Blower

Abstract

A semi-open type fan provided with a casing having an air guide section and a bell mouth has a narrow tip clearance and suppresses noise. The blower (101) is characterized in that a portion of the blade (4) is provided upstream of the upstream end (15) of the bellmouth (9), and the air guide section (8) has a protrusion (23) that protrudes in a direction toward the blade (4) on the inner wall (11) facing the blade (4) and downstream of the airflow from the downstream end (14) of the bellmouth (9).

Description

[Technical field]

[0001] The present disclosure relates to a blower equipped with a bellmouth. [Background technology]

[0002] Prior art discloses a blower provided with a casing having a cylindrical air guide section that covers the outer periphery of an impeller and an annular bell mouth that guides air into the air guide section (for example, Patent Document 1).

[0003] Also known is a so-called semi-open type blower in which a part of the blade or vane protrudes from a plane including a point located most upstream of the bellmouth. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6932295 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional technology, when a semi-open blade is applied to a blower provided with a casing having an air guide section and a bell mouth, the tip clearance, which is the distance between the blade and the air guide section, becomes large, which poses the problem that noise cannot be suppressed.

[0006] The present disclosure has been made to solve the problems described above, and has an object to provide a semi-open type blower having a casing with an air guide section and a bell mouth, which narrows the tip clearance and suppresses noise. [Means for solving the problem]

[0007] The blower according to the present disclosure comprises a boss that is driven to rotate around a rotation axis by a motor, blades that are arranged radially from the boss and generate an airflow by rotation, an air guide section arranged to cover the outer peripheral end of the blade, a downstream end section that is arranged between the upstream side of the airflow of the air guide section and the blade, and an upstream end section that is arranged to cover the upstream side of the air guide section, and a bellmouth having a downstream end section that is arranged to cover the upstream side of the air guide section, Opposite the outer edge of the wing, It is characterized by having a protruding portion that protrudes in a direction toward the blade. Effect of the Invention

[0008] According to the blower according to the present disclosure, the tip clearance can be narrowed and noise can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a blower according to a first embodiment of the present disclosure. [Diagram 2] 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. [Diagram 3] 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. [Figure 4] 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. [Diagram 5] 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. [Figure 6] 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. [Figure 7] 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. [Figure 8] 1 is a graph showing a relationship between an air volume Q and a noise level SPL in the blower according to the first embodiment of the present disclosure. [Figure 9]FIG. 11 is a schematic diagram illustrating a radial cross section of a blower according to a second embodiment of the present disclosure. [Figure 10] FIG. 11 is a schematic diagram showing a radial cross section of a blower according to a third embodiment of the present disclosure. [Figure 11] FIG. 11 is a schematic diagram illustrating a radial cross section of a blower according to a fourth embodiment of the present disclosure. [Figure 12] FIG. 11 is a schematic diagram illustrating a radial cross section of a blower according to a fifth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the drawings are schematic, and the interrelationships of sizes and positions shown in different drawings are not necessarily limited to those described and may be changed as appropriate. In addition, in the following description, similar components are illustrated with the same reference numerals, and their names and functions are the same or similar. Therefore, detailed description thereof may be omitted.

[0011] Embodiment 1 The blower 101 according to the first embodiment will be described with reference to Figures 1 to 8. Figure 1 is a perspective view of the blower 101 according to the first embodiment.

[0012] 1, blower 101 according to this embodiment includes impeller 1 and a casing 2 that surrounds impeller 1. Blower 101 also includes a motor (not shown).

[0013] The blower 101 is, for example, an axial flow blower. The blower 101 shown in Fig. 1 includes a propeller fan as an impeller 1. The blower 101 may be a mixed flow blower.

[0014] The impeller 1 draws in airflow from the top of the impeller 1 downward in the axial direction of the rotating shaft RS in the drawing (direction of arrow F), and expels the airflow to the bottom of the impeller 1 downward in the axial direction of the rotating shaft RS in the drawing (direction of arrow F). The side where the airflow is drawn in is the upstream side, and the side where the airflow is expelled is the downstream side. In other words, the upper side of the paper in FIG. 1 is the upstream side, and the lower side of the paper is the downstream side. The same applies to the following explanations. The upstream side and downstream side are not necessarily based on the impeller 1, but rather define the upstream side and downstream side for each configuration when the airflow is used as the reference for each configuration.

