Patent Publication Number: US-2023145011-A1

Title: Fan and electric hair dryer with improved air outlet performance

Description:
TECHNICAL FIELD 
     The present application relates to a technical field of household appliances, in particular to a fan and an electric hair dryer. 
     BACKGROUND 
     A hair dryer dries by generating wind with a specific temperature. After the hair dryer is powered on, a motor drives fan blades of a fan to rotate, and the air is sucked in from an air inlet. Heated by an electric heating element, the air is blown out from an air outlet after forming hot air. The fan is an important part of the hair dryer. 
     SUMMARY 
     In view of the deficiencies in the existing technologies, the present application provides a fan and a hair dryer, which can improve the air outlet performance. 
     In order to solve the above-mentioned technical problem, the present application adopts the following technical solution: 
     a fan including: an air cylinder, an interior of the air cylinder being hollow along an axial direction of the air cylinder to form a hollow cavity which extends through the air cylinder, the air cylinder having an air inlet and an air outlet; an air impeller, disposed inside the air cylinder and is configured for blowing the air cylinder to form a high-speed airflow; and a guide vane assembly, disposed inside the air cylinder and adjacent to the air impeller, the guide vane assembly being configured to rectify an airflow entering the air cylinder; wherein along an air inlet direction from the air inlet to the air outlet, an inner wall of the air cylinder includes an air inlet section, a socket section and an air outlet section which are connected in sequence; and the air impeller and the guide vane assembly are disposed on the socket section; the air inlet section is provided with a constriction area, the constriction area extends to form the air inlet, and the constriction area is configured to depressurize the airflow entering the air impeller; the air outlet section is provided with a flared area, the flared area extends to form the air outlet, and the flared area is configured to diffuse the airflow out of the guide vane assembly. 
     Preferably, the air inlet section includes: a first flat straight area substantially parallel to the axial direction of the air cylinder; and a first inclined surface area connected with the first flat straight area and the socket section, respectively; and the first inclined surface area and the axial direction of the air cylinder are disposed at a first included angle to form the constriction area; wherein the first inclined surface area is farther from the air inlet than the first flat straight area. 
     Preferably, the socket section includes a second flat straight area and a third flat straight area which are substantially parallel to the axial direction of the air cylinder; the second flat straight area is connected with the first inclined surface area and the third flat straight area, respectively; wherein the second flat straight area is farther from the air outlet section than the third flat straight area, a diameter of the second flat straight area is smaller than a diameter of the first flat straight area, the air impeller is mounted on the second flat straight area, and the guide vane assembly is mounted on the third flat straight area. 
     Preferably, the air outlet section includes: a fourth flat straight area substantially parallel to the axial direction of the air cylinder; and a second inclined surface area connected with the third flat straight area and the fourth flat straight area, respectively; the second inclined surface area and the axial direction of the air cylinder are disposed at a second included angle to form the flared area; wherein the second inclined surface area is farther from the air outlet than the fourth flat straight area, and a diameter of the fourth flat straight area is larger than a diameter of the third flat straight area. 
     Preferably, the constriction area is an arc or an arc chain formed by smooth connection of a plurality of arcs; or the constriction area is a straight line or a polyline formed by a plurality of straight lines. 
     Preferably, the air impeller is disposed adjacent to the air inlet section, the air impeller includes a wheel hub connected with an output shaft of a motor and a plurality of blades disposed on an outer wall of the wheel hub at equal intervals along a circumferential direction of the wheel hub, the number of the blades is n1; wherein the blades are configured such that a section in the circumferential direction of the wheel hub is arc-shaped, and a chord length B corresponding to the section increases as a diameter D of the blade increases; the number n1 of the blades, the chord length B and the diameter D of the blade satisfy the following relationship: 0.35&lt;(B*n1/D)&lt;0.48. 
     Preferably, the blade has a blade root connected to the wheel hub and a blade tip disposed away from the blade root; and wherein a gap between the blade tip and the inner wall of the air cylinder gradually decreases along the air inlet direction. 
     Preferably, the wheel hub is connected with the output shaft of the motor through a knurled nut; wherein an outer diameter of the wheel hub is gradually increasing in the air inlet direction, and a projection of an outer peripheral surface of the wheel hub in the axial direction is an arc or a smooth arc chain composed of a plurality of arcs. 
     Preferably, the guide vane assembly is disposed adjacent to the air outlet section, the guide vane assembly includes a motor fixing seat supporting the motor and guide vanes disposed on an outer wall of the motor fixing seat, the guide vanes are connected with the inner wall of the air cylinder so as to fix the motor to the air cylinder; wherein the air cylinder, the motor fixing seat and the wheel hub are disposed coaxially. 
     In order to solve the above-mentioned technical problem, another technical solution adopted in the present application is: 
     a hair dryer having the aforementioned fan. 
     Compared with the prior art, the present application has the following beneficial effects: 
     in the fan and the hair dryer provided by the present application, the constriction area is provided at the air inlet of the fan, and the flared area is provided at the air outlet of the fan. The constriction area is configured to depressurize the airflow entering the air impeller, while the flare area is configured to diffuse the airflow flowing out of the guide vane assembly, so that the air volume of the fan can still meet the usage requirements without increasing the rotational speed, and the noise problem can be effectively solved. 
     In view of the deficiencies in the above technologies, the present application provides a fan and a hair dryer, which can improve the air outlet speed. 
