WO2010081294A1 - 轴流式电子散热风扇 - Google Patents

轴流式电子散热风扇 Download PDF

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Publication number
WO2010081294A1
WO2010081294A1 PCT/CN2009/070147 CN2009070147W WO2010081294A1 WO 2010081294 A1 WO2010081294 A1 WO 2010081294A1 CN 2009070147 W CN2009070147 W CN 2009070147W WO 2010081294 A1 WO2010081294 A1 WO 2010081294A1
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WO
WIPO (PCT)
Prior art keywords
blade
blades
stage
fan
motor
Prior art date
Application number
PCT/CN2009/070147
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English (en)
French (fr)
Inventor
秦彪
Original Assignee
Qin Biao
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Qin Biao filed Critical Qin Biao
Priority to PCT/CN2009/070147 priority Critical patent/WO2010081294A1/zh
Publication of WO2010081294A1 publication Critical patent/WO2010081294A1/zh

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
    • F04D29/325—Rotors specially for elastic fluids for axial flow pumps for axial flow fans
    • F04D29/326—Rotors specially for elastic fluids for axial flow pumps for axial flow fans comprising a rotating shroud
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/02—Units comprising pumps and their driving means
    • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
    • F04D25/0606—Units comprising pumps and their driving means the pump being electrically driven the electric motor being specially adapted for integration in the pump
    • F04D25/0613—Units comprising pumps and their driving means the pump being electrically driven the electric motor being specially adapted for integration in the pump the electric motor being of the inside-out type, i.e. the rotor is arranged radially outside a central stator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
    • F04D29/38—Blades
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
    • F04D29/38—Blades
    • F04D29/388—Blades characterised by construction
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/16—Constructional details or arrangements
    • G06F1/20—Cooling means

Definitions

  • the present invention relates to a fan for heat dissipation of an electronic device and its device, particularly an axial flow fan.
  • the heat dissipation problem of electronic devices has become an unavoidable problem in the design and manufacture of electronic products.
  • the heat dissipation of CPU and GPU chips in computers has become a bottleneck in the development of computers.
  • the CPU heatsink has become the largest component on the motherboard. , is the biggest obstacle to the reduction of the size of the motherboard and the compactness.
  • the heat sink is typically constructed of a fan and a device with a plurality of convective heat transfer fins.
  • the fan is a very important part of the radiator.
  • the air volume of the fan must not only be high, but also the wind pressure must be high enough to overcome the air flow resistance generated by the convective heat exchange fins.
  • the electronic cooling fan has evolved from the basis of the ventilation fan. Considering the whole manufacturing cost and air volume, the heat generated by the electronic chip such as CPU is greatly improved, and the convection heat dissipation fin on the heat radiator is increased. The air flow resistance is greatly increased.
  • the design of the blades in the existing electronic cooling fan must be modified. However, due to the lack of professional aerodynamics and knowledge of the blade design principle, the newly introduced product or design is only increased by The size of the fan (such as the outer diameter) increases the fan speed to increase the air volume and wind pressure, but the noise is rapidly increased, and the air volume and wind pressure are not effectively improved.
  • the invention provides an axial flow type cooling fan, which is based on aerodynamics and a blade machine design principle, and combines the specific structure and manufacturing process of the electronic cooling fan to design the fan blades (fan blade blades and rectifying blades). More specific requirements have been put forward, and new structures have been proposed to make it more in line with air flow characteristics, reduce the flow loss (resistance) of air in the blades, effectively increase the wind pressure and air volume of the fan, and reduce the size of the fan. Make it more compact.
  • the fan is axial flow type, and the main components are: fan blade, motor, and the invention is characterized in that: the fan blade adopts a multi-stage blade structure,
  • the minimum projection distance between the blades in the axial direction is not more than a single-stage blade structure of 2.0 mm
  • vanes are respectively formed on two or more integrally injection-molded integral parts, the vanes on one integral part being sandwiched between the vanes on the other integral part;
  • the number of blade blades of the single-stage blade structure or the number of blades of the final stage of the blade of the multi-stage blade structure is not less than eight pieces.
  • the rotating blade blades drive the air flow and transmit the mechanical energy output from the motor to the air.
  • the mechanical energy (kinetic energy and potential energy) of the air is improved, that is, the speed and pressure of the air are improved.
  • the mechanical energy of the motor is mechanically lost during the process of feeding the air through the blade blades, that is, there is a problem of transportation efficiency, and the mechanical energy loss includes: air surface friction loss and eddy current loss. When a separation vortex appears on the surface of the blade, the eddy current loss will increase rapidly, and the blade efficiency Will drop sharply. Therefore, in order to effectively increase the air volume and wind pressure of the fan, it is necessary to control the eddy current loss.
  • the air After being driven by the rotating blades, the air is spirally moved and has a circumferential velocity.
  • the circumferential split speed kinetic energy is converted into static pressure potential energy, and the fan is added with a rectifier.
  • the arrangement of the convective heat exchange fins is arranged along the axial direction of the fan, so that the circumferential splitting speed is reduced, the angle of attack of the air relative to the convective heat exchange fins is reduced, and the convective heat exchange fins are reduced. Air flow loss (resistance).
