Series fan

Abstract

The present application provides a series fan to solve the problem of easy overheat of the circuit board of the existing series fan. It comprises two frame bodies, each having a ring frame, an assembly seat located in the ring frame and adjacent to one end of the ring frame, a plurality of connecting bodies connecting the ring frame and the assembly seat, the two frame bodies being connected in series in the axial direction with the end having the assembly seat, two stators assembled in the two frame bodies, the two stators each having a circuit board, the two circuit boards being located in the two assembly seats and arranged in opposite directions, and two fan wheels rotatably arranged in the two frame bodies, wherein the space accommodating the two circuit boards and the space accommodating the two fan wheels are connected by a communication part located between the two assembly seats.

Description

Technical Field

[0001] This invention relates to a cooling fan, and more particularly to a fan with two sets of fan wheels connected in series. Background Technology

[0002] Currently, for electronic products with high heat dissipation requirements, using ordinary cooling fans will result in insufficient heat dissipation efficiency. Therefore, it is necessary to use a series fan with two sets of fan wheels to increase airflow and air pressure, thereby enhancing the heat dissipation effect.

[0003] Existing series fans have an upper frame and a lower frame connected axially in series. Each of the upper and lower frames has a base near an opening at one end. A shaft tube protrudes from the base and is located inside the upper or lower frame. A winding assembly and a circuit board are attached to the shaft tube. When the upper and lower frames are connected, the two bases abut against each other, and the two bases are located between the two circuit boards. Therefore, holes for the shaft tube to pass through are required on the two circuit boards, which severely restricts the wiring space on the two circuit boards. An embodiment similar to this existing series fan has been disclosed in Taiwan Patent Publication No. I610027.

[0004] Therefore, please refer to Figure 1 Another existing series fan 9 has an upper frame 91 and a lower frame 92 that are both provided with a ring wall 94 protruding from the bottom of their base 93, and a circuit board 95 is housed in the space enclosed by the ring wall 94. In addition, a wire W passes through the base 93 and is electrically connected to the circuit board 95 and the winding assembly. In this way, the circuit board 95 of the series fan 9 no longer needs to be provided with a hole for the shaft tube to pass through, so that the circuit board 95 can have a larger wiring space.

[0005] However, in the existing series fan 9, when the upper frame 91 and the lower frame 92 are connected, the ring wall 94 of the upper frame 91 will abut against the ring wall 94 of the lower frame 92, making the two circuit boards 95 appear to be enclosed in a nearly closed space. On the other hand, as the performance requirements of the fan increase, the overall power consumption of the series fan 9 also increases. Therefore, when the series fan 9 is operating, the temperature rise of the circuit components on the two circuit boards 95 will also intensify. The nearly closed space will generate heat accumulation problems, causing the temperature of the circuit components on the two circuit boards 95 to be too high, resulting in excessive circuit loss, reduced fan performance, and even exceeding the upper limit of the temperature resistance specification.

[0006] Therefore, existing series fans do indeed need to be improved. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a series fan that, without requiring holes in the circuit board for the shaft tube to pass through, effectively enhances air convection around the circuit board, thereby facilitating heat dissipation of the circuit components on the circuit board.

[0008] A further object of the present invention is to provide a series fan that is easy to manufacture and assemble.

[0009] Another object of the present invention is to provide a series fan that can reduce production costs.

[0010] The directions or similar terms used throughout this invention, such as "front," "back," "left," "right," "top," "bottom," "inner," "outer," and "side," are used primarily with reference to the directions in the accompanying drawings unless otherwise specified. These directions or similar terms are only used to assist in explaining and understanding the various embodiments of this invention and are not intended to limit the invention.

[0011] The use of the quantifiers “a” or “an” for the elements and components described throughout this invention is for convenience and to provide the general meaning of the scope of the invention; in this invention, it should be interpreted as including one or at least one, and a single concept also includes multiple cases, unless it clearly means otherwise.

[0012] The terms "combination," "integration," or "assembly" used throughout this invention mainly refer to forms such as those that can be separated without damaging the components after connection, or those that make the components inseparable after connection. These are choices that those skilled in the art can make based on the material of the components to be connected or the assembly requirements.