     In order to solve the above-mentioned technical problem, the present application adopts the following technical solution: 
     a fan including: an air cylinder, an interior of the air cylinder being hollow along an axial direction of the air cylinder to form a hollow cavity extending through the air cylinder, the air cylinder having an air inlet and an air outlet; and an air outlet hood detachably disposed on the air outlet, the air outlet hood being provided with an annular air outlet for air outlet; wherein an outer ring and/or an inner ring of the annular air outlet is formed with an annular guide rib extending along a circumferential direction of the annular air outlet and extending toward the air inlet; the annular guide rib is configured to make an airflow cross section adjacent to the annular air outlet gradually decrease, so as to make an airflow in the air outlet hood cohesive, thereby increasing an air outlet speed of the annular air outlet. 
     Preferably, the annular guide rib disposed on the outer ring of the annular air outlet is a first annular guide rib, and the annular guide rib disposed on the inner ring of the annular air outlet is a second annular guide rib; wherein along a direction from the air inlet to the air outlet, an inner diameter of the first annular guide rib is gradually decreasing, and an outer diameter of the second annular guide rib is gradually increasing. 
     Preferably, an inner wall of the first annular guide rib is provided with at least a first inclined region section which forms an included angle α with an axial direction of the air outlet hood, so as to make the airflow in the air outlet hood cohesive; wherein a value range of the included angle α is: 0°≤α≤60°. 
     Preferably, an outer wall of the second annular guide rib is provided with at least a second inclined region section which forms an included angle β with an axial direction of the air outlet hood, so as to make the airflow in the air outlet hood cohesive; wherein a value range of the included angle β is: 0°≤α≤12°. 
     Preferably, the air outlet hood has an inner end surface and an outer end surface disposed opposite to the inner end surface, the annular guide rib is provided on the inner end surface, a center of the outer end surface is provided with a groove which is configured for mounting an indicator light assembly; and wherein the annular air outlet is annularly distributed on an outer circumference of the groove. 
     Preferably, the indicator light assembly includes a control panel and a light cover, the control panel is provided with an indicator light, the control board is disposed in the light cover and assembled with the light cover as a whole; and wherein the light cover is detachably disposed in the groove. 
     Preferably, an air nozzle is disposed at the air outlet, the air outlet has a first clamping structure, and the air nozzle has a second clamping structure matched with the first clamping structure; wherein after the air nozzle is clamped to the air outlet through the cooperation of the second clamping structure and the first clamping structure, the air nozzle is rotatable relative to the air cylinder. 
     Preferably, the first clamping structure includes a flange formed at the air outlet and a rib formed on an outer periphery of an end face of the air outlet hood; wherein the flange grows inwardly along a radial direction of the air outlet, the rib grows along the axial direction of the air outlet and abuts against the flange, and an inner ring hole diameter of the flange is smaller than an inner ring hole diameter of the rib to form a snap space; the second clamping structure includes a clamping edge formed on the air nozzle, and the clamping edge is configured to mate with the snap space. 
     Preferably, curved surfaces constricted inwardly are symmetrically formed on an wall surface of the air nozzle, so that the air nozzle has an air outlet with a flat mouth and an air inlet with a round mouth; the air nozzle includes an inner shell and an outer shell, the outer shell is sleeved on an outer circumference of the inner shell; wherein a connection structure is provided on a region section of a round opening of the outer shell corresponding to the curved surfaces, and the connection structure is configured for ultrasonic welding the inner shell and the outer shell. 
     In order to solve the above-mentioned technical problem, another technical solution adopted in the present application is: 
     a hair dryer having the aforementioned fan. 
     Compared with the prior art, the present application has the following beneficial effects: 
     in the fan and the hair dryer provided by the present application, the air outlet hood is based on the annular air outlet, and the annular guide rib is formed on the outer ring and/or the inner ring of the annular air outlet. As a result, the air outlet speed of the annular air outlet is effectively accelerated, the airflow is prevented from spreading at the annular air outlet, and the drying efficiency is effectively improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic perspective structural view of a fan in an embodiment of the present application; 
         FIG.  2    is a schematic exploded structural view of the fan in the embodiment of the present application; 
         FIG.  3    is a schematic cross-sectional view of the fan in the embodiment of the present application; 
         FIG.  4    is a schematic view of a first inclined surface area L 2  in an embodiment of the present application; 
         FIG.  5    is a schematic view of the first inclined surface area L 2  in another embodiment of the present application; 
         FIG.  6    is another schematic view of the first inclined surface area L 2  in another embodiment of the present application; 
         FIG.  7    is a schematic view of the first inclined surface area L 2  in another embodiment of the present application; 
         FIG.  8    is an enlarged structural view of an area A in  FIG.  7   ; 
         FIG.  9    is a schematic perspective structural view of an air impeller in an embodiment of the present application; 
         FIG.  10    is a schematic view along a front view direction of an air impeller in an embodiment of the present application; 
         FIG.  11    is a schematic cross-sectional view along a direction C-C in  FIG.  10   ; 
         FIG.  12    is a schematic structural view of a blade in an embodiment of the present application; 
         FIG.  13    is a schematic structural view of a guide vane in an embodiment of the present application; 
         FIG.  14    is a schematic view of a blade profile of a conventional guide vane; 
         FIG.  15    is a schematic structural view of a hair dryer in an embodiment of the present application; 
         FIG.  16    is a schematic view of a connection relationship between an air cylinder and an air outlet hood in an embodiment of the present application; 
         FIG.  17    is a schematic structural view of the air outlet hood in an embodiment of the present application; 
         FIG.  18    is a schematic structural view of the air outlet hood in an embodiment of the present application; 
         FIG.  19    is a schematic cross-sectional view of the air outlet hood in an embodiment of the present application; 
         FIG.  20    is a schematic cross-sectional view of the air cylinder in an embodiment of the present application; 
         FIG.  21    is an enlarged structure schematic view of a region A in  FIG.  1   ; 
         FIG.  22    is a schematic view of a positional relationship between the air cylinder and an air nozzle in an embodiment of the present application; 
         FIG.  23    is an exploded schematic view of the air cylinder and the air nozzle in an embodiment of the present application; 
         FIG.  24    is a schematic structural view of an indicator light assembly in an embodiment of the present application; 
         FIG.  25    is a schematic structural view of the air nozzle in an embodiment of the present application; 
         FIG.  26    is a schematic exploded structural view of the air nozzle in an embodiment of the present application; 
         FIG.  27    is an enlarged schematic view of a region B in  FIG.  11   ; and 
         FIG.  28    is a schematic view along a front view of a round opening of the outer shell in an embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION 
     The present application will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it with reference to the description. If there are descriptions involving “first”, “second”, etc., in the embodiments of the present application, the description of “first”, “second”, etc., are only used for the purpose of description, and should not be understood as indicating or implying their relative importance or implying the number of technical features indicated. Thus, a feature delimited with “first”, “second” may expressly or implicitly include at least one of that feature. 