  • FIG. 1 is a schematic view of a planar cascade, and is also a schematic view of a section of a circular cascade on a concentric cylindrical surface.
  • the blade and the rectifier in the present invention It belongs to the annular cascade.
  • the front line of the cascade is 11 or 22 in Fig.
  • the leaf distance t is the distance between the corresponding points of the two adjacent blades along the frontal line, and the ratio b/t of the chord length b to the leaf pitch is called the cascade consistency;
  • the pitch of the projection in the axial direction between the blades refers to the spacing d between two adjacent blades projected onto the frontal line;
  • the blade inlet geometric angle ⁇ 1 ⁇ and the exit geometric angle ⁇ 2 ⁇ are the blade-shaped midline at the leading edge The angle between the tangent of the trailing edge and the frontal line;
  • the inlet and outlet airflow angles ⁇ and ⁇ 2 are the angles between the relative velocity Wj, W 2 of the inlet and outlet airflow and the frontal line;
  • the airflow turning angle ⁇ ⁇ ⁇ - ⁇ is the angle through which the airflow passes through the cascade;
  • the inlet angle of attack ⁇ is the angle between the direction of the incoming flow and the tangent of the blade midline at the leading edge point:
  • the exit backward angle ⁇
  • Figure 2 is a plot of the characteristic curve obtained from the plane cascade experiment, showing the relationship between the nominal airflow corner angle ⁇ ⁇ * and the cascade consistency b/t and the rated outlet airflow angle ⁇ 2 *.
  • the airflow turning angle A ⁇ should not be greater than the value corresponding to the curve in Fig. 2, otherwise the flow loss of the airflow in the cascade will increase sharply, and the flow loss will occur.
  • the reason for the sharp increase is the separation of airflow on the back of the blade and the loss of eddy current.
  • FIG. 2 is an experimental result of a planar cascade, the design of the annular cascade involved in the present invention has practical guiding significance.
  • the way to increase the fan blade to the air energy is as follows: 1. Increase the fan blade rotation speed, but the fan noise increases, the motor bearing life is shortened; 2. Increase the airflow turning angle ⁇ ⁇ after the air flows through the fan blade. This is the first Recommended method.
  • the exit airflow angle ⁇ should be as right angle as possible, meaning that the exit geometry angle of the rectifying blades is large, which means that the airflow turning angle ⁇ ⁇ is large.
  • the blade cascade consistency of the blade will increase, that is, the blade density is large, and the projection between the blades in the axial direction may overlap. Since the cover of the electronic cooling fan, the fan blade, etc. are all injection molding processes, the manufacturing process is high in efficiency and low in cost. If the projections in the axial direction overlap, the injection molding cannot be divided, and the product cannot be Take out the mold, and the measures to solve this problem are:
  • Multi-stage blade structure the blade is divided into two or more stages, so that the airflow turning angle after the air flows through the blade is very large, but it is shared by the multi-stage blade, and the single-stage airflow turning angle is not large, which can be guaranteed Under high blade efficiency conditions, the density of the blades at each level is not high enough to be produced by injection molding.
  • the blade is divided into two sections in the axial direction, and the two sections are respectively arranged on two or more integral injection-molded integral parts, generally adopting two integral parts, such a single-stage blade structure, although the entire blade is between
  • the projection in the axial direction may overlap, but the axial projection between the partial blades on each integral part is left at a certain interval, which is guaranteed to be produced by an injection molding process.
  • the blades are divided into two or more integral injection molded integral parts, generally two integral parts are used, preferably evenly spaced, and the blades on one integral part are sandwiched between the blades of the other integral part. , constitutes a single-stage blade structure.
  • the axial direction projection between the blades on a single integral part is left with a certain distance, which can be manufactured by injection molding process.
  • the thickness of the cascade is not high, but the blades on the two parts are combined and the cascade consistency is doubled. Thus improve The nominal airflow corner after air flows through the cascade.
  • the fourth structure of the fan blade is limited. Due to the limited increase of the cascade stability, it must be noted that the bending angle and the exit geometric angle of the blade blade should not be too large, otherwise the flow loss caused by the airflow separation on the back of the blade may be sharply increased. . Different wind pressures and air volumes, optimum blade bending angles and outlet geometric angles are also different. According to the calculation and analysis of Figure 2, considering the specific application of the electronic cooling fan, the bending angle at the blade tip of the fan blade should not be greater than 28°, the exit geometry angle should not be greater than 48°. To increase the wind pressure and air volume of such a fan, it can be achieved by increasing the fan speed.
  • the geometric angle of the exit of the rectifying blades is large, but considering the various factors, it is generally appropriate to take the geometric angle of the outlet of the rectifying blades to be greater than 70°, but it is preferable that the geometric angle of the outlet is not less than 85°, so as to reduce the circumferential speed as much as possible. If the circumferential speed is to be eliminated, the exit geometry angle is greater than 90°, because there is an exit backward angle in the air flowing out of the rectifying blades, and the blade manufacturing difficulty is increased.
  • the number of blades at the entrance is too many.
  • the number of blades in the cooling fan is as small as 3 to 5 pieces.
  • Such a small blade blade is a simple imitation of the fan blade type, and lacks the basic performance of the blade machine principle knowledge, which is very unreasonable.
