JP2007309313A - Axial flow blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial flow blower capable of suppressing noise and vibration than a conventional axial flow blower in the case of using four webs. <P>SOLUTION: An angle of two adjacent virtual straight lines of first to fourth straight lines PL1 to PL4 corresponding to first to fourth webs 11A to 11D is 90°. The four webs 11A to 11D are provided so that an angle θ of the virtual straight lines PL1 and PL3 positioned at rotation direction side of the impeller 7 as viewed from a first virtual center line CL1 and the first virtual center line CL1 and an angle θ of the virtual straight lines PL2 and PL4 positioned at a rotation direction side as viewed from a third center line CL3 and the third virtual center line CL3 are in a range of 8° < θ < 14°. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an axial blower used for cooling electrical components and the like.

Japanese Patent Laid-Open No. 5-164089 [Patent Document 1] and the like show an example of a typical conventional example of an axial-flow fan 105 having four webs 101 to 104 as shown in FIG. . The outer end portions of the four webs 101 to 104 are fixed to an annular taper portion 107 of a wind tunnel provided on the discharge port 106 side. The discharge port 106 has four straight sides 108 to 111 arranged at intervals of 90 degrees and four arc sides 112 to 115 located between the two straight sides. The outer end portions of the four webs 101 to 104 are fixed to the tapered portion 107 at positions corresponding to the end portions of the arc sides 112 to 115, respectively. Here, a virtual center line CL passing through the rotation center line Cp and the centers of the straight sides 108 to 111 is assumed, and a virtual line PL passing through the inner end portion and the outer end portion of the webs 101 to 104 is assumed. When the angle θ from the virtual center line CL to the virtual line PL is measured in the direction of rotation of the impeller, the angle θ is a value close to about 65 degrees in the conventional axial fan.
Japanese Patent Laid-Open No. 5-164089 FIG.

  However, the structure of the conventional axial fan has a limit in reducing noise and vibration.

  An object of the present invention is to provide an axial blower capable of suppressing noise and vibration as compared with the conventional case when four webs are used.

  The axial blower of the present invention has a fan housing having a wind tunnel. The wind tunnel includes a cylindrical portion located at the center, an annular discharge side taper portion that is located between one end of the cylindrical portion and the discharge port and extends radially outward of the cylindrical portion, and the other end of the cylindrical portion and the suction port And an annular suction port side taper portion which is located between and extends radially outward of the cylindrical portion. The axial blower has an impeller disposed in the wind tunnel and having a plurality of blades, a rotor to which the impeller is fixed, a stator provided corresponding to the rotor, and a motor case. The motor case has a bottom wall portion located on the discharge port side and a peripheral wall portion formed continuously with the bottom wall portion and extending toward the suction port side, and the stator is fixed to the bottom wall portion. . Further, the axial blower includes four webs that are arranged at intervals in the rotation direction of the impeller and are located in the discharge port in the wind tunnel, and connect the motor case and the fan housing. The four webs are located between the outer end connected to the outlet side taper of the wind tunnel, the inner end connected to the peripheral wall of the motor case, and the outer end and the inner end. Each has a linear portion extending linearly between the two.

  In the present invention, the discharge port has a polygonal shape composed of a first to a fourth pair of straight sides that face each other about the rotation center line of the rotor and are arranged in order in the rotation direction of the impeller. Yes. In order to specify the shape of the discharge port, the first virtual center line passing through the center of the first pair of straight sides and the rotation center line, and the center of the second pair of straight sides and the rotation center line are determined. A second virtual center line passing through, a third virtual center line passing through the center of the third pair of straight sides and the rotation center line, and a second passing through the center of the fourth pair of straight sides and the rotation center line. 4 virtual center lines are virtualized. Under this hypothesis, the angle between two adjacent virtual center lines of the first to fourth virtual center lines is 45 degrees. The lengths of the first and third pairs of straight sides are equal, and the lengths of the second and fourth pairs of straight sides are equal. The distance between the intersection of the first and third virtual center lines and the first and third pair of straight sides and the rotation center line is the second and fourth virtual center lines and the second and fourth distances. Shorter than the distance between the intersection of the pair of straight sides and the rotation center line. Further, the lengths of the first and third pair of straight sides are determined so that one straight side of the first and third pair of straight sides exists outside the outer end portions of the four webs. It has been.

