Plastic magnetic injection molding assembly, injection molding method, motor and transmission pump

Abstract

The invention relates to the technical field of magnet application, in particular to a plastic magnetic injection molding assembly, an injection molding method, a motor and a transmission pump. The plastic ring is arranged between the rotating shaft and the plastic magnetic body of the plastic magnetic injection molding assembly, soft plastic can be used for providing buffering for cooling shrinkage of the plastic magnetic body to be subjected to injection molding in the injection molding process, the risk that the plastic magnetic body generates crack deformation is reduced, and therefore the problems that the plastic magnetic injection molding assembly cracks after injection molding and the reject ratio is high are solved; and the risk that the motor is stuck due to the fact that the magnet is thrown to be cracked when the motor runs at a high speed when a product with invisible cracks is loaded into the motor is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of magnet applications, and particularly to a plastic magnet injection molding component, an injection molding method, a motor, and a transmission pump. Background Art

[0002] As the core power output component of an electric motor, the rotor assembly has a huge market demand. The rotor assembly generally includes a rotating shaft and a magnet. The rotating shaft is used for the power output of the electric motor, and the magnet is the core design for the efficient energy conversion of the motor, which is circumferentially arranged outside the rotating shaft; the rotor assembly generally adopts an injection molding processing method. According to different types of magnets, the injection molding process of the rotor assembly is also different. For example, when the rotor magnet is a permanent magnet (sintered magnet), when adopting the injection molding processing method, the magnet is a formed structure that has been cured and processed. A plastic bracket is arranged between the rotating shaft and the magnet by interference fit or bonding, etc., and the rotating shaft and the magnet are connected into a whole through the plastic bracket to ensure that the magnet, the plastic bracket, and the rotating shaft are tightly connected and will not slide relative to each other. Then, the exposed parts of the magnet and the bracket are completely coated in the injection molding body by injection molding. Reference can be made to the patent document provided by the application number 202120793852.6.

[0003] With the development of technology, plastic magnets have become the first choice in many applications due to their processing advantages and design flexibility. Plastic magnets are injection molded from plastic magnet materials. The plastic magnet materials are made by mixing and granulating permanent magnet materials powder (such as neodymium iron boron NdFeB, ferrite, etc.) and polymer materials (such as PPS, nylon) through a twin-screw extruder. It combines the easy processability of plastics and the functionality of magnets and can be injection molded. The existing plastic magnet injection molding component directly injects the melted plastic magnet material outside a rigid rotating shaft (steel shaft, metal gear or bushing, etc.) and combines the two into a whole. During the processing, since the coefficient of thermal expansion (CTE) of the plastic magnet material is much higher than that of the rotating shaft, during the cooling process, the plastic magnet material shrinks and deforms inward, while the rotating shaft is hard and will not deform inward. The shrinkage rate of the plastic magnet material is significantly greater than that of the rotating shaft, resulting in a huge residual stress at the interface. When the residual stress exceeds the tensile strength of the plastic magnet material or the interface bonding strength, cracks will be generated and cracking will occur; if the product with invisible cracks is installed in the motor, the magnet is easily thrown and cracked during the high-speed operation of the motor, resulting in the motor being stuck. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that the plastic magnet injection molding component directly injects the melted plastic magnet material outside the rigid rotating shaft, and the plastic magnet material shrinks inward during cooling, which is prone to cracking, and provides a plastic magnet injection molding component, an injection molding method, a motor, and a transmission pump that can prevent cracking.

[0005] In a first aspect, the present invention provides a plastic magnet injection molding assembly, including a rotating shaft and a plastic magnet. The plastic magnet is sleeved outside the rotating shaft, and a plastic ring is provided between the rotating shaft and the plastic magnet, and the plastic ring is integrally connected to the plastic magnet.

[0006] By providing a plastic ring between the rotating shaft and the plastic magnet of the plastic magnet injection molding assembly, the plastic magnet is in direct contact with the plastic ring, which can effectively coordinate the thermal expansion difference and bonding strength between the rotating shaft and the plastic magnet material. During the injection molding process, the plastic ring can provide buffering for the injection molding of the plastic magnet, improve the interfacial bonding performance, and reduce the risk of cracks occurring due to the cooling shrinkage of the plastic magnet after injection molding.