[0015] The impeller 1 includes a boss 3 and a plurality of blades 4 provided on the outer periphery of the boss 3. A motor (not shown) is connected to the boss 3 and provided inside or downstream of the boss 3. The boss 3 is driven to rotate about a rotation axis RS by the driving force of the motor. The impeller 1 is driven to rotate about the rotation axis RS by the driving force of the motor. In FIG. 1, for example, the impeller rotates in a counterclockwise direction R when viewed from the top of the drawing.

[0016] The boss 3 is, for example, cylindrical. However, the boss 3 is not limited to being cylindrical, and may be, for example, a truncated cone shape or another shape.

[0017] The blades 4 are provided radially outward from the boss 3 on the outer periphery of the boss 3. The blades 4 generate an airflow by rotation. The blower 101 shown in Fig. 1 includes three blades 4. The number of blades 4 is not limited to three, and may be, for example, four or more.

[0018] Each of the blades 4 has a predetermined three-dimensional shape. The blades 4 are formed as forward-swept blades with a blade leading edge 5 facing forward in the direction of rotation (the direction of the arrow R) and extending forward. The blades 4 also have a blade trailing edge 6 located rearward of the blade leading edge 5 in the direction of rotation of the impeller 1 (the direction of the arrow R) and downstream of the blade leading edge 5. The blades 4 also have an outer circumferential edge 7 between the blade leading edge 5 and the blade trailing edge 6.

[0019] As shown in FIG. 1, the casing 2 is provided so as to cover the outer circumferential end 7 of the impeller 1 .

[0020] Fig. 2 is a schematic diagram showing a radial cross section of blower 101 according to embodiment 1. Specifically, Fig. 2 is a cross section obtained by rotating and projecting a cross section of blower 101 including rotation axis RS onto a plane parallel to rotation axis RS.

[0021] As shown in FIG. 2, the blade 4 has an outer peripheral end 7. The outer peripheral portion 25 is a region through which the outer peripheral end 7 of the blade 4 passes when a cross section including the rotation axis RS is rotated and projected onto a plane parallel to the rotation axis RS. The outer peripheral portion 25 includes, for example, a straight line shape. Therefore, the outer peripheral end 7 of the blade 4 is positioned to overlap with the outer peripheral portion 25 upon rotation. In the subsequent figures, the region shown between the boss 3 and the casing 2 is the region through which the blade 4 passes when rotated, projected onto a plane including the rotation axis RS.

[0022] As shown in FIG. 2, the casing 2 includes an air guide section 8 that covers the outer peripheral ends 7 of the multiple blades 4, a bellmouth 9 that guides airflow inside the air guide section 8, and a flange section 10 that is provided continuously with the bellmouth 9.

[0023] The air guide section 8 is provided so as to cover the outer peripheral end 7 of the blade 4. The air guide section 8 includes an inner wall 11 facing the blade 4 and an outer wall 26 opposite the inner wall 11. The inner wall 11 of the air guide section 8 has, for example, a shape that is axially symmetrical with respect to the rotation axis RS. The impeller 1 is disposed inside the air guide section 8, i.e., on the rotation axis RS side of the air guide section 8. The shape of the inner wall 11 of the air guide section 8 is desirably axially symmetrical with respect to the rotation axis RS, but may be non-axisymmetrical depending on the combination of the inner wall 11 and the three-dimensional shape of the impeller 1.

[0024] The air guide section 8 includes an intake end section 12 located on the upstream side and an exhaust end section 13 located on the downstream side. The airflow flows from the intake end section 12 to the exhaust end section 13 of the air guide section 8.

[0025] The bellmouth 9 is formed continuously with the flange portion 10. The bellmouth 9 has a cylindrical shape whose inner diameter changes in the axial direction of the rotation shaft RS. The bellmouth 9 is provided so as to cover the upstream side of the air guide section 8. In other words, the bellmouth 9 is provided so as to cover the suction side end 12 of the air guide section 8. The bellmouth 9 is provided away from the suction side end 12 located on the upstream side of the air guide section 8.