  Further, in order to specify the four webs, the first to fourth virtual straight lines that pass through the center of the outer end portion, the center of the inner end portion, and the center of the straight portion are arranged in order in the rotation direction of the impeller. To do. Under such a hypothesis, the angle between two adjacent virtual straight lines of the first to fourth virtual straight lines is 90 degrees. Further, the angle θ between the virtual straight line positioned on the impeller rotation direction side as viewed from the first virtual center line and the first virtual center line, and the impeller rotation direction side viewed from the third virtual center line. The four webs are arranged so that the angle θ between the virtual straight line and the third virtual center line is an angle within a range of 8 degrees <θ <14 degrees.

  When the above structure is adopted, noise measured on the outside of the fan housing and vibration generated in the fan housing can be greatly reduced as compared with the conventional structure. Although the theoretical reason for the reduction effect has not yet been clarified, it has been confirmed by tests that a special effect is generated by the combination of the above-mentioned constituent requirements.

  The shape of the suction port is preferably determined so as to be substantially congruent with the shape of the discharge port as seen from the direction in which the rotation center line extends.

  When the angle θ is 10 degrees, a great reduction effect can be obtained in both noise and vibration.

  Moreover, you may provide the 4 stationary blades of a 1st group along the 2nd and 4th virtual centerline on a discharge outlet side taper part. Further, adjacent to the boundary between the first pair of straight sides and the fourth pair of straight sides and the boundary between the second pair of straight sides and the third pair of straight sides on the outlet side taper portion In addition, the four stationary blades of the second group may be provided at positions corresponding to the first pair of straight sides and the third pair of straight sides. The four stationary blades of the second group are arranged at an angular interval of 90 degrees in the rotation direction of the impeller. Further, the eight stationary blades of the first and second groups preferably extend toward the rotation center line and along the rotation center line. In this way, the noise can be further reduced and the air volume can be increased as compared with the case where no stationary blade is provided.

  Moreover, you may form the electric wire accommodation groove | channel in which several electric wires are accommodated in one web among four webs. In this case, the width of the one web is larger than that of the remaining three webs. And the cross-sectional shape of the portion facing each of the plurality of blades in each linear portion of the four webs is such that the width dimension of the end portion on the suction port side is shorter than the width dimension of the end portion on the discharge port side. To do. In addition, the cross-sectional shape of the three webs is a shape having an inclined surface on the side surface located on the impeller rotation direction side when viewed from the suction port. Moreover, it is preferable that the cross-sectional shape of one web has inclined surfaces on both side surfaces located on the rotation direction side of the impeller and on the opposite side to the rotation direction as viewed from the suction port. When a web having such a cross-sectional shape is used, the noise reduction effect can be further ensured.

  According to the present invention, the noise measured outside the fan housing and the vibration generated in the fan housing can be greatly reduced as compared with the conventional structure.

  Hereinafter, an example of an embodiment of an axial blower of the present invention will be described in detail with reference to the drawings. 1A and 1B are a perspective view of an axial blower 1 as an example of an embodiment of the present invention, seen from the front right side diagonally upward, and the rear left side diagonally upward, with the lead wires removed. It is a perspective view. 2 (A) and 2 (B) are front views of the axial-flow fan according to the embodiment shown in FIG.