[0007] Preferably, the plastic ring is provided with a strengthening structure, and the strengthening structure is used for concave-convex cooperation with the plastic magnet, which can strengthen the interfacial bonding force between the plastic ring and the plastic magnet and reduce the crack risk. The strengthening structure can be a groove or a protrusion, etc.

[0008] Preferably, the strengthening structure is integrally formed on the circumferential surface of the plastic ring, and the strengthening structures are arranged at intervals in the circumferential direction, which can enhance the circumferential bonding force between the plastic magnet and the plastic ring and prevent the plastic magnet from rotating and misaligning relative to the plastic ring.

[0009] As another implementable manner, the strengthening structure can also be continuously arranged along the circumferential direction of the plastic ring and arranged at intervals in the axial direction to enhance the axial bonding force between the plastic magnet and the plastic ring.

[0010] Preferably, the strengthening structure is arranged along the axial direction of the plastic ring, and the end surface at at least one end of the strengthening structure in the axial direction does not exceed the end surface of the corresponding end of the plastic ring. Among them, the strengthening structure can be arranged parallel to the axial direction of the plastic ring, or can be arranged obliquely or spirally. By arranging the end surface at at least one end of the strengthening structure in the axial direction not to exceed the end surface of the corresponding end of the plastic ring, it is beneficial to enhance the bonding force between the plastic magnet and the plastic ring in the axial direction.

[0011] Preferably, the strengthening structures are evenly distributed in the circumferential direction, which is beneficial to the uniform shrinkage of the injection molding assembly and better runout.

[0012] Preferably, the rotating shaft is in the structure of a steel shaft, a metal gear or a shaft sleeve, and the rotating shaft can be set in different structural forms according to different scenarios, not limited to the above examples.

[0013] Preferably, the rotating shaft is provided with an anti-slip structure. The anti-slip structure can increase the surface roughness of the rotating shaft or be designed as a mechanical interlocking structure to enhance the interfacial bonding force between the rotating shaft and the plastic ring, and can better prevent sliding between the plastic ring and the rotating shaft. The anti-slip structure can be knurling, teeth, grooves or protrusions, etc.

[0014] In a second aspect, the present invention provides an injection molding method for a plastic magnetic injection molding component, which is applied to any of the above plastic magnetic injection molding components, and includes the following steps: S1: First, a plastic ring is obtained by plastic injection molding outside the rotating shaft. S2: Then, plastic magnetic material is injected outside the assembly of the rotating shaft and the plastic ring to form a plastic magnetic body.

[0015] In the present invention, a layer of plastic is first injected outside the rotating shaft to wrap the outer circle of the rotating shaft, forming a plastic ring. Then, plastic magnetic material is injected outside the assembly of the rotating shaft and the plastic ring to form a plastic magnetic body. Since there is a relatively soft plastic ring as a buffer between the plastic magnetic body and the rotating shaft, the risk of cracks appearing when the plastic magnetic body cools and shrinks is small.

[0016] In a third aspect, the present invention further provides an electric motor, including any of the above plastic magnetic injection molding components.

[0017] In a fourth aspect, the present invention further provides a transmission pump, including any of the above plastic magnetic injection molding components.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: By providing a plastic ring between the rotating shaft and the plastic magnetic body of the plastic magnetic injection molding component, the present invention can utilize the soft plastic to provide a buffer for the cooling and shrinking of the plastic magnetic body to be injection molded during the injection molding process, reduce the risk of crack deformation of the plastic magnetic body, thereby solving the problems of cracking and high defect rate after injection molding of the plastic magnetic injection molding component, and reducing the risk that the product with invisible cracks is installed in the electric motor and the magnet is cracked and the electric motor is jammed when the electric motor runs at high speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of a plastic magnetic injection molding component in Embodiment 1; Figure 2 is Figure 1 a side view of; Figure 3 is a schematic structural diagram of a plastic ring (the strengthening structure is a convex rib); Figure 4 is Figure 3 a front view of; Figure 5 is Figure 4 a side view of; Figure 6 is another schematic structural diagram of a plastic ring (assembled with a rotating shaft); Figure 7 is Figure 6 an end view of.

[0020] Reference numerals in the drawings: 1 - plastic magnetic body; 2 - plastic ring; 3 - rotating shaft; 4 - strengthening structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present invention will be further described in detail below in conjunction with specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. Any technology implemented based on the content of the present invention belongs to the scope of the present invention.

