A three-layer structure of a temperature-resistant brushless motor signal magnetic ring

Abstract

The utility model relates to a brushless motor technical field, concretely is a kind of temperature-resistant brushless motor signal magnetic ring three-layer structure, by metal ring, plastic piece and injection molding magnetic material are sequentially co-injection into one body. Plastic piece is located between metal ring and injection molding magnetic material, used as thermal expansion buffer layer, can absorb the stress generated due to the difference of expansion coefficient when cold and hot impact, prevent the cracking of magnetic material. The structure directly replaces the existing metal-magnetic material two-layer signal magnetic ring, without changing motor size chain and assembly process, can improve the reliability of rotor assembly, prolong the life of motor.

Description

Technical Field

[0001] This utility model relates to the field of brushless motor technology, and in particular to the signal magnetic ring structure of a brushless motor rotor, which is mainly used to improve the stability and reliability of the signal magnetic ring in high and low temperature environments; specifically, it is a three-layer structure of a temperature-resistant brushless motor signal magnetic ring. Background Technology

[0002] Brushless motors require a signal magnetic ring on the rotor shaft to provide a magnetic field signal to the Hall element for electronic commutation. Common signal magnetic ring structures include... Figure 2 As shown: The metal ring and the injection-molded magnetic material are directly injection molded into one piece. This structure is simple and low-cost, but it has the following drawbacks in practical use: Thermal expansion mismatch – The thermal expansion coefficients of the metal and the injection-molded magnetic material differ greatly. During high and low temperature storage or thermal shock, large tensile / compressive stresses are generated on the magnetic material side, which makes it very easy for microcracks to appear. Crack propagation – When the motor is running at high speed, the crack continues to propagate under the action of centrifugal force, resulting in magnetic pole damage, Hall signal distortion, and motor loss of steps, shaking or even stopping. Material ejection – When the crack is severe, blocky magnetic material will peel off from the metal ring and be ejected, causing the entire machine to fail instantly, reducing product lifespan and safety.

[0003] Therefore, the market urgently needs a signal magnetic ring structure that can alleviate thermal stress, inhibit crack initiation and propagation, and maintain stable magnetic properties. Utility Model Content

[0004] This invention aims to provide a signal magnetic ring structure with a plastic buffer layer. By adding a plastic component between the metal ring and the injection-molded magnetic material, the problem of magnetic material cracking due to thermal stress in the prior art is solved, thereby improving the stability and reliability of the signal magnetic ring.

[0005] To achieve the above objectives, this utility model is implemented as follows: A temperature-resistant three-layer structure for a brushless motor signal magnetic ring, comprising: Metal rings are used for press-fitting and fixing to the motor shaft and providing mechanical support; The plastic part is first injection molded into the metal ring to form an intermediate buffer layer; Injecting magnetic materials and then combining them with plastic parts through secondary injection molding to form magnetic poles; The plastic component is located between the metal ring and the injection-molded magnetic material to absorb the stress caused by the difference in their coefficients of thermal expansion, thus preventing the magnetic material from cracking.

[0006] Compared with the prior art, the present invention has the following advantages: 1) The plastic buffer layer blocks the direct transmission of thermal stress, preventing cracks in the magnetic material under thermal shock; 2) Three-layer integrated injection molding, maintaining the original dimensional chain without adding assembly steps; 3) Improve motor signal stability, extend service life, and reduce the risk of failure.

[0007] Furthermore, the axial thickness of the plastic part is 0.3 mm to 2 mm, and the difference in thermal expansion coefficient between the selected material and the injection-molded magnetic material is ≤30×10⁻. 6 The thermoplastic material at / ℃ ensures a cushioning effect while avoiding excessive thickness that could increase the air gap in the magnetic circuit, thus ensuring that the magnetic properties remain essentially unchanged.

[0008] Furthermore, the outer circumference of the metal ring is provided with knurling or annular grooves, which can significantly improve the bonding strength with the plastic parts and prevent interlayer slippage during high-speed rotation or temperature cycling.

[0009] Furthermore, the outer surface of the injection-molded magnetic material is evenly distributed with alternating N and S poles, and the number of magnetic poles matches the number of pole pairs of the motor. This allows it to directly replace the existing signal magnetic ring without changing the Hall detection circuit.

[0010] Furthermore, the metal ring, plastic parts, and injection-molded magnetic material are formed through two injection molding processes: first, the metal ring and plastic parts are coated with glue in the same mold, and then the plastic parts and magnetic material are coated with glue again in the same mold to form an integrated signal magnetic ring. The process is simple and suitable for mass automated production. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the rotor assembly of the present invention, showing the assembly relationship of the motor shaft (1), upper bearing (2), signal magnetic ring (3), rotor (4) and lower bearing (5).