  In these drawings, the axial blower 1 includes a fan housing 3 and an impeller 7 provided with seven blades (rotating blades 5) disposed in the fan housing 3 and rotating. Seven rotating blades 5 are attached to a cup-shaped rotating blade fixing member 6. As shown in FIGS. 1 and 2, the axial blower 1 further includes a motor 9 having a rotor and a stator (not shown) on which an impeller 7 is mounted, four webs 11A to 11D, and eight stationary blades 13A to 13A. 13H. In this example, the rotor has a structure in which a plurality of permanent magnets are fixed to the inner surface of the peripheral wall portion of a cup-shaped member fixed to a rotating shaft (not shown). The stator has a structure in which an excitation winding is mounted on the stator core. The stator is fixed to the bottom wall portion 10 </ b> A of the motor case 10. Also fixed in the motor case 10 is a circuit board on which a circuit for supplying an exciting current to the exciting winding is mounted. The motor case 10 has a bottom wall portion 10A located on the side of a discharge port 19 to be described later, and a peripheral wall portion 10B formed continuously with the bottom wall portion 10A and extending toward the suction port 18 side to be described later. Yes.

  The fan housing 3 has an annular suction port side flange 14 on one side (side where a suction port 18 described later) is provided in the direction (axial direction) in which the axis of the rotation shaft, that is, the rotation center line C extends (not shown). An annular discharge side flange 15 is provided on the other side in the axial direction (the side on which a discharge port 19 described later is provided). The fan housing 3 has a cylindrical portion 17 between both flanges 14 and 15. The suction port side flange 14 and the discharge port side flange 15 each have a substantially square contour shape. These four corners are respectively formed with through holes through which the mounting screws pass.

  A wind tunnel 20 having a suction port 18 and a discharge port 19 on both sides is formed by the internal spaces of the suction port side flange 14, the discharge port side flange 15, and the cylindrical portion 17. The wind tunnel 20 includes a cylindrical portion 21 located at the center, an annular discharge port side taper portion 23 that is located between one end 21a of the cylindrical portion 21 and the discharge port 19 and extends radially outward of the cylindrical portion 21, and a cylindrical shape. It is comprised between the other end 21b of the part 21 and the suction port 18, and the cyclic | annular suction port side taper part 25 extended in the radial direction outer side of the cylindrical part 21 is comprised.

  The four webs 11 </ b> A to 11 </ b> D that connect the motor case 10 and the fan housing 3 are an outer end portion 11 a that is connected to the outlet side taper portion 23 of the wind tunnel 20, and an inner side that is connected to the peripheral wall portion of the motor case 10. Each has an end portion 11b, and a linear portion 11c that is located between the outer end portion 11a and the inner end portion 11b and linearly extends between the two.

  As shown in FIG. 2 (B), the discharge ports 19 are opposed to each other around the rotation center line C of the rotor and are arranged in order in the rotation direction of the impeller 7 (the direction indicated by the arrow in FIG. 2). It has a polygonal shape composed of a fourth pair of straight sides (31a, 31b; 31c, 31d; 31e, 31f; 31g, 31h). The shape of the suction port 18 is also determined so as to be substantially congruent with the shape of the discharge port 19 when viewed from the direction in which the rotation center line C extends. In the present specification, in order to specify the shape of the discharge port 19, the first virtual center line CL1 passing through the center of the first pair of straight sides 31a and 31b and the rotation center line C, and the second pair A second virtual center line CL2 passing through the center of the straight sides 31c, 31d and the rotation center line C, and a third virtual center passing through the center of the third pair of straight sides 31e, 31f and the rotation center line C. A line CL3 and a fourth virtual center line CL4 passing through the center of the fourth pair of straight sides 31g and 31h and the rotation center line C are hypothesized. Under this imagination, the angle between two adjacent virtual center lines of the first to fourth virtual center lines CL1 to CL4 is 45 degrees. The lengths of the first pair of straight sides 31a and 31b and the third pair of straight sides 31e and 31f are equal. The lengths of the second pair of straight sides 31c and 31d and the fourth pair of straight sides 31g and 31h are equal. The distance between the intersection of the first and third virtual center lines CL1 and CL3 and the first and third pair of straight sides (31a, 31b; 31e, 31f) and the rotation center line C is second. In addition, the distance between the intersection of the fourth virtual center line CL2 and CL4 and the second and fourth pair of straight sides (31c, 31d; 31g, 31h) and the rotation center line C is shorter. That is, the length of the first and third pair of straight sides (31a, 31b; 31e, 31f) is longer than the length of the second and fourth pair of straight sides (31c, 31d; 31g, 31h). ing. As will be described later, the lengths of the first and third pair of straight sides (31a, 31b; 31e, 31f) are set to the first and first sides outside the outer end portions 11a of the four webs 11A to 11D. It is determined that one straight side of the three pairs of straight sides (31c, 31d; 31g, 31h) exists.

