Rotor structure for improving injection molding cracking of magnetic ring and improving assembly jumping of commutator and injection molding method

Abstract

The invention provides a rotor structure for improving injection molding cracking of a magnetic ring and improving assembly jumping of a commutator and an injection molding method, the rotor structure comprises a metal lining, the magnetic ring, a bearing, the commutator and an internal thread cavity, the internal thread cavity is connected with a motor output shaft, and the magnetic ring is arranged on the metal lining in a sleeving manner; after the metal lining extends towards the axial outer side of the magnetic ring, the outer wall of the metal lining is matched with the bearing inner ring, plastic is filled between the internal thread cavity and the metal lining, the commutator is arranged at one end of the metal lining, and an injection molding feeding port is formed in the metal lining in the radial direction. According to the invention, the technology of effectively improving the magnetic ring cracking is provided, and the rotor manufacturing precision is improved, so that the motor performance and stability are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of small and micro motor manufacturing, and specifically relates to a rotor structure and an injection molding method for improving injection molding cracking of a magnetic ring and enhancing assembly vibration of a commutator. Background Art

[0002] In the traditional manufacture of micro motor rotors, during the injection molding process of the rotor, due to the need to meet characteristic conditions such as high temperature and high pressure, as well as secondary damage caused by excessive shrinkage force due to excessive wall thickness during the cooling process, the magnetic ring will have defects such as cracking after injection molding; due to the shrinkage of plastic injection molding such as thermal expansion and contraction, the shaft diameter size at the installation of the two bearings is deformed, resulting in a large deviation in the runout of the commutator 5 based on the A~B axis after assembly, so that during the overall use process, the carbon brush cannot contact the two commutator disk surfaces at the same time, which easily leads to a poor thrust curve.

[0003] In addition, in the prior art, the bearing mounting surfaces are all matched with the clinker parts, and the dimensional accuracy is difficult to control, or the cost is relatively high. Summary of the invention

[0004] The present invention provides a rotor structure and an injection molding method for improving magnetic ring injection cracking and enhancing commutator assembly jump, a technology for effectively improving magnetic ring cracking, and improving rotor manufacturing accuracy, so as to improve motor performance and stability.

[0005] A rotor structure for improving the cracking of magnetic ring injection molding and improving the assembly runout of commutator, comprising a metal bushing, a magnetic ring, a bearing and an internal thread cavity, the internal thread cavity is connected to the motor output shaft, the magnetic ring is sleeved on the metal bushing, the outer wall of the metal bushing is matched with the inner ring of the bearing after the metal bushing extends axially outward from the magnetic ring, the space between the internal thread cavity and the metal bushing is filled with plastic, the commutator is arranged at one end of the metal bushing, the metal bushing is radially provided with an injection molding feed port, and the injection molding feed port penetrates the wall surface of the metal bushing. The invention newly adds a metal bushing, so that the rotor can use the metal bushing to resist part of the injection molding pressure during the injection molding process, and the secondary damage caused by excessive shrinkage force due to excessive wall thickness during the cooling process, reducing the risk of magnetic ring contraction pressure cracking, and effectively protecting the magnetic ring; at the same time, it can also meet the requirements of fully connecting the metal bushing and the magnetic ring into one, with better bonding force and stable installation; therefore, the invention not only solves the problem of magnetic ring cracking, but also improves the assembly runout of the commutator.

[0006] Preferably, the injection molding feed ports are respectively arranged on three radial planes of the metal bushing, and four injection molding feed ports are arranged on each radial plane. Multiple injection molding feed ports are arranged and evenly distributed on the cylindrical surface of the metal bushing, and the holes are evenly distributed on the cylindrical surface and radially, so that the plastic can flow into the mold cavity at a uniform speed and evenly to fill it fully during the injection process, and can also resist the high pressure of the rubber material just after injection and then enter through these small holes for secondary diversion.