[0026] The bellmouth 9 includes a downstream end 14 and an upstream end 15. The downstream end 14 is located at the most downstream side of the bellmouth 9, and is provided between the blades 4 of the impeller 1 and the upstream side of the air guide section 8. The upstream end 15 is located at the most upstream side of the bellmouth 9, and is provided so as to cover the upstream side of the air guide section 8. The bellmouth 9 is disposed near the suction side end 12 of the air guide section 8 so as to partially overlap with the air guide section 8 in the axial direction of the rotation shaft RS.

[0027] The bellmouth 9 has an inner circumferential surface 16 on the inside, i.e., on the side facing the impeller 1. The bellmouth 9 also has an outer circumferential surface 17 on the outside, i.e., on the side opposite the impeller 1.

[0028] The bellmouth 9 forms a first ventilation passage 18 on the inside. The bellmouth 9 also forms a second ventilation passage 19 on the outside. The second ventilation passage 19 is formed between the outer peripheral surface 17 of the bellmouth 9 and the inner wall 11 of the air guide section 8. The first ventilation passage 18 includes a third ventilation passage 20. The third ventilation passage 20 is an air passage formed between the bellmouth 9 and the blade 4 and between the air guide section 8 and the blade 4.

[0029] The inner circumferential surface 16 and the outer circumferential surface 17 of the bellmouth 9 are formed, for example, in a curved shape that is convex in the direction toward the blade 4. The inner circumferential surface 16 and the outer circumferential surface 17 of the bellmouth 9 are formed, for example, in an arc shape. Note that the inner circumferential surface 16 and the outer circumferential surface 17 of the bellmouth 9 may be partially curved, or may be formed by combining straight line shapes.

[0030] The flange portion 10 is provided continuous with the upstream end portion 15 of the bellmouth 9. The flange portion 10 is provided so as to cover the upstream side of the air guide portion 8.

[0031] The blade 4 is provided at a position facing the casing 2, and is provided upstream of the upstream end 15 of the bellmouth 9, a portion of which is included in the casing 2. That is, in terms of the positional relationship between the blade 4 and the bellmouth 9 in the direction of the rotation axis RS, the blade 4 is provided so that a portion of the blade 4 includes the upstream end 15 of the bellmouth 9 and protrudes upstream from a plane perpendicular to the rotation axis RS.

[0032] Incidentally, the impeller 1 in which some of the blades 4 are provided upstream of the casing 2 is often used in air conditioner outdoor units and ventilation fans, and is sometimes called a half-ducted or semi-open type.

[0033] Fig. 3 is a schematic diagram showing a radial cross section of blower 101 according to embodiment 1. Specifically, Fig. 3 is a cross section obtained by rotating and projecting a cross section of blower 101 including rotation axis RS onto a plane parallel to rotation axis RS. The flow of air in blower 101 according to embodiment 1 will be described with reference to Fig. 3.

[0034] The blower 101 takes in air from the upstream side of the blower 101, i.e., the upper side of the paper in Fig. 3, into the first ventilation passage 18. The air taken in the first ventilation passage 18 passes between the blades 4 attached to the impeller 1 arranged in the first ventilation passage 18 and between the casing 2 and the blades 4 in the direction of arrow F, and is discharged downstream, i.e., the lower side of the paper in Fig. 3.

[0035] In general, in a blower, a leakage flow from the downstream side to the upstream side of the blade occurs due to the rotational motion of the blade. When a tip clearance, which is the gap between the blade 4 and the air guide section 8, exists as in the blower 101 according to the present embodiment, a backflow 21 from the downstream side to the upstream side occurs at the outer circumferential end 7 of the blade 4 as shown in Fig. 3. The backflow 21 causes turbulence in the airflow, which causes noise.

[0036] A part of the airflow drawn by the impeller 1 flows into the first ventilation passage 18 along the bellmouth 9, and is drawn into the impeller 1. Energy is imparted to the airflow drawn into the impeller 1.

[0037] 3 is a part of the airflow passing through the first ventilation passage 18. The airflow F1 is taken into the first ventilation passage 18 from the upstream side of the blower 101, i.e., the upstream side of the flange portion 10 and the upstream side of the bellmouth 9. The airflow F1 passes between the bellmouth 9 and the blade 4 and between the air guide portion 8 and the blade 4, and is discharged from the discharge end portion 13 of the air guide portion 8 in the downstream direction of the blower 101. In other words, the airflow F1 is an airflow passing through the first ventilation passage 18, particularly the third ventilation passage 20.