  In the present specification, in order to specify the four webs 11A to 11D, first to fourth virtual straight lines PL1 to PL1 passing through the center of the outer end portion 11a, the center of the inner end portion 11b, and the center of the straight portion 11c are used. It is assumed that PL4 is arranged in order in the rotation direction of the impeller 7. The virtual straight line PL1 and the virtual straight line PL3 extend in parallel with each other, and the virtual straight line PL2 and the virtual straight line PL4 extend in parallel with each other. Under such a hypothesis, the angle between two adjacent virtual straight lines of the first to fourth virtual straight lines PL1 to PL4 is 90 degrees. Further, the angle θ between the virtual lines PL1 and PL3 located on the rotation direction side of the impeller 7 as viewed from the first virtual center line CL1 and the first virtual center line CL1, and the third virtual center line CL3. The angle θ between the virtual straight lines PL2 and PL4 located on the rotation direction side of the impeller 7 and the third virtual center line CL3 is set to four angles so that the angle is in the range of 8 degrees <θ <14 degrees. Webs 11A to 11D are arranged. In this embodiment, as shown in FIG. 2A, the angle θ is set to 10 degrees. When the four webs 11A to 11D are arranged in this way, as shown in FIG. 2B, virtual extension lines (EL1, EL1) extending along the sides (S1, S2, S3, and S4) of the fan housing 3 are provided. EL2, EL3 and EL4) and the sides (S1, S2, S3 and S4) of the fan housing 3 from the intersections (P1, P2, P3 and P4) of the second and fourth virtual center lines CL2 and CL4, respectively. And the intersections (P4, P1, P2) from the intersections (P5, P6, P7 and P8), respectively, with the distance between the intersections (P5, P6, P7 and P8) of the first to fourth virtual straight lines PL1 to PL4 as L1. When the distance to P3) is L2, the distance ratio between L1 and L2 is L1: L2 = 34%: 66% when the length of one side of the fan housing 3 is 100%. This relationship is considered to be the best relationship in the present embodiment.

  FIG. 3A shows an end view of the axial blower 1 excluding the electric wires (lead wires) when cut in a direction perpendicular to the axis at a position near the outlet 19. As shown in FIGS. 1, 2, and 3 (A), in the present embodiment, the first taper 23 along the second and fourth virtual center lines CL <b> 2 and CL <b> 4 is disposed on the discharge-side taper portion 23. Four stationary blades (13B, 13D, 13F, 13H) of the group are provided. Further, on the discharge port side taper portion 23, a boundary portion between the first pair of straight sides 31a, 31b and the fourth pair of straight sides 31g, 31h and the second pair of straight sides 31c, 31d and the third pair 4 pieces of the second group at positions corresponding to the first pair of straight sides 31a and 31b and the third pair of straight sides 31e and 31f, adjacent to the boundary between the pair of straight sides 31e and 31f. Stationary blades (13A, 13C, 13E, 13G) are provided. The four stationary blades (13A, 13C, 13E, 13G) of the second group are arranged at an angular interval of 90 degrees in the rotation direction of the impeller 7. The eight stationary blades 13A to 13H of the first and second groups extend toward the rotation center line C and along the rotation center line C, respectively.