     In the description of the present application, it should also be noted that, unless there are more explicit definitions and limitations, the terms “disposed” and “connected” should be understood in a broader sense. For example, the term “connected” may be a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection, or an indirect connection through an intermediate medium, or a communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood in specific situations. 
     In addition, if the meaning of “and/or” appears in the present application, it includes three concurrent solutions. Taking “A and/or B” as an example, it includes a solution A, or a solution B, or a solution that satisfies both the solution A and the solution B. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When a combination of technical solutions contradicts each other or cannot be realized, it shall be considered that such combination of technical solutions does not exist, and is not within the protection scope claimed in the present application. 
     Existing hair dryers are developing in a direction of small diameter and short body. This will inevitably require the diameter of the entire fan to be reduced accordingly, so that when the air volume of the fan needs to be guaranteed, the speed of the fan must be increased, which will lead to increased noise and affect the user&#39;s experience. 
     In view of this, as shown in  FIG.  1    to  FIG.  15   , embodiments of the present application provide a fan and a hair dryer with good air outlet performance. 
     Referring to  FIG.  1    to  FIG.  3   , in which  FIG.  1    is a schematic structural view of a fan in the present application,  FIG.  2    is a schematic exploded structural view of the fan in the present application, and  FIG.  3    is a schematic cross-sectional view of the fan in an embodiment of the present application, the fan includes an air cylinder  1100 , an air impeller  1400  and a guide vane assembly  1200 . An interior of the air cylinder  1100  is hollow along its axial direction so as to form a hollow cavity extending through the air cylinder  1100 . The air cylinder  1100  has an air inlet  1140  and an air outlet  1150 . The air impeller  1400  is disposed inside the air cylinder  1100  for blowing the air cylinder  1100  to form a high-speed airflow. The guide vane assembly  1200  is disposed inside the air cylinder  1100  and is disposed adjacent to the air impeller  1400 . The guide vane assembly  1200  is used to rectify an airflow entering the air cylinder  1100 . Wherein, along an air inlet direction from the air inlet  1140  to the air outlet  1150 , an inner wall of the air cylinder  1100  includes an air inlet section  1110 , a socket section  1120  and an air outlet section  1130  which are connected in sequence. The air impeller  1400  and the guide vane assembly  1200  are provided on the socket section  1120 . The air inlet section  1110  is provided with a constriction area. The constriction area extends to form the air inlet  1140 , and the constriction area is configured to depressurize the airflow entering the air impeller  1400 . The air outlet section  1130  is provided with a flared area. The flared area extends to form the air outlet  1150 , and the flared area is configured to diffuse the airflow flowing out of the guide vane assembly  1200 . The air impeller  1400  is disposed adjacent to the air inlet section  1110 , and the guide vane assembly  1200  is disposed adjacent to the air outlet section  1130 . 
     In the above-mentioned manner, the constriction area in the present application is configured to depressurize the airflow entering the air impeller  1400 , and the flared area is configured to diffuse the airflow flowing out of the guide vane assembly  1200 , so that the fan can still meet the demand for air volume without increasing the rotational speed of the fan, and effectively solve the noise problem. 
     Besides, continue to refer to  FIG.  3   , the air inlet section  1110  includes a first flat straight area L 1  and a first inclined surface area L 2 . The first inclined surface area L 2  is farther from the air inlet  1140  than the first flat straight area L 1 . The first flat straight area L 1  is substantially parallel to the axial direction of the air cylinder  1100 . Two ends of the first inclined surface area L 2  are connected with the first flat straight area L 1  and the socket section  1120 , respectively. In addition, the first inclined surface area L 2  and the axial direction of the air cylinder  1100  are disposed at a first included angle α 1  to form the constriction area. Therefore, when the fan works, the airflow firstly passes through the first flat straight area L 1  for rectification and then passes through the first inclined surface area L 2  for airflow acceleration, so that the airflow pressure at the air inlet  1140  of the air cylinder along the air inlet direction is gradually reduced, and the airflow can enter the air impeller  1400  at a lower pressure. By designing the air inlet  1140  as described above, the air pressure at the air inlet  1140  can be reduced, thereby preventing the airflow in the air cylinder  1100  from flowing back. 
