Rotor structure of fan and manufacturing method thereof

A rotor structure of a fan includes a bushing, a hub, a shaft and a plurality of blades. The hub has a top portion and a sidewall, and the top portion of the hub covers the bushing. The hub and the bushing are made by the same material. One end of the shaft is connected to the bushing, and the shaft is disposed inside the top portion. The blades are disposed on the outer side of the sidewall of the hub. A manufacturing method of the rotor structure is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 201310398834.8 filed in People's Republic of China on Sep. 4, 2013, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of Invention

The invention relates to a fan and a manufacturing method thereof and, in particular, to a rotor structure of a fan and a manufacturing method thereof.

Related Art

A rotor is commonly applied to a fan by a rivet bushing method.FIG. 1Ais a schematic sectional diagram of a conventional rotor structure, andFIG. 1Bis a flow chart of a manufacturing method of the conventional rotor structure. As shown inFIGS. 1A and 1B, the conventional rotor structure1includes a shaft11, a magnetically permeable shell12and a copper bushing13. The conventional manufacturing method includes the step S10in which the shaft11and the copper bushing13are connected to each other by interference fit, and thereby the shaft11is provided with the copper bushing13. The step S10also can be called a copper rivet process. Then, the shaft11is riveted to the magnetically permeable shell12through the copper bushing13(step S12), and in other words, the copper bushing13connected to the shaft11is riveted to the magnetically permeable shell12in this step. Finally, a hub14and a plurality of blades15are formed on the outer side of the magnetically permeable shell12by injection molding (step S14), and the blades15are disposed on the periphery of the hub14.

However, in the step S12of the manufacturing method of the conventional rotor1structure, the copper bushing13needs to be compressed to connect to the magnetically permeable shell12. Therefore, the structural strength and the resistance to shock of the conventional rotor structure1are limited in a certain degree. Especially in the case of the heavier conventional rotor1bearing larger inertial force during the motion of rotation, thus the structural strength will be overloaded. Therefore, the rivet portion of the conventional rotor1may be broken or loosed so that the shaft11separates from the magnetically permeable shell12, resulting in the dangerous situation in usage.

Besides, the copper bushing13has a larger weight and the production cost thereof is also relative higher. Furthermore, when the magnetically permeable shell12is riveted to the shaft11through the copper bushing13, a precise fit for the magnetically permeable shell12and the copper bushing13is required. In addition, the assembly error and insufficient connection strength may be caused by the fit condition of the jig and copper bushing13during the rivet process (S12).

Therefore, it is an important subject to provide a rotor structure of a fan and a manufacturing method thereof in which the copper bushing and the rivet process for the shaft and copper bushing are omitted so that the manufacturing process is simplified and the structural strength of the rotor structure is increased.

SUMMARY OF THE INVENTION

In view of the foregoing subject, an objective of the invention is to provide a rotor structure of a fan and a manufacturing method thereof in which the copper bushing and the rivet process for the shaft and copper bushing are omitted so that the manufacturing process is simplified and the structural strength of the rotor structure is increased.

To achieve the above objective, a rotor structure of a fan according to the invention includes a bushing, a hub, a shaft and a plurality of blades. The hub has a top portion and a sidewall, and the top portion of the hub covers the bushing. The hub and the bushing are made by the same material. One end of the shaft is connected to the bushing, and the shaft is disposed inside the top portion. The blades are disposed on the outer side of the sidewall of the hub.

In one embodiment, the end of the shaft includes a first connection portion connected to the bushing.

In one embodiment, the bushing is exposed from the top portion of the hub.

In one embodiment, the bushing includes at least two opposite second connection portions.

In one embodiment, the second connection portions are disposed at the edges of the bushing symmetrically.

In one embodiment, the second connection portions are disposed at the edges of the bushing asymmetrically.

In one embodiment, the bushing includes a main body and an extension extending from the main body along the shaft.

In one embodiment, the rotor structure further comprises a magnetically permeable shell disposed inside the sidewall of the hub.

To achieve the above objective, a manufacturing method of a rotor structure of a fan according to the invention comprises steps of: providing a shaft; forming a bushing on one end of the shaft by injection molding; and forming a hub on the bushing and a plurality of blades on the periphery of the hub by injection molding, wherein the hub has a top portion and a sidewall, the top portion covers the bushing, and the hub and the bushing are made by the same material.

In one embodiment, the step of forming the bushing on the end of the shaft by injection molding further comprises steps of: embossing the end to form a first connection portion, and forming the bushing on the first connection portion by injection molding.

In one embodiment, the step of forming the bushing on the end of the shaft by injection molding further comprises a step of: solidifying the bushing.