[0013] The tandem fan of the present invention includes: two frames, each having a ring frame, an assembly base located within the ring frame and adjacent to one end of the ring frame, a plurality of connectors connecting the ring frame and the assembly base, the two frames being axially connected in series at the ends having the assembly bases; two stators respectively assembled in the two frames, each stator having a circuit board, the two circuit boards being located in the two assembly bases and facing each other; and two fan wheels rotatably disposed in the two frames; wherein the space accommodating the two circuit boards and the space accommodating the two fan wheels are connected by a connecting portion located between the two assembly bases.

[0014] Therefore, the series fan of the present invention, through the connecting part, prevents the two circuit boards from being placed in a nearly enclosed space. Thus, even if the two circuit boards cause a temperature rise in the two first spaces, the relatively high-temperature airflow can still flow out of the two first spaces through the connecting part, thereby being guided to the outside. This effectively prevents heat accumulation in the two first spaces, enhances air convection around the two circuit boards, and facilitates heat dissipation of the circuit components on the two circuit boards. This allows the circuit components on both circuit boards to operate at appropriate ambient temperatures, avoiding excessive loop losses and maintaining normal fan performance, thus improving product reliability. Furthermore, the present invention avoids designs where the circuit boards operate in high-heat environments, allowing for the selection of lower-cost circuit board designs or circuit components, thereby reducing the production cost of the series fan.

[0015] Each of the two assembly bases may have a sidewall protruding from the outer surface of a chassis, and a connecting portion may be formed between the two facing but not abutting end edges of the two sidewalls. The two circuit boards may be located within the two sidewalls respectively. In this way, the connecting portion can be formed with a simple structure, and the multiple connectors can connect the sidewalls and / or chassis of the assembly base for greater stability, which improves the manufacturing convenience and quality of the two frames.

[0016] The sidewall protrudes from the chassis at a height greater than the axial distance from the outer surface of one substrate of the circuit board to the chassis. In this way, the circuit board is almost always located within the sidewall, which protects it and makes it less susceptible to impact during handling or assembly, thus reducing the circuit board damage rate.

[0017] The sidewall protrudes from the chassis at a height equal to the axial distance from the outer surface of one substrate of the circuit board to the chassis. In this way, in addition to protecting the circuit board, the sidewall further expands the range of the connecting portion, giving the series fan a better heat-avoidance effect.

[0018] The height of the sidewall protruding from the chassis can be less than or equal to the axial distance from the inner surface of one substrate of the circuit board to the chassis. In this way, the substrate of the circuit board can protrude outward from the sidewall, allowing the circuit board to have a larger volume within the connecting portion, thus improving the heat dissipation efficiency of the circuit board.

[0019] The inner surface of the substrate can abut against the edge of the sidewall. In this way, the sidewall can assist in positioning the circuit board, thereby improving the assembly stability and accuracy of the circuit board.

[0020] The axial distance between the end edges of the two side walls can be greater than or equal to the thickness of the chassis. This allows the tandem fan to effectively prevent heat buildup.

[0021] Each of the two mounting bases may have a chassis, and the two circuit boards may be located between the two chassis. The chassis does not have a structure surrounding the circuit board, and a connecting portion may be formed between the two chassis. In this way, the series fan can have a larger connecting portion, and the airflow between the circuit board and the chassis will be easier to flow outward, further improving the heat dissipation efficiency of the circuit board.

[0022] Each of the two assembly bases may have a chassis. The two ring frames or the plurality of connecting bodies may abut against each other and form a joint centerline. The outer surfaces of the two chassis may face each other but not abut against each other. Each frame may form a first space between the outer surface of the chassis and the joint centerline. A second space may be formed within the ring frame between the inner surface of the chassis and the opening at the other end. The circuit board may be located in the first space, and the fan wheel may be located in the second space. The two first spaces may face each other and be connected. Thus, the structure of the two assembly bases is simple, which improves the ease of manufacturing and assembly of the two frames.

[0023] Each assembly base may have multiple support pillars protruding from the outer surface of the chassis, and these support pillars may be attached to a substrate of the circuit board. In this way, the multiple support pillars can assist in positioning the circuit board, so that the circuit board can be stably placed in a predetermined position in the first space, and improve the air convection rate on both sides of the circuit board, making the operating temperature of the circuit board less likely to be too high. This has the effects of improving the assembly efficiency, assembly convenience and reliability of the circuit board.