[0038] The flange portion 10 and the bell mouth 9 are provided so as to cover the suction side end portion 12 located on the upstream side of the air guide portion 8, so that the suction side end portion 12 of the air guide portion 8 does not come into contact with the airflow F1.

[0039] 3 indicates an airflow passing through the second ventilation passage 19. The airflow F2 is drawn into the second ventilation passage 19 from the inlet of the second ventilation passage 19. The airflow F2 passes between the bellmouth 9 and the air guide section 8, and is discharged from the outlet of the second ventilation passage 19 to the third ventilation passage 20.

[0040] The inlet of the second ventilation passage 19 is formed between the suction side end 12 of the air guide section 8 and the bellmouth 9. The outlet of the second ventilation passage 19 is formed between the air guide section 8 and the downstream end 14 of the bellmouth 9.

[0041] The airflow F2 is drawn into the second ventilation passage 19, for example, from the rear surface 24 of the flange portion 10 or near the downstream discharge end portion 13. Since the pressure near the suction end portion 12 of the air guide portion 8 is lower than the pressure near the discharge end portion 13 of the air guide portion 8, the airflow is taken into the second ventilation passage 19 due to the pressure difference, and the airflow F2 passes through the second ventilation passage 19 due to the pressure difference.

[0042] The airflow F2 that has passed through the second ventilation passage 19 is supplied to the third ventilation passage 20 as a jet flow 22. The jet flow 22 suppresses the backflow 21 that occurs at the outer circumferential edge 7 of the blade 4, thereby making it possible to reduce noise.

[0043] Fig. 4 is a schematic diagram showing a radial cross section of blower 101 according to embodiment 1. Specifically, Fig. 4 is a cross section obtained by rotating and projecting a cross section of blower 101 including rotation axis RS onto a plane parallel to rotation axis RS. The shape of inner wall 11 of air guide section 8 according to embodiment 1 will be described with reference to Fig. 4.

[0044] The air guide section 8 has a protruding portion 23 that protrudes in the direction toward the blade 4, downstream of the airflow from the downstream end portion 14 of the bellmouth 9, on the inner wall 11 facing the blade 4. The outer wall 26 of the air guide section 8 has a shape that follows the protruding portion 23 of the inner wall 11, for example.

[0045] In a cross-sectional view rotated and projected onto a plane including the rotation axis RS, i.e., in Fig. 4, outer peripheral portion 25 through which outer peripheral end 7 of blade 4 passes includes, for example, a straight line shape. In a cross-sectional view rotated and projected onto a plane parallel to the rotation axis RS of blower 101, a straight line including outer peripheral end 7 of blade 4 is defined as line L.

[0046] In addition, in a cross section including the rotation axis RS of blade 4, the region through which outer circumferential end 7 passes within the region in which blade 4 rotates is defined as outer circumferential portion 25. In Fig. 4, outer circumferential portion 25 overlaps with outer circumferential end 7. That is, in a cross section obtained by rotating and projecting a cross section of blower 101 including the rotation axis RS onto a plane parallel to the rotation axis RS, the straight line including outer circumferential portion 25 is also line L.

[0047] An arbitrary point included in the inner wall 11 of the air guide section 8 is defined as point A. A perpendicular line drawn from point A to a line L through an arbitrary point included in the inner wall 11 of the air guide section 8 intersects with line L and defines point A'. The length of the line segment connecting point A and point A' is defined as ΔA.

[0048] Among the points A included in the inner wall 11 of the air guide section 8, the point that is the shortest in distance to the outer circumferential end 7, i.e., the point with the smallest distance ΔA, is defined as point Amin. Also, the point where a perpendicular line drawn from point Amin to the line L intersects with the line L is defined as point Amin'. The length of the line segment connecting points Amin and Amin' is defined as ΔAmin.

[0049] Point Amin' is a point on line L at which the distance between line L including outer periphery 25 and protrusion 23 of inner wall 11 in the region where blade 4 rotates is the smallest in a cross section including rotation axis RS of blade 4, and is defined as a first point. Point Amin is a point on inner wall 11 at which the distance between protrusion 23 of inner wall 11 and line L is the smallest, and is defined as a second point.