     Specifically, the constriction area corresponds to the first inclined surface area L 2 . There are many ways to realize the constriction area. Referring to  FIG.  4    to  FIG.  6   , the constriction area can be an arc or an arc chain formed by smooth connection of a plurality of arcs. Referring to  FIG.  7    and  FIG.  8   , the necking area may be a polyline formed by a straight line or a plurality of straight lines.  FIG.  4    is a schematic view when the first inclined surface area L 2  is a single circular arc R.  FIG.  5    and  FIG.  6    are schematic views showing that the first inclined surface area L 2  is formed by the smooth connection of two arcs with radii R 1  and R 2 , respectively. Of course, the first inclined surface area L 2  may also be formed by smooth connection of a plurality of arcs with different radii.  FIG.  3    is a schematic view showing that the first slope area L 2  is formed by a straight line. A first included angle α 1  is formed by the straight line and the axial direction of the air cylinder  100 . A value range of the first included angle α  1  is: 30°≤α 1 ≤60°.  FIG.  7    and  FIG.  8    are broken lines formed by three straight line segments in the first inclined surface area L 2 . In the air inlet direction from the air inlet  140  to the air outlet  1150 , the first inclined surface area L 2  sequentially includes a first straight line segment B 1  which forms an included angle β 1  with the axial direction of the air cylinder  1100 , a second straight line segment B 2  which forms an included angle β 2  with the axial direction of the air cylinder  1100 , and a third straight line segment B 3  which forms an included angle β 3  with the axial direction of the air cylinder  1100 . Of course, the first inclined surface area L 2  may also be a broken line composed of a plurality of straight line segments. The present application is not limited to this, and may also be a combination of an arc and a straight line, which is not further limited here. 
     Furthermore, the socket section  1120  includes a second flat straight area L 3  and a third flat straight area L 4  which are substantially parallel to the axial direction of the air cylinder  11100 . The second flat straight area L 3  is connected with the first inclined surface area L 2  and the third flat straight area L 4 , respectively. The second flat straight area L 3  is farther from the air outlet section  1130  than the third flat straight area L 4 . A diameter of the second flat straight area L 3  is smaller than a diameter of the first flat straight area L 1 . The air impeller  1400  is mounted in the second flat straight area L 3 . The guide vane assembly  1200  is installed in the third flat straight area L 4 . 
     Furthermore, referring to  FIG.  3   , the air outlet section  1130  includes a second inclined surface area L 5  and a fourth flat straight area L 6 . The fourth flat straight area L 6  is substantially parallel to the axial direction of the air cylinder  1100 . The second inclined surface area L 5  is connected with the third flat straight area L 4  and the fourth flat straight area L 6 , respectively. In addition, the second inclined surface area L 5  and the axial direction of the air cylinder  1100  are disposed at a second included angle α 2  to form a flared area. The second inclined surface area L 5  is farther from the air outlet  1150  than the fourth flat straight area L 6 . A diameter of the fourth flat straight area L 6  is larger than a diameter of the third flat straight area L 4 . Therefore, the airflow can be diffused in the air outlet section  1130 , so that the kinetic energy is converted into static pressure, the pressure resistance of the fan is improved, and the exhaust loss is reduced. 
     Furthermore, referring to  FIG.  3    in conjunction with  FIG.  9   , the air impeller  1400  is fastened on an output shaft of a motor  1300 . The air impeller is completely nested in the air cylinder  1100 , and can rotate around the output shaft of the motor  1300  in the air cylinder  1100 . The air impeller  1400  includes a wheel hub  1410  connected with the output shaft of the motor  1300  and blades  1420  arranged on an outer wall of the wheel hub  1410  at equal intervals along a circumferential direction of the wheel hub  1410 . The wheel hub  1410  is installed in the second flat straight area L 3 . The blades  1420  are located in the first inclined surface area L 2  and the second flat straight area L 3 . The blade  1420  has a blade root  1421  connected to the wheel hub  1410 , a blade tip  1422  disposed away from the blade root  1421 , a blade leading edge  1423  as a windward side and a blade trailing edge  1424  as a downwind side. The blade leading edge  1423  and the blade trailing edge  1424  are located on both sides of the blade root  1421  and the blade tip  1422 , respectively. In the second flat straight area L 3 , a gap between the blade tip  1422  and the inner wall of the air cylinder  1100  gradually decreases along the air inlet direction. In this way, a backflow of a top clearance of the blade  420  can be effectively prevented, thereby improving the efficiency of the fan. 
     Specifically, referring to  FIG.  12   , the blade  1420  is configured such that a section M in the circumferential direction of the wheel hub  1410  is arc-shaped, and a chord length B corresponding to the section M increases as the radius of the blade  1420  increases. That is, a cross-sectional shape of the blade  1420  in the circumferential direction of the wheel hub  1410  continuously changes according to the size of the radius of the blade  1420 . The plurality of blades  1420  are arranged in a twisted attitude on the outer wall of the wheel hub  1410 , and the blade leading edge and the blade trailing edge of adjacent two blades  1420  overlap. 