[0024] The circuit board includes a substrate, with multiple circuit components located on at least one side of the substrate. The circuit board may have at least one heat dissipation hole penetrating the substrate. This improves the air convection rate on both sides of the circuit board, thereby enhancing its heat dissipation efficiency. Attached Figure Description

[0025] Figure 1 : A cross-sectional view of an existing series fan assembly;

[0026] Figure 2 : An exploded perspective view of the first embodiment of the present invention;

[0027] Figure 3 : A partially exploded perspective view of the first embodiment of the present invention;

[0028] Figure 4 : A combined cross-sectional view of the first embodiment of the present invention;

[0029] Figure 5 : Figure 4 Enlarged view of area A;

[0030] Figure 6 : A partial cross-sectional view of the second embodiment of the present invention;

[0031] Figure 7 Partial cross-sectional view of the third embodiment of the present invention;

[0032] Figure 8 : A partially exploded perspective view of the fourth embodiment of the present invention;

[0033] Figure 9 : A partial combined cross-sectional view of the fourth embodiment of the present invention.

[0034] Explanation of reference numerals in the attached figures

[0035] [This Invention]

[0036] 1: Frame

[0037] 11: Frame

[0038] 12: Assembly base

[0039] 121: Chassis

[0040] 121a: Inner surface

[0041] 121b: Outer surface

[0042] 122: Shaft hole

[0043] 123: piercing

[0044] 124: Side wall

[0045] 125: Pillar

[0046] 13: Connector

[0047] 14: Shaft tube

[0048] 2: Stator

[0049] 21: Circuit Board

[0050] 211:Substrate

[0051] 212: Circuit elements

[0052] 213: Heat dissipation holes

[0053] 22: Foot Connection

[0054] 3: Fan wheel

[0055] C: Connecting part

[0056] D1, D2, D3, D4: Axial distance

[0057] E: End edge

[0058] F1: Outer surface

[0059] F2: Inner surface

[0060] H: Height

[0061] K: Opening

[0062] M: Combined with the center line

[0063] U: Shoulder

[0064] S1: First Space

[0065] S2: Second Space

[0066] T: Thickness

[0067] W: Conductor

[0068] [Existing Technology]

[0069] 9: Series Fan

[0070] 91: Top frame

[0071] 92: Bottom frame

[0072] 93: Base

[0073] 94: Surrounding Wall

[0074] 95: Circuit Board

[0075] W: Conductor. Detailed Implementation

[0076] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments of the present invention are described below in conjunction with the accompanying drawings; in addition, those symbols that are marked with the same symbols in different drawings are considered to be the same and their descriptions will be omitted.

[0077] Please refer to Figure 2 , Figure 4 As shown, it is the first embodiment of the series fan of the present invention, which includes two frames 1, two stators 2 and two fan wheels 3. The two frames 1 are connected in series axially, and each frame 1 has one of the aforementioned stators 2 and fan wheels 3.

[0078] The two frames 1 in this embodiment can have generally similar structures, wherein each frame 1 has a ring frame 11, and an assembly seat 12 is located inside the ring frame 11 and adjacent to one end of the ring frame 11. The two frames 1 are axially connected in series at the end with the assembly seat 12. The assembly seat 12 is connected to the ring frame 11 by a plurality of connectors 13; for example, but not limited to, the connectors 13 may be, for example, stator vanes with a flow guiding function. Each frame 1 also has a shaft tube 14, which protrudes from the assembly seat 12 and is located inside the ring frame 11. However, the two frames 1 are not limited to the form disclosed in the drawings of this embodiment, and the way they are combined is not limited. For example, snap-fit, locking, fitting, fastening, or gluing can all be implemented and achieve the purpose of combination, which can be adjusted by those skilled in the art according to the needs of use.

[0079] Please refer to Figure 3 , Figure 5 As shown in detail, the assembly base 12 may have a chassis 121, which has an inner surface 121a and an outer surface 121b facing each other. The inner surface 121a of the chassis 121 faces the interior of the ring frame 11. When the two frames 1 are axially connected in series, the two ring frames 11 or the plurality of connecting bodies 13 can abut against each other and form a joint centerline M. The outer surfaces 121b of the two chassis 121 face each other but do not abut against each other. In this way, each frame 1 can form a first space S1 between the outer surface 121b of the chassis 121 and the joint centerline M. In addition, a second space S2 is formed inside the ring frame 11 between the inner surface 121a of the chassis 121 and the opening K at the other end (please refer to the reference). Figure 4 The first space S1 and the second space S2 can respectively accommodate different components of the stator 2 (described in detail later). Furthermore, the center of the chassis 121 may have a shaft hole 122, and the outer periphery of the shaft hole 122 may have at least one through hole 123.