[0007] The present invention also includes a commutator that matches the inner hole at the end of the metal bushing, and the bearings are arranged in pairs at both ends of the metal bushing. After the rotor assembly is injection molded, the mounting hole of the commutator also matches the inner hole of the metal bushing, achieving overall concentricity. The bearings on both sides can directly match the metal bushing, and the processing accuracy is easy to ensure, thereby improving the direct assembly accuracy of the rotor and the commutator, thereby reducing the end face runout of the commutator, ensuring the coaxiality of the bearing and the magnetic ring, and also ensuring the verticality of the end face of the commutator conductive ring. The carbon brush and the commutator can have better and more stable contact, driving the motor to commutate more smoothly and having better output torque performance.

[0008] Preferably, a gap is provided between the metal bushing and the magnetic ring and filled with plastic. The high pressure of the rubber material just injected is then diverted from the injection inlet into the gap between the metal bushing and the magnetic ring, which can be used as an injection buffer surface. The plastic in the gap wraps the magnetic ring and the metal bushing into one, ensuring the stability of the installation.

[0009] Preferably, a chamfer of C0.5 is provided at the junction of the injection molding feed port and the outer wall of the metal bushing, so as to strengthen the wrapping force of the plastic on the metal bushing and improve the strength of the internal thread.

[0010] Preferably, the roughness of the inner wall of the metal bushing between the radial planes where the injection molding feed ports are located at both ends is greater than the roughness of other places on the inner wall of the metal bushing. The roughness on the inner wall of the injection molding feed port distribution area can be appropriately enlarged to improve the bonding force between the metal bushing and the plastic.

[0011] The present invention also provides an injection molding method for a rotor structure, which is used for the injection molding process of a rotor structure for improving the cracking of the magnetic ring injection molding and improving the assembly vibration of the commutator, and comprises a front mold, a rear mold and a mandrel, and comprises the following steps:

[0012] S1: The front mold and the rear mold are separated, and the mandrel is assembled on the rear mold for positioning; first separate the front and rear molds, and insert the mandrel into the hole of the rear mold.

[0013] S2: The inner hole of the metal bushing is matched with the outer diameter of the core shaft for installation, and the outer hole of the metal bushing is matched with the inner wall of the rear mold; at this time, the inner hole of the metal bushing is matched with the outer diameter of the core shaft, and the outer diameter of the metal bushing is matched with the positioning hole of the rear mold.

[0014] S3: Assemble the magnetic ring to the inner cavity of the front mold. At this time, the magnetic ring is assembled to the positioning hole of the front mold according to the positioning direction.

[0015] S4: mold closing, the rear mold moves toward the front mold until the mold is locked. The present invention also includes a limiting core arranged inside the front mold, the limiting core is used to connect with the end of the mandrel after mold closing, limit and position the mandrel, improve the stability of the injection molding process, and improve the precision.

[0016] S5: Turn on the equipment to start working and perform injection molding;

[0017] In the present invention, the injection molding process of step S5 includes: injection, pressure holding, cooling and mold opening steps. The high pressure of injection is 85-95 bar. During the injection molding process, the flow direction of the plastic is to enter from the injection molding inlet at the bottom of the front mold, then enter the injection molding feed inlet on the rightmost side of the metal bushing, then enter the gap between the core shaft and the metal bushing, and finally enter the gap between the metal bushing and the magnetic ring through the injection molding feed inlet for secondary diversion.

[0018] In the present invention, the clearance between the inner hole of the metal bushing and the outer wall of the core shaft 8) is less than φ0.04mm, and the clearance between the outer wall of the metal bushing 1) and the rear mold is less than φ0.04mm. The clearance between the two places needs to be controlled within the range of φ0.04mm, mainly to prevent the flash from being too large, causing blockage and centering displacement.