In one embodiment, the bushing is exposed from the top portion of the hub.

In one embodiment, the step of forming the bushing on the end of the shaft by injection molding further comprises a step of: forming at least two opposite second connection portions.

In one embodiment, the second connection portions are disposed at the edges of the bushing symmetrically.

In one embodiment, the second connection portions are disposed at the edges of the bushing asymmetrically.

In, one embodiment, the bushing includes a main body and an extension extending from the main body along the shaft.

In one embodiment, the step of forming the hub on the bushing and the blades by injection molding further comprises a step of: covering a magnetically permeable shell inside the sidewall of the hub.

As mentioned above, in the rotor structure of a fan and the manufacturing method thereof according to the invention, the bushing is first formed on the shaft by injection molding, and then the hub and the blades are formed on the bushing by injection molding, and the top portion of the hub covers the bushing. This two-steps injection molding process can leave out the conventional rivet step for the shaft and copper bushing, so the process can be simplified and the metal material (for the copper bushing) can be further saved in the invention. Therefore, the cost of the process and the production is reduced in the invention. Besides, the effect of even or same material distribution can be achieved in the invention by using the two-steps injection molding process, and the strength of the rotor structure can be thus enhanced. In detail, by using the same material to form the hub and bushing, the connection between the hub and shaft can be strengthened, and the strength of the rotor structure can be thus enhanced.

Besides, the end of the shaft includes the first connection portion that is formed by embossing processing. The first connection portion is a rugged structure that can strengthen the connection between the bushing and the shaft, so that the whole strength of the rotor structure is enhanced. Furthermore, the bushing includes at least two opposite second connection portions so as to increase the torsional resistance of the rotor structure during the rotation. The second connection portions can be disposed on the opposite edges of the bushing symmetrically, or can be disposed on the upper and lower edges respectively and asymmetrically. Especially, the said asymmetrical structure can increase the pulling-resistant force of the bushing to the mold so as to advantage the mold stripping procedure after forming the bushing.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2Ais a schematic diagram of a rotor structure according to an embodiment of the invention, andFIG. 2Bis a sectional diagram of the rotor structure inFIG. 2A. As shown inFIGS. 2A and 2B, a rotor structure2of a fan includes a hub21, a bushing22, a shaft23and a plurality of blades24. The hub21includes a top portion211and at least a sidewall212. The bushing22is connected to the top portion211of the hub21. The top portion211of the hub21covers the bushing22in this embodiment, and the bushing22is disposed inside and fixed to the top portion211. The hub21and the bushing22are made by the same material. One end231of the shaft23is connected to the bushing22. The shaft23is disposed inside the top portion211. The blades24are disposed on the periphery of outer surface of the sidewall212of the hub21.

The manufacturing method of the rotor structure2is illustrated as below in cooperation with the related figures.FIG. 3is a flowchart of a manufacturing method of a rotor structure according to an embodiment of the invention. As shown inFIGS. 2A, 2B and 3, the manufacturing method of the rotor structure2includes the steps of: providing a shaft (step S20); forming a bushing on one end of the shaft by injection molding (step S30); and forming a hub on the bushing and a plurality of blades on the periphery of the hub by injection molding, wherein the hub has a top portion and a sidewall, the top portion covers the bushing, and the hub and the bushing are made by the same material (step S40). In the steps S20and S30, a shaft23is provided, and a bushing22is formed on the end231of the shaft23by injection molding. In detail, the shaft23is positioned in the mold (not shown) that is designed according to the form of the bushing22, and then the injection molding process (or called the process of wrapping by injection) is performed after the mold is closed, so the bushing22is formed on the end231of the shaft23.

FIG. 4is a schematic diagram of the connection between the bushing and shaft inFIG. 2A. As shown inFIGS. 2B and 4, the bushing22preferably includes a main body222and at least two opposite second connection portions221extending from the main body222. In this embodiment, the bushing22includes two second connection portions221, and they are disposed at the opposite edges of the bushing22symmetrically. In detail, the said symmetrical disposition means the two second connection portions221are disposed on the opposite sides of the main body222of the bushing22. By disposing the second connection portions221at the edges of the bushing22in this embodiment, the torsional resistance of the rotor structure during the motion of rotation can be enhanced.FIG. 5is a flowchart of a manufacturing method of a rotor structure according to another embodiment of the invention. As shown inFIGS. 2B, 4 and 5, the step S30can further includes a step S32for forming at least two opposite second connection portions221on the bushing22. Since the second connection portions221are clearly illustrated as above, the description thereof is omitted here for conciseness.

