JP7487854B1 - Blower - Google Patents

Abstract

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

Description

This disclosure relates to a blower equipped with a bellmouth.

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

There is also known a type of blower known as a semi-open type, in which part of the blade or wing protrudes beyond the plane that includes the most upstream point of the bellmouth.

Patent No. 6932295

However, in conventional technology, when semi-open blades are applied to a blower equipped 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 creates the problem that noise cannot be suppressed.

The present disclosure has been made to solve the problems described above, and aims 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.

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 arranged between the upstream side of the airflow of the air guide section and the blade, and an upstream end arranged to cover the upstream side of the air guide section, a portion of the blade is arranged upstream of the upstream end of the bellmouth, and the air guide section is characterized in that the inner wall facing the blade has a protrusion that protrudes in the direction toward the blade , downstream of the airflow from the downstream end of the bellmouth, at a position opposite the outer peripheral end of the blade .

The blower disclosed herein allows for narrow tip clearance and reduced noise.

FIG. 1 is a perspective view of a blower according to a first embodiment of the present disclosure. 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. 1 is a schematic diagram illustrating a radial cross section of a blower according to a first embodiment of the present disclosure. 1 is a graph showing a relationship between an air volume Q and a noise level SPL in a blower according to a first embodiment of the present disclosure. FIG. 11 is a schematic diagram illustrating a radial cross section of a blower according to a second embodiment of the present disclosure. FIG. 13 is a schematic diagram showing a radial cross section of a blower according to a third embodiment of the present disclosure. FIG. 11 is a schematic diagram illustrating a radial cross section of a blower according to a fourth embodiment of the present disclosure. FIG. 13 is a schematic diagram illustrating a radial cross section of a blower according to a fifth embodiment of the present disclosure.

Hereinafter, an embodiment of the present disclosure will be described with reference to the attached 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 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.

Embodiment 1.
A blower 101 according to the first embodiment will be described with reference to Fig. 1 to Fig. 8. Fig. 1 is a perspective view of the blower 101 according to the first embodiment.

As shown in Fig. 1, the blower 101 according to this embodiment includes an impeller 1 and a casing 2 that surrounds the impeller 1. The blower 101 also includes a motor (not shown).

The blower 101 is, for example, an axial flow blower. The blower 101 shown in FIG. 1 is equipped with a propeller fan as an impeller 1. The blower 101 may also be a cross-flow blower.

Impeller 1 draws in airflow from the top of impeller 1 downward in the axial direction of rotating shaft RS (arrow F direction) in the drawing, and expels the airflow to the bottom of impeller 1 downward in the axial direction of rotating shaft RS (arrow F direction) in the drawing. 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 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.

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 is provided inside or downstream of the boss 3. The boss 3 is driven to rotate about the 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 the counterclockwise direction R when viewed from the top of the drawing.

The boss 3 is, for example, cylindrical. Note that the boss 3 is not limited to being cylindrical, and may be, for example, a truncated cone shape or another shape.

A plurality of blades 4 are provided radially outward from the boss 3 on the outer periphery of the boss 3. The blades 4 generate airflow by rotating. The blower 101 shown in FIG. 1 has three blades 4. The number of blades 4 is not limited to three, and may be, for example, four or more.

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 extending forward in the direction of rotation (arrow R direction). 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 (arrow R direction) and downstream of the blade leading edge 5. The blades 4 also have an outer peripheral edge 7 between the blade leading edge 5 and the blade trailing edge 6.

As shown in Figure 1, the casing 2 is arranged to cover the outer peripheral end 7 of the impeller 1.

Figure 2 is a schematic diagram showing a radial cross section of the blower 101 according to embodiment 1. Specifically, Figure 2 is a cross section of the blower 101 including the rotation axis RS, rotated and projected onto a plane parallel to the rotation axis RS.

As shown in Figure 2, the blade 4 has an outer peripheral end 7. The outer peripheral portion 25 is the area 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 so as to overlap with the outer peripheral portion 25 upon rotation. In the subsequent figures, the area shown between the boss 3 and the casing 2 is the area through which the blade 4 passes when rotated, projected onto a plane including the rotation axis RS.

As shown in FIG. 2, the casing 2 includes an air guide section 8 covering the outer peripheral ends 7 of the multiple blades 4, a bell mouth 9 that guides airflow inside the air guide section 8, and a flange section 10 provided continuously with the bell mouth 9.

The air guide section 8 is arranged 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, an axisymmetric shape with respect to the rotation axis RS. The impeller 1 is arranged inside the air guide section 8, i.e., on the rotation axis RS side of the air guide section 8. It is desirable that the shape of the inner wall 11 of the air guide section 8 is axisymmetric with respect to the rotation axis RS, but it may be non-axisymmetric depending on the combination of the inner wall 11 and the three-dimensional shape of the impeller 1.