  Further, one of the four webs 11A to 11D is formed with a wire housing groove 11d for housing a plurality of wires in one web 11D. In the present embodiment, as shown in FIGS. 3B and 3C, the width dimension W1 of the web 11D is larger than the width dimension W2 of the remaining three webs 11A to 11C. The cross-sectional shape of the portion of each of the four webs 11A to 11D facing the plurality of blades in the linear portion 11c is such that the width dimension W3 and W4 of the end portion on the suction port 18 side are the end portions on the discharge port 19 side. The shape is determined to be shorter than the width dimensions W1 and W2. Further, the cross-sectional shapes of the three webs 11A to 11C are shapes having an inclined surface 11e on the side surface located on the rotation direction side of the impeller 7 when viewed from the suction port 18. Further, the cross-sectional shape of the web 11D has inclined surfaces 11f and 11g on the side of the rotation direction of the impeller 7 as viewed from the suction port 18 and on both side surfaces located in the direction opposite to the rotation direction. When the webs 11A to 11D having such a cross-sectional shape are used, the noise reduction effect can be further ensured in combination with the arrangement structure of the webs 11A to 11D.

  FIG. 4 shows the positional relationship between the axial blower 1 and the microphones A to D when the microphones A to D are arranged with respect to the axial blower 1 in the noise test. FIG. 5 shows a conventional axial fan (conventional product) having the structure shown in FIG. 9 when the number of blades and the rotation speed of the impeller are the same, and an axial fan (present invention) of the present embodiment. 4 shows the result of measuring the change in sound pressure level with respect to the change in air volume using the four microphones A to D shown in FIG. The four lines of the conventional product and the four lines of the present invention shown in FIG. 5 are the output results of the four microphones. As can be seen from FIG. 5, it can be seen that the axial flow fan of the present invention can achieve a sound pressure level (noise) reduction effect of about 20% compared to the conventional product. FIGS. 6A and 6B show the results of measuring the vibration generated in the radial direction of the fan housing and the vibration generated in the axial direction for the conventional product and the product of the present invention, respectively. 6A and 6B, it can be seen that the vibration of the product of the present invention is smaller than that of the conventional product in both of the vibration generated in the radial direction and the vibration generated in the axial direction. That is, it can be seen that the occurrence of vibration can be reduced by employing the structure of the embodiment of the present invention.

  7A and 7B show changes in vibration acceleration when the attachment positions of the outer end portions of the webs 11A to 11D (positions and angles θ of the first to fourth virtual straight lines PL1 to PL4) are changed. It is a graph which shows the result of having measured. The horizontal axis in FIG. 7A indicates the distance α (mm) between the intersection points (P1, P2, P3, and P4) and the intersection points (P5, P6, P7, and P8), and FIG. Corresponds to L1. The vertical axis in FIG. 7A indicates the change rate (%) of vibration acceleration. Further, the horizontal axis of FIG. 7B represents the distance α indicating the horizontal axis of FIG. 7A described above by an angle θ (degrees), and the vertical axis of FIG. The rate of change (%) in vibration acceleration is shown in the same manner as the vertical axis of FIG. In addition, each graph of FIG. 7 has shown the measurement result when the vibration acceleration Lv of a conventional product is 100%. The length of one side of the fan housing 3 used in this experiment is 60 mm.

  8A and 8B show sound pressure levels when the attachment positions of the outer ends of the webs 11A to 11D (positions and angles θ of the first to fourth virtual straight lines PL1 to PL4) are changed. It is a graph which shows the result of having measured the change of. The horizontal axis in FIG. 8A indicates the distance α (mm) corresponding to L1 in FIG. 2B, similarly to the horizontal axis in FIGS. 7A and 7B described above. The vertical axis of (A) indicates the change rate (%) of the vibration acceleration, similarly to the horizontal axis of FIGS. 7 (A) and 7 (B). Further, the horizontal axis of FIG. 8B represents the distance α indicating the horizontal axis of FIGS. 7A and 7B described above by an angle θ (degrees), and the vertical axis of FIG. The axis indicates the rate of change (%) in vibration acceleration as in the vertical axis of FIG. In the graph of FIG. 8, the average value of the outputs of the four microphones shown in FIG. 4 is shown as a measurement result. Moreover, each graph of FIG. 8 has shown the measurement result when the average value of the sound pressure level of a conventional product is set to Lp. Incidentally, “Lp-4” on each vertical axis in FIG. 8 means that the sound pressure is 4 dB lower than Lp. The length dimension of one side of the fan housing 3 used in this experiment is also 60 mm.