  • the number of blade blades of the single-stage blade structure or the number of blades of the final stage of the blade of the multi-stage blade structure is at least not less than eight. Increasing the number of blades can reduce the axial dimension of the blade, but consider the blade strength and other issues.
  • FIG. 1 is a schematic view of a planar cascade, which is also a schematic cross-sectional view of a circular cascade on a concentric cylindrical surface.
  • FIG. 3 is a schematic cross-sectional view showing a two-stage blade structure of a fan of the present invention on a concentric cylindrical surface.
  • Fig. 4 is a schematic cross-sectional view showing the two-stage blade structure of the fan of the present invention on a concentric cylindrical surface, similar to Fig. 3, except that the blades in the first stage and the second stage are misaligned.
  • Fig. 5 is a schematic cross-sectional view showing the two-stage blade structure of the fan of the present invention on a concentric cylindrical surface, the first stage blade being integrated with a part of the second stage.
  • Fig. 6 is a schematic cross-sectional view showing a single-stage blade structure of a fan of the present invention, wherein the blade is cut into two sections in the axial direction.
  • Fig. 7 is a schematic cross-sectional view showing a fan of the present invention.
  • the fan blade adopts a two-stage blade structure, and the motor is a brushless DC motor.
  • Figure 8 is a schematic cross-sectional view of a fan of the present invention, with a rectifier disposed behind the blade.
  • Figure 9 is a cross-sectional view of a fan of the present invention with a rectifier disposed behind the blade.
  • Figure 10 is a developed perspective view of the main components of the fan shown in Figure 9.
  • Figure 11 is a schematic cross-sectional view of a fan of the present invention, the rectifier being a two-stage blade structure.
  • Figure 12 is a schematic cross-sectional view of a fan of the present invention having two blades and driven by the same motor.
  • Figure 13 is a schematic illustration of the radial bending of the fan blades.
  • Fig. 14 is a view showing the characteristic of the radial inclination of the fan blades.
  • Figure 3 shows a typical multi-stage blade structure (two-stage blade structure shown in Figure 3) with axial projection spacing between each stage of the blade, ensuring an injection molding process, the number of second stage blades More than the first level (more than double), that is, the number of blades in the rear stage is more than the number of blades in the previous stage, so the consistency of the cascade is increased, and the geometric angle of the exit of the blade is also increased, which can be higher according to FIG.
  • the rated airflow angle ⁇ ⁇ * that is to say, the blade with two or more stages of blade structure can obtain a higher rated airflow corner, and the effective mechanical energy of the blade to air transmission is further improved.
  • the size can be effectively reduced to make the fan more compact.
  • Fig. 4 The difference between Fig. 4 and Fig. 3 is that the blades in the second stage are misaligned with the first stage blades.
  • the advantage of this configuration is that if the airflow that appears on the first stage of the blade separates the vortex, it will not develop when it enters the second stage and will gradually disappear.
  • the structure shown in Fig. 5 is the derivative structure shown in Fig. 3.
  • the half of the blades in the second stage are integrated with the blades of the first stage, and also belong to the multi-stage blade structure.
  • Figure 6 shows a single-stage blade structure, but the blades are cut in the axial direction into two sections, respectively on two or more parts (generally two integral parts are used), although the axial direction between the entire blades The projections overlap, but after being cut, a certain distance is left between the axial projections of the blades on each component, which is guaranteed to be manufactured by an injection molding process.
  • Fig. 7 is a schematic view showing the characteristics of a fan of the present invention, and the blade 5 is a two-stage blade structure.
  • the first stage blade and the hub 1 of the blade 5 are an integral part, generally manufactured by an injection molding process, and the outer circumference of the first stage blade is provided with a hoop 6 for improving the strength of the blade; the second stage blade
  • the ring at its root is an integral part that fits over the rotor 4 of the motor.
  • the motor is a brushless DC motor, and a micro-miniature electronic cooling fan generally uses such a brushless DC motor.
  • the stator 2 of the motor is tightly fitted over the bearing sleeve 3.
  • the bearing sleeve 3 is a bearing 9.
  • One end of the shaft 8 is embedded in the shaft center of the hub 1.
  • the rotor 4 of the motor is a ring magnet, and the bearing sleeve 3 is fixed to the motor disk.
  • the motor disk 7 is a fixed part of the motor.
  • Fig. 8 shows a fan of the present invention, with a rectifier 11 disposed behind the blade 5, and the motor in the fan shown in Fig. 8 is also a brushless DC motor, and the circuit board 12 equipped with an electronic device such as a Hall is Between the stator 2 and the motor disk 7.
  • the fixed installation of the fan relies on the casing 10, and the support of the motor is fixed to the casing 10 through the bearing sleeve 3, the motor disk 7, and the blades of the rectifier 11.
  • the injection molding process is generally carried out by using a plastic injection process to integrally inject the motor disk 7 and the rectifying blades (all or part) and the casing 10 or part of the casing parts into one integral part.
  • Such a structure is not only high in production efficiency, low in cost, but also compact in structure and high in strength, and it is easy to ensure a uniform gap between the blade 5 and the inner wall of the casing 10. It is also shown that the bearing sleeve 3 and the motor disk 7 are the same integral part, which is more advantageous for ensuring strength and concentricity.
