting parts, thereby improving the stability and consistency of magnetic field changes.

[0027] (3) In addition, the durability and corrosion resistance of the magnetic core are further improved by heat treatment, annealing and surface hardening treatment, which extends the service life of the keyboard.

[0028] In summary, this invention provides an injection molding process for a magnetic axis core for a magnetic axis keyboard that is structurally sound, technologically efficient, and has stable performance, significantly improving the overall performance and reliability of the keyboard. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the shaft core body manufactured by injection molding process according to the present invention; Figure 2 This is a schematic diagram of the structure of the shaft core body of the present invention when it is installed in conjunction with the keys of the magnetic shaft keyboard; Figure 3 This is an exploded structural diagram of the shaft core body and the keys of the magnetic shaft keyboard of the present invention; Figure 4 This is a flowchart of the injection molding process for the magnetic shaft core of the magnetic shaft keyboard of the present invention.

[0030] The reference numerals in the figures include: 1. Shaft core body; 2. Reset elastic element; 3. Upper housing; 4. Lower housing; 41. Guide groove; 42. Guide sleeve; 11. Pressing section; 111. Insertion rib; 112. First protruding rib; 113. First inclined guide surface; 114. Limiting frame; 12. Guide section; 121. Limiting wall; 122. Guide rib; 13. Mating part. Detailed Implementation

[0031] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0032] Please see Figures 1 to 4 As shown, the injection molding process for a magnetic shaft core for a magnetic keyboard according to the present invention includes the following steps: S1 provides injection molding material and magnetic powder, and premixes magnetic powder into the injection molding material to form a plastic composite material; S2, providing an injection device with a molding die, a heating mechanism and a cooling demolding mechanism, wherein the molding die has a cavity with a shape structure for molding the required magnetic shaft core, and the plastic composite material is introduced into the heating mechanism of the injection device and heated to form a liquid plastic composite material; S3, the liquid plastic composite material obtained in step S2 is injected into the mold cavity using the injection mechanism of the injection equipment, and the liquid plastic composite material in the mold cavity is cooled and demolded using the cooling and demolding mechanism of the injection equipment to form the required shaft core body 1; the required shaft core body 1 has a mating part 13 for cooperating with the magnetic detection element of the external keyboard. S4, a magnetizing device is provided to magnetize the mating part 13 of the shaft core body 1 obtained in step S3, so that the mating part 13 forms a magnetic component, so that the mating part 13 of the shaft core body 1 can be detected by the magnetic field detection element of the external keyboard when it approaches the magnetic field detection element of the external keyboard during the pressing stroke.

[0033] Specifically, step S1 is used to prepare a plastic composite material that meets the requirements of injection molding and subsequent magnetization: the injection material is preferably a thermoplastic resin matrix that is wear-resistant, dimensionally stable, and suitable for keyboard core structure molding, such as PBT, PA, POM, or their blends; the magnetic powder is selected as a magnetic powder that can be magnetized to form a stable magnetization state or can produce a stable magnetic response. In this embodiment, POM and ferrite magnetic powder are preferably mixed to obtain the plastic composite material.

[0034] The premixing process preferably uses a high-speed mixer for dry mixing to initially and uniformly disperse the magnetic powder, and then it enters a twin-screw extruder for melt blending and granulation. The extrusion temperature is set within the melt processing window of the resin matrix to obtain uniformly dispersed and stable magnetic powder composite granules. For embodiments with higher consistency requirements, melt filtration and vacuum degassing can be added at the extrusion end to reduce the residue of bubbles and volatiles.

[0035] Compared to existing technologies that rely solely on simple stirring, which leads to magnetic powder agglomeration and dispersed magnetic properties after molding, this solution offers the advantages of more uniform magnetic powder dispersion and higher consistency in batch magnetic properties.

[0036] In this embodiment, step S2 is used to provide an injection equipment and mold system with "molding-melting-cooling demolding" capabilities: the injection equipment includes a heating mechanism, an injection mechanism and a cooling demolding mechanism, wherein the heating mechanism is preferably a barrel and screw plasticizing assembly with multi-stage temperature control, the injection mechanism is used to fill the mold cavity with liquid plastic composite material at a set pressure and speed, and the cooling demolding mechanism includes a mold temperature control circuit, an in-mold cooling channel and an ejection assembly.

[0037] The mold cavity of the molding die is machined according to the shape structure of the magnetic shaft core. The mold cavity has corresponding contour areas of pressing section 11, guide section 12 and mating part 13, and a structural space is reserved in the mating part 13 area to meet the changes in magnetic detection stroke. The mold material is preferably wear-resistant steel and the surface of the easily worn areas is strengthened to resist the wear caused by high filling magnetic powder.