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

The bell mouth 9 is formed continuously with the flange portion 10. The bell mouth 9 has a cylindrical shape with an inner diameter that changes in the axial direction of the rotation shaft RS. The bell mouth 9 is arranged so as to cover the upstream side of the air guide section 8. In other words, the bell mouth 9 is arranged so as to cover the suction side end 12 of the air guide section 8. The bell mouth 9 is arranged away from the suction side end 12 located upstream of the air guide section 8.

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 positioned 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 axis RS.

The bell mouth 9 has an inner peripheral surface 16 on the inside, i.e., on the side facing the impeller 1. The bell mouth 9 also has an outer peripheral surface 17 on the outside, i.e., on the side opposite the impeller 1.

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.

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 lines.

The flange portion 10 is provided continuously with the upstream end portion 15 of the bell mouth 9. The flange portion 10 is provided so as to cover the upstream side of the air guide portion 8.

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. In other words, in 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.

In addition, impellers 1 in which some of the blades 4 are located upstream of the casing 2 are often used in air conditioner outdoor units and ventilation fans, and are sometimes called half-ducted or semi-open type.

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

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.

In general, in a blower, the rotational motion of the blades causes leakage flow from the downstream side of the blade to the upstream side. When there is a tip clearance between the blade 4 and the air guide section 8, 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 Figure 3. The backflow 21 causes turbulence in the airflow, which causes noise.

Part of the airflow sucked in by the impeller 1 flows into the first ventilation passage 18 along the bell mouth 9 and is sucked into the impeller 1. Energy is imparted to the airflow sucked into the impeller 1.

F1 shown in Figure 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 section 8 and the blade 4, and is discharged from the discharge side end 13 of the air guide section 8 in the downstream direction of the blower 101. In other words, the airflow F1 is an airflow that passes through the first ventilation passage 18, particularly the third ventilation passage 20.

The flange portion 10 and the bell mouth 9 are arranged to cover the suction side end 12 located upstream of the air guide section 8, so that the suction side end 12 of the air guide section 8 does not come into contact with the air flow F1.

F2 shown in Figure 3 is 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 bell mouth 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.

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

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 13. Since the pressure near the suction end 12 of the air guide portion 8 is lower than the pressure near the discharge end 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.

The airflow F2 that has passed through the second ventilation passage 19 is supplied to the third ventilation passage 20 as a jet 22. The jet 22 suppresses the backflow 21 that occurs at the outer circumferential end 7 of the blade 4, thereby reducing noise.

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

The air guide section 8 has a protruding portion 23 that protrudes toward the blade 4 on the inner wall 11 facing the blade 4, downstream of the downstream end 14 of the bell mouth 9 in the airflow. 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.

In a cross-sectional view rotated and projected onto a plane including the rotation axis RS, i.e., in FIG. 4, the outer peripheral portion 25 through which the outer peripheral end 7 of the 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 the cross-section of the blower 101 including the rotation axis RS, a straight line including the outer peripheral end 7 of the blade 4 is defined as a straight line L.

In addition, in a cross section including the rotation axis RS of the blade 4, the region through which the outer peripheral end 7 passes among the regions in which the blade 4 rotates is defined as the outer peripheral portion 25. In Figure 4, the outer peripheral portion 25 overlaps with the outer peripheral end 7. That is, in a cross-sectional view obtained by rotating and projecting the cross section of the blower 101 including the rotation axis RS onto a plane parallel to the rotation axis RS, the straight line including the outer peripheral portion 25 is also the straight line L.

An arbitrary point included in the inner wall 11 of the air guide section 8 is defined as point A. An arbitrary point included in the inner wall 11 of the air guide section 8 is defined as point A', where a perpendicular line drawn from point A to a straight line L intersects with the straight line L. The length of the line segment connecting points A and A' is defined as ΔA.

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 peripheral end 7, i.e., the point with the smallest distance ΔA, is defined as point Amin. Also, the point where the perpendicular line drawn from point Amin to the line L intersects with line L is defined as point Amin'. The length of the line segment connecting points Amin and Amin' is defined as ΔAmin.

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

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 protrusion 23 that protrudes in the direction toward the blade 4 downstream of the downstream end 14 of the bellmouth 9.

When the semi-open type is applied to a blower 101 provided with a casing 2 having an air guide section 8 and a bell mouth 9, the tip clearance, which is the distance 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.