  • the fan shown in Fig. 9 is provided with a rectifier having a single-stage blade structure, and the rectifying blades are evenly divided into two parts - a rectifying blade A13 and a rectifying blade ⁇ 14, respectively, on two integral injection molded integral parts.
  • the rectifying blade B14 integrally connects the motor disk 7 and the casing 10 as an integral part for integral injection molding; the rectifying blade A13 and its blade root and the ring on the blade tip are another integral component.
  • the motor is also a DC brushless motor, and the board is placed on the cover 10, not shown.
  • the axial dimension of the motor is increased; when the rectifier is added, the axial dimension of the fan is increased.
  • the structural features shown in Figures 8 and 9 provide a solution for extending the portion of the motor rotor 4 that is axially wider than the blade above it into the root of the rectifier 11, i.e. Part of the rotor 4 extends into Inside the root of the rectifier 11.
  • Figure 11 shows a fan of the present invention
  • the motor is a brushless DC motor
  • the rectifier 11 is a two-stage blade structure
  • the casing 10 is also divided into two sections, the front section of the casing 10 (by the air inlet section) and the front stage
  • the rectifying blades are an integral part.
  • the rear stage rectifying blades and the rear section of the casing 10 and the motor disk 7 are another integral part and can be manufactured by an injection molding process.
  • a fan of the present invention shown in Fig. 12 has two blades 5, respectively on the two hubs 1, with a rectifier 11 between the two blades 5, and the two blades 5 are driven by the same motor,
  • the motor shown is a DC brushless motor.
  • the purpose of using this two-blade structure is to increase the fan blade's ability to drive air movement and increase the fan's wind pressure and air volume.
  • the force of the blade-driven air is proportional to the square of the velocity of the air relative to the blade, and the velocity at the blade tip (near the casing 10) in the blade is greater than the velocity at the blade root, and thus is obtained near the air at the blade tip.
  • the work ratio is much closer to the root of the blade, so the wind pressure of the air near the tip of the blade is higher than the root of the blade, that is, the radial wind pressure distribution of the fan is uneven. Uneven air pressure will cause uneven air flow in the convective heat transfer fins behind the fan, which is not conducive to the effective use of the entire convective heat transfer fins.