[0038] Compared to existing technologies that use universal molds, which result in rapid wear of high-filling materials and large dimensional drift, this solution has the advantages of higher molding stability and longer mold life.

[0039] Specifically, in this embodiment, step S2 includes process control of plasticizing the plastic composite material into liquid plastic composite material in the heating mechanism: in order to balance filling and magnetic powder dispersion stability, the barrel temperature is preferably set to a gradient mode of "low at the end and high at the beginning" to stabilize plasticization and reduce shear fluctuations; the screw back pressure is preferably set to a medium range to improve the mixing and degassing effect, while avoiding excessive shear leading to material degradation.

[0040] For embodiments with high magnetic powder content, a low-shear mixing screw structure can be selected and a suitable flow channel can be set at the nozzle to reduce the risk of powder separation and nozzle clogging. If a two-color device is used, the first barrel is used for plasticizing resin materials without magnetic powder, and the second barrel is used for plasticizing plastic composite materials containing magnetic powder. The two are set according to their respective material windows.

[0041] Compared to existing technologies where high-filler materials are prone to unstable plasticization and short shots and silver streaks, this solution has the advantages of more stable plasticization and fewer molding defects.

[0042] Specifically, in this embodiment, the injection molding process in step S3 adopts a cycle of "filling-holding pressure-cooling-demolding": the liquid plastic composite material obtained in step S2 is injected into the mold cavity through the injection mechanism. The injection speed is preferably fast at first and then slow to ensure filling of thin-walled areas and reduce jetting marks. During the holding pressure stage, shrinkage is compensated by maintaining pressure. The holding pressure time is preferably set to a slight margin after the product gate freezes to reduce shrinkage and warping. During the cooling stage, the mold temperature circuit is controlled by the cooling demolding mechanism, so that the core body 1 is fully shaped in the mold and then demolded by the ejection mechanism. During demolding, it is preferable to use a push plate or multi-point ejector pins for even ejection to avoid deformation of the guide section 12 and the mating part 13 under stress.

[0043] The molded core body 1 forms a mating part 13 for cooperating with an external keyboard magnetic detection element. The mating part 13 is located in the area corresponding to the lower end of the core or the column part. During the pressing stroke, the distance between the core body and the sensor changes, thereby generating a detectable magnetic field change.

[0044] Compared with the existing technology that uses secondary assembly of magnets, which leads to positional deviation and stroke signal drift, this solution has the advantages of more stable position of mating part 13 and more consistent magnetic field-stroke correspondence.

[0045] Specifically, in this embodiment, step S4 provides a magnetizing device and magnetizes the mating part 13: the magnetizing device preferably includes a magnetic yoke, an excitation coil and a pulse power supply (such as a capacitor discharge type magnetizing power supply), and the magnetic yoke forms a closed magnetic circuit to increase the effective magnetic flux and reduce the leakage magnetic field.

[0046] During magnetization, the shaft core body 1 is placed in the magnetization working position, so that the mating part 13 is located between the magnetic poles or at the magnetic yoke window. A strong instantaneous magnetic field is generated by pulse excitation to make the mating part 13 obtain a preset magnetization state.

[0047] For embodiments requiring high consistency, a limiting step and a clamping mechanism can be set at the magnetization station to ensure that the posture and height of the shaft core body 1 are consistent before magnetization, and a rapid magnetic flux sampling inspection can be performed after magnetization to remove abnormal parts.

[0048] Compared to existing technologies that involve directly magnetizing individual magnets and then assembling them, resulting in overlapping assembly tolerances, this solution has the advantages of having the magnetization position and the formed structure consistent with the reference, and higher signal consistency.

[0049] Specifically, the injection equipment provided in step S2 can be a two-color injection device or a single-color injection device to adapt to different structural requirements and cost targets: When the pressing section 11 and the guide section 12 need to have better wear resistance / low friction characteristics and the mating part 13 needs to have a high magnetic powder content, it is preferable to use a two-color injection molding machine to integrally mold the two materials.

[0050] When the entire shaft core is made of magnetic powder composite material and an overall magnetic response is required, it is preferable to use a single-color injection molding machine for one-time molding.

[0051] The choice between two-color and single-color depends on the magnetic field requirements, tactile requirements, and process efficiency of the finished product. Those skilled in the art can make the selection based on the target magnetic field amplitude and structural stress.

[0052] Compared to existing technologies that can only use a single structural route, making it difficult to balance performance and cost, this solution has the advantages of switchable process routes and greater product adaptability.