[0050] The air guide section 8 has a point Amin where ΔA is minimum, downstream of the downstream end 14 of the bellmouth 9. That is, the inner wall 11 of the air guide section 8 has a protruding portion 23 that protrudes in the direction toward the blade 4, downstream of the downstream end 14 of the bellmouth 9.

[0051] When the semi-open type is applied to a blower 101 provided with a casing 2 having an air guide section 8 and a bellmouth 9, the tip clearance, which is the gap between the blade 4 and the air guide section 8, becomes wider. When the tip clearance becomes wider, the effect of the jet 22 in suppressing the backflow 21 at the outer circumferential end 7 of the blade 4 becomes smaller.

[0052] Inner wall 11 of air guide section 8 is formed so that distance ΔA is smaller on the downstream side than on the upstream side, thereby generating a negative pressure gradient and accelerating jet flow 22 supplied to third ventilation passage 20. Accelerating jet flow 22 increases the momentum of jet flow 22. Increasing the momentum of jet flow 22 can further suppress backflow 21 at outer circumferential edge 7 of blade 4. Suppressing backflow 21 can reduce noise.

[0053] In other words, the inner wall 11 of the air guide section 8 has a protrusion 23 that protrudes toward the blade 4 downstream of the downstream end 14 of the bellmouth 9, thereby narrowing the tip clearance and suppressing noise.

[0054] It is desirable that the first point is included in the outer circumferential portion 25 of the area in which the blade 4 rotates. It is desirable that the point Amin' exists on the outer circumferential end 7. In other words, it is desirable that the inner wall 11 of the air guide section 8 has a shape that is formed in parallel to the line L or in a direction away from the line L downstream of the point Amin.

[0055] The flow velocity of the jet flow 22 flowing through the third ventilation passage 20 is the largest at the point where the distance between the inner wall 11 of the air guide section 8 and the outer peripheral edge 7 of the blade 4 is the smallest, that is, at the point Amin where the distance ΔA becomes the distance ΔAmin. Therefore, when the point Amin' is on the outer peripheral edge 7, the occurrence of the backflow 21 can be most effectively suppressed. By effectively suppressing the backflow 21, the noise can be reduced.

[0056] In addition, the inner wall 11 of the air guide section 8 is parallel to the line L downstream of the point Amin, and if there are multiple points Amin′, at least one of the multiple points Amin′ should be on the outer circumferential edge 7.

[0057] Fig. 5 is a schematic diagram showing a radial cross section of blower 101 according to embodiment 1. Specifically, Fig. 5 is a cross section obtained by rotating and projecting a cross section of blower 101 including rotation axis RS onto a plane parallel to rotation axis RS. The positional relationship between inner wall 11 and the bell mouth of air guide section 8 according to embodiment 1 and blades 4 will be described with reference to Fig. 5.

[0058] The downstream end 14 of the bellmouth 9, which is the point located most downstream of the bellmouth 9, is designated as point B. The point where a perpendicular line drawn from point B to line L intersects with line L is designated as point B'. The length of the line segment connecting points B and B' is designated as ΔB.

[0059] Also, an arbitrary point included in the inner wall 11 of the air guide section 8, downstream of point B and upstream of point Amin, is defined as point C. A point where a perpendicular line drawn from point C to line L intersects with line L is defined as point C'. The length of the line segment connecting point C and point C' is defined as ΔC.

[0060] Point C, which satisfies ΔC>ΔB and ΔC>ΔAmin, exists on inner wall 11 of air guide section 8. In other words, in third air passage 20, a curve connecting point B, point C, and point Amin has a shape that is convex toward air guide section 8.

[0061] The airflow F2 in the second ventilation passage 19 is slower than the airflow F2 passing through the third ventilation passage 20. That is, there is a speed difference between the airflow F2 and the airflow F1. The existence of point C, which satisfies ΔC>ΔB, downstream of point B and upstream of point Amin, allows the speed of the airflow F1 to be slowed down at the outlet of the second ventilation passage 19, that is, at the point where the jet flow 22 supplied from the second ventilation passage 19 joins the airflow F1. By slowing down the speed of the airflow F1 at the point where the jet flow 22 joins the airflow F1, the difference in speed between the jet flow 22 and the airflow F1 can be reduced, and the loss when the jet flow 22 and the airflow F1 join can be reduced.