  As can be seen from FIG. 7A, in the present embodiment, it is preferable that the attachment position (distance α) is smaller than 22 mm when viewed from the point of occurrence of vibration. When this is expressed by an angle θ (when the distance α is expressed by an angle θ), as shown in FIG. 7B, the angle θ is preferably larger than 8 degrees. In addition, as can be seen from FIG. 8A, in this embodiment, the mounting position (distance α) is preferably in a range larger than 18 mm and smaller than 29 mm from the viewpoint of noise generation. If this is represented by angle θ (distance α is represented by angle θ), as shown in FIG. 8B, angle θ is preferably in the range of greater than −7 degrees and smaller than 14 degrees. From these results, it can be seen that the web mounting position is preferably in the range of 18 mm <α <22 mm. If this is expressed by angle θ (distance α is expressed by angle θ), angle θ is in the range of 8 degrees <θ <14 degrees.

  The above measurement result is a comprehensive result generated from the shape of each part of the present embodiment.

  In the above embodiment, one web 11D has a structure for accommodating a lead wire, but it is needless to say that a structure in which the lead wire is simply pulled out as it is may be adopted.

(A) And (B) is the perspective view which looked at the axial flow fan of an example of an embodiment of the present invention from the front right side diagonally upper direction and the rear left side diagonally upper side, respectively, in a state excluding the lead wire. It is. (A) And (B) is a front view of the axial-flow fan of FIG. 1, respectively. (A) is an end view when the axial blower excluding the lead wire is cut in a direction perpendicular to the axis at a position near the discharge port, and (B) and (C) are B in FIG. -B line sectional drawing and CC line sectional drawing. It is a figure which shows the position of the microphone with respect to the axial-flow fan of this Embodiment in the case of a noise test. FIG. 4 shows a conventional axial blower (conventional product) having the structure shown in FIG. 9 with the same number of blades and the same number of revolutions of the impeller, and an axial blower (present product) of the present embodiment. It is a figure which shows the result of having measured the change of the sound pressure level with respect to the change of an air volume using two microphones. (A) And (B) is a figure which respectively shows the result of having measured the vibration generate | occur | produced in the radial direction of a fan housing, and the vibration generate | occur | produced in an axial direction about a conventional product and this invention product. (A) And (B) is a figure which shows the result of having measured the change of the vibration acceleration when changing the attachment position of the outer side edge part of a web, respectively. (A) And (B) is a figure which shows the result of having measured the change of the sound pressure level when changing the attachment position of a web outer side edge part, respectively. It is a figure which shows the structure of the conventional axial blower.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axial fan 3 Fan housing 5 Rotating blade 7 Impeller 10 Motor case 10A Bottom wall part 11A thru | or 11D Web 11a Outer edge part 11b Inner edge part 11c Linear part 13A thru | or 13H Stator blade 15 Outlet side flange C Rotation centerline CL1 thru | or CL4 1st to 4th virtual center lines PL1 to PL4 1st to 4th virtual straight lines 19 Discharge port 21 Cylindrical portion 21a One end of the cylindrical portion 21b Other end of the cylindrical portion 23 Discharge port side taper portion 31a to 31h Straight side

Claims (5)