[0053] Specifically, when using a two-color injection molding process, the molding die of the two-color injection equipment includes a first upper die and a first lower die, which are closed to form a first mold cavity. The equipment is equipped with two injection mechanisms corresponding to two different materials: the first injection mechanism injects a resin material without magnetic powder to form a pressing section 11 and a guiding section 12, preferably using a low-friction or wear-resistant modified material to improve the guide life; the second injection mechanism injects a liquid plastic composite material containing magnetic powder into the molding area corresponding to the first lower die to form a mating part 13, and the mating part 13 and the guiding section 12 are combined to form an integral whole through a welding / coating interface.

[0054] To avoid magnetic powder material contaminating the surface of the pressing section 11 or affecting its appearance, it is preferable to isolate the magnetic powder material flow channel from the non-magnetic powder material flow channel in the mold parting and gate layout, and to set a transition overlap structure at the interface to improve the bonding strength. Compared to existing technologies where retrofitting magnets or secondary bonding results in insufficient interface strength, this solution offers advantages such as stronger material interface bonding and higher reliability under long-term pressure.

[0055] Specifically, the "separate magnetization treatment of mating part 13" under the two-color injection process is achieved through structural and station control: since the pressing section 11 and the guiding section 12 are formed of non-magnetic powder material, they do not need to be magnetized. During magnetization, it is only necessary to make the mating part 13 in the effective magnetic pole area.

[0056] The preferred design of the support surface and the guide section 12 of the core in the magnetization station is to make the mating part 13 extend into the magnetic yoke window, and the pressing section 11 and the guide section 12 are in the weak magnetic field area or the shielding area, so as to realize individual magnetization.

[0057] For mass production, several shaft core bodies 1 can be placed in a multi-cavity magnetizing tray and magnetized simultaneously. The tray is provided with a limiting groove that cooperates with the guide section 12 to ensure that the mating part 13 of each shaft core is in the same magnetization position.

[0058] Compared to existing technologies where magnetizing the entire component leads to magnetization interference in unnecessary parts or uneven magnetic field distribution, this solution has the advantages of more precise magnetization area and more controllable magnetic field output.

[0059] Specifically, when using a single-color injection molding process, the molding mold of the single-color injection equipment includes a second upper mold and a second lower mold. The molds are closed to form a second mold cavity, and a single injection mechanism injects liquid plastic composite material containing magnetic powder into the mold cavity in one go, so that the shaft core body 1 is integrally formed. The shaft core body 1 as a whole constitutes a magnetic structure that can be magnetized. When magnetizing, the whole or part can be magnetized as needed.

[0060] To balance strength and flowability, the monochromatic solution preferably incorporates appropriate toughening or lubricating modifiers into the material. Furthermore, the mold gate location and venting structure are used to control weld lines and reduce gas retention, thus preventing burrs or jamming in the guide section 12. Compared to existing solutions involving multi-part assembly that result in cumulative dimensional errors, this solution offers the advantages of one-piece molding and higher dimensional consistency.

[0061] Specifically, after monochromatic integral molding, the entire core body 1 can be magnetized or selectively magnetized according to the detection scheme: when the magnetic field detection element requires a stronger or more linear magnetic field change, the area mainly composed of the mating part 13 can be selectively magnetized to form a clear gradient; when the detection element is not sensitive to the direction of the magnetic field or requires a larger magnetic response volume, the entire core body 1 can be magnetized.

[0062] To prevent the overall magnetization from causing adsorption on external metal parts, this embodiment preferably uses a shaft core structure design to concentrate the magnetism mainly near the mating part 13, and reduces magnetic adsorption interference in subsequent assembly by using the gap structure between the guide sleeve 42 of the lower housing 4 and the spring (reset elastic element 2).

[0063] Compared to existing technologies where the magnet volume is fixed, making it difficult to match different sensor solutions, this solution has the advantage of adjustable magnetization strategy and adaptability to different sensor windows.

[0064] Specifically, in this embodiment, step S3 further includes simultaneously forming a first annular groove on the shaft core body 1 to accommodate one end of the external reset elastic member 2 (preferably a reset spring); a second annular groove is formed on the lower housing 4 of the external magnetic shaft button to accommodate the other end of the reset spring. The two annular grooves together realize the positioning of the two ends of the spring and keep the spring and the mating part 13 at a gap, thus structurally avoiding friction, deflection or magnetic adsorption interference caused by direct contact between the spring and the mating part 13.

[0065] Correspondingly, an annular groove structure is provided in the core of the first upper mold to form the first annular groove in one step. The edge of the annular groove is preferably chamfered to reduce demolding resistance and stress concentration. Compared with the existing technology where the free drift of the spring end causes scratching of magnetic parts or noise, this solution has the advantages of more reliable spring positioning and higher tactile feel and signal stability.