[0012] Figure 2 This is a schematic diagram of the structure of a signal magnetic ring in the prior art, showing a two-layer structure in which the injection-molded magnetic material (3-1) and the metal ring (3-2) are directly bonded together.

[0013] Figure 3 This is a schematic diagram of the signal magnetic ring of this utility model, showing a three-layer structure in which a metal ring (6-1), a plastic part (6-2), and an injection-molded magnetic material (6-3) are sequentially combined. The plastic part (6-2) is located between the metal ring and the magnetic material and serves as a buffer layer. Detailed Implementation

[0014] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0015] Example 1: A rotor assembly, see Figure 1 It includes a motor shaft 1, an upper bearing 2, a signal magnetic ring 3, a rotor 4, and a lower bearing 5. The signal magnetic ring 3 adopts the three-layer structure of this invention, as detailed in the following description. Figure 3 The metal ring 6-1 is first injection molded into the plastic part 6-2, and then the magnetic material 6-3 is injection molded into the outer circumference of the plastic part 6-2 to form an inseparable whole with metal-plastic-magnetic material arranged in sequence.

[0016] Figure 2 The prior art features a two-layer structure: injection-molded magnetic material 3-1 is directly bonded to the metal ring 3-2, without an intermediate buffer layer. (Comparison) Figure 3 As can be seen, with the plastic part 6-2 as a barrier, the metal ring and the injection-molded magnetic material no longer come into direct contact, thereby cutting off the stress transmission path caused by thermal expansion mismatch.

[0017] Because the coefficient of thermal expansion of the plastic part 6-2 is between that of metal and injection-molded magnetic materials, and its elastic modulus is relatively low, the plastic layer can undergo slight elastic deformation when the ambient temperature changes drastically. This absorbs the tensile and compressive stresses caused by the difference in expansion between the metal ring and the magnetic material, preventing the stress from being directly transferred to the brittle magnetic material. This avoids the initiation and propagation of cracks, achieving a "thermal shock resistance" effect. At the same time, the plastic part covers the microscopic defects on the surface of the metal ring, eliminating local stress concentration points and improving the structural integrity under thermal cycling.

[0018] The signal magnetic ring 3 is press-fitted to the motor shaft 1 through the inner hole of the metal ring 6-1. After pressing, it is located between the upper bearing 2 and the rotor 4. The magnetic poles on its outer surface are opposite to the Hall element on the stator, realizing the rotor position detection function. The entire rotor assembly does not require changes to the existing motor dimension chain and assembly process. It can directly replace the original two-layer structure signal magnetic ring, solve the problem of magnetic material cracking, and improve motor reliability.

[0019] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A temperature-resistant three-layer structure for a brushless motor signal magnetic ring, characterized in that, include: Metal ring (6-1) is used to provide mechanical support and to fix it to the motor shaft; The plastic part (6-2) is integrally formed with the metal ring (6-1) by injection molding and serves as a buffer layer; Injection-molded magnetic material (6-3) is bonded to the plastic part (6-2) through secondary injection molding to form magnetic poles; The plastic part (6-2) is located between the metal ring (6-1) and the injection-molded magnetic material (6-3) to alleviate the stress caused by the difference in thermal expansion between the two and prevent the injection-molded magnetic material from cracking.

2. The three-layer structure of the temperature-resistant brushless motor signal magnetic ring according to claim 1, characterized in that, The axial thickness of the plastic part (6-2) is 0.3 mm to 2 mm, and the difference in thermal expansion coefficient between the selected plastic part and the injection-molded magnetic material is ≤30×10⁻. 6 Thermoplastics at / ℃.

3. The three-layer structure of the temperature-resistant brushless motor signal magnetic ring according to claim 1 or 2, characterized in that, The outer circumference of the metal ring (6-1) is provided with knurling or annular grooves to increase the bonding strength with the plastic part (6-2).

4. The three-layer structure of the temperature-resistant brushless motor signal magnetic ring according to claim 1, characterized in that, The outer surface of the injection-molded magnetic material (6-3) is evenly distributed with alternating N and S poles, and the number of magnetic poles matches the number of pole pairs of the motor.

5. The three-layer structure of the temperature-resistant brushless motor signal magnetic ring according to claim 1, characterized in that, The metal ring (6-1), plastic part (6-2), and injection-molded magnetic material (6-3) are formed by two injection molding processes. First, the metal ring and plastic part are coated with glue, and then the plastic part and magnetic material are coated with glue again in the same mold to form an integrated signal magnetic ring.

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