[0062] Because point C, which satisfies ΔC>ΔAmin, exists downstream of point B and upstream of point Amin, the airflow F1 that merges with the jet 22 is accelerated again near Amin, and the backflow 21 can be effectively suppressed near Amin.

[0063] Also, it is desirable that ΔAmin is small and ΔB is large. Figure 5 shows the case where ΔB>ΔAmin. However, ΔB<ΔAmin may also be satisfied.

[0064] Fig. 6 is a schematic diagram showing a radial cross section of blower 101 according to embodiment 1. Specifically, Fig. 6 is a cross section obtained by rotating and projecting a cross section of blower 101 including rotation axis RS onto a plane parallel to rotation axis RS. The positional relationship between inner wall 11 and bellmouth 9 of air guide section 8 according to embodiment 1 and blades 4 will be described with reference to Fig. 6.

[0065] The bellmouth 9 has, for example, a circular arc shape with a single curvature from the upstream end 15 to the downstream end 14. Of the points included on the inner circumferential surface 16 of the bellmouth 9, the point closest to the rotation axis RS, i.e., the point that is the smallest distance from the rotation axis RS, is defined as the minimum radius point B1 of the bellmouth 9.

[0066] It is desirable that minimum radius point B1 is located at the upstream end 15 of the bellmouth 9, downstream of point B2 which is the most upstream point of the bellmouth 9, and upstream of point B. In other words, it is desirable that the bellmouth 9 has a convex shape towards the blade 4 side between the upstream end 15 and the downstream end 14. Figure 6 shows the case where the apex of the convex shape on the blade 4 side is minimum radius point B1.

[0067] Let B1' be the point where the perpendicular line drawn from the minimum radius point B1 to the line L intersects with the line L. Let ΔB1 be the length of the line segment connecting points B1 and B1'.

[0068] 6, the distance between the minimum radius point B1 and the straight line L is smaller than the distance between the second point ΔAmin and the straight line L. That is, ΔB1<ΔAmin. The distance between the minimum radius point B1 and the straight line L is also smaller than the distance between the downstream end 14 and the straight line L. That is, ΔB1<ΔB.

[0069] Fig. 7 is a schematic diagram showing a radial cross section of blower 101 according to embodiment 1. Specifically, Fig. 7 is a cross section obtained by rotating and projecting a cross section of blower 101 including rotation axis RS onto a plane parallel to rotation axis RS. Casing 2 will be described with reference to Fig. 7.

[0070] 7, the flange portion 10 and the air guide portion 8, which are provided continuously with the bellmouth 9, may be provided partially continuous. By selecting a cross section including the rotation axis RS, there may be a cross section in which the flange portion 10 and the air guide portion 8 are connected and a cross section in which the flange portion 10 and the air guide portion 8 are not connected.

[0071] 2 to 7, the outer peripheral edge 7 of the blade 4 has a straight line shape, but the outer peripheral edge 7 may have a curved line shape. When the outer peripheral edge 7 has a curved line shape in the cross-sectional view rotated and projected onto a plane parallel to the rotation axis RS, the straight line L is, for example, a straight line that is parallel to a straight line obtained by approximating the curved outer peripheral edge 7 in the cross-sectional view rotated and projected onto a plane parallel to the rotation axis RS with a linear function, and is tangent to the outer peripheral edge 7.

[0072] FIG. 8 is a graph showing the relationship between air volume Q and noise level SPL (unit: dBA) in blower 101 according to embodiment 1. In FIG. 8, the horizontal axis is air volume Q [m3 / min] and the vertical axis is SPL [dBA]. Solid line g1 shows the results obtained in an experiment using blower 101. Dashed line g2 shows the results obtained in an experiment using a typical blower called a semi-open type, which is provided with a casing having an air guide section and a bell mouth. The shape of the impeller used in the typical blower called a semi-open type is the same as the shape of impeller 1 of blower 101. As shown in FIG. 8, the noise level obtained by blower 101 according to embodiment 1 has a noise reduction effect of up to about 2 dB over a wide range of air volumes Q, compared to a typical blower called a semi-open type.