The inner wall 11 of the air guide section 8 is formed so that the distance ΔA is smaller on the downstream side than on the upstream side, which generates a negative pressure gradient and accelerates the jet 22 supplied to the third ventilation passage 20. Accelerating the jet 22 increases the momentum of the jet 22. Increasing the momentum of the jet 22 makes it possible to further suppress the backflow 21 at the outer circumferential end 7 of the blade 4. Suppressing the backflow 21 makes it possible to reduce noise.

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 bell mouth 9, thereby narrowing the tip clearance and suppressing noise.

It is desirable that the first point is included in the outer periphery 25 of the area in which the blade 4 rotates. It is desirable that the point Amin' is located on the outer periphery 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 a direction that is parallel to the line L or away from the line L downstream of the point Amin.

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

In addition, if the inner wall 11 of the air guide section 8 is parallel to the straight line L downstream of point Amin and there are multiple points Amin', at least one of the multiple points Amin' must be on the outer peripheral end 7.

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

The downstream end 14 of the bellmouth 9 is the point located most downstream of the bellmouth 9. The point where a perpendicular line drawn from point B to line L intersects with line L is called point B'. The length of the line segment connecting points B and B' is called ΔB.

Also, any 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. The 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 points C and C' is defined as ΔC.

Point C, which satisfies ΔC>ΔB and ΔC>ΔAmin, exists on the inner wall 11 of the air guide section 8. In other words, the third ventilation passage 20 has a curved line connecting points B, C, and Amin that is convex toward the air guide section 8.

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, i.e., where the jet 22 supplied from the second ventilation passage 19 joins the airflow F1. By slowing down the speed of the airflow F1 where the jet 22 joins the airflow F1, the difference in speed between the jet 22 and the airflow F1 can be reduced, and the loss when the jet 22 and the airflow F1 join can be reduced.

Because there is a point C downstream of point B and upstream of point Amin, where ΔC > ΔAmin, the airflow F1 that merges with the jet 22 is accelerated again near Amin, and the backflow 21 can be effectively suppressed near Amin.

In addition, it is desirable for ΔAmin to be small and ΔB to be large. Figure 5 shows the case where ΔB>ΔAmin. However, ΔB<ΔAmin may also be the case.

Figure 6 is a schematic diagram showing a radial cross section of the blower 101 according to embodiment 1. Specifically, Figure 6 is a cross section obtained by rotating and projecting a cross section of the blower 101 including the rotation axis RS onto a plane parallel to the rotation axis RS. Using Figure 6, the positional relationship between the inner wall 11 and bell mouth 9 of the air guide section 8 according to embodiment 1 and the blades 4 will be described.

The bell mouth 9 has, for example, a circular arc shape with a single curvature from the upstream end 15 to the downstream end 14. Among the points included in the inner peripheral surface 16 of the bell mouth 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 bell mouth 9.

It is desirable that the 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 toward the blade 4 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 the minimum radius point B1.

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'.

As shown in Figure 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. Also, the distance between the minimum radius point B1 and the straight line L is smaller than the distance between the downstream end 14 and the straight line L. That is, ΔB1 < ΔB.

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

As shown in Figure 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.

2 to 7, the outer peripheral end 7 of the blade 4 has a straight line shape, but the outer peripheral end 7 may have a curved line shape. When the outer peripheral end 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 the straight line obtained by approximating the curved outer peripheral end 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 end 7.

Figure 8 is a graph showing the relationship between the air volume Q and the noise level SPL (unit: dBA) in the blower 101 according to the first embodiment. In Figure 8, the horizontal axis is the air volume Q [m3/min] and the vertical axis is the SPL [dBA]. The solid line g1 is the result obtained in an experiment using the blower 101. The dashed line g2 is the result obtained in an experiment using a blower called a general 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 general semi-open type blower is the same as the shape of the impeller 1 of the blower 101. As shown in Figure 8, the noise level obtained by the blower 101 according to the first embodiment has a noise reduction effect of up to about 2 dB for a wide range of air volumes Q compared to a general semi-open type blower.

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 denote the same or corresponding parts.

Figure 9 is a schematic diagram showing a radial cross section of the blower 102 according to embodiment 2. Specifically, Figure 9 is a cross section obtained by rotating and projecting a cross section of the blower 102 including the rotation axis RS onto a plane parallel to the rotation axis RS. The air guide section 31 will be described using Figure 9.

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 conforms to the protruding portion 23 of the inner wall 11, as shown in Figure 9, and may have a flat shape. The outer wall 26 may also have a shape that protrudes radially outward, or may have a curved shape.

Embodiment 3.
A blower 103 according to the third embodiment will be described with reference to Fig. 10. Descriptions of configurations similar to those of the first embodiment will be omitted. In Fig. 10, the same reference numerals as those in Figs. 1 to 9 denote the same or corresponding parts.