     Specifically, referring to  FIG.  9    to  FIG.  12   , a height of the blade  1420  is defined as a distance from the blade tip  1422  of the blade  1420  to the blade root  1421 . If a diameter at a certain height G of the blade  1420  is D, the following relationship is satisfied among the number n1 of blades  1420 , the chord length B at the blade height, and the diameter D of the blade  1420 : 0.35&lt;(B*n1/D)&lt;0.48, where the number n1 of blades  1420  satisfies 5≤n1≤13. Based on this, after the blade  1420  meets the above design, the chord length B gradually increases from the blade root  1421  to the blade tip  1422 , and the working power of the air impeller  1400  is enhanced under the same rotation speed. In addition, the installation angle of the blade  1420  from the blade root  1421  to the blade tip  1422  is less twisted, and the blade  1420  has high strength. 
     Referring to  FIG.  3    in conjunction with  FIG.  9   , considering the existence of assembly errors, after the air impeller  1400 , the guide vane assembly  1200  and the motor  1300  are all installed on the air cylinder  1100 , an axial distance between an interface f-f of the first flat straight area L 1  and the first inclined surface area L 2  and a leading edge point Q of the blade  1420  is less than 0.05*K; wherein the interface f-f is perpendicular to an axis of the air cylinder  1100 , the leading edge point Q of the blade  1420  is where the blade tip  1422  meets the blade leading edge  1423 , and K is a length of the first inclined surface area L 2  in the axial direction of the air cylinder  1100 . The best assembled state of the air impeller  1400  is that the leading edge point Q of the blade  1420  is located on the interface f-f. That is, the axial distance between the interface f-f and the leading edge point Q of the blade  1420  is zero. 
     Furthermore, referring to  FIG.  3    in conjunction with  FIG.  11   , an outer diameter of the wheel hub  1410  is gradually increasing in the air inlet direction. A diameter d 1  of a small end face of the wheel hub  1410  adjacent to the air inlet  1140  is smaller than a diameter d 2  of a large end face of the wheel hub  1410  away from the air inlet  1150 . Specifically, a projection of an outer peripheral surface of the wheel hub  1410  in the axial direction is an arc or a smooth arc chain composed of a plurality of arcs. That is, the outer peripheral surface of the wheel hub  1410  is formed by splicing one or more arc surfaces in its axial direction. When the projection of the outer peripheral surface of the wheel hub  1410  in the axial direction is a smooth arc chain composed of a plurality of arcs, the number of arc segments is n2, which satisfies n2 and the radius of each arc is different. Therefore, when the airflow enters the air cylinder  100  through the blades  1420 , the airflow can move along the outer wall of the wheel hub  1410  to the guide vane assembly  1200 , thereby avoiding a phenomenon of intake air backflow and airflow separation at the blade root  1421 . 
     Furthermore, continue to refer to  FIG.  3    in conjunction with  FIG.  11   , the wheel hub  1410  of the air impeller  1400  can be connected to the output shaft of the motor  1300  through a knurled nut  1500 . Specifically, an interference connection is adopted between the knurled nut  1500  and the output shaft of the motor  1300 . The wheel hub  1410  is provided with a mounting hole  1411  which is matched with the knurled nut  1500 . The knurled nut  1500  is press-fitted into the mounting hole  1411 . In order to facilitate press-fitting the knurled nut  1500  into the mounting hole  1411 , a groove  1412  is provided on the small end face of a front end of the wheel hub  1410 . The groove  1412  communicates with the mounting hole  1411 . A groove depth of the groove  1412  is c, and a value range of the groove depth c is: (d1/3)≤c≤(d1/2). An outer circumference of the knurled nut  1500  is provided with knurling, thereby increasing the bonding strength with the wheel hub  1410 , reducing the jitter between the air impeller  1400  and the output shaft of the motor  1300  when rotating, and reducing noise. 
     Furthermore, referring to  FIG.  2    in conjunction with  FIG.  3   , the guide vane assembly  1200  includes a motor fixing seat  1210  supporting the motor  1300  and a plurality of guide vanes  1220  disposed on an outer wall of the motor fixing seat  1210 . The guide vanes  1220  are connected to the motor fixing seat  1210  and the inner wall of the air cylinder  1100  in the third flat straight area L 4 , respectively, to fix the motor  1300  to the air cylinder  1100 . The number of guide vanes  1220  is n3, which satisfies 5≤n3≤13. On the one hand, the guide vanes  1220  fix the motor  1300  in the air cylinder  1100 , and on the other hand, the guide vanes  1220  play a guiding role in the airflow in the air impeller  1400 , so as to homogenize the airflow. The motor fixing seat  1210  has an accommodating groove  1211  for installing the motor  1300  and a through hole  1212  formed on a groove wall of the accommodating groove  1211  for passing the output shaft of the motor  1300  to a side of the air impeller  1400 . The output shaft of the motor  1300  is connected to the air impeller  1400  after passing through the above-mentioned through hole  1212 , so that when the motor  1300  rotates, the air impeller  1400  is driven to rotate. The air cylinder  1100 , the motor fixing seat  1210  and the wheel hub  1410  are arranged coaxially. 