[0066] Of course, in actual production, non-magnetic materials such as stainless steel can also be selected to make the reset elastic element 2.

[0067] Specifically, the mass percentage of magnetic powder in the plastic composite material is 60%-95%, and can be optimized according to the sensitivity of the magnetic field detection element and the space of the shaft core structure. In most magnetic shaft keyboard stroke detection scenarios, the magnetic powder content is preferably controlled at about 80%-90% to achieve a balance between magnetic response intensity, injection flowability and molding strength. When higher magnetic field output is required and the mold runner design allows, it can be increased to a higher range, and filling can be ensured by increasing the injection pressure, appropriately increasing the temperature of the front section of the barrel and strengthening the venting.

[0068] The preferred magnetic powder mass percentage is 88wt%, and the corresponding injection-molded NdFeB material can achieve a remanence Br on the order of approximately 0.52-0.57T. Under the common shaft-PCB assembly gap (on the order of approximately 3.5-4.5mm), the magnetic field at the sensor covers a range of approximately 36-77mT, thus falling into the ±80mT linear detection range, avoiding saturation of small-range devices, and ensuring sufficient travel resolution.

[0069] For implementations with low content, the signal amplitude can be compensated by increasing the volume of the mating part 13 or optimizing the magnetization direction.

[0070] Compared to existing technologies where mismatched magnetic powder content leads to insufficient magnetic field or increased molding defects, this solution has the advantage of being able to better balance magnetic properties and manufacturability.

[0071] Specifically, the magnetic powder material can be ferrite magnetic powder, rare earth permanent magnet powder, iron-based magnetic powder or alloy magnetic powder, and can be selected according to cost, temperature resistance and magnetic field requirements.

[0072] Ferrite magnetic powder is low in cost and has good corrosion resistance, making it suitable for conventional keyboards; Rare earth permanent magnet powder can achieve higher remanence, making it suitable for scenarios with large sensor gaps or requiring stronger signals; Iron-based magnetic powders and alloy magnetic powders can be used to obtain stable magnetic responses or to form a target magnetization distribution in conjunction with specific magnetization strategies.

[0073] Preferably, the magnetic powder can be surface-treated or coated to improve its compatibility with the resin and reduce the risk of moisture absorption and oxidation, and a dispersing agent can be added during the extrusion blending stage to reduce agglomeration.

[0074] Compared to existing technologies that limit the use of a single magnetic powder, making them easily circumvented by alternative materials, this solution offers the advantages of more flexible material selection and a wider range of protection.

[0075] Specifically, in this embodiment, the injection-molded shaft core body 1 has a pressing section 11 and a guiding section 12. The first upper mold is provided with a first concave mold core for molding the pressing section 11 and a second concave mold core for molding the guiding section 12 and the structural area corresponding to the mating part 13. The first concave mold core and the second concave mold core cooperate with the punch core of the first lower mold to form a first mold cavity. The pressing section 11 and the guiding section 12 are molded in one step from the corresponding area of ​​the first upper mold, and the mating part 13 is formed at a preset position by a magnetic powder material during the second injection, so that the mating part 13 is formed on the guiding section 12 and forms a firm bond with the guiding section 12.

[0076] To improve the reliability of the connection, a step, dovetail, or annular covering structure is preferably provided at the transition between the guide section 12 and the mating part 13, so that the secondary injection material forms a mechanical lock, and the welding is promoted by controlling the interface temperature in the mold. Compared with the existing technology where the magnetic parts and plastic parts are easily detached due to relying only on planar bonding, this solution has the advantages of a combination of mechanical locking and welding, and higher durability.

[0077] Specifically, in this embodiment, the pressing section 11 is formed with a cross-shaped insertion rib 111 that is installed in conjunction with an external keycap. The side of the cross-shaped insertion rib 111 is provided with a first protruding rib 112. The first protruding rib 112 extends along the length direction of the insertion rib 111 and forms a reinforcing rib in the thickness direction to improve the bending and torsional resistance of the insertion rib 111. The free end of the insertion rib 111 is provided with a first inclined guide surface 113, which plays a self-guiding role when assembling the keycap and reduces whitening or edge chipping caused by hard top.

[0078] To achieve this structure, corresponding ribs and guide cavities are pre-fabricated on the first and second die cores, and a reasonable slope is set in the demolding direction to facilitate smooth demolding; for embodiments with high-precision keycap mating, a fine texture can be set on the outer surface of the cross-shaped insert rib 111 to improve the stability of the friction mating.