[0019] In the present invention, the gap between the inner hole of the magnetic circle and the outer wall of the metal bushing is 0.25-0.5mm. After the mold is closed, a gap of a certain width is left between the inner hole of the magnetic circle and the outer diameter of the metal bushing. The reservation of this gap affects the force of the magnetic circle during the injection process and the saturation of the injection filling amount. If the gap is too large, the amount of glue entering will be too much, and the force on the magnetic circle will be greater. If the gap is too small, it will be difficult to inject glue, and it will not be easy to fill saturation. The wrapping strength between the magnetic circle and the metal bushing is poor. The gap is generally controlled within the range of 0.25-0.5mm, and it needs to be determined based on the characteristics of the plastic material and the mold.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Adding a metal bushing can alleviate the damage to the magnetic ring caused by the injection and holding pressure during the injection molding process; solve the problem of excessive wall thickness and uneven overall wall thickness of the clinker part inside the magnetic ring, which requires a larger injection pressure to saturate the part during production, and secondary damage caused by excessive shrinkage force due to excessive wall thickness during cooling, thereby avoiding cracking of the magnetic ring.

[0022] The assembly stability of the rotor assembly, commutator and bearing is better. The new solution directly wraps the magnetic ring and metal bushing with plastic into one piece. The bearing can directly cooperate with the metal bushing. The metal bushing is completed by machining, and the processing accuracy is easy to ensure. After assembling into the assembly, the bearing can be directly assembled on the metal bushing, which ensures the coaxiality of the bearing and the magnetic ring, and can also ensure the verticality of the end face of the commutator conductive ring.

[0023] The present invention improves the assembly accuracy of the rotor and the commutator, thereby reducing the end face runout of the commutator, and enables the carbon brush and the commutator to have better and more stable contact, so that the motor has the characteristics of more stable commutation and better output torque performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural cross-sectional view of a rotor structure for improving injection cracking of magnetic rings and enhancing assembly vibration of commutator according to the present invention.

[0025] Figure 2 It is a cross-sectional structural diagram of the metal bushing described in the present invention.

[0026] Figure 3 The present invention is a device structure diagram of a rotor structure injection molding method before mold closing.

[0027] Figure 4 The invention discloses a device structure diagram of a method for injection molding a rotor structure after mold closing.

[0028] Figure 5 The present invention is a flowchart of a method for injection molding a rotor structure.

[0029] Figure 6 yes Figure 4 Enlarged view of point B in the middle.

[0030] In the figure: 1-metal bushing, 101-injection molding feed port, 2-magnetic ring, 3-bearing, 4-internal thread cavity, 5-commutator, 6-front mold, 7-rear mold, 8-core shaft, 9-limiting core, 10-injection molding inlet. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] In the description of the present invention, it is necessary to understand that the terms "left", "right", "up", "down", "front", "back", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or structure referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0033] Embodiment 1:

[0034] like Figure 1 As shown, a rotor structure for improving the cracking of magnetic ring injection molding and improving the assembly jump of commutator includes a metal bushing 1, a magnetic ring 2, a bearing 3 and an internal thread cavity 4, the internal thread cavity 4 is connected to the output shaft of the motor, the magnetic ring 2 is sleeved on the metal bushing 1, and the metal bushing 1 extends axially outward from the magnetic ring 2 so that its outer wall cooperates with the inner ring of the bearing 3, plastic is filled between the internal thread cavity 4 and the metal bushing 1, and the commutator 5 is arranged at one end of the metal bushing 1.

[0035] like Figure 2 As shown, the metal bushing 1 is radially provided with an injection molding feed port 101 .

[0036] like Figure 2 As shown, in this embodiment, the injection molding feed ports 101 are respectively arranged on three radial planes, and each radial plane is provided with four injection molding feed ports 101. Multiple injection molding feed ports 101 are arranged and evenly distributed on the cylindrical surface of the metal bushing 1, and the holes are evenly distributed on the cylindrical surface and radially, so as to enable the plastic to flow into the mold cavity at a uniform speed and evenly to fill it fully during the injection process, and to resist the high pressure of the rubber material just after injection and then enter through these small holes for secondary diversion.

[0037] like Figure 2 As shown, the diameter of the injection molding feed port 101 is 3 mm. Changing the size can not only ensure that the strength of the metal bushing 1 is not affected, but also ensure that the plastic can smoothly flow into the gap between the metal bushing 1 and the magnetic ring 2 during the injection molding process.