     Furthermore, in order to reduce the dynamic and static interference effect between the air impeller  1400  and the guide vane  1220 , the blade shape of the guide vane  1220  is designed. Referring to  FIG.  13   , which is a schematic view of the blade profile of the guide vane  1220 . The blade profile of the guide vane  1220  includes a pressure surface profile  1221 , a trailing edge profile  1224  as a downwind side, a suction surface profile  1222 , and a leading edge profile  1223  as a windward side. The pressure surface profile  1221 , the trailing edge profile  1224 , the suction surface profile  1222  and the leading edge profile  1223  are connected end to end. The leading edge profile  1223  is a single arc, which is smoothly connected with a starting point of the pressure surface profile  1221  and a starting point of the suction surface profile  1222 . The trailing edge profile  1224  connects a tail end of the pressure surface profile  1221  and a tail end of the suction surface profile  1222 . The suction surface profile  1222  adopts a single arc design. The pressure surface profile  1221  is designed with two arcs, in which a 1/4 to 1/3 section from the leading edge of the guide vane  1220  to the chord length I of the blade adopts a profile arc H 1 , and the profile arc H 1  is smoothly linked with its subsequent profile arc H 2 . Please continue to refer to  FIG.  14   , which is a schematic view of a blade profile of a conventional guide vane profile. Compared with the conventional guide vane shape, the pressure surface profile  1221  of the present application is designed with two circular arcs, which can form a concave portion on a pressure front edge adjacent to the leading edge profile  1223 , thereby effectively reducing the static and dynamic interference effect between the air impeller  1400  and the guide vane  1220 . 
     Specifically, after the air impeller  1400 , the guide vane assembly  1200  and the motor  1300  are all installed to the air cylinder  1100 , considering the existence of assembly errors, a distance between the blade trailing edge  1424  of the air impeller  1400  and the blade leading edge in the axial direction of the air cylinder  1100  is defined as a distance a, a length of the fan wheel  1400  in the axial direction of the air cylinder  1100  is defined as a distance b, and the distance a and the distance b satisfy the relationship, 0.15b≤a≤0.45b, wherein the blade leading edge refers to a position where the leading edge profile  1223  is located. 
     Furthermore, in consideration of the stability of the fan during operation, a reinforcing rib  1160  is provided on the outer wall of the air cylinder  1100 . Referring to  FIG.  1   , the reinforcing rib  1160  includes a transverse rib  1162  parallel to the airflow direction of the air cylinder  1100  and an annular rib  1161  perpendicular to the airflow direction of the air cylinder  1100 . In this way, the stability and reliability of the connection between the air cylinder  1100  and an outer cylinder  1600  can be improved, thereby improving the stability of the fan during operation. 
     It can be understood that the fan in the present application can be applied to different usage scenarios, which will be described below with examples. 
     The fan in the present embodiments can be applied to a hair dryer. Referring to  FIG.  15   , the hair dryer includes an outer cylinder  1600 , the fan provided inside the outer cylinder  1600 , and a handle  1900  located outside the outer cylinder  1600 . The outer cylinder  1600  is hollow inside and provided with openings at both ends. The fan is located in a hollow cavity of the outer cylinder  1600 . An air inlet hood  1700  and an air outlet hood  1800  are provided at the openings at both ends of the outer cylinder  1600 , respectively. The air inlet hood  1700  is arranged adjacent to the fan. The handle  1900  is connected with the outer cylinder  1600  and is located below the outer cylinder  1600  to support the outer cylinder  1600 . 
     It can be understood that the above specific applications are only examples of the fans in the present application. Those skilled in the art can make adaptive adjustments according to the actual situation, which will not be repeated here. 
     In summary, in the present application, the air inlet section  1110  is divided into the first flat straight area L 1  and the first inclined surface area L 2 , when the airflow enters the fan from the outside, it is rectified through the first flat straight area L 1 , and accelerated and depressurized in the first inclined surface area L 2 , so that the airflow pressure along the air inlet direction is gradually reduced, and the airflow enters the air impeller  1400  at a lower pressure. Therefore, it can effectively prevent a pressure P 2  at an inlet of the air impeller  1400  being greater than a pressure P 1  at the air inlet  1140  due to the forced work and pressurization after the airflow enters the air impeller  1400 , thereby preventing the airflow from forming backflow, and avoiding the loss of air volume and efficiency. In the present application, the air outlet section  1130  is divided into the second inclined surface area L 5  and the fourth flat straight area L 6 . Therefore, the airflow can be diffused in the air outlet section  1130 , so that the kinetic energy is converted into static pressure, the pressure resistance of the fan is improved, and the exhaust loss is reduced. 
     A hair dryer dries wet hair by generating wind with a specific temperature. Drying efficiency is a main indicator for measuring the performance of the hair dryer. After the hair dryer is powered on, a motor drives an impeller to rotate, and the air is sucked in from the air inlet. The sucked air is heated by an electric heating element to form hot air and then blown out from the air outlet. At present, an annular air outlet of the air outlet hood on the market does not have a gathering effect on the air outlet, and the air outlet is easy to diffuse, which makes the air outlet speed slower, thereby affecting the drying efficiency. 
     In view of this, as shown in  FIG.  16    to  FIG.  28   , the present application provides a fan and a hair dryer with a faster air outlet speed. 
     Referring to  FIG.  16    to  FIG.  20   , in which  FIG.  16    is a schematic view of the connection relationship between the air cylinder  2100  and the air outlet hood  2200  in the present application,  FIG.  17    is a schematic structural view of the air outlet hood  2200  in the present application,  FIG.  18    and  FIG.  19    are schematic views of the air outlet hood  2200  according to an embodiment of the present application, the fan includes an air cylinder  2100  and an air outlet hood  2200 . An interior of the air cylinder  2100  is hollow along its axial direction to form a hollow cavity extending through the air cylinder  2100 . The air cylinder  2100  has an air inlet  2110  and an air outlet  2120 . The air outlet hood  2200  is detachably disposed on the air outlet  2120 . The air outlet hood  2200  is provided with an annular air outlet  2210  for air outlet. An outer ring and/or an inner ring of the annular air outlet  2210  is formed with a plurality of annular guide ribs  2220  extending along a circumferential direction of the annular air outlet  2210  and toward the air inlet  2110 . The annular guide ribs  2220  are configured to gradually reduce the airflow cross section near the annular air outlet  2210 , so that the airflow in the air outlet hood  2200  is cohesive, thereby increasing the air outlet speed of the annular air outlet  2210 . 