[0079] Compared to existing technologies where the cross-shaped keycaps are prone to loosening and misalignment during assembly causes keycaps to wobble, this solution offers the advantages of smoother assembly guidance and more stable keycap fixation.

[0080] Specifically, in this embodiment, the molded guide section 12 includes two symmetrically arranged limiting walls 121. The limiting walls 121 extend along the pressing direction of the shaft core body 1 and form a semi-enclosed structure, so that the guide section 12 forms an area with an opening in the circumferential direction. The opening is used to release the molding shrinkage stress, reduce the friction contact area, and reserve clearance for the external shell structure.

[0081] The inner side of the limiting wall 121 forms a sliding fit with the guide cavity wall of the outer button housing. The top or bottom of the limiting wall 121 can be provided with transition fillets to reduce scratches at the end of the stroke. In the mold design, the second concave core forms the shape of the limiting wall 121 and avoids thin-wall warping through reasonable parting.

[0082] Compared to existing technologies where fully enclosed guidance leads to high friction and is prone to jamming, this solution has the advantages of lower guiding resistance and a smoother pressing feel.

[0083] Specifically, in this embodiment, each limiting wall 121 is provided with a guide rib 122 extending along the pressing direction on the outer side. The guide rib 122 slides in cooperation with the guide groove 41 in the outer button housing. The "rib-groove" constraint restricts the circumferential rotation of the shaft core body 1 and guides it to move linearly along the preset pressing direction. The guide ribs 122 are preferably set in pairs symmetrically or in a number that matches the number of grooves in the housing to improve torsional stability.

[0084] To reduce wear and noise, a low-friction material can be used on the surface of the guide rib 122 or a lubricant can be added to the material formulation. An inlet chamfer can also be provided at the entrance of the guide groove 41 to reduce assembly scratches.

[0085] Compared to existing technologies that rely solely on cylindrical guidance, which leads to rotational sway and unstable trigger signals, this solution offers advantages such as better anti-rotation performance and more consistent travel trajectory.

[0086] Specifically, in this embodiment, two limiting frames 114 are also provided around the cross-shaped insert rib 111 of the pressing section 11 to form a semi-enclosed structure with an opening at the top and openings on both sides. The preset structure of the outer keycap is inserted between the cross-shaped insert rib 111 and the limiting frame 114 to form an assembly fit. The limiting frame 114 plays a limiting and supporting role when the keycap is subjected to lateral force, reducing the keycap shaking, and protecting the cross-shaped insert rib 111 from being excessively sheared during repeated assembly.

[0087] The limiting frame 114 and the pressing section 11 are integrally injection molded, and the inner side of the limiting frame 114 maintains a preset gap with the keycap structure for assembly. At the same time, the end of the limiting frame 114 can be provided with an guide slope to reduce assembly resistance. Compared with the existing technology that relies solely on the cross-shaped joint, resulting in large lateral wobble of the keycap, this solution has the advantages of more sufficient lateral support and higher key stability.

[0088] Specifically, in this embodiment, the shaft core body 1 is used to be installed inside the magnetic shaft button. The magnetic shaft button specifically includes an upper housing 3, a lower housing 4, and a reset elastic element 2. The shaft core body 1 is movably engaged with the upper housing 3 and the lower housing 4. The lower housing 4 is provided with a guide groove 41 that slides in cooperation with the guide rib 122. The middle part of the lower housing 4 is also provided with a guide sleeve 42 for accommodating the mating part 13. The guide sleeve 42 is preferably a circular cup-shaped structure.

[0089] Specifically, in this embodiment, after the magnetization process in step S4, a heat treatment or annealing process in step S5 is further performed to improve the internal stress and magnetization stability of the magnetic powder composite injection molded part.

[0090] The selected heat treatment equipment can be a hot air circulating oven or a constant temperature chamber. The shaft core body 1 is evenly placed on a tray to ensure uniform heating. The heat treatment process is preferably carried out in the range of 80°C to 110°C and held at this temperature for 60 to 180 minutes to promote resin chain relaxation, release residual injection stress, and reduce the risk of dimensional drift and magnetic attenuation caused by stress. For different resin matrices, a temperature close to the upper limit can be selected to shorten the time, provided that it does not exceed the material's heat distortion temperature.

[0091] Specifically, in this embodiment, the heat treatment equipment is a hot air circulating oven. After the core body 1 is magnetized, it is evenly placed on a heat-resistant tray. A preset distance is maintained between the core bodies 1 to ensure that the hot air can circulate fully in both the circumferential and axial directions of the core bodies 1, so that each core body 1 is heated evenly.