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

The impeller 32 of the blower 103 in this embodiment is an axial flow fan. In other words, the blower 103 is an axial flow blower.

As shown in Figure 10, it is desirable for the air guide section 33 to be arranged approximately parallel to the outer peripheral end 7 of the blades 34 of the impeller 32.

Embodiment 4.
A blower 104 according to the fourth embodiment will be described with reference to Fig. 11. Descriptions of configurations similar to those of the first embodiment will be omitted. In Fig. 11, the same reference numerals as those in Figs. 1 to 10 denote the same or corresponding parts.

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

In the blower 104 of embodiment 4, the inner wall 36 of the air guide section 35 has a streamlined shape.

Among the 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 bell mouth 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 the perpendicular line drawn from point Amax to the line L intersects with line L is defined as point Amax'. The length of the line segment connecting point Amax and point Amax' is defined as ΔAmax.

The inner wall 36 of the air guide section 35 has an approximately streamlined shape with a curvature, at least from point Amax to point Amin.

The airflow that flows into the second ventilation passage 19 from the inlet of the second ventilation passage 19 passes through point Amax on the inner wall 36 of the air guide section 35, and then experiences a negative pressure gradient in the flow direction. However, because the inner wall 36 of the air guide section 35 is approximately streamlined from point Amax to point Amin, the airflow can flow with reduced fluid resistance.

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. By allowing the jet flow 22 to flow while suppressing the energy consumption of the flow, the backflow 21 can be further suppressed and the noise can be further reduced.

Embodiment 5.
A blower 105 in the fifth embodiment will be described with reference to Fig. 12. Descriptions of the same configurations as those in the first and fourth embodiments will be omitted. In Fig. 12, the same reference numerals as those in Figs. 1 to 11 denote the same or corresponding parts.

Figure 12 is a schematic diagram showing a radial cross section of a blower 105 according to embodiment 5. Specifically, Figure 12 is a cross section of the blower 105 including the rotation axis RS, rotated and projected onto a plane parallel to the rotation axis RS.

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. The inner wall 36 may be smoothly connected to the point Amin downstream of the point Amin, for example, and may 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 an approximately streamlined shape from the point Amax to the point Amin.

The airflow flowing 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.

The inner wall 36 is formed so as to move away from the rotation axis RS downstream of point Amin, so that after the airflow flowing through the third ventilation passage 20 passes near point Amin, the airflow gradually decelerates while the static pressure is restored. The airflow passing downstream of point Amin on the inner wall 36 decelerates while the static pressure is restored, which prevents turbulence of the airflow, reduces noise, and improves ventilation performance.

Note that in each of the above embodiments described in this specification, the material, ingredients, dimensions, shape, relative positional relationship, or implementation conditions of each component may be described, but these are merely examples in all respects and each embodiment is not limited to what has been described. Thus, countless variations not exemplified are anticipated within the scope of each embodiment. For example, this includes cases in which any component is modified, added, or omitted, and further cases in which at least one component in at least one embodiment is extracted and combined with a component of another embodiment.

Needless to say, various design modifications are possible within the scope of the present invention as long as the objectives of the present invention are achieved and do not deviate from the gist of the present invention.

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 (10)

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,
the air guide section has an inner wall facing the blade, the inner wall being downstream of the downstream end of the bell mouth in the airflow, and the air guide section has a protrusion protruding in a direction toward the blade at a position opposite the outer circumferential end of the blade . The blower according to claim 1, characterized in that, in a cross section including the rotation axis, a point on a line tangent to an outer periphery of the area in which the blades rotate and a distance between the line and the protruding portion of the inner wall is set to a first point, the first point being included in the outer periphery of the area. The blower according to claim 2 , wherein the inner wall of the air guide portion is formed so that a distance from the rotation shaft increases from a position facing the first point to the downstream side of the air guide portion. 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 . When a point on the inner wall where a distance between the protrusion of the inner wall and a straight line tangent to an outer periphery of the region in which the blade rotates is a minimum is defined as a second point, the distance between the minimum radius point and the straight line is smaller than the distance between the second point and the straight line.
The blower of claim 4. The blower according to claim 4 , wherein a distance between the minimum radius point and a straight line tangent to an outer periphery of the region in which the blade rotates is smaller than a distance between the downstream end portion and the straight line. The blower according to claim 1 , wherein the bell mouth has a convex shape toward the blade between the upstream end and the downstream end. The blower according to claim 1 , wherein 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 according to claim 1 , wherein the bell mouth is formed in a curved shape. The air guide portion has an intake side end portion located on an upstream side of the airflow,
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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