[0022] In the description of the specific embodiments of the present invention, without special explanation, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the invention product / device / equipment is usually used. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present invention or simplifying the description in the specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present invention.

[0023] In addition, if terms such as "horizontal", "vertical", "hanging", "parallel", etc. appear, it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in the directions of "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still play its role in the solution of the present invention.

[0024] In addition, the expressions such as "first", "second", "third", etc. in the terms are only used to distinguish the description of the same or similar components, and should not be construed as emphasizing or implying the relative importance of specific components.

[0025] In addition, in the description of the embodiments of the present invention, "several", "multiple", "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., or even more than 9.

[0026] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, where the terms "set", "installed", "connected", "joined", "provided with", "laid", "arranged" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection, and can be connection means commonly used in the art such as welding, riveting, bolting, threaded connection, etc. Such a connection can be a mechanical connection, an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components.

[0027] Embodiment 1 As Figure 1 、 Figure 2 shown, a plastic magnet injection molding assembly includes a rotating shaft 3 and a plastic magnet 1. The plastic magnet 1 is sleeved outside the rotating shaft 3. A plastic ring 2 is provided between the rotating shaft 3 and the plastic magnet 1, and the plastic ring 2 is integrally connected to the plastic magnet 1.

[0028] By providing the plastic ring 2 between the rotating shaft 3 and the plastic magnet 1 of the plastic magnet injection molding assembly, the plastic magnet 1 is in direct contact with the plastic ring 2, which can effectively coordinate the thermal expansion difference and bonding strength between the rotating shaft 3 and the plastic magnet material. During the injection molding process, the plastic ring 2 can provide buffering for the injection molding of the plastic magnet 1, improve the interfacial bonding performance, and reduce the risk of cracks appearing due to the cooling shrinkage of the plastic magnet 1 after injection molding. The material compatibility between the plastic ring 2 and the plastic magnet 1 is good.

[0029] Furthermore, as Figures 3 - 7 shown, a strengthening structure 4 is provided on the outer surface of the plastic ring 2. The strengthening structure 4 is used for concave-convex cooperation with the plastic magnet 1, which can strengthen the interfacial bonding force between the plastic ring 2 and the plastic magnet 1 and reduce the crack risk. The strengthening structure 4 can be a protrusion (as Figures 3 - 5 shown) or a groove (as Figure 6 、 Figure 7 shown), etc. The groove and the protrusion can also be combined and provided on the plastic ring 2. The strengthening structure 4 and the plastic ring 2 are of an integrally formed structure, and during injection molding, a specific structure mold can be used for one-time injection molding. Specifically, in this embodiment, it is preferably to arrange the strengthening structure 4 at intervals along the circumferential direction of the plastic ring 2, which can enhance the circumferential bonding force between the plastic magnet 1 and the plastic ring 2 and prevent the plastic magnet 1 from rotating and misaligning relative to the plastic ring 2; the strengthening structure 4 is arranged along the axial direction of the plastic ring 2 and has a certain length. The strengthening structure 4 can be arranged parallel to the axial direction of the plastic ring 2, or can be arranged obliquely or spirally.

[0030] Further, in one or more embodiments, the end face of at least one end of the reinforcing structure 4 along the axial direction does not extend beyond the end face of the corresponding end of the plastic ring 2. By arranging the end face of at least one end of the reinforcing structure 4 along the axial direction not to extend beyond the end face of the corresponding end of the plastic ring 2, it is beneficial to enhance the bonding force between the plastic magnetic magnet 1 and the plastic ring 2 in the axial direction. Preferably, as Figure 3 , the end faces of both ends of the reinforcing structure 4 are set lower than the end faces of the corresponding ends of the plastic ring 2.

[0031] In one or more embodiments, the above-mentioned reinforcing structure 4 preferably adopts a raised rib structure, as Figures 3 - 5 shown. The side faces on the opposite sides of the reinforcing structure 4 can be set perpendicular to the surface of the plastic ring 2, or inclined with respect to the surface of the plastic ring 2, or adopt a concave arc surface to increase the contact area with the plastic magnetic magnet 1 and improve the interfacial bonding force.

[0032] Preferably, the reinforcing structure 4 is arranged uniformly in the circumferential direction, which is beneficial to the uniform shrinkage of the injection molded component and better runout.