[0092] In this embodiment, taking into account the feature that the shaft core body 1 is integrally injection molded from a plastic composite material with a magnetic powder mass percentage of 88wt%, the heat treatment process is preferably carried out under a constant temperature condition of 100℃ and continuously held at this temperature for 120 minutes.

[0093] This temperature is significantly lower than the heat distortion temperature of commonly used keyboard switch core injection molding resin. It can promote the relaxation and rearrangement of molecular chain segments in the resin matrix without causing deformation of the switch core body 1, and at the same time release the residual internal stress introduced by high magnetic powder filling, injection molding shearing and cooling shrinkage.

[0094] By performing a constant temperature treatment at 100℃ for 120 minutes, the internal temperature of the shaft core body 1 can be fully balanced, avoiding the problem of heat conduction lag caused by a high magnetic powder filling ratio. This effectively reduces the risk of dimensional drift in the shaft core body 1 during subsequent use and reduces the attenuation of magnetic field output at the mating part caused by micro-deformation of the structure.

[0095] Compared to existing magnetic shaft cores that do not undergo or only undergo short-term low-temperature treatment, this embodiment introduces the above-mentioned heat treatment process after magnetization, so that the core body 1 has more stable dimensional accuracy and magnetic output consistency during long-term pressing use, thereby improving the reliability and service life of magnetic shaft keyboard travel detection.

[0096] Compared to existing technologies that use the material directly after molding, resulting in insufficient stress release and long-term dimensional and signal drift, this solution has the advantages of better magnetization stability and higher long-term consistency.

[0097] Specifically, in this embodiment, the heat treatment / annealing step can also be combined with a magnetization strategy to form a more stable magnetization state: a preferred embodiment is to perform heat treatment immediately after magnetization, so that the magnetized micro-magnetic domain structure is fixed in a more stable stress environment, thereby improving the repeatability of the magnetic field output of the mating part 13; another preferred embodiment is to perform secondary compensation magnetization after heat treatment to eliminate the slight attenuation caused by the heat treatment process to local magnetization and further correct the magnetization direction.

[0098] For mass production, a cooling slow-descent zone can be set up after heat treatment to avoid secondary stress caused by sudden cooling. Compared with the existing technology where magnetization and post-treatment are disconnected and lead to batch fluctuations, this solution has the advantages of a more complete process closed loop and better batch consistency.

[0099] Specifically, in this embodiment, directional cooling technology can be used in the cooling and demolding process of step S3: cooling channels are set in the mold and cooling nozzles or local cooling inserts are configured in key parts so that different areas of the shaft core body 1 have different cooling rates. For example, cooling is strengthened in size-sensitive areas such as the mating part 13 and the guide rib 122 to reduce shrinkage differences, while relatively slow cooling is used in the relatively thick area of ​​the pressing section 11 to reduce internal stress. The cooling medium is preferably a temperature-controlled water circuit and is used in conjunction with a mold temperature controller to achieve stable mold temperature.

[0100] Directional cooling reduces warpage, shrinkage marks, and deformation of the guide section 12, and improves the smoothness of the fit between the guide rib 122 and the guide groove 41. Compared to existing technologies where uniform cooling leads to inconsistent shrinkage in areas of thinness difference and guide jamming, this solution offers advantages such as better dimensional stability and higher demolding yield.

[0101] Specifically, directional cooling can be optimized in conjunction with the demolding process: maintaining the temperature of critical areas to the demolding window before ejection, and preferably using multi-point synchronous ejection in the ejection mechanism to avoid damage to the guide ribs 122 by single-point ejection; for areas prone to sticking to the mold, wear-resistant and low-friction treatment can be applied to the mold cavity surface, or a suitable release agent process can be selected without affecting the performance of the magnetic powder composite material. For highly filled magnetic powder materials, it is preferable to increase the depth and position of the venting grooves to reduce scorching and gas streaks caused by gas retention.

[0102] Compared to existing technologies where high-filling materials are difficult to demold and cause significant ejection deformation, this solution offers the advantages of smoother demolding and fewer appearance and dimensional defects.

[0103] Preferably, after step S5 is completed, step S6 is further included for surface treatment to improve the wear resistance and corrosion resistance of the shaft core body 1: the surface treatment may be spraying treatment (such as wear-resistant coating), coating treatment (such as thin film or protective coating) or laser surface hardening treatment.

[0104] When applying a spray / coating, it is preferable to focus on treating the outer surface of the guide rib 122 and the contact area between the guide rib 122 and the keycap to reduce friction and wear. When applying a laser surface hardening, it is preferable to scan the guide rib 122 or the easily worn sliding surface to achieve higher surface hardness and lower wear, while avoiding excessive thermal impact on the magnetic area of ​​the mating part 13.