Otherwise, the two second connection portions221can also be disposed at the opposite edges of the bushing22asymmetrically (not shown), as a more favorable case. As an embodiment, the said asymmetrical disposition means the two second connection portions221are disposed at the upper and lower edges of the bushing22, respectively, to form an asymmetrical structure. In this embodiment, the two connection portions221asymmetrical are protrusions respectively disposed on the upper and lower edges of the bushing22oppositely, and the width of the second connection portion221protruding from the main body222is one sixteenth ( 1/16) of the radial length of the main body222as a favorable case. To be noted, the form of the second connection portion221is not limited in this invention, and it can have a concave form for example. Such kind of asymmetrical structure is more favorable for the mold stripping procedure of the injection molding process, in which the pulling-resistant force of the bushing22to the mold is increased due to the asymmetrical structure.

Favorably, a pre-process can be conducted to the shaft23before the step S30. As shown inFIGS. 2B and 5, before forming the bushing22on the end231of the shaft23by injection molding (step S30), the manufacturing method can further include a step S22, which is to emboss the end231of the shaft23to form a first connection portion232of the shaft23and then to form the bushing22on the first connection portion232by injection molding. In other words, the end231of the shaft23includes the first connection portion232, and the first connection portion232is a rugged structure formed by the emboss processing for example. In detail, in the emboss processing, an acid/alkali-resistant printing ink is applied to a pre-determined position of the end231of the shaft23in order to preserve the embossment, and then a little sulfuric acid solution and nitric acid solution containing cupric sulphate and iron(II) chloride as the metal corrosion solution is used to eat the unprotected portion to form the first connection portion232. Then, in the step S30(or the later section of the step S22), the bushing22is formed on the first connection portion232as well as the end231of the shaft23by injection molding to make the first connection portion232and the bushing22become a firmly-connected body. The first connection portion232can strengthen the connection between the bushing22and the shaft23, and the strength of the rotor structure2is thus increased.

In addition to the main body222, the bushing22can further include an extension223as shown inFIGS. 2B and 4. In this case, the extension223extends from the main body222along the axial direction of the shaft23to cover the whole embossment of the first connection portion232so that the connection between the bushing22and shaft23can be further strengthened. To be noted, by the specific design of the mold, the main body222and the extension223of the bushing22can be formed on the end231of the shaft23at the same time during the injection molding process.

In the step S40as shown inFIG. 3 or 5, the hub21and the blades24are formed on the bushing22by injection molding, and the blades24are disposed on the periphery of outer surface of the hub21, i.e. the periphery of outer surface of the sidewall212. In detail, the bushing22is positioned in the mold having the form according to the hub21and the blades24, and then the hub21and the blades24are formed on the bushing22by injection molding. The top portion211of the hub21covers the bushing22, which means the bushing22is disposed inside the top portion211and fixed to a predetermined position of the top portion211. In this embodiment, the main body222of the bushing22is completely contained by the top portion211of the hub21, so that the bushing22is not exposed to the outer surface of the top portion211for keeping the hub21a good appearance. Besides, in the steps S30and S40, the hub21and the bushing22are formed by using the same material in the two-steps injection molding processes. Preferably, the said material is a plastic material.

In the invention, the two-steps injection molding process is disclosed to form the bushing22on the shaft23first and then the hub21on the bushing22, and thereby the conventional rivet process for the shaft and bushing can be omitted and also the metal material (for the conventional copper bushing) can be saved, so the cost of the production and process can be reduced. Besides, in the conventional art, the hub is formed on the periphery of the magnetically permeable shell (riveted to the copper bushing) by injection molding (referring to the conventional step S14inFIG. 1B), however, this kind of one-step injection molding process often causes the problem of uneven material distribution, so the strength of the connection between the hub and shaft is decreased, and the strength of the whole rotor structure is thus deteriorated. By contrast, the even material distribution is achieved in the invention by using the two-steps injection molding process. Therefore, in the invention, the connections among the hub21, bushing22and shaft23are both strengthened more, in contrast to the prior art. In other words, by forming the hub21and the bushing22with the same material, the connection between the hub21and shaft23is strengthened, so that the torsion of the rotor structure2is maintained or even enhanced. Below is a torsion testing result between the rotor structure of the prior art and the rotor structure2of the invention with the same specifications. The rotor structure2of this embodiment has a radius of 12.5 mm, which means the distance from the sidewall212to the center of the shaft23is 12.5 mm. From the result of the testing, the maximum torsion of the conventional rotor structure is between 7.6 and 8.0 (kg-cm), but the maximum torsion of the rotor structure2of this embodiment can reach between 13.7 and 14.2 (kg-cm), which is more than double in quantity. Therefore, it is obvious that the rotor structure2of the invention can bear more torsion. In the case of the tensile testing result, the tensile that the rotor structure can bear generally must be greater than 20 kg/min. The tensile that the rotor structure of the prior art can bear is 25˜26 kg/min, and the tensile the rotor structure2of this embodiment can bear is up to 29˜30 kg/min, so the strength of the rotor structure2is obviously greater than the conventional rotor structure.