[0033] In one or more embodiments, the end faces of the plastic ring 2 and the plastic magnetic magnet 1 can be set flush, so that the inner side face of the plastic magnetic magnet 1 is in full contact with the plastic ring 2, avoiding direct contact between the plastic magnetic magnet 1 and the rotating shaft 3. At the same time, the plastic magnetic magnet 1 can increase the bonding force with the plastic ring 2 through the reinforcing structure 4, improving the anti-displacement ability in the axial and circumferential directions.

[0034] In one or more embodiments, according to the different thicknesses of the plastic magnetic magnet 1, the thickness of the plastic ring is different, but at least 0.3 mm. If it is too thin, stress concentration is likely to occur, and if it is too thick, the magnetic performance will be affected. The thickness of the plastic ring 2 is preferably set to 0.3 mm - 2 mm.

[0035] In one or more embodiments, the rotating shaft 3 is provided with an anti-slip structure. The anti-slip structure can increase the surface roughness of the rotating shaft 3 or be designed as a mechanical interlocking structure to enhance the interfacial bonding force between the rotating shaft 3 and the plastic ring 2, and can better prevent sliding between the plastic ring 2 and the rotating shaft 3. The anti-slip structure can be knurling, teeth, grooves or protrusions, etc.

[0036] In one or more embodiments, the rotating shaft 3 can be a solid shaft or a hollow shaft, and can be a symmetric structure or an asymmetric structure. The rotating shaft 3 can select different structural forms according to the actual working conditions, not limited to the above examples.

[0037] Embodiment 2 Based on Embodiment 1, this embodiment provides an injection molding method for a plastic magnetic injection molded component, including the following steps: S1: First, perform the first injection molding on the outside of the rotating shaft 3 with plastic to make the injection molding material tightly cover the rotating shaft 3 to obtain the plastic ring 2.

[0038] The plastic ring 2 can be made of high-toughness plastics such as PA6, PA66, and PBT. The plastics have good toughness and hardly crack during the cooling and shrinking process. Glass fiber can be optionally added for reinforcement.

[0039] S2: Then, a second injection molding is performed outside the assembly of the rotating shaft 3 and the plastic ring 2, injecting plastic magnetic material to obtain an annular plastic magnetic magnet 1. The plastic magnetic magnet 1 tightly wraps the plastic ring 2, thereby forming a plastic magnetic injection molded assembly.

[0040] During the second injection molding, the second injection molding can be carried out when the plastic ring 2 is not completely cooled, using the residual heat to promote interface fusion, or the second injection molding can be carried out after the plastic ring 2 is cooled. The temperature of the second injection molding is slightly lower than the first time to prevent the plastic ring 2 from being overly softened.

[0041] The injection molding process is an existing technology. Generally, the tooling used for injection molding consists of two oppositely arranged molds, that is, the two oppositely arranged molds surround the circumferential surface of the rotor assembly and are combined relatively to form an injection molding cavity. The injection mold is correspondingly provided with a core hole for accommodating the rotating shaft 3. During injection molding, the rotating shaft 3 is inserted into the core hole of the injection mold, and flowing injection molding material is injected into the injection mold and waits for solidification and molding. In this embodiment, it is formed by two-stage injection molding; during each injection molding, molds matching the structural shapes of the plastic ring 2 and the plastic magnetic magnet 1 are respectively used.

[0042] In this embodiment, a layer of plastic is first injection molded outside the rotating shaft 3 to wrap the outer circle of the rotating shaft 3, forming a plastic ring 2. Then, plastic magnetic material is injected outside the assembly of the rotating shaft 3 and the plastic ring 2 to form a plastic magnetic magnet 1. When injecting the plastic magnetic magnet 1, during the process of the plastic magnetic magnet 1 shrinking inward during injection cooling, the plastic magnetic material shrinks and deforms inward. There is already a relatively soft plastic ring 2 outside the rotating shaft 3 for buffering. The plastic ring 2 can absorb the amount of deformation and stress of the plastic magnetic material inward, preventing the plastic magnetic magnet 1 (or the plastic magnetic material) from generating large stress due to direct contact with the relatively hard rotating shaft that does not deform inward, thus avoiding the occurrence of cracks in the plastic magnetic magnet 1.