[0073] Embodiment 2 A blower 102 in the second embodiment will be described with reference to Fig. 9. Descriptions of configurations similar to those in the first embodiment will be omitted. In Fig. 9, the same reference numerals as those in Figs. 1 to 8 indicate the same or corresponding parts.

[0074] Fig. 9 is a schematic diagram showing a radial cross section of blower 102 according to embodiment 2. Specifically, Fig. 9 is a cross section obtained by rotating and projecting a cross section of blower 102 including rotation axis RS onto a plane parallel to rotation axis RS. Air guide section 31 will be described with reference to Fig. 9.

[0075] The inner wall 11 of the air guide section 31 has a protruding portion 23. The outer wall 26 on the side of the air guide section 31 opposite the blade 4 does not have a shape that follows the protruding portion 23 of the inner wall 11, and may have a flat shape, as shown in Fig. 9. The outer wall 26 may also have a shape that protrudes radially outward, or may have a curved shape.

[0076] Embodiment 3 Blower 103 in the third embodiment will be described with reference to Fig. 10. Description of the same configuration as in the first embodiment will be omitted. In Fig. 10, the same reference numerals as in Figs. 1 to 9 indicate the same or corresponding parts.

[0077] Fig. 10 is a schematic diagram showing a radial cross section of blower 103 according to embodiment 3. Specifically, Fig. 10 is a cross section obtained by rotating and projecting a cross section of blower 103 including rotation axis RS onto a plane parallel to rotation axis RS.

[0078] Impeller 32 of blower 103 according to the present embodiment is an axial flow fan, that is, blower 103 is an axial flow blower.

[0079] As shown in FIG. 10, it is desirable that the air guide portion 33 be provided approximately parallel to the outer circumferential end 7 of the blades 34 of the impeller 32 .

[0080] Embodiment 4 Fan 104 in embodiment 4 will be described with reference to Fig. 11. Description of the same configuration as in embodiment 1 will be omitted. In Fig. 11, the same reference numerals as in Figs. 1 to 10 indicate the same or corresponding parts.

[0081] Fig. 11 is a schematic diagram showing a radial cross section of blower 104 according to embodiment 4. Specifically, Fig. 11 is a cross section obtained by rotating and projecting a cross section of blower 104 including rotation axis RS onto a plane parallel to rotation axis RS.

[0082] In the fan 104 according to the fourth embodiment, the inner wall 36 of the air guide section 35 has a streamlined shape.

[0083] Among points A included in the inner wall 36 of the air guide section 35, the point that is downstream of the downstream end 14 of the bellmouth 9 and has the greatest distance from the outer circumferential end 7, i.e., the point with the greatest distance ΔA, is defined as point Amax. Also, the point where a perpendicular line drawn from point Amax to line L intersects with line L is defined as point Amax'. The length of the line segment connecting points Amax and Amax' is defined as ΔAmax.

[0084] The inner wall 36 of the air guide portion 35 has a substantially streamlined shape with a curvature at least from the point Amax to the point Amin.

[0085] The airflow that flows into the second ventilation passage 19 from the inlet of the second ventilation passage 19 has a negative pressure gradient in the flow direction after passing through point Amax included on the inner wall 36 of the air guide section 35. However, since the inner wall 36 of the air guide section 35 has a substantially streamlined shape from point Amax to point Amin, the airflow can flow with reduced fluid resistance.

[0086] Therefore, the jet flow 22 supplied from the second ventilation passage 19 and flowing toward the discharge end 13 of the air guide section 35 can flow while suppressing the energy consumption of the flow. Since the jet flow 22 can flow while suppressing the energy consumption of the flow, the backflow 21 can be further suppressed and the noise can be further reduced.

[0087] Embodiment 5. Fan 105 in embodiment 5 will be described with reference to Fig. 12. Descriptions of configurations similar to those in embodiments 1 and 4 will be omitted. In Fig. 12, the same reference numerals as those in Figs. 1 to 11 denote the same or corresponding parts.

[0088] Fig. 12 is a schematic diagram showing a radial cross section of blower 105 according to embodiment 5. Specifically, Fig. 12 is a cross section obtained by rotating and projecting a cross section of blower 105 including rotation axis RS onto a plane parallel to rotation axis RS.