A cylindrical portion located in the center, an annular discharge port side taper portion which is located between one end of the cylindrical portion and the discharge port and extends radially outward of the cylindrical portion, and the other end of the cylindrical portion and the suction port A fan housing including a wind tunnel including an annular suction port side taper portion which is located between and extending radially outward of the cylindrical portion;
An impeller disposed in the wind tunnel and having a plurality of blades;
A rotor to which the impeller is fixed;
A stator provided corresponding to the rotor;
A motor case having a bottom wall portion located on the discharge port side and a peripheral wall portion formed continuously with the bottom wall portion and extending toward the suction port side, wherein the stator is fixed to the bottom wall portion When,
Four webs arranged at intervals in the rotation direction of the impeller and positioned in the outlet of the wind tunnel to connect the motor case and the fan housing;
The four webs are an outer end connected to the outlet side taper portion of the wind tunnel, an inner end connected to the peripheral wall portion of the motor case, the outer end and the inner end. Are axial flow fans each having a linear portion that is positioned between and linearly extending between the two,
The discharge port has a polygonal shape composed of a first to a fourth pair of straight sides that face each other around the rotation center line of the rotor and are arranged in order in the rotation direction of the impeller.
A first virtual center line passing through the center of the first pair of straight sides and the rotation center line, and a second virtual center line passing through the center of the second pair of straight sides and the rotation center line A fourth virtual center line passing through the center of the third pair of straight sides and the rotation center line, and a fourth virtual center passing through the center of the fourth pair of straight sides and the rotation center line When a virtual center line is assumed, an angle between two adjacent virtual center lines of the first to fourth virtual center lines is 45 degrees, and the lengths of the first and third pair of straight sides are And the lengths of the second and fourth pair of straight sides are equal, and the intersection between the first and third virtual center lines and the first and third pair of straight sides and the rotation The distance between the center line is the intersection of the second and fourth virtual center lines and the second and fourth pair of straight sides and the center of rotation. Shorter than the distance between the,
The length of the first and third pair of straight sides is such that one of the first and third straight sides is present outside the outer end of the four webs. To be
The four webs are virtually arranged so that the center of the outer end portion, the center of the inner end portion, and the first to fourth virtual straight lines passing through the center of the straight portion are sequentially arranged in the rotation direction of the impeller. In this case, the angle between two adjacent virtual straight lines of the first to fourth virtual straight lines is 90 degrees, and the impeller is positioned on the rotation direction side as viewed from the first virtual center line. An angle θ between the virtual straight line and the first virtual center line, and between the virtual straight line and the third virtual center line located on the rotation direction side of the impeller when viewed from the third virtual center line. The axial flow blower is characterized in that the four webs are arranged so that the angle θ of the angle is in the range of 8 degrees <θ <14 degrees.   The axial blower according to claim 1, wherein the shape of the suction port is determined so as to be substantially congruent with the shape of the discharge port as viewed from a direction in which the rotation center line extends.   The axial-flow fan according to claim 1 or 2, wherein the angle θ is 10 degrees. On the discharge port side taper portion, four stationary blades of a first group are provided along the second and fourth virtual center lines,
On the outlet side taper portion, a boundary portion between the first pair of straight sides and the fourth pair of straight sides, the second pair of straight sides, and the third pair of straight sides The four stationary blades of the second group are provided at positions adjacent to the boundary portion and corresponding to the first pair of straight sides and the third pair of straight sides,
The four stationary blades of the second group are arranged at an angular interval of 90 degrees in the rotation direction of the impeller,
The axial flow fan according to claim 1 or 2, wherein the eight stationary blades of the first and second groups extend toward the rotation center line and along the rotation center line. Of the four webs, one of the webs is formed with a wire storage groove for storing a plurality of wires,
The one web is larger in width than the remaining three webs,
The cross-sectional shape of the portion of each of the four webs facing the plurality of blades in the linear portion is such that the width of the end on the suction port side is larger than the width of the end on the discharge port side. Short,
The cross-sectional shape of the three webs has an inclined surface on a side surface located on the rotation direction side of the impeller as viewed from the suction port,
5. The cross-sectional shape of the one web has inclined surfaces on both side surfaces located on the rotation direction side and the rotation direction side of the impeller as viewed from the suction port. An axial flow blower described in 1.

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