  • the methods for overcoming the uneven distribution of the radial wind pressure of the fan are as follows: (1) The blade blade is designed to be twisted in the radial direction to reduce the angle of attack relative to the air flow at the tip of the blade, because the angle of attack is reduced, and the force of the blade acting on the air (2) As shown in Figures 13 and 14, the blade blade 15 is designed to be curved or inclined in a radial direction toward the direction in which the blade rotates. Fig. 13 shows that the blade blade 15 is radially curved, and Fig. 14 shows that the blade blade 15 is radially inclined, so that the force exerted by the blade blade 14 on the air has a centripetal force, and thus the air is formed with a centripetal force.
  • the directional movement of the direction which is beneficial to increase the wind pressure near the root of the blade.
  • designing the rectifying blades to be curved or inclined in the radial direction can also help to increase the wind pressure at the root of the blades, but the direction of bending or tilting should be opposite to the direction in which the blades rotate, with the blade blades 15
  • the bending or tilting direction is reversed, because after the air leaves the rotating blade 5, there is a circumferential speed that coincides with the direction of rotation of the blade.
  • the rectifying blades are bent or tilted against the direction of rotation of the blades so that when air flows through the rectifier, the force acting on the air by the rectifying blades creates a centripetal force.
  • Fan blades are fan blades, rectifying blades (if the fan is equipped with a rectifier).

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  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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  • General Physics & Mathematics (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Description

轴流式电子散热风扇 所属技术领域
本发明涉及电子器件及其装置散热用的风扇， 特别是轴流式风扇。
背景技术
电子器件的散热问题， 已经成了电子产品设计制造中不可回避的问题， 特别是计算机中 CPU和 GPU芯片的散热， 已成了计算机发展中的瓶颈， CPU散热器成了主板上尺寸最大的 部件， 是主板尺寸的减小和紧凑化的最大阻碍。
散热器一般由风扇和带有许多对流换热肋片的装置构成。 风扇是散热器中非常重要的部 件， 风扇的风量不仅要高， 风压也必须足说够高， 以克服对流换热肋片产生的空气流动阻力。
现电子散热风扇是从通风风扇基础上发展演变过来的， 考虑更多的是整个制造成本和风 量，面对 CPU等电子芯片发热量大幅度提高，散热书器上的对流散热肋片增加带来的空气流动 阻力大幅度增加， 现有电子散热风扇中的叶片的设计必须修改， 但由于缺乏专业的空气动力 学和叶片机设计原理方面的知识作指导， 新推出的产品或设计只是通过增大风扇的尺寸 （如 外径），提高扇叶转速来提高风量和风压，但噪音迅速加大，风量和风压并没有得到有效提高。
中国专利申请， 申请号： 03142983.1 和申请号： 200610163711.6， 两项专利申请公开的 电子散热风扇中， 在扇叶后设置有整流器（也称静叶和固定叶片）， 目的是想减小扇叶后的空 气旋转速度（周向分速度）， 提高风扇的风压。但是这两项专利申请提供的风扇， 缺乏专业的 空气动力学和叶片机设计原理方面的知识作为设计指导， 甚至得出完全相反的错误结果， 也 就不可能设计出有效提高风量和风压的风扇。
发明内容
本发明提供了一种轴流式散热风扇， 是以空气动力学和叶片机设计原理为基础， 并结合 电子散热风扇具体结构以及制造工艺， 对风扇叶片 （扇叶叶片以及整流叶片） 的设计做出了 更为具体的要求， 并提出新的结构， 使之更符合空气流动特性， 减小空气在叶片中的流动损 失 （阻力）， 有效提高风扇的风压和风量， 并减小风扇尺寸， 使之更紧凑。