[0089] The inner wall 36 of the air guide section 35 is formed so as to be away from the rotation axis RS at least downstream of the point Amin. For example, the inner wall 36 may be smoothly connected to the point Amin downstream of the point Amin and have a sector shape with a central angle of 90 degrees, the radius of which is the same as the radius of the arc shape of the bellmouth 9. It is desirable that the inner wall 36 be a curved surface having a substantially streamlined shape from the point Amax to the point Amin.

[0090] The air flow that flows into the second ventilation passage 19 from its inlet flows into the third ventilation passage 20 and is accelerated by the negative pressure gradient before reaching point Amin on the inner wall 36 of the air guide section 35, thereby suppressing the backflow 21 that occurs at the outer peripheral end 7 of the blade 4.

[0091] Since the inner wall 36 is formed away from the rotation axis RS downstream of the point Amin, after the airflow flowing through the third ventilation passage 20 passes near the point Amin, the airflow gradually decelerates while the static pressure is restored. The airflow passing downstream of the point Amin of the inner wall 36 decelerates while the static pressure is restored, thereby preventing turbulence of the airflow, reducing noise, and improving the blowing performance.

[0092] In addition, in each of the above embodiments described in this specification, the material, material, size, shape, relative positional relationship, or implementation conditions of each component may be described, but these are examples in all aspects and are not limited to the embodiments described. Therefore, countless modified examples not exemplified are expected within the scope of each embodiment. For example, this includes cases where any component is modified, added, or omitted, and further cases where at least one component in at least one embodiment is extracted and combined with a component of another embodiment.

[0093] Needless to say, various design modifications are possible within the scope of the present invention without departing from the gist of the present invention. [Explanation of symbols]

[0094] 1, 32 impeller, 2 casing, 3 boss, 4, 34 blade, 7 outer circumferential end, 8, 31, 33, 35 air guide portion, 9 bell mouth, 10 flange portion, 11, 36 inner wall, 14 downstream end portion, 15 upstream end portion, 23 protrusion portion, 101, 102, 103, 104, 105 blower

Claims

1. a boss that is rotated around a rotation axis by a motor; Wings provided radially from the boss and configured to generate an airflow by rotation; A wind guide portion provided to cover an outer circumferential end of the blade; a bell mouth having a downstream end portion provided between the upstream side of the airflow of the air guide portion and the blade, and an upstream end portion provided so as to cover the upstream side of the air guide portion, a portion of the blade is provided upstream of the upstream end of the bell mouth, a blower characterized in that the air guide section has a protrusion that protrudes in a direction toward the blade, at a position downstream of the airflow from the downstream end of the bell mouth and facing the outer circumferential end of the blade.

2. In a cross section including the rotation axis, a point on a line that is tangent to an outer periphery of a region in which the blade rotates and a distance between the line and the protruding portion of the inner wall is set to a first point, and the first point is included in the outer periphery of the region. The blower of claim 1.

3. The inner wall of the air guide portion is formed so that the distance from the rotation axis increases from a position facing the first point to the downstream side of the air guide portion. The blower of claim 2.

4. The bell mouth has a minimum radius point between the upstream end and the downstream end, the minimum radius point being smaller than the radial distance between the upstream end and the downstream end and the rotation shaft. The blower of claim 1.

5. When a point on the inner wall where the distance between the protrusion of the inner wall and a line tangent to the outer periphery of the area in which the blade rotates is a minimum is defined as a second point, the distance between the minimum radius point and the line is smaller than the distance between the second point and the line. The blower of claim 4.

6. The distance between the minimum radius point and a straight line tangent to the outer periphery of the region in which the blade rotates is smaller than the distance between the downstream end and the straight line. The blower of claim 4.

7. The bell mouth is characterized in that it has a convex shape toward the blade between the upstream end and the downstream end. The blower of claim 1.

8. The inner wall of the air guide portion is formed in a curved shape from the upstream side of the air guide portion to the protruding portion. The blower of claim 1.

9. The bell mouth is formed in a curved shape. The blower of claim 1.

10. The air guide portion has an intake end portion located upstream of the air flow, The bell mouth and the suction side end of the air guide portion are provided apart from each other. The blower of claim 1.

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