[0105] Compared to existing technologies where the plastic sliding surface wears out quickly, leading to a decrease in feel and an increase in gaps, this solution has the advantages of longer wear resistance and better feel retention.

[0106] Specifically, the surface treatment in step S6 can also be coordinated with the keyboard assembly structure: the guide groove 41 of the outer key shell and the guide rib 122 of the shaft core are high-frequency sliding mating surfaces. It is preferable to form a low-friction coating or hardened layer on the surface of the guide rib 122, and to set a chamfer and deburring process at the entrance of the guide groove 41 of the shell, thereby reducing scratches and abnormal noises in the early stage of assembly; for the spraying scheme, it is preferable to control the coating thickness to achieve continuous coverage without affecting the guide mating gap, and to conduct a sliding resistance sampling inspection after curing to ensure batch consistency.

[0107] Compared to existing technologies where arbitrary surface treatment leads to the coating "eating up" the mating gap and causing jamming, this solution has the advantages of better assembly adaptability and higher sliding consistency.

[0108] Specifically, in this embodiment, when magnetizing the mating part, the non-matting part of the shaft core body 1 can be set in the magnetic shielding structure preset by the magnetizing device to achieve selective magnetization: the magnetic shielding structure is preferably a shielding sleeve, shielding cover or shielding block made of high magnetic permeability soft magnetic material (e.g. soft iron or high magnetic permeability alloy material), which forms a covering or semi-covering space around the non-matting part, so that the external magnetic field forms a bypass magnetic flux in the shielding structure, thereby significantly reducing the effective magnetic field at the non-matting part, and the mating part extends out from the opening of the shielding structure and is located in the effective magnetic pole area to complete magnetization.

[0109] To improve the shielding effect, the shielding structure and the magnetized yoke can form a continuous magnetic circuit, and the relative position of the shaft core within the shielding structure can be maintained by a clamping mechanism. Compared with the existing technology where the magnetization area is uncontrollable due to the field applied to the entire component during magnetization, this solution has the advantages of a more concentrated magnetization area and a more predictable magnetic field output.

[0110] Specifically, when magnetizing the mating parts, the shaft core body 1 is installed into the magnetizing fixture of the magnetizing equipment. The magnetizing fixture is equipped with a positioning structure that matches the guide section 12 of the shaft core body 1 to maintain its spatial posture. The positioning structure can be a positioning groove that matches the shape of the guide section 12, a limiting slide that matches the guide rib 122, or a support surface that matches the limiting wall 121, so that the shaft core can only be installed in the fixture in a single direction, thereby ensuring that the distance, direction and height of the mating parts relative to the magnetic poles are consistent.

[0111] The fixture can also be equipped with clamping plates or elastic clamps to prevent the shaft core from vibrating under the action of the magnetization pulse. Multiple shaft cores can also be clamped and magnetized simultaneously using a multi-station fixture to increase production capacity and reduce individual part variations. Compared to existing technologies where manual placement and magnetization lead to posture deviations and dispersion in magnetization direction, this solution offers advantages such as more reliable positioning and higher batch consistency.

[0112] Preferably, the magnetization process of the mating part may include at least two magnetization stages to obtain a magnetization distribution state that better meets the requirements of stroke detection: The first stage is preferably the pre-magnetization stage, in which a relatively low intensity or short pulse is used to orient the mating part so that the magnetic domains are initially aligned along the target direction. The second stage is preferably the saturation magnetization stage, which uses higher intensity pulses to make the mating parts reach a more sufficient level of magnetization and stabilize the output.

[0113] Another preferred embodiment involves changing the magnetic field direction in the second stage to form a composite magnetization distribution, thereby obtaining a more ideal magnetic field gradient in the pressing stroke direction. Compared to existing technologies where single magnetization leads to uneven magnetization or an unadjustable gradient, this solution offers advantages such as more designable magnetization distribution and easier optimization of detection linearity.

[0114] Preferably, the magnetization direction of the mating part is set parallel to the pressing direction of the shaft core body 1, so that the shaft core generates a magnetic field gradient that changes along the pressing direction during the pressing stroke: when magnetizing, the magnetic pole arrangement is adjusted so that the main direction of the magnetic field is consistent with the shaft core axis. When the mating part 13 is located above the sensor, the vertical displacement of the shaft core directly corresponds to the change in magnetic flux received by the sensor. The external magnetic field detection element can output an analog signal or digital signal corresponding to the displacement for adjustable trigger point or continuous stroke detection.