Favorably, as shown inFIGS. 2B and 5, after the step S30forming the bushing22on the end231of the shaft23by injection molding, the manufacturing method can further include a step S34, which is to solidify the bushing22. In detail, after the step S30for forming the bushing22by injection molding, the step S40forming the hub21and the blades24on the bushing22by injection molding can't be conducted until the step S34therebetween solidifying the bushing22is completed.

As shown inFIG. 2B, the rotor structure2can further include a magnetically permeable shell25, which is disposed inside the sidewall212of the hub21. In the manufacturing process, when the hub21and blades24are formed on the bushing22by injection molding (step S40), a magnetically permeable shell25can be covered inside the sidewall212of the hub21(step S42). In detail, the magnetically permeable shell25and the bushing22can be both positioned in the mold that is designed according to the form or shape of the hub21and blades24, and then the injection molding is conducted to form the hub21with the sidewall212covering the magnetically permeable shell25. Furthermore, the rotor structure2can further include a magnetic element26(referring toFIG. 2B), which is further disposed on the inner side of the formed magnetically permeable shell25. In detail, as shown inFIG. 2B, the magnetically permeable shell25is disposed on the inner side of the sidewall212of the hub21, and the magnetic element26is further disposed on the inner side of the formed magnetically permeable shell25. The magnetic element26can be also positioned in the mold, just like the magnetically permeable shell25and the bushing22, and then the injection molding is conducted. Since the related features are clearly illustrated as above, they are not described here for conciseness.

As shown inFIGS. 2A and 2B, the top portion211of the hub21can further include a plurality of balance holes27, which can be filled with some objects, such as balance weighting blocks, so as to make the rotation of the rotor structure2more balanced by adding additional weight on the hub21properly.

Other illustrative embodiments are shown inFIGS. 6A and 6B.FIG. 6Ais a schematic diagram of a rotor structure according to another embodiment of the invention, andFIG. 6Bis a sectional diagram of the rotor structure inFIG. 6A. A bushing22aof a rotor structure2aas shown inFIGS. 6A and 6B, which is similar to the bushing22of the rotor structure2aas shown inFIGS. 2A and 2Bof the above-mentioned embodiments. The bushing22aof this embodiment can be disposed in and fixed to a top portion211aof a hub21aof the rotor structure2a, and can be exposed from the top portion211aof the hub21a. In detail, in the step, which similar to step S30as shown inFIG. 3 or 5, forming the bushing22aon an end231aof a shaft23aof the rotor structure2aby injection molding (may referring to the step ofFIG. 3 or 5), a main body222aof the bushing22acan be formed as a larger or longer one by design of the mold. In the step, which similar to step S40as shown inFIG. 3 or 5, forming the hub21aon the busing22aby injection molding, the main body222aof the bushing22ais positioned in the mold so that the surface of the main body222aaway from the shaft23acontacts the mold, and then the injection molding is conducted to form the embodiment wherein the bushing22ais exposed from the top portion211aof the hub21a, as a feature of this embodiment.

In summary, in the rotor structure of a fan and the manufacturing method thereof according to the invention, the bushing is first formed on the shaft by injection molding, and then the hub and the blades are formed on the bushing by injection molding, and the top portion of the hub covers the bushing. This kind of two-steps injection molding process can leave out the conventional rivet step for the shaft and copper bushing, so the process can be simplified and the metal material (for the copper bushing) can be saved in the invention. Therefore, the cost of the process and production is reduced in the invention. Besides, the effect of even material distribution can be achieved in the invention by using the two-steps injection molding process, and the strength of the rotor structure can be thus enhanced. In detail, by using the same material to form the hub and bushing, all of the connections between the hub and shaft can be indirectly strengthened, and the strength of the rotor structure can be thus enhanced.

Besides, the end of the shaft includes the first connection portion that is formed by embossing processing. The first connection portion is a rugged structure that can strengthen the connection between the bushing and the shaft, so that the whole strength of the rotor structure is enhanced. Furthermore, the bushing includes at least two opposite second connection portions so as to increase the torsional resistance of the rotor structure during the rotation. The second connection portions can be disposed on opposite sides of the bushing symmetrically, or can be disposed on the upper and lower edges respectively and asymmetrically. Especially, the said asymmetrical structure can increase the pulling-resistant force of the bushing to the mold so as to advantage the mold stripping procedure after forming the bushing.