[0038] like Figure 1 As shown, this embodiment also includes a commutator 5 that matches the inner hole at the end of the metal bushing 1, and the bearings 3 are arranged in pairs at both ends of the metal bushing 1. After the rotor assembly is injection molded, the mounting hole of the commutator 5 also matches the inner hole of the metal bushing 1, achieving overall concentricity, and the bearings 3 on both sides can directly match the metal bushing 1.

[0039] like Figure 1As shown, in this embodiment, a gap is provided between the metal bushing 1 and the magnetic ring 2 and filled with plastic. The high pressure of the plastic just injected is then diverted from the injection inlet 101 into the gap between the metal bushing 1 and the magnetic ring 2, which can serve as an injection buffer surface.

[0040] like Figure 2 As shown, in this embodiment, a chamfer 102 with a C0.5 is provided at the junction of the injection molding feed port 101 and the outer wall of the metal bushing 1 to strengthen the wrapping force of the plastic on the metal bushing 1 and improve the strength of the internal thread.

[0041] In this embodiment, the roughness of the inner wall surface of the metal bushing 1 between the radial planes where the injection molding feed ports 101 at both ends are located is greater than the roughness of other places on the inner wall of the metal bushing 1. Figure 5 As shown in the figure, the roughness of the inner wall of the metal bushing 1 within the range of the AA segment is greater than the roughness of other places, that is, the roughness on the inner wall of the injection molding feed port 101 distribution area can be appropriately enlarged to improve the bonding force between the metal bushing 1 and the plastic.

[0042] Embodiment 2:

[0043] like Figure 5 As shown, this example is an injection molding method of a rotor structure, which is used for the injection molding process of the above-mentioned embodiment 1. The device used in this embodiment includes a front mold 6, a rear mold 7 and a core shaft 8. The core shaft 8 is consistent with the internal thread cavity 4, and includes the following steps:

[0044] S1: Figure 3 As shown, the front mold 6 and the rear mold 7 are separated, and the core shaft 8 is assembled to the rear mold 7 for positioning; first, the front and rear molds 7 are separated, and the core shaft 8 is inserted into the hole of the rear mold 7.

[0045] S2: Figure 3 As shown, the inner hole of the metal bushing 1 is matched with the outer diameter of the core shaft 8 for installation, and the outer hole of the metal bushing 1 is matched with the inner wall of the rear mold 7; at this time, the inner hole of the metal bushing 1 is matched with the outer diameter of the core shaft 8, and the outer diameter of the metal bushing 1 is matched with the positioning hole of the rear mold 7.

[0046] S3: Figure 3 As shown, the magnetic ring 2 is assembled to the inner cavity of the front mold 6. At this time, the magnetic ring 2 is assembled to the positioning hole of the front mold 6 according to the positioning direction.

[0047] S4: Figure 4 As shown, the mold is closed and the rear mold 7 moves toward the front mold 6 until the mold is locked.

[0048] S5: Figure 4 As shown, turn on the equipment and start working for injection molding.

[0049] In this embodiment, the injection molding process includes: injection, pressure holding, cooling and mold opening steps. The high injection pressure is about 85-95 bar.

[0050] like Figure 4 As shown, the arrow direction shows the flow direction of the plastic. During the injection molding process, the flow direction of the plastic is to enter from the injection molding inlet 10 at the lower part of the front mold 6, then enter the injection molding feed inlet 101 at the rightmost side of the metal bushing 1, then enter the gap between the core shaft 8 and the metal bushing 1, and finally enter the gap between the metal bushing 1 and the magnetic ring 2 through the injection molding feed inlet 101 for secondary diversion. Some plastic also enters the gap between the metal bushing 1 and the magnetic ring 2 directly after entering the injection molding inlet 10.

[0051] like Figure 4 As shown, in this embodiment, the fitting clearance between the inner hole of the metal bushing 1 and the outer wall of the core shaft 8 is less than φ0.04 mm, and the fitting clearance between the outer wall of the metal bushing 1 and the rear mold 7 is less than φ0.04 mm.