[0080] Furthermore, the assembly base 12 of this embodiment may also have a side wall 124, which protrudes from the outer surface 121b of the chassis 121 and is generally annular. The shaft hole 122 and the through hole 123 are both located within the area enclosed by the side wall 124. The connector 13 can be connected to the chassis 121 and / or the side wall 124, and the shaft tube 14 is located on the opposite side of the side wall 124. That is, the shaft tube 14 can be combined with the shaft hole 122 to protrude from the inner surface 121a of the chassis 121, or it can be integrally formed and connected to the chassis 121. When the two frames 1 are axially connected in series, the two first spaces S1 face each other and are connected, but the two side walls 124 do not abut each other. The axial distance D1 from the facing end edges E of the two side walls 124 to the connection centerline M can be the same or different, and the present invention does not limit this. Furthermore, although the side wall 124 is presented as a continuous ring structure in the accompanying drawings of this embodiment, in other embodiments, the side wall 124 may also be composed of a plurality of spaced-apart wall pieces arranged in a ring, or other similar structures; that is, the present invention does not limit the side wall 124 to necessarily being a continuous ring structure.

[0081] Please refer to Figure 3 , Figure 4 As shown, the two stators 2 are respectively assembled within the two frames 1; each stator 2 has a circuit board 21 located in the first space S1. The circuit board 21 has a substrate 211, and the circuit board 21 has multiple circuit elements 212 located on at least one side of the substrate 211. In this embodiment, multiple circuit elements 212 are located on each side of the circuit board 21, but this is not a limitation. To improve the air convection rate on both sides of the circuit board 21 in the first space S1, the circuit board 21 may also be provided with at least one heat dissipation hole 213 penetrating the substrate 211. Each stator 2 also has an external winding assembly (not shown in the figure), which is located in the second space S2. The winding assembly can be connected to the shaft tube 14 and can have multiple pins 22 that pass through the through holes 123 of the chassis 121 and protrude beyond the outer surface 121b, so as to electrically connect the multiple pins 22 to the circuit board 21 located in the first space S1; wherein, the wires W of the winding assembly can be electrically connected to the multiple pins 22 to electrically connect to the circuit board 21 located in the first space S1.

[0082] Please refer to Figure 3 , Figure 5As shown, in this embodiment, the circuit board 21 can be directly or indirectly mounted on the assembly base 12, for example, mounted on a shoulder U of the side wall 124; or mounted on multiple protrusions protruding inward from the side wall 124; or directly positioned in a predetermined position in the first space S1 using the multiple pins 22; or an insulating sleeve is provided over the multiple pins 22 for the circuit board 21 to abut and be positioned; or two or more of the aforementioned structures are used simultaneously, etc., and the present invention is not limited thereto. Furthermore, when the two frames 1 are axially connected in series, the two circuit boards 21 are arranged facing each other.

[0083] Please refer to again Figure 2 , Figure 4 As shown, the two fan wheels 3 are rotatably disposed within the two frames 1. More specifically, the two fan wheels 3 can be assembled into the shaft tubes 14 of the two frames 1 respectively. After the winding assemblies of the two stators 2 are energized, the two fan wheels 3 can be driven to rotate in the two second spaces S2 respectively, guiding airflow from one frame 1 into the other frame 1 and out of the other frame 1. The connection relationship and operating principle of the stators 2 and fan wheels 3 in each frame 1 are understandable to those skilled in the art, and therefore will not be described in detail here.

[0084] Please refer to Figure 5 As shown, the first space S1 accommodating the two circuit boards 21 and the second space S2 accommodating the two fan wheels 3 are connected by a connecting portion C located between the two mounting bases 12. In this embodiment, the connecting portion C can be formed between the two opposing but non-abutting end edges E of the two side walls 124; in other words, the axial distance D2 between the two end edges E is the width of the connecting portion C. Thus, when the series fan of this embodiment is operating, even if the two circuit boards 21 cause the two first spaces S1 to heat up, the relatively high-temperature airflow can flow out of the two first spaces S1 through the connecting portion C, and guided by the two fan wheels 3, flow out from one of the frames 1 to the outside of the series fan, which can effectively prevent heat accumulation in the two first spaces S1, so that the circuit components 212 on the two circuit boards 21 can be maintained at an appropriate ambient temperature.