     In the above manner, the annular air outlet  2210  of the air outlet hood  2200  in the present application is provided with the annular guide ribs  2220  which can make the airflow cohesive, so as to speed up the air outlet speed of the annular air outlet  2210  and prevent the airflow from spreading at the annular air outlet  2210 , thereby effectively improving the drying efficiency. 
     Furthermore, the annular air outlet  2210  in the present application is provided with a number of air distribution ribs distributed along a radial direction of the annular air outlet  2210 . The air distribution ribs are distributed on the annular air outlet  2210  in a circular array. Understandably, the annular guide ribs  2220  formed on the outer ring and/or the inner ring of the annular air outlet  1210 , includes three parallel situations: first, the annular guide ribs  2220  are only provided on the outer ring of the annular air outlet  2210 ; second, the annular guide ribs  2220  are only provided on the inner ring of the annular air outlet  2210 ; and third, the annular guide ribs  2220  are provided on the outer ring and the inner ring of the annular air outlet  2210  at the same time. Preferably, the annular guide ribs  2220  are arranged on the outer ring and the inner ring of the annular air outlet  2210  at the same time. Referring to  FIG.  18    and  FIG.  19   , in this arrangement, the airflow in the air outlet hood  2200  can be more easily cohesive, and the cohesion effect is good. 
     Specifically, the annular guide ribs  2220  are divided into a first annular guide rib  2221  and a second annular guide rib  2222  according to different installation positions. Referring to  FIG.  18    and  FIG.  19   , the annular guide rib  2220  disposed on the outer ring of the annular air outlet  2210  is the first annular guide rib  2221 , and the annular guide rib  2220  disposed on the inner ring of the annular air outlet  2210  is the second annular guide rib  2222 . Both the first annular guide rib  2221  and the second annular guide rib  2222  are formed by a 360° rotation around a central axis X of the air outlet hood  2200 . Along the direction from the air inlet  2110  to the air outlet  2120 , an inner diameter of the first annular guide rib  2221  is gradually decreasing, and an outer diameter of the second annular guide rib  2222  is gradually increasing. 
     Furthermore, an inner wall of the first annular guide rib  2221  is provided with at least a first inclined region section  22211  which forms an angle α with an axial direction of the air outlet hood  2200 , so that the airflow in the air outlet hood  2200  is cohesive. An outer wall of the second annular guide rib  2222  is provided with at least a second inclined region section  22221  which forms an angle β with the axial direction of the air outlet hood  2200 , so that the airflow in the air outlet hood  2200  is cohesive. Wherein a value range of the included angle α is: 0°≤α≤60°. A value range of the included angle β is: 0°≤α≤12°. Specifically, a projection of the first inclined region section  22211  and the second inclined region section  22221  on a vertical plane passing through the central axis X of the air outlet hood  2200  may be a straight line segment or an arc segment. The included angle between the arc segment and the axial direction of the air outlet hood  2200  is defined as the included angle between a line connecting a starting point and an ending point of the arc segment and the central axis X. 
     Furthermore, an indicator light assembly  2300  is also provided on the fan. The indicator light assembly  2300  is used to display whether a negative ion generator is in a working state or not. Referring to  FIG.  24   , the indicator light assembly  2300  includes a control board  2310  provided with an indicator light, and a light cover  2320 . The control board  2310  is disposed in the light cover  2320  and assembled with the light cover  2320  as a whole. The light cover  2320  is made of light-transmitting material. When the control panel  2310  is powered on, the indicator light illuminates the light cover  2320 , which can have a lighting effect showing the shape of the light cover  2320 . The shape of the light cover  2320  may be a ring, an elliptical ring, a circle, an ellipse or other shapes, which are not further limited herein. 
     Specifically, in order to make the light display position of the indicator light assembly  2300  more obvious and the installation more convenient, the indicator light assembly  2300  is installed on the air outlet hood  2200 . Referring to  FIG.  17    and  FIG.  18    in conjunction with  FIG.  23   , the air outlet hood  2200  has an inner end surface and an outer end surface disposed opposite to each other. The annular guide ribs  2220  are provided on the inner end surface. A groove  2230  is provided in a center of the outer end surface. The annular air outlet  2210  is annularly distributed on an outer circumference of the groove  2230 . The groove  2230  is configured for installing the indicator light assembly  2300 , so that the indicator light can be displayed on a front face of the air cylinder  2100  adjacent to the user, and the position is obvious and the lighting effect is better. The shape and size of the groove  2230  matches the shape and size of the indicator light assembly  2300 . The indicator light assembly  2300  and the groove  2230  are connected in a detachable manner. It can be understood that the indicator light assembly  2300  and the groove  2230  can be connected by a snap structure, or can be connected by a screw. In order to facilitate installation, in the present application, the indicator light assembly  1300  and the groove  1230  are connected by the snap structure. The snap structure includes a buckle  2321  arranged on the light cover  2320  and a snap hole  2231  arranged in the groove  2230  and matched with the buckle  2321 . 