[0052] like Figure 6 As shown, in this embodiment, the gap d between the inner hole of the magnetic ring 2 and the outer wall of the metal bushing 1 is 0.25-0.5 mm. After the mold is closed, a gap of a certain width is left between the inner hole of the magnetic ring 2 and the outer diameter of the metal bushing 1. The reservation of this gap affects the force of the magnetic ring 2 during the injection process and the saturation of the injection filling amount. If the gap is too large, the amount of glue entering will be too much, and the force on the magnetic ring 2 will be greater. If the gap is too small, it will be difficult to enter the glue, and it will not be easy to fill saturation, and the wrapping strength between the magnetic ring 2 and the metal bushing 1 will be poor. The gap is generally controlled within the range of 0.25-0.5 mm.

Claims

1. A rotor structure for improving the cracking of magnetic ring injection molding and improving the commutator assembly vibration, characterized in that The invention comprises a metal bushing (1), a magnetic ring (2), a bearing (3) and an internally threaded cavity (4); the internally threaded cavity (4) is connected to the output shaft of the motor; the magnetic ring (2) is sleeved on the metal bushing (1); after the metal bushing (1) extends axially outward from the magnetic ring (2), its outer wall matches the inner ring of the bearing (3); plastic is filled between the internally threaded cavity (4) and the metal bushing (1); the commutator (5) is arranged at one end of the metal bushing (1); and the metal bushing (1) is radially provided with an injection molding feed port (101).

2. A rotor structure for improving magnetic ring injection cracking and commutator assembly vibration according to claim 1, characterized in that: The injection molding feed inlets (101) are respectively arranged on three radial planes, and four injection molding feed inlets (101) are arranged on each radial plane.

3. A rotor structure for improving magnetic ring injection cracking and commutator assembly vibration according to claim 1, characterized in that: It also includes a commutator (5) that matches the inner hole at the end of the metal bushing (1), and the bearings (3) are arranged in pairs at both ends of the metal bushing (1).

4. A rotor structure for improving magnetic ring injection cracking and commutator assembly vibration according to claim 1, characterized in that: A gap is provided between the metal bushing (1) and the magnetic ring (2) and is filled with plastic.

5. A rotor structure for improving magnetic ring injection cracking and commutator assembly vibration according to claim 1, characterized in that: A chamfer (102) of C0.5 is provided at the junction of the injection molding feed port (101) and the outer wall of the metal bushing (1).

6. A rotor structure for improving magnetic ring injection cracking and commutator assembly vibration according to claim 2, characterized in that: The roughness of the inner wall surface of the metal bushing (1) between the radial planes where the injection molding feed ports (101) at both ends are located is greater than the roughness of other places on the inner wall of the metal bushing (1).

7. A method for injection molding a rotor structure, used for the injection molding of a rotor structure for improving the cracking of magnetic ring injection molding and improving the assembly vibration of the commutator as described in claims 1 to 5, comprising a front mold (6), a rear mold (7) and a mandrel (8), comprising the following steps S1: the front mold (6) and the rear mold (7) are separated, and the mandrel (8) is assembled onto the rear mold (7) for positioning; S2: Fitting the inner hole of the metal bushing (1) with the outer diameter of the mandrel (8), and fitting the outer hole of the metal bushing (1) with the inner wall of the rear mold (7); S3: Assemble the magnetic ring (2) onto the inner cavity of the front mold (6); S4: closing the mold, the rear mold (7) moves toward the front mold (6) until the mold is locked; S5: Turn on the equipment and start working for injection molding.

8. The method for injection molding a rotor structure according to claim 7, characterized in that The injection molding process includes the steps of injection, pressure holding, cooling and mold opening.

9. The method for injection molding a rotor structure according to claim 7, characterized in that: The matching clearance between the inner hole of the metal bushing (1) and the outer wall of the core shaft (8) is less than φ0.04 mm, and the matching clearance between the outer wall of the metal bushing (1) and the rear mold (7) is less than φ0.04 mm.

10. The method for injection molding a rotor structure according to claim 7, characterized in that: The gap between the inner hole of the magnetic ring (2) and the outer wall of the metal bushing (1) is 0.25 to 0.5 mm.

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