[0085] Furthermore, in this embodiment, the height H of the sidewall 124 protruding from the chassis 121 can be greater than the axial distance D3 from the outer surface F1 of the substrate 211 of the circuit board 21 to the chassis 121, so that the circuit board 21 can almost always be located within the sidewall 124, making it less likely to be impacted during handling or assembly. In addition, the axial distance D2 between the end edges E of the two sidewalls 124 can be greater than or equal to the thickness T of the chassis 121, so that the series fan in this embodiment can have a better heat-avoidance effect.

[0086] Please refer to Figure 6As shown, this is the second embodiment of the series fan of the present invention. This embodiment is largely the same as the first embodiment described above. In this embodiment, the height H of the side wall 124 protruding from the chassis 121 is approximately equal to the axial distance D3 from the outer surface F1 of the substrate 211 of the circuit board 21 to the chassis 121. In addition to protecting the circuit board 21, it can further expand the connecting portion C, so that the series fan of this embodiment can have a better effect in avoiding heat accumulation.

[0087] It is worth noting that although the accompanying drawings of this embodiment illustrate the positioning of the circuit board 21 in the predetermined position in the first space S1 using the plurality of pins 22, this is not a limitation. In other words, the circuit board 21 in this embodiment can also adopt the same positioning structure as the first embodiment described above, and the positioning structure of the circuit board 21 in each embodiment of the present invention can be arbitrarily replaced or adapted from the forms disclosed in other embodiments, which is understandable to those skilled in the art to which this invention pertains.

[0088] Please refer to Figure 7 As shown, this is the third embodiment of the series fan of the present invention, which is largely the same as the first embodiment described above. In this embodiment, the height H of the sidewall 124 protruding from the chassis 121 can be less than or equal to the axial distance D4 from the inner surface F2 of the substrate 211 of the circuit board 21 to the chassis 121, so that the substrate 211 of the circuit board 21 can protrude outward from the sidewall 124, allowing the circuit board 21 to have a larger volume for alignment in the connecting portion C, thereby improving the heat dissipation efficiency of the circuit board 21. On the other hand, the circuit board 21 of this embodiment can be positioned at a predetermined position in the first space S1 using the plurality of pins 22, and the inner surface F2 of the substrate 211 can also abut against the end edge E of the sidewall 124 for auxiliary positioning, but this is not a limitation.

[0089] Please refer to Figure 8 , Figure 9 As shown, this is the fourth embodiment of the series fan of the present invention; in this embodiment, the mounting base 12 does not have the side wall 124 (marked as...). Figure 3 In this embodiment, the two circuit boards 21 are located between the bases 121 of the two assembly seats 12, meaning that each base 121 does not have an annular structure surrounding the circuit board 21. In other words, the connecting portion C can be formed between the two bases 121 in this embodiment; thus, the connecting portion C can be larger, and the airflow between the circuit board 21 and the base 121 will be easier to flow outward. Therefore, the series fan in this embodiment can have a better effect in avoiding heat accumulation and improve the heat dissipation efficiency of the circuit board 21.

[0090] Furthermore, this embodiment provides another structure for positioning the circuit board 21; that is, the assembly base 12 may have multiple pillars 125 protruding from the outer surface 121b of the chassis 121, and the multiple pillars 125 may penetrate and connect to the circuit board 21, so that the circuit board 21 can be positioned at a predetermined position in the first space S1. It should be noted again that the structure for positioning the circuit board 21 disclosed in this embodiment can also be applied to any of the foregoing embodiments, and the structure for positioning the circuit board 21 disclosed in any of the foregoing embodiments can also be applied to the assembly base 12 of the form disclosed in this embodiment, so it is not limited to the mating form disclosed in the figures of each embodiment.

[0091] To verify the effectiveness of the connecting portion of the series fan of the present invention, therefore, Figure 1 The disclosed form in which the ring wall 94 of the upper frame 91 abuts against the ring wall 94 of the lower frame 92 is the "original design". Figure 6 The disclosed sidewall 124 protrudes from the chassis 121 at a height H approximately equal to the axial distance D3 from the outer surface F1 of the substrate 211 of the circuit board 21 to the chassis 121, which is a "modified design". The other structural conditions are the same. Under the same conditions of an upstream fan speed of 27,000 rpm, a downstream fan speed of 24,000 rpm, and an ambient temperature of 70°C, the operating temperatures of multiple circuit components on the air inlet and outlet side circuit boards were measured, and the results are shown in Table 1 below.