     Furthermore, referring to  FIG.  22    and  FIG.  23   , the fan is also provided with an air nozzle  2400 . The air nozzle  2400  is arranged at the air outlet  2120  for constraining the wind pattern. In order to make the installation of the air nozzle  2400  and the air cylinder  2100  more convenient, the air nozzle  2400  and the air cylinder  2100  are connected by a clamping connection. The air outlet  2120  has a first clamping structure. The air nozzle  2400  has a second clamping structure matched with the first clamping structure. After the air nozzle  2400  is clamped to the air outlet  2120  through the cooperation between the second clamping structure and the first clamping structure, the air nozzle  2400  can rotate 360° relative to the air cylinder  2100 . When the air nozzle  2400  needs to be disassembled from the air cylinder  2100 , the disassembly can be realized only by exerting a certain axial pulling force on the air nozzle  2400 . 
     Specifically, referring to  FIG.  20    and  FIG.  21   , the first clamping structure includes a flange  2121  formed at the air outlet  2120  and a rib  2240  formed on an outer periphery of the end surface of the air outlet hood  2200 . The flange  2121  grows inwardly along a radial direction of the air outlet  2120 . The rib  2240  grows along the axial direction of the air outlet  2120  and abuts against the flange  2121 . An inner diameter of the flange  2121  is smaller than an inner diameter of the rib  2240  so as to form a snap space. Referring to  FIG.  25    and  FIG.  26   , the second clamping structure includes a clamping edge  2440  formed on the air nozzle  2400 . The clamping edge  2440  is configured to mate with the snap space. Curved surfaces  2430  constricted inwardly are symmetrically arranged on the wall surface of the air nozzle  2400 , so that the air nozzle  2400  has a flat air outlet and a round air inlet. The clamping edge  2440  is disposed at an edge of the air inlet of the air nozzle  2400 . 
     Furthermore, considering the anti-scalding and wind-gathering effects, the air nozzle  2400  is designed as a double-layer structure. The air nozzle  2400  includes an inner shell  2410  and an outer shell  2420 . The outer shell  2420  is sleeved on an outer circumference of the inner shell  2410 . Shapes of the inner shell  2410  and the outer shell  2420  are similar, and both have a flat air outlet and a round air inlet. The clamping edge  2440  can be located at the air inlet of the outer shell  2420  or at the air inlet of the inner shell  2410 . In the present application, the clamping edge  2440  is a pair of arc-shaped convex edges which are symmetrically disposed at the air inlet of the inner shell  2410 . 
     Furthermore, in order to make the inner shell  2410  and the outer shell  2420  have better connection reliability and stability, the inner shell  2410  and the outer shell  2420  need to be fixedly connected by arranging a connection structure  2450 . Considering the appearance effect after the inner shell  2410  and the outer shell  2420  are connected and matched, ultrasonic welding is adopted between the inner shell  2410  and the outer shell  2420 . Accordingly, the above-described connection structure  2450  is configured for ultrasonic welding of the inner shell  2410  and the outer shell  2420 . 
     Specifically, the connection structure  2450  is located on an area segment of the round opening of the outer shell  2420  corresponding to the curved surface  2430 . Referring to  FIG.  27   , the connection structure  2450  includes a welding groove  2451  and a welding rib  2452  formed on the round opening of the outer shell  2420 . The welding groove  2451  and the welding rib  2452  are arranged adjacent to each other. Referring to  FIG.  28   , the welding groove  2451  is disposed on the round opening of the outer shell  2420  in a center-symmetrical manner. A central angle corresponding to the area where the welding groove  2451  is located is M, and the central angle M is 80°. The welding rib  2452  is disposed within the area where the welding groove  2451  is located. The welding rib  2452  may be continuous in a single segment, or may be arranged in multiple segments uniformly or non-uniformly within this range. An outer wall of the inner shell  2410  adjacent to the round opening is provided with an annular welding edge  2411  growing along its radial direction. The welding edge  2411  is used to mate with the connection structure  2450  to realize the fixed connection between the inner shell  2410  and the outer shell  2420 . 
     It can be understood that the fan in the present application can be applied to different usage scenarios, which will be described below with examples. 
     The fan in the present application can be applied to a hair dryer. The hair dryer includes the fan and a handle connected with the fan. The handle is located below the fan for supporting the fan. The handle has a built-in negative ion generator. An inside of the fan is provided with an emitting needle electrically connected with the negative ion generator. The emitting needle is connected with the negative ion generator through a wire. When the negative ion generator is activated, the indicator light of the indicator light assembly  2300  emits bright light, which can display the lighting effect in the shape of the light cover  2320 . 
     It can be understood that the above specific applications are only examples of the fan in the present application. Those skilled in the art can make adaptive adjustments according to the actual situation, which will not be repeated here. 
     In summary, the air outlet hood in the present application is based on the annular air outlet, and annular guide ribs are formed on the outer ring and/or the inner ring of the annular air outlet, thereby effectively speeding up the air outlet speed of the annular air outlet. It avoids the airflow from spreading at the annular air outlet, and effectively improves the drying efficiency. The control board of the indicator light assembly is assembled with the light cover as a whole, and is arranged on the air outlet hood through the light cover. The indicator light can be displayed on the front face of the air cylinder adjacent to the user, the installation is convenient, the position is obvious, and the lighting effect is better. The air nozzle and the air cylinder are connected by the snap connection, which has the advantage of convenient installation. The air nozzle is designed with the double-layer structure, which can effectively improve the anti-scalding and wind-gathering effects.