[0043] Specifically, before injection molding, it also includes the step of preprocessing the rotating shaft 3: 1) Roughen the surface of the rotating shaft 3: Knurling can be added to the surface of the rotating shaft 3 and a primer can be coated to prevent the plastic ring 2 from peeling off from the rotating shaft 3.

[0044] 2) Cleaning: Remove oil stains and oxides, which can be achieved by means such as sandblasting, solvent cleaning, or plasma treatment.

[0045] 3) Preheating to reduce the temperature difference between the injection molding material and the metal rotating shaft. The preheating temperature of the rotating shaft 3 matches the melting point of the plastic to avoid thermal shock.

[0046] After secondary injection molding, after the injection-molded component is formed, it is heat-treated at 80-100°C for 2-4 hours to release residual internal stress through annealing treatment, which is also beneficial to improving the crack phenomenon.

[0047] With the above structural scheme and injection molding process for the plastic magnet component, the problems of cracking after injection molding and high defect rate of the plastic magnet injection-molded component can be solved, the risk of the motor being stuck due to the magnet being thrown and cracked during high-speed operation of the motor when a product with invisible cracks is installed in the motor can be reduced, and the inspection cost can be reduced.

[0048] Embodiment 3 Based on Embodiment 1 or Embodiment 2, this embodiment further provides a motor that uses the above plastic magnet injection-molded component or a plastic magnet injection-molded component processed by the above injection molding method. The motor is used to convert electrical energy into mechanical energy (rotary / linear motion), and can be a micro wind turbine, a robot joint motor, a drone rotor motor, a hard disk drive spindle motor, etc., which are not limited to the above examples.

[0049] Embodiment 4 Based on Embodiment 1 or Embodiment 2, this embodiment further provides a drive pump that uses the above plastic magnet injection-molded component or a plastic magnet injection-molded component processed by the above injection molding method. The drive pump is used to convert mechanical energy into fluid energy (transporting or pressurizing liquids / gases), and can be an electronic water pump, an oil pump, a booster pump, a chemical pump, or an agricultural irrigation pump, etc., which are not limited to the above examples.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A plastic magnetic injection molding component, comprising a rotating shaft (3) and a plastic magnetic body (1), wherein the plastic magnetic body (1) is sleeved outside the rotating shaft (3), and is characterized in that: A plastic ring (2) is provided between the rotating shaft (3) and the plastic magnet (1), and the plastic ring (2) is integrally connected to the plastic magnet (1).

2. A plastic magnetic injection molding component according to claim 1, characterized in that: The plastic ring (2) is provided with a reinforcement structure (4), and the reinforcement structure (4) is used for concave-convex cooperation with the plastic magnet (1).

3. The plastic magnetic injection molding component according to claim 2, characterized in that: The reinforcement structures (4) are integrally formed on the circumferential surface of the plastic ring (2), and the reinforcement structures (4) are arranged at intervals along the circumferential direction.

4. The plastic magnetic injection molding component according to claim 3, characterized in that: The reinforcement structure (4) is arranged along the axial direction of the plastic ring (2), and at least one end surface of the reinforcement structure (4) along the axial direction does not exceed the end surface of the corresponding end of the plastic ring (2).

5. The plastic magnetic injection molding component according to claim 3, characterized in that: The thickness of the plastic ring (2) is 0.3 mm to 2 mm.

6. A plastic magnetic injection molding component according to any one of claims 1 to 5, characterized in that: The rotating shaft (3) is a steel shaft, a metal gear or a shaft sleeve.

7. A plastic magnetic injection molding component according to any one of claims 1 to 5, characterized in that: The rotating shaft (3) is provided with an anti-slip structure.

8. A method for injection molding a plastic magnetic injection molding component, characterized in that: Applicable to a plastic magnetic injection molding component as described in any one of claims 1 to 7, The following steps are involved: S1: First, a plastic ring (2) is obtained by plastic injection molding outside the rotating shaft (3); S2: injecting plastic magnetic material outside the assembly of the rotating shaft (3) and the plastic ring (2) to form a plastic magnetic body (1).

9. A motor, characterized in that: It comprises a plastic-magnetic injection molding component as described in any one of claims 1-7.

10. A transmission pump, characterized in that: It comprises a plastic-magnetic injection molding component as described in any one of claims 1-7.

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