本发明所采用的技术方案： 风扇为轴流式， 主要部件有： 扇叶、 电机， 本发明的特征在 于： 风扇叶片采用了多级叶片结构，
或所有叶片为一整体部件， 叶片之间轴向方向投影间距的最小处不大于 2.0毫米的单级 叶片结构、
或叶片在轴向分切成两段， 分别在两个或更多个一体注射成型的整体部件上的单级叶片 结构、
或叶片分别在两个或更多个一体注射成型的整体部件上， 一个整体部件上的叶片夹在另 外的整体部件上的叶片中间的单级叶片结构；
单级叶片结构的扇叶叶片数量或多级叶片结构的扇叶最后级的叶片数量不少于 8片。 旋转的扇叶叶片驱动空气流动， 将电机输出的机械能传输给空气， 空气的机械能（动能 和势能）得到提高， 即空气的速度和压力得到提高。 电机的机械能通过扇叶叶片输送给空气 的过程中有机械能损失， 即存在有输送效率问题， 机械能损失中包括有： 空气表面摩擦损失 和涡流流动损失。 当在叶片表面气流出现分离漩涡时， 涡流流动损失将迅速增加， 叶片效率 将急剧下降。 因而要有效提高风扇的风量和风压， 必须控制涡流流动损失。
空气经旋转的扇叶驱动后， 呈螺旋运动， 有周向分速度。 为了减小 （最好是消除） 周向 分速度， 将周向分速度动能转换成静压势能， 风扇增设整流器。 通常对流换热肋片的设置顺 着风扇轴向方向排列， 因而周向分速度减小， 就减小了空气相对于对流换热肋片的冲角， 可 减小对流换热肋片产生的空气流动损失 （阻力）。
扇叶和整流器都是由叶片 （扇叶叶片和整流叶片） 构成， 图 1为平面叶栅示意图， 也为 环形叶栅在同心圆柱面上的截面的展开示意图， 本发明中的扇叶以及整流器属于环形叶栅。 叶栅的额线为图 1中的 11或 22， 叶距 t为沿额线方向相邻两叶片对应点之间的距离， 弦长 b 与叶距的比值 b/t称为叶栅稠度； 叶片之间轴向方向的投影的间距是指两相邻的叶片投影到 额线上的之间的间距 d; 叶片进口几何角 β 1Α、 出口几何角 β 2Α为叶片的片型中线在前缘、 后缘的切线与额线之间的夹角； 叶栅进、 出口气流角 β 、 β 2为进、 出口气流相对速度 Wj、 W2与额线之间的夹角； 气流转折角 Δ β ί^- β 为气流通过叶栅时转过的角度； 进口冲角 ί为来流方向与叶片的叶型中线在前缘点的切线之间的夹角：出口落后角 δ为气流出口方向与 叶片的叶型中线在后缘点的切线之间的夹角， δ= β 2Α- β 2。 可以推导出气流转折角 Δ β = θ + ί _ δ， Θ为叶片弯折角， θ = β 2Α- β 1Α。
图 2是平面叶栅实验得出的额定特性曲线， 给出了额定气流转折角 Δ β *与叶栅稠度 b/t 以及额定出口气流角 β 2*之间的关系。 当出口气流角 β 2和叶栅稠度 b/t—定时， 气流转折角 A β不应大于根据图 2中曲线对应的值， 否则将引起气流在叶栅中的流动损失剧增， 其流动 损失剧增的原因是叶片背面出现气流分离，涡流损失所致。图 2虽然是平面叶栅的实验结果， 但对本发明所涉及的环形叶栅的设计一样有实际指导意义。
提高扇叶输送给空气能量的方式有： 1、提高扇叶旋转速度， 但风扇的噪音增加， 电机轴 承寿命减短； 2、 提高空气流经扇叶后的气流转折角 Δ β， 这是首先推荐的方法。
减小 （尽可能消除） 空气的周向速度， 即出口气流角 β要尽可能是直角， 意味着整流叶 片的出口几何角要大， 也就意味着气流转折角 Α β大。
以上说明： 无论是扇叶还是整流器（如果风扇设置有的话）， 都希望得到高的气流转折角
Δ β， 但根据图 2得出叶片的叶栅稠度将增大， 即叶片密度大， 叶片之间在轴向方向的投影 就可能要重叠。 由于电子散热风扇的壳罩、 扇叶等都是采用注射成型工艺， 这种制造工艺效 率高， 成本低， 如果叶片之间在轴向方向的投影有重叠， 注射成型就不能分模， 产品无法脱 模取出， 解决这个问题的措施有：
一、 采用多级叶片结构， 叶片分成两级或更多级， 这样空气流经叶片后的气流转折角虽 然非常大， 但被多级叶片分担， 单级的气流转折角不大， 可以保证在高的叶片效率条件下， 各级叶片的密度不会高到不能采用注射成型工艺生产。
二、 将叶片在轴向分切成两段， 两段分别在两个或更多个一体注射成型的整体部件上， 一般采用两个整体部件， 这样的单级叶片结构， 虽然整个叶片之间轴向方向的投影可能有重 叠， 但各个整体部件上的部分叶片之间轴向投影留有一定的间隔， 保证可以采用注射成型工 艺生产。
三、 将叶片分在两个或更多个一体注射成型的整体部件上， 一般采用两个整体部件， 最 好是间隔均匀分配， 一个整体部件上的叶片夹在另外的整体部件上的叶片中间， 就构成单级 叶片结构。 单个整体部件上的叶片之间轴向方向投影留有一定的间距， 保证可以采用注射成 型工艺制造， 叶栅稠度不高， 但两个部件上的叶片合在一起， 叶栅稠度提高一倍， 因而提高 了空气流经叶栅后的额定气流转折角。
四、 从结构简单、 叶片强度以及减小风扇轴向尺寸方面考虑， 所有叶片为一个整体部件 的单级叶片结构。 但尽可能提高叶栅稠度， 叶片之间轴向方向的投影间距留有 2毫米时， 就 能保证采用注射成型工艺制造。 由于叶片之间的间距从叶根到叶尖是变化的， 通常叶根处间 距小， 因而本发明的单级叶片之间轴向方向的投影的间距的最小处不大于 2毫米， 这样叶片 密度尽可能地得到提高。
无论是扇叶还是整流器（如果风扇设置有的话）， 单独或共同采用以上四种措施， 都将有 效地提高风扇的性能。
扇叶釆用所述第四种结构， 由于叶栅稠度提高有限， 设计时必须注意扇叶叶片的弯折角 和出口几何角不能太大， 否则会引起叶片背面气流分离带来的流动损失急剧增加。 不同的风 压以及风量， 最佳叶片弯折角以及出口几何角也不同， 依据图 2等的计算和分析， 考虑到电 子散热风扇的具体应用，扇叶叶片的叶尖处的弯折角不应大于 28°，出口几何角不应大于 48°。 要进一歩提高这样的风扇的风压和风量， 可通过提高扇叶转速来实现。
整流叶片的出口几何角要大， 但考虑多种因素， 一般整流叶片出口几何角取大于 70°比 较合适， 但最好是出口几何角不小于 85°， 这样尽可能减小周向速度。 如果要消除周向速度， 出口几何角就要大于 90°， 因为流出整流叶片的空气存在有出口落后角， 叶片制造成型难度 增加。