[0115] For embodiments requiring a stronger gradient, local bosses or reduced diameter areas can be formed on the mating structure to concentrate the magnetic flux, or the magnetic flux can be guided to concentrate at the end of the mating part through the shape of the yoke in the magnetizing fixture. Compared with the prior art, where the magnetization direction is random or inconsistent with the travel direction, resulting in signal curve distortion, this solution has the advantages of a clearer travel-signal correspondence and stronger adjustability.

[0116] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

Claims

1. An injection molding process for a magnetic shaft core for a magnetic keyboard, characterized in that, Includes the following steps: S1 provides injection molding material and magnetic powder, and premixes magnetic powder into the injection molding material to form a plastic composite material; S2, providing an injection device with a molding die and a heating mechanism, the molding die having a cavity with a shape structure for molding the required magnetic shaft core, the plastic composite material is introduced into the heating mechanism of the injection device and heated to form a liquid plastic composite material; S3, the liquid plastic composite material obtained in step S2 is injected into the mold cavity using the injection mechanism of the injection equipment to form the required shaft core body (1); the required shaft core body (1) has a mating part (13) for cooperating with the magnetic detection element of the external keyboard. S4, provide a magnetizing device, and use the magnetizing device to magnetize the mating part (13) of the shaft core body (1) obtained in step S3, so that the mating part (13) forms a magnet component, so that the mating part (13) of the shaft core body (1) can be detected by the magnetic field detection element of the external keyboard when it approaches the magnetic field detection element of the external keyboard during the pressing stroke.

2. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 1, characterized in that: The injection equipment provided in step S2 is a two-color injection equipment or a single-color injection equipment. The injection-molded shaft body (1) is integrally molded by a two-color injection molding process using a two-color injection equipment, or integrally molded by a single-color injection molding process using a single-color injection equipment.

3. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 2, characterized in that: When a two-color injection process is used, the two-color injection equipment includes a first upper mold and a first lower mold, which are closed to form a first mold cavity; the injection equipment includes two injection mechanisms, the first injection mechanism injects injection material without magnetic powder into the first upper mold after being heated and liquefied by a heating mechanism to form a pressing section (11) and a guiding section (12), and the second injection mechanism injects liquid plastic composite material containing magnetic powder into the first lower mold to form a mating part (13), and the mating part (13) constitutes a magnetic structure that can be magnetized, and the mating part (13) is individually magnetized.

4. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 2, characterized in that: When using a single-color injection molding process, the single-color injection equipment includes a second upper mold and a second lower mold, which are closed to form a second mold cavity; the single-color injection equipment includes an injection mechanism, which injects liquid plastic composite material containing magnetic powder into the second mold cavity, so that the shaft core body (1) is integrally formed from the liquid plastic composite material containing magnetic powder, and the shaft core body (1) as a whole constitutes a magnetic structure that can be magnetized.

5. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 3, characterized in that: Step S3 further includes forming a first annular groove on the shaft core body (1) for accommodating one end of the external reset elastic member (2), and the lower housing (4) of the external magnetic shaft button has a second annular groove for accommodating the other end of the external reset elastic member (2). The first annular groove and the second annular groove are used to keep the external reset elastic member (2) and the mating part (13) at a gap. The core of the first upper mold is provided with an annular groove structure for forming the first annular groove.

6. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 1, characterized in that: The mass percentage of magnetic powder in the plastic composite material is 60%-95%.

7. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 1, characterized in that: The magnetic powder is ferrite magnetic powder, rare earth permanent magnet powder, iron-based magnetic powder, or alloy magnetic powder.

8. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 3, characterized in that: The shaft core body (1) formed in step S3 also has a pressing section (11) and a guiding section (12). The first upper mold is provided with a first concave mold core for forming the pressing section (11), a second concave mold core for forming the guiding section (12) and the mating part (13). The first concave mold core, the second concave mold core and the punch core of the first lower mold surround to form the first mold cavity. The pressing section (11) and the guiding section (12) are integrally formed by the first upper mold. The mating part (13) is formed on the guiding section (12) and is formed together with the guiding section (12) by the second concave mold core of the first upper mold.

9. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 1, characterized in that, After the magnetization process in step S4, step S5 is also included: heat treatment or annealing of the shaft core body (1), wherein the heat treatment or annealing process includes heating the shaft core body (1) to a preset temperature and holding it at the preset temperature for a preset time; the preset temperature range is 80°C to 110°C and the preset time range is 60 minutes to 180 minutes.

10. The injection molding process for the magnetic shaft core of a magnetic keyboard according to claim 9, characterized in that, After step S5 is completed, step S6 is also included: surface treatment of the shaft core body (1), wherein the surface treatment is spraying, coating or laser surface hardening.

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