[0092] Table 1. Comparison of Temperature Difference between Original Design and Improved Design

[0093]

[0094]

[0095] As shown in Table 1 above, the improved series-connected fan design results in an average temperature reduction of approximately 5°C for multiple circuit components on its two circuit boards. Furthermore, experiments demonstrate that this invention… Figure 5 The first type of series fan with the assembly base 12 shown, the present invention as follows Figure 6 The second type of series fan with the assembly base 12 shown, the present invention as follows Figure 7 The third type of series fan of the assembly type 12 shown and the present invention as follows Figure 9 The fourth type of series fan in the assembly 12 shown has a cooling effect that is better than the third type of series fan, which is better than the second type of series fan, which is better than the first type of series fan. Furthermore, the higher the power consumption of the series fan of the present invention, the more obvious the temperature drop will be, and the effects on flow field, structure, noise, vibration, and mold flow can still meet the internal design specifications.

[0096] In summary, the series fan of the present invention, by connecting the first space accommodating the two circuit boards and the second space accommodating the two fan wheels through the connecting part, prevents the two circuit boards from being placed in a nearly enclosed space. Thus, even if the two circuit boards cause a temperature rise in the two first spaces, the relatively high-temperature airflow can still flow out of the two first spaces through the connecting part, thereby being guided to the outside. This effectively avoids heat accumulation in the two first spaces, enhances air convection around the two circuit boards, and facilitates heat dissipation of the circuit components on the two circuit boards. This allows the circuit components on both circuit boards to operate at appropriate ambient temperatures, avoids excessive loop losses, and maintains normal fan performance, thereby improving product reliability. Furthermore, the present invention can avoid designs where circuit boards operate in high-heat environments, allowing for the selection of lower-cost circuit board designs or circuit components to reduce the cost of the series fan; or, it can overcome the temperature rise design bottleneck for future demand for higher-performance fans.

[0097] Although the present invention has been disclosed using the above preferred embodiments, it is not intended to limit the present invention. Any modifications and alterations made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention shall still fall within the technical scope protected by the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A series fan, characterized in that, include: Two frames, each having a ring frame, an assembly base located inside the ring frame and adjacent to one end of the ring frame, and multiple connectors connecting the ring frame and the assembly base, the two frames being axially connected in series at the end having the assembly base; Two stators are respectively assembled in the two frames, each stator having a circuit board, and the two circuit boards are respectively located in the two assembly seats and facing each other; and Two fan wheels are rotatably mounted within the two frames, respectively; The space accommodating the two circuit boards and the space accommodating the two fan wheels are connected by a connecting portion located between the two assembly seats; each of the two assembly seats has a sidewall protruding from the outer surface of a chassis, and the connecting portion is formed between the two end edges of the two sidewalls facing each other but not abutting each other, and the height of the sidewall protruding from the chassis is less than or equal to the axial distance from the inner surface of a substrate of the circuit board to the chassis.

2. The series fan as described in claim 1, characterized in that, The inner surface of the substrate abuts against the end edge of the sidewall.

3. The series fan as described in claim 1 or 2, characterized in that, The axial distance between the end edges of the two sidewalls is greater than or equal to the thickness of the chassis.

4. The series fan as described in claim 1, characterized in that, Two ring frames or multiple connecting bodies abut against each other and form a joint centerline. The outer surfaces of the two chassis face each other but do not abut against each other. Each frame forms a first space between the outer surface of the chassis and the joint centerline. A second space is formed inside the ring frame between the inner surface of the chassis and the opening at the other end. The circuit board is located in the first space, and the fan wheel is located in the second space. The two first spaces face each other and are connected.

5. The series fan as described in claim 4, characterized in that, Each assembly has multiple supports protruding from the outer surface of the chassis, which are attached to the substrate of the circuit board.

6. The series fan as described in claim 1, characterized in that, Multiple circuit elements are located on at least one side of the substrate, and the circuit board has at least one heat dissipation hole penetrating the substrate.

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