乘坐飞机， 认真观察一下飞机的喷气发动机进口， 会发现进口处的叶片多得数不清。 而 现散热风扇中的叶片数量， 少的有 3〜5片， 这样少的扇叶叶片， 是简单仿用通风扇叶叶型， 缺乏叶片机原理知识的基本表现， 非常不合理。 对于电子散热用的风扇， 依据图 2曲线和考 虑到其他因素， 单级叶片结构的扇叶叶片数量或多级叶片结构的扇叶最后级的叶片数量， 最 少不少于 8片。 增加叶片数量， 可以减小扇叶的轴向尺寸， 但要考虑叶片强度等问题。
下面结合附图和实施例对本发明作进一步说明。
附图说明
图 1为平面叶栅示意图， 也为环形叶栅在同心圆柱面上的截面展开示意图。
图 2为平面叶栅额定特性曲线， A β *= 0.8 Δ β max, 表示额定转折角△ β *取值为最大 转折角 Α β max的百分之八十。
图 3为一种本发明风扇的两级叶片结构在同心圆柱面上的截面展开示意图。
图 4为一种本发明风扇的两级叶片结构在同心圆柱面上的截面展开示意图，与图 3类似， 不同之处为第一级叶片与第二级叶片中的叶片错位。
图 5为一种本发明风扇的两级叶片结构在同心圆柱面上的截面展开示意图， 第一级叶片 与第二级中的部分叶片合为一体。
图 6为一种本发明风扇的单级叶片结构的特征剖面示意图， 叶片在轴向裁切成两段。 图 7为一种本发明风扇的特征剖面示意图， 扇叶采用两级叶片结构， 电机为无刷直流电 机。
图 8为一种本发明风扇的特征剖面示意图， 扇叶后设置有整流器。
图 9为一种本发明风扇的剖面图， 扇叶后设有整流器。
图 10为图 9所示的风扇的主要部件的展开立体图。
图 11为一种本发明风扇的特征剖面示意图， 整流器为双级叶片结构。
图 12为一种本发明风扇的特征剖面示意图， 有两个扇叶， 并且由同一电机驱动。 图 13表示风扇叶片径向弯曲的特征示意图。
图 14表示风扇叶片径向倾斜的特征示意图。
图中， 1、 轮毂， 2、 定子， 3、 轴承套， 4、 转子， 5、 扇叶， 6、 箍环， 7、 电机盘， 8、 轴， 9、 轴承， 10、 壳罩， 11、 整流器， 12、 电路板， 13、 整流叶片 A， 14、 整流叶片 B， 15、 扇叶叶片， 16、 表示扇叶转动方向的箭头。
具体实施方式
图 3示出了典型的多级叶片结构（图 3所示的为两级叶片结构），每级的叶片之间都留有 轴向投影间距， 保证可采用注射成型工艺， 第二级叶片的数量比第一级多（多一倍）， 即后级 叶片片数多于前一级叶片片数， 因而叶栅稠度提高， 并且叶片的出口几何角也加大， 依据图 2可以得到更高的额定气流转折角 Δ β *， 也就是说， 采用两级或更多级叶片结构的扇叶， 可 得到更高的额定气流转折角， 扇叶向空气传输的有效机械能进一步提高， 风扇的轴向尺寸可 得到有效减小， 使风扇更紧凑。
图 4所示的与图 3的不同之处在于： 第二级中的叶片与第一级叶片有错位。 这种结构的 优点是： 如果在第一级叶片上出现的气流分离漩涡， 进入第二级时就不会发展， 并逐步消失。 图 5所示的结构是图 3所示的衍生结构， 第二级中的半数叶片与第一级的叶片连为一体， 也 属于多级叶片结构。
图 6所示的为单级叶片结构， 但叶片在轴向被裁切成两段， 分别在两个或更多个部件上 (一般采用两个整体部件）， 虽然整个叶片之间轴向方向的投影有重叠， 但被裁切后，各部件 上的部分叶片之间轴向投影留有一定距离， 保证可采用注射成型工艺制造。
图 7是一种本发明风扇的特征示意图， 扇叶 5为两级叶片结构。 扇叶 5的第一级叶片和 轮毂 1为一整体部件， 一般采用注塑成型工艺制造， 第一级叶片的外圆设置有箍环 6， 其作 用是提高该处叶片的强度； 第二级叶片和其根处的环为一整体部件， 套在电机的转子 4上。 电机为无刷直流电机， 微小型电子散热风扇一般都采用这样的无刷直流电机。 电机的定子 2 紧配合套在轴承套 3上， 轴承套 3内是轴承 9， 轴 8的一头嵌装在轮毂 1的轴心， 电机的转 子 4是一个环形磁铁， 轴承套 3固定在电机盘 7上， 电机盘 7为电机的固定部件。
图 8示出了本发明的一种风扇， 在扇叶 5后设有整流器 11， 图 8所示的风扇中的电机也 为无刷直流电机，装有霍尔等电子器件的电路板 12在定子 2和电机盘 7之间。风扇的固定安 装是依靠壳罩 10， 电机的支撑固定是通过轴承套 3、 电机盘 7， 再通过整流器 11的叶片连接 到壳罩 10。 采用注射成型工艺， 一般采用塑料注射工艺， 将电机盘 7与整流叶片 （全部或部 分） 以及壳罩 10或部分壳罩部件一体注射成型， 为一整体部件。这样的结构， 不仅生产效率 高， 成本低， 而且结构紧凑， 强度高， 容易保证扇叶 5与壳罩 10内圆壁之间的间隙均匀。 图 中还示出： 轴承套 3和电机盘 7为同一整体部件， 这样更有利于保证强度和同心度。
图 9所示的风扇设置有整流器， 整流器为单级叶片结构， 整流叶片间隔均匀地分成两部 分——整流叶片 A13 和整流叶片 Β 14， 分别在两个一体注射成型的整体部件上。 整流叶片 B14将电机盘 7和壳罩 10连接成一体， 为一体注射成型的整体部件； 整流叶片 A13和其叶 根、 叶尖上的环为另一整体部件。 电机也为直流无刷电机， 电路板设置在壳罩 10上， 没有示 出。
为增加扇叶动力， 即电机的驱动功率， 电机的轴向尺寸要增大； 增设整流器， 风扇的轴 向尺寸又会增大。 为了减小风扇轴向尺寸， 图 8、 9示出的结构特征， 提供了一种解决方案， 将电机转子 4比其上的扇叶轴向宽长出的部分伸到整流器 11根部内，即转子 4有部分伸入到 整流器 11的根部内。
图 11示出了一种本发明的风扇， 电机为直流无刷电机， 整流器 11为两级叶片结构， 壳 罩 10也分成两段， 壳罩 10的前段 （靠进气口段） 与前级整流叶片为一整体部件。 后级整流 叶片与壳罩 10的后段以及电机盘 7为另一整体部件， 可采用注射成型工艺制造。
图 12所示的一种本发明的风扇， 有两个扇叶 5， 分别在两轮毂 1上， 两个扇叶 5之间有 整流器 11， 两个扇叶 5由同一电机驱动， 图中所示的电机为直流无刷电机。 采用这种两扇叶 结构的目的： 增大扇叶驱动空气运动的能力， 提高风扇的风压、 风量。
扇叶叶片旋转时， 驱动空气， 给空气作功。 叶片驱动空气的作用力与空气相对于叶片的 速度的平方成正比， 扇叶中的叶片尖处 （靠近壳罩 10处） 的速度大于叶片根处的速度， 因 而靠近叶片尖处的空气得到的功比靠近叶片根处的多，因而靠近叶片尖处的空气的风压高于 叶片根处， 即风扇径向风压分布不均匀。风压不均匀会造成风扇后的对流换热肋片中的空气 流量不均匀， 这样不利于有效利用整个对流换热肋片。
克服风扇径向风压分布不均匀的方法有： （一） 扇叶叶片设计成沿径向扭转， 减小叶片 尖处相对空气流动的冲角， 因为冲角减小， 叶片作用于空气的力减小； （二）如图 13、 14所 示， 扇叶叶片 15设计成在径向朝着扇叶转动的方向弯曲或倾斜。 图 13示出扇叶叶片 15径 向弯曲， 图 14示出扇叶叶片 15径向倾斜， 这样可使得扇叶叶片 14作用于空气上的力有向 心分力， 因而空气会形成有向心方向的分向运动， 这样就有利于提高靠近叶片根处的风压。 同样的道理， 将整流叶片设计成在径向弯曲或倾斜， 也能有利于提高靠叶片根处的风压， 但 是弯曲或倾斜的方向应该反着扇叶旋转的方向， 与扇叶叶片 15的弯曲或倾斜方向相反， 因 为空气离开旋转的扇叶 5后，会有与扇叶旋转方向一致的周向分速度。整流叶片反着扇叶旋 转方向弯曲或倾斜， 则使得空气流经整流器时， 整流叶片作用于空气上的力会产生有向心分 力。
特别说明： 风扇叶片是指扇叶叶片、 整流叶片 （如果风扇设置有整流器的话）。

Claims

权 利 要 求 书
1、 一种电子散热风扇， 应用于电子器件或装置的散热， 结构为轴流式， 包括有： 扇叶 (5)、 电机， 其特征在于： 风扇叶片采用了多级叶片结构，
或所有叶片为一整体部件， 叶片之间轴向方向投影间距的最小处不大于 2.0毫米的单级 叶片结构、
或叶片在轴向分切成两段，分别在两个或更多个一体注射成型的整体部件上的单级叶片 结构、
或叶片分别在两个或更多个一体注射成型的整体部件上，一个整体部件上的叶片夹在另 外的整体部件上的叶片中间的单级叶片结构；
单级叶片结构的扇叶叶片数量或多级叶片结构的扇叶最后级的叶片数量不少于 8片。
2、 根据权利要求 1所述的电子散热风扇， 其特征在于： 整个扇叶 （5) 为一整体部件的 单级叶片结构的扇叶叶片， 叶尖处的叶片弯折角不大于 28°、 出口几何角不大于 48° 。
3、 根据权利要求 1所述的电子散热风扇， 其特征在于： 如果扇叶 （5)后设置有整流器 ( 11 )， 整流叶片的出口几何角或最后级整流叶片的出口几何角大于 70°。
4、 根据权利要求 1所述的电子散热风扇， 其特征在于： 电机为直流无刷电机。
5、 根据权利要求 1所述的电子散热风扇， 其特征在于： 扇叶叶片 （15) 朝着扇叶 （5) 转动的方向弯曲或倾斜。
6、 根据权利要求 1或 3所述的电子散热风扇， 其特征在于： 整流叶片反着扇叶 （5)转 动的方向弯曲或倾斜。
7、 根据权利要求 1所述的电子散热风扇， 其特征在于： 扇叶 （5) 上设置有箍环 （6)。
8、 根据权利要求 1或 3所述的电子散热风扇， 其特征在于： 部分或全部整流叶片与壳 罩 （10) 或部分壳罩部件、 以及电机的为一体注射成型的整体部件。
9、 根据权利要求 3所述的电子散热注射成型风扇， 其特征在于： 在整流器 （11 ) 后设 置有另一扇叶 （5)， 两个扇叶由同一电机驱动。
10、根据权利要求 9所述的电子散热风扇，其特征在于： 电机为直流无刷电机；转子（4) 有部分伸入到整流器 （6) 的根部内。
11、根据权利要求 1所述的电子散热风扇，其特征在于： 多级叶片结构的扇叶或整流器， 后级叶片片数要多于前一级叶片片数。
1
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US20110142611A1 (en) * 2009-12-14 2011-06-16 The University Of Tokyo Counter-rotating axial flow fan
CN114645865A (zh) * 2020-12-18 2022-06-21 日本电产株式会社 串联轴流风扇

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CN201068873Y (zh) * 2007-06-15 2008-06-04 秦彪 一种电子芯片散热风扇
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JPS5844299A (ja) * 1981-09-10 1983-03-15 Mitsubishi Electric Corp 翼車
CN1199011C (zh) * 2000-06-09 2005-04-27 Lg电子株式会社 带有无刷直流电机的轴流风扇
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US20020094271A1 (en) * 2001-01-16 2002-07-18 Yeuan Jian J. Axial flow fan structure
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US20110142611A1 (en) * 2009-12-14 2011-06-16 The University Of Tokyo Counter-rotating axial flow fan
US8764375B2 (en) * 2009-12-14 2014-07-01 The University Of Tokyo Counter-rotating axial flow fan
CN114645865A (zh) * 2020-12-18 2022-06-21 日本电产株式会社 串联轴流风扇
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CN114645865B (zh) * 2020-12-18 2024-04-26 日本电产株式会社 串联轴流风扇

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